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 * All advertising materials mentioning features or use of this software 36 * must display the following acknowledgement: 37 * This product includes software developed by Jeffrey M. Hsu. 38 * 39 * Copyright (c) 2001 Networks Associates Technologies, Inc. 40 * All rights reserved. 41 * 42 * This software was developed for the FreeBSD Project by Jonathan Lemon 43 * and NAI Labs, the Security Research Division of Network Associates, Inc. 44 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 45 * DARPA CHATS research program. 46 * 47 * Redistribution and use in source and binary forms, with or without 48 * modification, are permitted provided that the following conditions 49 * are met: 50 * 1. Redistributions of source code must retain the above copyright 51 * notice, this list of conditions and the following disclaimer. 52 * 2. Redistributions in binary form must reproduce the above copyright 53 * notice, this list of conditions and the following disclaimer in the 54 * documentation and/or other materials provided with the distribution. 55 * 3. The name of the author may not be used to endorse or promote 56 * products derived from this software without specific prior written 57 * permission. 58 * 59 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 62 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 69 * SUCH DAMAGE. 70 * 71 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $ 72 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.35 2008/11/22 11:03:35 sephe Exp $ 73 */ 74 75 #include "opt_inet6.h" 76 #include "opt_ipsec.h" 77 78 #include <sys/param.h> 79 #include <sys/systm.h> 80 #include <sys/kernel.h> 81 #include <sys/sysctl.h> 82 #include <sys/malloc.h> 83 #include <sys/mbuf.h> 84 #include <sys/md5.h> 85 #include <sys/proc.h> /* for proc0 declaration */ 86 #include <sys/random.h> 87 #include <sys/socket.h> 88 #include <sys/socketvar.h> 89 #include <sys/in_cksum.h> 90 91 #include <sys/msgport2.h> 92 #include <net/netmsg2.h> 93 94 #include <net/if.h> 95 #include <net/route.h> 96 97 #include <netinet/in.h> 98 #include <netinet/in_systm.h> 99 #include <netinet/ip.h> 100 #include <netinet/in_var.h> 101 #include <netinet/in_pcb.h> 102 #include <netinet/ip_var.h> 103 #include <netinet/ip6.h> 104 #ifdef INET6 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #endif 108 #include <netinet6/ip6_var.h> 109 #include <netinet6/in6_pcb.h> 110 #include <netinet/tcp.h> 111 #include <netinet/tcp_fsm.h> 112 #include <netinet/tcp_seq.h> 113 #include <netinet/tcp_timer.h> 114 #include <netinet/tcp_timer2.h> 115 #include <netinet/tcp_var.h> 116 #include <netinet6/tcp6_var.h> 117 118 #ifdef IPSEC 119 #include <netinet6/ipsec.h> 120 #ifdef INET6 121 #include <netinet6/ipsec6.h> 122 #endif 123 #include <netproto/key/key.h> 124 #endif /*IPSEC*/ 125 126 #ifdef FAST_IPSEC 127 #include <netproto/ipsec/ipsec.h> 128 #ifdef INET6 129 #include <netproto/ipsec/ipsec6.h> 130 #endif 131 #include <netproto/ipsec/key.h> 132 #define IPSEC 133 #endif /*FAST_IPSEC*/ 134 135 static int tcp_syncookies = 1; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 137 &tcp_syncookies, 0, 138 "Use TCP SYN cookies if the syncache overflows"); 139 140 static void syncache_drop(struct syncache *, struct syncache_head *); 141 static void syncache_free(struct syncache *); 142 static void syncache_insert(struct syncache *, struct syncache_head *); 143 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 144 static int syncache_respond(struct syncache *, struct mbuf *); 145 static struct socket *syncache_socket(struct syncache *, struct socket *, 146 struct mbuf *); 147 static void syncache_timer(void *); 148 static u_int32_t syncookie_generate(struct syncache *); 149 static struct syncache *syncookie_lookup(struct in_conninfo *, 150 struct tcphdr *, struct socket *); 151 152 /* 153 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 154 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 155 * the odds are that the user has given up attempting to connect by then. 156 */ 157 #define SYNCACHE_MAXREXMTS 3 158 159 /* Arbitrary values */ 160 #define TCP_SYNCACHE_HASHSIZE 512 161 #define TCP_SYNCACHE_BUCKETLIMIT 30 162 163 struct netmsg_sc_timer { 164 struct netmsg nm_netmsg; 165 struct msgrec *nm_mrec; /* back pointer to containing msgrec */ 166 }; 167 168 struct msgrec { 169 struct netmsg_sc_timer msg; 170 lwkt_port_t port; /* constant after init */ 171 int slot; /* constant after init */ 172 }; 173 174 static void syncache_timer_handler(netmsg_t); 175 176 struct tcp_syncache { 177 u_int hashsize; 178 u_int hashmask; 179 u_int bucket_limit; 180 u_int cache_limit; 181 u_int rexmt_limit; 182 u_int hash_secret; 183 }; 184 static struct tcp_syncache tcp_syncache; 185 186 TAILQ_HEAD(syncache_list, syncache); 187 188 struct tcp_syncache_percpu { 189 struct syncache_head *hashbase; 190 u_int cache_count; 191 struct syncache_list timerq[SYNCACHE_MAXREXMTS + 1]; 192 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 193 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1]; 194 }; 195 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU]; 196 197 static struct lwkt_port syncache_null_rport; 198 199 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 200 201 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 202 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 203 204 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 205 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 206 207 /* XXX JH */ 208 #if 0 209 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 210 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 211 #endif 212 213 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 214 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 215 216 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 217 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 218 219 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 220 221 #define SYNCACHE_HASH(inc, mask) \ 222 ((tcp_syncache.hash_secret ^ \ 223 (inc)->inc_faddr.s_addr ^ \ 224 ((inc)->inc_faddr.s_addr >> 16) ^ \ 225 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 226 227 #define SYNCACHE_HASH6(inc, mask) \ 228 ((tcp_syncache.hash_secret ^ \ 229 (inc)->inc6_faddr.s6_addr32[0] ^ \ 230 (inc)->inc6_faddr.s6_addr32[3] ^ \ 231 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 232 233 #define ENDPTS_EQ(a, b) ( \ 234 (a)->ie_fport == (b)->ie_fport && \ 235 (a)->ie_lport == (b)->ie_lport && \ 236 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 237 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 238 ) 239 240 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 241 242 static __inline void 243 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu, 244 struct syncache *sc, int slot) 245 { 246 sc->sc_rxtslot = slot; 247 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; 248 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq); 249 if (!callout_active(&syncache_percpu->tt_timerq[slot])) { 250 callout_reset(&syncache_percpu->tt_timerq[slot], 251 TCPTV_RTOBASE * tcp_backoff[slot], 252 syncache_timer, 253 &syncache_percpu->mrec[slot]); 254 } 255 } 256 257 static void 258 syncache_free(struct syncache *sc) 259 { 260 struct rtentry *rt; 261 #ifdef INET6 262 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 263 #else 264 const boolean_t isipv6 = FALSE; 265 #endif 266 267 if (sc->sc_ipopts) 268 m_free(sc->sc_ipopts); 269 270 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt; 271 if (rt != NULL) { 272 /* 273 * If this is the only reference to a protocol-cloned 274 * route, remove it immediately. 275 */ 276 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1) 277 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway, 278 rt_mask(rt), rt->rt_flags, NULL); 279 RTFREE(rt); 280 } 281 kfree(sc, M_SYNCACHE); 282 } 283 284 void 285 syncache_init(void) 286 { 287 int i, cpu; 288 289 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 290 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 291 tcp_syncache.cache_limit = 292 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 293 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 294 tcp_syncache.hash_secret = karc4random(); 295 296 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 297 &tcp_syncache.hashsize); 298 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 299 &tcp_syncache.cache_limit); 300 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 301 &tcp_syncache.bucket_limit); 302 if (!powerof2(tcp_syncache.hashsize)) { 303 kprintf("WARNING: syncache hash size is not a power of 2.\n"); 304 tcp_syncache.hashsize = 512; /* safe default */ 305 } 306 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 307 308 lwkt_initport_replyonly_null(&syncache_null_rport); 309 310 for (cpu = 0; cpu < ncpus2; cpu++) { 311 struct tcp_syncache_percpu *syncache_percpu; 312 313 syncache_percpu = &tcp_syncache_percpu[cpu]; 314 /* Allocate the hash table. */ 315 MALLOC(syncache_percpu->hashbase, struct syncache_head *, 316 tcp_syncache.hashsize * sizeof(struct syncache_head), 317 M_SYNCACHE, M_WAITOK); 318 319 /* Initialize the hash buckets. */ 320 for (i = 0; i < tcp_syncache.hashsize; i++) { 321 struct syncache_head *bucket; 322 323 bucket = &syncache_percpu->hashbase[i]; 324 TAILQ_INIT(&bucket->sch_bucket); 325 bucket->sch_length = 0; 326 } 327 328 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 329 /* Initialize the timer queues. */ 330 TAILQ_INIT(&syncache_percpu->timerq[i]); 331 callout_init(&syncache_percpu->tt_timerq[i]); 332 333 syncache_percpu->mrec[i].slot = i; 334 syncache_percpu->mrec[i].port = tcp_cport(cpu); 335 syncache_percpu->mrec[i].msg.nm_mrec = 336 &syncache_percpu->mrec[i]; 337 netmsg_init(&syncache_percpu->mrec[i].msg.nm_netmsg, 338 NULL, &syncache_null_rport, 339 0, syncache_timer_handler); 340 } 341 } 342 } 343 344 static void 345 syncache_insert(struct syncache *sc, struct syncache_head *sch) 346 { 347 struct tcp_syncache_percpu *syncache_percpu; 348 struct syncache *sc2; 349 int i; 350 351 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 352 353 /* 354 * Make sure that we don't overflow the per-bucket 355 * limit or the total cache size limit. 356 */ 357 if (sch->sch_length >= tcp_syncache.bucket_limit) { 358 /* 359 * The bucket is full, toss the oldest element. 360 */ 361 sc2 = TAILQ_FIRST(&sch->sch_bucket); 362 sc2->sc_tp->ts_recent = ticks; 363 syncache_drop(sc2, sch); 364 tcpstat.tcps_sc_bucketoverflow++; 365 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) { 366 /* 367 * The cache is full. Toss the oldest entry in the 368 * entire cache. This is the front entry in the 369 * first non-empty timer queue with the largest 370 * timeout value. 371 */ 372 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 373 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]); 374 while (sc2 && (sc2->sc_flags & SCF_MARKER)) 375 sc2 = TAILQ_NEXT(sc2, sc_timerq); 376 if (sc2 != NULL) 377 break; 378 } 379 sc2->sc_tp->ts_recent = ticks; 380 syncache_drop(sc2, NULL); 381 tcpstat.tcps_sc_cacheoverflow++; 382 } 383 384 /* Initialize the entry's timer. */ 385 syncache_timeout(syncache_percpu, sc, 0); 386 387 /* Put it into the bucket. */ 388 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 389 sch->sch_length++; 390 syncache_percpu->cache_count++; 391 tcpstat.tcps_sc_added++; 392 } 393 394 void 395 syncache_destroy(struct tcpcb *tp) 396 { 397 struct tcp_syncache_percpu *syncache_percpu; 398 struct syncache_head *bucket; 399 struct syncache *sc; 400 int i; 401 402 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 403 sc = NULL; 404 405 for (i = 0; i < tcp_syncache.hashsize; i++) { 406 bucket = &syncache_percpu->hashbase[i]; 407 TAILQ_FOREACH(sc, &bucket->sch_bucket, sc_hash) { 408 if (sc->sc_tp == tp) { 409 sc->sc_tp = NULL; 410 tp->t_flags &= ~TF_SYNCACHE; 411 break; 412 } 413 } 414 } 415 kprintf("Warning: delete stale syncache for tp=%p, sc=%p\n", tp, sc); 416 } 417 418 static void 419 syncache_drop(struct syncache *sc, struct syncache_head *sch) 420 { 421 struct tcp_syncache_percpu *syncache_percpu; 422 #ifdef INET6 423 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 424 #else 425 const boolean_t isipv6 = FALSE; 426 #endif 427 428 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 429 430 if (sch == NULL) { 431 if (isipv6) { 432 sch = &syncache_percpu->hashbase[ 433 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 434 } else { 435 sch = &syncache_percpu->hashbase[ 436 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 437 } 438 } 439 440 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 441 sch->sch_length--; 442 syncache_percpu->cache_count--; 443 444 /* 445 * Cleanup 446 */ 447 if (sc->sc_tp) { 448 sc->sc_tp->t_flags &= ~TF_SYNCACHE; 449 sc->sc_tp = NULL; 450 } 451 452 /* 453 * Remove the entry from the syncache timer/timeout queue. Note 454 * that we do not try to stop any running timer since we do not know 455 * whether the timer's message is in-transit or not. Since timeouts 456 * are fairly long, taking an unneeded callout does not detrimentally 457 * effect performance. 458 */ 459 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq); 460 461 syncache_free(sc); 462 } 463 464 /* 465 * Place a timeout message on the TCP thread's message queue. 466 * This routine runs in soft interrupt context. 467 * 468 * An invariant is for this routine to be called, the callout must 469 * have been active. Note that the callout is not deactivated until 470 * after the message has been processed in syncache_timer_handler() below. 471 */ 472 static void 473 syncache_timer(void *p) 474 { 475 struct netmsg_sc_timer *msg = p; 476 477 lwkt_sendmsg(msg->nm_mrec->port, &msg->nm_netmsg.nm_lmsg); 478 } 479 480 /* 481 * Service a timer message queued by timer expiration. 482 * This routine runs in the TCP protocol thread. 483 * 484 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 485 * If we have retransmitted an entry the maximum number of times, expire it. 486 * 487 * When we finish processing timed-out entries, we restart the timer if there 488 * are any entries still on the queue and deactivate it otherwise. Only after 489 * a timer has been deactivated here can it be restarted by syncache_timeout(). 490 */ 491 static void 492 syncache_timer_handler(netmsg_t netmsg) 493 { 494 struct tcp_syncache_percpu *syncache_percpu; 495 struct syncache *sc; 496 struct syncache marker; 497 struct syncache_list *list; 498 struct inpcb *inp; 499 int slot; 500 501 slot = ((struct netmsg_sc_timer *)netmsg)->nm_mrec->slot; 502 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 503 504 list = &syncache_percpu->timerq[slot]; 505 506 /* 507 * Use a marker to keep our place in the scan. syncache_drop() 508 * can block and cause any next pointer we cache to become stale. 509 */ 510 marker.sc_flags = SCF_MARKER; 511 TAILQ_INSERT_HEAD(list, &marker, sc_timerq); 512 513 while ((sc = TAILQ_NEXT(&marker, sc_timerq)) != NULL) { 514 /* 515 * Move the marker. 516 */ 517 TAILQ_REMOVE(list, &marker, sc_timerq); 518 TAILQ_INSERT_AFTER(list, sc, &marker, sc_timerq); 519 520 if (sc->sc_flags & SCF_MARKER) 521 continue; 522 523 if (ticks < sc->sc_rxttime) 524 break; /* finished because timerq sorted by time */ 525 if (sc->sc_tp == NULL) { 526 syncache_drop(sc, NULL); 527 tcpstat.tcps_sc_stale++; 528 continue; 529 } 530 inp = sc->sc_tp->t_inpcb; 531 if (slot == SYNCACHE_MAXREXMTS || 532 slot >= tcp_syncache.rexmt_limit || 533 inp == NULL || 534 inp->inp_gencnt != sc->sc_inp_gencnt) { 535 syncache_drop(sc, NULL); 536 tcpstat.tcps_sc_stale++; 537 continue; 538 } 539 /* 540 * syncache_respond() may call back into the syncache to 541 * to modify another entry, so do not obtain the next 542 * entry on the timer chain until it has completed. 543 */ 544 syncache_respond(sc, NULL); 545 tcpstat.tcps_sc_retransmitted++; 546 TAILQ_REMOVE(list, sc, sc_timerq); 547 syncache_timeout(syncache_percpu, sc, slot + 1); 548 } 549 TAILQ_REMOVE(list, &marker, sc_timerq); 550 551 if (sc != NULL) { 552 callout_reset(&syncache_percpu->tt_timerq[slot], 553 sc->sc_rxttime - ticks, syncache_timer, 554 &syncache_percpu->mrec[slot]); 555 } else { 556 callout_deactivate(&syncache_percpu->tt_timerq[slot]); 557 } 558 lwkt_replymsg(&netmsg->nm_lmsg, 0); 559 } 560 561 /* 562 * Find an entry in the syncache. 563 */ 564 struct syncache * 565 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 566 { 567 struct tcp_syncache_percpu *syncache_percpu; 568 struct syncache *sc; 569 struct syncache_head *sch; 570 571 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 572 #ifdef INET6 573 if (inc->inc_isipv6) { 574 sch = &syncache_percpu->hashbase[ 575 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 576 *schp = sch; 577 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 578 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 579 return (sc); 580 } else 581 #endif 582 { 583 sch = &syncache_percpu->hashbase[ 584 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 585 *schp = sch; 586 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 587 #ifdef INET6 588 if (sc->sc_inc.inc_isipv6) 589 continue; 590 #endif 591 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 592 return (sc); 593 } 594 } 595 return (NULL); 596 } 597 598 /* 599 * This function is called when we get a RST for a 600 * non-existent connection, so that we can see if the 601 * connection is in the syn cache. If it is, zap it. 602 */ 603 void 604 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 605 { 606 struct syncache *sc; 607 struct syncache_head *sch; 608 609 sc = syncache_lookup(inc, &sch); 610 if (sc == NULL) { 611 return; 612 } 613 /* 614 * If the RST bit is set, check the sequence number to see 615 * if this is a valid reset segment. 616 * RFC 793 page 37: 617 * In all states except SYN-SENT, all reset (RST) segments 618 * are validated by checking their SEQ-fields. A reset is 619 * valid if its sequence number is in the window. 620 * 621 * The sequence number in the reset segment is normally an 622 * echo of our outgoing acknowlegement numbers, but some hosts 623 * send a reset with the sequence number at the rightmost edge 624 * of our receive window, and we have to handle this case. 625 */ 626 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 627 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 628 syncache_drop(sc, sch); 629 tcpstat.tcps_sc_reset++; 630 } 631 } 632 633 void 634 syncache_badack(struct in_conninfo *inc) 635 { 636 struct syncache *sc; 637 struct syncache_head *sch; 638 639 sc = syncache_lookup(inc, &sch); 640 if (sc != NULL) { 641 syncache_drop(sc, sch); 642 tcpstat.tcps_sc_badack++; 643 } 644 } 645 646 void 647 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 648 { 649 struct syncache *sc; 650 struct syncache_head *sch; 651 652 /* we are called at splnet() here */ 653 sc = syncache_lookup(inc, &sch); 654 if (sc == NULL) 655 return; 656 657 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 658 if (ntohl(th->th_seq) != sc->sc_iss) 659 return; 660 661 /* 662 * If we've rertransmitted 3 times and this is our second error, 663 * we remove the entry. Otherwise, we allow it to continue on. 664 * This prevents us from incorrectly nuking an entry during a 665 * spurious network outage. 666 * 667 * See tcp_notify(). 668 */ 669 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 670 sc->sc_flags |= SCF_UNREACH; 671 return; 672 } 673 syncache_drop(sc, sch); 674 tcpstat.tcps_sc_unreach++; 675 } 676 677 /* 678 * Build a new TCP socket structure from a syncache entry. 679 * 680 * This is called from the context of the SYN+ACK 681 */ 682 static struct socket * 683 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 684 { 685 struct inpcb *inp = NULL, *linp; 686 struct socket *so; 687 struct tcpcb *tp; 688 lwkt_port_t port; 689 #ifdef INET6 690 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 691 #else 692 const boolean_t isipv6 = FALSE; 693 #endif 694 695 /* 696 * Ok, create the full blown connection, and set things up 697 * as they would have been set up if we had created the 698 * connection when the SYN arrived. If we can't create 699 * the connection, abort it. 700 */ 701 so = sonewconn(lso, SS_ISCONNECTED); 702 if (so == NULL) { 703 /* 704 * Drop the connection; we will send a RST if the peer 705 * retransmits the ACK, 706 */ 707 tcpstat.tcps_listendrop++; 708 goto abort; 709 } 710 711 /* 712 * Set the protocol processing port for the socket to the current 713 * port (that the connection came in on). 714 */ 715 sosetport(so, &curthread->td_msgport); 716 717 /* 718 * Insert new socket into hash list. 719 */ 720 inp = so->so_pcb; 721 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 722 if (isipv6) { 723 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 724 } else { 725 #ifdef INET6 726 inp->inp_vflag &= ~INP_IPV6; 727 inp->inp_vflag |= INP_IPV4; 728 inp->inp_flags &= ~IN6P_IPV6_V6ONLY; 729 #endif 730 inp->inp_laddr = sc->sc_inc.inc_laddr; 731 } 732 inp->inp_lport = sc->sc_inc.inc_lport; 733 if (in_pcbinsporthash(inp) != 0) { 734 /* 735 * Undo the assignments above if we failed to 736 * put the PCB on the hash lists. 737 */ 738 if (isipv6) 739 inp->in6p_laddr = kin6addr_any; 740 else 741 inp->inp_laddr.s_addr = INADDR_ANY; 742 inp->inp_lport = 0; 743 goto abort; 744 } 745 linp = so->so_pcb; 746 #ifdef IPSEC 747 /* copy old policy into new socket's */ 748 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp)) 749 kprintf("syncache_expand: could not copy policy\n"); 750 #endif 751 if (isipv6) { 752 struct in6_addr laddr6; 753 struct sockaddr_in6 sin6; 754 /* 755 * Inherit socket options from the listening socket. 756 * Note that in6p_inputopts are not (and should not be) 757 * copied, since it stores previously received options and is 758 * used to detect if each new option is different than the 759 * previous one and hence should be passed to a user. 760 * If we copied in6p_inputopts, a user would not be able to 761 * receive options just after calling the accept system call. 762 */ 763 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS; 764 if (linp->in6p_outputopts) 765 inp->in6p_outputopts = 766 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT); 767 inp->in6p_route = sc->sc_route6; 768 sc->sc_route6.ro_rt = NULL; 769 770 sin6.sin6_family = AF_INET6; 771 sin6.sin6_len = sizeof sin6; 772 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 773 sin6.sin6_port = sc->sc_inc.inc_fport; 774 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 775 laddr6 = inp->in6p_laddr; 776 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 777 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 778 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) { 779 inp->in6p_laddr = laddr6; 780 goto abort; 781 } 782 } else { 783 struct in_addr laddr; 784 struct sockaddr_in sin; 785 786 inp->inp_options = ip_srcroute(m); 787 if (inp->inp_options == NULL) { 788 inp->inp_options = sc->sc_ipopts; 789 sc->sc_ipopts = NULL; 790 } 791 inp->inp_route = sc->sc_route; 792 sc->sc_route.ro_rt = NULL; 793 794 sin.sin_family = AF_INET; 795 sin.sin_len = sizeof sin; 796 sin.sin_addr = sc->sc_inc.inc_faddr; 797 sin.sin_port = sc->sc_inc.inc_fport; 798 bzero(sin.sin_zero, sizeof sin.sin_zero); 799 laddr = inp->inp_laddr; 800 if (inp->inp_laddr.s_addr == INADDR_ANY) 801 inp->inp_laddr = sc->sc_inc.inc_laddr; 802 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) { 803 inp->inp_laddr = laddr; 804 goto abort; 805 } 806 } 807 808 /* 809 * The current port should be in the context of the SYN+ACK and 810 * so should match the tcp address port. 811 * 812 * XXX we may be running on the netisr thread instead of a tcp 813 * thread, in which case port will not match 814 * curthread->td_msgport. 815 */ 816 if (isipv6) { 817 port = tcp6_addrport(); 818 } else { 819 port = tcp_addrport(inp->inp_faddr.s_addr, inp->inp_fport, 820 inp->inp_laddr.s_addr, inp->inp_lport); 821 } 822 /*KKASSERT(port == &curthread->td_msgport);*/ 823 824 tp = intotcpcb(inp); 825 tp->t_state = TCPS_SYN_RECEIVED; 826 tp->iss = sc->sc_iss; 827 tp->irs = sc->sc_irs; 828 tcp_rcvseqinit(tp); 829 tcp_sendseqinit(tp); 830 tp->snd_wl1 = sc->sc_irs; 831 tp->rcv_up = sc->sc_irs + 1; 832 tp->rcv_wnd = sc->sc_wnd; 833 tp->rcv_adv += tp->rcv_wnd; 834 835 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY); 836 if (sc->sc_flags & SCF_NOOPT) 837 tp->t_flags |= TF_NOOPT; 838 if (sc->sc_flags & SCF_WINSCALE) { 839 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE; 840 tp->requested_s_scale = sc->sc_requested_s_scale; 841 tp->request_r_scale = sc->sc_request_r_scale; 842 } 843 if (sc->sc_flags & SCF_TIMESTAMP) { 844 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP; 845 tp->ts_recent = sc->sc_tsrecent; 846 tp->ts_recent_age = ticks; 847 } 848 if (sc->sc_flags & SCF_SACK_PERMITTED) 849 tp->t_flags |= TF_SACK_PERMITTED; 850 851 tcp_mss(tp, sc->sc_peer_mss); 852 853 /* 854 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 855 */ 856 if (sc->sc_rxtslot != 0) 857 tp->snd_cwnd = tp->t_maxseg; 858 tcp_create_timermsg(tp, port); 859 tcp_callout_reset(tp, tp->tt_keep, tcp_keepinit, tcp_timer_keep); 860 861 tcpstat.tcps_accepts++; 862 return (so); 863 864 abort: 865 if (so != NULL) 866 soabort_oncpu(so); 867 return (NULL); 868 } 869 870 /* 871 * This function gets called when we receive an ACK for a 872 * socket in the LISTEN state. We look up the connection 873 * in the syncache, and if its there, we pull it out of 874 * the cache and turn it into a full-blown connection in 875 * the SYN-RECEIVED state. 876 */ 877 int 878 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop, 879 struct mbuf *m) 880 { 881 struct syncache *sc; 882 struct syncache_head *sch; 883 struct socket *so; 884 885 sc = syncache_lookup(inc, &sch); 886 if (sc == NULL) { 887 /* 888 * There is no syncache entry, so see if this ACK is 889 * a returning syncookie. To do this, first: 890 * A. See if this socket has had a syncache entry dropped in 891 * the past. We don't want to accept a bogus syncookie 892 * if we've never received a SYN. 893 * B. check that the syncookie is valid. If it is, then 894 * cobble up a fake syncache entry, and return. 895 */ 896 if (!tcp_syncookies) 897 return (0); 898 sc = syncookie_lookup(inc, th, *sop); 899 if (sc == NULL) 900 return (0); 901 sch = NULL; 902 tcpstat.tcps_sc_recvcookie++; 903 } 904 905 /* 906 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 907 */ 908 if (th->th_ack != sc->sc_iss + 1) 909 return (0); 910 911 so = syncache_socket(sc, *sop, m); 912 if (so == NULL) { 913 #if 0 914 resetandabort: 915 /* XXXjlemon check this - is this correct? */ 916 tcp_respond(NULL, m, m, th, 917 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); 918 #endif 919 m_freem(m); /* XXX only needed for above */ 920 tcpstat.tcps_sc_aborted++; 921 } else { 922 tcpstat.tcps_sc_completed++; 923 } 924 if (sch == NULL) 925 syncache_free(sc); 926 else 927 syncache_drop(sc, sch); 928 *sop = so; 929 return (1); 930 } 931 932 /* 933 * Given a LISTEN socket and an inbound SYN request, add 934 * this to the syn cache, and send back a segment: 935 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 936 * to the source. 937 * 938 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 939 * Doing so would require that we hold onto the data and deliver it 940 * to the application. However, if we are the target of a SYN-flood 941 * DoS attack, an attacker could send data which would eventually 942 * consume all available buffer space if it were ACKed. By not ACKing 943 * the data, we avoid this DoS scenario. 944 */ 945 int 946 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 947 struct socket **sop, struct mbuf *m) 948 { 949 struct tcp_syncache_percpu *syncache_percpu; 950 struct tcpcb *tp; 951 struct socket *so; 952 struct syncache *sc = NULL; 953 struct syncache_head *sch; 954 struct mbuf *ipopts = NULL; 955 int win; 956 957 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 958 so = *sop; 959 tp = sototcpcb(so); 960 961 /* 962 * Remember the IP options, if any. 963 */ 964 #ifdef INET6 965 if (!inc->inc_isipv6) 966 #endif 967 ipopts = ip_srcroute(m); 968 969 /* 970 * See if we already have an entry for this connection. 971 * If we do, resend the SYN,ACK, and reset the retransmit timer. 972 * 973 * XXX 974 * The syncache should be re-initialized with the contents 975 * of the new SYN which may have different options. 976 */ 977 sc = syncache_lookup(inc, &sch); 978 if (sc != NULL) { 979 tcpstat.tcps_sc_dupsyn++; 980 if (ipopts) { 981 /* 982 * If we were remembering a previous source route, 983 * forget it and use the new one we've been given. 984 */ 985 if (sc->sc_ipopts) 986 m_free(sc->sc_ipopts); 987 sc->sc_ipopts = ipopts; 988 } 989 /* 990 * Update timestamp if present. 991 */ 992 if (sc->sc_flags & SCF_TIMESTAMP) 993 sc->sc_tsrecent = to->to_tsval; 994 995 /* Just update the TOF_SACK_PERMITTED for now. */ 996 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 997 sc->sc_flags |= SCF_SACK_PERMITTED; 998 else 999 sc->sc_flags &= ~SCF_SACK_PERMITTED; 1000 1001 /* 1002 * PCB may have changed, pick up new values. 1003 */ 1004 if (sc->sc_tp) { 1005 sc->sc_tp->t_flags &= ~TF_SYNCACHE; 1006 tp->t_flags |= TF_SYNCACHE; 1007 } 1008 sc->sc_tp = tp; 1009 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1010 if (syncache_respond(sc, m) == 0) { 1011 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], 1012 sc, sc_timerq); 1013 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot); 1014 tcpstat.tcps_sndacks++; 1015 tcpstat.tcps_sndtotal++; 1016 } 1017 *sop = NULL; 1018 return (1); 1019 } 1020 1021 /* 1022 * Fill in the syncache values. 1023 */ 1024 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1025 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1026 sc->sc_ipopts = ipopts; 1027 sc->sc_inc.inc_fport = inc->inc_fport; 1028 sc->sc_inc.inc_lport = inc->inc_lport; 1029 sc->sc_tp = tp; 1030 tp->t_flags |= TF_SYNCACHE; 1031 #ifdef INET6 1032 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1033 if (inc->inc_isipv6) { 1034 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1035 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1036 sc->sc_route6.ro_rt = NULL; 1037 } else 1038 #endif 1039 { 1040 sc->sc_inc.inc_faddr = inc->inc_faddr; 1041 sc->sc_inc.inc_laddr = inc->inc_laddr; 1042 sc->sc_route.ro_rt = NULL; 1043 } 1044 sc->sc_irs = th->th_seq; 1045 sc->sc_flags = 0; 1046 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 1047 if (tcp_syncookies) 1048 sc->sc_iss = syncookie_generate(sc); 1049 else 1050 sc->sc_iss = karc4random(); 1051 1052 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */ 1053 win = ssb_space(&so->so_rcv); 1054 win = imax(win, 0); 1055 win = imin(win, TCP_MAXWIN); 1056 sc->sc_wnd = win; 1057 1058 if (tcp_do_rfc1323) { 1059 /* 1060 * A timestamp received in a SYN makes 1061 * it ok to send timestamp requests and replies. 1062 */ 1063 if (to->to_flags & TOF_TS) { 1064 sc->sc_tsrecent = to->to_tsval; 1065 sc->sc_flags |= SCF_TIMESTAMP; 1066 } 1067 if (to->to_flags & TOF_SCALE) { 1068 int wscale = TCP_MIN_WINSHIFT; 1069 1070 /* Compute proper scaling value from buffer space */ 1071 while (wscale < TCP_MAX_WINSHIFT && 1072 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) { 1073 wscale++; 1074 } 1075 sc->sc_request_r_scale = wscale; 1076 sc->sc_requested_s_scale = to->to_requested_s_scale; 1077 sc->sc_flags |= SCF_WINSCALE; 1078 } 1079 } 1080 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1081 sc->sc_flags |= SCF_SACK_PERMITTED; 1082 if (tp->t_flags & TF_NOOPT) 1083 sc->sc_flags = SCF_NOOPT; 1084 1085 if (syncache_respond(sc, m) == 0) { 1086 syncache_insert(sc, sch); 1087 tcpstat.tcps_sndacks++; 1088 tcpstat.tcps_sndtotal++; 1089 } else { 1090 syncache_free(sc); 1091 tcpstat.tcps_sc_dropped++; 1092 } 1093 *sop = NULL; 1094 return (1); 1095 } 1096 1097 static int 1098 syncache_respond(struct syncache *sc, struct mbuf *m) 1099 { 1100 u_int8_t *optp; 1101 int optlen, error; 1102 u_int16_t tlen, hlen, mssopt; 1103 struct ip *ip = NULL; 1104 struct rtentry *rt; 1105 struct tcphdr *th; 1106 struct ip6_hdr *ip6 = NULL; 1107 #ifdef INET6 1108 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1109 #else 1110 const boolean_t isipv6 = FALSE; 1111 #endif 1112 1113 if (isipv6) { 1114 rt = tcp_rtlookup6(&sc->sc_inc); 1115 if (rt != NULL) 1116 mssopt = rt->rt_ifp->if_mtu - 1117 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1118 else 1119 mssopt = tcp_v6mssdflt; 1120 hlen = sizeof(struct ip6_hdr); 1121 } else { 1122 rt = tcp_rtlookup(&sc->sc_inc); 1123 if (rt != NULL) 1124 mssopt = rt->rt_ifp->if_mtu - 1125 (sizeof(struct ip) + sizeof(struct tcphdr)); 1126 else 1127 mssopt = tcp_mssdflt; 1128 hlen = sizeof(struct ip); 1129 } 1130 1131 /* Compute the size of the TCP options. */ 1132 if (sc->sc_flags & SCF_NOOPT) { 1133 optlen = 0; 1134 } else { 1135 optlen = TCPOLEN_MAXSEG + 1136 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1137 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1138 ((sc->sc_flags & SCF_SACK_PERMITTED) ? 1139 TCPOLEN_SACK_PERMITTED_ALIGNED : 0); 1140 } 1141 tlen = hlen + sizeof(struct tcphdr) + optlen; 1142 1143 /* 1144 * XXX 1145 * assume that the entire packet will fit in a header mbuf 1146 */ 1147 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1148 1149 /* 1150 * XXX shouldn't this reuse the mbuf if possible ? 1151 * Create the IP+TCP header from scratch. 1152 */ 1153 if (m) 1154 m_freem(m); 1155 1156 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 1157 if (m == NULL) 1158 return (ENOBUFS); 1159 m->m_data += max_linkhdr; 1160 m->m_len = tlen; 1161 m->m_pkthdr.len = tlen; 1162 m->m_pkthdr.rcvif = NULL; 1163 1164 if (isipv6) { 1165 ip6 = mtod(m, struct ip6_hdr *); 1166 ip6->ip6_vfc = IPV6_VERSION; 1167 ip6->ip6_nxt = IPPROTO_TCP; 1168 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1169 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1170 ip6->ip6_plen = htons(tlen - hlen); 1171 /* ip6_hlim is set after checksum */ 1172 /* ip6_flow = ??? */ 1173 1174 th = (struct tcphdr *)(ip6 + 1); 1175 } else { 1176 ip = mtod(m, struct ip *); 1177 ip->ip_v = IPVERSION; 1178 ip->ip_hl = sizeof(struct ip) >> 2; 1179 ip->ip_len = tlen; 1180 ip->ip_id = 0; 1181 ip->ip_off = 0; 1182 ip->ip_sum = 0; 1183 ip->ip_p = IPPROTO_TCP; 1184 ip->ip_src = sc->sc_inc.inc_laddr; 1185 ip->ip_dst = sc->sc_inc.inc_faddr; 1186 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1187 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1188 1189 /* 1190 * See if we should do MTU discovery. Route lookups are 1191 * expensive, so we will only unset the DF bit if: 1192 * 1193 * 1) path_mtu_discovery is disabled 1194 * 2) the SCF_UNREACH flag has been set 1195 */ 1196 if (path_mtu_discovery 1197 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1198 ip->ip_off |= IP_DF; 1199 } 1200 1201 th = (struct tcphdr *)(ip + 1); 1202 } 1203 th->th_sport = sc->sc_inc.inc_lport; 1204 th->th_dport = sc->sc_inc.inc_fport; 1205 1206 th->th_seq = htonl(sc->sc_iss); 1207 th->th_ack = htonl(sc->sc_irs + 1); 1208 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1209 th->th_x2 = 0; 1210 th->th_flags = TH_SYN | TH_ACK; 1211 th->th_win = htons(sc->sc_wnd); 1212 th->th_urp = 0; 1213 1214 /* Tack on the TCP options. */ 1215 if (optlen == 0) 1216 goto no_options; 1217 optp = (u_int8_t *)(th + 1); 1218 *optp++ = TCPOPT_MAXSEG; 1219 *optp++ = TCPOLEN_MAXSEG; 1220 *optp++ = (mssopt >> 8) & 0xff; 1221 *optp++ = mssopt & 0xff; 1222 1223 if (sc->sc_flags & SCF_WINSCALE) { 1224 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1225 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1226 sc->sc_request_r_scale); 1227 optp += 4; 1228 } 1229 1230 if (sc->sc_flags & SCF_TIMESTAMP) { 1231 u_int32_t *lp = (u_int32_t *)(optp); 1232 1233 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1234 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1235 *lp++ = htonl(ticks); 1236 *lp = htonl(sc->sc_tsrecent); 1237 optp += TCPOLEN_TSTAMP_APPA; 1238 } 1239 1240 if (sc->sc_flags & SCF_SACK_PERMITTED) { 1241 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 1242 optp += TCPOLEN_SACK_PERMITTED_ALIGNED; 1243 } 1244 1245 no_options: 1246 if (isipv6) { 1247 struct route_in6 *ro6 = &sc->sc_route6; 1248 1249 th->th_sum = 0; 1250 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1251 ip6->ip6_hlim = in6_selecthlim(NULL, 1252 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1253 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1254 sc->sc_tp->t_inpcb); 1255 } else { 1256 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1257 htons(tlen - hlen + IPPROTO_TCP)); 1258 m->m_pkthdr.csum_flags = CSUM_TCP; 1259 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1260 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 1261 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb); 1262 } 1263 return (error); 1264 } 1265 1266 /* 1267 * cookie layers: 1268 * 1269 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1270 * | peer iss | 1271 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1272 * | 0 |(A)| | 1273 * (A): peer mss index 1274 */ 1275 1276 /* 1277 * The values below are chosen to minimize the size of the tcp_secret 1278 * table, as well as providing roughly a 16 second lifetime for the cookie. 1279 */ 1280 1281 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1282 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1283 1284 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1285 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1286 #define SYNCOOKIE_TIMEOUT \ 1287 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1288 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1289 1290 static struct { 1291 u_int32_t ts_secbits[4]; 1292 u_int ts_expire; 1293 } tcp_secret[SYNCOOKIE_NSECRETS]; 1294 1295 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1296 1297 static MD5_CTX syn_ctx; 1298 1299 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1300 1301 struct md5_add { 1302 u_int32_t laddr, faddr; 1303 u_int32_t secbits[4]; 1304 u_int16_t lport, fport; 1305 }; 1306 1307 #ifdef CTASSERT 1308 CTASSERT(sizeof(struct md5_add) == 28); 1309 #endif 1310 1311 /* 1312 * Consider the problem of a recreated (and retransmitted) cookie. If the 1313 * original SYN was accepted, the connection is established. The second 1314 * SYN is inflight, and if it arrives with an ISN that falls within the 1315 * receive window, the connection is killed. 1316 * 1317 * However, since cookies have other problems, this may not be worth 1318 * worrying about. 1319 */ 1320 1321 static u_int32_t 1322 syncookie_generate(struct syncache *sc) 1323 { 1324 u_int32_t md5_buffer[4]; 1325 u_int32_t data; 1326 int idx, i; 1327 struct md5_add add; 1328 #ifdef INET6 1329 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1330 #else 1331 const boolean_t isipv6 = FALSE; 1332 #endif 1333 1334 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1335 if (tcp_secret[idx].ts_expire < ticks) { 1336 for (i = 0; i < 4; i++) 1337 tcp_secret[idx].ts_secbits[i] = karc4random(); 1338 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1339 } 1340 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1341 if (tcp_msstab[data] <= sc->sc_peer_mss) 1342 break; 1343 data = (data << SYNCOOKIE_WNDBITS) | idx; 1344 data ^= sc->sc_irs; /* peer's iss */ 1345 MD5Init(&syn_ctx); 1346 if (isipv6) { 1347 MD5Add(sc->sc_inc.inc6_laddr); 1348 MD5Add(sc->sc_inc.inc6_faddr); 1349 add.laddr = 0; 1350 add.faddr = 0; 1351 } else { 1352 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1353 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1354 } 1355 add.lport = sc->sc_inc.inc_lport; 1356 add.fport = sc->sc_inc.inc_fport; 1357 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1358 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1359 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1360 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1361 MD5Add(add); 1362 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1363 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1364 return (data); 1365 } 1366 1367 static struct syncache * 1368 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so) 1369 { 1370 u_int32_t md5_buffer[4]; 1371 struct syncache *sc; 1372 u_int32_t data; 1373 int wnd, idx; 1374 struct md5_add add; 1375 1376 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1377 idx = data & SYNCOOKIE_WNDMASK; 1378 if (tcp_secret[idx].ts_expire < ticks || 1379 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1380 return (NULL); 1381 MD5Init(&syn_ctx); 1382 #ifdef INET6 1383 if (inc->inc_isipv6) { 1384 MD5Add(inc->inc6_laddr); 1385 MD5Add(inc->inc6_faddr); 1386 add.laddr = 0; 1387 add.faddr = 0; 1388 } else 1389 #endif 1390 { 1391 add.laddr = inc->inc_laddr.s_addr; 1392 add.faddr = inc->inc_faddr.s_addr; 1393 } 1394 add.lport = inc->inc_lport; 1395 add.fport = inc->inc_fport; 1396 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1397 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1398 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1399 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1400 MD5Add(add); 1401 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1402 data ^= md5_buffer[0]; 1403 if (data & ~SYNCOOKIE_DATAMASK) 1404 return (NULL); 1405 data = data >> SYNCOOKIE_WNDBITS; 1406 1407 /* 1408 * Fill in the syncache values. 1409 * XXX duplicate code from syncache_add 1410 */ 1411 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1412 sc->sc_ipopts = NULL; 1413 sc->sc_inc.inc_fport = inc->inc_fport; 1414 sc->sc_inc.inc_lport = inc->inc_lport; 1415 #ifdef INET6 1416 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1417 if (inc->inc_isipv6) { 1418 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1419 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1420 sc->sc_route6.ro_rt = NULL; 1421 } else 1422 #endif 1423 { 1424 sc->sc_inc.inc_faddr = inc->inc_faddr; 1425 sc->sc_inc.inc_laddr = inc->inc_laddr; 1426 sc->sc_route.ro_rt = NULL; 1427 } 1428 sc->sc_irs = th->th_seq - 1; 1429 sc->sc_iss = th->th_ack - 1; 1430 wnd = ssb_space(&so->so_rcv); 1431 wnd = imax(wnd, 0); 1432 wnd = imin(wnd, TCP_MAXWIN); 1433 sc->sc_wnd = wnd; 1434 sc->sc_flags = 0; 1435 sc->sc_rxtslot = 0; 1436 sc->sc_peer_mss = tcp_msstab[data]; 1437 return (sc); 1438 } 1439