tcp_syncache.c revision 132307
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 132307 2004-07-17 19:44:13Z dwmalone $ 35 */ 36 37#include "opt_inet.h" 38#include "opt_inet6.h" 39#include "opt_ipsec.h" 40#include "opt_mac.h" 41#include "opt_random_ip_id.h" 42#include "opt_tcpdebug.h" 43#include "opt_tcp_sack.h" 44 45#include <sys/param.h> 46#include <sys/systm.h> 47#include <sys/kernel.h> 48#include <sys/sysctl.h> 49#include <sys/malloc.h> 50#include <sys/mac.h> 51#include <sys/mbuf.h> 52#include <sys/md5.h> 53#include <sys/proc.h> /* for proc0 declaration */ 54#include <sys/random.h> 55#include <sys/socket.h> 56#include <sys/socketvar.h> 57 58#include <net/if.h> 59#include <net/route.h> 60 61#include <netinet/in.h> 62#include <netinet/in_systm.h> 63#include <netinet/ip.h> 64#include <netinet/in_var.h> 65#include <netinet/in_pcb.h> 66#include <netinet/ip_var.h> 67#ifdef INET6 68#include <netinet/ip6.h> 69#include <netinet/icmp6.h> 70#include <netinet6/nd6.h> 71#include <netinet6/ip6_var.h> 72#include <netinet6/in6_pcb.h> 73#endif 74#include <netinet/tcp.h> 75#ifdef TCPDEBUG 76#include <netinet/tcpip.h> 77#endif 78#include <netinet/tcp_fsm.h> 79#include <netinet/tcp_seq.h> 80#include <netinet/tcp_timer.h> 81#include <netinet/tcp_var.h> 82#ifdef TCPDEBUG 83#include <netinet/tcp_debug.h> 84#endif 85#ifdef INET6 86#include <netinet6/tcp6_var.h> 87#endif 88 89#ifdef IPSEC 90#include <netinet6/ipsec.h> 91#ifdef INET6 92#include <netinet6/ipsec6.h> 93#endif 94#endif /*IPSEC*/ 95 96#ifdef FAST_IPSEC 97#include <netipsec/ipsec.h> 98#ifdef INET6 99#include <netipsec/ipsec6.h> 100#endif 101#include <netipsec/key.h> 102#endif /*FAST_IPSEC*/ 103 104#include <machine/in_cksum.h> 105#include <vm/uma.h> 106 107static int tcp_syncookies = 1; 108SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 109 &tcp_syncookies, 0, 110 "Use TCP SYN cookies if the syncache overflows"); 111 112static void syncache_drop(struct syncache *, struct syncache_head *); 113static void syncache_free(struct syncache *); 114static void syncache_insert(struct syncache *, struct syncache_head *); 115struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 116#ifdef TCPDEBUG 117static int syncache_respond(struct syncache *, struct mbuf *, struct socket *); 118#else 119static int syncache_respond(struct syncache *, struct mbuf *); 120#endif 121static struct socket *syncache_socket(struct syncache *, struct socket *, 122 struct mbuf *m); 123static void syncache_timer(void *); 124static u_int32_t syncookie_generate(struct syncache *, u_int32_t *); 125static struct syncache *syncookie_lookup(struct in_conninfo *, 126 struct tcphdr *, struct socket *); 127 128/* 129 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 130 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 131 * the odds are that the user has given up attempting to connect by then. 132 */ 133#define SYNCACHE_MAXREXMTS 3 134 135/* Arbitrary values */ 136#define TCP_SYNCACHE_HASHSIZE 512 137#define TCP_SYNCACHE_BUCKETLIMIT 30 138 139struct tcp_syncache { 140 struct syncache_head *hashbase; 141 uma_zone_t zone; 142 u_int hashsize; 143 u_int hashmask; 144 u_int bucket_limit; 145 u_int cache_count; 146 u_int cache_limit; 147 u_int rexmt_limit; 148 u_int hash_secret; 149 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 150 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 151}; 152static struct tcp_syncache tcp_syncache; 153 154SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 155 156SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 157 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 158 159SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 160 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 161 162SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 163 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 164 165SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 166 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 167 168SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 169 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 170 171static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 172 173#define SYNCACHE_HASH(inc, mask) \ 174 ((tcp_syncache.hash_secret ^ \ 175 (inc)->inc_faddr.s_addr ^ \ 176 ((inc)->inc_faddr.s_addr >> 16) ^ \ 177 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 178 179#define SYNCACHE_HASH6(inc, mask) \ 180 ((tcp_syncache.hash_secret ^ \ 181 (inc)->inc6_faddr.s6_addr32[0] ^ \ 182 (inc)->inc6_faddr.s6_addr32[3] ^ \ 183 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 184 185#define ENDPTS_EQ(a, b) ( \ 186 (a)->ie_fport == (b)->ie_fport && \ 187 (a)->ie_lport == (b)->ie_lport && \ 188 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 189 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 190) 191 192#define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 193 194#define SYNCACHE_TIMEOUT(sc, slot) do { \ 195 sc->sc_rxtslot = (slot); \ 196 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 197 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 198 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 199 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 200 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 201 syncache_timer, (void *)((intptr_t)(slot))); \ 202} while (0) 203 204static void 205syncache_free(struct syncache *sc) 206{ 207 if (sc->sc_ipopts) 208 (void) m_free(sc->sc_ipopts); 209 210 uma_zfree(tcp_syncache.zone, sc); 211} 212 213void 214syncache_init(void) 215{ 216 int i; 217 218 tcp_syncache.cache_count = 0; 219 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 220 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 221 tcp_syncache.cache_limit = 222 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 223 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 224 tcp_syncache.hash_secret = arc4random(); 225 226 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 227 &tcp_syncache.hashsize); 228 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 229 &tcp_syncache.cache_limit); 230 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 231 &tcp_syncache.bucket_limit); 232 if (!powerof2(tcp_syncache.hashsize)) { 233 printf("WARNING: syncache hash size is not a power of 2.\n"); 234 tcp_syncache.hashsize = 512; /* safe default */ 235 } 236 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 237 238 /* Allocate the hash table. */ 239 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 240 tcp_syncache.hashsize * sizeof(struct syncache_head), 241 M_SYNCACHE, M_WAITOK); 242 243 /* Initialize the hash buckets. */ 244 for (i = 0; i < tcp_syncache.hashsize; i++) { 245 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 246 tcp_syncache.hashbase[i].sch_length = 0; 247 } 248 249 /* Initialize the timer queues. */ 250 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 251 TAILQ_INIT(&tcp_syncache.timerq[i]); 252 callout_init(&tcp_syncache.tt_timerq[i], 253 debug_mpsafenet ? CALLOUT_MPSAFE : 0); 254 } 255 256 /* 257 * Allocate the syncache entries. Allow the zone to allocate one 258 * more entry than cache limit, so a new entry can bump out an 259 * older one. 260 */ 261 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 262 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 263 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 264 tcp_syncache.cache_limit -= 1; 265} 266 267static void 268syncache_insert(sc, sch) 269 struct syncache *sc; 270 struct syncache_head *sch; 271{ 272 struct syncache *sc2; 273 int i; 274 275 INP_INFO_WLOCK_ASSERT(&tcbinfo); 276 277 /* 278 * Make sure that we don't overflow the per-bucket 279 * limit or the total cache size limit. 280 */ 281 if (sch->sch_length >= tcp_syncache.bucket_limit) { 282 /* 283 * The bucket is full, toss the oldest element. 284 */ 285 sc2 = TAILQ_FIRST(&sch->sch_bucket); 286 sc2->sc_tp->ts_recent = ticks; 287 syncache_drop(sc2, sch); 288 tcpstat.tcps_sc_bucketoverflow++; 289 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 290 /* 291 * The cache is full. Toss the oldest entry in the 292 * entire cache. This is the front entry in the 293 * first non-empty timer queue with the largest 294 * timeout value. 295 */ 296 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 297 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 298 if (sc2 != NULL) 299 break; 300 } 301 sc2->sc_tp->ts_recent = ticks; 302 syncache_drop(sc2, NULL); 303 tcpstat.tcps_sc_cacheoverflow++; 304 } 305 306 /* Initialize the entry's timer. */ 307 SYNCACHE_TIMEOUT(sc, 0); 308 309 /* Put it into the bucket. */ 310 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 311 sch->sch_length++; 312 tcp_syncache.cache_count++; 313 tcpstat.tcps_sc_added++; 314} 315 316static void 317syncache_drop(sc, sch) 318 struct syncache *sc; 319 struct syncache_head *sch; 320{ 321 INP_INFO_WLOCK_ASSERT(&tcbinfo); 322 323 if (sch == NULL) { 324#ifdef INET6 325 if (sc->sc_inc.inc_isipv6) { 326 sch = &tcp_syncache.hashbase[ 327 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 328 } else 329#endif 330 { 331 sch = &tcp_syncache.hashbase[ 332 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 333 } 334 } 335 336 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 337 sch->sch_length--; 338 tcp_syncache.cache_count--; 339 340 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 341 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 342 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 343 344 syncache_free(sc); 345} 346 347/* 348 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 349 * If we have retransmitted an entry the maximum number of times, expire it. 350 */ 351static void 352syncache_timer(xslot) 353 void *xslot; 354{ 355 intptr_t slot = (intptr_t)xslot; 356 struct syncache *sc, *nsc; 357 struct inpcb *inp; 358 359 INP_INFO_WLOCK(&tcbinfo); 360 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 361 !callout_active(&tcp_syncache.tt_timerq[slot])) { 362 /* XXX can this happen? */ 363 INP_INFO_WUNLOCK(&tcbinfo); 364 return; 365 } 366 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 367 368 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 369 while (nsc != NULL) { 370 if (ticks < nsc->sc_rxttime) 371 break; 372 sc = nsc; 373 inp = sc->sc_tp->t_inpcb; 374 if (slot == SYNCACHE_MAXREXMTS || 375 slot >= tcp_syncache.rexmt_limit || 376 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 377 nsc = TAILQ_NEXT(sc, sc_timerq); 378 syncache_drop(sc, NULL); 379 tcpstat.tcps_sc_stale++; 380 continue; 381 } 382 /* 383 * syncache_respond() may call back into the syncache to 384 * to modify another entry, so do not obtain the next 385 * entry on the timer chain until it has completed. 386 */ 387#ifdef TCPDEBUG 388 (void) syncache_respond(sc, NULL, NULL); 389#else 390 (void) syncache_respond(sc, NULL); 391#endif 392 nsc = TAILQ_NEXT(sc, sc_timerq); 393 tcpstat.tcps_sc_retransmitted++; 394 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 395 SYNCACHE_TIMEOUT(sc, slot + 1); 396 } 397 if (nsc != NULL) 398 callout_reset(&tcp_syncache.tt_timerq[slot], 399 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 400 INP_INFO_WUNLOCK(&tcbinfo); 401} 402 403/* 404 * Find an entry in the syncache. 405 */ 406struct syncache * 407syncache_lookup(inc, schp) 408 struct in_conninfo *inc; 409 struct syncache_head **schp; 410{ 411 struct syncache *sc; 412 struct syncache_head *sch; 413 414 INP_INFO_WLOCK_ASSERT(&tcbinfo); 415 416#ifdef INET6 417 if (inc->inc_isipv6) { 418 sch = &tcp_syncache.hashbase[ 419 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 420 *schp = sch; 421 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 422 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 423 return (sc); 424 } 425 } else 426#endif 427 { 428 sch = &tcp_syncache.hashbase[ 429 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 430 *schp = sch; 431 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 432#ifdef INET6 433 if (sc->sc_inc.inc_isipv6) 434 continue; 435#endif 436 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 437 return (sc); 438 } 439 } 440 return (NULL); 441} 442 443/* 444 * This function is called when we get a RST for a 445 * non-existent connection, so that we can see if the 446 * connection is in the syn cache. If it is, zap it. 447 */ 448void 449syncache_chkrst(inc, th) 450 struct in_conninfo *inc; 451 struct tcphdr *th; 452{ 453 struct syncache *sc; 454 struct syncache_head *sch; 455 456 INP_INFO_WLOCK_ASSERT(&tcbinfo); 457 458 sc = syncache_lookup(inc, &sch); 459 if (sc == NULL) 460 return; 461 /* 462 * If the RST bit is set, check the sequence number to see 463 * if this is a valid reset segment. 464 * RFC 793 page 37: 465 * In all states except SYN-SENT, all reset (RST) segments 466 * are validated by checking their SEQ-fields. A reset is 467 * valid if its sequence number is in the window. 468 * 469 * The sequence number in the reset segment is normally an 470 * echo of our outgoing acknowlegement numbers, but some hosts 471 * send a reset with the sequence number at the rightmost edge 472 * of our receive window, and we have to handle this case. 473 */ 474 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 475 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 476 syncache_drop(sc, sch); 477 tcpstat.tcps_sc_reset++; 478 } 479} 480 481void 482syncache_badack(inc) 483 struct in_conninfo *inc; 484{ 485 struct syncache *sc; 486 struct syncache_head *sch; 487 488 INP_INFO_WLOCK_ASSERT(&tcbinfo); 489 490 sc = syncache_lookup(inc, &sch); 491 if (sc != NULL) { 492 syncache_drop(sc, sch); 493 tcpstat.tcps_sc_badack++; 494 } 495} 496 497void 498syncache_unreach(inc, th) 499 struct in_conninfo *inc; 500 struct tcphdr *th; 501{ 502 struct syncache *sc; 503 struct syncache_head *sch; 504 505 INP_INFO_WLOCK_ASSERT(&tcbinfo); 506 507 /* we are called at splnet() here */ 508 sc = syncache_lookup(inc, &sch); 509 if (sc == NULL) 510 return; 511 512 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 513 if (ntohl(th->th_seq) != sc->sc_iss) 514 return; 515 516 /* 517 * If we've rertransmitted 3 times and this is our second error, 518 * we remove the entry. Otherwise, we allow it to continue on. 519 * This prevents us from incorrectly nuking an entry during a 520 * spurious network outage. 521 * 522 * See tcp_notify(). 523 */ 524 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 525 sc->sc_flags |= SCF_UNREACH; 526 return; 527 } 528 syncache_drop(sc, sch); 529 tcpstat.tcps_sc_unreach++; 530} 531 532/* 533 * Build a new TCP socket structure from a syncache entry. 534 */ 535static struct socket * 536syncache_socket(sc, lso, m) 537 struct syncache *sc; 538 struct socket *lso; 539 struct mbuf *m; 540{ 541 struct inpcb *inp = NULL; 542 struct socket *so; 543 struct tcpcb *tp; 544 545 NET_ASSERT_GIANT(); 546 INP_INFO_WLOCK_ASSERT(&tcbinfo); 547 548 /* 549 * Ok, create the full blown connection, and set things up 550 * as they would have been set up if we had created the 551 * connection when the SYN arrived. If we can't create 552 * the connection, abort it. 553 */ 554 so = sonewconn(lso, SS_ISCONNECTED); 555 if (so == NULL) { 556 /* 557 * Drop the connection; we will send a RST if the peer 558 * retransmits the ACK, 559 */ 560 tcpstat.tcps_listendrop++; 561 goto abort2; 562 } 563#ifdef MAC 564 SOCK_LOCK(so); 565 mac_set_socket_peer_from_mbuf(m, so); 566 SOCK_UNLOCK(so); 567#endif 568 569 inp = sotoinpcb(so); 570 INP_LOCK(inp); 571 572 /* 573 * Insert new socket into hash list. 574 */ 575 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 576#ifdef INET6 577 if (sc->sc_inc.inc_isipv6) { 578 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 579 } else { 580 inp->inp_vflag &= ~INP_IPV6; 581 inp->inp_vflag |= INP_IPV4; 582#endif 583 inp->inp_laddr = sc->sc_inc.inc_laddr; 584#ifdef INET6 585 } 586#endif 587 inp->inp_lport = sc->sc_inc.inc_lport; 588 if (in_pcbinshash(inp) != 0) { 589 /* 590 * Undo the assignments above if we failed to 591 * put the PCB on the hash lists. 592 */ 593#ifdef INET6 594 if (sc->sc_inc.inc_isipv6) 595 inp->in6p_laddr = in6addr_any; 596 else 597#endif 598 inp->inp_laddr.s_addr = INADDR_ANY; 599 inp->inp_lport = 0; 600 goto abort; 601 } 602#ifdef IPSEC 603 /* copy old policy into new socket's */ 604 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 605 printf("syncache_expand: could not copy policy\n"); 606#endif 607#ifdef FAST_IPSEC 608 /* copy old policy into new socket's */ 609 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 610 printf("syncache_expand: could not copy policy\n"); 611#endif 612#ifdef INET6 613 if (sc->sc_inc.inc_isipv6) { 614 struct inpcb *oinp = sotoinpcb(lso); 615 struct in6_addr laddr6; 616 struct sockaddr_in6 sin6; 617 /* 618 * Inherit socket options from the listening socket. 619 * Note that in6p_inputopts are not (and should not be) 620 * copied, since it stores previously received options and is 621 * used to detect if each new option is different than the 622 * previous one and hence should be passed to a user. 623 * If we copied in6p_inputopts, a user would not be able to 624 * receive options just after calling the accept system call. 625 */ 626 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 627 if (oinp->in6p_outputopts) 628 inp->in6p_outputopts = 629 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 630 631 sin6.sin6_family = AF_INET6; 632 sin6.sin6_len = sizeof(sin6); 633 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 634 sin6.sin6_port = sc->sc_inc.inc_fport; 635 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 636 laddr6 = inp->in6p_laddr; 637 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 638 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 639 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 640 thread0.td_ucred)) { 641 inp->in6p_laddr = laddr6; 642 goto abort; 643 } 644 /* Override flowlabel from in6_pcbconnect. */ 645 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 646 inp->in6p_flowinfo |= sc->sc_flowlabel; 647 } else 648#endif 649 { 650 struct in_addr laddr; 651 struct sockaddr_in sin; 652 653 inp->inp_options = ip_srcroute(); 654 if (inp->inp_options == NULL) { 655 inp->inp_options = sc->sc_ipopts; 656 sc->sc_ipopts = NULL; 657 } 658 659 sin.sin_family = AF_INET; 660 sin.sin_len = sizeof(sin); 661 sin.sin_addr = sc->sc_inc.inc_faddr; 662 sin.sin_port = sc->sc_inc.inc_fport; 663 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 664 laddr = inp->inp_laddr; 665 if (inp->inp_laddr.s_addr == INADDR_ANY) 666 inp->inp_laddr = sc->sc_inc.inc_laddr; 667 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 668 thread0.td_ucred)) { 669 inp->inp_laddr = laddr; 670 goto abort; 671 } 672 } 673 674 tp = intotcpcb(inp); 675 tp->t_state = TCPS_SYN_RECEIVED; 676 tp->iss = sc->sc_iss; 677 tp->irs = sc->sc_irs; 678 tcp_rcvseqinit(tp); 679 tcp_sendseqinit(tp); 680 tp->snd_wl1 = sc->sc_irs; 681 tp->rcv_up = sc->sc_irs + 1; 682 tp->rcv_wnd = sc->sc_wnd; 683 tp->rcv_adv += tp->rcv_wnd; 684 685 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 686 if (sc->sc_flags & SCF_NOOPT) 687 tp->t_flags |= TF_NOOPT; 688 if (sc->sc_flags & SCF_WINSCALE) { 689 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 690 tp->requested_s_scale = sc->sc_requested_s_scale; 691 tp->request_r_scale = sc->sc_request_r_scale; 692 } 693 if (sc->sc_flags & SCF_TIMESTAMP) { 694 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 695 tp->ts_recent = sc->sc_tsrecent; 696 tp->ts_recent_age = ticks; 697 } 698 if (sc->sc_flags & SCF_CC) { 699 /* 700 * Initialization of the tcpcb for transaction; 701 * set SND.WND = SEG.WND, 702 * initialize CCsend and CCrecv. 703 */ 704 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 705 tp->cc_send = sc->sc_cc_send; 706 tp->cc_recv = sc->sc_cc_recv; 707 } 708#ifdef TCP_SIGNATURE 709 if (sc->sc_flags & SCF_SIGNATURE) 710 tp->t_flags |= TF_SIGNATURE; 711#endif 712 if (sc->sc_flags & SCF_SACK) { 713 tp->sack_enable = 1; 714 tp->t_flags |= TF_SACK_PERMIT; 715 } 716 /* 717 * Set up MSS and get cached values from tcp_hostcache. 718 * This might overwrite some of the defaults we just set. 719 */ 720 tcp_mss(tp, sc->sc_peer_mss); 721 722 /* 723 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 724 */ 725 if (sc->sc_rxtslot != 0) 726 tp->snd_cwnd = tp->t_maxseg; 727 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 728 729 INP_UNLOCK(inp); 730 731 tcpstat.tcps_accepts++; 732 return (so); 733 734abort: 735 INP_UNLOCK(inp); 736abort2: 737 if (so != NULL) 738 (void) soabort(so); 739 return (NULL); 740} 741 742/* 743 * This function gets called when we receive an ACK for a 744 * socket in the LISTEN state. We look up the connection 745 * in the syncache, and if its there, we pull it out of 746 * the cache and turn it into a full-blown connection in 747 * the SYN-RECEIVED state. 748 */ 749int 750syncache_expand(inc, th, sop, m) 751 struct in_conninfo *inc; 752 struct tcphdr *th; 753 struct socket **sop; 754 struct mbuf *m; 755{ 756 struct syncache *sc; 757 struct syncache_head *sch; 758 struct socket *so; 759 760 INP_INFO_WLOCK_ASSERT(&tcbinfo); 761 762 sc = syncache_lookup(inc, &sch); 763 if (sc == NULL) { 764 /* 765 * There is no syncache entry, so see if this ACK is 766 * a returning syncookie. To do this, first: 767 * A. See if this socket has had a syncache entry dropped in 768 * the past. We don't want to accept a bogus syncookie 769 * if we've never received a SYN. 770 * B. check that the syncookie is valid. If it is, then 771 * cobble up a fake syncache entry, and return. 772 */ 773 if (!tcp_syncookies) 774 return (0); 775 sc = syncookie_lookup(inc, th, *sop); 776 if (sc == NULL) 777 return (0); 778 sch = NULL; 779 tcpstat.tcps_sc_recvcookie++; 780 } 781 782 /* 783 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 784 */ 785 if (th->th_ack != sc->sc_iss + 1) 786 return (0); 787 788 so = syncache_socket(sc, *sop, m); 789 if (so == NULL) { 790#if 0 791resetandabort: 792 /* XXXjlemon check this - is this correct? */ 793 (void) tcp_respond(NULL, m, m, th, 794 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 795#endif 796 m_freem(m); /* XXX only needed for above */ 797 tcpstat.tcps_sc_aborted++; 798 } else 799 tcpstat.tcps_sc_completed++; 800 801 if (sch == NULL) 802 syncache_free(sc); 803 else 804 syncache_drop(sc, sch); 805 *sop = so; 806 return (1); 807} 808 809/* 810 * Given a LISTEN socket and an inbound SYN request, add 811 * this to the syn cache, and send back a segment: 812 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 813 * to the source. 814 * 815 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 816 * Doing so would require that we hold onto the data and deliver it 817 * to the application. However, if we are the target of a SYN-flood 818 * DoS attack, an attacker could send data which would eventually 819 * consume all available buffer space if it were ACKed. By not ACKing 820 * the data, we avoid this DoS scenario. 821 */ 822int 823syncache_add(inc, to, th, sop, m) 824 struct in_conninfo *inc; 825 struct tcpopt *to; 826 struct tcphdr *th; 827 struct socket **sop; 828 struct mbuf *m; 829{ 830 struct tcpcb *tp; 831 struct socket *so; 832 struct syncache *sc = NULL; 833 struct syncache_head *sch; 834 struct mbuf *ipopts = NULL; 835 struct rmxp_tao tao; 836 u_int32_t flowtmp; 837 int i, win; 838 839 INP_INFO_WLOCK_ASSERT(&tcbinfo); 840 841 so = *sop; 842 tp = sototcpcb(so); 843 bzero(&tao, sizeof(tao)); 844 845 /* 846 * Remember the IP options, if any. 847 */ 848#ifdef INET6 849 if (!inc->inc_isipv6) 850#endif 851 ipopts = ip_srcroute(); 852 853 /* 854 * See if we already have an entry for this connection. 855 * If we do, resend the SYN,ACK, and reset the retransmit timer. 856 * 857 * XXX 858 * should the syncache be re-initialized with the contents 859 * of the new SYN here (which may have different options?) 860 */ 861 sc = syncache_lookup(inc, &sch); 862 if (sc != NULL) { 863 tcpstat.tcps_sc_dupsyn++; 864 if (ipopts) { 865 /* 866 * If we were remembering a previous source route, 867 * forget it and use the new one we've been given. 868 */ 869 if (sc->sc_ipopts) 870 (void) m_free(sc->sc_ipopts); 871 sc->sc_ipopts = ipopts; 872 } 873 /* 874 * Update timestamp if present. 875 */ 876 if (sc->sc_flags & SCF_TIMESTAMP) 877 sc->sc_tsrecent = to->to_tsval; 878 /* 879 * PCB may have changed, pick up new values. 880 */ 881 sc->sc_tp = tp; 882 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 883#ifdef TCPDEBUG 884 if (syncache_respond(sc, m, so) == 0) { 885#else 886 if (syncache_respond(sc, m) == 0) { 887#endif 888 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 889 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 890 sc, sc_timerq); 891 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 892 tcpstat.tcps_sndacks++; 893 tcpstat.tcps_sndtotal++; 894 } 895 *sop = NULL; 896 return (1); 897 } 898 899 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 900 if (sc == NULL) { 901 /* 902 * The zone allocator couldn't provide more entries. 903 * Treat this as if the cache was full; drop the oldest 904 * entry and insert the new one. 905 */ 906 /* NB: guarded by INP_INFO_WLOCK(&tcbinfo) */ 907 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 908 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 909 if (sc != NULL) 910 break; 911 } 912 sc->sc_tp->ts_recent = ticks; 913 syncache_drop(sc, NULL); 914 tcpstat.tcps_sc_zonefail++; 915 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 916 if (sc == NULL) { 917 if (ipopts) 918 (void) m_free(ipopts); 919 return (0); 920 } 921 } 922 923 /* 924 * Fill in the syncache values. 925 */ 926 bzero(sc, sizeof(*sc)); 927 sc->sc_tp = tp; 928 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 929 sc->sc_ipopts = ipopts; 930 sc->sc_inc.inc_fport = inc->inc_fport; 931 sc->sc_inc.inc_lport = inc->inc_lport; 932#ifdef INET6 933 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 934 if (inc->inc_isipv6) { 935 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 936 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 937 } else 938#endif 939 { 940 sc->sc_inc.inc_faddr = inc->inc_faddr; 941 sc->sc_inc.inc_laddr = inc->inc_laddr; 942 } 943 sc->sc_irs = th->th_seq; 944 sc->sc_flags = 0; 945 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 946 sc->sc_flowlabel = 0; 947 if (tcp_syncookies) { 948 sc->sc_iss = syncookie_generate(sc, &flowtmp); 949 if (inc->inc_isipv6 && 950 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 951 sc->sc_flowlabel = flowtmp & IPV6_FLOWLABEL_MASK; 952 } 953 } else { 954 sc->sc_iss = arc4random(); 955 if (inc->inc_isipv6 && 956 (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL)) { 957 sc->sc_flowlabel = 958#ifdef RANDOM_IP_ID 959 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 960#else 961 (htonl(ip6_flow_seq++) & IPV6_FLOWLABEL_MASK); 962#endif 963 } 964 } 965 966 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 967 win = sbspace(&so->so_rcv); 968 win = imax(win, 0); 969 win = imin(win, TCP_MAXWIN); 970 sc->sc_wnd = win; 971 972 if (tcp_do_rfc1323) { 973 /* 974 * A timestamp received in a SYN makes 975 * it ok to send timestamp requests and replies. 976 */ 977 if (to->to_flags & TOF_TS) { 978 sc->sc_tsrecent = to->to_tsval; 979 sc->sc_flags |= SCF_TIMESTAMP; 980 } 981 if (to->to_flags & TOF_SCALE) { 982 int wscale = 0; 983 984 /* Compute proper scaling value from buffer space */ 985 while (wscale < TCP_MAX_WINSHIFT && 986 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 987 wscale++; 988 sc->sc_request_r_scale = wscale; 989 sc->sc_requested_s_scale = to->to_requested_s_scale; 990 sc->sc_flags |= SCF_WINSCALE; 991 } 992 } 993 if (tcp_do_rfc1644) { 994 /* 995 * A CC or CC.new option received in a SYN makes 996 * it ok to send CC in subsequent segments. 997 */ 998 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 999 sc->sc_cc_recv = to->to_cc; 1000 sc->sc_cc_send = CC_INC(tcp_ccgen); 1001 sc->sc_flags |= SCF_CC; 1002 } 1003 } 1004 if (tp->t_flags & TF_NOOPT) 1005 sc->sc_flags = SCF_NOOPT; 1006#ifdef TCP_SIGNATURE 1007 /* 1008 * If listening socket requested TCP digests, and received SYN 1009 * contains the option, flag this in the syncache so that 1010 * syncache_respond() will do the right thing with the SYN+ACK. 1011 * XXX Currently we always record the option by default and will 1012 * attempt to use it in syncache_respond(). 1013 */ 1014 if (to->to_flags & TOF_SIGNATURE) 1015 sc->sc_flags = SCF_SIGNATURE; 1016#endif 1017 1018 if (to->to_flags & TOF_SACK) 1019 sc->sc_flags |= SCF_SACK; 1020 1021 /* 1022 * XXX 1023 * We have the option here of not doing TAO (even if the segment 1024 * qualifies) and instead fall back to a normal 3WHS via the syncache. 1025 * This allows us to apply synflood protection to TAO-qualifying SYNs 1026 * also. However, there should be a hueristic to determine when to 1027 * do this, and is not present at the moment. 1028 */ 1029 1030 /* 1031 * Perform TAO test on incoming CC (SEG.CC) option, if any. 1032 * - compare SEG.CC against cached CC from the same host, if any. 1033 * - if SEG.CC > chached value, SYN must be new and is accepted 1034 * immediately: save new CC in the cache, mark the socket 1035 * connected, enter ESTABLISHED state, turn on flag to 1036 * send a SYN in the next segment. 1037 * A virtual advertised window is set in rcv_adv to 1038 * initialize SWS prevention. Then enter normal segment 1039 * processing: drop SYN, process data and FIN. 1040 * - otherwise do a normal 3-way handshake. 1041 */ 1042 if (tcp_do_rfc1644) 1043 tcp_hc_gettao(&sc->sc_inc, &tao); 1044 1045 if ((to->to_flags & TOF_CC) != 0) { 1046 if (((tp->t_flags & TF_NOPUSH) != 0) && 1047 sc->sc_flags & SCF_CC && tao.tao_cc != 0 && 1048 CC_GT(to->to_cc, tao.tao_cc)) { 1049 sc->sc_rxtslot = 0; 1050 so = syncache_socket(sc, *sop, m); 1051 if (so != NULL) { 1052 tao.tao_cc = to->to_cc; 1053 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1054 tao.tao_cc, 0); 1055 *sop = so; 1056 } 1057 syncache_free(sc); 1058 return (so != NULL); 1059 } 1060 } else { 1061 /* 1062 * No CC option, but maybe CC.NEW: invalidate cached value. 1063 */ 1064 if (tcp_do_rfc1644) { 1065 tao.tao_cc = 0; 1066 tcp_hc_updatetao(&sc->sc_inc, TCP_HC_TAO_CC, 1067 tao.tao_cc, 0); 1068 } 1069 } 1070 1071 /* 1072 * TAO test failed or there was no CC option, 1073 * do a standard 3-way handshake. 1074 */ 1075#ifdef TCPDEBUG 1076 if (syncache_respond(sc, m, so) == 0) { 1077#else 1078 if (syncache_respond(sc, m) == 0) { 1079#endif 1080 syncache_insert(sc, sch); 1081 tcpstat.tcps_sndacks++; 1082 tcpstat.tcps_sndtotal++; 1083 } else { 1084 syncache_free(sc); 1085 tcpstat.tcps_sc_dropped++; 1086 } 1087 *sop = NULL; 1088 return (1); 1089} 1090 1091#ifdef TCPDEBUG 1092static int 1093syncache_respond(sc, m, so) 1094 struct syncache *sc; 1095 struct mbuf *m; 1096 struct socket *so; 1097#else 1098static int 1099syncache_respond(sc, m) 1100 struct syncache *sc; 1101 struct mbuf *m; 1102#endif 1103{ 1104 u_int8_t *optp; 1105 int optlen, error; 1106 u_int16_t tlen, hlen, mssopt; 1107 struct ip *ip = NULL; 1108 struct tcphdr *th; 1109 struct inpcb *inp; 1110#ifdef INET6 1111 struct ip6_hdr *ip6 = NULL; 1112#endif 1113 1114 hlen = 1115#ifdef INET6 1116 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1117#endif 1118 sizeof(struct ip); 1119 1120 KASSERT((&sc->sc_inc) != NULL, ("syncache_respond with NULL in_conninfo pointer")); 1121 1122 /* Determine MSS we advertize to other end of connection */ 1123 mssopt = tcp_mssopt(&sc->sc_inc); 1124 1125 /* Compute the size of the TCP options. */ 1126 if (sc->sc_flags & SCF_NOOPT) { 1127 optlen = 0; 1128 } else { 1129 optlen = TCPOLEN_MAXSEG + 1130 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1131 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1132 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1133#ifdef TCP_SIGNATURE 1134 optlen += (sc->sc_flags & SCF_SIGNATURE) ? 1135 TCPOLEN_SIGNATURE + 2 : 0; 1136#endif 1137 optlen += ((sc->sc_flags & SCF_SACK) ? 4 : 0); 1138 } 1139 tlen = hlen + sizeof(struct tcphdr) + optlen; 1140 1141 /* 1142 * XXX 1143 * assume that the entire packet will fit in a header mbuf 1144 */ 1145 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1146 1147 /* 1148 * XXX shouldn't this reuse the mbuf if possible ? 1149 * Create the IP+TCP header from scratch. 1150 */ 1151 if (m) 1152 m_freem(m); 1153 1154 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1155 if (m == NULL) 1156 return (ENOBUFS); 1157 m->m_data += max_linkhdr; 1158 m->m_len = tlen; 1159 m->m_pkthdr.len = tlen; 1160 m->m_pkthdr.rcvif = NULL; 1161 inp = sc->sc_tp->t_inpcb; 1162 INP_LOCK(inp); 1163#ifdef MAC 1164 mac_create_mbuf_from_inpcb(inp, m); 1165#endif 1166 1167#ifdef INET6 1168 if (sc->sc_inc.inc_isipv6) { 1169 ip6 = mtod(m, struct ip6_hdr *); 1170 ip6->ip6_vfc = IPV6_VERSION; 1171 ip6->ip6_nxt = IPPROTO_TCP; 1172 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1173 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1174 ip6->ip6_plen = htons(tlen - hlen); 1175 /* ip6_hlim is set after checksum */ 1176 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1177 ip6->ip6_flow |= sc->sc_flowlabel; 1178 1179 th = (struct tcphdr *)(ip6 + 1); 1180 } else 1181#endif 1182 { 1183 ip = mtod(m, struct ip *); 1184 ip->ip_v = IPVERSION; 1185 ip->ip_hl = sizeof(struct ip) >> 2; 1186 ip->ip_len = tlen; 1187 ip->ip_id = 0; 1188 ip->ip_off = 0; 1189 ip->ip_sum = 0; 1190 ip->ip_p = IPPROTO_TCP; 1191 ip->ip_src = sc->sc_inc.inc_laddr; 1192 ip->ip_dst = sc->sc_inc.inc_faddr; 1193 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 1194 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 1195 1196 /* 1197 * See if we should do MTU discovery. Route lookups are 1198 * expensive, so we will only unset the DF bit if: 1199 * 1200 * 1) path_mtu_discovery is disabled 1201 * 2) the SCF_UNREACH flag has been set 1202 */ 1203 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1204 ip->ip_off |= IP_DF; 1205 1206 th = (struct tcphdr *)(ip + 1); 1207 } 1208 th->th_sport = sc->sc_inc.inc_lport; 1209 th->th_dport = sc->sc_inc.inc_fport; 1210 1211 th->th_seq = htonl(sc->sc_iss); 1212 th->th_ack = htonl(sc->sc_irs + 1); 1213 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1214 th->th_x2 = 0; 1215 th->th_flags = TH_SYN|TH_ACK; 1216 th->th_win = htons(sc->sc_wnd); 1217 th->th_urp = 0; 1218 1219 /* Tack on the TCP options. */ 1220 if (optlen != 0) { 1221 optp = (u_int8_t *)(th + 1); 1222 *optp++ = TCPOPT_MAXSEG; 1223 *optp++ = TCPOLEN_MAXSEG; 1224 *optp++ = (mssopt >> 8) & 0xff; 1225 *optp++ = mssopt & 0xff; 1226 1227 if (sc->sc_flags & SCF_WINSCALE) { 1228 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1229 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1230 sc->sc_request_r_scale); 1231 optp += 4; 1232 } 1233 1234 if (sc->sc_flags & SCF_TIMESTAMP) { 1235 u_int32_t *lp = (u_int32_t *)(optp); 1236 1237 /* Form timestamp option per appendix A of RFC 1323. */ 1238 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1239 *lp++ = htonl(ticks); 1240 *lp = htonl(sc->sc_tsrecent); 1241 optp += TCPOLEN_TSTAMP_APPA; 1242 } 1243 1244 /* 1245 * Send CC and CC.echo if we received CC from our peer. 1246 */ 1247 if (sc->sc_flags & SCF_CC) { 1248 u_int32_t *lp = (u_int32_t *)(optp); 1249 1250 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1251 *lp++ = htonl(sc->sc_cc_send); 1252 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1253 *lp = htonl(sc->sc_cc_recv); 1254 optp += TCPOLEN_CC_APPA * 2; 1255 } 1256 1257#ifdef TCP_SIGNATURE 1258 /* 1259 * Handle TCP-MD5 passive opener response. 1260 */ 1261 if (sc->sc_flags & SCF_SIGNATURE) { 1262 u_int8_t *bp = optp; 1263 int i; 1264 1265 *bp++ = TCPOPT_SIGNATURE; 1266 *bp++ = TCPOLEN_SIGNATURE; 1267 for (i = 0; i < TCP_SIGLEN; i++) 1268 *bp++ = 0; 1269 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1270 optp + 2, IPSEC_DIR_OUTBOUND); 1271 *bp++ = TCPOPT_NOP; 1272 *bp++ = TCPOPT_EOL; 1273 optp += TCPOLEN_SIGNATURE + 2; 1274 } 1275#endif /* TCP_SIGNATURE */ 1276 1277 if (sc->sc_flags & SCF_SACK) { 1278 *(u_int32_t *)optp = htonl(TCPOPT_SACK_PERMIT_HDR); 1279 optp += 4; 1280 } 1281 } 1282 1283#ifdef INET6 1284 if (sc->sc_inc.inc_isipv6) { 1285 th->th_sum = 0; 1286 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1287 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1288 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, inp); 1289 } else 1290#endif 1291 { 1292 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1293 htons(tlen - hlen + IPPROTO_TCP)); 1294 m->m_pkthdr.csum_flags = CSUM_TCP; 1295 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1296#ifdef TCPDEBUG 1297 /* 1298 * Trace. 1299 */ 1300 if (so != NULL && so->so_options & SO_DEBUG) { 1301 struct tcpcb *tp = sototcpcb(so); 1302 tcp_trace(TA_OUTPUT, tp->t_state, tp, 1303 mtod(m, void *), th, 0); 1304 } 1305#endif 1306 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, inp); 1307 } 1308 INP_UNLOCK(inp); 1309 return (error); 1310} 1311 1312/* 1313 * cookie layers: 1314 * 1315 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1316 * | peer iss | 1317 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1318 * | 0 |(A)| | 1319 * (A): peer mss index 1320 */ 1321 1322/* 1323 * The values below are chosen to minimize the size of the tcp_secret 1324 * table, as well as providing roughly a 16 second lifetime for the cookie. 1325 */ 1326 1327#define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1328#define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1329 1330#define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1331#define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1332#define SYNCOOKIE_TIMEOUT \ 1333 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1334#define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1335 1336static struct { 1337 u_int32_t ts_secbits[4]; 1338 u_int ts_expire; 1339} tcp_secret[SYNCOOKIE_NSECRETS]; 1340 1341static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1342 1343static MD5_CTX syn_ctx; 1344 1345#define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1346 1347struct md5_add { 1348 u_int32_t laddr, faddr; 1349 u_int32_t secbits[4]; 1350 u_int16_t lport, fport; 1351}; 1352 1353#ifdef CTASSERT 1354CTASSERT(sizeof(struct md5_add) == 28); 1355#endif 1356 1357/* 1358 * Consider the problem of a recreated (and retransmitted) cookie. If the 1359 * original SYN was accepted, the connection is established. The second 1360 * SYN is inflight, and if it arrives with an ISN that falls within the 1361 * receive window, the connection is killed. 1362 * 1363 * However, since cookies have other problems, this may not be worth 1364 * worrying about. 1365 */ 1366 1367static u_int32_t 1368syncookie_generate(struct syncache *sc, u_int32_t *flowid) 1369{ 1370 u_int32_t md5_buffer[4]; 1371 u_int32_t data; 1372 int idx, i; 1373 struct md5_add add; 1374 1375 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1376 1377 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1378 if (tcp_secret[idx].ts_expire < ticks) { 1379 for (i = 0; i < 4; i++) 1380 tcp_secret[idx].ts_secbits[i] = arc4random(); 1381 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1382 } 1383 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1384 if (tcp_msstab[data] <= sc->sc_peer_mss) 1385 break; 1386 data = (data << SYNCOOKIE_WNDBITS) | idx; 1387 data ^= sc->sc_irs; /* peer's iss */ 1388 MD5Init(&syn_ctx); 1389#ifdef INET6 1390 if (sc->sc_inc.inc_isipv6) { 1391 MD5Add(sc->sc_inc.inc6_laddr); 1392 MD5Add(sc->sc_inc.inc6_faddr); 1393 add.laddr = 0; 1394 add.faddr = 0; 1395 } else 1396#endif 1397 { 1398 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1399 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1400 } 1401 add.lport = sc->sc_inc.inc_lport; 1402 add.fport = sc->sc_inc.inc_fport; 1403 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1404 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1405 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1406 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1407 MD5Add(add); 1408 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1409 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1410 *flowid = md5_buffer[1]; 1411 return (data); 1412} 1413 1414static struct syncache * 1415syncookie_lookup(inc, th, so) 1416 struct in_conninfo *inc; 1417 struct tcphdr *th; 1418 struct socket *so; 1419{ 1420 u_int32_t md5_buffer[4]; 1421 struct syncache *sc; 1422 u_int32_t data; 1423 int wnd, idx; 1424 struct md5_add add; 1425 1426 /* NB: single threaded; could add INP_INFO_WLOCK_ASSERT(&tcbinfo) */ 1427 1428 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1429 idx = data & SYNCOOKIE_WNDMASK; 1430 if (tcp_secret[idx].ts_expire < ticks || 1431 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1432 return (NULL); 1433 MD5Init(&syn_ctx); 1434#ifdef INET6 1435 if (inc->inc_isipv6) { 1436 MD5Add(inc->inc6_laddr); 1437 MD5Add(inc->inc6_faddr); 1438 add.laddr = 0; 1439 add.faddr = 0; 1440 } else 1441#endif 1442 { 1443 add.laddr = inc->inc_laddr.s_addr; 1444 add.faddr = inc->inc_faddr.s_addr; 1445 } 1446 add.lport = inc->inc_lport; 1447 add.fport = inc->inc_fport; 1448 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1449 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1450 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1451 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1452 MD5Add(add); 1453 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1454 data ^= md5_buffer[0]; 1455 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1456 return (NULL); 1457 data = data >> SYNCOOKIE_WNDBITS; 1458 1459 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1460 if (sc == NULL) 1461 return (NULL); 1462 /* 1463 * Fill in the syncache values. 1464 * XXX duplicate code from syncache_add 1465 */ 1466 sc->sc_ipopts = NULL; 1467 sc->sc_inc.inc_fport = inc->inc_fport; 1468 sc->sc_inc.inc_lport = inc->inc_lport; 1469 sc->sc_tp = sototcpcb(so); 1470#ifdef INET6 1471 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1472 if (inc->inc_isipv6) { 1473 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1474 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1475 if (sc->sc_tp->t_inpcb->in6p_flags & IN6P_AUTOFLOWLABEL) 1476 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1477 } else 1478#endif 1479 { 1480 sc->sc_inc.inc_faddr = inc->inc_faddr; 1481 sc->sc_inc.inc_laddr = inc->inc_laddr; 1482 } 1483 sc->sc_irs = th->th_seq - 1; 1484 sc->sc_iss = th->th_ack - 1; 1485 wnd = sbspace(&so->so_rcv); 1486 wnd = imax(wnd, 0); 1487 wnd = imin(wnd, TCP_MAXWIN); 1488 sc->sc_wnd = wnd; 1489 sc->sc_flags = 0; 1490 sc->sc_rxtslot = 0; 1491 sc->sc_peer_mss = tcp_msstab[data]; 1492 return (sc); 1493} 1494