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 * $FreeBSD$ 30 */ 31 32 /* 33 * ip_fastforward gets its speed from processing the forwarded packet to 34 * completion (if_output on the other side) without any queues or netisr's. 35 * The receiving interface DMAs the packet into memory, the upper half of 36 * driver calls ip_fastforward, we do our routing table lookup and directly 37 * send it off to the outgoing interface which DMAs the packet to the 38 * network card. The only part of the packet we touch with the CPU is the 39 * IP header (unless there are complex firewall rules touching other parts 40 * of the packet, but that is up to you). We are essentially limited by bus 41 * bandwidth and how fast the network card/driver can set up receives and 42 * transmits. 43 * 44 * We handle basic errors, ip header errors, checksum errors, 45 * destination unreachable, fragmentation and fragmentation needed and 46 * report them via icmp to the sender. 47 * 48 * Else if something is not pure IPv4 unicast forwarding we fall back to 49 * the normal ip_input processing path. We should only be called from 50 * interfaces connected to the outside world. 51 * 52 * Firewalling is fully supported including divert, ipfw fwd and ipfilter 53 * ipnat and address rewrite. 54 * 55 * IPSEC is not supported if this host is a tunnel broker. IPSEC is 56 * supported for connections to/from local host. 57 * 58 * We try to do the least expensive (in CPU ops) checks and operations 59 * first to catch junk with as little overhead as possible. 60 * 61 * We take full advantage of hardware support for ip checksum and 62 * fragmentation offloading. 63 * 64 * We don't do ICMP redirect in the fast forwarding path. I have had my own 65 * cases where two core routers with Zebra routing suite would send millions 66 * ICMP redirects to connected hosts if the router to dest was not the default 67 * gateway. In one case it was filling the routing table of a host with close 68 * 300'000 cloned redirect entries until it ran out of kernel memory. However 69 * the networking code proved very robust and it didn't crash or went ill 70 * otherwise. 71 */ 72 73 /* 74 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which 75 * is being followed here. 76 */ 77 78 #include "opt_ipfw.h" 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/socket.h> 88 #include <sys/sysctl.h> 89 90 #include <net/pfil.h> 91 #include <net/if.h> 92 #include <net/if_types.h> 93 #include <net/if_var.h> 94 #include <net/if_dl.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/in_var.h> 100 #include <netinet/ip.h> 101 #include <netinet/ip_var.h> 102 #include <netinet/ip_icmp.h> 103 104 #include <machine/in_cksum.h> 105 106 static int ipfastforward_active = 0; 107 SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, 108 &ipfastforward_active, 0, "Enable fast IP forwarding"); 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 rtalloc_ign(ro, RTF_CLONING); 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_flags & IFF_RUNNING)) { 133 if (rt->rt_flags & RTF_GATEWAY) 134 dst = (struct sockaddr_in *)rt->rt_gateway; 135 } else { 136 ipstat.ips_noroute++; 137 ipstat.ips_cantforward++; 138 if (rt) 139 RTFREE(rt); 140 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL); 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 1; 150 * otherwise 0 is returned and the packet should be delivered 151 * to ip_input for full processing. 152 */ 153 int 154 ip_fastforward(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 in_ifaddr *ia = NULL; 161 struct ifaddr *ifa = NULL; 162 struct ifnet *ifp; 163 struct in_addr odest, dest; 164 u_short sum, ip_len; 165 int error = 0; 166 int hlen, mtu; 167 #ifdef IPFIREWALL_FORWARD 168 struct m_tag *fwd_tag; 169 #endif 170 171 /* 172 * Are we active and forwarding packets? 173 */ 174 if (!ipfastforward_active || !ipforwarding) 175 return 0; 176 177 M_ASSERTVALID(m); 178 M_ASSERTPKTHDR(m); 179 180 ro.ro_rt = NULL; 181 182 /* 183 * Step 1: check for packet drop conditions (and sanity checks) 184 */ 185 186 /* 187 * Is entire packet big enough? 188 */ 189 if (m->m_pkthdr.len < sizeof(struct ip)) { 190 ipstat.ips_tooshort++; 191 goto drop; 192 } 193 194 /* 195 * Is first mbuf large enough for ip header and is header present? 196 */ 197 if (m->m_len < sizeof (struct ip) && 198 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 199 ipstat.ips_toosmall++; 200 return 1; /* mbuf already free'd */ 201 } 202 203 ip = mtod(m, struct ip *); 204 205 /* 206 * Is it IPv4? 207 */ 208 if (ip->ip_v != IPVERSION) { 209 ipstat.ips_badvers++; 210 goto drop; 211 } 212 213 /* 214 * Is IP header length correct and is it in first mbuf? 215 */ 216 hlen = ip->ip_hl << 2; 217 if (hlen < sizeof(struct ip)) { /* minimum header length */ 218 ipstat.ips_badlen++; 219 goto drop; 220 } 221 if (hlen > m->m_len) { 222 if ((m = m_pullup(m, hlen)) == 0) { 223 ipstat.ips_badhlen++; 224 return 1; 225 } 226 ip = mtod(m, struct ip *); 227 } 228 229 /* 230 * Checksum correct? 231 */ 232 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) 233 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); 234 else { 235 if (hlen == sizeof(struct ip)) 236 sum = in_cksum_hdr(ip); 237 else 238 sum = in_cksum(m, hlen); 239 } 240 if (sum) { 241 ipstat.ips_badsum++; 242 goto drop; 243 } 244 245 /* 246 * Remeber that we have checked the IP header and found it valid. 247 */ 248 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID); 249 250 ip_len = ntohs(ip->ip_len); 251 252 /* 253 * Is IP length longer than packet we have got? 254 */ 255 if (m->m_pkthdr.len < ip_len) { 256 ipstat.ips_tooshort++; 257 goto drop; 258 } 259 260 /* 261 * Is packet longer than IP header tells us? If yes, truncate packet. 262 */ 263 if (m->m_pkthdr.len > ip_len) { 264 if (m->m_len == m->m_pkthdr.len) { 265 m->m_len = ip_len; 266 m->m_pkthdr.len = ip_len; 267 } else 268 m_adj(m, ip_len - m->m_pkthdr.len); 269 } 270 271 /* 272 * Is packet from or to 127/8? 273 */ 274 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET || 275 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) { 276 ipstat.ips_badaddr++; 277 goto drop; 278 } 279 280 #ifdef ALTQ 281 /* 282 * Is packet dropped by traffic conditioner? 283 */ 284 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 285 return 1; 286 #endif 287 288 /* 289 * Step 2: fallback conditions to normal ip_input path processing 290 */ 291 292 /* 293 * Only IP packets without options 294 */ 295 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 296 if (ip_doopts == 1) 297 return 0; 298 else if (ip_doopts == 2) { 299 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 300 0, NULL); 301 return 1; 302 } 303 /* else ignore IP options and continue */ 304 } 305 306 /* 307 * Only unicast IP, not from loopback, no L2 or IP broadcast, 308 * no multicast, no INADDR_ANY 309 * 310 * XXX: Probably some of these checks could be direct drop 311 * conditions. However it is not clear whether there are some 312 * hacks or obscure behaviours which make it neccessary to 313 * let ip_input handle it. We play safe here and let ip_input 314 * deal with it until it is proven that we can directly drop it. 315 */ 316 if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 317 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 318 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 319 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 320 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 321 ip->ip_dst.s_addr == INADDR_ANY ) 322 return 0; 323 324 /* 325 * Is it for a local address on this host? 326 */ 327 if (in_localip(ip->ip_dst)) 328 return 0; 329 330 /* 331 * Or is it for a local IP broadcast address on this host? 332 */ 333 if ((m->m_flags & M_BCAST) && 334 (m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST)) { 335 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) { 336 if (ifa->ifa_addr->sa_family != AF_INET) 337 continue; 338 ia = ifatoia(ifa); 339 if (ia->ia_netbroadcast.s_addr == ip->ip_dst.s_addr) 340 return 0; 341 if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr == 342 ip->ip_dst.s_addr) 343 return 0; 344 } 345 } 346 ipstat.ips_total++; 347 348 /* 349 * Step 3: incoming packet firewall processing 350 */ 351 352 /* 353 * Convert to host representation 354 */ 355 ip->ip_len = ntohs(ip->ip_len); 356 ip->ip_off = ntohs(ip->ip_off); 357 358 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 359 360 /* 361 * Run through list of ipfilter hooks for input packets 362 */ 363 if (inet_pfil_hook.ph_busy_count == -1) 364 goto passin; 365 366 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 367 m == NULL) 368 return 1; 369 370 M_ASSERTVALID(m); 371 M_ASSERTPKTHDR(m); 372 373 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 374 dest.s_addr = ip->ip_dst.s_addr; 375 376 /* 377 * Destination address changed? 378 */ 379 if (odest.s_addr != dest.s_addr) { 380 /* 381 * Is it now for a local address on this host? 382 */ 383 if (in_localip(dest)) 384 goto forwardlocal; 385 /* 386 * Go on with new destination address 387 */ 388 } 389 #ifdef IPFIREWALL_FORWARD 390 if (m->m_flags & M_FASTFWD_OURS) { 391 /* 392 * ipfw changed it for a local address on this host. 393 */ 394 goto forwardlocal; 395 } 396 #endif /* IPFIREWALL_FORWARD */ 397 398 passin: 399 /* 400 * Step 4: decrement TTL and look up route 401 */ 402 403 /* 404 * Check TTL 405 */ 406 #ifdef IPSTEALTH 407 if (!ipstealth) { 408 #endif 409 if (ip->ip_ttl <= IPTTLDEC) { 410 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, NULL); 411 return 1; 412 } 413 414 /* 415 * Decrement the TTL and incrementally change the IP header checksum. 416 * Don't bother doing this with hw checksum offloading, it's faster 417 * doing it right here. 418 */ 419 ip->ip_ttl -= IPTTLDEC; 420 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 421 ip->ip_sum -= ~htons(IPTTLDEC << 8); 422 else 423 ip->ip_sum += htons(IPTTLDEC << 8); 424 #ifdef IPSTEALTH 425 } 426 #endif 427 428 /* 429 * Find route to destination. 430 */ 431 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 432 return 1; /* icmp unreach already sent */ 433 ifp = ro.ro_rt->rt_ifp; 434 435 /* 436 * Immediately drop blackholed traffic. 437 */ 438 if (ro.ro_rt->rt_flags & RTF_BLACKHOLE) 439 goto drop; 440 441 /* 442 * Step 5: outgoing firewall packet processing 443 */ 444 445 /* 446 * Run through list of hooks for output packets. 447 */ 448 if (inet_pfil_hook.ph_busy_count == -1) 449 goto passout; 450 451 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 452 goto consumed; 453 } 454 455 M_ASSERTVALID(m); 456 M_ASSERTPKTHDR(m); 457 458 ip = mtod(m, struct ip *); 459 dest.s_addr = ip->ip_dst.s_addr; 460 461 /* 462 * Destination address changed? 463 */ 464 #ifndef IPFIREWALL_FORWARD 465 if (odest.s_addr != dest.s_addr) { 466 #else 467 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 468 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 469 #endif /* IPFIREWALL_FORWARD */ 470 /* 471 * Is it now for a local address on this host? 472 */ 473 #ifndef IPFIREWALL_FORWARD 474 if (in_localip(dest)) { 475 #else 476 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 477 #endif /* IPFIREWALL_FORWARD */ 478 forwardlocal: 479 /* 480 * Return packet for processing by ip_input(). 481 * Keep host byte order as expected at ip_input's 482 * "ours"-label. 483 */ 484 m->m_flags |= M_FASTFWD_OURS; 485 if (ro.ro_rt) 486 RTFREE(ro.ro_rt); 487 return 0; 488 } 489 /* 490 * Redo route lookup with new destination address 491 */ 492 #ifdef IPFIREWALL_FORWARD 493 if (fwd_tag) { 494 if (!in_localip(ip->ip_src) && !in_localaddr(ip->ip_dst)) 495 dest.s_addr = ((struct sockaddr_in *)(fwd_tag+1))->sin_addr.s_addr; 496 m_tag_delete(m, fwd_tag); 497 } 498 #endif /* IPFIREWALL_FORWARD */ 499 RTFREE(ro.ro_rt); 500 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 501 return 1; /* icmp unreach already sent */ 502 ifp = ro.ro_rt->rt_ifp; 503 } 504 505 passout: 506 /* 507 * Step 6: send off the packet 508 */ 509 510 /* 511 * Check if route is dampned (when ARP is unable to resolve) 512 */ 513 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 514 ro.ro_rt->rt_rmx.rmx_expire >= time_second) { 515 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL); 516 goto consumed; 517 } 518 519 #ifndef ALTQ 520 /* 521 * Check if there is enough space in the interface queue 522 */ 523 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= 524 ifp->if_snd.ifq_maxlen) { 525 ipstat.ips_odropped++; 526 /* would send source quench here but that is depreciated */ 527 goto drop; 528 } 529 #endif 530 531 /* 532 * Check if media link state of interface is not down 533 */ 534 if (ifp->if_link_state == LINK_STATE_DOWN) { 535 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL); 536 goto consumed; 537 } 538 539 /* 540 * Check if packet fits MTU or if hardware will fragement for us 541 */ 542 if (ro.ro_rt->rt_rmx.rmx_mtu) 543 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); 544 else 545 mtu = ifp->if_mtu; 546 547 if (ip->ip_len <= mtu || 548 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) { 549 /* 550 * Restore packet header fields to original values 551 */ 552 ip->ip_len = htons(ip->ip_len); 553 ip->ip_off = htons(ip->ip_off); 554 /* 555 * Send off the packet via outgoing interface 556 */ 557 error = (*ifp->if_output)(ifp, m, 558 (struct sockaddr *)dst, ro.ro_rt); 559 } else { 560 /* 561 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 562 */ 563 if (ip->ip_off & IP_DF) { 564 ipstat.ips_cantfrag++; 565 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 566 0, ifp); 567 goto consumed; 568 } else { 569 /* 570 * We have to fragement the packet 571 */ 572 m->m_pkthdr.csum_flags |= CSUM_IP; 573 /* 574 * ip_fragment expects ip_len and ip_off in host byte 575 * order but returns all packets in network byte order 576 */ 577 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist, 578 (~ifp->if_hwassist & CSUM_DELAY_IP))) { 579 goto drop; 580 } 581 KASSERT(m != NULL, ("null mbuf and no error")); 582 /* 583 * Send off the fragments via outgoing interface 584 */ 585 error = 0; 586 do { 587 m0 = m->m_nextpkt; 588 m->m_nextpkt = NULL; 589 590 error = (*ifp->if_output)(ifp, m, 591 (struct sockaddr *)dst, ro.ro_rt); 592 if (error) 593 break; 594 } while ((m = m0) != NULL); 595 if (error) { 596 /* Reclaim remaining fragments */ 597 for (; m; m = m0) { 598 m0 = m->m_nextpkt; 599 m->m_nextpkt = NULL; 600 m_freem(m); 601 } 602 } else 603 ipstat.ips_fragmented++; 604 } 605 } 606 607 if (error != 0) 608 ipstat.ips_odropped++; 609 else { 610 ro.ro_rt->rt_rmx.rmx_pksent++; 611 ipstat.ips_forward++; 612 ipstat.ips_fastforward++; 613 } 614 consumed: 615 RTFREE(ro.ro_rt); 616 return 1; 617 drop: 618 if (m) 619 m_freem(m); 620 if (ro.ro_rt) 621 RTFREE(ro.ro_rt); 622 return 1; 623 } 624