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/ucred.h> 57 #include <sys/vimage.h> 58 59 #include <vm/uma.h> 60 61 #include <net/if.h> 62 #include <net/route.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 #include <netinet/vinet.h> 89 90 #ifdef IPSEC 91 #include <netipsec/ipsec.h> 92 #ifdef INET6 93 #include <netipsec/ipsec6.h> 94 #endif 95 #include <netipsec/key.h> 96 #endif /*IPSEC*/ 97 98 #include <machine/in_cksum.h> 99 100 #include <security/mac/mac_framework.h> 101 102 #ifdef VIMAGE_GLOBALS 103 static struct tcp_syncache tcp_syncache; 104 static int tcp_syncookies; 105 static int tcp_syncookiesonly; 106 int tcp_sc_rst_sock_fail; 107 #endif 108 109 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, syncookies, 110 CTLFLAG_RW, tcp_syncookies, 0, 111 "Use TCP SYN cookies if the syncache overflows"); 112 113 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp, OID_AUTO, syncookies_only, 114 CTLFLAG_RW, tcp_syncookiesonly, 0, 115 "Use only TCP SYN cookies"); 116 117 #ifdef TCP_OFFLOAD_DISABLE 118 #define TOEPCB_ISSET(sc) (0) 119 #else 120 #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != NULL) 121 #endif 122 123 static void syncache_drop(struct syncache *, struct syncache_head *); 124 static void syncache_free(struct syncache *); 125 static void syncache_insert(struct syncache *, struct syncache_head *); 126 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 127 static int syncache_respond(struct syncache *); 128 static struct socket *syncache_socket(struct syncache *, struct socket *, 129 struct mbuf *m); 130 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch, 131 int docallout); 132 static void syncache_timer(void *); 133 static void syncookie_generate(struct syncache_head *, struct syncache *, 134 u_int32_t *); 135 static struct syncache 136 *syncookie_lookup(struct in_conninfo *, struct syncache_head *, 137 struct syncache *, struct tcpopt *, struct tcphdr *, 138 struct socket *); 139 140 /* 141 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 142 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds, 143 * the odds are that the user has given up attempting to connect by then. 144 */ 145 #define SYNCACHE_MAXREXMTS 3 146 147 /* Arbitrary values */ 148 #define TCP_SYNCACHE_HASHSIZE 512 149 #define TCP_SYNCACHE_BUCKETLIMIT 30 150 151 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 152 153 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 154 bucketlimit, CTLFLAG_RDTUN, 155 tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 156 157 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 158 cachelimit, CTLFLAG_RDTUN, 159 tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 160 161 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 162 count, CTLFLAG_RD, 163 tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 164 165 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 166 hashsize, CTLFLAG_RDTUN, 167 tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 168 169 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 170 rexmtlimit, CTLFLAG_RW, 171 tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 172 173 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_tcp_syncache, OID_AUTO, 174 rst_on_sock_fail, CTLFLAG_RW, 175 tcp_sc_rst_sock_fail, 0, "Send reset on socket allocation failure"); 176 177 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 178 179 #define SYNCACHE_HASH(inc, mask) \ 180 ((V_tcp_syncache.hash_secret ^ \ 181 (inc)->inc_faddr.s_addr ^ \ 182 ((inc)->inc_faddr.s_addr >> 16) ^ \ 183 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 184 185 #define SYNCACHE_HASH6(inc, mask) \ 186 ((V_tcp_syncache.hash_secret ^ \ 187 (inc)->inc6_faddr.s6_addr32[0] ^ \ 188 (inc)->inc6_faddr.s6_addr32[3] ^ \ 189 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 190 191 #define ENDPTS_EQ(a, b) ( \ 192 (a)->ie_fport == (b)->ie_fport && \ 193 (a)->ie_lport == (b)->ie_lport && \ 194 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 195 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 196 ) 197 198 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 199 200 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx) 201 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx) 202 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED) 203 204 /* 205 * Requires the syncache entry to be already removed from the bucket list. 206 */ 207 static void 208 syncache_free(struct syncache *sc) 209 { 210 INIT_VNET_INET(curvnet); 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 INIT_VNET_INET(curvnet); 227 int i; 228 229 V_tcp_syncookies = 1; 230 V_tcp_syncookiesonly = 0; 231 V_tcp_sc_rst_sock_fail = 1; 232 233 V_tcp_syncache.cache_count = 0; 234 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 235 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 236 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 237 V_tcp_syncache.hash_secret = arc4random(); 238 239 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 240 &V_tcp_syncache.hashsize); 241 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 242 &V_tcp_syncache.bucket_limit); 243 if (!powerof2(V_tcp_syncache.hashsize) || 244 V_tcp_syncache.hashsize == 0) { 245 printf("WARNING: syncache hash size is not a power of 2.\n"); 246 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 247 } 248 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1; 249 250 /* Set limits. */ 251 V_tcp_syncache.cache_limit = 252 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit; 253 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 254 &V_tcp_syncache.cache_limit); 255 256 /* Allocate the hash table. */ 257 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize * 258 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO); 259 260 /* Initialize the hash buckets. */ 261 for (i = 0; i < V_tcp_syncache.hashsize; i++) { 262 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket); 263 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head", 264 NULL, MTX_DEF); 265 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer, 266 &V_tcp_syncache.hashbase[i].sch_mtx, 0); 267 V_tcp_syncache.hashbase[i].sch_length = 0; 268 } 269 270 /* Create the syncache entry zone. */ 271 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 272 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 273 uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit); 274 } 275 276 /* 277 * Inserts a syncache entry into the specified bucket row. 278 * Locks and unlocks the syncache_head autonomously. 279 */ 280 static void 281 syncache_insert(struct syncache *sc, struct syncache_head *sch) 282 { 283 INIT_VNET_INET(sch->sch_vnet); 284 struct syncache *sc2; 285 286 SCH_LOCK(sch); 287 288 /* 289 * Make sure that we don't overflow the per-bucket limit. 290 * If the bucket is full, toss the oldest element. 291 */ 292 if (sch->sch_length >= V_tcp_syncache.bucket_limit) { 293 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket), 294 ("sch->sch_length incorrect")); 295 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head); 296 syncache_drop(sc2, sch); 297 V_tcpstat.tcps_sc_bucketoverflow++; 298 } 299 300 /* Put it into the bucket. */ 301 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash); 302 sch->sch_length++; 303 304 /* Reinitialize the bucket row's timer. */ 305 if (sch->sch_length == 1) 306 sch->sch_nextc = ticks + INT_MAX; 307 syncache_timeout(sc, sch, 1); 308 309 SCH_UNLOCK(sch); 310 311 V_tcp_syncache.cache_count++; 312 V_tcpstat.tcps_sc_added++; 313 } 314 315 /* 316 * Remove and free entry from syncache bucket row. 317 * Expects locked syncache head. 318 */ 319 static void 320 syncache_drop(struct syncache *sc, struct syncache_head *sch) 321 { 322 INIT_VNET_INET(sch->sch_vnet); 323 324 SCH_LOCK_ASSERT(sch); 325 326 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 327 sch->sch_length--; 328 329 #ifndef TCP_OFFLOAD_DISABLE 330 if (sc->sc_tu) 331 sc->sc_tu->tu_syncache_event(TOE_SC_DROP, sc->sc_toepcb); 332 #endif 333 syncache_free(sc); 334 V_tcp_syncache.cache_count--; 335 } 336 337 /* 338 * Engage/reengage time on bucket row. 339 */ 340 static void 341 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout) 342 { 343 sc->sc_rxttime = ticks + 344 TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]); 345 sc->sc_rxmits++; 346 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) { 347 sch->sch_nextc = sc->sc_rxttime; 348 if (docallout) 349 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks, 350 syncache_timer, (void *)sch); 351 } 352 } 353 354 /* 355 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 356 * If we have retransmitted an entry the maximum number of times, expire it. 357 * One separate timer for each bucket row. 358 */ 359 static void 360 syncache_timer(void *xsch) 361 { 362 struct syncache_head *sch = (struct syncache_head *)xsch; 363 struct syncache *sc, *nsc; 364 int tick = ticks; 365 char *s; 366 367 CURVNET_SET(sch->sch_vnet); 368 INIT_VNET_INET(sch->sch_vnet); 369 370 /* NB: syncache_head has already been locked by the callout. */ 371 SCH_LOCK_ASSERT(sch); 372 373 /* 374 * In the following cycle we may remove some entries and/or 375 * advance some timeouts, so re-initialize the bucket timer. 376 */ 377 sch->sch_nextc = tick + INT_MAX; 378 379 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) { 380 /* 381 * We do not check if the listen socket still exists 382 * and accept the case where the listen socket may be 383 * gone by the time we resend the SYN/ACK. We do 384 * not expect this to happens often. If it does, 385 * then the RST will be sent by the time the remote 386 * host does the SYN/ACK->ACK. 387 */ 388 if (TSTMP_GT(sc->sc_rxttime, tick)) { 389 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) 390 sch->sch_nextc = sc->sc_rxttime; 391 continue; 392 } 393 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) { 394 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 395 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, " 396 "giving up and removing syncache entry\n", 397 s, __func__); 398 free(s, M_TCPLOG); 399 } 400 syncache_drop(sc, sch); 401 V_tcpstat.tcps_sc_stale++; 402 continue; 403 } 404 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 405 log(LOG_DEBUG, "%s; %s: Response timeout, " 406 "retransmitting (%u) SYN|ACK\n", 407 s, __func__, sc->sc_rxmits); 408 free(s, M_TCPLOG); 409 } 410 411 (void) syncache_respond(sc); 412 V_tcpstat.tcps_sc_retransmitted++; 413 syncache_timeout(sc, sch, 0); 414 } 415 if (!TAILQ_EMPTY(&(sch)->sch_bucket)) 416 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick, 417 syncache_timer, (void *)(sch)); 418 CURVNET_RESTORE(); 419 } 420 421 /* 422 * Find an entry in the syncache. 423 * Returns always with locked syncache_head plus a matching entry or NULL. 424 */ 425 struct syncache * 426 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 427 { 428 INIT_VNET_INET(curvnet); 429 struct syncache *sc; 430 struct syncache_head *sch; 431 432 #ifdef INET6 433 if (inc->inc_isipv6) { 434 sch = &V_tcp_syncache.hashbase[ 435 SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)]; 436 *schp = sch; 437 438 SCH_LOCK(sch); 439 440 /* Circle through bucket row to find matching entry. */ 441 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 442 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 443 return (sc); 444 } 445 } else 446 #endif 447 { 448 sch = &V_tcp_syncache.hashbase[ 449 SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)]; 450 *schp = sch; 451 452 SCH_LOCK(sch); 453 454 /* Circle through bucket row to find matching entry. */ 455 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 456 #ifdef INET6 457 if (sc->sc_inc.inc_isipv6) 458 continue; 459 #endif 460 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 461 return (sc); 462 } 463 } 464 SCH_LOCK_ASSERT(*schp); 465 return (NULL); /* always returns with locked sch */ 466 } 467 468 /* 469 * This function is called when we get a RST for a 470 * non-existent connection, so that we can see if the 471 * connection is in the syn cache. If it is, zap it. 472 */ 473 void 474 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 475 { 476 INIT_VNET_INET(curvnet); 477 struct syncache *sc; 478 struct syncache_head *sch; 479 char *s = NULL; 480 481 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 482 SCH_LOCK_ASSERT(sch); 483 484 /* 485 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags. 486 * See RFC 793 page 65, section SEGMENT ARRIVES. 487 */ 488 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) { 489 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 490 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or " 491 "FIN flag set, segment ignored\n", s, __func__); 492 V_tcpstat.tcps_badrst++; 493 goto done; 494 } 495 496 /* 497 * No corresponding connection was found in syncache. 498 * If syncookies are enabled and possibly exclusively 499 * used, or we are under memory pressure, a valid RST 500 * may not find a syncache entry. In that case we're 501 * done and no SYN|ACK retransmissions will happen. 502 * Otherwise the the RST was misdirected or spoofed. 503 */ 504 if (sc == NULL) { 505 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 506 log(LOG_DEBUG, "%s; %s: Spurious RST without matching " 507 "syncache entry (possibly syncookie only), " 508 "segment ignored\n", s, __func__); 509 V_tcpstat.tcps_badrst++; 510 goto done; 511 } 512 513 /* 514 * If the RST bit is set, check the sequence number to see 515 * if this is a valid reset segment. 516 * RFC 793 page 37: 517 * In all states except SYN-SENT, all reset (RST) segments 518 * are validated by checking their SEQ-fields. A reset is 519 * valid if its sequence number is in the window. 520 * 521 * The sequence number in the reset segment is normally an 522 * echo of our outgoing acknowlegement numbers, but some hosts 523 * send a reset with the sequence number at the rightmost edge 524 * of our receive window, and we have to handle this case. 525 */ 526 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 527 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 528 syncache_drop(sc, sch); 529 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 530 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, " 531 "connection attempt aborted by remote endpoint\n", 532 s, __func__); 533 V_tcpstat.tcps_sc_reset++; 534 } else { 535 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 536 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != " 537 "IRS %u (+WND %u), segment ignored\n", 538 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd); 539 V_tcpstat.tcps_badrst++; 540 } 541 542 done: 543 if (s != NULL) 544 free(s, M_TCPLOG); 545 SCH_UNLOCK(sch); 546 } 547 548 void 549 syncache_badack(struct in_conninfo *inc) 550 { 551 INIT_VNET_INET(curvnet); 552 struct syncache *sc; 553 struct syncache_head *sch; 554 555 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 556 SCH_LOCK_ASSERT(sch); 557 if (sc != NULL) { 558 syncache_drop(sc, sch); 559 V_tcpstat.tcps_sc_badack++; 560 } 561 SCH_UNLOCK(sch); 562 } 563 564 void 565 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 566 { 567 INIT_VNET_INET(curvnet); 568 struct syncache *sc; 569 struct syncache_head *sch; 570 571 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 572 SCH_LOCK_ASSERT(sch); 573 if (sc == NULL) 574 goto done; 575 576 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 577 if (ntohl(th->th_seq) != sc->sc_iss) 578 goto done; 579 580 /* 581 * If we've rertransmitted 3 times and this is our second error, 582 * we remove the entry. Otherwise, we allow it to continue on. 583 * This prevents us from incorrectly nuking an entry during a 584 * spurious network outage. 585 * 586 * See tcp_notify(). 587 */ 588 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) { 589 sc->sc_flags |= SCF_UNREACH; 590 goto done; 591 } 592 syncache_drop(sc, sch); 593 V_tcpstat.tcps_sc_unreach++; 594 done: 595 SCH_UNLOCK(sch); 596 } 597 598 /* 599 * Build a new TCP socket structure from a syncache entry. 600 */ 601 static struct socket * 602 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 603 { 604 INIT_VNET_INET(lso->so_vnet); 605 struct inpcb *inp = NULL; 606 struct socket *so; 607 struct tcpcb *tp; 608 char *s; 609 610 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 611 612 /* 613 * Ok, create the full blown connection, and set things up 614 * as they would have been set up if we had created the 615 * connection when the SYN arrived. If we can't create 616 * the connection, abort it. 617 */ 618 so = sonewconn(lso, SS_ISCONNECTED); 619 if (so == NULL) { 620 /* 621 * Drop the connection; we will either send a RST or 622 * have the peer retransmit its SYN again after its 623 * RTO and try again. 624 */ 625 V_tcpstat.tcps_listendrop++; 626 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) { 627 log(LOG_DEBUG, "%s; %s: Socket create failed " 628 "due to limits or memory shortage\n", 629 s, __func__); 630 free(s, M_TCPLOG); 631 } 632 goto abort2; 633 } 634 #ifdef MAC 635 SOCK_LOCK(so); 636 mac_socketpeer_set_from_mbuf(m, so); 637 SOCK_UNLOCK(so); 638 #endif 639 640 inp = sotoinpcb(so); 641 inp->inp_inc.inc_fibnum = sc->sc_inc.inc_fibnum; 642 so->so_fibnum = sc->sc_inc.inc_fibnum; 643 INP_WLOCK(inp); 644 645 /* Insert new socket into PCB hash list. */ 646 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 647 #ifdef INET6 648 if (sc->sc_inc.inc_isipv6) { 649 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 650 } else { 651 inp->inp_vflag &= ~INP_IPV6; 652 inp->inp_vflag |= INP_IPV4; 653 #endif 654 inp->inp_laddr = sc->sc_inc.inc_laddr; 655 #ifdef INET6 656 } 657 #endif 658 inp->inp_lport = sc->sc_inc.inc_lport; 659 if (in_pcbinshash(inp) != 0) { 660 /* 661 * Undo the assignments above if we failed to 662 * put the PCB on the hash lists. 663 */ 664 #ifdef INET6 665 if (sc->sc_inc.inc_isipv6) 666 inp->in6p_laddr = in6addr_any; 667 else 668 #endif 669 inp->inp_laddr.s_addr = INADDR_ANY; 670 inp->inp_lport = 0; 671 goto abort; 672 } 673 #ifdef IPSEC 674 /* Copy old policy into new socket's. */ 675 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 676 printf("syncache_socket: could not copy policy\n"); 677 #endif 678 #ifdef INET6 679 if (sc->sc_inc.inc_isipv6) { 680 struct inpcb *oinp = sotoinpcb(lso); 681 struct in6_addr laddr6; 682 struct sockaddr_in6 sin6; 683 /* 684 * Inherit socket options from the listening socket. 685 * Note that in6p_inputopts are not (and should not be) 686 * copied, since it stores previously received options and is 687 * used to detect if each new option is different than the 688 * previous one and hence should be passed to a user. 689 * If we copied in6p_inputopts, a user would not be able to 690 * receive options just after calling the accept system call. 691 */ 692 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 693 if (oinp->in6p_outputopts) 694 inp->in6p_outputopts = 695 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 696 697 sin6.sin6_family = AF_INET6; 698 sin6.sin6_len = sizeof(sin6); 699 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 700 sin6.sin6_port = sc->sc_inc.inc_fport; 701 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 702 laddr6 = inp->in6p_laddr; 703 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 704 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 705 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, 706 thread0.td_ucred)) { 707 inp->in6p_laddr = laddr6; 708 goto abort; 709 } 710 /* Override flowlabel from in6_pcbconnect. */ 711 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK; 712 inp->in6p_flowinfo |= sc->sc_flowlabel; 713 } else 714 #endif 715 { 716 struct in_addr laddr; 717 struct sockaddr_in sin; 718 719 inp->inp_options = (m) ? ip_srcroute(m) : NULL; 720 721 if (inp->inp_options == NULL) { 722 inp->inp_options = sc->sc_ipopts; 723 sc->sc_ipopts = NULL; 724 } 725 726 sin.sin_family = AF_INET; 727 sin.sin_len = sizeof(sin); 728 sin.sin_addr = sc->sc_inc.inc_faddr; 729 sin.sin_port = sc->sc_inc.inc_fport; 730 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero)); 731 laddr = inp->inp_laddr; 732 if (inp->inp_laddr.s_addr == INADDR_ANY) 733 inp->inp_laddr = sc->sc_inc.inc_laddr; 734 if (in_pcbconnect(inp, (struct sockaddr *)&sin, 735 thread0.td_ucred)) { 736 inp->inp_laddr = laddr; 737 goto abort; 738 } 739 } 740 tp = intotcpcb(inp); 741 tp->t_state = TCPS_SYN_RECEIVED; 742 tp->iss = sc->sc_iss; 743 tp->irs = sc->sc_irs; 744 tcp_rcvseqinit(tp); 745 tcp_sendseqinit(tp); 746 tp->snd_wl1 = sc->sc_irs; 747 tp->snd_max = tp->iss + 1; 748 tp->snd_nxt = tp->iss + 1; 749 tp->rcv_up = sc->sc_irs + 1; 750 tp->rcv_wnd = sc->sc_wnd; 751 tp->rcv_adv += tp->rcv_wnd; 752 tp->last_ack_sent = tp->rcv_nxt; 753 754 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 755 if (sc->sc_flags & SCF_NOOPT) 756 tp->t_flags |= TF_NOOPT; 757 else { 758 if (sc->sc_flags & SCF_WINSCALE) { 759 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 760 tp->snd_scale = sc->sc_requested_s_scale; 761 tp->request_r_scale = sc->sc_requested_r_scale; 762 } 763 if (sc->sc_flags & SCF_TIMESTAMP) { 764 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 765 tp->ts_recent = sc->sc_tsreflect; 766 tp->ts_recent_age = ticks; 767 tp->ts_offset = sc->sc_tsoff; 768 } 769 #ifdef TCP_SIGNATURE 770 if (sc->sc_flags & SCF_SIGNATURE) 771 tp->t_flags |= TF_SIGNATURE; 772 #endif 773 if (sc->sc_flags & SCF_SACK) 774 tp->t_flags |= TF_SACK_PERMIT; 775 } 776 777 if (sc->sc_flags & SCF_ECN) 778 tp->t_flags |= TF_ECN_PERMIT; 779 780 /* 781 * Set up MSS and get cached values from tcp_hostcache. 782 * This might overwrite some of the defaults we just set. 783 */ 784 tcp_mss(tp, sc->sc_peer_mss); 785 786 /* 787 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 788 */ 789 if (sc->sc_rxmits) 790 tp->snd_cwnd = tp->t_maxseg; 791 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit); 792 793 INP_WUNLOCK(inp); 794 795 V_tcpstat.tcps_accepts++; 796 return (so); 797 798 abort: 799 INP_WUNLOCK(inp); 800 abort2: 801 if (so != NULL) 802 soabort(so); 803 return (NULL); 804 } 805 806 /* 807 * This function gets called when we receive an ACK for a 808 * socket in the LISTEN state. We look up the connection 809 * in the syncache, and if its there, we pull it out of 810 * the cache and turn it into a full-blown connection in 811 * the SYN-RECEIVED state. 812 */ 813 int 814 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 815 struct socket **lsop, struct mbuf *m) 816 { 817 INIT_VNET_INET(curvnet); 818 struct syncache *sc; 819 struct syncache_head *sch; 820 struct syncache scs; 821 char *s; 822 823 /* 824 * Global TCP locks are held because we manipulate the PCB lists 825 * and create a new socket. 826 */ 827 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 828 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK, 829 ("%s: can handle only ACK", __func__)); 830 831 sc = syncache_lookup(inc, &sch); /* returns locked sch */ 832 SCH_LOCK_ASSERT(sch); 833 if (sc == NULL) { 834 /* 835 * There is no syncache entry, so see if this ACK is 836 * a returning syncookie. To do this, first: 837 * A. See if this socket has had a syncache entry dropped in 838 * the past. We don't want to accept a bogus syncookie 839 * if we've never received a SYN. 840 * B. check that the syncookie is valid. If it is, then 841 * cobble up a fake syncache entry, and return. 842 */ 843 if (!V_tcp_syncookies) { 844 SCH_UNLOCK(sch); 845 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 846 log(LOG_DEBUG, "%s; %s: Spurious ACK, " 847 "segment rejected (syncookies disabled)\n", 848 s, __func__); 849 goto failed; 850 } 851 bzero(&scs, sizeof(scs)); 852 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop); 853 SCH_UNLOCK(sch); 854 if (sc == NULL) { 855 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 856 log(LOG_DEBUG, "%s; %s: Segment failed " 857 "SYNCOOKIE authentication, segment rejected " 858 "(probably spoofed)\n", s, __func__); 859 goto failed; 860 } 861 } else { 862 /* Pull out the entry to unlock the bucket row. */ 863 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 864 sch->sch_length--; 865 V_tcp_syncache.cache_count--; 866 SCH_UNLOCK(sch); 867 } 868 869 /* 870 * Segment validation: 871 * ACK must match our initial sequence number + 1 (the SYN|ACK). 872 */ 873 if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) { 874 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 875 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment " 876 "rejected\n", s, __func__, th->th_ack, sc->sc_iss); 877 goto failed; 878 } 879 880 /* 881 * The SEQ must fall in the window starting at the received 882 * initial receive sequence number + 1 (the SYN). 883 */ 884 if ((SEQ_LEQ(th->th_seq, sc->sc_irs) || 885 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) && 886 !TOEPCB_ISSET(sc)) { 887 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 888 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment " 889 "rejected\n", s, __func__, th->th_seq, sc->sc_irs); 890 goto failed; 891 } 892 893 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) { 894 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 895 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 896 "segment rejected\n", s, __func__); 897 goto failed; 898 } 899 /* 900 * If timestamps were negotiated the reflected timestamp 901 * must be equal to what we actually sent in the SYN|ACK. 902 */ 903 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts && 904 !TOEPCB_ISSET(sc)) { 905 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) 906 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, " 907 "segment rejected\n", 908 s, __func__, to->to_tsecr, sc->sc_ts); 909 goto failed; 910 } 911 912 *lsop = syncache_socket(sc, *lsop, m); 913 914 if (*lsop == NULL) 915 V_tcpstat.tcps_sc_aborted++; 916 else 917 V_tcpstat.tcps_sc_completed++; 918 919 /* how do we find the inp for the new socket? */ 920 if (sc != &scs) 921 syncache_free(sc); 922 return (1); 923 failed: 924 if (sc != NULL && sc != &scs) 925 syncache_free(sc); 926 if (s != NULL) 927 free(s, M_TCPLOG); 928 *lsop = NULL; 929 return (0); 930 } 931 932 int 933 tcp_offload_syncache_expand(struct in_conninfo *inc, struct tcpopt *to, 934 struct tcphdr *th, struct socket **lsop, struct mbuf *m) 935 { 936 INIT_VNET_INET(curvnet); 937 int rc; 938 939 INP_INFO_WLOCK(&V_tcbinfo); 940 rc = syncache_expand(inc, to, th, lsop, m); 941 INP_INFO_WUNLOCK(&V_tcbinfo); 942 943 return (rc); 944 } 945 946 /* 947 * Given a LISTEN socket and an inbound SYN request, add 948 * this to the syn cache, and send back a segment: 949 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 950 * to the source. 951 * 952 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 953 * Doing so would require that we hold onto the data and deliver it 954 * to the application. However, if we are the target of a SYN-flood 955 * DoS attack, an attacker could send data which would eventually 956 * consume all available buffer space if it were ACKed. By not ACKing 957 * the data, we avoid this DoS scenario. 958 */ 959 static void 960 _syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 961 struct inpcb *inp, struct socket **lsop, struct mbuf *m, 962 struct toe_usrreqs *tu, void *toepcb) 963 { 964 INIT_VNET_INET(inp->inp_vnet); 965 struct tcpcb *tp; 966 struct socket *so; 967 struct syncache *sc = NULL; 968 struct syncache_head *sch; 969 struct mbuf *ipopts = NULL; 970 u_int32_t flowtmp; 971 int win, sb_hiwat, ip_ttl, ip_tos, noopt; 972 char *s; 973 #ifdef INET6 974 int autoflowlabel = 0; 975 #endif 976 #ifdef MAC 977 struct label *maclabel; 978 #endif 979 struct syncache scs; 980 struct ucred *cred; 981 982 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 983 INP_WLOCK_ASSERT(inp); /* listen socket */ 984 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN, 985 ("%s: unexpected tcp flags", __func__)); 986 987 /* 988 * Combine all so/tp operations very early to drop the INP lock as 989 * soon as possible. 990 */ 991 so = *lsop; 992 tp = sototcpcb(so); 993 cred = crhold(so->so_cred); 994 995 #ifdef INET6 996 if (inc->inc_isipv6 && 997 (inp->in6p_flags & IN6P_AUTOFLOWLABEL)) 998 autoflowlabel = 1; 999 #endif 1000 ip_ttl = inp->inp_ip_ttl; 1001 ip_tos = inp->inp_ip_tos; 1002 win = sbspace(&so->so_rcv); 1003 sb_hiwat = so->so_rcv.sb_hiwat; 1004 noopt = (tp->t_flags & TF_NOOPT); 1005 1006 /* By the time we drop the lock these should no longer be used. */ 1007 so = NULL; 1008 tp = NULL; 1009 1010 #ifdef MAC 1011 if (mac_syncache_init(&maclabel) != 0) { 1012 INP_WUNLOCK(inp); 1013 INP_INFO_WUNLOCK(&V_tcbinfo); 1014 goto done; 1015 } else 1016 mac_syncache_create(maclabel, inp); 1017 #endif 1018 INP_WUNLOCK(inp); 1019 INP_INFO_WUNLOCK(&V_tcbinfo); 1020 1021 /* 1022 * Remember the IP options, if any. 1023 */ 1024 #ifdef INET6 1025 if (!inc->inc_isipv6) 1026 #endif 1027 ipopts = (m) ? ip_srcroute(m) : NULL; 1028 1029 /* 1030 * See if we already have an entry for this connection. 1031 * If we do, resend the SYN,ACK, and reset the retransmit timer. 1032 * 1033 * XXX: should the syncache be re-initialized with the contents 1034 * of the new SYN here (which may have different options?) 1035 * 1036 * XXX: We do not check the sequence number to see if this is a 1037 * real retransmit or a new connection attempt. The question is 1038 * how to handle such a case; either ignore it as spoofed, or 1039 * drop the current entry and create a new one? 1040 */ 1041 sc = syncache_lookup(inc, &sch); /* returns locked entry */ 1042 SCH_LOCK_ASSERT(sch); 1043 if (sc != NULL) { 1044 #ifndef TCP_OFFLOAD_DISABLE 1045 if (sc->sc_tu) 1046 sc->sc_tu->tu_syncache_event(TOE_SC_ENTRY_PRESENT, 1047 sc->sc_toepcb); 1048 #endif 1049 V_tcpstat.tcps_sc_dupsyn++; 1050 if (ipopts) { 1051 /* 1052 * If we were remembering a previous source route, 1053 * forget it and use the new one we've been given. 1054 */ 1055 if (sc->sc_ipopts) 1056 (void) m_free(sc->sc_ipopts); 1057 sc->sc_ipopts = ipopts; 1058 } 1059 /* 1060 * Update timestamp if present. 1061 */ 1062 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) 1063 sc->sc_tsreflect = to->to_tsval; 1064 else 1065 sc->sc_flags &= ~SCF_TIMESTAMP; 1066 #ifdef MAC 1067 /* 1068 * Since we have already unconditionally allocated label 1069 * storage, free it up. The syncache entry will already 1070 * have an initialized label we can use. 1071 */ 1072 mac_syncache_destroy(&maclabel); 1073 KASSERT(sc->sc_label != NULL, 1074 ("%s: label not initialized", __func__)); 1075 #endif 1076 /* Retransmit SYN|ACK and reset retransmit count. */ 1077 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) { 1078 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, " 1079 "resetting timer and retransmitting SYN|ACK\n", 1080 s, __func__); 1081 free(s, M_TCPLOG); 1082 } 1083 if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) { 1084 sc->sc_rxmits = 0; 1085 syncache_timeout(sc, sch, 1); 1086 V_tcpstat.tcps_sndacks++; 1087 V_tcpstat.tcps_sndtotal++; 1088 } 1089 SCH_UNLOCK(sch); 1090 goto done; 1091 } 1092 1093 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1094 if (sc == NULL) { 1095 /* 1096 * The zone allocator couldn't provide more entries. 1097 * Treat this as if the cache was full; drop the oldest 1098 * entry and insert the new one. 1099 */ 1100 V_tcpstat.tcps_sc_zonefail++; 1101 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) 1102 syncache_drop(sc, sch); 1103 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO); 1104 if (sc == NULL) { 1105 if (V_tcp_syncookies) { 1106 bzero(&scs, sizeof(scs)); 1107 sc = &scs; 1108 } else { 1109 SCH_UNLOCK(sch); 1110 if (ipopts) 1111 (void) m_free(ipopts); 1112 goto done; 1113 } 1114 } 1115 } 1116 1117 /* 1118 * Fill in the syncache values. 1119 */ 1120 #ifdef MAC 1121 sc->sc_label = maclabel; 1122 #endif 1123 sc->sc_cred = cred; 1124 cred = NULL; 1125 sc->sc_ipopts = ipopts; 1126 sc->sc_inc.inc_fibnum = inp->inp_inc.inc_fibnum; 1127 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1128 #ifdef INET6 1129 if (!inc->inc_isipv6) 1130 #endif 1131 { 1132 sc->sc_ip_tos = ip_tos; 1133 sc->sc_ip_ttl = ip_ttl; 1134 } 1135 #ifndef TCP_OFFLOAD_DISABLE 1136 sc->sc_tu = tu; 1137 sc->sc_toepcb = toepcb; 1138 #endif 1139 sc->sc_irs = th->th_seq; 1140 sc->sc_iss = arc4random(); 1141 sc->sc_flags = 0; 1142 sc->sc_flowlabel = 0; 1143 1144 /* 1145 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN]. 1146 * win was derived from socket earlier in the function. 1147 */ 1148 win = imax(win, 0); 1149 win = imin(win, TCP_MAXWIN); 1150 sc->sc_wnd = win; 1151 1152 if (V_tcp_do_rfc1323) { 1153 /* 1154 * A timestamp received in a SYN makes 1155 * it ok to send timestamp requests and replies. 1156 */ 1157 if (to->to_flags & TOF_TS) { 1158 sc->sc_tsreflect = to->to_tsval; 1159 sc->sc_ts = ticks; 1160 sc->sc_flags |= SCF_TIMESTAMP; 1161 } 1162 if (to->to_flags & TOF_SCALE) { 1163 int wscale = 0; 1164 1165 /* 1166 * Pick the smallest possible scaling factor that 1167 * will still allow us to scale up to sb_max, aka 1168 * kern.ipc.maxsockbuf. 1169 * 1170 * We do this because there are broken firewalls that 1171 * will corrupt the window scale option, leading to 1172 * the other endpoint believing that our advertised 1173 * window is unscaled. At scale factors larger than 1174 * 5 the unscaled window will drop below 1500 bytes, 1175 * leading to serious problems when traversing these 1176 * broken firewalls. 1177 * 1178 * With the default maxsockbuf of 256K, a scale factor 1179 * of 3 will be chosen by this algorithm. Those who 1180 * choose a larger maxsockbuf should watch out 1181 * for the compatiblity problems mentioned above. 1182 * 1183 * RFC1323: The Window field in a SYN (i.e., a <SYN> 1184 * or <SYN,ACK>) segment itself is never scaled. 1185 */ 1186 while (wscale < TCP_MAX_WINSHIFT && 1187 (TCP_MAXWIN << wscale) < sb_max) 1188 wscale++; 1189 sc->sc_requested_r_scale = wscale; 1190 sc->sc_requested_s_scale = to->to_wscale; 1191 sc->sc_flags |= SCF_WINSCALE; 1192 } 1193 } 1194 #ifdef TCP_SIGNATURE 1195 /* 1196 * If listening socket requested TCP digests, and received SYN 1197 * contains the option, flag this in the syncache so that 1198 * syncache_respond() will do the right thing with the SYN+ACK. 1199 * XXX: Currently we always record the option by default and will 1200 * attempt to use it in syncache_respond(). 1201 */ 1202 if (to->to_flags & TOF_SIGNATURE) 1203 sc->sc_flags |= SCF_SIGNATURE; 1204 #endif 1205 if (to->to_flags & TOF_SACKPERM) 1206 sc->sc_flags |= SCF_SACK; 1207 if (to->to_flags & TOF_MSS) 1208 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */ 1209 if (noopt) 1210 sc->sc_flags |= SCF_NOOPT; 1211 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn) 1212 sc->sc_flags |= SCF_ECN; 1213 1214 if (V_tcp_syncookies) { 1215 syncookie_generate(sch, sc, &flowtmp); 1216 #ifdef INET6 1217 if (autoflowlabel) 1218 sc->sc_flowlabel = flowtmp; 1219 #endif 1220 } else { 1221 #ifdef INET6 1222 if (autoflowlabel) 1223 sc->sc_flowlabel = 1224 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK); 1225 #endif 1226 } 1227 SCH_UNLOCK(sch); 1228 1229 /* 1230 * Do a standard 3-way handshake. 1231 */ 1232 if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) { 1233 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs) 1234 syncache_free(sc); 1235 else if (sc != &scs) 1236 syncache_insert(sc, sch); /* locks and unlocks sch */ 1237 V_tcpstat.tcps_sndacks++; 1238 V_tcpstat.tcps_sndtotal++; 1239 } else { 1240 if (sc != &scs) 1241 syncache_free(sc); 1242 V_tcpstat.tcps_sc_dropped++; 1243 } 1244 1245 done: 1246 if (cred != NULL) 1247 crfree(cred); 1248 #ifdef MAC 1249 if (sc == &scs) 1250 mac_syncache_destroy(&maclabel); 1251 #endif 1252 if (m) { 1253 1254 *lsop = NULL; 1255 m_freem(m); 1256 } 1257 } 1258 1259 static int 1260 syncache_respond(struct syncache *sc) 1261 { 1262 INIT_VNET_INET(curvnet); 1263 struct ip *ip = NULL; 1264 struct mbuf *m; 1265 struct tcphdr *th; 1266 int optlen, error; 1267 u_int16_t hlen, tlen, mssopt; 1268 struct tcpopt to; 1269 #ifdef INET6 1270 struct ip6_hdr *ip6 = NULL; 1271 #endif 1272 1273 hlen = 1274 #ifdef INET6 1275 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) : 1276 #endif 1277 sizeof(struct ip); 1278 tlen = hlen + sizeof(struct tcphdr); 1279 1280 /* Determine MSS we advertize to other end of connection. */ 1281 mssopt = tcp_mssopt(&sc->sc_inc); 1282 if (sc->sc_peer_mss) 1283 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss); 1284 1285 /* XXX: Assume that the entire packet will fit in a header mbuf. */ 1286 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN, 1287 ("syncache: mbuf too small")); 1288 1289 /* Create the IP+TCP header from scratch. */ 1290 m = m_gethdr(M_DONTWAIT, MT_DATA); 1291 if (m == NULL) 1292 return (ENOBUFS); 1293 #ifdef MAC 1294 mac_syncache_create_mbuf(sc->sc_label, m); 1295 #endif 1296 m->m_data += max_linkhdr; 1297 m->m_len = tlen; 1298 m->m_pkthdr.len = tlen; 1299 m->m_pkthdr.rcvif = NULL; 1300 1301 #ifdef INET6 1302 if (sc->sc_inc.inc_isipv6) { 1303 ip6 = mtod(m, struct ip6_hdr *); 1304 ip6->ip6_vfc = IPV6_VERSION; 1305 ip6->ip6_nxt = IPPROTO_TCP; 1306 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1307 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1308 ip6->ip6_plen = htons(tlen - hlen); 1309 /* ip6_hlim is set after checksum */ 1310 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK; 1311 ip6->ip6_flow |= sc->sc_flowlabel; 1312 1313 th = (struct tcphdr *)(ip6 + 1); 1314 } else 1315 #endif 1316 { 1317 ip = mtod(m, struct ip *); 1318 ip->ip_v = IPVERSION; 1319 ip->ip_hl = sizeof(struct ip) >> 2; 1320 ip->ip_len = tlen; 1321 ip->ip_id = 0; 1322 ip->ip_off = 0; 1323 ip->ip_sum = 0; 1324 ip->ip_p = IPPROTO_TCP; 1325 ip->ip_src = sc->sc_inc.inc_laddr; 1326 ip->ip_dst = sc->sc_inc.inc_faddr; 1327 ip->ip_ttl = sc->sc_ip_ttl; 1328 ip->ip_tos = sc->sc_ip_tos; 1329 1330 /* 1331 * See if we should do MTU discovery. Route lookups are 1332 * expensive, so we will only unset the DF bit if: 1333 * 1334 * 1) path_mtu_discovery is disabled 1335 * 2) the SCF_UNREACH flag has been set 1336 */ 1337 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0)) 1338 ip->ip_off |= IP_DF; 1339 1340 th = (struct tcphdr *)(ip + 1); 1341 } 1342 th->th_sport = sc->sc_inc.inc_lport; 1343 th->th_dport = sc->sc_inc.inc_fport; 1344 1345 th->th_seq = htonl(sc->sc_iss); 1346 th->th_ack = htonl(sc->sc_irs + 1); 1347 th->th_off = sizeof(struct tcphdr) >> 2; 1348 th->th_x2 = 0; 1349 th->th_flags = TH_SYN|TH_ACK; 1350 th->th_win = htons(sc->sc_wnd); 1351 th->th_urp = 0; 1352 1353 if (sc->sc_flags & SCF_ECN) { 1354 th->th_flags |= TH_ECE; 1355 V_tcpstat.tcps_ecn_shs++; 1356 } 1357 1358 /* Tack on the TCP options. */ 1359 if ((sc->sc_flags & SCF_NOOPT) == 0) { 1360 to.to_flags = 0; 1361 1362 to.to_mss = mssopt; 1363 to.to_flags = TOF_MSS; 1364 if (sc->sc_flags & SCF_WINSCALE) { 1365 to.to_wscale = sc->sc_requested_r_scale; 1366 to.to_flags |= TOF_SCALE; 1367 } 1368 if (sc->sc_flags & SCF_TIMESTAMP) { 1369 /* Virgin timestamp or TCP cookie enhanced one. */ 1370 to.to_tsval = sc->sc_ts; 1371 to.to_tsecr = sc->sc_tsreflect; 1372 to.to_flags |= TOF_TS; 1373 } 1374 if (sc->sc_flags & SCF_SACK) 1375 to.to_flags |= TOF_SACKPERM; 1376 #ifdef TCP_SIGNATURE 1377 if (sc->sc_flags & SCF_SIGNATURE) 1378 to.to_flags |= TOF_SIGNATURE; 1379 #endif 1380 optlen = tcp_addoptions(&to, (u_char *)(th + 1)); 1381 1382 /* Adjust headers by option size. */ 1383 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1384 m->m_len += optlen; 1385 m->m_pkthdr.len += optlen; 1386 1387 #ifdef TCP_SIGNATURE 1388 if (sc->sc_flags & SCF_SIGNATURE) 1389 tcp_signature_compute(m, 0, 0, optlen, 1390 to.to_signature, IPSEC_DIR_OUTBOUND); 1391 #endif 1392 #ifdef INET6 1393 if (sc->sc_inc.inc_isipv6) 1394 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen); 1395 else 1396 #endif 1397 ip->ip_len += optlen; 1398 } else 1399 optlen = 0; 1400 1401 #ifdef INET6 1402 if (sc->sc_inc.inc_isipv6) { 1403 th->th_sum = 0; 1404 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, 1405 tlen + optlen - hlen); 1406 ip6->ip6_hlim = in6_selecthlim(NULL, NULL); 1407 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL); 1408 } else 1409 #endif 1410 { 1411 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1412 htons(tlen + optlen - hlen + IPPROTO_TCP)); 1413 m->m_pkthdr.csum_flags = CSUM_TCP; 1414 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1415 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL); 1416 } 1417 return (error); 1418 } 1419 1420 void 1421 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 1422 struct inpcb *inp, struct socket **lsop, struct mbuf *m) 1423 { 1424 _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL); 1425 } 1426 1427 void 1428 tcp_offload_syncache_add(struct in_conninfo *inc, struct tcpopt *to, 1429 struct tcphdr *th, struct inpcb *inp, struct socket **lsop, 1430 struct toe_usrreqs *tu, void *toepcb) 1431 { 1432 INIT_VNET_INET(curvnet); 1433 1434 INP_INFO_WLOCK(&V_tcbinfo); 1435 INP_WLOCK(inp); 1436 _syncache_add(inc, to, th, inp, lsop, NULL, tu, toepcb); 1437 } 1438 1439 /* 1440 * The purpose of SYN cookies is to avoid keeping track of all SYN's we 1441 * receive and to be able to handle SYN floods from bogus source addresses 1442 * (where we will never receive any reply). SYN floods try to exhaust all 1443 * our memory and available slots in the SYN cache table to cause a denial 1444 * of service to legitimate users of the local host. 1445 * 1446 * The idea of SYN cookies is to encode and include all necessary information 1447 * about the connection setup state within the SYN-ACK we send back and thus 1448 * to get along without keeping any local state until the ACK to the SYN-ACK 1449 * arrives (if ever). Everything we need to know should be available from 1450 * the information we encoded in the SYN-ACK. 1451 * 1452 * More information about the theory behind SYN cookies and its first 1453 * discussion and specification can be found at: 1454 * http://cr.yp.to/syncookies.html (overview) 1455 * http://cr.yp.to/syncookies/archive (gory details) 1456 * 1457 * This implementation extends the orginal idea and first implementation 1458 * of FreeBSD by using not only the initial sequence number field to store 1459 * information but also the timestamp field if present. This way we can 1460 * keep track of the entire state we need to know to recreate the session in 1461 * its original form. Almost all TCP speakers implement RFC1323 timestamps 1462 * these days. For those that do not we still have to live with the known 1463 * shortcomings of the ISN only SYN cookies. 1464 * 1465 * Cookie layers: 1466 * 1467 * Initial sequence number we send: 1468 * 31|................................|0 1469 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP 1470 * D = MD5 Digest (first dword) 1471 * M = MSS index 1472 * R = Rotation of secret 1473 * P = Odd or Even secret 1474 * 1475 * The MD5 Digest is computed with over following parameters: 1476 * a) randomly rotated secret 1477 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6) 1478 * c) the received initial sequence number from remote host 1479 * d) the rotation offset and odd/even bit 1480 * 1481 * Timestamp we send: 1482 * 31|................................|0 1483 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5 1484 * D = MD5 Digest (third dword) (only as filler) 1485 * S = Requested send window scale 1486 * R = Requested receive window scale 1487 * A = SACK allowed 1488 * 5 = TCP-MD5 enabled (not implemented yet) 1489 * XORed with MD5 Digest (forth dword) 1490 * 1491 * The timestamp isn't cryptographically secure and doesn't need to be. 1492 * The double use of the MD5 digest dwords ties it to a specific remote/ 1493 * local host/port, remote initial sequence number and our local time 1494 * limited secret. A received timestamp is reverted (XORed) and then 1495 * the contained MD5 dword is compared to the computed one to ensure the 1496 * timestamp belongs to the SYN-ACK we sent. The other parameters may 1497 * have been tampered with but this isn't different from supplying bogus 1498 * values in the SYN in the first place. 1499 * 1500 * Some problems with SYN cookies remain however: 1501 * Consider the problem of a recreated (and retransmitted) cookie. If the 1502 * original SYN was accepted, the connection is established. The second 1503 * SYN is inflight, and if it arrives with an ISN that falls within the 1504 * receive window, the connection is killed. 1505 * 1506 * Notes: 1507 * A heuristic to determine when to accept syn cookies is not necessary. 1508 * An ACK flood would cause the syncookie verification to be attempted, 1509 * but a SYN flood causes syncookies to be generated. Both are of equal 1510 * cost, so there's no point in trying to optimize the ACK flood case. 1511 * Also, if you don't process certain ACKs for some reason, then all someone 1512 * would have to do is launch a SYN and ACK flood at the same time, which 1513 * would stop cookie verification and defeat the entire purpose of syncookies. 1514 */ 1515 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 }; 1516 1517 static void 1518 syncookie_generate(struct syncache_head *sch, struct syncache *sc, 1519 u_int32_t *flowlabel) 1520 { 1521 INIT_VNET_INET(curvnet); 1522 MD5_CTX ctx; 1523 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1524 u_int32_t data; 1525 u_int32_t *secbits; 1526 u_int off, pmss, mss; 1527 int i; 1528 1529 SCH_LOCK_ASSERT(sch); 1530 1531 /* Which of the two secrets to use. */ 1532 secbits = sch->sch_oddeven ? 1533 sch->sch_secbits_odd : sch->sch_secbits_even; 1534 1535 /* Reseed secret if too old. */ 1536 if (sch->sch_reseed < time_uptime) { 1537 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */ 1538 secbits = sch->sch_oddeven ? 1539 sch->sch_secbits_odd : sch->sch_secbits_even; 1540 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++) 1541 secbits[i] = arc4random(); 1542 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME; 1543 } 1544 1545 /* Secret rotation offset. */ 1546 off = sc->sc_iss & 0x7; /* iss was randomized before */ 1547 1548 /* Maximum segment size calculation. */ 1549 pmss = 1550 max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss); 1551 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--) 1552 if (tcp_sc_msstab[mss] <= pmss) 1553 break; 1554 1555 /* Fold parameters and MD5 digest into the ISN we will send. */ 1556 data = sch->sch_oddeven;/* odd or even secret, 1 bit */ 1557 data |= off << 1; /* secret offset, derived from iss, 3 bits */ 1558 data |= mss << 4; /* mss, 3 bits */ 1559 1560 MD5Init(&ctx); 1561 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1562 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1563 MD5Update(&ctx, secbits, off); 1564 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc)); 1565 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs)); 1566 MD5Update(&ctx, &data, sizeof(data)); 1567 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1568 1569 data |= (md5_buffer[0] << 7); 1570 sc->sc_iss = data; 1571 1572 #ifdef INET6 1573 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1574 #endif 1575 1576 /* Additional parameters are stored in the timestamp if present. */ 1577 if (sc->sc_flags & SCF_TIMESTAMP) { 1578 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */ 1579 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */ 1580 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */ 1581 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */ 1582 data |= md5_buffer[2] << 10; /* more digest bits */ 1583 data ^= md5_buffer[3]; 1584 sc->sc_ts = data; 1585 sc->sc_tsoff = data - ticks; /* after XOR */ 1586 } 1587 1588 V_tcpstat.tcps_sc_sendcookie++; 1589 } 1590 1591 static struct syncache * 1592 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch, 1593 struct syncache *sc, struct tcpopt *to, struct tcphdr *th, 1594 struct socket *so) 1595 { 1596 INIT_VNET_INET(curvnet); 1597 MD5_CTX ctx; 1598 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)]; 1599 u_int32_t data = 0; 1600 u_int32_t *secbits; 1601 tcp_seq ack, seq; 1602 int off, mss, wnd, flags; 1603 1604 SCH_LOCK_ASSERT(sch); 1605 1606 /* 1607 * Pull information out of SYN-ACK/ACK and 1608 * revert sequence number advances. 1609 */ 1610 ack = th->th_ack - 1; 1611 seq = th->th_seq - 1; 1612 off = (ack >> 1) & 0x7; 1613 mss = (ack >> 4) & 0x7; 1614 flags = ack & 0x7f; 1615 1616 /* Which of the two secrets to use. */ 1617 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even; 1618 1619 /* 1620 * The secret wasn't updated for the lifetime of a syncookie, 1621 * so this SYN-ACK/ACK is either too old (replay) or totally bogus. 1622 */ 1623 if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) { 1624 return (NULL); 1625 } 1626 1627 /* Recompute the digest so we can compare it. */ 1628 MD5Init(&ctx); 1629 MD5Update(&ctx, ((u_int8_t *)secbits) + off, 1630 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off); 1631 MD5Update(&ctx, secbits, off); 1632 MD5Update(&ctx, inc, sizeof(*inc)); 1633 MD5Update(&ctx, &seq, sizeof(seq)); 1634 MD5Update(&ctx, &flags, sizeof(flags)); 1635 MD5Final((u_int8_t *)&md5_buffer, &ctx); 1636 1637 /* Does the digest part of or ACK'ed ISS match? */ 1638 if ((ack & (~0x7f)) != (md5_buffer[0] << 7)) 1639 return (NULL); 1640 1641 /* Does the digest part of our reflected timestamp match? */ 1642 if (to->to_flags & TOF_TS) { 1643 data = md5_buffer[3] ^ to->to_tsecr; 1644 if ((data & (~0x3ff)) != (md5_buffer[2] << 10)) 1645 return (NULL); 1646 } 1647 1648 /* Fill in the syncache values. */ 1649 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo)); 1650 sc->sc_ipopts = NULL; 1651 1652 sc->sc_irs = seq; 1653 sc->sc_iss = ack; 1654 1655 #ifdef INET6 1656 if (inc->inc_isipv6) { 1657 if (sotoinpcb(so)->in6p_flags & IN6P_AUTOFLOWLABEL) 1658 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK; 1659 } else 1660 #endif 1661 { 1662 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl; 1663 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos; 1664 } 1665 1666 /* Additional parameters that were encoded in the timestamp. */ 1667 if (data) { 1668 sc->sc_flags |= SCF_TIMESTAMP; 1669 sc->sc_tsreflect = to->to_tsval; 1670 sc->sc_ts = to->to_tsecr; 1671 sc->sc_tsoff = to->to_tsecr - ticks; 1672 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0; 1673 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0; 1674 sc->sc_requested_s_scale = min((data >> 2) & 0xf, 1675 TCP_MAX_WINSHIFT); 1676 sc->sc_requested_r_scale = min((data >> 6) & 0xf, 1677 TCP_MAX_WINSHIFT); 1678 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale) 1679 sc->sc_flags |= SCF_WINSCALE; 1680 } else 1681 sc->sc_flags |= SCF_NOOPT; 1682 1683 wnd = sbspace(&so->so_rcv); 1684 wnd = imax(wnd, 0); 1685 wnd = imin(wnd, TCP_MAXWIN); 1686 sc->sc_wnd = wnd; 1687 1688 sc->sc_rxmits = 0; 1689 sc->sc_peer_mss = tcp_sc_msstab[mss]; 1690 1691 V_tcpstat.tcps_sc_recvcookie++; 1692 return (sc); 1693 } 1694 1695 /* 1696 * Returns the current number of syncache entries. This number 1697 * will probably change before you get around to calling 1698 * syncache_pcblist. 1699 */ 1700 1701 int 1702 syncache_pcbcount(void) 1703 { 1704 INIT_VNET_INET(curvnet); 1705 struct syncache_head *sch; 1706 int count, i; 1707 1708 for (count = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1709 /* No need to lock for a read. */ 1710 sch = &V_tcp_syncache.hashbase[i]; 1711 count += sch->sch_length; 1712 } 1713 return count; 1714 } 1715 1716 /* 1717 * Exports the syncache entries to userland so that netstat can display 1718 * them alongside the other sockets. This function is intended to be 1719 * called only from tcp_pcblist. 1720 * 1721 * Due to concurrency on an active system, the number of pcbs exported 1722 * may have no relation to max_pcbs. max_pcbs merely indicates the 1723 * amount of space the caller allocated for this function to use. 1724 */ 1725 int 1726 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported) 1727 { 1728 INIT_VNET_INET(curvnet); 1729 struct xtcpcb xt; 1730 struct syncache *sc; 1731 struct syncache_head *sch; 1732 int count, error, i; 1733 1734 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) { 1735 sch = &V_tcp_syncache.hashbase[i]; 1736 SCH_LOCK(sch); 1737 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 1738 if (count >= max_pcbs) { 1739 SCH_UNLOCK(sch); 1740 goto exit; 1741 } 1742 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0) 1743 continue; 1744 bzero(&xt, sizeof(xt)); 1745 xt.xt_len = sizeof(xt); 1746 if (sc->sc_inc.inc_isipv6) 1747 xt.xt_inp.inp_vflag = INP_IPV6; 1748 else 1749 xt.xt_inp.inp_vflag = INP_IPV4; 1750 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo)); 1751 xt.xt_tp.t_inpcb = &xt.xt_inp; 1752 xt.xt_tp.t_state = TCPS_SYN_RECEIVED; 1753 xt.xt_socket.xso_protocol = IPPROTO_TCP; 1754 xt.xt_socket.xso_len = sizeof (struct xsocket); 1755 xt.xt_socket.so_type = SOCK_STREAM; 1756 xt.xt_socket.so_state = SS_ISCONNECTING; 1757 error = SYSCTL_OUT(req, &xt, sizeof xt); 1758 if (error) { 1759 SCH_UNLOCK(sch); 1760 goto exit; 1761 } 1762 count++; 1763 } 1764 SCH_UNLOCK(sch); 1765 } 1766 exit: 1767 *pcbs_exported = count; 1768 return error; 1769 } 1770