sys/netinet6/ip6_forward.c

   1 /*      $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.4.2.7 2003/01/24 05:11:35 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 #include "opt_ip6fw.h"
  34 #include "opt_inet.h"
  35 #include "opt_inet6.h"
  36 #include "opt_ipsec.h"
  37
  38 #include <sys/param.h>
  39 #include <sys/systm.h>
  40 #include <sys/malloc.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/domain.h>
  43 #include <sys/protosw.h>
  44 #include <sys/socket.h>
  45 #include <sys/errno.h>
  46 #include <sys/time.h>
  47 #include <sys/kernel.h>
  48 #include <sys/syslog.h>
  49
  50 #include <net/if.h>
  51 #include <net/route.h>
  52
  53 #include <netinet/in.h>
  54 #include <netinet/in_var.h>
  55 #include <netinet/in_systm.h>
  56 #include <netinet/ip.h>
  57 #include <netinet/ip_var.h>
  58 #include <netinet6/in6_var.h>
  59 #include <netinet/ip6.h>
  60 #include <netinet6/ip6_var.h>
  61 #include <netinet/icmp6.h>
  62 #include <netinet6/nd6.h>
  63
  64 #include <netinet/in_pcb.h>
  65
  66 #ifdef IPSEC
  67 #include <netinet6/ipsec.h>
  68 #ifdef INET6
  69 #include <netinet6/ipsec6.h>
  70 #endif
  71 #include <netkey/key.h>
  72 #endif /* IPSEC */
  73
  74 #ifdef FAST_IPSEC
  75 #include <netipsec/ipsec.h>
  76 #include <netipsec/ipsec6.h>
  77 #include <netipsec/key.h>
  78 #define IPSEC
  79 #endif /* FAST_IPSEC */
  80
  81 #include <netinet6/ip6_fw.h>
  82
  83 #include <net/net_osdep.h>
  84
  85 extern int (*fr_checkp) __P((struct ip *, int, struct ifnet *, int, struct mbuf **));
  86
  87 struct  route_in6 ip6_forward_rt;
  88
  89 /*
  90  * Forward a packet.  If some error occurs return the sender
  91  * an icmp packet.  Note we can't always generate a meaningful
  92  * icmp message because icmp doesn't have a large enough repertoire
  93  * of codes and types.
  94  *
  95  * If not forwarding, just drop the packet.  This could be confusing
  96  * if ipforwarding was zero but some routing protocol was advancing
  97  * us as a gateway to somewhere.  However, we must let the routing
  98  * protocol deal with that.
  99  *
 100  */
 101
 102 void
 103 ip6_forward(m, srcrt)
 104         struct mbuf *m;
 105         int srcrt;
 106 {
 107         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 108         struct sockaddr_in6 *dst;
 109         struct rtentry *rt;
 110         int error, type = 0, code = 0;
 111         struct mbuf *mcopy = NULL;
 112         struct ifnet *origifp;  /* maybe unnecessary */
 113 #ifdef IPSEC
 114         struct secpolicy *sp = NULL;
 115 #endif
 116
 117 #ifdef IPSEC
 118         /*
 119          * Check AH/ESP integrity.
 120          */
 121         /*
 122          * Don't increment ip6s_cantforward because this is the check
 123          * before forwarding packet actually.
 124          */
 125         if (ipsec6_in_reject(m, NULL)) {
 126 #if !defined(FAST_IPSEC)
 127                 ipsec6stat.in_polvio++;
 128 #endif
 129                 m_freem(m);
 130                 return;
 131         }
 132 #endif /* IPSEC */
 133
 134         /*
 135          * Do not forward packets to multicast destination (should be handled
 136          * by ip6_mforward().
 137          * Do not forward packets with unspecified source.  It was discussed
 138          * in July 2000, on ipngwg mailing list.
 139          */
 140         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 141             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 142             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 143                 ip6stat.ip6s_cantforward++;
 144                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 145                 if (ip6_log_time + ip6_log_interval < time_second) {
 146                         ip6_log_time = time_second;
 147                         log(LOG_DEBUG,
 148                             "cannot forward "
 149                             "from %s to %s nxt %d received on %s\n",
 150                             ip6_sprintf(&ip6->ip6_src),
 151                             ip6_sprintf(&ip6->ip6_dst),
 152                             ip6->ip6_nxt,
 153                             if_name(m->m_pkthdr.rcvif));
 154                 }
 155                 m_freem(m);
 156                 return;
 157         }
 158
 159         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 160                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 161                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 162                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 163                 return;
 164         }
 165         ip6->ip6_hlim -= IPV6_HLIMDEC;
 166
 167         /*
 168          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 169          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 170          * we need to generate an ICMP6 message to the src.
 171          * Thanks to M_EXT, in most cases copy will not occur.
 172          *
 173          * It is important to save it before IPsec processing as IPsec
 174          * processing may modify the mbuf.
 175          */
 176         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 177
 178 #ifdef IPSEC
 179         /* get a security policy for this packet */
 180         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 181             &error);
 182         if (sp == NULL) {
 183                 ipsec6stat.out_inval++;
 184                 ip6stat.ip6s_cantforward++;
 185                 if (mcopy) {
 186 #if 0
 187                         /* XXX: what icmp ? */
 188 #else
 189                         m_freem(mcopy);
 190 #endif
 191                 }
 192                 m_freem(m);
 193                 return;
 194         }
 195
 196         error = 0;
 197
 198         /* check policy */
 199         switch (sp->policy) {
 200         case IPSEC_POLICY_DISCARD:
 201                 /*
 202                  * This packet is just discarded.
 203                  */
 204                 ipsec6stat.out_polvio++;
 205                 ip6stat.ip6s_cantforward++;
 206                 key_freesp(sp);
 207                 if (mcopy) {
 208 #if 0
 209                         /* XXX: what icmp ? */
 210 #else
 211                         m_freem(mcopy);
 212 #endif
 213                 }
 214                 m_freem(m);
 215                 return;
 216
 217         case IPSEC_POLICY_BYPASS:
 218         case IPSEC_POLICY_NONE:
 219                 /* no need to do IPsec. */
 220                 key_freesp(sp);
 221                 goto skip_ipsec;
 222
 223         case IPSEC_POLICY_IPSEC:
 224                 if (sp->req == NULL) {
 225                         /* XXX should be panic ? */
 226                         printf("ip6_forward: No IPsec request specified.\n");
 227                         ip6stat.ip6s_cantforward++;
 228                         key_freesp(sp);
 229                         if (mcopy) {
 230 #if 0
 231                                 /* XXX: what icmp ? */
 232 #else
 233                                 m_freem(mcopy);
 234 #endif
 235                         }
 236                         m_freem(m);
 237                         return;
 238                 }
 239                 /* do IPsec */
 240                 break;
 241
 242         case IPSEC_POLICY_ENTRUST:
 243         default:
 244                 /* should be panic ?? */
 245                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 246                 key_freesp(sp);
 247                 goto skip_ipsec;
 248         }
 249
 250     {
 251         struct ipsec_output_state state;
 252
 253         /*
 254          * All the extension headers will become inaccessible
 255          * (since they can be encrypted).
 256          * Don't panic, we need no more updates to extension headers
 257          * on inner IPv6 packet (since they are now encapsulated).
 258          *
 259          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 260          */
 261         bzero(&state, sizeof(state));
 262         state.m = m;
 263         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 264         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 265
 266         error = ipsec6_output_tunnel(&state, sp, 0);
 267
 268         m = state.m;
 269         key_freesp(sp);
 270
 271         if (error) {
 272                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 273                 switch (error) {
 274                 case EHOSTUNREACH:
 275                 case ENETUNREACH:
 276                 case EMSGSIZE:
 277                 case ENOBUFS:
 278                 case ENOMEM:
 279                         break;
 280                 default:
 281                         printf("ip6_output (ipsec): error code %d\n", error);
 282                         /* fall through */
 283                 case ENOENT:
 284                         /* don't show these error codes to the user */
 285                         break;
 286                 }
 287                 ip6stat.ip6s_cantforward++;
 288                 if (mcopy) {
 289 #if 0
 290                         /* XXX: what icmp ? */
 291 #else
 292                         m_freem(mcopy);
 293 #endif
 294                 }
 295                 m_freem(m);
 296                 return;
 297         }
 298     }
 299     skip_ipsec:
 300 #endif /* IPSEC */
 301
 302         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 303         if (!srcrt) {
 304                 /*
 305                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 306                  */
 307                 if (ip6_forward_rt.ro_rt == 0 ||
 308                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 309                         if (ip6_forward_rt.ro_rt) {
 310                                 RTFREE(ip6_forward_rt.ro_rt);
 311                                 ip6_forward_rt.ro_rt = 0;
 312                         }
 313                         /* this probably fails but give it a try again */
 314                         rtalloc_ign((struct route *)&ip6_forward_rt,
 315                                     RTF_PRCLONING);
 316                 }
 317
 318                 if (ip6_forward_rt.ro_rt == 0) {
 319                         ip6stat.ip6s_noroute++;
 320                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 321                         if (mcopy) {
 322                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 323                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 324                         }
 325                         m_freem(m);
 326                         return;
 327                 }
 328         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 329                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 330                 if (ip6_forward_rt.ro_rt) {
 331                         RTFREE(ip6_forward_rt.ro_rt);
 332                         ip6_forward_rt.ro_rt = 0;
 333                 }
 334                 bzero(dst, sizeof(*dst));
 335                 dst->sin6_len = sizeof(struct sockaddr_in6);
 336                 dst->sin6_family = AF_INET6;
 337                 dst->sin6_addr = ip6->ip6_dst;
 338
 339                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 340                 if (ip6_forward_rt.ro_rt == 0) {
 341                         ip6stat.ip6s_noroute++;
 342                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 343                         if (mcopy) {
 344                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 345                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 346                         }
 347                         m_freem(m);
 348                         return;
 349                 }
 350         }
 351         rt = ip6_forward_rt.ro_rt;
 352
 353         /*
 354          * Scope check: if a packet can't be delivered to its destination
 355          * for the reason that the destination is beyond the scope of the
 356          * source address, discard the packet and return an icmp6 destination
 357          * unreachable error with Code 2 (beyond scope of source address).
 358          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 359          */
 360         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 361             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 362                 ip6stat.ip6s_cantforward++;
 363                 ip6stat.ip6s_badscope++;
 364                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 365
 366                 if (ip6_log_time + ip6_log_interval < time_second) {
 367                         ip6_log_time = time_second;
 368                         log(LOG_DEBUG,
 369                             "cannot forward "
 370                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 371                             ip6_sprintf(&ip6->ip6_src),
 372                             ip6_sprintf(&ip6->ip6_dst),
 373                             ip6->ip6_nxt,
 374                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 375                 }
 376                 if (mcopy)
 377                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 378                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 379                 m_freem(m);
 380                 return;
 381         }
 382
 383         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 384                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 385                 if (mcopy) {
 386                         u_long mtu;
 387 #ifdef IPSEC
 388                         struct secpolicy *sp;
 389                         int ipsecerror;
 390                         size_t ipsechdrsiz;
 391 #endif
 392
 393                         mtu = rt->rt_ifp->if_mtu;
 394 #ifdef IPSEC
 395                         /*
 396                          * When we do IPsec tunnel ingress, we need to play
 397                          * with if_mtu value (decrement IPsec header size
 398                          * from mtu value).  The code is much simpler than v4
 399                          * case, as we have the outgoing interface for
 400                          * encapsulated packet as "rt->rt_ifp".
 401                          */
 402                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 403                                 IP_FORWARDING, &ipsecerror);
 404                         if (sp) {
 405                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 406                                         IPSEC_DIR_OUTBOUND, NULL);
 407                                 if (ipsechdrsiz < mtu)
 408                                         mtu -= ipsechdrsiz;
 409                         }
 410
 411                         /*
 412                          * if mtu becomes less than minimum MTU,
 413                          * tell minimum MTU (and I'll need to fragment it).
 414                          */
 415                         if (mtu < IPV6_MMTU)
 416                                 mtu = IPV6_MMTU;
 417 #endif
 418                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 419                 }
 420                 m_freem(m);
 421                 return;
 422         }
 423
 424         if (rt->rt_flags & RTF_GATEWAY)
 425                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 426
 427         /*
 428          * If we are to forward the packet using the same interface
 429          * as one we got the packet from, perhaps we should send a redirect
 430          * to sender to shortcut a hop.
 431          * Only send redirect if source is sending directly to us,
 432          * and if packet was not source routed (or has any options).
 433          * Also, don't send redirect if forwarding using a route
 434          * modified by a redirect.
 435          */
 436         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 437             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 438                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 439                         /*
 440                          * If the incoming interface is equal to the outgoing
 441                          * one, and the link attached to the interface is
 442                          * point-to-point, then it will be highly probable
 443                          * that a routing loop occurs. Thus, we immediately
 444                          * drop the packet and send an ICMPv6 error message.
 445                          *
 446                          * type/code is based on suggestion by Rich Draves.
 447                          * not sure if it is the best pick.
 448                          */
 449                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 450                                     ICMP6_DST_UNREACH_ADDR, 0);
 451                         m_freem(m);
 452                         return;
 453                 }
 454                 type = ND_REDIRECT;
 455         }
 456
 457         /*
 458          * Check with the firewall...
 459          */
 460         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 461                 u_short port = 0;
 462                 /* If ipfw says divert, we have to just drop packet */
 463                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 464                         m_freem(m);
 465                         goto freecopy;
 466                 }
 467                 if (!m)
 468                         goto freecopy;
 469         }
 470
 471         /*
 472          * Fake scoped addresses. Note that even link-local source or
 473          * destinaion can appear, if the originating node just sends the
 474          * packet to us (without address resolution for the destination).
 475          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 476          * link identifiers, we can do this stuff after making a copy for
 477          * returning an error.
 478          */
 479         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 480                 /*
 481                  * See corresponding comments in ip6_output.
 482                  * XXX: but is it possible that ip6_forward() sends a packet
 483                  *      to a loopback interface? I don't think so, and thus
 484                  *      I bark here. (jinmei@kame.net)
 485                  * XXX: it is common to route invalid packets to loopback.
 486                  *      also, the codepath will be visited on use of ::1 in
 487                  *      rthdr. (itojun)
 488                  */
 489 #if 1
 490                 if (0)
 491 #else
 492                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 493 #endif
 494                 {
 495                         printf("ip6_forward: outgoing interface is loopback. "
 496                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 497                                 ip6_sprintf(&ip6->ip6_src),
 498                                 ip6_sprintf(&ip6->ip6_dst),
 499                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 500                                 if_name(rt->rt_ifp));
 501                 }
 502
 503                 /* we can just use rcvif in forwarding. */
 504                 origifp = m->m_pkthdr.rcvif;
 505         }
 506         else
 507                 origifp = rt->rt_ifp;
 508 #ifndef SCOPEDROUTING
 509         /*
 510          * clear embedded scope identifiers if necessary.
 511          * in6_clearscope will touch the addresses only when necessary.
 512          */
 513         in6_clearscope(&ip6->ip6_src);
 514         in6_clearscope(&ip6->ip6_dst);
 515 #endif
 516
 517         /*
 518          * Check if we want to allow this packet to be processed.
 519          * Consider it to be bad if not.
 520          */
 521         if (fr_checkp) {
 522                 struct  mbuf    *m1 = m;
 523
 524                 if ((*fr_checkp)((struct ip *)ip6, sizeof(*ip6),
 525                                  rt->rt_ifp, 1, &m1) != 0)
 526                         goto freecopy;
 527                 m = m1;
 528                 if (m == NULL)
 529                         goto freecopy;
 530                 ip6 = mtod(m, struct ip6_hdr *);
 531         }
 532
 533         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 534         if (error) {
 535                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 536                 ip6stat.ip6s_cantforward++;
 537         } else {
 538                 ip6stat.ip6s_forward++;
 539                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 540                 if (type)
 541                         ip6stat.ip6s_redirectsent++;
 542                 else {
 543                         if (mcopy)
 544                                 goto freecopy;
 545                 }
 546         }
 547         if (mcopy == NULL)
 548                 return;
 549         switch (error) {
 550         case 0:
 551 #if 1
 552                 if (type == ND_REDIRECT) {
 553                         icmp6_redirect_output(mcopy, rt);
 554                         return;
 555                 }
 556 #endif
 557                 goto freecopy;
 558
 559         case EMSGSIZE:
 560                 /* xxx MTU is constant in PPP? */
 561                 goto freecopy;
 562
 563         case ENOBUFS:
 564                 /* Tell source to slow down like source quench in IP? */
 565                 goto freecopy;
 566
 567         case ENETUNREACH:       /* shouldn't happen, checked above */
 568         case EHOSTUNREACH:
 569         case ENETDOWN:
 570         case EHOSTDOWN:
 571         default:
 572                 type = ICMP6_DST_UNREACH;
 573                 code = ICMP6_DST_UNREACH_ADDR;
 574                 break;
 575         }
 576         icmp6_error(mcopy, type, code, 0);
 577         return;
 578
 579  freecopy:
 580         m_freem(mcopy);
 581         return;
 582 }