2 * Copyright (c) 2001 McAfee, Inc.
3 * Copyright (c) 2006 Andre Oppermann, Internet Business Solutions AG
6 * This software was developed for the FreeBSD Project by Jonathan Lemon
7 * and McAfee Research, the Security Research Division of McAfee, Inc. under
8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
9 * DARPA CHATS research program.
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/kernel.h>
43 #include <sys/sysctl.h>
45 #include <sys/mutex.h>
46 #include <sys/malloc.h>
49 #include <sys/proc.h> /* for proc0 declaration */
50 #include <sys/random.h>
51 #include <sys/socket.h>
52 #include <sys/socketvar.h>
53 #include <sys/syslog.h>
58 #include <net/route.h>
60 #include <netinet/in.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/ip.h>
63 #include <netinet/in_var.h>
64 #include <netinet/in_pcb.h>
65 #include <netinet/ip_var.h>
66 #include <netinet/ip_options.h>
68 #include <netinet/ip6.h>
69 #include <netinet/icmp6.h>
70 #include <netinet6/nd6.h>
71 #include <netinet6/ip6_var.h>
72 #include <netinet6/in6_pcb.h>
74 #include <netinet/tcp.h>
75 #include <netinet/tcp_fsm.h>
76 #include <netinet/tcp_seq.h>
77 #include <netinet/tcp_timer.h>
78 #include <netinet/tcp_var.h>
80 #include <netinet6/tcp6_var.h>
84 #include <netinet6/ipsec.h>
86 #include <netinet6/ipsec6.h>
91 #include <netipsec/ipsec.h>
93 #include <netipsec/ipsec6.h>
95 #include <netipsec/key.h>
98 #include <machine/in_cksum.h>
100 #include <security/mac/mac_framework.h>
102 static int tcp_syncookies = 1;
103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
105 "Use TCP SYN cookies if the syncache overflows");
107 static int tcp_syncookiesonly = 0;
108 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
109 &tcp_syncookiesonly, 0,
110 "Use only TCP SYN cookies");
112 #define SYNCOOKIE_SECRET_SIZE 8 /* dwords */
113 #define SYNCOOKIE_LIFETIME 16 /* seconds */
116 TAILQ_ENTRY(syncache) sc_hash;
117 struct in_conninfo sc_inc; /* addresses */
118 u_long sc_rxttime; /* retransmit time */
119 u_int16_t sc_rxmits; /* retransmit counter */
121 u_int32_t sc_tsreflect; /* timestamp to reflect */
122 u_int32_t sc_ts; /* our timestamp to send */
123 u_int32_t sc_tsoff; /* ts offset w/ syncookies */
124 u_int32_t sc_flowlabel; /* IPv6 flowlabel */
125 tcp_seq sc_irs; /* seq from peer */
126 tcp_seq sc_iss; /* our ISS */
127 struct mbuf *sc_ipopts; /* source route */
129 u_int16_t sc_peer_mss; /* peer's MSS */
130 u_int16_t sc_wnd; /* advertised window */
131 u_int8_t sc_ip_ttl; /* IPv4 TTL */
132 u_int8_t sc_ip_tos; /* IPv4 TOS */
133 u_int8_t sc_requested_s_scale:4,
134 sc_requested_r_scale:4;
136 #define SCF_NOOPT 0x01 /* no TCP options */
137 #define SCF_WINSCALE 0x02 /* negotiated window scaling */
138 #define SCF_TIMESTAMP 0x04 /* negotiated timestamps */
139 /* MSS is implicit */
140 #define SCF_UNREACH 0x10 /* icmp unreachable received */
141 #define SCF_SIGNATURE 0x20 /* send MD5 digests */
142 #define SCF_SACK 0x80 /* send SACK option */
144 struct label *sc_label; /* MAC label reference */
148 struct syncache_head {
150 TAILQ_HEAD(sch_head, syncache) sch_bucket;
151 struct callout sch_timer;
155 u_int32_t sch_secbits_odd[SYNCOOKIE_SECRET_SIZE];
156 u_int32_t sch_secbits_even[SYNCOOKIE_SECRET_SIZE];
157 u_int sch_reseed; /* time_uptime, seconds */
160 static void syncache_drop(struct syncache *, struct syncache_head *);
161 static void syncache_free(struct syncache *);
162 static void syncache_insert(struct syncache *, struct syncache_head *);
163 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
164 static int syncache_respond(struct syncache *);
165 static struct socket *syncache_socket(struct syncache *, struct socket *,
167 static void syncache_timer(void *);
168 static void syncookie_generate(struct syncache_head *, struct syncache *,
170 static struct syncache
171 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
172 struct syncache *, struct tcpopt *, struct tcphdr *,
176 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
177 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
178 * the odds are that the user has given up attempting to connect by then.
180 #define SYNCACHE_MAXREXMTS 3
182 /* Arbitrary values */
183 #define TCP_SYNCACHE_HASHSIZE 512
184 #define TCP_SYNCACHE_BUCKETLIMIT 30
186 struct tcp_syncache {
187 struct syncache_head *hashbase;
192 u_int cache_count; /* XXX: unprotected */
197 static struct tcp_syncache tcp_syncache;
199 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
201 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
202 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
204 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
205 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
207 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
208 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
210 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
211 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
213 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
214 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
216 int tcp_sc_rst_sock_fail = 1;
217 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail, CTLFLAG_RW,
218 &tcp_sc_rst_sock_fail, 0, "Send reset on socket allocation failure");
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)
243 #define SYNCACHE_TIMEOUT(sc, sch, co) do { \
245 (sc)->sc_rxttime = ticks + \
246 TCPTV_RTOBASE * tcp_backoff[(sc)->sc_rxmits - 1]; \
247 if ((sch)->sch_nextc > (sc)->sc_rxttime) \
248 (sch)->sch_nextc = (sc)->sc_rxttime; \
249 if (!TAILQ_EMPTY(&(sch)->sch_bucket) && !(co)) \
250 callout_reset(&(sch)->sch_timer, \
251 (sch)->sch_nextc - ticks, \
252 syncache_timer, (void *)(sch)); \
255 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
256 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
257 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
260 * Requires the syncache entry to be already removed from the bucket list.
263 syncache_free(struct syncache *sc)
266 (void) m_free(sc->sc_ipopts);
268 mac_destroy_syncache(&sc->sc_label);
271 uma_zfree(tcp_syncache.zone, sc);
279 tcp_syncache.cache_count = 0;
280 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
281 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
282 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
283 tcp_syncache.hash_secret = arc4random();
285 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
286 &tcp_syncache.hashsize);
287 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
288 &tcp_syncache.bucket_limit);
289 if (!powerof2(tcp_syncache.hashsize) || tcp_syncache.hashsize == 0) {
290 printf("WARNING: syncache hash size is not a power of 2.\n");
291 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
293 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
296 tcp_syncache.cache_limit =
297 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
298 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
299 &tcp_syncache.cache_limit);
301 /* Allocate the hash table. */
302 MALLOC(tcp_syncache.hashbase, struct syncache_head *,
303 tcp_syncache.hashsize * sizeof(struct syncache_head),
304 M_SYNCACHE, M_WAITOK | M_ZERO);
306 /* Initialize the hash buckets. */
307 for (i = 0; i < tcp_syncache.hashsize; i++) {
308 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket);
309 mtx_init(&tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
311 callout_init_mtx(&tcp_syncache.hashbase[i].sch_timer,
312 &tcp_syncache.hashbase[i].sch_mtx, 0);
313 tcp_syncache.hashbase[i].sch_length = 0;
316 /* Create the syncache entry zone. */
317 tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
318 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
319 uma_zone_set_max(tcp_syncache.zone, tcp_syncache.cache_limit);
323 * Inserts a syncache entry into the specified bucket row.
324 * Locks and unlocks the syncache_head autonomously.
327 syncache_insert(struct syncache *sc, struct syncache_head *sch)
329 struct syncache *sc2;
334 * Make sure that we don't overflow the per-bucket limit.
335 * If the bucket is full, toss the oldest element.
337 if (sch->sch_length >= tcp_syncache.bucket_limit) {
338 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
339 ("sch->sch_length incorrect"));
340 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
341 syncache_drop(sc2, sch);
342 tcpstat.tcps_sc_bucketoverflow++;
345 /* Put it into the bucket. */
346 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
349 /* Reinitialize the bucket row's timer. */
350 SYNCACHE_TIMEOUT(sc, sch, 1);
354 tcp_syncache.cache_count++;
355 tcpstat.tcps_sc_added++;
359 * Remove and free entry from syncache bucket row.
360 * Expects locked syncache head.
363 syncache_drop(struct syncache *sc, struct syncache_head *sch)
366 SCH_LOCK_ASSERT(sch);
368 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
372 tcp_syncache.cache_count--;
376 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
377 * If we have retransmitted an entry the maximum number of times, expire it.
378 * One separate timer for each bucket row.
381 syncache_timer(void *xsch)
383 struct syncache_head *sch = (struct syncache_head *)xsch;
384 struct syncache *sc, *nsc;
388 /* NB: syncache_head has already been locked by the callout. */
389 SCH_LOCK_ASSERT(sch);
391 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
393 * We do not check if the listen socket still exists
394 * and accept the case where the listen socket may be
395 * gone by the time we resend the SYN/ACK. We do
396 * not expect this to happens often. If it does,
397 * then the RST will be sent by the time the remote
398 * host does the SYN/ACK->ACK.
400 if (sc->sc_rxttime >= tick) {
401 if (sc->sc_rxttime < sch->sch_nextc)
402 sch->sch_nextc = sc->sc_rxttime;
406 if (sc->sc_rxmits > tcp_syncache.rexmt_limit) {
407 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
408 log(LOG_DEBUG, "%s; %s: Response timeout\n",
412 syncache_drop(sc, sch);
413 tcpstat.tcps_sc_stale++;
417 (void) syncache_respond(sc);
418 tcpstat.tcps_sc_retransmitted++;
419 SYNCACHE_TIMEOUT(sc, sch, 0);
421 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
422 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
423 syncache_timer, (void *)(sch));
427 * Find an entry in the syncache.
428 * Returns always with locked syncache_head plus a matching entry or NULL.
431 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
434 struct syncache_head *sch;
437 if (inc->inc_isipv6) {
438 sch = &tcp_syncache.hashbase[
439 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
444 /* Circle through bucket row to find matching entry. */
445 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
446 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
452 sch = &tcp_syncache.hashbase[
453 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
458 /* Circle through bucket row to find matching entry. */
459 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
461 if (sc->sc_inc.inc_isipv6)
464 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
468 SCH_LOCK_ASSERT(*schp);
469 return (NULL); /* always returns with locked sch */
473 * This function is called when we get a RST for a
474 * non-existent connection, so that we can see if the
475 * connection is in the syn cache. If it is, zap it.
478 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
481 struct syncache_head *sch;
483 sc = syncache_lookup(inc, &sch); /* returns locked sch */
484 SCH_LOCK_ASSERT(sch);
489 * If the RST bit is set, check the sequence number to see
490 * if this is a valid reset segment.
492 * In all states except SYN-SENT, all reset (RST) segments
493 * are validated by checking their SEQ-fields. A reset is
494 * valid if its sequence number is in the window.
496 * The sequence number in the reset segment is normally an
497 * echo of our outgoing acknowlegement numbers, but some hosts
498 * send a reset with the sequence number at the rightmost edge
499 * of our receive window, and we have to handle this case.
501 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
502 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
503 syncache_drop(sc, sch);
504 tcpstat.tcps_sc_reset++;
511 syncache_badack(struct in_conninfo *inc)
514 struct syncache_head *sch;
516 sc = syncache_lookup(inc, &sch); /* returns locked sch */
517 SCH_LOCK_ASSERT(sch);
519 syncache_drop(sc, sch);
520 tcpstat.tcps_sc_badack++;
526 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
529 struct syncache_head *sch;
531 sc = syncache_lookup(inc, &sch); /* returns locked sch */
532 SCH_LOCK_ASSERT(sch);
536 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
537 if (ntohl(th->th_seq) != sc->sc_iss)
541 * If we've rertransmitted 3 times and this is our second error,
542 * we remove the entry. Otherwise, we allow it to continue on.
543 * This prevents us from incorrectly nuking an entry during a
544 * spurious network outage.
548 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
549 sc->sc_flags |= SCF_UNREACH;
552 syncache_drop(sc, sch);
553 tcpstat.tcps_sc_unreach++;
559 * Build a new TCP socket structure from a syncache entry.
561 static struct socket *
562 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
564 struct inpcb *inp = NULL;
570 INP_INFO_WLOCK_ASSERT(&tcbinfo);
573 * Ok, create the full blown connection, and set things up
574 * as they would have been set up if we had created the
575 * connection when the SYN arrived. If we can't create
576 * the connection, abort it.
578 so = sonewconn(lso, SS_ISCONNECTED);
581 * Drop the connection; we will either send a RST or
582 * have the peer retransmit its SYN again after its
585 tcpstat.tcps_listendrop++;
586 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
587 log(LOG_DEBUG, "%s; %s: Socket create failed "
588 "due to limits or memory shortage\n",
596 mac_set_socket_peer_from_mbuf(m, so);
603 /* Insert new socket into PCB hash list. */
604 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
606 if (sc->sc_inc.inc_isipv6) {
607 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
609 inp->inp_vflag &= ~INP_IPV6;
610 inp->inp_vflag |= INP_IPV4;
612 inp->inp_laddr = sc->sc_inc.inc_laddr;
616 inp->inp_lport = sc->sc_inc.inc_lport;
617 if (in_pcbinshash(inp) != 0) {
619 * Undo the assignments above if we failed to
620 * put the PCB on the hash lists.
623 if (sc->sc_inc.inc_isipv6)
624 inp->in6p_laddr = in6addr_any;
627 inp->inp_laddr.s_addr = INADDR_ANY;
632 /* Copy old policy into new socket's. */
633 if (ipsec_copy_pcbpolicy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
634 printf("syncache_socket: could not copy policy\n");
637 /* Copy old policy into new socket's. */
638 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
639 printf("syncache_socket: could not copy policy\n");
642 if (sc->sc_inc.inc_isipv6) {
643 struct inpcb *oinp = sotoinpcb(lso);
644 struct in6_addr laddr6;
645 struct sockaddr_in6 sin6;
647 * Inherit socket options from the listening socket.
648 * Note that in6p_inputopts are not (and should not be)
649 * copied, since it stores previously received options and is
650 * used to detect if each new option is different than the
651 * previous one and hence should be passed to a user.
652 * If we copied in6p_inputopts, a user would not be able to
653 * receive options just after calling the accept system call.
655 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
656 if (oinp->in6p_outputopts)
657 inp->in6p_outputopts =
658 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
660 sin6.sin6_family = AF_INET6;
661 sin6.sin6_len = sizeof(sin6);
662 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
663 sin6.sin6_port = sc->sc_inc.inc_fport;
664 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
665 laddr6 = inp->in6p_laddr;
666 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
667 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
668 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6,
670 inp->in6p_laddr = laddr6;
673 /* Override flowlabel from in6_pcbconnect. */
674 inp->in6p_flowinfo &= ~IPV6_FLOWLABEL_MASK;
675 inp->in6p_flowinfo |= sc->sc_flowlabel;
679 struct in_addr laddr;
680 struct sockaddr_in sin;
682 inp->inp_options = ip_srcroute(m);
683 if (inp->inp_options == NULL) {
684 inp->inp_options = sc->sc_ipopts;
685 sc->sc_ipopts = NULL;
688 sin.sin_family = AF_INET;
689 sin.sin_len = sizeof(sin);
690 sin.sin_addr = sc->sc_inc.inc_faddr;
691 sin.sin_port = sc->sc_inc.inc_fport;
692 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
693 laddr = inp->inp_laddr;
694 if (inp->inp_laddr.s_addr == INADDR_ANY)
695 inp->inp_laddr = sc->sc_inc.inc_laddr;
696 if (in_pcbconnect(inp, (struct sockaddr *)&sin,
698 inp->inp_laddr = laddr;
703 tp->t_state = TCPS_SYN_RECEIVED;
704 tp->iss = sc->sc_iss;
705 tp->irs = sc->sc_irs;
708 tp->snd_wl1 = sc->sc_irs;
709 tp->snd_max = tp->iss + 1;
710 tp->snd_nxt = tp->iss + 1;
711 tp->rcv_up = sc->sc_irs + 1;
712 tp->rcv_wnd = sc->sc_wnd;
713 tp->rcv_adv += tp->rcv_wnd;
714 tp->last_ack_sent = tp->rcv_nxt;
716 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
717 if (sc->sc_flags & SCF_NOOPT)
718 tp->t_flags |= TF_NOOPT;
720 if (sc->sc_flags & SCF_WINSCALE) {
721 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
722 tp->snd_scale = sc->sc_requested_s_scale;
723 tp->request_r_scale = sc->sc_requested_r_scale;
725 if (sc->sc_flags & SCF_TIMESTAMP) {
726 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
727 tp->ts_recent = sc->sc_tsreflect;
728 tp->ts_recent_age = ticks;
729 tp->ts_offset = sc->sc_tsoff;
732 if (sc->sc_flags & SCF_SIGNATURE)
733 tp->t_flags |= TF_SIGNATURE;
735 if (sc->sc_flags & SCF_SACK)
736 tp->t_flags |= TF_SACK_PERMIT;
740 * Set up MSS and get cached values from tcp_hostcache.
741 * This might overwrite some of the defaults we just set.
743 tcp_mss(tp, sc->sc_peer_mss);
746 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
748 if (sc->sc_rxmits > 1)
749 tp->snd_cwnd = tp->t_maxseg;
750 tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
754 tcpstat.tcps_accepts++;
766 * This function gets called when we receive an ACK for a
767 * socket in the LISTEN state. We look up the connection
768 * in the syncache, and if its there, we pull it out of
769 * the cache and turn it into a full-blown connection in
770 * the SYN-RECEIVED state.
773 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
774 struct socket **lsop, struct mbuf *m)
777 struct syncache_head *sch;
782 * Global TCP locks are held because we manipulate the PCB lists
783 * and create a new socket.
785 INP_INFO_WLOCK_ASSERT(&tcbinfo);
786 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
787 ("%s: can handle only ACK", __func__));
789 sc = syncache_lookup(inc, &sch); /* returns locked sch */
790 SCH_LOCK_ASSERT(sch);
793 * There is no syncache entry, so see if this ACK is
794 * a returning syncookie. To do this, first:
795 * A. See if this socket has had a syncache entry dropped in
796 * the past. We don't want to accept a bogus syncookie
797 * if we've never received a SYN.
798 * B. check that the syncookie is valid. If it is, then
799 * cobble up a fake syncache entry, and return.
801 if (!tcp_syncookies) {
803 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
804 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
805 "segment rejected (syncookies disabled)\n",
809 bzero(&scs, sizeof(scs));
810 sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
813 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
814 log(LOG_DEBUG, "%s; %s: Segment failed "
815 "SYNCOOKIE authentication, segment rejected "
816 "(probably spoofed)\n", s, __func__);
819 tcpstat.tcps_sc_recvcookie++;
821 /* Pull out the entry to unlock the bucket row. */
822 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
824 tcp_syncache.cache_count--;
829 * Segment validation:
830 * ACK must match our initial sequence number + 1 (the SYN|ACK).
832 if (th->th_ack != sc->sc_iss + 1) {
833 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
834 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
835 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
839 * The SEQ must match the received initial receive sequence
840 * number + 1 (the SYN) because we didn't ACK any data that
841 * may have come with the SYN.
843 if (th->th_seq != sc->sc_irs + 1) {
844 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
845 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
846 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
850 * If timestamps were present in the SYN and we accepted
851 * them in our SYN|ACK we require them to be present from
852 * now on. And vice versa.
854 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
855 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
856 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
857 "segment rejected\n", s, __func__);
860 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
861 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
862 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
863 "segment rejected\n", s, __func__);
867 * If timestamps were negotiated the reflected timestamp
868 * must be equal to what we actually sent in the SYN|ACK.
870 if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts) {
871 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
872 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
873 "segment rejected\n",
874 s, __func__, to->to_tsecr, sc->sc_ts);
878 *lsop = syncache_socket(sc, *lsop, m);
881 tcpstat.tcps_sc_aborted++;
883 tcpstat.tcps_sc_completed++;
889 if (sc != NULL && sc != &scs)
898 * Given a LISTEN socket and an inbound SYN request, add
899 * this to the syn cache, and send back a segment:
900 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
903 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
904 * Doing so would require that we hold onto the data and deliver it
905 * to the application. However, if we are the target of a SYN-flood
906 * DoS attack, an attacker could send data which would eventually
907 * consume all available buffer space if it were ACKed. By not ACKing
908 * the data, we avoid this DoS scenario.
911 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
912 struct inpcb *inp, struct socket **lsop, struct mbuf *m)
916 struct syncache *sc = NULL;
917 struct syncache_head *sch;
918 struct mbuf *ipopts = NULL;
920 int win, sb_hiwat, ip_ttl, ip_tos, noopt;
922 int autoflowlabel = 0;
925 struct label *maclabel;
929 INP_INFO_WLOCK_ASSERT(&tcbinfo);
930 INP_LOCK_ASSERT(inp); /* listen socket */
933 * Combine all so/tp operations very early to drop the INP lock as
940 if (inc->inc_isipv6 &&
941 (inp->in6p_flags & IN6P_AUTOFLOWLABEL))
944 ip_ttl = inp->inp_ip_ttl;
945 ip_tos = inp->inp_ip_tos;
946 win = sbspace(&so->so_rcv);
947 sb_hiwat = so->so_rcv.sb_hiwat;
948 noopt = (tp->t_flags & TF_NOOPT);
954 if (mac_init_syncache(&maclabel) != 0) {
956 INP_INFO_WUNLOCK(&tcbinfo);
959 mac_init_syncache_from_inpcb(maclabel, inp);
962 INP_INFO_WUNLOCK(&tcbinfo);
965 * Remember the IP options, if any.
968 if (!inc->inc_isipv6)
970 ipopts = ip_srcroute(m);
973 * See if we already have an entry for this connection.
974 * If we do, resend the SYN,ACK, and reset the retransmit timer.
976 * XXX: should the syncache be re-initialized with the contents
977 * of the new SYN here (which may have different options?)
979 sc = syncache_lookup(inc, &sch); /* returns locked entry */
980 SCH_LOCK_ASSERT(sch);
982 tcpstat.tcps_sc_dupsyn++;
985 * If we were remembering a previous source route,
986 * forget it and use the new one we've been given.
989 (void) m_free(sc->sc_ipopts);
990 sc->sc_ipopts = ipopts;
993 * Update timestamp if present.
995 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
996 sc->sc_tsreflect = to->to_tsval;
998 sc->sc_flags &= ~SCF_TIMESTAMP;
1001 * Since we have already unconditionally allocated label
1002 * storage, free it up. The syncache entry will already
1003 * have an initialized label we can use.
1005 mac_destroy_syncache(&maclabel);
1006 KASSERT(sc->sc_label != NULL,
1007 ("%s: label not initialized", __func__));
1009 if (syncache_respond(sc) == 0) {
1010 SYNCACHE_TIMEOUT(sc, sch, 1);
1011 tcpstat.tcps_sndacks++;
1012 tcpstat.tcps_sndtotal++;
1018 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
1021 * The zone allocator couldn't provide more entries.
1022 * Treat this as if the cache was full; drop the oldest
1023 * entry and insert the new one.
1025 tcpstat.tcps_sc_zonefail++;
1026 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1027 syncache_drop(sc, sch);
1028 sc = uma_zalloc(tcp_syncache.zone, M_NOWAIT | M_ZERO);
1030 if (tcp_syncookies) {
1031 bzero(&scs, sizeof(scs));
1036 (void) m_free(ipopts);
1043 * Fill in the syncache values.
1046 sc->sc_label = maclabel;
1048 sc->sc_ipopts = ipopts;
1049 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1051 if (!inc->inc_isipv6)
1054 sc->sc_ip_tos = ip_tos;
1055 sc->sc_ip_ttl = ip_ttl;
1058 sc->sc_irs = th->th_seq;
1059 sc->sc_iss = arc4random();
1061 sc->sc_flowlabel = 0;
1064 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1065 * win was derived from socket earlier in the function.
1068 win = imin(win, TCP_MAXWIN);
1071 if (tcp_do_rfc1323) {
1073 * A timestamp received in a SYN makes
1074 * it ok to send timestamp requests and replies.
1076 if (to->to_flags & TOF_TS) {
1077 sc->sc_tsreflect = to->to_tsval;
1079 sc->sc_flags |= SCF_TIMESTAMP;
1081 if (to->to_flags & TOF_SCALE) {
1085 * Compute proper scaling value from buffer space.
1086 * Leave enough room for the socket buffer to grow
1087 * with auto sizing. This allows us to scale the
1088 * receive buffer over a wide range while not losing
1089 * any efficiency or fine granularity.
1091 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1092 * or <SYN,ACK>) segment itself is never scaled.
1094 while (wscale < TCP_MAX_WINSHIFT &&
1095 (0x1 << wscale) < tcp_minmss)
1097 sc->sc_requested_r_scale = wscale;
1098 sc->sc_requested_s_scale = to->to_wscale;
1099 sc->sc_flags |= SCF_WINSCALE;
1102 #ifdef TCP_SIGNATURE
1104 * If listening socket requested TCP digests, and received SYN
1105 * contains the option, flag this in the syncache so that
1106 * syncache_respond() will do the right thing with the SYN+ACK.
1107 * XXX: Currently we always record the option by default and will
1108 * attempt to use it in syncache_respond().
1110 if (to->to_flags & TOF_SIGNATURE)
1111 sc->sc_flags |= SCF_SIGNATURE;
1113 if (to->to_flags & TOF_SACK)
1114 sc->sc_flags |= SCF_SACK;
1115 if (to->to_flags & TOF_MSS)
1116 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1118 sc->sc_flags |= SCF_NOOPT;
1120 if (tcp_syncookies) {
1121 syncookie_generate(sch, sc, &flowtmp);
1124 sc->sc_flowlabel = flowtmp;
1130 (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
1136 * Do a standard 3-way handshake.
1138 if (syncache_respond(sc) == 0) {
1139 if (tcp_syncookies && tcp_syncookiesonly && sc != &scs)
1141 else if (sc != &scs)
1142 syncache_insert(sc, sch); /* locks and unlocks sch */
1143 tcpstat.tcps_sndacks++;
1144 tcpstat.tcps_sndtotal++;
1148 tcpstat.tcps_sc_dropped++;
1154 mac_destroy_syncache(&maclabel);
1162 syncache_respond(struct syncache *sc)
1164 struct ip *ip = NULL;
1168 u_int16_t hlen, tlen, mssopt;
1171 struct ip6_hdr *ip6 = NULL;
1176 (sc->sc_inc.inc_isipv6) ? sizeof(struct ip6_hdr) :
1179 tlen = hlen + sizeof(struct tcphdr);
1181 /* Determine MSS we advertize to other end of connection. */
1182 mssopt = tcp_mssopt(&sc->sc_inc);
1183 if (sc->sc_peer_mss)
1184 mssopt = max( min(sc->sc_peer_mss, mssopt), tcp_minmss);
1186 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1187 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1188 ("syncache: mbuf too small"));
1190 /* Create the IP+TCP header from scratch. */
1191 m = m_gethdr(M_DONTWAIT, MT_DATA);
1195 mac_create_mbuf_from_syncache(sc->sc_label, m);
1197 m->m_data += max_linkhdr;
1199 m->m_pkthdr.len = tlen;
1200 m->m_pkthdr.rcvif = NULL;
1203 if (sc->sc_inc.inc_isipv6) {
1204 ip6 = mtod(m, struct ip6_hdr *);
1205 ip6->ip6_vfc = IPV6_VERSION;
1206 ip6->ip6_nxt = IPPROTO_TCP;
1207 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1208 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1209 ip6->ip6_plen = htons(tlen - hlen);
1210 /* ip6_hlim is set after checksum */
1211 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1212 ip6->ip6_flow |= sc->sc_flowlabel;
1214 th = (struct tcphdr *)(ip6 + 1);
1218 ip = mtod(m, struct ip *);
1219 ip->ip_v = IPVERSION;
1220 ip->ip_hl = sizeof(struct ip) >> 2;
1225 ip->ip_p = IPPROTO_TCP;
1226 ip->ip_src = sc->sc_inc.inc_laddr;
1227 ip->ip_dst = sc->sc_inc.inc_faddr;
1228 ip->ip_ttl = sc->sc_ip_ttl;
1229 ip->ip_tos = sc->sc_ip_tos;
1232 * See if we should do MTU discovery. Route lookups are
1233 * expensive, so we will only unset the DF bit if:
1235 * 1) path_mtu_discovery is disabled
1236 * 2) the SCF_UNREACH flag has been set
1238 if (path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1239 ip->ip_off |= IP_DF;
1241 th = (struct tcphdr *)(ip + 1);
1243 th->th_sport = sc->sc_inc.inc_lport;
1244 th->th_dport = sc->sc_inc.inc_fport;
1246 th->th_seq = htonl(sc->sc_iss);
1247 th->th_ack = htonl(sc->sc_irs + 1);
1248 th->th_off = sizeof(struct tcphdr) >> 2;
1250 th->th_flags = TH_SYN|TH_ACK;
1251 th->th_win = htons(sc->sc_wnd);
1254 /* Tack on the TCP options. */
1255 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1259 to.to_flags = TOF_MSS;
1260 if (sc->sc_flags & SCF_WINSCALE) {
1261 to.to_wscale = sc->sc_requested_r_scale;
1262 to.to_flags |= TOF_SCALE;
1264 if (sc->sc_flags & SCF_TIMESTAMP) {
1265 /* Virgin timestamp or TCP cookie enhanced one. */
1266 to.to_tsval = sc->sc_ts;
1267 to.to_tsecr = sc->sc_tsreflect;
1268 to.to_flags |= TOF_TS;
1270 if (sc->sc_flags & SCF_SACK)
1271 to.to_flags |= TOF_SACKPERM;
1272 #ifdef TCP_SIGNATURE
1273 if (sc->sc_flags & SCF_SIGNATURE)
1274 to.to_flags |= TOF_SIGNATURE;
1276 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1278 #ifdef TCP_SIGNATURE
1279 tcp_signature_compute(m, sizeof(struct ip), 0, optlen,
1280 to.to_signature, IPSEC_DIR_OUTBOUND);
1283 /* Adjust headers by option size. */
1284 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1286 m->m_pkthdr.len += optlen;
1288 if (sc->sc_inc.inc_isipv6)
1289 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1292 ip->ip_len += optlen;
1297 if (sc->sc_inc.inc_isipv6) {
1299 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen,
1300 tlen + optlen - hlen);
1301 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1302 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1306 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1307 htons(tlen + optlen - hlen + IPPROTO_TCP));
1308 m->m_pkthdr.csum_flags = CSUM_TCP;
1309 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1310 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1316 * The purpose of SYN cookies is to avoid keeping track of all SYN's we
1317 * receive and to be able to handle SYN floods from bogus source addresses
1318 * (where we will never receive any reply). SYN floods try to exhaust all
1319 * our memory and available slots in the SYN cache table to cause a denial
1320 * of service to legitimate users of the local host.
1322 * The idea of SYN cookies is to encode and include all necessary information
1323 * about the connection setup state within the SYN-ACK we send back and thus
1324 * to get along without keeping any local state until the ACK to the SYN-ACK
1325 * arrives (if ever). Everything we need to know should be available from
1326 * the information we encoded in the SYN-ACK.
1328 * More information about the theory behind SYN cookies and its first
1329 * discussion and specification can be found at:
1330 * http://cr.yp.to/syncookies.html (overview)
1331 * http://cr.yp.to/syncookies/archive (gory details)
1333 * This implementation extends the orginal idea and first implementation
1334 * of FreeBSD by using not only the initial sequence number field to store
1335 * information but also the timestamp field if present. This way we can
1336 * keep track of the entire state we need to know to recreate the session in
1337 * its original form. Almost all TCP speakers implement RFC1323 timestamps
1338 * these days. For those that do not we still have to live with the known
1339 * shortcomings of the ISN only SYN cookies.
1343 * Initial sequence number we send:
1344 * 31|................................|0
1345 * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
1346 * D = MD5 Digest (first dword)
1348 * R = Rotation of secret
1349 * P = Odd or Even secret
1351 * The MD5 Digest is computed with over following parameters:
1352 * a) randomly rotated secret
1353 * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
1354 * c) the received initial sequence number from remote host
1355 * d) the rotation offset and odd/even bit
1357 * Timestamp we send:
1358 * 31|................................|0
1359 * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
1360 * D = MD5 Digest (third dword) (only as filler)
1361 * S = Requested send window scale
1362 * R = Requested receive window scale
1364 * 5 = TCP-MD5 enabled (not implemented yet)
1365 * XORed with MD5 Digest (forth dword)
1367 * The timestamp isn't cryptographically secure and doesn't need to be.
1368 * The double use of the MD5 digest dwords ties it to a specific remote/
1369 * local host/port, remote initial sequence number and our local time
1370 * limited secret. A received timestamp is reverted (XORed) and then
1371 * the contained MD5 dword is compared to the computed one to ensure the
1372 * timestamp belongs to the SYN-ACK we sent. The other parameters may
1373 * have been tampered with but this isn't different from supplying bogus
1374 * values in the SYN in the first place.
1376 * Some problems with SYN cookies remain however:
1377 * Consider the problem of a recreated (and retransmitted) cookie. If the
1378 * original SYN was accepted, the connection is established. The second
1379 * SYN is inflight, and if it arrives with an ISN that falls within the
1380 * receive window, the connection is killed.
1383 * A heuristic to determine when to accept syn cookies is not necessary.
1384 * An ACK flood would cause the syncookie verification to be attempted,
1385 * but a SYN flood causes syncookies to be generated. Both are of equal
1386 * cost, so there's no point in trying to optimize the ACK flood case.
1387 * Also, if you don't process certain ACKs for some reason, then all someone
1388 * would have to do is launch a SYN and ACK flood at the same time, which
1389 * would stop cookie verification and defeat the entire purpose of syncookies.
1391 static int tcp_sc_msstab[] = { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
1394 syncookie_generate(struct syncache_head *sch, struct syncache *sc,
1395 u_int32_t *flowlabel)
1398 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1401 u_int off, pmss, mss;
1404 SCH_LOCK_ASSERT(sch);
1406 /* Which of the two secrets to use. */
1407 secbits = sch->sch_oddeven ?
1408 sch->sch_secbits_odd : sch->sch_secbits_even;
1410 /* Reseed secret if too old. */
1411 if (sch->sch_reseed < time_uptime) {
1412 sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
1413 secbits = sch->sch_oddeven ?
1414 sch->sch_secbits_odd : sch->sch_secbits_even;
1415 for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
1416 secbits[i] = arc4random();
1417 sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
1420 /* Secret rotation offset. */
1421 off = sc->sc_iss & 0x7; /* iss was randomized before */
1423 /* Maximum segment size calculation. */
1424 pmss = max( min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), tcp_minmss);
1425 for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
1426 if (tcp_sc_msstab[mss] <= pmss)
1429 /* Fold parameters and MD5 digest into the ISN we will send. */
1430 data = sch->sch_oddeven;/* odd or even secret, 1 bit */
1431 data |= off << 1; /* secret offset, derived from iss, 3 bits */
1432 data |= mss << 4; /* mss, 3 bits */
1435 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1436 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1437 MD5Update(&ctx, secbits, off);
1438 MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
1439 MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
1440 MD5Update(&ctx, &data, sizeof(data));
1441 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1443 data |= (md5_buffer[0] << 7);
1447 *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1450 /* Additional parameters are stored in the timestamp if present. */
1451 if (sc->sc_flags & SCF_TIMESTAMP) {
1452 data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
1453 data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
1454 data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
1455 data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
1456 data |= md5_buffer[2] << 10; /* more digest bits */
1457 data ^= md5_buffer[3];
1459 sc->sc_tsoff = data - ticks; /* after XOR */
1465 static struct syncache *
1466 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
1467 struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
1471 u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
1475 int off, mss, wnd, flags;
1477 SCH_LOCK_ASSERT(sch);
1480 * Pull information out of SYN-ACK/ACK and
1481 * revert sequence number advances.
1483 ack = th->th_ack - 1;
1484 seq = th->th_seq - 1;
1485 off = (ack >> 1) & 0x7;
1486 mss = (ack >> 4) & 0x7;
1489 /* Which of the two secrets to use. */
1490 secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
1493 * The secret wasn't updated for the lifetime of a syncookie,
1494 * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
1496 if (sch->sch_reseed < time_uptime) {
1500 /* Recompute the digest so we can compare it. */
1502 MD5Update(&ctx, ((u_int8_t *)secbits) + off,
1503 SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
1504 MD5Update(&ctx, secbits, off);
1505 MD5Update(&ctx, inc, sizeof(*inc));
1506 MD5Update(&ctx, &seq, sizeof(seq));
1507 MD5Update(&ctx, &flags, sizeof(flags));
1508 MD5Final((u_int8_t *)&md5_buffer, &ctx);
1510 /* Does the digest part of or ACK'ed ISS match? */
1511 if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
1514 /* Does the digest part of our reflected timestamp match? */
1515 if (to->to_flags & TOF_TS) {
1516 data = md5_buffer[3] ^ to->to_tsecr;
1517 if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
1521 /* Fill in the syncache values. */
1522 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1523 sc->sc_ipopts = NULL;
1529 if (inc->inc_isipv6) {
1530 if (sotoinpcb(so)->in6p_flags & IN6P_AUTOFLOWLABEL)
1531 sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
1535 sc->sc_ip_ttl = sotoinpcb(so)->inp_ip_ttl;
1536 sc->sc_ip_tos = sotoinpcb(so)->inp_ip_tos;
1539 /* Additional parameters that were encoded in the timestamp. */
1541 sc->sc_flags |= SCF_TIMESTAMP;
1542 sc->sc_tsreflect = to->to_tsval;
1543 sc->sc_ts = to->to_tsecr;
1544 sc->sc_tsoff = to->to_tsecr - ticks;
1545 sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
1546 sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
1547 sc->sc_requested_s_scale = min((data >> 2) & 0xf,
1549 sc->sc_requested_r_scale = min((data >> 6) & 0xf,
1551 if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
1552 sc->sc_flags |= SCF_WINSCALE;
1554 sc->sc_flags |= SCF_NOOPT;
1556 wnd = sbspace(&so->so_rcv);
1558 wnd = imin(wnd, TCP_MAXWIN);
1562 sc->sc_peer_mss = tcp_sc_msstab[mss];