bsd/netinet6/ip6_forward.c

   1 /*
   2  * Copyright (c) 2008 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
  88 #include <netinet/in_pcb.h>
  89
  90 #if IPSEC
  91 #include <netinet6/ipsec.h>
  92 #if INET6
  93 #include <netinet6/ipsec6.h>
  94 #endif
  95 #include <netkey/key.h>
  96 extern int ipsec_bypass;
  97 #endif /* IPSEC */
  98 extern lck_mtx_t *ip6_mutex;
  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, int locked)
 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 #if IPSEC
 132         struct secpolicy *sp = NULL;
 133 #endif
 134         struct timeval timenow;
 135         int     tunneledv4 = 0;
 136
 137         getmicrotime(&timenow);
 138
 139
 140 #if IPSEC
 141         /*
 142          * Check AH/ESP integrity.
 143          */
 144         /*
 145          * Don't increment ip6s_cantforward because this is the check
 146          * before forwarding packet actually.
 147          */
 148         if (ipsec_bypass == 0) {
 149                 if (ipsec6_in_reject(m, NULL)) {
 150                         IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
 151                         m_freem(m);
 152                         return;
 153                 }
 154         }
 155 #endif /*IPSEC*/
 156
 157         /*
 158          * Do not forward packets to multicast destination (should be handled
 159          * by ip6_mforward().
 160          * Do not forward packets with unspecified source.  It was discussed
 161          * in July 2000, on ipngwg mailing list.
 162          */
 163         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 164             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 165             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 166                 ip6stat.ip6s_cantforward++;
 167                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 168                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 169                         ip6_log_time = timenow.tv_sec;
 170                         log(LOG_DEBUG,
 171                             "cannot forward "
 172                             "from %s to %s nxt %d received on %s\n",
 173                             ip6_sprintf(&ip6->ip6_src),
 174                             ip6_sprintf(&ip6->ip6_dst),
 175                             ip6->ip6_nxt,
 176                             if_name(m->m_pkthdr.rcvif));
 177                 }
 178                 m_freem(m);
 179                 return;
 180         }
 181
 182         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 183                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 184                 if (locked)
 185                         lck_mtx_unlock(ip6_mutex);
 186                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 187                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 188                 if (locked)
 189                         lck_mtx_lock(ip6_mutex);
 190                 return;
 191         }
 192         ip6->ip6_hlim -= IPV6_HLIMDEC;
 193
 194         /*
 195          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 196          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 197          * we need to generate an ICMP6 message to the src.
 198          * Thanks to M_EXT, in most cases copy will not occur.
 199          *
 200          * It is important to save it before IPsec processing as IPsec
 201          * processing may modify the mbuf.
 202          */
 203         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 204
 205 #if IPSEC
 206         if (ipsec_bypass != 0)
 207                 goto skip_ipsec;
 208         /* get a security policy for this packet */
 209         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 210             &error);
 211         if (sp == NULL) {
 212                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 213                 ip6stat.ip6s_cantforward++;
 214                 if (mcopy) {
 215 #if 0
 216                         /* XXX: what icmp ? */
 217 #else
 218                         m_freem(mcopy);
 219 #endif
 220                 }
 221                 m_freem(m);
 222                 return;
 223         }
 224
 225         error = 0;
 226
 227         /* check policy */
 228         switch (sp->policy) {
 229         case IPSEC_POLICY_DISCARD:
 230         case IPSEC_POLICY_GENERATE:
 231                 /*
 232                  * This packet is just discarded.
 233                  */
 234                 IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
 235                 ip6stat.ip6s_cantforward++;
 236                 key_freesp(sp, KEY_SADB_UNLOCKED);
 237                 if (mcopy) {
 238 #if 0
 239                         /* XXX: what icmp ? */
 240 #else
 241                         m_freem(mcopy);
 242 #endif
 243                 }
 244                 m_freem(m);
 245                 return;
 246
 247         case IPSEC_POLICY_BYPASS:
 248         case IPSEC_POLICY_NONE:
 249                 /* no need to do IPsec. */
 250                 key_freesp(sp, KEY_SADB_UNLOCKED);
 251                 goto skip_ipsec;
 252
 253         case IPSEC_POLICY_IPSEC:
 254                 if (sp->req == NULL) {
 255                         /* XXX should be panic ? */
 256                         printf("ip6_forward: No IPsec request specified.\n");
 257                         ip6stat.ip6s_cantforward++;
 258                         key_freesp(sp, KEY_SADB_UNLOCKED);
 259                         if (mcopy) {
 260 #if 0
 261                                 /* XXX: what icmp ? */
 262 #else
 263                                 m_freem(mcopy);
 264 #endif
 265                         }
 266                         m_freem(m);
 267                         return;
 268                 }
 269                 /* do IPsec */
 270                 break;
 271
 272         case IPSEC_POLICY_ENTRUST:
 273         default:
 274                 /* should be panic ?? */
 275                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 276                 key_freesp(sp, KEY_SADB_UNLOCKED);
 277                 goto skip_ipsec;
 278         }
 279
 280     {
 281         struct ipsec_output_state state;
 282
 283         /*
 284          * All the extension headers will become inaccessible
 285          * (since they can be encrypted).
 286          * Don't panic, we need no more updates to extension headers
 287          * on inner IPv6 packet (since they are now encapsulated).
 288          *
 289          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 290          */
 291         bzero(&state, sizeof(state));
 292         state.m = m;
 293         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 294         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 295
 296         if (locked)
 297                 lck_mtx_unlock(ip6_mutex);
 298         error = ipsec6_output_tunnel(&state, sp, 0, &tunneledv4);
 299         if (locked)
 300                 lck_mtx_lock(ip6_mutex);
 301         key_freesp(sp, KEY_SADB_UNLOCKED);
 302         if (tunneledv4)
 303                 return;  /* packet is gone - sent over IPv4 */
 304
 305         m = state.m;
 306         if (error) {
 307                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 308                 switch (error) {
 309                 case EHOSTUNREACH:
 310                 case ENETUNREACH:
 311                 case EMSGSIZE:
 312                 case ENOBUFS:
 313                 case ENOMEM:
 314                         break;
 315                 default:
 316                         printf("ip6_output (ipsec): error code %d\n", error);
 317                         /* fall through */
 318                 case ENOENT:
 319                         /* don't show these error codes to the user */
 320                         break;
 321                 }
 322                 ip6stat.ip6s_cantforward++;
 323                 if (mcopy) {
 324 #if 0
 325                         /* XXX: what icmp ? */
 326 #else
 327                         m_freem(mcopy);
 328 #endif
 329                 }
 330                 m_freem(m);
 331                 return;
 332         }
 333     }
 334     skip_ipsec:
 335 #endif /* IPSEC */
 336
 337         /*
 338          * If "locked", ip6forward_rt points to the globally defined
 339          * struct route cache which requires ip6_mutex, e.g. when this
 340          * is called from ip6_input().  Else the caller is responsible
 341          * for the struct route and its serialization (if needed), e.g.
 342          * when this is called from ip6_rthdr0().
 343          */
 344         if (locked)
 345                 lck_mtx_assert(ip6_mutex, LCK_MTX_ASSERT_OWNED);
 346         dst = (struct sockaddr_in6 *)&ip6forward_rt->ro_dst;
 347         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 348                 RT_LOCK(rt);
 349                 /* Take an extra ref for ourselves */
 350                 RT_ADDREF_LOCKED(rt);
 351         }
 352
 353         if (!srcrt) {
 354                 /*
 355                  * ip6forward_rt->ro_dst.sin6_addr is equal to ip6->ip6_dst
 356                  */
 357                 if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 358                     rt->generation_id != route_generation) {
 359                         if (rt != NULL) {
 360                                 /* Release extra ref */
 361                                 RT_REMREF_LOCKED(rt);
 362                                 RT_UNLOCK(rt);
 363                                 rtfree(rt);
 364                                 ip6forward_rt->ro_rt = NULL;
 365                         }
 366                         /* this probably fails but give it a try again */
 367                         rtalloc_ign((struct route *)ip6forward_rt,
 368                             RTF_PRCLONING);
 369                         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 370                                 RT_LOCK(rt);
 371                                 /* Take an extra ref for ourselves */
 372                                 RT_ADDREF_LOCKED(rt);
 373                         }
 374                 }
 375
 376                 if (rt == NULL) {
 377                         ip6stat.ip6s_noroute++;
 378                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 379                         if (mcopy) {
 380                                 if (locked)
 381                                         lck_mtx_unlock(ip6_mutex);
 382                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 383                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 384                                 if (locked)
 385                                         lck_mtx_lock(ip6_mutex);
 386                         }
 387                         m_freem(m);
 388                         return;
 389                 }
 390                 RT_LOCK_ASSERT_HELD(rt);
 391         } else if (rt == NULL || !(rt->rt_flags & RTF_UP) ||
 392             !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr) ||
 393             rt->generation_id != route_generation) {
 394                 if (rt != NULL) {
 395                         /* Release extra ref */
 396                         RT_REMREF_LOCKED(rt);
 397                         RT_UNLOCK(rt);
 398                         rtfree(rt);
 399                         ip6forward_rt->ro_rt = NULL;
 400                 }
 401                 bzero(dst, sizeof(*dst));
 402                 dst->sin6_len = sizeof(struct sockaddr_in6);
 403                 dst->sin6_family = AF_INET6;
 404                 dst->sin6_addr = ip6->ip6_dst;
 405
 406                 rtalloc_ign((struct route *)ip6forward_rt, RTF_PRCLONING);
 407                 if ((rt = ip6forward_rt->ro_rt) == NULL) {
 408                         ip6stat.ip6s_noroute++;
 409                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 410                         if (mcopy) {
 411                                 if (locked)
 412                                         lck_mtx_unlock(ip6_mutex);
 413                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 414                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 415                                 if (locked)
 416                                         lck_mtx_lock(ip6_mutex);
 417                         }
 418                         m_freem(m);
 419                         return;
 420                 }
 421                 RT_LOCK(rt);
 422                 /* Take an extra ref for ourselves */
 423                 RT_ADDREF_LOCKED(rt);
 424         }
 425
 426         /*
 427          * Scope check: if a packet can't be delivered to its destination
 428          * for the reason that the destination is beyond the scope of the
 429          * source address, discard the packet and return an icmp6 destination
 430          * unreachable error with Code 2 (beyond scope of source address).
 431          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 432          */
 433         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 434             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 435                 ip6stat.ip6s_cantforward++;
 436                 ip6stat.ip6s_badscope++;
 437                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 438
 439                 if (ip6_log_time + ip6_log_interval < timenow.tv_sec) {
 440                         ip6_log_time = timenow.tv_sec;
 441                         log(LOG_DEBUG,
 442                             "cannot forward "
 443                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 444                             ip6_sprintf(&ip6->ip6_src),
 445                             ip6_sprintf(&ip6->ip6_dst),
 446                             ip6->ip6_nxt,
 447                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 448                 }
 449                 /* Release extra ref */
 450                 RT_REMREF_LOCKED(rt);
 451                 RT_UNLOCK(rt);
 452                 if (mcopy) {
 453                         if (locked)
 454                                 lck_mtx_unlock(ip6_mutex);
 455                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 456                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 457                         if (locked)
 458                                 lck_mtx_lock(ip6_mutex);
 459                 }
 460                 m_freem(m);
 461                 return;
 462         }
 463
 464         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 465                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 466                 if (mcopy) {
 467                         uint32_t mtu;
 468 #if IPSEC
 469                         struct secpolicy *sp2;
 470                         int ipsecerror;
 471                         size_t ipsechdrsiz;
 472 #endif
 473
 474                         mtu = rt->rt_ifp->if_mtu;
 475 #if IPSEC
 476                         /*
 477                          * When we do IPsec tunnel ingress, we need to play
 478                          * with if_mtu value (decrement IPsec header size
 479                          * from mtu value).  The code is much simpler than v4
 480                          * case, as we have the outgoing interface for
 481                          * encapsulated packet as "rt->rt_ifp".
 482                          */
 483                         sp2 = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 484                                 IP_FORWARDING, &ipsecerror);
 485                         if (sp2) {
 486                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 487                                         IPSEC_DIR_OUTBOUND, NULL);
 488                                 if (ipsechdrsiz < mtu)
 489                                         mtu -= ipsechdrsiz;
 490                                 key_freesp(sp2, KEY_SADB_UNLOCKED);
 491                         }
 492                         /*
 493                          * if mtu becomes less than minimum MTU,
 494                          * tell minimum MTU (and I'll need to fragment it).
 495                          */
 496                         if (mtu < IPV6_MMTU)
 497                                 mtu = IPV6_MMTU;
 498 #endif
 499                         /* Release extra ref */
 500                         RT_REMREF_LOCKED(rt);
 501                         RT_UNLOCK(rt);
 502                         if (locked)
 503                                 lck_mtx_unlock(ip6_mutex);
 504                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 505                         if (locked)
 506                                 lck_mtx_lock(ip6_mutex);
 507                 } else {
 508                         /* Release extra ref */
 509                         RT_REMREF_LOCKED(rt);
 510                         RT_UNLOCK(rt);
 511                 }
 512                 m_freem(m);
 513                 return;
 514         }
 515
 516         if (rt->rt_flags & RTF_GATEWAY)
 517                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 518
 519         /*
 520          * If we are to forward the packet using the same interface
 521          * as one we got the packet from, perhaps we should send a redirect
 522          * to sender to shortcut a hop.
 523          * Only send redirect if source is sending directly to us,
 524          * and if packet was not source routed (or has any options).
 525          * Also, don't send redirect if forwarding using a route
 526          * modified by a redirect.
 527          */
 528         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 529             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 530                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 531                         /*
 532                          * If the incoming interface is equal to the outgoing
 533                          * one, and the link attached to the interface is
 534                          * point-to-point, then it will be highly probable
 535                          * that a routing loop occurs. Thus, we immediately
 536                          * drop the packet and send an ICMPv6 error message.
 537                          *
 538                          * type/code is based on suggestion by Rich Draves.
 539                          * not sure if it is the best pick.
 540                          */
 541                         RT_REMREF_LOCKED(rt);   /* Release extra ref */
 542                         RT_UNLOCK(rt);
 543                         if (locked)
 544                                 lck_mtx_unlock(ip6_mutex);
 545                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 546                                     ICMP6_DST_UNREACH_ADDR, 0);
 547                         if (locked)
 548                                 lck_mtx_lock(ip6_mutex);
 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                 ifp = rt->rt_ifp;
 561                 /* Drop the lock but retain the extra ref */
 562                 RT_UNLOCK(rt);
 563                 /* If ipfw says divert, we have to just drop packet */
 564                 if (ip6_fw_chk_ptr(&ip6, ifp, &port, &m)) {
 565                         m_freem(m);
 566                         goto freecopy;
 567                 }
 568                 if (!m) {
 569                         goto freecopy;
 570                 }
 571                 /* We still have the extra ref on rt */
 572                 RT_LOCK(rt);
 573         }
 574
 575         /*
 576          * Fake scoped addresses. Note that even link-local source or
 577          * destinaion can appear, if the originating node just sends the
 578          * packet to us (without address resolution for the destination).
 579          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 580          * link identifiers, we can do this stuff after making a copy for
 581          * returning an error.
 582          */
 583         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 584                 /*
 585                  * See corresponding comments in ip6_output.
 586                  * XXX: but is it possible that ip6_forward() sends a packet
 587                  *      to a loopback interface? I don't think so, and thus
 588                  *      I bark here. (jinmei@kame.net)
 589                  * XXX: it is common to route invalid packets to loopback.
 590                  *      also, the codepath will be visited on use of ::1 in
 591                  *      rthdr. (itojun)
 592                  */
 593 #if 1
 594                 if (0)
 595 #else
 596                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 597 #endif
 598                 {
 599                         printf("ip6_forward: outgoing interface is loopback. "
 600                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 601                                 ip6_sprintf(&ip6->ip6_src),
 602                                 ip6_sprintf(&ip6->ip6_dst),
 603                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 604                                 if_name(rt->rt_ifp));
 605                 }
 606
 607                 /* we can just use rcvif in forwarding. */
 608                 origifp = m->m_pkthdr.rcvif;
 609         }
 610         else
 611                 origifp = rt->rt_ifp;
 612 #ifndef SCOPEDROUTING
 613         /*
 614          * clear embedded scope identifiers if necessary.
 615          * in6_clearscope will touch the addresses only when necessary.
 616          */
 617         in6_clearscope(&ip6->ip6_src);
 618         in6_clearscope(&ip6->ip6_dst);
 619 #endif
 620
 621         ifp = rt->rt_ifp;
 622         /* Drop the lock but retain the extra ref */
 623         RT_UNLOCK(rt);
 624
 625 #if PF
 626         if (locked)
 627                 lck_mtx_unlock(ip6_mutex);
 628
 629         /* Invoke outbound packet filter */
 630         error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE);
 631
 632         if (locked)
 633                 lck_mtx_lock(ip6_mutex);
 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, locked);
 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         if (locked)
 699                 lck_mtx_unlock(ip6_mutex);
 700         icmp6_error(mcopy, type, code, 0);
 701         if (locked)
 702                 lck_mtx_lock(ip6_mutex);
 703         /* Release extra ref */
 704         RT_REMREF(rt);
 705         return;
 706
 707  freecopy:
 708         m_freem(mcopy);
 709         /* Release extra ref */
 710         RT_REMREF(rt);
 711         return;
 712 }