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