bsd/netinet6/ip6_forward.c

   1 /*
   2  * Copyright (c) 2009-2016 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 <net/net_osdep.h>
 101
 102 #if DUMMYNET
 103 #include <netinet/ip_fw.h>
 104 #include <netinet/ip_dummynet.h>
 105 #endif /* DUMMYNET */
 106
 107 #if PF
 108 #include <net/pfvar.h>
 109 #endif /* PF */
 110
 111 /*
 112  * Forward a packet.  If some error occurs return the sender
 113  * an icmp packet.  Note we can't always generate a meaningful
 114  * icmp message because icmp doesn't have a large enough repertoire
 115  * of codes and types.
 116  *
 117  * If not forwarding, just drop the packet.  This could be confusing
 118  * if ipforwarding was zero but some routing protocol was advancing
 119  * us as a gateway to somewhere.  However, we must let the routing
 120  * protocol deal with that.
 121  *
 122  */
 123
 124 struct mbuf *
 125 ip6_forward(struct mbuf *m, struct route_in6 *ip6forward_rt,
 126     int srcrt)
 127 {
 128         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 129         struct sockaddr_in6 *dst;
 130         struct rtentry *rt;
 131         int error, type = 0, code = 0;
 132         boolean_t proxy = FALSE;
 133         struct mbuf *mcopy = NULL;
 134         struct ifnet *ifp, *rcvifp, *origifp;   /* maybe unnecessary */
 135         u_int32_t inzone, outzone, len;
 136         struct in6_addr src_in6, dst_in6;
 137         uint64_t curtime = net_uptime();
 138 #if IPSEC
 139         struct secpolicy *sp = NULL;
 140 #endif
 141         unsigned int ifscope = IFSCOPE_NONE;
 142 #if PF
 143         struct pf_mtag *pf_mtag;
 144 #endif /* PF */
 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         if (pf_mtag != NULL && pf_mtag->pftag_rtableid != IFSCOPE_NONE) {
 168                 ifscope = pf_mtag->pftag_rtableid;
 169         }
 170
 171         /*
 172          * If the caller provides a route which is on a different interface
 173          * than the one specified for scoped forwarding, discard the route
 174          * and do a lookup below.
 175          */
 176         if (ifscope != IFSCOPE_NONE && (rt = ip6forward_rt->ro_rt) != NULL) {
 177                 RT_LOCK(rt);
 178                 if (rt->rt_ifp->if_index != ifscope) {
 179                         RT_UNLOCK(rt);
 180                         ROUTE_RELEASE(ip6forward_rt);
 181                         rt = NULL;
 182                 } else {
 183                         RT_UNLOCK(rt);
 184                 }
 185         }
 186 #endif /* PF */
 187
 188 #if IPSEC
 189         /*
 190          * Check AH/ESP integrity.
 191          */
 192         /*
 193          * Don't increment ip6s_cantforward because this is the check
 194          * before forwarding packet actually.
 195          */
 196         if (ipsec_bypass == 0) {
 197                 if (ipsec6_in_reject(m, NULL)) {
 198                         IPSEC_STAT_INCREMENT(ipsec6stat.in_polvio);
 199                         m_freem(m);
 200                         return NULL;
 201                 }
 202         }
 203 #endif /*IPSEC*/
 204
 205         /*
 206          * Do not forward packets to multicast destination.
 207          * Do not forward packets with unspecified source.  It was discussed
 208          * in July 2000, on ipngwg mailing list.
 209          */
 210         if ((m->m_flags & (M_BCAST | M_MCAST)) != 0 ||
 211             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 212             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 213                 ip6stat.ip6s_cantforward++;
 214                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 215                 if (ip6_log_time + ip6_log_interval < curtime) {
 216                         ip6_log_time = curtime;
 217                         log(LOG_DEBUG,
 218                             "cannot forward "
 219                             "from %s to %s nxt %d received on %s\n",
 220                             ip6_sprintf(&ip6->ip6_src),
 221                             ip6_sprintf(&ip6->ip6_dst),
 222                             ip6->ip6_nxt,
 223                             if_name(m->m_pkthdr.rcvif));
 224                 }
 225                 m_freem(m);
 226                 return NULL;
 227         }
 228
 229         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 230                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 231                 icmp6_error_flag(m, ICMP6_TIME_EXCEEDED,
 232                     ICMP6_TIME_EXCEED_TRANSIT, 0, 0);
 233                 return NULL;
 234         }
 235
 236         /*
 237          * See if the destination is a proxied address, and if so pretend
 238          * that it's for us.  This is mostly to handle NUD probes against
 239          * the proxied addresses.  We filter for ICMPv6 here and will let
 240          * icmp6_input handle the rest.
 241          */
 242         if (!srcrt && nd6_prproxy) {
 243                 VERIFY(!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst));
 244                 proxy = nd6_prproxy_isours(m, ip6, ip6forward_rt, ifscope);
 245                 /*
 246                  * Don't update hop limit while proxying; RFC 4389 4.1.
 247                  * Also skip IPsec forwarding path processing as this
 248                  * packet is not to be forwarded.
 249                  */
 250                 if (proxy) {
 251                         goto skip_ipsec;
 252                 }
 253         }
 254
 255         ip6->ip6_hlim -= IPV6_HLIMDEC;
 256
 257         /*
 258          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 259          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 260          * we need to generate an ICMP6 message to the src.
 261          * Thanks to M_EXT, in most cases copy will not occur.
 262          *
 263          * It is important to save it before IPsec processing as IPsec
 264          * processing may modify the mbuf.
 265          */
 266         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 267
 268 #if IPSEC
 269         if (ipsec_bypass != 0) {
 270                 goto skip_ipsec;
 271         }
 272         /* get a security policy for this packet */
 273         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 274             &error);
 275         if (sp == NULL) {
 276                 IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
 277                 ip6stat.ip6s_cantforward++;
 278                 if (mcopy) {
 279 #if 0
 280                         /* XXX: what icmp ? */
 281 #else
 282                         m_freem(mcopy);
 283 #endif
 284                 }
 285                 m_freem(m);
 286                 return NULL;
 287         }
 288
 289         error = 0;
 290
 291         /* check policy */
 292         switch (sp->policy) {
 293         case IPSEC_POLICY_DISCARD:
 294         case IPSEC_POLICY_GENERATE:
 295                 /*
 296                  * This packet is just discarded.
 297                  */
 298                 IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
 299                 ip6stat.ip6s_cantforward++;
 300                 key_freesp(sp, KEY_SADB_UNLOCKED);
 301                 if (mcopy) {
 302 #if 0
 303                         /* XXX: what icmp ? */
 304 #else
 305                         m_freem(mcopy);
 306 #endif
 307                 }
 308                 m_freem(m);
 309                 return NULL;
 310
 311         case IPSEC_POLICY_BYPASS:
 312         case IPSEC_POLICY_NONE:
 313                 /* no need to do IPsec. */
 314                 key_freesp(sp, KEY_SADB_UNLOCKED);
 315                 goto skip_ipsec;
 316
 317         case IPSEC_POLICY_IPSEC:
 318                 if (sp->req == NULL) {
 319                         /* XXX should be panic ? */
 320                         printf("ip6_forward: No IPsec request specified.\n");
 321                         ip6stat.ip6s_cantforward++;
 322                         key_freesp(sp, KEY_SADB_UNLOCKED);
 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 NULL;
 332                 }
 333                 /* do IPsec */
 334                 break;
 335
 336         case IPSEC_POLICY_ENTRUST:
 337         default:
 338                 /* should be panic ?? */
 339                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 340                 key_freesp(sp, KEY_SADB_UNLOCKED);
 341                 goto skip_ipsec;
 342         }
 343
 344         {
 345                 struct ipsec_output_state state;
 346
 347                 /*
 348                  * All the extension headers will become inaccessible
 349                  * (since they can be encrypted).
 350                  * Don't panic, we need no more updates to extension headers
 351                  * on inner IPv6 packet (since they are now encapsulated).
 352                  *
 353                  * IPv6 [ESP|AH] IPv6 [extension headers] payload
 354                  */
 355                 bzero(&state, sizeof(state));
 356                 state.m = m;
 357                 state.dst = NULL; /* update at ipsec6_output_tunnel() */
 358
 359                 error = ipsec6_output_tunnel(&state, sp, 0);
 360                 key_freesp(sp, KEY_SADB_UNLOCKED);
 361                 if (state.tunneled == 4) {
 362                         ROUTE_RELEASE(&state.ro);
 363                         return NULL; /* packet is gone - sent over IPv4 */
 364                 }
 365
 366                 m = state.m;
 367                 ROUTE_RELEASE(&state.ro);
 368
 369                 if (error) {
 370                         /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 371                         switch (error) {
 372                         case EHOSTUNREACH:
 373                         case ENETUNREACH:
 374                         case EMSGSIZE:
 375                         case ENOBUFS:
 376                         case ENOMEM:
 377                                 break;
 378                         default:
 379                                 printf("ip6_output (ipsec): error code %d\n", error);
 380                         /* fall through */
 381                         case ENOENT:
 382                                 /* don't show these error codes to the user */
 383                                 break;
 384                         }
 385                         ip6stat.ip6s_cantforward++;
 386                         if (mcopy) {
 387 #if 0
 388                                 /* XXX: what icmp ? */
 389 #else
 390                                 m_freem(mcopy);
 391 #endif
 392                         }
 393                         m_freem(m);
 394                         return NULL;
 395                 }
 396         }
 397 #endif /* IPSEC */
 398 skip_ipsec:
 399
 400         dst = (struct sockaddr_in6 *)&ip6forward_rt->ro_dst;
 401         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 402                 RT_LOCK(rt);
 403                 /* Take an extra ref for ourselves */
 404                 RT_ADDREF_LOCKED(rt);
 405         }
 406
 407         VERIFY(rt == NULL || rt == ip6forward_rt->ro_rt);
 408         if (!srcrt) {
 409                 /*
 410                  * ip6forward_rt->ro_dst.sin6_addr is equal to ip6->ip6_dst
 411                  */
 412                 if (ROUTE_UNUSABLE(ip6forward_rt)) {
 413                         if (rt != NULL) {
 414                                 /* Release extra ref */
 415                                 RT_REMREF_LOCKED(rt);
 416                                 RT_UNLOCK(rt);
 417                         }
 418                         ROUTE_RELEASE(ip6forward_rt);
 419
 420                         /* this probably fails but give it a try again */
 421                         rtalloc_scoped_ign((struct route *)ip6forward_rt,
 422                             RTF_PRCLONING, ifscope);
 423                         if ((rt = ip6forward_rt->ro_rt) != NULL) {
 424                                 RT_LOCK(rt);
 425                                 /* Take an extra ref for ourselves */
 426                                 RT_ADDREF_LOCKED(rt);
 427                         }
 428                 }
 429
 430                 if (rt == NULL) {
 431                         ip6stat.ip6s_noroute++;
 432                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 433                         if (mcopy) {
 434                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 435                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 436                         }
 437                         m_freem(m);
 438                         return NULL;
 439                 }
 440                 RT_LOCK_ASSERT_HELD(rt);
 441         } else if (ROUTE_UNUSABLE(ip6forward_rt) ||
 442             !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 443                 if (rt != NULL) {
 444                         /* Release extra ref */
 445                         RT_REMREF_LOCKED(rt);
 446                         RT_UNLOCK(rt);
 447                 }
 448                 ROUTE_RELEASE(ip6forward_rt);
 449
 450                 bzero(dst, sizeof(*dst));
 451                 dst->sin6_len = sizeof(struct sockaddr_in6);
 452                 dst->sin6_family = AF_INET6;
 453                 dst->sin6_addr = ip6->ip6_dst;
 454
 455                 rtalloc_scoped_ign((struct route *)ip6forward_rt,
 456                     RTF_PRCLONING, ifscope);
 457                 if ((rt = ip6forward_rt->ro_rt) == NULL) {
 458                         ip6stat.ip6s_noroute++;
 459                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 460                         if (mcopy) {
 461                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 462                                     ICMP6_DST_UNREACH_NOROUTE, 0);
 463                         }
 464                         m_freem(m);
 465                         return NULL;
 466                 }
 467                 RT_LOCK(rt);
 468                 /* Take an extra ref for ourselves */
 469                 RT_ADDREF_LOCKED(rt);
 470         }
 471
 472         /*
 473          * Source scope check: if a packet can't be delivered to its
 474          * destination for the reason that the destination is beyond the scope
 475          * of the source address, discard the packet and return an icmp6
 476          * destination unreachable error with Code 2 (beyond scope of source
 477          * address) unless we are proxying (source address is link local
 478          * for NUDs.)  We use a local copy of ip6_src, since in6_setscope()
 479          * will possibly modify its first argument.
 480          * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1]
 481          */
 482         src_in6 = ip6->ip6_src;
 483         if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) {
 484                 RT_REMREF_LOCKED(rt);
 485                 RT_UNLOCK(rt);
 486                 /* XXX: this should not happen */
 487                 ip6stat.ip6s_cantforward++;
 488                 ip6stat.ip6s_badscope++;
 489                 m_freem(m);
 490                 return NULL;
 491         }
 492         if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) {
 493                 RT_REMREF_LOCKED(rt);
 494                 RT_UNLOCK(rt);
 495                 ip6stat.ip6s_cantforward++;
 496                 ip6stat.ip6s_badscope++;
 497                 m_freem(m);
 498                 return NULL;
 499         }
 500
 501         if (inzone != outzone && !proxy) {
 502                 ip6stat.ip6s_cantforward++;
 503                 ip6stat.ip6s_badscope++;
 504                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 505
 506                 if (ip6_log_time + ip6_log_interval < curtime) {
 507                         ip6_log_time = curtime;
 508                         log(LOG_DEBUG,
 509                             "cannot forward "
 510                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 511                             ip6_sprintf(&ip6->ip6_src),
 512                             ip6_sprintf(&ip6->ip6_dst),
 513                             ip6->ip6_nxt,
 514                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 515                 }
 516                 /* Release extra ref */
 517                 RT_REMREF_LOCKED(rt);
 518                 RT_UNLOCK(rt);
 519                 if (mcopy) {
 520                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 521                             ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 522                 }
 523                 m_freem(m);
 524                 return NULL;
 525         }
 526
 527         /*
 528          * Destination scope check: if a packet is going to break the scope
 529          * zone of packet's destination address, discard it.  This case should
 530          * usually be prevented by appropriately-configured routing table, but
 531          * we need an explicit check because we may mistakenly forward the
 532          * packet to a different zone by (e.g.) a default route.
 533          */
 534         dst_in6 = ip6->ip6_dst;
 535         if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 ||
 536             in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
 537             inzone != outzone) {
 538                 RT_REMREF_LOCKED(rt);
 539                 RT_UNLOCK(rt);
 540                 ip6stat.ip6s_cantforward++;
 541                 ip6stat.ip6s_badscope++;
 542                 m_freem(m);
 543                 return NULL;
 544         }
 545
 546         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 547                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 548                 if (mcopy) {
 549                         uint32_t mtu;
 550 #if IPSEC
 551                         struct secpolicy *sp2;
 552                         int ipsecerror;
 553                         size_t ipsechdrsiz;
 554 #endif
 555
 556                         mtu = rt->rt_ifp->if_mtu;
 557 #if IPSEC
 558                         /*
 559                          * When we do IPsec tunnel ingress, we need to play
 560                          * with the link value (decrement IPsec header size
 561                          * from mtu value).  The code is much simpler than v4
 562                          * case, as we have the outgoing interface for
 563                          * encapsulated packet as "rt->rt_ifp".
 564                          */
 565                         sp2 = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 566                             IP_FORWARDING, &ipsecerror);
 567                         if (sp2) {
 568                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 569                                     IPSEC_DIR_OUTBOUND, NULL);
 570                                 if (ipsechdrsiz < mtu) {
 571                                         mtu -= ipsechdrsiz;
 572                                 }
 573                                 key_freesp(sp2, KEY_SADB_UNLOCKED);
 574                         }
 575                         /*
 576                          * if mtu becomes less than minimum MTU,
 577                          * tell minimum MTU (and I'll need to fragment it).
 578                          */
 579                         if (mtu < IPV6_MMTU) {
 580                                 mtu = IPV6_MMTU;
 581                         }
 582 #endif
 583                         /* Release extra ref */
 584                         RT_REMREF_LOCKED(rt);
 585                         RT_UNLOCK(rt);
 586                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 587                 } else {
 588                         /* Release extra ref */
 589                         RT_REMREF_LOCKED(rt);
 590                         RT_UNLOCK(rt);
 591                 }
 592                 m_freem(m);
 593                 return NULL;
 594         }
 595
 596         if (rt->rt_flags & RTF_GATEWAY) {
 597                 dst = (struct sockaddr_in6 *)(void *)rt->rt_gateway;
 598         }
 599
 600         /*
 601          * If we are to forward the packet using the same interface
 602          * as one we got the packet from, perhaps we should send a redirect
 603          * to sender to shortcut a hop.
 604          * Only send redirect if source is sending directly to us,
 605          * and if packet was not source routed (or has any options).
 606          * Also, don't send redirect if forwarding using a route
 607          * modified by a redirect.
 608          */
 609         if (!proxy &&
 610             ip6_sendredirects && rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 611             (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) {
 612                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 613                         /*
 614                          * If the incoming interface is equal to the outgoing
 615                          * one, and the link attached to the interface is
 616                          * point-to-point, then it will be highly probable
 617                          * that a routing loop occurs. Thus, we immediately
 618                          * drop the packet and send an ICMPv6 error message.
 619                          *
 620                          * type/code is based on suggestion by Rich Draves.
 621                          * not sure if it is the best pick.
 622                          */
 623                         RT_REMREF_LOCKED(rt);   /* Release extra ref */
 624                         RT_UNLOCK(rt);
 625                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 626                             ICMP6_DST_UNREACH_ADDR, 0);
 627                         m_freem(m);
 628                         return NULL;
 629                 }
 630                 type = ND_REDIRECT;
 631         }
 632         /*
 633          * Fake scoped addresses. Note that even link-local source or
 634          * destinaion can appear, if the originating node just sends the
 635          * packet to us (without address resolution for the destination).
 636          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 637          * link identifiers, we can do this stuff after making a copy for
 638          * returning an error.
 639          */
 640         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 641                 /*
 642                  * See corresponding comments in ip6_output.
 643                  * XXX: but is it possible that ip6_forward() sends a packet
 644                  *      to a loopback interface? I don't think so, and thus
 645                  *      I bark here. (jinmei@kame.net)
 646                  * XXX: it is common to route invalid packets to loopback.
 647                  *      also, the codepath will be visited on use of ::1 in
 648                  *      rthdr. (itojun)
 649                  */
 650 #if 1
 651                 if ((0))
 652 #else
 653                 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0)
 654 #endif
 655                 {
 656                         printf("ip6_forward: outgoing interface is loopback. "
 657                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 658                             ip6_sprintf(&ip6->ip6_src),
 659                             ip6_sprintf(&ip6->ip6_dst),
 660                             ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 661                             if_name(rt->rt_ifp));
 662                 }
 663
 664                 /* we can just use rcvif in forwarding. */
 665                 origifp = rcvifp = m->m_pkthdr.rcvif;
 666         } else if (nd6_prproxy) {
 667                 /*
 668                  * In the prefix proxying case, we need to inform nd6_output()
 669                  * about the inbound interface, so that any subsequent NS
 670                  * packets generated by nd6_prproxy_ns_output() will not be
 671                  * sent back to that same interface.
 672                  */
 673                 origifp = rcvifp = m->m_pkthdr.rcvif;
 674         } else {
 675                 rcvifp = m->m_pkthdr.rcvif;
 676                 origifp = rt->rt_ifp;
 677         }
 678         /*
 679          * clear embedded scope identifiers if necessary.
 680          * in6_clearscope will touch the addresses only when necessary.
 681          */
 682         in6_clearscope(&ip6->ip6_src);
 683         in6_clearscope(&ip6->ip6_dst);
 684
 685         ifp = rt->rt_ifp;
 686         /* Drop the lock but retain the extra ref */
 687         RT_UNLOCK(rt);
 688
 689         /*
 690          * If this is to be processed locally, let ip6_input have it.
 691          */
 692         if (proxy) {
 693                 VERIFY(m->m_pkthdr.pkt_flags & PKTF_PROXY_DST);
 694                 /* Release extra ref */
 695                 RT_REMREF(rt);
 696                 if (mcopy != NULL) {
 697                         m_freem(mcopy);
 698                 }
 699                 return m;
 700         }
 701
 702         /* Mark this packet as being forwarded from another interface */
 703         m->m_pkthdr.pkt_flags |= PKTF_FORWARDED;
 704
 705 #if PF
 706         if (PF_IS_ENABLED) {
 707 #if DUMMYNET
 708                 struct ip_fw_args args;
 709                 bzero(&args, sizeof(args));
 710
 711                 args.fwa_m = m;
 712                 args.fwa_oif = ifp;
 713                 args.fwa_oflags = 0;
 714                 args.fwa_ro6 = ip6forward_rt;
 715                 args.fwa_ro6_pmtu = ip6forward_rt;
 716                 args.fwa_mtu = rt->rt_ifp->if_mtu;
 717                 args.fwa_dst6 = dst;
 718                 args.fwa_origifp = origifp;
 719                 /* Invoke outbound packet filter */
 720                 error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, &args);
 721 #else /* !DUMMYNET */
 722                 error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, NULL);
 723 #endif /* !DUMMYNET */
 724                 if (error != 0 || m == NULL) {
 725                         if (m != NULL) {
 726                                 panic("%s: unexpected packet %p\n", __func__, m);
 727                                 /* NOTREACHED */
 728                         }
 729                         /* Already freed by callee */
 730                         goto senderr;
 731                 }
 732                 /*
 733                  * We do not use ip6 header again in the code below,
 734                  * however still adding the bit here so that any new
 735                  * code in future doesn't end up working with the
 736                  * wrong pointer
 737                  */
 738                 ip6 = mtod(m, struct ip6_hdr *);
 739         }
 740 #endif /* PF */
 741
 742         len = m_pktlen(m);
 743         error = nd6_output(ifp, origifp, m, dst, rt, NULL);
 744         if (error) {
 745                 in6_ifstat_inc(ifp, ifs6_out_discard);
 746                 ip6stat.ip6s_cantforward++;
 747         } else {
 748                 /*
 749                  * Increment stats on the source interface; the ones
 750                  * for destination interface has been taken care of
 751                  * during output above by virtue of PKTF_FORWARDED.
 752                  */
 753                 rcvifp->if_fpackets++;
 754                 rcvifp->if_fbytes += len;
 755
 756                 ip6stat.ip6s_forward++;
 757                 in6_ifstat_inc(ifp, ifs6_out_forward);
 758                 if (type) {
 759                         ip6stat.ip6s_redirectsent++;
 760                 } else {
 761                         if (mcopy) {
 762                                 goto freecopy;
 763                         }
 764                 }
 765         }
 766 #if PF
 767 senderr:
 768 #endif /* PF */
 769         if (mcopy == NULL) {
 770                 /* Release extra ref */
 771                 RT_REMREF(rt);
 772                 return NULL;
 773         }
 774         switch (error) {
 775         case 0:
 776 #if 1
 777                 if (type == ND_REDIRECT) {
 778                         icmp6_redirect_output(mcopy, rt);
 779                         /* Release extra ref */
 780                         RT_REMREF(rt);
 781                         return NULL;
 782                 }
 783 #endif
 784                 goto freecopy;
 785
 786         case EMSGSIZE:
 787                 /* xxx MTU is constant in PPP? */
 788                 goto freecopy;
 789
 790         case ENOBUFS:
 791                 /* Tell source to slow down like source quench in IP? */
 792                 goto freecopy;
 793
 794         case ENETUNREACH:       /* shouldn't happen, checked above */
 795         case EHOSTUNREACH:
 796         case ENETDOWN:
 797         case EHOSTDOWN:
 798         default:
 799                 type = ICMP6_DST_UNREACH;
 800                 code = ICMP6_DST_UNREACH_ADDR;
 801                 break;
 802         }
 803         icmp6_error(mcopy, type, code, 0);
 804         /* Release extra ref */
 805         RT_REMREF(rt);
 806         return NULL;
 807
 808 freecopy:
 809         m_freem(mcopy);
 810         /* Release extra ref */
 811         RT_REMREF(rt);
 812         return NULL;
 813 }