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         int     tunneledv4 = 0;
 138         unsigned int ifscope = IFSCOPE_NONE;
 139 #if PF
 140         struct pf_mtag *pf_mtag;
 141 #endif /* PF */
 142
 143         getmicrotime(&timenow);
 144 #if PF
 145         pf_mtag = pf_find_mtag(m);
 146         if (pf_mtag != NULL && pf_mtag->rtableid != IFSCOPE_NONE)
 147                 ifscope = pf_mtag->rtableid;
 148 #endif /* PF */
 149
 150 #if IPSEC
 151         /*
 152          * Check AH/ESP integrity.
 153          */
 154         /*
 155          * Don't increment ip6s_cantforward because this is the check
 156          * before forwarding packet actually.
 157          */
 158         if (ipsec_bypass == 0) {
 159                 if (ipsec6_in_reject(m, NULL)) {
 160                         IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
 161                         m_freem(m);
 162                         return;
 163                 }
 164         }
 165 #endif /*IPSEC*/
 166
 167         /*
 168          * Do not forward packets to multicast destination (should be handled
 169          * by ip6_mforward().
 170          * Do not forward packets with unspecified source.  It was discussed
 171          * in July 2000, on ipngwg mailing list.
 172          */
 173         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 174             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 175             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 176                 ip6stat.ip6s_cantforward++;
 177                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 178                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 179                         ip6_log_time = timenow.tv_sec;
 180                         log(LOG_DEBUG,
 181                             "cannot forward "
 182                             "from %s to %s nxt %d received on %s\n",
 183                             ip6_sprintf(&ip6->ip6_src),
 184                             ip6_sprintf(&ip6->ip6_dst),
 185                             ip6->ip6_nxt,
 186                             if_name(m->m_pkthdr.rcvif));
 187                 }
 188                 m_freem(m);
 189                 return;
 190         }
 191
 192         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 193                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 194                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 195                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 196                 return;
 197         }
 198         ip6->ip6_hlim -= IPV6_HLIMDEC;
 199
 200         /*
 201          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 202          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 203          * we need to generate an ICMP6 message to the src.
 204          * Thanks to M_EXT, in most cases copy will not occur.
 205          *
 206          * It is important to save it before IPsec processing as IPsec
 207          * processing may modify the mbuf.
 208          */
 209         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 210
 211 #if IPSEC
 212         if (ipsec_bypass != 0)
 213                 goto skip_ipsec;
 214         /* get a security policy for this packet */
 215         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 216             &error);
 217         if (sp == NULL) {
 218                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 219                 ip6stat.ip6s_cantforward++;
 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
 231         error = 0;
 232
 233         /* check policy */
 234         switch (sp->policy) {
 235         case IPSEC_POLICY_DISCARD:
 236         case IPSEC_POLICY_GENERATE:
 237                 /*
 238                  * This packet is just discarded.
 239                  */
 240                 IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
 241                 ip6stat.ip6s_cantforward++;
 242                 key_freesp(sp, KEY_SADB_UNLOCKED);
 243                 if (mcopy) {
 244 #if 0
 245                         /* XXX: what icmp ? */
 246 #else
 247                         m_freem(mcopy);
 248 #endif
 249                 }
 250                 m_freem(m);
 251                 return;
 252
 253         case IPSEC_POLICY_BYPASS:
 254         case IPSEC_POLICY_NONE:
 255                 /* no need to do IPsec. */
 256                 key_freesp(sp, KEY_SADB_UNLOCKED);
 257                 goto skip_ipsec;
 258
 259         case IPSEC_POLICY_IPSEC:
 260                 if (sp->req == NULL) {
 261                         /* XXX should be panic ? */
 262                         printf("ip6_forward: No IPsec request specified.\n");
 263                         ip6stat.ip6s_cantforward++;
 264                         key_freesp(sp, KEY_SADB_UNLOCKED);
 265                         if (mcopy) {
 266 #if 0
 267                                 /* XXX: what icmp ? */
 268 #else
 269                                 m_freem(mcopy);
 270 #endif
 271                         }
 272                         m_freem(m);
 273                         return;
 274                 }
 275                 /* do IPsec */
 276                 break;
 277
 278         case IPSEC_POLICY_ENTRUST:
 279         default:
 280                 /* should be panic ?? */
 281                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 282                 key_freesp(sp, KEY_SADB_UNLOCKED);
 283                 goto skip_ipsec;
 284         }
 285
 286     {
 287         struct ipsec_output_state state;
 288
 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, &tunneledv4);
 303         key_freesp(sp, KEY_SADB_UNLOCKED);
 304         if (tunneledv4)
 305                 return;  /* packet is gone - sent over IPv4 */
 306
 307         m = state.m;
 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                         /* fall through */
 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     skip_ipsec:
 337 #endif /* IPSEC */
 338
 339         dst = (struct sockaddr_in6 *)&ip6forward_rt->ro_dst;
 340         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 341                 RT_LOCK(rt);
 342                 /* Take an extra ref for ourselves */
 343                 RT_ADDREF_LOCKED(rt);
 344         }
 345
 346         if (!srcrt) {
 347                 /*
 348                  * ip6forward_rt->ro_dst.sin6_addr is equal to ip6->ip6_dst
 349                  */
 350                 if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 351                     rt->generation_id != route_generation) {
 352                         if (rt != NULL) {
 353                                 /* Release extra ref */
 354                                 RT_REMREF_LOCKED(rt);
 355                                 RT_UNLOCK(rt);
 356                                 rtfree(rt);
 357                                 ip6forward_rt->ro_rt = NULL;
 358                         }
 359                         /* this probably fails but give it a try again */
 360                         rtalloc_scoped_ign((struct route *)ip6forward_rt,
 361                             RTF_PRCLONING, ifscope);
 362                         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 363                                 RT_LOCK(rt);
 364                                 /* Take an extra ref for ourselves */
 365                                 RT_ADDREF_LOCKED(rt);
 366                         }
 367                 }
 368
 369                 if (rt == NULL) {
 370                         ip6stat.ip6s_noroute++;
 371                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 372                         if (mcopy)
 373                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 374                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 375                         m_freem(m);
 376                         return;
 377                 }
 378                 RT_LOCK_ASSERT_HELD(rt);
 379         } else if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 380             !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr) ||
 381             rt->generation_id != route_generation) {
 382                 if (rt != NULL) {
 383                         /* Release extra ref */
 384                         RT_REMREF_LOCKED(rt);
 385                         RT_UNLOCK(rt);
 386                         rtfree(rt);
 387                         ip6forward_rt->ro_rt = NULL;
 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_scoped_ign((struct route *)ip6forward_rt,
 395                     RTF_PRCLONING, ifscope);
 396                 if ((rt = ip6forward_rt->ro_rt) == NULL) {
 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                         m_freem(m);
 403                         return;
 404                 }
 405                 RT_LOCK(rt);
 406                 /* Take an extra ref for ourselves */
 407                 RT_ADDREF_LOCKED(rt);
 408         }
 409
 410         /*
 411          * Source scope check: if a packet can't be delivered to its
 412          * destination for the reason that the destination is beyond the scope
 413          * of the source address, discard the packet and return an icmp6
 414          * destination unreachable error with Code 2 (beyond scope of source
 415          * address).  We use a local copy of ip6_src, since in6_setscope()
 416          * will possibly modify its first argument.
 417          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
 418          */
 419         src_in6 = ip6->ip6_src;
 420         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
 421                 /* XXX: this should not happen */
 422                 ip6stat.ip6s_cantforward++;
 423                 ip6stat.ip6s_badscope++;
 424                 m_freem(m);
 425                 return;
 426         }
 427         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
 428                 ip6stat.ip6s_cantforward++;
 429                 ip6stat.ip6s_badscope++;
 430                 m_freem(m);
 431                 return;
 432         }
 433         if (inzone != outzone) {
 434                 ip6stat.ip6s_cantforward++;
 435                 ip6stat.ip6s_badscope++;
 436                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 437
 438                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 439                         ip6_log_time = timenow.tv_sec;
 440                         log(LOG_DEBUG,
 441                             "cannot forward "
 442                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 443                             ip6_sprintf(&ip6->ip6_src),
 444                             ip6_sprintf(&ip6->ip6_dst),
 445                             ip6->ip6_nxt,
 446                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 447                 }
 448                 /* Release extra ref */
 449                 RT_REMREF_LOCKED(rt);
 450                 RT_UNLOCK(rt);
 451                 if (mcopy) {
 452                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 453                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 454                 }
 455                 m_freem(m);
 456                 return;
 457         }
 458
 459         /*
 460          * Destination scope check: if a packet is going to break the scope
 461          * zone of packet's destination address, discard it.  This case should
 462          * usually be prevented by appropriately-configured routing table, but
 463          * we need an explicit check because we may mistakenly forward the
 464          * packet to a different zone by (e.g.) a default route.
 465          */
 466         dst_in6 = ip6->ip6_dst;
 467         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
 468             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
 469             inzone != outzone) {
 470                 ip6stat.ip6s_cantforward++;
 471                 ip6stat.ip6s_badscope++;
 472                 m_freem(m);
 473                 return;
 474         }
 475
 476         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 477                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 478                 if (mcopy) {
 479                         uint32_t mtu;
 480 #if IPSEC
 481                         struct secpolicy *sp2;
 482                         int ipsecerror;
 483                         size_t ipsechdrsiz;
 484 #endif
 485
 486                         mtu = rt->rt_ifp->if_mtu;
 487 #if IPSEC
 488                         /*
 489                          * When we do IPsec tunnel ingress, we need to play
 490                          * with the link value (decrement IPsec header size
 491                          * from mtu value).  The code is much simpler than v4
 492                          * case, as we have the outgoing interface for
 493                          * encapsulated packet as "rt->rt_ifp".
 494                          */
 495                         sp2 = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 496                                 IP_FORWARDING, &ipsecerror);
 497                         if (sp2) {
 498                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 499                                         IPSEC_DIR_OUTBOUND, NULL);
 500                                 if (ipsechdrsiz < mtu)
 501                                         mtu -= ipsechdrsiz;
 502                                 key_freesp(sp2, KEY_SADB_UNLOCKED);
 503                         }
 504                         /*
 505                          * if mtu becomes less than minimum MTU,
 506                          * tell minimum MTU (and I'll need to fragment it).
 507                          */
 508                         if (mtu < IPV6_MMTU)
 509                                 mtu = IPV6_MMTU;
 510 #endif
 511                         /* Release extra ref */
 512                         RT_REMREF_LOCKED(rt);
 513                         RT_UNLOCK(rt);
 514                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 515                 } else {
 516                         /* Release extra ref */
 517                         RT_REMREF_LOCKED(rt);
 518                         RT_UNLOCK(rt);
 519                 }
 520                 m_freem(m);
 521                 return;
 522         }
 523
 524         if (rt->rt_flags & RTF_GATEWAY)
 525                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 526
 527         /*
 528          * If we are to forward the packet using the same interface
 529          * as one we got the packet from, perhaps we should send a redirect
 530          * to sender to shortcut a hop.
 531          * Only send redirect if source is sending directly to us,
 532          * and if packet was not source routed (or has any options).
 533          * Also, don't send redirect if forwarding using a route
 534          * modified by a redirect.
 535          */
 536         if (ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 537             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 538                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 539                         /*
 540                          * If the incoming interface is equal to the outgoing
 541                          * one, and the link attached to the interface is
 542                          * point-to-point, then it will be highly probable
 543                          * that a routing loop occurs. Thus, we immediately
 544                          * drop the packet and send an ICMPv6 error message.
 545                          *
 546                          * type/code is based on suggestion by Rich Draves.
 547                          * not sure if it is the best pick.
 548                          */
 549                         RT_REMREF_LOCKED(rt);   /* Release extra ref */
 550                         RT_UNLOCK(rt);
 551                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 552                                     ICMP6_DST_UNREACH_ADDR, 0);
 553                         m_freem(m);
 554                         return;
 555                 }
 556                 type = ND_REDIRECT;
 557         }
 558
 559 #if IPFW2
 560         /*
 561          * Check with the firewall...
 562          */
 563         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 564                 u_short port = 0;
 565                 ifp = rt->rt_ifp;
 566                 /* Drop the lock but retain the extra ref */
 567                 RT_UNLOCK(rt);
 568                 /* If ipfw says divert, we have to just drop packet */
 569                 if (ip6_fw_chk_ptr(&ip6, ifp, &port, &m)) {
 570                         m_freem(m);
 571                         goto freecopy;
 572                 }
 573                 if (!m) {
 574                         goto freecopy;
 575                 }
 576                 /* We still have the extra ref on rt */
 577                 RT_LOCK(rt);
 578         }
 579 #endif
 580
 581         /*
 582          * Fake scoped addresses. Note that even link-local source or
 583          * destinaion can appear, if the originating node just sends the
 584          * packet to us (without address resolution for the destination).
 585          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 586          * link identifiers, we can do this stuff after making a copy for
 587          * returning an error.
 588          */
 589         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 590                 /*
 591                  * See corresponding comments in ip6_output.
 592                  * XXX: but is it possible that ip6_forward() sends a packet
 593                  *      to a loopback interface? I don't think so, and thus
 594                  *      I bark here. (jinmei@kame.net)
 595                  * XXX: it is common to route invalid packets to loopback.
 596                  *      also, the codepath will be visited on use of ::1 in
 597                  *      rthdr. (itojun)
 598                  */
 599 #if 1
 600                 if (0)
 601 #else
 602                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 603 #endif
 604                 {
 605                         printf("ip6_forward: outgoing interface is loopback. "
 606                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 607                                 ip6_sprintf(&ip6->ip6_src),
 608                                 ip6_sprintf(&ip6->ip6_dst),
 609                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 610                                 if_name(rt->rt_ifp));
 611                 }
 612
 613                 /* we can just use rcvif in forwarding. */
 614                 origifp = m->m_pkthdr.rcvif;
 615         }
 616         else
 617                 origifp = rt->rt_ifp;
 618         /*
 619          * clear embedded scope identifiers if necessary.
 620          * in6_clearscope will touch the addresses only when necessary.
 621          */
 622         in6_clearscope(&ip6->ip6_src);
 623         in6_clearscope(&ip6->ip6_dst);
 624
 625         ifp = rt->rt_ifp;
 626         /* Drop the lock but retain the extra ref */
 627         RT_UNLOCK(rt);
 628
 629 #if PF
 630         /* Invoke outbound packet filter */
 631         error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE);
 632
 633         if (error) {
 634                 if (m != NULL) {
 635                         panic("%s: unexpected packet %p\n", __func__, m);
 636                         /* NOTREACHED */
 637                 }
 638                 /* Already freed by callee */
 639                 goto senderr;
 640         }
 641         ip6 = mtod(m, struct ip6_hdr *);
 642 #endif /* PF */
 643
 644         error = nd6_output(ifp, origifp, m, dst, rt);
 645         if (error) {
 646                 in6_ifstat_inc(ifp, ifs6_out_discard);
 647                 ip6stat.ip6s_cantforward++;
 648         } else {
 649                 ip6stat.ip6s_forward++;
 650                 in6_ifstat_inc(ifp, ifs6_out_forward);
 651                 if (type)
 652                         ip6stat.ip6s_redirectsent++;
 653                 else {
 654                         if (mcopy) {
 655                                 goto freecopy;
 656                         }
 657                 }
 658         }
 659 #if PF
 660 senderr:
 661 #endif /* PF */
 662         if (mcopy == NULL) {
 663                 /* Release extra ref */
 664                 RT_REMREF(rt);
 665                 return;
 666         }
 667         switch (error) {
 668         case 0:
 669 #if 1
 670                 if (type == ND_REDIRECT) {
 671                         icmp6_redirect_output(mcopy, rt);
 672                         /* Release extra ref */
 673                         RT_REMREF(rt);
 674                         return;
 675                 }
 676 #endif
 677                 goto freecopy;
 678
 679         case EMSGSIZE:
 680                 /* xxx MTU is constant in PPP? */
 681                 goto freecopy;
 682
 683         case ENOBUFS:
 684                 /* Tell source to slow down like source quench in IP? */
 685                 goto freecopy;
 686
 687         case ENETUNREACH:       /* shouldn't happen, checked above */
 688         case EHOSTUNREACH:
 689         case ENETDOWN:
 690         case EHOSTDOWN:
 691         default:
 692                 type = ICMP6_DST_UNREACH;
 693                 code = ICMP6_DST_UNREACH_ADDR;
 694                 break;
 695         }
 696         icmp6_error(mcopy, type, code, 0);
 697         /* Release extra ref */
 698         RT_REMREF(rt);
 699         return;
 700
 701  freecopy:
 702         m_freem(mcopy);
 703         /* Release extra ref */
 704         RT_REMREF(rt);
 705         return;
 706 }