1 /* $FreeBSD$ */ 2 /* $KAME: ip6_forward.c,v 1.43 2000/07/16 07:50:49 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/mbuf.h> 41 #include <sys/domain.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/errno.h> 45 #include <sys/time.h> 46 #include <sys/syslog.h> 47 48 #include <net/if.h> 49 #include <net/route.h> 50 51 #include <netinet/in.h> 52 #include <netinet/in_var.h> 53 #include <netinet/ip_var.h> 54 #include <netinet/ip6.h> 55 #include <netinet6/ip6_var.h> 56 #include <netinet/icmp6.h> 57 #include <netinet6/nd6.h> 58 59 #ifdef IPSEC 60 #include <netinet6/ipsec.h> 61 #include <netinet6/ipsec6.h> 62 #include <netkey/key.h> 63 #endif /* IPSEC */ 64 65 #ifdef IPV6FIREWALL 66 #include <netinet6/ip6_fw.h> 67 #endif 68 69 #include <net/net_osdep.h> 70 71 struct route_in6 ip6_forward_rt; 72 73 /* 74 * Forward a packet. If some error occurs return the sender 75 * an icmp packet. Note we can't always generate a meaningful 76 * icmp message because icmp doesn't have a large enough repertoire 77 * of codes and types. 78 * 79 * If not forwarding, just drop the packet. This could be confusing 80 * if ipforwarding was zero but some routing protocol was advancing 81 * us as a gateway to somewhere. However, we must let the routing 82 * protocol deal with that. 83 * 84 */ 85 86 void 87 ip6_forward(m, srcrt) 88 struct mbuf *m; 89 int srcrt; 90 { 91 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 92 register struct sockaddr_in6 *dst; 93 register struct rtentry *rt; 94 int error, type = 0, code = 0; 95 struct mbuf *mcopy = NULL; 96 struct ifnet *origifp; /* maybe unnecessary */ 97 #ifdef IPSEC 98 struct secpolicy *sp = NULL; 99 #endif 100 101 #ifdef IPSEC 102 /* 103 * Check AH/ESP integrity. 104 */ 105 /* 106 * Don't increment ip6s_cantforward because this is the check 107 * before forwarding packet actually. 108 */ 109 if (ipsec6_in_reject(m, NULL)) { 110 ipsec6stat.in_polvio++; 111 m_freem(m); 112 return; 113 } 114 #endif /*IPSEC*/ 115 116 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 117 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) { 118 ip6stat.ip6s_cantforward++; 119 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 120 if (ip6_log_time + ip6_log_interval < time_second) { 121 ip6_log_time = time_second; 122 log(LOG_DEBUG, 123 "cannot forward " 124 "from %s to %s nxt %d received on %s\n", 125 ip6_sprintf(&ip6->ip6_src), 126 ip6_sprintf(&ip6->ip6_dst), 127 ip6->ip6_nxt, 128 if_name(m->m_pkthdr.rcvif)); 129 } 130 m_freem(m); 131 return; 132 } 133 134 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 135 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 136 icmp6_error(m, ICMP6_TIME_EXCEEDED, 137 ICMP6_TIME_EXCEED_TRANSIT, 0); 138 return; 139 } 140 ip6->ip6_hlim -= IPV6_HLIMDEC; 141 142 /* 143 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 144 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 145 * we need to generate an ICMP6 message to the src. 146 * Thanks to M_EXT, in most cases copy will not occur. 147 * 148 * It is important to save it before IPsec processing as IPsec 149 * processing may modify the mbuf. 150 */ 151 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 152 153 #ifdef IPSEC 154 /* get a security policy for this packet */ 155 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, 0, &error); 156 if (sp == NULL) { 157 ipsec6stat.out_inval++; 158 ip6stat.ip6s_cantforward++; 159 if (mcopy) { 160 #if 0 161 /* XXX: what icmp ? */ 162 #else 163 m_freem(mcopy); 164 #endif 165 } 166 m_freem(m); 167 return; 168 } 169 170 error = 0; 171 172 /* check policy */ 173 switch (sp->policy) { 174 case IPSEC_POLICY_DISCARD: 175 /* 176 * This packet is just discarded. 177 */ 178 ipsec6stat.out_polvio++; 179 ip6stat.ip6s_cantforward++; 180 key_freesp(sp); 181 if (mcopy) { 182 #if 0 183 /* XXX: what icmp ? */ 184 #else 185 m_freem(mcopy); 186 #endif 187 } 188 m_freem(m); 189 return; 190 191 case IPSEC_POLICY_BYPASS: 192 case IPSEC_POLICY_NONE: 193 /* no need to do IPsec. */ 194 key_freesp(sp); 195 goto skip_ipsec; 196 197 case IPSEC_POLICY_IPSEC: 198 if (sp->req == NULL) { 199 /* XXX should be panic ? */ 200 printf("ip6_forward: No IPsec request specified.\n"); 201 ip6stat.ip6s_cantforward++; 202 key_freesp(sp); 203 if (mcopy) { 204 #if 0 205 /* XXX: what icmp ? */ 206 #else 207 m_freem(mcopy); 208 #endif 209 } 210 m_freem(m); 211 return; 212 } 213 /* do IPsec */ 214 break; 215 216 case IPSEC_POLICY_ENTRUST: 217 default: 218 /* should be panic ?? */ 219 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 220 key_freesp(sp); 221 goto skip_ipsec; 222 } 223 224 { 225 struct ipsec_output_state state; 226 227 /* 228 * All the extension headers will become inaccessible 229 * (since they can be encrypted). 230 * Don't panic, we need no more updates to extension headers 231 * on inner IPv6 packet (since they are now encapsulated). 232 * 233 * IPv6 [ESP|AH] IPv6 [extension headers] payload 234 */ 235 bzero(&state, sizeof(state)); 236 state.m = m; 237 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 238 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 239 240 error = ipsec6_output_tunnel(&state, sp, 0); 241 242 m = state.m; 243 #if 0 /* XXX allocate a route (ro, dst) again later */ 244 ro = (struct route_in6 *)state.ro; 245 dst = (struct sockaddr_in6 *)state.dst; 246 #endif 247 key_freesp(sp); 248 249 if (error) { 250 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 251 switch (error) { 252 case EHOSTUNREACH: 253 case ENETUNREACH: 254 case EMSGSIZE: 255 case ENOBUFS: 256 case ENOMEM: 257 break; 258 default: 259 printf("ip6_output (ipsec): error code %d\n", error); 260 /*fall through*/ 261 case ENOENT: 262 /* don't show these error codes to the user */ 263 break; 264 } 265 ip6stat.ip6s_cantforward++; 266 if (mcopy) { 267 #if 0 268 /* XXX: what icmp ? */ 269 #else 270 m_freem(mcopy); 271 #endif 272 } 273 m_freem(m); 274 return; 275 } 276 } 277 skip_ipsec: 278 #endif /* IPSEC */ 279 280 dst = &ip6_forward_rt.ro_dst; 281 if (!srcrt) { 282 /* 283 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 284 */ 285 if (ip6_forward_rt.ro_rt == 0 || 286 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 287 if (ip6_forward_rt.ro_rt) { 288 RTFREE(ip6_forward_rt.ro_rt); 289 ip6_forward_rt.ro_rt = 0; 290 } 291 /* this probably fails but give it a try again */ 292 rtalloc_ign((struct route *)&ip6_forward_rt, 293 RTF_PRCLONING); 294 } 295 296 if (ip6_forward_rt.ro_rt == 0) { 297 ip6stat.ip6s_noroute++; 298 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 299 if (mcopy) { 300 icmp6_error(mcopy, ICMP6_DST_UNREACH, 301 ICMP6_DST_UNREACH_NOROUTE, 0); 302 } 303 m_freem(m); 304 return; 305 } 306 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 307 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 308 if (ip6_forward_rt.ro_rt) { 309 RTFREE(ip6_forward_rt.ro_rt); 310 ip6_forward_rt.ro_rt = 0; 311 } 312 bzero(dst, sizeof(*dst)); 313 dst->sin6_len = sizeof(struct sockaddr_in6); 314 dst->sin6_family = AF_INET6; 315 dst->sin6_addr = ip6->ip6_dst; 316 317 rtalloc_ign((struct route *)&ip6_forward_rt, RTF_PRCLONING); 318 if (ip6_forward_rt.ro_rt == 0) { 319 ip6stat.ip6s_noroute++; 320 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 321 if (mcopy) { 322 icmp6_error(mcopy, ICMP6_DST_UNREACH, 323 ICMP6_DST_UNREACH_NOROUTE, 0); 324 } 325 m_freem(m); 326 return; 327 } 328 } 329 rt = ip6_forward_rt.ro_rt; 330 331 /* 332 * Scope check: if a packet can't be delivered to its destination 333 * for the reason that the destination is beyond the scope of the 334 * source address, discard the packet and return an icmp6 destination 335 * unreachable error with Code 2 (beyond scope of source address). 336 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 337 */ 338 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 339 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 340 ip6stat.ip6s_cantforward++; 341 ip6stat.ip6s_badscope++; 342 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 343 344 if (ip6_log_time + ip6_log_interval < time_second) { 345 ip6_log_time = time_second; 346 log(LOG_DEBUG, 347 "cannot forward " 348 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 349 ip6_sprintf(&ip6->ip6_src), 350 ip6_sprintf(&ip6->ip6_dst), 351 ip6->ip6_nxt, 352 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 353 } 354 if (mcopy) 355 icmp6_error(mcopy, ICMP6_DST_UNREACH, 356 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 357 m_freem(m); 358 return; 359 } 360 361 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 362 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 363 if (mcopy) { 364 u_long mtu; 365 #ifdef IPSEC 366 struct secpolicy *sp; 367 int ipsecerror; 368 size_t ipsechdrsiz; 369 #endif 370 371 mtu = rt->rt_ifp->if_mtu; 372 #ifdef IPSEC 373 /* 374 * When we do IPsec tunnel ingress, we need to play 375 * with if_mtu value (decrement IPsec header size 376 * from mtu value). The code is much simpler than v4 377 * case, as we have the outgoing interface for 378 * encapsulated packet as "rt->rt_ifp". 379 */ 380 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 381 IP_FORWARDING, &ipsecerror); 382 if (sp) { 383 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 384 IPSEC_DIR_OUTBOUND, NULL); 385 if (ipsechdrsiz < mtu) 386 mtu -= ipsechdrsiz; 387 } 388 389 /* 390 * if mtu becomes less than minimum MTU, 391 * tell minimum MTU (and I'll need to fragment it). 392 */ 393 if (mtu < IPV6_MMTU) 394 mtu = IPV6_MMTU; 395 #endif 396 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 397 } 398 m_freem(m); 399 return; 400 } 401 402 if (rt->rt_flags & RTF_GATEWAY) 403 dst = (struct sockaddr_in6 *)rt->rt_gateway; 404 405 /* 406 * If we are to forward the packet using the same interface 407 * as one we got the packet from, perhaps we should send a redirect 408 * to sender to shortcut a hop. 409 * Only send redirect if source is sending directly to us, 410 * and if packet was not source routed (or has any options). 411 * Also, don't send redirect if forwarding using a route 412 * modified by a redirect. 413 */ 414 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 415 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) 416 type = ND_REDIRECT; 417 418 #ifdef IPV6FIREWALL 419 /* 420 * Check with the firewall... 421 */ 422 if (ip6_fw_chk_ptr) { 423 u_short port = 0; 424 /* If ipfw says divert, we have to just drop packet */ 425 if ((*ip6_fw_chk_ptr)(&ip6, rt->rt_ifp, &port, &m)) { 426 m_freem(m); 427 goto freecopy; 428 } 429 if (!m) 430 goto freecopy; 431 } 432 #endif 433 434 /* 435 * Fake scoped addresses. Note that even link-local source or 436 * destinaion can appear, if the originating node just sends the 437 * packet to us (without address resolution for the destination). 438 * Since both icmp6_error and icmp6_redirect_output fill the embedded 439 * link identifiers, we can do this stuff after make a copy for 440 * returning error. 441 */ 442 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 443 /* 444 * See corresponding comments in ip6_output. 445 * XXX: but is it possible that ip6_forward() sends a packet 446 * to a loopback interface? I don't think so, and thus 447 * I bark here. (jinmei@kame.net) 448 * XXX: it is common to route invalid packets to loopback. 449 * also, the codepath will be visited on use of ::1 in 450 * rthdr. (itojun) 451 */ 452 #if 1 453 if (0) 454 #else 455 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 456 #endif 457 { 458 printf("ip6_forward: outgoing interface is loopback. " 459 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 460 ip6_sprintf(&ip6->ip6_src), 461 ip6_sprintf(&ip6->ip6_dst), 462 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 463 if_name(rt->rt_ifp)); 464 } 465 466 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 467 origifp = ifindex2ifnet[ntohs(ip6->ip6_src.s6_addr16[1])]; 468 else if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 469 origifp = ifindex2ifnet[ntohs(ip6->ip6_dst.s6_addr16[1])]; 470 else 471 origifp = rt->rt_ifp; 472 } 473 else 474 origifp = rt->rt_ifp; 475 #ifndef FAKE_LOOPBACK_IF 476 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) == 0) 477 #else 478 if (1) 479 #endif 480 { 481 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 482 ip6->ip6_src.s6_addr16[1] = 0; 483 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 484 ip6->ip6_dst.s6_addr16[1] = 0; 485 } 486 487 #ifdef OLDIP6OUTPUT 488 error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m, 489 (struct sockaddr *)dst, 490 ip6_forward_rt.ro_rt); 491 #else 492 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 493 #endif 494 if (error) { 495 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 496 ip6stat.ip6s_cantforward++; 497 } else { 498 ip6stat.ip6s_forward++; 499 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 500 if (type) 501 ip6stat.ip6s_redirectsent++; 502 else { 503 if (mcopy) 504 goto freecopy; 505 } 506 } 507 if (mcopy == NULL) 508 return; 509 510 switch (error) { 511 case 0: 512 #if 1 513 if (type == ND_REDIRECT) { 514 icmp6_redirect_output(mcopy, rt); 515 return; 516 } 517 #endif 518 goto freecopy; 519 520 case EMSGSIZE: 521 /* xxx MTU is constant in PPP? */ 522 goto freecopy; 523 524 case ENOBUFS: 525 /* Tell source to slow down like source quench in IP? */ 526 goto freecopy; 527 528 case ENETUNREACH: /* shouldn't happen, checked above */ 529 case EHOSTUNREACH: 530 case ENETDOWN: 531 case EHOSTDOWN: 532 default: 533 type = ICMP6_DST_UNREACH; 534 code = ICMP6_DST_UNREACH_ADDR; 535 break; 536 } 537 icmp6_error(mcopy, type, code, 0); 538 return; 539 540 freecopy: 541 m_freem(mcopy); 542 return; 543 } 544