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_ipfw.h" 80 #include "opt_ipstealth.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/malloc.h> 86 #include <sys/mbuf.h> 87 #include <sys/protosw.h> 88 #include <sys/socket.h> 89 #include <sys/sysctl.h> 90 #include <sys/vimage.h> 91 92 #include <net/pfil.h> 93 #include <net/if.h> 94 #include <net/if_types.h> 95 #include <net/if_var.h> 96 #include <net/if_dl.h> 97 #include <net/route.h> 98 99 #include <netinet/in.h> 100 #include <netinet/in_systm.h> 101 #include <netinet/in_var.h> 102 #include <netinet/ip.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip_icmp.h> 105 #include <netinet/ip_options.h> 106 107 #include <machine/in_cksum.h> 108 109 static int ipfastforward_active = 0; 110 SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, 111 &ipfastforward_active, 0, "Enable fast IP forwarding"); 112 113 static struct sockaddr_in * 114 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) 115 { 116 struct sockaddr_in *dst; 117 struct rtentry *rt; 118 119 /* 120 * Find route to destination. 121 */ 122 bzero(ro, sizeof(*ro)); 123 dst = (struct sockaddr_in *)&ro->ro_dst; 124 dst->sin_family = AF_INET; 125 dst->sin_len = sizeof(*dst); 126 dst->sin_addr.s_addr = dest.s_addr; 127 in_rtalloc_ign(ro, RTF_CLONING, M_GETFIB(m)); 128 129 /* 130 * Route there and interface still up? 131 */ 132 rt = ro->ro_rt; 133 if (rt && (rt->rt_flags & RTF_UP) && 134 (rt->rt_ifp->if_flags & IFF_UP) && 135 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { 136 if (rt->rt_flags & RTF_GATEWAY) 137 dst = (struct sockaddr_in *)rt->rt_gateway; 138 } else { 139 V_ipstat.ips_noroute++; 140 V_ipstat.ips_cantforward++; 141 if (rt) 142 RTFREE(rt); 143 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 144 return NULL; 145 } 146 return dst; 147 } 148 149 /* 150 * Try to forward a packet based on the destination address. 151 * This is a fast path optimized for the plain forwarding case. 152 * If the packet is handled (and consumed) here then we return 1; 153 * otherwise 0 is returned and the packet should be delivered 154 * to ip_input for full processing. 155 */ 156 struct mbuf * 157 ip_fastforward(struct mbuf *m) 158 { 159 struct ip *ip; 160 struct mbuf *m0 = NULL; 161 struct route ro; 162 struct sockaddr_in *dst = NULL; 163 struct ifnet *ifp; 164 struct in_addr odest, dest; 165 u_short sum, ip_len; 166 int error = 0; 167 int hlen, mtu; 168 #ifdef IPFIREWALL_FORWARD 169 struct m_tag *fwd_tag; 170 #endif 171 172 /* 173 * Are we active and forwarding packets? 174 */ 175 if (!V_ipfastforward_active || !V_ipforwarding) 176 return m; 177 178 M_ASSERTVALID(m); 179 M_ASSERTPKTHDR(m); 180 181 ro.ro_rt = NULL; 182 183 /* 184 * Step 1: check for packet drop conditions (and sanity checks) 185 */ 186 187 /* 188 * Is entire packet big enough? 189 */ 190 if (m->m_pkthdr.len < sizeof(struct ip)) { 191 V_ipstat.ips_tooshort++; 192 goto drop; 193 } 194 195 /* 196 * Is first mbuf large enough for ip header and is header present? 197 */ 198 if (m->m_len < sizeof (struct ip) && 199 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 200 V_ipstat.ips_toosmall++; 201 return NULL; /* mbuf already free'd */ 202 } 203 204 ip = mtod(m, struct ip *); 205 206 /* 207 * Is it IPv4? 208 */ 209 if (ip->ip_v != IPVERSION) { 210 V_ipstat.ips_badvers++; 211 goto drop; 212 } 213 214 /* 215 * Is IP header length correct and is it in first mbuf? 216 */ 217 hlen = ip->ip_hl << 2; 218 if (hlen < sizeof(struct ip)) { /* minimum header length */ 219 V_ipstat.ips_badlen++; 220 goto drop; 221 } 222 if (hlen > m->m_len) { 223 if ((m = m_pullup(m, hlen)) == NULL) { 224 V_ipstat.ips_badhlen++; 225 return NULL; /* mbuf already free'd */ 226 } 227 ip = mtod(m, struct ip *); 228 } 229 230 /* 231 * Checksum correct? 232 */ 233 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) 234 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); 235 else { 236 if (hlen == sizeof(struct ip)) 237 sum = in_cksum_hdr(ip); 238 else 239 sum = in_cksum(m, hlen); 240 } 241 if (sum) { 242 V_ipstat.ips_badsum++; 243 goto drop; 244 } 245 246 /* 247 * Remember that we have checked the IP header and found it valid. 248 */ 249 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID); 250 251 ip_len = ntohs(ip->ip_len); 252 253 /* 254 * Is IP length longer than packet we have got? 255 */ 256 if (m->m_pkthdr.len < ip_len) { 257 V_ipstat.ips_tooshort++; 258 goto drop; 259 } 260 261 /* 262 * Is packet longer than IP header tells us? If yes, truncate packet. 263 */ 264 if (m->m_pkthdr.len > ip_len) { 265 if (m->m_len == m->m_pkthdr.len) { 266 m->m_len = ip_len; 267 m->m_pkthdr.len = ip_len; 268 } else 269 m_adj(m, ip_len - m->m_pkthdr.len); 270 } 271 272 /* 273 * Is packet from or to 127/8? 274 */ 275 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET || 276 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) { 277 V_ipstat.ips_badaddr++; 278 goto drop; 279 } 280 281 #ifdef ALTQ 282 /* 283 * Is packet dropped by traffic conditioner? 284 */ 285 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 286 goto drop; 287 #endif 288 289 /* 290 * Step 2: fallback conditions to normal ip_input path processing 291 */ 292 293 /* 294 * Only IP packets without options 295 */ 296 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 297 if (ip_doopts == 1) 298 return m; 299 else if (ip_doopts == 2) { 300 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 301 0, 0); 302 return NULL; /* mbuf already free'd */ 303 } 304 /* else ignore IP options and continue */ 305 } 306 307 /* 308 * Only unicast IP, not from loopback, no L2 or IP broadcast, 309 * no multicast, no INADDR_ANY 310 * 311 * XXX: Probably some of these checks could be direct drop 312 * conditions. However it is not clear whether there are some 313 * hacks or obscure behaviours which make it neccessary to 314 * let ip_input handle it. We play safe here and let ip_input 315 * deal with it until it is proven that we can directly drop it. 316 */ 317 if ((m->m_flags & (M_BCAST|M_MCAST)) || 318 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 319 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 320 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 321 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 322 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 323 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || 324 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 325 ip->ip_src.s_addr == INADDR_ANY || 326 ip->ip_dst.s_addr == INADDR_ANY ) 327 return m; 328 329 /* 330 * Is it for a local address on this host? 331 */ 332 if (in_localip(ip->ip_dst)) 333 return m; 334 335 V_ipstat.ips_total++; 336 337 /* 338 * Step 3: incoming packet firewall processing 339 */ 340 341 /* 342 * Convert to host representation 343 */ 344 ip->ip_len = ntohs(ip->ip_len); 345 ip->ip_off = ntohs(ip->ip_off); 346 347 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 348 349 /* 350 * Run through list of ipfilter hooks for input packets 351 */ 352 if (!PFIL_HOOKED(&inet_pfil_hook)) 353 goto passin; 354 355 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 356 m == NULL) 357 goto drop; 358 359 M_ASSERTVALID(m); 360 M_ASSERTPKTHDR(m); 361 362 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 363 dest.s_addr = ip->ip_dst.s_addr; 364 365 /* 366 * Destination address changed? 367 */ 368 if (odest.s_addr != dest.s_addr) { 369 /* 370 * Is it now for a local address on this host? 371 */ 372 if (in_localip(dest)) 373 goto forwardlocal; 374 /* 375 * Go on with new destination address 376 */ 377 } 378 #ifdef IPFIREWALL_FORWARD 379 if (m->m_flags & M_FASTFWD_OURS) { 380 /* 381 * ipfw changed it for a local address on this host. 382 */ 383 goto forwardlocal; 384 } 385 #endif /* IPFIREWALL_FORWARD */ 386 387 passin: 388 /* 389 * Step 4: decrement TTL and look up route 390 */ 391 392 /* 393 * Check TTL 394 */ 395 #ifdef IPSTEALTH 396 if (!V_ipstealth) { 397 #endif 398 if (ip->ip_ttl <= IPTTLDEC) { 399 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 400 return NULL; /* mbuf already free'd */ 401 } 402 403 /* 404 * Decrement the TTL and incrementally change the IP header checksum. 405 * Don't bother doing this with hw checksum offloading, it's faster 406 * doing it right here. 407 */ 408 ip->ip_ttl -= IPTTLDEC; 409 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 410 ip->ip_sum -= ~htons(IPTTLDEC << 8); 411 else 412 ip->ip_sum += htons(IPTTLDEC << 8); 413 #ifdef IPSTEALTH 414 } 415 #endif 416 417 /* 418 * Find route to destination. 419 */ 420 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 421 return NULL; /* icmp unreach already sent */ 422 ifp = ro.ro_rt->rt_ifp; 423 424 /* 425 * Immediately drop blackholed traffic, and directed broadcasts 426 * for either the all-ones or all-zero subnet addresses on 427 * locally attached networks. 428 */ 429 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 430 goto drop; 431 432 /* 433 * Step 5: outgoing firewall packet processing 434 */ 435 436 /* 437 * Run through list of hooks for output packets. 438 */ 439 if (!PFIL_HOOKED(&inet_pfil_hook)) 440 goto passout; 441 442 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 443 goto drop; 444 } 445 446 M_ASSERTVALID(m); 447 M_ASSERTPKTHDR(m); 448 449 ip = mtod(m, struct ip *); 450 dest.s_addr = ip->ip_dst.s_addr; 451 452 /* 453 * Destination address changed? 454 */ 455 #ifndef IPFIREWALL_FORWARD 456 if (odest.s_addr != dest.s_addr) { 457 #else 458 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 459 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 460 #endif /* IPFIREWALL_FORWARD */ 461 /* 462 * Is it now for a local address on this host? 463 */ 464 #ifndef IPFIREWALL_FORWARD 465 if (in_localip(dest)) { 466 #else 467 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 468 #endif /* IPFIREWALL_FORWARD */ 469 forwardlocal: 470 /* 471 * Return packet for processing by ip_input(). 472 * Keep host byte order as expected at ip_input's 473 * "ours"-label. 474 */ 475 m->m_flags |= M_FASTFWD_OURS; 476 if (ro.ro_rt) 477 RTFREE(ro.ro_rt); 478 return m; 479 } 480 /* 481 * Redo route lookup with new destination address 482 */ 483 #ifdef IPFIREWALL_FORWARD 484 if (fwd_tag) { 485 dest.s_addr = ((struct sockaddr_in *) 486 (fwd_tag + 1))->sin_addr.s_addr; 487 m_tag_delete(m, fwd_tag); 488 } 489 #endif /* IPFIREWALL_FORWARD */ 490 RTFREE(ro.ro_rt); 491 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 492 return NULL; /* icmp unreach already sent */ 493 ifp = ro.ro_rt->rt_ifp; 494 } 495 496 passout: 497 /* 498 * Step 6: send off the packet 499 */ 500 501 /* 502 * Check if route is dampned (when ARP is unable to resolve) 503 */ 504 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 505 (ro.ro_rt->rt_rmx.rmx_expire == 0 || 506 time_uptime < ro.ro_rt->rt_rmx.rmx_expire)) { 507 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 508 goto consumed; 509 } 510 511 #ifndef ALTQ 512 /* 513 * Check if there is enough space in the interface queue 514 */ 515 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= 516 ifp->if_snd.ifq_maxlen) { 517 V_ipstat.ips_odropped++; 518 /* would send source quench here but that is depreciated */ 519 goto drop; 520 } 521 #endif 522 523 /* 524 * Check if media link state of interface is not down 525 */ 526 if (ifp->if_link_state == LINK_STATE_DOWN) { 527 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 528 goto consumed; 529 } 530 531 /* 532 * Check if packet fits MTU or if hardware will fragment for us 533 */ 534 if (ro.ro_rt->rt_rmx.rmx_mtu) 535 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); 536 else 537 mtu = ifp->if_mtu; 538 539 if (ip->ip_len <= mtu || 540 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) { 541 /* 542 * Restore packet header fields to original values 543 */ 544 ip->ip_len = htons(ip->ip_len); 545 ip->ip_off = htons(ip->ip_off); 546 /* 547 * Send off the packet via outgoing interface 548 */ 549 error = (*ifp->if_output)(ifp, m, 550 (struct sockaddr *)dst, ro.ro_rt); 551 } else { 552 /* 553 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 554 */ 555 if (ip->ip_off & IP_DF) { 556 V_ipstat.ips_cantfrag++; 557 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 558 0, mtu); 559 goto consumed; 560 } else { 561 /* 562 * We have to fragment the packet 563 */ 564 m->m_pkthdr.csum_flags |= CSUM_IP; 565 /* 566 * ip_fragment expects ip_len and ip_off in host byte 567 * order but returns all packets in network byte order 568 */ 569 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist, 570 (~ifp->if_hwassist & CSUM_DELAY_IP))) { 571 goto drop; 572 } 573 KASSERT(m != NULL, ("null mbuf and no error")); 574 /* 575 * Send off the fragments via outgoing interface 576 */ 577 error = 0; 578 do { 579 m0 = m->m_nextpkt; 580 m->m_nextpkt = NULL; 581 582 error = (*ifp->if_output)(ifp, m, 583 (struct sockaddr *)dst, ro.ro_rt); 584 if (error) 585 break; 586 } while ((m = m0) != NULL); 587 if (error) { 588 /* Reclaim remaining fragments */ 589 for (m = m0; m; m = m0) { 590 m0 = m->m_nextpkt; 591 m_freem(m); 592 } 593 } else 594 V_ipstat.ips_fragmented++; 595 } 596 } 597 598 if (error != 0) 599 V_ipstat.ips_odropped++; 600 else { 601 ro.ro_rt->rt_rmx.rmx_pksent++; 602 V_ipstat.ips_forward++; 603 V_ipstat.ips_fastforward++; 604 } 605 consumed: 606 RTFREE(ro.ro_rt); 607 return NULL; 608 drop: 609 if (m) 610 m_freem(m); 611 if (ro.ro_rt) 612 RTFREE(ro.ro_rt); 613 return NULL; 614 } 615