bsd/netinet6/ip6_forward.c

   1 /*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.16 2002/10/16 02:25:05 sam Exp $   */
   2 /*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $    */
   3
   4 /*
   5  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the project nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33
  34 #include <sys/param.h>
  35 #include <sys/systm.h>
  36 #include <sys/malloc.h>
  37 #include <sys/mbuf.h>
  38 #include <sys/domain.h>
  39 #include <sys/protosw.h>
  40 #include <sys/socket.h>
  41 #include <sys/errno.h>
  42 #include <sys/time.h>
  43 #include <sys/kernel.h>
  44 #include <sys/syslog.h>
  45
  46 #include <net/if.h>
  47 #include <net/route.h>
  48
  49 #include <netinet/in.h>
  50 #include <netinet/in_var.h>
  51 #include <netinet/in_systm.h>
  52 #include <netinet/ip.h>
  53 #include <netinet/ip_var.h>
  54 #include <netinet6/in6_var.h>
  55 #include <netinet/ip6.h>
  56 #include <netinet6/ip6_var.h>
  57 #include <netinet/icmp6.h>
  58 #include <netinet6/nd6.h>
  59
  60 #include <netinet/in_pcb.h>
  61
  62 #if IPSEC
  63 #include <netinet6/ipsec.h>
  64 #if INET6
  65 #include <netinet6/ipsec6.h>
  66 #endif
  67 #include <netkey/key.h>
  68 extern int ipsec_bypass;
  69 #endif /* IPSEC */
  70
  71 #include <netinet6/ip6_fw.h>
  72
  73 #include <net/net_osdep.h>
  74
  75 struct  route_in6 ip6_forward_rt;
  76
  77 /*
  78  * Forward a packet.  If some error occurs return the sender
  79  * an icmp packet.  Note we can't always generate a meaningful
  80  * icmp message because icmp doesn't have a large enough repertoire
  81  * of codes and types.
  82  *
  83  * If not forwarding, just drop the packet.  This could be confusing
  84  * if ipforwarding was zero but some routing protocol was advancing
  85  * us as a gateway to somewhere.  However, we must let the routing
  86  * protocol deal with that.
  87  *
  88  */
  89
  90 void
  91 ip6_forward(m, srcrt)
  92         struct mbuf *m;
  93         int srcrt;
  94 {
  95         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  96         struct sockaddr_in6 *dst;
  97         struct rtentry *rt;
  98         int error, type = 0, code = 0;
  99         struct mbuf *mcopy = NULL;
 100         struct ifnet *origifp;  /* maybe unnecessary */
 101 #if IPSEC
 102         struct secpolicy *sp = NULL;
 103 #endif
 104
 105 #if IPSEC
 106         /*
 107          * Check AH/ESP integrity.
 108          */
 109         /*
 110          * Don't increment ip6s_cantforward because this is the check
 111          * before forwarding packet actually.
 112          */
 113         if (ipsec_bypass == 0 && ipsec6_in_reject(m, NULL)) {
 114                 ipsec6stat.in_polvio++;
 115                 m_freem(m);
 116                 return;
 117         }
 118 #endif /*IPSEC*/
 119
 120         /*
 121          * Do not forward packets to multicast destination (should be handled
 122          * by ip6_mforward().
 123          * Do not forward packets with unspecified source.  It was discussed
 124          * in July 2000, on ipngwg mailing list.
 125          */
 126         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 127             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 128             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 129                 ip6stat.ip6s_cantforward++;
 130                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 131                 if (ip6_log_time + ip6_log_interval < time_second) {
 132                         ip6_log_time = time_second;
 133                         log(LOG_DEBUG,
 134                             "cannot forward "
 135                             "from %s to %s nxt %d received on %s\n",
 136                             ip6_sprintf(&ip6->ip6_src),
 137                             ip6_sprintf(&ip6->ip6_dst),
 138                             ip6->ip6_nxt,
 139                             if_name(m->m_pkthdr.rcvif));
 140                 }
 141                 m_freem(m);
 142                 return;
 143         }
 144
 145         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 146                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 147                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 148                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 149                 return;
 150         }
 151         ip6->ip6_hlim -= IPV6_HLIMDEC;
 152
 153         /*
 154          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 155          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 156          * we need to generate an ICMP6 message to the src.
 157          * Thanks to M_EXT, in most cases copy will not occur.
 158          *
 159          * It is important to save it before IPsec processing as IPsec
 160          * processing may modify the mbuf.
 161          */
 162         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 163
 164 #if IPSEC
 165         if (ipsec_bypass != 0)
 166                 goto skip_ipsec;
 167
 168         /* get a security policy for this packet */
 169         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 170             &error);
 171         if (sp == NULL) {
 172                 ipsec6stat.out_inval++;
 173                 ip6stat.ip6s_cantforward++;
 174                 if (mcopy) {
 175 #if 0
 176                         /* XXX: what icmp ? */
 177 #else
 178                         m_freem(mcopy);
 179 #endif
 180                 }
 181                 m_freem(m);
 182                 return;
 183         }
 184
 185         error = 0;
 186
 187         /* check policy */
 188         switch (sp->policy) {
 189         case IPSEC_POLICY_DISCARD:
 190                 /*
 191                  * This packet is just discarded.
 192                  */
 193                 ipsec6stat.out_polvio++;
 194                 ip6stat.ip6s_cantforward++;
 195                 key_freesp(sp);
 196                 if (mcopy) {
 197 #if 0
 198                         /* XXX: what icmp ? */
 199 #else
 200                         m_freem(mcopy);
 201 #endif
 202                 }
 203                 m_freem(m);
 204                 return;
 205
 206         case IPSEC_POLICY_BYPASS:
 207         case IPSEC_POLICY_NONE:
 208                 /* no need to do IPsec. */
 209                 key_freesp(sp);
 210                 goto skip_ipsec;
 211
 212         case IPSEC_POLICY_IPSEC:
 213                 if (sp->req == NULL) {
 214                         /* XXX should be panic ? */
 215                         printf("ip6_forward: No IPsec request specified.\n");
 216                         ip6stat.ip6s_cantforward++;
 217                         key_freesp(sp);
 218                         if (mcopy) {
 219 #if 0
 220                                 /* XXX: what icmp ? */
 221 #else
 222                                 m_freem(mcopy);
 223 #endif
 224                         }
 225                         m_freem(m);
 226                         return;
 227                 }
 228                 /* do IPsec */
 229                 break;
 230
 231         case IPSEC_POLICY_ENTRUST:
 232         default:
 233                 /* should be panic ?? */
 234                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 235                 key_freesp(sp);
 236                 goto skip_ipsec;
 237         }
 238
 239     {
 240         struct ipsec_output_state state;
 241
 242         /*
 243          * All the extension headers will become inaccessible
 244          * (since they can be encrypted).
 245          * Don't panic, we need no more updates to extension headers
 246          * on inner IPv6 packet (since they are now encapsulated).
 247          *
 248          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 249          */
 250         bzero(&state, sizeof(state));
 251         state.m = m;
 252         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 253         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 254
 255         error = ipsec6_output_tunnel(&state, sp, 0);
 256
 257         m = state.m;
 258         key_freesp(sp);
 259
 260         if (error) {
 261                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 262                 switch (error) {
 263                 case EHOSTUNREACH:
 264                 case ENETUNREACH:
 265                 case EMSGSIZE:
 266                 case ENOBUFS:
 267                 case ENOMEM:
 268                         break;
 269                 default:
 270                         printf("ip6_output (ipsec): error code %d\n", error);
 271                         /* fall through */
 272                 case ENOENT:
 273                         /* don't show these error codes to the user */
 274                         break;
 275                 }
 276                 ip6stat.ip6s_cantforward++;
 277                 if (mcopy) {
 278 #if 0
 279                         /* XXX: what icmp ? */
 280 #else
 281                         m_freem(mcopy);
 282 #endif
 283                 }
 284                 m_freem(m);
 285                 return;
 286         }
 287     }
 288     skip_ipsec:
 289 #endif /* IPSEC */
 290
 291         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 292         if (!srcrt) {
 293                 /*
 294                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 295                  */
 296                 if (ip6_forward_rt.ro_rt == 0 ||
 297                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 298                         if (ip6_forward_rt.ro_rt) {
 299                                 rtfree(ip6_forward_rt.ro_rt);
 300                                 ip6_forward_rt.ro_rt = 0;
 301                         }
 302                         /* this probably fails but give it a try again */
 303                         rtalloc_ign((struct route *)&ip6_forward_rt,
 304                                     RTF_PRCLONING);
 305                 }
 306
 307                 if (ip6_forward_rt.ro_rt == 0) {
 308                         ip6stat.ip6s_noroute++;
 309                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 310                         if (mcopy) {
 311                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 312                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 313                         }
 314                         m_freem(m);
 315                         return;
 316                 }
 317         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 318                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 319                 if (ip6_forward_rt.ro_rt) {
 320                         rtfree(ip6_forward_rt.ro_rt);
 321                         ip6_forward_rt.ro_rt = 0;
 322                 }
 323                 bzero(dst, sizeof(*dst));
 324                 dst->sin6_len = sizeof(struct sockaddr_in6);
 325                 dst->sin6_family = AF_INET6;
 326                 dst->sin6_addr = ip6->ip6_dst;
 327
 328                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 329                 if (ip6_forward_rt.ro_rt == 0) {
 330                         ip6stat.ip6s_noroute++;
 331                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 332                         if (mcopy) {
 333                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 334                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 335                         }
 336                         m_freem(m);
 337                         return;
 338                 }
 339         }
 340         rt = ip6_forward_rt.ro_rt;
 341
 342         /*
 343          * Scope check: if a packet can't be delivered to its destination
 344          * for the reason that the destination is beyond the scope of the
 345          * source address, discard the packet and return an icmp6 destination
 346          * unreachable error with Code 2 (beyond scope of source address).
 347          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 348          */
 349         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 350             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 351                 ip6stat.ip6s_cantforward++;
 352                 ip6stat.ip6s_badscope++;
 353                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 354
 355                 if (ip6_log_time + ip6_log_interval < time_second) {
 356                         ip6_log_time = time_second;
 357                         log(LOG_DEBUG,
 358                             "cannot forward "
 359                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 360                             ip6_sprintf(&ip6->ip6_src),
 361                             ip6_sprintf(&ip6->ip6_dst),
 362                             ip6->ip6_nxt,
 363                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 364                 }
 365                 if (mcopy)
 366                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 367                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 368                 m_freem(m);
 369                 return;
 370         }
 371
 372         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 373                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 374                 if (mcopy) {
 375                         u_long mtu;
 376 #if IPSEC
 377                         struct secpolicy *sp;
 378                         int ipsecerror;
 379                         size_t ipsechdrsiz;
 380 #endif
 381
 382                         mtu = rt->rt_ifp->if_mtu;
 383 #if IPSEC
 384                         /*
 385                          * When we do IPsec tunnel ingress, we need to play
 386                          * with if_mtu value (decrement IPsec header size
 387                          * from mtu value).  The code is much simpler than v4
 388                          * case, as we have the outgoing interface for
 389                          * encapsulated packet as "rt->rt_ifp".
 390                          */
 391                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 392                                 IP_FORWARDING, &ipsecerror);
 393                         if (sp) {
 394                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 395                                         IPSEC_DIR_OUTBOUND, NULL);
 396                                 if (ipsechdrsiz < mtu)
 397                                         mtu -= ipsechdrsiz;
 398                         }
 399
 400                         /*
 401                          * if mtu becomes less than minimum MTU,
 402                          * tell minimum MTU (and I'll need to fragment it).
 403                          */
 404                         if (mtu < IPV6_MMTU)
 405                                 mtu = IPV6_MMTU;
 406 #endif
 407                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 408                 }
 409                 m_freem(m);
 410                 return;
 411         }
 412
 413         if (rt->rt_flags & RTF_GATEWAY)
 414                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 415
 416         /*
 417          * If we are to forward the packet using the same interface
 418          * as one we got the packet from, perhaps we should send a redirect
 419          * to sender to shortcut a hop.
 420          * Only send redirect if source is sending directly to us,
 421          * and if packet was not source routed (or has any options).
 422          * Also, don't send redirect if forwarding using a route
 423          * modified by a redirect.
 424          */
 425         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 426             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 427                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 428                         /*
 429                          * If the incoming interface is equal to the outgoing
 430                          * one, and the link attached to the interface is
 431                          * point-to-point, then it will be highly probable
 432                          * that a routing loop occurs. Thus, we immediately
 433                          * drop the packet and send an ICMPv6 error message.
 434                          *
 435                          * type/code is based on suggestion by Rich Draves.
 436                          * not sure if it is the best pick.
 437                          */
 438                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 439                                     ICMP6_DST_UNREACH_ADDR, 0);
 440                         m_freem(m);
 441                         return;
 442                 }
 443                 type = ND_REDIRECT;
 444         }
 445
 446         /*
 447          * Check with the firewall...
 448          */
 449         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 450                 u_short port = 0;
 451                 /* If ipfw says divert, we have to just drop packet */
 452                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 453                         m_freem(m);
 454                         goto freecopy;
 455                 }
 456                 if (!m)
 457                         goto freecopy;
 458         }
 459
 460         /*
 461          * Fake scoped addresses. Note that even link-local source or
 462          * destinaion can appear, if the originating node just sends the
 463          * packet to us (without address resolution for the destination).
 464          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 465          * link identifiers, we can do this stuff after making a copy for
 466          * returning an error.
 467          */
 468         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 469                 /*
 470                  * See corresponding comments in ip6_output.
 471                  * XXX: but is it possible that ip6_forward() sends a packet
 472                  *      to a loopback interface? I don't think so, and thus
 473                  *      I bark here. (jinmei@kame.net)
 474                  * XXX: it is common to route invalid packets to loopback.
 475                  *      also, the codepath will be visited on use of ::1 in
 476                  *      rthdr. (itojun)
 477                  */
 478 #if 1
 479                 if (0)
 480 #else
 481                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 482 #endif
 483                 {
 484                         printf("ip6_forward: outgoing interface is loopback. "
 485                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 486                                 ip6_sprintf(&ip6->ip6_src),
 487                                 ip6_sprintf(&ip6->ip6_dst),
 488                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 489                                 if_name(rt->rt_ifp));
 490                 }
 491
 492                 /* we can just use rcvif in forwarding. */
 493                 origifp = m->m_pkthdr.rcvif;
 494         }
 495         else
 496                 origifp = rt->rt_ifp;
 497 #ifndef SCOPEDROUTING
 498         /*
 499          * clear embedded scope identifiers if necessary.
 500          * in6_clearscope will touch the addresses only when necessary.
 501          */
 502         in6_clearscope(&ip6->ip6_src);
 503         in6_clearscope(&ip6->ip6_dst);
 504 #endif
 505
 506         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 507         if (error) {
 508                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 509                 ip6stat.ip6s_cantforward++;
 510         } else {
 511                 ip6stat.ip6s_forward++;
 512                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 513                 if (type)
 514                         ip6stat.ip6s_redirectsent++;
 515                 else {
 516                         if (mcopy)
 517                                 goto freecopy;
 518                 }
 519         }
 520         if (mcopy == NULL)
 521                 return;
 522
 523         switch (error) {
 524         case 0:
 525 #if 1
 526                 if (type == ND_REDIRECT) {
 527                         icmp6_redirect_output(mcopy, rt);
 528                         return;
 529                 }
 530 #endif
 531                 goto freecopy;
 532
 533         case EMSGSIZE:
 534                 /* xxx MTU is constant in PPP? */
 535                 goto freecopy;
 536
 537         case ENOBUFS:
 538                 /* Tell source to slow down like source quench in IP? */
 539                 goto freecopy;
 540
 541         case ENETUNREACH:       /* shouldn't happen, checked above */
 542         case EHOSTUNREACH:
 543         case ENETDOWN:
 544         case EHOSTDOWN:
 545         default:
 546                 type = ICMP6_DST_UNREACH;
 547                 code = ICMP6_DST_UNREACH_ADDR;
 548                 break;
 549         }
 550         icmp6_error(mcopy, type, code, 0);
 551         return;
 552
 553  freecopy:
 554         m_freem(mcopy);
 555         return;
 556 }