xref: /freebsd/sys/netinet6/ip6_forward.c (revision 952364486a4b9d135e4b28f7f88a8703a74eae6f)
1 /*-
2  * Copyright (C) 1995, 1996, 1997, and 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: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_ipfw.h"
38 #include "opt_ipsec.h"
39 #include "opt_ipstealth.h"
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/malloc.h>
44 #include <sys/mbuf.h>
45 #include <sys/domain.h>
46 #include <sys/protosw.h>
47 #include <sys/socket.h>
48 #include <sys/errno.h>
49 #include <sys/time.h>
50 #include <sys/kernel.h>
51 #include <sys/syslog.h>
52 
53 #include <net/if.h>
54 #include <net/if_var.h>
55 #include <net/netisr.h>
56 #include <net/route.h>
57 #include <net/pfil.h>
58 
59 #include <netinet/in.h>
60 #include <netinet/in_var.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/ip.h>
63 #include <netinet/ip_var.h>
64 #include <netinet6/in6_var.h>
65 #include <netinet/ip6.h>
66 #include <netinet6/ip6_var.h>
67 #include <netinet6/scope6_var.h>
68 #include <netinet/icmp6.h>
69 #include <netinet6/nd6.h>
70 
71 #include <netinet/in_pcb.h>
72 
73 #ifdef IPSEC
74 #include <netinet6/ip6_ipsec.h>
75 #include <netipsec/ipsec.h>
76 #include <netipsec/ipsec6.h>
77 #include <netipsec/key.h>
78 #endif /* IPSEC */
79 
80 /*
81  * Forward a packet.  If some error occurs return the sender
82  * an icmp packet.  Note we can't always generate a meaningful
83  * icmp message because icmp doesn't have a large enough repertoire
84  * of codes and types.
85  *
86  * If not forwarding, just drop the packet.  This could be confusing
87  * if ipforwarding was zero but some routing protocol was advancing
88  * us as a gateway to somewhere.  However, we must let the routing
89  * protocol deal with that.
90  *
91  */
92 void
93 ip6_forward(struct mbuf *m, int srcrt)
94 {
95 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
96 	struct sockaddr_in6 *dst = NULL;
97 	struct rtentry *rt = NULL;
98 	struct route_in6 rin6;
99 	int error, type = 0, code = 0;
100 	struct mbuf *mcopy = NULL;
101 	struct ifnet *origifp;	/* maybe unnecessary */
102 	u_int32_t inzone, outzone;
103 	struct in6_addr src_in6, dst_in6, odst;
104 #ifdef IPSEC
105 	struct secpolicy *sp = NULL;
106 #endif
107 #ifdef SCTP
108 	int sw_csum;
109 #endif
110 	struct m_tag *fwd_tag;
111 	char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
112 
113 	/*
114 	 * Do not forward packets to multicast destination (should be handled
115 	 * by ip6_mforward().
116 	 * Do not forward packets with unspecified source.  It was discussed
117 	 * in July 2000, on the ipngwg mailing list.
118 	 */
119 	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
120 	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
121 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
122 		IP6STAT_INC(ip6s_cantforward);
123 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
124 		if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
125 			V_ip6_log_time = time_uptime;
126 			log(LOG_DEBUG,
127 			    "cannot forward "
128 			    "from %s to %s nxt %d received on %s\n",
129 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
130 			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
131 			    ip6->ip6_nxt,
132 			    if_name(m->m_pkthdr.rcvif));
133 		}
134 		m_freem(m);
135 		return;
136 	}
137 #ifdef IPSEC
138 	/*
139 	 * Check if this packet has an active SA and needs to be dropped
140 	 * instead of forwarded.
141 	 */
142 	if (ip6_ipsec_fwd(m) != 0) {
143 		IP6STAT_INC(ip6s_cantforward);
144 		m_freem(m);
145 		return;
146 	}
147 #endif /* IPSEC */
148 
149 #ifdef IPSTEALTH
150 	if (!V_ip6stealth) {
151 #endif
152 	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
153 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
154 		icmp6_error(m, ICMP6_TIME_EXCEEDED,
155 				ICMP6_TIME_EXCEED_TRANSIT, 0);
156 		return;
157 	}
158 	ip6->ip6_hlim -= IPV6_HLIMDEC;
159 
160 #ifdef IPSTEALTH
161 	}
162 #endif
163 
164 	/*
165 	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
166 	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
167 	 * we need to generate an ICMP6 message to the src.
168 	 * Thanks to M_EXT, in most cases copy will not occur.
169 	 *
170 	 * It is important to save it before IPsec processing as IPsec
171 	 * processing may modify the mbuf.
172 	 */
173 	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
174 
175 #ifdef IPSEC
176 	/* get a security policy for this packet */
177 	sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, &error);
178 	if (sp == NULL) {
179 		IPSEC6STAT_INC(ips_out_inval);
180 		IP6STAT_INC(ip6s_cantforward);
181 		if (mcopy) {
182 #if 0
183 			/* XXX: what icmp ? */
184 #else
185 			m_freem(mcopy);
186 #endif
187 		}
188 		m_freem(m);
189 		return;
190 	}
191 
192 	error = 0;
193 
194 	/* check policy */
195 	switch (sp->policy) {
196 	case IPSEC_POLICY_DISCARD:
197 		/*
198 		 * This packet is just discarded.
199 		 */
200 		IPSEC6STAT_INC(ips_out_polvio);
201 		IP6STAT_INC(ip6s_cantforward);
202 		KEY_FREESP(&sp);
203 		if (mcopy) {
204 #if 0
205 			/* XXX: what icmp ? */
206 #else
207 			m_freem(mcopy);
208 #endif
209 		}
210 		m_freem(m);
211 		return;
212 
213 	case IPSEC_POLICY_BYPASS:
214 	case IPSEC_POLICY_NONE:
215 		/* no need to do IPsec. */
216 		KEY_FREESP(&sp);
217 		goto skip_ipsec;
218 
219 	case IPSEC_POLICY_IPSEC:
220 		if (sp->req == NULL) {
221 			/* XXX should be panic ? */
222 			printf("ip6_forward: No IPsec request specified.\n");
223 			IP6STAT_INC(ip6s_cantforward);
224 			KEY_FREESP(&sp);
225 			if (mcopy) {
226 #if 0
227 				/* XXX: what icmp ? */
228 #else
229 				m_freem(mcopy);
230 #endif
231 			}
232 			m_freem(m);
233 			return;
234 		}
235 		/* do IPsec */
236 		break;
237 
238 	case IPSEC_POLICY_ENTRUST:
239 	default:
240 		/* should be panic ?? */
241 		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
242 		KEY_FREESP(&sp);
243 		goto skip_ipsec;
244 	}
245 
246     {
247 	struct ipsecrequest *isr = NULL;
248 
249 	/*
250 	 * when the kernel forwards a packet, it is not proper to apply
251 	 * IPsec transport mode to the packet is not proper.  this check
252 	 * avoid from this.
253 	 * at present, if there is even a transport mode SA request in the
254 	 * security policy, the kernel does not apply IPsec to the packet.
255 	 * this check is not enough because the following case is valid.
256 	 *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
257 	 */
258 	for (isr = sp->req; isr; isr = isr->next) {
259 		if (isr->saidx.mode == IPSEC_MODE_ANY)
260 			goto doipsectunnel;
261 		if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
262 			goto doipsectunnel;
263 	}
264 
265 	/*
266 	 * if there's no need for tunnel mode IPsec, skip.
267 	 */
268 	if (!isr)
269 		goto skip_ipsec;
270 
271     doipsectunnel:
272 	/*
273 	 * All the extension headers will become inaccessible
274 	 * (since they can be encrypted).
275 	 * Don't panic, we need no more updates to extension headers
276 	 * on inner IPv6 packet (since they are now encapsulated).
277 	 *
278 	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
279 	 */
280 
281 	/*
282 	 * If we need to encapsulate the packet, do it here
283 	 * ipsec6_proces_packet will send the packet using ip6_output
284 	 */
285 	error = ipsec6_process_packet(m, sp->req);
286 
287 	KEY_FREESP(&sp);
288 
289 	if (error == EJUSTRETURN) {
290 		/*
291 		 * We had a SP with a level of 'use' and no SA. We
292 		 * will just continue to process the packet without
293 		 * IPsec processing.
294 		 */
295 		error = 0;
296 		goto skip_ipsec;
297 	}
298 
299 	if (error) {
300 		/* mbuf is already reclaimed in ipsec6_process_packet. */
301 		switch (error) {
302 		case EHOSTUNREACH:
303 		case ENETUNREACH:
304 		case EMSGSIZE:
305 		case ENOBUFS:
306 		case ENOMEM:
307 			break;
308 		default:
309 			printf("ip6_output (ipsec): error code %d\n", error);
310 			/* FALLTHROUGH */
311 		case ENOENT:
312 			/* don't show these error codes to the user */
313 			break;
314 		}
315 		IP6STAT_INC(ip6s_cantforward);
316 		if (mcopy) {
317 #if 0
318 			/* XXX: what icmp ? */
319 #else
320 			m_freem(mcopy);
321 #endif
322 		}
323 		return;
324 	} else {
325 		/*
326 		 * In the FAST IPSec case we have already
327 		 * re-injected the packet and it has been freed
328 		 * by the ipsec_done() function.  So, just clean
329 		 * up after ourselves.
330 		 */
331 		m = NULL;
332 		goto freecopy;
333 	}
334     }
335 skip_ipsec:
336 #endif
337 again:
338 	bzero(&rin6, sizeof(struct route_in6));
339 	dst = (struct sockaddr_in6 *)&rin6.ro_dst;
340 	dst->sin6_len = sizeof(struct sockaddr_in6);
341 	dst->sin6_family = AF_INET6;
342 	dst->sin6_addr = ip6->ip6_dst;
343 again2:
344 	rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m));
345 	if (rin6.ro_rt != NULL)
346 		RT_UNLOCK(rin6.ro_rt);
347 	else {
348 		IP6STAT_INC(ip6s_noroute);
349 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
350 		if (mcopy) {
351 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
352 			ICMP6_DST_UNREACH_NOROUTE, 0);
353 		}
354 		goto bad;
355 	}
356 	rt = rin6.ro_rt;
357 
358 	/*
359 	 * Source scope check: if a packet can't be delivered to its
360 	 * destination for the reason that the destination is beyond the scope
361 	 * of the source address, discard the packet and return an icmp6
362 	 * destination unreachable error with Code 2 (beyond scope of source
363 	 * address).  We use a local copy of ip6_src, since in6_setscope()
364 	 * will possibly modify its first argument.
365 	 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
366 	 */
367 	src_in6 = ip6->ip6_src;
368 	if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
369 		/* XXX: this should not happen */
370 		IP6STAT_INC(ip6s_cantforward);
371 		IP6STAT_INC(ip6s_badscope);
372 		goto bad;
373 	}
374 	if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
375 		IP6STAT_INC(ip6s_cantforward);
376 		IP6STAT_INC(ip6s_badscope);
377 		goto bad;
378 	}
379 	if (inzone != outzone) {
380 		IP6STAT_INC(ip6s_cantforward);
381 		IP6STAT_INC(ip6s_badscope);
382 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
383 
384 		if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
385 			V_ip6_log_time = time_uptime;
386 			log(LOG_DEBUG,
387 			    "cannot forward "
388 			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
389 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
390 			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
391 			    ip6->ip6_nxt,
392 			    if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
393 		}
394 		if (mcopy)
395 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
396 				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
397 		goto bad;
398 	}
399 
400 	/*
401 	 * Destination scope check: if a packet is going to break the scope
402 	 * zone of packet's destination address, discard it.  This case should
403 	 * usually be prevented by appropriately-configured routing table, but
404 	 * we need an explicit check because we may mistakenly forward the
405 	 * packet to a different zone by (e.g.) a default route.
406 	 */
407 	dst_in6 = ip6->ip6_dst;
408 	if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
409 	    in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
410 	    inzone != outzone) {
411 		IP6STAT_INC(ip6s_cantforward);
412 		IP6STAT_INC(ip6s_badscope);
413 		goto bad;
414 	}
415 
416 	if (rt->rt_flags & RTF_GATEWAY)
417 		dst = (struct sockaddr_in6 *)rt->rt_gateway;
418 
419 	/*
420 	 * If we are to forward the packet using the same interface
421 	 * as one we got the packet from, perhaps we should send a redirect
422 	 * to sender to shortcut a hop.
423 	 * Only send redirect if source is sending directly to us,
424 	 * and if packet was not source routed (or has any options).
425 	 * Also, don't send redirect if forwarding using a route
426 	 * modified by a redirect.
427 	 */
428 	if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
429 	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
430 		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
431 			/*
432 			 * If the incoming interface is equal to the outgoing
433 			 * one, and the link attached to the interface is
434 			 * point-to-point, then it will be highly probable
435 			 * that a routing loop occurs. Thus, we immediately
436 			 * drop the packet and send an ICMPv6 error message.
437 			 *
438 			 * type/code is based on suggestion by Rich Draves.
439 			 * not sure if it is the best pick.
440 			 */
441 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
442 				    ICMP6_DST_UNREACH_ADDR, 0);
443 			goto bad;
444 		}
445 		type = ND_REDIRECT;
446 	}
447 
448 	/*
449 	 * Fake scoped addresses. Note that even link-local source or
450 	 * destinaion can appear, if the originating node just sends the
451 	 * packet to us (without address resolution for the destination).
452 	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
453 	 * link identifiers, we can do this stuff after making a copy for
454 	 * returning an error.
455 	 */
456 	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
457 		/*
458 		 * See corresponding comments in ip6_output.
459 		 * XXX: but is it possible that ip6_forward() sends a packet
460 		 *      to a loopback interface? I don't think so, and thus
461 		 *      I bark here. (jinmei@kame.net)
462 		 * XXX: it is common to route invalid packets to loopback.
463 		 *	also, the codepath will be visited on use of ::1 in
464 		 *	rthdr. (itojun)
465 		 */
466 #if 1
467 		if (0)
468 #else
469 		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
470 #endif
471 		{
472 			printf("ip6_forward: outgoing interface is loopback. "
473 			       "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
474 			       ip6_sprintf(ip6bufs, &ip6->ip6_src),
475 			       ip6_sprintf(ip6bufd, &ip6->ip6_dst),
476 			       ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
477 			       if_name(rt->rt_ifp));
478 		}
479 
480 		/* we can just use rcvif in forwarding. */
481 		origifp = m->m_pkthdr.rcvif;
482 	}
483 	else
484 		origifp = rt->rt_ifp;
485 	/*
486 	 * clear embedded scope identifiers if necessary.
487 	 * in6_clearscope will touch the addresses only when necessary.
488 	 */
489 	in6_clearscope(&ip6->ip6_src);
490 	in6_clearscope(&ip6->ip6_dst);
491 
492 	/* Jump over all PFIL processing if hooks are not active. */
493 	if (!PFIL_HOOKED(&V_inet6_pfil_hook))
494 		goto pass;
495 
496 	odst = ip6->ip6_dst;
497 	/* Run through list of hooks for output packets. */
498 	error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL);
499 	if (error != 0 || m == NULL)
500 		goto freecopy;		/* consumed by filter */
501 	ip6 = mtod(m, struct ip6_hdr *);
502 
503 	/* See if destination IP address was changed by packet filter. */
504 	if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
505 		m->m_flags |= M_SKIP_FIREWALL;
506 		/* If destination is now ourself drop to ip6_input(). */
507 		if (in6_localip(&ip6->ip6_dst))
508 			m->m_flags |= M_FASTFWD_OURS;
509 		else
510 			goto again;	/* Redo the routing table lookup. */
511 	}
512 
513 	/* See if local, if yes, send it to netisr. */
514 	if (m->m_flags & M_FASTFWD_OURS) {
515 		if (m->m_pkthdr.rcvif == NULL)
516 			m->m_pkthdr.rcvif = V_loif;
517 		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
518 			m->m_pkthdr.csum_flags |=
519 			    CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
520 			m->m_pkthdr.csum_data = 0xffff;
521 		}
522 #ifdef SCTP
523 		if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
524 			m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
525 #endif
526 		error = netisr_queue(NETISR_IPV6, m);
527 		goto out;
528 	}
529 	/* Or forward to some other address? */
530 	if ((m->m_flags & M_IP6_NEXTHOP) &&
531 	    (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
532 		dst = (struct sockaddr_in6 *)&rin6.ro_dst;
533 		bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in6));
534 		m->m_flags |= M_SKIP_FIREWALL;
535 		m->m_flags &= ~M_IP6_NEXTHOP;
536 		m_tag_delete(m, fwd_tag);
537 		goto again2;
538 	}
539 
540 pass:
541 	/* See if the size was changed by the packet filter. */
542 	if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
543 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
544 		if (mcopy) {
545 			u_long mtu;
546 #ifdef IPSEC
547 			size_t ipsechdrsiz;
548 #endif /* IPSEC */
549 
550 			mtu = IN6_LINKMTU(rt->rt_ifp);
551 #ifdef IPSEC
552 			/*
553 			 * When we do IPsec tunnel ingress, we need to play
554 			 * with the link value (decrement IPsec header size
555 			 * from mtu value).  The code is much simpler than v4
556 			 * case, as we have the outgoing interface for
557 			 * encapsulated packet as "rt->rt_ifp".
558 			 */
559 			ipsechdrsiz = ipsec_hdrsiz(mcopy, IPSEC_DIR_OUTBOUND,
560 			    NULL);
561 			if (ipsechdrsiz < mtu)
562 				mtu -= ipsechdrsiz;
563 			/*
564 			 * if mtu becomes less than minimum MTU,
565 			 * tell minimum MTU (and I'll need to fragment it).
566 			 */
567 			if (mtu < IPV6_MMTU)
568 				mtu = IPV6_MMTU;
569 #endif /* IPSEC */
570 			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
571 		}
572 		goto bad;
573 	}
574 
575 	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
576 	if (error) {
577 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
578 		IP6STAT_INC(ip6s_cantforward);
579 	} else {
580 		IP6STAT_INC(ip6s_forward);
581 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
582 		if (type)
583 			IP6STAT_INC(ip6s_redirectsent);
584 		else {
585 			if (mcopy)
586 				goto freecopy;
587 		}
588 	}
589 
590 	if (mcopy == NULL)
591 		goto out;
592 	switch (error) {
593 	case 0:
594 		if (type == ND_REDIRECT) {
595 			icmp6_redirect_output(mcopy, rt);
596 			goto out;
597 		}
598 		goto freecopy;
599 
600 	case EMSGSIZE:
601 		/* xxx MTU is constant in PPP? */
602 		goto freecopy;
603 
604 	case ENOBUFS:
605 		/* Tell source to slow down like source quench in IP? */
606 		goto freecopy;
607 
608 	case ENETUNREACH:	/* shouldn't happen, checked above */
609 	case EHOSTUNREACH:
610 	case ENETDOWN:
611 	case EHOSTDOWN:
612 	default:
613 		type = ICMP6_DST_UNREACH;
614 		code = ICMP6_DST_UNREACH_ADDR;
615 		break;
616 	}
617 	icmp6_error(mcopy, type, code, 0);
618 	goto out;
619 
620  freecopy:
621 	m_freem(mcopy);
622 	goto out;
623 bad:
624 	m_freem(m);
625 out:
626 	if (rt != NULL)
627 		RTFREE(rt);
628 }
629