sys/netinet6/ip6_forward.c

   1 /*      $FreeBSD$       */
   2 /*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $    */
   3
   4 /*-
   5  * Copyright (C) 1995, 1996, 1997, and 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 #include "opt_inet.h"
  34 #include "opt_inet6.h"
  35 #include "opt_ipsec.h"
  36 #include "opt_ipstealth.h"
  37
  38 #include <sys/param.h>
  39 #include <sys/systm.h>
  40 #include <sys/malloc.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/domain.h>
  43 #include <sys/protosw.h>
  44 #include <sys/socket.h>
  45 #include <sys/errno.h>
  46 #include <sys/time.h>
  47 #include <sys/kernel.h>
  48 #include <sys/syslog.h>
  49
  50 #include <net/if.h>
  51 #include <net/route.h>
  52 #include <net/pfil.h>
  53
  54 #include <netinet/in.h>
  55 #include <netinet/in_var.h>
  56 #include <netinet/in_systm.h>
  57 #include <netinet/ip.h>
  58 #include <netinet/ip_var.h>
  59 #include <netinet6/in6_var.h>
  60 #include <netinet/ip6.h>
  61 #include <netinet6/ip6_var.h>
  62 #include <netinet6/scope6_var.h>
  63 #include <netinet/icmp6.h>
  64 #include <netinet6/nd6.h>
  65
  66 #include <netinet/in_pcb.h>
  67
  68 #ifdef IPSEC
  69 #include <netinet6/ipsec.h>
  70 #ifdef INET6
  71 #include <netinet6/ipsec6.h>
  72 #endif
  73 #include <netkey/key.h>
  74 #endif /* IPSEC */
  75
  76 #ifdef FAST_IPSEC
  77 #include <netipsec/ipsec.h>
  78 #include <netipsec/ipsec6.h>
  79 #include <netipsec/key.h>
  80 #define IPSEC
  81 #endif /* FAST_IPSEC */
  82
  83 #include <net/net_osdep.h>
  84
  85 #include <netinet6/ip6protosw.h>
  86
  87 struct  route_in6 ip6_forward_rt;
  88
  89 /*
  90  * Forward a packet.  If some error occurs return the sender
  91  * an icmp packet.  Note we can't always generate a meaningful
  92  * icmp message because icmp doesn't have a large enough repertoire
  93  * of codes and types.
  94  *
  95  * If not forwarding, just drop the packet.  This could be confusing
  96  * if ipforwarding was zero but some routing protocol was advancing
  97  * us as a gateway to somewhere.  However, we must let the routing
  98  * protocol deal with that.
  99  *
 100  */
 101
 102 void
 103 ip6_forward(m, srcrt)
 104         struct mbuf *m;
 105         int srcrt;
 106 {
 107         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 108         struct sockaddr_in6 *dst = NULL;
 109         struct rtentry *rt = NULL;
 110         int error, type = 0, code = 0;
 111         struct mbuf *mcopy = NULL;
 112         struct ifnet *origifp;  /* maybe unnecessary */
 113         u_int32_t inzone, outzone;
 114         struct in6_addr src_in6, dst_in6;
 115 #ifdef IPSEC
 116         struct secpolicy *sp = NULL;
 117         int ipsecrt = 0;
 118 #endif
 119
 120         GIANT_REQUIRED; /* XXX bz: ip6_forward_rt */
 121
 122 #ifdef IPSEC
 123         /*
 124          * Check AH/ESP integrity.
 125          */
 126         /*
 127          * Don't increment ip6s_cantforward because this is the check
 128          * before forwarding packet actually.
 129          */
 130         if (ipsec6_in_reject(m, NULL)) {
 131 #if !defined(FAST_IPSEC)
 132                 ipsec6stat.in_polvio++;
 133 #endif
 134                 m_freem(m);
 135                 return;
 136         }
 137 #endif /* IPSEC */
 138
 139         /*
 140          * Do not forward packets to multicast destination (should be handled
 141          * by ip6_mforward().
 142          * Do not forward packets with unspecified source.  It was discussed
 143          * in July 2000, on the ipngwg mailing list.
 144          */
 145         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 146             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 147             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 148                 ip6stat.ip6s_cantforward++;
 149                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 150                 if (ip6_log_time + ip6_log_interval < time_second) {
 151                         ip6_log_time = time_second;
 152                         log(LOG_DEBUG,
 153                             "cannot forward "
 154                             "from %s to %s nxt %d received on %s\n",
 155                             ip6_sprintf(&ip6->ip6_src),
 156                             ip6_sprintf(&ip6->ip6_dst),
 157                             ip6->ip6_nxt,
 158                             if_name(m->m_pkthdr.rcvif));
 159                 }
 160                 m_freem(m);
 161                 return;
 162         }
 163
 164 #ifdef IPSTEALTH
 165         if (!ip6stealth) {
 166 #endif
 167         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 168                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 169                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 170                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 171                 return;
 172         }
 173         ip6->ip6_hlim -= IPV6_HLIMDEC;
 174
 175 #ifdef IPSTEALTH
 176         }
 177 #endif
 178
 179         /*
 180          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 181          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 182          * we need to generate an ICMP6 message to the src.
 183          * Thanks to M_EXT, in most cases copy will not occur.
 184          *
 185          * It is important to save it before IPsec processing as IPsec
 186          * processing may modify the mbuf.
 187          */
 188         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 189
 190 #ifdef IPSEC
 191         /* get a security policy for this packet */
 192         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
 193             IP_FORWARDING, &error);
 194         if (sp == NULL) {
 195                 ipsec6stat.out_inval++;
 196                 ip6stat.ip6s_cantforward++;
 197                 if (mcopy) {
 198 #if 0
 199                         /* XXX: what icmp ? */
 200 #else
 201                         m_freem(mcopy);
 202 #endif
 203                 }
 204                 m_freem(m);
 205                 return;
 206         }
 207
 208         error = 0;
 209
 210         /* check policy */
 211         switch (sp->policy) {
 212         case IPSEC_POLICY_DISCARD:
 213                 /*
 214                  * This packet is just discarded.
 215                  */
 216                 ipsec6stat.out_polvio++;
 217                 ip6stat.ip6s_cantforward++;
 218                 key_freesp(sp);
 219                 if (mcopy) {
 220 #if 0
 221                         /* XXX: what icmp ? */
 222 #else
 223                         m_freem(mcopy);
 224 #endif
 225                 }
 226                 m_freem(m);
 227                 return;
 228
 229         case IPSEC_POLICY_BYPASS:
 230         case IPSEC_POLICY_NONE:
 231                 /* no need to do IPsec. */
 232                 key_freesp(sp);
 233                 goto skip_ipsec;
 234
 235         case IPSEC_POLICY_IPSEC:
 236                 if (sp->req == NULL) {
 237                         /* XXX should be panic ? */
 238                         printf("ip6_forward: No IPsec request specified.\n");
 239                         ip6stat.ip6s_cantforward++;
 240                         key_freesp(sp);
 241                         if (mcopy) {
 242 #if 0
 243                                 /* XXX: what icmp ? */
 244 #else
 245                                 m_freem(mcopy);
 246 #endif
 247                         }
 248                         m_freem(m);
 249                         return;
 250                 }
 251                 /* do IPsec */
 252                 break;
 253
 254         case IPSEC_POLICY_ENTRUST:
 255         default:
 256                 /* should be panic ?? */
 257                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 258                 key_freesp(sp);
 259                 goto skip_ipsec;
 260         }
 261
 262     {
 263         struct ipsecrequest *isr = NULL;
 264         struct ipsec_output_state state;
 265
 266         /*
 267          * when the kernel forwards a packet, it is not proper to apply
 268          * IPsec transport mode to the packet is not proper.  this check
 269          * avoid from this.
 270          * at present, if there is even a transport mode SA request in the
 271          * security policy, the kernel does not apply IPsec to the packet.
 272          * this check is not enough because the following case is valid.
 273          *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
 274          */
 275         for (isr = sp->req; isr; isr = isr->next) {
 276                 if (isr->saidx.mode == IPSEC_MODE_ANY)
 277                         goto doipsectunnel;
 278                 if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
 279                         goto doipsectunnel;
 280         }
 281
 282         /*
 283          * if there's no need for tunnel mode IPsec, skip.
 284          */
 285         if (!isr)
 286                 goto skip_ipsec;
 287
 288     doipsectunnel:
 289         /*
 290          * All the extension headers will become inaccessible
 291          * (since they can be encrypted).
 292          * Don't panic, we need no more updates to extension headers
 293          * on inner IPv6 packet (since they are now encapsulated).
 294          *
 295          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 296          */
 297         bzero(&state, sizeof(state));
 298         state.m = m;
 299         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 300         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 301
 302         error = ipsec6_output_tunnel(&state, sp, 0);
 303
 304         m = state.m;
 305         key_freesp(sp);
 306
 307         if (error) {
 308                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 309                 switch (error) {
 310                 case EHOSTUNREACH:
 311                 case ENETUNREACH:
 312                 case EMSGSIZE:
 313                 case ENOBUFS:
 314                 case ENOMEM:
 315                         break;
 316                 default:
 317                         printf("ip6_output (ipsec): error code %d\n", error);
 318                         /* FALLTHROUGH */
 319                 case ENOENT:
 320                         /* don't show these error codes to the user */
 321                         break;
 322                 }
 323                 ip6stat.ip6s_cantforward++;
 324                 if (mcopy) {
 325 #if 0
 326                         /* XXX: what icmp ? */
 327 #else
 328                         m_freem(mcopy);
 329 #endif
 330                 }
 331                 m_freem(m);
 332                 return;
 333         }
 334
 335         if (ip6 != mtod(m, struct ip6_hdr *)) {
 336                 /*
 337                  * now tunnel mode headers are added.  we are originating
 338                  * packet instead of forwarding the packet.
 339                  */
 340                 ip6_output(m, NULL, NULL, IPV6_FORWARDING/*XXX*/, NULL, NULL,
 341                     NULL);
 342                 goto freecopy;
 343         }
 344
 345         /* adjust pointer */
 346         dst = (struct sockaddr_in6 *)state.dst;
 347         rt = state.ro ? state.ro->ro_rt : NULL;
 348         if (dst != NULL && rt != NULL)
 349                 ipsecrt = 1;
 350     }
 351     skip_ipsec:
 352 #endif /* IPSEC */
 353
 354 #ifdef IPSEC
 355         if (ipsecrt)
 356                 goto skip_routing;
 357 #endif
 358
 359         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 360         if (!srcrt) {
 361                 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
 362                 if (ip6_forward_rt.ro_rt == 0 ||
 363                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 364                         if (ip6_forward_rt.ro_rt) {
 365                                 RTFREE(ip6_forward_rt.ro_rt);
 366                                 ip6_forward_rt.ro_rt = 0;
 367                         }
 368
 369                         /* this probably fails but give it a try again */
 370                         rtalloc((struct route *)&ip6_forward_rt);
 371                 }
 372
 373                 if (ip6_forward_rt.ro_rt == 0) {
 374                         ip6stat.ip6s_noroute++;
 375                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 376                         if (mcopy) {
 377                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 378                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 379                         }
 380                         m_freem(m);
 381                         return;
 382                 }
 383         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 384                    !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 385                 if (ip6_forward_rt.ro_rt) {
 386                         RTFREE(ip6_forward_rt.ro_rt);
 387                         ip6_forward_rt.ro_rt = 0;
 388                 }
 389                 bzero(dst, sizeof(*dst));
 390                 dst->sin6_len = sizeof(struct sockaddr_in6);
 391                 dst->sin6_family = AF_INET6;
 392                 dst->sin6_addr = ip6->ip6_dst;
 393
 394                 rtalloc((struct route *)&ip6_forward_rt);
 395                 if (ip6_forward_rt.ro_rt == 0) {
 396                         ip6stat.ip6s_noroute++;
 397                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 398                         if (mcopy) {
 399                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 400                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 401                         }
 402                         m_freem(m);
 403                         return;
 404                 }
 405         }
 406         rt = ip6_forward_rt.ro_rt;
 407 #ifdef IPSEC
 408     skip_routing:;
 409 #endif
 410
 411         /*
 412          * Source scope check: if a packet can't be delivered to its
 413          * destination for the reason that the destination is beyond the scope
 414          * of the source address, discard the packet and return an icmp6
 415          * destination unreachable error with Code 2 (beyond scope of source
 416          * address).  We use a local copy of ip6_src, since in6_setscope()
 417          * will possibly modify its first argument.
 418          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
 419          */
 420         src_in6 = ip6->ip6_src;
 421         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
 422                 /* XXX: this should not happen */
 423                 ip6stat.ip6s_cantforward++;
 424                 ip6stat.ip6s_badscope++;
 425                 m_freem(m);
 426                 return;
 427         }
 428         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
 429                 ip6stat.ip6s_cantforward++;
 430                 ip6stat.ip6s_badscope++;
 431                 m_freem(m);
 432                 return;
 433         }
 434         if (inzone != outzone
 435 #ifdef IPSEC
 436             && !ipsecrt
 437 #endif
 438             ) {
 439                 ip6stat.ip6s_cantforward++;
 440                 ip6stat.ip6s_badscope++;
 441                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 442
 443                 if (ip6_log_time + ip6_log_interval < time_second) {
 444                         ip6_log_time = time_second;
 445                         log(LOG_DEBUG,
 446                             "cannot forward "
 447                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 448                             ip6_sprintf(&ip6->ip6_src),
 449                             ip6_sprintf(&ip6->ip6_dst),
 450                             ip6->ip6_nxt,
 451                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 452                 }
 453                 if (mcopy)
 454                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 455                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 456                 m_freem(m);
 457                 return;
 458         }
 459
 460         /*
 461          * Destination scope check: if a packet is going to break the scope
 462          * zone of packet's destination address, discard it.  This case should
 463          * usually be prevented by appropriately-configured routing table, but
 464          * we need an explicit check because we may mistakenly forward the
 465          * packet to a different zone by (e.g.) a default route.
 466          */
 467         dst_in6 = ip6->ip6_dst;
 468         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
 469             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
 470             inzone != outzone) {
 471                 ip6stat.ip6s_cantforward++;
 472                 ip6stat.ip6s_badscope++;
 473                 m_freem(m);
 474                 return;
 475         }
 476
 477         if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
 478                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 479                 if (mcopy) {
 480                         u_long mtu;
 481 #ifdef IPSEC
 482                         struct secpolicy *sp;
 483                         int ipsecerror;
 484                         size_t ipsechdrsiz;
 485 #endif
 486
 487                         mtu = IN6_LINKMTU(rt->rt_ifp);
 488 #ifdef IPSEC
 489                         /*
 490                          * When we do IPsec tunnel ingress, we need to play
 491                          * with the link value (decrement IPsec header size
 492                          * from mtu value).  The code is much simpler than v4
 493                          * case, as we have the outgoing interface for
 494                          * encapsulated packet as "rt->rt_ifp".
 495                          */
 496                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 497                                 IP_FORWARDING, &ipsecerror);
 498                         if (sp) {
 499                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 500                                         IPSEC_DIR_OUTBOUND, NULL);
 501                                 if (ipsechdrsiz < mtu)
 502                                         mtu -= ipsechdrsiz;
 503                         }
 504
 505                         /*
 506                          * if mtu becomes less than minimum MTU,
 507                          * tell minimum MTU (and I'll need to fragment it).
 508                          */
 509                         if (mtu < IPV6_MMTU)
 510                                 mtu = IPV6_MMTU;
 511 #endif
 512                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 513                 }
 514                 m_freem(m);
 515                 return;
 516         }
 517
 518         if (rt->rt_flags & RTF_GATEWAY)
 519                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 520
 521         /*
 522          * If we are to forward the packet using the same interface
 523          * as one we got the packet from, perhaps we should send a redirect
 524          * to sender to shortcut a hop.
 525          * Only send redirect if source is sending directly to us,
 526          * and if packet was not source routed (or has any options).
 527          * Also, don't send redirect if forwarding using a route
 528          * modified by a redirect.
 529          */
 530         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 531 #ifdef IPSEC
 532             !ipsecrt &&
 533 #endif
 534             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 535                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 536                         /*
 537                          * If the incoming interface is equal to the outgoing
 538                          * one, and the link attached to the interface is
 539                          * point-to-point, then it will be highly probable
 540                          * that a routing loop occurs. Thus, we immediately
 541                          * drop the packet and send an ICMPv6 error message.
 542                          *
 543                          * type/code is based on suggestion by Rich Draves.
 544                          * not sure if it is the best pick.
 545                          */
 546                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 547                                     ICMP6_DST_UNREACH_ADDR, 0);
 548                         m_freem(m);
 549                         return;
 550                 }
 551                 type = ND_REDIRECT;
 552         }
 553
 554         /*
 555          * Fake scoped addresses. Note that even link-local source or
 556          * destinaion can appear, if the originating node just sends the
 557          * packet to us (without address resolution for the destination).
 558          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 559          * link identifiers, we can do this stuff after making a copy for
 560          * returning an error.
 561          */
 562         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 563                 /*
 564                  * See corresponding comments in ip6_output.
 565                  * XXX: but is it possible that ip6_forward() sends a packet
 566                  *      to a loopback interface? I don't think so, and thus
 567                  *      I bark here. (jinmei@kame.net)
 568                  * XXX: it is common to route invalid packets to loopback.
 569                  *      also, the codepath will be visited on use of ::1 in
 570                  *      rthdr. (itojun)
 571                  */
 572 #if 1
 573                 if (0)
 574 #else
 575                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 576 #endif
 577                 {
 578                         printf("ip6_forward: outgoing interface is loopback. "
 579                                "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 580                                ip6_sprintf(&ip6->ip6_src),
 581                                ip6_sprintf(&ip6->ip6_dst),
 582                                ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 583                                if_name(rt->rt_ifp));
 584                 }
 585
 586                 /* we can just use rcvif in forwarding. */
 587                 origifp = m->m_pkthdr.rcvif;
 588         }
 589         else
 590                 origifp = rt->rt_ifp;
 591         /*
 592          * clear embedded scope identifiers if necessary.
 593          * in6_clearscope will touch the addresses only when necessary.
 594          */
 595         in6_clearscope(&ip6->ip6_src);
 596         in6_clearscope(&ip6->ip6_dst);
 597
 598         /* Jump over all PFIL processing if hooks are not active. */
 599         if (!PFIL_HOOKED(&inet6_pfil_hook))
 600                 goto pass;
 601
 602         /* Run through list of hooks for output packets. */
 603         error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL);
 604         if (error != 0)
 605                 goto senderr;
 606         if (m == NULL)
 607                 goto freecopy;
 608         ip6 = mtod(m, struct ip6_hdr *);
 609
 610 pass:
 611         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 612         if (error) {
 613                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 614                 ip6stat.ip6s_cantforward++;
 615         } else {
 616                 ip6stat.ip6s_forward++;
 617                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 618                 if (type)
 619                         ip6stat.ip6s_redirectsent++;
 620                 else {
 621                         if (mcopy)
 622                                 goto freecopy;
 623                 }
 624         }
 625
 626 senderr:
 627         if (mcopy == NULL)
 628                 return;
 629         switch (error) {
 630         case 0:
 631                 if (type == ND_REDIRECT) {
 632                         icmp6_redirect_output(mcopy, rt);
 633                         return;
 634                 }
 635                 goto freecopy;
 636
 637         case EMSGSIZE:
 638                 /* xxx MTU is constant in PPP? */
 639                 goto freecopy;
 640
 641         case ENOBUFS:
 642                 /* Tell source to slow down like source quench in IP? */
 643                 goto freecopy;
 644
 645         case ENETUNREACH:       /* shouldn't happen, checked above */
 646         case EHOSTUNREACH:
 647         case ENETDOWN:
 648         case EHOSTDOWN:
 649         default:
 650                 type = ICMP6_DST_UNREACH;
 651                 code = ICMP6_DST_UNREACH_ADDR;
 652                 break;
 653         }
 654         icmp6_error(mcopy, type, code, 0);
 655         return;
 656
 657  freecopy:
 658         m_freem(mcopy);
 659         return;
 660 }