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 extern struct ip6protosw inet6sw[];
  84 extern u_char ip6_protox[IPPROTO_MAX];
  85
  86 struct  route_in6 ip6_forward_rt;
  87
  88 /*
  89  * Forward a packet.  If some error occurs return the sender
  90  * an icmp packet.  Note we can't always generate a meaningful
  91  * icmp message because icmp doesn't have a large enough repertoire
  92  * of codes and types.
  93  *
  94  * If not forwarding, just drop the packet.  This could be confusing
  95  * if ipforwarding was zero but some routing protocol was advancing
  96  * us as a gateway to somewhere.  However, we must let the routing
  97  * protocol deal with that.
  98  *
  99  */
 100
 101 void
 102 ip6_forward(m, srcrt)
 103         struct mbuf *m;
 104         int srcrt;
 105 {
 106         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
 107         struct sockaddr_in6 *dst;
 108         struct rtentry *rt;
 109         int error, type = 0, code = 0;
 110         struct mbuf *mcopy = NULL;
 111         struct ifnet *origifp;  /* maybe unnecessary */
 112 #ifdef PFIL_HOOKS
 113         struct packet_filter_hook *pfh;
 114         struct mbuf *m1;
 115         int rv;
 116 #endif /* PFIL_HOOKS */
 117 #ifdef IPSEC
 118         struct secpolicy *sp = NULL;
 119 #endif
 120
 121 #ifdef IPSEC
 122         /*
 123          * Check AH/ESP integrity.
 124          */
 125         /*
 126          * Don't increment ip6s_cantforward because this is the check
 127          * before forwarding packet actually.
 128          */
 129         if (ipsec6_in_reject(m, NULL)) {
 130                 ipsec6stat.in_polvio++;
 131                 m_freem(m);
 132                 return;
 133         }
 134 #endif /*IPSEC*/
 135
 136         /*
 137          * Do not forward packets to multicast destination (should be handled
 138          * by ip6_mforward().
 139          * Do not forward packets with unspecified source.  It was discussed
 140          * in July 2000, on ipngwg mailing list.
 141          */
 142         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 143             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
 144             IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 145                 ip6stat.ip6s_cantforward++;
 146                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 147                 if (ip6_log_time + ip6_log_interval < time_second) {
 148                         ip6_log_time = time_second;
 149                         log(LOG_DEBUG,
 150                             "cannot forward "
 151                             "from %s to %s nxt %d received on %s\n",
 152                             ip6_sprintf(&ip6->ip6_src),
 153                             ip6_sprintf(&ip6->ip6_dst),
 154                             ip6->ip6_nxt,
 155                             if_name(m->m_pkthdr.rcvif));
 156                 }
 157                 m_freem(m);
 158                 return;
 159         }
 160
 161         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 162                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 163                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 164                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 165                 return;
 166         }
 167         ip6->ip6_hlim -= IPV6_HLIMDEC;
 168
 169         /*
 170          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 171          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 172          * we need to generate an ICMP6 message to the src.
 173          * Thanks to M_EXT, in most cases copy will not occur.
 174          *
 175          * It is important to save it before IPsec processing as IPsec
 176          * processing may modify the mbuf.
 177          */
 178         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 179
 180 #ifdef IPSEC
 181         /* get a security policy for this packet */
 182         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING,
 183             &error);
 184         if (sp == NULL) {
 185                 ipsec6stat.out_inval++;
 186                 ip6stat.ip6s_cantforward++;
 187                 if (mcopy) {
 188 #if 0
 189                         /* XXX: what icmp ? */
 190 #else
 191                         m_freem(mcopy);
 192 #endif
 193                 }
 194                 m_freem(m);
 195                 return;
 196         }
 197
 198         error = 0;
 199
 200         /* check policy */
 201         switch (sp->policy) {
 202         case IPSEC_POLICY_DISCARD:
 203                 /*
 204                  * This packet is just discarded.
 205                  */
 206                 ipsec6stat.out_polvio++;
 207                 ip6stat.ip6s_cantforward++;
 208                 key_freesp(sp);
 209                 if (mcopy) {
 210 #if 0
 211                         /* XXX: what icmp ? */
 212 #else
 213                         m_freem(mcopy);
 214 #endif
 215                 }
 216                 m_freem(m);
 217                 return;
 218
 219         case IPSEC_POLICY_BYPASS:
 220         case IPSEC_POLICY_NONE:
 221                 /* no need to do IPsec. */
 222                 key_freesp(sp);
 223                 goto skip_ipsec;
 224
 225         case IPSEC_POLICY_IPSEC:
 226                 if (sp->req == NULL) {
 227                         /* XXX should be panic ? */
 228                         printf("ip6_forward: No IPsec request specified.\n");
 229                         ip6stat.ip6s_cantforward++;
 230                         key_freesp(sp);
 231                         if (mcopy) {
 232 #if 0
 233                                 /* XXX: what icmp ? */
 234 #else
 235                                 m_freem(mcopy);
 236 #endif
 237                         }
 238                         m_freem(m);
 239                         return;
 240                 }
 241                 /* do IPsec */
 242                 break;
 243
 244         case IPSEC_POLICY_ENTRUST:
 245         default:
 246                 /* should be panic ?? */
 247                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 248                 key_freesp(sp);
 249                 goto skip_ipsec;
 250         }
 251
 252     {
 253         struct ipsec_output_state state;
 254
 255         /*
 256          * All the extension headers will become inaccessible
 257          * (since they can be encrypted).
 258          * Don't panic, we need no more updates to extension headers
 259          * on inner IPv6 packet (since they are now encapsulated).
 260          *
 261          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 262          */
 263         bzero(&state, sizeof(state));
 264         state.m = m;
 265         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 266         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 267
 268         error = ipsec6_output_tunnel(&state, sp, 0);
 269
 270         m = state.m;
 271         key_freesp(sp);
 272
 273         if (error) {
 274                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 275                 switch (error) {
 276                 case EHOSTUNREACH:
 277                 case ENETUNREACH:
 278                 case EMSGSIZE:
 279                 case ENOBUFS:
 280                 case ENOMEM:
 281                         break;
 282                 default:
 283                         printf("ip6_output (ipsec): error code %d\n", error);
 284                         /*fall through*/
 285                 case ENOENT:
 286                         /* don't show these error codes to the user */
 287                         break;
 288                 }
 289                 ip6stat.ip6s_cantforward++;
 290                 if (mcopy) {
 291 #if 0
 292                         /* XXX: what icmp ? */
 293 #else
 294                         m_freem(mcopy);
 295 #endif
 296                 }
 297                 m_freem(m);
 298                 return;
 299         }
 300     }
 301     skip_ipsec:
 302 #endif /* IPSEC */
 303
 304         dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst;
 305         if (!srcrt) {
 306                 /*
 307                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 308                  */
 309                 if (ip6_forward_rt.ro_rt == 0 ||
 310                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 311                         if (ip6_forward_rt.ro_rt) {
 312                                 RTFREE(ip6_forward_rt.ro_rt);
 313                                 ip6_forward_rt.ro_rt = 0;
 314                         }
 315                         /* this probably fails but give it a try again */
 316                         rtalloc_ign((struct route *)&ip6_forward_rt,
 317                                     RTF_PRCLONING);
 318                 }
 319
 320                 if (ip6_forward_rt.ro_rt == 0) {
 321                         ip6stat.ip6s_noroute++;
 322                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 323                         if (mcopy) {
 324                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 325                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 326                         }
 327                         m_freem(m);
 328                         return;
 329                 }
 330         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 331                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 332                 if (ip6_forward_rt.ro_rt) {
 333                         RTFREE(ip6_forward_rt.ro_rt);
 334                         ip6_forward_rt.ro_rt = 0;
 335                 }
 336                 bzero(dst, sizeof(*dst));
 337                 dst->sin6_len = sizeof(struct sockaddr_in6);
 338                 dst->sin6_family = AF_INET6;
 339                 dst->sin6_addr = ip6->ip6_dst;
 340
 341                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 342                 if (ip6_forward_rt.ro_rt == 0) {
 343                         ip6stat.ip6s_noroute++;
 344                         in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute);
 345                         if (mcopy) {
 346                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 347                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 348                         }
 349                         m_freem(m);
 350                         return;
 351                 }
 352         }
 353         rt = ip6_forward_rt.ro_rt;
 354
 355         /*
 356          * Scope check: if a packet can't be delivered to its destination
 357          * for the reason that the destination is beyond the scope of the
 358          * source address, discard the packet and return an icmp6 destination
 359          * unreachable error with Code 2 (beyond scope of source address).
 360          * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
 361          */
 362         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 363             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 364                 ip6stat.ip6s_cantforward++;
 365                 ip6stat.ip6s_badscope++;
 366                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 367
 368                 if (ip6_log_time + ip6_log_interval < time_second) {
 369                         ip6_log_time = time_second;
 370                         log(LOG_DEBUG,
 371                             "cannot forward "
 372                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 373                             ip6_sprintf(&ip6->ip6_src),
 374                             ip6_sprintf(&ip6->ip6_dst),
 375                             ip6->ip6_nxt,
 376                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 377                 }
 378                 if (mcopy)
 379                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 380                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 381                 m_freem(m);
 382                 return;
 383         }
 384
 385         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 386                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 387                 if (mcopy) {
 388                         u_long mtu;
 389 #ifdef IPSEC
 390                         struct secpolicy *sp;
 391                         int ipsecerror;
 392                         size_t ipsechdrsiz;
 393 #endif
 394
 395                         mtu = rt->rt_ifp->if_mtu;
 396 #ifdef IPSEC
 397                         /*
 398                          * When we do IPsec tunnel ingress, we need to play
 399                          * with if_mtu value (decrement IPsec header size
 400                          * from mtu value).  The code is much simpler than v4
 401                          * case, as we have the outgoing interface for
 402                          * encapsulated packet as "rt->rt_ifp".
 403                          */
 404                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 405                                 IP_FORWARDING, &ipsecerror);
 406                         if (sp) {
 407                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 408                                         IPSEC_DIR_OUTBOUND, NULL);
 409                                 if (ipsechdrsiz < mtu)
 410                                         mtu -= ipsechdrsiz;
 411                         }
 412
 413                         /*
 414                          * if mtu becomes less than minimum MTU,
 415                          * tell minimum MTU (and I'll need to fragment it).
 416                          */
 417                         if (mtu < IPV6_MMTU)
 418                                 mtu = IPV6_MMTU;
 419 #endif
 420                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 421                 }
 422                 m_freem(m);
 423                 return;
 424         }
 425
 426         if (rt->rt_flags & RTF_GATEWAY)
 427                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 428
 429         /*
 430          * If we are to forward the packet using the same interface
 431          * as one we got the packet from, perhaps we should send a redirect
 432          * to sender to shortcut a hop.
 433          * Only send redirect if source is sending directly to us,
 434          * and if packet was not source routed (or has any options).
 435          * Also, don't send redirect if forwarding using a route
 436          * modified by a redirect.
 437          */
 438         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 439             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
 440                 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) {
 441                         /*
 442                          * If the incoming interface is equal to the outgoing
 443                          * one, and the link attached to the interface is
 444                          * point-to-point, then it will be highly probable
 445                          * that a routing loop occurs. Thus, we immediately
 446                          * drop the packet and send an ICMPv6 error message.
 447                          *
 448                          * type/code is based on suggestion by Rich Draves.
 449                          * not sure if it is the best pick.
 450                          */
 451                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 452                                     ICMP6_DST_UNREACH_ADDR, 0);
 453                         m_freem(m);
 454                         return;
 455                 }
 456                 type = ND_REDIRECT;
 457         }
 458
 459         /*
 460          * Check with the firewall...
 461          */
 462         if (ip6_fw_enable && ip6_fw_chk_ptr) {
 463                 u_short port = 0;
 464                 /* If ipfw says divert, we have to just drop packet */
 465                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 466                         m_freem(m);
 467                         goto freecopy;
 468                 }
 469                 if (!m)
 470                         goto freecopy;
 471         }
 472
 473         /*
 474          * Fake scoped addresses. Note that even link-local source or
 475          * destinaion can appear, if the originating node just sends the
 476          * packet to us (without address resolution for the destination).
 477          * Since both icmp6_error and icmp6_redirect_output fill the embedded
 478          * link identifiers, we can do this stuff after making a copy for
 479          * returning an error.
 480          */
 481         if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
 482                 /*
 483                  * See corresponding comments in ip6_output.
 484                  * XXX: but is it possible that ip6_forward() sends a packet
 485                  *      to a loopback interface? I don't think so, and thus
 486                  *      I bark here. (jinmei@kame.net)
 487                  * XXX: it is common to route invalid packets to loopback.
 488                  *      also, the codepath will be visited on use of ::1 in
 489                  *      rthdr. (itojun)
 490                  */
 491 #if 1
 492                 if (0)
 493 #else
 494                 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
 495 #endif
 496                 {
 497                         printf("ip6_forward: outgoing interface is loopback. "
 498                                 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 499                                 ip6_sprintf(&ip6->ip6_src),
 500                                 ip6_sprintf(&ip6->ip6_dst),
 501                                 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif),
 502                                 if_name(rt->rt_ifp));
 503                 }
 504
 505                 /* we can just use rcvif in forwarding. */
 506                 origifp = m->m_pkthdr.rcvif;
 507         }
 508         else
 509                 origifp = rt->rt_ifp;
 510 #ifndef SCOPEDROUTING
 511         /*
 512          * clear embedded scope identifiers if necessary.
 513          * in6_clearscope will touch the addresses only when necessary.
 514          */
 515         in6_clearscope(&ip6->ip6_src);
 516         in6_clearscope(&ip6->ip6_dst);
 517 #endif
 518
 519 #ifdef PFIL_HOOKS
 520         /*
 521          * Run through list of hooks for output packets.
 522          */
 523         m1 = m;
 524         pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh);
 525         for (; pfh; pfh = pfh->pfil_link.tqe_next)
 526                 if (pfh->pfil_func) {
 527                         rv = pfh->pfil_func(ip6, sizeof(*ip6),
 528                                             rt->rt_ifp, 1, &m1);
 529                         if (rv) {
 530                                 error = EHOSTUNREACH;
 531                                 goto freecopy;
 532                         }
 533                         m = m1;
 534                         if (m == NULL)
 535                                 goto freecopy;
 536                         ip6 = mtod(m, struct ip6_hdr *);
 537                 }
 538 #endif /* PFIL_HOOKS */
 539
 540         error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
 541         if (error) {
 542                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 543                 ip6stat.ip6s_cantforward++;
 544         } else {
 545                 ip6stat.ip6s_forward++;
 546                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 547                 if (type)
 548                         ip6stat.ip6s_redirectsent++;
 549                 else {
 550                         if (mcopy)
 551                                 goto freecopy;
 552                 }
 553         }
 554         if (mcopy == NULL)
 555                 return;
 556
 557         switch (error) {
 558         case 0:
 559 #if 1
 560                 if (type == ND_REDIRECT) {
 561                         icmp6_redirect_output(mcopy, rt);
 562                         return;
 563                 }
 564 #endif
 565                 goto freecopy;
 566
 567         case EMSGSIZE:
 568                 /* xxx MTU is constant in PPP? */
 569                 goto freecopy;
 570
 571         case ENOBUFS:
 572                 /* Tell source to slow down like source quench in IP? */
 573                 goto freecopy;
 574
 575         case ENETUNREACH:       /* shouldn't happen, checked above */
 576         case EHOSTUNREACH:
 577         case ENETDOWN:
 578         case EHOSTDOWN:
 579         default:
 580                 type = ICMP6_DST_UNREACH;
 581                 code = ICMP6_DST_UNREACH_ADDR;
 582                 break;
 583         }
 584         icmp6_error(mcopy, type, code, 0);
 585         return;
 586
 587  freecopy:
 588         m_freem(mcopy);
 589         return;
 590 }