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