mDNSResponder-171.4.tar.gz

[apple/mdnsresponder.git] / mDNSPosix / Responder.c

/* -*- Mode: C; tab-width: 4 -*-
 *
 * Copyright (c) 2002-2004 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.

    Change History (most recent first):

$Log: Responder.c,v $
Revision 1.33  2007/04/16 20:49:39  cheshire
Fix compile errors for mDNSPosix build

Revision 1.32  2006/08/14 23:24:46  cheshire
Re-licensed mDNSResponder daemon source code under Apache License, Version 2.0

Revision 1.31  2006/06/12 18:22:42  cheshire
<rdar://problem/4580067> mDNSResponder building warnings under Red Hat 64-bit (LP64) Linux

Revision 1.30  2005/10/26 22:21:16  cheshire
<rdar://problem/4149841> Potential buffer overflow in mDNSResponderPosix

Revision 1.29  2005/03/04 21:35:33  cheshire
<rdar://problem/4037201> Services.txt file not parsed properly when it contains more than one service

Revision 1.28  2005/01/11 01:55:26  ksekar
Fix compile errors in Posix debug build

Revision 1.27  2004/12/01 04:28:43  cheshire
<rdar://problem/3872803> Darwin patches for Solaris and Suse
Use version of daemon() provided in mDNSUNP.c instead of local copy

Revision 1.26  2004/11/30 22:37:01  cheshire
Update copyright dates and add "Mode: C; tab-width: 4" headers

Revision 1.25  2004/11/11 02:00:51  cheshire
Minor fixes to getopt, error message

Revision 1.24  2004/11/09 19:32:10  rpantos
Suggestion from Ademar de Souza Reis Jr. to allow comments in services file

Revision 1.23  2004/09/17 01:08:54  cheshire
Renamed mDNSClientAPI.h to mDNSEmbeddedAPI.h
  The name "mDNSClientAPI.h" is misleading to new developers looking at this code. The interfaces
  declared in that file are ONLY appropriate to single-address-space embedded applications.
  For clients on general-purpose computers, the interfaces defined in dns_sd.h should be used.

Revision 1.22  2004/09/16 01:58:22  cheshire
Fix compiler warnings

Revision 1.21  2004/06/15 03:48:07  cheshire
Update mDNSResponderPosix to take multiple name=val arguments in a sane way

Revision 1.20  2004/05/18 23:51:26  cheshire
Tidy up all checkin comments to use consistent "<rdar://problem/xxxxxxx>" format for bug numbers

Revision 1.19  2004/03/12 08:03:14  cheshire
Update comments

Revision 1.18  2004/01/25 00:00:55  cheshire
Change to use mDNSOpaque16fromIntVal() instead of shifting and masking

Revision 1.17  2003/12/11 19:11:55  cheshire
Fix compiler warning

Revision 1.16  2003/08/14 02:19:55  cheshire
<rdar://problem/3375491> Split generic ResourceRecord type into two separate types: AuthRecord and CacheRecord

Revision 1.15  2003/08/12 19:56:26  cheshire
Update to APSL 2.0

Revision 1.14  2003/08/06 18:20:51  cheshire
Makefile cleanup

Revision 1.13  2003/07/23 00:00:04  cheshire
Add comments

Revision 1.12  2003/07/15 01:55:16  cheshire
<rdar://problem/3315777> Need to implement service registration with subtypes

Revision 1.11  2003/07/14 18:11:54  cheshire
Fix stricter compiler warnings

Revision 1.10  2003/07/10 20:27:31  cheshire
<rdar://problem/3318717> mDNSResponder Posix version is missing a 'b' in the getopt option string

Revision 1.9  2003/07/02 21:19:59  cheshire
<rdar://problem/3313413> Update copyright notices, etc., in source code comments

Revision 1.8  2003/06/18 05:48:41  cheshire
Fix warnings

Revision 1.7  2003/05/06 00:00:50  cheshire
<rdar://problem/3248914> Rationalize naming of domainname manipulation functions

Revision 1.6  2003/03/08 00:35:56  cheshire
Switched to using new "mDNS_Execute" model (see "mDNSCore/Implementer Notes.txt")

Revision 1.5  2003/02/20 06:48:36  cheshire
<rdar://problem/3169535> Xserve RAID needs to do interface-specific registrations
Reviewed by: Josh Graessley, Bob Bradley

Revision 1.4  2003/01/28 03:07:46  cheshire
Add extra parameter to mDNS_RenameAndReregisterService(),
and add support for specifying a domain other than dot-local.

Revision 1.3  2002/09/21 20:44:53  zarzycki
Added APSL info

Revision 1.2  2002/09/19 04:20:44  cheshire
Remove high-ascii characters that confuse some systems

Revision 1.1  2002/09/17 06:24:35  cheshire
First checkin

*/

#include "mDNSEmbeddedAPI.h"// Defines the interface to the client layer above
#include "mDNSPosix.h"    // Defines the specific types needed to run mDNS on this platform

#include <assert.h>
#include <stdio.h>                      // For printf()
#include <stdlib.h>                     // For exit() etc.
#include <string.h>                     // For strlen() etc.
#include <unistd.h>                     // For select()
#include <errno.h>                      // For errno, EINTR
#include <signal.h>
#include <fcntl.h>

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark ***** Globals
#endif

static mDNS mDNSStorage;       // mDNS core uses this to store its globals
static mDNS_PlatformSupport PlatformStorage;  // Stores this platform's globals

mDNSexport const char ProgramName[] = "mDNSResponderPosix";

static const char *gProgramName = ProgramName;

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark ***** Signals
#endif

static volatile mDNSBool gReceivedSigUsr1;
static volatile mDNSBool gReceivedSigHup;
static volatile mDNSBool gStopNow;

// We support 4 signals.
//
// o SIGUSR1 toggles verbose mode on and off in debug builds
// o SIGHUP  triggers the program to re-read its preferences.
// o SIGINT  causes an orderly shutdown of the program.
// o SIGQUIT causes a somewhat orderly shutdown (direct but dangerous)
// o SIGKILL kills us dead (easy to implement :-)
//
// There are fatal race conditions in our signal handling, but there's not much 
// we can do about them while remaining within the Posix space.  Specifically, 
// if a signal arrives after we test the globals its sets but before we call 
// select, the signal will be dropped.  The user will have to send the signal 
// again.  Unfortunately, Posix does not have a "sigselect" to atomically 
// modify the signal mask and start a select.

static void HandleSigUsr1(int sigraised)
    // If we get a SIGUSR1 we toggle the state of the 
    // verbose mode.
{
    assert(sigraised == SIGUSR1);
    gReceivedSigUsr1 = mDNStrue;
}

static void HandleSigHup(int sigraised)
    // A handler for SIGHUP that causes us to break out of the 
    // main event loop when the user kill 1's us.  This has the 
    // effect of triggered the main loop to deregister the 
    // current services and re-read the preferences.
{
    assert(sigraised == SIGHUP);
        gReceivedSigHup = mDNStrue;
}

static void HandleSigInt(int sigraised)
    // A handler for SIGINT that causes us to break out of the 
    // main event loop when the user types ^C.  This has the 
    // effect of quitting the program.
{
    assert(sigraised == SIGINT);
    
    if (gMDNSPlatformPosixVerboseLevel > 0) {
        fprintf(stderr, "\nSIGINT\n");
    }
    gStopNow = mDNStrue;
}

static void HandleSigQuit(int sigraised)
    // If we get a SIGQUIT the user is desperate and we 
    // just call mDNS_Close directly.  This is definitely 
    // not safe (because it could reenter mDNS), but 
    // we presume that the user has already tried the safe 
    // alternatives.
{
    assert(sigraised == SIGQUIT);

    if (gMDNSPlatformPosixVerboseLevel > 0) {
        fprintf(stderr, "\nSIGQUIT\n");
    }
    mDNS_Close(&mDNSStorage);
    exit(0);
}

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark ***** Parameter Checking
#endif

static mDNSBool CheckThatRichTextNameIsUsable(const char *richTextName, mDNSBool printExplanation)
    // Checks that richTextName is reasonable 
    // label and, if it isn't and printExplanation is true, prints 
    // an explanation of why not.
{
    mDNSBool result = mDNStrue;
    if (result && strlen(richTextName) > 63) {
        if (printExplanation) {
            fprintf(stderr, 
                    "%s: Service name is too long (must be 63 characters or less)\n", 
                    gProgramName);
        }
        result = mDNSfalse;
    }
    if (result && richTextName[0] == 0) {
        if (printExplanation) {
            fprintf(stderr, "%s: Service name can't be empty\n", gProgramName);
        }
        result = mDNSfalse;
    }
    return result;
}

static mDNSBool CheckThatServiceTypeIsUsable(const char *serviceType, mDNSBool printExplanation)
    // Checks that serviceType is a reasonable service type 
    // label and, if it isn't and printExplanation is true, prints 
    // an explanation of why not.
{
    mDNSBool result;
    
    result = mDNStrue;
    if (result && strlen(serviceType) > 63) {
        if (printExplanation) {
            fprintf(stderr, 
                    "%s: Service type is too long (must be 63 characters or less)\n", 
                    gProgramName);
        }
        result = mDNSfalse;
    }
    if (result && serviceType[0] == 0) {
        if (printExplanation) {
            fprintf(stderr, 
                    "%s: Service type can't be empty\n", 
                    gProgramName);
        }
        result = mDNSfalse;
    }
    return result;
}

static mDNSBool CheckThatPortNumberIsUsable(long portNumber, mDNSBool printExplanation)
    // Checks that portNumber is a reasonable port number
    // and, if it isn't and printExplanation is true, prints 
    // an explanation of why not.
{
    mDNSBool result;
    
    result = mDNStrue;
    if (result && (portNumber <= 0 || portNumber > 65535)) {
        if (printExplanation) {
            fprintf(stderr, 
                    "%s: Port number specified by -p must be in range 1..65535\n", 
                    gProgramName);
        }
        result = mDNSfalse;
    }
    return result;
}

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark ***** Command Line Arguments
#endif

static const char kDefaultPIDFile[]     = "/var/run/mDNSResponder.pid";
static const char kDefaultServiceType[] = "_afpovertcp._tcp.";
static const char kDefaultServiceDomain[] = "local.";
enum {
    kDefaultPortNumber = 548
};

static void PrintUsage()
{
    fprintf(stderr, 
            "Usage: %s [-v level ] [-r] [-n name] [-t type] [-d domain] [-p port] [-f file] [-b] [-P pidfile] [-x name=val ...]\n", 
            gProgramName);
    fprintf(stderr, "          -v verbose mode, level is a number from 0 to 2\n");
    fprintf(stderr, "             0 = no debugging info (default)\n");
    fprintf(stderr, "             1 = standard debugging info\n");
    fprintf(stderr, "             2 = intense debugging info\n");
    fprintf(stderr, "             can be cycled kill -USR1\n");
    fprintf(stderr, "          -r also bind to port 53 (port 5353 is always bound)\n");
    fprintf(stderr, "          -n uses 'name' as the service name (required)\n");
    fprintf(stderr, "          -t uses 'type' as the service type (default is '%s')\n", kDefaultServiceType);
    fprintf(stderr, "          -d uses 'domain' as the service domain (default is '%s')\n", kDefaultServiceDomain);
    fprintf(stderr, "          -p uses 'port' as the port number (default is '%d')\n",  kDefaultPortNumber);
    fprintf(stderr, "          -f reads a service list from 'file'\n");
    fprintf(stderr, "          -b forces daemon (background) mode\n");
    fprintf(stderr, "          -P uses 'pidfile' as the PID file\n");
    fprintf(stderr, "             (default is '%s')\n",  kDefaultPIDFile);
    fprintf(stderr, "             only meaningful if -b also specified\n");
    fprintf(stderr, "          -x stores name=val in TXT record (default is empty).\n");
    fprintf(stderr, "             MUST be the last command-line argument;\n");
    fprintf(stderr, "             all subsequent arguments after -x are treated as name=val pairs.\n");
}

static   mDNSBool  gAvoidPort53      = mDNStrue;
static const char *gServiceName      = "";
static const char *gServiceType      = kDefaultServiceType;
static const char *gServiceDomain    = kDefaultServiceDomain;
static mDNSu8      gServiceText[sizeof(RDataBody)];
static mDNSu16     gServiceTextLen   = 0;
static        int  gPortNumber       = kDefaultPortNumber;
static const char *gServiceFile      = "";
static   mDNSBool  gDaemon           = mDNSfalse;
static const char *gPIDFile          = kDefaultPIDFile;

static void ParseArguments(int argc, char **argv)
    // Parses our command line arguments into the global variables 
    // listed above.
{
    int ch;
    
    // Set gProgramName to the last path component of argv[0]
    
    gProgramName = strrchr(argv[0], '/');
    if (gProgramName == NULL) {
        gProgramName = argv[0];
    } else {
        gProgramName += 1;
    }
    
    // Parse command line options using getopt.
    
    do {
        ch = getopt(argc, argv, "v:rn:t:d:p:f:dP:bx");
        if (ch != -1) {
            switch (ch) {
                case 'v':
                    gMDNSPlatformPosixVerboseLevel = atoi(optarg);
                    if (gMDNSPlatformPosixVerboseLevel < 0 || gMDNSPlatformPosixVerboseLevel > 2) {
                        fprintf(stderr, 
                                "%s: Verbose mode must be in the range 0..2\n", 
                                gProgramName);
                        exit(1);
                    }
                    break;
                case 'r':
                    gAvoidPort53 = mDNSfalse;
                    break;
                case 'n':
                    gServiceName = optarg;
                    if ( ! CheckThatRichTextNameIsUsable(gServiceName, mDNStrue) ) {
                        exit(1);
                    }
                    break;
                case 't':
                    gServiceType = optarg;
                    if ( ! CheckThatServiceTypeIsUsable(gServiceType, mDNStrue) ) {
                        exit(1);
                    }
                    break;
                case 'd':
                    gServiceDomain = optarg;
                    break;
                case 'p':
                    gPortNumber = atol(optarg);
                    if ( ! CheckThatPortNumberIsUsable(gPortNumber, mDNStrue) ) {
                        exit(1);
                    }
                    break;
                case 'f':
                    gServiceFile = optarg;
                    break;
                case 'b':
                    gDaemon = mDNStrue;
                    break;
                case 'P':
                    gPIDFile = optarg;
                    break;
                case 'x':
                        while (optind < argc)
                                {
                                gServiceText[gServiceTextLen] = strlen(argv[optind]);
                                memcpy(gServiceText+gServiceTextLen+1, argv[optind], gServiceText[gServiceTextLen]);
                                gServiceTextLen += 1 + gServiceText[gServiceTextLen];
                                optind++;
                                }
                        ch = -1;
                        break;
                case '?':
                default:
                    PrintUsage();
                    exit(1);
                    break;
            }
        }
    } while (ch != -1);

    // Check for any left over command line arguments.
    
    if (optind != argc) {
            PrintUsage();
        fprintf(stderr, "%s: Unexpected argument '%s'\n", gProgramName, argv[optind]);
        exit(1);
    }
    
    // Check for inconsistency between the arguments.
    
    if ( (gServiceName[0] == 0) && (gServiceFile[0] == 0) ) {
        PrintUsage();
        fprintf(stderr, "%s: You must specify a service name to register (-n) or a service file (-f).\n", gProgramName);
        exit(1);
    }
}

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark ***** Registration
#endif

typedef struct PosixService PosixService;

struct PosixService {
    ServiceRecordSet coreServ;
    PosixService *next;
    int serviceID;
};

static PosixService *gServiceList = NULL;

static void RegistrationCallback(mDNS *const m, ServiceRecordSet *const thisRegistration, mStatus status)
    // mDNS core calls this routine to tell us about the status of 
    // our registration.  The appropriate action to take depends 
    // entirely on the value of status.
{
    switch (status) {

        case mStatus_NoError:      
            debugf("Callback: %##s Name Registered",   thisRegistration->RR_SRV.resrec.name->c); 
            // Do nothing; our name was successfully registered.  We may 
            // get more call backs in the future.
            break;

        case mStatus_NameConflict: 
            debugf("Callback: %##s Name Conflict",     thisRegistration->RR_SRV.resrec.name->c); 

            // In the event of a conflict, this sample RegistrationCallback 
            // just calls mDNS_RenameAndReregisterService to automatically 
            // pick a new unique name for the service. For a device such as a 
            // printer, this may be appropriate.  For a device with a user 
            // interface, and a screen, and a keyboard, the appropriate response 
            // may be to prompt the user and ask them to choose a new name for 
            // the service.
            //
            // Also, what do we do if mDNS_RenameAndReregisterService returns an 
            // error.  Right now I have no place to send that error to.
            
            status = mDNS_RenameAndReregisterService(m, thisRegistration, mDNSNULL);
            assert(status == mStatus_NoError);
            break;

        case mStatus_MemFree:      
            debugf("Callback: %##s Memory Free",       thisRegistration->RR_SRV.resrec.name->c); 
            
            // When debugging is enabled, make sure that thisRegistration 
            // is not on our gServiceList.
            
            #if !defined(NDEBUG)
                {
                    PosixService *cursor;
                    
                    cursor = gServiceList;
                    while (cursor != NULL) {
                        assert(&cursor->coreServ != thisRegistration);
                        cursor = cursor->next;
                    }
                }
            #endif
            free(thisRegistration);
            break;

        default:                   
            debugf("Callback: %##s Unknown Status %ld", thisRegistration->RR_SRV.resrec.name->c, status); 
            break;
    }
}

static int gServiceID = 0;

static mStatus RegisterOneService(const char *  richTextName, 
                                  const char *  serviceType, 
                                  const char *  serviceDomain, 
                                  const mDNSu8  text[],
                                  mDNSu16       textLen,
                                  long          portNumber)
{
    mStatus             status;
    PosixService *      thisServ;
    domainlabel         name;
    domainname          type;
    domainname          domain;
    
    status = mStatus_NoError;
    thisServ = (PosixService *) malloc(sizeof(*thisServ));
    if (thisServ == NULL) {
        status = mStatus_NoMemoryErr;
    }
    if (status == mStatus_NoError) {
        MakeDomainLabelFromLiteralString(&name,  richTextName);
        MakeDomainNameFromDNSNameString(&type, serviceType);
        MakeDomainNameFromDNSNameString(&domain, serviceDomain);
        status = mDNS_RegisterService(&mDNSStorage, &thisServ->coreServ,
                &name, &type, &domain,                          // Name, type, domain
                NULL, mDNSOpaque16fromIntVal(portNumber),
                text, textLen,                                          // TXT data, length
                NULL, 0,                                                        // Subtypes
                mDNSInterface_Any,                                      // Interface ID
                RegistrationCallback, thisServ);        // Callback and context
    }
    if (status == mStatus_NoError) {
        thisServ->serviceID = gServiceID;
        gServiceID += 1;

        thisServ->next = gServiceList;
        gServiceList = thisServ;

        if (gMDNSPlatformPosixVerboseLevel > 0) {
            fprintf(stderr, 
                    "%s: Registered service %d, name '%s', type '%s', port %ld\n", 
                    gProgramName, 
                    thisServ->serviceID, 
                    richTextName,
                    serviceType,
                    portNumber);
        }
    } else {
        if (thisServ != NULL) {
            free(thisServ);
        }
    }
    return status;
}

static mDNSBool ReadALine(char *buf, size_t bufSize, FILE *fp)
// Read a line, skipping over any blank lines or lines starting with '#'
{
        mDNSBool good, skip;
        do {
                good = (fgets(buf, bufSize, fp) != NULL);
                skip = (good && (buf[0] == '#'));
        } while (good && skip);
        if (good)
        {
                int             len = strlen( buf);
                if ( buf[len - 1] == '\r' || buf[len - 1] == '\n')
                        buf[len - 1] = '\0';
        }
    return good;
}

static mStatus RegisterServicesInFile(const char *filePath)
{
    mStatus     status = mStatus_NoError;
    FILE *      fp = fopen(filePath, "r");
    int         junk;
    
    if (fp == NULL) {
        status = mStatus_UnknownErr;
    }
    if (status == mStatus_NoError) {
        mDNSBool good = mDNStrue;
        do {
                        int         ch;
                        char name[256];
                        char type[256];
                        const char *dom = kDefaultServiceDomain;
                        char rawText[1024];
                        mDNSu8  text[sizeof(RDataBody)];
                        unsigned int textLen = 0;
                        char port[256];

            // Skip over any blank lines.
            do ch = fgetc(fp); while ( ch == '\n' || ch == '\r' );
            if (ch != EOF) good = (ungetc(ch, fp) == ch);
            
            // Read three lines, check them for validity, and register the service.
                        good = ReadALine(name, sizeof(name), fp);               
                        if (good) {
                                good = ReadALine(type, sizeof(type), fp);
                        }
                        if (good) {
                                char *p = type;
                                while (*p && *p != ' ') p++;
                                if (*p) {
                                        *p = 0;
                                        dom = p+1;
                                }
                        }
                        if (good) {
                                good = ReadALine(port, sizeof(port), fp);
                        }
                        if (good) {
                                good =     CheckThatRichTextNameIsUsable(name, mDNSfalse)
                                                && CheckThatServiceTypeIsUsable(type, mDNSfalse)
                                                && CheckThatPortNumberIsUsable(atol(port), mDNSfalse);
                        }
                        if (good) {
                                while (1) {
                                        int len;
                                        if (!ReadALine(rawText, sizeof(rawText), fp)) break;
                                        len = strlen(rawText);
                                        if (len <= 255)
                                                {
                                                unsigned int newlen = textLen + 1 + len;
                                                if (len == 0 || newlen >= sizeof(text)) break;
                                                text[textLen] = len;
                                                memcpy(text + textLen + 1, rawText, len);
                                                textLen = newlen;
                                                }
                                        else
                                                fprintf(stderr, "%s: TXT attribute too long for name = %s, type = %s, port = %s\n", 
                                                        gProgramName, name, type, port);
                                }
                        }
                        if (good) {
                                status = RegisterOneService(name, type, dom, text, textLen, atol(port));
                                if (status != mStatus_NoError) {
                                        fprintf(stderr, "%s: Failed to register service, name = %s, type = %s, port = %s\n", 
                                                        gProgramName, name, type, port);
                                        status = mStatus_NoError;       // keep reading
                                }
                        }
        } while (good && !feof(fp));

        if ( ! good ) {
            fprintf(stderr, "%s: Error reading service file %s\n", gProgramName, filePath);
        }
    }
    
    if (fp != NULL) {
        junk = fclose(fp);
        assert(junk == 0);
    }
    
    return status;
}

static mStatus RegisterOurServices(void)
{
    mStatus status;
    
    status = mStatus_NoError;
    if (gServiceName[0] != 0) {
        status = RegisterOneService(gServiceName, 
                                    gServiceType, 
                                    gServiceDomain, 
                                    gServiceText, gServiceTextLen, 
                                    gPortNumber);
    }
    if (status == mStatus_NoError && gServiceFile[0] != 0) {
        status = RegisterServicesInFile(gServiceFile);
    }
    return status;
}

static void DeregisterOurServices(void)
{
    PosixService *thisServ;
    int thisServID;
    
    while (gServiceList != NULL) {
        thisServ = gServiceList;
        gServiceList = thisServ->next;

        thisServID = thisServ->serviceID;
        
        mDNS_DeregisterService(&mDNSStorage, &thisServ->coreServ);

        if (gMDNSPlatformPosixVerboseLevel > 0) {
            fprintf(stderr, 
                    "%s: Deregistered service %d\n",
                    gProgramName, 
                    thisServ->serviceID);
        }
    }
}

#if COMPILER_LIKES_PRAGMA_MARK
#pragma mark **** Main
#endif

int main(int argc, char **argv)
{
    mStatus status;
    int     result;

    // Parse our command line arguments.  This won't come back if there's an error.
    
    ParseArguments(argc, argv);

    // If we're told to run as a daemon, then do that straight away.
    // Note that we don't treat the inability to create our PID 
    // file as an error.  Also note that we assign getpid to a long 
    // because printf has no format specified for pid_t.
    
    if (gDaemon) {
        if (gMDNSPlatformPosixVerboseLevel > 0) {
            fprintf(stderr, "%s: Starting in daemon mode\n", gProgramName);
        }
        daemon(0,0);
        {
            FILE *fp;
            int  junk;
            
            fp = fopen(gPIDFile, "w");
            if (fp != NULL) {
                fprintf(fp, "%ld\n", (long) getpid());
                junk = fclose(fp);
                assert(junk == 0);
            }
        }
    } else {
        if (gMDNSPlatformPosixVerboseLevel > 0) {
            fprintf(stderr, "%s: Starting in foreground mode, PID %ld\n", gProgramName, (long) getpid());
        }
    }

    status = mDNS_Init(&mDNSStorage, &PlatformStorage,
        mDNS_Init_NoCache, mDNS_Init_ZeroCacheSize,
        mDNS_Init_AdvertiseLocalAddresses,
        mDNS_Init_NoInitCallback, mDNS_Init_NoInitCallbackContext);
    if (status != mStatus_NoError) return(2);

        status = RegisterOurServices();
    if (status != mStatus_NoError) return(2);
    
    signal(SIGHUP,  HandleSigHup);      // SIGHUP has to be sent by kill -HUP <pid>
    signal(SIGINT,  HandleSigInt);      // SIGINT is what you get for a Ctrl-C
    signal(SIGQUIT, HandleSigQuit);     // SIGQUIT is what you get for a Ctrl-\ (indeed)
    signal(SIGUSR1, HandleSigUsr1);     // SIGUSR1 has to be sent by kill -USR1 <pid>

        while (!gStopNow)
                {
                int nfds = 0;
                fd_set readfds;
                struct timeval timeout;
                int result;
                
                // 1. Set up the fd_set as usual here.
                // This example client has no file descriptors of its own,
                // but a real application would call FD_SET to add them to the set here
                FD_ZERO(&readfds);
                
                // 2. Set up the timeout.
                // This example client has no other work it needs to be doing,
                // so we set an effectively infinite timeout
                timeout.tv_sec = 0x3FFFFFFF;
                timeout.tv_usec = 0;
                
                // 3. Give the mDNSPosix layer a chance to add its information to the fd_set and timeout
                mDNSPosixGetFDSet(&mDNSStorage, &nfds, &readfds, &timeout);
                
                // 4. Call select as normal
                verbosedebugf("select(%d, %d.%06d)", nfds, timeout.tv_sec, timeout.tv_usec);
                result = select(nfds, &readfds, NULL, NULL, &timeout);
                
                if (result < 0)
                        {
                        verbosedebugf("select() returned %d errno %d", result, errno);
                        if (errno != EINTR) gStopNow = mDNStrue;
                        else
                                {
                                if (gReceivedSigUsr1)
                                        {
                                        gReceivedSigUsr1 = mDNSfalse;
                                        gMDNSPlatformPosixVerboseLevel += 1;
                                        if (gMDNSPlatformPosixVerboseLevel > 2)
                                                gMDNSPlatformPosixVerboseLevel = 0;
                                        if ( gMDNSPlatformPosixVerboseLevel > 0 )
                                                fprintf(stderr, "\nVerbose level %d\n", gMDNSPlatformPosixVerboseLevel);
                                        }
                                if (gReceivedSigHup)
                                        {
                                        if (gMDNSPlatformPosixVerboseLevel > 0)
                                                fprintf(stderr, "\nSIGHUP\n");
                                        gReceivedSigHup = mDNSfalse;
                                        DeregisterOurServices();
                                        status = mDNSPlatformPosixRefreshInterfaceList(&mDNSStorage);
                                        if (status != mStatus_NoError) break;
                                        status = RegisterOurServices();
                                        if (status != mStatus_NoError) break;
                                        }
                                }
                        }
                else
                        {
                        // 5. Call mDNSPosixProcessFDSet to let the mDNSPosix layer do its work
                        mDNSPosixProcessFDSet(&mDNSStorage, &readfds);
                        
                        // 6. This example client has no other work it needs to be doing,
                        // but a real client would do its work here
                        // ... (do work) ...
                        }
                }

        debugf("Exiting");
    
        DeregisterOurServices();
        mDNS_Close(&mDNSStorage);

    if (status == mStatus_NoError) {
        result = 0;
    } else {
        result = 2;
    }
    if ( (result != 0) || (gMDNSPlatformPosixVerboseLevel > 0) ) {
        fprintf(stderr, "%s: Finished with status %d, result %d\n", gProgramName, (int)status, result);
    }
    
    return result;
}