1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the project nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * $KAME: ip6_forward.c,v 1.69 2001/05/17 03:48:30 itojun Exp $ 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_ipstealth.h" 41 #include "opt_sctp.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/domain.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/errno.h> 51 #include <sys/time.h> 52 #include <sys/kernel.h> 53 #include <sys/syslog.h> 54 55 #include <net/if.h> 56 #include <net/if_var.h> 57 #include <net/netisr.h> 58 #include <net/route.h> 59 #include <net/route/nhop.h> 60 #include <net/pfil.h> 61 62 #include <netinet/in.h> 63 #include <netinet/in_var.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/ip_var.h> 67 #include <netinet6/in6_var.h> 68 #include <netinet/ip6.h> 69 #include <netinet6/in6_fib.h> 70 #include <netinet6/ip6_var.h> 71 #include <netinet6/scope6_var.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/nd6.h> 74 75 #include <netinet/in_pcb.h> 76 77 #include <netipsec/ipsec_support.h> 78 79 /* 80 * Forward a packet. If some error occurs return the sender 81 * an icmp packet. Note we can't always generate a meaningful 82 * icmp message because icmp doesn't have a large enough repertoire 83 * of codes and types. 84 * 85 * If not forwarding, just drop the packet. This could be confusing 86 * if ipforwarding was zero but some routing protocol was advancing 87 * us as a gateway to somewhere. However, we must let the routing 88 * protocol deal with that. 89 * 90 */ 91 void 92 ip6_forward(struct mbuf *m, int srcrt) 93 { 94 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 95 struct sockaddr_in6 dst; 96 struct nhop_object *nh = NULL; 97 int error, type = 0, code = 0; 98 struct mbuf *mcopy = NULL; 99 struct ifnet *origifp; /* maybe unnecessary */ 100 u_int32_t inzone, outzone; 101 struct in6_addr odst; 102 struct m_tag *fwd_tag; 103 char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN]; 104 105 /* 106 * Do not forward packets to multicast destination (should be handled 107 * by ip6_mforward(). 108 * Do not forward packets with unspecified source. It was discussed 109 * in July 2000, on the ipngwg mailing list. 110 */ 111 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 112 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 113 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 114 IP6STAT_INC(ip6s_cantforward); 115 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 116 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 117 V_ip6_log_time = time_uptime; 118 log(LOG_DEBUG, 119 "cannot forward " 120 "from %s to %s nxt %d received on %s\n", 121 ip6_sprintf(ip6bufs, &ip6->ip6_src), 122 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 123 ip6->ip6_nxt, 124 if_name(m->m_pkthdr.rcvif)); 125 } 126 m_freem(m); 127 return; 128 } 129 130 if ( 131 #ifdef IPSTEALTH 132 V_ip6stealth == 0 && 133 #endif 134 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 } 140 141 /* 142 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 143 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 144 * we need to generate an ICMP6 message to the src. 145 * Thanks to M_EXT, in most cases copy will not occur. 146 * 147 * It is important to save it before IPsec processing as IPsec 148 * processing may modify the mbuf. 149 */ 150 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 151 M_NOWAIT); 152 #ifdef IPSTEALTH 153 if (V_ip6stealth == 0) 154 #endif 155 ip6->ip6_hlim -= IPV6_HLIMDEC; 156 157 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 158 if (IPSEC_ENABLED(ipv6)) { 159 if ((error = IPSEC_FORWARD(ipv6, m)) != 0) { 160 /* mbuf consumed by IPsec */ 161 m_freem(mcopy); 162 if (error != EINPROGRESS) 163 IP6STAT_INC(ip6s_cantforward); 164 return; 165 } 166 /* No IPsec processing required */ 167 } 168 #endif 169 /* 170 * ip6_forward() operates with IPv6 addresses with deembedded scope. 171 * 172 * There are 3 sources of IPv6 destination address: 173 * 174 * 1) ip6_input(), where ip6_dst contains deembedded address. 175 * In order to deal with forwarding of link-local packets, 176 * calculate the scope based on input interface (RFC 4007, clause 9). 177 * 2) packet filters changing ip6_dst directly. It would embed scope 178 * for LL addresses, so in6_localip() performs properly. 179 * 3) packet filters attaching PACKET_TAG_IPFORWARD would embed 180 * scope for the nexthop. 181 */ 182 bzero(&dst, sizeof(struct sockaddr_in6)); 183 dst.sin6_family = AF_INET6; 184 dst.sin6_addr = ip6->ip6_dst; 185 dst.sin6_scope_id = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 186 again: 187 nh = fib6_lookup(M_GETFIB(m), &dst.sin6_addr, dst.sin6_scope_id, 188 NHR_REF, m->m_pkthdr.flowid); 189 if (nh == NULL) { 190 IP6STAT_INC(ip6s_noroute); 191 in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_noroute); 192 if (mcopy) { 193 icmp6_error(mcopy, ICMP6_DST_UNREACH, 194 ICMP6_DST_UNREACH_NOROUTE, 0); 195 } 196 goto bad; 197 } 198 199 /* 200 * Source scope check: if a packet can't be delivered to its 201 * destination for the reason that the destination is beyond the scope 202 * of the source address, discard the packet and return an icmp6 203 * destination unreachable error with Code 2 (beyond scope of source 204 * address). 205 * [draft-ietf-ipngwg-icmp-v3-04.txt, Section 3.1] 206 */ 207 outzone = in6_get_unicast_scopeid(&ip6->ip6_src, nh->nh_ifp); 208 inzone = in6_get_unicast_scopeid(&ip6->ip6_src, m->m_pkthdr.rcvif); 209 if (inzone != outzone) { 210 IP6STAT_INC(ip6s_cantforward); 211 IP6STAT_INC(ip6s_badscope); 212 in6_ifstat_inc(nh->nh_ifp, ifs6_in_discard); 213 214 if (V_ip6_log_time + V_ip6_log_interval < time_uptime) { 215 V_ip6_log_time = time_uptime; 216 log(LOG_DEBUG, 217 "cannot forward " 218 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 219 ip6_sprintf(ip6bufs, &ip6->ip6_src), 220 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 221 ip6->ip6_nxt, 222 if_name(m->m_pkthdr.rcvif), if_name(nh->nh_ifp)); 223 } 224 if (mcopy) 225 icmp6_error(mcopy, ICMP6_DST_UNREACH, 226 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 227 goto bad; 228 } 229 230 /* 231 * Destination scope check: if a packet is going to break the scope 232 * zone of packet's destination address, discard it. This case should 233 * usually be prevented by appropriately-configured routing table, but 234 * we need an explicit check because we may mistakenly forward the 235 * packet to a different zone by (e.g.) a default route. 236 */ 237 inzone = in6_get_unicast_scopeid(&ip6->ip6_dst, m->m_pkthdr.rcvif); 238 outzone = in6_get_unicast_scopeid(&ip6->ip6_dst, nh->nh_ifp); 239 240 if (inzone != outzone) { 241 IP6STAT_INC(ip6s_cantforward); 242 IP6STAT_INC(ip6s_badscope); 243 goto bad; 244 } 245 246 if (nh->nh_flags & NHF_GATEWAY) { 247 /* Store gateway address in deembedded form */ 248 dst.sin6_addr = nh->gw6_sa.sin6_addr; 249 dst.sin6_scope_id = ntohs(in6_getscope(&dst.sin6_addr)); 250 in6_clearscope(&dst.sin6_addr); 251 } 252 253 /* 254 * If we are to forward the packet using the same interface 255 * as one we got the packet from, perhaps we should send a redirect 256 * to sender to shortcut a hop. 257 * Only send redirect if source is sending directly to us, 258 * and if packet was not source routed (or has any options). 259 * Also, don't send redirect if forwarding using a route 260 * modified by a redirect. 261 */ 262 if (V_ip6_sendredirects && nh->nh_ifp == m->m_pkthdr.rcvif && !srcrt && 263 (nh->nh_flags & NHF_REDIRECT) == 0) { 264 if ((nh->nh_ifp->if_flags & IFF_POINTOPOINT) != 0) { 265 /* 266 * If the incoming interface is equal to the outgoing 267 * one, and the link attached to the interface is 268 * point-to-point, then it will be highly probable 269 * that a routing loop occurs. Thus, we immediately 270 * drop the packet and send an ICMPv6 error message. 271 * 272 * type/code is based on suggestion by Rich Draves. 273 * not sure if it is the best pick. 274 */ 275 icmp6_error(mcopy, ICMP6_DST_UNREACH, 276 ICMP6_DST_UNREACH_ADDR, 0); 277 goto bad; 278 } 279 type = ND_REDIRECT; 280 } 281 282 /* 283 * Fake scoped addresses. Note that even link-local source or 284 * destinaion can appear, if the originating node just sends the 285 * packet to us (without address resolution for the destination). 286 * Since both icmp6_error and icmp6_redirect_output fill the embedded 287 * link identifiers, we can do this stuff after making a copy for 288 * returning an error. 289 */ 290 if ((nh->nh_ifp->if_flags & IFF_LOOPBACK) != 0) { 291 /* 292 * See corresponding comments in ip6_output. 293 * XXX: but is it possible that ip6_forward() sends a packet 294 * to a loopback interface? I don't think so, and thus 295 * I bark here. (jinmei@kame.net) 296 * XXX: it is common to route invalid packets to loopback. 297 * also, the codepath will be visited on use of ::1 in 298 * rthdr. (itojun) 299 */ 300 #if 1 301 if (0) 302 #else 303 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 304 #endif 305 { 306 printf("ip6_forward: outgoing interface is loopback. " 307 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 308 ip6_sprintf(ip6bufs, &ip6->ip6_src), 309 ip6_sprintf(ip6bufd, &ip6->ip6_dst), 310 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 311 if_name(nh->nh_ifp)); 312 } 313 314 /* we can just use rcvif in forwarding. */ 315 origifp = m->m_pkthdr.rcvif; 316 } 317 else 318 origifp = nh->nh_ifp; 319 /* 320 * clear embedded scope identifiers if necessary. 321 * in6_clearscope will touch the addresses only when necessary. 322 */ 323 in6_clearscope(&ip6->ip6_src); 324 in6_clearscope(&ip6->ip6_dst); 325 326 /* Jump over all PFIL processing if hooks are not active. */ 327 if (!PFIL_HOOKED_OUT(V_inet6_pfil_head)) 328 goto pass; 329 330 odst = ip6->ip6_dst; 331 /* Run through list of hooks for forwarded packets. */ 332 if (pfil_run_hooks(V_inet6_pfil_head, &m, nh->nh_ifp, PFIL_OUT | 333 PFIL_FWD, NULL) != PFIL_PASS) 334 goto freecopy; 335 ip6 = mtod(m, struct ip6_hdr *); 336 337 /* See if destination IP address was changed by packet filter. */ 338 if (!IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst)) { 339 m->m_flags |= M_SKIP_FIREWALL; 340 /* If destination is now ourself drop to ip6_input(). */ 341 if (in6_localip(&ip6->ip6_dst)) 342 m->m_flags |= M_FASTFWD_OURS; 343 else { 344 NH_FREE(nh); 345 346 /* Update address and scopeid. Assume scope is embedded */ 347 dst.sin6_scope_id = ntohs(in6_getscope(&ip6->ip6_dst)); 348 dst.sin6_addr = ip6->ip6_dst; 349 in6_clearscope(&dst.sin6_addr); 350 goto again; /* Redo the routing table lookup. */ 351 } 352 } 353 354 /* See if local, if yes, send it to netisr. */ 355 if (m->m_flags & M_FASTFWD_OURS) { 356 if (m->m_pkthdr.rcvif == NULL) 357 m->m_pkthdr.rcvif = V_loif; 358 if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA_IPV6) { 359 m->m_pkthdr.csum_flags |= 360 CSUM_DATA_VALID_IPV6 | CSUM_PSEUDO_HDR; 361 m->m_pkthdr.csum_data = 0xffff; 362 } 363 #if defined(SCTP) || defined(SCTP_SUPPORT) 364 if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) 365 m->m_pkthdr.csum_flags |= CSUM_SCTP_VALID; 366 #endif 367 error = netisr_queue(NETISR_IPV6, m); 368 goto out; 369 } 370 /* Or forward to some other address? */ 371 if ((m->m_flags & M_IP6_NEXTHOP) && 372 (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) { 373 struct sockaddr_in6 *gw6 = (struct sockaddr_in6 *)(fwd_tag + 1); 374 375 /* Update address and scopeid. Assume scope is embedded */ 376 dst.sin6_scope_id = ntohs(in6_getscope(&gw6->sin6_addr)); 377 dst.sin6_addr = gw6->sin6_addr; 378 in6_clearscope(&dst.sin6_addr); 379 380 m->m_flags |= M_SKIP_FIREWALL; 381 m->m_flags &= ~M_IP6_NEXTHOP; 382 m_tag_delete(m, fwd_tag); 383 NH_FREE(nh); 384 goto again; 385 } 386 387 pass: 388 /* See if the size was changed by the packet filter. */ 389 /* TODO: change to nh->nh_mtu */ 390 if (m->m_pkthdr.len > IN6_LINKMTU(nh->nh_ifp)) { 391 in6_ifstat_inc(nh->nh_ifp, ifs6_in_toobig); 392 if (mcopy) 393 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 394 IN6_LINKMTU(nh->nh_ifp)); 395 goto bad; 396 } 397 398 /* Currently LLE layer stores embedded IPv6 addresses */ 399 if (IN6_IS_SCOPE_LINKLOCAL(&dst.sin6_addr)) { 400 in6_set_unicast_scopeid(&dst.sin6_addr, dst.sin6_scope_id); 401 dst.sin6_scope_id = 0; 402 } 403 error = nd6_output_ifp(nh->nh_ifp, origifp, m, &dst, NULL); 404 if (error) { 405 in6_ifstat_inc(nh->nh_ifp, ifs6_out_discard); 406 IP6STAT_INC(ip6s_cantforward); 407 } else { 408 IP6STAT_INC(ip6s_forward); 409 in6_ifstat_inc(nh->nh_ifp, ifs6_out_forward); 410 if (type) 411 IP6STAT_INC(ip6s_redirectsent); 412 else { 413 if (mcopy) 414 goto freecopy; 415 } 416 } 417 418 if (mcopy == NULL) 419 goto out; 420 switch (error) { 421 case 0: 422 if (type == ND_REDIRECT) { 423 icmp6_redirect_output(mcopy, nh); 424 goto out; 425 } 426 goto freecopy; 427 428 case EMSGSIZE: 429 /* xxx MTU is constant in PPP? */ 430 goto freecopy; 431 432 case ENOBUFS: 433 /* Tell source to slow down like source quench in IP? */ 434 goto freecopy; 435 436 case ENETUNREACH: /* shouldn't happen, checked above */ 437 case EHOSTUNREACH: 438 case ENETDOWN: 439 case EHOSTDOWN: 440 default: 441 type = ICMP6_DST_UNREACH; 442 code = ICMP6_DST_UNREACH_ADDR; 443 break; 444 } 445 icmp6_error(mcopy, type, code, 0); 446 goto out; 447 448 freecopy: 449 m_freem(mcopy); 450 goto out; 451 bad: 452 m_freem(m); 453 out: 454 if (nh != NULL) 455 NH_FREE(nh); 456 } 457