1 /* $NetBSD: ip6_forward.c,v 1.103 2024/06/29 13:00:44 riastradh Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.109 2002/09/11 08:10:17 sakane 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 <sys/cdefs.h> 34 __KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.103 2024/06/29 13:00:44 riastradh Exp $"); 35 36 #ifdef _KERNEL_OPT 37 #include "opt_gateway.h" 38 #include "opt_ipsec.h" 39 #endif 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/mbuf.h> 44 #include <sys/errno.h> 45 #include <sys/time.h> 46 #include <sys/kernel.h> 47 #include <sys/syslog.h> 48 #include <sys/percpu.h> 49 50 #include <net/if.h> 51 #include <net/route.h> 52 #include <net/pfil.h> 53 54 #include <netinet/in.h> 55 #include <netinet/in_var.h> 56 #include <netinet/ip_var.h> 57 #include <netinet/ip6.h> 58 #include <netinet6/ip6_var.h> 59 #include <netinet6/ip6_private.h> 60 #include <netinet6/scope6_var.h> 61 #include <netinet/icmp6.h> 62 #include <netinet6/nd6.h> 63 64 #ifdef IPSEC 65 #include <netipsec/ipsec.h> 66 #include <netipsec/ipsec6.h> 67 #include <netipsec/key.h> 68 #endif 69 70 extern percpu_t *ip6_forward_rt_percpu; 71 72 extern pfil_head_t *inet6_pfil_hook; /* XXX */ 73 74 static void __printflike(4, 5) 75 ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp, 76 const struct ifnet *dstifp, const char *fmt, ...) 77 { 78 char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN]; 79 char reason[256]; 80 va_list ap; 81 net_stat_ref_t ip6s; 82 83 /* update statistics */ 84 ip6s = IP6_STAT_GETREF(); 85 _NET_STATINC_REF(ip6s, IP6_STAT_CANTFORWARD); 86 if (dstifp) 87 _NET_STATINC_REF(ip6s, IP6_STAT_BADSCOPE); 88 IP6_STAT_PUTREF(); 89 90 if (dstifp) 91 in6_ifstat_inc(dstifp, ifs6_in_discard); 92 93 if (ip6_log_time + ip6_log_interval >= time_uptime) 94 return; 95 ip6_log_time = time_uptime; 96 97 va_start(ap, fmt); 98 vsnprintf(reason, sizeof(reason), fmt, ap); 99 va_end(ap); 100 101 log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n", 102 IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?", 103 IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?", 104 ip6->ip6_nxt, reason); 105 } 106 107 /* 108 * Forward a packet. If some error occurs return the sender 109 * an icmp packet. Note we can't always generate a meaningful 110 * icmp message because icmp doesn't have a large enough repertoire 111 * of codes and types. 112 * 113 * If not forwarding, just drop the packet. This could be confusing 114 * if ipforwarding was zero but some routing protocol was advancing 115 * us as a gateway to somewhere. However, we must let the routing 116 * protocol deal with that. 117 */ 118 void 119 ip6_forward(struct mbuf *m, int srcrt, struct ifnet *rcvif) 120 { 121 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 122 const struct sockaddr_in6 *dst; 123 struct rtentry *rt = NULL; 124 int error = 0, type = 0, code = 0; 125 struct mbuf *mcopy = NULL; 126 struct ifnet *origifp; /* maybe unnecessary */ 127 uint32_t inzone, outzone; 128 struct in6_addr src_in6, dst_in6; 129 struct route *ro = NULL; 130 #ifdef IPSEC 131 int needipsec = 0; 132 struct secpolicy *sp = NULL; 133 #endif 134 135 /* 136 * Clear any in-bound checksum flags for this packet. 137 */ 138 m->m_pkthdr.csum_flags = 0; 139 140 /* 141 * Do not forward packets to multicast destination (should be handled 142 * by ip6_mforward()). Do not forward packets with unspecified source. 143 * It was discussed in July 2000, on ipngwg mailing list. 144 */ 145 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 146 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 147 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 148 ip6_cantforward(ip6, rcvif, NULL, 149 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : 150 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : 151 "unspec/src"); 152 goto drop; 153 } 154 155 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 156 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 157 icmp6_error(m, ICMP6_TIME_EXCEEDED, 158 ICMP6_TIME_EXCEED_TRANSIT, 0); 159 goto out; 160 } 161 ip6->ip6_hlim -= IPV6_HLIMDEC; 162 163 /* 164 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 165 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 166 * we need to generate an ICMP6 message to the src. 167 * Thanks to M_EXT, in most cases copy will not occur. 168 * 169 * It is important to save it before IPsec processing as IPsec 170 * processing may modify the mbuf. 171 */ 172 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 173 M_DONTWAIT); 174 175 #ifdef IPSEC 176 if (ipsec_used) { 177 /* Check the security policy (SP) for the packet */ 178 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error); 179 if (error != 0) { 180 /* 181 * Hack: -EINVAL is used to signal that a packet 182 * should be silently discarded. This is typically 183 * because we asked key management for an SA and 184 * it was delayed (e.g. kicked up to IKE). 185 */ 186 if (error == -EINVAL) 187 error = 0; 188 m_freem(m); 189 IP6_STATINC(IP6_STAT_IPSECDROP_OUT); 190 goto freecopy; 191 } 192 } 193 #endif 194 195 ro = rtcache_percpu_getref(ip6_forward_rt_percpu); 196 if (srcrt) { 197 union { 198 struct sockaddr dst; 199 struct sockaddr_in6 dst6; 200 } u; 201 202 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 203 rt = rtcache_lookup(ro, &u.dst); 204 if (rt == NULL) { 205 IP6_STATINC(IP6_STAT_NOROUTE); 206 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 207 if (mcopy) { 208 icmp6_error(mcopy, ICMP6_DST_UNREACH, 209 ICMP6_DST_UNREACH_NOROUTE, 0); 210 } 211 goto drop; 212 } 213 } else if ((rt = rtcache_validate(ro)) == NULL && 214 (rt = rtcache_update(ro, 1)) == NULL) { 215 /* 216 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 217 * ip6->ip6_dst 218 */ 219 IP6_STATINC(IP6_STAT_NOROUTE); 220 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 221 if (mcopy) { 222 icmp6_error(mcopy, ICMP6_DST_UNREACH, 223 ICMP6_DST_UNREACH_NOROUTE, 0); 224 } 225 goto drop; 226 } 227 dst = satocsin6(rtcache_getdst(ro)); 228 229 /* 230 * Source scope check: if a packet can't be delivered to its 231 * destination for the reason that the destination is beyond the scope 232 * of the source address, discard the packet and return an icmp6 233 * destination unreachable error with Code 2 (beyond scope of source 234 * address). We use a local copy of ip6_src, since in6_setscope() 235 * will possibly modify its first argument. 236 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 237 */ 238 src_in6 = ip6->ip6_src; 239 inzone = outzone = ~0; 240 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || 241 in6_setscope(&src_in6, rcvif, &inzone) != 0 || 242 inzone != outzone) { 243 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 244 "src[%s] inzone %d outzone %d", 245 in6_getscopename(&ip6->ip6_src), inzone, outzone); 246 if (mcopy) 247 icmp6_error(mcopy, ICMP6_DST_UNREACH, 248 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 249 goto drop; 250 } 251 252 #ifdef IPSEC 253 /* 254 * If we need to encapsulate the packet, do it here. 255 * ipsec6_process_packet will send the packet using ip6_output. 256 */ 257 if (needipsec) { 258 int s = splsoftnet(); 259 error = ipsec6_process_packet(m, sp->req, 0); 260 splx(s); 261 /* m is freed */ 262 if (mcopy) 263 goto freecopy; 264 goto out; 265 } 266 #endif 267 268 /* 269 * Destination scope check: if a packet is going to break the scope 270 * zone of packet's destination address, discard it. This case should 271 * usually be prevented by appropriately-configured routing table, but 272 * we need an explicit check because we may mistakenly forward the 273 * packet to a different zone by (e.g.) a default route. 274 */ 275 dst_in6 = ip6->ip6_dst; 276 inzone = outzone = ~0; 277 if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 || 278 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 279 inzone != outzone) { 280 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 281 "dst[%s] inzone %d outzone %d", 282 in6_getscopename(&ip6->ip6_dst), inzone, outzone); 283 if (mcopy) 284 icmp6_error(mcopy, ICMP6_DST_UNREACH, 285 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 286 goto drop; 287 } 288 289 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 290 IP6_STATINC(IP6_STAT_TOOBIG); 291 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 292 if (mcopy) 293 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 294 rt->rt_ifp->if_mtu); 295 goto drop; 296 } 297 298 if (rt->rt_flags & RTF_GATEWAY) 299 dst = (struct sockaddr_in6 *)rt->rt_gateway; 300 301 /* 302 * If we are to forward the packet using the same interface 303 * as one we got the packet from, perhaps we should send a redirect 304 * to sender to shortcut a hop. 305 * Only send redirect if source is sending directly to us, 306 * and if packet was not source routed (or has any options). 307 * Also, don't send redirect if forwarding using a route 308 * modified by a redirect. 309 */ 310 if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects && 311 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 312 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 313 nd6_is_addr_neighbor(satocsin6(rtcache_getdst(ro)), 314 rt->rt_ifp)) { 315 /* 316 * If the incoming interface is equal to the outgoing 317 * one, the link attached to the interface is 318 * point-to-point, and the IPv6 destination is 319 * regarded as on-link on the link, then it will be 320 * highly probable that the destination address does 321 * not exist on the link and that the packet is going 322 * to loop. Thus, we immediately drop the packet and 323 * send an ICMPv6 error message. 324 * For other routing loops, we dare to let the packet 325 * go to the loop, so that a remote diagnosing host 326 * can detect the loop by traceroute. 327 * type/code is based on suggestion by Rich Draves. 328 * not sure if it is the best pick. 329 */ 330 icmp6_error(mcopy, ICMP6_DST_UNREACH, 331 ICMP6_DST_UNREACH_ADDR, 0); 332 goto drop; 333 } 334 type = ND_REDIRECT; 335 } 336 337 /* 338 * Fake scoped addresses. Note that even link-local source or 339 * destination can appear, if the originating node just sends the 340 * packet to us (without address resolution for the destination). 341 * Since both icmp6_error and icmp6_redirect_output fill the embedded 342 * link identifiers, we can do this stuff after making a copy for 343 * returning an error. 344 */ 345 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 346 /* 347 * See corresponding comments in ip6_output. 348 * XXX: but is it possible that ip6_forward() sends a packet 349 * to a loopback interface? I don't think so, and thus 350 * I bark here. (jinmei (at) kame.net) 351 * XXX: it is common to route invalid packets to loopback. 352 * also, the codepath will be visited on use of ::1 in 353 * rthdr. (itojun) 354 */ 355 #if 1 356 if (0) 357 #else 358 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 359 #endif 360 { 361 char ip6bufs[INET6_ADDRSTRLEN]; 362 char ip6bufd[INET6_ADDRSTRLEN]; 363 364 printf("ip6_forward: outgoing interface is loopback. " 365 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 366 IN6_PRINT(ip6bufs, &ip6->ip6_src), 367 IN6_PRINT(ip6bufd, &ip6->ip6_dst), 368 ip6->ip6_nxt, if_name(rcvif), 369 if_name(rt->rt_ifp)); 370 } 371 372 /* we can just use rcvif in forwarding. */ 373 origifp = rcvif; 374 } else { 375 origifp = rt->rt_ifp; 376 } 377 378 /* 379 * clear embedded scope identifiers if necessary. 380 * in6_clearscope will touch the addresses only when necessary. 381 */ 382 in6_clearscope(&ip6->ip6_src); 383 in6_clearscope(&ip6->ip6_dst); 384 385 /* 386 * Run through list of hooks for output packets. 387 */ 388 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 389 PFIL_OUT)) != 0) { 390 IP6_STATINC(IP6_STAT_PFILDROP_OUT); 391 goto senderr; 392 } 393 if (m == NULL) { 394 IP6_STATINC(IP6_STAT_PFILDROP_OUT); 395 goto freecopy; 396 } 397 ip6 = mtod(m, struct ip6_hdr *); 398 399 error = ip6_if_output(rt->rt_ifp, origifp, m, dst, rt); 400 if (error) { 401 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 402 IP6_STATINC(IP6_STAT_CANTFORWARD); 403 } else { 404 IP6_STATINC(IP6_STAT_FORWARD); 405 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 406 if (type) 407 IP6_STATINC(IP6_STAT_REDIRECTSENT); 408 else { 409 #ifdef GATEWAY 410 /* Need to release rt here */ 411 rtcache_unref(rt, ro); 412 rt = NULL; 413 if (mcopy->m_flags & M_CANFASTFWD) 414 ip6flow_create(ro, mcopy); 415 #endif 416 if (mcopy) 417 goto freecopy; 418 } 419 } 420 421 senderr: 422 if (mcopy == NULL) 423 goto out; 424 switch (error) { 425 case 0: 426 if (type == ND_REDIRECT) { 427 icmp6_redirect_output(mcopy, rt); 428 goto out; 429 } 430 goto freecopy; 431 432 case EMSGSIZE: 433 /* xxx MTU is constant in PPP? */ 434 goto freecopy; 435 436 case ENOBUFS: 437 /* Tell source to slow down like source quench in IP? */ 438 goto freecopy; 439 440 case ENETUNREACH: /* shouldn't happen, checked above */ 441 case EHOSTUNREACH: 442 case ENETDOWN: 443 case EHOSTDOWN: 444 default: 445 type = ICMP6_DST_UNREACH; 446 code = ICMP6_DST_UNREACH_ADDR; 447 break; 448 } 449 icmp6_error(mcopy, type, code, 0); 450 goto out; 451 452 freecopy: 453 m_freem(mcopy); 454 goto out; 455 456 drop: 457 m_freem(m); 458 459 out: 460 #ifdef IPSEC 461 if (sp != NULL) 462 KEY_SP_UNREF(&sp); 463 #endif 464 rtcache_unref(rt, ro); 465 if (ro != NULL) 466 rtcache_percpu_putref(ip6_forward_rt_percpu); 467 return; 468 } 469
Indexes created Mon Sep 22 13:09:51 GMT 2025