xref: /freebsd/sys/netinet6/ip6_forward.c (revision 298f5fdc242b760e70cd3494e3a4f1f50b20664d)
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 <netipsec/ipsec.h>
75 #include <netipsec/ipsec6.h>
76 #include <netipsec/key.h>
77 #endif /* IPSEC */
78 
79 #include <netinet6/ip6protosw.h>
80 
81 /*
82  * Forward a packet.  If some error occurs return the sender
83  * an icmp packet.  Note we can't always generate a meaningful
84  * icmp message because icmp doesn't have a large enough repertoire
85  * of codes and types.
86  *
87  * If not forwarding, just drop the packet.  This could be confusing
88  * if ipforwarding was zero but some routing protocol was advancing
89  * us as a gateway to somewhere.  However, we must let the routing
90  * protocol deal with that.
91  *
92  */
93 void
94 ip6_forward(struct mbuf *m, int srcrt)
95 {
96 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
97 	struct sockaddr_in6 *dst = NULL;
98 	struct rtentry *rt = NULL;
99 	struct route_in6 rin6;
100 	int error, type = 0, code = 0;
101 	struct mbuf *mcopy = NULL;
102 	struct ifnet *origifp;	/* maybe unnecessary */
103 	u_int32_t inzone, outzone;
104 	struct in6_addr src_in6, dst_in6, odst;
105 #ifdef IPSEC
106 	struct secpolicy *sp = NULL;
107 #endif
108 #ifdef SCTP
109 	int sw_csum;
110 #endif
111 	struct m_tag *fwd_tag;
112 	char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
113 
114 #ifdef IPSEC
115 	/*
116 	 * Check AH/ESP integrity.
117 	 */
118 	/*
119 	 * Don't increment ip6s_cantforward because this is the check
120 	 * before forwarding packet actually.
121 	 */
122 	if (ipsec6_in_reject(m, NULL)) {
123 		IPSEC6STAT_INC(ips_in_polvio);
124 		m_freem(m);
125 		return;
126 	}
127 #endif /* IPSEC */
128 
129 	/*
130 	 * Do not forward packets to multicast destination (should be handled
131 	 * by ip6_mforward().
132 	 * Do not forward packets with unspecified source.  It was discussed
133 	 * in July 2000, on the ipngwg mailing list.
134 	 */
135 	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
136 	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
137 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
138 		IP6STAT_INC(ip6s_cantforward);
139 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
140 		if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
141 			V_ip6_log_time = time_uptime;
142 			log(LOG_DEBUG,
143 			    "cannot forward "
144 			    "from %s to %s nxt %d received on %s\n",
145 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
146 			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
147 			    ip6->ip6_nxt,
148 			    if_name(m->m_pkthdr.rcvif));
149 		}
150 		m_freem(m);
151 		return;
152 	}
153 
154 #ifdef IPSTEALTH
155 	if (!V_ip6stealth) {
156 #endif
157 	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
158 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
159 		icmp6_error(m, ICMP6_TIME_EXCEEDED,
160 				ICMP6_TIME_EXCEED_TRANSIT, 0);
161 		return;
162 	}
163 	ip6->ip6_hlim -= IPV6_HLIMDEC;
164 
165 #ifdef IPSTEALTH
166 	}
167 #endif
168 
169 	/*
170 	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
171 	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
172 	 * we need to generate an ICMP6 message to the src.
173 	 * Thanks to M_EXT, in most cases copy will not occur.
174 	 *
175 	 * It is important to save it before IPsec processing as IPsec
176 	 * processing may modify the mbuf.
177 	 */
178 	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
179 
180 #ifdef IPSEC
181 	/* get a security policy for this packet */
182 	sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
183 	    IP_FORWARDING, &error);
184 	if (sp == NULL) {
185 		IPSEC6STAT_INC(ips_out_inval);
186 		IP6STAT_INC(ip6s_cantforward);
187 		if (mcopy) {
188 #if 0
189 			/* XXX: what icmp ? */
190 #else
191 			m_freem(mcopy);
192 #endif
193 		}
194 		m_freem(m);
195 		return;
196 	}
197 
198 	error = 0;
199 
200 	/* check policy */
201 	switch (sp->policy) {
202 	case IPSEC_POLICY_DISCARD:
203 		/*
204 		 * This packet is just discarded.
205 		 */
206 		IPSEC6STAT_INC(ips_out_polvio);
207 		IP6STAT_INC(ip6s_cantforward);
208 		KEY_FREESP(&sp);
209 		if (mcopy) {
210 #if 0
211 			/* XXX: what icmp ? */
212 #else
213 			m_freem(mcopy);
214 #endif
215 		}
216 		m_freem(m);
217 		return;
218 
219 	case IPSEC_POLICY_BYPASS:
220 	case IPSEC_POLICY_NONE:
221 		/* no need to do IPsec. */
222 		KEY_FREESP(&sp);
223 		goto skip_ipsec;
224 
225 	case IPSEC_POLICY_IPSEC:
226 		if (sp->req == NULL) {
227 			/* XXX should be panic ? */
228 			printf("ip6_forward: No IPsec request specified.\n");
229 			IP6STAT_INC(ip6s_cantforward);
230 			KEY_FREESP(&sp);
231 			if (mcopy) {
232 #if 0
233 				/* XXX: what icmp ? */
234 #else
235 				m_freem(mcopy);
236 #endif
237 			}
238 			m_freem(m);
239 			return;
240 		}
241 		/* do IPsec */
242 		break;
243 
244 	case IPSEC_POLICY_ENTRUST:
245 	default:
246 		/* should be panic ?? */
247 		printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
248 		KEY_FREESP(&sp);
249 		goto skip_ipsec;
250 	}
251 
252     {
253 	struct ipsecrequest *isr = NULL;
254 
255 	/*
256 	 * when the kernel forwards a packet, it is not proper to apply
257 	 * IPsec transport mode to the packet is not proper.  this check
258 	 * avoid from this.
259 	 * at present, if there is even a transport mode SA request in the
260 	 * security policy, the kernel does not apply IPsec to the packet.
261 	 * this check is not enough because the following case is valid.
262 	 *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
263 	 */
264 	for (isr = sp->req; isr; isr = isr->next) {
265 		if (isr->saidx.mode == IPSEC_MODE_ANY)
266 			goto doipsectunnel;
267 		if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
268 			goto doipsectunnel;
269 	}
270 
271 	/*
272 	 * if there's no need for tunnel mode IPsec, skip.
273 	 */
274 	if (!isr)
275 		goto skip_ipsec;
276 
277     doipsectunnel:
278 	/*
279 	 * All the extension headers will become inaccessible
280 	 * (since they can be encrypted).
281 	 * Don't panic, we need no more updates to extension headers
282 	 * on inner IPv6 packet (since they are now encapsulated).
283 	 *
284 	 * IPv6 [ESP|AH] IPv6 [extension headers] payload
285 	 */
286 
287 	/*
288 	 * If we need to encapsulate the packet, do it here
289 	 * ipsec6_proces_packet will send the packet using ip6_output
290 	 */
291 	error = ipsec6_process_packet(m, sp->req);
292 
293 	KEY_FREESP(&sp);
294 
295 	if (error == EJUSTRETURN) {
296 		/*
297 		 * We had a SP with a level of 'use' and no SA. We
298 		 * will just continue to process the packet without
299 		 * IPsec processing.
300 		 */
301 		error = 0;
302 		goto skip_ipsec;
303 	}
304 
305 	if (error) {
306 		/* mbuf is already reclaimed in ipsec6_process_packet. */
307 		switch (error) {
308 		case EHOSTUNREACH:
309 		case ENETUNREACH:
310 		case EMSGSIZE:
311 		case ENOBUFS:
312 		case ENOMEM:
313 			break;
314 		default:
315 			printf("ip6_output (ipsec): error code %d\n", error);
316 			/* FALLTHROUGH */
317 		case ENOENT:
318 			/* don't show these error codes to the user */
319 			break;
320 		}
321 		IP6STAT_INC(ip6s_cantforward);
322 		if (mcopy) {
323 #if 0
324 			/* XXX: what icmp ? */
325 #else
326 			m_freem(mcopy);
327 #endif
328 		}
329 		return;
330 	} else {
331 		/*
332 		 * In the FAST IPSec case we have already
333 		 * re-injected the packet and it has been freed
334 		 * by the ipsec_done() function.  So, just clean
335 		 * up after ourselves.
336 		 */
337 		m = NULL;
338 		goto freecopy;
339 	}
340     }
341 skip_ipsec:
342 #endif
343 again:
344 	bzero(&rin6, sizeof(struct route_in6));
345 	dst = (struct sockaddr_in6 *)&rin6.ro_dst;
346 	dst->sin6_len = sizeof(struct sockaddr_in6);
347 	dst->sin6_family = AF_INET6;
348 	dst->sin6_addr = ip6->ip6_dst;
349 again2:
350 	rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m));
351 	if (rin6.ro_rt != NULL)
352 		RT_UNLOCK(rin6.ro_rt);
353 	else {
354 		IP6STAT_INC(ip6s_noroute);
355 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
356 		if (mcopy) {
357 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
358 			ICMP6_DST_UNREACH_NOROUTE, 0);
359 		}
360 		goto bad;
361 	}
362 	rt = rin6.ro_rt;
363 
364 	/*
365 	 * Source scope check: if a packet can't be delivered to its
366 	 * destination for the reason that the destination is beyond the scope
367 	 * of the source address, discard the packet and return an icmp6
368 	 * destination unreachable error with Code 2 (beyond scope of source
369 	 * address).  We use a local copy of ip6_src, since in6_setscope()
370 	 * will possibly modify its first argument.
371 	 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
372 	 */
373 	src_in6 = ip6->ip6_src;
374 	if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
375 		/* XXX: this should not happen */
376 		IP6STAT_INC(ip6s_cantforward);
377 		IP6STAT_INC(ip6s_badscope);
378 		goto bad;
379 	}
380 	if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
381 		IP6STAT_INC(ip6s_cantforward);
382 		IP6STAT_INC(ip6s_badscope);
383 		goto bad;
384 	}
385 	if (inzone != outzone) {
386 		IP6STAT_INC(ip6s_cantforward);
387 		IP6STAT_INC(ip6s_badscope);
388 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
389 
390 		if (V_ip6_log_time + V_ip6_log_interval < time_uptime) {
391 			V_ip6_log_time = time_uptime;
392 			log(LOG_DEBUG,
393 			    "cannot forward "
394 			    "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
395 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
396 			    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
397 			    ip6->ip6_nxt,
398 			    if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
399 		}
400 		if (mcopy)
401 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
402 				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
403 		goto bad;
404 	}
405 
406 	/*
407 	 * Destination scope check: if a packet is going to break the scope
408 	 * zone of packet's destination address, discard it.  This case should
409 	 * usually be prevented by appropriately-configured routing table, but
410 	 * we need an explicit check because we may mistakenly forward the
411 	 * packet to a different zone by (e.g.) a default route.
412 	 */
413 	dst_in6 = ip6->ip6_dst;
414 	if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
415 	    in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
416 	    inzone != outzone) {
417 		IP6STAT_INC(ip6s_cantforward);
418 		IP6STAT_INC(ip6s_badscope);
419 		goto bad;
420 	}
421 
422 	if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
423 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
424 		if (mcopy) {
425 			u_long mtu;
426 #ifdef IPSEC
427 			struct secpolicy *sp;
428 			int ipsecerror;
429 			size_t ipsechdrsiz;
430 #endif /* IPSEC */
431 
432 			mtu = IN6_LINKMTU(rt->rt_ifp);
433 #ifdef IPSEC
434 			/*
435 			 * When we do IPsec tunnel ingress, we need to play
436 			 * with the link value (decrement IPsec header size
437 			 * from mtu value).  The code is much simpler than v4
438 			 * case, as we have the outgoing interface for
439 			 * encapsulated packet as "rt->rt_ifp".
440 			 */
441 			sp = ipsec_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
442 				IP_FORWARDING, &ipsecerror);
443 			if (sp) {
444 				ipsechdrsiz = ipsec_hdrsiz(mcopy,
445 					IPSEC_DIR_OUTBOUND, NULL);
446 				if (ipsechdrsiz < mtu)
447 					mtu -= ipsechdrsiz;
448 			}
449 
450 			/*
451 			 * if mtu becomes less than minimum MTU,
452 			 * tell minimum MTU (and I'll need to fragment it).
453 			 */
454 			if (mtu < IPV6_MMTU)
455 				mtu = IPV6_MMTU;
456 #endif /* IPSEC */
457 			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
458 		}
459 		goto bad;
460 	}
461 
462 	if (rt->rt_flags & RTF_GATEWAY)
463 		dst = (struct sockaddr_in6 *)rt->rt_gateway;
464 
465 	/*
466 	 * If we are to forward the packet using the same interface
467 	 * as one we got the packet from, perhaps we should send a redirect
468 	 * to sender to shortcut a hop.
469 	 * Only send redirect if source is sending directly to us,
470 	 * and if packet was not source routed (or has any options).
471 	 * Also, don't send redirect if forwarding using a route
472 	 * modified by a redirect.
473 	 */
474 	if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
475 	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
476 		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
477 			/*
478 			 * If the incoming interface is equal to the outgoing
479 			 * one, and the link attached to the interface is
480 			 * point-to-point, then it will be highly probable
481 			 * that a routing loop occurs. Thus, we immediately
482 			 * drop the packet and send an ICMPv6 error message.
483 			 *
484 			 * type/code is based on suggestion by Rich Draves.
485 			 * not sure if it is the best pick.
486 			 */
487 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
488 				    ICMP6_DST_UNREACH_ADDR, 0);
489 			goto bad;
490 		}
491 		type = ND_REDIRECT;
492 	}
493 
494 	/*
495 	 * Fake scoped addresses. Note that even link-local source or
496 	 * destinaion can appear, if the originating node just sends the
497 	 * packet to us (without address resolution for the destination).
498 	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
499 	 * link identifiers, we can do this stuff after making a copy for
500 	 * returning an error.
501 	 */
502 	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
503 		/*
504 		 * See corresponding comments in ip6_output.
505 		 * XXX: but is it possible that ip6_forward() sends a packet
506 		 *      to a loopback interface? I don't think so, and thus
507 		 *      I bark here. (jinmei@kame.net)
508 		 * XXX: it is common to route invalid packets to loopback.
509 		 *	also, the codepath will be visited on use of ::1 in
510 		 *	rthdr. (itojun)
511 		 */
512 #if 1
513 		if (0)
514 #else
515 		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
516 #endif
517 		{
518 			printf("ip6_forward: outgoing interface is loopback. "
519 			       "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
520 			       ip6_sprintf(ip6bufs, &ip6->ip6_src),
521 			       ip6_sprintf(ip6bufd, &ip6->ip6_dst),
522 			       ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
523 			       if_name(rt->rt_ifp));
524 		}
525 
526 		/* we can just use rcvif in forwarding. */
527 		origifp = m->m_pkthdr.rcvif;
528 	}
529 	else
530 		origifp = rt->rt_ifp;
531 	/*
532 	 * clear embedded scope identifiers if necessary.
533 	 * in6_clearscope will touch the addresses only when necessary.
534 	 */
535 	in6_clearscope(&ip6->ip6_src);
536 	in6_clearscope(&ip6->ip6_dst);
537 
538 	/* Jump over all PFIL processing if hooks are not active. */
539 	if (!PFIL_HOOKED(&V_inet6_pfil_hook))
540 		goto pass;
541 
542 	odst = ip6->ip6_dst;
543 	/* Run through list of hooks for output packets. */
544 	error = pfil_run_hooks(&V_inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL);
545 	if (error != 0 || m == NULL)
546 		goto freecopy;		/* consumed by filter */
547 	ip6 = mtod(m, struct ip6_hdr *);
548 
549 	/* See if destination IP address was changed by packet filter. */
550 	if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) {
551 		m->m_flags |= M_SKIP_FIREWALL;
552 		/* If destination is now ourself drop to ip6_input(). */
553 		if (in6_localip(&ip6->ip6_dst)) {
554 			m->m_flags |= M_FASTFWD_OURS;
555 			if (m->m_pkthdr.rcvif == NULL)
556 				m->m_pkthdr.rcvif = V_loif;
557 			if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
558 				m->m_pkthdr.csum_flags |=
559 				    CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
560 				m->m_pkthdr.csum_data = 0xffff;
561 			}
562 #ifdef SCTP
563 			if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
564 				m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
565 #endif
566 			error = netisr_queue(NETISR_IPV6, m);
567 			goto out;
568 		} else
569 			goto again;	/* Redo the routing table lookup. */
570 	}
571 
572 	/* See if local, if yes, send it to netisr. */
573 	if (m->m_flags & M_FASTFWD_OURS) {
574 		if (m->m_pkthdr.rcvif == NULL)
575 			m->m_pkthdr.rcvif = V_loif;
576 		if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) {
577 			m->m_pkthdr.csum_flags |=
578 			    CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR;
579 			m->m_pkthdr.csum_data = 0xffff;
580 		}
581 #ifdef SCTP
582 		if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6)
583 			m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID;
584 #endif
585 		error = netisr_queue(NETISR_IPV6, m);
586 		goto out;
587 	}
588 	/* Or forward to some other address? */
589 	if ((m->m_flags & M_IP6_NEXTHOP) &&
590 	    (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
591 		dst = (struct sockaddr_in6 *)&rin6.ro_dst;
592 		bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in6));
593 		m->m_flags |= M_SKIP_FIREWALL;
594 		m->m_flags &= ~M_IP6_NEXTHOP;
595 		m_tag_delete(m, fwd_tag);
596 		goto again2;
597 	}
598 
599 pass:
600 	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
601 	if (error) {
602 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
603 		IP6STAT_INC(ip6s_cantforward);
604 	} else {
605 		IP6STAT_INC(ip6s_forward);
606 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
607 		if (type)
608 			IP6STAT_INC(ip6s_redirectsent);
609 		else {
610 			if (mcopy)
611 				goto freecopy;
612 		}
613 	}
614 
615 	if (mcopy == NULL)
616 		goto out;
617 	switch (error) {
618 	case 0:
619 		if (type == ND_REDIRECT) {
620 			icmp6_redirect_output(mcopy, rt);
621 			goto out;
622 		}
623 		goto freecopy;
624 
625 	case EMSGSIZE:
626 		/* xxx MTU is constant in PPP? */
627 		goto freecopy;
628 
629 	case ENOBUFS:
630 		/* Tell source to slow down like source quench in IP? */
631 		goto freecopy;
632 
633 	case ENETUNREACH:	/* shouldn't happen, checked above */
634 	case EHOSTUNREACH:
635 	case ENETDOWN:
636 	case EHOSTDOWN:
637 	default:
638 		type = ICMP6_DST_UNREACH;
639 		code = ICMP6_DST_UNREACH_ADDR;
640 		break;
641 	}
642 	icmp6_error(mcopy, type, code, 0);
643 	goto out;
644 
645  freecopy:
646 	m_freem(mcopy);
647 	goto out;
648 bad:
649 	m_freem(m);
650 out:
651 	if (rt != NULL)
652 		RTFREE(rt);
653 }
654