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 * $FreeBSD$ 35 */ 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_mac.h" 41 #include "opt_random_ip_id.h" 42 #include "opt_tcpdebug.h" 43 #include "opt_tcp_sack.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/kernel.h> 48 #include <sys/sysctl.h> 49 #include <sys/malloc.h> 50 #include <sys/mac.h> 51 #include <sys/mbuf.h> 52 #include <sys/md5.h> 53 #include <sys/proc.h> /* for proc0 declaration */ 54 #include <sys/random.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 #ifdef INET6 68 #include <netinet/ip6.h> 69 #include <netinet/icmp6.h> 70 #include <netinet6/nd6.h> 71 #include <netinet6/ip6_var.h> 72 #include <netinet6/in6_pcb.h> 73 #endif 74 #include <netinet/tcp.h> 75 #ifdef TCPDEBUG 76 #include <netinet/tcpip.h> 77 #endif 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #ifdef TCPDEBUG 83 #include <netinet/tcp_debug.h> 84 #endif 85 #ifdef INET6 86 #include <netinet6/tcp6_var.h> 87 #endif 88 89 #ifdef IPSEC 90 #include <netinet6/ipsec.h> 91 #ifdef INET6 92 #include <netinet6/ipsec6.h> 93 #endif 94 #endif /*IPSEC*/ 95 96 #ifdef FAST_IPSEC 97 #include <netipsec/ipsec.h> 98 #ifdef INET6 99 #include <netipsec/ipsec6.h> 100 #endif 101 #include <netipsec/key.h> 102 #endif /*FAST_IPSEC*/ 103 104 #include <machine/in_cksum.h> 105 #include <vm/uma.h> 106 107 static int tcp_syncookies = 1; 108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 109 &tcp_syncookies, 0, 110 "Use TCP SYN cookies if the syncache overflows"); 111 112 static void syncache_drop(struct syncache *, struct syncache_head *); 113 static void syncache_free(struct syncache *); 114 static void syncache_insert(struct syncache *, struct syncache_head *); 115 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 116 #ifdef TCPDEBUG 117 static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 118 #else 119 static int syncache_respond(struct syncache *, struct mbuf *); 120 #endif 121 static struct socket *syncache_socket(struct syncache *, struct socket *, 122 struct mbuf *m); 123 static void syncache_timer(void *); 124 static u_int32_t syncookie_generate(struct syncache *, u_int32_t *); 125 static struct syncache *syncookie_lookup(struct in_conninfo *, 126 struct tcphdr *, struct socket *); 127 128 /* 129 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 130 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 131 * the odds are that the user has given up attempting to connect by then. 132 */ 133 #define SYNCACHE_MAXREXMTS 3 134 135 /* Arbitrary values */ 136 #define TCP_SYNCACHE_HASHSIZE 512 137 #define TCP_SYNCACHE_BUCKETLIMIT 30 138 139 struct tcp_syncache { 140 struct syncache_head *hashbase; 141 uma_zone_t zone; 142 u_int hashsize; 143 u_int hashmask; 144 u_int bucket_limit; 145 u_int cache_count; 146 u_int cache_limit; 147 u_int rexmt_limit; 148 u_int hash_secret; 149 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 150 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 151 }; 152 static struct tcp_syncache tcp_syncache; 153 154 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 155 156 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 157 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 158 159 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 160 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 161 162 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 163 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 164 165 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 166 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 167 168 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 169 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 170 171 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 172 173 #define SYNCACHE_HASH(inc, mask) \ 174 ((tcp_syncache.hash_secret ^ \ 175 (inc)->inc_faddr.s_addr ^ \ 176 ((inc)->inc_faddr.s_addr >> 16) ^ \ 177 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 178 179 #define SYNCACHE_HASH6(inc, mask) \ 180 ((tcp_syncache.hash_secret ^ \ 181 (inc)->inc6_faddr.s6_addr32[0] ^ \ 182 (inc)->inc6_faddr.s6_addr32[3] ^ \ 183 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 184 185 #define ENDPTS_EQ(a, b) ( \ 186 (a)->ie_fport == (b)->ie_fport && \ 187 (a)->ie_lport == (b)->ie_lport && \ 188 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 189 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 190 ) 191 192 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 193 194 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 195 sc->sc_rxtslot = (slot); \ 196 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 197 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 198 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 199 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 200 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 201 syncache_timer, (void *)((intptr_t)(slot))); \ 202 } while (0) 203 204 static void 205 syncache_free(struct syncache *sc) 206 { 207 if (sc->sc_ipopts) 208 (void) m_free(sc->sc_ipopts); 209 210 uma_zfree(tcp_syncache.zone, sc); 211 } 212 213 void 214 syncache_init(void) 215 { 216 int i; 217 218 tcp_syncache.cache_count = 0; 219 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 220 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 221 tcp_syncache.cache_limit = 222 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 223 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 224 tcp_syncache.hash_secret = arc4random(); 225 226 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 227 &tcp_syncache.hashsize); 228 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 229 &tcp_syncache.cache_limit); 230 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 231 &tcp_syncache.bucket_limit); 232 if (!powerof2(tcp_syncache.hashsize)) { 233 printf("WARNING: syncache hash size is not a power of 2.\n"); 234 tcp_syncache.hashsize = 512; /* safe default */ 235 } 236 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 237 238 /* Allocate the hash table. */ 239 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 240 tcp_syncache.hashsize * sizeof(struct syncache_head), 241 M_SYNCACHE, M_WAITOK); 242 243 /* Initialize the hash buckets. */ 244 for (i = 0; i < tcp_syncache.hashsize; i++) { 245 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 246 tcp_syncache.hashbase[i].sch_length = 0; 247 } 248 249 /* Initialize the timer queues. */ 250 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 251 TAILQ_INIT(&tcp_syncache.timerq[i]); 252 callout_init(&tcp_syncache.tt_timerq[i], 253 debug_mpsafenet ? CALLOUT_MPSAFE : 0); 254 } 255 256 /* 257 * Allocate the syncache entries. Allow the zone to allocate one 258 * more entry than cache limit, so a new entry can bump out an 259 * older one. 260 */ 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 tcp_syncache.cache_limit -= 1; 265 } 266 267 static void 268 syncache_insert(sc, sch) 269 struct syncache *sc; 270 struct syncache_head *sch; 271 { 272 struct syncache *sc2; 273 int i; 274 275 INP_INFO_WLOCK_ASSERT(&tcbinfo); 276 277 /* 278 * Make sure that we don't overflow the per-bucket 279 * limit or the total cache size limit. 280 */ 281 if (sch->sch_length >= tcp_syncache.bucket_limit) { 282 /* 283 * The bucket is full, toss the oldest element. 284 */ 285 sc2 = TAILQ_FIRST(&sch->sch_bucket); 286 sc2->sc_tp->ts_recent = ticks; 287 syncache_drop(sc2, sch); 288 tcpstat.tcps_sc_bucketoverflow++; 289 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 290 /* 291 * The cache is full. Toss the oldest entry in the 292 * entire cache. This is the front entry in the 293 * first non-empty timer queue with the largest 294 * timeout value. 295 */ 296 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 297 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 298 if (sc2 != NULL) 299 break; 300 } 301 sc2->sc_tp->ts_recent = ticks; 302 syncache_drop(sc2, NULL); 303 tcpstat.tcps_sc_cacheoverflow++; 304 } 305 306 /* Initialize the entry's timer. */ 307 SYNCACHE_TIMEOUT(sc, 0); 308 309 /* Put it into the bucket. */ 310 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 311 sch->sch_length++; 312 tcp_syncache.cache_count++; 313 tcpstat.tcps_sc_added++; 314 } 315 316 static void 317 syncache_drop(sc, sch) 318 struct syncache *sc; 319 struct syncache_head *sch; 320 { 321 INP_INFO_WLOCK_ASSERT(&tcbinfo); 322 323 if (sch == NULL) { 324 #ifdef INET6 325 if (sc->sc_inc.inc_isipv6) { 326 sch = &tcp_syncache.hashbase[ 327 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 328 } else 329 #endif 330 { 331 sch = &tcp_syncache.hashbase[ 332 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 333 } 334 } 335 336 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 337 sch->sch_length--; 338 tcp_syncache.cache_count--; 339 340 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 341 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 342 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 343 344 syncache_free(sc); 345 } 346 347 /* 348 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 349 * If we have retransmitted an entry the maximum number of times, expire it. 350 */ 351 static void 352 syncache_timer(xslot) 353 void *xslot; 354 { 355 intptr_t slot = (intptr_t)xslot; 356 struct syncache *sc, *nsc; 357 struct inpcb *inp; 358 359 INP_INFO_WLOCK(&tcbinfo); 360 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 361 !callout_active(&tcp_syncache.tt_timerq[slot])) { 362 /* XXX can this happen? */ 363 INP_INFO_WUNLOCK(&tcbinfo); 364 return; 365 } 366 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 367 368 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 369 while (nsc != NULL) { 370 if (ticks < nsc->sc_rxttime) 371 break; 372 sc = nsc; 373 inp = sc->sc_tp->t_inpcb; 374 if (slot == SYNCACHE_MAXREXMTS || 375 slot >= tcp_syncache.rexmt_limit || 376 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 377 nsc = TAILQ_NEXT(sc, sc_timerq); 378 syncache_drop(sc, NULL); 379 tcpstat.tcps_sc_stale++; 380 continue; 381 } 382 /* 383 * syncache_respond() may call back into the syncache to 384 * to modify another entry, so do not obtain the next 385 * entry on the timer chain until it has completed. 386 */ 387 #ifdef TCPDEBUG 388 (void) syncache_respond(sc, NULL, NULL); 389 #else 390 (void) syncache_respond(sc, NULL); 391 #endif 392 nsc = TAILQ_NEXT(sc, sc_timerq); 393 tcpstat.tcps_sc_retransmitted++; 394 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 395 SYNCACHE_TIMEOUT(sc, slot + 1); 396 } 397 if (nsc != NULL) 398 callout_reset(&tcp_syncache.tt_timerq[slot], 399 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 400 INP_INFO_WUNLOCK(&tcbinfo); 401 } 402 403 /* 404 * Find an entry in the syncache. 405 */ 406 struct syncache * 407 syncache_lookup(inc, schp) 408 struct in_conninfo *inc; 409 struct syncache_head **schp; 410 { 411 struct syncache *sc; 412 struct syncache_head *sch; 413 414 INP_INFO_WLOCK_ASSERT(&tcbinfo); 415 416 #ifdef INET6 417 if (inc->inc_isipv6) { 418 sch = &tcp_syncache.hashbase[ 419 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 420 *schp = sch; 421 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 422 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 423 return (sc); 424 } 425 } else 426 #endif 427 { 428 sch = &tcp_syncache.hashbase[ 429 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 430 *schp = sch; 431 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 432 #ifdef INET6 433 if (sc->sc_inc.inc_isipv6) 434 continue; 435 #endif 436 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 437 return (sc); 438 } 439 } 440 return (NULL); 441 } 442 443 /* 444 * This function is called when we get a RST for a 445 * non-existent connection, so that we can see if the 446 * connection is in the syn cache. If it is, zap it. 447 */ 448 void 449 syncache_chkrst(inc, th) 450 struct in_conninfo *inc; 451 struct tcphdr *th; 452 { 453 struct syncache *sc; 454 struct syncache_head *sch; 455 456 INP_INFO_WLOCK_ASSERT(&tcbinfo); 457 458 sc = syncache_lookup(inc, &sch); 459 if (sc == NULL) 460 return; 461 /* 462 * If the RST bit is set, check the sequence number to see 463 * if this is a valid reset segment. 464 * RFC 793 page 37: 465 * In all states except SYN-SENT, all reset (RST) segments 466 * are validated by checking their SEQ-fields. A reset is 467 * valid if its sequence number is in the window. 468 * 469 * The sequence number in the reset segment is normally an 470 * echo of our outgoing acknowlegement numbers, but some hosts 471 * send a reset with the sequence number at the rightmost edge 472 * of our receive window, and we have to handle this case. 473 */ 474 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 475 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 476 syncache_drop(sc, sch); 477 tcpstat.tcps_sc_reset++; 478 } 479 } 480 481 void 482 syncache_badack(inc) 483 struct in_conninfo *inc; 484 { 485 struct syncache *sc; 486 struct syncache_head *sch; 487 488 INP_INFO_WLOCK_ASSERT(&tcbinfo); 489 490 sc = syncache_lookup(inc, &sch); 491 if (sc != NULL) { 492 syncache_drop(sc, sch); 493 tcpstat.tcps_sc_badack++; 494 } 495 } 496 497 void 498 syncache_unreach(inc, th) 499 struct in_conninfo *inc; 500 struct tcphdr *th; 501 { 502 struct syncache *sc; 503 struct syncache_head *sch; 504 505 INP_INFO_WLOCK_ASSERT(&tcbinfo); 506 507 /* we are called at splnet() here */ 508 sc = syncache_lookup(inc, &sch); 509 if (sc == NULL) 510 return; 511 512 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 513 if (ntohl(th->th_seq) != sc->sc_iss) 514 return; 515 516 /* 517 * If we've rertransmitted 3 times and this is our second error, 518 * we remove the entry. Otherwise, we allow it to continue on. 519 * This prevents us from incorrectly nuking an entry during a 520 * spurious network outage. 521 * 522 * See tcp_notify(). 523 */ 524 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 525 sc->sc_flags |= SCF_UNREACH; 526 return; 527 } 528 syncache_drop(sc, sch); 529 tcpstat.tcps_sc_unreach++; 530 } 531 532 /* 533 * Build a new TCP socket structure from a syncache entry. 534 */ 535 static struct socket * 536 syncache_socket(sc, lso, m) 537 struct syncache *sc; 538 struct socket *lso; 539 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 /* 573 * Insert new socket into hash list. 574 */ 575 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 576 #ifdef INET6 577 if (sc->sc_inc.inc_isipv6) { 578 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 579 } else { 580 inp->inp_vflag &= ~INP_IPV6; 581 inp->inp_vflag |= INP_IPV4; 582 #endif 583 inp->inp_laddr = sc->sc_inc.inc_laddr; 584 #ifdef INET6 585 } 586 #endif 587 inp->inp_lport = sc->sc_inc.inc_lport; 588 if (in_pcbinshash(inp) != 0) { 589 /* 590 * Undo the assignments above if we failed to 591 * put the PCB on the hash lists. 592 */ 593 #ifdef INET6 594 if (sc->sc_inc.inc_isipv6) 595 inp->in6p_laddr = in6addr_any; 596 else 597 #endif 598 inp->inp_laddr.s_addr = INADDR_ANY; 599 inp->inp_lport = 0; 600 goto abort; 601 } 602 #ifdef IPSEC 603 /* copy old policy into new socket's */ 604 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 605 printf("syncache_expand: could not copy policy\n"); 606 #endif 607 #ifdef FAST_IPSEC 608 /* copy old policy into new socket's */ 609 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 610 printf("syncache_expand: could not copy policy\n"); 611 #endif 612 #ifdef INET6 613 if (sc->sc_inc.inc_isipv6) { 614 struct inpcb *oinp = sotoinpcb(lso); 615 struct in6_addr laddr6; 616 struct sockaddr_in6 sin6; 617 /* 618 * Inherit socket options from the listening socket. 619 * Note that in6p_inputopts are not (and should not be) 620 * copied, since it stores previously received options and is 621 * used to detect if each new option is different than the 622 * previous one and hence should be passed to a user. 623 * If we copied in6p_inputopts, a user would not be able to 624 * receive options just after calling the accept system call. 625 */ 626 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 627 if (oinp->in6p_outputopts) 628 inp->in6p_outputopts = 629 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 630 631 sin6.sin6_family = AF_INET6; 632 sin6.sin6_len = sizeof(sin6); 633 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 634 sin6.sin6_port = sc->sc_inc.inc_fport; 635 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 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, 640 thread0.td_ucred)) { 641 inp->in6p_laddr = laddr6; 642 goto abort; 643 } 644 /* Override flowlabel from in6_pcbconnect. */ 645 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 646 inp->in6p_flowinfo |= sc->sc_flowlabel; 647 } else 648 #endif 649 { 650 struct in_addr laddr; 651 struct sockaddr_in sin; 652 653 inp->inp_options = ip_srcroute(); 654 if (inp->inp_options == NULL) { 655 inp->inp_options = sc->sc_ipopts; 656 sc->sc_ipopts = NULL; 657 } 658 659 sin.sin_family = AF_INET; 660 sin.sin_len = sizeof(sin); 661 sin.sin_addr = sc->sc_inc.inc_faddr; 662 sin.sin_port = sc->sc_inc.inc_fport; 663 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 664 laddr = inp->inp_laddr; 665 if (inp->inp_laddr.s_addr == INADDR_ANY) 666 inp->inp_laddr = sc->sc_inc.inc_laddr; 667 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 668 thread0.td_ucred)) { 669 inp->inp_laddr = laddr; 670 goto abort; 671 } 672 } 673 674 tp = intotcpcb(inp); 675 tp->t_state = TCPS_SYN_RECEIVED; 676 tp->iss = sc->sc_iss; 677 tp->irs = sc->sc_irs; 678 tcp_rcvseqinit(tp); 679 tcp_sendseqinit(tp); 680 tp->snd_wl1 = sc->sc_irs; 681 tp->rcv_up = sc->sc_irs + 1; 682 tp->rcv_wnd = sc->sc_wnd; 683 tp->rcv_adv += tp->rcv_wnd; 684 685 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 686 if (sc->sc_flags & SCF_NOOPT) 687 tp->t_flags |= TF_NOOPT; 688 if (sc->sc_flags & SCF_WINSCALE) { 689 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 690 tp->requested_s_scale = sc->sc_requested_s_scale; 691 tp->request_r_scale = sc->sc_request_r_scale; 692 } 693 if (sc->sc_flags & SCF_TIMESTAMP) { 694 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 695 tp->ts_recent = sc->sc_tsrecent; 696 tp->ts_recent_age = ticks; 697 } 698 if (sc->sc_flags & SCF_CC) { 699 /* 700 * Initialization of the tcpcb for transaction; 701 * set SND.WND = SEG.WND, 702 * initialize CCsend and CCrecv. 703 */ 704 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 705 tp->cc_send = sc->sc_cc_send; 706 tp->cc_recv = sc->sc_cc_recv; 707 } 708 #ifdef TCP_SIGNATURE 709 if (sc->sc_flags & SCF_SIGNATURE) 710 tp->t_flags |= TF_SIGNATURE; 711 #endif 712 if (sc->sc_flags & SCF_SACK) { 713 tp->sack_enable = 1; 714 tp->t_flags |= TF_SACK_PERMIT; 715 } 716 /* 717 * Set up MSS and get cached values from tcp_hostcache. 718 * This might overwrite some of the defaults we just set. 719 */ 720 tcp_mss(tp, sc->sc_peer_mss); 721 722 /* 723 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 724 */ 725 if (sc->sc_rxtslot != 0) 726 tp->snd_cwnd = tp->t_maxseg; 727 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 728 729 INP_UNLOCK(inp); 730 731 tcpstat.tcps_accepts++; 732 return (so); 733 734 abort: 735 INP_UNLOCK(inp); 736 abort2: 737 if (so != NULL) 738 (void) soabort(so); 739 return (NULL); 740 } 741 742 /* 743 * This function gets called when we receive an ACK for a 744 * socket in the LISTEN state. We look up the connection 745 * in the syncache, and if its there, we pull it out of 746 * the cache and turn it into a full-blown connection in 747 * the SYN-RECEIVED state. 748 */ 749 int 750 syncache_expand(inc, th, sop, m) 751 struct in_conninfo *inc; 752 struct tcphdr *th; 753 struct socket **sop; 754 struct mbuf *m; 755 { 756 struct syncache *sc; 757 struct syncache_head *sch; 758 struct socket *so; 759 760 INP_INFO_WLOCK_ASSERT(&tcbinfo); 761 762 sc = syncache_lookup(inc, &sch); 763 if (sc == NULL) { 764 /* 765 * There is no syncache entry, so see if this ACK is 766 * a returning syncookie. To do this, first: 767 * A. See if this socket has had a syncache entry dropped in 768 * the past. We don't want to accept a bogus syncookie 769 * if we've never received a SYN. 770 * B. check that the syncookie is valid. If it is, then 771 * cobble up a fake syncache entry, and return. 772 */ 773 if (!tcp_syncookies) 774 return (0); 775 sc = syncookie_lookup(inc, th, *sop); 776 if (sc == NULL) 777 return (0); 778 sch = NULL; 779 tcpstat.tcps_sc_recvcookie++; 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 return (0); 787 788 so = syncache_socket(sc, *sop, m); 789 if (so == NULL) { 790 #if 0 791 resetandabort: 792 /* XXXjlemon check this - is this correct? */ 793 (void) tcp_respond(NULL, m, m, th, 794 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 795 #endif 796 m_freem(m); /* XXX only needed for above */ 797 tcpstat.tcps_sc_aborted++; 798 } else 799 tcpstat.tcps_sc_completed++; 800 801 if (sch == NULL) 802 syncache_free(sc); 803 else 804 syncache_drop(sc, sch); 805 *sop = so; 806 return (1); 807 } 808 809 /* 810 * Given a LISTEN socket and an inbound SYN request, add 811 * this to the syn cache, and send back a segment: 812 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 813 * to the source. 814 * 815 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 816 * Doing so would require that we hold onto the data and deliver it 817 * to the application. However, if we are the target of a SYN-flood 818 * DoS attack, an attacker could send data which would eventually 819 * consume all available buffer space if it were ACKed. By not ACKing 820 * the data, we avoid this DoS scenario. 821 */ 822 int 823 syncache_add(inc, to, th, sop, m) 824 struct in_conninfo *inc; 825 struct tcpopt *to; 826 struct tcphdr *th; 827 struct socket **sop; 828 struct mbuf *m; 829 { 830 struct tcpcb *tp; 831 struct socket *so; 832 struct syncache *sc = NULL; 833 struct syncache_head *sch; 834 struct mbuf *ipopts = NULL; 835 struct rmxp_tao tao; 836 u_int32_t flowtmp; 837 int i, win; 838 839 INP_INFO_WLOCK_ASSERT(&tcbinfo); 840 841 so = *sop; 842 tp = sototcpcb(so); 843 bzero(&tao, sizeof(tao)); 844 845 /* 846 * Remember the IP options, if any. 847 */ 848 #ifdef INET6 849 if (!inc->inc_isipv6) 850 #endif 851 ipopts = ip_srcroute(); 852 853 /* 854 * See if we already have an entry for this connection. 855 * If we do, resend the SYN,ACK, and reset the retransmit timer. 856 * 857 * XXX 858 * should the syncache be re-initialized with the contents 859 * of the new SYN here (which may have different options?) 860 */ 861 sc = syncache_lookup(inc, &sch); 862 if (sc != NULL) { 863 tcpstat.tcps_sc_dupsyn++; 864 if (ipopts) { 865 /* 866 * If we were remembering a previous source route, 867 * forget it and use the new one we've been given. 868 */ 869 if (sc->sc_ipopts) 870 (void) m_free(sc->sc_ipopts); 871 sc->sc_ipopts = ipopts; 872 } 873 /* 874 * Update timestamp if present. 875 */ 876 if (sc->sc_flags & SCF_TIMESTAMP) 877 sc->sc_tsrecent = to->to_tsval; 878 /* 879 * PCB may have changed, pick up new values. 880 */ 881 sc->sc_tp = tp; 882 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 883 #ifdef TCPDEBUG 884 if (syncache_respond(sc, m, so) == 0) { 885 #else 886 if (syncache_respond(sc, m) == 0) { 887 #endif 888 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 889 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 890 sc, sc_timerq); 891 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 892 tcpstat.tcps_sndacks++; 893 tcpstat.tcps_sndtotal++; 894 } 895 *sop = NULL; 896 return (1); 897 } 898 899 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 900 if (sc == NULL) { 901 /* 902 * The zone allocator couldn't provide more entries. 903 * Treat this as if the cache was full; drop the oldest 904 * entry and insert the new one. 905 */ 906 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 907 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 908 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 909 if (sc != NULL) 910 break; 911 } 912 sc->sc_tp->ts_recent = ticks; 913 syncache_drop(sc, NULL); 914 tcpstat.tcps_sc_zonefail++; 915 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 916 if (sc == NULL) { 917 if (ipopts) 918 (void) m_free(ipopts); 919 return (0); 920 } 921 } 922 923 /* 924 * Fill in the syncache values. 925 */ 926 bzero(sc, sizeof(*sc)); 927 sc->sc_tp = tp; 928 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 929 sc->sc_ipopts = ipopts; 930 sc->sc_inc.inc_fport = inc->inc_fport; 931 sc->sc_inc.inc_lport = inc->inc_lport; 932 #ifdef INET6 933 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 934 if (inc->inc_isipv6) { 935 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 936 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 937 } else 938 #endif 939 { 940 sc->sc_inc.inc_faddr = inc->inc_faddr; 941 sc->sc_inc.inc_laddr = inc->inc_laddr; 942 } 943 sc->sc_irs = th->th_seq; 944 sc->sc_flags = 0; 945 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 946 sc->sc_flowlabel = 0; 947 if (tcp_syncookies) { 948 sc->sc_iss = syncookie_generate(sc, &flowtmp); 949 #ifdef INET6 950 if (inc->inc_isipv6 && 951 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 952 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK; 953 } 954 #endif 955 } else { 956 sc->sc_iss = arc4random(); 957 #ifdef INET6 958 if (inc->inc_isipv6 && 959 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 960 sc->sc_flowlabel = 961 #ifdef RANDOM_IP_ID 962 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 963 #else 964 (htonl(ip6_flow_seq++) & IPV6_FLOWLABEL_MASK); 965 #endif 966 } 967 #endif 968 } 969 970 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 971 win = sbspace(&so->so_rcv); 972 win = imax(win, 0); 973 win = imin(win, TCP_MAXWIN); 974 sc->sc_wnd = win; 975 976 if (tcp_do_rfc1323) { 977 /* 978 * A timestamp received in a SYN makes 979 * it ok to send timestamp requests and replies. 980 */ 981 if (to->to_flags & TOF_TS) { 982 sc->sc_tsrecent = to->to_tsval; 983 sc->sc_flags |= SCF_TIMESTAMP; 984 } 985 if (to->to_flags & TOF_SCALE) { 986 int wscale = 0; 987 988 /* Compute proper scaling value from buffer space */ 989 while (wscale < TCP_MAX_WINSHIFT && 990 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 991 wscale++; 992 sc->sc_request_r_scale = wscale; 993 sc->sc_requested_s_scale = to->to_requested_s_scale; 994 sc->sc_flags |= SCF_WINSCALE; 995 } 996 } 997 if (tcp_do_rfc1644) { 998 /* 999 * A CC or CC.new option received in a SYN makes 1000 * it ok to send CC in subsequent segments. 1001 */ 1002 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 1003 sc->sc_cc_recv = to->to_cc; 1004 sc->sc_cc_send = CC_INC(tcp_ccgen); 1005 sc->sc_flags |= SCF_CC; 1006 } 1007 } 1008 if (tp->t_flags & TF_NOOPT) 1009 sc->sc_flags = SCF_NOOPT; 1010 #ifdef TCP_SIGNATURE 1011 /* 1012 * If listening socket requested TCP digests, and received SYN 1013 * contains the option, flag this in the syncache so that 1014 * syncache_respond() will do the right thing with the SYN+ACK. 1015 * XXX Currently we always record the option by default and will 1016 * attempt to use it in syncache_respond(). 1017 */ 1018 if (to->to_flags & TOF_SIGNATURE) 1019 sc->sc_flags = SCF_SIGNATURE; 1020 #endif 1021 1022 if (to->to_flags & TOF_SACK) 1023 sc->sc_flags |= SCF_SACK; 1024 1025 /* 1026 * XXX 1027 * We have the option here of not doing TAO (even if the segment 1028 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1029 * This allows us to apply synflood protection to TAO-qualifying SYNs 1030 * also. However, there should be a hueristic to determine when to 1031 * do this, and is not present at the moment. 1032 */ 1033 1034 /* 1035 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1036 * - compare SEG.CC against cached CC from the same host, if any. 1037 * - if SEG.CC > chached value, SYN must be new and is accepted 1038 * immediately: save new CC in the cache, mark the socket 1039 * connected, enter ESTABLISHED state, turn on flag to 1040 * send a SYN in the next segment. 1041 * A virtual advertised window is set in rcv_adv to 1042 * initialize SWS prevention. Then enter normal segment 1043 * processing: drop SYN, process data and FIN. 1044 * - otherwise do a normal 3-way handshake. 1045 */ 1046 if (tcp_do_rfc1644) 1047 tcp_hc_gettao(&sc->sc_inc, &tao); 1048 1049 if ((to->to_flags & TOF_CC) != 0) { 1050 if (((tp->t_flags & TF_NOPUSH) != 0) && 1051 sc->sc_flags & SCF_CC && tao.tao_cc != 0 && 1052 CC_GT(to->to_cc, tao.tao_cc)) { 1053 sc->sc_rxtslot = 0; 1054 so = syncache_socket(sc, *sop, m); 1055 if (so != NULL) { 1056 tao.tao_cc = to->to_cc; 1057 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1058 tao.tao_cc, 0); 1059 *sop = so; 1060 } 1061 syncache_free(sc); 1062 return (so != NULL); 1063 } 1064 } else { 1065 /* 1066 * No CC option, but maybe CC.NEW: invalidate cached value. 1067 */ 1068 if (tcp_do_rfc1644) { 1069 tao.tao_cc = 0; 1070 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1071 tao.tao_cc, 0); 1072 } 1073 } 1074 1075 /* 1076 * TAO test failed or there was no CC option, 1077 * do a standard 3-way handshake. 1078 */ 1079 #ifdef TCPDEBUG 1080 if (syncache_respond(sc, m, so) == 0) { 1081 #else 1082 if (syncache_respond(sc, m) == 0) { 1083 #endif 1084 syncache_insert(sc, sch); 1085 tcpstat.tcps_sndacks++; 1086 tcpstat.tcps_sndtotal++; 1087 } else { 1088 syncache_free(sc); 1089 tcpstat.tcps_sc_dropped++; 1090 } 1091 *sop = NULL; 1092 return (1); 1093 } 1094 1095 #ifdef TCPDEBUG 1096 static int 1097 syncache_respond(sc, m, so) 1098 struct syncache *sc; 1099 struct mbuf *m; 1100 struct socket *so; 1101 #else 1102 static int 1103 syncache_respond(sc, m) 1104 struct syncache *sc; 1105 struct mbuf *m; 1106 #endif 1107 { 1108 u_int8_t *optp; 1109 int optlen, error; 1110 u_int16_t tlen, hlen, mssopt; 1111 struct ip *ip = NULL; 1112 struct tcphdr *th; 1113 struct inpcb *inp; 1114 #ifdef INET6 1115 struct ip6_hdr *ip6 = NULL; 1116 #endif 1117 1118 hlen = 1119 #ifdef INET6 1120 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1121 #endif 1122 sizeof(struct ip); 1123 1124 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1125 1126 /* Determine MSS we advertize to other end of connection */ 1127 mssopt = tcp_mssopt(&sc->sc_inc); 1128 1129 /* Compute the size of the TCP options. */ 1130 if (sc->sc_flags & SCF_NOOPT) { 1131 optlen = 0; 1132 } else { 1133 optlen = TCPOLEN_MAXSEG + 1134 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1135 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1136 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1137 #ifdef TCP_SIGNATURE 1138 optlen += (sc->sc_flags & SCF_SIGNATURE) ? 1139 TCPOLEN_SIGNATURE + 2 : 0; 1140 #endif 1141 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0); 1142 } 1143 tlen = hlen + sizeof(struct tcphdr) + optlen; 1144 1145 /* 1146 * XXX 1147 * assume that the entire packet will fit in a header mbuf 1148 */ 1149 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1150 1151 /* 1152 * XXX shouldn't this reuse the mbuf if possible ? 1153 * Create the IP+TCP header from scratch. 1154 */ 1155 if (m) 1156 m_freem(m); 1157 1158 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1159 if (m == NULL) 1160 return (ENOBUFS); 1161 m->m_data += max_linkhdr; 1162 m->m_len = tlen; 1163 m->m_pkthdr.len = tlen; 1164 m->m_pkthdr.rcvif = NULL; 1165 inp = sc->sc_tp->t_inpcb; 1166 INP_LOCK(inp); 1167 #ifdef MAC 1168 mac_create_mbuf_from_inpcb(inp, m); 1169 #endif 1170 1171 #ifdef INET6 1172 if (sc->sc_inc.inc_isipv6) { 1173 ip6 = mtod(m, struct ip6_hdr *); 1174 ip6->ip6_vfc = IPV6_VERSION; 1175 ip6->ip6_nxt = IPPROTO_TCP; 1176 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1177 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1178 ip6->ip6_plen = htons(tlen - hlen); 1179 /* ip6_hlim is set after checksum */ 1180 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1181 ip6->ip6_flow |= sc->sc_flowlabel; 1182 1183 th = (struct tcphdr *)(ip6 + 1); 1184 } else 1185 #endif 1186 { 1187 ip = mtod(m, struct ip *); 1188 ip->ip_v = IPVERSION; 1189 ip->ip_hl = sizeof(struct ip) >> 2; 1190 ip->ip_len = tlen; 1191 ip->ip_id = 0; 1192 ip->ip_off = 0; 1193 ip->ip_sum = 0; 1194 ip->ip_p = IPPROTO_TCP; 1195 ip->ip_src = sc->sc_inc.inc_laddr; 1196 ip->ip_dst = sc->sc_inc.inc_faddr; 1197 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1198 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1199 1200 /* 1201 * See if we should do MTU discovery. Route lookups are 1202 * expensive, so we will only unset the DF bit if: 1203 * 1204 * 1) path_mtu_discovery is disabled 1205 * 2) the SCF_UNREACH flag has been set 1206 */ 1207 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1208 ip->ip_off |= IP_DF; 1209 1210 th = (struct tcphdr *)(ip + 1); 1211 } 1212 th->th_sport = sc->sc_inc.inc_lport; 1213 th->th_dport = sc->sc_inc.inc_fport; 1214 1215 th->th_seq = htonl(sc->sc_iss); 1216 th->th_ack = htonl(sc->sc_irs + 1); 1217 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1218 th->th_x2 = 0; 1219 th->th_flags = TH_SYN|TH_ACK; 1220 th->th_win = htons(sc->sc_wnd); 1221 th->th_urp = 0; 1222 1223 /* Tack on the TCP options. */ 1224 if (optlen != 0) { 1225 optp = (u_int8_t *)(th + 1); 1226 *optp++ = TCPOPT_MAXSEG; 1227 *optp++ = TCPOLEN_MAXSEG; 1228 *optp++ = (mssopt >> 8) & 0xff; 1229 *optp++ = mssopt & 0xff; 1230 1231 if (sc->sc_flags & SCF_WINSCALE) { 1232 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1233 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1234 sc->sc_request_r_scale); 1235 optp += 4; 1236 } 1237 1238 if (sc->sc_flags & SCF_TIMESTAMP) { 1239 u_int32_t *lp = (u_int32_t *)(optp); 1240 1241 /* Form timestamp option per appendix A of RFC 1323. */ 1242 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1243 *lp++ = htonl(ticks); 1244 *lp = htonl(sc->sc_tsrecent); 1245 optp += TCPOLEN_TSTAMP_APPA; 1246 } 1247 1248 /* 1249 * Send CC and CC.echo if we received CC from our peer. 1250 */ 1251 if (sc->sc_flags & SCF_CC) { 1252 u_int32_t *lp = (u_int32_t *)(optp); 1253 1254 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1255 *lp++ = htonl(sc->sc_cc_send); 1256 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1257 *lp = htonl(sc->sc_cc_recv); 1258 optp += TCPOLEN_CC_APPA * 2; 1259 } 1260 1261 #ifdef TCP_SIGNATURE 1262 /* 1263 * Handle TCP-MD5 passive opener response. 1264 */ 1265 if (sc->sc_flags & SCF_SIGNATURE) { 1266 u_int8_t *bp = optp; 1267 int i; 1268 1269 *bp++ = TCPOPT_SIGNATURE; 1270 *bp++ = TCPOLEN_SIGNATURE; 1271 for (i = 0; i < TCP_SIGLEN; i++) 1272 *bp++ = 0; 1273 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1274 optp + 2, IPSEC_DIR_OUTBOUND); 1275 *bp++ = TCPOPT_NOP; 1276 *bp++ = TCPOPT_EOL; 1277 optp += TCPOLEN_SIGNATURE + 2; 1278 } 1279 #endif /* TCP_SIGNATURE */ 1280 1281 if (sc->sc_flags & SCF_SACK) { 1282 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR); 1283 optp += 4; 1284 } 1285 } 1286 1287 #ifdef INET6 1288 if (sc->sc_inc.inc_isipv6) { 1289 th->th_sum = 0; 1290 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1291 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1292 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1293 } else 1294 #endif 1295 { 1296 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1297 htons(tlen - hlen + IPPROTO_TCP)); 1298 m->m_pkthdr.csum_flags = CSUM_TCP; 1299 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1300 #ifdef TCPDEBUG 1301 /* 1302 * Trace. 1303 */ 1304 if (so != NULL && so->so_options & SO_DEBUG) { 1305 struct tcpcb *tp = sototcpcb(so); 1306 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1307 mtod(m, void *), th, 0); 1308 } 1309 #endif 1310 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1311 } 1312 INP_UNLOCK(inp); 1313 return (error); 1314 } 1315 1316 /* 1317 * cookie layers: 1318 * 1319 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1320 * | peer iss | 1321 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1322 * | 0 |(A)| | 1323 * (A): peer mss index 1324 */ 1325 1326 /* 1327 * The values below are chosen to minimize the size of the tcp_secret 1328 * table, as well as providing roughly a 16 second lifetime for the cookie. 1329 */ 1330 1331 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1332 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1333 1334 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1335 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1336 #define SYNCOOKIE_TIMEOUT \ 1337 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1338 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1339 1340 static struct { 1341 u_int32_t ts_secbits[4]; 1342 u_int ts_expire; 1343 } tcp_secret[SYNCOOKIE_NSECRETS]; 1344 1345 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1346 1347 static MD5_CTX syn_ctx; 1348 1349 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1350 1351 struct md5_add { 1352 u_int32_t laddr, faddr; 1353 u_int32_t secbits[4]; 1354 u_int16_t lport, fport; 1355 }; 1356 1357 #ifdef CTASSERT 1358 CTASSERT(sizeof(struct md5_add) == 28); 1359 #endif 1360 1361 /* 1362 * Consider the problem of a recreated (and retransmitted) cookie. If the 1363 * original SYN was accepted, the connection is established. The second 1364 * SYN is inflight, and if it arrives with an ISN that falls within the 1365 * receive window, the connection is killed. 1366 * 1367 * However, since cookies have other problems, this may not be worth 1368 * worrying about. 1369 */ 1370 1371 static u_int32_t 1372 syncookie_generate(struct syncache *sc, u_int32_t *flowid) 1373 { 1374 u_int32_t md5_buffer[4]; 1375 u_int32_t data; 1376 int idx, i; 1377 struct md5_add add; 1378 1379 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1380 1381 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1382 if (tcp_secret[idx].ts_expire < ticks) { 1383 for (i = 0; i < 4; i++) 1384 tcp_secret[idx].ts_secbits[i] = arc4random(); 1385 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1386 } 1387 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1388 if (tcp_msstab[data] <= sc->sc_peer_mss) 1389 break; 1390 data = (data << SYNCOOKIE_WNDBITS) | idx; 1391 data ^= sc->sc_irs; /* peer's iss */ 1392 MD5Init(&syn_ctx); 1393 #ifdef INET6 1394 if (sc->sc_inc.inc_isipv6) { 1395 MD5Add(sc->sc_inc.inc6_laddr); 1396 MD5Add(sc->sc_inc.inc6_faddr); 1397 add.laddr = 0; 1398 add.faddr = 0; 1399 } else 1400 #endif 1401 { 1402 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1403 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1404 } 1405 add.lport = sc->sc_inc.inc_lport; 1406 add.fport = sc->sc_inc.inc_fport; 1407 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1408 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1409 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1410 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1411 MD5Add(add); 1412 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1413 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1414 *flowid = md5_buffer[1]; 1415 return (data); 1416 } 1417 1418 static struct syncache * 1419 syncookie_lookup(inc, th, so) 1420 struct in_conninfo *inc; 1421 struct tcphdr *th; 1422 struct socket *so; 1423 { 1424 u_int32_t md5_buffer[4]; 1425 struct syncache *sc; 1426 u_int32_t data; 1427 int wnd, idx; 1428 struct md5_add add; 1429 1430 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1431 1432 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1433 idx = data & SYNCOOKIE_WNDMASK; 1434 if (tcp_secret[idx].ts_expire < ticks || 1435 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1436 return (NULL); 1437 MD5Init(&syn_ctx); 1438 #ifdef INET6 1439 if (inc->inc_isipv6) { 1440 MD5Add(inc->inc6_laddr); 1441 MD5Add(inc->inc6_faddr); 1442 add.laddr = 0; 1443 add.faddr = 0; 1444 } else 1445 #endif 1446 { 1447 add.laddr = inc->inc_laddr.s_addr; 1448 add.faddr = inc->inc_faddr.s_addr; 1449 } 1450 add.lport = inc->inc_lport; 1451 add.fport = inc->inc_fport; 1452 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1453 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1454 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1455 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1456 MD5Add(add); 1457 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1458 data ^= md5_buffer[0]; 1459 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1460 return (NULL); 1461 data = data >> SYNCOOKIE_WNDBITS; 1462 1463 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1464 if (sc == NULL) 1465 return (NULL); 1466 /* 1467 * Fill in the syncache values. 1468 * XXX duplicate code from syncache_add 1469 */ 1470 sc->sc_ipopts = NULL; 1471 sc->sc_inc.inc_fport = inc->inc_fport; 1472 sc->sc_inc.inc_lport = inc->inc_lport; 1473 sc->sc_tp = sototcpcb(so); 1474 #ifdef INET6 1475 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1476 if (inc->inc_isipv6) { 1477 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1478 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1479 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL) 1480 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1481 } else 1482 #endif 1483 { 1484 sc->sc_inc.inc_faddr = inc->inc_faddr; 1485 sc->sc_inc.inc_laddr = inc->inc_laddr; 1486 } 1487 sc->sc_irs = th->th_seq - 1; 1488 sc->sc_iss = th->th_ack - 1; 1489 wnd = sbspace(&so->so_rcv); 1490 wnd = imax(wnd, 0); 1491 wnd = imin(wnd, TCP_MAXWIN); 1492 sc->sc_wnd = wnd; 1493 sc->sc_flags = 0; 1494 sc->sc_rxtslot = 0; 1495 sc->sc_peer_mss = tcp_msstab[data]; 1496 return (sc); 1497 } 1498