Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_syncache.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
1 /*- 2 * Copyright (c) 2001 Networks Associates Technology, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by Jonathan Lemon 6 * and NAI Labs, the Security Research Division of Network Associates, Inc. 7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 8 * DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. The name of the author may not be used to endorse or promote 19 * products derived from this software without specific prior written 20 * permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $FreeBSD: releng/5.3/sys/netinet/tcp_syncache.c 136588 2004-10-16 08:43:07Z cvs2svn $ 35 */ 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_mac.h" 41 #include "opt_tcpdebug.h" 42 #include "opt_tcp_sack.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/kernel.h> 47 #include <sys/sysctl.h> 48 #include <sys/malloc.h> 49 #include <sys/mac.h> 50 #include <sys/mbuf.h> 51 #include <sys/md5.h> 52 #include <sys/proc.h> /* for proc0 declaration */ 53 #include <sys/random.h> 54 #include <sys/socket.h> 55 #include <sys/socketvar.h> 56 57 #include <net/if.h> 58 #include <net/route.h> 59 60 #include <netinet/in.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/ip.h> 63 #include <netinet/in_var.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/ip_var.h> 66 #ifdef INET6 67 #include <netinet/ip6.h> 68 #include <netinet/icmp6.h> 69 #include <netinet6/nd6.h> 70 #include <netinet6/ip6_var.h> 71 #include <netinet6/in6_pcb.h> 72 #endif 73 #include <netinet/tcp.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcpip.h> 76 #endif 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #ifdef TCPDEBUG 82 #include <netinet/tcp_debug.h> 83 #endif 84 #ifdef INET6 85 #include <netinet6/tcp6_var.h> 86 #endif 87 88 #ifdef IPSEC 89 #include <netinet6/ipsec.h> 90 #ifdef INET6 91 #include <netinet6/ipsec6.h> 92 #endif 93 #endif /*IPSEC*/ 94 95 #ifdef FAST_IPSEC 96 #include <netipsec/ipsec.h> 97 #ifdef INET6 98 #include <netipsec/ipsec6.h> 99 #endif 100 #include <netipsec/key.h> 101 #endif /*FAST_IPSEC*/ 102 103 #include <machine/in_cksum.h> 104 #include <vm/uma.h> 105 106 static int tcp_syncookies = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 108 &tcp_syncookies, 0, 109 "Use TCP SYN cookies if the syncache overflows"); 110 111 static void syncache_drop(struct syncache *, struct syncache_head *); 112 static void syncache_free(struct syncache *); 113 static void syncache_insert(struct syncache *, struct syncache_head *); 114 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 115 #ifdef TCPDEBUG 116 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 117 #else 118 static int syncache_respond(struct syncache *, struct mbuf *); 119 #endif 120 static struct socket *syncache_socket(struct syncache *, struct socket *, 121 struct mbuf *m); 122 static void syncache_timer(void *); 123 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *); 124 static struct syncache *syncookie_lookup(struct in_conninfo *, 125 struct tcphdr *, struct socket *); 126 127 /* 128 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 129 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 130 * the odds are that the user has given up attempting to connect by then. 131 */ 132 #define SYNCACHE_MAXREXMTS 3 133 134 /* Arbitrary values */ 135 #define TCP_SYNCACHE_HASHSIZE 512 136 #define TCP_SYNCACHE_BUCKETLIMIT 30 137 138 struct tcp_syncache { 139 struct syncache_head *hashbase; 140 uma_zone_t zone; 141 u_int hashsize; 142 u_int hashmask; 143 u_int bucket_limit; 144 u_int cache_count; 145 u_int cache_limit; 146 u_int rexmt_limit; 147 u_int hash_secret; 148 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 149 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 150 }; 151 static struct tcp_syncache tcp_syncache; 152 153 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 154 155 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 156 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 157 158 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 159 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 160 161 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 162 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 163 164 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 165 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 166 167 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 168 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 169 170 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 171 172 #define SYNCACHE_HASH(inc, mask) \ 173 ((tcp_syncache.hash_secret ^ \ 174 (inc)->inc_faddr.s_addr ^ \ 175 ((inc)->inc_faddr.s_addr >> 16) ^ \ 176 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 177 178 #define SYNCACHE_HASH6(inc, mask) \ 179 ((tcp_syncache.hash_secret ^ \ 180 (inc)->inc6_faddr.s6_addr32[0] ^ \ 181 (inc)->inc6_faddr.s6_addr32[3] ^ \ 182 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 183 184 #define ENDPTS_EQ(a, b) ( \ 185 (a)->ie_fport == (b)->ie_fport && \ 186 (a)->ie_lport == (b)->ie_lport && \ 187 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 188 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 189 ) 190 191 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 192 193 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 194 sc->sc_rxtslot = (slot); \ 195 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 196 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 197 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 198 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 199 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 200 syncache_timer, (void *)((intptr_t)(slot))); \ 201 } while (0) 202 203 static void 204 syncache_free(struct syncache *sc) 205 { 206 if (sc->sc_ipopts) 207 (void) m_free(sc->sc_ipopts); 208 209 uma_zfree(tcp_syncache.zone, sc); 210 } 211 212 void 213 syncache_init(void) 214 { 215 int i; 216 217 tcp_syncache.cache_count = 0; 218 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 219 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 220 tcp_syncache.cache_limit = 221 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 222 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 223 tcp_syncache.hash_secret = arc4random(); 224 225 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 226 &tcp_syncache.hashsize); 227 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 228 &tcp_syncache.cache_limit); 229 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 230 &tcp_syncache.bucket_limit); 231 if (!powerof2(tcp_syncache.hashsize)) { 232 printf("WARNING: syncache hash size is not a power of 2.\n"); 233 tcp_syncache.hashsize = 512; /* safe default */ 234 } 235 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 236 237 /* Allocate the hash table. */ 238 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 239 tcp_syncache.hashsize * sizeof(struct syncache_head), 240 M_SYNCACHE, M_WAITOK); 241 242 /* Initialize the hash buckets. */ 243 for (i = 0; i < tcp_syncache.hashsize; i++) { 244 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 245 tcp_syncache.hashbase[i].sch_length = 0; 246 } 247 248 /* Initialize the timer queues. */ 249 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 250 TAILQ_INIT(&tcp_syncache.timerq[i]); 251 callout_init(&tcp_syncache.tt_timerq[i], 252 debug_mpsafenet ? CALLOUT_MPSAFE : 0); 253 } 254 255 /* 256 * Allocate the syncache entries. Allow the zone to allocate one 257 * more entry than cache limit, so a new entry can bump out an 258 * older one. 259 */ 260 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 261 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 262 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 263 tcp_syncache.cache_limit -= 1; 264 } 265 266 static void 267 syncache_insert(sc, sch) 268 struct syncache *sc; 269 struct syncache_head *sch; 270 { 271 struct syncache *sc2; 272 int i; 273 274 INP_INFO_WLOCK_ASSERT(&tcbinfo); 275 276 /* 277 * Make sure that we don't overflow the per-bucket 278 * limit or the total cache size limit. 279 */ 280 if (sch->sch_length >= tcp_syncache.bucket_limit) { 281 /* 282 * The bucket is full, toss the oldest element. 283 */ 284 sc2 = TAILQ_FIRST(&sch->sch_bucket); 285 sc2->sc_tp->ts_recent = ticks; 286 syncache_drop(sc2, sch); 287 tcpstat.tcps_sc_bucketoverflow++; 288 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 289 /* 290 * The cache is full. Toss the oldest entry in the 291 * entire cache. This is the front entry in the 292 * first non-empty timer queue with the largest 293 * timeout value. 294 */ 295 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 296 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 297 if (sc2 != NULL) 298 break; 299 } 300 sc2->sc_tp->ts_recent = ticks; 301 syncache_drop(sc2, NULL); 302 tcpstat.tcps_sc_cacheoverflow++; 303 } 304 305 /* Initialize the entry's timer. */ 306 SYNCACHE_TIMEOUT(sc, 0); 307 308 /* Put it into the bucket. */ 309 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 310 sch->sch_length++; 311 tcp_syncache.cache_count++; 312 tcpstat.tcps_sc_added++; 313 } 314 315 static void 316 syncache_drop(sc, sch) 317 struct syncache *sc; 318 struct syncache_head *sch; 319 { 320 INP_INFO_WLOCK_ASSERT(&tcbinfo); 321 322 if (sch == NULL) { 323 #ifdef INET6 324 if (sc->sc_inc.inc_isipv6) { 325 sch = &tcp_syncache.hashbase[ 326 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 327 } else 328 #endif 329 { 330 sch = &tcp_syncache.hashbase[ 331 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 332 } 333 } 334 335 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 336 sch->sch_length--; 337 tcp_syncache.cache_count--; 338 339 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 340 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 341 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 342 343 syncache_free(sc); 344 } 345 346 /* 347 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 348 * If we have retransmitted an entry the maximum number of times, expire it. 349 */ 350 static void 351 syncache_timer(xslot) 352 void *xslot; 353 { 354 intptr_t slot = (intptr_t)xslot; 355 struct syncache *sc, *nsc; 356 struct inpcb *inp; 357 358 INP_INFO_WLOCK(&tcbinfo); 359 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 360 !callout_active(&tcp_syncache.tt_timerq[slot])) { 361 /* XXX can this happen? */ 362 INP_INFO_WUNLOCK(&tcbinfo); 363 return; 364 } 365 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 366 367 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 368 while (nsc != NULL) { 369 if (ticks < nsc->sc_rxttime) 370 break; 371 sc = nsc; 372 inp = sc->sc_tp->t_inpcb; 373 if (slot == SYNCACHE_MAXREXMTS || 374 slot >= tcp_syncache.rexmt_limit || 375 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 376 nsc = TAILQ_NEXT(sc, sc_timerq); 377 syncache_drop(sc, NULL); 378 tcpstat.tcps_sc_stale++; 379 continue; 380 } 381 /* 382 * syncache_respond() may call back into the syncache to 383 * to modify another entry, so do not obtain the next 384 * entry on the timer chain until it has completed. 385 */ 386 #ifdef TCPDEBUG 387 (void) syncache_respond(sc, NULL, NULL); 388 #else 389 (void) syncache_respond(sc, NULL); 390 #endif 391 nsc = TAILQ_NEXT(sc, sc_timerq); 392 tcpstat.tcps_sc_retransmitted++; 393 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 394 SYNCACHE_TIMEOUT(sc, slot + 1); 395 } 396 if (nsc != NULL) 397 callout_reset(&tcp_syncache.tt_timerq[slot], 398 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 399 INP_INFO_WUNLOCK(&tcbinfo); 400 } 401 402 /* 403 * Find an entry in the syncache. 404 */ 405 struct syncache * 406 syncache_lookup(inc, schp) 407 struct in_conninfo *inc; 408 struct syncache_head **schp; 409 { 410 struct syncache *sc; 411 struct syncache_head *sch; 412 413 INP_INFO_WLOCK_ASSERT(&tcbinfo); 414 415 #ifdef INET6 416 if (inc->inc_isipv6) { 417 sch = &tcp_syncache.hashbase[ 418 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 419 *schp = sch; 420 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 421 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 422 return (sc); 423 } 424 } else 425 #endif 426 { 427 sch = &tcp_syncache.hashbase[ 428 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 429 *schp = sch; 430 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 431 #ifdef INET6 432 if (sc->sc_inc.inc_isipv6) 433 continue; 434 #endif 435 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 436 return (sc); 437 } 438 } 439 return (NULL); 440 } 441 442 /* 443 * This function is called when we get a RST for a 444 * non-existent connection, so that we can see if the 445 * connection is in the syn cache. If it is, zap it. 446 */ 447 void 448 syncache_chkrst(inc, th) 449 struct in_conninfo *inc; 450 struct tcphdr *th; 451 { 452 struct syncache *sc; 453 struct syncache_head *sch; 454 455 INP_INFO_WLOCK_ASSERT(&tcbinfo); 456 457 sc = syncache_lookup(inc, &sch); 458 if (sc == NULL) 459 return; 460 /* 461 * If the RST bit is set, check the sequence number to see 462 * if this is a valid reset segment. 463 * RFC 793 page 37: 464 * In all states except SYN-SENT, all reset (RST) segments 465 * are validated by checking their SEQ-fields. A reset is 466 * valid if its sequence number is in the window. 467 * 468 * The sequence number in the reset segment is normally an 469 * echo of our outgoing acknowlegement numbers, but some hosts 470 * send a reset with the sequence number at the rightmost edge 471 * of our receive window, and we have to handle this case. 472 */ 473 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 474 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 475 syncache_drop(sc, sch); 476 tcpstat.tcps_sc_reset++; 477 } 478 } 479 480 void 481 syncache_badack(inc) 482 struct in_conninfo *inc; 483 { 484 struct syncache *sc; 485 struct syncache_head *sch; 486 487 INP_INFO_WLOCK_ASSERT(&tcbinfo); 488 489 sc = syncache_lookup(inc, &sch); 490 if (sc != NULL) { 491 syncache_drop(sc, sch); 492 tcpstat.tcps_sc_badack++; 493 } 494 } 495 496 void 497 syncache_unreach(inc, th) 498 struct in_conninfo *inc; 499 struct tcphdr *th; 500 { 501 struct syncache *sc; 502 struct syncache_head *sch; 503 504 INP_INFO_WLOCK_ASSERT(&tcbinfo); 505 506 /* we are called at splnet() here */ 507 sc = syncache_lookup(inc, &sch); 508 if (sc == NULL) 509 return; 510 511 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 512 if (ntohl(th->th_seq) != sc->sc_iss) 513 return; 514 515 /* 516 * If we've rertransmitted 3 times and this is our second error, 517 * we remove the entry. Otherwise, we allow it to continue on. 518 * This prevents us from incorrectly nuking an entry during a 519 * spurious network outage. 520 * 521 * See tcp_notify(). 522 */ 523 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 524 sc->sc_flags |= SCF_UNREACH; 525 return; 526 } 527 syncache_drop(sc, sch); 528 tcpstat.tcps_sc_unreach++; 529 } 530 531 /* 532 * Build a new TCP socket structure from a syncache entry. 533 */ 534 static struct socket * 535 syncache_socket(sc, lso, m) 536 struct syncache *sc; 537 struct socket *lso; 538 struct mbuf *m; 539 { 540 struct inpcb *inp = NULL; 541 struct socket *so; 542 struct tcpcb *tp; 543 544 NET_ASSERT_GIANT(); 545 INP_INFO_WLOCK_ASSERT(&tcbinfo); 546 547 /* 548 * Ok, create the full blown connection, and set things up 549 * as they would have been set up if we had created the 550 * connection when the SYN arrived. If we can't create 551 * the connection, abort it. 552 */ 553 so = sonewconn(lso, SS_ISCONNECTED); 554 if (so == NULL) { 555 /* 556 * Drop the connection; we will send a RST if the peer 557 * retransmits the ACK, 558 */ 559 tcpstat.tcps_listendrop++; 560 goto abort2; 561 } 562 #ifdef MAC 563 SOCK_LOCK(so); 564 mac_set_socket_peer_from_mbuf(m, so); 565 SOCK_UNLOCK(so); 566 #endif 567 568 inp = sotoinpcb(so); 569 INP_LOCK(inp); 570 571 /* 572 * Insert new socket into hash list. 573 */ 574 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 575 #ifdef INET6 576 if (sc->sc_inc.inc_isipv6) { 577 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 578 } else { 579 inp->inp_vflag &= ~INP_IPV6; 580 inp->inp_vflag |= INP_IPV4; 581 #endif 582 inp->inp_laddr = sc->sc_inc.inc_laddr; 583 #ifdef INET6 584 } 585 #endif 586 inp->inp_lport = sc->sc_inc.inc_lport; 587 if (in_pcbinshash(inp) != 0) { 588 /* 589 * Undo the assignments above if we failed to 590 * put the PCB on the hash lists. 591 */ 592 #ifdef INET6 593 if (sc->sc_inc.inc_isipv6) 594 inp->in6p_laddr = in6addr_any; 595 else 596 #endif 597 inp->inp_laddr.s_addr = INADDR_ANY; 598 inp->inp_lport = 0; 599 goto abort; 600 } 601 #ifdef IPSEC 602 /* copy old policy into new socket's */ 603 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 604 printf("syncache_expand: could not copy policy\n"); 605 #endif 606 #ifdef FAST_IPSEC 607 /* copy old policy into new socket's */ 608 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 609 printf("syncache_expand: could not copy policy\n"); 610 #endif 611 #ifdef INET6 612 if (sc->sc_inc.inc_isipv6) { 613 struct inpcb *oinp = sotoinpcb(lso); 614 struct in6_addr laddr6; 615 struct sockaddr_in6 sin6; 616 /* 617 * Inherit socket options from the listening socket. 618 * Note that in6p_inputopts are not (and should not be) 619 * copied, since it stores previously received options and is 620 * used to detect if each new option is different than the 621 * previous one and hence should be passed to a user. 622 * If we copied in6p_inputopts, a user would not be able to 623 * receive options just after calling the accept system call. 624 */ 625 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 626 if (oinp->in6p_outputopts) 627 inp->in6p_outputopts = 628 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 629 630 sin6.sin6_family = AF_INET6; 631 sin6.sin6_len = sizeof(sin6); 632 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 633 sin6.sin6_port = sc->sc_inc.inc_fport; 634 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 635 laddr6 = inp->in6p_laddr; 636 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 637 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 638 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 639 thread0.td_ucred)) { 640 inp->in6p_laddr = laddr6; 641 goto abort; 642 } 643 /* Override flowlabel from in6_pcbconnect. */ 644 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 645 inp->in6p_flowinfo |= sc->sc_flowlabel; 646 } else 647 #endif 648 { 649 struct in_addr laddr; 650 struct sockaddr_in sin; 651 652 inp->inp_options = ip_srcroute(m); 653 if (inp->inp_options == NULL) { 654 inp->inp_options = sc->sc_ipopts; 655 sc->sc_ipopts = NULL; 656 } 657 658 sin.sin_family = AF_INET; 659 sin.sin_len = sizeof(sin); 660 sin.sin_addr = sc->sc_inc.inc_faddr; 661 sin.sin_port = sc->sc_inc.inc_fport; 662 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 663 laddr = inp->inp_laddr; 664 if (inp->inp_laddr.s_addr == INADDR_ANY) 665 inp->inp_laddr = sc->sc_inc.inc_laddr; 666 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 667 thread0.td_ucred)) { 668 inp->inp_laddr = laddr; 669 goto abort; 670 } 671 } 672 673 tp = intotcpcb(inp); 674 tp->t_state = TCPS_SYN_RECEIVED; 675 tp->iss = sc->sc_iss; 676 tp->irs = sc->sc_irs; 677 tcp_rcvseqinit(tp); 678 tcp_sendseqinit(tp); 679 tp->snd_wl1 = sc->sc_irs; 680 tp->rcv_up = sc->sc_irs + 1; 681 tp->rcv_wnd = sc->sc_wnd; 682 tp->rcv_adv += tp->rcv_wnd; 683 684 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 685 if (sc->sc_flags & SCF_NOOPT) 686 tp->t_flags |= TF_NOOPT; 687 if (sc->sc_flags & SCF_WINSCALE) { 688 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 689 tp->requested_s_scale = sc->sc_requested_s_scale; 690 tp->request_r_scale = sc->sc_request_r_scale; 691 } 692 if (sc->sc_flags & SCF_TIMESTAMP) { 693 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 694 tp->ts_recent = sc->sc_tsrecent; 695 tp->ts_recent_age = ticks; 696 } 697 if (sc->sc_flags & SCF_CC) { 698 /* 699 * Initialization of the tcpcb for transaction; 700 * set SND.WND = SEG.WND, 701 * initialize CCsend and CCrecv. 702 */ 703 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 704 tp->cc_send = sc->sc_cc_send; 705 tp->cc_recv = sc->sc_cc_recv; 706 } 707 #ifdef TCP_SIGNATURE 708 if (sc->sc_flags & SCF_SIGNATURE) 709 tp->t_flags |= TF_SIGNATURE; 710 #endif 711 if (sc->sc_flags & SCF_SACK) { 712 tp->sack_enable = 1; 713 tp->t_flags |= TF_SACK_PERMIT; 714 } 715 /* 716 * Set up MSS and get cached values from tcp_hostcache. 717 * This might overwrite some of the defaults we just set. 718 */ 719 tcp_mss(tp, sc->sc_peer_mss); 720 721 /* 722 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 723 */ 724 if (sc->sc_rxtslot != 0) 725 tp->snd_cwnd = tp->t_maxseg; 726 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 727 728 INP_UNLOCK(inp); 729 730 tcpstat.tcps_accepts++; 731 return (so); 732 733 abort: 734 INP_UNLOCK(inp); 735 abort2: 736 if (so != NULL) 737 (void) soabort(so); 738 return (NULL); 739 } 740 741 /* 742 * This function gets called when we receive an ACK for a 743 * socket in the LISTEN state. We look up the connection 744 * in the syncache, and if its there, we pull it out of 745 * the cache and turn it into a full-blown connection in 746 * the SYN-RECEIVED state. 747 */ 748 int 749 syncache_expand(inc, th, sop, m) 750 struct in_conninfo *inc; 751 struct tcphdr *th; 752 struct socket **sop; 753 struct mbuf *m; 754 { 755 struct syncache *sc; 756 struct syncache_head *sch; 757 struct socket *so; 758 759 INP_INFO_WLOCK_ASSERT(&tcbinfo); 760 761 sc = syncache_lookup(inc, &sch); 762 if (sc == NULL) { 763 /* 764 * There is no syncache entry, so see if this ACK is 765 * a returning syncookie. To do this, first: 766 * A. See if this socket has had a syncache entry dropped in 767 * the past. We don't want to accept a bogus syncookie 768 * if we've never received a SYN. 769 * B. check that the syncookie is valid. If it is, then 770 * cobble up a fake syncache entry, and return. 771 */ 772 if (!tcp_syncookies) 773 return (0); 774 sc = syncookie_lookup(inc, th, *sop); 775 if (sc == NULL) 776 return (0); 777 sch = NULL; 778 tcpstat.tcps_sc_recvcookie++; 779 } 780 781 /* 782 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 783 */ 784 if (th->th_ack != sc->sc_iss + 1) 785 return (0); 786 787 so = syncache_socket(sc, *sop, m); 788 if (so == NULL) { 789 #if 0 790 resetandabort: 791 /* XXXjlemon check this - is this correct? */ 792 (void) tcp_respond(NULL, m, m, th, 793 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 794 #endif 795 m_freem(m); /* XXX only needed for above */ 796 tcpstat.tcps_sc_aborted++; 797 } else 798 tcpstat.tcps_sc_completed++; 799 800 if (sch == NULL) 801 syncache_free(sc); 802 else 803 syncache_drop(sc, sch); 804 *sop = so; 805 return (1); 806 } 807 808 /* 809 * Given a LISTEN socket and an inbound SYN request, add 810 * this to the syn cache, and send back a segment: 811 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 812 * to the source. 813 * 814 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 815 * Doing so would require that we hold onto the data and deliver it 816 * to the application. However, if we are the target of a SYN-flood 817 * DoS attack, an attacker could send data which would eventually 818 * consume all available buffer space if it were ACKed. By not ACKing 819 * the data, we avoid this DoS scenario. 820 */ 821 int 822 syncache_add(inc, to, th, sop, m) 823 struct in_conninfo *inc; 824 struct tcpopt *to; 825 struct tcphdr *th; 826 struct socket **sop; 827 struct mbuf *m; 828 { 829 struct tcpcb *tp; 830 struct socket *so; 831 struct syncache *sc = NULL; 832 struct syncache_head *sch; 833 struct mbuf *ipopts = NULL; 834 struct rmxp_tao tao; 835 u_int32_t flowtmp; 836 int i, win; 837 838 INP_INFO_WLOCK_ASSERT(&tcbinfo); 839 840 so = *sop; 841 tp = sototcpcb(so); 842 bzero(&tao, sizeof(tao)); 843 844 /* 845 * Remember the IP options, if any. 846 */ 847 #ifdef INET6 848 if (!inc->inc_isipv6) 849 #endif 850 ipopts = ip_srcroute(m); 851 852 /* 853 * See if we already have an entry for this connection. 854 * If we do, resend the SYN,ACK, and reset the retransmit timer. 855 * 856 * XXX 857 * should the syncache be re-initialized with the contents 858 * of the new SYN here (which may have different options?) 859 */ 860 sc = syncache_lookup(inc, &sch); 861 if (sc != NULL) { 862 tcpstat.tcps_sc_dupsyn++; 863 if (ipopts) { 864 /* 865 * If we were remembering a previous source route, 866 * forget it and use the new one we've been given. 867 */ 868 if (sc->sc_ipopts) 869 (void) m_free(sc->sc_ipopts); 870 sc->sc_ipopts = ipopts; 871 } 872 /* 873 * Update timestamp if present. 874 */ 875 if (sc->sc_flags & SCF_TIMESTAMP) 876 sc->sc_tsrecent = to->to_tsval; 877 /* 878 * PCB may have changed, pick up new values. 879 */ 880 sc->sc_tp = tp; 881 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 882 #ifdef TCPDEBUG 883 if (syncache_respond(sc, m, so) == 0) { 884 #else 885 if (syncache_respond(sc, m) == 0) { 886 #endif 887 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 888 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 889 sc, sc_timerq); 890 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 891 tcpstat.tcps_sndacks++; 892 tcpstat.tcps_sndtotal++; 893 } 894 *sop = NULL; 895 return (1); 896 } 897 898 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 899 if (sc == NULL) { 900 /* 901 * The zone allocator couldn't provide more entries. 902 * Treat this as if the cache was full; drop the oldest 903 * entry and insert the new one. 904 */ 905 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 906 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 907 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 908 if (sc != NULL) 909 break; 910 } 911 sc->sc_tp->ts_recent = ticks; 912 syncache_drop(sc, NULL); 913 tcpstat.tcps_sc_zonefail++; 914 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 915 if (sc == NULL) { 916 if (ipopts) 917 (void) m_free(ipopts); 918 return (0); 919 } 920 } 921 922 /* 923 * Fill in the syncache values. 924 */ 925 bzero(sc, sizeof(*sc)); 926 sc->sc_tp = tp; 927 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 928 sc->sc_ipopts = ipopts; 929 sc->sc_inc.inc_fport = inc->inc_fport; 930 sc->sc_inc.inc_lport = inc->inc_lport; 931 #ifdef INET6 932 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 933 if (inc->inc_isipv6) { 934 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 935 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 936 } else 937 #endif 938 { 939 sc->sc_inc.inc_faddr = inc->inc_faddr; 940 sc->sc_inc.inc_laddr = inc->inc_laddr; 941 } 942 sc->sc_irs = th->th_seq; 943 sc->sc_flags = 0; 944 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 945 sc->sc_flowlabel = 0; 946 if (tcp_syncookies) { 947 sc->sc_iss = syncookie_generate(sc, &flowtmp); 948 #ifdef INET6 949 if (inc->inc_isipv6 && 950 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 951 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK; 952 } 953 #endif 954 } else { 955 sc->sc_iss = arc4random(); 956 #ifdef INET6 957 if (inc->inc_isipv6 && 958 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 959 sc->sc_flowlabel = 960 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 961 } 962 #endif 963 } 964 965 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 966 win = sbspace(&so->so_rcv); 967 win = imax(win, 0); 968 win = imin(win, TCP_MAXWIN); 969 sc->sc_wnd = win; 970 971 if (tcp_do_rfc1323) { 972 /* 973 * A timestamp received in a SYN makes 974 * it ok to send timestamp requests and replies. 975 */ 976 if (to->to_flags & TOF_TS) { 977 sc->sc_tsrecent = to->to_tsval; 978 sc->sc_flags |= SCF_TIMESTAMP; 979 } 980 if (to->to_flags & TOF_SCALE) { 981 int wscale = 0; 982 983 /* Compute proper scaling value from buffer space */ 984 while (wscale < TCP_MAX_WINSHIFT && 985 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 986 wscale++; 987 sc->sc_request_r_scale = wscale; 988 sc->sc_requested_s_scale = to->to_requested_s_scale; 989 sc->sc_flags |= SCF_WINSCALE; 990 } 991 } 992 if (tcp_do_rfc1644) { 993 /* 994 * A CC or CC.new option received in a SYN makes 995 * it ok to send CC in subsequent segments. 996 */ 997 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 998 sc->sc_cc_recv = to->to_cc; 999 sc->sc_cc_send = CC_INC(tcp_ccgen); 1000 sc->sc_flags |= SCF_CC; 1001 } 1002 } 1003 if (tp->t_flags & TF_NOOPT) 1004 sc->sc_flags = SCF_NOOPT; 1005 #ifdef TCP_SIGNATURE 1006 /* 1007 * If listening socket requested TCP digests, and received SYN 1008 * contains the option, flag this in the syncache so that 1009 * syncache_respond() will do the right thing with the SYN+ACK. 1010 * XXX Currently we always record the option by default and will 1011 * attempt to use it in syncache_respond(). 1012 */ 1013 if (to->to_flags & TOF_SIGNATURE) 1014 sc->sc_flags = SCF_SIGNATURE; 1015 #endif 1016 1017 if (to->to_flags & TOF_SACK) 1018 sc->sc_flags |= SCF_SACK; 1019 1020 /* 1021 * XXX 1022 * We have the option here of not doing TAO (even if the segment 1023 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1024 * This allows us to apply synflood protection to TAO-qualifying SYNs 1025 * also. However, there should be a hueristic to determine when to 1026 * do this, and is not present at the moment. 1027 */ 1028 1029 /* 1030 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1031 * - compare SEG.CC against cached CC from the same host, if any. 1032 * - if SEG.CC > chached value, SYN must be new and is accepted 1033 * immediately: save new CC in the cache, mark the socket 1034 * connected, enter ESTABLISHED state, turn on flag to 1035 * send a SYN in the next segment. 1036 * A virtual advertised window is set in rcv_adv to 1037 * initialize SWS prevention. Then enter normal segment 1038 * processing: drop SYN, process data and FIN. 1039 * - otherwise do a normal 3-way handshake. 1040 */ 1041 if (tcp_do_rfc1644) 1042 tcp_hc_gettao(&sc->sc_inc, &tao); 1043 1044 if ((to->to_flags & TOF_CC) != 0) { 1045 if (((tp->t_flags & TF_NOPUSH) != 0) && 1046 sc->sc_flags & SCF_CC && tao.tao_cc != 0 && 1047 CC_GT(to->to_cc, tao.tao_cc)) { 1048 sc->sc_rxtslot = 0; 1049 so = syncache_socket(sc, *sop, m); 1050 if (so != NULL) { 1051 tao.tao_cc = to->to_cc; 1052 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1053 tao.tao_cc, 0); 1054 *sop = so; 1055 } 1056 syncache_free(sc); 1057 return (so != NULL); 1058 } 1059 } else { 1060 /* 1061 * No CC option, but maybe CC.NEW: invalidate cached value. 1062 */ 1063 if (tcp_do_rfc1644) { 1064 tao.tao_cc = 0; 1065 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1066 tao.tao_cc, 0); 1067 } 1068 } 1069 1070 /* 1071 * TAO test failed or there was no CC option, 1072 * do a standard 3-way handshake. 1073 */ 1074 #ifdef TCPDEBUG 1075 if (syncache_respond(sc, m, so) == 0) { 1076 #else 1077 if (syncache_respond(sc, m) == 0) { 1078 #endif 1079 syncache_insert(sc, sch); 1080 tcpstat.tcps_sndacks++; 1081 tcpstat.tcps_sndtotal++; 1082 } else { 1083 syncache_free(sc); 1084 tcpstat.tcps_sc_dropped++; 1085 } 1086 *sop = NULL; 1087 return (1); 1088 } 1089 1090 #ifdef TCPDEBUG 1091 static int 1092 syncache_respond(sc, m, so) 1093 struct syncache *sc; 1094 struct mbuf *m; 1095 struct socket *so; 1096 #else 1097 static int 1098 syncache_respond(sc, m) 1099 struct syncache *sc; 1100 struct mbuf *m; 1101 #endif 1102 { 1103 u_int8_t *optp; 1104 int optlen, error; 1105 u_int16_t tlen, hlen, mssopt; 1106 struct ip *ip = NULL; 1107 struct tcphdr *th; 1108 struct inpcb *inp; 1109 #ifdef INET6 1110 struct ip6_hdr *ip6 = NULL; 1111 #endif 1112 1113 hlen = 1114 #ifdef INET6 1115 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1116 #endif 1117 sizeof(struct ip); 1118 1119 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1120 1121 /* Determine MSS we advertize to other end of connection */ 1122 mssopt = tcp_mssopt(&sc->sc_inc); 1123 1124 /* Compute the size of the TCP options. */ 1125 if (sc->sc_flags & SCF_NOOPT) { 1126 optlen = 0; 1127 } else { 1128 optlen = TCPOLEN_MAXSEG + 1129 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1130 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1131 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1132 #ifdef TCP_SIGNATURE 1133 optlen += (sc->sc_flags & SCF_SIGNATURE) ? 1134 TCPOLEN_SIGNATURE + 2 : 0; 1135 #endif 1136 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0); 1137 } 1138 tlen = hlen + sizeof(struct tcphdr) + optlen; 1139 1140 /* 1141 * XXX 1142 * assume that the entire packet will fit in a header mbuf 1143 */ 1144 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1145 1146 /* 1147 * XXX shouldn't this reuse the mbuf if possible ? 1148 * Create the IP+TCP header from scratch. 1149 */ 1150 if (m) 1151 m_freem(m); 1152 1153 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1154 if (m == NULL) 1155 return (ENOBUFS); 1156 m->m_data += max_linkhdr; 1157 m->m_len = tlen; 1158 m->m_pkthdr.len = tlen; 1159 m->m_pkthdr.rcvif = NULL; 1160 inp = sc->sc_tp->t_inpcb; 1161 INP_LOCK(inp); 1162 #ifdef MAC 1163 mac_create_mbuf_from_inpcb(inp, m); 1164 #endif 1165 1166 #ifdef INET6 1167 if (sc->sc_inc.inc_isipv6) { 1168 ip6 = mtod(m, struct ip6_hdr *); 1169 ip6->ip6_vfc = IPV6_VERSION; 1170 ip6->ip6_nxt = IPPROTO_TCP; 1171 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1172 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1173 ip6->ip6_plen = htons(tlen - hlen); 1174 /* ip6_hlim is set after checksum */ 1175 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1176 ip6->ip6_flow |= sc->sc_flowlabel; 1177 1178 th = (struct tcphdr *)(ip6 + 1); 1179 } else 1180 #endif 1181 { 1182 ip = mtod(m, struct ip *); 1183 ip->ip_v = IPVERSION; 1184 ip->ip_hl = sizeof(struct ip) >> 2; 1185 ip->ip_len = tlen; 1186 ip->ip_id = 0; 1187 ip->ip_off = 0; 1188 ip->ip_sum = 0; 1189 ip->ip_p = IPPROTO_TCP; 1190 ip->ip_src = sc->sc_inc.inc_laddr; 1191 ip->ip_dst = sc->sc_inc.inc_faddr; 1192 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1193 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1194 1195 /* 1196 * See if we should do MTU discovery. Route lookups are 1197 * expensive, so we will only unset the DF bit if: 1198 * 1199 * 1) path_mtu_discovery is disabled 1200 * 2) the SCF_UNREACH flag has been set 1201 */ 1202 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1203 ip->ip_off |= IP_DF; 1204 1205 th = (struct tcphdr *)(ip + 1); 1206 } 1207 th->th_sport = sc->sc_inc.inc_lport; 1208 th->th_dport = sc->sc_inc.inc_fport; 1209 1210 th->th_seq = htonl(sc->sc_iss); 1211 th->th_ack = htonl(sc->sc_irs + 1); 1212 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1213 th->th_x2 = 0; 1214 th->th_flags = TH_SYN|TH_ACK; 1215 th->th_win = htons(sc->sc_wnd); 1216 th->th_urp = 0; 1217 1218 /* Tack on the TCP options. */ 1219 if (optlen != 0) { 1220 optp = (u_int8_t *)(th + 1); 1221 *optp++ = TCPOPT_MAXSEG; 1222 *optp++ = TCPOLEN_MAXSEG; 1223 *optp++ = (mssopt >> 8) & 0xff; 1224 *optp++ = mssopt & 0xff; 1225 1226 if (sc->sc_flags & SCF_WINSCALE) { 1227 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1228 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1229 sc->sc_request_r_scale); 1230 optp += 4; 1231 } 1232 1233 if (sc->sc_flags & SCF_TIMESTAMP) { 1234 u_int32_t *lp = (u_int32_t *)(optp); 1235 1236 /* Form timestamp option per appendix A of RFC 1323. */ 1237 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1238 *lp++ = htonl(ticks); 1239 *lp = htonl(sc->sc_tsrecent); 1240 optp += TCPOLEN_TSTAMP_APPA; 1241 } 1242 1243 /* 1244 * Send CC and CC.echo if we received CC from our peer. 1245 */ 1246 if (sc->sc_flags & SCF_CC) { 1247 u_int32_t *lp = (u_int32_t *)(optp); 1248 1249 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1250 *lp++ = htonl(sc->sc_cc_send); 1251 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1252 *lp = htonl(sc->sc_cc_recv); 1253 optp += TCPOLEN_CC_APPA * 2; 1254 } 1255 1256 #ifdef TCP_SIGNATURE 1257 /* 1258 * Handle TCP-MD5 passive opener response. 1259 */ 1260 if (sc->sc_flags & SCF_SIGNATURE) { 1261 u_int8_t *bp = optp; 1262 int i; 1263 1264 *bp++ = TCPOPT_SIGNATURE; 1265 *bp++ = TCPOLEN_SIGNATURE; 1266 for (i = 0; i < TCP_SIGLEN; i++) 1267 *bp++ = 0; 1268 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1269 optp + 2, IPSEC_DIR_OUTBOUND); 1270 *bp++ = TCPOPT_NOP; 1271 *bp++ = TCPOPT_EOL; 1272 optp += TCPOLEN_SIGNATURE + 2; 1273 } 1274 #endif /* TCP_SIGNATURE */ 1275 1276 if (sc->sc_flags & SCF_SACK) { 1277 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR); 1278 optp += 4; 1279 } 1280 } 1281 1282 #ifdef INET6 1283 if (sc->sc_inc.inc_isipv6) { 1284 th->th_sum = 0; 1285 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1286 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1287 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1288 } else 1289 #endif 1290 { 1291 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1292 htons(tlen - hlen + IPPROTO_TCP)); 1293 m->m_pkthdr.csum_flags = CSUM_TCP; 1294 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1295 #ifdef TCPDEBUG 1296 /* 1297 * Trace. 1298 */ 1299 if (so != NULL && so->so_options & SO_DEBUG) { 1300 struct tcpcb *tp = sototcpcb(so); 1301 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1302 mtod(m, void *), th, 0); 1303 } 1304 #endif 1305 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1306 } 1307 INP_UNLOCK(inp); 1308 return (error); 1309 } 1310 1311 /* 1312 * cookie layers: 1313 * 1314 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1315 * | peer iss | 1316 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1317 * | 0 |(A)| | 1318 * (A): peer mss index 1319 */ 1320 1321 /* 1322 * The values below are chosen to minimize the size of the tcp_secret 1323 * table, as well as providing roughly a 16 second lifetime for the cookie. 1324 */ 1325 1326 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1327 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1328 1329 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1330 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1331 #define SYNCOOKIE_TIMEOUT \ 1332 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1333 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1334 1335 static struct { 1336 u_int32_t ts_secbits[4]; 1337 u_int ts_expire; 1338 } tcp_secret[SYNCOOKIE_NSECRETS]; 1339 1340 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1341 1342 static MD5_CTX syn_ctx; 1343 1344 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1345 1346 struct md5_add { 1347 u_int32_t laddr, faddr; 1348 u_int32_t secbits[4]; 1349 u_int16_t lport, fport; 1350 }; 1351 1352 #ifdef CTASSERT 1353 CTASSERT(sizeof(struct md5_add) == 28); 1354 #endif 1355 1356 /* 1357 * Consider the problem of a recreated (and retransmitted) cookie. If the 1358 * original SYN was accepted, the connection is established. The second 1359 * SYN is inflight, and if it arrives with an ISN that falls within the 1360 * receive window, the connection is killed. 1361 * 1362 * However, since cookies have other problems, this may not be worth 1363 * worrying about. 1364 */ 1365 1366 static u_int32_t 1367 syncookie_generate(struct syncache *sc, u_int32_t *flowid) 1368 { 1369 u_int32_t md5_buffer[4]; 1370 u_int32_t data; 1371 int idx, i; 1372 struct md5_add add; 1373 1374 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1375 1376 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1377 if (tcp_secret[idx].ts_expire < ticks) { 1378 for (i = 0; i < 4; i++) 1379 tcp_secret[idx].ts_secbits[i] = arc4random(); 1380 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1381 } 1382 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1383 if (tcp_msstab[data] <= sc->sc_peer_mss) 1384 break; 1385 data = (data << SYNCOOKIE_WNDBITS) | idx; 1386 data ^= sc->sc_irs; /* peer's iss */ 1387 MD5Init(&syn_ctx); 1388 #ifdef INET6 1389 if (sc->sc_inc.inc_isipv6) { 1390 MD5Add(sc->sc_inc.inc6_laddr); 1391 MD5Add(sc->sc_inc.inc6_faddr); 1392 add.laddr = 0; 1393 add.faddr = 0; 1394 } else 1395 #endif 1396 { 1397 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1398 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1399 } 1400 add.lport = sc->sc_inc.inc_lport; 1401 add.fport = sc->sc_inc.inc_fport; 1402 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1403 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1404 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1405 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1406 MD5Add(add); 1407 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1408 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1409 *flowid = md5_buffer[1]; 1410 return (data); 1411 } 1412 1413 static struct syncache * 1414 syncookie_lookup(inc, th, so) 1415 struct in_conninfo *inc; 1416 struct tcphdr *th; 1417 struct socket *so; 1418 { 1419 u_int32_t md5_buffer[4]; 1420 struct syncache *sc; 1421 u_int32_t data; 1422 int wnd, idx; 1423 struct md5_add add; 1424 1425 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1426 1427 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1428 idx = data & SYNCOOKIE_WNDMASK; 1429 if (tcp_secret[idx].ts_expire < ticks || 1430 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1431 return (NULL); 1432 MD5Init(&syn_ctx); 1433 #ifdef INET6 1434 if (inc->inc_isipv6) { 1435 MD5Add(inc->inc6_laddr); 1436 MD5Add(inc->inc6_faddr); 1437 add.laddr = 0; 1438 add.faddr = 0; 1439 } else 1440 #endif 1441 { 1442 add.laddr = inc->inc_laddr.s_addr; 1443 add.faddr = inc->inc_faddr.s_addr; 1444 } 1445 add.lport = inc->inc_lport; 1446 add.fport = inc->inc_fport; 1447 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1448 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1449 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1450 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1451 MD5Add(add); 1452 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1453 data ^= md5_buffer[0]; 1454 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1455 return (NULL); 1456 data = data >> SYNCOOKIE_WNDBITS; 1457 1458 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1459 if (sc == NULL) 1460 return (NULL); 1461 /* 1462 * Fill in the syncache values. 1463 * XXX duplicate code from syncache_add 1464 */ 1465 sc->sc_ipopts = NULL; 1466 sc->sc_inc.inc_fport = inc->inc_fport; 1467 sc->sc_inc.inc_lport = inc->inc_lport; 1468 sc->sc_tp = sototcpcb(so); 1469 #ifdef INET6 1470 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1471 if (inc->inc_isipv6) { 1472 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1473 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1474 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL) 1475 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1476 } else 1477 #endif 1478 { 1479 sc->sc_inc.inc_faddr = inc->inc_faddr; 1480 sc->sc_inc.inc_laddr = inc->inc_laddr; 1481 } 1482 sc->sc_irs = th->th_seq - 1; 1483 sc->sc_iss = th->th_ack - 1; 1484 wnd = sbspace(&so->so_rcv); 1485 wnd = imax(wnd, 0); 1486 wnd = imin(wnd, TCP_MAXWIN); 1487 sc->sc_wnd = wnd; 1488 sc->sc_flags = 0; 1489 sc->sc_rxtslot = 0; 1490 sc->sc_peer_mss = tcp_msstab[data]; 1491 return (sc); 1492 }
Cache object: d08f96fbb1e99b9fe263b4039480eea2
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]