tcp_syncache.c revision 130989
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: head/sys/netinet/tcp_syncache.c 130989 2004-06-23 21:04:37Z ps $ 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 106static int tcp_syncookies = 1; 107SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 108 &tcp_syncookies, 0, 109 "Use TCP SYN cookies if the syncache overflows"); 110 111static void syncache_drop(struct syncache *, struct syncache_head *); 112static void syncache_free(struct syncache *); 113static void syncache_insert(struct syncache *, struct syncache_head *); 114struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 115#ifdef TCPDEBUG 116static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 117#else 118static int syncache_respond(struct syncache *, struct mbuf *); 119#endif 120static struct socket *syncache_socket(struct syncache *, struct socket *, 121 struct mbuf *m); 122static void syncache_timer(void *); 123static u_int32_t syncookie_generate(struct syncache *); 124static 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 138struct 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}; 151static struct tcp_syncache tcp_syncache; 152 153SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 154 155SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 156 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 157 158SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 159 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 160 161SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 162 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 163 164SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 165 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 166 167SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 168 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 169 170static 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 203static void 204syncache_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 212void 213syncache_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 266static void 267syncache_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 315static void 316syncache_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 */ 350static void 351syncache_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 */ 405struct syncache * 406syncache_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 */ 447void 448syncache_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 480void 481syncache_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 496void 497syncache_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 */ 534static struct socket * 535syncache_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 } else 644#endif 645 { 646 struct in_addr laddr; 647 struct sockaddr_in sin; 648 649 inp->inp_options = ip_srcroute(); 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 if (sc->sc_flags & SCF_CC) { 695 /* 696 * Initialization of the tcpcb for transaction; 697 * set SND.WND = SEG.WND, 698 * initialize CCsend and CCrecv. 699 */ 700 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 701 tp->cc_send = sc->sc_cc_send; 702 tp->cc_recv = sc->sc_cc_recv; 703 } 704#ifdef TCP_SIGNATURE 705 if (sc->sc_flags & SCF_SIGNATURE) 706 tp->t_flags |= TF_SIGNATURE; 707#endif 708 if (sc->sc_flags & SCF_SACK) { 709 tp->sack_enable = 1; 710 tp->t_flags |= TF_SACK_PERMIT; 711 } 712 /* 713 * Set up MSS and get cached values from tcp_hostcache. 714 * This might overwrite some of the defaults we just set. 715 */ 716 tcp_mss(tp, sc->sc_peer_mss); 717 718 /* 719 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 720 */ 721 if (sc->sc_rxtslot != 0) 722 tp->snd_cwnd = tp->t_maxseg; 723 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 724 725 INP_UNLOCK(inp); 726 727 tcpstat.tcps_accepts++; 728 return (so); 729 730abort: 731 INP_UNLOCK(inp); 732abort2: 733 if (so != NULL) 734 (void) soabort(so); 735 return (NULL); 736} 737 738/* 739 * This function gets called when we receive an ACK for a 740 * socket in the LISTEN state. We look up the connection 741 * in the syncache, and if its there, we pull it out of 742 * the cache and turn it into a full-blown connection in 743 * the SYN-RECEIVED state. 744 */ 745int 746syncache_expand(inc, th, sop, m) 747 struct in_conninfo *inc; 748 struct tcphdr *th; 749 struct socket **sop; 750 struct mbuf *m; 751{ 752 struct syncache *sc; 753 struct syncache_head *sch; 754 struct socket *so; 755 756 INP_INFO_WLOCK_ASSERT(&tcbinfo); 757 758 sc = syncache_lookup(inc, &sch); 759 if (sc == NULL) { 760 /* 761 * There is no syncache entry, so see if this ACK is 762 * a returning syncookie. To do this, first: 763 * A. See if this socket has had a syncache entry dropped in 764 * the past. We don't want to accept a bogus syncookie 765 * if we've never received a SYN. 766 * B. check that the syncookie is valid. If it is, then 767 * cobble up a fake syncache entry, and return. 768 */ 769 if (!tcp_syncookies) 770 return (0); 771 sc = syncookie_lookup(inc, th, *sop); 772 if (sc == NULL) 773 return (0); 774 sch = NULL; 775 tcpstat.tcps_sc_recvcookie++; 776 } 777 778 /* 779 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 780 */ 781 if (th->th_ack != sc->sc_iss + 1) 782 return (0); 783 784 so = syncache_socket(sc, *sop, m); 785 if (so == NULL) { 786#if 0 787resetandabort: 788 /* XXXjlemon check this - is this correct? */ 789 (void) tcp_respond(NULL, m, m, th, 790 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 791#endif 792 m_freem(m); /* XXX only needed for above */ 793 tcpstat.tcps_sc_aborted++; 794 } else 795 tcpstat.tcps_sc_completed++; 796 797 if (sch == NULL) 798 syncache_free(sc); 799 else 800 syncache_drop(sc, sch); 801 *sop = so; 802 return (1); 803} 804 805/* 806 * Given a LISTEN socket and an inbound SYN request, add 807 * this to the syn cache, and send back a segment: 808 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 809 * to the source. 810 * 811 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 812 * Doing so would require that we hold onto the data and deliver it 813 * to the application. However, if we are the target of a SYN-flood 814 * DoS attack, an attacker could send data which would eventually 815 * consume all available buffer space if it were ACKed. By not ACKing 816 * the data, we avoid this DoS scenario. 817 */ 818int 819syncache_add(inc, to, th, sop, m) 820 struct in_conninfo *inc; 821 struct tcpopt *to; 822 struct tcphdr *th; 823 struct socket **sop; 824 struct mbuf *m; 825{ 826 struct tcpcb *tp; 827 struct socket *so; 828 struct syncache *sc = NULL; 829 struct syncache_head *sch; 830 struct mbuf *ipopts = NULL; 831 struct rmxp_tao tao; 832 int i, win; 833 834 INP_INFO_WLOCK_ASSERT(&tcbinfo); 835 836 so = *sop; 837 tp = sototcpcb(so); 838 bzero(&tao, sizeof(tao)); 839 840 /* 841 * Remember the IP options, if any. 842 */ 843#ifdef INET6 844 if (!inc->inc_isipv6) 845#endif 846 ipopts = ip_srcroute(); 847 848 /* 849 * See if we already have an entry for this connection. 850 * If we do, resend the SYN,ACK, and reset the retransmit timer. 851 * 852 * XXX 853 * should the syncache be re-initialized with the contents 854 * of the new SYN here (which may have different options?) 855 */ 856 sc = syncache_lookup(inc, &sch); 857 if (sc != NULL) { 858 tcpstat.tcps_sc_dupsyn++; 859 if (ipopts) { 860 /* 861 * If we were remembering a previous source route, 862 * forget it and use the new one we've been given. 863 */ 864 if (sc->sc_ipopts) 865 (void) m_free(sc->sc_ipopts); 866 sc->sc_ipopts = ipopts; 867 } 868 /* 869 * Update timestamp if present. 870 */ 871 if (sc->sc_flags & SCF_TIMESTAMP) 872 sc->sc_tsrecent = to->to_tsval; 873 /* 874 * PCB may have changed, pick up new values. 875 */ 876 sc->sc_tp = tp; 877 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 878#ifdef TCPDEBUG 879 if (syncache_respond(sc, m, so) == 0) { 880#else 881 if (syncache_respond(sc, m) == 0) { 882#endif 883 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 884 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 885 sc, sc_timerq); 886 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 887 tcpstat.tcps_sndacks++; 888 tcpstat.tcps_sndtotal++; 889 } 890 *sop = NULL; 891 return (1); 892 } 893 894 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 895 if (sc == NULL) { 896 /* 897 * The zone allocator couldn't provide more entries. 898 * Treat this as if the cache was full; drop the oldest 899 * entry and insert the new one. 900 */ 901 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 902 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 903 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 904 if (sc != NULL) 905 break; 906 } 907 sc->sc_tp->ts_recent = ticks; 908 syncache_drop(sc, NULL); 909 tcpstat.tcps_sc_zonefail++; 910 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 911 if (sc == NULL) { 912 if (ipopts) 913 (void) m_free(ipopts); 914 return (0); 915 } 916 } 917 918 /* 919 * Fill in the syncache values. 920 */ 921 bzero(sc, sizeof(*sc)); 922 sc->sc_tp = tp; 923 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 924 sc->sc_ipopts = ipopts; 925 sc->sc_inc.inc_fport = inc->inc_fport; 926 sc->sc_inc.inc_lport = inc->inc_lport; 927#ifdef INET6 928 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 929 if (inc->inc_isipv6) { 930 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 931 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 932 } else 933#endif 934 { 935 sc->sc_inc.inc_faddr = inc->inc_faddr; 936 sc->sc_inc.inc_laddr = inc->inc_laddr; 937 } 938 sc->sc_irs = th->th_seq; 939 sc->sc_flags = 0; 940 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 941 if (tcp_syncookies) 942 sc->sc_iss = syncookie_generate(sc); 943 else 944 sc->sc_iss = arc4random(); 945 946 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 947 win = sbspace(&so->so_rcv); 948 win = imax(win, 0); 949 win = imin(win, TCP_MAXWIN); 950 sc->sc_wnd = win; 951 952 if (tcp_do_rfc1323) { 953 /* 954 * A timestamp received in a SYN makes 955 * it ok to send timestamp requests and replies. 956 */ 957 if (to->to_flags & TOF_TS) { 958 sc->sc_tsrecent = to->to_tsval; 959 sc->sc_flags |= SCF_TIMESTAMP; 960 } 961 if (to->to_flags & TOF_SCALE) { 962 int wscale = 0; 963 964 /* Compute proper scaling value from buffer space */ 965 while (wscale < TCP_MAX_WINSHIFT && 966 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 967 wscale++; 968 sc->sc_request_r_scale = wscale; 969 sc->sc_requested_s_scale = to->to_requested_s_scale; 970 sc->sc_flags |= SCF_WINSCALE; 971 } 972 } 973 if (tcp_do_rfc1644) { 974 /* 975 * A CC or CC.new option received in a SYN makes 976 * it ok to send CC in subsequent segments. 977 */ 978 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 979 sc->sc_cc_recv = to->to_cc; 980 sc->sc_cc_send = CC_INC(tcp_ccgen); 981 sc->sc_flags |= SCF_CC; 982 } 983 } 984 if (tp->t_flags & TF_NOOPT) 985 sc->sc_flags = SCF_NOOPT; 986#ifdef TCP_SIGNATURE 987 /* 988 * If listening socket requested TCP digests, and received SYN 989 * contains the option, flag this in the syncache so that 990 * syncache_respond() will do the right thing with the SYN+ACK. 991 * XXX Currently we always record the option by default and will 992 * attempt to use it in syncache_respond(). 993 */ 994 if (to->to_flags & TOF_SIGNATURE) 995 sc->sc_flags = SCF_SIGNATURE; 996#endif 997 998 if (to->to_flags & TOF_SACK) 999 sc->sc_flags |= SCF_SACK; 1000 1001 /* 1002 * XXX 1003 * We have the option here of not doing TAO (even if the segment 1004 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1005 * This allows us to apply synflood protection to TAO-qualifying SYNs 1006 * also. However, there should be a hueristic to determine when to 1007 * do this, and is not present at the moment. 1008 */ 1009 1010 /* 1011 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1012 * - compare SEG.CC against cached CC from the same host, if any. 1013 * - if SEG.CC > chached value, SYN must be new and is accepted 1014 * immediately: save new CC in the cache, mark the socket 1015 * connected, enter ESTABLISHED state, turn on flag to 1016 * send a SYN in the next segment. 1017 * A virtual advertised window is set in rcv_adv to 1018 * initialize SWS prevention. Then enter normal segment 1019 * processing: drop SYN, process data and FIN. 1020 * - otherwise do a normal 3-way handshake. 1021 */ 1022 if (tcp_do_rfc1644) 1023 tcp_hc_gettao(&sc->sc_inc, &tao); 1024 1025 if ((to->to_flags & TOF_CC) != 0) { 1026 if (((tp->t_flags & TF_NOPUSH) != 0) && 1027 sc->sc_flags & SCF_CC && tao.tao_cc != 0 && 1028 CC_GT(to->to_cc, tao.tao_cc)) { 1029 sc->sc_rxtslot = 0; 1030 so = syncache_socket(sc, *sop, m); 1031 if (so != NULL) { 1032 tao.tao_cc = to->to_cc; 1033 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1034 tao.tao_cc, 0); 1035 *sop = so; 1036 } 1037 syncache_free(sc); 1038 return (so != NULL); 1039 } 1040 } else { 1041 /* 1042 * No CC option, but maybe CC.NEW: invalidate cached value. 1043 */ 1044 if (tcp_do_rfc1644) { 1045 tao.tao_cc = 0; 1046 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1047 tao.tao_cc, 0); 1048 } 1049 } 1050 1051 /* 1052 * TAO test failed or there was no CC option, 1053 * do a standard 3-way handshake. 1054 */ 1055#ifdef TCPDEBUG 1056 if (syncache_respond(sc, m, so) == 0) { 1057#else 1058 if (syncache_respond(sc, m) == 0) { 1059#endif 1060 syncache_insert(sc, sch); 1061 tcpstat.tcps_sndacks++; 1062 tcpstat.tcps_sndtotal++; 1063 } else { 1064 syncache_free(sc); 1065 tcpstat.tcps_sc_dropped++; 1066 } 1067 *sop = NULL; 1068 return (1); 1069} 1070 1071#ifdef TCPDEBUG 1072static int 1073syncache_respond(sc, m, so) 1074 struct syncache *sc; 1075 struct mbuf *m; 1076 struct socket *so; 1077#else 1078static int 1079syncache_respond(sc, m) 1080 struct syncache *sc; 1081 struct mbuf *m; 1082#endif 1083{ 1084 u_int8_t *optp; 1085 int optlen, error; 1086 u_int16_t tlen, hlen, mssopt; 1087 struct ip *ip = NULL; 1088 struct tcphdr *th; 1089 struct inpcb *inp; 1090#ifdef INET6 1091 struct ip6_hdr *ip6 = NULL; 1092#endif 1093 1094 hlen = 1095#ifdef INET6 1096 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1097#endif 1098 sizeof(struct ip); 1099 1100 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1101 1102 /* Determine MSS we advertize to other end of connection */ 1103 mssopt = tcp_mssopt(&sc->sc_inc); 1104 1105 /* Compute the size of the TCP options. */ 1106 if (sc->sc_flags & SCF_NOOPT) { 1107 optlen = 0; 1108 } else { 1109 optlen = TCPOLEN_MAXSEG + 1110 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1111 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1112 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1113#ifdef TCP_SIGNATURE 1114 optlen += (sc->sc_flags & SCF_SIGNATURE) ? 1115 TCPOLEN_SIGNATURE + 2 : 0; 1116#endif 1117 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0); 1118 } 1119 tlen = hlen + sizeof(struct tcphdr) + optlen; 1120 1121 /* 1122 * XXX 1123 * assume that the entire packet will fit in a header mbuf 1124 */ 1125 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1126 1127 /* 1128 * XXX shouldn't this reuse the mbuf if possible ? 1129 * Create the IP+TCP header from scratch. 1130 */ 1131 if (m) 1132 m_freem(m); 1133 1134 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1135 if (m == NULL) 1136 return (ENOBUFS); 1137 m->m_data += max_linkhdr; 1138 m->m_len = tlen; 1139 m->m_pkthdr.len = tlen; 1140 m->m_pkthdr.rcvif = NULL; 1141 inp = sc->sc_tp->t_inpcb; 1142 INP_LOCK(inp); 1143#ifdef MAC 1144 mac_create_mbuf_from_inpcb(inp, m); 1145#endif 1146 1147#ifdef INET6 1148 if (sc->sc_inc.inc_isipv6) { 1149 ip6 = mtod(m, struct ip6_hdr *); 1150 ip6->ip6_vfc = IPV6_VERSION; 1151 ip6->ip6_nxt = IPPROTO_TCP; 1152 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1153 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1154 ip6->ip6_plen = htons(tlen - hlen); 1155 /* ip6_hlim is set after checksum */ 1156 /* ip6_flow = ??? */ 1157 1158 th = (struct tcphdr *)(ip6 + 1); 1159 } else 1160#endif 1161 { 1162 ip = mtod(m, struct ip *); 1163 ip->ip_v = IPVERSION; 1164 ip->ip_hl = sizeof(struct ip) >> 2; 1165 ip->ip_len = tlen; 1166 ip->ip_id = 0; 1167 ip->ip_off = 0; 1168 ip->ip_sum = 0; 1169 ip->ip_p = IPPROTO_TCP; 1170 ip->ip_src = sc->sc_inc.inc_laddr; 1171 ip->ip_dst = sc->sc_inc.inc_faddr; 1172 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1173 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1174 1175 /* 1176 * See if we should do MTU discovery. Route lookups are 1177 * expensive, so we will only unset the DF bit if: 1178 * 1179 * 1) path_mtu_discovery is disabled 1180 * 2) the SCF_UNREACH flag has been set 1181 */ 1182 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1183 ip->ip_off |= IP_DF; 1184 1185 th = (struct tcphdr *)(ip + 1); 1186 } 1187 th->th_sport = sc->sc_inc.inc_lport; 1188 th->th_dport = sc->sc_inc.inc_fport; 1189 1190 th->th_seq = htonl(sc->sc_iss); 1191 th->th_ack = htonl(sc->sc_irs + 1); 1192 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1193 th->th_x2 = 0; 1194 th->th_flags = TH_SYN|TH_ACK; 1195 th->th_win = htons(sc->sc_wnd); 1196 th->th_urp = 0; 1197 1198 /* Tack on the TCP options. */ 1199 if (optlen != 0) { 1200 optp = (u_int8_t *)(th + 1); 1201 *optp++ = TCPOPT_MAXSEG; 1202 *optp++ = TCPOLEN_MAXSEG; 1203 *optp++ = (mssopt >> 8) & 0xff; 1204 *optp++ = mssopt & 0xff; 1205 1206 if (sc->sc_flags & SCF_WINSCALE) { 1207 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1208 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1209 sc->sc_request_r_scale); 1210 optp += 4; 1211 } 1212 1213 if (sc->sc_flags & SCF_TIMESTAMP) { 1214 u_int32_t *lp = (u_int32_t *)(optp); 1215 1216 /* Form timestamp option per appendix A of RFC 1323. */ 1217 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1218 *lp++ = htonl(ticks); 1219 *lp = htonl(sc->sc_tsrecent); 1220 optp += TCPOLEN_TSTAMP_APPA; 1221 } 1222 1223 /* 1224 * Send CC and CC.echo if we received CC from our peer. 1225 */ 1226 if (sc->sc_flags & SCF_CC) { 1227 u_int32_t *lp = (u_int32_t *)(optp); 1228 1229 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1230 *lp++ = htonl(sc->sc_cc_send); 1231 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1232 *lp = htonl(sc->sc_cc_recv); 1233 optp += TCPOLEN_CC_APPA * 2; 1234 } 1235 1236#ifdef TCP_SIGNATURE 1237 /* 1238 * Handle TCP-MD5 passive opener response. 1239 */ 1240 if (sc->sc_flags & SCF_SIGNATURE) { 1241 u_int8_t *bp = optp; 1242 int i; 1243 1244 *bp++ = TCPOPT_SIGNATURE; 1245 *bp++ = TCPOLEN_SIGNATURE; 1246 for (i = 0; i < TCP_SIGLEN; i++) 1247 *bp++ = 0; 1248 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1249 optp + 2, IPSEC_DIR_OUTBOUND); 1250 *bp++ = TCPOPT_NOP; 1251 *bp++ = TCPOPT_EOL; 1252 optp += TCPOLEN_SIGNATURE + 2; 1253 } 1254#endif /* TCP_SIGNATURE */ 1255 1256 if (sc->sc_flags & SCF_SACK) { 1257 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR); 1258 optp += 4; 1259 } 1260 } 1261 1262#ifdef INET6 1263 if (sc->sc_inc.inc_isipv6) { 1264 th->th_sum = 0; 1265 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1266 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1267 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1268 } else 1269#endif 1270 { 1271 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1272 htons(tlen - hlen + IPPROTO_TCP)); 1273 m->m_pkthdr.csum_flags = CSUM_TCP; 1274 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1275#ifdef TCPDEBUG 1276 /* 1277 * Trace. 1278 */ 1279 if (so != NULL && so->so_options & SO_DEBUG) { 1280 struct tcpcb *tp = sototcpcb(so); 1281 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1282 mtod(m, void *), th, 0); 1283 } 1284#endif 1285 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1286 } 1287 INP_UNLOCK(inp); 1288 return (error); 1289} 1290 1291/* 1292 * cookie layers: 1293 * 1294 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1295 * | peer iss | 1296 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1297 * | 0 |(A)| | 1298 * (A): peer mss index 1299 */ 1300 1301/* 1302 * The values below are chosen to minimize the size of the tcp_secret 1303 * table, as well as providing roughly a 16 second lifetime for the cookie. 1304 */ 1305 1306#define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1307#define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1308 1309#define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1310#define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1311#define SYNCOOKIE_TIMEOUT \ 1312 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1313#define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1314 1315static struct { 1316 u_int32_t ts_secbits[4]; 1317 u_int ts_expire; 1318} tcp_secret[SYNCOOKIE_NSECRETS]; 1319 1320static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1321 1322static MD5_CTX syn_ctx; 1323 1324#define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1325 1326struct md5_add { 1327 u_int32_t laddr, faddr; 1328 u_int32_t secbits[4]; 1329 u_int16_t lport, fport; 1330}; 1331 1332#ifdef CTASSERT 1333CTASSERT(sizeof(struct md5_add) == 28); 1334#endif 1335 1336/* 1337 * Consider the problem of a recreated (and retransmitted) cookie. If the 1338 * original SYN was accepted, the connection is established. The second 1339 * SYN is inflight, and if it arrives with an ISN that falls within the 1340 * receive window, the connection is killed. 1341 * 1342 * However, since cookies have other problems, this may not be worth 1343 * worrying about. 1344 */ 1345 1346static u_int32_t 1347syncookie_generate(struct syncache *sc) 1348{ 1349 u_int32_t md5_buffer[4]; 1350 u_int32_t data; 1351 int idx, i; 1352 struct md5_add add; 1353 1354 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1355 1356 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1357 if (tcp_secret[idx].ts_expire < ticks) { 1358 for (i = 0; i < 4; i++) 1359 tcp_secret[idx].ts_secbits[i] = arc4random(); 1360 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1361 } 1362 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1363 if (tcp_msstab[data] <= sc->sc_peer_mss) 1364 break; 1365 data = (data << SYNCOOKIE_WNDBITS) | idx; 1366 data ^= sc->sc_irs; /* peer's iss */ 1367 MD5Init(&syn_ctx); 1368#ifdef INET6 1369 if (sc->sc_inc.inc_isipv6) { 1370 MD5Add(sc->sc_inc.inc6_laddr); 1371 MD5Add(sc->sc_inc.inc6_faddr); 1372 add.laddr = 0; 1373 add.faddr = 0; 1374 } else 1375#endif 1376 { 1377 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1378 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1379 } 1380 add.lport = sc->sc_inc.inc_lport; 1381 add.fport = sc->sc_inc.inc_fport; 1382 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1383 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1384 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1385 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1386 MD5Add(add); 1387 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1388 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1389 return (data); 1390} 1391 1392static struct syncache * 1393syncookie_lookup(inc, th, so) 1394 struct in_conninfo *inc; 1395 struct tcphdr *th; 1396 struct socket *so; 1397{ 1398 u_int32_t md5_buffer[4]; 1399 struct syncache *sc; 1400 u_int32_t data; 1401 int wnd, idx; 1402 struct md5_add add; 1403 1404 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1405 1406 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1407 idx = data & SYNCOOKIE_WNDMASK; 1408 if (tcp_secret[idx].ts_expire < ticks || 1409 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1410 return (NULL); 1411 MD5Init(&syn_ctx); 1412#ifdef INET6 1413 if (inc->inc_isipv6) { 1414 MD5Add(inc->inc6_laddr); 1415 MD5Add(inc->inc6_faddr); 1416 add.laddr = 0; 1417 add.faddr = 0; 1418 } else 1419#endif 1420 { 1421 add.laddr = inc->inc_laddr.s_addr; 1422 add.faddr = inc->inc_faddr.s_addr; 1423 } 1424 add.lport = inc->inc_lport; 1425 add.fport = inc->inc_fport; 1426 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1427 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1428 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1429 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1430 MD5Add(add); 1431 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1432 data ^= md5_buffer[0]; 1433 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1434 return (NULL); 1435 data = data >> SYNCOOKIE_WNDBITS; 1436 1437 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1438 if (sc == NULL) 1439 return (NULL); 1440 /* 1441 * Fill in the syncache values. 1442 * XXX duplicate code from syncache_add 1443 */ 1444 sc->sc_ipopts = NULL; 1445 sc->sc_inc.inc_fport = inc->inc_fport; 1446 sc->sc_inc.inc_lport = inc->inc_lport; 1447#ifdef INET6 1448 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1449 if (inc->inc_isipv6) { 1450 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1451 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1452 } else 1453#endif 1454 { 1455 sc->sc_inc.inc_faddr = inc->inc_faddr; 1456 sc->sc_inc.inc_laddr = inc->inc_laddr; 1457 } 1458 sc->sc_irs = th->th_seq - 1; 1459 sc->sc_iss = th->th_ack - 1; 1460 wnd = sbspace(&so->so_rcv); 1461 wnd = imax(wnd, 0); 1462 wnd = imin(wnd, TCP_MAXWIN); 1463 sc->sc_wnd = wnd; 1464 sc->sc_flags = 0; 1465 sc->sc_rxtslot = 0; 1466 sc->sc_peer_mss = tcp_msstab[data]; 1467 return (sc); 1468} 1469