1 /* 2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * All advertising materials mentioning features or use of this software 53 * must display the following acknowledgement: 54 * This product includes software developed by Jeffrey M. Hsu. 55 * 56 * Copyright (c) 2001 Networks Associates Technologies, Inc. 57 * All rights reserved. 58 * 59 * This software was developed for the FreeBSD Project by Jonathan Lemon 60 * and NAI Labs, the Security Research Division of Network Associates, Inc. 61 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 62 * DARPA CHATS research program. 63 * 64 * Redistribution and use in source and binary forms, with or without 65 * modification, are permitted provided that the following conditions 66 * are met: 67 * 1. Redistributions of source code must retain the above copyright 68 * notice, this list of conditions and the following disclaimer. 69 * 2. Redistributions in binary form must reproduce the above copyright 70 * notice, this list of conditions and the following disclaimer in the 71 * documentation and/or other materials provided with the distribution. 72 * 3. The name of the author may not be used to endorse or promote 73 * products derived from this software without specific prior written 74 * permission. 75 * 76 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 77 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 78 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 79 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 80 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 81 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 82 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 83 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 84 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 85 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 86 * SUCH DAMAGE. 87 * 88 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $ 89 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.15 2004/07/08 22:07:35 hsu Exp $ 90 */ 91 92 #include "opt_inet6.h" 93 #include "opt_ipsec.h" 94 95 #include <sys/param.h> 96 #include <sys/systm.h> 97 #include <sys/kernel.h> 98 #include <sys/sysctl.h> 99 #include <sys/malloc.h> 100 #include <sys/mbuf.h> 101 #include <sys/md5.h> 102 #include <sys/proc.h> /* for proc0 declaration */ 103 #include <sys/random.h> 104 #include <sys/socket.h> 105 #include <sys/socketvar.h> 106 #include <sys/in_cksum.h> 107 108 #include <net/if.h> 109 #include <net/route.h> 110 111 #include <netinet/in.h> 112 #include <netinet/in_systm.h> 113 #include <netinet/ip.h> 114 #include <netinet/in_var.h> 115 #include <netinet/in_pcb.h> 116 #include <netinet/ip_var.h> 117 #ifdef INET6 118 #include <netinet/ip6.h> 119 #include <netinet/icmp6.h> 120 #include <netinet6/nd6.h> 121 #include <netinet6/ip6_var.h> 122 #include <netinet6/in6_pcb.h> 123 #endif 124 #include <netinet/tcp.h> 125 #include <netinet/tcp_fsm.h> 126 #include <netinet/tcp_seq.h> 127 #include <netinet/tcp_timer.h> 128 #include <netinet/tcp_var.h> 129 #ifdef INET6 130 #include <netinet6/tcp6_var.h> 131 #endif 132 133 #ifdef IPSEC 134 #include <netinet6/ipsec.h> 135 #ifdef INET6 136 #include <netinet6/ipsec6.h> 137 #endif 138 #include <netproto/key/key.h> 139 #endif /*IPSEC*/ 140 141 #ifdef FAST_IPSEC 142 #include <netipsec/ipsec.h> 143 #ifdef INET6 144 #include <netipsec/ipsec6.h> 145 #endif 146 #include <netipsec/key.h> 147 #define IPSEC 148 #endif /*FAST_IPSEC*/ 149 150 #include <vm/vm_zone.h> 151 152 static int tcp_syncookies = 1; 153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 154 &tcp_syncookies, 0, 155 "Use TCP SYN cookies if the syncache overflows"); 156 157 static void syncache_drop(struct syncache *, struct syncache_head *); 158 static void syncache_free(struct syncache *); 159 static void syncache_insert(struct syncache *, struct syncache_head *); 160 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 161 static int syncache_respond(struct syncache *, struct mbuf *); 162 static struct socket *syncache_socket(struct syncache *, struct socket *); 163 static void syncache_timer(void *); 164 static u_int32_t syncookie_generate(struct syncache *); 165 static struct syncache *syncookie_lookup(struct in_conninfo *, 166 struct tcphdr *, struct socket *); 167 168 /* 169 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 170 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 171 * the odds are that the user has given up attempting to connect by then. 172 */ 173 #define SYNCACHE_MAXREXMTS 3 174 175 /* Arbitrary values */ 176 #define TCP_SYNCACHE_HASHSIZE 512 177 #define TCP_SYNCACHE_BUCKETLIMIT 30 178 179 struct tcp_syncache { 180 struct syncache_head *hashbase; 181 struct vm_zone *zone; 182 u_int hashsize; 183 u_int hashmask; 184 u_int bucket_limit; 185 u_int cache_count; 186 u_int cache_limit; 187 u_int rexmt_limit; 188 u_int hash_secret; 189 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1]; 190 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 191 }; 192 static struct tcp_syncache tcp_syncache; 193 194 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 195 196 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 197 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 198 199 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 200 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 201 202 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 203 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 204 205 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 206 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 207 208 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 209 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 210 211 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 212 213 #define SYNCACHE_HASH(inc, mask) \ 214 ((tcp_syncache.hash_secret ^ \ 215 (inc)->inc_faddr.s_addr ^ \ 216 ((inc)->inc_faddr.s_addr >> 16) ^ \ 217 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 218 219 #define SYNCACHE_HASH6(inc, mask) \ 220 ((tcp_syncache.hash_secret ^ \ 221 (inc)->inc6_faddr.s6_addr32[0] ^ \ 222 (inc)->inc6_faddr.s6_addr32[3] ^ \ 223 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 224 225 #define ENDPTS_EQ(a, b) ( \ 226 (a)->ie_fport == (b)->ie_fport && \ 227 (a)->ie_lport == (b)->ie_lport && \ 228 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 229 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 230 ) 231 232 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 233 234 #define SYNCACHE_TIMEOUT(sc, slot) do { \ 235 sc->sc_rxtslot = slot; \ 236 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; \ 237 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[slot], sc, sc_timerq); \ 238 if (!callout_active(&tcp_syncache.tt_timerq[slot])) \ 239 callout_reset(&tcp_syncache.tt_timerq[slot], \ 240 TCPTV_RTOBASE * tcp_backoff[slot], \ 241 syncache_timer, (void *)((intptr_t)slot)); \ 242 } while (0) 243 244 static void 245 syncache_free(struct syncache *sc) 246 { 247 struct rtentry *rt; 248 249 if (sc->sc_ipopts) 250 (void) m_free(sc->sc_ipopts); 251 #ifdef INET6 252 if (sc->sc_inc.inc_isipv6) 253 rt = sc->sc_route6.ro_rt; 254 else 255 #endif 256 rt = sc->sc_route.ro_rt; 257 if (rt != NULL) { 258 /* 259 * If this is the only reference to a protocol cloned 260 * route, remove it immediately. 261 */ 262 if (rt->rt_flags & RTF_WASCLONED && 263 (sc->sc_flags & SCF_KEEPROUTE) == 0 && 264 rt->rt_refcnt == 1) 265 rtrequest(RTM_DELETE, rt_key(rt), 266 rt->rt_gateway, rt_mask(rt), 267 rt->rt_flags, NULL); 268 RTFREE(rt); 269 } 270 zfree(tcp_syncache.zone, sc); 271 } 272 273 void 274 syncache_init(void) 275 { 276 int i; 277 278 tcp_syncache.cache_count = 0; 279 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 280 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 281 tcp_syncache.cache_limit = 282 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 283 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 284 tcp_syncache.hash_secret = arc4random(); 285 286 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 287 &tcp_syncache.hashsize); 288 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 289 &tcp_syncache.cache_limit); 290 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 291 &tcp_syncache.bucket_limit); 292 if (!powerof2(tcp_syncache.hashsize)) { 293 printf("WARNING: syncache hash size is not a power of 2.\n"); 294 tcp_syncache.hashsize = 512; /* safe default */ 295 } 296 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 297 298 /* Allocate the hash table. */ 299 MALLOC(tcp_syncache.hashbase, struct syncache_head *, 300 tcp_syncache.hashsize * sizeof(struct syncache_head), 301 M_SYNCACHE, M_WAITOK); 302 303 /* Initialize the hash buckets. */ 304 for (i = 0; i < tcp_syncache.hashsize; i++) { 305 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket); 306 tcp_syncache.hashbase[i].sch_length = 0; 307 } 308 309 /* Initialize the timer queues. */ 310 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 311 TAILQ_INIT(&tcp_syncache.timerq[i]); 312 callout_init(&tcp_syncache.tt_timerq[i]); 313 } 314 315 /* 316 * Allocate the syncache entries. Allow the zone to allocate one 317 * more entry than cache limit, so a new entry can bump out an 318 * older one. 319 */ 320 tcp_syncache.zone = zinit("syncache", sizeof(struct syncache), 321 tcp_syncache.cache_limit, ZONE_INTERRUPT, 0); 322 tcp_syncache.cache_limit -= 1; 323 } 324 325 static void 326 syncache_insert(sc, sch) 327 struct syncache *sc; 328 struct syncache_head *sch; 329 { 330 struct syncache *sc2; 331 int i; 332 333 /* 334 * Make sure that we don't overflow the per-bucket 335 * limit or the total cache size limit. 336 */ 337 if (sch->sch_length >= tcp_syncache.bucket_limit) { 338 /* 339 * The bucket is full, toss the oldest element. 340 */ 341 sc2 = TAILQ_FIRST(&sch->sch_bucket); 342 sc2->sc_tp->ts_recent = ticks; 343 syncache_drop(sc2, sch); 344 tcpstat.tcps_sc_bucketoverflow++; 345 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) { 346 /* 347 * The cache is full. Toss the oldest entry in the 348 * entire cache. This is the front entry in the 349 * first non-empty timer queue with the largest 350 * timeout value. 351 */ 352 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 353 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]); 354 if (sc2 != NULL) 355 break; 356 } 357 sc2->sc_tp->ts_recent = ticks; 358 syncache_drop(sc2, NULL); 359 tcpstat.tcps_sc_cacheoverflow++; 360 } 361 362 /* Initialize the entry's timer. */ 363 SYNCACHE_TIMEOUT(sc, 0); 364 365 /* Put it into the bucket. */ 366 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 367 sch->sch_length++; 368 tcp_syncache.cache_count++; 369 tcpstat.tcps_sc_added++; 370 } 371 372 static void 373 syncache_drop(sc, sch) 374 struct syncache *sc; 375 struct syncache_head *sch; 376 { 377 378 if (sch == NULL) { 379 #ifdef INET6 380 if (sc->sc_inc.inc_isipv6) { 381 sch = &tcp_syncache.hashbase[ 382 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 383 } else 384 #endif 385 { 386 sch = &tcp_syncache.hashbase[ 387 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 388 } 389 } 390 391 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 392 sch->sch_length--; 393 tcp_syncache.cache_count--; 394 395 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq); 396 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot])) 397 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]); 398 399 syncache_free(sc); 400 } 401 402 /* 403 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 404 * If we have retransmitted an entry the maximum number of times, expire it. 405 */ 406 static void 407 syncache_timer(xslot) 408 void *xslot; 409 { 410 intptr_t slot = (intptr_t)xslot; 411 struct syncache *sc, *nsc; 412 struct inpcb *inp; 413 int s; 414 415 s = splnet(); 416 if (callout_pending(&tcp_syncache.tt_timerq[slot]) || 417 !callout_active(&tcp_syncache.tt_timerq[slot])) { 418 splx(s); 419 return; 420 } 421 callout_deactivate(&tcp_syncache.tt_timerq[slot]); 422 423 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]); 424 while (nsc != NULL) { 425 if (ticks < nsc->sc_rxttime) 426 break; 427 sc = nsc; 428 inp = sc->sc_tp->t_inpcb; 429 if (slot == SYNCACHE_MAXREXMTS || 430 slot >= tcp_syncache.rexmt_limit || 431 inp->inp_gencnt != sc->sc_inp_gencnt) { 432 nsc = TAILQ_NEXT(sc, sc_timerq); 433 syncache_drop(sc, NULL); 434 tcpstat.tcps_sc_stale++; 435 continue; 436 } 437 /* 438 * syncache_respond() may call back into the syncache to 439 * to modify another entry, so do not obtain the next 440 * entry on the timer chain until it has completed. 441 */ 442 (void) syncache_respond(sc, NULL); 443 nsc = TAILQ_NEXT(sc, sc_timerq); 444 tcpstat.tcps_sc_retransmitted++; 445 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq); 446 SYNCACHE_TIMEOUT(sc, slot + 1); 447 } 448 if (nsc != NULL) 449 callout_reset(&tcp_syncache.tt_timerq[slot], 450 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot)); 451 splx(s); 452 } 453 454 /* 455 * Find an entry in the syncache. 456 */ 457 struct syncache * 458 syncache_lookup(inc, schp) 459 struct in_conninfo *inc; 460 struct syncache_head **schp; 461 { 462 struct syncache *sc; 463 struct syncache_head *sch; 464 465 #ifdef INET6 466 if (inc->inc_isipv6) { 467 sch = &tcp_syncache.hashbase[ 468 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 469 *schp = sch; 470 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 471 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 472 return (sc); 473 } else 474 #endif 475 { 476 sch = &tcp_syncache.hashbase[ 477 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 478 *schp = sch; 479 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 480 #ifdef INET6 481 if (sc->sc_inc.inc_isipv6) 482 continue; 483 #endif 484 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 485 return (sc); 486 } 487 } 488 return (NULL); 489 } 490 491 /* 492 * This function is called when we get a RST for a 493 * non-existent connection, so that we can see if the 494 * connection is in the syn cache. If it is, zap it. 495 */ 496 void 497 syncache_chkrst(inc, th) 498 struct in_conninfo *inc; 499 struct tcphdr *th; 500 { 501 struct syncache *sc; 502 struct syncache_head *sch; 503 504 sc = syncache_lookup(inc, &sch); 505 if (sc == NULL) 506 return; 507 /* 508 * If the RST bit is set, check the sequence number to see 509 * if this is a valid reset segment. 510 * RFC 793 page 37: 511 * In all states except SYN-SENT, all reset (RST) segments 512 * are validated by checking their SEQ-fields. A reset is 513 * valid if its sequence number is in the window. 514 * 515 * The sequence number in the reset segment is normally an 516 * echo of our outgoing acknowlegement numbers, but some hosts 517 * send a reset with the sequence number at the rightmost edge 518 * of our receive window, and we have to handle this case. 519 */ 520 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 521 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 522 syncache_drop(sc, sch); 523 tcpstat.tcps_sc_reset++; 524 } 525 } 526 527 void 528 syncache_badack(inc) 529 struct in_conninfo *inc; 530 { 531 struct syncache *sc; 532 struct syncache_head *sch; 533 534 sc = syncache_lookup(inc, &sch); 535 if (sc != NULL) { 536 syncache_drop(sc, sch); 537 tcpstat.tcps_sc_badack++; 538 } 539 } 540 541 void 542 syncache_unreach(inc, th) 543 struct in_conninfo *inc; 544 struct tcphdr *th; 545 { 546 struct syncache *sc; 547 struct syncache_head *sch; 548 549 /* we are called at splnet() here */ 550 sc = syncache_lookup(inc, &sch); 551 if (sc == NULL) 552 return; 553 554 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 555 if (ntohl(th->th_seq) != sc->sc_iss) 556 return; 557 558 /* 559 * If we've rertransmitted 3 times and this is our second error, 560 * we remove the entry. Otherwise, we allow it to continue on. 561 * This prevents us from incorrectly nuking an entry during a 562 * spurious network outage. 563 * 564 * See tcp_notify(). 565 */ 566 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 567 sc->sc_flags |= SCF_UNREACH; 568 return; 569 } 570 syncache_drop(sc, sch); 571 tcpstat.tcps_sc_unreach++; 572 } 573 574 /* 575 * Build a new TCP socket structure from a syncache entry. 576 */ 577 static struct socket * 578 syncache_socket(sc, lso) 579 struct syncache *sc; 580 struct socket *lso; 581 { 582 struct inpcb *inp = NULL; 583 struct socket *so; 584 struct tcpcb *tp; 585 586 /* 587 * Ok, create the full blown connection, and set things up 588 * as they would have been set up if we had created the 589 * connection when the SYN arrived. If we can't create 590 * the connection, abort it. 591 */ 592 so = sonewconn(lso, SS_ISCONNECTED); 593 if (so == NULL) { 594 /* 595 * Drop the connection; we will send a RST if the peer 596 * retransmits the ACK, 597 */ 598 tcpstat.tcps_listendrop++; 599 goto abort; 600 } 601 602 inp = sotoinpcb(so); 603 604 /* 605 * Insert new socket into hash list. 606 */ 607 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 608 #ifdef INET6 609 if (sc->sc_inc.inc_isipv6) { 610 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 611 } else { 612 inp->inp_vflag &= ~INP_IPV6; 613 inp->inp_vflag |= INP_IPV4; 614 #endif 615 inp->inp_laddr = sc->sc_inc.inc_laddr; 616 #ifdef INET6 617 } 618 #endif 619 inp->inp_lport = sc->sc_inc.inc_lport; 620 if (in_pcbinsporthash(inp) != 0) { 621 /* 622 * Undo the assignments above if we failed to 623 * put the PCB on the hash lists. 624 */ 625 #ifdef INET6 626 if (sc->sc_inc.inc_isipv6) 627 inp->in6p_laddr = in6addr_any; 628 else 629 #endif 630 inp->inp_laddr.s_addr = INADDR_ANY; 631 inp->inp_lport = 0; 632 goto abort; 633 } 634 #ifdef IPSEC 635 /* copy old policy into new socket's */ 636 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp)) 637 printf("syncache_expand: could not copy policy\n"); 638 #endif 639 #ifdef INET6 640 if (sc->sc_inc.inc_isipv6) { 641 struct inpcb *oinp = sotoinpcb(lso); 642 struct in6_addr laddr6; 643 struct sockaddr_in6 sin6; 644 /* 645 * Inherit socket options from the listening socket. 646 * Note that in6p_inputopts are not (and should not be) 647 * copied, since it stores previously received options and is 648 * used to detect if each new option is different than the 649 * previous one and hence should be passed to a user. 650 * If we copied in6p_inputopts, a user would not be able to 651 * receive options just after calling the accept system call. 652 */ 653 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; 654 if (oinp->in6p_outputopts) 655 inp->in6p_outputopts = 656 ip6_copypktopts(oinp->in6p_outputopts, M_INTWAIT); 657 inp->in6p_route = sc->sc_route6; 658 sc->sc_route6.ro_rt = NULL; 659 660 sin6.sin6_family = AF_INET6; 661 sin6.sin6_len = sizeof sin6; 662 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 663 sin6.sin6_port = sc->sc_inc.inc_fport; 664 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 665 laddr6 = inp->in6p_laddr; 666 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 667 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 668 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) { 669 inp->in6p_laddr = laddr6; 670 goto abort; 671 } 672 } else 673 #endif 674 { 675 struct in_addr laddr; 676 struct sockaddr_in sin; 677 678 inp->inp_options = ip_srcroute(); 679 if (inp->inp_options == NULL) { 680 inp->inp_options = sc->sc_ipopts; 681 sc->sc_ipopts = NULL; 682 } 683 inp->inp_route = sc->sc_route; 684 sc->sc_route.ro_rt = NULL; 685 686 sin.sin_family = AF_INET; 687 sin.sin_len = sizeof sin; 688 sin.sin_addr = sc->sc_inc.inc_faddr; 689 sin.sin_port = sc->sc_inc.inc_fport; 690 bzero(sin.sin_zero, sizeof sin.sin_zero); 691 laddr = inp->inp_laddr; 692 if (inp->inp_laddr.s_addr == INADDR_ANY) 693 inp->inp_laddr = sc->sc_inc.inc_laddr; 694 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) { 695 inp->inp_laddr = laddr; 696 goto abort; 697 } 698 } 699 700 tp = intotcpcb(inp); 701 tp->t_state = TCPS_SYN_RECEIVED; 702 tp->iss = sc->sc_iss; 703 tp->irs = sc->sc_irs; 704 tcp_rcvseqinit(tp); 705 tcp_sendseqinit(tp); 706 tp->snd_wl1 = sc->sc_irs; 707 tp->rcv_up = sc->sc_irs + 1; 708 tp->rcv_wnd = sc->sc_wnd; 709 tp->rcv_adv += tp->rcv_wnd; 710 711 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY); 712 if (sc->sc_flags & SCF_NOOPT) 713 tp->t_flags |= TF_NOOPT; 714 if (sc->sc_flags & SCF_WINSCALE) { 715 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; 716 tp->requested_s_scale = sc->sc_requested_s_scale; 717 tp->request_r_scale = sc->sc_request_r_scale; 718 } 719 if (sc->sc_flags & SCF_TIMESTAMP) { 720 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; 721 tp->ts_recent = sc->sc_tsrecent; 722 tp->ts_recent_age = ticks; 723 } 724 if (sc->sc_flags & SCF_CC) { 725 /* 726 * Initialization of the tcpcb for transaction; 727 * set SND.WND = SEG.WND, 728 * initialize CCsend and CCrecv. 729 */ 730 tp->t_flags |= TF_REQ_CC|TF_RCVD_CC; 731 tp->cc_send = sc->sc_cc_send; 732 tp->cc_recv = sc->sc_cc_recv; 733 } 734 735 tcp_mss(tp, sc->sc_peer_mss); 736 737 /* 738 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 739 */ 740 if (sc->sc_rxtslot != 0) 741 tp->snd_cwnd = tp->t_maxseg; 742 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); 743 744 tcpstat.tcps_accepts++; 745 return (so); 746 747 abort: 748 if (so != NULL) 749 (void) soabort(so); 750 return (NULL); 751 } 752 753 /* 754 * This function gets called when we receive an ACK for a 755 * socket in the LISTEN state. We look up the connection 756 * in the syncache, and if its there, we pull it out of 757 * the cache and turn it into a full-blown connection in 758 * the SYN-RECEIVED state. 759 */ 760 int 761 syncache_expand(inc, th, sop, m) 762 struct in_conninfo *inc; 763 struct tcphdr *th; 764 struct socket **sop; 765 struct mbuf *m; 766 { 767 struct syncache *sc; 768 struct syncache_head *sch; 769 struct socket *so; 770 771 sc = syncache_lookup(inc, &sch); 772 if (sc == NULL) { 773 /* 774 * There is no syncache entry, so see if this ACK is 775 * a returning syncookie. To do this, first: 776 * A. See if this socket has had a syncache entry dropped in 777 * the past. We don't want to accept a bogus syncookie 778 * if we've never received a SYN. 779 * B. check that the syncookie is valid. If it is, then 780 * cobble up a fake syncache entry, and return. 781 */ 782 if (!tcp_syncookies) 783 return (0); 784 sc = syncookie_lookup(inc, th, *sop); 785 if (sc == NULL) 786 return (0); 787 sch = NULL; 788 tcpstat.tcps_sc_recvcookie++; 789 } 790 791 /* 792 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 793 */ 794 if (th->th_ack != sc->sc_iss + 1) 795 return (0); 796 797 so = syncache_socket(sc, *sop); 798 if (so == NULL) { 799 #if 0 800 resetandabort: 801 /* XXXjlemon check this - is this correct? */ 802 (void) tcp_respond(NULL, m, m, th, 803 th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); 804 #endif 805 m_freem(m); /* XXX only needed for above */ 806 tcpstat.tcps_sc_aborted++; 807 } else { 808 sc->sc_flags |= SCF_KEEPROUTE; 809 tcpstat.tcps_sc_completed++; 810 } 811 if (sch == NULL) 812 syncache_free(sc); 813 else 814 syncache_drop(sc, sch); 815 *sop = so; 816 return (1); 817 } 818 819 /* 820 * Given a LISTEN socket and an inbound SYN request, add 821 * this to the syn cache, and send back a segment: 822 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 823 * to the source. 824 * 825 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 826 * Doing so would require that we hold onto the data and deliver it 827 * to the application. However, if we are the target of a SYN-flood 828 * DoS attack, an attacker could send data which would eventually 829 * consume all available buffer space if it were ACKed. By not ACKing 830 * the data, we avoid this DoS scenario. 831 */ 832 int 833 syncache_add(inc, to, th, sop, m) 834 struct in_conninfo *inc; 835 struct tcpopt *to; 836 struct tcphdr *th; 837 struct socket **sop; 838 struct mbuf *m; 839 { 840 struct tcpcb *tp; 841 struct socket *so; 842 struct syncache *sc = NULL; 843 struct syncache_head *sch; 844 struct mbuf *ipopts = NULL; 845 struct rmxp_tao *taop; 846 int win; 847 848 so = *sop; 849 tp = sototcpcb(so); 850 851 /* 852 * Remember the IP options, if any. 853 */ 854 #ifdef INET6 855 if (!inc->inc_isipv6) 856 #endif 857 ipopts = ip_srcroute(); 858 859 /* 860 * See if we already have an entry for this connection. 861 * If we do, resend the SYN,ACK, and reset the retransmit timer. 862 * 863 * XXX 864 * should the syncache be re-initialized with the contents 865 * of the new SYN here (which may have different options?) 866 */ 867 sc = syncache_lookup(inc, &sch); 868 if (sc != NULL) { 869 tcpstat.tcps_sc_dupsyn++; 870 if (ipopts) { 871 /* 872 * If we were remembering a previous source route, 873 * forget it and use the new one we've been given. 874 */ 875 if (sc->sc_ipopts) 876 (void) m_free(sc->sc_ipopts); 877 sc->sc_ipopts = ipopts; 878 } 879 /* 880 * Update timestamp if present. 881 */ 882 if (sc->sc_flags & SCF_TIMESTAMP) 883 sc->sc_tsrecent = to->to_tsval; 884 /* 885 * PCB may have changed, pick up new values. 886 */ 887 sc->sc_tp = tp; 888 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 889 if (syncache_respond(sc, m) == 0) { 890 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], 891 sc, sc_timerq); 892 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot); 893 tcpstat.tcps_sndacks++; 894 tcpstat.tcps_sndtotal++; 895 } 896 *sop = NULL; 897 return (1); 898 } 899 900 /* 901 * This allocation is guaranteed to succeed because we 902 * preallocate one more syncache entry than cache_limit. 903 */ 904 sc = zalloc(tcp_syncache.zone); 905 906 /* 907 * Fill in the syncache values. 908 */ 909 sc->sc_tp = tp; 910 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 911 sc->sc_ipopts = ipopts; 912 sc->sc_inc.inc_fport = inc->inc_fport; 913 sc->sc_inc.inc_lport = inc->inc_lport; 914 #ifdef INET6 915 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 916 if (inc->inc_isipv6) { 917 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 918 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 919 sc->sc_route6.ro_rt = NULL; 920 } else 921 #endif 922 { 923 sc->sc_inc.inc_faddr = inc->inc_faddr; 924 sc->sc_inc.inc_laddr = inc->inc_laddr; 925 sc->sc_route.ro_rt = NULL; 926 } 927 sc->sc_irs = th->th_seq; 928 sc->sc_flags = 0; 929 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 930 if (tcp_syncookies) 931 sc->sc_iss = syncookie_generate(sc); 932 else 933 sc->sc_iss = arc4random(); 934 935 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */ 936 win = sbspace(&so->so_rcv); 937 win = imax(win, 0); 938 win = imin(win, TCP_MAXWIN); 939 sc->sc_wnd = win; 940 941 if (tcp_do_rfc1323) { 942 /* 943 * A timestamp received in a SYN makes 944 * it ok to send timestamp requests and replies. 945 */ 946 if (to->to_flags & TOF_TS) { 947 sc->sc_tsrecent = to->to_tsval; 948 sc->sc_flags |= SCF_TIMESTAMP; 949 } 950 if (to->to_flags & TOF_SCALE) { 951 int wscale = 0; 952 953 /* Compute proper scaling value from buffer space */ 954 while (wscale < TCP_MAX_WINSHIFT && 955 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat) 956 wscale++; 957 sc->sc_request_r_scale = wscale; 958 sc->sc_requested_s_scale = to->to_requested_s_scale; 959 sc->sc_flags |= SCF_WINSCALE; 960 } 961 } 962 if (tcp_do_rfc1644) { 963 /* 964 * A CC or CC.new option received in a SYN makes 965 * it ok to send CC in subsequent segments. 966 */ 967 if (to->to_flags & (TOF_CC|TOF_CCNEW)) { 968 sc->sc_cc_recv = to->to_cc; 969 sc->sc_cc_send = CC_INC(tcp_ccgen); 970 sc->sc_flags |= SCF_CC; 971 } 972 } 973 if (tp->t_flags & TF_NOOPT) 974 sc->sc_flags = SCF_NOOPT; 975 976 /* 977 * XXX 978 * We have the option here of not doing TAO (even if the segment 979 * qualifies) and instead fall back to a normal 3WHS via the syncache. 980 * This allows us to apply synflood protection to TAO-qualifying SYNs 981 * also. However, there should be a hueristic to determine when to 982 * do this, and is not present at the moment. 983 */ 984 985 /* 986 * Perform TAO test on incoming CC (SEG.CC) option, if any. 987 * - compare SEG.CC against cached CC from the same host, if any. 988 * - if SEG.CC > chached value, SYN must be new and is accepted 989 * immediately: save new CC in the cache, mark the socket 990 * connected, enter ESTABLISHED state, turn on flag to 991 * send a SYN in the next segment. 992 * A virtual advertised window is set in rcv_adv to 993 * initialize SWS prevention. Then enter normal segment 994 * processing: drop SYN, process data and FIN. 995 * - otherwise do a normal 3-way handshake. 996 */ 997 taop = tcp_gettaocache(&sc->sc_inc); 998 if ((to->to_flags & TOF_CC) != 0) { 999 if (((tp->t_flags & TF_NOPUSH) != 0) && 1000 sc->sc_flags & SCF_CC && 1001 taop != NULL && taop->tao_cc != 0 && 1002 CC_GT(to->to_cc, taop->tao_cc)) { 1003 sc->sc_rxtslot = 0; 1004 so = syncache_socket(sc, *sop); 1005 if (so != NULL) { 1006 sc->sc_flags |= SCF_KEEPROUTE; 1007 taop->tao_cc = to->to_cc; 1008 *sop = so; 1009 } 1010 syncache_free(sc); 1011 return (so != NULL); 1012 } 1013 } else { 1014 /* 1015 * No CC option, but maybe CC.NEW: invalidate cached value. 1016 */ 1017 if (taop != NULL) 1018 taop->tao_cc = 0; 1019 } 1020 /* 1021 * TAO test failed or there was no CC option, 1022 * do a standard 3-way handshake. 1023 */ 1024 if (syncache_respond(sc, m) == 0) { 1025 syncache_insert(sc, sch); 1026 tcpstat.tcps_sndacks++; 1027 tcpstat.tcps_sndtotal++; 1028 } else { 1029 syncache_free(sc); 1030 tcpstat.tcps_sc_dropped++; 1031 } 1032 *sop = NULL; 1033 return (1); 1034 } 1035 1036 static int 1037 syncache_respond(sc, m) 1038 struct syncache *sc; 1039 struct mbuf *m; 1040 { 1041 u_int8_t *optp; 1042 int optlen, error; 1043 u_int16_t tlen, hlen, mssopt; 1044 struct ip *ip = NULL; 1045 struct rtentry *rt; 1046 struct tcphdr *th; 1047 #ifdef INET6 1048 struct ip6_hdr *ip6 = NULL; 1049 #endif 1050 1051 #ifdef INET6 1052 if (sc->sc_inc.inc_isipv6) { 1053 rt = tcp_rtlookup6(&sc->sc_inc); 1054 if (rt != NULL) 1055 mssopt = rt->rt_ifp->if_mtu - 1056 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1057 else 1058 mssopt = tcp_v6mssdflt; 1059 hlen = sizeof(struct ip6_hdr); 1060 } else 1061 #endif 1062 { 1063 rt = tcp_rtlookup(&sc->sc_inc); 1064 if (rt != NULL) 1065 mssopt = rt->rt_ifp->if_mtu - 1066 (sizeof(struct ip) + sizeof(struct tcphdr)); 1067 else 1068 mssopt = tcp_mssdflt; 1069 hlen = sizeof(struct ip); 1070 } 1071 1072 /* Compute the size of the TCP options. */ 1073 if (sc->sc_flags & SCF_NOOPT) { 1074 optlen = 0; 1075 } else { 1076 optlen = TCPOLEN_MAXSEG + 1077 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1078 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1079 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0); 1080 } 1081 tlen = hlen + sizeof(struct tcphdr) + optlen; 1082 1083 /* 1084 * XXX 1085 * assume that the entire packet will fit in a header mbuf 1086 */ 1087 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1088 1089 /* 1090 * XXX shouldn't this reuse the mbuf if possible ? 1091 * Create the IP+TCP header from scratch. 1092 */ 1093 if (m) 1094 m_freem(m); 1095 1096 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 1097 if (m == NULL) 1098 return (ENOBUFS); 1099 m->m_data += max_linkhdr; 1100 m->m_len = tlen; 1101 m->m_pkthdr.len = tlen; 1102 m->m_pkthdr.rcvif = NULL; 1103 1104 #ifdef INET6 1105 if (sc->sc_inc.inc_isipv6) { 1106 ip6 = mtod(m, struct ip6_hdr *); 1107 ip6->ip6_vfc = IPV6_VERSION; 1108 ip6->ip6_nxt = IPPROTO_TCP; 1109 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1110 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1111 ip6->ip6_plen = htons(tlen - hlen); 1112 /* ip6_hlim is set after checksum */ 1113 /* ip6_flow = ??? */ 1114 1115 th = (struct tcphdr *)(ip6 + 1); 1116 } else 1117 #endif 1118 { 1119 ip = mtod(m, struct ip *); 1120 ip->ip_v = IPVERSION; 1121 ip->ip_hl = sizeof(struct ip) >> 2; 1122 ip->ip_len = tlen; 1123 ip->ip_id = 0; 1124 ip->ip_off = 0; 1125 ip->ip_sum = 0; 1126 ip->ip_p = IPPROTO_TCP; 1127 ip->ip_src = sc->sc_inc.inc_laddr; 1128 ip->ip_dst = sc->sc_inc.inc_faddr; 1129 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1130 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1131 1132 /* 1133 * See if we should do MTU discovery. Route lookups are expensive, 1134 * so we will only unset the DF bit if: 1135 * 1136 * 1) path_mtu_discovery is disabled 1137 * 2) the SCF_UNREACH flag has been set 1138 */ 1139 if (path_mtu_discovery 1140 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1141 ip->ip_off |= IP_DF; 1142 } 1143 1144 th = (struct tcphdr *)(ip + 1); 1145 } 1146 th->th_sport = sc->sc_inc.inc_lport; 1147 th->th_dport = sc->sc_inc.inc_fport; 1148 1149 th->th_seq = htonl(sc->sc_iss); 1150 th->th_ack = htonl(sc->sc_irs + 1); 1151 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1152 th->th_x2 = 0; 1153 th->th_flags = TH_SYN|TH_ACK; 1154 th->th_win = htons(sc->sc_wnd); 1155 th->th_urp = 0; 1156 1157 /* Tack on the TCP options. */ 1158 if (optlen == 0) 1159 goto no_options; 1160 optp = (u_int8_t *)(th + 1); 1161 *optp++ = TCPOPT_MAXSEG; 1162 *optp++ = TCPOLEN_MAXSEG; 1163 *optp++ = (mssopt >> 8) & 0xff; 1164 *optp++ = mssopt & 0xff; 1165 1166 if (sc->sc_flags & SCF_WINSCALE) { 1167 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1168 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1169 sc->sc_request_r_scale); 1170 optp += 4; 1171 } 1172 1173 if (sc->sc_flags & SCF_TIMESTAMP) { 1174 u_int32_t *lp = (u_int32_t *)(optp); 1175 1176 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1177 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1178 *lp++ = htonl(ticks); 1179 *lp = htonl(sc->sc_tsrecent); 1180 optp += TCPOLEN_TSTAMP_APPA; 1181 } 1182 1183 /* 1184 * Send CC and CC.echo if we received CC from our peer. 1185 */ 1186 if (sc->sc_flags & SCF_CC) { 1187 u_int32_t *lp = (u_int32_t *)(optp); 1188 1189 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC)); 1190 *lp++ = htonl(sc->sc_cc_send); 1191 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO)); 1192 *lp = htonl(sc->sc_cc_recv); 1193 optp += TCPOLEN_CC_APPA * 2; 1194 } 1195 no_options: 1196 1197 #ifdef INET6 1198 if (sc->sc_inc.inc_isipv6) { 1199 struct route_in6 *ro6 = &sc->sc_route6; 1200 1201 th->th_sum = 0; 1202 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1203 ip6->ip6_hlim = in6_selecthlim(NULL, 1204 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1205 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1206 sc->sc_tp->t_inpcb); 1207 } else 1208 #endif 1209 { 1210 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1211 htons(tlen - hlen + IPPROTO_TCP)); 1212 m->m_pkthdr.csum_flags = CSUM_TCP; 1213 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1214 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL, 1215 sc->sc_tp->t_inpcb); 1216 } 1217 return (error); 1218 } 1219 1220 /* 1221 * cookie layers: 1222 * 1223 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1224 * | peer iss | 1225 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1226 * | 0 |(A)| | 1227 * (A): peer mss index 1228 */ 1229 1230 /* 1231 * The values below are chosen to minimize the size of the tcp_secret 1232 * table, as well as providing roughly a 16 second lifetime for the cookie. 1233 */ 1234 1235 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1236 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1237 1238 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1239 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1240 #define SYNCOOKIE_TIMEOUT \ 1241 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1242 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1243 1244 static struct { 1245 u_int32_t ts_secbits[4]; 1246 u_int ts_expire; 1247 } tcp_secret[SYNCOOKIE_NSECRETS]; 1248 1249 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1250 1251 static MD5_CTX syn_ctx; 1252 1253 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1254 1255 struct md5_add { 1256 u_int32_t laddr, faddr; 1257 u_int32_t secbits[4]; 1258 u_int16_t lport, fport; 1259 }; 1260 1261 #ifdef CTASSERT 1262 CTASSERT(sizeof(struct md5_add) == 28); 1263 #endif 1264 1265 /* 1266 * Consider the problem of a recreated (and retransmitted) cookie. If the 1267 * original SYN was accepted, the connection is established. The second 1268 * SYN is inflight, and if it arrives with an ISN that falls within the 1269 * receive window, the connection is killed. 1270 * 1271 * However, since cookies have other problems, this may not be worth 1272 * worrying about. 1273 */ 1274 1275 static u_int32_t 1276 syncookie_generate(struct syncache *sc) 1277 { 1278 u_int32_t md5_buffer[4]; 1279 u_int32_t data; 1280 int idx, i; 1281 struct md5_add add; 1282 1283 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1284 if (tcp_secret[idx].ts_expire < ticks) { 1285 for (i = 0; i < 4; i++) 1286 tcp_secret[idx].ts_secbits[i] = arc4random(); 1287 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1288 } 1289 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1290 if (tcp_msstab[data] <= sc->sc_peer_mss) 1291 break; 1292 data = (data << SYNCOOKIE_WNDBITS) | idx; 1293 data ^= sc->sc_irs; /* peer's iss */ 1294 MD5Init(&syn_ctx); 1295 #ifdef INET6 1296 if (sc->sc_inc.inc_isipv6) { 1297 MD5Add(sc->sc_inc.inc6_laddr); 1298 MD5Add(sc->sc_inc.inc6_faddr); 1299 add.laddr = 0; 1300 add.faddr = 0; 1301 } else 1302 #endif 1303 { 1304 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1305 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1306 } 1307 add.lport = sc->sc_inc.inc_lport; 1308 add.fport = sc->sc_inc.inc_fport; 1309 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1310 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1311 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1312 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1313 MD5Add(add); 1314 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1315 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1316 return (data); 1317 } 1318 1319 static struct syncache * 1320 syncookie_lookup(inc, th, so) 1321 struct in_conninfo *inc; 1322 struct tcphdr *th; 1323 struct socket *so; 1324 { 1325 u_int32_t md5_buffer[4]; 1326 struct syncache *sc; 1327 u_int32_t data; 1328 int wnd, idx; 1329 struct md5_add add; 1330 1331 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1332 idx = data & SYNCOOKIE_WNDMASK; 1333 if (tcp_secret[idx].ts_expire < ticks || 1334 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1335 return (NULL); 1336 MD5Init(&syn_ctx); 1337 #ifdef INET6 1338 if (inc->inc_isipv6) { 1339 MD5Add(inc->inc6_laddr); 1340 MD5Add(inc->inc6_faddr); 1341 add.laddr = 0; 1342 add.faddr = 0; 1343 } else 1344 #endif 1345 { 1346 add.laddr = inc->inc_laddr.s_addr; 1347 add.faddr = inc->inc_faddr.s_addr; 1348 } 1349 add.lport = inc->inc_lport; 1350 add.fport = inc->inc_fport; 1351 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1352 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1353 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1354 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1355 MD5Add(add); 1356 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1357 data ^= md5_buffer[0]; 1358 if ((data & ~SYNCOOKIE_DATAMASK) != 0) 1359 return (NULL); 1360 data = data >> SYNCOOKIE_WNDBITS; 1361 1362 /* 1363 * This allocation is guaranteed to succeed because we 1364 * preallocate one more syncache entry than cache_limit. 1365 */ 1366 sc = zalloc(tcp_syncache.zone); 1367 1368 /* 1369 * Fill in the syncache values. 1370 * XXX duplicate code from syncache_add 1371 */ 1372 sc->sc_ipopts = NULL; 1373 sc->sc_inc.inc_fport = inc->inc_fport; 1374 sc->sc_inc.inc_lport = inc->inc_lport; 1375 #ifdef INET6 1376 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1377 if (inc->inc_isipv6) { 1378 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1379 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1380 sc->sc_route6.ro_rt = NULL; 1381 } else 1382 #endif 1383 { 1384 sc->sc_inc.inc_faddr = inc->inc_faddr; 1385 sc->sc_inc.inc_laddr = inc->inc_laddr; 1386 sc->sc_route.ro_rt = NULL; 1387 } 1388 sc->sc_irs = th->th_seq - 1; 1389 sc->sc_iss = th->th_ack - 1; 1390 wnd = sbspace(&so->so_rcv); 1391 wnd = imax(wnd, 0); 1392 wnd = imin(wnd, TCP_MAXWIN); 1393 sc->sc_wnd = wnd; 1394 sc->sc_flags = 0; 1395 sc->sc_rxtslot = 0; 1396 sc->sc_peer_mss = tcp_msstab[data]; 1397 return (sc); 1398 } 1399