1 /* $OpenBSD: ip6_forward.c,v 1.40 2008/06/11 19:00:50 mcbride 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 63 #include <netinet/ip_ipsp.h> 64 #include <netinet/ip_ah.h> 65 #include <netinet/ip_esp.h> 66 #include <netinet/udp.h> 67 #include <netinet/tcp.h> 68 #include <net/pfkeyv2.h> 69 #endif 70 71 struct route_in6 ip6_forward_rt; 72 int ip6_forward_rtableid; 73 74 /* 75 * Forward a packet. If some error occurs return the sender 76 * an icmp packet. Note we can't always generate a meaningful 77 * icmp message because icmp doesn't have a large enough repertoire 78 * of codes and types. 79 * 80 * If not forwarding, just drop the packet. This could be confusing 81 * if ipforwarding was zero but some routing protocol was advancing 82 * us as a gateway to somewhere. However, we must let the routing 83 * protocol deal with that. 84 * 85 */ 86 87 void 88 ip6_forward(struct mbuf *m, int srcrt) 89 { 90 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 91 struct sockaddr_in6 *dst; 92 struct rtentry *rt; 93 int error = 0, type = 0, code = 0; 94 struct mbuf *mcopy = NULL; 95 struct ifnet *origifp; /* maybe unnecessary */ 96 #ifdef IPSEC 97 u_int8_t sproto = 0; 98 struct m_tag *mtag; 99 union sockaddr_union sdst; 100 struct tdb_ident *tdbi; 101 u_int32_t sspi; 102 struct tdb *tdb; 103 int s; 104 #endif /* IPSEC */ 105 int rtableid = 0; 106 107 /* 108 * Do not forward packets to multicast destination (should be handled 109 * by ip6_mforward(). 110 * Do not forward packets with unspecified source. It was discussed 111 * in July 2000, on ipngwg mailing list. 112 */ 113 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 114 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 115 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 116 ip6stat.ip6s_cantforward++; 117 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 118 if (ip6_log_time + ip6_log_interval < time_second) { 119 ip6_log_time = time_second; 120 log(LOG_DEBUG, 121 "cannot forward " 122 "from %s to %s nxt %d received on %s\n", 123 ip6_sprintf(&ip6->ip6_src), 124 ip6_sprintf(&ip6->ip6_dst), 125 ip6->ip6_nxt, 126 m->m_pkthdr.rcvif->if_xname); 127 } 128 m_freem(m); 129 return; 130 } 131 132 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 133 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 134 icmp6_error(m, ICMP6_TIME_EXCEEDED, 135 ICMP6_TIME_EXCEED_TRANSIT, 0); 136 return; 137 } 138 ip6->ip6_hlim -= IPV6_HLIMDEC; 139 140 #ifdef IPSEC 141 if (!ipsec_in_use) 142 goto done_spd; 143 144 s = splnet(); 145 146 /* 147 * Check if there was an outgoing SA bound to the flow 148 * from a transport protocol. 149 */ 150 151 /* Do we have any pending SAs to apply ? */ 152 mtag = m_tag_find(m, PACKET_TAG_IPSEC_PENDING_TDB, NULL); 153 if (mtag != NULL) { 154 #ifdef DIAGNOSTIC 155 if (mtag->m_tag_len != sizeof (struct tdb_ident)) 156 panic("ip6_forward: tag of length %d (should be %d", 157 mtag->m_tag_len, sizeof (struct tdb_ident)); 158 #endif 159 tdbi = (struct tdb_ident *)(mtag + 1); 160 tdb = gettdb(tdbi->spi, &tdbi->dst, tdbi->proto); 161 if (tdb == NULL) 162 error = -EINVAL; 163 m_tag_delete(m, mtag); 164 } else 165 tdb = ipsp_spd_lookup(m, AF_INET6, sizeof(struct ip6_hdr), 166 &error, IPSP_DIRECTION_OUT, NULL, NULL); 167 168 if (tdb == NULL) { 169 splx(s); 170 171 if (error == 0) { 172 /* 173 * No IPsec processing required, we'll just send the 174 * packet out. 175 */ 176 sproto = 0; 177 178 /* Fall through to routing/multicast handling */ 179 } else { 180 /* 181 * -EINVAL is used to indicate that the packet should 182 * be silently dropped, typically because we've asked 183 * key management for an SA. 184 */ 185 if (error == -EINVAL) /* Should silently drop packet */ 186 error = 0; 187 188 goto freecopy; 189 } 190 } else { 191 /* Loop detection */ 192 for (mtag = m_tag_first(m); mtag != NULL; 193 mtag = m_tag_next(m, mtag)) { 194 if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE && 195 mtag->m_tag_id != 196 PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED) 197 continue; 198 tdbi = (struct tdb_ident *)(mtag + 1); 199 if (tdbi->spi == tdb->tdb_spi && 200 tdbi->proto == tdb->tdb_sproto && 201 !bcmp(&tdbi->dst, &tdb->tdb_dst, 202 sizeof(union sockaddr_union))) { 203 splx(s); 204 sproto = 0; /* mark as no-IPsec-needed */ 205 goto done_spd; 206 } 207 } 208 209 /* We need to do IPsec */ 210 bcopy(&tdb->tdb_dst, &sdst, sizeof(sdst)); 211 sspi = tdb->tdb_spi; 212 sproto = tdb->tdb_sproto; 213 splx(s); 214 } 215 216 /* Fall through to the routing/multicast handling code */ 217 done_spd: 218 #endif /* IPSEC */ 219 220 #if NPF > 0 221 rtableid = m->m_pkthdr.pf.rtableid; 222 #endif 223 224 /* 225 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 226 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 227 * we need to generate an ICMP6 message to the src. 228 * Thanks to M_EXT, in most cases copy will not occur. 229 * 230 * It is important to save it before IPsec processing as IPsec 231 * processing may modify the mbuf. 232 */ 233 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 234 235 dst = &ip6_forward_rt.ro_dst; 236 if (!srcrt) { 237 /* 238 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 239 */ 240 if (ip6_forward_rt.ro_rt == 0 || 241 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0 || 242 ip6_forward_rtableid != rtableid) { 243 if (ip6_forward_rt.ro_rt) { 244 RTFREE(ip6_forward_rt.ro_rt); 245 ip6_forward_rt.ro_rt = 0; 246 } 247 /* this probably fails but give it a try again */ 248 rtalloc_mpath((struct route *)&ip6_forward_rt, 249 &ip6->ip6_src.s6_addr32[0], rtableid); 250 ip6_forward_rtableid = rtableid; 251 } 252 253 if (ip6_forward_rt.ro_rt == 0) { 254 ip6stat.ip6s_noroute++; 255 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 256 if (mcopy) { 257 icmp6_error(mcopy, ICMP6_DST_UNREACH, 258 ICMP6_DST_UNREACH_NOROUTE, 0); 259 } 260 m_freem(m); 261 return; 262 } 263 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 264 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 265 if (ip6_forward_rt.ro_rt) { 266 RTFREE(ip6_forward_rt.ro_rt); 267 ip6_forward_rt.ro_rt = 0; 268 } 269 bzero(dst, sizeof(*dst)); 270 dst->sin6_len = sizeof(struct sockaddr_in6); 271 dst->sin6_family = AF_INET6; 272 dst->sin6_addr = ip6->ip6_dst; 273 274 rtalloc_mpath((struct route *)&ip6_forward_rt, 275 &ip6->ip6_src.s6_addr32[0], 0); 276 277 if (ip6_forward_rt.ro_rt == 0) { 278 ip6stat.ip6s_noroute++; 279 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 280 if (mcopy) { 281 icmp6_error(mcopy, ICMP6_DST_UNREACH, 282 ICMP6_DST_UNREACH_NOROUTE, 0); 283 } 284 m_freem(m); 285 return; 286 } 287 } 288 rt = ip6_forward_rt.ro_rt; 289 290 /* 291 * Scope check: if a packet can't be delivered to its destination 292 * for the reason that the destination is beyond the scope of the 293 * source address, discard the packet and return an icmp6 destination 294 * unreachable error with Code 2 (beyond scope of source address). 295 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 296 */ 297 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 298 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 299 ip6stat.ip6s_cantforward++; 300 ip6stat.ip6s_badscope++; 301 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 302 303 if (ip6_log_time + ip6_log_interval < time_second) { 304 ip6_log_time = time_second; 305 log(LOG_DEBUG, 306 "cannot forward " 307 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 308 ip6_sprintf(&ip6->ip6_src), 309 ip6_sprintf(&ip6->ip6_dst), 310 ip6->ip6_nxt, 311 m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname); 312 } 313 if (mcopy) 314 icmp6_error(mcopy, ICMP6_DST_UNREACH, 315 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 316 m_freem(m); 317 goto freert; 318 } 319 320 #ifdef IPSEC 321 /* 322 * Check if the packet needs encapsulation. 323 * ipsp_process_packet will never come back to here. 324 * XXX ipsp_process_packet() calls ip6_output(), and there'll be no 325 * PMTU notification. is it okay? 326 */ 327 if (sproto != 0) { 328 s = splnet(); 329 330 tdb = gettdb(sspi, &sdst, sproto); 331 if (tdb == NULL) { 332 splx(s); 333 error = EHOSTUNREACH; 334 m_freem(m); 335 goto senderr; /*XXX*/ 336 } 337 338 m->m_flags &= ~(M_BCAST | M_MCAST); /* just in case */ 339 340 /* Callee frees mbuf */ 341 error = ipsp_process_packet(m, tdb, AF_INET6, 0); 342 splx(s); 343 m_freem(mcopy); 344 goto freert; 345 } 346 #endif /* IPSEC */ 347 348 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 349 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 350 if (mcopy) { 351 u_long mtu; 352 353 mtu = IN6_LINKMTU(rt->rt_ifp); 354 355 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 356 } 357 m_freem(m); 358 goto freert; 359 } 360 361 if (rt->rt_flags & RTF_GATEWAY) 362 dst = (struct sockaddr_in6 *)rt->rt_gateway; 363 364 /* 365 * If we are to forward the packet using the same interface 366 * as one we got the packet from, perhaps we should send a redirect 367 * to sender to shortcut a hop. 368 * Only send redirect if source is sending directly to us, 369 * and if packet was not source routed (or has any options). 370 * Also, don't send redirect if forwarding using a route 371 * modified by a redirect. 372 */ 373 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects && 374 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 375 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 376 nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) { 377 /* 378 * If the incoming interface is equal to the outgoing 379 * one, the link attached to the interface is 380 * point-to-point, and the IPv6 destination is 381 * regarded as on-link on the link, then it will be 382 * highly probable that the destination address does 383 * not exist on the link and that the packet is going 384 * to loop. Thus, we immediately drop the packet and 385 * send an ICMPv6 error message. 386 * For other routing loops, we dare to let the packet 387 * go to the loop, so that a remote diagnosing host 388 * can detect the loop by traceroute. 389 * type/code is based on suggestion by Rich Draves. 390 * not sure if it is the best pick. 391 */ 392 icmp6_error(mcopy, ICMP6_DST_UNREACH, 393 ICMP6_DST_UNREACH_ADDR, 0); 394 m_freem(m); 395 goto freert; 396 } 397 type = ND_REDIRECT; 398 } 399 400 /* 401 * Fake scoped addresses. Note that even link-local source or 402 * destinaion can appear, if the originating node just sends the 403 * packet to us (without address resolution for the destination). 404 * Since both icmp6_error and icmp6_redirect_output fill the embedded 405 * link identifiers, we can do this stuff after making a copy for 406 * returning an error. 407 */ 408 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 409 /* 410 * See corresponding comments in ip6_output. 411 * XXX: but is it possible that ip6_forward() sends a packet 412 * to a loopback interface? I don't think so, and thus 413 * I bark here. (jinmei@kame.net) 414 * XXX: it is common to route invalid packets to loopback. 415 * also, the codepath will be visited on use of ::1 in 416 * rthdr. (itojun) 417 */ 418 #if 1 419 if (0) 420 #else 421 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 422 #endif 423 { 424 printf("ip6_forward: outgoing interface is loopback. " 425 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 426 ip6_sprintf(&ip6->ip6_src), 427 ip6_sprintf(&ip6->ip6_dst), 428 ip6->ip6_nxt, m->m_pkthdr.rcvif->if_xname, 429 rt->rt_ifp->if_xname); 430 } 431 432 /* we can just use rcvif in forwarding. */ 433 origifp = m->m_pkthdr.rcvif; 434 } 435 else 436 origifp = rt->rt_ifp; 437 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) 438 ip6->ip6_src.s6_addr16[1] = 0; 439 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) 440 ip6->ip6_dst.s6_addr16[1] = 0; 441 442 #if NPF > 0 443 if (pf_test6(PF_OUT, rt->rt_ifp, &m, NULL) != PF_PASS) { 444 m_freem(m); 445 goto senderr; 446 } 447 if (m == NULL) 448 goto senderr; 449 450 ip6 = mtod(m, struct ip6_hdr *); 451 #endif 452 453 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 454 if (error) { 455 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 456 ip6stat.ip6s_cantforward++; 457 } else { 458 ip6stat.ip6s_forward++; 459 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 460 if (type) 461 ip6stat.ip6s_redirectsent++; 462 else { 463 if (mcopy) 464 goto freecopy; 465 } 466 } 467 468 #if NPF > 0 || defined(IPSEC) 469 senderr: 470 #endif 471 if (mcopy == NULL) 472 goto freert; 473 switch (error) { 474 case 0: 475 if (type == ND_REDIRECT) { 476 icmp6_redirect_output(mcopy, rt); 477 goto freert; 478 } 479 goto freecopy; 480 481 case EMSGSIZE: 482 /* xxx MTU is constant in PPP? */ 483 goto freecopy; 484 485 case ENOBUFS: 486 /* Tell source to slow down like source quench in IP? */ 487 goto freecopy; 488 489 case ENETUNREACH: /* shouldn't happen, checked above */ 490 case EHOSTUNREACH: 491 case ENETDOWN: 492 case EHOSTDOWN: 493 default: 494 type = ICMP6_DST_UNREACH; 495 code = ICMP6_DST_UNREACH_ADDR; 496 break; 497 } 498 icmp6_error(mcopy, type, code, 0); 499 goto freert; 500 501 freecopy: 502 m_freem(mcopy); 503 freert: 504 #ifndef SMALL_KERNEL 505 if (ip6_multipath && ip6_forward_rt.ro_rt && 506 (ip6_forward_rt.ro_rt->rt_flags & RTF_MPATH)) { 507 RTFREE(ip6_forward_rt.ro_rt); 508 ip6_forward_rt.ro_rt = 0; 509 } 510 #endif 511 return; 512 } 513