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 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_second) { 144 ip6_log_time = time_second; 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 /* fall through */ 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 /* 303 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 304 */ 305 if (ip6_forward_rt.ro_rt == NULL || 306 !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) { 307 if (ip6_forward_rt.ro_rt) { 308 RTFREE(ip6_forward_rt.ro_rt); 309 ip6_forward_rt.ro_rt = 0; 310 } 311 /* this probably fails but give it a try again */ 312 rtalloc_ign((struct route *)&ip6_forward_rt, 313 RTF_PRCLONING); 314 } 315 316 if (ip6_forward_rt.ro_rt == NULL) { 317 ip6stat.ip6s_noroute++; 318 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 319 if (mcopy) { 320 icmp6_error(mcopy, ICMP6_DST_UNREACH, 321 ICMP6_DST_UNREACH_NOROUTE, 0); 322 } 323 m_freem(m); 324 return; 325 } 326 } else if ((rt = ip6_forward_rt.ro_rt) == NULL || 327 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 328 if (ip6_forward_rt.ro_rt) { 329 RTFREE(ip6_forward_rt.ro_rt); 330 ip6_forward_rt.ro_rt = 0; 331 } 332 bzero(dst, sizeof(*dst)); 333 dst->sin6_len = sizeof(struct sockaddr_in6); 334 dst->sin6_family = AF_INET6; 335 dst->sin6_addr = ip6->ip6_dst; 336 337 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 338 if (ip6_forward_rt.ro_rt == NULL) { 339 ip6stat.ip6s_noroute++; 340 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 341 if (mcopy) { 342 icmp6_error(mcopy, ICMP6_DST_UNREACH, 343 ICMP6_DST_UNREACH_NOROUTE, 0); 344 } 345 m_freem(m); 346 return; 347 } 348 } 349 rt = ip6_forward_rt.ro_rt; 350 351 /* 352 * Scope check: if a packet can't be delivered to its destination 353 * for the reason that the destination is beyond the scope of the 354 * source address, discard the packet and return an icmp6 destination 355 * unreachable error with Code 2 (beyond scope of source address). 356 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 357 */ 358 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 359 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 360 ip6stat.ip6s_cantforward++; 361 ip6stat.ip6s_badscope++; 362 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 363 364 if (ip6_log_time + ip6_log_interval < time_second) { 365 ip6_log_time = time_second; 366 log(LOG_DEBUG, 367 "cannot forward " 368 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 369 ip6_sprintf(&ip6->ip6_src), 370 ip6_sprintf(&ip6->ip6_dst), 371 ip6->ip6_nxt, 372 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 373 } 374 if (mcopy) 375 icmp6_error(mcopy, ICMP6_DST_UNREACH, 376 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 377 m_freem(m); 378 return; 379 } 380 381 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 382 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 383 if (mcopy) { 384 u_long mtu; 385 #ifdef IPSEC 386 struct secpolicy *sp; 387 int ipsecerror; 388 size_t ipsechdrsiz; 389 #endif 390 391 mtu = rt->rt_ifp->if_mtu; 392 #ifdef IPSEC 393 /* 394 * When we do IPsec tunnel ingress, we need to play 395 * with if_mtu value (decrement IPsec header size 396 * from mtu value). The code is much simpler than v4 397 * case, as we have the outgoing interface for 398 * encapsulated packet as "rt->rt_ifp". 399 */ 400 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 401 IP_FORWARDING, &ipsecerror); 402 if (sp) { 403 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 404 IPSEC_DIR_OUTBOUND, NULL); 405 if (ipsechdrsiz < mtu) 406 mtu -= ipsechdrsiz; 407 } 408 409 /* 410 * if mtu becomes less than minimum MTU, 411 * tell minimum MTU (and I'll need to fragment it). 412 */ 413 if (mtu < IPV6_MMTU) 414 mtu = IPV6_MMTU; 415 #endif 416 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 417 } 418 m_freem(m); 419 return; 420 } 421 422 if (rt->rt_flags & RTF_GATEWAY) 423 dst = (struct sockaddr_in6 *)rt->rt_gateway; 424 425 /* 426 * If we are to forward the packet using the same interface 427 * as one we got the packet from, perhaps we should send a redirect 428 * to sender to shortcut a hop. 429 * Only send redirect if source is sending directly to us, 430 * and if packet was not source routed (or has any options). 431 * Also, don't send redirect if forwarding using a route 432 * modified by a redirect. 433 */ 434 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 435 (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) { 436 if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) { 437 /* 438 * If the incoming interface is equal to the outgoing 439 * one, and the link attached to the interface is 440 * point-to-point, then it will be highly probable 441 * that a routing loop occurs. Thus, we immediately 442 * drop the packet and send an ICMPv6 error message. 443 * 444 * type/code is based on suggestion by Rich Draves. 445 * not sure if it is the best pick. 446 */ 447 icmp6_error(mcopy, ICMP6_DST_UNREACH, 448 ICMP6_DST_UNREACH_ADDR, 0); 449 m_freem(m); 450 return; 451 } 452 type = ND_REDIRECT; 453 } 454 455 /* 456 * Check with the firewall... 457 */ 458 if (ip6_fw_enable && ip6_fw_chk_ptr) { 459 u_short port = 0; 460 /* If ipfw says divert, we have to just drop packet */ 461 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 462 m_freem(m); 463 goto freecopy; 464 } 465 if (!m) 466 goto freecopy; 467 } 468 469 /* 470 * Fake scoped addresses. Note that even link-local source or 471 * destinaion can appear, if the originating node just sends the 472 * packet to us (without address resolution for the destination). 473 * Since both icmp6_error and icmp6_redirect_output fill the embedded 474 * link identifiers, we can do this stuff after making a copy for 475 * returning an error. 476 */ 477 if (rt->rt_ifp->if_flags & IFF_LOOPBACK) { 478 /* 479 * See corresponding comments in ip6_output. 480 * XXX: but is it possible that ip6_forward() sends a packet 481 * to a loopback interface? I don't think so, and thus 482 * I bark here. (jinmei@kame.net) 483 * XXX: it is common to route invalid packets to loopback. 484 * also, the codepath will be visited on use of ::1 in 485 * rthdr. (itojun) 486 */ 487 #if 1 488 if (0) 489 #else 490 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0) 491 #endif 492 { 493 kprintf("ip6_forward: outgoing interface is loopback. " 494 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 495 ip6_sprintf(&ip6->ip6_src), 496 ip6_sprintf(&ip6->ip6_dst), 497 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 498 if_name(rt->rt_ifp)); 499 } 500 501 /* we can just use rcvif in forwarding. */ 502 origifp = m->m_pkthdr.rcvif; 503 } 504 else 505 origifp = rt->rt_ifp; 506 /* 507 * clear embedded scope identifiers if necessary. 508 * in6_clearscope will touch the addresses only when necessary. 509 */ 510 in6_clearscope(&ip6->ip6_src); 511 in6_clearscope(&ip6->ip6_dst); 512 513 /* 514 * Run through list of hooks for output packets. 515 */ 516 if (pfil_has_hooks(&inet6_pfil_hook)) { 517 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 518 PFIL_OUT); 519 if (error != 0) 520 goto senderr; 521 if (m == NULL) 522 goto freecopy; 523 ip6 = mtod(m, struct ip6_hdr *); 524 } 525 526 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 527 if (error) { 528 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 529 ip6stat.ip6s_cantforward++; 530 } else { 531 ip6stat.ip6s_forward++; 532 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 533 if (type) 534 ip6stat.ip6s_redirectsent++; 535 else { 536 if (mcopy) 537 goto freecopy; 538 } 539 } 540 senderr: 541 if (mcopy == NULL) 542 return; 543 switch (error) { 544 case 0: 545 #if 1 546 if (type == ND_REDIRECT) { 547 icmp6_redirect_output(mcopy, rt); 548 return; 549 } 550 #endif 551 goto freecopy; 552 553 case EMSGSIZE: 554 /* xxx MTU is constant in PPP? */ 555 goto freecopy; 556 557 case ENOBUFS: 558 /* Tell source to slow down like source quench in IP? */ 559 goto freecopy; 560 561 case ENETUNREACH: /* shouldn't happen, checked above */ 562 case EHOSTUNREACH: 563 case ENETDOWN: 564 case EHOSTDOWN: 565 default: 566 type = ICMP6_DST_UNREACH; 567 code = ICMP6_DST_UNREACH_ADDR; 568 break; 569 } 570 icmp6_error(mcopy, type, code, 0); 571 return; 572 573 freecopy: 574 m_freem(mcopy); 575 return; 576 } 577