1 /*- 2 * Copyright (c) 2003 Andre Oppermann, Internet Business Solutions AG 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /* 31 * ip_fastforward gets its speed from processing the forwarded packet to 32 * completion (if_output on the other side) without any queues or netisr's. 33 * The receiving interface DMAs the packet into memory, the upper half of 34 * driver calls ip_fastforward, we do our routing table lookup and directly 35 * send it off to the outgoing interface, which DMAs the packet to the 36 * network card. The only part of the packet we touch with the CPU is the 37 * IP header (unless there are complex firewall rules touching other parts 38 * of the packet, but that is up to you). We are essentially limited by bus 39 * bandwidth and how fast the network card/driver can set up receives and 40 * transmits. 41 * 42 * We handle basic errors, IP header errors, checksum errors, 43 * destination unreachable, fragmentation and fragmentation needed and 44 * report them via ICMP to the sender. 45 * 46 * Else if something is not pure IPv4 unicast forwarding we fall back to 47 * the normal ip_input processing path. We should only be called from 48 * interfaces connected to the outside world. 49 * 50 * Firewalling is fully supported including divert, ipfw fwd and ipfilter 51 * ipnat and address rewrite. 52 * 53 * IPSEC is not supported if this host is a tunnel broker. IPSEC is 54 * supported for connections to/from local host. 55 * 56 * We try to do the least expensive (in CPU ops) checks and operations 57 * first to catch junk with as little overhead as possible. 58 * 59 * We take full advantage of hardware support for IP checksum and 60 * fragmentation offloading. 61 * 62 * We don't do ICMP redirect in the fast forwarding path. I have had my own 63 * cases where two core routers with Zebra routing suite would send millions 64 * ICMP redirects to connected hosts if the destination router was not the 65 * default gateway. In one case it was filling the routing table of a host 66 * with approximately 300.000 cloned redirect entries until it ran out of 67 * kernel memory. However the networking code proved very robust and it didn't 68 * crash or fail in other ways. 69 */ 70 71 /* 72 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which 73 * is being followed here. 74 */ 75 76 #include <sys/cdefs.h> 77 __FBSDID("$FreeBSD$"); 78 79 #include "opt_ipstealth.h" 80 81 #include <sys/param.h> 82 #include <sys/systm.h> 83 #include <sys/kernel.h> 84 #include <sys/malloc.h> 85 #include <sys/mbuf.h> 86 #include <sys/protosw.h> 87 #include <sys/sdt.h> 88 #include <sys/socket.h> 89 #include <sys/sysctl.h> 90 91 #include <net/pfil.h> 92 #include <net/if.h> 93 #include <net/if_types.h> 94 #include <net/if_var.h> 95 #include <net/if_dl.h> 96 #include <net/route.h> 97 #include <net/vnet.h> 98 99 #include <netinet/in.h> 100 #include <netinet/in_kdtrace.h> 101 #include <netinet/in_systm.h> 102 #include <netinet/in_var.h> 103 #include <netinet/ip.h> 104 #include <netinet/ip_var.h> 105 #include <netinet/ip_icmp.h> 106 #include <netinet/ip_options.h> 107 108 #include <machine/in_cksum.h> 109 110 static struct sockaddr_in * 111 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) 112 { 113 struct sockaddr_in *dst; 114 struct rtentry *rt; 115 116 /* 117 * Find route to destination. 118 */ 119 bzero(ro, sizeof(*ro)); 120 dst = (struct sockaddr_in *)&ro->ro_dst; 121 dst->sin_family = AF_INET; 122 dst->sin_len = sizeof(*dst); 123 dst->sin_addr.s_addr = dest.s_addr; 124 in_rtalloc_ign(ro, 0, M_GETFIB(m)); 125 126 /* 127 * Route there and interface still up? 128 */ 129 rt = ro->ro_rt; 130 if (rt && (rt->rt_flags & RTF_UP) && 131 (rt->rt_ifp->if_flags & IFF_UP) && 132 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { 133 if (rt->rt_flags & RTF_GATEWAY) 134 dst = (struct sockaddr_in *)rt->rt_gateway; 135 } else { 136 IPSTAT_INC(ips_noroute); 137 IPSTAT_INC(ips_cantforward); 138 if (rt) 139 RTFREE(rt); 140 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 141 return NULL; 142 } 143 return dst; 144 } 145 146 /* 147 * Try to forward a packet based on the destination address. 148 * This is a fast path optimized for the plain forwarding case. 149 * If the packet is handled (and consumed) here then we return NULL; 150 * otherwise mbuf is returned and the packet should be delivered 151 * to ip_input for full processing. 152 */ 153 struct mbuf * 154 ip_tryforward(struct mbuf *m) 155 { 156 struct ip *ip; 157 struct mbuf *m0 = NULL; 158 struct route ro; 159 struct sockaddr_in *dst = NULL; 160 struct ifnet *ifp; 161 struct in_addr odest, dest; 162 uint16_t ip_len, ip_off; 163 int error = 0; 164 int mtu; 165 struct m_tag *fwd_tag = NULL; 166 167 /* 168 * Are we active and forwarding packets? 169 */ 170 171 M_ASSERTVALID(m); 172 M_ASSERTPKTHDR(m); 173 174 bzero(&ro, sizeof(ro)); 175 176 177 #ifdef ALTQ 178 /* 179 * Is packet dropped by traffic conditioner? 180 */ 181 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 182 goto drop; 183 #endif 184 185 /* 186 * Only IP packets without options 187 */ 188 ip = mtod(m, struct ip *); 189 190 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 191 if (V_ip_doopts == 1) 192 return m; 193 else if (V_ip_doopts == 2) { 194 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 195 0, 0); 196 return NULL; /* mbuf already free'd */ 197 } 198 /* else ignore IP options and continue */ 199 } 200 201 /* 202 * Only unicast IP, not from loopback, no L2 or IP broadcast, 203 * no multicast, no INADDR_ANY 204 * 205 * XXX: Probably some of these checks could be direct drop 206 * conditions. However it is not clear whether there are some 207 * hacks or obscure behaviours which make it necessary to 208 * let ip_input handle it. We play safe here and let ip_input 209 * deal with it until it is proven that we can directly drop it. 210 */ 211 if ((m->m_flags & (M_BCAST|M_MCAST)) || 212 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 213 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 214 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 215 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 216 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 217 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || 218 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 219 ip->ip_src.s_addr == INADDR_ANY || 220 ip->ip_dst.s_addr == INADDR_ANY ) 221 return m; 222 223 /* 224 * Is it for a local address on this host? 225 */ 226 if (in_localip(ip->ip_dst)) 227 return m; 228 229 IPSTAT_INC(ips_total); 230 231 /* 232 * Step 3: incoming packet firewall processing 233 */ 234 235 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 236 237 /* 238 * Run through list of ipfilter hooks for input packets 239 */ 240 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 241 goto passin; 242 243 if (pfil_run_hooks( 244 &V_inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 245 m == NULL) 246 goto drop; 247 248 M_ASSERTVALID(m); 249 M_ASSERTPKTHDR(m); 250 251 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 252 dest.s_addr = ip->ip_dst.s_addr; 253 254 /* 255 * Destination address changed? 256 */ 257 if (odest.s_addr != dest.s_addr) { 258 /* 259 * Is it now for a local address on this host? 260 */ 261 if (in_localip(dest)) 262 goto forwardlocal; 263 /* 264 * Go on with new destination address 265 */ 266 } 267 268 if (m->m_flags & M_FASTFWD_OURS) { 269 /* 270 * ipfw changed it for a local address on this host. 271 */ 272 goto forwardlocal; 273 } 274 275 passin: 276 /* 277 * Step 4: decrement TTL and look up route 278 */ 279 280 /* 281 * Check TTL 282 */ 283 #ifdef IPSTEALTH 284 if (!V_ipstealth) { 285 #endif 286 if (ip->ip_ttl <= IPTTLDEC) { 287 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 288 return NULL; /* mbuf already free'd */ 289 } 290 291 /* 292 * Decrement the TTL and incrementally change the IP header checksum. 293 * Don't bother doing this with hw checksum offloading, it's faster 294 * doing it right here. 295 */ 296 ip->ip_ttl -= IPTTLDEC; 297 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 298 ip->ip_sum -= ~htons(IPTTLDEC << 8); 299 else 300 ip->ip_sum += htons(IPTTLDEC << 8); 301 #ifdef IPSTEALTH 302 } 303 #endif 304 305 /* 306 * Find route to destination. 307 */ 308 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 309 return NULL; /* icmp unreach already sent */ 310 ifp = ro.ro_rt->rt_ifp; 311 312 /* 313 * Immediately drop blackholed traffic, and directed broadcasts 314 * for either the all-ones or all-zero subnet addresses on 315 * locally attached networks. 316 */ 317 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 318 goto drop; 319 320 /* 321 * Step 5: outgoing firewall packet processing 322 */ 323 324 /* 325 * Run through list of hooks for output packets. 326 */ 327 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 328 goto passout; 329 330 if (pfil_run_hooks(&V_inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 331 goto drop; 332 } 333 334 M_ASSERTVALID(m); 335 M_ASSERTPKTHDR(m); 336 337 ip = mtod(m, struct ip *); 338 dest.s_addr = ip->ip_dst.s_addr; 339 340 /* 341 * Destination address changed? 342 */ 343 if (m->m_flags & M_IP_NEXTHOP) 344 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 345 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 346 /* 347 * Is it now for a local address on this host? 348 */ 349 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 350 forwardlocal: 351 /* 352 * Return packet for processing by ip_input(). 353 */ 354 m->m_flags |= M_FASTFWD_OURS; 355 if (ro.ro_rt) 356 RTFREE(ro.ro_rt); 357 return m; 358 } 359 /* 360 * Redo route lookup with new destination address 361 */ 362 if (fwd_tag) { 363 dest.s_addr = ((struct sockaddr_in *) 364 (fwd_tag + 1))->sin_addr.s_addr; 365 m_tag_delete(m, fwd_tag); 366 m->m_flags &= ~M_IP_NEXTHOP; 367 } 368 RTFREE(ro.ro_rt); 369 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 370 return NULL; /* icmp unreach already sent */ 371 ifp = ro.ro_rt->rt_ifp; 372 } 373 374 passout: 375 /* 376 * Step 6: send off the packet 377 */ 378 ip_len = ntohs(ip->ip_len); 379 ip_off = ntohs(ip->ip_off); 380 381 /* 382 * Check if route is dampned (when ARP is unable to resolve) 383 */ 384 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 385 (ro.ro_rt->rt_expire == 0 || time_uptime < ro.ro_rt->rt_expire)) { 386 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 387 goto consumed; 388 } 389 390 /* 391 * Check if media link state of interface is not down 392 */ 393 if (ifp->if_link_state == LINK_STATE_DOWN) { 394 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 395 goto consumed; 396 } 397 398 /* 399 * Check if packet fits MTU or if hardware will fragment for us 400 */ 401 if (ro.ro_rt->rt_mtu) 402 mtu = min(ro.ro_rt->rt_mtu, ifp->if_mtu); 403 else 404 mtu = ifp->if_mtu; 405 406 if (ip_len <= mtu) { 407 /* 408 * Avoid confusing lower layers. 409 */ 410 m_clrprotoflags(m); 411 /* 412 * Send off the packet via outgoing interface 413 */ 414 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL); 415 error = (*ifp->if_output)(ifp, m, 416 (struct sockaddr *)dst, &ro); 417 } else { 418 /* 419 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 420 */ 421 if (ip_off & IP_DF) { 422 IPSTAT_INC(ips_cantfrag); 423 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 424 0, mtu); 425 goto consumed; 426 } else { 427 /* 428 * We have to fragment the packet 429 */ 430 m->m_pkthdr.csum_flags |= CSUM_IP; 431 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist)) 432 goto drop; 433 KASSERT(m != NULL, ("null mbuf and no error")); 434 /* 435 * Send off the fragments via outgoing interface 436 */ 437 error = 0; 438 do { 439 m0 = m->m_nextpkt; 440 m->m_nextpkt = NULL; 441 /* 442 * Avoid confusing lower layers. 443 */ 444 m_clrprotoflags(m); 445 446 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL); 447 error = (*ifp->if_output)(ifp, m, 448 (struct sockaddr *)dst, &ro); 449 if (error) 450 break; 451 } while ((m = m0) != NULL); 452 if (error) { 453 /* Reclaim remaining fragments */ 454 for (m = m0; m; m = m0) { 455 m0 = m->m_nextpkt; 456 m_freem(m); 457 } 458 } else 459 IPSTAT_INC(ips_fragmented); 460 } 461 } 462 463 if (error != 0) 464 IPSTAT_INC(ips_odropped); 465 else { 466 counter_u64_add(ro.ro_rt->rt_pksent, 1); 467 IPSTAT_INC(ips_forward); 468 IPSTAT_INC(ips_fastforward); 469 } 470 consumed: 471 RTFREE(ro.ro_rt); 472 return NULL; 473 drop: 474 if (m) 475 m_freem(m); 476 if (ro.ro_rt) 477 RTFREE(ro.ro_rt); 478 return NULL; 479 } 480