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_inet.h" 76 #include "opt_inet6.h" 77 #include "opt_ipsec.h" 78 79 #include <sys/param.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/sysctl.h> 83 #include <sys/malloc.h> 84 #include <sys/mbuf.h> 85 #include <sys/md5.h> 86 #include <sys/proc.h> /* for proc0 declaration */ 87 #include <sys/random.h> 88 #include <sys/socket.h> 89 #include <sys/socketvar.h> 90 #include <sys/in_cksum.h> 91 92 #include <sys/msgport2.h> 93 #include <net/netmsg2.h> 94 95 #include <net/if.h> 96 #include <net/route.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/ip.h> 101 #include <netinet/in_var.h> 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #ifdef INET6 106 #include <netinet/icmp6.h> 107 #include <netinet6/nd6.h> 108 #endif 109 #include <netinet6/ip6_var.h> 110 #include <netinet6/in6_pcb.h> 111 #include <netinet/tcp.h> 112 #include <netinet/tcp_fsm.h> 113 #include <netinet/tcp_seq.h> 114 #include <netinet/tcp_timer.h> 115 #include <netinet/tcp_timer2.h> 116 #include <netinet/tcp_var.h> 117 #include <netinet6/tcp6_var.h> 118 119 #ifdef IPSEC 120 #include <netinet6/ipsec.h> 121 #ifdef INET6 122 #include <netinet6/ipsec6.h> 123 #endif 124 #include <netproto/key/key.h> 125 #endif /*IPSEC*/ 126 127 #ifdef FAST_IPSEC 128 #include <netproto/ipsec/ipsec.h> 129 #ifdef INET6 130 #include <netproto/ipsec/ipsec6.h> 131 #endif 132 #include <netproto/ipsec/key.h> 133 #define IPSEC 134 #endif /*FAST_IPSEC*/ 135 136 static int tcp_syncookies = 1; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW, 138 &tcp_syncookies, 0, 139 "Use TCP SYN cookies if the syncache overflows"); 140 141 static void syncache_drop(struct syncache *, struct syncache_head *); 142 static void syncache_free(struct syncache *); 143 static void syncache_insert(struct syncache *, struct syncache_head *); 144 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **); 145 static int syncache_respond(struct syncache *, struct mbuf *); 146 static struct socket *syncache_socket(struct syncache *, struct socket *, 147 struct mbuf *); 148 static void syncache_timer(void *); 149 static u_int32_t syncookie_generate(struct syncache *); 150 static struct syncache *syncookie_lookup(struct in_conninfo *, 151 struct tcphdr *, struct socket *); 152 153 /* 154 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies. 155 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds, 156 * the odds are that the user has given up attempting to connect by then. 157 */ 158 #define SYNCACHE_MAXREXMTS 3 159 160 /* Arbitrary values */ 161 #define TCP_SYNCACHE_HASHSIZE 512 162 #define TCP_SYNCACHE_BUCKETLIMIT 30 163 164 struct netmsg_sc_timer { 165 struct netmsg_base base; 166 struct msgrec *nm_mrec; /* back pointer to containing msgrec */ 167 }; 168 169 struct msgrec { 170 struct netmsg_sc_timer msg; 171 lwkt_port_t port; /* constant after init */ 172 int slot; /* constant after init */ 173 }; 174 175 static void syncache_timer_handler(netmsg_t); 176 177 struct tcp_syncache { 178 u_int hashsize; 179 u_int hashmask; 180 u_int bucket_limit; 181 u_int cache_limit; 182 u_int rexmt_limit; 183 u_int hash_secret; 184 }; 185 static struct tcp_syncache tcp_syncache; 186 187 TAILQ_HEAD(syncache_list, syncache); 188 189 struct tcp_syncache_percpu { 190 struct syncache_head *hashbase; 191 u_int cache_count; 192 struct syncache_list timerq[SYNCACHE_MAXREXMTS + 1]; 193 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1]; 194 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1]; 195 }; 196 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU]; 197 198 static struct lwkt_port syncache_null_rport; 199 200 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache"); 201 202 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD, 203 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache"); 204 205 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD, 206 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache"); 207 208 /* XXX JH */ 209 #if 0 210 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD, 211 &tcp_syncache.cache_count, 0, "Current number of entries in syncache"); 212 #endif 213 214 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD, 215 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable"); 216 217 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW, 218 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions"); 219 220 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache"); 221 222 #define SYNCACHE_HASH(inc, mask) \ 223 ((tcp_syncache.hash_secret ^ \ 224 (inc)->inc_faddr.s_addr ^ \ 225 ((inc)->inc_faddr.s_addr >> 16) ^ \ 226 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 227 228 #define SYNCACHE_HASH6(inc, mask) \ 229 ((tcp_syncache.hash_secret ^ \ 230 (inc)->inc6_faddr.s6_addr32[0] ^ \ 231 (inc)->inc6_faddr.s6_addr32[3] ^ \ 232 (inc)->inc_fport ^ (inc)->inc_lport) & mask) 233 234 #define ENDPTS_EQ(a, b) ( \ 235 (a)->ie_fport == (b)->ie_fport && \ 236 (a)->ie_lport == (b)->ie_lport && \ 237 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \ 238 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \ 239 ) 240 241 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0) 242 243 static __inline void 244 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu, 245 struct syncache *sc, int slot) 246 { 247 sc->sc_rxtslot = slot; 248 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; 249 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq); 250 if (!callout_active(&syncache_percpu->tt_timerq[slot])) { 251 callout_reset(&syncache_percpu->tt_timerq[slot], 252 TCPTV_RTOBASE * tcp_backoff[slot], 253 syncache_timer, 254 &syncache_percpu->mrec[slot]); 255 } 256 } 257 258 static void 259 syncache_free(struct syncache *sc) 260 { 261 struct rtentry *rt; 262 #ifdef INET6 263 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 264 #else 265 const boolean_t isipv6 = FALSE; 266 #endif 267 268 if (sc->sc_ipopts) 269 m_free(sc->sc_ipopts); 270 271 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt; 272 if (rt != NULL) { 273 /* 274 * If this is the only reference to a protocol-cloned 275 * route, remove it immediately. 276 */ 277 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1) 278 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway, 279 rt_mask(rt), rt->rt_flags, NULL); 280 RTFREE(rt); 281 } 282 kfree(sc, M_SYNCACHE); 283 } 284 285 void 286 syncache_init(void) 287 { 288 int i, cpu; 289 290 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE; 291 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT; 292 tcp_syncache.cache_limit = 293 tcp_syncache.hashsize * tcp_syncache.bucket_limit; 294 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS; 295 tcp_syncache.hash_secret = karc4random(); 296 297 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize", 298 &tcp_syncache.hashsize); 299 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit", 300 &tcp_syncache.cache_limit); 301 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit", 302 &tcp_syncache.bucket_limit); 303 if (!powerof2(tcp_syncache.hashsize)) { 304 kprintf("WARNING: syncache hash size is not a power of 2.\n"); 305 tcp_syncache.hashsize = 512; /* safe default */ 306 } 307 tcp_syncache.hashmask = tcp_syncache.hashsize - 1; 308 309 lwkt_initport_replyonly_null(&syncache_null_rport); 310 311 for (cpu = 0; cpu < ncpus2; cpu++) { 312 struct tcp_syncache_percpu *syncache_percpu; 313 314 syncache_percpu = &tcp_syncache_percpu[cpu]; 315 /* Allocate the hash table. */ 316 MALLOC(syncache_percpu->hashbase, struct syncache_head *, 317 tcp_syncache.hashsize * sizeof(struct syncache_head), 318 M_SYNCACHE, M_WAITOK); 319 320 /* Initialize the hash buckets. */ 321 for (i = 0; i < tcp_syncache.hashsize; i++) { 322 struct syncache_head *bucket; 323 324 bucket = &syncache_percpu->hashbase[i]; 325 TAILQ_INIT(&bucket->sch_bucket); 326 bucket->sch_length = 0; 327 } 328 329 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) { 330 /* Initialize the timer queues. */ 331 TAILQ_INIT(&syncache_percpu->timerq[i]); 332 callout_init(&syncache_percpu->tt_timerq[i]); 333 334 syncache_percpu->mrec[i].slot = i; 335 syncache_percpu->mrec[i].port = cpu_portfn(cpu); 336 syncache_percpu->mrec[i].msg.nm_mrec = 337 &syncache_percpu->mrec[i]; 338 netmsg_init(&syncache_percpu->mrec[i].msg.base, 339 NULL, &syncache_null_rport, 340 0, syncache_timer_handler); 341 } 342 } 343 } 344 345 static void 346 syncache_insert(struct syncache *sc, struct syncache_head *sch) 347 { 348 struct tcp_syncache_percpu *syncache_percpu; 349 struct syncache *sc2; 350 int i; 351 352 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 353 354 /* 355 * Make sure that we don't overflow the per-bucket 356 * limit or the total cache size limit. 357 */ 358 if (sch->sch_length >= tcp_syncache.bucket_limit) { 359 /* 360 * The bucket is full, toss the oldest element. 361 */ 362 sc2 = TAILQ_FIRST(&sch->sch_bucket); 363 sc2->sc_tp->ts_recent = ticks; 364 syncache_drop(sc2, sch); 365 tcpstat.tcps_sc_bucketoverflow++; 366 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) { 367 /* 368 * The cache is full. Toss the oldest entry in the 369 * entire cache. This is the front entry in the 370 * first non-empty timer queue with the largest 371 * timeout value. 372 */ 373 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) { 374 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]); 375 while (sc2 && (sc2->sc_flags & SCF_MARKER)) 376 sc2 = TAILQ_NEXT(sc2, sc_timerq); 377 if (sc2 != NULL) 378 break; 379 } 380 sc2->sc_tp->ts_recent = ticks; 381 syncache_drop(sc2, NULL); 382 tcpstat.tcps_sc_cacheoverflow++; 383 } 384 385 /* Initialize the entry's timer. */ 386 syncache_timeout(syncache_percpu, sc, 0); 387 388 /* Put it into the bucket. */ 389 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash); 390 sch->sch_length++; 391 syncache_percpu->cache_count++; 392 tcpstat.tcps_sc_added++; 393 } 394 395 void 396 syncache_destroy(struct tcpcb *tp) 397 { 398 struct tcp_syncache_percpu *syncache_percpu; 399 struct syncache_head *bucket; 400 struct syncache *sc; 401 int i; 402 403 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 404 sc = NULL; 405 406 for (i = 0; i < tcp_syncache.hashsize; i++) { 407 bucket = &syncache_percpu->hashbase[i]; 408 TAILQ_FOREACH(sc, &bucket->sch_bucket, sc_hash) { 409 if (sc->sc_tp == tp) 410 sc->sc_tp = NULL; 411 } 412 } 413 } 414 415 static void 416 syncache_drop(struct syncache *sc, struct syncache_head *sch) 417 { 418 struct tcp_syncache_percpu *syncache_percpu; 419 #ifdef INET6 420 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 421 #else 422 const boolean_t isipv6 = FALSE; 423 #endif 424 425 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 426 427 if (sch == NULL) { 428 if (isipv6) { 429 sch = &syncache_percpu->hashbase[ 430 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)]; 431 } else { 432 sch = &syncache_percpu->hashbase[ 433 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)]; 434 } 435 } 436 437 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash); 438 sch->sch_length--; 439 syncache_percpu->cache_count--; 440 441 /* 442 * Cleanup 443 */ 444 if (sc->sc_tp) 445 sc->sc_tp = NULL; 446 447 /* 448 * Remove the entry from the syncache timer/timeout queue. Note 449 * that we do not try to stop any running timer since we do not know 450 * whether the timer's message is in-transit or not. Since timeouts 451 * are fairly long, taking an unneeded callout does not detrimentally 452 * effect performance. 453 */ 454 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq); 455 456 syncache_free(sc); 457 } 458 459 /* 460 * Place a timeout message on the TCP thread's message queue. 461 * This routine runs in soft interrupt context. 462 * 463 * An invariant is for this routine to be called, the callout must 464 * have been active. Note that the callout is not deactivated until 465 * after the message has been processed in syncache_timer_handler() below. 466 */ 467 static void 468 syncache_timer(void *p) 469 { 470 struct netmsg_sc_timer *msg = p; 471 472 lwkt_sendmsg(msg->nm_mrec->port, &msg->base.lmsg); 473 } 474 475 /* 476 * Service a timer message queued by timer expiration. 477 * This routine runs in the TCP protocol thread. 478 * 479 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. 480 * If we have retransmitted an entry the maximum number of times, expire it. 481 * 482 * When we finish processing timed-out entries, we restart the timer if there 483 * are any entries still on the queue and deactivate it otherwise. Only after 484 * a timer has been deactivated here can it be restarted by syncache_timeout(). 485 */ 486 static void 487 syncache_timer_handler(netmsg_t msg) 488 { 489 struct tcp_syncache_percpu *syncache_percpu; 490 struct syncache *sc; 491 struct syncache marker; 492 struct syncache_list *list; 493 struct inpcb *inp; 494 int slot; 495 496 slot = ((struct netmsg_sc_timer *)msg)->nm_mrec->slot; 497 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 498 499 list = &syncache_percpu->timerq[slot]; 500 501 /* 502 * Use a marker to keep our place in the scan. syncache_drop() 503 * can block and cause any next pointer we cache to become stale. 504 */ 505 marker.sc_flags = SCF_MARKER; 506 TAILQ_INSERT_HEAD(list, &marker, sc_timerq); 507 508 while ((sc = TAILQ_NEXT(&marker, sc_timerq)) != NULL) { 509 /* 510 * Move the marker. 511 */ 512 TAILQ_REMOVE(list, &marker, sc_timerq); 513 TAILQ_INSERT_AFTER(list, sc, &marker, sc_timerq); 514 515 if (sc->sc_flags & SCF_MARKER) 516 continue; 517 518 if (ticks < sc->sc_rxttime) 519 break; /* finished because timerq sorted by time */ 520 if (sc->sc_tp == NULL) { 521 syncache_drop(sc, NULL); 522 tcpstat.tcps_sc_stale++; 523 continue; 524 } 525 inp = sc->sc_tp->t_inpcb; 526 if (slot == SYNCACHE_MAXREXMTS || 527 slot >= tcp_syncache.rexmt_limit || 528 inp == NULL || 529 inp->inp_gencnt != sc->sc_inp_gencnt) { 530 syncache_drop(sc, NULL); 531 tcpstat.tcps_sc_stale++; 532 continue; 533 } 534 /* 535 * syncache_respond() may call back into the syncache to 536 * to modify another entry, so do not obtain the next 537 * entry on the timer chain until it has completed. 538 */ 539 syncache_respond(sc, NULL); 540 tcpstat.tcps_sc_retransmitted++; 541 TAILQ_REMOVE(list, sc, sc_timerq); 542 syncache_timeout(syncache_percpu, sc, slot + 1); 543 } 544 TAILQ_REMOVE(list, &marker, sc_timerq); 545 546 if (sc != NULL) { 547 callout_reset(&syncache_percpu->tt_timerq[slot], 548 sc->sc_rxttime - ticks, syncache_timer, 549 &syncache_percpu->mrec[slot]); 550 } else { 551 callout_deactivate(&syncache_percpu->tt_timerq[slot]); 552 } 553 lwkt_replymsg(&msg->base.lmsg, 0); 554 } 555 556 /* 557 * Find an entry in the syncache. 558 */ 559 struct syncache * 560 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp) 561 { 562 struct tcp_syncache_percpu *syncache_percpu; 563 struct syncache *sc; 564 struct syncache_head *sch; 565 566 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 567 #ifdef INET6 568 if (inc->inc_isipv6) { 569 sch = &syncache_percpu->hashbase[ 570 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)]; 571 *schp = sch; 572 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) 573 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 574 return (sc); 575 } else 576 #endif 577 { 578 sch = &syncache_percpu->hashbase[ 579 SYNCACHE_HASH(inc, tcp_syncache.hashmask)]; 580 *schp = sch; 581 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) { 582 #ifdef INET6 583 if (sc->sc_inc.inc_isipv6) 584 continue; 585 #endif 586 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie)) 587 return (sc); 588 } 589 } 590 return (NULL); 591 } 592 593 /* 594 * This function is called when we get a RST for a 595 * non-existent connection, so that we can see if the 596 * connection is in the syn cache. If it is, zap it. 597 */ 598 void 599 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th) 600 { 601 struct syncache *sc; 602 struct syncache_head *sch; 603 604 sc = syncache_lookup(inc, &sch); 605 if (sc == NULL) { 606 return; 607 } 608 /* 609 * If the RST bit is set, check the sequence number to see 610 * if this is a valid reset segment. 611 * RFC 793 page 37: 612 * In all states except SYN-SENT, all reset (RST) segments 613 * are validated by checking their SEQ-fields. A reset is 614 * valid if its sequence number is in the window. 615 * 616 * The sequence number in the reset segment is normally an 617 * echo of our outgoing acknowlegement numbers, but some hosts 618 * send a reset with the sequence number at the rightmost edge 619 * of our receive window, and we have to handle this case. 620 */ 621 if (SEQ_GEQ(th->th_seq, sc->sc_irs) && 622 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) { 623 syncache_drop(sc, sch); 624 tcpstat.tcps_sc_reset++; 625 } 626 } 627 628 void 629 syncache_badack(struct in_conninfo *inc) 630 { 631 struct syncache *sc; 632 struct syncache_head *sch; 633 634 sc = syncache_lookup(inc, &sch); 635 if (sc != NULL) { 636 syncache_drop(sc, sch); 637 tcpstat.tcps_sc_badack++; 638 } 639 } 640 641 void 642 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th) 643 { 644 struct syncache *sc; 645 struct syncache_head *sch; 646 647 /* we are called at splnet() here */ 648 sc = syncache_lookup(inc, &sch); 649 if (sc == NULL) 650 return; 651 652 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 653 if (ntohl(th->th_seq) != sc->sc_iss) 654 return; 655 656 /* 657 * If we've rertransmitted 3 times and this is our second error, 658 * we remove the entry. Otherwise, we allow it to continue on. 659 * This prevents us from incorrectly nuking an entry during a 660 * spurious network outage. 661 * 662 * See tcp_notify(). 663 */ 664 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) { 665 sc->sc_flags |= SCF_UNREACH; 666 return; 667 } 668 syncache_drop(sc, sch); 669 tcpstat.tcps_sc_unreach++; 670 } 671 672 /* 673 * Build a new TCP socket structure from a syncache entry. 674 * 675 * This is called from the context of the SYN+ACK 676 */ 677 static struct socket * 678 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m) 679 { 680 struct inpcb *inp = NULL, *linp; 681 struct socket *so; 682 struct tcpcb *tp; 683 lwkt_port_t port; 684 #ifdef INET6 685 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 686 #else 687 const boolean_t isipv6 = FALSE; 688 #endif 689 690 /* 691 * Ok, create the full blown connection, and set things up 692 * as they would have been set up if we had created the 693 * connection when the SYN arrived. If we can't create 694 * the connection, abort it. 695 * 696 * Set the protocol processing port for the socket to the current 697 * port (that the connection came in on). 698 */ 699 so = sonewconn(lso, SS_ISCONNECTED); 700 if (so == NULL) { 701 /* 702 * Drop the connection; we will send a RST if the peer 703 * retransmits the ACK, 704 */ 705 tcpstat.tcps_listendrop++; 706 goto abort; 707 } 708 709 /* 710 * Insert new socket into hash list. 711 */ 712 inp = so->so_pcb; 713 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6; 714 if (isipv6) { 715 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 716 } else { 717 #ifdef INET6 718 inp->inp_vflag &= ~INP_IPV6; 719 inp->inp_vflag |= INP_IPV4; 720 inp->inp_flags &= ~IN6P_IPV6_V6ONLY; 721 #endif 722 inp->inp_laddr = sc->sc_inc.inc_laddr; 723 } 724 inp->inp_lport = sc->sc_inc.inc_lport; 725 if (in_pcbinsporthash(inp) != 0) { 726 /* 727 * Undo the assignments above if we failed to 728 * put the PCB on the hash lists. 729 */ 730 if (isipv6) 731 inp->in6p_laddr = kin6addr_any; 732 else 733 inp->inp_laddr.s_addr = INADDR_ANY; 734 inp->inp_lport = 0; 735 goto abort; 736 } 737 linp = lso->so_pcb; 738 #ifdef IPSEC 739 /* copy old policy into new socket's */ 740 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp)) 741 kprintf("syncache_expand: could not copy policy\n"); 742 #endif 743 if (isipv6) { 744 struct in6_addr laddr6; 745 struct sockaddr_in6 sin6; 746 /* 747 * Inherit socket options from the listening socket. 748 * Note that in6p_inputopts are not (and should not be) 749 * copied, since it stores previously received options and is 750 * used to detect if each new option is different than the 751 * previous one and hence should be passed to a user. 752 * If we copied in6p_inputopts, a user would not be able to 753 * receive options just after calling the accept system call. 754 */ 755 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS; 756 if (linp->in6p_outputopts) 757 inp->in6p_outputopts = 758 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT); 759 inp->in6p_route = sc->sc_route6; 760 sc->sc_route6.ro_rt = NULL; 761 762 sin6.sin6_family = AF_INET6; 763 sin6.sin6_len = sizeof sin6; 764 sin6.sin6_addr = sc->sc_inc.inc6_faddr; 765 sin6.sin6_port = sc->sc_inc.inc_fport; 766 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0; 767 laddr6 = inp->in6p_laddr; 768 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 769 inp->in6p_laddr = sc->sc_inc.inc6_laddr; 770 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) { 771 inp->in6p_laddr = laddr6; 772 goto abort; 773 } 774 } else { 775 struct in_addr laddr; 776 struct sockaddr_in sin; 777 778 inp->inp_options = ip_srcroute(m); 779 if (inp->inp_options == NULL) { 780 inp->inp_options = sc->sc_ipopts; 781 sc->sc_ipopts = NULL; 782 } 783 inp->inp_route = sc->sc_route; 784 sc->sc_route.ro_rt = NULL; 785 786 sin.sin_family = AF_INET; 787 sin.sin_len = sizeof sin; 788 sin.sin_addr = sc->sc_inc.inc_faddr; 789 sin.sin_port = sc->sc_inc.inc_fport; 790 bzero(sin.sin_zero, sizeof sin.sin_zero); 791 laddr = inp->inp_laddr; 792 if (inp->inp_laddr.s_addr == INADDR_ANY) 793 inp->inp_laddr = sc->sc_inc.inc_laddr; 794 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) { 795 inp->inp_laddr = laddr; 796 goto abort; 797 } 798 } 799 800 /* 801 * The current port should be in the context of the SYN+ACK and 802 * so should match the tcp address port. 803 * 804 * XXX we may be running on the netisr thread instead of a tcp 805 * thread, in which case port will not match 806 * curthread->td_msgport. 807 */ 808 if (isipv6) { 809 port = tcp6_addrport(); 810 } else { 811 port = tcp_addrport(inp->inp_faddr.s_addr, inp->inp_fport, 812 inp->inp_laddr.s_addr, inp->inp_lport); 813 } 814 if (port != &curthread->td_msgport) { 815 print_backtrace(-1); 816 kprintf("TCP PORT MISMATCH %p vs %p\n", 817 port, &curthread->td_msgport); 818 } 819 /*KKASSERT(port == &curthread->td_msgport);*/ 820 821 tp = intotcpcb(inp); 822 tp->t_state = TCPS_SYN_RECEIVED; 823 tp->iss = sc->sc_iss; 824 tp->irs = sc->sc_irs; 825 tcp_rcvseqinit(tp); 826 tcp_sendseqinit(tp); 827 tp->snd_wl1 = sc->sc_irs; 828 tp->rcv_up = sc->sc_irs + 1; 829 tp->rcv_wnd = sc->sc_wnd; 830 tp->rcv_adv += tp->rcv_wnd; 831 832 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY); 833 if (sc->sc_flags & SCF_NOOPT) 834 tp->t_flags |= TF_NOOPT; 835 if (sc->sc_flags & SCF_WINSCALE) { 836 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE; 837 tp->requested_s_scale = sc->sc_requested_s_scale; 838 tp->request_r_scale = sc->sc_request_r_scale; 839 } 840 if (sc->sc_flags & SCF_TIMESTAMP) { 841 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP; 842 tp->ts_recent = sc->sc_tsrecent; 843 tp->ts_recent_age = ticks; 844 } 845 if (sc->sc_flags & SCF_SACK_PERMITTED) 846 tp->t_flags |= TF_SACK_PERMITTED; 847 848 #ifdef TCP_SIGNATURE 849 if (sc->sc_flags & SCF_SIGNATURE) 850 tp->t_flags |= TF_SIGNATURE; 851 #endif /* TCP_SIGNATURE */ 852 853 854 tcp_mss(tp, sc->sc_peer_mss); 855 856 /* 857 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment. 858 */ 859 if (sc->sc_rxtslot != 0) 860 tp->snd_cwnd = tp->t_maxseg; 861 tcp_create_timermsg(tp, port); 862 tcp_callout_reset(tp, tp->tt_keep, tcp_keepinit, tcp_timer_keep); 863 864 tcpstat.tcps_accepts++; 865 return (so); 866 867 abort: 868 if (so != NULL) 869 soabort_oncpu(so); 870 return (NULL); 871 } 872 873 /* 874 * This function gets called when we receive an ACK for a 875 * socket in the LISTEN state. We look up the connection 876 * in the syncache, and if its there, we pull it out of 877 * the cache and turn it into a full-blown connection in 878 * the SYN-RECEIVED state. 879 */ 880 int 881 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop, 882 struct mbuf *m) 883 { 884 struct syncache *sc; 885 struct syncache_head *sch; 886 struct socket *so; 887 888 sc = syncache_lookup(inc, &sch); 889 if (sc == NULL) { 890 /* 891 * There is no syncache entry, so see if this ACK is 892 * a returning syncookie. To do this, first: 893 * A. See if this socket has had a syncache entry dropped in 894 * the past. We don't want to accept a bogus syncookie 895 * if we've never received a SYN. 896 * B. check that the syncookie is valid. If it is, then 897 * cobble up a fake syncache entry, and return. 898 */ 899 if (!tcp_syncookies) 900 return (0); 901 sc = syncookie_lookup(inc, th, *sop); 902 if (sc == NULL) 903 return (0); 904 sch = NULL; 905 tcpstat.tcps_sc_recvcookie++; 906 } 907 908 /* 909 * If seg contains an ACK, but not for our SYN/ACK, send a RST. 910 */ 911 if (th->th_ack != sc->sc_iss + 1) 912 return (0); 913 914 so = syncache_socket(sc, *sop, m); 915 if (so == NULL) { 916 #if 0 917 resetandabort: 918 /* XXXjlemon check this - is this correct? */ 919 tcp_respond(NULL, m, m, th, 920 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); 921 #endif 922 m_freem(m); /* XXX only needed for above */ 923 tcpstat.tcps_sc_aborted++; 924 } else { 925 tcpstat.tcps_sc_completed++; 926 } 927 if (sch == NULL) 928 syncache_free(sc); 929 else 930 syncache_drop(sc, sch); 931 *sop = so; 932 return (1); 933 } 934 935 /* 936 * Given a LISTEN socket and an inbound SYN request, add 937 * this to the syn cache, and send back a segment: 938 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 939 * to the source. 940 * 941 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. 942 * Doing so would require that we hold onto the data and deliver it 943 * to the application. However, if we are the target of a SYN-flood 944 * DoS attack, an attacker could send data which would eventually 945 * consume all available buffer space if it were ACKed. By not ACKing 946 * the data, we avoid this DoS scenario. 947 */ 948 int 949 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th, 950 struct socket **sop, struct mbuf *m) 951 { 952 struct tcp_syncache_percpu *syncache_percpu; 953 struct tcpcb *tp; 954 struct socket *so; 955 struct syncache *sc = NULL; 956 struct syncache_head *sch; 957 struct mbuf *ipopts = NULL; 958 int win; 959 960 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid]; 961 so = *sop; 962 tp = sototcpcb(so); 963 964 /* 965 * Remember the IP options, if any. 966 */ 967 #ifdef INET6 968 if (!inc->inc_isipv6) 969 #endif 970 ipopts = ip_srcroute(m); 971 972 /* 973 * See if we already have an entry for this connection. 974 * If we do, resend the SYN,ACK, and reset the retransmit timer. 975 * 976 * XXX 977 * The syncache should be re-initialized with the contents 978 * of the new SYN which may have different options. 979 */ 980 sc = syncache_lookup(inc, &sch); 981 if (sc != NULL) { 982 tcpstat.tcps_sc_dupsyn++; 983 if (ipopts) { 984 /* 985 * If we were remembering a previous source route, 986 * forget it and use the new one we've been given. 987 */ 988 if (sc->sc_ipopts) 989 m_free(sc->sc_ipopts); 990 sc->sc_ipopts = ipopts; 991 } 992 /* 993 * Update timestamp if present. 994 */ 995 if (sc->sc_flags & SCF_TIMESTAMP) 996 sc->sc_tsrecent = to->to_tsval; 997 998 /* Just update the TOF_SACK_PERMITTED for now. */ 999 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1000 sc->sc_flags |= SCF_SACK_PERMITTED; 1001 else 1002 sc->sc_flags &= ~SCF_SACK_PERMITTED; 1003 1004 /* 1005 * PCB may have changed, pick up new values. 1006 */ 1007 sc->sc_tp = tp; 1008 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1009 if (syncache_respond(sc, m) == 0) { 1010 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], 1011 sc, sc_timerq); 1012 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot); 1013 tcpstat.tcps_sndacks++; 1014 tcpstat.tcps_sndtotal++; 1015 } 1016 *sop = NULL; 1017 return (1); 1018 } 1019 1020 /* 1021 * Fill in the syncache values. 1022 */ 1023 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1024 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt; 1025 sc->sc_ipopts = ipopts; 1026 sc->sc_inc.inc_fport = inc->inc_fport; 1027 sc->sc_inc.inc_lport = inc->inc_lport; 1028 sc->sc_tp = tp; 1029 #ifdef INET6 1030 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1031 if (inc->inc_isipv6) { 1032 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1033 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1034 sc->sc_route6.ro_rt = NULL; 1035 } else 1036 #endif 1037 { 1038 sc->sc_inc.inc_faddr = inc->inc_faddr; 1039 sc->sc_inc.inc_laddr = inc->inc_laddr; 1040 sc->sc_route.ro_rt = NULL; 1041 } 1042 sc->sc_irs = th->th_seq; 1043 sc->sc_flags = 0; 1044 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0; 1045 if (tcp_syncookies) 1046 sc->sc_iss = syncookie_generate(sc); 1047 else 1048 sc->sc_iss = karc4random(); 1049 1050 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */ 1051 win = ssb_space(&so->so_rcv); 1052 win = imax(win, 0); 1053 win = imin(win, TCP_MAXWIN); 1054 sc->sc_wnd = win; 1055 1056 if (tcp_do_rfc1323) { 1057 /* 1058 * A timestamp received in a SYN makes 1059 * it ok to send timestamp requests and replies. 1060 */ 1061 if (to->to_flags & TOF_TS) { 1062 sc->sc_tsrecent = to->to_tsval; 1063 sc->sc_flags |= SCF_TIMESTAMP; 1064 } 1065 if (to->to_flags & TOF_SCALE) { 1066 int wscale = TCP_MIN_WINSHIFT; 1067 1068 /* Compute proper scaling value from buffer space */ 1069 while (wscale < TCP_MAX_WINSHIFT && 1070 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) { 1071 wscale++; 1072 } 1073 sc->sc_request_r_scale = wscale; 1074 sc->sc_requested_s_scale = to->to_requested_s_scale; 1075 sc->sc_flags |= SCF_WINSCALE; 1076 } 1077 } 1078 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED)) 1079 sc->sc_flags |= SCF_SACK_PERMITTED; 1080 if (tp->t_flags & TF_NOOPT) 1081 sc->sc_flags = SCF_NOOPT; 1082 #ifdef TCP_SIGNATURE 1083 /* 1084 * If listening socket requested TCP digests, and received SYN 1085 * contains the option, flag this in the syncache so that 1086 * syncache_respond() will do the right thing with the SYN+ACK. 1087 * XXX Currently we always record the option by default and will 1088 * attempt to use it in syncache_respond(). 1089 */ 1090 if (to->to_flags & TOF_SIGNATURE) 1091 sc->sc_flags = SCF_SIGNATURE; 1092 #endif /* TCP_SIGNATURE */ 1093 1094 if (syncache_respond(sc, m) == 0) { 1095 syncache_insert(sc, sch); 1096 tcpstat.tcps_sndacks++; 1097 tcpstat.tcps_sndtotal++; 1098 } else { 1099 syncache_free(sc); 1100 tcpstat.tcps_sc_dropped++; 1101 } 1102 *sop = NULL; 1103 return (1); 1104 } 1105 1106 static int 1107 syncache_respond(struct syncache *sc, struct mbuf *m) 1108 { 1109 u_int8_t *optp; 1110 int optlen, error; 1111 u_int16_t tlen, hlen, mssopt; 1112 struct ip *ip = NULL; 1113 struct rtentry *rt; 1114 struct tcphdr *th; 1115 struct ip6_hdr *ip6 = NULL; 1116 #ifdef INET6 1117 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1118 #else 1119 const boolean_t isipv6 = FALSE; 1120 #endif 1121 1122 if (isipv6) { 1123 rt = tcp_rtlookup6(&sc->sc_inc); 1124 if (rt != NULL) 1125 mssopt = rt->rt_ifp->if_mtu - 1126 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)); 1127 else 1128 mssopt = tcp_v6mssdflt; 1129 hlen = sizeof(struct ip6_hdr); 1130 } else { 1131 rt = tcp_rtlookup(&sc->sc_inc); 1132 if (rt != NULL) 1133 mssopt = rt->rt_ifp->if_mtu - 1134 (sizeof(struct ip) + sizeof(struct tcphdr)); 1135 else 1136 mssopt = tcp_mssdflt; 1137 hlen = sizeof(struct ip); 1138 } 1139 1140 /* Compute the size of the TCP options. */ 1141 if (sc->sc_flags & SCF_NOOPT) { 1142 optlen = 0; 1143 } else { 1144 optlen = TCPOLEN_MAXSEG + 1145 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) + 1146 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) + 1147 ((sc->sc_flags & SCF_SACK_PERMITTED) ? 1148 TCPOLEN_SACK_PERMITTED_ALIGNED : 0); 1149 #ifdef TCP_SIGNATURE 1150 optlen += ((sc->sc_flags & SCF_SIGNATURE) ? 1151 (TCPOLEN_SIGNATURE + 2) : 0); 1152 #endif /* TCP_SIGNATURE */ 1153 } 1154 tlen = hlen + sizeof(struct tcphdr) + optlen; 1155 1156 /* 1157 * XXX 1158 * assume that the entire packet will fit in a header mbuf 1159 */ 1160 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small")); 1161 1162 /* 1163 * XXX shouldn't this reuse the mbuf if possible ? 1164 * Create the IP+TCP header from scratch. 1165 */ 1166 if (m) 1167 m_freem(m); 1168 1169 m = m_gethdr(MB_DONTWAIT, MT_HEADER); 1170 if (m == NULL) 1171 return (ENOBUFS); 1172 m->m_data += max_linkhdr; 1173 m->m_len = tlen; 1174 m->m_pkthdr.len = tlen; 1175 m->m_pkthdr.rcvif = NULL; 1176 1177 if (isipv6) { 1178 ip6 = mtod(m, struct ip6_hdr *); 1179 ip6->ip6_vfc = IPV6_VERSION; 1180 ip6->ip6_nxt = IPPROTO_TCP; 1181 ip6->ip6_src = sc->sc_inc.inc6_laddr; 1182 ip6->ip6_dst = sc->sc_inc.inc6_faddr; 1183 ip6->ip6_plen = htons(tlen - hlen); 1184 /* ip6_hlim is set after checksum */ 1185 /* ip6_flow = ??? */ 1186 1187 th = (struct tcphdr *)(ip6 + 1); 1188 } else { 1189 ip = mtod(m, struct ip *); 1190 ip->ip_v = IPVERSION; 1191 ip->ip_hl = sizeof(struct ip) >> 2; 1192 ip->ip_len = tlen; 1193 ip->ip_id = 0; 1194 ip->ip_off = 0; 1195 ip->ip_sum = 0; 1196 ip->ip_p = IPPROTO_TCP; 1197 ip->ip_src = sc->sc_inc.inc_laddr; 1198 ip->ip_dst = sc->sc_inc.inc_faddr; 1199 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */ 1200 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */ 1201 1202 /* 1203 * See if we should do MTU discovery. Route lookups are 1204 * expensive, so we will only unset the DF bit if: 1205 * 1206 * 1) path_mtu_discovery is disabled 1207 * 2) the SCF_UNREACH flag has been set 1208 */ 1209 if (path_mtu_discovery 1210 && ((sc->sc_flags & SCF_UNREACH) == 0)) { 1211 ip->ip_off |= IP_DF; 1212 } 1213 1214 th = (struct tcphdr *)(ip + 1); 1215 } 1216 th->th_sport = sc->sc_inc.inc_lport; 1217 th->th_dport = sc->sc_inc.inc_fport; 1218 1219 th->th_seq = htonl(sc->sc_iss); 1220 th->th_ack = htonl(sc->sc_irs + 1); 1221 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 1222 th->th_x2 = 0; 1223 th->th_flags = TH_SYN | TH_ACK; 1224 th->th_win = htons(sc->sc_wnd); 1225 th->th_urp = 0; 1226 1227 /* Tack on the TCP options. */ 1228 if (optlen == 0) 1229 goto no_options; 1230 optp = (u_int8_t *)(th + 1); 1231 *optp++ = TCPOPT_MAXSEG; 1232 *optp++ = TCPOLEN_MAXSEG; 1233 *optp++ = (mssopt >> 8) & 0xff; 1234 *optp++ = mssopt & 0xff; 1235 1236 if (sc->sc_flags & SCF_WINSCALE) { 1237 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | 1238 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 1239 sc->sc_request_r_scale); 1240 optp += 4; 1241 } 1242 1243 if (sc->sc_flags & SCF_TIMESTAMP) { 1244 u_int32_t *lp = (u_int32_t *)(optp); 1245 1246 /* Form timestamp option as shown in appendix A of RFC 1323. */ 1247 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 1248 *lp++ = htonl(ticks); 1249 *lp = htonl(sc->sc_tsrecent); 1250 optp += TCPOLEN_TSTAMP_APPA; 1251 } 1252 1253 #ifdef TCP_SIGNATURE 1254 /* 1255 * Handle TCP-MD5 passive opener response. 1256 */ 1257 if (sc->sc_flags & SCF_SIGNATURE) { 1258 u_int8_t *bp = optp; 1259 int i; 1260 1261 *bp++ = TCPOPT_SIGNATURE; 1262 *bp++ = TCPOLEN_SIGNATURE; 1263 for (i = 0; i < TCP_SIGLEN; i++) 1264 *bp++ = 0; 1265 tcpsignature_compute(m, 0, optlen, 1266 optp + 2, IPSEC_DIR_OUTBOUND); 1267 *bp++ = TCPOPT_NOP; 1268 *bp++ = TCPOPT_EOL; 1269 optp += TCPOLEN_SIGNATURE + 2; 1270 } 1271 #endif /* TCP_SIGNATURE */ 1272 1273 if (sc->sc_flags & SCF_SACK_PERMITTED) { 1274 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); 1275 optp += TCPOLEN_SACK_PERMITTED_ALIGNED; 1276 } 1277 1278 no_options: 1279 if (isipv6) { 1280 struct route_in6 *ro6 = &sc->sc_route6; 1281 1282 th->th_sum = 0; 1283 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); 1284 ip6->ip6_hlim = in6_selecthlim(NULL, 1285 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); 1286 error = ip6_output(m, NULL, ro6, 0, NULL, NULL, 1287 sc->sc_tp->t_inpcb); 1288 } else { 1289 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1290 htons(tlen - hlen + IPPROTO_TCP)); 1291 m->m_pkthdr.csum_flags = CSUM_TCP; 1292 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1293 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 1294 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb); 1295 } 1296 return (error); 1297 } 1298 1299 /* 1300 * cookie layers: 1301 * 1302 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 1303 * | peer iss | 1304 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .| 1305 * | 0 |(A)| | 1306 * (A): peer mss index 1307 */ 1308 1309 /* 1310 * The values below are chosen to minimize the size of the tcp_secret 1311 * table, as well as providing roughly a 16 second lifetime for the cookie. 1312 */ 1313 1314 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */ 1315 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */ 1316 1317 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1) 1318 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS) 1319 #define SYNCOOKIE_TIMEOUT \ 1320 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT)) 1321 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK) 1322 1323 static struct { 1324 u_int32_t ts_secbits[4]; 1325 u_int ts_expire; 1326 } tcp_secret[SYNCOOKIE_NSECRETS]; 1327 1328 static int tcp_msstab[] = { 0, 536, 1460, 8960 }; 1329 1330 static MD5_CTX syn_ctx; 1331 1332 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v)) 1333 1334 struct md5_add { 1335 u_int32_t laddr, faddr; 1336 u_int32_t secbits[4]; 1337 u_int16_t lport, fport; 1338 }; 1339 1340 #ifdef CTASSERT 1341 CTASSERT(sizeof(struct md5_add) == 28); 1342 #endif 1343 1344 /* 1345 * Consider the problem of a recreated (and retransmitted) cookie. If the 1346 * original SYN was accepted, the connection is established. The second 1347 * SYN is inflight, and if it arrives with an ISN that falls within the 1348 * receive window, the connection is killed. 1349 * 1350 * However, since cookies have other problems, this may not be worth 1351 * worrying about. 1352 */ 1353 1354 static u_int32_t 1355 syncookie_generate(struct syncache *sc) 1356 { 1357 u_int32_t md5_buffer[4]; 1358 u_int32_t data; 1359 int idx, i; 1360 struct md5_add add; 1361 #ifdef INET6 1362 const boolean_t isipv6 = sc->sc_inc.inc_isipv6; 1363 #else 1364 const boolean_t isipv6 = FALSE; 1365 #endif 1366 1367 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK; 1368 if (tcp_secret[idx].ts_expire < ticks) { 1369 for (i = 0; i < 4; i++) 1370 tcp_secret[idx].ts_secbits[i] = karc4random(); 1371 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT; 1372 } 1373 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--) 1374 if (tcp_msstab[data] <= sc->sc_peer_mss) 1375 break; 1376 data = (data << SYNCOOKIE_WNDBITS) | idx; 1377 data ^= sc->sc_irs; /* peer's iss */ 1378 MD5Init(&syn_ctx); 1379 if (isipv6) { 1380 MD5Add(sc->sc_inc.inc6_laddr); 1381 MD5Add(sc->sc_inc.inc6_faddr); 1382 add.laddr = 0; 1383 add.faddr = 0; 1384 } else { 1385 add.laddr = sc->sc_inc.inc_laddr.s_addr; 1386 add.faddr = sc->sc_inc.inc_faddr.s_addr; 1387 } 1388 add.lport = sc->sc_inc.inc_lport; 1389 add.fport = sc->sc_inc.inc_fport; 1390 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1391 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1392 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1393 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1394 MD5Add(add); 1395 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1396 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK); 1397 return (data); 1398 } 1399 1400 static struct syncache * 1401 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so) 1402 { 1403 u_int32_t md5_buffer[4]; 1404 struct syncache *sc; 1405 u_int32_t data; 1406 int wnd, idx; 1407 struct md5_add add; 1408 1409 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */ 1410 idx = data & SYNCOOKIE_WNDMASK; 1411 if (tcp_secret[idx].ts_expire < ticks || 1412 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks) 1413 return (NULL); 1414 MD5Init(&syn_ctx); 1415 #ifdef INET6 1416 if (inc->inc_isipv6) { 1417 MD5Add(inc->inc6_laddr); 1418 MD5Add(inc->inc6_faddr); 1419 add.laddr = 0; 1420 add.faddr = 0; 1421 } else 1422 #endif 1423 { 1424 add.laddr = inc->inc_laddr.s_addr; 1425 add.faddr = inc->inc_faddr.s_addr; 1426 } 1427 add.lport = inc->inc_lport; 1428 add.fport = inc->inc_fport; 1429 add.secbits[0] = tcp_secret[idx].ts_secbits[0]; 1430 add.secbits[1] = tcp_secret[idx].ts_secbits[1]; 1431 add.secbits[2] = tcp_secret[idx].ts_secbits[2]; 1432 add.secbits[3] = tcp_secret[idx].ts_secbits[3]; 1433 MD5Add(add); 1434 MD5Final((u_char *)&md5_buffer, &syn_ctx); 1435 data ^= md5_buffer[0]; 1436 if (data & ~SYNCOOKIE_DATAMASK) 1437 return (NULL); 1438 data = data >> SYNCOOKIE_WNDBITS; 1439 1440 /* 1441 * Fill in the syncache values. 1442 * XXX duplicate code from syncache_add 1443 */ 1444 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO); 1445 sc->sc_ipopts = NULL; 1446 sc->sc_inc.inc_fport = inc->inc_fport; 1447 sc->sc_inc.inc_lport = inc->inc_lport; 1448 #ifdef INET6 1449 sc->sc_inc.inc_isipv6 = inc->inc_isipv6; 1450 if (inc->inc_isipv6) { 1451 sc->sc_inc.inc6_faddr = inc->inc6_faddr; 1452 sc->sc_inc.inc6_laddr = inc->inc6_laddr; 1453 sc->sc_route6.ro_rt = NULL; 1454 } else 1455 #endif 1456 { 1457 sc->sc_inc.inc_faddr = inc->inc_faddr; 1458 sc->sc_inc.inc_laddr = inc->inc_laddr; 1459 sc->sc_route.ro_rt = NULL; 1460 } 1461 sc->sc_irs = th->th_seq - 1; 1462 sc->sc_iss = th->th_ack - 1; 1463 wnd = ssb_space(&so->so_rcv); 1464 wnd = imax(wnd, 0); 1465 wnd = imin(wnd, TCP_MAXWIN); 1466 sc->sc_wnd = wnd; 1467 sc->sc_flags = 0; 1468 sc->sc_rxtslot = 0; 1469 sc->sc_peer_mss = tcp_msstab[data]; 1470 return (sc); 1471 } 1472