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 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/sysctl.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/md5.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/random.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/in_var.h> 59 #include <netinet/in_pcb.h> 60 #include <netinet/ip_var.h> 61 #ifdef INET6 62 #include <netinet/ip6.h> 63 #include <netinet/icmp6.h> 64 #include <netinet6/nd6.h> 65 #include <netinet6/ip6_var.h> 66 #include <netinet6/in6_pcb.h> 67 #endif 68 #include <netinet/tcp.h> 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #ifdef INET6 74 #include <netinet6/tcp6_var.h> 75 #endif 76 77 #ifdef IPSEC 78 #include <netinet6/ipsec.h> 79 #ifdef INET6 80 #include <netinet6/ipsec6.h> 81 #endif 82 #include <netkey/key.h> 83 #endif /*IPSEC*/ 84 85 #include <machine/in_cksum.h> 86 #include <vm/uma.h> 87 88 static int tcp_syncookies = 1; 89 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 90 &tcp_syncookies, 0, 91 "Use TCP SYN cookies if the syncache overflows"); 92 93 static void syncache_drop(struct syncache *, struct syncache_head *); 94 static void syncache_free(struct syncache *); 95 static void syncache_insert(struct syncache *, struct syncache_head *); 96 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 97 static int syncache_respond(struct syncache *, struct mbuf *); 98 static struct socket *syncache_socket(struct syncache *, struct socket *); 99 static void syncache_timer(void *); 100 static u_int32_t syncookie_generate(struct syncache *); 101 static struct syncache *syncookie_lookup(struct in_conninfo *, 102 struct tcphdr *, struct socket *); 103 104 /* 105 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 106 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 107 * the odds are that the user has given up attempting to connect by then. 108 */ 109 #define SYNCACHE_MAXREXMTS 3 110 111 /* Arbitrary values */ 112 #define TCP_SYNCACHE_HASHSIZE 512 113 #define TCP_SYNCACHE_BUCKETLIMIT 30 114 115 struct tcp_syncache { 116 struct syncache_head *hashbase; 117 uma_zone_t zone; 118 u_int hashsize; 119 u_int hashmask; 120 u_int bucket_limit; 121 u_int cache_count; 122 u_int cache_limit; 123 u_int rexmt_limit; 124 u_int hash_secret; 125 u_int next_reseed; 126 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 127 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 128 }; 129 static struct tcp_syncache tcp_syncache; 130 131 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 132 133 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 134 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 135 136 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 137 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 138 139 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 140 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 141 142 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 143 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 144 145 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 146 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 147 148 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 149 150 #define SYNCACHE_HASH(inc, mask) \ 151 ((tcp_syncache.hash_secret ^ \ 152 (inc)->inc_faddr.s_addr ^ \ 153 ((inc)->inc_faddr.s_addr >> 16) ^ \ 154 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 155 156 #define SYNCACHE_HASH6(inc, mask) \ 157 ((tcp_syncache.hash_secret ^ \ 158 (inc)->inc6_faddr.s6_addr32[0] ^ \ 159 (inc)->inc6_faddr.s6_addr32[3] ^ \ 160 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 161 162 #define ENDPTS_EQ(a, b) ( \ 163 (a)->ie_fport == (b)->ie_fport && \ 164 (a)->ie_lport == (b)->ie_lport && \ 165 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 166 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 167 ) 168 169 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 170 171 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 172 sc->sc_rxtslot = slot; \ 173 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; \ 174 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[slot], sc, sc_timerq); \ 175 if (!callout_active(&tcp_syncache.tt_timerq[slot])) \ 176 callout_reset(&tcp_syncache.tt_timerq[slot], \ 177 TCPTV_RTOBASE * tcp_backoff[slot], \ 178 syncache_timer, (void *)((intptr_t)slot)); \ 179 } while (0) 180 181 static void 182 syncache_free(struct syncache *sc) 183 { 184 struct rtentry *rt; 185 186 if (sc->sc_ipopts) 187 (void) m_free(sc->sc_ipopts); 188 #ifdef INET6 189 if (sc->sc_inc.inc_isipv6) 190 rt = sc->sc_route6.ro_rt; 191 else 192 #endif 193 rt = sc->sc_route.ro_rt; 194 if (rt != NULL) { 195 /* 196 * If this is the only reference to a protocol cloned 197 * route, remove it immediately. 198 */ 199 if (rt->rt_flags & RTF_WASCLONED && 200 (sc->sc_flags & SCF_KEEPROUTE) == 0 && 201 rt->rt_refcnt == 1) 202 rtrequest(RTM_DELETE, rt_key(rt), 203 rt->rt_gateway, rt_mask(rt), 204 rt->rt_flags, NULL); 205 RTFREE(rt); 206 } 207 uma_zfree(tcp_syncache.zone, sc); 208 } 209 210 void 211 syncache_init(void) 212 { 213 int i; 214 215 tcp_syncache.cache_count = 0; 216 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 217 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 218 tcp_syncache.cache_limit = 219 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 220 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 221 tcp_syncache.next_reseed = 0; 222 tcp_syncache.hash_secret = arc4random(); 223 224 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 225 &tcp_syncache.hashsize); 226 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 227 &tcp_syncache.cache_limit); 228 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 229 &tcp_syncache.bucket_limit); 230 if (!powerof2(tcp_syncache.hashsize)) { 231 printf("WARNING: syncache hash size is not a power of 2.\n"); 232 tcp_syncache.hashsize = 512; /* safe default */ 233 } 234 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 235 236 /* Allocate the hash table. */ 237 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 238 tcp_syncache.hashsize * sizeof(struct syncache_head), 239 M_SYNCACHE, M_WAITOK | M_ZERO); 240 241 /* Initialize the hash buckets. */ 242 for (i = 0; i < tcp_syncache.hashsize; i++) { 243 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 244 tcp_syncache.hashbase[i].sch_length = 0; 245 } 246 247 /* Initialize the timer queues. */ 248 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 249 TAILQ_INIT(&tcp_syncache.timerq[i]); 250 callout_init(&tcp_syncache.tt_timerq[i], 0); 251 } 252 253 /* 254 * Allocate the syncache entries. Allow the zone to allocate one 255 * more entry than cache limit, so a new entry can bump out an 256 * older one. 257 */ 258 tcp_syncache.cache_limit -= 1; 259 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache), 260 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE); 261 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit); 262 } 263 264 static void 265 syncache_insert(sc, sch) 266 struct syncache *sc; 267 struct syncache_head *sch; 268 { 269 struct syncache *sc2; 270 int s, i; 271 272 /* 273 * Make sure that we don't overflow the per-bucket 274 * limit or the total cache size limit. 275 */ 276 s = splnet(); 277 if (sch->sch_length >= tcp_syncache.bucket_limit) { 278 /* 279 * The bucket is full, toss the oldest element. 280 */ 281 sc2 = TAILQ_FIRST(&sch->sch_bucket); 282 sc2->sc_tp->ts_recent = ticks; 283 syncache_drop(sc2, sch); 284 tcpstat.tcps_sc_bucketoverflow++; 285 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 286 /* 287 * The cache is full. Toss the oldest entry in the 288 * entire cache. This is the front entry in the 289 * first non-empty timer queue with the largest 290 * timeout value. 291 */ 292 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 293 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 294 if (sc2 != NULL) 295 break; 296 } 297 sc2->sc_tp->ts_recent = ticks; 298 syncache_drop(sc2, NULL); 299 tcpstat.tcps_sc_cacheoverflow++; 300 } 301 302 /* Initialize the entry's timer. */ 303 SYNCACHE_TIMEOUT(sc, 0); 304 305 /* Put it into the bucket. */ 306 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 307 sch->sch_length++; 308 tcp_syncache.cache_count++; 309 tcpstat.tcps_sc_added++; 310 splx(s); 311 } 312 313 static void 314 syncache_drop(sc, sch) 315 struct syncache *sc; 316 struct syncache_head *sch; 317 { 318 int s; 319 320 if (sch == NULL) { 321 #ifdef INET6 322 if (sc->sc_inc.inc_isipv6) { 323 sch = &tcp_syncache.hashbase[ 324 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 325 } else 326 #endif 327 { 328 sch = &tcp_syncache.hashbase[ 329 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 330 } 331 } 332 333 s = splnet(); 334 335 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 336 sch->sch_length--; 337 tcp_syncache.cache_count--; 338 339 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 340 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 341 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 342 splx(s); 343 344 syncache_free(sc); 345 } 346 347 /* 348 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 349 * If we have retransmitted an entry the maximum number of times, expire it. 350 */ 351 static void 352 syncache_timer(xslot) 353 void *xslot; 354 { 355 intptr_t slot = (intptr_t)xslot; 356 struct syncache *sc, *nsc; 357 struct inpcb *inp; 358 int s; 359 360 s = splnet(); 361 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 362 !callout_active(&tcp_syncache.tt_timerq[slot])) { 363 splx(s); 364 return; 365 } 366 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 367 368 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 369 while (nsc != NULL) { 370 if (ticks < nsc->sc_rxttime) 371 break; 372 sc = nsc; 373 nsc = TAILQ_NEXT(sc, sc_timerq); 374 inp = sc->sc_tp->t_inpcb; 375 if (slot == SYNCACHE_MAXREXMTS || 376 slot >= tcp_syncache.rexmt_limit || 377 inp->inp_gencnt != sc->sc_inp_gencnt) { 378 syncache_drop(sc, NULL); 379 tcpstat.tcps_sc_stale++; 380 continue; 381 } 382 (void) syncache_respond(sc, NULL); 383 tcpstat.tcps_sc_retransmitted++; 384 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 385 SYNCACHE_TIMEOUT(sc, slot + 1); 386 } 387 if (nsc != NULL) 388 callout_reset(&tcp_syncache.tt_timerq[slot], 389 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 390 splx(s); 391 } 392 393 /* 394 * Find an entry in the syncache. 395 */ 396 struct syncache * 397 syncache_lookup(inc, schp) 398 struct in_conninfo *inc; 399 struct syncache_head **schp; 400 { 401 struct syncache *sc; 402 struct syncache_head *sch; 403 int s; 404 405 #ifdef INET6 406 if (inc->inc_isipv6) { 407 sch = &tcp_syncache.hashbase[ 408 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 409 *schp = sch; 410 s = splnet(); 411 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 412 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 413 splx(s); 414 return (sc); 415 } 416 } 417 splx(s); 418 } else 419 #endif 420 { 421 sch = &tcp_syncache.hashbase[ 422 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 423 *schp = sch; 424 s = splnet(); 425 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 426 #ifdef INET6 427 if (sc->sc_inc.inc_isipv6) 428 continue; 429 #endif 430 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) { 431 splx(s); 432 return (sc); 433 } 434 } 435 splx(s); 436 } 437 return (NULL); 438 } 439 440 /* 441 * This function is called when we get a RST for a 442 * non-existent connection, so that we can see if the 443 * connection is in the syn cache. If it is, zap it. 444 */ 445 void 446 syncache_chkrst(inc, th) 447 struct in_conninfo *inc; 448 struct tcphdr *th; 449 { 450 struct syncache *sc; 451 struct syncache_head *sch; 452 453 sc = syncache_lookup(inc, &sch); 454 if (sc == NULL) 455 return; 456 /* 457 * If the RST bit is set, check the sequence number to see 458 * if this is a valid reset segment. 459 * RFC 793 page 37: 460 * In all states except SYN-SENT, all reset (RST) segments 461 * are validated by checking their SEQ-fields. A reset is 462 * valid if its sequence number is in the window. 463 * 464 * The sequence number in the reset segment is normally an 465 * echo of our outgoing acknowlegement numbers, but some hosts 466 * send a reset with the sequence number at the rightmost edge 467 * of our receive window, and we have to handle this case. 468 */ 469 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 470 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 471 syncache_drop(sc, sch); 472 tcpstat.tcps_sc_reset++; 473 } 474 } 475 476 void 477 syncache_badack(inc) 478 struct in_conninfo *inc; 479 { 480 struct syncache *sc; 481 struct syncache_head *sch; 482 483 sc = syncache_lookup(inc, &sch); 484 if (sc != NULL) { 485 syncache_drop(sc, sch); 486 tcpstat.tcps_sc_badack++; 487 } 488 } 489 490 void 491 syncache_unreach(inc, th) 492 struct in_conninfo *inc; 493 struct tcphdr *th; 494 { 495 struct syncache *sc; 496 struct syncache_head *sch; 497 498 /* we are called at splnet() here */ 499 sc = syncache_lookup(inc, &sch); 500 if (sc == NULL) 501 return; 502 503 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 504 if (ntohl(th->th_seq) != sc->sc_iss) 505 return; 506 507 /* 508 * If we've rertransmitted 3 times and this is our second error, 509 * we remove the entry. Otherwise, we allow it to continue on. 510 * This prevents us from incorrectly nuking an entry during a 511 * spurious network outage. 512 * 513 * See tcp_notify(). 514 */ 515 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 516 sc->sc_flags |= SCF_UNREACH; 517 return; 518 } 519 syncache_drop(sc, sch); 520 tcpstat.tcps_sc_unreach++; 521 } 522 523 /* 524 * Build a new TCP socket structure from a syncache entry. 525 */ 526 static struct socket * 527 syncache_socket(sc, lso) 528 struct syncache *sc; 529 struct socket *lso; 530 { 531 struct inpcb *inp = NULL; 532 struct socket *so; 533 struct tcpcb *tp; 534 535 /* 536 * Ok, create the full blown connection, and set things up 537 * as they would have been set up if we had created the 538 * connection when the SYN arrived. If we can't create 539 * the connection, abort it. 540 */ 541 so = sonewconn(lso, SS_ISCONNECTED); 542 if (so == NULL) { 543 /* 544 * Drop the connection; we will send a RST if the peer 545 * retransmits the ACK, 546 */ 547 tcpstat.tcps_listendrop++; 548 goto abort; 549 } 550 551 inp = sotoinpcb(so); 552 553 /* 554 * Insert new socket into hash list. 555 */ 556 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 557 #ifdef INET6 558 if (sc->sc_inc.inc_isipv6) { 559 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 560 } else { 561 inp->inp_vflag &= ~INP_IPV6; 562 inp->inp_vflag |= INP_IPV4; 563 #endif 564 inp->inp_laddr = sc->sc_inc.inc_laddr; 565 #ifdef INET6 566 } 567 #endif 568 inp->inp_lport = sc->sc_inc.inc_lport; 569 if (in_pcbinshash(inp) != 0) { 570 /* 571 * Undo the assignments above if we failed to 572 * put the PCB on the hash lists. 573 */ 574 #ifdef INET6 575 if (sc->sc_inc.inc_isipv6) 576 inp->in6p_laddr = in6addr_any; 577 else 578 #endif 579 inp->inp_laddr.s_addr = INADDR_ANY; 580 inp->inp_lport = 0; 581 goto abort; 582 } 583 #ifdef IPSEC 584 /* copy old policy into new socket's */ 585 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 586 printf("syncache_expand: could not copy policy\n"); 587 #endif 588 #ifdef INET6 589 if (sc->sc_inc.inc_isipv6) { 590 struct inpcb *oinp = sotoinpcb(lso); 591 struct in6_addr laddr6; 592 struct sockaddr_in6 *sin6; 593 /* 594 * Inherit socket options from the listening socket. 595 * Note that in6p_inputopts are not (and should not be) 596 * copied, since it stores previously received options and is 597 * used to detect if each new option is different than the 598 * previous one and hence should be passed to a user. 599 * If we copied in6p_inputopts, a user would not be able to 600 * receive options just after calling the accept system call. 601 */ 602 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 603 if (oinp->in6p_outputopts) 604 inp->in6p_outputopts = 605 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT); 606 inp->in6p_route = sc->sc_route6; 607 sc->sc_route6.ro_rt = NULL; 608 609 MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, 610 M_SONAME, M_NOWAIT | M_ZERO); 611 if (sin6 == NULL) 612 goto abort; 613 sin6->sin6_family = AF_INET6; 614 sin6->sin6_len = sizeof(*sin6); 615 sin6->sin6_addr = sc->sc_inc.inc6_faddr; 616 sin6->sin6_port = sc->sc_inc.inc_fport; 617 laddr6 = inp->in6p_laddr; 618 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 619 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 620 if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &thread0)) { 621 inp->in6p_laddr = laddr6; 622 FREE(sin6, M_SONAME); 623 goto abort; 624 } 625 FREE(sin6, M_SONAME); 626 } else 627 #endif 628 { 629 struct in_addr laddr; 630 struct sockaddr_in *sin; 631 632 inp->inp_options = ip_srcroute(); 633 if (inp->inp_options == NULL) { 634 inp->inp_options = sc->sc_ipopts; 635 sc->sc_ipopts = NULL; 636 } 637 inp->inp_route = sc->sc_route; 638 sc->sc_route.ro_rt = NULL; 639 640 MALLOC(sin, struct sockaddr_in *, sizeof *sin, 641 M_SONAME, M_NOWAIT | M_ZERO); 642 if (sin == NULL) 643 goto abort; 644 sin->sin_family = AF_INET; 645 sin->sin_len = sizeof(*sin); 646 sin->sin_addr = sc->sc_inc.inc_faddr; 647 sin->sin_port = sc->sc_inc.inc_fport; 648 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 649 laddr = inp->inp_laddr; 650 if (inp->inp_laddr.s_addr == INADDR_ANY) 651 inp->inp_laddr = sc->sc_inc.inc_laddr; 652 if (in_pcbconnect(inp, (struct sockaddr *)sin, &thread0)) { 653 inp->inp_laddr = laddr; 654 FREE(sin, M_SONAME); 655 goto abort; 656 } 657 FREE(sin, M_SONAME); 658 } 659 660 tp = intotcpcb(inp); 661 tp->t_state = TCPS_SYN_RECEIVED; 662 tp->iss = sc->sc_iss; 663 tp->irs = sc->sc_irs; 664 tcp_rcvseqinit(tp); 665 tcp_sendseqinit(tp); 666 tp->snd_wl1 = sc->sc_irs; 667 tp->rcv_up = sc->sc_irs + 1; 668 tp->rcv_wnd = sc->sc_wnd; 669 tp->rcv_adv += tp->rcv_wnd; 670 671 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 672 if (sc->sc_flags & SCF_NOOPT) 673 tp->t_flags |= TF_NOOPT; 674 if (sc->sc_flags & SCF_WINSCALE) { 675 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 676 tp->requested_s_scale = sc->sc_requested_s_scale; 677 tp->request_r_scale = sc->sc_request_r_scale; 678 } 679 if (sc->sc_flags & SCF_TIMESTAMP) { 680 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 681 tp->ts_recent = sc->sc_tsrecent; 682 tp->ts_recent_age = ticks; 683 } 684 if (sc->sc_flags & SCF_CC) { 685 /* 686 * Initialization of the tcpcb for transaction; 687 * set SND.WND = SEG.WND, 688 * initialize CCsend and CCrecv. 689 */ 690 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 691 tp->cc_send = sc->sc_cc_send; 692 tp->cc_recv = sc->sc_cc_recv; 693 } 694 695 tcp_mss(tp, sc->sc_peer_mss); 696 697 /* 698 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 699 */ 700 if (sc->sc_rxtslot != 0) 701 tp->snd_cwnd = tp->t_maxseg; 702 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 703 704 tcpstat.tcps_accepts++; 705 return (so); 706 707 abort: 708 if (so != NULL) 709 (void) soabort(so); 710 return (NULL); 711 } 712 713 /* 714 * This function gets called when we receive an ACK for a 715 * socket in the LISTEN state. We look up the connection 716 * in the syncache, and if its there, we pull it out of 717 * the cache and turn it into a full-blown connection in 718 * the SYN-RECEIVED state. 719 */ 720 int 721 syncache_expand(inc, th, sop, m) 722 struct in_conninfo *inc; 723 struct tcphdr *th; 724 struct socket **sop; 725 struct mbuf *m; 726 { 727 struct syncache *sc; 728 struct syncache_head *sch; 729 struct socket *so; 730 731 sc = syncache_lookup(inc, &sch); 732 if (sc == NULL) { 733 /* 734 * There is no syncache entry, so see if this ACK is 735 * a returning syncookie. To do this, first: 736 * A. See if this socket has had a syncache entry dropped in 737 * the past. We don't want to accept a bogus syncookie 738 * if we've never received a SYN. 739 * B. check that the syncookie is valid. If it is, then 740 * cobble up a fake syncache entry, and return. 741 */ 742 if (!tcp_syncookies) 743 return (0); 744 sc = syncookie_lookup(inc, th, *sop); 745 if (sc == NULL) 746 return (0); 747 sch = NULL; 748 tcpstat.tcps_sc_recvcookie++; 749 } 750 751 /* 752 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 753 */ 754 if (th->th_ack != sc->sc_iss + 1) 755 return (0); 756 757 so = syncache_socket(sc, *sop); 758 if (so == NULL) { 759 #if 0 760 resetandabort: 761 /* XXXjlemon check this - is this correct? */ 762 (void) tcp_respond(NULL, m, m, th, 763 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 764 #endif 765 m_freem(m); /* XXX only needed for above */ 766 tcpstat.tcps_sc_aborted++; 767 } else { 768 sc->sc_flags |= SCF_KEEPROUTE; 769 tcpstat.tcps_sc_completed++; 770 } 771 if (sch == NULL) 772 syncache_free(sc); 773 else 774 syncache_drop(sc, sch); 775 *sop = so; 776 return (1); 777 } 778 779 /* 780 * Given a LISTEN socket and an inbound SYN request, add 781 * this to the syn cache, and send back a segment: 782 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 783 * to the source. 784 * 785 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 786 * Doing so would require that we hold onto the data and deliver it 787 * to the application. However, if we are the target of a SYN-flood 788 * DoS attack, an attacker could send data which would eventually 789 * consume all available buffer space if it were ACKed. By not ACKing 790 * the data, we avoid this DoS scenario. 791 */ 792 int 793 syncache_add(inc, to, th, sop, m) 794 struct in_conninfo *inc; 795 struct tcpopt *to; 796 struct tcphdr *th; 797 struct socket **sop; 798 struct mbuf *m; 799 { 800 struct tcpcb *tp; 801 struct socket *so; 802 struct syncache *sc = NULL; 803 struct syncache_head *sch; 804 struct mbuf *ipopts = NULL; 805 struct rmxp_tao *taop; 806 int i, s, win; 807 808 so = *sop; 809 tp = sototcpcb(so); 810 811 /* 812 * Remember the IP options, if any. 813 */ 814 #ifdef INET6 815 if (!inc->inc_isipv6) 816 #endif 817 ipopts = ip_srcroute(); 818 819 /* 820 * See if we already have an entry for this connection. 821 * If we do, resend the SYN,ACK, and reset the retransmit timer. 822 * 823 * XXX 824 * should the syncache be re-initialized with the contents 825 * of the new SYN here (which may have different options?) 826 */ 827 sc = syncache_lookup(inc, &sch); 828 if (sc != NULL) { 829 tcpstat.tcps_sc_dupsyn++; 830 if (ipopts) { 831 /* 832 * If we were remembering a previous source route, 833 * forget it and use the new one we've been given. 834 */ 835 if (sc->sc_ipopts) 836 (void) m_free(sc->sc_ipopts); 837 sc->sc_ipopts = ipopts; 838 } 839 /* 840 * Update timestamp if present. 841 */ 842 if (sc->sc_flags & SCF_TIMESTAMP) 843 sc->sc_tsrecent = to->to_tsval; 844 /* 845 * PCB may have changed, pick up new values. 846 */ 847 sc->sc_tp = tp; 848 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 849 if (syncache_respond(sc, m) == 0) { 850 s = splnet(); 851 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 852 sc, sc_timerq); 853 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 854 splx(s); 855 tcpstat.tcps_sndacks++; 856 tcpstat.tcps_sndtotal++; 857 } 858 *sop = NULL; 859 return (1); 860 } 861 862 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 863 if (sc == NULL) { 864 /* 865 * The zone allocator couldn't provide more entries. 866 * Treat this as if the cache was full; drop the oldest 867 * entry and insert the new one. 868 */ 869 s = splnet(); 870 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 871 sc = TAILQ_FIRST(&tcp_syncache.timerq[i]); 872 if (sc != NULL) 873 break; 874 } 875 sc->sc_tp->ts_recent = ticks; 876 syncache_drop(sc, NULL); 877 splx(s); 878 tcpstat.tcps_sc_zonefail++; 879 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 880 if (sc == NULL) { 881 if (ipopts) 882 (void) m_free(ipopts); 883 return (0); 884 } 885 } 886 887 /* 888 * Fill in the syncache values. 889 */ 890 bzero(sc, sizeof(*sc)); 891 sc->sc_tp = tp; 892 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 893 sc->sc_ipopts = ipopts; 894 sc->sc_inc.inc_fport = inc->inc_fport; 895 sc->sc_inc.inc_lport = inc->inc_lport; 896 #ifdef INET6 897 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 898 if (inc->inc_isipv6) { 899 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 900 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 901 sc->sc_route6.ro_rt = NULL; 902 } else 903 #endif 904 { 905 sc->sc_inc.inc_faddr = inc->inc_faddr; 906 sc->sc_inc.inc_laddr = inc->inc_laddr; 907 sc->sc_route.ro_rt = NULL; 908 } 909 sc->sc_irs = th->th_seq; 910 if (tcp_syncookies) 911 sc->sc_iss = syncookie_generate(sc); 912 else 913 sc->sc_iss = arc4random(); 914 915 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 916 win = sbspace(&so->so_rcv); 917 win = imax(win, 0); 918 win = imin(win, TCP_MAXWIN); 919 sc->sc_wnd = win; 920 921 sc->sc_flags = 0; 922 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 923 if (tcp_do_rfc1323) { 924 /* 925 * A timestamp received in a SYN makes 926 * it ok to send timestamp requests and replies. 927 */ 928 if (to->to_flags & TOF_TS) { 929 sc->sc_tsrecent = to->to_tsval; 930 sc->sc_flags |= SCF_TIMESTAMP; 931 } 932 if (to->to_flags & TOF_SCALE) { 933 int wscale = 0; 934 935 /* Compute proper scaling value from buffer space */ 936 while (wscale < TCP_MAX_WINSHIFT && 937 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 938 wscale++; 939 sc->sc_request_r_scale = wscale; 940 sc->sc_requested_s_scale = to->to_requested_s_scale; 941 sc->sc_flags |= SCF_WINSCALE; 942 } 943 } 944 if (tcp_do_rfc1644) { 945 /* 946 * A CC or CC.new option received in a SYN makes 947 * it ok to send CC in subsequent segments. 948 */ 949 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 950 sc->sc_cc_recv = to->to_cc; 951 sc->sc_cc_send = CC_INC(tcp_ccgen); 952 sc->sc_flags |= SCF_CC; 953 } 954 } 955 if (tp->t_flags & TF_NOOPT) 956 sc->sc_flags = SCF_NOOPT; 957 958 /* 959 * XXX 960 * We have the option here of not doing TAO (even if the segment 961 * qualifies) and instead fall back to a normal 3WHS via the syncache. 962 * This allows us to apply synflood protection to TAO-qualifying SYNs 963 * also. However, there should be a hueristic to determine when to 964 * do this, and is not present at the moment. 965 */ 966 967 /* 968 * Perform TAO test on incoming CC (SEG.CC) option, if any. 969 * - compare SEG.CC against cached CC from the same host, if any. 970 * - if SEG.CC > chached value, SYN must be new and is accepted 971 * immediately: save new CC in the cache, mark the socket 972 * connected, enter ESTABLISHED state, turn on flag to 973 * send a SYN in the next segment. 974 * A virtual advertised window is set in rcv_adv to 975 * initialize SWS prevention. Then enter normal segment 976 * processing: drop SYN, process data and FIN. 977 * - otherwise do a normal 3-way handshake. 978 */ 979 taop = tcp_gettaocache(&sc->sc_inc); 980 if ((to->to_flags & TOF_CC) != 0) { 981 if (((tp->t_flags & TF_NOPUSH) != 0) && 982 sc->sc_flags & SCF_CC && 983 taop != NULL && taop->tao_cc != 0 && 984 CC_GT(to->to_cc, taop->tao_cc)) { 985 sc->sc_rxtslot = 0; 986 so = syncache_socket(sc, *sop); 987 if (so != NULL) { 988 sc->sc_flags |= SCF_KEEPROUTE; 989 taop->tao_cc = to->to_cc; 990 *sop = so; 991 } 992 syncache_free(sc); 993 return (so != NULL); 994 } 995 } else { 996 /* 997 * No CC option, but maybe CC.NEW: invalidate cached value. 998 */ 999 if (taop != NULL) 1000 taop->tao_cc = 0; 1001 } 1002 /* 1003 * TAO test failed or there was no CC option, 1004 * do a standard 3-way handshake. 1005 */ 1006 if (syncache_respond(sc, m) == 0) { 1007 syncache_insert(sc, sch); 1008 tcpstat.tcps_sndacks++; 1009 tcpstat.tcps_sndtotal++; 1010 } else { 1011 syncache_free(sc); 1012 tcpstat.tcps_sc_dropped++; 1013 } 1014 *sop = NULL; 1015 return (1); 1016 } 1017 1018 static int 1019 syncache_respond(sc, m) 1020 struct syncache *sc; 1021 struct mbuf *m; 1022 { 1023 u_int8_t *optp; 1024 int optlen, error; 1025 u_int16_t tlen, hlen, mssopt; 1026 struct ip *ip = NULL; 1027 struct rtentry *rt; 1028 struct tcphdr *th; 1029 #ifdef INET6 1030 struct ip6_hdr *ip6 = NULL; 1031 #endif 1032 1033 #ifdef INET6 1034 if (sc->sc_inc.inc_isipv6) { 1035 rt = tcp_rtlookup6(&sc->sc_inc); 1036 if (rt != NULL) 1037 mssopt = rt->rt_ifp->if_mtu - 1038 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1039 else 1040 mssopt = tcp_v6mssdflt; 1041 hlen = sizeof(struct ip6_hdr); 1042 } else 1043 #endif 1044 { 1045 rt = tcp_rtlookup(&sc->sc_inc); 1046 if (rt != NULL) 1047 mssopt = rt->rt_ifp->if_mtu - 1048 (sizeof(struct ip) + sizeof(struct tcphdr)); 1049 else 1050 mssopt = tcp_mssdflt; 1051 hlen = sizeof(struct ip); 1052 } 1053 1054 /* Compute the size of the TCP options. */ 1055 if (sc->sc_flags & SCF_NOOPT) { 1056 optlen = 0; 1057 } else { 1058 optlen = TCPOLEN_MAXSEG + 1059 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1060 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1061 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1062 } 1063 tlen = hlen + sizeof(struct tcphdr) + optlen; 1064 1065 /* 1066 * XXX 1067 * assume that the entire packet will fit in a header mbuf 1068 */ 1069 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1070 1071 /* 1072 * XXX shouldn't this reuse the mbuf if possible ? 1073 * Create the IP+TCP header from scratch. 1074 */ 1075 if (m) 1076 m_freem(m); 1077 1078 m = m_gethdr(M_DONTWAIT, MT_HEADER); 1079 if (m == NULL) 1080 return (ENOBUFS); 1081 m->m_data += max_linkhdr; 1082 m->m_len = tlen; 1083 m->m_pkthdr.len = tlen; 1084 m->m_pkthdr.rcvif = NULL; 1085 1086 #ifdef IPSEC 1087 /* use IPsec policy on listening socket to send SYN,ACK */ 1088 if (ipsec_setsocket(m, sc->sc_tp->t_inpcb->inp_socket) != 0) { 1089 m_freem(m); 1090 return (ENOBUFS); 1091 } 1092 #endif 1093 1094 #ifdef INET6 1095 if (sc->sc_inc.inc_isipv6) { 1096 ip6 = mtod(m, struct ip6_hdr *); 1097 ip6->ip6_vfc = IPV6_VERSION; 1098 ip6->ip6_nxt = IPPROTO_TCP; 1099 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1100 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1101 ip6->ip6_plen = htons(tlen - hlen); 1102 /* ip6_hlim is set after checksum */ 1103 /* ip6_flow = ??? */ 1104 1105 th = (struct tcphdr *)(ip6 + 1); 1106 } else 1107 #endif 1108 { 1109 ip = mtod(m, struct ip *); 1110 ip->ip_v = IPVERSION; 1111 ip->ip_hl = sizeof(struct ip) >> 2; 1112 ip->ip_tos = 0; 1113 ip->ip_len = tlen; 1114 ip->ip_id = 0; 1115 ip->ip_off = 0; 1116 ip->ip_ttl = ip_defttl; 1117 ip->ip_sum = 0; 1118 ip->ip_p = IPPROTO_TCP; 1119 ip->ip_src = sc->sc_inc.inc_laddr; 1120 ip->ip_dst = sc->sc_inc.inc_faddr; 1121 1122 th = (struct tcphdr *)(ip + 1); 1123 } 1124 th->th_sport = sc->sc_inc.inc_lport; 1125 th->th_dport = sc->sc_inc.inc_fport; 1126 1127 th->th_seq = htonl(sc->sc_iss); 1128 th->th_ack = htonl(sc->sc_irs + 1); 1129 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1130 th->th_x2 = 0; 1131 th->th_flags = TH_SYN|TH_ACK; 1132 th->th_win = htons(sc->sc_wnd); 1133 th->th_urp = 0; 1134 1135 /* Tack on the TCP options. */ 1136 if (optlen == 0) 1137 goto no_options; 1138 optp = (u_int8_t *)(th + 1); 1139 *optp++ = TCPOPT_MAXSEG; 1140 *optp++ = TCPOLEN_MAXSEG; 1141 *optp++ = (mssopt >> 8) & 0xff; 1142 *optp++ = mssopt & 0xff; 1143 1144 if (sc->sc_flags & SCF_WINSCALE) { 1145 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1146 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1147 sc->sc_request_r_scale); 1148 optp += 4; 1149 } 1150 1151 if (sc->sc_flags & SCF_TIMESTAMP) { 1152 u_int32_t *lp = (u_int32_t *)(optp); 1153 1154 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1155 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1156 *lp++ = htonl(ticks); 1157 *lp = htonl(sc->sc_tsrecent); 1158 optp += TCPOLEN_TSTAMP_APPA; 1159 } 1160 1161 /* 1162 * Send CC and CC.echo if we received CC from our peer. 1163 */ 1164 if (sc->sc_flags & SCF_CC) { 1165 u_int32_t *lp = (u_int32_t *)(optp); 1166 1167 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1168 *lp++ = htonl(sc->sc_cc_send); 1169 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1170 *lp = htonl(sc->sc_cc_recv); 1171 optp += TCPOLEN_CC_APPA * 2; 1172 } 1173 no_options: 1174 1175 #ifdef INET6 1176 if (sc->sc_inc.inc_isipv6) { 1177 struct route_in6 *ro6 = &sc->sc_route6; 1178 1179 th->th_sum = 0; 1180 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1181 ip6->ip6_hlim = in6_selecthlim(NULL, 1182 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1183 error = ip6_output(m, NULL, ro6, 0, NULL, NULL); 1184 } else 1185 #endif 1186 { 1187 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1188 htons(tlen - hlen + IPPROTO_TCP)); 1189 m->m_pkthdr.csum_flags = CSUM_TCP; 1190 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1191 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL); 1192 } 1193 return (error); 1194 } 1195 1196 /* 1197 * cookie layers: 1198 * 1199 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1200 * | peer iss | 1201 * | MD5(laddr,faddr,lport,fport,secret) |. . . . . . .| 1202 * | 0 |(A)| | 1203 * (A): peer mss index 1204 */ 1205 1206 /* 1207 * The values below are chosen to minimize the size of the tcp_secret 1208 * table, as well as providing roughly a 4 second lifetime for the cookie. 1209 */ 1210 1211 #define SYNCOOKIE_HASHSHIFT 2 /* log2(# of 32bit words from hash) */ 1212 #define SYNCOOKIE_WNDBITS 7 /* exposed bits for window indexing */ 1213 #define SYNCOOKIE_TIMESHIFT 5 /* scale ticks to window time units */ 1214 1215 #define SYNCOOKIE_HASHMASK ((1 << SYNCOOKIE_HASHSHIFT) - 1) 1216 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1217 #define SYNCOOKIE_NSECRETS (1 << (SYNCOOKIE_WNDBITS - SYNCOOKIE_HASHSHIFT)) 1218 #define SYNCOOKIE_TIMEOUT \ 1219 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1220 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1221 1222 static struct { 1223 u_int32_t ts_secbits; 1224 u_int ts_expire; 1225 } tcp_secret[SYNCOOKIE_NSECRETS]; 1226 1227 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1228 1229 static MD5_CTX syn_ctx; 1230 1231 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1232 1233 /* 1234 * Consider the problem of a recreated (and retransmitted) cookie. If the 1235 * original SYN was accepted, the connection is established. The second 1236 * SYN is inflight, and if it arrives with an ISN that falls within the 1237 * receive window, the connection is killed. 1238 * 1239 * However, since cookies have other problems, this may not be worth 1240 * worrying about. 1241 */ 1242 1243 static u_int32_t 1244 syncookie_generate(struct syncache *sc) 1245 { 1246 u_int32_t md5_buffer[4]; 1247 u_int32_t data; 1248 int wnd, idx; 1249 1250 wnd = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1251 idx = wnd >> SYNCOOKIE_HASHSHIFT; 1252 if (tcp_secret[idx].ts_expire < ticks) { 1253 tcp_secret[idx].ts_secbits = arc4random(); 1254 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1255 } 1256 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1257 if (tcp_msstab[data] <= sc->sc_peer_mss) 1258 break; 1259 data = (data << SYNCOOKIE_WNDBITS) | wnd; 1260 data ^= sc->sc_irs; /* peer's iss */ 1261 MD5Init(&syn_ctx); 1262 #ifdef INET6 1263 if (sc->sc_inc.inc_isipv6) { 1264 MD5Add(sc->sc_inc.inc6_laddr); 1265 MD5Add(sc->sc_inc.inc6_faddr); 1266 } else 1267 #endif 1268 { 1269 MD5Add(sc->sc_inc.inc_laddr); 1270 MD5Add(sc->sc_inc.inc_faddr); 1271 } 1272 MD5Add(sc->sc_inc.inc_lport); 1273 MD5Add(sc->sc_inc.inc_fport); 1274 MD5Add(tcp_secret[idx].ts_secbits); 1275 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1276 data ^= (md5_buffer[wnd & SYNCOOKIE_HASHMASK] & ~SYNCOOKIE_WNDMASK); 1277 return (data); 1278 } 1279 1280 static struct syncache * 1281 syncookie_lookup(inc, th, so) 1282 struct in_conninfo *inc; 1283 struct tcphdr *th; 1284 struct socket *so; 1285 { 1286 u_int32_t md5_buffer[4]; 1287 struct syncache *sc; 1288 u_int32_t data; 1289 int wnd, idx; 1290 1291 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1292 wnd = data & SYNCOOKIE_WNDMASK; 1293 idx = wnd >> SYNCOOKIE_HASHSHIFT; 1294 if (tcp_secret[idx].ts_expire < ticks || 1295 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1296 return (NULL); 1297 MD5Init(&syn_ctx); 1298 #ifdef INET6 1299 if (inc->inc_isipv6) { 1300 MD5Add(inc->inc6_laddr); 1301 MD5Add(inc->inc6_faddr); 1302 } else 1303 #endif 1304 { 1305 MD5Add(inc->inc_laddr); 1306 MD5Add(inc->inc_faddr); 1307 } 1308 MD5Add(inc->inc_lport); 1309 MD5Add(inc->inc_fport); 1310 MD5Add(tcp_secret[idx].ts_secbits); 1311 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1312 data ^= md5_buffer[wnd & SYNCOOKIE_HASHMASK]; 1313 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1314 return (NULL); 1315 data = data >> SYNCOOKIE_WNDBITS; 1316 1317 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT); 1318 if (sc == NULL) 1319 return (NULL); 1320 /* 1321 * Fill in the syncache values. 1322 * XXX duplicate code from syncache_add 1323 */ 1324 sc->sc_ipopts = NULL; 1325 sc->sc_inc.inc_fport = inc->inc_fport; 1326 sc->sc_inc.inc_lport = inc->inc_lport; 1327 #ifdef INET6 1328 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1329 if (inc->inc_isipv6) { 1330 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1331 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1332 sc->sc_route6.ro_rt = NULL; 1333 } else 1334 #endif 1335 { 1336 sc->sc_inc.inc_faddr = inc->inc_faddr; 1337 sc->sc_inc.inc_laddr = inc->inc_laddr; 1338 sc->sc_route.ro_rt = NULL; 1339 } 1340 sc->sc_irs = th->th_seq - 1; 1341 sc->sc_iss = th->th_ack - 1; 1342 wnd = sbspace(&so->so_rcv); 1343 wnd = imax(wnd, 0); 1344 wnd = imin(wnd, TCP_MAXWIN); 1345 sc->sc_wnd = wnd; 1346 sc->sc_flags = 0; 1347 sc->sc_rxtslot = 0; 1348 sc->sc_peer_mss = tcp_msstab[data]; 1349 return (sc); 1350 } 1351