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 u_int32_t srczone, dstzone; 112 #ifdef IPSEC 113 struct secpolicy *sp = NULL; 114 #endif 115 116 #ifdef IPSEC 117 /* 118 * Check AH/ESP integrity. 119 */ 120 /* 121 * Don't increment ip6s_cantforward because this is the check 122 * before forwarding packet actually. 123 */ 124 if (ipsec6_in_reject(m, NULL)) { 125 #if !defined(FAST_IPSEC) 126 ipsec6stat.in_polvio++; 127 #endif 128 m_freem(m); 129 return; 130 } 131 #endif /* IPSEC */ 132 133 /* 134 * Do not forward packets to multicast destination (should be handled 135 * by ip6_mforward(). 136 * Do not forward packets with unspecified source. It was discussed 137 * in July 2000, on the ipngwg mailing list. 138 */ 139 if ((m->m_flags & (M_BCAST | M_MCAST)) != 0 || 140 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 141 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 142 ip6stat.ip6s_cantforward++; 143 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 144 if (ip6_log_time + ip6_log_interval < time_uptime) { 145 ip6_log_time = time_uptime; 146 log(LOG_DEBUG, 147 "cannot forward " 148 "from %s to %s nxt %d received on %s\n", 149 ip6_sprintf(&ip6->ip6_src), 150 ip6_sprintf(&ip6->ip6_dst), 151 ip6->ip6_nxt, 152 if_name(m->m_pkthdr.rcvif)); 153 } 154 m_freem(m); 155 return; 156 } 157 158 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 159 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 160 icmp6_error(m, ICMP6_TIME_EXCEEDED, 161 ICMP6_TIME_EXCEED_TRANSIT, 0); 162 return; 163 } 164 ip6->ip6_hlim -= IPV6_HLIMDEC; 165 166 /* 167 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 168 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 169 * we need to generate an ICMP6 message to the src. 170 * Thanks to M_EXT, in most cases copy will not occur. 171 * 172 * It is important to save it before IPsec processing as IPsec 173 * processing may modify the mbuf. 174 */ 175 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 176 177 #ifdef IPSEC 178 /* get a security policy for this packet */ 179 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 180 &error); 181 if (sp == NULL) { 182 ipsec6stat.out_inval++; 183 ip6stat.ip6s_cantforward++; 184 if (mcopy) { 185 #if 0 186 /* XXX: what icmp ? */ 187 #else 188 m_freem(mcopy); 189 #endif 190 } 191 m_freem(m); 192 return; 193 } 194 195 error = 0; 196 197 /* check policy */ 198 switch (sp->policy) { 199 case IPSEC_POLICY_DISCARD: 200 /* 201 * This packet is just discarded. 202 */ 203 ipsec6stat.out_polvio++; 204 ip6stat.ip6s_cantforward++; 205 key_freesp(sp); 206 if (mcopy) { 207 #if 0 208 /* XXX: what icmp ? */ 209 #else 210 m_freem(mcopy); 211 #endif 212 } 213 m_freem(m); 214 return; 215 216 case IPSEC_POLICY_BYPASS: 217 case IPSEC_POLICY_NONE: 218 /* no need to do IPsec. */ 219 key_freesp(sp); 220 goto skip_ipsec; 221 222 case IPSEC_POLICY_IPSEC: 223 if (sp->req == NULL) { 224 /* XXX should be panic ? */ 225 kprintf("ip6_forward: No IPsec request specified.\n"); 226 ip6stat.ip6s_cantforward++; 227 key_freesp(sp); 228 if (mcopy) { 229 #if 0 230 /* XXX: what icmp ? */ 231 #else 232 m_freem(mcopy); 233 #endif 234 } 235 m_freem(m); 236 return; 237 } 238 /* do IPsec */ 239 break; 240 241 case IPSEC_POLICY_ENTRUST: 242 default: 243 /* should be panic ?? */ 244 kprintf("ip6_forward: Invalid policy found. %d\n", sp->policy); 245 key_freesp(sp); 246 goto skip_ipsec; 247 } 248 249 { 250 struct ipsec_output_state state; 251 252 /* 253 * All the extension headers will become inaccessible 254 * (since they can be encrypted). 255 * Don't panic, we need no more updates to extension headers 256 * on inner IPv6 packet (since they are now encapsulated). 257 * 258 * IPv6 [ESP|AH] IPv6 [extension headers] payload 259 */ 260 bzero(&state, sizeof(state)); 261 state.m = m; 262 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 263 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 264 265 error = ipsec6_output_tunnel(&state, sp, 0); 266 267 m = state.m; 268 key_freesp(sp); 269 270 if (error) { 271 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 272 switch (error) { 273 case EHOSTUNREACH: 274 case ENETUNREACH: 275 case EMSGSIZE: 276 case ENOBUFS: 277 case ENOMEM: 278 break; 279 default: 280 kprintf("ip6_output (ipsec): error code %d\n", error); 281 /* FALLTHROUGH */ 282 case ENOENT: 283 /* don't show these error codes to the user */ 284 break; 285 } 286 ip6stat.ip6s_cantforward++; 287 if (mcopy) { 288 #if 0 289 /* XXX: what icmp ? */ 290 #else 291 m_freem(mcopy); 292 #endif 293 } 294 m_freem(m); 295 return; 296 } 297 } 298 skip_ipsec: 299 #endif /* IPSEC */ 300 301 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 302 if (!srcrt) { 303 /* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst */ 304 if (ip6_forward_rt.ro_rt == NULL || 305 !(ip6_forward_rt.ro_rt->rt_flags & RTF_UP)) { 306 if (ip6_forward_rt.ro_rt) { 307 RTFREE(ip6_forward_rt.ro_rt); 308 ip6_forward_rt.ro_rt = 0; 309 } 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_addr2zoneid(m->m_pkthdr.rcvif, &ip6->ip6_src, &srczone) || 359 in6_addr2zoneid(rt->rt_ifp, &ip6->ip6_src, &dstzone) || 360 srczone != dstzone) { 361 ip6stat.ip6s_cantforward++; 362 ip6stat.ip6s_badscope++; 363 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 364 365 if (ip6_log_time + ip6_log_interval < time_uptime) { 366 ip6_log_time = time_uptime; 367 log(LOG_DEBUG, 368 "cannot forward " 369 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 370 ip6_sprintf(&ip6->ip6_src), 371 ip6_sprintf(&ip6->ip6_dst), 372 ip6->ip6_nxt, 373 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 374 } 375 if (mcopy) 376 icmp6_error(mcopy, ICMP6_DST_UNREACH, 377 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 378 m_freem(m); 379 return; 380 } 381 382 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 383 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 384 if (mcopy) { 385 u_long mtu; 386 #ifdef IPSEC 387 struct secpolicy *sp; 388 int ipsecerror; 389 size_t ipsechdrsiz; 390 #endif 391 392 mtu = IN6_LINKMTU(rt->rt_ifp); 393 #ifdef IPSEC 394 /* 395 * When we do IPsec tunnel ingress, we need to play 396 * with if_mtu value (decrement IPsec header size 397 * from mtu value). The code is much simpler than v4 398 * case, as we have the outgoing interface for 399 * encapsulated packet as "rt->rt_ifp". 400 */ 401 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 402 IP_FORWARDING, &ipsecerror); 403 if (sp) { 404 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 405 IPSEC_DIR_OUTBOUND, NULL); 406 if (ipsechdrsiz < mtu) 407 mtu -= ipsechdrsiz; 408 } 409 410 /* 411 * if mtu becomes less than minimum MTU, 412 * tell minimum MTU (and I'll need to fragment it). 413 */ 414 if (mtu < IPV6_MMTU) 415 mtu = IPV6_MMTU; 416 #endif 417 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 418 } 419 m_freem(m); 420 return; 421 } 422 423 if (rt->rt_flags & RTF_GATEWAY) 424 dst = (struct sockaddr_in6 *)rt->rt_gateway; 425 426 /* 427 * If we are to forward the packet using the same interface 428 * as one we got the packet from, perhaps we should send a redirect 429 * to sender to shortcut a hop. 430 * Only send redirect if source is sending directly to us, 431 * and if packet was not source routed (or has any options). 432 * Also, don't send redirect if forwarding using a route 433 * modified by a redirect. 434 */ 435 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 436 (rt->rt_flags & (RTF_DYNAMIC | RTF_MODIFIED)) == 0) { 437 if (rt->rt_ifp->if_flags & IFF_POINTOPOINT) { 438 /* 439 * If the incoming interface is equal to the outgoing 440 * one, and the link attached to the interface is 441 * point-to-point, then it will be highly probable 442 * that a routing loop occurs. Thus, we immediately 443 * drop the packet and send an ICMPv6 error message. 444 * 445 * type/code is based on suggestion by Rich Draves. 446 * not sure if it is the best pick. 447 */ 448 icmp6_error(mcopy, ICMP6_DST_UNREACH, 449 ICMP6_DST_UNREACH_ADDR, 0); 450 m_freem(m); 451 return; 452 } 453 type = ND_REDIRECT; 454 } 455 456 /* 457 * Check with the firewall... 458 */ 459 if (ip6_fw_enable && ip6_fw_chk_ptr) { 460 u_short port = 0; 461 /* If ipfw says divert, we have to just drop packet */ 462 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 463 m_freem(m); 464 goto freecopy; 465 } 466 if (!m) 467 goto freecopy; 468 } 469 470 /* 471 * Fake scoped addresses. Note that even link-local source or 472 * destinaion can appear, if the originating node just sends the 473 * packet to us (without address resolution for the destination). 474 * Since both icmp6_error and icmp6_redirect_output fill the embedded 475 * link identifiers, we can do this stuff after making a copy for 476 * returning an error. 477 */ 478 if (rt->rt_ifp->if_flags & IFF_LOOPBACK) { 479 /* 480 * See corresponding comments in ip6_output. 481 * XXX: but is it possible that ip6_forward() sends a packet 482 * to a loopback interface? I don't think so, and thus 483 * I bark here. (jinmei@kame.net) 484 * XXX: it is common to route invalid packets to loopback. 485 * also, the codepath will be visited on use of ::1 in 486 * rthdr. (itojun) 487 */ 488 #if 1 489 if (0) 490 #else 491 if ((rt->rt_flags & (RTF_BLACKHOLE | RTF_REJECT)) == 0) 492 #endif 493 { 494 kprintf("ip6_forward: outgoing interface is loopback. " 495 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 496 ip6_sprintf(&ip6->ip6_src), 497 ip6_sprintf(&ip6->ip6_dst), 498 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 499 if_name(rt->rt_ifp)); 500 } 501 502 /* we can just use rcvif in forwarding. */ 503 origifp = m->m_pkthdr.rcvif; 504 } 505 else 506 origifp = rt->rt_ifp; 507 /* 508 * clear embedded scope identifiers if necessary. 509 * in6_clearscope will touch the addresses only when necessary. 510 */ 511 in6_clearscope(&ip6->ip6_src); 512 in6_clearscope(&ip6->ip6_dst); 513 514 /* 515 * Run through list of hooks for output packets. 516 */ 517 if (pfil_has_hooks(&inet6_pfil_hook)) { 518 error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 519 PFIL_OUT); 520 if (error != 0) 521 goto senderr; 522 if (m == NULL) 523 goto freecopy; 524 ip6 = mtod(m, struct ip6_hdr *); 525 } 526 527 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 528 if (error) { 529 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 530 ip6stat.ip6s_cantforward++; 531 } else { 532 ip6stat.ip6s_forward++; 533 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 534 if (type) 535 ip6stat.ip6s_redirectsent++; 536 else { 537 if (mcopy) 538 goto freecopy; 539 } 540 } 541 senderr: 542 if (mcopy == NULL) 543 return; 544 switch (error) { 545 case 0: 546 if (type == ND_REDIRECT) { 547 icmp6_redirect_output(mcopy, rt); 548 return; 549 } 550 goto freecopy; 551 552 case EMSGSIZE: 553 /* xxx MTU is constant in PPP? */ 554 goto freecopy; 555 556 case ENOBUFS: 557 /* Tell source to slow down like source quench in IP? */ 558 goto freecopy; 559 560 case ENETUNREACH: /* shouldn't happen, checked above */ 561 case EHOSTUNREACH: 562 case ENETDOWN: 563 case EHOSTDOWN: 564 default: 565 type = ICMP6_DST_UNREACH; 566 code = ICMP6_DST_UNREACH_ADDR; 567 break; 568 } 569 icmp6_error(mcopy, type, code, 0); 570 return; 571 572 freecopy: 573 m_freem(mcopy); 574 return; 575 } 576