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sys/netinet/tcp_syncache.c
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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/5.2/sys/netinet/tcp_syncache.c 122922 2003-11-20 20:07:39Z andre $ 35 */ 36 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_mac.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/malloc.h> 47 #include <sys/mac.h> 48 #include <sys/mbuf.h> 49 #include <sys/md5.h> 50 #include <sys/proc.h> /* for proc0 declaration */ 51 #include <sys/random.h> 52 #include <sys/socket.h> 53 #include <sys/socketvar.h> 54 55 #include <net/if.h> 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_var.h> 62 #include <netinet/in_pcb.h> 63 #include <netinet/ip_var.h> 64 #ifdef INET6 65 #include <netinet/ip6.h> 66 #include <netinet/icmp6.h> 67 #include <netinet6/nd6.h> 68 #include <netinet6/ip6_var.h> 69 #include <netinet6/in6_pcb.h> 70 #endif 71 #include <netinet/tcp.h> 72 #ifdef TCPDEBUG 73 #include <netinet/tcpip.h> 74 #endif 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #ifdef TCPDEBUG 80 #include <netinet/tcp_debug.h> 81 #endif 82 #ifdef INET6 83 #include <netinet6/tcp6_var.h> 84 #endif 85 86 #ifdef IPSEC 87 #include <netinet6/ipsec.h> 88 #ifdef INET6 89 #include <netinet6/ipsec6.h> 90 #endif 91 #endif /*IPSEC*/ 92 93 #ifdef FAST_IPSEC 94 #include <netipsec/ipsec.h> 95 #ifdef INET6 96 #include <netipsec/ipsec6.h> 97 #endif 98 #include <netipsec/key.h> 99 #endif /*FAST_IPSEC*/ 100 101 #include <machine/in_cksum.h> 102 #include <vm/uma.h> 103 104 static int tcp_syncookies = 1; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 106 &tcp_syncookies, 0, 107 "Use TCP SYN cookies if the syncache overflows"); 108 109 static void syncache_drop(struct syncache *, struct syncache_head *); 110 static void syncache_free(struct syncache *); 111 static void syncache_insert(struct syncache *, struct syncache_head *); 112 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 113 #ifdef TCPDEBUG 114 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 115 #else 116 static int syncache_respond(struct syncache *, struct mbuf *); 117 #endif 118 static struct socket *syncache_socket(struct syncache *, struct socket *, 119 struct mbuf *m); 120 static void syncache_timer(void *); 121 static u_int32_t syncookie_generate(struct syncache *); 122 static struct syncache *syncookie_lookup(struct in_conninfo *, 123 struct tcphdr *, struct socket *); 124 125 /* 126 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 127 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 128 * the odds are that the user has given up attempting to connect by then. 129 */ 130 #define SYNCACHE_MAXREXMTS 3 131 132 /* Arbitrary values */ 133 #define TCP_SYNCACHE_HASHSIZE 512 134 #define TCP_SYNCACHE_BUCKETLIMIT 30 135 136 struct tcp_syncache { 137 struct syncache_head *hashbase; 138 uma_zone_t zone; 139 u_int hashsize; 140 u_int hashmask; 141 u_int bucket_limit; 142 u_int cache_count; 143 u_int cache_limit; 144 u_int rexmt_limit; 145 u_int hash_secret; 146 u_int next_reseed; 147 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 148 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 149 }; 150 static struct tcp_syncache tcp_syncache; 151 152 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 153 154 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 155 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 156 157 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 158 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 159 160 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 161 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 162 163 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 164 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 165 166 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 167 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 168 169 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 170 171 #define SYNCACHE_HASH(inc, mask) \ 172 ((tcp_syncache.hash_secret ^ \ 173 (inc)->inc_faddr.s_addr ^ \ 174 ((inc)->inc_faddr.s_addr >> 16) ^ \ 175 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 176 177 #define SYNCACHE_HASH6(inc, mask) \ 178 ((tcp_syncache.hash_secret ^ \ 179 (inc)->inc6_faddr.s6_addr32[0] ^ \ 180 (inc)->inc6_faddr.s6_addr32[3] ^ \ 181 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 182 183 #define ENDPTS_EQ(a, b) ( \ 184 (a)->ie_fport == (b)->ie_fport && \ 185 (a)->ie_lport == (b)->ie_lport && \ 186 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 187 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 188 ) 189 190 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 191 192 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 193 sc->sc_rxtslot = (slot); \ 194 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 195 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 196 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 197 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 198 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 199 syncache_timer, (void *)((intptr_t)(slot))); \ 200 } while (0) 201 202 static void 203 syncache_free(struct syncache *sc) 204 { 205 if (sc->sc_ipopts) 206 (void) m_free(sc->sc_ipopts); 207 208 uma_zfree(tcp_syncache.zone, sc); 209 } 210 211 void 212 syncache_init(void) 213 { 214 int i; 215 216 tcp_syncache.cache_count = 0; 217 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 218 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 219 tcp_syncache.cache_limit = 220 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 221 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 222 tcp_syncache.next_reseed = 0; 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.cache_limit -= 1; 261 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 262 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 263 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 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 GIANT_REQUIRED; /* XXX until socket locking */ 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 mac_set_socket_peer_from_mbuf(m, so); 564 #endif 565 566 inp = sotoinpcb(so); 567 INP_LOCK(inp); 568 569 /* 570 * Insert new socket into hash list. 571 */ 572 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 573 #ifdef INET6 574 if (sc->sc_inc.inc_isipv6) { 575 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 576 } else { 577 inp->inp_vflag &= ~INP_IPV6; 578 inp->inp_vflag |= INP_IPV4; 579 #endif 580 inp->inp_laddr = sc->sc_inc.inc_laddr; 581 #ifdef INET6 582 } 583 #endif 584 inp->inp_lport = sc->sc_inc.inc_lport; 585 if (in_pcbinshash(inp) != 0) { 586 /* 587 * Undo the assignments above if we failed to 588 * put the PCB on the hash lists. 589 */ 590 #ifdef INET6 591 if (sc->sc_inc.inc_isipv6) 592 inp->in6p_laddr = in6addr_any; 593 else 594 #endif 595 inp->inp_laddr.s_addr = INADDR_ANY; 596 inp->inp_lport = 0; 597 goto abort; 598 } 599 #ifdef IPSEC 600 /* copy old policy into new socket's */ 601 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 602 printf("syncache_expand: could not copy policy\n"); 603 #endif 604 #ifdef FAST_IPSEC 605 /* copy old policy into new socket's */ 606 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 607 printf("syncache_expand: could not copy policy\n"); 608 #endif 609 #ifdef INET6 610 if (sc->sc_inc.inc_isipv6) { 611 struct inpcb *oinp = sotoinpcb(lso); 612 struct in6_addr laddr6; 613 struct sockaddr_in6 *sin6; 614 /* 615 * Inherit socket options from the listening socket. 616 * Note that in6p_inputopts are not (and should not be) 617 * copied, since it stores previously received options and is 618 * used to detect if each new option is different than the 619 * previous one and hence should be passed to a user. 620 * If we copied in6p_inputopts, a user would not be able to 621 * receive options just after calling the accept system call. 622 */ 623 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 624 if (oinp->in6p_outputopts) 625 inp->in6p_outputopts = 626 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 627 628 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 629 M_SONAME, M_NOWAIT | M_ZERO); 630 if (sin6 == NULL) 631 goto abort; 632 sin6->sin6_family = AF_INET6; 633 sin6->sin6_len = sizeof(*sin6); 634 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 635 sin6->sin6_port = sc->sc_inc.inc_fport; 636 laddr6 = inp->in6p_laddr; 637 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 638 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 639 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 640 inp->in6p_laddr = laddr6; 641 FREE(sin6, M_SONAME); 642 goto abort; 643 } 644 FREE(sin6, M_SONAME); 645 } else 646 #endif 647 { 648 struct in_addr laddr; 649 struct sockaddr_in *sin; 650 651 inp->inp_options = ip_srcroute(); 652 if (inp->inp_options == NULL) { 653 inp->inp_options = sc->sc_ipopts; 654 sc->sc_ipopts = NULL; 655 } 656 657 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 658 M_SONAME, M_NOWAIT | M_ZERO); 659 if (sin == NULL) 660 goto abort; 661 sin->sin_family = AF_INET; 662 sin->sin_len = sizeof(*sin); 663 sin->sin_addr = sc->sc_inc.inc_faddr; 664 sin->sin_port = sc->sc_inc.inc_fport; 665 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 666 laddr = inp->inp_laddr; 667 if (inp->inp_laddr.s_addr == INADDR_ANY) 668 inp->inp_laddr = sc->sc_inc.inc_laddr; 669 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 670 inp->inp_laddr = laddr; 671 FREE(sin, M_SONAME); 672 goto abort; 673 } 674 FREE(sin, M_SONAME); 675 } 676 677 tp = intotcpcb(inp); 678 tp->t_state = TCPS_SYN_RECEIVED; 679 tp->iss = sc->sc_iss; 680 tp->irs = sc->sc_irs; 681 tcp_rcvseqinit(tp); 682 tcp_sendseqinit(tp); 683 tp->snd_wl1 = sc->sc_irs; 684 tp->rcv_up = sc->sc_irs + 1; 685 tp->rcv_wnd = sc->sc_wnd; 686 tp->rcv_adv += tp->rcv_wnd; 687 688 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 689 if (sc->sc_flags & SCF_NOOPT) 690 tp->t_flags |= TF_NOOPT; 691 if (sc->sc_flags & SCF_WINSCALE) { 692 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 693 tp->requested_s_scale = sc->sc_requested_s_scale; 694 tp->request_r_scale = sc->sc_request_r_scale; 695 } 696 if (sc->sc_flags & SCF_TIMESTAMP) { 697 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 698 tp->ts_recent = sc->sc_tsrecent; 699 tp->ts_recent_age = ticks; 700 } 701 if (sc->sc_flags & SCF_CC) { 702 /* 703 * Initialization of the tcpcb for transaction; 704 * set SND.WND = SEG.WND, 705 * initialize CCsend and CCrecv. 706 */ 707 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 708 tp->cc_send = sc->sc_cc_send; 709 tp->cc_recv = sc->sc_cc_recv; 710 } 711 712 /* 713 * Set up MSS and get cached values from tcp_hostcache. 714 * This might overwrite some of the defaults we just set. 715 */ 716 tcp_mss(tp, sc->sc_peer_mss); 717 718 /* 719 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 720 */ 721 if (sc->sc_rxtslot != 0) 722 tp->snd_cwnd = tp->t_maxseg; 723 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 724 725 INP_UNLOCK(inp); 726 727 tcpstat.tcps_accepts++; 728 return (so); 729 730 abort: 731 INP_UNLOCK(inp); 732 abort2: 733 if (so != NULL) 734 (void) soabort(so); 735 return (NULL); 736 } 737 738 /* 739 * This function gets called when we receive an ACK for a 740 * socket in the LISTEN state. We look up the connection 741 * in the syncache, and if its there, we pull it out of 742 * the cache and turn it into a full-blown connection in 743 * the SYN-RECEIVED state. 744 */ 745 int 746 syncache_expand(inc, th, sop, m) 747 struct in_conninfo *inc; 748 struct tcphdr *th; 749 struct socket **sop; 750 struct mbuf *m; 751 { 752 struct syncache *sc; 753 struct syncache_head *sch; 754 struct socket *so; 755 756 INP_INFO_WLOCK_ASSERT(&tcbinfo); 757 758 sc = syncache_lookup(inc, &sch); 759 if (sc == NULL) { 760 /* 761 * There is no syncache entry, so see if this ACK is 762 * a returning syncookie. To do this, first: 763 * A. See if this socket has had a syncache entry dropped in 764 * the past. We don't want to accept a bogus syncookie 765 * if we've never received a SYN. 766 * B. check that the syncookie is valid. If it is, then 767 * cobble up a fake syncache entry, and return. 768 */ 769 if (!tcp_syncookies) 770 return (0); 771 sc = syncookie_lookup(inc, th, *sop); 772 if (sc == NULL) 773 return (0); 774 sch = NULL; 775 tcpstat.tcps_sc_recvcookie++; 776 } 777 778 /* 779 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 780 */ 781 if (th->th_ack != sc->sc_iss + 1) 782 return (0); 783 784 so = syncache_socket(sc, *sop, m); 785 if (so == NULL) { 786 #if 0 787 resetandabort: 788 /* XXXjlemon check this - is this correct? */ 789 (void) tcp_respond(NULL, m, m, th, 790 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 791 #endif 792 m_freem(m); /* XXX only needed for above */ 793 tcpstat.tcps_sc_aborted++; 794 } else 795 tcpstat.tcps_sc_completed++; 796 797 if (sch == NULL) 798 syncache_free(sc); 799 else 800 syncache_drop(sc, sch); 801 *sop = so; 802 return (1); 803 } 804 805 /* 806 * Given a LISTEN socket and an inbound SYN request, add 807 * this to the syn cache, and send back a segment: 808 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 809 * to the source. 810 * 811 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 812 * Doing so would require that we hold onto the data and deliver it 813 * to the application. However, if we are the target of a SYN-flood 814 * DoS attack, an attacker could send data which would eventually 815 * consume all available buffer space if it were ACKed. By not ACKing 816 * the data, we avoid this DoS scenario. 817 */ 818 int 819 syncache_add(inc, to, th, sop, m) 820 struct in_conninfo *inc; 821 struct tcpopt *to; 822 struct tcphdr *th; 823 struct socket **sop; 824 struct mbuf *m; 825 { 826 struct tcpcb *tp; 827 struct socket *so; 828 struct syncache *sc = NULL; 829 struct syncache_head *sch; 830 struct mbuf *ipopts = NULL; 831 struct rmxp_tao tao; 832 int i, win; 833 834 INP_INFO_WLOCK_ASSERT(&tcbinfo); 835 836 so = *sop; 837 tp = sototcpcb(so); 838 bzero(&tao, sizeof(tao)); 839 840 /* 841 * Remember the IP options, if any. 842 */ 843 #ifdef INET6 844 if (!inc->inc_isipv6) 845 #endif 846 ipopts = ip_srcroute(); 847 848 /* 849 * See if we already have an entry for this connection. 850 * If we do, resend the SYN,ACK, and reset the retransmit timer. 851 * 852 * XXX 853 * should the syncache be re-initialized with the contents 854 * of the new SYN here (which may have different options?) 855 */ 856 sc = syncache_lookup(inc, &sch); 857 if (sc != NULL) { 858 tcpstat.tcps_sc_dupsyn++; 859 if (ipopts) { 860 /* 861 * If we were remembering a previous source route, 862 * forget it and use the new one we've been given. 863 */ 864 if (sc->sc_ipopts) 865 (void) m_free(sc->sc_ipopts); 866 sc->sc_ipopts = ipopts; 867 } 868 /* 869 * Update timestamp if present. 870 */ 871 if (sc->sc_flags & SCF_TIMESTAMP) 872 sc->sc_tsrecent = to->to_tsval; 873 /* 874 * PCB may have changed, pick up new values. 875 */ 876 sc->sc_tp = tp; 877 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 878 #ifdef TCPDEBUG 879 if (syncache_respond(sc, m, so) == 0) { 880 #else 881 if (syncache_respond(sc, m) == 0) { 882 #endif 883 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 884 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 885 sc, sc_timerq); 886 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 887 tcpstat.tcps_sndacks++; 888 tcpstat.tcps_sndtotal++; 889 } 890 *sop = NULL; 891 return (1); 892 } 893 894 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 895 if (sc == NULL) { 896 /* 897 * The zone allocator couldn't provide more entries. 898 * Treat this as if the cache was full; drop the oldest 899 * entry and insert the new one. 900 */ 901 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 902 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 903 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 904 if (sc != NULL) 905 break; 906 } 907 sc->sc_tp->ts_recent = ticks; 908 syncache_drop(sc, NULL); 909 tcpstat.tcps_sc_zonefail++; 910 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 911 if (sc == NULL) { 912 if (ipopts) 913 (void) m_free(ipopts); 914 return (0); 915 } 916 } 917 918 /* 919 * Fill in the syncache values. 920 */ 921 bzero(sc, sizeof(*sc)); 922 sc->sc_tp = tp; 923 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 924 sc->sc_ipopts = ipopts; 925 sc->sc_inc.inc_fport = inc->inc_fport; 926 sc->sc_inc.inc_lport = inc->inc_lport; 927 #ifdef INET6 928 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 929 if (inc->inc_isipv6) { 930 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 931 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 932 } else 933 #endif 934 { 935 sc->sc_inc.inc_faddr = inc->inc_faddr; 936 sc->sc_inc.inc_laddr = inc->inc_laddr; 937 } 938 sc->sc_irs = th->th_seq; 939 sc->sc_flags = 0; 940 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 941 if (tcp_syncookies) 942 sc->sc_iss = syncookie_generate(sc); 943 else 944 sc->sc_iss = arc4random(); 945 946 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 947 win = sbspace(&so->so_rcv); 948 win = imax(win, 0); 949 win = imin(win, TCP_MAXWIN); 950 sc->sc_wnd = win; 951 952 if (tcp_do_rfc1323) { 953 /* 954 * A timestamp received in a SYN makes 955 * it ok to send timestamp requests and replies. 956 */ 957 if (to->to_flags & TOF_TS) { 958 sc->sc_tsrecent = to->to_tsval; 959 sc->sc_flags |= SCF_TIMESTAMP; 960 } 961 if (to->to_flags & TOF_SCALE) { 962 int wscale = 0; 963 964 /* Compute proper scaling value from buffer space */ 965 while (wscale < TCP_MAX_WINSHIFT && 966 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 967 wscale++; 968 sc->sc_request_r_scale = wscale; 969 sc->sc_requested_s_scale = to->to_requested_s_scale; 970 sc->sc_flags |= SCF_WINSCALE; 971 } 972 } 973 if (tcp_do_rfc1644) { 974 /* 975 * A CC or CC.new option received in a SYN makes 976 * it ok to send CC in subsequent segments. 977 */ 978 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 979 sc->sc_cc_recv = to->to_cc; 980 sc->sc_cc_send = CC_INC(tcp_ccgen); 981 sc->sc_flags |= SCF_CC; 982 } 983 } 984 if (tp->t_flags & TF_NOOPT) 985 sc->sc_flags = SCF_NOOPT; 986 987 /* 988 * XXX 989 * We have the option here of not doing TAO (even if the segment 990 * qualifies) and instead fall back to a normal 3WHS via the syncache. 991 * This allows us to apply synflood protection to TAO-qualifying SYNs 992 * also. However, there should be a hueristic to determine when to 993 * do this, and is not present at the moment. 994 */ 995 996 /* 997 * Perform TAO test on incoming CC (SEG.CC) option, if any. 998 * - compare SEG.CC against cached CC from the same host, if any. 999 * - if SEG.CC > chached value, SYN must be new and is accepted 1000 * immediately: save new CC in the cache, mark the socket 1001 * connected, enter ESTABLISHED state, turn on flag to 1002 * send a SYN in the next segment. 1003 * A virtual advertised window is set in rcv_adv to 1004 * initialize SWS prevention. Then enter normal segment 1005 * processing: drop SYN, process data and FIN. 1006 * - otherwise do a normal 3-way handshake. 1007 */ 1008 if (tcp_do_rfc1644) 1009 tcp_hc_gettao(&sc->sc_inc, &tao); 1010 1011 if ((to->to_flags & TOF_CC) != 0) { 1012 if (((tp->t_flags & TF_NOPUSH) != 0) && 1013 sc->sc_flags & SCF_CC && tao.tao_cc != 0 && 1014 CC_GT(to->to_cc, tao.tao_cc)) { 1015 sc->sc_rxtslot = 0; 1016 so = syncache_socket(sc, *sop, m); 1017 if (so != NULL) { 1018 tao.tao_cc = to->to_cc; 1019 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1020 tao.tao_cc, 0); 1021 *sop = so; 1022 } 1023 syncache_free(sc); 1024 return (so != NULL); 1025 } 1026 } else { 1027 /* 1028 * No CC option, but maybe CC.NEW: invalidate cached value. 1029 */ 1030 if (tcp_do_rfc1644) { 1031 tao.tao_cc = 0; 1032 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1033 tao.tao_cc, 0); 1034 } 1035 } 1036 1037 /* 1038 * TAO test failed or there was no CC option, 1039 * do a standard 3-way handshake. 1040 */ 1041 #ifdef TCPDEBUG 1042 if (syncache_respond(sc, m, so) == 0) { 1043 #else 1044 if (syncache_respond(sc, m) == 0) { 1045 #endif 1046 syncache_insert(sc, sch); 1047 tcpstat.tcps_sndacks++; 1048 tcpstat.tcps_sndtotal++; 1049 } else { 1050 syncache_free(sc); 1051 tcpstat.tcps_sc_dropped++; 1052 } 1053 *sop = NULL; 1054 return (1); 1055 } 1056 1057 #ifdef TCPDEBUG 1058 static int 1059 syncache_respond(sc, m, so) 1060 struct syncache *sc; 1061 struct mbuf *m; 1062 struct socket *so; 1063 #else 1064 static int 1065 syncache_respond(sc, m) 1066 struct syncache *sc; 1067 struct mbuf *m; 1068 #endif 1069 { 1070 u_int8_t *optp; 1071 int optlen, error; 1072 u_int16_t tlen, hlen, mssopt; 1073 struct ip *ip = NULL; 1074 struct tcphdr *th; 1075 struct inpcb *inp; 1076 #ifdef INET6 1077 struct ip6_hdr *ip6 = NULL; 1078 #endif 1079 1080 hlen = 1081 #ifdef INET6 1082 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1083 #endif 1084 sizeof(struct ip); 1085 1086 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1087 1088 /* Determine MSS we advertize to other end of connection */ 1089 mssopt = tcp_mssopt(&sc->sc_inc); 1090 1091 /* Compute the size of the TCP options. */ 1092 if (sc->sc_flags & SCF_NOOPT) { 1093 optlen = 0; 1094 } else { 1095 optlen = TCPOLEN_MAXSEG + 1096 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1097 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1098 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1099 } 1100 tlen = hlen + sizeof(struct tcphdr) + optlen; 1101 1102 /* 1103 * XXX 1104 * assume that the entire packet will fit in a header mbuf 1105 */ 1106 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1107 1108 /* 1109 * XXX shouldn't this reuse the mbuf if possible ? 1110 * Create the IP+TCP header from scratch. 1111 */ 1112 if (m) 1113 m_freem(m); 1114 1115 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1116 if (m == NULL) 1117 return (ENOBUFS); 1118 m->m_data += max_linkhdr; 1119 m->m_len = tlen; 1120 m->m_pkthdr.len = tlen; 1121 m->m_pkthdr.rcvif = NULL; 1122 inp = sc->sc_tp->t_inpcb; 1123 INP_LOCK(inp); 1124 #ifdef MAC 1125 mac_create_mbuf_from_socket(inp->inp_socket, m); 1126 #endif 1127 1128 #ifdef INET6 1129 if (sc->sc_inc.inc_isipv6) { 1130 ip6 = mtod(m, struct ip6_hdr *); 1131 ip6->ip6_vfc = IPV6_VERSION; 1132 ip6->ip6_nxt = IPPROTO_TCP; 1133 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1134 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1135 ip6->ip6_plen = htons(tlen - hlen); 1136 /* ip6_hlim is set after checksum */ 1137 /* ip6_flow = ??? */ 1138 1139 th = (struct tcphdr *)(ip6 + 1); 1140 } else 1141 #endif 1142 { 1143 ip = mtod(m, struct ip *); 1144 ip->ip_v = IPVERSION; 1145 ip->ip_hl = sizeof(struct ip) >> 2; 1146 ip->ip_len = tlen; 1147 ip->ip_id = 0; 1148 ip->ip_off = 0; 1149 ip->ip_sum = 0; 1150 ip->ip_p = IPPROTO_TCP; 1151 ip->ip_src = sc->sc_inc.inc_laddr; 1152 ip->ip_dst = sc->sc_inc.inc_faddr; 1153 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1154 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1155 1156 /* 1157 * See if we should do MTU discovery. Route lookups are 1158 * expensive, so we will only unset the DF bit if: 1159 * 1160 * 1) path_mtu_discovery is disabled 1161 * 2) the SCF_UNREACH flag has been set 1162 */ 1163 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1164 ip->ip_off |= IP_DF; 1165 1166 th = (struct tcphdr *)(ip + 1); 1167 } 1168 th->th_sport = sc->sc_inc.inc_lport; 1169 th->th_dport = sc->sc_inc.inc_fport; 1170 1171 th->th_seq = htonl(sc->sc_iss); 1172 th->th_ack = htonl(sc->sc_irs + 1); 1173 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1174 th->th_x2 = 0; 1175 th->th_flags = TH_SYN|TH_ACK; 1176 th->th_win = htons(sc->sc_wnd); 1177 th->th_urp = 0; 1178 1179 /* Tack on the TCP options. */ 1180 if (optlen != 0) { 1181 optp = (u_int8_t *)(th + 1); 1182 *optp++ = TCPOPT_MAXSEG; 1183 *optp++ = TCPOLEN_MAXSEG; 1184 *optp++ = (mssopt >> 8) & 0xff; 1185 *optp++ = mssopt & 0xff; 1186 1187 if (sc->sc_flags & SCF_WINSCALE) { 1188 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1189 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1190 sc->sc_request_r_scale); 1191 optp += 4; 1192 } 1193 1194 if (sc->sc_flags & SCF_TIMESTAMP) { 1195 u_int32_t *lp = (u_int32_t *)(optp); 1196 1197 /* Form timestamp option per appendix A of RFC 1323. */ 1198 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1199 *lp++ = htonl(ticks); 1200 *lp = htonl(sc->sc_tsrecent); 1201 optp += TCPOLEN_TSTAMP_APPA; 1202 } 1203 1204 /* 1205 * Send CC and CC.echo if we received CC from our peer. 1206 */ 1207 if (sc->sc_flags & SCF_CC) { 1208 u_int32_t *lp = (u_int32_t *)(optp); 1209 1210 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1211 *lp++ = htonl(sc->sc_cc_send); 1212 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1213 *lp = htonl(sc->sc_cc_recv); 1214 optp += TCPOLEN_CC_APPA * 2; 1215 } 1216 } 1217 1218 #ifdef INET6 1219 if (sc->sc_inc.inc_isipv6) { 1220 th->th_sum = 0; 1221 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1222 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1223 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1224 } else 1225 #endif 1226 { 1227 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1228 htons(tlen - hlen + IPPROTO_TCP)); 1229 m->m_pkthdr.csum_flags = CSUM_TCP; 1230 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1231 #ifdef TCPDEBUG 1232 /* 1233 * Trace. 1234 */ 1235 if (so != NULL && so->so_options & SO_DEBUG) { 1236 struct tcpcb *tp = sototcpcb(so); 1237 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1238 mtod(m, void *), th, 0); 1239 } 1240 #endif 1241 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1242 } 1243 INP_UNLOCK(inp); 1244 return (error); 1245 } 1246 1247 /* 1248 * cookie layers: 1249 * 1250 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1251 * | peer iss | 1252 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1253 * | 0 |(A)| | 1254 * (A): peer mss index 1255 */ 1256 1257 /* 1258 * The values below are chosen to minimize the size of the tcp_secret 1259 * table, as well as providing roughly a 16 second lifetime for the cookie. 1260 */ 1261 1262 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1263 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1264 1265 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1266 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1267 #define SYNCOOKIE_TIMEOUT \ 1268 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1269 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1270 1271 static struct { 1272 u_int32_t ts_secbits[4]; 1273 u_int ts_expire; 1274 } tcp_secret[SYNCOOKIE_NSECRETS]; 1275 1276 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1277 1278 static MD5_CTX syn_ctx; 1279 1280 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1281 1282 struct md5_add { 1283 u_int32_t laddr, faddr; 1284 u_int32_t secbits[4]; 1285 u_int16_t lport, fport; 1286 }; 1287 1288 #ifdef CTASSERT 1289 CTASSERT(sizeof(struct md5_add) == 28); 1290 #endif 1291 1292 /* 1293 * Consider the problem of a recreated (and retransmitted) cookie. If the 1294 * original SYN was accepted, the connection is established. The second 1295 * SYN is inflight, and if it arrives with an ISN that falls within the 1296 * receive window, the connection is killed. 1297 * 1298 * However, since cookies have other problems, this may not be worth 1299 * worrying about. 1300 */ 1301 1302 static u_int32_t 1303 syncookie_generate(struct syncache *sc) 1304 { 1305 u_int32_t md5_buffer[4]; 1306 u_int32_t data; 1307 int idx, i; 1308 struct md5_add add; 1309 1310 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1311 1312 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1313 if (tcp_secret[idx].ts_expire < ticks) { 1314 for (i = 0; i < 4; i++) 1315 tcp_secret[idx].ts_secbits[i] = arc4random(); 1316 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1317 } 1318 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1319 if (tcp_msstab[data] <= sc->sc_peer_mss) 1320 break; 1321 data = (data << SYNCOOKIE_WNDBITS) | idx; 1322 data ^= sc->sc_irs; /* peer's iss */ 1323 MD5Init(&syn_ctx); 1324 #ifdef INET6 1325 if (sc->sc_inc.inc_isipv6) { 1326 MD5Add(sc->sc_inc.inc6_laddr); 1327 MD5Add(sc->sc_inc.inc6_faddr); 1328 add.laddr = 0; 1329 add.faddr = 0; 1330 } else 1331 #endif 1332 { 1333 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1334 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1335 } 1336 add.lport = sc->sc_inc.inc_lport; 1337 add.fport = sc->sc_inc.inc_fport; 1338 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1339 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1340 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1341 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1342 MD5Add(add); 1343 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1344 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1345 return (data); 1346 } 1347 1348 static struct syncache * 1349 syncookie_lookup(inc, th, so) 1350 struct in_conninfo *inc; 1351 struct tcphdr *th; 1352 struct socket *so; 1353 { 1354 u_int32_t md5_buffer[4]; 1355 struct syncache *sc; 1356 u_int32_t data; 1357 int wnd, idx; 1358 struct md5_add add; 1359 1360 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1361 1362 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1363 idx = data & SYNCOOKIE_WNDMASK; 1364 if (tcp_secret[idx].ts_expire < ticks || 1365 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1366 return (NULL); 1367 MD5Init(&syn_ctx); 1368 #ifdef INET6 1369 if (inc->inc_isipv6) { 1370 MD5Add(inc->inc6_laddr); 1371 MD5Add(inc->inc6_faddr); 1372 add.laddr = 0; 1373 add.faddr = 0; 1374 } else 1375 #endif 1376 { 1377 add.laddr = inc->inc_laddr.s_addr; 1378 add.faddr = inc->inc_faddr.s_addr; 1379 } 1380 add.lport = inc->inc_lport; 1381 add.fport = inc->inc_fport; 1382 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1383 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1384 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1385 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1386 MD5Add(add); 1387 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1388 data ^= md5_buffer[0]; 1389 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1390 return (NULL); 1391 data = data >> SYNCOOKIE_WNDBITS; 1392 1393 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1394 if (sc == NULL) 1395 return (NULL); 1396 /* 1397 * Fill in the syncache values. 1398 * XXX duplicate code from syncache_add 1399 */ 1400 sc->sc_ipopts = NULL; 1401 sc->sc_inc.inc_fport = inc->inc_fport; 1402 sc->sc_inc.inc_lport = inc->inc_lport; 1403 #ifdef INET6 1404 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1405 if (inc->inc_isipv6) { 1406 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1407 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1408 } else 1409 #endif 1410 { 1411 sc->sc_inc.inc_faddr = inc->inc_faddr; 1412 sc->sc_inc.inc_laddr = inc->inc_laddr; 1413 } 1414 sc->sc_irs = th->th_seq - 1; 1415 sc->sc_iss = th->th_ack - 1; 1416 wnd = sbspace(&so->so_rcv); 1417 wnd = imax(wnd, 0); 1418 wnd = imin(wnd, TCP_MAXWIN); 1419 sc->sc_wnd = wnd; 1420 sc->sc_flags = 0; 1421 sc->sc_rxtslot = 0; 1422 sc->sc_peer_mss = tcp_msstab[data]; 1423 return (sc); 1424 }
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