xnu-6153.141.1.tar.gz

[apple/xnu.git] / bsd / netinet / igmp.c

/*
 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*-
 * Copyright (c) 2007-2009 Bruce Simpson.
 * Copyright (c) 1988 Stephen Deering.
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Stephen Deering of Stanford University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)igmp.c      8.1 (Berkeley) 7/19/93
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

/*
 * Internet Group Management Protocol (IGMP) routines.
 * [RFC1112, RFC2236, RFC3376]
 *
 * Written by Steve Deering, Stanford, May 1988.
 * Modified by Rosen Sharma, Stanford, Aug 1994.
 * Modified by Bill Fenner, Xerox PARC, Feb 1995.
 * Modified to fully comply to IGMPv2 by Bill Fenner, Oct 1995.
 * Significantly rewritten for IGMPv3, VIMAGE, and SMP by Bruce Simpson.
 *
 * MULTICAST Revision: 3.5.1.4
 */

#include <sys/cdefs.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/protosw.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/mcache.h>

#include <libkern/libkern.h>
#include <kern/zalloc.h>

#include <net/if.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/igmp.h>
#include <netinet/igmp_var.h>
#include <netinet/kpi_ipfilter_var.h>

SLIST_HEAD(igmp_inm_relhead, in_multi);

static void     igi_initvar(struct igmp_ifinfo *, struct ifnet *, int);
static struct igmp_ifinfo *igi_alloc(int);
static void     igi_free(struct igmp_ifinfo *);
static void     igi_delete(const struct ifnet *, struct igmp_inm_relhead *);
static void     igmp_dispatch_queue(struct igmp_ifinfo *, struct ifqueue *,
    int, const int);
static void     igmp_final_leave(struct in_multi *, struct igmp_ifinfo *,
    struct igmp_tparams *);
static int      igmp_handle_state_change(struct in_multi *,
    struct igmp_ifinfo *, struct igmp_tparams *);
static int      igmp_initial_join(struct in_multi *, struct igmp_ifinfo *,
    struct igmp_tparams *);
static int      igmp_input_v1_query(struct ifnet *, const struct ip *,
    const struct igmp *);
static int      igmp_input_v2_query(struct ifnet *, const struct ip *,
    const struct igmp *);
static int      igmp_input_v3_query(struct ifnet *, const struct ip *,
    /*const*/ struct igmpv3 *);
static int      igmp_input_v3_group_query(struct in_multi *,
    int, /*const*/ struct igmpv3 *);
static int      igmp_input_v1_report(struct ifnet *, struct mbuf *,
    /*const*/ struct ip *, /*const*/ struct igmp *);
static int      igmp_input_v2_report(struct ifnet *, struct mbuf *,
    /*const*/ struct ip *, /*const*/ struct igmp *);
static void     igmp_sendpkt(struct mbuf *);
static __inline__ int   igmp_isgroupreported(const struct in_addr);
static struct mbuf *igmp_ra_alloc(void);
#ifdef IGMP_DEBUG
static const char *igmp_rec_type_to_str(const int);
#endif
static uint32_t igmp_set_version(struct igmp_ifinfo *, const int);
static void     igmp_flush_relq(struct igmp_ifinfo *,
    struct igmp_inm_relhead *);
static int      igmp_v1v2_queue_report(struct in_multi *, const int);
static void     igmp_v1v2_process_group_timer(struct in_multi *, const int);
static void     igmp_v1v2_process_querier_timers(struct igmp_ifinfo *);
static uint32_t igmp_v2_update_group(struct in_multi *, const int);
static void     igmp_v3_cancel_link_timers(struct igmp_ifinfo *);
static uint32_t igmp_v3_dispatch_general_query(struct igmp_ifinfo *);
static struct mbuf *
igmp_v3_encap_report(struct ifnet *, struct mbuf *);
static int      igmp_v3_enqueue_group_record(struct ifqueue *,
    struct in_multi *, const int, const int, const int);
static int      igmp_v3_enqueue_filter_change(struct ifqueue *,
    struct in_multi *);
static void     igmp_v3_process_group_timers(struct igmp_ifinfo *,
    struct ifqueue *, struct ifqueue *, struct in_multi *,
    const int);
static int      igmp_v3_merge_state_changes(struct in_multi *,
    struct ifqueue *);
static void     igmp_v3_suppress_group_record(struct in_multi *);
static int      sysctl_igmp_ifinfo SYSCTL_HANDLER_ARGS;
static int      sysctl_igmp_gsr SYSCTL_HANDLER_ARGS;
static int      sysctl_igmp_default_version SYSCTL_HANDLER_ARGS;

static int igmp_timeout_run;            /* IGMP timer is scheduled to run */
static void igmp_timeout(void *);
static void igmp_sched_timeout(void);

static struct mbuf *m_raopt;            /* Router Alert option */

static int querier_present_timers_running;      /* IGMPv1/v2 older version
                                                 * querier present */
static int interface_timers_running;            /* IGMPv3 general
                                                 * query response */
static int state_change_timers_running;         /* IGMPv3 state-change
                                                 * retransmit */
static int current_state_timers_running;        /* IGMPv1/v2 host
                                                 * report; IGMPv3 g/sg
                                                 * query response */

/*
 * Subsystem lock macros.
 */
#define IGMP_LOCK()                     \
        lck_mtx_lock(&igmp_mtx)
#define IGMP_LOCK_ASSERT_HELD()         \
        LCK_MTX_ASSERT(&igmp_mtx, LCK_MTX_ASSERT_OWNED)
#define IGMP_LOCK_ASSERT_NOTHELD()      \
        LCK_MTX_ASSERT(&igmp_mtx, LCK_MTX_ASSERT_NOTOWNED)
#define IGMP_UNLOCK()                   \
        lck_mtx_unlock(&igmp_mtx)

static LIST_HEAD(, igmp_ifinfo) igi_head;
static struct igmpstat_v3 igmpstat_v3 = {
        .igps_version = IGPS_VERSION_3,
        .igps_len = sizeof(struct igmpstat_v3),
};
static struct igmpstat igmpstat; /* old IGMPv2 stats structure */
static struct timeval igmp_gsrdelay = {.tv_sec = 10, .tv_usec = 0};

static int igmp_recvifkludge = 1;
static int igmp_sendra = 1;
static int igmp_sendlocal = 1;
static int igmp_v1enable = 1;
static int igmp_v2enable = 1;
static int igmp_legacysupp = 0;
static int igmp_default_version = IGMP_VERSION_3;

SYSCTL_STRUCT(_net_inet_igmp, IGMPCTL_STATS, stats, CTLFLAG_RD | CTLFLAG_LOCKED,
    &igmpstat, igmpstat, "");
SYSCTL_STRUCT(_net_inet_igmp, OID_AUTO, v3stats,
    CTLFLAG_RD | CTLFLAG_LOCKED, &igmpstat_v3, igmpstat_v3, "");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, recvifkludge, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_recvifkludge, 0,
    "Rewrite IGMPv1/v2 reports from 0.0.0.0 to contain subnet address");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, sendra, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_sendra, 0,
    "Send IP Router Alert option in IGMPv2/v3 messages");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, sendlocal, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_sendlocal, 0,
    "Send IGMP membership reports for 224.0.0.0/24 groups");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, v1enable, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_v1enable, 0,
    "Enable backwards compatibility with IGMPv1");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, v2enable, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_v2enable, 0,
    "Enable backwards compatibility with IGMPv2");
SYSCTL_INT(_net_inet_igmp, OID_AUTO, legacysupp, CTLFLAG_RW | CTLFLAG_LOCKED,
    &igmp_legacysupp, 0,
    "Allow v1/v2 reports to suppress v3 group responses");
SYSCTL_PROC(_net_inet_igmp, OID_AUTO, default_version,
    CTLTYPE_INT | CTLFLAG_RW,
    &igmp_default_version, 0, sysctl_igmp_default_version, "I",
    "Default version of IGMP to run on each interface");
SYSCTL_PROC(_net_inet_igmp, OID_AUTO, gsrdelay,
    CTLTYPE_INT | CTLFLAG_RW,
    &igmp_gsrdelay.tv_sec, 0, sysctl_igmp_gsr, "I",
    "Rate limit for IGMPv3 Group-and-Source queries in seconds");
#ifdef IGMP_DEBUG
int igmp_debug = 0;
SYSCTL_INT(_net_inet_igmp, OID_AUTO,
    debug, CTLFLAG_RW | CTLFLAG_LOCKED, &igmp_debug, 0, "");
#endif

SYSCTL_NODE(_net_inet_igmp, OID_AUTO, ifinfo, CTLFLAG_RD | CTLFLAG_LOCKED,
    sysctl_igmp_ifinfo, "Per-interface IGMPv3 state");

/* Lock group and attribute for igmp_mtx */
static lck_attr_t       *igmp_mtx_attr;
static lck_grp_t        *igmp_mtx_grp;
static lck_grp_attr_t   *igmp_mtx_grp_attr;

/*
 * Locking and reference counting:
 *
 * igmp_mtx mainly protects igi_head.  In cases where both igmp_mtx and
 * in_multihead_lock must be held, the former must be acquired first in order
 * to maintain lock ordering.  It is not a requirement that igmp_mtx be
 * acquired first before in_multihead_lock, but in case both must be acquired
 * in succession, the correct lock ordering must be followed.
 *
 * Instead of walking the if_multiaddrs list at the interface and returning
 * the ifma_protospec value of a matching entry, we search the global list
 * of in_multi records and find it that way; this is done with in_multihead
 * lock held.  Doing so avoids the race condition issues that many other BSDs
 * suffer from (therefore in our implementation, ifma_protospec will never be
 * NULL for as long as the in_multi is valid.)
 *
 * The above creates a requirement for the in_multi to stay in in_multihead
 * list even after the final IGMP leave (in IGMPv3 mode) until no longer needs
 * be retransmitted (this is not required for IGMPv1/v2.)  In order to handle
 * this, the request and reference counts of the in_multi are bumped up when
 * the state changes to IGMP_LEAVING_MEMBER, and later dropped in the timeout
 * handler.  Each in_multi holds a reference to the underlying igmp_ifinfo.
 *
 * Thus, the permitted lock oder is:
 *
 *      igmp_mtx, in_multihead_lock, inm_lock, igi_lock
 *
 * Any may be taken independently, but if any are held at the same time,
 * the above lock order must be followed.
 */
static decl_lck_mtx_data(, igmp_mtx);
static int igmp_timers_are_running;

#define IGMP_ADD_DETACHED_INM(_head, _inm) {                            \
        SLIST_INSERT_HEAD(_head, _inm, inm_dtle);                       \
}

#define IGMP_REMOVE_DETACHED_INM(_head) {                               \
        struct in_multi *_inm, *_inm_tmp;                               \
        SLIST_FOREACH_SAFE(_inm, _head, inm_dtle, _inm_tmp) {           \
                SLIST_REMOVE(_head, _inm, in_multi, inm_dtle);          \
                INM_REMREF(_inm);                                       \
        }                                                               \
        VERIFY(SLIST_EMPTY(_head));                                     \
}

#define IGI_ZONE_MAX            64              /* maximum elements in zone */
#define IGI_ZONE_NAME           "igmp_ifinfo"   /* zone name */

static unsigned int igi_size;                   /* size of zone element */
static struct zone *igi_zone;                   /* zone for igmp_ifinfo */

/* Store IGMPv3 record count in the module private scratch space */
#define vt_nrecs        pkt_mpriv.__mpriv_u.__mpriv32[0].__mpriv32_u.__val16[0]

static __inline void
igmp_save_context(struct mbuf *m, struct ifnet *ifp)
{
        m->m_pkthdr.rcvif = ifp;
}

static __inline void
igmp_scrub_context(struct mbuf *m)
{
        m->m_pkthdr.rcvif = NULL;
}

#ifdef IGMP_DEBUG
static __inline const char *
inet_ntop_haddr(in_addr_t haddr, char *buf, socklen_t size)
{
        struct in_addr ia;

        ia.s_addr = htonl(haddr);
        return inet_ntop(AF_INET, &ia, buf, size);
}
#endif

/*
 * Restore context from a queued IGMP output chain.
 * Return saved ifp.
 */
static __inline struct ifnet *
igmp_restore_context(struct mbuf *m)
{
        return m->m_pkthdr.rcvif;
}

/*
 * Retrieve or set default IGMP version.
 */
static int
sysctl_igmp_default_version SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2)
        int      error;
        int      new;

        IGMP_LOCK();

        error = SYSCTL_OUT(req, arg1, sizeof(int));
        if (error || !req->newptr) {
                goto out_locked;
        }

        new = igmp_default_version;

        error = SYSCTL_IN(req, &new, sizeof(int));
        if (error) {
                goto out_locked;
        }

        if (new < IGMP_VERSION_1 || new > IGMP_VERSION_3) {
                error = EINVAL;
                goto out_locked;
        }

        IGMP_PRINTF(("%s: change igmp_default_version from %d to %d\n",
            __func__, igmp_default_version, new));

        igmp_default_version = new;

out_locked:
        IGMP_UNLOCK();
        return error;
}

/*
 * Retrieve or set threshold between group-source queries in seconds.
 *
 */
static int
sysctl_igmp_gsr SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int error;
        int i;

        IGMP_LOCK();

        i = igmp_gsrdelay.tv_sec;

        error = sysctl_handle_int(oidp, &i, 0, req);
        if (error || !req->newptr) {
                goto out_locked;
        }

        if (i < -1 || i >= 60) {
                error = EINVAL;
                goto out_locked;
        }

        igmp_gsrdelay.tv_sec = i;

out_locked:
        IGMP_UNLOCK();
        return error;
}

/*
 * Expose struct igmp_ifinfo to userland, keyed by ifindex.
 * For use by ifmcstat(8).
 *
 */
static int
sysctl_igmp_ifinfo SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp)
        int                     *name;
        int                      error;
        u_int                    namelen;
        struct ifnet            *ifp;
        struct igmp_ifinfo      *igi;
        struct igmp_ifinfo_u    igi_u;

        name = (int *)arg1;
        namelen = arg2;

        if (req->newptr != USER_ADDR_NULL) {
                return EPERM;
        }

        if (namelen != 1) {
                return EINVAL;
        }

        IGMP_LOCK();

        if (name[0] <= 0 || name[0] > (u_int)if_index) {
                error = ENOENT;
                goto out_locked;
        }

        error = ENOENT;

        ifnet_head_lock_shared();
        ifp = ifindex2ifnet[name[0]];
        ifnet_head_done();
        if (ifp == NULL) {
                goto out_locked;
        }

        bzero(&igi_u, sizeof(igi_u));

        LIST_FOREACH(igi, &igi_head, igi_link) {
                IGI_LOCK(igi);
                if (ifp != igi->igi_ifp) {
                        IGI_UNLOCK(igi);
                        continue;
                }
                igi_u.igi_ifindex = igi->igi_ifp->if_index;
                igi_u.igi_version = igi->igi_version;
                igi_u.igi_v1_timer = igi->igi_v1_timer;
                igi_u.igi_v2_timer = igi->igi_v2_timer;
                igi_u.igi_v3_timer = igi->igi_v3_timer;
                igi_u.igi_flags = igi->igi_flags;
                igi_u.igi_rv = igi->igi_rv;
                igi_u.igi_qi = igi->igi_qi;
                igi_u.igi_qri = igi->igi_qri;
                igi_u.igi_uri = igi->igi_uri;
                IGI_UNLOCK(igi);

                error = SYSCTL_OUT(req, &igi_u, sizeof(igi_u));
                break;
        }

out_locked:
        IGMP_UNLOCK();
        return error;
}

/*
 * Dispatch an entire queue of pending packet chains
 *
 * Must not be called with inm_lock held.
 */
static void
igmp_dispatch_queue(struct igmp_ifinfo *igi, struct ifqueue *ifq, int limit,
    const int loop)
{
        struct mbuf *m;
        struct ip *ip;

        if (igi != NULL) {
                IGI_LOCK_ASSERT_HELD(igi);
        }

        for (;;) {
                IF_DEQUEUE(ifq, m);
                if (m == NULL) {
                        break;
                }
                IGMP_PRINTF(("%s: dispatch 0x%llx from 0x%llx\n", __func__,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifq),
                    (uint64_t)VM_KERNEL_ADDRPERM(m)));
                ip = mtod(m, struct ip *);
                if (loop) {
                        m->m_flags |= M_IGMP_LOOP;
                }
                if (igi != NULL) {
                        IGI_UNLOCK(igi);
                }
                igmp_sendpkt(m);
                if (igi != NULL) {
                        IGI_LOCK(igi);
                }
                if (--limit == 0) {
                        break;
                }
        }

        if (igi != NULL) {
                IGI_LOCK_ASSERT_HELD(igi);
        }
}

/*
 * Filter outgoing IGMP report state by group.
 *
 * Reports are ALWAYS suppressed for ALL-HOSTS (224.0.0.1).
 * If the net.inet.igmp.sendlocal sysctl is 0, then IGMP reports are
 * disabled for all groups in the 224.0.0.0/24 link-local scope. However,
 * this may break certain IGMP snooping switches which rely on the old
 * report behaviour.
 *
 * Return zero if the given group is one for which IGMP reports
 * should be suppressed, or non-zero if reports should be issued.
 */

static __inline__
int
igmp_isgroupreported(const struct in_addr addr)
{
        if (in_allhosts(addr) ||
            ((!igmp_sendlocal && IN_LOCAL_GROUP(ntohl(addr.s_addr))))) {
                return 0;
        }

        return 1;
}

/*
 * Construct a Router Alert option to use in outgoing packets.
 */
static struct mbuf *
igmp_ra_alloc(void)
{
        struct mbuf     *m;
        struct ipoption *p;

        MGET(m, M_WAITOK, MT_DATA);
        p = mtod(m, struct ipoption *);
        p->ipopt_dst.s_addr = INADDR_ANY;
        p->ipopt_list[0] = (char)IPOPT_RA;      /* Router Alert Option */
        p->ipopt_list[1] = 0x04;        /* 4 bytes long */
        p->ipopt_list[2] = IPOPT_EOL;   /* End of IP option list */
        p->ipopt_list[3] = 0x00;        /* pad byte */
        m->m_len = sizeof(p->ipopt_dst) + p->ipopt_list[1];

        return m;
}

/*
 * Attach IGMP when PF_INET is attached to an interface.
 */
struct igmp_ifinfo *
igmp_domifattach(struct ifnet *ifp, int how)
{
        struct igmp_ifinfo *igi;

        IGMP_PRINTF(("%s: called for ifp 0x%llx(%s)\n",
            __func__, (uint64_t)VM_KERNEL_ADDRPERM(ifp), ifp->if_name));

        igi = igi_alloc(how);
        if (igi == NULL) {
                return NULL;
        }

        IGMP_LOCK();

        IGI_LOCK(igi);
        igi_initvar(igi, ifp, 0);
        igi->igi_debug |= IFD_ATTACHED;
        IGI_ADDREF_LOCKED(igi); /* hold a reference for igi_head */
        IGI_ADDREF_LOCKED(igi); /* hold a reference for caller */
        IGI_UNLOCK(igi);
        ifnet_lock_shared(ifp);
        igmp_initsilent(ifp, igi);
        ifnet_lock_done(ifp);

        LIST_INSERT_HEAD(&igi_head, igi, igi_link);

        IGMP_UNLOCK();

        IGMP_PRINTF(("%s: allocate igmp_ifinfo for ifp 0x%llx(%s)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), ifp->if_name));

        return igi;
}

/*
 * Attach IGMP when PF_INET is reattached to an interface.  Caller is
 * expected to have an outstanding reference to the igi.
 */
void
igmp_domifreattach(struct igmp_ifinfo *igi)
{
        struct ifnet *ifp;

        IGMP_LOCK();

        IGI_LOCK(igi);
        VERIFY(!(igi->igi_debug & IFD_ATTACHED));
        ifp = igi->igi_ifp;
        VERIFY(ifp != NULL);
        igi_initvar(igi, ifp, 1);
        igi->igi_debug |= IFD_ATTACHED;
        IGI_ADDREF_LOCKED(igi); /* hold a reference for igi_head */
        IGI_UNLOCK(igi);
        ifnet_lock_shared(ifp);
        igmp_initsilent(ifp, igi);
        ifnet_lock_done(ifp);

        LIST_INSERT_HEAD(&igi_head, igi, igi_link);

        IGMP_UNLOCK();

        IGMP_PRINTF(("%s: reattached igmp_ifinfo for ifp 0x%llx(%s)\n",
            __func__, (uint64_t)VM_KERNEL_ADDRPERM(ifp), ifp->if_name));
}

/*
 * Hook for domifdetach.
 */
void
igmp_domifdetach(struct ifnet *ifp)
{
        SLIST_HEAD(, in_multi) inm_dthead;

        SLIST_INIT(&inm_dthead);

        IGMP_PRINTF(("%s: called for ifp 0x%llx(%s%d)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), ifp->if_name, ifp->if_unit));

        IGMP_LOCK();
        igi_delete(ifp, (struct igmp_inm_relhead *)&inm_dthead);
        IGMP_UNLOCK();

        /* Now that we're dropped all locks, release detached records */
        IGMP_REMOVE_DETACHED_INM(&inm_dthead);
}

/*
 * Called at interface detach time.  Note that we only flush all deferred
 * responses and record releases; all remaining inm records and their source
 * entries related to this interface are left intact, in order to handle
 * the reattach case.
 */
static void
igi_delete(const struct ifnet *ifp, struct igmp_inm_relhead *inm_dthead)
{
        struct igmp_ifinfo *igi, *tigi;

        IGMP_LOCK_ASSERT_HELD();

        LIST_FOREACH_SAFE(igi, &igi_head, igi_link, tigi) {
                IGI_LOCK(igi);
                if (igi->igi_ifp == ifp) {
                        /*
                         * Free deferred General Query responses.
                         */
                        IF_DRAIN(&igi->igi_gq);
                        IF_DRAIN(&igi->igi_v2q);
                        igmp_flush_relq(igi, inm_dthead);
                        VERIFY(SLIST_EMPTY(&igi->igi_relinmhead));
                        igi->igi_debug &= ~IFD_ATTACHED;
                        IGI_UNLOCK(igi);

                        LIST_REMOVE(igi, igi_link);
                        IGI_REMREF(igi); /* release igi_head reference */
                        return;
                }
                IGI_UNLOCK(igi);
        }
        panic("%s: igmp_ifinfo not found for ifp %p(%s)\n", __func__,
            ifp, ifp->if_xname);
}

__private_extern__ void
igmp_initsilent(struct ifnet *ifp, struct igmp_ifinfo *igi)
{
        ifnet_lock_assert(ifp, IFNET_LCK_ASSERT_OWNED);

        IGI_LOCK_ASSERT_NOTHELD(igi);
        IGI_LOCK(igi);
        if (!(ifp->if_flags & IFF_MULTICAST)) {
                igi->igi_flags |= IGIF_SILENT;
        } else {
                igi->igi_flags &= ~IGIF_SILENT;
        }
        IGI_UNLOCK(igi);
}

static void
igi_initvar(struct igmp_ifinfo *igi, struct ifnet *ifp, int reattach)
{
        IGI_LOCK_ASSERT_HELD(igi);

        igi->igi_ifp = ifp;
        igi->igi_version = igmp_default_version;
        igi->igi_flags = 0;
        igi->igi_rv = IGMP_RV_INIT;
        igi->igi_qi = IGMP_QI_INIT;
        igi->igi_qri = IGMP_QRI_INIT;
        igi->igi_uri = IGMP_URI_INIT;

        if (!reattach) {
                SLIST_INIT(&igi->igi_relinmhead);
        }

        /*
         * Responses to general queries are subject to bounds.
         */
        igi->igi_gq.ifq_maxlen =  IGMP_MAX_RESPONSE_PACKETS;
        igi->igi_v2q.ifq_maxlen = IGMP_MAX_RESPONSE_PACKETS;
}

static struct igmp_ifinfo *
igi_alloc(int how)
{
        struct igmp_ifinfo *igi;

        igi = (how == M_WAITOK) ? zalloc(igi_zone) : zalloc_noblock(igi_zone);
        if (igi != NULL) {
                bzero(igi, igi_size);
                lck_mtx_init(&igi->igi_lock, igmp_mtx_grp, igmp_mtx_attr);
                igi->igi_debug |= IFD_ALLOC;
        }
        return igi;
}

static void
igi_free(struct igmp_ifinfo *igi)
{
        IGI_LOCK(igi);
        if (igi->igi_debug & IFD_ATTACHED) {
                panic("%s: attached igi=%p is being freed", __func__, igi);
                /* NOTREACHED */
        } else if (igi->igi_ifp != NULL) {
                panic("%s: ifp not NULL for igi=%p", __func__, igi);
                /* NOTREACHED */
        } else if (!(igi->igi_debug & IFD_ALLOC)) {
                panic("%s: igi %p cannot be freed", __func__, igi);
                /* NOTREACHED */
        } else if (igi->igi_refcnt != 0) {
                panic("%s: non-zero refcnt igi=%p", __func__, igi);
                /* NOTREACHED */
        }
        igi->igi_debug &= ~IFD_ALLOC;
        IGI_UNLOCK(igi);

        lck_mtx_destroy(&igi->igi_lock, igmp_mtx_grp);
        zfree(igi_zone, igi);
}

void
igi_addref(struct igmp_ifinfo *igi, int locked)
{
        if (!locked) {
                IGI_LOCK_SPIN(igi);
        } else {
                IGI_LOCK_ASSERT_HELD(igi);
        }

        if (++igi->igi_refcnt == 0) {
                panic("%s: igi=%p wraparound refcnt", __func__, igi);
                /* NOTREACHED */
        }
        if (!locked) {
                IGI_UNLOCK(igi);
        }
}

void
igi_remref(struct igmp_ifinfo *igi)
{
        SLIST_HEAD(, in_multi) inm_dthead;
        struct ifnet *ifp;

        IGI_LOCK_SPIN(igi);

        if (igi->igi_refcnt == 0) {
                panic("%s: igi=%p negative refcnt", __func__, igi);
                /* NOTREACHED */
        }

        --igi->igi_refcnt;
        if (igi->igi_refcnt > 0) {
                IGI_UNLOCK(igi);
                return;
        }

        ifp = igi->igi_ifp;
        igi->igi_ifp = NULL;
        IF_DRAIN(&igi->igi_gq);
        IF_DRAIN(&igi->igi_v2q);
        SLIST_INIT(&inm_dthead);
        igmp_flush_relq(igi, (struct igmp_inm_relhead *)&inm_dthead);
        VERIFY(SLIST_EMPTY(&igi->igi_relinmhead));
        IGI_UNLOCK(igi);

        /* Now that we're dropped all locks, release detached records */
        IGMP_REMOVE_DETACHED_INM(&inm_dthead);

        IGMP_PRINTF(("%s: freeing igmp_ifinfo for ifp 0x%llx(%s)\n",
            __func__, (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));

        igi_free(igi);
}

/*
 * Process a received IGMPv1 query.
 * Return non-zero if the message should be dropped.
 */
static int
igmp_input_v1_query(struct ifnet *ifp, const struct ip *ip,
    const struct igmp *igmp)
{
        struct igmp_ifinfo      *igi;
        struct in_multi         *inm;
        struct in_multistep     step;
        struct igmp_tparams     itp = { .qpt = 0, .it = 0, .cst = 0, .sct = 0 };

        IGMP_LOCK_ASSERT_NOTHELD();

        /*
         * IGMPv1 Host Membership Queries SHOULD always be addressed to
         * 224.0.0.1. They are always treated as General Queries.
         * igmp_group is always ignored. Do not drop it as a userland
         * daemon may wish to see it.
         */
        if (!in_allhosts(ip->ip_dst) || !in_nullhost(igmp->igmp_group)) {
                IGMPSTAT_INC(igps_rcv_badqueries);
                OIGMPSTAT_INC(igps_rcv_badqueries);
                goto done;
        }
        IGMPSTAT_INC(igps_rcv_gen_queries);

        igi = IGMP_IFINFO(ifp);
        VERIFY(igi != NULL);

        IGI_LOCK(igi);
        if (igi->igi_flags & IGIF_LOOPBACK) {
                IGMP_PRINTF(("%s: ignore v1 query on IGIF_LOOPBACK "
                    "ifp 0x%llx(%s)\n", __func__,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                IGI_UNLOCK(igi);
                goto done;
        }
        /*
         * Switch to IGMPv1 host compatibility mode.
         */
        itp.qpt = igmp_set_version(igi, IGMP_VERSION_1);
        IGI_UNLOCK(igi);

        IGMP_PRINTF(("%s: process v1 query on ifp 0x%llx(%s)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));

        /*
         * Start the timers in all of our group records
         * for the interface on which the query arrived,
         * except those which are already running.
         */
        in_multihead_lock_shared();
        IN_FIRST_MULTI(step, inm);
        while (inm != NULL) {
                INM_LOCK(inm);
                if (inm->inm_ifp != ifp || inm->inm_timer != 0) {
                        goto next;
                }

                switch (inm->inm_state) {
                case IGMP_NOT_MEMBER:
                case IGMP_SILENT_MEMBER:
                        break;
                case IGMP_G_QUERY_PENDING_MEMBER:
                case IGMP_SG_QUERY_PENDING_MEMBER:
                case IGMP_REPORTING_MEMBER:
                case IGMP_IDLE_MEMBER:
                case IGMP_LAZY_MEMBER:
                case IGMP_SLEEPING_MEMBER:
                case IGMP_AWAKENING_MEMBER:
                        inm->inm_state = IGMP_REPORTING_MEMBER;
                        inm->inm_timer = IGMP_RANDOM_DELAY(IGMP_V1V2_MAX_RI);
                        itp.cst = 1;
                        break;
                case IGMP_LEAVING_MEMBER:
                        break;
                }
next:
                INM_UNLOCK(inm);
                IN_NEXT_MULTI(step, inm);
        }
        in_multihead_lock_done();
done:
        igmp_set_timeout(&itp);

        return 0;
}

/*
 * Process a received IGMPv2 general or group-specific query.
 */
static int
igmp_input_v2_query(struct ifnet *ifp, const struct ip *ip,
    const struct igmp *igmp)
{
        struct igmp_ifinfo      *igi;
        struct in_multi         *inm;
        int                      is_general_query;
        uint16_t                 timer;
        struct igmp_tparams      itp = { .qpt = 0, .it = 0, .cst = 0, .sct = 0 };

        IGMP_LOCK_ASSERT_NOTHELD();

        is_general_query = 0;

        /*
         * Validate address fields upfront.
         */
        if (in_nullhost(igmp->igmp_group)) {
                /*
                 * IGMPv2 General Query.
                 * If this was not sent to the all-hosts group, ignore it.
                 */
                if (!in_allhosts(ip->ip_dst)) {
                        goto done;
                }
                IGMPSTAT_INC(igps_rcv_gen_queries);
                is_general_query = 1;
        } else {
                /* IGMPv2 Group-Specific Query. */
                IGMPSTAT_INC(igps_rcv_group_queries);
        }

        igi = IGMP_IFINFO(ifp);
        VERIFY(igi != NULL);

        IGI_LOCK(igi);
        if (igi->igi_flags & IGIF_LOOPBACK) {
                IGMP_PRINTF(("%s: ignore v2 query on IGIF_LOOPBACK "
                    "ifp 0x%llx(%s)\n", __func__,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                IGI_UNLOCK(igi);
                goto done;
        }
        /*
         * Ignore v2 query if in v1 Compatibility Mode.
         */
        if (igi->igi_version == IGMP_VERSION_1) {
                IGI_UNLOCK(igi);
                goto done;
        }
        itp.qpt = igmp_set_version(igi, IGMP_VERSION_2);
        IGI_UNLOCK(igi);

        timer = igmp->igmp_code / IGMP_TIMER_SCALE;
        if (timer == 0) {
                timer = 1;
        }

        if (is_general_query) {
                struct in_multistep step;

                IGMP_PRINTF(("%s: process v2 general query on ifp 0x%llx(%s)\n",
                    __func__, (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                /*
                 * For each reporting group joined on this
                 * interface, kick the report timer.
                 */
                in_multihead_lock_shared();
                IN_FIRST_MULTI(step, inm);
                while (inm != NULL) {
                        INM_LOCK(inm);
                        if (inm->inm_ifp == ifp) {
                                itp.cst += igmp_v2_update_group(inm, timer);
                        }
                        INM_UNLOCK(inm);
                        IN_NEXT_MULTI(step, inm);
                }
                in_multihead_lock_done();
        } else {
                /*
                 * Group-specific IGMPv2 query, we need only
                 * look up the single group to process it.
                 */
                in_multihead_lock_shared();
                IN_LOOKUP_MULTI(&igmp->igmp_group, ifp, inm);
                in_multihead_lock_done();
                if (inm != NULL) {
                        INM_LOCK(inm);
                        IGMP_INET_PRINTF(igmp->igmp_group,
                            ("process v2 query %s on ifp 0x%llx(%s)\n",
                            _igmp_inet_buf,
                            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                        itp.cst = igmp_v2_update_group(inm, timer);
                        INM_UNLOCK(inm);
                        INM_REMREF(inm); /* from IN_LOOKUP_MULTI */
                }
        }
done:
        igmp_set_timeout(&itp);

        return 0;
}

/*
 * Update the report timer on a group in response to an IGMPv2 query.
 *
 * If we are becoming the reporting member for this group, start the timer.
 * If we already are the reporting member for this group, and timer is
 * below the threshold, reset it.
 *
 * We may be updating the group for the first time since we switched
 * to IGMPv3. If we are, then we must clear any recorded source lists,
 * and transition to REPORTING state; the group timer is overloaded
 * for group and group-source query responses.
 *
 * Unlike IGMPv3, the delay per group should be jittered
 * to avoid bursts of IGMPv2 reports.
 */
static uint32_t
igmp_v2_update_group(struct in_multi *inm, const int timer)
{
        IGMP_INET_PRINTF(inm->inm_addr, ("%s: %s/%s timer=%d\n",
            __func__, _igmp_inet_buf, if_name(inm->inm_ifp),
            timer));

        INM_LOCK_ASSERT_HELD(inm);

        switch (inm->inm_state) {
        case IGMP_NOT_MEMBER:
        case IGMP_SILENT_MEMBER:
                break;
        case IGMP_REPORTING_MEMBER:
                if (inm->inm_timer != 0 &&
                    inm->inm_timer <= timer) {
                        IGMP_PRINTF(("%s: REPORTING and timer running, "
                            "skipping.\n", __func__));
                        break;
                }
        /* FALLTHROUGH */
        case IGMP_SG_QUERY_PENDING_MEMBER:
        case IGMP_G_QUERY_PENDING_MEMBER:
        case IGMP_IDLE_MEMBER:
        case IGMP_LAZY_MEMBER:
        case IGMP_AWAKENING_MEMBER:
                IGMP_PRINTF(("%s: ->REPORTING\n", __func__));
                inm->inm_state = IGMP_REPORTING_MEMBER;
                inm->inm_timer = IGMP_RANDOM_DELAY(timer);
                break;
        case IGMP_SLEEPING_MEMBER:
                IGMP_PRINTF(("%s: ->AWAKENING\n", __func__));
                inm->inm_state = IGMP_AWAKENING_MEMBER;
                break;
        case IGMP_LEAVING_MEMBER:
                break;
        }

        return inm->inm_timer;
}

/*
 * Process a received IGMPv3 general, group-specific or
 * group-and-source-specific query.
 * Assumes m has already been pulled up to the full IGMP message length.
 * Return 0 if successful, otherwise an appropriate error code is returned.
 */
static int
igmp_input_v3_query(struct ifnet *ifp, const struct ip *ip,
    /*const*/ struct igmpv3 *igmpv3)
{
        struct igmp_ifinfo      *igi;
        struct in_multi         *inm;
        int                      is_general_query;
        uint32_t                 maxresp, nsrc, qqi;
        uint16_t                 timer;
        uint8_t                  qrv;
        struct igmp_tparams      itp = { .qpt = 0, .it = 0, .cst = 0, .sct = 0 };

        IGMP_LOCK_ASSERT_NOTHELD();

        is_general_query = 0;

        IGMP_PRINTF(("%s: process v3 query on ifp 0x%llx(%s)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));

        maxresp = igmpv3->igmp_code;    /* in 1/10ths of a second */
        if (maxresp >= 128) {
                maxresp = IGMP_MANT(igmpv3->igmp_code) <<
                    (IGMP_EXP(igmpv3->igmp_code) + 3);
        }

        /*
         * Robustness must never be less than 2 for on-wire IGMPv3.
         * FUTURE: Check if ifp has IGIF_LOOPBACK set, as we will make
         * an exception for interfaces whose IGMPv3 state changes
         * are redirected to loopback (e.g. MANET).
         */
        qrv = IGMP_QRV(igmpv3->igmp_misc);
        if (qrv < 2) {
                IGMP_PRINTF(("%s: clamping qrv %d to %d\n", __func__,
                    qrv, IGMP_RV_INIT));
                qrv = IGMP_RV_INIT;
        }

        qqi = igmpv3->igmp_qqi;
        if (qqi >= 128) {
                qqi = IGMP_MANT(igmpv3->igmp_qqi) <<
                    (IGMP_EXP(igmpv3->igmp_qqi) + 3);
        }

        timer = maxresp / IGMP_TIMER_SCALE;
        if (timer == 0) {
                timer = 1;
        }

        nsrc = ntohs(igmpv3->igmp_numsrc);

        /*
         * Validate address fields and versions upfront before
         * accepting v3 query.
         */
        if (in_nullhost(igmpv3->igmp_group)) {
                /*
                 * IGMPv3 General Query.
                 *
                 * General Queries SHOULD be directed to 224.0.0.1.
                 * A general query with a source list has undefined
                 * behaviour; discard it.
                 */
                IGMPSTAT_INC(igps_rcv_gen_queries);
                if (!in_allhosts(ip->ip_dst) || nsrc > 0) {
                        IGMPSTAT_INC(igps_rcv_badqueries);
                        OIGMPSTAT_INC(igps_rcv_badqueries);
                        goto done;
                }
                is_general_query = 1;
        } else {
                /* Group or group-source specific query. */
                if (nsrc == 0) {
                        IGMPSTAT_INC(igps_rcv_group_queries);
                } else {
                        IGMPSTAT_INC(igps_rcv_gsr_queries);
                }
        }

        igi = IGMP_IFINFO(ifp);
        VERIFY(igi != NULL);

        IGI_LOCK(igi);
        if (igi->igi_flags & IGIF_LOOPBACK) {
                IGMP_PRINTF(("%s: ignore v3 query on IGIF_LOOPBACK "
                    "ifp 0x%llx(%s)\n", __func__,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                IGI_UNLOCK(igi);
                goto done;
        }

        /*
         * Discard the v3 query if we're in Compatibility Mode.
         * The RFC is not obviously worded that hosts need to stay in
         * compatibility mode until the Old Version Querier Present
         * timer expires.
         */
        if (igi->igi_version != IGMP_VERSION_3) {
                IGMP_PRINTF(("%s: ignore v3 query in v%d mode on "
                    "ifp 0x%llx(%s)\n", __func__, igi->igi_version,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                IGI_UNLOCK(igi);
                goto done;
        }

        itp.qpt = igmp_set_version(igi, IGMP_VERSION_3);
        igi->igi_rv = qrv;
        igi->igi_qi = qqi;
        igi->igi_qri = MAX(timer, IGMP_QRI_MIN);

        IGMP_PRINTF(("%s: qrv %d qi %d qri %d\n", __func__, igi->igi_rv,
            igi->igi_qi, igi->igi_qri));

        if (is_general_query) {
                /*
                 * Schedule a current-state report on this ifp for
                 * all groups, possibly containing source lists.
                 * If there is a pending General Query response
                 * scheduled earlier than the selected delay, do
                 * not schedule any other reports.
                 * Otherwise, reset the interface timer.
                 */
                IGMP_PRINTF(("%s: process v3 general query on ifp 0x%llx(%s)\n",
                    __func__, (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                if (igi->igi_v3_timer == 0 || igi->igi_v3_timer >= timer) {
                        itp.it = igi->igi_v3_timer = IGMP_RANDOM_DELAY(timer);
                }
                IGI_UNLOCK(igi);
        } else {
                IGI_UNLOCK(igi);
                /*
                 * Group-source-specific queries are throttled on
                 * a per-group basis to defeat denial-of-service attempts.
                 * Queries for groups we are not a member of on this
                 * link are simply ignored.
                 */
                in_multihead_lock_shared();
                IN_LOOKUP_MULTI(&igmpv3->igmp_group, ifp, inm);
                in_multihead_lock_done();
                if (inm == NULL) {
                        goto done;
                }

                INM_LOCK(inm);
                if (nsrc > 0) {
                        if (!ratecheck(&inm->inm_lastgsrtv,
                            &igmp_gsrdelay)) {
                                IGMP_PRINTF(("%s: GS query throttled.\n",
                                    __func__));
                                IGMPSTAT_INC(igps_drop_gsr_queries);
                                INM_UNLOCK(inm);
                                INM_REMREF(inm); /* from IN_LOOKUP_MULTI */
                                goto done;
                        }
                }
                IGMP_INET_PRINTF(igmpv3->igmp_group,
                    ("process v3 %s query on ifp 0x%llx(%s)\n", _igmp_inet_buf,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                /*
                 * If there is a pending General Query response
                 * scheduled sooner than the selected delay, no
                 * further report need be scheduled.
                 * Otherwise, prepare to respond to the
                 * group-specific or group-and-source query.
                 */
                IGI_LOCK(igi);
                itp.it = igi->igi_v3_timer;
                IGI_UNLOCK(igi);
                if (itp.it == 0 || itp.it >= timer) {
                        (void) igmp_input_v3_group_query(inm, timer, igmpv3);
                        itp.cst = inm->inm_timer;
                }
                INM_UNLOCK(inm);
                INM_REMREF(inm); /* from IN_LOOKUP_MULTI */
        }
done:
        if (itp.it > 0) {
                IGMP_PRINTF(("%s: v3 general query response scheduled in "
                    "T+%d seconds on ifp 0x%llx(%s)\n", __func__, itp.it,
                    (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
        }
        igmp_set_timeout(&itp);

        return 0;
}

/*
 * Process a recieved IGMPv3 group-specific or group-and-source-specific
 * query.
 * Return <0 if any error occured. Currently this is ignored.
 */
static int
igmp_input_v3_group_query(struct in_multi *inm,
    int timer, /*const*/ struct igmpv3 *igmpv3)
{
        int                      retval;
        uint16_t                 nsrc;

        INM_LOCK_ASSERT_HELD(inm);

        retval = 0;

        switch (inm->inm_state) {
        case IGMP_NOT_MEMBER:
        case IGMP_SILENT_MEMBER:
        case IGMP_SLEEPING_MEMBER:
        case IGMP_LAZY_MEMBER:
        case IGMP_AWAKENING_MEMBER:
        case IGMP_IDLE_MEMBER:
        case IGMP_LEAVING_MEMBER:
                return retval;
        case IGMP_REPORTING_MEMBER:
        case IGMP_G_QUERY_PENDING_MEMBER:
        case IGMP_SG_QUERY_PENDING_MEMBER:
                break;
        }

        nsrc = ntohs(igmpv3->igmp_numsrc);

        /*
         * Deal with group-specific queries upfront.
         * If any group query is already pending, purge any recorded
         * source-list state if it exists, and schedule a query response
         * for this group-specific query.
         */
        if (nsrc == 0) {
                if (inm->inm_state == IGMP_G_QUERY_PENDING_MEMBER ||
                    inm->inm_state == IGMP_SG_QUERY_PENDING_MEMBER) {
                        inm_clear_recorded(inm);
                        timer = min(inm->inm_timer, timer);
                }
                inm->inm_state = IGMP_G_QUERY_PENDING_MEMBER;
                inm->inm_timer = IGMP_RANDOM_DELAY(timer);
                return retval;
        }

        /*
         * Deal with the case where a group-and-source-specific query has
         * been received but a group-specific query is already pending.
         */
        if (inm->inm_state == IGMP_G_QUERY_PENDING_MEMBER) {
                timer = min(inm->inm_timer, timer);
                inm->inm_timer = IGMP_RANDOM_DELAY(timer);
                return retval;
        }

        /*
         * Finally, deal with the case where a group-and-source-specific
         * query has been received, where a response to a previous g-s-r
         * query exists, or none exists.
         * In this case, we need to parse the source-list which the Querier
         * has provided us with and check if we have any source list filter
         * entries at T1 for these sources. If we do not, there is no need
         * schedule a report and the query may be dropped.
         * If we do, we must record them and schedule a current-state
         * report for those sources.
         * FIXME: Handling source lists larger than 1 mbuf requires that
         * we pass the mbuf chain pointer down to this function, and use
         * m_getptr() to walk the chain.
         */
        if (inm->inm_nsrc > 0) {
                const struct in_addr    *ap;
                int                      i, nrecorded;

                ap = (const struct in_addr *)(igmpv3 + 1);
                nrecorded = 0;
                for (i = 0; i < nsrc; i++, ap++) {
                        retval = inm_record_source(inm, ap->s_addr);
                        if (retval < 0) {
                                break;
                        }
                        nrecorded += retval;
                }
                if (nrecorded > 0) {
                        IGMP_PRINTF(("%s: schedule response to SG query\n",
                            __func__));
                        inm->inm_state = IGMP_SG_QUERY_PENDING_MEMBER;
                        inm->inm_timer = IGMP_RANDOM_DELAY(timer);
                }
        }

        return retval;
}

/*
 * Process a received IGMPv1 host membership report.
 *
 * NOTE: 0.0.0.0 workaround breaks const correctness.
 */
static int
igmp_input_v1_report(struct ifnet *ifp, struct mbuf *m, /*const*/ struct ip *ip,
    /*const*/ struct igmp *igmp)
{
        struct in_ifaddr *ia;
        struct in_multi *inm;

        IGMPSTAT_INC(igps_rcv_reports);
        OIGMPSTAT_INC(igps_rcv_reports);

        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
                return 0;
        }

        if (!IN_MULTICAST(ntohl(igmp->igmp_group.s_addr) ||
            !in_hosteq(igmp->igmp_group, ip->ip_dst))) {
                IGMPSTAT_INC(igps_rcv_badreports);
                OIGMPSTAT_INC(igps_rcv_badreports);
                return EINVAL;
        }

        /*
         * RFC 3376, Section 4.2.13, 9.2, 9.3:
         * Booting clients may use the source address 0.0.0.0. Some
         * IGMP daemons may not know how to use IP_RECVIF to determine
         * the interface upon which this message was received.
         * Replace 0.0.0.0 with the subnet address if told to do so.
         */
        if (igmp_recvifkludge && in_nullhost(ip->ip_src)) {
                IFP_TO_IA(ifp, ia);
                if (ia != NULL) {
                        IFA_LOCK(&ia->ia_ifa);
                        ip->ip_src.s_addr = htonl(ia->ia_subnet);
                        IFA_UNLOCK(&ia->ia_ifa);
                        IFA_REMREF(&ia->ia_ifa);
                }
        }

        IGMP_INET_PRINTF(igmp->igmp_group,
            ("process v1 report %s on ifp 0x%llx(%s)\n", _igmp_inet_buf,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));

        /*
         * IGMPv1 report suppression.
         * If we are a member of this group, and our membership should be
         * reported, stop our group timer and transition to the 'lazy' state.
         */
        in_multihead_lock_shared();
        IN_LOOKUP_MULTI(&igmp->igmp_group, ifp, inm);
        in_multihead_lock_done();
        if (inm != NULL) {
                struct igmp_ifinfo *igi;

                INM_LOCK(inm);

                igi = inm->inm_igi;
                VERIFY(igi != NULL);

                IGMPSTAT_INC(igps_rcv_ourreports);
                OIGMPSTAT_INC(igps_rcv_ourreports);

                /*
                 * If we are in IGMPv3 host mode, do not allow the
                 * other host's IGMPv1 report to suppress our reports
                 * unless explicitly configured to do so.
                 */
                IGI_LOCK(igi);
                if (igi->igi_version == IGMP_VERSION_3) {
                        if (igmp_legacysupp) {
                                igmp_v3_suppress_group_record(inm);
                        }
                        IGI_UNLOCK(igi);
                        INM_UNLOCK(inm);
                        INM_REMREF(inm); /* from IN_LOOKUP_MULTI */
                        return 0;
                }

                INM_LOCK_ASSERT_HELD(inm);
                inm->inm_timer = 0;

                switch (inm->inm_state) {
                case IGMP_NOT_MEMBER:
                case IGMP_SILENT_MEMBER:
                        break;
                case IGMP_IDLE_MEMBER:
                case IGMP_LAZY_MEMBER:
                case IGMP_AWAKENING_MEMBER:
                        IGMP_INET_PRINTF(igmp->igmp_group,
                            ("report suppressed for %s on ifp 0x%llx(%s)\n",
                            _igmp_inet_buf,
                            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                case IGMP_SLEEPING_MEMBER:
                        inm->inm_state = IGMP_SLEEPING_MEMBER;
                        break;
                case IGMP_REPORTING_MEMBER:
                        IGMP_INET_PRINTF(igmp->igmp_group,
                            ("report suppressed for %s on ifp 0x%llx(%s)\n",
                            _igmp_inet_buf,
                            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));
                        if (igi->igi_version == IGMP_VERSION_1) {
                                inm->inm_state = IGMP_LAZY_MEMBER;
                        } else if (igi->igi_version == IGMP_VERSION_2) {
                                inm->inm_state = IGMP_SLEEPING_MEMBER;
                        }
                        break;
                case IGMP_G_QUERY_PENDING_MEMBER:
                case IGMP_SG_QUERY_PENDING_MEMBER:
                case IGMP_LEAVING_MEMBER:
                        break;
                }
                IGI_UNLOCK(igi);
                INM_UNLOCK(inm);
                INM_REMREF(inm); /* from IN_LOOKUP_MULTI */
        }

        return 0;
}

/*
 * Process a received IGMPv2 host membership report.
 *
 * NOTE: 0.0.0.0 workaround breaks const correctness.
 */
static int
igmp_input_v2_report(struct ifnet *ifp, struct mbuf *m, /*const*/ struct ip *ip,
    /*const*/ struct igmp *igmp)
{
        struct in_ifaddr *ia;
        struct in_multi *inm;

        /*
         * Make sure we don't hear our own membership report.  Fast
         * leave requires knowing that we are the only member of a
         * group.
         */
        IFP_TO_IA(ifp, ia);
        if (ia != NULL) {
                IFA_LOCK(&ia->ia_ifa);
                if (in_hosteq(ip->ip_src, IA_SIN(ia)->sin_addr)) {
                        IFA_UNLOCK(&ia->ia_ifa);
                        IFA_REMREF(&ia->ia_ifa);
                        return 0;
                }
                IFA_UNLOCK(&ia->ia_ifa);
        }

        IGMPSTAT_INC(igps_rcv_reports);
        OIGMPSTAT_INC(igps_rcv_reports);

        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (m->m_pkthdr.pkt_flags & PKTF_LOOP)) {
                if (ia != NULL) {
                        IFA_REMREF(&ia->ia_ifa);
                }
                return 0;
        }

        if (!IN_MULTICAST(ntohl(igmp->igmp_group.s_addr)) ||
            !in_hosteq(igmp->igmp_group, ip->ip_dst)) {
                if (ia != NULL) {
                        IFA_REMREF(&ia->ia_ifa);
                }
                IGMPSTAT_INC(igps_rcv_badreports);
                OIGMPSTAT_INC(igps_rcv_badreports);
                return EINVAL;
        }

        /*
         * RFC 3376, Section 4.2.13, 9.2, 9.3:
         * Booting clients may use the source address 0.0.0.0. Some
         * IGMP daemons may not know how to use IP_RECVIF to determine
         * the interface upon which this message was received.
         * Replace 0.0.0.0 with the subnet address if told to do so.
         */
        if (igmp_recvifkludge && in_nullhost(ip->ip_src)) {
                if (ia != NULL) {
                        IFA_LOCK(&ia->ia_ifa);
                        ip->ip_src.s_addr = htonl(ia->ia_subnet);
                        IFA_UNLOCK(&ia->ia_ifa);
                }
        }
        if (ia != NULL) {
                IFA_REMREF(&ia->ia_ifa);
        }

        IGMP_INET_PRINTF(igmp->igmp_group,
            ("process v2 report %s on ifp 0x%llx(%s)\n", _igmp_inet_buf,
            (uint64_t)VM_KERNEL_ADDRPERM(ifp), if_name(ifp)));

        /*
         * IGMPv2 report suppression.
         * If we are a member of this group, and our membership should be
         * reported, and our group timer is pending or about to be reset,
         * stop our group timer by transitioning to the 'lazy' state.
         */
        in_multihead_lock_shared();
        IN_LOOKUP_MULTI(&igmp->igmp_group, ifp, inm);
        in_multihead_lock_done();
        if (inm != NULL) {
                struct igmp_ifinfo *igi;

                INM_LOCK(inm);
                igi = inm->inm_igi;
                VERIFY(igi != NULL);

                IGMPSTAT_INC(igps_rcv_ourreports);
                OIGMPSTAT_INC(igps_rcv_ourreports);

                /*
                 * If we are in IGMPv3 host mode, do not allow the
                 * other host's IGMPv1 report to suppress our reports
                 * unless explicitly configured to do so.
                 */
                IGI_LOCK(igi);
                if (igi->igi_version == IGMP_VERSION_3) {
                        if (igmp_legacysupp) {
                                igmp_v3_suppress_group_record(inm);
                        }
                        IGI_UNLOCK(igi);
                        INM_UNLOCK(inm);
                        INM_REMREF(inm);
                        return 0;
                }

                inm->inm_timer = 0;

                switch (inm->inm_state) {
                case IGMP_NOT_MEMBER:
                case IGMP_SILENT_MEMBER:
                case IGMP_SLEEPING_MEMBER:
                        break;
                case IGMP_REPORTING_MEMBER:
                case IGMP_IDLE_MEMBER:
                case IGMP_AWAKENING_MEMBER:
                        IGMP_INET_PRINTF(igmp->igmp_group,
                            ("report suppressed for %s on ifp 0x%llx(%s)\n",
                            _igmp_inet_buf, (uint64_t)VM_KERNEL_ADDRPERM(ifp),
                            if_name(ifp)));
                case IGMP_LAZY_MEMBER:
                        inm->inm_state = IGMP_LAZY_MEMBER;
                        break;
                case IGMP_G_QUERY_PENDING_MEMBER:
                case IGMP_SG_QUERY_PENDING_MEMBER:
                case IGMP_LEAVING_MEMBER:
                        break;
                }
                IGI_UNLOCK(igi);
                INM_UNLOCK(inm);
                INM_REMREF(inm);
        }

        return 0;
}

void
igmp_input(struct mbuf *m, int off)
{
        int iphlen;
        struct ifnet *ifp;
        struct igmp *igmp;
        struct ip *ip;
        int igmplen;
        int minlen;
        int queryver;

        IGMP_PRINTF(("%s: called w/mbuf (0x%llx,%d)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(m), off));

        ifp = m->m_pkthdr.rcvif;

        IGMPSTAT_INC(igps_rcv_total);
        OIGMPSTAT_INC(igps_rcv_total);

        /* Expect 32-bit aligned data pointer on strict-align platforms */
        MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);

        ip = mtod(m, struct ip *);
        iphlen = off;

        /* By now, ip_len no longer contains the length of IP header */
        igmplen = ip->ip_len;

        /*
         * Validate lengths.
         */
        if (igmplen < IGMP_MINLEN) {
                IGMPSTAT_INC(igps_rcv_tooshort);
                OIGMPSTAT_INC(igps_rcv_tooshort);
                m_freem(m);
                return;
        }

        /*
         * Always pullup to the minimum size for v1/v2 or v3
         * to amortize calls to m_pulldown().
         */
        if (igmplen >= IGMP_V3_QUERY_MINLEN) {
                minlen = IGMP_V3_QUERY_MINLEN;
        } else {
                minlen = IGMP_MINLEN;
        }

        /* A bit more expensive than M_STRUCT_GET, but ensures alignment */
        M_STRUCT_GET0(igmp, struct igmp *, m, off, minlen);
        if (igmp == NULL) {
                IGMPSTAT_INC(igps_rcv_tooshort);
                OIGMPSTAT_INC(igps_rcv_tooshort);
                return;
        }
        /* N.B.: we assume the packet was correctly aligned in ip_input. */

        /*
         * Validate checksum.
         */
        m->m_data += iphlen;
        m->m_len -= iphlen;
        if (in_cksum(m, igmplen)) {
                IGMPSTAT_INC(igps_rcv_badsum);
                OIGMPSTAT_INC(igps_rcv_badsum);
                m_freem(m);
                return;
        }
        m->m_data -= iphlen;
        m->m_len += iphlen;

        /*
         * IGMP control traffic is link-scope, and must have a TTL of 1.
         * DVMRP traffic (e.g. mrinfo, mtrace) is an exception;
         * probe packets may come from beyond the LAN.
         */
        if (igmp->igmp_type != IGMP_DVMRP && ip->ip_ttl != 1) {
                IGMPSTAT_INC(igps_rcv_badttl);
                m_freem(m);
                return;
        }

        switch (igmp->igmp_type) {
        case IGMP_HOST_MEMBERSHIP_QUERY:
                if (igmplen == IGMP_MINLEN) {
                        if (igmp->igmp_code == 0) {
                                queryver = IGMP_VERSION_1;
                        } else {
                                queryver = IGMP_VERSION_2;
                        }
                } else if (igmplen >= IGMP_V3_QUERY_MINLEN) {
                        queryver = IGMP_VERSION_3;
                } else {
                        IGMPSTAT_INC(igps_rcv_tooshort);
                        OIGMPSTAT_INC(igps_rcv_tooshort);
                        m_freem(m);
                        return;
                }

                OIGMPSTAT_INC(igps_rcv_queries);

                switch (queryver) {
                case IGMP_VERSION_1:
                        IGMPSTAT_INC(igps_rcv_v1v2_queries);
                        if (!igmp_v1enable) {
                                break;
                        }
                        if (igmp_input_v1_query(ifp, ip, igmp) != 0) {
                                m_freem(m);
                                return;
                        }
                        break;

                case IGMP_VERSION_2:
                        IGMPSTAT_INC(igps_rcv_v1v2_queries);
                        if (!igmp_v2enable) {
                                break;
                        }
                        if (igmp_input_v2_query(ifp, ip, igmp) != 0) {
                                m_freem(m);
                                return;
                        }
                        break;

                case IGMP_VERSION_3: {
                        struct igmpv3 *igmpv3;
                        uint16_t igmpv3len;
                        uint16_t srclen;
                        int nsrc;

                        IGMPSTAT_INC(igps_rcv_v3_queries);
                        igmpv3 = (struct igmpv3 *)igmp;
                        /*
                         * Validate length based on source count.
                         */
                        nsrc = ntohs(igmpv3->igmp_numsrc);
                        /*
                         * The max vaue of nsrc is limited by the
                         * MTU of the network on which the datagram
                         * is received
                         */
                        if (nsrc < 0 || nsrc > IGMP_V3_QUERY_MAX_SRCS) {
                                IGMPSTAT_INC(igps_rcv_tooshort);
                                OIGMPSTAT_INC(igps_rcv_tooshort);
                                m_freem(m);
                                return;
                        }
                        srclen = sizeof(struct in_addr) * nsrc;
                        if (igmplen < (IGMP_V3_QUERY_MINLEN + srclen)) {
                                IGMPSTAT_INC(igps_rcv_tooshort);
                                OIGMPSTAT_INC(igps_rcv_tooshort);
                                m_freem(m);
                                return;
                        }
                        igmpv3len = IGMP_V3_QUERY_MINLEN + srclen;
                        /*
                         * A bit more expensive than M_STRUCT_GET,
                         * but ensures alignment.
                         */
                        M_STRUCT_GET0(igmpv3, struct igmpv3 *, m,
                            off, igmpv3len);
                        if (igmpv3 == NULL) {
                                IGMPSTAT_INC(igps_rcv_tooshort);
                                OIGMPSTAT_INC(igps_rcv_tooshort);
                                return;
                        }
                        /*
                         * N.B.: we assume the packet was correctly
                         * aligned in ip_input.
                         */
                        if (igmp_input_v3_query(ifp, ip, igmpv3) != 0) {
                                m_freem(m);
                                return;
                        }
                }
                break;
                }
                break;

        case IGMP_v1_HOST_MEMBERSHIP_REPORT:
                if (!igmp_v1enable) {
                        break;
                }
                if (igmp_input_v1_report(ifp, m, ip, igmp) != 0) {
                        m_freem(m);
                        return;
                }
                break;

        case IGMP_v2_HOST_MEMBERSHIP_REPORT:
                if (!igmp_v2enable) {
                        break;
                }
                if (!ip_checkrouteralert(m)) {
                        IGMPSTAT_INC(igps_rcv_nora);
                }
                if (igmp_input_v2_report(ifp, m, ip, igmp) != 0) {
                        m_freem(m);
                        return;
                }
                break;

        case IGMP_v3_HOST_MEMBERSHIP_REPORT:
                /*
                 * Hosts do not need to process IGMPv3 membership reports,
                 * as report suppression is no longer required.
                 */
                if (!ip_checkrouteralert(m)) {
                        IGMPSTAT_INC(igps_rcv_nora);
                }
                break;

        default:
                break;
        }

        IGMP_LOCK_ASSERT_NOTHELD();
        /*
         * Pass all valid IGMP packets up to any process(es) listening on a
         * raw IGMP socket.
         */
        rip_input(m, off);
}

/*
 * Schedule IGMP timer based on various parameters; caller must ensure that
 * lock ordering is maintained as this routine acquires IGMP global lock.
 */
void
igmp_set_timeout(struct igmp_tparams *itp)
{
        IGMP_LOCK_ASSERT_NOTHELD();
        VERIFY(itp != NULL);

        if (itp->qpt != 0 || itp->it != 0 || itp->cst != 0 || itp->sct != 0) {
                IGMP_LOCK();
                if (itp->qpt != 0) {
                        querier_present_timers_running = 1;
                }
                if (itp->it != 0) {
                        interface_timers_running = 1;
                }
                if (itp->cst != 0) {
                        current_state_timers_running = 1;
                }
                if (itp->sct != 0) {
                        state_change_timers_running = 1;
                }
                igmp_sched_timeout();
                IGMP_UNLOCK();
        }
}

/*
 * IGMP timer handler (per 1 second).
 */
static void
igmp_timeout(void *arg)
{
#pragma unused(arg)
        struct ifqueue           scq;   /* State-change packets */
        struct ifqueue           qrq;   /* Query response packets */
        struct ifnet            *ifp;
        struct igmp_ifinfo      *igi;
        struct in_multi         *inm;
        int                      loop = 0, uri_sec = 0;
        SLIST_HEAD(, in_multi)  inm_dthead;

        SLIST_INIT(&inm_dthead);

        /*
         * Update coarse-grained networking timestamp (in sec.); the idea
         * is to piggy-back on the timeout callout to update the counter
         * returnable via net_uptime().
         */
        net_update_uptime();

        IGMP_LOCK();

        IGMP_PRINTF(("%s: qpt %d, it %d, cst %d, sct %d\n", __func__,
            querier_present_timers_running, interface_timers_running,
            current_state_timers_running, state_change_timers_running));

        /*
         * IGMPv1/v2 querier present timer processing.
         */
        if (querier_present_timers_running) {
                querier_present_timers_running = 0;
                LIST_FOREACH(igi, &igi_head, igi_link) {
                        IGI_LOCK(igi);
                        igmp_v1v2_process_querier_timers(igi);
                        if (igi->igi_v1_timer > 0 || igi->igi_v2_timer > 0) {
                                querier_present_timers_running = 1;
                        }
                        IGI_UNLOCK(igi);
                }
        }

        /*
         * IGMPv3 General Query response timer processing.
         */
        if (interface_timers_running) {
                IGMP_PRINTF(("%s: interface timers running\n", __func__));
                interface_timers_running = 0;
                LIST_FOREACH(igi, &igi_head, igi_link) {
                        IGI_LOCK(igi);
                        if (igi->igi_version != IGMP_VERSION_3) {
                                IGI_UNLOCK(igi);
                                continue;
                        }
                        if (igi->igi_v3_timer == 0) {
                                /* Do nothing. */
                        } else if (--igi->igi_v3_timer == 0) {
                                if (igmp_v3_dispatch_general_query(igi) > 0) {
                                        interface_timers_running = 1;
                                }
                        } else {
                                interface_timers_running = 1;
                        }
                        IGI_UNLOCK(igi);
                }
        }

        if (!current_state_timers_running &&
            !state_change_timers_running) {
                goto out_locked;
        }

        current_state_timers_running = 0;
        state_change_timers_running = 0;

        memset(&qrq, 0, sizeof(struct ifqueue));
        qrq.ifq_maxlen = IGMP_MAX_G_GS_PACKETS;

        memset(&scq, 0, sizeof(struct ifqueue));
        scq.ifq_maxlen =  IGMP_MAX_STATE_CHANGE_PACKETS;

        IGMP_PRINTF(("%s: state change timers running\n", __func__));

        /*
         * IGMPv1/v2/v3 host report and state-change timer processing.
         * Note: Processing a v3 group timer may remove a node.
         */
        LIST_FOREACH(igi, &igi_head, igi_link) {
                struct in_multistep step;

                IGI_LOCK(igi);
                ifp = igi->igi_ifp;
                loop = (igi->igi_flags & IGIF_LOOPBACK) ? 1 : 0;
                uri_sec = IGMP_RANDOM_DELAY(igi->igi_uri);
                IGI_UNLOCK(igi);

                in_multihead_lock_shared();
                IN_FIRST_MULTI(step, inm);
                while (inm != NULL) {
                        INM_LOCK(inm);
                        if (inm->inm_ifp != ifp) {
                                goto next;
                        }

                        IGI_LOCK(igi);
                        switch (igi->igi_version) {
                        case IGMP_VERSION_1:
                        case IGMP_VERSION_2:
                                igmp_v1v2_process_group_timer(inm,
                                    igi->igi_version);
                                break;
                        case IGMP_VERSION_3:
                                igmp_v3_process_group_timers(igi, &qrq,
                                    &scq, inm, uri_sec);
                                break;
                        }
                        IGI_UNLOCK(igi);
next:
                        INM_UNLOCK(inm);
                        IN_NEXT_MULTI(step, inm);
                }
                in_multihead_lock_done();

                IGI_LOCK(igi);
                if (igi->igi_version == IGMP_VERSION_1 ||
                    igi->igi_version == IGMP_VERSION_2) {
                        igmp_dispatch_queue(igi, &igi->igi_v2q, 0, loop);
                } else if (igi->igi_version == IGMP_VERSION_3) {
                        IGI_UNLOCK(igi);
                        igmp_dispatch_queue(NULL, &qrq, 0, loop);
                        igmp_dispatch_queue(NULL, &scq, 0, loop);
                        VERIFY(qrq.ifq_len == 0);
                        VERIFY(scq.ifq_len == 0);
                        IGI_LOCK(igi);
                }
                /*
                 * In case there are still any pending membership reports
                 * which didn't get drained at version change time.
                 */
                IF_DRAIN(&igi->igi_v2q);
                /*
                 * Release all deferred inm records, and drain any locally
                 * enqueued packets; do it even if the current IGMP version
                 * for the link is no longer IGMPv3, in order to handle the
                 * version change case.
                 */
                igmp_flush_relq(igi, (struct igmp_inm_relhead *)&inm_dthead);
                VERIFY(SLIST_EMPTY(&igi->igi_relinmhead));
                IGI_UNLOCK(igi);

                IF_DRAIN(&qrq);
                IF_DRAIN(&scq);
        }

out_locked:
        /* re-arm the timer if there's work to do */
        igmp_timeout_run = 0;
        igmp_sched_timeout();
        IGMP_UNLOCK();

        /* Now that we're dropped all locks, release detached records */
        IGMP_REMOVE_DETACHED_INM(&inm_dthead);
}

static void
igmp_sched_timeout(void)
{
        IGMP_LOCK_ASSERT_HELD();

        if (!igmp_timeout_run &&
            (querier_present_timers_running || current_state_timers_running ||
            interface_timers_running || state_change_timers_running)) {
                igmp_timeout_run = 1;
                timeout(igmp_timeout, NULL, hz);
        }
}

/*
 * Free the in_multi reference(s) for this IGMP lifecycle.
 *
 * Caller must be holding igi_lock.
 */
static void
igmp_flush_relq(struct igmp_ifinfo *igi, struct igmp_inm_relhead *inm_dthead)
{
        struct in_multi *inm;

again:
        IGI_LOCK_ASSERT_HELD(igi);
        inm = SLIST_FIRST(&igi->igi_relinmhead);
        if (inm != NULL) {
                int lastref;

                SLIST_REMOVE_HEAD(&igi->igi_relinmhead, inm_nrele);
                IGI_UNLOCK(igi);

                in_multihead_lock_exclusive();
                INM_LOCK(inm);
                VERIFY(inm->inm_nrelecnt != 0);
                inm->inm_nrelecnt--;
                lastref = in_multi_detach(inm);
                VERIFY(!lastref || (!(inm->inm_debug & IFD_ATTACHED) &&
                    inm->inm_reqcnt == 0));
                INM_UNLOCK(inm);
                in_multihead_lock_done();
                /* from igi_relinmhead */
                INM_REMREF(inm);
                /* from in_multihead list */
                if (lastref) {
                        /*
                         * Defer releasing our final reference, as we
                         * are holding the IGMP lock at this point, and
                         * we could end up with locking issues later on
                         * (while issuing SIOCDELMULTI) when this is the
                         * final reference count.  Let the caller do it
                         * when it is safe.
                         */
                        IGMP_ADD_DETACHED_INM(inm_dthead, inm);
                }
                IGI_LOCK(igi);
                goto again;
        }
}

/*
 * Update host report group timer for IGMPv1/v2.
 * Will update the global pending timer flags.
 */
static void
igmp_v1v2_process_group_timer(struct in_multi *inm, const int igmp_version)
{
        int report_timer_expired;

        IGMP_LOCK_ASSERT_HELD();
        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_HELD(inm->inm_igi);

        if (inm->inm_timer == 0) {
                report_timer_expired = 0;
        } else if (--inm->inm_timer == 0) {
                report_timer_expired = 1;
        } else {
                current_state_timers_running = 1;
                /* caller will schedule timer */
                return;
        }

        switch (inm->inm_state) {
        case IGMP_NOT_MEMBER:
        case IGMP_SILENT_MEMBER:
        case IGMP_IDLE_MEMBER:
        case IGMP_LAZY_MEMBER:
        case IGMP_SLEEPING_MEMBER:
        case IGMP_AWAKENING_MEMBER:
                break;
        case IGMP_REPORTING_MEMBER:
                if (report_timer_expired) {
                        inm->inm_state = IGMP_IDLE_MEMBER;
                        (void) igmp_v1v2_queue_report(inm,
                            (igmp_version == IGMP_VERSION_2) ?
                            IGMP_v2_HOST_MEMBERSHIP_REPORT :
                            IGMP_v1_HOST_MEMBERSHIP_REPORT);
                        INM_LOCK_ASSERT_HELD(inm);
                        IGI_LOCK_ASSERT_HELD(inm->inm_igi);
                }
                break;
        case IGMP_G_QUERY_PENDING_MEMBER:
        case IGMP_SG_QUERY_PENDING_MEMBER:
        case IGMP_LEAVING_MEMBER:
                break;
        }
}

/*
 * Update a group's timers for IGMPv3.
 * Will update the global pending timer flags.
 * Note: Unlocked read from igi.
 */
static void
igmp_v3_process_group_timers(struct igmp_ifinfo *igi,
    struct ifqueue *qrq, struct ifqueue *scq,
    struct in_multi *inm, const int uri_sec)
{
        int query_response_timer_expired;
        int state_change_retransmit_timer_expired;

        IGMP_LOCK_ASSERT_HELD();
        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_HELD(igi);
        VERIFY(igi == inm->inm_igi);

        query_response_timer_expired = 0;
        state_change_retransmit_timer_expired = 0;

        /*
         * During a transition from v1/v2 compatibility mode back to v3,
         * a group record in REPORTING state may still have its group
         * timer active. This is a no-op in this function; it is easier
         * to deal with it here than to complicate the timeout path.
         */
        if (inm->inm_timer == 0) {
                query_response_timer_expired = 0;
        } else if (--inm->inm_timer == 0) {
                query_response_timer_expired = 1;
        } else {
                current_state_timers_running = 1;
                /* caller will schedule timer */
        }

        if (inm->inm_sctimer == 0) {
                state_change_retransmit_timer_expired = 0;
        } else if (--inm->inm_sctimer == 0) {
                state_change_retransmit_timer_expired = 1;
        } else {
                state_change_timers_running = 1;
                /* caller will schedule timer */
        }

        /* We are in timer callback, so be quick about it. */
        if (!state_change_retransmit_timer_expired &&
            !query_response_timer_expired) {
                return;
        }

        switch (inm->inm_state) {
        case IGMP_NOT_MEMBER:
        case IGMP_SILENT_MEMBER:
        case IGMP_SLEEPING_MEMBER:
        case IGMP_LAZY_MEMBER:
        case IGMP_AWAKENING_MEMBER:
        case IGMP_IDLE_MEMBER:
                break;
        case IGMP_G_QUERY_PENDING_MEMBER:
        case IGMP_SG_QUERY_PENDING_MEMBER:
                /*
                 * Respond to a previously pending Group-Specific
                 * or Group-and-Source-Specific query by enqueueing
                 * the appropriate Current-State report for
                 * immediate transmission.
                 */
                if (query_response_timer_expired) {
                        int retval;

                        retval = igmp_v3_enqueue_group_record(qrq, inm, 0, 1,
                            (inm->inm_state == IGMP_SG_QUERY_PENDING_MEMBER));
                        IGMP_PRINTF(("%s: enqueue record = %d\n",
                            __func__, retval));
                        inm->inm_state = IGMP_REPORTING_MEMBER;
                        /* XXX Clear recorded sources for next time. */
                        inm_clear_recorded(inm);
                }
        /* FALLTHROUGH */
        case IGMP_REPORTING_MEMBER:
        case IGMP_LEAVING_MEMBER:
                if (state_change_retransmit_timer_expired) {
                        /*
                         * State-change retransmission timer fired.
                         * If there are any further pending retransmissions,
                         * set the global pending state-change flag, and
                         * reset the timer.
                         */
                        if (--inm->inm_scrv > 0) {
                                inm->inm_sctimer = uri_sec;
                                state_change_timers_running = 1;
                                /* caller will schedule timer */
                        }
                        /*
                         * Retransmit the previously computed state-change
                         * report. If there are no further pending
                         * retransmissions, the mbuf queue will be consumed.
                         * Update T0 state to T1 as we have now sent
                         * a state-change.
                         */
                        (void) igmp_v3_merge_state_changes(inm, scq);

                        inm_commit(inm);
                        IGMP_INET_PRINTF(inm->inm_addr,
                            ("%s: T1 -> T0 for %s/%s\n", __func__,
                            _igmp_inet_buf, if_name(inm->inm_ifp)));

                        /*
                         * If we are leaving the group for good, make sure
                         * we release IGMP's reference to it.
                         * This release must be deferred using a SLIST,
                         * as we are called from a loop which traverses
                         * the in_multihead list.
                         */
                        if (inm->inm_state == IGMP_LEAVING_MEMBER &&
                            inm->inm_scrv == 0) {
                                inm->inm_state = IGMP_NOT_MEMBER;
                                /*
                                 * A reference has already been held in
                                 * igmp_final_leave() for this inm, so
                                 * no need to hold another one.  We also
                                 * bumped up its request count then, so
                                 * that it stays in in_multihead.  Both
                                 * of them will be released when it is
                                 * dequeued later on.
                                 */
                                VERIFY(inm->inm_nrelecnt != 0);
                                SLIST_INSERT_HEAD(&igi->igi_relinmhead,
                                    inm, inm_nrele);
                        }
                }
                break;
        }
}

/*
 * Suppress a group's pending response to a group or source/group query.
 *
 * Do NOT suppress state changes. This leads to IGMPv3 inconsistency.
 * Do NOT update ST1/ST0 as this operation merely suppresses
 * the currently pending group record.
 * Do NOT suppress the response to a general query. It is possible but
 * it would require adding another state or flag.
 */
static void
igmp_v3_suppress_group_record(struct in_multi *inm)
{
        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_HELD(inm->inm_igi);

        VERIFY(inm->inm_igi->igi_version == IGMP_VERSION_3);

        if (inm->inm_state != IGMP_G_QUERY_PENDING_MEMBER ||
            inm->inm_state != IGMP_SG_QUERY_PENDING_MEMBER) {
                return;
        }

        if (inm->inm_state == IGMP_SG_QUERY_PENDING_MEMBER) {
                inm_clear_recorded(inm);
        }

        inm->inm_timer = 0;
        inm->inm_state = IGMP_REPORTING_MEMBER;
}

/*
 * Switch to a different IGMP version on the given interface,
 * as per Section 7.2.1.
 */
static uint32_t
igmp_set_version(struct igmp_ifinfo *igi, const int igmp_version)
{
        int old_version_timer;

        IGI_LOCK_ASSERT_HELD(igi);

        IGMP_PRINTF(("%s: switching to v%d on ifp 0x%llx(%s)\n", __func__,
            igmp_version, (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
            if_name(igi->igi_ifp)));

        if (igmp_version == IGMP_VERSION_1 || igmp_version == IGMP_VERSION_2) {
                /*
                 * Compute the "Older Version Querier Present" timer as per
                 * Section 8.12, in seconds.
                 */
                old_version_timer = igi->igi_rv * igi->igi_qi + igi->igi_qri;

                if (igmp_version == IGMP_VERSION_1) {
                        igi->igi_v1_timer = old_version_timer;
                        igi->igi_v2_timer = 0;
                } else if (igmp_version == IGMP_VERSION_2) {
                        igi->igi_v1_timer = 0;
                        igi->igi_v2_timer = old_version_timer;
                }
        }

        if (igi->igi_v1_timer == 0 && igi->igi_v2_timer > 0) {
                if (igi->igi_version != IGMP_VERSION_2) {
                        igi->igi_version = IGMP_VERSION_2;
                        igmp_v3_cancel_link_timers(igi);
                }
        } else if (igi->igi_v1_timer > 0) {
                if (igi->igi_version != IGMP_VERSION_1) {
                        igi->igi_version = IGMP_VERSION_1;
                        igmp_v3_cancel_link_timers(igi);
                }
        }

        IGI_LOCK_ASSERT_HELD(igi);

        return MAX(igi->igi_v1_timer, igi->igi_v2_timer);
}

/*
 * Cancel pending IGMPv3 timers for the given link and all groups
 * joined on it; state-change, general-query, and group-query timers.
 *
 * Only ever called on a transition from v3 to Compatibility mode. Kill
 * the timers stone dead (this may be expensive for large N groups), they
 * will be restarted if Compatibility Mode deems that they must be due to
 * query processing.
 */
static void
igmp_v3_cancel_link_timers(struct igmp_ifinfo *igi)
{
        struct ifnet            *ifp;
        struct in_multi         *inm;
        struct in_multistep     step;

        IGI_LOCK_ASSERT_HELD(igi);

        IGMP_PRINTF(("%s: cancel v3 timers on ifp 0x%llx(%s)\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp), if_name(igi->igi_ifp)));

        /*
         * Stop the v3 General Query Response on this link stone dead.
         * If timer is woken up due to interface_timers_running,
         * the flag will be cleared if there are no pending link timers.
         */
        igi->igi_v3_timer = 0;

        /*
         * Now clear the current-state and state-change report timers
         * for all memberships scoped to this link.
         */
        ifp = igi->igi_ifp;
        IGI_UNLOCK(igi);

        in_multihead_lock_shared();
        IN_FIRST_MULTI(step, inm);
        while (inm != NULL) {
                INM_LOCK(inm);
                if (inm->inm_ifp != ifp) {
                        goto next;
                }

                switch (inm->inm_state) {
                case IGMP_NOT_MEMBER:
                case IGMP_SILENT_MEMBER:
                case IGMP_IDLE_MEMBER:
                case IGMP_LAZY_MEMBER:
                case IGMP_SLEEPING_MEMBER:
                case IGMP_AWAKENING_MEMBER:
                        /*
                         * These states are either not relevant in v3 mode,
                         * or are unreported. Do nothing.
                         */
                        break;
                case IGMP_LEAVING_MEMBER:
                        /*
                         * If we are leaving the group and switching to
                         * compatibility mode, we need to release the final
                         * reference held for issuing the INCLUDE {}, and
                         * transition to REPORTING to ensure the host leave
                         * message is sent upstream to the old querier --
                         * transition to NOT would lose the leave and race.
                         * During igmp_final_leave(), we bumped up both the
                         * request and reference counts.  Since we cannot
                         * call in_multi_detach() here, defer this task to
                         * the timer routine.
                         */
                        VERIFY(inm->inm_nrelecnt != 0);
                        IGI_LOCK(igi);
                        SLIST_INSERT_HEAD(&igi->igi_relinmhead, inm, inm_nrele);
                        IGI_UNLOCK(igi);
                /* FALLTHROUGH */
                case IGMP_G_QUERY_PENDING_MEMBER:
                case IGMP_SG_QUERY_PENDING_MEMBER:
                        inm_clear_recorded(inm);
                /* FALLTHROUGH */
                case IGMP_REPORTING_MEMBER:
                        inm->inm_state = IGMP_REPORTING_MEMBER;
                        break;
                }
                /*
                 * Always clear state-change and group report timers.
                 * Free any pending IGMPv3 state-change records.
                 */
                inm->inm_sctimer = 0;
                inm->inm_timer = 0;
                IF_DRAIN(&inm->inm_scq);
next:
                INM_UNLOCK(inm);
                IN_NEXT_MULTI(step, inm);
        }
        in_multihead_lock_done();

        IGI_LOCK(igi);
}

/*
 * Update the Older Version Querier Present timers for a link.
 * See Section 7.2.1 of RFC 3376.
 */
static void
igmp_v1v2_process_querier_timers(struct igmp_ifinfo *igi)
{
        IGI_LOCK_ASSERT_HELD(igi);

        if (igi->igi_v1_timer == 0 && igi->igi_v2_timer == 0) {
                /*
                 * IGMPv1 and IGMPv2 Querier Present timers expired.
                 *
                 * Revert to IGMPv3.
                 */
                if (igi->igi_version != IGMP_VERSION_3) {
                        IGMP_PRINTF(("%s: transition from v%d -> v%d "
                            "on 0x%llx(%s)\n", __func__,
                            igi->igi_version, IGMP_VERSION_3,
                            (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
                            if_name(igi->igi_ifp)));
                        igi->igi_version = IGMP_VERSION_3;
                        IF_DRAIN(&igi->igi_v2q);
                }
        } else if (igi->igi_v1_timer == 0 && igi->igi_v2_timer > 0) {
                /*
                 * IGMPv1 Querier Present timer expired,
                 * IGMPv2 Querier Present timer running.
                 * If IGMPv2 was disabled since last timeout,
                 * revert to IGMPv3.
                 * If IGMPv2 is enabled, revert to IGMPv2.
                 */
                if (!igmp_v2enable) {
                        IGMP_PRINTF(("%s: transition from v%d -> v%d "
                            "on 0x%llx(%s%d)\n", __func__,
                            igi->igi_version, IGMP_VERSION_3,
                            (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
                            igi->igi_ifp->if_name, igi->igi_ifp->if_unit));
                        igi->igi_v2_timer = 0;
                        igi->igi_version = IGMP_VERSION_3;
                        IF_DRAIN(&igi->igi_v2q);
                } else {
                        --igi->igi_v2_timer;
                        if (igi->igi_version != IGMP_VERSION_2) {
                                IGMP_PRINTF(("%s: transition from v%d -> v%d "
                                    "on 0x%llx(%s)\n", __func__,
                                    igi->igi_version, IGMP_VERSION_2,
                                    (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
                                    if_name(igi->igi_ifp)));
                                igi->igi_version = IGMP_VERSION_2;
                                IF_DRAIN(&igi->igi_gq);
                                igmp_v3_cancel_link_timers(igi);
                        }
                }
        } else if (igi->igi_v1_timer > 0) {
                /*
                 * IGMPv1 Querier Present timer running.
                 * Stop IGMPv2 timer if running.
                 *
                 * If IGMPv1 was disabled since last timeout,
                 * revert to IGMPv3.
                 * If IGMPv1 is enabled, reset IGMPv2 timer if running.
                 */
                if (!igmp_v1enable) {
                        IGMP_PRINTF(("%s: transition from v%d -> v%d "
                            "on 0x%llx(%s%d)\n", __func__,
                            igi->igi_version, IGMP_VERSION_3,
                            (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
                            igi->igi_ifp->if_name, igi->igi_ifp->if_unit));
                        igi->igi_v1_timer = 0;
                        igi->igi_version = IGMP_VERSION_3;
                        IF_DRAIN(&igi->igi_v2q);
                } else {
                        --igi->igi_v1_timer;
                }
                if (igi->igi_v2_timer > 0) {
                        IGMP_PRINTF(("%s: cancel v2 timer on 0x%llx(%s%d)\n",
                            __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(igi->igi_ifp),
                            igi->igi_ifp->if_name, igi->igi_ifp->if_unit));
                        igi->igi_v2_timer = 0;
                }
        }
}

/*
 * Dispatch an IGMPv1/v2 host report or leave message.
 * These are always small enough to fit inside a single mbuf.
 */
static int
igmp_v1v2_queue_report(struct in_multi *inm, const int type)
{
        struct ifnet            *ifp;
        struct igmp             *igmp;
        struct ip               *ip;
        struct mbuf             *m;
        int                     error = 0;

        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_HELD(inm->inm_igi);

        ifp = inm->inm_ifp;

        MGETHDR(m, M_DONTWAIT, MT_DATA);
        if (m == NULL) {
                return ENOMEM;
        }
        MH_ALIGN(m, sizeof(struct ip) + sizeof(struct igmp));

        m->m_pkthdr.len = sizeof(struct ip) + sizeof(struct igmp);

        m->m_data += sizeof(struct ip);
        m->m_len = sizeof(struct igmp);

        igmp = mtod(m, struct igmp *);
        igmp->igmp_type = type;
        igmp->igmp_code = 0;
        igmp->igmp_group = inm->inm_addr;
        igmp->igmp_cksum = 0;
        igmp->igmp_cksum = in_cksum(m, sizeof(struct igmp));

        m->m_data -= sizeof(struct ip);
        m->m_len += sizeof(struct ip);

        ip = mtod(m, struct ip *);
        ip->ip_tos = 0;
        ip->ip_len = sizeof(struct ip) + sizeof(struct igmp);
        ip->ip_off = 0;
        ip->ip_p = IPPROTO_IGMP;
        ip->ip_src.s_addr = INADDR_ANY;

        if (type == IGMP_HOST_LEAVE_MESSAGE) {
                ip->ip_dst.s_addr = htonl(INADDR_ALLRTRS_GROUP);
        } else {
                ip->ip_dst = inm->inm_addr;
        }

        igmp_save_context(m, ifp);

        m->m_flags |= M_IGMPV2;
        if (inm->inm_igi->igi_flags & IGIF_LOOPBACK) {
                m->m_flags |= M_IGMP_LOOP;
        }

        /*
         * Due to the fact that at this point we are possibly holding
         * in_multihead_lock in shared or exclusive mode, we can't call
         * igmp_sendpkt() here since that will eventually call ip_output(),
         * which will try to lock in_multihead_lock and cause a deadlock.
         * Instead we defer the work to the igmp_timeout() thread, thus
         * avoiding unlocking in_multihead_lock here.
         */
        if (IF_QFULL(&inm->inm_igi->igi_v2q)) {
                IGMP_PRINTF(("%s: v1/v2 outbound queue full\n", __func__));
                error = ENOMEM;
                m_freem(m);
        } else {
                IF_ENQUEUE(&inm->inm_igi->igi_v2q, m);
                VERIFY(error == 0);
        }
        return error;
}

/*
 * Process a state change from the upper layer for the given IPv4 group.
 *
 * Each socket holds a reference on the in_multi in its own ip_moptions.
 * The socket layer will have made the necessary updates to the group
 * state, it is now up to IGMP to issue a state change report if there
 * has been any change between T0 (when the last state-change was issued)
 * and T1 (now).
 *
 * We use the IGMPv3 state machine at group level. The IGMP module
 * however makes the decision as to which IGMP protocol version to speak.
 * A state change *from* INCLUDE {} always means an initial join.
 * A state change *to* INCLUDE {} always means a final leave.
 *
 * FUTURE: If IGIF_V3LITE is enabled for this interface, then we can
 * save ourselves a bunch of work; any exclusive mode groups need not
 * compute source filter lists.
 */
int
igmp_change_state(struct in_multi *inm, struct igmp_tparams *itp)
{
        struct igmp_ifinfo *igi;
        struct ifnet *ifp;
        int error = 0;

        VERIFY(itp != NULL);
        bzero(itp, sizeof(*itp));

        INM_LOCK_ASSERT_HELD(inm);
        VERIFY(inm->inm_igi != NULL);
        IGI_LOCK_ASSERT_NOTHELD(inm->inm_igi);

        /*
         * Try to detect if the upper layer just asked us to change state
         * for an interface which has now gone away.
         */
        VERIFY(inm->inm_ifma != NULL);
        ifp = inm->inm_ifma->ifma_ifp;
        /*
         * Sanity check that netinet's notion of ifp is the same as net's.
         */
        VERIFY(inm->inm_ifp == ifp);

        igi = IGMP_IFINFO(ifp);
        VERIFY(igi != NULL);

        /*
         * If we detect a state transition to or from MCAST_UNDEFINED
         * for this group, then we are starting or finishing an IGMP
         * life cycle for this group.
         */
        if (inm->inm_st[1].iss_fmode != inm->inm_st[0].iss_fmode) {
                IGMP_PRINTF(("%s: inm transition %d -> %d\n", __func__,
                    inm->inm_st[0].iss_fmode, inm->inm_st[1].iss_fmode));
                if (inm->inm_st[0].iss_fmode == MCAST_UNDEFINED) {
                        IGMP_PRINTF(("%s: initial join\n", __func__));
                        error = igmp_initial_join(inm, igi, itp);
                        goto out;
                } else if (inm->inm_st[1].iss_fmode == MCAST_UNDEFINED) {
                        IGMP_PRINTF(("%s: final leave\n", __func__));
                        igmp_final_leave(inm, igi, itp);
                        goto out;
                }
        } else {
                IGMP_PRINTF(("%s: filter set change\n", __func__));
        }

        error = igmp_handle_state_change(inm, igi, itp);
out:
        return error;
}

/*
 * Perform the initial join for an IGMP group.
 *
 * When joining a group:
 *  If the group should have its IGMP traffic suppressed, do nothing.
 *  IGMPv1 starts sending IGMPv1 host membership reports.
 *  IGMPv2 starts sending IGMPv2 host membership reports.
 *  IGMPv3 will schedule an IGMPv3 state-change report containing the
 *  initial state of the membership.
 */
static int
igmp_initial_join(struct in_multi *inm, struct igmp_ifinfo *igi,
    struct igmp_tparams *itp)
{
        struct ifnet            *ifp;
        struct ifqueue          *ifq;
        int                      error, retval, syncstates;

        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_NOTHELD(igi);
        VERIFY(itp != NULL);

        IGMP_INET_PRINTF(inm->inm_addr,
            ("%s: initial join %s on ifp 0x%llx(%s)\n", __func__,
            _igmp_inet_buf, (uint64_t)VM_KERNEL_ADDRPERM(inm->inm_ifp),
            if_name(inm->inm_ifp)));

        error = 0;
        syncstates = 1;

        ifp = inm->inm_ifp;

        IGI_LOCK(igi);
        VERIFY(igi->igi_ifp == ifp);

        /*
         * Groups joined on loopback or marked as 'not reported',
         * e.g. 224.0.0.1, enter the IGMP_SILENT_MEMBER state and
         * are never reported in any IGMP protocol exchanges.
         * All other groups enter the appropriate IGMP state machine
         * for the version in use on this link.
         * A link marked as IGIF_SILENT causes IGMP to be completely
         * disabled for the link.
         */
        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (igi->igi_flags & IGIF_SILENT) ||
            !igmp_isgroupreported(inm->inm_addr)) {
                IGMP_PRINTF(("%s: not kicking state machine for silent group\n",
                    __func__));
                inm->inm_state = IGMP_SILENT_MEMBER;
                inm->inm_timer = 0;
        } else {
                /*
                 * Deal with overlapping in_multi lifecycle.
                 * If this group was LEAVING, then make sure
                 * we drop the reference we picked up to keep the
                 * group around for the final INCLUDE {} enqueue.
                 * Since we cannot call in_multi_detach() here,
                 * defer this task to the timer routine.
                 */
                if (igi->igi_version == IGMP_VERSION_3 &&
                    inm->inm_state == IGMP_LEAVING_MEMBER) {
                        VERIFY(inm->inm_nrelecnt != 0);
                        SLIST_INSERT_HEAD(&igi->igi_relinmhead, inm, inm_nrele);
                }

                inm->inm_state = IGMP_REPORTING_MEMBER;

                switch (igi->igi_version) {
                case IGMP_VERSION_1:
                case IGMP_VERSION_2:
                        inm->inm_state = IGMP_IDLE_MEMBER;
                        error = igmp_v1v2_queue_report(inm,
                            (igi->igi_version == IGMP_VERSION_2) ?
                            IGMP_v2_HOST_MEMBERSHIP_REPORT :
                            IGMP_v1_HOST_MEMBERSHIP_REPORT);

                        INM_LOCK_ASSERT_HELD(inm);
                        IGI_LOCK_ASSERT_HELD(igi);

                        if (error == 0) {
                                inm->inm_timer =
                                    IGMP_RANDOM_DELAY(IGMP_V1V2_MAX_RI);
                                itp->cst = 1;
                        }
                        break;

                case IGMP_VERSION_3:
                        /*
                         * Defer update of T0 to T1, until the first copy
                         * of the state change has been transmitted.
                         */
                        syncstates = 0;

                        /*
                         * Immediately enqueue a State-Change Report for
                         * this interface, freeing any previous reports.
                         * Don't kick the timers if there is nothing to do,
                         * or if an error occurred.
                         */
                        ifq = &inm->inm_scq;
                        IF_DRAIN(ifq);
                        retval = igmp_v3_enqueue_group_record(ifq, inm, 1,
                            0, 0);
                        itp->cst = (ifq->ifq_len > 0);
                        IGMP_PRINTF(("%s: enqueue record = %d\n",
                            __func__, retval));
                        if (retval <= 0) {
                                error = retval * -1;
                                break;
                        }

                        /*
                         * Schedule transmission of pending state-change
                         * report up to RV times for this link. The timer
                         * will fire at the next igmp_timeout (1 second),
                         * giving us an opportunity to merge the reports.
                         */
                        if (igi->igi_flags & IGIF_LOOPBACK) {
                                inm->inm_scrv = 1;
                        } else {
                                VERIFY(igi->igi_rv > 1);
                                inm->inm_scrv = igi->igi_rv;
                        }
                        inm->inm_sctimer = 1;
                        itp->sct = 1;

                        error = 0;
                        break;
                }
        }
        IGI_UNLOCK(igi);

        /*
         * Only update the T0 state if state change is atomic,
         * i.e. we don't need to wait for a timer to fire before we
         * can consider the state change to have been communicated.
         */
        if (syncstates) {
                inm_commit(inm);
                IGMP_INET_PRINTF(inm->inm_addr,
                    ("%s: T1 -> T0 for %s/%s\n", __func__,
                    _igmp_inet_buf, if_name(inm->inm_ifp)));
        }

        return error;
}

/*
 * Issue an intermediate state change during the IGMP life-cycle.
 */
static int
igmp_handle_state_change(struct in_multi *inm, struct igmp_ifinfo *igi,
    struct igmp_tparams *itp)
{
        struct ifnet            *ifp;
        int                      retval = 0;

        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_NOTHELD(igi);
        VERIFY(itp != NULL);

        IGMP_INET_PRINTF(inm->inm_addr,
            ("%s: state change for %s on ifp 0x%llx(%s)\n", __func__,
            _igmp_inet_buf, (uint64_t)VM_KERNEL_ADDRPERM(inm->inm_ifp),
            if_name(inm->inm_ifp)));

        ifp = inm->inm_ifp;

        IGI_LOCK(igi);
        VERIFY(igi->igi_ifp == ifp);

        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (igi->igi_flags & IGIF_SILENT) ||
            !igmp_isgroupreported(inm->inm_addr) ||
            (igi->igi_version != IGMP_VERSION_3)) {
                IGI_UNLOCK(igi);
                if (!igmp_isgroupreported(inm->inm_addr)) {
                        IGMP_PRINTF(("%s: not kicking state "
                            "machine for silent group\n", __func__));
                }
                IGMP_PRINTF(("%s: nothing to do\n", __func__));
                inm_commit(inm);
                IGMP_INET_PRINTF(inm->inm_addr,
                    ("%s: T1 -> T0 for %s/%s\n", __func__,
                    _igmp_inet_buf, inm->inm_ifp->if_name));
                goto done;
        }

        IF_DRAIN(&inm->inm_scq);

        retval = igmp_v3_enqueue_group_record(&inm->inm_scq, inm, 1, 0, 0);
        itp->cst = (inm->inm_scq.ifq_len > 0);
        IGMP_PRINTF(("%s: enqueue record = %d\n", __func__, retval));
        if (retval <= 0) {
                IGI_UNLOCK(igi);
                retval *= -1;
                goto done;
        }
        /*
         * If record(s) were enqueued, start the state-change
         * report timer for this group.
         */
        inm->inm_scrv = ((igi->igi_flags & IGIF_LOOPBACK) ? 1 : igi->igi_rv);
        inm->inm_sctimer = 1;
        itp->sct = 1;
        IGI_UNLOCK(igi);
done:
        return retval;
}

/*
 * Perform the final leave for an IGMP group.
 *
 * When leaving a group:
 *  IGMPv1 does nothing.
 *  IGMPv2 sends a host leave message, if and only if we are the reporter.
 *  IGMPv3 enqueues a state-change report containing a transition
 *  to INCLUDE {} for immediate transmission.
 */
static void
igmp_final_leave(struct in_multi *inm, struct igmp_ifinfo *igi,
    struct igmp_tparams *itp)
{
        int syncstates = 1;

        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_NOTHELD(igi);
        VERIFY(itp != NULL);

        IGMP_INET_PRINTF(inm->inm_addr,
            ("%s: final leave %s on ifp 0x%llx(%s)\n", __func__,
            _igmp_inet_buf, (uint64_t)VM_KERNEL_ADDRPERM(inm->inm_ifp),
            if_name(inm->inm_ifp)));

        switch (inm->inm_state) {
        case IGMP_NOT_MEMBER:
        case IGMP_SILENT_MEMBER:
        case IGMP_LEAVING_MEMBER:
                /* Already leaving or left; do nothing. */
                IGMP_PRINTF(("%s: not kicking state machine for silent group\n",
                    __func__));
                break;
        case IGMP_REPORTING_MEMBER:
        case IGMP_IDLE_MEMBER:
        case IGMP_G_QUERY_PENDING_MEMBER:
        case IGMP_SG_QUERY_PENDING_MEMBER:
                IGI_LOCK(igi);
                if (igi->igi_version == IGMP_VERSION_2) {
                        if (inm->inm_state == IGMP_G_QUERY_PENDING_MEMBER ||
                            inm->inm_state == IGMP_SG_QUERY_PENDING_MEMBER) {
                                panic("%s: IGMPv3 state reached, not IGMPv3 "
                                    "mode\n", __func__);
                                /* NOTREACHED */
                        }
                        /* scheduler timer if enqueue is successful */
                        itp->cst = (igmp_v1v2_queue_report(inm,
                            IGMP_HOST_LEAVE_MESSAGE) == 0);

                        INM_LOCK_ASSERT_HELD(inm);
                        IGI_LOCK_ASSERT_HELD(igi);

                        inm->inm_state = IGMP_NOT_MEMBER;
                } else if (igi->igi_version == IGMP_VERSION_3) {
                        /*
                         * Stop group timer and all pending reports.
                         * Immediately enqueue a state-change report
                         * TO_IN {} to be sent on the next timeout,
                         * giving us an opportunity to merge reports.
                         */
                        IF_DRAIN(&inm->inm_scq);
                        inm->inm_timer = 0;
                        if (igi->igi_flags & IGIF_LOOPBACK) {
                                inm->inm_scrv = 1;
                        } else {
                                inm->inm_scrv = igi->igi_rv;
                        }
                        IGMP_INET_PRINTF(inm->inm_addr,
                            ("%s: Leaving %s/%s with %d "
                            "pending retransmissions.\n", __func__,
                            _igmp_inet_buf, if_name(inm->inm_ifp),
                            inm->inm_scrv));
                        if (inm->inm_scrv == 0) {
                                inm->inm_state = IGMP_NOT_MEMBER;
                                inm->inm_sctimer = 0;
                        } else {
                                int retval;
                                /*
                                 * Stick around in the in_multihead list;
                                 * the final detach will be issued by
                                 * igmp_v3_process_group_timers() when
                                 * the retransmit timer expires.
                                 */
                                INM_ADDREF_LOCKED(inm);
                                VERIFY(inm->inm_debug & IFD_ATTACHED);
                                inm->inm_reqcnt++;
                                VERIFY(inm->inm_reqcnt >= 1);
                                inm->inm_nrelecnt++;
                                VERIFY(inm->inm_nrelecnt != 0);

                                retval = igmp_v3_enqueue_group_record(
                                        &inm->inm_scq, inm, 1, 0, 0);
                                itp->cst = (inm->inm_scq.ifq_len > 0);
                                KASSERT(retval != 0,
                                    ("%s: enqueue record = %d\n", __func__,
                                    retval));

                                inm->inm_state = IGMP_LEAVING_MEMBER;
                                inm->inm_sctimer = 1;
                                itp->sct = 1;
                                syncstates = 0;
                        }
                }
                IGI_UNLOCK(igi);
                break;
        case IGMP_LAZY_MEMBER:
        case IGMP_SLEEPING_MEMBER:
        case IGMP_AWAKENING_MEMBER:
                /* Our reports are suppressed; do nothing. */
                break;
        }

        if (syncstates) {
                inm_commit(inm);
                IGMP_INET_PRINTF(inm->inm_addr,
                    ("%s: T1 -> T0 for %s/%s\n", __func__,
                    _igmp_inet_buf, if_name(inm->inm_ifp)));
                inm->inm_st[1].iss_fmode = MCAST_UNDEFINED;
                IGMP_INET_PRINTF(inm->inm_addr,
                    ("%s: T1 now MCAST_UNDEFINED for %s/%s\n",
                    __func__, _igmp_inet_buf, if_name(inm->inm_ifp)));
        }
}

/*
 * Enqueue an IGMPv3 group record to the given output queue.
 *
 * XXX This function could do with having the allocation code
 * split out, and the multiple-tree-walks coalesced into a single
 * routine as has been done in igmp_v3_enqueue_filter_change().
 *
 * If is_state_change is zero, a current-state record is appended.
 * If is_state_change is non-zero, a state-change report is appended.
 *
 * If is_group_query is non-zero, an mbuf packet chain is allocated.
 * If is_group_query is zero, and if there is a packet with free space
 * at the tail of the queue, it will be appended to providing there
 * is enough free space.
 * Otherwise a new mbuf packet chain is allocated.
 *
 * If is_source_query is non-zero, each source is checked to see if
 * it was recorded for a Group-Source query, and will be omitted if
 * it is not both in-mode and recorded.
 *
 * The function will attempt to allocate leading space in the packet
 * for the IP/IGMP header to be prepended without fragmenting the chain.
 *
 * If successful the size of all data appended to the queue is returned,
 * otherwise an error code less than zero is returned, or zero if
 * no record(s) were appended.
 */
static int
igmp_v3_enqueue_group_record(struct ifqueue *ifq, struct in_multi *inm,
    const int is_state_change, const int is_group_query,
    const int is_source_query)
{
        struct igmp_grouprec     ig;
        struct igmp_grouprec    *pig;
        struct ifnet            *ifp;
        struct ip_msource       *ims, *nims;
        struct mbuf             *m0, *m, *md;
        int                      error, is_filter_list_change;
        int                      minrec0len, m0srcs, msrcs, nbytes, off;
        int                      record_has_sources;
        int                      now;
        int                      type;
        in_addr_t                naddr;
        uint8_t                  mode;
        u_int16_t                ig_numsrc;

        INM_LOCK_ASSERT_HELD(inm);
        IGI_LOCK_ASSERT_HELD(inm->inm_igi);

        error = 0;
        ifp = inm->inm_ifp;
        is_filter_list_change = 0;
        m = NULL;
        m0 = NULL;
        m0srcs = 0;
        msrcs = 0;
        nbytes = 0;
        nims = NULL;
        record_has_sources = 1;
        pig = NULL;
        type = IGMP_DO_NOTHING;
        mode = inm->inm_st[1].iss_fmode;

        /*
         * If we did not transition out of ASM mode during t0->t1,
         * and there are no source nodes to process, we can skip
         * the generation of source records.
         */
        if (inm->inm_st[0].iss_asm > 0 && inm->inm_st[1].iss_asm > 0 &&
            inm->inm_nsrc == 0) {
                record_has_sources = 0;
        }

        if (is_state_change) {
                /*
                 * Queue a state change record.
                 * If the mode did not change, and there are non-ASM
                 * listeners or source filters present,
                 * we potentially need to issue two records for the group.
                 * If we are transitioning to MCAST_UNDEFINED, we need
                 * not send any sources.
                 * If there are ASM listeners, and there was no filter
                 * mode transition of any kind, do nothing.
                 */
                if (mode != inm->inm_st[0].iss_fmode) {
                        if (mode == MCAST_EXCLUDE) {
                                IGMP_PRINTF(("%s: change to EXCLUDE\n",
                                    __func__));
                                type = IGMP_CHANGE_TO_EXCLUDE_MODE;
                        } else {
                                IGMP_PRINTF(("%s: change to INCLUDE\n",
                                    __func__));
                                type = IGMP_CHANGE_TO_INCLUDE_MODE;
                                if (mode == MCAST_UNDEFINED) {
                                        record_has_sources = 0;
                                }
                        }
                } else {
                        if (record_has_sources) {
                                is_filter_list_change = 1;
                        } else {
                                type = IGMP_DO_NOTHING;
                        }
                }
        } else {
                /*
                 * Queue a current state record.
                 */
                if (mode == MCAST_EXCLUDE) {
                        type = IGMP_MODE_IS_EXCLUDE;
                } else if (mode == MCAST_INCLUDE) {
                        type = IGMP_MODE_IS_INCLUDE;
                        VERIFY(inm->inm_st[1].iss_asm == 0);
                }
        }

        /*
         * Generate the filter list changes using a separate function.
         */
        if (is_filter_list_change) {
                return igmp_v3_enqueue_filter_change(ifq, inm);
        }

        if (type == IGMP_DO_NOTHING) {
                IGMP_INET_PRINTF(inm->inm_addr,
                    ("%s: nothing to do for %s/%s\n",
                    __func__, _igmp_inet_buf,
                    if_name(inm->inm_ifp)));
                return 0;
        }

        /*
         * If any sources are present, we must be able to fit at least
         * one in the trailing space of the tail packet's mbuf,
         * ideally more.
         */
        minrec0len = sizeof(struct igmp_grouprec);
        if (record_has_sources) {
                minrec0len += sizeof(in_addr_t);
        }

        IGMP_INET_PRINTF(inm->inm_addr,
            ("%s: queueing %s for %s/%s\n", __func__,
            igmp_rec_type_to_str(type), _igmp_inet_buf,
            if_name(inm->inm_ifp)));

        /*
         * Check if we have a packet in the tail of the queue for this
         * group into which the first group record for this group will fit.
         * Otherwise allocate a new packet.
         * Always allocate leading space for IP+RA_OPT+IGMP+REPORT.
         * Note: Group records for G/GSR query responses MUST be sent
         * in their own packet.
         */
        m0 = ifq->ifq_tail;
        if (!is_group_query &&
            m0 != NULL &&
            (m0->m_pkthdr.vt_nrecs + 1 <= IGMP_V3_REPORT_MAXRECS) &&
            (m0->m_pkthdr.len + minrec0len) <
            (ifp->if_mtu - IGMP_LEADINGSPACE)) {
                m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                    sizeof(struct igmp_grouprec)) / sizeof(in_addr_t);
                m = m0;
                IGMP_PRINTF(("%s: use existing packet\n", __func__));
        } else {
                if (IF_QFULL(ifq)) {
                        IGMP_PRINTF(("%s: outbound queue full\n", __func__));
                        return -ENOMEM;
                }
                m = NULL;
                m0srcs = (ifp->if_mtu - IGMP_LEADINGSPACE -
                    sizeof(struct igmp_grouprec)) / sizeof(in_addr_t);
                if (!is_state_change && !is_group_query) {
                        m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
                        if (m) {
                                m->m_data += IGMP_LEADINGSPACE;
                        }
                }
                if (m == NULL) {
                        m = m_gethdr(M_DONTWAIT, MT_DATA);
                        if (m) {
                                MH_ALIGN(m, IGMP_LEADINGSPACE);
                        }
                }
                if (m == NULL) {
                        return -ENOMEM;
                }

                igmp_save_context(m, ifp);

                IGMP_PRINTF(("%s: allocated first packet\n", __func__));
        }

        /*
         * Append group record.
         * If we have sources, we don't know how many yet.
         */
        ig.ig_type = type;
        ig.ig_datalen = 0;
        ig.ig_numsrc = 0;
        ig.ig_group = inm->inm_addr;
        if (!m_append(m, sizeof(struct igmp_grouprec), (void *)&ig)) {
                if (m != m0) {
                        m_freem(m);
                }
                IGMP_PRINTF(("%s: m_append() failed.\n", __func__));
                return -ENOMEM;
        }
        nbytes += sizeof(struct igmp_grouprec);

        /*
         * Append as many sources as will fit in the first packet.
         * If we are appending to a new packet, the chain allocation
         * may potentially use clusters; use m_getptr() in this case.
         * If we are appending to an existing packet, we need to obtain
         * a pointer to the group record after m_append(), in case a new
         * mbuf was allocated.
         * Only append sources which are in-mode at t1. If we are
         * transitioning to MCAST_UNDEFINED state on the group, do not
         * include source entries.
         * Only report recorded sources in our filter set when responding
         * to a group-source query.
         */
        if (record_has_sources) {
                if (m == m0) {
                        md = m_last(m);
                        pig = (struct igmp_grouprec *)(void *)
                            (mtod(md, uint8_t *) + md->m_len - nbytes);
                } else {
                        md = m_getptr(m, 0, &off);
                        pig = (struct igmp_grouprec *)(void *)
                            (mtod(md, uint8_t *) + off);
                }
                msrcs = 0;
                RB_FOREACH_SAFE(ims, ip_msource_tree, &inm->inm_srcs, nims) {
#ifdef IGMP_DEBUG
                        char buf[MAX_IPv4_STR_LEN];

                        inet_ntop_haddr(ims->ims_haddr, buf, sizeof(buf));
                        IGMP_PRINTF(("%s: visit node %s\n", __func__, buf));
#endif
                        now = ims_get_mode(inm, ims, 1);
                        IGMP_PRINTF(("%s: node is %d\n", __func__, now));
                        if ((now != mode) ||
                            (now == mode && mode == MCAST_UNDEFINED)) {
                                IGMP_PRINTF(("%s: skip node\n", __func__));
                                continue;
                        }
                        if (is_source_query && ims->ims_stp == 0) {
                                IGMP_PRINTF(("%s: skip unrecorded node\n",
                                    __func__));
                                continue;
                        }
                        IGMP_PRINTF(("%s: append node\n", __func__));
                        naddr = htonl(ims->ims_haddr);
                        if (!m_append(m, sizeof(in_addr_t), (void *)&naddr)) {
                                if (m != m0) {
                                        m_freem(m);
                                }
                                IGMP_PRINTF(("%s: m_append() failed.\n",
                                    __func__));
                                return -ENOMEM;
                        }
                        nbytes += sizeof(in_addr_t);
                        ++msrcs;
                        if (msrcs == m0srcs) {
                                break;
                        }
                }
                IGMP_PRINTF(("%s: msrcs is %d this packet\n", __func__,
                    msrcs));
                ig_numsrc = htons(msrcs);
                bcopy(&ig_numsrc, &pig->ig_numsrc, sizeof(ig_numsrc));
                nbytes += (msrcs * sizeof(in_addr_t));
        }

        if (is_source_query && msrcs == 0) {
                IGMP_PRINTF(("%s: no recorded sources to report\n", __func__));
                if (m != m0) {
                        m_freem(m);
                }
                return 0;
        }

        /*
         * We are good to go with first packet.
         */
        if (m != m0) {
                IGMP_PRINTF(("%s: enqueueing first packet\n", __func__));
                m->m_pkthdr.vt_nrecs = 1;
                IF_ENQUEUE(ifq, m);
        } else {
                m->m_pkthdr.vt_nrecs++;
        }
        /*
         * No further work needed if no source list in packet(s).
         */
        if (!record_has_sources) {
                return nbytes;
        }

        /*
         * Whilst sources remain to be announced, we need to allocate
         * a new packet and fill out as many sources as will fit.
         * Always try for a cluster first.
         */
        while (nims != NULL) {
                if (IF_QFULL(ifq)) {
                        IGMP_PRINTF(("%s: outbound queue full\n", __func__));
                        return -ENOMEM;
                }
                m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
                if (m) {
                        m->m_data += IGMP_LEADINGSPACE;
                }
                if (m == NULL) {
                        m = m_gethdr(M_DONTWAIT, MT_DATA);
                        if (m) {
                                MH_ALIGN(m, IGMP_LEADINGSPACE);
                        }
                }
                if (m == NULL) {
                        return -ENOMEM;
                }
                igmp_save_context(m, ifp);
                md = m_getptr(m, 0, &off);
                pig = (struct igmp_grouprec *)(void *)
                    (mtod(md, uint8_t *) + off);
                IGMP_PRINTF(("%s: allocated next packet\n", __func__));

                if (!m_append(m, sizeof(struct igmp_grouprec), (void *)&ig)) {
                        if (m != m0) {
                                m_freem(m);
                        }
                        IGMP_PRINTF(("%s: m_append() failed.\n", __func__));
                        return -ENOMEM;
                }
                m->m_pkthdr.vt_nrecs = 1;
                nbytes += sizeof(struct igmp_grouprec);

                m0srcs = (ifp->if_mtu - IGMP_LEADINGSPACE -
                    sizeof(struct igmp_grouprec)) / sizeof(in_addr_t);

                msrcs = 0;
                RB_FOREACH_FROM(ims, ip_msource_tree, nims) {
#ifdef IGMP_DEBUG
                        char buf[MAX_IPv4_STR_LEN];

                        inet_ntop_haddr(ims->ims_haddr, buf, sizeof(buf));
                        IGMP_PRINTF(("%s: visit node %s\n", __func__, buf));
#endif
                        now = ims_get_mode(inm, ims, 1);
                        if ((now != mode) ||
                            (now == mode && mode == MCAST_UNDEFINED)) {
                                IGMP_PRINTF(("%s: skip node\n", __func__));
                                continue;
                        }
                        if (is_source_query && ims->ims_stp == 0) {
                                IGMP_PRINTF(("%s: skip unrecorded node\n",
                                    __func__));
                                continue;
                        }
                        IGMP_PRINTF(("%s: append node\n", __func__));
                        naddr = htonl(ims->ims_haddr);
                        if (!m_append(m, sizeof(in_addr_t), (void *)&naddr)) {
                                if (m != m0) {
                                        m_freem(m);
                                }
                                IGMP_PRINTF(("%s: m_append() failed.\n",
                                    __func__));
                                return -ENOMEM;
                        }
                        ++msrcs;
                        if (msrcs == m0srcs) {
                                break;
                        }
                }
                ig_numsrc = htons(msrcs);
                bcopy(&ig_numsrc, &pig->ig_numsrc, sizeof(ig_numsrc));
                nbytes += (msrcs * sizeof(in_addr_t));

                IGMP_PRINTF(("%s: enqueueing next packet\n", __func__));
                IF_ENQUEUE(ifq, m);
        }

        return nbytes;
}

/*
 * Type used to mark record pass completion.
 * We exploit the fact we can cast to this easily from the
 * current filter modes on each ip_msource node.
 */
typedef enum {
        REC_NONE = 0x00,        /* MCAST_UNDEFINED */
        REC_ALLOW = 0x01,       /* MCAST_INCLUDE */
        REC_BLOCK = 0x02,       /* MCAST_EXCLUDE */
        REC_FULL = REC_ALLOW | REC_BLOCK
} rectype_t;

/*
 * Enqueue an IGMPv3 filter list change to the given output queue.
 *
 * Source list filter state is held in an RB-tree. When the filter list
 * for a group is changed without changing its mode, we need to compute
 * the deltas between T0 and T1 for each source in the filter set,
 * and enqueue the appropriate ALLOW_NEW/BLOCK_OLD records.
 *
 * As we may potentially queue two record types, and the entire R-B tree
 * needs to be walked at once, we break this out into its own function
 * so we can generate a tightly packed queue of packets.
 *
 * XXX This could be written to only use one tree walk, although that makes
 * serializing into the mbuf chains a bit harder. For now we do two walks
 * which makes things easier on us, and it may or may not be harder on
 * the L2 cache.
 *
 * If successful the size of all data appended to the queue is returned,
 * otherwise an error code less than zero is returned, or zero if
 * no record(s) were appended.
 */
static int
igmp_v3_enqueue_filter_change(struct ifqueue *ifq, struct in_multi *inm)
{
        static const int MINRECLEN =
            sizeof(struct igmp_grouprec) + sizeof(in_addr_t);
        struct ifnet            *ifp;
        struct igmp_grouprec     ig;
        struct igmp_grouprec    *pig;
        struct ip_msource       *ims, *nims;
        struct mbuf             *m, *m0, *md;
        in_addr_t                naddr;
        int                      m0srcs, nbytes, npbytes, off, rsrcs, schanged;
        int                      nallow, nblock;
        uint8_t                  mode, now, then;
        rectype_t                crt, drt, nrt;
        u_int16_t                ig_numsrc;

        INM_LOCK_ASSERT_HELD(inm);

        if (inm->inm_nsrc == 0 ||
            (inm->inm_st[0].iss_asm > 0 && inm->inm_st[1].iss_asm > 0)) {
                return 0;
        }

        ifp = inm->inm_ifp;                     /* interface */
        mode = inm->inm_st[1].iss_fmode;        /* filter mode at t1 */
        crt = REC_NONE; /* current group record type */
        drt = REC_NONE; /* mask of completed group record types */
        nrt = REC_NONE; /* record type for current node */
        m0srcs = 0;     /* # source which will fit in current mbuf chain */
        nbytes = 0;     /* # of bytes appended to group's state-change queue */
        npbytes = 0;    /* # of bytes appended this packet */
        rsrcs = 0;      /* # sources encoded in current record */
        schanged = 0;   /* # nodes encoded in overall filter change */
        nallow = 0;     /* # of source entries in ALLOW_NEW */
        nblock = 0;     /* # of source entries in BLOCK_OLD */
        nims = NULL;    /* next tree node pointer */

        /*
         * For each possible filter record mode.
         * The first kind of source we encounter tells us which
         * is the first kind of record we start appending.
         * If a node transitioned to UNDEFINED at t1, its mode is treated
         * as the inverse of the group's filter mode.
         */
        while (drt != REC_FULL) {
                do {
                        m0 = ifq->ifq_tail;
                        if (m0 != NULL &&
                            (m0->m_pkthdr.vt_nrecs + 1 <=
                            IGMP_V3_REPORT_MAXRECS) &&
                            (m0->m_pkthdr.len + MINRECLEN) <
                            (ifp->if_mtu - IGMP_LEADINGSPACE)) {
                                m = m0;
                                m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                                    sizeof(struct igmp_grouprec)) /
                                    sizeof(in_addr_t);
                                IGMP_PRINTF(("%s: use previous packet\n",
                                    __func__));
                        } else {
                                m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
                                if (m) {
                                        m->m_data += IGMP_LEADINGSPACE;
                                }
                                if (m == NULL) {
                                        m = m_gethdr(M_DONTWAIT, MT_DATA);
                                        if (m) {
                                                MH_ALIGN(m, IGMP_LEADINGSPACE);
                                        }
                                }
                                if (m == NULL) {
                                        IGMP_PRINTF(("%s: m_get*() failed\n",
                                            __func__));
                                        return -ENOMEM;
                                }
                                m->m_pkthdr.vt_nrecs = 0;
                                igmp_save_context(m, ifp);
                                m0srcs = (ifp->if_mtu - IGMP_LEADINGSPACE -
                                    sizeof(struct igmp_grouprec)) /
                                    sizeof(in_addr_t);
                                npbytes = 0;
                                IGMP_PRINTF(("%s: allocated new packet\n",
                                    __func__));
                        }
                        /*
                         * Append the IGMP group record header to the
                         * current packet's data area.
                         * Recalculate pointer to free space for next
                         * group record, in case m_append() allocated
                         * a new mbuf or cluster.
                         */
                        memset(&ig, 0, sizeof(ig));
                        ig.ig_group = inm->inm_addr;
                        if (!m_append(m, sizeof(ig), (void *)&ig)) {
                                if (m != m0) {
                                        m_freem(m);
                                }
                                IGMP_PRINTF(("%s: m_append() failed\n",
                                    __func__));
                                return -ENOMEM;
                        }
                        npbytes += sizeof(struct igmp_grouprec);
                        if (m != m0) {
                                /* new packet; offset in c hain */
                                md = m_getptr(m, npbytes -
                                    sizeof(struct igmp_grouprec), &off);
                                pig = (struct igmp_grouprec *)(void *)(mtod(md,
                                    uint8_t *) + off);
                        } else {
                                /* current packet; offset from last append */
                                md = m_last(m);
                                pig = (struct igmp_grouprec *)(void *)(mtod(md,
                                    uint8_t *) + md->m_len -
                                    sizeof(struct igmp_grouprec));
                        }
                        /*
                         * Begin walking the tree for this record type
                         * pass, or continue from where we left off
                         * previously if we had to allocate a new packet.
                         * Only report deltas in-mode at t1.
                         * We need not report included sources as allowed
                         * if we are in inclusive mode on the group,
                         * however the converse is not true.
                         */
                        rsrcs = 0;
                        if (nims == NULL) {
                                nims = RB_MIN(ip_msource_tree, &inm->inm_srcs);
                        }
                        RB_FOREACH_FROM(ims, ip_msource_tree, nims) {
#ifdef IGMP_DEBUG
                                char buf[MAX_IPv4_STR_LEN];

                                inet_ntop_haddr(ims->ims_haddr, buf, sizeof(buf));
                                IGMP_PRINTF(("%s: visit node %s\n", __func__, buf));
#endif
                                now = ims_get_mode(inm, ims, 1);
                                then = ims_get_mode(inm, ims, 0);
                                IGMP_PRINTF(("%s: mode: t0 %d, t1 %d\n",
                                    __func__, then, now));
                                if (now == then) {
                                        IGMP_PRINTF(("%s: skip unchanged\n",
                                            __func__));
                                        continue;
                                }
                                if (mode == MCAST_EXCLUDE &&
                                    now == MCAST_INCLUDE) {
                                        IGMP_PRINTF(("%s: skip IN src on EX "
                                            "group\n", __func__));
                                        continue;
                                }
                                nrt = (rectype_t)now;
                                if (nrt == REC_NONE) {
                                        nrt = (rectype_t)(~mode & REC_FULL);
                                }
                                if (schanged++ == 0) {
                                        crt = nrt;
                                } else if (crt != nrt) {
                                        continue;
                                }
                                naddr = htonl(ims->ims_haddr);
                                if (!m_append(m, sizeof(in_addr_t),
                                    (void *)&naddr)) {
                                        if (m != m0) {
                                                m_freem(m);
                                        }
                                        IGMP_PRINTF(("%s: m_append() failed\n",
                                            __func__));
                                        return -ENOMEM;
                                }
                                nallow += !!(crt == REC_ALLOW);
                                nblock += !!(crt == REC_BLOCK);
                                if (++rsrcs == m0srcs) {
                                        break;
                                }
                        }
                        /*
                         * If we did not append any tree nodes on this
                         * pass, back out of allocations.
                         */
                        if (rsrcs == 0) {
                                npbytes -= sizeof(struct igmp_grouprec);
                                if (m != m0) {
                                        IGMP_PRINTF(("%s: m_free(m)\n",
                                            __func__));
                                        m_freem(m);
                                } else {
                                        IGMP_PRINTF(("%s: m_adj(m, -ig)\n",
                                            __func__));
                                        m_adj(m, -((int)sizeof(
                                                    struct igmp_grouprec)));
                                }
                                continue;
                        }
                        npbytes += (rsrcs * sizeof(in_addr_t));
                        if (crt == REC_ALLOW) {
                                pig->ig_type = IGMP_ALLOW_NEW_SOURCES;
                        } else if (crt == REC_BLOCK) {
                                pig->ig_type = IGMP_BLOCK_OLD_SOURCES;
                        }
                        ig_numsrc = htons(rsrcs);
                        bcopy(&ig_numsrc, &pig->ig_numsrc, sizeof(ig_numsrc));
                        /*
                         * Count the new group record, and enqueue this
                         * packet if it wasn't already queued.
                         */
                        m->m_pkthdr.vt_nrecs++;
                        if (m != m0) {
                                IF_ENQUEUE(ifq, m);
                        }
                        nbytes += npbytes;
                } while (nims != NULL);
                drt |= crt;
                crt = (~crt & REC_FULL);
        }

        IGMP_PRINTF(("%s: queued %d ALLOW_NEW, %d BLOCK_OLD\n", __func__,
            nallow, nblock));

        return nbytes;
}

static int
igmp_v3_merge_state_changes(struct in_multi *inm, struct ifqueue *ifscq)
{
        struct ifqueue  *gq;
        struct mbuf     *m;             /* pending state-change */
        struct mbuf     *m0;            /* copy of pending state-change */
        struct mbuf     *mt;            /* last state-change in packet */
        struct mbuf     *n;
        int              docopy, domerge;
        u_int            recslen;

        INM_LOCK_ASSERT_HELD(inm);

        docopy = 0;
        domerge = 0;
        recslen = 0;

        /*
         * If there are further pending retransmissions, make a writable
         * copy of each queued state-change message before merging.
         */
        if (inm->inm_scrv > 0) {
                docopy = 1;
        }

        gq = &inm->inm_scq;
#ifdef IGMP_DEBUG
        if (gq->ifq_head == NULL) {
                IGMP_PRINTF(("%s: WARNING: queue for inm 0x%llx is empty\n",
                    __func__, (uint64_t)VM_KERNEL_ADDRPERM(inm)));
        }
#endif

        /*
         * Use IF_REMQUEUE() instead of IF_DEQUEUE() below, since the
         * packet might not always be at the head of the ifqueue.
         */
        m = gq->ifq_head;
        while (m != NULL) {
                /*
                 * Only merge the report into the current packet if
                 * there is sufficient space to do so; an IGMPv3 report
                 * packet may only contain 65,535 group records.
                 * Always use a simple mbuf chain concatentation to do this,
                 * as large state changes for single groups may have
                 * allocated clusters.
                 */
                domerge = 0;
                mt = ifscq->ifq_tail;
                if (mt != NULL) {
                        recslen = m_length(m);

                        if ((mt->m_pkthdr.vt_nrecs +
                            m->m_pkthdr.vt_nrecs <=
                            IGMP_V3_REPORT_MAXRECS) &&
                            (mt->m_pkthdr.len + recslen <=
                            (inm->inm_ifp->if_mtu - IGMP_LEADINGSPACE))) {
                                domerge = 1;
                        }
                }

                if (!domerge && IF_QFULL(gq)) {
                        IGMP_PRINTF(("%s: outbound queue full, skipping whole "
                            "packet 0x%llx\n", __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(m)));
                        n = m->m_nextpkt;
                        if (!docopy) {
                                IF_REMQUEUE(gq, m);
                                m_freem(m);
                        }
                        m = n;
                        continue;
                }

                if (!docopy) {
                        IGMP_PRINTF(("%s: dequeueing 0x%llx\n", __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(m)));
                        n = m->m_nextpkt;
                        IF_REMQUEUE(gq, m);
                        m0 = m;
                        m = n;
                } else {
                        IGMP_PRINTF(("%s: copying 0x%llx\n", __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(m)));
                        m0 = m_dup(m, M_NOWAIT);
                        if (m0 == NULL) {
                                return ENOMEM;
                        }
                        m0->m_nextpkt = NULL;
                        m = m->m_nextpkt;
                }

                if (!domerge) {
                        IGMP_PRINTF(("%s: queueing 0x%llx to ifscq 0x%llx)\n",
                            __func__, (uint64_t)VM_KERNEL_ADDRPERM(m0),
                            (uint64_t)VM_KERNEL_ADDRPERM(ifscq)));
                        IF_ENQUEUE(ifscq, m0);
                } else {
                        struct mbuf *mtl;       /* last mbuf of packet mt */

                        IGMP_PRINTF(("%s: merging 0x%llx with ifscq tail "
                            "0x%llx)\n", __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(m0),
                            (uint64_t)VM_KERNEL_ADDRPERM(mt)));

                        mtl = m_last(mt);
                        m0->m_flags &= ~M_PKTHDR;
                        mt->m_pkthdr.len += recslen;
                        mt->m_pkthdr.vt_nrecs +=
                            m0->m_pkthdr.vt_nrecs;

                        mtl->m_next = m0;
                }
        }

        return 0;
}

/*
 * Respond to a pending IGMPv3 General Query.
 */
static uint32_t
igmp_v3_dispatch_general_query(struct igmp_ifinfo *igi)
{
        struct ifnet            *ifp;
        struct in_multi         *inm;
        struct in_multistep     step;
        int                      retval, loop;

        IGI_LOCK_ASSERT_HELD(igi);

        VERIFY(igi->igi_version == IGMP_VERSION_3);

        ifp = igi->igi_ifp;
        IGI_UNLOCK(igi);

        in_multihead_lock_shared();
        IN_FIRST_MULTI(step, inm);
        while (inm != NULL) {
                INM_LOCK(inm);
                if (inm->inm_ifp != ifp) {
                        goto next;
                }

                switch (inm->inm_state) {
                case IGMP_NOT_MEMBER:
                case IGMP_SILENT_MEMBER:
                        break;
                case IGMP_REPORTING_MEMBER:
                case IGMP_IDLE_MEMBER:
                case IGMP_LAZY_MEMBER:
                case IGMP_SLEEPING_MEMBER:
                case IGMP_AWAKENING_MEMBER:
                        inm->inm_state = IGMP_REPORTING_MEMBER;
                        IGI_LOCK(igi);
                        retval = igmp_v3_enqueue_group_record(&igi->igi_gq,
                            inm, 0, 0, 0);
                        IGI_UNLOCK(igi);
                        IGMP_PRINTF(("%s: enqueue record = %d\n",
                            __func__, retval));
                        break;
                case IGMP_G_QUERY_PENDING_MEMBER:
                case IGMP_SG_QUERY_PENDING_MEMBER:
                case IGMP_LEAVING_MEMBER:
                        break;
                }
next:
                INM_UNLOCK(inm);
                IN_NEXT_MULTI(step, inm);
        }
        in_multihead_lock_done();

        IGI_LOCK(igi);
        loop = (igi->igi_flags & IGIF_LOOPBACK) ? 1 : 0;
        igmp_dispatch_queue(igi, &igi->igi_gq, IGMP_MAX_RESPONSE_BURST,
            loop);
        IGI_LOCK_ASSERT_HELD(igi);
        /*
         * Slew transmission of bursts over 1 second intervals.
         */
        if (igi->igi_gq.ifq_head != NULL) {
                igi->igi_v3_timer = 1 + IGMP_RANDOM_DELAY(
                        IGMP_RESPONSE_BURST_INTERVAL);
        }

        return igi->igi_v3_timer;
}

/*
 * Transmit the next pending IGMP message in the output queue.
 *
 * Must not be called with inm_lock or igi_lock held.
 */
static void
igmp_sendpkt(struct mbuf *m)
{
        struct ip_moptions      *imo;
        struct mbuf             *ipopts, *m0;
        int                     error;
        struct route            ro;
        struct ifnet            *ifp;

        IGMP_PRINTF(("%s: transmit 0x%llx\n", __func__,
            (uint64_t)VM_KERNEL_ADDRPERM(m)));

        ifp = igmp_restore_context(m);
        /*
         * Check if the ifnet is still attached.
         */
        if (ifp == NULL || !ifnet_is_attached(ifp, 0)) {
                IGMP_PRINTF(("%s: dropped 0x%llx as ifp went away.\n",
                    __func__, (uint64_t)VM_KERNEL_ADDRPERM(m)));
                m_freem(m);
                OSAddAtomic(1, &ipstat.ips_noroute);
                return;
        }

        ipopts = igmp_sendra ? m_raopt : NULL;

        imo = ip_allocmoptions(M_WAITOK);
        if (imo == NULL) {
                m_freem(m);
                return;
        }

        imo->imo_multicast_ttl  = 1;
        imo->imo_multicast_vif  = -1;
        imo->imo_multicast_loop = 0;

        /*
         * If the user requested that IGMP traffic be explicitly
         * redirected to the loopback interface (e.g. they are running a
         * MANET interface and the routing protocol needs to see the
         * updates), handle this now.
         */
        if (m->m_flags & M_IGMP_LOOP) {
                imo->imo_multicast_ifp = lo_ifp;
        } else {
                imo->imo_multicast_ifp = ifp;
        }

        if (m->m_flags & M_IGMPV2) {
                m0 = m;
        } else {
                m0 = igmp_v3_encap_report(ifp, m);
                if (m0 == NULL) {
                        /*
                         * If igmp_v3_encap_report() failed, then M_PREPEND()
                         * already freed the original mbuf chain.
                         * This means that we don't have to m_freem(m) here.
                         */
                        IGMP_PRINTF(("%s: dropped 0x%llx\n", __func__,
                            (uint64_t)VM_KERNEL_ADDRPERM(m)));
                        IMO_REMREF(imo);
                        atomic_add_32(&ipstat.ips_odropped, 1);
                        return;
                }
        }

        igmp_scrub_context(m0);
        m->m_flags &= ~(M_PROTOFLAGS | M_IGMP_LOOP);
        m0->m_pkthdr.rcvif = lo_ifp;
#ifdef MAC
        mac_netinet_igmp_send(ifp, m0);
#endif

        if (ifp->if_eflags & IFEF_TXSTART) {
                /*
                 * Use control service class if the interface supports
                 * transmit-start model.
                 */
                (void) m_set_service_class(m0, MBUF_SC_CTL);
        }
        bzero(&ro, sizeof(ro));
        error = ip_output(m0, ipopts, &ro, 0, imo, NULL);
        ROUTE_RELEASE(&ro);

        IMO_REMREF(imo);

        if (error) {
                IGMP_PRINTF(("%s: ip_output(0x%llx) = %d\n", __func__,
                    (uint64_t)VM_KERNEL_ADDRPERM(m0), error));
                return;
        }

        IGMPSTAT_INC(igps_snd_reports);
        OIGMPSTAT_INC(igps_snd_reports);
}
/*
 * Encapsulate an IGMPv3 report.
 *
 * The internal mbuf flag M_IGMPV3_HDR is used to indicate that the mbuf
 * chain has already had its IP/IGMPv3 header prepended. In this case
 * the function will not attempt to prepend; the lengths and checksums
 * will however be re-computed.
 *
 * Returns a pointer to the new mbuf chain head, or NULL if the
 * allocation failed.
 */
static struct mbuf *
igmp_v3_encap_report(struct ifnet *ifp, struct mbuf *m)
{
        struct igmp_report      *igmp;
        struct ip               *ip;
        int                      hdrlen, igmpreclen;

        VERIFY((m->m_flags & M_PKTHDR));

        igmpreclen = m_length(m);
        hdrlen = sizeof(struct ip) + sizeof(struct igmp_report);

        if (m->m_flags & M_IGMPV3_HDR) {
                igmpreclen -= hdrlen;
        } else {
                M_PREPEND(m, hdrlen, M_DONTWAIT, 1);
                if (m == NULL) {
                        return NULL;
                }
                m->m_flags |= M_IGMPV3_HDR;
        }

        IGMP_PRINTF(("%s: igmpreclen is %d\n", __func__, igmpreclen));

        m->m_data += sizeof(struct ip);
        m->m_len -= sizeof(struct ip);

        igmp = mtod(m, struct igmp_report *);
        igmp->ir_type = IGMP_v3_HOST_MEMBERSHIP_REPORT;
        igmp->ir_rsv1 = 0;
        igmp->ir_rsv2 = 0;
        igmp->ir_numgrps = htons(m->m_pkthdr.vt_nrecs);
        igmp->ir_cksum = 0;
        igmp->ir_cksum = in_cksum(m, sizeof(struct igmp_report) + igmpreclen);
        m->m_pkthdr.vt_nrecs = 0;

        m->m_data -= sizeof(struct ip);
        m->m_len += sizeof(struct ip);

        ip = mtod(m, struct ip *);
        ip->ip_tos = IPTOS_PREC_INTERNETCONTROL;
        ip->ip_len = hdrlen + igmpreclen;
        ip->ip_off = IP_DF;
        ip->ip_p = IPPROTO_IGMP;
        ip->ip_sum = 0;

        ip->ip_src.s_addr = INADDR_ANY;

        if (m->m_flags & M_IGMP_LOOP) {
                struct in_ifaddr *ia;

                IFP_TO_IA(ifp, ia);
                if (ia != NULL) {
                        IFA_LOCK(&ia->ia_ifa);
                        ip->ip_src = ia->ia_addr.sin_addr;
                        IFA_UNLOCK(&ia->ia_ifa);
                        IFA_REMREF(&ia->ia_ifa);
                }
        }

        ip->ip_dst.s_addr = htonl(INADDR_ALLRPTS_GROUP);

        return m;
}

#ifdef IGMP_DEBUG
static const char *
igmp_rec_type_to_str(const int type)
{
        switch (type) {
        case IGMP_CHANGE_TO_EXCLUDE_MODE:
                return "TO_EX";
        case IGMP_CHANGE_TO_INCLUDE_MODE:
                return "TO_IN";
        case IGMP_MODE_IS_EXCLUDE:
                return "MODE_EX";
        case IGMP_MODE_IS_INCLUDE:
                return "MODE_IN";
        case IGMP_ALLOW_NEW_SOURCES:
                return "ALLOW_NEW";
        case IGMP_BLOCK_OLD_SOURCES:
                return "BLOCK_OLD";
        default:
                break;
        }
        return "unknown";
}
#endif

void
igmp_init(struct protosw *pp, struct domain *dp)
{
#pragma unused(dp)
        static int igmp_initialized = 0;

        VERIFY((pp->pr_flags & (PR_INITIALIZED | PR_ATTACHED)) == PR_ATTACHED);

        if (igmp_initialized) {
                return;
        }
        igmp_initialized = 1;

        IGMP_PRINTF(("%s: initializing\n", __func__));

        igmp_timers_are_running = 0;

        /* Setup lock group and attribute for igmp_mtx */
        igmp_mtx_grp_attr = lck_grp_attr_alloc_init();
        igmp_mtx_grp = lck_grp_alloc_init("igmp_mtx", igmp_mtx_grp_attr);
        igmp_mtx_attr = lck_attr_alloc_init();
        lck_mtx_init(&igmp_mtx, igmp_mtx_grp, igmp_mtx_attr);

        LIST_INIT(&igi_head);
        m_raopt = igmp_ra_alloc();

        igi_size = sizeof(struct igmp_ifinfo);
        igi_zone = zinit(igi_size, IGI_ZONE_MAX * igi_size,
            0, IGI_ZONE_NAME);
        if (igi_zone == NULL) {
                panic("%s: failed allocating %s", __func__, IGI_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(igi_zone, Z_EXPAND, TRUE);
        zone_change(igi_zone, Z_CALLERACCT, FALSE);
}