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 #include <netinet/tcp_offload.h> 85 #ifdef INET6 86 #include <netinet6/tcp6_var.h> 87 #endif 88 89 #ifdef IPSEC 90 #include <netipsec/ipsec.h> 91 #ifdef INET6 92 #include <netipsec/ipsec6.h> 93 #endif 94 #include <netipsec/key.h> 95 #endif /*IPSEC*/ 96 97 #include <machine/in_cksum.h> 98 99 #include <security/mac/mac_framework.h> 100 101 static VNET_DEFINE(int, tcp_syncookies) = 1; 102 #define V_tcp_syncookies VNET(tcp_syncookies) 103 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 104 &VNET_NAME(tcp_syncookies), 0, 105 "Use TCP SYN cookies if the syncache overflows"); 106 107 static VNET_DEFINE(int, tcp_syncookiesonly) = 0; 108 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly) 109 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 110 &VNET_NAME(tcp_syncookiesonly), 0, 111 "Use only TCP SYN cookies"); 112 113 #ifdef TCP_OFFLOAD_DISABLE 114 #define TOEPCB_ISSET(sc) (0) 115 #else 116 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 117 #endif 118 119 static void syncache_drop(struct syncache *, struct syncache_head *); 120 static void syncache_free(struct syncache *); 121 static void syncache_insert(struct syncache *, struct syncache_head *); 122 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 123 static int syncache_respond(struct syncache *); 124 static struct socket *syncache_socket(struct syncache *, struct socket *, 125 struct mbuf *m); 126 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 127 int docallout); 128 static void syncache_timer(void *); 129 static void syncookie_generate(struct syncache_head *, struct syncache *, 130 u_int32_t *); 131 static struct syncache 132 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 133 struct syncache *, struct tcpopt *, struct tcphdr *, 134 struct socket *); 135 136 /* 137 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 138 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 139 * the odds are that the user has given up attempting to connect by then. 140 */ 141 #define SYNCACHE_MAXREXMTS 3 142 143 /* Arbitrary values */ 144 #define TCP_SYNCACHE_HASHSIZE 512 145 #define TCP_SYNCACHE_BUCKETLIMIT 30 146 147 static VNET_DEFINE(struct tcp_syncache, tcp_syncache); 148 #define V_tcp_syncache VNET(tcp_syncache) 149 150 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 151 152 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 153 &VNET_NAME(tcp_syncache.bucket_limit), 0, 154 "Per-bucket hash limit for syncache"); 155 156 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 157 &VNET_NAME(tcp_syncache.cache_limit), 0, 158 "Overall entry limit for syncache"); 159 160 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 161 &VNET_NAME(tcp_syncache.cache_count), 0, 162 "Current number of entries in syncache"); 163 164 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 165 &VNET_NAME(tcp_syncache.hashsize), 0, 166 "Size of TCP syncache hashtable"); 167 168 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 169 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 170 "Limit on SYN/ACK retransmissions"); 171 172 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 173 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 174 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 175 "Send reset on socket allocation failure"); 176 177 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 178 179 #define SYNCACHE_HASH(inc, mask) \ 180 ((V_tcp_syncache.hash_secret ^ \ 181 (inc)->inc_faddr.s_addr ^ \ 182 ((inc)->inc_faddr.s_addr >> 16) ^ \ 183 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 184 185 #define SYNCACHE_HASH6(inc, mask) \ 186 ((V_tcp_syncache.hash_secret ^ \ 187 (inc)->inc6_faddr.s6_addr32[0] ^ \ 188 (inc)->inc6_faddr.s6_addr32[3] ^ \ 189 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 190 191 #define ENDPTS_EQ(a, b) ( \ 192 (a)->ie_fport == (b)->ie_fport && \ 193 (a)->ie_lport == (b)->ie_lport && \ 194 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 195 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 196 ) 197 198 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 199 200 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 201 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 202 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 203 204 /* 205 * Requires the syncache entry to be already removed from the bucket list. 206 */ 207 static void 208 syncache_free(struct syncache *sc) 209 { 210 211 if (sc->sc_ipopts) 212 (void) m_free(sc->sc_ipopts); 213 if (sc->sc_cred) 214 crfree(sc->sc_cred); 215 #ifdef MAC 216 mac_syncache_destroy(&sc->sc_label); 217 #endif 218 219 uma_zfree(V_tcp_syncache.zone, sc); 220 } 221 222 void 223 syncache_init(void) 224 { 225 int i; 226 227 V_tcp_syncache.cache_count = 0; 228 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 229 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 230 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 231 V_tcp_syncache.hash_secret = arc4random(); 232 233 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 234 &V_tcp_syncache.hashsize); 235 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 236 &V_tcp_syncache.bucket_limit); 237 if (!powerof2(V_tcp_syncache.hashsize) || 238 V_tcp_syncache.hashsize == 0) { 239 printf("WARNING: syncache hash size is not a power of 2.\n"); 240 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 241 } 242 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 243 244 /* Set limits. */ 245 V_tcp_syncache.cache_limit = 246 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 247 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 248 &V_tcp_syncache.cache_limit); 249 250 /* Allocate the hash table. */ 251 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 252 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 253 254 /* Initialize the hash buckets. */ 255 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 256 #ifdef VIMAGE 257 V_tcp_syncache.hashbase[i].sch_vnet = curvnet; 258 #endif 259 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 260 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 261 NULL, MTX_DEF); 262 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 263 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 264 V_tcp_syncache.hashbase[i].sch_length = 0; 265 } 266 267 /* Create the syncache entry zone. */ 268 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 269 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 270 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 271 } 272 273 #ifdef VIMAGE 274 void 275 syncache_destroy(void) 276 { 277 struct syncache_head *sch; 278 struct syncache *sc, *nsc; 279 int i; 280 281 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 282 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 283 284 sch = &V_tcp_syncache.hashbase[i]; 285 callout_drain(&sch->sch_timer); 286 287 SCH_LOCK(sch); 288 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 289 syncache_drop(sc, sch); 290 SCH_UNLOCK(sch); 291 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 292 ("%s: sch->sch_bucket not empty", __func__)); 293 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 294 __func__, sch->sch_length)); 295 mtx_destroy(&sch->sch_mtx); 296 } 297 298 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0", 299 __func__, V_tcp_syncache.cache_count)); 300 301 /* Free the allocated global resources. */ 302 uma_zdestroy(V_tcp_syncache.zone); 303 free(V_tcp_syncache.hashbase, M_SYNCACHE); 304 } 305 #endif 306 307 /* 308 * Inserts a syncache entry into the specified bucket row. 309 * Locks and unlocks the syncache_head autonomously. 310 */ 311 static void 312 syncache_insert(struct syncache *sc, struct syncache_head *sch) 313 { 314 struct syncache *sc2; 315 316 SCH_LOCK(sch); 317 318 /* 319 * Make sure that we don't overflow the per-bucket limit. 320 * If the bucket is full, toss the oldest element. 321 */ 322 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 323 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 324 ("sch->sch_length incorrect")); 325 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 326 syncache_drop(sc2, sch); 327 TCPSTAT_INC(tcps_sc_bucketoverflow); 328 } 329 330 /* Put it into the bucket. */ 331 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 332 sch->sch_length++; 333 334 /* Reinitialize the bucket row's timer. */ 335 if (sch->sch_length == 1) 336 sch->sch_nextc = ticks + INT_MAX; 337 syncache_timeout(sc, sch, 1); 338 339 SCH_UNLOCK(sch); 340 341 V_tcp_syncache.cache_count++; 342 TCPSTAT_INC(tcps_sc_added); 343 } 344 345 /* 346 * Remove and free entry from syncache bucket row. 347 * Expects locked syncache head. 348 */ 349 static void 350 syncache_drop(struct syncache *sc, struct syncache_head *sch) 351 { 352 353 SCH_LOCK_ASSERT(sch); 354 355 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 356 sch->sch_length--; 357 358 #ifndef TCP_OFFLOAD_DISABLE 359 if (sc->sc_tu) 360 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 361 #endif 362 syncache_free(sc); 363 V_tcp_syncache.cache_count--; 364 } 365 366 /* 367 * Engage/reengage time on bucket row. 368 */ 369 static void 370 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 371 { 372 sc->sc_rxttime = ticks + 373 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 374 sc->sc_rxmits++; 375 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 376 sch->sch_nextc = sc->sc_rxttime; 377 if (docallout) 378 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 379 syncache_timer, (void *)sch); 380 } 381 } 382 383 /* 384 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 385 * If we have retransmitted an entry the maximum number of times, expire it. 386 * One separate timer for each bucket row. 387 */ 388 static void 389 syncache_timer(void *xsch) 390 { 391 struct syncache_head *sch = (struct syncache_head *)xsch; 392 struct syncache *sc, *nsc; 393 int tick = ticks; 394 char *s; 395 396 CURVNET_SET(sch->sch_vnet); 397 398 /* NB: syncache_head has already been locked by the callout. */ 399 SCH_LOCK_ASSERT(sch); 400 401 /* 402 * In the following cycle we may remove some entries and/or 403 * advance some timeouts, so re-initialize the bucket timer. 404 */ 405 sch->sch_nextc = tick + INT_MAX; 406 407 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 408 /* 409 * We do not check if the listen socket still exists 410 * and accept the case where the listen socket may be 411 * gone by the time we resend the SYN/ACK. We do 412 * not expect this to happens often. If it does, 413 * then the RST will be sent by the time the remote 414 * host does the SYN/ACK->ACK. 415 */ 416 if (TSTMP_GT(sc->sc_rxttime, tick)) { 417 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 418 sch->sch_nextc = sc->sc_rxttime; 419 continue; 420 } 421 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 422 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 423 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 424 "giving up and removing syncache entry\n", 425 s, __func__); 426 free(s, M_TCPLOG); 427 } 428 syncache_drop(sc, sch); 429 TCPSTAT_INC(tcps_sc_stale); 430 continue; 431 } 432 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 433 log(LOG_DEBUG, "%s; %s: Response timeout, " 434 "retransmitting (%u) SYN|ACK\n", 435 s, __func__, sc->sc_rxmits); 436 free(s, M_TCPLOG); 437 } 438 439 (void) syncache_respond(sc); 440 TCPSTAT_INC(tcps_sc_retransmitted); 441 syncache_timeout(sc, sch, 0); 442 } 443 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 444 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 445 syncache_timer, (void *)(sch)); 446 CURVNET_RESTORE(); 447 } 448 449 /* 450 * Find an entry in the syncache. 451 * Returns always with locked syncache_head plus a matching entry or NULL. 452 */ 453 struct syncache * 454 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 455 { 456 struct syncache *sc; 457 struct syncache_head *sch; 458 459 #ifdef INET6 460 if (inc->inc_flags & INC_ISIPV6) { 461 sch = &V_tcp_syncache.hashbase[ 462 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 463 *schp = sch; 464 465 SCH_LOCK(sch); 466 467 /* Circle through bucket row to find matching entry. */ 468 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 469 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 470 return (sc); 471 } 472 } else 473 #endif 474 { 475 sch = &V_tcp_syncache.hashbase[ 476 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 477 *schp = sch; 478 479 SCH_LOCK(sch); 480 481 /* Circle through bucket row to find matching entry. */ 482 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 483 #ifdef INET6 484 if (sc->sc_inc.inc_flags & INC_ISIPV6) 485 continue; 486 #endif 487 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 488 return (sc); 489 } 490 } 491 SCH_LOCK_ASSERT(*schp); 492 return (NULL); /* always returns with locked sch */ 493 } 494 495 /* 496 * This function is called when we get a RST for a 497 * non-existent connection, so that we can see if the 498 * connection is in the syn cache. If it is, zap it. 499 */ 500 void 501 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 502 { 503 struct syncache *sc; 504 struct syncache_head *sch; 505 char *s = NULL; 506 507 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 508 SCH_LOCK_ASSERT(sch); 509 510 /* 511 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 512 * See RFC 793 page 65, section SEGMENT ARRIVES. 513 */ 514 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 515 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 516 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 517 "FIN flag set, segment ignored\n", s, __func__); 518 TCPSTAT_INC(tcps_badrst); 519 goto done; 520 } 521 522 /* 523 * No corresponding connection was found in syncache. 524 * If syncookies are enabled and possibly exclusively 525 * used, or we are under memory pressure, a valid RST 526 * may not find a syncache entry. In that case we're 527 * done and no SYN|ACK retransmissions will happen. 528 * Otherwise the RST was misdirected or spoofed. 529 */ 530 if (sc == NULL) { 531 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 532 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 533 "syncache entry (possibly syncookie only), " 534 "segment ignored\n", s, __func__); 535 TCPSTAT_INC(tcps_badrst); 536 goto done; 537 } 538 539 /* 540 * If the RST bit is set, check the sequence number to see 541 * if this is a valid reset segment. 542 * RFC 793 page 37: 543 * In all states except SYN-SENT, all reset (RST) segments 544 * are validated by checking their SEQ-fields. A reset is 545 * valid if its sequence number is in the window. 546 * 547 * The sequence number in the reset segment is normally an 548 * echo of our outgoing acknowlegement numbers, but some hosts 549 * send a reset with the sequence number at the rightmost edge 550 * of our receive window, and we have to handle this case. 551 */ 552 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 553 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 554 syncache_drop(sc, sch); 555 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 556 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 557 "connection attempt aborted by remote endpoint\n", 558 s, __func__); 559 TCPSTAT_INC(tcps_sc_reset); 560 } else { 561 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 562 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 563 "IRS %u (+WND %u), segment ignored\n", 564 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 565 TCPSTAT_INC(tcps_badrst); 566 } 567 568 done: 569 if (s != NULL) 570 free(s, M_TCPLOG); 571 SCH_UNLOCK(sch); 572 } 573 574 void 575 syncache_badack(struct in_conninfo *inc) 576 { 577 struct syncache *sc; 578 struct syncache_head *sch; 579 580 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 581 SCH_LOCK_ASSERT(sch); 582 if (sc != NULL) { 583 syncache_drop(sc, sch); 584 TCPSTAT_INC(tcps_sc_badack); 585 } 586 SCH_UNLOCK(sch); 587 } 588 589 void 590 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 591 { 592 struct syncache *sc; 593 struct syncache_head *sch; 594 595 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 596 SCH_LOCK_ASSERT(sch); 597 if (sc == NULL) 598 goto done; 599 600 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 601 if (ntohl(th->th_seq) != sc->sc_iss) 602 goto done; 603 604 /* 605 * If we've rertransmitted 3 times and this is our second error, 606 * we remove the entry. Otherwise, we allow it to continue on. 607 * This prevents us from incorrectly nuking an entry during a 608 * spurious network outage. 609 * 610 * See tcp_notify(). 611 */ 612 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 613 sc->sc_flags |= SCF_UNREACH; 614 goto done; 615 } 616 syncache_drop(sc, sch); 617 TCPSTAT_INC(tcps_sc_unreach); 618 done: 619 SCH_UNLOCK(sch); 620 } 621 622 /* 623 * Build a new TCP socket structure from a syncache entry. 624 */ 625 static struct socket * 626 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 627 { 628 struct inpcb *inp = NULL; 629 struct socket *so; 630 struct tcpcb *tp; 631 int error; 632 char *s; 633 634 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 635 636 /* 637 * Ok, create the full blown connection, and set things up 638 * as they would have been set up if we had created the 639 * connection when the SYN arrived. If we can't create 640 * the connection, abort it. 641 */ 642 so = sonewconn(lso, SS_ISCONNECTED); 643 if (so == NULL) { 644 /* 645 * Drop the connection; we will either send a RST or 646 * have the peer retransmit its SYN again after its 647 * RTO and try again. 648 */ 649 TCPSTAT_INC(tcps_listendrop); 650 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 651 log(LOG_DEBUG, "%s; %s: Socket create failed " 652 "due to limits or memory shortage\n", 653 s, __func__); 654 free(s, M_TCPLOG); 655 } 656 goto abort2; 657 } 658 #ifdef MAC 659 mac_socketpeer_set_from_mbuf(m, so); 660 #endif 661 662 inp = sotoinpcb(so); 663 inp->inp_inc.inc_fibnum = so->so_fibnum; 664 INP_WLOCK(inp); 665 INP_HASH_WLOCK(&V_tcbinfo); 666 667 /* Insert new socket into PCB hash list. */ 668 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 669 #ifdef INET6 670 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 671 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 672 } else { 673 inp->inp_vflag &= ~INP_IPV6; 674 inp->inp_vflag |= INP_IPV4; 675 #endif 676 inp->inp_laddr = sc->sc_inc.inc_laddr; 677 #ifdef INET6 678 } 679 #endif 680 681 /* 682 * Install in the reservation hash table for now, but don't yet 683 * install a connection group since the full 4-tuple isn't yet 684 * configured. 685 */ 686 inp->inp_lport = sc->sc_inc.inc_lport; 687 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 688 /* 689 * Undo the assignments above if we failed to 690 * put the PCB on the hash lists. 691 */ 692 #ifdef INET6 693 if (sc->sc_inc.inc_flags & INC_ISIPV6) 694 inp->in6p_laddr = in6addr_any; 695 else 696 #endif 697 inp->inp_laddr.s_addr = INADDR_ANY; 698 inp->inp_lport = 0; 699 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 700 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 701 "with error %i\n", 702 s, __func__, error); 703 free(s, M_TCPLOG); 704 } 705 INP_HASH_WUNLOCK(&V_tcbinfo); 706 goto abort; 707 } 708 #ifdef IPSEC 709 /* Copy old policy into new socket's. */ 710 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 711 printf("syncache_socket: could not copy policy\n"); 712 #endif 713 #ifdef INET6 714 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 715 struct inpcb *oinp = sotoinpcb(lso); 716 struct in6_addr laddr6; 717 struct sockaddr_in6 sin6; 718 /* 719 * Inherit socket options from the listening socket. 720 * Note that in6p_inputopts are not (and should not be) 721 * copied, since it stores previously received options and is 722 * used to detect if each new option is different than the 723 * previous one and hence should be passed to a user. 724 * If we copied in6p_inputopts, a user would not be able to 725 * receive options just after calling the accept system call. 726 */ 727 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 728 if (oinp->in6p_outputopts) 729 inp->in6p_outputopts = 730 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 731 732 sin6.sin6_family = AF_INET6; 733 sin6.sin6_len = sizeof(sin6); 734 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 735 sin6.sin6_port = sc->sc_inc.inc_fport; 736 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 737 laddr6 = inp->in6p_laddr; 738 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 739 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 740 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 741 thread0.td_ucred, m)) != 0) { 742 inp->in6p_laddr = laddr6; 743 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 744 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 745 "with error %i\n", 746 s, __func__, error); 747 free(s, M_TCPLOG); 748 } 749 INP_HASH_WUNLOCK(&V_tcbinfo); 750 goto abort; 751 } 752 /* Override flowlabel from in6_pcbconnect. */ 753 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 754 inp->inp_flow |= sc->sc_flowlabel; 755 } 756 #endif /* INET6 */ 757 #if defined(INET) && defined(INET6) 758 else 759 #endif 760 #ifdef INET 761 { 762 struct in_addr laddr; 763 struct sockaddr_in sin; 764 765 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 766 767 if (inp->inp_options == NULL) { 768 inp->inp_options = sc->sc_ipopts; 769 sc->sc_ipopts = NULL; 770 } 771 772 sin.sin_family = AF_INET; 773 sin.sin_len = sizeof(sin); 774 sin.sin_addr = sc->sc_inc.inc_faddr; 775 sin.sin_port = sc->sc_inc.inc_fport; 776 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 777 laddr = inp->inp_laddr; 778 if (inp->inp_laddr.s_addr == INADDR_ANY) 779 inp->inp_laddr = sc->sc_inc.inc_laddr; 780 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 781 thread0.td_ucred, m)) != 0) { 782 inp->inp_laddr = laddr; 783 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 784 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 785 "with error %i\n", 786 s, __func__, error); 787 free(s, M_TCPLOG); 788 } 789 INP_HASH_WUNLOCK(&V_tcbinfo); 790 goto abort; 791 } 792 } 793 #endif /* INET */ 794 INP_HASH_WUNLOCK(&V_tcbinfo); 795 tp = intotcpcb(inp); 796 tp->t_state = TCPS_SYN_RECEIVED; 797 tp->iss = sc->sc_iss; 798 tp->irs = sc->sc_irs; 799 tcp_rcvseqinit(tp); 800 tcp_sendseqinit(tp); 801 tp->snd_wl1 = sc->sc_irs; 802 tp->snd_max = tp->iss + 1; 803 tp->snd_nxt = tp->iss + 1; 804 tp->rcv_up = sc->sc_irs + 1; 805 tp->rcv_wnd = sc->sc_wnd; 806 tp->rcv_adv += tp->rcv_wnd; 807 tp->last_ack_sent = tp->rcv_nxt; 808 809 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 810 if (sc->sc_flags & SCF_NOOPT) 811 tp->t_flags |= TF_NOOPT; 812 else { 813 if (sc->sc_flags & SCF_WINSCALE) { 814 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 815 tp->snd_scale = sc->sc_requested_s_scale; 816 tp->request_r_scale = sc->sc_requested_r_scale; 817 } 818 if (sc->sc_flags & SCF_TIMESTAMP) { 819 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 820 tp->ts_recent = sc->sc_tsreflect; 821 tp->ts_recent_age = ticks; 822 tp->ts_offset = sc->sc_tsoff; 823 } 824 #ifdef TCP_SIGNATURE 825 if (sc->sc_flags & SCF_SIGNATURE) 826 tp->t_flags |= TF_SIGNATURE; 827 #endif 828 if (sc->sc_flags & SCF_SACK) 829 tp->t_flags |= TF_SACK_PERMIT; 830 } 831 832 if (sc->sc_flags & SCF_ECN) 833 tp->t_flags |= TF_ECN_PERMIT; 834 835 /* 836 * Set up MSS and get cached values from tcp_hostcache. 837 * This might overwrite some of the defaults we just set. 838 */ 839 tcp_mss(tp, sc->sc_peer_mss); 840 841 /* 842 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 843 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 844 */ 845 if (sc->sc_rxmits > 1) 846 tp->snd_cwnd = tp->t_maxseg; 847 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 848 849 INP_WUNLOCK(inp); 850 851 TCPSTAT_INC(tcps_accepts); 852 return (so); 853 854 abort: 855 INP_WUNLOCK(inp); 856 abort2: 857 if (so != NULL) 858 soabort(so); 859 return (NULL); 860 } 861 862 /* 863 * This function gets called when we receive an ACK for a 864 * socket in the LISTEN state. We look up the connection 865 * in the syncache, and if its there, we pull it out of 866 * the cache and turn it into a full-blown connection in 867 * the SYN-RECEIVED state. 868 */ 869 int 870 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 871 struct socket **lsop, struct mbuf *m) 872 { 873 struct syncache *sc; 874 struct syncache_head *sch; 875 struct syncache scs; 876 char *s; 877 878 /* 879 * Global TCP locks are held because we manipulate the PCB lists 880 * and create a new socket. 881 */ 882 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 883 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 884 ("%s: can handle only ACK", __func__)); 885 886 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 887 SCH_LOCK_ASSERT(sch); 888 if (sc == NULL) { 889 /* 890 * There is no syncache entry, so see if this ACK is 891 * a returning syncookie. To do this, first: 892 * A. See if this socket has had a syncache entry dropped in 893 * the past. We don't want to accept a bogus syncookie 894 * if we've never received a SYN. 895 * B. check that the syncookie is valid. If it is, then 896 * cobble up a fake syncache entry, and return. 897 */ 898 if (!V_tcp_syncookies) { 899 SCH_UNLOCK(sch); 900 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 901 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 902 "segment rejected (syncookies disabled)\n", 903 s, __func__); 904 goto failed; 905 } 906 bzero(&scs, sizeof(scs)); 907 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 908 SCH_UNLOCK(sch); 909 if (sc == NULL) { 910 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 911 log(LOG_DEBUG, "%s; %s: Segment failed " 912 "SYNCOOKIE authentication, segment rejected " 913 "(probably spoofed)\n", s, __func__); 914 goto failed; 915 } 916 } else { 917 /* Pull out the entry to unlock the bucket row. */ 918 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 919 sch->sch_length--; 920 V_tcp_syncache.cache_count--; 921 SCH_UNLOCK(sch); 922 } 923 924 /* 925 * Segment validation: 926 * ACK must match our initial sequence number + 1 (the SYN|ACK). 927 */ 928 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 929 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 930 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 931 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 932 goto failed; 933 } 934 935 /* 936 * The SEQ must fall in the window starting at the received 937 * initial receive sequence number + 1 (the SYN). 938 */ 939 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 940 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 941 !TOEPCB_ISSET(sc)) { 942 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 943 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 944 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 945 goto failed; 946 } 947 948 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 949 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 950 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 951 "segment rejected\n", s, __func__); 952 goto failed; 953 } 954 /* 955 * If timestamps were negotiated the reflected timestamp 956 * must be equal to what we actually sent in the SYN|ACK. 957 */ 958 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 959 !TOEPCB_ISSET(sc)) { 960 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 961 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 962 "segment rejected\n", 963 s, __func__, to->to_tsecr, sc->sc_ts); 964 goto failed; 965 } 966 967 *lsop = syncache_socket(sc, *lsop, m); 968 969 if (*lsop == NULL) 970 TCPSTAT_INC(tcps_sc_aborted); 971 else 972 TCPSTAT_INC(tcps_sc_completed); 973 974 /* how do we find the inp for the new socket? */ 975 if (sc != &scs) 976 syncache_free(sc); 977 return (1); 978 failed: 979 if (sc != NULL && sc != &scs) 980 syncache_free(sc); 981 if (s != NULL) 982 free(s, M_TCPLOG); 983 *lsop = NULL; 984 return (0); 985 } 986 987 int 988 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo, 989 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 990 { 991 struct tcpopt to; 992 int rc; 993 994 bzero(&to, sizeof(struct tcpopt)); 995 to.to_mss = toeo->to_mss; 996 to.to_wscale = toeo->to_wscale; 997 to.to_flags = toeo->to_flags; 998 999 INP_INFO_WLOCK(&V_tcbinfo); 1000 rc = syncache_expand(inc, &to, th, lsop, m); 1001 INP_INFO_WUNLOCK(&V_tcbinfo); 1002 1003 return (rc); 1004 } 1005 1006 /* 1007 * Given a LISTEN socket and an inbound SYN request, add 1008 * this to the syn cache, and send back a segment: 1009 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1010 * to the source. 1011 * 1012 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1013 * Doing so would require that we hold onto the data and deliver it 1014 * to the application. However, if we are the target of a SYN-flood 1015 * DoS attack, an attacker could send data which would eventually 1016 * consume all available buffer space if it were ACKed. By not ACKing 1017 * the data, we avoid this DoS scenario. 1018 */ 1019 static void 1020 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1021 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 1022 struct toe_usrreqs *tu, void *toepcb) 1023 { 1024 struct tcpcb *tp; 1025 struct socket *so; 1026 struct syncache *sc = NULL; 1027 struct syncache_head *sch; 1028 struct mbuf *ipopts = NULL; 1029 u_int32_t flowtmp; 1030 u_int ltflags; 1031 int win, sb_hiwat, ip_ttl, ip_tos; 1032 char *s; 1033 #ifdef INET6 1034 int autoflowlabel = 0; 1035 #endif 1036 #ifdef MAC 1037 struct label *maclabel; 1038 #endif 1039 struct syncache scs; 1040 struct ucred *cred; 1041 1042 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1043 INP_WLOCK_ASSERT(inp); /* listen socket */ 1044 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1045 ("%s: unexpected tcp flags", __func__)); 1046 1047 /* 1048 * Combine all so/tp operations very early to drop the INP lock as 1049 * soon as possible. 1050 */ 1051 so = *lsop; 1052 tp = sototcpcb(so); 1053 cred = crhold(so->so_cred); 1054 1055 #ifdef INET6 1056 if ((inc->inc_flags & INC_ISIPV6) && 1057 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1058 autoflowlabel = 1; 1059 #endif 1060 ip_ttl = inp->inp_ip_ttl; 1061 ip_tos = inp->inp_ip_tos; 1062 win = sbspace(&so->so_rcv); 1063 sb_hiwat = so->so_rcv.sb_hiwat; 1064 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1065 1066 /* By the time we drop the lock these should no longer be used. */ 1067 so = NULL; 1068 tp = NULL; 1069 1070 #ifdef MAC 1071 if (mac_syncache_init(&maclabel) != 0) { 1072 INP_WUNLOCK(inp); 1073 INP_INFO_WUNLOCK(&V_tcbinfo); 1074 goto done; 1075 } else 1076 mac_syncache_create(maclabel, inp); 1077 #endif 1078 INP_WUNLOCK(inp); 1079 INP_INFO_WUNLOCK(&V_tcbinfo); 1080 1081 /* 1082 * Remember the IP options, if any. 1083 */ 1084 #ifdef INET6 1085 if (!(inc->inc_flags & INC_ISIPV6)) 1086 #endif 1087 #ifdef INET 1088 ipopts = (m) ? ip_srcroute(m) : NULL; 1089 #else 1090 ipopts = NULL; 1091 #endif 1092 1093 /* 1094 * See if we already have an entry for this connection. 1095 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1096 * 1097 * XXX: should the syncache be re-initialized with the contents 1098 * of the new SYN here (which may have different options?) 1099 * 1100 * XXX: We do not check the sequence number to see if this is a 1101 * real retransmit or a new connection attempt. The question is 1102 * how to handle such a case; either ignore it as spoofed, or 1103 * drop the current entry and create a new one? 1104 */ 1105 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1106 SCH_LOCK_ASSERT(sch); 1107 if (sc != NULL) { 1108 #ifndef TCP_OFFLOAD_DISABLE 1109 if (sc->sc_tu) 1110 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1111 sc->sc_toepcb); 1112 #endif 1113 TCPSTAT_INC(tcps_sc_dupsyn); 1114 if (ipopts) { 1115 /* 1116 * If we were remembering a previous source route, 1117 * forget it and use the new one we've been given. 1118 */ 1119 if (sc->sc_ipopts) 1120 (void) m_free(sc->sc_ipopts); 1121 sc->sc_ipopts = ipopts; 1122 } 1123 /* 1124 * Update timestamp if present. 1125 */ 1126 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1127 sc->sc_tsreflect = to->to_tsval; 1128 else 1129 sc->sc_flags &= ~SCF_TIMESTAMP; 1130 #ifdef MAC 1131 /* 1132 * Since we have already unconditionally allocated label 1133 * storage, free it up. The syncache entry will already 1134 * have an initialized label we can use. 1135 */ 1136 mac_syncache_destroy(&maclabel); 1137 #endif 1138 /* Retransmit SYN|ACK and reset retransmit count. */ 1139 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1140 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1141 "resetting timer and retransmitting SYN|ACK\n", 1142 s, __func__); 1143 free(s, M_TCPLOG); 1144 } 1145 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1146 sc->sc_rxmits = 0; 1147 syncache_timeout(sc, sch, 1); 1148 TCPSTAT_INC(tcps_sndacks); 1149 TCPSTAT_INC(tcps_sndtotal); 1150 } 1151 SCH_UNLOCK(sch); 1152 goto done; 1153 } 1154 1155 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1156 if (sc == NULL) { 1157 /* 1158 * The zone allocator couldn't provide more entries. 1159 * Treat this as if the cache was full; drop the oldest 1160 * entry and insert the new one. 1161 */ 1162 TCPSTAT_INC(tcps_sc_zonefail); 1163 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1164 syncache_drop(sc, sch); 1165 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1166 if (sc == NULL) { 1167 if (V_tcp_syncookies) { 1168 bzero(&scs, sizeof(scs)); 1169 sc = &scs; 1170 } else { 1171 SCH_UNLOCK(sch); 1172 if (ipopts) 1173 (void) m_free(ipopts); 1174 goto done; 1175 } 1176 } 1177 } 1178 1179 /* 1180 * Fill in the syncache values. 1181 */ 1182 #ifdef MAC 1183 sc->sc_label = maclabel; 1184 #endif 1185 sc->sc_cred = cred; 1186 cred = NULL; 1187 sc->sc_ipopts = ipopts; 1188 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1189 #ifdef INET6 1190 if (!(inc->inc_flags & INC_ISIPV6)) 1191 #endif 1192 { 1193 sc->sc_ip_tos = ip_tos; 1194 sc->sc_ip_ttl = ip_ttl; 1195 } 1196 #ifndef TCP_OFFLOAD_DISABLE 1197 sc->sc_tu = tu; 1198 sc->sc_toepcb = toepcb; 1199 #endif 1200 sc->sc_irs = th->th_seq; 1201 sc->sc_iss = arc4random(); 1202 sc->sc_flags = 0; 1203 sc->sc_flowlabel = 0; 1204 1205 /* 1206 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1207 * win was derived from socket earlier in the function. 1208 */ 1209 win = imax(win, 0); 1210 win = imin(win, TCP_MAXWIN); 1211 sc->sc_wnd = win; 1212 1213 if (V_tcp_do_rfc1323) { 1214 /* 1215 * A timestamp received in a SYN makes 1216 * it ok to send timestamp requests and replies. 1217 */ 1218 if (to->to_flags & TOF_TS) { 1219 sc->sc_tsreflect = to->to_tsval; 1220 sc->sc_ts = ticks; 1221 sc->sc_flags |= SCF_TIMESTAMP; 1222 } 1223 if (to->to_flags & TOF_SCALE) { 1224 int wscale = 0; 1225 1226 /* 1227 * Pick the smallest possible scaling factor that 1228 * will still allow us to scale up to sb_max, aka 1229 * kern.ipc.maxsockbuf. 1230 * 1231 * We do this because there are broken firewalls that 1232 * will corrupt the window scale option, leading to 1233 * the other endpoint believing that our advertised 1234 * window is unscaled. At scale factors larger than 1235 * 5 the unscaled window will drop below 1500 bytes, 1236 * leading to serious problems when traversing these 1237 * broken firewalls. 1238 * 1239 * With the default maxsockbuf of 256K, a scale factor 1240 * of 3 will be chosen by this algorithm. Those who 1241 * choose a larger maxsockbuf should watch out 1242 * for the compatiblity problems mentioned above. 1243 * 1244 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1245 * or <SYN,ACK>) segment itself is never scaled. 1246 */ 1247 while (wscale < TCP_MAX_WINSHIFT && 1248 (TCP_MAXWIN << wscale) < sb_max) 1249 wscale++; 1250 sc->sc_requested_r_scale = wscale; 1251 sc->sc_requested_s_scale = to->to_wscale; 1252 sc->sc_flags |= SCF_WINSCALE; 1253 } 1254 } 1255 #ifdef TCP_SIGNATURE 1256 /* 1257 * If listening socket requested TCP digests, and received SYN 1258 * contains the option, flag this in the syncache so that 1259 * syncache_respond() will do the right thing with the SYN+ACK. 1260 * XXX: Currently we always record the option by default and will 1261 * attempt to use it in syncache_respond(). 1262 */ 1263 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE) 1264 sc->sc_flags |= SCF_SIGNATURE; 1265 #endif 1266 if (to->to_flags & TOF_SACKPERM) 1267 sc->sc_flags |= SCF_SACK; 1268 if (to->to_flags & TOF_MSS) 1269 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1270 if (ltflags & TF_NOOPT) 1271 sc->sc_flags |= SCF_NOOPT; 1272 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1273 sc->sc_flags |= SCF_ECN; 1274 1275 if (V_tcp_syncookies) { 1276 syncookie_generate(sch, sc, &flowtmp); 1277 #ifdef INET6 1278 if (autoflowlabel) 1279 sc->sc_flowlabel = flowtmp; 1280 #endif 1281 } else { 1282 #ifdef INET6 1283 if (autoflowlabel) 1284 sc->sc_flowlabel = 1285 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1286 #endif 1287 } 1288 SCH_UNLOCK(sch); 1289 1290 /* 1291 * Do a standard 3-way handshake. 1292 */ 1293 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1294 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1295 syncache_free(sc); 1296 else if (sc != &scs) 1297 syncache_insert(sc, sch); /* locks and unlocks sch */ 1298 TCPSTAT_INC(tcps_sndacks); 1299 TCPSTAT_INC(tcps_sndtotal); 1300 } else { 1301 if (sc != &scs) 1302 syncache_free(sc); 1303 TCPSTAT_INC(tcps_sc_dropped); 1304 } 1305 1306 done: 1307 if (cred != NULL) 1308 crfree(cred); 1309 #ifdef MAC 1310 if (sc == &scs) 1311 mac_syncache_destroy(&maclabel); 1312 #endif 1313 if (m) { 1314 1315 *lsop = NULL; 1316 m_freem(m); 1317 } 1318 } 1319 1320 static int 1321 syncache_respond(struct syncache *sc) 1322 { 1323 struct ip *ip = NULL; 1324 struct mbuf *m; 1325 struct tcphdr *th = NULL; 1326 int optlen, error = 0; /* Make compiler happy */ 1327 u_int16_t hlen, tlen, mssopt; 1328 struct tcpopt to; 1329 #ifdef INET6 1330 struct ip6_hdr *ip6 = NULL; 1331 #endif 1332 1333 hlen = 1334 #ifdef INET6 1335 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1336 #endif 1337 sizeof(struct ip); 1338 tlen = hlen + sizeof(struct tcphdr); 1339 1340 /* Determine MSS we advertize to other end of connection. */ 1341 mssopt = tcp_mssopt(&sc->sc_inc); 1342 if (sc->sc_peer_mss) 1343 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1344 1345 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1346 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1347 ("syncache: mbuf too small")); 1348 1349 /* Create the IP+TCP header from scratch. */ 1350 m = m_gethdr(M_DONTWAIT, MT_DATA); 1351 if (m == NULL) 1352 return (ENOBUFS); 1353 #ifdef MAC 1354 mac_syncache_create_mbuf(sc->sc_label, m); 1355 #endif 1356 m->m_data += max_linkhdr; 1357 m->m_len = tlen; 1358 m->m_pkthdr.len = tlen; 1359 m->m_pkthdr.rcvif = NULL; 1360 1361 #ifdef INET6 1362 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1363 ip6 = mtod(m, struct ip6_hdr *); 1364 ip6->ip6_vfc = IPV6_VERSION; 1365 ip6->ip6_nxt = IPPROTO_TCP; 1366 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1367 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1368 ip6->ip6_plen = htons(tlen - hlen); 1369 /* ip6_hlim is set after checksum */ 1370 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1371 ip6->ip6_flow |= sc->sc_flowlabel; 1372 1373 th = (struct tcphdr *)(ip6 + 1); 1374 } 1375 #endif 1376 #if defined(INET6) && defined(INET) 1377 else 1378 #endif 1379 #ifdef INET 1380 { 1381 ip = mtod(m, struct ip *); 1382 ip->ip_v = IPVERSION; 1383 ip->ip_hl = sizeof(struct ip) >> 2; 1384 ip->ip_len = tlen; 1385 ip->ip_id = 0; 1386 ip->ip_off = 0; 1387 ip->ip_sum = 0; 1388 ip->ip_p = IPPROTO_TCP; 1389 ip->ip_src = sc->sc_inc.inc_laddr; 1390 ip->ip_dst = sc->sc_inc.inc_faddr; 1391 ip->ip_ttl = sc->sc_ip_ttl; 1392 ip->ip_tos = sc->sc_ip_tos; 1393 1394 /* 1395 * See if we should do MTU discovery. Route lookups are 1396 * expensive, so we will only unset the DF bit if: 1397 * 1398 * 1) path_mtu_discovery is disabled 1399 * 2) the SCF_UNREACH flag has been set 1400 */ 1401 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1402 ip->ip_off |= IP_DF; 1403 1404 th = (struct tcphdr *)(ip + 1); 1405 } 1406 #endif /* INET */ 1407 th->th_sport = sc->sc_inc.inc_lport; 1408 th->th_dport = sc->sc_inc.inc_fport; 1409 1410 th->th_seq = htonl(sc->sc_iss); 1411 th->th_ack = htonl(sc->sc_irs + 1); 1412 th->th_off = sizeof(struct tcphdr) >> 2; 1413 th->th_x2 = 0; 1414 th->th_flags = TH_SYN|TH_ACK; 1415 th->th_win = htons(sc->sc_wnd); 1416 th->th_urp = 0; 1417 1418 if (sc->sc_flags & SCF_ECN) { 1419 th->th_flags |= TH_ECE; 1420 TCPSTAT_INC(tcps_ecn_shs); 1421 } 1422 1423 /* Tack on the TCP options. */ 1424 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1425 to.to_flags = 0; 1426 1427 to.to_mss = mssopt; 1428 to.to_flags = TOF_MSS; 1429 if (sc->sc_flags & SCF_WINSCALE) { 1430 to.to_wscale = sc->sc_requested_r_scale; 1431 to.to_flags |= TOF_SCALE; 1432 } 1433 if (sc->sc_flags & SCF_TIMESTAMP) { 1434 /* Virgin timestamp or TCP cookie enhanced one. */ 1435 to.to_tsval = sc->sc_ts; 1436 to.to_tsecr = sc->sc_tsreflect; 1437 to.to_flags |= TOF_TS; 1438 } 1439 if (sc->sc_flags & SCF_SACK) 1440 to.to_flags |= TOF_SACKPERM; 1441 #ifdef TCP_SIGNATURE 1442 if (sc->sc_flags & SCF_SIGNATURE) 1443 to.to_flags |= TOF_SIGNATURE; 1444 #endif 1445 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1446 1447 /* Adjust headers by option size. */ 1448 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1449 m->m_len += optlen; 1450 m->m_pkthdr.len += optlen; 1451 1452 #ifdef TCP_SIGNATURE 1453 if (sc->sc_flags & SCF_SIGNATURE) 1454 tcp_signature_compute(m, 0, 0, optlen, 1455 to.to_signature, IPSEC_DIR_OUTBOUND); 1456 #endif 1457 #ifdef INET6 1458 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1459 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1460 else 1461 #endif 1462 ip->ip_len += optlen; 1463 } else 1464 optlen = 0; 1465 1466 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1467 #ifdef INET6 1468 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1469 th->th_sum = 0; 1470 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1471 tlen + optlen - hlen); 1472 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1473 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1474 } 1475 #endif 1476 #if defined(INET6) && defined(INET) 1477 else 1478 #endif 1479 #ifdef INET 1480 { 1481 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1482 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1483 m->m_pkthdr.csum_flags = CSUM_TCP; 1484 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1485 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1486 } 1487 #endif 1488 return (error); 1489 } 1490 1491 void 1492 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1493 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1494 { 1495 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1496 } 1497 1498 void 1499 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo, 1500 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1501 struct toe_usrreqs *tu, void *toepcb) 1502 { 1503 struct tcpopt to; 1504 1505 bzero(&to, sizeof(struct tcpopt)); 1506 to.to_mss = toeo->to_mss; 1507 to.to_wscale = toeo->to_wscale; 1508 to.to_flags = toeo->to_flags; 1509 1510 INP_INFO_WLOCK(&V_tcbinfo); 1511 INP_WLOCK(inp); 1512 1513 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb); 1514 } 1515 1516 /* 1517 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1518 * receive and to be able to handle SYN floods from bogus source addresses 1519 * (where we will never receive any reply). SYN floods try to exhaust all 1520 * our memory and available slots in the SYN cache table to cause a denial 1521 * of service to legitimate users of the local host. 1522 * 1523 * The idea of SYN cookies is to encode and include all necessary information 1524 * about the connection setup state within the SYN-ACK we send back and thus 1525 * to get along without keeping any local state until the ACK to the SYN-ACK 1526 * arrives (if ever). Everything we need to know should be available from 1527 * the information we encoded in the SYN-ACK. 1528 * 1529 * More information about the theory behind SYN cookies and its first 1530 * discussion and specification can be found at: 1531 * http://cr.yp.to/syncookies.html (overview) 1532 * http://cr.yp.to/syncookies/archive (gory details) 1533 * 1534 * This implementation extends the orginal idea and first implementation 1535 * of FreeBSD by using not only the initial sequence number field to store 1536 * information but also the timestamp field if present. This way we can 1537 * keep track of the entire state we need to know to recreate the session in 1538 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1539 * these days. For those that do not we still have to live with the known 1540 * shortcomings of the ISN only SYN cookies. 1541 * 1542 * Cookie layers: 1543 * 1544 * Initial sequence number we send: 1545 * 31|................................|0 1546 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1547 * D = MD5 Digest (first dword) 1548 * M = MSS index 1549 * R = Rotation of secret 1550 * P = Odd or Even secret 1551 * 1552 * The MD5 Digest is computed with over following parameters: 1553 * a) randomly rotated secret 1554 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1555 * c) the received initial sequence number from remote host 1556 * d) the rotation offset and odd/even bit 1557 * 1558 * Timestamp we send: 1559 * 31|................................|0 1560 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1561 * D = MD5 Digest (third dword) (only as filler) 1562 * S = Requested send window scale 1563 * R = Requested receive window scale 1564 * A = SACK allowed 1565 * 5 = TCP-MD5 enabled (not implemented yet) 1566 * XORed with MD5 Digest (forth dword) 1567 * 1568 * The timestamp isn't cryptographically secure and doesn't need to be. 1569 * The double use of the MD5 digest dwords ties it to a specific remote/ 1570 * local host/port, remote initial sequence number and our local time 1571 * limited secret. A received timestamp is reverted (XORed) and then 1572 * the contained MD5 dword is compared to the computed one to ensure the 1573 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1574 * have been tampered with but this isn't different from supplying bogus 1575 * values in the SYN in the first place. 1576 * 1577 * Some problems with SYN cookies remain however: 1578 * Consider the problem of a recreated (and retransmitted) cookie. If the 1579 * original SYN was accepted, the connection is established. The second 1580 * SYN is inflight, and if it arrives with an ISN that falls within the 1581 * receive window, the connection is killed. 1582 * 1583 * Notes: 1584 * A heuristic to determine when to accept syn cookies is not necessary. 1585 * An ACK flood would cause the syncookie verification to be attempted, 1586 * but a SYN flood causes syncookies to be generated. Both are of equal 1587 * cost, so there's no point in trying to optimize the ACK flood case. 1588 * Also, if you don't process certain ACKs for some reason, then all someone 1589 * would have to do is launch a SYN and ACK flood at the same time, which 1590 * would stop cookie verification and defeat the entire purpose of syncookies. 1591 */ 1592 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1593 1594 static void 1595 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1596 u_int32_t *flowlabel) 1597 { 1598 MD5_CTX ctx; 1599 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1600 u_int32_t data; 1601 u_int32_t *secbits; 1602 u_int off, pmss, mss; 1603 int i; 1604 1605 SCH_LOCK_ASSERT(sch); 1606 1607 /* Which of the two secrets to use. */ 1608 secbits = sch->sch_oddeven ? 1609 sch->sch_secbits_odd : sch->sch_secbits_even; 1610 1611 /* Reseed secret if too old. */ 1612 if (sch->sch_reseed < time_uptime) { 1613 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1614 secbits = sch->sch_oddeven ? 1615 sch->sch_secbits_odd : sch->sch_secbits_even; 1616 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1617 secbits[i] = arc4random(); 1618 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1619 } 1620 1621 /* Secret rotation offset. */ 1622 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1623 1624 /* Maximum segment size calculation. */ 1625 pmss = 1626 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1627 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1628 if (tcp_sc_msstab[mss] <= pmss) 1629 break; 1630 1631 /* Fold parameters and MD5 digest into the ISN we will send. */ 1632 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1633 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1634 data |= mss << 4; /* mss, 3 bits */ 1635 1636 MD5Init(&ctx); 1637 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1638 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1639 MD5Update(&ctx, secbits, off); 1640 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1641 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1642 MD5Update(&ctx, &data, sizeof(data)); 1643 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1644 1645 data |= (md5_buffer[0] << 7); 1646 sc->sc_iss = data; 1647 1648 #ifdef INET6 1649 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1650 #endif 1651 1652 /* Additional parameters are stored in the timestamp if present. */ 1653 if (sc->sc_flags & SCF_TIMESTAMP) { 1654 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1655 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1656 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1657 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1658 data |= md5_buffer[2] << 10; /* more digest bits */ 1659 data ^= md5_buffer[3]; 1660 sc->sc_ts = data; 1661 sc->sc_tsoff = data - ticks; /* after XOR */ 1662 } 1663 1664 TCPSTAT_INC(tcps_sc_sendcookie); 1665 } 1666 1667 static struct syncache * 1668 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1669 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1670 struct socket *so) 1671 { 1672 MD5_CTX ctx; 1673 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1674 u_int32_t data = 0; 1675 u_int32_t *secbits; 1676 tcp_seq ack, seq; 1677 int off, mss, wnd, flags; 1678 1679 SCH_LOCK_ASSERT(sch); 1680 1681 /* 1682 * Pull information out of SYN-ACK/ACK and 1683 * revert sequence number advances. 1684 */ 1685 ack = th->th_ack - 1; 1686 seq = th->th_seq - 1; 1687 off = (ack >> 1) & 0x7; 1688 mss = (ack >> 4) & 0x7; 1689 flags = ack & 0x7f; 1690 1691 /* Which of the two secrets to use. */ 1692 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1693 1694 /* 1695 * The secret wasn't updated for the lifetime of a syncookie, 1696 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1697 */ 1698 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1699 return (NULL); 1700 } 1701 1702 /* Recompute the digest so we can compare it. */ 1703 MD5Init(&ctx); 1704 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1705 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1706 MD5Update(&ctx, secbits, off); 1707 MD5Update(&ctx, inc, sizeof(*inc)); 1708 MD5Update(&ctx, &seq, sizeof(seq)); 1709 MD5Update(&ctx, &flags, sizeof(flags)); 1710 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1711 1712 /* Does the digest part of or ACK'ed ISS match? */ 1713 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1714 return (NULL); 1715 1716 /* Does the digest part of our reflected timestamp match? */ 1717 if (to->to_flags & TOF_TS) { 1718 data = md5_buffer[3] ^ to->to_tsecr; 1719 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1720 return (NULL); 1721 } 1722 1723 /* Fill in the syncache values. */ 1724 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1725 sc->sc_ipopts = NULL; 1726 1727 sc->sc_irs = seq; 1728 sc->sc_iss = ack; 1729 1730 #ifdef INET6 1731 if (inc->inc_flags & INC_ISIPV6) { 1732 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1733 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1734 } else 1735 #endif 1736 { 1737 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1738 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1739 } 1740 1741 /* Additional parameters that were encoded in the timestamp. */ 1742 if (data) { 1743 sc->sc_flags |= SCF_TIMESTAMP; 1744 sc->sc_tsreflect = to->to_tsval; 1745 sc->sc_ts = to->to_tsecr; 1746 sc->sc_tsoff = to->to_tsecr - ticks; 1747 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1748 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1749 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1750 TCP_MAX_WINSHIFT); 1751 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1752 TCP_MAX_WINSHIFT); 1753 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1754 sc->sc_flags |= SCF_WINSCALE; 1755 } else 1756 sc->sc_flags |= SCF_NOOPT; 1757 1758 wnd = sbspace(&so->so_rcv); 1759 wnd = imax(wnd, 0); 1760 wnd = imin(wnd, TCP_MAXWIN); 1761 sc->sc_wnd = wnd; 1762 1763 sc->sc_rxmits = 0; 1764 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1765 1766 TCPSTAT_INC(tcps_sc_recvcookie); 1767 return (sc); 1768 } 1769 1770 /* 1771 * Returns the current number of syncache entries. This number 1772 * will probably change before you get around to calling 1773 * syncache_pcblist. 1774 */ 1775 1776 int 1777 syncache_pcbcount(void) 1778 { 1779 struct syncache_head *sch; 1780 int count, i; 1781 1782 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1783 /* No need to lock for a read. */ 1784 sch = &V_tcp_syncache.hashbase[i]; 1785 count += sch->sch_length; 1786 } 1787 return count; 1788 } 1789 1790 /* 1791 * Exports the syncache entries to userland so that netstat can display 1792 * them alongside the other sockets. This function is intended to be 1793 * called only from tcp_pcblist. 1794 * 1795 * Due to concurrency on an active system, the number of pcbs exported 1796 * may have no relation to max_pcbs. max_pcbs merely indicates the 1797 * amount of space the caller allocated for this function to use. 1798 */ 1799 int 1800 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1801 { 1802 struct xtcpcb xt; 1803 struct syncache *sc; 1804 struct syncache_head *sch; 1805 int count, error, i; 1806 1807 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1808 sch = &V_tcp_syncache.hashbase[i]; 1809 SCH_LOCK(sch); 1810 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1811 if (count >= max_pcbs) { 1812 SCH_UNLOCK(sch); 1813 goto exit; 1814 } 1815 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1816 continue; 1817 bzero(&xt, sizeof(xt)); 1818 xt.xt_len = sizeof(xt); 1819 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1820 xt.xt_inp.inp_vflag = INP_IPV6; 1821 else 1822 xt.xt_inp.inp_vflag = INP_IPV4; 1823 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1824 xt.xt_tp.t_inpcb = &xt.xt_inp; 1825 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1826 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1827 xt.xt_socket.xso_len = sizeof (struct xsocket); 1828 xt.xt_socket.so_type = SOCK_STREAM; 1829 xt.xt_socket.so_state = SS_ISCONNECTING; 1830 error = SYSCTL_OUT(req, &xt, sizeof xt); 1831 if (error) { 1832 SCH_UNLOCK(sch); 1833 goto exit; 1834 } 1835 count++; 1836 } 1837 SCH_UNLOCK(sch); 1838 } 1839 exit: 1840 *pcbs_exported = count; 1841 return error; 1842 } 1843