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 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, 151 "TCP SYN cache"); 152 153 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 154 &VNET_NAME(tcp_syncache.bucket_limit), 0, 155 "Per-bucket hash limit for syncache"); 156 157 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 158 &VNET_NAME(tcp_syncache.cache_limit), 0, 159 "Overall entry limit for syncache"); 160 161 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 162 &VNET_NAME(tcp_syncache.cache_count), 0, 163 "Current number of entries in syncache"); 164 165 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 166 &VNET_NAME(tcp_syncache.hashsize), 0, 167 "Size of TCP syncache hashtable"); 168 169 SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 170 &VNET_NAME(tcp_syncache.rexmt_limit), 0, 171 "Limit on SYN/ACK retransmissions"); 172 173 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1; 174 SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, 175 CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0, 176 "Send reset on socket allocation failure"); 177 178 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 179 180 #define SYNCACHE_HASH(inc, mask) \ 181 ((V_tcp_syncache.hash_secret ^ \ 182 (inc)->inc_faddr.s_addr ^ \ 183 ((inc)->inc_faddr.s_addr >> 16) ^ \ 184 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 185 186 #define SYNCACHE_HASH6(inc, mask) \ 187 ((V_tcp_syncache.hash_secret ^ \ 188 (inc)->inc6_faddr.s6_addr32[0] ^ \ 189 (inc)->inc6_faddr.s6_addr32[3] ^ \ 190 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 191 192 #define ENDPTS_EQ(a, b) ( \ 193 (a)->ie_fport == (b)->ie_fport && \ 194 (a)->ie_lport == (b)->ie_lport && \ 195 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 196 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 197 ) 198 199 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 200 201 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 202 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 203 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 204 205 /* 206 * Requires the syncache entry to be already removed from the bucket list. 207 */ 208 static void 209 syncache_free(struct syncache *sc) 210 { 211 212 if (sc->sc_ipopts) 213 (void) m_free(sc->sc_ipopts); 214 if (sc->sc_cred) 215 crfree(sc->sc_cred); 216 #ifdef MAC 217 mac_syncache_destroy(&sc->sc_label); 218 #endif 219 220 uma_zfree(V_tcp_syncache.zone, sc); 221 } 222 223 void 224 syncache_init(void) 225 { 226 int i; 227 228 V_tcp_syncache.cache_count = 0; 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 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 272 } 273 274 #ifdef VIMAGE 275 void 276 syncache_destroy(void) 277 { 278 struct syncache_head *sch; 279 struct syncache *sc, *nsc; 280 int i; 281 282 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */ 283 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 284 285 sch = &V_tcp_syncache.hashbase[i]; 286 callout_drain(&sch->sch_timer); 287 288 SCH_LOCK(sch); 289 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) 290 syncache_drop(sc, sch); 291 SCH_UNLOCK(sch); 292 KASSERT(TAILQ_EMPTY(&sch->sch_bucket), 293 ("%s: sch->sch_bucket not empty", __func__)); 294 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0", 295 __func__, sch->sch_length)); 296 mtx_destroy(&sch->sch_mtx); 297 } 298 299 KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0", 300 __func__, V_tcp_syncache.cache_count)); 301 302 /* Free the allocated global resources. */ 303 uma_zdestroy(V_tcp_syncache.zone); 304 free(V_tcp_syncache.hashbase, M_SYNCACHE); 305 } 306 #endif 307 308 /* 309 * Inserts a syncache entry into the specified bucket row. 310 * Locks and unlocks the syncache_head autonomously. 311 */ 312 static void 313 syncache_insert(struct syncache *sc, struct syncache_head *sch) 314 { 315 struct syncache *sc2; 316 317 SCH_LOCK(sch); 318 319 /* 320 * Make sure that we don't overflow the per-bucket limit. 321 * If the bucket is full, toss the oldest element. 322 */ 323 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 324 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 325 ("sch->sch_length incorrect")); 326 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 327 syncache_drop(sc2, sch); 328 TCPSTAT_INC(tcps_sc_bucketoverflow); 329 } 330 331 /* Put it into the bucket. */ 332 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 333 sch->sch_length++; 334 335 /* Reinitialize the bucket row's timer. */ 336 if (sch->sch_length == 1) 337 sch->sch_nextc = ticks + INT_MAX; 338 syncache_timeout(sc, sch, 1); 339 340 SCH_UNLOCK(sch); 341 342 V_tcp_syncache.cache_count++; 343 TCPSTAT_INC(tcps_sc_added); 344 } 345 346 /* 347 * Remove and free entry from syncache bucket row. 348 * Expects locked syncache head. 349 */ 350 static void 351 syncache_drop(struct syncache *sc, struct syncache_head *sch) 352 { 353 354 SCH_LOCK_ASSERT(sch); 355 356 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 357 sch->sch_length--; 358 359 #ifndef TCP_OFFLOAD_DISABLE 360 if (sc->sc_tu) 361 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 362 #endif 363 syncache_free(sc); 364 V_tcp_syncache.cache_count--; 365 } 366 367 /* 368 * Engage/reengage time on bucket row. 369 */ 370 static void 371 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 372 { 373 sc->sc_rxttime = ticks + 374 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 375 sc->sc_rxmits++; 376 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 377 sch->sch_nextc = sc->sc_rxttime; 378 if (docallout) 379 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 380 syncache_timer, (void *)sch); 381 } 382 } 383 384 /* 385 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 386 * If we have retransmitted an entry the maximum number of times, expire it. 387 * One separate timer for each bucket row. 388 */ 389 static void 390 syncache_timer(void *xsch) 391 { 392 struct syncache_head *sch = (struct syncache_head *)xsch; 393 struct syncache *sc, *nsc; 394 int tick = ticks; 395 char *s; 396 397 CURVNET_SET(sch->sch_vnet); 398 399 /* NB: syncache_head has already been locked by the callout. */ 400 SCH_LOCK_ASSERT(sch); 401 402 /* 403 * In the following cycle we may remove some entries and/or 404 * advance some timeouts, so re-initialize the bucket timer. 405 */ 406 sch->sch_nextc = tick + INT_MAX; 407 408 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 409 /* 410 * We do not check if the listen socket still exists 411 * and accept the case where the listen socket may be 412 * gone by the time we resend the SYN/ACK. We do 413 * not expect this to happens often. If it does, 414 * then the RST will be sent by the time the remote 415 * host does the SYN/ACK->ACK. 416 */ 417 if (TSTMP_GT(sc->sc_rxttime, tick)) { 418 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 419 sch->sch_nextc = sc->sc_rxttime; 420 continue; 421 } 422 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 423 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 424 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 425 "giving up and removing syncache entry\n", 426 s, __func__); 427 free(s, M_TCPLOG); 428 } 429 syncache_drop(sc, sch); 430 TCPSTAT_INC(tcps_sc_stale); 431 continue; 432 } 433 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 434 log(LOG_DEBUG, "%s; %s: Response timeout, " 435 "retransmitting (%u) SYN|ACK\n", 436 s, __func__, sc->sc_rxmits); 437 free(s, M_TCPLOG); 438 } 439 440 (void) syncache_respond(sc); 441 TCPSTAT_INC(tcps_sc_retransmitted); 442 syncache_timeout(sc, sch, 0); 443 } 444 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 445 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 446 syncache_timer, (void *)(sch)); 447 CURVNET_RESTORE(); 448 } 449 450 /* 451 * Find an entry in the syncache. 452 * Returns always with locked syncache_head plus a matching entry or NULL. 453 */ 454 struct syncache * 455 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 456 { 457 struct syncache *sc; 458 struct syncache_head *sch; 459 460 #ifdef INET6 461 if (inc->inc_flags & INC_ISIPV6) { 462 sch = &V_tcp_syncache.hashbase[ 463 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 464 *schp = sch; 465 466 SCH_LOCK(sch); 467 468 /* Circle through bucket row to find matching entry. */ 469 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 470 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 471 return (sc); 472 } 473 } else 474 #endif 475 { 476 sch = &V_tcp_syncache.hashbase[ 477 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 478 *schp = sch; 479 480 SCH_LOCK(sch); 481 482 /* Circle through bucket row to find matching entry. */ 483 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 484 #ifdef INET6 485 if (sc->sc_inc.inc_flags & INC_ISIPV6) 486 continue; 487 #endif 488 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 489 return (sc); 490 } 491 } 492 SCH_LOCK_ASSERT(*schp); 493 return (NULL); /* always returns with locked sch */ 494 } 495 496 /* 497 * This function is called when we get a RST for a 498 * non-existent connection, so that we can see if the 499 * connection is in the syn cache. If it is, zap it. 500 */ 501 void 502 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 503 { 504 struct syncache *sc; 505 struct syncache_head *sch; 506 char *s = NULL; 507 508 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 509 SCH_LOCK_ASSERT(sch); 510 511 /* 512 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 513 * See RFC 793 page 65, section SEGMENT ARRIVES. 514 */ 515 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 516 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 517 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 518 "FIN flag set, segment ignored\n", s, __func__); 519 TCPSTAT_INC(tcps_badrst); 520 goto done; 521 } 522 523 /* 524 * No corresponding connection was found in syncache. 525 * If syncookies are enabled and possibly exclusively 526 * used, or we are under memory pressure, a valid RST 527 * may not find a syncache entry. In that case we're 528 * done and no SYN|ACK retransmissions will happen. 529 * Otherwise the RST was misdirected or spoofed. 530 */ 531 if (sc == NULL) { 532 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 533 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 534 "syncache entry (possibly syncookie only), " 535 "segment ignored\n", s, __func__); 536 TCPSTAT_INC(tcps_badrst); 537 goto done; 538 } 539 540 /* 541 * If the RST bit is set, check the sequence number to see 542 * if this is a valid reset segment. 543 * RFC 793 page 37: 544 * In all states except SYN-SENT, all reset (RST) segments 545 * are validated by checking their SEQ-fields. A reset is 546 * valid if its sequence number is in the window. 547 * 548 * The sequence number in the reset segment is normally an 549 * echo of our outgoing acknowlegement numbers, but some hosts 550 * send a reset with the sequence number at the rightmost edge 551 * of our receive window, and we have to handle this case. 552 */ 553 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 554 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 555 syncache_drop(sc, sch); 556 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 557 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 558 "connection attempt aborted by remote endpoint\n", 559 s, __func__); 560 TCPSTAT_INC(tcps_sc_reset); 561 } else { 562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 563 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 564 "IRS %u (+WND %u), segment ignored\n", 565 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 566 TCPSTAT_INC(tcps_badrst); 567 } 568 569 done: 570 if (s != NULL) 571 free(s, M_TCPLOG); 572 SCH_UNLOCK(sch); 573 } 574 575 void 576 syncache_badack(struct in_conninfo *inc) 577 { 578 struct syncache *sc; 579 struct syncache_head *sch; 580 581 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 582 SCH_LOCK_ASSERT(sch); 583 if (sc != NULL) { 584 syncache_drop(sc, sch); 585 TCPSTAT_INC(tcps_sc_badack); 586 } 587 SCH_UNLOCK(sch); 588 } 589 590 void 591 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 592 { 593 struct syncache *sc; 594 struct syncache_head *sch; 595 596 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 597 SCH_LOCK_ASSERT(sch); 598 if (sc == NULL) 599 goto done; 600 601 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 602 if (ntohl(th->th_seq) != sc->sc_iss) 603 goto done; 604 605 /* 606 * If we've rertransmitted 3 times and this is our second error, 607 * we remove the entry. Otherwise, we allow it to continue on. 608 * This prevents us from incorrectly nuking an entry during a 609 * spurious network outage. 610 * 611 * See tcp_notify(). 612 */ 613 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 614 sc->sc_flags |= SCF_UNREACH; 615 goto done; 616 } 617 syncache_drop(sc, sch); 618 TCPSTAT_INC(tcps_sc_unreach); 619 done: 620 SCH_UNLOCK(sch); 621 } 622 623 /* 624 * Build a new TCP socket structure from a syncache entry. 625 */ 626 static struct socket * 627 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 628 { 629 struct inpcb *inp = NULL; 630 struct socket *so; 631 struct tcpcb *tp; 632 int error; 633 char *s; 634 635 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 636 637 /* 638 * Ok, create the full blown connection, and set things up 639 * as they would have been set up if we had created the 640 * connection when the SYN arrived. If we can't create 641 * the connection, abort it. 642 */ 643 so = sonewconn(lso, SS_ISCONNECTED); 644 if (so == NULL) { 645 /* 646 * Drop the connection; we will either send a RST or 647 * have the peer retransmit its SYN again after its 648 * RTO and try again. 649 */ 650 TCPSTAT_INC(tcps_listendrop); 651 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 652 log(LOG_DEBUG, "%s; %s: Socket create failed " 653 "due to limits or memory shortage\n", 654 s, __func__); 655 free(s, M_TCPLOG); 656 } 657 goto abort2; 658 } 659 #ifdef MAC 660 mac_socketpeer_set_from_mbuf(m, so); 661 #endif 662 663 inp = sotoinpcb(so); 664 inp->inp_inc.inc_fibnum = so->so_fibnum; 665 INP_WLOCK(inp); 666 INP_HASH_WLOCK(&V_tcbinfo); 667 668 /* Insert new socket into PCB hash list. */ 669 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags; 670 #ifdef INET6 671 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 672 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 673 } else { 674 inp->inp_vflag &= ~INP_IPV6; 675 inp->inp_vflag |= INP_IPV4; 676 #endif 677 inp->inp_laddr = sc->sc_inc.inc_laddr; 678 #ifdef INET6 679 } 680 #endif 681 682 /* 683 * Install in the reservation hash table for now, but don't yet 684 * install a connection group since the full 4-tuple isn't yet 685 * configured. 686 */ 687 inp->inp_lport = sc->sc_inc.inc_lport; 688 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) { 689 /* 690 * Undo the assignments above if we failed to 691 * put the PCB on the hash lists. 692 */ 693 #ifdef INET6 694 if (sc->sc_inc.inc_flags & INC_ISIPV6) 695 inp->in6p_laddr = in6addr_any; 696 else 697 #endif 698 inp->inp_laddr.s_addr = INADDR_ANY; 699 inp->inp_lport = 0; 700 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 701 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed " 702 "with error %i\n", 703 s, __func__, error); 704 free(s, M_TCPLOG); 705 } 706 INP_HASH_WUNLOCK(&V_tcbinfo); 707 goto abort; 708 } 709 #ifdef IPSEC 710 /* Copy old policy into new socket's. */ 711 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 712 printf("syncache_socket: could not copy policy\n"); 713 #endif 714 #ifdef INET6 715 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 716 struct inpcb *oinp = sotoinpcb(lso); 717 struct in6_addr laddr6; 718 struct sockaddr_in6 sin6; 719 /* 720 * Inherit socket options from the listening socket. 721 * Note that in6p_inputopts are not (and should not be) 722 * copied, since it stores previously received options and is 723 * used to detect if each new option is different than the 724 * previous one and hence should be passed to a user. 725 * If we copied in6p_inputopts, a user would not be able to 726 * receive options just after calling the accept system call. 727 */ 728 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 729 if (oinp->in6p_outputopts) 730 inp->in6p_outputopts = 731 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 732 733 sin6.sin6_family = AF_INET6; 734 sin6.sin6_len = sizeof(sin6); 735 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 736 sin6.sin6_port = sc->sc_inc.inc_fport; 737 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 738 laddr6 = inp->in6p_laddr; 739 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 740 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 741 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6, 742 thread0.td_ucred, m)) != 0) { 743 inp->in6p_laddr = laddr6; 744 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 745 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed " 746 "with error %i\n", 747 s, __func__, error); 748 free(s, M_TCPLOG); 749 } 750 INP_HASH_WUNLOCK(&V_tcbinfo); 751 goto abort; 752 } 753 /* Override flowlabel from in6_pcbconnect. */ 754 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK; 755 inp->inp_flow |= sc->sc_flowlabel; 756 } 757 #endif /* INET6 */ 758 #if defined(INET) && defined(INET6) 759 else 760 #endif 761 #ifdef INET 762 { 763 struct in_addr laddr; 764 struct sockaddr_in sin; 765 766 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 767 768 if (inp->inp_options == NULL) { 769 inp->inp_options = sc->sc_ipopts; 770 sc->sc_ipopts = NULL; 771 } 772 773 sin.sin_family = AF_INET; 774 sin.sin_len = sizeof(sin); 775 sin.sin_addr = sc->sc_inc.inc_faddr; 776 sin.sin_port = sc->sc_inc.inc_fport; 777 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 778 laddr = inp->inp_laddr; 779 if (inp->inp_laddr.s_addr == INADDR_ANY) 780 inp->inp_laddr = sc->sc_inc.inc_laddr; 781 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin, 782 thread0.td_ucred, m)) != 0) { 783 inp->inp_laddr = laddr; 784 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 785 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed " 786 "with error %i\n", 787 s, __func__, error); 788 free(s, M_TCPLOG); 789 } 790 INP_HASH_WUNLOCK(&V_tcbinfo); 791 goto abort; 792 } 793 } 794 #endif /* INET */ 795 INP_HASH_WUNLOCK(&V_tcbinfo); 796 tp = intotcpcb(inp); 797 tp->t_state = TCPS_SYN_RECEIVED; 798 tp->iss = sc->sc_iss; 799 tp->irs = sc->sc_irs; 800 tcp_rcvseqinit(tp); 801 tcp_sendseqinit(tp); 802 tp->snd_wl1 = sc->sc_irs; 803 tp->snd_max = tp->iss + 1; 804 tp->snd_nxt = tp->iss + 1; 805 tp->rcv_up = sc->sc_irs + 1; 806 tp->rcv_wnd = sc->sc_wnd; 807 tp->rcv_adv += tp->rcv_wnd; 808 tp->last_ack_sent = tp->rcv_nxt; 809 810 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 811 if (sc->sc_flags & SCF_NOOPT) 812 tp->t_flags |= TF_NOOPT; 813 else { 814 if (sc->sc_flags & SCF_WINSCALE) { 815 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 816 tp->snd_scale = sc->sc_requested_s_scale; 817 tp->request_r_scale = sc->sc_requested_r_scale; 818 } 819 if (sc->sc_flags & SCF_TIMESTAMP) { 820 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 821 tp->ts_recent = sc->sc_tsreflect; 822 tp->ts_recent_age = ticks; 823 tp->ts_offset = sc->sc_tsoff; 824 } 825 #ifdef TCP_SIGNATURE 826 if (sc->sc_flags & SCF_SIGNATURE) 827 tp->t_flags |= TF_SIGNATURE; 828 #endif 829 if (sc->sc_flags & SCF_SACK) 830 tp->t_flags |= TF_SACK_PERMIT; 831 } 832 833 if (sc->sc_flags & SCF_ECN) 834 tp->t_flags |= TF_ECN_PERMIT; 835 836 /* 837 * Set up MSS and get cached values from tcp_hostcache. 838 * This might overwrite some of the defaults we just set. 839 */ 840 tcp_mss(tp, sc->sc_peer_mss); 841 842 /* 843 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 844 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits. 845 */ 846 if (sc->sc_rxmits > 1) 847 tp->snd_cwnd = tp->t_maxseg; 848 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 849 850 INP_WUNLOCK(inp); 851 852 TCPSTAT_INC(tcps_accepts); 853 return (so); 854 855 abort: 856 INP_WUNLOCK(inp); 857 abort2: 858 if (so != NULL) 859 soabort(so); 860 return (NULL); 861 } 862 863 /* 864 * This function gets called when we receive an ACK for a 865 * socket in the LISTEN state. We look up the connection 866 * in the syncache, and if its there, we pull it out of 867 * the cache and turn it into a full-blown connection in 868 * the SYN-RECEIVED state. 869 */ 870 int 871 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 872 struct socket **lsop, struct mbuf *m) 873 { 874 struct syncache *sc; 875 struct syncache_head *sch; 876 struct syncache scs; 877 char *s; 878 879 /* 880 * Global TCP locks are held because we manipulate the PCB lists 881 * and create a new socket. 882 */ 883 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 884 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 885 ("%s: can handle only ACK", __func__)); 886 887 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 888 SCH_LOCK_ASSERT(sch); 889 if (sc == NULL) { 890 /* 891 * There is no syncache entry, so see if this ACK is 892 * a returning syncookie. To do this, first: 893 * A. See if this socket has had a syncache entry dropped in 894 * the past. We don't want to accept a bogus syncookie 895 * if we've never received a SYN. 896 * B. check that the syncookie is valid. If it is, then 897 * cobble up a fake syncache entry, and return. 898 */ 899 if (!V_tcp_syncookies) { 900 SCH_UNLOCK(sch); 901 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 902 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 903 "segment rejected (syncookies disabled)\n", 904 s, __func__); 905 goto failed; 906 } 907 bzero(&scs, sizeof(scs)); 908 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 909 SCH_UNLOCK(sch); 910 if (sc == NULL) { 911 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 912 log(LOG_DEBUG, "%s; %s: Segment failed " 913 "SYNCOOKIE authentication, segment rejected " 914 "(probably spoofed)\n", s, __func__); 915 goto failed; 916 } 917 } else { 918 /* Pull out the entry to unlock the bucket row. */ 919 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 920 sch->sch_length--; 921 V_tcp_syncache.cache_count--; 922 SCH_UNLOCK(sch); 923 } 924 925 /* 926 * Segment validation: 927 * ACK must match our initial sequence number + 1 (the SYN|ACK). 928 */ 929 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 930 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 931 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 932 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 933 goto failed; 934 } 935 936 /* 937 * The SEQ must fall in the window starting at the received 938 * initial receive sequence number + 1 (the SYN). 939 */ 940 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 941 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 942 !TOEPCB_ISSET(sc)) { 943 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 944 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 945 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 946 goto failed; 947 } 948 949 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 950 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 951 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 952 "segment rejected\n", s, __func__); 953 goto failed; 954 } 955 /* 956 * If timestamps were negotiated the reflected timestamp 957 * must be equal to what we actually sent in the SYN|ACK. 958 */ 959 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 960 !TOEPCB_ISSET(sc)) { 961 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 962 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 963 "segment rejected\n", 964 s, __func__, to->to_tsecr, sc->sc_ts); 965 goto failed; 966 } 967 968 *lsop = syncache_socket(sc, *lsop, m); 969 970 if (*lsop == NULL) 971 TCPSTAT_INC(tcps_sc_aborted); 972 else 973 TCPSTAT_INC(tcps_sc_completed); 974 975 /* how do we find the inp for the new socket? */ 976 if (sc != &scs) 977 syncache_free(sc); 978 return (1); 979 failed: 980 if (sc != NULL && sc != &scs) 981 syncache_free(sc); 982 if (s != NULL) 983 free(s, M_TCPLOG); 984 *lsop = NULL; 985 return (0); 986 } 987 988 int 989 tcp_offload_syncache_expand(struct in_conninfo *inc, struct toeopt *toeo, 990 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 991 { 992 struct tcpopt to; 993 int rc; 994 995 bzero(&to, sizeof(struct tcpopt)); 996 to.to_mss = toeo->to_mss; 997 to.to_wscale = toeo->to_wscale; 998 to.to_flags = toeo->to_flags; 999 1000 INP_INFO_WLOCK(&V_tcbinfo); 1001 rc = syncache_expand(inc, &to, th, lsop, m); 1002 INP_INFO_WUNLOCK(&V_tcbinfo); 1003 1004 return (rc); 1005 } 1006 1007 /* 1008 * Given a LISTEN socket and an inbound SYN request, add 1009 * this to the syn cache, and send back a segment: 1010 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 1011 * to the source. 1012 * 1013 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 1014 * Doing so would require that we hold onto the data and deliver it 1015 * to the application. However, if we are the target of a SYN-flood 1016 * DoS attack, an attacker could send data which would eventually 1017 * consume all available buffer space if it were ACKed. By not ACKing 1018 * the data, we avoid this DoS scenario. 1019 */ 1020 static void 1021 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1022 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 1023 struct toe_usrreqs *tu, void *toepcb) 1024 { 1025 struct tcpcb *tp; 1026 struct socket *so; 1027 struct syncache *sc = NULL; 1028 struct syncache_head *sch; 1029 struct mbuf *ipopts = NULL; 1030 u_int32_t flowtmp; 1031 u_int ltflags; 1032 int win, sb_hiwat, ip_ttl, ip_tos; 1033 char *s; 1034 #ifdef INET6 1035 int autoflowlabel = 0; 1036 #endif 1037 #ifdef MAC 1038 struct label *maclabel; 1039 #endif 1040 struct syncache scs; 1041 struct ucred *cred; 1042 1043 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1044 INP_WLOCK_ASSERT(inp); /* listen socket */ 1045 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1046 ("%s: unexpected tcp flags", __func__)); 1047 1048 /* 1049 * Combine all so/tp operations very early to drop the INP lock as 1050 * soon as possible. 1051 */ 1052 so = *lsop; 1053 tp = sototcpcb(so); 1054 cred = crhold(so->so_cred); 1055 1056 #ifdef INET6 1057 if ((inc->inc_flags & INC_ISIPV6) && 1058 (inp->inp_flags & IN6P_AUTOFLOWLABEL)) 1059 autoflowlabel = 1; 1060 #endif 1061 ip_ttl = inp->inp_ip_ttl; 1062 ip_tos = inp->inp_ip_tos; 1063 win = sbspace(&so->so_rcv); 1064 sb_hiwat = so->so_rcv.sb_hiwat; 1065 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE)); 1066 1067 /* By the time we drop the lock these should no longer be used. */ 1068 so = NULL; 1069 tp = NULL; 1070 1071 #ifdef MAC 1072 if (mac_syncache_init(&maclabel) != 0) { 1073 INP_WUNLOCK(inp); 1074 INP_INFO_WUNLOCK(&V_tcbinfo); 1075 goto done; 1076 } else 1077 mac_syncache_create(maclabel, inp); 1078 #endif 1079 INP_WUNLOCK(inp); 1080 INP_INFO_WUNLOCK(&V_tcbinfo); 1081 1082 /* 1083 * Remember the IP options, if any. 1084 */ 1085 #ifdef INET6 1086 if (!(inc->inc_flags & INC_ISIPV6)) 1087 #endif 1088 #ifdef INET 1089 ipopts = (m) ? ip_srcroute(m) : NULL; 1090 #else 1091 ipopts = NULL; 1092 #endif 1093 1094 /* 1095 * See if we already have an entry for this connection. 1096 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1097 * 1098 * XXX: should the syncache be re-initialized with the contents 1099 * of the new SYN here (which may have different options?) 1100 * 1101 * XXX: We do not check the sequence number to see if this is a 1102 * real retransmit or a new connection attempt. The question is 1103 * how to handle such a case; either ignore it as spoofed, or 1104 * drop the current entry and create a new one? 1105 */ 1106 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1107 SCH_LOCK_ASSERT(sch); 1108 if (sc != NULL) { 1109 #ifndef TCP_OFFLOAD_DISABLE 1110 if (sc->sc_tu) 1111 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1112 sc->sc_toepcb); 1113 #endif 1114 TCPSTAT_INC(tcps_sc_dupsyn); 1115 if (ipopts) { 1116 /* 1117 * If we were remembering a previous source route, 1118 * forget it and use the new one we've been given. 1119 */ 1120 if (sc->sc_ipopts) 1121 (void) m_free(sc->sc_ipopts); 1122 sc->sc_ipopts = ipopts; 1123 } 1124 /* 1125 * Update timestamp if present. 1126 */ 1127 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1128 sc->sc_tsreflect = to->to_tsval; 1129 else 1130 sc->sc_flags &= ~SCF_TIMESTAMP; 1131 #ifdef MAC 1132 /* 1133 * Since we have already unconditionally allocated label 1134 * storage, free it up. The syncache entry will already 1135 * have an initialized label we can use. 1136 */ 1137 mac_syncache_destroy(&maclabel); 1138 #endif 1139 /* Retransmit SYN|ACK and reset retransmit count. */ 1140 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1141 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1142 "resetting timer and retransmitting SYN|ACK\n", 1143 s, __func__); 1144 free(s, M_TCPLOG); 1145 } 1146 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1147 sc->sc_rxmits = 0; 1148 syncache_timeout(sc, sch, 1); 1149 TCPSTAT_INC(tcps_sndacks); 1150 TCPSTAT_INC(tcps_sndtotal); 1151 } 1152 SCH_UNLOCK(sch); 1153 goto done; 1154 } 1155 1156 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1157 if (sc == NULL) { 1158 /* 1159 * The zone allocator couldn't provide more entries. 1160 * Treat this as if the cache was full; drop the oldest 1161 * entry and insert the new one. 1162 */ 1163 TCPSTAT_INC(tcps_sc_zonefail); 1164 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1165 syncache_drop(sc, sch); 1166 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1167 if (sc == NULL) { 1168 if (V_tcp_syncookies) { 1169 bzero(&scs, sizeof(scs)); 1170 sc = &scs; 1171 } else { 1172 SCH_UNLOCK(sch); 1173 if (ipopts) 1174 (void) m_free(ipopts); 1175 goto done; 1176 } 1177 } 1178 } 1179 1180 /* 1181 * Fill in the syncache values. 1182 */ 1183 #ifdef MAC 1184 sc->sc_label = maclabel; 1185 #endif 1186 sc->sc_cred = cred; 1187 cred = NULL; 1188 sc->sc_ipopts = ipopts; 1189 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1190 #ifdef INET6 1191 if (!(inc->inc_flags & INC_ISIPV6)) 1192 #endif 1193 { 1194 sc->sc_ip_tos = ip_tos; 1195 sc->sc_ip_ttl = ip_ttl; 1196 } 1197 #ifndef TCP_OFFLOAD_DISABLE 1198 sc->sc_tu = tu; 1199 sc->sc_toepcb = toepcb; 1200 #endif 1201 sc->sc_irs = th->th_seq; 1202 sc->sc_iss = arc4random(); 1203 sc->sc_flags = 0; 1204 sc->sc_flowlabel = 0; 1205 1206 /* 1207 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1208 * win was derived from socket earlier in the function. 1209 */ 1210 win = imax(win, 0); 1211 win = imin(win, TCP_MAXWIN); 1212 sc->sc_wnd = win; 1213 1214 if (V_tcp_do_rfc1323) { 1215 /* 1216 * A timestamp received in a SYN makes 1217 * it ok to send timestamp requests and replies. 1218 */ 1219 if (to->to_flags & TOF_TS) { 1220 sc->sc_tsreflect = to->to_tsval; 1221 sc->sc_ts = ticks; 1222 sc->sc_flags |= SCF_TIMESTAMP; 1223 } 1224 if (to->to_flags & TOF_SCALE) { 1225 int wscale = 0; 1226 1227 /* 1228 * Pick the smallest possible scaling factor that 1229 * will still allow us to scale up to sb_max, aka 1230 * kern.ipc.maxsockbuf. 1231 * 1232 * We do this because there are broken firewalls that 1233 * will corrupt the window scale option, leading to 1234 * the other endpoint believing that our advertised 1235 * window is unscaled. At scale factors larger than 1236 * 5 the unscaled window will drop below 1500 bytes, 1237 * leading to serious problems when traversing these 1238 * broken firewalls. 1239 * 1240 * With the default maxsockbuf of 256K, a scale factor 1241 * of 3 will be chosen by this algorithm. Those who 1242 * choose a larger maxsockbuf should watch out 1243 * for the compatiblity problems mentioned above. 1244 * 1245 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1246 * or <SYN,ACK>) segment itself is never scaled. 1247 */ 1248 while (wscale < TCP_MAX_WINSHIFT && 1249 (TCP_MAXWIN << wscale) < sb_max) 1250 wscale++; 1251 sc->sc_requested_r_scale = wscale; 1252 sc->sc_requested_s_scale = to->to_wscale; 1253 sc->sc_flags |= SCF_WINSCALE; 1254 } 1255 } 1256 #ifdef TCP_SIGNATURE 1257 /* 1258 * If listening socket requested TCP digests, and received SYN 1259 * contains the option, flag this in the syncache so that 1260 * syncache_respond() will do the right thing with the SYN+ACK. 1261 * XXX: Currently we always record the option by default and will 1262 * attempt to use it in syncache_respond(). 1263 */ 1264 if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE) 1265 sc->sc_flags |= SCF_SIGNATURE; 1266 #endif 1267 if (to->to_flags & TOF_SACKPERM) 1268 sc->sc_flags |= SCF_SACK; 1269 if (to->to_flags & TOF_MSS) 1270 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1271 if (ltflags & TF_NOOPT) 1272 sc->sc_flags |= SCF_NOOPT; 1273 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1274 sc->sc_flags |= SCF_ECN; 1275 1276 if (V_tcp_syncookies) { 1277 syncookie_generate(sch, sc, &flowtmp); 1278 #ifdef INET6 1279 if (autoflowlabel) 1280 sc->sc_flowlabel = flowtmp; 1281 #endif 1282 } else { 1283 #ifdef INET6 1284 if (autoflowlabel) 1285 sc->sc_flowlabel = 1286 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1287 #endif 1288 } 1289 SCH_UNLOCK(sch); 1290 1291 /* 1292 * Do a standard 3-way handshake. 1293 */ 1294 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1295 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1296 syncache_free(sc); 1297 else if (sc != &scs) 1298 syncache_insert(sc, sch); /* locks and unlocks sch */ 1299 TCPSTAT_INC(tcps_sndacks); 1300 TCPSTAT_INC(tcps_sndtotal); 1301 } else { 1302 if (sc != &scs) 1303 syncache_free(sc); 1304 TCPSTAT_INC(tcps_sc_dropped); 1305 } 1306 1307 done: 1308 if (cred != NULL) 1309 crfree(cred); 1310 #ifdef MAC 1311 if (sc == &scs) 1312 mac_syncache_destroy(&maclabel); 1313 #endif 1314 if (m) { 1315 1316 *lsop = NULL; 1317 m_freem(m); 1318 } 1319 } 1320 1321 static int 1322 syncache_respond(struct syncache *sc) 1323 { 1324 struct ip *ip = NULL; 1325 struct mbuf *m; 1326 struct tcphdr *th = NULL; 1327 int optlen, error = 0; /* Make compiler happy */ 1328 u_int16_t hlen, tlen, mssopt; 1329 struct tcpopt to; 1330 #ifdef INET6 1331 struct ip6_hdr *ip6 = NULL; 1332 #endif 1333 1334 hlen = 1335 #ifdef INET6 1336 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) : 1337 #endif 1338 sizeof(struct ip); 1339 tlen = hlen + sizeof(struct tcphdr); 1340 1341 /* Determine MSS we advertize to other end of connection. */ 1342 mssopt = tcp_mssopt(&sc->sc_inc); 1343 if (sc->sc_peer_mss) 1344 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1345 1346 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1347 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1348 ("syncache: mbuf too small")); 1349 1350 /* Create the IP+TCP header from scratch. */ 1351 m = m_gethdr(M_DONTWAIT, MT_DATA); 1352 if (m == NULL) 1353 return (ENOBUFS); 1354 #ifdef MAC 1355 mac_syncache_create_mbuf(sc->sc_label, m); 1356 #endif 1357 m->m_data += max_linkhdr; 1358 m->m_len = tlen; 1359 m->m_pkthdr.len = tlen; 1360 m->m_pkthdr.rcvif = NULL; 1361 1362 #ifdef INET6 1363 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1364 ip6 = mtod(m, struct ip6_hdr *); 1365 ip6->ip6_vfc = IPV6_VERSION; 1366 ip6->ip6_nxt = IPPROTO_TCP; 1367 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1368 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1369 ip6->ip6_plen = htons(tlen - hlen); 1370 /* ip6_hlim is set after checksum */ 1371 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1372 ip6->ip6_flow |= sc->sc_flowlabel; 1373 1374 th = (struct tcphdr *)(ip6 + 1); 1375 } 1376 #endif 1377 #if defined(INET6) && defined(INET) 1378 else 1379 #endif 1380 #ifdef INET 1381 { 1382 ip = mtod(m, struct ip *); 1383 ip->ip_v = IPVERSION; 1384 ip->ip_hl = sizeof(struct ip) >> 2; 1385 ip->ip_len = tlen; 1386 ip->ip_id = 0; 1387 ip->ip_off = 0; 1388 ip->ip_sum = 0; 1389 ip->ip_p = IPPROTO_TCP; 1390 ip->ip_src = sc->sc_inc.inc_laddr; 1391 ip->ip_dst = sc->sc_inc.inc_faddr; 1392 ip->ip_ttl = sc->sc_ip_ttl; 1393 ip->ip_tos = sc->sc_ip_tos; 1394 1395 /* 1396 * See if we should do MTU discovery. Route lookups are 1397 * expensive, so we will only unset the DF bit if: 1398 * 1399 * 1) path_mtu_discovery is disabled 1400 * 2) the SCF_UNREACH flag has been set 1401 */ 1402 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1403 ip->ip_off |= IP_DF; 1404 1405 th = (struct tcphdr *)(ip + 1); 1406 } 1407 #endif /* INET */ 1408 th->th_sport = sc->sc_inc.inc_lport; 1409 th->th_dport = sc->sc_inc.inc_fport; 1410 1411 th->th_seq = htonl(sc->sc_iss); 1412 th->th_ack = htonl(sc->sc_irs + 1); 1413 th->th_off = sizeof(struct tcphdr) >> 2; 1414 th->th_x2 = 0; 1415 th->th_flags = TH_SYN|TH_ACK; 1416 th->th_win = htons(sc->sc_wnd); 1417 th->th_urp = 0; 1418 1419 if (sc->sc_flags & SCF_ECN) { 1420 th->th_flags |= TH_ECE; 1421 TCPSTAT_INC(tcps_ecn_shs); 1422 } 1423 1424 /* Tack on the TCP options. */ 1425 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1426 to.to_flags = 0; 1427 1428 to.to_mss = mssopt; 1429 to.to_flags = TOF_MSS; 1430 if (sc->sc_flags & SCF_WINSCALE) { 1431 to.to_wscale = sc->sc_requested_r_scale; 1432 to.to_flags |= TOF_SCALE; 1433 } 1434 if (sc->sc_flags & SCF_TIMESTAMP) { 1435 /* Virgin timestamp or TCP cookie enhanced one. */ 1436 to.to_tsval = sc->sc_ts; 1437 to.to_tsecr = sc->sc_tsreflect; 1438 to.to_flags |= TOF_TS; 1439 } 1440 if (sc->sc_flags & SCF_SACK) 1441 to.to_flags |= TOF_SACKPERM; 1442 #ifdef TCP_SIGNATURE 1443 if (sc->sc_flags & SCF_SIGNATURE) 1444 to.to_flags |= TOF_SIGNATURE; 1445 #endif 1446 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1447 1448 /* Adjust headers by option size. */ 1449 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1450 m->m_len += optlen; 1451 m->m_pkthdr.len += optlen; 1452 1453 #ifdef TCP_SIGNATURE 1454 if (sc->sc_flags & SCF_SIGNATURE) 1455 tcp_signature_compute(m, 0, 0, optlen, 1456 to.to_signature, IPSEC_DIR_OUTBOUND); 1457 #endif 1458 #ifdef INET6 1459 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1460 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1461 else 1462 #endif 1463 ip->ip_len += optlen; 1464 } else 1465 optlen = 0; 1466 1467 M_SETFIB(m, sc->sc_inc.inc_fibnum); 1468 #ifdef INET6 1469 if (sc->sc_inc.inc_flags & INC_ISIPV6) { 1470 th->th_sum = 0; 1471 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1472 tlen + optlen - hlen); 1473 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1474 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1475 } 1476 #endif 1477 #if defined(INET6) && defined(INET) 1478 else 1479 #endif 1480 #ifdef INET 1481 { 1482 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1483 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1484 m->m_pkthdr.csum_flags = CSUM_TCP; 1485 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1486 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1487 } 1488 #endif 1489 return (error); 1490 } 1491 1492 void 1493 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1494 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1495 { 1496 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1497 } 1498 1499 void 1500 tcp_offload_syncache_add(struct in_conninfo *inc, struct toeopt *toeo, 1501 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1502 struct toe_usrreqs *tu, void *toepcb) 1503 { 1504 struct tcpopt to; 1505 1506 bzero(&to, sizeof(struct tcpopt)); 1507 to.to_mss = toeo->to_mss; 1508 to.to_wscale = toeo->to_wscale; 1509 to.to_flags = toeo->to_flags; 1510 1511 INP_INFO_WLOCK(&V_tcbinfo); 1512 INP_WLOCK(inp); 1513 1514 _syncache_add(inc, &to, th, inp, lsop, NULL, tu, toepcb); 1515 } 1516 1517 /* 1518 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1519 * receive and to be able to handle SYN floods from bogus source addresses 1520 * (where we will never receive any reply). SYN floods try to exhaust all 1521 * our memory and available slots in the SYN cache table to cause a denial 1522 * of service to legitimate users of the local host. 1523 * 1524 * The idea of SYN cookies is to encode and include all necessary information 1525 * about the connection setup state within the SYN-ACK we send back and thus 1526 * to get along without keeping any local state until the ACK to the SYN-ACK 1527 * arrives (if ever). Everything we need to know should be available from 1528 * the information we encoded in the SYN-ACK. 1529 * 1530 * More information about the theory behind SYN cookies and its first 1531 * discussion and specification can be found at: 1532 * http://cr.yp.to/syncookies.html (overview) 1533 * http://cr.yp.to/syncookies/archive (gory details) 1534 * 1535 * This implementation extends the orginal idea and first implementation 1536 * of FreeBSD by using not only the initial sequence number field to store 1537 * information but also the timestamp field if present. This way we can 1538 * keep track of the entire state we need to know to recreate the session in 1539 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1540 * these days. For those that do not we still have to live with the known 1541 * shortcomings of the ISN only SYN cookies. 1542 * 1543 * Cookie layers: 1544 * 1545 * Initial sequence number we send: 1546 * 31|................................|0 1547 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1548 * D = MD5 Digest (first dword) 1549 * M = MSS index 1550 * R = Rotation of secret 1551 * P = Odd or Even secret 1552 * 1553 * The MD5 Digest is computed with over following parameters: 1554 * a) randomly rotated secret 1555 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1556 * c) the received initial sequence number from remote host 1557 * d) the rotation offset and odd/even bit 1558 * 1559 * Timestamp we send: 1560 * 31|................................|0 1561 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1562 * D = MD5 Digest (third dword) (only as filler) 1563 * S = Requested send window scale 1564 * R = Requested receive window scale 1565 * A = SACK allowed 1566 * 5 = TCP-MD5 enabled (not implemented yet) 1567 * XORed with MD5 Digest (forth dword) 1568 * 1569 * The timestamp isn't cryptographically secure and doesn't need to be. 1570 * The double use of the MD5 digest dwords ties it to a specific remote/ 1571 * local host/port, remote initial sequence number and our local time 1572 * limited secret. A received timestamp is reverted (XORed) and then 1573 * the contained MD5 dword is compared to the computed one to ensure the 1574 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1575 * have been tampered with but this isn't different from supplying bogus 1576 * values in the SYN in the first place. 1577 * 1578 * Some problems with SYN cookies remain however: 1579 * Consider the problem of a recreated (and retransmitted) cookie. If the 1580 * original SYN was accepted, the connection is established. The second 1581 * SYN is inflight, and if it arrives with an ISN that falls within the 1582 * receive window, the connection is killed. 1583 * 1584 * Notes: 1585 * A heuristic to determine when to accept syn cookies is not necessary. 1586 * An ACK flood would cause the syncookie verification to be attempted, 1587 * but a SYN flood causes syncookies to be generated. Both are of equal 1588 * cost, so there's no point in trying to optimize the ACK flood case. 1589 * Also, if you don't process certain ACKs for some reason, then all someone 1590 * would have to do is launch a SYN and ACK flood at the same time, which 1591 * would stop cookie verification and defeat the entire purpose of syncookies. 1592 */ 1593 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1594 1595 static void 1596 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1597 u_int32_t *flowlabel) 1598 { 1599 MD5_CTX ctx; 1600 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1601 u_int32_t data; 1602 u_int32_t *secbits; 1603 u_int off, pmss, mss; 1604 int i; 1605 1606 SCH_LOCK_ASSERT(sch); 1607 1608 /* Which of the two secrets to use. */ 1609 secbits = sch->sch_oddeven ? 1610 sch->sch_secbits_odd : sch->sch_secbits_even; 1611 1612 /* Reseed secret if too old. */ 1613 if (sch->sch_reseed < time_uptime) { 1614 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1615 secbits = sch->sch_oddeven ? 1616 sch->sch_secbits_odd : sch->sch_secbits_even; 1617 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1618 secbits[i] = arc4random(); 1619 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1620 } 1621 1622 /* Secret rotation offset. */ 1623 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1624 1625 /* Maximum segment size calculation. */ 1626 pmss = 1627 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1628 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1629 if (tcp_sc_msstab[mss] <= pmss) 1630 break; 1631 1632 /* Fold parameters and MD5 digest into the ISN we will send. */ 1633 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1634 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1635 data |= mss << 4; /* mss, 3 bits */ 1636 1637 MD5Init(&ctx); 1638 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1639 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1640 MD5Update(&ctx, secbits, off); 1641 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1642 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1643 MD5Update(&ctx, &data, sizeof(data)); 1644 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1645 1646 data |= (md5_buffer[0] << 7); 1647 sc->sc_iss = data; 1648 1649 #ifdef INET6 1650 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1651 #endif 1652 1653 /* Additional parameters are stored in the timestamp if present. */ 1654 if (sc->sc_flags & SCF_TIMESTAMP) { 1655 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1656 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1657 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1658 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1659 data |= md5_buffer[2] << 10; /* more digest bits */ 1660 data ^= md5_buffer[3]; 1661 sc->sc_ts = data; 1662 sc->sc_tsoff = data - ticks; /* after XOR */ 1663 } 1664 1665 TCPSTAT_INC(tcps_sc_sendcookie); 1666 } 1667 1668 static struct syncache * 1669 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1670 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1671 struct socket *so) 1672 { 1673 MD5_CTX ctx; 1674 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1675 u_int32_t data = 0; 1676 u_int32_t *secbits; 1677 tcp_seq ack, seq; 1678 int off, mss, wnd, flags; 1679 1680 SCH_LOCK_ASSERT(sch); 1681 1682 /* 1683 * Pull information out of SYN-ACK/ACK and 1684 * revert sequence number advances. 1685 */ 1686 ack = th->th_ack - 1; 1687 seq = th->th_seq - 1; 1688 off = (ack >> 1) & 0x7; 1689 mss = (ack >> 4) & 0x7; 1690 flags = ack & 0x7f; 1691 1692 /* Which of the two secrets to use. */ 1693 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1694 1695 /* 1696 * The secret wasn't updated for the lifetime of a syncookie, 1697 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1698 */ 1699 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1700 return (NULL); 1701 } 1702 1703 /* Recompute the digest so we can compare it. */ 1704 MD5Init(&ctx); 1705 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1706 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1707 MD5Update(&ctx, secbits, off); 1708 MD5Update(&ctx, inc, sizeof(*inc)); 1709 MD5Update(&ctx, &seq, sizeof(seq)); 1710 MD5Update(&ctx, &flags, sizeof(flags)); 1711 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1712 1713 /* Does the digest part of or ACK'ed ISS match? */ 1714 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1715 return (NULL); 1716 1717 /* Does the digest part of our reflected timestamp match? */ 1718 if (to->to_flags & TOF_TS) { 1719 data = md5_buffer[3] ^ to->to_tsecr; 1720 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1721 return (NULL); 1722 } 1723 1724 /* Fill in the syncache values. */ 1725 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1726 sc->sc_ipopts = NULL; 1727 1728 sc->sc_irs = seq; 1729 sc->sc_iss = ack; 1730 1731 #ifdef INET6 1732 if (inc->inc_flags & INC_ISIPV6) { 1733 if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL) 1734 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1735 } else 1736 #endif 1737 { 1738 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1739 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1740 } 1741 1742 /* Additional parameters that were encoded in the timestamp. */ 1743 if (data) { 1744 sc->sc_flags |= SCF_TIMESTAMP; 1745 sc->sc_tsreflect = to->to_tsval; 1746 sc->sc_ts = to->to_tsecr; 1747 sc->sc_tsoff = to->to_tsecr - ticks; 1748 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1749 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1750 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1751 TCP_MAX_WINSHIFT); 1752 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1753 TCP_MAX_WINSHIFT); 1754 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1755 sc->sc_flags |= SCF_WINSCALE; 1756 } else 1757 sc->sc_flags |= SCF_NOOPT; 1758 1759 wnd = sbspace(&so->so_rcv); 1760 wnd = imax(wnd, 0); 1761 wnd = imin(wnd, TCP_MAXWIN); 1762 sc->sc_wnd = wnd; 1763 1764 sc->sc_rxmits = 0; 1765 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1766 1767 TCPSTAT_INC(tcps_sc_recvcookie); 1768 return (sc); 1769 } 1770 1771 /* 1772 * Returns the current number of syncache entries. This number 1773 * will probably change before you get around to calling 1774 * syncache_pcblist. 1775 */ 1776 1777 int 1778 syncache_pcbcount(void) 1779 { 1780 struct syncache_head *sch; 1781 int count, i; 1782 1783 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1784 /* No need to lock for a read. */ 1785 sch = &V_tcp_syncache.hashbase[i]; 1786 count += sch->sch_length; 1787 } 1788 return count; 1789 } 1790 1791 /* 1792 * Exports the syncache entries to userland so that netstat can display 1793 * them alongside the other sockets. This function is intended to be 1794 * called only from tcp_pcblist. 1795 * 1796 * Due to concurrency on an active system, the number of pcbs exported 1797 * may have no relation to max_pcbs. max_pcbs merely indicates the 1798 * amount of space the caller allocated for this function to use. 1799 */ 1800 int 1801 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1802 { 1803 struct xtcpcb xt; 1804 struct syncache *sc; 1805 struct syncache_head *sch; 1806 int count, error, i; 1807 1808 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1809 sch = &V_tcp_syncache.hashbase[i]; 1810 SCH_LOCK(sch); 1811 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1812 if (count >= max_pcbs) { 1813 SCH_UNLOCK(sch); 1814 goto exit; 1815 } 1816 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1817 continue; 1818 bzero(&xt, sizeof(xt)); 1819 xt.xt_len = sizeof(xt); 1820 if (sc->sc_inc.inc_flags & INC_ISIPV6) 1821 xt.xt_inp.inp_vflag = INP_IPV6; 1822 else 1823 xt.xt_inp.inp_vflag = INP_IPV4; 1824 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1825 xt.xt_tp.t_inpcb = &xt.xt_inp; 1826 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1827 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1828 xt.xt_socket.xso_len = sizeof (struct xsocket); 1829 xt.xt_socket.so_type = SOCK_STREAM; 1830 xt.xt_socket.so_state = SS_ISCONNECTING; 1831 error = SYSCTL_OUT(req, &xt, sizeof xt); 1832 if (error) { 1833 SCH_UNLOCK(sch); 1834 goto exit; 1835 } 1836 count++; 1837 } 1838 SCH_UNLOCK(sch); 1839 } 1840 exit: 1841 *pcbs_exported = count; 1842 return error; 1843 } 1844