1 /* $FreeBSD: src/sys/netinet6/ip6_forward.c,v 1.4.2.7 2003/01/24 05:11:35 sam Exp $ */ 2 /* $DragonFly: src/sys/netinet6/ip6_forward.c,v 1.13 2006/12/22 23:57:53 swildner Exp $ */ 3 /* $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ */ 4 5 /* 6 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the project nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include "opt_ip6fw.h" 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/malloc.h> 42 #include <sys/mbuf.h> 43 #include <sys/domain.h> 44 #include <sys/protosw.h> 45 #include <sys/socket.h> 46 #include <sys/errno.h> 47 #include <sys/time.h> 48 #include <sys/kernel.h> 49 #include <sys/syslog.h> 50 51 #include <net/if.h> 52 #include <net/route.h> 53 #include <net/pfil.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_var.h> 57 #include <netinet/in_systm.h> 58 #include <netinet/ip.h> 59 #include <netinet/ip_var.h> 60 #include <netinet6/in6_var.h> 61 #include <netinet/ip6.h> 62 #include <netinet6/ip6_var.h> 63 #include <netinet/icmp6.h> 64 #include <netinet6/nd6.h> 65 66 #include <netinet/in_pcb.h> 67 68 #ifdef IPSEC 69 #include <netinet6/ipsec.h> 70 #ifdef INET6 71 #include <netinet6/ipsec6.h> 72 #endif 73 #include <netproto/key/key.h> 74 #endif /* IPSEC */ 75 76 #ifdef FAST_IPSEC 77 #include <netproto/ipsec/ipsec.h> 78 #include <netproto/ipsec/ipsec6.h> 79 #include <netproto/ipsec/key.h> 80 #define IPSEC 81 #endif /* FAST_IPSEC */ 82 83 #include <net/ip6fw/ip6_fw.h> 84 85 #include <net/net_osdep.h> 86 87 struct route_in6 ip6_forward_rt; 88 89 /* 90 * Forward a packet. If some error occurs return the sender 91 * an icmp packet. Note we can't always generate a meaningful 92 * icmp message because icmp doesn't have a large enough repertoire 93 * of codes and types. 94 * 95 * If not forwarding, just drop the packet. This could be confusing 96 * if ipforwarding was zero but some routing protocol was advancing 97 * us as a gateway to somewhere. However, we must let the routing 98 * protocol deal with that. 99 * 100 */ 101 102 void 103 ip6_forward(struct mbuf *m, int srcrt) 104 { 105 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 106 struct sockaddr_in6 *dst; 107 struct rtentry *rt; 108 int error, type = 0, code = 0; 109 struct mbuf *mcopy = NULL; 110 struct ifnet *origifp; /* maybe unnecessary */ 111 #ifdef IPSEC 112 struct secpolicy *sp = NULL; 113 #endif 114 115 #ifdef IPSEC 116 /* 117 * Check AH/ESP integrity. 118 */ 119 /* 120 * Don't increment ip6s_cantforward because this is the check 121 * before forwarding packet actually. 122 */ 123 if (ipsec6_in_reject(m, NULL)) { 124 #if !defined(FAST_IPSEC) 125 ipsec6stat.in_polvio++; 126 #endif 127 m_freem(m); 128 return; 129 } 130 #endif /* IPSEC */ 131 132 /* 133 * Do not forward packets to multicast destination (should be handled 134 * by ip6_mforward(). 135 * Do not forward packets with unspecified source. It was discussed 136 * in July 2000, on the ipngwg mailing list. 137 */ 138 if ((m->m_flags & (M_BCAST | M_MCAST)) != 0 || 139 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 140 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 141 ip6stat.ip6s_cantforward++; 142 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 143 if (ip6_log_time + ip6_log_interval < time_uptime) { 144 ip6_log_time = time_uptime; 145 log(LOG_DEBUG, 146 "cannot forward " 147 "from %s to %s nxt %d received on %s\n", 148 ip6_sprintf(&ip6->ip6_src), 149 ip6_sprintf(&ip6->ip6_dst), 150 ip6->ip6_nxt, 151 if_name(m->m_pkthdr.rcvif)); 152 } 153 m_freem(m); 154 return; 155 } 156 157 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 158 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 159 icmp6_error(m, ICMP6_TIME_EXCEEDED, 160 ICMP6_TIME_EXCEED_TRANSIT, 0); 161 return; 162 } 163 ip6->ip6_hlim -= IPV6_HLIMDEC; 164 165 /* 166 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 167 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 168 * we need to generate an ICMP6 message to the src. 169 * Thanks to M_EXT, in most cases copy will not occur. 170 * 171 * It is important to save it before IPsec processing as IPsec 172 * processing may modify the mbuf. 173 */ 174 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 175 176 #ifdef IPSEC 177 /* get a security policy for this packet */ 178 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 179 &error); 180 if (sp == NULL) { 181 ipsec6stat.out_inval++; 182 ip6stat.ip6s_cantforward++; 183 if (mcopy) { 184 #if 0 185 /* XXX: what icmp ? */ 186 #else 187 m_freem(mcopy); 188 #endif 189 } 190 m_freem(m); 191 return; 192 } 193 194 error = 0; 195 196 /* check policy */ 197 switch (sp->policy) { 198 case IPSEC_POLICY_DISCARD: 199 /* 200 * This packet is just discarded. 201 */ 202 ipsec6stat.out_polvio++; 203 ip6stat.ip6s_cantforward++; 204 key_freesp(sp); 205 if (mcopy) { 206 #if 0 207 /* XXX: what icmp ? */ 208 #else 209 m_freem(mcopy); 210 #endif 211 } 212 m_freem(m); 213 return; 214 215 case IPSEC_POLICY_BYPASS: 216 case IPSEC_POLICY_NONE: 217 /* no need to do IPsec. */ 218 key_freesp(sp); 219 goto skip_ipsec; 220 221 case IPSEC_POLICY_IPSEC: 222 if (sp->req == NULL) { 223 /* XXX should be panic ? */ 224 kprintf("ip6_forward: No IPsec request specified.\n"); 225 ip6stat.ip6s_cantforward++; 226 key_freesp(sp); 227 if (mcopy) { 228 #if 0 229 /* XXX: what icmp ? */ 230 #else 231 m_freem(mcopy); 232 #endif 233 } 234 m_freem(m); 235 return; 236 } 237 /* do IPsec */ 238 break; 239 240 case IPSEC_POLICY_ENTRUST: 241 default: 242 /* should be panic ?? */ 243 kprintf("ip6_forward: Invalid policy found. %d\n", sp->policy); 244 key_freesp(sp); 245 goto skip_ipsec; 246 } 247 248 { 249 struct ipsec_output_state state; 250 251 /* 252 * All the extension headers will become inaccessible 253 * (since they can be encrypted). 254 * Don't panic, we need no more updates to extension headers 255 * on inner IPv6 packet (since they are now encapsulated). 256 * 257 * IPv6 [ESP|AH] IPv6 [extension headers] payload 258 */ 259 bzero(&state, sizeof(state)); 260 state.m = m; 261 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 262 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 263 264 error = ipsec6_output_tunnel(&state, sp, 0); 265 266 m = state.m; 267 key_freesp(sp); 268 269 if (error) { 270 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 271 switch (error) { 272 case EHOSTUNREACH: 273 case ENETUNREACH: 274 case EMSGSIZE: 275 case ENOBUFS: 276 case ENOMEM: 277 break; 278 default: 279 kprintf("ip6_output (ipsec): error code %d\n", error); 280 /* FALLTHROUGH */ 281 case ENOENT: 282 /* don't show these error codes to the user */ 283 break; 284 } 285 ip6stat.ip6s_cantforward++; 286 if (mcopy) { 287 #if 0 288 /* XXX: what icmp ? */ 289 #else 290 m_freem(mcopy); 291 #endif 292 } 293 m_freem(m); 294 return; 295 } 296 } 297 skip_ipsec: 298 #endif /* IPSEC */ 299 300 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 301 if (!srcrt) { 302 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */ 303 if (ip6_forward_rt.ro_rt == NULL || 304 !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) { 305 if (ip6_forward_rt.ro_rt) { 306 RTFREE(ip6_forward_rt.ro_rt); 307 ip6_forward_rt.ro_rt = 0; 308 } 309 310 /* this probably fails but give it a try again */ 311 rtalloc_ign((struct route *)&ip6_forward_rt, 312 RTF_PRCLONING); 313 } 314 315 if (ip6_forward_rt.ro_rt == NULL) { 316 ip6stat.ip6s_noroute++; 317 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 318 if (mcopy) { 319 icmp6_error(mcopy, ICMP6_DST_UNREACH, 320 ICMP6_DST_UNREACH_NOROUTE, 0); 321 } 322 m_freem(m); 323 return; 324 } 325 } else if ((rt = ip6_forward_rt.ro_rt) == NULL || 326 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 327 if (ip6_forward_rt.ro_rt) { 328 RTFREE(ip6_forward_rt.ro_rt); 329 ip6_forward_rt.ro_rt = 0; 330 } 331 bzero(dst, sizeof(*dst)); 332 dst->sin6_len = sizeof(struct sockaddr_in6); 333 dst->sin6_family = AF_INET6; 334 dst->sin6_addr = ip6->ip6_dst; 335 336 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 337 if (ip6_forward_rt.ro_rt == NULL) { 338 ip6stat.ip6s_noroute++; 339 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 340 if (mcopy) { 341 icmp6_error(mcopy, ICMP6_DST_UNREACH, 342 ICMP6_DST_UNREACH_NOROUTE, 0); 343 } 344 m_freem(m); 345 return; 346 } 347 } 348 rt = ip6_forward_rt.ro_rt; 349 350 /* 351 * Scope check: if a packet can't be delivered to its destination 352 * for the reason that the destination is beyond the scope of the 353 * source address, discard the packet and return an icmp6 destination 354 * unreachable error with Code 2 (beyond scope of source address). 355 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 356 */ 357 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 358 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 359 ip6stat.ip6s_cantforward++; 360 ip6stat.ip6s_badscope++; 361 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 362 363 if (ip6_log_time + ip6_log_interval < time_uptime) { 364 ip6_log_time = time_uptime; 365 log(LOG_DEBUG, 366 "cannot forward " 367 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 368 ip6_sprintf(&ip6->ip6_src), 369 ip6_sprintf(&ip6->ip6_dst), 370 ip6->ip6_nxt, 371 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 372 } 373 if (mcopy) 374 icmp6_error(mcopy, ICMP6_DST_UNREACH, 375 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 376 m_freem(m); 377 return; 378 } 379 380 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 381 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 382 if (mcopy) { 383 u_long mtu; 384 #ifdef IPSEC 385 struct secpolicy *sp; 386 int ipsecerror; 387 size_t ipsechdrsiz; 388 #endif 389 390 mtu = rt->rt_ifp->if_mtu; 391 #ifdef IPSEC 392 /* 393 * When we do IPsec tunnel ingress, we need to play 394 * with if_mtu value (decrement IPsec header size 395 * from mtu value). The code is much simpler than v4 396 * case, as we have the outgoing interface for 397 * encapsulated packet as "rt->rt_ifp". 398 */ 399 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 400 IP_FORWARDING, &ipsecerror); 401 if (sp) { 402 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 403 IPSEC_DIR_OUTBOUND, NULL); 404 if (ipsechdrsiz < mtu) 405 mtu -= ipsechdrsiz; 406 } 407 408 /* 409 * if mtu becomes less than minimum MTU, 410 * tell minimum MTU (and I'll need to fragment it). 411 */ 412 if (mtu < IPV6_MMTU) 413 mtu = IPV6_MMTU; 414 #endif 415 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 416 } 417 m_freem(m); 418 return; 419 } 420 421 if (rt->rt_flags & RTF_GATEWAY) 422 dst = (struct sockaddr_in6 *)rt->rt_gateway; 423 424 /* 425 * If we are to forward the packet using the same interface 426 * as one we got the packet from, perhaps we should send a redirect 427 * to sender to shortcut a hop. 428 * Only send redirect if source is sending directly to us, 429 * and if packet was not source routed (or has any options). 430 * Also, don't send redirect if forwarding using a route 431 * modified by a redirect. 432 */ 433 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 434 (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) { 435 if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) { 436 /* 437 * If the incoming interface is equal to the outgoing 438 * one, and the link attached to the interface is 439 * point-to-point, then it will be highly probable 440 * that a routing loop occurs. Thus, we immediately 441 * drop the packet and send an ICMPv6 error message. 442 * 443 * type/code is based on suggestion by Rich Draves. 444 * not sure if it is the best pick. 445 */ 446 icmp6_error(mcopy, ICMP6_DST_UNREACH, 447 ICMP6_DST_UNREACH_ADDR, 0); 448 m_freem(m); 449 return; 450 } 451 type = ND_REDIRECT; 452 } 453 454 /* 455 * Check with the firewall... 456 */ 457 if (ip6_fw_enable && ip6_fw_chk_ptr) { 458 u_short port = 0; 459 /* If ipfw says divert, we have to just drop packet */ 460 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 461 m_freem(m); 462 goto freecopy; 463 } 464 if (!m) 465 goto freecopy; 466 } 467 468 /* 469 * Fake scoped addresses. Note that even link-local source or 470 * destinaion can appear, if the originating node just sends the 471 * packet to us (without address resolution for the destination). 472 * Since both icmp6_error and icmp6_redirect_output fill the embedded 473 * link identifiers, we can do this stuff after making a copy for 474 * returning an error. 475 */ 476 if (rt->rt_ifp->if_flags & IFF_LOOPBACK) { 477 /* 478 * See corresponding comments in ip6_output. 479 * XXX: but is it possible that ip6_forward() sends a packet 480 * to a loopback interface? I don't think so, and thus 481 * I bark here. (jinmei@kame.net) 482 * XXX: it is common to route invalid packets to loopback. 483 * also, the codepath will be visited on use of ::1 in 484 * rthdr. (itojun) 485 */ 486 #if 1 487 if (0) 488 #else 489 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0) 490 #endif 491 { 492 kprintf("ip6_forward: outgoing interface is loopback. " 493 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 494 ip6_sprintf(&ip6->ip6_src), 495 ip6_sprintf(&ip6->ip6_dst), 496 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 497 if_name(rt->rt_ifp)); 498 } 499 500 /* we can just use rcvif in forwarding. */ 501 origifp = m->m_pkthdr.rcvif; 502 } 503 else 504 origifp = rt->rt_ifp; 505 /* 506 * clear embedded scope identifiers if necessary. 507 * in6_clearscope will touch the addresses only when necessary. 508 */ 509 in6_clearscope(&ip6->ip6_src); 510 in6_clearscope(&ip6->ip6_dst); 511 512 /* 513 * Run through list of hooks for output packets. 514 */ 515 if (pfil_has_hooks(&inet6_pfil_hook)) { 516 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 517 PFIL_OUT); 518 if (error != 0) 519 goto senderr; 520 if (m == NULL) 521 goto freecopy; 522 ip6 = mtod(m, struct ip6_hdr *); 523 } 524 525 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 526 if (error) { 527 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 528 ip6stat.ip6s_cantforward++; 529 } else { 530 ip6stat.ip6s_forward++; 531 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 532 if (type) 533 ip6stat.ip6s_redirectsent++; 534 else { 535 if (mcopy) 536 goto freecopy; 537 } 538 } 539 senderr: 540 if (mcopy == NULL) 541 return; 542 switch (error) { 543 case 0: 544 if (type == ND_REDIRECT) { 545 icmp6_redirect_output(mcopy, rt); 546 return; 547 } 548 goto freecopy; 549 550 case EMSGSIZE: 551 /* xxx MTU is constant in PPP? */ 552 goto freecopy; 553 554 case ENOBUFS: 555 /* Tell source to slow down like source quench in IP? */ 556 goto freecopy; 557 558 case ENETUNREACH: /* shouldn't happen, checked above */ 559 case EHOSTUNREACH: 560 case ENETDOWN: 561 case EHOSTDOWN: 562 default: 563 type = ICMP6_DST_UNREACH; 564 code = ICMP6_DST_UNREACH_ADDR; 565 break; 566 } 567 icmp6_error(mcopy, type, code, 0); 568 return; 569 570 freecopy: 571 m_freem(mcopy); 572 return; 573 } 574