1 /* $FreeBSD$ */ 2 /* $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ */ 3 4 /* 5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the project nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #include "opt_ip6fw.h" 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/domain.h> 43 #include <sys/protosw.h> 44 #include <sys/socket.h> 45 #include <sys/errno.h> 46 #include <sys/time.h> 47 #include <sys/kernel.h> 48 #include <sys/syslog.h> 49 50 #include <net/if.h> 51 #include <net/route.h> 52 #ifdef PFIL_HOOKS 53 #include <net/pfil.h> 54 #endif 55 56 #include <netinet/in.h> 57 #include <netinet/in_var.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/ip_var.h> 61 #include <netinet6/in6_var.h> 62 #include <netinet/ip6.h> 63 #include <netinet6/ip6_var.h> 64 #include <netinet/icmp6.h> 65 #include <netinet6/nd6.h> 66 67 #include <netinet/in_pcb.h> 68 69 #ifdef IPSEC 70 #include <netinet6/ipsec.h> 71 #ifdef INET6 72 #include <netinet6/ipsec6.h> 73 #endif 74 #include <netkey/key.h> 75 #endif /* IPSEC */ 76 77 #include <netinet6/ip6_fw.h> 78 79 #include <net/net_osdep.h> 80 81 #include <netinet6/ip6protosw.h> 82 83 extern struct ip6protosw inet6sw[]; 84 extern u_char ip6_protox[IPPROTO_MAX]; 85 86 struct route_in6 ip6_forward_rt; 87 88 /* 89 * Forward a packet. If some error occurs return the sender 90 * an icmp packet. Note we can't always generate a meaningful 91 * icmp message because icmp doesn't have a large enough repertoire 92 * of codes and types. 93 * 94 * If not forwarding, just drop the packet. This could be confusing 95 * if ipforwarding was zero but some routing protocol was advancing 96 * us as a gateway to somewhere. However, we must let the routing 97 * protocol deal with that. 98 * 99 */ 100 101 void 102 ip6_forward(m, srcrt) 103 struct mbuf *m; 104 int srcrt; 105 { 106 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 107 struct sockaddr_in6 *dst; 108 struct rtentry *rt; 109 int error, type = 0, code = 0; 110 struct mbuf *mcopy = NULL; 111 struct ifnet *origifp; /* maybe unnecessary */ 112 #ifdef PFIL_HOOKS 113 struct packet_filter_hook *pfh; 114 struct mbuf *m1; 115 int rv; 116 #endif /* PFIL_HOOKS */ 117 #ifdef IPSEC 118 struct secpolicy *sp = NULL; 119 #endif 120 121 #ifdef IPSEC 122 /* 123 * Check AH/ESP integrity. 124 */ 125 /* 126 * Don't increment ip6s_cantforward because this is the check 127 * before forwarding packet actually. 128 */ 129 if (ipsec6_in_reject(m, NULL)) { 130 ipsec6stat.in_polvio++; 131 m_freem(m); 132 return; 133 } 134 #endif /*IPSEC*/ 135 136 /* 137 * Do not forward packets to multicast destination (should be handled 138 * by ip6_mforward(). 139 * Do not forward packets with unspecified source. It was discussed 140 * in July 2000, on ipngwg mailing list. 141 */ 142 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 143 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 144 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 145 ip6stat.ip6s_cantforward++; 146 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 147 if (ip6_log_time + ip6_log_interval < time_second) { 148 ip6_log_time = time_second; 149 log(LOG_DEBUG, 150 "cannot forward " 151 "from %s to %s nxt %d received on %s\n", 152 ip6_sprintf(&ip6->ip6_src), 153 ip6_sprintf(&ip6->ip6_dst), 154 ip6->ip6_nxt, 155 if_name(m->m_pkthdr.rcvif)); 156 } 157 m_freem(m); 158 return; 159 } 160 161 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 162 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 163 icmp6_error(m, ICMP6_TIME_EXCEEDED, 164 ICMP6_TIME_EXCEED_TRANSIT, 0); 165 return; 166 } 167 ip6->ip6_hlim -= IPV6_HLIMDEC; 168 169 /* 170 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 171 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 172 * we need to generate an ICMP6 message to the src. 173 * Thanks to M_EXT, in most cases copy will not occur. 174 * 175 * It is important to save it before IPsec processing as IPsec 176 * processing may modify the mbuf. 177 */ 178 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 179 180 #ifdef IPSEC 181 /* get a security policy for this packet */ 182 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 183 &error); 184 if (sp == NULL) { 185 ipsec6stat.out_inval++; 186 ip6stat.ip6s_cantforward++; 187 if (mcopy) { 188 #if 0 189 /* XXX: what icmp ? */ 190 #else 191 m_freem(mcopy); 192 #endif 193 } 194 m_freem(m); 195 return; 196 } 197 198 error = 0; 199 200 /* check policy */ 201 switch (sp->policy) { 202 case IPSEC_POLICY_DISCARD: 203 /* 204 * This packet is just discarded. 205 */ 206 ipsec6stat.out_polvio++; 207 ip6stat.ip6s_cantforward++; 208 key_freesp(sp); 209 if (mcopy) { 210 #if 0 211 /* XXX: what icmp ? */ 212 #else 213 m_freem(mcopy); 214 #endif 215 } 216 m_freem(m); 217 return; 218 219 case IPSEC_POLICY_BYPASS: 220 case IPSEC_POLICY_NONE: 221 /* no need to do IPsec. */ 222 key_freesp(sp); 223 goto skip_ipsec; 224 225 case IPSEC_POLICY_IPSEC: 226 if (sp->req == NULL) { 227 /* XXX should be panic ? */ 228 printf("ip6_forward: No IPsec request specified.\n"); 229 ip6stat.ip6s_cantforward++; 230 key_freesp(sp); 231 if (mcopy) { 232 #if 0 233 /* XXX: what icmp ? */ 234 #else 235 m_freem(mcopy); 236 #endif 237 } 238 m_freem(m); 239 return; 240 } 241 /* do IPsec */ 242 break; 243 244 case IPSEC_POLICY_ENTRUST: 245 default: 246 /* should be panic ?? */ 247 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 248 key_freesp(sp); 249 goto skip_ipsec; 250 } 251 252 { 253 struct ipsec_output_state state; 254 255 /* 256 * All the extension headers will become inaccessible 257 * (since they can be encrypted). 258 * Don't panic, we need no more updates to extension headers 259 * on inner IPv6 packet (since they are now encapsulated). 260 * 261 * IPv6 [ESP|AH] IPv6 [extension headers] payload 262 */ 263 bzero(&state, sizeof(state)); 264 state.m = m; 265 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 266 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 267 268 error = ipsec6_output_tunnel(&state, sp, 0); 269 270 m = state.m; 271 key_freesp(sp); 272 273 if (error) { 274 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 275 switch (error) { 276 case EHOSTUNREACH: 277 case ENETUNREACH: 278 case EMSGSIZE: 279 case ENOBUFS: 280 case ENOMEM: 281 break; 282 default: 283 printf("ip6_output (ipsec): error code %d\n", error); 284 /*fall through*/ 285 case ENOENT: 286 /* don't show these error codes to the user */ 287 break; 288 } 289 ip6stat.ip6s_cantforward++; 290 if (mcopy) { 291 #if 0 292 /* XXX: what icmp ? */ 293 #else 294 m_freem(mcopy); 295 #endif 296 } 297 m_freem(m); 298 return; 299 } 300 } 301 skip_ipsec: 302 #endif /* IPSEC */ 303 304 dst = (struct sockaddr_in6 *)&ip6_forward_rt.ro_dst; 305 if (!srcrt) { 306 /* 307 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 308 */ 309 if (ip6_forward_rt.ro_rt == 0 || 310 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 311 if (ip6_forward_rt.ro_rt) { 312 RTFREE(ip6_forward_rt.ro_rt); 313 ip6_forward_rt.ro_rt = 0; 314 } 315 /* this probably fails but give it a try again */ 316 rtalloc_ign((struct route *)&ip6_forward_rt, 317 RTF_PRCLONING); 318 } 319 320 if (ip6_forward_rt.ro_rt == 0) { 321 ip6stat.ip6s_noroute++; 322 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 323 if (mcopy) { 324 icmp6_error(mcopy, ICMP6_DST_UNREACH, 325 ICMP6_DST_UNREACH_NOROUTE, 0); 326 } 327 m_freem(m); 328 return; 329 } 330 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 331 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 332 if (ip6_forward_rt.ro_rt) { 333 RTFREE(ip6_forward_rt.ro_rt); 334 ip6_forward_rt.ro_rt = 0; 335 } 336 bzero(dst, sizeof(*dst)); 337 dst->sin6_len = sizeof(struct sockaddr_in6); 338 dst->sin6_family = AF_INET6; 339 dst->sin6_addr = ip6->ip6_dst; 340 341 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 342 if (ip6_forward_rt.ro_rt == 0) { 343 ip6stat.ip6s_noroute++; 344 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 345 if (mcopy) { 346 icmp6_error(mcopy, ICMP6_DST_UNREACH, 347 ICMP6_DST_UNREACH_NOROUTE, 0); 348 } 349 m_freem(m); 350 return; 351 } 352 } 353 rt = ip6_forward_rt.ro_rt; 354 355 /* 356 * Scope check: if a packet can't be delivered to its destination 357 * for the reason that the destination is beyond the scope of the 358 * source address, discard the packet and return an icmp6 destination 359 * unreachable error with Code 2 (beyond scope of source address). 360 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 361 */ 362 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 363 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 364 ip6stat.ip6s_cantforward++; 365 ip6stat.ip6s_badscope++; 366 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 367 368 if (ip6_log_time + ip6_log_interval < time_second) { 369 ip6_log_time = time_second; 370 log(LOG_DEBUG, 371 "cannot forward " 372 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 373 ip6_sprintf(&ip6->ip6_src), 374 ip6_sprintf(&ip6->ip6_dst), 375 ip6->ip6_nxt, 376 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 377 } 378 if (mcopy) 379 icmp6_error(mcopy, ICMP6_DST_UNREACH, 380 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 381 m_freem(m); 382 return; 383 } 384 385 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 386 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 387 if (mcopy) { 388 u_long mtu; 389 #ifdef IPSEC 390 struct secpolicy *sp; 391 int ipsecerror; 392 size_t ipsechdrsiz; 393 #endif 394 395 mtu = rt->rt_ifp->if_mtu; 396 #ifdef IPSEC 397 /* 398 * When we do IPsec tunnel ingress, we need to play 399 * with if_mtu value (decrement IPsec header size 400 * from mtu value). The code is much simpler than v4 401 * case, as we have the outgoing interface for 402 * encapsulated packet as "rt->rt_ifp". 403 */ 404 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 405 IP_FORWARDING, &ipsecerror); 406 if (sp) { 407 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 408 IPSEC_DIR_OUTBOUND, NULL); 409 if (ipsechdrsiz < mtu) 410 mtu -= ipsechdrsiz; 411 } 412 413 /* 414 * if mtu becomes less than minimum MTU, 415 * tell minimum MTU (and I'll need to fragment it). 416 */ 417 if (mtu < IPV6_MMTU) 418 mtu = IPV6_MMTU; 419 #endif 420 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 421 } 422 m_freem(m); 423 return; 424 } 425 426 if (rt->rt_flags & RTF_GATEWAY) 427 dst = (struct sockaddr_in6 *)rt->rt_gateway; 428 429 /* 430 * If we are to forward the packet using the same interface 431 * as one we got the packet from, perhaps we should send a redirect 432 * to sender to shortcut a hop. 433 * Only send redirect if source is sending directly to us, 434 * and if packet was not source routed (or has any options). 435 * Also, don't send redirect if forwarding using a route 436 * modified by a redirect. 437 */ 438 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 439 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 440 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) != 0) { 441 /* 442 * If the incoming interface is equal to the outgoing 443 * one, and the link attached to the interface is 444 * point-to-point, then it will be highly probable 445 * that a routing loop occurs. Thus, we immediately 446 * drop the packet and send an ICMPv6 error message. 447 * 448 * type/code is based on suggestion by Rich Draves. 449 * not sure if it is the best pick. 450 */ 451 icmp6_error(mcopy, ICMP6_DST_UNREACH, 452 ICMP6_DST_UNREACH_ADDR, 0); 453 m_freem(m); 454 return; 455 } 456 type = ND_REDIRECT; 457 } 458 459 /* 460 * Check with the firewall... 461 */ 462 if (ip6_fw_enable && ip6_fw_chk_ptr) { 463 u_short port = 0; 464 /* If ipfw says divert, we have to just drop packet */ 465 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 466 m_freem(m); 467 goto freecopy; 468 } 469 if (!m) 470 goto freecopy; 471 } 472 473 /* 474 * Fake scoped addresses. Note that even link-local source or 475 * destinaion can appear, if the originating node just sends the 476 * packet to us (without address resolution for the destination). 477 * Since both icmp6_error and icmp6_redirect_output fill the embedded 478 * link identifiers, we can do this stuff after making a copy for 479 * returning an error. 480 */ 481 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 482 /* 483 * See corresponding comments in ip6_output. 484 * XXX: but is it possible that ip6_forward() sends a packet 485 * to a loopback interface? I don't think so, and thus 486 * I bark here. (jinmei@kame.net) 487 * XXX: it is common to route invalid packets to loopback. 488 * also, the codepath will be visited on use of ::1 in 489 * rthdr. (itojun) 490 */ 491 #if 1 492 if (0) 493 #else 494 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 495 #endif 496 { 497 printf("ip6_forward: outgoing interface is loopback. " 498 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 499 ip6_sprintf(&ip6->ip6_src), 500 ip6_sprintf(&ip6->ip6_dst), 501 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 502 if_name(rt->rt_ifp)); 503 } 504 505 /* we can just use rcvif in forwarding. */ 506 origifp = m->m_pkthdr.rcvif; 507 } 508 else 509 origifp = rt->rt_ifp; 510 #ifndef SCOPEDROUTING 511 /* 512 * clear embedded scope identifiers if necessary. 513 * in6_clearscope will touch the addresses only when necessary. 514 */ 515 in6_clearscope(&ip6->ip6_src); 516 in6_clearscope(&ip6->ip6_dst); 517 #endif 518 519 #ifdef PFIL_HOOKS 520 /* 521 * Run through list of hooks for output packets. 522 */ 523 m1 = m; 524 pfh = pfil_hook_get(PFIL_OUT, &inet6sw[ip6_protox[IPPROTO_IPV6]].pr_pfh); 525 for (; pfh; pfh = pfh->pfil_link.tqe_next) 526 if (pfh->pfil_func) { 527 rv = pfh->pfil_func(ip6, sizeof(*ip6), 528 rt->rt_ifp, 1, &m1); 529 if (rv) { 530 error = EHOSTUNREACH; 531 goto freecopy; 532 } 533 m = m1; 534 if (m == NULL) 535 goto freecopy; 536 ip6 = mtod(m, struct ip6_hdr *); 537 } 538 #endif /* PFIL_HOOKS */ 539 540 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 541 if (error) { 542 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 543 ip6stat.ip6s_cantforward++; 544 } else { 545 ip6stat.ip6s_forward++; 546 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 547 if (type) 548 ip6stat.ip6s_redirectsent++; 549 else { 550 if (mcopy) 551 goto freecopy; 552 } 553 } 554 if (mcopy == NULL) 555 return; 556 557 switch (error) { 558 case 0: 559 #if 1 560 if (type == ND_REDIRECT) { 561 icmp6_redirect_output(mcopy, rt); 562 return; 563 } 564 #endif 565 goto freecopy; 566 567 case EMSGSIZE: 568 /* xxx MTU is constant in PPP? */ 569 goto freecopy; 570 571 case ENOBUFS: 572 /* Tell source to slow down like source quench in IP? */ 573 goto freecopy; 574 575 case ENETUNREACH: /* shouldn't happen, checked above */ 576 case EHOSTUNREACH: 577 case ENETDOWN: 578 case EHOSTDOWN: 579 default: 580 type = ICMP6_DST_UNREACH; 581 code = ICMP6_DST_UNREACH_ADDR; 582 break; 583 } 584 icmp6_error(mcopy, type, code, 0); 585 return; 586 587 freecopy: 588 m_freem(mcopy); 589 return; 590 } 591