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
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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
35 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
37 * License terms: all terms for the DragonFly license above plus the following:
39 * 4. All advertising materials mentioning features or use of this software
40 * must display the following acknowledgement:
42 * This product includes software developed by Jeffrey M. Hsu
43 * for the DragonFly Project.
45 * This requirement may be waived with permission from Jeffrey Hsu.
46 * This requirement will sunset and may be removed on July 8 2005,
47 * after which the standard DragonFly license (as shown above) will
52 * All advertising materials mentioning features or use of this software
53 * must display the following acknowledgement:
54 * This product includes software developed by Jeffrey M. Hsu.
56 * Copyright (c) 2001 Networks Associates Technologies, Inc.
57 * All rights reserved.
59 * This software was developed for the FreeBSD Project by Jonathan Lemon
60 * and NAI Labs, the Security Research Division of Network Associates, Inc.
61 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
62 * DARPA CHATS research program.
64 * Redistribution and use in source and binary forms, with or without
65 * modification, are permitted provided that the following conditions
67 * 1. Redistributions of source code must retain the above copyright
68 * notice, this list of conditions and the following disclaimer.
69 * 2. Redistributions in binary form must reproduce the above copyright
70 * notice, this list of conditions and the following disclaimer in the
71 * documentation and/or other materials provided with the distribution.
72 * 3. The name of the author may not be used to endorse or promote
73 * products derived from this software without specific prior written
76 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
77 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
78 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
79 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
80 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
81 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
82 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
83 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
84 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
85 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
88 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $
89 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.26 2006/09/03 18:29:17 dillon Exp $
92 #include "opt_inet6.h"
93 #include "opt_ipsec.h"
95 #include <sys/param.h>
96 #include <sys/systm.h>
97 #include <sys/kernel.h>
98 #include <sys/sysctl.h>
99 #include <sys/malloc.h>
100 #include <sys/mbuf.h>
102 #include <sys/proc.h> /* for proc0 declaration */
103 #include <sys/random.h>
104 #include <sys/socket.h>
105 #include <sys/socketvar.h>
106 #include <sys/in_cksum.h>
108 #include <sys/msgport2.h>
111 #include <net/route.h>
113 #include <netinet/in.h>
114 #include <netinet/in_systm.h>
115 #include <netinet/ip.h>
116 #include <netinet/in_var.h>
117 #include <netinet/in_pcb.h>
118 #include <netinet/ip_var.h>
119 #include <netinet/ip6.h>
121 #include <netinet/icmp6.h>
122 #include <netinet6/nd6.h>
124 #include <netinet6/ip6_var.h>
125 #include <netinet6/in6_pcb.h>
126 #include <netinet/tcp.h>
127 #include <netinet/tcp_fsm.h>
128 #include <netinet/tcp_seq.h>
129 #include <netinet/tcp_timer.h>
130 #include <netinet/tcp_var.h>
131 #include <netinet6/tcp6_var.h>
134 #include <netinet6/ipsec.h>
136 #include <netinet6/ipsec6.h>
138 #include <netproto/key/key.h>
142 #include <netproto/ipsec/ipsec.h>
144 #include <netproto/ipsec/ipsec6.h>
146 #include <netproto/ipsec/key.h>
148 #endif /*FAST_IPSEC*/
150 #include <vm/vm_zone.h>
152 static int tcp_syncookies = 1;
153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
155 "Use TCP SYN cookies if the syncache overflows");
157 static void syncache_drop(struct syncache *, struct syncache_head *);
158 static void syncache_free(struct syncache *);
159 static void syncache_insert(struct syncache *, struct syncache_head *);
160 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
161 static int syncache_respond(struct syncache *, struct mbuf *);
162 static struct socket *syncache_socket(struct syncache *, struct socket *);
163 static void syncache_timer(void *);
164 static u_int32_t syncookie_generate(struct syncache *);
165 static struct syncache *syncookie_lookup(struct in_conninfo *,
166 struct tcphdr *, struct socket *);
169 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
170 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
171 * the odds are that the user has given up attempting to connect by then.
173 #define SYNCACHE_MAXREXMTS 3
175 /* Arbitrary values */
176 #define TCP_SYNCACHE_HASHSIZE 512
177 #define TCP_SYNCACHE_BUCKETLIMIT 30
179 struct netmsg_sc_timer {
180 struct lwkt_msg nm_lmsg;
181 struct msgrec *nm_mrec; /* back pointer to containing msgrec */
185 struct netmsg_sc_timer msg;
186 lwkt_port_t port; /* constant after init */
187 int slot; /* constant after init */
190 static int syncache_timer_handler(lwkt_msg_t);
192 struct tcp_syncache {
193 struct vm_zone *zone;
201 static struct tcp_syncache tcp_syncache;
203 struct tcp_syncache_percpu {
204 struct syncache_head *hashbase;
206 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1];
207 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
208 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1];
210 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU];
212 static struct lwkt_port syncache_null_rport;
214 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
216 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD,
217 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
219 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD,
220 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
224 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
225 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
228 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD,
229 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
231 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
232 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
234 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
236 #define SYNCACHE_HASH(inc, mask) \
237 ((tcp_syncache.hash_secret ^ \
238 (inc)->inc_faddr.s_addr ^ \
239 ((inc)->inc_faddr.s_addr >> 16) ^ \
240 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
242 #define SYNCACHE_HASH6(inc, mask) \
243 ((tcp_syncache.hash_secret ^ \
244 (inc)->inc6_faddr.s6_addr32[0] ^ \
245 (inc)->inc6_faddr.s6_addr32[3] ^ \
246 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
248 #define ENDPTS_EQ(a, b) ( \
249 (a)->ie_fport == (b)->ie_fport && \
250 (a)->ie_lport == (b)->ie_lport && \
251 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
252 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
255 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
258 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu,
259 struct syncache *sc, int slot)
261 sc->sc_rxtslot = slot;
262 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot];
263 TAILQ_INSERT_TAIL(&syncache_percpu->timerq[slot], sc, sc_timerq);
264 if (!callout_active(&syncache_percpu->tt_timerq[slot])) {
265 callout_reset(&syncache_percpu->tt_timerq[slot],
266 TCPTV_RTOBASE * tcp_backoff[slot],
268 &syncache_percpu->mrec[slot]);
273 syncache_free(struct syncache *sc)
277 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
279 const boolean_t isipv6 = FALSE;
283 m_free(sc->sc_ipopts);
285 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt;
288 * If this is the only reference to a protocol-cloned
289 * route, remove it immediately.
291 if ((rt->rt_flags & RTF_WASCLONED) && rt->rt_refcnt == 1)
292 rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
293 rt_mask(rt), rt->rt_flags, NULL);
297 zfree(tcp_syncache.zone, sc);
305 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
306 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
307 tcp_syncache.cache_limit =
308 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
309 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
310 tcp_syncache.hash_secret = karc4random();
312 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
313 &tcp_syncache.hashsize);
314 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
315 &tcp_syncache.cache_limit);
316 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
317 &tcp_syncache.bucket_limit);
318 if (!powerof2(tcp_syncache.hashsize)) {
319 printf("WARNING: syncache hash size is not a power of 2.\n");
320 tcp_syncache.hashsize = 512; /* safe default */
322 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
324 lwkt_initport_null_rport(&syncache_null_rport, NULL);
326 for (cpu = 0; cpu < ncpus2; cpu++) {
327 struct tcp_syncache_percpu *syncache_percpu;
329 syncache_percpu = &tcp_syncache_percpu[cpu];
330 /* Allocate the hash table. */
331 MALLOC(syncache_percpu->hashbase, struct syncache_head *,
332 tcp_syncache.hashsize * sizeof(struct syncache_head),
333 M_SYNCACHE, M_WAITOK);
335 /* Initialize the hash buckets. */
336 for (i = 0; i < tcp_syncache.hashsize; i++) {
337 struct syncache_head *bucket;
339 bucket = &syncache_percpu->hashbase[i];
340 TAILQ_INIT(&bucket->sch_bucket);
341 bucket->sch_length = 0;
344 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
345 /* Initialize the timer queues. */
346 TAILQ_INIT(&syncache_percpu->timerq[i]);
347 callout_init(&syncache_percpu->tt_timerq[i]);
349 syncache_percpu->mrec[i].slot = i;
350 syncache_percpu->mrec[i].port = tcp_cport(cpu);
351 syncache_percpu->mrec[i].msg.nm_mrec =
352 &syncache_percpu->mrec[i];
353 lwkt_initmsg(&syncache_percpu->mrec[i].msg.nm_lmsg,
354 &syncache_null_rport, 0,
355 lwkt_cmd_func(syncache_timer_handler),
361 * Allocate the syncache entries. Allow the zone to allocate one
362 * more entry than cache limit, so a new entry can bump out an
365 tcp_syncache.zone = zinit("syncache", sizeof(struct syncache),
366 tcp_syncache.cache_limit * ncpus2, ZONE_INTERRUPT, 0);
367 tcp_syncache.cache_limit -= 1;
371 syncache_insert(struct syncache *sc, struct syncache_head *sch)
373 struct tcp_syncache_percpu *syncache_percpu;
374 struct syncache *sc2;
377 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
380 * Make sure that we don't overflow the per-bucket
381 * limit or the total cache size limit.
383 if (sch->sch_length >= tcp_syncache.bucket_limit) {
385 * The bucket is full, toss the oldest element.
387 sc2 = TAILQ_FIRST(&sch->sch_bucket);
388 sc2->sc_tp->ts_recent = ticks;
389 syncache_drop(sc2, sch);
390 tcpstat.tcps_sc_bucketoverflow++;
391 } else if (syncache_percpu->cache_count >= tcp_syncache.cache_limit) {
393 * The cache is full. Toss the oldest entry in the
394 * entire cache. This is the front entry in the
395 * first non-empty timer queue with the largest
398 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
399 sc2 = TAILQ_FIRST(&syncache_percpu->timerq[i]);
403 sc2->sc_tp->ts_recent = ticks;
404 syncache_drop(sc2, NULL);
405 tcpstat.tcps_sc_cacheoverflow++;
408 /* Initialize the entry's timer. */
409 syncache_timeout(syncache_percpu, sc, 0);
411 /* Put it into the bucket. */
412 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
414 syncache_percpu->cache_count++;
415 tcpstat.tcps_sc_added++;
419 syncache_drop(struct syncache *sc, struct syncache_head *sch)
421 struct tcp_syncache_percpu *syncache_percpu;
423 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
425 const boolean_t isipv6 = FALSE;
428 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
432 sch = &syncache_percpu->hashbase[
433 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
435 sch = &syncache_percpu->hashbase[
436 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
440 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
442 syncache_percpu->cache_count--;
445 * Remove the entry from the syncache timer/timeout queue. Note
446 * that we do not try to stop any running timer since we do not know
447 * whether the timer's message is in-transit or not. Since timeouts
448 * are fairly long, taking an unneeded callout does not detrimentally
449 * effect performance.
451 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq);
457 * Place a timeout message on the TCP thread's message queue.
458 * This routine runs in soft interrupt context.
460 * An invariant is for this routine to be called, the callout must
461 * have been active. Note that the callout is not deactivated until
462 * after the message has been processed in syncache_timer_handler() below.
465 syncache_timer(void *p)
467 struct netmsg_sc_timer *msg = p;
469 lwkt_sendmsg(msg->nm_mrec->port, &msg->nm_lmsg);
473 * Service a timer message queued by timer expiration.
474 * This routine runs in the TCP protocol thread.
476 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
477 * If we have retransmitted an entry the maximum number of times, expire it.
479 * When we finish processing timed-out entries, we restart the timer if there
480 * are any entries still on the queue and deactivate it otherwise. Only after
481 * a timer has been deactivated here can it be restarted by syncache_timeout().
484 syncache_timer_handler(lwkt_msg_t msg)
486 struct tcp_syncache_percpu *syncache_percpu;
487 struct syncache *sc, *nsc;
491 slot = ((struct netmsg_sc_timer *)msg)->nm_mrec->slot;
492 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
494 nsc = TAILQ_FIRST(&syncache_percpu->timerq[slot]);
495 while (nsc != NULL) {
496 if (ticks < nsc->sc_rxttime)
497 break; /* finished because timerq sorted by time */
499 inp = sc->sc_tp->t_inpcb;
500 if (slot == SYNCACHE_MAXREXMTS ||
501 slot >= tcp_syncache.rexmt_limit ||
502 inp->inp_gencnt != sc->sc_inp_gencnt) {
503 nsc = TAILQ_NEXT(sc, sc_timerq);
504 syncache_drop(sc, NULL);
505 tcpstat.tcps_sc_stale++;
509 * syncache_respond() may call back into the syncache to
510 * to modify another entry, so do not obtain the next
511 * entry on the timer chain until it has completed.
513 syncache_respond(sc, NULL);
514 nsc = TAILQ_NEXT(sc, sc_timerq);
515 tcpstat.tcps_sc_retransmitted++;
516 TAILQ_REMOVE(&syncache_percpu->timerq[slot], sc, sc_timerq);
517 syncache_timeout(syncache_percpu, sc, slot + 1);
520 callout_reset(&syncache_percpu->tt_timerq[slot],
521 nsc->sc_rxttime - ticks, syncache_timer,
522 &syncache_percpu->mrec[slot]);
524 callout_deactivate(&syncache_percpu->tt_timerq[slot]);
526 lwkt_replymsg(msg, 0);
531 * Find an entry in the syncache.
534 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
536 struct tcp_syncache_percpu *syncache_percpu;
538 struct syncache_head *sch;
540 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
542 if (inc->inc_isipv6) {
543 sch = &syncache_percpu->hashbase[
544 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
546 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
547 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
552 sch = &syncache_percpu->hashbase[
553 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
555 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
557 if (sc->sc_inc.inc_isipv6)
560 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
568 * This function is called when we get a RST for a
569 * non-existent connection, so that we can see if the
570 * connection is in the syn cache. If it is, zap it.
573 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
576 struct syncache_head *sch;
578 sc = syncache_lookup(inc, &sch);
582 * If the RST bit is set, check the sequence number to see
583 * if this is a valid reset segment.
585 * In all states except SYN-SENT, all reset (RST) segments
586 * are validated by checking their SEQ-fields. A reset is
587 * valid if its sequence number is in the window.
589 * The sequence number in the reset segment is normally an
590 * echo of our outgoing acknowlegement numbers, but some hosts
591 * send a reset with the sequence number at the rightmost edge
592 * of our receive window, and we have to handle this case.
594 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
595 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
596 syncache_drop(sc, sch);
597 tcpstat.tcps_sc_reset++;
602 syncache_badack(struct in_conninfo *inc)
605 struct syncache_head *sch;
607 sc = syncache_lookup(inc, &sch);
609 syncache_drop(sc, sch);
610 tcpstat.tcps_sc_badack++;
615 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
618 struct syncache_head *sch;
620 /* we are called at splnet() here */
621 sc = syncache_lookup(inc, &sch);
625 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
626 if (ntohl(th->th_seq) != sc->sc_iss)
630 * If we've rertransmitted 3 times and this is our second error,
631 * we remove the entry. Otherwise, we allow it to continue on.
632 * This prevents us from incorrectly nuking an entry during a
633 * spurious network outage.
637 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
638 sc->sc_flags |= SCF_UNREACH;
641 syncache_drop(sc, sch);
642 tcpstat.tcps_sc_unreach++;
646 * Build a new TCP socket structure from a syncache entry.
648 static struct socket *
649 syncache_socket(struct syncache *sc, struct socket *lso)
651 struct inpcb *inp = NULL, *linp;
655 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
657 const boolean_t isipv6 = FALSE;
661 * Ok, create the full blown connection, and set things up
662 * as they would have been set up if we had created the
663 * connection when the SYN arrived. If we can't create
664 * the connection, abort it.
666 so = sonewconn(lso, SS_ISCONNECTED);
669 * Drop the connection; we will send a RST if the peer
670 * retransmits the ACK,
672 tcpstat.tcps_listendrop++;
679 * Insert new socket into hash list.
681 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
683 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
686 inp->inp_vflag &= ~INP_IPV6;
687 inp->inp_vflag |= INP_IPV4;
689 inp->inp_laddr = sc->sc_inc.inc_laddr;
691 inp->inp_lport = sc->sc_inc.inc_lport;
692 if (in_pcbinsporthash(inp) != 0) {
694 * Undo the assignments above if we failed to
695 * put the PCB on the hash lists.
698 inp->in6p_laddr = kin6addr_any;
700 inp->inp_laddr.s_addr = INADDR_ANY;
706 /* copy old policy into new socket's */
707 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp))
708 printf("syncache_expand: could not copy policy\n");
711 struct in6_addr laddr6;
712 struct sockaddr_in6 sin6;
714 * Inherit socket options from the listening socket.
715 * Note that in6p_inputopts are not (and should not be)
716 * copied, since it stores previously received options and is
717 * used to detect if each new option is different than the
718 * previous one and hence should be passed to a user.
719 * If we copied in6p_inputopts, a user would not be able to
720 * receive options just after calling the accept system call.
722 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS;
723 if (linp->in6p_outputopts)
724 inp->in6p_outputopts =
725 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT);
726 inp->in6p_route = sc->sc_route6;
727 sc->sc_route6.ro_rt = NULL;
729 sin6.sin6_family = AF_INET6;
730 sin6.sin6_len = sizeof sin6;
731 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
732 sin6.sin6_port = sc->sc_inc.inc_fport;
733 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
734 laddr6 = inp->in6p_laddr;
735 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
736 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
737 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) {
738 inp->in6p_laddr = laddr6;
742 struct in_addr laddr;
743 struct sockaddr_in sin;
745 inp->inp_options = ip_srcroute();
746 if (inp->inp_options == NULL) {
747 inp->inp_options = sc->sc_ipopts;
748 sc->sc_ipopts = NULL;
750 inp->inp_route = sc->sc_route;
751 sc->sc_route.ro_rt = NULL;
753 sin.sin_family = AF_INET;
754 sin.sin_len = sizeof sin;
755 sin.sin_addr = sc->sc_inc.inc_faddr;
756 sin.sin_port = sc->sc_inc.inc_fport;
757 bzero(sin.sin_zero, sizeof sin.sin_zero);
758 laddr = inp->inp_laddr;
759 if (inp->inp_laddr.s_addr == INADDR_ANY)
760 inp->inp_laddr = sc->sc_inc.inc_laddr;
761 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) {
762 inp->inp_laddr = laddr;
768 tp->t_state = TCPS_SYN_RECEIVED;
769 tp->iss = sc->sc_iss;
770 tp->irs = sc->sc_irs;
773 tp->snd_wl1 = sc->sc_irs;
774 tp->rcv_up = sc->sc_irs + 1;
775 tp->rcv_wnd = sc->sc_wnd;
776 tp->rcv_adv += tp->rcv_wnd;
778 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
779 if (sc->sc_flags & SCF_NOOPT)
780 tp->t_flags |= TF_NOOPT;
781 if (sc->sc_flags & SCF_WINSCALE) {
782 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE;
783 tp->requested_s_scale = sc->sc_requested_s_scale;
784 tp->request_r_scale = sc->sc_request_r_scale;
786 if (sc->sc_flags & SCF_TIMESTAMP) {
787 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP;
788 tp->ts_recent = sc->sc_tsrecent;
789 tp->ts_recent_age = ticks;
791 if (sc->sc_flags & SCF_CC) {
793 * Initialization of the tcpcb for transaction;
794 * set SND.WND = SEG.WND,
795 * initialize CCsend and CCrecv.
797 tp->t_flags |= TF_REQ_CC | TF_RCVD_CC;
798 tp->cc_send = sc->sc_cc_send;
799 tp->cc_recv = sc->sc_cc_recv;
801 if (sc->sc_flags & SCF_SACK_PERMITTED)
802 tp->t_flags |= TF_SACK_PERMITTED;
804 tcp_mss(tp, sc->sc_peer_mss);
807 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
809 if (sc->sc_rxtslot != 0)
810 tp->snd_cwnd = tp->t_maxseg;
811 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
813 tcpstat.tcps_accepts++;
823 * This function gets called when we receive an ACK for a
824 * socket in the LISTEN state. We look up the connection
825 * in the syncache, and if its there, we pull it out of
826 * the cache and turn it into a full-blown connection in
827 * the SYN-RECEIVED state.
830 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop,
834 struct syncache_head *sch;
837 sc = syncache_lookup(inc, &sch);
840 * There is no syncache entry, so see if this ACK is
841 * a returning syncookie. To do this, first:
842 * A. See if this socket has had a syncache entry dropped in
843 * the past. We don't want to accept a bogus syncookie
844 * if we've never received a SYN.
845 * B. check that the syncookie is valid. If it is, then
846 * cobble up a fake syncache entry, and return.
850 sc = syncookie_lookup(inc, th, *sop);
854 tcpstat.tcps_sc_recvcookie++;
858 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
860 if (th->th_ack != sc->sc_iss + 1)
863 so = syncache_socket(sc, *sop);
867 /* XXXjlemon check this - is this correct? */
868 tcp_respond(NULL, m, m, th,
869 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK);
871 m_freem(m); /* XXX only needed for above */
872 tcpstat.tcps_sc_aborted++;
874 tcpstat.tcps_sc_completed++;
879 syncache_drop(sc, sch);
885 * Given a LISTEN socket and an inbound SYN request, add
886 * this to the syn cache, and send back a segment:
887 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
890 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
891 * Doing so would require that we hold onto the data and deliver it
892 * to the application. However, if we are the target of a SYN-flood
893 * DoS attack, an attacker could send data which would eventually
894 * consume all available buffer space if it were ACKed. By not ACKing
895 * the data, we avoid this DoS scenario.
898 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
899 struct socket **sop, struct mbuf *m)
901 struct tcp_syncache_percpu *syncache_percpu;
904 struct syncache *sc = NULL;
905 struct syncache_head *sch;
906 struct mbuf *ipopts = NULL;
907 struct rmxp_tao *taop;
910 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
915 * Remember the IP options, if any.
918 if (!inc->inc_isipv6)
920 ipopts = ip_srcroute();
923 * See if we already have an entry for this connection.
924 * If we do, resend the SYN,ACK, and reset the retransmit timer.
927 * The syncache should be re-initialized with the contents
928 * of the new SYN which may have different options.
930 sc = syncache_lookup(inc, &sch);
932 tcpstat.tcps_sc_dupsyn++;
935 * If we were remembering a previous source route,
936 * forget it and use the new one we've been given.
939 m_free(sc->sc_ipopts);
940 sc->sc_ipopts = ipopts;
943 * Update timestamp if present.
945 if (sc->sc_flags & SCF_TIMESTAMP)
946 sc->sc_tsrecent = to->to_tsval;
948 /* Just update the TOF_SACK_PERMITTED for now. */
949 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
950 sc->sc_flags |= SCF_SACK_PERMITTED;
952 sc->sc_flags &= ~SCF_SACK_PERMITTED;
955 * PCB may have changed, pick up new values.
958 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
959 if (syncache_respond(sc, m) == 0) {
960 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot],
962 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot);
963 tcpstat.tcps_sndacks++;
964 tcpstat.tcps_sndtotal++;
971 * This allocation is guaranteed to succeed because we
972 * preallocate one more syncache entry than cache_limit.
974 sc = zalloc(tcp_syncache.zone);
977 * Fill in the syncache values.
980 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
981 sc->sc_ipopts = ipopts;
982 sc->sc_inc.inc_fport = inc->inc_fport;
983 sc->sc_inc.inc_lport = inc->inc_lport;
985 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
986 if (inc->inc_isipv6) {
987 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
988 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
989 sc->sc_route6.ro_rt = NULL;
993 sc->sc_inc.inc_faddr = inc->inc_faddr;
994 sc->sc_inc.inc_laddr = inc->inc_laddr;
995 sc->sc_route.ro_rt = NULL;
997 sc->sc_irs = th->th_seq;
999 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
1001 sc->sc_iss = syncookie_generate(sc);
1003 sc->sc_iss = karc4random();
1005 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */
1006 win = sbspace(&so->so_rcv);
1008 win = imin(win, TCP_MAXWIN);
1011 if (tcp_do_rfc1323) {
1013 * A timestamp received in a SYN makes
1014 * it ok to send timestamp requests and replies.
1016 if (to->to_flags & TOF_TS) {
1017 sc->sc_tsrecent = to->to_tsval;
1018 sc->sc_flags |= SCF_TIMESTAMP;
1020 if (to->to_flags & TOF_SCALE) {
1023 /* Compute proper scaling value from buffer space */
1024 while (wscale < TCP_MAX_WINSHIFT &&
1025 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat)
1027 sc->sc_request_r_scale = wscale;
1028 sc->sc_requested_s_scale = to->to_requested_s_scale;
1029 sc->sc_flags |= SCF_WINSCALE;
1032 if (tcp_do_rfc1644) {
1034 * A CC or CC.new option received in a SYN makes
1035 * it ok to send CC in subsequent segments.
1037 if (to->to_flags & (TOF_CC | TOF_CCNEW)) {
1038 sc->sc_cc_recv = to->to_cc;
1039 sc->sc_cc_send = CC_INC(tcp_ccgen);
1040 sc->sc_flags |= SCF_CC;
1043 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
1044 sc->sc_flags |= SCF_SACK_PERMITTED;
1045 if (tp->t_flags & TF_NOOPT)
1046 sc->sc_flags = SCF_NOOPT;
1050 * We have the option here of not doing TAO (even if the segment
1051 * qualifies) and instead fall back to a normal 3WHS via the syncache.
1052 * This allows us to apply synflood protection to TAO-qualifying SYNs
1053 * also. However, there should be a hueristic to determine when to
1054 * do this, and is not present at the moment.
1058 * Perform TAO test on incoming CC (SEG.CC) option, if any.
1059 * - compare SEG.CC against cached CC from the same host, if any.
1060 * - if SEG.CC > chached value, SYN must be new and is accepted
1061 * immediately: save new CC in the cache, mark the socket
1062 * connected, enter ESTABLISHED state, turn on flag to
1063 * send a SYN in the next segment.
1064 * A virtual advertised window is set in rcv_adv to
1065 * initialize SWS prevention. Then enter normal segment
1066 * processing: drop SYN, process data and FIN.
1067 * - otherwise do a normal 3-way handshake.
1069 taop = tcp_gettaocache(&sc->sc_inc);
1070 if (to->to_flags & TOF_CC) {
1071 if ((tp->t_flags & TF_NOPUSH) &&
1072 sc->sc_flags & SCF_CC &&
1073 taop != NULL && taop->tao_cc != 0 &&
1074 CC_GT(to->to_cc, taop->tao_cc)) {
1076 so = syncache_socket(sc, *sop);
1078 taop->tao_cc = to->to_cc;
1082 return (so != NULL);
1086 * No CC option, but maybe CC.NEW: invalidate cached value.
1092 * TAO test failed or there was no CC option,
1093 * do a standard 3-way handshake.
1095 if (syncache_respond(sc, m) == 0) {
1096 syncache_insert(sc, sch);
1097 tcpstat.tcps_sndacks++;
1098 tcpstat.tcps_sndtotal++;
1101 tcpstat.tcps_sc_dropped++;
1108 syncache_respond(struct syncache *sc, struct mbuf *m)
1112 u_int16_t tlen, hlen, mssopt;
1113 struct ip *ip = NULL;
1116 struct ip6_hdr *ip6 = NULL;
1118 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1120 const boolean_t isipv6 = FALSE;
1124 rt = tcp_rtlookup6(&sc->sc_inc);
1126 mssopt = rt->rt_ifp->if_mtu -
1127 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr));
1129 mssopt = tcp_v6mssdflt;
1130 hlen = sizeof(struct ip6_hdr);
1132 rt = tcp_rtlookup(&sc->sc_inc);
1134 mssopt = rt->rt_ifp->if_mtu -
1135 (sizeof(struct ip) + sizeof(struct tcphdr));
1137 mssopt = tcp_mssdflt;
1138 hlen = sizeof(struct ip);
1141 /* Compute the size of the TCP options. */
1142 if (sc->sc_flags & SCF_NOOPT) {
1145 optlen = TCPOLEN_MAXSEG +
1146 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1147 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1148 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0) +
1149 ((sc->sc_flags & SCF_SACK_PERMITTED) ?
1150 TCPOLEN_SACK_PERMITTED_ALIGNED : 0);
1152 tlen = hlen + sizeof(struct tcphdr) + optlen;
1156 * assume that the entire packet will fit in a header mbuf
1158 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1161 * XXX shouldn't this reuse the mbuf if possible ?
1162 * Create the IP+TCP header from scratch.
1167 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
1170 m->m_data += max_linkhdr;
1172 m->m_pkthdr.len = tlen;
1173 m->m_pkthdr.rcvif = NULL;
1176 ip6 = mtod(m, struct ip6_hdr *);
1177 ip6->ip6_vfc = IPV6_VERSION;
1178 ip6->ip6_nxt = IPPROTO_TCP;
1179 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1180 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1181 ip6->ip6_plen = htons(tlen - hlen);
1182 /* ip6_hlim is set after checksum */
1183 /* ip6_flow = ??? */
1185 th = (struct tcphdr *)(ip6 + 1);
1187 ip = mtod(m, struct ip *);
1188 ip->ip_v = IPVERSION;
1189 ip->ip_hl = sizeof(struct ip) >> 2;
1194 ip->ip_p = IPPROTO_TCP;
1195 ip->ip_src = sc->sc_inc.inc_laddr;
1196 ip->ip_dst = sc->sc_inc.inc_faddr;
1197 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */
1198 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */
1201 * See if we should do MTU discovery. Route lookups are
1202 * expensive, so we will only unset the DF bit if:
1204 * 1) path_mtu_discovery is disabled
1205 * 2) the SCF_UNREACH flag has been set
1207 if (path_mtu_discovery
1208 && ((sc->sc_flags & SCF_UNREACH) == 0)) {
1209 ip->ip_off |= IP_DF;
1212 th = (struct tcphdr *)(ip + 1);
1214 th->th_sport = sc->sc_inc.inc_lport;
1215 th->th_dport = sc->sc_inc.inc_fport;
1217 th->th_seq = htonl(sc->sc_iss);
1218 th->th_ack = htonl(sc->sc_irs + 1);
1219 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1221 th->th_flags = TH_SYN | TH_ACK;
1222 th->th_win = htons(sc->sc_wnd);
1225 /* Tack on the TCP options. */
1228 optp = (u_int8_t *)(th + 1);
1229 *optp++ = TCPOPT_MAXSEG;
1230 *optp++ = TCPOLEN_MAXSEG;
1231 *optp++ = (mssopt >> 8) & 0xff;
1232 *optp++ = mssopt & 0xff;
1234 if (sc->sc_flags & SCF_WINSCALE) {
1235 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1236 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1237 sc->sc_request_r_scale);
1241 if (sc->sc_flags & SCF_TIMESTAMP) {
1242 u_int32_t *lp = (u_int32_t *)(optp);
1244 /* Form timestamp option as shown in appendix A of RFC 1323. */
1245 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1246 *lp++ = htonl(ticks);
1247 *lp = htonl(sc->sc_tsrecent);
1248 optp += TCPOLEN_TSTAMP_APPA;
1252 * Send CC and CC.echo if we received CC from our peer.
1254 if (sc->sc_flags & SCF_CC) {
1255 u_int32_t *lp = (u_int32_t *)(optp);
1257 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
1258 *lp++ = htonl(sc->sc_cc_send);
1259 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
1260 *lp = htonl(sc->sc_cc_recv);
1261 optp += TCPOLEN_CC_APPA * 2;
1264 if (sc->sc_flags & SCF_SACK_PERMITTED) {
1265 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
1266 optp += TCPOLEN_SACK_PERMITTED_ALIGNED;
1271 struct route_in6 *ro6 = &sc->sc_route6;
1274 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1275 ip6->ip6_hlim = in6_selecthlim(NULL,
1276 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
1277 error = ip6_output(m, NULL, ro6, 0, NULL, NULL,
1278 sc->sc_tp->t_inpcb);
1280 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1281 htons(tlen - hlen + IPPROTO_TCP));
1282 m->m_pkthdr.csum_flags = CSUM_TCP;
1283 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1284 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL,
1285 sc->sc_tp->t_inpcb);
1293 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1295 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1297 * (A): peer mss index
1301 * The values below are chosen to minimize the size of the tcp_secret
1302 * table, as well as providing roughly a 16 second lifetime for the cookie.
1305 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1306 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1308 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1309 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1310 #define SYNCOOKIE_TIMEOUT \
1311 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1312 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1315 u_int32_t ts_secbits[4];
1317 } tcp_secret[SYNCOOKIE_NSECRETS];
1319 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1321 static MD5_CTX syn_ctx;
1323 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1326 u_int32_t laddr, faddr;
1327 u_int32_t secbits[4];
1328 u_int16_t lport, fport;
1332 CTASSERT(sizeof(struct md5_add) == 28);
1336 * Consider the problem of a recreated (and retransmitted) cookie. If the
1337 * original SYN was accepted, the connection is established. The second
1338 * SYN is inflight, and if it arrives with an ISN that falls within the
1339 * receive window, the connection is killed.
1341 * However, since cookies have other problems, this may not be worth
1346 syncookie_generate(struct syncache *sc)
1348 u_int32_t md5_buffer[4];
1353 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1355 const boolean_t isipv6 = FALSE;
1358 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1359 if (tcp_secret[idx].ts_expire < ticks) {
1360 for (i = 0; i < 4; i++)
1361 tcp_secret[idx].ts_secbits[i] = karc4random();
1362 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1364 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1365 if (tcp_msstab[data] <= sc->sc_peer_mss)
1367 data = (data << SYNCOOKIE_WNDBITS) | idx;
1368 data ^= sc->sc_irs; /* peer's iss */
1371 MD5Add(sc->sc_inc.inc6_laddr);
1372 MD5Add(sc->sc_inc.inc6_faddr);
1376 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1377 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1379 add.lport = sc->sc_inc.inc_lport;
1380 add.fport = sc->sc_inc.inc_fport;
1381 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1382 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1383 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1384 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1386 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1387 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1391 static struct syncache *
1392 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so)
1394 u_int32_t md5_buffer[4];
1395 struct syncache *sc;
1400 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1401 idx = data & SYNCOOKIE_WNDMASK;
1402 if (tcp_secret[idx].ts_expire < ticks ||
1403 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1407 if (inc->inc_isipv6) {
1408 MD5Add(inc->inc6_laddr);
1409 MD5Add(inc->inc6_faddr);
1415 add.laddr = inc->inc_laddr.s_addr;
1416 add.faddr = inc->inc_faddr.s_addr;
1418 add.lport = inc->inc_lport;
1419 add.fport = inc->inc_fport;
1420 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1421 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1422 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1423 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1425 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1426 data ^= md5_buffer[0];
1427 if (data & ~SYNCOOKIE_DATAMASK)
1429 data = data >> SYNCOOKIE_WNDBITS;
1432 * This allocation is guaranteed to succeed because we
1433 * preallocate one more syncache entry than cache_limit.
1435 sc = zalloc(tcp_syncache.zone);
1438 * Fill in the syncache values.
1439 * XXX duplicate code from syncache_add
1441 sc->sc_ipopts = NULL;
1442 sc->sc_inc.inc_fport = inc->inc_fport;
1443 sc->sc_inc.inc_lport = inc->inc_lport;
1445 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1446 if (inc->inc_isipv6) {
1447 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1448 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1449 sc->sc_route6.ro_rt = NULL;
1453 sc->sc_inc.inc_faddr = inc->inc_faddr;
1454 sc->sc_inc.inc_laddr = inc->inc_laddr;
1455 sc->sc_route.ro_rt = NULL;
1457 sc->sc_irs = th->th_seq - 1;
1458 sc->sc_iss = th->th_ack - 1;
1459 wnd = sbspace(&so->so_rcv);
1461 wnd = imin(wnd, TCP_MAXWIN);
1465 sc->sc_peer_mss = tcp_msstab[data];