/*      $NetBSD: mld6.c,v 1.102 2025/06/05 06:29:27 ozaki-r Exp $       */
/*      $KAME: mld6.c,v 1.25 2001/01/16 14:14:18 itojun Exp $   */

/*
 * Copyright (C) 1998 WIDE Project.
 * All rights reserved.
 *
 * 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 project 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 PROJECT 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 PROJECT 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.
 */

/*
 * 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
 */

/*
 * Copyright (c) 1988 Stephen Deering.
 *
 * This code is derived from software contributed to Berkeley by
 * Stephen Deering of Stanford University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)igmp.c      8.1 (Berkeley) 7/19/93
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: mld6.c,v 1.102 2025/06/05 06:29:27 ozaki-r Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#include "opt_net_mpsafe.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <sys/kernel.h>
#include <sys/callout.h>
#include <sys/cprng.h>
#include <sys/rwlock.h>

#include <net/if.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/icmp6_private.h>
#include <netinet6/mld6_var.h>

static krwlock_t        in6_multilock __cacheline_aligned;

/*
 * Protocol constants
 */

/*
 * time between repetitions of a node's initial report of interest in a
 * multicast address(in seconds)
 */
#define MLD_UNSOLICITED_REPORT_INTERVAL 10

static struct ip6_pktopts ip6_opts;

static void mld_start_listening(struct in6_multi *);
static void mld_stop_listening(struct in6_multi *);

static struct mld_hdr *mld_allocbuf(struct mbuf **, struct in6_multi *, int);
static void mld_sendpkt(struct in6_multi *, int, const struct in6_addr *);
static void mld_starttimer(struct in6_multi *);
static void mld_stoptimer(struct in6_multi *);
static u_long mld_timerresid(struct in6_multi *);

static void in6m_ref(struct in6_multi *);
static void in6m_unref(struct in6_multi *);
static void in6m_destroy(struct in6_multi *);

void
mld_init(void)
{
        static u_int8_t hbh_buf[8];
        struct ip6_hbh *hbh = (struct ip6_hbh *)hbh_buf;
        u_int16_t rtalert_code = htons((u_int16_t)IP6OPT_RTALERT_MLD);

        /* ip6h_nxt will be fill in later */
        hbh->ip6h_len = 0;      /* (8 >> 3) - 1 */

        /* XXX: grotty hard coding... */
        hbh_buf[2] = IP6OPT_PADN;       /* 2 byte padding */
        hbh_buf[3] = 0;
        hbh_buf[4] = IP6OPT_RTALERT;
        hbh_buf[5] = IP6OPT_RTALERT_LEN - 2;
        memcpy(&hbh_buf[6], (void *)&rtalert_code, sizeof(u_int16_t));

        ip6_opts.ip6po_hbh = hbh;
        /* We will specify the hoplimit by a multicast option. */
        ip6_opts.ip6po_hlim = -1;
        ip6_opts.ip6po_prefer_tempaddr = IP6PO_TEMPADDR_NOTPREFER;

        rw_init(&in6_multilock);
}

static void
mld_starttimer(struct in6_multi *in6m)
{
        struct timeval now;

        KASSERT(rw_write_held(&in6_multilock));
        KASSERTMSG(in6m->in6m_timer != IN6M_TIMER_UNDEF,
            "in6m_timer=%d", in6m->in6m_timer);

        microtime(&now);
        in6m->in6m_timer_expire.tv_sec = now.tv_sec + in6m->in6m_timer / hz;
        in6m->in6m_timer_expire.tv_usec = now.tv_usec +
            (in6m->in6m_timer % hz) * (1000000 / hz);
        if (in6m->in6m_timer_expire.tv_usec > 1000000) {
                in6m->in6m_timer_expire.tv_sec++;
                in6m->in6m_timer_expire.tv_usec -= 1000000;
        }

        /* start or restart the timer */
        callout_schedule(&in6m->in6m_timer_ch, in6m->in6m_timer);
}

/*
 * mld_stoptimer releases in6_multilock when calling callout_halt.
 * The caller must ensure in6m won't be freed while releasing the lock.
 */
static void
mld_stoptimer(struct in6_multi *in6m)
{

        KASSERT(rw_write_held(&in6_multilock));

        if (in6m->in6m_timer == IN6M_TIMER_UNDEF)
                return;

        rw_exit(&in6_multilock);

        callout_halt(&in6m->in6m_timer_ch, NULL);

        rw_enter(&in6_multilock, RW_WRITER);

        in6m->in6m_timer = IN6M_TIMER_UNDEF;
}

static void
mld_timeo(void *arg)
{
        struct in6_multi *in6m = arg;

        KASSERTMSG(in6m->in6m_refcount > 0, "in6m_refcount=%d",
            in6m->in6m_refcount);

        KERNEL_LOCK_UNLESS_NET_MPSAFE();
        rw_enter(&in6_multilock, RW_WRITER);
        if (in6m->in6m_timer == IN6M_TIMER_UNDEF)
                goto out;

        in6m->in6m_timer = IN6M_TIMER_UNDEF;

        switch (in6m->in6m_state) {
        case MLD_REPORTPENDING:
                mld_start_listening(in6m);
                break;
        default:
                mld_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
                break;
        }

out:
        rw_exit(&in6_multilock);
        KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

static u_long
mld_timerresid(struct in6_multi *in6m)
{
        struct timeval now, diff;

        microtime(&now);

        if (now.tv_sec > in6m->in6m_timer_expire.tv_sec ||
            (now.tv_sec == in6m->in6m_timer_expire.tv_sec &&
            now.tv_usec > in6m->in6m_timer_expire.tv_usec)) {
                return (0);
        }
        diff = in6m->in6m_timer_expire;
        diff.tv_sec -= now.tv_sec;
        diff.tv_usec -= now.tv_usec;
        if (diff.tv_usec < 0) {
                diff.tv_sec--;
                diff.tv_usec += 1000000;
        }

        /* return the remaining time in milliseconds */
        return diff.tv_sec * 1000 + diff.tv_usec / 1000;
}

static void
mld_start_listening(struct in6_multi *in6m)
{
        struct in6_addr all_in6;

        KASSERT(rw_write_held(&in6_multilock));

        /*
         * RFC2710 page 10:
         * The node never sends a Report or Done for the link-scope all-nodes
         * address.
         * MLD messages are never sent for multicast addresses whose scope is 0
         * (reserved) or 1 (node-local).
         */
        all_in6 = in6addr_linklocal_allnodes;
        if (in6_setscope(&all_in6, in6m->in6m_ifp, NULL)) {
                /* XXX: this should not happen! */
                in6m->in6m_timer = 0;
                in6m->in6m_state = MLD_OTHERLISTENER;
        }
        if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &all_in6) ||
            IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) < IPV6_ADDR_SCOPE_LINKLOCAL) {
                in6m->in6m_timer = IN6M_TIMER_UNDEF;
                in6m->in6m_state = MLD_OTHERLISTENER;
        } else {
                mld_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
                in6m->in6m_timer = cprng_fast32() %
                    (MLD_UNSOLICITED_REPORT_INTERVAL * hz);
                in6m->in6m_state = MLD_IREPORTEDLAST;

                mld_starttimer(in6m);
        }
}

static void
mld_stop_listening(struct in6_multi *in6m)
{
        struct in6_addr allnode, allrouter;

        KASSERT(rw_lock_held(&in6_multilock));

        allnode = in6addr_linklocal_allnodes;
        if (in6_setscope(&allnode, in6m->in6m_ifp, NULL)) {
                /* XXX: this should not happen! */
                return;
        }
        allrouter = in6addr_linklocal_allrouters;
        if (in6_setscope(&allrouter, in6m->in6m_ifp, NULL)) {
                /* XXX impossible */
                return;
        }

        if (in6m->in6m_state == MLD_IREPORTEDLAST &&
            (!IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &allnode)) &&
            IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) >
            IPV6_ADDR_SCOPE_INTFACELOCAL) {
                mld_sendpkt(in6m, MLD_LISTENER_DONE, &allrouter);
        }
}

void
mld_input(struct mbuf *m, int off)
{
        struct ip6_hdr *ip6;
        struct mld_hdr *mldh;
        struct ifnet *ifp;
        struct in6_multi *in6m = NULL;
        struct in6_addr mld_addr, all_in6;
        u_long timer = 0;       /* timer value in the MLD query header */
        struct psref psref;

        ifp = m_get_rcvif_psref(m, &psref);
        if (__predict_false(ifp == NULL))
                goto out;
        IP6_EXTHDR_GET(mldh, struct mld_hdr *, m, off, sizeof(*mldh));
        if (mldh == NULL) {
                ICMP6_STATINC(ICMP6_STAT_TOOSHORT);
                goto out_nodrop;
        }

        ip6 = mtod(m, struct ip6_hdr *);

        /* source address validation */
        if (!IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src)) {
                /*
                 * RFC3590 allows the IPv6 unspecified address as the source
                 * address of MLD report and done messages.  However, as this
                 * same document says, this special rule is for snooping
                 * switches and the RFC requires routers to discard MLD packets
                 * with the unspecified source address.  The RFC only talks
                 * about hosts receiving an MLD query or report in Security
                 * Considerations, but this is probably the correct intention.
                 * RFC3590 does not talk about other cases than link-local and
                 * the unspecified source addresses, but we believe the same
                 * rule should be applied.
                 * As a result, we only allow link-local addresses as the
                 * source address; otherwise, simply discard the packet.
                 */
#if 0
                /*
                 * XXX: do not log in an input path to avoid log flooding,
                 * though RFC3590 says "SHOULD log" if the source of a query
                 * is the unspecified address.
                 */
                char ip6bufs[INET6_ADDRSTRLEN];
                char ip6bufm[INET6_ADDRSTRLEN];
                log(LOG_INFO,
                    "mld_input: src %s is not link-local (grp=%s)\n",
                    IN6_PRINT(ip6bufs,&ip6->ip6_src),
                    IN6_PRINT(ip6bufm, &mldh->mld_addr));
#endif
                goto out;
        }

        /*
         * make a copy for local work (in6_setscope() may modify the 1st arg)
         */
        mld_addr = mldh->mld_addr;
        if (in6_setscope(&mld_addr, ifp, NULL)) {
                /* XXX: this should not happen! */
                goto out;
        }

        /*
         * In the MLD specification, there are 3 states and a flag.
         *
         * In Non-Listener state, we simply don't have a membership record.
         * In Delaying Listener state, our timer is running (in6m->in6m_timer)
         * In Idle Listener state, our timer is not running
         * (in6m->in6m_timer==IN6M_TIMER_UNDEF)
         *
         * The flag is in6m->in6m_state, it is set to MLD_OTHERLISTENER if
         * we have heard a report from another member, or MLD_IREPORTEDLAST
         * if we sent the last report.
         */
        switch (mldh->mld_type) {
        case MLD_LISTENER_QUERY: {
                struct in6_multi *next;

                if (ifp->if_flags & IFF_LOOPBACK)
                        break;

                if (!IN6_IS_ADDR_UNSPECIFIED(&mld_addr) &&
                    !IN6_IS_ADDR_MULTICAST(&mld_addr))
                        break;  /* print error or log stat? */

                all_in6 = in6addr_linklocal_allnodes;
                if (in6_setscope(&all_in6, ifp, NULL)) {
                        /* XXX: this should not happen! */
                        break;
                }

                /*
                 * - Start the timers in all of our membership records
                 *   that the query applies to for the interface on
                 *   which the query arrived excl. those that belong
                 *   to the "all-nodes" group (ff02::1).
                 * - Restart any timer that is already running but has
                 *   a value longer than the requested timeout.
                 * - Use the value specified in the query message as
                 *   the maximum timeout.
                 */
                timer = ntohs(mldh->mld_maxdelay);

                rw_enter(&in6_multilock, RW_WRITER);
                /*
                 * mld_stoptimer and mld_sendpkt release in6_multilock
                 * temporarily, so we have to prevent in6m from being freed
                 * while releasing the lock by having an extra reference to it.
                 *
                 * Also in6_purge_multi might remove items from the list of the
                 * ifp while releasing the lock. Fortunately in6_purge_multi is
                 * never executed as long as we have a psref of the ifp.
                 */
                LIST_FOREACH_SAFE(in6m, &ifp->if_multiaddrs, in6m_entry, next) {
                        if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &all_in6) ||
                            IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) <
                            IPV6_ADDR_SCOPE_LINKLOCAL)
                                continue;

                        if (in6m->in6m_state == MLD_REPORTPENDING)
                                continue; /* we are not yet ready */

                        if (!IN6_IS_ADDR_UNSPECIFIED(&mld_addr) &&
                            !IN6_ARE_ADDR_EQUAL(&mld_addr, &in6m->in6m_addr))
                                continue;

                        if (timer == 0) {
                                in6m_ref(in6m);

                                /* send a report immediately */
                                mld_stoptimer(in6m);
                                mld_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
                                in6m->in6m_state = MLD_IREPORTEDLAST;

                                in6m_unref(in6m); /* May free in6m */
                        } else if (in6m->in6m_timer == IN6M_TIMER_UNDEF ||
                            mld_timerresid(in6m) > timer) {
                                in6m->in6m_timer =
                                   1 + (cprng_fast32() % timer) * hz / 1000;
                                mld_starttimer(in6m);
                        }
                }
                rw_exit(&in6_multilock);
                break;
            }

        case MLD_LISTENER_REPORT:
                /*
                 * For fast leave to work, we have to know that we are the
                 * last person to send a report for this group.  Reports
                 * can potentially get looped back if we are a multicast
                 * router, so discard reports sourced by me.
                 * Note that it is impossible to check IFF_LOOPBACK flag of
                 * ifp for this purpose, since ip6_mloopback pass the physical
                 * interface to looutput.
                 */
                if (m->m_flags & M_LOOP) /* XXX: grotty flag, but efficient */
                        break;

                if (!IN6_IS_ADDR_MULTICAST(&mldh->mld_addr))
                        break;

                /*
                 * If we belong to the group being reported, stop
                 * our timer for that group.
                 */
                rw_enter(&in6_multilock, RW_WRITER);
                in6m = in6_lookup_multi(&mld_addr, ifp);
                if (in6m) {
                        in6m_ref(in6m);
                        mld_stoptimer(in6m); /* transit to idle state */
                        in6m->in6m_state = MLD_OTHERLISTENER; /* clear flag */
                        in6m_unref(in6m);
                        in6m = NULL; /* in6m might be freed */
                }
                rw_exit(&in6_multilock);
                break;
        default:                /* this is impossible */
#if 0
                /*
                 * this case should be impossible because of filtering in
                 * icmp6_input().  But we explicitly disabled this part
                 * just in case.
                 */
                log(LOG_ERR, "mld_input: illegal type(%d)", mldh->mld_type);
#endif
                break;
        }

out:
        m_freem(m);
out_nodrop:
        m_put_rcvif_psref(ifp, &psref);
}

/*
 * XXX mld_sendpkt must be called with in6_multilock held and
 * will release in6_multilock before calling ip6_output and
 * returning to avoid locking against myself in ip6_output.
 */
static void
mld_sendpkt(struct in6_multi *in6m, int type, const struct in6_addr *dst)
{
        struct mbuf *mh;
        struct mld_hdr *mldh;
        struct ip6_hdr *ip6 = NULL;
        struct ip6_moptions im6o;
        struct in6_ifaddr *ia = NULL;
        struct ifnet *ifp = in6m->in6m_ifp;
        int ignflags;
        struct psref psref;
        int bound;

        KASSERT(rw_write_held(&in6_multilock));

        /*
         * At first, find a link local address on the outgoing interface
         * to use as the source address of the MLD packet.
         * We do not reject tentative addresses for MLD report to deal with
         * the case where we first join a link-local address.
         */
        ignflags = (IN6_IFF_NOTREADY|IN6_IFF_ANYCAST) & ~IN6_IFF_TENTATIVE;
        bound = curlwp_bind();
        ia = in6ifa_ifpforlinklocal_psref(ifp, ignflags, &psref);
        if (ia == NULL) {
                curlwp_bindx(bound);
                return;
        }
        if ((ia->ia6_flags & IN6_IFF_TENTATIVE)) {
                ia6_release(ia, &psref);
                ia = NULL;
        }

        /* Allocate two mbufs to store IPv6 header and MLD header */
        mldh = mld_allocbuf(&mh, in6m, type);
        if (mldh == NULL) {
                ia6_release(ia, &psref);
                curlwp_bindx(bound);
                return;
        }

        /* fill src/dst here */
        ip6 = mtod(mh, struct ip6_hdr *);
        ip6->ip6_src = ia ? ia->ia_addr.sin6_addr : in6addr_any;
        ip6->ip6_dst = dst ? *dst : in6m->in6m_addr;
        ia6_release(ia, &psref);
        curlwp_bindx(bound);

        mldh->mld_addr = in6m->in6m_addr;
        in6_clearscope(&mldh->mld_addr); /* XXX */
        mldh->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6, sizeof(struct ip6_hdr),
            sizeof(struct mld_hdr));

        /* construct multicast option */
        memset(&im6o, 0, sizeof(im6o));
        im6o.im6o_multicast_if_index = if_get_index(ifp);
        im6o.im6o_multicast_hlim = 1;

        /*
         * Request loopback of the report if we are acting as a multicast
         * router, so that the process-level routing daemon can hear it.
         */
        im6o.im6o_multicast_loop = (ip6_mrouter != NULL);

        /* increment output statistics */
        ICMP6_STATINC(ICMP6_STAT_OUTHIST + type);
        icmp6_ifstat_inc(ifp, ifs6_out_msg);
        switch (type) {
        case MLD_LISTENER_QUERY:
                icmp6_ifstat_inc(ifp, ifs6_out_mldquery);
                break;
        case MLD_LISTENER_REPORT:
                icmp6_ifstat_inc(ifp, ifs6_out_mldreport);
                break;
        case MLD_LISTENER_DONE:
                icmp6_ifstat_inc(ifp, ifs6_out_mlddone);
                break;
        }

        /* XXX we cannot call ip6_output with holding in6_multilock */
        rw_exit(&in6_multilock);

        ip6_output(mh, &ip6_opts, NULL, ia ? 0 : IPV6_UNSPECSRC,
            &im6o, NULL, NULL);

        rw_enter(&in6_multilock, RW_WRITER);
}

static struct mld_hdr *
mld_allocbuf(struct mbuf **mh, struct in6_multi *in6m, int type)
{
        struct mbuf *md;
        struct mld_hdr *mldh;
        struct ip6_hdr *ip6;

        /*
         * Allocate mbufs to store ip6 header and MLD header.
         * We allocate 2 mbufs and make chain in advance because
         * it is more convenient when inserting the hop-by-hop option later.
         */
        MGETHDR(*mh, M_DONTWAIT, MT_HEADER);
        if (*mh == NULL)
                return NULL;
        MGET(md, M_DONTWAIT, MT_DATA);
        if (md == NULL) {
                m_free(*mh);
                *mh = NULL;
                return NULL;
        }
        (*mh)->m_next = md;
        md->m_next = NULL;

        m_reset_rcvif((*mh));
        (*mh)->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct mld_hdr);
        (*mh)->m_len = sizeof(struct ip6_hdr);
        m_align(*mh, sizeof(struct ip6_hdr));

        /* fill in the ip6 header */
        ip6 = mtod(*mh, struct ip6_hdr *);
        memset(ip6, 0, sizeof(*ip6));
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        /* ip6_plen will be set later */
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        /* ip6_hlim will be set by im6o.im6o_multicast_hlim */
        /* ip6_src/dst will be set by mld_sendpkt() or mld_sendbuf() */

        /* fill in the MLD header as much as possible */
        md->m_len = sizeof(struct mld_hdr);
        mldh = mtod(md, struct mld_hdr *);
        memset(mldh, 0, sizeof(struct mld_hdr));
        mldh->mld_type = type;
        return mldh;
}

static void
in6m_ref(struct in6_multi *in6m)
{

        KASSERT(rw_write_held(&in6_multilock));
        in6m->in6m_refcount++;
}

static void
in6m_unref(struct in6_multi *in6m)
{

        KASSERT(rw_write_held(&in6_multilock));
        if (--in6m->in6m_refcount == 0)
                in6m_destroy(in6m);
}

/*
 * Add an address to the list of IP6 multicast addresses for a given interface.
 */
struct  in6_multi *
in6_addmulti(struct in6_addr *maddr6, struct ifnet *ifp, int *errorp,
    int timer)
{
        struct  sockaddr_in6 sin6;
        struct  in6_multi *in6m;

        *errorp = 0;

        rw_enter(&in6_multilock, RW_WRITER);
        /*
         * See if address already in list.
         */
        in6m = in6_lookup_multi(maddr6, ifp);
        if (in6m != NULL) {
                /*
                 * Found it; just increment the reference count.
                 */
                in6m->in6m_refcount++;
        } else {
                /*
                 * New address; allocate a new multicast record
                 * and link it into the interface's multicast list.
                 */
                in6m = malloc(sizeof(*in6m), M_IPMADDR, M_NOWAIT|M_ZERO);
                if (in6m == NULL) {
                        *errorp = ENOBUFS;
                        goto out;
                }

                in6m->in6m_addr = *maddr6;
                in6m->in6m_ifp = ifp;
                in6m->in6m_refcount = 1;
                in6m->in6m_timer = IN6M_TIMER_UNDEF;
                callout_init(&in6m->in6m_timer_ch, CALLOUT_MPSAFE);
                callout_setfunc(&in6m->in6m_timer_ch, mld_timeo, in6m);

                LIST_INSERT_HEAD(&ifp->if_multiaddrs, in6m, in6m_entry);

                /*
                 * Ask the network driver to update its multicast reception
                 * filter appropriately for the new address.
                 */
                sockaddr_in6_init(&sin6, maddr6, 0, 0, 0);
                *errorp = if_mcast_op(ifp, SIOCADDMULTI, sin6tosa(&sin6));
                if (*errorp) {
                        callout_destroy(&in6m->in6m_timer_ch);
                        LIST_REMOVE(in6m, in6m_entry);
                        free(in6m, M_IPMADDR);
                        in6m = NULL;
                        goto out;
                }

                in6m->in6m_timer = timer;
                if (in6m->in6m_timer > 0) {
                        in6m->in6m_state = MLD_REPORTPENDING;
                        mld_starttimer(in6m);
                        goto out;
                }

                /*
                 * Let MLD6 know that we have joined a new IP6 multicast
                 * group.
                 */
                mld_start_listening(in6m);
        }
out:
        rw_exit(&in6_multilock);
        return in6m;
}

static void
in6m_destroy(struct in6_multi *in6m)
{
        struct sockaddr_in6 sin6;

        KASSERT(rw_write_held(&in6_multilock));
        KASSERTMSG(in6m->in6m_refcount == 0, "in6m_refcount=%d",
            in6m->in6m_refcount);

        /*
         * Unlink from list if it's listed.  This must be done before
         * mld_stop_listening because it releases in6_multilock and that allows
         * someone to look up the removing in6m from the list and add a
         * reference to the entry unexpectedly.
         */
        if (in6_lookup_multi(&in6m->in6m_addr, in6m->in6m_ifp) != NULL)
                LIST_REMOVE(in6m, in6m_entry);

        /*
         * No remaining claims to this record; let MLD6 know
         * that we are leaving the multicast group.
         */
        mld_stop_listening(in6m);

        /*
         * Delete all references of this multicasting group from
         * the membership arrays
         */
        in6_purge_mcast_references(in6m);

        /*
         * Notify the network driver to update its multicast
         * reception filter.
         */
        sockaddr_in6_init(&sin6, &in6m->in6m_addr, 0, 0, 0);
        if_mcast_op(in6m->in6m_ifp, SIOCDELMULTI, sin6tosa(&sin6));

        /* Tell mld_timeo we're halting the timer */
        in6m->in6m_timer = IN6M_TIMER_UNDEF;

        rw_exit(&in6_multilock);
        callout_halt(&in6m->in6m_timer_ch, NULL);
        callout_destroy(&in6m->in6m_timer_ch);

        free(in6m, M_IPMADDR);
        rw_enter(&in6_multilock, RW_WRITER);
}

/*
 * Delete a multicast address record.
 */
void
in6_delmulti_locked(struct in6_multi *in6m)
{

        KASSERT(rw_write_held(&in6_multilock));
        KASSERTMSG(in6m->in6m_refcount > 0, "in6m_refcount=%d",
            in6m->in6m_refcount);

        /*
         * The caller should have a reference to in6m. So we don't need to care
         * of releasing the lock in mld_stoptimer.
         */
        mld_stoptimer(in6m);
        if (--in6m->in6m_refcount == 0)
                in6m_destroy(in6m);
}

void
in6_delmulti(struct in6_multi *in6m)
{

        rw_enter(&in6_multilock, RW_WRITER);
        in6_delmulti_locked(in6m);
        rw_exit(&in6_multilock);
}

/*
 * Look up the in6_multi record for a given IP6 multicast address
 * on a given interface. If no matching record is found, "in6m"
 * returns NULL.
 */
struct in6_multi *
in6_lookup_multi(const struct in6_addr *addr, const struct ifnet *ifp)
{
        struct in6_multi *in6m;

        KASSERT(rw_lock_held(&in6_multilock));

        LIST_FOREACH(in6m, &ifp->if_multiaddrs, in6m_entry) {
                if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, addr))
                        break;
        }
        return in6m;
}

void
in6_lookup_and_delete_multi(const struct in6_addr *addr,
    const struct ifnet *ifp)
{
        struct in6_multi *in6m;

        rw_enter(&in6_multilock, RW_WRITER);
        in6m = in6_lookup_multi(addr, ifp);
        if (in6m != NULL)
                in6_delmulti_locked(in6m);
        rw_exit(&in6_multilock);
}

bool
in6_multi_group(const struct in6_addr *addr, const struct ifnet *ifp)
{
        bool ingroup;

        rw_enter(&in6_multilock, RW_READER);
        ingroup = in6_lookup_multi(addr, ifp) != NULL;
        rw_exit(&in6_multilock);

        return ingroup;
}

/*
 * Purge in6_multi records associated to the interface.
 */
void
in6_purge_multi(struct ifnet *ifp)
{
        struct in6_multi *in6m, *next;

        rw_enter(&in6_multilock, RW_WRITER);
        LIST_FOREACH_SAFE(in6m, &ifp->if_multiaddrs, in6m_entry, next) {
                LIST_REMOVE(in6m, in6m_entry);
                /*
                 * Normally multicast addresses are already purged at this
                 * point. Remaining references aren't accessible via ifp,
                 * so what we can do here is to prevent ifp from being
                 * accessed via in6m by removing it from the list of ifp.
                 */
                mld_stoptimer(in6m);
        }
        rw_exit(&in6_multilock);
}

void
in6_multi_lock(int op)
{

        rw_enter(&in6_multilock, op);
}

void
in6_multi_unlock(void)
{

        rw_exit(&in6_multilock);
}

bool
in6_multi_locked(int op)
{

        switch (op) {
        case RW_READER:
                return rw_read_held(&in6_multilock);
        case RW_WRITER:
                return rw_write_held(&in6_multilock);
        default:
                return rw_lock_held(&in6_multilock);
        }
}

struct in6_multi_mship *
in6_joingroup(struct ifnet *ifp, struct in6_addr *addr, int *errorp, int timer)
{
        struct in6_multi_mship *imm;

        imm = malloc(sizeof(*imm), M_IPMADDR, M_NOWAIT|M_ZERO);
        if (imm == NULL) {
                *errorp = ENOBUFS;
                return NULL;
        }

        imm->i6mm_maddr = in6_addmulti(addr, ifp, errorp, timer);
        if (!imm->i6mm_maddr) {
                /* *errorp is already set */
                free(imm, M_IPMADDR);
                return NULL;
        }
        return imm;
}

int
in6_leavegroup(struct in6_multi_mship *imm)
{
        struct in6_multi *in6m;

        rw_enter(&in6_multilock, RW_WRITER);
        in6m = imm->i6mm_maddr;
        imm->i6mm_maddr = NULL;
        if (in6m != NULL) {
                in6_delmulti_locked(in6m);
        }
        rw_exit(&in6_multilock);
        free(imm, M_IPMADDR);
        return 0;
}

/*
 * DEPRECATED: keep it just to avoid breaking old sysctl users.
 */
static int
in6_mkludge_sysctl(SYSCTLFN_ARGS)
{

        if (namelen != 1)
                return EINVAL;
        *oldlenp = 0;
        return 0;
}

static int
in6_multicast_sysctl(SYSCTLFN_ARGS)
{
        struct ifnet *ifp;
        struct ifaddr *ifa;
        struct in6_ifaddr *ia6;
        struct in6_multi *in6m;
        uint32_t tmp;
        int error;
        size_t written;
        struct psref psref, psref_ia;
        int bound, s;

        if (namelen != 1)
                return EINVAL;

        rw_enter(&in6_multilock, RW_READER);

        bound = curlwp_bind();
        ifp = if_get_byindex(name[0], &psref);
        if (ifp == NULL) {
                curlwp_bindx(bound);
                rw_exit(&in6_multilock);
                return ENODEV;
        }

        if (oldp == NULL) {
                *oldlenp = 0;
                s = pserialize_read_enter();
                IFADDR_READER_FOREACH(ifa, ifp) {
                        LIST_FOREACH(in6m, &ifp->if_multiaddrs, in6m_entry) {
                                *oldlenp += 2 * sizeof(struct in6_addr) +
                                    sizeof(uint32_t);
                        }
                }
                pserialize_read_exit(s);
                if_put(ifp, &psref);
                curlwp_bindx(bound);
                rw_exit(&in6_multilock);
                return 0;
        }

        error = 0;
        written = 0;
        ifa = if_first_addr_psref(ifp, AF_INET6, &psref_ia);
        if (ifa != NULL) {
                ia6 = ifatoia6(ifa);
                LIST_FOREACH(in6m, &ifp->if_multiaddrs, in6m_entry) {
                        if (written + 2 * sizeof(struct in6_addr) +
                            sizeof(uint32_t) > *oldlenp)
                                goto done;
                        /*
                         * XXX return the first IPv6 address to keep backward
                         * compatibility, however now multicast addresses
                         * don't belong to any IPv6 addresses so it should be
                         * unnecessary.
                         */
                        error = sysctl_copyout(l, &ia6->ia_addr.sin6_addr,
                            oldp, sizeof(struct in6_addr));
                        if (error)
                                goto done;
                        oldp = (char *)oldp + sizeof(struct in6_addr);
                        written += sizeof(struct in6_addr);
                        error = sysctl_copyout(l, &in6m->in6m_addr,
                            oldp, sizeof(struct in6_addr));
                        if (error)
                                goto done;
                        oldp = (char *)oldp + sizeof(struct in6_addr);
                        written += sizeof(struct in6_addr);
                        tmp = in6m->in6m_refcount;
                        error = sysctl_copyout(l, &tmp, oldp, sizeof(tmp));
                        if (error)
                                goto done;
                        oldp = (char *)oldp + sizeof(tmp);
                        written += sizeof(tmp);
                }
                ifa_release(ifa, &psref_ia);
        }
done:
        if_put(ifp, &psref);
        curlwp_bindx(bound);
        rw_exit(&in6_multilock);
        *oldlenp = written;
        return error;
}

void
in6_sysctl_multicast_setup(struct sysctllog **clog)
{

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "inet6", NULL,
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, CTL_EOL);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "multicast",
                       SYSCTL_DESCR("Multicast information"),
                       in6_multicast_sysctl, 0, NULL, 0,
                       CTL_NET, PF_INET6, CTL_CREATE, CTL_EOL);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "multicast_kludge",
                       SYSCTL_DESCR("multicast kludge information"),
                       in6_mkludge_sysctl, 0, NULL, 0,
                       CTL_NET, PF_INET6, CTL_CREATE, CTL_EOL);
}