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sys/netinet6/ip6_forward.c

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  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: src/sys/netinet6/ip6_forward.c,v 1.46 2008/12/02 21:37:28 bz Exp $");
 34 
 35 #include "opt_inet.h"
 36 #include "opt_inet6.h"
 37 #include "opt_ipsec.h"
 38 #include "opt_ipstealth.h"
 39 
 40 #include <sys/param.h>
 41 #include <sys/systm.h>
 42 #include <sys/malloc.h>
 43 #include <sys/mbuf.h>
 44 #include <sys/domain.h>
 45 #include <sys/protosw.h>
 46 #include <sys/socket.h>
 47 #include <sys/errno.h>
 48 #include <sys/time.h>
 49 #include <sys/kernel.h>
 50 #include <sys/syslog.h>
 51 #include <sys/vimage.h>
 52 
 53 #include <net/if.h>
 54 #include <net/route.h>
 55 #include <net/pfil.h>
 56 
 57 #include <netinet/in.h>
 58 #include <netinet/in_var.h>
 59 #include <netinet/in_systm.h>
 60 #include <netinet/ip.h>
 61 #include <netinet/ip_var.h>
 62 #include <netinet6/in6_var.h>
 63 #include <netinet/ip6.h>
 64 #include <netinet6/ip6_var.h>
 65 #include <netinet6/scope6_var.h>
 66 #include <netinet/icmp6.h>
 67 #include <netinet6/nd6.h>
 68 #include <netinet6/vinet6.h>
 69 
 70 #include <netinet/in_pcb.h>
 71 
 72 #ifdef IPSEC
 73 #include <netipsec/ipsec.h>
 74 #include <netipsec/ipsec6.h>
 75 #include <netipsec/key.h>
 76 #endif /* IPSEC */
 77 
 78 #include <netinet6/ip6protosw.h>
 79 
 80 #ifdef VIMAGE_GLOBALS
 81 struct  route_in6 ip6_forward_rt;
 82 #endif
 83 
 84 /*
 85  * Forward a packet.  If some error occurs return the sender
 86  * an icmp packet.  Note we can't always generate a meaningful
 87  * icmp message because icmp doesn't have a large enough repertoire
 88  * of codes and types.
 89  *
 90  * If not forwarding, just drop the packet.  This could be confusing
 91  * if ipforwarding was zero but some routing protocol was advancing
 92  * us as a gateway to somewhere.  However, we must let the routing
 93  * protocol deal with that.
 94  *
 95  */
 96 void
 97 ip6_forward(struct mbuf *m, int srcrt)
 98 {
 99         INIT_VNET_INET6(curvnet);
100         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
101         struct sockaddr_in6 *dst = NULL;
102         struct rtentry *rt = NULL;
103         int error, type = 0, code = 0;
104         struct mbuf *mcopy = NULL;
105         struct ifnet *origifp;  /* maybe unnecessary */
106         u_int32_t inzone, outzone;
107         struct in6_addr src_in6, dst_in6;
108 #ifdef IPSEC
109         INIT_VNET_IPSEC(curvnet);
110         struct secpolicy *sp = NULL;
111         int ipsecrt = 0;
112 #endif
113         char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
114 
115         /* GIANT_REQUIRED; */ /* XXX bz: ip6_forward_rt */
116 
117 #ifdef IPSEC
118         /*
119          * Check AH/ESP integrity.
120          */
121         /*
122          * Don't increment ip6s_cantforward because this is the check
123          * before forwarding packet actually.
124          */
125         if (ipsec6_in_reject(m, NULL)) {
126                 V_ipsec6stat.in_polvio++;
127                 m_freem(m);
128                 return;
129         }
130 #endif /* IPSEC */
131 
132         /*
133          * Do not forward packets to multicast destination (should be handled
134          * by ip6_mforward().
135          * Do not forward packets with unspecified source.  It was discussed
136          * in July 2000, on the ipngwg mailing list.
137          */
138         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
139             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
140             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
141                 V_ip6stat.ip6s_cantforward++;
142                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
143                 if (V_ip6_log_time + V_ip6_log_interval < time_second) {
144                         V_ip6_log_time = time_second;
145                         log(LOG_DEBUG,
146                             "cannot forward "
147                             "from %s to %s nxt %d received on %s\n",
148                             ip6_sprintf(ip6bufs, &ip6->ip6_src),
149                             ip6_sprintf(ip6bufd, &ip6->ip6_dst),
150                             ip6->ip6_nxt,
151                             if_name(m->m_pkthdr.rcvif));
152                 }
153                 m_freem(m);
154                 return;
155         }
156 
157 #ifdef IPSTEALTH
158         if (!V_ip6stealth) {
159 #endif
160         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
161                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
162                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
163                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
164                 return;
165         }
166         ip6->ip6_hlim -= IPV6_HLIMDEC;
167 
168 #ifdef IPSTEALTH
169         }
170 #endif
171 
172         /*
173          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
174          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
175          * we need to generate an ICMP6 message to the src.
176          * Thanks to M_EXT, in most cases copy will not occur.
177          *
178          * It is important to save it before IPsec processing as IPsec
179          * processing may modify the mbuf.
180          */
181         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
182 
183 #ifdef IPSEC
184         /* get a security policy for this packet */
185         sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
186             IP_FORWARDING, &error);
187         if (sp == NULL) {
188                 V_ipsec6stat.out_inval++;
189                 V_ip6stat.ip6s_cantforward++;
190                 if (mcopy) {
191 #if 0
192                         /* XXX: what icmp ? */
193 #else
194                         m_freem(mcopy);
195 #endif
196                 }
197                 m_freem(m);
198                 return;
199         }
200 
201         error = 0;
202 
203         /* check policy */
204         switch (sp->policy) {
205         case IPSEC_POLICY_DISCARD:
206                 /*
207                  * This packet is just discarded.
208                  */
209                 V_ipsec6stat.out_polvio++;
210                 V_ip6stat.ip6s_cantforward++;
211                 KEY_FREESP(&sp);
212                 if (mcopy) {
213 #if 0
214                         /* XXX: what icmp ? */
215 #else
216                         m_freem(mcopy);
217 #endif
218                 }
219                 m_freem(m);
220                 return;
221 
222         case IPSEC_POLICY_BYPASS:
223         case IPSEC_POLICY_NONE:
224                 /* no need to do IPsec. */
225                 KEY_FREESP(&sp);
226                 goto skip_ipsec;
227 
228         case IPSEC_POLICY_IPSEC:
229                 if (sp->req == NULL) {
230                         /* XXX should be panic ? */
231                         printf("ip6_forward: No IPsec request specified.\n");
232                         V_ip6stat.ip6s_cantforward++;
233                         KEY_FREESP(&sp);
234                         if (mcopy) {
235 #if 0
236                                 /* XXX: what icmp ? */
237 #else
238                                 m_freem(mcopy);
239 #endif
240                         }
241                         m_freem(m);
242                         return;
243                 }
244                 /* do IPsec */
245                 break;
246 
247         case IPSEC_POLICY_ENTRUST:
248         default:
249                 /* should be panic ?? */
250                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
251                 KEY_FREESP(&sp);
252                 goto skip_ipsec;
253         }
254 
255     {
256         struct ipsecrequest *isr = NULL;
257         struct ipsec_output_state state;
258 
259         /*
260          * when the kernel forwards a packet, it is not proper to apply
261          * IPsec transport mode to the packet is not proper.  this check
262          * avoid from this.
263          * at present, if there is even a transport mode SA request in the
264          * security policy, the kernel does not apply IPsec to the packet.
265          * this check is not enough because the following case is valid.
266          *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
267          */
268         for (isr = sp->req; isr; isr = isr->next) {
269                 if (isr->saidx.mode == IPSEC_MODE_ANY)
270                         goto doipsectunnel;
271                 if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
272                         goto doipsectunnel;
273         }
274 
275         /*
276          * if there's no need for tunnel mode IPsec, skip.
277          */
278         if (!isr)
279                 goto skip_ipsec;
280 
281     doipsectunnel:
282         /*
283          * All the extension headers will become inaccessible
284          * (since they can be encrypted).
285          * Don't panic, we need no more updates to extension headers
286          * on inner IPv6 packet (since they are now encapsulated).
287          *
288          * IPv6 [ESP|AH] IPv6 [extension headers] payload
289          */
290         bzero(&state, sizeof(state));
291         state.m = m;
292         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
293         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
294 
295         error = ipsec6_output_tunnel(&state, sp, 0);
296 
297         m = state.m;
298         KEY_FREESP(&sp);
299 
300         if (error) {
301                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
302                 switch (error) {
303                 case EHOSTUNREACH:
304                 case ENETUNREACH:
305                 case EMSGSIZE:
306                 case ENOBUFS:
307                 case ENOMEM:
308                         break;
309                 default:
310                         printf("ip6_output (ipsec): error code %d\n", error);
311                         /* FALLTHROUGH */
312                 case ENOENT:
313                         /* don't show these error codes to the user */
314                         break;
315                 }
316                 V_ip6stat.ip6s_cantforward++;
317                 if (mcopy) {
318 #if 0
319                         /* XXX: what icmp ? */
320 #else
321                         m_freem(mcopy);
322 #endif
323                 }
324                 m_freem(m);
325                 return;
326         } else {
327                 /*
328                  * In the FAST IPSec case we have already
329                  * re-injected the packet and it has been freed
330                  * by the ipsec_done() function.  So, just clean
331                  * up after ourselves.
332                  */
333                 m = NULL;
334                 goto freecopy;
335         }
336 
337         if ((m != NULL) && (ip6 != mtod(m, struct ip6_hdr *)) ){
338                 /*
339                  * now tunnel mode headers are added.  we are originating
340                  * packet instead of forwarding the packet.
341                  */
342                 ip6_output(m, NULL, NULL, IPV6_FORWARDING/*XXX*/, NULL, NULL,
343                     NULL);
344                 goto freecopy;
345         }
346 
347         /* adjust pointer */
348         dst = (struct sockaddr_in6 *)state.dst;
349         rt = state.ro ? state.ro->ro_rt : NULL;
350         if (dst != NULL && rt != NULL)
351                 ipsecrt = 1;
352     }
353     skip_ipsec:
354 #endif /* IPSEC */
355 
356 #ifdef IPSEC
357         if (ipsecrt)
358                 goto skip_routing;
359 #endif
360 
361         dst = (struct sockaddr_in6 *)&V_ip6_forward_rt.ro_dst;
362         if (!srcrt) {
363                 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
364                 if (V_ip6_forward_rt.ro_rt == 0 ||
365                     (V_ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
366                         if (V_ip6_forward_rt.ro_rt) {
367                                 RTFREE(V_ip6_forward_rt.ro_rt);
368                                 V_ip6_forward_rt.ro_rt = 0;
369                         }
370 
371                         /* this probably fails but give it a try again */
372                         rtalloc((struct route *)&V_ip6_forward_rt);
373                 }
374 
375                 if (V_ip6_forward_rt.ro_rt == 0) {
376                         V_ip6stat.ip6s_noroute++;
377                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
378                         if (mcopy) {
379                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
380                                             ICMP6_DST_UNREACH_NOROUTE, 0);
381                         }
382                         m_freem(m);
383                         return;
384                 }
385         } else if ((rt = V_ip6_forward_rt.ro_rt) == 0 ||
386                    !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
387                 if (V_ip6_forward_rt.ro_rt) {
388                         RTFREE(V_ip6_forward_rt.ro_rt);
389                         V_ip6_forward_rt.ro_rt = 0;
390                 }
391                 bzero(dst, sizeof(*dst));
392                 dst->sin6_len = sizeof(struct sockaddr_in6);
393                 dst->sin6_family = AF_INET6;
394                 dst->sin6_addr = ip6->ip6_dst;
395 
396                 rtalloc((struct route *)&V_ip6_forward_rt);
397                 if (V_ip6_forward_rt.ro_rt == 0) {
398                         V_ip6stat.ip6s_noroute++;
399                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
400                         if (mcopy) {
401                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
402                                             ICMP6_DST_UNREACH_NOROUTE, 0);
403                         }
404                         m_freem(m);
405                         return;
406                 }
407         }
408         rt = V_ip6_forward_rt.ro_rt;
409 #ifdef IPSEC
410     skip_routing:;
411 #endif
412 
413         /*
414          * Source scope check: if a packet can't be delivered to its
415          * destination for the reason that the destination is beyond the scope
416          * of the source address, discard the packet and return an icmp6
417          * destination unreachable error with Code 2 (beyond scope of source
418          * address).  We use a local copy of ip6_src, since in6_setscope()
419          * will possibly modify its first argument.
420          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
421          */
422         src_in6 = ip6->ip6_src;
423         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
424                 /* XXX: this should not happen */
425                 V_ip6stat.ip6s_cantforward++;
426                 V_ip6stat.ip6s_badscope++;
427                 m_freem(m);
428                 return;
429         }
430         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
431                 V_ip6stat.ip6s_cantforward++;
432                 V_ip6stat.ip6s_badscope++;
433                 m_freem(m);
434                 return;
435         }
436         if (inzone != outzone
437 #ifdef IPSEC
438             && !ipsecrt
439 #endif
440             ) {
441                 V_ip6stat.ip6s_cantforward++;
442                 V_ip6stat.ip6s_badscope++;
443                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
444 
445                 if (V_ip6_log_time + V_ip6_log_interval < time_second) {
446                         V_ip6_log_time = time_second;
447                         log(LOG_DEBUG,
448                             "cannot forward "
449                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
450                             ip6_sprintf(ip6bufs, &ip6->ip6_src),
451                             ip6_sprintf(ip6bufd, &ip6->ip6_dst),
452                             ip6->ip6_nxt,
453                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
454                 }
455                 if (mcopy)
456                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
457                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
458                 m_freem(m);
459                 return;
460         }
461 
462         /*
463          * Destination scope check: if a packet is going to break the scope
464          * zone of packet's destination address, discard it.  This case should
465          * usually be prevented by appropriately-configured routing table, but
466          * we need an explicit check because we may mistakenly forward the
467          * packet to a different zone by (e.g.) a default route.
468          */
469         dst_in6 = ip6->ip6_dst;
470         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
471             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
472             inzone != outzone) {
473                 V_ip6stat.ip6s_cantforward++;
474                 V_ip6stat.ip6s_badscope++;
475                 m_freem(m);
476                 return;
477         }
478 
479         if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
480                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
481                 if (mcopy) {
482                         u_long mtu;
483 #ifdef IPSEC
484                         struct secpolicy *sp;
485                         int ipsecerror;
486                         size_t ipsechdrsiz;
487 #endif /* IPSEC */
488 
489                         mtu = IN6_LINKMTU(rt->rt_ifp);
490 #ifdef IPSEC
491                         /*
492                          * When we do IPsec tunnel ingress, we need to play
493                          * with the link value (decrement IPsec header size
494                          * from mtu value).  The code is much simpler than v4
495                          * case, as we have the outgoing interface for
496                          * encapsulated packet as "rt->rt_ifp".
497                          */
498                         sp = ipsec_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
499                                 IP_FORWARDING, &ipsecerror);
500                         if (sp) {
501                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
502                                         IPSEC_DIR_OUTBOUND, NULL);
503                                 if (ipsechdrsiz < mtu)
504                                         mtu -= ipsechdrsiz;
505                         }
506 
507                         /*
508                          * if mtu becomes less than minimum MTU,
509                          * tell minimum MTU (and I'll need to fragment it).
510                          */
511                         if (mtu < IPV6_MMTU)
512                                 mtu = IPV6_MMTU;
513 #endif /* IPSEC */
514                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
515                 }
516                 m_freem(m);
517                 return;
518         }
519 
520         if (rt->rt_flags & RTF_GATEWAY)
521                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
522 
523         /*
524          * If we are to forward the packet using the same interface
525          * as one we got the packet from, perhaps we should send a redirect
526          * to sender to shortcut a hop.
527          * Only send redirect if source is sending directly to us,
528          * and if packet was not source routed (or has any options).
529          * Also, don't send redirect if forwarding using a route
530          * modified by a redirect.
531          */
532         if (V_ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
533 #ifdef IPSEC
534             !ipsecrt &&
535 #endif /* IPSEC */
536             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
537                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
538                         /*
539                          * If the incoming interface is equal to the outgoing
540                          * one, and the link attached to the interface is
541                          * point-to-point, then it will be highly probable
542                          * that a routing loop occurs. Thus, we immediately
543                          * drop the packet and send an ICMPv6 error message.
544                          *
545                          * type/code is based on suggestion by Rich Draves.
546                          * not sure if it is the best pick.
547                          */
548                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
549                                     ICMP6_DST_UNREACH_ADDR, 0);
550                         m_freem(m);
551                         return;
552                 }
553                 type = ND_REDIRECT;
554         }
555 
556         /*
557          * Fake scoped addresses. Note that even link-local source or
558          * destinaion can appear, if the originating node just sends the
559          * packet to us (without address resolution for the destination).
560          * Since both icmp6_error and icmp6_redirect_output fill the embedded
561          * link identifiers, we can do this stuff after making a copy for
562          * returning an error.
563          */
564         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
565                 /*
566                  * See corresponding comments in ip6_output.
567                  * XXX: but is it possible that ip6_forward() sends a packet
568                  *      to a loopback interface? I don't think so, and thus
569                  *      I bark here. (jinmei@kame.net)
570                  * XXX: it is common to route invalid packets to loopback.
571                  *      also, the codepath will be visited on use of ::1 in
572                  *      rthdr. (itojun)
573                  */
574 #if 1
575                 if (0)
576 #else
577                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
578 #endif
579                 {
580                         printf("ip6_forward: outgoing interface is loopback. "
581                                "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
582                                ip6_sprintf(ip6bufs, &ip6->ip6_src),
583                                ip6_sprintf(ip6bufd, &ip6->ip6_dst),
584                                ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
585                                if_name(rt->rt_ifp));
586                 }
587 
588                 /* we can just use rcvif in forwarding. */
589                 origifp = m->m_pkthdr.rcvif;
590         }
591         else
592                 origifp = rt->rt_ifp;
593         /*
594          * clear embedded scope identifiers if necessary.
595          * in6_clearscope will touch the addresses only when necessary.
596          */
597         in6_clearscope(&ip6->ip6_src);
598         in6_clearscope(&ip6->ip6_dst);
599 
600         /* Jump over all PFIL processing if hooks are not active. */
601         if (!PFIL_HOOKED(&inet6_pfil_hook))
602                 goto pass;
603 
604         /* Run through list of hooks for output packets. */
605         error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL);
606         if (error != 0)
607                 goto senderr;
608         if (m == NULL)
609                 goto freecopy;
610         ip6 = mtod(m, struct ip6_hdr *);
611 
612 pass:
613         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
614         if (error) {
615                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
616                 V_ip6stat.ip6s_cantforward++;
617         } else {
618                 V_ip6stat.ip6s_forward++;
619                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
620                 if (type)
621                         V_ip6stat.ip6s_redirectsent++;
622                 else {
623                         if (mcopy)
624                                 goto freecopy;
625                 }
626         }
627 
628 senderr:
629         if (mcopy == NULL)
630                 return;
631         switch (error) {
632         case 0:
633                 if (type == ND_REDIRECT) {
634                         icmp6_redirect_output(mcopy, rt);
635                         return;
636                 }
637                 goto freecopy;
638 
639         case EMSGSIZE:
640                 /* xxx MTU is constant in PPP? */
641                 goto freecopy;
642 
643         case ENOBUFS:
644                 /* Tell source to slow down like source quench in IP? */
645                 goto freecopy;
646 
647         case ENETUNREACH:       /* shouldn't happen, checked above */
648         case EHOSTUNREACH:
649         case ENETDOWN:
650         case EHOSTDOWN:
651         default:
652                 type = ICMP6_DST_UNREACH;
653                 code = ICMP6_DST_UNREACH_ADDR;
654                 break;
655         }
656         icmp6_error(mcopy, type, code, 0);
657         return;
658 
659  freecopy:
660         m_freem(mcopy);
661         return;
662 }
663 

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