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_mac.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/vimage.h> 57 58 #include <vm/uma.h> 59 60 #include <net/if.h> 61 #include <net/route.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/ip.h> 66 #include <netinet/in_var.h> 67 #include <netinet/in_pcb.h> 68 #include <netinet/ip_var.h> 69 #include <netinet/ip_options.h> 70 #ifdef INET6 71 #include <netinet/ip6.h> 72 #include <netinet/icmp6.h> 73 #include <netinet6/nd6.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/in6_pcb.h> 76 #endif 77 #include <netinet/tcp.h> 78 #include <netinet/tcp_fsm.h> 79 #include <netinet/tcp_seq.h> 80 #include <netinet/tcp_timer.h> 81 #include <netinet/tcp_var.h> 82 #include <netinet/tcp_syncache.h> 83 #include <netinet/tcp_offload.h> 84 #ifdef INET6 85 #include <netinet6/tcp6_var.h> 86 #endif 87 88 #ifdef IPSEC 89 #include <netipsec/ipsec.h> 90 #ifdef INET6 91 #include <netipsec/ipsec6.h> 92 #endif 93 #include <netipsec/key.h> 94 #endif /*IPSEC*/ 95 96 #include <machine/in_cksum.h> 97 98 #include <security/mac/mac_framework.h> 99 100 static int tcp_syncookies = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 102 &tcp_syncookies, 0, 103 "Use TCP SYN cookies if the syncache overflows"); 104 105 static int tcp_syncookiesonly = 0; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW, 107 &tcp_syncookiesonly, 0, 108 "Use only TCP SYN cookies"); 109 110 #define SYNCOOKIE_SECRET_SIZE 8 /* dwords */ 111 #define SYNCOOKIE_LIFETIME 16 /* seconds */ 112 113 struct syncache { 114 TAILQ_ENTRY(syncache) sc_hash; 115 struct in_conninfo sc_inc; /* addresses */ 116 int sc_rxttime; /* retransmit time */ 117 u_int16_t sc_rxmits; /* retransmit counter */ 118 119 u_int32_t sc_tsreflect; /* timestamp to reflect */ 120 u_int32_t sc_ts; /* our timestamp to send */ 121 u_int32_t sc_tsoff; /* ts offset w/ syncookies */ 122 u_int32_t sc_flowlabel; /* IPv6 flowlabel */ 123 tcp_seq sc_irs; /* seq from peer */ 124 tcp_seq sc_iss; /* our ISS */ 125 struct mbuf *sc_ipopts; /* source route */ 126 127 u_int16_t sc_peer_mss; /* peer's MSS */ 128 u_int16_t sc_wnd; /* advertised window */ 129 u_int8_t sc_ip_ttl; /* IPv4 TTL */ 130 u_int8_t sc_ip_tos; /* IPv4 TOS */ 131 u_int8_t sc_requested_s_scale:4, 132 sc_requested_r_scale:4; 133 u_int16_t sc_flags; 134 #define SCF_NOOPT 0x01 /* no TCP options */ 135 #define SCF_WINSCALE 0x02 /* negotiated window scaling */ 136 #define SCF_TIMESTAMP 0x04 /* negotiated timestamps */ 137 /* MSS is implicit */ 138 #define SCF_UNREACH 0x10 /* icmp unreachable received */ 139 #define SCF_SIGNATURE 0x20 /* send MD5 digests */ 140 #define SCF_SACK 0x80 /* send SACK option */ 141 #define SCF_ECN 0x100 /* send ECN setup packet */ 142 #ifndef TCP_OFFLOAD_DISABLE 143 struct toe_usrreqs *sc_tu; /* TOE operations */ 144 void *sc_toepcb; /* TOE protocol block */ 145 #endif 146 #ifdef MAC 147 struct label *sc_label; /* MAC label reference */ 148 #endif 149 }; 150 151 #ifdef TCP_OFFLOAD_DISABLE 152 #define TOEPCB_ISSET(sc) (0) 153 #else 154 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 155 #endif 156 157 158 struct syncache_head { 159 struct mtx sch_mtx; 160 TAILQ_HEAD(sch_head, syncache) sch_bucket; 161 struct callout sch_timer; 162 int sch_nextc; 163 u_int sch_length; 164 u_int sch_oddeven; 165 u_int32_t sch_secbits_odd[SYNCOOKIE_SECRET_SIZE]; 166 u_int32_t sch_secbits_even[SYNCOOKIE_SECRET_SIZE]; 167 u_int sch_reseed; /* time_uptime, seconds */ 168 }; 169 170 static void syncache_drop(struct syncache *, struct syncache_head *); 171 static void syncache_free(struct syncache *); 172 static void syncache_insert(struct syncache *, struct syncache_head *); 173 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 174 static int syncache_respond(struct syncache *); 175 static struct socket *syncache_socket(struct syncache *, struct socket *, 176 struct mbuf *m); 177 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 178 int docallout); 179 static void syncache_timer(void *); 180 static void syncookie_generate(struct syncache_head *, struct syncache *, 181 u_int32_t *); 182 static struct syncache 183 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 184 struct syncache *, struct tcpopt *, struct tcphdr *, 185 struct socket *); 186 187 /* 188 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 189 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 190 * the odds are that the user has given up attempting to connect by then. 191 */ 192 #define SYNCACHE_MAXREXMTS 3 193 194 /* Arbitrary values */ 195 #define TCP_SYNCACHE_HASHSIZE 512 196 #define TCP_SYNCACHE_BUCKETLIMIT 30 197 198 struct tcp_syncache { 199 struct syncache_head *hashbase; 200 uma_zone_t zone; 201 u_int hashsize; 202 u_int hashmask; 203 u_int bucket_limit; 204 u_int cache_count; /* XXX: unprotected */ 205 u_int cache_limit; 206 u_int rexmt_limit; 207 u_int hash_secret; 208 }; 209 static struct tcp_syncache tcp_syncache; 210 211 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 212 213 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN, 214 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 215 216 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN, 217 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 218 219 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 220 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 221 222 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN, 223 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 224 225 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 226 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 227 228 int tcp_sc_rst_sock_fail = 1; 229 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, CTLFLAG_RW, 230 &tcp_sc_rst_sock_fail, 0, "Send reset on socket allocation failure"); 231 232 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 233 234 #define SYNCACHE_HASH(inc, mask) \ 235 ((V_tcp_syncache.hash_secret ^ \ 236 (inc)->inc_faddr.s_addr ^ \ 237 ((inc)->inc_faddr.s_addr >> 16) ^ \ 238 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 239 240 #define SYNCACHE_HASH6(inc, mask) \ 241 ((V_tcp_syncache.hash_secret ^ \ 242 (inc)->inc6_faddr.s6_addr32[0] ^ \ 243 (inc)->inc6_faddr.s6_addr32[3] ^ \ 244 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 245 246 #define ENDPTS_EQ(a, b) ( \ 247 (a)->ie_fport == (b)->ie_fport && \ 248 (a)->ie_lport == (b)->ie_lport && \ 249 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 250 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 251 ) 252 253 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 254 255 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 256 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 257 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 258 259 /* 260 * Requires the syncache entry to be already removed from the bucket list. 261 */ 262 static void 263 syncache_free(struct syncache *sc) 264 { 265 if (sc->sc_ipopts) 266 (void) m_free(sc->sc_ipopts); 267 #ifdef MAC 268 mac_syncache_destroy(&sc->sc_label); 269 #endif 270 271 uma_zfree(V_tcp_syncache.zone, sc); 272 } 273 274 void 275 syncache_init(void) 276 { 277 int i; 278 279 V_tcp_syncache.cache_count = 0; 280 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 281 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 282 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 283 V_tcp_syncache.hash_secret = arc4random(); 284 285 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 286 &V_tcp_syncache.hashsize); 287 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 288 &V_tcp_syncache.bucket_limit); 289 if (!powerof2(V_tcp_syncache.hashsize) || 290 V_tcp_syncache.hashsize == 0) { 291 printf("WARNING: syncache hash size is not a power of 2.\n"); 292 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 293 } 294 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 295 296 /* Set limits. */ 297 V_tcp_syncache.cache_limit = 298 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 299 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 300 &V_tcp_syncache.cache_limit); 301 302 /* Allocate the hash table. */ 303 MALLOC(V_tcp_syncache.hashbase, struct syncache_head *, 304 V_tcp_syncache.hashsize * sizeof(struct syncache_head), 305 M_SYNCACHE, M_WAITOK | M_ZERO); 306 307 /* Initialize the hash buckets. */ 308 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 309 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 310 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 311 NULL, MTX_DEF); 312 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 313 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 314 V_tcp_syncache.hashbase[i].sch_length = 0; 315 } 316 317 /* Create the syncache entry zone. */ 318 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 319 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 320 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 321 } 322 323 /* 324 * Inserts a syncache entry into the specified bucket row. 325 * Locks and unlocks the syncache_head autonomously. 326 */ 327 static void 328 syncache_insert(struct syncache *sc, struct syncache_head *sch) 329 { 330 struct syncache *sc2; 331 332 SCH_LOCK(sch); 333 334 /* 335 * Make sure that we don't overflow the per-bucket limit. 336 * If the bucket is full, toss the oldest element. 337 */ 338 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 339 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 340 ("sch->sch_length incorrect")); 341 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 342 syncache_drop(sc2, sch); 343 V_tcpstat.tcps_sc_bucketoverflow++; 344 } 345 346 /* Put it into the bucket. */ 347 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 348 sch->sch_length++; 349 350 /* Reinitialize the bucket row's timer. */ 351 if (sch->sch_length == 1) 352 sch->sch_nextc = ticks + INT_MAX; 353 syncache_timeout(sc, sch, 1); 354 355 SCH_UNLOCK(sch); 356 357 V_tcp_syncache.cache_count++; 358 V_tcpstat.tcps_sc_added++; 359 } 360 361 /* 362 * Remove and free entry from syncache bucket row. 363 * Expects locked syncache head. 364 */ 365 static void 366 syncache_drop(struct syncache *sc, struct syncache_head *sch) 367 { 368 369 SCH_LOCK_ASSERT(sch); 370 371 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 372 sch->sch_length--; 373 374 #ifndef TCP_OFFLOAD_DISABLE 375 if (sc->sc_tu) 376 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 377 #endif 378 syncache_free(sc); 379 V_tcp_syncache.cache_count--; 380 } 381 382 /* 383 * Engage/reengage time on bucket row. 384 */ 385 static void 386 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 387 { 388 sc->sc_rxttime = ticks + 389 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 390 sc->sc_rxmits++; 391 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 392 sch->sch_nextc = sc->sc_rxttime; 393 if (docallout) 394 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 395 syncache_timer, (void *)sch); 396 } 397 } 398 399 /* 400 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 401 * If we have retransmitted an entry the maximum number of times, expire it. 402 * One separate timer for each bucket row. 403 */ 404 static void 405 syncache_timer(void *xsch) 406 { 407 struct syncache_head *sch = (struct syncache_head *)xsch; 408 struct syncache *sc, *nsc; 409 int tick = ticks; 410 char *s; 411 412 /* NB: syncache_head has already been locked by the callout. */ 413 SCH_LOCK_ASSERT(sch); 414 415 /* 416 * In the following cycle we may remove some entries and/or 417 * advance some timeouts, so re-initialize the bucket timer. 418 */ 419 sch->sch_nextc = tick + INT_MAX; 420 421 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 422 /* 423 * We do not check if the listen socket still exists 424 * and accept the case where the listen socket may be 425 * gone by the time we resend the SYN/ACK. We do 426 * not expect this to happens often. If it does, 427 * then the RST will be sent by the time the remote 428 * host does the SYN/ACK->ACK. 429 */ 430 if (TSTMP_GT(sc->sc_rxttime, tick)) { 431 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 432 sch->sch_nextc = sc->sc_rxttime; 433 continue; 434 } 435 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 436 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 437 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 438 "giving up and removing syncache entry\n", 439 s, __func__); 440 free(s, M_TCPLOG); 441 } 442 syncache_drop(sc, sch); 443 V_tcpstat.tcps_sc_stale++; 444 continue; 445 } 446 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 447 log(LOG_DEBUG, "%s; %s: Response timeout, " 448 "retransmitting (%u) SYN|ACK\n", 449 s, __func__, sc->sc_rxmits); 450 free(s, M_TCPLOG); 451 } 452 453 (void) syncache_respond(sc); 454 V_tcpstat.tcps_sc_retransmitted++; 455 syncache_timeout(sc, sch, 0); 456 } 457 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 458 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 459 syncache_timer, (void *)(sch)); 460 } 461 462 /* 463 * Find an entry in the syncache. 464 * Returns always with locked syncache_head plus a matching entry or NULL. 465 */ 466 struct syncache * 467 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 468 { 469 struct syncache *sc; 470 struct syncache_head *sch; 471 472 #ifdef INET6 473 if (inc->inc_isipv6) { 474 sch = &V_tcp_syncache.hashbase[ 475 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 476 *schp = sch; 477 478 SCH_LOCK(sch); 479 480 /* Circle through bucket row to find matching entry. */ 481 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 482 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 483 return (sc); 484 } 485 } else 486 #endif 487 { 488 sch = &V_tcp_syncache.hashbase[ 489 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 490 *schp = sch; 491 492 SCH_LOCK(sch); 493 494 /* Circle through bucket row to find matching entry. */ 495 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 496 #ifdef INET6 497 if (sc->sc_inc.inc_isipv6) 498 continue; 499 #endif 500 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 501 return (sc); 502 } 503 } 504 SCH_LOCK_ASSERT(*schp); 505 return (NULL); /* always returns with locked sch */ 506 } 507 508 /* 509 * This function is called when we get a RST for a 510 * non-existent connection, so that we can see if the 511 * connection is in the syn cache. If it is, zap it. 512 */ 513 void 514 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 515 { 516 struct syncache *sc; 517 struct syncache_head *sch; 518 char *s = NULL; 519 520 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 521 SCH_LOCK_ASSERT(sch); 522 523 /* 524 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 525 * See RFC 793 page 65, section SEGMENT ARRIVES. 526 */ 527 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 528 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 529 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 530 "FIN flag set, segment ignored\n", s, __func__); 531 V_tcpstat.tcps_badrst++; 532 goto done; 533 } 534 535 /* 536 * No corresponding connection was found in syncache. 537 * If syncookies are enabled and possibly exclusively 538 * used, or we are under memory pressure, a valid RST 539 * may not find a syncache entry. In that case we're 540 * done and no SYN|ACK retransmissions will happen. 541 * Otherwise the the RST was misdirected or spoofed. 542 */ 543 if (sc == NULL) { 544 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 545 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 546 "syncache entry (possibly syncookie only), " 547 "segment ignored\n", s, __func__); 548 V_tcpstat.tcps_badrst++; 549 goto done; 550 } 551 552 /* 553 * If the RST bit is set, check the sequence number to see 554 * if this is a valid reset segment. 555 * RFC 793 page 37: 556 * In all states except SYN-SENT, all reset (RST) segments 557 * are validated by checking their SEQ-fields. A reset is 558 * valid if its sequence number is in the window. 559 * 560 * The sequence number in the reset segment is normally an 561 * echo of our outgoing acknowlegement numbers, but some hosts 562 * send a reset with the sequence number at the rightmost edge 563 * of our receive window, and we have to handle this case. 564 */ 565 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 566 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 567 syncache_drop(sc, sch); 568 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 569 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 570 "connection attempt aborted by remote endpoint\n", 571 s, __func__); 572 V_tcpstat.tcps_sc_reset++; 573 } else { 574 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 575 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 576 "IRS %u (+WND %u), segment ignored\n", 577 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 578 V_tcpstat.tcps_badrst++; 579 } 580 581 done: 582 if (s != NULL) 583 free(s, M_TCPLOG); 584 SCH_UNLOCK(sch); 585 } 586 587 void 588 syncache_badack(struct in_conninfo *inc) 589 { 590 struct syncache *sc; 591 struct syncache_head *sch; 592 593 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 594 SCH_LOCK_ASSERT(sch); 595 if (sc != NULL) { 596 syncache_drop(sc, sch); 597 V_tcpstat.tcps_sc_badack++; 598 } 599 SCH_UNLOCK(sch); 600 } 601 602 void 603 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 604 { 605 struct syncache *sc; 606 struct syncache_head *sch; 607 608 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 609 SCH_LOCK_ASSERT(sch); 610 if (sc == NULL) 611 goto done; 612 613 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 614 if (ntohl(th->th_seq) != sc->sc_iss) 615 goto done; 616 617 /* 618 * If we've rertransmitted 3 times and this is our second error, 619 * we remove the entry. Otherwise, we allow it to continue on. 620 * This prevents us from incorrectly nuking an entry during a 621 * spurious network outage. 622 * 623 * See tcp_notify(). 624 */ 625 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 626 sc->sc_flags |= SCF_UNREACH; 627 goto done; 628 } 629 syncache_drop(sc, sch); 630 V_tcpstat.tcps_sc_unreach++; 631 done: 632 SCH_UNLOCK(sch); 633 } 634 635 /* 636 * Build a new TCP socket structure from a syncache entry. 637 */ 638 static struct socket * 639 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 640 { 641 struct inpcb *inp = NULL; 642 struct socket *so; 643 struct tcpcb *tp; 644 char *s; 645 646 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 647 648 /* 649 * Ok, create the full blown connection, and set things up 650 * as they would have been set up if we had created the 651 * connection when the SYN arrived. If we can't create 652 * the connection, abort it. 653 */ 654 so = sonewconn(lso, SS_ISCONNECTED); 655 if (so == NULL) { 656 /* 657 * Drop the connection; we will either send a RST or 658 * have the peer retransmit its SYN again after its 659 * RTO and try again. 660 */ 661 V_tcpstat.tcps_listendrop++; 662 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 663 log(LOG_DEBUG, "%s; %s: Socket create failed " 664 "due to limits or memory shortage\n", 665 s, __func__); 666 free(s, M_TCPLOG); 667 } 668 goto abort2; 669 } 670 #ifdef MAC 671 SOCK_LOCK(so); 672 mac_socketpeer_set_from_mbuf(m, so); 673 SOCK_UNLOCK(so); 674 #endif 675 676 inp = sotoinpcb(so); 677 inp->inp_inc.inc_fibnum = sc->sc_inc.inc_fibnum; 678 so->so_fibnum = sc->sc_inc.inc_fibnum; 679 INP_WLOCK(inp); 680 681 /* Insert new socket into PCB hash list. */ 682 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 683 #ifdef INET6 684 if (sc->sc_inc.inc_isipv6) { 685 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 686 } else { 687 inp->inp_vflag &= ~INP_IPV6; 688 inp->inp_vflag |= INP_IPV4; 689 #endif 690 inp->inp_laddr = sc->sc_inc.inc_laddr; 691 #ifdef INET6 692 } 693 #endif 694 inp->inp_lport = sc->sc_inc.inc_lport; 695 if (in_pcbinshash(inp) != 0) { 696 /* 697 * Undo the assignments above if we failed to 698 * put the PCB on the hash lists. 699 */ 700 #ifdef INET6 701 if (sc->sc_inc.inc_isipv6) 702 inp->in6p_laddr = in6addr_any; 703 else 704 #endif 705 inp->inp_laddr.s_addr = INADDR_ANY; 706 inp->inp_lport = 0; 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_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 (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 742 thread0.td_ucred)) { 743 inp->in6p_laddr = laddr6; 744 goto abort; 745 } 746 /* Override flowlabel from in6_pcbconnect. */ 747 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 748 inp->in6p_flowinfo |= sc->sc_flowlabel; 749 } else 750 #endif 751 { 752 struct in_addr laddr; 753 struct sockaddr_in sin; 754 755 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 756 757 if (inp->inp_options == NULL) { 758 inp->inp_options = sc->sc_ipopts; 759 sc->sc_ipopts = NULL; 760 } 761 762 sin.sin_family = AF_INET; 763 sin.sin_len = sizeof(sin); 764 sin.sin_addr = sc->sc_inc.inc_faddr; 765 sin.sin_port = sc->sc_inc.inc_fport; 766 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 767 laddr = inp->inp_laddr; 768 if (inp->inp_laddr.s_addr == INADDR_ANY) 769 inp->inp_laddr = sc->sc_inc.inc_laddr; 770 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 771 thread0.td_ucred)) { 772 inp->inp_laddr = laddr; 773 goto abort; 774 } 775 } 776 tp = intotcpcb(inp); 777 tp->t_state = TCPS_SYN_RECEIVED; 778 tp->iss = sc->sc_iss; 779 tp->irs = sc->sc_irs; 780 tcp_rcvseqinit(tp); 781 tcp_sendseqinit(tp); 782 tp->snd_wl1 = sc->sc_irs; 783 tp->snd_max = tp->iss + 1; 784 tp->snd_nxt = tp->iss + 1; 785 tp->rcv_up = sc->sc_irs + 1; 786 tp->rcv_wnd = sc->sc_wnd; 787 tp->rcv_adv += tp->rcv_wnd; 788 tp->last_ack_sent = tp->rcv_nxt; 789 790 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 791 if (sc->sc_flags & SCF_NOOPT) 792 tp->t_flags |= TF_NOOPT; 793 else { 794 if (sc->sc_flags & SCF_WINSCALE) { 795 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 796 tp->snd_scale = sc->sc_requested_s_scale; 797 tp->request_r_scale = sc->sc_requested_r_scale; 798 } 799 if (sc->sc_flags & SCF_TIMESTAMP) { 800 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 801 tp->ts_recent = sc->sc_tsreflect; 802 tp->ts_recent_age = ticks; 803 tp->ts_offset = sc->sc_tsoff; 804 } 805 #ifdef TCP_SIGNATURE 806 if (sc->sc_flags & SCF_SIGNATURE) 807 tp->t_flags |= TF_SIGNATURE; 808 #endif 809 if (sc->sc_flags & SCF_SACK) 810 tp->t_flags |= TF_SACK_PERMIT; 811 } 812 813 if (sc->sc_flags & SCF_ECN) 814 tp->t_flags |= TF_ECN_PERMIT; 815 816 /* 817 * Set up MSS and get cached values from tcp_hostcache. 818 * This might overwrite some of the defaults we just set. 819 */ 820 tcp_mss(tp, sc->sc_peer_mss); 821 822 /* 823 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 824 */ 825 if (sc->sc_rxmits) 826 tp->snd_cwnd = tp->t_maxseg; 827 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 828 829 INP_WUNLOCK(inp); 830 831 V_tcpstat.tcps_accepts++; 832 return (so); 833 834 abort: 835 INP_WUNLOCK(inp); 836 abort2: 837 if (so != NULL) 838 soabort(so); 839 return (NULL); 840 } 841 842 /* 843 * This function gets called when we receive an ACK for a 844 * socket in the LISTEN state. We look up the connection 845 * in the syncache, and if its there, we pull it out of 846 * the cache and turn it into a full-blown connection in 847 * the SYN-RECEIVED state. 848 */ 849 int 850 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 851 struct socket **lsop, struct mbuf *m) 852 { 853 struct syncache *sc; 854 struct syncache_head *sch; 855 struct syncache scs; 856 char *s; 857 858 /* 859 * Global TCP locks are held because we manipulate the PCB lists 860 * and create a new socket. 861 */ 862 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 863 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 864 ("%s: can handle only ACK", __func__)); 865 866 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 867 SCH_LOCK_ASSERT(sch); 868 if (sc == NULL) { 869 /* 870 * There is no syncache entry, so see if this ACK is 871 * a returning syncookie. To do this, first: 872 * A. See if this socket has had a syncache entry dropped in 873 * the past. We don't want to accept a bogus syncookie 874 * if we've never received a SYN. 875 * B. check that the syncookie is valid. If it is, then 876 * cobble up a fake syncache entry, and return. 877 */ 878 if (!tcp_syncookies) { 879 SCH_UNLOCK(sch); 880 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 881 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 882 "segment rejected (syncookies disabled)\n", 883 s, __func__); 884 goto failed; 885 } 886 bzero(&scs, sizeof(scs)); 887 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 888 SCH_UNLOCK(sch); 889 if (sc == NULL) { 890 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 891 log(LOG_DEBUG, "%s; %s: Segment failed " 892 "SYNCOOKIE authentication, segment rejected " 893 "(probably spoofed)\n", s, __func__); 894 goto failed; 895 } 896 } else { 897 /* Pull out the entry to unlock the bucket row. */ 898 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 899 sch->sch_length--; 900 V_tcp_syncache.cache_count--; 901 SCH_UNLOCK(sch); 902 } 903 904 /* 905 * Segment validation: 906 * ACK must match our initial sequence number + 1 (the SYN|ACK). 907 */ 908 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 909 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 910 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 911 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 912 goto failed; 913 } 914 915 /* 916 * The SEQ must fall in the window starting at the received 917 * initial receive sequence number + 1 (the SYN). 918 */ 919 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 920 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 921 !TOEPCB_ISSET(sc)) { 922 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 923 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 924 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 925 goto failed; 926 } 927 928 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 929 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 930 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 931 "segment rejected\n", s, __func__); 932 goto failed; 933 } 934 /* 935 * If timestamps were negotiated the reflected timestamp 936 * must be equal to what we actually sent in the SYN|ACK. 937 */ 938 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 939 !TOEPCB_ISSET(sc)) { 940 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 941 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 942 "segment rejected\n", 943 s, __func__, to->to_tsecr, sc->sc_ts); 944 goto failed; 945 } 946 947 *lsop = syncache_socket(sc, *lsop, m); 948 949 if (*lsop == NULL) 950 V_tcpstat.tcps_sc_aborted++; 951 else 952 V_tcpstat.tcps_sc_completed++; 953 954 /* how do we find the inp for the new socket? */ 955 if (sc != &scs) 956 syncache_free(sc); 957 return (1); 958 failed: 959 if (sc != NULL && sc != &scs) 960 syncache_free(sc); 961 if (s != NULL) 962 free(s, M_TCPLOG); 963 *lsop = NULL; 964 return (0); 965 } 966 967 int 968 tcp_offload_syncache_expand(struct in_conninfo *inc, struct tcpopt *to, 969 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 970 { 971 int rc; 972 973 INP_INFO_WLOCK(&V_tcbinfo); 974 rc = syncache_expand(inc, to, th, lsop, m); 975 INP_INFO_WUNLOCK(&V_tcbinfo); 976 977 return (rc); 978 } 979 980 /* 981 * Given a LISTEN socket and an inbound SYN request, add 982 * this to the syn cache, and send back a segment: 983 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 984 * to the source. 985 * 986 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 987 * Doing so would require that we hold onto the data and deliver it 988 * to the application. However, if we are the target of a SYN-flood 989 * DoS attack, an attacker could send data which would eventually 990 * consume all available buffer space if it were ACKed. By not ACKing 991 * the data, we avoid this DoS scenario. 992 */ 993 static void 994 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 995 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 996 struct toe_usrreqs *tu, void *toepcb) 997 { 998 struct tcpcb *tp; 999 struct socket *so; 1000 struct syncache *sc = NULL; 1001 struct syncache_head *sch; 1002 struct mbuf *ipopts = NULL; 1003 u_int32_t flowtmp; 1004 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 1005 char *s; 1006 #ifdef INET6 1007 int autoflowlabel = 0; 1008 #endif 1009 #ifdef MAC 1010 struct label *maclabel; 1011 #endif 1012 struct syncache scs; 1013 1014 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1015 INP_WLOCK_ASSERT(inp); /* listen socket */ 1016 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 1017 ("%s: unexpected tcp flags", __func__)); 1018 1019 /* 1020 * Combine all so/tp operations very early to drop the INP lock as 1021 * soon as possible. 1022 */ 1023 so = *lsop; 1024 tp = sototcpcb(so); 1025 1026 #ifdef INET6 1027 if (inc->inc_isipv6 && 1028 (inp->in6p_flags & IN6P_AUTOFLOWLABEL)) 1029 autoflowlabel = 1; 1030 #endif 1031 ip_ttl = inp->inp_ip_ttl; 1032 ip_tos = inp->inp_ip_tos; 1033 win = sbspace(&so->so_rcv); 1034 sb_hiwat = so->so_rcv.sb_hiwat; 1035 noopt = (tp->t_flags & TF_NOOPT); 1036 1037 so = NULL; 1038 tp = NULL; 1039 1040 #ifdef MAC 1041 if (mac_syncache_init(&maclabel) != 0) { 1042 INP_WUNLOCK(inp); 1043 INP_INFO_WUNLOCK(&V_tcbinfo); 1044 goto done; 1045 } else 1046 mac_syncache_create(maclabel, inp); 1047 #endif 1048 INP_WUNLOCK(inp); 1049 INP_INFO_WUNLOCK(&V_tcbinfo); 1050 1051 /* 1052 * Remember the IP options, if any. 1053 */ 1054 #ifdef INET6 1055 if (!inc->inc_isipv6) 1056 #endif 1057 ipopts = (m) ? ip_srcroute(m) : NULL; 1058 1059 /* 1060 * See if we already have an entry for this connection. 1061 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1062 * 1063 * XXX: should the syncache be re-initialized with the contents 1064 * of the new SYN here (which may have different options?) 1065 * 1066 * XXX: We do not check the sequence number to see if this is a 1067 * real retransmit or a new connection attempt. The question is 1068 * how to handle such a case; either ignore it as spoofed, or 1069 * drop the current entry and create a new one? 1070 */ 1071 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1072 SCH_LOCK_ASSERT(sch); 1073 if (sc != NULL) { 1074 #ifndef TCP_OFFLOAD_DISABLE 1075 if (sc->sc_tu) 1076 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1077 sc->sc_toepcb); 1078 #endif 1079 V_tcpstat.tcps_sc_dupsyn++; 1080 if (ipopts) { 1081 /* 1082 * If we were remembering a previous source route, 1083 * forget it and use the new one we've been given. 1084 */ 1085 if (sc->sc_ipopts) 1086 (void) m_free(sc->sc_ipopts); 1087 sc->sc_ipopts = ipopts; 1088 } 1089 /* 1090 * Update timestamp if present. 1091 */ 1092 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1093 sc->sc_tsreflect = to->to_tsval; 1094 else 1095 sc->sc_flags &= ~SCF_TIMESTAMP; 1096 #ifdef MAC 1097 /* 1098 * Since we have already unconditionally allocated label 1099 * storage, free it up. The syncache entry will already 1100 * have an initialized label we can use. 1101 */ 1102 mac_syncache_destroy(&maclabel); 1103 KASSERT(sc->sc_label != NULL, 1104 ("%s: label not initialized", __func__)); 1105 #endif 1106 /* Retransmit SYN|ACK and reset retransmit count. */ 1107 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1108 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1109 "resetting timer and retransmitting SYN|ACK\n", 1110 s, __func__); 1111 free(s, M_TCPLOG); 1112 } 1113 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1114 sc->sc_rxmits = 0; 1115 syncache_timeout(sc, sch, 1); 1116 V_tcpstat.tcps_sndacks++; 1117 V_tcpstat.tcps_sndtotal++; 1118 } 1119 SCH_UNLOCK(sch); 1120 goto done; 1121 } 1122 1123 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1124 if (sc == NULL) { 1125 /* 1126 * The zone allocator couldn't provide more entries. 1127 * Treat this as if the cache was full; drop the oldest 1128 * entry and insert the new one. 1129 */ 1130 V_tcpstat.tcps_sc_zonefail++; 1131 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1132 syncache_drop(sc, sch); 1133 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1134 if (sc == NULL) { 1135 if (tcp_syncookies) { 1136 bzero(&scs, sizeof(scs)); 1137 sc = &scs; 1138 } else { 1139 SCH_UNLOCK(sch); 1140 if (ipopts) 1141 (void) m_free(ipopts); 1142 goto done; 1143 } 1144 } 1145 } 1146 1147 /* 1148 * Fill in the syncache values. 1149 */ 1150 #ifdef MAC 1151 sc->sc_label = maclabel; 1152 #endif 1153 sc->sc_ipopts = ipopts; 1154 sc->sc_inc.inc_fibnum = inp->inp_inc.inc_fibnum; 1155 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1156 #ifdef INET6 1157 if (!inc->inc_isipv6) 1158 #endif 1159 { 1160 sc->sc_ip_tos = ip_tos; 1161 sc->sc_ip_ttl = ip_ttl; 1162 } 1163 #ifndef TCP_OFFLOAD_DISABLE 1164 sc->sc_tu = tu; 1165 sc->sc_toepcb = toepcb; 1166 #endif 1167 sc->sc_irs = th->th_seq; 1168 sc->sc_iss = arc4random(); 1169 sc->sc_flags = 0; 1170 sc->sc_flowlabel = 0; 1171 1172 /* 1173 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1174 * win was derived from socket earlier in the function. 1175 */ 1176 win = imax(win, 0); 1177 win = imin(win, TCP_MAXWIN); 1178 sc->sc_wnd = win; 1179 1180 if (V_tcp_do_rfc1323) { 1181 /* 1182 * A timestamp received in a SYN makes 1183 * it ok to send timestamp requests and replies. 1184 */ 1185 if (to->to_flags & TOF_TS) { 1186 sc->sc_tsreflect = to->to_tsval; 1187 sc->sc_ts = ticks; 1188 sc->sc_flags |= SCF_TIMESTAMP; 1189 } 1190 if (to->to_flags & TOF_SCALE) { 1191 int wscale = 0; 1192 1193 /* 1194 * Pick the smallest possible scaling factor that 1195 * will still allow us to scale up to sb_max, aka 1196 * kern.ipc.maxsockbuf. 1197 * 1198 * We do this because there are broken firewalls that 1199 * will corrupt the window scale option, leading to 1200 * the other endpoint believing that our advertised 1201 * window is unscaled. At scale factors larger than 1202 * 5 the unscaled window will drop below 1500 bytes, 1203 * leading to serious problems when traversing these 1204 * broken firewalls. 1205 * 1206 * With the default maxsockbuf of 256K, a scale factor 1207 * of 3 will be chosen by this algorithm. Those who 1208 * choose a larger maxsockbuf should watch out 1209 * for the compatiblity problems mentioned above. 1210 * 1211 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1212 * or <SYN,ACK>) segment itself is never scaled. 1213 */ 1214 while (wscale < TCP_MAX_WINSHIFT && 1215 (TCP_MAXWIN << wscale) < sb_max) 1216 wscale++; 1217 sc->sc_requested_r_scale = wscale; 1218 sc->sc_requested_s_scale = to->to_wscale; 1219 sc->sc_flags |= SCF_WINSCALE; 1220 } 1221 } 1222 #ifdef TCP_SIGNATURE 1223 /* 1224 * If listening socket requested TCP digests, and received SYN 1225 * contains the option, flag this in the syncache so that 1226 * syncache_respond() will do the right thing with the SYN+ACK. 1227 * XXX: Currently we always record the option by default and will 1228 * attempt to use it in syncache_respond(). 1229 */ 1230 if (to->to_flags & TOF_SIGNATURE) 1231 sc->sc_flags |= SCF_SIGNATURE; 1232 #endif 1233 if (to->to_flags & TOF_SACKPERM) 1234 sc->sc_flags |= SCF_SACK; 1235 if (to->to_flags & TOF_MSS) 1236 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1237 if (noopt) 1238 sc->sc_flags |= SCF_NOOPT; 1239 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1240 sc->sc_flags |= SCF_ECN; 1241 1242 if (tcp_syncookies) { 1243 syncookie_generate(sch, sc, &flowtmp); 1244 #ifdef INET6 1245 if (autoflowlabel) 1246 sc->sc_flowlabel = flowtmp; 1247 #endif 1248 } else { 1249 #ifdef INET6 1250 if (autoflowlabel) 1251 sc->sc_flowlabel = 1252 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1253 #endif 1254 } 1255 SCH_UNLOCK(sch); 1256 1257 /* 1258 * Do a standard 3-way handshake. 1259 */ 1260 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1261 if (tcp_syncookies && tcp_syncookiesonly && sc != &scs) 1262 syncache_free(sc); 1263 else if (sc != &scs) 1264 syncache_insert(sc, sch); /* locks and unlocks sch */ 1265 V_tcpstat.tcps_sndacks++; 1266 V_tcpstat.tcps_sndtotal++; 1267 } else { 1268 if (sc != &scs) 1269 syncache_free(sc); 1270 V_tcpstat.tcps_sc_dropped++; 1271 } 1272 1273 done: 1274 #ifdef MAC 1275 if (sc == &scs) 1276 mac_syncache_destroy(&maclabel); 1277 #endif 1278 if (m) { 1279 1280 *lsop = NULL; 1281 m_freem(m); 1282 } 1283 return; 1284 } 1285 1286 static int 1287 syncache_respond(struct syncache *sc) 1288 { 1289 struct ip *ip = NULL; 1290 struct mbuf *m; 1291 struct tcphdr *th; 1292 int optlen, error; 1293 u_int16_t hlen, tlen, mssopt; 1294 struct tcpopt to; 1295 #ifdef INET6 1296 struct ip6_hdr *ip6 = NULL; 1297 #endif 1298 1299 hlen = 1300 #ifdef INET6 1301 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1302 #endif 1303 sizeof(struct ip); 1304 tlen = hlen + sizeof(struct tcphdr); 1305 1306 /* Determine MSS we advertize to other end of connection. */ 1307 mssopt = tcp_mssopt(&sc->sc_inc); 1308 if (sc->sc_peer_mss) 1309 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1310 1311 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1312 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1313 ("syncache: mbuf too small")); 1314 1315 /* Create the IP+TCP header from scratch. */ 1316 m = m_gethdr(M_DONTWAIT, MT_DATA); 1317 if (m == NULL) 1318 return (ENOBUFS); 1319 #ifdef MAC 1320 mac_syncache_create_mbuf(sc->sc_label, m); 1321 #endif 1322 m->m_data += max_linkhdr; 1323 m->m_len = tlen; 1324 m->m_pkthdr.len = tlen; 1325 m->m_pkthdr.rcvif = NULL; 1326 1327 #ifdef INET6 1328 if (sc->sc_inc.inc_isipv6) { 1329 ip6 = mtod(m, struct ip6_hdr *); 1330 ip6->ip6_vfc = IPV6_VERSION; 1331 ip6->ip6_nxt = IPPROTO_TCP; 1332 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1333 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1334 ip6->ip6_plen = htons(tlen - hlen); 1335 /* ip6_hlim is set after checksum */ 1336 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1337 ip6->ip6_flow |= sc->sc_flowlabel; 1338 1339 th = (struct tcphdr *)(ip6 + 1); 1340 } else 1341 #endif 1342 { 1343 ip = mtod(m, struct ip *); 1344 ip->ip_v = IPVERSION; 1345 ip->ip_hl = sizeof(struct ip) >> 2; 1346 ip->ip_len = tlen; 1347 ip->ip_id = 0; 1348 ip->ip_off = 0; 1349 ip->ip_sum = 0; 1350 ip->ip_p = IPPROTO_TCP; 1351 ip->ip_src = sc->sc_inc.inc_laddr; 1352 ip->ip_dst = sc->sc_inc.inc_faddr; 1353 ip->ip_ttl = sc->sc_ip_ttl; 1354 ip->ip_tos = sc->sc_ip_tos; 1355 1356 /* 1357 * See if we should do MTU discovery. Route lookups are 1358 * expensive, so we will only unset the DF bit if: 1359 * 1360 * 1) path_mtu_discovery is disabled 1361 * 2) the SCF_UNREACH flag has been set 1362 */ 1363 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1364 ip->ip_off |= IP_DF; 1365 1366 th = (struct tcphdr *)(ip + 1); 1367 } 1368 th->th_sport = sc->sc_inc.inc_lport; 1369 th->th_dport = sc->sc_inc.inc_fport; 1370 1371 th->th_seq = htonl(sc->sc_iss); 1372 th->th_ack = htonl(sc->sc_irs + 1); 1373 th->th_off = sizeof(struct tcphdr) >> 2; 1374 th->th_x2 = 0; 1375 th->th_flags = TH_SYN|TH_ACK; 1376 th->th_win = htons(sc->sc_wnd); 1377 th->th_urp = 0; 1378 1379 if (sc->sc_flags & SCF_ECN) { 1380 th->th_flags |= TH_ECE; 1381 V_tcpstat.tcps_ecn_shs++; 1382 } 1383 1384 /* Tack on the TCP options. */ 1385 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1386 to.to_flags = 0; 1387 1388 to.to_mss = mssopt; 1389 to.to_flags = TOF_MSS; 1390 if (sc->sc_flags & SCF_WINSCALE) { 1391 to.to_wscale = sc->sc_requested_r_scale; 1392 to.to_flags |= TOF_SCALE; 1393 } 1394 if (sc->sc_flags & SCF_TIMESTAMP) { 1395 /* Virgin timestamp or TCP cookie enhanced one. */ 1396 to.to_tsval = sc->sc_ts; 1397 to.to_tsecr = sc->sc_tsreflect; 1398 to.to_flags |= TOF_TS; 1399 } 1400 if (sc->sc_flags & SCF_SACK) 1401 to.to_flags |= TOF_SACKPERM; 1402 #ifdef TCP_SIGNATURE 1403 if (sc->sc_flags & SCF_SIGNATURE) 1404 to.to_flags |= TOF_SIGNATURE; 1405 #endif 1406 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1407 1408 /* Adjust headers by option size. */ 1409 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1410 m->m_len += optlen; 1411 m->m_pkthdr.len += optlen; 1412 1413 #ifdef TCP_SIGNATURE 1414 if (sc->sc_flags & SCF_SIGNATURE) 1415 tcp_signature_compute(m, sizeof(struct ip), 0, optlen, 1416 to.to_signature, IPSEC_DIR_OUTBOUND); 1417 #endif 1418 #ifdef INET6 1419 if (sc->sc_inc.inc_isipv6) 1420 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1421 else 1422 #endif 1423 ip->ip_len += optlen; 1424 } else 1425 optlen = 0; 1426 1427 #ifdef INET6 1428 if (sc->sc_inc.inc_isipv6) { 1429 th->th_sum = 0; 1430 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1431 tlen + optlen - hlen); 1432 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1433 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1434 } else 1435 #endif 1436 { 1437 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1438 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1439 m->m_pkthdr.csum_flags = CSUM_TCP; 1440 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1441 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1442 } 1443 return (error); 1444 } 1445 1446 void 1447 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1448 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1449 { 1450 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1451 } 1452 1453 void 1454 tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, 1455 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1456 struct toe_usrreqs *tu, void *toepcb) 1457 { 1458 1459 INP_INFO_WLOCK(&V_tcbinfo); 1460 INP_WLOCK(inp); 1461 _syncache_add(inc, to, th, inp, lsop, NULL, tu, toepcb); 1462 } 1463 1464 /* 1465 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1466 * receive and to be able to handle SYN floods from bogus source addresses 1467 * (where we will never receive any reply). SYN floods try to exhaust all 1468 * our memory and available slots in the SYN cache table to cause a denial 1469 * of service to legitimate users of the local host. 1470 * 1471 * The idea of SYN cookies is to encode and include all necessary information 1472 * about the connection setup state within the SYN-ACK we send back and thus 1473 * to get along without keeping any local state until the ACK to the SYN-ACK 1474 * arrives (if ever). Everything we need to know should be available from 1475 * the information we encoded in the SYN-ACK. 1476 * 1477 * More information about the theory behind SYN cookies and its first 1478 * discussion and specification can be found at: 1479 * http://cr.yp.to/syncookies.html (overview) 1480 * http://cr.yp.to/syncookies/archive (gory details) 1481 * 1482 * This implementation extends the orginal idea and first implementation 1483 * of FreeBSD by using not only the initial sequence number field to store 1484 * information but also the timestamp field if present. This way we can 1485 * keep track of the entire state we need to know to recreate the session in 1486 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1487 * these days. For those that do not we still have to live with the known 1488 * shortcomings of the ISN only SYN cookies. 1489 * 1490 * Cookie layers: 1491 * 1492 * Initial sequence number we send: 1493 * 31|................................|0 1494 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1495 * D = MD5 Digest (first dword) 1496 * M = MSS index 1497 * R = Rotation of secret 1498 * P = Odd or Even secret 1499 * 1500 * The MD5 Digest is computed with over following parameters: 1501 * a) randomly rotated secret 1502 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1503 * c) the received initial sequence number from remote host 1504 * d) the rotation offset and odd/even bit 1505 * 1506 * Timestamp we send: 1507 * 31|................................|0 1508 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1509 * D = MD5 Digest (third dword) (only as filler) 1510 * S = Requested send window scale 1511 * R = Requested receive window scale 1512 * A = SACK allowed 1513 * 5 = TCP-MD5 enabled (not implemented yet) 1514 * XORed with MD5 Digest (forth dword) 1515 * 1516 * The timestamp isn't cryptographically secure and doesn't need to be. 1517 * The double use of the MD5 digest dwords ties it to a specific remote/ 1518 * local host/port, remote initial sequence number and our local time 1519 * limited secret. A received timestamp is reverted (XORed) and then 1520 * the contained MD5 dword is compared to the computed one to ensure the 1521 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1522 * have been tampered with but this isn't different from supplying bogus 1523 * values in the SYN in the first place. 1524 * 1525 * Some problems with SYN cookies remain however: 1526 * Consider the problem of a recreated (and retransmitted) cookie. If the 1527 * original SYN was accepted, the connection is established. The second 1528 * SYN is inflight, and if it arrives with an ISN that falls within the 1529 * receive window, the connection is killed. 1530 * 1531 * Notes: 1532 * A heuristic to determine when to accept syn cookies is not necessary. 1533 * An ACK flood would cause the syncookie verification to be attempted, 1534 * but a SYN flood causes syncookies to be generated. Both are of equal 1535 * cost, so there's no point in trying to optimize the ACK flood case. 1536 * Also, if you don't process certain ACKs for some reason, then all someone 1537 * would have to do is launch a SYN and ACK flood at the same time, which 1538 * would stop cookie verification and defeat the entire purpose of syncookies. 1539 */ 1540 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1541 1542 static void 1543 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1544 u_int32_t *flowlabel) 1545 { 1546 MD5_CTX ctx; 1547 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1548 u_int32_t data; 1549 u_int32_t *secbits; 1550 u_int off, pmss, mss; 1551 int i; 1552 1553 SCH_LOCK_ASSERT(sch); 1554 1555 /* Which of the two secrets to use. */ 1556 secbits = sch->sch_oddeven ? 1557 sch->sch_secbits_odd : sch->sch_secbits_even; 1558 1559 /* Reseed secret if too old. */ 1560 if (sch->sch_reseed < time_uptime) { 1561 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1562 secbits = sch->sch_oddeven ? 1563 sch->sch_secbits_odd : sch->sch_secbits_even; 1564 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1565 secbits[i] = arc4random(); 1566 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1567 } 1568 1569 /* Secret rotation offset. */ 1570 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1571 1572 /* Maximum segment size calculation. */ 1573 pmss = 1574 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1575 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1576 if (tcp_sc_msstab[mss] <= pmss) 1577 break; 1578 1579 /* Fold parameters and MD5 digest into the ISN we will send. */ 1580 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1581 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1582 data |= mss << 4; /* mss, 3 bits */ 1583 1584 MD5Init(&ctx); 1585 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1586 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1587 MD5Update(&ctx, secbits, off); 1588 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1589 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1590 MD5Update(&ctx, &data, sizeof(data)); 1591 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1592 1593 data |= (md5_buffer[0] << 7); 1594 sc->sc_iss = data; 1595 1596 #ifdef INET6 1597 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1598 #endif 1599 1600 /* Additional parameters are stored in the timestamp if present. */ 1601 if (sc->sc_flags & SCF_TIMESTAMP) { 1602 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1603 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1604 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1605 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1606 data |= md5_buffer[2] << 10; /* more digest bits */ 1607 data ^= md5_buffer[3]; 1608 sc->sc_ts = data; 1609 sc->sc_tsoff = data - ticks; /* after XOR */ 1610 } 1611 1612 V_tcpstat.tcps_sc_sendcookie++; 1613 return; 1614 } 1615 1616 static struct syncache * 1617 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1618 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1619 struct socket *so) 1620 { 1621 MD5_CTX ctx; 1622 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1623 u_int32_t data = 0; 1624 u_int32_t *secbits; 1625 tcp_seq ack, seq; 1626 int off, mss, wnd, flags; 1627 1628 SCH_LOCK_ASSERT(sch); 1629 1630 /* 1631 * Pull information out of SYN-ACK/ACK and 1632 * revert sequence number advances. 1633 */ 1634 ack = th->th_ack - 1; 1635 seq = th->th_seq - 1; 1636 off = (ack >> 1) & 0x7; 1637 mss = (ack >> 4) & 0x7; 1638 flags = ack & 0x7f; 1639 1640 /* Which of the two secrets to use. */ 1641 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1642 1643 /* 1644 * The secret wasn't updated for the lifetime of a syncookie, 1645 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1646 */ 1647 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1648 return (NULL); 1649 } 1650 1651 /* Recompute the digest so we can compare it. */ 1652 MD5Init(&ctx); 1653 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1654 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1655 MD5Update(&ctx, secbits, off); 1656 MD5Update(&ctx, inc, sizeof(*inc)); 1657 MD5Update(&ctx, &seq, sizeof(seq)); 1658 MD5Update(&ctx, &flags, sizeof(flags)); 1659 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1660 1661 /* Does the digest part of or ACK'ed ISS match? */ 1662 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1663 return (NULL); 1664 1665 /* Does the digest part of our reflected timestamp match? */ 1666 if (to->to_flags & TOF_TS) { 1667 data = md5_buffer[3] ^ to->to_tsecr; 1668 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1669 return (NULL); 1670 } 1671 1672 /* Fill in the syncache values. */ 1673 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1674 sc->sc_ipopts = NULL; 1675 1676 sc->sc_irs = seq; 1677 sc->sc_iss = ack; 1678 1679 #ifdef INET6 1680 if (inc->inc_isipv6) { 1681 if (sotoinpcb(so)->in6p_flags & IN6P_AUTOFLOWLABEL) 1682 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1683 } else 1684 #endif 1685 { 1686 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1687 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1688 } 1689 1690 /* Additional parameters that were encoded in the timestamp. */ 1691 if (data) { 1692 sc->sc_flags |= SCF_TIMESTAMP; 1693 sc->sc_tsreflect = to->to_tsval; 1694 sc->sc_ts = to->to_tsecr; 1695 sc->sc_tsoff = to->to_tsecr - ticks; 1696 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1697 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1698 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1699 TCP_MAX_WINSHIFT); 1700 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1701 TCP_MAX_WINSHIFT); 1702 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1703 sc->sc_flags |= SCF_WINSCALE; 1704 } else 1705 sc->sc_flags |= SCF_NOOPT; 1706 1707 wnd = sbspace(&so->so_rcv); 1708 wnd = imax(wnd, 0); 1709 wnd = imin(wnd, TCP_MAXWIN); 1710 sc->sc_wnd = wnd; 1711 1712 sc->sc_rxmits = 0; 1713 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1714 1715 V_tcpstat.tcps_sc_recvcookie++; 1716 return (sc); 1717 } 1718 1719 /* 1720 * Returns the current number of syncache entries. This number 1721 * will probably change before you get around to calling 1722 * syncache_pcblist. 1723 */ 1724 1725 int 1726 syncache_pcbcount(void) 1727 { 1728 struct syncache_head *sch; 1729 int count, i; 1730 1731 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1732 /* No need to lock for a read. */ 1733 sch = &V_tcp_syncache.hashbase[i]; 1734 count += sch->sch_length; 1735 } 1736 return count; 1737 } 1738 1739 /* 1740 * Exports the syncache entries to userland so that netstat can display 1741 * them alongside the other sockets. This function is intended to be 1742 * called only from tcp_pcblist. 1743 * 1744 * Due to concurrency on an active system, the number of pcbs exported 1745 * may have no relation to max_pcbs. max_pcbs merely indicates the 1746 * amount of space the caller allocated for this function to use. 1747 */ 1748 int 1749 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1750 { 1751 struct xtcpcb xt; 1752 struct syncache *sc; 1753 struct syncache_head *sch; 1754 int count, error, i; 1755 1756 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1757 sch = &V_tcp_syncache.hashbase[i]; 1758 SCH_LOCK(sch); 1759 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1760 if (count >= max_pcbs) { 1761 SCH_UNLOCK(sch); 1762 goto exit; 1763 } 1764 bzero(&xt, sizeof(xt)); 1765 xt.xt_len = sizeof(xt); 1766 if (sc->sc_inc.inc_isipv6) 1767 xt.xt_inp.inp_vflag = INP_IPV6; 1768 else 1769 xt.xt_inp.inp_vflag = INP_IPV4; 1770 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1771 xt.xt_tp.t_inpcb = &xt.xt_inp; 1772 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1773 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1774 xt.xt_socket.xso_len = sizeof (struct xsocket); 1775 xt.xt_socket.so_type = SOCK_STREAM; 1776 xt.xt_socket.so_state = SS_ISCONNECTING; 1777 error = SYSCTL_OUT(req, &xt, sizeof xt); 1778 if (error) { 1779 SCH_UNLOCK(sch); 1780 goto exit; 1781 } 1782 count++; 1783 } 1784 SCH_UNLOCK(sch); 1785 } 1786 exit: 1787 *pcbs_exported = count; 1788 return error; 1789 } 1790