1 /*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Jonathan Lemon 7 * and McAfee Research, the Security Research Division of McAfee, Inc. under 8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 9 * DARPA CHATS research program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * $FreeBSD$ 33 */ 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_mac.h" 39 #include "opt_tcpdebug.h" 40 #include "opt_tcp_sack.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/lock.h> 47 #include <sys/mutex.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/rwlock.h> 55 #include <sys/socket.h> 56 #include <sys/socketvar.h> 57 58 #include <net/if.h> 59 #include <net/route.h> 60 61 #include <netinet/in.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/in_var.h> 65 #include <netinet/in_pcb.h> 66 #include <netinet/ip_var.h> 67 #include <netinet/ip_options.h> 68 #ifdef INET6 69 #include <netinet/ip6.h> 70 #include <netinet/icmp6.h> 71 #include <netinet6/nd6.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/in6_pcb.h> 74 #endif 75 #include <netinet/tcp.h> 76 #ifdef TCPDEBUG 77 #include <netinet/tcpip.h> 78 #endif 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #ifdef TCPDEBUG 84 #include <netinet/tcp_debug.h> 85 #endif 86 #ifdef INET6 87 #include <netinet6/tcp6_var.h> 88 #endif 89 90 #ifdef IPSEC 91 #include <netinet6/ipsec.h> 92 #ifdef INET6 93 #include <netinet6/ipsec6.h> 94 #endif 95 #endif /*IPSEC*/ 96 97 #ifdef FAST_IPSEC 98 #include <netipsec/ipsec.h> 99 #ifdef INET6 100 #include <netipsec/ipsec6.h> 101 #endif 102 #include <netipsec/key.h> 103 #endif /*FAST_IPSEC*/ 104 105 #include <machine/in_cksum.h> 106 #include <vm/uma.h> 107 108 static int tcp_syncookies = 1; 109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 110 &tcp_syncookies, 0, 111 "Use TCP SYN cookies if the syncache overflows"); 112 113 struct syncache { 114 TAILQ_ENTRY(syncache) sc_hash; 115 struct in_conninfo sc_inc; /* addresses */ 116 u_long sc_rxttime; /* retransmit time */ 117 u_int16_t sc_rxmits; /* retransmit counter */ 118 119 u_int32_t sc_tsreflect; /* timestamp to reflect */ 120 u_int32_t sc_flowlabel; /* IPv6 flowlabel */ 121 tcp_seq sc_irs; /* seq from peer */ 122 tcp_seq sc_iss; /* our ISS */ 123 struct mbuf *sc_ipopts; /* source route */ 124 125 u_int16_t sc_peer_mss; /* peer's MSS */ 126 u_int16_t sc_wnd; /* advertised window */ 127 u_int8_t sc_ip_ttl; /* IPv4 TTL */ 128 u_int8_t sc_ip_tos; /* IPv4 TOS */ 129 u_int8_t sc_requested_s_scale:4, 130 sc_requested_r_scale:4; 131 u_int8_t sc_flags; 132 #define SCF_NOOPT 0x01 /* no TCP options */ 133 #define SCF_WINSCALE 0x02 /* negotiated window scaling */ 134 #define SCF_TIMESTAMP 0x04 /* negotiated timestamps */ 135 /* MSS is implicit */ 136 #define SCF_UNREACH 0x10 /* icmp unreachable received */ 137 #define SCF_SIGNATURE 0x20 /* send MD5 digests */ 138 #define SCF_SACK 0x80 /* send SACK option */ 139 }; 140 141 struct syncache_head { 142 struct mtx sch_mtx; 143 TAILQ_HEAD(sch_head, syncache) sch_bucket; 144 struct callout sch_timer; 145 int sch_nextc; 146 u_int sch_length; 147 }; 148 149 static void syncache_drop(struct syncache *, struct syncache_head *); 150 static void syncache_free(struct syncache *); 151 static void syncache_insert(struct syncache *, struct syncache_head *); 152 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 153 static int syncache_respond(struct syncache *, struct mbuf *); 154 static struct socket *syncache_socket(struct syncache *, struct socket *, 155 struct mbuf *m); 156 static void syncache_timer(void *); 157 static void syncookie_init(void); 158 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *); 159 static struct syncache 160 *syncookie_lookup(struct in_conninfo *, struct tcphdr *, 161 struct socket *); 162 163 /* 164 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 165 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 166 * the odds are that the user has given up attempting to connect by then. 167 */ 168 #define SYNCACHE_MAXREXMTS 3 169 170 /* Arbitrary values */ 171 #define TCP_SYNCACHE_HASHSIZE 512 172 #define TCP_SYNCACHE_BUCKETLIMIT 30 173 174 struct tcp_syncache { 175 struct syncache_head *hashbase; 176 uma_zone_t zone; 177 u_int hashsize; 178 u_int hashmask; 179 u_int bucket_limit; 180 u_int cache_count; /* XXX: unprotected */ 181 u_int cache_limit; 182 u_int rexmt_limit; 183 u_int hash_secret; 184 }; 185 static struct tcp_syncache tcp_syncache; 186 187 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 188 189 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 190 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 191 192 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 193 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 194 195 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 196 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 197 198 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 199 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 200 201 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 202 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 203 204 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 205 206 #define SYNCACHE_HASH(inc, mask) \ 207 ((tcp_syncache.hash_secret ^ \ 208 (inc)->inc_faddr.s_addr ^ \ 209 ((inc)->inc_faddr.s_addr >> 16) ^ \ 210 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 211 212 #define SYNCACHE_HASH6(inc, mask) \ 213 ((tcp_syncache.hash_secret ^ \ 214 (inc)->inc6_faddr.s6_addr32[0] ^ \ 215 (inc)->inc6_faddr.s6_addr32[3] ^ \ 216 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 217 218 #define ENDPTS_EQ(a, b) ( \ 219 (a)->ie_fport == (b)->ie_fport && \ 220 (a)->ie_lport == (b)->ie_lport && \ 221 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 222 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 223 ) 224 225 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 226 227 #define SYNCACHE_TIMEOUT(sc, sch, co) do { \ 228 (sc)->sc_rxmits++; \ 229 (sc)->sc_rxttime = ticks + \ 230 TCPTV_RTOBASE * tcp_backoff[(sc)->sc_rxmits - 1]; \ 231 if ((sch)->sch_nextc > (sc)->sc_rxttime) \ 232 (sch)->sch_nextc = (sc)->sc_rxttime; \ 233 if (!TAILQ_EMPTY(&(sch)->sch_bucket) && !(co)) \ 234 callout_reset(&(sch)->sch_timer, \ 235 (sch)->sch_nextc - ticks, \ 236 syncache_timer, (void *)(sch)); \ 237 } while (0) 238 239 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 240 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 241 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 242 243 /* 244 * Requires the syncache entry to be already removed from the bucket list. 245 */ 246 static void 247 syncache_free(struct syncache *sc) 248 { 249 if (sc->sc_ipopts) 250 (void) m_free(sc->sc_ipopts); 251 252 uma_zfree(tcp_syncache.zone, sc); 253 } 254 255 void 256 syncache_init(void) 257 { 258 int i; 259 260 tcp_syncache.cache_count = 0; 261 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 262 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 263 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 264 tcp_syncache.hash_secret = arc4random(); 265 266 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 267 &tcp_syncache.hashsize); 268 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 269 &tcp_syncache.bucket_limit); 270 if (!powerof2(tcp_syncache.hashsize) || tcp_syncache.hashsize == 0) { 271 printf("WARNING: syncache hash size is not a power of 2.\n"); 272 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 273 } 274 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 275 276 /* Set limits. */ 277 tcp_syncache.cache_limit = 278 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 279 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 280 &tcp_syncache.cache_limit); 281 282 /* Allocate the hash table. */ 283 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 284 tcp_syncache.hashsize * sizeof(struct syncache_head), 285 M_SYNCACHE, M_WAITOK | M_ZERO); 286 287 /* Initialize the hash buckets. */ 288 for (i = 0; i < tcp_syncache.hashsize; i++) { 289 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 290 mtx_init(&tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 291 NULL, MTX_DEF); 292 callout_init_mtx(&tcp_syncache.hashbase[i].sch_timer, 293 &tcp_syncache.hashbase[i].sch_mtx, 0); 294 tcp_syncache.hashbase[i].sch_length = 0; 295 } 296 297 syncookie_init(); 298 299 /* Create the syncache entry zone. */ 300 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 301 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 302 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 303 } 304 305 /* 306 * Inserts a syncache entry into the specified bucket row. 307 * Locks and unlocks the syncache_head autonomously. 308 */ 309 static void 310 syncache_insert(struct syncache *sc, struct syncache_head *sch) 311 { 312 struct syncache *sc2; 313 314 SCH_LOCK(sch); 315 316 /* 317 * Make sure that we don't overflow the per-bucket limit. 318 * If the bucket is full, toss the oldest element. 319 */ 320 if (sch->sch_length >= tcp_syncache.bucket_limit) { 321 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 322 ("sch->sch_length incorrect")); 323 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 324 syncache_drop(sc2, sch); 325 tcpstat.tcps_sc_bucketoverflow++; 326 } 327 328 /* Put it into the bucket. */ 329 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 330 sch->sch_length++; 331 332 /* Reinitialize the bucket row's timer. */ 333 SYNCACHE_TIMEOUT(sc, sch, 1); 334 335 SCH_UNLOCK(sch); 336 337 tcp_syncache.cache_count++; 338 tcpstat.tcps_sc_added++; 339 } 340 341 /* 342 * Remove and free entry from syncache bucket row. 343 * Expects locked syncache head. 344 */ 345 static void 346 syncache_drop(struct syncache *sc, struct syncache_head *sch) 347 { 348 349 SCH_LOCK_ASSERT(sch); 350 351 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 352 sch->sch_length--; 353 354 syncache_free(sc); 355 tcp_syncache.cache_count--; 356 } 357 358 /* 359 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 360 * If we have retransmitted an entry the maximum number of times, expire it. 361 * One separate timer for each bucket row. 362 */ 363 static void 364 syncache_timer(void *xsch) 365 { 366 struct syncache_head *sch = (struct syncache_head *)xsch; 367 struct syncache *sc, *nsc; 368 int tick = ticks; 369 370 /* NB: syncache_head has already been locked by the callout. */ 371 SCH_LOCK_ASSERT(sch); 372 373 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 374 /* 375 * We do not check if the listen socket still exists 376 * and accept the case where the listen socket may be 377 * gone by the time we resend the SYN/ACK. We do 378 * not expect this to happens often. If it does, 379 * then the RST will be sent by the time the remote 380 * host does the SYN/ACK->ACK. 381 */ 382 if (sc->sc_rxttime >= tick) { 383 if (sc->sc_rxttime < sch->sch_nextc) 384 sch->sch_nextc = sc->sc_rxttime; 385 continue; 386 } 387 388 if (sc->sc_rxmits > tcp_syncache.rexmt_limit) { 389 syncache_drop(sc, sch); 390 tcpstat.tcps_sc_stale++; 391 continue; 392 } 393 394 (void) syncache_respond(sc, NULL); 395 tcpstat.tcps_sc_retransmitted++; 396 SYNCACHE_TIMEOUT(sc, sch, 0); 397 } 398 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 399 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 400 syncache_timer, (void *)(sch)); 401 } 402 403 /* 404 * Find an entry in the syncache. 405 * Returns always with locked syncache_head plus a matching entry or NULL. 406 */ 407 struct syncache * 408 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 409 { 410 struct syncache *sc; 411 struct syncache_head *sch; 412 413 #ifdef INET6 414 if (inc->inc_isipv6) { 415 sch = &tcp_syncache.hashbase[ 416 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 417 *schp = sch; 418 419 SCH_LOCK(sch); 420 421 /* Circle through bucket row to find matching entry. */ 422 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 423 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 424 return (sc); 425 } 426 } else 427 #endif 428 { 429 sch = &tcp_syncache.hashbase[ 430 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 431 *schp = sch; 432 433 SCH_LOCK(sch); 434 435 /* Circle through bucket row to find matching entry. */ 436 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 437 #ifdef INET6 438 if (sc->sc_inc.inc_isipv6) 439 continue; 440 #endif 441 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 442 return (sc); 443 } 444 } 445 SCH_LOCK_ASSERT(*schp); 446 return (NULL); /* always returns with locked sch */ 447 } 448 449 /* 450 * This function is called when we get a RST for a 451 * non-existent connection, so that we can see if the 452 * connection is in the syn cache. If it is, zap it. 453 */ 454 void 455 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 456 { 457 struct syncache *sc; 458 struct syncache_head *sch; 459 460 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 461 SCH_LOCK_ASSERT(sch); 462 if (sc == NULL) 463 goto done; 464 465 /* 466 * If the RST bit is set, check the sequence number to see 467 * if this is a valid reset segment. 468 * RFC 793 page 37: 469 * In all states except SYN-SENT, all reset (RST) segments 470 * are validated by checking their SEQ-fields. A reset is 471 * valid if its sequence number is in the window. 472 * 473 * The sequence number in the reset segment is normally an 474 * echo of our outgoing acknowlegement numbers, but some hosts 475 * send a reset with the sequence number at the rightmost edge 476 * of our receive window, and we have to handle this case. 477 */ 478 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 479 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 480 syncache_drop(sc, sch); 481 tcpstat.tcps_sc_reset++; 482 } 483 done: 484 SCH_UNLOCK(sch); 485 } 486 487 void 488 syncache_badack(struct in_conninfo *inc) 489 { 490 struct syncache *sc; 491 struct syncache_head *sch; 492 493 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 494 SCH_LOCK_ASSERT(sch); 495 if (sc != NULL) { 496 syncache_drop(sc, sch); 497 tcpstat.tcps_sc_badack++; 498 } 499 SCH_UNLOCK(sch); 500 } 501 502 void 503 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 504 { 505 struct syncache *sc; 506 struct syncache_head *sch; 507 508 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 509 SCH_LOCK_ASSERT(sch); 510 if (sc == NULL) 511 goto done; 512 513 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 514 if (ntohl(th->th_seq) != sc->sc_iss) 515 goto done; 516 517 /* 518 * If we've rertransmitted 3 times and this is our second error, 519 * we remove the entry. Otherwise, we allow it to continue on. 520 * This prevents us from incorrectly nuking an entry during a 521 * spurious network outage. 522 * 523 * See tcp_notify(). 524 */ 525 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 526 sc->sc_flags |= SCF_UNREACH; 527 goto done; 528 } 529 syncache_drop(sc, sch); 530 tcpstat.tcps_sc_unreach++; 531 done: 532 SCH_UNLOCK(sch); 533 } 534 535 /* 536 * Build a new TCP socket structure from a syncache entry. 537 */ 538 static struct socket * 539 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 540 { 541 struct inpcb *inp = NULL; 542 struct socket *so; 543 struct tcpcb *tp; 544 545 NET_ASSERT_GIANT(); 546 INP_INFO_WLOCK_ASSERT(&tcbinfo); 547 548 /* 549 * Ok, create the full blown connection, and set things up 550 * as they would have been set up if we had created the 551 * connection when the SYN arrived. If we can't create 552 * the connection, abort it. 553 */ 554 so = sonewconn(lso, SS_ISCONNECTED); 555 if (so == NULL) { 556 /* 557 * Drop the connection; we will send a RST if the peer 558 * retransmits the ACK, 559 */ 560 tcpstat.tcps_listendrop++; 561 goto abort2; 562 } 563 #ifdef MAC 564 SOCK_LOCK(so); 565 mac_set_socket_peer_from_mbuf(m, so); 566 SOCK_UNLOCK(so); 567 #endif 568 569 inp = sotoinpcb(so); 570 INP_LOCK(inp); 571 572 /* Insert new socket into PCB hash list. */ 573 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 574 #ifdef INET6 575 if (sc->sc_inc.inc_isipv6) { 576 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 577 } else { 578 inp->inp_vflag &= ~INP_IPV6; 579 inp->inp_vflag |= INP_IPV4; 580 #endif 581 inp->inp_laddr = sc->sc_inc.inc_laddr; 582 #ifdef INET6 583 } 584 #endif 585 inp->inp_lport = sc->sc_inc.inc_lport; 586 if (in_pcbinshash(inp) != 0) { 587 /* 588 * Undo the assignments above if we failed to 589 * put the PCB on the hash lists. 590 */ 591 #ifdef INET6 592 if (sc->sc_inc.inc_isipv6) 593 inp->in6p_laddr = in6addr_any; 594 else 595 #endif 596 inp->inp_laddr.s_addr = INADDR_ANY; 597 inp->inp_lport = 0; 598 goto abort; 599 } 600 #ifdef IPSEC 601 /* Copy old policy into new socket's. */ 602 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 603 printf("syncache_socket: could not copy policy\n"); 604 #endif 605 #ifdef FAST_IPSEC 606 /* Copy old policy into new socket's. */ 607 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 608 printf("syncache_socket: could not copy policy\n"); 609 #endif 610 #ifdef INET6 611 if (sc->sc_inc.inc_isipv6) { 612 struct inpcb *oinp = sotoinpcb(lso); 613 struct in6_addr laddr6; 614 struct sockaddr_in6 sin6; 615 /* 616 * Inherit socket options from the listening socket. 617 * Note that in6p_inputopts are not (and should not be) 618 * copied, since it stores previously received options and is 619 * used to detect if each new option is different than the 620 * previous one and hence should be passed to a user. 621 * If we copied in6p_inputopts, a user would not be able to 622 * receive options just after calling the accept system call. 623 */ 624 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 625 if (oinp->in6p_outputopts) 626 inp->in6p_outputopts = 627 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 628 629 sin6.sin6_family = AF_INET6; 630 sin6.sin6_len = sizeof(sin6); 631 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 632 sin6.sin6_port = sc->sc_inc.inc_fport; 633 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 634 laddr6 = inp->in6p_laddr; 635 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 636 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 637 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 638 thread0.td_ucred)) { 639 inp->in6p_laddr = laddr6; 640 goto abort; 641 } 642 /* Override flowlabel from in6_pcbconnect. */ 643 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 644 inp->in6p_flowinfo |= sc->sc_flowlabel; 645 } else 646 #endif 647 { 648 struct in_addr laddr; 649 struct sockaddr_in sin; 650 651 inp->inp_options = ip_srcroute(m); 652 if (inp->inp_options == NULL) { 653 inp->inp_options = sc->sc_ipopts; 654 sc->sc_ipopts = NULL; 655 } 656 657 sin.sin_family = AF_INET; 658 sin.sin_len = sizeof(sin); 659 sin.sin_addr = sc->sc_inc.inc_faddr; 660 sin.sin_port = sc->sc_inc.inc_fport; 661 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 662 laddr = inp->inp_laddr; 663 if (inp->inp_laddr.s_addr == INADDR_ANY) 664 inp->inp_laddr = sc->sc_inc.inc_laddr; 665 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 666 thread0.td_ucred)) { 667 inp->inp_laddr = laddr; 668 goto abort; 669 } 670 } 671 tp = intotcpcb(inp); 672 tp->t_state = TCPS_SYN_RECEIVED; 673 tp->iss = sc->sc_iss; 674 tp->irs = sc->sc_irs; 675 tcp_rcvseqinit(tp); 676 tcp_sendseqinit(tp); 677 tp->snd_wl1 = sc->sc_irs; 678 tp->rcv_up = sc->sc_irs + 1; 679 tp->rcv_wnd = sc->sc_wnd; 680 tp->rcv_adv += tp->rcv_wnd; 681 682 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 683 if (sc->sc_flags & SCF_NOOPT) 684 tp->t_flags |= TF_NOOPT; 685 else { 686 if (sc->sc_flags & SCF_WINSCALE) { 687 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 688 tp->snd_scale = sc->sc_requested_s_scale; 689 tp->request_r_scale = sc->sc_requested_r_scale; 690 } 691 if (sc->sc_flags & SCF_TIMESTAMP) { 692 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 693 tp->ts_recent = sc->sc_tsreflect; 694 tp->ts_recent_age = ticks; 695 } 696 #ifdef TCP_SIGNATURE 697 if (sc->sc_flags & SCF_SIGNATURE) 698 tp->t_flags |= TF_SIGNATURE; 699 #endif 700 if (sc->sc_flags & SCF_SACK) { 701 tp->sack_enable = 1; 702 tp->t_flags |= TF_SACK_PERMIT; 703 } 704 } 705 706 /* 707 * Set up MSS and get cached values from tcp_hostcache. 708 * This might overwrite some of the defaults we just set. 709 */ 710 tcp_mss(tp, sc->sc_peer_mss); 711 712 /* 713 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 714 */ 715 if (sc->sc_rxmits > 1) 716 tp->snd_cwnd = tp->t_maxseg; 717 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 718 719 INP_UNLOCK(inp); 720 721 tcpstat.tcps_accepts++; 722 return (so); 723 724 abort: 725 INP_UNLOCK(inp); 726 abort2: 727 if (so != NULL) 728 soabort(so); 729 return (NULL); 730 } 731 732 /* 733 * This function gets called when we receive an ACK for a 734 * socket in the LISTEN state. We look up the connection 735 * in the syncache, and if its there, we pull it out of 736 * the cache and turn it into a full-blown connection in 737 * the SYN-RECEIVED state. 738 */ 739 int 740 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, 741 struct socket **lsop, struct mbuf *m) 742 { 743 struct syncache *sc; 744 struct syncache_head *sch; 745 struct socket *so; 746 747 /* 748 * Global TCP locks are held because we manipulate the PCB lists 749 * and create a new socket. 750 */ 751 INP_INFO_WLOCK_ASSERT(&tcbinfo); 752 753 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 754 SCH_LOCK_ASSERT(sch); 755 if (sc == NULL) { 756 /* 757 * There is no syncache entry, so see if this ACK is 758 * a returning syncookie. To do this, first: 759 * A. See if this socket has had a syncache entry dropped in 760 * the past. We don't want to accept a bogus syncookie 761 * if we've never received a SYN. 762 * B. check that the syncookie is valid. If it is, then 763 * cobble up a fake syncache entry, and return. 764 */ 765 SCH_UNLOCK(sch); 766 sch = NULL; 767 768 if (!tcp_syncookies) 769 goto failed; 770 sc = syncookie_lookup(inc, th, *lsop); 771 if (sc == NULL) 772 goto failed; 773 tcpstat.tcps_sc_recvcookie++; 774 } else { 775 /* Pull out the entry to unlock the bucket row. */ 776 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 777 sch->sch_length--; 778 tcp_syncache.cache_count--; 779 SCH_UNLOCK(sch); 780 } 781 782 /* 783 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 784 */ 785 if (th->th_ack != sc->sc_iss + 1) 786 goto failed; 787 788 so = syncache_socket(sc, *lsop, m); 789 790 if (so == NULL) { 791 #if 0 792 resetandabort: 793 /* XXXjlemon check this - is this correct? */ 794 (void) tcp_respond(NULL, m, m, th, 795 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 796 #endif 797 m_freem(m); /* XXX: only needed for above */ 798 tcpstat.tcps_sc_aborted++; 799 if (sch != NULL) { 800 syncache_insert(sc, sch); /* try again later */ 801 sc = NULL; 802 } 803 goto failed; 804 } else 805 tcpstat.tcps_sc_completed++; 806 *lsop = so; 807 808 syncache_free(sc); 809 return (1); 810 failed: 811 if (sc != NULL) 812 syncache_free(sc); 813 return (0); 814 } 815 816 /* 817 * Given a LISTEN socket and an inbound SYN request, add 818 * this to the syn cache, and send back a segment: 819 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 820 * to the source. 821 * 822 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 823 * Doing so would require that we hold onto the data and deliver it 824 * to the application. However, if we are the target of a SYN-flood 825 * DoS attack, an attacker could send data which would eventually 826 * consume all available buffer space if it were ACKed. By not ACKing 827 * the data, we avoid this DoS scenario. 828 */ 829 int 830 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 831 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 832 { 833 struct tcpcb *tp; 834 struct socket *so; 835 struct syncache *sc = NULL; 836 struct syncache_head *sch; 837 struct mbuf *ipopts = NULL; 838 u_int32_t flowtmp; 839 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 840 #ifdef INET6 841 int autoflowlabel = 0; 842 #endif 843 844 INP_INFO_WLOCK_ASSERT(&tcbinfo); 845 INP_LOCK_ASSERT(inp); /* listen socket */ 846 847 /* 848 * Combine all so/tp operations very early to drop the INP lock as 849 * soon as possible. 850 */ 851 so = *lsop; 852 tp = sototcpcb(so); 853 854 #ifdef INET6 855 if (inc->inc_isipv6 && 856 (inp->in6p_flags & IN6P_AUTOFLOWLABEL)) 857 autoflowlabel = 1; 858 #endif 859 ip_ttl = inp->inp_ip_ttl; 860 ip_tos = inp->inp_ip_tos; 861 win = sbspace(&so->so_rcv); 862 sb_hiwat = so->so_rcv.sb_hiwat; 863 noopt = (tp->t_flags & TF_NOOPT); 864 865 so = NULL; 866 tp = NULL; 867 868 INP_UNLOCK(inp); 869 INP_INFO_WUNLOCK(&tcbinfo); 870 871 /* 872 * Remember the IP options, if any. 873 */ 874 #ifdef INET6 875 if (!inc->inc_isipv6) 876 #endif 877 ipopts = ip_srcroute(m); 878 879 /* 880 * See if we already have an entry for this connection. 881 * If we do, resend the SYN,ACK, and reset the retransmit timer. 882 * 883 * XXX: should the syncache be re-initialized with the contents 884 * of the new SYN here (which may have different options?) 885 */ 886 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 887 SCH_LOCK_ASSERT(sch); 888 if (sc != NULL) { 889 tcpstat.tcps_sc_dupsyn++; 890 if (ipopts) { 891 /* 892 * If we were remembering a previous source route, 893 * forget it and use the new one we've been given. 894 */ 895 if (sc->sc_ipopts) 896 (void) m_free(sc->sc_ipopts); 897 sc->sc_ipopts = ipopts; 898 } 899 /* 900 * Update timestamp if present. 901 */ 902 if (sc->sc_flags & SCF_TIMESTAMP) 903 sc->sc_tsreflect = to->to_tsval; 904 if (syncache_respond(sc, m) == 0) { 905 SYNCACHE_TIMEOUT(sc, sch, 1); 906 tcpstat.tcps_sndacks++; 907 tcpstat.tcps_sndtotal++; 908 } 909 SCH_UNLOCK(sch); 910 goto done; 911 } 912 913 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO); 914 if (sc == NULL) { 915 /* 916 * The zone allocator couldn't provide more entries. 917 * Treat this as if the cache was full; drop the oldest 918 * entry and insert the new one. 919 */ 920 tcpstat.tcps_sc_zonefail++; 921 sc = TAILQ_LAST(&sch->sch_bucket, sch_head); 922 syncache_drop(sc, sch); 923 SCH_UNLOCK(sch); 924 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO); 925 if (sc == NULL) { 926 if (ipopts) 927 (void) m_free(ipopts); 928 goto done; 929 } 930 } else 931 SCH_UNLOCK(sch); 932 933 /* 934 * Fill in the syncache values. 935 */ 936 sc->sc_ipopts = ipopts; 937 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 938 #ifdef INET6 939 if (!inc->inc_isipv6) 940 #endif 941 { 942 sc->sc_ip_tos = ip_tos; 943 sc->sc_ip_ttl = ip_ttl; 944 } 945 sc->sc_irs = th->th_seq; 946 sc->sc_flags = 0; 947 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 948 sc->sc_flowlabel = 0; 949 if (tcp_syncookies) { 950 sc->sc_iss = syncookie_generate(sc, &flowtmp); 951 #ifdef INET6 952 if (autoflowlabel) 953 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK; 954 #endif 955 } else { 956 sc->sc_iss = arc4random(); 957 #ifdef INET6 958 if (autoflowlabel) 959 sc->sc_flowlabel = 960 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 961 #endif 962 } 963 964 /* 965 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 966 * win was derived from socket earlier in the function. 967 */ 968 win = imax(win, 0); 969 win = imin(win, TCP_MAXWIN); 970 sc->sc_wnd = win; 971 972 if (tcp_do_rfc1323) { 973 /* 974 * A timestamp received in a SYN makes 975 * it ok to send timestamp requests and replies. 976 */ 977 if (to->to_flags & TOF_TS) { 978 sc->sc_tsreflect = to->to_tsval; 979 sc->sc_flags |= SCF_TIMESTAMP; 980 } 981 if (to->to_flags & TOF_SCALE) { 982 int wscale = 0; 983 984 /* Compute proper scaling value from buffer space */ 985 while (wscale < TCP_MAX_WINSHIFT && 986 (TCP_MAXWIN << wscale) < sb_hiwat) 987 wscale++; 988 sc->sc_requested_r_scale = wscale; 989 sc->sc_requested_s_scale = to->to_requested_s_scale; 990 sc->sc_flags |= SCF_WINSCALE; 991 } 992 } 993 #ifdef TCP_SIGNATURE 994 /* 995 * If listening socket requested TCP digests, and received SYN 996 * contains the option, flag this in the syncache so that 997 * syncache_respond() will do the right thing with the SYN+ACK. 998 * XXX: Currently we always record the option by default and will 999 * attempt to use it in syncache_respond(). 1000 */ 1001 if (to->to_flags & TOF_SIGNATURE) 1002 sc->sc_flags |= SCF_SIGNATURE; 1003 #endif 1004 1005 if (to->to_flags & TOF_SACK) 1006 sc->sc_flags |= SCF_SACK; 1007 if (noopt) 1008 sc->sc_flags |= SCF_NOOPT; 1009 1010 /* 1011 * Do a standard 3-way handshake. 1012 */ 1013 if (syncache_respond(sc, m) == 0) { 1014 syncache_insert(sc, sch); /* locks and unlocks sch */ 1015 tcpstat.tcps_sndacks++; 1016 tcpstat.tcps_sndtotal++; 1017 } else { 1018 syncache_free(sc); 1019 tcpstat.tcps_sc_dropped++; 1020 } 1021 1022 done: 1023 *lsop = NULL; 1024 return (1); 1025 } 1026 1027 static int 1028 syncache_respond(struct syncache *sc, struct mbuf *m) 1029 { 1030 struct ip *ip = NULL; 1031 struct tcphdr *th; 1032 int optlen, error; 1033 u_int16_t tlen, hlen, mssopt; 1034 u_int8_t *optp; 1035 #ifdef INET6 1036 struct ip6_hdr *ip6 = NULL; 1037 #endif 1038 #ifdef MAC 1039 struct inpcb *inp = NULL; 1040 #endif 1041 1042 hlen = 1043 #ifdef INET6 1044 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1045 #endif 1046 sizeof(struct ip); 1047 1048 /* Determine MSS we advertize to other end of connection. */ 1049 mssopt = tcp_mssopt(&sc->sc_inc); 1050 if (sc->sc_peer_mss) 1051 mssopt = max( min(sc->sc_peer_mss, mssopt), tcp_minmss); 1052 1053 /* Compute the size of the TCP options. */ 1054 if (sc->sc_flags & SCF_NOOPT) { 1055 optlen = 0; 1056 } else { 1057 optlen = TCPOLEN_MAXSEG + 1058 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1059 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); 1060 #ifdef TCP_SIGNATURE 1061 if (sc->sc_flags & SCF_SIGNATURE) 1062 optlen += TCPOLEN_SIGNATURE; 1063 #endif 1064 if (sc->sc_flags & SCF_SACK) 1065 optlen += TCPOLEN_SACK_PERMITTED; 1066 optlen = roundup2(optlen, 4); 1067 } 1068 tlen = hlen + sizeof(struct tcphdr) + optlen; 1069 1070 /* 1071 * XXX: Assume that the entire packet will fit in a header mbuf. 1072 */ 1073 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1074 1075 /* Create the IP+TCP header from scratch. */ 1076 if (m) 1077 m_freem(m); 1078 1079 m = m_gethdr(M_DONTWAIT, MT_DATA); 1080 if (m == NULL) 1081 return (ENOBUFS); 1082 m->m_data += max_linkhdr; 1083 m->m_len = tlen; 1084 m->m_pkthdr.len = tlen; 1085 m->m_pkthdr.rcvif = NULL; 1086 1087 #ifdef MAC 1088 /* 1089 * For MAC look up the inpcb to get access to the label information. 1090 * We don't store the inpcb pointer in struct syncache to make locking 1091 * less complicated and to save locking operations. However for MAC 1092 * this gives a slight overhead as we have to do a full pcblookup here. 1093 */ 1094 INP_INFO_RLOCK(&tcbinfo); 1095 if (inp == NULL) { 1096 #ifdef INET6 /* && MAC */ 1097 if (sc->sc_inc.inc_isipv6) 1098 inp = in6_pcblookup_hash(&tcbinfo, 1099 &sc->sc_inc.inc6_faddr, sc->sc_inc.inc_fport, 1100 &sc->sc_inc.inc6_laddr, sc->sc_inc.inc_lport, 1101 1, NULL); 1102 else 1103 #endif /* INET6 */ 1104 inp = in_pcblookup_hash(&tcbinfo, 1105 sc->sc_inc.inc_faddr, sc->sc_inc.inc_fport, 1106 sc->sc_inc.inc_laddr, sc->sc_inc.inc_lport, 1107 1, NULL); 1108 if (inp == NULL) { 1109 m_freem(m); 1110 INP_INFO_RUNLOCK(&tcbinfo); 1111 return (ESHUTDOWN); 1112 } 1113 } 1114 INP_LOCK(inp); 1115 if (!inp->inp_socket->so_options & SO_ACCEPTCONN) { 1116 m_freem(m); 1117 INP_UNLOCK(inp); 1118 INP_INFO_RUNLOCK(&tcbinfo); 1119 return (ESHUTDOWN); 1120 } 1121 mac_create_mbuf_from_inpcb(inp, m); 1122 INP_UNLOCK(inp); 1123 INP_INFO_RUNLOCK(&tcbinfo); 1124 #endif /* MAC */ 1125 1126 #ifdef INET6 1127 if (sc->sc_inc.inc_isipv6) { 1128 ip6 = mtod(m, struct ip6_hdr *); 1129 ip6->ip6_vfc = IPV6_VERSION; 1130 ip6->ip6_nxt = IPPROTO_TCP; 1131 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1132 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1133 ip6->ip6_plen = htons(tlen - hlen); 1134 /* ip6_hlim is set after checksum */ 1135 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1136 ip6->ip6_flow |= sc->sc_flowlabel; 1137 1138 th = (struct tcphdr *)(ip6 + 1); 1139 } else 1140 #endif 1141 { 1142 ip = mtod(m, struct ip *); 1143 ip->ip_v = IPVERSION; 1144 ip->ip_hl = sizeof(struct ip) >> 2; 1145 ip->ip_len = tlen; 1146 ip->ip_id = 0; 1147 ip->ip_off = 0; 1148 ip->ip_sum = 0; 1149 ip->ip_p = IPPROTO_TCP; 1150 ip->ip_src = sc->sc_inc.inc_laddr; 1151 ip->ip_dst = sc->sc_inc.inc_faddr; 1152 ip->ip_ttl = sc->sc_ip_ttl; 1153 ip->ip_tos = sc->sc_ip_tos; 1154 1155 /* 1156 * See if we should do MTU discovery. Route lookups are 1157 * expensive, so we will only unset the DF bit if: 1158 * 1159 * 1) path_mtu_discovery is disabled 1160 * 2) the SCF_UNREACH flag has been set 1161 */ 1162 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1163 ip->ip_off |= IP_DF; 1164 1165 th = (struct tcphdr *)(ip + 1); 1166 } 1167 th->th_sport = sc->sc_inc.inc_lport; 1168 th->th_dport = sc->sc_inc.inc_fport; 1169 1170 th->th_seq = htonl(sc->sc_iss); 1171 th->th_ack = htonl(sc->sc_irs + 1); 1172 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1173 th->th_x2 = 0; 1174 th->th_flags = TH_SYN|TH_ACK; 1175 th->th_win = htons(sc->sc_wnd); 1176 th->th_urp = 0; 1177 1178 /* Tack on the TCP options. */ 1179 if (optlen != 0) { 1180 optp = (u_int8_t *)(th + 1); 1181 *optp++ = TCPOPT_MAXSEG; 1182 *optp++ = TCPOLEN_MAXSEG; 1183 *optp++ = (mssopt >> 8) & 0xff; 1184 *optp++ = mssopt & 0xff; 1185 1186 if (sc->sc_flags & SCF_WINSCALE) { 1187 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1188 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1189 sc->sc_requested_r_scale); 1190 optp += 4; 1191 } 1192 1193 if (sc->sc_flags & SCF_TIMESTAMP) { 1194 u_int32_t *lp = (u_int32_t *)(optp); 1195 1196 /* Form timestamp option per appendix A of RFC 1323. */ 1197 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1198 *lp++ = htonl(ticks); 1199 *lp = htonl(sc->sc_tsreflect); 1200 optp += TCPOLEN_TSTAMP_APPA; 1201 } 1202 1203 #ifdef TCP_SIGNATURE 1204 /* 1205 * Handle TCP-MD5 passive opener response. 1206 */ 1207 if (sc->sc_flags & SCF_SIGNATURE) { 1208 u_int8_t *bp = optp; 1209 int i; 1210 1211 *bp++ = TCPOPT_SIGNATURE; 1212 *bp++ = TCPOLEN_SIGNATURE; 1213 for (i = 0; i < TCP_SIGLEN; i++) 1214 *bp++ = 0; 1215 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1216 optp + 2, IPSEC_DIR_OUTBOUND); 1217 optp += TCPOLEN_SIGNATURE; 1218 } 1219 #endif /* TCP_SIGNATURE */ 1220 1221 if (sc->sc_flags & SCF_SACK) { 1222 *optp++ = TCPOPT_SACK_PERMITTED; 1223 *optp++ = TCPOLEN_SACK_PERMITTED; 1224 } 1225 1226 { 1227 /* Pad TCP options to a 4 byte boundary */ 1228 int padlen = optlen - (optp - (u_int8_t *)(th + 1)); 1229 while (padlen-- > 0) 1230 *optp++ = TCPOPT_EOL; 1231 } 1232 } 1233 1234 #ifdef INET6 1235 if (sc->sc_inc.inc_isipv6) { 1236 th->th_sum = 0; 1237 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1238 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1239 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1240 } else 1241 #endif 1242 { 1243 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1244 htons(tlen - hlen + IPPROTO_TCP)); 1245 m->m_pkthdr.csum_flags = CSUM_TCP; 1246 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1247 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1248 } 1249 return (error); 1250 } 1251 1252 /* 1253 * cookie layers: 1254 * 1255 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1256 * | peer iss | 1257 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1258 * | 0 |(A)| | 1259 * (A): peer mss index 1260 */ 1261 1262 /* 1263 * The values below are chosen to minimize the size of the tcp_secret 1264 * table, as well as providing roughly a 16 second lifetime for the cookie. 1265 */ 1266 1267 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1268 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1269 1270 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1271 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1272 #define SYNCOOKIE_TIMEOUT \ 1273 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1274 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1275 1276 #define SYNCOOKIE_RLOCK(ts) (rw_rlock(&(ts).ts_rwmtx)) 1277 #define SYNCOOKIE_RUNLOCK(ts) (rw_runlock(&(ts).ts_rwmtx)) 1278 #define SYNCOOKIE_TRY_UPGRADE(ts) (rw_try_upgrade(&(ts).ts_rwmtx)) 1279 #define SYNCOOKIE_DOWNGRADE(ts) (rw_downgrade(&(ts).ts_rwmtx)) 1280 1281 static struct { 1282 struct rwlock ts_rwmtx; 1283 u_int ts_expire; /* ticks */ 1284 u_int32_t ts_secbits[4]; 1285 } tcp_secret[SYNCOOKIE_NSECRETS]; 1286 1287 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1288 1289 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1290 1291 struct md5_add { 1292 u_int32_t laddr, faddr; 1293 u_int32_t secbits[4]; 1294 u_int16_t lport, fport; 1295 }; 1296 1297 #ifdef CTASSERT 1298 CTASSERT(sizeof(struct md5_add) == 28); 1299 #endif 1300 1301 /* 1302 * Consider the problem of a recreated (and retransmitted) cookie. If the 1303 * original SYN was accepted, the connection is established. The second 1304 * SYN is inflight, and if it arrives with an ISN that falls within the 1305 * receive window, the connection is killed. 1306 * 1307 * However, since cookies have other problems, this may not be worth 1308 * worrying about. 1309 */ 1310 1311 static void 1312 syncookie_init(void) { 1313 int idx; 1314 1315 for (idx = 0; idx < SYNCOOKIE_NSECRETS; idx++) { 1316 rw_init(&(tcp_secret[idx].ts_rwmtx), "tcp_secret"); 1317 } 1318 } 1319 1320 static u_int32_t 1321 syncookie_generate(struct syncache *sc, u_int32_t *flowid) 1322 { 1323 u_int32_t md5_buffer[4]; 1324 u_int32_t data; 1325 int idx, i; 1326 struct md5_add add; 1327 MD5_CTX syn_ctx; 1328 1329 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1330 SYNCOOKIE_RLOCK(tcp_secret[idx]); 1331 if (tcp_secret[idx].ts_expire < time_uptime && 1332 SYNCOOKIE_TRY_UPGRADE(tcp_secret[idx]) ) { 1333 /* need write access */ 1334 for (i = 0; i < 4; i++) 1335 tcp_secret[idx].ts_secbits[i] = arc4random(); 1336 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1337 SYNCOOKIE_DOWNGRADE(tcp_secret[idx]); 1338 } 1339 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1340 if (tcp_msstab[data] <= sc->sc_peer_mss) 1341 break; 1342 data = (data << SYNCOOKIE_WNDBITS) | idx; 1343 data ^= sc->sc_irs; /* peer's iss */ 1344 MD5Init(&syn_ctx); 1345 #ifdef INET6 1346 if (sc->sc_inc.inc_isipv6) { 1347 MD5Add(sc->sc_inc.inc6_laddr); 1348 MD5Add(sc->sc_inc.inc6_faddr); 1349 add.laddr = 0; 1350 add.faddr = 0; 1351 } else 1352 #endif 1353 { 1354 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1355 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1356 } 1357 add.lport = sc->sc_inc.inc_lport; 1358 add.fport = sc->sc_inc.inc_fport; 1359 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1360 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1361 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1362 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1363 SYNCOOKIE_RUNLOCK(tcp_secret[idx]); 1364 MD5Add(add); 1365 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1366 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1367 *flowid = md5_buffer[1]; 1368 return (data); 1369 } 1370 1371 static struct syncache * 1372 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so) 1373 { 1374 u_int32_t md5_buffer[4]; 1375 struct syncache *sc; 1376 u_int32_t data; 1377 int wnd, idx; 1378 struct md5_add add; 1379 MD5_CTX syn_ctx; 1380 1381 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1382 idx = data & SYNCOOKIE_WNDMASK; 1383 SYNCOOKIE_RLOCK(tcp_secret[idx]); 1384 if (tcp_secret[idx].ts_expire < ticks || 1385 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) { 1386 SYNCOOKIE_RUNLOCK(tcp_secret[idx]); 1387 return (NULL); 1388 } 1389 MD5Init(&syn_ctx); 1390 #ifdef INET6 1391 if (inc->inc_isipv6) { 1392 MD5Add(inc->inc6_laddr); 1393 MD5Add(inc->inc6_faddr); 1394 add.laddr = 0; 1395 add.faddr = 0; 1396 } else 1397 #endif 1398 { 1399 add.laddr = inc->inc_laddr.s_addr; 1400 add.faddr = inc->inc_faddr.s_addr; 1401 } 1402 add.lport = inc->inc_lport; 1403 add.fport = inc->inc_fport; 1404 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1405 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1406 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1407 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1408 SYNCOOKIE_RUNLOCK(tcp_secret[idx]); 1409 MD5Add(add); 1410 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1411 data ^= md5_buffer[0]; 1412 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1413 return (NULL); 1414 data = data >> SYNCOOKIE_WNDBITS; 1415 1416 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO); 1417 if (sc == NULL) 1418 return (NULL); 1419 /* 1420 * Fill in the syncache values. 1421 * XXX: duplicate code from syncache_add 1422 */ 1423 sc->sc_ipopts = NULL; 1424 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1425 #ifdef INET6 1426 if (inc->inc_isipv6) { 1427 if (sotoinpcb(so)->in6p_flags & IN6P_AUTOFLOWLABEL) 1428 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1429 } else 1430 #endif 1431 { 1432 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1433 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1434 } 1435 sc->sc_irs = th->th_seq - 1; 1436 sc->sc_iss = th->th_ack - 1; 1437 wnd = sbspace(&so->so_rcv); 1438 wnd = imax(wnd, 0); 1439 wnd = imin(wnd, TCP_MAXWIN); 1440 sc->sc_wnd = wnd; 1441 sc->sc_flags = 0; 1442 sc->sc_rxmits = 0; 1443 sc->sc_peer_mss = tcp_msstab[data]; 1444 return (sc); 1445 } 1446