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 1.6 2003/12/02 08:00:22 asmodai 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 #include "opt_pfil_hooks.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/domain.h> 45 #include <sys/protosw.h> 46 #include <sys/socket.h> 47 #include <sys/errno.h> 48 #include <sys/time.h> 49 #include <sys/kernel.h> 50 #include <sys/syslog.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 #ifdef PFIL_HOOKS 55 #include <net/pfil.h> 56 #endif 57 58 #include <netinet/in.h> 59 #include <netinet/in_var.h> 60 #include <netinet/in_systm.h> 61 #include <netinet/ip.h> 62 #include <netinet/ip_var.h> 63 #include <netinet6/in6_var.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #include <netinet/icmp6.h> 67 #include <netinet6/nd6.h> 68 69 #include <netinet/in_pcb.h> 70 71 #ifdef IPSEC 72 #include <netinet6/ipsec.h> 73 #ifdef INET6 74 #include <netinet6/ipsec6.h> 75 #endif 76 #include <netproto/key/key.h> 77 #endif /* IPSEC */ 78 79 #ifdef FAST_IPSEC 80 #include "ipsec.h" 81 #include "ipsec6.h" 82 #include <netipsec/key.h> 83 #define IPSEC 84 #endif /* FAST_IPSEC */ 85 86 #include <net/ip6fw/ip6_fw.h> 87 88 #include <net/net_osdep.h> 89 90 struct route_in6 ip6_forward_rt; 91 92 /* 93 * Forward a packet. If some error occurs return the sender 94 * an icmp packet. Note we can't always generate a meaningful 95 * icmp message because icmp doesn't have a large enough repertoire 96 * of codes and types. 97 * 98 * If not forwarding, just drop the packet. This could be confusing 99 * if ipforwarding was zero but some routing protocol was advancing 100 * us as a gateway to somewhere. However, we must let the routing 101 * protocol deal with that. 102 * 103 */ 104 105 void 106 ip6_forward(m, srcrt) 107 struct mbuf *m; 108 int srcrt; 109 { 110 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 111 struct sockaddr_in6 *dst; 112 struct rtentry *rt; 113 int error, type = 0, code = 0; 114 struct mbuf *mcopy = NULL; 115 struct ifnet *origifp; /* maybe unnecessary */ 116 #ifdef IPSEC 117 struct secpolicy *sp = NULL; 118 #endif 119 120 #ifdef IPSEC 121 /* 122 * Check AH/ESP integrity. 123 */ 124 /* 125 * Don't increment ip6s_cantforward because this is the check 126 * before forwarding packet actually. 127 */ 128 if (ipsec6_in_reject(m, NULL)) { 129 #if !defined(FAST_IPSEC) 130 ipsec6stat.in_polvio++; 131 #endif 132 m_freem(m); 133 return; 134 } 135 #endif /* IPSEC */ 136 137 /* 138 * Do not forward packets to multicast destination (should be handled 139 * by ip6_mforward(). 140 * Do not forward packets with unspecified source. It was discussed 141 * in July 2000, on ipngwg mailing list. 142 */ 143 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 144 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 145 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 146 ip6stat.ip6s_cantforward++; 147 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 148 if (ip6_log_time + ip6_log_interval < time_second) { 149 ip6_log_time = time_second; 150 log(LOG_DEBUG, 151 "cannot forward " 152 "from %s to %s nxt %d received on %s\n", 153 ip6_sprintf(&ip6->ip6_src), 154 ip6_sprintf(&ip6->ip6_dst), 155 ip6->ip6_nxt, 156 if_name(m->m_pkthdr.rcvif)); 157 } 158 m_freem(m); 159 return; 160 } 161 162 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 163 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 164 icmp6_error(m, ICMP6_TIME_EXCEEDED, 165 ICMP6_TIME_EXCEED_TRANSIT, 0); 166 return; 167 } 168 ip6->ip6_hlim -= IPV6_HLIMDEC; 169 170 /* 171 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 172 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 173 * we need to generate an ICMP6 message to the src. 174 * Thanks to M_EXT, in most cases copy will not occur. 175 * 176 * It is important to save it before IPsec processing as IPsec 177 * processing may modify the mbuf. 178 */ 179 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 180 181 #ifdef IPSEC 182 /* get a security policy for this packet */ 183 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 184 &error); 185 if (sp == NULL) { 186 ipsec6stat.out_inval++; 187 ip6stat.ip6s_cantforward++; 188 if (mcopy) { 189 #if 0 190 /* XXX: what icmp ? */ 191 #else 192 m_freem(mcopy); 193 #endif 194 } 195 m_freem(m); 196 return; 197 } 198 199 error = 0; 200 201 /* check policy */ 202 switch (sp->policy) { 203 case IPSEC_POLICY_DISCARD: 204 /* 205 * This packet is just discarded. 206 */ 207 ipsec6stat.out_polvio++; 208 ip6stat.ip6s_cantforward++; 209 key_freesp(sp); 210 if (mcopy) { 211 #if 0 212 /* XXX: what icmp ? */ 213 #else 214 m_freem(mcopy); 215 #endif 216 } 217 m_freem(m); 218 return; 219 220 case IPSEC_POLICY_BYPASS: 221 case IPSEC_POLICY_NONE: 222 /* no need to do IPsec. */ 223 key_freesp(sp); 224 goto skip_ipsec; 225 226 case IPSEC_POLICY_IPSEC: 227 if (sp->req == NULL) { 228 /* XXX should be panic ? */ 229 printf("ip6_forward: No IPsec request specified.\n"); 230 ip6stat.ip6s_cantforward++; 231 key_freesp(sp); 232 if (mcopy) { 233 #if 0 234 /* XXX: what icmp ? */ 235 #else 236 m_freem(mcopy); 237 #endif 238 } 239 m_freem(m); 240 return; 241 } 242 /* do IPsec */ 243 break; 244 245 case IPSEC_POLICY_ENTRUST: 246 default: 247 /* should be panic ?? */ 248 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 249 key_freesp(sp); 250 goto skip_ipsec; 251 } 252 253 { 254 struct ipsec_output_state state; 255 256 /* 257 * All the extension headers will become inaccessible 258 * (since they can be encrypted). 259 * Don't panic, we need no more updates to extension headers 260 * on inner IPv6 packet (since they are now encapsulated). 261 * 262 * IPv6 [ESP|AH] IPv6 [extension headers] payload 263 */ 264 bzero(&state, sizeof(state)); 265 state.m = m; 266 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 267 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 268 269 error = ipsec6_output_tunnel(&state, sp, 0); 270 271 m = state.m; 272 key_freesp(sp); 273 274 if (error) { 275 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 276 switch (error) { 277 case EHOSTUNREACH: 278 case ENETUNREACH: 279 case EMSGSIZE: 280 case ENOBUFS: 281 case ENOMEM: 282 break; 283 default: 284 printf("ip6_output (ipsec): error code %d\n", error); 285 /* fall through */ 286 case ENOENT: 287 /* don't show these error codes to the user */ 288 break; 289 } 290 ip6stat.ip6s_cantforward++; 291 if (mcopy) { 292 #if 0 293 /* XXX: what icmp ? */ 294 #else 295 m_freem(mcopy); 296 #endif 297 } 298 m_freem(m); 299 return; 300 } 301 } 302 skip_ipsec: 303 #endif /* IPSEC */ 304 305 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 306 if (!srcrt) { 307 /* 308 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 309 */ 310 if (ip6_forward_rt.ro_rt == 0 || 311 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 312 if (ip6_forward_rt.ro_rt) { 313 RTFREE(ip6_forward_rt.ro_rt); 314 ip6_forward_rt.ro_rt = 0; 315 } 316 /* this probably fails but give it a try again */ 317 rtalloc_ign((struct route *)&ip6_forward_rt, 318 RTF_PRCLONING); 319 } 320 321 if (ip6_forward_rt.ro_rt == 0) { 322 ip6stat.ip6s_noroute++; 323 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 324 if (mcopy) { 325 icmp6_error(mcopy, ICMP6_DST_UNREACH, 326 ICMP6_DST_UNREACH_NOROUTE, 0); 327 } 328 m_freem(m); 329 return; 330 } 331 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 332 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 333 if (ip6_forward_rt.ro_rt) { 334 RTFREE(ip6_forward_rt.ro_rt); 335 ip6_forward_rt.ro_rt = 0; 336 } 337 bzero(dst, sizeof(*dst)); 338 dst->sin6_len = sizeof(struct sockaddr_in6); 339 dst->sin6_family = AF_INET6; 340 dst->sin6_addr = ip6->ip6_dst; 341 342 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 343 if (ip6_forward_rt.ro_rt == 0) { 344 ip6stat.ip6s_noroute++; 345 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 346 if (mcopy) { 347 icmp6_error(mcopy, ICMP6_DST_UNREACH, 348 ICMP6_DST_UNREACH_NOROUTE, 0); 349 } 350 m_freem(m); 351 return; 352 } 353 } 354 rt = ip6_forward_rt.ro_rt; 355 356 /* 357 * Scope check: if a packet can't be delivered to its destination 358 * for the reason that the destination is beyond the scope of the 359 * source address, discard the packet and return an icmp6 destination 360 * unreachable error with Code 2 (beyond scope of source address). 361 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 362 */ 363 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 364 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 365 ip6stat.ip6s_cantforward++; 366 ip6stat.ip6s_badscope++; 367 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 368 369 if (ip6_log_time + ip6_log_interval < time_second) { 370 ip6_log_time = time_second; 371 log(LOG_DEBUG, 372 "cannot forward " 373 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 374 ip6_sprintf(&ip6->ip6_src), 375 ip6_sprintf(&ip6->ip6_dst), 376 ip6->ip6_nxt, 377 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 378 } 379 if (mcopy) 380 icmp6_error(mcopy, ICMP6_DST_UNREACH, 381 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 382 m_freem(m); 383 return; 384 } 385 386 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 387 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 388 if (mcopy) { 389 u_long mtu; 390 #ifdef IPSEC 391 struct secpolicy *sp; 392 int ipsecerror; 393 size_t ipsechdrsiz; 394 #endif 395 396 mtu = rt->rt_ifp->if_mtu; 397 #ifdef IPSEC 398 /* 399 * When we do IPsec tunnel ingress, we need to play 400 * with if_mtu value (decrement IPsec header size 401 * from mtu value). The code is much simpler than v4 402 * case, as we have the outgoing interface for 403 * encapsulated packet as "rt->rt_ifp". 404 */ 405 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 406 IP_FORWARDING, &ipsecerror); 407 if (sp) { 408 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 409 IPSEC_DIR_OUTBOUND, NULL); 410 if (ipsechdrsiz < mtu) 411 mtu -= ipsechdrsiz; 412 } 413 414 /* 415 * if mtu becomes less than minimum MTU, 416 * tell minimum MTU (and I'll need to fragment it). 417 */ 418 if (mtu < IPV6_MMTU) 419 mtu = IPV6_MMTU; 420 #endif 421 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 422 } 423 m_freem(m); 424 return; 425 } 426 427 if (rt->rt_flags & RTF_GATEWAY) 428 dst = (struct sockaddr_in6 *)rt->rt_gateway; 429 430 /* 431 * If we are to forward the packet using the same interface 432 * as one we got the packet from, perhaps we should send a redirect 433 * to sender to shortcut a hop. 434 * Only send redirect if source is sending directly to us, 435 * and if packet was not source routed (or has any options). 436 * Also, don't send redirect if forwarding using a route 437 * modified by a redirect. 438 */ 439 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 440 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 441 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 442 /* 443 * If the incoming interface is equal to the outgoing 444 * one, and the link attached to the interface is 445 * point-to-point, then it will be highly probable 446 * that a routing loop occurs. Thus, we immediately 447 * drop the packet and send an ICMPv6 error message. 448 * 449 * type/code is based on suggestion by Rich Draves. 450 * not sure if it is the best pick. 451 */ 452 icmp6_error(mcopy, ICMP6_DST_UNREACH, 453 ICMP6_DST_UNREACH_ADDR, 0); 454 m_freem(m); 455 return; 456 } 457 type = ND_REDIRECT; 458 } 459 460 /* 461 * Check with the firewall... 462 */ 463 if (ip6_fw_enable && ip6_fw_chk_ptr) { 464 u_short port = 0; 465 /* If ipfw says divert, we have to just drop packet */ 466 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 467 m_freem(m); 468 goto freecopy; 469 } 470 if (!m) 471 goto freecopy; 472 } 473 474 /* 475 * Fake scoped addresses. Note that even link-local source or 476 * destinaion can appear, if the originating node just sends the 477 * packet to us (without address resolution for the destination). 478 * Since both icmp6_error and icmp6_redirect_output fill the embedded 479 * link identifiers, we can do this stuff after making a copy for 480 * returning an error. 481 */ 482 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 483 /* 484 * See corresponding comments in ip6_output. 485 * XXX: but is it possible that ip6_forward() sends a packet 486 * to a loopback interface? I don't think so, and thus 487 * I bark here. (jinmei@kame.net) 488 * XXX: it is common to route invalid packets to loopback. 489 * also, the codepath will be visited on use of ::1 in 490 * rthdr. (itojun) 491 */ 492 #if 1 493 if (0) 494 #else 495 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 496 #endif 497 { 498 printf("ip6_forward: outgoing interface is loopback. " 499 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 500 ip6_sprintf(&ip6->ip6_src), 501 ip6_sprintf(&ip6->ip6_dst), 502 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 503 if_name(rt->rt_ifp)); 504 } 505 506 /* we can just use rcvif in forwarding. */ 507 origifp = m->m_pkthdr.rcvif; 508 } 509 else 510 origifp = rt->rt_ifp; 511 #ifndef SCOPEDROUTING 512 /* 513 * clear embedded scope identifiers if necessary. 514 * in6_clearscope will touch the addresses only when necessary. 515 */ 516 in6_clearscope(&ip6->ip6_src); 517 in6_clearscope(&ip6->ip6_dst); 518 #endif 519 520 #ifdef PFIL_HOOKS 521 /* 522 * Run through list of hooks for output packets. 523 */ 524 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, PFIL_OUT); 525 if (error != 0) 526 goto senderr; 527 if (m == NULL) 528 goto freecopy; 529 ip6 = mtod(m, struct ip6_hdr *); 530 #endif /* PFIL_HOOKS */ 531 532 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 533 if (error) { 534 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 535 ip6stat.ip6s_cantforward++; 536 } else { 537 ip6stat.ip6s_forward++; 538 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 539 if (type) 540 ip6stat.ip6s_redirectsent++; 541 else { 542 if (mcopy) 543 goto freecopy; 544 } 545 } 546 #ifdef PFIL_HOOKS 547 senderr: 548 #endif 549 if (mcopy == NULL) 550 return; 551 switch (error) { 552 case 0: 553 #if 1 554 if (type == ND_REDIRECT) { 555 icmp6_redirect_output(mcopy, rt); 556 return; 557 } 558 #endif 559 goto freecopy; 560 561 case EMSGSIZE: 562 /* xxx MTU is constant in PPP? */ 563 goto freecopy; 564 565 case ENOBUFS: 566 /* Tell source to slow down like source quench in IP? */ 567 goto freecopy; 568 569 case ENETUNREACH: /* shouldn't happen, checked above */ 570 case EHOSTUNREACH: 571 case ENETDOWN: 572 case EHOSTDOWN: 573 default: 574 type = ICMP6_DST_UNREACH; 575 code = ICMP6_DST_UNREACH_ADDR; 576 break; 577 } 578 icmp6_error(mcopy, type, code, 0); 579 return; 580 581 freecopy: 582 m_freem(mcopy); 583 return; 584 } 585