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 1.11 2005/02/01 16:09:37 hrs 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
  39 #include <sys/param.h>
  40 #include <sys/systm.h>
  41 #include <sys/malloc.h>
  42 #include <sys/mbuf.h>
  43 #include <sys/domain.h>
  44 #include <sys/protosw.h>
  45 #include <sys/socket.h>
  46 #include <sys/errno.h>
  47 #include <sys/time.h>
  48 #include <sys/kernel.h>
  49 #include <sys/syslog.h>
  50
  51 #include <net/if.h>
  52 #include <net/route.h>
  53 #include <net/pfil.h>
  54
  55 #include <netinet/in.h>
  56 #include <netinet/in_var.h>
  57 #include <netinet/in_systm.h>
  58 #include <netinet/ip.h>
  59 #include <netinet/ip_var.h>
  60 #include <netinet6/in6_var.h>
  61 #include <netinet/ip6.h>
  62 #include <netinet6/ip6_var.h>
  63 #include <netinet/icmp6.h>
  64 #include <netinet6/nd6.h>
  65
  66 #include <netinet/in_pcb.h>
  67
  68 #ifdef IPSEC
  69 #include <netinet6/ipsec.h>
  70 #ifdef INET6
  71 #include <netinet6/ipsec6.h>
  72 #endif
  73 #include <netproto/key/key.h>
  74 #endif /* IPSEC */
  75
  76 #ifdef FAST_IPSEC
  77 #include <netproto/ipsec/ipsec.h>
  78 #include <netproto/ipsec/ipsec6.h>
  79 #include <netproto/ipsec/key.h>
  80 #define IPSEC
  81 #endif /* FAST_IPSEC */
  82
  83 #include <net/ip6fw/ip6_fw.h>
  84
  85 #include <net/net_osdep.h>
  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(struct mbuf *m, int srcrt)
 104 {
 105         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 106         struct sockaddr_in6 *dst;
 107         struct rtentry *rt;
 108         int error, type = 0, code = 0;
 109         struct mbuf *mcopy = NULL;
 110         struct ifnet *origifp;  /* maybe unnecessary */
 111 #ifdef IPSEC
 112         struct secpolicy *sp = NULL;
 113 #endif
 114
 115 #ifdef IPSEC
 116         /*
 117          * Check AH/ESP integrity.
 118          */
 119         /*
 120          * Don't increment ip6s_cantforward because this is the check
 121          * before forwarding packet actually.
 122          */
 123         if (ipsec6_in_reject(m, NULL)) {
 124 #if !defined(FAST_IPSEC)
 125                 ipsec6stat.in_polvio++;
 126 #endif
 127                 m_freem(m);
 128                 return;
 129         }
 130 #endif /* IPSEC */
 131
 132         /*
 133          * Do not forward packets to multicast destination (should be handled
 134          * by ip6_mforward().
 135          * Do not forward packets with unspecified source.  It was discussed
 136          * in July 2000, on ipngwg mailing list.
 137          */
 138         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 139             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 140             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 141                 ip6stat.ip6s_cantforward++;
 142                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 143                 if (ip6_log_time + ip6_log_interval < time_second) {
 144                         ip6_log_time = time_second;
 145                         log(LOG_DEBUG,
 146                             "cannot forward "
 147                             "from %s to %s nxt %d received on %s\n",
 148                             ip6_sprintf(&ip6->ip6_src),
 149                             ip6_sprintf(&ip6->ip6_dst),
 150                             ip6->ip6_nxt,
 151                             if_name(m->m_pkthdr.rcvif));
 152                 }
 153                 m_freem(m);
 154                 return;
 155         }
 156
 157         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 158                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 159                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 160                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 161                 return;
 162         }
 163         ip6->ip6_hlim -= IPV6_HLIMDEC;
 164
 165         /*
 166          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 167          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 168          * we need to generate an ICMP6 message to the src.
 169          * Thanks to M_EXT, in most cases copy will not occur.
 170          *
 171          * It is important to save it before IPsec processing as IPsec
 172          * processing may modify the mbuf.
 173          */
 174         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 175
 176 #ifdef IPSEC
 177         /* get a security policy for this packet */
 178         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 179             &error);
 180         if (sp == NULL) {
 181                 ipsec6stat.out_inval++;
 182                 ip6stat.ip6s_cantforward++;
 183                 if (mcopy) {
 184 #if 0
 185                         /* XXX: what icmp ? */
 186 #else
 187                         m_freem(mcopy);
 188 #endif
 189                 }
 190                 m_freem(m);
 191                 return;
 192         }
 193
 194         error = 0;
 195
 196         /* check policy */
 197         switch (sp->policy) {
 198         case IPSEC_POLICY_DISCARD:
 199                 /*
 200                  * This packet is just discarded.
 201                  */
 202                 ipsec6stat.out_polvio++;
 203                 ip6stat.ip6s_cantforward++;
 204                 key_freesp(sp);
 205                 if (mcopy) {
 206 #if 0
 207                         /* XXX: what icmp ? */
 208 #else
 209                         m_freem(mcopy);
 210 #endif
 211                 }
 212                 m_freem(m);
 213                 return;
 214
 215         case IPSEC_POLICY_BYPASS:
 216         case IPSEC_POLICY_NONE:
 217                 /* no need to do IPsec. */
 218                 key_freesp(sp);
 219                 goto skip_ipsec;
 220
 221         case IPSEC_POLICY_IPSEC:
 222                 if (sp->req == NULL) {
 223                         /* XXX should be panic ? */
 224                         printf("ip6_forward: No IPsec request specified.\n");
 225                         ip6stat.ip6s_cantforward++;
 226                         key_freesp(sp);
 227                         if (mcopy) {
 228 #if 0
 229                                 /* XXX: what icmp ? */
 230 #else
 231                                 m_freem(mcopy);
 232 #endif
 233                         }
 234                         m_freem(m);
 235                         return;
 236                 }
 237                 /* do IPsec */
 238                 break;
 239
 240         case IPSEC_POLICY_ENTRUST:
 241         default:
 242                 /* should be panic ?? */
 243                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 244                 key_freesp(sp);
 245                 goto skip_ipsec;
 246         }
 247
 248     {
 249         struct ipsec_output_state state;
 250
 251         /*
 252          * All the extension headers will become inaccessible
 253          * (since they can be encrypted).
 254          * Don't panic, we need no more updates to extension headers
 255          * on inner IPv6 packet (since they are now encapsulated).
 256          *
 257          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 258          */
 259         bzero(&state, sizeof(state));
 260         state.m = m;
 261         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 262         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 263
 264         error = ipsec6_output_tunnel(&state, sp, 0);
 265
 266         m = state.m;
 267         key_freesp(sp);
 268
 269         if (error) {
 270                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 271                 switch (error) {
 272                 case EHOSTUNREACH:
 273                 case ENETUNREACH:
 274                 case EMSGSIZE:
 275                 case ENOBUFS:
 276                 case ENOMEM:
 277                         break;
 278                 default:
 279                         printf("ip6_output (ipsec): error code %d\n", error);
 280                         /* fall through */
 281                 case ENOENT:
 282                         /* don't show these error codes to the user */
 283                         break;
 284                 }
 285                 ip6stat.ip6s_cantforward++;
 286                 if (mcopy) {
 287 #if 0
 288                         /* XXX: what icmp ? */
 289 #else
 290                         m_freem(mcopy);
 291 #endif
 292                 }
 293                 m_freem(m);
 294                 return;
 295         }
 296     }
 297     skip_ipsec:
 298 #endif /* IPSEC */
 299
 300         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 301         if (!srcrt) {
 302                 /*
 303                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 304                  */
 305                 if (ip6_forward_rt.ro_rt == 0 ||
 306                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 307                         if (ip6_forward_rt.ro_rt) {
 308                                 RTFREE(ip6_forward_rt.ro_rt);
 309                                 ip6_forward_rt.ro_rt = 0;
 310                         }
 311                         /* this probably fails but give it a try again */
 312                         rtalloc_ign((struct route *)&ip6_forward_rt,
 313                                     RTF_PRCLONING);
 314                 }
 315
 316                 if (ip6_forward_rt.ro_rt == 0) {
 317                         ip6stat.ip6s_noroute++;
 318                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 319                         if (mcopy) {
 320                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 321                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 322                         }
 323                         m_freem(m);
 324                         return;
 325                 }
 326         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 327                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 328                 if (ip6_forward_rt.ro_rt) {
 329                         RTFREE(ip6_forward_rt.ro_rt);
 330                         ip6_forward_rt.ro_rt = 0;
 331                 }
 332                 bzero(dst, sizeof(*dst));
 333                 dst->sin6_len = sizeof(struct sockaddr_in6);
 334                 dst->sin6_family = AF_INET6;
 335                 dst->sin6_addr = ip6->ip6_dst;
 336
 337                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 338                 if (ip6_forward_rt.ro_rt == 0) {
 339                         ip6stat.ip6s_noroute++;
 340                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 341                         if (mcopy) {
 342                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 343                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 344                         }
 345                         m_freem(m);
 346                         return;
 347                 }
 348         }
 349         rt = ip6_forward_rt.ro_rt;
 350
 351         /*
 352          * Scope check: if a packet can't be delivered to its destination
 353          * for the reason that the destination is beyond the scope of the
 354          * source address, discard the packet and return an icmp6 destination
 355          * unreachable error with Code 2 (beyond scope of source address).
 356          * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1]
 357          */
 358         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 359             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 360                 ip6stat.ip6s_cantforward++;
 361                 ip6stat.ip6s_badscope++;
 362                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 363
 364                 if (ip6_log_time + ip6_log_interval < time_second) {
 365                         ip6_log_time = time_second;
 366                         log(LOG_DEBUG,
 367                             "cannot forward "
 368                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 369                             ip6_sprintf(&ip6->ip6_src),
 370                             ip6_sprintf(&ip6->ip6_dst),
 371                             ip6->ip6_nxt,
 372                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 373                 }
 374                 if (mcopy)
 375                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 376                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 377                 m_freem(m);
 378                 return;
 379         }
 380
 381         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 382                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 383                 if (mcopy) {
 384                         u_long mtu;
 385 #ifdef IPSEC
 386                         struct secpolicy *sp;
 387                         int ipsecerror;
 388                         size_t ipsechdrsiz;
 389 #endif
 390
 391                         mtu = rt->rt_ifp->if_mtu;
 392 #ifdef IPSEC
 393                         /*
 394                          * When we do IPsec tunnel ingress, we need to play
 395                          * with if_mtu value (decrement IPsec header size
 396                          * from mtu value).  The code is much simpler than v4
 397                          * case, as we have the outgoing interface for
 398                          * encapsulated packet as "rt->rt_ifp".
 399                          */
 400                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 401                                 IP_FORWARDING, &ipsecerror);
 402                         if (sp) {
 403                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 404                                         IPSEC_DIR_OUTBOUND, NULL);
 405                                 if (ipsechdrsiz < mtu)
 406                                         mtu -= ipsechdrsiz;
 407                         }
 408
 409                         /*
 410                          * if mtu becomes less than minimum MTU,
 411                          * tell minimum MTU (and I'll need to fragment it).
 412                          */
 413                         if (mtu < IPV6_MMTU)
 414                                 mtu = IPV6_MMTU;
 415 #endif
 416                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 417                 }
 418                 m_freem(m);
 419                 return;
 420         }
 421
 422         if (rt->rt_flags & RTF_GATEWAY)
 423                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 424
 425         /*
 426          * If we are to forward the packet using the same interface
 427          * as one we got the packet from, perhaps we should send a redirect
 428          * to sender to shortcut a hop.
 429          * Only send redirect if source is sending directly to us,
 430          * and if packet was not source routed (or has any options).
 431          * Also, don't send redirect if forwarding using a route
 432          * modified by a redirect.
 433          */
 434         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 435             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 436                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 437                         /*
 438                          * If the incoming interface is equal to the outgoing
 439                          * one, and the link attached to the interface is
 440                          * point-to-point, then it will be highly probable
 441                          * that a routing loop occurs. Thus, we immediately
 442                          * drop the packet and send an ICMPv6 error message.
 443                          *
 444                          * type/code is based on suggestion by Rich Draves.
 445                          * not sure if it is the best pick.
 446                          */
 447                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 448                                     ICMP6_DST_UNREACH_ADDR, 0);
 449                         m_freem(m);
 450                         return;
 451                 }
 452                 type = ND_REDIRECT;
 453         }
 454
 455         /*
 456          * Check with the firewall...
 457          */
 458         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 459                 u_short port = 0;
 460                 /* If ipfw says divert, we have to just drop packet */
 461                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 462                         m_freem(m);
 463                         goto freecopy;
 464                 }
 465                 if (!m)
 466                         goto freecopy;
 467         }
 468
 469         /*
 470          * Fake scoped addresses. Note that even link-local source or
 471          * destinaion can appear, if the originating node just sends the
 472          * packet to us (without address resolution for the destination).
 473          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 474          * link identifiers, we can do this stuff after making a copy for
 475          * returning an error.
 476          */
 477         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 478                 /*
 479                  * See corresponding comments in ip6_output.
 480                  * XXX: but is it possible that ip6_forward() sends a packet
 481                  *      to a loopback interface? I don't think so, and thus
 482                  *      I bark here. (jinmei@kame.net)
 483                  * XXX: it is common to route invalid packets to loopback.
 484                  *      also, the codepath will be visited on use of ::1 in
 485                  *      rthdr. (itojun)
 486                  */
 487 #if 1
 488                 if (0)
 489 #else
 490                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 491 #endif
 492                 {
 493                         printf("ip6_forward: outgoing interface is loopback. "
 494                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 495                                 ip6_sprintf(&ip6->ip6_src),
 496                                 ip6_sprintf(&ip6->ip6_dst),
 497                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 498                                 if_name(rt->rt_ifp));
 499                 }
 500
 501                 /* we can just use rcvif in forwarding. */
 502                 origifp = m->m_pkthdr.rcvif;
 503         }
 504         else
 505                 origifp = rt->rt_ifp;
 506         /*
 507          * clear embedded scope identifiers if necessary.
 508          * in6_clearscope will touch the addresses only when necessary.
 509          */
 510         in6_clearscope(&ip6->ip6_src);
 511         in6_clearscope(&ip6->ip6_dst);
 512
 513         /*
 514          * Run through list of hooks for output packets.
 515          */
 516         if (pfil_has_hooks(&inet6_pfil_hook)) {
 517                 error = pfil_run_hooks(&inet6_pfil_hook, &m,
 518                                         rt->rt_ifp, PFIL_OUT);
 519                 if (error != 0)
 520                         goto senderr;
 521                 if (m == NULL)
 522                         goto freecopy;
 523                 ip6 = mtod(m, struct ip6_hdr *);
 524         }
 525
 526         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 527         if (error) {
 528                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 529                 ip6stat.ip6s_cantforward++;
 530         } else {
 531                 ip6stat.ip6s_forward++;
 532                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 533                 if (type)
 534                         ip6stat.ip6s_redirectsent++;
 535                 else {
 536                         if (mcopy)
 537                                 goto freecopy;
 538                 }
 539         }
 540 senderr:
 541         if (mcopy == NULL)
 542                 return;
 543         switch (error) {
 544         case 0:
 545 #if 1
 546                 if (type == ND_REDIRECT) {
 547                         icmp6_redirect_output(mcopy, rt);
 548                         return;
 549                 }
 550 #endif
 551                 goto freecopy;
 552
 553         case EMSGSIZE:
 554                 /* xxx MTU is constant in PPP? */
 555                 goto freecopy;
 556
 557         case ENOBUFS:
 558                 /* Tell source to slow down like source quench in IP? */
 559                 goto freecopy;
 560
 561         case ENETUNREACH:       /* shouldn't happen, checked above */
 562         case EHOSTUNREACH:
 563         case ENETDOWN:
 564         case EHOSTDOWN:
 565         default:
 566                 type = ICMP6_DST_UNREACH;
 567                 code = ICMP6_DST_UNREACH_ADDR;
 568                 break;
 569         }
 570         icmp6_error(mcopy, type, code, 0);
 571         return;
 572
 573  freecopy:
 574         m_freem(mcopy);
 575         return;
 576 }