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 * $FreeBSD$ 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 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 373 !callout_active(&tcp_syncache.tt_timerq[slot])) { 374 splx(s); 375 return; 376 } 377 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 378 379 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 380 INP_INFO_RLOCK(&tcbinfo); 381 while (nsc != NULL) { 382 if (ticks < nsc->sc_rxttime) 383 break; 384 sc = nsc; 385 inp = sc->sc_tp->t_inpcb; 386 INP_LOCK(inp); 387 if (slot == SYNCACHE_MAXREXMTS || 388 slot >= tcp_syncache.rexmt_limit || 389 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 INP_UNLOCK(inp); 394 continue; 395 } 396 /* 397 * syncache_respond() may call back into the syncache to 398 * to modify another entry, so do not obtain the next 399 * entry on the timer chain until it has completed. 400 */ 401 (void) syncache_respond(sc, NULL); 402 INP_UNLOCK(inp); 403 nsc = TAILQ_NEXT(sc, sc_timerq); 404 tcpstat.tcps_sc_retransmitted++; 405 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 406 SYNCACHE_TIMEOUT(sc, slot + 1); 407 } 408 INP_INFO_RUNLOCK(&tcbinfo); 409 if (nsc != NULL) 410 callout_reset(&tcp_syncache.tt_timerq[slot], 411 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 412 splx(s); 413 } 414 415 /* 416 * Find an entry in the syncache. 417 */ 418 struct syncache * 419 syncache_lookup(inc, schp) 420 struct in_conninfo *inc; 421 struct syncache_head **schp; 422 { 423 struct syncache *sc; 424 struct syncache_head *sch; 425 int s; 426 427 #ifdef INET6 428 if (inc->inc_isipv6) { 429 sch = &tcp_syncache.hashbase[ 430 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 431 *schp = sch; 432 s = splnet(); 433 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 434 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 435 splx(s); 436 return (sc); 437 } 438 } 439 splx(s); 440 } else 441 #endif 442 { 443 sch = &tcp_syncache.hashbase[ 444 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 445 *schp = sch; 446 s = splnet(); 447 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 448 #ifdef INET6 449 if (sc->sc_inc.inc_isipv6) 450 continue; 451 #endif 452 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 453 splx(s); 454 return (sc); 455 } 456 } 457 splx(s); 458 } 459 return (NULL); 460 } 461 462 /* 463 * This function is called when we get a RST for a 464 * non-existent connection, so that we can see if the 465 * connection is in the syn cache. If it is, zap it. 466 */ 467 void 468 syncache_chkrst(inc, th) 469 struct in_conninfo *inc; 470 struct tcphdr *th; 471 { 472 struct syncache *sc; 473 struct syncache_head *sch; 474 475 sc = syncache_lookup(inc, &sch); 476 if (sc == NULL) 477 return; 478 /* 479 * If the RST bit is set, check the sequence number to see 480 * if this is a valid reset segment. 481 * RFC 793 page 37: 482 * In all states except SYN-SENT, all reset (RST) segments 483 * are validated by checking their SEQ-fields. A reset is 484 * valid if its sequence number is in the window. 485 * 486 * The sequence number in the reset segment is normally an 487 * echo of our outgoing acknowlegement numbers, but some hosts 488 * send a reset with the sequence number at the rightmost edge 489 * of our receive window, and we have to handle this case. 490 */ 491 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 492 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 493 syncache_drop(sc, sch); 494 tcpstat.tcps_sc_reset++; 495 } 496 } 497 498 void 499 syncache_badack(inc) 500 struct in_conninfo *inc; 501 { 502 struct syncache *sc; 503 struct syncache_head *sch; 504 505 sc = syncache_lookup(inc, &sch); 506 if (sc != NULL) { 507 syncache_drop(sc, sch); 508 tcpstat.tcps_sc_badack++; 509 } 510 } 511 512 void 513 syncache_unreach(inc, th) 514 struct in_conninfo *inc; 515 struct tcphdr *th; 516 { 517 struct syncache *sc; 518 struct syncache_head *sch; 519 520 /* we are called at splnet() here */ 521 sc = syncache_lookup(inc, &sch); 522 if (sc == NULL) 523 return; 524 525 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 526 if (ntohl(th->th_seq) != sc->sc_iss) 527 return; 528 529 /* 530 * If we've rertransmitted 3 times and this is our second error, 531 * we remove the entry. Otherwise, we allow it to continue on. 532 * This prevents us from incorrectly nuking an entry during a 533 * spurious network outage. 534 * 535 * See tcp_notify(). 536 */ 537 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 538 sc->sc_flags |= SCF_UNREACH; 539 return; 540 } 541 syncache_drop(sc, sch); 542 tcpstat.tcps_sc_unreach++; 543 } 544 545 /* 546 * Build a new TCP socket structure from a syncache entry. 547 */ 548 static struct socket * 549 syncache_socket(sc, lso, m) 550 struct syncache *sc; 551 struct socket *lso; 552 struct mbuf *m; 553 { 554 struct inpcb *inp = NULL; 555 struct socket *so; 556 struct tcpcb *tp; 557 558 /* 559 * Ok, create the full blown connection, and set things up 560 * as they would have been set up if we had created the 561 * connection when the SYN arrived. If we can't create 562 * the connection, abort it. 563 */ 564 so = sonewconn(lso, SS_ISCONNECTED); 565 if (so == NULL) { 566 /* 567 * Drop the connection; we will send a RST if the peer 568 * retransmits the ACK, 569 */ 570 tcpstat.tcps_listendrop++; 571 goto abort; 572 } 573 #ifdef MAC 574 mac_set_socket_peer_from_mbuf(m, so); 575 #endif 576 577 inp = sotoinpcb(so); 578 579 /* 580 * Insert new socket into hash list. 581 */ 582 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 583 #ifdef INET6 584 if (sc->sc_inc.inc_isipv6) { 585 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 586 } else { 587 inp->inp_vflag &= ~INP_IPV6; 588 inp->inp_vflag |= INP_IPV4; 589 #endif 590 inp->inp_laddr = sc->sc_inc.inc_laddr; 591 #ifdef INET6 592 } 593 #endif 594 inp->inp_lport = sc->sc_inc.inc_lport; 595 if (in_pcbinshash(inp) != 0) { 596 /* 597 * Undo the assignments above if we failed to 598 * put the PCB on the hash lists. 599 */ 600 #ifdef INET6 601 if (sc->sc_inc.inc_isipv6) 602 inp->in6p_laddr = in6addr_any; 603 else 604 #endif 605 inp->inp_laddr.s_addr = INADDR_ANY; 606 inp->inp_lport = 0; 607 goto abort; 608 } 609 #ifdef IPSEC 610 /* copy old policy into new socket's */ 611 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 612 printf("syncache_expand: could not copy policy\n"); 613 #endif 614 #ifdef INET6 615 if (sc->sc_inc.inc_isipv6) { 616 struct inpcb *oinp = sotoinpcb(lso); 617 struct in6_addr laddr6; 618 struct sockaddr_in6 *sin6; 619 /* 620 * Inherit socket options from the listening socket. 621 * Note that in6p_inputopts are not (and should not be) 622 * copied, since it stores previously received options and is 623 * used to detect if each new option is different than the 624 * previous one and hence should be passed to a user. 625 * If we copied in6p_inputopts, a user would not be able to 626 * receive options just after calling the accept system call. 627 */ 628 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 629 if (oinp->in6p_outputopts) 630 inp->in6p_outputopts = 631 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 632 inp->in6p_route = sc->sc_route6; 633 sc->sc_route6.ro_rt = NULL; 634 635 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 636 M_SONAME, M_NOWAIT | M_ZERO); 637 if (sin6 == NULL) 638 goto abort; 639 sin6->sin6_family = AF_INET6; 640 sin6->sin6_len = sizeof(*sin6); 641 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 642 sin6->sin6_port = sc->sc_inc.inc_fport; 643 laddr6 = inp->in6p_laddr; 644 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 645 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 646 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 647 inp->in6p_laddr = laddr6; 648 FREE(sin6, M_SONAME); 649 goto abort; 650 } 651 FREE(sin6, M_SONAME); 652 } else 653 #endif 654 { 655 struct in_addr laddr; 656 struct sockaddr_in *sin; 657 658 inp->inp_options = ip_srcroute(); 659 if (inp->inp_options == NULL) { 660 inp->inp_options = sc->sc_ipopts; 661 sc->sc_ipopts = NULL; 662 } 663 inp->inp_route = sc->sc_route; 664 sc->sc_route.ro_rt = NULL; 665 666 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 667 M_SONAME, M_NOWAIT | M_ZERO); 668 if (sin == NULL) 669 goto abort; 670 sin->sin_family = AF_INET; 671 sin->sin_len = sizeof(*sin); 672 sin->sin_addr = sc->sc_inc.inc_faddr; 673 sin->sin_port = sc->sc_inc.inc_fport; 674 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 675 laddr = inp->inp_laddr; 676 if (inp->inp_laddr.s_addr == INADDR_ANY) 677 inp->inp_laddr = sc->sc_inc.inc_laddr; 678 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 679 inp->inp_laddr = laddr; 680 FREE(sin, M_SONAME); 681 goto abort; 682 } 683 FREE(sin, M_SONAME); 684 } 685 686 tp = intotcpcb(inp); 687 tp->t_state = TCPS_SYN_RECEIVED; 688 tp->iss = sc->sc_iss; 689 tp->irs = sc->sc_irs; 690 tcp_rcvseqinit(tp); 691 tcp_sendseqinit(tp); 692 tp->snd_wl1 = sc->sc_irs; 693 tp->rcv_up = sc->sc_irs + 1; 694 tp->rcv_wnd = sc->sc_wnd; 695 tp->rcv_adv += tp->rcv_wnd; 696 697 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 698 if (sc->sc_flags & SCF_NOOPT) 699 tp->t_flags |= TF_NOOPT; 700 if (sc->sc_flags & SCF_WINSCALE) { 701 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 702 tp->requested_s_scale = sc->sc_requested_s_scale; 703 tp->request_r_scale = sc->sc_request_r_scale; 704 } 705 if (sc->sc_flags & SCF_TIMESTAMP) { 706 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 707 tp->ts_recent = sc->sc_tsrecent; 708 tp->ts_recent_age = ticks; 709 } 710 if (sc->sc_flags & SCF_CC) { 711 /* 712 * Initialization of the tcpcb for transaction; 713 * set SND.WND = SEG.WND, 714 * initialize CCsend and CCrecv. 715 */ 716 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 717 tp->cc_send = sc->sc_cc_send; 718 tp->cc_recv = sc->sc_cc_recv; 719 } 720 721 tcp_mss(tp, sc->sc_peer_mss); 722 723 /* 724 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 725 */ 726 if (sc->sc_rxtslot != 0) 727 tp->snd_cwnd = tp->t_maxseg; 728 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 729 730 tcpstat.tcps_accepts++; 731 return (so); 732 733 abort: 734 if (so != NULL) 735 (void) soabort(so); 736 return (NULL); 737 } 738 739 /* 740 * This function gets called when we receive an ACK for a 741 * socket in the LISTEN state. We look up the connection 742 * in the syncache, and if its there, we pull it out of 743 * the cache and turn it into a full-blown connection in 744 * the SYN-RECEIVED state. 745 */ 746 int 747 syncache_expand(inc, th, sop, m) 748 struct in_conninfo *inc; 749 struct tcphdr *th; 750 struct socket **sop; 751 struct mbuf *m; 752 { 753 struct syncache *sc; 754 struct syncache_head *sch; 755 struct socket *so; 756 757 sc = syncache_lookup(inc, &sch); 758 if (sc == NULL) { 759 /* 760 * There is no syncache entry, so see if this ACK is 761 * a returning syncookie. To do this, first: 762 * A. See if this socket has had a syncache entry dropped in 763 * the past. We don't want to accept a bogus syncookie 764 * if we've never received a SYN. 765 * B. check that the syncookie is valid. If it is, then 766 * cobble up a fake syncache entry, and return. 767 */ 768 if (!tcp_syncookies) 769 return (0); 770 sc = syncookie_lookup(inc, th, *sop); 771 if (sc == NULL) 772 return (0); 773 sch = NULL; 774 tcpstat.tcps_sc_recvcookie++; 775 } 776 777 /* 778 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 779 */ 780 if (th->th_ack != sc->sc_iss + 1) 781 return (0); 782 783 so = syncache_socket(sc, *sop, m); 784 if (so == NULL) { 785 #if 0 786 resetandabort: 787 /* XXXjlemon check this - is this correct? */ 788 (void) tcp_respond(NULL, m, m, th, 789 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 790 #endif 791 m_freem(m); /* XXX only needed for above */ 792 tcpstat.tcps_sc_aborted++; 793 } else { 794 sc->sc_flags |= SCF_KEEPROUTE; 795 tcpstat.tcps_sc_completed++; 796 } 797 if (sch == NULL) 798 syncache_free(sc); 799 else 800 syncache_drop(sc, sch); 801 *sop = so; 802 return (1); 803 } 804 805 /* 806 * Given a LISTEN socket and an inbound SYN request, add 807 * this to the syn cache, and send back a segment: 808 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 809 * to the source. 810 * 811 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 812 * Doing so would require that we hold onto the data and deliver it 813 * to the application. However, if we are the target of a SYN-flood 814 * DoS attack, an attacker could send data which would eventually 815 * consume all available buffer space if it were ACKed. By not ACKing 816 * the data, we avoid this DoS scenario. 817 */ 818 int 819 syncache_add(inc, to, th, sop, m) 820 struct in_conninfo *inc; 821 struct tcpopt *to; 822 struct tcphdr *th; 823 struct socket **sop; 824 struct mbuf *m; 825 { 826 struct tcpcb *tp; 827 struct socket *so; 828 struct syncache *sc = NULL; 829 struct syncache_head *sch; 830 struct mbuf *ipopts = NULL; 831 struct rmxp_tao *taop; 832 int i, s, win; 833 834 so = *sop; 835 tp = sototcpcb(so); 836 837 /* 838 * Remember the IP options, if any. 839 */ 840 #ifdef INET6 841 if (!inc->inc_isipv6) 842 #endif 843 ipopts = ip_srcroute(); 844 845 /* 846 * See if we already have an entry for this connection. 847 * If we do, resend the SYN,ACK, and reset the retransmit timer. 848 * 849 * XXX 850 * should the syncache be re-initialized with the contents 851 * of the new SYN here (which may have different options?) 852 */ 853 sc = syncache_lookup(inc, &sch); 854 if (sc != NULL) { 855 tcpstat.tcps_sc_dupsyn++; 856 if (ipopts) { 857 /* 858 * If we were remembering a previous source route, 859 * forget it and use the new one we've been given. 860 */ 861 if (sc->sc_ipopts) 862 (void) m_free(sc->sc_ipopts); 863 sc->sc_ipopts = ipopts; 864 } 865 /* 866 * Update timestamp if present. 867 */ 868 if (sc->sc_flags & SCF_TIMESTAMP) 869 sc->sc_tsrecent = to->to_tsval; 870 /* 871 * PCB may have changed, pick up new values. 872 */ 873 sc->sc_tp = tp; 874 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 875 if (syncache_respond(sc, m) == 0) { 876 s = splnet(); 877 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 878 sc, sc_timerq); 879 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 880 splx(s); 881 tcpstat.tcps_sndacks++; 882 tcpstat.tcps_sndtotal++; 883 } 884 *sop = NULL; 885 return (1); 886 } 887 888 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 889 if (sc == NULL) { 890 /* 891 * The zone allocator couldn't provide more entries. 892 * Treat this as if the cache was full; drop the oldest 893 * entry and insert the new one. 894 */ 895 s = splnet(); 896 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 897 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 898 if (sc != NULL) 899 break; 900 } 901 sc->sc_tp->ts_recent = ticks; 902 syncache_drop(sc, NULL); 903 splx(s); 904 tcpstat.tcps_sc_zonefail++; 905 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 906 if (sc == NULL) { 907 if (ipopts) 908 (void) m_free(ipopts); 909 return (0); 910 } 911 } 912 913 /* 914 * Fill in the syncache values. 915 */ 916 bzero(sc, sizeof(*sc)); 917 sc->sc_tp = tp; 918 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 919 sc->sc_ipopts = ipopts; 920 sc->sc_inc.inc_fport = inc->inc_fport; 921 sc->sc_inc.inc_lport = inc->inc_lport; 922 #ifdef INET6 923 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 924 if (inc->inc_isipv6) { 925 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 926 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 927 sc->sc_route6.ro_rt = NULL; 928 } else 929 #endif 930 { 931 sc->sc_inc.inc_faddr = inc->inc_faddr; 932 sc->sc_inc.inc_laddr = inc->inc_laddr; 933 sc->sc_route.ro_rt = NULL; 934 } 935 sc->sc_irs = th->th_seq; 936 if (tcp_syncookies) 937 sc->sc_iss = syncookie_generate(sc); 938 else 939 sc->sc_iss = arc4random(); 940 941 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 942 win = sbspace(&so->so_rcv); 943 win = imax(win, 0); 944 win = imin(win, TCP_MAXWIN); 945 sc->sc_wnd = win; 946 947 sc->sc_flags = 0; 948 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 949 if (tcp_do_rfc1323) { 950 /* 951 * A timestamp received in a SYN makes 952 * it ok to send timestamp requests and replies. 953 */ 954 if (to->to_flags & TOF_TS) { 955 sc->sc_tsrecent = to->to_tsval; 956 sc->sc_flags |= SCF_TIMESTAMP; 957 } 958 if (to->to_flags & TOF_SCALE) { 959 int wscale = 0; 960 961 /* Compute proper scaling value from buffer space */ 962 while (wscale < TCP_MAX_WINSHIFT && 963 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 964 wscale++; 965 sc->sc_request_r_scale = wscale; 966 sc->sc_requested_s_scale = to->to_requested_s_scale; 967 sc->sc_flags |= SCF_WINSCALE; 968 } 969 } 970 if (tcp_do_rfc1644) { 971 /* 972 * A CC or CC.new option received in a SYN makes 973 * it ok to send CC in subsequent segments. 974 */ 975 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 976 sc->sc_cc_recv = to->to_cc; 977 sc->sc_cc_send = CC_INC(tcp_ccgen); 978 sc->sc_flags |= SCF_CC; 979 } 980 } 981 if (tp->t_flags & TF_NOOPT) 982 sc->sc_flags = SCF_NOOPT; 983 984 /* 985 * XXX 986 * We have the option here of not doing TAO (even if the segment 987 * qualifies) and instead fall back to a normal 3WHS via the syncache. 988 * This allows us to apply synflood protection to TAO-qualifying SYNs 989 * also. However, there should be a hueristic to determine when to 990 * do this, and is not present at the moment. 991 */ 992 993 /* 994 * Perform TAO test on incoming CC (SEG.CC) option, if any. 995 * - compare SEG.CC against cached CC from the same host, if any. 996 * - if SEG.CC > chached value, SYN must be new and is accepted 997 * immediately: save new CC in the cache, mark the socket 998 * connected, enter ESTABLISHED state, turn on flag to 999 * send a SYN in the next segment. 1000 * A virtual advertised window is set in rcv_adv to 1001 * initialize SWS prevention. Then enter normal segment 1002 * processing: drop SYN, process data and FIN. 1003 * - otherwise do a normal 3-way handshake. 1004 */ 1005 taop = tcp_gettaocache(&sc->sc_inc); 1006 if ((to->to_flags & TOF_CC) != 0) { 1007 if (((tp->t_flags & TF_NOPUSH) != 0) && 1008 sc->sc_flags & SCF_CC && 1009 taop != NULL && taop->tao_cc != 0 && 1010 CC_GT(to->to_cc, taop->tao_cc)) { 1011 sc->sc_rxtslot = 0; 1012 so = syncache_socket(sc, *sop, m); 1013 if (so != NULL) { 1014 sc->sc_flags |= SCF_KEEPROUTE; 1015 taop->tao_cc = to->to_cc; 1016 *sop = so; 1017 } 1018 syncache_free(sc); 1019 return (so != NULL); 1020 } 1021 } else { 1022 /* 1023 * No CC option, but maybe CC.NEW: invalidate cached value. 1024 */ 1025 if (taop != NULL) 1026 taop->tao_cc = 0; 1027 } 1028 /* 1029 * TAO test failed or there was no CC option, 1030 * do a standard 3-way handshake. 1031 */ 1032 if (syncache_respond(sc, m) == 0) { 1033 syncache_insert(sc, sch); 1034 tcpstat.tcps_sndacks++; 1035 tcpstat.tcps_sndtotal++; 1036 } else { 1037 syncache_free(sc); 1038 tcpstat.tcps_sc_dropped++; 1039 } 1040 *sop = NULL; 1041 return (1); 1042 } 1043 1044 static int 1045 syncache_respond(sc, m) 1046 struct syncache *sc; 1047 struct mbuf *m; 1048 { 1049 u_int8_t *optp; 1050 int optlen, error; 1051 u_int16_t tlen, hlen, mssopt; 1052 struct ip *ip = NULL; 1053 struct rtentry *rt; 1054 struct tcphdr *th; 1055 #ifdef INET6 1056 struct ip6_hdr *ip6 = NULL; 1057 #endif 1058 1059 #ifdef INET6 1060 if (sc->sc_inc.inc_isipv6) { 1061 rt = tcp_rtlookup6(&sc->sc_inc); 1062 if (rt != NULL) 1063 mssopt = rt->rt_ifp->if_mtu - 1064 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1065 else 1066 mssopt = tcp_v6mssdflt; 1067 hlen = sizeof(struct ip6_hdr); 1068 } else 1069 #endif 1070 { 1071 rt = tcp_rtlookup(&sc->sc_inc); 1072 if (rt != NULL) 1073 mssopt = rt->rt_ifp->if_mtu - 1074 (sizeof(struct ip) + sizeof(struct tcphdr)); 1075 else 1076 mssopt = tcp_mssdflt; 1077 hlen = sizeof(struct ip); 1078 } 1079 1080 /* Compute the size of the TCP options. */ 1081 if (sc->sc_flags & SCF_NOOPT) { 1082 optlen = 0; 1083 } else { 1084 optlen = TCPOLEN_MAXSEG + 1085 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1086 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1087 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1088 } 1089 tlen = hlen + sizeof(struct tcphdr) + optlen; 1090 1091 /* 1092 * XXX 1093 * assume that the entire packet will fit in a header mbuf 1094 */ 1095 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1096 1097 /* 1098 * XXX shouldn't this reuse the mbuf if possible ? 1099 * Create the IP+TCP header from scratch. 1100 */ 1101 if (m) 1102 m_freem(m); 1103 1104 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1105 if (m == NULL) 1106 return (ENOBUFS); 1107 m->m_data += max_linkhdr; 1108 m->m_len = tlen; 1109 m->m_pkthdr.len = tlen; 1110 m->m_pkthdr.rcvif = NULL; 1111 #ifdef MAC 1112 mac_create_mbuf_from_socket(sc->sc_tp->t_inpcb->inp_socket, m); 1113 #endif 1114 1115 #ifdef INET6 1116 if (sc->sc_inc.inc_isipv6) { 1117 ip6 = mtod(m, struct ip6_hdr *); 1118 ip6->ip6_vfc = IPV6_VERSION; 1119 ip6->ip6_nxt = IPPROTO_TCP; 1120 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1121 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1122 ip6->ip6_plen = htons(tlen - hlen); 1123 /* ip6_hlim is set after checksum */ 1124 /* ip6_flow = ??? */ 1125 1126 th = (struct tcphdr *)(ip6 + 1); 1127 } else 1128 #endif 1129 { 1130 ip = mtod(m, struct ip *); 1131 ip->ip_v = IPVERSION; 1132 ip->ip_hl = sizeof(struct ip) >> 2; 1133 ip->ip_len = tlen; 1134 ip->ip_id = 0; 1135 ip->ip_off = 0; 1136 ip->ip_sum = 0; 1137 ip->ip_p = IPPROTO_TCP; 1138 ip->ip_src = sc->sc_inc.inc_laddr; 1139 ip->ip_dst = sc->sc_inc.inc_faddr; 1140 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1141 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1142 1143 /* 1144 * See if we should do MTU discovery. Route lookups are expensive, 1145 * so we will only unset the DF bit if: 1146 * 1147 * 1) path_mtu_discovery is disabled 1148 * 2) the SCF_UNREACH flag has been set 1149 */ 1150 if (path_mtu_discovery 1151 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1152 ip->ip_off |= IP_DF; 1153 } 1154 1155 th = (struct tcphdr *)(ip + 1); 1156 } 1157 th->th_sport = sc->sc_inc.inc_lport; 1158 th->th_dport = sc->sc_inc.inc_fport; 1159 1160 th->th_seq = htonl(sc->sc_iss); 1161 th->th_ack = htonl(sc->sc_irs + 1); 1162 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1163 th->th_x2 = 0; 1164 th->th_flags = TH_SYN|TH_ACK; 1165 th->th_win = htons(sc->sc_wnd); 1166 th->th_urp = 0; 1167 1168 /* Tack on the TCP options. */ 1169 if (optlen == 0) 1170 goto no_options; 1171 optp = (u_int8_t *)(th + 1); 1172 *optp++ = TCPOPT_MAXSEG; 1173 *optp++ = TCPOLEN_MAXSEG; 1174 *optp++ = (mssopt >> 8) & 0xff; 1175 *optp++ = mssopt & 0xff; 1176 1177 if (sc->sc_flags & SCF_WINSCALE) { 1178 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1179 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1180 sc->sc_request_r_scale); 1181 optp += 4; 1182 } 1183 1184 if (sc->sc_flags & SCF_TIMESTAMP) { 1185 u_int32_t *lp = (u_int32_t *)(optp); 1186 1187 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1188 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1189 *lp++ = htonl(ticks); 1190 *lp = htonl(sc->sc_tsrecent); 1191 optp += TCPOLEN_TSTAMP_APPA; 1192 } 1193 1194 /* 1195 * Send CC and CC.echo if we received CC from our peer. 1196 */ 1197 if (sc->sc_flags & SCF_CC) { 1198 u_int32_t *lp = (u_int32_t *)(optp); 1199 1200 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1201 *lp++ = htonl(sc->sc_cc_send); 1202 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1203 *lp = htonl(sc->sc_cc_recv); 1204 optp += TCPOLEN_CC_APPA * 2; 1205 } 1206 no_options: 1207 1208 #ifdef INET6 1209 if (sc->sc_inc.inc_isipv6) { 1210 struct route_in6 *ro6 = &sc->sc_route6; 1211 1212 th->th_sum = 0; 1213 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1214 ip6->ip6_hlim = in6_selecthlim(NULL, 1215 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1216 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1217 sc->sc_tp->t_inpcb); 1218 } else 1219 #endif 1220 { 1221 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1222 htons(tlen - hlen + IPPROTO_TCP)); 1223 m->m_pkthdr.csum_flags = CSUM_TCP; 1224 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1225 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL, 1226 sc->sc_tp->t_inpcb); 1227 } 1228 return (error); 1229 } 1230 1231 /* 1232 * cookie layers: 1233 * 1234 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1235 * | peer iss | 1236 * | MD5(laddr,faddr,lport,fport,secret) |. . . . . . .| 1237 * | 0 |(A)| | 1238 * (A): peer mss index 1239 */ 1240 1241 /* 1242 * The values below are chosen to minimize the size of the tcp_secret 1243 * table, as well as providing roughly a 4 second lifetime for the cookie. 1244 */ 1245 1246 #define SYNCOOKIE_HASHSHIFT 2 /* log2(# of 32bit words from hash) */ 1247 #define SYNCOOKIE_WNDBITS 7 /* exposed bits for window indexing */ 1248 #define SYNCOOKIE_TIMESHIFT 5 /* scale ticks to window time units */ 1249 1250 #define SYNCOOKIE_HASHMASK ((1 << SYNCOOKIE_HASHSHIFT) - 1) 1251 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1252 #define SYNCOOKIE_NSECRETS (1 << (SYNCOOKIE_WNDBITS - SYNCOOKIE_HASHSHIFT)) 1253 #define SYNCOOKIE_TIMEOUT \ 1254 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1255 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1256 1257 static struct { 1258 u_int32_t ts_secbits; 1259 u_int ts_expire; 1260 } tcp_secret[SYNCOOKIE_NSECRETS]; 1261 1262 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1263 1264 static MD5_CTX syn_ctx; 1265 1266 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1267 1268 /* 1269 * Consider the problem of a recreated (and retransmitted) cookie. If the 1270 * original SYN was accepted, the connection is established. The second 1271 * SYN is inflight, and if it arrives with an ISN that falls within the 1272 * receive window, the connection is killed. 1273 * 1274 * However, since cookies have other problems, this may not be worth 1275 * worrying about. 1276 */ 1277 1278 static u_int32_t 1279 syncookie_generate(struct syncache *sc) 1280 { 1281 u_int32_t md5_buffer[4]; 1282 u_int32_t data; 1283 int wnd, idx; 1284 1285 wnd = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1286 idx = wnd >> SYNCOOKIE_HASHSHIFT; 1287 if (tcp_secret[idx].ts_expire < ticks) { 1288 tcp_secret[idx].ts_secbits = arc4random(); 1289 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1290 } 1291 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1292 if (tcp_msstab[data] <= sc->sc_peer_mss) 1293 break; 1294 data = (data << SYNCOOKIE_WNDBITS) | wnd; 1295 data ^= sc->sc_irs; /* peer's iss */ 1296 MD5Init(&syn_ctx); 1297 #ifdef INET6 1298 if (sc->sc_inc.inc_isipv6) { 1299 MD5Add(sc->sc_inc.inc6_laddr); 1300 MD5Add(sc->sc_inc.inc6_faddr); 1301 } else 1302 #endif 1303 { 1304 MD5Add(sc->sc_inc.inc_laddr); 1305 MD5Add(sc->sc_inc.inc_faddr); 1306 } 1307 MD5Add(sc->sc_inc.inc_lport); 1308 MD5Add(sc->sc_inc.inc_fport); 1309 MD5Add(tcp_secret[idx].ts_secbits); 1310 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1311 data ^= (md5_buffer[wnd & SYNCOOKIE_HASHMASK] & ~SYNCOOKIE_WNDMASK); 1312 return (data); 1313 } 1314 1315 static struct syncache * 1316 syncookie_lookup(inc, th, so) 1317 struct in_conninfo *inc; 1318 struct tcphdr *th; 1319 struct socket *so; 1320 { 1321 u_int32_t md5_buffer[4]; 1322 struct syncache *sc; 1323 u_int32_t data; 1324 int wnd, idx; 1325 1326 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1327 wnd = data & SYNCOOKIE_WNDMASK; 1328 idx = wnd >> SYNCOOKIE_HASHSHIFT; 1329 if (tcp_secret[idx].ts_expire < ticks || 1330 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1331 return (NULL); 1332 MD5Init(&syn_ctx); 1333 #ifdef INET6 1334 if (inc->inc_isipv6) { 1335 MD5Add(inc->inc6_laddr); 1336 MD5Add(inc->inc6_faddr); 1337 } else 1338 #endif 1339 { 1340 MD5Add(inc->inc_laddr); 1341 MD5Add(inc->inc_faddr); 1342 } 1343 MD5Add(inc->inc_lport); 1344 MD5Add(inc->inc_fport); 1345 MD5Add(tcp_secret[idx].ts_secbits); 1346 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1347 data ^= md5_buffer[wnd & SYNCOOKIE_HASHMASK]; 1348 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1349 return (NULL); 1350 data = data >> SYNCOOKIE_WNDBITS; 1351 1352 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1353 if (sc == NULL) 1354 return (NULL); 1355 /* 1356 * Fill in the syncache values. 1357 * XXX duplicate code from syncache_add 1358 */ 1359 sc->sc_ipopts = NULL; 1360 sc->sc_inc.inc_fport = inc->inc_fport; 1361 sc->sc_inc.inc_lport = inc->inc_lport; 1362 #ifdef INET6 1363 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1364 if (inc->inc_isipv6) { 1365 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1366 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1367 sc->sc_route6.ro_rt = NULL; 1368 } else 1369 #endif 1370 { 1371 sc->sc_inc.inc_faddr = inc->inc_faddr; 1372 sc->sc_inc.inc_laddr = inc->inc_laddr; 1373 sc->sc_route.ro_rt = NULL; 1374 } 1375 sc->sc_irs = th->th_seq - 1; 1376 sc->sc_iss = th->th_ack - 1; 1377 wnd = sbspace(&so->so_rcv); 1378 wnd = imax(wnd, 0); 1379 wnd = imin(wnd, TCP_MAXWIN); 1380 sc->sc_wnd = wnd; 1381 sc->sc_flags = 0; 1382 sc->sc_rxtslot = 0; 1383 sc->sc_peer_mss = tcp_msstab[data]; 1384 return (sc); 1385 } 1386