udp6: allow udp_tun_func_t() to indicate it did not eat the packet

[FreeBSD/FreeBSD.git] / sys / netinet6 / mld6.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2009 Bruce Simpson.
 *
 * 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. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 *      $KAME: mld6.c,v 1.27 2001/04/04 05:17:30 itojun Exp $
 */

/*-
 * 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. 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
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_inet.h"
#include "opt_inet6.h"

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

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

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/mld6.h>
#include <netinet6/mld6_var.h>

#include <security/mac/mac_framework.h>

#ifndef KTR_MLD
#define KTR_MLD KTR_INET6
#endif

static void     mli_delete_locked(const struct ifnet *);
static void     mld_dispatch_packet(struct mbuf *);
static void     mld_dispatch_queue(struct mbufq *, int);
static void     mld_final_leave(struct in6_multi *, struct mld_ifsoftc *);
static void     mld_fasttimo_vnet(struct in6_multi_head *inmh);
static int      mld_handle_state_change(struct in6_multi *,
                    struct mld_ifsoftc *);
static int      mld_initial_join(struct in6_multi *, struct mld_ifsoftc *,
                    const int);
#ifdef KTR
static char *   mld_rec_type_to_str(const int);
#endif
static void     mld_set_version(struct mld_ifsoftc *, const int);
static void     mld_slowtimo_vnet(void);
static int      mld_v1_input_query(struct ifnet *, const struct ip6_hdr *,
                    /*const*/ struct mld_hdr *);
static int      mld_v1_input_report(struct ifnet *, const struct ip6_hdr *,
                    /*const*/ struct mld_hdr *);
static void     mld_v1_process_group_timer(struct in6_multi_head *,
                    struct in6_multi *);
static void     mld_v1_process_querier_timers(struct mld_ifsoftc *);
static int      mld_v1_transmit_report(struct in6_multi *, const int);
static void     mld_v1_update_group(struct in6_multi *, const int);
static void     mld_v2_cancel_link_timers(struct mld_ifsoftc *);
static void     mld_v2_dispatch_general_query(struct mld_ifsoftc *);
static struct mbuf *
                mld_v2_encap_report(struct ifnet *, struct mbuf *);
static int      mld_v2_enqueue_filter_change(struct mbufq *,
                    struct in6_multi *);
static int      mld_v2_enqueue_group_record(struct mbufq *,
                    struct in6_multi *, const int, const int, const int,
                    const int);
static int      mld_v2_input_query(struct ifnet *, const struct ip6_hdr *,
                    struct mbuf *, struct mldv2_query *, const int, const int);
static int      mld_v2_merge_state_changes(struct in6_multi *,
                    struct mbufq *);
static void     mld_v2_process_group_timers(struct in6_multi_head *,
                    struct mbufq *, struct mbufq *,
                    struct in6_multi *, const int);
static int      mld_v2_process_group_query(struct in6_multi *,
                    struct mld_ifsoftc *mli, int, struct mbuf *,
                    struct mldv2_query *, const int);
static int      sysctl_mld_gsr(SYSCTL_HANDLER_ARGS);
static int      sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS);

/*
 * Normative references: RFC 2710, RFC 3590, RFC 3810.
 *
 * Locking:
 *  * The MLD subsystem lock ends up being system-wide for the moment,
 *    but could be per-VIMAGE later on.
 *  * The permitted lock order is: IN6_MULTI_LOCK, MLD_LOCK, IF_ADDR_LOCK.
 *    Any may be taken independently; if any are held at the same
 *    time, the above lock order must be followed.
 *  * IN6_MULTI_LOCK covers in_multi.
 *  * MLD_LOCK covers per-link state and any global variables in this file.
 *  * IF_ADDR_LOCK covers if_multiaddrs, which is used for a variety of
 *    per-link state iterators.
 *
 *  XXX LOR PREVENTION
 *  A special case for IPv6 is the in6_setscope() routine. ip6_output()
 *  will not accept an ifp; it wants an embedded scope ID, unlike
 *  ip_output(), which happily takes the ifp given to it. The embedded
 *  scope ID is only used by MLD to select the outgoing interface.
 *
 *  During interface attach and detach, MLD will take MLD_LOCK *after*
 *  the IF_AFDATA_LOCK.
 *  As in6_setscope() takes IF_AFDATA_LOCK then SCOPE_LOCK, we can't call
 *  it with MLD_LOCK held without triggering an LOR. A netisr with indirect
 *  dispatch could work around this, but we'd rather not do that, as it
 *  can introduce other races.
 *
 *  As such, we exploit the fact that the scope ID is just the interface
 *  index, and embed it in the IPv6 destination address accordingly.
 *  This is potentially NOT VALID for MLDv1 reports, as they
 *  are always sent to the multicast group itself; as MLDv2
 *  reports are always sent to ff02::16, this is not an issue
 *  when MLDv2 is in use.
 *
 *  This does not however eliminate the LOR when ip6_output() itself
 *  calls in6_setscope() internally whilst MLD_LOCK is held. This will
 *  trigger a LOR warning in WITNESS when the ifnet is detached.
 *
 *  The right answer is probably to make IF_AFDATA_LOCK an rwlock, given
 *  how it's used across the network stack. Here we're simply exploiting
 *  the fact that MLD runs at a similar layer in the stack to scope6.c.
 *
 * VIMAGE:
 *  * Each in6_multi corresponds to an ifp, and each ifp corresponds
 *    to a vnet in ifp->if_vnet.
 */
static struct mtx                mld_mtx;
static MALLOC_DEFINE(M_MLD, "mld", "mld state");

#define MLD_EMBEDSCOPE(pin6, zoneid)                                    \
        if (IN6_IS_SCOPE_LINKLOCAL(pin6) ||                             \
            IN6_IS_ADDR_MC_INTFACELOCAL(pin6))                          \
                (pin6)->s6_addr16[1] = htons((zoneid) & 0xFFFF)         \

/*
 * VIMAGE-wide globals.
 */
VNET_DEFINE_STATIC(struct timeval, mld_gsrdelay) = {10, 0};
VNET_DEFINE_STATIC(LIST_HEAD(, mld_ifsoftc), mli_head);
VNET_DEFINE_STATIC(int, interface_timers_running6);
VNET_DEFINE_STATIC(int, state_change_timers_running6);
VNET_DEFINE_STATIC(int, current_state_timers_running6);

#define V_mld_gsrdelay                  VNET(mld_gsrdelay)
#define V_mli_head                      VNET(mli_head)
#define V_interface_timers_running6     VNET(interface_timers_running6)
#define V_state_change_timers_running6  VNET(state_change_timers_running6)
#define V_current_state_timers_running6 VNET(current_state_timers_running6)

SYSCTL_DECL(_net_inet6);        /* Note: Not in any common header. */

SYSCTL_NODE(_net_inet6, OID_AUTO, mld, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "IPv6 Multicast Listener Discovery");

/*
 * Virtualized sysctls.
 */
SYSCTL_PROC(_net_inet6_mld, OID_AUTO, gsrdelay,
    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
    &VNET_NAME(mld_gsrdelay.tv_sec), 0, sysctl_mld_gsr, "I",
    "Rate limit for MLDv2 Group-and-Source queries in seconds");

/*
 * Non-virtualized sysctls.
 */
static SYSCTL_NODE(_net_inet6_mld, OID_AUTO, ifinfo,
    CTLFLAG_RD | CTLFLAG_MPSAFE, sysctl_mld_ifinfo,
    "Per-interface MLDv2 state");

static int      mld_v1enable = 1;
SYSCTL_INT(_net_inet6_mld, OID_AUTO, v1enable, CTLFLAG_RWTUN,
    &mld_v1enable, 0, "Enable fallback to MLDv1");

static int      mld_v2enable = 1;
SYSCTL_INT(_net_inet6_mld, OID_AUTO, v2enable, CTLFLAG_RWTUN,
    &mld_v2enable, 0, "Enable MLDv2");

static int      mld_use_allow = 1;
SYSCTL_INT(_net_inet6_mld, OID_AUTO, use_allow, CTLFLAG_RWTUN,
    &mld_use_allow, 0, "Use ALLOW/BLOCK for RFC 4604 SSM joins/leaves");

/*
 * Packed Router Alert option structure declaration.
 */
struct mld_raopt {
        struct ip6_hbh          hbh;
        struct ip6_opt          pad;
        struct ip6_opt_router   ra;
} __packed;

/*
 * Router Alert hop-by-hop option header.
 */
static struct mld_raopt mld_ra = {
        .hbh = { 0, 0 },
        .pad = { .ip6o_type = IP6OPT_PADN, 0 },
        .ra = {
            .ip6or_type = IP6OPT_ROUTER_ALERT,
            .ip6or_len = IP6OPT_RTALERT_LEN - 2,
            .ip6or_value[0] = ((IP6OPT_RTALERT_MLD >> 8) & 0xFF),
            .ip6or_value[1] = (IP6OPT_RTALERT_MLD & 0xFF)
        }
};
static struct ip6_pktopts mld_po;

static __inline void
mld_save_context(struct mbuf *m, struct ifnet *ifp)
{

#ifdef VIMAGE
        m->m_pkthdr.PH_loc.ptr = ifp->if_vnet;
#endif /* VIMAGE */
        m->m_pkthdr.rcvif = ifp;
        m->m_pkthdr.flowid = ifp->if_index;
}

static __inline void
mld_scrub_context(struct mbuf *m)
{

        m->m_pkthdr.PH_loc.ptr = NULL;
        m->m_pkthdr.flowid = 0;
}

/*
 * Restore context from a queued output chain.
 * Return saved ifindex.
 *
 * VIMAGE: The assertion is there to make sure that we
 * actually called CURVNET_SET() with what's in the mbuf chain.
 */
static __inline uint32_t
mld_restore_context(struct mbuf *m)
{

#if defined(VIMAGE) && defined(INVARIANTS)
        KASSERT(curvnet == m->m_pkthdr.PH_loc.ptr,
            ("%s: called when curvnet was not restored: cuvnet %p m ptr %p",
            __func__, curvnet, m->m_pkthdr.PH_loc.ptr));
#endif
        return (m->m_pkthdr.flowid);
}

/*
 * Retrieve or set threshold between group-source queries in seconds.
 *
 * VIMAGE: Assume curvnet set by caller.
 * SMPng: NOTE: Serialized by MLD lock.
 */
static int
sysctl_mld_gsr(SYSCTL_HANDLER_ARGS)
{
        int error;
        int i;

        error = sysctl_wire_old_buffer(req, sizeof(int));
        if (error)
                return (error);

        MLD_LOCK();

        i = V_mld_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;
        }

        CTR2(KTR_MLD, "change mld_gsrdelay from %d to %d",
             V_mld_gsrdelay.tv_sec, i);
        V_mld_gsrdelay.tv_sec = i;

out_locked:
        MLD_UNLOCK();
        return (error);
}

/*
 * Expose struct mld_ifsoftc to userland, keyed by ifindex.
 * For use by ifmcstat(8).
 *
 * VIMAGE: Assume curvnet set by caller. The node handler itself
 * is not directly virtualized.
 */
static int
sysctl_mld_ifinfo(SYSCTL_HANDLER_ARGS)
{
        struct epoch_tracker     et;
        int                     *name;
        int                      error;
        u_int                    namelen;
        struct ifnet            *ifp;
        struct mld_ifsoftc      *mli;

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

        if (req->newptr != NULL)
                return (EPERM);

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

        error = sysctl_wire_old_buffer(req, sizeof(struct mld_ifinfo));
        if (error)
                return (error);

        IN6_MULTI_LOCK();
        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();
        NET_EPOCH_ENTER(et);

        error = ENOENT;
        ifp = ifnet_byindex(name[0]);
        if (ifp == NULL)
                goto out_locked;

        LIST_FOREACH(mli, &V_mli_head, mli_link) {
                if (ifp == mli->mli_ifp) {
                        struct mld_ifinfo info;

                        info.mli_version = mli->mli_version;
                        info.mli_v1_timer = mli->mli_v1_timer;
                        info.mli_v2_timer = mli->mli_v2_timer;
                        info.mli_flags = mli->mli_flags;
                        info.mli_rv = mli->mli_rv;
                        info.mli_qi = mli->mli_qi;
                        info.mli_qri = mli->mli_qri;
                        info.mli_uri = mli->mli_uri;
                        error = SYSCTL_OUT(req, &info, sizeof(info));
                        break;
                }
        }

out_locked:
        NET_EPOCH_EXIT(et);
        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();
        IN6_MULTI_UNLOCK();
        return (error);
}

/*
 * Dispatch an entire queue of pending packet chains.
 * VIMAGE: Assumes the vnet pointer has been set.
 */
static void
mld_dispatch_queue(struct mbufq *mq, int limit)
{
        struct mbuf *m;

        while ((m = mbufq_dequeue(mq)) != NULL) {
                CTR3(KTR_MLD, "%s: dispatch %p from %p", __func__, mq, m);
                mld_dispatch_packet(m);
                if (--limit == 0)
                        break;
        }
}

/*
 * Filter outgoing MLD report state by group.
 *
 * Reports are ALWAYS suppressed for ALL-HOSTS (ff02::1)
 * and node-local addresses. However, kernel and socket consumers
 * always embed the KAME scope ID in the address provided, so strip it
 * when performing comparison.
 * Note: This is not the same as the *multicast* scope.
 *
 * Return zero if the given group is one for which MLD reports
 * should be suppressed, or non-zero if reports should be issued.
 */
static __inline int
mld_is_addr_reported(const struct in6_addr *addr)
{

        KASSERT(IN6_IS_ADDR_MULTICAST(addr), ("%s: not multicast", __func__));

        if (IPV6_ADDR_MC_SCOPE(addr) == IPV6_ADDR_SCOPE_NODELOCAL)
                return (0);

        if (IPV6_ADDR_MC_SCOPE(addr) == IPV6_ADDR_SCOPE_LINKLOCAL) {
                struct in6_addr tmp = *addr;
                in6_clearscope(&tmp);
                if (IN6_ARE_ADDR_EQUAL(&tmp, &in6addr_linklocal_allnodes))
                        return (0);
        }

        return (1);
}

/*
 * Attach MLD when PF_INET6 is attached to an interface.  Assumes that the
 * current VNET is set by the caller.
 */
struct mld_ifsoftc *
mld_domifattach(struct ifnet *ifp)
{
        struct mld_ifsoftc *mli;

        CTR3(KTR_MLD, "%s: called for ifp %p(%s)", __func__, ifp, if_name(ifp));

        mli = malloc(sizeof(struct mld_ifsoftc), M_MLD, M_WAITOK | M_ZERO);
        mli->mli_ifp = ifp;
        mli->mli_version = MLD_VERSION_2;
        mli->mli_flags = 0;
        mli->mli_rv = MLD_RV_INIT;
        mli->mli_qi = MLD_QI_INIT;
        mli->mli_qri = MLD_QRI_INIT;
        mli->mli_uri = MLD_URI_INIT;
        mbufq_init(&mli->mli_gq, MLD_MAX_RESPONSE_PACKETS);
        if ((ifp->if_flags & IFF_MULTICAST) == 0)
                mli->mli_flags |= MLIF_SILENT;
        if (mld_use_allow)
                mli->mli_flags |= MLIF_USEALLOW;

        MLD_LOCK();
        LIST_INSERT_HEAD(&V_mli_head, mli, mli_link);
        MLD_UNLOCK();

        return (mli);
}

/*
 * Hook for ifdetach.
 *
 * NOTE: Some finalization tasks need to run before the protocol domain
 * is detached, but also before the link layer does its cleanup.
 * Run before link-layer cleanup; cleanup groups, but do not free MLD state.
 *
 * SMPng: Caller must hold IN6_MULTI_LOCK().
 * Must take IF_ADDR_LOCK() to cover if_multiaddrs iterator.
 * XXX This routine is also bitten by unlocked ifma_protospec access.
 */
void
mld_ifdetach(struct ifnet *ifp, struct in6_multi_head *inmh)
{
        struct epoch_tracker     et;
        struct mld_ifsoftc      *mli;
        struct ifmultiaddr      *ifma;
        struct in6_multi        *inm;

        CTR3(KTR_MLD, "%s: called for ifp %p(%s)", __func__, ifp,
            if_name(ifp));

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK();

        mli = MLD_IFINFO(ifp);
        IF_ADDR_WLOCK(ifp);
        /*
         * Extract list of in6_multi associated with the detaching ifp
         * which the PF_INET6 layer is about to release.
         */
        NET_EPOCH_ENTER(et);
        CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                inm = in6m_ifmultiaddr_get_inm(ifma);
                if (inm == NULL)
                        continue;
                in6m_disconnect_locked(inmh, inm);

                if (mli->mli_version == MLD_VERSION_2) {
                        in6m_clear_recorded(inm);

                        /*
                         * We need to release the final reference held
                         * for issuing the INCLUDE {}.
                         */
                        if (inm->in6m_state == MLD_LEAVING_MEMBER) {
                                inm->in6m_state = MLD_NOT_MEMBER;
                                in6m_rele_locked(inmh, inm);
                        }
                }
        }
        NET_EPOCH_EXIT(et);
        IF_ADDR_WUNLOCK(ifp);
        MLD_UNLOCK();
}

/*
 * Hook for domifdetach.
 * Runs after link-layer cleanup; free MLD state.
 *
 * SMPng: Normally called with IF_AFDATA_LOCK held.
 */
void
mld_domifdetach(struct ifnet *ifp)
{

        CTR3(KTR_MLD, "%s: called for ifp %p(%s)",
            __func__, ifp, if_name(ifp));

        MLD_LOCK();
        mli_delete_locked(ifp);
        MLD_UNLOCK();
}

static void
mli_delete_locked(const struct ifnet *ifp)
{
        struct mld_ifsoftc *mli, *tmli;

        CTR3(KTR_MLD, "%s: freeing mld_ifsoftc for ifp %p(%s)",
            __func__, ifp, if_name(ifp));

        MLD_LOCK_ASSERT();

        LIST_FOREACH_SAFE(mli, &V_mli_head, mli_link, tmli) {
                if (mli->mli_ifp == ifp) {
                        /*
                         * Free deferred General Query responses.
                         */
                        mbufq_drain(&mli->mli_gq);

                        LIST_REMOVE(mli, mli_link);

                        free(mli, M_MLD);
                        return;
                }
        }
}

/*
 * Process a received MLDv1 general or address-specific query.
 * Assumes that the query header has been pulled up to sizeof(mld_hdr).
 *
 * NOTE: Can't be fully const correct as we temporarily embed scope ID in
 * mld_addr. This is OK as we own the mbuf chain.
 */
static int
mld_v1_input_query(struct ifnet *ifp, const struct ip6_hdr *ip6,
    /*const*/ struct mld_hdr *mld)
{
        struct ifmultiaddr      *ifma;
        struct mld_ifsoftc      *mli;
        struct in6_multi        *inm;
        int                      is_general_query;
        uint16_t                 timer;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        NET_EPOCH_ASSERT();

        is_general_query = 0;

        if (!mld_v1enable) {
                CTR3(KTR_MLD, "ignore v1 query %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &mld->mld_addr),
                    ifp, if_name(ifp));
                return (0);
        }

        /*
         * RFC3810 Section 6.2: MLD queries must originate from
         * a router's link-local address.
         */
        if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
                CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                    ifp, if_name(ifp));
                return (0);
        }

        /*
         * Do address field validation upfront before we accept
         * the query.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr)) {
                /*
                 * MLDv1 General Query.
                 * If this was not sent to the all-nodes group, ignore it.
                 */
                struct in6_addr          dst;

                dst = ip6->ip6_dst;
                in6_clearscope(&dst);
                if (!IN6_ARE_ADDR_EQUAL(&dst, &in6addr_linklocal_allnodes))
                        return (EINVAL);
                is_general_query = 1;
        } else {
                /*
                 * Embed scope ID of receiving interface in MLD query for
                 * lookup whilst we don't hold other locks.
                 */
                in6_setscope(&mld->mld_addr, ifp, NULL);
        }

        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();

        /*
         * Switch to MLDv1 host compatibility mode.
         */
        mli = MLD_IFINFO(ifp);
        KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));
        mld_set_version(mli, MLD_VERSION_1);

        timer = (ntohs(mld->mld_maxdelay) * PR_FASTHZ) / MLD_TIMER_SCALE;
        if (timer == 0)
                timer = 1;

        if (is_general_query) {
                /*
                 * For each reporting group joined on this
                 * interface, kick the report timer.
                 */
                CTR2(KTR_MLD, "process v1 general query on ifp %p(%s)",
                         ifp, if_name(ifp));
                CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                        inm = in6m_ifmultiaddr_get_inm(ifma);
                        if (inm == NULL)
                                continue;
                        mld_v1_update_group(inm, timer);
                }
        } else {
                /*
                 * MLDv1 Group-Specific Query.
                 * If this is a group-specific MLDv1 query, we need only
                 * look up the single group to process it.
                 */
                inm = in6m_lookup_locked(ifp, &mld->mld_addr);
                if (inm != NULL) {
                        CTR3(KTR_MLD, "process v1 query %s on ifp %p(%s)",
                            ip6_sprintf(ip6tbuf, &mld->mld_addr),
                            ifp, if_name(ifp));
                        mld_v1_update_group(inm, timer);
                }
                /* XXX Clear embedded scope ID as userland won't expect it. */
                in6_clearscope(&mld->mld_addr);
        }

        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();

        return (0);
}

/*
 * Update the report timer on a group in response to an MLDv1 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 MLDv2. 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 MLDv2, the delay per group should be jittered
 * to avoid bursts of MLDv1 reports.
 */
static void
mld_v1_update_group(struct in6_multi *inm, const int timer)
{
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        CTR4(KTR_MLD, "%s: %s/%s timer=%d", __func__,
            ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            if_name(inm->in6m_ifp), timer);

        IN6_MULTI_LIST_LOCK_ASSERT();

        switch (inm->in6m_state) {
        case MLD_NOT_MEMBER:
        case MLD_SILENT_MEMBER:
                break;
        case MLD_REPORTING_MEMBER:
                if (inm->in6m_timer != 0 &&
                    inm->in6m_timer <= timer) {
                        CTR1(KTR_MLD, "%s: REPORTING and timer running, "
                            "skipping.", __func__);
                        break;
                }
                /* FALLTHROUGH */
        case MLD_SG_QUERY_PENDING_MEMBER:
        case MLD_G_QUERY_PENDING_MEMBER:
        case MLD_IDLE_MEMBER:
        case MLD_LAZY_MEMBER:
        case MLD_AWAKENING_MEMBER:
                CTR1(KTR_MLD, "%s: ->REPORTING", __func__);
                inm->in6m_state = MLD_REPORTING_MEMBER;
                inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                V_current_state_timers_running6 = 1;
                break;
        case MLD_SLEEPING_MEMBER:
                CTR1(KTR_MLD, "%s: ->AWAKENING", __func__);
                inm->in6m_state = MLD_AWAKENING_MEMBER;
                break;
        case MLD_LEAVING_MEMBER:
                break;
        }
}

/*
 * Process a received MLDv2 general, group-specific or
 * group-and-source-specific query.
 *
 * Assumes that mld points to a struct mldv2_query which is stored in
 * contiguous memory.
 *
 * Return 0 if successful, otherwise an appropriate error code is returned.
 */
static int
mld_v2_input_query(struct ifnet *ifp, const struct ip6_hdr *ip6,
    struct mbuf *m, struct mldv2_query *mld, const int off, const int icmp6len)
{
        struct mld_ifsoftc      *mli;
        struct in6_multi        *inm;
        uint32_t                 maxdelay, nsrc, qqi;
        int                      is_general_query;
        uint16_t                 timer;
        uint8_t                  qrv;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        NET_EPOCH_ASSERT();

        if (!mld_v2enable) {
                CTR3(KTR_MLD, "ignore v2 query src %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                    ifp, if_name(ifp));
                return (0);
        }

        /*
         * RFC3810 Section 6.2: MLD queries must originate from
         * a router's link-local address.
         */
        if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
                CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                    ifp, if_name(ifp));
                return (0);
        }

        is_general_query = 0;

        CTR2(KTR_MLD, "input v2 query on ifp %p(%s)", ifp, if_name(ifp));

        maxdelay = ntohs(mld->mld_maxdelay);    /* in 1/10ths of a second */
        if (maxdelay >= 32768) {
                maxdelay = (MLD_MRC_MANT(maxdelay) | 0x1000) <<
                           (MLD_MRC_EXP(maxdelay) + 3);
        }
        timer = (maxdelay * PR_FASTHZ) / MLD_TIMER_SCALE;
        if (timer == 0)
                timer = 1;

        qrv = MLD_QRV(mld->mld_misc);
        if (qrv < 2) {
                CTR3(KTR_MLD, "%s: clamping qrv %d to %d", __func__,
                    qrv, MLD_RV_INIT);
                qrv = MLD_RV_INIT;
        }

        qqi = mld->mld_qqi;
        if (qqi >= 128) {
                qqi = MLD_QQIC_MANT(mld->mld_qqi) <<
                     (MLD_QQIC_EXP(mld->mld_qqi) + 3);
        }

        nsrc = ntohs(mld->mld_numsrc);
        if (nsrc > MLD_MAX_GS_SOURCES)
                return (EMSGSIZE);
        if (icmp6len < sizeof(struct mldv2_query) +
            (nsrc * sizeof(struct in6_addr)))
                return (EMSGSIZE);

        /*
         * Do further input validation upfront to avoid resetting timers
         * should we need to discard this query.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr)) {
                /*
                 * A general query with a source list has undefined
                 * behaviour; discard it.
                 */
                if (nsrc > 0)
                        return (EINVAL);
                is_general_query = 1;
        } else {
                /*
                 * Embed scope ID of receiving interface in MLD query for
                 * lookup whilst we don't hold other locks (due to KAME
                 * locking lameness). We own this mbuf chain just now.
                 */
                in6_setscope(&mld->mld_addr, ifp, NULL);
        }

        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();

        mli = MLD_IFINFO(ifp);
        KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));

        /*
         * Discard the v2 query if we're in Compatibility Mode.
         * The RFC is pretty clear that hosts need to stay in MLDv1 mode
         * until the Old Version Querier Present timer expires.
         */
        if (mli->mli_version != MLD_VERSION_2)
                goto out_locked;

        mld_set_version(mli, MLD_VERSION_2);
        mli->mli_rv = qrv;
        mli->mli_qi = qqi;
        mli->mli_qri = maxdelay;

        CTR4(KTR_MLD, "%s: qrv %d qi %d maxdelay %d", __func__, qrv, qqi,
            maxdelay);

        if (is_general_query) {
                /*
                 * MLDv2 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.
                 */
                CTR2(KTR_MLD, "process v2 general query on ifp %p(%s)",
                    ifp, if_name(ifp));
                if (mli->mli_v2_timer == 0 || mli->mli_v2_timer >= timer) {
                        mli->mli_v2_timer = MLD_RANDOM_DELAY(timer);
                        V_interface_timers_running6 = 1;
                }
        } else {
                /*
                 * MLDv2 Group-specific or Group-and-source-specific Query.
                 *
                 * 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.
                 */
                inm = in6m_lookup_locked(ifp, &mld->mld_addr);
                if (inm == NULL)
                        goto out_locked;
                if (nsrc > 0) {
                        if (!ratecheck(&inm->in6m_lastgsrtv,
                            &V_mld_gsrdelay)) {
                                CTR1(KTR_MLD, "%s: GS query throttled.",
                                    __func__);
                                goto out_locked;
                        }
                }
                CTR2(KTR_MLD, "process v2 group query on ifp %p(%s)",
                     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.
                 */
                if (mli->mli_v2_timer == 0 || mli->mli_v2_timer >= timer)
                        mld_v2_process_group_query(inm, mli, timer, m, mld, off);

                /* XXX Clear embedded scope ID as userland won't expect it. */
                in6_clearscope(&mld->mld_addr);
        }

out_locked:
        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();

        return (0);
}

/*
 * Process a received MLDv2 group-specific or group-and-source-specific
 * query.
 * Return <0 if any error occurred. Currently this is ignored.
 */
static int
mld_v2_process_group_query(struct in6_multi *inm, struct mld_ifsoftc *mli,
    int timer, struct mbuf *m0, struct mldv2_query *mld, const int off)
{
        int                      retval;
        uint16_t                 nsrc;

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        retval = 0;

        switch (inm->in6m_state) {
        case MLD_NOT_MEMBER:
        case MLD_SILENT_MEMBER:
        case MLD_SLEEPING_MEMBER:
        case MLD_LAZY_MEMBER:
        case MLD_AWAKENING_MEMBER:
        case MLD_IDLE_MEMBER:
        case MLD_LEAVING_MEMBER:
                return (retval);
                break;
        case MLD_REPORTING_MEMBER:
        case MLD_G_QUERY_PENDING_MEMBER:
        case MLD_SG_QUERY_PENDING_MEMBER:
                break;
        }

        nsrc = ntohs(mld->mld_numsrc);

        /* Length should be checked by calling function. */
        KASSERT((m0->m_flags & M_PKTHDR) == 0 ||
            m0->m_pkthdr.len >= off + sizeof(struct mldv2_query) +
            nsrc * sizeof(struct in6_addr),
            ("mldv2 packet is too short: (%d bytes < %zd bytes, m=%p)",
            m0->m_pkthdr.len, off + sizeof(struct mldv2_query) +
            nsrc * sizeof(struct in6_addr), m0));

        /*
         * 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->in6m_state == MLD_G_QUERY_PENDING_MEMBER ||
                    inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER) {
                        in6m_clear_recorded(inm);
                        timer = min(inm->in6m_timer, timer);
                }
                inm->in6m_state = MLD_G_QUERY_PENDING_MEMBER;
                inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                V_current_state_timers_running6 = 1;
                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->in6m_state == MLD_G_QUERY_PENDING_MEMBER) {
                timer = min(inm->in6m_timer, timer);
                inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                V_current_state_timers_running6 = 1;
                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.
         */
        if (inm->in6m_nsrc > 0) {
                struct in6_addr          srcaddr;
                int                      i, nrecorded;
                int                      soff;

                soff = off + sizeof(struct mldv2_query);
                nrecorded = 0;
                for (i = 0; i < nsrc; i++) {
                        m_copydata(m0, soff, sizeof(struct in6_addr),
                            (caddr_t)&srcaddr);
                        retval = in6m_record_source(inm, &srcaddr);
                        if (retval < 0)
                                break;
                        nrecorded += retval;
                        soff += sizeof(struct in6_addr);
                }
                if (nrecorded > 0) {
                        CTR1(KTR_MLD,
                            "%s: schedule response to SG query", __func__);
                        inm->in6m_state = MLD_SG_QUERY_PENDING_MEMBER;
                        inm->in6m_timer = MLD_RANDOM_DELAY(timer);
                        V_current_state_timers_running6 = 1;
                }
        }

        return (retval);
}

/*
 * Process a received MLDv1 host membership report.
 * Assumes mld points to mld_hdr in pulled up mbuf chain.
 *
 * NOTE: Can't be fully const correct as we temporarily embed scope ID in
 * mld_addr. This is OK as we own the mbuf chain.
 */
static int
mld_v1_input_report(struct ifnet *ifp, const struct ip6_hdr *ip6,
    /*const*/ struct mld_hdr *mld)
{
        struct in6_addr          src, dst;
        struct in6_ifaddr       *ia;
        struct in6_multi        *inm;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        NET_EPOCH_ASSERT();

        if (!mld_v1enable) {
                CTR3(KTR_MLD, "ignore v1 report %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &mld->mld_addr),
                    ifp, if_name(ifp));
                return (0);
        }

        if (ifp->if_flags & IFF_LOOPBACK)
                return (0);

        /*
         * MLDv1 reports must originate from a host's link-local address,
         * or the unspecified address (when booting).
         */
        src = ip6->ip6_src;
        in6_clearscope(&src);
        if (!IN6_IS_SCOPE_LINKLOCAL(&src) && !IN6_IS_ADDR_UNSPECIFIED(&src)) {
                CTR3(KTR_MLD, "ignore v1 query src %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &ip6->ip6_src),
                    ifp, if_name(ifp));
                return (EINVAL);
        }

        /*
         * RFC2710 Section 4: MLDv1 reports must pertain to a multicast
         * group, and must be directed to the group itself.
         */
        dst = ip6->ip6_dst;
        in6_clearscope(&dst);
        if (!IN6_IS_ADDR_MULTICAST(&mld->mld_addr) ||
            !IN6_ARE_ADDR_EQUAL(&mld->mld_addr, &dst)) {
                CTR3(KTR_MLD, "ignore v1 query dst %s on ifp %p(%s)",
                    ip6_sprintf(ip6tbuf, &ip6->ip6_dst),
                    ifp, if_name(ifp));
                return (EINVAL);
        }

        /*
         * Make sure we don't hear our own membership report, as fast
         * leave requires knowing that we are the only member of a
         * group. Assume we used the link-local address if available,
         * otherwise look for ::.
         *
         * XXX Note that scope ID comparison is needed for the address
         * returned by in6ifa_ifpforlinklocal(), but SHOULD NOT be
         * performed for the on-wire address.
         */
        ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
        if ((ia && IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, IA6_IN6(ia))) ||
            (ia == NULL && IN6_IS_ADDR_UNSPECIFIED(&src))) {
                if (ia != NULL)
                        ifa_free(&ia->ia_ifa);
                return (0);
        }
        if (ia != NULL)
                ifa_free(&ia->ia_ifa);

        CTR3(KTR_MLD, "process v1 report %s on ifp %p(%s)",
            ip6_sprintf(ip6tbuf, &mld->mld_addr), ifp, if_name(ifp));

        /*
         * Embed scope ID of receiving interface in MLD query for lookup
         * whilst we don't hold other locks (due to KAME locking lameness).
         */
        if (!IN6_IS_ADDR_UNSPECIFIED(&mld->mld_addr))
                in6_setscope(&mld->mld_addr, ifp, NULL);

        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();

        /*
         * MLDv1 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.
         */
        inm = in6m_lookup_locked(ifp, &mld->mld_addr);
        if (inm != NULL) {
                struct mld_ifsoftc *mli;

                mli = inm->in6m_mli;
                KASSERT(mli != NULL,
                    ("%s: no mli for ifp %p", __func__, ifp));

                /*
                 * If we are in MLDv2 host mode, do not allow the
                 * other host's MLDv1 report to suppress our reports.
                 */
                if (mli->mli_version == MLD_VERSION_2)
                        goto out_locked;

                inm->in6m_timer = 0;

                switch (inm->in6m_state) {
                case MLD_NOT_MEMBER:
                case MLD_SILENT_MEMBER:
                case MLD_SLEEPING_MEMBER:
                        break;
                case MLD_REPORTING_MEMBER:
                case MLD_IDLE_MEMBER:
                case MLD_AWAKENING_MEMBER:
                        CTR3(KTR_MLD,
                            "report suppressed for %s on ifp %p(%s)",
                            ip6_sprintf(ip6tbuf, &mld->mld_addr),
                            ifp, if_name(ifp));
                case MLD_LAZY_MEMBER:
                        inm->in6m_state = MLD_LAZY_MEMBER;
                        break;
                case MLD_G_QUERY_PENDING_MEMBER:
                case MLD_SG_QUERY_PENDING_MEMBER:
                case MLD_LEAVING_MEMBER:
                        break;
                }
        }

out_locked:
        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();

        /* XXX Clear embedded scope ID as userland won't expect it. */
        in6_clearscope(&mld->mld_addr);

        return (0);
}

/*
 * MLD input path.
 *
 * Assume query messages which fit in a single ICMPv6 message header
 * have been pulled up.
 * Assume that userland will want to see the message, even if it
 * otherwise fails kernel input validation; do not free it.
 * Pullup may however free the mbuf chain m if it fails.
 *
 * Return IPPROTO_DONE if we freed m. Otherwise, return 0.
 */
int
mld_input(struct mbuf **mp, int off, int icmp6len)
{
        struct ifnet    *ifp;
        struct ip6_hdr  *ip6;
        struct mbuf     *m;
        struct mld_hdr  *mld;
        int              mldlen;

        m = *mp;
        CTR3(KTR_MLD, "%s: called w/mbuf (%p,%d)", __func__, m, off);

        ifp = m->m_pkthdr.rcvif;

        /* Pullup to appropriate size. */
        if (m->m_len < off + sizeof(*mld)) {
                m = m_pullup(m, off + sizeof(*mld));
                if (m == NULL) {
                        ICMP6STAT_INC(icp6s_badlen);
                        return (IPPROTO_DONE);
                }
        }
        mld = (struct mld_hdr *)(mtod(m, uint8_t *) + off);
        if (mld->mld_type == MLD_LISTENER_QUERY &&
            icmp6len >= sizeof(struct mldv2_query)) {
                mldlen = sizeof(struct mldv2_query);
        } else {
                mldlen = sizeof(struct mld_hdr);
        }
        if (m->m_len < off + mldlen) {
                m = m_pullup(m, off + mldlen);
                if (m == NULL) {
                        ICMP6STAT_INC(icp6s_badlen);
                        return (IPPROTO_DONE);
                }
        }
        *mp = m;
        ip6 = mtod(m, struct ip6_hdr *);
        mld = (struct mld_hdr *)(mtod(m, uint8_t *) + off);

        /*
         * Userland needs to see all of this traffic for implementing
         * the endpoint discovery portion of multicast routing.
         */
        switch (mld->mld_type) {
        case MLD_LISTENER_QUERY:
                icmp6_ifstat_inc(ifp, ifs6_in_mldquery);
                if (icmp6len == sizeof(struct mld_hdr)) {
                        if (mld_v1_input_query(ifp, ip6, mld) != 0)
                                return (0);
                } else if (icmp6len >= sizeof(struct mldv2_query)) {
                        if (mld_v2_input_query(ifp, ip6, m,
                            (struct mldv2_query *)mld, off, icmp6len) != 0)
                                return (0);
                }
                break;
        case MLD_LISTENER_REPORT:
                icmp6_ifstat_inc(ifp, ifs6_in_mldreport);
                if (mld_v1_input_report(ifp, ip6, mld) != 0)
                        return (0);
                break;
        case MLDV2_LISTENER_REPORT:
                icmp6_ifstat_inc(ifp, ifs6_in_mldreport);
                break;
        case MLD_LISTENER_DONE:
                icmp6_ifstat_inc(ifp, ifs6_in_mlddone);
                break;
        default:
                break;
        }

        return (0);
}

/*
 * Fast timeout handler (global).
 * VIMAGE: Timeout handlers are expected to service all vimages.
 */
void
mld_fasttimo(void)
{
        struct in6_multi_head inmh;
        VNET_ITERATOR_DECL(vnet_iter);

        SLIST_INIT(&inmh);

        VNET_LIST_RLOCK_NOSLEEP();
        VNET_FOREACH(vnet_iter) {
                CURVNET_SET(vnet_iter);
                mld_fasttimo_vnet(&inmh);
                CURVNET_RESTORE();
        }
        VNET_LIST_RUNLOCK_NOSLEEP();
        in6m_release_list_deferred(&inmh);
}

/*
 * Fast timeout handler (per-vnet).
 *
 * VIMAGE: Assume caller has set up our curvnet.
 */
static void
mld_fasttimo_vnet(struct in6_multi_head *inmh)
{
        struct epoch_tracker     et;
        struct mbufq             scq;   /* State-change packets */
        struct mbufq             qrq;   /* Query response packets */
        struct ifnet            *ifp;
        struct mld_ifsoftc      *mli;
        struct ifmultiaddr      *ifma;
        struct in6_multi        *inm;
        int                      uri_fasthz;

        uri_fasthz = 0;

        /*
         * Quick check to see if any work needs to be done, in order to
         * minimize the overhead of fasttimo processing.
         * SMPng: XXX Unlocked reads.
         */
        if (!V_current_state_timers_running6 &&
            !V_interface_timers_running6 &&
            !V_state_change_timers_running6)
                return;

        IN6_MULTI_LIST_LOCK();
        MLD_LOCK();

        /*
         * MLDv2 General Query response timer processing.
         */
        if (V_interface_timers_running6) {
                CTR1(KTR_MLD, "%s: interface timers running", __func__);

                V_interface_timers_running6 = 0;
                LIST_FOREACH(mli, &V_mli_head, mli_link) {
                        if (mli->mli_v2_timer == 0) {
                                /* Do nothing. */
                        } else if (--mli->mli_v2_timer == 0) {
                                mld_v2_dispatch_general_query(mli);
                        } else {
                                V_interface_timers_running6 = 1;
                        }
                }
        }

        if (!V_current_state_timers_running6 &&
            !V_state_change_timers_running6)
                goto out_locked;

        V_current_state_timers_running6 = 0;
        V_state_change_timers_running6 = 0;

        CTR1(KTR_MLD, "%s: state change timers running", __func__);

        /*
         * MLD host report and state-change timer processing.
         * Note: Processing a v2 group timer may remove a node.
         */
        LIST_FOREACH(mli, &V_mli_head, mli_link) {
                ifp = mli->mli_ifp;

                if (mli->mli_version == MLD_VERSION_2) {
                        uri_fasthz = MLD_RANDOM_DELAY(mli->mli_uri *
                            PR_FASTHZ);
                        mbufq_init(&qrq, MLD_MAX_G_GS_PACKETS);
                        mbufq_init(&scq, MLD_MAX_STATE_CHANGE_PACKETS);
                }

                NET_EPOCH_ENTER(et);
                IF_ADDR_WLOCK(ifp);
                CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                        inm = in6m_ifmultiaddr_get_inm(ifma);
                        if (inm == NULL)
                                continue;
                        switch (mli->mli_version) {
                        case MLD_VERSION_1:
                                mld_v1_process_group_timer(inmh, inm);
                                break;
                        case MLD_VERSION_2:
                                mld_v2_process_group_timers(inmh, &qrq,
                                    &scq, inm, uri_fasthz);
                                break;
                        }
                }
                IF_ADDR_WUNLOCK(ifp);

                switch (mli->mli_version) {
                case MLD_VERSION_1:
                        /*
                         * Transmit reports for this lifecycle.  This
                         * is done while not holding IF_ADDR_LOCK
                         * since this can call
                         * in6ifa_ifpforlinklocal() which locks
                         * IF_ADDR_LOCK internally as well as
                         * ip6_output() to transmit a packet.
                         */
                        while ((inm = SLIST_FIRST(inmh)) != NULL) {
                                SLIST_REMOVE_HEAD(inmh, in6m_defer);
                                (void)mld_v1_transmit_report(inm,
                                    MLD_LISTENER_REPORT);
                        }
                        break;
                case MLD_VERSION_2:
                        mld_dispatch_queue(&qrq, 0);
                        mld_dispatch_queue(&scq, 0);
                        break;
                }
                NET_EPOCH_EXIT(et);
        }

out_locked:
        MLD_UNLOCK();
        IN6_MULTI_LIST_UNLOCK();
}

/*
 * Update host report group timer.
 * Will update the global pending timer flags.
 */
static void
mld_v1_process_group_timer(struct in6_multi_head *inmh, struct in6_multi *inm)
{
        int report_timer_expired;

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        if (inm->in6m_timer == 0) {
                report_timer_expired = 0;
        } else if (--inm->in6m_timer == 0) {
                report_timer_expired = 1;
        } else {
                V_current_state_timers_running6 = 1;
                return;
        }

        switch (inm->in6m_state) {
        case MLD_NOT_MEMBER:
        case MLD_SILENT_MEMBER:
        case MLD_IDLE_MEMBER:
        case MLD_LAZY_MEMBER:
        case MLD_SLEEPING_MEMBER:
        case MLD_AWAKENING_MEMBER:
                break;
        case MLD_REPORTING_MEMBER:
                if (report_timer_expired) {
                        inm->in6m_state = MLD_IDLE_MEMBER;
                        SLIST_INSERT_HEAD(inmh, inm, in6m_defer);
                }
                break;
        case MLD_G_QUERY_PENDING_MEMBER:
        case MLD_SG_QUERY_PENDING_MEMBER:
        case MLD_LEAVING_MEMBER:
                break;
        }
}

/*
 * Update a group's timers for MLDv2.
 * Will update the global pending timer flags.
 * Note: Unlocked read from mli.
 */
static void
mld_v2_process_group_timers(struct in6_multi_head *inmh,
    struct mbufq *qrq, struct mbufq *scq,
    struct in6_multi *inm, const int uri_fasthz)
{
        int query_response_timer_expired;
        int state_change_retransmit_timer_expired;
#ifdef KTR
        char ip6tbuf[INET6_ADDRSTRLEN];
#endif

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        query_response_timer_expired = 0;
        state_change_retransmit_timer_expired = 0;

        /*
         * During a transition from compatibility mode back to MLDv2,
         * 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 slow-timeout path.
         */
        if (inm->in6m_timer == 0) {
                query_response_timer_expired = 0;
        } else if (--inm->in6m_timer == 0) {
                query_response_timer_expired = 1;
        } else {
                V_current_state_timers_running6 = 1;
        }

        if (inm->in6m_sctimer == 0) {
                state_change_retransmit_timer_expired = 0;
        } else if (--inm->in6m_sctimer == 0) {
                state_change_retransmit_timer_expired = 1;
        } else {
                V_state_change_timers_running6 = 1;
        }

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

        switch (inm->in6m_state) {
        case MLD_NOT_MEMBER:
        case MLD_SILENT_MEMBER:
        case MLD_SLEEPING_MEMBER:
        case MLD_LAZY_MEMBER:
        case MLD_AWAKENING_MEMBER:
        case MLD_IDLE_MEMBER:
                break;
        case MLD_G_QUERY_PENDING_MEMBER:
        case MLD_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 __unused;

                        retval = mld_v2_enqueue_group_record(qrq, inm, 0, 1,
                            (inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER),
                            0);
                        CTR2(KTR_MLD, "%s: enqueue record = %d",
                            __func__, retval);
                        inm->in6m_state = MLD_REPORTING_MEMBER;
                        in6m_clear_recorded(inm);
                }
                /* FALLTHROUGH */
        case MLD_REPORTING_MEMBER:
        case MLD_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->in6m_scrv > 0) {
                                inm->in6m_sctimer = uri_fasthz;
                                V_state_change_timers_running6 = 1;
                        }
                        /*
                         * 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)mld_v2_merge_state_changes(inm, scq);

                        in6m_commit(inm);
                        CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                            ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                            if_name(inm->in6m_ifp));

                        /*
                         * If we are leaving the group for good, make sure
                         * we release MLD's reference to it.
                         * This release must be deferred using a SLIST,
                         * as we are called from a loop which traverses
                         * the in_ifmultiaddr TAILQ.
                         */
                        if (inm->in6m_state == MLD_LEAVING_MEMBER &&
                            inm->in6m_scrv == 0) {
                                inm->in6m_state = MLD_NOT_MEMBER;
                                in6m_disconnect_locked(inmh, inm);
                                in6m_rele_locked(inmh, inm);
                        }
                }
                break;
        }
}

/*
 * Switch to a different version on the given interface,
 * as per Section 9.12.
 */
static void
mld_set_version(struct mld_ifsoftc *mli, const int version)
{
        int old_version_timer;

        MLD_LOCK_ASSERT();

        CTR4(KTR_MLD, "%s: switching to v%d on ifp %p(%s)", __func__,
            version, mli->mli_ifp, if_name(mli->mli_ifp));

        if (version == MLD_VERSION_1) {
                /*
                 * Compute the "Older Version Querier Present" timer as per
                 * Section 9.12.
                 */
                old_version_timer = (mli->mli_rv * mli->mli_qi) + mli->mli_qri;
                old_version_timer *= PR_SLOWHZ;
                mli->mli_v1_timer = old_version_timer;
        }

        if (mli->mli_v1_timer > 0 && mli->mli_version != MLD_VERSION_1) {
                mli->mli_version = MLD_VERSION_1;
                mld_v2_cancel_link_timers(mli);
        }
}

/*
 * Cancel pending MLDv2 timers for the given link and all groups
 * joined on it; state-change, general-query, and group-query timers.
 */
static void
mld_v2_cancel_link_timers(struct mld_ifsoftc *mli)
{
        struct epoch_tracker     et;
        struct in6_multi_head    inmh;
        struct ifmultiaddr      *ifma;
        struct ifnet            *ifp;
        struct in6_multi        *inm;

        CTR3(KTR_MLD, "%s: cancel v2 timers on ifp %p(%s)", __func__,
            mli->mli_ifp, if_name(mli->mli_ifp));

        SLIST_INIT(&inmh);
        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        /*
         * Fast-track this potentially expensive operation
         * by checking all the global 'timer pending' flags.
         */
        if (!V_interface_timers_running6 &&
            !V_state_change_timers_running6 &&
            !V_current_state_timers_running6)
                return;

        mli->mli_v2_timer = 0;

        ifp = mli->mli_ifp;

        IF_ADDR_WLOCK(ifp);
        NET_EPOCH_ENTER(et);
        CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                inm = in6m_ifmultiaddr_get_inm(ifma);
                if (inm == NULL)
                        continue;
                switch (inm->in6m_state) {
                case MLD_NOT_MEMBER:
                case MLD_SILENT_MEMBER:
                case MLD_IDLE_MEMBER:
                case MLD_LAZY_MEMBER:
                case MLD_SLEEPING_MEMBER:
                case MLD_AWAKENING_MEMBER:
                        break;
                case MLD_LEAVING_MEMBER:
                        /*
                         * If we are leaving the group and switching
                         * version, we need to release the final
                         * reference held for issuing the INCLUDE {}.
                         */
                        if (inm->in6m_refcount == 1)
                                in6m_disconnect_locked(&inmh, inm);
                        in6m_rele_locked(&inmh, inm);
                        /* FALLTHROUGH */
                case MLD_G_QUERY_PENDING_MEMBER:
                case MLD_SG_QUERY_PENDING_MEMBER:
                        in6m_clear_recorded(inm);
                        /* FALLTHROUGH */
                case MLD_REPORTING_MEMBER:
                        inm->in6m_sctimer = 0;
                        inm->in6m_timer = 0;
                        inm->in6m_state = MLD_REPORTING_MEMBER;
                        /*
                         * Free any pending MLDv2 state-change records.
                         */
                        mbufq_drain(&inm->in6m_scq);
                        break;
                }
        }
        NET_EPOCH_EXIT(et);
        IF_ADDR_WUNLOCK(ifp);
        in6m_release_list_deferred(&inmh);
}

/*
 * Global slowtimo handler.
 * VIMAGE: Timeout handlers are expected to service all vimages.
 */
void
mld_slowtimo(void)
{
        VNET_ITERATOR_DECL(vnet_iter);

        VNET_LIST_RLOCK_NOSLEEP();
        VNET_FOREACH(vnet_iter) {
                CURVNET_SET(vnet_iter);
                mld_slowtimo_vnet();
                CURVNET_RESTORE();
        }
        VNET_LIST_RUNLOCK_NOSLEEP();
}

/*
 * Per-vnet slowtimo handler.
 */
static void
mld_slowtimo_vnet(void)
{
        struct mld_ifsoftc *mli;

        MLD_LOCK();

        LIST_FOREACH(mli, &V_mli_head, mli_link) {
                mld_v1_process_querier_timers(mli);
        }

        MLD_UNLOCK();
}

/*
 * Update the Older Version Querier Present timers for a link.
 * See Section 9.12 of RFC 3810.
 */
static void
mld_v1_process_querier_timers(struct mld_ifsoftc *mli)
{

        MLD_LOCK_ASSERT();

        if (mli->mli_version != MLD_VERSION_2 && --mli->mli_v1_timer == 0) {
                /*
                 * MLDv1 Querier Present timer expired; revert to MLDv2.
                 */
                CTR5(KTR_MLD,
                    "%s: transition from v%d -> v%d on %p(%s)",
                    __func__, mli->mli_version, MLD_VERSION_2,
                    mli->mli_ifp, if_name(mli->mli_ifp));
                mli->mli_version = MLD_VERSION_2;
        }
}

/*
 * Transmit an MLDv1 report immediately.
 */
static int
mld_v1_transmit_report(struct in6_multi *in6m, const int type)
{
        struct ifnet            *ifp;
        struct in6_ifaddr       *ia;
        struct ip6_hdr          *ip6;
        struct mbuf             *mh, *md;
        struct mld_hdr          *mld;

        NET_EPOCH_ASSERT();
        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        ifp = in6m->in6m_ifp;
        /* in process of being freed */
        if (ifp == NULL)
                return (0);
        ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
        /* ia may be NULL if link-local address is tentative. */

        mh = m_gethdr(M_NOWAIT, MT_DATA);
        if (mh == NULL) {
                if (ia != NULL)
                        ifa_free(&ia->ia_ifa);
                return (ENOMEM);
        }
        md = m_get(M_NOWAIT, MT_DATA);
        if (md == NULL) {
                m_free(mh);
                if (ia != NULL)
                        ifa_free(&ia->ia_ifa);
                return (ENOMEM);
        }
        mh->m_next = md;

        /*
         * FUTURE: Consider increasing alignment by ETHER_HDR_LEN, so
         * that ether_output() does not need to allocate another mbuf
         * for the header in the most common case.
         */
        M_ALIGN(mh, sizeof(struct ip6_hdr));
        mh->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct mld_hdr);
        mh->m_len = sizeof(struct ip6_hdr);

        ip6 = mtod(mh, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_src = ia ? ia->ia_addr.sin6_addr : in6addr_any;
        ip6->ip6_dst = in6m->in6m_addr;

        md->m_len = sizeof(struct mld_hdr);
        mld = mtod(md, struct mld_hdr *);
        mld->mld_type = type;
        mld->mld_code = 0;
        mld->mld_cksum = 0;
        mld->mld_maxdelay = 0;
        mld->mld_reserved = 0;
        mld->mld_addr = in6m->in6m_addr;
        in6_clearscope(&mld->mld_addr);
        mld->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6,
            sizeof(struct ip6_hdr), sizeof(struct mld_hdr));

        mld_save_context(mh, ifp);
        mh->m_flags |= M_MLDV1;

        mld_dispatch_packet(mh);

        if (ia != NULL)
                ifa_free(&ia->ia_ifa);
        return (0);
}

/*
 * Process a state change from the upper layer for the given IPv6 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 MLD 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 MLDv2 state machine at group level. The MLd module
 * however makes the decision as to which MLD protocol version to speak.
 * A state change *from* INCLUDE {} always means an initial join.
 * A state change *to* INCLUDE {} always means a final leave.
 *
 * If delay is non-zero, and the state change is an initial multicast
 * join, the state change report will be delayed by 'delay' ticks
 * in units of PR_FASTHZ if MLDv1 is active on the link; otherwise
 * the initial MLDv2 state change report will be delayed by whichever
 * is sooner, a pending state-change timer or delay itself.
 *
 * VIMAGE: curvnet should have been set by caller, as this routine
 * is called from the socket option handlers.
 */
int
mld_change_state(struct in6_multi *inm, const int delay)
{
        struct mld_ifsoftc *mli;
        struct ifnet *ifp;
        int error;

        IN6_MULTI_LIST_LOCK_ASSERT();

        error = 0;

        /*
         * Check if the in6_multi has already been disconnected.
         */
        if (inm->in6m_ifp == NULL) {
                CTR1(KTR_MLD, "%s: inm is disconnected", __func__);
                return (0);
        }

        /*
         * Try to detect if the upper layer just asked us to change state
         * for an interface which has now gone away.
         */
        KASSERT(inm->in6m_ifma != NULL, ("%s: no ifma", __func__));
        ifp = inm->in6m_ifma->ifma_ifp;
        if (ifp == NULL)
                return (0);
        /*
         * Sanity check that netinet6's notion of ifp is the
         * same as net's.
         */
        KASSERT(inm->in6m_ifp == ifp, ("%s: bad ifp", __func__));

        MLD_LOCK();
        mli = MLD_IFINFO(ifp);
        KASSERT(mli != NULL, ("%s: no mld_ifsoftc for ifp %p", __func__, ifp));

        /*
         * If we detect a state transition to or from MCAST_UNDEFINED
         * for this group, then we are starting or finishing an MLD
         * life cycle for this group.
         */
        if (inm->in6m_st[1].iss_fmode != inm->in6m_st[0].iss_fmode) {
                CTR3(KTR_MLD, "%s: inm transition %d -> %d", __func__,
                    inm->in6m_st[0].iss_fmode, inm->in6m_st[1].iss_fmode);
                if (inm->in6m_st[0].iss_fmode == MCAST_UNDEFINED) {
                        CTR1(KTR_MLD, "%s: initial join", __func__);
                        error = mld_initial_join(inm, mli, delay);
                        goto out_locked;
                } else if (inm->in6m_st[1].iss_fmode == MCAST_UNDEFINED) {
                        CTR1(KTR_MLD, "%s: final leave", __func__);
                        mld_final_leave(inm, mli);
                        goto out_locked;
                }
        } else {
                CTR1(KTR_MLD, "%s: filter set change", __func__);
        }

        error = mld_handle_state_change(inm, mli);

out_locked:
        MLD_UNLOCK();
        return (error);
}

/*
 * Perform the initial join for an MLD group.
 *
 * When joining a group:
 *  If the group should have its MLD traffic suppressed, do nothing.
 *  MLDv1 starts sending MLDv1 host membership reports.
 *  MLDv2 will schedule an MLDv2 state-change report containing the
 *  initial state of the membership.
 *
 * If the delay argument is non-zero, then we must delay sending the
 * initial state change for delay ticks (in units of PR_FASTHZ).
 */
static int
mld_initial_join(struct in6_multi *inm, struct mld_ifsoftc *mli,
    const int delay)
{
        struct epoch_tracker     et;
        struct ifnet            *ifp;
        struct mbufq            *mq;
        int                      error, retval, syncstates;
        int                      odelay;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        CTR4(KTR_MLD, "%s: initial join %s on ifp %p(%s)",
            __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            inm->in6m_ifp, if_name(inm->in6m_ifp));

        error = 0;
        syncstates = 1;

        ifp = inm->in6m_ifp;

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        KASSERT(mli && mli->mli_ifp == ifp, ("%s: inconsistent ifp", __func__));

        /*
         * Groups joined on loopback or marked as 'not reported',
         * enter the MLD_SILENT_MEMBER state and
         * are never reported in any protocol exchanges.
         * All other groups enter the appropriate state machine
         * for the version in use on this link.
         * A link marked as MLIF_SILENT causes MLD to be completely
         * disabled for the link.
         */
        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (mli->mli_flags & MLIF_SILENT) ||
            !mld_is_addr_reported(&inm->in6m_addr)) {
                CTR1(KTR_MLD,
"%s: not kicking state machine for silent group", __func__);
                inm->in6m_state = MLD_SILENT_MEMBER;
                inm->in6m_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.
                 */
                if (mli->mli_version == MLD_VERSION_2 &&
                    inm->in6m_state == MLD_LEAVING_MEMBER) {
                        inm->in6m_refcount--;
                        MPASS(inm->in6m_refcount > 0);
                }
                inm->in6m_state = MLD_REPORTING_MEMBER;

                switch (mli->mli_version) {
                case MLD_VERSION_1:
                        /*
                         * If a delay was provided, only use it if
                         * it is greater than the delay normally
                         * used for an MLDv1 state change report,
                         * and delay sending the initial MLDv1 report
                         * by not transitioning to the IDLE state.
                         */
                        odelay = MLD_RANDOM_DELAY(MLD_V1_MAX_RI * PR_FASTHZ);
                        if (delay) {
                                inm->in6m_timer = max(delay, odelay);
                                V_current_state_timers_running6 = 1;
                        } else {
                                inm->in6m_state = MLD_IDLE_MEMBER;
                                NET_EPOCH_ENTER(et);
                                error = mld_v1_transmit_report(inm,
                                     MLD_LISTENER_REPORT);
                                NET_EPOCH_EXIT(et);
                                if (error == 0) {
                                        inm->in6m_timer = odelay;
                                        V_current_state_timers_running6 = 1;
                                }
                        }
                        break;

                case MLD_VERSION_2:
                        /*
                         * 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.
                         */
                        mq = &inm->in6m_scq;
                        mbufq_drain(mq);
                        retval = mld_v2_enqueue_group_record(mq, inm, 1,
                            0, 0, (mli->mli_flags & MLIF_USEALLOW));
                        CTR2(KTR_MLD, "%s: enqueue record = %d",
                            __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 mld_fasttimo (~200ms),
                         * giving us an opportunity to merge the reports.
                         *
                         * If a delay was provided to this function, only
                         * use this delay if sooner than the existing one.
                         */
                        KASSERT(mli->mli_rv > 1,
                           ("%s: invalid robustness %d", __func__,
                            mli->mli_rv));
                        inm->in6m_scrv = mli->mli_rv;
                        if (delay) {
                                if (inm->in6m_sctimer > 1) {
                                        inm->in6m_sctimer =
                                            min(inm->in6m_sctimer, delay);
                                } else
                                        inm->in6m_sctimer = delay;
                        } else
                                inm->in6m_sctimer = 1;
                        V_state_change_timers_running6 = 1;

                        error = 0;
                        break;
                }
        }

        /*
         * 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) {
                in6m_commit(inm);
                CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                    ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                    if_name(inm->in6m_ifp));
        }

        return (error);
}

/*
 * Issue an intermediate state change during the life-cycle.
 */
static int
mld_handle_state_change(struct in6_multi *inm, struct mld_ifsoftc *mli)
{
        struct ifnet            *ifp;
        int                      retval;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        CTR4(KTR_MLD, "%s: state change for %s on ifp %p(%s)",
            __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            inm->in6m_ifp, if_name(inm->in6m_ifp));

        ifp = inm->in6m_ifp;

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        KASSERT(mli && mli->mli_ifp == ifp,
            ("%s: inconsistent ifp", __func__));

        if ((ifp->if_flags & IFF_LOOPBACK) ||
            (mli->mli_flags & MLIF_SILENT) ||
            !mld_is_addr_reported(&inm->in6m_addr) ||
            (mli->mli_version != MLD_VERSION_2)) {
                if (!mld_is_addr_reported(&inm->in6m_addr)) {
                        CTR1(KTR_MLD,
"%s: not kicking state machine for silent group", __func__);
                }
                CTR1(KTR_MLD, "%s: nothing to do", __func__);
                in6m_commit(inm);
                CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                    ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                    if_name(inm->in6m_ifp));
                return (0);
        }

        mbufq_drain(&inm->in6m_scq);

        retval = mld_v2_enqueue_group_record(&inm->in6m_scq, inm, 1, 0, 0,
            (mli->mli_flags & MLIF_USEALLOW));
        CTR2(KTR_MLD, "%s: enqueue record = %d", __func__, retval);
        if (retval <= 0)
                return (-retval);

        /*
         * If record(s) were enqueued, start the state-change
         * report timer for this group.
         */
        inm->in6m_scrv = mli->mli_rv;
        inm->in6m_sctimer = 1;
        V_state_change_timers_running6 = 1;

        return (0);
}

/*
 * Perform the final leave for a multicast address.
 *
 * When leaving a group:
 *  MLDv1 sends a DONE message, if and only if we are the reporter.
 *  MLDv2 enqueues a state-change report containing a transition
 *  to INCLUDE {} for immediate transmission.
 */
static void
mld_final_leave(struct in6_multi *inm, struct mld_ifsoftc *mli)
{
        struct epoch_tracker     et;
        int syncstates;
#ifdef KTR
        char ip6tbuf[INET6_ADDRSTRLEN];
#endif

        syncstates = 1;

        CTR4(KTR_MLD, "%s: final leave %s on ifp %p(%s)",
            __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            inm->in6m_ifp, if_name(inm->in6m_ifp));

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        switch (inm->in6m_state) {
        case MLD_NOT_MEMBER:
        case MLD_SILENT_MEMBER:
        case MLD_LEAVING_MEMBER:
                /* Already leaving or left; do nothing. */
                CTR1(KTR_MLD,
"%s: not kicking state machine for silent group", __func__);
                break;
        case MLD_REPORTING_MEMBER:
        case MLD_IDLE_MEMBER:
        case MLD_G_QUERY_PENDING_MEMBER:
        case MLD_SG_QUERY_PENDING_MEMBER:
                if (mli->mli_version == MLD_VERSION_1) {
#ifdef INVARIANTS
                        if (inm->in6m_state == MLD_G_QUERY_PENDING_MEMBER ||
                            inm->in6m_state == MLD_SG_QUERY_PENDING_MEMBER)
                        panic("%s: MLDv2 state reached, not MLDv2 mode",
                             __func__);
#endif
                        NET_EPOCH_ENTER(et);
                        mld_v1_transmit_report(inm, MLD_LISTENER_DONE);
                        NET_EPOCH_EXIT(et);
                        inm->in6m_state = MLD_NOT_MEMBER;
                        V_current_state_timers_running6 = 1;
                } else if (mli->mli_version == MLD_VERSION_2) {
                        /*
                         * Stop group timer and all pending reports.
                         * Immediately enqueue a state-change report
                         * TO_IN {} to be sent on the next fast timeout,
                         * giving us an opportunity to merge reports.
                         */
                        mbufq_drain(&inm->in6m_scq);
                        inm->in6m_timer = 0;
                        inm->in6m_scrv = mli->mli_rv;
                        CTR4(KTR_MLD, "%s: Leaving %s/%s with %d "
                            "pending retransmissions.", __func__,
                            ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                            if_name(inm->in6m_ifp), inm->in6m_scrv);
                        if (inm->in6m_scrv == 0) {
                                inm->in6m_state = MLD_NOT_MEMBER;
                                inm->in6m_sctimer = 0;
                        } else {
                                int retval __diagused;

                                in6m_acquire_locked(inm);

                                retval = mld_v2_enqueue_group_record(
                                    &inm->in6m_scq, inm, 1, 0, 0,
                                    (mli->mli_flags & MLIF_USEALLOW));
                                KASSERT(retval != 0,
                                    ("%s: enqueue record = %d", __func__,
                                     retval));

                                inm->in6m_state = MLD_LEAVING_MEMBER;
                                inm->in6m_sctimer = 1;
                                V_state_change_timers_running6 = 1;
                                syncstates = 0;
                        }
                        break;
                }
                break;
        case MLD_LAZY_MEMBER:
        case MLD_SLEEPING_MEMBER:
        case MLD_AWAKENING_MEMBER:
                /* Our reports are suppressed; do nothing. */
                break;
        }

        if (syncstates) {
                in6m_commit(inm);
                CTR3(KTR_MLD, "%s: T1 -> T0 for %s/%s", __func__,
                    ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                    if_name(inm->in6m_ifp));
                inm->in6m_st[1].iss_fmode = MCAST_UNDEFINED;
                CTR3(KTR_MLD, "%s: T1 now MCAST_UNDEFINED for %p/%s",
                    __func__, &inm->in6m_addr, if_name(inm->in6m_ifp));
        }
}

/*
 * Enqueue an MLDv2 group record to the given output queue.
 *
 * 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.
 *
 * If use_block_allow is non-zero, state change reports for initial join
 * and final leave, on an inclusive mode group with a source list, will be
 * rewritten to use the ALLOW_NEW and BLOCK_OLD record types, respectively.
 *
 * The function will attempt to allocate leading space in the packet
 * for the IPv6+ICMP headers 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
mld_v2_enqueue_group_record(struct mbufq *mq, struct in6_multi *inm,
    const int is_state_change, const int is_group_query,
    const int is_source_query, const int use_block_allow)
{
        struct mldv2_record      mr;
        struct mldv2_record     *pmr;
        struct ifnet            *ifp;
        struct ip6_msource      *ims, *nims;
        struct mbuf             *m0, *m, *md;
        int                      is_filter_list_change;
        int                      minrec0len, m0srcs, msrcs, nbytes, off;
        int                      record_has_sources;
        int                      now;
        int                      type;
        uint8_t                  mode;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        IN6_MULTI_LIST_LOCK_ASSERT();

        ifp = inm->in6m_ifp;
        is_filter_list_change = 0;
        m = NULL;
        m0 = NULL;
        m0srcs = 0;
        msrcs = 0;
        nbytes = 0;
        nims = NULL;
        record_has_sources = 1;
        pmr = NULL;
        type = MLD_DO_NOTHING;
        mode = inm->in6m_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->in6m_st[0].iss_asm > 0 && inm->in6m_st[1].iss_asm > 0 &&
            inm->in6m_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 there are ASM listeners, and there was no filter
                 * mode transition of any kind, do nothing.
                 *
                 * If we are transitioning to MCAST_UNDEFINED, we need
                 * not send any sources. A transition to/from this state is
                 * considered inclusive with some special treatment.
                 *
                 * If we are rewriting initial joins/leaves to use
                 * ALLOW/BLOCK, and the group's membership is inclusive,
                 * we need to send sources in all cases.
                 */
                if (mode != inm->in6m_st[0].iss_fmode) {
                        if (mode == MCAST_EXCLUDE) {
                                CTR1(KTR_MLD, "%s: change to EXCLUDE",
                                    __func__);
                                type = MLD_CHANGE_TO_EXCLUDE_MODE;
                        } else {
                                CTR1(KTR_MLD, "%s: change to INCLUDE",
                                    __func__);
                                if (use_block_allow) {
                                        /*
                                         * XXX
                                         * Here we're interested in state
                                         * edges either direction between
                                         * MCAST_UNDEFINED and MCAST_INCLUDE.
                                         * Perhaps we should just check
                                         * the group state, rather than
                                         * the filter mode.
                                         */
                                        if (mode == MCAST_UNDEFINED) {
                                                type = MLD_BLOCK_OLD_SOURCES;
                                        } else {
                                                type = MLD_ALLOW_NEW_SOURCES;
                                        }
                                } else {
                                        type = MLD_CHANGE_TO_INCLUDE_MODE;
                                        if (mode == MCAST_UNDEFINED)
                                                record_has_sources = 0;
                                }
                        }
                } else {
                        if (record_has_sources) {
                                is_filter_list_change = 1;
                        } else {
                                type = MLD_DO_NOTHING;
                        }
                }
        } else {
                /*
                 * Queue a current state record.
                 */
                if (mode == MCAST_EXCLUDE) {
                        type = MLD_MODE_IS_EXCLUDE;
                } else if (mode == MCAST_INCLUDE) {
                        type = MLD_MODE_IS_INCLUDE;
                        KASSERT(inm->in6m_st[1].iss_asm == 0,
                            ("%s: inm %p is INCLUDE but ASM count is %d",
                             __func__, inm, inm->in6m_st[1].iss_asm));
                }
        }

        /*
         * Generate the filter list changes using a separate function.
         */
        if (is_filter_list_change)
                return (mld_v2_enqueue_filter_change(mq, inm));

        if (type == MLD_DO_NOTHING) {
                CTR3(KTR_MLD, "%s: nothing to do for %s/%s",
                    __func__, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
                    if_name(inm->in6m_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 mldv2_record);
        if (record_has_sources)
                minrec0len += sizeof(struct in6_addr);

        CTR4(KTR_MLD, "%s: queueing %s for %s/%s", __func__,
            mld_rec_type_to_str(type),
            ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            if_name(inm->in6m_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 IP6+RA+ICMPV6+REPORT.
         * Note: Group records for G/GSR query responses MUST be sent
         * in their own packet.
         */
        m0 = mbufq_last(mq);
        if (!is_group_query &&
            m0 != NULL &&
            (m0->m_pkthdr.PH_vt.vt_nrecs + 1 <= MLD_V2_REPORT_MAXRECS) &&
            (m0->m_pkthdr.len + minrec0len) <
             (ifp->if_mtu - MLD_MTUSPACE)) {
                m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                            sizeof(struct mldv2_record)) /
                            sizeof(struct in6_addr);
                m = m0;
                CTR1(KTR_MLD, "%s: use existing packet", __func__);
        } else {
                if (mbufq_full(mq)) {
                        CTR1(KTR_MLD, "%s: outbound queue full", __func__);
                        return (-ENOMEM);
                }
                m = NULL;
                m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                    sizeof(struct mldv2_record)) / sizeof(struct in6_addr);
                if (!is_state_change && !is_group_query)
                        m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                if (m == NULL)
                        m = m_gethdr(M_NOWAIT, MT_DATA);
                if (m == NULL)
                        return (-ENOMEM);

                mld_save_context(m, ifp);

                CTR1(KTR_MLD, "%s: allocated first packet", __func__);
        }

        /*
         * Append group record.
         * If we have sources, we don't know how many yet.
         */
        mr.mr_type = type;
        mr.mr_datalen = 0;
        mr.mr_numsrc = 0;
        mr.mr_addr = inm->in6m_addr;
        in6_clearscope(&mr.mr_addr);
        if (!m_append(m, sizeof(struct mldv2_record), (void *)&mr)) {
                if (m != m0)
                        m_freem(m);
                CTR1(KTR_MLD, "%s: m_append() failed.", __func__);
                return (-ENOMEM);
        }
        nbytes += sizeof(struct mldv2_record);

        /*
         * 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, and
         * use_block_allow is zero, do not include source entries.
         * Otherwise, we need to include this source in the report.
         *
         * 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);
                        pmr = (struct mldv2_record *)(mtod(md, uint8_t *) +
                            md->m_len - nbytes);
                } else {
                        md = m_getptr(m, 0, &off);
                        pmr = (struct mldv2_record *)(mtod(md, uint8_t *) +
                            off);
                }
                msrcs = 0;
                RB_FOREACH_SAFE(ims, ip6_msource_tree, &inm->in6m_srcs,
                    nims) {
                        CTR2(KTR_MLD, "%s: visit node %s", __func__,
                            ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                        now = im6s_get_mode(inm, ims, 1);
                        CTR2(KTR_MLD, "%s: node is %d", __func__, now);
                        if ((now != mode) ||
                            (now == mode &&
                             (!use_block_allow && mode == MCAST_UNDEFINED))) {
                                CTR1(KTR_MLD, "%s: skip node", __func__);
                                continue;
                        }
                        if (is_source_query && ims->im6s_stp == 0) {
                                CTR1(KTR_MLD, "%s: skip unrecorded node",
                                    __func__);
                                continue;
                        }
                        CTR1(KTR_MLD, "%s: append node", __func__);
                        if (!m_append(m, sizeof(struct in6_addr),
                            (void *)&ims->im6s_addr)) {
                                if (m != m0)
                                        m_freem(m);
                                CTR1(KTR_MLD, "%s: m_append() failed.",
                                    __func__);
                                return (-ENOMEM);
                        }
                        nbytes += sizeof(struct in6_addr);
                        ++msrcs;
                        if (msrcs == m0srcs)
                                break;
                }
                CTR2(KTR_MLD, "%s: msrcs is %d this packet", __func__,
                    msrcs);
                pmr->mr_numsrc = htons(msrcs);
                nbytes += (msrcs * sizeof(struct in6_addr));
        }

        if (is_source_query && msrcs == 0) {
                CTR1(KTR_MLD, "%s: no recorded sources to report", __func__);
                if (m != m0)
                        m_freem(m);
                return (0);
        }

        /*
         * We are good to go with first packet.
         */
        if (m != m0) {
                CTR1(KTR_MLD, "%s: enqueueing first packet", __func__);
                m->m_pkthdr.PH_vt.vt_nrecs = 1;
                mbufq_enqueue(mq, m);
        } else
                m->m_pkthdr.PH_vt.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 (mbufq_full(mq)) {
                        CTR1(KTR_MLD, "%s: outbound queue full", __func__);
                        return (-ENOMEM);
                }
                m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                if (m == NULL)
                        m = m_gethdr(M_NOWAIT, MT_DATA);
                if (m == NULL)
                        return (-ENOMEM);
                mld_save_context(m, ifp);
                md = m_getptr(m, 0, &off);
                pmr = (struct mldv2_record *)(mtod(md, uint8_t *) + off);
                CTR1(KTR_MLD, "%s: allocated next packet", __func__);

                if (!m_append(m, sizeof(struct mldv2_record), (void *)&mr)) {
                        if (m != m0)
                                m_freem(m);
                        CTR1(KTR_MLD, "%s: m_append() failed.", __func__);
                        return (-ENOMEM);
                }
                m->m_pkthdr.PH_vt.vt_nrecs = 1;
                nbytes += sizeof(struct mldv2_record);

                m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                    sizeof(struct mldv2_record)) / sizeof(struct in6_addr);

                msrcs = 0;
                RB_FOREACH_FROM(ims, ip6_msource_tree, nims) {
                        CTR2(KTR_MLD, "%s: visit node %s",
                            __func__, ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                        now = im6s_get_mode(inm, ims, 1);
                        if ((now != mode) ||
                            (now == mode &&
                             (!use_block_allow && mode == MCAST_UNDEFINED))) {
                                CTR1(KTR_MLD, "%s: skip node", __func__);
                                continue;
                        }
                        if (is_source_query && ims->im6s_stp == 0) {
                                CTR1(KTR_MLD, "%s: skip unrecorded node",
                                    __func__);
                                continue;
                        }
                        CTR1(KTR_MLD, "%s: append node", __func__);
                        if (!m_append(m, sizeof(struct in6_addr),
                            (void *)&ims->im6s_addr)) {
                                if (m != m0)
                                        m_freem(m);
                                CTR1(KTR_MLD, "%s: m_append() failed.",
                                    __func__);
                                return (-ENOMEM);
                        }
                        ++msrcs;
                        if (msrcs == m0srcs)
                                break;
                }
                pmr->mr_numsrc = htons(msrcs);
                nbytes += (msrcs * sizeof(struct in6_addr));

                CTR1(KTR_MLD, "%s: enqueueing next packet", __func__);
                mbufq_enqueue(mq, 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 MLDv2 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
mld_v2_enqueue_filter_change(struct mbufq *mq, struct in6_multi *inm)
{
        static const int MINRECLEN =
            sizeof(struct mldv2_record) + sizeof(struct in6_addr);
        struct ifnet            *ifp;
        struct mldv2_record      mr;
        struct mldv2_record     *pmr;
        struct ip6_msource      *ims, *nims;
        struct mbuf             *m, *m0, *md;
        int                      m0srcs, nbytes, npbytes, off, rsrcs, schanged;
        uint8_t                  mode, now, then;
        rectype_t                crt, drt, nrt;
#ifdef KTR
        int                      nallow, nblock;
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        IN6_MULTI_LIST_LOCK_ASSERT();

        if (inm->in6m_nsrc == 0 ||
            (inm->in6m_st[0].iss_asm > 0 && inm->in6m_st[1].iss_asm > 0))
                return (0);

        ifp = inm->in6m_ifp;                    /* interface */
        mode = inm->in6m_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 */
        npbytes = 0;    /* # of bytes appended this packet */
        nbytes = 0;     /* # of bytes appended to group's state-change queue */
        rsrcs = 0;      /* # sources encoded in current record */
        schanged = 0;   /* # nodes encoded in overall filter change */
#ifdef KTR
        nallow = 0;     /* # of source entries in ALLOW_NEW */
        nblock = 0;     /* # of source entries in BLOCK_OLD */
#endif
        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 = mbufq_last(mq);
                        if (m0 != NULL &&
                            (m0->m_pkthdr.PH_vt.vt_nrecs + 1 <=
                             MLD_V2_REPORT_MAXRECS) &&
                            (m0->m_pkthdr.len + MINRECLEN) <
                             (ifp->if_mtu - MLD_MTUSPACE)) {
                                m = m0;
                                m0srcs = (ifp->if_mtu - m0->m_pkthdr.len -
                                            sizeof(struct mldv2_record)) /
                                            sizeof(struct in6_addr);
                                CTR1(KTR_MLD,
                                    "%s: use previous packet", __func__);
                        } else {
                                m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
                                if (m == NULL)
                                        m = m_gethdr(M_NOWAIT, MT_DATA);
                                if (m == NULL) {
                                        CTR1(KTR_MLD,
                                            "%s: m_get*() failed", __func__);
                                        return (-ENOMEM);
                                }
                                m->m_pkthdr.PH_vt.vt_nrecs = 0;
                                mld_save_context(m, ifp);
                                m0srcs = (ifp->if_mtu - MLD_MTUSPACE -
                                    sizeof(struct mldv2_record)) /
                                    sizeof(struct in6_addr);
                                npbytes = 0;
                                CTR1(KTR_MLD,
                                    "%s: allocated new packet", __func__);
                        }
                        /*
                         * Append the MLD 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(&mr, 0, sizeof(mr));
                        mr.mr_addr = inm->in6m_addr;
                        in6_clearscope(&mr.mr_addr);
                        if (!m_append(m, sizeof(mr), (void *)&mr)) {
                                if (m != m0)
                                        m_freem(m);
                                CTR1(KTR_MLD,
                                    "%s: m_append() failed", __func__);
                                return (-ENOMEM);
                        }
                        npbytes += sizeof(struct mldv2_record);
                        if (m != m0) {
                                /* new packet; offset in chain */
                                md = m_getptr(m, npbytes -
                                    sizeof(struct mldv2_record), &off);
                                pmr = (struct mldv2_record *)(mtod(md,
                                    uint8_t *) + off);
                        } else {
                                /* current packet; offset from last append */
                                md = m_last(m);
                                pmr = (struct mldv2_record *)(mtod(md,
                                    uint8_t *) + md->m_len -
                                    sizeof(struct mldv2_record));
                        }
                        /*
                         * 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(ip6_msource_tree,
                                    &inm->in6m_srcs);
                        }
                        RB_FOREACH_FROM(ims, ip6_msource_tree, nims) {
                                CTR2(KTR_MLD, "%s: visit node %s", __func__,
                                    ip6_sprintf(ip6tbuf, &ims->im6s_addr));
                                now = im6s_get_mode(inm, ims, 1);
                                then = im6s_get_mode(inm, ims, 0);
                                CTR3(KTR_MLD, "%s: mode: t0 %d, t1 %d",
                                    __func__, then, now);
                                if (now == then) {
                                        CTR1(KTR_MLD,
                                            "%s: skip unchanged", __func__);
                                        continue;
                                }
                                if (mode == MCAST_EXCLUDE &&
                                    now == MCAST_INCLUDE) {
                                        CTR1(KTR_MLD,
                                            "%s: skip IN src on EX group",
                                            __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;
                                if (!m_append(m, sizeof(struct in6_addr),
                                    (void *)&ims->im6s_addr)) {
                                        if (m != m0)
                                                m_freem(m);
                                        CTR1(KTR_MLD,
                                            "%s: m_append() failed", __func__);
                                        return (-ENOMEM);
                                }
#ifdef KTR
                                nallow += !!(crt == REC_ALLOW);
                                nblock += !!(crt == REC_BLOCK);
#endif
                                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 mldv2_record);
                                if (m != m0) {
                                        CTR1(KTR_MLD,
                                            "%s: m_free(m)", __func__);
                                        m_freem(m);
                                } else {
                                        CTR1(KTR_MLD,
                                            "%s: m_adj(m, -mr)", __func__);
                                        m_adj(m, -((int)sizeof(
                                            struct mldv2_record)));
                                }
                                continue;
                        }
                        npbytes += (rsrcs * sizeof(struct in6_addr));
                        if (crt == REC_ALLOW)
                                pmr->mr_type = MLD_ALLOW_NEW_SOURCES;
                        else if (crt == REC_BLOCK)
                                pmr->mr_type = MLD_BLOCK_OLD_SOURCES;
                        pmr->mr_numsrc = htons(rsrcs);
                        /*
                         * Count the new group record, and enqueue this
                         * packet if it wasn't already queued.
                         */
                        m->m_pkthdr.PH_vt.vt_nrecs++;
                        if (m != m0)
                                mbufq_enqueue(mq, m);
                        nbytes += npbytes;
                } while (nims != NULL);
                drt |= crt;
                crt = (~crt & REC_FULL);
        }

        CTR3(KTR_MLD, "%s: queued %d ALLOW_NEW, %d BLOCK_OLD", __func__,
            nallow, nblock);

        return (nbytes);
}

static int
mld_v2_merge_state_changes(struct in6_multi *inm, struct mbufq *scq)
{
        struct mbufq    *gq;
        struct mbuf     *m;             /* pending state-change */
        struct mbuf     *m0;            /* copy of pending state-change */
        struct mbuf     *mt;            /* last state-change in packet */
        int              docopy, domerge;
        u_int            recslen;

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

        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        /*
         * If there are further pending retransmissions, make a writable
         * copy of each queued state-change message before merging.
         */
        if (inm->in6m_scrv > 0)
                docopy = 1;

        gq = &inm->in6m_scq;
#ifdef KTR
        if (mbufq_first(gq) == NULL) {
                CTR2(KTR_MLD, "%s: WARNING: queue for inm %p is empty",
                    __func__, inm);
        }
#endif

        m = mbufq_first(gq);
        while (m != NULL) {
                /*
                 * Only merge the report into the current packet if
                 * there is sufficient space to do so; an MLDv2 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 = mbufq_last(scq);
                if (mt != NULL) {
                        recslen = m_length(m, NULL);

                        if ((mt->m_pkthdr.PH_vt.vt_nrecs +
                            m->m_pkthdr.PH_vt.vt_nrecs <=
                            MLD_V2_REPORT_MAXRECS) &&
                            (mt->m_pkthdr.len + recslen <=
                            (inm->in6m_ifp->if_mtu - MLD_MTUSPACE)))
                                domerge = 1;
                }

                if (!domerge && mbufq_full(gq)) {
                        CTR2(KTR_MLD,
                            "%s: outbound queue full, skipping whole packet %p",
                            __func__, m);
                        mt = m->m_nextpkt;
                        if (!docopy)
                                m_freem(m);
                        m = mt;
                        continue;
                }

                if (!docopy) {
                        CTR2(KTR_MLD, "%s: dequeueing %p", __func__, m);
                        m0 = mbufq_dequeue(gq);
                        m = m0->m_nextpkt;
                } else {
                        CTR2(KTR_MLD, "%s: copying %p", __func__, m);
                        m0 = m_dup(m, M_NOWAIT);
                        if (m0 == NULL)
                                return (ENOMEM);
                        m0->m_nextpkt = NULL;
                        m = m->m_nextpkt;
                }

                if (!domerge) {
                        CTR3(KTR_MLD, "%s: queueing %p to scq %p)",
                            __func__, m0, scq);
                        mbufq_enqueue(scq, m0);
                } else {
                        struct mbuf *mtl;       /* last mbuf of packet mt */

                        CTR3(KTR_MLD, "%s: merging %p with ifscq tail %p)",
                            __func__, m0, mt);

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

                        mtl->m_next = m0;
                }
        }

        return (0);
}

/*
 * Respond to a pending MLDv2 General Query.
 */
static void
mld_v2_dispatch_general_query(struct mld_ifsoftc *mli)
{
        struct ifmultiaddr      *ifma;
        struct ifnet            *ifp;
        struct in6_multi        *inm;
        int                      retval __unused;

        NET_EPOCH_ASSERT();
        IN6_MULTI_LIST_LOCK_ASSERT();
        MLD_LOCK_ASSERT();

        KASSERT(mli->mli_version == MLD_VERSION_2,
            ("%s: called when version %d", __func__, mli->mli_version));

        /*
         * Check that there are some packets queued. If so, send them first.
         * For large number of groups the reply to general query can take
         * many packets, we should finish sending them before starting of
         * queuing the new reply.
         */
        if (mbufq_len(&mli->mli_gq) != 0)
                goto send;

        ifp = mli->mli_ifp;

        CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                inm = in6m_ifmultiaddr_get_inm(ifma);
                if (inm == NULL)
                        continue;
                KASSERT(ifp == inm->in6m_ifp,
                    ("%s: inconsistent ifp", __func__));

                switch (inm->in6m_state) {
                case MLD_NOT_MEMBER:
                case MLD_SILENT_MEMBER:
                        break;
                case MLD_REPORTING_MEMBER:
                case MLD_IDLE_MEMBER:
                case MLD_LAZY_MEMBER:
                case MLD_SLEEPING_MEMBER:
                case MLD_AWAKENING_MEMBER:
                        inm->in6m_state = MLD_REPORTING_MEMBER;
                        retval = mld_v2_enqueue_group_record(&mli->mli_gq,
                            inm, 0, 0, 0, 0);
                        CTR2(KTR_MLD, "%s: enqueue record = %d",
                            __func__, retval);
                        break;
                case MLD_G_QUERY_PENDING_MEMBER:
                case MLD_SG_QUERY_PENDING_MEMBER:
                case MLD_LEAVING_MEMBER:
                        break;
                }
        }

send:
        mld_dispatch_queue(&mli->mli_gq, MLD_MAX_RESPONSE_BURST);

        /*
         * Slew transmission of bursts over 500ms intervals.
         */
        if (mbufq_first(&mli->mli_gq) != NULL) {
                mli->mli_v2_timer = 1 + MLD_RANDOM_DELAY(
                    MLD_RESPONSE_BURST_INTERVAL);
                V_interface_timers_running6 = 1;
        }
}

/*
 * Transmit the next pending message in the output queue.
 *
 * VIMAGE: Needs to store/restore vnet pointer on a per-mbuf-chain basis.
 * MRT: Nothing needs to be done, as MLD traffic is always local to
 * a link and uses a link-scope multicast address.
 */
static void
mld_dispatch_packet(struct mbuf *m)
{
        struct ip6_moptions      im6o;
        struct ifnet            *ifp;
        struct ifnet            *oifp;
        struct mbuf             *m0;
        struct mbuf             *md;
        struct ip6_hdr          *ip6;
        struct mld_hdr          *mld;
        int                      error;
        int                      off;
        int                      type;
        uint32_t                 ifindex;

        CTR2(KTR_MLD, "%s: transmit %p", __func__, m);
        NET_EPOCH_ASSERT();

        /*
         * Set VNET image pointer from enqueued mbuf chain
         * before doing anything else. Whilst we use interface
         * indexes to guard against interface detach, they are
         * unique to each VIMAGE and must be retrieved.
         */
        ifindex = mld_restore_context(m);

        /*
         * Check if the ifnet still exists. This limits the scope of
         * any race in the absence of a global ifp lock for low cost
         * (an array lookup).
         */
        ifp = ifnet_byindex(ifindex);
        if (ifp == NULL) {
                CTR3(KTR_MLD, "%s: dropped %p as ifindex %u went away.",
                    __func__, m, ifindex);
                m_freem(m);
                IP6STAT_INC(ip6s_noroute);
                goto out;
        }

        im6o.im6o_multicast_hlim  = 1;
        im6o.im6o_multicast_loop = (V_ip6_mrouter != NULL);
        im6o.im6o_multicast_ifp = ifp;

        if (m->m_flags & M_MLDV1) {
                m0 = m;
        } else {
                m0 = mld_v2_encap_report(ifp, m);
                if (m0 == NULL) {
                        CTR2(KTR_MLD, "%s: dropped %p", __func__, m);
                        IP6STAT_INC(ip6s_odropped);
                        goto out;
                }
        }

        mld_scrub_context(m0);
        m_clrprotoflags(m);
        m0->m_pkthdr.rcvif = V_loif;

        ip6 = mtod(m0, struct ip6_hdr *);
#if 0
        (void)in6_setscope(&ip6->ip6_dst, ifp, NULL);   /* XXX LOR */
#else
        /*
         * XXX XXX Break some KPI rules to prevent an LOR which would
         * occur if we called in6_setscope() at transmission.
         * See comments at top of file.
         */
        MLD_EMBEDSCOPE(&ip6->ip6_dst, ifp->if_index);
#endif

        /*
         * Retrieve the ICMPv6 type before handoff to ip6_output(),
         * so we can bump the stats.
         */
        md = m_getptr(m0, sizeof(struct ip6_hdr), &off);
        mld = (struct mld_hdr *)(mtod(md, uint8_t *) + off);
        type = mld->mld_type;

        oifp = NULL;
        error = ip6_output(m0, &mld_po, NULL, IPV6_UNSPECSRC, &im6o,
            &oifp, NULL);
        if (error) {
                CTR3(KTR_MLD, "%s: ip6_output(%p) = %d", __func__, m0, error);
                goto out;
        }
        ICMP6STAT_INC(icp6s_outhist[type]);
        if (oifp != NULL) {
                icmp6_ifstat_inc(oifp, ifs6_out_msg);
                switch (type) {
                case MLD_LISTENER_REPORT:
                case MLDV2_LISTENER_REPORT:
                        icmp6_ifstat_inc(oifp, ifs6_out_mldreport);
                        break;
                case MLD_LISTENER_DONE:
                        icmp6_ifstat_inc(oifp, ifs6_out_mlddone);
                        break;
                }
        }
out:
        return;
}

/*
 * Encapsulate an MLDv2 report.
 *
 * KAME IPv6 requires that hop-by-hop options be passed separately,
 * and that the IPv6 header be prepended in a separate mbuf.
 *
 * Returns a pointer to the new mbuf chain head, or NULL if the
 * allocation failed.
 */
static struct mbuf *
mld_v2_encap_report(struct ifnet *ifp, struct mbuf *m)
{
        struct mbuf             *mh;
        struct mldv2_report     *mld;
        struct ip6_hdr          *ip6;
        struct in6_ifaddr       *ia;
        int                      mldreclen;

        KASSERT(ifp != NULL, ("%s: null ifp", __func__));
        KASSERT((m->m_flags & M_PKTHDR),
            ("%s: mbuf chain %p is !M_PKTHDR", __func__, m));

        /*
         * RFC3590: OK to send as :: or tentative during DAD.
         */
        NET_EPOCH_ASSERT();
        ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST);
        if (ia == NULL)
                CTR1(KTR_MLD, "%s: warning: ia is NULL", __func__);

        mh = m_gethdr(M_NOWAIT, MT_DATA);
        if (mh == NULL) {
                if (ia != NULL)
                        ifa_free(&ia->ia_ifa);
                m_freem(m);
                return (NULL);
        }
        M_ALIGN(mh, sizeof(struct ip6_hdr) + sizeof(struct mldv2_report));

        mldreclen = m_length(m, NULL);
        CTR2(KTR_MLD, "%s: mldreclen is %d", __func__, mldreclen);

        mh->m_len = sizeof(struct ip6_hdr) + sizeof(struct mldv2_report);
        mh->m_pkthdr.len = sizeof(struct ip6_hdr) +
            sizeof(struct mldv2_report) + mldreclen;

        ip6 = mtod(mh, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_src = ia ? ia->ia_addr.sin6_addr : in6addr_any;
        if (ia != NULL)
                ifa_free(&ia->ia_ifa);
        ip6->ip6_dst = in6addr_linklocal_allv2routers;
        /* scope ID will be set in netisr */

        mld = (struct mldv2_report *)(ip6 + 1);
        mld->mld_type = MLDV2_LISTENER_REPORT;
        mld->mld_code = 0;
        mld->mld_cksum = 0;
        mld->mld_v2_reserved = 0;
        mld->mld_v2_numrecs = htons(m->m_pkthdr.PH_vt.vt_nrecs);
        m->m_pkthdr.PH_vt.vt_nrecs = 0;

        mh->m_next = m;
        mld->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6,
            sizeof(struct ip6_hdr), sizeof(struct mldv2_report) + mldreclen);
        return (mh);
}

#ifdef KTR
static char *
mld_rec_type_to_str(const int type)
{

        switch (type) {
                case MLD_CHANGE_TO_EXCLUDE_MODE:
                        return "TO_EX";
                        break;
                case MLD_CHANGE_TO_INCLUDE_MODE:
                        return "TO_IN";
                        break;
                case MLD_MODE_IS_EXCLUDE:
                        return "MODE_EX";
                        break;
                case MLD_MODE_IS_INCLUDE:
                        return "MODE_IN";
                        break;
                case MLD_ALLOW_NEW_SOURCES:
                        return "ALLOW_NEW";
                        break;
                case MLD_BLOCK_OLD_SOURCES:
                        return "BLOCK_OLD";
                        break;
                default:
                        break;
        }
        return "unknown";
}
#endif

static void
mld_init(void *unused __unused)
{

        CTR1(KTR_MLD, "%s: initializing", __func__);
        MLD_LOCK_INIT();

        ip6_initpktopts(&mld_po);
        mld_po.ip6po_hlim = 1;
        mld_po.ip6po_hbh = &mld_ra.hbh;
        mld_po.ip6po_prefer_tempaddr = IP6PO_TEMPADDR_NOTPREFER;
        mld_po.ip6po_flags = IP6PO_DONTFRAG;
}
SYSINIT(mld_init, SI_SUB_PROTO_MC, SI_ORDER_MIDDLE, mld_init, NULL);

static void
mld_uninit(void *unused __unused)
{

        CTR1(KTR_MLD, "%s: tearing down", __func__);
        MLD_LOCK_DESTROY();
}
SYSUNINIT(mld_uninit, SI_SUB_PROTO_MC, SI_ORDER_MIDDLE, mld_uninit, NULL);

static void
vnet_mld_init(const void *unused __unused)
{

        CTR1(KTR_MLD, "%s: initializing", __func__);

        LIST_INIT(&V_mli_head);
}
VNET_SYSINIT(vnet_mld_init, SI_SUB_PROTO_MC, SI_ORDER_ANY, vnet_mld_init,
    NULL);

static void
vnet_mld_uninit(const void *unused __unused)
{

        /* This can happen if we shutdown the network stack. */
        CTR1(KTR_MLD, "%s: tearing down", __func__);
}
VNET_SYSUNINIT(vnet_mld_uninit, SI_SUB_PROTO_MC, SI_ORDER_ANY, vnet_mld_uninit,
    NULL);

static int
mld_modevent(module_t mod, int type, void *unused __unused)
{

    switch (type) {
    case MOD_LOAD:
    case MOD_UNLOAD:
        break;
    default:
        return (EOPNOTSUPP);
    }
    return (0);
}

static moduledata_t mld_mod = {
    "mld",
    mld_modevent,
    0
};
DECLARE_MODULE(mld, mld_mod, SI_SUB_PROTO_MC, SI_ORDER_ANY);