HAMMER 60I/Many: Mirroring
[dragonfly.git] / sys / netinet / tcp_syncache.c
blob4032e621c93e995fbb66ec3233ae0897afe37044
1 /*
2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
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.
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.
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.
39 * Copyright (c) 2001 Networks Associates Technologies, Inc.
40 * All rights reserved.
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.
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.
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.
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 1.31 2007/05/24 05:51:29 dillon Exp $
75 #include "opt_inet6.h"
76 #include "opt_ipsec.h"
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>
91 #include <sys/msgport2.h>
92 #include <net/netmsg2.h>
94 #include <net/if.h>
95 #include <net/route.h>
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_var.h>
115 #include <netinet6/tcp6_var.h>
117 #ifdef IPSEC
118 #include <netinet6/ipsec.h>
119 #ifdef INET6
120 #include <netinet6/ipsec6.h>
121 #endif
122 #include <netproto/key/key.h>
123 #endif /*IPSEC*/
125 #ifdef FAST_IPSEC
126 #include <netproto/ipsec/ipsec.h>
127 #ifdef INET6
128 #include <netproto/ipsec/ipsec6.h>
129 #endif
130 #include <netproto/ipsec/key.h>
131 #define IPSEC
132 #endif /*FAST_IPSEC*/
134 #include <vm/vm_zone.h>
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");
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 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 *);
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.
157 #define SYNCACHE_MAXREXMTS 3
159 /* Arbitrary values */
160 #define TCP_SYNCACHE_HASHSIZE 512
161 #define TCP_SYNCACHE_BUCKETLIMIT 30
163 struct netmsg_sc_timer {
164 struct netmsg nm_netmsg;
165 struct msgrec *nm_mrec; /* back pointer to containing msgrec */
168 struct msgrec {
169 struct netmsg_sc_timer msg;
170 lwkt_port_t port; /* constant after init */
171 int slot; /* constant after init */
174 static void syncache_timer_handler(netmsg_t);
176 struct tcp_syncache {
177 struct vm_zone *zone;
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;
185 static struct tcp_syncache tcp_syncache;
187 struct tcp_syncache_percpu {
188 struct syncache_head *hashbase;
189 u_int cache_count;
190 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1];
191 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
192 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1];
194 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU];
196 static struct lwkt_port syncache_null_rport;
198 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
200 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD,
201 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
203 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD,
204 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
206 /* XXX JH */
207 #if 0
208 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
209 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
210 #endif
212 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD,
213 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
215 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
216 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
218 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
220 #define SYNCACHE_HASH(inc, mask) \
221 ((tcp_syncache.hash_secret ^ \
222 (inc)->inc_faddr.s_addr ^ \
223 ((inc)->inc_faddr.s_addr >> 16) ^ \
224 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
226 #define SYNCACHE_HASH6(inc, mask) \
227 ((tcp_syncache.hash_secret ^ \
228 (inc)->inc6_faddr.s6_addr32[0] ^ \
229 (inc)->inc6_faddr.s6_addr32[3] ^ \
230 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
232 #define ENDPTS_EQ(a, b) ( \
233 (a)->ie_fport == (b)->ie_fport && \
234 (a)->ie_lport == (b)->ie_lport && \
235 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
236 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
239 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
241 static __inline void
242 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu,
243 struct syncache *sc, int slot)
245 sc->sc_rxtslot = slot;
246 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot];
247 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq);
248 if (!callout_active(&syncache_percpu->tt_timerq[slot])) {
249 callout_reset(&syncache_percpu->tt_timerq[slot],
250 TCPTV_RTOBASE * tcp_backoff[slot],
251 syncache_timer,
252 &syncache_percpu->mrec[slot]);
256 static void
257 syncache_free(struct syncache *sc)
259 struct rtentry *rt;
260 #ifdef INET6
261 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
262 #else
263 const boolean_t isipv6 = FALSE;
264 #endif
266 if (sc->sc_ipopts)
267 m_free(sc->sc_ipopts);
269 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt;
270 if (rt != NULL) {
272 * If this is the only reference to a protocol-cloned
273 * route, remove it immediately.
275 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1)
276 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
277 rt_mask(rt), rt->rt_flags, NULL);
278 RTFREE(rt);
281 zfree(tcp_syncache.zone, sc);
284 void
285 syncache_init(void)
287 int i, cpu;
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();
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 */
306 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
308 lwkt_initport_replyonly_null(&syncache_null_rport);
310 for (cpu = 0; cpu < ncpus2; cpu++) {
311 struct tcp_syncache_percpu *syncache_percpu;
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);
319 /* Initialize the hash buckets. */
320 for (i = 0; i < tcp_syncache.hashsize; i++) {
321 struct syncache_head *bucket;
323 bucket = &syncache_percpu->hashbase[i];
324 TAILQ_INIT(&bucket->sch_bucket);
325 bucket->sch_length = 0;
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]);
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 &syncache_null_rport, 0,
339 syncache_timer_handler);
344 * Allocate the syncache entries. Allow the zone to allocate one
345 * more entry than cache limit, so a new entry can bump out an
346 * older one.
348 tcp_syncache.zone = zinit("syncache", sizeof(struct syncache),
349 tcp_syncache.cache_limit * ncpus2, ZONE_INTERRUPT, 0);
350 tcp_syncache.cache_limit -= 1;
353 static void
354 syncache_insert(struct syncache *sc, struct syncache_head *sch)
356 struct tcp_syncache_percpu *syncache_percpu;
357 struct syncache *sc2;
358 int i;
360 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
363 * Make sure that we don't overflow the per-bucket
364 * limit or the total cache size limit.
366 if (sch->sch_length >= tcp_syncache.bucket_limit) {
368 * The bucket is full, toss the oldest element.
370 sc2 = TAILQ_FIRST(&sch->sch_bucket);
371 sc2->sc_tp->ts_recent = ticks;
372 syncache_drop(sc2, sch);
373 tcpstat.tcps_sc_bucketoverflow++;
374 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) {
376 * The cache is full. Toss the oldest entry in the
377 * entire cache. This is the front entry in the
378 * first non-empty timer queue with the largest
379 * timeout value.
381 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
382 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]);
383 if (sc2 != NULL)
384 break;
386 sc2->sc_tp->ts_recent = ticks;
387 syncache_drop(sc2, NULL);
388 tcpstat.tcps_sc_cacheoverflow++;
391 /* Initialize the entry's timer. */
392 syncache_timeout(syncache_percpu, sc, 0);
394 /* Put it into the bucket. */
395 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
396 sch->sch_length++;
397 syncache_percpu->cache_count++;
398 tcpstat.tcps_sc_added++;
401 static void
402 syncache_drop(struct syncache *sc, struct syncache_head *sch)
404 struct tcp_syncache_percpu *syncache_percpu;
405 #ifdef INET6
406 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
407 #else
408 const boolean_t isipv6 = FALSE;
409 #endif
411 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
413 if (sch == NULL) {
414 if (isipv6) {
415 sch = &syncache_percpu->hashbase[
416 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
417 } else {
418 sch = &syncache_percpu->hashbase[
419 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
423 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
424 sch->sch_length--;
425 syncache_percpu->cache_count--;
428 * Remove the entry from the syncache timer/timeout queue. Note
429 * that we do not try to stop any running timer since we do not know
430 * whether the timer's message is in-transit or not. Since timeouts
431 * are fairly long, taking an unneeded callout does not detrimentally
432 * effect performance.
434 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq);
436 syncache_free(sc);
440 * Place a timeout message on the TCP thread's message queue.
441 * This routine runs in soft interrupt context.
443 * An invariant is for this routine to be called, the callout must
444 * have been active. Note that the callout is not deactivated until
445 * after the message has been processed in syncache_timer_handler() below.
447 static void
448 syncache_timer(void *p)
450 struct netmsg_sc_timer *msg = p;
452 lwkt_sendmsg(msg->nm_mrec->port, &msg->nm_netmsg.nm_lmsg);
456 * Service a timer message queued by timer expiration.
457 * This routine runs in the TCP protocol thread.
459 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
460 * If we have retransmitted an entry the maximum number of times, expire it.
462 * When we finish processing timed-out entries, we restart the timer if there
463 * are any entries still on the queue and deactivate it otherwise. Only after
464 * a timer has been deactivated here can it be restarted by syncache_timeout().
466 static void
467 syncache_timer_handler(netmsg_t netmsg)
469 struct tcp_syncache_percpu *syncache_percpu;
470 struct syncache *sc, *nsc;
471 struct inpcb *inp;
472 int slot;
474 slot = ((struct netmsg_sc_timer *)netmsg)->nm_mrec->slot;
475 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
477 nsc = TAILQ_FIRST(&syncache_percpu->timerq[slot]);
478 while (nsc != NULL) {
479 if (ticks < nsc->sc_rxttime)
480 break; /* finished because timerq sorted by time */
481 sc = nsc;
482 inp = sc->sc_tp->t_inpcb;
483 if (slot == SYNCACHE_MAXREXMTS ||
484 slot >= tcp_syncache.rexmt_limit ||
485 inp->inp_gencnt != sc->sc_inp_gencnt) {
486 nsc = TAILQ_NEXT(sc, sc_timerq);
487 syncache_drop(sc, NULL);
488 tcpstat.tcps_sc_stale++;
489 continue;
492 * syncache_respond() may call back into the syncache to
493 * to modify another entry, so do not obtain the next
494 * entry on the timer chain until it has completed.
496 syncache_respond(sc, NULL);
497 nsc = TAILQ_NEXT(sc, sc_timerq);
498 tcpstat.tcps_sc_retransmitted++;
499 TAILQ_REMOVE(&syncache_percpu->timerq[slot], sc, sc_timerq);
500 syncache_timeout(syncache_percpu, sc, slot + 1);
502 if (nsc != NULL)
503 callout_reset(&syncache_percpu->tt_timerq[slot],
504 nsc->sc_rxttime - ticks, syncache_timer,
505 &syncache_percpu->mrec[slot]);
506 else
507 callout_deactivate(&syncache_percpu->tt_timerq[slot]);
509 lwkt_replymsg(&netmsg->nm_lmsg, 0);
513 * Find an entry in the syncache.
515 struct syncache *
516 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
518 struct tcp_syncache_percpu *syncache_percpu;
519 struct syncache *sc;
520 struct syncache_head *sch;
522 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
523 #ifdef INET6
524 if (inc->inc_isipv6) {
525 sch = &syncache_percpu->hashbase[
526 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
527 *schp = sch;
528 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
529 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
530 return (sc);
531 } else
532 #endif
534 sch = &syncache_percpu->hashbase[
535 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
536 *schp = sch;
537 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
538 #ifdef INET6
539 if (sc->sc_inc.inc_isipv6)
540 continue;
541 #endif
542 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
543 return (sc);
546 return (NULL);
550 * This function is called when we get a RST for a
551 * non-existent connection, so that we can see if the
552 * connection is in the syn cache. If it is, zap it.
554 void
555 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
557 struct syncache *sc;
558 struct syncache_head *sch;
560 sc = syncache_lookup(inc, &sch);
561 if (sc == NULL)
562 return;
564 * If the RST bit is set, check the sequence number to see
565 * if this is a valid reset segment.
566 * RFC 793 page 37:
567 * In all states except SYN-SENT, all reset (RST) segments
568 * are validated by checking their SEQ-fields. A reset is
569 * valid if its sequence number is in the window.
571 * The sequence number in the reset segment is normally an
572 * echo of our outgoing acknowlegement numbers, but some hosts
573 * send a reset with the sequence number at the rightmost edge
574 * of our receive window, and we have to handle this case.
576 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
577 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
578 syncache_drop(sc, sch);
579 tcpstat.tcps_sc_reset++;
583 void
584 syncache_badack(struct in_conninfo *inc)
586 struct syncache *sc;
587 struct syncache_head *sch;
589 sc = syncache_lookup(inc, &sch);
590 if (sc != NULL) {
591 syncache_drop(sc, sch);
592 tcpstat.tcps_sc_badack++;
596 void
597 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
599 struct syncache *sc;
600 struct syncache_head *sch;
602 /* we are called at splnet() here */
603 sc = syncache_lookup(inc, &sch);
604 if (sc == NULL)
605 return;
607 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
608 if (ntohl(th->th_seq) != sc->sc_iss)
609 return;
612 * If we've rertransmitted 3 times and this is our second error,
613 * we remove the entry. Otherwise, we allow it to continue on.
614 * This prevents us from incorrectly nuking an entry during a
615 * spurious network outage.
617 * See tcp_notify().
619 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
620 sc->sc_flags |= SCF_UNREACH;
621 return;
623 syncache_drop(sc, sch);
624 tcpstat.tcps_sc_unreach++;
628 * Build a new TCP socket structure from a syncache entry.
630 static struct socket *
631 syncache_socket(struct syncache *sc, struct socket *lso)
633 struct inpcb *inp = NULL, *linp;
634 struct socket *so;
635 struct tcpcb *tp;
636 #ifdef INET6
637 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
638 #else
639 const boolean_t isipv6 = FALSE;
640 #endif
643 * Ok, create the full blown connection, and set things up
644 * as they would have been set up if we had created the
645 * connection when the SYN arrived. If we can't create
646 * the connection, abort it.
648 so = sonewconn(lso, SS_ISCONNECTED);
649 if (so == NULL) {
651 * Drop the connection; we will send a RST if the peer
652 * retransmits the ACK,
654 tcpstat.tcps_listendrop++;
655 goto abort;
658 inp = so->so_pcb;
661 * Insert new socket into hash list.
663 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
664 if (isipv6) {
665 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
666 } else {
667 #ifdef INET6
668 inp->inp_vflag &= ~INP_IPV6;
669 inp->inp_vflag |= INP_IPV4;
670 #endif
671 inp->inp_laddr = sc->sc_inc.inc_laddr;
673 inp->inp_lport = sc->sc_inc.inc_lport;
674 if (in_pcbinsporthash(inp) != 0) {
676 * Undo the assignments above if we failed to
677 * put the PCB on the hash lists.
679 if (isipv6)
680 inp->in6p_laddr = kin6addr_any;
681 else
682 inp->inp_laddr.s_addr = INADDR_ANY;
683 inp->inp_lport = 0;
684 goto abort;
686 linp = so->so_pcb;
687 #ifdef IPSEC
688 /* copy old policy into new socket's */
689 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp))
690 kprintf("syncache_expand: could not copy policy\n");
691 #endif
692 if (isipv6) {
693 struct in6_addr laddr6;
694 struct sockaddr_in6 sin6;
696 * Inherit socket options from the listening socket.
697 * Note that in6p_inputopts are not (and should not be)
698 * copied, since it stores previously received options and is
699 * used to detect if each new option is different than the
700 * previous one and hence should be passed to a user.
701 * If we copied in6p_inputopts, a user would not be able to
702 * receive options just after calling the accept system call.
704 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS;
705 if (linp->in6p_outputopts)
706 inp->in6p_outputopts =
707 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT);
708 inp->in6p_route = sc->sc_route6;
709 sc->sc_route6.ro_rt = NULL;
711 sin6.sin6_family = AF_INET6;
712 sin6.sin6_len = sizeof sin6;
713 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
714 sin6.sin6_port = sc->sc_inc.inc_fport;
715 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
716 laddr6 = inp->in6p_laddr;
717 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
718 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
719 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) {
720 inp->in6p_laddr = laddr6;
721 goto abort;
723 } else {
724 struct in_addr laddr;
725 struct sockaddr_in sin;
727 inp->inp_options = ip_srcroute();
728 if (inp->inp_options == NULL) {
729 inp->inp_options = sc->sc_ipopts;
730 sc->sc_ipopts = NULL;
732 inp->inp_route = sc->sc_route;
733 sc->sc_route.ro_rt = NULL;
735 sin.sin_family = AF_INET;
736 sin.sin_len = sizeof sin;
737 sin.sin_addr = sc->sc_inc.inc_faddr;
738 sin.sin_port = sc->sc_inc.inc_fport;
739 bzero(sin.sin_zero, sizeof sin.sin_zero);
740 laddr = inp->inp_laddr;
741 if (inp->inp_laddr.s_addr == INADDR_ANY)
742 inp->inp_laddr = sc->sc_inc.inc_laddr;
743 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) {
744 inp->inp_laddr = laddr;
745 goto abort;
749 tp = intotcpcb(inp);
750 tp->t_state = TCPS_SYN_RECEIVED;
751 tp->iss = sc->sc_iss;
752 tp->irs = sc->sc_irs;
753 tcp_rcvseqinit(tp);
754 tcp_sendseqinit(tp);
755 tp->snd_wl1 = sc->sc_irs;
756 tp->rcv_up = sc->sc_irs + 1;
757 tp->rcv_wnd = sc->sc_wnd;
758 tp->rcv_adv += tp->rcv_wnd;
760 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
761 if (sc->sc_flags & SCF_NOOPT)
762 tp->t_flags |= TF_NOOPT;
763 if (sc->sc_flags & SCF_WINSCALE) {
764 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE;
765 tp->requested_s_scale = sc->sc_requested_s_scale;
766 tp->request_r_scale = sc->sc_request_r_scale;
768 if (sc->sc_flags & SCF_TIMESTAMP) {
769 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP;
770 tp->ts_recent = sc->sc_tsrecent;
771 tp->ts_recent_age = ticks;
773 if (sc->sc_flags & SCF_CC) {
775 * Initialization of the tcpcb for transaction;
776 * set SND.WND = SEG.WND,
777 * initialize CCsend and CCrecv.
779 tp->t_flags |= TF_REQ_CC | TF_RCVD_CC;
780 tp->cc_send = sc->sc_cc_send;
781 tp->cc_recv = sc->sc_cc_recv;
783 if (sc->sc_flags & SCF_SACK_PERMITTED)
784 tp->t_flags |= TF_SACK_PERMITTED;
786 tcp_mss(tp, sc->sc_peer_mss);
789 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
791 if (sc->sc_rxtslot != 0)
792 tp->snd_cwnd = tp->t_maxseg;
793 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
795 tcpstat.tcps_accepts++;
796 return (so);
798 abort:
799 if (so != NULL)
800 soabort(so);
801 return (NULL);
805 * This function gets called when we receive an ACK for a
806 * socket in the LISTEN state. We look up the connection
807 * in the syncache, and if its there, we pull it out of
808 * the cache and turn it into a full-blown connection in
809 * the SYN-RECEIVED state.
812 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop,
813 struct mbuf *m)
815 struct syncache *sc;
816 struct syncache_head *sch;
817 struct socket *so;
819 sc = syncache_lookup(inc, &sch);
820 if (sc == NULL) {
822 * There is no syncache entry, so see if this ACK is
823 * a returning syncookie. To do this, first:
824 * A. See if this socket has had a syncache entry dropped in
825 * the past. We don't want to accept a bogus syncookie
826 * if we've never received a SYN.
827 * B. check that the syncookie is valid. If it is, then
828 * cobble up a fake syncache entry, and return.
830 if (!tcp_syncookies)
831 return (0);
832 sc = syncookie_lookup(inc, th, *sop);
833 if (sc == NULL)
834 return (0);
835 sch = NULL;
836 tcpstat.tcps_sc_recvcookie++;
840 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
842 if (th->th_ack != sc->sc_iss + 1)
843 return (0);
845 so = syncache_socket(sc, *sop);
846 if (so == NULL) {
847 #if 0
848 resetandabort:
849 /* XXXjlemon check this - is this correct? */
850 tcp_respond(NULL, m, m, th,
851 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK);
852 #endif
853 m_freem(m); /* XXX only needed for above */
854 tcpstat.tcps_sc_aborted++;
855 } else {
856 tcpstat.tcps_sc_completed++;
858 if (sch == NULL)
859 syncache_free(sc);
860 else
861 syncache_drop(sc, sch);
862 *sop = so;
863 return (1);
867 * Given a LISTEN socket and an inbound SYN request, add
868 * this to the syn cache, and send back a segment:
869 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
870 * to the source.
872 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
873 * Doing so would require that we hold onto the data and deliver it
874 * to the application. However, if we are the target of a SYN-flood
875 * DoS attack, an attacker could send data which would eventually
876 * consume all available buffer space if it were ACKed. By not ACKing
877 * the data, we avoid this DoS scenario.
880 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
881 struct socket **sop, struct mbuf *m)
883 struct tcp_syncache_percpu *syncache_percpu;
884 struct tcpcb *tp;
885 struct socket *so;
886 struct syncache *sc = NULL;
887 struct syncache_head *sch;
888 struct mbuf *ipopts = NULL;
889 struct rmxp_tao *taop;
890 int win;
892 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
893 so = *sop;
894 tp = sototcpcb(so);
897 * Remember the IP options, if any.
899 #ifdef INET6
900 if (!inc->inc_isipv6)
901 #endif
902 ipopts = ip_srcroute();
905 * See if we already have an entry for this connection.
906 * If we do, resend the SYN,ACK, and reset the retransmit timer.
908 * XXX
909 * The syncache should be re-initialized with the contents
910 * of the new SYN which may have different options.
912 sc = syncache_lookup(inc, &sch);
913 if (sc != NULL) {
914 tcpstat.tcps_sc_dupsyn++;
915 if (ipopts) {
917 * If we were remembering a previous source route,
918 * forget it and use the new one we've been given.
920 if (sc->sc_ipopts)
921 m_free(sc->sc_ipopts);
922 sc->sc_ipopts = ipopts;
925 * Update timestamp if present.
927 if (sc->sc_flags & SCF_TIMESTAMP)
928 sc->sc_tsrecent = to->to_tsval;
930 /* Just update the TOF_SACK_PERMITTED for now. */
931 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
932 sc->sc_flags |= SCF_SACK_PERMITTED;
933 else
934 sc->sc_flags &= ~SCF_SACK_PERMITTED;
937 * PCB may have changed, pick up new values.
939 sc->sc_tp = tp;
940 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
941 if (syncache_respond(sc, m) == 0) {
942 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot],
943 sc, sc_timerq);
944 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot);
945 tcpstat.tcps_sndacks++;
946 tcpstat.tcps_sndtotal++;
948 *sop = NULL;
949 return (1);
953 * This allocation is guaranteed to succeed because we
954 * preallocate one more syncache entry than cache_limit.
956 sc = zalloc(tcp_syncache.zone);
959 * Fill in the syncache values.
961 sc->sc_tp = tp;
962 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
963 sc->sc_ipopts = ipopts;
964 sc->sc_inc.inc_fport = inc->inc_fport;
965 sc->sc_inc.inc_lport = inc->inc_lport;
966 #ifdef INET6
967 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
968 if (inc->inc_isipv6) {
969 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
970 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
971 sc->sc_route6.ro_rt = NULL;
972 } else
973 #endif
975 sc->sc_inc.inc_faddr = inc->inc_faddr;
976 sc->sc_inc.inc_laddr = inc->inc_laddr;
977 sc->sc_route.ro_rt = NULL;
979 sc->sc_irs = th->th_seq;
980 sc->sc_flags = 0;
981 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
982 if (tcp_syncookies)
983 sc->sc_iss = syncookie_generate(sc);
984 else
985 sc->sc_iss = karc4random();
987 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */
988 win = ssb_space(&so->so_rcv);
989 win = imax(win, 0);
990 win = imin(win, TCP_MAXWIN);
991 sc->sc_wnd = win;
993 if (tcp_do_rfc1323) {
995 * A timestamp received in a SYN makes
996 * it ok to send timestamp requests and replies.
998 if (to->to_flags & TOF_TS) {
999 sc->sc_tsrecent = to->to_tsval;
1000 sc->sc_flags |= SCF_TIMESTAMP;
1002 if (to->to_flags & TOF_SCALE) {
1003 int wscale = 0;
1005 /* Compute proper scaling value from buffer space */
1006 while (wscale < TCP_MAX_WINSHIFT &&
1007 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat)
1008 wscale++;
1009 sc->sc_request_r_scale = wscale;
1010 sc->sc_requested_s_scale = to->to_requested_s_scale;
1011 sc->sc_flags |= SCF_WINSCALE;
1014 if (tcp_do_rfc1644) {
1016 * A CC or CC.new option received in a SYN makes
1017 * it ok to send CC in subsequent segments.
1019 if (to->to_flags & (TOF_CC | TOF_CCNEW)) {
1020 sc->sc_cc_recv = to->to_cc;
1021 sc->sc_cc_send = CC_INC(tcp_ccgen);
1022 sc->sc_flags |= SCF_CC;
1025 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
1026 sc->sc_flags |= SCF_SACK_PERMITTED;
1027 if (tp->t_flags & TF_NOOPT)
1028 sc->sc_flags = SCF_NOOPT;
1031 * XXX
1032 * We have the option here of not doing TAO (even if the segment
1033 * qualifies) and instead fall back to a normal 3WHS via the syncache.
1034 * This allows us to apply synflood protection to TAO-qualifying SYNs
1035 * also. However, there should be a hueristic to determine when to
1036 * do this, and is not present at the moment.
1040 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1041 * - compare SEG.CC against cached CC from the same host, if any.
1042 * - if SEG.CC > chached value, SYN must be new and is accepted
1043 * immediately: save new CC in the cache, mark the socket
1044 * connected, enter ESTABLISHED state, turn on flag to
1045 * send a SYN in the next segment.
1046 * A virtual advertised window is set in rcv_adv to
1047 * initialize SWS prevention. Then enter normal segment
1048 * processing: drop SYN, process data and FIN.
1049 * - otherwise do a normal 3-way handshake.
1051 taop = tcp_gettaocache(&sc->sc_inc);
1052 if (to->to_flags & TOF_CC) {
1053 if ((tp->t_flags & TF_NOPUSH) &&
1054 sc->sc_flags & SCF_CC &&
1055 taop != NULL && taop->tao_cc != 0 &&
1056 CC_GT(to->to_cc, taop->tao_cc)) {
1057 sc->sc_rxtslot = 0;
1058 so = syncache_socket(sc, *sop);
1059 if (so != NULL) {
1060 taop->tao_cc = to->to_cc;
1061 *sop = so;
1063 syncache_free(sc);
1064 return (so != NULL);
1066 } else {
1068 * No CC option, but maybe CC.NEW: invalidate cached value.
1070 if (taop != NULL)
1071 taop->tao_cc = 0;
1074 * TAO test failed or there was no CC option,
1075 * do a standard 3-way handshake.
1077 if (syncache_respond(sc, m) == 0) {
1078 syncache_insert(sc, sch);
1079 tcpstat.tcps_sndacks++;
1080 tcpstat.tcps_sndtotal++;
1081 } else {
1082 syncache_free(sc);
1083 tcpstat.tcps_sc_dropped++;
1085 *sop = NULL;
1086 return (1);
1089 static int
1090 syncache_respond(struct syncache *sc, struct mbuf *m)
1092 u_int8_t *optp;
1093 int optlen, error;
1094 u_int16_t tlen, hlen, mssopt;
1095 struct ip *ip = NULL;
1096 struct rtentry *rt;
1097 struct tcphdr *th;
1098 struct ip6_hdr *ip6 = NULL;
1099 #ifdef INET6
1100 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1101 #else
1102 const boolean_t isipv6 = FALSE;
1103 #endif
1105 if (isipv6) {
1106 rt = tcp_rtlookup6(&sc->sc_inc);
1107 if (rt != NULL)
1108 mssopt = rt->rt_ifp->if_mtu -
1109 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr));
1110 else
1111 mssopt = tcp_v6mssdflt;
1112 hlen = sizeof(struct ip6_hdr);
1113 } else {
1114 rt = tcp_rtlookup(&sc->sc_inc);
1115 if (rt != NULL)
1116 mssopt = rt->rt_ifp->if_mtu -
1117 (sizeof(struct ip) + sizeof(struct tcphdr));
1118 else
1119 mssopt = tcp_mssdflt;
1120 hlen = sizeof(struct ip);
1123 /* Compute the size of the TCP options. */
1124 if (sc->sc_flags & SCF_NOOPT) {
1125 optlen = 0;
1126 } else {
1127 optlen = TCPOLEN_MAXSEG +
1128 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1129 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1130 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0) +
1131 ((sc->sc_flags & SCF_SACK_PERMITTED) ?
1132 TCPOLEN_SACK_PERMITTED_ALIGNED : 0);
1134 tlen = hlen + sizeof(struct tcphdr) + optlen;
1137 * XXX
1138 * assume that the entire packet will fit in a header mbuf
1140 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1143 * XXX shouldn't this reuse the mbuf if possible ?
1144 * Create the IP+TCP header from scratch.
1146 if (m)
1147 m_freem(m);
1149 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
1150 if (m == NULL)
1151 return (ENOBUFS);
1152 m->m_data += max_linkhdr;
1153 m->m_len = tlen;
1154 m->m_pkthdr.len = tlen;
1155 m->m_pkthdr.rcvif = NULL;
1157 if (isipv6) {
1158 ip6 = mtod(m, struct ip6_hdr *);
1159 ip6->ip6_vfc = IPV6_VERSION;
1160 ip6->ip6_nxt = IPPROTO_TCP;
1161 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1162 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1163 ip6->ip6_plen = htons(tlen - hlen);
1164 /* ip6_hlim is set after checksum */
1165 /* ip6_flow = ??? */
1167 th = (struct tcphdr *)(ip6 + 1);
1168 } else {
1169 ip = mtod(m, struct ip *);
1170 ip->ip_v = IPVERSION;
1171 ip->ip_hl = sizeof(struct ip) >> 2;
1172 ip->ip_len = tlen;
1173 ip->ip_id = 0;
1174 ip->ip_off = 0;
1175 ip->ip_sum = 0;
1176 ip->ip_p = IPPROTO_TCP;
1177 ip->ip_src = sc->sc_inc.inc_laddr;
1178 ip->ip_dst = sc->sc_inc.inc_faddr;
1179 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */
1180 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */
1183 * See if we should do MTU discovery. Route lookups are
1184 * expensive, so we will only unset the DF bit if:
1186 * 1) path_mtu_discovery is disabled
1187 * 2) the SCF_UNREACH flag has been set
1189 if (path_mtu_discovery
1190 && ((sc->sc_flags & SCF_UNREACH) == 0)) {
1191 ip->ip_off |= IP_DF;
1194 th = (struct tcphdr *)(ip + 1);
1196 th->th_sport = sc->sc_inc.inc_lport;
1197 th->th_dport = sc->sc_inc.inc_fport;
1199 th->th_seq = htonl(sc->sc_iss);
1200 th->th_ack = htonl(sc->sc_irs + 1);
1201 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1202 th->th_x2 = 0;
1203 th->th_flags = TH_SYN | TH_ACK;
1204 th->th_win = htons(sc->sc_wnd);
1205 th->th_urp = 0;
1207 /* Tack on the TCP options. */
1208 if (optlen == 0)
1209 goto no_options;
1210 optp = (u_int8_t *)(th + 1);
1211 *optp++ = TCPOPT_MAXSEG;
1212 *optp++ = TCPOLEN_MAXSEG;
1213 *optp++ = (mssopt >> 8) & 0xff;
1214 *optp++ = mssopt & 0xff;
1216 if (sc->sc_flags & SCF_WINSCALE) {
1217 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1218 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1219 sc->sc_request_r_scale);
1220 optp += 4;
1223 if (sc->sc_flags & SCF_TIMESTAMP) {
1224 u_int32_t *lp = (u_int32_t *)(optp);
1226 /* Form timestamp option as shown in appendix A of RFC 1323. */
1227 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1228 *lp++ = htonl(ticks);
1229 *lp = htonl(sc->sc_tsrecent);
1230 optp += TCPOLEN_TSTAMP_APPA;
1234 * Send CC and CC.echo if we received CC from our peer.
1236 if (sc->sc_flags & SCF_CC) {
1237 u_int32_t *lp = (u_int32_t *)(optp);
1239 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
1240 *lp++ = htonl(sc->sc_cc_send);
1241 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
1242 *lp = htonl(sc->sc_cc_recv);
1243 optp += TCPOLEN_CC_APPA * 2;
1246 if (sc->sc_flags & SCF_SACK_PERMITTED) {
1247 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
1248 optp += TCPOLEN_SACK_PERMITTED_ALIGNED;
1251 no_options:
1252 if (isipv6) {
1253 struct route_in6 *ro6 = &sc->sc_route6;
1255 th->th_sum = 0;
1256 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1257 ip6->ip6_hlim = in6_selecthlim(NULL,
1258 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
1259 error = ip6_output(m, NULL, ro6, 0, NULL, NULL,
1260 sc->sc_tp->t_inpcb);
1261 } else {
1262 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1263 htons(tlen - hlen + IPPROTO_TCP));
1264 m->m_pkthdr.csum_flags = CSUM_TCP;
1265 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1266 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL,
1267 sc->sc_tp->t_inpcb);
1269 return (error);
1273 * cookie layers:
1275 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1276 * | peer iss |
1277 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1278 * | 0 |(A)| |
1279 * (A): peer mss index
1283 * The values below are chosen to minimize the size of the tcp_secret
1284 * table, as well as providing roughly a 16 second lifetime for the cookie.
1287 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1288 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1290 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1291 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1292 #define SYNCOOKIE_TIMEOUT \
1293 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1294 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1296 static struct {
1297 u_int32_t ts_secbits[4];
1298 u_int ts_expire;
1299 } tcp_secret[SYNCOOKIE_NSECRETS];
1301 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1303 static MD5_CTX syn_ctx;
1305 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1307 struct md5_add {
1308 u_int32_t laddr, faddr;
1309 u_int32_t secbits[4];
1310 u_int16_t lport, fport;
1313 #ifdef CTASSERT
1314 CTASSERT(sizeof(struct md5_add) == 28);
1315 #endif
1318 * Consider the problem of a recreated (and retransmitted) cookie. If the
1319 * original SYN was accepted, the connection is established. The second
1320 * SYN is inflight, and if it arrives with an ISN that falls within the
1321 * receive window, the connection is killed.
1323 * However, since cookies have other problems, this may not be worth
1324 * worrying about.
1327 static u_int32_t
1328 syncookie_generate(struct syncache *sc)
1330 u_int32_t md5_buffer[4];
1331 u_int32_t data;
1332 int idx, i;
1333 struct md5_add add;
1334 #ifdef INET6
1335 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1336 #else
1337 const boolean_t isipv6 = FALSE;
1338 #endif
1340 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1341 if (tcp_secret[idx].ts_expire < ticks) {
1342 for (i = 0; i < 4; i++)
1343 tcp_secret[idx].ts_secbits[i] = karc4random();
1344 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1346 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1347 if (tcp_msstab[data] <= sc->sc_peer_mss)
1348 break;
1349 data = (data << SYNCOOKIE_WNDBITS) | idx;
1350 data ^= sc->sc_irs; /* peer's iss */
1351 MD5Init(&syn_ctx);
1352 if (isipv6) {
1353 MD5Add(sc->sc_inc.inc6_laddr);
1354 MD5Add(sc->sc_inc.inc6_faddr);
1355 add.laddr = 0;
1356 add.faddr = 0;
1357 } else {
1358 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1359 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1361 add.lport = sc->sc_inc.inc_lport;
1362 add.fport = sc->sc_inc.inc_fport;
1363 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1364 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1365 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1366 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1367 MD5Add(add);
1368 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1369 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1370 return (data);
1373 static struct syncache *
1374 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so)
1376 u_int32_t md5_buffer[4];
1377 struct syncache *sc;
1378 u_int32_t data;
1379 int wnd, idx;
1380 struct md5_add add;
1382 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1383 idx = data & SYNCOOKIE_WNDMASK;
1384 if (tcp_secret[idx].ts_expire < ticks ||
1385 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1386 return (NULL);
1387 MD5Init(&syn_ctx);
1388 #ifdef INET6
1389 if (inc->inc_isipv6) {
1390 MD5Add(inc->inc6_laddr);
1391 MD5Add(inc->inc6_faddr);
1392 add.laddr = 0;
1393 add.faddr = 0;
1394 } else
1395 #endif
1397 add.laddr = inc->inc_laddr.s_addr;
1398 add.faddr = inc->inc_faddr.s_addr;
1400 add.lport = inc->inc_lport;
1401 add.fport = inc->inc_fport;
1402 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1403 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1404 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1405 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1406 MD5Add(add);
1407 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1408 data ^= md5_buffer[0];
1409 if (data & ~SYNCOOKIE_DATAMASK)
1410 return (NULL);
1411 data = data >> SYNCOOKIE_WNDBITS;
1414 * This allocation is guaranteed to succeed because we
1415 * preallocate one more syncache entry than cache_limit.
1417 sc = zalloc(tcp_syncache.zone);
1420 * Fill in the syncache values.
1421 * XXX duplicate code from syncache_add
1423 sc->sc_ipopts = NULL;
1424 sc->sc_inc.inc_fport = inc->inc_fport;
1425 sc->sc_inc.inc_lport = inc->inc_lport;
1426 #ifdef INET6
1427 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1428 if (inc->inc_isipv6) {
1429 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1430 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1431 sc->sc_route6.ro_rt = NULL;
1432 } else
1433 #endif
1435 sc->sc_inc.inc_faddr = inc->inc_faddr;
1436 sc->sc_inc.inc_laddr = inc->inc_laddr;
1437 sc->sc_route.ro_rt = NULL;
1439 sc->sc_irs = th->th_seq - 1;
1440 sc->sc_iss = th->th_ack - 1;
1441 wnd = ssb_space(&so->so_rcv);
1442 wnd = imax(wnd, 0);
1443 wnd = imin(wnd, TCP_MAXWIN);
1444 sc->sc_wnd = wnd;
1445 sc->sc_flags = 0;
1446 sc->sc_rxtslot = 0;
1447 sc->sc_peer_mss = tcp_msstab[data];
1448 return (sc);