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sys/netinet/tcp_syncache.c
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1 /*- 2 * Copyright (c) 2001 Networks Associates Technology, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by Jonathan Lemon 6 * and NAI Labs, the Security Research Division of Network Associates, Inc. 7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 8 * DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. The name of the author may not be used to endorse or promote 19 * products derived from this software without specific prior written 20 * permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $FreeBSD: releng/5.0/sys/netinet/tcp_syncache.c 111352 2003-02-23 20:19:43Z nectar $ 35 */ 36 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/malloc.h> 46 #include <sys/mac.h> 47 #include <sys/mbuf.h> 48 #include <sys/md5.h> 49 #include <sys/proc.h> /* for proc0 declaration */ 50 #include <sys/random.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 54 #include <net/if.h> 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_var.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #ifdef INET6 64 #include <netinet/ip6.h> 65 #include <netinet/icmp6.h> 66 #include <netinet6/nd6.h> 67 #include <netinet6/ip6_var.h> 68 #include <netinet6/in6_pcb.h> 69 #endif 70 #include <netinet/tcp.h> 71 #include <netinet/tcp_fsm.h> 72 #include <netinet/tcp_seq.h> 73 #include <netinet/tcp_timer.h> 74 #include <netinet/tcp_var.h> 75 #ifdef INET6 76 #include <netinet6/tcp6_var.h> 77 #endif 78 79 #ifdef IPSEC 80 #include <netinet6/ipsec.h> 81 #ifdef INET6 82 #include <netinet6/ipsec6.h> 83 #endif 84 #endif /*IPSEC*/ 85 86 #ifdef FAST_IPSEC 87 #include <netipsec/ipsec.h> 88 #ifdef INET6 89 #include <netipsec/ipsec6.h> 90 #endif 91 #include <netipsec/key.h> 92 #define IPSEC 93 #endif /*FAST_IPSEC*/ 94 95 #include <machine/in_cksum.h> 96 #include <vm/uma.h> 97 98 static int tcp_syncookies = 1; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 100 &tcp_syncookies, 0, 101 "Use TCP SYN cookies if the syncache overflows"); 102 103 static void syncache_drop(struct syncache *, struct syncache_head *); 104 static void syncache_free(struct syncache *); 105 static void syncache_insert(struct syncache *, struct syncache_head *); 106 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 107 static int syncache_respond(struct syncache *, struct mbuf *); 108 static struct socket *syncache_socket(struct syncache *, struct socket *, 109 struct mbuf *m); 110 static void syncache_timer(void *); 111 static u_int32_t syncookie_generate(struct syncache *); 112 static struct syncache *syncookie_lookup(struct in_conninfo *, 113 struct tcphdr *, struct socket *); 114 115 /* 116 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 117 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 118 * the odds are that the user has given up attempting to connect by then. 119 */ 120 #define SYNCACHE_MAXREXMTS 3 121 122 /* Arbitrary values */ 123 #define TCP_SYNCACHE_HASHSIZE 512 124 #define TCP_SYNCACHE_BUCKETLIMIT 30 125 126 struct tcp_syncache { 127 struct syncache_head *hashbase; 128 uma_zone_t zone; 129 u_int hashsize; 130 u_int hashmask; 131 u_int bucket_limit; 132 u_int cache_count; 133 u_int cache_limit; 134 u_int rexmt_limit; 135 u_int hash_secret; 136 u_int next_reseed; 137 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 138 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 139 }; 140 static struct tcp_syncache tcp_syncache; 141 142 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 143 144 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 145 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 146 147 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 148 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 149 150 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 151 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 152 153 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 154 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 155 156 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 157 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 158 159 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 160 161 #define SYNCACHE_HASH(inc, mask) \ 162 ((tcp_syncache.hash_secret ^ \ 163 (inc)->inc_faddr.s_addr ^ \ 164 ((inc)->inc_faddr.s_addr >> 16) ^ \ 165 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 166 167 #define SYNCACHE_HASH6(inc, mask) \ 168 ((tcp_syncache.hash_secret ^ \ 169 (inc)->inc6_faddr.s6_addr32[0] ^ \ 170 (inc)->inc6_faddr.s6_addr32[3] ^ \ 171 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 172 173 #define ENDPTS_EQ(a, b) ( \ 174 (a)->ie_fport == (b)->ie_fport && \ 175 (a)->ie_lport == (b)->ie_lport && \ 176 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 177 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 178 ) 179 180 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 181 182 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 183 sc->sc_rxtslot = (slot); \ 184 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[(slot)]; \ 185 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[(slot)], sc, sc_timerq); \ 186 if (!callout_active(&tcp_syncache.tt_timerq[(slot)])) \ 187 callout_reset(&tcp_syncache.tt_timerq[(slot)], \ 188 TCPTV_RTOBASE * tcp_backoff[(slot)], \ 189 syncache_timer, (void *)((intptr_t)(slot))); \ 190 } while (0) 191 192 static void 193 syncache_free(struct syncache *sc) 194 { 195 struct rtentry *rt; 196 197 if (sc->sc_ipopts) 198 (void) m_free(sc->sc_ipopts); 199 #ifdef INET6 200 if (sc->sc_inc.inc_isipv6) 201 rt = sc->sc_route6.ro_rt; 202 else 203 #endif 204 rt = sc->sc_route.ro_rt; 205 if (rt != NULL) { 206 /* 207 * If this is the only reference to a protocol cloned 208 * route, remove it immediately. 209 */ 210 if (rt->rt_flags & RTF_WASCLONED && 211 (sc->sc_flags & SCF_KEEPROUTE) == 0 && 212 rt->rt_refcnt == 1) 213 rtrequest(RTM_DELETE, rt_key(rt), 214 rt->rt_gateway, rt_mask(rt), 215 rt->rt_flags, NULL); 216 RTFREE(rt); 217 } 218 uma_zfree(tcp_syncache.zone, sc); 219 } 220 221 void 222 syncache_init(void) 223 { 224 int i; 225 226 tcp_syncache.cache_count = 0; 227 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 228 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 229 tcp_syncache.cache_limit = 230 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 231 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 232 tcp_syncache.next_reseed = 0; 233 tcp_syncache.hash_secret = arc4random(); 234 235 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 236 &tcp_syncache.hashsize); 237 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 238 &tcp_syncache.cache_limit); 239 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 240 &tcp_syncache.bucket_limit); 241 if (!powerof2(tcp_syncache.hashsize)) { 242 printf("WARNING: syncache hash size is not a power of 2.\n"); 243 tcp_syncache.hashsize = 512; /* safe default */ 244 } 245 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 246 247 /* Allocate the hash table. */ 248 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 249 tcp_syncache.hashsize * sizeof(struct syncache_head), 250 M_SYNCACHE, M_WAITOK); 251 252 /* Initialize the hash buckets. */ 253 for (i = 0; i < tcp_syncache.hashsize; i++) { 254 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 255 tcp_syncache.hashbase[i].sch_length = 0; 256 } 257 258 /* Initialize the timer queues. */ 259 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 260 TAILQ_INIT(&tcp_syncache.timerq[i]); 261 callout_init(&tcp_syncache.tt_timerq[i], 0); 262 } 263 264 /* 265 * Allocate the syncache entries. Allow the zone to allocate one 266 * more entry than cache limit, so a new entry can bump out an 267 * older one. 268 */ 269 tcp_syncache.cache_limit -= 1; 270 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 271 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 272 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 273 } 274 275 static void 276 syncache_insert(sc, sch) 277 struct syncache *sc; 278 struct syncache_head *sch; 279 { 280 struct syncache *sc2; 281 int s, i; 282 283 /* 284 * Make sure that we don't overflow the per-bucket 285 * limit or the total cache size limit. 286 */ 287 s = splnet(); 288 if (sch->sch_length >= tcp_syncache.bucket_limit) { 289 /* 290 * The bucket is full, toss the oldest element. 291 */ 292 sc2 = TAILQ_FIRST(&sch->sch_bucket); 293 sc2->sc_tp->ts_recent = ticks; 294 syncache_drop(sc2, sch); 295 tcpstat.tcps_sc_bucketoverflow++; 296 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 297 /* 298 * The cache is full. Toss the oldest entry in the 299 * entire cache. This is the front entry in the 300 * first non-empty timer queue with the largest 301 * timeout value. 302 */ 303 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 304 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 305 if (sc2 != NULL) 306 break; 307 } 308 sc2->sc_tp->ts_recent = ticks; 309 syncache_drop(sc2, NULL); 310 tcpstat.tcps_sc_cacheoverflow++; 311 } 312 313 /* Initialize the entry's timer. */ 314 SYNCACHE_TIMEOUT(sc, 0); 315 316 /* Put it into the bucket. */ 317 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 318 sch->sch_length++; 319 tcp_syncache.cache_count++; 320 tcpstat.tcps_sc_added++; 321 splx(s); 322 } 323 324 static void 325 syncache_drop(sc, sch) 326 struct syncache *sc; 327 struct syncache_head *sch; 328 { 329 int s; 330 331 if (sch == NULL) { 332 #ifdef INET6 333 if (sc->sc_inc.inc_isipv6) { 334 sch = &tcp_syncache.hashbase[ 335 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 336 } else 337 #endif 338 { 339 sch = &tcp_syncache.hashbase[ 340 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 341 } 342 } 343 344 s = splnet(); 345 346 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 347 sch->sch_length--; 348 tcp_syncache.cache_count--; 349 350 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 351 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 352 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 353 splx(s); 354 355 syncache_free(sc); 356 } 357 358 /* 359 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 360 * If we have retransmitted an entry the maximum number of times, expire it. 361 */ 362 static void 363 syncache_timer(xslot) 364 void *xslot; 365 { 366 intptr_t slot = (intptr_t)xslot; 367 struct syncache *sc, *nsc; 368 struct inpcb *inp; 369 int s; 370 371 s = splnet(); 372 INP_INFO_WLOCK(&tcbinfo); 373 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 374 !callout_active(&tcp_syncache.tt_timerq[slot])) { 375 INP_INFO_WUNLOCK(&tcbinfo); 376 splx(s); 377 return; 378 } 379 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 380 381 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 382 while (nsc != NULL) { 383 if (ticks < nsc->sc_rxttime) 384 break; 385 sc = nsc; 386 inp = sc->sc_tp->t_inpcb; 387 if (slot == SYNCACHE_MAXREXMTS || 388 slot >= tcp_syncache.rexmt_limit || 389 inp == NULL || inp->inp_gencnt != sc->sc_inp_gencnt) { 390 nsc = TAILQ_NEXT(sc, sc_timerq); 391 syncache_drop(sc, NULL); 392 tcpstat.tcps_sc_stale++; 393 continue; 394 } 395 /* 396 * syncache_respond() may call back into the syncache to 397 * to modify another entry, so do not obtain the next 398 * entry on the timer chain until it has completed. 399 */ 400 (void) syncache_respond(sc, NULL); 401 nsc = TAILQ_NEXT(sc, sc_timerq); 402 tcpstat.tcps_sc_retransmitted++; 403 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 404 SYNCACHE_TIMEOUT(sc, slot + 1); 405 } 406 if (nsc != NULL) 407 callout_reset(&tcp_syncache.tt_timerq[slot], 408 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 409 INP_INFO_WUNLOCK(&tcbinfo); 410 splx(s); 411 } 412 413 /* 414 * Find an entry in the syncache. 415 */ 416 struct syncache * 417 syncache_lookup(inc, schp) 418 struct in_conninfo *inc; 419 struct syncache_head **schp; 420 { 421 struct syncache *sc; 422 struct syncache_head *sch; 423 int s; 424 425 #ifdef INET6 426 if (inc->inc_isipv6) { 427 sch = &tcp_syncache.hashbase[ 428 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 429 *schp = sch; 430 s = splnet(); 431 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 432 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 433 splx(s); 434 return (sc); 435 } 436 } 437 splx(s); 438 } else 439 #endif 440 { 441 sch = &tcp_syncache.hashbase[ 442 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 443 *schp = sch; 444 s = splnet(); 445 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 446 #ifdef INET6 447 if (sc->sc_inc.inc_isipv6) 448 continue; 449 #endif 450 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 451 splx(s); 452 return (sc); 453 } 454 } 455 splx(s); 456 } 457 return (NULL); 458 } 459 460 /* 461 * This function is called when we get a RST for a 462 * non-existent connection, so that we can see if the 463 * connection is in the syn cache. If it is, zap it. 464 */ 465 void 466 syncache_chkrst(inc, th) 467 struct in_conninfo *inc; 468 struct tcphdr *th; 469 { 470 struct syncache *sc; 471 struct syncache_head *sch; 472 473 sc = syncache_lookup(inc, &sch); 474 if (sc == NULL) 475 return; 476 /* 477 * If the RST bit is set, check the sequence number to see 478 * if this is a valid reset segment. 479 * RFC 793 page 37: 480 * In all states except SYN-SENT, all reset (RST) segments 481 * are validated by checking their SEQ-fields. A reset is 482 * valid if its sequence number is in the window. 483 * 484 * The sequence number in the reset segment is normally an 485 * echo of our outgoing acknowlegement numbers, but some hosts 486 * send a reset with the sequence number at the rightmost edge 487 * of our receive window, and we have to handle this case. 488 */ 489 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 490 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 491 syncache_drop(sc, sch); 492 tcpstat.tcps_sc_reset++; 493 } 494 } 495 496 void 497 syncache_badack(inc) 498 struct in_conninfo *inc; 499 { 500 struct syncache *sc; 501 struct syncache_head *sch; 502 503 sc = syncache_lookup(inc, &sch); 504 if (sc != NULL) { 505 syncache_drop(sc, sch); 506 tcpstat.tcps_sc_badack++; 507 } 508 } 509 510 void 511 syncache_unreach(inc, th) 512 struct in_conninfo *inc; 513 struct tcphdr *th; 514 { 515 struct syncache *sc; 516 struct syncache_head *sch; 517 518 /* we are called at splnet() here */ 519 sc = syncache_lookup(inc, &sch); 520 if (sc == NULL) 521 return; 522 523 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 524 if (ntohl(th->th_seq) != sc->sc_iss) 525 return; 526 527 /* 528 * If we've rertransmitted 3 times and this is our second error, 529 * we remove the entry. Otherwise, we allow it to continue on. 530 * This prevents us from incorrectly nuking an entry during a 531 * spurious network outage. 532 * 533 * See tcp_notify(). 534 */ 535 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 536 sc->sc_flags |= SCF_UNREACH; 537 return; 538 } 539 syncache_drop(sc, sch); 540 tcpstat.tcps_sc_unreach++; 541 } 542 543 /* 544 * Build a new TCP socket structure from a syncache entry. 545 */ 546 static struct socket * 547 syncache_socket(sc, lso, m) 548 struct syncache *sc; 549 struct socket *lso; 550 struct mbuf *m; 551 { 552 struct inpcb *inp = NULL; 553 struct socket *so; 554 struct tcpcb *tp; 555 556 /* 557 * Ok, create the full blown connection, and set things up 558 * as they would have been set up if we had created the 559 * connection when the SYN arrived. If we can't create 560 * the connection, abort it. 561 */ 562 so = sonewconn(lso, SS_ISCONNECTED); 563 if (so == NULL) { 564 /* 565 * Drop the connection; we will send a RST if the peer 566 * retransmits the ACK, 567 */ 568 tcpstat.tcps_listendrop++; 569 goto abort; 570 } 571 #ifdef MAC 572 mac_set_socket_peer_from_mbuf(m, so); 573 #endif 574 575 inp = sotoinpcb(so); 576 577 /* 578 * Insert new socket into hash list. 579 */ 580 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 581 #ifdef INET6 582 if (sc->sc_inc.inc_isipv6) { 583 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 584 } else { 585 inp->inp_vflag &= ~INP_IPV6; 586 inp->inp_vflag |= INP_IPV4; 587 #endif 588 inp->inp_laddr = sc->sc_inc.inc_laddr; 589 #ifdef INET6 590 } 591 #endif 592 inp->inp_lport = sc->sc_inc.inc_lport; 593 if (in_pcbinshash(inp) != 0) { 594 /* 595 * Undo the assignments above if we failed to 596 * put the PCB on the hash lists. 597 */ 598 #ifdef INET6 599 if (sc->sc_inc.inc_isipv6) 600 inp->in6p_laddr = in6addr_any; 601 else 602 #endif 603 inp->inp_laddr.s_addr = INADDR_ANY; 604 inp->inp_lport = 0; 605 goto abort; 606 } 607 #ifdef IPSEC 608 /* copy old policy into new socket's */ 609 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 610 printf("syncache_expand: could not copy policy\n"); 611 #endif 612 #ifdef INET6 613 if (sc->sc_inc.inc_isipv6) { 614 struct inpcb *oinp = sotoinpcb(lso); 615 struct in6_addr laddr6; 616 struct sockaddr_in6 *sin6; 617 /* 618 * Inherit socket options from the listening socket. 619 * Note that in6p_inputopts are not (and should not be) 620 * copied, since it stores previously received options and is 621 * used to detect if each new option is different than the 622 * previous one and hence should be passed to a user. 623 * If we copied in6p_inputopts, a user would not be able to 624 * receive options just after calling the accept system call. 625 */ 626 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 627 if (oinp->in6p_outputopts) 628 inp->in6p_outputopts = 629 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 630 inp->in6p_route = sc->sc_route6; 631 sc->sc_route6.ro_rt = NULL; 632 633 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 634 M_SONAME, M_NOWAIT | M_ZERO); 635 if (sin6 == NULL) 636 goto abort; 637 sin6->sin6_family = AF_INET6; 638 sin6->sin6_len = sizeof(*sin6); 639 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 640 sin6->sin6_port = sc->sc_inc.inc_fport; 641 laddr6 = inp->in6p_laddr; 642 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 643 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 644 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 645 inp->in6p_laddr = laddr6; 646 FREE(sin6, M_SONAME); 647 goto abort; 648 } 649 FREE(sin6, M_SONAME); 650 } else 651 #endif 652 { 653 struct in_addr laddr; 654 struct sockaddr_in *sin; 655 656 inp->inp_options = ip_srcroute(); 657 if (inp->inp_options == NULL) { 658 inp->inp_options = sc->sc_ipopts; 659 sc->sc_ipopts = NULL; 660 } 661 inp->inp_route = sc->sc_route; 662 sc->sc_route.ro_rt = NULL; 663 664 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 665 M_SONAME, M_NOWAIT | M_ZERO); 666 if (sin == NULL) 667 goto abort; 668 sin->sin_family = AF_INET; 669 sin->sin_len = sizeof(*sin); 670 sin->sin_addr = sc->sc_inc.inc_faddr; 671 sin->sin_port = sc->sc_inc.inc_fport; 672 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 673 laddr = inp->inp_laddr; 674 if (inp->inp_laddr.s_addr == INADDR_ANY) 675 inp->inp_laddr = sc->sc_inc.inc_laddr; 676 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 677 inp->inp_laddr = laddr; 678 FREE(sin, M_SONAME); 679 goto abort; 680 } 681 FREE(sin, M_SONAME); 682 } 683 684 tp = intotcpcb(inp); 685 tp->t_state = TCPS_SYN_RECEIVED; 686 tp->iss = sc->sc_iss; 687 tp->irs = sc->sc_irs; 688 tcp_rcvseqinit(tp); 689 tcp_sendseqinit(tp); 690 tp->snd_wl1 = sc->sc_irs; 691 tp->rcv_up = sc->sc_irs + 1; 692 tp->rcv_wnd = sc->sc_wnd; 693 tp->rcv_adv += tp->rcv_wnd; 694 695 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 696 if (sc->sc_flags & SCF_NOOPT) 697 tp->t_flags |= TF_NOOPT; 698 if (sc->sc_flags & SCF_WINSCALE) { 699 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 700 tp->requested_s_scale = sc->sc_requested_s_scale; 701 tp->request_r_scale = sc->sc_request_r_scale; 702 } 703 if (sc->sc_flags & SCF_TIMESTAMP) { 704 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 705 tp->ts_recent = sc->sc_tsrecent; 706 tp->ts_recent_age = ticks; 707 } 708 if (sc->sc_flags & SCF_CC) { 709 /* 710 * Initialization of the tcpcb for transaction; 711 * set SND.WND = SEG.WND, 712 * initialize CCsend and CCrecv. 713 */ 714 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 715 tp->cc_send = sc->sc_cc_send; 716 tp->cc_recv = sc->sc_cc_recv; 717 } 718 719 tcp_mss(tp, sc->sc_peer_mss); 720 721 /* 722 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 723 */ 724 if (sc->sc_rxtslot != 0) 725 tp->snd_cwnd = tp->t_maxseg; 726 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 727 728 tcpstat.tcps_accepts++; 729 return (so); 730 731 abort: 732 if (so != NULL) 733 (void) soabort(so); 734 return (NULL); 735 } 736 737 /* 738 * This function gets called when we receive an ACK for a 739 * socket in the LISTEN state. We look up the connection 740 * in the syncache, and if its there, we pull it out of 741 * the cache and turn it into a full-blown connection in 742 * the SYN-RECEIVED state. 743 */ 744 int 745 syncache_expand(inc, th, sop, m) 746 struct in_conninfo *inc; 747 struct tcphdr *th; 748 struct socket **sop; 749 struct mbuf *m; 750 { 751 struct syncache *sc; 752 struct syncache_head *sch; 753 struct socket *so; 754 755 sc = syncache_lookup(inc, &sch); 756 if (sc == NULL) { 757 /* 758 * There is no syncache entry, so see if this ACK is 759 * a returning syncookie. To do this, first: 760 * A. See if this socket has had a syncache entry dropped in 761 * the past. We don't want to accept a bogus syncookie 762 * if we've never received a SYN. 763 * B. check that the syncookie is valid. If it is, then 764 * cobble up a fake syncache entry, and return. 765 */ 766 if (!tcp_syncookies) 767 return (0); 768 sc = syncookie_lookup(inc, th, *sop); 769 if (sc == NULL) 770 return (0); 771 sch = NULL; 772 tcpstat.tcps_sc_recvcookie++; 773 } 774 775 /* 776 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 777 */ 778 if (th->th_ack != sc->sc_iss + 1) 779 return (0); 780 781 so = syncache_socket(sc, *sop, m); 782 if (so == NULL) { 783 #if 0 784 resetandabort: 785 /* XXXjlemon check this - is this correct? */ 786 (void) tcp_respond(NULL, m, m, th, 787 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 788 #endif 789 m_freem(m); /* XXX only needed for above */ 790 tcpstat.tcps_sc_aborted++; 791 } else { 792 sc->sc_flags |= SCF_KEEPROUTE; 793 tcpstat.tcps_sc_completed++; 794 } 795 if (sch == NULL) 796 syncache_free(sc); 797 else 798 syncache_drop(sc, sch); 799 *sop = so; 800 return (1); 801 } 802 803 /* 804 * Given a LISTEN socket and an inbound SYN request, add 805 * this to the syn cache, and send back a segment: 806 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 807 * to the source. 808 * 809 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 810 * Doing so would require that we hold onto the data and deliver it 811 * to the application. However, if we are the target of a SYN-flood 812 * DoS attack, an attacker could send data which would eventually 813 * consume all available buffer space if it were ACKed. By not ACKing 814 * the data, we avoid this DoS scenario. 815 */ 816 int 817 syncache_add(inc, to, th, sop, m) 818 struct in_conninfo *inc; 819 struct tcpopt *to; 820 struct tcphdr *th; 821 struct socket **sop; 822 struct mbuf *m; 823 { 824 struct tcpcb *tp; 825 struct socket *so; 826 struct syncache *sc = NULL; 827 struct syncache_head *sch; 828 struct mbuf *ipopts = NULL; 829 struct rmxp_tao *taop; 830 int i, s, win; 831 832 so = *sop; 833 tp = sototcpcb(so); 834 835 /* 836 * Remember the IP options, if any. 837 */ 838 #ifdef INET6 839 if (!inc->inc_isipv6) 840 #endif 841 ipopts = ip_srcroute(); 842 843 /* 844 * See if we already have an entry for this connection. 845 * If we do, resend the SYN,ACK, and reset the retransmit timer. 846 * 847 * XXX 848 * should the syncache be re-initialized with the contents 849 * of the new SYN here (which may have different options?) 850 */ 851 sc = syncache_lookup(inc, &sch); 852 if (sc != NULL) { 853 tcpstat.tcps_sc_dupsyn++; 854 if (ipopts) { 855 /* 856 * If we were remembering a previous source route, 857 * forget it and use the new one we've been given. 858 */ 859 if (sc->sc_ipopts) 860 (void) m_free(sc->sc_ipopts); 861 sc->sc_ipopts = ipopts; 862 } 863 /* 864 * Update timestamp if present. 865 */ 866 if (sc->sc_flags & SCF_TIMESTAMP) 867 sc->sc_tsrecent = to->to_tsval; 868 /* 869 * PCB may have changed, pick up new values. 870 */ 871 sc->sc_tp = tp; 872 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 873 if (syncache_respond(sc, m) == 0) { 874 s = splnet(); 875 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 876 sc, sc_timerq); 877 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 878 splx(s); 879 tcpstat.tcps_sndacks++; 880 tcpstat.tcps_sndtotal++; 881 } 882 *sop = NULL; 883 return (1); 884 } 885 886 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 887 if (sc == NULL) { 888 /* 889 * The zone allocator couldn't provide more entries. 890 * Treat this as if the cache was full; drop the oldest 891 * entry and insert the new one. 892 */ 893 s = splnet(); 894 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 895 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 896 if (sc != NULL) 897 break; 898 } 899 sc->sc_tp->ts_recent = ticks; 900 syncache_drop(sc, NULL); 901 splx(s); 902 tcpstat.tcps_sc_zonefail++; 903 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 904 if (sc == NULL) { 905 if (ipopts) 906 (void) m_free(ipopts); 907 return (0); 908 } 909 } 910 911 /* 912 * Fill in the syncache values. 913 */ 914 bzero(sc, sizeof(*sc)); 915 sc->sc_tp = tp; 916 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 917 sc->sc_ipopts = ipopts; 918 sc->sc_inc.inc_fport = inc->inc_fport; 919 sc->sc_inc.inc_lport = inc->inc_lport; 920 #ifdef INET6 921 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 922 if (inc->inc_isipv6) { 923 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 924 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 925 sc->sc_route6.ro_rt = NULL; 926 } else 927 #endif 928 { 929 sc->sc_inc.inc_faddr = inc->inc_faddr; 930 sc->sc_inc.inc_laddr = inc->inc_laddr; 931 sc->sc_route.ro_rt = NULL; 932 } 933 sc->sc_irs = th->th_seq; 934 if (tcp_syncookies) 935 sc->sc_iss = syncookie_generate(sc); 936 else 937 sc->sc_iss = arc4random(); 938 939 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 940 win = sbspace(&so->so_rcv); 941 win = imax(win, 0); 942 win = imin(win, TCP_MAXWIN); 943 sc->sc_wnd = win; 944 945 sc->sc_flags = 0; 946 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 947 if (tcp_do_rfc1323) { 948 /* 949 * A timestamp received in a SYN makes 950 * it ok to send timestamp requests and replies. 951 */ 952 if (to->to_flags & TOF_TS) { 953 sc->sc_tsrecent = to->to_tsval; 954 sc->sc_flags |= SCF_TIMESTAMP; 955 } 956 if (to->to_flags & TOF_SCALE) { 957 int wscale = 0; 958 959 /* Compute proper scaling value from buffer space */ 960 while (wscale < TCP_MAX_WINSHIFT && 961 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 962 wscale++; 963 sc->sc_request_r_scale = wscale; 964 sc->sc_requested_s_scale = to->to_requested_s_scale; 965 sc->sc_flags |= SCF_WINSCALE; 966 } 967 } 968 if (tcp_do_rfc1644) { 969 /* 970 * A CC or CC.new option received in a SYN makes 971 * it ok to send CC in subsequent segments. 972 */ 973 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 974 sc->sc_cc_recv = to->to_cc; 975 sc->sc_cc_send = CC_INC(tcp_ccgen); 976 sc->sc_flags |= SCF_CC; 977 } 978 } 979 if (tp->t_flags & TF_NOOPT) 980 sc->sc_flags = SCF_NOOPT; 981 982 /* 983 * XXX 984 * We have the option here of not doing TAO (even if the segment 985 * qualifies) and instead fall back to a normal 3WHS via the syncache. 986 * This allows us to apply synflood protection to TAO-qualifying SYNs 987 * also. However, there should be a hueristic to determine when to 988 * do this, and is not present at the moment. 989 */ 990 991 /* 992 * Perform TAO test on incoming CC (SEG.CC) option, if any. 993 * - compare SEG.CC against cached CC from the same host, if any. 994 * - if SEG.CC > chached value, SYN must be new and is accepted 995 * immediately: save new CC in the cache, mark the socket 996 * connected, enter ESTABLISHED state, turn on flag to 997 * send a SYN in the next segment. 998 * A virtual advertised window is set in rcv_adv to 999 * initialize SWS prevention. Then enter normal segment 1000 * processing: drop SYN, process data and FIN. 1001 * - otherwise do a normal 3-way handshake. 1002 */ 1003 taop = tcp_gettaocache(&sc->sc_inc); 1004 if ((to->to_flags & TOF_CC) != 0) { 1005 if (((tp->t_flags & TF_NOPUSH) != 0) && 1006 sc->sc_flags & SCF_CC && 1007 taop != NULL && taop->tao_cc != 0 && 1008 CC_GT(to->to_cc, taop->tao_cc)) { 1009 sc->sc_rxtslot = 0; 1010 so = syncache_socket(sc, *sop, m); 1011 if (so != NULL) { 1012 sc->sc_flags |= SCF_KEEPROUTE; 1013 taop->tao_cc = to->to_cc; 1014 *sop = so; 1015 } 1016 syncache_free(sc); 1017 return (so != NULL); 1018 } 1019 } else { 1020 /* 1021 * No CC option, but maybe CC.NEW: invalidate cached value. 1022 */ 1023 if (taop != NULL) 1024 taop->tao_cc = 0; 1025 } 1026 /* 1027 * TAO test failed or there was no CC option, 1028 * do a standard 3-way handshake. 1029 */ 1030 if (syncache_respond(sc, m) == 0) { 1031 syncache_insert(sc, sch); 1032 tcpstat.tcps_sndacks++; 1033 tcpstat.tcps_sndtotal++; 1034 } else { 1035 syncache_free(sc); 1036 tcpstat.tcps_sc_dropped++; 1037 } 1038 *sop = NULL; 1039 return (1); 1040 } 1041 1042 static int 1043 syncache_respond(sc, m) 1044 struct syncache *sc; 1045 struct mbuf *m; 1046 { 1047 u_int8_t *optp; 1048 int optlen, error; 1049 u_int16_t tlen, hlen, mssopt; 1050 struct ip *ip = NULL; 1051 struct rtentry *rt; 1052 struct tcphdr *th; 1053 #ifdef INET6 1054 struct ip6_hdr *ip6 = NULL; 1055 #endif 1056 1057 #ifdef INET6 1058 if (sc->sc_inc.inc_isipv6) { 1059 rt = tcp_rtlookup6(&sc->sc_inc); 1060 if (rt != NULL) 1061 mssopt = rt->rt_ifp->if_mtu - 1062 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1063 else 1064 mssopt = tcp_v6mssdflt; 1065 hlen = sizeof(struct ip6_hdr); 1066 } else 1067 #endif 1068 { 1069 rt = tcp_rtlookup(&sc->sc_inc); 1070 if (rt != NULL) 1071 mssopt = rt->rt_ifp->if_mtu - 1072 (sizeof(struct ip) + sizeof(struct tcphdr)); 1073 else 1074 mssopt = tcp_mssdflt; 1075 hlen = sizeof(struct ip); 1076 } 1077 1078 /* Compute the size of the TCP options. */ 1079 if (sc->sc_flags & SCF_NOOPT) { 1080 optlen = 0; 1081 } else { 1082 optlen = TCPOLEN_MAXSEG + 1083 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1084 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1085 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1086 } 1087 tlen = hlen + sizeof(struct tcphdr) + optlen; 1088 1089 /* 1090 * XXX 1091 * assume that the entire packet will fit in a header mbuf 1092 */ 1093 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1094 1095 /* 1096 * XXX shouldn't this reuse the mbuf if possible ? 1097 * Create the IP+TCP header from scratch. 1098 */ 1099 if (m) 1100 m_freem(m); 1101 1102 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1103 if (m == NULL) 1104 return (ENOBUFS); 1105 m->m_data += max_linkhdr; 1106 m->m_len = tlen; 1107 m->m_pkthdr.len = tlen; 1108 m->m_pkthdr.rcvif = NULL; 1109 #ifdef MAC 1110 mac_create_mbuf_from_socket(sc->sc_tp->t_inpcb->inp_socket, m); 1111 #endif 1112 1113 #ifdef INET6 1114 if (sc->sc_inc.inc_isipv6) { 1115 ip6 = mtod(m, struct ip6_hdr *); 1116 ip6->ip6_vfc = IPV6_VERSION; 1117 ip6->ip6_nxt = IPPROTO_TCP; 1118 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1119 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1120 ip6->ip6_plen = htons(tlen - hlen); 1121 /* ip6_hlim is set after checksum */ 1122 /* ip6_flow = ??? */ 1123 1124 th = (struct tcphdr *)(ip6 + 1); 1125 } else 1126 #endif 1127 { 1128 ip = mtod(m, struct ip *); 1129 ip->ip_v = IPVERSION; 1130 ip->ip_hl = sizeof(struct ip) >> 2; 1131 ip->ip_len = tlen; 1132 ip->ip_id = 0; 1133 ip->ip_off = 0; 1134 ip->ip_sum = 0; 1135 ip->ip_p = IPPROTO_TCP; 1136 ip->ip_src = sc->sc_inc.inc_laddr; 1137 ip->ip_dst = sc->sc_inc.inc_faddr; 1138 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1139 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1140 1141 /* 1142 * See if we should do MTU discovery. Route lookups are expensive, 1143 * so we will only unset the DF bit if: 1144 * 1145 * 1) path_mtu_discovery is disabled 1146 * 2) the SCF_UNREACH flag has been set 1147 */ 1148 if (path_mtu_discovery 1149 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1150 ip->ip_off |= IP_DF; 1151 } 1152 1153 th = (struct tcphdr *)(ip + 1); 1154 } 1155 th->th_sport = sc->sc_inc.inc_lport; 1156 th->th_dport = sc->sc_inc.inc_fport; 1157 1158 th->th_seq = htonl(sc->sc_iss); 1159 th->th_ack = htonl(sc->sc_irs + 1); 1160 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1161 th->th_x2 = 0; 1162 th->th_flags = TH_SYN|TH_ACK; 1163 th->th_win = htons(sc->sc_wnd); 1164 th->th_urp = 0; 1165 1166 /* Tack on the TCP options. */ 1167 if (optlen == 0) 1168 goto no_options; 1169 optp = (u_int8_t *)(th + 1); 1170 *optp++ = TCPOPT_MAXSEG; 1171 *optp++ = TCPOLEN_MAXSEG; 1172 *optp++ = (mssopt >> 8) & 0xff; 1173 *optp++ = mssopt & 0xff; 1174 1175 if (sc->sc_flags & SCF_WINSCALE) { 1176 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1177 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1178 sc->sc_request_r_scale); 1179 optp += 4; 1180 } 1181 1182 if (sc->sc_flags & SCF_TIMESTAMP) { 1183 u_int32_t *lp = (u_int32_t *)(optp); 1184 1185 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1186 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1187 *lp++ = htonl(ticks); 1188 *lp = htonl(sc->sc_tsrecent); 1189 optp += TCPOLEN_TSTAMP_APPA; 1190 } 1191 1192 /* 1193 * Send CC and CC.echo if we received CC from our peer. 1194 */ 1195 if (sc->sc_flags & SCF_CC) { 1196 u_int32_t *lp = (u_int32_t *)(optp); 1197 1198 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1199 *lp++ = htonl(sc->sc_cc_send); 1200 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1201 *lp = htonl(sc->sc_cc_recv); 1202 optp += TCPOLEN_CC_APPA * 2; 1203 } 1204 no_options: 1205 1206 #ifdef INET6 1207 if (sc->sc_inc.inc_isipv6) { 1208 struct route_in6 *ro6 = &sc->sc_route6; 1209 1210 th->th_sum = 0; 1211 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1212 ip6->ip6_hlim = in6_selecthlim(NULL, 1213 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1214 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1215 sc->sc_tp->t_inpcb); 1216 } else 1217 #endif 1218 { 1219 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1220 htons(tlen - hlen + IPPROTO_TCP)); 1221 m->m_pkthdr.csum_flags = CSUM_TCP; 1222 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1223 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL, 1224 sc->sc_tp->t_inpcb); 1225 } 1226 return (error); 1227 } 1228 1229 /* 1230 * cookie layers: 1231 * 1232 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1233 * | peer iss | 1234 * | MD5(laddr,faddr,lport,fport,secret) |. . . . . . .| 1235 * | 0 |(A)| | 1236 * (A): peer mss index 1237 */ 1238 1239 /* 1240 * The values below are chosen to minimize the size of the tcp_secret 1241 * table, as well as providing roughly a 16 second lifetime for the cookie. 1242 */ 1243 1244 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1245 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1246 1247 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1248 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1249 #define SYNCOOKIE_TIMEOUT \ 1250 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1251 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1252 1253 static struct { 1254 u_int32_t ts_secbits[4]; 1255 u_int ts_expire; 1256 } tcp_secret[SYNCOOKIE_NSECRETS]; 1257 1258 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1259 1260 static MD5_CTX syn_ctx; 1261 1262 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1263 1264 struct md5_add { 1265 u_int32_t laddr, faddr; 1266 u_int32_t secbits[4]; 1267 u_int16_t lport, fport; 1268 }; 1269 1270 #ifdef CTASSERT 1271 CTASSERT(sizeof(struct md5_add) == 28); 1272 #endif 1273 1274 /* 1275 * Consider the problem of a recreated (and retransmitted) cookie. If the 1276 * original SYN was accepted, the connection is established. The second 1277 * SYN is inflight, and if it arrives with an ISN that falls within the 1278 * receive window, the connection is killed. 1279 * 1280 * However, since cookies have other problems, this may not be worth 1281 * worrying about. 1282 */ 1283 1284 static u_int32_t 1285 syncookie_generate(struct syncache *sc) 1286 { 1287 u_int32_t md5_buffer[4]; 1288 u_int32_t data; 1289 int idx, i; 1290 struct md5_add add; 1291 1292 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1293 if (tcp_secret[idx].ts_expire < ticks) { 1294 for (i = 0; i < 4; i++) 1295 tcp_secret[idx].ts_secbits[i] = arc4random(); 1296 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1297 } 1298 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1299 if (tcp_msstab[data] <= sc->sc_peer_mss) 1300 break; 1301 data = (data << SYNCOOKIE_WNDBITS) | idx; 1302 data ^= sc->sc_irs; /* peer's iss */ 1303 MD5Init(&syn_ctx); 1304 #ifdef INET6 1305 if (sc->sc_inc.inc_isipv6) { 1306 MD5Add(sc->sc_inc.inc6_laddr); 1307 MD5Add(sc->sc_inc.inc6_faddr); 1308 add.laddr = 0; 1309 add.faddr = 0; 1310 } else 1311 #endif 1312 { 1313 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1314 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1315 } 1316 add.lport = sc->sc_inc.inc_lport; 1317 add.fport = sc->sc_inc.inc_fport; 1318 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1319 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1320 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1321 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1322 MD5Add(add); 1323 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1324 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1325 return (data); 1326 } 1327 1328 static struct syncache * 1329 syncookie_lookup(inc, th, so) 1330 struct in_conninfo *inc; 1331 struct tcphdr *th; 1332 struct socket *so; 1333 { 1334 u_int32_t md5_buffer[4]; 1335 struct syncache *sc; 1336 u_int32_t data; 1337 int wnd, idx; 1338 struct md5_add add; 1339 1340 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1341 idx = data & SYNCOOKIE_WNDMASK; 1342 if (tcp_secret[idx].ts_expire < ticks || 1343 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1344 return (NULL); 1345 MD5Init(&syn_ctx); 1346 #ifdef INET6 1347 if (inc->inc_isipv6) { 1348 MD5Add(inc->inc6_laddr); 1349 MD5Add(inc->inc6_faddr); 1350 add.laddr = 0; 1351 add.faddr = 0; 1352 } else 1353 #endif 1354 { 1355 add.laddr = inc->inc_laddr.s_addr; 1356 add.faddr = inc->inc_faddr.s_addr; 1357 } 1358 add.lport = inc->inc_lport; 1359 add.fport = inc->inc_fport; 1360 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1361 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1362 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1363 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1364 MD5Add(add); 1365 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1366 data ^= md5_buffer[0]; 1367 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1368 return (NULL); 1369 data = data >> SYNCOOKIE_WNDBITS; 1370 1371 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1372 if (sc == NULL) 1373 return (NULL); 1374 /* 1375 * Fill in the syncache values. 1376 * XXX duplicate code from syncache_add 1377 */ 1378 sc->sc_ipopts = NULL; 1379 sc->sc_inc.inc_fport = inc->inc_fport; 1380 sc->sc_inc.inc_lport = inc->inc_lport; 1381 #ifdef INET6 1382 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1383 if (inc->inc_isipv6) { 1384 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1385 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1386 sc->sc_route6.ro_rt = NULL; 1387 } else 1388 #endif 1389 { 1390 sc->sc_inc.inc_faddr = inc->inc_faddr; 1391 sc->sc_inc.inc_laddr = inc->inc_laddr; 1392 sc->sc_route.ro_rt = NULL; 1393 } 1394 sc->sc_irs = th->th_seq - 1; 1395 sc->sc_iss = th->th_ack - 1; 1396 wnd = sbspace(&so->so_rcv); 1397 wnd = imax(wnd, 0); 1398 wnd = imin(wnd, TCP_MAXWIN); 1399 sc->sc_wnd = wnd; 1400 sc->sc_flags = 0; 1401 sc->sc_rxtslot = 0; 1402 sc->sc_peer_mss = tcp_msstab[data]; 1403 return (sc); 1404 }
Cache object: aceaa9992736ad7b741c2738af7b6bb7
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