nfscl: Fix another deadlock related to the NFSv4 clientID lock

[FreeBSD/FreeBSD.git] / sys / netinet6 / in6_mcast.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2009 Bruce Simpson.
 * 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. 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.
 */

/*
 * IPv6 multicast socket, group, and socket option processing module.
 * Normative references: RFC 2292, RFC 3492, RFC 3542, RFC 3678, RFC 3810.
 */

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

#include "opt_inet6.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/priv.h>
#include <sys/taskqueue.h>
#include <sys/tree.h>

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

#include <netinet/in.h>
#include <netinet/udp.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/udp_var.h>
#include <netinet6/in6_fib.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet6/ip6_var.h>
#include <netinet/in_pcb.h>
#include <netinet/tcp_var.h>
#include <netinet6/nd6.h>
#include <netinet6/mld6_var.h>
#include <netinet6/scope6_var.h>

#ifndef KTR_MLD
#define KTR_MLD KTR_INET6
#endif

#ifndef __SOCKUNION_DECLARED
union sockunion {
        struct sockaddr_storage ss;
        struct sockaddr         sa;
        struct sockaddr_dl      sdl;
        struct sockaddr_in6     sin6;
};
typedef union sockunion sockunion_t;
#define __SOCKUNION_DECLARED
#endif /* __SOCKUNION_DECLARED */

static MALLOC_DEFINE(M_IN6MFILTER, "in6_mfilter",
    "IPv6 multicast PCB-layer source filter");
MALLOC_DEFINE(M_IP6MADDR, "in6_multi", "IPv6 multicast group");
static MALLOC_DEFINE(M_IP6MOPTS, "ip6_moptions", "IPv6 multicast options");
static MALLOC_DEFINE(M_IP6MSOURCE, "ip6_msource",
    "IPv6 multicast MLD-layer source filter");

RB_GENERATE(ip6_msource_tree, ip6_msource, im6s_link, ip6_msource_cmp);

/*
 * Locking:
 * - Lock order is: Giant, IN6_MULTI_LOCK, INP_WLOCK,
 *   IN6_MULTI_LIST_LOCK, MLD_LOCK, IF_ADDR_LOCK.
 * - The IF_ADDR_LOCK is implicitly taken by in6m_lookup() earlier, however
 *   it can be taken by code in net/if.c also.
 * - ip6_moptions and in6_mfilter are covered by the INP_WLOCK.
 *
 * struct in6_multi is covered by IN6_MULTI_LOCK. There isn't strictly
 * any need for in6_multi itself to be virtualized -- it is bound to an ifp
 * anyway no matter what happens.
 */
struct mtx in6_multi_list_mtx;
MTX_SYSINIT(in6_multi_mtx, &in6_multi_list_mtx, "in6_multi_list_mtx", MTX_DEF);

struct mtx in6_multi_free_mtx;
MTX_SYSINIT(in6_multi_free_mtx, &in6_multi_free_mtx, "in6_multi_free_mtx", MTX_DEF);

struct sx in6_multi_sx;
SX_SYSINIT(in6_multi_sx, &in6_multi_sx, "in6_multi_sx");



static void     im6f_commit(struct in6_mfilter *);
static int      im6f_get_source(struct in6_mfilter *imf,
                    const struct sockaddr_in6 *psin,
                    struct in6_msource **);
static struct in6_msource *
                im6f_graft(struct in6_mfilter *, const uint8_t,
                    const struct sockaddr_in6 *);
static void     im6f_leave(struct in6_mfilter *);
static int      im6f_prune(struct in6_mfilter *, const struct sockaddr_in6 *);
static void     im6f_purge(struct in6_mfilter *);
static void     im6f_rollback(struct in6_mfilter *);
static void     im6f_reap(struct in6_mfilter *);
static struct in6_mfilter *
                im6o_match_group(const struct ip6_moptions *,
                    const struct ifnet *, const struct sockaddr *);
static struct in6_msource *
                im6o_match_source(struct in6_mfilter *, const struct sockaddr *);
static void     im6s_merge(struct ip6_msource *ims,
                    const struct in6_msource *lims, const int rollback);
static int      in6_getmulti(struct ifnet *, const struct in6_addr *,
                    struct in6_multi **);
static int      in6m_get_source(struct in6_multi *inm,
                    const struct in6_addr *addr, const int noalloc,
                    struct ip6_msource **pims);
#ifdef KTR
static int      in6m_is_ifp_detached(const struct in6_multi *);
#endif
static int      in6m_merge(struct in6_multi *, /*const*/ struct in6_mfilter *);
static void     in6m_purge(struct in6_multi *);
static void     in6m_reap(struct in6_multi *);
static struct ip6_moptions *
                in6p_findmoptions(struct inpcb *);
static int      in6p_get_source_filters(struct inpcb *, struct sockopt *);
static int      in6p_join_group(struct inpcb *, struct sockopt *);
static int      in6p_leave_group(struct inpcb *, struct sockopt *);
static struct ifnet *
                in6p_lookup_mcast_ifp(const struct inpcb *,
                    const struct sockaddr_in6 *);
static int      in6p_block_unblock_source(struct inpcb *, struct sockopt *);
static int      in6p_set_multicast_if(struct inpcb *, struct sockopt *);
static int      in6p_set_source_filters(struct inpcb *, struct sockopt *);
static int      sysctl_ip6_mcast_filters(SYSCTL_HANDLER_ARGS);

SYSCTL_DECL(_net_inet6_ip6);    /* XXX Not in any common header. */

static SYSCTL_NODE(_net_inet6_ip6, OID_AUTO, mcast, CTLFLAG_RW, 0,
    "IPv6 multicast");

static u_long in6_mcast_maxgrpsrc = IPV6_MAX_GROUP_SRC_FILTER;
SYSCTL_ULONG(_net_inet6_ip6_mcast, OID_AUTO, maxgrpsrc,
    CTLFLAG_RWTUN, &in6_mcast_maxgrpsrc, 0,
    "Max source filters per group");

static u_long in6_mcast_maxsocksrc = IPV6_MAX_SOCK_SRC_FILTER;
SYSCTL_ULONG(_net_inet6_ip6_mcast, OID_AUTO, maxsocksrc,
    CTLFLAG_RWTUN, &in6_mcast_maxsocksrc, 0,
    "Max source filters per socket");

/* TODO Virtualize this switch. */
int in6_mcast_loop = IPV6_DEFAULT_MULTICAST_LOOP;
SYSCTL_INT(_net_inet6_ip6_mcast, OID_AUTO, loop, CTLFLAG_RWTUN,
    &in6_mcast_loop, 0, "Loopback multicast datagrams by default");

static SYSCTL_NODE(_net_inet6_ip6_mcast, OID_AUTO, filters,
    CTLFLAG_RD | CTLFLAG_MPSAFE, sysctl_ip6_mcast_filters,
    "Per-interface stack-wide source filters");

#ifdef KTR
/*
 * Inline function which wraps assertions for a valid ifp.
 * The ifnet layer will set the ifma's ifp pointer to NULL if the ifp
 * is detached.
 */
static int __inline
in6m_is_ifp_detached(const struct in6_multi *inm)
{
        struct ifnet *ifp;

        KASSERT(inm->in6m_ifma != NULL, ("%s: no ifma", __func__));
        ifp = inm->in6m_ifma->ifma_ifp;
        if (ifp != NULL) {
                /*
                 * Sanity check that network-layer notion of ifp is the
                 * same as that of link-layer.
                 */
                KASSERT(inm->in6m_ifp == ifp, ("%s: bad ifp", __func__));
        }

        return (ifp == NULL);
}
#endif

/*
 * Initialize an in6_mfilter structure to a known state at t0, t1
 * with an empty source filter list.
 */
static __inline void
im6f_init(struct in6_mfilter *imf, const int st0, const int st1)
{
        memset(imf, 0, sizeof(struct in6_mfilter));
        RB_INIT(&imf->im6f_sources);
        imf->im6f_st[0] = st0;
        imf->im6f_st[1] = st1;
}

struct in6_mfilter *
ip6_mfilter_alloc(const int mflags, const int st0, const int st1)
{
        struct in6_mfilter *imf;

        imf = malloc(sizeof(*imf), M_IN6MFILTER, mflags);

        if (imf != NULL)
                im6f_init(imf, st0, st1);

        return (imf);
}

void
ip6_mfilter_free(struct in6_mfilter *imf)
{

        im6f_purge(imf);
        free(imf, M_IN6MFILTER);
}

/*
 * Find an IPv6 multicast group entry for this ip6_moptions instance
 * which matches the specified group, and optionally an interface.
 * Return its index into the array, or -1 if not found.
 */
static struct in6_mfilter *
im6o_match_group(const struct ip6_moptions *imo, const struct ifnet *ifp,
    const struct sockaddr *group)
{
        const struct sockaddr_in6 *gsin6;
        struct in6_mfilter *imf;
        struct in6_multi *inm;

        gsin6 = (const struct sockaddr_in6 *)group;

        IP6_MFILTER_FOREACH(imf, &imo->im6o_head) {
                inm = imf->im6f_in6m;
                if (inm == NULL)
                        continue;
                if ((ifp == NULL || (inm->in6m_ifp == ifp)) &&
                    IN6_ARE_ADDR_EQUAL(&inm->in6m_addr,
                    &gsin6->sin6_addr)) {
                        break;
                }
        }
        return (imf);
}

/*
 * Find an IPv6 multicast source entry for this imo which matches
 * the given group index for this socket, and source address.
 *
 * XXX TODO: The scope ID, if present in src, is stripped before
 * any comparison. We SHOULD enforce scope/zone checks where the source
 * filter entry has a link scope.
 *
 * NOTE: This does not check if the entry is in-mode, merely if
 * it exists, which may not be the desired behaviour.
 */
static struct in6_msource *
im6o_match_source(struct in6_mfilter *imf, const struct sockaddr *src)
{
        struct ip6_msource       find;
        struct ip6_msource      *ims;
        const sockunion_t       *psa;

        KASSERT(src->sa_family == AF_INET6, ("%s: !AF_INET6", __func__));

        psa = (const sockunion_t *)src;
        find.im6s_addr = psa->sin6.sin6_addr;
        in6_clearscope(&find.im6s_addr);                /* XXX */
        ims = RB_FIND(ip6_msource_tree, &imf->im6f_sources, &find);

        return ((struct in6_msource *)ims);
}

/*
 * Perform filtering for multicast datagrams on a socket by group and source.
 *
 * Returns 0 if a datagram should be allowed through, or various error codes
 * if the socket was not a member of the group, or the source was muted, etc.
 */
int
im6o_mc_filter(const struct ip6_moptions *imo, const struct ifnet *ifp,
    const struct sockaddr *group, const struct sockaddr *src)
{
        struct in6_mfilter *imf;
        struct in6_msource *ims;
        int mode;

        KASSERT(ifp != NULL, ("%s: null ifp", __func__));

        imf = im6o_match_group(imo, ifp, group);
        if (imf == NULL)
                return (MCAST_NOTGMEMBER);

        /*
         * Check if the source was included in an (S,G) join.
         * Allow reception on exclusive memberships by default,
         * reject reception on inclusive memberships by default.
         * Exclude source only if an in-mode exclude filter exists.
         * Include source only if an in-mode include filter exists.
         * NOTE: We are comparing group state here at MLD t1 (now)
         * with socket-layer t0 (since last downcall).
         */
        mode = imf->im6f_st[1];
        ims = im6o_match_source(imf, src);

        if ((ims == NULL && mode == MCAST_INCLUDE) ||
            (ims != NULL && ims->im6sl_st[0] != mode))
                return (MCAST_NOTSMEMBER);

        return (MCAST_PASS);
}

/*
 * Find and return a reference to an in6_multi record for (ifp, group),
 * and bump its reference count.
 * If one does not exist, try to allocate it, and update link-layer multicast
 * filters on ifp to listen for group.
 * Assumes the IN6_MULTI lock is held across the call.
 * Return 0 if successful, otherwise return an appropriate error code.
 */
static int
in6_getmulti(struct ifnet *ifp, const struct in6_addr *group,
    struct in6_multi **pinm)
{
        struct epoch_tracker     et;
        struct sockaddr_in6      gsin6;
        struct ifmultiaddr      *ifma;
        struct in6_multi        *inm;
        int                      error;

        error = 0;

        /*
         * XXX: Accesses to ifma_protospec must be covered by IF_ADDR_LOCK;
         * if_addmulti() takes this mutex itself, so we must drop and
         * re-acquire around the call.
         */
        IN6_MULTI_LOCK_ASSERT();
        IN6_MULTI_LIST_LOCK();
        IF_ADDR_WLOCK(ifp);
        NET_EPOCH_ENTER_ET(et);
        /*
         * Does ifp support IPv6 multicasts?
         */
        if (ifp->if_afdata[AF_INET6] == NULL)
                error = ENODEV;
        else
                inm = in6m_lookup_locked(ifp, group);
        NET_EPOCH_EXIT_ET(et);

        if (error != 0)
                goto out_locked;

        if (inm != NULL) {
                /*
                 * If we already joined this group, just bump the
                 * refcount and return it.
                 */
                KASSERT(inm->in6m_refcount >= 1,
                    ("%s: bad refcount %d", __func__, inm->in6m_refcount));
                in6m_acquire_locked(inm);
                *pinm = inm;
                goto out_locked;
        }

        memset(&gsin6, 0, sizeof(gsin6));
        gsin6.sin6_family = AF_INET6;
        gsin6.sin6_len = sizeof(struct sockaddr_in6);
        gsin6.sin6_addr = *group;

        /*
         * Check if a link-layer group is already associated
         * with this network-layer group on the given ifnet.
         */
        IN6_MULTI_LIST_UNLOCK();
        IF_ADDR_WUNLOCK(ifp);
        error = if_addmulti(ifp, (struct sockaddr *)&gsin6, &ifma);
        if (error != 0)
                return (error);
        IN6_MULTI_LIST_LOCK();
        IF_ADDR_WLOCK(ifp);

        /*
         * If something other than netinet6 is occupying the link-layer
         * group, print a meaningful error message and back out of
         * the allocation.
         * Otherwise, bump the refcount on the existing network-layer
         * group association and return it.
         */
        if (ifma->ifma_protospec != NULL) {
                inm = (struct in6_multi *)ifma->ifma_protospec;
#ifdef INVARIANTS
                KASSERT(ifma->ifma_addr != NULL, ("%s: no ifma_addr",
                    __func__));
                KASSERT(ifma->ifma_addr->sa_family == AF_INET6,
                    ("%s: ifma not AF_INET6", __func__));
                KASSERT(inm != NULL, ("%s: no ifma_protospec", __func__));
                if (inm->in6m_ifma != ifma || inm->in6m_ifp != ifp ||
                    !IN6_ARE_ADDR_EQUAL(&inm->in6m_addr, group))
                        panic("%s: ifma %p is inconsistent with %p (%p)",
                            __func__, ifma, inm, group);
#endif
                in6m_acquire_locked(inm);
                *pinm = inm;
                goto out_locked;
        }

        IF_ADDR_WLOCK_ASSERT(ifp);

        /*
         * A new in6_multi record is needed; allocate and initialize it.
         * We DO NOT perform an MLD join as the in6_ layer may need to
         * push an initial source list down to MLD to support SSM.
         *
         * The initial source filter state is INCLUDE, {} as per the RFC.
         * Pending state-changes per group are subject to a bounds check.
         */
        inm = malloc(sizeof(*inm), M_IP6MADDR, M_NOWAIT | M_ZERO);
        if (inm == NULL) {
                IN6_MULTI_LIST_UNLOCK();
                IF_ADDR_WUNLOCK(ifp);
                if_delmulti_ifma(ifma);
                return (ENOMEM);
        }
        inm->in6m_addr = *group;
        inm->in6m_ifp = ifp;
        inm->in6m_mli = MLD_IFINFO(ifp);
        inm->in6m_ifma = ifma;
        inm->in6m_refcount = 1;
        inm->in6m_state = MLD_NOT_MEMBER;
        mbufq_init(&inm->in6m_scq, MLD_MAX_STATE_CHANGES);

        inm->in6m_st[0].iss_fmode = MCAST_UNDEFINED;
        inm->in6m_st[1].iss_fmode = MCAST_UNDEFINED;
        RB_INIT(&inm->in6m_srcs);

        ifma->ifma_protospec = inm;
        *pinm = inm;

 out_locked:
        IN6_MULTI_LIST_UNLOCK();
        IF_ADDR_WUNLOCK(ifp);
        return (error);
}

/*
 * Drop a reference to an in6_multi record.
 *
 * If the refcount drops to 0, free the in6_multi record and
 * delete the underlying link-layer membership.
 */
static void
in6m_release(struct in6_multi *inm)
{
        struct ifmultiaddr *ifma;
        struct ifnet *ifp;

        CTR2(KTR_MLD, "%s: refcount is %d", __func__, inm->in6m_refcount);

        MPASS(inm->in6m_refcount == 0);
        CTR2(KTR_MLD, "%s: freeing inm %p", __func__, inm);

        ifma = inm->in6m_ifma;
        ifp = inm->in6m_ifp;
        MPASS(ifma->ifma_llifma == NULL);

        /* XXX this access is not covered by IF_ADDR_LOCK */
        CTR2(KTR_MLD, "%s: purging ifma %p", __func__, ifma);
        KASSERT(ifma->ifma_protospec == NULL,
            ("%s: ifma_protospec != NULL", __func__));
        if (ifp == NULL)
                ifp = ifma->ifma_ifp;

        if (ifp != NULL) {
                CURVNET_SET(ifp->if_vnet);
                in6m_purge(inm);
                free(inm, M_IP6MADDR);
                if_delmulti_ifma_flags(ifma, 1);
                CURVNET_RESTORE();
                if_rele(ifp);
        } else {
                in6m_purge(inm);
                free(inm, M_IP6MADDR);
                if_delmulti_ifma_flags(ifma, 1);
        }
}

/*
 * Interface detach can happen in a taskqueue thread context, so we must use a
 * dedicated thread to avoid deadlocks when draining in6m_release tasks.
 */
TASKQUEUE_DEFINE_THREAD(in6m_free);
static struct in6_multi_head in6m_free_list = SLIST_HEAD_INITIALIZER();
static void in6m_release_task(void *arg __unused, int pending __unused);
static struct task in6m_free_task = TASK_INITIALIZER(0, in6m_release_task, NULL);

void
in6m_release_list_deferred(struct in6_multi_head *inmh)
{
        if (SLIST_EMPTY(inmh))
                return;
        mtx_lock(&in6_multi_free_mtx);
        SLIST_CONCAT(&in6m_free_list, inmh, in6_multi, in6m_nrele);
        mtx_unlock(&in6_multi_free_mtx);
        taskqueue_enqueue(taskqueue_in6m_free, &in6m_free_task);
}

void
in6m_release_wait(void *arg __unused)
{

        /*
         * Make sure all pending multicast addresses are freed before
         * the VNET or network device is destroyed:
         */
        taskqueue_drain_all(taskqueue_in6m_free);
}
#ifdef VIMAGE
VNET_SYSUNINIT(in6m_release_wait, SI_SUB_PROTO_DOMAIN, SI_ORDER_FIRST, in6m_release_wait, NULL);
#endif

void
in6m_disconnect_locked(struct in6_multi_head *inmh, struct in6_multi *inm)
{
        struct ifnet *ifp;
        struct ifaddr *ifa;
        struct in6_ifaddr *ifa6;
        struct in6_multi_mship *imm, *imm_tmp;
        struct ifmultiaddr *ifma, *ll_ifma;

        IN6_MULTI_LIST_LOCK_ASSERT();

        ifp = inm->in6m_ifp;
        if (ifp == NULL)
                return;         /* already called */

        inm->in6m_ifp = NULL;
        IF_ADDR_WLOCK_ASSERT(ifp);
        ifma = inm->in6m_ifma;
        if (ifma == NULL)
                return;

        if_ref(ifp);
        if (ifma->ifma_flags & IFMA_F_ENQUEUED) {
                CK_STAILQ_REMOVE(&ifp->if_multiaddrs, ifma, ifmultiaddr, ifma_link);
                ifma->ifma_flags &= ~IFMA_F_ENQUEUED;
        }
        MCDPRINTF("removed ifma: %p from %s\n", ifma, ifp->if_xname);
        if ((ll_ifma = ifma->ifma_llifma) != NULL) {
                MPASS(ifma != ll_ifma);
                ifma->ifma_llifma = NULL;
                MPASS(ll_ifma->ifma_llifma == NULL);
                MPASS(ll_ifma->ifma_ifp == ifp);
                if (--ll_ifma->ifma_refcount == 0) {
                        if (ll_ifma->ifma_flags & IFMA_F_ENQUEUED) {
                                CK_STAILQ_REMOVE(&ifp->if_multiaddrs, ll_ifma, ifmultiaddr, ifma_link);
                                ll_ifma->ifma_flags &= ~IFMA_F_ENQUEUED;
                        }
                        MCDPRINTF("removed ll_ifma: %p from %s\n", ll_ifma, ifp->if_xname);
                        if_freemulti(ll_ifma);
                }
        }
        CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;
                ifa6 = (void *)ifa;
                LIST_FOREACH_SAFE(imm, &ifa6->ia6_memberships,
                    i6mm_chain, imm_tmp) {
                        if (inm == imm->i6mm_maddr) {
                                LIST_REMOVE(imm, i6mm_chain);
                                free(imm, M_IP6MADDR);
                                in6m_rele_locked(inmh, inm);
                        }
                }
        }
}

static void
in6m_release_task(void *arg __unused, int pending __unused)
{
        struct in6_multi_head in6m_free_tmp;
        struct in6_multi *inm, *tinm;

        SLIST_INIT(&in6m_free_tmp);
        mtx_lock(&in6_multi_free_mtx);
        SLIST_CONCAT(&in6m_free_tmp, &in6m_free_list, in6_multi, in6m_nrele);
        mtx_unlock(&in6_multi_free_mtx);
        IN6_MULTI_LOCK();
        SLIST_FOREACH_SAFE(inm, &in6m_free_tmp, in6m_nrele, tinm) {
                SLIST_REMOVE_HEAD(&in6m_free_tmp, in6m_nrele);
                in6m_release(inm);
        }
        IN6_MULTI_UNLOCK();
}

/*
 * Clear recorded source entries for a group.
 * Used by the MLD code. Caller must hold the IN6_MULTI lock.
 * FIXME: Should reap.
 */
void
in6m_clear_recorded(struct in6_multi *inm)
{
        struct ip6_msource      *ims;

        IN6_MULTI_LIST_LOCK_ASSERT();

        RB_FOREACH(ims, ip6_msource_tree, &inm->in6m_srcs) {
                if (ims->im6s_stp) {
                        ims->im6s_stp = 0;
                        --inm->in6m_st[1].iss_rec;
                }
        }
        KASSERT(inm->in6m_st[1].iss_rec == 0,
            ("%s: iss_rec %d not 0", __func__, inm->in6m_st[1].iss_rec));
}

/*
 * Record a source as pending for a Source-Group MLDv2 query.
 * This lives here as it modifies the shared tree.
 *
 * inm is the group descriptor.
 * naddr is the address of the source to record in network-byte order.
 *
 * If the net.inet6.mld.sgalloc sysctl is non-zero, we will
 * lazy-allocate a source node in response to an SG query.
 * Otherwise, no allocation is performed. This saves some memory
 * with the trade-off that the source will not be reported to the
 * router if joined in the window between the query response and
 * the group actually being joined on the local host.
 *
 * VIMAGE: XXX: Currently the mld_sgalloc feature has been removed.
 * This turns off the allocation of a recorded source entry if
 * the group has not been joined.
 *
 * Return 0 if the source didn't exist or was already marked as recorded.
 * Return 1 if the source was marked as recorded by this function.
 * Return <0 if any error occurred (negated errno code).
 */
int
in6m_record_source(struct in6_multi *inm, const struct in6_addr *addr)
{
        struct ip6_msource       find;
        struct ip6_msource      *ims, *nims;

        IN6_MULTI_LIST_LOCK_ASSERT();

        find.im6s_addr = *addr;
        ims = RB_FIND(ip6_msource_tree, &inm->in6m_srcs, &find);
        if (ims && ims->im6s_stp)
                return (0);
        if (ims == NULL) {
                if (inm->in6m_nsrc == in6_mcast_maxgrpsrc)
                        return (-ENOSPC);
                nims = malloc(sizeof(struct ip6_msource), M_IP6MSOURCE,
                    M_NOWAIT | M_ZERO);
                if (nims == NULL)
                        return (-ENOMEM);
                nims->im6s_addr = find.im6s_addr;
                RB_INSERT(ip6_msource_tree, &inm->in6m_srcs, nims);
                ++inm->in6m_nsrc;
                ims = nims;
        }

        /*
         * Mark the source as recorded and update the recorded
         * source count.
         */
        ++ims->im6s_stp;
        ++inm->in6m_st[1].iss_rec;

        return (1);
}

/*
 * Return a pointer to an in6_msource owned by an in6_mfilter,
 * given its source address.
 * Lazy-allocate if needed. If this is a new entry its filter state is
 * undefined at t0.
 *
 * imf is the filter set being modified.
 * addr is the source address.
 *
 * SMPng: May be called with locks held; malloc must not block.
 */
static int
im6f_get_source(struct in6_mfilter *imf, const struct sockaddr_in6 *psin,
    struct in6_msource **plims)
{
        struct ip6_msource       find;
        struct ip6_msource      *ims, *nims;
        struct in6_msource      *lims;
        int                      error;

        error = 0;
        ims = NULL;
        lims = NULL;

        find.im6s_addr = psin->sin6_addr;
        ims = RB_FIND(ip6_msource_tree, &imf->im6f_sources, &find);
        lims = (struct in6_msource *)ims;
        if (lims == NULL) {
                if (imf->im6f_nsrc == in6_mcast_maxsocksrc)
                        return (ENOSPC);
                nims = malloc(sizeof(struct in6_msource), M_IN6MFILTER,
                    M_NOWAIT | M_ZERO);
                if (nims == NULL)
                        return (ENOMEM);
                lims = (struct in6_msource *)nims;
                lims->im6s_addr = find.im6s_addr;
                lims->im6sl_st[0] = MCAST_UNDEFINED;
                RB_INSERT(ip6_msource_tree, &imf->im6f_sources, nims);
                ++imf->im6f_nsrc;
        }

        *plims = lims;

        return (error);
}

/*
 * Graft a source entry into an existing socket-layer filter set,
 * maintaining any required invariants and checking allocations.
 *
 * The source is marked as being in the new filter mode at t1.
 *
 * Return the pointer to the new node, otherwise return NULL.
 */
static struct in6_msource *
im6f_graft(struct in6_mfilter *imf, const uint8_t st1,
    const struct sockaddr_in6 *psin)
{
        struct ip6_msource      *nims;
        struct in6_msource      *lims;

        nims = malloc(sizeof(struct in6_msource), M_IN6MFILTER,
            M_NOWAIT | M_ZERO);
        if (nims == NULL)
                return (NULL);
        lims = (struct in6_msource *)nims;
        lims->im6s_addr = psin->sin6_addr;
        lims->im6sl_st[0] = MCAST_UNDEFINED;
        lims->im6sl_st[1] = st1;
        RB_INSERT(ip6_msource_tree, &imf->im6f_sources, nims);
        ++imf->im6f_nsrc;

        return (lims);
}

/*
 * Prune a source entry from an existing socket-layer filter set,
 * maintaining any required invariants and checking allocations.
 *
 * The source is marked as being left at t1, it is not freed.
 *
 * Return 0 if no error occurred, otherwise return an errno value.
 */
static int
im6f_prune(struct in6_mfilter *imf, const struct sockaddr_in6 *psin)
{
        struct ip6_msource       find;
        struct ip6_msource      *ims;
        struct in6_msource      *lims;

        find.im6s_addr = psin->sin6_addr;
        ims = RB_FIND(ip6_msource_tree, &imf->im6f_sources, &find);
        if (ims == NULL)
                return (ENOENT);
        lims = (struct in6_msource *)ims;
        lims->im6sl_st[1] = MCAST_UNDEFINED;
        return (0);
}

/*
 * Revert socket-layer filter set deltas at t1 to t0 state.
 */
static void
im6f_rollback(struct in6_mfilter *imf)
{
        struct ip6_msource      *ims, *tims;
        struct in6_msource      *lims;

        RB_FOREACH_SAFE(ims, ip6_msource_tree, &imf->im6f_sources, tims) {
                lims = (struct in6_msource *)ims;
                if (lims->im6sl_st[0] == lims->im6sl_st[1]) {
                        /* no change at t1 */
                        continue;
                } else if (lims->im6sl_st[0] != MCAST_UNDEFINED) {
                        /* revert change to existing source at t1 */
                        lims->im6sl_st[1] = lims->im6sl_st[0];
                } else {
                        /* revert source added t1 */
                        CTR2(KTR_MLD, "%s: free ims %p", __func__, ims);
                        RB_REMOVE(ip6_msource_tree, &imf->im6f_sources, ims);
                        free(ims, M_IN6MFILTER);
                        imf->im6f_nsrc--;
                }
        }
        imf->im6f_st[1] = imf->im6f_st[0];
}

/*
 * Mark socket-layer filter set as INCLUDE {} at t1.
 */
static void
im6f_leave(struct in6_mfilter *imf)
{
        struct ip6_msource      *ims;
        struct in6_msource      *lims;

        RB_FOREACH(ims, ip6_msource_tree, &imf->im6f_sources) {
                lims = (struct in6_msource *)ims;
                lims->im6sl_st[1] = MCAST_UNDEFINED;
        }
        imf->im6f_st[1] = MCAST_INCLUDE;
}

/*
 * Mark socket-layer filter set deltas as committed.
 */
static void
im6f_commit(struct in6_mfilter *imf)
{
        struct ip6_msource      *ims;
        struct in6_msource      *lims;

        RB_FOREACH(ims, ip6_msource_tree, &imf->im6f_sources) {
                lims = (struct in6_msource *)ims;
                lims->im6sl_st[0] = lims->im6sl_st[1];
        }
        imf->im6f_st[0] = imf->im6f_st[1];
}

/*
 * Reap unreferenced sources from socket-layer filter set.
 */
static void
im6f_reap(struct in6_mfilter *imf)
{
        struct ip6_msource      *ims, *tims;
        struct in6_msource      *lims;

        RB_FOREACH_SAFE(ims, ip6_msource_tree, &imf->im6f_sources, tims) {
                lims = (struct in6_msource *)ims;
                if ((lims->im6sl_st[0] == MCAST_UNDEFINED) &&
                    (lims->im6sl_st[1] == MCAST_UNDEFINED)) {
                        CTR2(KTR_MLD, "%s: free lims %p", __func__, ims);
                        RB_REMOVE(ip6_msource_tree, &imf->im6f_sources, ims);
                        free(ims, M_IN6MFILTER);
                        imf->im6f_nsrc--;
                }
        }
}

/*
 * Purge socket-layer filter set.
 */
static void
im6f_purge(struct in6_mfilter *imf)
{
        struct ip6_msource      *ims, *tims;

        RB_FOREACH_SAFE(ims, ip6_msource_tree, &imf->im6f_sources, tims) {
                CTR2(KTR_MLD, "%s: free ims %p", __func__, ims);
                RB_REMOVE(ip6_msource_tree, &imf->im6f_sources, ims);
                free(ims, M_IN6MFILTER);
                imf->im6f_nsrc--;
        }
        imf->im6f_st[0] = imf->im6f_st[1] = MCAST_UNDEFINED;
        KASSERT(RB_EMPTY(&imf->im6f_sources),
            ("%s: im6f_sources not empty", __func__));
}

/*
 * Look up a source filter entry for a multicast group.
 *
 * inm is the group descriptor to work with.
 * addr is the IPv6 address to look up.
 * noalloc may be non-zero to suppress allocation of sources.
 * *pims will be set to the address of the retrieved or allocated source.
 *
 * SMPng: NOTE: may be called with locks held.
 * Return 0 if successful, otherwise return a non-zero error code.
 */
static int
in6m_get_source(struct in6_multi *inm, const struct in6_addr *addr,
    const int noalloc, struct ip6_msource **pims)
{
        struct ip6_msource       find;
        struct ip6_msource      *ims, *nims;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        find.im6s_addr = *addr;
        ims = RB_FIND(ip6_msource_tree, &inm->in6m_srcs, &find);
        if (ims == NULL && !noalloc) {
                if (inm->in6m_nsrc == in6_mcast_maxgrpsrc)
                        return (ENOSPC);
                nims = malloc(sizeof(struct ip6_msource), M_IP6MSOURCE,
                    M_NOWAIT | M_ZERO);
                if (nims == NULL)
                        return (ENOMEM);
                nims->im6s_addr = *addr;
                RB_INSERT(ip6_msource_tree, &inm->in6m_srcs, nims);
                ++inm->in6m_nsrc;
                ims = nims;
                CTR3(KTR_MLD, "%s: allocated %s as %p", __func__,
                    ip6_sprintf(ip6tbuf, addr), ims);
        }

        *pims = ims;
        return (0);
}

/*
 * Merge socket-layer source into MLD-layer source.
 * If rollback is non-zero, perform the inverse of the merge.
 */
static void
im6s_merge(struct ip6_msource *ims, const struct in6_msource *lims,
    const int rollback)
{
        int n = rollback ? -1 : 1;
#ifdef KTR
        char ip6tbuf[INET6_ADDRSTRLEN];

        ip6_sprintf(ip6tbuf, &lims->im6s_addr);
#endif

        if (lims->im6sl_st[0] == MCAST_EXCLUDE) {
                CTR3(KTR_MLD, "%s: t1 ex -= %d on %s", __func__, n, ip6tbuf);
                ims->im6s_st[1].ex -= n;
        } else if (lims->im6sl_st[0] == MCAST_INCLUDE) {
                CTR3(KTR_MLD, "%s: t1 in -= %d on %s", __func__, n, ip6tbuf);
                ims->im6s_st[1].in -= n;
        }

        if (lims->im6sl_st[1] == MCAST_EXCLUDE) {
                CTR3(KTR_MLD, "%s: t1 ex += %d on %s", __func__, n, ip6tbuf);
                ims->im6s_st[1].ex += n;
        } else if (lims->im6sl_st[1] == MCAST_INCLUDE) {
                CTR3(KTR_MLD, "%s: t1 in += %d on %s", __func__, n, ip6tbuf);
                ims->im6s_st[1].in += n;
        }
}

/*
 * Atomically update the global in6_multi state, when a membership's
 * filter list is being updated in any way.
 *
 * imf is the per-inpcb-membership group filter pointer.
 * A fake imf may be passed for in-kernel consumers.
 *
 * XXX This is a candidate for a set-symmetric-difference style loop
 * which would eliminate the repeated lookup from root of ims nodes,
 * as they share the same key space.
 *
 * If any error occurred this function will back out of refcounts
 * and return a non-zero value.
 */
static int
in6m_merge(struct in6_multi *inm, /*const*/ struct in6_mfilter *imf)
{
        struct ip6_msource      *ims, *nims;
        struct in6_msource      *lims;
        int                      schanged, error;
        int                      nsrc0, nsrc1;

        schanged = 0;
        error = 0;
        nsrc1 = nsrc0 = 0;
        IN6_MULTI_LIST_LOCK_ASSERT();

        /*
         * Update the source filters first, as this may fail.
         * Maintain count of in-mode filters at t0, t1. These are
         * used to work out if we transition into ASM mode or not.
         * Maintain a count of source filters whose state was
         * actually modified by this operation.
         */
        RB_FOREACH(ims, ip6_msource_tree, &imf->im6f_sources) {
                lims = (struct in6_msource *)ims;
                if (lims->im6sl_st[0] == imf->im6f_st[0]) nsrc0++;
                if (lims->im6sl_st[1] == imf->im6f_st[1]) nsrc1++;
                if (lims->im6sl_st[0] == lims->im6sl_st[1]) continue;
                error = in6m_get_source(inm, &lims->im6s_addr, 0, &nims);
                ++schanged;
                if (error)
                        break;
                im6s_merge(nims, lims, 0);
        }
        if (error) {
                struct ip6_msource *bims;

                RB_FOREACH_REVERSE_FROM(ims, ip6_msource_tree, nims) {
                        lims = (struct in6_msource *)ims;
                        if (lims->im6sl_st[0] == lims->im6sl_st[1])
                                continue;
                        (void)in6m_get_source(inm, &lims->im6s_addr, 1, &bims);
                        if (bims == NULL)
                                continue;
                        im6s_merge(bims, lims, 1);
                }
                goto out_reap;
        }

        CTR3(KTR_MLD, "%s: imf filters in-mode: %d at t0, %d at t1",
            __func__, nsrc0, nsrc1);

        /* Handle transition between INCLUDE {n} and INCLUDE {} on socket. */
        if (imf->im6f_st[0] == imf->im6f_st[1] &&
            imf->im6f_st[1] == MCAST_INCLUDE) {
                if (nsrc1 == 0) {
                        CTR1(KTR_MLD, "%s: --in on inm at t1", __func__);
                        --inm->in6m_st[1].iss_in;
                }
        }

        /* Handle filter mode transition on socket. */
        if (imf->im6f_st[0] != imf->im6f_st[1]) {
                CTR3(KTR_MLD, "%s: imf transition %d to %d",
                    __func__, imf->im6f_st[0], imf->im6f_st[1]);

                if (imf->im6f_st[0] == MCAST_EXCLUDE) {
                        CTR1(KTR_MLD, "%s: --ex on inm at t1", __func__);
                        --inm->in6m_st[1].iss_ex;
                } else if (imf->im6f_st[0] == MCAST_INCLUDE) {
                        CTR1(KTR_MLD, "%s: --in on inm at t1", __func__);
                        --inm->in6m_st[1].iss_in;
                }

                if (imf->im6f_st[1] == MCAST_EXCLUDE) {
                        CTR1(KTR_MLD, "%s: ex++ on inm at t1", __func__);
                        inm->in6m_st[1].iss_ex++;
                } else if (imf->im6f_st[1] == MCAST_INCLUDE && nsrc1 > 0) {
                        CTR1(KTR_MLD, "%s: in++ on inm at t1", __func__);
                        inm->in6m_st[1].iss_in++;
                }
        }

        /*
         * Track inm filter state in terms of listener counts.
         * If there are any exclusive listeners, stack-wide
         * membership is exclusive.
         * Otherwise, if only inclusive listeners, stack-wide is inclusive.
         * If no listeners remain, state is undefined at t1,
         * and the MLD lifecycle for this group should finish.
         */
        if (inm->in6m_st[1].iss_ex > 0) {
                CTR1(KTR_MLD, "%s: transition to EX", __func__);
                inm->in6m_st[1].iss_fmode = MCAST_EXCLUDE;
        } else if (inm->in6m_st[1].iss_in > 0) {
                CTR1(KTR_MLD, "%s: transition to IN", __func__);
                inm->in6m_st[1].iss_fmode = MCAST_INCLUDE;
        } else {
                CTR1(KTR_MLD, "%s: transition to UNDEF", __func__);
                inm->in6m_st[1].iss_fmode = MCAST_UNDEFINED;
        }

        /* Decrement ASM listener count on transition out of ASM mode. */
        if (imf->im6f_st[0] == MCAST_EXCLUDE && nsrc0 == 0) {
                if ((imf->im6f_st[1] != MCAST_EXCLUDE) ||
                    (imf->im6f_st[1] == MCAST_EXCLUDE && nsrc1 > 0)) {
                        CTR1(KTR_MLD, "%s: --asm on inm at t1", __func__);
                        --inm->in6m_st[1].iss_asm;
                }
        }

        /* Increment ASM listener count on transition to ASM mode. */
        if (imf->im6f_st[1] == MCAST_EXCLUDE && nsrc1 == 0) {
                CTR1(KTR_MLD, "%s: asm++ on inm at t1", __func__);
                inm->in6m_st[1].iss_asm++;
        }

        CTR3(KTR_MLD, "%s: merged imf %p to inm %p", __func__, imf, inm);
        in6m_print(inm);

out_reap:
        if (schanged > 0) {
                CTR1(KTR_MLD, "%s: sources changed; reaping", __func__);
                in6m_reap(inm);
        }
        return (error);
}

/*
 * Mark an in6_multi's filter set deltas as committed.
 * Called by MLD after a state change has been enqueued.
 */
void
in6m_commit(struct in6_multi *inm)
{
        struct ip6_msource      *ims;

        CTR2(KTR_MLD, "%s: commit inm %p", __func__, inm);
        CTR1(KTR_MLD, "%s: pre commit:", __func__);
        in6m_print(inm);

        RB_FOREACH(ims, ip6_msource_tree, &inm->in6m_srcs) {
                ims->im6s_st[0] = ims->im6s_st[1];
        }
        inm->in6m_st[0] = inm->in6m_st[1];
}

/*
 * Reap unreferenced nodes from an in6_multi's filter set.
 */
static void
in6m_reap(struct in6_multi *inm)
{
        struct ip6_msource      *ims, *tims;

        RB_FOREACH_SAFE(ims, ip6_msource_tree, &inm->in6m_srcs, tims) {
                if (ims->im6s_st[0].ex > 0 || ims->im6s_st[0].in > 0 ||
                    ims->im6s_st[1].ex > 0 || ims->im6s_st[1].in > 0 ||
                    ims->im6s_stp != 0)
                        continue;
                CTR2(KTR_MLD, "%s: free ims %p", __func__, ims);
                RB_REMOVE(ip6_msource_tree, &inm->in6m_srcs, ims);
                free(ims, M_IP6MSOURCE);
                inm->in6m_nsrc--;
        }
}

/*
 * Purge all source nodes from an in6_multi's filter set.
 */
static void
in6m_purge(struct in6_multi *inm)
{
        struct ip6_msource      *ims, *tims;

        RB_FOREACH_SAFE(ims, ip6_msource_tree, &inm->in6m_srcs, tims) {
                CTR2(KTR_MLD, "%s: free ims %p", __func__, ims);
                RB_REMOVE(ip6_msource_tree, &inm->in6m_srcs, ims);
                free(ims, M_IP6MSOURCE);
                inm->in6m_nsrc--;
        }
        /* Free state-change requests that might be queued. */
        mbufq_drain(&inm->in6m_scq);
}

/*
 * Join a multicast address w/o sources.
 * KAME compatibility entry point.
 *
 * SMPng: Assume no mc locks held by caller.
 */
int
in6_joingroup(struct ifnet *ifp, const struct in6_addr *mcaddr,
    /*const*/ struct in6_mfilter *imf, struct in6_multi **pinm,
    const int delay)
{
        int error;

        IN6_MULTI_LOCK();
        error = in6_joingroup_locked(ifp, mcaddr, NULL, pinm, delay);
        IN6_MULTI_UNLOCK();
        return (error);
}

/*
 * Join a multicast group; real entry point.
 *
 * Only preserves atomicity at inm level.
 * NOTE: imf argument cannot be const due to sys/tree.h limitations.
 *
 * If the MLD downcall fails, the group is not joined, and an error
 * code is returned.
 */
int
in6_joingroup_locked(struct ifnet *ifp, const struct in6_addr *mcaddr,
    /*const*/ struct in6_mfilter *imf, struct in6_multi **pinm,
    const int delay)
{
        struct in6_multi_head    inmh;
        struct in6_mfilter       timf;
        struct in6_multi        *inm;
        struct ifmultiaddr *ifma;
        int                      error;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

#ifdef INVARIANTS
        /*
         * Sanity: Check scope zone ID was set for ifp, if and
         * only if group is scoped to an interface.
         */
        KASSERT(IN6_IS_ADDR_MULTICAST(mcaddr),
            ("%s: not a multicast address", __func__));
        if (IN6_IS_ADDR_MC_LINKLOCAL(mcaddr) ||
            IN6_IS_ADDR_MC_INTFACELOCAL(mcaddr)) {
                KASSERT(mcaddr->s6_addr16[1] != 0,
                    ("%s: scope zone ID not set", __func__));
        }
#endif

        IN6_MULTI_LOCK_ASSERT();
        IN6_MULTI_LIST_UNLOCK_ASSERT();

        CTR4(KTR_MLD, "%s: join %s on %p(%s))", __func__,
            ip6_sprintf(ip6tbuf, mcaddr), ifp, if_name(ifp));

        error = 0;
        inm = NULL;

        /*
         * If no imf was specified (i.e. kernel consumer),
         * fake one up and assume it is an ASM join.
         */
        if (imf == NULL) {
                im6f_init(&timf, MCAST_UNDEFINED, MCAST_EXCLUDE);
                imf = &timf;
        }
        error = in6_getmulti(ifp, mcaddr, &inm);
        if (error) {
                CTR1(KTR_MLD, "%s: in6_getmulti() failure", __func__);
                return (error);
        }

        IN6_MULTI_LIST_LOCK();
        CTR1(KTR_MLD, "%s: merge inm state", __func__);
        error = in6m_merge(inm, imf);
        if (error) {
                CTR1(KTR_MLD, "%s: failed to merge inm state", __func__);
                goto out_in6m_release;
        }

        CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
        error = mld_change_state(inm, delay);
        if (error) {
                CTR1(KTR_MLD, "%s: failed to update source", __func__);
                goto out_in6m_release;
        }

out_in6m_release:
        SLIST_INIT(&inmh);
        if (error) {
                CTR2(KTR_MLD, "%s: dropping ref on %p", __func__, inm);
                IF_ADDR_RLOCK(ifp);
                CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                        if (ifma->ifma_protospec == inm) {
                                ifma->ifma_protospec = NULL;
                                break;
                        }
                }
                in6m_disconnect_locked(&inmh, inm);
                in6m_rele_locked(&inmh, inm);
                IF_ADDR_RUNLOCK(ifp);
        } else {
                *pinm = inm;
        }
        IN6_MULTI_LIST_UNLOCK();
        in6m_release_list_deferred(&inmh);
        return (error);
}

/*
 * Leave a multicast group; unlocked entry point.
 */
int
in6_leavegroup(struct in6_multi *inm, /*const*/ struct in6_mfilter *imf)
{
        int error;

        IN6_MULTI_LOCK();
        error = in6_leavegroup_locked(inm, imf);
        IN6_MULTI_UNLOCK();
        return (error);
}

/*
 * Leave a multicast group; real entry point.
 * All source filters will be expunged.
 *
 * Only preserves atomicity at inm level.
 *
 * Holding the write lock for the INP which contains imf
 * is highly advisable. We can't assert for it as imf does not
 * contain a back-pointer to the owning inp.
 *
 * Note: This is not the same as in6m_release(*) as this function also
 * makes a state change downcall into MLD.
 */
int
in6_leavegroup_locked(struct in6_multi *inm, /*const*/ struct in6_mfilter *imf)
{
        struct in6_multi_head    inmh;
        struct in6_mfilter       timf;
        struct ifnet *ifp;
        int                      error;
#ifdef KTR
        char                     ip6tbuf[INET6_ADDRSTRLEN];
#endif

        error = 0;

        IN6_MULTI_LOCK_ASSERT();

        CTR5(KTR_MLD, "%s: leave inm %p, %s/%s, imf %p", __func__,
            inm, ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            (in6m_is_ifp_detached(inm) ? "null" : if_name(inm->in6m_ifp)),
            imf);

        /*
         * If no imf was specified (i.e. kernel consumer),
         * fake one up and assume it is an ASM join.
         */
        if (imf == NULL) {
                im6f_init(&timf, MCAST_EXCLUDE, MCAST_UNDEFINED);
                imf = &timf;
        }

        /*
         * Begin state merge transaction at MLD layer.
         *
         * As this particular invocation should not cause any memory
         * to be allocated, and there is no opportunity to roll back
         * the transaction, it MUST NOT fail.
         */

        ifp = inm->in6m_ifp;
        IN6_MULTI_LIST_LOCK();
        CTR1(KTR_MLD, "%s: merge inm state", __func__);
        error = in6m_merge(inm, imf);
        KASSERT(error == 0, ("%s: failed to merge inm state", __func__));

        CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
        error = 0;
        if (ifp)
                error = mld_change_state(inm, 0);
        if (error)
                CTR1(KTR_MLD, "%s: failed mld downcall", __func__);

        CTR2(KTR_MLD, "%s: dropping ref on %p", __func__, inm);
        if (ifp)
                IF_ADDR_WLOCK(ifp);

        SLIST_INIT(&inmh);
        if (inm->in6m_refcount == 1)
                in6m_disconnect_locked(&inmh, inm);
        in6m_rele_locked(&inmh, inm);
        if (ifp)
                IF_ADDR_WUNLOCK(ifp);
        IN6_MULTI_LIST_UNLOCK();
        in6m_release_list_deferred(&inmh);
        return (error);
}


/*
 * Block or unblock an ASM multicast source on an inpcb.
 * This implements the delta-based API described in RFC 3678.
 *
 * The delta-based API applies only to exclusive-mode memberships.
 * An MLD downcall will be performed.
 *
 * SMPng: NOTE: Must take Giant as a join may create a new ifma.
 *
 * Return 0 if successful, otherwise return an appropriate error code.
 */
static int
in6p_block_unblock_source(struct inpcb *inp, struct sockopt *sopt)
{
        struct group_source_req          gsr;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
        struct ip6_moptions             *imo;
        struct in6_msource              *ims;
        struct in6_multi                        *inm;
        uint16_t                         fmode;
        int                              error, doblock;
#ifdef KTR
        char                             ip6tbuf[INET6_ADDRSTRLEN];
#endif

        ifp = NULL;
        error = 0;
        doblock = 0;

        memset(&gsr, 0, sizeof(struct group_source_req));
        gsa = (sockunion_t *)&gsr.gsr_group;
        ssa = (sockunion_t *)&gsr.gsr_source;

        switch (sopt->sopt_name) {
        case MCAST_BLOCK_SOURCE:
        case MCAST_UNBLOCK_SOURCE:
                error = sooptcopyin(sopt, &gsr,
                    sizeof(struct group_source_req),
                    sizeof(struct group_source_req));
                if (error)
                        return (error);

                if (gsa->sin6.sin6_family != AF_INET6 ||
                    gsa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                        return (EINVAL);

                if (ssa->sin6.sin6_family != AF_INET6 ||
                    ssa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                        return (EINVAL);

                if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
                        return (EADDRNOTAVAIL);

                ifp = ifnet_byindex(gsr.gsr_interface);

                if (sopt->sopt_name == MCAST_BLOCK_SOURCE)
                        doblock = 1;
                break;

        default:
                CTR2(KTR_MLD, "%s: unknown sopt_name %d",
                    __func__, sopt->sopt_name);
                return (EOPNOTSUPP);
                break;
        }

        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);

        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);

        /*
         * Check if we are actually a member of this group.
         */
        imo = in6p_findmoptions(inp);
        imf = im6o_match_group(imo, ifp, &gsa->sa);
        if (imf == NULL) {
                error = EADDRNOTAVAIL;
                goto out_in6p_locked;
        }
        inm = imf->im6f_in6m;

        /*
         * Attempting to use the delta-based API on an
         * non exclusive-mode membership is an error.
         */
        fmode = imf->im6f_st[0];
        if (fmode != MCAST_EXCLUDE) {
                error = EINVAL;
                goto out_in6p_locked;
        }

        /*
         * Deal with error cases up-front:
         *  Asked to block, but already blocked; or
         *  Asked to unblock, but nothing to unblock.
         * If adding a new block entry, allocate it.
         */
        ims = im6o_match_source(imf, &ssa->sa);
        if ((ims != NULL && doblock) || (ims == NULL && !doblock)) {
                CTR3(KTR_MLD, "%s: source %s %spresent", __func__,
                    ip6_sprintf(ip6tbuf, &ssa->sin6.sin6_addr),
                    doblock ? "" : "not ");
                error = EADDRNOTAVAIL;
                goto out_in6p_locked;
        }

        INP_WLOCK_ASSERT(inp);

        /*
         * Begin state merge transaction at socket layer.
         */
        if (doblock) {
                CTR2(KTR_MLD, "%s: %s source", __func__, "block");
                ims = im6f_graft(imf, fmode, &ssa->sin6);
                if (ims == NULL)
                        error = ENOMEM;
        } else {
                CTR2(KTR_MLD, "%s: %s source", __func__, "allow");
                error = im6f_prune(imf, &ssa->sin6);
        }

        if (error) {
                CTR1(KTR_MLD, "%s: merge imf state failed", __func__);
                goto out_im6f_rollback;
        }

        /*
         * Begin state merge transaction at MLD layer.
         */
        IN6_MULTI_LIST_LOCK();
        CTR1(KTR_MLD, "%s: merge inm state", __func__);
        error = in6m_merge(inm, imf);
        if (error)
                CTR1(KTR_MLD, "%s: failed to merge inm state", __func__);
        else {
                CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
                error = mld_change_state(inm, 0);
                if (error)
                        CTR1(KTR_MLD, "%s: failed mld downcall", __func__);
        }

        IN6_MULTI_LIST_UNLOCK();

out_im6f_rollback:
        if (error)
                im6f_rollback(imf);
        else
                im6f_commit(imf);

        im6f_reap(imf);

out_in6p_locked:
        INP_WUNLOCK(inp);
        return (error);
}

/*
 * Given an inpcb, return its multicast options structure pointer.  Accepts
 * an unlocked inpcb pointer, but will return it locked.  May sleep.
 *
 * SMPng: NOTE: Potentially calls malloc(M_WAITOK) with Giant held.
 * SMPng: NOTE: Returns with the INP write lock held.
 */
static struct ip6_moptions *
in6p_findmoptions(struct inpcb *inp)
{
        struct ip6_moptions      *imo;

        INP_WLOCK(inp);
        if (inp->in6p_moptions != NULL)
                return (inp->in6p_moptions);

        INP_WUNLOCK(inp);

        imo = malloc(sizeof(*imo), M_IP6MOPTS, M_WAITOK);

        imo->im6o_multicast_ifp = NULL;
        imo->im6o_multicast_hlim = V_ip6_defmcasthlim;
        imo->im6o_multicast_loop = in6_mcast_loop;
        STAILQ_INIT(&imo->im6o_head);

        INP_WLOCK(inp);
        if (inp->in6p_moptions != NULL) {
                free(imo, M_IP6MOPTS);
                return (inp->in6p_moptions);
        }
        inp->in6p_moptions = imo;
        return (imo);
}

/*
 * Discard the IPv6 multicast options (and source filters).
 *
 * SMPng: NOTE: assumes INP write lock is held.
 *
 * XXX can all be safely deferred to epoch_call
 *
 */

static void
inp_gcmoptions(struct ip6_moptions *imo)
{
        struct in6_mfilter *imf;
        struct in6_multi *inm;
        struct ifnet *ifp;

        while ((imf = ip6_mfilter_first(&imo->im6o_head)) != NULL) {
                ip6_mfilter_remove(&imo->im6o_head, imf);

                im6f_leave(imf);
                if ((inm = imf->im6f_in6m) != NULL) {
                        if ((ifp = inm->in6m_ifp) != NULL) {
                                CURVNET_SET(ifp->if_vnet);
                                (void)in6_leavegroup(inm, imf);
                                CURVNET_RESTORE();
                        } else {
                                (void)in6_leavegroup(inm, imf);
                        }
                }
                ip6_mfilter_free(imf);
        }
        free(imo, M_IP6MOPTS);
}

void
ip6_freemoptions(struct ip6_moptions *imo)
{
        if (imo == NULL)
                return;
        inp_gcmoptions(imo);
}

/*
 * Atomically get source filters on a socket for an IPv6 multicast group.
 * Called with INP lock held; returns with lock released.
 */
static int
in6p_get_source_filters(struct inpcb *inp, struct sockopt *sopt)
{
        struct __msfilterreq     msfr;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
        struct ip6_moptions     *imo;
        struct in6_mfilter      *imf;
        struct ip6_msource      *ims;
        struct in6_msource      *lims;
        struct sockaddr_in6     *psin;
        struct sockaddr_storage *ptss;
        struct sockaddr_storage *tss;
        int                      error;
        size_t                   nsrcs, ncsrcs;

        INP_WLOCK_ASSERT(inp);

        imo = inp->in6p_moptions;
        KASSERT(imo != NULL, ("%s: null ip6_moptions", __func__));

        INP_WUNLOCK(inp);

        error = sooptcopyin(sopt, &msfr, sizeof(struct __msfilterreq),
            sizeof(struct __msfilterreq));
        if (error)
                return (error);

        if (msfr.msfr_group.ss_family != AF_INET6 ||
            msfr.msfr_group.ss_len != sizeof(struct sockaddr_in6))
                return (EINVAL);

        gsa = (sockunion_t *)&msfr.msfr_group;
        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);

        if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
                return (EADDRNOTAVAIL);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
        if (ifp == NULL)
                return (EADDRNOTAVAIL);
        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);

        INP_WLOCK(inp);

        /*
         * Lookup group on the socket.
         */
        imf = im6o_match_group(imo, ifp, &gsa->sa);
        if (imf == NULL) {
                INP_WUNLOCK(inp);
                return (EADDRNOTAVAIL);
        }

        /*
         * Ignore memberships which are in limbo.
         */
        if (imf->im6f_st[1] == MCAST_UNDEFINED) {
                INP_WUNLOCK(inp);
                return (EAGAIN);
        }
        msfr.msfr_fmode = imf->im6f_st[1];

        /*
         * If the user specified a buffer, copy out the source filter
         * entries to userland gracefully.
         * We only copy out the number of entries which userland
         * has asked for, but we always tell userland how big the
         * buffer really needs to be.
         */
        if (msfr.msfr_nsrcs > in6_mcast_maxsocksrc)
                msfr.msfr_nsrcs = in6_mcast_maxsocksrc;
        tss = NULL;
        if (msfr.msfr_srcs != NULL && msfr.msfr_nsrcs > 0) {
                tss = malloc(sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs,
                    M_TEMP, M_NOWAIT | M_ZERO);
                if (tss == NULL) {
                        INP_WUNLOCK(inp);
                        return (ENOBUFS);
                }
        }

        /*
         * Count number of sources in-mode at t0.
         * If buffer space exists and remains, copy out source entries.
         */
        nsrcs = msfr.msfr_nsrcs;
        ncsrcs = 0;
        ptss = tss;
        RB_FOREACH(ims, ip6_msource_tree, &imf->im6f_sources) {
                lims = (struct in6_msource *)ims;
                if (lims->im6sl_st[0] == MCAST_UNDEFINED ||
                    lims->im6sl_st[0] != imf->im6f_st[0])
                        continue;
                ++ncsrcs;
                if (tss != NULL && nsrcs > 0) {
                        psin = (struct sockaddr_in6 *)ptss;
                        psin->sin6_family = AF_INET6;
                        psin->sin6_len = sizeof(struct sockaddr_in6);
                        psin->sin6_addr = lims->im6s_addr;
                        psin->sin6_port = 0;
                        --nsrcs;
                        ++ptss;
                }
        }

        INP_WUNLOCK(inp);

        if (tss != NULL) {
                error = copyout(tss, msfr.msfr_srcs,
                    sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
                free(tss, M_TEMP);
                if (error)
                        return (error);
        }

        msfr.msfr_nsrcs = ncsrcs;
        error = sooptcopyout(sopt, &msfr, sizeof(struct __msfilterreq));

        return (error);
}

/*
 * Return the IP multicast options in response to user getsockopt().
 */
int
ip6_getmoptions(struct inpcb *inp, struct sockopt *sopt)
{
        struct ip6_moptions     *im6o;
        int                      error;
        u_int                    optval;

        INP_WLOCK(inp);
        im6o = inp->in6p_moptions;
        /*
         * If socket is neither of type SOCK_RAW or SOCK_DGRAM,
         * or is a divert socket, reject it.
         */
        if (inp->inp_socket->so_proto->pr_protocol == IPPROTO_DIVERT ||
            (inp->inp_socket->so_proto->pr_type != SOCK_RAW &&
            inp->inp_socket->so_proto->pr_type != SOCK_DGRAM)) {
                INP_WUNLOCK(inp);
                return (EOPNOTSUPP);
        }

        error = 0;
        switch (sopt->sopt_name) {
        case IPV6_MULTICAST_IF:
                if (im6o == NULL || im6o->im6o_multicast_ifp == NULL) {
                        optval = 0;
                } else {
                        optval = im6o->im6o_multicast_ifp->if_index;
                }
                INP_WUNLOCK(inp);
                error = sooptcopyout(sopt, &optval, sizeof(u_int));
                break;

        case IPV6_MULTICAST_HOPS:
                if (im6o == NULL)
                        optval = V_ip6_defmcasthlim;
                else
                        optval = im6o->im6o_multicast_hlim;
                INP_WUNLOCK(inp);
                error = sooptcopyout(sopt, &optval, sizeof(u_int));
                break;

        case IPV6_MULTICAST_LOOP:
                if (im6o == NULL)
                        optval = in6_mcast_loop; /* XXX VIMAGE */
                else
                        optval = im6o->im6o_multicast_loop;
                INP_WUNLOCK(inp);
                error = sooptcopyout(sopt, &optval, sizeof(u_int));
                break;

        case IPV6_MSFILTER:
                if (im6o == NULL) {
                        error = EADDRNOTAVAIL;
                        INP_WUNLOCK(inp);
                } else {
                        error = in6p_get_source_filters(inp, sopt);
                }
                break;

        default:
                INP_WUNLOCK(inp);
                error = ENOPROTOOPT;
                break;
        }

        INP_UNLOCK_ASSERT(inp);

        return (error);
}

/*
 * Look up the ifnet to use for a multicast group membership,
 * given the address of an IPv6 group.
 *
 * This routine exists to support legacy IPv6 multicast applications.
 *
 * Use the socket's current FIB number for any required FIB lookup. Look up the
 * group address in the unicast FIB, and use its ifp; usually, this points to
 * the default next-hop.  If the FIB lookup fails, return NULL.
 *
 * FUTURE: Support multiple forwarding tables for IPv6.
 *
 * Returns NULL if no ifp could be found.
 */
static struct ifnet *
in6p_lookup_mcast_ifp(const struct inpcb *inp, const struct sockaddr_in6 *gsin6)
{
        struct nhop6_basic      nh6;
        struct in6_addr         dst;
        uint32_t                scopeid;
        uint32_t                fibnum;

        KASSERT(gsin6->sin6_family == AF_INET6,
            ("%s: not AF_INET6 group", __func__));

        in6_splitscope(&gsin6->sin6_addr, &dst, &scopeid);
        fibnum = inp->inp_inc.inc_fibnum;
        if (fib6_lookup_nh_basic(fibnum, &dst, scopeid, 0, 0, &nh6) != 0)
                return (NULL);

        return (nh6.nh_ifp);
}

/*
 * Join an IPv6 multicast group, possibly with a source.
 *
 * FIXME: The KAME use of the unspecified address (::)
 * to join *all* multicast groups is currently unsupported.
 */
static int
in6p_join_group(struct inpcb *inp, struct sockopt *sopt)
{
        struct in6_multi_head            inmh;
        struct group_source_req          gsr;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
        struct ip6_moptions             *imo;
        struct in6_multi                *inm;
        struct in6_msource              *lims;
        int                              error, is_new;

        SLIST_INIT(&inmh);
        ifp = NULL;
        lims = NULL;
        error = 0;

        memset(&gsr, 0, sizeof(struct group_source_req));
        gsa = (sockunion_t *)&gsr.gsr_group;
        gsa->ss.ss_family = AF_UNSPEC;
        ssa = (sockunion_t *)&gsr.gsr_source;
        ssa->ss.ss_family = AF_UNSPEC;

        /*
         * Chew everything into struct group_source_req.
         * Overwrite the port field if present, as the sockaddr
         * being copied in may be matched with a binary comparison.
         * Ignore passed-in scope ID.
         */
        switch (sopt->sopt_name) {
        case IPV6_JOIN_GROUP: {
                struct ipv6_mreq mreq;

                error = sooptcopyin(sopt, &mreq, sizeof(struct ipv6_mreq),
                    sizeof(struct ipv6_mreq));
                if (error)
                        return (error);

                gsa->sin6.sin6_family = AF_INET6;
                gsa->sin6.sin6_len = sizeof(struct sockaddr_in6);
                gsa->sin6.sin6_addr = mreq.ipv6mr_multiaddr;

                if (mreq.ipv6mr_interface == 0) {
                        ifp = in6p_lookup_mcast_ifp(inp, &gsa->sin6);
                } else {
                        if (V_if_index < mreq.ipv6mr_interface)
                                return (EADDRNOTAVAIL);
                        ifp = ifnet_byindex(mreq.ipv6mr_interface);
                }
                CTR3(KTR_MLD, "%s: ipv6mr_interface = %d, ifp = %p",
                    __func__, mreq.ipv6mr_interface, ifp);
        } break;

        case MCAST_JOIN_GROUP:
        case MCAST_JOIN_SOURCE_GROUP:
                if (sopt->sopt_name == MCAST_JOIN_GROUP) {
                        error = sooptcopyin(sopt, &gsr,
                            sizeof(struct group_req),
                            sizeof(struct group_req));
                } else if (sopt->sopt_name == MCAST_JOIN_SOURCE_GROUP) {
                        error = sooptcopyin(sopt, &gsr,
                            sizeof(struct group_source_req),
                            sizeof(struct group_source_req));
                }
                if (error)
                        return (error);

                if (gsa->sin6.sin6_family != AF_INET6 ||
                    gsa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                        return (EINVAL);

                if (sopt->sopt_name == MCAST_JOIN_SOURCE_GROUP) {
                        if (ssa->sin6.sin6_family != AF_INET6 ||
                            ssa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                                return (EINVAL);
                        if (IN6_IS_ADDR_MULTICAST(&ssa->sin6.sin6_addr))
                                return (EINVAL);
                        /*
                         * TODO: Validate embedded scope ID in source
                         * list entry against passed-in ifp, if and only
                         * if source list filter entry is iface or node local.
                         */
                        in6_clearscope(&ssa->sin6.sin6_addr);
                        ssa->sin6.sin6_port = 0;
                        ssa->sin6.sin6_scope_id = 0;
                }

                if (gsr.gsr_interface == 0 || V_if_index < gsr.gsr_interface)
                        return (EADDRNOTAVAIL);
                ifp = ifnet_byindex(gsr.gsr_interface);
                break;

        default:
                CTR2(KTR_MLD, "%s: unknown sopt_name %d",
                    __func__, sopt->sopt_name);
                return (EOPNOTSUPP);
                break;
        }

        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);

        if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0)
                return (EADDRNOTAVAIL);

        gsa->sin6.sin6_port = 0;
        gsa->sin6.sin6_scope_id = 0;

        /*
         * Always set the scope zone ID on memberships created from userland.
         * Use the passed-in ifp to do this.
         * XXX The in6_setscope() return value is meaningless.
         * XXX SCOPE6_LOCK() is taken by in6_setscope().
         */
        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);

        IN6_MULTI_LOCK();

        /*
         * Find the membership in the membership list.
         */
        imo = in6p_findmoptions(inp);
        imf = im6o_match_group(imo, ifp, &gsa->sa);
        if (imf == NULL) {
                is_new = 1;
                inm = NULL;

                if (ip6_mfilter_count(&imo->im6o_head) >= IPV6_MAX_MEMBERSHIPS) {
                        error = ENOMEM;
                        goto out_in6p_locked;
                }
        } else {
                is_new = 0;
                inm = imf->im6f_in6m;

                if (ssa->ss.ss_family != AF_UNSPEC) {
                        /*
                         * MCAST_JOIN_SOURCE_GROUP on an exclusive membership
                         * is an error. On an existing inclusive membership,
                         * it just adds the source to the filter list.
                         */
                        if (imf->im6f_st[1] != MCAST_INCLUDE) {
                                error = EINVAL;
                                goto out_in6p_locked;
                        }
                        /*
                         * Throw out duplicates.
                         *
                         * XXX FIXME: This makes a naive assumption that
                         * even if entries exist for *ssa in this imf,
                         * they will be rejected as dupes, even if they
                         * are not valid in the current mode (in-mode).
                         *
                         * in6_msource is transactioned just as for anything
                         * else in SSM -- but note naive use of in6m_graft()
                         * below for allocating new filter entries.
                         *
                         * This is only an issue if someone mixes the
                         * full-state SSM API with the delta-based API,
                         * which is discouraged in the relevant RFCs.
                         */
                        lims = im6o_match_source(imf, &ssa->sa);
                        if (lims != NULL /*&&
                            lims->im6sl_st[1] == MCAST_INCLUDE*/) {
                                error = EADDRNOTAVAIL;
                                goto out_in6p_locked;
                        }
                } else {
                        /*
                         * MCAST_JOIN_GROUP alone, on any existing membership,
                         * is rejected, to stop the same inpcb tying up
                         * multiple refs to the in_multi.
                         * On an existing inclusive membership, this is also
                         * an error; if you want to change filter mode,
                         * you must use the userland API setsourcefilter().
                         * XXX We don't reject this for imf in UNDEFINED
                         * state at t1, because allocation of a filter
                         * is atomic with allocation of a membership.
                         */
                        error = EADDRINUSE;
                        goto out_in6p_locked;
                }
        }

        /*
         * Begin state merge transaction at socket layer.
         */
        INP_WLOCK_ASSERT(inp);

        /*
         * Graft new source into filter list for this inpcb's
         * membership of the group. The in6_multi may not have
         * been allocated yet if this is a new membership, however,
         * the in_mfilter slot will be allocated and must be initialized.
         *
         * Note: Grafting of exclusive mode filters doesn't happen
         * in this path.
         * XXX: Should check for non-NULL lims (node exists but may
         * not be in-mode) for interop with full-state API.
         */
        if (ssa->ss.ss_family != AF_UNSPEC) {
                /* Membership starts in IN mode */
                if (is_new) {
                        CTR1(KTR_MLD, "%s: new join w/source", __func__);
                        imf = ip6_mfilter_alloc(M_NOWAIT, MCAST_UNDEFINED, MCAST_INCLUDE);
                        if (imf == NULL) {
                                error = ENOMEM;
                                goto out_in6p_locked;
                        }
                } else {
                        CTR2(KTR_MLD, "%s: %s source", __func__, "allow");
                }
                lims = im6f_graft(imf, MCAST_INCLUDE, &ssa->sin6);
                if (lims == NULL) {
                        CTR1(KTR_MLD, "%s: merge imf state failed",
                            __func__);
                        error = ENOMEM;
                        goto out_in6p_locked;
                }
        } else {
                /* No address specified; Membership starts in EX mode */
                if (is_new) {
                        CTR1(KTR_MLD, "%s: new join w/o source", __func__);
                        imf = ip6_mfilter_alloc(M_NOWAIT, MCAST_UNDEFINED, MCAST_EXCLUDE);
                        if (imf == NULL) {
                                error = ENOMEM;
                                goto out_in6p_locked;
                        }
                }
        }

        /*
         * Begin state merge transaction at MLD layer.
         */
        if (is_new) {
                in_pcbref(inp);
                INP_WUNLOCK(inp);

                error = in6_joingroup_locked(ifp, &gsa->sin6.sin6_addr, imf,
                    &imf->im6f_in6m, 0);

                INP_WLOCK(inp);
                if (in_pcbrele_wlocked(inp)) {
                        error = ENXIO;
                        goto out_in6p_unlocked;
                }
                if (error) {
                        goto out_in6p_locked;
                }
                /*
                 * NOTE: Refcount from in6_joingroup_locked()
                 * is protecting membership.
                 */
                ip6_mfilter_insert(&imo->im6o_head, imf);
        } else {
                CTR1(KTR_MLD, "%s: merge inm state", __func__);
                IN6_MULTI_LIST_LOCK();
                error = in6m_merge(inm, imf);
                if (error) {
                        CTR1(KTR_MLD, "%s: failed to merge inm state",
                            __func__);
                        IN6_MULTI_LIST_UNLOCK();
                        im6f_rollback(imf);
                        im6f_reap(imf);
                        goto out_in6p_locked;
                }
                CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
                error = mld_change_state(inm, 0);
                IN6_MULTI_LIST_UNLOCK();

                if (error) {
                        CTR1(KTR_MLD, "%s: failed mld downcall",
                             __func__);
                        im6f_rollback(imf);
                        im6f_reap(imf);
                        goto out_in6p_locked;
                }
        }

        im6f_commit(imf);
        imf = NULL;

out_in6p_locked:
        INP_WUNLOCK(inp);
out_in6p_unlocked:
        IN6_MULTI_UNLOCK();

        if (is_new && imf) {
                if (imf->im6f_in6m != NULL) {
                        struct in6_multi_head inmh;

                        SLIST_INIT(&inmh);
                        SLIST_INSERT_HEAD(&inmh, imf->im6f_in6m, in6m_defer);
                        in6m_release_list_deferred(&inmh);
                }
                ip6_mfilter_free(imf);
        }
        return (error);
}

/*
 * Leave an IPv6 multicast group on an inpcb, possibly with a source.
 */
static int
in6p_leave_group(struct inpcb *inp, struct sockopt *sopt)
{
        struct ipv6_mreq                 mreq;
        struct group_source_req          gsr;
        sockunion_t                     *gsa, *ssa;
        struct ifnet                    *ifp;
        struct in6_mfilter              *imf;
        struct ip6_moptions             *imo;
        struct in6_msource              *ims;
        struct in6_multi                *inm;
        uint32_t                         ifindex;
        int                              error;
        bool                             is_final;
#ifdef KTR
        char                             ip6tbuf[INET6_ADDRSTRLEN];
#endif

        ifp = NULL;
        ifindex = 0;
        error = 0;
        is_final = true;

        memset(&gsr, 0, sizeof(struct group_source_req));
        gsa = (sockunion_t *)&gsr.gsr_group;
        gsa->ss.ss_family = AF_UNSPEC;
        ssa = (sockunion_t *)&gsr.gsr_source;
        ssa->ss.ss_family = AF_UNSPEC;

        /*
         * Chew everything passed in up into a struct group_source_req
         * as that is easier to process.
         * Note: Any embedded scope ID in the multicast group passed
         * in by userland is ignored, the interface index is the recommended
         * mechanism to specify an interface; see below.
         */
        switch (sopt->sopt_name) {
        case IPV6_LEAVE_GROUP:
                error = sooptcopyin(sopt, &mreq, sizeof(struct ipv6_mreq),
                    sizeof(struct ipv6_mreq));
                if (error)
                        return (error);
                gsa->sin6.sin6_family = AF_INET6;
                gsa->sin6.sin6_len = sizeof(struct sockaddr_in6);
                gsa->sin6.sin6_addr = mreq.ipv6mr_multiaddr;
                gsa->sin6.sin6_port = 0;
                gsa->sin6.sin6_scope_id = 0;
                ifindex = mreq.ipv6mr_interface;
                break;

        case MCAST_LEAVE_GROUP:
        case MCAST_LEAVE_SOURCE_GROUP:
                if (sopt->sopt_name == MCAST_LEAVE_GROUP) {
                        error = sooptcopyin(sopt, &gsr,
                            sizeof(struct group_req),
                            sizeof(struct group_req));
                } else if (sopt->sopt_name == MCAST_LEAVE_SOURCE_GROUP) {
                        error = sooptcopyin(sopt, &gsr,
                            sizeof(struct group_source_req),
                            sizeof(struct group_source_req));
                }
                if (error)
                        return (error);

                if (gsa->sin6.sin6_family != AF_INET6 ||
                    gsa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                        return (EINVAL);
                if (sopt->sopt_name == MCAST_LEAVE_SOURCE_GROUP) {
                        if (ssa->sin6.sin6_family != AF_INET6 ||
                            ssa->sin6.sin6_len != sizeof(struct sockaddr_in6))
                                return (EINVAL);
                        if (IN6_IS_ADDR_MULTICAST(&ssa->sin6.sin6_addr))
                                return (EINVAL);
                        /*
                         * TODO: Validate embedded scope ID in source
                         * list entry against passed-in ifp, if and only
                         * if source list filter entry is iface or node local.
                         */
                        in6_clearscope(&ssa->sin6.sin6_addr);
                }
                gsa->sin6.sin6_port = 0;
                gsa->sin6.sin6_scope_id = 0;
                ifindex = gsr.gsr_interface;
                break;

        default:
                CTR2(KTR_MLD, "%s: unknown sopt_name %d",
                    __func__, sopt->sopt_name);
                return (EOPNOTSUPP);
                break;
        }

        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);

        /*
         * Validate interface index if provided. If no interface index
         * was provided separately, attempt to look the membership up
         * from the default scope as a last resort to disambiguate
         * the membership we are being asked to leave.
         * XXX SCOPE6 lock potentially taken here.
         */
        if (ifindex != 0) {
                if (V_if_index < ifindex)
                        return (EADDRNOTAVAIL);
                ifp = ifnet_byindex(ifindex);
                if (ifp == NULL)
                        return (EADDRNOTAVAIL);
                (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);
        } else {
                error = sa6_embedscope(&gsa->sin6, V_ip6_use_defzone);
                if (error)
                        return (EADDRNOTAVAIL);
                /*
                 * Some badly behaved applications don't pass an ifindex
                 * or a scope ID, which is an API violation. In this case,
                 * perform a lookup as per a v6 join.
                 *
                 * XXX For now, stomp on zone ID for the corner case.
                 * This is not the 'KAME way', but we need to see the ifp
                 * directly until such time as this implementation is
                 * refactored, assuming the scope IDs are the way to go.
                 */
                ifindex = ntohs(gsa->sin6.sin6_addr.s6_addr16[1]);
                if (ifindex == 0) {
                        CTR2(KTR_MLD, "%s: warning: no ifindex, looking up "
                            "ifp for group %s.", __func__,
                            ip6_sprintf(ip6tbuf, &gsa->sin6.sin6_addr));
                        ifp = in6p_lookup_mcast_ifp(inp, &gsa->sin6);
                } else {
                        ifp = ifnet_byindex(ifindex);
                }
                if (ifp == NULL)
                        return (EADDRNOTAVAIL);
        }

        CTR2(KTR_MLD, "%s: ifp = %p", __func__, ifp);
        KASSERT(ifp != NULL, ("%s: ifp did not resolve", __func__));

        IN6_MULTI_LOCK();

        /*
         * Find the membership in the membership list.
         */
        imo = in6p_findmoptions(inp);
        imf = im6o_match_group(imo, ifp, &gsa->sa);
        if (imf == NULL) {
                error = EADDRNOTAVAIL;
                goto out_in6p_locked;
        }
        inm = imf->im6f_in6m;

        if (ssa->ss.ss_family != AF_UNSPEC)
                is_final = false;

        /*
         * Begin state merge transaction at socket layer.
         */
        INP_WLOCK_ASSERT(inp);

        /*
         * If we were instructed only to leave a given source, do so.
         * MCAST_LEAVE_SOURCE_GROUP is only valid for inclusive memberships.
         */
        if (is_final) {
                ip6_mfilter_remove(&imo->im6o_head, imf);
                im6f_leave(imf);

                /*
                 * Give up the multicast address record to which
                 * the membership points.
                 */
                (void)in6_leavegroup_locked(inm, imf);
        } else {
                if (imf->im6f_st[0] == MCAST_EXCLUDE) {
                        error = EADDRNOTAVAIL;
                        goto out_in6p_locked;
                }
                ims = im6o_match_source(imf, &ssa->sa);
                if (ims == NULL) {
                        CTR3(KTR_MLD, "%s: source %p %spresent", __func__,
                            ip6_sprintf(ip6tbuf, &ssa->sin6.sin6_addr),
                            "not ");
                        error = EADDRNOTAVAIL;
                        goto out_in6p_locked;
                }
                CTR2(KTR_MLD, "%s: %s source", __func__, "block");
                error = im6f_prune(imf, &ssa->sin6);
                if (error) {
                        CTR1(KTR_MLD, "%s: merge imf state failed",
                            __func__);
                        goto out_in6p_locked;
                }
        }

        /*
         * Begin state merge transaction at MLD layer.
         */
        if (!is_final) {
                CTR1(KTR_MLD, "%s: merge inm state", __func__);
                IN6_MULTI_LIST_LOCK();
                error = in6m_merge(inm, imf);
                if (error) {
                        CTR1(KTR_MLD, "%s: failed to merge inm state",
                            __func__);
                        IN6_MULTI_LIST_UNLOCK();
                        im6f_rollback(imf);
                        im6f_reap(imf);
                        goto out_in6p_locked;
                }

                CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
                error = mld_change_state(inm, 0);
                IN6_MULTI_LIST_UNLOCK();
                if (error) {
                        CTR1(KTR_MLD, "%s: failed mld downcall",
                             __func__);
                        im6f_rollback(imf);
                        im6f_reap(imf);
                        goto out_in6p_locked;
                }
        }

        im6f_commit(imf);
        im6f_reap(imf);

out_in6p_locked:
        INP_WUNLOCK(inp);

        if (is_final && imf)
                ip6_mfilter_free(imf);

        IN6_MULTI_UNLOCK();
        return (error);
}

/*
 * Select the interface for transmitting IPv6 multicast datagrams.
 *
 * Either an instance of struct in6_addr or an instance of struct ipv6_mreqn
 * may be passed to this socket option. An address of in6addr_any or an
 * interface index of 0 is used to remove a previous selection.
 * When no interface is selected, one is chosen for every send.
 */
static int
in6p_set_multicast_if(struct inpcb *inp, struct sockopt *sopt)
{
        struct ifnet            *ifp;
        struct ip6_moptions     *imo;
        u_int                    ifindex;
        int                      error;

        if (sopt->sopt_valsize != sizeof(u_int))
                return (EINVAL);

        error = sooptcopyin(sopt, &ifindex, sizeof(u_int), sizeof(u_int));
        if (error)
                return (error);
        if (V_if_index < ifindex)
                return (EINVAL);
        if (ifindex == 0)
                ifp = NULL;
        else {
                ifp = ifnet_byindex(ifindex);
                if (ifp == NULL)
                        return (EINVAL);
                if ((ifp->if_flags & IFF_MULTICAST) == 0)
                        return (EADDRNOTAVAIL);
        }
        imo = in6p_findmoptions(inp);
        imo->im6o_multicast_ifp = ifp;
        INP_WUNLOCK(inp);

        return (0);
}

/*
 * Atomically set source filters on a socket for an IPv6 multicast group.
 *
 * SMPng: NOTE: Potentially calls malloc(M_WAITOK) with Giant held.
 */
static int
in6p_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
{
        struct __msfilterreq     msfr;
        sockunion_t             *gsa;
        struct ifnet            *ifp;
        struct in6_mfilter      *imf;
        struct ip6_moptions     *imo;
        struct in6_multi                *inm;
        int                      error;

        error = sooptcopyin(sopt, &msfr, sizeof(struct __msfilterreq),
            sizeof(struct __msfilterreq));
        if (error)
                return (error);

        if (msfr.msfr_nsrcs > in6_mcast_maxsocksrc)
                return (ENOBUFS);

        if (msfr.msfr_fmode != MCAST_EXCLUDE &&
            msfr.msfr_fmode != MCAST_INCLUDE)
                return (EINVAL);

        if (msfr.msfr_group.ss_family != AF_INET6 ||
            msfr.msfr_group.ss_len != sizeof(struct sockaddr_in6))
                return (EINVAL);

        gsa = (sockunion_t *)&msfr.msfr_group;
        if (!IN6_IS_ADDR_MULTICAST(&gsa->sin6.sin6_addr))
                return (EINVAL);

        gsa->sin6.sin6_port = 0;        /* ignore port */

        if (msfr.msfr_ifindex == 0 || V_if_index < msfr.msfr_ifindex)
                return (EADDRNOTAVAIL);
        ifp = ifnet_byindex(msfr.msfr_ifindex);
        if (ifp == NULL)
                return (EADDRNOTAVAIL);
        (void)in6_setscope(&gsa->sin6.sin6_addr, ifp, NULL);

        /*
         * Take the INP write lock.
         * Check if this socket is a member of this group.
         */
        imo = in6p_findmoptions(inp);
        imf = im6o_match_group(imo, ifp, &gsa->sa);
        if (imf == NULL) {
                error = EADDRNOTAVAIL;
                goto out_in6p_locked;
        }
        inm = imf->im6f_in6m;

        /*
         * Begin state merge transaction at socket layer.
         */
        INP_WLOCK_ASSERT(inp);

        imf->im6f_st[1] = msfr.msfr_fmode;

        /*
         * Apply any new source filters, if present.
         * Make a copy of the user-space source vector so
         * that we may copy them with a single copyin. This
         * allows us to deal with page faults up-front.
         */
        if (msfr.msfr_nsrcs > 0) {
                struct in6_msource      *lims;
                struct sockaddr_in6     *psin;
                struct sockaddr_storage *kss, *pkss;
                int                      i;

                INP_WUNLOCK(inp);
 
                CTR2(KTR_MLD, "%s: loading %lu source list entries",
                    __func__, (unsigned long)msfr.msfr_nsrcs);
                kss = malloc(sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs,
                    M_TEMP, M_WAITOK);
                error = copyin(msfr.msfr_srcs, kss,
                    sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
                if (error) {
                        free(kss, M_TEMP);
                        return (error);
                }

                INP_WLOCK(inp);

                /*
                 * Mark all source filters as UNDEFINED at t1.
                 * Restore new group filter mode, as im6f_leave()
                 * will set it to INCLUDE.
                 */
                im6f_leave(imf);
                imf->im6f_st[1] = msfr.msfr_fmode;

                /*
                 * Update socket layer filters at t1, lazy-allocating
                 * new entries. This saves a bunch of memory at the
                 * cost of one RB_FIND() per source entry; duplicate
                 * entries in the msfr_nsrcs vector are ignored.
                 * If we encounter an error, rollback transaction.
                 *
                 * XXX This too could be replaced with a set-symmetric
                 * difference like loop to avoid walking from root
                 * every time, as the key space is common.
                 */
                for (i = 0, pkss = kss; i < msfr.msfr_nsrcs; i++, pkss++) {
                        psin = (struct sockaddr_in6 *)pkss;
                        if (psin->sin6_family != AF_INET6) {
                                error = EAFNOSUPPORT;
                                break;
                        }
                        if (psin->sin6_len != sizeof(struct sockaddr_in6)) {
                                error = EINVAL;
                                break;
                        }
                        if (IN6_IS_ADDR_MULTICAST(&psin->sin6_addr)) {
                                error = EINVAL;
                                break;
                        }
                        /*
                         * TODO: Validate embedded scope ID in source
                         * list entry against passed-in ifp, if and only
                         * if source list filter entry is iface or node local.
                         */
                        in6_clearscope(&psin->sin6_addr);
                        error = im6f_get_source(imf, psin, &lims);
                        if (error)
                                break;
                        lims->im6sl_st[1] = imf->im6f_st[1];
                }
                free(kss, M_TEMP);
        }

        if (error)
                goto out_im6f_rollback;

        INP_WLOCK_ASSERT(inp);
        IN6_MULTI_LIST_LOCK();

        /*
         * Begin state merge transaction at MLD layer.
         */
        CTR1(KTR_MLD, "%s: merge inm state", __func__);
        error = in6m_merge(inm, imf);
        if (error)
                CTR1(KTR_MLD, "%s: failed to merge inm state", __func__);
        else {
                CTR1(KTR_MLD, "%s: doing mld downcall", __func__);
                error = mld_change_state(inm, 0);
                if (error)
                        CTR1(KTR_MLD, "%s: failed mld downcall", __func__);
        }

        IN6_MULTI_LIST_UNLOCK();

out_im6f_rollback:
        if (error)
                im6f_rollback(imf);
        else
                im6f_commit(imf);

        im6f_reap(imf);

out_in6p_locked:
        INP_WUNLOCK(inp);
        return (error);
}

/*
 * Set the IP multicast options in response to user setsockopt().
 *
 * Many of the socket options handled in this function duplicate the
 * functionality of socket options in the regular unicast API. However,
 * it is not possible to merge the duplicate code, because the idempotence
 * of the IPv6 multicast part of the BSD Sockets API must be preserved;
 * the effects of these options must be treated as separate and distinct.
 *
 * SMPng: XXX: Unlocked read of inp_socket believed OK.
 */
int
ip6_setmoptions(struct inpcb *inp, struct sockopt *sopt)
{
        struct ip6_moptions     *im6o;
        int                      error;

        error = 0;

        /*
         * If socket is neither of type SOCK_RAW or SOCK_DGRAM,
         * or is a divert socket, reject it.
         */
        if (inp->inp_socket->so_proto->pr_protocol == IPPROTO_DIVERT ||
            (inp->inp_socket->so_proto->pr_type != SOCK_RAW &&
             inp->inp_socket->so_proto->pr_type != SOCK_DGRAM))
                return (EOPNOTSUPP);

        switch (sopt->sopt_name) {
        case IPV6_MULTICAST_IF:
                error = in6p_set_multicast_if(inp, sopt);
                break;

        case IPV6_MULTICAST_HOPS: {
                int hlim;

                if (sopt->sopt_valsize != sizeof(int)) {
                        error = EINVAL;
                        break;
                }
                error = sooptcopyin(sopt, &hlim, sizeof(hlim), sizeof(int));
                if (error)
                        break;
                if (hlim < -1 || hlim > 255) {
                        error = EINVAL;
                        break;
                } else if (hlim == -1) {
                        hlim = V_ip6_defmcasthlim;
                }
                im6o = in6p_findmoptions(inp);
                im6o->im6o_multicast_hlim = hlim;
                INP_WUNLOCK(inp);
                break;
        }

        case IPV6_MULTICAST_LOOP: {
                u_int loop;

                /*
                 * Set the loopback flag for outgoing multicast packets.
                 * Must be zero or one.
                 */
                if (sopt->sopt_valsize != sizeof(u_int)) {
                        error = EINVAL;
                        break;
                }
                error = sooptcopyin(sopt, &loop, sizeof(u_int), sizeof(u_int));
                if (error)
                        break;
                if (loop > 1) {
                        error = EINVAL;
                        break;
                }
                im6o = in6p_findmoptions(inp);
                im6o->im6o_multicast_loop = loop;
                INP_WUNLOCK(inp);
                break;
        }

        case IPV6_JOIN_GROUP:
        case MCAST_JOIN_GROUP:
        case MCAST_JOIN_SOURCE_GROUP:
                error = in6p_join_group(inp, sopt);
                break;

        case IPV6_LEAVE_GROUP:
        case MCAST_LEAVE_GROUP:
        case MCAST_LEAVE_SOURCE_GROUP:
                error = in6p_leave_group(inp, sopt);
                break;

        case MCAST_BLOCK_SOURCE:
        case MCAST_UNBLOCK_SOURCE:
                error = in6p_block_unblock_source(inp, sopt);
                break;

        case IPV6_MSFILTER:
                error = in6p_set_source_filters(inp, sopt);
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        INP_UNLOCK_ASSERT(inp);

        return (error);
}

/*
 * Expose MLD's multicast filter mode and source list(s) to userland,
 * keyed by (ifindex, group).
 * The filter mode is written out as a uint32_t, followed by
 * 0..n of struct in6_addr.
 * For use by ifmcstat(8).
 * SMPng: NOTE: unlocked read of ifindex space.
 */
static int
sysctl_ip6_mcast_filters(SYSCTL_HANDLER_ARGS)
{
        struct in6_addr                  mcaddr;
        struct in6_addr                  src;
        struct ifnet                    *ifp;
        struct ifmultiaddr              *ifma;
        struct in6_multi                *inm;
        struct ip6_msource              *ims;
        int                             *name;
        int                              retval;
        u_int                            namelen;
        uint32_t                         fmode, ifindex;
#ifdef KTR
        char                             ip6tbuf[INET6_ADDRSTRLEN];
#endif

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

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

        /* int: ifindex + 4 * 32 bits of IPv6 address */
        if (namelen != 5)
                return (EINVAL);

        ifindex = name[0];
        if (ifindex <= 0 || ifindex > V_if_index) {
                CTR2(KTR_MLD, "%s: ifindex %u out of range",
                    __func__, ifindex);
                return (ENOENT);
        }

        memcpy(&mcaddr, &name[1], sizeof(struct in6_addr));
        if (!IN6_IS_ADDR_MULTICAST(&mcaddr)) {
                CTR2(KTR_MLD, "%s: group %s is not multicast",
                    __func__, ip6_sprintf(ip6tbuf, &mcaddr));
                return (EINVAL);
        }

        ifp = ifnet_byindex(ifindex);
        if (ifp == NULL) {
                CTR2(KTR_MLD, "%s: no ifp for ifindex %u",
                    __func__, ifindex);
                return (ENOENT);
        }
        /*
         * Internal MLD lookups require that scope/zone ID is set.
         */
        (void)in6_setscope(&mcaddr, ifp, NULL);

        retval = sysctl_wire_old_buffer(req,
            sizeof(uint32_t) + (in6_mcast_maxgrpsrc * sizeof(struct in6_addr)));
        if (retval)
                return (retval);

        IN6_MULTI_LOCK();
        IN6_MULTI_LIST_LOCK();
        IF_ADDR_RLOCK(ifp);
        CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                inm = in6m_ifmultiaddr_get_inm(ifma);
                if (inm == NULL)
                        continue;
                if (!IN6_ARE_ADDR_EQUAL(&inm->in6m_addr, &mcaddr))
                        continue;
                fmode = inm->in6m_st[1].iss_fmode;
                retval = SYSCTL_OUT(req, &fmode, sizeof(uint32_t));
                if (retval != 0)
                        break;
                RB_FOREACH(ims, ip6_msource_tree, &inm->in6m_srcs) {
                        CTR2(KTR_MLD, "%s: visit node %p", __func__, ims);
                        /*
                         * Only copy-out sources which are in-mode.
                         */
                        if (fmode != im6s_get_mode(inm, ims, 1)) {
                                CTR1(KTR_MLD, "%s: skip non-in-mode",
                                    __func__);
                                continue;
                        }
                        src = ims->im6s_addr;
                        retval = SYSCTL_OUT(req, &src,
                            sizeof(struct in6_addr));
                        if (retval != 0)
                                break;
                }
        }
        IF_ADDR_RUNLOCK(ifp);

        IN6_MULTI_LIST_UNLOCK();
        IN6_MULTI_UNLOCK();

        return (retval);
}

#ifdef KTR

static const char *in6m_modestrs[] = { "un", "in", "ex" };

static const char *
in6m_mode_str(const int mode)
{

        if (mode >= MCAST_UNDEFINED && mode <= MCAST_EXCLUDE)
                return (in6m_modestrs[mode]);
        return ("??");
}

static const char *in6m_statestrs[] = {
        "not-member",
        "silent",
        "idle",
        "lazy",
        "sleeping",
        "awakening",
        "query-pending",
        "sg-query-pending",
        "leaving"
};

static const char *
in6m_state_str(const int state)
{

        if (state >= MLD_NOT_MEMBER && state <= MLD_LEAVING_MEMBER)
                return (in6m_statestrs[state]);
        return ("??");
}

/*
 * Dump an in6_multi structure to the console.
 */
void
in6m_print(const struct in6_multi *inm)
{
        int t;
        char ip6tbuf[INET6_ADDRSTRLEN];

        if ((ktr_mask & KTR_MLD) == 0)
                return;

        printf("%s: --- begin in6m %p ---\n", __func__, inm);
        printf("addr %s ifp %p(%s) ifma %p\n",
            ip6_sprintf(ip6tbuf, &inm->in6m_addr),
            inm->in6m_ifp,
            if_name(inm->in6m_ifp),
            inm->in6m_ifma);
        printf("timer %u state %s refcount %u scq.len %u\n",
            inm->in6m_timer,
            in6m_state_str(inm->in6m_state),
            inm->in6m_refcount,
            mbufq_len(&inm->in6m_scq));
        printf("mli %p nsrc %lu sctimer %u scrv %u\n",
            inm->in6m_mli,
            inm->in6m_nsrc,
            inm->in6m_sctimer,
            inm->in6m_scrv);
        for (t = 0; t < 2; t++) {
                printf("t%d: fmode %s asm %u ex %u in %u rec %u\n", t,
                    in6m_mode_str(inm->in6m_st[t].iss_fmode),
                    inm->in6m_st[t].iss_asm,
                    inm->in6m_st[t].iss_ex,
                    inm->in6m_st[t].iss_in,
                    inm->in6m_st[t].iss_rec);
        }
        printf("%s: --- end in6m %p ---\n", __func__, inm);
}

#else /* !KTR */

void
in6m_print(const struct in6_multi *inm)
{

}

#endif /* KTR */