FreeBSD/Linux Kernel Cross Reference
sys/netinet6/in6_mcast.c

     /*
      * 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: releng/10.3/sys/netinet6/in6_mcast.c 281911 2015-04-24 02:12:25Z ae $");
    
    #include "opt_inet6.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/protosw.h>
    #include <sys/socket.h>
    #include <sys/socketvar.h>
    #include <sys/protosw.h>
    #include <sys/sysctl.h>
    #include <sys/priv.h>
    #include <sys/ktr.h>
    #include <sys/tree.h>
    
    #include <net/if.h>
    #include <net/if_dl.h>
    #include <net/route.h>
    #include <net/vnet.h>
    
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    #include <netinet6/in6_var.h>
    #include <netinet/ip6.h>
    #include <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");
    static 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, INP_WLOCK, IN6_MULTI_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_mtx;
   MTX_SYSINIT(in6_multi_mtx, &in6_multi_mtx, "in6_multi_mtx", MTX_DEF);
   
   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 int      im6o_grow(struct ip6_moptions *);
   static size_t   im6o_match_group(const struct ip6_moptions *,
                       const struct ifnet *, const struct sockaddr *);
   static struct in6_msource *
                   im6o_match_source(const struct ip6_moptions *, const size_t,
                       const struct sockaddr *);
   static void     im6s_merge(struct ip6_msource *ims,
                       const struct in6_msource *lims, const int rollback);
   static int      in6_mc_get(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_RW | CTLFLAG_TUN, &in6_mcast_maxgrpsrc, 0,
       "Max source filters per group");
   TUNABLE_ULONG("net.inet6.ip6.mcast.maxgrpsrc", &in6_mcast_maxgrpsrc);
   
   static u_long in6_mcast_maxsocksrc = IPV6_MAX_SOCK_SRC_FILTER;
   SYSCTL_ULONG(_net_inet6_ip6_mcast, OID_AUTO, maxsocksrc,
       CTLFLAG_RW | CTLFLAG_TUN, &in6_mcast_maxsocksrc, 0,
       "Max source filters per socket");
   TUNABLE_ULONG("net.inet6.ip6.mcast.maxsocksrc", &in6_mcast_maxsocksrc);
   
   /* TODO Virtualize this switch. */
   int in6_mcast_loop = IPV6_DEFAULT_MULTICAST_LOOP;
   SYSCTL_INT(_net_inet6_ip6_mcast, OID_AUTO, loop, CTLFLAG_RW | CTLFLAG_TUN,
       &in6_mcast_loop, 0, "Loopback multicast datagrams by default");
   TUNABLE_INT("net.inet6.ip6.mcast.loop", &in6_mcast_loop);
   
   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;
   }
   
   /*
    * Resize the ip6_moptions vector to the next power-of-two minus 1.
    * May be called with locks held; do not sleep.
    */
   static int
   im6o_grow(struct ip6_moptions *imo)
   {
           struct in6_multi        **nmships;
           struct in6_multi        **omships;
           struct in6_mfilter       *nmfilters;
           struct in6_mfilter       *omfilters;
           size_t                    idx;
           size_t                    newmax;
           size_t                    oldmax;
   
           nmships = NULL;
           nmfilters = NULL;
           omships = imo->im6o_membership;
           omfilters = imo->im6o_mfilters;
           oldmax = imo->im6o_max_memberships;
           newmax = ((oldmax + 1) * 2) - 1;
   
           if (newmax <= IPV6_MAX_MEMBERSHIPS) {
                   nmships = (struct in6_multi **)realloc(omships,
                       sizeof(struct in6_multi *) * newmax, M_IP6MOPTS, M_NOWAIT);
                   nmfilters = (struct in6_mfilter *)realloc(omfilters,
                       sizeof(struct in6_mfilter) * newmax, M_IN6MFILTER,
                       M_NOWAIT);
                   if (nmships != NULL && nmfilters != NULL) {
                           /* Initialize newly allocated source filter heads. */
                           for (idx = oldmax; idx < newmax; idx++) {
                                   im6f_init(&nmfilters[idx], MCAST_UNDEFINED,
                                       MCAST_EXCLUDE);
                           }
                           imo->im6o_max_memberships = newmax;
                           imo->im6o_membership = nmships;
                           imo->im6o_mfilters = nmfilters;
                   }
           }
   
           if (nmships == NULL || nmfilters == NULL) {
                   if (nmships != NULL)
                           free(nmships, M_IP6MOPTS);
                   if (nmfilters != NULL)
                           free(nmfilters, M_IN6MFILTER);
                   return (ETOOMANYREFS);
           }
   
           return (0);
   }
   
   /*
    * 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 size_t
   im6o_match_group(const struct ip6_moptions *imo, const struct ifnet *ifp,
       const struct sockaddr *group)
   {
           const struct sockaddr_in6 *gsin6;
           struct in6_multi        **pinm;
           int               idx;
           int               nmships;
   
           gsin6 = (const struct sockaddr_in6 *)group;
   
           /* The im6o_membership array may be lazy allocated. */
           if (imo->im6o_membership == NULL || imo->im6o_num_memberships == 0)
                   return (-1);
   
           nmships = imo->im6o_num_memberships;
           pinm = &imo->im6o_membership[0];
           for (idx = 0; idx < nmships; idx++, pinm++) {
                   if (*pinm == NULL)
                           continue;
                   if ((ifp == NULL || ((*pinm)->in6m_ifp == ifp)) &&
                       IN6_ARE_ADDR_EQUAL(&(*pinm)->in6m_addr,
                       &gsin6->sin6_addr)) {
                           break;
                   }
           }
           if (idx >= nmships)
                   idx = -1;
   
           return (idx);
   }
   
   /*
    * 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(const struct ip6_moptions *imo, const size_t gidx,
       const struct sockaddr *src)
   {
           struct ip6_msource       find;
           struct in6_mfilter      *imf;
           struct ip6_msource      *ims;
           const sockunion_t       *psa;
   
           KASSERT(src->sa_family == AF_INET6, ("%s: !AF_INET6", __func__));
           KASSERT(gidx != -1 && gidx < imo->im6o_num_memberships,
               ("%s: invalid index %d\n", __func__, (int)gidx));
   
           /* The im6o_mfilters array may be lazy allocated. */
           if (imo->im6o_mfilters == NULL)
                   return (NULL);
           imf = &imo->im6o_mfilters[gidx];
   
           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)
   {
           size_t gidx;
           struct in6_msource *ims;
           int mode;
   
           KASSERT(ifp != NULL, ("%s: null ifp", __func__));
   
           gidx = im6o_match_group(imo, ifp, group);
           if (gidx == -1)
                   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 = imo->im6o_mfilters[gidx].im6f_st[1];
           ims = im6o_match_source(imo, gidx, 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_mc_get(struct ifnet *ifp, const struct in6_addr *group,
       struct in6_multi **pinm)
   {
           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();
           IF_ADDR_WLOCK(ifp);
   
           inm = in6m_lookup_locked(ifp, group);
           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));
                   ++inm->in6m_refcount;
                   *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.
            */
           IF_ADDR_WUNLOCK(ifp);
           error = if_addmulti(ifp, (struct sockaddr *)&gsin6, &ifma);
           if (error != 0)
                   return (error);
           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
                   ++inm->in6m_refcount;
                   *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) {
                   if_delmulti_ifma(ifma);
                   error = ENOMEM;
                   goto out_locked;
           }
           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;
           IFQ_SET_MAXLEN(&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:
           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.
    */
   void
   in6m_release_locked(struct in6_multi *inm)
   {
           struct ifmultiaddr *ifma;
   
           IN6_MULTI_LOCK_ASSERT();
   
           CTR2(KTR_MLD, "%s: refcount is %d", __func__, inm->in6m_refcount);
   
           if (--inm->in6m_refcount > 0) {
                   CTR2(KTR_MLD, "%s: refcount is now %d", __func__,
                       inm->in6m_refcount);
                   return;
           }
   
           CTR2(KTR_MLD, "%s: freeing inm %p", __func__, inm);
   
           ifma = inm->in6m_ifma;
   
           /* XXX this access is not covered by IF_ADDR_LOCK */
           CTR2(KTR_MLD, "%s: purging ifma %p", __func__, ifma);
           KASSERT(ifma->ifma_protospec == inm,
               ("%s: ifma_protospec != inm", __func__));
           ifma->ifma_protospec = NULL;
   
           in6m_purge(inm);
   
           free(inm, M_IP6MADDR);
   
           if_delmulti_ifma(ifma);
   }
   
   /*
    * 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_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 occured (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_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;
   
           /*
            * 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. */
          _IF_DRAIN(&inm->in6m_scq);
  }
  
  /*
   * Join a multicast address w/o sources.
   * KAME compatibility entry point.
   *
   * SMPng: Assume no mc locks held by caller.
   */
  struct in6_multi_mship *
  in6_joingroup(struct ifnet *ifp, struct in6_addr *mcaddr,
      int *errorp, int delay)
  {
          struct in6_multi_mship *imm;
          int error;
  
          imm = malloc(sizeof(*imm), M_IP6MADDR, M_NOWAIT);
          if (imm == NULL) {
                  *errorp = ENOBUFS;
                  return (NULL);
          }
  
          delay = (delay * PR_FASTHZ) / hz;
  
          error = in6_mc_join(ifp, mcaddr, NULL, &imm->i6mm_maddr, delay);
          if (error) {
                  *errorp = error;
                  free(imm, M_IP6MADDR);
                  return (NULL);
          }
  
          return (imm);
  }
  
  /*
   * Leave a multicast address w/o sources.
   * KAME compatibility entry point.
   *
   * SMPng: Assume no mc locks held by caller.
   */
  int
  in6_leavegroup(struct in6_multi_mship *imm)
  {
  
          if (imm->i6mm_maddr != NULL)
                  in6_mc_leave(imm->i6mm_maddr, NULL);
          free(imm,  M_IP6MADDR);
          return 0;
  }
  
  /*
   * Join a multicast group; unlocked entry point.
   *
   * SMPng: XXX: in6_mc_join() is called from in6_control() when upper
   * locks are not held. Fortunately, ifp is unlikely to have been detached
   * at this point, so we assume it's OK to recurse.
   */
  int
  in6_mc_join(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_mc_join_locked(ifp, mcaddr, imf, 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_mc_join_locked(struct ifnet *ifp, const struct in6_addr *mcaddr,
      /*const*/ struct in6_mfilter *imf, struct in6_multi **pinm,
      const int delay)
  {
          struct in6_mfilter       timf;
          struct in6_multi        *inm;
          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();
  
          CTR4(KTR_MLD, "%s: join %s on %p(%s))", __func__,
              ip6_sprintf(ip6tbuf, mcaddr), ifp, ifp->if_xname);
  
          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_mc_get(ifp, mcaddr, &inm);
          if (error) {
                  CTR1(KTR_MLD, "%s: in6_mc_get() failure", __func__);
                  return (error);
          }
  
          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:
          if (error) {
                  CTR2(KTR_MLD, "%s: dropping ref on %p", __func__, inm);
                  in6m_release_locked(inm);
          } else {
                  *pinm = inm;
          }
  
          return (error);
  }
  
  /*
   * Leave a multicast group; unlocked entry point.
   */
  int
  in6_mc_leave(struct in6_multi *inm, /*const*/ struct in6_mfilter *imf)
  {
          struct ifnet *ifp;
          int error;
  
          ifp = inm->in6m_ifp;
  
          IN6_MULTI_LOCK();
          error = in6_mc_leave_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_mc_leave_locked(struct in6_multi *inm, /*const*/ struct in6_mfilter *imf)
  {
          struct in6_mfilter       timf;
          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" : inm->in6m_ifp->if_xname),
              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.
           */
          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 = 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);
          in6m_release_locked(inm);
  
          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;
          size_t                           idx;
          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);
          idx = im6o_match_group(imo, ifp, &gsa->sa);
          if (idx == -1 || imo->im6o_mfilters == NULL) {
                  error = EADDRNOTAVAIL;
                  goto out_in6p_locked;
          }
  
          KASSERT(imo->im6o_mfilters != NULL,
              ("%s: im6o_mfilters not allocated", __func__));
          imf = &imo->im6o_mfilters[idx];
          inm = imo->im6o_membership[idx];
  
          /*
           * 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(imo, idx, &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_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_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;
          struct in6_multi                **immp;
          struct in6_mfilter       *imfp;
          size_t                    idx;
  
          INP_WLOCK(inp);
          if (inp->in6p_moptions != NULL)
                  return (inp->in6p_moptions);
  
          INP_WUNLOCK(inp);
  
          imo = malloc(sizeof(*imo), M_IP6MOPTS, M_WAITOK);
          immp = malloc(sizeof(*immp) * IPV6_MIN_MEMBERSHIPS, M_IP6MOPTS,
              M_WAITOK | M_ZERO);
          imfp = malloc(sizeof(struct in6_mfilter) * IPV6_MIN_MEMBERSHIPS,
              M_IN6MFILTER, M_WAITOK);
  
          imo->im6o_multicast_ifp = NULL;
          imo->im6o_multicast_hlim = V_ip6_defmcasthlim;
          imo->im6o_multicast_loop = in6_mcast_loop;
          imo->im6o_num_memberships = 0;
          imo->im6o_max_memberships = IPV6_MIN_MEMBERSHIPS;
          imo->im6o_membership = immp;
  
          /* Initialize per-group source filters. */
          for (idx = 0; idx < IPV6_MIN_MEMBERSHIPS; idx++)
                  im6f_init(&imfp[idx], MCAST_UNDEFINED, MCAST_EXCLUDE);
          imo->im6o_mfilters = imfp;
  
          INP_WLOCK(inp);
          if (inp->in6p_moptions != NULL) {
                  free(imfp, M_IN6MFILTER);
                  free(immp, M_IP6MOPTS);
                  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.
   */
  void
  ip6_freemoptions(struct ip6_moptions *imo)
  {
          struct in6_mfilter      *imf;
          size_t                   idx, nmships;
  
          KASSERT(imo != NULL, ("%s: ip6_moptions is NULL", __func__));
  
          nmships = imo->im6o_num_memberships;
          for (idx = 0; idx < nmships; ++idx) {
                  imf = imo->im6o_mfilters ? &imo->im6o_mfilters[idx] : NULL;
                  if (imf)
                          im6f_leave(imf);
                  /* XXX this will thrash the lock(s) */
                  (void)in6_mc_leave(imo->im6o_membership[idx], imf);
                  if (imf)
                          im6f_purge(imf);
          }
  
          if (imo->im6o_mfilters)
                  free(imo->im6o_mfilters, M_IN6MFILTER);
          free(imo->im6o_membership, M_IP6MOPTS);
          free(imo, M_IP6MOPTS);
  }
  
  /*
   * 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                   idx, 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.
           */
          idx = im6o_match_group(imo, ifp, &gsa->sa);
          if (idx == -1 || imo->im6o_mfilters == NULL) {
                  INP_WUNLOCK(inp);
                  return (EADDRNOTAVAIL);
          }
          imf = &imo->im6o_mfilters[idx];
  
          /*
           * 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.
   *
   * If inp is non-NULL, use this 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 *in6p,
      const struct sockaddr_in6 *gsin6)
  {
          struct route_in6         ro6;
          struct ifnet            *ifp;
  
          KASSERT(in6p->inp_vflag & INP_IPV6,
              ("%s: not INP_IPV6 inpcb", __func__));
          KASSERT(gsin6->sin6_family == AF_INET6,
              ("%s: not AF_INET6 group", __func__));
  
          ifp = NULL;
          memset(&ro6, 0, sizeof(struct route_in6));
          memcpy(&ro6.ro_dst, gsin6, sizeof(struct sockaddr_in6));
          rtalloc_ign_fib((struct route *)&ro6, 0,
              in6p ? in6p->inp_inc.inc_fibnum : RT_DEFAULT_FIB);
          if (ro6.ro_rt != NULL) {
                  ifp = ro6.ro_rt->rt_ifp;
                  KASSERT(ifp != NULL, ("%s: null ifp", __func__));
                  RTFREE(ro6.ro_rt);
          }
  
          return (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 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;
          size_t                           idx;
          int                              error, is_new;
  
          ifp = NULL;
          imf = NULL;
          lims = NULL;
          error = 0;
          is_new = 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);
  
          imo = in6p_findmoptions(inp);
          idx = im6o_match_group(imo, ifp, &gsa->sa);
          if (idx == -1) {
                  is_new = 1;
          } else {
                  inm = imo->im6o_membership[idx];
                  imf = &imo->im6o_mfilters[idx];
                  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(imo, idx, &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 = EINVAL;
                          goto out_in6p_locked;
                  }
          }
  
          /*
           * Begin state merge transaction at socket layer.
           */
          INP_WLOCK_ASSERT(inp);
  
          if (is_new) {
                  if (imo->im6o_num_memberships == imo->im6o_max_memberships) {
                          error = im6o_grow(imo);
                          if (error)
                                  goto out_in6p_locked;
                  }
                  /*
                   * Allocate the new slot upfront so we can deal with
                   * grafting the new source filter in same code path
                   * as for join-source on existing membership.
                   */
                  idx = imo->im6o_num_memberships;
                  imo->im6o_membership[idx] = NULL;
                  imo->im6o_num_memberships++;
                  KASSERT(imo->im6o_mfilters != NULL,
                      ("%s: im6f_mfilters vector was not allocated", __func__));
                  imf = &imo->im6o_mfilters[idx];
                  KASSERT(RB_EMPTY(&imf->im6f_sources),
                      ("%s: im6f_sources not empty", __func__));
          }
  
          /*
           * 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__);
                          im6f_init(imf, MCAST_UNDEFINED, MCAST_INCLUDE);
                  } 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_im6o_free;
                  }
          } else {
                  /* No address specified; Membership starts in EX mode */
                  if (is_new) {
                          CTR1(KTR_MLD, "%s: new join w/o source", __func__);
                          im6f_init(imf, MCAST_UNDEFINED, MCAST_EXCLUDE);
                  }
          }
  
          /*
           * Begin state merge transaction at MLD layer.
           */
          IN6_MULTI_LOCK();
  
          if (is_new) {
                  error = in6_mc_join_locked(ifp, &gsa->sin6.sin6_addr, imf,
                      &inm, 0);
                  if (error) {
                          IN6_MULTI_UNLOCK();
                          goto out_im6o_free;
                  }
                  imo->im6o_membership[idx] = inm;
          } else {
                  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_UNLOCK();
          INP_WLOCK_ASSERT(inp);
          if (error) {
                  im6f_rollback(imf);
                  if (is_new)
                          im6f_purge(imf);
                  else
                          im6f_reap(imf);
          } else {
                  im6f_commit(imf);
          }
  
  out_im6o_free:
          if (error && is_new) {
                  imo->im6o_membership[idx] = NULL;
                  --imo->im6o_num_memberships;
          }
  
  out_in6p_locked:
          INP_WUNLOCK(inp);
          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;
          size_t                           idx;
          int                              error, is_final;
  #ifdef KTR
          char                             ip6tbuf[INET6_ADDRSTRLEN];
  #endif
  
          ifp = NULL;
          ifindex = 0;
          error = 0;
          is_final = 1;
  
          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__));
  
          /*
           * Find the membership in the membership array.
           */
          imo = in6p_findmoptions(inp);
          idx = im6o_match_group(imo, ifp, &gsa->sa);
          if (idx == -1) {
                  error = EADDRNOTAVAIL;
                  goto out_in6p_locked;
          }
          inm = imo->im6o_membership[idx];
          imf = &imo->im6o_mfilters[idx];
  
          if (ssa->ss.ss_family != AF_UNSPEC)
                  is_final = 0;
  
          /*
           * 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) {
                  im6f_leave(imf);
          } else {
                  if (imf->im6f_st[0] == MCAST_EXCLUDE) {
                          error = EADDRNOTAVAIL;
                          goto out_in6p_locked;
                  }
                  ims = im6o_match_source(imo, idx, &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.
           */
          IN6_MULTI_LOCK();
  
          if (is_final) {
                  /*
                   * Give up the multicast address record to which
                   * the membership points.
                   */
                  (void)in6_mc_leave_locked(inm, imf);
          } else {
                  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_UNLOCK();
  
          if (error)
                  im6f_rollback(imf);
          else
                  im6f_commit(imf);
  
          im6f_reap(imf);
  
          if (is_final) {
                  /* Remove the gap in the membership array. */
                  for (++idx; idx < imo->im6o_num_memberships; ++idx) {
                          imo->im6o_membership[idx-1] = imo->im6o_membership[idx];
                          imo->im6o_mfilters[idx-1] = imo->im6o_mfilters[idx];
                  }
                  imo->im6o_num_memberships--;
          }
  
  out_in6p_locked:
          INP_WUNLOCK(inp);
          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;
          size_t                   idx;
          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);
          idx = im6o_match_group(imo, ifp, &gsa->sa);
          if (idx == -1 || imo->im6o_mfilters == NULL) {
                  error = EADDRNOTAVAIL;
                  goto out_in6p_locked;
          }
          inm = imo->im6o_membership[idx];
          imf = &imo->im6o_mfilters[idx];
  
          /*
           * 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_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_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();
  
          IF_ADDR_RLOCK(ifp);
          TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
                  if (ifma->ifma_addr->sa_family != AF_INET6 ||
                      ifma->ifma_protospec == NULL)
                          continue;
                  inm = (struct in6_multi *)ifma->ifma_protospec;
                  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_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,
              inm->in6m_ifp->if_xname,
              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,
              inm->in6m_scq.ifq_len);
          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 */

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