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 * 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
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
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
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 $
76 #include "opt_inet6.h"
77 #include "opt_ipsec.h"
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>
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>
92 #include <sys/msgport2.h>
93 #include <net/netmsg2.h>
96 #include <net/route.h>
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>
106 #include <netinet/icmp6.h>
107 #include <netinet6/nd6.h>
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>
120 #include <netinet6/ipsec.h>
122 #include <netinet6/ipsec6.h>
124 #include <netproto/key/key.h>
128 #include <netproto/ipsec/ipsec.h>
130 #include <netproto/ipsec/ipsec6.h>
132 #include <netproto/ipsec/key.h>
134 #endif /*FAST_IPSEC*/
136 static int tcp_syncookies = 1;
137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
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 *,
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 *);
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.
158 #define SYNCACHE_MAXREXMTS 3
160 /* Arbitrary values */
161 #define TCP_SYNCACHE_HASHSIZE 512
162 #define TCP_SYNCACHE_BUCKETLIMIT 30
164 struct netmsg_sc_timer {
165 struct netmsg nm_netmsg;
166 struct msgrec *nm_mrec; /* back pointer to containing msgrec */
170 struct netmsg_sc_timer msg;
171 lwkt_port_t port; /* constant after init */
172 int slot; /* constant after init */
175 static void syncache_timer_handler(netmsg_t);
177 struct tcp_syncache {
185 static struct tcp_syncache tcp_syncache;
187 TAILQ_HEAD(syncache_list, syncache);
189 struct tcp_syncache_percpu {
190 struct syncache_head *hashbase;
192 struct syncache_list timerq[SYNCACHE_MAXREXMTS + 1];
193 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
194 struct msgrec mrec[SYNCACHE_MAXREXMTS + 1];
196 static struct tcp_syncache_percpu tcp_syncache_percpu[MAXCPU];
198 static struct lwkt_port syncache_null_rport;
200 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
202 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD,
203 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
205 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD,
206 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
210 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
211 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
214 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD,
215 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
217 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
218 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
220 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
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)
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)
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 \
241 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
244 syncache_timeout(struct tcp_syncache_percpu *syncache_percpu,
245 struct syncache *sc, int slot)
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],
254 &syncache_percpu->mrec[slot]);
259 syncache_free(struct syncache *sc)
263 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
265 const boolean_t isipv6 = FALSE;
269 m_free(sc->sc_ipopts);
271 rt = isipv6 ? sc->sc_route6.ro_rt : sc->sc_route.ro_rt;
274 * If this is the only reference to a protocol-cloned
275 * route, remove it immediately.
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);
282 kfree(sc, M_SYNCACHE);
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();
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 */
307 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
309 lwkt_initport_replyonly_null(&syncache_null_rport);
311 for (cpu = 0; cpu < ncpus2; cpu++) {
312 struct tcp_syncache_percpu *syncache_percpu;
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);
320 /* Initialize the hash buckets. */
321 for (i = 0; i < tcp_syncache.hashsize; i++) {
322 struct syncache_head *bucket;
324 bucket = &syncache_percpu->hashbase[i];
325 TAILQ_INIT(&bucket->sch_bucket);
326 bucket->sch_length = 0;
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]);
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.nm_netmsg,
339 NULL, &syncache_null_rport,
340 0, syncache_timer_handler);
346 syncache_insert(struct syncache *sc, struct syncache_head *sch)
348 struct tcp_syncache_percpu *syncache_percpu;
349 struct syncache *sc2;
352 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
355 * Make sure that we don't overflow the per-bucket
356 * limit or the total cache size limit.
358 if (sch->sch_length >= tcp_syncache.bucket_limit) {
360 * The bucket is full, toss the oldest element.
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) {
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
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);
380 sc2->sc_tp->ts_recent = ticks;
381 syncache_drop(sc2, NULL);
382 tcpstat.tcps_sc_cacheoverflow++;
385 /* Initialize the entry's timer. */
386 syncache_timeout(syncache_percpu, sc, 0);
388 /* Put it into the bucket. */
389 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
391 syncache_percpu->cache_count++;
392 tcpstat.tcps_sc_added++;
396 syncache_destroy(struct tcpcb *tp)
398 struct tcp_syncache_percpu *syncache_percpu;
399 struct syncache_head *bucket;
403 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
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) {
411 tp->t_flags &= ~TF_SYNCACHE;
416 kprintf("Warning: delete stale syncache for tp=%p, sc=%p\n", tp, sc);
420 syncache_drop(struct syncache *sc, struct syncache_head *sch)
422 struct tcp_syncache_percpu *syncache_percpu;
424 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
426 const boolean_t isipv6 = FALSE;
429 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
433 sch = &syncache_percpu->hashbase[
434 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
436 sch = &syncache_percpu->hashbase[
437 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
441 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
443 syncache_percpu->cache_count--;
449 sc->sc_tp->t_flags &= ~TF_SYNCACHE;
454 * Remove the entry from the syncache timer/timeout queue. Note
455 * that we do not try to stop any running timer since we do not know
456 * whether the timer's message is in-transit or not. Since timeouts
457 * are fairly long, taking an unneeded callout does not detrimentally
458 * effect performance.
460 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot], sc, sc_timerq);
466 * Place a timeout message on the TCP thread's message queue.
467 * This routine runs in soft interrupt context.
469 * An invariant is for this routine to be called, the callout must
470 * have been active. Note that the callout is not deactivated until
471 * after the message has been processed in syncache_timer_handler() below.
474 syncache_timer(void *p)
476 struct netmsg_sc_timer *msg = p;
478 lwkt_sendmsg(msg->nm_mrec->port, &msg->nm_netmsg.nm_lmsg);
482 * Service a timer message queued by timer expiration.
483 * This routine runs in the TCP protocol thread.
485 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
486 * If we have retransmitted an entry the maximum number of times, expire it.
488 * When we finish processing timed-out entries, we restart the timer if there
489 * are any entries still on the queue and deactivate it otherwise. Only after
490 * a timer has been deactivated here can it be restarted by syncache_timeout().
493 syncache_timer_handler(netmsg_t netmsg)
495 struct tcp_syncache_percpu *syncache_percpu;
497 struct syncache marker;
498 struct syncache_list *list;
502 slot = ((struct netmsg_sc_timer *)netmsg)->nm_mrec->slot;
503 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
505 list = &syncache_percpu->timerq[slot];
508 * Use a marker to keep our place in the scan. syncache_drop()
509 * can block and cause any next pointer we cache to become stale.
511 marker.sc_flags = SCF_MARKER;
512 TAILQ_INSERT_HEAD(list, &marker, sc_timerq);
514 while ((sc = TAILQ_NEXT(&marker, sc_timerq)) != NULL) {
518 TAILQ_REMOVE(list, &marker, sc_timerq);
519 TAILQ_INSERT_AFTER(list, sc, &marker, sc_timerq);
521 if (sc->sc_flags & SCF_MARKER)
524 if (ticks < sc->sc_rxttime)
525 break; /* finished because timerq sorted by time */
526 if (sc->sc_tp == NULL) {
527 syncache_drop(sc, NULL);
528 tcpstat.tcps_sc_stale++;
531 inp = sc->sc_tp->t_inpcb;
532 if (slot == SYNCACHE_MAXREXMTS ||
533 slot >= tcp_syncache.rexmt_limit ||
535 inp->inp_gencnt != sc->sc_inp_gencnt) {
536 syncache_drop(sc, NULL);
537 tcpstat.tcps_sc_stale++;
541 * syncache_respond() may call back into the syncache to
542 * to modify another entry, so do not obtain the next
543 * entry on the timer chain until it has completed.
545 syncache_respond(sc, NULL);
546 tcpstat.tcps_sc_retransmitted++;
547 TAILQ_REMOVE(list, sc, sc_timerq);
548 syncache_timeout(syncache_percpu, sc, slot + 1);
550 TAILQ_REMOVE(list, &marker, sc_timerq);
553 callout_reset(&syncache_percpu->tt_timerq[slot],
554 sc->sc_rxttime - ticks, syncache_timer,
555 &syncache_percpu->mrec[slot]);
557 callout_deactivate(&syncache_percpu->tt_timerq[slot]);
559 lwkt_replymsg(&netmsg->nm_lmsg, 0);
563 * Find an entry in the syncache.
566 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
568 struct tcp_syncache_percpu *syncache_percpu;
570 struct syncache_head *sch;
572 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
574 if (inc->inc_isipv6) {
575 sch = &syncache_percpu->hashbase[
576 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
578 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
579 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
584 sch = &syncache_percpu->hashbase[
585 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
587 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
589 if (sc->sc_inc.inc_isipv6)
592 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
600 * This function is called when we get a RST for a
601 * non-existent connection, so that we can see if the
602 * connection is in the syn cache. If it is, zap it.
605 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
608 struct syncache_head *sch;
610 sc = syncache_lookup(inc, &sch);
615 * If the RST bit is set, check the sequence number to see
616 * if this is a valid reset segment.
618 * In all states except SYN-SENT, all reset (RST) segments
619 * are validated by checking their SEQ-fields. A reset is
620 * valid if its sequence number is in the window.
622 * The sequence number in the reset segment is normally an
623 * echo of our outgoing acknowlegement numbers, but some hosts
624 * send a reset with the sequence number at the rightmost edge
625 * of our receive window, and we have to handle this case.
627 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
628 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
629 syncache_drop(sc, sch);
630 tcpstat.tcps_sc_reset++;
635 syncache_badack(struct in_conninfo *inc)
638 struct syncache_head *sch;
640 sc = syncache_lookup(inc, &sch);
642 syncache_drop(sc, sch);
643 tcpstat.tcps_sc_badack++;
648 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
651 struct syncache_head *sch;
653 /* we are called at splnet() here */
654 sc = syncache_lookup(inc, &sch);
658 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
659 if (ntohl(th->th_seq) != sc->sc_iss)
663 * If we've rertransmitted 3 times and this is our second error,
664 * we remove the entry. Otherwise, we allow it to continue on.
665 * This prevents us from incorrectly nuking an entry during a
666 * spurious network outage.
670 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
671 sc->sc_flags |= SCF_UNREACH;
674 syncache_drop(sc, sch);
675 tcpstat.tcps_sc_unreach++;
679 * Build a new TCP socket structure from a syncache entry.
681 * This is called from the context of the SYN+ACK
683 static struct socket *
684 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
686 struct inpcb *inp = NULL, *linp;
691 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
693 const boolean_t isipv6 = FALSE;
697 * Ok, create the full blown connection, and set things up
698 * as they would have been set up if we had created the
699 * connection when the SYN arrived. If we can't create
700 * the connection, abort it.
702 so = sonewconn(lso, SS_ISCONNECTED);
705 * Drop the connection; we will send a RST if the peer
706 * retransmits the ACK,
708 tcpstat.tcps_listendrop++;
713 * Set the protocol processing port for the socket to the current
714 * port (that the connection came in on).
716 sosetport(so, &curthread->td_msgport);
719 * Insert new socket into hash list.
722 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
724 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
727 inp->inp_vflag &= ~INP_IPV6;
728 inp->inp_vflag |= INP_IPV4;
729 inp->inp_flags &= ~IN6P_IPV6_V6ONLY;
731 inp->inp_laddr = sc->sc_inc.inc_laddr;
733 inp->inp_lport = sc->sc_inc.inc_lport;
734 if (in_pcbinsporthash(inp) != 0) {
736 * Undo the assignments above if we failed to
737 * put the PCB on the hash lists.
740 inp->in6p_laddr = kin6addr_any;
742 inp->inp_laddr.s_addr = INADDR_ANY;
748 /* copy old policy into new socket's */
749 if (ipsec_copy_policy(linp->inp_sp, inp->inp_sp))
750 kprintf("syncache_expand: could not copy policy\n");
753 struct in6_addr laddr6;
754 struct sockaddr_in6 sin6;
756 * Inherit socket options from the listening socket.
757 * Note that in6p_inputopts are not (and should not be)
758 * copied, since it stores previously received options and is
759 * used to detect if each new option is different than the
760 * previous one and hence should be passed to a user.
761 * If we copied in6p_inputopts, a user would not be able to
762 * receive options just after calling the accept system call.
764 inp->inp_flags |= linp->inp_flags & INP_CONTROLOPTS;
765 if (linp->in6p_outputopts)
766 inp->in6p_outputopts =
767 ip6_copypktopts(linp->in6p_outputopts, M_INTWAIT);
768 inp->in6p_route = sc->sc_route6;
769 sc->sc_route6.ro_rt = NULL;
771 sin6.sin6_family = AF_INET6;
772 sin6.sin6_len = sizeof sin6;
773 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
774 sin6.sin6_port = sc->sc_inc.inc_fport;
775 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
776 laddr6 = inp->in6p_laddr;
777 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
778 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
779 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) {
780 inp->in6p_laddr = laddr6;
784 struct in_addr laddr;
785 struct sockaddr_in sin;
787 inp->inp_options = ip_srcroute(m);
788 if (inp->inp_options == NULL) {
789 inp->inp_options = sc->sc_ipopts;
790 sc->sc_ipopts = NULL;
792 inp->inp_route = sc->sc_route;
793 sc->sc_route.ro_rt = NULL;
795 sin.sin_family = AF_INET;
796 sin.sin_len = sizeof sin;
797 sin.sin_addr = sc->sc_inc.inc_faddr;
798 sin.sin_port = sc->sc_inc.inc_fport;
799 bzero(sin.sin_zero, sizeof sin.sin_zero);
800 laddr = inp->inp_laddr;
801 if (inp->inp_laddr.s_addr == INADDR_ANY)
802 inp->inp_laddr = sc->sc_inc.inc_laddr;
803 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) {
804 inp->inp_laddr = laddr;
810 * The current port should be in the context of the SYN+ACK and
811 * so should match the tcp address port.
813 * XXX we may be running on the netisr thread instead of a tcp
814 * thread, in which case port will not match
815 * curthread->td_msgport.
818 port = tcp6_addrport();
820 port = tcp_addrport(inp->inp_faddr.s_addr, inp->inp_fport,
821 inp->inp_laddr.s_addr, inp->inp_lport);
823 /*KKASSERT(port == &curthread->td_msgport);*/
826 tp->t_state = TCPS_SYN_RECEIVED;
827 tp->iss = sc->sc_iss;
828 tp->irs = sc->sc_irs;
831 tp->snd_wl1 = sc->sc_irs;
832 tp->rcv_up = sc->sc_irs + 1;
833 tp->rcv_wnd = sc->sc_wnd;
834 tp->rcv_adv += tp->rcv_wnd;
836 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
837 if (sc->sc_flags & SCF_NOOPT)
838 tp->t_flags |= TF_NOOPT;
839 if (sc->sc_flags & SCF_WINSCALE) {
840 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE;
841 tp->requested_s_scale = sc->sc_requested_s_scale;
842 tp->request_r_scale = sc->sc_request_r_scale;
844 if (sc->sc_flags & SCF_TIMESTAMP) {
845 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP;
846 tp->ts_recent = sc->sc_tsrecent;
847 tp->ts_recent_age = ticks;
849 if (sc->sc_flags & SCF_SACK_PERMITTED)
850 tp->t_flags |= TF_SACK_PERMITTED;
853 if (sc->sc_flags & SCF_SIGNATURE)
854 tp->t_flags |= TF_SIGNATURE;
855 #endif /* TCP_SIGNATURE */
858 tcp_mss(tp, sc->sc_peer_mss);
861 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
863 if (sc->sc_rxtslot != 0)
864 tp->snd_cwnd = tp->t_maxseg;
865 tcp_create_timermsg(tp, port);
866 tcp_callout_reset(tp, tp->tt_keep, tcp_keepinit, tcp_timer_keep);
868 tcpstat.tcps_accepts++;
878 * This function gets called when we receive an ACK for a
879 * socket in the LISTEN state. We look up the connection
880 * in the syncache, and if its there, we pull it out of
881 * the cache and turn it into a full-blown connection in
882 * the SYN-RECEIVED state.
885 syncache_expand(struct in_conninfo *inc, struct tcphdr *th, struct socket **sop,
889 struct syncache_head *sch;
892 sc = syncache_lookup(inc, &sch);
895 * There is no syncache entry, so see if this ACK is
896 * a returning syncookie. To do this, first:
897 * A. See if this socket has had a syncache entry dropped in
898 * the past. We don't want to accept a bogus syncookie
899 * if we've never received a SYN.
900 * B. check that the syncookie is valid. If it is, then
901 * cobble up a fake syncache entry, and return.
905 sc = syncookie_lookup(inc, th, *sop);
909 tcpstat.tcps_sc_recvcookie++;
913 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
915 if (th->th_ack != sc->sc_iss + 1)
918 so = syncache_socket(sc, *sop, m);
922 /* XXXjlemon check this - is this correct? */
923 tcp_respond(NULL, m, m, th,
924 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK);
926 m_freem(m); /* XXX only needed for above */
927 tcpstat.tcps_sc_aborted++;
929 tcpstat.tcps_sc_completed++;
934 syncache_drop(sc, sch);
940 * Given a LISTEN socket and an inbound SYN request, add
941 * this to the syn cache, and send back a segment:
942 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
945 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
946 * Doing so would require that we hold onto the data and deliver it
947 * to the application. However, if we are the target of a SYN-flood
948 * DoS attack, an attacker could send data which would eventually
949 * consume all available buffer space if it were ACKed. By not ACKing
950 * the data, we avoid this DoS scenario.
953 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
954 struct socket **sop, struct mbuf *m)
956 struct tcp_syncache_percpu *syncache_percpu;
959 struct syncache *sc = NULL;
960 struct syncache_head *sch;
961 struct mbuf *ipopts = NULL;
964 syncache_percpu = &tcp_syncache_percpu[mycpu->gd_cpuid];
969 * Remember the IP options, if any.
972 if (!inc->inc_isipv6)
974 ipopts = ip_srcroute(m);
977 * See if we already have an entry for this connection.
978 * If we do, resend the SYN,ACK, and reset the retransmit timer.
981 * The syncache should be re-initialized with the contents
982 * of the new SYN which may have different options.
984 sc = syncache_lookup(inc, &sch);
986 tcpstat.tcps_sc_dupsyn++;
989 * If we were remembering a previous source route,
990 * forget it and use the new one we've been given.
993 m_free(sc->sc_ipopts);
994 sc->sc_ipopts = ipopts;
997 * Update timestamp if present.
999 if (sc->sc_flags & SCF_TIMESTAMP)
1000 sc->sc_tsrecent = to->to_tsval;
1002 /* Just update the TOF_SACK_PERMITTED for now. */
1003 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
1004 sc->sc_flags |= SCF_SACK_PERMITTED;
1006 sc->sc_flags &= ~SCF_SACK_PERMITTED;
1009 * PCB may have changed, pick up new values.
1012 sc->sc_tp->t_flags &= ~TF_SYNCACHE;
1013 tp->t_flags |= TF_SYNCACHE;
1016 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
1017 if (syncache_respond(sc, m) == 0) {
1018 TAILQ_REMOVE(&syncache_percpu->timerq[sc->sc_rxtslot],
1020 syncache_timeout(syncache_percpu, sc, sc->sc_rxtslot);
1021 tcpstat.tcps_sndacks++;
1022 tcpstat.tcps_sndtotal++;
1029 * Fill in the syncache values.
1031 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO);
1032 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
1033 sc->sc_ipopts = ipopts;
1034 sc->sc_inc.inc_fport = inc->inc_fport;
1035 sc->sc_inc.inc_lport = inc->inc_lport;
1037 tp->t_flags |= TF_SYNCACHE;
1039 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1040 if (inc->inc_isipv6) {
1041 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1042 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1043 sc->sc_route6.ro_rt = NULL;
1047 sc->sc_inc.inc_faddr = inc->inc_faddr;
1048 sc->sc_inc.inc_laddr = inc->inc_laddr;
1049 sc->sc_route.ro_rt = NULL;
1051 sc->sc_irs = th->th_seq;
1053 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
1055 sc->sc_iss = syncookie_generate(sc);
1057 sc->sc_iss = karc4random();
1059 /* Initial receive window: clip ssb_space to [0 .. TCP_MAXWIN] */
1060 win = ssb_space(&so->so_rcv);
1062 win = imin(win, TCP_MAXWIN);
1065 if (tcp_do_rfc1323) {
1067 * A timestamp received in a SYN makes
1068 * it ok to send timestamp requests and replies.
1070 if (to->to_flags & TOF_TS) {
1071 sc->sc_tsrecent = to->to_tsval;
1072 sc->sc_flags |= SCF_TIMESTAMP;
1074 if (to->to_flags & TOF_SCALE) {
1075 int wscale = TCP_MIN_WINSHIFT;
1077 /* Compute proper scaling value from buffer space */
1078 while (wscale < TCP_MAX_WINSHIFT &&
1079 (TCP_MAXWIN << wscale) < so->so_rcv.ssb_hiwat) {
1082 sc->sc_request_r_scale = wscale;
1083 sc->sc_requested_s_scale = to->to_requested_s_scale;
1084 sc->sc_flags |= SCF_WINSCALE;
1087 if (tcp_do_sack && (to->to_flags & TOF_SACK_PERMITTED))
1088 sc->sc_flags |= SCF_SACK_PERMITTED;
1089 if (tp->t_flags & TF_NOOPT)
1090 sc->sc_flags = SCF_NOOPT;
1091 #ifdef TCP_SIGNATURE
1093 * If listening socket requested TCP digests, and received SYN
1094 * contains the option, flag this in the syncache so that
1095 * syncache_respond() will do the right thing with the SYN+ACK.
1096 * XXX Currently we always record the option by default and will
1097 * attempt to use it in syncache_respond().
1099 if (to->to_flags & TOF_SIGNATURE)
1100 sc->sc_flags = SCF_SIGNATURE;
1101 #endif /* TCP_SIGNATURE */
1103 if (syncache_respond(sc, m) == 0) {
1104 syncache_insert(sc, sch);
1105 tcpstat.tcps_sndacks++;
1106 tcpstat.tcps_sndtotal++;
1109 tcpstat.tcps_sc_dropped++;
1116 syncache_respond(struct syncache *sc, struct mbuf *m)
1120 u_int16_t tlen, hlen, mssopt;
1121 struct ip *ip = NULL;
1124 struct ip6_hdr *ip6 = NULL;
1126 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1128 const boolean_t isipv6 = FALSE;
1132 rt = tcp_rtlookup6(&sc->sc_inc);
1134 mssopt = rt->rt_ifp->if_mtu -
1135 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr));
1137 mssopt = tcp_v6mssdflt;
1138 hlen = sizeof(struct ip6_hdr);
1140 rt = tcp_rtlookup(&sc->sc_inc);
1142 mssopt = rt->rt_ifp->if_mtu -
1143 (sizeof(struct ip) + sizeof(struct tcphdr));
1145 mssopt = tcp_mssdflt;
1146 hlen = sizeof(struct ip);
1149 /* Compute the size of the TCP options. */
1150 if (sc->sc_flags & SCF_NOOPT) {
1153 optlen = TCPOLEN_MAXSEG +
1154 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1155 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1156 ((sc->sc_flags & SCF_SACK_PERMITTED) ?
1157 TCPOLEN_SACK_PERMITTED_ALIGNED : 0);
1158 #ifdef TCP_SIGNATURE
1159 optlen += ((sc->sc_flags & SCF_SIGNATURE) ?
1160 (TCPOLEN_SIGNATURE + 2) : 0);
1161 #endif /* TCP_SIGNATURE */
1163 tlen = hlen + sizeof(struct tcphdr) + optlen;
1167 * assume that the entire packet will fit in a header mbuf
1169 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1172 * XXX shouldn't this reuse the mbuf if possible ?
1173 * Create the IP+TCP header from scratch.
1178 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
1181 m->m_data += max_linkhdr;
1183 m->m_pkthdr.len = tlen;
1184 m->m_pkthdr.rcvif = NULL;
1187 ip6 = mtod(m, struct ip6_hdr *);
1188 ip6->ip6_vfc = IPV6_VERSION;
1189 ip6->ip6_nxt = IPPROTO_TCP;
1190 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1191 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1192 ip6->ip6_plen = htons(tlen - hlen);
1193 /* ip6_hlim is set after checksum */
1194 /* ip6_flow = ??? */
1196 th = (struct tcphdr *)(ip6 + 1);
1198 ip = mtod(m, struct ip *);
1199 ip->ip_v = IPVERSION;
1200 ip->ip_hl = sizeof(struct ip) >> 2;
1205 ip->ip_p = IPPROTO_TCP;
1206 ip->ip_src = sc->sc_inc.inc_laddr;
1207 ip->ip_dst = sc->sc_inc.inc_faddr;
1208 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */
1209 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */
1212 * See if we should do MTU discovery. Route lookups are
1213 * expensive, so we will only unset the DF bit if:
1215 * 1) path_mtu_discovery is disabled
1216 * 2) the SCF_UNREACH flag has been set
1218 if (path_mtu_discovery
1219 && ((sc->sc_flags & SCF_UNREACH) == 0)) {
1220 ip->ip_off |= IP_DF;
1223 th = (struct tcphdr *)(ip + 1);
1225 th->th_sport = sc->sc_inc.inc_lport;
1226 th->th_dport = sc->sc_inc.inc_fport;
1228 th->th_seq = htonl(sc->sc_iss);
1229 th->th_ack = htonl(sc->sc_irs + 1);
1230 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1232 th->th_flags = TH_SYN | TH_ACK;
1233 th->th_win = htons(sc->sc_wnd);
1236 /* Tack on the TCP options. */
1239 optp = (u_int8_t *)(th + 1);
1240 *optp++ = TCPOPT_MAXSEG;
1241 *optp++ = TCPOLEN_MAXSEG;
1242 *optp++ = (mssopt >> 8) & 0xff;
1243 *optp++ = mssopt & 0xff;
1245 if (sc->sc_flags & SCF_WINSCALE) {
1246 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1247 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1248 sc->sc_request_r_scale);
1252 if (sc->sc_flags & SCF_TIMESTAMP) {
1253 u_int32_t *lp = (u_int32_t *)(optp);
1255 /* Form timestamp option as shown in appendix A of RFC 1323. */
1256 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1257 *lp++ = htonl(ticks);
1258 *lp = htonl(sc->sc_tsrecent);
1259 optp += TCPOLEN_TSTAMP_APPA;
1262 #ifdef TCP_SIGNATURE
1264 * Handle TCP-MD5 passive opener response.
1266 if (sc->sc_flags & SCF_SIGNATURE) {
1267 u_int8_t *bp = optp;
1270 *bp++ = TCPOPT_SIGNATURE;
1271 *bp++ = TCPOLEN_SIGNATURE;
1272 for (i = 0; i < TCP_SIGLEN; i++)
1274 tcpsignature_compute(m, 0, optlen,
1275 optp + 2, IPSEC_DIR_OUTBOUND);
1278 optp += TCPOLEN_SIGNATURE + 2;
1280 #endif /* TCP_SIGNATURE */
1282 if (sc->sc_flags & SCF_SACK_PERMITTED) {
1283 *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
1284 optp += TCPOLEN_SACK_PERMITTED_ALIGNED;
1289 struct route_in6 *ro6 = &sc->sc_route6;
1292 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1293 ip6->ip6_hlim = in6_selecthlim(NULL,
1294 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
1295 error = ip6_output(m, NULL, ro6, 0, NULL, NULL,
1296 sc->sc_tp->t_inpcb);
1298 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1299 htons(tlen - hlen + IPPROTO_TCP));
1300 m->m_pkthdr.csum_flags = CSUM_TCP;
1301 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1302 error = ip_output(m, sc->sc_ipopts, &sc->sc_route,
1303 IP_DEBUGROUTE, NULL, sc->sc_tp->t_inpcb);
1311 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1313 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1315 * (A): peer mss index
1319 * The values below are chosen to minimize the size of the tcp_secret
1320 * table, as well as providing roughly a 16 second lifetime for the cookie.
1323 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1324 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1326 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1327 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1328 #define SYNCOOKIE_TIMEOUT \
1329 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1330 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1333 u_int32_t ts_secbits[4];
1335 } tcp_secret[SYNCOOKIE_NSECRETS];
1337 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1339 static MD5_CTX syn_ctx;
1341 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1344 u_int32_t laddr, faddr;
1345 u_int32_t secbits[4];
1346 u_int16_t lport, fport;
1350 CTASSERT(sizeof(struct md5_add) == 28);
1354 * Consider the problem of a recreated (and retransmitted) cookie. If the
1355 * original SYN was accepted, the connection is established. The second
1356 * SYN is inflight, and if it arrives with an ISN that falls within the
1357 * receive window, the connection is killed.
1359 * However, since cookies have other problems, this may not be worth
1364 syncookie_generate(struct syncache *sc)
1366 u_int32_t md5_buffer[4];
1371 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1373 const boolean_t isipv6 = FALSE;
1376 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1377 if (tcp_secret[idx].ts_expire < ticks) {
1378 for (i = 0; i < 4; i++)
1379 tcp_secret[idx].ts_secbits[i] = karc4random();
1380 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1382 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1383 if (tcp_msstab[data] <= sc->sc_peer_mss)
1385 data = (data << SYNCOOKIE_WNDBITS) | idx;
1386 data ^= sc->sc_irs; /* peer's iss */
1389 MD5Add(sc->sc_inc.inc6_laddr);
1390 MD5Add(sc->sc_inc.inc6_faddr);
1394 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1395 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1397 add.lport = sc->sc_inc.inc_lport;
1398 add.fport = sc->sc_inc.inc_fport;
1399 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1400 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1401 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1402 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1404 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1405 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1409 static struct syncache *
1410 syncookie_lookup(struct in_conninfo *inc, struct tcphdr *th, struct socket *so)
1412 u_int32_t md5_buffer[4];
1413 struct syncache *sc;
1418 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1419 idx = data & SYNCOOKIE_WNDMASK;
1420 if (tcp_secret[idx].ts_expire < ticks ||
1421 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1425 if (inc->inc_isipv6) {
1426 MD5Add(inc->inc6_laddr);
1427 MD5Add(inc->inc6_faddr);
1433 add.laddr = inc->inc_laddr.s_addr;
1434 add.faddr = inc->inc_faddr.s_addr;
1436 add.lport = inc->inc_lport;
1437 add.fport = inc->inc_fport;
1438 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1439 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1440 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1441 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1443 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1444 data ^= md5_buffer[0];
1445 if (data & ~SYNCOOKIE_DATAMASK)
1447 data = data >> SYNCOOKIE_WNDBITS;
1450 * Fill in the syncache values.
1451 * XXX duplicate code from syncache_add
1453 sc = kmalloc(sizeof(struct syncache), M_SYNCACHE, M_WAITOK|M_ZERO);
1454 sc->sc_ipopts = NULL;
1455 sc->sc_inc.inc_fport = inc->inc_fport;
1456 sc->sc_inc.inc_lport = inc->inc_lport;
1458 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1459 if (inc->inc_isipv6) {
1460 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1461 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1462 sc->sc_route6.ro_rt = NULL;
1466 sc->sc_inc.inc_faddr = inc->inc_faddr;
1467 sc->sc_inc.inc_laddr = inc->inc_laddr;
1468 sc->sc_route.ro_rt = NULL;
1470 sc->sc_irs = th->th_seq - 1;
1471 sc->sc_iss = th->th_ack - 1;
1472 wnd = ssb_space(&so->so_rcv);
1474 wnd = imin(wnd, TCP_MAXWIN);
1478 sc->sc_peer_mss = tcp_msstab[data];