bsd/netinet6/ip6_forward.c

   1 /*      $KAME: ip6_forward.c,v 1.29 2000/02/26 18:08:38 itojun Exp $    */
   2
   3 /*
   4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the project nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #if (defined(__FreeBSD__) && __FreeBSD__ >= 3)
  33 #include "opt_ip6fw.h"
  34 #include "opt_inet.h"
  35 #endif
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/malloc.h>
  40 #include <sys/mbuf.h>
  41 #include <sys/domain.h>
  42 #include <sys/protosw.h>
  43 #include <sys/socket.h>
  44 #include <sys/errno.h>
  45 #include <sys/time.h>
  46 #include <sys/kernel.h>
  47 #include <sys/syslog.h>
  48
  49 #include <net/if.h>
  50 #include <net/route.h>
  51
  52 #include <netinet/in.h>
  53 #include <netinet/in_var.h>
  54 #include <netinet/ip_var.h>
  55 #include <netinet/ip6.h>
  56 #include <netinet6/ip6_var.h>
  57 #include <netinet/icmp6.h>
  58 #include <netinet6/nd6.h>
  59
  60 #if IPSEC_IPV6FWD
  61 #include <netinet6/ipsec.h>
  62 #include <netkey/key.h>
  63 #include <netkey/key_debug.h>
  64 #endif /* IPSEC_IPV6FWD */
  65
  66 #if IPV6FIREWALL
  67 #include <netinet6/ip6_fw.h>
  68 #endif
  69
  70 #if MIP6
  71 #include <netinet6/mip6.h>
  72 #endif
  73
  74 #include <net/net_osdep.h>
  75
  76 struct  route_in6 ip6_forward_rt;
  77
  78 /*
  79  * Forward a packet.  If some error occurs return the sender
  80  * an icmp packet.  Note we can't always generate a meaningful
  81  * icmp message because icmp doesn't have a large enough repertoire
  82  * of codes and types.
  83  *
  84  * If not forwarding, just drop the packet.  This could be confusing
  85  * if ipforwarding was zero but some routing protocol was advancing
  86  * us as a gateway to somewhere.  However, we must let the routing
  87  * protocol deal with that.
  88  *
  89  */
  90
  91 void
  92 ip6_forward(m, srcrt)
  93         struct mbuf *m;
  94         int srcrt;
  95 {
  96         struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
  97         register struct sockaddr_in6 *dst;
  98         register struct rtentry *rt;
  99         int error, type = 0, code = 0;
 100         struct mbuf *mcopy = NULL;
 101 #if IPSEC_IPV6FWD
 102         struct secpolicy *sp = NULL;
 103 #endif
 104 #if !(defined(__FreeBSD__) && __FreeBSD__ >= 3) && !defined(__APPLE__)
 105         long time_second = time.tv_sec;
 106 #endif
 107
 108 #if IPSEC_IPV6FWD
 109         /*
 110          * Check AH/ESP integrity.
 111          */
 112         /*
 113          * Don't increment ip6s_cantforward because this is the check
 114          * before forwarding packet actually.
 115          */
 116         if (ipsec6_in_reject(m, NULL)) {
 117                 ipsec6stat.in_polvio++;
 118                 m_freem(m);
 119                 return;
 120         }
 121 #endif /*IPSEC_IPV6FWD*/
 122
 123         if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
 124             IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
 125                 ip6stat.ip6s_cantforward++;
 126                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 127                 if (ip6_log_time + ip6_log_interval < time_second) {
 128                         ip6_log_time = time_second;
 129                         log(LOG_DEBUG,
 130                             "cannot forward "
 131                             "from %s to %s nxt %d received on %s\n",
 132                             ip6_sprintf(&ip6->ip6_src),
 133                             ip6_sprintf(&ip6->ip6_dst),
 134                             ip6->ip6_nxt,
 135                             if_name(m->m_pkthdr.rcvif));
 136                 }
 137                 m_freem(m);
 138                 return;
 139         }
 140
 141         if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
 142                 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
 143                 icmp6_error(m, ICMP6_TIME_EXCEEDED,
 144                                 ICMP6_TIME_EXCEED_TRANSIT, 0);
 145                 return;
 146         }
 147         ip6->ip6_hlim -= IPV6_HLIMDEC;
 148
 149         /*
 150          * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
 151          * size of IPv6 + ICMPv6 headers) bytes of the packet in case
 152          * we need to generate an ICMP6 message to the src.
 153          * Thanks to M_EXT, in most cases copy will not occur.
 154          *
 155          * It is important to save it before IPsec processing as IPsec
 156          * processing may modify the mbuf.
 157          */
 158         mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
 159
 160
 161 #if IPSEC_IPV6FWD
 162         /* get a security policy for this packet */
 163         sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 0, &error);
 164         if (sp == NULL) {
 165                 ipsec6stat.out_inval++;
 166                 ip6stat.ip6s_cantforward++;
 167                 if (mcopy) {
 168 #if 0
 169                         /* XXX: what icmp ? */
 170 #else
 171                         m_freem(mcopy);
 172 #endif
 173                 }
 174                 m_freem(m);
 175                 return;
 176         }
 177
 178         error = 0;
 179
 180         /* check policy */
 181         switch (sp->policy) {
 182         case IPSEC_POLICY_DISCARD:
 183                 /*
 184                  * This packet is just discarded.
 185                  */
 186                 ipsec6stat.out_polvio++;
 187                 ip6stat.ip6s_cantforward++;
 188                 key_freesp(sp);
 189                 if (mcopy) {
 190 #if 0
 191                         /* XXX: what icmp ? */
 192 #else
 193                         m_freem(mcopy);
 194 #endif
 195                 }
 196                 m_freem(m);
 197                 return;
 198
 199         case IPSEC_POLICY_BYPASS:
 200         case IPSEC_POLICY_NONE:
 201                 /* no need to do IPsec. */
 202                 key_freesp(sp);
 203                 goto skip_ipsec;
 204
 205         case IPSEC_POLICY_IPSEC:
 206                 if (sp->req == NULL) {
 207                         /* XXX should be panic ? */
 208                         printf("ip6_forward: No IPsec request specified.\n");
 209                         ip6stat.ip6s_cantforward++;
 210                         key_freesp(sp);
 211                         if (mcopy) {
 212 #if 0
 213                                 /* XXX: what icmp ? */
 214 #else
 215                                 m_freem(mcopy);
 216 #endif
 217                         }
 218                         m_freem(m);
 219                         return;
 220                 }
 221                 /* do IPsec */
 222                 break;
 223
 224         case IPSEC_POLICY_ENTRUST:
 225         default:
 226                 /* should be panic ?? */
 227                 printf("ip6_forward: Invalid policy found. %d\n", sp->policy);
 228                 key_freesp(sp);
 229                 goto skip_ipsec;
 230         }
 231
 232     {
 233         struct ipsec_output_state state;
 234
 235         /*
 236          * All the extension headers will become inaccessible
 237          * (since they can be encrypted).
 238          * Don't panic, we need no more updates to extension headers
 239          * on inner IPv6 packet (since they are now encapsulated).
 240          *
 241          * IPv6 [ESP|AH] IPv6 [extension headers] payload
 242          */
 243         bzero(&state, sizeof(state));
 244         state.m = m;
 245         state.ro = NULL;        /* update at ipsec6_output_tunnel() */
 246         state.dst = NULL;       /* update at ipsec6_output_tunnel() */
 247
 248         error = ipsec6_output_tunnel(&state, sp, 0);
 249
 250         m = state.m;
 251 #if 0   /* XXX allocate a route (ro, dst) again later */
 252         ro = (struct route_in6 *)state.ro;
 253         dst = (struct sockaddr_in6 *)state.dst;
 254 #endif
 255         key_freesp(sp);
 256
 257         if (error) {
 258                 /* mbuf is already reclaimed in ipsec6_output_tunnel. */
 259                 switch (error) {
 260                 case EHOSTUNREACH:
 261                 case ENETUNREACH:
 262                 case EMSGSIZE:
 263                 case ENOBUFS:
 264                 case ENOMEM:
 265                         break;
 266                 default:
 267                         printf("ip6_output (ipsec): error code %d\n", error);
 268                         /*fall through*/
 269                 case ENOENT:
 270                         /* don't show these error codes to the user */
 271                         break;
 272                 }
 273                 ip6stat.ip6s_cantforward++;
 274                 if (mcopy) {
 275 #if 0
 276                         /* XXX: what icmp ? */
 277 #else
 278                         m_freem(mcopy);
 279 #endif
 280                 }
 281                 m_freem(m);
 282                 return;
 283         }
 284     }
 285     skip_ipsec:
 286 #endif /* IPSEC_IPV6FWD */
 287
 288 #if MIP6
 289         {
 290                 struct   mip6_bc   *bc;
 291
 292                 bc = mip6_bc_find(&ip6->ip6_dst);
 293                 if ((bc != NULL) && (bc->hr_flag)) {
 294                         if (mip6_tunnel_output(&m, bc) != 0) {
 295                                 ip6stat.ip6s_cantforward++;
 296                                 if (mcopy)
 297                                         m_freem(mcopy);
 298                                 m_freem(m);
 299                                 return;
 300                         }
 301                 }
 302                 ip6 = mtod(m, struct ip6_hdr *);        /* m has changed */
 303         }
 304 #endif
 305
 306         dst = &ip6_forward_rt.ro_dst;
 307         if (!srcrt) {
 308                 /*
 309                  * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
 310                  */
 311                 if (ip6_forward_rt.ro_rt == 0 ||
 312                     (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) {
 313                         if (ip6_forward_rt.ro_rt) {
 314                                 RTFREE(ip6_forward_rt.ro_rt);
 315                                 ip6_forward_rt.ro_rt = 0;
 316                         }
 317                         /* this probably fails but give it a try again */
 318 #if __FreeBSD__ || defined(__APPLE__)
 319                         rtalloc_ign((struct route *)&ip6_forward_rt,
 320                                     RTF_PRCLONING);
 321 #else
 322                         rtalloc((struct route *)&ip6_forward_rt);
 323 #endif
 324                 }
 325
 326                 if (ip6_forward_rt.ro_rt == 0) {
 327                         ip6stat.ip6s_noroute++;
 328                         /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
 329                         if (mcopy) {
 330                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 331                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 332                         }
 333                         m_freem(m);
 334                         return;
 335                 }
 336         } else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
 337                  !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
 338                 if (ip6_forward_rt.ro_rt) {
 339                         RTFREE(ip6_forward_rt.ro_rt);
 340                         ip6_forward_rt.ro_rt = 0;
 341                 }
 342                 bzero(dst, sizeof(*dst));
 343                 dst->sin6_len = sizeof(struct sockaddr_in6);
 344                 dst->sin6_family = AF_INET6;
 345                 dst->sin6_addr = ip6->ip6_dst;
 346
 347 #if __FreeBSD__ || defined(__APPLE__)
 348                 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING);
 349 #else
 350                 rtalloc((struct route *)&ip6_forward_rt);
 351 #endif
 352                 if (ip6_forward_rt.ro_rt == 0) {
 353                         ip6stat.ip6s_noroute++;
 354                         /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
 355                         if (mcopy) {
 356                                 icmp6_error(mcopy, ICMP6_DST_UNREACH,
 357                                             ICMP6_DST_UNREACH_NOROUTE, 0);
 358                         }
 359                         m_freem(m);
 360                         return;
 361                 }
 362         }
 363         rt = ip6_forward_rt.ro_rt;
 364
 365         /*
 366          * Scope check: if a packet can't be delivered to its destination
 367          * for the reason that the destination is beyond the scope of the
 368          * source address, discard the packet and return an icmp6 destination
 369          * unreachable error with Code 2 (beyond scope of source address).
 370          * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
 371          */
 372         if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
 373             in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
 374                 ip6stat.ip6s_cantforward++;
 375                 ip6stat.ip6s_badscope++;
 376                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
 377
 378                 if (ip6_log_time + ip6_log_interval < time_second) {
 379                         ip6_log_time = time_second;
 380                         log(LOG_DEBUG,
 381                             "cannot forward "
 382                             "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
 383                             ip6_sprintf(&ip6->ip6_src),
 384                             ip6_sprintf(&ip6->ip6_dst),
 385                             ip6->ip6_nxt,
 386                             if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp));
 387                 }
 388                 if (mcopy)
 389                         icmp6_error(mcopy, ICMP6_DST_UNREACH,
 390                                     ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
 391                 m_freem(m);
 392                 return;
 393         }
 394
 395         if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) {
 396                 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
 397                 if (mcopy) {
 398                         u_long mtu;
 399 #if IPSEC_IPV6FWD
 400                         struct secpolicy *sp;
 401                         int ipsecerror;
 402                         size_t ipsechdrsiz;
 403 #endif
 404
 405                         mtu = rt->rt_ifp->if_mtu;
 406 #if IPSEC_IPV6FWD
 407                         /*
 408                          * When we do IPsec tunnel ingress, we need to play
 409                          * with if_mtu value (decrement IPsec header size
 410                          * from mtu value).  The code is much simpler than v4
 411                          * case, as we have the outgoing interface for
 412                          * encapsulated packet as "rt->rt_ifp".
 413                          */
 414                         sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND,
 415                                 IP_FORWARDING, &ipsecerror);
 416                         if (sp) {
 417                                 ipsechdrsiz = ipsec6_hdrsiz(mcopy,
 418                                         IPSEC_DIR_OUTBOUND, NULL);
 419                                 if (ipsechdrsiz < mtu)
 420                                         mtu -= ipsechdrsiz;
 421                         }
 422
 423                         /*
 424                          * if mtu becomes less than minimum MTU,
 425                          * tell minimum MTU (and I'll need to fragment it).
 426                          */
 427                         if (mtu < IPV6_MMTU)
 428                                 mtu = IPV6_MMTU;
 429 #endif
 430                         icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
 431                 }
 432                 m_freem(m);
 433                 return;
 434         }
 435
 436         if (rt->rt_flags & RTF_GATEWAY)
 437                 dst = (struct sockaddr_in6 *)rt->rt_gateway;
 438
 439         /*
 440          * If we are to forward the packet using the same interface
 441          * as one we got the packet from, perhaps we should send a redirect
 442          * to sender to shortcut a hop.
 443          * Only send redirect if source is sending directly to us,
 444          * and if packet was not source routed (or has any options).
 445          * Also, don't send redirect if forwarding using a route
 446          * modified by a redirect.
 447          */
 448         if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt &&
 449             (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0)
 450                 type = ND_REDIRECT;
 451
 452 #if IPV6FIREWALL
 453         /*
 454          * Check with the firewall...
 455          */
 456         if (ip6_fw_chk_ptr) {
 457                 u_short port = 0;
 458                 /* If ipfw says divert, we have to just drop packet */
 459                 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) {
 460                         m_freem(m);
 461                         goto freecopy;
 462                 }
 463                 if (!m)
 464                         goto freecopy;
 465         }
 466 #endif
 467
 468 #if OLDIP6OUTPUT
 469         error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m,
 470                                          (struct sockaddr *)dst,
 471                                          ip6_forward_rt.ro_rt);
 472 #else
 473         error = nd6_output(rt->rt_ifp, m, dst, rt);
 474 #endif
 475         if (error) {
 476                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
 477                 ip6stat.ip6s_cantforward++;
 478         } else {
 479                 ip6stat.ip6s_forward++;
 480                 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
 481                 if (type)
 482                         ip6stat.ip6s_redirectsent++;
 483                 else {
 484                         if (mcopy)
 485                                 goto freecopy;
 486                 }
 487         }
 488         if (mcopy == NULL)
 489                 return;
 490
 491         switch (error) {
 492         case 0:
 493 #if 1
 494                 if (type == ND_REDIRECT) {
 495                         icmp6_redirect_output(mcopy, rt);
 496                         return;
 497                 }
 498 #endif
 499                 goto freecopy;
 500
 501         case EMSGSIZE:
 502                 /* xxx MTU is constant in PPP? */
 503                 goto freecopy;
 504
 505         case ENOBUFS:
 506                 /* Tell source to slow down like source quench in IP? */
 507                 goto freecopy;
 508
 509         case ENETUNREACH:       /* shouldn't happen, checked above */
 510         case EHOSTUNREACH:
 511         case ENETDOWN:
 512         case EHOSTDOWN:
 513         default:
 514                 type = ICMP6_DST_UNREACH;
 515                 code = ICMP6_DST_UNREACH_ADDR;
 516                 break;
 517         }
 518         icmp6_error(mcopy, type, code, 0);
 519         return;
 520
 521  freecopy:
 522         m_freem(mcopy);
 523         return;
 524 }