1/*- 2 * Copyright (c) 2001 McAfee, Inc. 3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG 4 * All rights reserved. 5 * 6 * This software was developed for the FreeBSD Project by Jonathan Lemon 7 * and McAfee Research, the Security Research Division of McAfee, Inc. under 8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 9 * DARPA CHATS research program. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33#include <sys/cdefs.h> 34__FBSDID("$FreeBSD$"); 35 36#include "opt_inet.h" 37#include "opt_inet6.h" 38#include "opt_ipsec.h" 39#include "opt_pcbgroup.h" 40 41#include <sys/param.h> 42#include <sys/systm.h> 43#include <sys/kernel.h> 44#include <sys/sysctl.h> 45#include <sys/limits.h> 46#include <sys/lock.h> 47#include <sys/mutex.h> 48#include <sys/malloc.h> 49#include <sys/mbuf.h> 50#include <sys/md5.h> 51#include <sys/proc.h> /* for proc0 declaration */ 52#include <sys/random.h> 53#include <sys/socket.h> 54#include <sys/socketvar.h> 55#include <sys/syslog.h> 56#include <sys/ucred.h> 57 58#include <vm/uma.h> 59 60#include <net/if.h> 61#include <net/route.h> 62#include <net/vnet.h> 63 64#include <netinet/in.h> 65#include <netinet/in_systm.h> 66#include <netinet/ip.h> 67#include <netinet/in_var.h> 68#include <netinet/in_pcb.h> 69#include <netinet/ip_var.h> 70#include <netinet/ip_options.h> 71#ifdef INET6 72#include <netinet/ip6.h> 73#include <netinet/icmp6.h> 74#include <netinet6/nd6.h> 75#include <netinet6/ip6_var.h> 76#include <netinet6/in6_pcb.h> 77#endif 78#include <netinet/tcp.h> 79#include <netinet/tcp_fsm.h> 80#include <netinet/tcp_seq.h> 81#include <netinet/tcp_timer.h> 82#include <netinet/tcp_var.h> 83#include <netinet/tcp_syncache.h> 84#ifdef INET6 85#include <netinet6/tcp6_var.h> 86#endif 87#ifdef TCP_OFFLOAD 88#include <netinet/toecore.h> 89#endif 90 91#ifdef IPSEC 92#include <netipsec/ipsec.h> 93#ifdef INET6 94#include <netipsec/ipsec6.h> 95#endif 96#include <netipsec/key.h> 97#endif /*IPSEC*/ 98 99#include <machine/in_cksum.h> 100 101#include <security/mac/mac_framework.h> 102 103static VNET_DEFINE(int, tcp_syncookies) = 1; 104#define V_tcp_syncookies VNET(tcp_syncookies) 105SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 106 &VNET_NAME(tcp_syncookies), 0, 107 "Use TCP SYN cookies if the syncache overflows"); 108 109static VNET_DEFINE(int, tcp_syncookiesonly) = 0; 110#define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 111SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 112 &VNET_NAME(tcp_syncookiesonly), 0, 113 "Use only TCP SYN cookies"); 114 115#ifdef TCP_OFFLOAD 116#define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL) 117#endif 118 119static void syncache_drop(struct syncache *, struct syncache_head *); 120static void syncache_free(struct syncache *); 121static void syncache_insert(struct syncache *, struct syncache_head *); 122struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 123static int syncache_respond(struct syncache *); 124static struct socket *syncache_socket(struct syncache *, struct socket *, 125 struct mbuf *m); 126static int syncache_sysctl_count(SYSCTL_HANDLER_ARGS); 127static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 128 int docallout); 129static void syncache_timer(void *); 130static void syncookie_generate(struct syncache_head *, struct syncache *, 131 u_int32_t *); 132static struct syncache 133 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 134 struct syncache *, struct tcpopt *, struct tcphdr *, 135 struct socket *); 136 137/* 138 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 139 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 140 * the odds are that the user has given up attempting to connect by then. 141 */ 142#define SYNCACHE_MAXREXMTS 3 143 144/* Arbitrary values */ 145#define TCP_SYNCACHE_HASHSIZE 512 146#define TCP_SYNCACHE_BUCKETLIMIT 30 147 148static VNET_DEFINE(struct tcp_syncache, tcp_syncache); 149#define V_tcp_syncache VNET(tcp_syncache) 150 151static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 152 "TCP SYN cache"); 153 154SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 155 &VNET_NAME(tcp_syncache.bucket_limit), 0, 156 "Per-bucket hash limit for syncache"); 157 158SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 159 &VNET_NAME(tcp_syncache.cache_limit), 0, 160 "Overall entry limit for syncache"); 161 162SYSCTL_VNET_PROC(_net_inet_tcp_syncache, OID_AUTO, count, (CTLTYPE_UINT|CTLFLAG_RD), 163 NULL, 0, &syncache_sysctl_count, "IU", 164 "Current number of entries in syncache"); 165 166SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 167 &VNET_NAME(tcp_syncache.hashsize), 0, 168 "Size of TCP syncache hashtable"); 169 170SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 171 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 172 "Limit on SYN/ACK retransmissions"); 173 174VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 175SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 176 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 177 "Send reset on socket allocation failure"); 178 179static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 180 181#define SYNCACHE_HASH(inc, mask) \ 182 ((V_tcp_syncache.hash_secret ^ \ 183 (inc)->inc_faddr.s_addr ^ \ 184 ((inc)->inc_faddr.s_addr >> 16) ^ \ 185 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 186 187#define SYNCACHE_HASH6(inc, mask) \ 188 ((V_tcp_syncache.hash_secret ^ \ 189 (inc)->inc6_faddr.s6_addr32[0] ^ \ 190 (inc)->inc6_faddr.s6_addr32[3] ^ \ 191 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 192 193#define ENDPTS_EQ(a, b) ( \ 194 (a)->ie_fport == (b)->ie_fport && \ 195 (a)->ie_lport == (b)->ie_lport && \ 196 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 197 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 198) 199 200#define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 201 202#define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 203#define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 204#define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 205 206/* 207 * Requires the syncache entry to be already removed from the bucket list. 208 */ 209static void 210syncache_free(struct syncache *sc) 211{ 212 213 if (sc->sc_ipopts) 214 (void) m_free(sc->sc_ipopts); 215 if (sc->sc_cred) 216 crfree(sc->sc_cred); 217#ifdef MAC 218 mac_syncache_destroy(&sc->sc_label); 219#endif 220 221 uma_zfree(V_tcp_syncache.zone, sc); 222} 223 224void 225syncache_init(void) 226{ 227 int i; 228 229 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 230 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 231 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 232 V_tcp_syncache.hash_secret = arc4random(); 233 234 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 235 &V_tcp_syncache.hashsize); 236 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 237 &V_tcp_syncache.bucket_limit); 238 if (!powerof2(V_tcp_syncache.hashsize) || 239 V_tcp_syncache.hashsize == 0) { 240 printf("WARNING: syncache hash size is not a power of 2.\n"); 241 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 242 } 243 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 244 245 /* Set limits. */ 246 V_tcp_syncache.cache_limit = 247 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 248 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 249 &V_tcp_syncache.cache_limit); 250 251 /* Allocate the hash table. */ 252 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 253 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 254 255 /* Initialize the hash buckets. */ 256 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 257#ifdef VIMAGE 258 V_tcp_syncache.hashbase[i].sch_vnet = curvnet; 259#endif 260 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 261 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 262 NULL, MTX_DEF); 263 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 264 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 265 V_tcp_syncache.hashbase[i].sch_length = 0; 266 } 267 268 /* Create the syncache entry zone. */ 269 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 270 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 271 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone, 272 V_tcp_syncache.cache_limit); 273} 274 275#ifdef VIMAGE 276void 277syncache_destroy(void) 278{ 279 struct syncache_head *sch; 280 struct syncache *sc, *nsc; 281 int i; 282 283 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 284 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 285 286 sch = &V_tcp_syncache.hashbase[i]; 287 callout_drain(&sch->sch_timer); 288 289 SCH_LOCK(sch); 290 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 291 syncache_drop(sc, sch); 292 SCH_UNLOCK(sch); 293 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 294 ("%s: sch->sch_bucket not empty", __func__)); 295 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 296 __func__, sch->sch_length)); 297 mtx_destroy(&sch->sch_mtx); 298 } 299 300 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0, 301 ("%s: cache_count not 0", __func__)); 302 303 /* Free the allocated global resources. */ 304 uma_zdestroy(V_tcp_syncache.zone); 305 free(V_tcp_syncache.hashbase, M_SYNCACHE); 306} 307#endif 308 309static int 310syncache_sysctl_count(SYSCTL_HANDLER_ARGS) 311{ 312 int count; 313 314 count = uma_zone_get_cur(V_tcp_syncache.zone); 315 return (sysctl_handle_int(oidp, &count, 0, req)); 316} 317 318/* 319 * Inserts a syncache entry into the specified bucket row. 320 * Locks and unlocks the syncache_head autonomously. 321 */ 322static void 323syncache_insert(struct syncache *sc, struct syncache_head *sch) 324{ 325 struct syncache *sc2; 326 327 SCH_LOCK(sch); 328 329 /* 330 * Make sure that we don't overflow the per-bucket limit. 331 * If the bucket is full, toss the oldest element. 332 */ 333 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 334 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 335 ("sch->sch_length incorrect")); 336 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 337 syncache_drop(sc2, sch); 338 TCPSTAT_INC(tcps_sc_bucketoverflow); 339 } 340 341 /* Put it into the bucket. */ 342 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 343 sch->sch_length++; 344 345#ifdef TCP_OFFLOAD 346 if (ADDED_BY_TOE(sc)) { 347 struct toedev *tod = sc->sc_tod; 348 349 tod->tod_syncache_added(tod, sc->sc_todctx); 350 } 351#endif 352 353 /* Reinitialize the bucket row's timer. */ 354 if (sch->sch_length == 1) 355 sch->sch_nextc = ticks + INT_MAX; 356 syncache_timeout(sc, sch, 1); 357 358 SCH_UNLOCK(sch); 359 360 TCPSTAT_INC(tcps_sc_added); 361} 362 363/* 364 * Remove and free entry from syncache bucket row. 365 * Expects locked syncache head. 366 */ 367static void 368syncache_drop(struct syncache *sc, struct syncache_head *sch) 369{ 370 371 SCH_LOCK_ASSERT(sch); 372 373 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 374 sch->sch_length--; 375 376#ifdef TCP_OFFLOAD 377 if (ADDED_BY_TOE(sc)) { 378 struct toedev *tod = sc->sc_tod; 379 380 tod->tod_syncache_removed(tod, sc->sc_todctx); 381 } 382#endif 383 384 syncache_free(sc); 385} 386 387/* 388 * Engage/reengage time on bucket row. 389 */ 390static void 391syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 392{ 393 sc->sc_rxttime = ticks + 394 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 395 sc->sc_rxmits++; 396 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 397 sch->sch_nextc = sc->sc_rxttime; 398 if (docallout) 399 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 400 syncache_timer, (void *)sch); 401 } 402} 403 404/* 405 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 406 * If we have retransmitted an entry the maximum number of times, expire it. 407 * One separate timer for each bucket row. 408 */ 409static void 410syncache_timer(void *xsch) 411{ 412 struct syncache_head *sch = (struct syncache_head *)xsch; 413 struct syncache *sc, *nsc; 414 int tick = ticks; 415 char *s; 416 417 CURVNET_SET(sch->sch_vnet); 418 419 /* NB: syncache_head has already been locked by the callout. */ 420 SCH_LOCK_ASSERT(sch); 421 422 /* 423 * In the following cycle we may remove some entries and/or 424 * advance some timeouts, so re-initialize the bucket timer. 425 */ 426 sch->sch_nextc = tick + INT_MAX; 427 428 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 429 /* 430 * We do not check if the listen socket still exists 431 * and accept the case where the listen socket may be 432 * gone by the time we resend the SYN/ACK. We do 433 * not expect this to happens often. If it does, 434 * then the RST will be sent by the time the remote 435 * host does the SYN/ACK->ACK. 436 */ 437 if (TSTMP_GT(sc->sc_rxttime, tick)) { 438 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 439 sch->sch_nextc = sc->sc_rxttime; 440 continue; 441 } 442 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 443 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 444 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 445 "giving up and removing syncache entry\n", 446 s, __func__); 447 free(s, M_TCPLOG); 448 } 449 syncache_drop(sc, sch); 450 TCPSTAT_INC(tcps_sc_stale); 451 continue; 452 } 453 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 454 log(LOG_DEBUG, "%s; %s: Response timeout, " 455 "retransmitting (%u) SYN|ACK\n", 456 s, __func__, sc->sc_rxmits); 457 free(s, M_TCPLOG); 458 } 459 460 (void) syncache_respond(sc); 461 TCPSTAT_INC(tcps_sc_retransmitted); 462 syncache_timeout(sc, sch, 0); 463 } 464 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 465 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 466 syncache_timer, (void *)(sch)); 467 CURVNET_RESTORE(); 468} 469 470/* 471 * Find an entry in the syncache. 472 * Returns always with locked syncache_head plus a matching entry or NULL. 473 */ 474struct syncache * 475syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 476{ 477 struct syncache *sc; 478 struct syncache_head *sch; 479 480#ifdef INET6 481 if (inc->inc_flags & INC_ISIPV6) { 482 sch = &V_tcp_syncache.hashbase[ 483 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 484 *schp = sch; 485 486 SCH_LOCK(sch); 487 488 /* Circle through bucket row to find matching entry. */ 489 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 490 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 491 return (sc); 492 } 493 } else 494#endif 495 { 496 sch = &V_tcp_syncache.hashbase[ 497 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 498 *schp = sch; 499 500 SCH_LOCK(sch); 501 502 /* Circle through bucket row to find matching entry. */ 503 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 504#ifdef INET6 505 if (sc->sc_inc.inc_flags & INC_ISIPV6) 506 continue; 507#endif 508 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 509 return (sc); 510 } 511 } 512 SCH_LOCK_ASSERT(*schp); 513 return (NULL); /* always returns with locked sch */ 514} 515 516/* 517 * This function is called when we get a RST for a 518 * non-existent connection, so that we can see if the 519 * connection is in the syn cache. If it is, zap it. 520 */ 521void 522syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 523{ 524 struct syncache *sc; 525 struct syncache_head *sch; 526 char *s = NULL; 527 528 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 529 SCH_LOCK_ASSERT(sch); 530 531 /* 532 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 533 * See RFC 793 page 65, section SEGMENT ARRIVES. 534 */ 535 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 536 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 537 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 538 "FIN flag set, segment ignored\n", s, __func__); 539 TCPSTAT_INC(tcps_badrst); 540 goto done; 541 } 542 543 /* 544 * No corresponding connection was found in syncache. 545 * If syncookies are enabled and possibly exclusively 546 * used, or we are under memory pressure, a valid RST 547 * may not find a syncache entry. In that case we're 548 * done and no SYN|ACK retransmissions will happen. 549 * Otherwise the RST was misdirected or spoofed. 550 */ 551 if (sc == NULL) { 552 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 553 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 554 "syncache entry (possibly syncookie only), " 555 "segment ignored\n", s, __func__); 556 TCPSTAT_INC(tcps_badrst); 557 goto done; 558 } 559 560 /* 561 * If the RST bit is set, check the sequence number to see 562 * if this is a valid reset segment. 563 * RFC 793 page 37: 564 * In all states except SYN-SENT, all reset (RST) segments 565 * are validated by checking their SEQ-fields. A reset is 566 * valid if its sequence number is in the window. 567 * 568 * The sequence number in the reset segment is normally an 569 * echo of our outgoing acknowlegement numbers, but some hosts 570 * send a reset with the sequence number at the rightmost edge 571 * of our receive window, and we have to handle this case. 572 */ 573 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 574 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 575 syncache_drop(sc, sch); 576 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 577 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 578 "connection attempt aborted by remote endpoint\n", 579 s, __func__); 580 TCPSTAT_INC(tcps_sc_reset); 581 } else { 582 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 583 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 584 "IRS %u (+WND %u), segment ignored\n", 585 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 586 TCPSTAT_INC(tcps_badrst); 587 } 588 589done: 590 if (s != NULL) 591 free(s, M_TCPLOG); 592 SCH_UNLOCK(sch); 593} 594 595void 596syncache_badack(struct in_conninfo *inc) 597{ 598 struct syncache *sc; 599 struct syncache_head *sch; 600 601 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 602 SCH_LOCK_ASSERT(sch); 603 if (sc != NULL) { 604 syncache_drop(sc, sch); 605 TCPSTAT_INC(tcps_sc_badack); 606 } 607 SCH_UNLOCK(sch); 608} 609 610void 611syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 612{ 613 struct syncache *sc; 614 struct syncache_head *sch; 615 616 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 617 SCH_LOCK_ASSERT(sch); 618 if (sc == NULL) 619 goto done; 620 621 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 622 if (ntohl(th->th_seq) != sc->sc_iss) 623 goto done; 624 625 /* 626 * If we've rertransmitted 3 times and this is our second error, 627 * we remove the entry. Otherwise, we allow it to continue on. 628 * This prevents us from incorrectly nuking an entry during a 629 * spurious network outage. 630 * 631 * See tcp_notify(). 632 */ 633 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 634 sc->sc_flags |= SCF_UNREACH; 635 goto done; 636 } 637 syncache_drop(sc, sch); 638 TCPSTAT_INC(tcps_sc_unreach); 639done: 640 SCH_UNLOCK(sch); 641} 642 643/* 644 * Build a new TCP socket structure from a syncache entry. 645 */ 646static struct socket * 647syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 648{ 649 struct inpcb *inp = NULL; 650 struct socket *so; 651 struct tcpcb *tp; 652 int error; 653 char *s; 654 655 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 656 657 /* 658 * Ok, create the full blown connection, and set things up 659 * as they would have been set up if we had created the 660 * connection when the SYN arrived. If we can't create 661 * the connection, abort it. 662 */ 663 so = sonewconn(lso, SS_ISCONNECTED); 664 if (so == NULL) { 665 /* 666 * Drop the connection; we will either send a RST or 667 * have the peer retransmit its SYN again after its 668 * RTO and try again. 669 */ 670 TCPSTAT_INC(tcps_listendrop); 671 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 672 log(LOG_DEBUG, "%s; %s: Socket create failed " 673 "due to limits or memory shortage\n", 674 s, __func__); 675 free(s, M_TCPLOG); 676 } 677 goto abort2; 678 } 679#ifdef MAC 680 mac_socketpeer_set_from_mbuf(m, so); 681#endif 682 683 inp = sotoinpcb(so); 684 inp->inp_inc.inc_fibnum = so->so_fibnum; 685 INP_WLOCK(inp); 686 INP_HASH_WLOCK(&V_tcbinfo); 687 688 /* Insert new socket into PCB hash list. */ 689 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 690#ifdef INET6 691 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 692 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 693 } else { 694 inp->inp_vflag &= ~INP_IPV6; 695 inp->inp_vflag |= INP_IPV4; 696#endif 697 inp->inp_laddr = sc->sc_inc.inc_laddr; 698#ifdef INET6 699 } 700#endif 701 702 /* 703 * Install in the reservation hash table for now, but don't yet 704 * install a connection group since the full 4-tuple isn't yet 705 * configured. 706 */ 707 inp->inp_lport = sc->sc_inc.inc_lport; 708 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 709 /* 710 * Undo the assignments above if we failed to 711 * put the PCB on the hash lists. 712 */ 713#ifdef INET6 714 if (sc->sc_inc.inc_flags & INC_ISIPV6) 715 inp->in6p_laddr = in6addr_any; 716 else 717#endif 718 inp->inp_laddr.s_addr = INADDR_ANY; 719 inp->inp_lport = 0; 720 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 721 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 722 "with error %i\n", 723 s, __func__, error); 724 free(s, M_TCPLOG); 725 } 726 INP_HASH_WUNLOCK(&V_tcbinfo); 727 goto abort; 728 } 729#ifdef IPSEC 730 /* Copy old policy into new socket's. */ 731 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 732 printf("syncache_socket: could not copy policy\n"); 733#endif 734#ifdef INET6 735 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 736 struct inpcb *oinp = sotoinpcb(lso); 737 struct in6_addr laddr6; 738 struct sockaddr_in6 sin6; 739 /* 740 * Inherit socket options from the listening socket. 741 * Note that in6p_inputopts are not (and should not be) 742 * copied, since it stores previously received options and is 743 * used to detect if each new option is different than the 744 * previous one and hence should be passed to a user. 745 * If we copied in6p_inputopts, a user would not be able to 746 * receive options just after calling the accept system call. 747 */ 748 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 749 if (oinp->in6p_outputopts) 750 inp->in6p_outputopts = 751 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 752 753 sin6.sin6_family = AF_INET6; 754 sin6.sin6_len = sizeof(sin6); 755 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 756 sin6.sin6_port = sc->sc_inc.inc_fport; 757 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 758 laddr6 = inp->in6p_laddr; 759 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 760 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 761 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 762 thread0.td_ucred, m)) != 0) { 763 inp->in6p_laddr = laddr6; 764 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 765 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 766 "with error %i\n", 767 s, __func__, error); 768 free(s, M_TCPLOG); 769 } 770 INP_HASH_WUNLOCK(&V_tcbinfo); 771 goto abort; 772 } 773 /* Override flowlabel from in6_pcbconnect. */ 774 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 775 inp->inp_flow |= sc->sc_flowlabel; 776 } 777#endif /* INET6 */ 778#if defined(INET) && defined(INET6) 779 else 780#endif 781#ifdef INET 782 { 783 struct in_addr laddr; 784 struct sockaddr_in sin; 785 786 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 787 788 if (inp->inp_options == NULL) { 789 inp->inp_options = sc->sc_ipopts; 790 sc->sc_ipopts = NULL; 791 } 792 793 sin.sin_family = AF_INET; 794 sin.sin_len = sizeof(sin); 795 sin.sin_addr = sc->sc_inc.inc_faddr; 796 sin.sin_port = sc->sc_inc.inc_fport; 797 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 798 laddr = inp->inp_laddr; 799 if (inp->inp_laddr.s_addr == INADDR_ANY) 800 inp->inp_laddr = sc->sc_inc.inc_laddr; 801 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 802 thread0.td_ucred, m)) != 0) { 803 inp->inp_laddr = laddr; 804 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 805 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 806 "with error %i\n", 807 s, __func__, error); 808 free(s, M_TCPLOG); 809 } 810 INP_HASH_WUNLOCK(&V_tcbinfo); 811 goto abort; 812 } 813 } 814#endif /* INET */ 815 INP_HASH_WUNLOCK(&V_tcbinfo); 816 tp = intotcpcb(inp); 817 tp->t_state = TCPS_SYN_RECEIVED; 818 tp->iss = sc->sc_iss; 819 tp->irs = sc->sc_irs; 820 tcp_rcvseqinit(tp); 821 tcp_sendseqinit(tp); 822 tp->snd_wl1 = sc->sc_irs; 823 tp->snd_max = tp->iss + 1; 824 tp->snd_nxt = tp->iss + 1; 825 tp->rcv_up = sc->sc_irs + 1; 826 tp->rcv_wnd = sc->sc_wnd; 827 tp->rcv_adv += tp->rcv_wnd; 828 tp->last_ack_sent = tp->rcv_nxt; 829 830 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 831 if (sc->sc_flags & SCF_NOOPT) 832 tp->t_flags |= TF_NOOPT; 833 else { 834 if (sc->sc_flags & SCF_WINSCALE) { 835 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 836 tp->snd_scale = sc->sc_requested_s_scale; 837 tp->request_r_scale = sc->sc_requested_r_scale; 838 } 839 if (sc->sc_flags & SCF_TIMESTAMP) { 840 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 841 tp->ts_recent = sc->sc_tsreflect; 842 tp->ts_recent_age = tcp_ts_getticks(); 843 tp->ts_offset = sc->sc_tsoff; 844 } 845#ifdef TCP_SIGNATURE 846 if (sc->sc_flags & SCF_SIGNATURE) 847 tp->t_flags |= TF_SIGNATURE; 848#endif 849 if (sc->sc_flags & SCF_SACK) 850 tp->t_flags |= TF_SACK_PERMIT; 851 } 852 853 if (sc->sc_flags & SCF_ECN) 854 tp->t_flags |= TF_ECN_PERMIT; 855 856 /* 857 * Set up MSS and get cached values from tcp_hostcache. 858 * This might overwrite some of the defaults we just set. 859 */ 860 tcp_mss(tp, sc->sc_peer_mss); 861 862 /* 863 * If the SYN,ACK was retransmitted, indicate that CWND to be 864 * limited to one segment in cc_conn_init(). 865 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 866 */ 867 if (sc->sc_rxmits > 1) 868 tp->snd_cwnd = 1; 869 870#ifdef TCP_OFFLOAD 871 /* 872 * Allow a TOE driver to install its hooks. Note that we hold the 873 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a 874 * new connection before the TOE driver has done its thing. 875 */ 876 if (ADDED_BY_TOE(sc)) { 877 struct toedev *tod = sc->sc_tod; 878 879 tod->tod_offload_socket(tod, sc->sc_todctx, so); 880 } 881#endif 882 /* 883 * Copy and activate timers. 884 */ 885 tp->t_keepinit = sototcpcb(lso)->t_keepinit; 886 tp->t_keepidle = sototcpcb(lso)->t_keepidle; 887 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl; 888 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt; 889 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp)); 890 891 INP_WUNLOCK(inp); 892 893 TCPSTAT_INC(tcps_accepts); 894 return (so); 895 896abort: 897 INP_WUNLOCK(inp); 898abort2: 899 if (so != NULL) 900 soabort(so); 901 return (NULL); 902} 903 904/* 905 * This function gets called when we receive an ACK for a 906 * socket in the LISTEN state. We look up the connection 907 * in the syncache, and if its there, we pull it out of 908 * the cache and turn it into a full-blown connection in 909 * the SYN-RECEIVED state. 910 */ 911int 912syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 913 struct socket **lsop, struct mbuf *m) 914{ 915 struct syncache *sc; 916 struct syncache_head *sch; 917 struct syncache scs; 918 char *s; 919 920 /* 921 * Global TCP locks are held because we manipulate the PCB lists 922 * and create a new socket. 923 */ 924 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 925 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 926 ("%s: can handle only ACK", __func__)); 927 928 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 929 SCH_LOCK_ASSERT(sch); 930 if (sc == NULL) { 931 /* 932 * There is no syncache entry, so see if this ACK is 933 * a returning syncookie. To do this, first: 934 * A. See if this socket has had a syncache entry dropped in 935 * the past. We don't want to accept a bogus syncookie 936 * if we've never received a SYN. 937 * B. check that the syncookie is valid. If it is, then 938 * cobble up a fake syncache entry, and return. 939 */ 940 if (!V_tcp_syncookies) { 941 SCH_UNLOCK(sch); 942 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 943 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 944 "segment rejected (syncookies disabled)\n", 945 s, __func__); 946 goto failed; 947 } 948 bzero(&scs, sizeof(scs)); 949 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 950 SCH_UNLOCK(sch); 951 if (sc == NULL) { 952 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 953 log(LOG_DEBUG, "%s; %s: Segment failed " 954 "SYNCOOKIE authentication, segment rejected " 955 "(probably spoofed)\n", s, __func__); 956 goto failed; 957 } 958 } else { 959 /* Pull out the entry to unlock the bucket row. */ 960 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 961 sch->sch_length--; 962#ifdef TCP_OFFLOAD 963 if (ADDED_BY_TOE(sc)) { 964 struct toedev *tod = sc->sc_tod; 965 966 tod->tod_syncache_removed(tod, sc->sc_todctx); 967 } 968#endif 969 SCH_UNLOCK(sch); 970 } 971 972 /* 973 * Segment validation: 974 * ACK must match our initial sequence number + 1 (the SYN|ACK). 975 */ 976 if (th->th_ack != sc->sc_iss + 1) { 977 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 978 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 979 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 980 goto failed; 981 } 982 983 /* 984 * The SEQ must fall in the window starting at the received 985 * initial receive sequence number + 1 (the SYN). 986 */ 987 if (SEQ_LEQ(th->th_seq, sc->sc_irs) || 988 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 989 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 990 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 991 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 992 goto failed; 993 } 994 995 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 996 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 997 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 998 "segment rejected\n", s, __func__); 999 goto failed; 1000 } 1001 /* 1002 * If timestamps were negotiated the reflected timestamp 1003 * must be equal to what we actually sent in the SYN|ACK. 1004 */ 1005 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts) { 1006 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 1007 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 1008 "segment rejected\n", 1009 s, __func__, to->to_tsecr, sc->sc_ts); 1010 goto failed; 1011 } 1012 1013 *lsop = syncache_socket(sc, *lsop, m); 1014 1015 if (*lsop == NULL) 1016 TCPSTAT_INC(tcps_sc_aborted); 1017 else 1018 TCPSTAT_INC(tcps_sc_completed); 1019 1020/* how do we find the inp for the new socket? */ 1021 if (sc != &scs) 1022 syncache_free(sc); 1023 return (1); 1024failed: 1025 if (sc != NULL && sc != &scs) 1026 syncache_free(sc); 1027 if (s != NULL) 1028 free(s, M_TCPLOG); 1029 *lsop = NULL; 1030 return (0); 1031} 1032 1033/* 1034 * Given a LISTEN socket and an inbound SYN request, add 1035 * this to the syn cache, and send back a segment: 1036 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1037 * to the source. 1038 * 1039 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1040 * Doing so would require that we hold onto the data and deliver it 1041 * to the application. However, if we are the target of a SYN-flood 1042 * DoS attack, an attacker could send data which would eventually 1043 * consume all available buffer space if it were ACKed. By not ACKing 1044 * the data, we avoid this DoS scenario. 1045 */ 1046static void 1047_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1048 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod, 1049 void *todctx) 1050{ 1051 struct tcpcb *tp; 1052 struct socket *so; 1053 struct syncache *sc = NULL; 1054 struct syncache_head *sch; 1055 struct mbuf *ipopts = NULL; 1056 u_int32_t flowtmp; 1057 u_int ltflags; 1058 int win, sb_hiwat, ip_ttl, ip_tos; 1059 char *s; 1060#ifdef INET6 1061 int autoflowlabel = 0; 1062#endif 1063#ifdef MAC 1064 struct label *maclabel; 1065#endif 1066 struct syncache scs; 1067 struct ucred *cred; 1068 1069 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1070 INP_WLOCK_ASSERT(inp); /* listen socket */ 1071 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1072 ("%s: unexpected tcp flags", __func__)); 1073 1074 /* 1075 * Combine all so/tp operations very early to drop the INP lock as 1076 * soon as possible. 1077 */ 1078 so = *lsop; 1079 tp = sototcpcb(so); 1080 cred = crhold(so->so_cred); 1081 1082#ifdef INET6 1083 if ((inc->inc_flags & INC_ISIPV6) && 1084 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1085 autoflowlabel = 1; 1086#endif 1087 ip_ttl = inp->inp_ip_ttl; 1088 ip_tos = inp->inp_ip_tos; 1089 win = sbspace(&so->so_rcv); 1090 sb_hiwat = so->so_rcv.sb_hiwat; 1091 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1092 1093 /* By the time we drop the lock these should no longer be used. */ 1094 so = NULL; 1095 tp = NULL; 1096 1097#ifdef MAC 1098 if (mac_syncache_init(&maclabel) != 0) { 1099 INP_WUNLOCK(inp); 1100 INP_INFO_WUNLOCK(&V_tcbinfo); 1101 goto done; 1102 } else 1103 mac_syncache_create(maclabel, inp); 1104#endif 1105 INP_WUNLOCK(inp); 1106 INP_INFO_WUNLOCK(&V_tcbinfo); 1107 1108 /* 1109 * Remember the IP options, if any. 1110 */ 1111#ifdef INET6 1112 if (!(inc->inc_flags & INC_ISIPV6)) 1113#endif 1114#ifdef INET 1115 ipopts = (m) ? ip_srcroute(m) : NULL; 1116#else 1117 ipopts = NULL; 1118#endif 1119 1120 /* 1121 * See if we already have an entry for this connection. 1122 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1123 * 1124 * XXX: should the syncache be re-initialized with the contents 1125 * of the new SYN here (which may have different options?) 1126 * 1127 * XXX: We do not check the sequence number to see if this is a 1128 * real retransmit or a new connection attempt. The question is 1129 * how to handle such a case; either ignore it as spoofed, or 1130 * drop the current entry and create a new one? 1131 */ 1132 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1133 SCH_LOCK_ASSERT(sch); 1134 if (sc != NULL) { 1135 TCPSTAT_INC(tcps_sc_dupsyn); 1136 if (ipopts) { 1137 /* 1138 * If we were remembering a previous source route, 1139 * forget it and use the new one we've been given. 1140 */ 1141 if (sc->sc_ipopts) 1142 (void) m_free(sc->sc_ipopts); 1143 sc->sc_ipopts = ipopts; 1144 } 1145 /* 1146 * Update timestamp if present. 1147 */ 1148 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1149 sc->sc_tsreflect = to->to_tsval; 1150 else 1151 sc->sc_flags &= ~SCF_TIMESTAMP; 1152#ifdef MAC 1153 /* 1154 * Since we have already unconditionally allocated label 1155 * storage, free it up. The syncache entry will already 1156 * have an initialized label we can use. 1157 */ 1158 mac_syncache_destroy(&maclabel); 1159#endif 1160 /* Retransmit SYN|ACK and reset retransmit count. */ 1161 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1162 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1163 "resetting timer and retransmitting SYN|ACK\n", 1164 s, __func__); 1165 free(s, M_TCPLOG); 1166 } 1167 if (syncache_respond(sc) == 0) { 1168 sc->sc_rxmits = 0; 1169 syncache_timeout(sc, sch, 1); 1170 TCPSTAT_INC(tcps_sndacks); 1171 TCPSTAT_INC(tcps_sndtotal); 1172 } 1173 SCH_UNLOCK(sch); 1174 goto done; 1175 } 1176 1177 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1178 if (sc == NULL) { 1179 /* 1180 * The zone allocator couldn't provide more entries. 1181 * Treat this as if the cache was full; drop the oldest 1182 * entry and insert the new one. 1183 */ 1184 TCPSTAT_INC(tcps_sc_zonefail); 1185 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1186 syncache_drop(sc, sch); 1187 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1188 if (sc == NULL) { 1189 if (V_tcp_syncookies) { 1190 bzero(&scs, sizeof(scs)); 1191 sc = &scs; 1192 } else { 1193 SCH_UNLOCK(sch); 1194 if (ipopts) 1195 (void) m_free(ipopts); 1196 goto done; 1197 } 1198 } 1199 } 1200 1201 /* 1202 * Fill in the syncache values. 1203 */ 1204#ifdef MAC 1205 sc->sc_label = maclabel; 1206#endif 1207 sc->sc_cred = cred; 1208 cred = NULL; 1209 sc->sc_ipopts = ipopts; 1210 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1211#ifdef INET6 1212 if (!(inc->inc_flags & INC_ISIPV6)) 1213#endif 1214 { 1215 sc->sc_ip_tos = ip_tos; 1216 sc->sc_ip_ttl = ip_ttl; 1217 } 1218#ifdef TCP_OFFLOAD 1219 sc->sc_tod = tod; 1220 sc->sc_todctx = todctx; 1221#endif 1222 sc->sc_irs = th->th_seq; 1223 sc->sc_iss = arc4random(); 1224 sc->sc_flags = 0; 1225 sc->sc_flowlabel = 0; 1226 1227 /* 1228 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1229 * win was derived from socket earlier in the function. 1230 */ 1231 win = imax(win, 0); 1232 win = imin(win, TCP_MAXWIN); 1233 sc->sc_wnd = win; 1234 1235 if (V_tcp_do_rfc1323) { 1236 /* 1237 * A timestamp received in a SYN makes 1238 * it ok to send timestamp requests and replies. 1239 */ 1240 if (to->to_flags & TOF_TS) { 1241 sc->sc_tsreflect = to->to_tsval; 1242 sc->sc_ts = tcp_ts_getticks(); 1243 sc->sc_flags |= SCF_TIMESTAMP; 1244 } 1245 if (to->to_flags & TOF_SCALE) { 1246 int wscale = 0; 1247 1248 /* 1249 * Pick the smallest possible scaling factor that 1250 * will still allow us to scale up to sb_max, aka 1251 * kern.ipc.maxsockbuf. 1252 * 1253 * We do this because there are broken firewalls that 1254 * will corrupt the window scale option, leading to 1255 * the other endpoint believing that our advertised 1256 * window is unscaled. At scale factors larger than 1257 * 5 the unscaled window will drop below 1500 bytes, 1258 * leading to serious problems when traversing these 1259 * broken firewalls. 1260 * 1261 * With the default maxsockbuf of 256K, a scale factor 1262 * of 3 will be chosen by this algorithm. Those who 1263 * choose a larger maxsockbuf should watch out 1264 * for the compatiblity problems mentioned above. 1265 * 1266 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1267 * or <SYN,ACK>) segment itself is never scaled. 1268 */ 1269 while (wscale < TCP_MAX_WINSHIFT && 1270 (TCP_MAXWIN << wscale) < sb_max) 1271 wscale++; 1272 sc->sc_requested_r_scale = wscale; 1273 sc->sc_requested_s_scale = to->to_wscale; 1274 sc->sc_flags |= SCF_WINSCALE; 1275 } 1276 } 1277#ifdef TCP_SIGNATURE 1278 /* 1279 * If listening socket requested TCP digests, and received SYN 1280 * contains the option, flag this in the syncache so that 1281 * syncache_respond() will do the right thing with the SYN+ACK. 1282 * XXX: Currently we always record the option by default and will 1283 * attempt to use it in syncache_respond(). 1284 */ 1285 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE) 1286 sc->sc_flags |= SCF_SIGNATURE; 1287#endif 1288 if (to->to_flags & TOF_SACKPERM) 1289 sc->sc_flags |= SCF_SACK; 1290 if (to->to_flags & TOF_MSS) 1291 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1292 if (ltflags & TF_NOOPT) 1293 sc->sc_flags |= SCF_NOOPT; 1294 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1295 sc->sc_flags |= SCF_ECN; 1296 1297 if (V_tcp_syncookies) { 1298 syncookie_generate(sch, sc, &flowtmp); 1299#ifdef INET6 1300 if (autoflowlabel) 1301 sc->sc_flowlabel = flowtmp; 1302#endif 1303 } else { 1304#ifdef INET6 1305 if (autoflowlabel) 1306 sc->sc_flowlabel = 1307 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1308#endif 1309 } 1310 SCH_UNLOCK(sch); 1311 1312 /* 1313 * Do a standard 3-way handshake. 1314 */ 1315 if (syncache_respond(sc) == 0) { 1316 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1317 syncache_free(sc); 1318 else if (sc != &scs) 1319 syncache_insert(sc, sch); /* locks and unlocks sch */ 1320 TCPSTAT_INC(tcps_sndacks); 1321 TCPSTAT_INC(tcps_sndtotal); 1322 } else { 1323 if (sc != &scs) 1324 syncache_free(sc); 1325 TCPSTAT_INC(tcps_sc_dropped); 1326 } 1327 1328done: 1329 if (cred != NULL) 1330 crfree(cred); 1331#ifdef MAC 1332 if (sc == &scs) 1333 mac_syncache_destroy(&maclabel); 1334#endif 1335 if (m) { 1336 1337 *lsop = NULL; 1338 m_freem(m); 1339 } 1340} 1341 1342static int 1343syncache_respond(struct syncache *sc) 1344{ 1345 struct ip *ip = NULL; 1346 struct mbuf *m; 1347 struct tcphdr *th = NULL; 1348 int optlen, error = 0; /* Make compiler happy */ 1349 u_int16_t hlen, tlen, mssopt; 1350 struct tcpopt to; 1351#ifdef INET6 1352 struct ip6_hdr *ip6 = NULL; 1353#endif 1354 1355 hlen = 1356#ifdef INET6 1357 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1358#endif 1359 sizeof(struct ip); 1360 tlen = hlen + sizeof(struct tcphdr); 1361 1362 /* Determine MSS we advertize to other end of connection. */ 1363 mssopt = tcp_mssopt(&sc->sc_inc); 1364 if (sc->sc_peer_mss) 1365 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1366 1367 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1368 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1369 ("syncache: mbuf too small")); 1370 1371 /* Create the IP+TCP header from scratch. */ 1372 m = m_gethdr(M_DONTWAIT, MT_DATA); 1373 if (m == NULL) 1374 return (ENOBUFS); 1375#ifdef MAC 1376 mac_syncache_create_mbuf(sc->sc_label, m); 1377#endif 1378 m->m_data += max_linkhdr; 1379 m->m_len = tlen; 1380 m->m_pkthdr.len = tlen; 1381 m->m_pkthdr.rcvif = NULL; 1382 1383#ifdef INET6 1384 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1385 ip6 = mtod(m, struct ip6_hdr *); 1386 ip6->ip6_vfc = IPV6_VERSION; 1387 ip6->ip6_nxt = IPPROTO_TCP; 1388 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1389 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1390 ip6->ip6_plen = htons(tlen - hlen); 1391 /* ip6_hlim is set after checksum */ 1392 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1393 ip6->ip6_flow |= sc->sc_flowlabel; 1394 1395 th = (struct tcphdr *)(ip6 + 1); 1396 } 1397#endif 1398#if defined(INET6) && defined(INET) 1399 else 1400#endif 1401#ifdef INET 1402 { 1403 ip = mtod(m, struct ip *); 1404 ip->ip_v = IPVERSION; 1405 ip->ip_hl = sizeof(struct ip) >> 2; 1406 ip->ip_len = tlen; 1407 ip->ip_id = 0; 1408 ip->ip_off = 0; 1409 ip->ip_sum = 0; 1410 ip->ip_p = IPPROTO_TCP; 1411 ip->ip_src = sc->sc_inc.inc_laddr; 1412 ip->ip_dst = sc->sc_inc.inc_faddr; 1413 ip->ip_ttl = sc->sc_ip_ttl; 1414 ip->ip_tos = sc->sc_ip_tos; 1415 1416 /* 1417 * See if we should do MTU discovery. Route lookups are 1418 * expensive, so we will only unset the DF bit if: 1419 * 1420 * 1) path_mtu_discovery is disabled 1421 * 2) the SCF_UNREACH flag has been set 1422 */ 1423 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1424 ip->ip_off |= IP_DF; 1425 1426 th = (struct tcphdr *)(ip + 1); 1427 } 1428#endif /* INET */ 1429 th->th_sport = sc->sc_inc.inc_lport; 1430 th->th_dport = sc->sc_inc.inc_fport; 1431 1432 th->th_seq = htonl(sc->sc_iss); 1433 th->th_ack = htonl(sc->sc_irs + 1); 1434 th->th_off = sizeof(struct tcphdr) >> 2; 1435 th->th_x2 = 0; 1436 th->th_flags = TH_SYN|TH_ACK; 1437 th->th_win = htons(sc->sc_wnd); 1438 th->th_urp = 0; 1439 1440 if (sc->sc_flags & SCF_ECN) { 1441 th->th_flags |= TH_ECE; 1442 TCPSTAT_INC(tcps_ecn_shs); 1443 } 1444 1445 /* Tack on the TCP options. */ 1446 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1447 to.to_flags = 0; 1448 1449 to.to_mss = mssopt; 1450 to.to_flags = TOF_MSS; 1451 if (sc->sc_flags & SCF_WINSCALE) { 1452 to.to_wscale = sc->sc_requested_r_scale; 1453 to.to_flags |= TOF_SCALE; 1454 } 1455 if (sc->sc_flags & SCF_TIMESTAMP) { 1456 /* Virgin timestamp or TCP cookie enhanced one. */ 1457 to.to_tsval = sc->sc_ts; 1458 to.to_tsecr = sc->sc_tsreflect; 1459 to.to_flags |= TOF_TS; 1460 } 1461 if (sc->sc_flags & SCF_SACK) 1462 to.to_flags |= TOF_SACKPERM; 1463#ifdef TCP_SIGNATURE 1464 if (sc->sc_flags & SCF_SIGNATURE) 1465 to.to_flags |= TOF_SIGNATURE; 1466#endif 1467 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1468 1469 /* Adjust headers by option size. */ 1470 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1471 m->m_len += optlen; 1472 m->m_pkthdr.len += optlen; 1473 1474#ifdef TCP_SIGNATURE 1475 if (sc->sc_flags & SCF_SIGNATURE) 1476 tcp_signature_compute(m, 0, 0, optlen, 1477 to.to_signature, IPSEC_DIR_OUTBOUND); 1478#endif 1479#ifdef INET6 1480 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1481 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1482 else 1483#endif 1484 ip->ip_len += optlen; 1485 } else 1486 optlen = 0; 1487 1488 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1489 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1490#ifdef INET6 1491 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1492 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1493 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen, 1494 IPPROTO_TCP, 0); 1495 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1496#ifdef TCP_OFFLOAD 1497 if (ADDED_BY_TOE(sc)) { 1498 struct toedev *tod = sc->sc_tod; 1499 1500 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1501 1502 return (error); 1503 } 1504#endif 1505 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1506 } 1507#endif 1508#if defined(INET6) && defined(INET) 1509 else 1510#endif 1511#ifdef INET 1512 { 1513 m->m_pkthdr.csum_flags = CSUM_TCP; 1514 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1515 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1516#ifdef TCP_OFFLOAD 1517 if (ADDED_BY_TOE(sc)) { 1518 struct toedev *tod = sc->sc_tod; 1519 1520 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m); 1521 1522 return (error); 1523 } 1524#endif 1525 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1526 } 1527#endif 1528 return (error); 1529} 1530 1531void 1532syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1533 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1534{ 1535 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1536} 1537 1538void 1539tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1540 struct inpcb *inp, struct socket **lsop, void *tod, void *todctx) 1541{ 1542 1543 _syncache_add(inc, to, th, inp, lsop, NULL, tod, todctx); 1544} 1545/* 1546 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1547 * receive and to be able to handle SYN floods from bogus source addresses 1548 * (where we will never receive any reply). SYN floods try to exhaust all 1549 * our memory and available slots in the SYN cache table to cause a denial 1550 * of service to legitimate users of the local host. 1551 * 1552 * The idea of SYN cookies is to encode and include all necessary information 1553 * about the connection setup state within the SYN-ACK we send back and thus 1554 * to get along without keeping any local state until the ACK to the SYN-ACK 1555 * arrives (if ever). Everything we need to know should be available from 1556 * the information we encoded in the SYN-ACK. 1557 * 1558 * More information about the theory behind SYN cookies and its first 1559 * discussion and specification can be found at: 1560 * http://cr.yp.to/syncookies.html (overview) 1561 * http://cr.yp.to/syncookies/archive (gory details) 1562 * 1563 * This implementation extends the orginal idea and first implementation 1564 * of FreeBSD by using not only the initial sequence number field to store 1565 * information but also the timestamp field if present. This way we can 1566 * keep track of the entire state we need to know to recreate the session in 1567 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1568 * these days. For those that do not we still have to live with the known 1569 * shortcomings of the ISN only SYN cookies. 1570 * 1571 * Cookie layers: 1572 * 1573 * Initial sequence number we send: 1574 * 31|................................|0 1575 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1576 * D = MD5 Digest (first dword) 1577 * M = MSS index 1578 * R = Rotation of secret 1579 * P = Odd or Even secret 1580 * 1581 * The MD5 Digest is computed with over following parameters: 1582 * a) randomly rotated secret 1583 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1584 * c) the received initial sequence number from remote host 1585 * d) the rotation offset and odd/even bit 1586 * 1587 * Timestamp we send: 1588 * 31|................................|0 1589 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1590 * D = MD5 Digest (third dword) (only as filler) 1591 * S = Requested send window scale 1592 * R = Requested receive window scale 1593 * A = SACK allowed 1594 * 5 = TCP-MD5 enabled (not implemented yet) 1595 * XORed with MD5 Digest (forth dword) 1596 * 1597 * The timestamp isn't cryptographically secure and doesn't need to be. 1598 * The double use of the MD5 digest dwords ties it to a specific remote/ 1599 * local host/port, remote initial sequence number and our local time 1600 * limited secret. A received timestamp is reverted (XORed) and then 1601 * the contained MD5 dword is compared to the computed one to ensure the 1602 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1603 * have been tampered with but this isn't different from supplying bogus 1604 * values in the SYN in the first place. 1605 * 1606 * Some problems with SYN cookies remain however: 1607 * Consider the problem of a recreated (and retransmitted) cookie. If the 1608 * original SYN was accepted, the connection is established. The second 1609 * SYN is inflight, and if it arrives with an ISN that falls within the 1610 * receive window, the connection is killed. 1611 * 1612 * Notes: 1613 * A heuristic to determine when to accept syn cookies is not necessary. 1614 * An ACK flood would cause the syncookie verification to be attempted, 1615 * but a SYN flood causes syncookies to be generated. Both are of equal 1616 * cost, so there's no point in trying to optimize the ACK flood case. 1617 * Also, if you don't process certain ACKs for some reason, then all someone 1618 * would have to do is launch a SYN and ACK flood at the same time, which 1619 * would stop cookie verification and defeat the entire purpose of syncookies. 1620 */ 1621static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1622 1623static void 1624syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1625 u_int32_t *flowlabel) 1626{ 1627 MD5_CTX ctx; 1628 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1629 u_int32_t data; 1630 u_int32_t *secbits; 1631 u_int off, pmss, mss; 1632 int i; 1633 1634 SCH_LOCK_ASSERT(sch); 1635 1636 /* Which of the two secrets to use. */ 1637 secbits = sch->sch_oddeven ? 1638 sch->sch_secbits_odd : sch->sch_secbits_even; 1639 1640 /* Reseed secret if too old. */ 1641 if (sch->sch_reseed < time_uptime) { 1642 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1643 secbits = sch->sch_oddeven ? 1644 sch->sch_secbits_odd : sch->sch_secbits_even; 1645 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1646 secbits[i] = arc4random(); 1647 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1648 } 1649 1650 /* Secret rotation offset. */ 1651 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1652 1653 /* Maximum segment size calculation. */ 1654 pmss = 1655 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1656 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1657 if (tcp_sc_msstab[mss] <= pmss) 1658 break; 1659 1660 /* Fold parameters and MD5 digest into the ISN we will send. */ 1661 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1662 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1663 data |= mss << 4; /* mss, 3 bits */ 1664 1665 MD5Init(&ctx); 1666 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1667 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1668 MD5Update(&ctx, secbits, off); 1669 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1670 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1671 MD5Update(&ctx, &data, sizeof(data)); 1672 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1673 1674 data |= (md5_buffer[0] << 7); 1675 sc->sc_iss = data; 1676 1677#ifdef INET6 1678 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1679#endif 1680 1681 /* Additional parameters are stored in the timestamp if present. */ 1682 if (sc->sc_flags & SCF_TIMESTAMP) { 1683 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1684 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1685 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1686 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1687 data |= md5_buffer[2] << 10; /* more digest bits */ 1688 data ^= md5_buffer[3]; 1689 sc->sc_ts = data; 1690 sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */ 1691 } 1692 1693 TCPSTAT_INC(tcps_sc_sendcookie); 1694} 1695 1696static struct syncache * 1697syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1698 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1699 struct socket *so) 1700{ 1701 MD5_CTX ctx; 1702 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1703 u_int32_t data = 0; 1704 u_int32_t *secbits; 1705 tcp_seq ack, seq; 1706 int off, mss, wnd, flags; 1707 1708 SCH_LOCK_ASSERT(sch); 1709 1710 /* 1711 * Pull information out of SYN-ACK/ACK and 1712 * revert sequence number advances. 1713 */ 1714 ack = th->th_ack - 1; 1715 seq = th->th_seq - 1; 1716 off = (ack >> 1) & 0x7; 1717 mss = (ack >> 4) & 0x7; 1718 flags = ack & 0x7f; 1719 1720 /* Which of the two secrets to use. */ 1721 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1722 1723 /* 1724 * The secret wasn't updated for the lifetime of a syncookie, 1725 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1726 */ 1727 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1728 return (NULL); 1729 } 1730 1731 /* Recompute the digest so we can compare it. */ 1732 MD5Init(&ctx); 1733 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1734 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1735 MD5Update(&ctx, secbits, off); 1736 MD5Update(&ctx, inc, sizeof(*inc)); 1737 MD5Update(&ctx, &seq, sizeof(seq)); 1738 MD5Update(&ctx, &flags, sizeof(flags)); 1739 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1740 1741 /* Does the digest part of or ACK'ed ISS match? */ 1742 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1743 return (NULL); 1744 1745 /* Does the digest part of our reflected timestamp match? */ 1746 if (to->to_flags & TOF_TS) { 1747 data = md5_buffer[3] ^ to->to_tsecr; 1748 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1749 return (NULL); 1750 } 1751 1752 /* Fill in the syncache values. */ 1753 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1754 sc->sc_ipopts = NULL; 1755 1756 sc->sc_irs = seq; 1757 sc->sc_iss = ack; 1758 1759#ifdef INET6 1760 if (inc->inc_flags & INC_ISIPV6) { 1761 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1762 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1763 } else 1764#endif 1765 { 1766 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1767 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1768 } 1769 1770 /* Additional parameters that were encoded in the timestamp. */ 1771 if (data) { 1772 sc->sc_flags |= SCF_TIMESTAMP; 1773 sc->sc_tsreflect = to->to_tsval; 1774 sc->sc_ts = to->to_tsecr; 1775 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks(); 1776 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1777 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1778 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1779 TCP_MAX_WINSHIFT); 1780 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1781 TCP_MAX_WINSHIFT); 1782 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1783 sc->sc_flags |= SCF_WINSCALE; 1784 } else 1785 sc->sc_flags |= SCF_NOOPT; 1786 1787 wnd = sbspace(&so->so_rcv); 1788 wnd = imax(wnd, 0); 1789 wnd = imin(wnd, TCP_MAXWIN); 1790 sc->sc_wnd = wnd; 1791 1792 sc->sc_rxmits = 0; 1793 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1794 1795 TCPSTAT_INC(tcps_sc_recvcookie); 1796 return (sc); 1797} 1798 1799/* 1800 * Returns the current number of syncache entries. This number 1801 * will probably change before you get around to calling 1802 * syncache_pcblist. 1803 */ 1804 1805int 1806syncache_pcbcount(void) 1807{ 1808 struct syncache_head *sch; 1809 int count, i; 1810 1811 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1812 /* No need to lock for a read. */ 1813 sch = &V_tcp_syncache.hashbase[i]; 1814 count += sch->sch_length; 1815 } 1816 return count; 1817} 1818 1819/* 1820 * Exports the syncache entries to userland so that netstat can display 1821 * them alongside the other sockets. This function is intended to be 1822 * called only from tcp_pcblist. 1823 * 1824 * Due to concurrency on an active system, the number of pcbs exported 1825 * may have no relation to max_pcbs. max_pcbs merely indicates the 1826 * amount of space the caller allocated for this function to use. 1827 */ 1828int 1829syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1830{ 1831 struct xtcpcb xt; 1832 struct syncache *sc; 1833 struct syncache_head *sch; 1834 int count, error, i; 1835 1836 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1837 sch = &V_tcp_syncache.hashbase[i]; 1838 SCH_LOCK(sch); 1839 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1840 if (count >= max_pcbs) { 1841 SCH_UNLOCK(sch); 1842 goto exit; 1843 } 1844 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1845 continue; 1846 bzero(&xt, sizeof(xt)); 1847 xt.xt_len = sizeof(xt); 1848 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1849 xt.xt_inp.inp_vflag = INP_IPV6; 1850 else 1851 xt.xt_inp.inp_vflag = INP_IPV4; 1852 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1853 xt.xt_tp.t_inpcb = &xt.xt_inp; 1854 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1855 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1856 xt.xt_socket.xso_len = sizeof (struct xsocket); 1857 xt.xt_socket.so_type = SOCK_STREAM; 1858 xt.xt_socket.so_state = SS_ISCONNECTING; 1859 error = SYSCTL_OUT(req, &xt, sizeof xt); 1860 if (error) { 1861 SCH_UNLOCK(sch); 1862 goto exit; 1863 } 1864 count++; 1865 } 1866 SCH_UNLOCK(sch); 1867 } 1868exit: 1869 *pcbs_exported = count; 1870 return error; 1871} 1872