mDNSResponder-333.10.tar.gz

[apple/mdnsresponder.git] / mDNSCore / mDNS.c

/* -*- Mode: C; tab-width: 4 -*-
 *
 * Copyright (c) 2002-2006 Apple Computer, Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This code is completely 100% portable C. It does not depend on any external header files
 * from outside the mDNS project -- all the types it expects to find are defined right here.
 * 
 * The previous point is very important: This file does not depend on any external
 * header files. It should compile on *any* platform that has a C compiler, without
 * making *any* assumptions about availability of so-called "standard" C functions,
 * routines, or types (which may or may not be present on any given platform).

 * Formatting notes:
 * This code follows the "Whitesmiths style" C indentation rules. Plenty of discussion
 * on C indentation can be found on the web, such as <http://www.kafejo.com/komp/1tbs.htm>,
 * but for the sake of brevity here I will say just this: Curly braces are not syntactially
 * part of an "if" statement; they are the beginning and ending markers of a compound statement;
 * therefore common sense dictates that if they are part of a compound statement then they
 * should be indented to the same level as everything else in that compound statement.
 * Indenting curly braces at the same level as the "if" implies that curly braces are
 * part of the "if", which is false. (This is as misleading as people who write "char* x,y;"
 * thinking that variables x and y are both of type "char*" -- and anyone who doesn't
 * understand why variable y is not of type "char*" just proves the point that poor code
 * layout leads people to unfortunate misunderstandings about how the C language really works.)
 */

#include "DNSCommon.h"                  // Defines general DNS untility routines
#include "uDNS.h"                                               // Defines entry points into unicast-specific routines

// Disable certain benign warnings with Microsoft compilers
#if(defined(_MSC_VER))
        // Disable "conditional expression is constant" warning for debug macros.
        // Otherwise, this generates warnings for the perfectly natural construct "while(1)"
        // If someone knows a variant way of writing "while(1)" that doesn't generate warning messages, please let us know
        #pragma warning(disable:4127)
        
        // Disable "assignment within conditional expression".
        // Other compilers understand the convention that if you place the assignment expression within an extra pair
        // of parentheses, this signals to the compiler that you really intended an assignment and no warning is necessary.
        // The Microsoft compiler doesn't understand this convention, so in the absense of any other way to signal
        // to the compiler that the assignment is intentional, we have to just turn this warning off completely.
        #pragma warning(disable:4706)
#endif

#if APPLE_OSX_mDNSResponder

#include <WebFilterDNS/WebFilterDNS.h>

#if ! NO_WCF
WCFConnection *WCFConnectionNew(void) __attribute__((weak_import));
void WCFConnectionDealloc(WCFConnection* c) __attribute__((weak_import));

// Do we really need to define a macro for "if"?
#define CHECK_WCF_FUNCTION(X) if (X)
#endif // ! NO_WCF

#else

#define NO_WCF 1
#endif // APPLE_OSX_mDNSResponder

// Forward declarations
mDNSlocal void BeginSleepProcessing(mDNS *const m);
mDNSlocal void RetrySPSRegistrations(mDNS *const m);
mDNSlocal void SendWakeup(mDNS *const m, mDNSInterfaceID InterfaceID, mDNSEthAddr *EthAddr, mDNSOpaque48 *password);
mDNSlocal mDNSBool CacheRecordRmvEventsForQuestion(mDNS *const m, DNSQuestion *q);
mDNSlocal mDNSBool LocalRecordRmvEventsForQuestion(mDNS *const m, DNSQuestion *q);
mDNSlocal void mDNS_PurgeBeforeResolve(mDNS *const m, DNSQuestion *q);

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark - Program Constants
#endif

#define NO_HINFO 1


// Any records bigger than this are considered 'large' records
#define SmallRecordLimit 1024

#define kMaxUpdateCredits 10
#define kUpdateCreditRefreshInterval (mDNSPlatformOneSecond * 6)

mDNSexport const char *const mDNS_DomainTypeNames[] =
        {
         "b._dns-sd._udp.",             // Browse
        "db._dns-sd._udp.",             // Default Browse
        "lb._dns-sd._udp.",             // Automatic Browse
         "r._dns-sd._udp.",             // Registration
        "dr._dns-sd._udp."              // Default Registration
        };

#ifdef UNICAST_DISABLED
#define uDNS_IsActiveQuery(q, u) mDNSfalse
#endif

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - General Utility Functions
#endif

// If there is a authoritative LocalOnly record that answers questions of type A, AAAA and CNAME
// this returns true. Main use is to handle /etc/hosts records. 
#define LORecordAnswersAddressType(rr) ((rr)->ARType == AuthRecordLocalOnly && \
                                                                        (rr)->resrec.RecordType & kDNSRecordTypeUniqueMask && \
                                                                        ((rr)->resrec.rrtype == kDNSType_A || (rr)->resrec.rrtype == kDNSType_AAAA || \
                                                                        (rr)->resrec.rrtype == kDNSType_CNAME))

#define FollowCNAME(q, rr, AddRecord)   (AddRecord && (q)->qtype != kDNSType_CNAME && \
                                                                                (rr)->RecordType != kDNSRecordTypePacketNegative && \
                                                                                (rr)->rrtype == kDNSType_CNAME)

mDNSlocal void SetNextQueryStopTime(mDNS *const m, const DNSQuestion *const q)
        {
        if (m->mDNS_busy != m->mDNS_reentrancy+1)
                LogMsg("SetNextQueryTime: Lock not held! mDNS_busy (%ld) mDNS_reentrancy (%ld)", m->mDNS_busy, m->mDNS_reentrancy);

#if ForceAlerts
        if (m->mDNS_busy != m->mDNS_reentrancy+1) *(long*)0 = 0;
#endif

        if (m->NextScheduledStopTime - q->StopTime > 0)
                m->NextScheduledStopTime = q->StopTime;
        }

mDNSexport void SetNextQueryTime(mDNS *const m, const DNSQuestion *const q)
        {
        if (m->mDNS_busy != m->mDNS_reentrancy+1)
                LogMsg("SetNextQueryTime: Lock not held! mDNS_busy (%ld) mDNS_reentrancy (%ld)", m->mDNS_busy, m->mDNS_reentrancy);

#if ForceAlerts
        if (m->mDNS_busy != m->mDNS_reentrancy+1) *(long*)0 = 0;
#endif

        if (ActiveQuestion(q))
                {
                // Depending on whether this is a multicast or unicast question we want to set either:
                // m->NextScheduledQuery = NextQSendTime(q) or
                // m->NextuDNSEvent      = NextQSendTime(q)
                mDNSs32 *const timer = mDNSOpaque16IsZero(q->TargetQID) ? &m->NextScheduledQuery : &m->NextuDNSEvent;
                if (*timer - NextQSendTime(q) > 0)
                        *timer = NextQSendTime(q);
                }
        }

mDNSlocal void ReleaseAuthEntity(AuthHash *r, AuthEntity *e)
        {
#if APPLE_OSX_mDNSResponder && MACOSX_MDNS_MALLOC_DEBUGGING >= 1
        unsigned int i;
        for (i=0; i<sizeof(*e); i++) ((char*)e)[i] = 0xFF;
#endif
        e->next = r->rrauth_free;
        r->rrauth_free = e;
        r->rrauth_totalused--;
        }

mDNSlocal void ReleaseAuthGroup(AuthHash *r, AuthGroup **cp)
        {
        AuthEntity *e = (AuthEntity *)(*cp);
        LogMsg("ReleaseAuthGroup:  Releasing AuthGroup %##s", (*cp)->name->c);
        if ((*cp)->rrauth_tail != &(*cp)->members)
                LogMsg("ERROR: (*cp)->members == mDNSNULL but (*cp)->rrauth_tail != &(*cp)->members)");
        if ((*cp)->name != (domainname*)((*cp)->namestorage)) mDNSPlatformMemFree((*cp)->name);
        (*cp)->name = mDNSNULL;
        *cp = (*cp)->next;                      // Cut record from list
        ReleaseAuthEntity(r, e);
        }

mDNSlocal AuthEntity *GetAuthEntity(AuthHash *r, const AuthGroup *const PreserveAG)
        {
        AuthEntity *e = mDNSNULL;

        if (r->rrauth_lock) { LogMsg("GetFreeCacheRR ERROR! Cache already locked!"); return(mDNSNULL); }
        r->rrauth_lock = 1;
        
        if (!r->rrauth_free)
                {
                // We allocate just one AuthEntity at a time because we need to be able
                // free them all individually which normally happens when we parse /etc/hosts into
                // AuthHash where we add the "new" entries and discard (free) the already added
                // entries. If we allocate as chunks, we can't free them individually.
                AuthEntity *storage = mDNSPlatformMemAllocate(sizeof(AuthEntity));
                storage->next = mDNSNULL;
                r->rrauth_free = storage;
                }
        
        // If we still have no free records, recycle all the records we can.
        // Enumerating the entire auth is moderately expensive, so when we do it, we reclaim all the records we can in one pass.
        if (!r->rrauth_free)
                {
                mDNSu32 oldtotalused = r->rrauth_totalused;
                mDNSu32 slot;
                for (slot = 0; slot < AUTH_HASH_SLOTS; slot++)
                        {
                        AuthGroup **cp = &r->rrauth_hash[slot];
                        while (*cp)
                                {
                                if ((*cp)->members || (*cp)==PreserveAG) cp=&(*cp)->next;
                                else ReleaseAuthGroup(r, cp);
                                }
                        }
                LogInfo("GetAuthEntity: Recycled %d records to reduce auth cache from %d to %d",
                        oldtotalused - r->rrauth_totalused, oldtotalused, r->rrauth_totalused);
                }

        if (r->rrauth_free)     // If there are records in the free list, take one
                {
                e = r->rrauth_free;
                r->rrauth_free = e->next;
                if (++r->rrauth_totalused >= r->rrauth_report)
                        {
                        LogInfo("RR Auth now using %ld objects", r->rrauth_totalused);
                        if      (r->rrauth_report <  100) r->rrauth_report += 10;
                        else if (r->rrauth_report < 1000) r->rrauth_report += 100;
                        else                               r->rrauth_report += 1000;
                        }
                mDNSPlatformMemZero(e, sizeof(*e));
                }

        r->rrauth_lock = 0;

        return(e);
        }

mDNSexport AuthGroup *AuthGroupForName(AuthHash *r, const mDNSu32 slot, const mDNSu32 namehash, const domainname *const name)
        {
        AuthGroup *ag;
        for (ag = r->rrauth_hash[slot]; ag; ag=ag->next)
                if (ag->namehash == namehash && SameDomainName(ag->name, name))
                        break;
        return(ag);
        }

mDNSexport AuthGroup *AuthGroupForRecord(AuthHash *r, const mDNSu32 slot, const ResourceRecord *const rr)
        {
        return(AuthGroupForName(r, slot, rr->namehash, rr->name));
        }

mDNSlocal AuthGroup *GetAuthGroup(AuthHash *r, const mDNSu32 slot, const ResourceRecord *const rr)
        {
        mDNSu16 namelen = DomainNameLength(rr->name);
        AuthGroup *ag = (AuthGroup*)GetAuthEntity(r, mDNSNULL);
        if (!ag) { LogMsg("GetAuthGroup: Failed to allocate memory for %##s", rr->name->c); return(mDNSNULL); }
        ag->next         = r->rrauth_hash[slot];
        ag->namehash     = rr->namehash;
        ag->members      = mDNSNULL;
        ag->rrauth_tail  = &ag->members;
        ag->name         = (domainname*)ag->namestorage;
        ag->NewLocalOnlyRecords = mDNSNULL;
        if (namelen > InlineCacheGroupNameSize) ag->name = mDNSPlatformMemAllocate(namelen);
        if (!ag->name)
                {
                LogMsg("GetAuthGroup: Failed to allocate name storage for %##s", rr->name->c);
                ReleaseAuthEntity(r, (AuthEntity*)ag);
                return(mDNSNULL);
                }
        AssignDomainName(ag->name, rr->name);

        if (AuthGroupForRecord(r, slot, rr)) LogMsg("GetAuthGroup: Already have AuthGroup for %##s", rr->name->c);
        r->rrauth_hash[slot] = ag;
        if (AuthGroupForRecord(r, slot, rr) != ag) LogMsg("GetAuthGroup: Not finding AuthGroup for %##s", rr->name->c);
        
        return(ag);
        }

// Returns the AuthGroup in which the AuthRecord was inserted
mDNSexport AuthGroup *InsertAuthRecord(mDNS *const m, AuthHash *r, AuthRecord *rr)
        {
        AuthGroup *ag;
        const mDNSu32 slot = AuthHashSlot(rr->resrec.name);
        ag = AuthGroupForRecord(r, slot, &rr->resrec);
        if (!ag) ag = GetAuthGroup(r, slot, &rr->resrec);       // If we don't have a AuthGroup for this name, make one now
        if (ag)
                {
                LogInfo("InsertAuthRecord: inserting auth record %s from table", ARDisplayString(m, rr));
                *(ag->rrauth_tail) = rr;                                // Append this record to tail of cache slot list
                ag->rrauth_tail = &(rr->next);                  // Advance tail pointer
                }
        return ag;
        }

mDNSexport AuthGroup *RemoveAuthRecord(mDNS *const m, AuthHash *r, AuthRecord *rr)
        {
        AuthGroup *a;
        AuthGroup **ag = &a;
        AuthRecord **rp;
        const mDNSu32 slot = AuthHashSlot(rr->resrec.name);

        a = AuthGroupForRecord(r, slot, &rr->resrec);
        if (!a) { LogMsg("RemoveAuthRecord: ERROR!! AuthGroup not found for %s", ARDisplayString(m, rr)); return mDNSNULL; }
        rp = &(*ag)->members;
        while (*rp)
                {
                if (*rp != rr)
                        rp=&(*rp)->next;
                else
                        {
                        // We don't break here, so that we can set the tail below without tracking "prev" pointers

                        LogInfo("RemoveAuthRecord: removing auth record %s from table", ARDisplayString(m, rr));
                        *rp = (*rp)->next;                      // Cut record from list
                        }
                }
        // TBD: If there are no more members, release authgroup ?
        (*ag)->rrauth_tail = rp;
        return a;
        }

mDNSexport CacheGroup *CacheGroupForName(const mDNS *const m, const mDNSu32 slot, const mDNSu32 namehash, const domainname *const name)
        {
        CacheGroup *cg;
        for (cg = m->rrcache_hash[slot]; cg; cg=cg->next)
                if (cg->namehash == namehash && SameDomainName(cg->name, name))
                        break;
        return(cg);
        }

mDNSlocal CacheGroup *CacheGroupForRecord(const mDNS *const m, const mDNSu32 slot, const ResourceRecord *const rr)
        {
        return(CacheGroupForName(m, slot, rr->namehash, rr->name));
        }

mDNSexport mDNSBool mDNS_AddressIsLocalSubnet(mDNS *const m, const mDNSInterfaceID InterfaceID, const mDNSAddr *addr)
        {
        NetworkInterfaceInfo *intf;

        if (addr->type == mDNSAddrType_IPv4)
                {
                // Normally we resist touching the NotAnInteger fields, but here we're doing tricky bitwise masking so we make an exception
                if (mDNSv4AddressIsLinkLocal(&addr->ip.v4)) return(mDNStrue);
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                        if (intf->ip.type == addr->type && intf->InterfaceID == InterfaceID && intf->McastTxRx)
                                if (((intf->ip.ip.v4.NotAnInteger ^ addr->ip.v4.NotAnInteger) & intf->mask.ip.v4.NotAnInteger) == 0)
                                        return(mDNStrue);
                }

        if (addr->type == mDNSAddrType_IPv6)
                {
                if (mDNSv6AddressIsLinkLocal(&addr->ip.v6)) return(mDNStrue);
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                        if (intf->ip.type == addr->type && intf->InterfaceID == InterfaceID && intf->McastTxRx)
                                if ((((intf->ip.ip.v6.l[0] ^ addr->ip.v6.l[0]) & intf->mask.ip.v6.l[0]) == 0) &&
                                        (((intf->ip.ip.v6.l[1] ^ addr->ip.v6.l[1]) & intf->mask.ip.v6.l[1]) == 0) &&
                                        (((intf->ip.ip.v6.l[2] ^ addr->ip.v6.l[2]) & intf->mask.ip.v6.l[2]) == 0) &&
                                        (((intf->ip.ip.v6.l[3] ^ addr->ip.v6.l[3]) & intf->mask.ip.v6.l[3]) == 0))
                                                return(mDNStrue);
                }

        return(mDNSfalse);
        }

mDNSlocal NetworkInterfaceInfo *FirstInterfaceForID(mDNS *const m, const mDNSInterfaceID InterfaceID)
        {
        NetworkInterfaceInfo *intf = m->HostInterfaces;
        while (intf && intf->InterfaceID != InterfaceID) intf = intf->next;
        return(intf);
        }

mDNSexport char *InterfaceNameForID(mDNS *const m, const mDNSInterfaceID InterfaceID)
        {
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);
        return(intf ? intf->ifname : mDNSNULL);
        }

// Caller should hold the lock
mDNSlocal void GenerateNegativeResponse(mDNS *const m)
        {
        DNSQuestion *q;
        if (!m->CurrentQuestion) { LogMsg("GenerateNegativeResponse: ERROR!! CurrentQuestion not set"); return; }
        q = m->CurrentQuestion;
        LogInfo("GenerateNegativeResponse: Generating negative response for question %##s (%s)", q->qname.c, DNSTypeName(q->qtype));

        MakeNegativeCacheRecord(m, &m->rec.r, &q->qname, q->qnamehash, q->qtype, q->qclass, 60, mDNSInterface_Any, mDNSNULL);
        AnswerCurrentQuestionWithResourceRecord(m, &m->rec.r, QC_addnocache);
        if (m->CurrentQuestion == q) { q->ThisQInterval = 0; }                          // Deactivate this question
        // Don't touch the question after this
        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
        }

mDNSlocal void AnswerQuestionByFollowingCNAME(mDNS *const m, DNSQuestion *q, ResourceRecord *rr)
        {
        const mDNSBool selfref = SameDomainName(&q->qname, &rr->rdata->u.name);
        if (q->CNAMEReferrals >= 10 || selfref)
                LogMsg("AnswerQuestionByFollowingCNAME: %p %##s (%s) NOT following CNAME referral %d%s for %s",
                        q, q->qname.c, DNSTypeName(q->qtype), q->CNAMEReferrals, selfref ? " (Self-Referential)" : "", RRDisplayString(m, rr));
        else
                {
                const mDNSu32 c = q->CNAMEReferrals + 1;                // Stash a copy of the new q->CNAMEReferrals value

                // The SameDomainName check above is to ignore bogus CNAME records that point right back at
                // themselves. Without that check we can get into a case where we have two duplicate questions,
                // A and B, and when we stop question A, UpdateQuestionDuplicates copies the value of CNAMEReferrals
                // from A to B, and then A is re-appended to the end of the list as a duplicate of B (because
                // the target name is still the same), and then when we stop question B, UpdateQuestionDuplicates
                // copies the B's value of CNAMEReferrals back to A, and we end up not incrementing CNAMEReferrals
                // for either of them. This is not a problem for CNAME loops of two or more records because in
                // those cases the newly re-appended question A has a different target name and therefore cannot be
                // a duplicate of any other question ('B') which was itself a duplicate of the previous question A.

                // Right now we just stop and re-use the existing query. If we really wanted to be 100% perfect,
                // and track CNAMEs coming and going, we should really create a subordinate query here,
                // which we would subsequently cancel and retract if the CNAME referral record were removed.
                // In reality this is such a corner case we'll ignore it until someone actually needs it.

                LogInfo("AnswerQuestionByFollowingCNAME: %p %##s (%s) following CNAME referral %d for %s",
                        q, q->qname.c, DNSTypeName(q->qtype), q->CNAMEReferrals, RRDisplayString(m, rr));

                mDNS_StopQuery_internal(m, q);                                                          // Stop old query
                AssignDomainName(&q->qname, &rr->rdata->u.name);                        // Update qname
                q->qnamehash = DomainNameHashValue(&q->qname);                          // and namehash
                // If a unicast query results in a CNAME that points to a .local, we need to re-try
                // this as unicast. Setting the mDNSInterface_Unicast tells mDNS_StartQuery_internal
                // to try this as unicast query even though it is a .local name
                if (!mDNSOpaque16IsZero(q->TargetQID) && IsLocalDomain(&q->qname))
                        {
                        LogInfo("AnswerQuestionByFollowingCNAME: Resolving a .local CNAME %p %##s (%s) Record %s",
                                q, q->qname.c, DNSTypeName(q->qtype), RRDisplayString(m, rr));
                        q->InterfaceID = mDNSInterface_Unicast;
                        }
                mDNS_StartQuery_internal(m, q);                                                         // start new query
                // Record how many times we've done this. We need to do this *after* mDNS_StartQuery_internal,
                // because mDNS_StartQuery_internal re-initializes CNAMEReferrals to zero
                q->CNAMEReferrals = c;
                }
        }

// For a single given DNSQuestion pointed to by CurrentQuestion, deliver an add/remove result for the single given AuthRecord
// Note: All the callers should use the m->CurrentQuestion to see if the question is still valid or not
mDNSlocal void AnswerLocalQuestionWithLocalAuthRecord(mDNS *const m, AuthRecord *rr, QC_result AddRecord)
        {
        DNSQuestion *q = m->CurrentQuestion;
        mDNSBool followcname;

        if (!q)
                {
                LogMsg("AnswerLocalQuestionWithLocalAuthRecord: ERROR!! CurrentQuestion NULL while answering with %s", ARDisplayString(m, rr));
                return;
                }
                
        followcname = FollowCNAME(q, &rr->resrec, AddRecord);

        // We should not be delivering results for record types Unregistered, Deregistering, and (unverified) Unique
        if (!(rr->resrec.RecordType & kDNSRecordTypeActiveMask))
                {
                LogMsg("AnswerLocalQuestionWithLocalAuthRecord: *NOT* delivering %s event for local record type %X %s",
                        AddRecord ? "Add" : "Rmv", rr->resrec.RecordType, ARDisplayString(m, rr));
                return;
                }

        // Indicate that we've given at least one positive answer for this record, so we should be prepared to send a goodbye for it
        if (AddRecord) rr->AnsweredLocalQ = mDNStrue;
        mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
        if (q->QuestionCallback && !q->NoAnswer)
                {
                q->CurrentAnswers += AddRecord ? 1 : -1;
                if (LORecordAnswersAddressType(rr))
                        {
                        if (!followcname || q->ReturnIntermed)
                                {
                                // Don't send this packet on the wire as we answered from /etc/hosts
                                q->ThisQInterval = 0;
                                q->LOAddressAnswers += AddRecord ? 1 : -1;
                                q->QuestionCallback(m, q, &rr->resrec, AddRecord);
                                }
                        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                        // The callback above could have caused the question to stop. Detect that
                        // using m->CurrentQuestion
                        if (followcname && m->CurrentQuestion == q)
                                AnswerQuestionByFollowingCNAME(m, q, &rr->resrec);
                        return;
                        }
                else
                        q->QuestionCallback(m, q, &rr->resrec, AddRecord);
                }
        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
        }

mDNSlocal void AnswerInterfaceAnyQuestionsWithLocalAuthRecord(mDNS *const m, AuthRecord *rr, QC_result AddRecord)
        {
        if (m->CurrentQuestion)
                LogMsg("AnswerInterfaceAnyQuestionsWithLocalAuthRecord: ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
                {
                mDNSBool answered;
                DNSQuestion *q = m->CurrentQuestion;
                if (RRAny(rr))
                        answered = ResourceRecordAnswersQuestion(&rr->resrec, q);
                else
                        answered = LocalOnlyRecordAnswersQuestion(rr, q);
                if (answered)
                        AnswerLocalQuestionWithLocalAuthRecord(m, rr, AddRecord);               // MUST NOT dereference q again
                if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                        m->CurrentQuestion = q->next;
                }
        m->CurrentQuestion = mDNSNULL;
        }

// When a new local AuthRecord is created or deleted, AnswerAllLocalQuestionsWithLocalAuthRecord()
// delivers the appropriate add/remove events to listening questions:
// 1. It runs though all our LocalOnlyQuestions delivering answers as appropriate,
//    stopping if it reaches a NewLocalOnlyQuestion -- brand-new questions are handled by AnswerNewLocalOnlyQuestion().
// 2. If the AuthRecord is marked mDNSInterface_LocalOnly or mDNSInterface_P2P, then it also runs though
//    our main question list, delivering answers to mDNSInterface_Any questions as appropriate,
//    stopping if it reaches a NewQuestion -- brand-new questions are handled by AnswerNewQuestion().
//
// AnswerAllLocalQuestionsWithLocalAuthRecord is used by the m->NewLocalRecords loop in mDNS_Execute(),
// and by mDNS_Deregister_internal()

mDNSlocal void AnswerAllLocalQuestionsWithLocalAuthRecord(mDNS *const m, AuthRecord *rr, QC_result AddRecord)
        {
        if (m->CurrentQuestion)
                LogMsg("AnswerAllLocalQuestionsWithLocalAuthRecord ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));

        m->CurrentQuestion = m->LocalOnlyQuestions;
        while (m->CurrentQuestion && m->CurrentQuestion != m->NewLocalOnlyQuestions)
                {
                mDNSBool answered;
                DNSQuestion *q = m->CurrentQuestion;
                // We are called with both LocalOnly/P2P record or a regular AuthRecord
                if (RRAny(rr))
                        answered = ResourceRecordAnswersQuestion(&rr->resrec, q);
                else
                        answered = LocalOnlyRecordAnswersQuestion(rr, q);
                if (answered)
                        AnswerLocalQuestionWithLocalAuthRecord(m, rr, AddRecord);                       // MUST NOT dereference q again
                if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                        m->CurrentQuestion = q->next;
                }

        m->CurrentQuestion = mDNSNULL;

        // If this AuthRecord is marked LocalOnly or P2P, then we want to deliver it to all local 'mDNSInterface_Any' questions
        if (rr->ARType == AuthRecordLocalOnly || rr->ARType == AuthRecordP2P)
                AnswerInterfaceAnyQuestionsWithLocalAuthRecord(m, rr, AddRecord);

        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Resource Record Utility Functions
#endif

#define RRTypeIsAddressType(T) ((T) == kDNSType_A || (T) == kDNSType_AAAA)

#define ResourceRecordIsValidAnswer(RR) ( ((RR)->             resrec.RecordType & kDNSRecordTypeActiveMask)  && \
                ((RR)->Additional1 == mDNSNULL || ((RR)->Additional1->resrec.RecordType & kDNSRecordTypeActiveMask)) && \
                ((RR)->Additional2 == mDNSNULL || ((RR)->Additional2->resrec.RecordType & kDNSRecordTypeActiveMask)) && \
                ((RR)->DependentOn == mDNSNULL || ((RR)->DependentOn->resrec.RecordType & kDNSRecordTypeActiveMask))  )

#define ResourceRecordIsValidInterfaceAnswer(RR, INTID) \
        (ResourceRecordIsValidAnswer(RR) && \
        ((RR)->resrec.InterfaceID == mDNSInterface_Any || (RR)->resrec.InterfaceID == (INTID)))

#define DefaultProbeCountForTypeUnique ((mDNSu8)3)
#define DefaultProbeCountForRecordType(X)      ((X) == kDNSRecordTypeUnique ? DefaultProbeCountForTypeUnique : (mDNSu8)0)

#define InitialAnnounceCount ((mDNSu8)8)

// For goodbye packets we set the count to 3, and for wakeups we set it to 18
// (which will be up to 15 wakeup attempts over the course of 30 seconds,
// and then if the machine fails to wake, 3 goodbye packets).
#define GoodbyeCount ((mDNSu8)3)
#define WakeupCount ((mDNSu8)18)

// Number of wakeups we send if WakeOnResolve is set in the question
#define InitialWakeOnResolveCount ((mDNSu8)3)

// Note that the announce intervals use exponential backoff, doubling each time. The probe intervals do not.
// This means that because the announce interval is doubled after sending the first packet, the first
// observed on-the-wire inter-packet interval between announcements is actually one second.
// The half-second value here may be thought of as a conceptual (non-existent) half-second delay *before* the first packet is sent.
#define DefaultProbeIntervalForTypeUnique (mDNSPlatformOneSecond/4)
#define DefaultAnnounceIntervalForTypeShared (mDNSPlatformOneSecond/2)
#define DefaultAnnounceIntervalForTypeUnique (mDNSPlatformOneSecond/2)

#define DefaultAPIntervalForRecordType(X)  ((X) & kDNSRecordTypeActiveSharedMask ? DefaultAnnounceIntervalForTypeShared : \
                                                                                        (X) & kDNSRecordTypeUnique           ? DefaultProbeIntervalForTypeUnique    : \
                                                                                        (X) & kDNSRecordTypeActiveUniqueMask ? DefaultAnnounceIntervalForTypeUnique : 0)

#define TimeToAnnounceThisRecord(RR,time) ((RR)->AnnounceCount && (time) - ((RR)->LastAPTime + (RR)->ThisAPInterval) >= 0)
#define TimeToSendThisRecord(RR,time) ((TimeToAnnounceThisRecord(RR,time) || (RR)->ImmedAnswer) && ResourceRecordIsValidAnswer(RR))
#define TicksTTL(RR) ((mDNSs32)(RR)->resrec.rroriginalttl * mDNSPlatformOneSecond)
#define RRExpireTime(RR) ((RR)->TimeRcvd + TicksTTL(RR))

#define MaxUnansweredQueries 4

// SameResourceRecordSignature returns true if two resources records have the same name, type, and class, and may be sent
// (or were received) on the same interface (i.e. if *both* records specify an interface, then it has to match).
// TTL and rdata may differ.
// This is used for cache flush management:
// When sending a unique record, all other records matching "SameResourceRecordSignature" must also be sent
// When receiving a unique record, all old cache records matching "SameResourceRecordSignature" are flushed

// SameResourceRecordNameClassInterface is functionally the same as SameResourceRecordSignature, except rrtype does not have to match

#define SameResourceRecordSignature(A,B) (A)->resrec.rrtype == (B)->resrec.rrtype && SameResourceRecordNameClassInterface((A),(B))

mDNSlocal mDNSBool SameResourceRecordNameClassInterface(const AuthRecord *const r1, const AuthRecord *const r2)
        {
        if (!r1) { LogMsg("SameResourceRecordSignature ERROR: r1 is NULL"); return(mDNSfalse); }
        if (!r2) { LogMsg("SameResourceRecordSignature ERROR: r2 is NULL"); return(mDNSfalse); }
        if (r1->resrec.InterfaceID &&
                r2->resrec.InterfaceID &&
                r1->resrec.InterfaceID != r2->resrec.InterfaceID) return(mDNSfalse);
        return(mDNSBool)(
                r1->resrec.rrclass  == r2->resrec.rrclass &&
                r1->resrec.namehash == r2->resrec.namehash &&
                SameDomainName(r1->resrec.name, r2->resrec.name));
        }

// PacketRRMatchesSignature behaves as SameResourceRecordSignature, except that types may differ if our
// authoratative record is unique (as opposed to shared). For unique records, we are supposed to have
// complete ownership of *all* types for this name, so *any* record type with the same name is a conflict.
// In addition, when probing we send our questions with the wildcard type kDNSQType_ANY,
// so a response of any type should match, even if it is not actually the type the client plans to use.

// For now, to make it easier to avoid false conflicts, we treat SPS Proxy records like shared records,
// and require the rrtypes to match for the rdata to be considered potentially conflicting
mDNSlocal mDNSBool PacketRRMatchesSignature(const CacheRecord *const pktrr, const AuthRecord *const authrr)
        {
        if (!pktrr)  { LogMsg("PacketRRMatchesSignature ERROR: pktrr is NULL"); return(mDNSfalse); }
        if (!authrr) { LogMsg("PacketRRMatchesSignature ERROR: authrr is NULL"); return(mDNSfalse); }
        if (pktrr->resrec.InterfaceID &&
                authrr->resrec.InterfaceID &&
                pktrr->resrec.InterfaceID != authrr->resrec.InterfaceID) return(mDNSfalse);
        if (!(authrr->resrec.RecordType & kDNSRecordTypeUniqueMask) || authrr->WakeUp.HMAC.l[0])
                if (pktrr->resrec.rrtype != authrr->resrec.rrtype) return(mDNSfalse);
        return(mDNSBool)(
                pktrr->resrec.rrclass == authrr->resrec.rrclass &&
                pktrr->resrec.namehash == authrr->resrec.namehash &&
                SameDomainName(pktrr->resrec.name, authrr->resrec.name));
        }

// CacheRecord *ka is the CacheRecord from the known answer list in the query.
// This is the information that the requester believes to be correct.
// AuthRecord *rr is the answer we are proposing to give, if not suppressed.
// This is the information that we believe to be correct.
// We've already determined that we plan to give this answer on this interface
// (either the record is non-specific, or it is specific to this interface)
// so now we just need to check the name, type, class, rdata and TTL.
mDNSlocal mDNSBool ShouldSuppressKnownAnswer(const CacheRecord *const ka, const AuthRecord *const rr)
        {
        // If RR signature is different, or data is different, then don't suppress our answer
        if (!IdenticalResourceRecord(&ka->resrec, &rr->resrec)) return(mDNSfalse);
        
        // If the requester's indicated TTL is less than half the real TTL,
        // we need to give our answer before the requester's copy expires.
        // If the requester's indicated TTL is at least half the real TTL,
        // then we can suppress our answer this time.
        // If the requester's indicated TTL is greater than the TTL we believe,
        // then that's okay, and we don't need to do anything about it.
        // (If two responders on the network are offering the same information,
        // that's okay, and if they are offering the information with different TTLs,
        // the one offering the lower TTL should defer to the one offering the higher TTL.)
        return(mDNSBool)(ka->resrec.rroriginalttl >= rr->resrec.rroriginalttl / 2);
        }

mDNSlocal void SetNextAnnounceProbeTime(mDNS *const m, const AuthRecord *const rr)
        {
        if (rr->resrec.RecordType == kDNSRecordTypeUnique)
                {
                if ((rr->LastAPTime + rr->ThisAPInterval) - m->timenow > mDNSPlatformOneSecond * 10)
                        {
                        LogMsg("SetNextAnnounceProbeTime: ProbeCount %d Next in %d %s", rr->ProbeCount, (rr->LastAPTime + rr->ThisAPInterval) - m->timenow, ARDisplayString(m, rr));
                        LogMsg("SetNextAnnounceProbeTime: m->SuppressProbes %d m->timenow %d diff %d", m->SuppressProbes, m->timenow, m->SuppressProbes - m->timenow);
                        }
                if (m->NextScheduledProbe - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
                        m->NextScheduledProbe = (rr->LastAPTime + rr->ThisAPInterval);
                // Some defensive code:
                // If (rr->LastAPTime + rr->ThisAPInterval) happens to be far in the past, we don't want to allow
                // NextScheduledProbe to be set excessively in the past, because that can cause bad things to happen.
                // See: <rdar://problem/7795434> mDNS: Sometimes advertising stops working and record interval is set to zero
                if (m->NextScheduledProbe - m->timenow < 0)
                        m->NextScheduledProbe = m->timenow;
                }
        else if (rr->AnnounceCount && (ResourceRecordIsValidAnswer(rr) || rr->resrec.RecordType == kDNSRecordTypeDeregistering))
                {
                if (m->NextScheduledResponse - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
                        m->NextScheduledResponse = (rr->LastAPTime + rr->ThisAPInterval);
                }
        }

mDNSlocal void InitializeLastAPTime(mDNS *const m, AuthRecord *const rr)
        {
        // For reverse-mapping Sleep Proxy PTR records, probe interval is one second
        rr->ThisAPInterval = rr->AddressProxy.type ? mDNSPlatformOneSecond : DefaultAPIntervalForRecordType(rr->resrec.RecordType);

        // * If this is a record type that's going to probe, then we use the m->SuppressProbes time.
        // * Otherwise, if it's not going to probe, but m->SuppressProbes is set because we have other
        //   records that are going to probe, then we delay its first announcement so that it will
        //   go out synchronized with the first announcement for the other records that *are* probing.
        //   This is a minor performance tweak that helps keep groups of related records synchronized together.
        //   The addition of "interval / 2" is to make sure that, in the event that any of the probes are
        //   delayed by a few milliseconds, this announcement does not inadvertently go out *before* the probing is complete.
        //   When the probing is complete and those records begin to announce, these records will also be picked up and accelerated,
        //   because they will meet the criterion of being at least half-way to their scheduled announcement time.
        // * If it's not going to probe and m->SuppressProbes is not already set then we should announce immediately.

        if (rr->ProbeCount)
                {
                // If we have no probe suppression time set, or it is in the past, set it now
                if (m->SuppressProbes == 0 || m->SuppressProbes - m->timenow < 0)
                        {
                        // To allow us to aggregate probes when a group of services are registered together,
                        // the first probe is delayed 1/4 second. This means the common-case behaviour is:
                        // 1/4 second wait; probe
                        // 1/4 second wait; probe
                        // 1/4 second wait; probe
                        // 1/4 second wait; announce (i.e. service is normally announced exactly one second after being registered)
                        m->SuppressProbes = NonZeroTime(m->timenow + DefaultProbeIntervalForTypeUnique/2 + mDNSRandom(DefaultProbeIntervalForTypeUnique/2));

                        // If we already have a *probe* scheduled to go out sooner, then use that time to get better aggregation
                        if (m->SuppressProbes - m->NextScheduledProbe >= 0)
                                m->SuppressProbes = NonZeroTime(m->NextScheduledProbe);
                        if (m->SuppressProbes - m->timenow < 0)         // Make sure we don't set m->SuppressProbes excessively in the past
                                m->SuppressProbes = m->timenow;

                        // If we already have a *query* scheduled to go out sooner, then use that time to get better aggregation
                        if (m->SuppressProbes - m->NextScheduledQuery >= 0)
                                m->SuppressProbes = NonZeroTime(m->NextScheduledQuery);
                        if (m->SuppressProbes - m->timenow < 0)         // Make sure we don't set m->SuppressProbes excessively in the past
                                m->SuppressProbes = m->timenow;

                        // except... don't expect to be able to send before the m->SuppressSending timer fires
                        if (m->SuppressSending && m->SuppressProbes - m->SuppressSending < 0)
                                m->SuppressProbes = NonZeroTime(m->SuppressSending);

                        if (m->SuppressProbes - m->timenow > mDNSPlatformOneSecond * 8)
                                {
                                LogMsg("InitializeLastAPTime ERROR m->SuppressProbes %d m->NextScheduledProbe %d m->NextScheduledQuery %d m->SuppressSending %d %d",
                                        m->SuppressProbes     - m->timenow,
                                        m->NextScheduledProbe - m->timenow,
                                        m->NextScheduledQuery - m->timenow,
                                        m->SuppressSending,
                                        m->SuppressSending    - m->timenow);
                                m->SuppressProbes = NonZeroTime(m->timenow + DefaultProbeIntervalForTypeUnique/2 + mDNSRandom(DefaultProbeIntervalForTypeUnique/2));
                                }
                        }
                rr->LastAPTime = m->SuppressProbes - rr->ThisAPInterval;
                }
        else if (m->SuppressProbes && m->SuppressProbes - m->timenow >= 0)
                rr->LastAPTime = m->SuppressProbes - rr->ThisAPInterval + DefaultProbeIntervalForTypeUnique * DefaultProbeCountForTypeUnique + rr->ThisAPInterval / 2;
        else
                rr->LastAPTime = m->timenow - rr->ThisAPInterval;

        // For reverse-mapping Sleep Proxy PTR records we don't want to start probing instantly -- we
        // wait one second to give the client a chance to go to sleep, and then start our ARP/NDP probing.
        // After three probes one second apart with no answer, we conclude the client is now sleeping
        // and we can begin broadcasting our announcements to take over ownership of that IP address.
        // If we don't wait for the client to go to sleep, then when the client sees our ARP Announcements there's a risk
        // (depending on the OS and networking stack it's using) that it might interpret it as a conflict and change its IP address.
        if (rr->AddressProxy.type) rr->LastAPTime = m->timenow;

        // Unsolicited Neighbor Advertisements (RFC 2461 Section 7.2.6) give us fast address cache updating,
        // but some older IPv6 clients get confused by them, so for now we don't send them. Without Unsolicited
        // Neighbor Advertisements we have to rely on Neighbor Unreachability Detection instead, which is slower.
        // Given this, we'll do our best to wake for existing IPv6 connections, but we don't want to encourage
        // new ones for sleeping clients, so we'll we send deletions for our SPS clients' AAAA records.
        if (m->KnownBugs & mDNS_KnownBug_LimitedIPv6)
                if (rr->WakeUp.HMAC.l[0] && rr->resrec.rrtype == kDNSType_AAAA)
                        rr->LastAPTime = m->timenow - rr->ThisAPInterval + mDNSPlatformOneSecond * 10;
        
        // Set LastMCTime to now, to inhibit multicast responses
        // (no need to send additional multicast responses when we're announcing anyway)
        rr->LastMCTime      = m->timenow;
        rr->LastMCInterface = mDNSInterfaceMark;
        
        SetNextAnnounceProbeTime(m, rr);
        }

mDNSlocal const domainname *SetUnicastTargetToHostName(mDNS *const m, AuthRecord *rr)
        {
        const domainname *target;
        if (rr->AutoTarget)
                {
                // For autotunnel services pointing at our IPv6 ULA we don't need or want a NAT mapping, but for all other
                // advertised services referencing our uDNS hostname, we want NAT mappings automatically created as appropriate,
                // with the port number in our advertised SRV record automatically tracking the external mapped port.
                DomainAuthInfo *AuthInfo = GetAuthInfoForName_internal(m, rr->resrec.name);
                if (!AuthInfo || !AuthInfo->AutoTunnel) rr->AutoTarget = Target_AutoHostAndNATMAP;
                }

        target = GetServiceTarget(m, rr);
        if (!target || target->c[0] == 0)
                {
                // defer registration until we've got a target
                LogInfo("SetUnicastTargetToHostName No target for %s", ARDisplayString(m, rr));
                rr->state = regState_NoTarget;
                return mDNSNULL;
                }
        else
                {
                LogInfo("SetUnicastTargetToHostName target %##s for resource record %s", target->c, ARDisplayString(m,rr));
                return target;
                }
        }

// Right now this only applies to mDNS (.local) services where the target host is always m->MulticastHostname
// Eventually we should unify this with GetServiceTarget() in uDNS.c
mDNSlocal void SetTargetToHostName(mDNS *const m, AuthRecord *const rr)
        {
        domainname *const target = GetRRDomainNameTarget(&rr->resrec);
        const domainname *newname = &m->MulticastHostname;

        if (!target) LogInfo("SetTargetToHostName: Don't know how to set the target of rrtype %s", DNSTypeName(rr->resrec.rrtype));

        if (!(rr->ForceMCast || rr->ARType == AuthRecordLocalOnly || rr->ARType == AuthRecordP2P || IsLocalDomain(&rr->namestorage)))
                {
                const domainname *const n = SetUnicastTargetToHostName(m, rr);
                if (n) newname = n;
                else { target->c[0] = 0; SetNewRData(&rr->resrec, mDNSNULL, 0); return; }
                }

        if (target && SameDomainName(target, newname))
                debugf("SetTargetToHostName: Target of %##s is already %##s", rr->resrec.name->c, target->c);
        
        if (target && !SameDomainName(target, newname))
                {
                AssignDomainName(target, newname);
                SetNewRData(&rr->resrec, mDNSNULL, 0);          // Update rdlength, rdestimate, rdatahash
                
                // If we're in the middle of probing this record, we need to start again,
                // because changing its rdata may change the outcome of the tie-breaker.
                // (If the record type is kDNSRecordTypeUnique (unconfirmed unique) then DefaultProbeCountForRecordType is non-zero.)
                rr->ProbeCount     = DefaultProbeCountForRecordType(rr->resrec.RecordType);

                // If we've announced this record, we really should send a goodbye packet for the old rdata before
                // changing to the new rdata. However, in practice, we only do SetTargetToHostName for unique records,
                // so when we announce them we'll set the kDNSClass_UniqueRRSet and clear any stale data that way.
                if (rr->RequireGoodbye && rr->resrec.RecordType == kDNSRecordTypeShared)
                        debugf("Have announced shared record %##s (%s) at least once: should have sent a goodbye packet before updating",
                                rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));

                rr->AnnounceCount  = InitialAnnounceCount;
                rr->RequireGoodbye = mDNSfalse;
                InitializeLastAPTime(m, rr);
                }
        }

mDNSlocal void AcknowledgeRecord(mDNS *const m, AuthRecord *const rr)
        {
        if (rr->RecordCallback)
                {
                // CAUTION: MUST NOT do anything more with rr after calling rr->Callback(), because the client's callback function
                // is allowed to do anything, including starting/stopping queries, registering/deregistering records, etc.
                rr->Acknowledged = mDNStrue;
                mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                rr->RecordCallback(m, rr, mStatus_NoError);
                mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                }
        }

mDNSexport void ActivateUnicastRegistration(mDNS *const m, AuthRecord *const rr)
        {
        // Make sure that we don't activate the SRV record and associated service records, if it is in
        // NoTarget state. First time when a service is being instantiated, SRV record may be in NoTarget state.
        // We should not activate any of the other reords (PTR, TXT) that are part of the service. When
        // the target becomes available, the records will be reregistered.
        if (rr->resrec.rrtype != kDNSType_SRV)
                {
                AuthRecord *srvRR = mDNSNULL;
                if (rr->resrec.rrtype == kDNSType_PTR)
                        srvRR = rr->Additional1;
                else if (rr->resrec.rrtype == kDNSType_TXT)
                        srvRR = rr->DependentOn;
                if (srvRR)
                        {
                        if (srvRR->resrec.rrtype != kDNSType_SRV)
                                {
                                LogMsg("ActivateUnicastRegistration: ERROR!! Resource record %s wrong, expecting SRV type", ARDisplayString(m, srvRR));
                                }
                        else
                                {
                                LogInfo("ActivateUnicastRegistration: Found Service Record %s in state %d for %##s (%s)",
                                        ARDisplayString(m, srvRR), srvRR->state, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                                rr->state = srvRR->state;
                                }
                        }
                }

        if (rr->state == regState_NoTarget)
                {
                LogInfo("ActivateUnicastRegistration record %s in regState_NoTarget, not activating", ARDisplayString(m, rr));
                return;
                }
        // When we wake up from sleep, we call ActivateUnicastRegistration. It is possible that just before we went to sleep,
        // the service/record was being deregistered. In that case, we should not try to register again. For the cases where
        // the records are deregistered due to e.g., no target for the SRV record, we would have returned from above if it
        // was already in NoTarget state. If it was in the process of deregistration but did not complete fully before we went
        // to sleep, then it is okay to start in Pending state as we will go back to NoTarget state if we don't have a target.
        if (rr->resrec.RecordType == kDNSRecordTypeDeregistering)
                {
                LogInfo("ActivateUnicastRegistration: Resource record %s, current state %d, moving to DeregPending", ARDisplayString(m, rr), rr->state);
                rr->state = regState_DeregPending;
                }
        else
                {
                LogInfo("ActivateUnicastRegistration: Resource record %s, current state %d, moving to Pending", ARDisplayString(m, rr), rr->state);
                rr->state = regState_Pending;
                }
        rr->ProbeCount     = 0;
        rr->AnnounceCount  = 0;
        rr->ThisAPInterval = INIT_RECORD_REG_INTERVAL;
        rr->LastAPTime     = m->timenow - rr->ThisAPInterval;
        rr->expire         = 0; // Forget about all the leases, start fresh
        rr->uselease       = mDNStrue;
        rr->updateid       = zeroID;
        rr->SRVChanged     = mDNSfalse;
        rr->updateError    = mStatus_NoError;
        // RestartRecordGetZoneData calls this function whenever a new interface gets registered with core.
        // The records might already be registered with the server and hence could have NAT state.
        if (rr->NATinfo.clientContext)
                {
                mDNS_StopNATOperation_internal(m, &rr->NATinfo);
                rr->NATinfo.clientContext = mDNSNULL;
                }
        if (rr->nta) { CancelGetZoneData(m, rr->nta); rr->nta = mDNSNULL; }
        if (rr->tcp) { DisposeTCPConn(rr->tcp);       rr->tcp = mDNSNULL; }
        if (m->NextuDNSEvent - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
                m->NextuDNSEvent = (rr->LastAPTime + rr->ThisAPInterval);
        }

// Two records qualify to be local duplicates if:
// (a) the RecordTypes are the same, or
// (b) one is Unique and the other Verified
// (c) either is in the process of deregistering
#define RecordLDT(A,B) ((A)->resrec.RecordType == (B)->resrec.RecordType || \
        ((A)->resrec.RecordType | (B)->resrec.RecordType) == (kDNSRecordTypeUnique | kDNSRecordTypeVerified) || \
        ((A)->resrec.RecordType == kDNSRecordTypeDeregistering || (B)->resrec.RecordType == kDNSRecordTypeDeregistering))

#define RecordIsLocalDuplicate(A,B) \
        ((A)->resrec.InterfaceID == (B)->resrec.InterfaceID && RecordLDT((A),(B)) && IdenticalResourceRecord(&(A)->resrec, &(B)->resrec))

mDNSlocal AuthRecord *CheckAuthIdenticalRecord(AuthHash *r, AuthRecord *rr)
        {
        AuthGroup *a;
        AuthGroup **ag = &a;
        AuthRecord **rp;
        const mDNSu32 slot = AuthHashSlot(rr->resrec.name);

        a = AuthGroupForRecord(r, slot, &rr->resrec);
        if (!a) return mDNSNULL;
        rp = &(*ag)->members;
        while (*rp)
                {
                if (!RecordIsLocalDuplicate(*rp, rr))
                        rp=&(*rp)->next;
                else
                        {
                        if ((*rp)->resrec.RecordType == kDNSRecordTypeDeregistering)
                                {
                                (*rp)->AnnounceCount = 0;
                                rp=&(*rp)->next;
                                }
                        else return *rp;
                        }
                }
        return (mDNSNULL);
        }

mDNSlocal mDNSBool CheckAuthRecordConflict(AuthHash *r, AuthRecord *rr)
        {
        AuthGroup *a;
        AuthGroup **ag = &a;
        AuthRecord **rp;
        const mDNSu32 slot = AuthHashSlot(rr->resrec.name);

        a = AuthGroupForRecord(r, slot, &rr->resrec);
        if (!a) return mDNSfalse;
        rp = &(*ag)->members;
        while (*rp)
                {
                const AuthRecord *s1 = rr->RRSet ? rr->RRSet : rr;
                const AuthRecord *s2 = (*rp)->RRSet ? (*rp)->RRSet : *rp;
                if (s1 != s2 && SameResourceRecordSignature((*rp), rr) && !IdenticalSameNameRecord(&(*rp)->resrec, &rr->resrec))
                        return mDNStrue;
                else
                        rp=&(*rp)->next;
                }
        return (mDNSfalse);
        }

// checks to see if "rr" is already present
mDNSlocal AuthRecord *CheckAuthSameRecord(AuthHash *r, AuthRecord *rr)
        {
        AuthGroup *a;
        AuthGroup **ag = &a;
        AuthRecord **rp;
        const mDNSu32 slot = AuthHashSlot(rr->resrec.name);

        a = AuthGroupForRecord(r, slot, &rr->resrec);
        if (!a) return mDNSNULL;
        rp = &(*ag)->members;
        while (*rp)
                {
                if (*rp != rr)
                        rp=&(*rp)->next;
                else
                        {
                        return *rp;
                        }
                }
        return (mDNSNULL);
        }

// Exported so uDNS.c can call this
mDNSexport mStatus mDNS_Register_internal(mDNS *const m, AuthRecord *const rr)
        {
        domainname *target = GetRRDomainNameTarget(&rr->resrec);
        AuthRecord *r;
        AuthRecord **p = &m->ResourceRecords;
        AuthRecord **d = &m->DuplicateRecords;

        if ((mDNSs32)rr->resrec.rroriginalttl <= 0)
                { LogMsg("mDNS_Register_internal: TTL %X should be 1 - 0x7FFFFFFF %s", rr->resrec.rroriginalttl, ARDisplayString(m, rr)); return(mStatus_BadParamErr); }

        if (!rr->resrec.RecordType)
                { LogMsg("mDNS_Register_internal: RecordType must be non-zero %s", ARDisplayString(m, rr)); return(mStatus_BadParamErr); }

        if (m->ShutdownTime)
                { LogMsg("mDNS_Register_internal: Shutting down, can't register %s", ARDisplayString(m, rr)); return(mStatus_ServiceNotRunning); }
        
        if (m->DivertMulticastAdvertisements && !AuthRecord_uDNS(rr))
                {
                mDNSInterfaceID previousID = rr->resrec.InterfaceID;
                if (rr->resrec.InterfaceID == mDNSInterface_Any || rr->resrec.InterfaceID == mDNSInterface_P2P)
                        {
                        rr->resrec.InterfaceID = mDNSInterface_LocalOnly;
                        rr->ARType = AuthRecordLocalOnly;
                        }
                if (rr->resrec.InterfaceID != mDNSInterface_LocalOnly)
                        {
                        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, rr->resrec.InterfaceID);
                        if (intf && !intf->Advertise){ rr->resrec.InterfaceID = mDNSInterface_LocalOnly; rr->ARType = AuthRecordLocalOnly; }
                        }
                if (rr->resrec.InterfaceID != previousID)
                        LogInfo("mDNS_Register_internal: Diverting record to local-only %s", ARDisplayString(m, rr));
                }

        if (RRLocalOnly(rr))
                {
                if (CheckAuthSameRecord(&m->rrauth, rr))
                        {
                        LogMsg("mDNS_Register_internal: ERROR!! Tried to register LocalOnly AuthRecord %p %##s (%s) that's already in the list",
                                rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                        return(mStatus_AlreadyRegistered);
                        }
                }
        else
                {
                while (*p && *p != rr) p=&(*p)->next;
                if (*p)
                        {
                        LogMsg("mDNS_Register_internal: ERROR!! Tried to register AuthRecord %p %##s (%s) that's already in the list",
                                rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                        return(mStatus_AlreadyRegistered);
                        }
                }

        while (*d && *d != rr) d=&(*d)->next;
        if (*d)
                {
                LogMsg("mDNS_Register_internal: ERROR!! Tried to register AuthRecord %p %##s (%s) that's already in the Duplicate list",
                                rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                return(mStatus_AlreadyRegistered);
                }

        if (rr->DependentOn)
                {
                if (rr->resrec.RecordType == kDNSRecordTypeUnique)
                        rr->resrec.RecordType =  kDNSRecordTypeVerified;
                else
                        {
                        LogMsg("mDNS_Register_internal: ERROR! %##s (%s): rr->DependentOn && RecordType != kDNSRecordTypeUnique",
                                rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                        return(mStatus_Invalid);
                        }
                if (!(rr->DependentOn->resrec.RecordType & (kDNSRecordTypeUnique | kDNSRecordTypeVerified | kDNSRecordTypeKnownUnique)))
                        {
                        LogMsg("mDNS_Register_internal: ERROR! %##s (%s): rr->DependentOn->RecordType bad type %X",
                                rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype), rr->DependentOn->resrec.RecordType);
                        return(mStatus_Invalid);
                        }
                }

        // If this resource record is referencing a specific interface, make sure it exists.
        // Skip checks for LocalOnly and P2P as they are not valid InterfaceIDs. Also, for scoped
        // entries in /etc/hosts skip that check as that interface may not be valid at this time.
        if (rr->resrec.InterfaceID && rr->ARType != AuthRecordLocalOnly && rr->ARType != AuthRecordP2P)
                {
                NetworkInterfaceInfo *intf = FirstInterfaceForID(m, rr->resrec.InterfaceID);
                if (!intf)
                        {
                        debugf("mDNS_Register_internal: Bogus InterfaceID %p in resource record", rr->resrec.InterfaceID);
                        return(mStatus_BadReferenceErr);
                        }
                }

        rr->next = mDNSNULL;

        // Field Group 1: The actual information pertaining to this resource record
        // Set up by client prior to call

        // Field Group 2: Persistent metadata for Authoritative Records
//      rr->Additional1       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//      rr->Additional2       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//      rr->DependentOn       = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//      rr->RRSet             = set to mDNSNULL  in mDNS_SetupResourceRecord; may be overridden by client
//      rr->Callback          = already set      in mDNS_SetupResourceRecord
//      rr->Context           = already set      in mDNS_SetupResourceRecord
//      rr->RecordType        = already set      in mDNS_SetupResourceRecord
//      rr->HostTarget        = set to mDNSfalse in mDNS_SetupResourceRecord; may be overridden by client
//      rr->AllowRemoteQuery  = set to mDNSfalse in mDNS_SetupResourceRecord; may be overridden by client
        // Make sure target is not uninitialized data, or we may crash writing debugging log messages
        if (rr->AutoTarget && target) target->c[0] = 0;

        // Field Group 3: Transient state for Authoritative Records
        rr->Acknowledged      = mDNSfalse;
        rr->ProbeCount        = DefaultProbeCountForRecordType(rr->resrec.RecordType);
        rr->AnnounceCount     = InitialAnnounceCount;
        rr->RequireGoodbye    = mDNSfalse;
        rr->AnsweredLocalQ    = mDNSfalse;
        rr->IncludeInProbe    = mDNSfalse;
        rr->ImmedUnicast      = mDNSfalse;
        rr->SendNSECNow       = mDNSNULL;
        rr->ImmedAnswer       = mDNSNULL;
        rr->ImmedAdditional   = mDNSNULL;
        rr->SendRNow          = mDNSNULL;
        rr->v4Requester       = zerov4Addr;
        rr->v6Requester       = zerov6Addr;
        rr->NextResponse      = mDNSNULL;
        rr->NR_AnswerTo       = mDNSNULL;
        rr->NR_AdditionalTo   = mDNSNULL;
        if (!rr->AutoTarget) InitializeLastAPTime(m, rr);
//      rr->LastAPTime        = Set for us in InitializeLastAPTime()
//      rr->LastMCTime        = Set for us in InitializeLastAPTime()
//      rr->LastMCInterface   = Set for us in InitializeLastAPTime()
        rr->NewRData          = mDNSNULL;
        rr->newrdlength       = 0;
        rr->UpdateCallback    = mDNSNULL;
        rr->UpdateCredits     = kMaxUpdateCredits;
        rr->NextUpdateCredit  = 0;
        rr->UpdateBlocked     = 0;

        // For records we're holding as proxy (except reverse-mapping PTR records) two announcements is sufficient
        if (rr->WakeUp.HMAC.l[0] && !rr->AddressProxy.type) rr->AnnounceCount = 2;

        // Field Group 4: Transient uDNS state for Authoritative Records
        rr->state             = regState_Zero;
        rr->uselease          = 0;
        rr->expire            = 0;
        rr->Private           = 0;
        rr->updateid          = zeroID;
        rr->zone              = rr->resrec.name;
        rr->nta               = mDNSNULL;
        rr->tcp               = mDNSNULL;
        rr->OrigRData         = 0;
        rr->OrigRDLen         = 0;
        rr->InFlightRData     = 0;
        rr->InFlightRDLen     = 0;
        rr->QueuedRData       = 0;
        rr->QueuedRDLen       = 0;
        //mDNSPlatformMemZero(&rr->NATinfo, sizeof(rr->NATinfo));
        // We should be recording the actual internal port for this service record here. Once we initiate our NAT mapping
        // request we'll subsequently overwrite srv.port with the allocated external NAT port -- potentially multiple
        // times with different values if the external NAT port changes during the lifetime of the service registration.
        //if (rr->resrec.rrtype == kDNSType_SRV) rr->NATinfo.IntPort = rr->resrec.rdata->u.srv.port;

//      rr->resrec.interface         = already set in mDNS_SetupResourceRecord
//      rr->resrec.name->c           = MUST be set by client
//      rr->resrec.rrtype            = already set in mDNS_SetupResourceRecord
//      rr->resrec.rrclass           = already set in mDNS_SetupResourceRecord
//      rr->resrec.rroriginalttl     = already set in mDNS_SetupResourceRecord
//      rr->resrec.rdata             = MUST be set by client, unless record type is CNAME or PTR and rr->HostTarget is set

        // BIND named (name daemon) doesn't allow TXT records with zero-length rdata. This is strictly speaking correct,
        // since RFC 1035 specifies a TXT record as "One or more <character-string>s", not "Zero or more <character-string>s".
        // Since some legacy apps try to create zero-length TXT records, we'll silently correct it here.
        if (rr->resrec.rrtype == kDNSType_TXT && rr->resrec.rdlength == 0) { rr->resrec.rdlength = 1; rr->resrec.rdata->u.txt.c[0] = 0; }

        if (rr->AutoTarget)
                {
                SetTargetToHostName(m, rr);     // Also sets rdlength and rdestimate for us, and calls InitializeLastAPTime();
#ifndef UNICAST_DISABLED
                // If we have no target record yet, SetTargetToHostName will set rr->state == regState_NoTarget
                // In this case we leave the record half-formed in the list, and later we'll remove it from the list and re-add it properly.
                if (rr->state == regState_NoTarget)
                        {
                        // Initialize the target so that we don't crash while logging etc.
                        domainname *tar = GetRRDomainNameTarget(&rr->resrec);
                        if (tar) tar->c[0] = 0;
                        LogInfo("mDNS_Register_internal: record %s in NoTarget state", ARDisplayString(m, rr));
                        }
#endif
                }
        else
                {
                rr->resrec.rdlength   = GetRDLength(&rr->resrec, mDNSfalse);
                rr->resrec.rdestimate = GetRDLength(&rr->resrec, mDNStrue);
                }

        if (!ValidateDomainName(rr->resrec.name))
                { LogMsg("Attempt to register record with invalid name: %s", ARDisplayString(m, rr)); return(mStatus_Invalid); }

        // Don't do this until *after* we've set rr->resrec.rdlength
        if (!ValidateRData(rr->resrec.rrtype, rr->resrec.rdlength, rr->resrec.rdata))
                { LogMsg("Attempt to register record with invalid rdata: %s", ARDisplayString(m, rr)); return(mStatus_Invalid); }

        rr->resrec.namehash   = DomainNameHashValue(rr->resrec.name);
        rr->resrec.rdatahash  = target ? DomainNameHashValue(target) : RDataHashValue(&rr->resrec);
        
        if (RRLocalOnly(rr))
                {
                // If this is supposed to be unique, make sure we don't have any name conflicts.
                // If we found a conflict, we may still want to insert the record in the list but mark it appropriately
                // (kDNSRecordTypeDeregistering) so that we deliver RMV events to the application. But this causes more
                // complications and not clear whether there are any benefits. See rdar:9304275 for details.
                // Hence, just bail out.
                if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                        {
                        if (CheckAuthRecordConflict(&m->rrauth, rr))
                                {
                                LogInfo("mDNS_Register_internal: Name conflict %s (%p), InterfaceID %p", ARDisplayString(m, rr), rr, rr->resrec.InterfaceID);
                                return mStatus_NameConflict;
                                }
                        }
                }

        // For uDNS records, we don't support duplicate checks at this time.
#ifndef UNICAST_DISABLED
        if (AuthRecord_uDNS(rr))
                {
                if (!m->NewLocalRecords) m->NewLocalRecords = rr;
                // When we called SetTargetToHostName, it may have caused mDNS_Register_internal to be re-entered, appending new
                // records to the list, so we now need to update p to advance to the new end to the list before appending our new record.
                // Note that for AutoTunnel this should never happen, but this check makes the code future-proof.
                while (*p) p=&(*p)->next;
                *p = rr;
                if (rr->resrec.RecordType == kDNSRecordTypeUnique) rr->resrec.RecordType = kDNSRecordTypeVerified;
                rr->ProbeCount    = 0;
                rr->AnnounceCount = 0;
                if (rr->state != regState_NoTarget) ActivateUnicastRegistration(m, rr);
                return(mStatus_NoError);                        // <--- Note: For unicast records, code currently bails out at this point
                }
#endif

        // Now that we've finished building our new record, make sure it's not identical to one we already have
        if (RRLocalOnly(rr))
                {
                rr->ProbeCount    = 0;
                rr->AnnounceCount = 0;
                r = CheckAuthIdenticalRecord(&m->rrauth, rr);
                }
        else
                {
                for (r = m->ResourceRecords; r; r=r->next)
                        if (RecordIsLocalDuplicate(r, rr))
                                {
                                if (r->resrec.RecordType == kDNSRecordTypeDeregistering) r->AnnounceCount = 0;
                                else break;
                                }
                }

        if (r)
                {
                debugf("mDNS_Register_internal:Adding to duplicate list %s", ARDisplayString(m,rr));
                *d = rr;
                // If the previous copy of this record is already verified unique,
                // then indicate that we should move this record promptly to kDNSRecordTypeUnique state.
                // Setting ProbeCount to zero will cause SendQueries() to advance this record to
                // kDNSRecordTypeVerified state and call the client callback at the next appropriate time.
                if (rr->resrec.RecordType == kDNSRecordTypeUnique && r->resrec.RecordType == kDNSRecordTypeVerified)
                        rr->ProbeCount = 0;
                }
        else
                {
                debugf("mDNS_Register_internal: Adding to active record list %s", ARDisplayString(m,rr));
                if (RRLocalOnly(rr))
                        {
                        AuthGroup *ag;
                        ag = InsertAuthRecord(m, &m->rrauth, rr);
                        if (ag && !ag->NewLocalOnlyRecords) {
                                m->NewLocalOnlyRecords = mDNStrue;
                                ag->NewLocalOnlyRecords = rr;
                        }
                        // No probing for LocalOnly records, Acknowledge them right away
                        if (rr->resrec.RecordType == kDNSRecordTypeUnique) rr->resrec.RecordType = kDNSRecordTypeVerified;
                        AcknowledgeRecord(m, rr);
                        return(mStatus_NoError);
                        }
                else
                        {
                        if (!m->NewLocalRecords) m->NewLocalRecords = rr;
                        *p = rr;
                        }
                }

        if (!AuthRecord_uDNS(rr))       // This check is superfluous, given that for unicast records we (currently) bail out above
                {
                // For records that are not going to probe, acknowledge them right away
                if (rr->resrec.RecordType != kDNSRecordTypeUnique && rr->resrec.RecordType != kDNSRecordTypeDeregistering)
                        AcknowledgeRecord(m, rr);

                // Adding a record may affect whether or not we should sleep
                mDNS_UpdateAllowSleep(m);
                }

        return(mStatus_NoError);
        }

mDNSlocal void RecordProbeFailure(mDNS *const m, const AuthRecord *const rr)
        {
        m->ProbeFailTime = m->timenow;
        m->NumFailedProbes++;
        // If we've had fifteen or more probe failures, rate-limit to one every five seconds.
        // If a bunch of hosts have all been configured with the same name, then they'll all
        // conflict and run through the same series of names: name-2, name-3, name-4, etc.,
        // up to name-10. After that they'll start adding random increments in the range 1-100,
        // so they're more likely to branch out in the available namespace and settle on a set of
        // unique names quickly. If after five more tries the host is still conflicting, then we
        // may have a serious problem, so we start rate-limiting so we don't melt down the network.
        if (m->NumFailedProbes >= 15)
                {
                m->SuppressProbes = NonZeroTime(m->timenow + mDNSPlatformOneSecond * 5);
                LogMsg("Excessive name conflicts (%lu) for %##s (%s); rate limiting in effect",
                        m->NumFailedProbes, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                }
        }

mDNSlocal void CompleteRDataUpdate(mDNS *const m, AuthRecord *const rr)
        {
        RData *OldRData = rr->resrec.rdata;
        mDNSu16 OldRDLen = rr->resrec.rdlength;
        SetNewRData(&rr->resrec, rr->NewRData, rr->newrdlength);        // Update our rdata
        rr->NewRData = mDNSNULL;                                                                        // Clear the NewRData pointer ...
        if (rr->UpdateCallback)
                rr->UpdateCallback(m, rr, OldRData, OldRDLen);                  // ... and let the client know
        }

// Note: mDNS_Deregister_internal can call a user callback, which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
// Exported so uDNS.c can call this
mDNSexport mStatus mDNS_Deregister_internal(mDNS *const m, AuthRecord *const rr, mDNS_Dereg_type drt)
        {
        AuthRecord *r2;
        mDNSu8 RecordType = rr->resrec.RecordType;
        AuthRecord **p = &m->ResourceRecords;   // Find this record in our list of active records
        mDNSBool dupList = mDNSfalse;

        if (RRLocalOnly(rr))
                {
                AuthGroup *a;
                AuthGroup **ag = &a;
                AuthRecord **rp;
                const mDNSu32 slot = AuthHashSlot(rr->resrec.name);
        
                a = AuthGroupForRecord(&m->rrauth, slot, &rr->resrec);
                if (!a) return mDNSfalse;
                rp = &(*ag)->members;
                while (*rp && *rp != rr) rp=&(*rp)->next;
                p = rp;
                }
        else
                {
                while (*p && *p != rr) p=&(*p)->next;
                }

        if (*p)
                {
                // We found our record on the main list. See if there are any duplicates that need special handling.
                if (drt == mDNS_Dereg_conflict)         // If this was a conflict, see that all duplicates get the same treatment
                        {
                        // Scan for duplicates of rr, and mark them for deregistration at the end of this routine, after we've finished
                        // deregistering rr. We need to do this scan *before* we give the client the chance to free and reuse the rr memory.
                        for (r2 = m->DuplicateRecords; r2; r2=r2->next) if (RecordIsLocalDuplicate(r2, rr)) r2->ProbeCount = 0xFF;
                        }
                else
                        {
                        // Before we delete the record (and potentially send a goodbye packet)
                        // first see if we have a record on the duplicate list ready to take over from it.
                        AuthRecord **d = &m->DuplicateRecords;
                        while (*d && !RecordIsLocalDuplicate(*d, rr)) d=&(*d)->next;
                        if (*d)
                                {
                                AuthRecord *dup = *d;
                                debugf("mDNS_Register_internal: Duplicate record %p taking over from %p %##s (%s)",
                                        dup, rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                                *d        = dup->next;          // Cut replacement record from DuplicateRecords list
                                if (RRLocalOnly(rr))
                                        {
                                        dup->next = mDNSNULL;
                                        if (!InsertAuthRecord(m, &m->rrauth, dup)) LogMsg("mDNS_Deregister_internal: ERROR!! cannot insert %s", ARDisplayString(m, dup));
                                        }
                                else
                                        {
                                        dup->next = rr->next;           // And then...
                                        rr->next  = dup;                        // ... splice it in right after the record we're about to delete
                                        }
                                dup->resrec.RecordType        = rr->resrec.RecordType;
                                dup->ProbeCount      = rr->ProbeCount;
                                dup->AnnounceCount   = rr->AnnounceCount;
                                dup->RequireGoodbye  = rr->RequireGoodbye;
                                dup->AnsweredLocalQ  = rr->AnsweredLocalQ;
                                dup->ImmedAnswer     = rr->ImmedAnswer;
                                dup->ImmedUnicast    = rr->ImmedUnicast;
                                dup->ImmedAdditional = rr->ImmedAdditional;
                                dup->v4Requester     = rr->v4Requester;
                                dup->v6Requester     = rr->v6Requester;
                                dup->ThisAPInterval  = rr->ThisAPInterval;
                                dup->LastAPTime      = rr->LastAPTime;
                                dup->LastMCTime      = rr->LastMCTime;
                                dup->LastMCInterface = rr->LastMCInterface;
                                dup->Private         = rr->Private;
                                dup->state           = rr->state;
                                rr->RequireGoodbye = mDNSfalse;
                                rr->AnsweredLocalQ = mDNSfalse;
                                }
                        }
                }
        else
                {
                // We didn't find our record on the main list; try the DuplicateRecords list instead.
                p = &m->DuplicateRecords;
                while (*p && *p != rr) p=&(*p)->next;
                // If we found our record on the duplicate list, then make sure we don't send a goodbye for it
                if (*p) { rr->RequireGoodbye = mDNSfalse; dupList = mDNStrue; }
                if (*p) debugf("mDNS_Deregister_internal: Deleting DuplicateRecord %p %##s (%s)",
                        rr, rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
                }

        if (!*p)
                {
                // No need to log an error message if we already know this is a potentially repeated deregistration
                if (drt != mDNS_Dereg_repeat)
                        LogMsg("mDNS_Deregister_internal: Record %p not found in list %s", rr, ARDisplayString(m,rr));
                return(mStatus_BadReferenceErr);
                }

        // If this is a shared record and we've announced it at least once,
        // we need to retract that announcement before we delete the record

        // If this is a record (including mDNSInterface_LocalOnly records) for which we've given local-only answers then
        // it's tempting to just do "AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNSfalse)" here, but that would not not be safe.
        // The AnswerAllLocalQuestionsWithLocalAuthRecord routine walks the question list invoking client callbacks, using the "m->CurrentQuestion"
        // mechanism to cope with the client callback modifying the question list while that's happening.
        // However, mDNS_Deregister could have been called from a client callback (e.g. from the domain enumeration callback FoundDomain)
        // which means that the "m->CurrentQuestion" mechanism is already in use to protect that list, so we can't use it twice.
        // More generally, if we invoke callbacks from within a client callback, then those callbacks could deregister other
        // records, thereby invoking yet more callbacks, without limit.
        // The solution is to defer delivering the "Remove" events until mDNS_Execute time, just like we do for sending
        // actual goodbye packets.
        
#ifndef UNICAST_DISABLED
        if (AuthRecord_uDNS(rr))
                {
                if (rr->RequireGoodbye)
                        {
                        if (rr->tcp) { DisposeTCPConn(rr->tcp); rr->tcp = mDNSNULL; }
                        rr->resrec.RecordType    = kDNSRecordTypeDeregistering;
                        m->LocalRemoveEvents     = mDNStrue;
                        uDNS_DeregisterRecord(m, rr);
                        // At this point unconditionally we bail out
                        // Either uDNS_DeregisterRecord will have completed synchronously, and called CompleteDeregistration,
                        // which calls us back here with RequireGoodbye set to false, or it will have initiated the deregistration
                        // process and will complete asynchronously. Either way we don't need to do anything more here.
                        return(mStatus_NoError);
                        }
                // Sometimes the records don't complete proper deregistration i.e., don't wait for a response
                // from the server. In that case, if the records have been part of a group update, clear the
                // state here. Some recors e.g., AutoTunnel gets reused without ever being completely initialized
                rr->updateid = zeroID;

                // We defer cleaning up NAT state only after sending goodbyes. This is important because
                // RecordRegistrationGotZoneData guards against creating NAT state if clientContext is non-NULL.
                // This happens today when we turn on/off interface where we get multiple network transitions
                // and RestartRecordGetZoneData triggers re-registration of the resource records even though
                // they may be in Registered state which causes NAT information to be setup multiple times. Defering
                // the cleanup here keeps clientContext non-NULL and hence prevents that. Note that cleaning up
                // NAT state here takes care of the case where we did not send goodbyes at all.
                if (rr->NATinfo.clientContext)
                        {
                        mDNS_StopNATOperation_internal(m, &rr->NATinfo);
                        rr->NATinfo.clientContext = mDNSNULL;
                        }
                if (rr->nta) { CancelGetZoneData(m, rr->nta); rr->nta = mDNSNULL; }
                if (rr->tcp) { DisposeTCPConn(rr->tcp);       rr->tcp = mDNSNULL; }
                }
#endif // UNICAST_DISABLED

        if      (RecordType == kDNSRecordTypeUnregistered)
                LogMsg("mDNS_Deregister_internal: %s already marked kDNSRecordTypeUnregistered", ARDisplayString(m, rr));
        else if (RecordType == kDNSRecordTypeDeregistering)
                {
                LogMsg("mDNS_Deregister_internal: %s already marked kDNSRecordTypeDeregistering", ARDisplayString(m, rr));
                return(mStatus_BadReferenceErr);
                }

        // <rdar://problem/7457925> Local-only questions don't get remove events for unique records
        // We may want to consider changing this code so that we generate local-only question "rmv"
        // events (and maybe goodbye packets too) for unique records as well as for shared records
        // Note: If we change the logic for this "if" statement, need to ensure that the code in
        // CompleteDeregistration() sets the appropriate state variables to gaurantee that "else"
        // clause will execute here and the record will be cut from the list.
        if (rr->WakeUp.HMAC.l[0] ||
                (RecordType == kDNSRecordTypeShared && (rr->RequireGoodbye || rr->AnsweredLocalQ)))
                {
                verbosedebugf("mDNS_Deregister_internal: Starting deregistration for %s", ARDisplayString(m, rr));
                rr->resrec.RecordType    = kDNSRecordTypeDeregistering;
                rr->resrec.rroriginalttl = 0;
                rr->AnnounceCount        = rr->WakeUp.HMAC.l[0] ? WakeupCount : (drt == mDNS_Dereg_rapid) ? 1 : GoodbyeCount;
                rr->ThisAPInterval       = mDNSPlatformOneSecond * 2;
                rr->LastAPTime           = m->timenow - rr->ThisAPInterval;
                m->LocalRemoveEvents     = mDNStrue;
                if (m->NextScheduledResponse - (m->timenow + mDNSPlatformOneSecond/10) >= 0)
                        m->NextScheduledResponse = (m->timenow + mDNSPlatformOneSecond/10);
                }
        else
                {
                if (!dupList && RRLocalOnly(rr))
                        {
                        AuthGroup *ag = RemoveAuthRecord(m, &m->rrauth, rr);
                        if (ag->NewLocalOnlyRecords == rr) ag->NewLocalOnlyRecords = rr->next;
                        }
                else
                        {
                        *p = rr->next;                                  // Cut this record from the list
                        if (m->NewLocalRecords == rr) m->NewLocalRecords = rr->next;
                        }
                // If someone is about to look at this, bump the pointer forward
                if (m->CurrentRecord   == rr) m->CurrentRecord   = rr->next;
                rr->next = mDNSNULL;

                // Should we generate local remove events here?
                // i.e. something like:
                // if (rr->AnsweredLocalQ) { AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNSfalse); rr->AnsweredLocalQ = mDNSfalse; }

                verbosedebugf("mDNS_Deregister_internal: Deleting record for %s", ARDisplayString(m, rr));
                rr->resrec.RecordType = kDNSRecordTypeUnregistered;

                if ((drt == mDNS_Dereg_conflict || drt == mDNS_Dereg_repeat) && RecordType == kDNSRecordTypeShared)
                        debugf("mDNS_Deregister_internal: Cannot have a conflict on a shared record! %##s (%s)",
                                rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));

                // If we have an update queued up which never executed, give the client a chance to free that memory
                if (rr->NewRData) CompleteRDataUpdate(m, rr);   // Update our rdata, clear the NewRData pointer, and return memory to the client


                // CAUTION: MUST NOT do anything more with rr after calling rr->Callback(), because the client's callback function
                // is allowed to do anything, including starting/stopping queries, registering/deregistering records, etc.
                // In this case the likely client action to the mStatus_MemFree message is to free the memory,
                // so any attempt to touch rr after this is likely to lead to a crash.
                if (drt != mDNS_Dereg_conflict)
                        {
                        mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                        LogInfo("mDNS_Deregister_internal: mStatus_MemFree for %s", ARDisplayString(m, rr));
                        if (rr->RecordCallback)
                                rr->RecordCallback(m, rr, mStatus_MemFree);                     // MUST NOT touch rr after this
                        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                        }
                else
                        {
                        RecordProbeFailure(m, rr);
                        mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                        if (rr->RecordCallback)
                                rr->RecordCallback(m, rr, mStatus_NameConflict);        // MUST NOT touch rr after this
                        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                        // Now that we've finished deregistering rr, check our DuplicateRecords list for any that we marked previously.
                        // Note that with all the client callbacks going on, by the time we get here all the
                        // records we marked may have been explicitly deregistered by the client anyway.
                        r2 = m->DuplicateRecords;
                        while (r2)
                                {
                                if (r2->ProbeCount != 0xFF) r2 = r2->next;
                                else { mDNS_Deregister_internal(m, r2, mDNS_Dereg_conflict); r2 = m->DuplicateRecords; }
                                }
                        }
                }
        mDNS_UpdateAllowSleep(m);
        return(mStatus_NoError);
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Packet Sending Functions
#endif

mDNSlocal void AddRecordToResponseList(AuthRecord ***nrpp, AuthRecord *rr, AuthRecord *add)
        {
        if (rr->NextResponse == mDNSNULL && *nrpp != &rr->NextResponse)
                {
                **nrpp = rr;
                // NR_AdditionalTo must point to a record with NR_AnswerTo set (and not NR_AdditionalTo)
                // If 'add' does not meet this requirement, then follow its NR_AdditionalTo pointer to a record that does
                // The referenced record will definitely be acceptable (by recursive application of this rule)
                if (add && add->NR_AdditionalTo) add = add->NR_AdditionalTo;
                rr->NR_AdditionalTo = add;
                *nrpp = &rr->NextResponse;
                }
        debugf("AddRecordToResponseList: %##s (%s) already in list", rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype));
        }

mDNSlocal void AddAdditionalsToResponseList(mDNS *const m, AuthRecord *ResponseRecords, AuthRecord ***nrpp, const mDNSInterfaceID InterfaceID)
        {
        AuthRecord  *rr, *rr2;
        for (rr=ResponseRecords; rr; rr=rr->NextResponse)                       // For each record we plan to put
                {
                // (Note: This is an "if", not a "while". If we add a record, we'll find it again
                // later in the "for" loop, and we will follow further "additional" links then.)
                if (rr->Additional1 && ResourceRecordIsValidInterfaceAnswer(rr->Additional1, InterfaceID))
                        AddRecordToResponseList(nrpp, rr->Additional1, rr);

                if (rr->Additional2 && ResourceRecordIsValidInterfaceAnswer(rr->Additional2, InterfaceID))
                        AddRecordToResponseList(nrpp, rr->Additional2, rr);

                // For SRV records, automatically add the Address record(s) for the target host
                if (rr->resrec.rrtype == kDNSType_SRV)
                        {
                        for (rr2=m->ResourceRecords; rr2; rr2=rr2->next)                                        // Scan list of resource records
                                if (RRTypeIsAddressType(rr2->resrec.rrtype) &&                                  // For all address records (A/AAAA) ...
                                        ResourceRecordIsValidInterfaceAnswer(rr2, InterfaceID) &&       // ... which are valid for answer ...
                                        rr->resrec.rdatahash == rr2->resrec.namehash &&                 // ... whose name is the name of the SRV target
                                        SameDomainName(&rr->resrec.rdata->u.srv.target, rr2->resrec.name))
                                        AddRecordToResponseList(nrpp, rr2, rr);
                        }
                else if (RRTypeIsAddressType(rr->resrec.rrtype))        // For A or AAAA, put counterpart as additional
                        {
                        for (rr2=m->ResourceRecords; rr2; rr2=rr2->next)                                        // Scan list of resource records
                                if (RRTypeIsAddressType(rr2->resrec.rrtype) &&                                  // For all address records (A/AAAA) ...
                                        ResourceRecordIsValidInterfaceAnswer(rr2, InterfaceID) &&       // ... which are valid for answer ...
                                        rr->resrec.namehash == rr2->resrec.namehash &&                          // ... and have the same name
                                        SameDomainName(rr->resrec.name, rr2->resrec.name))
                                        AddRecordToResponseList(nrpp, rr2, rr);
                        }
                else if (rr->resrec.rrtype == kDNSType_PTR)                     // For service PTR, see if we want to add DeviceInfo record
                        {
                        if (ResourceRecordIsValidInterfaceAnswer(&m->DeviceInfo, InterfaceID) &&
                                SameDomainLabel(rr->resrec.rdata->u.name.c, m->DeviceInfo.resrec.name->c))
                                AddRecordToResponseList(nrpp, &m->DeviceInfo, rr);
                        }
                }
        }

mDNSlocal void SendDelayedUnicastResponse(mDNS *const m, const mDNSAddr *const dest, const mDNSInterfaceID InterfaceID)
        {
        AuthRecord *rr;
        AuthRecord  *ResponseRecords = mDNSNULL;
        AuthRecord **nrp             = &ResponseRecords;

        // Make a list of all our records that need to be unicast to this destination
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                {
                // If we find we can no longer unicast this answer, clear ImmedUnicast
                if (rr->ImmedAnswer == mDNSInterfaceMark               ||
                        mDNSSameIPv4Address(rr->v4Requester, onesIPv4Addr) ||
                        mDNSSameIPv6Address(rr->v6Requester, onesIPv6Addr)  )
                        rr->ImmedUnicast = mDNSfalse;

                if (rr->ImmedUnicast && rr->ImmedAnswer == InterfaceID)
                        if ((dest->type == mDNSAddrType_IPv4 && mDNSSameIPv4Address(rr->v4Requester, dest->ip.v4)) ||
                                (dest->type == mDNSAddrType_IPv6 && mDNSSameIPv6Address(rr->v6Requester, dest->ip.v6)))
                                {
                                rr->ImmedAnswer  = mDNSNULL;                            // Clear the state fields
                                rr->ImmedUnicast = mDNSfalse;
                                rr->v4Requester  = zerov4Addr;
                                rr->v6Requester  = zerov6Addr;
                                if (rr->NextResponse == mDNSNULL && nrp != &rr->NextResponse)   // rr->NR_AnswerTo
                                        { rr->NR_AnswerTo = (mDNSu8*)~0; *nrp = rr; nrp = &rr->NextResponse; }
                                }
                }

        AddAdditionalsToResponseList(m, ResponseRecords, &nrp, InterfaceID);

        while (ResponseRecords)
                {
                mDNSu8 *responseptr = m->omsg.data;
                mDNSu8 *newptr;
                InitializeDNSMessage(&m->omsg.h, zeroID, ResponseFlags);
                
                // Put answers in the packet
                while (ResponseRecords && ResponseRecords->NR_AnswerTo)
                        {
                        rr = ResponseRecords;
                        if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                                rr->resrec.rrclass |= kDNSClass_UniqueRRSet;            // Temporarily set the cache flush bit so PutResourceRecord will set it
                        newptr = PutResourceRecord(&m->omsg, responseptr, &m->omsg.h.numAnswers, &rr->resrec);
                        rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;                   // Make sure to clear cache flush bit back to normal state
                        if (!newptr && m->omsg.h.numAnswers) break;     // If packet full, send it now
                        if (newptr) responseptr = newptr;
                        ResponseRecords = rr->NextResponse;
                        rr->NextResponse    = mDNSNULL;
                        rr->NR_AnswerTo     = mDNSNULL;
                        rr->NR_AdditionalTo = mDNSNULL;
                        rr->RequireGoodbye  = mDNStrue;
                        }
                
                // Add additionals, if there's space
                while (ResponseRecords && !ResponseRecords->NR_AnswerTo)
                        {
                        rr = ResponseRecords;
                        if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                                rr->resrec.rrclass |= kDNSClass_UniqueRRSet;            // Temporarily set the cache flush bit so PutResourceRecord will set it
                        newptr = PutResourceRecord(&m->omsg, responseptr, &m->omsg.h.numAdditionals, &rr->resrec);
                        rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;                   // Make sure to clear cache flush bit back to normal state
                        
                        if (newptr) responseptr = newptr;
                        if (newptr && m->omsg.h.numAnswers) rr->RequireGoodbye = mDNStrue;
                        else if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask) rr->ImmedAnswer = mDNSInterfaceMark;
                        ResponseRecords = rr->NextResponse;
                        rr->NextResponse    = mDNSNULL;
                        rr->NR_AnswerTo     = mDNSNULL;
                        rr->NR_AdditionalTo = mDNSNULL;
                        }

                if (m->omsg.h.numAnswers)
                        mDNSSendDNSMessage(m, &m->omsg, responseptr, InterfaceID, mDNSNULL, dest, MulticastDNSPort, mDNSNULL, mDNSNULL);
                }
        }

// CompleteDeregistration guarantees that on exit the record will have been cut from the m->ResourceRecords list
// and the client's mStatus_MemFree callback will have been invoked
mDNSexport void CompleteDeregistration(mDNS *const m, AuthRecord *rr)
        {
        LogInfo("CompleteDeregistration: called for Resource record %s", ARDisplayString(m, rr));
        // Clearing rr->RequireGoodbye signals mDNS_Deregister_internal() that
        // it should go ahead and immediately dispose of this registration
        rr->resrec.RecordType = kDNSRecordTypeShared;
        rr->RequireGoodbye    = mDNSfalse;
        rr->WakeUp.HMAC       = zeroEthAddr;
        if (rr->AnsweredLocalQ) { AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNSfalse); rr->AnsweredLocalQ = mDNSfalse; }
        mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);             // Don't touch rr after this
        }

// DiscardDeregistrations is used on shutdown and sleep to discard (forcibly and immediately)
// any deregistering records that remain in the m->ResourceRecords list.
// DiscardDeregistrations calls mDNS_Deregister_internal which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void DiscardDeregistrations(mDNS *const m)
        {
        if (m->CurrentRecord)
                LogMsg("DiscardDeregistrations ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        m->CurrentRecord = m->ResourceRecords;
        
        while (m->CurrentRecord)
                {
                AuthRecord *rr = m->CurrentRecord;
                if (!AuthRecord_uDNS(rr) && rr->resrec.RecordType == kDNSRecordTypeDeregistering)
                        CompleteDeregistration(m, rr);          // Don't touch rr after this
                else
                        m->CurrentRecord = rr->next;
                }
        }

mDNSlocal mStatus GetLabelDecimalValue(const mDNSu8 *const src, mDNSu8 *dst)
        {
        int i, val = 0;
        if (src[0] < 1 || src[0] > 3) return(mStatus_Invalid);
        for (i=1; i<=src[0]; i++)
                {
                if (src[i] < '0' || src[i] > '9') return(mStatus_Invalid);
                val = val * 10 + src[i] - '0';
                }
        if (val > 255) return(mStatus_Invalid);
        *dst = (mDNSu8)val;
        return(mStatus_NoError);
        }

mDNSlocal mStatus GetIPv4FromName(mDNSAddr *const a, const domainname *const name)
        {
        int skip = CountLabels(name) - 6;
        if (skip < 0) { LogMsg("GetIPFromName: Need six labels in IPv4 reverse mapping name %##s", name); return mStatus_Invalid; }
        if (GetLabelDecimalValue(SkipLeadingLabels(name, skip+3)->c, &a->ip.v4.b[0]) ||
                GetLabelDecimalValue(SkipLeadingLabels(name, skip+2)->c, &a->ip.v4.b[1]) ||
                GetLabelDecimalValue(SkipLeadingLabels(name, skip+1)->c, &a->ip.v4.b[2]) ||
                GetLabelDecimalValue(SkipLeadingLabels(name, skip+0)->c, &a->ip.v4.b[3])) return mStatus_Invalid;
        a->type = mDNSAddrType_IPv4;
        return(mStatus_NoError);
        }

#define HexVal(X) ( ((X) >= '0' && (X) <= '9') ? ((X) - '0'     ) :   \
                                        ((X) >= 'A' && (X) <= 'F') ? ((X) - 'A' + 10) :   \
                                        ((X) >= 'a' && (X) <= 'f') ? ((X) - 'a' + 10) : -1)

mDNSlocal mStatus GetIPv6FromName(mDNSAddr *const a, const domainname *const name)
        {
        int i, h, l;
        const domainname *n;

        int skip = CountLabels(name) - 34;
        if (skip < 0) { LogMsg("GetIPFromName: Need 34 labels in IPv6 reverse mapping name %##s", name); return mStatus_Invalid; }

        n = SkipLeadingLabels(name, skip);
        for (i=0; i<16; i++)
                {
                if (n->c[0] != 1) return mStatus_Invalid;
                l = HexVal(n->c[1]);
                n = (const domainname *)(n->c + 2);

                if (n->c[0] != 1) return mStatus_Invalid;
                h = HexVal(n->c[1]);
                n = (const domainname *)(n->c + 2);

                if (l<0 || h<0) return mStatus_Invalid;
                a->ip.v6.b[15-i] = (mDNSu8)((h << 4) | l);
                }

        a->type = mDNSAddrType_IPv6;
        return(mStatus_NoError);
        }

mDNSlocal mDNSs32 ReverseMapDomainType(const domainname *const name)
        {
        int skip = CountLabels(name) - 2;
        if (skip >= 0)
                {
                const domainname *suffix = SkipLeadingLabels(name, skip);
                if (SameDomainName(suffix, (const domainname*)"\x7" "in-addr" "\x4" "arpa")) return mDNSAddrType_IPv4;
                if (SameDomainName(suffix, (const domainname*)"\x3" "ip6"     "\x4" "arpa")) return mDNSAddrType_IPv6;
                }
        return(mDNSAddrType_None);
        }

mDNSlocal void SendARP(mDNS *const m, const mDNSu8 op, const AuthRecord *const rr,
        const mDNSv4Addr *const spa, const mDNSEthAddr *const tha, const mDNSv4Addr *const tpa, const mDNSEthAddr *const dst)
        {
        int i;
        mDNSu8 *ptr = m->omsg.data;
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, rr->resrec.InterfaceID);
        if (!intf) { LogMsg("SendARP: No interface with InterfaceID %p found %s", rr->resrec.InterfaceID, ARDisplayString(m,rr)); return; }

        // 0x00 Destination address
        for (i=0; i<6; i++) *ptr++ = dst->b[i];

        // 0x06 Source address (Note: Since we don't currently set the BIOCSHDRCMPLT option, BPF will fill in the real interface address for us)
        for (i=0; i<6; i++) *ptr++ = intf->MAC.b[0];

        // 0x0C ARP Ethertype (0x0806)
        *ptr++ = 0x08; *ptr++ = 0x06;

        // 0x0E ARP header
        *ptr++ = 0x00; *ptr++ = 0x01;   // Hardware address space; Ethernet = 1
        *ptr++ = 0x08; *ptr++ = 0x00;   // Protocol address space; IP = 0x0800
        *ptr++ = 6;                                             // Hardware address length
        *ptr++ = 4;                                             // Protocol address length
        *ptr++ = 0x00; *ptr++ = op;             // opcode; Request = 1, Response = 2

        // 0x16 Sender hardware address (our MAC address)
        for (i=0; i<6; i++) *ptr++ = intf->MAC.b[i];

        // 0x1C Sender protocol address
        for (i=0; i<4; i++) *ptr++ = spa->b[i];

        // 0x20 Target hardware address
        for (i=0; i<6; i++) *ptr++ = tha->b[i];

        // 0x26 Target protocol address
        for (i=0; i<4; i++) *ptr++ = tpa->b[i];

        // 0x2A Total ARP Packet length 42 bytes
        mDNSPlatformSendRawPacket(m->omsg.data, ptr, rr->resrec.InterfaceID);
        }

mDNSlocal mDNSu16 CheckSum(const void *const data, mDNSs32 length, mDNSu32 sum)
        {
        const mDNSu16 *ptr = data;
        while (length > 0) { length -= 2; sum += *ptr++; }
        sum = (sum & 0xFFFF) + (sum >> 16);
        sum = (sum & 0xFFFF) + (sum >> 16);
        return(sum != 0xFFFF ? sum : 0);
        }

mDNSlocal mDNSu16 IPv6CheckSum(const mDNSv6Addr *const src, const mDNSv6Addr *const dst, const mDNSu8 protocol, const void *const data, const mDNSu32 length)
        {
        IPv6PseudoHeader ph;
        ph.src = *src;
        ph.dst = *dst;
        ph.len.b[0] = length >> 24;
        ph.len.b[1] = length >> 16;
        ph.len.b[2] = length >> 8;
        ph.len.b[3] = length;
        ph.pro.b[0] = 0;
        ph.pro.b[1] = 0;
        ph.pro.b[2] = 0;
        ph.pro.b[3] = protocol;
        return CheckSum(&ph, sizeof(ph), CheckSum(data, length, 0));
        }

mDNSlocal void SendNDP(mDNS *const m, const mDNSu8 op, const mDNSu8 flags, const AuthRecord *const rr,
        const mDNSv6Addr *const spa, const mDNSEthAddr *const tha, const mDNSv6Addr *const tpa, const mDNSEthAddr *const dst)
        {
        int i;
        mDNSOpaque16 checksum;
        mDNSu8 *ptr = m->omsg.data;
        // Some recipient hosts seem to ignore Neighbor Solicitations if the IPv6-layer destination address is not the
        // appropriate IPv6 solicited node multicast address, so we use that IPv6-layer destination address, even though
        // at the Ethernet-layer we unicast the packet to the intended target, to avoid wasting network bandwidth.
        const mDNSv6Addr mc = { { 0xFF,0x02,0x00,0x00, 0,0,0,0, 0,0,0,1, 0xFF,tpa->b[0xD],tpa->b[0xE],tpa->b[0xF] } };
        const mDNSv6Addr *const v6dst = (op == NDP_Sol) ? &mc : tpa;
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, rr->resrec.InterfaceID);
        if (!intf) { LogMsg("SendNDP: No interface with InterfaceID %p found %s", rr->resrec.InterfaceID, ARDisplayString(m,rr)); return; }

        // 0x00 Destination address
        for (i=0; i<6; i++) *ptr++ = dst->b[i];
        // Right now we only send Neighbor Solicitations to verify whether the host we're proxying for has gone to sleep yet.
        // Since we know who we're looking for, we send it via Ethernet-layer unicast, rather than bothering every host on the
        // link with a pointless link-layer multicast.
        // Should we want to send traditional Neighbor Solicitations in the future, where we really don't know in advance what
        // Ethernet-layer address we're looking for, we'll need to send to the appropriate Ethernet-layer multicast address:
        // *ptr++ = 0x33;
        // *ptr++ = 0x33;
        // *ptr++ = 0xFF;
        // *ptr++ = tpa->b[0xD];
        // *ptr++ = tpa->b[0xE];
        // *ptr++ = tpa->b[0xF];

        // 0x06 Source address (Note: Since we don't currently set the BIOCSHDRCMPLT option, BPF will fill in the real interface address for us)
        for (i=0; i<6; i++) *ptr++ = (tha ? *tha : intf->MAC).b[i];

        // 0x0C IPv6 Ethertype (0x86DD)
        *ptr++ = 0x86; *ptr++ = 0xDD;

        // 0x0E IPv6 header
        *ptr++ = 0x60; *ptr++ = 0x00; *ptr++ = 0x00; *ptr++ = 0x00;             // Version, Traffic Class, Flow Label
        *ptr++ = 0x00; *ptr++ = 0x20;                                                                   // Length
        *ptr++ = 0x3A;                                                                                                  // Protocol == ICMPv6
        *ptr++ = 0xFF;                                                                                                  // Hop Limit

        // 0x16 Sender IPv6 address
        for (i=0; i<16; i++) *ptr++ = spa->b[i];

        // 0x26 Destination IPv6 address
        for (i=0; i<16; i++) *ptr++ = v6dst->b[i];

        // 0x36 NDP header
        *ptr++ = op;                                    // 0x87 == Neighbor Solicitation, 0x88 == Neighbor Advertisement
        *ptr++ = 0x00;                                  // Code
        *ptr++ = 0x00; *ptr++ = 0x00;   // Checksum placeholder (0x38, 0x39)
        *ptr++ = flags;
        *ptr++ = 0x00; *ptr++ = 0x00; *ptr++ = 0x00;

        if (op == NDP_Sol)      // Neighbor Solicitation. The NDP "target" is the address we seek.
                {
                // 0x3E NDP target.
                for (i=0; i<16; i++) *ptr++ = tpa->b[i];
                // 0x4E Source Link-layer Address
                // <http://www.ietf.org/rfc/rfc2461.txt>
                // MUST NOT be included when the source IP address is the unspecified address.
                // Otherwise, on link layers that have addresses this option MUST be included
                // in multicast solicitations and SHOULD be included in unicast solicitations.
                if (!mDNSIPv6AddressIsZero(*spa))
                        {
                        *ptr++ = NDP_SrcLL;     // Option Type 1 == Source Link-layer Address
                        *ptr++ = 0x01;          // Option length 1 (in units of 8 octets)
                        for (i=0; i<6; i++) *ptr++ = (tha ? *tha : intf->MAC).b[i];
                        }
                }
        else                    // Neighbor Advertisement. The NDP "target" is the address we're giving information about.
                {
                // 0x3E NDP target.
                for (i=0; i<16; i++) *ptr++ = spa->b[i];
                // 0x4E Target Link-layer Address
                *ptr++ = NDP_TgtLL;     // Option Type 2 == Target Link-layer Address
                *ptr++ = 0x01;          // Option length 1 (in units of 8 octets)
                for (i=0; i<6; i++) *ptr++ = (tha ? *tha : intf->MAC).b[i];
                }

        // 0x4E or 0x56 Total NDP Packet length 78 or 86 bytes
        m->omsg.data[0x13] = ptr - &m->omsg.data[0x36];         // Compute actual length
        checksum.NotAnInteger = ~IPv6CheckSum(spa, v6dst, 0x3A, &m->omsg.data[0x36], m->omsg.data[0x13]);
        m->omsg.data[0x38] = checksum.b[0];
        m->omsg.data[0x39] = checksum.b[1];

        mDNSPlatformSendRawPacket(m->omsg.data, ptr, rr->resrec.InterfaceID);
        }

mDNSlocal void SetupOwnerOpt(const mDNS *const m, const NetworkInterfaceInfo *const intf, rdataOPT *const owner)
        {
        owner->u.owner.vers     = 0;
        owner->u.owner.seq      = m->SleepSeqNum;
        owner->u.owner.HMAC     = m->PrimaryMAC;
        owner->u.owner.IMAC     = intf->MAC;
        owner->u.owner.password = zeroEthAddr;

        // Don't try to compute the optlen until *after* we've set up the data fields
        // Right now the DNSOpt_Owner_Space macro does not depend on the owner->u.owner being set up correctly, but in the future it might
        owner->opt              = kDNSOpt_Owner;
        owner->optlen           = DNSOpt_Owner_Space(&m->PrimaryMAC, &intf->MAC) - 4;
        }

mDNSlocal void GrantUpdateCredit(AuthRecord *rr)
        {
        if (++rr->UpdateCredits >= kMaxUpdateCredits) rr->NextUpdateCredit = 0;
        else rr->NextUpdateCredit = NonZeroTime(rr->NextUpdateCredit + kUpdateCreditRefreshInterval);
        }

// Note about acceleration of announcements to facilitate automatic coalescing of
// multiple independent threads of announcements into a single synchronized thread:
// The announcements in the packet may be at different stages of maturity;
// One-second interval, two-second interval, four-second interval, and so on.
// After we've put in all the announcements that are due, we then consider
// whether there are other nearly-due announcements that are worth accelerating.
// To be eligible for acceleration, a record MUST NOT be older (further along
// its timeline) than the most mature record we've already put in the packet.
// In other words, younger records can have their timelines accelerated to catch up
// with their elder bretheren; this narrows the age gap and helps them eventually get in sync.
// Older records cannot have their timelines accelerated; this would just widen
// the gap between them and their younger bretheren and get them even more out of sync.

// Note: SendResponses calls mDNS_Deregister_internal which can call a user callback, which may change
// the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void SendResponses(mDNS *const m)
        {
        int pktcount = 0;
        AuthRecord *rr, *r2;
        mDNSs32 maxExistingAnnounceInterval = 0;
        const NetworkInterfaceInfo *intf = GetFirstActiveInterface(m->HostInterfaces);

        m->NextScheduledResponse = m->timenow + 0x78000000;

        if (m->SleepState == SleepState_Transferring) RetrySPSRegistrations(m);

        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (rr->ImmedUnicast)
                        {
                        mDNSAddr v4 = { mDNSAddrType_IPv4, {{{0}}} };
                        mDNSAddr v6 = { mDNSAddrType_IPv6, {{{0}}} };
                        v4.ip.v4 = rr->v4Requester;
                        v6.ip.v6 = rr->v6Requester;
                        if (!mDNSIPv4AddressIsZero(rr->v4Requester)) SendDelayedUnicastResponse(m, &v4, rr->ImmedAnswer);
                        if (!mDNSIPv6AddressIsZero(rr->v6Requester)) SendDelayedUnicastResponse(m, &v6, rr->ImmedAnswer);
                        if (rr->ImmedUnicast)
                                {
                                LogMsg("SendResponses: ERROR: rr->ImmedUnicast still set: %s", ARDisplayString(m, rr));
                                rr->ImmedUnicast = mDNSfalse;
                                }
                        }

        // ***
        // *** 1. Setup: Set the SendRNow and ImmedAnswer fields to indicate which interface(s) the records need to be sent on
        // ***

        // Run through our list of records, and decide which ones we're going to announce on all interfaces
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                {
                while (rr->NextUpdateCredit && m->timenow - rr->NextUpdateCredit >= 0) GrantUpdateCredit(rr);
                if (TimeToAnnounceThisRecord(rr, m->timenow))
                        {
                        if (rr->resrec.RecordType == kDNSRecordTypeDeregistering)
                                {
                                if (!rr->WakeUp.HMAC.l[0])
                                        {
                                        if (rr->AnnounceCount) rr->ImmedAnswer = mDNSInterfaceMark;             // Send goodbye packet on all interfaces
                                        }
                                else
                                        {
                                        LogSPS("SendResponses: Sending wakeup %2d for %.6a %s", rr->AnnounceCount-3, &rr->WakeUp.IMAC, ARDisplayString(m, rr));
                                        SendWakeup(m, rr->resrec.InterfaceID, &rr->WakeUp.IMAC, &rr->WakeUp.password);
                                        for (r2 = rr; r2; r2=r2->next)
                                                if (r2->AnnounceCount && r2->resrec.InterfaceID == rr->resrec.InterfaceID && mDNSSameEthAddress(&r2->WakeUp.IMAC, &rr->WakeUp.IMAC))
                                                        {
                                                        // For now we only want to send a single Unsolicited Neighbor Advertisement restoring the address to the original
                                                        // owner, because these packets can cause some IPv6 stacks to falsely conclude that there's an address conflict.
                                                        if (r2->AddressProxy.type == mDNSAddrType_IPv6 && r2->AnnounceCount == WakeupCount)
                                                                {
                                                                LogSPS("NDP Announcement %2d Releasing traffic for H-MAC %.6a I-MAC %.6a %s",
                                                                        r2->AnnounceCount-3, &r2->WakeUp.HMAC, &r2->WakeUp.IMAC, ARDisplayString(m,r2));
                                                                SendNDP(m, NDP_Adv, NDP_Override, r2, &r2->AddressProxy.ip.v6, &r2->WakeUp.IMAC, &AllHosts_v6, &AllHosts_v6_Eth);
                                                                }
                                                        r2->LastAPTime = m->timenow;
                                                        // After 15 wakeups without success (maybe host has left the network) send three goodbyes instead
                                                        if (--r2->AnnounceCount <= GoodbyeCount) r2->WakeUp.HMAC = zeroEthAddr;
                                                        }
                                        }
                                }
                        else if (ResourceRecordIsValidAnswer(rr))
                                {
                                if (rr->AddressProxy.type)
                                        {
                                        rr->AnnounceCount--;
                                        rr->ThisAPInterval *= 2;
                                        rr->LastAPTime = m->timenow;
                                        if (rr->AddressProxy.type == mDNSAddrType_IPv4)
                                                {
                                                LogSPS("ARP Announcement %2d Capturing traffic for H-MAC %.6a I-MAC %.6a %s",
                                                        rr->AnnounceCount, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m,rr));
                                                SendARP(m, 1, rr, &rr->AddressProxy.ip.v4, &zeroEthAddr, &rr->AddressProxy.ip.v4, &onesEthAddr);
                                                }
                                        else if (rr->AddressProxy.type == mDNSAddrType_IPv6)
                                                {
                                                LogSPS("NDP Announcement %2d Capturing traffic for H-MAC %.6a I-MAC %.6a %s",
                                                        rr->AnnounceCount, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m,rr));
                                                SendNDP(m, NDP_Adv, NDP_Override, rr, &rr->AddressProxy.ip.v6, mDNSNULL, &AllHosts_v6, &AllHosts_v6_Eth);
                                                }
                                        }
                                else
                                        {
                                        rr->ImmedAnswer = mDNSInterfaceMark;            // Send on all interfaces
                                        if (maxExistingAnnounceInterval < rr->ThisAPInterval)
                                                maxExistingAnnounceInterval = rr->ThisAPInterval;
                                        if (rr->UpdateBlocked) rr->UpdateBlocked = 0;
                                        }
                                }
                        }
                }

        // Any interface-specific records we're going to send are marked as being sent on all appropriate interfaces (which is just one)
        // Eligible records that are more than half-way to their announcement time are accelerated
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if ((rr->resrec.InterfaceID && rr->ImmedAnswer) ||
                        (rr->ThisAPInterval <= maxExistingAnnounceInterval &&
                        TimeToAnnounceThisRecord(rr, m->timenow + rr->ThisAPInterval/2) &&
                        !rr->AddressProxy.type &&                                       // Don't include ARP Annoucements when considering which records to accelerate
                        ResourceRecordIsValidAnswer(rr)))
                        rr->ImmedAnswer = mDNSInterfaceMark;            // Send on all interfaces

        // When sending SRV records (particularly when announcing a new service) automatically add related Address record(s) as additionals
        // Note: Currently all address records are interface-specific, so it's safe to set ImmedAdditional to their InterfaceID,
        // which will be non-null. If by some chance there is an address record that's not interface-specific (should never happen)
        // then all that means is that it won't get sent -- which would not be the end of the world.
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                {
                if (rr->ImmedAnswer && rr->resrec.rrtype == kDNSType_SRV)
                        for (r2=m->ResourceRecords; r2; r2=r2->next)                            // Scan list of resource records
                                if (RRTypeIsAddressType(r2->resrec.rrtype) &&                   // For all address records (A/AAAA) ...
                                        ResourceRecordIsValidAnswer(r2) &&                                      // ... which are valid for answer ...
                                        rr->LastMCTime - r2->LastMCTime >= 0 &&                         // ... which we have not sent recently ...
                                        rr->resrec.rdatahash == r2->resrec.namehash &&          // ... whose name is the name of the SRV target
                                        SameDomainName(&rr->resrec.rdata->u.srv.target, r2->resrec.name) &&
                                        (rr->ImmedAnswer == mDNSInterfaceMark || rr->ImmedAnswer == r2->resrec.InterfaceID))
                                        r2->ImmedAdditional = r2->resrec.InterfaceID;           // ... then mark this address record for sending too
                // We also make sure we send the DeviceInfo TXT record too, if necessary
                // We check for RecordType == kDNSRecordTypeShared because we don't want to tag the
                // DeviceInfo TXT record onto a goodbye packet (RecordType == kDNSRecordTypeDeregistering).
                if (rr->ImmedAnswer && rr->resrec.RecordType == kDNSRecordTypeShared && rr->resrec.rrtype == kDNSType_PTR)
                        if (ResourceRecordIsValidAnswer(&m->DeviceInfo) && SameDomainLabel(rr->resrec.rdata->u.name.c, m->DeviceInfo.resrec.name->c))
                                {
                                if (!m->DeviceInfo.ImmedAnswer) m->DeviceInfo.ImmedAnswer = rr->ImmedAnswer;
                                else                            m->DeviceInfo.ImmedAnswer = mDNSInterfaceMark;
                                }
                }

        // If there's a record which is supposed to be unique that we're going to send, then make sure that we give
        // the whole RRSet as an atomic unit. That means that if we have any other records with the same name/type/class
        // then we need to mark them for sending too. Otherwise, if we set the kDNSClass_UniqueRRSet bit on a
        // record, then other RRSet members that have not been sent recently will get flushed out of client caches.
        // -- If a record is marked to be sent on a certain interface, make sure the whole set is marked to be sent on that interface
        // -- If any record is marked to be sent on all interfaces, make sure the whole set is marked to be sent on all interfaces
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                        {
                        if (rr->ImmedAnswer)                    // If we're sending this as answer, see that its whole RRSet is similarly marked
                                {
                                for (r2 = m->ResourceRecords; r2; r2=r2->next)
                                        if (ResourceRecordIsValidAnswer(r2))
                                                if (r2->ImmedAnswer != mDNSInterfaceMark &&
                                                        r2->ImmedAnswer != rr->ImmedAnswer && SameResourceRecordSignature(r2, rr))
                                                        r2->ImmedAnswer = !r2->ImmedAnswer ? rr->ImmedAnswer : mDNSInterfaceMark;
                                }
                        else if (rr->ImmedAdditional)   // If we're sending this as additional, see that its whole RRSet is similarly marked
                                {
                                for (r2 = m->ResourceRecords; r2; r2=r2->next)
                                        if (ResourceRecordIsValidAnswer(r2))
                                                if (r2->ImmedAdditional != rr->ImmedAdditional && SameResourceRecordSignature(r2, rr))
                                                        r2->ImmedAdditional = rr->ImmedAdditional;
                                }
                        }

        // Now set SendRNow state appropriately
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                {
                if (rr->ImmedAnswer == mDNSInterfaceMark)               // Sending this record on all appropriate interfaces
                        {
                        rr->SendRNow = !intf ? mDNSNULL : (rr->resrec.InterfaceID) ? rr->resrec.InterfaceID : intf->InterfaceID;
                        rr->ImmedAdditional = mDNSNULL;                         // No need to send as additional if sending as answer
                        rr->LastMCTime      = m->timenow;
                        rr->LastMCInterface = rr->ImmedAnswer;
                        // If we're announcing this record, and it's at least half-way to its ordained time, then consider this announcement done
                        if (TimeToAnnounceThisRecord(rr, m->timenow + rr->ThisAPInterval/2))
                                {
                                rr->AnnounceCount--;
                                if (rr->resrec.RecordType != kDNSRecordTypeDeregistering)
                                        rr->ThisAPInterval *= 2;
                                rr->LastAPTime = m->timenow;
                                debugf("Announcing %##s (%s) %d", rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype), rr->AnnounceCount);
                                }
                        }
                else if (rr->ImmedAnswer)                                               // Else, just respond to a single query on single interface:
                        {
                        rr->SendRNow        = rr->ImmedAnswer;          // Just respond on that interface
                        rr->ImmedAdditional = mDNSNULL;                         // No need to send as additional too
                        rr->LastMCTime      = m->timenow;
                        rr->LastMCInterface = rr->ImmedAnswer;
                        }
                SetNextAnnounceProbeTime(m, rr);
                //if (rr->SendRNow) LogMsg("%-15.4a %s", &rr->v4Requester, ARDisplayString(m, rr));
                }

        // ***
        // *** 2. Loop through interface list, sending records as appropriate
        // ***

        while (intf)
                {
                const int OwnerRecordSpace = (m->AnnounceOwner && intf->MAC.l[0]) ? DNSOpt_Header_Space + DNSOpt_Owner_Space(&m->PrimaryMAC, &intf->MAC) : 0;
                int numDereg    = 0;
                int numAnnounce = 0;
                int numAnswer   = 0;
                mDNSu8 *responseptr = m->omsg.data;
                mDNSu8 *newptr;
                InitializeDNSMessage(&m->omsg.h, zeroID, ResponseFlags);
        
                // First Pass. Look for:
                // 1. Deregistering records that need to send their goodbye packet
                // 2. Updated records that need to retract their old data
                // 3. Answers and announcements we need to send
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        {

                        // Skip this interface if the record InterfaceID is *Any and the record is not 
                        // appropriate for the interface type.
                        if ((rr->SendRNow == intf->InterfaceID) &&
                                ((rr->resrec.InterfaceID == mDNSInterface_Any) && !mDNSPlatformValidRecordForInterface(rr, intf)))
                                {
                                        LogInfo("SendResponses: Not Sending %s, on %s", ARDisplayString(m, rr), InterfaceNameForID(m, rr->SendRNow));
                                        rr->SendRNow = GetNextActiveInterfaceID(intf);
                                }
                        else if (rr->SendRNow == intf->InterfaceID)
                                {
                                RData  *OldRData    = rr->resrec.rdata;
                                mDNSu16 oldrdlength = rr->resrec.rdlength;
                                mDNSu8 active = (mDNSu8)
                                        (rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                        (m->SleepState != SleepState_Sleeping || intf->SPSAddr[0].type || intf->SPSAddr[1].type || intf->SPSAddr[2].type));
                                newptr = mDNSNULL;
                                if (rr->NewRData && active)
                                        {
                                        // See if we should send a courtesy "goodbye" for the old data before we replace it.
                                        if (ResourceRecordIsValidAnswer(rr) && rr->resrec.RecordType == kDNSRecordTypeShared && rr->RequireGoodbye)
                                                {
                                                newptr = PutRR_OS_TTL(responseptr, &m->omsg.h.numAnswers, &rr->resrec, 0);
                                                if (newptr) { responseptr = newptr; numDereg++; rr->RequireGoodbye = mDNSfalse; }
                                                else continue; // If this packet is already too full to hold the goodbye for this record, skip it for now and we'll retry later
                                                }
                                        SetNewRData(&rr->resrec, rr->NewRData, rr->newrdlength);
                                        }
                                
                                if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                                        rr->resrec.rrclass |= kDNSClass_UniqueRRSet;            // Temporarily set the cache flush bit so PutResourceRecord will set it
                                newptr = PutRR_OS_TTL(responseptr, &m->omsg.h.numAnswers, &rr->resrec, active ? rr->resrec.rroriginalttl : 0);
                                rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;                   // Make sure to clear cache flush bit back to normal state
                                if (newptr)
                                        {
                                        responseptr = newptr;
                                        rr->RequireGoodbye = active;
                                        if (rr->resrec.RecordType == kDNSRecordTypeDeregistering) numDereg++;
                                        else if (rr->LastAPTime == m->timenow) numAnnounce++; else numAnswer++;
                                        }

                                if (rr->NewRData && active)
                                        SetNewRData(&rr->resrec, OldRData, oldrdlength);

                                // The first time through (pktcount==0), if this record is verified unique
                                // (i.e. typically A, AAAA, SRV, TXT and reverse-mapping PTR), set the flag to add an NSEC too.
                                if (!pktcount && active && (rr->resrec.RecordType & kDNSRecordTypeActiveUniqueMask) && !rr->SendNSECNow)
                                        rr->SendNSECNow = mDNSInterfaceMark;

                                if (newptr)             // If succeeded in sending, advance to next interface
                                        {
                                        // If sending on all interfaces, go to next interface; else we're finished now
                                        if (rr->ImmedAnswer == mDNSInterfaceMark && rr->resrec.InterfaceID == mDNSInterface_Any)
                                                rr->SendRNow = GetNextActiveInterfaceID(intf);
                                        else
                                                rr->SendRNow = mDNSNULL;
                                        }
                                }
                        }
        
                // Second Pass. Add additional records, if there's space.
                newptr = responseptr;
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->ImmedAdditional == intf->InterfaceID)
                                if (ResourceRecordIsValidAnswer(rr))
                                        {
                                        // If we have at least one answer already in the packet, then plan to add additionals too
                                        mDNSBool SendAdditional = (m->omsg.h.numAnswers > 0);
                                        
                                        // If we're not planning to send any additionals, but this record is a unique one, then
                                        // make sure we haven't already sent any other members of its RRSet -- if we have, then they
                                        // will have had the cache flush bit set, so now we need to finish the job and send the rest.
                                        if (!SendAdditional && (rr->resrec.RecordType & kDNSRecordTypeUniqueMask))
                                                {
                                                const AuthRecord *a;
                                                for (a = m->ResourceRecords; a; a=a->next)
                                                        if (a->LastMCTime      == m->timenow &&
                                                                a->LastMCInterface == intf->InterfaceID &&
                                                                SameResourceRecordSignature(a, rr)) { SendAdditional = mDNStrue; break; }
                                                }
                                        if (!SendAdditional)                                    // If we don't want to send this after all,
                                                rr->ImmedAdditional = mDNSNULL;         // then cancel its ImmedAdditional field
                                        else if (newptr)                                                // Else, try to add it if we can
                                                {
                                                // The first time through (pktcount==0), if this record is verified unique
                                                // (i.e. typically A, AAAA, SRV, TXT and reverse-mapping PTR), set the flag to add an NSEC too.
                                                if (!pktcount && (rr->resrec.RecordType & kDNSRecordTypeActiveUniqueMask) && !rr->SendNSECNow)
                                                        rr->SendNSECNow = mDNSInterfaceMark;

                                                if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                                                        rr->resrec.rrclass |= kDNSClass_UniqueRRSet;    // Temporarily set the cache flush bit so PutResourceRecord will set it
                                                newptr = PutRR_OS(newptr, &m->omsg.h.numAdditionals, &rr->resrec);
                                                rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;           // Make sure to clear cache flush bit back to normal state
                                                if (newptr)
                                                        {
                                                        responseptr = newptr;
                                                        rr->ImmedAdditional = mDNSNULL;
                                                        rr->RequireGoodbye = mDNStrue;
                                                        // If we successfully put this additional record in the packet, we record LastMCTime & LastMCInterface.
                                                        // This matters particularly in the case where we have more than one IPv6 (or IPv4) address, because otherwise,
                                                        // when we see our own multicast with the cache flush bit set, if we haven't set LastMCTime, then we'll get
                                                        // all concerned and re-announce our record again to make sure it doesn't get flushed from peer caches.
                                                        rr->LastMCTime      = m->timenow;
                                                        rr->LastMCInterface = intf->InterfaceID;
                                                        }
                                                }
                                        }

                // Third Pass. Add NSEC records, if there's space.
                // When we're generating an NSEC record in response to a specify query for that type
                // (recognized by rr->SendNSECNow == intf->InterfaceID) we should really put the NSEC in the Answer Section,
                // not Additional Section, but for now it's easier to handle both cases in this Additional Section loop here.
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->SendNSECNow == mDNSInterfaceMark || rr->SendNSECNow == intf->InterfaceID)
                                {
                                AuthRecord nsec;
                                mDNS_SetupResourceRecord(&nsec, mDNSNULL, mDNSInterface_Any, kDNSType_NSEC, rr->resrec.rroriginalttl, kDNSRecordTypeUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
                                nsec.resrec.rrclass |= kDNSClass_UniqueRRSet;
                                AssignDomainName(&nsec.namestorage, rr->resrec.name);
                                mDNSPlatformMemZero(nsec.rdatastorage.u.nsec.bitmap, sizeof(nsec.rdatastorage.u.nsec.bitmap));
                                for (r2 = m->ResourceRecords; r2; r2=r2->next)
                                        if (ResourceRecordIsValidAnswer(r2) && SameResourceRecordNameClassInterface(r2, rr))
                                                {
                                                if (r2->resrec.rrtype >= kDNSQType_ANY) { LogMsg("Can't create NSEC for record %s", ARDisplayString(m, r2)); break; }
                                                else nsec.rdatastorage.u.nsec.bitmap[r2->resrec.rrtype >> 3] |= 128 >> (r2->resrec.rrtype & 7);
                                                }
                                newptr = responseptr;
                                if (!r2)        // If we successfully built our NSEC record, add it to the packet now
                                        {
                                        newptr = PutRR_OS(responseptr, &m->omsg.h.numAdditionals, &nsec.resrec);
                                        if (newptr) responseptr = newptr;
                                        }

                                // If we successfully put the NSEC record, clear the SendNSECNow flag
                                // If we consider this NSEC optional, then we unconditionally clear the SendNSECNow flag, even if we fail to put this additional record
                                if (newptr || rr->SendNSECNow == mDNSInterfaceMark)
                                        {
                                        rr->SendNSECNow = mDNSNULL;
                                        // Run through remainder of list clearing SendNSECNow flag for all other records which would generate the same NSEC
                                        for (r2 = rr->next; r2; r2=r2->next)
                                                if (SameResourceRecordNameClassInterface(r2, rr))
                                                        if (r2->SendNSECNow == mDNSInterfaceMark || r2->SendNSECNow == intf->InterfaceID)
                                                                r2->SendNSECNow = mDNSNULL;
                                        }
                                }

                if (m->omsg.h.numAnswers || m->omsg.h.numAdditionals)
                        {
                        // If we have data to send, add OWNER option if necessary, then send packet

                        if (OwnerRecordSpace)
                                {
                                AuthRecord opt;
                                mDNS_SetupResourceRecord(&opt, mDNSNULL, mDNSInterface_Any, kDNSType_OPT, kStandardTTL, kDNSRecordTypeKnownUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
                                opt.resrec.rrclass    = NormalMaxDNSMessageData;
                                opt.resrec.rdlength   = sizeof(rdataOPT);       // One option in this OPT record
                                opt.resrec.rdestimate = sizeof(rdataOPT);
                                SetupOwnerOpt(m, intf, &opt.resrec.rdata->u.opt[0]);
                                newptr = PutResourceRecord(&m->omsg, responseptr, &m->omsg.h.numAdditionals, &opt.resrec);
                                if (newptr) { responseptr = newptr; LogSPS("SendResponses put   %s", ARDisplayString(m, &opt)); }
                                else if (m->omsg.h.numAnswers + m->omsg.h.numAuthorities + m->omsg.h.numAdditionals == 1)
                                        LogSPS("SendResponses: No space in packet for Owner OPT record (%d/%d/%d/%d) %s",
                                                m->omsg.h.numQuestions, m->omsg.h.numAnswers, m->omsg.h.numAuthorities, m->omsg.h.numAdditionals, ARDisplayString(m, &opt));
                                else
                                        LogMsg("SendResponses: How did we fail to have space for Owner OPT record (%d/%d/%d/%d) %s",
                                                m->omsg.h.numQuestions, m->omsg.h.numAnswers, m->omsg.h.numAuthorities, m->omsg.h.numAdditionals, ARDisplayString(m, &opt));
                                }

                        debugf("SendResponses: Sending %d Deregistration%s, %d Announcement%s, %d Answer%s, %d Additional%s on %p",
                                numDereg,                 numDereg                 == 1 ? "" : "s",
                                numAnnounce,              numAnnounce              == 1 ? "" : "s",
                                numAnswer,                numAnswer                == 1 ? "" : "s",
                                m->omsg.h.numAdditionals, m->omsg.h.numAdditionals == 1 ? "" : "s", intf->InterfaceID);

                        if (intf->IPv4Available) mDNSSendDNSMessage(m, &m->omsg, responseptr, intf->InterfaceID, mDNSNULL, &AllDNSLinkGroup_v4, MulticastDNSPort, mDNSNULL, mDNSNULL);
                        if (intf->IPv6Available) mDNSSendDNSMessage(m, &m->omsg, responseptr, intf->InterfaceID, mDNSNULL, &AllDNSLinkGroup_v6, MulticastDNSPort, mDNSNULL, mDNSNULL);
                        if (!m->SuppressSending) m->SuppressSending = NonZeroTime(m->timenow + (mDNSPlatformOneSecond+9)/10);
                        if (++pktcount >= 1000) { LogMsg("SendResponses exceeded loop limit %d: giving up", pktcount); break; }
                        // There might be more things to send on this interface, so go around one more time and try again.
                        }
                else    // Nothing more to send on this interface; go to next
                        {
                        const NetworkInterfaceInfo *next = GetFirstActiveInterface(intf->next);
                        #if MDNS_DEBUGMSGS && 0
                        const char *const msg = next ? "SendResponses: Nothing more on %p; moving to %p" : "SendResponses: Nothing more on %p";
                        debugf(msg, intf, next);
                        #endif
                        intf = next;
                        pktcount = 0;           // When we move to a new interface, reset packet count back to zero -- NSEC generation logic uses it
                        }
                }

        // ***
        // *** 3. Cleanup: Now that everything is sent, call client callback functions, and reset state variables
        // ***

        if (m->CurrentRecord)
                LogMsg("SendResponses ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        m->CurrentRecord = m->ResourceRecords;
        while (m->CurrentRecord)
                {
                rr = m->CurrentRecord;
                m->CurrentRecord = rr->next;

                if (rr->SendRNow)
                        {
                        if (rr->ARType != AuthRecordLocalOnly && rr->ARType != AuthRecordP2P)
                                LogMsg("SendResponses: No active interface %p to send: %p %02X %s", rr->SendRNow, rr->resrec.InterfaceID, rr->resrec.RecordType, ARDisplayString(m, rr));
                        rr->SendRNow = mDNSNULL;
                        }

                if (rr->ImmedAnswer || rr->resrec.RecordType == kDNSRecordTypeDeregistering)
                        {
                        if (rr->NewRData) CompleteRDataUpdate(m, rr);   // Update our rdata, clear the NewRData pointer, and return memory to the client
        
                        if (rr->resrec.RecordType == kDNSRecordTypeDeregistering && rr->AnnounceCount == 0)
                                {
                                // For Unicast, when we get the response from the server, we will call CompleteDeregistration
                                if (!AuthRecord_uDNS(rr)) CompleteDeregistration(m, rr);                // Don't touch rr after this
                                }
                        else
                                {
                                rr->ImmedAnswer  = mDNSNULL;
                                rr->ImmedUnicast = mDNSfalse;
                                rr->v4Requester  = zerov4Addr;
                                rr->v6Requester  = zerov6Addr;
                                }
                        }
                }
        verbosedebugf("SendResponses: Next in %ld ticks", m->NextScheduledResponse - m->timenow);
        }

// Calling CheckCacheExpiration() is an expensive operation because it has to look at the entire cache,
// so we want to be lazy about how frequently we do it.
// 1. If a cache record is currently referenced by *no* active questions,
//    then we don't mind expiring it up to a minute late (who will know?)
// 2. Else, if a cache record is due for some of its final expiration queries,
//    we'll allow them to be late by up to 2% of the TTL
// 3. Else, if a cache record has completed all its final expiration queries without success,
//    and is expiring, and had an original TTL more than ten seconds, we'll allow it to be one second late
// 4. Else, it is expiring and had an original TTL of ten seconds or less (includes explicit goodbye packets),
//    so allow at most 1/10 second lateness
// 5. For records with rroriginalttl set to zero, that means we really want to delete them immediately
//    (we have a new record with DelayDelivery set, waiting for the old record to go away before we can notify clients).
#define CacheCheckGracePeriod(RR) (                                                   \
        ((RR)->CRActiveQuestion == mDNSNULL            ) ? (60 * mDNSPlatformOneSecond) : \
        ((RR)->UnansweredQueries < MaxUnansweredQueries) ? (TicksTTL(rr)/50)            : \
        ((RR)->resrec.rroriginalttl > 10               ) ? (mDNSPlatformOneSecond)      : \
        ((RR)->resrec.rroriginalttl > 0                ) ? (mDNSPlatformOneSecond/10)   : 0)

#define NextCacheCheckEvent(RR) ((RR)->NextRequiredQuery + CacheCheckGracePeriod(RR))

mDNSexport void ScheduleNextCacheCheckTime(mDNS *const m, const mDNSu32 slot, const mDNSs32 event)
        {
        if (m->rrcache_nextcheck[slot] - event > 0)
                m->rrcache_nextcheck[slot] = event;
        if (m->NextCacheCheck          - event > 0)
                m->NextCacheCheck          = event;
        }

// Note: MUST call SetNextCacheCheckTimeForRecord any time we change:
// rr->TimeRcvd
// rr->resrec.rroriginalttl
// rr->UnansweredQueries
// rr->CRActiveQuestion
mDNSlocal void SetNextCacheCheckTimeForRecord(mDNS *const m, CacheRecord *const rr)
        {
        rr->NextRequiredQuery = RRExpireTime(rr);

        // If we have an active question, then see if we want to schedule a refresher query for this record.
        // Usually we expect to do four queries, at 80-82%, 85-87%, 90-92% and then 95-97% of the TTL.
        if (rr->CRActiveQuestion && rr->UnansweredQueries < MaxUnansweredQueries)
                {
                rr->NextRequiredQuery -= TicksTTL(rr)/20 * (MaxUnansweredQueries - rr->UnansweredQueries);
                rr->NextRequiredQuery += mDNSRandom((mDNSu32)TicksTTL(rr)/50);
                verbosedebugf("SetNextCacheCheckTimeForRecord: NextRequiredQuery in %ld sec CacheCheckGracePeriod %d ticks for %s",
                        (rr->NextRequiredQuery - m->timenow) / mDNSPlatformOneSecond, CacheCheckGracePeriod(rr), CRDisplayString(m,rr));
                }

        ScheduleNextCacheCheckTime(m, HashSlot(rr->resrec.name), NextCacheCheckEvent(rr));
        }

#define kMinimumReconfirmTime                     ((mDNSu32)mDNSPlatformOneSecond *  5)
#define kDefaultReconfirmTimeForWake              ((mDNSu32)mDNSPlatformOneSecond *  5)
#define kDefaultReconfirmTimeForNoAnswer          ((mDNSu32)mDNSPlatformOneSecond *  5)
#define kDefaultReconfirmTimeForFlappingInterface ((mDNSu32)mDNSPlatformOneSecond * 30)

mDNSlocal mStatus mDNS_Reconfirm_internal(mDNS *const m, CacheRecord *const rr, mDNSu32 interval)
        {
        if (interval < kMinimumReconfirmTime)
                interval = kMinimumReconfirmTime;
        if (interval > 0x10000000)      // Make sure interval doesn't overflow when we multiply by four below
                interval = 0x10000000;

        // If the expected expiration time for this record is more than interval+33%, then accelerate its expiration
        if (RRExpireTime(rr) - m->timenow > (mDNSs32)((interval * 4) / 3))
                {
                // Add a 33% random amount to the interval, to avoid synchronization between multiple hosts
                // For all the reconfirmations in a given batch, we want to use the same random value
                // so that the reconfirmation questions can be grouped into a single query packet
                if (!m->RandomReconfirmDelay) m->RandomReconfirmDelay = 1 + mDNSRandom(0x3FFFFFFF);
                interval += m->RandomReconfirmDelay % ((interval/3) + 1);
                rr->TimeRcvd          = m->timenow - (mDNSs32)interval * 3;
                rr->resrec.rroriginalttl     = (interval * 4 + mDNSPlatformOneSecond - 1) / mDNSPlatformOneSecond;
                SetNextCacheCheckTimeForRecord(m, rr);
                }
        debugf("mDNS_Reconfirm_internal:%6ld ticks to go for %s %p",
                RRExpireTime(rr) - m->timenow, CRDisplayString(m, rr), rr->CRActiveQuestion);
        return(mStatus_NoError);
        }

#define MaxQuestionInterval         (3600 * mDNSPlatformOneSecond)

// BuildQuestion puts a question into a DNS Query packet and if successful, updates the value of queryptr.
// It also appends to the list of known answer records that need to be included,
// and updates the forcast for the size of the known answer section.
mDNSlocal mDNSBool BuildQuestion(mDNS *const m, DNSMessage *query, mDNSu8 **queryptr, DNSQuestion *q,
        CacheRecord ***kalistptrptr, mDNSu32 *answerforecast)
        {
        mDNSBool ucast = (q->LargeAnswers || q->RequestUnicast) && m->CanReceiveUnicastOn5353;
        mDNSu16 ucbit = (mDNSu16)(ucast ? kDNSQClass_UnicastResponse : 0);
        const mDNSu8 *const limit = query->data + NormalMaxDNSMessageData;
        mDNSu8 *newptr = putQuestion(query, *queryptr, limit - *answerforecast, &q->qname, q->qtype, (mDNSu16)(q->qclass | ucbit));
        if (!newptr)
                {
                debugf("BuildQuestion: No more space in this packet for question %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                return(mDNSfalse);
                }
        else
                {
                mDNSu32 forecast = *answerforecast;
                const mDNSu32 slot = HashSlot(&q->qname);
                const CacheGroup *const cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
                CacheRecord *rr;
                CacheRecord **ka = *kalistptrptr;       // Make a working copy of the pointer we're going to update

                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)                         // If we have a resource record in our cache,
                        if (rr->resrec.InterfaceID == q->SendQNow &&                                    // received on this interface
                                !(rr->resrec.RecordType & kDNSRecordTypeUniqueMask) &&          // which is a shared (i.e. not unique) record type
                                rr->NextInKAList == mDNSNULL && ka != &rr->NextInKAList &&      // which is not already in the known answer list
                                rr->resrec.rdlength <= SmallRecordLimit &&                                      // which is small enough to sensibly fit in the packet
                                SameNameRecordAnswersQuestion(&rr->resrec, q) &&                        // which answers our question
                                rr->TimeRcvd + TicksTTL(rr)/2 - m->timenow >                            // and its half-way-to-expiry time is at least 1 second away
                                                                                                mDNSPlatformOneSecond)          // (also ensures we never include goodbye records with TTL=1)
                                {
                                // We don't want to include unique records in the Known Answer section. The Known Answer section
                                // is intended to suppress floods of shared-record replies from many other devices on the network.
                                // That concept really does not apply to unique records, and indeed if we do send a query for
                                // which we have a unique record already in our cache, then including that unique record as a
                                // Known Answer, so as to suppress the only answer we were expecting to get, makes little sense.

                                *ka = rr;       // Link this record into our known answer chain
                                ka = &rr->NextInKAList;
                                // We forecast: compressed name (2) type (2) class (2) TTL (4) rdlength (2) rdata (n)
                                forecast += 12 + rr->resrec.rdestimate;
                                // If we're trying to put more than one question in this packet, and it doesn't fit
                                // then undo that last question and try again next time
                                if (query->h.numQuestions > 1 && newptr + forecast >= limit)
                                        {
                                        debugf("BuildQuestion: Retracting question %##s (%s) new forecast total %d",
                                                q->qname.c, DNSTypeName(q->qtype), newptr + forecast - query->data);
                                        query->h.numQuestions--;
                                        ka = *kalistptrptr;             // Go back to where we started and retract these answer records
                                        while (*ka) { CacheRecord *c = *ka; *ka = mDNSNULL; ka = &c->NextInKAList; }
                                        return(mDNSfalse);              // Return false, so we'll try again in the next packet
                                        }
                                }

                // Success! Update our state pointers, increment UnansweredQueries as appropriate, and return
                *queryptr        = newptr;                              // Update the packet pointer
                *answerforecast  = forecast;                    // Update the forecast
                *kalistptrptr    = ka;                                  // Update the known answer list pointer
                if (ucast) q->ExpectUnicastResp = NonZeroTime(m->timenow);

                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)                         // For every resource record in our cache,
                        if (rr->resrec.InterfaceID == q->SendQNow &&                                    // received on this interface
                                rr->NextInKAList == mDNSNULL && ka != &rr->NextInKAList &&      // which is not in the known answer list
                                SameNameRecordAnswersQuestion(&rr->resrec, q))                          // which answers our question
                                        {
                                        rr->UnansweredQueries++;                                                                // indicate that we're expecting a response
                                        rr->LastUnansweredTime = m->timenow;
                                        SetNextCacheCheckTimeForRecord(m, rr);
                                        }

                return(mDNStrue);
                }
        }

// When we have a query looking for a specified name, but there appear to be no answers with
// that name, ReconfirmAntecedents() is called with depth=0 to start the reconfirmation process
// for any records in our cache that reference the given name (e.g. PTR and SRV records).
// For any such cache record we find, we also recursively call ReconfirmAntecedents() for *its* name.
// We increment depth each time we recurse, to guard against possible infinite loops, with a limit of 5.
// A typical reconfirmation scenario might go like this:
// Depth 0: Name "myhost.local" has no address records
// Depth 1: SRV "My Service._example._tcp.local." refers to "myhost.local"; may be stale
// Depth 2: PTR "_example._tcp.local." refers to "My Service"; may be stale
// Depth 3: PTR "_services._dns-sd._udp.local." refers to "_example._tcp.local."; may be stale
// Currently depths 4 and 5 are not expected to occur; if we did get to depth 5 we'd reconfim any records we
// found referring to the given name, but not recursively descend any further reconfirm *their* antecedents.
mDNSlocal void ReconfirmAntecedents(mDNS *const m, const domainname *const name, const mDNSu32 namehash, const int depth)
        {
        mDNSu32 slot;
        CacheGroup *cg;
        CacheRecord *cr;
        debugf("ReconfirmAntecedents (depth=%d) for %##s", depth, name->c);
        FORALL_CACHERECORDS(slot, cg, cr)
                {
                domainname *crtarget = GetRRDomainNameTarget(&cr->resrec);
                if (crtarget && cr->resrec.rdatahash == namehash && SameDomainName(crtarget, name))
                        {
                        LogInfo("ReconfirmAntecedents: Reconfirming (depth=%d) %s", depth, CRDisplayString(m, cr));
                        mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForNoAnswer);
                        if (depth < 5) ReconfirmAntecedents(m, cr->resrec.name, cr->resrec.namehash, depth+1);
                        }
                }
        }

// If we get no answer for a AAAA query, then before doing an automatic implicit ReconfirmAntecedents
// we check if we have an address record for the same name. If we do have an IPv4 address for a given
// name but not an IPv6 address, that's okay (it just means the device doesn't do IPv6) so the failure
// to get a AAAA response is not grounds to doubt the PTR/SRV chain that lead us to that name.
mDNSlocal const CacheRecord *CacheHasAddressTypeForName(mDNS *const m, const domainname *const name, const mDNSu32 namehash)
        {
        CacheGroup *const cg = CacheGroupForName(m, HashSlot(name), namehash, name);
        const CacheRecord *cr = cg ? cg->members : mDNSNULL;
        while (cr && !RRTypeIsAddressType(cr->resrec.rrtype)) cr=cr->next;
        return(cr);
        }

mDNSlocal const CacheRecord *FindSPSInCache1(mDNS *const m, const DNSQuestion *const q, const CacheRecord *const c0, const CacheRecord *const c1)
        {
        CacheGroup *const cg = CacheGroupForName(m, HashSlot(&q->qname), q->qnamehash, &q->qname);
        const CacheRecord *cr, *bestcr = mDNSNULL;
        mDNSu32 bestmetric = 1000000;
        for (cr = cg ? cg->members : mDNSNULL; cr; cr=cr->next)
                if (cr->resrec.rrtype == kDNSType_PTR && cr->resrec.rdlength >= 6)                                              // If record is PTR type, with long enough name,
                        if (cr != c0 && cr != c1)                                                                                                                       // that's not one we've seen before,
                                if (SameNameRecordAnswersQuestion(&cr->resrec, q))                                                              // and answers our browse query,
                                        if (!IdenticalSameNameRecord(&cr->resrec, &m->SPSRecords.RR_PTR.resrec))        // and is not our own advertised service...
                                                {
                                                mDNSu32 metric = SPSMetric(cr->resrec.rdata->u.name.c);
                                                if (bestmetric > metric) { bestmetric = metric; bestcr = cr; }
                                                }
        return(bestcr);
        }

// Finds the three best Sleep Proxies we currently have in our cache
mDNSexport void FindSPSInCache(mDNS *const m, const DNSQuestion *const q, const CacheRecord *sps[3])
        {
        sps[0] =                      FindSPSInCache1(m, q, mDNSNULL, mDNSNULL);
        sps[1] = !sps[0] ? mDNSNULL : FindSPSInCache1(m, q, sps[0],   mDNSNULL);
        sps[2] = !sps[1] ? mDNSNULL : FindSPSInCache1(m, q, sps[0],   sps[1]);
        }

// Only DupSuppressInfos newer than the specified 'time' are allowed to remain active
mDNSlocal void ExpireDupSuppressInfo(DupSuppressInfo ds[DupSuppressInfoSize], mDNSs32 time)
        {
        int i;
        for (i=0; i<DupSuppressInfoSize; i++) if (ds[i].Time - time < 0) ds[i].InterfaceID = mDNSNULL;
        }

mDNSlocal void ExpireDupSuppressInfoOnInterface(DupSuppressInfo ds[DupSuppressInfoSize], mDNSs32 time, mDNSInterfaceID InterfaceID)
        {
        int i;
        for (i=0; i<DupSuppressInfoSize; i++) if (ds[i].InterfaceID == InterfaceID && ds[i].Time - time < 0) ds[i].InterfaceID = mDNSNULL;
        }

mDNSlocal mDNSBool SuppressOnThisInterface(const DupSuppressInfo ds[DupSuppressInfoSize], const NetworkInterfaceInfo * const intf)
        {
        int i;
        mDNSBool v4 = !intf->IPv4Available;             // If this interface doesn't do v4, we don't need to find a v4 duplicate of this query
        mDNSBool v6 = !intf->IPv6Available;             // If this interface doesn't do v6, we don't need to find a v6 duplicate of this query
        for (i=0; i<DupSuppressInfoSize; i++)
                if (ds[i].InterfaceID == intf->InterfaceID)
                        {
                        if      (ds[i].Type == mDNSAddrType_IPv4) v4 = mDNStrue;
                        else if (ds[i].Type == mDNSAddrType_IPv6) v6 = mDNStrue;
                        if (v4 && v6) return(mDNStrue);
                        }
        return(mDNSfalse);
        }

mDNSlocal int RecordDupSuppressInfo(DupSuppressInfo ds[DupSuppressInfoSize], mDNSs32 Time, mDNSInterfaceID InterfaceID, mDNSs32 Type)
        {
        int i, j;

        // See if we have this one in our list somewhere already
        for (i=0; i<DupSuppressInfoSize; i++) if (ds[i].InterfaceID == InterfaceID && ds[i].Type == Type) break;

        // If not, find a slot we can re-use
        if (i >= DupSuppressInfoSize)
                {
                i = 0;
                for (j=1; j<DupSuppressInfoSize && ds[i].InterfaceID; j++)
                        if (!ds[j].InterfaceID || ds[j].Time - ds[i].Time < 0)
                                i = j;
                }
        
        // Record the info about this query we saw
        ds[i].Time        = Time;
        ds[i].InterfaceID = InterfaceID;
        ds[i].Type        = Type;
        
        return(i);
        }

mDNSlocal void mDNSSendWakeOnResolve(mDNS *const m, DNSQuestion *q)
        {
        int len, i, cnt;
        mDNSInterfaceID InterfaceID = q->InterfaceID;
        domainname *d = &q->qname;

        // We can't send magic packets without knowing which interface to send it on.
        if (InterfaceID == mDNSInterface_Any || InterfaceID == mDNSInterface_LocalOnly || InterfaceID == mDNSInterface_P2P)
                {
                LogMsg("mDNSSendWakeOnResolve: ERROR!! Invalid InterfaceID %p for question %##s", InterfaceID, q->qname.c);
                return;
                }

        // Split MAC@IPAddress and pass them separately
        len = d->c[0];
        i = 1;
        cnt = 0;
        for (i = 1; i < len; i++)
                {
                if (d->c[i] == '@')
                        {
                        char EthAddr[18];       // ethernet adddress : 12 bytes + 5 ":" + 1 NULL byte
                        char IPAddr[47];    // Max IP address len: 46 bytes (IPv6) + 1 NULL byte
                        if (cnt != 5)
                                {
                                LogMsg("mDNSSendWakeOnResolve: ERROR!! Malformed Ethernet address %##s, cnt %d", q->qname.c, cnt);
                                return;
                                }
                        if ((i - 1) > (int) (sizeof(EthAddr) - 1))
                                {
                                LogMsg("mDNSSendWakeOnResolve: ERROR!! Malformed Ethernet address %##s, length %d", q->qname.c, i - 1);
                                return;
                                }
                        if ((len - i) > (int)(sizeof(IPAddr) - 1))
                                {
                                LogMsg("mDNSSendWakeOnResolve: ERROR!! Malformed IP address %##s, length %d", q->qname.c, len - i);
                                return;
                                }
                        mDNSPlatformMemCopy(EthAddr, &d->c[1], i - 1);
                        EthAddr[i - 1] = 0;
                        mDNSPlatformMemCopy(IPAddr, &d->c[i + 1], len - i);
                        IPAddr[len - i] = 0;
                        mDNSPlatformSendWakeupPacket(m, InterfaceID, EthAddr, IPAddr, InitialWakeOnResolveCount - q->WakeOnResolveCount);
                        return;
                        }
                else if (d->c[i] == ':')
                        cnt++;
                }
        LogMsg("mDNSSendWakeOnResolve: ERROR!! Malformed WakeOnResolve name %##s", q->qname.c);
        }
                

mDNSlocal mDNSBool AccelerateThisQuery(mDNS *const m, DNSQuestion *q)
        {
        // If more than 90% of the way to the query time, we should unconditionally accelerate it
        if (TimeToSendThisQuestion(q, m->timenow + q->ThisQInterval/10))
                return(mDNStrue);

        // If half-way to next scheduled query time, only accelerate if it will add less than 512 bytes to the packet
        if (TimeToSendThisQuestion(q, m->timenow + q->ThisQInterval/2))
                {
                // We forecast: qname (n) type (2) class (2)
                mDNSu32 forecast = (mDNSu32)DomainNameLength(&q->qname) + 4;
                const mDNSu32 slot = HashSlot(&q->qname);
                const CacheGroup *const cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
                const CacheRecord *rr;
                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)                         // If we have a resource record in our cache,
                        if (rr->resrec.rdlength <= SmallRecordLimit &&                                  // which is small enough to sensibly fit in the packet
                                SameNameRecordAnswersQuestion(&rr->resrec, q) &&                        // which answers our question
                                rr->TimeRcvd + TicksTTL(rr)/2 - m->timenow >= 0 &&                      // and it is less than half-way to expiry
                                rr->NextRequiredQuery - (m->timenow + q->ThisQInterval) > 0)// and we'll ask at least once again before NextRequiredQuery
                                {
                                // We forecast: compressed name (2) type (2) class (2) TTL (4) rdlength (2) rdata (n)
                                forecast += 12 + rr->resrec.rdestimate;
                                if (forecast >= 512) return(mDNSfalse); // If this would add 512 bytes or more to the packet, don't accelerate
                                }
                return(mDNStrue);
                }

        return(mDNSfalse);
        }

// How Standard Queries are generated:
// 1. The Question Section contains the question
// 2. The Additional Section contains answers we already know, to suppress duplicate responses

// How Probe Queries are generated:
// 1. The Question Section contains queries for the name we intend to use, with QType=ANY because
// if some other host is already using *any* records with this name, we want to know about it.
// 2. The Authority Section contains the proposed values we intend to use for one or more
// of our records with that name (analogous to the Update section of DNS Update packets)
// because if some other host is probing at the same time, we each want to know what the other is
// planning, in order to apply the tie-breaking rule to see who gets to use the name and who doesn't.

mDNSlocal void SendQueries(mDNS *const m)
        {
        mDNSu32 slot;
        CacheGroup *cg;
        CacheRecord *cr;
        AuthRecord *ar;
        int pktcount = 0;
        DNSQuestion *q;
        // For explanation of maxExistingQuestionInterval logic, see comments for maxExistingAnnounceInterval
        mDNSs32 maxExistingQuestionInterval = 0;
        const NetworkInterfaceInfo *intf = GetFirstActiveInterface(m->HostInterfaces);
        CacheRecord *KnownAnswerList = mDNSNULL;

        // 1. If time for a query, work out what we need to do

        // We're expecting to send a query anyway, so see if any expiring cache records are close enough
        // to their NextRequiredQuery to be worth batching them together with this one
        FORALL_CACHERECORDS(slot, cg, cr)
                if (cr->CRActiveQuestion && cr->UnansweredQueries < MaxUnansweredQueries)
                        if (m->timenow + TicksTTL(cr)/50 - cr->NextRequiredQuery >= 0)
                                {
                                debugf("Sending %d%% cache expiration query for %s", 80 + 5 * cr->UnansweredQueries, CRDisplayString(m, cr));
                                q = cr->CRActiveQuestion;
                                ExpireDupSuppressInfoOnInterface(q->DupSuppress, m->timenow - TicksTTL(cr)/20, cr->resrec.InterfaceID);
                                // For uDNS queries (TargetQID non-zero) we adjust LastQTime,
                                // and bump UnansweredQueries so that we don't spin trying to send the same cache expiration query repeatedly
                                if      (q->Target.type)                        q->SendQNow = mDNSInterfaceMark;        // If targeted query, mark it
                                else if (!mDNSOpaque16IsZero(q->TargetQID))     { q->LastQTime = m->timenow - q->ThisQInterval; cr->UnansweredQueries++; }
                                else if (q->SendQNow == mDNSNULL)               q->SendQNow = cr->resrec.InterfaceID;
                                else if (q->SendQNow != cr->resrec.InterfaceID) q->SendQNow = mDNSInterfaceMark;
                                }

        // Scan our list of questions to see which:
        //     *WideArea*  queries need to be sent
        //     *unicast*   queries need to be sent
        //     *multicast* queries we're definitely going to send
        if (m->CurrentQuestion)
                LogMsg("SendQueries ERROR m->CurrentQuestion already set: %##s (%s)", m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
                {
                q = m->CurrentQuestion;
                if (q->Target.type && (q->SendQNow || TimeToSendThisQuestion(q, m->timenow)))
                        {
                        mDNSu8       *qptr        = m->omsg.data;
                        const mDNSu8 *const limit = m->omsg.data + sizeof(m->omsg.data);

                        // If we fail to get a new on-demand socket (should only happen cases of the most extreme resource exhaustion), we'll try again next time
                        if (!q->LocalSocket) q->LocalSocket = mDNSPlatformUDPSocket(m, zeroIPPort);
                        if (q->LocalSocket)
                                {
                                InitializeDNSMessage(&m->omsg.h, q->TargetQID, QueryFlags);
                                qptr = putQuestion(&m->omsg, qptr, limit, &q->qname, q->qtype, q->qclass);
                                mDNSSendDNSMessage(m, &m->omsg, qptr, mDNSInterface_Any, q->LocalSocket, &q->Target, q->TargetPort, mDNSNULL, mDNSNULL);
                                q->ThisQInterval    *= QuestionIntervalStep;
                                }
                        if (q->ThisQInterval > MaxQuestionInterval)
                                q->ThisQInterval = MaxQuestionInterval;
                        q->LastQTime         = m->timenow;
                        q->LastQTxTime       = m->timenow;
                        q->RecentAnswerPkts  = 0;
                        q->SendQNow          = mDNSNULL;
                        q->ExpectUnicastResp = NonZeroTime(m->timenow);
                        }
                else if (mDNSOpaque16IsZero(q->TargetQID) && !q->Target.type && TimeToSendThisQuestion(q, m->timenow))
                        {
                        //LogInfo("Time to send %##s (%s) %d", q->qname.c, DNSTypeName(q->qtype), m->timenow - NextQSendTime(q));
                        q->SendQNow = mDNSInterfaceMark;                // Mark this question for sending on all interfaces
                        if (maxExistingQuestionInterval < q->ThisQInterval)
                                maxExistingQuestionInterval = q->ThisQInterval;
                        }
                // If m->CurrentQuestion wasn't modified out from under us, advance it now
                // We can't do this at the start of the loop because uDNS_CheckCurrentQuestion() depends on having
                // m->CurrentQuestion point to the right question
                if (q == m->CurrentQuestion) m->CurrentQuestion = m->CurrentQuestion->next;
                }
        while (m->CurrentQuestion)
                {
                LogInfo("SendQueries question loop 1: Skipping NewQuestion %##s (%s)", m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
                m->CurrentQuestion = m->CurrentQuestion->next;
                }
        m->CurrentQuestion = mDNSNULL;

        // Scan our list of questions
        // (a) to see if there are any more that are worth accelerating, and
        // (b) to update the state variables for *all* the questions we're going to send
        // Note: Don't set NextScheduledQuery until here, because uDNS_CheckCurrentQuestion in the loop above can add new questions to the list,
        // which causes NextScheduledQuery to get (incorrectly) set to m->timenow. Setting it here is the right place, because the very
        // next thing we do is scan the list and call SetNextQueryTime() for every question we find, so we know we end up with the right value.
        m->NextScheduledQuery = m->timenow + 0x78000000;
        for (q = m->Questions; q && q != m->NewQuestions; q=q->next)
                {
                if (mDNSOpaque16IsZero(q->TargetQID) && (q->SendQNow ||
                        (!q->Target.type && ActiveQuestion(q) && q->ThisQInterval <= maxExistingQuestionInterval && AccelerateThisQuery(m,q))))
                        {
                        // If at least halfway to next query time, advance to next interval
                        // If less than halfway to next query time, then
                        // treat this as logically a repeat of the last transmission, without advancing the interval
                        if (m->timenow - (q->LastQTime + (q->ThisQInterval/2)) >= 0)
                                {
                                //LogInfo("Accelerating %##s (%s) %d", q->qname.c, DNSTypeName(q->qtype), m->timenow - NextQSendTime(q));
                                q->SendQNow = mDNSInterfaceMark;        // Mark this question for sending on all interfaces
                                debugf("SendQueries: %##s (%s) next interval %d seconds RequestUnicast = %d",
                                        q->qname.c, DNSTypeName(q->qtype), q->ThisQInterval / InitialQuestionInterval, q->RequestUnicast);
                                q->ThisQInterval *= QuestionIntervalStep;
                                if (q->ThisQInterval > MaxQuestionInterval)
                                        q->ThisQInterval = MaxQuestionInterval;
                                else if (q->CurrentAnswers == 0 && q->ThisQInterval == InitialQuestionInterval * QuestionIntervalStep3 && !q->RequestUnicast &&
                                                !(RRTypeIsAddressType(q->qtype) && CacheHasAddressTypeForName(m, &q->qname, q->qnamehash)))
                                        {
                                        // Generally don't need to log this.
                                        // It's not especially noteworthy if a query finds no results -- this usually happens for domain
                                        // enumeration queries in the LL subdomain (e.g. "db._dns-sd._udp.0.0.254.169.in-addr.arpa")
                                        // and when there simply happen to be no instances of the service the client is looking
                                        // for (e.g. iTunes is set to look for RAOP devices, and the current network has none).
                                        debugf("SendQueries: Zero current answers for %##s (%s); will reconfirm antecedents",
                                                q->qname.c, DNSTypeName(q->qtype));
                                        // Sending third query, and no answers yet; time to begin doubting the source
                                        ReconfirmAntecedents(m, &q->qname, q->qnamehash, 0);
                                        }
                                }

                        // Mark for sending. (If no active interfaces, then don't even try.)
                        q->SendOnAll = (q->SendQNow == mDNSInterfaceMark);
                        if (q->SendOnAll)
                                {
                                q->SendQNow  = !intf ? mDNSNULL : (q->InterfaceID) ? q->InterfaceID : intf->InterfaceID;
                                q->LastQTime = m->timenow;
                                }

                        // If we recorded a duplicate suppression for this question less than half an interval ago,
                        // then we consider it recent enough that we don't need to do an identical query ourselves.
                        ExpireDupSuppressInfo(q->DupSuppress, m->timenow - q->ThisQInterval/2);

                        q->LastQTxTime      = m->timenow;
                        q->RecentAnswerPkts = 0;
                        if (q->RequestUnicast) q->RequestUnicast--;
                        }
                // For all questions (not just the ones we're sending) check what the next scheduled event will be
                // We don't need to consider NewQuestions here because for those we'll set m->NextScheduledQuery in AnswerNewQuestion
                SetNextQueryTime(m,q);
                }

        // 2. Scan our authoritative RR list to see what probes we might need to send

        m->NextScheduledProbe = m->timenow + 0x78000000;

        if (m->CurrentRecord)
                LogMsg("SendQueries ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        m->CurrentRecord = m->ResourceRecords;
        while (m->CurrentRecord)
                {
                ar = m->CurrentRecord;
                m->CurrentRecord = ar->next;
                if (!AuthRecord_uDNS(ar) && ar->resrec.RecordType == kDNSRecordTypeUnique)      // For all records that are still probing...
                        {
                        // 1. If it's not reached its probe time, just make sure we update m->NextScheduledProbe correctly
                        if (m->timenow - (ar->LastAPTime + ar->ThisAPInterval) < 0)
                                {
                                SetNextAnnounceProbeTime(m, ar);
                                }
                        // 2. else, if it has reached its probe time, mark it for sending and then update m->NextScheduledProbe correctly
                        else if (ar->ProbeCount)
                                {
                                if (ar->AddressProxy.type == mDNSAddrType_IPv4)
                                        {
                                        LogSPS("SendQueries ARP Probe %d %s %s", ar->ProbeCount, InterfaceNameForID(m, ar->resrec.InterfaceID), ARDisplayString(m,ar));
                                        SendARP(m, 1, ar, &zerov4Addr, &zeroEthAddr, &ar->AddressProxy.ip.v4, &ar->WakeUp.IMAC);
                                        }
                                else if (ar->AddressProxy.type == mDNSAddrType_IPv6)
                                        {
                                        LogSPS("SendQueries NDP Probe %d %s %s", ar->ProbeCount, InterfaceNameForID(m, ar->resrec.InterfaceID), ARDisplayString(m,ar));
                                        // IPv6 source = zero
                                        // No target hardware address
                                        // IPv6 target address is address we're probing
                                        // Ethernet destination address is Ethernet interface address of the Sleep Proxy client we're probing
                                        SendNDP(m, NDP_Sol, 0, ar, &zerov6Addr, mDNSNULL, &ar->AddressProxy.ip.v6, &ar->WakeUp.IMAC);
                                        }
                                // Mark for sending. (If no active interfaces, then don't even try.)
                                ar->SendRNow   = (!intf || ar->WakeUp.HMAC.l[0]) ? mDNSNULL : ar->resrec.InterfaceID ? ar->resrec.InterfaceID : intf->InterfaceID;
                                ar->LastAPTime = m->timenow;
                                // When we have a late conflict that resets a record to probing state we use a special marker value greater
                                // than DefaultProbeCountForTypeUnique. Here we detect that state and reset ar->ProbeCount back to the right value.
                                if (ar->ProbeCount > DefaultProbeCountForTypeUnique)
                                        ar->ProbeCount = DefaultProbeCountForTypeUnique;
                                ar->ProbeCount--;
                                SetNextAnnounceProbeTime(m, ar);
                                if (ar->ProbeCount == 0)
                                        {
                                        // If this is the last probe for this record, then see if we have any matching records
                                        // on our duplicate list which should similarly have their ProbeCount cleared to zero...
                                        AuthRecord *r2;
                                        for (r2 = m->DuplicateRecords; r2; r2=r2->next)
                                                if (r2->resrec.RecordType == kDNSRecordTypeUnique && RecordIsLocalDuplicate(r2, ar))
                                                        r2->ProbeCount = 0;
                                        // ... then acknowledge this record to the client.
                                        // We do this optimistically, just as we're about to send the third probe.
                                        // This helps clients that both advertise and browse, and want to filter themselves
                                        // from the browse results list, because it helps ensure that the registration
                                        // confirmation will be delivered 1/4 second *before* the browse "add" event.
                                        // A potential downside is that we could deliver a registration confirmation and then find out
                                        // moments later that there's a name conflict, but applications have to be prepared to handle
                                        // late conflicts anyway (e.g. on connection of network cable, etc.), so this is nothing new.
                                        if (!ar->Acknowledged) AcknowledgeRecord(m, ar);
                                        }
                                }
                        // else, if it has now finished probing, move it to state Verified,
                        // and update m->NextScheduledResponse so it will be announced
                        else
                                {
                                if (!ar->Acknowledged) AcknowledgeRecord(m, ar);        // Defensive, just in case it got missed somehow
                                ar->resrec.RecordType     = kDNSRecordTypeVerified;
                                ar->ThisAPInterval = DefaultAnnounceIntervalForTypeUnique;
                                ar->LastAPTime     = m->timenow - DefaultAnnounceIntervalForTypeUnique;
                                SetNextAnnounceProbeTime(m, ar);
                                }
                        }
                }
        m->CurrentRecord = m->DuplicateRecords;
        while (m->CurrentRecord)
                {
                ar = m->CurrentRecord;
                m->CurrentRecord = ar->next;
                if (ar->resrec.RecordType == kDNSRecordTypeUnique && ar->ProbeCount == 0 && !ar->Acknowledged)
                        AcknowledgeRecord(m, ar);
                }

        // 3. Now we know which queries and probes we're sending,
        // go through our interface list sending the appropriate queries on each interface
        while (intf)
                {
                const int OwnerRecordSpace = (m->AnnounceOwner && intf->MAC.l[0]) ? DNSOpt_Header_Space + DNSOpt_Owner_Space(&m->PrimaryMAC, &intf->MAC) : 0;
                mDNSu8 *queryptr = m->omsg.data;
                InitializeDNSMessage(&m->omsg.h, zeroID, QueryFlags);
                if (KnownAnswerList) verbosedebugf("SendQueries:   KnownAnswerList set... Will continue from previous packet");
                if (!KnownAnswerList)
                        {
                        // Start a new known-answer list
                        CacheRecord **kalistptr = &KnownAnswerList;
                        mDNSu32 answerforecast = OwnerRecordSpace;              // We start by assuming we'll need at least enough space to put the Owner Option
                        
                        // Put query questions in this packet
                        for (q = m->Questions; q && q != m->NewQuestions; q=q->next)
                                {
                                if (mDNSOpaque16IsZero(q->TargetQID) && (q->SendQNow == intf->InterfaceID))
                                        {
                                        debugf("SendQueries: %s question for %##s (%s) at %d forecast total %d",
                                                SuppressOnThisInterface(q->DupSuppress, intf) ? "Suppressing" : "Putting    ",
                                                q->qname.c, DNSTypeName(q->qtype), queryptr - m->omsg.data, queryptr + answerforecast - m->omsg.data);

                                        // If we're suppressing this question, or we successfully put it, update its SendQNow state
                                        if (SuppressOnThisInterface(q->DupSuppress, intf) ||
                                                BuildQuestion(m, &m->omsg, &queryptr, q, &kalistptr, &answerforecast))
                                                {
                                                q->SendQNow = (q->InterfaceID || !q->SendOnAll) ? mDNSNULL : GetNextActiveInterfaceID(intf);
                                                if (q->WakeOnResolveCount)
                                                        {
                                                        mDNSSendWakeOnResolve(m, q);
                                                        q->WakeOnResolveCount--;
                                                        }
                                                }
                                        }
                                }

                        // Put probe questions in this packet
                        for (ar = m->ResourceRecords; ar; ar=ar->next)
                                if (ar->SendRNow == intf->InterfaceID)
                                        {
                                        mDNSBool ucast = (ar->ProbeCount >= DefaultProbeCountForTypeUnique-1) && m->CanReceiveUnicastOn5353;
                                        mDNSu16 ucbit = (mDNSu16)(ucast ? kDNSQClass_UnicastResponse : 0);
                                        const mDNSu8 *const limit = m->omsg.data + (m->omsg.h.numQuestions ? NormalMaxDNSMessageData : AbsoluteMaxDNSMessageData);
                                        // We forecast: compressed name (2) type (2) class (2) TTL (4) rdlength (2) rdata (n)
                                        mDNSu32 forecast = answerforecast + 12 + ar->resrec.rdestimate;
                                        mDNSu8 *newptr = putQuestion(&m->omsg, queryptr, limit - forecast, ar->resrec.name, kDNSQType_ANY, (mDNSu16)(ar->resrec.rrclass | ucbit));
                                        if (newptr)
                                                {
                                                queryptr       = newptr;
                                                answerforecast = forecast;
                                                ar->SendRNow = (ar->resrec.InterfaceID) ? mDNSNULL : GetNextActiveInterfaceID(intf);
                                                ar->IncludeInProbe = mDNStrue;
                                                verbosedebugf("SendQueries:   Put Question %##s (%s) probecount %d",
                                                        ar->resrec.name->c, DNSTypeName(ar->resrec.rrtype), ar->ProbeCount);
                                                }
                                        }
                        }

                // Put our known answer list (either new one from this question or questions, or remainder of old one from last time)
                while (KnownAnswerList)
                        {
                        CacheRecord *ka = KnownAnswerList;
                        mDNSu32 SecsSinceRcvd = ((mDNSu32)(m->timenow - ka->TimeRcvd)) / mDNSPlatformOneSecond;
                        mDNSu8 *newptr = PutResourceRecordTTLWithLimit(&m->omsg, queryptr, &m->omsg.h.numAnswers,
                                &ka->resrec, ka->resrec.rroriginalttl - SecsSinceRcvd, m->omsg.data + NormalMaxDNSMessageData - OwnerRecordSpace);
                        if (newptr)
                                {
                                verbosedebugf("SendQueries:   Put %##s (%s) at %d - %d",
                                        ka->resrec.name->c, DNSTypeName(ka->resrec.rrtype), queryptr - m->omsg.data, newptr - m->omsg.data);
                                queryptr = newptr;
                                KnownAnswerList = ka->NextInKAList;
                                ka->NextInKAList = mDNSNULL;
                                }
                        else
                                {
                                // If we ran out of space and we have more than one question in the packet, that's an error --
                                // we shouldn't have put more than one question if there was a risk of us running out of space.
                                if (m->omsg.h.numQuestions > 1)
                                        LogMsg("SendQueries:   Put %d answers; No more space for known answers", m->omsg.h.numAnswers);
                                m->omsg.h.flags.b[0] |= kDNSFlag0_TC;
                                break;
                                }
                        }

                for (ar = m->ResourceRecords; ar; ar=ar->next)
                        if (ar->IncludeInProbe)
                                {
                                mDNSu8 *newptr = PutResourceRecord(&m->omsg, queryptr, &m->omsg.h.numAuthorities, &ar->resrec);
                                ar->IncludeInProbe = mDNSfalse;
                                if (newptr) queryptr = newptr;
                                else LogMsg("SendQueries:   How did we fail to have space for the Update record %s", ARDisplayString(m,ar));
                                }

                if (queryptr > m->omsg.data)
                        {
                        if (OwnerRecordSpace)
                                {
                                AuthRecord opt;
                                mDNS_SetupResourceRecord(&opt, mDNSNULL, mDNSInterface_Any, kDNSType_OPT, kStandardTTL, kDNSRecordTypeKnownUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
                                opt.resrec.rrclass    = NormalMaxDNSMessageData;
                                opt.resrec.rdlength   = sizeof(rdataOPT);       // One option in this OPT record
                                opt.resrec.rdestimate = sizeof(rdataOPT);
                                SetupOwnerOpt(m, intf, &opt.resrec.rdata->u.opt[0]);
                                LogSPS("SendQueries putting %s", ARDisplayString(m, &opt));
                                queryptr = PutResourceRecordTTLWithLimit(&m->omsg, queryptr, &m->omsg.h.numAdditionals,
                                        &opt.resrec, opt.resrec.rroriginalttl, m->omsg.data + AbsoluteMaxDNSMessageData);
                                if (!queryptr)
                                        LogMsg("SendQueries: How did we fail to have space for the OPT record (%d/%d/%d/%d) %s",
                                                m->omsg.h.numQuestions, m->omsg.h.numAnswers, m->omsg.h.numAuthorities, m->omsg.h.numAdditionals, ARDisplayString(m, &opt));
                                if (queryptr > m->omsg.data + NormalMaxDNSMessageData)
                                        if (m->omsg.h.numQuestions != 1 || m->omsg.h.numAnswers != 0 || m->omsg.h.numAuthorities != 1 || m->omsg.h.numAdditionals != 1)
                                                LogMsg("SendQueries: Why did we generate oversized packet with OPT record %p %p %p (%d/%d/%d/%d) %s",
                                                        m->omsg.data, m->omsg.data + NormalMaxDNSMessageData, queryptr,
                                                        m->omsg.h.numQuestions, m->omsg.h.numAnswers, m->omsg.h.numAuthorities, m->omsg.h.numAdditionals, ARDisplayString(m, &opt));
                                }

                        if ((m->omsg.h.flags.b[0] & kDNSFlag0_TC) && m->omsg.h.numQuestions > 1)
                                LogMsg("SendQueries: Should not have more than one question (%d) in a truncated packet", m->omsg.h.numQuestions);
                        debugf("SendQueries:   Sending %d Question%s %d Answer%s %d Update%s on %p",
                                m->omsg.h.numQuestions,   m->omsg.h.numQuestions   == 1 ? "" : "s",
                                m->omsg.h.numAnswers,     m->omsg.h.numAnswers     == 1 ? "" : "s",
                                m->omsg.h.numAuthorities, m->omsg.h.numAuthorities == 1 ? "" : "s", intf->InterfaceID);
                        if (intf->IPv4Available) mDNSSendDNSMessage(m, &m->omsg, queryptr, intf->InterfaceID, mDNSNULL, &AllDNSLinkGroup_v4, MulticastDNSPort, mDNSNULL, mDNSNULL);
                        if (intf->IPv6Available) mDNSSendDNSMessage(m, &m->omsg, queryptr, intf->InterfaceID, mDNSNULL, &AllDNSLinkGroup_v6, MulticastDNSPort, mDNSNULL, mDNSNULL);
                        if (!m->SuppressSending) m->SuppressSending = NonZeroTime(m->timenow + (mDNSPlatformOneSecond+9)/10);
                        if (++pktcount >= 1000)
                                { LogMsg("SendQueries exceeded loop limit %d: giving up", pktcount); break; }
                        // There might be more records left in the known answer list, or more questions to send
                        // on this interface, so go around one more time and try again.
                        }
                else    // Nothing more to send on this interface; go to next
                        {
                        const NetworkInterfaceInfo *next = GetFirstActiveInterface(intf->next);
                        #if MDNS_DEBUGMSGS && 0
                        const char *const msg = next ? "SendQueries:   Nothing more on %p; moving to %p" : "SendQueries:   Nothing more on %p";
                        debugf(msg, intf, next);
                        #endif
                        intf = next;
                        }
                }

        // 4. Final housekeeping
        
        // 4a. Debugging check: Make sure we announced all our records
        for (ar = m->ResourceRecords; ar; ar=ar->next)
                if (ar->SendRNow)
                        {
                        if (ar->ARType != AuthRecordLocalOnly && ar->ARType != AuthRecordP2P)
                                LogMsg("SendQueries: No active interface %p to send probe: %p %s", ar->SendRNow, ar->resrec.InterfaceID, ARDisplayString(m, ar));
                        ar->SendRNow = mDNSNULL;
                        }

        // 4b. When we have lingering cache records that we're keeping around for a few seconds in the hope
        // that their interface which went away might come back again, the logic will want to send queries
        // for those records, but we can't because their interface isn't here any more, so to keep the
        // state machine ticking over we just pretend we did so.
        // If the interface does not come back in time, the cache record will expire naturally
        FORALL_CACHERECORDS(slot, cg, cr)
                if (cr->CRActiveQuestion && cr->UnansweredQueries < MaxUnansweredQueries)
                        if (m->timenow + TicksTTL(cr)/50 - cr->NextRequiredQuery >= 0)
                                {
                                cr->UnansweredQueries++;
                                cr->CRActiveQuestion->SendQNow = mDNSNULL;
                                SetNextCacheCheckTimeForRecord(m, cr);
                                }

        // 4c. Debugging check: Make sure we sent all our planned questions
        // Do this AFTER the lingering cache records check above, because that will prevent spurious warnings for questions
        // we legitimately couldn't send because the interface is no longer available
        for (q = m->Questions; q; q=q->next)
                if (q->SendQNow)
                        {
                        DNSQuestion *x;
                        for (x = m->NewQuestions; x; x=x->next) if (x == q) break;      // Check if this question is a NewQuestion
                        LogMsg("SendQueries: No active interface %p to send %s question: %p %##s (%s)", q->SendQNow, x ? "new" : "old", q->InterfaceID, q->qname.c, DNSTypeName(q->qtype));
                        q->SendQNow = mDNSNULL;
                        }
        }

mDNSlocal void SendWakeup(mDNS *const m, mDNSInterfaceID InterfaceID, mDNSEthAddr *EthAddr, mDNSOpaque48 *password)
        {
        int i, j;
        mDNSu8 *ptr = m->omsg.data;
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);
        if (!intf) { LogMsg("SendARP: No interface with InterfaceID %p found", InterfaceID); return; }

        // 0x00 Destination address
        for (i=0; i<6; i++) *ptr++ = EthAddr->b[i];

        // 0x06 Source address (Note: Since we don't currently set the BIOCSHDRCMPLT option, BPF will fill in the real interface address for us)
        for (i=0; i<6; i++) *ptr++ = intf->MAC.b[0];

        // 0x0C Ethertype (0x0842)
        *ptr++ = 0x08;
        *ptr++ = 0x42;

        // 0x0E Wakeup sync sequence
        for (i=0; i<6; i++) *ptr++ = 0xFF;

        // 0x14 Wakeup data
        for (j=0; j<16; j++) for (i=0; i<6; i++) *ptr++ = EthAddr->b[i];

        // 0x74 Password
        for (i=0; i<6; i++) *ptr++ = password->b[i];

        mDNSPlatformSendRawPacket(m->omsg.data, ptr, InterfaceID);

        // For Ethernet switches that don't flood-foward packets with unknown unicast destination MAC addresses,
        // broadcast is the only reliable way to get a wakeup packet to the intended target machine.
        // For 802.11 WPA networks, where a sleeping target machine may have missed a broadcast/multicast
        // key rotation, unicast is the only way to get a wakeup packet to the intended target machine.
        // So, we send one of each, unicast first, then broadcast second.
        for (i=0; i<6; i++) m->omsg.data[i] = 0xFF;
        mDNSPlatformSendRawPacket(m->omsg.data, ptr, InterfaceID);
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - RR List Management & Task Management
#endif

// Whenever a question is answered, reset its state so that we don't query
// the network repeatedly. This happens first time when we answer the question and
// and later when we refresh the cache.
mDNSlocal void ResetQuestionState(mDNS *const m, DNSQuestion *q)
        {
        q->LastQTime        = m->timenow;
        q->LastQTxTime      = m->timenow;
        q->RecentAnswerPkts = 0;
        q->ThisQInterval    = MaxQuestionInterval;
        q->RequestUnicast   = mDNSfalse;
        // Reset unansweredQueries so that we don't penalize this server later when we
        // start sending queries when the cache expires.
        q->unansweredQueries = 0;
        debugf("ResetQuestionState: Set MaxQuestionInterval for %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
        }

// Note: AnswerCurrentQuestionWithResourceRecord can call a user callback, which may change the record list and/or question list.
// Any code walking either list must use the m->CurrentQuestion (and possibly m->CurrentRecord) mechanism to protect against this.
// In fact, to enforce this, the routine will *only* answer the question currently pointed to by m->CurrentQuestion,
// which will be auto-advanced (possibly to NULL) if the client callback cancels the question.
mDNSexport void AnswerCurrentQuestionWithResourceRecord(mDNS *const m, CacheRecord *const rr, const QC_result AddRecord)
        {
        DNSQuestion *const q = m->CurrentQuestion;
        mDNSBool followcname = FollowCNAME(q, &rr->resrec, AddRecord);

        verbosedebugf("AnswerCurrentQuestionWithResourceRecord:%4lu %s TTL %d %s",
                q->CurrentAnswers, AddRecord ? "Add" : "Rmv", rr->resrec.rroriginalttl, CRDisplayString(m, rr));

        // Normally we don't send out the unicast query if we have answered using our local only auth records e.g., /etc/hosts.
        // But if the query for "A" record has a local answer but query for "AAAA" record has no local answer, we might
        // send the AAAA query out which will come back with CNAME and will also answer the "A" query. To prevent that,
        // we check to see if that query already has a unique local answer.
        if (q->LOAddressAnswers)
                {
                LogInfo("AnswerCurrentQuestionWithResourceRecord: Question %p %##s (%s) not answering with record %s due to "
                        "LOAddressAnswers %d", q, q->qname.c, DNSTypeName(q->qtype), ARDisplayString(m, rr),
                        q->LOAddressAnswers);
                return;
                }

        if (QuerySuppressed(q))
                {
                // If the query is suppressed, then we don't want to answer from the cache. But if this query is
                // supposed to time out, we still want to callback the clients. We do this only for TimeoutQuestions
                // that are timing out, which we know are answered with Negative cache record when timing out.
                if (!q->TimeoutQuestion || rr->resrec.RecordType != kDNSRecordTypePacketNegative || (m->timenow - q->StopTime < 0))
                        return;
                }

        // Note: Use caution here. In the case of records with rr->DelayDelivery set, AnswerCurrentQuestionWithResourceRecord(... mDNStrue)
        // may be called twice, once when the record is received, and again when it's time to notify local clients.
        // If any counters or similar are added here, care must be taken to ensure that they are not double-incremented by this.

        rr->LastUsed = m->timenow;
        if (AddRecord == QC_add && !q->DuplicateOf && rr->CRActiveQuestion != q)
                {
                if (!rr->CRActiveQuestion) m->rrcache_active++; // If not previously active, increment rrcache_active count
                debugf("AnswerCurrentQuestionWithResourceRecord: Updating CRActiveQuestion from %p to %p for cache record %s, CurrentAnswer %d",
                        rr->CRActiveQuestion, q, CRDisplayString(m,rr), q->CurrentAnswers);
                rr->CRActiveQuestion = q;                                               // We know q is non-null
                SetNextCacheCheckTimeForRecord(m, rr);
                }

        // If this is:
        // (a) a no-cache add, where we've already done at least one 'QM' query, or
        // (b) a normal add, where we have at least one unique-type answer,
        // then there's no need to keep polling the network.
        // (If we have an answer in the cache, then we'll automatically ask again in time to stop it expiring.)
        // We do this for mDNS questions and uDNS one-shot questions, but not for
        // uDNS LongLived questions, because that would mess up our LLQ lease renewal timing.
        if ((AddRecord == QC_addnocache && !q->RequestUnicast) ||
                (AddRecord == QC_add && (q->ExpectUnique || (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask))))
                if (ActiveQuestion(q) && (mDNSOpaque16IsZero(q->TargetQID) || !q->LongLived))
                        {
                        ResetQuestionState(m, q);
                        }

        if (rr->DelayDelivery) return;          // We'll come back later when CacheRecordDeferredAdd() calls us

        // Only deliver negative answers if client has explicitly requested them
        if (rr->resrec.RecordType == kDNSRecordTypePacketNegative || (q->qtype != kDNSType_NSEC && RRAssertsNonexistence(&rr->resrec, q->qtype)))
                if (!AddRecord || !q->ReturnIntermed) return;

        // For CNAME results to non-CNAME questions, only inform the client if they explicitly requested that
        if (q->QuestionCallback && !q->NoAnswer && (!followcname || q->ReturnIntermed))
                {
                mDNS_DropLockBeforeCallback();          // Allow client (and us) to legally make mDNS API calls
                if (q->qtype != kDNSType_NSEC && RRAssertsNonexistence(&rr->resrec, q->qtype))
                        {
                        CacheRecord neg;
                        MakeNegativeCacheRecord(m, &neg, &q->qname, q->qnamehash, q->qtype, q->qclass, 1, rr->resrec.InterfaceID, q->qDNSServer);
                        q->QuestionCallback(m, q, &neg.resrec, AddRecord);
                        }
                else
                        q->QuestionCallback(m, q, &rr->resrec, AddRecord);
                mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                }
        // Note: Proceed with caution here because client callback function is allowed to do anything,
        // including starting/stopping queries, registering/deregistering records, etc.

        if (followcname && m->CurrentQuestion == q)
                AnswerQuestionByFollowingCNAME(m, q, &rr->resrec);
        }

// New Questions are answered through AnswerNewQuestion. But there may not have been any
// matching cache records for the questions when it is called. There are two possibilities.
//
// 1) There are no cache records
// 2) There are cache records but the DNSServers between question and cache record don't match.
//
// In the case of (1), where there are no cache records and later we add them when we get a response,
// CacheRecordAdd/CacheRecordDeferredAdd will take care of adding the cache and delivering the ADD
// events to the application. If we already have a cache entry, then no ADD events are delivered
// unless the RDATA has changed
//
// In the case of (2) where we had the cache records and did not answer because of the DNSServer mismatch,
// we need to answer them whenever we change the DNSServer.  But we can't do it at the instant the DNSServer
// changes because when we do the callback, the question can get deleted and the calling function would not
// know how to handle it. So, we run this function from mDNS_Execute to handle DNSServer changes on the
// question

mDNSlocal void AnswerQuestionsForDNSServerChanges(mDNS *const m)
        {
        DNSQuestion *q;
        DNSQuestion *qnext;
        CacheRecord *rr;
        mDNSu32 slot;
        CacheGroup *cg;

        if (m->CurrentQuestion)
                LogMsg("AnswerQuestionsForDNSServerChanges: ERROR m->CurrentQuestion already set: %##s (%s)",
                                m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));

        for (q = m->Questions; q && q != m->NewQuestions; q = qnext)
                {
                qnext = q->next;

                // multicast or DNSServers did not change.
                if (mDNSOpaque16IsZero(q->TargetQID)) continue;
                if (!q->deliverAddEvents) continue;

                // We are going to look through the cache for this question since it changed
                // its DNSserver last time. Reset it so that we don't call them again. Calling
                // them again will deliver duplicate events to the application
                q->deliverAddEvents = mDNSfalse;
                if (QuerySuppressed(q)) continue;
                m->CurrentQuestion = q;
                slot = HashSlot(&q->qname);
                cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                        {
                        if (SameNameRecordAnswersQuestion(&rr->resrec, q))
                                {
                                LogInfo("AnswerQuestionsForDNSServerChanges: Calling AnswerCurrentQuestionWithResourceRecord for question %p %##s using resource record %s",
                                        q, q->qname.c, CRDisplayString(m, rr));
                                // When this question penalizes a DNS server and has no more DNS servers to pick, we normally
                                // deliver a negative cache response and suspend the question for 60 seconds (see uDNS_CheckCurrentQuestion).
                                // But sometimes we may already find the negative cache entry and deliver that here as the process
                                // of changing DNS servers. When the cache entry is about to expire, we will resend the question and
                                // that time, we need to make sure that we have a valid DNS server. Otherwise, we will deliver
                                // a negative cache response without trying the server.
                                if (!q->qDNSServer && !q->DuplicateOf && rr->resrec.RecordType == kDNSRecordTypePacketNegative)
                                        {
                                        DNSQuestion *qptr;
                                        SetValidDNSServers(m, q);
                                        q->qDNSServer = GetServerForQuestion(m, q);
                                        for (qptr = q->next ; qptr; qptr = qptr->next)
                                                if (qptr->DuplicateOf == q) { qptr->validDNSServers = q->validDNSServers; qptr->qDNSServer = q->qDNSServer; }
                                        }
                                q->CurrentAnswers++;
                                if (rr->resrec.rdlength > SmallRecordLimit) q->LargeAnswers++;
                                if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) q->UniqueAnswers++;
                                AnswerCurrentQuestionWithResourceRecord(m, rr, QC_add);
                                if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                                }
                        }
                }
                m->CurrentQuestion = mDNSNULL;
        }

mDNSlocal void CacheRecordDeferredAdd(mDNS *const m, CacheRecord *rr)
        {
        rr->DelayDelivery = 0;
        if (m->CurrentQuestion)
                LogMsg("CacheRecordDeferredAdd ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
                {
                DNSQuestion *q = m->CurrentQuestion;
                if (ResourceRecordAnswersQuestion(&rr->resrec, q))
                        AnswerCurrentQuestionWithResourceRecord(m, rr, QC_add);
                if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                        m->CurrentQuestion = q->next;
                }
        m->CurrentQuestion = mDNSNULL;
        }

mDNSlocal mDNSs32 CheckForSoonToExpireRecords(mDNS *const m, const domainname *const name, const mDNSu32 namehash, const mDNSu32 slot)
        {
        const mDNSs32 threshhold = m->timenow + mDNSPlatformOneSecond;  // See if there are any records expiring within one second
        const mDNSs32 start      = m->timenow - 0x10000000;
        mDNSs32 delay = start;
        CacheGroup *cg = CacheGroupForName(m, slot, namehash, name);
        const CacheRecord *rr;
        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                if (threshhold - RRExpireTime(rr) >= 0)         // If we have records about to expire within a second
                        if (delay - RRExpireTime(rr) < 0)               // then delay until after they've been deleted
                                delay = RRExpireTime(rr);
        if (delay - start > 0) return(NonZeroTime(delay));
        else return(0);
        }

// CacheRecordAdd is only called from CreateNewCacheEntry, *never* directly as a result of a client API call.
// If new questions are created as a result of invoking client callbacks, they will be added to
// the end of the question list, and m->NewQuestions will be set to indicate the first new question.
// rr is a new CacheRecord just received into our cache
// (kDNSRecordTypePacketAns/PacketAnsUnique/PacketAdd/PacketAddUnique).
// Note: CacheRecordAdd calls AnswerCurrentQuestionWithResourceRecord which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void CacheRecordAdd(mDNS *const m, CacheRecord *rr)
        {
        DNSQuestion *q;

        // We stop when we get to NewQuestions -- if we increment their CurrentAnswers/LargeAnswers/UniqueAnswers
        // counters here we'll end up double-incrementing them when we do it again in AnswerNewQuestion().
        for (q = m->Questions; q && q != m->NewQuestions; q=q->next)
                {
                if (ResourceRecordAnswersQuestion(&rr->resrec, q))
                        {
                        // If this question is one that's actively sending queries, and it's received ten answers within one
                        // second of sending the last query packet, then that indicates some radical network topology change,
                        // so reset its exponential backoff back to the start. We must be at least at the eight-second interval
                        // to do this. If we're at the four-second interval, or less, there's not much benefit accelerating
                        // because we will anyway send another query within a few seconds. The first reset query is sent out
                        // randomized over the next four seconds to reduce possible synchronization between machines.
                        if (q->LastAnswerPktNum != m->PktNum)
                                {
                                q->LastAnswerPktNum = m->PktNum;
                                if (mDNSOpaque16IsZero(q->TargetQID) && ActiveQuestion(q) && ++q->RecentAnswerPkts >= 10 &&
                                        q->ThisQInterval > InitialQuestionInterval * QuestionIntervalStep3 && m->timenow - q->LastQTxTime < mDNSPlatformOneSecond)
                                        {
                                        LogMsg("CacheRecordAdd: %##s (%s) got immediate answer burst (%d); restarting exponential backoff sequence (%d)",
                                                q->qname.c, DNSTypeName(q->qtype), q->RecentAnswerPkts, q->ThisQInterval);
                                        q->LastQTime      = m->timenow - InitialQuestionInterval + (mDNSs32)mDNSRandom((mDNSu32)mDNSPlatformOneSecond*4);
                                        q->ThisQInterval  = InitialQuestionInterval;
                                        SetNextQueryTime(m,q);
                                        }
                                }
                        verbosedebugf("CacheRecordAdd %p %##s (%s) %lu %#a:%d question %p", rr, rr->resrec.name->c,
                                DNSTypeName(rr->resrec.rrtype), rr->resrec.rroriginalttl, rr->resrec.rDNSServer ?
                                &rr->resrec.rDNSServer->addr : mDNSNULL, mDNSVal16(rr->resrec.rDNSServer ?
                                rr->resrec.rDNSServer->port : zeroIPPort), q);
                        q->CurrentAnswers++;
                        q->unansweredQueries = 0;
                        if (rr->resrec.rdlength > SmallRecordLimit) q->LargeAnswers++;
                        if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) q->UniqueAnswers++;
                        if (q->CurrentAnswers > 4000)
                                {
                                static int msgcount = 0;
                                if (msgcount++ < 10)
                                        LogMsg("CacheRecordAdd: %##s (%s) has %d answers; shedding records to resist DOS attack",
                                                q->qname.c, DNSTypeName(q->qtype), q->CurrentAnswers);
                                rr->resrec.rroriginalttl = 0;
                                rr->UnansweredQueries = MaxUnansweredQueries;
                                }
                        }
                }

        if (!rr->DelayDelivery)
                {
                if (m->CurrentQuestion)
                        LogMsg("CacheRecordAdd ERROR m->CurrentQuestion already set: %##s (%s)", m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
                m->CurrentQuestion = m->Questions;
                while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
                        {
                        q = m->CurrentQuestion;
                        if (ResourceRecordAnswersQuestion(&rr->resrec, q))
                                AnswerCurrentQuestionWithResourceRecord(m, rr, QC_add);
                        if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                                m->CurrentQuestion = q->next;
                        }
                m->CurrentQuestion = mDNSNULL;
                }

        SetNextCacheCheckTimeForRecord(m, rr);
        }

// NoCacheAnswer is only called from mDNSCoreReceiveResponse, *never* directly as a result of a client API call.
// If new questions are created as a result of invoking client callbacks, they will be added to
// the end of the question list, and m->NewQuestions will be set to indicate the first new question.
// rr is a new CacheRecord just received from the wire (kDNSRecordTypePacketAns/AnsUnique/Add/AddUnique)
// but we don't have any place to cache it. We'll deliver question 'add' events now, but we won't have any
// way to deliver 'remove' events in future, nor will we be able to include this in known-answer lists,
// so we immediately bump ThisQInterval up to MaxQuestionInterval to avoid pounding the network.
// Note: NoCacheAnswer calls AnswerCurrentQuestionWithResourceRecord which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void NoCacheAnswer(mDNS *const m, CacheRecord *rr)
        {
        LogMsg("No cache space: Delivering non-cached result for %##s", m->rec.r.resrec.name->c);
        if (m->CurrentQuestion)
                LogMsg("NoCacheAnswer ERROR m->CurrentQuestion already set: %##s (%s)", m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        // We do this for *all* questions, not stopping when we get to m->NewQuestions,
        // since we're not caching the record and we'll get no opportunity to do this later
        while (m->CurrentQuestion)
                {
                DNSQuestion *q = m->CurrentQuestion;
                if (ResourceRecordAnswersQuestion(&rr->resrec, q))
                        AnswerCurrentQuestionWithResourceRecord(m, rr, QC_addnocache);  // QC_addnocache means "don't expect remove events for this"
                if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                        m->CurrentQuestion = q->next;
                }
        m->CurrentQuestion = mDNSNULL;
        }

// CacheRecordRmv is only called from CheckCacheExpiration, which is called from mDNS_Execute.
// Note that CacheRecordRmv is *only* called for records that are referenced by at least one active question.
// If new questions are created as a result of invoking client callbacks, they will be added to
// the end of the question list, and m->NewQuestions will be set to indicate the first new question.
// rr is an existing cache CacheRecord that just expired and is being deleted
// (kDNSRecordTypePacketAns/PacketAnsUnique/PacketAdd/PacketAddUnique).
// Note: CacheRecordRmv calls AnswerCurrentQuestionWithResourceRecord which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void CacheRecordRmv(mDNS *const m, CacheRecord *rr)
        {
        if (m->CurrentQuestion)
                LogMsg("CacheRecordRmv ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;

        // We stop when we get to NewQuestions -- for new questions their CurrentAnswers/LargeAnswers/UniqueAnswers counters
        // will all still be zero because we haven't yet gone through the cache counting how many answers we have for them.
        while (m->CurrentQuestion && m->CurrentQuestion != m->NewQuestions)
                {
                DNSQuestion *q = m->CurrentQuestion;
                // When a question enters suppressed state, we generate RMV events and generate a negative
                // response. A cache may be present that answers this question e.g., cache entry generated
                // before the question became suppressed. We need to skip the suppressed questions here as
                // the RMV event has already been generated.
                if (!QuerySuppressed(q) && ResourceRecordAnswersQuestion(&rr->resrec, q))
                        {
                        verbosedebugf("CacheRecordRmv %p %s", rr, CRDisplayString(m, rr));
                        q->FlappingInterface1 = mDNSNULL;
                        q->FlappingInterface2 = mDNSNULL;
                
                        // When a question changes DNS server, it is marked with deliverAddEvents if we find any
                        // cache entry corresponding to the new DNS server. Before we deliver the ADD event, the
                        // cache entry may be removed in which case CurrentAnswers can be zero.
                        if (q->deliverAddEvents && !q->CurrentAnswers)
                                {
                                LogInfo("CacheRecordRmv: Question %p %##s (%s) deliverAddEvents set, DNSServer %#a:%d",
                                        q, q->qname.c, DNSTypeName(q->qtype), q->qDNSServer ? &q->qDNSServer->addr : mDNSNULL,
                                        mDNSVal16(q->qDNSServer ? q->qDNSServer->port : zeroIPPort));
                                m->CurrentQuestion = q->next;
                                continue;
                                }
                        if (q->CurrentAnswers == 0)
                                LogMsg("CacheRecordRmv ERROR!!: How can CurrentAnswers already be zero for %p %##s (%s) DNSServer %#a:%d",
                                        q, q->qname.c, DNSTypeName(q->qtype), q->qDNSServer ? &q->qDNSServer->addr : mDNSNULL,
                                        mDNSVal16(q->qDNSServer ? q->qDNSServer->port : zeroIPPort));
                        else
                                {
                                q->CurrentAnswers--;
                                if (rr->resrec.rdlength > SmallRecordLimit) q->LargeAnswers--;
                                if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) q->UniqueAnswers--;
                                }
                        if (rr->resrec.rdata->MaxRDLength) // Never generate "remove" events for negative results
                                {
                                if (q->CurrentAnswers == 0)
                                        {
                                        LogInfo("CacheRecordRmv: Last answer for %##s (%s) expired from cache; will reconfirm antecedents",
                                                q->qname.c, DNSTypeName(q->qtype));
                                        ReconfirmAntecedents(m, &q->qname, q->qnamehash, 0);
                                        }
                                AnswerCurrentQuestionWithResourceRecord(m, rr, QC_rmv);
                                }
                        }
                if (m->CurrentQuestion == q)    // If m->CurrentQuestion was not auto-advanced, do it ourselves now
                        m->CurrentQuestion = q->next;
                }
        m->CurrentQuestion = mDNSNULL;
        }

mDNSlocal void ReleaseCacheEntity(mDNS *const m, CacheEntity *e)
        {
#if APPLE_OSX_mDNSResponder && MACOSX_MDNS_MALLOC_DEBUGGING >= 1
        unsigned int i;
        for (i=0; i<sizeof(*e); i++) ((char*)e)[i] = 0xFF;
#endif
        e->next = m->rrcache_free;
        m->rrcache_free = e;
        m->rrcache_totalused--;
        }

mDNSlocal void ReleaseCacheGroup(mDNS *const m, CacheGroup **cp)
        {
        CacheEntity *e = (CacheEntity *)(*cp);
        //LogMsg("ReleaseCacheGroup:  Releasing CacheGroup for %p, %##s", (*cp)->name->c, (*cp)->name->c);
        if ((*cp)->rrcache_tail != &(*cp)->members)
                LogMsg("ERROR: (*cp)->members == mDNSNULL but (*cp)->rrcache_tail != &(*cp)->members)");
        //if ((*cp)->name != (domainname*)((*cp)->namestorage))
        //      LogMsg("ReleaseCacheGroup: %##s, %p %p", (*cp)->name->c, (*cp)->name, (domainname*)((*cp)->namestorage));
        if ((*cp)->name != (domainname*)((*cp)->namestorage)) mDNSPlatformMemFree((*cp)->name);
        (*cp)->name = mDNSNULL;
        *cp = (*cp)->next;                      // Cut record from list
        ReleaseCacheEntity(m, e);
        }

mDNSlocal void ReleaseCacheRecord(mDNS *const m, CacheRecord *r)
        {
        //LogMsg("ReleaseCacheRecord: Releasing %s", CRDisplayString(m, r));
        if (r->resrec.rdata && r->resrec.rdata != (RData*)&r->smallrdatastorage) mDNSPlatformMemFree(r->resrec.rdata);
        r->resrec.rdata = mDNSNULL;
        ReleaseCacheEntity(m, (CacheEntity *)r);
        }

// Note: We want to be careful that we deliver all the CacheRecordRmv calls before delivering
// CacheRecordDeferredAdd calls. The in-order nature of the cache lists ensures that all
// callbacks for old records are delivered before callbacks for newer records.
mDNSlocal void CheckCacheExpiration(mDNS *const m, const mDNSu32 slot, CacheGroup *const cg)
        {
        CacheRecord **rp = &cg->members;

        if (m->lock_rrcache) { LogMsg("CheckCacheExpiration ERROR! Cache already locked!"); return; }
        m->lock_rrcache = 1;

        while (*rp)
                {
                CacheRecord *const rr = *rp;
                mDNSs32 event = RRExpireTime(rr);
                if (m->timenow - event >= 0)    // If expired, delete it
                        {
                        *rp = rr->next;                         // Cut it from the list
                        verbosedebugf("CheckCacheExpiration: Deleting%7d %7d %p %s",
                                m->timenow - rr->TimeRcvd, rr->resrec.rroriginalttl, rr->CRActiveQuestion, CRDisplayString(m, rr));
                        if (rr->CRActiveQuestion)       // If this record has one or more active questions, tell them it's going away
                                {
                                DNSQuestion *q = rr->CRActiveQuestion;
                                // When a cache record is about to expire, we expect to do four queries at 80-82%, 85-87%, 90-92% and
                                // then 95-97% of the TTL. If the DNS server does not respond, then we will remove the cache entry
                                // before we pick a new DNS server. As the question interval is set to MaxQuestionInterval, we may
                                // not send out a query anytime soon. Hence, we need to reset the question interval. If this is
                                // a normal deferred ADD case, then AnswerCurrentQuestionWithResourceRecord will reset it to
                                // MaxQuestionInterval. If we have inactive questions referring to negative cache entries,
                                // don't ressurect them as they will deliver duplicate "No such Record" ADD events
                                if (!mDNSOpaque16IsZero(q->TargetQID) && !q->LongLived && ActiveQuestion(q))
                                        {
                                        q->ThisQInterval = InitialQuestionInterval;
                                        q->LastQTime     = m->timenow - q->ThisQInterval;
                                        SetNextQueryTime(m, q);
                                        }
                                CacheRecordRmv(m, rr);
                                m->rrcache_active--;
                                }
                        ReleaseCacheRecord(m, rr);
                        }
                else                                                    // else, not expired; see if we need to query
                        {
                        // If waiting to delay delivery, do nothing until then
                        if (rr->DelayDelivery && rr->DelayDelivery - m->timenow > 0)
                                event = rr->DelayDelivery;
                        else
                                {
                                if (rr->DelayDelivery) CacheRecordDeferredAdd(m, rr);
                                if (rr->CRActiveQuestion && rr->UnansweredQueries < MaxUnansweredQueries)
                                        {
                                        if (m->timenow - rr->NextRequiredQuery < 0)             // If not yet time for next query
                                                event = NextCacheCheckEvent(rr);                        // then just record when we want the next query
                                        else                                                                                    // else trigger our question to go out now
                                                {
                                                // Set NextScheduledQuery to timenow so that SendQueries() will run.
                                                // SendQueries() will see that we have records close to expiration, and send FEQs for them.
                                                m->NextScheduledQuery = m->timenow;
                                                // After sending the query we'll increment UnansweredQueries and call SetNextCacheCheckTimeForRecord(),
                                                // which will correctly update m->NextCacheCheck for us.
                                                event = m->timenow + 0x3FFFFFFF;
                                                }
                                        }
                                }
                        verbosedebugf("CheckCacheExpiration:%6d %5d %s",
                                (event - m->timenow) / mDNSPlatformOneSecond, CacheCheckGracePeriod(rr), CRDisplayString(m, rr));
                        if (m->rrcache_nextcheck[slot] - event > 0)
                                m->rrcache_nextcheck[slot] = event;
                        rp = &rr->next;
                        }
                }
        if (cg->rrcache_tail != rp) verbosedebugf("CheckCacheExpiration: Updating CacheGroup tail from %p to %p", cg->rrcache_tail, rp);
        cg->rrcache_tail = rp;
        m->lock_rrcache = 0;
        }

mDNSlocal void AnswerNewQuestion(mDNS *const m)
        {
        mDNSBool ShouldQueryImmediately = mDNStrue;
        DNSQuestion *const q = m->NewQuestions;         // Grab the question we're going to answer
        mDNSu32 slot = HashSlot(&q->qname);
        CacheGroup *const cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
        AuthRecord *lr;
        AuthGroup *ag;
        mDNSBool AnsweredFromCache = mDNSfalse;

        verbosedebugf("AnswerNewQuestion: Answering %##s (%s)", q->qname.c, DNSTypeName(q->qtype));

        if (cg) CheckCacheExpiration(m, slot, cg);
        if (m->NewQuestions != q) { LogInfo("AnswerNewQuestion: Question deleted while doing CheckCacheExpiration"); goto exit; }
        m->NewQuestions = q->next;
        // Advance NewQuestions to the next *after* calling CheckCacheExpiration, because if we advance it first
        // then CheckCacheExpiration may give this question add/remove callbacks, and it's not yet ready for that.
        //
        // Also, CheckCacheExpiration() calls CacheRecordDeferredAdd() and CacheRecordRmv(), which invoke
        // client callbacks, which may delete their own or any other question. Our mechanism for detecting
        // whether our current m->NewQuestions question got deleted by one of these callbacks is to store the
        // value of m->NewQuestions in 'q' before calling CheckCacheExpiration(), and then verify afterwards
        // that they're still the same. If m->NewQuestions has changed (because mDNS_StopQuery_internal
        // advanced it), that means the question was deleted, so we no longer need to worry about answering
        // it (and indeed 'q' is now a dangling pointer, so dereferencing it at all would be bad, and the
        // values we computed for slot and cg are now stale and relate to a question that no longer exists).
        //
        // We can't use the usual m->CurrentQuestion mechanism for this because  CacheRecordDeferredAdd() and
        // CacheRecordRmv() both use that themselves when walking the list of (non-new) questions generating callbacks.
        // Fortunately mDNS_StopQuery_internal auto-advances both m->CurrentQuestion *AND* m->NewQuestions when
        // deleting a question, so luckily we have an easy alternative way of detecting if our question got deleted.
        
        if (m->lock_rrcache) LogMsg("AnswerNewQuestion ERROR! Cache already locked!");
        // This should be safe, because calling the client's question callback may cause the
        // question list to be modified, but should not ever cause the rrcache list to be modified.
        // If the client's question callback deletes the question, then m->CurrentQuestion will
        // be advanced, and we'll exit out of the loop
        m->lock_rrcache = 1;
        if (m->CurrentQuestion)
                LogMsg("AnswerNewQuestion ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = q;         // Indicate which question we're answering, so we'll know if it gets deleted

        if (q->NoAnswer == NoAnswer_Fail)
                {
                LogMsg("AnswerNewQuestion: NoAnswer_Fail %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                MakeNegativeCacheRecord(m, &m->rec.r, &q->qname, q->qnamehash, q->qtype, q->qclass, 60, mDNSInterface_Any, q->qDNSServer);
                q->NoAnswer = NoAnswer_Normal;          // Temporarily turn off answer suppression
                AnswerCurrentQuestionWithResourceRecord(m, &m->rec.r, QC_addnocache);
                // Don't touch the question if it has been stopped already
                if (m->CurrentQuestion == q) q->NoAnswer = NoAnswer_Fail;               // Restore NoAnswer state
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }
        if (m->CurrentQuestion != q) { LogInfo("AnswerNewQuestion: Question deleted while generating NoAnswer_Fail response"); goto exit; }

        // See if we want to tell it about LocalOnly records
        if (m->CurrentRecord)
                LogMsg("AnswerNewQuestion ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        slot = AuthHashSlot(&q->qname);
        ag = AuthGroupForName(&m->rrauth, slot, q->qnamehash, &q->qname);
        if (ag)
                {
                m->CurrentRecord = ag->members;
                while (m->CurrentRecord && m->CurrentRecord != ag->NewLocalOnlyRecords)
                        {
                        AuthRecord *rr = m->CurrentRecord;
                        m->CurrentRecord = rr->next;
                        //
                        // If the question is mDNSInterface_LocalOnly, all records local to the machine should be used
                        // to answer the query. This is handled in AnswerNewLocalOnlyQuestion.
                        //
                        // We handle mDNSInterface_Any and scoped questions here. See LocalOnlyRecordAnswersQuestion for more
                        // details on how we handle this case. For P2P we just handle "Interface_Any" questions. For LocalOnly
                        // we handle both mDNSInterface_Any and scoped questions.

                        if (rr->ARType == AuthRecordLocalOnly || (rr->ARType == AuthRecordP2P && q->InterfaceID == mDNSInterface_Any))
                                if (LocalOnlyRecordAnswersQuestion(rr, q))
                                        {
                                        AnswerLocalQuestionWithLocalAuthRecord(m, rr, mDNStrue);
                                        if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                                        }
                        }
                }
        m->CurrentRecord = mDNSNULL;
        
        if (m->CurrentQuestion != q) { LogInfo("AnswerNewQuestion: Question deleted while while giving LocalOnly record answers"); goto exit; }

        if (q->LOAddressAnswers)
                {
                LogInfo("AnswerNewQuestion: Question %p %##s (%s) answered using local auth records LOAddressAnswers %d",
                        q, q->qname.c, DNSTypeName(q->qtype), q->LOAddressAnswers);
                goto exit;
                }

        // Before we go check the cache and ship this query on the wire, we have to be sure that there are
        // no local records that could possibly answer this question. As we did not check the NewLocalRecords, we
        // need to just peek at them to see whether it will answer this question. If it would answer, pretend
        // that we answered. AnswerAllLocalQuestionsWithLocalAuthRecord will answer shortly. This happens normally
        // when we add new /etc/hosts entries and restart the question. It is a new question and also a new record.
        if (ag)
                {
                lr = ag->NewLocalOnlyRecords;
                while (lr)
                        {
                        if (LORecordAnswersAddressType(lr) && LocalOnlyRecordAnswersQuestion(lr, q))
                                {
                                LogInfo("AnswerNewQuestion: Question %p %##s (%s) will be answered using new local auth records "
                                        " LOAddressAnswers %d", q, q->qname.c, DNSTypeName(q->qtype), q->LOAddressAnswers);
                                goto exit;
                                }
                        lr = lr->next;
                        }
                }
        

        // If we are not supposed to answer this question, generate a negative response.
        // Temporarily suspend the SuppressQuery so that AnswerCurrentQuestionWithResourceRecord can answer the question
        if (QuerySuppressed(q)) { q->SuppressQuery = mDNSfalse; GenerateNegativeResponse(m); q->SuppressQuery = mDNStrue; }
        else
                {
                CacheRecord *rr;
                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                        if (SameNameRecordAnswersQuestion(&rr->resrec, q))
                                {
                                // SecsSinceRcvd is whole number of elapsed seconds, rounded down
                                mDNSu32 SecsSinceRcvd = ((mDNSu32)(m->timenow - rr->TimeRcvd)) / mDNSPlatformOneSecond;
                                if (rr->resrec.rroriginalttl <= SecsSinceRcvd)
                                        {
                                        LogMsg("AnswerNewQuestion: How is rr->resrec.rroriginalttl %lu <= SecsSinceRcvd %lu for %s %d %d",
                                                rr->resrec.rroriginalttl, SecsSinceRcvd, CRDisplayString(m, rr), m->timenow, rr->TimeRcvd);
                                        continue;       // Go to next one in loop
                                        }
        
                                // If this record set is marked unique, then that means we can reasonably assume we have the whole set
                                // -- we don't need to rush out on the network and query immediately to see if there are more answers out there
                                if ((rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) || (q->ExpectUnique))
                                        ShouldQueryImmediately = mDNSfalse;
                                q->CurrentAnswers++;
                                if (rr->resrec.rdlength > SmallRecordLimit) q->LargeAnswers++;
                                if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) q->UniqueAnswers++;
                                AnsweredFromCache = mDNStrue;
                                AnswerCurrentQuestionWithResourceRecord(m, rr, QC_add);
                                if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                                }
                        else if (RRTypeIsAddressType(rr->resrec.rrtype) && RRTypeIsAddressType(q->qtype))
                                ShouldQueryImmediately = mDNSfalse;
                }
        // We don't use LogInfo for this "Question deleted" message because it happens so routinely that
        // it's not remotely remarkable, and therefore unlikely to be of much help tracking down bugs.
        if (m->CurrentQuestion != q) { debugf("AnswerNewQuestion: Question deleted while giving cache answers"); goto exit; }

        // Neither a local record nor a cache entry could answer this question. If this question need to be retried
        // with search domains, generate a negative response which will now retry after appending search domains.
        // If the query was suppressed above, we already generated a negative response. When it gets unsuppressed,
        // we will retry with search domains.
        if (!QuerySuppressed(q) && !AnsweredFromCache && q->RetryWithSearchDomains)
                {
                LogInfo("AnswerNewQuestion: Generating response for retrying with search domains %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                GenerateNegativeResponse(m);
                }

        if (m->CurrentQuestion != q) { debugf("AnswerNewQuestion: Question deleted while giving negative answer"); goto exit; }

        // Note: When a query gets suppressed or retried with search domains, we de-activate the question.
        // Hence we don't execute the following block of code for those cases.
        if (ShouldQueryImmediately && ActiveQuestion(q))
                {
                debugf("AnswerNewQuestion: ShouldQueryImmediately %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                q->ThisQInterval  = InitialQuestionInterval;
                q->LastQTime      = m->timenow - q->ThisQInterval;
                if (mDNSOpaque16IsZero(q->TargetQID))           // For mDNS, spread packets to avoid a burst of simultaneous queries
                        {
                        // Compute random delay in the range 1-6 seconds, then divide by 50 to get 20-120ms
                        if (!m->RandomQueryDelay)
                                m->RandomQueryDelay = (mDNSPlatformOneSecond + mDNSRandom(mDNSPlatformOneSecond*5) - 1) / 50 + 1;
                        q->LastQTime += m->RandomQueryDelay;
                        }
                }

        // IN ALL CASES make sure that m->NextScheduledQuery is set appropriately.
        // In cases where m->NewQuestions->DelayAnswering is set, we may have delayed generating our
        // answers for this question until *after* its scheduled transmission time, in which case
        // m->NextScheduledQuery may now be set to 'never', and in that case -- even though we're *not* doing
        // ShouldQueryImmediately -- we still need to make sure we set m->NextScheduledQuery correctly.
        SetNextQueryTime(m,q);

exit:
        m->CurrentQuestion = mDNSNULL;
        m->lock_rrcache = 0;
        }

// When a NewLocalOnlyQuestion is created, AnswerNewLocalOnlyQuestion runs though our ResourceRecords delivering any
// appropriate answers, stopping if it reaches a NewLocalOnlyRecord -- these will be handled by AnswerAllLocalQuestionsWithLocalAuthRecord
mDNSlocal void AnswerNewLocalOnlyQuestion(mDNS *const m)
        {
        mDNSu32 slot;
        AuthGroup *ag;
        DNSQuestion *q = m->NewLocalOnlyQuestions;              // Grab the question we're going to answer
        m->NewLocalOnlyQuestions = q->next;                             // Advance NewLocalOnlyQuestions to the next (if any)

        debugf("AnswerNewLocalOnlyQuestion: Answering %##s (%s)", q->qname.c, DNSTypeName(q->qtype));

        if (m->CurrentQuestion)
                LogMsg("AnswerNewLocalOnlyQuestion ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = q;         // Indicate which question we're answering, so we'll know if it gets deleted

        if (m->CurrentRecord)
                LogMsg("AnswerNewLocalOnlyQuestion ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));

        // 1. First walk the LocalOnly records answering the LocalOnly question
        // 2. As LocalOnly questions should also be answered by any other Auth records local to the machine,
        //    walk the ResourceRecords list delivering the answers
        slot = AuthHashSlot(&q->qname);
        ag = AuthGroupForName(&m->rrauth, slot, q->qnamehash, &q->qname);
        if (ag)
                {
                m->CurrentRecord = ag->members;
                while (m->CurrentRecord && m->CurrentRecord != ag->NewLocalOnlyRecords)
                        {
                        AuthRecord *rr = m->CurrentRecord;
                        m->CurrentRecord = rr->next;
                        if (LocalOnlyRecordAnswersQuestion(rr, q))
                                {
                                AnswerLocalQuestionWithLocalAuthRecord(m, rr, mDNStrue);
                                if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                                }
                        }
                }

        if (m->CurrentQuestion == q)
                {
                m->CurrentRecord = m->ResourceRecords;

                while (m->CurrentRecord && m->CurrentRecord != m->NewLocalRecords)
                        {
                        AuthRecord *rr = m->CurrentRecord;
                        m->CurrentRecord = rr->next;
                        if (ResourceRecordAnswersQuestion(&rr->resrec, q))
                                {
                                AnswerLocalQuestionWithLocalAuthRecord(m, rr, mDNStrue);
                                if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                                }
                        }
                }

        m->CurrentQuestion = mDNSNULL;
        m->CurrentRecord   = mDNSNULL;
        }

mDNSlocal CacheEntity *GetCacheEntity(mDNS *const m, const CacheGroup *const PreserveCG)
        {
        CacheEntity *e = mDNSNULL;

        if (m->lock_rrcache) { LogMsg("GetFreeCacheRR ERROR! Cache already locked!"); return(mDNSNULL); }
        m->lock_rrcache = 1;
        
        // If we have no free records, ask the client layer to give us some more memory
        if (!m->rrcache_free && m->MainCallback)
                {
                if (m->rrcache_totalused != m->rrcache_size)
                        LogMsg("GetFreeCacheRR: count mismatch: m->rrcache_totalused %lu != m->rrcache_size %lu",
                                m->rrcache_totalused, m->rrcache_size);
                
                // We don't want to be vulnerable to a malicious attacker flooding us with an infinite
                // number of bogus records so that we keep growing our cache until the machine runs out of memory.
                // To guard against this, if our cache grows above 512kB (approx 3168 records at 164 bytes each),
                // and we're actively using less than 1/32 of that cache, then we purge all the unused records
                // and recycle them, instead of allocating more memory.
                if (m->rrcache_size > 5000 && m->rrcache_size / 32 > m->rrcache_active)
                        LogInfo("Possible denial-of-service attack in progress: m->rrcache_size %lu; m->rrcache_active %lu",
                                m->rrcache_size, m->rrcache_active);
                else
                        {
                        mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                        m->MainCallback(m, mStatus_GrowCache);
                        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                        }
                }
        
        // If we still have no free records, recycle all the records we can.
        // Enumerating the entire cache is moderately expensive, so when we do it, we reclaim all the records we can in one pass.
        if (!m->rrcache_free)
                {
                mDNSu32 oldtotalused = m->rrcache_totalused;
                mDNSu32 slot;
                for (slot = 0; slot < CACHE_HASH_SLOTS; slot++)
                        {
                        CacheGroup **cp = &m->rrcache_hash[slot];
                        while (*cp)
                                {
                                CacheRecord **rp = &(*cp)->members;
                                while (*rp)
                                        {
                                        // Records that answer still-active questions are not candidates for recycling
                                        // Records that are currently linked into the CacheFlushRecords list may not be recycled, or we'll crash
                                        if ((*rp)->CRActiveQuestion || (*rp)->NextInCFList)
                                                rp=&(*rp)->next;
                                        else
                                                {
                                                CacheRecord *rr = *rp;
                                                *rp = (*rp)->next;                      // Cut record from list
                                                ReleaseCacheRecord(m, rr);
                                                }
                                        }
                                if ((*cp)->rrcache_tail != rp)
                                        verbosedebugf("GetFreeCacheRR: Updating rrcache_tail[%lu] from %p to %p", slot, (*cp)->rrcache_tail, rp);
                                (*cp)->rrcache_tail = rp;
                                if ((*cp)->members || (*cp)==PreserveCG) cp=&(*cp)->next;
                                else ReleaseCacheGroup(m, cp);
                                }
                        }
                LogInfo("GetCacheEntity recycled %d records to reduce cache from %d to %d",
                        oldtotalused - m->rrcache_totalused, oldtotalused, m->rrcache_totalused);
                }

        if (m->rrcache_free)    // If there are records in the free list, take one
                {
                e = m->rrcache_free;
                m->rrcache_free = e->next;
                if (++m->rrcache_totalused >= m->rrcache_report)
                        {
                        LogInfo("RR Cache now using %ld objects", m->rrcache_totalused);
                        if      (m->rrcache_report <  100) m->rrcache_report += 10;
                        else if (m->rrcache_report < 1000) m->rrcache_report += 100;
                        else                               m->rrcache_report += 1000;
                        }
                mDNSPlatformMemZero(e, sizeof(*e));
                }

        m->lock_rrcache = 0;

        return(e);
        }

mDNSlocal CacheRecord *GetCacheRecord(mDNS *const m, CacheGroup *cg, mDNSu16 RDLength)
        {
        CacheRecord *r = (CacheRecord *)GetCacheEntity(m, cg);
        if (r)
                {
                r->resrec.rdata = (RData*)&r->smallrdatastorage;        // By default, assume we're usually going to be using local storage
                if (RDLength > InlineCacheRDSize)                       // If RDLength is too big, allocate extra storage
                        {
                        r->resrec.rdata = (RData*)mDNSPlatformMemAllocate(sizeofRDataHeader + RDLength);
                        if (r->resrec.rdata) r->resrec.rdata->MaxRDLength = r->resrec.rdlength = RDLength;
                        else { ReleaseCacheEntity(m, (CacheEntity*)r); r = mDNSNULL; }
                        }
                }
        return(r);
        }

mDNSlocal CacheGroup *GetCacheGroup(mDNS *const m, const mDNSu32 slot, const ResourceRecord *const rr)
        {
        mDNSu16 namelen = DomainNameLength(rr->name);
        CacheGroup *cg = (CacheGroup*)GetCacheEntity(m, mDNSNULL);
        if (!cg) { LogMsg("GetCacheGroup: Failed to allocate memory for %##s", rr->name->c); return(mDNSNULL); }
        cg->next         = m->rrcache_hash[slot];
        cg->namehash     = rr->namehash;
        cg->members      = mDNSNULL;
        cg->rrcache_tail = &cg->members;
        cg->name         = (domainname*)cg->namestorage;
        //LogMsg("GetCacheGroup: %-10s %d-byte cache name %##s",
        //      (namelen > InlineCacheGroupNameSize) ? "Allocating" : "Inline", namelen, rr->name->c);
        if (namelen > InlineCacheGroupNameSize) cg->name = mDNSPlatformMemAllocate(namelen);
        if (!cg->name)
                {
                LogMsg("GetCacheGroup: Failed to allocate name storage for %##s", rr->name->c);
                ReleaseCacheEntity(m, (CacheEntity*)cg);
                return(mDNSNULL);
                }
        AssignDomainName(cg->name, rr->name);

        if (CacheGroupForRecord(m, slot, rr)) LogMsg("GetCacheGroup: Already have CacheGroup for %##s", rr->name->c);
        m->rrcache_hash[slot] = cg;
        if (CacheGroupForRecord(m, slot, rr) != cg) LogMsg("GetCacheGroup: Not finding CacheGroup for %##s", rr->name->c);
        
        return(cg);
        }

mDNSexport void mDNS_PurgeCacheResourceRecord(mDNS *const m, CacheRecord *rr)
        {
        if (m->mDNS_busy != m->mDNS_reentrancy+1)
                LogMsg("mDNS_PurgeCacheResourceRecord: Lock not held! mDNS_busy (%ld) mDNS_reentrancy (%ld)", m->mDNS_busy, m->mDNS_reentrancy);
        // Make sure we mark this record as thoroughly expired -- we don't ever want to give
        // a positive answer using an expired record (e.g. from an interface that has gone away).
        // We don't want to clear CRActiveQuestion here, because that would leave the record subject to
        // summary deletion without giving the proper callback to any questions that are monitoring it.
        // By setting UnansweredQueries to MaxUnansweredQueries we ensure it won't trigger any further expiration queries.
        rr->TimeRcvd          = m->timenow - mDNSPlatformOneSecond * 60;
        rr->UnansweredQueries = MaxUnansweredQueries;
        rr->resrec.rroriginalttl     = 0;
        SetNextCacheCheckTimeForRecord(m, rr);
        }

mDNSexport mDNSs32 mDNS_TimeNow(const mDNS *const m)
        {
        mDNSs32 time;
        mDNSPlatformLock(m);
        if (m->mDNS_busy)
                {
                LogMsg("mDNS_TimeNow called while holding mDNS lock. This is incorrect. Code protected by lock should just use m->timenow.");
                if (!m->timenow) LogMsg("mDNS_TimeNow: m->mDNS_busy is %ld but m->timenow not set", m->mDNS_busy);
                }
        
        if (m->timenow) time = m->timenow;
        else            time = mDNS_TimeNow_NoLock(m);
        mDNSPlatformUnlock(m);
        return(time);
        }

// To avoid pointless CPU thrash, we use SetSPSProxyListChanged(X) to record the last interface that
// had its Sleep Proxy client list change, and defer to actual BPF reconfiguration to mDNS_Execute().
// (GetNextScheduledEvent() returns "now" when m->SPSProxyListChanged is set)
#define SetSPSProxyListChanged(X) do { \
        if (m->SPSProxyListChanged && m->SPSProxyListChanged != (X)) mDNSPlatformUpdateProxyList(m, m->SPSProxyListChanged); \
        m->SPSProxyListChanged = (X); } while(0)

// Called from mDNS_Execute() to expire stale proxy records
mDNSlocal void CheckProxyRecords(mDNS *const m, AuthRecord *list)
        {
        m->CurrentRecord = list;
        while (m->CurrentRecord)
                {
                AuthRecord *rr = m->CurrentRecord;
                if (rr->resrec.RecordType != kDNSRecordTypeDeregistering && rr->WakeUp.HMAC.l[0])
                        {
                        // If m->SPSSocket is NULL that means we're not acting as a sleep proxy any more,
                        // so we need to cease proxying for *all* records we may have, expired or not.
                        if (m->SPSSocket && m->timenow - rr->TimeExpire < 0)    // If proxy record not expired yet, update m->NextScheduledSPS
                                {
                                if (m->NextScheduledSPS - rr->TimeExpire > 0)
                                        m->NextScheduledSPS = rr->TimeExpire;
                                }
                        else                                                                                                    // else proxy record expired, so remove it
                                {
                                LogSPS("CheckProxyRecords: Removing %d H-MAC %.6a I-MAC %.6a %d %s",
                                        m->ProxyRecords, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, rr->WakeUp.seq, ARDisplayString(m, rr));
                                SetSPSProxyListChanged(rr->resrec.InterfaceID);
                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
                                // Don't touch rr after this -- memory may have been free'd
                                }
                        }
                // Mustn't advance m->CurrentRecord until *after* mDNS_Deregister_internal, because
                // new records could have been added to the end of the list as a result of that call.
                if (m->CurrentRecord == rr) // If m->CurrentRecord was not advanced for us, do it now
                        m->CurrentRecord = rr->next;
                }
        }

mDNSlocal void CheckRmvEventsForLocalRecords(mDNS *const m)
        {
        while (m->CurrentRecord)
                {
                AuthRecord *rr = m->CurrentRecord;
                if (rr->AnsweredLocalQ && rr->resrec.RecordType == kDNSRecordTypeDeregistering)
                        {
                        debugf("CheckRmvEventsForLocalRecords: Generating local RMV events for %s", ARDisplayString(m, rr));
                        rr->resrec.RecordType = kDNSRecordTypeShared;
                        AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNSfalse);
                        if (m->CurrentRecord == rr)     // If rr still exists in list, restore its state now
                                {
                                rr->resrec.RecordType = kDNSRecordTypeDeregistering;
                                rr->AnsweredLocalQ = mDNSfalse;
                                // SendResponses normally calls CompleteDeregistration after sending goodbyes.
                                // For LocalOnly records, we don't do that and hence we need to do that here.
                                if (RRLocalOnly(rr)) CompleteDeregistration(m, rr);
                                }
                        }
                if (m->CurrentRecord == rr)             // If m->CurrentRecord was not auto-advanced, do it ourselves now
                        m->CurrentRecord = rr->next;
                }
        }

mDNSlocal void TimeoutQuestions(mDNS *const m)
        {
        m->NextScheduledStopTime = m->timenow + 0x3FFFFFFF;
        if (m->CurrentQuestion)
                LogMsg("TimeoutQuestions ERROR m->CurrentQuestion already set: %##s (%s)", m->CurrentQuestion->qname.c,
                        DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        while (m->CurrentQuestion)
                {
                DNSQuestion *const q = m->CurrentQuestion;
                if (q->StopTime)
                        {
                        if (m->timenow - q->StopTime >= 0)
                                {
                                LogInfo("TimeoutQuestions: question %##s timed out, time %d", q->qname.c, m->timenow - q->StopTime);
                                GenerateNegativeResponse(m);
                                if (m->CurrentQuestion == q) q->StopTime = 0;
                                }
                        else
                                {
                                if (m->NextScheduledStopTime - q->StopTime > 0)
                                        m->NextScheduledStopTime = q->StopTime;
                                }
                        }
                // If m->CurrentQuestion wasn't modified out from under us, advance it now
                // We can't do this at the start of the loop because GenerateNegativeResponse
                // depends on having m->CurrentQuestion point to the right question
                if (m->CurrentQuestion == q)
                        m->CurrentQuestion = q->next;
                }
        m->CurrentQuestion = mDNSNULL;
        }

mDNSexport mDNSs32 mDNS_Execute(mDNS *const m)
        {
        mDNS_Lock(m);   // Must grab lock before trying to read m->timenow

        if (m->timenow - m->NextScheduledEvent >= 0)
                {
                int i;
                AuthRecord *head, *tail;
                mDNSu32 slot;
                AuthGroup *ag;

                verbosedebugf("mDNS_Execute");

                if (m->CurrentQuestion)
                        LogMsg("mDNS_Execute: ERROR m->CurrentQuestion already set: %##s (%s)",
                                m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        
                if (m->CurrentRecord)
                        LogMsg("mDNS_Execute: ERROR m->CurrentRecord already set: %s", ARDisplayString(m, m->CurrentRecord));
        
                // 1. If we're past the probe suppression time, we can clear it
                if (m->SuppressProbes && m->timenow - m->SuppressProbes >= 0) m->SuppressProbes = 0;
        
                // 2. If it's been more than ten seconds since the last probe failure, we can clear the counter
                if (m->NumFailedProbes && m->timenow - m->ProbeFailTime >= mDNSPlatformOneSecond * 10) m->NumFailedProbes = 0;
                
                // 3. Purge our cache of stale old records
                if (m->rrcache_size && m->timenow - m->NextCacheCheck >= 0)
                        {
                        mDNSu32 numchecked = 0;
                        m->NextCacheCheck = m->timenow + 0x3FFFFFFF;
                        for (slot = 0; slot < CACHE_HASH_SLOTS; slot++)
                                {
                                if (m->timenow - m->rrcache_nextcheck[slot] >= 0)
                                        {
                                        CacheGroup **cp = &m->rrcache_hash[slot];
                                        m->rrcache_nextcheck[slot] = m->timenow + 0x3FFFFFFF;
                                        while (*cp)
                                                {
                                                debugf("m->NextCacheCheck %4d Slot %3d %##s", numchecked, slot, *cp ? (*cp)->name : (domainname*)"\x04NULL");
                                                numchecked++;
                                                CheckCacheExpiration(m, slot, *cp);
                                                if ((*cp)->members) cp=&(*cp)->next;
                                                else ReleaseCacheGroup(m, cp);
                                                }
                                        }
                                // Even if we didn't need to actually check this slot yet, still need to
                                // factor its nextcheck time into our overall NextCacheCheck value
                                if (m->NextCacheCheck - m->rrcache_nextcheck[slot] > 0)
                                        m->NextCacheCheck = m->rrcache_nextcheck[slot];
                                }
                        debugf("m->NextCacheCheck %4d checked, next in %d", numchecked, m->NextCacheCheck - m->timenow);
                        }
        
                if (m->timenow - m->NextScheduledSPS >= 0)
                        {
                        m->NextScheduledSPS = m->timenow + 0x3FFFFFFF;
                        CheckProxyRecords(m, m->DuplicateRecords);      // Clear m->DuplicateRecords first, then m->ResourceRecords
                        CheckProxyRecords(m, m->ResourceRecords);
                        }

                SetSPSProxyListChanged(mDNSNULL);               // Perform any deferred BPF reconfiguration now

                // Clear AnnounceOwner if necessary. (Do this *before* SendQueries() and SendResponses().)
                if (m->AnnounceOwner && m->timenow - m->AnnounceOwner >= 0) m->AnnounceOwner = 0;

                if (m->DelaySleep && m->timenow - m->DelaySleep >= 0)
                        {
                        m->DelaySleep = 0;
                        if (m->SleepState == SleepState_Transferring)
                                {
                                LogSPS("Re-sleep delay passed; now checking for Sleep Proxy Servers");
                                BeginSleepProcessing(m);
                                }
                        }

                // 4. See if we can answer any of our new local questions from the cache
                for (i=0; m->NewQuestions && i<1000; i++)
                        {
                        if (m->NewQuestions->DelayAnswering && m->timenow - m->NewQuestions->DelayAnswering < 0) break;
                        AnswerNewQuestion(m);
                        }
                if (i >= 1000) LogMsg("mDNS_Execute: AnswerNewQuestion exceeded loop limit");

                // Make sure we deliver *all* local RMV events, and clear the corresponding rr->AnsweredLocalQ flags, *before*
                // we begin generating *any* new ADD events in the m->NewLocalOnlyQuestions and m->NewLocalRecords loops below.
                for (i=0; i<1000 && m->LocalRemoveEvents; i++)
                        {
                        m->LocalRemoveEvents = mDNSfalse;
                        m->CurrentRecord = m->ResourceRecords;
                        CheckRmvEventsForLocalRecords(m);
                        // Walk the LocalOnly records and deliver the RMV events
                        for (slot = 0; slot < AUTH_HASH_SLOTS; slot++)
                                for (ag = m->rrauth.rrauth_hash[slot]; ag; ag = ag->next)
                                        {
                                        m->CurrentRecord = ag->members;
                                        if (m->CurrentRecord) CheckRmvEventsForLocalRecords(m);
                                        }
                        }

                if (i >= 1000) LogMsg("mDNS_Execute: m->LocalRemoveEvents exceeded loop limit");
                                
                for (i=0; m->NewLocalOnlyQuestions && i<1000; i++) AnswerNewLocalOnlyQuestion(m);
                if (i >= 1000) LogMsg("mDNS_Execute: AnswerNewLocalOnlyQuestion exceeded loop limit");

                head = tail = mDNSNULL;
                for (i=0; i<1000 && m->NewLocalRecords && m->NewLocalRecords != head; i++)
                        {
                        AuthRecord *rr = m->NewLocalRecords;
                        m->NewLocalRecords = m->NewLocalRecords->next;
                        if (LocalRecordReady(rr))
                                {
                                debugf("mDNS_Execute: Delivering Add event with LocalAuthRecord %s", ARDisplayString(m, rr));
                                AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNStrue);
                                }
                        else if (!rr->next)
                                {
                                // If we have just one record that is not ready, we don't have to unlink and
                                // reinsert. As the NewLocalRecords will be NULL for this case, the loop will
                                // terminate and set the NewLocalRecords to rr.
                                debugf("mDNS_Execute: Just one LocalAuthRecord %s, breaking out of the loop early", ARDisplayString(m, rr));
                                if (head != mDNSNULL || m->NewLocalRecords != mDNSNULL)
                                        LogMsg("mDNS_Execute: ERROR!!: head %p, NewLocalRecords %p", head, m->NewLocalRecords);
                                        
                                head = rr;
                                }
                        else
                                {
                                AuthRecord **p = &m->ResourceRecords;   // Find this record in our list of active records
                                debugf("mDNS_Execute: Skipping LocalAuthRecord %s", ARDisplayString(m, rr));
                                // if this is the first record we are skipping, move to the end of the list.
                                // if we have already skipped records before, append it at the end.
                                while (*p && *p != rr) p=&(*p)->next;
                                if (*p) *p = rr->next;                                  // Cut this record from the list
                                else { LogMsg("mDNS_Execute: ERROR!! Cannot find record %s in ResourceRecords list", ARDisplayString(m, rr)); break; }
                                if (!head)
                                        {
                                        while (*p) p=&(*p)->next;
                                        *p = rr;
                                        head = tail = rr;
                                        }
                                else
                                        {
                                        tail->next = rr;
                                        tail = rr;
                                        }
                                rr->next = mDNSNULL;
                                }
                        }
                m->NewLocalRecords = head;
                debugf("mDNS_Execute: Setting NewLocalRecords to %s", (head ? ARDisplayString(m, head) : "NULL"));

                if (i >= 1000) LogMsg("mDNS_Execute: m->NewLocalRecords exceeded loop limit");

                // Check to see if we have any new LocalOnly/P2P records to examine for delivering
                // to our local questions
                if (m->NewLocalOnlyRecords)
                        {
                        m->NewLocalOnlyRecords = mDNSfalse;
                        for (slot = 0; slot < AUTH_HASH_SLOTS; slot++)
                                for (ag = m->rrauth.rrauth_hash[slot]; ag; ag = ag->next)
                                        {
                                        for (i=0; i<100 && ag->NewLocalOnlyRecords; i++)
                                                {
                                                AuthRecord *rr = ag->NewLocalOnlyRecords;
                                                ag->NewLocalOnlyRecords = ag->NewLocalOnlyRecords->next;
                                                // LocalOnly records should always be ready as they never probe
                                                if (LocalRecordReady(rr))
                                                        {
                                                        debugf("mDNS_Execute: Delivering Add event with LocalAuthRecord %s", ARDisplayString(m, rr));
                                                        AnswerAllLocalQuestionsWithLocalAuthRecord(m, rr, mDNStrue);
                                                        }
                                                else LogMsg("mDNS_Execute: LocalOnlyRecord %s not ready", ARDisplayString(m, rr));
                                                }
                                        // We limit about 100 per AuthGroup that can be serviced at a time
                                        if (i >= 100) LogMsg("mDNS_Execute: ag->NewLocalOnlyRecords exceeded loop limit");
                                        }
                        }

                // 5. Some questions may have picked a new DNS server and the cache may answer these questions now.
                AnswerQuestionsForDNSServerChanges(m);

                // 6. See what packets we need to send
                if (m->mDNSPlatformStatus != mStatus_NoError || (m->SleepState == SleepState_Sleeping))
                        DiscardDeregistrations(m);
                if (m->mDNSPlatformStatus == mStatus_NoError && (m->SuppressSending == 0 || m->timenow - m->SuppressSending >= 0))
                        {
                        // If the platform code is ready, and we're not suppressing packet generation right now
                        // then send our responses, probes, and questions.
                        // We check the cache first, because there might be records close to expiring that trigger questions to refresh them.
                        // We send queries next, because there might be final-stage probes that complete their probing here, causing
                        // them to advance to announcing state, and we want those to be included in any announcements we send out.
                        // Finally, we send responses, including the previously mentioned records that just completed probing.
                        m->SuppressSending = 0;
        
                        // 7. Send Query packets. This may cause some probing records to advance to announcing state
                        if (m->timenow - m->NextScheduledQuery >= 0 || m->timenow - m->NextScheduledProbe >= 0) SendQueries(m);
                        if (m->timenow - m->NextScheduledQuery >= 0)
                                {
                                DNSQuestion *q;
                                LogMsg("mDNS_Execute: SendQueries didn't send all its queries (%d - %d = %d) will try again in one second",
                                        m->timenow, m->NextScheduledQuery, m->timenow - m->NextScheduledQuery);
                                m->NextScheduledQuery = m->timenow + mDNSPlatformOneSecond;
                                for (q = m->Questions; q && q != m->NewQuestions; q=q->next)
                                        if (ActiveQuestion(q) && m->timenow - NextQSendTime(q) >= 0)
                                                LogMsg("mDNS_Execute: SendQueries didn't send %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                                }
                        if (m->timenow - m->NextScheduledProbe >= 0)
                                {
                                LogMsg("mDNS_Execute: SendQueries didn't send all its probes (%d - %d = %d) will try again in one second",
                                        m->timenow, m->NextScheduledProbe, m->timenow - m->NextScheduledProbe);
                                m->NextScheduledProbe = m->timenow + mDNSPlatformOneSecond;
                                }
        
                        // 8. Send Response packets, including probing records just advanced to announcing state
                        if (m->timenow - m->NextScheduledResponse >= 0) SendResponses(m);
                        if (m->timenow - m->NextScheduledResponse >= 0)
                                {
                                LogMsg("mDNS_Execute: SendResponses didn't send all its responses; will try again in one second");
                                m->NextScheduledResponse = m->timenow + mDNSPlatformOneSecond;
                                }
                        }

                // Clear RandomDelay values, ready to pick a new different value next time
                m->RandomQueryDelay     = 0;
                m->RandomReconfirmDelay = 0;

                if (m->NextScheduledStopTime && m->timenow - m->NextScheduledStopTime >= 0) TimeoutQuestions(m);
#ifndef UNICAST_DISABLED
                if (m->NextSRVUpdate && m->timenow - m->NextSRVUpdate >= 0) UpdateAllSRVRecords(m);
                if (m->timenow - m->NextScheduledNATOp >= 0) CheckNATMappings(m);
                if (m->timenow - m->NextuDNSEvent >= 0) uDNS_Tasks(m);
#endif
                }

        // Note about multi-threaded systems:
        // On a multi-threaded system, some other thread could run right after the mDNS_Unlock(),
        // performing mDNS API operations that change our next scheduled event time.
        //
        // On multi-threaded systems (like the current Windows implementation) that have a single main thread
        // calling mDNS_Execute() (and other threads allowed to call mDNS API routines) it is the responsibility
        // of the mDNSPlatformUnlock() routine to signal some kind of stateful condition variable that will
        // signal whatever blocking primitive the main thread is using, so that it will wake up and execute one
        // more iteration of its loop, and immediately call mDNS_Execute() again. The signal has to be stateful
        // in the sense that if the main thread has not yet entered its blocking primitive, then as soon as it
        // does, the state of the signal will be noticed, causing the blocking primitive to return immediately
        // without blocking. This avoids the race condition between the signal from the other thread arriving
        // just *before* or just *after* the main thread enters the blocking primitive.
        //
        // On multi-threaded systems (like the current Mac OS 9 implementation) that are entirely timer-driven,
        // with no main mDNS_Execute() thread, it is the responsibility of the mDNSPlatformUnlock() routine to
        // set the timer according to the m->NextScheduledEvent value, and then when the timer fires, the timer
        // callback function should call mDNS_Execute() (and ignore the return value, which may already be stale
        // by the time it gets to the timer callback function).

        mDNS_Unlock(m);         // Calling mDNS_Unlock is what gives m->NextScheduledEvent its new value
        return(m->NextScheduledEvent);
        }

mDNSlocal void SuspendLLQs(mDNS *m)
        {
        DNSQuestion *q;
        for (q = m->Questions; q; q = q->next)
                if (ActiveQuestion(q) && !mDNSOpaque16IsZero(q->TargetQID) && q->LongLived && q->state == LLQ_Established)
                        { q->ReqLease = 0; sendLLQRefresh(m, q); }
        }

mDNSlocal mDNSBool QuestionHasLocalAnswers(mDNS *const m, DNSQuestion *q)
        {
        AuthRecord *rr;
        mDNSu32 slot;
        AuthGroup *ag;

        slot = AuthHashSlot(&q->qname);
        ag = AuthGroupForName(&m->rrauth, slot, q->qnamehash, &q->qname);
        if (ag)
                {
                for (rr = ag->members; rr; rr=rr->next)
                        // Filter the /etc/hosts records - LocalOnly, Unique, A/AAAA/CNAME
                        if (LORecordAnswersAddressType(rr) && LocalOnlyRecordAnswersQuestion(rr, q))
                                {
                                LogInfo("QuestionHasLocalAnswers: Question %p %##s (%s) has local answer %s", q, q->qname.c, DNSTypeName(q->qtype), ARDisplayString(m, rr));
                                return mDNStrue;
                                }
                }
        return mDNSfalse;
        }

// ActivateUnicastQuery() is called from three places:
// 1. When a new question is created
// 2. On wake from sleep
// 3. When the DNS configuration changes
// In case 1 we don't want to mess with our established ThisQInterval and LastQTime (ScheduleImmediately is false)
// In cases 2 and 3 we do want to cause the question to be resent immediately (ScheduleImmediately is true)
mDNSlocal void ActivateUnicastQuery(mDNS *const m, DNSQuestion *const question, mDNSBool ScheduleImmediately)
        {
        // For now this AutoTunnel stuff is specific to Mac OS X.
        // In the future, if there's demand, we may see if we can abstract it out cleanly into the platform layer
#if APPLE_OSX_mDNSResponder
        // Even though BTMM client tunnels are only useful for AAAA queries, we need to treat v4 and v6 queries equally.
        // Otherwise we can get the situation where the A query completes really fast (with an NXDOMAIN result) and the
        // caller then gives up waiting for the AAAA result while we're still in the process of setting up the tunnel.
        // To level the playing field, we block both A and AAAA queries while tunnel setup is in progress, and then
        // returns results for both at the same time. If we are looking for the _autotunnel6 record, then skip this logic
        // as this would trigger looking up _autotunnel6._autotunnel6 and end up failing the original query.

        if (RRTypeIsAddressType(question->qtype) && PrivateQuery(question) &&
                !SameDomainLabel(question->qname.c, (const mDNSu8 *)"\x0c_autotunnel6")&& question->QuestionCallback != AutoTunnelCallback)
                {
                question->NoAnswer = NoAnswer_Suspended;
                AddNewClientTunnel(m, question);
                return;
                }
#endif // APPLE_OSX_mDNSResponder

        if (!question->DuplicateOf)
                {
                debugf("ActivateUnicastQuery: %##s %s%s%s",
                        question->qname.c, DNSTypeName(question->qtype), PrivateQuery(question) ? " (Private)" : "", ScheduleImmediately ? " ScheduleImmediately" : "");
                question->CNAMEReferrals = 0;
                if (question->nta) { CancelGetZoneData(m, question->nta); question->nta = mDNSNULL; }
                if (question->LongLived)
                        {
                        question->state = LLQ_InitialRequest;
                        question->id = zeroOpaque64;
                        question->servPort = zeroIPPort;
                        if (question->tcp) { DisposeTCPConn(question->tcp); question->tcp = mDNSNULL; }
                        }
                // If the question has local answers, then we don't want answers from outside
                if (ScheduleImmediately && !QuestionHasLocalAnswers(m, question))
                        {
                        question->ThisQInterval = InitialQuestionInterval;
                        question->LastQTime     = m->timenow - question->ThisQInterval;
                        SetNextQueryTime(m, question);
                        }
                }
        }

// Caller should hold the lock
mDNSexport void mDNSCoreRestartAddressQueries(mDNS *const m, mDNSBool SearchDomainsChanged, FlushCache flushCacheRecords,
        CallbackBeforeStartQuery BeforeStartCallback, void *context)
        {
        DNSQuestion *q;
        DNSQuestion *restart = mDNSNULL;

        if (!m->mDNS_busy) LogMsg("mDNSCoreRestartAddressQueries: ERROR!! Lock not held");

        // 1. Flush the cache records
        if (flushCacheRecords) flushCacheRecords(m);

        // 2. Even though we may have purged the cache records above, before it can generate RMV event
        // we are going to stop the question. Hence we need to deliver the RMV event before we
        // stop the question.
        //
        // CurrentQuestion is used by RmvEventsForQuestion below. While delivering RMV events, the
        // application callback can potentially stop the current question (detected by CurrentQuestion) or
        // *any* other question which could be the next one that we may process here. RestartQuestion
        // points to the "next" question which will be automatically advanced in mDNS_StopQuery_internal
        // if the "next" question is stopped while the CurrentQuestion is stopped

        if (m->RestartQuestion)
                LogMsg("mDNSCoreRestartAddressQueries: ERROR!! m->RestartQuestion already set: %##s (%s)",
                        m->RestartQuestion->qname.c, DNSTypeName(m->RestartQuestion->qtype));

        m->RestartQuestion = m->Questions;
        while (m->RestartQuestion)
                {
                q = m->RestartQuestion;
                m->RestartQuestion = q->next;
                // GetZoneData questions are referenced by other questions (original query that started the GetZoneData
                // question)  through their "nta" pointer. Normally when the original query stops, it stops the
                // GetZoneData question and also frees the memory (See CancelGetZoneData). If we stop the GetZoneData
                // question followed by the original query that refers to this GetZoneData question, we will end up
                // freeing the GetZoneData question and then start the "freed" question at the end. 

                if (IsGetZoneDataQuestion(q))
                        {
                        DNSQuestion *refq = q->next;
                        LogInfo("mDNSCoreRestartAddressQueries: Skipping GetZoneDataQuestion %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                        // debug stuff, we just try to find the referencing question and don't do much with it
                        while (refq)
                                {
                                if (q == &refq->nta->question)
                                        {
                                        LogInfo("mDNSCoreRestartAddressQueries: Question %p %##s (%s) referring to GetZoneDataQuestion %p, not stopping", refq, refq->qname.c, DNSTypeName(refq->qtype), q);
                                        }
                                refq = refq->next;
                                }
                        continue;
                        }

                // This function is called when /etc/hosts changes and that could affect A, AAAA and CNAME queries
                if (q->qtype != kDNSType_A && q->qtype != kDNSType_AAAA && q->qtype != kDNSType_CNAME) continue;

                // If the search domains did not change, then we restart all the queries. Otherwise, only
                // for queries for which we "might" have appended search domains ("might" because we may
                // find results before we apply search domains even though AppendSearchDomains is set to 1)
                if (!SearchDomainsChanged || q->AppendSearchDomains)
                        {
                        // NOTE: CacheRecordRmvEventsForQuestion will not generate RMV events for queries that have non-zero
                        // LOAddressAnswers. Hence it is important that we call CacheRecordRmvEventsForQuestion before
                        // LocalRecordRmvEventsForQuestion (which decrements LOAddressAnswers). Let us say that
                        // /etc/hosts has an A Record for web.apple.com. Any queries for web.apple.com will be answered locally.
                        // But this can't prevent a CNAME/AAAA query to not to be sent on the wire. When it is sent on the wire,
                        // it could create cache entries. When we are restarting queries, we can't deliver the cache RMV events
                        // for the original query using these cache entries as ADDs were never delivered using these cache
                        // entries and hence this order is needed.

                        // If the query is suppressed, the RMV events won't be delivered
                        if (!CacheRecordRmvEventsForQuestion(m, q)) { LogInfo("mDNSCoreRestartAddressQueries: Question deleted while delivering Cache Record RMV events"); continue; }

                        // SuppressQuery status does not affect questions that are answered using local records
                        if (!LocalRecordRmvEventsForQuestion(m, q)) { LogInfo("mDNSCoreRestartAddressQueries: Question deleted while delivering Local Record RMV events"); continue; }

                        LogInfo("mDNSCoreRestartAddressQueries: Stop question %p %##s (%s), AppendSearchDomains %d, qnameOrig %p", q,
                                q->qname.c, DNSTypeName(q->qtype), q->AppendSearchDomains, q->qnameOrig);
                        mDNS_StopQuery_internal(m, q);
                        // Reset state so that it looks like it was in the beginning i.e it should look at /etc/hosts, cache
                        // and then search domains should be appended. At the beginning, qnameOrig was NULL.
                        if (q->qnameOrig)
                                {
                                LogInfo("mDNSCoreRestartAddressQueries: qnameOrig %##s", q->qnameOrig);
                                AssignDomainName(&q->qname, q->qnameOrig);
                                mDNSPlatformMemFree(q->qnameOrig);
                                q->qnameOrig = mDNSNULL;
                                q->RetryWithSearchDomains = ApplySearchDomainsFirst(q) ? 1 : 0;
                                }
                        q->SearchListIndex = 0;
                        q->next = restart;
                        restart = q;
                        }
                }

        // 3. Callback before we start the query
        if (BeforeStartCallback) BeforeStartCallback(m, context);

        // 4. Restart all the stopped queries
        while (restart)
                {
                q = restart;
                restart = restart->next;
                q->next = mDNSNULL;
                LogInfo("mDNSCoreRestartAddressQueries: Start question %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                mDNS_StartQuery_internal(m, q);
                }
        }

mDNSexport void mDNSCoreRestartQueries(mDNS *const m)
        {
        DNSQuestion *q;

#ifndef UNICAST_DISABLED
        // Retrigger all our uDNS questions
        if (m->CurrentQuestion)
                LogMsg("mDNSCoreRestartQueries: ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));
        m->CurrentQuestion = m->Questions;
        while (m->CurrentQuestion)
                {
                q = m->CurrentQuestion;
                m->CurrentQuestion = m->CurrentQuestion->next;
                if (!mDNSOpaque16IsZero(q->TargetQID) && ActiveQuestion(q)) ActivateUnicastQuery(m, q, mDNStrue);
                }
#endif

        // Retrigger all our mDNS questions
        for (q = m->Questions; q; q=q->next)                            // Scan our list of questions
                if (mDNSOpaque16IsZero(q->TargetQID) && ActiveQuestion(q))
                        {
                        q->ThisQInterval    = InitialQuestionInterval;  // MUST be > zero for an active question
                        q->RequestUnicast   = 2;                                                // Set to 2 because is decremented once *before* we check it
                        q->LastQTime        = m->timenow - q->ThisQInterval;
                        q->RecentAnswerPkts = 0;
                        ExpireDupSuppressInfo(q->DupSuppress, m->timenow);
                        m->NextScheduledQuery = m->timenow;
                        }
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Power Management (Sleep/Wake)
#endif

mDNSexport void mDNS_UpdateAllowSleep(mDNS *const m)
        {
#ifndef IDLESLEEPCONTROL_DISABLED
        mDNSBool allowSleep = mDNStrue;
        char     reason[128];
        
        reason[0] = 0;
        
        if (m->SystemSleepOnlyIfWakeOnLAN)
                {
                // Don't sleep if we are a proxy for any services
                if (m->ProxyRecords)
                        {
                        allowSleep = mDNSfalse;
                        mDNS_snprintf(reason, sizeof(reason), "sleep proxy for %d records", m->ProxyRecords);
                        LogInfo("Sleep disabled because we are proxying %d records", m->ProxyRecords);
                        }

                if (allowSleep && mDNSCoreHaveAdvertisedMulticastServices(m))
                        {
                        // Scan the list of active interfaces
                        NetworkInterfaceInfo *intf;
                        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                                {
                                if (intf->McastTxRx && !intf->Loopback)
                                        {
                                        // Disallow sleep if this interface doesn't support NetWake
                                        if (!intf->NetWake)
                                                {
                                                allowSleep = mDNSfalse;
                                                mDNS_snprintf(reason, sizeof(reason), "%s does not support NetWake", intf->ifname);
                                                LogInfo("Sleep disabled because %s does not support NetWake", intf->ifname);
                                                break;
                                                }

                                        // Disallow sleep if there is no sleep proxy server
                                        if (FindSPSInCache1(m, &intf->NetWakeBrowse, mDNSNULL, mDNSNULL) == mDNSNULL)
                                                {
                                                allowSleep = mDNSfalse;
                                                mDNS_snprintf(reason, sizeof(reason), "%s does not support NetWake", intf->ifname);
                                                LogInfo("Sleep disabled because %s has no sleep proxy", intf->ifname);
                                                break;
                                                }
                                        }
                                }
                        }
                }
        
        // Call the platform code to enable/disable sleep
        mDNSPlatformSetAllowSleep(m, allowSleep, reason);
#endif /* !defined(IDLESLEEPCONTROL_DISABLED) */
        }

mDNSlocal void SendSPSRegistrationForOwner(mDNS *const m, NetworkInterfaceInfo *const intf, const mDNSOpaque16 id, const OwnerOptData *const owner)
        {
        const int optspace = DNSOpt_Header_Space + DNSOpt_LeaseData_Space + DNSOpt_Owner_Space(&m->PrimaryMAC, &intf->MAC);
        const int sps = intf->NextSPSAttempt / 3;
        AuthRecord *rr;

        if (!intf->SPSAddr[sps].type)
                {
                intf->NextSPSAttemptTime = m->timenow + mDNSPlatformOneSecond;
                if (m->NextScheduledSPRetry - intf->NextSPSAttemptTime > 0)
                        m->NextScheduledSPRetry = intf->NextSPSAttemptTime;
                LogSPS("SendSPSRegistration: %s SPS %d (%d) %##s not yet resolved", intf->ifname, intf->NextSPSAttempt, sps, intf->NetWakeResolve[sps].qname.c);
                goto exit;
                }

        // Mark our mDNS records (not unicast records) for transfer to SPS
        if (mDNSOpaque16IsZero(id))
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->resrec.RecordType > kDNSRecordTypeDeregistering)
                                if (rr->resrec.InterfaceID == intf->InterfaceID || (!rr->resrec.InterfaceID && (rr->ForceMCast || IsLocalDomain(rr->resrec.name))))
                                        if (mDNSPlatformMemSame(owner, &rr->WakeUp, sizeof(*owner)))
                                                rr->SendRNow = mDNSInterfaceMark;       // mark it now

        while (1)
                {
                mDNSu8 *p = m->omsg.data;
                // To comply with RFC 2782, PutResourceRecord suppresses name compression for SRV records in unicast updates.
                // For now we follow that same logic for SPS registrations too.
                // If we decide to compress SRV records in SPS registrations in the future, we can achieve that by creating our
                // initial DNSMessage with h.flags set to zero, and then update it to UpdateReqFlags right before sending the packet.
                InitializeDNSMessage(&m->omsg.h, mDNSOpaque16IsZero(id) ? mDNS_NewMessageID(m) : id, UpdateReqFlags);

                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->SendRNow || (!mDNSOpaque16IsZero(id) && !AuthRecord_uDNS(rr) && mDNSSameOpaque16(rr->updateid, id) && m->timenow - (rr->LastAPTime + rr->ThisAPInterval) >= 0))
                                if (mDNSPlatformMemSame(owner, &rr->WakeUp, sizeof(*owner)))
                                        {
                                        mDNSu8 *newptr;
                                        const mDNSu8 *const limit = m->omsg.data + (m->omsg.h.mDNS_numUpdates ? NormalMaxDNSMessageData : AbsoluteMaxDNSMessageData) - optspace;
                                        if (rr->resrec.RecordType & kDNSRecordTypeUniqueMask)
                                                rr->resrec.rrclass |= kDNSClass_UniqueRRSet;    // Temporarily set the 'unique' bit so PutResourceRecord will set it
                                        newptr = PutResourceRecordTTLWithLimit(&m->omsg, p, &m->omsg.h.mDNS_numUpdates, &rr->resrec, rr->resrec.rroriginalttl, limit);
                                        rr->resrec.rrclass &= ~kDNSClass_UniqueRRSet;           // Make sure to clear 'unique' bit back to normal state
                                        if (!newptr)
                                                LogSPS("SendSPSRegistration put %s FAILED %d/%d %s", intf->ifname, p - m->omsg.data, limit - m->omsg.data, ARDisplayString(m, rr));
                                        else
                                                {
                                                LogSPS("SendSPSRegistration put %s %s", intf->ifname, ARDisplayString(m, rr));
                                                rr->SendRNow       = mDNSNULL;
                                                rr->ThisAPInterval = mDNSPlatformOneSecond;
                                                rr->LastAPTime     = m->timenow;
                                                rr->updateid       = m->omsg.h.id;
                                                if (m->NextScheduledResponse - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
                                                        m->NextScheduledResponse = (rr->LastAPTime + rr->ThisAPInterval);
                                                p = newptr;
                                                }
                                        }

                if (!m->omsg.h.mDNS_numUpdates) break;
                else
                        {
                        AuthRecord opt;
                        mDNS_SetupResourceRecord(&opt, mDNSNULL, mDNSInterface_Any, kDNSType_OPT, kStandardTTL, kDNSRecordTypeKnownUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
                        opt.resrec.rrclass    = NormalMaxDNSMessageData;
                        opt.resrec.rdlength   = sizeof(rdataOPT) * 2;   // Two options in this OPT record
                        opt.resrec.rdestimate = sizeof(rdataOPT) * 2;
                        opt.resrec.rdata->u.opt[0].opt           = kDNSOpt_Lease;
                        opt.resrec.rdata->u.opt[0].optlen        = DNSOpt_LeaseData_Space - 4;
                        opt.resrec.rdata->u.opt[0].u.updatelease = DEFAULT_UPDATE_LEASE;
                        if (!owner->HMAC.l[0])                                                                                  // If no owner data,
                                SetupOwnerOpt(m, intf, &opt.resrec.rdata->u.opt[1]);            // use our own interface information
                        else                                                                                                                    // otherwise, use the owner data we were given
                                {
                                opt.resrec.rdata->u.opt[1].u.owner = *owner;
                                opt.resrec.rdata->u.opt[1].opt     = kDNSOpt_Owner;
                                opt.resrec.rdata->u.opt[1].optlen  = DNSOpt_Owner_Space(&owner->HMAC, &owner->IMAC) - 4;
                                }
                        LogSPS("SendSPSRegistration put %s %s", intf->ifname, ARDisplayString(m, &opt));
                        p = PutResourceRecordTTLWithLimit(&m->omsg, p, &m->omsg.h.numAdditionals, &opt.resrec, opt.resrec.rroriginalttl, m->omsg.data + AbsoluteMaxDNSMessageData);
                        if (!p)
                                LogMsg("SendSPSRegistration: Failed to put OPT record (%d updates) %s", m->omsg.h.mDNS_numUpdates, ARDisplayString(m, &opt));
                        else
                                {
                                mStatus err;

                                LogSPS("SendSPSRegistration: Sending Update %s %d (%d) id %5d with %d records %d bytes to %#a:%d", intf->ifname, intf->NextSPSAttempt, sps,
                                        mDNSVal16(m->omsg.h.id), m->omsg.h.mDNS_numUpdates, p - m->omsg.data, &intf->SPSAddr[sps], mDNSVal16(intf->SPSPort[sps]));
                                // if (intf->NextSPSAttempt < 5) m->omsg.h.flags = zeroID;      // For simulating packet loss
                                err = mDNSSendDNSMessage(m, &m->omsg, p, intf->InterfaceID, mDNSNULL, &intf->SPSAddr[sps], intf->SPSPort[sps], mDNSNULL, mDNSNULL);
                                if (err) LogSPS("SendSPSRegistration: mDNSSendDNSMessage err %d", err);
                                if (err && intf->SPSAddr[sps].type == mDNSAddrType_IPv6 && intf->NetWakeResolve[sps].ThisQInterval == -1)
                                        {
                                        LogSPS("SendSPSRegistration %d %##s failed to send to IPv6 address; will try IPv4 instead", sps, intf->NetWakeResolve[sps].qname.c);
                                        intf->NetWakeResolve[sps].qtype = kDNSType_A;
                                        mDNS_StartQuery_internal(m, &intf->NetWakeResolve[sps]);
                                        return;
                                        }
                                }
                        }
                }

        intf->NextSPSAttemptTime = m->timenow + mDNSPlatformOneSecond * 10;             // If successful, update NextSPSAttemptTime

exit:
        if (mDNSOpaque16IsZero(id) && intf->NextSPSAttempt < 8) intf->NextSPSAttempt++;
        }

mDNSlocal mDNSBool RecordIsFirstOccurrenceOfOwner(mDNS *const m, const AuthRecord *const rr)
        {
        AuthRecord *ar;
        for (ar = m->ResourceRecords; ar && ar != rr; ar=ar->next)
                if (mDNSPlatformMemSame(&rr->WakeUp, &ar->WakeUp, sizeof(rr->WakeUp))) return mDNSfalse;
        return mDNStrue;
        }

mDNSlocal void SendSPSRegistration(mDNS *const m, NetworkInterfaceInfo *const intf, const mDNSOpaque16 id)
        {
        AuthRecord *ar;
        OwnerOptData owner = zeroOwner;

        SendSPSRegistrationForOwner(m, intf, id, &owner);

        for (ar = m->ResourceRecords; ar; ar=ar->next)
                {
                if (!mDNSPlatformMemSame(&owner, &ar->WakeUp, sizeof(owner)) && RecordIsFirstOccurrenceOfOwner(m, ar))
                        {
                        owner = ar->WakeUp;
                        SendSPSRegistrationForOwner(m, intf, id, &owner);
                        }
                }
        }

// RetrySPSRegistrations is called from SendResponses, with the lock held
mDNSlocal void RetrySPSRegistrations(mDNS *const m)
        {
        AuthRecord *rr;
        NetworkInterfaceInfo *intf;

        // First make sure none of our interfaces' NextSPSAttemptTimes are inadvertently set to m->timenow + mDNSPlatformOneSecond * 10
        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                if (intf->NextSPSAttempt && intf->NextSPSAttemptTime == m->timenow + mDNSPlatformOneSecond * 10)
                        intf->NextSPSAttemptTime++;

        // Retry any record registrations that are due
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (!AuthRecord_uDNS(rr) && !mDNSOpaque16IsZero(rr->updateid) && m->timenow - (rr->LastAPTime + rr->ThisAPInterval) >= 0)
                        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                                if (!rr->resrec.InterfaceID || rr->resrec.InterfaceID == intf->InterfaceID)
                                        {
                                        LogSPS("RetrySPSRegistrations: %s", ARDisplayString(m, rr));
                                        SendSPSRegistration(m, intf, rr->updateid);
                                        }

        // For interfaces where we did an SPS registration attempt, increment intf->NextSPSAttempt
        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                if (intf->NextSPSAttempt && intf->NextSPSAttemptTime == m->timenow + mDNSPlatformOneSecond * 10 && intf->NextSPSAttempt < 8)
                        intf->NextSPSAttempt++;
        }

mDNSlocal void NetWakeResolve(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
        {
        NetworkInterfaceInfo *intf = (NetworkInterfaceInfo *)question->QuestionContext;
        int sps = (int)(question - intf->NetWakeResolve);
        (void)m;                        // Unused
        LogSPS("NetWakeResolve: SPS: %d Add: %d %s", sps, AddRecord, RRDisplayString(m, answer));

        if (!AddRecord) return;                                                                                         // Don't care about REMOVE events
        if (answer->rrtype != question->qtype) return;                                          // Don't care about CNAMEs

        // if (answer->rrtype == kDNSType_AAAA && sps == 0) return;     // To test failing to resolve sleep proxy's address

        if (answer->rrtype == kDNSType_SRV)
                {
                // 1. Got the SRV record; now look up the target host's IPv6 link-local address
                mDNS_StopQuery(m, question);
                intf->SPSPort[sps] = answer->rdata->u.srv.port;
                AssignDomainName(&question->qname, &answer->rdata->u.srv.target);
                question->qtype = kDNSType_AAAA;
                mDNS_StartQuery(m, question);
                }
        else if (answer->rrtype == kDNSType_AAAA && answer->rdlength == sizeof(mDNSv6Addr) && mDNSv6AddressIsLinkLocal(&answer->rdata->u.ipv6))
                {
                // 2. Got the target host's IPv6 link-local address; record address and initiate an SPS registration if appropriate
                mDNS_StopQuery(m, question);
                question->ThisQInterval = -1;
                intf->SPSAddr[sps].type = mDNSAddrType_IPv6;
                intf->SPSAddr[sps].ip.v6 = answer->rdata->u.ipv6;
                mDNS_Lock(m);
                if (sps == intf->NextSPSAttempt/3) SendSPSRegistration(m, intf, zeroID);        // If we're ready for this result, use it now
                mDNS_Unlock(m);
                }
        else if (answer->rrtype == kDNSType_AAAA && answer->rdlength == 0)
                {
                // 3. Got negative response -- target host apparently has IPv6 disabled -- so try looking up the target host's IPv4 address(es) instead
                mDNS_StopQuery(m, question);
                LogSPS("NetWakeResolve: SPS %d %##s has no IPv6 address, will try IPv4 instead", sps, question->qname.c);
                question->qtype = kDNSType_A;
                mDNS_StartQuery(m, question);
                }
        else if (answer->rrtype == kDNSType_A && answer->rdlength == sizeof(mDNSv4Addr))
                {
                // 4. Got an IPv4 address for the target host; record address and initiate an SPS registration if appropriate
                mDNS_StopQuery(m, question);
                question->ThisQInterval = -1;
                intf->SPSAddr[sps].type = mDNSAddrType_IPv4;
                intf->SPSAddr[sps].ip.v4 = answer->rdata->u.ipv4;
                mDNS_Lock(m);
                if (sps == intf->NextSPSAttempt/3) SendSPSRegistration(m, intf, zeroID);        // If we're ready for this result, use it now
                mDNS_Unlock(m);
                }
        }

mDNSexport mDNSBool mDNSCoreHaveAdvertisedMulticastServices(mDNS *const m)
        {
        AuthRecord *rr;
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (rr->resrec.rrtype == kDNSType_SRV && !AuthRecord_uDNS(rr) && !mDNSSameIPPort(rr->resrec.rdata->u.srv.port, DiscardPort))
                        return mDNStrue;
        return mDNSfalse;
        }

mDNSlocal void SendSleepGoodbyes(mDNS *const m)
        {
        AuthRecord *rr;
        m->SleepState = SleepState_Sleeping;

#ifndef UNICAST_DISABLED
        SleepRecordRegistrations(m);    // If we have no SPS, need to deregister our uDNS records
#endif /* UNICAST_DISABLED */

        // Mark all the records we need to deregister and send them
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (rr->resrec.RecordType == kDNSRecordTypeShared && rr->RequireGoodbye)
                        rr->ImmedAnswer = mDNSInterfaceMark;
        SendResponses(m);
        }

// BeginSleepProcessing is called, with the lock held, from either mDNS_Execute or mDNSCoreMachineSleep
mDNSlocal void BeginSleepProcessing(mDNS *const m)
        {
        mDNSBool SendGoodbyes = mDNStrue;
        const CacheRecord *sps[3] = { mDNSNULL };

        m->NextScheduledSPRetry = m->timenow;

        if      (!m->SystemWakeOnLANEnabled)                  LogSPS("BeginSleepProcessing: m->SystemWakeOnLANEnabled is false");
        else if (!mDNSCoreHaveAdvertisedMulticastServices(m)) LogSPS("BeginSleepProcessing: No advertised services");
        else    // If we have at least one advertised service
                {
                NetworkInterfaceInfo *intf;
                for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                        {
                        if (!intf->NetWake) LogSPS("BeginSleepProcessing: %-6s not capable of magic packet wakeup", intf->ifname);
#if APPLE_OSX_mDNSResponder
                        else if (ActivateLocalProxy(m, intf->ifname) == mStatus_NoError)
                                {
                                SendGoodbyes = mDNSfalse;
                                LogSPS("BeginSleepProcessing: %-6s using local proxy", intf->ifname);
                                // This will leave m->SleepState set to SleepState_Transferring,
                                // which is okay because with no outstanding resolves, or updates in flight,
                                // mDNSCoreReadyForSleep() will conclude correctly that all the updates have already completed
                                }
#endif // APPLE_OSX_mDNSResponder
                        else
                                {
                                FindSPSInCache(m, &intf->NetWakeBrowse, sps);
                                if (!sps[0]) LogSPS("BeginSleepProcessing: %-6s %#a No Sleep Proxy Server found (Next Browse Q in %d, interval %d)",
                                        intf->ifname, &intf->ip, NextQSendTime(&intf->NetWakeBrowse) - m->timenow, intf->NetWakeBrowse.ThisQInterval);
                                else
                                        {
                                        int i;
                                        SendGoodbyes = mDNSfalse;
                                        intf->NextSPSAttempt = 0;
                                        intf->NextSPSAttemptTime = m->timenow + mDNSPlatformOneSecond;
                                        // Don't need to set m->NextScheduledSPRetry here because we already set "m->NextScheduledSPRetry = m->timenow" above
                                        for (i=0; i<3; i++)
                                                {
#if ForceAlerts
                                                if (intf->SPSAddr[i].type)
                                                        { LogMsg("BeginSleepProcessing: %s %d intf->SPSAddr[i].type %d", intf->ifname, i, intf->SPSAddr[i].type); *(long*)0 = 0; }
                                                if (intf->NetWakeResolve[i].ThisQInterval >= 0)
                                                        { LogMsg("BeginSleepProcessing: %s %d intf->NetWakeResolve[i].ThisQInterval %d", intf->ifname, i, intf->NetWakeResolve[i].ThisQInterval); *(long*)0 = 0; }
#endif
                                                intf->SPSAddr[i].type = mDNSAddrType_None;
                                                if (intf->NetWakeResolve[i].ThisQInterval >= 0) mDNS_StopQuery(m, &intf->NetWakeResolve[i]);
                                                intf->NetWakeResolve[i].ThisQInterval = -1;
                                                if (sps[i])
                                                        {
                                                        LogSPS("BeginSleepProcessing: %-6s Found Sleep Proxy Server %d TTL %d %s", intf->ifname, i, sps[i]->resrec.rroriginalttl, CRDisplayString(m, sps[i]));
                                                        mDNS_SetupQuestion(&intf->NetWakeResolve[i], intf->InterfaceID, &sps[i]->resrec.rdata->u.name, kDNSType_SRV, NetWakeResolve, intf);
                                                        intf->NetWakeResolve[i].ReturnIntermed = mDNStrue;
                                                        mDNS_StartQuery_internal(m, &intf->NetWakeResolve[i]);
                                                        }
                                                }
                                        }
                                }
                        }
                }

        if (SendGoodbyes)       // If we didn't find even one Sleep Proxy
                {
                LogSPS("BeginSleepProcessing: Not registering with Sleep Proxy Server");
                SendSleepGoodbyes(m);
                }
        }

// Call mDNSCoreMachineSleep(m, mDNStrue) when the machine is about to go to sleep.
// Call mDNSCoreMachineSleep(m, mDNSfalse) when the machine is has just woken up.
// Normally, the platform support layer below mDNSCore should call this, not the client layer above.
mDNSexport void mDNSCoreMachineSleep(mDNS *const m, mDNSBool sleep)
        {
        AuthRecord *rr;

        LogSPS("%s (old state %d) at %ld", sleep ? "Sleeping" : "Waking", m->SleepState, m->timenow);

        if (sleep && !m->SleepState)            // Going to sleep
                {
                mDNS_Lock(m);
                // If we're going to sleep, need to stop advertising that we're a Sleep Proxy Server
                if (m->SPSSocket)
                        {
                        mDNSu8 oldstate = m->SPSState;
                        mDNS_DropLockBeforeCallback();          // mDNS_DeregisterService expects to be called without the lock held, so we emulate that here
                        m->SPSState = 2;
                        if (oldstate == 1) mDNS_DeregisterService(m, &m->SPSRecords);
                        mDNS_ReclaimLockAfterCallback();
                        }

                m->SleepState = SleepState_Transferring;
                if (m->SystemWakeOnLANEnabled && m->DelaySleep)
                        {
                        // If we just woke up moments ago, allow ten seconds for networking to stabilize before going back to sleep
                        LogSPS("mDNSCoreMachineSleep: Re-sleeping immediately after waking; will delay for %d ticks", m->DelaySleep - m->timenow);
                        m->SleepLimit = NonZeroTime(m->DelaySleep + mDNSPlatformOneSecond * 10);
                        }
                else
                        {
                        m->DelaySleep = 0;
                        m->SleepLimit = NonZeroTime(m->timenow + mDNSPlatformOneSecond * 10);
                        BeginSleepProcessing(m);
                        }

#ifndef UNICAST_DISABLED
                SuspendLLQs(m);
#endif
                mDNS_Unlock(m);
                // RemoveAutoTunnel6Record needs to be called outside the lock, as it grabs the lock also.
#if APPLE_OSX_mDNSResponder
                RemoveAutoTunnel6Record(m);
#endif
                LogSPS("mDNSCoreMachineSleep: m->SleepState %d (%s) seq %d", m->SleepState,
                        m->SleepState == SleepState_Transferring ? "Transferring" :
                        m->SleepState == SleepState_Sleeping     ? "Sleeping"     : "?", m->SleepSeqNum);
                }
        else if (!sleep)                // Waking up
                {
                mDNSu32 slot;
                CacheGroup *cg;
                CacheRecord *cr;
                NetworkInterfaceInfo *intf;

                mDNS_Lock(m);
                // Reset SleepLimit back to 0 now that we're awake again.
                m->SleepLimit = 0;

                // If we were previously sleeping, but now we're not, increment m->SleepSeqNum to indicate that we're entering a new period of wakefulness
                if (m->SleepState != SleepState_Awake)
                        {
                        m->SleepState = SleepState_Awake;
                        m->SleepSeqNum++;
                        // If the machine wakes and then immediately tries to sleep again (e.g. a maintenance wake)
                        // then we enforce a minimum delay of 16 seconds before we begin sleep processing.
                        // This is to allow time for the Ethernet link to come up, DHCP to get an address, mDNS to issue queries, etc.,
                        // before we make our determination of whether there's a Sleep Proxy out there we should register with.
                        m->DelaySleep = NonZeroTime(m->timenow + mDNSPlatformOneSecond * 16);
                        }

                if (m->SPSState == 3)
                        {
                        m->SPSState = 0;
                        mDNSCoreBeSleepProxyServer_internal(m, m->SPSType, m->SPSPortability, m->SPSMarginalPower, m->SPSTotalPower);
                        }

                // In case we gave up waiting and went to sleep before we got an ack from the Sleep Proxy,
                // on wake we go through our record list and clear updateid back to zero
                for (rr = m->ResourceRecords; rr; rr=rr->next) rr->updateid = zeroID;

                // ... and the same for NextSPSAttempt
                for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next)) intf->NextSPSAttempt = -1;

                // Restart unicast and multicast queries
                mDNSCoreRestartQueries(m);

                // and reactivtate service registrations
                m->NextSRVUpdate = NonZeroTime(m->timenow + mDNSPlatformOneSecond);
                LogInfo("mDNSCoreMachineSleep waking: NextSRVUpdate in %d %d", m->NextSRVUpdate - m->timenow, m->timenow);

                // 2. Re-validate our cache records
                FORALL_CACHERECORDS(slot, cg, cr)
                        mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForWake);

                // 3. Retrigger probing and announcing for all our authoritative records
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (AuthRecord_uDNS(rr))
                                {
                                ActivateUnicastRegistration(m, rr);
                                }
                        else
                                {
                                if (rr->resrec.RecordType == kDNSRecordTypeVerified && !rr->DependentOn) rr->resrec.RecordType = kDNSRecordTypeUnique;
                                rr->ProbeCount     = DefaultProbeCountForRecordType(rr->resrec.RecordType);
                                rr->AnnounceCount  = InitialAnnounceCount;
                                rr->SendNSECNow    = mDNSNULL;
                                InitializeLastAPTime(m, rr);
                                }

                // 4. Refresh NAT mappings
                // We don't want to have to assume that all hardware can necessarily keep accurate
                // track of passage of time while asleep, so on wake we refresh our NAT mappings
                // We typically wake up with no interfaces active, so there's no need to rush to try to find our external address.
                // When we get a network configuration change, mDNSMacOSXNetworkChanged calls uDNS_SetupDNSConfig, which calls
                // mDNS_SetPrimaryInterfaceInfo, which then sets m->retryGetAddr to immediately request our external address from the NAT gateway.
                m->retryIntervalGetAddr = NATMAP_INIT_RETRY;
                m->retryGetAddr         = m->timenow + mDNSPlatformOneSecond * 5;
                LogInfo("mDNSCoreMachineSleep: retryGetAddr in %d %d", m->retryGetAddr - m->timenow, m->timenow);
                RecreateNATMappings(m);
                mDNS_Unlock(m);
                }
        }

mDNSexport mDNSBool mDNSCoreReadyForSleep(mDNS *m, mDNSs32 now)
        {
        DNSQuestion *q;
        AuthRecord *rr;
        NetworkInterfaceInfo *intf;

        mDNS_Lock(m);

        if (m->DelaySleep) goto notready;

        // If we've not hit the sleep limit time, and it's not time for our next retry, we can skip these checks
        if (m->SleepLimit - now > 0 && m->NextScheduledSPRetry - now > 0) goto notready;

        m->NextScheduledSPRetry = now + 0x40000000UL;

        // See if we might need to retransmit any lost Sleep Proxy Registrations
        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                if (intf->NextSPSAttempt >= 0)
                        {
                        if (now - intf->NextSPSAttemptTime >= 0)
                                {
                                LogSPS("mDNSCoreReadyForSleep: retrying for %s SPS %d try %d",
                                        intf->ifname, intf->NextSPSAttempt/3, intf->NextSPSAttempt);
                                SendSPSRegistration(m, intf, zeroID);
                                // Don't need to "goto notready" here, because if we do still have record registrations
                                // that have not been acknowledged yet, we'll catch that in the record list scan below.
                                }
                        else
                                if (m->NextScheduledSPRetry - intf->NextSPSAttemptTime > 0)
                                        m->NextScheduledSPRetry = intf->NextSPSAttemptTime;
                        }

        // Scan list of interfaces, and see if we're still waiting for any sleep proxy resolves to complete
        for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                {
                int sps = (intf->NextSPSAttempt == 0) ? 0 : (intf->NextSPSAttempt-1)/3;
                if (intf->NetWakeResolve[sps].ThisQInterval >= 0)
                        {
                        LogSPS("mDNSCoreReadyForSleep: waiting for SPS Resolve %s %##s (%s)",
                                intf->ifname, intf->NetWakeResolve[sps].qname.c, DNSTypeName(intf->NetWakeResolve[sps].qtype));
                        goto spsnotready;
                        }
                }

        // Scan list of registered records
        for (rr = m->ResourceRecords; rr; rr = rr->next)
                if (!AuthRecord_uDNS(rr))
                        if (!mDNSOpaque16IsZero(rr->updateid))
                                { LogSPS("mDNSCoreReadyForSleep: waiting for SPS Update ID %d %s", mDNSVal16(rr->updateid), ARDisplayString(m,rr)); goto spsnotready; }

        // Scan list of private LLQs, and make sure they've all completed their handshake with the server
        for (q = m->Questions; q; q = q->next)
                if (!mDNSOpaque16IsZero(q->TargetQID) && q->LongLived && q->ReqLease == 0 && q->tcp)
                        {
                        LogSPS("mDNSCoreReadyForSleep: waiting for LLQ %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                        goto notready;
                        }

        // Scan list of registered records
        for (rr = m->ResourceRecords; rr; rr = rr->next)
                if (AuthRecord_uDNS(rr))
                        {
                        if (rr->state == regState_Refresh && rr->tcp)
                                { LogSPS("mDNSCoreReadyForSleep: waiting for Record Update ID %d %s", mDNSVal16(rr->updateid), ARDisplayString(m,rr)); goto notready; }
                        #if APPLE_OSX_mDNSResponder
                        if (!RecordReadyForSleep(m, rr)) { LogSPS("mDNSCoreReadyForSleep: waiting for %s", ARDisplayString(m, rr)); goto notready; }
                        #endif
                        }

        mDNS_Unlock(m);
        return mDNStrue;

spsnotready:

        // If we failed to complete sleep proxy registration within ten seconds, we give up on that
        // and allow up to ten seconds more to complete wide-area deregistration instead
        if (now - m->SleepLimit >= 0)
                {
                LogMsg("Failed to register with SPS, now sending goodbyes");

                for (intf = GetFirstActiveInterface(m->HostInterfaces); intf; intf = GetFirstActiveInterface(intf->next))
                        if (intf->NetWakeBrowse.ThisQInterval >= 0)
                                {
                                LogSPS("ReadyForSleep mDNS_DeactivateNetWake %s %##s (%s)",
                                        intf->ifname, intf->NetWakeResolve[0].qname.c, DNSTypeName(intf->NetWakeResolve[0].qtype));
                                mDNS_DeactivateNetWake_internal(m, intf);
                                }

                for (rr = m->ResourceRecords; rr; rr = rr->next)
                        if (!AuthRecord_uDNS(rr))
                                if (!mDNSOpaque16IsZero(rr->updateid))
                                        {
                                        LogSPS("ReadyForSleep clearing updateid for %s", ARDisplayString(m, rr));
                                        rr->updateid = zeroID;
                                        }

                // We'd really like to allow up to ten seconds more here,
                // but if we don't respond to the sleep notification within 30 seconds
                // we'll be put back to sleep forcibly without the chance to schedule the next maintenance wake.
                // Right now we wait 16 sec after wake for all the interfaces to come up, then we wait up to 10 seconds
                // more for SPS resolves and record registrations to complete, which puts us at 26 seconds.
                // If we allow just one more second to send our goodbyes, that puts us at 27 seconds.
                m->SleepLimit = now + mDNSPlatformOneSecond * 1;

                SendSleepGoodbyes(m);
                }

notready:
        mDNS_Unlock(m);
        return mDNSfalse;
        }

mDNSexport mDNSs32 mDNSCoreIntervalToNextWake(mDNS *const m, mDNSs32 now)
        {
        AuthRecord *ar;

        // Even when we have no wake-on-LAN-capable interfaces, or we failed to find a sleep proxy, or we have other
        // failure scenarios, we still want to wake up in at most 120 minutes, to see if the network environment has changed.
        // E.g. we might wake up and find no wireless network because the base station got rebooted just at that moment,
        // and if that happens we don't want to just give up and go back to sleep and never try again.
        mDNSs32 e = now + (120 * 60 * mDNSPlatformOneSecond);           // Sleep for at most 120 minutes

        NATTraversalInfo *nat;
        for (nat = m->NATTraversals; nat; nat=nat->next)
                if (nat->Protocol && nat->ExpiryTime && nat->ExpiryTime - now > mDNSPlatformOneSecond*4)
                        {
                        mDNSs32 t = nat->ExpiryTime - (nat->ExpiryTime - now) / 10;             // Wake up when 90% of the way to the expiry time
                        if (e - t > 0) e = t;
                        LogSPS("ComputeWakeTime: %p %s Int %5d Ext %5d Err %d Retry %5d Interval %5d Expire %5d Wake %5d",
                                nat, nat->Protocol == NATOp_MapTCP ? "TCP" : "UDP",
                                mDNSVal16(nat->IntPort), mDNSVal16(nat->ExternalPort), nat->Result,
                                nat->retryPortMap ? (nat->retryPortMap - now) / mDNSPlatformOneSecond : 0,
                                nat->retryInterval / mDNSPlatformOneSecond,
                                nat->ExpiryTime ? (nat->ExpiryTime - now) / mDNSPlatformOneSecond : 0,
                                (t - now) / mDNSPlatformOneSecond);
                        }

        // This loop checks both the time we need to renew wide-area registrations,
        // and the time we need to renew Sleep Proxy registrations
        for (ar = m->ResourceRecords; ar; ar = ar->next)
                if (ar->expire && ar->expire - now > mDNSPlatformOneSecond*4)
                        {
                        mDNSs32 t = ar->expire - (ar->expire - now) / 10;               // Wake up when 90% of the way to the expiry time
                        if (e - t > 0) e = t;
                        LogSPS("ComputeWakeTime: %p Int %7d Next %7d Expire %7d Wake %7d %s",
                                ar, ar->ThisAPInterval / mDNSPlatformOneSecond,
                                (ar->LastAPTime + ar->ThisAPInterval - now) / mDNSPlatformOneSecond,
                                ar->expire ? (ar->expire - now) / mDNSPlatformOneSecond : 0,
                                (t - now) / mDNSPlatformOneSecond, ARDisplayString(m, ar));
                        }

        return(e - now);
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Packet Reception Functions
#endif

#define MustSendRecord(RR) ((RR)->NR_AnswerTo || (RR)->NR_AdditionalTo)

mDNSlocal mDNSu8 *GenerateUnicastResponse(const DNSMessage *const query, const mDNSu8 *const end,
        const mDNSInterfaceID InterfaceID, mDNSBool LegacyQuery, DNSMessage *const response, AuthRecord *ResponseRecords)
        {
        mDNSu8          *responseptr     = response->data;
        const mDNSu8    *const limit     = response->data + sizeof(response->data);
        const mDNSu8    *ptr             = query->data;
        AuthRecord  *rr;
        mDNSu32          maxttl = 0x70000000;
        int i;

        // Initialize the response fields so we can answer the questions
        InitializeDNSMessage(&response->h, query->h.id, ResponseFlags);

        // ***
        // *** 1. Write out the list of questions we are actually going to answer with this packet
        // ***
        if (LegacyQuery)
                {
                maxttl = kStaticCacheTTL;
                for (i=0; i<query->h.numQuestions; i++)                                         // For each question...
                        {
                        DNSQuestion q;
                        ptr = getQuestion(query, ptr, end, InterfaceID, &q);    // get the question...
                        if (!ptr) return(mDNSNULL);
        
                        for (rr=ResponseRecords; rr; rr=rr->NextResponse)               // and search our list of proposed answers
                                {
                                if (rr->NR_AnswerTo == ptr)                                                     // If we're going to generate a record answering this question
                                        {                                                                                               // then put the question in the question section
                                        responseptr = putQuestion(response, responseptr, limit, &q.qname, q.qtype, q.qclass);
                                        if (!responseptr) { debugf("GenerateUnicastResponse: Ran out of space for questions!"); return(mDNSNULL); }
                                        break;          // break out of the ResponseRecords loop, and go on to the next question
                                        }
                                }
                        }
        
                if (response->h.numQuestions == 0) { LogMsg("GenerateUnicastResponse: ERROR! Why no questions?"); return(mDNSNULL); }
                }

        // ***
        // *** 2. Write Answers
        // ***
        for (rr=ResponseRecords; rr; rr=rr->NextResponse)
                if (rr->NR_AnswerTo)
                        {
                        mDNSu8 *p = PutResourceRecordTTL(response, responseptr, &response->h.numAnswers, &rr->resrec,
                                maxttl < rr->resrec.rroriginalttl ? maxttl : rr->resrec.rroriginalttl);
                        if (p) responseptr = p;
                        else { debugf("GenerateUnicastResponse: Ran out of space for answers!"); response->h.flags.b[0] |= kDNSFlag0_TC; }
                        }

        // ***
        // *** 3. Write Additionals
        // ***
        for (rr=ResponseRecords; rr; rr=rr->NextResponse)
                if (rr->NR_AdditionalTo && !rr->NR_AnswerTo)
                        {
                        mDNSu8 *p = PutResourceRecordTTL(response, responseptr, &response->h.numAdditionals, &rr->resrec,
                                maxttl < rr->resrec.rroriginalttl ? maxttl : rr->resrec.rroriginalttl);
                        if (p) responseptr = p;
                        else debugf("GenerateUnicastResponse: No more space for additionals");
                        }

        return(responseptr);
        }

// AuthRecord *our is our Resource Record
// CacheRecord *pkt is the Resource Record from the response packet we've witnessed on the network
// Returns 0 if there is no conflict
// Returns +1 if there was a conflict and we won
// Returns -1 if there was a conflict and we lost and have to rename
mDNSlocal int CompareRData(const AuthRecord *const our, const CacheRecord *const pkt)
        {
        mDNSu8 ourdata[256], *ourptr = ourdata, *ourend;
        mDNSu8 pktdata[256], *pktptr = pktdata, *pktend;
        if (!our) { LogMsg("CompareRData ERROR: our is NULL"); return(+1); }
        if (!pkt) { LogMsg("CompareRData ERROR: pkt is NULL"); return(+1); }

        ourend = putRData(mDNSNULL, ourdata, ourdata + sizeof(ourdata), &our->resrec);
        pktend = putRData(mDNSNULL, pktdata, pktdata + sizeof(pktdata), &pkt->resrec);
        while (ourptr < ourend && pktptr < pktend && *ourptr == *pktptr) { ourptr++; pktptr++; }
        if (ourptr >= ourend && pktptr >= pktend) return(0);                    // If data identical, not a conflict

        if (ourptr >= ourend) return(-1);                                                               // Our data ran out first; We lost
        if (pktptr >= pktend) return(+1);                                                               // Packet data ran out first; We won
        if (*pktptr > *ourptr) return(-1);                                                              // Our data is numerically lower; We lost
        if (*pktptr < *ourptr) return(+1);                                                              // Packet data is numerically lower; We won
        
        LogMsg("CompareRData ERROR: Invalid state");
        return(-1);
        }

// See if we have an authoritative record that's identical to this packet record,
// whose canonical DependentOn record is the specified master record.
// The DependentOn pointer is typically used for the TXT record of service registrations
// It indicates that there is no inherent conflict detection for the TXT record
// -- it depends on the SRV record to resolve name conflicts
// If we find any identical ResourceRecords in our authoritative list, then follow their DependentOn
// pointer chain (if any) to make sure we reach the canonical DependentOn record
// If the record has no DependentOn, then just return that record's pointer
// Returns NULL if we don't have any local RRs that are identical to the one from the packet
mDNSlocal mDNSBool MatchDependentOn(const mDNS *const m, const CacheRecord *const pktrr, const AuthRecord *const master)
        {
        const AuthRecord *r1;
        for (r1 = m->ResourceRecords; r1; r1=r1->next)
                {
                if (IdenticalResourceRecord(&r1->resrec, &pktrr->resrec))
                        {
                        const AuthRecord *r2 = r1;
                        while (r2->DependentOn) r2 = r2->DependentOn;
                        if (r2 == master) return(mDNStrue);
                        }
                }
        for (r1 = m->DuplicateRecords; r1; r1=r1->next)
                {
                if (IdenticalResourceRecord(&r1->resrec, &pktrr->resrec))
                        {
                        const AuthRecord *r2 = r1;
                        while (r2->DependentOn) r2 = r2->DependentOn;
                        if (r2 == master) return(mDNStrue);
                        }
                }
        return(mDNSfalse);
        }

// Find the canonical RRSet pointer for this RR received in a packet.
// If we find any identical AuthRecord in our authoritative list, then follow its RRSet
// pointers (if any) to make sure we return the canonical member of this name/type/class
// Returns NULL if we don't have any local RRs that are identical to the one from the packet
mDNSlocal const AuthRecord *FindRRSet(const mDNS *const m, const CacheRecord *const pktrr)
        {
        const AuthRecord *rr;
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                {
                if (IdenticalResourceRecord(&rr->resrec, &pktrr->resrec))
                        {
                        while (rr->RRSet && rr != rr->RRSet) rr = rr->RRSet;
                        return(rr);
                        }
                }
        return(mDNSNULL);
        }

// PacketRRConflict is called when we've received an RR (pktrr) which has the same name
// as one of our records (our) but different rdata.
// 1. If our record is not a type that's supposed to be unique, we don't care.
// 2a. If our record is marked as dependent on some other record for conflict detection, ignore this one.
// 2b. If the packet rr exactly matches one of our other RRs, and *that* record's DependentOn pointer
//     points to our record, ignore this conflict (e.g. the packet record matches one of our
//     TXT records, and that record is marked as dependent on 'our', its SRV record).
// 3. If we have some *other* RR that exactly matches the one from the packet, and that record and our record
//    are members of the same RRSet, then this is not a conflict.
mDNSlocal mDNSBool PacketRRConflict(const mDNS *const m, const AuthRecord *const our, const CacheRecord *const pktrr)
        {
        // If not supposed to be unique, not a conflict
        if (!(our->resrec.RecordType & kDNSRecordTypeUniqueMask)) return(mDNSfalse);

        // If a dependent record, not a conflict
        if (our->DependentOn || MatchDependentOn(m, pktrr, our)) return(mDNSfalse);
        else
                {
                // If the pktrr matches a member of ourset, not a conflict
                const AuthRecord *ourset = our->RRSet ? our->RRSet : our;
                const AuthRecord *pktset = FindRRSet(m, pktrr);
                if (pktset == ourset) return(mDNSfalse);

                // For records we're proxying, where we don't know the full
                // relationship between the records, having any matching record
                // in our AuthRecords list is sufficient evidence of non-conflict
                if (our->WakeUp.HMAC.l[0] && pktset) return(mDNSfalse);
                }

        // Okay, this is a conflict
        return(mDNStrue);
        }

// Note: ResolveSimultaneousProbe calls mDNS_Deregister_internal which can call a user callback, which may change
// the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSlocal void ResolveSimultaneousProbe(mDNS *const m, const DNSMessage *const query, const mDNSu8 *const end,
        DNSQuestion *q, AuthRecord *our)
        {
        int i;
        const mDNSu8 *ptr = LocateAuthorities(query, end);
        mDNSBool FoundUpdate = mDNSfalse;

        for (i = 0; i < query->h.numAuthorities; i++)
                {
                ptr = GetLargeResourceRecord(m, query, ptr, end, q->InterfaceID, kDNSRecordTypePacketAuth, &m->rec);
                if (!ptr) break;
                if (m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative && ResourceRecordAnswersQuestion(&m->rec.r.resrec, q))
                        {
                        FoundUpdate = mDNStrue;
                        if (PacketRRConflict(m, our, &m->rec.r))
                                {
                                int result          = (int)our->resrec.rrclass - (int)m->rec.r.resrec.rrclass;
                                if (!result) result = (int)our->resrec.rrtype  - (int)m->rec.r.resrec.rrtype;
                                if (!result) result = CompareRData(our, &m->rec.r);
                                if (result)
                                        {
                                        const char *const msg = (result < 0) ? "lost:" : (result > 0) ? "won: " : "tie: ";
                                        LogMsg("ResolveSimultaneousProbe: %p Pkt Record:        %08lX %s", q->InterfaceID, m->rec.r.resrec.rdatahash, CRDisplayString(m, &m->rec.r));
                                        LogMsg("ResolveSimultaneousProbe: %p Our Record %d %s %08lX %s", our->resrec.InterfaceID, our->ProbeCount, msg, our->resrec.rdatahash, ARDisplayString(m, our));
                                        }
                                // If we lost the tie-break for simultaneous probes, we don't immediately give up, because we might be seeing stale packets on the network.
                                // Instead we pause for one second, to give the other host (if real) a chance to establish its name, and then try probing again.
                                // If there really is another live host out there with the same name, it will answer our probes and we'll then rename.
                                if (result < 0)
                                        {
                                        m->SuppressProbes   = NonZeroTime(m->timenow + mDNSPlatformOneSecond);
                                        our->ProbeCount     = DefaultProbeCountForTypeUnique;
                                        our->AnnounceCount  = InitialAnnounceCount;
                                        InitializeLastAPTime(m, our);
                                        goto exit;
                                        }
                                }
#if 0
                        else
                                {
                                LogMsg("ResolveSimultaneousProbe: %p Pkt Record:        %08lX %s", q->InterfaceID, m->rec.r.resrec.rdatahash, CRDisplayString(m, &m->rec.r));
                                LogMsg("ResolveSimultaneousProbe: %p Our Record %d ign:  %08lX %s", our->resrec.InterfaceID, our->ProbeCount, our->resrec.rdatahash, ARDisplayString(m, our));
                                }
#endif
                        }
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }
        if (!FoundUpdate)
                LogInfo("ResolveSimultaneousProbe: %##s (%s): No Update Record found", our->resrec.name->c, DNSTypeName(our->resrec.rrtype));
exit:
        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
        }

mDNSlocal CacheRecord *FindIdenticalRecordInCache(const mDNS *const m, const ResourceRecord *const pktrr)
        {
        mDNSu32 slot = HashSlot(pktrr->name);
        CacheGroup *cg = CacheGroupForRecord(m, slot, pktrr);
        CacheRecord *rr;
        mDNSBool match;
        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                {
                match = !pktrr->InterfaceID ? pktrr->rDNSServer == rr->resrec.rDNSServer : pktrr->InterfaceID == rr->resrec.InterfaceID;
                if (match && IdenticalSameNameRecord(pktrr, &rr->resrec)) break;
                }
        return(rr);
        }

// Called from mDNSCoreReceiveUpdate when we get a sleep proxy registration request,
// to check our lists and discard any stale duplicates of this record we already have
mDNSlocal void ClearIdenticalProxyRecords(mDNS *const m, const OwnerOptData *const owner, AuthRecord *const thelist)
        {
        if (m->CurrentRecord)
                LogMsg("ClearIdenticalProxyRecords ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        m->CurrentRecord = thelist;
        while (m->CurrentRecord)
                {
                AuthRecord *const rr = m->CurrentRecord;
                if (m->rec.r.resrec.InterfaceID == rr->resrec.InterfaceID && mDNSSameEthAddress(&owner->HMAC, &rr->WakeUp.HMAC))
                        if (IdenticalResourceRecord(&rr->resrec, &m->rec.r.resrec))
                                {
                                LogSPS("ClearIdenticalProxyRecords: Removing %3d H-MAC %.6a I-MAC %.6a %d %d %s",
                                        m->ProxyRecords, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, rr->WakeUp.seq, owner->seq, ARDisplayString(m, rr));
                                rr->WakeUp.HMAC = zeroEthAddr;  // Clear HMAC so that mDNS_Deregister_internal doesn't waste packets trying to wake this host
                                rr->RequireGoodbye = mDNSfalse; // and we don't want to send goodbye for it
                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
                                SetSPSProxyListChanged(m->rec.r.resrec.InterfaceID);
                                }
                // Mustn't advance m->CurrentRecord until *after* mDNS_Deregister_internal, because
                // new records could have been added to the end of the list as a result of that call.
                if (m->CurrentRecord == rr) // If m->CurrentRecord was not advanced for us, do it now
                        m->CurrentRecord = rr->next;
                }
        }

// Called from ProcessQuery when we get an mDNS packet with an owner record in it
mDNSlocal void ClearProxyRecords(mDNS *const m, const OwnerOptData *const owner, AuthRecord *const thelist)
        {
        if (m->CurrentRecord)
                LogMsg("ClearProxyRecords ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
        m->CurrentRecord = thelist;
        while (m->CurrentRecord)
                {
                AuthRecord *const rr = m->CurrentRecord;
                if (m->rec.r.resrec.InterfaceID == rr->resrec.InterfaceID && mDNSSameEthAddress(&owner->HMAC, &rr->WakeUp.HMAC))
                        if (owner->seq != rr->WakeUp.seq || m->timenow - rr->TimeRcvd > mDNSPlatformOneSecond * 60)
                                {
                                if (rr->AddressProxy.type == mDNSAddrType_IPv6)
                                        {
                                        // We don't do this here because we know that the host is waking up at this point, so we don't send
                                        // Unsolicited Neighbor Advertisements -- even Neighbor Advertisements agreeing with what the host should be
                                        // saying itself -- because it can cause some IPv6 stacks to falsely conclude that there's an address conflict.
                                        #if MDNS_USE_Unsolicited_Neighbor_Advertisements
                                        LogSPS("NDP Announcement -- Releasing traffic for H-MAC %.6a I-MAC %.6a %s",
                                                &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m,rr));
                                        SendNDP(m, NDP_Adv, NDP_Override, rr, &rr->AddressProxy.ip.v6, &rr->WakeUp.IMAC, &AllHosts_v6, &AllHosts_v6_Eth);
                                        #endif
                                        }
                                LogSPS("ClearProxyRecords: Removing %3d AC %2d %02X H-MAC %.6a I-MAC %.6a %d %d %s",
                                        m->ProxyRecords, rr->AnnounceCount, rr->resrec.RecordType,
                                        &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, rr->WakeUp.seq, owner->seq, ARDisplayString(m, rr));
                                if (rr->resrec.RecordType == kDNSRecordTypeDeregistering) rr->resrec.RecordType = kDNSRecordTypeShared;
                                rr->WakeUp.HMAC = zeroEthAddr;  // Clear HMAC so that mDNS_Deregister_internal doesn't waste packets trying to wake this host
                                rr->RequireGoodbye = mDNSfalse; // and we don't want to send goodbye for it, since real host is now back and functional
                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
                                SetSPSProxyListChanged(m->rec.r.resrec.InterfaceID);
                                }
                // Mustn't advance m->CurrentRecord until *after* mDNS_Deregister_internal, because
                // new records could have been added to the end of the list as a result of that call.
                if (m->CurrentRecord == rr) // If m->CurrentRecord was not advanced for us, do it now
                        m->CurrentRecord = rr->next;
                }
        }

// ProcessQuery examines a received query to see if we have any answers to give
mDNSlocal mDNSu8 *ProcessQuery(mDNS *const m, const DNSMessage *const query, const mDNSu8 *const end,
        const mDNSAddr *srcaddr, const mDNSInterfaceID InterfaceID, mDNSBool LegacyQuery, mDNSBool QueryWasMulticast,
        mDNSBool QueryWasLocalUnicast, DNSMessage *const response)
        {
        mDNSBool      FromLocalSubnet    = srcaddr && mDNS_AddressIsLocalSubnet(m, InterfaceID, srcaddr);
        AuthRecord   *ResponseRecords    = mDNSNULL;
        AuthRecord  **nrp                = &ResponseRecords;
        CacheRecord  *ExpectedAnswers    = mDNSNULL;                    // Records in our cache we expect to see updated
        CacheRecord **eap                = &ExpectedAnswers;
        DNSQuestion  *DupQuestions       = mDNSNULL;                    // Our questions that are identical to questions in this packet
        DNSQuestion **dqp                = &DupQuestions;
        mDNSs32       delayresponse      = 0;
        mDNSBool      SendLegacyResponse = mDNSfalse;
        const mDNSu8 *ptr;
        mDNSu8       *responseptr        = mDNSNULL;
        AuthRecord   *rr;
        int i;

        // ***
        // *** 1. Look in Additional Section for an OPT record
        // ***
        ptr = LocateOptRR(query, end, DNSOpt_OwnerData_ID_Space);
        if (ptr)
                {
                ptr = GetLargeResourceRecord(m, query, ptr, end, InterfaceID, kDNSRecordTypePacketAdd, &m->rec);
                if (ptr && m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative && m->rec.r.resrec.rrtype == kDNSType_OPT)
                        {
                        const rdataOPT *opt;
                        const rdataOPT *const e = (const rdataOPT *)&m->rec.r.resrec.rdata->u.data[m->rec.r.resrec.rdlength];
                        // Find owner sub-option(s). We verify that the MAC is non-zero, otherwise we could inadvertently
                        // delete all our own AuthRecords (which are identified by having zero MAC tags on them).
                        for (opt = &m->rec.r.resrec.rdata->u.opt[0]; opt < e; opt++)
                                if (opt->opt == kDNSOpt_Owner && opt->u.owner.vers == 0 && opt->u.owner.HMAC.l[0])
                                        {
                                        ClearProxyRecords(m, &opt->u.owner, m->DuplicateRecords);
                                        ClearProxyRecords(m, &opt->u.owner, m->ResourceRecords);
                                        }
                        }
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }

        // ***
        // *** 2. Parse Question Section and mark potential answers
        // ***
        ptr = query->data;
        for (i=0; i<query->h.numQuestions; i++)                                         // For each question...
                {
                mDNSBool QuestionNeedsMulticastResponse;
                int NumAnswersForThisQuestion = 0;
                AuthRecord *NSECAnswer = mDNSNULL;
                DNSQuestion pktq, *q;
                ptr = getQuestion(query, ptr, end, InterfaceID, &pktq); // get the question...
                if (!ptr) goto exit;

                // The only queries that *need* a multicast response are:
                // * Queries sent via multicast
                // * from port 5353
                // * that don't have the kDNSQClass_UnicastResponse bit set
                // These queries need multicast responses because other clients will:
                // * suppress their own identical questions when they see these questions, and
                // * expire their cache records if they don't see the expected responses
                // For other queries, we may still choose to send the occasional multicast response anyway,
                // to keep our neighbours caches warm, and for ongoing conflict detection.
                QuestionNeedsMulticastResponse = QueryWasMulticast && !LegacyQuery && !(pktq.qclass & kDNSQClass_UnicastResponse);
                // Clear the UnicastResponse flag -- don't want to confuse the rest of the code that follows later
                pktq.qclass &= ~kDNSQClass_UnicastResponse;
                
                // Note: We use the m->CurrentRecord mechanism here because calling ResolveSimultaneousProbe
                // can result in user callbacks which may change the record list and/or question list.
                // Also note: we just mark potential answer records here, without trying to build the
                // "ResponseRecords" list, because we don't want to risk user callbacks deleting records
                // from that list while we're in the middle of trying to build it.
                if (m->CurrentRecord)
                        LogMsg("ProcessQuery ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
                m->CurrentRecord = m->ResourceRecords;
                while (m->CurrentRecord)
                        {
                        rr = m->CurrentRecord;
                        m->CurrentRecord = rr->next;
                        if (AnyTypeRecordAnswersQuestion(&rr->resrec, &pktq) && (QueryWasMulticast || QueryWasLocalUnicast || rr->AllowRemoteQuery))
                                {
                                if (RRTypeAnswersQuestionType(&rr->resrec, pktq.qtype))
                                        {
                                        if (rr->resrec.RecordType == kDNSRecordTypeUnique)
                                                ResolveSimultaneousProbe(m, query, end, &pktq, rr);
                                        else if (ResourceRecordIsValidAnswer(rr))
                                                {
                                                NumAnswersForThisQuestion++;
                                                // Note: We should check here if this is a probe-type query, and if so, generate an immediate
                                                // unicast answer back to the source, because timeliness in answering probes is important.
        
                                                // Notes:
                                                // NR_AnswerTo pointing into query packet means "answer via immediate legacy unicast" (may *also* choose to multicast)
                                                // NR_AnswerTo == (mDNSu8*)~1             means "answer via delayed unicast" (to modern querier; may promote to multicast instead)
                                                // NR_AnswerTo == (mDNSu8*)~0             means "definitely answer via multicast" (can't downgrade to unicast later)
                                                // If we're not multicasting this record because the kDNSQClass_UnicastResponse bit was set,
                                                // but the multicast querier is not on a matching subnet (e.g. because of overlaid subnets on one link)
                                                // then we'll multicast it anyway (if we unicast, the receiver will ignore it because it has an apparently non-local source)
                                                if (QuestionNeedsMulticastResponse || (!FromLocalSubnet && QueryWasMulticast && !LegacyQuery))
                                                        {
                                                        // We only mark this question for sending if it is at least one second since the last time we multicast it
                                                        // on this interface. If it is more than a second, or LastMCInterface is different, then we may multicast it.
                                                        // This is to guard against the case where someone blasts us with queries as fast as they can.
                                                        if (m->timenow - (rr->LastMCTime + mDNSPlatformOneSecond) >= 0 ||
                                                                (rr->LastMCInterface != mDNSInterfaceMark && rr->LastMCInterface != InterfaceID))
                                                                rr->NR_AnswerTo = (mDNSu8*)~0;
                                                        }
                                                else if (!rr->NR_AnswerTo) rr->NR_AnswerTo = LegacyQuery ? ptr : (mDNSu8*)~1;
                                                }
                                        }
                                else if ((rr->resrec.RecordType & kDNSRecordTypeActiveUniqueMask) && ResourceRecordIsValidAnswer(rr))
                                        {
                                        // If we don't have any answers for this question, but we do own another record with the same name,
                                        // then we'll want to mark it to generate an NSEC record on this interface
                                        if (!NSECAnswer) NSECAnswer = rr;
                                        }
                                }
                        }

                if (NumAnswersForThisQuestion == 0 && NSECAnswer)
                        {
                        NumAnswersForThisQuestion++;
                        NSECAnswer->SendNSECNow = InterfaceID;
                        m->NextScheduledResponse = m->timenow;
                        }

                // If we couldn't answer this question, someone else might be able to,
                // so use random delay on response to reduce collisions
                if (NumAnswersForThisQuestion == 0) delayresponse = mDNSPlatformOneSecond;      // Divided by 50 = 20ms

#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                if (QuestionNeedsMulticastResponse)
#else
                // We only do the following accelerated cache expiration and duplicate question suppression processing
                // for non-truncated multicast queries with multicast responses.
                // For any query generating a unicast response we don't do this because we can't assume we will see the response.
                // For truncated queries we don't do this because a response we're expecting might be suppressed by a subsequent
                // known-answer packet, and when there's packet loss we can't safely assume we'll receive *all* known-answer packets.
                if (QuestionNeedsMulticastResponse && !(query->h.flags.b[0] & kDNSFlag0_TC))
#endif
                        {
                        const mDNSu32 slot = HashSlot(&pktq.qname);
                        CacheGroup *cg = CacheGroupForName(m, slot, pktq.qnamehash, &pktq.qname);
                        CacheRecord *cr;

                        // Make a list indicating which of our own cache records we expect to see updated as a result of this query
                        // Note: Records larger than 1K are not habitually multicast, so don't expect those to be updated
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                        if (!(query->h.flags.b[0] & kDNSFlag0_TC))
#endif
                                for (cr = cg ? cg->members : mDNSNULL; cr; cr=cr->next)
                                        if (SameNameRecordAnswersQuestion(&cr->resrec, &pktq) && cr->resrec.rdlength <= SmallRecordLimit)
                                                if (!cr->NextInKAList && eap != &cr->NextInKAList)
                                                        {
                                                        *eap = cr;
                                                        eap = &cr->NextInKAList;
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                                                        if (cr->MPUnansweredQ == 0 || m->timenow - cr->MPLastUnansweredQT >= mDNSPlatformOneSecond)
                                                                {
                                                                // Although MPUnansweredQ is only really used for multi-packet query processing,
                                                                // we increment it for both single-packet and multi-packet queries, so that it stays in sync
                                                                // with the MPUnansweredKA value, which by necessity is incremented for both query types.
                                                                cr->MPUnansweredQ++;
                                                                cr->MPLastUnansweredQT = m->timenow;
                                                                cr->MPExpectingKA = mDNStrue;
                                                                }
#endif
                                                        }
        
                        // Check if this question is the same as any of mine.
                        // We only do this for non-truncated queries. Right now it would be too complicated to try
                        // to keep track of duplicate suppression state between multiple packets, especially when we
                        // can't guarantee to receive all of the Known Answer packets that go with a particular query.
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                        if (!(query->h.flags.b[0] & kDNSFlag0_TC))
#endif
                                for (q = m->Questions; q; q=q->next)
                                        if (!q->Target.type && ActiveQuestion(q) && m->timenow - q->LastQTxTime > mDNSPlatformOneSecond / 4)
                                                if (!q->InterfaceID || q->InterfaceID == InterfaceID)
                                                        if (q->NextInDQList == mDNSNULL && dqp != &q->NextInDQList)
                                                                if (q->qtype == pktq.qtype &&
                                                                        q->qclass == pktq.qclass &&
                                                                        q->qnamehash == pktq.qnamehash && SameDomainName(&q->qname, &pktq.qname))
                                                                        { *dqp = q; dqp = &q->NextInDQList; }
                        }
                }

        // ***
        // *** 3. Now we can safely build the list of marked answers
        // ***
        for (rr = m->ResourceRecords; rr; rr=rr->next)                          // Now build our list of potential answers
                if (rr->NR_AnswerTo)                                                                    // If we marked the record...
                        AddRecordToResponseList(&nrp, rr, mDNSNULL);            // ... add it to the list

        // ***
        // *** 4. Add additional records
        // ***
        AddAdditionalsToResponseList(m, ResponseRecords, &nrp, InterfaceID);

        // ***
        // *** 5. Parse Answer Section and cancel any records disallowed by Known-Answer list
        // ***
        for (i=0; i<query->h.numAnswers; i++)                                           // For each record in the query's answer section...
                {
                // Get the record...
                CacheRecord *ourcacherr;
                ptr = GetLargeResourceRecord(m, query, ptr, end, InterfaceID, kDNSRecordTypePacketAns, &m->rec);
                if (!ptr) goto exit;
                if (m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative)
                        {
                        // See if this Known-Answer suppresses any of our currently planned answers
                        for (rr=ResponseRecords; rr; rr=rr->NextResponse)
                                if (MustSendRecord(rr) && ShouldSuppressKnownAnswer(&m->rec.r, rr))
                                        { rr->NR_AnswerTo = mDNSNULL; rr->NR_AdditionalTo = mDNSNULL; }
        
                        // See if this Known-Answer suppresses any previously scheduled answers (for multi-packet KA suppression)
                        for (rr=m->ResourceRecords; rr; rr=rr->next)
                                {
                                // If we're planning to send this answer on this interface, and only on this interface, then allow KA suppression
                                if (rr->ImmedAnswer == InterfaceID && ShouldSuppressKnownAnswer(&m->rec.r, rr))
                                        {
                                        if (srcaddr->type == mDNSAddrType_IPv4)
                                                {
                                                if (mDNSSameIPv4Address(rr->v4Requester, srcaddr->ip.v4)) rr->v4Requester = zerov4Addr;
                                                }
                                        else if (srcaddr->type == mDNSAddrType_IPv6)
                                                {
                                                if (mDNSSameIPv6Address(rr->v6Requester, srcaddr->ip.v6)) rr->v6Requester = zerov6Addr;
                                                }
                                        if (mDNSIPv4AddressIsZero(rr->v4Requester) && mDNSIPv6AddressIsZero(rr->v6Requester))
                                                {
                                                rr->ImmedAnswer  = mDNSNULL;
                                                rr->ImmedUnicast = mDNSfalse;
        #if MDNS_LOG_ANSWER_SUPPRESSION_TIMES
                                                LogMsg("Suppressed after%4d: %s", m->timenow - rr->ImmedAnswerMarkTime, ARDisplayString(m, rr));
        #endif
                                                }
                                        }
                                }
        
                        ourcacherr = FindIdenticalRecordInCache(m, &m->rec.r.resrec);
        
        #if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                        // See if this Known-Answer suppresses any answers we were expecting for our cache records. We do this always,
                        // even if the TC bit is not set (the TC bit will *not* be set in the *last* packet of a multi-packet KA list).
                        if (ourcacherr && ourcacherr->MPExpectingKA && m->timenow - ourcacherr->MPLastUnansweredQT < mDNSPlatformOneSecond)
                                {
                                ourcacherr->MPUnansweredKA++;
                                ourcacherr->MPExpectingKA = mDNSfalse;
                                }
        #endif
        
                        // Having built our ExpectedAnswers list from the questions in this packet, we then remove
                        // any records that are suppressed by the Known Answer list in this packet.
                        eap = &ExpectedAnswers;
                        while (*eap)
                                {
                                CacheRecord *cr = *eap;
                                if (cr->resrec.InterfaceID == InterfaceID && IdenticalResourceRecord(&m->rec.r.resrec, &cr->resrec))
                                        { *eap = cr->NextInKAList; cr->NextInKAList = mDNSNULL; }
                                else eap = &cr->NextInKAList;
                                }
                        
                        // See if this Known-Answer is a surprise to us. If so, we shouldn't suppress our own query.
                        if (!ourcacherr)
                                {
                                dqp = &DupQuestions;
                                while (*dqp)
                                        {
                                        DNSQuestion *q = *dqp;
                                        if (ResourceRecordAnswersQuestion(&m->rec.r.resrec, q))
                                                { *dqp = q->NextInDQList; q->NextInDQList = mDNSNULL; }
                                        else dqp = &q->NextInDQList;
                                        }
                                }
                        }
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }

        // ***
        // *** 6. Cancel any additionals that were added because of now-deleted records
        // ***
        for (rr=ResponseRecords; rr; rr=rr->NextResponse)
                if (rr->NR_AdditionalTo && !MustSendRecord(rr->NR_AdditionalTo))
                        { rr->NR_AnswerTo = mDNSNULL; rr->NR_AdditionalTo = mDNSNULL; }

        // ***
        // *** 7. Mark the send flags on the records we plan to send
        // ***
        for (rr=ResponseRecords; rr; rr=rr->NextResponse)
                {
                if (rr->NR_AnswerTo)
                        {
                        mDNSBool SendMulticastResponse = mDNSfalse;             // Send modern multicast response
                        mDNSBool SendUnicastResponse   = mDNSfalse;             // Send modern unicast response (not legacy unicast response)
                        
                        // If it's been a while since we multicast this, then send a multicast response for conflict detection, etc.
                        if (m->timenow - (rr->LastMCTime + TicksTTL(rr)/4) >= 0)
                                {
                                SendMulticastResponse = mDNStrue;
                                // If this record was marked for modern (delayed) unicast response, then mark it as promoted to
                                // multicast response instead (don't want to end up ALSO setting SendUnicastResponse in the check below).
                                // If this record was marked for legacy unicast response, then we mustn't change the NR_AnswerTo value.
                                if (rr->NR_AnswerTo == (mDNSu8*)~1) rr->NR_AnswerTo = (mDNSu8*)~0;
                                }
                        
                        // If the client insists on a multicast response, then we'd better send one
                        if      (rr->NR_AnswerTo == (mDNSu8*)~0) SendMulticastResponse = mDNStrue;
                        else if (rr->NR_AnswerTo == (mDNSu8*)~1) SendUnicastResponse   = mDNStrue;
                        else if (rr->NR_AnswerTo)                SendLegacyResponse    = mDNStrue;
        
                        if (SendMulticastResponse || SendUnicastResponse)
                                {
#if MDNS_LOG_ANSWER_SUPPRESSION_TIMES
                                rr->ImmedAnswerMarkTime = m->timenow;
#endif
                                m->NextScheduledResponse = m->timenow;
                                // If we're already planning to send this on another interface, just send it on all interfaces
                                if (rr->ImmedAnswer && rr->ImmedAnswer != InterfaceID)
                                        rr->ImmedAnswer = mDNSInterfaceMark;
                                else
                                        {
                                        rr->ImmedAnswer = InterfaceID;                  // Record interface to send it on
                                        if (SendUnicastResponse) rr->ImmedUnicast = mDNStrue;
                                        if (srcaddr->type == mDNSAddrType_IPv4)
                                                {
                                                if      (mDNSIPv4AddressIsZero(rr->v4Requester))                rr->v4Requester = srcaddr->ip.v4;
                                                else if (!mDNSSameIPv4Address(rr->v4Requester, srcaddr->ip.v4)) rr->v4Requester = onesIPv4Addr;
                                                }
                                        else if (srcaddr->type == mDNSAddrType_IPv6)
                                                {
                                                if      (mDNSIPv6AddressIsZero(rr->v6Requester))                rr->v6Requester = srcaddr->ip.v6;
                                                else if (!mDNSSameIPv6Address(rr->v6Requester, srcaddr->ip.v6)) rr->v6Requester = onesIPv6Addr;
                                                }
                                        }
                                }
                        // If TC flag is set, it means we should expect that additional known answers may be coming in another packet,
                        // so we allow roughly half a second before deciding to reply (we've observed inter-packet delays of 100-200ms on 802.11)
                        // else, if record is a shared one, spread responses over 100ms to avoid implosion of simultaneous responses
                        // else, for a simple unique record reply, we can reply immediately; no need for delay
                        if      (query->h.flags.b[0] & kDNSFlag0_TC)            delayresponse = mDNSPlatformOneSecond * 20;     // Divided by 50 = 400ms
                        else if (rr->resrec.RecordType == kDNSRecordTypeShared) delayresponse = mDNSPlatformOneSecond;          // Divided by 50 = 20ms
                        }
                else if (rr->NR_AdditionalTo && rr->NR_AdditionalTo->NR_AnswerTo == (mDNSu8*)~0)
                        {
                        // Since additional records are an optimization anyway, we only ever send them on one interface at a time
                        // If two clients on different interfaces do queries that invoke the same optional additional answer,
                        // then the earlier client is out of luck
                        rr->ImmedAdditional = InterfaceID;
                        // No need to set m->NextScheduledResponse here
                        // We'll send these additional records when we send them, or not, as the case may be
                        }
                }

        // ***
        // *** 8. If we think other machines are likely to answer these questions, set our packet suppression timer
        // ***
        if (delayresponse && (!m->SuppressSending || (m->SuppressSending - m->timenow) < (delayresponse + 49) / 50))
                {
#if MDNS_LOG_ANSWER_SUPPRESSION_TIMES
                mDNSs32 oldss = m->SuppressSending;
                if (oldss && delayresponse)
                        LogMsg("Current SuppressSending delay%5ld; require%5ld", m->SuppressSending - m->timenow, (delayresponse + 49) / 50);
#endif
                // Pick a random delay:
                // We start with the base delay chosen above (typically either 1 second or 20 seconds),
                // and add a random value in the range 0-5 seconds (making 1-6 seconds or 20-25 seconds).
                // This is an integer value, with resolution determined by the platform clock rate.
                // We then divide that by 50 to get the delay value in ticks. We defer the division until last
                // to get better results on platforms with coarse clock granularity (e.g. ten ticks per second).
                // The +49 before dividing is to ensure we round up, not down, to ensure that even
                // on platforms where the native clock rate is less than fifty ticks per second,
                // we still guarantee that the final calculated delay is at least one platform tick.
                // We want to make sure we don't ever allow the delay to be zero ticks,
                // because if that happens we'll fail the Bonjour Conformance Test.
                // Our final computed delay is 20-120ms for normal delayed replies,
                // or 400-500ms in the case of multi-packet known-answer lists.
                m->SuppressSending = m->timenow + (delayresponse + (mDNSs32)mDNSRandom((mDNSu32)mDNSPlatformOneSecond*5) + 49) / 50;
                if (m->SuppressSending == 0) m->SuppressSending = 1;
#if MDNS_LOG_ANSWER_SUPPRESSION_TIMES
                if (oldss && delayresponse)
                        LogMsg("Set     SuppressSending to   %5ld", m->SuppressSending - m->timenow);
#endif
                }

        // ***
        // *** 9. If query is from a legacy client, or from a new client requesting a unicast reply, then generate a unicast response too
        // ***
        if (SendLegacyResponse)
                responseptr = GenerateUnicastResponse(query, end, InterfaceID, LegacyQuery, response, ResponseRecords);

exit:
        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
        
        // ***
        // *** 10. Finally, clear our link chains ready for use next time
        // ***
        while (ResponseRecords)
                {
                rr = ResponseRecords;
                ResponseRecords = rr->NextResponse;
                rr->NextResponse    = mDNSNULL;
                rr->NR_AnswerTo     = mDNSNULL;
                rr->NR_AdditionalTo = mDNSNULL;
                }
        
        while (ExpectedAnswers)
                {
                CacheRecord *cr = ExpectedAnswers;
                ExpectedAnswers = cr->NextInKAList;
                cr->NextInKAList = mDNSNULL;
                
                // For non-truncated queries, we can definitively say that we should expect
                // to be seeing a response for any records still left in the ExpectedAnswers list
                if (!(query->h.flags.b[0] & kDNSFlag0_TC))
                        if (cr->UnansweredQueries == 0 || m->timenow - cr->LastUnansweredTime >= mDNSPlatformOneSecond)
                                {
                                cr->UnansweredQueries++;
                                cr->LastUnansweredTime = m->timenow;
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                                if (cr->UnansweredQueries > 1)
                                        debugf("ProcessQuery: (!TC) UAQ %lu MPQ %lu MPKA %lu %s",
                                                cr->UnansweredQueries, cr->MPUnansweredQ, cr->MPUnansweredKA, CRDisplayString(m, cr));
#endif
                                SetNextCacheCheckTimeForRecord(m, cr);
                                }

                // If we've seen multiple unanswered queries for this record,
                // then mark it to expire in five seconds if we don't get a response by then.
                if (cr->UnansweredQueries >= MaxUnansweredQueries)
                        {
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                        // Only show debugging message if this record was not about to expire anyway
                        if (RRExpireTime(cr) - m->timenow > 4 * mDNSPlatformOneSecond)
                                debugf("ProcessQuery: (Max) UAQ %lu MPQ %lu MPKA %lu mDNS_Reconfirm() for %s",
                                        cr->UnansweredQueries, cr->MPUnansweredQ, cr->MPUnansweredKA, CRDisplayString(m, cr));
#endif
                        mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForNoAnswer);
                        }
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
                // Make a guess, based on the multi-packet query / known answer counts, whether we think we
                // should have seen an answer for this. (We multiply MPQ by 4 and MPKA by 5, to allow for
                // possible packet loss of up to 20% of the additional KA packets.)
                else if (cr->MPUnansweredQ * 4 > cr->MPUnansweredKA * 5 + 8)
                        {
                        // We want to do this conservatively.
                        // If there are so many machines on the network that they have to use multi-packet known-answer lists,
                        // then we don't want them to all hit the network simultaneously with their final expiration queries.
                        // By setting the record to expire in four minutes, we achieve two things:
                        // (a) the 90-95% final expiration queries will be less bunched together
                        // (b) we allow some time for us to witness enough other failed queries that we don't have to do our own
                        mDNSu32 remain = (mDNSu32)(RRExpireTime(cr) - m->timenow) / 4;
                        if (remain > 240 * (mDNSu32)mDNSPlatformOneSecond)
                                remain = 240 * (mDNSu32)mDNSPlatformOneSecond;
                        
                        // Only show debugging message if this record was not about to expire anyway
                        if (RRExpireTime(cr) - m->timenow > 4 * mDNSPlatformOneSecond)
                                debugf("ProcessQuery: (MPQ) UAQ %lu MPQ %lu MPKA %lu mDNS_Reconfirm() for %s",
                                        cr->UnansweredQueries, cr->MPUnansweredQ, cr->MPUnansweredKA, CRDisplayString(m, cr));

                        if (remain <= 60 * (mDNSu32)mDNSPlatformOneSecond)
                                cr->UnansweredQueries++;        // Treat this as equivalent to one definite unanswered query
                        cr->MPUnansweredQ  = 0;                 // Clear MPQ/MPKA statistics
                        cr->MPUnansweredKA = 0;
                        cr->MPExpectingKA  = mDNSfalse;
                        
                        if (remain < kDefaultReconfirmTimeForNoAnswer)
                                remain = kDefaultReconfirmTimeForNoAnswer;
                        mDNS_Reconfirm_internal(m, cr, remain);
                        }
#endif
                }
        
        while (DupQuestions)
                {
                DNSQuestion *q = DupQuestions;
                DupQuestions = q->NextInDQList;
                q->NextInDQList = mDNSNULL;
                i = RecordDupSuppressInfo(q->DupSuppress, m->timenow, InterfaceID, srcaddr->type);
                debugf("ProcessQuery: Recorded DSI for %##s (%s) on %p/%s %d", q->qname.c, DNSTypeName(q->qtype), InterfaceID,
                        srcaddr->type == mDNSAddrType_IPv4 ? "v4" : "v6", i);
                }
        
        return(responseptr);
        }

mDNSlocal void mDNSCoreReceiveQuery(mDNS *const m, const DNSMessage *const msg, const mDNSu8 *const end,
        const mDNSAddr *srcaddr, const mDNSIPPort srcport, const mDNSAddr *dstaddr, mDNSIPPort dstport,
        const mDNSInterfaceID InterfaceID)
        {
        mDNSu8    *responseend = mDNSNULL;
        mDNSBool   QueryWasLocalUnicast = srcaddr && dstaddr &&
                !mDNSAddrIsDNSMulticast(dstaddr) && mDNS_AddressIsLocalSubnet(m, InterfaceID, srcaddr);
        
        if (!InterfaceID && dstaddr && mDNSAddrIsDNSMulticast(dstaddr))
                {
                LogMsg("Ignoring Query from %#-15a:%-5d to %#-15a:%-5d on 0x%p with "
                        "%2d Question%s %2d Answer%s %2d Authorit%s %2d Additional%s %d bytes (Multicast, but no InterfaceID)",
                        srcaddr, mDNSVal16(srcport), dstaddr, mDNSVal16(dstport), InterfaceID,
                        msg->h.numQuestions,   msg->h.numQuestions   == 1 ? ", "   : "s,",
                        msg->h.numAnswers,     msg->h.numAnswers     == 1 ? ", "   : "s,",
                        msg->h.numAuthorities, msg->h.numAuthorities == 1 ? "y,  " : "ies,",
                        msg->h.numAdditionals, msg->h.numAdditionals == 1 ? " "    : "s", end - msg->data);
                return;
                }

        verbosedebugf("Received Query from %#-15a:%-5d to %#-15a:%-5d on 0x%p with "
                "%2d Question%s %2d Answer%s %2d Authorit%s %2d Additional%s %d bytes",
                srcaddr, mDNSVal16(srcport), dstaddr, mDNSVal16(dstport), InterfaceID,
                msg->h.numQuestions,   msg->h.numQuestions   == 1 ? ", "   : "s,",
                msg->h.numAnswers,     msg->h.numAnswers     == 1 ? ", "   : "s,",
                msg->h.numAuthorities, msg->h.numAuthorities == 1 ? "y,  " : "ies,",
                msg->h.numAdditionals, msg->h.numAdditionals == 1 ? " "    : "s", end - msg->data);
        
        responseend = ProcessQuery(m, msg, end, srcaddr, InterfaceID,
                !mDNSSameIPPort(srcport, MulticastDNSPort), mDNSAddrIsDNSMulticast(dstaddr), QueryWasLocalUnicast, &m->omsg);

        if (responseend)        // If responseend is non-null, that means we built a unicast response packet
                {
                debugf("Unicast Response: %d Question%s, %d Answer%s, %d Additional%s to %#-15a:%d on %p/%ld",
                        m->omsg.h.numQuestions,   m->omsg.h.numQuestions   == 1 ? "" : "s",
                        m->omsg.h.numAnswers,     m->omsg.h.numAnswers     == 1 ? "" : "s",
                        m->omsg.h.numAdditionals, m->omsg.h.numAdditionals == 1 ? "" : "s",
                        srcaddr, mDNSVal16(srcport), InterfaceID, srcaddr->type);
                mDNSSendDNSMessage(m, &m->omsg, responseend, InterfaceID, mDNSNULL, srcaddr, srcport, mDNSNULL, mDNSNULL);
                }
        }

#if 0
mDNSlocal mDNSBool TrustedSource(const mDNS *const m, const mDNSAddr *const srcaddr)
        {
        DNSServer *s;
        (void)m; // Unused
        (void)srcaddr; // Unused
        for (s = m->DNSServers; s; s = s->next)
                if (mDNSSameAddress(srcaddr, &s->addr)) return(mDNStrue);
        return(mDNSfalse);
        }
#endif

struct UDPSocket_struct
        {
        mDNSIPPort port; // MUST BE FIRST FIELD -- mDNSCoreReceive expects every UDPSocket_struct to begin with mDNSIPPort port
        };

mDNSlocal DNSQuestion *ExpectingUnicastResponseForQuestion(const mDNS *const m, const mDNSIPPort port, const mDNSOpaque16 id, const DNSQuestion *const question, mDNSBool tcp)
        {
        DNSQuestion *q;
        for (q = m->Questions; q; q=q->next)
                {
                if (!tcp && !q->LocalSocket) continue;
                if (mDNSSameIPPort(tcp ? q->tcpSrcPort : q->LocalSocket->port, port)     &&
                        mDNSSameOpaque16(q->TargetQID,         id)       &&
                        q->qtype                  == question->qtype     &&
                        q->qclass                 == question->qclass    &&
                        q->qnamehash              == question->qnamehash &&
                        SameDomainName(&q->qname, &question->qname))
                        return(q);
                }
        return(mDNSNULL);
        }

// This function is called when we receive a unicast response. This could be the case of a unicast response from the
// DNS server or a response to the QU query. Hence, the cache record's InterfaceId can be both NULL or non-NULL (QU case)
mDNSlocal DNSQuestion *ExpectingUnicastResponseForRecord(mDNS *const m,
        const mDNSAddr *const srcaddr, const mDNSBool SrcLocal, const mDNSIPPort port, const mDNSOpaque16 id, const CacheRecord *const rr, mDNSBool tcp)
        {
        DNSQuestion *q;
        (void)id;
        (void)srcaddr;

        for (q = m->Questions; q; q=q->next)
                {
                if (!q->DuplicateOf && ResourceRecordAnswersUnicastResponse(&rr->resrec, q))
                        {
                        if (!mDNSOpaque16IsZero(q->TargetQID))
                                {
                                debugf("ExpectingUnicastResponseForRecord msg->h.id %d q->TargetQID %d for %s", mDNSVal16(id), mDNSVal16(q->TargetQID), CRDisplayString(m, rr));

                                if (mDNSSameOpaque16(q->TargetQID, id))
                                        {
                                        mDNSIPPort srcp;
                                        if (!tcp)
                                                {
                                                srcp = q->LocalSocket ? q->LocalSocket->port : zeroIPPort;
                                                }
                                        else
                                                {
                                                srcp = q->tcpSrcPort;
                                                }
                                        if (mDNSSameIPPort(srcp, port)) return(q);
                                        
                                //      if (mDNSSameAddress(srcaddr, &q->Target))                   return(mDNStrue);
                                //      if (q->LongLived && mDNSSameAddress(srcaddr, &q->servAddr)) return(mDNStrue); Shouldn't need this now that we have LLQType checking
                                //      if (TrustedSource(m, srcaddr))                              return(mDNStrue);
                                        LogInfo("WARNING: Ignoring suspect uDNS response for %##s (%s) [q->Target %#a:%d] from %#a:%d %s",
                                                q->qname.c, DNSTypeName(q->qtype), &q->Target, mDNSVal16(srcp), srcaddr, mDNSVal16(port), CRDisplayString(m, rr));
                                        return(mDNSNULL);
                                        }
                                }
                        else
                                {
                                if (SrcLocal && q->ExpectUnicastResp && (mDNSu32)(m->timenow - q->ExpectUnicastResp) < (mDNSu32)(mDNSPlatformOneSecond*2))
                                        return(q);
                                }
                        }
                }
        return(mDNSNULL);
        }

// Certain data types need more space for in-memory storage than their in-packet rdlength would imply
// Currently this applies only to rdata types containing more than one domainname,
// or types where the domainname is not the last item in the structure.
// In addition, NSEC currently requires less space for in-memory storage than its in-packet representation.
mDNSlocal mDNSu16 GetRDLengthMem(const ResourceRecord *const rr)
        {
        switch (rr->rrtype)
                {
                case kDNSType_SOA: return sizeof(rdataSOA);
                case kDNSType_RP:  return sizeof(rdataRP);
                case kDNSType_PX:  return sizeof(rdataPX);
                case kDNSType_NSEC:return sizeof(rdataNSEC);
                default:           return rr->rdlength;
                }
        }

mDNSexport CacheRecord *CreateNewCacheEntry(mDNS *const m, const mDNSu32 slot, CacheGroup *cg, mDNSs32 delay)
        {
        CacheRecord *rr = mDNSNULL;
        mDNSu16 RDLength = GetRDLengthMem(&m->rec.r.resrec);

        if (!m->rec.r.resrec.InterfaceID) debugf("CreateNewCacheEntry %s", CRDisplayString(m, &m->rec.r));

        //if (RDLength > InlineCacheRDSize)
        //      LogInfo("Rdata len %4d > InlineCacheRDSize %d %s", RDLength, InlineCacheRDSize, CRDisplayString(m, &m->rec.r));

        if (!cg) cg = GetCacheGroup(m, slot, &m->rec.r.resrec); // If we don't have a CacheGroup for this name, make one now
        if (cg)  rr = GetCacheRecord(m, cg, RDLength);  // Make a cache record, being careful not to recycle cg
        if (!rr) NoCacheAnswer(m, &m->rec.r);
        else
                {
                RData *saveptr = rr->resrec.rdata;              // Save the rr->resrec.rdata pointer
                *rr = m->rec.r;                                                 // Block copy the CacheRecord object
                rr->resrec.rdata  = saveptr;                            // Restore rr->resrec.rdata after the structure assignment
                rr->resrec.name   = cg->name;                   // And set rr->resrec.name to point into our CacheGroup header
                rr->DelayDelivery = delay;

                // If this is an oversized record with external storage allocated, copy rdata to external storage
                if      (rr->resrec.rdata == (RData*)&rr->smallrdatastorage && RDLength > InlineCacheRDSize)
                        LogMsg("rr->resrec.rdata == &rr->rdatastorage but length > InlineCacheRDSize %##s", m->rec.r.resrec.name->c);
                else if (rr->resrec.rdata != (RData*)&rr->smallrdatastorage && RDLength <= InlineCacheRDSize)
                        LogMsg("rr->resrec.rdata != &rr->rdatastorage but length <= InlineCacheRDSize %##s", m->rec.r.resrec.name->c);
                if (RDLength > InlineCacheRDSize)
                        mDNSPlatformMemCopy(rr->resrec.rdata, m->rec.r.resrec.rdata, sizeofRDataHeader + RDLength);

                rr->next = mDNSNULL;                                    // Clear 'next' pointer
                *(cg->rrcache_tail) = rr;                               // Append this record to tail of cache slot list
                cg->rrcache_tail = &(rr->next);                 // Advance tail pointer

                CacheRecordAdd(m, rr);  // CacheRecordAdd calls SetNextCacheCheckTimeForRecord(m, rr); for us
                }
        return(rr);
        }

mDNSlocal void RefreshCacheRecord(mDNS *const m, CacheRecord *rr, mDNSu32 ttl)
        {
        rr->TimeRcvd             = m->timenow;
        rr->resrec.rroriginalttl = ttl;
        rr->UnansweredQueries = 0;
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
        rr->MPUnansweredQ     = 0;
        rr->MPUnansweredKA    = 0;
        rr->MPExpectingKA     = mDNSfalse;
#endif
        SetNextCacheCheckTimeForRecord(m, rr);
        }

mDNSexport void GrantCacheExtensions(mDNS *const m, DNSQuestion *q, mDNSu32 lease)
        {
        CacheRecord *rr;
        const mDNSu32 slot = HashSlot(&q->qname);
        CacheGroup *cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                if (rr->CRActiveQuestion == q)
                        {
                        //LogInfo("GrantCacheExtensions: new lease %d / %s", lease, CRDisplayString(m, rr));
                        RefreshCacheRecord(m, rr, lease);
                        }
        }

mDNSlocal mDNSu32 GetEffectiveTTL(const uDNS_LLQType LLQType, mDNSu32 ttl)              // TTL in seconds
        {
        if      (LLQType == uDNS_LLQ_Entire) ttl = kLLQ_DefLease;
        else if (LLQType == uDNS_LLQ_Events)
                {
                // If the TTL is -1 for uDNS LLQ event packet, that means "remove"
                if (ttl == 0xFFFFFFFF) ttl = 0;
                else                   ttl = kLLQ_DefLease;
                }
        else    // else not LLQ (standard uDNS response)
                {
                // The TTL is already capped to a maximum value in GetLargeResourceRecord, but just to be extra safe we
                // also do this check here to make sure we can't get overflow below when we add a quarter to the TTL
                if (ttl > 0x60000000UL / mDNSPlatformOneSecond) ttl = 0x60000000UL / mDNSPlatformOneSecond;

                // Adjustment factor to avoid race condition:
                // Suppose real record as TTL of 3600, and our local caching server has held it for 3500 seconds, so it returns an aged TTL of 100.
                // If we do our normal refresh at 80% of the TTL, our local caching server will return 20 seconds, so we'll do another
                // 80% refresh after 16 seconds, and then the server will return 4 seconds, and so on, in the fashion of Zeno's paradox.
                // To avoid this, we extend the record's effective TTL to give it a little extra grace period.
                // We adjust the 100 second TTL to 126. This means that when we do our 80% query at 101 seconds,
                // the cached copy at our local caching server will already have expired, so the server will be forced
                // to fetch a fresh copy from the authoritative server, and then return a fresh record with the full TTL of 3600 seconds.
                ttl += ttl/4 + 2;

                // For mDNS, TTL zero means "delete this record"
                // For uDNS, TTL zero means: this data is true at this moment, but don't cache it.
                // For the sake of network efficiency, we impose a minimum effective TTL of 15 seconds.
                // This means that we'll do our 80, 85, 90, 95% queries at 12.00, 12.75, 13.50, 14.25 seconds
                // respectively, and then if we get no response, delete the record from the cache at 15 seconds.
                // This gives the server up to three seconds to respond between when we send our 80% query at 12 seconds
                // and when we delete the record at 15 seconds. Allowing cache lifetimes less than 15 seconds would
                // (with the current code) result in the server having even less than three seconds to respond
                // before we deleted the record and reported a "remove" event to any active questions.
                // Furthermore, with the current code, if we were to allow a TTL of less than 2 seconds
                // then things really break (e.g. we end up making a negative cache entry).
                // In the future we may want to revisit this and consider properly supporting non-cached (TTL=0) uDNS answers.
                if (ttl < 15) ttl = 15;
                }
        
        return ttl;
        }

// Note: mDNSCoreReceiveResponse calls mDNS_Deregister_internal which can call a user callback, which may change
// the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
// InterfaceID non-NULL tells us the interface this multicast response was received on
// InterfaceID NULL tells us this was a unicast response
// dstaddr NULL tells us we received this over an outgoing TCP connection we made
mDNSlocal void mDNSCoreReceiveResponse(mDNS *const m,
        const DNSMessage *const response, const mDNSu8 *end,
        const mDNSAddr *srcaddr, const mDNSIPPort srcport, const mDNSAddr *dstaddr, mDNSIPPort dstport,
        const mDNSInterfaceID InterfaceID)
        {
        int i;
        mDNSBool ResponseMCast    = dstaddr && mDNSAddrIsDNSMulticast(dstaddr);
        mDNSBool ResponseSrcLocal = !srcaddr || mDNS_AddressIsLocalSubnet(m, InterfaceID, srcaddr);
        DNSQuestion *llqMatch = mDNSNULL;
        uDNS_LLQType LLQType      = uDNS_recvLLQResponse(m, response, end, srcaddr, srcport, &llqMatch);

        // "(CacheRecord*)1" is a special (non-zero) end-of-list marker
        // We use this non-zero marker so that records in our CacheFlushRecords list will always have NextInCFList
        // set non-zero, and that tells GetCacheEntity() that they're not, at this moment, eligible for recycling.
        CacheRecord *CacheFlushRecords = (CacheRecord*)1;
        CacheRecord **cfp = &CacheFlushRecords;

        // All records in a DNS response packet are treated as equally valid statements of truth. If we want
        // to guard against spoof responses, then the only credible protection against that is cryptographic
        // security, e.g. DNSSEC., not worring about which section in the spoof packet contained the record
        int firstauthority  =                   response->h.numAnswers;
        int firstadditional = firstauthority  + response->h.numAuthorities;
        int totalrecords    = firstadditional + response->h.numAdditionals;
        const mDNSu8 *ptr   = response->data;
        DNSServer *uDNSServer = mDNSNULL;

        debugf("Received Response from %#-15a addressed to %#-15a on %p with "
                "%2d Question%s %2d Answer%s %2d Authorit%s %2d Additional%s %d bytes LLQType %d",
                srcaddr, dstaddr, InterfaceID,
                response->h.numQuestions,   response->h.numQuestions   == 1 ? ", "   : "s,",
                response->h.numAnswers,     response->h.numAnswers     == 1 ? ", "   : "s,",
                response->h.numAuthorities, response->h.numAuthorities == 1 ? "y,  " : "ies,",
                response->h.numAdditionals, response->h.numAdditionals == 1 ? " "    : "s", end - response->data, LLQType);

        // According to RFC 2181 <http://www.ietf.org/rfc/rfc2181.txt>
        //    When a DNS client receives a reply with TC
        //    set, it should ignore that response, and query again, using a
        //    mechanism, such as a TCP connection, that will permit larger replies.
        // It feels wrong to be throwing away data after the network went to all the trouble of delivering it to us, but
        // delivering some records of the RRSet first and then the remainder a couple of milliseconds later was causing
        // failures in our Microsoft Active Directory client, which expects to get the entire set of answers at once.
        // <rdar://problem/6690034> Can't bind to Active Directory
        // In addition, if the client immediately canceled its query after getting the initial partial response, then we'll
        // abort our TCP connection, and not complete the operation, and end up with an incomplete RRSet in our cache.
        // Next time there's a query for this RRSet we'll see answers in our cache, and assume we have the whole RRSet already,
        // and not even do the TCP query.
        // Accordingly, if we get a uDNS reply with kDNSFlag0_TC set, we bail out and wait for the TCP response containing the entire RRSet.
        if (!InterfaceID && (response->h.flags.b[0] & kDNSFlag0_TC)) return;

        if (LLQType == uDNS_LLQ_Ignore) return;

        // 1. We ignore questions (if any) in mDNS response packets
        // 2. If this is an LLQ response, we handle it much the same
        // 3. If we get a uDNS UDP response with the TC (truncated) bit set, then we can't treat this
        //    answer as being the authoritative complete RRSet, and respond by deleting all other
        //    matching cache records that don't appear in this packet.
        // Otherwise, this is a authoritative uDNS answer, so arrange for any stale records to be purged
        if (ResponseMCast || LLQType == uDNS_LLQ_Events || (response->h.flags.b[0] & kDNSFlag0_TC))
                ptr = LocateAnswers(response, end);
        // Otherwise, for one-shot queries, any answers in our cache that are not also contained
        // in this response packet are immediately deemed to be invalid.
        else
                {
                mDNSu8 rcode = (mDNSu8)(response->h.flags.b[1] & kDNSFlag1_RC_Mask);
                mDNSBool failure = !(rcode == kDNSFlag1_RC_NoErr || rcode == kDNSFlag1_RC_NXDomain || rcode == kDNSFlag1_RC_NotAuth);
                mDNSBool returnEarly = mDNSfalse;
                // We could possibly combine this with the similar loop at the end of this function --
                // instead of tagging cache records here and then rescuing them if we find them in the answer section,
                // we could instead use the "m->PktNum" mechanism to tag each cache record with the packet number in
                // which it was received (or refreshed), and then at the end if we find any cache records which
                // answer questions in this packet's question section, but which aren't tagged with this packet's
                // packet number, then we deduce they are old and delete them
                for (i = 0; i < response->h.numQuestions && ptr && ptr < end; i++)
                        {
                        DNSQuestion q, *qptr = mDNSNULL;
                        ptr = getQuestion(response, ptr, end, InterfaceID, &q);
                        if (ptr && (qptr = ExpectingUnicastResponseForQuestion(m, dstport, response->h.id, &q, !dstaddr)))
                                {
                                if (!failure)
                                        {
                                        CacheRecord *rr;
                                        const mDNSu32 slot = HashSlot(&q.qname);
                                        CacheGroup *cg = CacheGroupForName(m, slot, q.qnamehash, &q.qname);
                                        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                                                if (SameNameRecordAnswersQuestion(&rr->resrec, qptr))
                                                        {
                                                        debugf("uDNS marking %p %##s (%s) %p %s", q.InterfaceID, q.qname.c, DNSTypeName(q.qtype),
                                                                rr->resrec.InterfaceID, CRDisplayString(m, rr));
                                                        // Don't want to disturb rroriginalttl here, because code below might need it for the exponential backoff doubling algorithm
                                                        rr->TimeRcvd          = m->timenow - TicksTTL(rr) - 1;
                                                        rr->UnansweredQueries = MaxUnansweredQueries;
                                                        }
                                        }
                                else
                                        {
                                        if (qptr)
                                                {
                                                LogInfo("mDNSCoreReceiveResponse: Server %p responded with code %d to query %##s (%s)", qptr->qDNSServer, rcode, q.qname.c, DNSTypeName(q.qtype));
                                                PenalizeDNSServer(m, qptr);
                                                }
                                        returnEarly = mDNStrue;
                                        }
                                }
                        }
                if (returnEarly)
                        {
                        LogInfo("Ignoring %2d Answer%s %2d Authorit%s %2d Additional%s",
                                response->h.numAnswers,     response->h.numAnswers     == 1 ? ", " : "s,",
                                response->h.numAuthorities, response->h.numAuthorities == 1 ? "y,  " : "ies,",
                                response->h.numAdditionals, response->h.numAdditionals == 1 ? "" : "s");
                        // not goto exit because we won't have any CacheFlushRecords and we do not want to
                        // generate negative cache entries (we want to query the next server)
                        return;
                        }
                }

        for (i = 0; i < totalrecords && ptr && ptr < end; i++)
                {
                // All responses sent via LL multicast are acceptable for caching
                // All responses received over our outbound TCP connections are acceptable for caching
                mDNSBool AcceptableResponse = ResponseMCast || !dstaddr || LLQType;
                // (Note that just because we are willing to cache something, that doesn't necessarily make it a trustworthy answer
                // to any specific question -- any code reading records from the cache needs to make that determination for itself.)

                const mDNSu8 RecordType =
                        (i < firstauthority ) ? (mDNSu8)kDNSRecordTypePacketAns  :
                        (i < firstadditional) ? (mDNSu8)kDNSRecordTypePacketAuth : (mDNSu8)kDNSRecordTypePacketAdd;
                ptr = GetLargeResourceRecord(m, response, ptr, end, InterfaceID, RecordType, &m->rec);
                if (!ptr) goto exit;            // Break out of the loop and clean up our CacheFlushRecords list before exiting
                if (m->rec.r.resrec.RecordType == kDNSRecordTypePacketNegative) { m->rec.r.resrec.RecordType = 0; continue; }

                // Don't want to cache OPT or TSIG pseudo-RRs
                if (m->rec.r.resrec.rrtype == kDNSType_TSIG) { m->rec.r.resrec.RecordType = 0; continue; }
                if (m->rec.r.resrec.rrtype == kDNSType_OPT)
                        {
                        const rdataOPT *opt;
                        const rdataOPT *const e = (const rdataOPT *)&m->rec.r.resrec.rdata->u.data[m->rec.r.resrec.rdlength];
                        // Find owner sub-option(s). We verify that the MAC is non-zero, otherwise we could inadvertently
                        // delete all our own AuthRecords (which are identified by having zero MAC tags on them).
                        for (opt = &m->rec.r.resrec.rdata->u.opt[0]; opt < e; opt++)
                                if (opt->opt == kDNSOpt_Owner && opt->u.owner.vers == 0 && opt->u.owner.HMAC.l[0])
                                        {
                                        ClearProxyRecords(m, &opt->u.owner, m->DuplicateRecords);
                                        ClearProxyRecords(m, &opt->u.owner, m->ResourceRecords);
                                        }
                        m->rec.r.resrec.RecordType = 0;
                        continue;
                        }

                // if a CNAME record points to itself, then don't add it to the cache
                if ((m->rec.r.resrec.rrtype == kDNSType_CNAME) && SameDomainName(m->rec.r.resrec.name, &m->rec.r.resrec.rdata->u.name))
                        {
                        LogInfo("mDNSCoreReceiveResponse: CNAME loop domain name %##s", m->rec.r.resrec.name->c);
                        m->rec.r.resrec.RecordType = 0;
                        continue;
                        }

                // When we receive uDNS LLQ responses, we assume a long cache lifetime --
                // In the case of active LLQs, we'll get remove events when the records actually do go away
                // In the case of polling LLQs, we assume the record remains valid until the next poll
                if (!mDNSOpaque16IsZero(response->h.id))
                        m->rec.r.resrec.rroriginalttl = GetEffectiveTTL(LLQType, m->rec.r.resrec.rroriginalttl);

                // If response was not sent via LL multicast,
                // then see if it answers a recent query of ours, which would also make it acceptable for caching.
                if (!ResponseMCast)
                        {
                        if (LLQType)
                                {
                                // For Long Lived queries that are both sent over UDP and Private TCP, LLQType is set.
                                // Even though it is AcceptableResponse, we need a matching DNSServer pointer for the
                                // queries to get ADD/RMV events. To lookup the question, we can't use
                                // ExpectingUnicastResponseForRecord as the port numbers don't match. uDNS_recvLLQRespose
                                // has already matched the question using the 64 bit Id in the packet and we use that here.

                                if (llqMatch != mDNSNULL) m->rec.r.resrec.rDNSServer = uDNSServer = llqMatch->qDNSServer;
                                }
                        else if (!AcceptableResponse || !dstaddr)
                                {
                                // For responses that come over TCP (Responses that can't fit within UDP) or TLS (Private queries
                                // that are not long lived e.g., AAAA lookup in a Private domain), it is indicated by !dstaddr.
                                // Even though it is AcceptableResponse, we still need a DNSServer pointer for the resource records that
                                // we create.

                                DNSQuestion *q = ExpectingUnicastResponseForRecord(m, srcaddr, ResponseSrcLocal, dstport, response->h.id, &m->rec.r, !dstaddr);

                                // Intialize the DNS server on the resource record which will now filter what questions we answer with
                                // this record.
                                //
                                // We could potentially lookup the DNS server based on the source address, but that may not work always
                                // and that's why ExpectingUnicastResponseForRecord does not try to verify whether the response came
                                // from the DNS server that queried. We follow the same logic here. If we can find a matching quetion based
                                // on the "id" and "source port", then this response answers the question and assume the response
                                // came from the same DNS server that we sent the query to.

                                if (q != mDNSNULL)
                                        {
                                        AcceptableResponse = mDNStrue;
                                        if (!InterfaceID)
                                                {
                                                debugf("mDNSCoreReceiveResponse: InterfaceID %p %##s (%s)", q->InterfaceID, q->qname.c, DNSTypeName(q->qtype));
                                                m->rec.r.resrec.rDNSServer = uDNSServer = q->qDNSServer;
                                                }
                                        }
                                else
                                        {
                                        // If we can't find a matching question, we need to see whether we have seen records earlier that matched
                                        // the question. The code below does that. So, make this record unacceptable for now
                                        if (!InterfaceID)
                                                {
                                                debugf("mDNSCoreReceiveResponse: Can't find question for record name %##s", m->rec.r.resrec.name->c);
                                                AcceptableResponse = mDNSfalse;
                                                }
                                        }
                                }
                        }

                // 1. Check that this packet resource record does not conflict with any of ours
                if (mDNSOpaque16IsZero(response->h.id) && m->rec.r.resrec.rrtype != kDNSType_NSEC)
                        {
                        if (m->CurrentRecord)
                                LogMsg("mDNSCoreReceiveResponse ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
                        m->CurrentRecord = m->ResourceRecords;
                        while (m->CurrentRecord)
                                {
                                AuthRecord *rr = m->CurrentRecord;
                                m->CurrentRecord = rr->next;
                                // We accept all multicast responses, and unicast responses resulting from queries we issued
                                // For other unicast responses, this code accepts them only for responses with an
                                // (apparently) local source address that pertain to a record of our own that's in probing state
                                if (!AcceptableResponse && !(ResponseSrcLocal && rr->resrec.RecordType == kDNSRecordTypeUnique)) continue;

                                if (PacketRRMatchesSignature(&m->rec.r, rr))            // If interface, name, type (if shared record) and class match...
                                        {
                                        // ... check to see if type and rdata are identical
                                        if (IdenticalSameNameRecord(&m->rec.r.resrec, &rr->resrec))
                                                {
                                                // If the RR in the packet is identical to ours, just check they're not trying to lower the TTL on us
                                                if (m->rec.r.resrec.rroriginalttl >= rr->resrec.rroriginalttl/2 || m->SleepState)
                                                        {
                                                        // If we were planning to send on this -- and only this -- interface, then we don't need to any more
                                                        if      (rr->ImmedAnswer == InterfaceID) { rr->ImmedAnswer = mDNSNULL; rr->ImmedUnicast = mDNSfalse; }
                                                        }
                                                else
                                                        {
                                                        if      (rr->ImmedAnswer == mDNSNULL)    { rr->ImmedAnswer = InterfaceID;       m->NextScheduledResponse = m->timenow; }
                                                        else if (rr->ImmedAnswer != InterfaceID) { rr->ImmedAnswer = mDNSInterfaceMark; m->NextScheduledResponse = m->timenow; }
                                                        }
                                                }
                                        // else, the packet RR has different type or different rdata -- check to see if this is a conflict
                                        else if (m->rec.r.resrec.rroriginalttl > 0 && PacketRRConflict(m, rr, &m->rec.r))
                                                {
                                                LogInfo("mDNSCoreReceiveResponse: Pkt Record: %08lX %s", m->rec.r.resrec.rdatahash, CRDisplayString(m, &m->rec.r));
                                                LogInfo("mDNSCoreReceiveResponse: Our Record: %08lX %s", rr->     resrec.rdatahash, ARDisplayString(m, rr));
        
                                                // If this record is marked DependentOn another record for conflict detection purposes,
                                                // then *that* record has to be bumped back to probing state to resolve the conflict
                                                if (rr->DependentOn)
                                                        {
                                                        while (rr->DependentOn) rr = rr->DependentOn;
                                                        LogInfo("mDNSCoreReceiveResponse: Dep Record: %08lX %s", rr->     resrec.rdatahash, ARDisplayString(m, rr));
                                                        }
        
                                                // If we've just whacked this record's ProbeCount, don't need to do it again
                                                if (rr->ProbeCount > DefaultProbeCountForTypeUnique)
                                                        LogInfo("mDNSCoreReceiveResponse: Already reset to Probing: %s", ARDisplayString(m, rr));
                                                else if (rr->ProbeCount == DefaultProbeCountForTypeUnique)
                                                        LogMsg("mDNSCoreReceiveResponse: Ignoring response received before we even began probing: %s", ARDisplayString(m, rr));
                                                else
                                                        {
                                                        LogMsg("mDNSCoreReceiveResponse: Received from %#a:%d %s", srcaddr, mDNSVal16(srcport), CRDisplayString(m, &m->rec.r));
                                                        // If we'd previously verified this record, put it back to probing state and try again
                                                        if (rr->resrec.RecordType == kDNSRecordTypeVerified)
                                                                {
                                                                LogMsg("mDNSCoreReceiveResponse: Resetting to Probing: %s", ARDisplayString(m, rr));
                                                                rr->resrec.RecordType     = kDNSRecordTypeUnique;
                                                                // We set ProbeCount to one more than the usual value so we know we've already touched this record.
                                                                // This is because our single probe for "example-name.local" could yield a response with (say) two A records and
                                                                // three AAAA records in it, and we don't want to call RecordProbeFailure() five times and count that as five conflicts.
                                                                // This special value is recognised and reset to DefaultProbeCountForTypeUnique in SendQueries().
                                                                rr->ProbeCount     = DefaultProbeCountForTypeUnique + 1;
                                                                rr->AnnounceCount  = InitialAnnounceCount;
                                                                InitializeLastAPTime(m, rr);
                                                                RecordProbeFailure(m, rr);      // Repeated late conflicts also cause us to back off to the slower probing rate
                                                                }
                                                        // If we're probing for this record, we just failed
                                                        else if (rr->resrec.RecordType == kDNSRecordTypeUnique)
                                                                {
                                                                LogMsg("mDNSCoreReceiveResponse: ProbeCount %d; will deregister %s", rr->ProbeCount, ARDisplayString(m, rr));
                                                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_conflict);
                                                                }
                                                        // We assumed this record must be unique, but we were wrong. (e.g. There are two mDNSResponders on the
                                                        // same machine giving different answers for the reverse mapping record, or there are two machines on the
                                                        // network using the same IP address.) This is simply a misconfiguration, and there's nothing we can do
                                                        // to fix it -- e.g. it's not our job to be trying to change the machine's IP address. We just discard our
                                                        // record to avoid continued conflicts (as we do for a conflict on our Unique records) and get on with life.
                                                        else if (rr->resrec.RecordType == kDNSRecordTypeKnownUnique)
                                                                {
                                                                LogMsg("mDNSCoreReceiveResponse: Unexpected conflict discarding %s", ARDisplayString(m, rr));
                                                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_conflict);
                                                                }
                                                        else
                                                                LogMsg("mDNSCoreReceiveResponse: Unexpected record type %X %s", rr->resrec.RecordType, ARDisplayString(m, rr));
                                                        }
                                                }
                                        // Else, matching signature, different type or rdata, but not a considered a conflict.
                                        // If the packet record has the cache-flush bit set, then we check to see if we
                                        // have any record(s) of the same type that we should re-assert to rescue them
                                        // (see note about "multi-homing and bridged networks" at the end of this function).
                                        else if (m->rec.r.resrec.rrtype == rr->resrec.rrtype)
                                                if ((m->rec.r.resrec.RecordType & kDNSRecordTypePacketUniqueMask) && m->timenow - rr->LastMCTime > mDNSPlatformOneSecond/2)
                                                        { rr->ImmedAnswer = mDNSInterfaceMark; m->NextScheduledResponse = m->timenow; }
                                        }
                                }
                        }

                if (!AcceptableResponse)
                        {
                        const CacheRecord *cr;
                        for (cr = CacheFlushRecords; cr != (CacheRecord*)1; cr = cr->NextInCFList)
                                {
                                domainname *target = GetRRDomainNameTarget(&cr->resrec);
                                // When we issue a query for A record, the response might contain both a CNAME and A records. Only the CNAME would
                                // match the question and we already created a cache entry in the previous pass of this loop. Now when we process
                                // the A record, it does not match the question because the record name here is the CNAME. Hence we try to
                                // match with the previous records to make it an AcceptableResponse. We have to be careful about setting the
                                // DNSServer value that we got in the previous pass. This can happen for other record types like SRV also.

                                if (target && cr->resrec.rdatahash == m->rec.r.resrec.namehash && SameDomainName(target, m->rec.r.resrec.name))
                                        {
                                        debugf("mDNSCoreReceiveResponse: Found a matching entry for %##s in the CacheFlushRecords", m->rec.r.resrec.name->c);
                                        AcceptableResponse = mDNStrue;
                                        m->rec.r.resrec.rDNSServer = uDNSServer;
                                        break;
                                        }
                                }
                        }

                // 2. See if we want to add this packet resource record to our cache
                // We only try to cache answers if we have a cache to put them in
                // Also, we ignore any apparent attempts at cache poisoning unicast to us that do not answer any outstanding active query
                if (!AcceptableResponse) LogInfo("mDNSCoreReceiveResponse ignoring %s", CRDisplayString(m, &m->rec.r));
                if (m->rrcache_size && AcceptableResponse)
                        {
                        const mDNSu32 slot = HashSlot(m->rec.r.resrec.name);
                        CacheGroup *cg = CacheGroupForRecord(m, slot, &m->rec.r.resrec);
                        CacheRecord *rr;

                        // 2a. Check if this packet resource record is already in our cache
                        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                                {
                                mDNSBool match = !InterfaceID ? m->rec.r.resrec.rDNSServer == rr->resrec.rDNSServer : rr->resrec.InterfaceID == InterfaceID;
                                // If we found this exact resource record, refresh its TTL
                                if (match && IdenticalSameNameRecord(&m->rec.r.resrec, &rr->resrec))
                                        {
                                        if (m->rec.r.resrec.rdlength > InlineCacheRDSize)
                                                verbosedebugf("Found record size %5d interface %p already in cache: %s",
                                                        m->rec.r.resrec.rdlength, InterfaceID, CRDisplayString(m, &m->rec.r));
                                        
                                        if (m->rec.r.resrec.RecordType & kDNSRecordTypePacketUniqueMask)
                                                {
                                                // If this packet record has the kDNSClass_UniqueRRSet flag set, then add it to our cache flushing list
                                                if (rr->NextInCFList == mDNSNULL && cfp != &rr->NextInCFList && LLQType != uDNS_LLQ_Events)
                                                        { *cfp = rr; cfp = &rr->NextInCFList; *cfp = (CacheRecord*)1; }

                                                // If this packet record is marked unique, and our previous cached copy was not, then fix it
                                                if (!(rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask))
                                                        {
                                                        DNSQuestion *q;
                                                        for (q = m->Questions; q; q=q->next) if (ResourceRecordAnswersQuestion(&rr->resrec, q)) q->UniqueAnswers++;
                                                        rr->resrec.RecordType = m->rec.r.resrec.RecordType;
                                                        }
                                                }

                                        if (!SameRDataBody(&m->rec.r.resrec, &rr->resrec.rdata->u, SameDomainNameCS))
                                                {
                                                // If the rdata of the packet record differs in name capitalization from the record in our cache
                                                // then mDNSPlatformMemSame will detect this. In this case, throw the old record away, so that clients get
                                                // a 'remove' event for the record with the old capitalization, and then an 'add' event for the new one.
                                                // <rdar://problem/4015377> mDNS -F returns the same domain multiple times with different casing
                                                rr->resrec.rroriginalttl = 0;
                                                rr->TimeRcvd = m->timenow;
                                                rr->UnansweredQueries = MaxUnansweredQueries;
                                                SetNextCacheCheckTimeForRecord(m, rr);
                                                LogInfo("Discarding due to domainname case change old: %s", CRDisplayString(m,rr));
                                                LogInfo("Discarding due to domainname case change new: %s", CRDisplayString(m,&m->rec.r));
                                                LogInfo("Discarding due to domainname case change in %d slot %3d in %d %d",
                                                        NextCacheCheckEvent(rr) - m->timenow, slot, m->rrcache_nextcheck[slot] - m->timenow, m->NextCacheCheck - m->timenow);
                                                // DO NOT break out here -- we want to continue as if we never found it
                                                }
                                        else if (m->rec.r.resrec.rroriginalttl > 0)
                                                {
                                                DNSQuestion *q;
                                                //if (rr->resrec.rroriginalttl == 0) LogMsg("uDNS rescuing %s", CRDisplayString(m, rr));
                                                RefreshCacheRecord(m, rr, m->rec.r.resrec.rroriginalttl);

                                                // We have to reset the question interval to MaxQuestionInterval so that we don't keep
                                                // polling the network once we get a valid response back. For the first time when a new
                                                // cache entry is created, AnswerCurrentQuestionWithResourceRecord does that.
                                                // Subsequently, if we reissue questions from within the mDNSResponder e.g., DNS server
                                                // configuration changed, without flushing the cache, we reset the question interval here.
                                                // Currently, we do this for for both multicast and unicast questions as long as the record
                                                // type is unique. For unicast, resource record is always unique and for multicast it is
                                                // true for records like A etc. but not for PTR.
                                                if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask)
                                                        {
                                                        for (q = m->Questions; q; q=q->next)
                                                                {
                                                                if (!q->DuplicateOf && !q->LongLived &&
                                                                        ActiveQuestion(q) && ResourceRecordAnswersQuestion(&rr->resrec, q))
                                                                        {
                                                                        ResetQuestionState(m, q);
                                                                        debugf("mDNSCoreReceiveResponse: Set MaxQuestionInterval for %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                                                                        break;          // Why break here? Aren't there other questions we might want to look at?-- SC July 2010
                                                                        }
                                                                }
                                                        }
                                                break;
                                                }
                                        else
                                                {
                                                // If the packet TTL is zero, that means we're deleting this record.
                                                // To give other hosts on the network a chance to protest, we push the deletion
                                                // out one second into the future. Also, we set UnansweredQueries to MaxUnansweredQueries.
                                                // Otherwise, we'll do final queries for this record at 80% and 90% of its apparent
                                                // lifetime (800ms and 900ms from now) which is a pointless waste of network bandwidth.
                                                // If record's current expiry time is more than a second from now, we set it to expire in one second.
                                                // If the record is already going to expire in less than one second anyway, we leave it alone --
                                                // we don't want to let the goodbye packet *extend* the record's lifetime in our cache.
                                                debugf("DE for %s", CRDisplayString(m, rr));
                                                if (RRExpireTime(rr) - m->timenow > mDNSPlatformOneSecond)
                                                        {
                                                        rr->resrec.rroriginalttl = 1;
                                                        rr->TimeRcvd = m->timenow;
                                                        rr->UnansweredQueries = MaxUnansweredQueries;
                                                        SetNextCacheCheckTimeForRecord(m, rr);
                                                        }
                                                break;
                                                }
                                        }
                                }

                        // If packet resource record not in our cache, add it now
                        // (unless it is just a deletion of a record we never had, in which case we don't care)
                        if (!rr && m->rec.r.resrec.rroriginalttl > 0)
                                {
                                const mDNSBool AddToCFList = (m->rec.r.resrec.RecordType & kDNSRecordTypePacketUniqueMask) && (LLQType != uDNS_LLQ_Events);
                                const mDNSs32 delay = AddToCFList ? NonZeroTime(m->timenow + mDNSPlatformOneSecond) :
                                        CheckForSoonToExpireRecords(m, m->rec.r.resrec.name, m->rec.r.resrec.namehash, slot);
                                // If unique, assume we may have to delay delivery of this 'add' event.
                                // Below, where we walk the CacheFlushRecords list, we either call CacheRecordDeferredAdd()
                                // to immediately to generate answer callbacks, or we call ScheduleNextCacheCheckTime()
                                // to schedule an mDNS_Execute task at the appropriate time.
                                rr = CreateNewCacheEntry(m, slot, cg, delay);
                                if (rr)
                                        {
                                        if (AddToCFList) { *cfp = rr; cfp = &rr->NextInCFList; *cfp = (CacheRecord*)1; }
                                        else if (rr->DelayDelivery) ScheduleNextCacheCheckTime(m, slot, rr->DelayDelivery);
                                        }
                                }
                        }
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }

exit:
        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it

        // If we've just received one or more records with their cache flush bits set,
        // then scan that cache slot to see if there are any old stale records we need to flush
        while (CacheFlushRecords != (CacheRecord*)1)
                {
                CacheRecord *r1 = CacheFlushRecords, *r2;
                const mDNSu32 slot = HashSlot(r1->resrec.name);
                const CacheGroup *cg = CacheGroupForRecord(m, slot, &r1->resrec);
                CacheFlushRecords = CacheFlushRecords->NextInCFList;
                r1->NextInCFList = mDNSNULL;
                
                // Look for records in the cache with the same signature as this new one with the cache flush
                // bit set, and either (a) if they're fresh, just make sure the whole RRSet has the same TTL
                // (as required by DNS semantics) or (b) if they're old, mark them for deletion in one second.
                // We make these TTL adjustments *only* for records that still have *more* than one second
                // remaining to live. Otherwise, a record that we tagged for deletion half a second ago
                // (and now has half a second remaining) could inadvertently get its life extended, by either
                // (a) if we got an explicit goodbye packet half a second ago, the record would be considered
                // "fresh" and would be incorrectly resurrected back to the same TTL as the rest of the RRSet,
                // or (b) otherwise, the record would not be fully resurrected, but would be reset to expire
                // in one second, thereby inadvertently delaying its actual expiration, instead of hastening it.
                // If this were to happen repeatedly, the record's expiration could be deferred indefinitely.
                // To avoid this, we need to ensure that the cache flushing operation will only act to
                // *decrease* a record's remaining lifetime, never *increase* it.
                for (r2 = cg ? cg->members : mDNSNULL; r2; r2=r2->next)
                        // For Unicast (null InterfaceID) the DNSservers should also match
                        if ((r1->resrec.InterfaceID == r2->resrec.InterfaceID) &&
                                (r1->resrec.InterfaceID || (r1->resrec.rDNSServer == r2->resrec.rDNSServer)) &&
                                r1->resrec.rrtype      == r2->resrec.rrtype &&
                                r1->resrec.rrclass     == r2->resrec.rrclass)
                                {
                                // If record is recent, just ensure the whole RRSet has the same TTL (as required by DNS semantics)
                                // else, if record is old, mark it to be flushed
                                if (m->timenow - r2->TimeRcvd < mDNSPlatformOneSecond && RRExpireTime(r2) - m->timenow > mDNSPlatformOneSecond)
                                        {
                                        // If we find mismatched TTLs in an RRSet, correct them.
                                        // We only do this for records with a TTL of 2 or higher. It's possible to have a
                                        // goodbye announcement with the cache flush bit set (or a case-change on record rdata,
                                        // which we treat as a goodbye followed by an addition) and in that case it would be
                                        // inappropriate to synchronize all the other records to a TTL of 0 (or 1).
                                        // We suppress the message for the specific case of correcting from 240 to 60 for type TXT,
                                        // because certain early Bonjour devices are known to have this specific mismatch, and
                                        // there's no point filling syslog with messages about something we already know about.
                                        // We also don't log this for uDNS responses, since a caching name server is obliged
                                        // to give us an aged TTL to correct for how long it has held the record,
                                        // so our received TTLs are expected to vary in that case
                                        if (r2->resrec.rroriginalttl != r1->resrec.rroriginalttl && r1->resrec.rroriginalttl > 1)
                                                {
                                                if (!(r2->resrec.rroriginalttl == 240 && r1->resrec.rroriginalttl == 60 && r2->resrec.rrtype == kDNSType_TXT) &&
                                                        mDNSOpaque16IsZero(response->h.id))
                                                        LogInfo("Correcting TTL from %4d to %4d for %s",
                                                                r2->resrec.rroriginalttl, r1->resrec.rroriginalttl, CRDisplayString(m, r2));
                                                r2->resrec.rroriginalttl = r1->resrec.rroriginalttl;
                                                }
                                        r2->TimeRcvd = m->timenow;
                                        }
                                else                            // else, if record is old, mark it to be flushed
                                        {
                                        verbosedebugf("Cache flush new %p age %d expire in %d %s", r1, m->timenow - r1->TimeRcvd, RRExpireTime(r1) - m->timenow, CRDisplayString(m, r1));
                                        verbosedebugf("Cache flush old %p age %d expire in %d %s", r2, m->timenow - r2->TimeRcvd, RRExpireTime(r2) - m->timenow, CRDisplayString(m, r2));
                                        // We set stale records to expire in one second.
                                        // This gives the owner a chance to rescue it if necessary.
                                        // This is important in the case of multi-homing and bridged networks:
                                        //   Suppose host X is on Ethernet. X then connects to an AirPort base station, which happens to be
                                        //   bridged onto the same Ethernet. When X announces its AirPort IP address with the cache-flush bit
                                        //   set, the AirPort packet will be bridged onto the Ethernet, and all other hosts on the Ethernet
                                        //   will promptly delete their cached copies of the (still valid) Ethernet IP address record.
                                        //   By delaying the deletion by one second, we give X a change to notice that this bridging has
                                        //   happened, and re-announce its Ethernet IP address to rescue it from deletion from all our caches.

                                        // We set UnansweredQueries to MaxUnansweredQueries to avoid expensive and unnecessary
                                        // final expiration queries for this record.

                                        // If a record is deleted twice, first with an explicit DE record, then a second time by virtue of the cache
                                        // flush bit on the new record replacing it, then we allow the record to be deleted immediately, without the usual
                                        // one-second grace period. This improves responsiveness for mDNS_Update(), as used for things like iChat status updates.
                                        // <rdar://problem/5636422> Updating TXT records is too slow
                                        // We check for "rroriginalttl == 1" because we want to include records tagged by the "packet TTL is zero" check above,
                                        // which sets rroriginalttl to 1, but not records tagged by the rdata case-change check, which sets rroriginalttl to 0.
                                        if (r2->TimeRcvd == m->timenow && r2->resrec.rroriginalttl == 1 && r2->UnansweredQueries == MaxUnansweredQueries)
                                                {
                                                LogInfo("Cache flush for DE record %s", CRDisplayString(m, r2));
                                                r2->resrec.rroriginalttl = 0;
                                                }
                                        else if (RRExpireTime(r2) - m->timenow > mDNSPlatformOneSecond)
                                                {
                                                // We only set a record to expire in one second if it currently has *more* than a second to live
                                                // If it's already due to expire in a second or less, we just leave it alone
                                                r2->resrec.rroriginalttl = 1;
                                                r2->UnansweredQueries = MaxUnansweredQueries;
                                                r2->TimeRcvd = m->timenow - 1;
                                                // We use (m->timenow - 1) instead of m->timenow, because we use that to identify records
                                                // that we marked for deletion via an explicit DE record
                                                }
                                        }
                                SetNextCacheCheckTimeForRecord(m, r2);
                                }

                if (r1->DelayDelivery)  // If we were planning to delay delivery of this record, see if we still need to
                        {
                        r1->DelayDelivery = CheckForSoonToExpireRecords(m, r1->resrec.name, r1->resrec.namehash, slot);
                        // If no longer delaying, deliver answer now, else schedule delivery for the appropriate time
                        if (!r1->DelayDelivery) CacheRecordDeferredAdd(m, r1);
                        else ScheduleNextCacheCheckTime(m, slot, r1->DelayDelivery);
                        }
                }

        // See if we need to generate negative cache entries for unanswered unicast questions
        ptr = response->data;
        for (i = 0; i < response->h.numQuestions && ptr && ptr < end; i++)
                {
                DNSQuestion q;
                DNSQuestion *qptr = mDNSNULL;
                ptr = getQuestion(response, ptr, end, InterfaceID, &q);
                if (ptr && (qptr = ExpectingUnicastResponseForQuestion(m, dstport, response->h.id, &q, !dstaddr)))
                        {
                        CacheRecord *rr, *neg = mDNSNULL;
                        mDNSu32 slot = HashSlot(&q.qname);
                        CacheGroup *cg = CacheGroupForName(m, slot, q.qnamehash, &q.qname);
                        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                                if (SameNameRecordAnswersQuestion(&rr->resrec, qptr))
                                        {
                                        // 1. If we got a fresh answer to this query, then don't need to generate a negative entry
                                        if (RRExpireTime(rr) - m->timenow > 0) break;
                                        // 2. If we already had a negative entry, keep track of it so we can resurrect it instead of creating a new one
                                        if (rr->resrec.RecordType == kDNSRecordTypePacketNegative) neg = rr;
                                        }
                        // When we're doing parallel unicast and multicast queries for dot-local names (for supporting Microsoft
                        // Active Directory sites) we don't want to waste memory making negative cache entries for all the unicast answers.
                        // Otherwise we just fill up our cache with negative entries for just about every single multicast name we ever look up
                        // (since the Microsoft Active Directory server is going to assert that pretty much every single multicast name doesn't exist).
                        // This is not only a waste of memory, but there's also the problem of those negative entries confusing us later -- e.g. we
                        // suppress sending our mDNS query packet because we think we already have a valid (negative) answer to that query in our cache.
                        // The one exception is that we *DO* want to make a negative cache entry for "local. SOA", for the (common) case where we're
                        // *not* on a Microsoft Active Directory network, and there is no authoritative server for "local". Note that this is not
                        // in conflict with the mDNS spec, because that spec says, "Multicast DNS Zones have no SOA record," so it's okay to cache
                        // negative answers for "local. SOA" from a uDNS server, because the mDNS spec already says that such records do not exist :-)
                        if (!InterfaceID && q.qtype != kDNSType_SOA && IsLocalDomain(&q.qname))
                                {
                                // If we did not find a positive answer and we can append search domains to this question,
                                // generate a negative response (without creating a cache entry) to append search domains.
                                if (qptr->AppendSearchDomains && !rr)
                                        {
                                        LogInfo("mDNSCoreReceiveResponse: Generate negative response for %##s (%s)", q.qname.c, DNSTypeName(q.qtype));
                                        m->CurrentQuestion = qptr;
                                        GenerateNegativeResponse(m);
                                        m->CurrentQuestion = mDNSNULL;
                                        }
                                else LogInfo("mDNSCoreReceiveResponse: Skipping check to see if we need to generate a negative cache entry for %##s (%s)", q.qname.c, DNSTypeName(q.qtype));
                                }
                        else
                                {
                                if (!rr)
                                        {
                                        // We start off assuming a negative caching TTL of 60 seconds
                                        // but then look to see if we can find an SOA authority record to tell us a better value we should be using
                                        mDNSu32 negttl = 60;
                                        int repeat = 0;
                                        const domainname *name = &q.qname;
                                        mDNSu32           hash = q.qnamehash;
        
                                        // Special case for our special Microsoft Active Directory "local SOA" check.
                                        // Some cheap home gateways don't include an SOA record in the authority section when
                                        // they send negative responses, so we don't know how long to cache the negative result.
                                        // Because we don't want to keep hitting the root name servers with our query to find
                                        // if we're on a network using Microsoft Active Directory using "local" as a private
                                        // internal top-level domain, we make sure to cache the negative result for at least one day.
                                        if (q.qtype == kDNSType_SOA && SameDomainName(&q.qname, &localdomain)) negttl = 60 * 60 * 24;
        
                                        // If we're going to make (or update) a negative entry, then look for the appropriate TTL from the SOA record
                                        if (response->h.numAuthorities && (ptr = LocateAuthorities(response, end)) != mDNSNULL)
                                                {
                                                ptr = GetLargeResourceRecord(m, response, ptr, end, InterfaceID, kDNSRecordTypePacketAuth, &m->rec);
                                                if (ptr && m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative && m->rec.r.resrec.rrtype == kDNSType_SOA)
                                                        {
                                                        const rdataSOA *const soa = (const rdataSOA *)m->rec.r.resrec.rdata->u.data;
                                                        mDNSu32 ttl_s = soa->min;
                                                        // We use the lesser of the SOA.MIN field and the SOA record's TTL, *except*
                                                        // for the SOA record for ".", where the record is reported as non-cacheable
                                                        // (TTL zero) for some reason, so in this case we just take the SOA record's TTL as-is
                                                        if (ttl_s > m->rec.r.resrec.rroriginalttl && m->rec.r.resrec.name->c[0])
                                                                ttl_s = m->rec.r.resrec.rroriginalttl;
                                                        if (negttl < ttl_s) negttl = ttl_s;
                
                                                        // Special check for SOA queries: If we queried for a.b.c.d.com, and got no answer,
                                                        // with an Authority Section SOA record for d.com, then this is a hint that the authority
                                                        // is d.com, and consequently SOA records b.c.d.com and c.d.com don't exist either.
                                                        // To do this we set the repeat count so the while loop below will make a series of negative cache entries for us
                                                        if (q.qtype == kDNSType_SOA)
                                                                {
                                                                int qcount = CountLabels(&q.qname);
                                                                int scount = CountLabels(m->rec.r.resrec.name);
                                                                if (qcount - 1 > scount)
                                                                        if (SameDomainName(SkipLeadingLabels(&q.qname, qcount - scount), m->rec.r.resrec.name))
                                                                                repeat = qcount - 1 - scount;
                                                                }
                                                        }
                                                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                                                }
        
                                        // If we already had a negative entry in the cache, then we double our existing negative TTL. This is to avoid
                                        // the case where the record doesn't exist (e.g. particularly for things like our lb._dns-sd._udp.<domain> query),
                                        // and the server returns no SOA record (or an SOA record with a small MIN TTL) so we assume a TTL
                                        // of 60 seconds, and we end up polling the server every minute for a record that doesn't exist.
                                        // With this fix in place, when this happens, we double the effective TTL each time (up to one hour),
                                        // so that we back off our polling rate and don't keep hitting the server continually.
                                        if (neg)
                                                {
                                                if (negttl < neg->resrec.rroriginalttl * 2)
                                                        negttl = neg->resrec.rroriginalttl * 2;
                                                if (negttl > 3600)
                                                        negttl = 3600;
                                                }
        
                                        negttl = GetEffectiveTTL(LLQType, negttl);      // Add 25% grace period if necessary
        
                                        // If we already had a negative cache entry just update it, else make one or more new negative cache entries
                                        if (neg)
                                                {
                                                debugf("mDNSCoreReceiveResponse: Renewing negative TTL from %d to %d %s", neg->resrec.rroriginalttl, negttl, CRDisplayString(m, neg));
                                                RefreshCacheRecord(m, neg, negttl);
                                                // When we created the cache for the first time and answered the question, the question's
                                                // interval was set to MaxQuestionInterval. If the cache is about to expire and we are resending
                                                // the queries, the interval should still be at MaxQuestionInterval. If the query is being
                                                // restarted (setting it to InitialQuestionInterval) for other reasons e.g., wakeup,
                                                // we should reset its question interval here to MaxQuestionInterval.
                                                ResetQuestionState(m, qptr);
                                                }
                                        else while (1)
                                                {
                                                debugf("mDNSCoreReceiveResponse making negative cache entry TTL %d for %##s (%s)", negttl, name->c, DNSTypeName(q.qtype));
                                                MakeNegativeCacheRecord(m, &m->rec.r, name, hash, q.qtype, q.qclass, negttl, mDNSInterface_Any, qptr->qDNSServer);
                                                CreateNewCacheEntry(m, slot, cg, 0);    // We never need any delivery delay for these generated negative cache records
                                                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                                                if (!repeat) break;
                                                repeat--;
                                                name = (const domainname *)(name->c + 1 + name->c[0]);
                                                hash = DomainNameHashValue(name);
                                                slot = HashSlot(name);
                                                cg   = CacheGroupForName(m, slot, hash, name);
                                                }
                                        }
                                }
                        }
                }
        }

// ScheduleWakeup causes all proxy records with WakeUp.HMAC matching mDNSEthAddr 'e' to be deregistered, causing
// multiple wakeup magic packets to be sent if appropriate, and all records to be ultimately freed after a few seconds.
// ScheduleWakeup is called on mDNS record conflicts, ARP conflicts, NDP conflicts, or reception of trigger traffic
// that warrants waking the sleeping host.
// ScheduleWakeup must be called with the lock held (ScheduleWakeupForList uses mDNS_Deregister_internal)

mDNSlocal void ScheduleWakeupForList(mDNS *const m, mDNSInterfaceID InterfaceID, mDNSEthAddr *e, AuthRecord *const thelist)
        {
        // We don't need to use the m->CurrentRecord mechanism here because the target HMAC is nonzero,
        // so all we're doing is marking the record to generate a few wakeup packets
        AuthRecord *rr;
        if (!e->l[0]) { LogMsg("ScheduleWakeupForList ERROR: Target HMAC is zero"); return; }
        for (rr = thelist; rr; rr = rr->next) 
                if (rr->resrec.InterfaceID == InterfaceID && rr->resrec.RecordType != kDNSRecordTypeDeregistering && mDNSSameEthAddress(&rr->WakeUp.HMAC, e))
                        {
                        LogInfo("ScheduleWakeupForList: Scheduling wakeup packets for %s", ARDisplayString(m, rr));
                        mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
                        }
        }

mDNSlocal void ScheduleWakeup(mDNS *const m, mDNSInterfaceID InterfaceID, mDNSEthAddr *e)
        {
        if (!e->l[0]) { LogMsg("ScheduleWakeup ERROR: Target HMAC is zero"); return; }
        ScheduleWakeupForList(m, InterfaceID, e, m->DuplicateRecords);
        ScheduleWakeupForList(m, InterfaceID, e, m->ResourceRecords);
        }

mDNSlocal void SPSRecordCallback(mDNS *const m, AuthRecord *const ar, mStatus result)
        {
        if (result && result != mStatus_MemFree)
                LogInfo("SPS Callback %d %s", result, ARDisplayString(m, ar));

        if (result == mStatus_NameConflict)
                {
                mDNS_Lock(m);
                LogMsg("%-7s Conflicting mDNS -- waking %.6a %s", InterfaceNameForID(m, ar->resrec.InterfaceID), &ar->WakeUp.HMAC, ARDisplayString(m, ar));
                if (ar->WakeUp.HMAC.l[0])
                        {
                        SendWakeup(m, ar->resrec.InterfaceID, &ar->WakeUp.IMAC, &ar->WakeUp.password);  // Send one wakeup magic packet
                        ScheduleWakeup(m, ar->resrec.InterfaceID, &ar->WakeUp.HMAC);                                    // Schedule all other records with the same owner to be woken
                        }
                mDNS_Unlock(m);
                }

        if (result == mStatus_NameConflict || result == mStatus_MemFree)
                {
                m->ProxyRecords--;
                mDNSPlatformMemFree(ar);
                mDNS_UpdateAllowSleep(m);
                }
        }

mDNSlocal void mDNSCoreReceiveUpdate(mDNS *const m,
        const DNSMessage *const msg, const mDNSu8 *end,
        const mDNSAddr *srcaddr, const mDNSIPPort srcport, const mDNSAddr *dstaddr, mDNSIPPort dstport,
        const mDNSInterfaceID InterfaceID)
        {
        int i;
        AuthRecord opt;
        mDNSu8 *p = m->omsg.data;
        OwnerOptData owner = zeroOwner;         // Need to zero this, so we'll know if this Update packet was missing its Owner option
        mDNSu32 updatelease = 0;
        const mDNSu8 *ptr;

        LogSPS("Received Update from %#-15a:%-5d to %#-15a:%-5d on 0x%p with "
                "%2d Question%s %2d Answer%s %2d Authorit%s %2d Additional%s %d bytes",
                srcaddr, mDNSVal16(srcport), dstaddr, mDNSVal16(dstport), InterfaceID,
                msg->h.numQuestions,   msg->h.numQuestions   == 1 ? ", "   : "s,",
                msg->h.numAnswers,     msg->h.numAnswers     == 1 ? ", "   : "s,",
                msg->h.numAuthorities, msg->h.numAuthorities == 1 ? "y,  " : "ies,",
                msg->h.numAdditionals, msg->h.numAdditionals == 1 ? " "    : "s", end - msg->data);

        if (!InterfaceID || !m->SPSSocket || !mDNSSameIPPort(dstport, m->SPSSocket->port)) return;

        if (mDNS_PacketLoggingEnabled)
                DumpPacket(m, mStatus_NoError, mDNSfalse, "UDP", srcaddr, srcport, dstaddr, dstport, msg, end);

        ptr = LocateOptRR(msg, end, DNSOpt_LeaseData_Space + DNSOpt_OwnerData_ID_Space);
        if (ptr)
                {
                ptr = GetLargeResourceRecord(m, msg, ptr, end, 0, kDNSRecordTypePacketAdd, &m->rec);
                if (ptr && m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative && m->rec.r.resrec.rrtype == kDNSType_OPT)
                        {
                        const rdataOPT *o;
                        const rdataOPT *const e = (const rdataOPT *)&m->rec.r.resrec.rdata->u.data[m->rec.r.resrec.rdlength];
                        for (o = &m->rec.r.resrec.rdata->u.opt[0]; o < e; o++)
                                {
                                if      (o->opt == kDNSOpt_Lease)                         updatelease = o->u.updatelease;
                                else if (o->opt == kDNSOpt_Owner && o->u.owner.vers == 0) owner       = o->u.owner;
                                }
                        }
                m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                }

        InitializeDNSMessage(&m->omsg.h, msg->h.id, UpdateRespFlags);

        if (!updatelease || !owner.HMAC.l[0])
                {
                static int msgs = 0;
                if (msgs < 100)
                        {
                        msgs++;
                        LogMsg("Refusing sleep proxy registration from %#a:%d:%s%s", srcaddr, mDNSVal16(srcport),
                                !updatelease ? " No lease" : "", !owner.HMAC.l[0] ? " No owner" : "");
                        }
                m->omsg.h.flags.b[1] |= kDNSFlag1_RC_FormErr;
                }
        else if (m->ProxyRecords + msg->h.mDNS_numUpdates > MAX_PROXY_RECORDS)
                {
                static int msgs = 0;
                if (msgs < 100)
                        {
                        msgs++;
                        LogMsg("Refusing sleep proxy registration from %#a:%d: Too many records %d + %d = %d > %d", srcaddr, mDNSVal16(srcport),
                                m->ProxyRecords, msg->h.mDNS_numUpdates, m->ProxyRecords + msg->h.mDNS_numUpdates, MAX_PROXY_RECORDS);
                        }
                m->omsg.h.flags.b[1] |= kDNSFlag1_RC_Refused;
                }
        else
                {
                LogSPS("Received Update for H-MAC %.6a I-MAC %.6a Password %.6a seq %d", &owner.HMAC, &owner.IMAC, &owner.password, owner.seq);
        
                if (updatelease > 24 * 60 * 60)
                        updatelease = 24 * 60 * 60;
        
                if (updatelease > 0x40000000UL / mDNSPlatformOneSecond)
                        updatelease = 0x40000000UL / mDNSPlatformOneSecond;
        
                ptr = LocateAuthorities(msg, end);
                for (i = 0; i < msg->h.mDNS_numUpdates && ptr && ptr < end; i++)
                        {
                        ptr = GetLargeResourceRecord(m, msg, ptr, end, InterfaceID, kDNSRecordTypePacketAuth, &m->rec);
                        if (ptr && m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative)
                                {
                                mDNSu16 RDLengthMem = GetRDLengthMem(&m->rec.r.resrec);
                                AuthRecord *ar = mDNSPlatformMemAllocate(sizeof(AuthRecord) - sizeof(RDataBody) + RDLengthMem);
                                if (!ar) { m->omsg.h.flags.b[1] |= kDNSFlag1_RC_Refused; break; }
                                else
                                        {
                                        mDNSu8 RecordType = m->rec.r.resrec.RecordType & kDNSRecordTypePacketUniqueMask ? kDNSRecordTypeUnique : kDNSRecordTypeShared;
                                        m->rec.r.resrec.rrclass &= ~kDNSClass_UniqueRRSet;
                                        ClearIdenticalProxyRecords(m, &owner, m->DuplicateRecords);     // Make sure we don't have any old stale duplicates of this record
                                        ClearIdenticalProxyRecords(m, &owner, m->ResourceRecords);
                                        mDNS_SetupResourceRecord(ar, mDNSNULL, InterfaceID, m->rec.r.resrec.rrtype, m->rec.r.resrec.rroriginalttl, RecordType, AuthRecordAny, SPSRecordCallback, ar);
                                        AssignDomainName(&ar->namestorage, m->rec.r.resrec.name);
                                        ar->resrec.rdlength = GetRDLength(&m->rec.r.resrec, mDNSfalse);
                                        ar->resrec.rdata->MaxRDLength = RDLengthMem;
                                        mDNSPlatformMemCopy(ar->resrec.rdata->u.data, m->rec.r.resrec.rdata->u.data, RDLengthMem);
                                        ar->ForceMCast = mDNStrue;
                                        ar->WakeUp     = owner;
                                        if (m->rec.r.resrec.rrtype == kDNSType_PTR)
                                                {
                                                mDNSs32 t = ReverseMapDomainType(m->rec.r.resrec.name);
                                                if      (t == mDNSAddrType_IPv4) GetIPv4FromName(&ar->AddressProxy, m->rec.r.resrec.name);
                                                else if (t == mDNSAddrType_IPv6) GetIPv6FromName(&ar->AddressProxy, m->rec.r.resrec.name);
                                                debugf("mDNSCoreReceiveUpdate: PTR %d %d %#a %s", t, ar->AddressProxy.type, &ar->AddressProxy, ARDisplayString(m, ar));
                                                if (ar->AddressProxy.type) SetSPSProxyListChanged(InterfaceID);
                                                }
                                        ar->TimeRcvd   = m->timenow;
                                        ar->TimeExpire = m->timenow + updatelease * mDNSPlatformOneSecond;
                                        if (m->NextScheduledSPS - ar->TimeExpire > 0)
                                                m->NextScheduledSPS = ar->TimeExpire;
                                        mDNS_Register_internal(m, ar);
                                        // Unsolicited Neighbor Advertisements (RFC 2461 Section 7.2.6) give us fast address cache updating,
                                        // but some older IPv6 clients get confused by them, so for now we don't send them. Without Unsolicited
                                        // Neighbor Advertisements we have to rely on Neighbor Unreachability Detection instead, which is slower.
                                        // Given this, we'll do our best to wake for existing IPv6 connections, but we don't want to encourage
                                        // new ones for sleeping clients, so we'll we send deletions for our SPS clients' AAAA records.
                                        if (m->KnownBugs & mDNS_KnownBug_LimitedIPv6)
                                                if (ar->resrec.rrtype == kDNSType_AAAA) ar->resrec.rroriginalttl = 0;
                                        m->ProxyRecords++;
                                        mDNS_UpdateAllowSleep(m);
                                        LogSPS("SPS Registered %4d %X %s", m->ProxyRecords, RecordType, ARDisplayString(m,ar));
                                        }
                                }
                        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                        }

                if (m->omsg.h.flags.b[1] & kDNSFlag1_RC_Mask)
                        {
                        LogMsg("Refusing sleep proxy registration from %#a:%d: Out of memory", srcaddr, mDNSVal16(srcport));
                        ClearProxyRecords(m, &owner, m->DuplicateRecords);
                        ClearProxyRecords(m, &owner, m->ResourceRecords);
                        }
                else
                        {
                        mDNS_SetupResourceRecord(&opt, mDNSNULL, mDNSInterface_Any, kDNSType_OPT, kStandardTTL, kDNSRecordTypeKnownUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
                        opt.resrec.rrclass    = NormalMaxDNSMessageData;
                        opt.resrec.rdlength   = sizeof(rdataOPT);       // One option in this OPT record
                        opt.resrec.rdestimate = sizeof(rdataOPT);
                        opt.resrec.rdata->u.opt[0].opt           = kDNSOpt_Lease;
                        opt.resrec.rdata->u.opt[0].u.updatelease = updatelease;
                        p = PutResourceRecordTTLWithLimit(&m->omsg, p, &m->omsg.h.numAdditionals, &opt.resrec, opt.resrec.rroriginalttl, m->omsg.data + AbsoluteMaxDNSMessageData);
                        }
                }

        if (p) mDNSSendDNSMessage(m, &m->omsg, p, InterfaceID, m->SPSSocket, srcaddr, srcport, mDNSNULL, mDNSNULL);
        }

mDNSlocal void mDNSCoreReceiveUpdateR(mDNS *const m, const DNSMessage *const msg, const mDNSu8 *end, const mDNSInterfaceID InterfaceID)
        {
        if (InterfaceID)
                {
                mDNSu32 updatelease = 60 * 60;          // If SPS fails to indicate lease time, assume one hour
                const mDNSu8 *ptr = LocateOptRR(msg, end, DNSOpt_LeaseData_Space);
                if (ptr)
                        {
                        ptr = GetLargeResourceRecord(m, msg, ptr, end, 0, kDNSRecordTypePacketAdd, &m->rec);
                        if (ptr && m->rec.r.resrec.RecordType != kDNSRecordTypePacketNegative && m->rec.r.resrec.rrtype == kDNSType_OPT)
                                {
                                const rdataOPT *o;
                                const rdataOPT *const e = (const rdataOPT *)&m->rec.r.resrec.rdata->u.data[m->rec.r.resrec.rdlength];
                                for (o = &m->rec.r.resrec.rdata->u.opt[0]; o < e; o++)
                                        if (o->opt == kDNSOpt_Lease)
                                                {
                                                updatelease = o->u.updatelease;
                                                LogSPS("Sleep Proxy granted lease time %4d seconds", updatelease);
                                                }
                                }
                        m->rec.r.resrec.RecordType = 0;         // Clear RecordType to show we're not still using it
                        }

                if (m->CurrentRecord)
                        LogMsg("mDNSCoreReceiveUpdateR ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));
                m->CurrentRecord = m->ResourceRecords;
                while (m->CurrentRecord)
                        {
                        AuthRecord *const rr = m->CurrentRecord;
                        if (rr->resrec.InterfaceID == InterfaceID || (!rr->resrec.InterfaceID && (rr->ForceMCast || IsLocalDomain(rr->resrec.name))))
                                if (mDNSSameOpaque16(rr->updateid, msg->h.id))
                                        {
                                        rr->updateid = zeroID;
                                        rr->expire   = NonZeroTime(m->timenow + updatelease * mDNSPlatformOneSecond);
                                        LogSPS("Sleep Proxy %s record %5d %s", rr->WakeUp.HMAC.l[0] ? "transferred" : "registered", updatelease, ARDisplayString(m,rr));
                                        if (rr->WakeUp.HMAC.l[0])
                                                {
                                                rr->WakeUp.HMAC = zeroEthAddr;  // Clear HMAC so that mDNS_Deregister_internal doesn't waste packets trying to wake this host
                                                rr->RequireGoodbye = mDNSfalse; // and we don't want to send goodbye for it
                                                mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
                                                }
                                        }
                        // Mustn't advance m->CurrentRecord until *after* mDNS_Deregister_internal, because
                        // new records could have been added to the end of the list as a result of that call.
                        if (m->CurrentRecord == rr) // If m->CurrentRecord was not advanced for us, do it now
                                m->CurrentRecord = rr->next;
                        }
                }
        // If we were waiting to go to sleep, then this SPS registration or wide-area record deletion
        // may have been the thing we were waiting for, so schedule another check to see if we can sleep now.
        if (m->SleepLimit) m->NextScheduledSPRetry = m->timenow;
        }

mDNSexport void MakeNegativeCacheRecord(mDNS *const m, CacheRecord *const cr,
        const domainname *const name, const mDNSu32 namehash, const mDNSu16 rrtype, const mDNSu16 rrclass, mDNSu32 ttl_seconds, mDNSInterfaceID InterfaceID, DNSServer *dnsserver)
        {
        if (cr == &m->rec.r && m->rec.r.resrec.RecordType)
                {
                LogMsg("MakeNegativeCacheRecord: m->rec appears to be already in use for %s", CRDisplayString(m, &m->rec.r));
#if ForceAlerts
                *(long*)0 = 0;
#endif
                }

        // Create empty resource record
        cr->resrec.RecordType    = kDNSRecordTypePacketNegative;
        cr->resrec.InterfaceID   = InterfaceID;
        cr->resrec.rDNSServer    = dnsserver;
        cr->resrec.name          = name;        // Will be updated to point to cg->name when we call CreateNewCacheEntry
        cr->resrec.rrtype        = rrtype;
        cr->resrec.rrclass       = rrclass;
        cr->resrec.rroriginalttl = ttl_seconds;
        cr->resrec.rdlength      = 0;
        cr->resrec.rdestimate    = 0;
        cr->resrec.namehash      = namehash;
        cr->resrec.rdatahash     = 0;
        cr->resrec.rdata = (RData*)&cr->smallrdatastorage;
        cr->resrec.rdata->MaxRDLength = 0;

        cr->NextInKAList       = mDNSNULL;
        cr->TimeRcvd           = m->timenow;
        cr->DelayDelivery      = 0;
        cr->NextRequiredQuery  = m->timenow;
        cr->LastUsed           = m->timenow;
        cr->CRActiveQuestion   = mDNSNULL;
        cr->UnansweredQueries  = 0;
        cr->LastUnansweredTime = 0;
#if ENABLE_MULTI_PACKET_QUERY_SNOOPING
        cr->MPUnansweredQ      = 0;
        cr->MPLastUnansweredQT = 0;
        cr->MPUnansweredKA     = 0;
        cr->MPExpectingKA      = mDNSfalse;
#endif
        cr->NextInCFList       = mDNSNULL;
        }

mDNSexport void mDNSCoreReceive(mDNS *const m, void *const pkt, const mDNSu8 *const end,
        const mDNSAddr *const srcaddr, const mDNSIPPort srcport, const mDNSAddr *dstaddr, const mDNSIPPort dstport,
        const mDNSInterfaceID InterfaceID)
        {
        mDNSInterfaceID ifid = InterfaceID;
        DNSMessage  *msg  = (DNSMessage *)pkt;
        const mDNSu8 StdQ = kDNSFlag0_QR_Query    | kDNSFlag0_OP_StdQuery;
        const mDNSu8 StdR = kDNSFlag0_QR_Response | kDNSFlag0_OP_StdQuery;
        const mDNSu8 UpdQ = kDNSFlag0_QR_Query    | kDNSFlag0_OP_Update;
        const mDNSu8 UpdR = kDNSFlag0_QR_Response | kDNSFlag0_OP_Update;
        mDNSu8 QR_OP;
        mDNSu8 *ptr = mDNSNULL;
        mDNSBool TLS = (dstaddr == (mDNSAddr *)1);      // For debug logs: dstaddr = 0 means TCP; dstaddr = 1 means TLS
        if (TLS) dstaddr = mDNSNULL;

#ifndef UNICAST_DISABLED
        if (mDNSSameAddress(srcaddr, &m->Router))
                {
#ifdef _LEGACY_NAT_TRAVERSAL_
                if (mDNSSameIPPort(srcport, SSDPPort) || (m->SSDPSocket && mDNSSameIPPort(dstport, m->SSDPSocket->port)))
                        {
                        mDNS_Lock(m);
                        LNT_ConfigureRouterInfo(m, InterfaceID, pkt, (mDNSu16)(end - (mDNSu8 *)pkt));
                        mDNS_Unlock(m);
                        return;
                        }
#endif
                if (mDNSSameIPPort(srcport, NATPMPPort))
                        {
                        mDNS_Lock(m);
                        uDNS_ReceiveNATPMPPacket(m, InterfaceID, pkt, (mDNSu16)(end - (mDNSu8 *)pkt));
                        mDNS_Unlock(m);
                        return;
                        }
                }
#ifdef _LEGACY_NAT_TRAVERSAL_
        else if (m->SSDPSocket && mDNSSameIPPort(dstport, m->SSDPSocket->port)) { debugf("Ignoring SSDP response from %#a:%d", srcaddr, mDNSVal16(srcport)); return; }
#endif

#endif
        if ((unsigned)(end - (mDNSu8 *)pkt) < sizeof(DNSMessageHeader))
                {
                LogMsg("DNS Message from %#a:%d to %#a:%d length %d too short", srcaddr, mDNSVal16(srcport), dstaddr, mDNSVal16(dstport), end - (mDNSu8 *)pkt);
                return;
                }
        QR_OP = (mDNSu8)(msg->h.flags.b[0] & kDNSFlag0_QROP_Mask);
        // Read the integer parts which are in IETF byte-order (MSB first, LSB second)
        ptr = (mDNSu8 *)&msg->h.numQuestions;
        msg->h.numQuestions   = (mDNSu16)((mDNSu16)ptr[0] << 8 | ptr[1]);
        msg->h.numAnswers     = (mDNSu16)((mDNSu16)ptr[2] << 8 | ptr[3]);
        msg->h.numAuthorities = (mDNSu16)((mDNSu16)ptr[4] << 8 | ptr[5]);
        msg->h.numAdditionals = (mDNSu16)((mDNSu16)ptr[6] << 8 | ptr[7]);

        if (!m) { LogMsg("mDNSCoreReceive ERROR m is NULL"); return; }
        
        // We use zero addresses and all-ones addresses at various places in the code to indicate special values like "no address"
        // If we accept and try to process a packet with zero or all-ones source address, that could really mess things up
        if (srcaddr && !mDNSAddressIsValid(srcaddr)) { debugf("mDNSCoreReceive ignoring packet from %#a", srcaddr); return; }

        mDNS_Lock(m);
        m->PktNum++;
#ifndef UNICAST_DISABLED
        if (!dstaddr || (!mDNSAddressIsAllDNSLinkGroup(dstaddr) && (QR_OP == StdR || QR_OP == UpdR)))
                if (!mDNSOpaque16IsZero(msg->h.id)) // uDNS_ReceiveMsg only needs to get real uDNS responses, not "QU" mDNS responses
                        {
                        ifid = mDNSInterface_Any;
                        if (mDNS_PacketLoggingEnabled)
                                DumpPacket(m, mStatus_NoError, mDNSfalse, TLS ? "TLS" : !dstaddr ? "TCP" : "UDP", srcaddr, srcport, dstaddr, dstport, msg, end);
                        uDNS_ReceiveMsg(m, msg, end, srcaddr, srcport);
                        // Note: mDNSCore also needs to get access to received unicast responses
                        }
#endif
        if      (QR_OP == StdQ) mDNSCoreReceiveQuery   (m, msg, end, srcaddr, srcport, dstaddr, dstport, ifid);
        else if (QR_OP == StdR) mDNSCoreReceiveResponse(m, msg, end, srcaddr, srcport, dstaddr, dstport, ifid);
        else if (QR_OP == UpdQ) mDNSCoreReceiveUpdate  (m, msg, end, srcaddr, srcport, dstaddr, dstport, InterfaceID);
        else if (QR_OP == UpdR) mDNSCoreReceiveUpdateR (m, msg, end,                                     InterfaceID);
        else
                {
                LogMsg("Unknown DNS packet type %02X%02X from %#-15a:%-5d to %#-15a:%-5d length %d on %p (ignored)",
                        msg->h.flags.b[0], msg->h.flags.b[1], srcaddr, mDNSVal16(srcport), dstaddr, mDNSVal16(dstport), end - (mDNSu8 *)pkt, InterfaceID);
                if (mDNS_LoggingEnabled)
                        {
                        int i = 0;
                        while (i<end - (mDNSu8 *)pkt)
                                {
                                char buffer[128];
                                char *p = buffer + mDNS_snprintf(buffer, sizeof(buffer), "%04X", i);
                                do if (i<end - (mDNSu8 *)pkt) p += mDNS_snprintf(p, sizeof(buffer), " %02X", ((mDNSu8 *)pkt)[i]); while (++i & 15);
                                LogInfo("%s", buffer);
                                }
                        }
                }
        // Packet reception often causes a change to the task list:
        // 1. Inbound queries can cause us to need to send responses
        // 2. Conflicing response packets received from other hosts can cause us to need to send defensive responses
        // 3. Other hosts announcing deletion of shared records can cause us to need to re-assert those records
        // 4. Response packets that answer questions may cause our client to issue new questions
        mDNS_Unlock(m);
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Searcher Functions
#endif

// Targets are considered the same if both queries are untargeted, or
// if both are targeted to the same address+port
// (If Target address is zero, TargetPort is undefined)
#define SameQTarget(A,B) (((A)->Target.type == mDNSAddrType_None && (B)->Target.type == mDNSAddrType_None) || \
        (mDNSSameAddress(&(A)->Target, &(B)->Target) && mDNSSameIPPort((A)->TargetPort, (B)->TargetPort)))

// Note: We explicitly disallow making a public query be a duplicate of a private one. This is to avoid the
// circular deadlock where a client does a query for something like "dns-sd -Q _dns-query-tls._tcp.company.com SRV"
// and we have a key for company.com, so we try to locate the private query server for company.com, which necessarily entails
// doing a standard DNS query for the _dns-query-tls._tcp SRV record for company.com. If we make the latter (public) query
// a duplicate of the former (private) query, then it will block forever waiting for an answer that will never come.
//
// We keep SuppressUnusable questions separate so that we can return a quick response to them and not get blocked behind
// the queries that are not marked SuppressUnusable. But if the query is not suppressed, they are treated the same as
// non-SuppressUnusable questions. This should be fine as the goal of SuppressUnusable is to return quickly only if it
// is suppressed. If it is not suppressed, we do try all the DNS servers for valid answers like any other question.
// The main reason for this design is that cache entries point to a *single* question and that question is responsible
// for keeping the cache fresh as long as it is active. Having multiple active question for a single cache entry
// breaks this design principle.

// If IsLLQ(Q) is true, it means the question is both:
// (a) long-lived and
// (b) being performed by a unicast DNS long-lived query (either full LLQ, or polling)
// for multicast questions, we don't want to treat LongLived as anything special
#define IsLLQ(Q) ((Q)->LongLived && !mDNSOpaque16IsZero((Q)->TargetQID))

mDNSlocal DNSQuestion *FindDuplicateQuestion(const mDNS *const m, const DNSQuestion *const question)
        {
        DNSQuestion *q;
        // Note: A question can only be marked as a duplicate of one that occurs *earlier* in the list.
        // This prevents circular references, where two questions are each marked as a duplicate of the other.
        // Accordingly, we break out of the loop when we get to 'question', because there's no point searching
        // further in the list.
        for (q = m->Questions; q && q != question; q=q->next)           // Scan our list for another question
                if (q->InterfaceID == question->InterfaceID &&                  // with the same InterfaceID,
                        SameQTarget(q, question)                &&                      // and same unicast/multicast target settings
                        q->qtype      == question->qtype        &&                      // type,
                        q->qclass     == question->qclass       &&                      // class,
                        IsLLQ(q)      == IsLLQ(question)        &&                      // and long-lived status matches
                        (!q->AuthInfo || question->AuthInfo)    &&                      // to avoid deadlock, don't make public query dup of a private one
                        (q->SuppressQuery == question->SuppressQuery) &&        // Questions that are suppressed/not suppressed
                        q->qnamehash  == question->qnamehash    &&
                        SameDomainName(&q->qname, &question->qname))            // and name
                        return(q);
        return(mDNSNULL);
        }

// This is called after a question is deleted, in case other identical questions were being suppressed as duplicates
mDNSlocal void UpdateQuestionDuplicates(mDNS *const m, DNSQuestion *const question)
        {
        DNSQuestion *q;
        DNSQuestion *first = mDNSNULL;

        // This is referring to some other question as duplicate. No other question can refer to this
        // question as a duplicate.
        if (question->DuplicateOf)
                {
                LogInfo("UpdateQuestionDuplicates: question %p %##s (%s) duplicate of %p %##s (%s)",
                        question, question->qname.c, DNSTypeName(question->qtype),
                        question->DuplicateOf, question->DuplicateOf->qname.c, DNSTypeName(question->DuplicateOf->qtype));
                return;
                }

        for (q = m->Questions; q; q=q->next)            // Scan our list of questions
                if (q->DuplicateOf == question)                 // To see if any questions were referencing this as their duplicate
                        {
                        q->DuplicateOf = first;
                        if (!first)
                                {
                                first = q;
                                // If q used to be a duplicate, but now is not,
                                // then inherit the state from the question that's going away
                                q->LastQTime         = question->LastQTime;
                                q->ThisQInterval     = question->ThisQInterval;
                                q->ExpectUnicastResp = question->ExpectUnicastResp;
                                q->LastAnswerPktNum  = question->LastAnswerPktNum;
                                q->RecentAnswerPkts  = question->RecentAnswerPkts;
                                q->RequestUnicast    = question->RequestUnicast;
                                q->LastQTxTime       = question->LastQTxTime;
                                q->CNAMEReferrals    = question->CNAMEReferrals;
                                q->nta               = question->nta;
                                q->servAddr          = question->servAddr;
                                q->servPort          = question->servPort;
                                q->qDNSServer        = question->qDNSServer;
                                q->validDNSServers   = question->validDNSServers;
                                q->unansweredQueries = question->unansweredQueries;
                                q->noServerResponse  = question->noServerResponse;
                                q->triedAllServersOnce = question->triedAllServersOnce;

                                q->TargetQID         = question->TargetQID;
                                q->LocalSocket       = question->LocalSocket;

                                q->state             = question->state;
                        //      q->tcp               = question->tcp;
                                q->ReqLease          = question->ReqLease;
                                q->expire            = question->expire;
                                q->ntries            = question->ntries;
                                q->id                = question->id;

                                question->LocalSocket = mDNSNULL;
                                question->nta        = mDNSNULL;        // If we've got a GetZoneData in progress, transfer it to the newly active question
                        //      question->tcp        = mDNSNULL;

                                if (q->LocalSocket)
                                        debugf("UpdateQuestionDuplicates transferred LocalSocket pointer for %##s (%s)", q->qname.c, DNSTypeName(q->qtype));

                                if (q->nta)
                                        {
                                        LogInfo("UpdateQuestionDuplicates transferred nta pointer for %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                                        q->nta->ZoneDataContext = q;
                                        }

                                // Need to work out how to safely transfer this state too -- appropriate context pointers need to be updated or the code will crash
                                if (question->tcp) LogInfo("UpdateQuestionDuplicates did not transfer tcp pointer");

                                if (question->state == LLQ_Established)
                                        {
                                        LogInfo("UpdateQuestionDuplicates transferred LLQ state for %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                                        question->state = 0;    // Must zero question->state, or mDNS_StopQuery_internal will clean up and cancel our LLQ from the server
                                        }

                                SetNextQueryTime(m,q);
                                }
                        }
        }

mDNSexport McastResolver *mDNS_AddMcastResolver(mDNS *const m, const domainname *d, const mDNSInterfaceID interface, mDNSu32 timeout)
        {
        McastResolver **p = &m->McastResolvers;
        McastResolver *tmp = mDNSNULL;
        
        if (!d) d = (const domainname *)"";

        LogInfo("mDNS_AddMcastResolver: Adding %##s, InterfaceID %p, timeout %u", d->c, interface, timeout);

        if (m->mDNS_busy != m->mDNS_reentrancy+1)
                LogMsg("mDNS_AddMcastResolver: Lock not held! mDNS_busy (%ld) mDNS_reentrancy (%ld)", m->mDNS_busy, m->mDNS_reentrancy);

        while (*p)      // Check if we already have this {interface, domain} tuple registered
                {
                if ((*p)->interface == interface && SameDomainName(&(*p)->domain, d))
                        {
                        if (!((*p)->flags & DNSServer_FlagDelete)) LogMsg("Note: Mcast Resolver domain %##s (%p) registered more than once", d->c, interface);
                        (*p)->flags &= ~DNSServer_FlagDelete;
                        tmp = *p;
                        *p = tmp->next;
                        tmp->next = mDNSNULL;
                        }
                else
                        p=&(*p)->next;
                }

        if (tmp) *p = tmp; // move to end of list, to ensure ordering from platform layer
        else
                {
                // allocate, add to list
                *p = mDNSPlatformMemAllocate(sizeof(**p));
                if (!*p) LogMsg("mDNS_AddMcastResolver: ERROR!! - malloc");
                else
                        {
                        (*p)->interface = interface;
                        (*p)->flags     = DNSServer_FlagNew;
                        (*p)->timeout   = timeout;
                        AssignDomainName(&(*p)->domain, d);
                        (*p)->next = mDNSNULL;
                        }
                }
        return(*p);
        }

mDNSinline mDNSs32 PenaltyTimeForServer(mDNS *m, DNSServer *server)
        {
        mDNSs32 ptime = 0;
        if (server->penaltyTime != 0)
                {
                ptime = server->penaltyTime - m->timenow;
                if (ptime < 0)
                        {
                        // This should always be a positive value between 0 and DNSSERVER_PENALTY_TIME
                        // If it does not get reset in ResetDNSServerPenalties for some reason, we do it
                        // here
                        LogMsg("PenaltyTimeForServer: PenaltyTime negative %d, (server penaltyTime %d, timenow %d) resetting the penalty",
                                ptime, server->penaltyTime, m->timenow);
                        server->penaltyTime = 0;
                        ptime = 0;
                        }
                }
        return ptime;
        }

//Checks to see whether the newname is a better match for the name, given the best one we have
//seen so far (given in bestcount).
//Returns -1 if the newname is not a better match
//Returns 0 if the newname is the same as the old match
//Returns 1 if the newname is a better match
mDNSlocal int BetterMatchForName(const domainname *name, int namecount, const domainname *newname, int newcount,
        int bestcount)
        {
        // If the name contains fewer labels than the new server's domain or the new name
        // contains fewer labels than the current best, then it can't possibly be a better match
        if (namecount < newcount || newcount < bestcount) return -1;

        // If there is no match, return -1 and the caller will skip this newname for
        // selection
        //
        // If we find a match and the number of labels is the same as bestcount, then
        // we return 0 so that the caller can do additional logic to pick one of
        // the best based on some other factors e.g., penaltyTime
        //
        // If we find a match and the number of labels is more than bestcount, then we
        // return 1 so that the caller can pick this over the old one.
        //
        // Note: newcount can either be equal or greater than bestcount beause of the
        // check above.

        if (SameDomainName(SkipLeadingLabels(name, namecount - newcount), newname))
                return bestcount == newcount ? 0 : 1;
        else
                return -1;
        }

// Normally, we have McastResolvers for .local, in-addr.arpa and ip6.arpa. But there
// can be queries that can forced to multicast (ForceMCast) even though they don't end in these
// names. In that case, we give a default timeout of 5 seconds
#define DEFAULT_MCAST_TIMEOUT   5
mDNSlocal mDNSu32 GetTimeoutForMcastQuestion(mDNS *m, DNSQuestion *question)
        {
        McastResolver *curmatch = mDNSNULL;
        int bestmatchlen = -1, namecount = CountLabels(&question->qname);
        McastResolver *curr;
        int bettermatch, currcount;
        for (curr = m->McastResolvers; curr; curr = curr->next)
                {
                currcount = CountLabels(&curr->domain);
                bettermatch = BetterMatchForName(&question->qname, namecount, &curr->domain, currcount, bestmatchlen);
                // Take the first best match. If there are multiple equally good matches (bettermatch = 0), we take
                // the timeout value from the first one
                if (bettermatch == 1)
                        {
                        curmatch = curr;
                        bestmatchlen = currcount;
                        }
                }
        LogInfo("GetTimeoutForMcastQuestion: question %##s curmatch %p, Timeout %d", question->qname.c, curmatch,
                curmatch ? curmatch->timeout : DEFAULT_MCAST_TIMEOUT);
        return ( curmatch ? curmatch->timeout : DEFAULT_MCAST_TIMEOUT);
        }

// Returns true if it is a Domain Enumeration Query
mDNSexport mDNSBool DomainEnumQuery(const domainname *qname)
        {
        const mDNSu8 *mDNS_DEQLabels[] = { (const mDNSu8 *)"\001b", (const mDNSu8 *)"\002db", (const mDNSu8 *)"\002lb",
                (const mDNSu8 *)"\001r", (const mDNSu8 *)"\002dr", (const mDNSu8 *)mDNSNULL, };
        const domainname *d = qname;
        const mDNSu8 *label;
        int i = 0;

        // We need at least 3 labels (DEQ prefix) + one more label to make a meaningful DE query
        if (CountLabels(qname) < 4) { debugf("DomainEnumQuery: question %##s, not enough labels", qname->c); return mDNSfalse; }

        label = (const mDNSu8 *)d;
        while (mDNS_DEQLabels[i] != (const mDNSu8 *)mDNSNULL)
                {
                if (SameDomainLabel(mDNS_DEQLabels[i], label)) {debugf("DomainEnumQuery: DEQ %##s, label1 match", qname->c); break;}
                i++;
                }
        if (mDNS_DEQLabels[i] == (const mDNSu8 *)mDNSNULL)
                {
                debugf("DomainEnumQuery: Not a DEQ %##s, label1 mismatch", qname->c);
                return mDNSfalse;
                }
        debugf("DomainEnumQuery: DEQ %##s, label1 match", qname->c);

        // CountLabels already verified the number of labels 
        d = (const domainname *)(d->c + 1 + d->c[0]);   // Second Label
        label = (const mDNSu8 *)d;
        if (!SameDomainLabel(label, (const mDNSu8 *)"\007_dns-sd"))
                {
                debugf("DomainEnumQuery: Not a DEQ %##s, label2 mismatch", qname->c);
                return(mDNSfalse);
                }
        debugf("DomainEnumQuery: DEQ %##s, label2 match", qname->c);

        d = (const domainname *)(d->c + 1 + d->c[0]);   // Third Label
        label = (const mDNSu8 *)d;
        if (!SameDomainLabel(label, (const mDNSu8 *)"\004_udp"))
                {
                debugf("DomainEnumQuery: Not a DEQ %##s, label3 mismatch", qname->c);
                return(mDNSfalse);
                }
        debugf("DomainEnumQuery: DEQ %##s, label3 match", qname->c);

        debugf("DomainEnumQuery: Question %##s is a Domain Enumeration query", qname->c);

        return mDNStrue;
        }

// Sets all the Valid DNS servers for a question
mDNSexport mDNSu32 SetValidDNSServers(mDNS *m, DNSQuestion *question)
        {
        DNSServer *curmatch = mDNSNULL;
        int bestmatchlen = -1, namecount = CountLabels(&question->qname);
        DNSServer *curr;
        int bettermatch, currcount;
        int index = 0;
        mDNSu32 timeout = 0;
        mDNSBool DEQuery;

        question->validDNSServers = zeroOpaque64;
        DEQuery = DomainEnumQuery(&question->qname);
        for (curr = m->DNSServers; curr; curr = curr->next)
                {
                debugf("SetValidDNSServers: Parsing DNS server Address %#a (Domain %##s), Scope: %d", &curr->addr, curr->domain.c, curr->scoped);
                // skip servers that will soon be deleted
                if (curr->flags & DNSServer_FlagDelete)
                        { debugf("SetValidDNSServers: Delete set for index %d, DNS server %#a (Domain %##s), scoped %d", index, &curr->addr, curr->domain.c, curr->scoped); continue; }

                // This happens normally when you unplug the interface where we reset the interfaceID to mDNSInterface_Any for all
                // the DNS servers whose scope match the interfaceID. Few seconds later, we also receive the updated DNS configuration.
                // But any questions that has mDNSInterface_Any scope that are started/restarted before we receive the update
                // (e.g., CheckSuppressUnusableQuestions is called when interfaces are deregistered with the core) should not
                // match the scoped entries by mistake. 
                //
                // Note: DNS configuration change will help pick the new dns servers but currently it does not affect the timeout

                if (curr->scoped && curr->interface == mDNSInterface_Any)
                        { debugf("SetValidDNSServers: Scoped DNS server %#a (Domain %##s) with Interface Any", &curr->addr, curr->domain.c); continue; }

                currcount = CountLabels(&curr->domain);
                if ((!DEQuery || !curr->cellIntf) &&
                        ((!curr->scoped && (!question->InterfaceID || (question->InterfaceID == mDNSInterface_Unicast))) ||
                        (curr->interface == question->InterfaceID)))
                        {
                        bettermatch = BetterMatchForName(&question->qname, namecount, &curr->domain, currcount, bestmatchlen);

                        // If we found a better match (bettermatch == 1) then clear all the bits
                        // corresponding to the old DNSServers that we have may set before and start fresh.
                        // If we find an equal match, then include that DNSServer also by setting the corresponding
                        // bit
                        if ((bettermatch == 1) || (bettermatch == 0))
                                {
                                curmatch = curr;
                                bestmatchlen = currcount;
                                if (bettermatch) { debugf("SetValidDNSServers: Resetting all the bits"); question->validDNSServers = zeroOpaque64; timeout = 0; }
                                debugf("SetValidDNSServers: question %##s Setting the bit for DNS server Address %#a (Domain %##s), Scoped:%d index %d,"
                                        " Timeout %d, interface %p", question->qname.c, &curr->addr, curr->domain.c, curr->scoped, index, curr->timeout,
                                        curr->interface);
                                timeout += curr->timeout;
                                if (DEQuery) debugf("DomainEnumQuery: Question %##s, DNSServer %#a, cell %d", question->qname.c, &curr->addr, curr->cellIntf);
                                bit_set_opaque64(question->validDNSServers, index);
                                }
                        }
                index++;
                }
        question->noServerResponse = 0;
        
        debugf("SetValidDNSServers: ValidDNSServer bits  0x%x%x for question %p %##s (%s)",
                question->validDNSServers.l[1], question->validDNSServers.l[0], question, question->qname.c, DNSTypeName(question->qtype));
        // If there are no matching resolvers, then use the default value to timeout
        return (timeout ? timeout : DEFAULT_UDNS_TIMEOUT);
        }

// Get the Best server that matches a name. If you find penalized servers, look for the one
// that will come out of the penalty box soon
mDNSlocal DNSServer *GetBestServer(mDNS *m, const domainname *name, mDNSInterfaceID InterfaceID, mDNSOpaque64 validBits, int *selected, mDNSBool nameMatch)
        {
        DNSServer *curmatch = mDNSNULL;
        int bestmatchlen = -1, namecount = name ? CountLabels(name) : 0;
        DNSServer *curr;
        mDNSs32 bestPenaltyTime, currPenaltyTime;
        int bettermatch, currcount;
        int index = 0;
        int currindex = -1;

        debugf("GetBestServer: ValidDNSServer bits  0x%x%x", validBits.l[1], validBits.l[0]);
        bestPenaltyTime = DNSSERVER_PENALTY_TIME + 1;
        for (curr = m->DNSServers; curr; curr = curr->next)
                {
                // skip servers that will soon be deleted
                if (curr->flags & DNSServer_FlagDelete)
                        { debugf("GetBestServer: Delete set for index %d, DNS server %#a (Domain %##s), scoped %d", index, &curr->addr, curr->domain.c, curr->scoped); continue; }

                // Check if this is a valid DNSServer
                if (!bit_get_opaque64(validBits, index)) { debugf("GetBestServer: continuing for index %d", index); index++; continue; }

                currcount = CountLabels(&curr->domain);
                currPenaltyTime = PenaltyTimeForServer(m, curr);

                debugf("GetBestServer: Address %#a (Domain %##s), PenaltyTime(abs) %d, PenaltyTime(rel) %d",
                        &curr->addr, curr->domain.c, curr->penaltyTime, currPenaltyTime);

                // If there are multiple best servers for a given question, we will pick the first one
                // if none of them are penalized. If some of them are penalized in that list, we pick
                // the least penalized one. BetterMatchForName walks through all best matches and
                // "currPenaltyTime < bestPenaltyTime" check lets us either pick the first best server
                // in the list when there are no penalized servers and least one among them
                // when there are some penalized servers
                //
                // Notes on InterfaceID matching:
                //
                // 1) A DNSServer entry may have an InterfaceID but the scoped flag may not be set. This
                // is the old way of specifying an InterfaceID option for DNSServer. We recoginize these
                // entries by "scoped" being false. These are like any other unscoped entries except that
                // if it is picked e.g., domain match, when the packet is sent out later, the packet will
                // be sent out on that interface. Theese entries can be matched by either specifying a
                // zero InterfaceID or non-zero InterfaceID on the question. Specifying an InterfaceID on
                // the question will cause an extra check on matching the InterfaceID on the question
                // against the DNSServer.
                // 
                // 2) A DNSServer may also have both scoped set and InterfaceID non-NULL. This
                // is the new way of specifying an InterfaceID option for DNSServer. These will be considered
                // only when the question has non-zero interfaceID.

                if ((!curr->scoped && !InterfaceID) || (curr->interface == InterfaceID))
                        {

                        // If we know that all the names are already equally good matches, then skip calling BetterMatchForName.
                        // This happens when we initially walk all the DNS servers and set the validity bit on the question.
                        // Actually we just need PenaltyTime match, but for the sake of readability we just skip the expensive
                        // part and still do some redundant steps e.g., InterfaceID match

                        if (nameMatch) bettermatch = BetterMatchForName(name, namecount, &curr->domain, currcount, bestmatchlen);
                        else bettermatch = 0;

                        // If we found a better match (bettermatch == 1) then we don't need to
                        // compare penalty times. But if we found an equal match, then we compare
                        // the penalty times to pick a better match

                        if ((bettermatch == 1) || ((bettermatch == 0) && currPenaltyTime < bestPenaltyTime))
                                { currindex = index; curmatch = curr; bestmatchlen = currcount; bestPenaltyTime = currPenaltyTime; }
                        }
                index++;
                }
        if (selected) *selected = currindex;
        return curmatch;
        }

// Look up a DNS Server, matching by name and InterfaceID
mDNSexport DNSServer *GetServerForName(mDNS *m, const domainname *name, mDNSInterfaceID InterfaceID)
    {
        DNSServer *curmatch = mDNSNULL;
        char *ifname = mDNSNULL;        // for logging purposes only
        mDNSOpaque64 allValid;

        if ((InterfaceID == mDNSInterface_Unicast) || (InterfaceID == mDNSInterface_LocalOnly))
                InterfaceID = mDNSNULL;

        if (InterfaceID) ifname = InterfaceNameForID(m, InterfaceID);

        // By passing in all ones, we make sure that every DNS server is considered
        allValid.l[0] = allValid.l[1] = 0xFFFFFFFF;

        curmatch = GetBestServer(m, name, InterfaceID, allValid, mDNSNULL, mDNStrue);

        if (curmatch != mDNSNULL)
                LogInfo("GetServerForName: DNS server %#a:%d (Penalty Time Left %d) (Scope %s:%p) found for name %##s", &curmatch->addr,
                    mDNSVal16(curmatch->port), (curmatch->penaltyTime ? (curmatch->penaltyTime - m->timenow) : 0), ifname ? ifname : "None",
                InterfaceID, name);
        else
                LogInfo("GetServerForName: no DNS server (Scope %s:%p) found for name %##s", ifname ? ifname : "None", InterfaceID, name);

        return(curmatch);
        }

// Look up a DNS Server for a question within its valid DNSServer bits
mDNSexport DNSServer *GetServerForQuestion(mDNS *m, DNSQuestion *question)
    {
        DNSServer *curmatch = mDNSNULL;
        char *ifname = mDNSNULL;        // for logging purposes only
        mDNSInterfaceID InterfaceID = question->InterfaceID;
        const domainname *name = &question->qname;
        int currindex;

        if ((InterfaceID == mDNSInterface_Unicast) || (InterfaceID == mDNSInterface_LocalOnly))
                InterfaceID = mDNSNULL;

        if (InterfaceID) ifname = InterfaceNameForID(m, InterfaceID);

        if (!mDNSOpaque64IsZero(&question->validDNSServers))
                {
                curmatch = GetBestServer(m, name, InterfaceID, question->validDNSServers, &currindex, mDNSfalse);
                if (currindex != -1) bit_clr_opaque64(question->validDNSServers, currindex);
                }

        if (curmatch != mDNSNULL)
                LogInfo("GetServerForQuestion: %p DNS server %#a:%d (Penalty Time Left %d) (Scope %s:%p) found for name %##s (%s)", question, &curmatch->addr,
                    mDNSVal16(curmatch->port), (curmatch->penaltyTime ? (curmatch->penaltyTime - m->timenow) : 0), ifname ? ifname : "None",
                InterfaceID, name, DNSTypeName(question->qtype));
        else
                LogInfo("GetServerForQuestion: %p no DNS server (Scope %s:%p) found for name %##s (%s)", question, ifname ? ifname : "None", InterfaceID, name, DNSTypeName(question->qtype));

        return(curmatch);
        }


#define ValidQuestionTarget(Q) (((Q)->Target.type == mDNSAddrType_IPv4 || (Q)->Target.type == mDNSAddrType_IPv6) && \
        (mDNSSameIPPort((Q)->TargetPort, UnicastDNSPort) || mDNSSameIPPort((Q)->TargetPort, MulticastDNSPort)))

// Called in normal client context (lock not held)
mDNSlocal void LLQNATCallback(mDNS *m, NATTraversalInfo *n)
        {
        DNSQuestion *q;
        (void)n;    // Unused
        mDNS_Lock(m);
        LogInfo("LLQNATCallback external address:port %.4a:%u, NAT result %d", &n->ExternalAddress, mDNSVal16(n->ExternalPort), n->Result);
        for (q = m->Questions; q; q=q->next)
                if (ActiveQuestion(q) && !mDNSOpaque16IsZero(q->TargetQID) && q->LongLived)
                        startLLQHandshake(m, q);        // If ExternalPort is zero, will do StartLLQPolling instead
#if APPLE_OSX_mDNSResponder
        UpdateAutoTunnelDomainStatuses(m);
#endif
        mDNS_Unlock(m);
        }

mDNSlocal mDNSBool ShouldSuppressQuery(mDNS *const m, domainname *qname, mDNSu16 qtype, mDNSInterfaceID InterfaceID)
        {
        NetworkInterfaceInfo *i;
        mDNSs32 iptype;
        DomainAuthInfo *AuthInfo;

        if (qtype == kDNSType_A) iptype = mDNSAddrType_IPv4;
        else if (qtype == kDNSType_AAAA) iptype = mDNSAddrType_IPv6;
        else { LogInfo("ShouldSuppressQuery: Query not suppressed for %##s, qtype %s, not A/AAAA type", qname, DNSTypeName(qtype)); return mDNSfalse; }

        // We still want the ability to be able to listen to the local services and hence
        // don't fail .local requests. We always have a loopback interface which we don't
        // check here.
        if (InterfaceID != mDNSInterface_Unicast && IsLocalDomain(qname)) { LogInfo("ShouldSuppressQuery: Query not suppressed for %##s, qtype %s, Local question", qname, DNSTypeName(qtype)); return mDNSfalse; }

        // Skip Private domains as we have special addresses to get the hosts in the Private domain
        AuthInfo = GetAuthInfoForName_internal(m, qname);
        if (AuthInfo && !AuthInfo->deltime && AuthInfo->AutoTunnel)
                { LogInfo("ShouldSuppressQuery: Query not suppressed for %##s, qtype %s, Private Domain", qname, DNSTypeName(qtype)); return mDNSfalse; }

        // Match on Type, Address and InterfaceID
        //
        // Check whether we are looking for a name that ends in .local, then presence of a link-local
        // address on the interface is sufficient.
        for (i = m->HostInterfaces; i; i = i->next)
                {
                if (i->ip.type != iptype) continue;

                if (!InterfaceID || (InterfaceID == mDNSInterface_LocalOnly) || (InterfaceID == mDNSInterface_P2P) ||
                        (InterfaceID == mDNSInterface_Unicast) || (i->InterfaceID == InterfaceID))
                        {
                        if (iptype == mDNSAddrType_IPv4 && !mDNSv4AddressIsLoopback(&i->ip.ip.v4) && !mDNSv4AddressIsLinkLocal(&i->ip.ip.v4))
                                {
                                LogInfo("ShouldSuppressQuery: Query not suppressed for %##s, qtype %s, Local Address %.4a found", qname, DNSTypeName(qtype),
                                        &i->ip.ip.v4);
                                return mDNSfalse;
                                }
                        else if (iptype == mDNSAddrType_IPv6 &&
                                !mDNSv6AddressIsLoopback(&i->ip.ip.v6) &&
                                !mDNSv6AddressIsLinkLocal(&i->ip.ip.v6) &&
                                !mDNSSameIPv6Address(i->ip.ip.v6, m->AutoTunnelHostAddr) &&
                                !mDNSSameIPv6Address(i->ip.ip.v6, m->AutoTunnelRelayAddrOut))
                                {
                                LogInfo("ShouldSuppressQuery: Query not suppressed for %##s, qtype %s, Local Address %.16a found", qname, DNSTypeName(qtype),
                                        &i->ip.ip.v6);
                                return mDNSfalse;
                                }
                        }
                }
        LogInfo("ShouldSuppressQuery: Query suppressed for %##s, qtype %s, because no matching interface found", qname, DNSTypeName(qtype));
        return mDNStrue;
        }

mDNSlocal void CacheRecordRmvEventsForCurrentQuestion(mDNS *const m, DNSQuestion *q)
        {
        CacheRecord *rr;
        mDNSu32 slot;
        CacheGroup *cg;

        slot = HashSlot(&q->qname);
        cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                {
                // Don't deliver RMV events for negative records
                if (rr->resrec.RecordType == kDNSRecordTypePacketNegative)
                        {
                        LogInfo("CacheRecordRmvEventsForCurrentQuestion: CacheRecord %s Suppressing RMV events for question %p %##s (%s), CRActiveQuestion %p, CurrentAnswers %d",
                                CRDisplayString(m, rr), q, q->qname.c, DNSTypeName(q->qtype), rr->CRActiveQuestion, q->CurrentAnswers);
                        continue;
                        }

                if (SameNameRecordAnswersQuestion(&rr->resrec, q))
                        {
                        LogInfo("CacheRecordRmvEventsForCurrentQuestion: Calling AnswerCurrentQuestionWithResourceRecord (RMV) for question %##s using resource record %s LocalAnswers %d",
                                q->qname.c, CRDisplayString(m, rr), q->LOAddressAnswers);

                        q->CurrentAnswers--;
                        if (rr->resrec.rdlength > SmallRecordLimit) q->LargeAnswers--;
                        if (rr->resrec.RecordType & kDNSRecordTypePacketUniqueMask) q->UniqueAnswers--;

                        if (rr->CRActiveQuestion == q)
                                {
                                DNSQuestion *qptr;
                                // If this was the active question for this cache entry, it was the one that was
                                // responsible for keeping the cache entry fresh when the cache entry was reaching
                                // its expiry. We need to handover the responsibility to someone else. Otherwise,
                                // when the cache entry is about to expire, we won't find an active question
                                // (pointed by CRActiveQuestion) to refresh the cache.
                                for (qptr = m->Questions; qptr; qptr=qptr->next)
                                        if (qptr != q && ActiveQuestion(qptr) && ResourceRecordAnswersQuestion(&rr->resrec, qptr))
                                                break;

                                if (qptr)
                                        LogInfo("CacheRecordRmvEventsForCurrentQuestion: Updating CRActiveQuestion to %p for cache record %s, "
                                                "Original question CurrentAnswers %d, new question CurrentAnswers %d, SuppressUnusable %d, SuppressQuery %d",
                                                qptr, CRDisplayString(m,rr), q->CurrentAnswers, qptr->CurrentAnswers, qptr->SuppressUnusable, qptr->SuppressQuery);

                                rr->CRActiveQuestion = qptr;            // Question used to be active; new value may or may not be null
                                if (!qptr) m->rrcache_active--; // If no longer active, decrement rrcache_active count
                                }
                        AnswerCurrentQuestionWithResourceRecord(m, rr, QC_rmv);
                        if (m->CurrentQuestion != q) break;             // If callback deleted q, then we're finished here
                        }
                }
        }

mDNSlocal mDNSBool IsQuestionNew(mDNS *const m, DNSQuestion *question)
        {
        DNSQuestion *q;
        for (q = m->NewQuestions; q; q = q->next)
                if (q == question) return mDNStrue;
        return mDNSfalse;
        }

mDNSlocal mDNSBool LocalRecordRmvEventsForQuestion(mDNS *const m, DNSQuestion *q)
        {
        AuthRecord *rr;
        mDNSu32 slot;
        AuthGroup *ag;

        if (m->CurrentQuestion)
                LogMsg("LocalRecordRmvEventsForQuestion: ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));

        if (IsQuestionNew(m, q))
                {
                LogInfo("LocalRecordRmvEventsForQuestion: New Question %##s (%s)", q->qname.c, DNSTypeName(q->qtype));
                return mDNStrue;
                }
        m->CurrentQuestion = q;
        slot = AuthHashSlot(&q->qname);
        ag = AuthGroupForName(&m->rrauth, slot, q->qnamehash, &q->qname);
        if (ag)
                {
                for (rr = ag->members; rr; rr=rr->next)
                        // Filter the /etc/hosts records - LocalOnly, Unique, A/AAAA/CNAME
                        if (LORecordAnswersAddressType(rr) && LocalOnlyRecordAnswersQuestion(rr, q))
                                {
                                LogInfo("LocalRecordRmvEventsForQuestion: Delivering possible Rmv events with record %s",
                                        ARDisplayString(m, rr));
                                if (q->CurrentAnswers <= 0 || q->LOAddressAnswers <= 0)
                                        {
                                        LogMsg("LocalRecordRmvEventsForQuestion: ERROR!! CurrentAnswers or LOAddressAnswers is zero %p %##s"
                                                " (%s) CurrentAnswers %d, LOAddressAnswers %d", q, q->qname.c, DNSTypeName(q->qtype),
                                                q->CurrentAnswers, q->LOAddressAnswers);
                                        continue;
                                        }
                                AnswerLocalQuestionWithLocalAuthRecord(m, rr, QC_rmv);          // MUST NOT dereference q again
                                if (m->CurrentQuestion != q) { m->CurrentQuestion = mDNSNULL; return mDNSfalse; }
                                }
                }
        m->CurrentQuestion = mDNSNULL;
        return mDNStrue;
        }

// Returns false if the question got deleted while delivering the RMV events
// The caller should handle the case 
mDNSlocal mDNSBool CacheRecordRmvEventsForQuestion(mDNS *const m, DNSQuestion *q)
        {
        if (m->CurrentQuestion)
                LogMsg("CacheRecordRmvEventsForQuestion: ERROR m->CurrentQuestion already set: %##s (%s)",
                        m->CurrentQuestion->qname.c, DNSTypeName(m->CurrentQuestion->qtype));

        // If it is a new question, we have not delivered any ADD events yet. So, don't deliver RMV events.
        // If this question was answered using local auth records, then you can't deliver RMVs using cache
        if (!IsQuestionNew(m, q) && !q->LOAddressAnswers) 
                {
                m->CurrentQuestion = q;
                CacheRecordRmvEventsForCurrentQuestion(m, q);
                if (m->CurrentQuestion != q) { m->CurrentQuestion = mDNSNULL; return mDNSfalse; }
                m->CurrentQuestion = mDNSNULL;
                }
        else { LogInfo("CacheRecordRmvEventsForQuestion: Question %p %##s (%s) is a new question", q, q->qname.c, DNSTypeName(q->qtype)); }
        return mDNStrue;
        }

// The caller should hold the lock
mDNSexport void CheckSuppressUnusableQuestions(mDNS *const m)
        {
        DNSQuestion *q;
        DNSQuestion *restart = mDNSNULL;

        // We look through all questions including new questions. During network change events,
        // we potentially restart questions here in this function that ends up as new questions,
        // which may be suppressed at this instance. Before it is handled we get another network
        // event that changes the status e.g., address becomes available. If we did not process
        // new questions, we would never change its SuppressQuery status.
        //
        // CurrentQuestion is used by RmvEventsForQuestion below. While delivering RMV events, the
        // application callback can potentially stop the current question (detected by CurrentQuestion) or
        // *any* other question which could be the next one that we may process here. RestartQuestion
        // points to the "next" question which will be automatically advanced in mDNS_StopQuery_internal
        // if the "next" question is stopped while the CurrentQuestion is stopped
        if (m->RestartQuestion)
                LogMsg("CheckSuppressUnusableQuestions: ERROR!! m->RestartQuestion already set: %##s (%s)",
                        m->RestartQuestion->qname.c, DNSTypeName(m->RestartQuestion->qtype));
        m->RestartQuestion = m->Questions;
        while (m->RestartQuestion)
                {
                q = m->RestartQuestion;
                m->RestartQuestion = q->next;
                if (!mDNSOpaque16IsZero(q->TargetQID) && q->SuppressUnusable)
                        {
                        mDNSBool old = q->SuppressQuery;
                        q->SuppressQuery = ShouldSuppressQuery(m, &q->qname, q->qtype, q->InterfaceID);
                        if (q->SuppressQuery != old)
                                {
                                // NOTE: CacheRecordRmvEventsForQuestion will not generate RMV events for queries that have non-zero
                                // LOddressAnswers. Hence it is important that we call CacheRecordRmvEventsForQuestion before
                                // LocalRecordRmvEventsForQuestion (which decrements LOAddressAnswers)

                                if (q->SuppressQuery)
                                        {
                                        // Previously it was not suppressed, Generate RMV events for the ADDs that we might have delivered before
                                        // followed by a negative cache response. Temporarily turn off suppression so that
                                        // AnswerCurrentQuestionWithResourceRecord can answer the question
                                        q->SuppressQuery = mDNSfalse;
                                        if (!CacheRecordRmvEventsForQuestion(m, q)) { LogInfo("CheckSuppressUnusableQuestions: Question deleted while delivering RMV events"); continue; }
                                        q->SuppressQuery = mDNStrue;
                                        }

                                // SuppressUnusable does not affect questions that are answered from the local records (/etc/hosts)
                                // and SuppressQuery status does not mean anything for these questions. As we are going to stop the
                                // question below, we need to deliver the RMV events so that the ADDs that will be delivered during
                                // the restart will not be a duplicate ADD
                                if (!LocalRecordRmvEventsForQuestion(m, q)) { LogInfo("CheckSuppressUnusableQuestions: Question deleted while delivering RMV events"); continue; }

                                // There are two cases here.
                                //
                                // 1. Previously it was suppressed and now it is not suppressed, restart the question so
                                // that it will start as a new question. Note that we can't just call ActivateUnicastQuery
                                // because when we get the response, if we had entries in the cache already, it will not answer
                                // this question if the cache entry did not change. Hence, we need to restart
                                // the query so that it can be answered from the cache.
                                //
                                // 2. Previously it was not suppressed and now it is suppressed. We need to restart the questions
                                // so that we redo the duplicate checks in mDNS_StartQuery_internal. A SuppressUnusable question
                                // is a duplicate of non-SuppressUnusable question if it is not suppressed (SuppressQuery is false).
                                // A SuppressUnusable question is not a duplicate of non-SuppressUnusable question if it is suppressed
                                // (SuppressQuery is true). The reason for this is that when a question is suppressed, we want an
                                // immediate response and not want to be blocked behind a question that is querying DNS servers. When 
                                // the question is not suppressed, we don't want two active questions sending packets on the wire.
                                // This affects both efficiency and also the current design where there is only one active question
                                // pointed to from a cache entry.
                                //
                                // We restart queries in a two step process by first calling stop and build a temporary list which we
                                // will restart at the end. The main reason for the two step process is to handle duplicate questions.
                                // If there are duplicate questions, calling stop inherits the values from another question on the list (which
                                // will soon become the real question) including q->ThisQInterval which might be zero if it was
                                // suppressed before. At the end when we have restarted all questions, none of them is active as each
                                // inherits from one another and we need to reactivate one of the questions here which is a little hacky.
                                //
                                // It is much cleaner and less error prone to build a list of questions and restart at the end.

                                LogInfo("CheckSuppressUnusableQuestions: Stop question %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                                mDNS_StopQuery_internal(m, q);
                                q->next = restart;
                                restart = q;
                                }
                        }
                }
        while (restart)
                {
                q = restart;
                restart = restart->next;
                q->next = mDNSNULL;
                LogInfo("CheckSuppressUnusableQuestions: Start question %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                mDNS_StartQuery_internal(m, q);
                }
        }

mDNSexport mStatus mDNS_StartQuery_internal(mDNS *const m, DNSQuestion *const question)
        {
        if (question->Target.type && !ValidQuestionTarget(question))
                {
                LogMsg("mDNS_StartQuery_internal: Warning! Target.type = %ld port = %u (Client forgot to initialize before calling mDNS_StartQuery? for question %##s)",
                        question->Target.type, mDNSVal16(question->TargetPort), question->qname.c);
                question->Target.type = mDNSAddrType_None;
                }

        if (!question->Target.type) question->TargetPort = zeroIPPort;  // If no question->Target specified clear TargetPort

        question->TargetQID =
#ifndef UNICAST_DISABLED
                (question->Target.type || Question_uDNS(question)) ? mDNS_NewMessageID(m) :
#endif // UNICAST_DISABLED
                zeroID;

        debugf("mDNS_StartQuery: %##s (%s)", question->qname.c, DNSTypeName(question->qtype));

        if (m->rrcache_size == 0)       // Can't do queries if we have no cache space allocated
                return(mStatus_NoCache);
        else
                {
                int i;
                DNSQuestion **q;
                
                if (!ValidateDomainName(&question->qname))
                        {
                        LogMsg("Attempt to start query with invalid qname %##s (%s)", question->qname.c, DNSTypeName(question->qtype));
                        return(mStatus_Invalid);
                        }

                // Note: It important that new questions are appended at the *end* of the list, not prepended at the start
                q = &m->Questions;
                if (question->InterfaceID == mDNSInterface_LocalOnly || question->InterfaceID == mDNSInterface_P2P) q = &m->LocalOnlyQuestions;
                while (*q && *q != question) q=&(*q)->next;

                if (*q)
                        {
                        LogMsg("Error! Tried to add a question %##s (%s) %p that's already in the active list",
                                question->qname.c, DNSTypeName(question->qtype), question);
                        return(mStatus_AlreadyRegistered);
                        }

                *q = question;

                // If this question is referencing a specific interface, verify it exists
                if (question->InterfaceID && question->InterfaceID != mDNSInterface_LocalOnly && question->InterfaceID != mDNSInterface_Unicast && question->InterfaceID != mDNSInterface_P2P)
                        {
                        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, question->InterfaceID);
                        if (!intf)
                                LogMsg("Note: InterfaceID %p for question %##s (%s) not currently found in active interface list",
                                        question->InterfaceID, question->qname.c, DNSTypeName(question->qtype));
                        }

                // Note: In the case where we already have the answer to this question in our cache, that may be all the client
                // wanted, and they may immediately cancel their question. In this case, sending an actual query on the wire would
                // be a waste. For that reason, we schedule our first query to go out in half a second (InitialQuestionInterval).
                // If AnswerNewQuestion() finds that we have *no* relevant answers currently in our cache, then it will accelerate
                // that to go out immediately.
                question->next              = mDNSNULL;
                question->qnamehash         = DomainNameHashValue(&question->qname);    // MUST do this before FindDuplicateQuestion()
                question->DelayAnswering    = CheckForSoonToExpireRecords(m, &question->qname, question->qnamehash, HashSlot(&question->qname));
                question->LastQTime         = m->timenow;
                question->ThisQInterval     = InitialQuestionInterval;                                  // MUST be > zero for an active question
                question->ExpectUnicastResp = 0;
                question->LastAnswerPktNum  = m->PktNum;
                question->RecentAnswerPkts  = 0;
                question->CurrentAnswers    = 0;
                question->LargeAnswers      = 0;
                question->UniqueAnswers     = 0;
                question->LOAddressAnswers  = 0;
                question->FlappingInterface1 = mDNSNULL;
                question->FlappingInterface2 = mDNSNULL;
                // Must do AuthInfo and SuppressQuery before calling FindDuplicateQuestion()
                question->AuthInfo          = GetAuthInfoForQuestion(m, question);
                if (question->SuppressUnusable)
                        question->SuppressQuery = ShouldSuppressQuery(m, &question->qname, question->qtype, question->InterfaceID);
                else
                        question->SuppressQuery = 0;
                question->DuplicateOf       = FindDuplicateQuestion(m, question);
                question->NextInDQList      = mDNSNULL;
                question->SendQNow          = mDNSNULL;
                question->SendOnAll         = mDNSfalse;
                question->RequestUnicast    = 0;
                question->LastQTxTime       = m->timenow;
                question->CNAMEReferrals    = 0;

                // We'll create our question->LocalSocket on demand, if needed.
                // We won't need one for duplicate questions, or from questions answered immediately out of the cache.
                // We also don't need one for LLQs because (when we're using NAT) we want them all to share a single
                // NAT mapping for receiving inbound add/remove events.
                question->LocalSocket       = mDNSNULL;
                question->deliverAddEvents  = mDNSfalse;
                question->qDNSServer        = mDNSNULL;
                question->unansweredQueries = 0;
                question->nta               = mDNSNULL;
                question->servAddr          = zeroAddr;
                question->servPort          = zeroIPPort;
                question->tcp               = mDNSNULL;
                question->NoAnswer          = NoAnswer_Normal;

                question->state             = LLQ_InitialRequest;
                question->ReqLease          = 0;
                question->expire            = 0;
                question->ntries            = 0;
                question->id                = zeroOpaque64;
                question->validDNSServers   = zeroOpaque64;
                question->triedAllServersOnce = 0;
                question->noServerResponse  = 0;
                question->StopTime = 0;
                if (question->WakeOnResolve)
                        {
                        question->WakeOnResolveCount = InitialWakeOnResolveCount;
                        mDNS_PurgeBeforeResolve(m, question);
                        }
                else
                        question->WakeOnResolveCount = 0;

                if (question->DuplicateOf) question->AuthInfo = question->DuplicateOf->AuthInfo;

                for (i=0; i<DupSuppressInfoSize; i++)
                        question->DupSuppress[i].InterfaceID = mDNSNULL;

                debugf("mDNS_StartQuery: Question %##s (%s) Interface %p Now %d Send in %d Answer in %d (%p) %s (%p)",
                        question->qname.c, DNSTypeName(question->qtype), question->InterfaceID, m->timenow,
                        NextQSendTime(question) - m->timenow,
                        question->DelayAnswering ? question->DelayAnswering - m->timenow : 0,
                        question, question->DuplicateOf ? "duplicate of" : "not duplicate", question->DuplicateOf);

                if (question->DelayAnswering)
                        LogInfo("mDNS_StartQuery_internal: Delaying answering for %d ticks while cache stabilizes for %##s (%s)",
                                question->DelayAnswering - m->timenow, question->qname.c, DNSTypeName(question->qtype));

                if (question->InterfaceID == mDNSInterface_LocalOnly || question->InterfaceID == mDNSInterface_P2P)
                        {
                        if (!m->NewLocalOnlyQuestions) m->NewLocalOnlyQuestions = question;
                        }
                else
                        {
                        if (!m->NewQuestions) m->NewQuestions = question;

                        // If the question's id is non-zero, then it's Wide Area
                        // MUST NOT do this Wide Area setup until near the end of
                        // mDNS_StartQuery_internal -- this code may itself issue queries (e.g. SOA,
                        // NS, etc.) and if we haven't finished setting up our own question and setting
                        // m->NewQuestions if necessary then we could end up recursively re-entering
                        // this routine with the question list data structures in an inconsistent state.
                        if (!mDNSOpaque16IsZero(question->TargetQID))
                                {
                                // Duplicate questions should have the same DNSServers so that when we find
                                // a matching resource record, all of them get the answers. Calling GetServerForQuestion
                                // for the duplicate question may get a different DNS server from the original question
                                mDNSu32 timeout = SetValidDNSServers(m, question);
                                // We set the timeout whenever mDNS_StartQuery_internal is called. This means if we have
                                // a networking change/search domain change that calls this function again we keep
                                // reinitializing the timeout value which means it may never timeout. If this becomes
                                // a common case in the future, we can easily fix this by adding extra state that
                                // indicates that we have already set the StopTime.
                                if (question->TimeoutQuestion)
                                        question->StopTime = NonZeroTime(m->timenow + timeout * mDNSPlatformOneSecond);
                                if (question->DuplicateOf)
                                        {
                                        question->validDNSServers = question->DuplicateOf->validDNSServers;
                                        question->qDNSServer = question->DuplicateOf->qDNSServer;
                                        LogInfo("mDNS_StartQuery_internal: Duplicate question %p (%p) %##s (%s), Timeout %d, DNS Server %#a:%d",
                                                question, question->DuplicateOf, question->qname.c, DNSTypeName(question->qtype), timeout,
                                                question->qDNSServer ? &question->qDNSServer->addr : mDNSNULL,
                                            mDNSVal16(question->qDNSServer ? question->qDNSServer->port : zeroIPPort));
                                        }
                                else
                                        {
                                        question->qDNSServer = GetServerForQuestion(m, question);
                                        LogInfo("mDNS_StartQuery_internal: question %p %##s (%s) Timeout %d, DNS Server %#a:%d",
                                                question, question->qname.c, DNSTypeName(question->qtype), timeout,
                                                question->qDNSServer ? &question->qDNSServer->addr : mDNSNULL,
                                            mDNSVal16(question->qDNSServer ? question->qDNSServer->port : zeroIPPort));
                                        }
                                ActivateUnicastQuery(m, question, mDNSfalse);

                                // If long-lived query, and we don't have our NAT mapping active, start it now
                                if (question->LongLived && !m->LLQNAT.clientContext)
                                        {
                                        m->LLQNAT.Protocol       = NATOp_MapUDP;
                                        m->LLQNAT.IntPort        = m->UnicastPort4;
                                        m->LLQNAT.RequestedPort  = m->UnicastPort4;
                                        m->LLQNAT.clientCallback = LLQNATCallback;
                                        m->LLQNAT.clientContext  = (void*)1; // Means LLQ NAT Traversal is active
                                        mDNS_StartNATOperation_internal(m, &m->LLQNAT);
                                        }
                                        
#if APPLE_OSX_mDNSResponder
                                if (question->LongLived)
                                        UpdateAutoTunnelDomainStatuses(m);
#endif
                                        
                                }
                        else
                                {
                                if (question->TimeoutQuestion)
                                        question->StopTime = NonZeroTime(m->timenow + GetTimeoutForMcastQuestion(m, question) * mDNSPlatformOneSecond);
                                }
                        if (question->StopTime) SetNextQueryStopTime(m, question);
                        SetNextQueryTime(m,question);
                        }

                return(mStatus_NoError);
                }
        }

// CancelGetZoneData is an internal routine (i.e. must be called with the lock already held)
mDNSexport void CancelGetZoneData(mDNS *const m, ZoneData *nta)
        {
        debugf("CancelGetZoneData %##s (%s)", nta->question.qname.c, DNSTypeName(nta->question.qtype));
        // This function may be called anytime to free the zone information.The question may or may not have stopped.
        // If it was already stopped, mDNS_StopQuery_internal would have set q->ThisQInterval to -1 and should not
        // call it again
        if (nta->question.ThisQInterval != -1)
                {
                mDNS_StopQuery_internal(m, &nta->question);
                if (nta->question.ThisQInterval != -1)
                        LogMsg("CancelGetZoneData: Question %##s (%s) ThisQInterval %d not -1", nta->question.qname.c, DNSTypeName(nta->question.qtype), nta->question.ThisQInterval);
                }
        mDNSPlatformMemFree(nta);
        }

mDNSexport mStatus mDNS_StopQuery_internal(mDNS *const m, DNSQuestion *const question)
        {
        const mDNSu32 slot = HashSlot(&question->qname);
        CacheGroup *cg = CacheGroupForName(m, slot, question->qnamehash, &question->qname);
        CacheRecord *rr;
        DNSQuestion **qp = &m->Questions;
        
        //LogInfo("mDNS_StopQuery_internal %##s (%s)", question->qname.c, DNSTypeName(question->qtype));

        if (question->InterfaceID == mDNSInterface_LocalOnly || question->InterfaceID == mDNSInterface_P2P) qp = &m->LocalOnlyQuestions;
        while (*qp && *qp != question) qp=&(*qp)->next;
        if (*qp) *qp = (*qp)->next;
        else
                {
#if !ForceAlerts
                if (question->ThisQInterval >= 0)       // Only log error message if the query was supposed to be active
#endif
                        LogMsg("mDNS_StopQuery_internal: Question %##s (%s) not found in active list",
                                question->qname.c, DNSTypeName(question->qtype));
#if ForceAlerts
                *(long*)0 = 0;
#endif
                return(mStatus_BadReferenceErr);
                }

        // Take care to cut question from list *before* calling UpdateQuestionDuplicates
        UpdateQuestionDuplicates(m, question);
        // But don't trash ThisQInterval until afterwards.
        question->ThisQInterval = -1;

        // If there are any cache records referencing this as their active question, then see if there is any
        // other question that is also referencing them, else their CRActiveQuestion needs to get set to NULL.
        for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                {
                if (rr->CRActiveQuestion == question)
                        {
                        DNSQuestion *q;
                        // Checking for ActiveQuestion filters questions that are suppressed also
                        // as suppressed questions are not active
                        for (q = m->Questions; q; q=q->next)            // Scan our list of questions
                                if (ActiveQuestion(q) && ResourceRecordAnswersQuestion(&rr->resrec, q))
                                        break;
                        if (q)
                                debugf("mDNS_StopQuery_internal: Updating CRActiveQuestion to %p for cache record %s, Original question CurrentAnswers %d, new question "
                                        "CurrentAnswers %d, SuppressQuery %d", q, CRDisplayString(m,rr), question->CurrentAnswers, q->CurrentAnswers, q->SuppressQuery);
                        rr->CRActiveQuestion = q;               // Question used to be active; new value may or may not be null
                        if (!q) m->rrcache_active--;    // If no longer active, decrement rrcache_active count
                        }
                }

        // If we just deleted the question that CacheRecordAdd() or CacheRecordRmv() is about to look at,
        // bump its pointer forward one question.
        if (m->CurrentQuestion == question)
                {
                debugf("mDNS_StopQuery_internal: Just deleted the currently active question: %##s (%s)",
                        question->qname.c, DNSTypeName(question->qtype));
                m->CurrentQuestion = question->next;
                }

        if (m->NewQuestions == question)
                {
                debugf("mDNS_StopQuery_internal: Just deleted a new question that wasn't even answered yet: %##s (%s)",
                        question->qname.c, DNSTypeName(question->qtype));
                m->NewQuestions = question->next;
                }

        if (m->NewLocalOnlyQuestions == question) m->NewLocalOnlyQuestions = question->next;

        if (m->RestartQuestion == question)
                {
                LogMsg("mDNS_StopQuery_internal: Just deleted the current restart question: %##s (%s)",
                        question->qname.c, DNSTypeName(question->qtype));
                m->RestartQuestion = question->next;
                }

        // Take care not to trash question->next until *after* we've updated m->CurrentQuestion and m->NewQuestions
        question->next = mDNSNULL;

        // LogMsg("mDNS_StopQuery_internal: Question %##s (%s) removed", question->qname.c, DNSTypeName(question->qtype));

        // And finally, cancel any associated GetZoneData operation that's still running.
        // Must not do this until last, because there's a good chance the GetZoneData question is the next in the list,
        // so if we delete it earlier in this routine, we could find that our "question->next" pointer above is already
        // invalid before we even use it. By making sure that we update m->CurrentQuestion and m->NewQuestions if necessary
        // *first*, then they're all ready to be updated a second time if necessary when we cancel our GetZoneData query.
        if (question->tcp) { DisposeTCPConn(question->tcp); question->tcp = mDNSNULL; }
        if (question->LocalSocket) { mDNSPlatformUDPClose(question->LocalSocket); question->LocalSocket = mDNSNULL; }
        if (!mDNSOpaque16IsZero(question->TargetQID) && question->LongLived)
                {
                // Scan our list to see if any more wide-area LLQs remain. If not, stop our NAT Traversal.
                DNSQuestion *q;
                for (q = m->Questions; q; q=q->next)
                        if (!mDNSOpaque16IsZero(q->TargetQID) && q->LongLived) break;
                if (!q)
                        {
                        if (!m->LLQNAT.clientContext)           // Should never happen, but just in case...
                                LogMsg("mDNS_StopQuery ERROR LLQNAT.clientContext NULL");
                        else
                                {
                                LogInfo("Stopping LLQNAT");
                                mDNS_StopNATOperation_internal(m, &m->LLQNAT);
                                m->LLQNAT.clientContext = mDNSNULL; // Means LLQ NAT Traversal not running
                                }
                        }

                // If necessary, tell server it can delete this LLQ state
                if (question->state == LLQ_Established)
                        {
                        question->ReqLease = 0;
                        sendLLQRefresh(m, question);
                        // If we need need to make a TCP connection to cancel the LLQ, that's going to take a little while.
                        // We clear the tcp->question backpointer so that when the TCP connection completes, it doesn't
                        // crash trying to access our cancelled question, but we don't cancel the TCP operation itself --
                        // we let that run out its natural course and complete asynchronously.
                        if (question->tcp)
                                {
                                question->tcp->question = mDNSNULL;
                                question->tcp           = mDNSNULL;
                                }
                        }
#if APPLE_OSX_mDNSResponder
                UpdateAutoTunnelDomainStatuses(m);
#endif
                }
        // wait until we send the refresh above which needs the nta
        if (question->nta) { CancelGetZoneData(m, question->nta); question->nta = mDNSNULL; }

        return(mStatus_NoError);
        }

mDNSexport mStatus mDNS_StartQuery(mDNS *const m, DNSQuestion *const question)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_StartQuery_internal(m, question);
        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_StopQuery(mDNS *const m, DNSQuestion *const question)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_StopQuery_internal(m, question);
        mDNS_Unlock(m);
        return(status);
        }

// Note that mDNS_StopQueryWithRemoves() does not currently implement the full generality of the other APIs
// Specifically, question callbacks invoked as a result of this call cannot themselves make API calls.
// We invoke the callback without using mDNS_DropLockBeforeCallback/mDNS_ReclaimLockAfterCallback
// specifically to catch and report if the client callback does try to make API calls
mDNSexport mStatus mDNS_StopQueryWithRemoves(mDNS *const m, DNSQuestion *const question)
        {
        mStatus status;
        DNSQuestion *qq;
        mDNS_Lock(m);

        // Check if question is new -- don't want to give remove events for a question we haven't even answered yet
        for (qq = m->NewQuestions; qq; qq=qq->next) if (qq == question) break;

        status = mDNS_StopQuery_internal(m, question);
        if (status == mStatus_NoError && !qq)
                {
                const CacheRecord *rr;
                const mDNSu32 slot = HashSlot(&question->qname);
                CacheGroup *const cg = CacheGroupForName(m, slot, question->qnamehash, &question->qname);
                LogInfo("Generating terminal removes for %##s (%s)", question->qname.c, DNSTypeName(question->qtype));
                for (rr = cg ? cg->members : mDNSNULL; rr; rr=rr->next)
                        if (rr->resrec.RecordType != kDNSRecordTypePacketNegative && SameNameRecordAnswersQuestion(&rr->resrec, question))
                                {
                                // Don't use mDNS_DropLockBeforeCallback() here, since we don't allow API calls
                                if (question->QuestionCallback)
                                        question->QuestionCallback(m, question, &rr->resrec, mDNSfalse);
                                }
                }
        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_Reconfirm(mDNS *const m, CacheRecord *const cr)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForNoAnswer);
        if (status == mStatus_NoError) ReconfirmAntecedents(m, cr->resrec.name, cr->resrec.namehash, 0);
        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_ReconfirmByValue(mDNS *const m, ResourceRecord *const rr)
        {
        mStatus status = mStatus_BadReferenceErr;
        CacheRecord *cr;
        mDNS_Lock(m);
        cr = FindIdenticalRecordInCache(m, rr);
        debugf("mDNS_ReconfirmByValue: %p %s", cr, RRDisplayString(m, rr));
        if (cr) status = mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForNoAnswer);
        if (status == mStatus_NoError) ReconfirmAntecedents(m, cr->resrec.name, cr->resrec.namehash, 0);
        mDNS_Unlock(m);
        return(status);
        }

mDNSlocal mStatus mDNS_StartBrowse_internal(mDNS *const m, DNSQuestion *const question,
        const domainname *const srv, const domainname *const domain,
        const mDNSInterfaceID InterfaceID, mDNSBool ForceMCast, mDNSQuestionCallback *Callback, void *Context)
        {
        question->InterfaceID      = InterfaceID;
        question->Target           = zeroAddr;
        question->qtype            = kDNSType_PTR;
        question->qclass           = kDNSClass_IN;
        question->LongLived        = mDNStrue;
        question->ExpectUnique     = mDNSfalse;
        question->ForceMCast       = ForceMCast;
        question->ReturnIntermed   = mDNSfalse;
        question->SuppressUnusable = mDNSfalse;
        question->SearchListIndex  = 0;
        question->AppendSearchDomains = 0;
        question->RetryWithSearchDomains = mDNSfalse;
        question->TimeoutQuestion  = 0;
        question->WakeOnResolve    = 0;
        question->qnameOrig        = mDNSNULL;
        question->QuestionCallback = Callback;
        question->QuestionContext  = Context;
        if (!ConstructServiceName(&question->qname, mDNSNULL, srv, domain)) return(mStatus_BadParamErr);

        return(mDNS_StartQuery_internal(m, question));
        }

mDNSexport mStatus mDNS_StartBrowse(mDNS *const m, DNSQuestion *const question,
        const domainname *const srv, const domainname *const domain,
        const mDNSInterfaceID InterfaceID, mDNSBool ForceMCast, mDNSQuestionCallback *Callback, void *Context)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_StartBrowse_internal(m, question, srv, domain, InterfaceID, ForceMCast, Callback, Context);
        mDNS_Unlock(m);
        return(status);
        }

mDNSlocal mDNSBool MachineHasActiveIPv6(mDNS *const m)
        {
        NetworkInterfaceInfo *intf;
        for (intf = m->HostInterfaces; intf; intf = intf->next)
        if (intf->ip.type == mDNSAddrType_IPv6) return(mDNStrue);
        return(mDNSfalse);
        }

mDNSlocal void FoundServiceInfoSRV(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
        {
        ServiceInfoQuery *query = (ServiceInfoQuery *)question->QuestionContext;
        mDNSBool PortChanged = !mDNSSameIPPort(query->info->port, answer->rdata->u.srv.port);
        if (!AddRecord) return;
        if (answer->rrtype != kDNSType_SRV) return;

        query->info->port = answer->rdata->u.srv.port;

        // If this is our first answer, then set the GotSRV flag and start the address query
        if (!query->GotSRV)
                {
                query->GotSRV             = mDNStrue;
                query->qAv4.InterfaceID   = answer->InterfaceID;
                AssignDomainName(&query->qAv4.qname, &answer->rdata->u.srv.target);
                query->qAv6.InterfaceID   = answer->InterfaceID;
                AssignDomainName(&query->qAv6.qname, &answer->rdata->u.srv.target);
                mDNS_StartQuery(m, &query->qAv4);
                // Only do the AAAA query if this machine actually has IPv6 active
                if (MachineHasActiveIPv6(m)) mDNS_StartQuery(m, &query->qAv6);
                }
        // If this is not our first answer, only re-issue the address query if the target host name has changed
        else if ((query->qAv4.InterfaceID != query->qSRV.InterfaceID && query->qAv4.InterfaceID != answer->InterfaceID) ||
                !SameDomainName(&query->qAv4.qname, &answer->rdata->u.srv.target))
                {
                mDNS_StopQuery(m, &query->qAv4);
                if (query->qAv6.ThisQInterval >= 0) mDNS_StopQuery(m, &query->qAv6);
                if (SameDomainName(&query->qAv4.qname, &answer->rdata->u.srv.target) && !PortChanged)
                        {
                        // If we get here, it means:
                        // 1. This is not our first SRV answer
                        // 2. The interface ID is different, but the target host and port are the same
                        // This implies that we're seeing the exact same SRV record on more than one interface, so we should
                        // make our address queries at least as broad as the original SRV query so that we catch all the answers.
                        query->qAv4.InterfaceID = query->qSRV.InterfaceID;      // Will be mDNSInterface_Any, or a specific interface
                        query->qAv6.InterfaceID = query->qSRV.InterfaceID;
                        }
                else
                        {
                        query->qAv4.InterfaceID   = answer->InterfaceID;
                        AssignDomainName(&query->qAv4.qname, &answer->rdata->u.srv.target);
                        query->qAv6.InterfaceID   = answer->InterfaceID;
                        AssignDomainName(&query->qAv6.qname, &answer->rdata->u.srv.target);
                        }
                debugf("FoundServiceInfoSRV: Restarting address queries for %##s (%s)", query->qAv4.qname.c, DNSTypeName(query->qAv4.qtype));
                mDNS_StartQuery(m, &query->qAv4);
                // Only do the AAAA query if this machine actually has IPv6 active
                if (MachineHasActiveIPv6(m)) mDNS_StartQuery(m, &query->qAv6);
                }
        else if (query->ServiceInfoQueryCallback && query->GotADD && query->GotTXT && PortChanged)
                {
                if (++query->Answers >= 100)
                        debugf("**** WARNING **** Have given %lu answers for %##s (SRV) %##s %u",
                                query->Answers, query->qSRV.qname.c, answer->rdata->u.srv.target.c,
                                mDNSVal16(answer->rdata->u.srv.port));
                query->ServiceInfoQueryCallback(m, query);
                }
        // CAUTION: MUST NOT do anything more with query after calling query->Callback(), because the client's
        // callback function is allowed to do anything, including deleting this query and freeing its memory.
        }

mDNSlocal void FoundServiceInfoTXT(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
        {
        ServiceInfoQuery *query = (ServiceInfoQuery *)question->QuestionContext;
        if (!AddRecord) return;
        if (answer->rrtype != kDNSType_TXT) return;
        if (answer->rdlength > sizeof(query->info->TXTinfo)) return;

        query->GotTXT       = mDNStrue;
        query->info->TXTlen = answer->rdlength;
        query->info->TXTinfo[0] = 0;            // In case answer->rdlength is zero
        mDNSPlatformMemCopy(query->info->TXTinfo, answer->rdata->u.txt.c, answer->rdlength);

        verbosedebugf("FoundServiceInfoTXT: %##s GotADD=%d", query->info->name.c, query->GotADD);

        // CAUTION: MUST NOT do anything more with query after calling query->Callback(), because the client's
        // callback function is allowed to do anything, including deleting this query and freeing its memory.
        if (query->ServiceInfoQueryCallback && query->GotADD)
                {
                if (++query->Answers >= 100)
                        debugf("**** WARNING **** have given %lu answers for %##s (TXT) %#s...",
                                query->Answers, query->qSRV.qname.c, answer->rdata->u.txt.c);
                query->ServiceInfoQueryCallback(m, query);
                }
        }

mDNSlocal void FoundServiceInfo(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
        {
        ServiceInfoQuery *query = (ServiceInfoQuery *)question->QuestionContext;
        //LogInfo("FoundServiceInfo %d %s", AddRecord, RRDisplayString(m, answer));
        if (!AddRecord) return;
        
        if (answer->rrtype == kDNSType_A)
                {
                query->info->ip.type = mDNSAddrType_IPv4;
                query->info->ip.ip.v4 = answer->rdata->u.ipv4;
                }
        else if (answer->rrtype == kDNSType_AAAA)
                {
                query->info->ip.type = mDNSAddrType_IPv6;
                query->info->ip.ip.v6 = answer->rdata->u.ipv6;
                }
        else
                {
                debugf("FoundServiceInfo: answer %##s type %d (%s) unexpected", answer->name->c, answer->rrtype, DNSTypeName(answer->rrtype));
                return;
                }

        query->GotADD = mDNStrue;
        query->info->InterfaceID = answer->InterfaceID;

        verbosedebugf("FoundServiceInfo v%ld: %##s GotTXT=%d", query->info->ip.type, query->info->name.c, query->GotTXT);

        // CAUTION: MUST NOT do anything more with query after calling query->Callback(), because the client's
        // callback function is allowed to do anything, including deleting this query and freeing its memory.
        if (query->ServiceInfoQueryCallback && query->GotTXT)
                {
                if (++query->Answers >= 100)
                        debugf(answer->rrtype == kDNSType_A ?
                                "**** WARNING **** have given %lu answers for %##s (A) %.4a" :
                                "**** WARNING **** have given %lu answers for %##s (AAAA) %.16a",
                                query->Answers, query->qSRV.qname.c, &answer->rdata->u.data);
                query->ServiceInfoQueryCallback(m, query);
                }
        }

// On entry, the client must have set the name and InterfaceID fields of the ServiceInfo structure
// If the query is not interface-specific, then InterfaceID may be zero
// Each time the Callback is invoked, the remainder of the fields will have been filled in
// In addition, InterfaceID will be updated to give the interface identifier corresponding to that response
mDNSexport mStatus mDNS_StartResolveService(mDNS *const m,
        ServiceInfoQuery *query, ServiceInfo *info, mDNSServiceInfoQueryCallback *Callback, void *Context)
        {
        mStatus status;
        mDNS_Lock(m);

        query->qSRV.ThisQInterval       = -1;           // So that mDNS_StopResolveService() knows whether to cancel this question
        query->qSRV.InterfaceID         = info->InterfaceID;
        query->qSRV.Target              = zeroAddr;
        AssignDomainName(&query->qSRV.qname, &info->name);
        query->qSRV.qtype               = kDNSType_SRV;
        query->qSRV.qclass              = kDNSClass_IN;
        query->qSRV.LongLived           = mDNSfalse;
        query->qSRV.ExpectUnique        = mDNStrue;
        query->qSRV.ForceMCast          = mDNSfalse;
        query->qSRV.ReturnIntermed      = mDNSfalse;
        query->qSRV.SuppressUnusable    = mDNSfalse;
        query->qSRV.SearchListIndex     = 0;
        query->qSRV.AppendSearchDomains = 0;
        query->qSRV.RetryWithSearchDomains = mDNSfalse;
        query->qSRV.TimeoutQuestion     = 0;
        query->qSRV.WakeOnResolve       = 0;
        query->qSRV.qnameOrig           = mDNSNULL;
        query->qSRV.QuestionCallback    = FoundServiceInfoSRV;
        query->qSRV.QuestionContext     = query;

        query->qTXT.ThisQInterval       = -1;           // So that mDNS_StopResolveService() knows whether to cancel this question
        query->qTXT.InterfaceID         = info->InterfaceID;
        query->qTXT.Target              = zeroAddr;
        AssignDomainName(&query->qTXT.qname, &info->name);
        query->qTXT.qtype               = kDNSType_TXT;
        query->qTXT.qclass              = kDNSClass_IN;
        query->qTXT.LongLived           = mDNSfalse;
        query->qTXT.ExpectUnique        = mDNStrue;
        query->qTXT.ForceMCast          = mDNSfalse;
        query->qTXT.ReturnIntermed      = mDNSfalse;
        query->qTXT.SuppressUnusable    = mDNSfalse;
        query->qTXT.SearchListIndex     = 0;
        query->qTXT.AppendSearchDomains = 0;
        query->qTXT.RetryWithSearchDomains = mDNSfalse;
        query->qTXT.TimeoutQuestion     = 0;
        query->qTXT.WakeOnResolve       = 0;
        query->qTXT.qnameOrig           = mDNSNULL;
        query->qTXT.QuestionCallback    = FoundServiceInfoTXT;
        query->qTXT.QuestionContext     = query;

        query->qAv4.ThisQInterval       = -1;           // So that mDNS_StopResolveService() knows whether to cancel this question
        query->qAv4.InterfaceID         = info->InterfaceID;
        query->qAv4.Target              = zeroAddr;
        query->qAv4.qname.c[0]          = 0;
        query->qAv4.qtype               = kDNSType_A;
        query->qAv4.qclass              = kDNSClass_IN;
        query->qAv4.LongLived           = mDNSfalse;
        query->qAv4.ExpectUnique        = mDNStrue;
        query->qAv4.ForceMCast          = mDNSfalse;
        query->qAv4.ReturnIntermed      = mDNSfalse;
        query->qAv4.SuppressUnusable    = mDNSfalse;
        query->qAv4.SearchListIndex     = 0;
        query->qAv4.AppendSearchDomains = 0;
        query->qAv4.RetryWithSearchDomains = mDNSfalse;
        query->qAv4.TimeoutQuestion     = 0;
        query->qAv4.WakeOnResolve       = 0;
        query->qAv4.qnameOrig           = mDNSNULL;
        query->qAv4.QuestionCallback    = FoundServiceInfo;
        query->qAv4.QuestionContext     = query;

        query->qAv6.ThisQInterval       = -1;           // So that mDNS_StopResolveService() knows whether to cancel this question
        query->qAv6.InterfaceID         = info->InterfaceID;
        query->qAv6.Target              = zeroAddr;
        query->qAv6.qname.c[0]          = 0;
        query->qAv6.qtype               = kDNSType_AAAA;
        query->qAv6.qclass              = kDNSClass_IN;
        query->qAv6.LongLived           = mDNSfalse;
        query->qAv6.ExpectUnique        = mDNStrue;
        query->qAv6.ForceMCast          = mDNSfalse;
        query->qAv6.ReturnIntermed      = mDNSfalse;
        query->qAv6.SuppressUnusable    = mDNSfalse;
        query->qAv6.SearchListIndex     = 0;
        query->qAv6.AppendSearchDomains = 0;
        query->qAv6.RetryWithSearchDomains = mDNSfalse;
        query->qAv6.TimeoutQuestion     = 0;
        query->qAv6.WakeOnResolve       = 0;
        query->qAv6.qnameOrig           = mDNSNULL;
        query->qAv6.QuestionCallback    = FoundServiceInfo;
        query->qAv6.QuestionContext     = query;

        query->GotSRV                   = mDNSfalse;
        query->GotTXT                   = mDNSfalse;
        query->GotADD                   = mDNSfalse;
        query->Answers                  = 0;

        query->info                     = info;
        query->ServiceInfoQueryCallback = Callback;
        query->ServiceInfoQueryContext  = Context;

//      info->name      = Must already be set up by client
//      info->interface = Must already be set up by client
        info->ip        = zeroAddr;
        info->port      = zeroIPPort;
        info->TXTlen    = 0;

        // We use mDNS_StartQuery_internal here because we're already holding the lock
        status = mDNS_StartQuery_internal(m, &query->qSRV);
        if (status == mStatus_NoError) status = mDNS_StartQuery_internal(m, &query->qTXT);
        if (status != mStatus_NoError) mDNS_StopResolveService(m, query);

        mDNS_Unlock(m);
        return(status);
        }

mDNSexport void    mDNS_StopResolveService (mDNS *const m, ServiceInfoQuery *q)
        {
        mDNS_Lock(m);
        // We use mDNS_StopQuery_internal here because we're already holding the lock
        if (q->qSRV.ThisQInterval >= 0) mDNS_StopQuery_internal(m, &q->qSRV);
        if (q->qTXT.ThisQInterval >= 0) mDNS_StopQuery_internal(m, &q->qTXT);
        if (q->qAv4.ThisQInterval >= 0) mDNS_StopQuery_internal(m, &q->qAv4);
        if (q->qAv6.ThisQInterval >= 0) mDNS_StopQuery_internal(m, &q->qAv6);
        mDNS_Unlock(m);
        }

mDNSexport mStatus mDNS_GetDomains(mDNS *const m, DNSQuestion *const question, mDNS_DomainType DomainType, const domainname *dom,
        const mDNSInterfaceID InterfaceID, mDNSQuestionCallback *Callback, void *Context)
        {
        question->InterfaceID      = InterfaceID;
        question->Target           = zeroAddr;
        question->qtype            = kDNSType_PTR;
        question->qclass           = kDNSClass_IN;
        question->LongLived        = mDNSfalse;
        question->ExpectUnique     = mDNSfalse;
        question->ForceMCast       = mDNSfalse;
        question->ReturnIntermed   = mDNSfalse;
        question->SuppressUnusable = mDNSfalse;
        question->SearchListIndex  = 0;
        question->AppendSearchDomains = 0;
        question->RetryWithSearchDomains = mDNSfalse;
        question->TimeoutQuestion  = 0;
        question->WakeOnResolve    = 0;
        question->qnameOrig        = mDNSNULL;
        question->QuestionCallback = Callback;
        question->QuestionContext  = Context;
        if (DomainType > mDNS_DomainTypeMax) return(mStatus_BadParamErr);
        if (!MakeDomainNameFromDNSNameString(&question->qname, mDNS_DomainTypeNames[DomainType])) return(mStatus_BadParamErr);
        if (!dom) dom = &localdomain;
        if (!AppendDomainName(&question->qname, dom)) return(mStatus_BadParamErr);
        return(mDNS_StartQuery(m, question));
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Responder Functions
#endif

mDNSexport mStatus mDNS_Register(mDNS *const m, AuthRecord *const rr)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_Register_internal(m, rr);
        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_Update(mDNS *const m, AuthRecord *const rr, mDNSu32 newttl,
        const mDNSu16 newrdlength, RData *const newrdata, mDNSRecordUpdateCallback *Callback)
        {
        if (!ValidateRData(rr->resrec.rrtype, newrdlength, newrdata))
                {
                LogMsg("Attempt to update record with invalid rdata: %s", GetRRDisplayString_rdb(&rr->resrec, &newrdata->u, m->MsgBuffer));
                return(mStatus_Invalid);
                }
        
        mDNS_Lock(m);

        // If TTL is unspecified, leave TTL unchanged
        if (newttl == 0) newttl = rr->resrec.rroriginalttl;

        // If we already have an update queued up which has not gone through yet, give the client a chance to free that memory
        if (rr->NewRData)
                {
                RData *n = rr->NewRData;
                rr->NewRData = mDNSNULL;                                                        // Clear the NewRData pointer ...
                if (rr->UpdateCallback)
                        rr->UpdateCallback(m, rr, n, rr->newrdlength);  // ...and let the client free this memory, if necessary
                }

        rr->NewRData             = newrdata;
        rr->newrdlength          = newrdlength;
        rr->UpdateCallback       = Callback;

#ifndef UNICAST_DISABLED
        if (rr->ARType != AuthRecordLocalOnly && rr->ARType != AuthRecordP2P && !IsLocalDomain(rr->resrec.name))
                {
                mStatus status = uDNS_UpdateRecord(m, rr);
                // The caller frees the memory on error, don't retain stale pointers
                if (status != mStatus_NoError) { rr->NewRData = mDNSNULL; rr->newrdlength = 0; }
                mDNS_Unlock(m);
                return(status);
                }
#endif

        if (RRLocalOnly(rr) || (rr->resrec.rroriginalttl == newttl &&
                rr->resrec.rdlength == newrdlength && mDNSPlatformMemSame(rr->resrec.rdata->u.data, newrdata->u.data, newrdlength)))
                CompleteRDataUpdate(m, rr);
        else
                {
                rr->AnnounceCount = InitialAnnounceCount;
                InitializeLastAPTime(m, rr);
                while (rr->NextUpdateCredit && m->timenow - rr->NextUpdateCredit >= 0) GrantUpdateCredit(rr);
                if (!rr->UpdateBlocked && rr->UpdateCredits) rr->UpdateCredits--;
                if (!rr->NextUpdateCredit) rr->NextUpdateCredit = NonZeroTime(m->timenow + kUpdateCreditRefreshInterval);
                if (rr->AnnounceCount > rr->UpdateCredits + 1) rr->AnnounceCount = (mDNSu8)(rr->UpdateCredits + 1);
                if (rr->UpdateCredits <= 5)
                        {
                        mDNSu32 delay = 6 - rr->UpdateCredits;          // Delay 1 second, then 2, then 3, etc. up to 6 seconds maximum
                        if (!rr->UpdateBlocked) rr->UpdateBlocked = NonZeroTime(m->timenow + (mDNSs32)delay * mDNSPlatformOneSecond);
                        rr->ThisAPInterval *= 4;
                        rr->LastAPTime = rr->UpdateBlocked - rr->ThisAPInterval;
                        LogMsg("Excessive update rate for %##s; delaying announcement by %ld second%s",
                                rr->resrec.name->c, delay, delay > 1 ? "s" : "");
                        }
                rr->resrec.rroriginalttl = newttl;
                }

        mDNS_Unlock(m);
        return(mStatus_NoError);
        }

// Note: mDNS_Deregister calls mDNS_Deregister_internal which can call a user callback, which may change
// the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSexport mStatus mDNS_Deregister(mDNS *const m, AuthRecord *const rr)
        {
        mStatus status;
        mDNS_Lock(m);
        status = mDNS_Deregister_internal(m, rr, mDNS_Dereg_normal);
        mDNS_Unlock(m);
        return(status);
        }

// Circular reference: AdvertiseInterface references mDNS_HostNameCallback, which calls mDNS_SetFQDN, which call AdvertiseInterface
mDNSlocal void mDNS_HostNameCallback(mDNS *const m, AuthRecord *const rr, mStatus result);

mDNSlocal NetworkInterfaceInfo *FindFirstAdvertisedInterface(mDNS *const m)
        {
        NetworkInterfaceInfo *intf;
        for (intf = m->HostInterfaces; intf; intf = intf->next)
                if (intf->Advertise) break;
        return(intf);
        }

mDNSlocal void AdvertiseInterface(mDNS *const m, NetworkInterfaceInfo *set)
        {
        char buffer[MAX_REVERSE_MAPPING_NAME];
        NetworkInterfaceInfo *primary = FindFirstAdvertisedInterface(m);
        if (!primary) primary = set; // If no existing advertised interface, this new NetworkInterfaceInfo becomes our new primary

        // Send dynamic update for non-linklocal IPv4 Addresses
        mDNS_SetupResourceRecord(&set->RR_A,     mDNSNULL, set->InterfaceID, kDNSType_A,     kHostNameTTL, kDNSRecordTypeUnique,      AuthRecordAny, mDNS_HostNameCallback, set);
        mDNS_SetupResourceRecord(&set->RR_PTR,   mDNSNULL, set->InterfaceID, kDNSType_PTR,   kHostNameTTL, kDNSRecordTypeKnownUnique, AuthRecordAny, mDNSNULL, mDNSNULL);
        mDNS_SetupResourceRecord(&set->RR_HINFO, mDNSNULL, set->InterfaceID, kDNSType_HINFO, kHostNameTTL, kDNSRecordTypeUnique,      AuthRecordAny, mDNSNULL, mDNSNULL);

#if ANSWER_REMOTE_HOSTNAME_QUERIES
        set->RR_A    .AllowRemoteQuery  = mDNStrue;
        set->RR_PTR  .AllowRemoteQuery  = mDNStrue;
        set->RR_HINFO.AllowRemoteQuery  = mDNStrue;
#endif
        // 1. Set up Address record to map from host name ("foo.local.") to IP address
        // 2. Set up reverse-lookup PTR record to map from our address back to our host name
        AssignDomainName(&set->RR_A.namestorage, &m->MulticastHostname);
        if (set->ip.type == mDNSAddrType_IPv4)
                {
                set->RR_A.resrec.rrtype = kDNSType_A;
                set->RR_A.resrec.rdata->u.ipv4 = set->ip.ip.v4;
                // Note: This is reverse order compared to a normal dotted-decimal IP address, so we can't use our customary "%.4a" format code
                mDNS_snprintf(buffer, sizeof(buffer), "%d.%d.%d.%d.in-addr.arpa.",
                        set->ip.ip.v4.b[3], set->ip.ip.v4.b[2], set->ip.ip.v4.b[1], set->ip.ip.v4.b[0]);
                }
        else if (set->ip.type == mDNSAddrType_IPv6)
                {
                int i;
                set->RR_A.resrec.rrtype = kDNSType_AAAA;
                set->RR_A.resrec.rdata->u.ipv6 = set->ip.ip.v6;
                for (i = 0; i < 16; i++)
                        {
                        static const char hexValues[] = "0123456789ABCDEF";
                        buffer[i * 4    ] = hexValues[set->ip.ip.v6.b[15 - i] & 0x0F];
                        buffer[i * 4 + 1] = '.';
                        buffer[i * 4 + 2] = hexValues[set->ip.ip.v6.b[15 - i] >> 4];
                        buffer[i * 4 + 3] = '.';
                        }
                mDNS_snprintf(&buffer[64], sizeof(buffer)-64, "ip6.arpa.");
                }

        MakeDomainNameFromDNSNameString(&set->RR_PTR.namestorage, buffer);
        set->RR_PTR.AutoTarget = Target_AutoHost;       // Tell mDNS that the target of this PTR is to be kept in sync with our host name
        set->RR_PTR.ForceMCast = mDNStrue;                      // This PTR points to our dot-local name, so don't ever try to write it into a uDNS server

        set->RR_A.RRSet = &primary->RR_A;                       // May refer to self

        mDNS_Register_internal(m, &set->RR_A);
        mDNS_Register_internal(m, &set->RR_PTR);

        if (!NO_HINFO && m->HIHardware.c[0] > 0 && m->HISoftware.c[0] > 0 && m->HIHardware.c[0] + m->HISoftware.c[0] <= 254)
                {
                mDNSu8 *p = set->RR_HINFO.resrec.rdata->u.data;
                AssignDomainName(&set->RR_HINFO.namestorage, &m->MulticastHostname);
                set->RR_HINFO.DependentOn = &set->RR_A;
                mDNSPlatformMemCopy(p, &m->HIHardware, 1 + (mDNSu32)m->HIHardware.c[0]);
                p += 1 + (int)p[0];
                mDNSPlatformMemCopy(p, &m->HISoftware, 1 + (mDNSu32)m->HISoftware.c[0]);
                mDNS_Register_internal(m, &set->RR_HINFO);
                }
        else
                {
                debugf("Not creating HINFO record: platform support layer provided no information");
                set->RR_HINFO.resrec.RecordType = kDNSRecordTypeUnregistered;
                }
        }

mDNSlocal void DeadvertiseInterface(mDNS *const m, NetworkInterfaceInfo *set)
        {
        NetworkInterfaceInfo *intf;
        
    // If we still have address records referring to this one, update them
        NetworkInterfaceInfo *primary = FindFirstAdvertisedInterface(m);
        AuthRecord *A = primary ? &primary->RR_A : mDNSNULL;
        for (intf = m->HostInterfaces; intf; intf = intf->next)
                if (intf->RR_A.RRSet == &set->RR_A)
                        intf->RR_A.RRSet = A;

        // Unregister these records.
        // When doing the mDNS_Exit processing, we first call DeadvertiseInterface for each interface, so by the time the platform
        // support layer gets to call mDNS_DeregisterInterface, the address and PTR records have already been deregistered for it.
        // Also, in the event of a name conflict, one or more of our records will have been forcibly deregistered.
        // To avoid unnecessary and misleading warning messages, we check the RecordType before calling mDNS_Deregister_internal().
        if (set->RR_A.    resrec.RecordType) mDNS_Deregister_internal(m, &set->RR_A,     mDNS_Dereg_normal);
        if (set->RR_PTR.  resrec.RecordType) mDNS_Deregister_internal(m, &set->RR_PTR,   mDNS_Dereg_normal);
        if (set->RR_HINFO.resrec.RecordType) mDNS_Deregister_internal(m, &set->RR_HINFO, mDNS_Dereg_normal);
        }

mDNSexport void mDNS_SetFQDN(mDNS *const m)
        {
        domainname newmname;
        NetworkInterfaceInfo *intf;
        AuthRecord *rr;
        newmname.c[0] = 0;

        if (!AppendDomainLabel(&newmname, &m->hostlabel))  { LogMsg("ERROR: mDNS_SetFQDN: Cannot create MulticastHostname"); return; }
        if (!AppendLiteralLabelString(&newmname, "local")) { LogMsg("ERROR: mDNS_SetFQDN: Cannot create MulticastHostname"); return; }

        mDNS_Lock(m);

        if (SameDomainNameCS(&m->MulticastHostname, &newmname)) debugf("mDNS_SetFQDN - hostname unchanged");
        else
                {
                AssignDomainName(&m->MulticastHostname, &newmname);
        
                // 1. Stop advertising our address records on all interfaces
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                        if (intf->Advertise) DeadvertiseInterface(m, intf);
        
                // 2. Start advertising our address records using the new name
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                        if (intf->Advertise) AdvertiseInterface(m, intf);
                }

        // 3. Make sure that any AutoTarget SRV records (and the like) get updated
        for (rr = m->ResourceRecords;  rr; rr=rr->next) if (rr->AutoTarget) SetTargetToHostName(m, rr);
        for (rr = m->DuplicateRecords; rr; rr=rr->next) if (rr->AutoTarget) SetTargetToHostName(m, rr);
        
        mDNS_Unlock(m);
        }

mDNSlocal void mDNS_HostNameCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
        {
        (void)rr;       // Unused parameter
        
        #if MDNS_DEBUGMSGS
                {
                char *msg = "Unknown result";
                if      (result == mStatus_NoError)      msg = "Name registered";
                else if (result == mStatus_NameConflict) msg = "Name conflict";
                debugf("mDNS_HostNameCallback: %##s (%s) %s (%ld)", rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype), msg, result);
                }
        #endif

        if (result == mStatus_NoError)
                {
                // Notify the client that the host name is successfully registered
                if (m->MainCallback)
                        m->MainCallback(m, mStatus_NoError);
                }
        else if (result == mStatus_NameConflict)
                {
                domainlabel oldlabel = m->hostlabel;

                // 1. First give the client callback a chance to pick a new name
                if (m->MainCallback)
                        m->MainCallback(m, mStatus_NameConflict);

                // 2. If the client callback didn't do it, add (or increment) an index ourselves
                // This needs to be case-INSENSITIVE compare, because we need to know that the name has been changed so as to
                // remedy the conflict, and a name that differs only in capitalization will just suffer the exact same conflict again.
                if (SameDomainLabel(m->hostlabel.c, oldlabel.c))
                        IncrementLabelSuffix(&m->hostlabel, mDNSfalse);
                
                // 3. Generate the FQDNs from the hostlabel,
                // and make sure all SRV records, etc., are updated to reference our new hostname
                mDNS_SetFQDN(m);
                LogMsg("Local Hostname %#s.local already in use; will try %#s.local instead", oldlabel.c, m->hostlabel.c);
                }
        else if (result == mStatus_MemFree)
                {
                // .local hostnames do not require goodbyes - we ignore the MemFree (which is sent directly by
                // mDNS_Deregister_internal), and allow the caller to deallocate immediately following mDNS_DeadvertiseInterface
                debugf("mDNS_HostNameCallback: MemFree (ignored)");
                }
        else
                LogMsg("mDNS_HostNameCallback: Unknown error %d for registration of record %s", result,  rr->resrec.name->c);
        }

mDNSlocal void UpdateInterfaceProtocols(mDNS *const m, NetworkInterfaceInfo *active)
        {
        NetworkInterfaceInfo *intf;
        active->IPv4Available = mDNSfalse;
        active->IPv6Available = mDNSfalse;
        for (intf = m->HostInterfaces; intf; intf = intf->next)
                if (intf->InterfaceID == active->InterfaceID)
                        {
                        if (intf->ip.type == mDNSAddrType_IPv4 && intf->McastTxRx) active->IPv4Available = mDNStrue;
                        if (intf->ip.type == mDNSAddrType_IPv6 && intf->McastTxRx) active->IPv6Available = mDNStrue;
                        }
        }

mDNSlocal void RestartRecordGetZoneData(mDNS * const m)
        {
        AuthRecord *rr;
        LogInfo("RestartRecordGetZoneData: ResourceRecords");
        for (rr = m->ResourceRecords; rr; rr=rr->next)
                if (AuthRecord_uDNS(rr) && rr->state != regState_NoTarget)
                        {
                        debugf("RestartRecordGetZoneData: StartGetZoneData for %##s", rr->resrec.name->c);
                        // Zero out the updateid so that if we have a pending response from the server, it won't
                        // be accepted as a valid response. If we accept the response, we might free the new "nta"
                        if (rr->nta) { rr->updateid = zeroID; CancelGetZoneData(m, rr->nta); }
                        rr->nta = StartGetZoneData(m, rr->resrec.name, ZoneServiceUpdate, RecordRegistrationGotZoneData, rr);
                        }
        }

mDNSlocal void InitializeNetWakeState(mDNS *const m, NetworkInterfaceInfo *set)
        {
        int i;
        set->NetWakeBrowse.ThisQInterval = -1;
        for (i=0; i<3; i++)
                {
                set->NetWakeResolve[i].ThisQInterval = -1;
                set->SPSAddr[i].type = mDNSAddrType_None;
                }
        set->NextSPSAttempt     = -1;
        set->NextSPSAttemptTime = m->timenow;
        }

mDNSexport void mDNS_ActivateNetWake_internal(mDNS *const m, NetworkInterfaceInfo *set)
        {
        NetworkInterfaceInfo *p = m->HostInterfaces;
        while (p && p != set) p=p->next;
        if (!p) { LogMsg("mDNS_ActivateNetWake_internal: NetworkInterfaceInfo %p not found in active list", set); return; }

        if (set->InterfaceActive)
                {
                LogSPS("ActivateNetWake for %s (%#a)", set->ifname, &set->ip);
                mDNS_StartBrowse_internal(m, &set->NetWakeBrowse, &SleepProxyServiceType, &localdomain, set->InterfaceID, mDNSfalse, m->SPSBrowseCallback, set);
                }
        }

mDNSexport void mDNS_DeactivateNetWake_internal(mDNS *const m, NetworkInterfaceInfo *set)
        {
        NetworkInterfaceInfo *p = m->HostInterfaces;
        while (p && p != set) p=p->next;
        if (!p) { LogMsg("mDNS_DeactivateNetWake_internal: NetworkInterfaceInfo %p not found in active list", set); return; }

        if (set->NetWakeBrowse.ThisQInterval >= 0)
                {
                int i;
                LogSPS("DeactivateNetWake for %s (%#a)", set->ifname, &set->ip);

                // Stop our browse and resolve operations
                mDNS_StopQuery_internal(m, &set->NetWakeBrowse);
                for (i=0; i<3; i++) if (set->NetWakeResolve[i].ThisQInterval >= 0) mDNS_StopQuery_internal(m, &set->NetWakeResolve[i]);

                // Make special call to the browse callback to let it know it can to remove all records for this interface
                if (m->SPSBrowseCallback)
                        {
                        mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                        m->SPSBrowseCallback(m, &set->NetWakeBrowse, mDNSNULL, mDNSfalse);
                        mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                        }

                // Reset our variables back to initial state, so we're ready for when NetWake is turned back on
                // (includes resetting NetWakeBrowse.ThisQInterval back to -1)
                InitializeNetWakeState(m, set);
                }
        }

mDNSexport mStatus mDNS_RegisterInterface(mDNS *const m, NetworkInterfaceInfo *set, mDNSBool flapping)
        {
        AuthRecord *rr;
        mDNSBool FirstOfType = mDNStrue;
        NetworkInterfaceInfo **p = &m->HostInterfaces;

        if (!set->InterfaceID)
                { LogMsg("mDNS_RegisterInterface: Error! Tried to register a NetworkInterfaceInfo %#a with zero InterfaceID", &set->ip); return(mStatus_Invalid); }

        if (!mDNSAddressIsValidNonZero(&set->mask))
                { LogMsg("mDNS_RegisterInterface: Error! Tried to register a NetworkInterfaceInfo %#a with invalid mask %#a", &set->ip, &set->mask); return(mStatus_Invalid); }

        mDNS_Lock(m);
        
        // Assume this interface will be active now, unless we find a duplicate already in the list
        set->InterfaceActive = mDNStrue;
        set->IPv4Available   = (mDNSu8)(set->ip.type == mDNSAddrType_IPv4 && set->McastTxRx);
        set->IPv6Available   = (mDNSu8)(set->ip.type == mDNSAddrType_IPv6 && set->McastTxRx);
        
        InitializeNetWakeState(m, set);

        // Scan list to see if this InterfaceID is already represented
        while (*p)
                {
                if (*p == set)
                        {
                        LogMsg("mDNS_RegisterInterface: Error! Tried to register a NetworkInterfaceInfo that's already in the list");
                        mDNS_Unlock(m);
                        return(mStatus_AlreadyRegistered);
                        }

                if ((*p)->InterfaceID == set->InterfaceID)
                        {
                        // This InterfaceID already represented by a different interface in the list, so mark this instance inactive for now
                        set->InterfaceActive = mDNSfalse;
                        if (set->ip.type == (*p)->ip.type) FirstOfType = mDNSfalse;
                        if (set->ip.type == mDNSAddrType_IPv4 && set->McastTxRx) (*p)->IPv4Available = mDNStrue;
                        if (set->ip.type == mDNSAddrType_IPv6 && set->McastTxRx) (*p)->IPv6Available = mDNStrue;
                        }

                p=&(*p)->next;
                }

        set->next = mDNSNULL;
        *p = set;
        
        if (set->Advertise)
                AdvertiseInterface(m, set);

        LogInfo("mDNS_RegisterInterface: InterfaceID %p %s (%#a) %s", set->InterfaceID, set->ifname, &set->ip,
                set->InterfaceActive ?
                        "not represented in list; marking active and retriggering queries" :
                        "already represented in list; marking inactive for now");
        
        if (set->NetWake) mDNS_ActivateNetWake_internal(m, set);

        // In early versions of OS X the IPv6 address remains on an interface even when the interface is turned off,
        // giving the false impression that there's an active representative of this interface when there really isn't.
        // Therefore, when registering an interface, we want to re-trigger our questions and re-probe our Resource Records,
        // even if we believe that we previously had an active representative of this interface.
        if (set->McastTxRx && (FirstOfType || set->InterfaceActive))
                {
                DNSQuestion *q;
                // Normally, after an interface comes up, we pause half a second before beginning probing.
                // This is to guard against cases where there's rapid interface changes, where we could be confused by
                // seeing packets we ourselves sent just moments ago (perhaps when this interface had a different address)
                // which are then echoed back after a short delay by some Ethernet switches and some 802.11 base stations.
                // We don't want to do a probe, and then see a stale echo of an announcement we ourselves sent,
                // and think it's a conflicting answer to our probe.
                // In the case of a flapping interface, we pause for five seconds, and reduce the announcement count to one packet.
                const mDNSs32 probedelay  = flapping ? mDNSPlatformOneSecond * 5 : mDNSPlatformOneSecond / 2;
                const mDNSu8  numannounce = flapping ? (mDNSu8)1                 : InitialAnnounceCount;

                // Use a small amount of randomness:
                // In the case of a network administrator turning on an Ethernet hub so that all the
                // connected machines establish link at exactly the same time, we don't want them all
                // to go and hit the network with identical queries at exactly the same moment.
                // We set a random delay of up to InitialQuestionInterval (1/3 second).
                // We must *never* set m->SuppressSending to more than that (or set it repeatedly in a way
                // that causes mDNSResponder to remain in a prolonged state of SuppressSending, because
                // suppressing packet sending for more than about 1/3 second can cause protocol correctness
                // to start to break down (e.g. we don't answer probes fast enough, and get name conflicts).
                // See <rdar://problem/4073853> mDNS: m->SuppressSending set too enthusiastically
                if (!m->SuppressSending) m->SuppressSending = m->timenow + (mDNSs32)mDNSRandom((mDNSu32)InitialQuestionInterval);

                if (flapping) LogMsg("mDNS_RegisterInterface: Frequent transitions for interface %s (%#a)", set->ifname, &set->ip);

                LogInfo("mDNS_RegisterInterface: %s (%#a) probedelay %d", set->ifname, &set->ip, probedelay);
                if (m->SuppressProbes == 0 ||
                        m->SuppressProbes - NonZeroTime(m->timenow + probedelay) < 0)
                        m->SuppressProbes = NonZeroTime(m->timenow + probedelay);

                // Include OWNER option in packets for 60 seconds after connecting to the network. Setting
                // it here also handles the wake up case as the network link comes UP after waking causing
                // us to reconnect to the network. If we do this as part of the wake up code, it is possible
                // that the network link comes UP after 60 seconds and we never set the OWNER option
                m->AnnounceOwner = NonZeroTime(m->timenow + 60 * mDNSPlatformOneSecond);
                LogInfo("mDNS_RegisterInterface: Setting AnnounceOwner");

                for (q = m->Questions; q; q=q->next)                                                            // Scan our list of questions
                        if (mDNSOpaque16IsZero(q->TargetQID))
                                if (!q->InterfaceID || q->InterfaceID == set->InterfaceID)              // If non-specific Q, or Q on this specific interface,
                                        {                                                                                                                       // then reactivate this question
                                        // If flapping, delay between first and second queries is nine seconds instead of one second
                                        mDNSBool dodelay = flapping && (q->FlappingInterface1 == set->InterfaceID || q->FlappingInterface2 == set->InterfaceID);
                                        mDNSs32 initial  = dodelay ? InitialQuestionInterval * QuestionIntervalStep2 : InitialQuestionInterval;
                                        mDNSs32 qdelay   = dodelay ? mDNSPlatformOneSecond * 5 : 0;
                                        if (dodelay) LogInfo("No cache records expired for %##s (%s); okay to delay questions a little", q->qname.c, DNSTypeName(q->qtype));
                                                
                                        if (!q->ThisQInterval || q->ThisQInterval > initial)
                                                {
                                                q->ThisQInterval = initial;
                                                q->RequestUnicast = 2; // Set to 2 because is decremented once *before* we check it
                                                }
                                        q->LastQTime = m->timenow - q->ThisQInterval + qdelay;
                                        q->RecentAnswerPkts = 0;
                                        SetNextQueryTime(m,q);
                                        }
                
                // For all our non-specific authoritative resource records (and any dormant records specific to this interface)
                // we now need them to re-probe if necessary, and then re-announce.
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (!AuthRecord_uDNS(rr))
                                if (!rr->resrec.InterfaceID || rr->resrec.InterfaceID == set->InterfaceID)
                                        {
                                        if (rr->resrec.RecordType == kDNSRecordTypeVerified && !rr->DependentOn) rr->resrec.RecordType = kDNSRecordTypeUnique;
                                        rr->ProbeCount     = DefaultProbeCountForRecordType(rr->resrec.RecordType);
                                        if (rr->AnnounceCount < numannounce) rr->AnnounceCount  = numannounce;
                                        rr->SendNSECNow    = mDNSNULL;
                                        InitializeLastAPTime(m, rr);
                                        }
                }

        RestartRecordGetZoneData(m);

        CheckSuppressUnusableQuestions(m);

        mDNS_UpdateAllowSleep(m);

        mDNS_Unlock(m);
        return(mStatus_NoError);
        }

// Note: mDNS_DeregisterInterface calls mDNS_Deregister_internal which can call a user callback, which may change
// the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSexport void mDNS_DeregisterInterface(mDNS *const m, NetworkInterfaceInfo *set, mDNSBool flapping)
        {
        NetworkInterfaceInfo **p = &m->HostInterfaces;
        mDNSBool revalidate = mDNSfalse;

        mDNS_Lock(m);

        // Find this record in our list
        while (*p && *p != set) p=&(*p)->next;
        if (!*p) { debugf("mDNS_DeregisterInterface: NetworkInterfaceInfo not found in list"); mDNS_Unlock(m); return; }

        mDNS_DeactivateNetWake_internal(m, set);

        // Unlink this record from our list
        *p = (*p)->next;
        set->next = mDNSNULL;

        if (!set->InterfaceActive)
                {
                // If this interface not the active member of its set, update the v4/v6Available flags for the active member
                NetworkInterfaceInfo *intf;
                for (intf = m->HostInterfaces; intf; intf = intf->next)
                        if (intf->InterfaceActive && intf->InterfaceID == set->InterfaceID)
                                UpdateInterfaceProtocols(m, intf);
                }
        else
                {
                NetworkInterfaceInfo *intf = FirstInterfaceForID(m, set->InterfaceID);
                if (intf)
                        {
                        LogInfo("mDNS_DeregisterInterface: Another representative of InterfaceID %p %s (%#a) exists;"
                                " making it active", set->InterfaceID, set->ifname, &set->ip);
                        if (intf->InterfaceActive)
                                LogMsg("mDNS_DeregisterInterface: ERROR intf->InterfaceActive already set for %s (%#a)", set->ifname, &set->ip);
                        intf->InterfaceActive = mDNStrue;
                        UpdateInterfaceProtocols(m, intf);

                        if (intf->NetWake) mDNS_ActivateNetWake_internal(m, intf);
                        
                        // See if another representative *of the same type* exists. If not, we mave have gone from
                        // dual-stack to v6-only (or v4-only) so we need to reconfirm which records are still valid.
                        for (intf = m->HostInterfaces; intf; intf = intf->next)
                                if (intf->InterfaceID == set->InterfaceID && intf->ip.type == set->ip.type)
                                        break;
                        if (!intf) revalidate = mDNStrue;
                        }
                else
                        {
                        mDNSu32 slot;
                        CacheGroup *cg;
                        CacheRecord *rr;
                        DNSQuestion *q;
                        DNSServer *s;

                        LogInfo("mDNS_DeregisterInterface: Last representative of InterfaceID %p %s (%#a) deregistered;"
                                " marking questions etc. dormant", set->InterfaceID, set->ifname, &set->ip);

                        if (set->McastTxRx && flapping)
                                LogMsg("DeregisterInterface: Frequent transitions for interface %s (%#a)", set->ifname, &set->ip);

                        // 1. Deactivate any questions specific to this interface, and tag appropriate questions
                        // so that mDNS_RegisterInterface() knows how swiftly it needs to reactivate them
                        for (q = m->Questions; q; q=q->next)
                                {
                                if (q->InterfaceID == set->InterfaceID) q->ThisQInterval = 0;
                                if (!q->InterfaceID || q->InterfaceID == set->InterfaceID)
                                        {
                                        q->FlappingInterface2 = q->FlappingInterface1;
                                        q->FlappingInterface1 = set->InterfaceID;               // Keep history of the last two interfaces to go away
                                        }
                                }

                        // 2. Flush any cache records received on this interface
                        revalidate = mDNSfalse;         // Don't revalidate if we're flushing the records
                        FORALL_CACHERECORDS(slot, cg, rr)
                                if (rr->resrec.InterfaceID == set->InterfaceID)
                                        {
                                        // If this interface is deemed flapping,
                                        // postpone deleting the cache records in case the interface comes back again
                                        if (set->McastTxRx && flapping)
                                                {
                                                // For a flapping interface we want these record to go away after 30 seconds
                                                mDNS_Reconfirm_internal(m, rr, kDefaultReconfirmTimeForFlappingInterface);
                                                // We set UnansweredQueries = MaxUnansweredQueries so we don't waste time doing any queries for them --
                                                // if the interface does come back, any relevant questions will be reactivated anyway
                                                rr->UnansweredQueries = MaxUnansweredQueries;
                                                }
                                        else
                                                mDNS_PurgeCacheResourceRecord(m, rr);
                                        }

                        // 3. Any DNS servers specific to this interface are now unusable
                        for (s = m->DNSServers; s; s = s->next)
                                if (s->interface == set->InterfaceID)
                                        {
                                        s->interface = mDNSInterface_Any;
                                        s->teststate = DNSServer_Disabled;
                                        }
                        }
                }

        // If we were advertising on this interface, deregister those address and reverse-lookup records now
        if (set->Advertise) DeadvertiseInterface(m, set);

        // If we have any cache records received on this interface that went away, then re-verify them.
        // In some versions of OS X the IPv6 address remains on an interface even when the interface is turned off,
        // giving the false impression that there's an active representative of this interface when there really isn't.
        // Don't need to do this when shutting down, because *all* interfaces are about to go away
        if (revalidate && !m->ShutdownTime)
                {
                mDNSu32 slot;
                CacheGroup *cg;
                CacheRecord *rr;
                FORALL_CACHERECORDS(slot, cg, rr)
                        if (rr->resrec.InterfaceID == set->InterfaceID)
                                mDNS_Reconfirm_internal(m, rr, kDefaultReconfirmTimeForFlappingInterface);
                }

        CheckSuppressUnusableQuestions(m);

        mDNS_UpdateAllowSleep(m);

        mDNS_Unlock(m);
        }

mDNSlocal void ServiceCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
        {
        ServiceRecordSet *sr = (ServiceRecordSet *)rr->RecordContext;
        (void)m;        // Unused parameter

        #if MDNS_DEBUGMSGS
                {
                char *msg = "Unknown result";
                if      (result == mStatus_NoError)      msg = "Name Registered";
                else if (result == mStatus_NameConflict) msg = "Name Conflict";
                else if (result == mStatus_MemFree)      msg = "Memory Free";
                debugf("ServiceCallback: %##s (%s) %s (%d)", rr->resrec.name->c, DNSTypeName(rr->resrec.rrtype), msg, result);
                }
        #endif

        // Only pass on the NoError acknowledgement for the SRV record (when it finishes probing)
        if (result == mStatus_NoError && rr != &sr->RR_SRV) return;

        // If we got a name conflict on either SRV or TXT, forcibly deregister this service, and record that we did that
        if (result == mStatus_NameConflict)
                {
                sr->Conflict = mDNStrue;                                // Record that this service set had a conflict
                mDNS_DeregisterService(m, sr);                  // Unlink the records from our list
                return;
                }
        
        if (result == mStatus_MemFree)
                {
                // If the SRV/TXT/PTR records, or the _services._dns-sd._udp record, or any of the subtype PTR records,
                // are still in the process of deregistering, don't pass on the NameConflict/MemFree message until
                // every record is finished cleaning up.
                mDNSu32 i;
                ExtraResourceRecord *e = sr->Extras;

                if (sr->RR_SRV.resrec.RecordType != kDNSRecordTypeUnregistered) return;
                if (sr->RR_TXT.resrec.RecordType != kDNSRecordTypeUnregistered) return;
                if (sr->RR_PTR.resrec.RecordType != kDNSRecordTypeUnregistered) return;
                if (sr->RR_ADV.resrec.RecordType != kDNSRecordTypeUnregistered) return;
                for (i=0; i<sr->NumSubTypes; i++) if (sr->SubTypes[i].resrec.RecordType != kDNSRecordTypeUnregistered) return;

                while (e)
                        {
                        if (e->r.resrec.RecordType != kDNSRecordTypeUnregistered) return;
                        e = e->next;
                        }

                // If this ServiceRecordSet was forcibly deregistered, and now its memory is ready for reuse,
                // then we can now report the NameConflict to the client
                if (sr->Conflict) result = mStatus_NameConflict;

                }

        LogInfo("ServiceCallback: All records %s for %##s", (result == mStatus_MemFree ? "Unregistered": "Registered"), sr->RR_PTR.resrec.name->c);
        // CAUTION: MUST NOT do anything more with sr after calling sr->Callback(), because the client's callback
        // function is allowed to do anything, including deregistering this service and freeing its memory.
        if (sr->ServiceCallback)
                sr->ServiceCallback(m, sr, result);
        }

mDNSlocal void NSSCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
        {
        ServiceRecordSet *sr = (ServiceRecordSet *)rr->RecordContext;
        if (sr->ServiceCallback)
                sr->ServiceCallback(m, sr, result);
        }

// Note:
// Name is first label of domain name (any dots in the name are actual dots, not label separators)
// Type is service type (e.g. "_ipp._tcp.")
// Domain is fully qualified domain name (i.e. ending with a null label)
// We always register a TXT, even if it is empty (so that clients are not
// left waiting forever looking for a nonexistent record.)
// If the host parameter is mDNSNULL or the root domain (ASCII NUL),
// then the default host name (m->MulticastHostname) is automatically used
// If the optional target host parameter is set, then the storage it points to must remain valid for the lifetime of the service registration
mDNSexport mStatus mDNS_RegisterService(mDNS *const m, ServiceRecordSet *sr,
        const domainlabel *const name, const domainname *const type, const domainname *const domain,
        const domainname *const host, mDNSIPPort port, const mDNSu8 txtinfo[], mDNSu16 txtlen,
        AuthRecord *SubTypes, mDNSu32 NumSubTypes,
        mDNSInterfaceID InterfaceID, mDNSServiceCallback Callback, void *Context, mDNSu32 flags)
        {
        mStatus err;
        mDNSu32 i;
        mDNSu32 hostTTL;
        AuthRecType artype;
        mDNSu8 recordType = (flags & regFlagKnownUnique) ? kDNSRecordTypeKnownUnique : kDNSRecordTypeUnique;

        sr->ServiceCallback = Callback;
        sr->ServiceContext  = Context;
        sr->Conflict        = mDNSfalse;

        sr->Extras          = mDNSNULL;
        sr->NumSubTypes     = NumSubTypes;
        sr->SubTypes        = SubTypes;
        
        if (InterfaceID == mDNSInterface_LocalOnly)
                artype = AuthRecordLocalOnly;
        else if (InterfaceID == mDNSInterface_P2P)
                artype = AuthRecordP2P;
        else if ((InterfaceID == mDNSInterface_Any) && (flags & regFlagIncludeP2P))
                artype = AuthRecordAnyIncludeP2P;
        else
                artype = AuthRecordAny;

        // Initialize the AuthRecord objects to sane values
        // Need to initialize everything correctly *before* making the decision whether to do a RegisterNoSuchService and bail out
        mDNS_SetupResourceRecord(&sr->RR_ADV, mDNSNULL, InterfaceID, kDNSType_PTR, kStandardTTL, kDNSRecordTypeAdvisory, artype, ServiceCallback, sr);
        mDNS_SetupResourceRecord(&sr->RR_PTR, mDNSNULL, InterfaceID, kDNSType_PTR, kStandardTTL, kDNSRecordTypeShared,   artype, ServiceCallback, sr);

        if (SameDomainName(type, (const domainname *) "\x4" "_ubd" "\x4" "_tcp"))
                hostTTL = kHostNameSmallTTL;
        else
                hostTTL = kHostNameTTL;

        mDNS_SetupResourceRecord(&sr->RR_SRV, mDNSNULL, InterfaceID, kDNSType_SRV, hostTTL, recordType, artype, ServiceCallback, sr);
        mDNS_SetupResourceRecord(&sr->RR_TXT, mDNSNULL, InterfaceID, kDNSType_TXT, kStandardTTL, kDNSRecordTypeUnique, artype, ServiceCallback, sr);

        // If port number is zero, that means the client is really trying to do a RegisterNoSuchService
        if (mDNSIPPortIsZero(port))
                return(mDNS_RegisterNoSuchService(m, &sr->RR_SRV, name, type, domain, mDNSNULL, InterfaceID, NSSCallback, sr, (flags & regFlagIncludeP2P)));

        // If the client is registering an oversized TXT record,
        // it is the client's responsibility to alloate a ServiceRecordSet structure that is large enough for it
        if (sr->RR_TXT.resrec.rdata->MaxRDLength < txtlen)
                sr->RR_TXT.resrec.rdata->MaxRDLength = txtlen;

        // Set up the record names
        // For now we only create an advisory record for the main type, not for subtypes
        // We need to gain some operational experience before we decide if there's a need to create them for subtypes too
        if (ConstructServiceName(&sr->RR_ADV.namestorage, (const domainlabel*)"\x09_services", (const domainname*)"\x07_dns-sd\x04_udp", domain) == mDNSNULL)
                return(mStatus_BadParamErr);
        if (ConstructServiceName(&sr->RR_PTR.namestorage, mDNSNULL, type, domain) == mDNSNULL) return(mStatus_BadParamErr);
        if (ConstructServiceName(&sr->RR_SRV.namestorage, name,     type, domain) == mDNSNULL) return(mStatus_BadParamErr);
        AssignDomainName(&sr->RR_TXT.namestorage, sr->RR_SRV.resrec.name);
        
        // 1. Set up the ADV record rdata to advertise our service type
        AssignDomainName(&sr->RR_ADV.resrec.rdata->u.name, sr->RR_PTR.resrec.name);

        // 2. Set up the PTR record rdata to point to our service name
        // We set up two additionals, so when a client asks for this PTR we automatically send the SRV and the TXT too
        // Note: uDNS registration code assumes that Additional1 points to the SRV record
        AssignDomainName(&sr->RR_PTR.resrec.rdata->u.name, sr->RR_SRV.resrec.name);
        sr->RR_PTR.Additional1 = &sr->RR_SRV;
        sr->RR_PTR.Additional2 = &sr->RR_TXT;

        // 2a. Set up any subtype PTRs to point to our service name
        // If the client is using subtypes, it is the client's responsibility to have
        // already set the first label of the record name to the subtype being registered
        for (i=0; i<NumSubTypes; i++)
                {
                domainname st;
                AssignDomainName(&st, sr->SubTypes[i].resrec.name);
                st.c[1+st.c[0]] = 0;                    // Only want the first label, not the whole FQDN (particularly for mDNS_RenameAndReregisterService())
                AppendDomainName(&st, type);
                mDNS_SetupResourceRecord(&sr->SubTypes[i], mDNSNULL, InterfaceID, kDNSType_PTR, kStandardTTL, kDNSRecordTypeShared, artype, ServiceCallback, sr);
                if (ConstructServiceName(&sr->SubTypes[i].namestorage, mDNSNULL, &st, domain) == mDNSNULL) return(mStatus_BadParamErr);
                AssignDomainName(&sr->SubTypes[i].resrec.rdata->u.name, &sr->RR_SRV.namestorage);
                sr->SubTypes[i].Additional1 = &sr->RR_SRV;
                sr->SubTypes[i].Additional2 = &sr->RR_TXT;
                }

        // 3. Set up the SRV record rdata.
        sr->RR_SRV.resrec.rdata->u.srv.priority = 0;
        sr->RR_SRV.resrec.rdata->u.srv.weight   = 0;
        sr->RR_SRV.resrec.rdata->u.srv.port     = port;

        // Setting AutoTarget tells DNS that the target of this SRV is to be automatically kept in sync with our host name
        if (host && host->c[0]) AssignDomainName(&sr->RR_SRV.resrec.rdata->u.srv.target, host);
        else { sr->RR_SRV.AutoTarget = Target_AutoHost; sr->RR_SRV.resrec.rdata->u.srv.target.c[0] = '\0'; }

        // 4. Set up the TXT record rdata,
        // and set DependentOn because we're depending on the SRV record to find and resolve conflicts for us
        // Note: uDNS registration code assumes that DependentOn points to the SRV record
        if (txtinfo == mDNSNULL) sr->RR_TXT.resrec.rdlength = 0;
        else if (txtinfo != sr->RR_TXT.resrec.rdata->u.txt.c)
                {
                sr->RR_TXT.resrec.rdlength = txtlen;
                if (sr->RR_TXT.resrec.rdlength > sr->RR_TXT.resrec.rdata->MaxRDLength) return(mStatus_BadParamErr);
                mDNSPlatformMemCopy(sr->RR_TXT.resrec.rdata->u.txt.c, txtinfo, txtlen);
                }
        sr->RR_TXT.DependentOn = &sr->RR_SRV;

        mDNS_Lock(m);
        // It is important that we register SRV first. uDNS assumes that SRV is registered first so
        // that if the SRV cannot find a target, rest of the records that belong to this service
        // will not be activated.
        err = mDNS_Register_internal(m, &sr->RR_SRV);
        // If we can't register the SRV record due to errors, bail out. It has not been inserted in
        // any list and hence no need to deregister. We could probably do similar checks for other
        // records below and bail out. For now, this seems to be sufficient to address rdar://9304275
        if (err)
                {
                mDNS_Unlock(m);
                return err;
                }
        if (!err) err = mDNS_Register_internal(m, &sr->RR_TXT);
        // We register the RR_PTR last, because we want to be sure that in the event of a forced call to
        // mDNS_StartExit, the RR_PTR will be the last one to be forcibly deregistered, since that is what triggers
        // the mStatus_MemFree callback to ServiceCallback, which in turn passes on the mStatus_MemFree back to
        // the client callback, which is then at liberty to free the ServiceRecordSet memory at will. We need to
        // make sure we've deregistered all our records and done any other necessary cleanup before that happens.
        if (!err) err = mDNS_Register_internal(m, &sr->RR_ADV);
        for (i=0; i<NumSubTypes; i++) if (!err) err = mDNS_Register_internal(m, &sr->SubTypes[i]);
        if (!err) err = mDNS_Register_internal(m, &sr->RR_PTR);

        mDNS_Unlock(m);
        
        if (err) mDNS_DeregisterService(m, sr);
        return(err);
        }

mDNSexport mStatus mDNS_AddRecordToService(mDNS *const m, ServiceRecordSet *sr,
        ExtraResourceRecord *extra, RData *rdata, mDNSu32 ttl,  mDNSu32 includeP2P)
        {
        ExtraResourceRecord **e;
        mStatus status;
        AuthRecType artype;
        mDNSInterfaceID InterfaceID = sr->RR_PTR.resrec.InterfaceID;

        if (InterfaceID == mDNSInterface_LocalOnly)
                artype = AuthRecordLocalOnly;
        if (InterfaceID == mDNSInterface_P2P)
                artype = AuthRecordP2P;
        else if ((InterfaceID == mDNSInterface_Any) && includeP2P)
                artype = AuthRecordAnyIncludeP2P;
        else
                artype = AuthRecordAny;

        extra->next = mDNSNULL;
        mDNS_SetupResourceRecord(&extra->r, rdata, sr->RR_PTR.resrec.InterfaceID,
                extra->r.resrec.rrtype, ttl, kDNSRecordTypeUnique, artype, ServiceCallback, sr);
        AssignDomainName(&extra->r.namestorage, sr->RR_SRV.resrec.name);
        
        mDNS_Lock(m);
        e = &sr->Extras;
        while (*e) e = &(*e)->next;

        if (ttl == 0) ttl = kStandardTTL;

        extra->r.DependentOn = &sr->RR_SRV;

        debugf("mDNS_AddRecordToService adding record to %##s %s %d",
                extra->r.resrec.name->c, DNSTypeName(extra->r.resrec.rrtype), extra->r.resrec.rdlength);

        status = mDNS_Register_internal(m, &extra->r);
        if (status == mStatus_NoError) *e = extra;

        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_RemoveRecordFromService(mDNS *const m, ServiceRecordSet *sr, ExtraResourceRecord *extra,
        mDNSRecordCallback MemFreeCallback, void *Context)
        {
        ExtraResourceRecord **e;
        mStatus status;

        mDNS_Lock(m);
        e = &sr->Extras;
        while (*e && *e != extra) e = &(*e)->next;
        if (!*e)
                {
                debugf("mDNS_RemoveRecordFromService failed to remove record from %##s", extra->r.resrec.name->c);
                status = mStatus_BadReferenceErr;
                }
        else
                {
                debugf("mDNS_RemoveRecordFromService removing record from %##s", extra->r.resrec.name->c);
                extra->r.RecordCallback = MemFreeCallback;
                extra->r.RecordContext  = Context;
                *e = (*e)->next;
                status = mDNS_Deregister_internal(m, &extra->r, mDNS_Dereg_normal);
                }
        mDNS_Unlock(m);
        return(status);
        }

mDNSexport mStatus mDNS_RenameAndReregisterService(mDNS *const m, ServiceRecordSet *const sr, const domainlabel *newname)
        {
        // Note: Don't need to use mDNS_Lock(m) here, because this code is just using public routines
        // mDNS_RegisterService() and mDNS_AddRecordToService(), which do the right locking internally.
        domainlabel name1, name2;
        domainname type, domain;
        const domainname *host = sr->RR_SRV.AutoTarget ? mDNSNULL : &sr->RR_SRV.resrec.rdata->u.srv.target;
        ExtraResourceRecord *extras = sr->Extras;
        mStatus err;

        DeconstructServiceName(sr->RR_SRV.resrec.name, &name1, &type, &domain);
        if (!newname)
                {
                name2 = name1;
                IncrementLabelSuffix(&name2, mDNStrue);
                newname = &name2;
                }
        
        if (SameDomainName(&domain, &localdomain))
                debugf("%##s service renamed from \"%#s\" to \"%#s\"", type.c, name1.c, newname->c);
        else debugf("%##s service (domain %##s) renamed from \"%#s\" to \"%#s\"",type.c, domain.c, name1.c, newname->c);

        err = mDNS_RegisterService(m, sr, newname, &type, &domain,
                host, sr->RR_SRV.resrec.rdata->u.srv.port, sr->RR_TXT.resrec.rdata->u.txt.c, sr->RR_TXT.resrec.rdlength,
                sr->SubTypes, sr->NumSubTypes,
                sr->RR_PTR.resrec.InterfaceID, sr->ServiceCallback, sr->ServiceContext, 0);

        // mDNS_RegisterService() just reset sr->Extras to NULL.
        // Fortunately we already grabbed ourselves a copy of this pointer (above), so we can now run
        // through the old list of extra records, and re-add them to our freshly created service registration
        while (!err && extras)
                {
                ExtraResourceRecord *e = extras;
                extras = extras->next;
                err = mDNS_AddRecordToService(m, sr, e, e->r.resrec.rdata, e->r.resrec.rroriginalttl, 0);
                }
        
        return(err);
        }

// Note: mDNS_DeregisterService calls mDNS_Deregister_internal which can call a user callback,
// which may change the record list and/or question list.
// Any code walking either list must use the CurrentQuestion and/or CurrentRecord mechanism to protect against this.
mDNSexport mStatus mDNS_DeregisterService_drt(mDNS *const m, ServiceRecordSet *sr, mDNS_Dereg_type drt)
        {
        // If port number is zero, that means this was actually registered using mDNS_RegisterNoSuchService()
        if (mDNSIPPortIsZero(sr->RR_SRV.resrec.rdata->u.srv.port)) return(mDNS_DeregisterNoSuchService(m, &sr->RR_SRV));

        if (sr->RR_PTR.resrec.RecordType == kDNSRecordTypeUnregistered)
                {
                debugf("Service set for %##s already deregistered", sr->RR_SRV.resrec.name->c);
                return(mStatus_BadReferenceErr);
                }
        else if (sr->RR_PTR.resrec.RecordType == kDNSRecordTypeDeregistering)
                {
                LogInfo("Service set for %##s already in the process of deregistering", sr->RR_SRV.resrec.name->c);
                // Avoid race condition:
                // If a service gets a conflict, then we set the Conflict flag to tell us to generate
                // an mStatus_NameConflict message when we get the mStatus_MemFree for our PTR record.
                // If the client happens to deregister the service in the middle of that process, then
                // we clear the flag back to the normal state, so that we deliver a plain mStatus_MemFree
                // instead of incorrectly promoting it to mStatus_NameConflict.
                // This race condition is exposed particularly when the conformance test generates
                // a whole batch of simultaneous conflicts across a range of services all advertised
                // using the same system default name, and if we don't take this precaution then
                // we end up incrementing m->nicelabel multiple times instead of just once.
                // <rdar://problem/4060169> Bug when auto-renaming Computer Name after name collision
                sr->Conflict = mDNSfalse;
                return(mStatus_NoError);
                }
        else
                {
                mDNSu32 i;
                mStatus status;
                ExtraResourceRecord *e;
                mDNS_Lock(m);
                e = sr->Extras;
        
                // We use mDNS_Dereg_repeat because, in the event of a collision, some or all of the
                // SRV, TXT, or Extra records could have already been automatically deregistered, and that's okay
                mDNS_Deregister_internal(m, &sr->RR_SRV, mDNS_Dereg_repeat);
                mDNS_Deregister_internal(m, &sr->RR_TXT, mDNS_Dereg_repeat);
                
                mDNS_Deregister_internal(m, &sr->RR_ADV, drt);
        
                // We deregister all of the extra records, but we leave the sr->Extras list intact
                // in case the client wants to do a RenameAndReregister and reinstate the registration
                while (e)
                        {
                        mDNS_Deregister_internal(m, &e->r, mDNS_Dereg_repeat);
                        e = e->next;
                        }

                for (i=0; i<sr->NumSubTypes; i++)
                        mDNS_Deregister_internal(m, &sr->SubTypes[i], drt);

                status = mDNS_Deregister_internal(m, &sr->RR_PTR, drt);
                mDNS_Unlock(m);
                return(status);
                }
        }

// Create a registration that asserts that no such service exists with this name.
// This can be useful where there is a given function is available through several protocols.
// For example, a printer called "Stuart's Printer" may implement printing via the "pdl-datastream" and "IPP"
// protocols, but not via "LPR". In this case it would be prudent for the printer to assert the non-existence of an
// "LPR" service called "Stuart's Printer". Without this precaution, another printer than offers only "LPR" printing
// could inadvertently advertise its service under the same name "Stuart's Printer", which might be confusing for users.
mDNSexport mStatus mDNS_RegisterNoSuchService(mDNS *const m, AuthRecord *const rr,
        const domainlabel *const name, const domainname *const type, const domainname *const domain,
        const domainname *const host,
        const mDNSInterfaceID InterfaceID, mDNSRecordCallback Callback, void *Context, mDNSBool includeP2P)
        {
        AuthRecType artype;

        if (InterfaceID == mDNSInterface_LocalOnly)
                artype = AuthRecordLocalOnly;
        else if (InterfaceID == mDNSInterface_P2P)
                artype = AuthRecordP2P;
        else if ((InterfaceID == mDNSInterface_Any) && includeP2P)
                artype = AuthRecordAnyIncludeP2P;
        else
                artype = AuthRecordAny;

        mDNS_SetupResourceRecord(rr, mDNSNULL, InterfaceID, kDNSType_SRV, kHostNameTTL, kDNSRecordTypeUnique, artype, Callback, Context);
        if (ConstructServiceName(&rr->namestorage, name, type, domain) == mDNSNULL) return(mStatus_BadParamErr);
        rr->resrec.rdata->u.srv.priority    = 0;
        rr->resrec.rdata->u.srv.weight      = 0;
        rr->resrec.rdata->u.srv.port        = zeroIPPort;
        if (host && host->c[0]) AssignDomainName(&rr->resrec.rdata->u.srv.target, host);
        else rr->AutoTarget = Target_AutoHost;
        return(mDNS_Register(m, rr));
        }

mDNSexport mStatus mDNS_AdvertiseDomains(mDNS *const m, AuthRecord *rr,
        mDNS_DomainType DomainType, const mDNSInterfaceID InterfaceID, char *domname)
        {
        AuthRecType artype;

        if (InterfaceID == mDNSInterface_LocalOnly)
                artype = AuthRecordLocalOnly;
        else if (InterfaceID == mDNSInterface_P2P)
                artype = AuthRecordP2P;
        else
                artype = AuthRecordAny;
        mDNS_SetupResourceRecord(rr, mDNSNULL, InterfaceID, kDNSType_PTR, kStandardTTL, kDNSRecordTypeShared, artype, mDNSNULL, mDNSNULL);
        if (!MakeDomainNameFromDNSNameString(&rr->namestorage, mDNS_DomainTypeNames[DomainType])) return(mStatus_BadParamErr);
        if (!MakeDomainNameFromDNSNameString(&rr->resrec.rdata->u.name, domname))                 return(mStatus_BadParamErr);
        return(mDNS_Register(m, rr));
        }
        
mDNSlocal mDNSBool mDNS_IdUsedInResourceRecordsList(mDNS * const m, mDNSOpaque16 id)
        {
        AuthRecord *r;
        for (r = m->ResourceRecords; r; r=r->next) if (mDNSSameOpaque16(id, r->updateid)) return mDNStrue;
        return mDNSfalse;
        }
        
mDNSlocal mDNSBool mDNS_IdUsedInQuestionsList(mDNS * const m, mDNSOpaque16 id)
        {
        DNSQuestion *q;
        for (q = m->Questions; q; q=q->next) if (mDNSSameOpaque16(id, q->TargetQID)) return mDNStrue;
        return mDNSfalse;
        }
        
mDNSexport mDNSOpaque16 mDNS_NewMessageID(mDNS * const m)
        {
        mDNSOpaque16 id;
        int i;

        for (i=0; i<10; i++)
                {
                id = mDNSOpaque16fromIntVal(1 + (mDNSu16)mDNSRandom(0xFFFE));
                if (!mDNS_IdUsedInResourceRecordsList(m, id) && !mDNS_IdUsedInQuestionsList(m, id)) break;
                }
                
        debugf("mDNS_NewMessageID: %5d", mDNSVal16(id));

        return id;
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Sleep Proxy Server
#endif

mDNSlocal void RestartARPProbing(mDNS *const m, AuthRecord *const rr)
        {
        // If we see an ARP from a machine we think is sleeping, then either
        // (i) the machine has woken, or
        // (ii) it's just a stray old packet from before the machine slept
        // To handle the second case, we reset ProbeCount, so we'll suppress our own answers for a while, to avoid
        // generating ARP conflicts with a waking machine, and set rr->LastAPTime so we'll start probing again in 10 seconds.
        // If the machine has just woken then we'll discard our records when we see the first new mDNS probe from that machine.
        // If it was a stray old packet, then after 10 seconds we'll probe again and then start answering ARPs again. In this case we *do*
        // need to send new ARP Announcements, because the owner's ARP broadcasts will have updated neighboring ARP caches, so we need to
        // re-assert our (temporary) ownership of that IP address in order to receive subsequent packets addressed to that IPv4 address.
        
        rr->resrec.RecordType = kDNSRecordTypeUnique;
        rr->ProbeCount        = DefaultProbeCountForTypeUnique;

        // If we haven't started announcing yet (and we're not already in ten-second-delay mode) the machine is probably
        // still going to sleep, so we just reset rr->ProbeCount so we'll continue probing until it stops responding.
        // If we *have* started announcing, the machine is probably in the process of waking back up, so in that case
        // we're more cautious and we wait ten seconds before probing it again. We do this because while waking from
        // sleep, some network interfaces tend to lose or delay inbound packets, and without this delay, if the waking machine
        // didn't answer our three probes within three seconds then we'd announce and cause it an unnecessary address conflict.
        if (rr->AnnounceCount == InitialAnnounceCount && m->timenow - rr->LastAPTime >= 0)
                InitializeLastAPTime(m, rr);
        else
                {
                rr->AnnounceCount  = InitialAnnounceCount;
                rr->ThisAPInterval = mDNSPlatformOneSecond;
                rr->LastAPTime     = m->timenow + mDNSPlatformOneSecond * 9;    // Send first packet at rr->LastAPTime + rr->ThisAPInterval, i.e. 10 seconds from now
                SetNextAnnounceProbeTime(m, rr);
                }
        }

mDNSlocal void mDNSCoreReceiveRawARP(mDNS *const m, const ARP_EthIP *const arp, const mDNSInterfaceID InterfaceID)
        {
        static const mDNSOpaque16 ARP_op_request = { { 0, 1 } };
        AuthRecord *rr;
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);
        if (!intf) return;

        mDNS_Lock(m);

        // Pass 1:
        // Process ARP Requests and Probes (but not Announcements), and generate an ARP Reply if necessary.
        // We also process ARPs from our own kernel (and 'answer' them by injecting a local ARP table entry)
        // We ignore ARP Announcements here -- Announcements are not questions, they're assertions, so we don't need to answer them.
        // The times we might need to react to an ARP Announcement are:
        // (i) as an indication that the host in question has not gone to sleep yet (so we should delay beginning to proxy for it) or
        // (ii) if it's a conflicting Announcement from another host
        // -- and we check for these in Pass 2 below.
        if (mDNSSameOpaque16(arp->op, ARP_op_request) && !mDNSSameIPv4Address(arp->spa, arp->tpa))
                {
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->resrec.InterfaceID == InterfaceID && rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                rr->AddressProxy.type == mDNSAddrType_IPv4 && mDNSSameIPv4Address(rr->AddressProxy.ip.v4, arp->tpa))
                                {
                                static const char msg1[] = "ARP Req from owner -- re-probing";
                                static const char msg2[] = "Ignoring  ARP Request from      ";
                                static const char msg3[] = "Creating Local ARP Cache entry  ";
                                static const char msg4[] = "Answering ARP Request from      ";
                                const char *const msg = mDNSSameEthAddress(&arp->sha, &rr->WakeUp.IMAC) ? msg1 :
                                                                                (rr->AnnounceCount == InitialAnnounceCount)     ? msg2 :
                                                                                mDNSSameEthAddress(&arp->sha, &intf->MAC)       ? msg3 : msg4;
                                LogSPS("%-7s %s %.6a %.4a for %.4a -- H-MAC %.6a I-MAC %.6a %s",
                                        intf->ifname, msg, &arp->sha, &arp->spa, &arp->tpa, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m, rr));
                                if      (msg == msg1) RestartARPProbing(m, rr);
                                else if (msg == msg3) mDNSPlatformSetLocalAddressCacheEntry(m, &rr->AddressProxy, &rr->WakeUp.IMAC, InterfaceID);
                                else if (msg == msg4) SendARP(m, 2, rr, &arp->tpa, &arp->sha, &arp->spa, &arp->sha);
                                }
                }

        // Pass 2:
        // For all types of ARP packet we check the Sender IP address to make sure it doesn't conflict with any AddressProxy record we're holding.
        // (Strictly speaking we're only checking Announcement/Request/Reply packets, since ARP Probes have zero Sender IP address,
        // so by definition (and by design) they can never conflict with any real (i.e. non-zero) IP address).
        // We ignore ARPs we sent ourselves (Sender MAC address is our MAC address) because our own proxy ARPs do not constitute a conflict that we need to handle.
        // If we see an apparently conflicting ARP, we check the sender hardware address:
        //   If the sender hardware address is the original owner this is benign, so we just suppress our own proxy answering for a while longer.
        //   If the sender hardware address is *not* the original owner, then this is a conflict, and we need to wake the sleeping machine to handle it.
        if (mDNSSameEthAddress(&arp->sha, &intf->MAC))
                debugf("ARP from self for %.4a", &arp->tpa);
        else
                {
                if (!mDNSSameIPv4Address(arp->spa, zerov4Addr))
                        for (rr = m->ResourceRecords; rr; rr=rr->next)
                                if (rr->resrec.InterfaceID == InterfaceID && rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                        rr->AddressProxy.type == mDNSAddrType_IPv4 && mDNSSameIPv4Address(rr->AddressProxy.ip.v4, arp->spa))
                                        {
                                        RestartARPProbing(m, rr);
                                        if (mDNSSameEthAddress(&arp->sha, &rr->WakeUp.IMAC))
                                                LogSPS("%-7s ARP %s from owner %.6a %.4a for %-15.4a -- re-starting probing for %s", intf->ifname,
                                                        mDNSSameIPv4Address(arp->spa, arp->tpa) ? "Announcement " : mDNSSameOpaque16(arp->op, ARP_op_request) ? "Request      " : "Response     ",
                                                        &arp->sha, &arp->spa, &arp->tpa, ARDisplayString(m, rr));
                                        else
                                                {
                                                LogMsg("%-7s Conflicting ARP from %.6a %.4a for %.4a -- waking H-MAC %.6a I-MAC %.6a %s", intf->ifname,
                                                        &arp->sha, &arp->spa, &arp->tpa, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m, rr));
                                                ScheduleWakeup(m, rr->resrec.InterfaceID, &rr->WakeUp.HMAC);
                                                }
                                        }
                }

        mDNS_Unlock(m);
        }

/*
// Option 1 is Source Link Layer Address Option
// Option 2 is Target Link Layer Address Option
mDNSlocal const mDNSEthAddr *GetLinkLayerAddressOption(const IPv6NDP *const ndp, const mDNSu8 *const end, mDNSu8 op)
        {
        const mDNSu8 *options = (mDNSu8 *)(ndp+1);
        while (options < end)
                {
                debugf("NDP Option %02X len %2d %d", options[0], options[1], end - options);
                if (options[0] == op && options[1] == 1) return (const mDNSEthAddr*)(options+2);
                options += options[1] * 8;
                }
        return mDNSNULL;
        }
*/

mDNSlocal void mDNSCoreReceiveRawND(mDNS *const m, const mDNSEthAddr *const sha, const mDNSv6Addr *spa,
        const IPv6NDP *const ndp, const mDNSu8 *const end, const mDNSInterfaceID InterfaceID)
        {
        AuthRecord *rr;
        NetworkInterfaceInfo *intf = FirstInterfaceForID(m, InterfaceID);
        if (!intf) return;

        mDNS_Lock(m);

        // Pass 1: Process Neighbor Solicitations, and generate a Neighbor Advertisement if necessary.
        if (ndp->type == NDP_Sol)
                {
                //const mDNSEthAddr *const sha = GetLinkLayerAddressOption(ndp, end, NDP_SrcLL);
                (void)end;
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->resrec.InterfaceID == InterfaceID && rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                rr->AddressProxy.type == mDNSAddrType_IPv6 && mDNSSameIPv6Address(rr->AddressProxy.ip.v6, ndp->target))
                                {
                                static const char msg1[] = "NDP Req from owner -- re-probing";
                                static const char msg2[] = "Ignoring  NDP Request from      ";
                                static const char msg3[] = "Creating Local NDP Cache entry  ";
                                static const char msg4[] = "Answering NDP Request from      ";
                                static const char msg5[] = "Answering NDP Probe   from      ";
                                const char *const msg = sha && mDNSSameEthAddress(sha, &rr->WakeUp.IMAC) ? msg1 :
                                                                                (rr->AnnounceCount == InitialAnnounceCount)      ? msg2 :
                                                                                sha && mDNSSameEthAddress(sha, &intf->MAC)       ? msg3 :
                                                                                spa && mDNSIPv6AddressIsZero(*spa)               ? msg4 : msg5;
                                LogSPS("%-7s %s %.6a %.16a for %.16a -- H-MAC %.6a I-MAC %.6a %s",
                                        intf->ifname, msg, sha, spa, &ndp->target, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m, rr));
                                if      (msg == msg1) RestartARPProbing(m, rr);
                                else if (msg == msg3)
                                        {
                                        if (!(m->KnownBugs & mDNS_KnownBug_LimitedIPv6))
                                                mDNSPlatformSetLocalAddressCacheEntry(m, &rr->AddressProxy, &rr->WakeUp.IMAC, InterfaceID);
                                        }
                                else if (msg == msg4) SendNDP(m, NDP_Adv, NDP_Solicited, rr, &ndp->target, mDNSNULL, spa,          sha             );
                                else if (msg == msg5) SendNDP(m, NDP_Adv, 0,             rr, &ndp->target, mDNSNULL, &AllHosts_v6, &AllHosts_v6_Eth);
                                }
                }

        // Pass 2: For all types of NDP packet we check the Sender IP address to make sure it doesn't conflict with any AddressProxy record we're holding.
        if (mDNSSameEthAddress(sha, &intf->MAC))
                debugf("NDP from self for %.16a", &ndp->target);
        else
                {
                // For Neighbor Advertisements we check the Target address field, not the actual IPv6 source address.
                // When a machine has both link-local and routable IPv6 addresses, it may send NDP packets making assertions
                // about its routable IPv6 address, using its link-local address as the source address for all NDP packets.
                // Hence it is the NDP target address we care about, not the actual packet source address.
                if (ndp->type == NDP_Adv) spa = &ndp->target;
                if (!mDNSSameIPv6Address(*spa, zerov6Addr))
                        for (rr = m->ResourceRecords; rr; rr=rr->next)
                                if (rr->resrec.InterfaceID == InterfaceID && rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                        rr->AddressProxy.type == mDNSAddrType_IPv6 && mDNSSameIPv6Address(rr->AddressProxy.ip.v6, *spa))
                                        {
                                        RestartARPProbing(m, rr);
                                        if (mDNSSameEthAddress(sha, &rr->WakeUp.IMAC))
                                                LogSPS("%-7s NDP %s from owner %.6a %.16a for %.16a -- re-starting probing for %s", intf->ifname,
                                                        ndp->type == NDP_Sol ? "Solicitation " : "Advertisement", sha, spa, &ndp->target, ARDisplayString(m, rr));
                                        else
                                                {
                                                LogMsg("%-7s Conflicting NDP from %.6a %.16a for %.16a -- waking H-MAC %.6a I-MAC %.6a %s", intf->ifname,
                                                        sha, spa, &ndp->target, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m, rr));
                                                ScheduleWakeup(m, rr->resrec.InterfaceID, &rr->WakeUp.HMAC);
                                                }
                                        }
                }

        mDNS_Unlock(m);
        }

mDNSlocal void mDNSCoreReceiveRawTransportPacket(mDNS *const m, const mDNSEthAddr *const sha, const mDNSAddr *const src, const mDNSAddr *const dst, const mDNSu8 protocol,
        const mDNSu8 *const p, const TransportLayerPacket *const t, const mDNSu8 *const end, const mDNSInterfaceID InterfaceID, const mDNSu16 len)
        {
        const mDNSIPPort port = (protocol == 0x06) ? t->tcp.dst : (protocol == 0x11) ? t->udp.dst : zeroIPPort;
        mDNSBool wake = mDNSfalse;

        switch (protocol)
                {
                #define XX wake ? "Received" : "Ignoring", end-p
                case 0x01:      LogSPS("Ignoring %d-byte ICMP from %#a to %#a", end-p, src, dst);
                                        break;

                case 0x06:      {
                                        #define SSH_AsNumber 22
                                        static const mDNSIPPort SSH = { { SSH_AsNumber >> 8, SSH_AsNumber & 0xFF } };

                                        // Plan to wake if
                                        // (a) RST is not set, AND
                                        // (b) packet is SYN, SYN+FIN, or plain data packet (no SYN or FIN). We won't wake for FIN alone.
                                        wake = (!(t->tcp.flags & 4) && (t->tcp.flags & 3) != 1);

                                        // For now, to reduce spurious wakeups, we wake only for TCP SYN,
                                        // except for ssh connections, where we'll wake for plain data packets too
                                        if (!mDNSSameIPPort(port, SSH) && !(t->tcp.flags & 2)) wake = mDNSfalse;

                                        LogSPS("%s %d-byte TCP from %#a:%d to %#a:%d%s%s%s", XX,
                                                src, mDNSVal16(t->tcp.src), dst, mDNSVal16(port),
                                                (t->tcp.flags & 2) ? " SYN" : "",
                                                (t->tcp.flags & 1) ? " FIN" : "",
                                                (t->tcp.flags & 4) ? " RST" : "");
                                        }
                                        break;

                case 0x11:      {
                                        #define ARD_AsNumber 3283
                                        static const mDNSIPPort ARD = { { ARD_AsNumber >> 8, ARD_AsNumber & 0xFF } };
                                        const mDNSu16 udplen = (mDNSu16)((mDNSu16)t->bytes[4] << 8 | t->bytes[5]);              // Length *including* 8-byte UDP header
                                        if (udplen >= sizeof(UDPHeader))
                                                {
                                                const mDNSu16 datalen = udplen - sizeof(UDPHeader);
                                                wake = mDNStrue;

                                                // For Back to My Mac UDP port 4500 (IPSEC) packets, we do some special handling
                                                if (mDNSSameIPPort(port, IPSECPort))
                                                        {
                                                        // Specifically ignore NAT keepalive packets
                                                        if (datalen == 1 && end >= &t->bytes[9] && t->bytes[8] == 0xFF) wake = mDNSfalse;
                                                        else
                                                                {
                                                                // Skip over the Non-ESP Marker if present
                                                                const mDNSBool NonESP = (end >= &t->bytes[12] && t->bytes[8] == 0 && t->bytes[9] == 0 && t->bytes[10] == 0 && t->bytes[11] == 0);
                                                                const IKEHeader *const ike    = (IKEHeader *)(t + (NonESP ? 12 : 8));
                                                                const mDNSu16          ikelen = datalen - (NonESP ? 4 : 0);
                                                                if (ikelen >= sizeof(IKEHeader) && end >= ((mDNSu8 *)ike) + sizeof(IKEHeader))
                                                                        if ((ike->Version & 0x10) == 0x10)
                                                                                {
                                                                                // ExchangeType ==  5 means 'Informational' <http://www.ietf.org/rfc/rfc2408.txt>
                                                                                // ExchangeType == 34 means 'IKE_SA_INIT'   <http://www.iana.org/assignments/ikev2-parameters>
                                                                                if (ike->ExchangeType == 5 || ike->ExchangeType == 34) wake = mDNSfalse;
                                                                                LogSPS("%s %d-byte IKE ExchangeType %d", XX, ike->ExchangeType);
                                                                                }
                                                                }
                                                        }

                                                // For now, because we haven't yet worked out a clean elegant way to do this, we just special-case the
                                                // Apple Remote Desktop port number -- we ignore all packets to UDP 3283 (the "Net Assistant" port),
                                                // except for Apple Remote Desktop's explicit manual wakeup packet, which looks like this:
                                                // UDP header (8 bytes)
                                                // Payload: 13 88 00 6a 41 4e 41 20 (8 bytes) ffffffffffff (6 bytes) 16xMAC (96 bytes) = 110 bytes total
                                                if (mDNSSameIPPort(port, ARD)) wake = (datalen >= 110 && end >= &t->bytes[10] && t->bytes[8] == 0x13 && t->bytes[9] == 0x88);

                                                LogSPS("%s %d-byte UDP from %#a:%d to %#a:%d", XX, src, mDNSVal16(t->udp.src), dst, mDNSVal16(port));
                                                }
                                        }
                                        break;

                case 0x3A:      if (&t->bytes[len] <= end)
                                                {
                                                mDNSu16 checksum = IPv6CheckSum(&src->ip.v6, &dst->ip.v6, protocol, t->bytes, len);
                                                if (!checksum) mDNSCoreReceiveRawND(m, sha, &src->ip.v6, &t->ndp, &t->bytes[len], InterfaceID);
                                                else LogInfo("IPv6CheckSum bad %04X %02X%02X from %#a to %#a", checksum, t->bytes[2], t->bytes[3], src, dst);
                                                }
                                        break;

                default:        LogSPS("Ignoring %d-byte IP packet unknown protocol %d from %#a to %#a", end-p, protocol, src, dst);
                                        break;
                }

        if (wake)
                {
                AuthRecord *rr, *r2;

                mDNS_Lock(m);
                for (rr = m->ResourceRecords; rr; rr=rr->next)
                        if (rr->resrec.InterfaceID == InterfaceID &&
                                rr->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                rr->AddressProxy.type && mDNSSameAddress(&rr->AddressProxy, dst))
                                {
                                const mDNSu8 *const tp = (protocol == 6) ? (const mDNSu8 *)"\x4_tcp" : (const mDNSu8 *)"\x4_udp";
                                for (r2 = m->ResourceRecords; r2; r2=r2->next)
                                        if (r2->resrec.InterfaceID == InterfaceID && mDNSSameEthAddress(&r2->WakeUp.HMAC, &rr->WakeUp.HMAC) &&
                                                r2->resrec.RecordType != kDNSRecordTypeDeregistering &&
                                                r2->resrec.rrtype == kDNSType_SRV && mDNSSameIPPort(r2->resrec.rdata->u.srv.port, port) &&
                                                SameDomainLabel(ThirdLabel(r2->resrec.name)->c, tp))
                                                break;
                                if (!r2 && mDNSSameIPPort(port, IPSECPort)) r2 = rr;    // So that we wake for BTMM IPSEC packets, even without a matching SRV record
                                if (r2)
                                        {
                                        LogMsg("Waking host at %s %#a H-MAC %.6a I-MAC %.6a for %s",
                                                InterfaceNameForID(m, rr->resrec.InterfaceID), dst, &rr->WakeUp.HMAC, &rr->WakeUp.IMAC, ARDisplayString(m, r2));
                                        ScheduleWakeup(m, rr->resrec.InterfaceID, &rr->WakeUp.HMAC);
                                        }
                                else
                                        LogSPS("Sleeping host at %s %#a %.6a has no service on %#s %d",
                                                InterfaceNameForID(m, rr->resrec.InterfaceID), dst, &rr->WakeUp.HMAC, tp, mDNSVal16(port));
                                }
                mDNS_Unlock(m);
                }
        }

mDNSexport void mDNSCoreReceiveRawPacket(mDNS *const m, const mDNSu8 *const p, const mDNSu8 *const end, const mDNSInterfaceID InterfaceID)
        {
        static const mDNSOpaque16 Ethertype_ARP  = { { 0x08, 0x06 } };  // Ethertype 0x0806 = ARP
        static const mDNSOpaque16 Ethertype_IPv4 = { { 0x08, 0x00 } };  // Ethertype 0x0800 = IPv4
        static const mDNSOpaque16 Ethertype_IPv6 = { { 0x86, 0xDD } };  // Ethertype 0x86DD = IPv6
        static const mDNSOpaque16 ARP_hrd_eth    = { { 0x00, 0x01 } };  // Hardware address space (Ethernet = 1)
        static const mDNSOpaque16 ARP_pro_ip     = { { 0x08, 0x00 } };  // Protocol address space (IP = 0x0800)

        // Note: BPF guarantees that the NETWORK LAYER header will be word aligned, not the link-layer header.
        // In other words, we can safely assume that pkt below (ARP, IPv4 or IPv6) is properly word aligned,
        // but if pkt is 4-byte aligned, that necessarily means that eth CANNOT also be 4-byte aligned
        // since it points to a an address 14 bytes before pkt.
        const EthernetHeader     *const eth = (const EthernetHeader *)p;
        const NetworkLayerPacket *const pkt = (const NetworkLayerPacket *)(eth+1);
        mDNSAddr src, dst;
        #define RequiredCapLen(P) ((P)==0x01 ? 4 : (P)==0x06 ? 20 : (P)==0x11 ? 8 : (P)==0x3A ? 24 : 0)

        // Is ARP? Length must be at least 14 + 28 = 42 bytes
        if (end >= p+42 && mDNSSameOpaque16(eth->ethertype, Ethertype_ARP) && mDNSSameOpaque16(pkt->arp.hrd, ARP_hrd_eth) && mDNSSameOpaque16(pkt->arp.pro, ARP_pro_ip))
                mDNSCoreReceiveRawARP(m, &pkt->arp, InterfaceID);
        // Is IPv4 with zero fragmentation offset? Length must be at least 14 + 20 = 34 bytes
        else if (end >= p+34 && mDNSSameOpaque16(eth->ethertype, Ethertype_IPv4) && (pkt->v4.flagsfrags.b[0] & 0x1F) == 0 && pkt->v4.flagsfrags.b[1] == 0)
                {
                const mDNSu8 *const trans = p + 14 + (pkt->v4.vlen & 0xF) * 4;
                debugf("Got IPv4 %02X from %.4a to %.4a", pkt->v4.protocol, &pkt->v4.src, &pkt->v4.dst);
                src.type = mDNSAddrType_IPv4; src.ip.v4 = pkt->v4.src;
                dst.type = mDNSAddrType_IPv4; dst.ip.v4 = pkt->v4.dst;
                if (end >= trans + RequiredCapLen(pkt->v4.protocol))
                        mDNSCoreReceiveRawTransportPacket(m, &eth->src, &src, &dst, pkt->v4.protocol, p, (TransportLayerPacket*)trans, end, InterfaceID, 0);
                }
        // Is IPv6? Length must be at least 14 + 28 = 42 bytes
        else if (end >= p+54 && mDNSSameOpaque16(eth->ethertype, Ethertype_IPv6))
                {
                const mDNSu8 *const trans = p + 54;
                debugf("Got IPv6  %02X from %.16a to %.16a", pkt->v6.pro, &pkt->v6.src, &pkt->v6.dst);
                src.type = mDNSAddrType_IPv6; src.ip.v6 = pkt->v6.src;
                dst.type = mDNSAddrType_IPv6; dst.ip.v6 = pkt->v6.dst;
                if (end >= trans + RequiredCapLen(pkt->v6.pro))
                        mDNSCoreReceiveRawTransportPacket(m, &eth->src, &src, &dst, pkt->v6.pro, p, (TransportLayerPacket*)trans, end, InterfaceID,
                                (mDNSu16)pkt->bytes[4] << 8 | pkt->bytes[5]);
                }
        }

mDNSlocal void ConstructSleepProxyServerName(mDNS *const m, domainlabel *name)
        {
        name->c[0] = (mDNSu8)mDNS_snprintf((char*)name->c+1, 62, "%d-%d-%d-%d %#s",
                m->SPSType, m->SPSPortability, m->SPSMarginalPower, m->SPSTotalPower, &m->nicelabel);
        }

mDNSlocal void SleepProxyServerCallback(mDNS *const m, ServiceRecordSet *const srs, mStatus result)
        {
        if (result == mStatus_NameConflict)
                mDNS_RenameAndReregisterService(m, srs, mDNSNULL);
        else if (result == mStatus_MemFree)
                {
                if (m->SleepState)
                        m->SPSState = 3;
                else
                        {
                        m->SPSState = (mDNSu8)(m->SPSSocket != mDNSNULL);
                        if (m->SPSState)
                                {
                                domainlabel name;
                                ConstructSleepProxyServerName(m, &name);
                                mDNS_RegisterService(m, srs,
                                        &name, &SleepProxyServiceType, &localdomain,
                                        mDNSNULL, m->SPSSocket->port,                           // Host, port
                                        (mDNSu8 *)"", 1,                                                        // TXT data, length
                                        mDNSNULL, 0,                                                            // Subtypes (none)
                                        mDNSInterface_Any,                                                      // Interface ID
                                        SleepProxyServerCallback, mDNSNULL, 0);         // Callback, context, flags
                                }
                        LogSPS("Sleep Proxy Server %#s %s", srs->RR_SRV.resrec.name->c, m->SPSState ? "started" : "stopped");
                        }
                }
        }

// Called with lock held
mDNSexport void mDNSCoreBeSleepProxyServer_internal(mDNS *const m, mDNSu8 sps, mDNSu8 port, mDNSu8 marginalpower, mDNSu8 totpower)
        {
        // This routine uses mDNS_DeregisterService and calls SleepProxyServerCallback, so we execute in user callback context
        mDNS_DropLockBeforeCallback();

        // If turning off SPS, close our socket
        // (Do this first, BEFORE calling mDNS_DeregisterService below)
        if (!sps && m->SPSSocket) { mDNSPlatformUDPClose(m->SPSSocket); m->SPSSocket = mDNSNULL; }

        // If turning off, or changing type, deregister old name
        if (m->SPSState == 1 && sps != m->SPSType)
                { m->SPSState = 2; mDNS_DeregisterService_drt(m, &m->SPSRecords, sps ? mDNS_Dereg_rapid : mDNS_Dereg_normal); }

        // Record our new SPS parameters
        m->SPSType          = sps;
        m->SPSPortability   = port;
        m->SPSMarginalPower = marginalpower;
        m->SPSTotalPower    = totpower;

        // If turning on, open socket and advertise service
        if (sps)
                {
                if (!m->SPSSocket)
                        {
                        m->SPSSocket = mDNSPlatformUDPSocket(m, zeroIPPort);
                        if (!m->SPSSocket) { LogMsg("mDNSCoreBeSleepProxyServer: Failed to allocate SPSSocket"); goto fail; }
                        }
                if (m->SPSState == 0) SleepProxyServerCallback(m, &m->SPSRecords, mStatus_MemFree);
                }
        else if (m->SPSState)
                {
                LogSPS("mDNSCoreBeSleepProxyServer turning off from state %d; will wake clients", m->SPSState);
                m->NextScheduledSPS = m->timenow;
                }
fail:
        mDNS_ReclaimLockAfterCallback();
        }

// ***************************************************************************
#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark -
#pragma mark - Startup and Shutdown
#endif

mDNSlocal void mDNS_GrowCache_internal(mDNS *const m, CacheEntity *storage, mDNSu32 numrecords)
        {
        if (storage && numrecords)
                {
                mDNSu32 i;
                debugf("Adding cache storage for %d more records (%d bytes)", numrecords, numrecords*sizeof(CacheEntity));
                for (i=0; i<numrecords; i++) storage[i].next = &storage[i+1];
                storage[numrecords-1].next = m->rrcache_free;
                m->rrcache_free = storage;
                m->rrcache_size += numrecords;
                }
        }

mDNSexport void mDNS_GrowCache(mDNS *const m, CacheEntity *storage, mDNSu32 numrecords)
        {
        mDNS_Lock(m);
        mDNS_GrowCache_internal(m, storage, numrecords);
        mDNS_Unlock(m);
        }

mDNSexport mStatus mDNS_Init(mDNS *const m, mDNS_PlatformSupport *const p,
        CacheEntity *rrcachestorage, mDNSu32 rrcachesize,
        mDNSBool AdvertiseLocalAddresses, mDNSCallback *Callback, void *Context)
        {
        mDNSu32 slot;
        mDNSs32 timenow;
        mStatus result;
        
        if (!rrcachestorage) rrcachesize = 0;
        
        m->p                             = p;
        m->KnownBugs                     = 0;
        m->CanReceiveUnicastOn5353       = mDNSfalse; // Assume we can't receive unicasts on 5353, unless platform layer tells us otherwise
        m->AdvertiseLocalAddresses       = AdvertiseLocalAddresses;
        m->DivertMulticastAdvertisements = mDNSfalse;
        m->mDNSPlatformStatus            = mStatus_Waiting;
        m->UnicastPort4                  = zeroIPPort;
        m->UnicastPort6                  = zeroIPPort;
        m->PrimaryMAC                    = zeroEthAddr;
        m->MainCallback                  = Callback;
        m->MainContext                   = Context;
        m->rec.r.resrec.RecordType       = 0;

        // For debugging: To catch and report locking failures
        m->mDNS_busy               = 0;
        m->mDNS_reentrancy         = 0;
        m->ShutdownTime            = 0;
        m->lock_rrcache            = 0;
        m->lock_Questions          = 0;
        m->lock_Records            = 0;

        // Task Scheduling variables
        result = mDNSPlatformTimeInit();
        if (result != mStatus_NoError) return(result);
        m->timenow_adjust = (mDNSs32)mDNSRandom(0xFFFFFFFF);
        timenow = mDNS_TimeNow_NoLock(m);

        m->timenow                 = 0;         // MUST only be set within mDNS_Lock/mDNS_Unlock section
        m->timenow_last            = timenow;
        m->NextScheduledEvent      = timenow;
        m->SuppressSending         = timenow;
        m->NextCacheCheck          = timenow + 0x78000000;
        m->NextScheduledQuery      = timenow + 0x78000000;
        m->NextScheduledProbe      = timenow + 0x78000000;
        m->NextScheduledResponse   = timenow + 0x78000000;
        m->NextScheduledNATOp      = timenow + 0x78000000;
        m->NextScheduledSPS        = timenow + 0x78000000;
        m->NextScheduledStopTime   = timenow + 0x78000000;
        m->RandomQueryDelay        = 0;
        m->RandomReconfirmDelay    = 0;
        m->PktNum                  = 0;
        m->LocalRemoveEvents       = mDNSfalse;
        m->SleepState              = SleepState_Awake;
        m->SleepSeqNum             = 0;
        m->SystemWakeOnLANEnabled  = mDNSfalse;
        m->AnnounceOwner           = NonZeroTime(timenow + 60 * mDNSPlatformOneSecond);
        m->DelaySleep              = 0;
        m->SleepLimit              = 0;

        // These fields only required for mDNS Searcher...
        m->Questions               = mDNSNULL;
        m->NewQuestions            = mDNSNULL;
        m->CurrentQuestion         = mDNSNULL;
        m->LocalOnlyQuestions      = mDNSNULL;
        m->NewLocalOnlyQuestions   = mDNSNULL;
        m->RestartQuestion             = mDNSNULL;
        m->rrcache_size            = 0;
        m->rrcache_totalused       = 0;
        m->rrcache_active          = 0;
        m->rrcache_report          = 10;
        m->rrcache_free            = mDNSNULL;

        for (slot = 0; slot < CACHE_HASH_SLOTS; slot++)
                {
                m->rrcache_hash[slot]      = mDNSNULL;
                m->rrcache_nextcheck[slot] = timenow + 0x78000000;;
                }

        mDNS_GrowCache_internal(m, rrcachestorage, rrcachesize);
        m->rrauth.rrauth_free            = mDNSNULL;

        for (slot = 0; slot < AUTH_HASH_SLOTS; slot++)
                m->rrauth.rrauth_hash[slot] = mDNSNULL;

        // Fields below only required for mDNS Responder...
        m->hostlabel.c[0]          = 0;
        m->nicelabel.c[0]          = 0;
        m->MulticastHostname.c[0]  = 0;
        m->HIHardware.c[0]         = 0;
        m->HISoftware.c[0]         = 0;
        m->ResourceRecords         = mDNSNULL;
        m->DuplicateRecords        = mDNSNULL;
        m->NewLocalRecords         = mDNSNULL;
        m->NewLocalOnlyRecords     = mDNSfalse;
        m->CurrentRecord           = mDNSNULL;
        m->HostInterfaces          = mDNSNULL;
        m->ProbeFailTime           = 0;
        m->NumFailedProbes         = 0;
        m->SuppressProbes          = 0;

#ifndef UNICAST_DISABLED
        m->NextuDNSEvent            = timenow + 0x78000000;
        m->NextSRVUpdate            = timenow + 0x78000000;

        m->DNSServers               = mDNSNULL;

        m->Router                   = zeroAddr;
        m->AdvertisedV4             = zeroAddr;
        m->AdvertisedV6             = zeroAddr;

        m->AuthInfoList             = mDNSNULL;

        m->ReverseMap.ThisQInterval = -1;
        m->StaticHostname.c[0]      = 0;
        m->FQDN.c[0]                = 0;
        m->Hostnames                = mDNSNULL;
        m->AutoTunnelHostAddr.b[0]  = 0;
        m->AutoTunnelHostAddrActive = mDNSfalse;
        m->AutoTunnelLabel.c[0]     = 0;

        m->StartWABQueries          = mDNSfalse;
        m->RegisterAutoTunnel6      = mDNStrue;

        // NAT traversal fields
        m->NATTraversals            = mDNSNULL;
        m->CurrentNATTraversal      = mDNSNULL;
        m->retryIntervalGetAddr     = 0;        // delta between time sent and retry
        m->retryGetAddr             = timenow + 0x78000000;     // absolute time when we retry
        m->ExternalAddress          = zerov4Addr;

        m->NATMcastRecvskt          = mDNSNULL;
        m->LastNATupseconds         = 0;
        m->LastNATReplyLocalTime    = timenow;
        m->LastNATMapResultCode     = NATErr_None;

        m->UPnPInterfaceID          = 0;
        m->SSDPSocket               = mDNSNULL;
        m->SSDPWANPPPConnection     = mDNSfalse;
        m->UPnPRouterPort           = zeroIPPort;
        m->UPnPSOAPPort             = zeroIPPort;
        m->UPnPRouterURL            = mDNSNULL;
        m->UPnPWANPPPConnection     = mDNSfalse;
        m->UPnPSOAPURL              = mDNSNULL;
        m->UPnPRouterAddressString  = mDNSNULL;
        m->UPnPSOAPAddressString    = mDNSNULL;
        m->SPSType                  = 0;
        m->SPSPortability           = 0;
        m->SPSMarginalPower         = 0;
        m->SPSTotalPower            = 0;
        m->SPSState                 = 0;
        m->SPSProxyListChanged      = mDNSNULL;
        m->SPSSocket                = mDNSNULL;
        m->SPSBrowseCallback        = mDNSNULL;
        m->ProxyRecords             = 0;

#endif

#if APPLE_OSX_mDNSResponder
        m->TunnelClients            = mDNSNULL;

#if ! NO_WCF
        CHECK_WCF_FUNCTION(WCFConnectionNew)
                {
                m->WCF = WCFConnectionNew();
                if (!m->WCF) { LogMsg("WCFConnectionNew failed"); return -1; }
                }
#endif

#endif

        result = mDNSPlatformInit(m);

#ifndef UNICAST_DISABLED
        // It's better to do this *after* the platform layer has set up the
        // interface list and security credentials
        uDNS_SetupDNSConfig(m);                                         // Get initial DNS configuration
#endif

        return(result);
        }

mDNSexport void mDNS_ConfigChanged(mDNS *const m)
        {
        if (m->SPSState == 1)
                {
                domainlabel name, newname;
                domainname type, domain;
                DeconstructServiceName(m->SPSRecords.RR_SRV.resrec.name, &name, &type, &domain);
                ConstructSleepProxyServerName(m, &newname);
                if (!SameDomainLabelCS(name.c, newname.c))
                        {
                        LogSPS("Renaming SPS from “%#s” to “%#s”", name.c, newname.c);
                        // When SleepProxyServerCallback gets the mStatus_MemFree message,
                        // it will reregister the service under the new name
                        m->SPSState = 2;
                        mDNS_DeregisterService_drt(m, &m->SPSRecords, mDNS_Dereg_rapid);
                        }
                }
        
        if (m->MainCallback)
                m->MainCallback(m, mStatus_ConfigChanged);
        }

mDNSlocal void DynDNSHostNameCallback(mDNS *const m, AuthRecord *const rr, mStatus result)
        {
        (void)m;        // unused
        debugf("NameStatusCallback: result %d for registration of name %##s", result, rr->resrec.name->c);
        mDNSPlatformDynDNSHostNameStatusChanged(rr->resrec.name, result);
        }

mDNSlocal void PurgeOrReconfirmCacheRecord(mDNS *const m, CacheRecord *cr, const DNSServer * const ptr, mDNSBool lameduck)
        {
        mDNSBool purge = cr->resrec.RecordType == kDNSRecordTypePacketNegative ||
                                         cr->resrec.rrtype     == kDNSType_A ||
                                         cr->resrec.rrtype     == kDNSType_AAAA ||
                                         cr->resrec.rrtype     == kDNSType_SRV;

        (void) lameduck;
        (void) ptr;
        debugf("PurgeOrReconfirmCacheRecord: %s cache record due to %s server %p %#a:%d (%##s): %s",
                purge    ? "purging"   : "reconfirming",
                lameduck ? "lame duck" : "new",
                ptr, &ptr->addr, mDNSVal16(ptr->port), ptr->domain.c, CRDisplayString(m, cr));

        if (purge)
                {
                LogInfo("PurgeorReconfirmCacheRecord: Purging Resourcerecord %s, RecordType %x", CRDisplayString(m, cr), cr->resrec.RecordType);
                mDNS_PurgeCacheResourceRecord(m, cr);
                }
        else
                {
                LogInfo("PurgeorReconfirmCacheRecord: Reconfirming Resourcerecord %s, RecordType %x", CRDisplayString(m, cr), cr->resrec.RecordType);
                mDNS_Reconfirm_internal(m, cr, kDefaultReconfirmTimeForNoAnswer);
                }
        }

mDNSlocal void mDNS_PurgeBeforeResolve(mDNS *const m, DNSQuestion *q)
        {
        const mDNSu32 slot = HashSlot(&q->qname);
        CacheGroup *const cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
        CacheRecord *rp;

        for (rp = cg ? cg->members : mDNSNULL; rp; rp = rp->next)
                {
                if (SameNameRecordAnswersQuestion(&rp->resrec, q))
                        {
                        LogInfo("mDNS_PurgeBeforeResolve: Flushing %s", CRDisplayString(m, rp));
                        mDNS_PurgeCacheResourceRecord(m, rp);
                        }
                }
        }

mDNSlocal void CacheRecordResetDNSServer(mDNS *const m, DNSQuestion *q, DNSServer *new)
        {
        const mDNSu32 slot = HashSlot(&q->qname);
        CacheGroup *const cg = CacheGroupForName(m, slot, q->qnamehash, &q->qname);
        CacheRecord *rp;
        mDNSBool found = mDNSfalse;
        mDNSBool foundNew = mDNSfalse;
        DNSServer *old = q->qDNSServer;
        mDNSBool newQuestion = IsQuestionNew(m, q);
        DNSQuestion *qptr;

        // This function is called when the DNSServer is updated to the new question. There may already be
        // some cache entries matching the old DNSServer and/or new DNSServer. There are four cases. In the
        // following table, "Yes" denotes that a cache entry was found for old/new DNSServer.
        //
        //                                      old DNSServer           new DNSServer
        //
        //      Case 1                          Yes                                     Yes
        //  Case 2                              No                                      Yes
        //  Case 3                              Yes                                     No
        //  Case 4                              No                                      No
        //
        // Case 1: There are cache entries for both old and new DNSServer. We handle this case by simply
        //                 expiring the old Cache entries, deliver a RMV event (if an ADD event was delivered before)
        //                 followed by the ADD event of the cache entries corresponding to the new server. This
        //                 case happens when we pick a DNSServer, issue a query and get a valid response and create
        //                 cache entries after which it stops responding. Another query (non-duplicate) picks a different
        //             DNSServer and creates identical cache entries (perhaps through records in Additional records).
        //                 Now if the first one expires and tries to pick the new DNSServer (the original DNSServer
        //                 is not responding) we will find cache entries corresponding to both DNSServers.
        //
        // Case 2: There are no cache entries for the old DNSServer but there are some for the new DNSServer.
        //                 This means we should deliver an ADD event. Normally ADD events are delivered by
        //                 AnswerNewQuestion if it is a new question. So, we check to see if it is a new question
        //                 and if so, leave it to AnswerNewQuestion to deliver it. Otherwise, we use
        //                 AnswerQuestionsForDNSServerChanges to deliver the ADD event. This case happens when a
        //                 question picks a DNS server for which AnswerNewQuestion could not deliver an answer even
        //         though there were potential cache entries but DNSServer did not match. Now when we
        //         pick a new DNSServer, those cache entries may answer this question.
        //
        // Case 3: There are the cache entries for the old DNSServer but none for the new. We just move
        //                 the old cache entries to point to the new DNSServer and the caller is expected to
        //                 do a purge or reconfirm to delete or validate the RDATA. We don't need to do anything
        //                 special for delivering ADD events, as it should have been done/will be done by
        //                 AnswerNewQuestion. This case happens when we picked a DNSServer, sent the query and
        //                 got a response and the cache is expired now and we are reissuing the question but the
        //                 original DNSServer does not respond.
        //
        // Case 4: There are no cache entries either for the old or for the new DNSServer. There is nothing
        //                 much we can do here.
        //
        // Case 2 and 3 are the most common while case 4 is possible when no DNSServers are working. Case 1
        // is relatively less likely to happen in practice

        // Temporarily set the DNSServer to look for the matching records for the new DNSServer.
        q->qDNSServer = new;
        for (rp = cg ? cg->members : mDNSNULL; rp; rp = rp->next)
                {
                if (SameNameRecordAnswersQuestion(&rp->resrec, q))
                        {
                        LogInfo("CacheRecordResetDNSServer: Found cache record %##s for new DNSServer address: %#a", rp->resrec.name->c,
                                (rp->resrec.rDNSServer != mDNSNULL ?  &rp->resrec.rDNSServer->addr : mDNSNULL));
                        foundNew = mDNStrue;
                        break;
                        }
                }
        q->qDNSServer = old;

        for (rp = cg ? cg->members : mDNSNULL; rp; rp = rp->next)
                {
                if (SameNameRecordAnswersQuestion(&rp->resrec, q))
                        {
                        // Case1
                        found = mDNStrue;
                        if (foundNew)
                                {
                                LogInfo("CacheRecordResetDNSServer: Flushing Resourcerecord %##s, before:%#a, after:%#a", rp->resrec.name->c,
                                        (rp->resrec.rDNSServer != mDNSNULL ?  &rp->resrec.rDNSServer->addr : mDNSNULL),
                                        (new != mDNSNULL ?  &new->addr : mDNSNULL));
                                mDNS_PurgeCacheResourceRecord(m, rp);
                                if (newQuestion)
                                        {
                                        // "q" is not a duplicate question. If it is a newQuestion, then the CRActiveQuestion can't be
                                        // possibly set as it is set only when we deliver the ADD event to the question.
                                        if (rp->CRActiveQuestion != mDNSNULL)
                                                {
                                                LogMsg("CacheRecordResetDNSServer: ERROR!!: CRActiveQuestion %p set, current question %p, name %##s", rp->CRActiveQuestion, q, q->qname.c);
                                                rp->CRActiveQuestion = mDNSNULL;
                                                }
                                        // if this is a new question, then we never delivered an ADD yet, so don't deliver the RMV.
                                        continue;
                                        }
                                }
                        LogInfo("CacheRecordResetDNSServer: resetting cache record %##s DNSServer address before:%#a,"
                                " after:%#a, CRActiveQuestion %p", rp->resrec.name->c, (rp->resrec.rDNSServer != mDNSNULL ?
                                &rp->resrec.rDNSServer->addr : mDNSNULL), (new != mDNSNULL ?  &new->addr : mDNSNULL),
                                rp->CRActiveQuestion);
                        // Though we set it to the new DNS server, the caller is *assumed* to do either a purge
                        // or reconfirm or send out questions to the "new" server to verify whether the cached
                        // RDATA is valid
                        rp->resrec.rDNSServer = new;
                        }
                }

        // Case 1 and Case 2
        if ((found && foundNew) || (!found && foundNew))
                {
                if (newQuestion)
                        LogInfo("CacheRecordResetDNSServer: deliverAddEvents not set for question %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                else if (QuerySuppressed(q))
                        LogInfo("CacheRecordResetDNSServer: deliverAddEvents not set for suppressed question %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                else
                        {
                        LogInfo("CacheRecordResetDNSServer: deliverAddEvents set for %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                        q->deliverAddEvents = mDNStrue;
                        for (qptr = q->next; qptr; qptr = qptr->next)
                                if (qptr->DuplicateOf == q) qptr->deliverAddEvents = mDNStrue;
                        }
                return;
                }

        // Case 3 and Case 4
        return;
        }

mDNSexport void DNSServerChangeForQuestion(mDNS *const m, DNSQuestion *q, DNSServer *new)
        {
        DNSQuestion *qptr;

        // 1. Whenever we change the DNS server, we change the message identifier also so that response
        // from the old server is not accepted as a response from the new server but only messages
        // from the new server are accepted as valid responses. We do it irrespective of whether "new"
        // is NULL or not. It is possible that we send two queries, no responses, pick a new DNS server
        // which is NULL and now the response comes back and will try to penalize the DNS server which
        // is NULL. By setting the messageID here, we will not accept that as a valid response.

        q->TargetQID = mDNS_NewMessageID(m);
                
        // 2. Move the old cache records to point them at the new DNSServer so that we can deliver the ADD/RMV events
        // appropriately. At any point in time, we want all the cache records point only to one DNSServer for a given
        // question. "DNSServer" here is the DNSServer object and not the DNS server itself. It is possible to
        // have the same DNS server address in two objects, one scoped and another not scoped. But, the cache is per
        // DNSServer object. By maintaining the question and the cache entries point to the same DNSServer
        // always, the cache maintenance and delivery of ADD/RMV events becomes simpler.
        //
        // CacheRecordResetDNSServer should be called only once for the non-duplicate question as once the cache
        // entries are moved to point to the new DNSServer, we don't need to call it for the duplicate question
        // and it is wrong to call for the duplicate question as it's decision to mark deliverAddevents will be
        // incorrect.

        if (q->DuplicateOf)
                LogMsg("DNSServerChangeForQuestion: ERROR: Called for duplicate question %##s", q->qname.c);
        else
                CacheRecordResetDNSServer(m, q, new);

        // 3. Make sure all the duplicate questions point to the same DNSServer so that delivery
        // of events for all of them are consistent. Duplicates for a question are always inserted
        // after in the list.
        q->qDNSServer = new;
        for (qptr = q->next ; qptr; qptr = qptr->next)
                {
                if (qptr->DuplicateOf == q) { qptr->validDNSServers = q->validDNSServers; qptr->qDNSServer = new; }
                }
        }
        
mDNSexport mStatus uDNS_SetupDNSConfig(mDNS *const m)
        {
        mDNSu32 slot;
        CacheGroup *cg;
        CacheRecord *cr;

        mDNSAddr     v4, v6, r;
        domainname   fqdn;
        DNSServer   *ptr, **p = &m->DNSServers;
        const DNSServer *oldServers = m->DNSServers;
        DNSQuestion *q;
        McastResolver *mr, **mres = &m->McastResolvers;
        
        debugf("uDNS_SetupDNSConfig: entry");

        // Let the platform layer get the current DNS information
        // The m->StartWABQueries is set when we get the first domain enumeration query (no need to hit the network
        // with domain enumeration queries until we actually need that information). Even if it is not set, we still
        // need to setup the search domains so that we can append them to queries that need them.

        uDNS_SetupSearchDomains(m, m->StartWABQueries ? UDNS_START_WAB_QUERY : 0);

        mDNS_Lock(m);

        for (ptr = m->DNSServers; ptr; ptr = ptr->next)
                {
                ptr->penaltyTime = 0;
                ptr->flags |= DNSServer_FlagDelete;
                }

        // We handle the mcast resolvers here itself as mDNSPlatformSetDNSConfig looks at
        // mcast resolvers. Today we get both mcast and ucast configuration using the same
        // API
        for (mr = m->McastResolvers; mr; mr = mr->next)
                mr->flags |= McastResolver_FlagDelete;

        mDNSPlatformSetDNSConfig(m, mDNStrue, mDNSfalse, &fqdn, mDNSNULL, mDNSNULL);

        // For now, we just delete the mcast resolvers. We don't deal with cache or
        // questions here. Neither question nor cache point to mcast resolvers. Questions
        // do inherit the timeout values from mcast resolvers. But we don't bother
        // affecting them as they never change.
        while (*mres)
                {
                if (((*mres)->flags & DNSServer_FlagDelete) != 0)
                        {
                        mr = *mres;
                        *mres = (*mres)->next;
                        debugf("uDNS_SetupDNSConfig: Deleting mcast resolver %##s", mr, mr->domain.c);
                        mDNSPlatformMemFree(mr);
                        }
                else
                        {
                        (*mres)->flags &= ~McastResolver_FlagNew;
                        mres = &(*mres)->next;
                        }
                }

        // Mark the records to be flushed that match a new resolver. We need to do this before
        // we walk the questions below where we change the DNSServer pointer of the cache
        // record
        FORALL_CACHERECORDS(slot, cg, cr)
                {
                if (cr->resrec.InterfaceID) continue;

                // We just mark them for purge or reconfirm. We can't affect the DNSServer pointer
                // here as the code below that calls CacheRecordResetDNSServer relies on this
                //
                // The new DNSServer may be a scoped or non-scoped one. We use the active question's
                // InterfaceID for looking up the right DNS server
                ptr = GetServerForName(m, cr->resrec.name, cr->CRActiveQuestion ? cr->CRActiveQuestion->InterfaceID : mDNSNULL);

                // Purge or Reconfirm if this cache entry would use the new DNS server
                if (ptr && (ptr != cr->resrec.rDNSServer))
                        {
                        // As the DNSServers for this cache record is not the same anymore, we don't
                        // want any new questions to pick this old value
                        if (cr->CRActiveQuestion == mDNSNULL)
                                {
                                LogInfo("uDNS_SetupDNSConfig: Purging Resourcerecord %s", CRDisplayString(m, cr));
                                mDNS_PurgeCacheResourceRecord(m, cr);
                                }
                        else
                                {
                                LogInfo("uDNS_SetupDNSConfig: Purging/Reconfirming Resourcerecord %s", CRDisplayString(m, cr));
                                PurgeOrReconfirmCacheRecord(m, cr, ptr, mDNSfalse);
                                }
                        }
                }
        // Update our qDNSServer pointers before we go and free the DNSServer object memory
        for (q = m->Questions; q; q=q->next)
                if (!mDNSOpaque16IsZero(q->TargetQID))
                        {
                        DNSServer *s, *t;
                        DNSQuestion *qptr;
                        if (q->DuplicateOf) continue;
                        SetValidDNSServers(m, q);
                        q->triedAllServersOnce = 0;
                        s = GetServerForQuestion(m, q);
                        t = q->qDNSServer;
                        if (t != s)
                                {
                                // If DNS Server for this question has changed, reactivate it
                                debugf("uDNS_SetupDNSConfig: Updating DNS Server from %p %#a:%d (%##s) to %p %#a:%d (%##s) for %##s (%s)",
                                        t, t ? &t->addr : mDNSNULL, mDNSVal16(t ? t->port : zeroIPPort), t ? t->domain.c : (mDNSu8*)"",
                                        s, s ? &s->addr : mDNSNULL, mDNSVal16(s ? s->port : zeroIPPort), s ? s->domain.c : (mDNSu8*)"",
                                        q->qname.c, DNSTypeName(q->qtype));

                                // After we reset the DNSServer pointer on the cache records here, three things could happen:
                                //
                                // 1) The query gets sent out and when the actual response comes back later it is possible
                                // that the response has the same RDATA, in which case we update our cache entry.
                                // If the response is different, then the entry will expire and a new entry gets added.
                                // For the latter case to generate a RMV followed by ADD events, we need to reset the DNS
                                // server here to match the question and the cache record.
                                //
                                // 2) We might have marked the cache entries for purge above and for us to be able to generate the RMV
                                // events for the questions, the DNSServer on the question should match the Cache Record
                                //
                                // 3) We might have marked the cache entries for reconfirm above, for which we send the query out which is
                                // the same as the first case above.

                                DNSServerChangeForQuestion(m, q, s);
                                q->unansweredQueries = 0;
                                // We still need to pick a new DNSServer for the questions that have been
                                // suppressed, but it is wrong to activate the query as DNS server change
                                // could not possibly change the status of SuppressUnusable questions
                                if (!QuerySuppressed(q))
                                        {
                                        debugf("uDNS_SetupDNSConfig: Activating query %p %##s (%s)", q, q->qname.c, DNSTypeName(q->qtype));
                                        ActivateUnicastQuery(m, q, mDNStrue);
                                        // ActivateUnicastQuery is called for duplicate questions also as it does something
                                        // special for AutoTunnel questions
                                        for (qptr = q->next ; qptr; qptr = qptr->next)
                                                {
                                                if (qptr->DuplicateOf == q) ActivateUnicastQuery(m, qptr, mDNStrue);
                                                }
                                        }
                                }
                        else
                                {
                                debugf("uDNS_SetupDNSConfig: Not Updating DNS server question %p %##s (%s) DNS server %#a:%d %p %d",
                                        q, q->qname.c, DNSTypeName(q->qtype), t ? &t->addr : mDNSNULL, mDNSVal16(t ? t->port : zeroIPPort), q->DuplicateOf, q->SuppressUnusable);
                                for (qptr = q->next ; qptr; qptr = qptr->next)
                                        if (qptr->DuplicateOf == q) { qptr->validDNSServers = q->validDNSServers; qptr->qDNSServer = q->qDNSServer; }
                                }
                        }

        while (*p)
                {
                if (((*p)->flags & DNSServer_FlagDelete) != 0)
                        {
                        // Scan our cache, looking for uDNS records that we would have queried this server for.
                        // We reconfirm any records that match, because in this world of split DNS, firewalls, etc.
                        // different DNS servers can give different answers to the same question.
                        ptr = *p;
                        FORALL_CACHERECORDS(slot, cg, cr)
                                {
                                if (cr->resrec.InterfaceID) continue;
                                if (cr->resrec.rDNSServer == ptr)
                                        {
                                        // If we don't have an active question for this cache record, neither Purge can
                                        // generate RMV events nor Reconfirm can send queries out. Just set the DNSServer
                                        // pointer on the record NULL so that we don't point to freed memory (We might dereference
                                        // DNSServer pointers from resource record for logging purposes).
                                        //
                                        // If there is an active question, point to its DNSServer as long as it does not point to the
                                        // freed one. We already went through the questions above and made them point at either the
                                        // new server or NULL if there is no server and also affected the cache entries that match
                                        // this question. Hence, whenever we hit a resource record with a DNSServer that is just
                                        // about to be deleted, we should never have an active question. The code below just tries to
                                        // be careful logging messages if we ever hit this case.

                                        if (cr->CRActiveQuestion)
                                                {
                                                DNSQuestion *qptr = cr->CRActiveQuestion;
                                                if (qptr->qDNSServer == mDNSNULL)
                                                        LogMsg("uDNS_SetupDNSConfig: Cache Record %s match: Active question %##s (%s) with DNSServer Address NULL, Server to be deleted %#a",
                                                                CRDisplayString(m, cr), qptr->qname.c, DNSTypeName(qptr->qtype), &ptr->addr);
                                                else
                                                        LogMsg("uDNS_SetupDNSConfig: Cache Record %s match: Active question %##s (%s) DNSServer Address %#a, Server to be deleted %#a",
                                                                CRDisplayString(m, cr),  qptr->qname.c, DNSTypeName(qptr->qtype), &qptr->qDNSServer->addr, &ptr->addr);

                                                if (qptr->qDNSServer == ptr)
                                                        {
                                                        qptr->validDNSServers = zeroOpaque64;
                                                        qptr->qDNSServer = mDNSNULL;
                                                        cr->resrec.rDNSServer = mDNSNULL;
                                                        }
                                                else
                                                        {
                                                        cr->resrec.rDNSServer = qptr->qDNSServer;
                                                        }
                                                }
                                        else
                                                {
                                                LogInfo("uDNS_SetupDNSConfig: Cache Record %##s has no Active question, Record's DNSServer Address %#a, Server to be deleted %#a",
                                                        cr->resrec.name, &cr->resrec.rDNSServer->addr, &ptr->addr);
                                                cr->resrec.rDNSServer = mDNSNULL;
                                                }
                                                
                                        PurgeOrReconfirmCacheRecord(m, cr, ptr, mDNStrue);
                                        }
                                }
                        *p = (*p)->next;
                        debugf("uDNS_SetupDNSConfig: Deleting server %p %#a:%d (%##s)", ptr, &ptr->addr, mDNSVal16(ptr->port), ptr->domain.c);
                        mDNSPlatformMemFree(ptr);
                        NumUnicastDNSServers--;
                        }
                else
                        {
                        (*p)->flags &= ~DNSServer_FlagNew;
                        p = &(*p)->next;
                        }
                }

        // If we now have no DNS servers at all and we used to have some, then immediately purge all unicast cache records (including for LLQs).
        // This is important for giving prompt remove events when the user disconnects the Ethernet cable or turns off wireless.
        // Otherwise, stale data lingers for 5-10 seconds, which is not the user-experience people expect from Bonjour.
        // Similarly, if we now have some DNS servers and we used to have none, we want to purge any fake negative results we may have generated.
        if ((m->DNSServers != mDNSNULL) != (oldServers != mDNSNULL))
                {
                int count = 0;
                FORALL_CACHERECORDS(slot, cg, cr) if (!cr->resrec.InterfaceID) { mDNS_PurgeCacheResourceRecord(m, cr); count++; }
                LogInfo("uDNS_SetupDNSConfig: %s available; purged %d unicast DNS records from cache",
                        m->DNSServers ? "DNS server became" : "No DNS servers", count);

                // Force anything that needs to get zone data to get that information again
                RestartRecordGetZoneData(m);
                }

        // Did our FQDN change?
        if (!SameDomainName(&fqdn, &m->FQDN))
                {
                if (m->FQDN.c[0]) mDNS_RemoveDynDNSHostName(m, &m->FQDN);

                AssignDomainName(&m->FQDN, &fqdn);

                if (m->FQDN.c[0])
                        {
                        mDNSPlatformDynDNSHostNameStatusChanged(&m->FQDN, 1);
                        mDNS_AddDynDNSHostName(m, &m->FQDN, DynDNSHostNameCallback, mDNSNULL);
                        }
                }

        mDNS_Unlock(m);

        // handle router and primary interface changes
        v4 = v6 = r = zeroAddr;
        v4.type = r.type = mDNSAddrType_IPv4;

        if (mDNSPlatformGetPrimaryInterface(m, &v4, &v6, &r) == mStatus_NoError && !mDNSv4AddressIsLinkLocal(&v4.ip.v4))
                {
                mDNS_SetPrimaryInterfaceInfo(m,
                        !mDNSIPv4AddressIsZero(v4.ip.v4) ? &v4 : mDNSNULL,
                        !mDNSIPv6AddressIsZero(v6.ip.v6) ? &v6 : mDNSNULL,
                        !mDNSIPv4AddressIsZero(r .ip.v4) ? &r  : mDNSNULL);
                }
        else
                {
                mDNS_SetPrimaryInterfaceInfo(m, mDNSNULL, mDNSNULL, mDNSNULL);
                if (m->FQDN.c[0]) mDNSPlatformDynDNSHostNameStatusChanged(&m->FQDN, 1); // Set status to 1 to indicate temporary failure
                }

        debugf("uDNS_SetupDNSConfig: number of unicast DNS servers %d", NumUnicastDNSServers);
        return mStatus_NoError;
        }

mDNSexport void mDNSCoreInitComplete(mDNS *const m, mStatus result)
        {
        m->mDNSPlatformStatus = result;
        if (m->MainCallback)
                {
                mDNS_Lock(m);
                mDNS_DropLockBeforeCallback();          // Allow client to legally make mDNS API calls from the callback
                m->MainCallback(m, mStatus_NoError);
                mDNS_ReclaimLockAfterCallback();        // Decrement mDNS_reentrancy to block mDNS API calls again
                mDNS_Unlock(m);
                }
        }

mDNSlocal void DeregLoop(mDNS *const m, AuthRecord *const start)
        {
        m->CurrentRecord = start;
        while (m->CurrentRecord)
                {
                AuthRecord *rr = m->CurrentRecord;
                LogInfo("DeregLoop: %s deregistration for %p %02X %s",
                        (rr->resrec.RecordType != kDNSRecordTypeDeregistering) ? "Initiating  " : "Accelerating",
                        rr, rr->resrec.RecordType, ARDisplayString(m, rr));
                if (rr->resrec.RecordType != kDNSRecordTypeDeregistering)
                        mDNS_Deregister_internal(m, rr, mDNS_Dereg_rapid);
                else if (rr->AnnounceCount > 1)
                        {
                        rr->AnnounceCount = 1;
                        rr->LastAPTime = m->timenow - rr->ThisAPInterval;
                        }
                // Mustn't advance m->CurrentRecord until *after* mDNS_Deregister_internal, because
                // new records could have been added to the end of the list as a result of that call.
                if (m->CurrentRecord == rr) // If m->CurrentRecord was not advanced for us, do it now
                        m->CurrentRecord = rr->next;
                }
        }

mDNSexport void mDNS_StartExit(mDNS *const m)
        {
        NetworkInterfaceInfo *intf;
        AuthRecord *rr;

        mDNS_Lock(m);

        LogInfo("mDNS_StartExit");
        m->ShutdownTime = NonZeroTime(m->timenow + mDNSPlatformOneSecond * 5);

        mDNSCoreBeSleepProxyServer_internal(m, 0, 0, 0, 0);

#if APPLE_OSX_mDNSResponder
#if ! NO_WCF
        CHECK_WCF_FUNCTION(WCFConnectionDealloc)
                {
                if (m->WCF) WCFConnectionDealloc((WCFConnection *)m->WCF);
                }
#endif
#endif

#ifndef UNICAST_DISABLED
        {
        SearchListElem *s;
        SuspendLLQs(m);
        // Don't need to do SleepRecordRegistrations() here
        // because we deregister all records and services later in this routine
        while (m->Hostnames) mDNS_RemoveDynDNSHostName(m, &m->Hostnames->fqdn);

        // For each member of our SearchList, deregister any records it may have created, and cut them from the list.
        // Otherwise they'll be forcibly deregistered for us (without being cut them from the appropriate list)
        // and we may crash because the list still contains dangling pointers.
        for (s = SearchList; s; s = s->next)
                while (s->AuthRecs)
                        {
                        ARListElem *dereg = s->AuthRecs;
                        s->AuthRecs = s->AuthRecs->next;
                        mDNS_Deregister_internal(m, &dereg->ar, mDNS_Dereg_normal);     // Memory will be freed in the FreeARElemCallback
                        }
        }
#endif

        for (intf = m->HostInterfaces; intf; intf = intf->next)
                if (intf->Advertise)
                        DeadvertiseInterface(m, intf);

        // Shut down all our active NAT Traversals
        while (m->NATTraversals)
                {
                NATTraversalInfo *t = m->NATTraversals;
                mDNS_StopNATOperation_internal(m, t);           // This will cut 't' from the list, thereby advancing m->NATTraversals in the process

                // After stopping the NAT Traversal, we zero out the fields.
                // This has particularly important implications for our AutoTunnel records --
                // when we deregister our AutoTunnel records below, we don't want their mStatus_MemFree
                // handlers to just turn around and attempt to re-register those same records.
                // Clearing t->ExternalPort/t->RequestedPort will cause the mStatus_MemFree callback handlers
                // to not do this.
                t->ExternalAddress = zerov4Addr;
                t->ExternalPort    = zeroIPPort;
                t->RequestedPort   = zeroIPPort;
                t->Lifetime        = 0;
                t->Result          = mStatus_NoError;
                }

        // Make sure there are nothing but deregistering records remaining in the list
        if (m->CurrentRecord)
                LogMsg("mDNS_StartExit: ERROR m->CurrentRecord already set %s", ARDisplayString(m, m->CurrentRecord));

        // We're in the process of shutting down, so queries, etc. are no longer available.
        // Consequently, determining certain information, e.g. the uDNS update server's IP
        // address, will not be possible.  The records on the main list are more likely to
        // already contain such information, so we deregister the duplicate records first.
        LogInfo("mDNS_StartExit: Deregistering duplicate resource records");
        DeregLoop(m, m->DuplicateRecords);
        LogInfo("mDNS_StartExit: Deregistering resource records");
        DeregLoop(m, m->ResourceRecords);
        
        // If we scheduled a response to send goodbye packets, we set NextScheduledResponse to now. Normally when deregistering records,
        // we allow up to 100ms delay (to help improve record grouping) but when shutting down we don't want any such delay.
        if (m->NextScheduledResponse - m->timenow < mDNSPlatformOneSecond)
                {
                m->NextScheduledResponse = m->timenow;
                m->SuppressSending = 0;
                }

        if (m->ResourceRecords) LogInfo("mDNS_StartExit: Sending final record deregistrations");
        else                    LogInfo("mDNS_StartExit: No deregistering records remain");

        for (rr = m->DuplicateRecords; rr; rr = rr->next)
                LogMsg("mDNS_StartExit: Should not still have Duplicate Records remaining: %02X %s", rr->resrec.RecordType, ARDisplayString(m, rr));

        // If any deregistering records remain, send their deregistration announcements before we exit
        if (m->mDNSPlatformStatus != mStatus_NoError) DiscardDeregistrations(m);

        mDNS_Unlock(m);

        LogInfo("mDNS_StartExit: done");
        }

mDNSexport void mDNS_FinalExit(mDNS *const m)
        {
        mDNSu32 rrcache_active = 0;
        mDNSu32 rrcache_totalused = 0;
        mDNSu32 slot;
        AuthRecord *rr;

        LogInfo("mDNS_FinalExit: mDNSPlatformClose");
        mDNSPlatformClose(m);

        rrcache_totalused = m->rrcache_totalused;
        for (slot = 0; slot < CACHE_HASH_SLOTS; slot++)
                {
                while (m->rrcache_hash[slot])
                        {
                        CacheGroup *cg = m->rrcache_hash[slot];
                        while (cg->members)
                                {
                                CacheRecord *cr = cg->members;
                                cg->members = cg->members->next;
                                if (cr->CRActiveQuestion) rrcache_active++;
                                ReleaseCacheRecord(m, cr);
                                }
                        cg->rrcache_tail = &cg->members;
                        ReleaseCacheGroup(m, &m->rrcache_hash[slot]);
                        }
                }
        debugf("mDNS_FinalExit: RR Cache was using %ld records, %lu active", rrcache_totalused, rrcache_active);
        if (rrcache_active != m->rrcache_active)
                LogMsg("*** ERROR *** rrcache_active %lu != m->rrcache_active %lu", rrcache_active, m->rrcache_active);

        for (rr = m->ResourceRecords; rr; rr = rr->next)
                LogMsg("mDNS_FinalExit failed to send goodbye for: %p %02X %s", rr, rr->resrec.RecordType, ARDisplayString(m, rr));

        LogInfo("mDNS_FinalExit: done");
        }