xref: /freebsd/sys/netinet6/mld6.c (revision a9148abd9da5db2f1c682fb17bed791845fc41c9)
1 /*-
2  * Copyright (C) 1998 WIDE Project.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the project nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  *	$KAME: mld6.c,v 1.27 2001/04/04 05:17:30 itojun Exp $
30  */
31 
32 /*-
33  * Copyright (c) 1988 Stephen Deering.
34  * Copyright (c) 1992, 1993
35  *	The Regents of the University of California.  All rights reserved.
36  *
37  * This code is derived from software contributed to Berkeley by
38  * Stephen Deering of Stanford University.
39  *
40  * Redistribution and use in source and binary forms, with or without
41  * modification, are permitted provided that the following conditions
42  * are met:
43  * 1. Redistributions of source code must retain the above copyright
44  *    notice, this list of conditions and the following disclaimer.
45  * 2. Redistributions in binary form must reproduce the above copyright
46  *    notice, this list of conditions and the following disclaimer in the
47  *    documentation and/or other materials provided with the distribution.
48  * 4. Neither the name of the University nor the names of its contributors
49  *    may be used to endorse or promote products derived from this software
50  *    without specific prior written permission.
51  *
52  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
53  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
54  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
55  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
56  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
57  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
58  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
59  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
60  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
61  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
62  * SUCH DAMAGE.
63  *
64  *	@(#)igmp.c	8.1 (Berkeley) 7/19/93
65  */
66 
67 #include <sys/cdefs.h>
68 __FBSDID("$FreeBSD$");
69 
70 #include "opt_inet.h"
71 #include "opt_inet6.h"
72 
73 #include <sys/param.h>
74 #include <sys/systm.h>
75 #include <sys/mbuf.h>
76 #include <sys/socket.h>
77 #include <sys/protosw.h>
78 #include <sys/syslog.h>
79 #include <sys/kernel.h>
80 #include <sys/callout.h>
81 #include <sys/malloc.h>
82 #include <sys/vimage.h>
83 
84 #include <net/if.h>
85 
86 #include <netinet/in.h>
87 #include <netinet/in_var.h>
88 #include <netinet6/in6_var.h>
89 #include <netinet/ip6.h>
90 #include <netinet6/ip6_var.h>
91 #include <netinet6/scope6_var.h>
92 #include <netinet/icmp6.h>
93 #include <netinet6/mld6_var.h>
94 
95 /*
96  * Protocol constants
97  */
98 
99 /* denotes that the MLD max response delay field specifies time in milliseconds */
100 #define MLD_TIMER_SCALE	1000
101 /*
102  * time between repetitions of a node's initial report of interest in a
103  * multicast address(in seconds)
104  */
105 #define MLD_UNSOLICITED_REPORT_INTERVAL	10
106 
107 static struct ip6_pktopts ip6_opts;
108 
109 static void mld6_sendpkt(struct in6_multi *, int, const struct in6_addr *);
110 static void mld_starttimer(struct in6_multi *);
111 static void mld_stoptimer(struct in6_multi *);
112 static void mld_timeo(struct in6_multi *);
113 static u_long mld_timerresid(struct in6_multi *);
114 
115 void
116 mld6_init(void)
117 {
118 	INIT_VNET_INET6(curvnet);
119 	static u_int8_t hbh_buf[8];
120 	struct ip6_hbh *hbh = (struct ip6_hbh *)hbh_buf;
121 	u_int16_t rtalert_code = htons((u_int16_t)IP6OPT_RTALERT_MLD);
122 
123 	/* ip6h_nxt will be fill in later */
124 	hbh->ip6h_len = 0;	/* (8 >> 3) - 1 */
125 
126 	/* XXX: grotty hard coding... */
127 	hbh_buf[2] = IP6OPT_PADN;	/* 2 byte padding */
128 	hbh_buf[3] = 0;
129 	hbh_buf[4] = IP6OPT_ROUTER_ALERT;
130 	hbh_buf[5] = IP6OPT_RTALERT_LEN - 2;
131 	bcopy((caddr_t)&rtalert_code, &hbh_buf[6], sizeof(u_int16_t));
132 
133 	ip6_initpktopts(&V_ip6_opts);
134 	V_ip6_opts.ip6po_hbh = hbh;
135 }
136 
137 static void
138 mld_starttimer(struct in6_multi *in6m)
139 {
140 	struct timeval now;
141 
142 	microtime(&now);
143 	in6m->in6m_timer_expire.tv_sec = now.tv_sec + in6m->in6m_timer / hz;
144 	in6m->in6m_timer_expire.tv_usec = now.tv_usec +
145 	    (in6m->in6m_timer % hz) * (1000000 / hz);
146 	if (in6m->in6m_timer_expire.tv_usec > 1000000) {
147 		in6m->in6m_timer_expire.tv_sec++;
148 		in6m->in6m_timer_expire.tv_usec -= 1000000;
149 	}
150 
151 	/* start or restart the timer */
152 	callout_reset(in6m->in6m_timer_ch, in6m->in6m_timer,
153 	    (void (*)(void *))mld_timeo, in6m);
154 }
155 
156 static void
157 mld_stoptimer(struct in6_multi *in6m)
158 {
159 	if (in6m->in6m_timer == IN6M_TIMER_UNDEF)
160 		return;
161 
162 	callout_stop(in6m->in6m_timer_ch);
163 	in6m->in6m_timer = IN6M_TIMER_UNDEF;
164 }
165 
166 static void
167 mld_timeo(struct in6_multi *in6m)
168 {
169 	int s = splnet();
170 
171 	in6m->in6m_timer = IN6M_TIMER_UNDEF;
172 
173 	callout_stop(in6m->in6m_timer_ch);
174 
175 	switch (in6m->in6m_state) {
176 	case MLD_REPORTPENDING:
177 		mld6_start_listening(in6m);
178 		break;
179 	default:
180 		mld6_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
181 		break;
182 	}
183 
184 	splx(s);
185 }
186 
187 static u_long
188 mld_timerresid(struct in6_multi *in6m)
189 {
190 	struct timeval now, diff;
191 
192 	microtime(&now);
193 
194 	if (now.tv_sec > in6m->in6m_timer_expire.tv_sec ||
195 	    (now.tv_sec == in6m->in6m_timer_expire.tv_sec &&
196 	    now.tv_usec > in6m->in6m_timer_expire.tv_usec)) {
197 		return (0);
198 	}
199 	diff = in6m->in6m_timer_expire;
200 	diff.tv_sec -= now.tv_sec;
201 	diff.tv_usec -= now.tv_usec;
202 	if (diff.tv_usec < 0) {
203 		diff.tv_sec--;
204 		diff.tv_usec += 1000000;
205 	}
206 
207 	/* return the remaining time in milliseconds */
208 	return (diff.tv_sec * 1000 + diff.tv_usec / 1000);
209 }
210 
211 void
212 mld6_start_listening(struct in6_multi *in6m)
213 {
214 	struct in6_addr all_in6;
215 	int s = splnet();
216 
217 	/*
218 	 * RFC2710 page 10:
219 	 * The node never sends a Report or Done for the link-scope all-nodes
220 	 * address.
221 	 * MLD messages are never sent for multicast addresses whose scope is 0
222 	 * (reserved) or 1 (node-local).
223 	 */
224 	all_in6 = in6addr_linklocal_allnodes;
225 	if (in6_setscope(&all_in6, in6m->in6m_ifp, NULL)) {
226 		/* XXX: this should not happen! */
227 		in6m->in6m_timer = 0;
228 		in6m->in6m_state = MLD_OTHERLISTENER;
229 	}
230 	if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &all_in6) ||
231 	    IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) <
232 	    IPV6_ADDR_SCOPE_LINKLOCAL) {
233 		in6m->in6m_timer = 0;
234 		in6m->in6m_state = MLD_OTHERLISTENER;
235 	} else {
236 		mld6_sendpkt(in6m, MLD_LISTENER_REPORT, NULL);
237 		in6m->in6m_timer = arc4random() %
238 			MLD_UNSOLICITED_REPORT_INTERVAL * hz;
239 		in6m->in6m_state = MLD_IREPORTEDLAST;
240 
241 		mld_starttimer(in6m);
242 	}
243 	splx(s);
244 }
245 
246 void
247 mld6_stop_listening(struct in6_multi *in6m)
248 {
249 	struct in6_addr allnode, allrouter;
250 
251 	allnode = in6addr_linklocal_allnodes;
252 	if (in6_setscope(&allnode, in6m->in6m_ifp, NULL)) {
253 		/* XXX: this should not happen! */
254 		return;
255 	}
256 	allrouter = in6addr_linklocal_allrouters;
257 	if (in6_setscope(&allrouter, in6m->in6m_ifp, NULL)) {
258 		/* XXX impossible */
259 		return;
260 	}
261 	if (in6m->in6m_state == MLD_IREPORTEDLAST &&
262 	    !IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &allnode) &&
263 	    IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) >
264 	    IPV6_ADDR_SCOPE_INTFACELOCAL) {
265 		mld6_sendpkt(in6m, MLD_LISTENER_DONE, &allrouter);
266 	}
267 }
268 
269 void
270 mld6_input(struct mbuf *m, int off)
271 {
272 	INIT_VNET_INET6(curvnet);
273 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
274 	struct mld_hdr *mldh;
275 	struct ifnet *ifp = m->m_pkthdr.rcvif;
276 	struct in6_multi *in6m;
277 	struct in6_addr mld_addr, all_in6;
278 	struct in6_ifaddr *ia;
279 	struct ifmultiaddr *ifma;
280 	u_long timer;		/* timer value in the MLD query header */
281 
282 #ifndef PULLDOWN_TEST
283 	IP6_EXTHDR_CHECK(m, off, sizeof(*mldh),);
284 	mldh = (struct mld_hdr *)(mtod(m, caddr_t) + off);
285 #else
286 	IP6_EXTHDR_GET(mldh, struct mld_hdr *, m, off, sizeof(*mldh));
287 	if (mldh == NULL) {
288 		V_icmp6stat.icp6s_tooshort++;
289 		return;
290 	}
291 #endif
292 
293 	/* source address validation */
294 	ip6 = mtod(m, struct ip6_hdr *); /* in case mpullup */
295 	if (!IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src)) {
296 		char ip6bufs[INET6_ADDRSTRLEN], ip6bufg[INET6_ADDRSTRLEN];
297 		log(LOG_ERR,
298 		    "mld6_input: src %s is not link-local (grp=%s)\n",
299 		    ip6_sprintf(ip6bufs, &ip6->ip6_src),
300 		    ip6_sprintf(ip6bufg, &mldh->mld_addr));
301 		/*
302 		 * spec (RFC2710) does not explicitly
303 		 * specify to discard the packet from a non link-local
304 		 * source address. But we believe it's expected to do so.
305 		 * XXX: do we have to allow :: as source?
306 		 */
307 		m_freem(m);
308 		return;
309 	}
310 
311 	/*
312 	 * make a copy for local work (in6_setscope() may modify the 1st arg)
313 	 */
314 	mld_addr = mldh->mld_addr;
315 	if (in6_setscope(&mld_addr, ifp, NULL)) {
316 		/* XXX: this should not happen! */
317 		m_free(m);
318 		return;
319 	}
320 
321 	/*
322 	 * In the MLD6 specification, there are 3 states and a flag.
323 	 *
324 	 * In Non-Listener state, we simply don't have a membership record.
325 	 * In Delaying Listener state, our timer is running (in6m->in6m_timer)
326 	 * In Idle Listener state, our timer is not running
327 	 * (in6m->in6m_timer==IN6M_TIMER_UNDEF)
328 	 *
329 	 * The flag is in6m->in6m_state, it is set to MLD_OTHERLISTENER if
330 	 * we have heard a report from another member, or MLD_IREPORTEDLAST
331 	 * if we sent the last report.
332 	 */
333 	switch(mldh->mld_type) {
334 	case MLD_LISTENER_QUERY:
335 		if (ifp->if_flags & IFF_LOOPBACK)
336 			break;
337 
338 		if (!IN6_IS_ADDR_UNSPECIFIED(&mld_addr) &&
339 		    !IN6_IS_ADDR_MULTICAST(&mld_addr))
340 			break;	/* print error or log stat? */
341 
342 		all_in6 = in6addr_linklocal_allnodes;
343 		if (in6_setscope(&all_in6, ifp, NULL)) {
344 			/* XXX: this should not happen! */
345 			break;
346 		}
347 
348 		/*
349 		 * - Start the timers in all of our membership records
350 		 *   that the query applies to for the interface on
351 		 *   which the query arrived excl. those that belong
352 		 *   to the "all-nodes" group (ff02::1).
353 		 * - Restart any timer that is already running but has
354 		 *   A value longer than the requested timeout.
355 		 * - Use the value specified in the query message as
356 		 *   the maximum timeout.
357 		 */
358 		timer = ntohs(mldh->mld_maxdelay);
359 
360 		IFP_TO_IA6(ifp, ia);
361 		if (ia == NULL)
362 			break;
363 
364 		/*
365 		 * XXX: System timer resolution is too low to handle Max
366 		 * Response Delay, so set 1 to the internal timer even if
367 		 * the calculated value equals to zero when Max Response
368 		 * Delay is positive.
369 		 */
370 		timer = ntohs(mldh->mld_maxdelay) * PR_FASTHZ / MLD_TIMER_SCALE;
371 		if (timer == 0 && mldh->mld_maxdelay)
372 			timer = 1;
373 
374 		IF_ADDR_LOCK(ifp);
375 		TAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
376 			if (ifma->ifma_addr->sa_family != AF_INET6)
377 				continue;
378 			in6m = (struct in6_multi *)ifma->ifma_protospec;
379 
380 			if (IN6_ARE_ADDR_EQUAL(&in6m->in6m_addr, &all_in6) ||
381 			    IPV6_ADDR_MC_SCOPE(&in6m->in6m_addr) <
382 			    IPV6_ADDR_SCOPE_LINKLOCAL)
383 				continue;
384 
385 			if (IN6_IS_ADDR_UNSPECIFIED(&mld_addr) ||
386 			    IN6_ARE_ADDR_EQUAL(&mld_addr, &in6m->in6m_addr)) {
387 				if (timer == 0) {
388 					/* send a report immediately */
389 					mld_stoptimer(in6m);
390 					mld6_sendpkt(in6m, MLD_LISTENER_REPORT,
391 						NULL);
392 					in6m->in6m_timer = 0; /* reset timer */
393 					in6m->in6m_state = MLD_IREPORTEDLAST;
394 				}
395 				else if (in6m->in6m_timer == IN6M_TIMER_UNDEF ||
396 				    mld_timerresid(in6m) > timer) {
397 					in6m->in6m_timer =
398 					   1 + (arc4random() % timer) * hz / 1000;
399 					mld_starttimer(in6m);
400 				}
401 			}
402 		}
403 		IF_ADDR_UNLOCK(ifp);
404 		break;
405 
406 	case MLD_LISTENER_REPORT:
407 		/*
408 		 * For fast leave to work, we have to know that we are the
409 		 * last person to send a report for this group.  Reports
410 		 * can potentially get looped back if we are a multicast
411 		 * router, so discard reports sourced by me.
412 		 * Note that it is impossible to check IFF_LOOPBACK flag of
413 		 * ifp for this purpose, since ip6_mloopback pass the physical
414 		 * interface to looutput.
415 		 */
416 		if (m->m_flags & M_LOOP) /* XXX: grotty flag, but efficient */
417 			break;
418 
419 		if (!IN6_IS_ADDR_MULTICAST(&mld_addr))
420 			break;
421 
422 		/*
423 		 * If we belong to the group being reported, stop
424 		 * our timer for that group.
425 		 */
426 		IN6_LOOKUP_MULTI(mld_addr, ifp, in6m);
427 		if (in6m) {
428 			in6m->in6m_timer = 0; /* transit to idle state */
429 			in6m->in6m_state = MLD_OTHERLISTENER; /* clear flag */
430 		}
431 		break;
432 	default:		/* this is impossible */
433 		log(LOG_ERR, "mld6_input: illegal type(%d)", mldh->mld_type);
434 		break;
435 	}
436 
437 	m_freem(m);
438 }
439 
440 static void
441 mld6_sendpkt(struct in6_multi *in6m, int type, const struct in6_addr *dst)
442 {
443 	INIT_VNET_INET6(curvnet);
444 	struct mbuf *mh, *md;
445 	struct mld_hdr *mldh;
446 	struct ip6_hdr *ip6;
447 	struct ip6_moptions im6o;
448 	struct in6_ifaddr *ia;
449 	struct ifnet *ifp = in6m->in6m_ifp;
450 	struct ifnet *outif = NULL;
451 
452 	/*
453 	 * At first, find a link local address on the outgoing interface
454 	 * to use as the source address of the MLD packet.
455 	 */
456 	if ((ia = in6ifa_ifpforlinklocal(ifp, IN6_IFF_NOTREADY|IN6_IFF_ANYCAST))
457 	    == NULL)
458 		return;
459 
460 	/*
461 	 * Allocate mbufs to store ip6 header and MLD header.
462 	 * We allocate 2 mbufs and make chain in advance because
463 	 * it is more convenient when inserting the hop-by-hop option later.
464 	 */
465 	MGETHDR(mh, M_DONTWAIT, MT_HEADER);
466 	if (mh == NULL)
467 		return;
468 	MGET(md, M_DONTWAIT, MT_DATA);
469 	if (md == NULL) {
470 		m_free(mh);
471 		return;
472 	}
473 	mh->m_next = md;
474 
475 	mh->m_pkthdr.rcvif = NULL;
476 	mh->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct mld_hdr);
477 	mh->m_len = sizeof(struct ip6_hdr);
478 	MH_ALIGN(mh, sizeof(struct ip6_hdr));
479 
480 	/* fill in the ip6 header */
481 	ip6 = mtod(mh, struct ip6_hdr *);
482 	ip6->ip6_flow = 0;
483 	ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
484 	ip6->ip6_vfc |= IPV6_VERSION;
485 	/* ip6_plen will be set later */
486 	ip6->ip6_nxt = IPPROTO_ICMPV6;
487 	/* ip6_hlim will be set by im6o.im6o_multicast_hlim */
488 	ip6->ip6_src = ia->ia_addr.sin6_addr;
489 	ip6->ip6_dst = dst ? *dst : in6m->in6m_addr;
490 
491 	/* fill in the MLD header */
492 	md->m_len = sizeof(struct mld_hdr);
493 	mldh = mtod(md, struct mld_hdr *);
494 	mldh->mld_type = type;
495 	mldh->mld_code = 0;
496 	mldh->mld_cksum = 0;
497 	/* XXX: we assume the function will not be called for query messages */
498 	mldh->mld_maxdelay = 0;
499 	mldh->mld_reserved = 0;
500 	mldh->mld_addr = in6m->in6m_addr;
501 	in6_clearscope(&mldh->mld_addr); /* XXX */
502 	mldh->mld_cksum = in6_cksum(mh, IPPROTO_ICMPV6, sizeof(struct ip6_hdr),
503 				    sizeof(struct mld_hdr));
504 
505 	/* construct multicast option */
506 	bzero(&im6o, sizeof(im6o));
507 	im6o.im6o_multicast_ifp = ifp;
508 	im6o.im6o_multicast_hlim = 1;
509 
510 	/*
511 	 * Request loopback of the report if we are acting as a multicast
512 	 * router, so that the process-level routing daemon can hear it.
513 	 */
514 	im6o.im6o_multicast_loop = (ip6_mrouter != NULL);
515 
516 	/* increment output statictics */
517 	V_icmp6stat.icp6s_outhist[type]++;
518 
519 	ip6_output(mh, &V_ip6_opts, NULL, 0, &im6o, &outif, NULL);
520 	if (outif) {
521 		icmp6_ifstat_inc(outif, ifs6_out_msg);
522 		switch (type) {
523 		case MLD_LISTENER_QUERY:
524 			icmp6_ifstat_inc(outif, ifs6_out_mldquery);
525 			break;
526 		case MLD_LISTENER_REPORT:
527 			icmp6_ifstat_inc(outif, ifs6_out_mldreport);
528 			break;
529 		case MLD_LISTENER_DONE:
530 			icmp6_ifstat_inc(outif, ifs6_out_mlddone);
531 			break;
532 		}
533 	}
534 }
535 
536 /*
537  * Add an address to the list of IP6 multicast addresses for a given interface.
538  * Add source addresses to the list also, if upstream router is MLDv2 capable
539  * and the number of source is not 0.
540  */
541 struct in6_multi *
542 in6_addmulti(struct in6_addr *maddr6, struct ifnet *ifp,
543     int *errorp, int delay)
544 {
545 	struct in6_multi *in6m;
546 
547 	*errorp = 0;
548 	in6m = NULL;
549 
550 	IFF_LOCKGIANT(ifp);
551 	/*IN6_MULTI_LOCK();*/
552 
553 	IN6_LOOKUP_MULTI(*maddr6, ifp, in6m);
554 	if (in6m != NULL) {
555 		/*
556 		 * If we already joined this group, just bump the
557 		 * refcount and return it.
558 		 */
559 		KASSERT(in6m->in6m_refcount >= 1,
560 		    ("%s: bad refcount %d", __func__, in6m->in6m_refcount));
561 		++in6m->in6m_refcount;
562 	} else do {
563 		struct in6_multi *nin6m;
564 		struct ifmultiaddr *ifma;
565 		struct sockaddr_in6 sa6;
566 
567 		bzero(&sa6, sizeof(sa6));
568 		sa6.sin6_family = AF_INET6;
569 		sa6.sin6_len = sizeof(struct sockaddr_in6);
570 		sa6.sin6_addr = *maddr6;
571 
572 		*errorp = if_addmulti(ifp, (struct sockaddr *)&sa6, &ifma);
573 		if (*errorp)
574 			break;
575 
576 		/*
577 		 * If ifma->ifma_protospec is null, then if_addmulti() created
578 		 * a new record.  Otherwise, bump refcount, and we are done.
579 		 */
580 		if (ifma->ifma_protospec != NULL) {
581 			in6m = ifma->ifma_protospec;
582 			++in6m->in6m_refcount;
583 			break;
584 		}
585 
586 		nin6m = malloc(sizeof(*nin6m), M_IP6MADDR, M_NOWAIT | M_ZERO);
587 		if (nin6m == NULL) {
588 			if_delmulti_ifma(ifma);
589 			break;
590 		}
591 
592 		nin6m->in6m_addr = *maddr6;
593 		nin6m->in6m_ifp = ifp;
594 		nin6m->in6m_refcount = 1;
595 		nin6m->in6m_ifma = ifma;
596 		ifma->ifma_protospec = nin6m;
597 
598 		nin6m->in6m_timer_ch = malloc(sizeof(*nin6m->in6m_timer_ch),
599 		    M_IP6MADDR, M_NOWAIT);
600 		if (nin6m->in6m_timer_ch == NULL) {
601 			free(nin6m, M_IP6MADDR);
602 			if_delmulti_ifma(ifma);
603 			break;
604 		}
605 
606 		LIST_INSERT_HEAD(&in6_multihead, nin6m, in6m_entry);
607 
608 		callout_init(nin6m->in6m_timer_ch, 0);
609 		nin6m->in6m_timer = delay;
610 		if (nin6m->in6m_timer > 0) {
611 			nin6m->in6m_state = MLD_REPORTPENDING;
612 			mld_starttimer(nin6m);
613 		}
614 
615 		mld6_start_listening(nin6m);
616 
617 		in6m = nin6m;
618 
619 	} while (0);
620 
621 	/*IN6_MULTI_UNLOCK();*/
622 	IFF_UNLOCKGIANT(ifp);
623 
624 	return (in6m);
625 }
626 
627 /*
628  * Delete a multicast address record.
629  *
630  * TODO: Locking, as per netinet.
631  */
632 void
633 in6_delmulti(struct in6_multi *in6m)
634 {
635 	struct ifmultiaddr *ifma;
636 
637 	KASSERT(in6m->in6m_refcount >= 1, ("%s: freeing freed in6m", __func__));
638 
639 	if (--in6m->in6m_refcount == 0) {
640 		mld_stoptimer(in6m);
641 		mld6_stop_listening(in6m);
642 
643 		ifma = in6m->in6m_ifma;
644 		KASSERT(ifma->ifma_protospec == in6m,
645 		    ("%s: ifma_protospec != in6m", __func__));
646 		ifma->ifma_protospec = NULL;
647 
648 		LIST_REMOVE(in6m, in6m_entry);
649 		free(in6m->in6m_timer_ch, M_IP6MADDR);
650 		free(in6m, M_IP6MADDR);
651 
652 		if_delmulti_ifma(ifma);
653 	}
654 }
655