ip_fastfwd.c revision 254523
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: head/sys/netinet/ip_fastfwd.c 254523 2013-08-19 13:27:32Z andre $"); 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 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_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 109static VNET_DEFINE(int, ipfastforward_active); 110#define V_ipfastforward_active VNET(ipfastforward_active) 111 112SYSCTL_VNET_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, 113 &VNET_NAME(ipfastforward_active), 0, "Enable fast IP forwarding"); 114 115static struct sockaddr_in * 116ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) 117{ 118 struct sockaddr_in *dst; 119 struct rtentry *rt; 120 121 /* 122 * Find route to destination. 123 */ 124 bzero(ro, sizeof(*ro)); 125 dst = (struct sockaddr_in *)&ro->ro_dst; 126 dst->sin_family = AF_INET; 127 dst->sin_len = sizeof(*dst); 128 dst->sin_addr.s_addr = dest.s_addr; 129 in_rtalloc_ign(ro, 0, M_GETFIB(m)); 130 131 /* 132 * Route there and interface still up? 133 */ 134 rt = ro->ro_rt; 135 if (rt && (rt->rt_flags & RTF_UP) && 136 (rt->rt_ifp->if_flags & IFF_UP) && 137 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { 138 if (rt->rt_flags & RTF_GATEWAY) 139 dst = (struct sockaddr_in *)rt->rt_gateway; 140 } else { 141 IPSTAT_INC(ips_noroute); 142 IPSTAT_INC(ips_cantforward); 143 if (rt) 144 RTFREE(rt); 145 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 146 return NULL; 147 } 148 return dst; 149} 150 151/* 152 * Try to forward a packet based on the destination address. 153 * This is a fast path optimized for the plain forwarding case. 154 * If the packet is handled (and consumed) here then we return NULL; 155 * otherwise mbuf is returned and the packet should be delivered 156 * to ip_input for full processing. 157 */ 158struct mbuf * 159ip_fastforward(struct mbuf *m) 160{ 161 struct ip *ip; 162 struct mbuf *m0 = NULL; 163 struct route ro; 164 struct sockaddr_in *dst = NULL; 165 struct ifnet *ifp; 166 struct in_addr odest, dest; 167 uint16_t sum, ip_len, ip_off; 168 int error = 0; 169 int hlen, mtu; 170 struct m_tag *fwd_tag = NULL; 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 bzero(&ro, sizeof(ro)); 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 IPSTAT_INC(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 IPSTAT_INC(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 IPSTAT_INC(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 IPSTAT_INC(ips_badhlen); 220 goto drop; 221 } 222 if (hlen > m->m_len) { 223 if ((m = m_pullup(m, hlen)) == NULL) { 224 IPSTAT_INC(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 IPSTAT_INC(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 IPSTAT_INC(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 IPSTAT_INC(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 IPSTAT_INC(ips_total); 336 337 /* 338 * Step 3: incoming packet firewall processing 339 */ 340 341 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 342 343 /* 344 * Run through list of ipfilter hooks for input packets 345 */ 346 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 347 goto passin; 348 349 if (pfil_run_hooks( 350 &V_inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 351 m == NULL) 352 goto drop; 353 354 M_ASSERTVALID(m); 355 M_ASSERTPKTHDR(m); 356 357 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 358 dest.s_addr = ip->ip_dst.s_addr; 359 360 /* 361 * Destination address changed? 362 */ 363 if (odest.s_addr != dest.s_addr) { 364 /* 365 * Is it now for a local address on this host? 366 */ 367 if (in_localip(dest)) 368 goto forwardlocal; 369 /* 370 * Go on with new destination address 371 */ 372 } 373 374 if (m->m_flags & M_FASTFWD_OURS) { 375 /* 376 * ipfw changed it for a local address on this host. 377 */ 378 goto forwardlocal; 379 } 380 381passin: 382 /* 383 * Step 4: decrement TTL and look up route 384 */ 385 386 /* 387 * Check TTL 388 */ 389#ifdef IPSTEALTH 390 if (!V_ipstealth) { 391#endif 392 if (ip->ip_ttl <= IPTTLDEC) { 393 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 394 return NULL; /* mbuf already free'd */ 395 } 396 397 /* 398 * Decrement the TTL and incrementally change the IP header checksum. 399 * Don't bother doing this with hw checksum offloading, it's faster 400 * doing it right here. 401 */ 402 ip->ip_ttl -= IPTTLDEC; 403 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 404 ip->ip_sum -= ~htons(IPTTLDEC << 8); 405 else 406 ip->ip_sum += htons(IPTTLDEC << 8); 407#ifdef IPSTEALTH 408 } 409#endif 410 411 /* 412 * Find route to destination. 413 */ 414 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 415 return NULL; /* icmp unreach already sent */ 416 ifp = ro.ro_rt->rt_ifp; 417 418 /* 419 * Immediately drop blackholed traffic, and directed broadcasts 420 * for either the all-ones or all-zero subnet addresses on 421 * locally attached networks. 422 */ 423 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 424 goto drop; 425 426 /* 427 * Step 5: outgoing firewall packet processing 428 */ 429 430 /* 431 * Run through list of hooks for output packets. 432 */ 433 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 434 goto passout; 435 436 if (pfil_run_hooks(&V_inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 437 goto drop; 438 } 439 440 M_ASSERTVALID(m); 441 M_ASSERTPKTHDR(m); 442 443 ip = mtod(m, struct ip *); 444 dest.s_addr = ip->ip_dst.s_addr; 445 446 /* 447 * Destination address changed? 448 */ 449 if (m->m_flags & M_IP_NEXTHOP) 450 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 451 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 452 /* 453 * Is it now for a local address on this host? 454 */ 455 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 456forwardlocal: 457 /* 458 * Return packet for processing by ip_input(). 459 */ 460 m->m_flags |= M_FASTFWD_OURS; 461 if (ro.ro_rt) 462 RTFREE(ro.ro_rt); 463 return m; 464 } 465 /* 466 * Redo route lookup with new destination address 467 */ 468 if (fwd_tag) { 469 dest.s_addr = ((struct sockaddr_in *) 470 (fwd_tag + 1))->sin_addr.s_addr; 471 m_tag_delete(m, fwd_tag); 472 m->m_flags &= ~M_IP_NEXTHOP; 473 } 474 RTFREE(ro.ro_rt); 475 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 476 return NULL; /* icmp unreach already sent */ 477 ifp = ro.ro_rt->rt_ifp; 478 } 479 480passout: 481 /* 482 * Step 6: send off the packet 483 */ 484 ip_len = ntohs(ip->ip_len); 485 ip_off = ntohs(ip->ip_off); 486 487 /* 488 * Check if route is dampned (when ARP is unable to resolve) 489 */ 490 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 491 (ro.ro_rt->rt_rmx.rmx_expire == 0 || 492 time_uptime < ro.ro_rt->rt_rmx.rmx_expire)) { 493 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 494 goto consumed; 495 } 496 497#ifndef ALTQ 498 /* 499 * Check if there is enough space in the interface queue 500 */ 501 if ((ifp->if_snd.ifq_len + ip_len / ifp->if_mtu + 1) >= 502 ifp->if_snd.ifq_maxlen) { 503 IPSTAT_INC(ips_odropped); 504 /* would send source quench here but that is depreciated */ 505 goto drop; 506 } 507#endif 508 509 /* 510 * Check if media link state of interface is not down 511 */ 512 if (ifp->if_link_state == LINK_STATE_DOWN) { 513 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 514 goto consumed; 515 } 516 517 /* 518 * Check if packet fits MTU or if hardware will fragment for us 519 */ 520 if (ro.ro_rt->rt_rmx.rmx_mtu) 521 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); 522 else 523 mtu = ifp->if_mtu; 524 525 if (ip_len <= mtu || 526 (ifp->if_hwassist & CSUM_FRAGMENT && (ip_off & IP_DF) == 0)) { 527 /* 528 * Avoid confusing lower layers. 529 */ 530 m_clrprotoflags(m); 531 /* 532 * Send off the packet via outgoing interface 533 */ 534 error = (*ifp->if_output)(ifp, m, 535 (struct sockaddr *)dst, &ro); 536 } else { 537 /* 538 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 539 */ 540 if (ip_off & IP_DF) { 541 IPSTAT_INC(ips_cantfrag); 542 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 543 0, mtu); 544 goto consumed; 545 } else { 546 /* 547 * We have to fragment the packet 548 */ 549 m->m_pkthdr.csum_flags |= CSUM_IP; 550 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist)) 551 goto drop; 552 KASSERT(m != NULL, ("null mbuf and no error")); 553 /* 554 * Send off the fragments via outgoing interface 555 */ 556 error = 0; 557 do { 558 m0 = m->m_nextpkt; 559 m->m_nextpkt = NULL; 560 /* 561 * Avoid confusing lower layers. 562 */ 563 m_clrprotoflags(m); 564 565 error = (*ifp->if_output)(ifp, m, 566 (struct sockaddr *)dst, &ro); 567 if (error) 568 break; 569 } while ((m = m0) != NULL); 570 if (error) { 571 /* Reclaim remaining fragments */ 572 for (m = m0; m; m = m0) { 573 m0 = m->m_nextpkt; 574 m_freem(m); 575 } 576 } else 577 IPSTAT_INC(ips_fragmented); 578 } 579 } 580 581 if (error != 0) 582 IPSTAT_INC(ips_odropped); 583 else { 584 ro.ro_rt->rt_rmx.rmx_pksent++; 585 IPSTAT_INC(ips_forward); 586 IPSTAT_INC(ips_fastforward); 587 } 588consumed: 589 RTFREE(ro.ro_rt); 590 return NULL; 591drop: 592 if (m) 593 m_freem(m); 594 if (ro.ro_rt) 595 RTFREE(ro.ro_rt); 596 return NULL; 597} 598