1 /* $OpenBSD: ip6_forward.c,v 1.109 2023/04/05 13:56:31 kn Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei 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 "pf.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/mbuf.h> 38 #include <sys/socket.h> 39 #include <sys/errno.h> 40 #include <sys/time.h> 41 #include <sys/kernel.h> 42 #include <sys/syslog.h> 43 44 #include <net/if.h> 45 #include <net/if_var.h> 46 #include <net/if_enc.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/ip_var.h> 51 #include <netinet6/in6_var.h> 52 #include <netinet/ip6.h> 53 #include <netinet6/ip6_var.h> 54 #include <netinet/icmp6.h> 55 #include <netinet6/nd6.h> 56 57 #if NPF > 0 58 #include <net/pfvar.h> 59 #endif 60 61 #ifdef IPSEC 62 #include <netinet/ip_ipsp.h> 63 #include <netinet/ip_ah.h> 64 #include <netinet/ip_esp.h> 65 #include <netinet/udp.h> 66 #include <netinet/tcp.h> 67 #endif 68 69 /* 70 * Forward a packet. If some error occurs return the sender 71 * an icmp packet. Note we can't always generate a meaningful 72 * icmp message because icmp doesn't have a large enough repertoire 73 * of codes and types. 74 * 75 * If not forwarding, just drop the packet. This could be confusing 76 * if ipforwarding was zero but some routing protocol was advancing 77 * us as a gateway to somewhere. However, we must let the routing 78 * protocol deal with that. 79 * 80 */ 81 82 void 83 ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt) 84 { 85 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 86 struct sockaddr_in6 *sin6; 87 struct route_in6 ro; 88 struct ifnet *ifp = NULL; 89 int error = 0, type = 0, code = 0, destmtu = 0; 90 struct mbuf *mcopy = NULL; 91 #ifdef IPSEC 92 struct tdb *tdb = NULL; 93 #endif /* IPSEC */ 94 char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN]; 95 96 /* 97 * Do not forward packets to multicast destination (should be handled 98 * by ip6_mforward(). 99 * Do not forward packets with unspecified source. It was discussed 100 * in July 2000, on ipngwg mailing list. 101 */ 102 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 103 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 104 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 105 time_t uptime; 106 107 ip6stat_inc(ip6s_cantforward); 108 uptime = getuptime(); 109 110 if (ip6_log_time + ip6_log_interval < uptime) { 111 ip6_log_time = uptime; 112 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 113 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 114 log(LOG_DEBUG, 115 "cannot forward " 116 "from %s to %s nxt %d received on interface %u\n", 117 src6, dst6, 118 ip6->ip6_nxt, 119 m->m_pkthdr.ph_ifidx); 120 } 121 m_freem(m); 122 goto out; 123 } 124 125 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 126 icmp6_error(m, ICMP6_TIME_EXCEEDED, 127 ICMP6_TIME_EXCEED_TRANSIT, 0); 128 goto out; 129 } 130 ip6->ip6_hlim -= IPV6_HLIMDEC; 131 132 /* 133 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 134 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 135 * we need to generate an ICMP6 message to the src. 136 * Thanks to M_EXT, in most cases copy will not occur. 137 * 138 * It is important to save it before IPsec processing as IPsec 139 * processing may modify the mbuf. 140 */ 141 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 142 M_NOWAIT); 143 144 #if NPF > 0 145 reroute: 146 #endif 147 148 #ifdef IPSEC 149 if (ipsec_in_use) { 150 error = ip6_output_ipsec_lookup(m, NULL, &tdb); 151 if (error) { 152 /* 153 * -EINVAL is used to indicate that the packet should 154 * be silently dropped, typically because we've asked 155 * key management for an SA. 156 */ 157 if (error == -EINVAL) /* Should silently drop packet */ 158 error = 0; 159 160 m_freem(m); 161 goto freecopy; 162 } 163 } 164 #endif /* IPSEC */ 165 166 memset(&ro, 0, sizeof(ro)); 167 sin6 = &ro.ro_dst; 168 sin6->sin6_family = AF_INET6; 169 sin6->sin6_len = sizeof(*sin6); 170 sin6->sin6_addr = ip6->ip6_dst; 171 172 if (!rtisvalid(rt)) { 173 rtfree(rt); 174 rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0], 175 m->m_pkthdr.ph_rtableid); 176 if (rt == NULL) { 177 ip6stat_inc(ip6s_noroute); 178 if (mcopy) { 179 icmp6_error(mcopy, ICMP6_DST_UNREACH, 180 ICMP6_DST_UNREACH_NOROUTE, 0); 181 } 182 m_freem(m); 183 goto out; 184 } 185 } 186 187 /* 188 * Scope check: if a packet can't be delivered to its destination 189 * for the reason that the destination is beyond the scope of the 190 * source address, discard the packet and return an icmp6 destination 191 * unreachable error with Code 2 (beyond scope of source address). 192 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 193 */ 194 if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) != 195 in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) { 196 time_t uptime; 197 198 ip6stat_inc(ip6s_cantforward); 199 ip6stat_inc(ip6s_badscope); 200 uptime = getuptime(); 201 202 if (ip6_log_time + ip6_log_interval < uptime) { 203 ip6_log_time = uptime; 204 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 205 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 206 log(LOG_DEBUG, 207 "cannot forward " 208 "src %s, dst %s, nxt %d, rcvif %u, outif %u\n", 209 src6, dst6, 210 ip6->ip6_nxt, 211 m->m_pkthdr.ph_ifidx, rt->rt_ifidx); 212 } 213 if (mcopy) 214 icmp6_error(mcopy, ICMP6_DST_UNREACH, 215 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 216 m_freem(m); 217 goto out; 218 } 219 220 #ifdef IPSEC 221 /* 222 * Check if the packet needs encapsulation. 223 * ipsp_process_packet will never come back to here. 224 */ 225 if (tdb != NULL) { 226 /* Callee frees mbuf */ 227 ro.ro_rt = rt; 228 ro.ro_tableid = m->m_pkthdr.ph_rtableid; 229 error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1); 230 rt = ro.ro_rt; 231 if (error) 232 goto senderr; 233 goto freecopy; 234 } 235 #endif /* IPSEC */ 236 237 if (rt->rt_flags & RTF_GATEWAY) 238 sin6 = satosin6(rt->rt_gateway); 239 240 /* 241 * If we are to forward the packet using the same interface 242 * as one we got the packet from, perhaps we should send a redirect 243 * to sender to shortcut a hop. 244 * Only send redirect if source is sending directly to us, 245 * and if packet was not source routed (or has any options). 246 * Also, don't send redirect if forwarding using a route 247 * modified by a redirect. 248 */ 249 ifp = if_get(rt->rt_ifidx); 250 if (ifp == NULL) { 251 m_freem(m); 252 goto freecopy; 253 } 254 if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt && 255 ip6_sendredirects && 256 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 257 if ((ifp->if_flags & IFF_POINTOPOINT) && 258 nd6_is_addr_neighbor(&ro.ro_dst, ifp)) { 259 /* 260 * If the incoming interface is equal to the outgoing 261 * one, the link attached to the interface is 262 * point-to-point, and the IPv6 destination is 263 * regarded as on-link on the link, then it will be 264 * highly probable that the destination address does 265 * not exist on the link and that the packet is going 266 * to loop. Thus, we immediately drop the packet and 267 * send an ICMPv6 error message. 268 * For other routing loops, we dare to let the packet 269 * go to the loop, so that a remote diagnosing host 270 * can detect the loop by traceroute. 271 * type/code is based on suggestion by Rich Draves. 272 * not sure if it is the best pick. 273 */ 274 if (mcopy) 275 icmp6_error(mcopy, ICMP6_DST_UNREACH, 276 ICMP6_DST_UNREACH_ADDR, 0); 277 m_freem(m); 278 goto out; 279 } 280 type = ND_REDIRECT; 281 } 282 283 /* 284 * Fake scoped addresses. Note that even link-local source or 285 * destination can appear, if the originating node just sends the 286 * packet to us (without address resolution for the destination). 287 * Since both icmp6_error and icmp6_redirect_output fill the embedded 288 * link identifiers, we can do this stuff after making a copy for 289 * returning an error. 290 */ 291 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) 292 ip6->ip6_src.s6_addr16[1] = 0; 293 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) 294 ip6->ip6_dst.s6_addr16[1] = 0; 295 296 #if NPF > 0 297 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) { 298 m_freem(m); 299 goto senderr; 300 } 301 if (m == NULL) 302 goto senderr; 303 ip6 = mtod(m, struct ip6_hdr *); 304 if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) == 305 (PF_TAG_REROUTE | PF_TAG_GENERATED)) { 306 /* already rerun the route lookup, go on */ 307 m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE); 308 } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) { 309 /* tag as generated to skip over pf_test on rerun */ 310 m->m_pkthdr.pf.flags |= PF_TAG_GENERATED; 311 srcrt = 1; 312 rtfree(rt); 313 rt = NULL; 314 if_put(ifp); 315 ifp = NULL; 316 goto reroute; 317 } 318 #endif 319 in6_proto_cksum_out(m, ifp); 320 321 /* Check the size after pf_test to give pf a chance to refragment. */ 322 if (m->m_pkthdr.len > ifp->if_mtu) { 323 if (mcopy) 324 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 325 ifp->if_mtu); 326 m_freem(m); 327 goto out; 328 } 329 330 error = ifp->if_output(ifp, m, sin6tosa(sin6), rt); 331 if (error) { 332 ip6stat_inc(ip6s_cantforward); 333 } else { 334 ip6stat_inc(ip6s_forward); 335 if (type) 336 ip6stat_inc(ip6s_redirectsent); 337 else { 338 if (mcopy) 339 goto freecopy; 340 } 341 } 342 343 #if NPF > 0 || defined(IPSEC) 344 senderr: 345 #endif 346 if (mcopy == NULL) 347 goto out; 348 349 switch (error) { 350 case 0: 351 if (type == ND_REDIRECT) { 352 icmp6_redirect_output(mcopy, rt); 353 goto out; 354 } 355 goto freecopy; 356 357 case EMSGSIZE: 358 type = ICMP6_PACKET_TOO_BIG; 359 code = 0; 360 if (rt != NULL) { 361 if (rt->rt_mtu) { 362 destmtu = rt->rt_mtu; 363 } else { 364 struct ifnet *destifp; 365 366 destifp = if_get(rt->rt_ifidx); 367 if (destifp != NULL) 368 destmtu = destifp->if_mtu; 369 if_put(destifp); 370 } 371 } 372 ip6stat_inc(ip6s_cantfrag); 373 if (destmtu == 0) 374 goto freecopy; 375 break; 376 377 case EACCES: 378 /* 379 * pf(4) blocked the packet. There is no need to send an ICMP 380 * packet back since pf(4) takes care of it. 381 */ 382 goto freecopy; 383 384 case ENOBUFS: 385 /* Tell source to slow down like source quench in IP? */ 386 goto freecopy; 387 388 case ENETUNREACH: /* shouldn't happen, checked above */ 389 case EHOSTUNREACH: 390 case ENETDOWN: 391 case EHOSTDOWN: 392 default: 393 type = ICMP6_DST_UNREACH; 394 code = ICMP6_DST_UNREACH_ADDR; 395 break; 396 } 397 icmp6_error(mcopy, type, code, destmtu); 398 goto out; 399 400 freecopy: 401 m_freem(mcopy); 402 out: 403 rtfree(rt); 404 if_put(ifp); 405 #ifdef IPSEC 406 tdb_unref(tdb); 407 #endif /* IPSEC */ 408 } 409