sys/netinet6/ip6_forward.c

   1 /*      $FreeBSD$       */
   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 #ifdef PFIL_HOOKS
  53 #include <net/pfil.h>
  54 #endif
  55
  56 #include <netinet/in.h>
  57 #include <netinet/in_var.h>
  58 #include <netinet/in_systm.h>
  59 #include <netinet/ip.h>
  60 #include <netinet/ip_var.h>
  61 #include <netinet6/in6_var.h>
  62 #include <netinet/ip6.h>
  63 #include <netinet6/ip6_var.h>
  64 #include <netinet/icmp6.h>
  65 #include <netinet6/nd6.h>
  66
  67 #include <netinet/in_pcb.h>
  68
  69 #ifdef IPSEC
  70 #include <netinet6/ipsec.h>
  71 #ifdef INET6
  72 #include <netinet6/ipsec6.h>
  73 #endif
  74 #include <netkey/key.h>
  75 #endif /* IPSEC */
  76
  77 #include <netinet6/ip6_fw.h>
  78
  79 #include <net/net_osdep.h>
  80
  81 #include <netinet6/ip6protosw.h>
  82
  83 struct  route_in6 ip6_forward_rt;
  84
  85 /*
  86  * Forward a packet.  If some error occurs return the sender
  87  * an icmp packet.  Note we can't always generate a meaningful
  88  * icmp message because icmp doesn't have a large enough repertoire
  89  * of codes and types.
  90  *
  91  * If not forwarding, just drop the packet.  This could be confusing
  92  * if ipforwarding was zero but some routing protocol was advancing
  93  * us as a gateway to somewhere.  However, we must let the routing
  94  * protocol deal with that.
  95  *
  96  */
  97
  98 void
  99 ip6_forward(m, srcrt)
 100         struct mbuf *m;
 101         int srcrt;
 102 {
 103         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 104         struct sockaddr_in6 *dst;
 105         struct rtentry *rt;
 106         int error, type = 0, code = 0;
 107         struct mbuf *mcopy = NULL;
 108         struct ifnet *origifp;  /* maybe unnecessary */
 109 #ifdef PFIL_HOOKS
 110         struct packet_filter_hook *pfh;
 111         struct mbuf *m1;
 112         int rv;
 113 #endif /* PFIL_HOOKS */
 114 #ifdef IPSEC
 115         struct secpolicy *sp = NULL;
 116 #endif
 117
 118 #ifdef IPSEC
 119         /*
 120          * Check AH/ESP integrity.
 121          */
 122         /*
 123          * Don't increment ip6s_cantforward because this is the check
 124          * before forwarding packet actually.
 125          */
 126         if (ipsec6_in_reject(m, NULL)) {
 127                 ipsec6stat.in_polvio++;
 128                 m_freem(m);
 129                 return;
 130         }
 131 #endif /*IPSEC*/
 132
 133         /*
 134          * Do not forward packets to multicast destination (should be handled
 135          * by ip6_mforward().
 136          * Do not forward packets with unspecified source.  It was discussed
 137          * in July 2000, on ipngwg mailing list.
 138          */
 139         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 140             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 141             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 142                 ip6stat.ip6s_cantforward++;
 143                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 144                 if (ip6_log_time + ip6_log_interval < time_second) {
 145                         ip6_log_time = time_second;
 146                         log(LOG_DEBUG,
 147                             "cannot forward "
 148                             "from %s to %s nxt %d received on %s\n",
 149                             ip6_sprintf(&ip6->ip6_src),
 150                             ip6_sprintf(&ip6->ip6_dst),
 151                             ip6->ip6_nxt,
 152                             if_name(m->m_pkthdr.rcvif));
 153                 }
 154                 m_freem(m);
 155                 return;
 156         }
 157
 158         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 159                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 160                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 161                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 162                 return;
 163         }
 164         ip6->ip6_hlim -= IPV6_HLIMDEC;
 165
 166         /*
 167          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 168          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 169          * we need to generate an ICMP6 message to the src.
 170          * Thanks to M_EXT, in most cases copy will not occur.
 171          *
 172          * It is important to save it before IPsec processing as IPsec
 173          * processing may modify the mbuf.
 174          */
 175         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 176
 177 #ifdef IPSEC
 178         /* get a security policy for this packet */
 179         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 180             &error);
 181         if (sp == NULL) {
 182                 ipsec6stat.out_inval++;
 183                 ip6stat.ip6s_cantforward++;
 184                 if (mcopy) {
 185 #if 0
 186                         /* XXX: what icmp ? */
 187 #else
 188                         m_freem(mcopy);
 189 #endif
 190                 }
 191                 m_freem(m);
 192                 return;
 193         }
 194
 195         error = 0;
 196
 197         /* check policy */
 198         switch (sp->policy) {
 199         case IPSEC_POLICY_DISCARD:
 200                 /*
 201                  * This packet is just discarded.
 202                  */
 203                 ipsec6stat.out_polvio++;
 204                 ip6stat.ip6s_cantforward++;
 205                 key_freesp(sp);
 206                 if (mcopy) {
 207 #if 0
 208                         /* XXX: what icmp ? */
 209 #else
 210                         m_freem(mcopy);
 211 #endif
 212                 }
 213                 m_freem(m);
 214                 return;
 215
 216         case IPSEC_POLICY_BYPASS:
 217         case IPSEC_POLICY_NONE:
 218                 /* no need to do IPsec. */
 219                 key_freesp(sp);
 220                 goto skip_ipsec;
 221
 222         case IPSEC_POLICY_IPSEC:
 223                 if (sp->req == NULL) {
 224                         /* XXX should be panic ? */
 225                         printf("ip6_forward: No IPsec request specified.\n");
 226                         ip6stat.ip6s_cantforward++;
 227                         key_freesp(sp);
 228                         if (mcopy) {
 229 #if 0
 230                                 /* XXX: what icmp ? */
 231 #else
 232                                 m_freem(mcopy);
 233 #endif
 234                         }
 235                         m_freem(m);
 236                         return;
 237                 }
 238                 /* do IPsec */
 239                 break;
 240
 241         case IPSEC_POLICY_ENTRUST:
 242         default:
 243                 /* should be panic ?? */
 244                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 245                 key_freesp(sp);
 246                 goto skip_ipsec;
 247         }
 248
 249     {
 250         struct ipsec_output_state state;
 251
 252         /*
 253          * All the extension headers will become inaccessible
 254          * (since they can be encrypted).
 255          * Don't panic, we need no more updates to extension headers
 256          * on inner IPv6 packet (since they are now encapsulated).
 257          *
 258          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 259          */
 260         bzero(&state, sizeof(state));
 261         state.m = m;
 262         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 263         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 264
 265         error = ipsec6_output_tunnel(&state, sp, 0);
 266
 267         m = state.m;
 268         key_freesp(sp);
 269
 270         if (error) {
 271                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 272                 switch (error) {
 273                 case EHOSTUNREACH:
 274                 case ENETUNREACH:
 275                 case EMSGSIZE:
 276                 case ENOBUFS:
 277                 case ENOMEM:
 278                         break;
 279                 default:
 280                         printf("ip6_output (ipsec): error code %d\n", error);
 281                         /*fall through*/
 282                 case ENOENT:
 283                         /* don't show these error codes to the user */
 284                         break;
 285                 }
 286                 ip6stat.ip6s_cantforward++;
 287                 if (mcopy) {
 288 #if 0
 289                         /* XXX: what icmp ? */
 290 #else
 291                         m_freem(mcopy);
 292 #endif
 293                 }
 294                 m_freem(m);
 295                 return;
 296         }
 297     }
 298     skip_ipsec:
 299 #endif /* IPSEC */
 300
 301         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 302         if (!srcrt) {
 303                 /*
 304                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 305                  */
 306                 if (ip6_forward_rt.ro_rt == 0 ||
 307                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 308                         if (ip6_forward_rt.ro_rt) {
 309                                 RTFREE(ip6_forward_rt.ro_rt);
 310                                 ip6_forward_rt.ro_rt = 0;
 311                         }
 312                         /* this probably fails but give it a try again */
 313                         rtalloc_ign((struct route *)&ip6_forward_rt,
 314                                     RTF_PRCLONING);
 315                 }
 316
 317                 if (ip6_forward_rt.ro_rt == 0) {
 318                         ip6stat.ip6s_noroute++;
 319                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 320                         if (mcopy) {
 321                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 322                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 323                         }
 324                         m_freem(m);
 325                         return;
 326                 }
 327         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 328                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 329                 if (ip6_forward_rt.ro_rt) {
 330                         RTFREE(ip6_forward_rt.ro_rt);
 331                         ip6_forward_rt.ro_rt = 0;
 332                 }
 333                 bzero(dst, sizeof(*dst));
 334                 dst->sin6_len = sizeof(struct sockaddr_in6);
 335                 dst->sin6_family = AF_INET6;
 336                 dst->sin6_addr = ip6->ip6_dst;
 337
 338                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 339                 if (ip6_forward_rt.ro_rt == 0) {
 340                         ip6stat.ip6s_noroute++;
 341                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 342                         if (mcopy) {
 343                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 344                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 345                         }
 346                         m_freem(m);
 347                         return;
 348                 }
 349         }
 350         rt = ip6_forward_rt.ro_rt;
 351
 352         /*
 353          * Scope check: if a packet can't be delivered to its destination
 354          * for the reason that the destination is beyond the scope of the
 355          * source address, discard the packet and return an icmp6 destination
 356          * unreachable error with Code 2 (beyond scope of source address).
 357          * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
 358          */
 359         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 360             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 361                 ip6stat.ip6s_cantforward++;
 362                 ip6stat.ip6s_badscope++;
 363                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 364
 365                 if (ip6_log_time + ip6_log_interval < time_second) {
 366                         ip6_log_time = time_second;
 367                         log(LOG_DEBUG,
 368                             "cannot forward "
 369                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 370                             ip6_sprintf(&ip6->ip6_src),
 371                             ip6_sprintf(&ip6->ip6_dst),
 372                             ip6->ip6_nxt,
 373                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 374                 }
 375                 if (mcopy)
 376                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 377                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 378                 m_freem(m);
 379                 return;
 380         }
 381
 382         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 383                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 384                 if (mcopy) {
 385                         u_long mtu;
 386 #ifdef IPSEC
 387                         struct secpolicy *sp;
 388                         int ipsecerror;
 389                         size_t ipsechdrsiz;
 390 #endif
 391
 392                         mtu = rt->rt_ifp->if_mtu;
 393 #ifdef IPSEC
 394                         /*
 395                          * When we do IPsec tunnel ingress, we need to play
 396                          * with if_mtu value (decrement IPsec header size
 397                          * from mtu value).  The code is much simpler than v4
 398                          * case, as we have the outgoing interface for
 399                          * encapsulated packet as "rt->rt_ifp".
 400                          */
 401                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 402                                 IP_FORWARDING, &ipsecerror);
 403                         if (sp) {
 404                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 405                                         IPSEC_DIR_OUTBOUND, NULL);
 406                                 if (ipsechdrsiz < mtu)
 407                                         mtu -= ipsechdrsiz;
 408                         }
 409
 410                         /*
 411                          * if mtu becomes less than minimum MTU,
 412                          * tell minimum MTU (and I'll need to fragment it).
 413                          */
 414                         if (mtu < IPV6_MMTU)
 415                                 mtu = IPV6_MMTU;
 416 #endif
 417                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 418                 }
 419                 m_freem(m);
 420                 return;
 421         }
 422
 423         if (rt->rt_flags & RTF_GATEWAY)
 424                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 425
 426         /*
 427          * If we are to forward the packet using the same interface
 428          * as one we got the packet from, perhaps we should send a redirect
 429          * to sender to shortcut a hop.
 430          * Only send redirect if source is sending directly to us,
 431          * and if packet was not source routed (or has any options).
 432          * Also, don't send redirect if forwarding using a route
 433          * modified by a redirect.
 434          */
 435         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 436             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 437                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 438                         /*
 439                          * If the incoming interface is equal to the outgoing
 440                          * one, and the link attached to the interface is
 441                          * point-to-point, then it will be highly probable
 442                          * that a routing loop occurs. Thus, we immediately
 443                          * drop the packet and send an ICMPv6 error message.
 444                          *
 445                          * type/code is based on suggestion by Rich Draves.
 446                          * not sure if it is the best pick.
 447                          */
 448                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 449                                     ICMP6_DST_UNREACH_ADDR, 0);
 450                         m_freem(m);
 451                         return;
 452                 }
 453                 type = ND_REDIRECT;
 454         }
 455
 456         /*
 457          * Check with the firewall...
 458          */
 459         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 460                 u_short port = 0;
 461                 /* If ipfw says divert, we have to just drop packet */
 462                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 463                         m_freem(m);
 464                         goto freecopy;
 465                 }
 466                 if (!m)
 467                         goto freecopy;
 468         }
 469
 470         /*
 471          * Fake scoped addresses. Note that even link-local source or
 472          * destinaion can appear, if the originating node just sends the
 473          * packet to us (without address resolution for the destination).
 474          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 475          * link identifiers, we can do this stuff after making a copy for
 476          * returning an error.
 477          */
 478         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 479                 /*
 480                  * See corresponding comments in ip6_output.
 481                  * XXX: but is it possible that ip6_forward() sends a packet
 482                  *      to a loopback interface? I don't think so, and thus
 483                  *      I bark here. (jinmei@kame.net)
 484                  * XXX: it is common to route invalid packets to loopback.
 485                  *      also, the codepath will be visited on use of ::1 in
 486                  *      rthdr. (itojun)
 487                  */
 488 #if 1
 489                 if (0)
 490 #else
 491                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 492 #endif
 493                 {
 494                         printf("ip6_forward: outgoing interface is loopback. "
 495                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 496                                 ip6_sprintf(&ip6->ip6_src),
 497                                 ip6_sprintf(&ip6->ip6_dst),
 498                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 499                                 if_name(rt->rt_ifp));
 500                 }
 501
 502                 /* we can just use rcvif in forwarding. */
 503                 origifp = m->m_pkthdr.rcvif;
 504         }
 505         else
 506                 origifp = rt->rt_ifp;
 507 #ifndef SCOPEDROUTING
 508         /*
 509          * clear embedded scope identifiers if necessary.
 510          * in6_clearscope will touch the addresses only when necessary.
 511          */
 512         in6_clearscope(&ip6->ip6_src);
 513         in6_clearscope(&ip6->ip6_dst);
 514 #endif
 515
 516 #ifdef PFIL_HOOKS
 517         /*
 518          * Run through list of hooks for output packets.
 519          */
 520         m1 = m;
 521         pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh);
 522         for (; pfh; pfh = pfh->pfil_link.tqe_next)
 523                 if (pfh->pfil_func) {
 524                         rv = pfh->pfil_func(ip6, sizeof(*ip6),
 525                                             rt->rt_ifp, 1, &m1);
 526                         if (rv) {
 527                                 error = EHOSTUNREACH;
 528                                 goto freecopy;
 529                         }
 530                         m = m1;
 531                         if (m == NULL)
 532                                 goto freecopy;
 533                         ip6 = mtod(m, struct ip6_hdr *);
 534                 }
 535 #endif /* PFIL_HOOKS */
 536
 537         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 538         if (error) {
 539                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 540                 ip6stat.ip6s_cantforward++;
 541         } else {
 542                 ip6stat.ip6s_forward++;
 543                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 544                 if (type)
 545                         ip6stat.ip6s_redirectsent++;
 546                 else {
 547                         if (mcopy)
 548                                 goto freecopy;
 549                 }
 550         }
 551         if (mcopy == NULL)
 552                 return;
 553
 554         switch (error) {
 555         case 0:
 556 #if 1
 557                 if (type == ND_REDIRECT) {
 558                         icmp6_redirect_output(mcopy, rt);
 559                         return;
 560                 }
 561 #endif
 562                 goto freecopy;
 563
 564         case EMSGSIZE:
 565                 /* xxx MTU is constant in PPP? */
 566                 goto freecopy;
 567
 568         case ENOBUFS:
 569                 /* Tell source to slow down like source quench in IP? */
 570                 goto freecopy;
 571
 572         case ENETUNREACH:       /* shouldn't happen, checked above */
 573         case EHOSTUNREACH:
 574         case ENETDOWN:
 575         case EHOSTDOWN:
 576         default:
 577                 type = ICMP6_DST_UNREACH;
 578                 code = ICMP6_DST_UNREACH_ADDR;
 579                 break;
 580         }
 581         icmp6_error(mcopy, type, code, 0);
 582         return;
 583
 584  freecopy:
 585         m_freem(mcopy);
 586         return;
 587 }