The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/netinet6/mld6.c

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    1 /*      $FreeBSD: releng/6.0/sys/netinet6/mld6.c 151166 2005-10-09 06:51:11Z ume $      */
    2 /*      $KAME: mld6.c,v 1.27 2001/04/04 05:17:30 itojun Exp $   */
    3 
    4 /*-
    5  * Copyright (C) 1998 WIDE Project.
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. Neither the name of the project nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  */
   32 
   33 /*-
   34  * Copyright (c) 1988 Stephen Deering.
   35  * Copyright (c) 1992, 1993
   36  *      The Regents of the University of California.  All rights reserved.
   37  *
   38  * This code is derived from software contributed to Berkeley by
   39  * Stephen Deering of Stanford University.
   40  *
   41  * Redistribution and use in source and binary forms, with or without
   42  * modification, are permitted provided that the following conditions
   43  * are met:
   44  * 1. Redistributions of source code must retain the above copyright
   45  *    notice, this list of conditions and the following disclaimer.
   46  * 2. Redistributions in binary form must reproduce the above copyright
   47  *    notice, this list of conditions and the following disclaimer in the
   48  *    documentation and/or other materials provided with the distribution.
   49  * 4. Neither the name of the University nor the names of its contributors
   50  *    may be used to endorse or promote products derived from this software
   51  *    without specific prior written permission.
   52  *
   53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   56  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   63  * SUCH DAMAGE.
   64  *
   65  *      @(#)igmp.c      8.1 (Berkeley) 7/19/93
   66  */
   67 
   68 #include "opt_inet.h"
   69 #include "opt_inet6.h"
   70 
   71 #include <sys/param.h>
   72 #include <sys/systm.h>
   73 #include <sys/mbuf.h>
   74 #include <sys/socket.h>
   75 #include <sys/protosw.h>
   76 #include <sys/syslog.h>
   77 #include <sys/malloc.h>
   78 
   79 #include <net/if.h>
   80 
   81 #include <netinet/in.h>
   82 #include <netinet/in_var.h>
   83 #include <netinet/ip6.h>
   84 #include <netinet6/ip6_var.h>
   85 #include <netinet/icmp6.h>
   86 #include <netinet6/mld6_var.h>
   87 
   88 #include <net/net_osdep.h>
   89 
   90 /*
   91  * Protocol constants
   92  */
   93 
   94 /* denotes that the MLD max response delay field specifies time in milliseconds */
   95 #define MLD_TIMER_SCALE 1000
   96 /*
   97  * time between repetitions of a node's initial report of interest in a
   98  * multicast address(in seconds)
   99  */
  100 #define MLD_UNSOLICITED_REPORT_INTERVAL 10
  101 
  102 static struct ip6_pktopts ip6_opts;
  103 static int mld6_timers_are_running;
  104 /* XXX: These are necessary for KAME's link-local hack */
  105 static struct in6_addr mld6_all_nodes_linklocal = IN6ADDR_LINKLOCAL_ALLNODES_INIT;
  106 static struct in6_addr mld6_all_routers_linklocal = IN6ADDR_LINKLOCAL_ALLROUTERS_INIT;
  107 
  108 static void mld6_sendpkt(struct in6_multi *, int, const struct in6_addr *);
  109 
  110 void
  111 mld6_init()
  112 {
  113         static u_int8_t hbh_buf[8];
  114         struct ip6_hbh *hbh = (struct ip6_hbh *)hbh_buf;
  115         u_int16_t rtalert_code = htons((u_int16_t)IP6OPT_RTALERT_MLD);
  116 
  117         mld6_timers_are_running = 0;
  118 
  119         /* ip6h_nxt will be fill in later */
  120         hbh->ip6h_len = 0;      /* (8 >> 3) - 1 */
  121 
  122         /* XXX: grotty hard coding... */
  123         hbh_buf[2] = IP6OPT_PADN;       /* 2 byte padding */
  124         hbh_buf[3] = 0;
  125         hbh_buf[4] = IP6OPT_ROUTER_ALERT;
  126         hbh_buf[5] = IP6OPT_RTALERT_LEN - 2;
  127         bcopy((caddr_t)&rtalert_code, &hbh_buf[6], sizeof(u_int16_t));
  128 
  129         ip6_initpktopts(&ip6_opts);
  130         ip6_opts.ip6po_hbh = hbh;
  131 }
  132 
  133 void
  134 mld6_start_listening(in6m)
  135         struct in6_multi *in6m;
  136 {
  137         int s = splnet();
  138 
  139         /*
  140          * RFC2710 page 10:
  141          * The node never sends a Report or Done for the link-scope all-nodes
  142          * address.
  143          * MLD messages are never sent for multicast addresses whose scope is 0
  144          * (reserved) or 1 (node-local).
  145          */
  146         mld6_all_nodes_linklocal.s6_addr16[1] =
  147                 htons(in6m->in6m_ifp->if_index); /* XXX */
  148         if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &mld6_all_nodes_linklocal) ||
  149             IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) < IPV6_ADDR_SCOPE_LINKLOCAL) {
  150                 in6m->in6m_timer = 0;
  151                 in6m->in6m_state = MLD_OTHERLISTENER;
  152         } else {
  153                 mld6_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
  154                 in6m->in6m_timer =
  155                         MLD_RANDOM_DELAY(MLD_UNSOLICITED_REPORT_INTERVAL *
  156                                          PR_FASTHZ);
  157                 in6m->in6m_state = MLD_IREPORTEDLAST;
  158                 mld6_timers_are_running = 1;
  159         }
  160         splx(s);
  161 }
  162 
  163 void
  164 mld6_stop_listening(in6m)
  165         struct in6_multi *in6m;
  166 {
  167         mld6_all_nodes_linklocal.s6_addr16[1] =
  168                 htons(in6m->in6m_ifp->if_index); /* XXX */
  169         mld6_all_routers_linklocal.s6_addr16[1] =
  170                 htons(in6m->in6m_ifp->if_index); /* XXX: necessary when mrouting */
  171 
  172         if (in6m->in6m_state == MLD_IREPORTEDLAST &&
  173             (!IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &mld6_all_nodes_linklocal)) &&
  174             IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) > IPV6_ADDR_SCOPE_INTFACELOCAL)
  175                 mld6_sendpkt(in6m, MLD_LISTENER_DONE,
  176                              &mld6_all_routers_linklocal);
  177 }
  178 
  179 void
  180 mld6_input(m, off)
  181         struct mbuf *m;
  182         int off;
  183 {
  184         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  185         struct mld_hdr *mldh;
  186         struct ifnet *ifp = m->m_pkthdr.rcvif;
  187         struct in6_multi *in6m;
  188         struct in6_ifaddr *ia;
  189         struct ifmultiaddr *ifma;
  190         int timer;              /* timer value in the MLD query header */
  191 
  192 #ifndef PULLDOWN_TEST
  193         IP6_EXTHDR_CHECK(m, off, sizeof(*mldh),);
  194         mldh = (struct mld_hdr *)(mtod(m, caddr_t) + off);
  195 #else
  196         IP6_EXTHDR_GET(mldh, struct mld_hdr *, m, off, sizeof(*mldh));
  197         if (mldh == NULL) {
  198                 icmp6stat.icp6s_tooshort++;
  199                 return;
  200         }
  201 #endif
  202 
  203         /* source address validation */
  204         ip6 = mtod(m, struct ip6_hdr *); /* in case mpullup */
  205         if (!IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src)) {
  206                 log(LOG_ERR,
  207                     "mld6_input: src %s is not link-local (grp=%s)\n",
  208                     ip6_sprintf(&ip6->ip6_src),
  209                     ip6_sprintf(&mldh->mld_addr));
  210                 /*
  211                  * spec (RFC2710) does not explicitly
  212                  * specify to discard the packet from a non link-local
  213                  * source address. But we believe it's expected to do so.
  214                  * XXX: do we have to allow :: as source?
  215                  */
  216                 m_freem(m);
  217                 return;
  218         }
  219 
  220         /*
  221          * In the MLD6 specification, there are 3 states and a flag.
  222          *
  223          * In Non-Listener state, we simply don't have a membership record.
  224          * In Delaying Listener state, our timer is running (in6m->in6m_timer)
  225          * In Idle Listener state, our timer is not running (in6m->in6m_timer==0)
  226          *
  227          * The flag is in6m->in6m_state, it is set to MLD_OTHERLISTENER if
  228          * we have heard a report from another member, or MLD_IREPORTEDLAST
  229          * if we sent the last report.
  230          */
  231         switch(mldh->mld_type) {
  232         case MLD_LISTENER_QUERY:
  233                 if (ifp->if_flags & IFF_LOOPBACK)
  234                         break;
  235 
  236                 if (!IN6_IS_ADDR_UNSPECIFIED(&mldh->mld_addr) &&
  237                     !IN6_IS_ADDR_MULTICAST(&mldh->mld_addr))
  238                         break;  /* print error or log stat? */
  239                 if (IN6_IS_ADDR_MC_LINKLOCAL(&mldh->mld_addr))
  240                         mldh->mld_addr.s6_addr16[1] =
  241                                 htons(ifp->if_index); /* XXX */
  242 
  243                 /*
  244                  * - Start the timers in all of our membership records
  245                  *   that the query applies to for the interface on
  246                  *   which the query arrived excl. those that belong
  247                  *   to the "all-nodes" group (ff02::1).
  248                  * - Restart any timer that is already running but has
  249                  *   A value longer than the requested timeout.
  250                  * - Use the value specified in the query message as
  251                  *   the maximum timeout.
  252                  */
  253                 IFP_TO_IA6(ifp, ia);
  254                 if (ia == NULL)
  255                         break;
  256 
  257                 /*
  258                  * XXX: System timer resolution is too low to handle Max
  259                  * Response Delay, so set 1 to the internal timer even if
  260                  * the calculated value equals to zero when Max Response
  261                  * Delay is positive.
  262                  */
  263                 timer = ntohs(mldh->mld_maxdelay) * PR_FASTHZ / MLD_TIMER_SCALE;
  264                 if (timer == 0 && mldh->mld_maxdelay)
  265                         timer = 1;
  266                 mld6_all_nodes_linklocal.s6_addr16[1] =
  267                         htons(ifp->if_index); /* XXX */
  268 
  269                 IF_ADDR_LOCK(ifp);
  270                 TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
  271                         if (ifma->ifma_addr->sa_family != AF_INET6)
  272                                 continue;
  273                         in6m = (struct in6_multi *)ifma->ifma_protospec;
  274 
  275                         if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr,
  276                                         &mld6_all_nodes_linklocal) ||
  277                             IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) <
  278                             IPV6_ADDR_SCOPE_LINKLOCAL)
  279                                 continue;
  280 
  281                         if (IN6_IS_ADDR_UNSPECIFIED(&mldh->mld_addr) ||
  282                             IN6_ARE_ADDR_EQUAL(&mldh->mld_addr,
  283                                                 &in6m->in6m_addr))
  284                         {
  285                                 if (timer == 0) {
  286                                         /* send a report immediately */
  287                                         mld6_sendpkt(in6m, MLD_LISTENER_REPORT,
  288                                                 NULL);
  289                                         in6m->in6m_timer = 0; /* reset timer */
  290                                         in6m->in6m_state = MLD_IREPORTEDLAST;
  291                                 }
  292                                 else if (in6m->in6m_timer == 0 || /*idle state*/
  293                                         in6m->in6m_timer > timer) {
  294                                         in6m->in6m_timer =
  295                                                 MLD_RANDOM_DELAY(timer);
  296                                         mld6_timers_are_running = 1;
  297                                 }
  298                         }
  299                 }
  300                 IF_ADDR_UNLOCK(ifp);
  301 
  302                 if (IN6_IS_ADDR_MC_LINKLOCAL(&mldh->mld_addr))
  303                         mldh->mld_addr.s6_addr16[1] = 0; /* XXX */
  304                 break;
  305 
  306         case MLD_LISTENER_REPORT:
  307                 /*
  308                  * For fast leave to work, we have to know that we are the
  309                  * last person to send a report for this group.  Reports
  310                  * can potentially get looped back if we are a multicast
  311                  * router, so discard reports sourced by me.
  312                  * Note that it is impossible to check IFF_LOOPBACK flag of
  313                  * ifp for this purpose, since ip6_mloopback pass the physical
  314                  * interface to looutput.
  315                  */
  316                 if (m->m_flags & M_LOOP) /* XXX: grotty flag, but efficient */
  317                         break;
  318 
  319                 if (!IN6_IS_ADDR_MULTICAST(&mldh->mld_addr))
  320                         break;
  321 
  322                 if (IN6_IS_ADDR_MC_LINKLOCAL(&mldh->mld_addr))
  323                         mldh->mld_addr.s6_addr16[1] =
  324                                 htons(ifp->if_index); /* XXX */
  325                 /*
  326                  * If we belong to the group being reported, stop
  327                  * our timer for that group.
  328                  */
  329                 IN6_LOOKUP_MULTI(mldh->mld_addr, ifp, in6m);
  330                 if (in6m) {
  331                         in6m->in6m_timer = 0; /* transit to idle state */
  332                         in6m->in6m_state = MLD_OTHERLISTENER; /* clear flag */
  333                 }
  334 
  335                 if (IN6_IS_ADDR_MC_LINKLOCAL(&mldh->mld_addr))
  336                         mldh->mld_addr.s6_addr16[1] = 0; /* XXX */
  337                 break;
  338         default:                /* this is impossible */
  339                 log(LOG_ERR, "mld6_input: illegal type(%d)", mldh->mld_type);
  340                 break;
  341         }
  342 
  343         m_freem(m);
  344 }
  345 
  346 void
  347 mld6_fasttimeo()
  348 {
  349         struct in6_multi *in6m;
  350         struct in6_multistep step;
  351         int s;
  352 
  353         /*
  354          * Quick check to see if any work needs to be done, in order
  355          * to minimize the overhead of fasttimo processing.
  356          */
  357         if (!mld6_timers_are_running)
  358                 return;
  359 
  360         s = splnet();
  361 
  362         mld6_timers_are_running = 0;
  363         IN6_FIRST_MULTI(step, in6m);
  364         while (in6m != NULL) {
  365                 if (in6m->in6m_timer == 0) {
  366                         /* do nothing */
  367                 } else if (--in6m->in6m_timer == 0) {
  368                         mld6_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
  369                         in6m->in6m_state = MLD_IREPORTEDLAST;
  370                 } else {
  371                         mld6_timers_are_running = 1;
  372                 }
  373                 IN6_NEXT_MULTI(step, in6m);
  374         }
  375 
  376         splx(s);
  377 }
  378 
  379 static void
  380 mld6_sendpkt(in6m, type, dst)
  381         struct in6_multi *in6m;
  382         int type;
  383         const struct in6_addr *dst;
  384 {
  385         struct mbuf *mh, *md;
  386         struct mld_hdr *mldh;
  387         struct ip6_hdr *ip6;
  388         struct ip6_moptions im6o;
  389         struct in6_ifaddr *ia;
  390         struct ifnet *ifp = in6m->in6m_ifp;
  391         struct ifnet *outif = NULL;
  392 
  393         /*
  394          * At first, find a link local address on the outgoing interface
  395          * to use as the source address of the MLD packet.
  396          */
  397         if ((ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST))
  398             == NULL)
  399                 return;
  400 
  401         /*
  402          * Allocate mbufs to store ip6 header and MLD header.
  403          * We allocate 2 mbufs and make chain in advance because
  404          * it is more convenient when inserting the hop-by-hop option later.
  405          */
  406         MGETHDR(mh, M_DONTWAIT, MT_HEADER);
  407         if (mh == NULL)
  408                 return;
  409         MGET(md, M_DONTWAIT, MT_DATA);
  410         if (md == NULL) {
  411                 m_free(mh);
  412                 return;
  413         }
  414         mh->m_next = md;
  415 
  416         mh->m_pkthdr.rcvif = NULL;
  417         mh->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct mld_hdr);
  418         mh->m_len = sizeof(struct ip6_hdr);
  419         MH_ALIGN(mh, sizeof(struct ip6_hdr));
  420 
  421         /* fill in the ip6 header */
  422         ip6 = mtod(mh, struct ip6_hdr *);
  423         ip6->ip6_flow = 0;
  424         ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
  425         ip6->ip6_vfc |= IPV6_VERSION;
  426         /* ip6_plen will be set later */
  427         ip6->ip6_nxt = IPPROTO_ICMPV6;
  428         /* ip6_hlim will be set by im6o.im6o_multicast_hlim */
  429         ip6->ip6_src = ia->ia_addr.sin6_addr;
  430         ip6->ip6_dst = dst ? *dst : in6m->in6m_addr;
  431 
  432         /* fill in the MLD header */
  433         md->m_len = sizeof(struct mld_hdr);
  434         mldh = mtod(md, struct mld_hdr *);
  435         mldh->mld_type = type;
  436         mldh->mld_code = 0;
  437         mldh->mld_cksum = 0;
  438         /* XXX: we assume the function will not be called for query messages */
  439         mldh->mld_maxdelay = 0;
  440         mldh->mld_reserved = 0;
  441         mldh->mld_addr = in6m->in6m_addr;
  442         if (IN6_IS_ADDR_MC_LINKLOCAL(&mldh->mld_addr))
  443                 mldh->mld_addr.s6_addr16[1] = 0; /* XXX */
  444         mldh->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6, sizeof(struct ip6_hdr),
  445                                     sizeof(struct mld_hdr));
  446 
  447         /* construct multicast option */
  448         bzero(&im6o, sizeof(im6o));
  449         im6o.im6o_multicast_ifp = ifp;
  450         im6o.im6o_multicast_hlim = 1;
  451 
  452         /*
  453          * Request loopback of the report if we are acting as a multicast
  454          * router, so that the process-level routing daemon can hear it.
  455          */
  456         im6o.im6o_multicast_loop = (ip6_mrouter != NULL);
  457 
  458         /* increment output statictics */
  459         icmp6stat.icp6s_outhist[type]++;
  460 
  461         ip6_output(mh, &ip6_opts, NULL, 0, &im6o, &outif, NULL);
  462         if (outif) {
  463                 icmp6_ifstat_inc(outif, ifs6_out_msg);
  464                 switch (type) {
  465                 case MLD_LISTENER_QUERY:
  466                         icmp6_ifstat_inc(outif, ifs6_out_mldquery);
  467                         break;
  468                 case MLD_LISTENER_REPORT:
  469                         icmp6_ifstat_inc(outif, ifs6_out_mldreport);
  470                         break;
  471                 case MLD_LISTENER_DONE:
  472                         icmp6_ifstat_inc(outif, ifs6_out_mlddone);
  473                         break;
  474                 }
  475         }
  476 }
  477 
  478 /*
  479  * Add an address to the list of IP6 multicast addresses for a given interface.
  480  * Add source addresses to the list also, if upstream router is MLDv2 capable
  481  * and the number of source is not 0.
  482  */
  483 struct  in6_multi *
  484 in6_addmulti(maddr6, ifp, errorp)
  485         struct in6_addr *maddr6;
  486         struct ifnet *ifp;
  487         int *errorp;
  488 {
  489         struct in6_multi *in6m;
  490         struct ifmultiaddr *ifma;
  491         struct sockaddr_in6 sa6;
  492         int     s = splnet();
  493 
  494         *errorp = 0;
  495 
  496         /*
  497          * Call generic routine to add membership or increment
  498          * refcount.  It wants addresses in the form of a sockaddr,
  499          * so we build one here (being careful to zero the unused bytes).
  500          */
  501         bzero(&sa6, sizeof(sa6));
  502         sa6.sin6_family = AF_INET6;
  503         sa6.sin6_len = sizeof(struct sockaddr_in6);
  504         sa6.sin6_addr = *maddr6;
  505         *errorp = if_addmulti(ifp, (struct sockaddr *)&sa6, &ifma);
  506         if (*errorp) {
  507                 splx(s);
  508                 return 0;
  509         }
  510 
  511         /*
  512          * If ifma->ifma_protospec is null, then if_addmulti() created
  513          * a new record.  Otherwise, we are done.
  514          */
  515         if (ifma->ifma_protospec != NULL) {
  516                 splx(s);
  517                 return ifma->ifma_protospec;
  518         }
  519 
  520         /* XXX - if_addmulti uses M_WAITOK.  Can this really be called
  521            at interrupt time?  If so, need to fix if_addmulti. XXX */
  522         in6m = (struct in6_multi *)malloc(sizeof(*in6m), M_IPMADDR, M_NOWAIT);
  523         if (in6m == NULL) {
  524                 splx(s);
  525                 return (NULL);
  526         }
  527 
  528         bzero(in6m, sizeof *in6m);
  529         in6m->in6m_addr = *maddr6;
  530         in6m->in6m_ifp = ifp;
  531         in6m->in6m_refcount = 1;
  532         in6m->in6m_ifma = ifma;
  533         ifma->ifma_protospec = in6m;
  534         LIST_INSERT_HEAD(&in6_multihead, in6m, in6m_entry);
  535 
  536         /*
  537          * Let MLD6 know that we have joined a new IPv6 multicast
  538          * group.
  539          */
  540         mld6_start_listening(in6m);
  541         splx(s);
  542         return (in6m);
  543 }
  544 
  545 /*
  546  * Delete a multicast address record.
  547  */
  548 void
  549 in6_delmulti(in6m)
  550         struct in6_multi *in6m;
  551 {
  552         struct ifmultiaddr *ifma = in6m->in6m_ifma;
  553         int     s = splnet();
  554 
  555         if (ifma->ifma_refcount == 1) {
  556                 /*
  557                  * No remaining claims to this record; let MLD6 know
  558                  * that we are leaving the multicast group.
  559                  */
  560                 mld6_stop_listening(in6m);
  561                 ifma->ifma_protospec = NULL;
  562                 LIST_REMOVE(in6m, in6m_entry);
  563                 free(in6m, M_IPMADDR);
  564         }
  565         /* XXX - should be separate API for when we have an ifma? */
  566         if_delmulti(ifma->ifma_ifp, ifma->ifma_addr);
  567         splx(s);
  568 }

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