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_ip6fw.h"
  34 #include "opt_inet.h"
  35 #include "opt_inet6.h"
  36 #include "opt_ipsec.h"
  37 #include "opt_ipstealth.h"
  38
  39 #include <sys/param.h>
  40 #include <sys/systm.h>
  41 #include <sys/malloc.h>
  42 #include <sys/mbuf.h>
  43 #include <sys/domain.h>
  44 #include <sys/protosw.h>
  45 #include <sys/socket.h>
  46 #include <sys/errno.h>
  47 #include <sys/time.h>
  48 #include <sys/kernel.h>
  49 #include <sys/syslog.h>
  50
  51 #include <net/if.h>
  52 #include <net/route.h>
  53 #include <net/pfil.h>
  54
  55 #include <netinet/in.h>
  56 #include <netinet/in_var.h>
  57 #include <netinet/in_systm.h>
  58 #include <netinet/ip.h>
  59 #include <netinet/ip_var.h>
  60 #include <netinet6/in6_var.h>
  61 #include <netinet/ip6.h>
  62 #include <netinet6/ip6_var.h>
  63 #include <netinet6/scope6_var.h>
  64 #include <netinet/icmp6.h>
  65 #include <netinet6/nd6.h>
  66
  67 #include <netinet/in_pcb.h>
  68
  69 #ifdef IPSEC
  70 #include <netinet6/ipsec.h>
  71 #ifdef INET6
  72 #include <netinet6/ipsec6.h>
  73 #endif
  74 #include <netkey/key.h>
  75 #endif /* IPSEC */
  76
  77 #ifdef FAST_IPSEC
  78 #include <netipsec/ipsec.h>
  79 #include <netipsec/ipsec6.h>
  80 #include <netipsec/key.h>
  81 #define IPSEC
  82 #endif /* FAST_IPSEC */
  83
  84 #include <netinet6/ip6_fw.h>
  85
  86 #include <net/net_osdep.h>
  87
  88 #include <netinet6/ip6protosw.h>
  89
  90 struct  route_in6 ip6_forward_rt;
  91
  92 /*
  93  * Forward a packet.  If some error occurs return the sender
  94  * an icmp packet.  Note we can't always generate a meaningful
  95  * icmp message because icmp doesn't have a large enough repertoire
  96  * of codes and types.
  97  *
  98  * If not forwarding, just drop the packet.  This could be confusing
  99  * if ipforwarding was zero but some routing protocol was advancing
 100  * us as a gateway to somewhere.  However, we must let the routing
 101  * protocol deal with that.
 102  *
 103  */
 104
 105 void
 106 ip6_forward(m, srcrt)
 107         struct mbuf *m;
 108         int srcrt;
 109 {
 110         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 111         struct sockaddr_in6 *dst = NULL;
 112         struct rtentry *rt = NULL;
 113         int error, type = 0, code = 0;
 114         struct mbuf *mcopy = NULL;
 115         struct ifnet *origifp;  /* maybe unnecessary */
 116         u_int32_t inzone, outzone;
 117         struct in6_addr src_in6, dst_in6;
 118 #ifdef IPSEC
 119         struct secpolicy *sp = NULL;
 120         int ipsecrt = 0;
 121 #endif
 122
 123 #ifdef IPSEC
 124         /*
 125          * Check AH/ESP integrity.
 126          */
 127         /*
 128          * Don't increment ip6s_cantforward because this is the check
 129          * before forwarding packet actually.
 130          */
 131         if (ipsec6_in_reject(m, NULL)) {
 132 #if !defined(FAST_IPSEC)
 133                 ipsec6stat.in_polvio++;
 134 #endif
 135                 m_freem(m);
 136                 return;
 137         }
 138 #endif /* IPSEC */
 139
 140         /*
 141          * Do not forward packets to multicast destination (should be handled
 142          * by ip6_mforward().
 143          * Do not forward packets with unspecified source.  It was discussed
 144          * in July 2000, on the ipngwg mailing list.
 145          */
 146         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 147             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 148             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 149                 ip6stat.ip6s_cantforward++;
 150                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 151                 if (ip6_log_time + ip6_log_interval < time_second) {
 152                         ip6_log_time = time_second;
 153                         log(LOG_DEBUG,
 154                             "cannot forward "
 155                             "from %s to %s nxt %d received on %s\n",
 156                             ip6_sprintf(&ip6->ip6_src),
 157                             ip6_sprintf(&ip6->ip6_dst),
 158                             ip6->ip6_nxt,
 159                             if_name(m->m_pkthdr.rcvif));
 160                 }
 161                 m_freem(m);
 162                 return;
 163         }
 164
 165 #ifdef IPSTEALTH
 166         if (!ip6stealth) {
 167 #endif
 168         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 169                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 170                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 171                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 172                 return;
 173         }
 174         ip6->ip6_hlim -= IPV6_HLIMDEC;
 175
 176 #ifdef IPSTEALTH
 177         }
 178 #endif
 179
 180         /*
 181          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 182          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 183          * we need to generate an ICMP6 message to the src.
 184          * Thanks to M_EXT, in most cases copy will not occur.
 185          *
 186          * It is important to save it before IPsec processing as IPsec
 187          * processing may modify the mbuf.
 188          */
 189         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 190
 191 #ifdef IPSEC
 192         /* get a security policy for this packet */
 193         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
 194             IP_FORWARDING, &error);
 195         if (sp == NULL) {
 196                 ipsec6stat.out_inval++;
 197                 ip6stat.ip6s_cantforward++;
 198                 if (mcopy) {
 199 #if 0
 200                         /* XXX: what icmp ? */
 201 #else
 202                         m_freem(mcopy);
 203 #endif
 204                 }
 205                 m_freem(m);
 206                 return;
 207         }
 208
 209         error = 0;
 210
 211         /* check policy */
 212         switch (sp->policy) {
 213         case IPSEC_POLICY_DISCARD:
 214                 /*
 215                  * This packet is just discarded.
 216                  */
 217                 ipsec6stat.out_polvio++;
 218                 ip6stat.ip6s_cantforward++;
 219                 key_freesp(sp);
 220                 if (mcopy) {
 221 #if 0
 222                         /* XXX: what icmp ? */
 223 #else
 224                         m_freem(mcopy);
 225 #endif
 226                 }
 227                 m_freem(m);
 228                 return;
 229
 230         case IPSEC_POLICY_BYPASS:
 231         case IPSEC_POLICY_NONE:
 232                 /* no need to do IPsec. */
 233                 key_freesp(sp);
 234                 goto skip_ipsec;
 235
 236         case IPSEC_POLICY_IPSEC:
 237                 if (sp->req == NULL) {
 238                         /* XXX should be panic ? */
 239                         printf("ip6_forward: No IPsec request specified.\n");
 240                         ip6stat.ip6s_cantforward++;
 241                         key_freesp(sp);
 242                         if (mcopy) {
 243 #if 0
 244                                 /* XXX: what icmp ? */
 245 #else
 246                                 m_freem(mcopy);
 247 #endif
 248                         }
 249                         m_freem(m);
 250                         return;
 251                 }
 252                 /* do IPsec */
 253                 break;
 254
 255         case IPSEC_POLICY_ENTRUST:
 256         default:
 257                 /* should be panic ?? */
 258                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 259                 key_freesp(sp);
 260                 goto skip_ipsec;
 261         }
 262
 263     {
 264         struct ipsecrequest *isr = NULL;
 265         struct ipsec_output_state state;
 266
 267         /*
 268          * when the kernel forwards a packet, it is not proper to apply
 269          * IPsec transport mode to the packet is not proper.  this check
 270          * avoid from this.
 271          * at present, if there is even a transport mode SA request in the
 272          * security policy, the kernel does not apply IPsec to the packet.
 273          * this check is not enough because the following case is valid.
 274          *      ipsec esp/tunnel/xxx-xxx/require esp/transport//require;
 275          */
 276         for (isr = sp->req; isr; isr = isr->next) {
 277                 if (isr->saidx.mode == IPSEC_MODE_ANY)
 278                         goto doipsectunnel;
 279                 if (isr->saidx.mode == IPSEC_MODE_TUNNEL)
 280                         goto doipsectunnel;
 281         }
 282
 283         /*
 284          * if there's no need for tunnel mode IPsec, skip.
 285          */
 286         if (!isr)
 287                 goto skip_ipsec;
 288
 289     doipsectunnel:
 290         /*
 291          * All the extension headers will become inaccessible
 292          * (since they can be encrypted).
 293          * Don't panic, we need no more updates to extension headers
 294          * on inner IPv6 packet (since they are now encapsulated).
 295          *
 296          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 297          */
 298         bzero(&state, sizeof(state));
 299         state.m = m;
 300         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 301         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 302
 303         error = ipsec6_output_tunnel(&state, sp, 0);
 304
 305         m = state.m;
 306         key_freesp(sp);
 307
 308         if (error) {
 309                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 310                 switch (error) {
 311                 case EHOSTUNREACH:
 312                 case ENETUNREACH:
 313                 case EMSGSIZE:
 314                 case ENOBUFS:
 315                 case ENOMEM:
 316                         break;
 317                 default:
 318                         printf("ip6_output (ipsec): error code %d\n", error);
 319                         /* FALLTHROUGH */
 320                 case ENOENT:
 321                         /* don't show these error codes to the user */
 322                         break;
 323                 }
 324                 ip6stat.ip6s_cantforward++;
 325                 if (mcopy) {
 326 #if 0
 327                         /* XXX: what icmp ? */
 328 #else
 329                         m_freem(mcopy);
 330 #endif
 331                 }
 332                 m_freem(m);
 333                 return;
 334         }
 335
 336         if (ip6 != mtod(m, struct ip6_hdr *)) {
 337                 /*
 338                  * now tunnel mode headers are added.  we are originating
 339                  * packet instead of forwarding the packet.
 340                  */
 341                 ip6_output(m, NULL, NULL, IPV6_FORWARDING/*XXX*/, NULL, NULL,
 342                     NULL);
 343                 goto freecopy;
 344         }
 345
 346         /* adjust pointer */
 347         dst = (struct sockaddr_in6 *)state.dst;
 348         rt = state.ro ? state.ro->ro_rt : NULL;
 349         if (dst != NULL && rt != NULL)
 350                 ipsecrt = 1;
 351     }
 352     skip_ipsec:
 353 #endif /* IPSEC */
 354
 355 #ifdef IPSEC
 356         if (ipsecrt)
 357                 goto skip_routing;
 358 #endif
 359
 360         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 361         if (!srcrt) {
 362                 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */
 363                 if (ip6_forward_rt.ro_rt == 0 ||
 364                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 365                         if (ip6_forward_rt.ro_rt) {
 366                                 RTFREE(ip6_forward_rt.ro_rt);
 367                                 ip6_forward_rt.ro_rt = 0;
 368                         }
 369
 370                         /* this probably fails but give it a try again */
 371                         rtalloc((struct route *)&ip6_forward_rt);
 372                 }
 373
 374                 if (ip6_forward_rt.ro_rt == 0) {
 375                         ip6stat.ip6s_noroute++;
 376                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 377                         if (mcopy) {
 378                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 379                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 380                         }
 381                         m_freem(m);
 382                         return;
 383                 }
 384         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 385                    !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 386                 if (ip6_forward_rt.ro_rt) {
 387                         RTFREE(ip6_forward_rt.ro_rt);
 388                         ip6_forward_rt.ro_rt = 0;
 389                 }
 390                 bzero(dst, sizeof(*dst));
 391                 dst->sin6_len = sizeof(struct sockaddr_in6);
 392                 dst->sin6_family = AF_INET6;
 393                 dst->sin6_addr = ip6->ip6_dst;
 394
 395                 rtalloc((struct route *)&ip6_forward_rt);
 396                 if (ip6_forward_rt.ro_rt == 0) {
 397                         ip6stat.ip6s_noroute++;
 398                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 399                         if (mcopy) {
 400                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 401                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 402                         }
 403                         m_freem(m);
 404                         return;
 405                 }
 406         }
 407         rt = ip6_forward_rt.ro_rt;
 408 #ifdef IPSEC
 409     skip_routing:;
 410 #endif
 411
 412         /*
 413          * Source scope check: if a packet can't be delivered to its
 414          * destination for the reason that the destination is beyond the scope
 415          * of the source address, discard the packet and return an icmp6
 416          * destination unreachable error with Code 2 (beyond scope of source
 417          * address).  We use a local copy of ip6_src, since in6_setscope()
 418          * will possibly modify its first argument.
 419          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
 420          */
 421         src_in6 = ip6->ip6_src;
 422         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
 423                 /* XXX: this should not happen */
 424                 ip6stat.ip6s_cantforward++;
 425                 ip6stat.ip6s_badscope++;
 426                 m_freem(m);
 427                 return;
 428         }
 429         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
 430                 ip6stat.ip6s_cantforward++;
 431                 ip6stat.ip6s_badscope++;
 432                 m_freem(m);
 433                 return;
 434         }
 435         if (inzone != outzone
 436 #ifdef IPSEC
 437             && !ipsecrt
 438 #endif
 439             ) {
 440                 ip6stat.ip6s_cantforward++;
 441                 ip6stat.ip6s_badscope++;
 442                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 443
 444                 if (ip6_log_time + ip6_log_interval < time_second) {
 445                         ip6_log_time = time_second;
 446                         log(LOG_DEBUG,
 447                             "cannot forward "
 448                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 449                             ip6_sprintf(&ip6->ip6_src),
 450                             ip6_sprintf(&ip6->ip6_dst),
 451                             ip6->ip6_nxt,
 452                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 453                 }
 454                 if (mcopy)
 455                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 456                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 457                 m_freem(m);
 458                 return;
 459         }
 460
 461         /*
 462          * Destination scope check: if a packet is going to break the scope
 463          * zone of packet's destination address, discard it.  This case should
 464          * usually be prevented by appropriately-configured routing table, but
 465          * we need an explicit check because we may mistakenly forward the
 466          * packet to a different zone by (e.g.) a default route.
 467          */
 468         dst_in6 = ip6->ip6_dst;
 469         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
 470             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
 471             inzone != outzone) {
 472                 ip6stat.ip6s_cantforward++;
 473                 ip6stat.ip6s_badscope++;
 474                 m_freem(m);
 475                 return;
 476         }
 477
 478         if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
 479                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 480                 if (mcopy) {
 481                         u_long mtu;
 482 #ifdef IPSEC
 483                         struct secpolicy *sp;
 484                         int ipsecerror;
 485                         size_t ipsechdrsiz;
 486 #endif
 487
 488                         mtu = IN6_LINKMTU(rt->rt_ifp);
 489 #ifdef IPSEC
 490                         /*
 491                          * When we do IPsec tunnel ingress, we need to play
 492                          * with the link value (decrement IPsec header size
 493                          * from mtu value).  The code is much simpler than v4
 494                          * case, as we have the outgoing interface for
 495                          * encapsulated packet as "rt->rt_ifp".
 496                          */
 497                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 498                                 IP_FORWARDING, &ipsecerror);
 499                         if (sp) {
 500                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 501                                         IPSEC_DIR_OUTBOUND, NULL);
 502                                 if (ipsechdrsiz < mtu)
 503                                         mtu -= ipsechdrsiz;
 504                         }
 505
 506                         /*
 507                          * if mtu becomes less than minimum MTU,
 508                          * tell minimum MTU (and I'll need to fragment it).
 509                          */
 510                         if (mtu < IPV6_MMTU)
 511                                 mtu = IPV6_MMTU;
 512 #endif
 513                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 514                 }
 515                 m_freem(m);
 516                 return;
 517         }
 518
 519         if (rt->rt_flags & RTF_GATEWAY)
 520                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 521
 522         /*
 523          * If we are to forward the packet using the same interface
 524          * as one we got the packet from, perhaps we should send a redirect
 525          * to sender to shortcut a hop.
 526          * Only send redirect if source is sending directly to us,
 527          * and if packet was not source routed (or has any options).
 528          * Also, don't send redirect if forwarding using a route
 529          * modified by a redirect.
 530          */
 531         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 532 #ifdef IPSEC
 533             !ipsecrt &&
 534 #endif
 535             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 536                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 537                         /*
 538                          * If the incoming interface is equal to the outgoing
 539                          * one, and the link attached to the interface is
 540                          * point-to-point, then it will be highly probable
 541                          * that a routing loop occurs. Thus, we immediately
 542                          * drop the packet and send an ICMPv6 error message.
 543                          *
 544                          * type/code is based on suggestion by Rich Draves.
 545                          * not sure if it is the best pick.
 546                          */
 547                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 548                                     ICMP6_DST_UNREACH_ADDR, 0);
 549                         m_freem(m);
 550                         return;
 551                 }
 552                 type = ND_REDIRECT;
 553         }
 554
 555         /*
 556          * Check with the firewall...
 557          */
 558         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 559                 u_short port = 0;
 560                 /* If ipfw says divert, we have to just drop packet */
 561                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 562                         m_freem(m);
 563                         goto freecopy;
 564                 }
 565                 if (!m)
 566                         goto freecopy;
 567         }
 568
 569         /*
 570          * Fake scoped addresses. Note that even link-local source or
 571          * destinaion can appear, if the originating node just sends the
 572          * packet to us (without address resolution for the destination).
 573          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 574          * link identifiers, we can do this stuff after making a copy for
 575          * returning an error.
 576          */
 577         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 578                 /*
 579                  * See corresponding comments in ip6_output.
 580                  * XXX: but is it possible that ip6_forward() sends a packet
 581                  *      to a loopback interface? I don't think so, and thus
 582                  *      I bark here. (jinmei@kame.net)
 583                  * XXX: it is common to route invalid packets to loopback.
 584                  *      also, the codepath will be visited on use of ::1 in
 585                  *      rthdr. (itojun)
 586                  */
 587 #if 1
 588                 if (0)
 589 #else
 590                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 591 #endif
 592                 {
 593                         printf("ip6_forward: outgoing interface is loopback. "
 594                                "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 595                                ip6_sprintf(&ip6->ip6_src),
 596                                ip6_sprintf(&ip6->ip6_dst),
 597                                ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 598                                if_name(rt->rt_ifp));
 599                 }
 600
 601                 /* we can just use rcvif in forwarding. */
 602                 origifp = m->m_pkthdr.rcvif;
 603         }
 604         else
 605                 origifp = rt->rt_ifp;
 606         /*
 607          * clear embedded scope identifiers if necessary.
 608          * in6_clearscope will touch the addresses only when necessary.
 609          */
 610         in6_clearscope(&ip6->ip6_src);
 611         in6_clearscope(&ip6->ip6_dst);
 612
 613         /* Jump over all PFIL processing if hooks are not active. */
 614         if (!PFIL_HOOKED(&inet6_pfil_hook))
 615                 goto pass;
 616
 617         /* Run through list of hooks for output packets. */
 618         error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT, NULL);
 619         if (error != 0)
 620                 goto senderr;
 621         if (m == NULL)
 622                 goto freecopy;
 623         ip6 = mtod(m, struct ip6_hdr *);
 624
 625 pass:
 626         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 627         if (error) {
 628                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 629                 ip6stat.ip6s_cantforward++;
 630         } else {
 631                 ip6stat.ip6s_forward++;
 632                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 633                 if (type)
 634                         ip6stat.ip6s_redirectsent++;
 635                 else {
 636                         if (mcopy)
 637                                 goto freecopy;
 638                 }
 639         }
 640
 641 senderr:
 642         if (mcopy == NULL)
 643                 return;
 644         switch (error) {
 645         case 0:
 646                 if (type == ND_REDIRECT) {
 647                         icmp6_redirect_output(mcopy, rt);
 648                         return;
 649                 }
 650                 goto freecopy;
 651
 652         case EMSGSIZE:
 653                 /* xxx MTU is constant in PPP? */
 654                 goto freecopy;
 655
 656         case ENOBUFS:
 657                 /* Tell source to slow down like source quench in IP? */
 658                 goto freecopy;
 659
 660         case ENETUNREACH:       /* shouldn't happen, checked above */
 661         case EHOSTUNREACH:
 662         case ENETDOWN:
 663         case EHOSTDOWN:
 664         default:
 665                 type = ICMP6_DST_UNREACH;
 666                 code = ICMP6_DST_UNREACH_ADDR;
 667                 break;
 668         }
 669         icmp6_error(mcopy, type, code, 0);
 670         return;
 671
 672  freecopy:
 673         m_freem(mcopy);
 674         return;
 675 }