bsd/netinet6/ip6_forward.c

   1 /*
   2  * Copyright (c) 2009-2020 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 #include <netinet6/ipsec6.h>
  94 #include <netkey/key.h>
  95 extern int ipsec_bypass;
  96 #endif /* IPSEC */
  97
  98 #include <net/net_osdep.h>
  99
 100 #if DUMMYNET
 101 #include <netinet/ip_dummynet.h>
 102 #endif /* DUMMYNET */
 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 struct mbuf *
 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         boolean_t proxy = FALSE;
 130         struct mbuf *mcopy = NULL;
 131         struct ifnet *ifp, *rcvifp, *origifp;   /* maybe unnecessary */
 132         u_int32_t inzone, outzone, len = 0, pktcnt = 0;
 133         struct in6_addr src_in6, dst_in6;
 134         uint64_t curtime = net_uptime();
 135 #if IPSEC
 136         struct secpolicy *sp = NULL;
 137 #endif
 138         unsigned int ifscope = IFSCOPE_NONE;
 139 #if PF
 140         struct pf_mtag *pf_mtag;
 141         struct pf_fragment_tag *pf_ftagp, pf_ftag;
 142         boolean_t pf_ftag_valid = FALSE;
 143 #endif /* PF */
 144         uint32_t mpktlen = 0;
 145
 146         /*
 147          * In the prefix proxying case, the route to the proxied node normally
 148          * gets created by nd6_prproxy_ns_output(), as part of forwarding a
 149          * NS (NUD/AR) packet to the proxied node.  In the event that such
 150          * packet did not arrive in time before the correct route gets created,
 151          * ip6_input() would have performed a rtalloc() which most likely will
 152          * create the wrong cloned route; this route points back to the same
 153          * interface as the inbound interface, since the parent non-scoped
 154          * prefix route points there.  Therefore we check if that is the case
 155          * and perform the necessary fixup to get the correct route installed.
 156          */
 157         if (!srcrt && nd6_prproxy &&
 158             (rt = ip6forward_rt->ro_rt) != NULL && (rt->rt_flags & RTF_PROXY)) {
 159                 nd6_proxy_find_fwdroute(m->m_pkthdr.rcvif, ip6forward_rt);
 160                 if ((rt = ip6forward_rt->ro_rt) != NULL) {
 161                         ifscope = rt->rt_ifp->if_index;
 162                 }
 163         }
 164
 165 #if PF
 166         pf_mtag = pf_find_mtag(m);
 167         /*
 168          * save the PF fragmentation metadata as m_copy() removes the
 169          * mbufs tags from the original mbuf.
 170          */
 171         pf_ftagp = pf_find_fragment_tag(m);
 172         if (pf_ftagp != NULL) {
 173                 ASSERT(pf_mtag->pftag_flags & PF_TAG_REASSEMBLED);
 174                 pf_ftag = *pf_ftagp;
 175                 pf_ftag_valid = TRUE;
 176                 mpktlen = pf_ftag.ft_maxlen;
 177                 ASSERT(mpktlen);
 178         }
 179         if (pf_mtag != NULL && pf_mtag->pftag_rtableid != IFSCOPE_NONE) {
 180                 ifscope = pf_mtag->pftag_rtableid;
 181         }
 182         pf_mtag = NULL;
 183         pf_ftagp = NULL;
 184         /*
 185          * If the caller provides a route which is on a different interface
 186          * than the one specified for scoped forwarding, discard the route
 187          * and do a lookup below.
 188          */
 189         if (ifscope != IFSCOPE_NONE && (rt = ip6forward_rt->ro_rt) != NULL) {
 190                 RT_LOCK(rt);
 191                 if (rt->rt_ifp->if_index != ifscope) {
 192                         RT_UNLOCK(rt);
 193                         ROUTE_RELEASE(ip6forward_rt);
 194                         rt = NULL;
 195                 } else {
 196                         RT_UNLOCK(rt);
 197                 }
 198         }
 199 #endif /* PF */
 200
 201 #if IPSEC
 202         /*
 203          * Check AH/ESP integrity.
 204          */
 205         /*
 206          * Don't increment ip6s_cantforward because this is the check
 207          * before forwarding packet actually.
 208          */
 209         if (ipsec_bypass == 0) {
 210                 if (ipsec6_in_reject(m, NULL)) {
 211                         IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
 212                         m_freem(m);
 213                         return NULL;
 214                 }
 215         }
 216 #endif /*IPSEC*/
 217
 218         /*
 219          * Do not forward packets to multicast destination.
 220          * Do not forward packets with unspecified source.  It was discussed
 221          * in July 2000, on ipngwg mailing list.
 222          */
 223         if ((m->m_flags & (M_BCAST | M_MCAST)) != 0 ||
 224             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 225             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 226                 ip6stat.ip6s_cantforward++;
 227                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 228                 if (ip6_log_time + ip6_log_interval < curtime) {
 229                         ip6_log_time = curtime;
 230                         log(LOG_DEBUG,
 231                             "cannot forward "
 232                             "from %s to %s nxt %d received on %s\n",
 233                             ip6_sprintf(&ip6->ip6_src),
 234                             ip6_sprintf(&ip6->ip6_dst),
 235                             ip6->ip6_nxt,
 236                             if_name(m->m_pkthdr.rcvif));
 237                 }
 238                 m_freem(m);
 239                 return NULL;
 240         }
 241
 242         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 243                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 244                 icmp6_error_flag(m, ICMP6_TIME_EXCEEDED,
 245                     ICMP6_TIME_EXCEED_TRANSIT, 0, 0);
 246                 return NULL;
 247         }
 248
 249         /*
 250          * See if the destination is a proxied address, and if so pretend
 251          * that it's for us.  This is mostly to handle NUD probes against
 252          * the proxied addresses.  We filter for ICMPv6 here and will let
 253          * icmp6_input handle the rest.
 254          */
 255         if (!srcrt && nd6_prproxy) {
 256                 VERIFY(!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst));
 257                 proxy = nd6_prproxy_isours(m, ip6, ip6forward_rt, ifscope);
 258                 /*
 259                  * Don't update hop limit while proxying; RFC 4389 4.1.
 260                  * Also skip IPsec forwarding path processing as this
 261                  * packet is not to be forwarded.
 262                  */
 263                 if (proxy) {
 264                         goto skip_ipsec;
 265                 }
 266         }
 267
 268         ip6->ip6_hlim -= IPV6_HLIMDEC;
 269
 270         /*
 271          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 272          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 273          * we need to generate an ICMP6 message to the src.
 274          * Thanks to M_EXT, in most cases copy will not occur.
 275          *
 276          * It is important to save it before IPsec processing as IPsec
 277          * processing may modify the mbuf.
 278          */
 279         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 280
 281 #if IPSEC
 282         if (ipsec_bypass != 0) {
 283                 goto skip_ipsec;
 284         }
 285         /* get a security policy for this packet */
 286         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 287             &error);
 288         if (sp == NULL) {
 289                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 290                 ip6stat.ip6s_cantforward++;
 291                 if (mcopy) {
 292 #if 0
 293                         /* XXX: what icmp ? */
 294 #else
 295                         m_freem(mcopy);
 296 #endif
 297                 }
 298                 m_freem(m);
 299                 return NULL;
 300         }
 301
 302         error = 0;
 303
 304         /* check policy */
 305         switch (sp->policy) {
 306         case IPSEC_POLICY_DISCARD:
 307         case IPSEC_POLICY_GENERATE:
 308                 /*
 309                  * This packet is just discarded.
 310                  */
 311                 IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
 312                 ip6stat.ip6s_cantforward++;
 313                 key_freesp(sp, KEY_SADB_UNLOCKED);
 314                 if (mcopy) {
 315 #if 0
 316                         /* XXX: what icmp ? */
 317 #else
 318                         m_freem(mcopy);
 319 #endif
 320                 }
 321                 m_freem(m);
 322                 return NULL;
 323
 324         case IPSEC_POLICY_BYPASS:
 325         case IPSEC_POLICY_NONE:
 326                 /* no need to do IPsec. */
 327                 key_freesp(sp, KEY_SADB_UNLOCKED);
 328                 goto skip_ipsec;
 329
 330         case IPSEC_POLICY_IPSEC:
 331                 if (sp->req == NULL) {
 332                         /* XXX should be panic ? */
 333                         printf("ip6_forward: No IPsec request specified.\n");
 334                         ip6stat.ip6s_cantforward++;
 335                         key_freesp(sp, KEY_SADB_UNLOCKED);
 336                         if (mcopy) {
 337 #if 0
 338                                 /* XXX: what icmp ? */
 339 #else
 340                                 m_freem(mcopy);
 341 #endif
 342                         }
 343                         m_freem(m);
 344                         return NULL;
 345                 }
 346                 /* do IPsec */
 347                 break;
 348
 349         case IPSEC_POLICY_ENTRUST:
 350         default:
 351                 /* should be panic ?? */
 352                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 353                 key_freesp(sp, KEY_SADB_UNLOCKED);
 354                 goto skip_ipsec;
 355         }
 356
 357         {
 358                 struct ipsec_output_state state;
 359
 360                 /*
 361                  * All the extension headers will become inaccessible
 362                  * (since they can be encrypted).
 363                  * Don't panic, we need no more updates to extension headers
 364                  * on inner IPv6 packet (since they are now encapsulated).
 365                  *
 366                  * IPv6 [ESP|AH] IPv6 [extension headers] payload
 367                  */
 368                 bzero(&state, sizeof(state));
 369                 state.m = m;
 370                 state.dst = NULL; /* update at ipsec6_output_tunnel() */
 371
 372                 error = ipsec6_output_tunnel(&state, sp, 0);
 373                 key_freesp(sp, KEY_SADB_UNLOCKED);
 374                 if (state.tunneled == 4) {
 375                         ROUTE_RELEASE(&state.ro);
 376                         return NULL; /* packet is gone - sent over IPv4 */
 377                 }
 378
 379                 m = state.m;
 380                 ROUTE_RELEASE(&state.ro);
 381
 382                 if (error) {
 383                         /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 384                         switch (error) {
 385                         case EHOSTUNREACH:
 386                         case ENETUNREACH:
 387                         case EMSGSIZE:
 388                         case ENOBUFS:
 389                         case ENOMEM:
 390                                 break;
 391                         default:
 392                                 printf("ip6_output (ipsec): error code %d\n", error);
 393                                 OS_FALLTHROUGH;
 394                         case ENOENT:
 395                                 /* don't show these error codes to the user */
 396                                 break;
 397                         }
 398                         ip6stat.ip6s_cantforward++;
 399                         if (mcopy) {
 400 #if 0
 401                                 /* XXX: what icmp ? */
 402 #else
 403                                 m_freem(mcopy);
 404 #endif
 405                         }
 406                         m_freem(m);
 407                         return NULL;
 408                 }
 409         }
 410 #endif /* IPSEC */
 411 skip_ipsec:
 412
 413         dst = (struct sockaddr_in6 *)&ip6forward_rt->ro_dst;
 414         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 415                 RT_LOCK(rt);
 416                 /* Take an extra ref for ourselves */
 417                 RT_ADDREF_LOCKED(rt);
 418         }
 419
 420         VERIFY(rt == NULL || rt == ip6forward_rt->ro_rt);
 421         if (!srcrt) {
 422                 /*
 423                  * ip6forward_rt->ro_dst.sin6_addr is equal to ip6->ip6_dst
 424                  */
 425                 if (ROUTE_UNUSABLE(ip6forward_rt)) {
 426                         if (rt != NULL) {
 427                                 /* Release extra ref */
 428                                 RT_REMREF_LOCKED(rt);
 429                                 RT_UNLOCK(rt);
 430                         }
 431                         ROUTE_RELEASE(ip6forward_rt);
 432
 433                         /* this probably fails but give it a try again */
 434                         rtalloc_scoped_ign((struct route *)ip6forward_rt,
 435                             RTF_PRCLONING, ifscope);
 436                         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 437                                 RT_LOCK(rt);
 438                                 /* Take an extra ref for ourselves */
 439                                 RT_ADDREF_LOCKED(rt);
 440                         }
 441                 }
 442
 443                 if (rt == NULL) {
 444                         ip6stat.ip6s_noroute++;
 445                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 446                         if (mcopy) {
 447                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 448                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 449                         }
 450                         m_freem(m);
 451                         return NULL;
 452                 }
 453                 RT_LOCK_ASSERT_HELD(rt);
 454         } else if (ROUTE_UNUSABLE(ip6forward_rt) ||
 455             !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 456                 if (rt != NULL) {
 457                         /* Release extra ref */
 458                         RT_REMREF_LOCKED(rt);
 459                         RT_UNLOCK(rt);
 460                 }
 461                 ROUTE_RELEASE(ip6forward_rt);
 462
 463                 bzero(dst, sizeof(*dst));
 464                 dst->sin6_len = sizeof(struct sockaddr_in6);
 465                 dst->sin6_family = AF_INET6;
 466                 dst->sin6_addr = ip6->ip6_dst;
 467
 468                 rtalloc_scoped_ign((struct route *)ip6forward_rt,
 469                     RTF_PRCLONING, ifscope);
 470                 if ((rt = ip6forward_rt->ro_rt) == NULL) {
 471                         ip6stat.ip6s_noroute++;
 472                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 473                         if (mcopy) {
 474                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 475                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 476                         }
 477                         m_freem(m);
 478                         return NULL;
 479                 }
 480                 RT_LOCK(rt);
 481                 /* Take an extra ref for ourselves */
 482                 RT_ADDREF_LOCKED(rt);
 483         }
 484
 485         /*
 486          * Source scope check: if a packet can't be delivered to its
 487          * destination for the reason that the destination is beyond the scope
 488          * of the source address, discard the packet and return an icmp6
 489          * destination unreachable error with Code 2 (beyond scope of source
 490          * address) unless we are proxying (source address is link local
 491          * for NUDs.)  We use a local copy of ip6_src, since in6_setscope()
 492          * will possibly modify its first argument.
 493          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
 494          */
 495         src_in6 = ip6->ip6_src;
 496         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
 497                 RT_REMREF_LOCKED(rt);
 498                 RT_UNLOCK(rt);
 499                 /* XXX: this should not happen */
 500                 ip6stat.ip6s_cantforward++;
 501                 ip6stat.ip6s_badscope++;
 502                 m_freem(m);
 503                 return NULL;
 504         }
 505         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
 506                 RT_REMREF_LOCKED(rt);
 507                 RT_UNLOCK(rt);
 508                 ip6stat.ip6s_cantforward++;
 509                 ip6stat.ip6s_badscope++;
 510                 m_freem(m);
 511                 return NULL;
 512         }
 513
 514         if (inzone != outzone && !proxy) {
 515                 ip6stat.ip6s_cantforward++;
 516                 ip6stat.ip6s_badscope++;
 517                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 518
 519                 if (ip6_log_time + ip6_log_interval < curtime) {
 520                         ip6_log_time = curtime;
 521                         log(LOG_DEBUG,
 522                             "cannot forward "
 523                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 524                             ip6_sprintf(&ip6->ip6_src),
 525                             ip6_sprintf(&ip6->ip6_dst),
 526                             ip6->ip6_nxt,
 527                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 528                 }
 529                 /* Release extra ref */
 530                 RT_REMREF_LOCKED(rt);
 531                 RT_UNLOCK(rt);
 532                 if (mcopy) {
 533                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 534                             ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 535                 }
 536                 m_freem(m);
 537                 return NULL;
 538         }
 539
 540         /*
 541          * Destination scope check: if a packet is going to break the scope
 542          * zone of packet's destination address, discard it.  This case should
 543          * usually be prevented by appropriately-configured routing table, but
 544          * we need an explicit check because we may mistakenly forward the
 545          * packet to a different zone by (e.g.) a default route.
 546          */
 547         dst_in6 = ip6->ip6_dst;
 548         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
 549             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
 550             inzone != outzone) {
 551                 RT_REMREF_LOCKED(rt);
 552                 RT_UNLOCK(rt);
 553                 ip6stat.ip6s_cantforward++;
 554                 ip6stat.ip6s_badscope++;
 555                 m_freem(m);
 556                 return NULL;
 557         }
 558
 559         if (mpktlen == 0) {
 560                 mpktlen = m->m_pkthdr.len;
 561         }
 562
 563         if (mpktlen > rt->rt_ifp->if_mtu) {
 564                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 565                 if (mcopy) {
 566                         uint32_t mtu;
 567 #if IPSEC
 568                         struct secpolicy *sp2;
 569                         int ipsecerror;
 570                         size_t ipsechdrsiz;
 571 #endif
 572
 573                         mtu = rt->rt_ifp->if_mtu;
 574 #if IPSEC
 575                         /*
 576                          * When we do IPsec tunnel ingress, we need to play
 577                          * with the link value (decrement IPsec header size
 578                          * from mtu value).  The code is much simpler than v4
 579                          * case, as we have the outgoing interface for
 580                          * encapsulated packet as "rt->rt_ifp".
 581                          */
 582                         sp2 = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 583                             IP_FORWARDING, &ipsecerror);
 584                         if (sp2) {
 585                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 586                                     IPSEC_DIR_OUTBOUND, NULL);
 587                                 if (ipsechdrsiz < mtu) {
 588                                         mtu -= ipsechdrsiz;
 589                                 }
 590                                 key_freesp(sp2, KEY_SADB_UNLOCKED);
 591                         }
 592                         /*
 593                          * if mtu becomes less than minimum MTU,
 594                          * tell minimum MTU (and I'll need to fragment it).
 595                          */
 596                         if (mtu < IPV6_MMTU) {
 597                                 mtu = IPV6_MMTU;
 598                         }
 599 #endif
 600                         /* Release extra ref */
 601                         RT_REMREF_LOCKED(rt);
 602                         RT_UNLOCK(rt);
 603                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 604                 } else {
 605                         /* Release extra ref */
 606                         RT_REMREF_LOCKED(rt);
 607                         RT_UNLOCK(rt);
 608                 }
 609                 m_freem(m);
 610                 return NULL;
 611         }
 612
 613         if (rt->rt_flags & RTF_GATEWAY) {
 614                 dst = (struct sockaddr_in6 *)(void *)rt->rt_gateway;
 615         }
 616
 617         /*
 618          * If we are to forward the packet using the same interface
 619          * as one we got the packet from, perhaps we should send a redirect
 620          * to sender to shortcut a hop.
 621          * Only send redirect if source is sending directly to us,
 622          * and if packet was not source routed (or has any options).
 623          * Also, don't send redirect if forwarding using a route
 624          * modified by a redirect.
 625          */
 626         if (!proxy &&
 627             ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 628             (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) {
 629                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 630                         /*
 631                          * If the incoming interface is equal to the outgoing
 632                          * one, and the link attached to the interface is
 633                          * point-to-point, then it will be highly probable
 634                          * that a routing loop occurs. Thus, we immediately
 635                          * drop the packet and send an ICMPv6 error message.
 636                          *
 637                          * type/code is based on suggestion by Rich Draves.
 638                          * not sure if it is the best pick.
 639                          */
 640                         RT_REMREF_LOCKED(rt);   /* Release extra ref */
 641                         RT_UNLOCK(rt);
 642                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 643                             ICMP6_DST_UNREACH_ADDR, 0);
 644                         m_freem(m);
 645                         return NULL;
 646                 }
 647                 type = ND_REDIRECT;
 648         }
 649         /*
 650          * Fake scoped addresses. Note that even link-local source or
 651          * destinaion can appear, if the originating node just sends the
 652          * packet to us (without address resolution for the destination).
 653          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 654          * link identifiers, we can do this stuff after making a copy for
 655          * returning an error.
 656          */
 657         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 658                 /*
 659                  * See corresponding comments in ip6_output.
 660                  * XXX: but is it possible that ip6_forward() sends a packet
 661                  *      to a loopback interface? I don't think so, and thus
 662                  *      I bark here. (jinmei@kame.net)
 663                  * XXX: it is common to route invalid packets to loopback.
 664                  *      also, the codepath will be visited on use of ::1 in
 665                  *      rthdr. (itojun)
 666                  */
 667 #if 1
 668                 if ((0))
 669 #else
 670                 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0)
 671 #endif
 672                 {
 673                         printf("ip6_forward: outgoing interface is loopback. "
 674                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 675                             ip6_sprintf(&ip6->ip6_src),
 676                             ip6_sprintf(&ip6->ip6_dst),
 677                             ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 678                             if_name(rt->rt_ifp));
 679                 }
 680
 681                 /* we can just use rcvif in forwarding. */
 682                 origifp = rcvifp = m->m_pkthdr.rcvif;
 683         } else if (nd6_prproxy) {
 684                 /*
 685                  * In the prefix proxying case, we need to inform nd6_output()
 686                  * about the inbound interface, so that any subsequent NS
 687                  * packets generated by nd6_prproxy_ns_output() will not be
 688                  * sent back to that same interface.
 689                  */
 690                 origifp = rcvifp = m->m_pkthdr.rcvif;
 691         } else {
 692                 rcvifp = m->m_pkthdr.rcvif;
 693                 origifp = rt->rt_ifp;
 694         }
 695         /*
 696          * clear embedded scope identifiers if necessary.
 697          * in6_clearscope will touch the addresses only when necessary.
 698          */
 699         in6_clearscope(&ip6->ip6_src);
 700         in6_clearscope(&ip6->ip6_dst);
 701
 702         ifp = rt->rt_ifp;
 703         /* Drop the lock but retain the extra ref */
 704         RT_UNLOCK(rt);
 705
 706         /*
 707          * If this is to be processed locally, let ip6_input have it.
 708          */
 709         if (proxy) {
 710                 VERIFY(m->m_pkthdr.pkt_flags & PKTF_PROXY_DST);
 711                 /* Release extra ref */
 712                 RT_REMREF(rt);
 713                 if (mcopy != NULL) {
 714                         m_freem(mcopy);
 715                 }
 716                 return m;
 717         }
 718
 719         /* Mark this packet as being forwarded from another interface */
 720         m->m_pkthdr.pkt_flags |= PKTF_FORWARDED;
 721
 722 #if PF
 723         if (PF_IS_ENABLED) {
 724                 /*
 725                  * PF refragments any packet which it reassembled due to scrub
 726                  * rules, in which case it will set the PF_TAG_REFRAGMENTED
 727                  * flag in PF mbuf tag.
 728                  */
 729                 if (pf_ftag_valid) {
 730                         pf_copy_fragment_tag(m, &pf_ftag, M_DONTWAIT);
 731                 }
 732 #if DUMMYNET
 733                 struct ip_fw_args args;
 734                 bzero(&args, sizeof(args));
 735
 736                 args.fwa_m = m;
 737                 args.fwa_oif = ifp;
 738                 args.fwa_oflags = 0;
 739                 args.fwa_ro6 = ip6forward_rt;
 740                 args.fwa_ro6_pmtu = ip6forward_rt;
 741                 args.fwa_mtu = rt->rt_ifp->if_mtu;
 742                 args.fwa_dst6 = dst;
 743                 args.fwa_origifp = origifp;
 744                 /* Invoke outbound packet filter */
 745                 error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, &args);
 746 #else /* !DUMMYNET */
 747                 error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, NULL);
 748 #endif /* !DUMMYNET */
 749                 if (error != 0 || m == NULL) {
 750                         if (m != NULL) {
 751                                 panic("%s: unexpected packet %p\n", __func__, m);
 752                                 /* NOTREACHED */
 753                         }
 754                         /* Already freed by callee */
 755                         goto senderr;
 756                 }
 757
 758                 pf_mtag = pf_find_mtag(m);
 759                 /*
 760                  * refragmented packets from PF.
 761                  */
 762                 if ((pf_mtag->pftag_flags & PF_TAG_REFRAGMENTED) != 0) {
 763                         struct mbuf *t;
 764
 765                         pf_mtag->pftag_flags &= ~PF_TAG_REFRAGMENTED;
 766                         /* for statistics */
 767                         t = m;
 768                         while (t != NULL) {
 769                                 pktcnt++;
 770                                 len += m_pktlen(t);
 771                                 t = t->m_nextpkt;
 772                         }
 773
 774                         /*
 775                          * nd6_output() frees packetchain in both success and
 776                          * failure cases.
 777                          */
 778                         error = nd6_output(ifp, origifp, m, dst, rt, NULL);
 779                         m = NULL;
 780                         goto sent;
 781                 }
 782                 /*
 783                  * We do not use ip6 header again in the code below,
 784                  * however still adding the bit here so that any new
 785                  * code in future doesn't end up working with the
 786                  * wrong pointer
 787                  */
 788                 ip6 = mtod(m, struct ip6_hdr *);
 789         }
 790 #endif /* PF */
 791
 792         len = m_pktlen(m);
 793         pktcnt = 1;
 794         error = nd6_output(ifp, origifp, m, dst, rt, NULL);
 795 sent:
 796         if (error) {
 797                 in6_ifstat_add(ifp, ifs6_out_discard, pktcnt);
 798                 ip6stat.ip6s_cantforward += pktcnt;
 799         } else {
 800                 /*
 801                  * Increment stats on the source interface; the ones
 802                  * for destination interface has been taken care of
 803                  * during output above by virtue of PKTF_FORWARDED.
 804                  */
 805                 rcvifp->if_fpackets += pktcnt;
 806                 rcvifp->if_fbytes += len;
 807
 808                 ip6stat.ip6s_forward += pktcnt;
 809                 in6_ifstat_add(ifp, ifs6_out_forward, pktcnt);
 810                 if (type) {
 811                         ip6stat.ip6s_redirectsent++;
 812                 } else {
 813                         if (mcopy) {
 814                                 goto freecopy;
 815                         }
 816                 }
 817         }
 818 #if PF
 819 senderr:
 820 #endif /* PF */
 821         if (mcopy == NULL) {
 822                 /* Release extra ref */
 823                 RT_REMREF(rt);
 824                 return NULL;
 825         }
 826         switch (error) {
 827         case 0:
 828 #if 1
 829                 if (type == ND_REDIRECT) {
 830                         icmp6_redirect_output(mcopy, rt);
 831                         /* Release extra ref */
 832                         RT_REMREF(rt);
 833                         return NULL;
 834                 }
 835 #endif
 836                 goto freecopy;
 837
 838         case EMSGSIZE:
 839                 /* xxx MTU is constant in PPP? */
 840                 goto freecopy;
 841
 842         case ENOBUFS:
 843                 /* Tell source to slow down like source quench in IP? */
 844                 goto freecopy;
 845
 846         case ENETUNREACH:       /* shouldn't happen, checked above */
 847         case EHOSTUNREACH:
 848         case ENETDOWN:
 849         case EHOSTDOWN:
 850         default:
 851                 type = ICMP6_DST_UNREACH;
 852                 code = ICMP6_DST_UNREACH_ADDR;
 853                 break;
 854         }
 855         icmp6_error(mcopy, type, code, 0);
 856         /* Release extra ref */
 857         RT_REMREF(rt);
 858         return NULL;
 859
 860 freecopy:
 861         m_freem(mcopy);
 862         /* Release extra ref */
 863         RT_REMREF(rt);
 864         return NULL;
 865 }