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 /*      $DragonFly: src/sys/netinet6/ip6_forward.c,v 1.6 2003/12/02 08:00:22 asmodai Exp $      */
   3 /*      $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $    */
   4
   5 /*
   6  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. Neither the name of the project nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "opt_ip6fw.h"
  35 #include "opt_inet.h"
  36 #include "opt_inet6.h"
  37 #include "opt_ipsec.h"
  38 #include "opt_pfil_hooks.h"
  39
  40 #include <sys/param.h>
  41 #include <sys/systm.h>
  42 #include <sys/malloc.h>
  43 #include <sys/mbuf.h>
  44 #include <sys/domain.h>
  45 #include <sys/protosw.h>
  46 #include <sys/socket.h>
  47 #include <sys/errno.h>
  48 #include <sys/time.h>
  49 #include <sys/kernel.h>
  50 #include <sys/syslog.h>
  51
  52 #include <net/if.h>
  53 #include <net/route.h>
  54 #ifdef PFIL_HOOKS
  55 #include <net/pfil.h>
  56 #endif
  57
  58 #include <netinet/in.h>
  59 #include <netinet/in_var.h>
  60 #include <netinet/in_systm.h>
  61 #include <netinet/ip.h>
  62 #include <netinet/ip_var.h>
  63 #include <netinet6/in6_var.h>
  64 #include <netinet/ip6.h>
  65 #include <netinet6/ip6_var.h>
  66 #include <netinet/icmp6.h>
  67 #include <netinet6/nd6.h>
  68
  69 #include <netinet/in_pcb.h>
  70
  71 #ifdef IPSEC
  72 #include <netinet6/ipsec.h>
  73 #ifdef INET6
  74 #include <netinet6/ipsec6.h>
  75 #endif
  76 #include <netproto/key/key.h>
  77 #endif /* IPSEC */
  78
  79 #ifdef FAST_IPSEC
  80 #include "ipsec.h"
  81 #include "ipsec6.h"
  82 #include <netipsec/key.h>
  83 #define IPSEC
  84 #endif /* FAST_IPSEC */
  85
  86 #include <net/ip6fw/ip6_fw.h>
  87
  88 #include <net/net_osdep.h>
  89
  90 struct  route_in6 ip6_forward_rt;
  91
  92 /*
  93  * Forward a packet.  If some error occurs return the sender
  94  * an icmp packet.  Note we can't always generate a meaningful
  95  * icmp message because icmp doesn't have a large enough repertoire
  96  * of codes and types.
  97  *
  98  * If not forwarding, just drop the packet.  This could be confusing
  99  * if ipforwarding was zero but some routing protocol was advancing
 100  * us as a gateway to somewhere.  However, we must let the routing
 101  * protocol deal with that.
 102  *
 103  */
 104
 105 void
 106 ip6_forward(m, srcrt)
 107         struct mbuf *m;
 108         int srcrt;
 109 {
 110         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 111         struct sockaddr_in6 *dst;
 112         struct rtentry *rt;
 113         int error, type = 0, code = 0;
 114         struct mbuf *mcopy = NULL;
 115         struct ifnet *origifp;  /* maybe unnecessary */
 116 #ifdef IPSEC
 117         struct secpolicy *sp = NULL;
 118 #endif
 119
 120 #ifdef IPSEC
 121         /*
 122          * Check AH/ESP integrity.
 123          */
 124         /*
 125          * Don't increment ip6s_cantforward because this is the check
 126          * before forwarding packet actually.
 127          */
 128         if (ipsec6_in_reject(m, NULL)) {
 129 #if !defined(FAST_IPSEC)
 130                 ipsec6stat.in_polvio++;
 131 #endif
 132                 m_freem(m);
 133                 return;
 134         }
 135 #endif /* IPSEC */
 136
 137         /*
 138          * Do not forward packets to multicast destination (should be handled
 139          * by ip6_mforward().
 140          * Do not forward packets with unspecified source.  It was discussed
 141          * in July 2000, on ipngwg mailing list.
 142          */
 143         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 144             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 145             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 146                 ip6stat.ip6s_cantforward++;
 147                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 148                 if (ip6_log_time + ip6_log_interval < time_second) {
 149                         ip6_log_time = time_second;
 150                         log(LOG_DEBUG,
 151                             "cannot forward "
 152                             "from %s to %s nxt %d received on %s\n",
 153                             ip6_sprintf(&ip6->ip6_src),
 154                             ip6_sprintf(&ip6->ip6_dst),
 155                             ip6->ip6_nxt,
 156                             if_name(m->m_pkthdr.rcvif));
 157                 }
 158                 m_freem(m);
 159                 return;
 160         }
 161
 162         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 163                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 164                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 165                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 166                 return;
 167         }
 168         ip6->ip6_hlim -= IPV6_HLIMDEC;
 169
 170         /*
 171          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 172          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 173          * we need to generate an ICMP6 message to the src.
 174          * Thanks to M_EXT, in most cases copy will not occur.
 175          *
 176          * It is important to save it before IPsec processing as IPsec
 177          * processing may modify the mbuf.
 178          */
 179         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 180
 181 #ifdef IPSEC
 182         /* get a security policy for this packet */
 183         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 184             &error);
 185         if (sp == NULL) {
 186                 ipsec6stat.out_inval++;
 187                 ip6stat.ip6s_cantforward++;
 188                 if (mcopy) {
 189 #if 0
 190                         /* XXX: what icmp ? */
 191 #else
 192                         m_freem(mcopy);
 193 #endif
 194                 }
 195                 m_freem(m);
 196                 return;
 197         }
 198
 199         error = 0;
 200
 201         /* check policy */
 202         switch (sp->policy) {
 203         case IPSEC_POLICY_DISCARD:
 204                 /*
 205                  * This packet is just discarded.
 206                  */
 207                 ipsec6stat.out_polvio++;
 208                 ip6stat.ip6s_cantforward++;
 209                 key_freesp(sp);
 210                 if (mcopy) {
 211 #if 0
 212                         /* XXX: what icmp ? */
 213 #else
 214                         m_freem(mcopy);
 215 #endif
 216                 }
 217                 m_freem(m);
 218                 return;
 219
 220         case IPSEC_POLICY_BYPASS:
 221         case IPSEC_POLICY_NONE:
 222                 /* no need to do IPsec. */
 223                 key_freesp(sp);
 224                 goto skip_ipsec;
 225
 226         case IPSEC_POLICY_IPSEC:
 227                 if (sp->req == NULL) {
 228                         /* XXX should be panic ? */
 229                         printf("ip6_forward: No IPsec request specified.\n");
 230                         ip6stat.ip6s_cantforward++;
 231                         key_freesp(sp);
 232                         if (mcopy) {
 233 #if 0
 234                                 /* XXX: what icmp ? */
 235 #else
 236                                 m_freem(mcopy);
 237 #endif
 238                         }
 239                         m_freem(m);
 240                         return;
 241                 }
 242                 /* do IPsec */
 243                 break;
 244
 245         case IPSEC_POLICY_ENTRUST:
 246         default:
 247                 /* should be panic ?? */
 248                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 249                 key_freesp(sp);
 250                 goto skip_ipsec;
 251         }
 252
 253     {
 254         struct ipsec_output_state state;
 255
 256         /*
 257          * All the extension headers will become inaccessible
 258          * (since they can be encrypted).
 259          * Don't panic, we need no more updates to extension headers
 260          * on inner IPv6 packet (since they are now encapsulated).
 261          *
 262          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 263          */
 264         bzero(&state, sizeof(state));
 265         state.m = m;
 266         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 267         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 268
 269         error = ipsec6_output_tunnel(&state, sp, 0);
 270
 271         m = state.m;
 272         key_freesp(sp);
 273
 274         if (error) {
 275                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 276                 switch (error) {
 277                 case EHOSTUNREACH:
 278                 case ENETUNREACH:
 279                 case EMSGSIZE:
 280                 case ENOBUFS:
 281                 case ENOMEM:
 282                         break;
 283                 default:
 284                         printf("ip6_output (ipsec): error code %d\n", error);
 285                         /* fall through */
 286                 case ENOENT:
 287                         /* don't show these error codes to the user */
 288                         break;
 289                 }
 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;
 300         }
 301     }
 302     skip_ipsec:
 303 #endif /* IPSEC */
 304
 305         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 306         if (!srcrt) {
 307                 /*
 308                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 309                  */
 310                 if (ip6_forward_rt.ro_rt == 0 ||
 311                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 312                         if (ip6_forward_rt.ro_rt) {
 313                                 RTFREE(ip6_forward_rt.ro_rt);
 314                                 ip6_forward_rt.ro_rt = 0;
 315                         }
 316                         /* this probably fails but give it a try again */
 317                         rtalloc_ign((struct route *)&ip6_forward_rt,
 318                                     RTF_PRCLONING);
 319                 }
 320
 321                 if (ip6_forward_rt.ro_rt == 0) {
 322                         ip6stat.ip6s_noroute++;
 323                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 324                         if (mcopy) {
 325                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 326                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 327                         }
 328                         m_freem(m);
 329                         return;
 330                 }
 331         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 332                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 333                 if (ip6_forward_rt.ro_rt) {
 334                         RTFREE(ip6_forward_rt.ro_rt);
 335                         ip6_forward_rt.ro_rt = 0;
 336                 }
 337                 bzero(dst, sizeof(*dst));
 338                 dst->sin6_len = sizeof(struct sockaddr_in6);
 339                 dst->sin6_family = AF_INET6;
 340                 dst->sin6_addr = ip6->ip6_dst;
 341
 342                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 343                 if (ip6_forward_rt.ro_rt == 0) {
 344                         ip6stat.ip6s_noroute++;
 345                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 346                         if (mcopy) {
 347                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 348                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 349                         }
 350                         m_freem(m);
 351                         return;
 352                 }
 353         }
 354         rt = ip6_forward_rt.ro_rt;
 355
 356         /*
 357          * Scope check: if a packet can't be delivered to its destination
 358          * for the reason that the destination is beyond the scope of the
 359          * source address, discard the packet and return an icmp6 destination
 360          * unreachable error with Code 2 (beyond scope of source address).
 361          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 362          */
 363         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 364             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 365                 ip6stat.ip6s_cantforward++;
 366                 ip6stat.ip6s_badscope++;
 367                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 368
 369                 if (ip6_log_time + ip6_log_interval < time_second) {
 370                         ip6_log_time = time_second;
 371                         log(LOG_DEBUG,
 372                             "cannot forward "
 373                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 374                             ip6_sprintf(&ip6->ip6_src),
 375                             ip6_sprintf(&ip6->ip6_dst),
 376                             ip6->ip6_nxt,
 377                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 378                 }
 379                 if (mcopy)
 380                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 381                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 382                 m_freem(m);
 383                 return;
 384         }
 385
 386         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 387                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 388                 if (mcopy) {
 389                         u_long mtu;
 390 #ifdef IPSEC
 391                         struct secpolicy *sp;
 392                         int ipsecerror;
 393                         size_t ipsechdrsiz;
 394 #endif
 395
 396                         mtu = rt->rt_ifp->if_mtu;
 397 #ifdef IPSEC
 398                         /*
 399                          * When we do IPsec tunnel ingress, we need to play
 400                          * with if_mtu value (decrement IPsec header size
 401                          * from mtu value).  The code is much simpler than v4
 402                          * case, as we have the outgoing interface for
 403                          * encapsulated packet as "rt->rt_ifp".
 404                          */
 405                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 406                                 IP_FORWARDING, &ipsecerror);
 407                         if (sp) {
 408                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 409                                         IPSEC_DIR_OUTBOUND, NULL);
 410                                 if (ipsechdrsiz < mtu)
 411                                         mtu -= ipsechdrsiz;
 412                         }
 413
 414                         /*
 415                          * if mtu becomes less than minimum MTU,
 416                          * tell minimum MTU (and I'll need to fragment it).
 417                          */
 418                         if (mtu < IPV6_MMTU)
 419                                 mtu = IPV6_MMTU;
 420 #endif
 421                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 422                 }
 423                 m_freem(m);
 424                 return;
 425         }
 426
 427         if (rt->rt_flags & RTF_GATEWAY)
 428                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 429
 430         /*
 431          * If we are to forward the packet using the same interface
 432          * as one we got the packet from, perhaps we should send a redirect
 433          * to sender to shortcut a hop.
 434          * Only send redirect if source is sending directly to us,
 435          * and if packet was not source routed (or has any options).
 436          * Also, don't send redirect if forwarding using a route
 437          * modified by a redirect.
 438          */
 439         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 440             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 441                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 442                         /*
 443                          * If the incoming interface is equal to the outgoing
 444                          * one, and the link attached to the interface is
 445                          * point-to-point, then it will be highly probable
 446                          * that a routing loop occurs. Thus, we immediately
 447                          * drop the packet and send an ICMPv6 error message.
 448                          *
 449                          * type/code is based on suggestion by Rich Draves.
 450                          * not sure if it is the best pick.
 451                          */
 452                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 453                                     ICMP6_DST_UNREACH_ADDR, 0);
 454                         m_freem(m);
 455                         return;
 456                 }
 457                 type = ND_REDIRECT;
 458         }
 459
 460         /*
 461          * Check with the firewall...
 462          */
 463         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 464                 u_short port = 0;
 465                 /* If ipfw says divert, we have to just drop packet */
 466                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 467                         m_freem(m);
 468                         goto freecopy;
 469                 }
 470                 if (!m)
 471                         goto freecopy;
 472         }
 473
 474         /*
 475          * Fake scoped addresses. Note that even link-local source or
 476          * destinaion can appear, if the originating node just sends the
 477          * packet to us (without address resolution for the destination).
 478          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 479          * link identifiers, we can do this stuff after making a copy for
 480          * returning an error.
 481          */
 482         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 483                 /*
 484                  * See corresponding comments in ip6_output.
 485                  * XXX: but is it possible that ip6_forward() sends a packet
 486                  *      to a loopback interface? I don't think so, and thus
 487                  *      I bark here. (jinmei@kame.net)
 488                  * XXX: it is common to route invalid packets to loopback.
 489                  *      also, the codepath will be visited on use of ::1 in
 490                  *      rthdr. (itojun)
 491                  */
 492 #if 1
 493                 if (0)
 494 #else
 495                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 496 #endif
 497                 {
 498                         printf("ip6_forward: outgoing interface is loopback. "
 499                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 500                                 ip6_sprintf(&ip6->ip6_src),
 501                                 ip6_sprintf(&ip6->ip6_dst),
 502                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 503                                 if_name(rt->rt_ifp));
 504                 }
 505
 506                 /* we can just use rcvif in forwarding. */
 507                 origifp = m->m_pkthdr.rcvif;
 508         }
 509         else
 510                 origifp = rt->rt_ifp;
 511 #ifndef SCOPEDROUTING
 512         /*
 513          * clear embedded scope identifiers if necessary.
 514          * in6_clearscope will touch the addresses only when necessary.
 515          */
 516         in6_clearscope(&ip6->ip6_src);
 517         in6_clearscope(&ip6->ip6_dst);
 518 #endif
 519
 520 #ifdef PFIL_HOOKS
 521         /*
 522          * Run through list of hooks for output packets.
 523          */
 524         error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT);
 525         if (error != 0)
 526                 goto senderr;
 527         if (m == NULL)
 528                 goto freecopy;
 529         ip6 = mtod(m, struct ip6_hdr *);
 530 #endif /* PFIL_HOOKS */
 531
 532         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 533         if (error) {
 534                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 535                 ip6stat.ip6s_cantforward++;
 536         } else {
 537                 ip6stat.ip6s_forward++;
 538                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 539                 if (type)
 540                         ip6stat.ip6s_redirectsent++;
 541                 else {
 542                         if (mcopy)
 543                                 goto freecopy;
 544                 }
 545         }
 546 #ifdef PFIL_HOOKS
 547 senderr:
 548 #endif
 549         if (mcopy == NULL)
 550                 return;
 551         switch (error) {
 552         case 0:
 553 #if 1
 554                 if (type == ND_REDIRECT) {
 555                         icmp6_redirect_output(mcopy, rt);
 556                         return;
 557                 }
 558 #endif
 559                 goto freecopy;
 560
 561         case EMSGSIZE:
 562                 /* xxx MTU is constant in PPP? */
 563                 goto freecopy;
 564
 565         case ENOBUFS:
 566                 /* Tell source to slow down like source quench in IP? */
 567                 goto freecopy;
 568
 569         case ENETUNREACH:       /* shouldn't happen, checked above */
 570         case EHOSTUNREACH:
 571         case ENETDOWN:
 572         case EHOSTDOWN:
 573         default:
 574                 type = ICMP6_DST_UNREACH;
 575                 code = ICMP6_DST_UNREACH_ADDR;
 576                 break;
 577         }
 578         icmp6_error(mcopy, type, code, 0);
 579         return;
 580
 581  freecopy:
 582         m_freem(mcopy);
 583         return;
 584 }