1 /* $OpenBSD: ip6_forward.c,v 1.20 2001/12/07 09:16:07 itojun Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei 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 "pf.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/malloc.h> 38 #include <sys/mbuf.h> 39 #include <sys/domain.h> 40 #include <sys/protosw.h> 41 #include <sys/socket.h> 42 #include <sys/errno.h> 43 #include <sys/time.h> 44 #include <sys/kernel.h> 45 #include <sys/syslog.h> 46 47 #include <net/if.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_var.h> 52 #include <netinet/ip_var.h> 53 #include <netinet/ip6.h> 54 #include <netinet6/ip6_var.h> 55 #include <netinet/icmp6.h> 56 #include <netinet6/nd6.h> 57 58 #if NPF > 0 59 #include <net/pfvar.h> 60 #endif 61 62 #ifdef IPSEC_IPV6FWD 63 #include <netinet6/ipsec.h> 64 #include <netkey/key.h> 65 #include <netkey/key_debug.h> 66 #endif /* IPSEC_IPV6FWD */ 67 68 struct route_in6 ip6_forward_rt; 69 70 /* 71 * Forward a packet. If some error occurs return the sender 72 * an icmp packet. Note we can't always generate a meaningful 73 * icmp message because icmp doesn't have a large enough repertoire 74 * of codes and types. 75 * 76 * If not forwarding, just drop the packet. This could be confusing 77 * if ipforwarding was zero but some routing protocol was advancing 78 * us as a gateway to somewhere. However, we must let the routing 79 * protocol deal with that. 80 * 81 */ 82 83 void 84 ip6_forward(m, srcrt) 85 struct mbuf *m; 86 int srcrt; 87 { 88 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 89 struct sockaddr_in6 *dst; 90 struct rtentry *rt; 91 int error, type = 0, code = 0; 92 struct mbuf *mcopy = NULL; 93 long time_second = time.tv_sec; 94 struct ifnet *origifp; /* maybe unnecessary */ 95 96 #ifdef IPSEC_IPV6FWD 97 struct secpolicy *sp = NULL; 98 #endif 99 100 #ifdef IPSEC_IPV6FWD 101 /* 102 * Check AH/ESP integrity. 103 */ 104 /* 105 * Don't increment ip6s_cantforward because this is the check 106 * before forwarding packet actually. 107 */ 108 if (ipsec6_in_reject(m, NULL)) { 109 ipsec6stat.in_polvio++; 110 m_freem(m); 111 return; 112 } 113 #endif /*IPSEC_IPV6FWD*/ 114 115 /* 116 * Do not forward packets to multicast destination (should be handled 117 * by ip6_mforward(). 118 * Do not forward packets with unspecified source. It was discussed 119 * in July 2000, on ipngwg mailing list. 120 */ 121 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 122 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 123 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 124 ip6stat.ip6s_cantforward++; 125 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 126 if (ip6_log_time + ip6_log_interval < time_second) { 127 ip6_log_time = time_second; 128 log(LOG_DEBUG, 129 "cannot forward " 130 "from %s to %s nxt %d received on %s\n", 131 ip6_sprintf(&ip6->ip6_src), 132 ip6_sprintf(&ip6->ip6_dst), 133 ip6->ip6_nxt, 134 m->m_pkthdr.rcvif->if_xname); 135 } 136 m_freem(m); 137 return; 138 } 139 140 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 141 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 142 icmp6_error(m, ICMP6_TIME_EXCEEDED, 143 ICMP6_TIME_EXCEED_TRANSIT, 0); 144 return; 145 } 146 ip6->ip6_hlim -= IPV6_HLIMDEC; 147 148 /* 149 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 150 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 151 * we need to generate an ICMP6 message to the src. 152 * Thanks to M_EXT, in most cases copy will not occur. 153 * 154 * It is important to save it before IPsec processing as IPsec 155 * processing may modify the mbuf. 156 */ 157 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 158 159 #ifdef IPSEC_IPV6FWD 160 /* get a security policy for this packet */ 161 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 0, &error); 162 if (sp == NULL) { 163 ipsec6stat.out_inval++; 164 ip6stat.ip6s_cantforward++; 165 if (mcopy) { 166 #if 0 167 /* XXX: what icmp ? */ 168 #else 169 m_freem(mcopy); 170 #endif 171 } 172 m_freem(m); 173 return; 174 } 175 176 error = 0; 177 178 /* check policy */ 179 switch (sp->policy) { 180 case IPSEC_POLICY_DISCARD: 181 /* 182 * This packet is just discarded. 183 */ 184 ipsec6stat.out_polvio++; 185 ip6stat.ip6s_cantforward++; 186 key_freesp(sp); 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 case IPSEC_POLICY_BYPASS: 198 case IPSEC_POLICY_NONE: 199 /* no need to do IPsec. */ 200 key_freesp(sp); 201 goto skip_ipsec; 202 203 case IPSEC_POLICY_IPSEC: 204 if (sp->req == NULL) { 205 /* XXX should be panic ? */ 206 printf("ip6_forward: No IPsec request specified.\n"); 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 /* do IPsec */ 220 break; 221 222 case IPSEC_POLICY_ENTRUST: 223 default: 224 /* should be panic ?? */ 225 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 226 key_freesp(sp); 227 goto skip_ipsec; 228 } 229 230 { 231 struct ipsec_output_state state; 232 233 /* 234 * All the extension headers will become inaccessible 235 * (since they can be encrypted). 236 * Don't panic, we need no more updates to extension headers 237 * on inner IPv6 packet (since they are now encapsulated). 238 * 239 * IPv6 [ESP|AH] IPv6 [extension headers] payload 240 */ 241 bzero(&state, sizeof(state)); 242 state.m = m; 243 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 244 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 245 246 error = ipsec6_output_tunnel(&state, sp, 0); 247 248 m = state.m; 249 #if 0 /* XXX allocate a route (ro, dst) again later */ 250 ro = (struct route_in6 *)state.ro; 251 dst = (struct sockaddr_in6 *)state.dst; 252 #endif 253 key_freesp(sp); 254 255 if (error) { 256 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 257 switch (error) { 258 case EHOSTUNREACH: 259 case ENETUNREACH: 260 case EMSGSIZE: 261 case ENOBUFS: 262 case ENOMEM: 263 break; 264 default: 265 printf("ip6_output (ipsec): error code %d\n", error); 266 /* fall through */ 267 case ENOENT: 268 /* don't show these error codes to the user */ 269 break; 270 } 271 ip6stat.ip6s_cantforward++; 272 if (mcopy) { 273 #if 0 274 /* XXX: what icmp ? */ 275 #else 276 m_freem(mcopy); 277 #endif 278 } 279 m_freem(m); 280 return; 281 } 282 } 283 skip_ipsec: 284 #endif /* IPSEC_IPV6FWD */ 285 286 dst = &ip6_forward_rt.ro_dst; 287 if (!srcrt) { 288 /* 289 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 290 */ 291 if (ip6_forward_rt.ro_rt == 0 || 292 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 293 if (ip6_forward_rt.ro_rt) { 294 RTFREE(ip6_forward_rt.ro_rt); 295 ip6_forward_rt.ro_rt = 0; 296 } 297 /* this probably fails but give it a try again */ 298 rtalloc((struct route *)&ip6_forward_rt); 299 } 300 301 if (ip6_forward_rt.ro_rt == 0) { 302 ip6stat.ip6s_noroute++; 303 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 304 if (mcopy) { 305 icmp6_error(mcopy, ICMP6_DST_UNREACH, 306 ICMP6_DST_UNREACH_NOROUTE, 0); 307 } 308 m_freem(m); 309 return; 310 } 311 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 312 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 313 if (ip6_forward_rt.ro_rt) { 314 RTFREE(ip6_forward_rt.ro_rt); 315 ip6_forward_rt.ro_rt = 0; 316 } 317 bzero(dst, sizeof(*dst)); 318 dst->sin6_len = sizeof(struct sockaddr_in6); 319 dst->sin6_family = AF_INET6; 320 dst->sin6_addr = ip6->ip6_dst; 321 322 rtalloc((struct route *)&ip6_forward_rt); 323 324 if (ip6_forward_rt.ro_rt == 0) { 325 ip6stat.ip6s_noroute++; 326 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 327 if (mcopy) { 328 icmp6_error(mcopy, ICMP6_DST_UNREACH, 329 ICMP6_DST_UNREACH_NOROUTE, 0); 330 } 331 m_freem(m); 332 return; 333 } 334 } 335 rt = ip6_forward_rt.ro_rt; 336 337 /* 338 * Scope check: if a packet can't be delivered to its destination 339 * for the reason that the destination is beyond the scope of the 340 * source address, discard the packet and return an icmp6 destination 341 * unreachable error with Code 2 (beyond scope of source address). 342 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 343 */ 344 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 345 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 346 ip6stat.ip6s_cantforward++; 347 ip6stat.ip6s_badscope++; 348 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 349 350 if (ip6_log_time + ip6_log_interval < time_second) { 351 ip6_log_time = time_second; 352 log(LOG_DEBUG, 353 "cannot forward " 354 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 355 ip6_sprintf(&ip6->ip6_src), 356 ip6_sprintf(&ip6->ip6_dst), 357 ip6->ip6_nxt, 358 m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname); 359 } 360 if (mcopy) 361 icmp6_error(mcopy, ICMP6_DST_UNREACH, 362 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 363 m_freem(m); 364 return; 365 } 366 367 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 368 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 369 if (mcopy) { 370 u_long mtu; 371 #ifdef IPSEC_IPV6FWD 372 struct secpolicy *sp; 373 int ipsecerror; 374 size_t ipsechdrsiz; 375 #endif 376 377 mtu = rt->rt_ifp->if_mtu; 378 #ifdef IPSEC_IPV6FWD 379 /* 380 * When we do IPsec tunnel ingress, we need to play 381 * with if_mtu value (decrement IPsec header size 382 * from mtu value). The code is much simpler than v4 383 * case, as we have the outgoing interface for 384 * encapsulated packet as "rt->rt_ifp". 385 */ 386 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 387 IP_FORWARDING, &ipsecerror); 388 if (sp) { 389 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 390 IPSEC_DIR_OUTBOUND, NULL); 391 if (ipsechdrsiz < mtu) 392 mtu -= ipsechdrsiz; 393 } 394 395 /* 396 * if mtu becomes less than minimum MTU, 397 * tell minimum MTU (and I'll need to fragment it). 398 */ 399 if (mtu < IPV6_MMTU) 400 mtu = IPV6_MMTU; 401 #endif 402 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 403 } 404 m_freem(m); 405 return; 406 } 407 408 if (rt->rt_flags & RTF_GATEWAY) 409 dst = (struct sockaddr_in6 *)rt->rt_gateway; 410 411 /* 412 * If we are to forward the packet using the same interface 413 * as one we got the packet from, perhaps we should send a redirect 414 * to sender to shortcut a hop. 415 * Only send redirect if source is sending directly to us, 416 * and if packet was not source routed (or has any options). 417 * Also, don't send redirect if forwarding using a route 418 * modified by a redirect. 419 */ 420 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 421 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 422 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 423 nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) { 424 /* 425 * If the incoming interface is equal to the outgoing 426 * one, the link attached to the interface is 427 * point-to-point, and the IPv6 destination is 428 * regarded as on-link on the link, then it will be 429 * highly probable that the destination address does 430 * not exist on the link and that the packet is going 431 * to loop. Thus, we immediately drop the packet and 432 * send an ICMPv6 error message. 433 * For other routing loops, we dare to let the packet 434 * go to the loop, so that a remote diagnosing host 435 * can detect the loop by traceroute. 436 * type/code is based on suggestion by Rich Draves. 437 * not sure if it is the best pick. 438 */ 439 icmp6_error(mcopy, ICMP6_DST_UNREACH, 440 ICMP6_DST_UNREACH_ADDR, 0); 441 m_freem(m); 442 return; 443 } 444 type = ND_REDIRECT; 445 } 446 447 /* 448 * Fake scoped addresses. Note that even link-local source or 449 * destinaion can appear, if the originating node just sends the 450 * packet to us (without address resolution for the destination). 451 * Since both icmp6_error and icmp6_redirect_output fill the embedded 452 * link identifiers, we can do this stuff after making a copy for 453 * returning an error. 454 */ 455 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 456 /* 457 * See corresponding comments in ip6_output. 458 * XXX: but is it possible that ip6_forward() sends a packet 459 * to a loopback interface? I don't think so, and thus 460 * I bark here. (jinmei@kame.net) 461 * XXX: it is common to route invalid packets to loopback. 462 * also, the codepath will be visited on use of ::1 in 463 * rthdr. (itojun) 464 */ 465 #if 1 466 if (0) 467 #else 468 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 469 #endif 470 { 471 printf("ip6_forward: outgoing interface is loopback. " 472 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 473 ip6_sprintf(&ip6->ip6_src), 474 ip6_sprintf(&ip6->ip6_dst), 475 ip6->ip6_nxt, m->m_pkthdr.rcvif->if_xname, 476 rt->rt_ifp->if_xname); 477 } 478 479 /* we can just use rcvif in forwarding. */ 480 origifp = m->m_pkthdr.rcvif; 481 } 482 else 483 origifp = rt->rt_ifp; 484 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 485 ip6->ip6_src.s6_addr16[1] = 0; 486 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 487 ip6->ip6_dst.s6_addr16[1] = 0; 488 489 #if NPF > 0 490 if (pf_test6(PF_OUT, rt->rt_ifp, &m) != PF_PASS) { 491 m_freem(m); 492 goto senderr; 493 } 494 if (m == NULL) 495 goto senderr; 496 497 ip6 = mtod(m, struct ip6_hdr *); 498 #endif 499 500 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 501 if (error) { 502 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 503 ip6stat.ip6s_cantforward++; 504 } else { 505 ip6stat.ip6s_forward++; 506 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 507 if (type) 508 ip6stat.ip6s_redirectsent++; 509 else { 510 if (mcopy) 511 goto freecopy; 512 } 513 } 514 515 #if NPF > 0 516 senderr: 517 #endif 518 if (mcopy == NULL) 519 return; 520 switch (error) { 521 case 0: 522 #if 1 523 if (type == ND_REDIRECT) { 524 icmp6_redirect_output(mcopy, rt); 525 return; 526 } 527 #endif 528 goto freecopy; 529 530 case EMSGSIZE: 531 /* xxx MTU is constant in PPP? */ 532 goto freecopy; 533 534 case ENOBUFS: 535 /* Tell source to slow down like source quench in IP? */ 536 goto freecopy; 537 538 case ENETUNREACH: /* shouldn't happen, checked above */ 539 case EHOSTUNREACH: 540 case ENETDOWN: 541 case EHOSTDOWN: 542 default: 543 type = ICMP6_DST_UNREACH; 544 code = ICMP6_DST_UNREACH_ADDR; 545 break; 546 } 547 icmp6_error(mcopy, type, code, 0); 548 return; 549 550 freecopy: 551 m_freem(mcopy); 552 return; 553 } 554