1 /*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by Jonathan Lemon 6 * and McAfee Research, the Security Research Division of McAfee, Inc. under 7 * 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * $FreeBSD$ 32 */ 33 34 #include "opt_inet.h" 35 #include "opt_inet6.h" 36 #include "opt_ipsec.h" 37 #include "opt_mac.h" 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_sack.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/malloc.h> 46 #include <sys/mac.h> 47 #include <sys/mbuf.h> 48 #include <sys/md5.h> 49 #include <sys/proc.h> /* for proc0 declaration */ 50 #include <sys/random.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 54 #include <net/if.h> 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_var.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #ifdef INET6 64 #include <netinet/ip6.h> 65 #include <netinet/icmp6.h> 66 #include <netinet6/nd6.h> 67 #include <netinet6/ip6_var.h> 68 #include <netinet6/in6_pcb.h> 69 #endif 70 #include <netinet/tcp.h> 71 #ifdef TCPDEBUG 72 #include <netinet/tcpip.h> 73 #endif 74 #include <netinet/tcp_fsm.h> 75 #include <netinet/tcp_seq.h> 76 #include <netinet/tcp_timer.h> 77 #include <netinet/tcp_var.h> 78 #ifdef TCPDEBUG 79 #include <netinet/tcp_debug.h> 80 #endif 81 #ifdef INET6 82 #include <netinet6/tcp6_var.h> 83 #endif 84 85 #ifdef IPSEC 86 #include <netinet6/ipsec.h> 87 #ifdef INET6 88 #include <netinet6/ipsec6.h> 89 #endif 90 #endif /*IPSEC*/ 91 92 #ifdef FAST_IPSEC 93 #include <netipsec/ipsec.h> 94 #ifdef INET6 95 #include <netipsec/ipsec6.h> 96 #endif 97 #include <netipsec/key.h> 98 #endif /*FAST_IPSEC*/ 99 100 #include <machine/in_cksum.h> 101 #include <vm/uma.h> 102 103 static int tcp_syncookies = 1; 104 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 105 &tcp_syncookies, 0, 106 "Use TCP SYN cookies if the syncache overflows"); 107 108 static void syncache_drop(struct syncache *, struct syncache_head *); 109 static void syncache_free(struct syncache *); 110 static void syncache_insert(struct syncache *, struct syncache_head *); 111 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 112 #ifdef TCPDEBUG 113 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 114 #else 115 static int syncache_respond(struct syncache *, struct mbuf *); 116 #endif 117 static struct socket *syncache_socket(struct syncache *, struct socket *, 118 struct mbuf *m); 119 static void syncache_timer(void *); 120 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *); 121 static struct syncache *syncookie_lookup(struct in_conninfo *, 122 struct tcphdr *, struct socket *); 123 124 /* 125 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 126 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 127 * the odds are that the user has given up attempting to connect by then. 128 */ 129 #define SYNCACHE_MAXREXMTS 3 130 131 /* Arbitrary values */ 132 #define TCP_SYNCACHE_HASHSIZE 512 133 #define TCP_SYNCACHE_BUCKETLIMIT 30 134 135 struct tcp_syncache { 136 struct syncache_head *hashbase; 137 uma_zone_t zone; 138 u_int hashsize; 139 u_int hashmask; 140 u_int bucket_limit; 141 u_int cache_count; 142 u_int cache_limit; 143 u_int rexmt_limit; 144 u_int hash_secret; 145 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 146 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 147 }; 148 static struct tcp_syncache tcp_syncache; 149 150 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 151 152 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 153 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 154 155 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 156 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 157 158 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 159 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 160 161 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 162 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 163 164 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 165 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 166 167 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 168 169 #define SYNCACHE_HASH(inc, mask) \ 170 ((tcp_syncache.hash_secret ^ \ 171 (inc)->inc_faddr.s_addr ^ \ 172 ((inc)->inc_faddr.s_addr >> 16) ^ \ 173 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 174 175 #define SYNCACHE_HASH6(inc, mask) \ 176 ((tcp_syncache.hash_secret ^ \ 177 (inc)->inc6_faddr.s6_addr32[0] ^ \ 178 (inc)->inc6_faddr.s6_addr32[3] ^ \ 179 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 180 181 #define ENDPTS_EQ(a, b) ( \ 182 (a)->ie_fport == (b)->ie_fport && \ 183 (a)->ie_lport == (b)->ie_lport && \ 184 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 185 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 186 ) 187 188 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 189 190 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 191 sc->sc_rxtslot = (slot); \ 192 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 193 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 194 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 195 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 196 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 197 syncache_timer, (void *)((intptr_t)(slot))); \ 198 } while (0) 199 200 static void 201 syncache_free(struct syncache *sc) 202 { 203 if (sc->sc_ipopts) 204 (void) m_free(sc->sc_ipopts); 205 206 uma_zfree(tcp_syncache.zone, sc); 207 } 208 209 void 210 syncache_init(void) 211 { 212 int i; 213 214 tcp_syncache.cache_count = 0; 215 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 216 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 217 tcp_syncache.cache_limit = 218 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 219 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 220 tcp_syncache.hash_secret = arc4random(); 221 222 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 223 &tcp_syncache.hashsize); 224 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 225 &tcp_syncache.cache_limit); 226 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 227 &tcp_syncache.bucket_limit); 228 if (!powerof2(tcp_syncache.hashsize)) { 229 printf("WARNING: syncache hash size is not a power of 2.\n"); 230 tcp_syncache.hashsize = 512; /* safe default */ 231 } 232 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 233 234 /* Allocate the hash table. */ 235 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 236 tcp_syncache.hashsize * sizeof(struct syncache_head), 237 M_SYNCACHE, M_WAITOK); 238 239 /* Initialize the hash buckets. */ 240 for (i = 0; i < tcp_syncache.hashsize; i++) { 241 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 242 tcp_syncache.hashbase[i].sch_length = 0; 243 } 244 245 /* Initialize the timer queues. */ 246 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 247 TAILQ_INIT(&tcp_syncache.timerq[i]); 248 callout_init(&tcp_syncache.tt_timerq[i], NET_CALLOUT_MPSAFE); 249 } 250 251 /* 252 * Allocate the syncache entries. Allow the zone to allocate one 253 * more entry than cache limit, so a new entry can bump out an 254 * older one. 255 */ 256 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 257 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 258 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 259 tcp_syncache.cache_limit -= 1; 260 } 261 262 static void 263 syncache_insert(sc, sch) 264 struct syncache *sc; 265 struct syncache_head *sch; 266 { 267 struct syncache *sc2; 268 int i; 269 270 INP_INFO_WLOCK_ASSERT(&tcbinfo); 271 272 /* 273 * Make sure that we don't overflow the per-bucket 274 * limit or the total cache size limit. 275 */ 276 if (sch->sch_length >= tcp_syncache.bucket_limit) { 277 /* 278 * The bucket is full, toss the oldest element. 279 */ 280 sc2 = TAILQ_FIRST(&sch->sch_bucket); 281 sc2->sc_tp->ts_recent = ticks; 282 syncache_drop(sc2, sch); 283 tcpstat.tcps_sc_bucketoverflow++; 284 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 285 /* 286 * The cache is full. Toss the oldest entry in the 287 * entire cache. This is the front entry in the 288 * first non-empty timer queue with the largest 289 * timeout value. 290 */ 291 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 292 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 293 if (sc2 != NULL) 294 break; 295 } 296 sc2->sc_tp->ts_recent = ticks; 297 syncache_drop(sc2, NULL); 298 tcpstat.tcps_sc_cacheoverflow++; 299 } 300 301 /* Initialize the entry's timer. */ 302 SYNCACHE_TIMEOUT(sc, 0); 303 304 /* Put it into the bucket. */ 305 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 306 sch->sch_length++; 307 tcp_syncache.cache_count++; 308 tcpstat.tcps_sc_added++; 309 } 310 311 static void 312 syncache_drop(sc, sch) 313 struct syncache *sc; 314 struct syncache_head *sch; 315 { 316 INP_INFO_WLOCK_ASSERT(&tcbinfo); 317 318 if (sch == NULL) { 319 #ifdef INET6 320 if (sc->sc_inc.inc_isipv6) { 321 sch = &tcp_syncache.hashbase[ 322 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 323 } else 324 #endif 325 { 326 sch = &tcp_syncache.hashbase[ 327 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 328 } 329 } 330 331 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 332 sch->sch_length--; 333 tcp_syncache.cache_count--; 334 335 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 336 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 337 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 338 339 syncache_free(sc); 340 } 341 342 /* 343 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 344 * If we have retransmitted an entry the maximum number of times, expire it. 345 */ 346 static void 347 syncache_timer(xslot) 348 void *xslot; 349 { 350 intptr_t slot = (intptr_t)xslot; 351 struct syncache *sc, *nsc; 352 struct inpcb *inp; 353 354 INP_INFO_WLOCK(&tcbinfo); 355 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 356 !callout_active(&tcp_syncache.tt_timerq[slot])) { 357 /* XXX can this happen? */ 358 INP_INFO_WUNLOCK(&tcbinfo); 359 return; 360 } 361 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 362 363 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 364 while (nsc != NULL) { 365 if (ticks < nsc->sc_rxttime) 366 break; 367 sc = nsc; 368 inp = sc->sc_tp->t_inpcb; 369 if (slot == SYNCACHE_MAXREXMTS || 370 slot >= tcp_syncache.rexmt_limit || 371 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 372 nsc = TAILQ_NEXT(sc, sc_timerq); 373 syncache_drop(sc, NULL); 374 tcpstat.tcps_sc_stale++; 375 continue; 376 } 377 /* 378 * syncache_respond() may call back into the syncache to 379 * to modify another entry, so do not obtain the next 380 * entry on the timer chain until it has completed. 381 */ 382 #ifdef TCPDEBUG 383 (void) syncache_respond(sc, NULL, NULL); 384 #else 385 (void) syncache_respond(sc, NULL); 386 #endif 387 nsc = TAILQ_NEXT(sc, sc_timerq); 388 tcpstat.tcps_sc_retransmitted++; 389 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 390 SYNCACHE_TIMEOUT(sc, slot + 1); 391 } 392 if (nsc != NULL) 393 callout_reset(&tcp_syncache.tt_timerq[slot], 394 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 395 INP_INFO_WUNLOCK(&tcbinfo); 396 } 397 398 /* 399 * Find an entry in the syncache. 400 */ 401 struct syncache * 402 syncache_lookup(inc, schp) 403 struct in_conninfo *inc; 404 struct syncache_head **schp; 405 { 406 struct syncache *sc; 407 struct syncache_head *sch; 408 409 INP_INFO_WLOCK_ASSERT(&tcbinfo); 410 411 #ifdef INET6 412 if (inc->inc_isipv6) { 413 sch = &tcp_syncache.hashbase[ 414 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 415 *schp = sch; 416 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 417 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 418 return (sc); 419 } 420 } else 421 #endif 422 { 423 sch = &tcp_syncache.hashbase[ 424 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 425 *schp = sch; 426 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 427 #ifdef INET6 428 if (sc->sc_inc.inc_isipv6) 429 continue; 430 #endif 431 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 432 return (sc); 433 } 434 } 435 return (NULL); 436 } 437 438 /* 439 * This function is called when we get a RST for a 440 * non-existent connection, so that we can see if the 441 * connection is in the syn cache. If it is, zap it. 442 */ 443 void 444 syncache_chkrst(inc, th) 445 struct in_conninfo *inc; 446 struct tcphdr *th; 447 { 448 struct syncache *sc; 449 struct syncache_head *sch; 450 451 INP_INFO_WLOCK_ASSERT(&tcbinfo); 452 453 sc = syncache_lookup(inc, &sch); 454 if (sc == NULL) 455 return; 456 /* 457 * If the RST bit is set, check the sequence number to see 458 * if this is a valid reset segment. 459 * RFC 793 page 37: 460 * In all states except SYN-SENT, all reset (RST) segments 461 * are validated by checking their SEQ-fields. A reset is 462 * valid if its sequence number is in the window. 463 * 464 * The sequence number in the reset segment is normally an 465 * echo of our outgoing acknowlegement numbers, but some hosts 466 * send a reset with the sequence number at the rightmost edge 467 * of our receive window, and we have to handle this case. 468 */ 469 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 470 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 471 syncache_drop(sc, sch); 472 tcpstat.tcps_sc_reset++; 473 } 474 } 475 476 void 477 syncache_badack(inc) 478 struct in_conninfo *inc; 479 { 480 struct syncache *sc; 481 struct syncache_head *sch; 482 483 INP_INFO_WLOCK_ASSERT(&tcbinfo); 484 485 sc = syncache_lookup(inc, &sch); 486 if (sc != NULL) { 487 syncache_drop(sc, sch); 488 tcpstat.tcps_sc_badack++; 489 } 490 } 491 492 void 493 syncache_unreach(inc, th) 494 struct in_conninfo *inc; 495 struct tcphdr *th; 496 { 497 struct syncache *sc; 498 struct syncache_head *sch; 499 500 INP_INFO_WLOCK_ASSERT(&tcbinfo); 501 502 /* we are called at splnet() here */ 503 sc = syncache_lookup(inc, &sch); 504 if (sc == NULL) 505 return; 506 507 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 508 if (ntohl(th->th_seq) != sc->sc_iss) 509 return; 510 511 /* 512 * If we've rertransmitted 3 times and this is our second error, 513 * we remove the entry. Otherwise, we allow it to continue on. 514 * This prevents us from incorrectly nuking an entry during a 515 * spurious network outage. 516 * 517 * See tcp_notify(). 518 */ 519 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 520 sc->sc_flags |= SCF_UNREACH; 521 return; 522 } 523 syncache_drop(sc, sch); 524 tcpstat.tcps_sc_unreach++; 525 } 526 527 /* 528 * Build a new TCP socket structure from a syncache entry. 529 */ 530 static struct socket * 531 syncache_socket(sc, lso, m) 532 struct syncache *sc; 533 struct socket *lso; 534 struct mbuf *m; 535 { 536 struct inpcb *inp = NULL; 537 struct socket *so; 538 struct tcpcb *tp; 539 540 NET_ASSERT_GIANT(); 541 INP_INFO_WLOCK_ASSERT(&tcbinfo); 542 543 /* 544 * Ok, create the full blown connection, and set things up 545 * as they would have been set up if we had created the 546 * connection when the SYN arrived. If we can't create 547 * the connection, abort it. 548 */ 549 so = sonewconn(lso, SS_ISCONNECTED); 550 if (so == NULL) { 551 /* 552 * Drop the connection; we will send a RST if the peer 553 * retransmits the ACK, 554 */ 555 tcpstat.tcps_listendrop++; 556 goto abort2; 557 } 558 #ifdef MAC 559 SOCK_LOCK(so); 560 mac_set_socket_peer_from_mbuf(m, so); 561 SOCK_UNLOCK(so); 562 #endif 563 564 inp = sotoinpcb(so); 565 INP_LOCK(inp); 566 567 /* 568 * Insert new socket into hash list. 569 */ 570 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 571 #ifdef INET6 572 if (sc->sc_inc.inc_isipv6) { 573 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 574 } else { 575 inp->inp_vflag &= ~INP_IPV6; 576 inp->inp_vflag |= INP_IPV4; 577 #endif 578 inp->inp_laddr = sc->sc_inc.inc_laddr; 579 #ifdef INET6 580 } 581 #endif 582 inp->inp_lport = sc->sc_inc.inc_lport; 583 if (in_pcbinshash(inp) != 0) { 584 /* 585 * Undo the assignments above if we failed to 586 * put the PCB on the hash lists. 587 */ 588 #ifdef INET6 589 if (sc->sc_inc.inc_isipv6) 590 inp->in6p_laddr = in6addr_any; 591 else 592 #endif 593 inp->inp_laddr.s_addr = INADDR_ANY; 594 inp->inp_lport = 0; 595 goto abort; 596 } 597 #ifdef IPSEC 598 /* copy old policy into new socket's */ 599 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 600 printf("syncache_expand: could not copy policy\n"); 601 #endif 602 #ifdef FAST_IPSEC 603 /* copy old policy into new socket's */ 604 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 605 printf("syncache_expand: could not copy policy\n"); 606 #endif 607 #ifdef INET6 608 if (sc->sc_inc.inc_isipv6) { 609 struct inpcb *oinp = sotoinpcb(lso); 610 struct in6_addr laddr6; 611 struct sockaddr_in6 sin6; 612 /* 613 * Inherit socket options from the listening socket. 614 * Note that in6p_inputopts are not (and should not be) 615 * copied, since it stores previously received options and is 616 * used to detect if each new option is different than the 617 * previous one and hence should be passed to a user. 618 * If we copied in6p_inputopts, a user would not be able to 619 * receive options just after calling the accept system call. 620 */ 621 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 622 if (oinp->in6p_outputopts) 623 inp->in6p_outputopts = 624 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 625 626 sin6.sin6_family = AF_INET6; 627 sin6.sin6_len = sizeof(sin6); 628 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 629 sin6.sin6_port = sc->sc_inc.inc_fport; 630 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 631 laddr6 = inp->in6p_laddr; 632 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 633 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 634 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 635 thread0.td_ucred)) { 636 inp->in6p_laddr = laddr6; 637 goto abort; 638 } 639 /* Override flowlabel from in6_pcbconnect. */ 640 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 641 inp->in6p_flowinfo |= sc->sc_flowlabel; 642 } else 643 #endif 644 { 645 struct in_addr laddr; 646 struct sockaddr_in sin; 647 648 inp->inp_options = ip_srcroute(m); 649 if (inp->inp_options == NULL) { 650 inp->inp_options = sc->sc_ipopts; 651 sc->sc_ipopts = NULL; 652 } 653 654 sin.sin_family = AF_INET; 655 sin.sin_len = sizeof(sin); 656 sin.sin_addr = sc->sc_inc.inc_faddr; 657 sin.sin_port = sc->sc_inc.inc_fport; 658 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 659 laddr = inp->inp_laddr; 660 if (inp->inp_laddr.s_addr == INADDR_ANY) 661 inp->inp_laddr = sc->sc_inc.inc_laddr; 662 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 663 thread0.td_ucred)) { 664 inp->inp_laddr = laddr; 665 goto abort; 666 } 667 } 668 669 tp = intotcpcb(inp); 670 tp->t_state = TCPS_SYN_RECEIVED; 671 tp->iss = sc->sc_iss; 672 tp->irs = sc->sc_irs; 673 tcp_rcvseqinit(tp); 674 tcp_sendseqinit(tp); 675 tp->snd_wl1 = sc->sc_irs; 676 tp->rcv_up = sc->sc_irs + 1; 677 tp->rcv_wnd = sc->sc_wnd; 678 tp->rcv_adv += tp->rcv_wnd; 679 680 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 681 if (sc->sc_flags & SCF_NOOPT) 682 tp->t_flags |= TF_NOOPT; 683 if (sc->sc_flags & SCF_WINSCALE) { 684 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 685 tp->requested_s_scale = sc->sc_requested_s_scale; 686 tp->request_r_scale = sc->sc_request_r_scale; 687 } 688 if (sc->sc_flags & SCF_TIMESTAMP) { 689 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 690 tp->ts_recent = sc->sc_tsrecent; 691 tp->ts_recent_age = ticks; 692 } 693 #ifdef TCP_SIGNATURE 694 if (sc->sc_flags & SCF_SIGNATURE) 695 tp->t_flags |= TF_SIGNATURE; 696 #endif 697 if (sc->sc_flags & SCF_SACK) { 698 tp->sack_enable = 1; 699 tp->t_flags |= TF_SACK_PERMIT; 700 } 701 /* 702 * Set up MSS and get cached values from tcp_hostcache. 703 * This might overwrite some of the defaults we just set. 704 */ 705 tcp_mss(tp, sc->sc_peer_mss); 706 707 /* 708 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 709 */ 710 if (sc->sc_rxtslot != 0) 711 tp->snd_cwnd = tp->t_maxseg; 712 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 713 714 INP_UNLOCK(inp); 715 716 tcpstat.tcps_accepts++; 717 return (so); 718 719 abort: 720 INP_UNLOCK(inp); 721 abort2: 722 if (so != NULL) 723 (void) soabort(so); 724 return (NULL); 725 } 726 727 /* 728 * This function gets called when we receive an ACK for a 729 * socket in the LISTEN state. We look up the connection 730 * in the syncache, and if its there, we pull it out of 731 * the cache and turn it into a full-blown connection in 732 * the SYN-RECEIVED state. 733 */ 734 int 735 syncache_expand(inc, th, sop, m) 736 struct in_conninfo *inc; 737 struct tcphdr *th; 738 struct socket **sop; 739 struct mbuf *m; 740 { 741 struct syncache *sc; 742 struct syncache_head *sch; 743 struct socket *so; 744 745 INP_INFO_WLOCK_ASSERT(&tcbinfo); 746 747 sc = syncache_lookup(inc, &sch); 748 if (sc == NULL) { 749 /* 750 * There is no syncache entry, so see if this ACK is 751 * a returning syncookie. To do this, first: 752 * A. See if this socket has had a syncache entry dropped in 753 * the past. We don't want to accept a bogus syncookie 754 * if we've never received a SYN. 755 * B. check that the syncookie is valid. If it is, then 756 * cobble up a fake syncache entry, and return. 757 */ 758 if (!tcp_syncookies) 759 return (0); 760 sc = syncookie_lookup(inc, th, *sop); 761 if (sc == NULL) 762 return (0); 763 sch = NULL; 764 tcpstat.tcps_sc_recvcookie++; 765 } 766 767 /* 768 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 769 */ 770 if (th->th_ack != sc->sc_iss + 1) 771 return (0); 772 773 so = syncache_socket(sc, *sop, m); 774 if (so == NULL) { 775 #if 0 776 resetandabort: 777 /* XXXjlemon check this - is this correct? */ 778 (void) tcp_respond(NULL, m, m, th, 779 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 780 #endif 781 m_freem(m); /* XXX only needed for above */ 782 tcpstat.tcps_sc_aborted++; 783 } else 784 tcpstat.tcps_sc_completed++; 785 786 if (sch == NULL) 787 syncache_free(sc); 788 else 789 syncache_drop(sc, sch); 790 *sop = so; 791 return (1); 792 } 793 794 /* 795 * Given a LISTEN socket and an inbound SYN request, add 796 * this to the syn cache, and send back a segment: 797 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 798 * to the source. 799 * 800 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 801 * Doing so would require that we hold onto the data and deliver it 802 * to the application. However, if we are the target of a SYN-flood 803 * DoS attack, an attacker could send data which would eventually 804 * consume all available buffer space if it were ACKed. By not ACKing 805 * the data, we avoid this DoS scenario. 806 */ 807 int 808 syncache_add(inc, to, th, sop, m) 809 struct in_conninfo *inc; 810 struct tcpopt *to; 811 struct tcphdr *th; 812 struct socket **sop; 813 struct mbuf *m; 814 { 815 struct tcpcb *tp; 816 struct socket *so; 817 struct syncache *sc = NULL; 818 struct syncache_head *sch; 819 struct mbuf *ipopts = NULL; 820 u_int32_t flowtmp; 821 int i, win; 822 823 INP_INFO_WLOCK_ASSERT(&tcbinfo); 824 825 so = *sop; 826 tp = sototcpcb(so); 827 828 /* 829 * Remember the IP options, if any. 830 */ 831 #ifdef INET6 832 if (!inc->inc_isipv6) 833 #endif 834 ipopts = ip_srcroute(m); 835 836 /* 837 * See if we already have an entry for this connection. 838 * If we do, resend the SYN,ACK, and reset the retransmit timer. 839 * 840 * XXX 841 * should the syncache be re-initialized with the contents 842 * of the new SYN here (which may have different options?) 843 */ 844 sc = syncache_lookup(inc, &sch); 845 if (sc != NULL) { 846 tcpstat.tcps_sc_dupsyn++; 847 if (ipopts) { 848 /* 849 * If we were remembering a previous source route, 850 * forget it and use the new one we've been given. 851 */ 852 if (sc->sc_ipopts) 853 (void) m_free(sc->sc_ipopts); 854 sc->sc_ipopts = ipopts; 855 } 856 /* 857 * Update timestamp if present. 858 */ 859 if (sc->sc_flags & SCF_TIMESTAMP) 860 sc->sc_tsrecent = to->to_tsval; 861 /* 862 * PCB may have changed, pick up new values. 863 */ 864 sc->sc_tp = tp; 865 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 866 #ifdef TCPDEBUG 867 if (syncache_respond(sc, m, so) == 0) { 868 #else 869 if (syncache_respond(sc, m) == 0) { 870 #endif 871 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 872 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 873 sc, sc_timerq); 874 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 875 tcpstat.tcps_sndacks++; 876 tcpstat.tcps_sndtotal++; 877 } 878 *sop = NULL; 879 return (1); 880 } 881 882 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 883 if (sc == NULL) { 884 /* 885 * The zone allocator couldn't provide more entries. 886 * Treat this as if the cache was full; drop the oldest 887 * entry and insert the new one. 888 */ 889 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 890 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 891 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 892 if (sc != NULL) 893 break; 894 } 895 sc->sc_tp->ts_recent = ticks; 896 syncache_drop(sc, NULL); 897 tcpstat.tcps_sc_zonefail++; 898 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 899 if (sc == NULL) { 900 if (ipopts) 901 (void) m_free(ipopts); 902 return (0); 903 } 904 } 905 906 /* 907 * Fill in the syncache values. 908 */ 909 bzero(sc, sizeof(*sc)); 910 sc->sc_tp = tp; 911 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 912 sc->sc_ipopts = ipopts; 913 sc->sc_inc.inc_fport = inc->inc_fport; 914 sc->sc_inc.inc_lport = inc->inc_lport; 915 #ifdef INET6 916 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 917 if (inc->inc_isipv6) { 918 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 919 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 920 } else 921 #endif 922 { 923 sc->sc_inc.inc_faddr = inc->inc_faddr; 924 sc->sc_inc.inc_laddr = inc->inc_laddr; 925 } 926 sc->sc_irs = th->th_seq; 927 sc->sc_flags = 0; 928 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 929 sc->sc_flowlabel = 0; 930 if (tcp_syncookies) { 931 sc->sc_iss = syncookie_generate(sc, &flowtmp); 932 #ifdef INET6 933 if (inc->inc_isipv6 && 934 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 935 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK; 936 } 937 #endif 938 } else { 939 sc->sc_iss = arc4random(); 940 #ifdef INET6 941 if (inc->inc_isipv6 && 942 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 943 sc->sc_flowlabel = 944 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 945 } 946 #endif 947 } 948 949 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 950 win = sbspace(&so->so_rcv); 951 win = imax(win, 0); 952 win = imin(win, TCP_MAXWIN); 953 sc->sc_wnd = win; 954 955 if (tcp_do_rfc1323) { 956 /* 957 * A timestamp received in a SYN makes 958 * it ok to send timestamp requests and replies. 959 */ 960 if (to->to_flags & TOF_TS) { 961 sc->sc_tsrecent = to->to_tsval; 962 sc->sc_flags |= SCF_TIMESTAMP; 963 } 964 if (to->to_flags & TOF_SCALE) { 965 int wscale = 0; 966 967 /* Compute proper scaling value from buffer space */ 968 while (wscale < TCP_MAX_WINSHIFT && 969 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 970 wscale++; 971 sc->sc_request_r_scale = wscale; 972 sc->sc_requested_s_scale = to->to_requested_s_scale; 973 sc->sc_flags |= SCF_WINSCALE; 974 } 975 } 976 if (tp->t_flags & TF_NOOPT) 977 sc->sc_flags = SCF_NOOPT; 978 #ifdef TCP_SIGNATURE 979 /* 980 * If listening socket requested TCP digests, and received SYN 981 * contains the option, flag this in the syncache so that 982 * syncache_respond() will do the right thing with the SYN+ACK. 983 * XXX Currently we always record the option by default and will 984 * attempt to use it in syncache_respond(). 985 */ 986 if (to->to_flags & TOF_SIGNATURE) 987 sc->sc_flags = SCF_SIGNATURE; 988 #endif 989 990 if (to->to_flags & TOF_SACK) 991 sc->sc_flags |= SCF_SACK; 992 993 /* 994 * Do a standard 3-way handshake. 995 */ 996 #ifdef TCPDEBUG 997 if (syncache_respond(sc, m, so) == 0) { 998 #else 999 if (syncache_respond(sc, m) == 0) { 1000 #endif 1001 syncache_insert(sc, sch); 1002 tcpstat.tcps_sndacks++; 1003 tcpstat.tcps_sndtotal++; 1004 } else { 1005 syncache_free(sc); 1006 tcpstat.tcps_sc_dropped++; 1007 } 1008 *sop = NULL; 1009 return (1); 1010 } 1011 1012 #ifdef TCPDEBUG 1013 static int 1014 syncache_respond(sc, m, so) 1015 struct syncache *sc; 1016 struct mbuf *m; 1017 struct socket *so; 1018 #else 1019 static int 1020 syncache_respond(sc, m) 1021 struct syncache *sc; 1022 struct mbuf *m; 1023 #endif 1024 { 1025 u_int8_t *optp; 1026 int optlen, error; 1027 u_int16_t tlen, hlen, mssopt; 1028 struct ip *ip = NULL; 1029 struct tcphdr *th; 1030 struct inpcb *inp; 1031 #ifdef INET6 1032 struct ip6_hdr *ip6 = NULL; 1033 #endif 1034 1035 hlen = 1036 #ifdef INET6 1037 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1038 #endif 1039 sizeof(struct ip); 1040 1041 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1042 1043 /* Determine MSS we advertize to other end of connection */ 1044 mssopt = tcp_mssopt(&sc->sc_inc); 1045 1046 /* Compute the size of the TCP options. */ 1047 if (sc->sc_flags & SCF_NOOPT) { 1048 optlen = 0; 1049 } else { 1050 optlen = TCPOLEN_MAXSEG + 1051 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1052 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); 1053 #ifdef TCP_SIGNATURE 1054 if (sc->sc_flags & SCF_SIGNATURE) 1055 optlen += TCPOLEN_SIGNATURE; 1056 #endif 1057 if (sc->sc_flags & SCF_SACK) 1058 optlen += TCPOLEN_SACK_PERMITTED; 1059 optlen = roundup2(optlen, 4); 1060 } 1061 tlen = hlen + sizeof(struct tcphdr) + optlen; 1062 1063 /* 1064 * XXX 1065 * assume that the entire packet will fit in a header mbuf 1066 */ 1067 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1068 1069 /* 1070 * XXX shouldn't this reuse the mbuf if possible ? 1071 * Create the IP+TCP header from scratch. 1072 */ 1073 if (m) 1074 m_freem(m); 1075 1076 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1077 if (m == NULL) 1078 return (ENOBUFS); 1079 m->m_data += max_linkhdr; 1080 m->m_len = tlen; 1081 m->m_pkthdr.len = tlen; 1082 m->m_pkthdr.rcvif = NULL; 1083 inp = sc->sc_tp->t_inpcb; 1084 INP_LOCK(inp); 1085 #ifdef MAC 1086 mac_create_mbuf_from_inpcb(inp, m); 1087 #endif 1088 1089 #ifdef INET6 1090 if (sc->sc_inc.inc_isipv6) { 1091 ip6 = mtod(m, struct ip6_hdr *); 1092 ip6->ip6_vfc = IPV6_VERSION; 1093 ip6->ip6_nxt = IPPROTO_TCP; 1094 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1095 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1096 ip6->ip6_plen = htons(tlen - hlen); 1097 /* ip6_hlim is set after checksum */ 1098 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1099 ip6->ip6_flow |= sc->sc_flowlabel; 1100 1101 th = (struct tcphdr *)(ip6 + 1); 1102 } else 1103 #endif 1104 { 1105 ip = mtod(m, struct ip *); 1106 ip->ip_v = IPVERSION; 1107 ip->ip_hl = sizeof(struct ip) >> 2; 1108 ip->ip_len = tlen; 1109 ip->ip_id = 0; 1110 ip->ip_off = 0; 1111 ip->ip_sum = 0; 1112 ip->ip_p = IPPROTO_TCP; 1113 ip->ip_src = sc->sc_inc.inc_laddr; 1114 ip->ip_dst = sc->sc_inc.inc_faddr; 1115 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1116 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1117 1118 /* 1119 * See if we should do MTU discovery. Route lookups are 1120 * expensive, so we will only unset the DF bit if: 1121 * 1122 * 1) path_mtu_discovery is disabled 1123 * 2) the SCF_UNREACH flag has been set 1124 */ 1125 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1126 ip->ip_off |= IP_DF; 1127 1128 th = (struct tcphdr *)(ip + 1); 1129 } 1130 th->th_sport = sc->sc_inc.inc_lport; 1131 th->th_dport = sc->sc_inc.inc_fport; 1132 1133 th->th_seq = htonl(sc->sc_iss); 1134 th->th_ack = htonl(sc->sc_irs + 1); 1135 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1136 th->th_x2 = 0; 1137 th->th_flags = TH_SYN|TH_ACK; 1138 th->th_win = htons(sc->sc_wnd); 1139 th->th_urp = 0; 1140 1141 /* Tack on the TCP options. */ 1142 if (optlen != 0) { 1143 optp = (u_int8_t *)(th + 1); 1144 *optp++ = TCPOPT_MAXSEG; 1145 *optp++ = TCPOLEN_MAXSEG; 1146 *optp++ = (mssopt >> 8) & 0xff; 1147 *optp++ = mssopt & 0xff; 1148 1149 if (sc->sc_flags & SCF_WINSCALE) { 1150 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1151 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1152 sc->sc_request_r_scale); 1153 optp += 4; 1154 } 1155 1156 if (sc->sc_flags & SCF_TIMESTAMP) { 1157 u_int32_t *lp = (u_int32_t *)(optp); 1158 1159 /* Form timestamp option per appendix A of RFC 1323. */ 1160 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1161 *lp++ = htonl(ticks); 1162 *lp = htonl(sc->sc_tsrecent); 1163 optp += TCPOLEN_TSTAMP_APPA; 1164 } 1165 1166 #ifdef TCP_SIGNATURE 1167 /* 1168 * Handle TCP-MD5 passive opener response. 1169 */ 1170 if (sc->sc_flags & SCF_SIGNATURE) { 1171 u_int8_t *bp = optp; 1172 int i; 1173 1174 *bp++ = TCPOPT_SIGNATURE; 1175 *bp++ = TCPOLEN_SIGNATURE; 1176 for (i = 0; i < TCP_SIGLEN; i++) 1177 *bp++ = 0; 1178 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1179 optp + 2, IPSEC_DIR_OUTBOUND); 1180 optp += TCPOLEN_SIGNATURE; 1181 } 1182 #endif /* TCP_SIGNATURE */ 1183 1184 if (sc->sc_flags & SCF_SACK) { 1185 *optp++ = TCPOPT_SACK_PERMITTED; 1186 *optp++ = TCPOLEN_SACK_PERMITTED; 1187 } 1188 1189 { 1190 /* Pad TCP options to a 4 byte boundary */ 1191 int padlen = optlen - (optp - (u_int8_t *)(th + 1)); 1192 while (padlen-- > 0) 1193 *optp++ = TCPOPT_EOL; 1194 } 1195 } 1196 1197 #ifdef INET6 1198 if (sc->sc_inc.inc_isipv6) { 1199 th->th_sum = 0; 1200 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1201 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1202 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1203 } else 1204 #endif 1205 { 1206 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1207 htons(tlen - hlen + IPPROTO_TCP)); 1208 m->m_pkthdr.csum_flags = CSUM_TCP; 1209 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1210 #ifdef TCPDEBUG 1211 /* 1212 * Trace. 1213 */ 1214 if (so != NULL && so->so_options & SO_DEBUG) { 1215 struct tcpcb *tp = sototcpcb(so); 1216 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1217 mtod(m, void *), th, 0); 1218 } 1219 #endif 1220 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1221 } 1222 INP_UNLOCK(inp); 1223 return (error); 1224 } 1225 1226 /* 1227 * cookie layers: 1228 * 1229 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1230 * | peer iss | 1231 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1232 * | 0 |(A)| | 1233 * (A): peer mss index 1234 */ 1235 1236 /* 1237 * The values below are chosen to minimize the size of the tcp_secret 1238 * table, as well as providing roughly a 16 second lifetime for the cookie. 1239 */ 1240 1241 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1242 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1243 1244 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1245 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1246 #define SYNCOOKIE_TIMEOUT \ 1247 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1248 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1249 1250 static struct { 1251 u_int32_t ts_secbits[4]; 1252 u_int ts_expire; 1253 } tcp_secret[SYNCOOKIE_NSECRETS]; 1254 1255 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1256 1257 static MD5_CTX syn_ctx; 1258 1259 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1260 1261 struct md5_add { 1262 u_int32_t laddr, faddr; 1263 u_int32_t secbits[4]; 1264 u_int16_t lport, fport; 1265 }; 1266 1267 #ifdef CTASSERT 1268 CTASSERT(sizeof(struct md5_add) == 28); 1269 #endif 1270 1271 /* 1272 * Consider the problem of a recreated (and retransmitted) cookie. If the 1273 * original SYN was accepted, the connection is established. The second 1274 * SYN is inflight, and if it arrives with an ISN that falls within the 1275 * receive window, the connection is killed. 1276 * 1277 * However, since cookies have other problems, this may not be worth 1278 * worrying about. 1279 */ 1280 1281 static u_int32_t 1282 syncookie_generate(struct syncache *sc, u_int32_t *flowid) 1283 { 1284 u_int32_t md5_buffer[4]; 1285 u_int32_t data; 1286 int idx, i; 1287 struct md5_add add; 1288 1289 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1290 1291 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1292 if (tcp_secret[idx].ts_expire < ticks) { 1293 for (i = 0; i < 4; i++) 1294 tcp_secret[idx].ts_secbits[i] = arc4random(); 1295 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1296 } 1297 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1298 if (tcp_msstab[data] <= sc->sc_peer_mss) 1299 break; 1300 data = (data << SYNCOOKIE_WNDBITS) | idx; 1301 data ^= sc->sc_irs; /* peer's iss */ 1302 MD5Init(&syn_ctx); 1303 #ifdef INET6 1304 if (sc->sc_inc.inc_isipv6) { 1305 MD5Add(sc->sc_inc.inc6_laddr); 1306 MD5Add(sc->sc_inc.inc6_faddr); 1307 add.laddr = 0; 1308 add.faddr = 0; 1309 } else 1310 #endif 1311 { 1312 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1313 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1314 } 1315 add.lport = sc->sc_inc.inc_lport; 1316 add.fport = sc->sc_inc.inc_fport; 1317 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1318 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1319 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1320 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1321 MD5Add(add); 1322 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1323 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1324 *flowid = md5_buffer[1]; 1325 return (data); 1326 } 1327 1328 static struct syncache * 1329 syncookie_lookup(inc, th, so) 1330 struct in_conninfo *inc; 1331 struct tcphdr *th; 1332 struct socket *so; 1333 { 1334 u_int32_t md5_buffer[4]; 1335 struct syncache *sc; 1336 u_int32_t data; 1337 int wnd, idx; 1338 struct md5_add add; 1339 1340 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1341 1342 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1343 idx = data & SYNCOOKIE_WNDMASK; 1344 if (tcp_secret[idx].ts_expire < ticks || 1345 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1346 return (NULL); 1347 MD5Init(&syn_ctx); 1348 #ifdef INET6 1349 if (inc->inc_isipv6) { 1350 MD5Add(inc->inc6_laddr); 1351 MD5Add(inc->inc6_faddr); 1352 add.laddr = 0; 1353 add.faddr = 0; 1354 } else 1355 #endif 1356 { 1357 add.laddr = inc->inc_laddr.s_addr; 1358 add.faddr = inc->inc_faddr.s_addr; 1359 } 1360 add.lport = inc->inc_lport; 1361 add.fport = inc->inc_fport; 1362 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1363 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1364 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1365 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1366 MD5Add(add); 1367 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1368 data ^= md5_buffer[0]; 1369 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1370 return (NULL); 1371 data = data >> SYNCOOKIE_WNDBITS; 1372 1373 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1374 if (sc == NULL) 1375 return (NULL); 1376 /* 1377 * Fill in the syncache values. 1378 * XXX duplicate code from syncache_add 1379 */ 1380 sc->sc_ipopts = NULL; 1381 sc->sc_inc.inc_fport = inc->inc_fport; 1382 sc->sc_inc.inc_lport = inc->inc_lport; 1383 sc->sc_tp = sototcpcb(so); 1384 #ifdef INET6 1385 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1386 if (inc->inc_isipv6) { 1387 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1388 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1389 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL) 1390 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1391 } else 1392 #endif 1393 { 1394 sc->sc_inc.inc_faddr = inc->inc_faddr; 1395 sc->sc_inc.inc_laddr = inc->inc_laddr; 1396 } 1397 sc->sc_irs = th->th_seq - 1; 1398 sc->sc_iss = th->th_ack - 1; 1399 wnd = sbspace(&so->so_rcv); 1400 wnd = imax(wnd, 0); 1401 wnd = imin(wnd, TCP_MAXWIN); 1402 sc->sc_wnd = wnd; 1403 sc->sc_flags = 0; 1404 sc->sc_rxtslot = 0; 1405 sc->sc_peer_mss = tcp_msstab[data]; 1406 return (sc); 1407 } 1408