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 1.2 2003/06/17 04:28:52 dillon 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 54 #include <netinet/in.h> 55 #include <netinet/in_var.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/ip_var.h> 59 #include <netinet6/in6_var.h> 60 #include <netinet/ip6.h> 61 #include <netinet6/ip6_var.h> 62 #include <netinet/icmp6.h> 63 #include <netinet6/nd6.h> 64 65 #include <netinet/in_pcb.h> 66 67 #ifdef IPSEC 68 #include <netinet6/ipsec.h> 69 #ifdef INET6 70 #include <netinet6/ipsec6.h> 71 #endif 72 #include <netkey/key.h> 73 #endif /* IPSEC */ 74 75 #ifdef FAST_IPSEC 76 #include <netipsec/ipsec.h> 77 #include <netipsec/ipsec6.h> 78 #include <netipsec/key.h> 79 #define IPSEC 80 #endif /* FAST_IPSEC */ 81 82 #include <netinet6/ip6_fw.h> 83 84 #include <net/net_osdep.h> 85 86 extern int (*fr_checkp) __P((struct ip *, int, struct ifnet *, int, struct mbuf **)); 87 88 struct route_in6 ip6_forward_rt; 89 90 /* 91 * Forward a packet. If some error occurs return the sender 92 * an icmp packet. Note we can't always generate a meaningful 93 * icmp message because icmp doesn't have a large enough repertoire 94 * of codes and types. 95 * 96 * If not forwarding, just drop the packet. This could be confusing 97 * if ipforwarding was zero but some routing protocol was advancing 98 * us as a gateway to somewhere. However, we must let the routing 99 * protocol deal with that. 100 * 101 */ 102 103 void 104 ip6_forward(m, srcrt) 105 struct mbuf *m; 106 int srcrt; 107 { 108 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 109 struct sockaddr_in6 *dst; 110 struct rtentry *rt; 111 int error, type = 0, code = 0; 112 struct mbuf *mcopy = NULL; 113 struct ifnet *origifp; /* maybe unnecessary */ 114 #ifdef IPSEC 115 struct secpolicy *sp = NULL; 116 #endif 117 118 #ifdef IPSEC 119 /* 120 * Check AH/ESP integrity. 121 */ 122 /* 123 * Don't increment ip6s_cantforward because this is the check 124 * before forwarding packet actually. 125 */ 126 if (ipsec6_in_reject(m, NULL)) { 127 #if !defined(FAST_IPSEC) 128 ipsec6stat.in_polvio++; 129 #endif 130 m_freem(m); 131 return; 132 } 133 #endif /* IPSEC */ 134 135 /* 136 * Do not forward packets to multicast destination (should be handled 137 * by ip6_mforward(). 138 * Do not forward packets with unspecified source. It was discussed 139 * in July 2000, on ipngwg mailing list. 140 */ 141 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 142 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 143 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 144 ip6stat.ip6s_cantforward++; 145 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 146 if (ip6_log_time + ip6_log_interval < time_second) { 147 ip6_log_time = time_second; 148 log(LOG_DEBUG, 149 "cannot forward " 150 "from %s to %s nxt %d received on %s\n", 151 ip6_sprintf(&ip6->ip6_src), 152 ip6_sprintf(&ip6->ip6_dst), 153 ip6->ip6_nxt, 154 if_name(m->m_pkthdr.rcvif)); 155 } 156 m_freem(m); 157 return; 158 } 159 160 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 161 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 162 icmp6_error(m, ICMP6_TIME_EXCEEDED, 163 ICMP6_TIME_EXCEED_TRANSIT, 0); 164 return; 165 } 166 ip6->ip6_hlim -= IPV6_HLIMDEC; 167 168 /* 169 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 170 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 171 * we need to generate an ICMP6 message to the src. 172 * Thanks to M_EXT, in most cases copy will not occur. 173 * 174 * It is important to save it before IPsec processing as IPsec 175 * processing may modify the mbuf. 176 */ 177 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 178 179 #ifdef IPSEC 180 /* get a security policy for this packet */ 181 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 182 &error); 183 if (sp == NULL) { 184 ipsec6stat.out_inval++; 185 ip6stat.ip6s_cantforward++; 186 if (mcopy) { 187 #if 0 188 /* XXX: what icmp ? */ 189 #else 190 m_freem(mcopy); 191 #endif 192 } 193 m_freem(m); 194 return; 195 } 196 197 error = 0; 198 199 /* check policy */ 200 switch (sp->policy) { 201 case IPSEC_POLICY_DISCARD: 202 /* 203 * This packet is just discarded. 204 */ 205 ipsec6stat.out_polvio++; 206 ip6stat.ip6s_cantforward++; 207 key_freesp(sp); 208 if (mcopy) { 209 #if 0 210 /* XXX: what icmp ? */ 211 #else 212 m_freem(mcopy); 213 #endif 214 } 215 m_freem(m); 216 return; 217 218 case IPSEC_POLICY_BYPASS: 219 case IPSEC_POLICY_NONE: 220 /* no need to do IPsec. */ 221 key_freesp(sp); 222 goto skip_ipsec; 223 224 case IPSEC_POLICY_IPSEC: 225 if (sp->req == NULL) { 226 /* XXX should be panic ? */ 227 printf("ip6_forward: No IPsec request specified.\n"); 228 ip6stat.ip6s_cantforward++; 229 key_freesp(sp); 230 if (mcopy) { 231 #if 0 232 /* XXX: what icmp ? */ 233 #else 234 m_freem(mcopy); 235 #endif 236 } 237 m_freem(m); 238 return; 239 } 240 /* do IPsec */ 241 break; 242 243 case IPSEC_POLICY_ENTRUST: 244 default: 245 /* should be panic ?? */ 246 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 247 key_freesp(sp); 248 goto skip_ipsec; 249 } 250 251 { 252 struct ipsec_output_state state; 253 254 /* 255 * All the extension headers will become inaccessible 256 * (since they can be encrypted). 257 * Don't panic, we need no more updates to extension headers 258 * on inner IPv6 packet (since they are now encapsulated). 259 * 260 * IPv6 [ESP|AH] IPv6 [extension headers] payload 261 */ 262 bzero(&state, sizeof(state)); 263 state.m = m; 264 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 265 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 266 267 error = ipsec6_output_tunnel(&state, sp, 0); 268 269 m = state.m; 270 key_freesp(sp); 271 272 if (error) { 273 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 274 switch (error) { 275 case EHOSTUNREACH: 276 case ENETUNREACH: 277 case EMSGSIZE: 278 case ENOBUFS: 279 case ENOMEM: 280 break; 281 default: 282 printf("ip6_output (ipsec): error code %d\n", error); 283 /* fall through */ 284 case ENOENT: 285 /* don't show these error codes to the user */ 286 break; 287 } 288 ip6stat.ip6s_cantforward++; 289 if (mcopy) { 290 #if 0 291 /* XXX: what icmp ? */ 292 #else 293 m_freem(mcopy); 294 #endif 295 } 296 m_freem(m); 297 return; 298 } 299 } 300 skip_ipsec: 301 #endif /* IPSEC */ 302 303 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 304 if (!srcrt) { 305 /* 306 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 307 */ 308 if (ip6_forward_rt.ro_rt == 0 || 309 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 310 if (ip6_forward_rt.ro_rt) { 311 RTFREE(ip6_forward_rt.ro_rt); 312 ip6_forward_rt.ro_rt = 0; 313 } 314 /* this probably fails but give it a try again */ 315 rtalloc_ign((struct route *)&ip6_forward_rt, 316 RTF_PRCLONING); 317 } 318 319 if (ip6_forward_rt.ro_rt == 0) { 320 ip6stat.ip6s_noroute++; 321 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 322 if (mcopy) { 323 icmp6_error(mcopy, ICMP6_DST_UNREACH, 324 ICMP6_DST_UNREACH_NOROUTE, 0); 325 } 326 m_freem(m); 327 return; 328 } 329 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 330 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 331 if (ip6_forward_rt.ro_rt) { 332 RTFREE(ip6_forward_rt.ro_rt); 333 ip6_forward_rt.ro_rt = 0; 334 } 335 bzero(dst, sizeof(*dst)); 336 dst->sin6_len = sizeof(struct sockaddr_in6); 337 dst->sin6_family = AF_INET6; 338 dst->sin6_addr = ip6->ip6_dst; 339 340 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 341 if (ip6_forward_rt.ro_rt == 0) { 342 ip6stat.ip6s_noroute++; 343 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 344 if (mcopy) { 345 icmp6_error(mcopy, ICMP6_DST_UNREACH, 346 ICMP6_DST_UNREACH_NOROUTE, 0); 347 } 348 m_freem(m); 349 return; 350 } 351 } 352 rt = ip6_forward_rt.ro_rt; 353 354 /* 355 * Scope check: if a packet can't be delivered to its destination 356 * for the reason that the destination is beyond the scope of the 357 * source address, discard the packet and return an icmp6 destination 358 * unreachable error with Code 2 (beyond scope of source address). 359 * [draft-ietf-ipngwg-icmp-v3-02.txt, Section 3.1] 360 */ 361 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 362 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 363 ip6stat.ip6s_cantforward++; 364 ip6stat.ip6s_badscope++; 365 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 366 367 if (ip6_log_time + ip6_log_interval < time_second) { 368 ip6_log_time = time_second; 369 log(LOG_DEBUG, 370 "cannot forward " 371 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 372 ip6_sprintf(&ip6->ip6_src), 373 ip6_sprintf(&ip6->ip6_dst), 374 ip6->ip6_nxt, 375 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 376 } 377 if (mcopy) 378 icmp6_error(mcopy, ICMP6_DST_UNREACH, 379 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 380 m_freem(m); 381 return; 382 } 383 384 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 385 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 386 if (mcopy) { 387 u_long mtu; 388 #ifdef IPSEC 389 struct secpolicy *sp; 390 int ipsecerror; 391 size_t ipsechdrsiz; 392 #endif 393 394 mtu = rt->rt_ifp->if_mtu; 395 #ifdef IPSEC 396 /* 397 * When we do IPsec tunnel ingress, we need to play 398 * with if_mtu value (decrement IPsec header size 399 * from mtu value). The code is much simpler than v4 400 * case, as we have the outgoing interface for 401 * encapsulated packet as "rt->rt_ifp". 402 */ 403 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 404 IP_FORWARDING, &ipsecerror); 405 if (sp) { 406 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 407 IPSEC_DIR_OUTBOUND, NULL); 408 if (ipsechdrsiz < mtu) 409 mtu -= ipsechdrsiz; 410 } 411 412 /* 413 * if mtu becomes less than minimum MTU, 414 * tell minimum MTU (and I'll need to fragment it). 415 */ 416 if (mtu < IPV6_MMTU) 417 mtu = IPV6_MMTU; 418 #endif 419 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 420 } 421 m_freem(m); 422 return; 423 } 424 425 if (rt->rt_flags & RTF_GATEWAY) 426 dst = (struct sockaddr_in6 *)rt->rt_gateway; 427 428 /* 429 * If we are to forward the packet using the same interface 430 * as one we got the packet from, perhaps we should send a redirect 431 * to sender to shortcut a hop. 432 * Only send redirect if source is sending directly to us, 433 * and if packet was not source routed (or has any options). 434 * Also, don't send redirect if forwarding using a route 435 * modified by a redirect. 436 */ 437 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 438 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 439 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 440 /* 441 * If the incoming interface is equal to the outgoing 442 * one, and the link attached to the interface is 443 * point-to-point, then it will be highly probable 444 * that a routing loop occurs. Thus, we immediately 445 * drop the packet and send an ICMPv6 error message. 446 * 447 * type/code is based on suggestion by Rich Draves. 448 * not sure if it is the best pick. 449 */ 450 icmp6_error(mcopy, ICMP6_DST_UNREACH, 451 ICMP6_DST_UNREACH_ADDR, 0); 452 m_freem(m); 453 return; 454 } 455 type = ND_REDIRECT; 456 } 457 458 /* 459 * Check with the firewall... 460 */ 461 if (ip6_fw_enable && ip6_fw_chk_ptr) { 462 u_short port = 0; 463 /* If ipfw says divert, we have to just drop packet */ 464 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 465 m_freem(m); 466 goto freecopy; 467 } 468 if (!m) 469 goto freecopy; 470 } 471 472 /* 473 * Fake scoped addresses. Note that even link-local source or 474 * destinaion can appear, if the originating node just sends the 475 * packet to us (without address resolution for the destination). 476 * Since both icmp6_error and icmp6_redirect_output fill the embedded 477 * link identifiers, we can do this stuff after making a copy for 478 * returning an error. 479 */ 480 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 481 /* 482 * See corresponding comments in ip6_output. 483 * XXX: but is it possible that ip6_forward() sends a packet 484 * to a loopback interface? I don't think so, and thus 485 * I bark here. (jinmei@kame.net) 486 * XXX: it is common to route invalid packets to loopback. 487 * also, the codepath will be visited on use of ::1 in 488 * rthdr. (itojun) 489 */ 490 #if 1 491 if (0) 492 #else 493 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 494 #endif 495 { 496 printf("ip6_forward: outgoing interface is loopback. " 497 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 498 ip6_sprintf(&ip6->ip6_src), 499 ip6_sprintf(&ip6->ip6_dst), 500 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 501 if_name(rt->rt_ifp)); 502 } 503 504 /* we can just use rcvif in forwarding. */ 505 origifp = m->m_pkthdr.rcvif; 506 } 507 else 508 origifp = rt->rt_ifp; 509 #ifndef SCOPEDROUTING 510 /* 511 * clear embedded scope identifiers if necessary. 512 * in6_clearscope will touch the addresses only when necessary. 513 */ 514 in6_clearscope(&ip6->ip6_src); 515 in6_clearscope(&ip6->ip6_dst); 516 #endif 517 518 /* 519 * Check if we want to allow this packet to be processed. 520 * Consider it to be bad if not. 521 */ 522 if (fr_checkp) { 523 struct mbuf *m1 = m; 524 525 if ((*fr_checkp)((struct ip *)ip6, sizeof(*ip6), 526 rt->rt_ifp, 1, &m1) != 0) 527 goto freecopy; 528 m = m1; 529 if (m == NULL) 530 goto freecopy; 531 ip6 = mtod(m, struct ip6_hdr *); 532 } 533 534 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 535 if (error) { 536 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 537 ip6stat.ip6s_cantforward++; 538 } else { 539 ip6stat.ip6s_forward++; 540 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 541 if (type) 542 ip6stat.ip6s_redirectsent++; 543 else { 544 if (mcopy) 545 goto freecopy; 546 } 547 } 548 if (mcopy == NULL) 549 return; 550 switch (error) { 551 case 0: 552 #if 1 553 if (type == ND_REDIRECT) { 554 icmp6_redirect_output(mcopy, rt); 555 return; 556 } 557 #endif 558 goto freecopy; 559 560 case EMSGSIZE: 561 /* xxx MTU is constant in PPP? */ 562 goto freecopy; 563 564 case ENOBUFS: 565 /* Tell source to slow down like source quench in IP? */ 566 goto freecopy; 567 568 case ENETUNREACH: /* shouldn't happen, checked above */ 569 case EHOSTUNREACH: 570 case ENETDOWN: 571 case EHOSTDOWN: 572 default: 573 type = ICMP6_DST_UNREACH; 574 code = ICMP6_DST_UNREACH_ADDR; 575 break; 576 } 577 icmp6_error(mcopy, type, code, 0); 578 return; 579 580 freecopy: 581 m_freem(mcopy); 582 return; 583 } 584