bsd/netinet6/ip6_forward.c

   1 /*
   2  * Copyright (c) 2009-2010 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.16 2002/10/16 02:25:05 sam Exp $   */
  30 /*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $    */
  31
  32 /*
  33  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
  34  * All rights reserved.
  35  *
  36  * Redistribution and use in source and binary forms, with or without
  37  * modification, are permitted provided that the following conditions
  38  * are met:
  39  * 1. Redistributions of source code must retain the above copyright
  40  *    notice, this list of conditions and the following disclaimer.
  41  * 2. Redistributions in binary form must reproduce the above copyright
  42  *    notice, this list of conditions and the following disclaimer in the
  43  *    documentation and/or other materials provided with the distribution.
  44  * 3. Neither the name of the project nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61
  62 #include <sys/param.h>
  63 #include <sys/systm.h>
  64 #include <sys/malloc.h>
  65 #include <sys/mbuf.h>
  66 #include <sys/domain.h>
  67 #include <sys/protosw.h>
  68 #include <sys/socket.h>
  69 #include <sys/errno.h>
  70 #include <sys/time.h>
  71 #include <sys/kernel.h>
  72 #include <sys/syslog.h>
  73
  74 #include <net/if.h>
  75 #include <net/route.h>
  76
  77 #include <netinet/in.h>
  78 #include <netinet/in_var.h>
  79 #include <netinet/in_systm.h>
  80 #include <netinet/ip.h>
  81 #include <netinet/ip_var.h>
  82 #include <netinet6/in6_var.h>
  83 #include <netinet/ip6.h>
  84 #include <netinet6/ip6_var.h>
  85 #include <netinet/icmp6.h>
  86 #include <netinet6/nd6.h>
  87 #include <netinet6/scope6_var.h>
  88
  89 #include <netinet/in_pcb.h>
  90
  91 #if IPSEC
  92 #include <netinet6/ipsec.h>
  93 #if INET6
  94 #include <netinet6/ipsec6.h>
  95 #endif
  96 #include <netkey/key.h>
  97 extern int ipsec_bypass;
  98 #endif /* IPSEC */
  99
 100 #include <netinet6/ip6_fw.h>
 101
 102 #include <net/net_osdep.h>
 103
 104 #if PF
 105 #include <net/pfvar.h>
 106 #endif /* PF */
 107
 108 /*
 109  * Forward a packet.  If some error occurs return the sender
 110  * an icmp packet.  Note we can't always generate a meaningful
 111  * icmp message because icmp doesn't have a large enough repertoire
 112  * of codes and types.
 113  *
 114  * If not forwarding, just drop the packet.  This could be confusing
 115  * if ipforwarding was zero but some routing protocol was advancing
 116  * us as a gateway to somewhere.  However, we must let the routing
 117  * protocol deal with that.
 118  *
 119  */
 120
 121 void
 122 ip6_forward(struct mbuf *m, struct route_in6 *ip6forward_rt,
 123     int srcrt)
 124 {
 125         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 126         struct sockaddr_in6 *dst;
 127         struct rtentry *rt;
 128         int error, type = 0, code = 0;
 129         struct mbuf *mcopy = NULL;
 130         struct ifnet *ifp, *origifp;    /* maybe unnecessary */
 131         u_int32_t inzone, outzone;
 132         struct in6_addr src_in6, dst_in6;
 133 #if IPSEC
 134         struct secpolicy *sp = NULL;
 135 #endif
 136         struct timeval timenow;
 137         unsigned int ifscope = IFSCOPE_NONE;
 138 #if PF
 139         struct pf_mtag *pf_mtag;
 140 #endif /* PF */
 141
 142         getmicrotime(&timenow);
 143 #if PF
 144         pf_mtag = pf_find_mtag(m);
 145         if (pf_mtag != NULL && pf_mtag->rtableid != IFSCOPE_NONE)
 146                 ifscope = pf_mtag->rtableid;
 147 #endif /* PF */
 148
 149 #if IPSEC
 150         /*
 151          * Check AH/ESP integrity.
 152          */
 153         /*
 154          * Don't increment ip6s_cantforward because this is the check
 155          * before forwarding packet actually.
 156          */
 157         if (ipsec_bypass == 0) {
 158                 if (ipsec6_in_reject(m, NULL)) {
 159                         IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
 160                         m_freem(m);
 161                         return;
 162                 }
 163         }
 164 #endif /*IPSEC*/
 165
 166         /*
 167          * Do not forward packets to multicast destination (should be handled
 168          * by ip6_mforward().
 169          * Do not forward packets with unspecified source.  It was discussed
 170          * in July 2000, on ipngwg mailing list.
 171          */
 172         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 173             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 174             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 175                 ip6stat.ip6s_cantforward++;
 176                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 177                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 178                         ip6_log_time = timenow.tv_sec;
 179                         log(LOG_DEBUG,
 180                             "cannot forward "
 181                             "from %s to %s nxt %d received on %s\n",
 182                             ip6_sprintf(&ip6->ip6_src),
 183                             ip6_sprintf(&ip6->ip6_dst),
 184                             ip6->ip6_nxt,
 185                             if_name(m->m_pkthdr.rcvif));
 186                 }
 187                 m_freem(m);
 188                 return;
 189         }
 190
 191         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 192                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 193                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 194                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 195                 return;
 196         }
 197         ip6->ip6_hlim -= IPV6_HLIMDEC;
 198
 199         /*
 200          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 201          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 202          * we need to generate an ICMP6 message to the src.
 203          * Thanks to M_EXT, in most cases copy will not occur.
 204          *
 205          * It is important to save it before IPsec processing as IPsec
 206          * processing may modify the mbuf.
 207          */
 208         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 209
 210 #if IPSEC
 211         if (ipsec_bypass != 0)
 212                 goto skip_ipsec;
 213         /* get a security policy for this packet */
 214         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 215             &error);
 216         if (sp == NULL) {
 217                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 218                 ip6stat.ip6s_cantforward++;
 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
 230         error = 0;
 231
 232         /* check policy */
 233         switch (sp->policy) {
 234         case IPSEC_POLICY_DISCARD:
 235         case IPSEC_POLICY_GENERATE:
 236                 /*
 237                  * This packet is just discarded.
 238                  */
 239                 IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
 240                 ip6stat.ip6s_cantforward++;
 241                 key_freesp(sp, KEY_SADB_UNLOCKED);
 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         case IPSEC_POLICY_BYPASS:
 253         case IPSEC_POLICY_NONE:
 254                 /* no need to do IPsec. */
 255                 key_freesp(sp, KEY_SADB_UNLOCKED);
 256                 goto skip_ipsec;
 257
 258         case IPSEC_POLICY_IPSEC:
 259                 if (sp->req == NULL) {
 260                         /* XXX should be panic ? */
 261                         printf("ip6_forward: No IPsec request specified.\n");
 262                         ip6stat.ip6s_cantforward++;
 263                         key_freesp(sp, KEY_SADB_UNLOCKED);
 264                         if (mcopy) {
 265 #if 0
 266                                 /* XXX: what icmp ? */
 267 #else
 268                                 m_freem(mcopy);
 269 #endif
 270                         }
 271                         m_freem(m);
 272                         return;
 273                 }
 274                 /* do IPsec */
 275                 break;
 276
 277         case IPSEC_POLICY_ENTRUST:
 278         default:
 279                 /* should be panic ?? */
 280                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 281                 key_freesp(sp, KEY_SADB_UNLOCKED);
 282                 goto skip_ipsec;
 283         }
 284
 285     {
 286         struct ipsec_output_state state;
 287
 288         /*
 289          * All the extension headers will become inaccessible
 290          * (since they can be encrypted).
 291          * Don't panic, we need no more updates to extension headers
 292          * on inner IPv6 packet (since they are now encapsulated).
 293          *
 294          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 295          */
 296         bzero(&state, sizeof(state));
 297         state.m = m;
 298         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 299
 300         error = ipsec6_output_tunnel(&state, sp, 0);
 301         key_freesp(sp, KEY_SADB_UNLOCKED);
 302         if (state.tunneled == 4)
 303                 return;  /* packet is gone - sent over IPv4 */
 304
 305         m = state.m;
 306         if (state.ro.ro_rt) {
 307                 rtfree(state.ro.ro_rt);
 308                 state.ro.ro_rt = NULL;
 309         }
 310         if (error) {
 311                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 312                 switch (error) {
 313                 case EHOSTUNREACH:
 314                 case ENETUNREACH:
 315                 case EMSGSIZE:
 316                 case ENOBUFS:
 317                 case ENOMEM:
 318                         break;
 319                 default:
 320                         printf("ip6_output (ipsec): error code %d\n", error);
 321                         /* fall through */
 322                 case ENOENT:
 323                         /* don't show these error codes to the user */
 324                         break;
 325                 }
 326                 ip6stat.ip6s_cantforward++;
 327                 if (mcopy) {
 328 #if 0
 329                         /* XXX: what icmp ? */
 330 #else
 331                         m_freem(mcopy);
 332 #endif
 333                 }
 334                 m_freem(m);
 335                 return;
 336         }
 337     }
 338     skip_ipsec:
 339 #endif /* IPSEC */
 340
 341         dst = (struct sockaddr_in6 *)&ip6forward_rt->ro_dst;
 342         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 343                 RT_LOCK(rt);
 344                 /* Take an extra ref for ourselves */
 345                 RT_ADDREF_LOCKED(rt);
 346         }
 347
 348         if (!srcrt) {
 349                 /*
 350                  * ip6forward_rt->ro_dst.sin6_addr is equal to ip6->ip6_dst
 351                  */
 352                 if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 353                     rt->generation_id != route_generation) {
 354                         if (rt != NULL) {
 355                                 /* Release extra ref */
 356                                 RT_REMREF_LOCKED(rt);
 357                                 RT_UNLOCK(rt);
 358                                 rtfree(rt);
 359                                 ip6forward_rt->ro_rt = NULL;
 360                         }
 361                         /* this probably fails but give it a try again */
 362                         rtalloc_scoped_ign((struct route *)ip6forward_rt,
 363                             RTF_PRCLONING, ifscope);
 364                         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 365                                 RT_LOCK(rt);
 366                                 /* Take an extra ref for ourselves */
 367                                 RT_ADDREF_LOCKED(rt);
 368                         }
 369                 }
 370
 371                 if (rt == NULL) {
 372                         ip6stat.ip6s_noroute++;
 373                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 374                         if (mcopy)
 375                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 376                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 377                         m_freem(m);
 378                         return;
 379                 }
 380                 RT_LOCK_ASSERT_HELD(rt);
 381         } else if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 382             !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr) ||
 383             rt->generation_id != route_generation) {
 384                 if (rt != NULL) {
 385                         /* Release extra ref */
 386                         RT_REMREF_LOCKED(rt);
 387                         RT_UNLOCK(rt);
 388                         rtfree(rt);
 389                         ip6forward_rt->ro_rt = NULL;
 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_scoped_ign((struct route *)ip6forward_rt,
 397                     RTF_PRCLONING, ifscope);
 398                 if ((rt = ip6forward_rt->ro_rt) == NULL) {
 399                         ip6stat.ip6s_noroute++;
 400                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 401                         if (mcopy)
 402                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 403                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 404                         m_freem(m);
 405                         return;
 406                 }
 407                 RT_LOCK(rt);
 408                 /* Take an extra ref for ourselves */
 409                 RT_ADDREF_LOCKED(rt);
 410         }
 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                 ip6stat.ip6s_cantforward++;
 437                 ip6stat.ip6s_badscope++;
 438                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 439
 440                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 441                         ip6_log_time = timenow.tv_sec;
 442                         log(LOG_DEBUG,
 443                             "cannot forward "
 444                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 445                             ip6_sprintf(&ip6->ip6_src),
 446                             ip6_sprintf(&ip6->ip6_dst),
 447                             ip6->ip6_nxt,
 448                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 449                 }
 450                 /* Release extra ref */
 451                 RT_REMREF_LOCKED(rt);
 452                 RT_UNLOCK(rt);
 453                 if (mcopy) {
 454                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 455                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 456                 }
 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 > rt->rt_ifp->if_mtu) {
 479                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 480                 if (mcopy) {
 481                         uint32_t mtu;
 482 #if IPSEC
 483                         struct secpolicy *sp2;
 484                         int ipsecerror;
 485                         size_t ipsechdrsiz;
 486 #endif
 487
 488                         mtu = rt->rt_ifp->if_mtu;
 489 #if 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                         sp2 = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 498                                 IP_FORWARDING, &ipsecerror);
 499                         if (sp2) {
 500                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 501                                         IPSEC_DIR_OUTBOUND, NULL);
 502                                 if (ipsechdrsiz < mtu)
 503                                         mtu -= ipsechdrsiz;
 504                                 key_freesp(sp2, KEY_SADB_UNLOCKED);
 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                         /* Release extra ref */
 514                         RT_REMREF_LOCKED(rt);
 515                         RT_UNLOCK(rt);
 516                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 517                 } else {
 518                         /* Release extra ref */
 519                         RT_REMREF_LOCKED(rt);
 520                         RT_UNLOCK(rt);
 521                 }
 522                 m_freem(m);
 523                 return;
 524         }
 525
 526         if (rt->rt_flags & RTF_GATEWAY)
 527                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 528
 529         /*
 530          * If we are to forward the packet using the same interface
 531          * as one we got the packet from, perhaps we should send a redirect
 532          * to sender to shortcut a hop.
 533          * Only send redirect if source is sending directly to us,
 534          * and if packet was not source routed (or has any options).
 535          * Also, don't send redirect if forwarding using a route
 536          * modified by a redirect.
 537          */
 538         if (ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 539             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 540                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 541                         /*
 542                          * If the incoming interface is equal to the outgoing
 543                          * one, and the link attached to the interface is
 544                          * point-to-point, then it will be highly probable
 545                          * that a routing loop occurs. Thus, we immediately
 546                          * drop the packet and send an ICMPv6 error message.
 547                          *
 548                          * type/code is based on suggestion by Rich Draves.
 549                          * not sure if it is the best pick.
 550                          */
 551                         RT_REMREF_LOCKED(rt);   /* Release extra ref */
 552                         RT_UNLOCK(rt);
 553                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 554                                     ICMP6_DST_UNREACH_ADDR, 0);
 555                         m_freem(m);
 556                         return;
 557                 }
 558                 type = ND_REDIRECT;
 559         }
 560
 561 #if IPFW2
 562         /*
 563          * Check with the firewall...
 564          */
 565         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 566                 u_short port = 0;
 567                 ifp = rt->rt_ifp;
 568                 /* Drop the lock but retain the extra ref */
 569                 RT_UNLOCK(rt);
 570                 /* If ipfw says divert, we have to just drop packet */
 571                 if (ip6_fw_chk_ptr(&ip6, ifp, &port, &m)) {
 572                         m_freem(m);
 573                         goto freecopy;
 574                 }
 575                 if (!m) {
 576                         goto freecopy;
 577                 }
 578                 /* We still have the extra ref on rt */
 579                 RT_LOCK(rt);
 580         }
 581 #endif
 582
 583         /*
 584          * Fake scoped addresses. Note that even link-local source or
 585          * destinaion can appear, if the originating node just sends the
 586          * packet to us (without address resolution for the destination).
 587          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 588          * link identifiers, we can do this stuff after making a copy for
 589          * returning an error.
 590          */
 591         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 592                 /*
 593                  * See corresponding comments in ip6_output.
 594                  * XXX: but is it possible that ip6_forward() sends a packet
 595                  *      to a loopback interface? I don't think so, and thus
 596                  *      I bark here. (jinmei@kame.net)
 597                  * XXX: it is common to route invalid packets to loopback.
 598                  *      also, the codepath will be visited on use of ::1 in
 599                  *      rthdr. (itojun)
 600                  */
 601 #if 1
 602                 if (0)
 603 #else
 604                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 605 #endif
 606                 {
 607                         printf("ip6_forward: outgoing interface is loopback. "
 608                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 609                                 ip6_sprintf(&ip6->ip6_src),
 610                                 ip6_sprintf(&ip6->ip6_dst),
 611                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 612                                 if_name(rt->rt_ifp));
 613                 }
 614
 615                 /* we can just use rcvif in forwarding. */
 616                 origifp = m->m_pkthdr.rcvif;
 617         }
 618         else
 619                 origifp = rt->rt_ifp;
 620         /*
 621          * clear embedded scope identifiers if necessary.
 622          * in6_clearscope will touch the addresses only when necessary.
 623          */
 624         in6_clearscope(&ip6->ip6_src);
 625         in6_clearscope(&ip6->ip6_dst);
 626
 627         ifp = rt->rt_ifp;
 628         /* Drop the lock but retain the extra ref */
 629         RT_UNLOCK(rt);
 630
 631 #if PF
 632         /* Invoke outbound packet filter */
 633         error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE);
 634
 635         if (error) {
 636                 if (m != NULL) {
 637                         panic("%s: unexpected packet %p\n", __func__, m);
 638                         /* NOTREACHED */
 639                 }
 640                 /* Already freed by callee */
 641                 goto senderr;
 642         }
 643         ip6 = mtod(m, struct ip6_hdr *);
 644 #endif /* PF */
 645
 646         error = nd6_output(ifp, origifp, m, dst, rt);
 647         if (error) {
 648                 in6_ifstat_inc(ifp, ifs6_out_discard);
 649                 ip6stat.ip6s_cantforward++;
 650         } else {
 651                 ip6stat.ip6s_forward++;
 652                 in6_ifstat_inc(ifp, ifs6_out_forward);
 653                 if (type)
 654                         ip6stat.ip6s_redirectsent++;
 655                 else {
 656                         if (mcopy) {
 657                                 goto freecopy;
 658                         }
 659                 }
 660         }
 661 #if PF
 662 senderr:
 663 #endif /* PF */
 664         if (mcopy == NULL) {
 665                 /* Release extra ref */
 666                 RT_REMREF(rt);
 667                 return;
 668         }
 669         switch (error) {
 670         case 0:
 671 #if 1
 672                 if (type == ND_REDIRECT) {
 673                         icmp6_redirect_output(mcopy, rt);
 674                         /* Release extra ref */
 675                         RT_REMREF(rt);
 676                         return;
 677                 }
 678 #endif
 679                 goto freecopy;
 680
 681         case EMSGSIZE:
 682                 /* xxx MTU is constant in PPP? */
 683                 goto freecopy;
 684
 685         case ENOBUFS:
 686                 /* Tell source to slow down like source quench in IP? */
 687                 goto freecopy;
 688
 689         case ENETUNREACH:       /* shouldn't happen, checked above */
 690         case EHOSTUNREACH:
 691         case ENETDOWN:
 692         case EHOSTDOWN:
 693         default:
 694                 type = ICMP6_DST_UNREACH;
 695                 code = ICMP6_DST_UNREACH_ADDR;
 696                 break;
 697         }
 698         icmp6_error(mcopy, type, code, 0);
 699         /* Release extra ref */
 700         RT_REMREF(rt);
 701         return;
 702
 703  freecopy:
 704         m_freem(mcopy);
 705         /* Release extra ref */
 706         RT_REMREF(rt);
 707         return;
 708 }