1 /* $NetBSD: ip6_forward.c,v 1.98 2019/11/01 04:23:21 knakahara 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 1.98 2019/11/01 04:23:21 knakahara 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 uint64_t *ip6s; 82 83 /* update statistics */ 84 ip6s = IP6_STAT_GETREF(); 85 ip6s[IP6_STAT_CANTFORWARD]++; 86 if (dstifp) 87 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) 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 ifnet *rcvif = NULL; 130 struct psref psref; 131 struct route *ro = NULL; 132 #ifdef IPSEC 133 int needipsec = 0; 134 struct secpolicy *sp = NULL; 135 #endif 136 137 /* 138 * Clear any in-bound checksum flags for this packet. 139 */ 140 m->m_pkthdr.csum_flags = 0; 141 142 rcvif = m_get_rcvif_psref(m, &psref); 143 if (__predict_false(rcvif == NULL)) 144 goto drop; 145 146 /* 147 * Do not forward packets to multicast destination (should be handled 148 * by ip6_mforward()). Do not forward packets with unspecified source. 149 * It was discussed in July 2000, on ipngwg mailing list. 150 */ 151 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 152 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 153 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 154 ip6_cantforward(ip6, rcvif, NULL, 155 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : 156 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : 157 "unspec/src"); 158 goto drop; 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 goto out; 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_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 179 M_DONTWAIT); 180 181 #ifdef IPSEC 182 if (ipsec_used) { 183 /* Check the security policy (SP) for the packet */ 184 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error); 185 if (error != 0) { 186 /* 187 * Hack: -EINVAL is used to signal that a packet 188 * should be silently discarded. This is typically 189 * because we asked key management for an SA and 190 * it was delayed (e.g. kicked up to IKE). 191 */ 192 if (error == -EINVAL) 193 error = 0; 194 m_freem(m); 195 goto freecopy; 196 } 197 } 198 #endif 199 200 ro = rtcache_percpu_getref(ip6_forward_rt_percpu); 201 if (srcrt) { 202 union { 203 struct sockaddr dst; 204 struct sockaddr_in6 dst6; 205 } u; 206 207 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 208 rt = rtcache_lookup(ro, &u.dst); 209 if (rt == NULL) { 210 IP6_STATINC(IP6_STAT_NOROUTE); 211 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 212 if (mcopy) { 213 icmp6_error(mcopy, ICMP6_DST_UNREACH, 214 ICMP6_DST_UNREACH_NOROUTE, 0); 215 } 216 goto drop; 217 } 218 } else if ((rt = rtcache_validate(ro)) == NULL && 219 (rt = rtcache_update(ro, 1)) == NULL) { 220 /* 221 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 222 * ip6->ip6_dst 223 */ 224 IP6_STATINC(IP6_STAT_NOROUTE); 225 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 226 if (mcopy) { 227 icmp6_error(mcopy, ICMP6_DST_UNREACH, 228 ICMP6_DST_UNREACH_NOROUTE, 0); 229 } 230 goto drop; 231 } 232 dst = satocsin6(rtcache_getdst(ro)); 233 234 /* 235 * Source scope check: if a packet can't be delivered to its 236 * destination for the reason that the destination is beyond the scope 237 * of the source address, discard the packet and return an icmp6 238 * destination unreachable error with Code 2 (beyond scope of source 239 * address). We use a local copy of ip6_src, since in6_setscope() 240 * will possibly modify its first argument. 241 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 242 */ 243 src_in6 = ip6->ip6_src; 244 inzone = outzone = ~0; 245 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || 246 in6_setscope(&src_in6, rcvif, &inzone) != 0 || 247 inzone != outzone) { 248 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 249 "src[%s] inzone %d outzone %d", 250 in6_getscopename(&ip6->ip6_src), inzone, outzone); 251 if (mcopy) 252 icmp6_error(mcopy, ICMP6_DST_UNREACH, 253 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 254 goto drop; 255 } 256 257 #ifdef IPSEC 258 /* 259 * If we need to encapsulate the packet, do it here. 260 * ipsec6_process_packet will send the packet using ip6_output. 261 */ 262 if (needipsec) { 263 int s = splsoftnet(); 264 error = ipsec6_process_packet(m, sp->req, 0); 265 splx(s); 266 /* m is freed */ 267 if (mcopy) 268 goto freecopy; 269 goto out; 270 } 271 #endif 272 273 /* 274 * Destination scope check: if a packet is going to break the scope 275 * zone of packet's destination address, discard it. This case should 276 * usually be prevented by appropriately-configured routing table, but 277 * we need an explicit check because we may mistakenly forward the 278 * packet to a different zone by (e.g.) a default route. 279 */ 280 dst_in6 = ip6->ip6_dst; 281 inzone = outzone = ~0; 282 if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 || 283 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 284 inzone != outzone) { 285 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 286 "dst[%s] inzone %d outzone %d", 287 in6_getscopename(&ip6->ip6_dst), inzone, outzone); 288 if (mcopy) 289 icmp6_error(mcopy, ICMP6_DST_UNREACH, 290 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 291 goto drop; 292 } 293 294 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 295 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 296 if (mcopy) { 297 u_long mtu; 298 299 mtu = IN6_LINKMTU(rt->rt_ifp); 300 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 301 } 302 goto drop; 303 } 304 305 if (rt->rt_flags & RTF_GATEWAY) 306 dst = (struct sockaddr_in6 *)rt->rt_gateway; 307 308 /* 309 * If we are to forward the packet using the same interface 310 * as one we got the packet from, perhaps we should send a redirect 311 * to sender to shortcut a hop. 312 * Only send redirect if source is sending directly to us, 313 * and if packet was not source routed (or has any options). 314 * Also, don't send redirect if forwarding using a route 315 * modified by a redirect. 316 */ 317 if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects && 318 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 319 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 320 nd6_is_addr_neighbor(satocsin6(rtcache_getdst(ro)), 321 rt->rt_ifp)) { 322 /* 323 * If the incoming interface is equal to the outgoing 324 * one, the link attached to the interface is 325 * point-to-point, and the IPv6 destination is 326 * regarded as on-link on the link, then it will be 327 * highly probable that the destination address does 328 * not exist on the link and that the packet is going 329 * to loop. Thus, we immediately drop the packet and 330 * send an ICMPv6 error message. 331 * For other routing loops, we dare to let the packet 332 * go to the loop, so that a remote diagnosing host 333 * can detect the loop by traceroute. 334 * type/code is based on suggestion by Rich Draves. 335 * not sure if it is the best pick. 336 */ 337 icmp6_error(mcopy, ICMP6_DST_UNREACH, 338 ICMP6_DST_UNREACH_ADDR, 0); 339 goto drop; 340 } 341 type = ND_REDIRECT; 342 } 343 344 /* 345 * Fake scoped addresses. Note that even link-local source or 346 * destination can appear, if the originating node just sends the 347 * packet to us (without address resolution for the destination). 348 * Since both icmp6_error and icmp6_redirect_output fill the embedded 349 * link identifiers, we can do this stuff after making a copy for 350 * returning an error. 351 */ 352 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 353 /* 354 * See corresponding comments in ip6_output. 355 * XXX: but is it possible that ip6_forward() sends a packet 356 * to a loopback interface? I don't think so, and thus 357 * I bark here. (jinmei@kame.net) 358 * XXX: it is common to route invalid packets to loopback. 359 * also, the codepath will be visited on use of ::1 in 360 * rthdr. (itojun) 361 */ 362 #if 1 363 if (0) 364 #else 365 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 366 #endif 367 { 368 char ip6bufs[INET6_ADDRSTRLEN]; 369 char ip6bufd[INET6_ADDRSTRLEN]; 370 371 printf("ip6_forward: outgoing interface is loopback. " 372 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 373 IN6_PRINT(ip6bufs, &ip6->ip6_src), 374 IN6_PRINT(ip6bufd, &ip6->ip6_dst), 375 ip6->ip6_nxt, if_name(rcvif), 376 if_name(rt->rt_ifp)); 377 } 378 379 /* we can just use rcvif in forwarding. */ 380 origifp = rcvif; 381 } else { 382 origifp = rt->rt_ifp; 383 } 384 385 /* 386 * clear embedded scope identifiers if necessary. 387 * in6_clearscope will touch the addresses only when necessary. 388 */ 389 in6_clearscope(&ip6->ip6_src); 390 in6_clearscope(&ip6->ip6_dst); 391 392 /* 393 * Run through list of hooks for output packets. 394 */ 395 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 396 PFIL_OUT)) != 0) { 397 IP6_STATINC(IP6_STAT_PFILDROP_OUT); 398 goto senderr; 399 } 400 if (m == NULL) { 401 IP6_STATINC(IP6_STAT_PFILDROP_OUT); 402 goto freecopy; 403 } 404 ip6 = mtod(m, struct ip6_hdr *); 405 406 error = ip6_if_output(rt->rt_ifp, origifp, m, dst, rt); 407 if (error) { 408 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 409 IP6_STATINC(IP6_STAT_CANTFORWARD); 410 } else { 411 IP6_STATINC(IP6_STAT_FORWARD); 412 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 413 if (type) 414 IP6_STATINC(IP6_STAT_REDIRECTSENT); 415 else { 416 #ifdef GATEWAY 417 /* Need to release rt here */ 418 rtcache_unref(rt, ro); 419 rt = NULL; 420 if (mcopy->m_flags & M_CANFASTFWD) 421 ip6flow_create(ro, mcopy); 422 #endif 423 if (mcopy) 424 goto freecopy; 425 } 426 } 427 428 senderr: 429 if (mcopy == NULL) 430 goto out; 431 switch (error) { 432 case 0: 433 if (type == ND_REDIRECT) { 434 icmp6_redirect_output(mcopy, rt); 435 goto out; 436 } 437 goto freecopy; 438 439 case EMSGSIZE: 440 /* xxx MTU is constant in PPP? */ 441 goto freecopy; 442 443 case ENOBUFS: 444 /* Tell source to slow down like source quench in IP? */ 445 goto freecopy; 446 447 case ENETUNREACH: /* shouldn't happen, checked above */ 448 case EHOSTUNREACH: 449 case ENETDOWN: 450 case EHOSTDOWN: 451 default: 452 type = ICMP6_DST_UNREACH; 453 code = ICMP6_DST_UNREACH_ADDR; 454 break; 455 } 456 icmp6_error(mcopy, type, code, 0); 457 goto out; 458 459 freecopy: 460 m_freem(mcopy); 461 goto out; 462 463 drop: 464 m_freem(m); 465 466 out: 467 #ifdef IPSEC 468 if (sp != NULL) 469 KEY_SP_UNREF(&sp); 470 #endif 471 rtcache_unref(rt, ro); 472 if (ro != NULL) 473 rtcache_percpu_putref(ip6_forward_rt_percpu); 474 if (rcvif != NULL) 475 m_put_rcvif_psref(rcvif, &psref); 476 return; 477 } 478