2 * Copyright (c) 2001 McAfee, Inc.
3 * Copyright (c) 2006,2013 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. [2001 McAfee, Inc.]
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
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
39 #include "opt_pcbgroup.h"
41 #include <sys/param.h>
42 #include <sys/systm.h>
44 #include <sys/refcount.h>
45 #include <sys/kernel.h>
46 #include <sys/sysctl.h>
47 #include <sys/limits.h>
49 #include <sys/mutex.h>
50 #include <sys/malloc.h>
52 #include <sys/proc.h> /* for proc0 declaration */
53 #include <sys/random.h>
54 #include <sys/socket.h>
55 #include <sys/socketvar.h>
56 #include <sys/syslog.h>
57 #include <sys/ucred.h>
60 #include <crypto/siphash/siphash.h>
65 #include <net/if_var.h>
66 #include <net/route.h>
69 #include <netinet/in.h>
70 #include <netinet/in_systm.h>
71 #include <netinet/ip.h>
72 #include <netinet/in_var.h>
73 #include <netinet/in_pcb.h>
74 #include <netinet/ip_var.h>
75 #include <netinet/ip_options.h>
77 #include <netinet/ip6.h>
78 #include <netinet/icmp6.h>
79 #include <netinet6/nd6.h>
80 #include <netinet6/ip6_var.h>
81 #include <netinet6/in6_pcb.h>
83 #include <netinet/tcp.h>
85 #include <netinet/tcp_fastopen.h>
87 #include <netinet/tcp_fsm.h>
88 #include <netinet/tcp_seq.h>
89 #include <netinet/tcp_timer.h>
90 #include <netinet/tcp_var.h>
91 #include <netinet/tcp_syncache.h>
93 #include <netinet6/tcp6_var.h>
96 #include <netinet/toecore.h>
99 #include <netipsec/ipsec_support.h>
101 #include <machine/in_cksum.h>
103 #include <security/mac/mac_framework.h>
105 static VNET_DEFINE(int, tcp_syncookies) = 1;
106 #define V_tcp_syncookies VNET(tcp_syncookies)
107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW,
108 &VNET_NAME(tcp_syncookies), 0,
109 "Use TCP SYN cookies if the syncache overflows");
111 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
112 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW,
114 &VNET_NAME(tcp_syncookiesonly), 0,
115 "Use only TCP SYN cookies");
118 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
121 static void syncache_drop(struct syncache *, struct syncache_head *);
122 static void syncache_free(struct syncache *);
123 static void syncache_insert(struct syncache *, struct syncache_head *);
124 static int syncache_respond(struct syncache *, struct syncache_head *, int,
125 const struct mbuf *);
126 static struct socket *syncache_socket(struct syncache *, struct socket *,
128 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
130 static void syncache_timer(void *);
132 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
133 uint8_t *, uintptr_t);
134 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
135 static struct syncache
136 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
137 struct syncache *, struct tcphdr *, struct tcpopt *,
139 static void syncookie_reseed(void *);
141 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
142 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
147 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
148 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
149 * the odds are that the user has given up attempting to connect by then.
151 #define SYNCACHE_MAXREXMTS 3
153 /* Arbitrary values */
154 #define TCP_SYNCACHE_HASHSIZE 512
155 #define TCP_SYNCACHE_BUCKETLIMIT 30
157 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
158 #define V_tcp_syncache VNET(tcp_syncache)
160 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0,
163 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
164 &VNET_NAME(tcp_syncache.bucket_limit), 0,
165 "Per-bucket hash limit for syncache");
167 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
168 &VNET_NAME(tcp_syncache.cache_limit), 0,
169 "Overall entry limit for syncache");
171 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
172 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
174 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
175 &VNET_NAME(tcp_syncache.hashsize), 0,
176 "Size of TCP syncache hashtable");
178 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_VNET | CTLFLAG_RW,
179 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
180 "Limit on SYN/ACK retransmissions");
182 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
183 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
184 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
185 "Send reset on socket allocation failure");
187 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
189 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
190 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
191 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
194 * Requires the syncache entry to be already removed from the bucket list.
197 syncache_free(struct syncache *sc)
201 (void) m_free(sc->sc_ipopts);
205 mac_syncache_destroy(&sc->sc_label);
208 uma_zfree(V_tcp_syncache.zone, sc);
216 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
217 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
218 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
219 V_tcp_syncache.hash_secret = arc4random();
221 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
222 &V_tcp_syncache.hashsize);
223 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
224 &V_tcp_syncache.bucket_limit);
225 if (!powerof2(V_tcp_syncache.hashsize) ||
226 V_tcp_syncache.hashsize == 0) {
227 printf("WARNING: syncache hash size is not a power of 2.\n");
228 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
230 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
233 V_tcp_syncache.cache_limit =
234 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
235 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
236 &V_tcp_syncache.cache_limit);
238 /* Allocate the hash table. */
239 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
240 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
243 V_tcp_syncache.vnet = curvnet;
246 /* Initialize the hash buckets. */
247 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
248 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
249 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
251 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
252 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
253 V_tcp_syncache.hashbase[i].sch_length = 0;
254 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
255 V_tcp_syncache.hashbase[i].sch_last_overflow =
256 -(SYNCOOKIE_LIFETIME + 1);
259 /* Create the syncache entry zone. */
260 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
261 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
262 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
263 V_tcp_syncache.cache_limit);
265 /* Start the SYN cookie reseeder callout. */
266 callout_init(&V_tcp_syncache.secret.reseed, 1);
267 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
268 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
269 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
270 syncookie_reseed, &V_tcp_syncache);
275 syncache_destroy(void)
277 struct syncache_head *sch;
278 struct syncache *sc, *nsc;
282 * Stop the re-seed timer before freeing resources. No need to
283 * possibly schedule it another time.
285 callout_drain(&V_tcp_syncache.secret.reseed);
287 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
288 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
290 sch = &V_tcp_syncache.hashbase[i];
291 callout_drain(&sch->sch_timer);
294 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
295 syncache_drop(sc, sch);
297 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
298 ("%s: sch->sch_bucket not empty", __func__));
299 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
300 __func__, sch->sch_length));
301 mtx_destroy(&sch->sch_mtx);
304 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
305 ("%s: cache_count not 0", __func__));
307 /* Free the allocated global resources. */
308 uma_zdestroy(V_tcp_syncache.zone);
309 free(V_tcp_syncache.hashbase, M_SYNCACHE);
314 * Inserts a syncache entry into the specified bucket row.
315 * Locks and unlocks the syncache_head autonomously.
318 syncache_insert(struct syncache *sc, struct syncache_head *sch)
320 struct syncache *sc2;
325 * Make sure that we don't overflow the per-bucket limit.
326 * If the bucket is full, toss the oldest element.
328 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
329 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
330 ("sch->sch_length incorrect"));
331 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
332 sch->sch_last_overflow = time_uptime;
333 syncache_drop(sc2, sch);
334 TCPSTAT_INC(tcps_sc_bucketoverflow);
337 /* Put it into the bucket. */
338 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
342 if (ADDED_BY_TOE(sc)) {
343 struct toedev *tod = sc->sc_tod;
345 tod->tod_syncache_added(tod, sc->sc_todctx);
349 /* Reinitialize the bucket row's timer. */
350 if (sch->sch_length == 1)
351 sch->sch_nextc = ticks + INT_MAX;
352 syncache_timeout(sc, sch, 1);
356 TCPSTATES_INC(TCPS_SYN_RECEIVED);
357 TCPSTAT_INC(tcps_sc_added);
361 * Remove and free entry from syncache bucket row.
362 * Expects locked syncache head.
365 syncache_drop(struct syncache *sc, struct syncache_head *sch)
368 SCH_LOCK_ASSERT(sch);
370 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
371 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
375 if (ADDED_BY_TOE(sc)) {
376 struct toedev *tod = sc->sc_tod;
378 tod->tod_syncache_removed(tod, sc->sc_todctx);
386 * Engage/reengage time on bucket row.
389 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
391 sc->sc_rxttime = ticks +
392 TCPTV_RTOBASE * (tcp_syn_backoff[sc->sc_rxmits]);
394 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
395 sch->sch_nextc = sc->sc_rxttime;
397 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
398 syncache_timer, (void *)sch);
403 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
404 * If we have retransmitted an entry the maximum number of times, expire it.
405 * One separate timer for each bucket row.
408 syncache_timer(void *xsch)
410 struct syncache_head *sch = (struct syncache_head *)xsch;
411 struct syncache *sc, *nsc;
415 CURVNET_SET(sch->sch_sc->vnet);
417 /* NB: syncache_head has already been locked by the callout. */
418 SCH_LOCK_ASSERT(sch);
421 * In the following cycle we may remove some entries and/or
422 * advance some timeouts, so re-initialize the bucket timer.
424 sch->sch_nextc = tick + INT_MAX;
426 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
428 * We do not check if the listen socket still exists
429 * and accept the case where the listen socket may be
430 * gone by the time we resend the SYN/ACK. We do
431 * not expect this to happens often. If it does,
432 * then the RST will be sent by the time the remote
433 * host does the SYN/ACK->ACK.
435 if (TSTMP_GT(sc->sc_rxttime, tick)) {
436 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
437 sch->sch_nextc = sc->sc_rxttime;
440 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
441 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
442 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
443 "giving up and removing syncache entry\n",
447 syncache_drop(sc, sch);
448 TCPSTAT_INC(tcps_sc_stale);
451 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
452 log(LOG_DEBUG, "%s; %s: Response timeout, "
453 "retransmitting (%u) SYN|ACK\n",
454 s, __func__, sc->sc_rxmits);
458 syncache_respond(sc, sch, 1, NULL);
459 TCPSTAT_INC(tcps_sc_retransmitted);
460 syncache_timeout(sc, sch, 0);
462 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
463 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
464 syncache_timer, (void *)(sch));
469 * Find an entry in the syncache.
470 * Returns always with locked syncache_head plus a matching entry or NULL.
472 static struct syncache *
473 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
476 struct syncache_head *sch;
480 * The hash is built on foreign port + local port + foreign address.
481 * We rely on the fact that struct in_conninfo starts with 16 bits
482 * of foreign port, then 16 bits of local port then followed by 128
483 * bits of foreign address. In case of IPv4 address, the first 3
484 * 32-bit words of the address always are zeroes.
486 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
487 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
489 sch = &V_tcp_syncache.hashbase[hash];
493 /* Circle through bucket row to find matching entry. */
494 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
495 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
496 sizeof(struct in_endpoints)) == 0)
499 return (sc); /* Always returns with locked sch. */
503 * This function is called when we get a RST for a
504 * non-existent connection, so that we can see if the
505 * connection is in the syn cache. If it is, zap it.
508 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
511 struct syncache_head *sch;
514 sc = syncache_lookup(inc, &sch); /* returns locked sch */
515 SCH_LOCK_ASSERT(sch);
518 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
519 * See RFC 793 page 65, section SEGMENT ARRIVES.
521 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
522 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
523 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
524 "FIN flag set, segment ignored\n", s, __func__);
525 TCPSTAT_INC(tcps_badrst);
530 * No corresponding connection was found in syncache.
531 * If syncookies are enabled and possibly exclusively
532 * used, or we are under memory pressure, a valid RST
533 * may not find a syncache entry. In that case we're
534 * done and no SYN|ACK retransmissions will happen.
535 * Otherwise the RST was misdirected or spoofed.
538 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
539 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
540 "syncache entry (possibly syncookie only), "
541 "segment ignored\n", s, __func__);
542 TCPSTAT_INC(tcps_badrst);
547 * If the RST bit is set, check the sequence number to see
548 * if this is a valid reset segment.
550 * In all states except SYN-SENT, all reset (RST) segments
551 * are validated by checking their SEQ-fields. A reset is
552 * valid if its sequence number is in the window.
554 * The sequence number in the reset segment is normally an
555 * echo of our outgoing acknowlegement numbers, but some hosts
556 * send a reset with the sequence number at the rightmost edge
557 * of our receive window, and we have to handle this case.
559 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
560 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
561 syncache_drop(sc, sch);
562 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
563 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
564 "connection attempt aborted by remote endpoint\n",
566 TCPSTAT_INC(tcps_sc_reset);
568 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
569 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
570 "IRS %u (+WND %u), segment ignored\n",
571 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
572 TCPSTAT_INC(tcps_badrst);
582 syncache_badack(struct in_conninfo *inc)
585 struct syncache_head *sch;
587 sc = syncache_lookup(inc, &sch); /* returns locked sch */
588 SCH_LOCK_ASSERT(sch);
590 syncache_drop(sc, sch);
591 TCPSTAT_INC(tcps_sc_badack);
597 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq)
600 struct syncache_head *sch;
602 sc = syncache_lookup(inc, &sch); /* returns locked sch */
603 SCH_LOCK_ASSERT(sch);
607 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
608 if (ntohl(th_seq) != sc->sc_iss)
612 * If we've rertransmitted 3 times and this is our second error,
613 * we remove the entry. Otherwise, we allow it to continue on.
614 * This prevents us from incorrectly nuking an entry during a
615 * spurious network outage.
619 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
620 sc->sc_flags |= SCF_UNREACH;
623 syncache_drop(sc, sch);
624 TCPSTAT_INC(tcps_sc_unreach);
630 * Build a new TCP socket structure from a syncache entry.
632 * On success return the newly created socket with its underlying inp locked.
634 static struct socket *
635 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
637 struct tcp_function_block *blk;
638 struct inpcb *inp = NULL;
644 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
647 * Ok, create the full blown connection, and set things up
648 * as they would have been set up if we had created the
649 * connection when the SYN arrived. If we can't create
650 * the connection, abort it.
652 so = sonewconn(lso, 0);
655 * Drop the connection; we will either send a RST or
656 * have the peer retransmit its SYN again after its
659 TCPSTAT_INC(tcps_listendrop);
660 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
661 log(LOG_DEBUG, "%s; %s: Socket create failed "
662 "due to limits or memory shortage\n",
669 mac_socketpeer_set_from_mbuf(m, so);
673 inp->inp_inc.inc_fibnum = so->so_fibnum;
676 * Exclusive pcbinfo lock is not required in syncache socket case even
677 * if two inpcb locks can be acquired simultaneously:
678 * - the inpcb in LISTEN state,
679 * - the newly created inp.
681 * In this case, an inp cannot be at same time in LISTEN state and
682 * just created by an accept() call.
684 INP_HASH_WLOCK(&V_tcbinfo);
686 /* Insert new socket into PCB hash list. */
687 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
689 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
690 inp->inp_vflag &= ~INP_IPV4;
691 inp->inp_vflag |= INP_IPV6;
692 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
694 inp->inp_vflag &= ~INP_IPV6;
695 inp->inp_vflag |= INP_IPV4;
697 inp->inp_laddr = sc->sc_inc.inc_laddr;
703 * If there's an mbuf and it has a flowid, then let's initialise the
704 * inp with that particular flowid.
706 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
707 inp->inp_flowid = m->m_pkthdr.flowid;
708 inp->inp_flowtype = M_HASHTYPE_GET(m);
712 * Install in the reservation hash table for now, but don't yet
713 * install a connection group since the full 4-tuple isn't yet
716 inp->inp_lport = sc->sc_inc.inc_lport;
717 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
719 * Undo the assignments above if we failed to
720 * put the PCB on the hash lists.
723 if (sc->sc_inc.inc_flags & INC_ISIPV6)
724 inp->in6p_laddr = in6addr_any;
727 inp->inp_laddr.s_addr = INADDR_ANY;
729 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
730 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
735 INP_HASH_WUNLOCK(&V_tcbinfo);
739 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
740 struct inpcb *oinp = sotoinpcb(lso);
741 struct in6_addr laddr6;
742 struct sockaddr_in6 sin6;
744 * Inherit socket options from the listening socket.
745 * Note that in6p_inputopts are not (and should not be)
746 * copied, since it stores previously received options and is
747 * used to detect if each new option is different than the
748 * previous one and hence should be passed to a user.
749 * If we copied in6p_inputopts, a user would not be able to
750 * receive options just after calling the accept system call.
752 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
753 if (oinp->in6p_outputopts)
754 inp->in6p_outputopts =
755 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
757 sin6.sin6_family = AF_INET6;
758 sin6.sin6_len = sizeof(sin6);
759 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
760 sin6.sin6_port = sc->sc_inc.inc_fport;
761 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
762 laddr6 = inp->in6p_laddr;
763 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
764 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
765 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
766 thread0.td_ucred, m)) != 0) {
767 inp->in6p_laddr = laddr6;
768 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
769 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
774 INP_HASH_WUNLOCK(&V_tcbinfo);
777 /* Override flowlabel from in6_pcbconnect. */
778 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
779 inp->inp_flow |= sc->sc_flowlabel;
782 #if defined(INET) && defined(INET6)
787 struct in_addr laddr;
788 struct sockaddr_in sin;
790 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
792 if (inp->inp_options == NULL) {
793 inp->inp_options = sc->sc_ipopts;
794 sc->sc_ipopts = NULL;
797 sin.sin_family = AF_INET;
798 sin.sin_len = sizeof(sin);
799 sin.sin_addr = sc->sc_inc.inc_faddr;
800 sin.sin_port = sc->sc_inc.inc_fport;
801 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
802 laddr = inp->inp_laddr;
803 if (inp->inp_laddr.s_addr == INADDR_ANY)
804 inp->inp_laddr = sc->sc_inc.inc_laddr;
805 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
806 thread0.td_ucred, m)) != 0) {
807 inp->inp_laddr = laddr;
808 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
809 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
814 INP_HASH_WUNLOCK(&V_tcbinfo);
819 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
820 /* Copy old policy into new socket's. */
821 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
822 printf("syncache_socket: could not copy policy\n");
824 INP_HASH_WUNLOCK(&V_tcbinfo);
826 tcp_state_change(tp, TCPS_SYN_RECEIVED);
827 tp->iss = sc->sc_iss;
828 tp->irs = sc->sc_irs;
831 blk = sototcpcb(lso)->t_fb;
832 if (blk != tp->t_fb) {
834 * Our parents t_fb was not the default,
835 * we need to release our ref on tp->t_fb and
836 * pickup one on the new entry.
838 struct tcp_function_block *rblk;
840 rblk = find_and_ref_tcp_fb(blk);
841 KASSERT(rblk != NULL,
842 ("cannot find blk %p out of syncache?", blk));
843 if (tp->t_fb->tfb_tcp_fb_fini)
844 (*tp->t_fb->tfb_tcp_fb_fini)(tp);
845 refcount_release(&tp->t_fb->tfb_refcnt);
847 if (tp->t_fb->tfb_tcp_fb_init) {
848 (*tp->t_fb->tfb_tcp_fb_init)(tp);
851 tp->snd_wl1 = sc->sc_irs;
852 tp->snd_max = tp->iss + 1;
853 tp->snd_nxt = tp->iss + 1;
854 tp->rcv_up = sc->sc_irs + 1;
855 tp->rcv_wnd = sc->sc_wnd;
856 tp->rcv_adv += tp->rcv_wnd;
857 tp->last_ack_sent = tp->rcv_nxt;
859 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
860 if (sc->sc_flags & SCF_NOOPT)
861 tp->t_flags |= TF_NOOPT;
863 if (sc->sc_flags & SCF_WINSCALE) {
864 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
865 tp->snd_scale = sc->sc_requested_s_scale;
866 tp->request_r_scale = sc->sc_requested_r_scale;
868 if (sc->sc_flags & SCF_TIMESTAMP) {
869 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
870 tp->ts_recent = sc->sc_tsreflect;
871 tp->ts_recent_age = tcp_ts_getticks();
872 tp->ts_offset = sc->sc_tsoff;
874 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
875 if (sc->sc_flags & SCF_SIGNATURE)
876 tp->t_flags |= TF_SIGNATURE;
878 if (sc->sc_flags & SCF_SACK)
879 tp->t_flags |= TF_SACK_PERMIT;
882 if (sc->sc_flags & SCF_ECN)
883 tp->t_flags |= TF_ECN_PERMIT;
886 * Set up MSS and get cached values from tcp_hostcache.
887 * This might overwrite some of the defaults we just set.
889 tcp_mss(tp, sc->sc_peer_mss);
892 * If the SYN,ACK was retransmitted, indicate that CWND to be
893 * limited to one segment in cc_conn_init().
894 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
896 if (sc->sc_rxmits > 1)
901 * Allow a TOE driver to install its hooks. Note that we hold the
902 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
903 * new connection before the TOE driver has done its thing.
905 if (ADDED_BY_TOE(sc)) {
906 struct toedev *tod = sc->sc_tod;
908 tod->tod_offload_socket(tod, sc->sc_todctx, so);
912 * Copy and activate timers.
914 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
915 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
916 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
917 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
918 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
920 TCPSTAT_INC(tcps_accepts);
932 * This function gets called when we receive an ACK for a
933 * socket in the LISTEN state. We look up the connection
934 * in the syncache, and if its there, we pull it out of
935 * the cache and turn it into a full-blown connection in
936 * the SYN-RECEIVED state.
938 * On syncache_socket() success the newly created socket
939 * has its underlying inp locked.
942 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
943 struct socket **lsop, struct mbuf *m)
946 struct syncache_head *sch;
951 * Global TCP locks are held because we manipulate the PCB lists
952 * and create a new socket.
954 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
955 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
956 ("%s: can handle only ACK", __func__));
958 sc = syncache_lookup(inc, &sch); /* returns locked sch */
959 SCH_LOCK_ASSERT(sch);
963 * Test code for syncookies comparing the syncache stored
964 * values with the reconstructed values from the cookie.
967 syncookie_cmp(inc, sch, sc, th, to, *lsop);
972 * There is no syncache entry, so see if this ACK is
973 * a returning syncookie. To do this, first:
974 * A. Check if syncookies are used in case of syncache
976 * B. See if this socket has had a syncache entry dropped in
977 * the recent past. We don't want to accept a bogus
978 * syncookie if we've never received a SYN or accept it
980 * C. check that the syncookie is valid. If it is, then
981 * cobble up a fake syncache entry, and return.
983 if (!V_tcp_syncookies) {
985 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
986 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
987 "segment rejected (syncookies disabled)\n",
991 if (!V_tcp_syncookiesonly &&
992 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) {
994 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
995 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
996 "segment rejected (no syncache entry)\n",
1000 bzero(&scs, sizeof(scs));
1001 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop);
1004 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1005 log(LOG_DEBUG, "%s; %s: Segment failed "
1006 "SYNCOOKIE authentication, segment rejected "
1007 "(probably spoofed)\n", s, __func__);
1010 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1011 /* If received ACK has MD5 signature, check it. */
1012 if ((to->to_flags & TOF_SIGNATURE) != 0 &&
1013 (!TCPMD5_ENABLED() ||
1014 TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
1016 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1017 log(LOG_DEBUG, "%s; %s: Segment rejected, "
1018 "MD5 signature doesn't match.\n",
1022 TCPSTAT_INC(tcps_sig_err_sigopt);
1023 return (-1); /* Do not send RST */
1025 #endif /* TCP_SIGNATURE */
1027 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1029 * If listening socket requested TCP digests, check that
1030 * received ACK has signature and it is correct.
1031 * If not, drop the ACK and leave sc entry in th cache,
1032 * because SYN was received with correct signature.
1034 if (sc->sc_flags & SCF_SIGNATURE) {
1035 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1037 TCPSTAT_INC(tcps_sig_err_nosigopt);
1039 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1040 log(LOG_DEBUG, "%s; %s: Segment "
1041 "rejected, MD5 signature wasn't "
1042 "provided.\n", s, __func__);
1045 return (-1); /* Do not send RST */
1047 if (!TCPMD5_ENABLED() ||
1048 TCPMD5_INPUT(m, th, to->to_signature) != 0) {
1049 /* Doesn't match or no SA */
1051 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1052 log(LOG_DEBUG, "%s; %s: Segment "
1053 "rejected, MD5 signature doesn't "
1054 "match.\n", s, __func__);
1057 return (-1); /* Do not send RST */
1060 #endif /* TCP_SIGNATURE */
1062 * Pull out the entry to unlock the bucket row.
1064 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
1065 * tcp_state_change(). The tcpcb is not existent at this
1066 * moment. A new one will be allocated via syncache_socket->
1067 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then
1068 * syncache_socket() will change it to TCPS_SYN_RECEIVED.
1070 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
1071 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
1074 if (ADDED_BY_TOE(sc)) {
1075 struct toedev *tod = sc->sc_tod;
1077 tod->tod_syncache_removed(tod, sc->sc_todctx);
1084 * Segment validation:
1085 * ACK must match our initial sequence number + 1 (the SYN|ACK).
1087 if (th->th_ack != sc->sc_iss + 1) {
1088 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1089 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
1090 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
1095 * The SEQ must fall in the window starting at the received
1096 * initial receive sequence number + 1 (the SYN).
1098 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
1099 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
1100 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1101 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
1102 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
1107 * If timestamps were not negotiated during SYN/ACK they
1108 * must not appear on any segment during this session.
1110 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
1111 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1112 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1113 "segment rejected\n", s, __func__);
1118 * If timestamps were negotiated during SYN/ACK they should
1119 * appear on every segment during this session.
1120 * XXXAO: This is only informal as there have been unverified
1121 * reports of non-compliants stacks.
1123 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
1124 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1125 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1126 "no action\n", s, __func__);
1133 * If timestamps were negotiated, the reflected timestamp
1134 * must be equal to what we actually sent in the SYN|ACK
1135 * except in the case of 0. Some boxes are known for sending
1136 * broken timestamp replies during the 3whs (and potentially
1137 * during the connection also).
1139 * Accept the final ACK of 3whs with reflected timestamp of 0
1140 * instead of sending a RST and deleting the syncache entry.
1142 if ((to->to_flags & TOF_TS) && to->to_tsecr &&
1143 to->to_tsecr != sc->sc_ts) {
1144 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1145 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
1146 "segment rejected\n",
1147 s, __func__, to->to_tsecr, sc->sc_ts);
1151 *lsop = syncache_socket(sc, *lsop, m);
1154 TCPSTAT_INC(tcps_sc_aborted);
1156 TCPSTAT_INC(tcps_sc_completed);
1158 /* how do we find the inp for the new socket? */
1163 if (sc != NULL && sc != &scs)
1173 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m,
1174 uint64_t response_cookie)
1178 unsigned int *pending_counter;
1181 * Global TCP locks are held because we manipulate the PCB lists
1182 * and create a new socket.
1184 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1186 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending;
1187 *lsop = syncache_socket(sc, *lsop, m);
1188 if (*lsop == NULL) {
1189 TCPSTAT_INC(tcps_sc_aborted);
1190 atomic_subtract_int(pending_counter, 1);
1192 inp = sotoinpcb(*lsop);
1193 tp = intotcpcb(inp);
1194 tp->t_flags |= TF_FASTOPEN;
1195 tp->t_tfo_cookie = response_cookie;
1196 tp->snd_max = tp->iss;
1197 tp->snd_nxt = tp->iss;
1198 tp->t_tfo_pending = pending_counter;
1199 TCPSTAT_INC(tcps_sc_completed);
1202 #endif /* TCP_RFC7413 */
1205 * Given a LISTEN socket and an inbound SYN request, add
1206 * this to the syn cache, and send back a segment:
1207 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1210 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1211 * Doing so would require that we hold onto the data and deliver it
1212 * to the application. However, if we are the target of a SYN-flood
1213 * DoS attack, an attacker could send data which would eventually
1214 * consume all available buffer space if it were ACKed. By not ACKing
1215 * the data, we avoid this DoS scenario.
1217 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
1218 * cookie is processed, V_tcp_fastopen_enabled set to true, and the
1219 * TCP_FASTOPEN socket option is set. In this case, a new socket is created
1220 * and returned via lsop, the mbuf is not freed so that tcp_input() can
1221 * queue its data to the socket, and 1 is returned to indicate the
1222 * TFO-socket-creation path was taken.
1225 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1226 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod,
1231 struct syncache *sc = NULL;
1232 struct syncache_head *sch;
1233 struct mbuf *ipopts = NULL;
1235 int win, sb_hiwat, ip_ttl, ip_tos;
1239 int autoflowlabel = 0;
1242 struct label *maclabel;
1244 struct syncache scs;
1247 uint64_t tfo_response_cookie;
1248 int tfo_cookie_valid = 0;
1249 int tfo_response_cookie_valid = 0;
1252 INP_WLOCK_ASSERT(inp); /* listen socket */
1253 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1254 ("%s: unexpected tcp flags", __func__));
1257 * Combine all so/tp operations very early to drop the INP lock as
1262 cred = crhold(so->so_cred);
1265 if ((inc->inc_flags & INC_ISIPV6) &&
1266 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1269 ip_ttl = inp->inp_ip_ttl;
1270 ip_tos = inp->inp_ip_tos;
1271 win = sbspace(&so->so_rcv);
1272 sb_hiwat = so->so_rcv.sb_hiwat;
1273 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1276 if (V_tcp_fastopen_enabled && (tp->t_flags & TF_FASTOPEN) &&
1277 (tp->t_tfo_pending != NULL) && (to->to_flags & TOF_FASTOPEN)) {
1279 * Limit the number of pending TFO connections to
1280 * approximately half of the queue limit. This prevents TFO
1281 * SYN floods from starving the service by filling the
1282 * listen queue with bogus TFO connections.
1284 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
1285 (so->so_qlimit / 2)) {
1288 result = tcp_fastopen_check_cookie(inc,
1289 to->to_tfo_cookie, to->to_tfo_len,
1290 &tfo_response_cookie);
1291 tfo_cookie_valid = (result > 0);
1292 tfo_response_cookie_valid = (result >= 0);
1294 atomic_subtract_int(tp->t_tfo_pending, 1);
1298 /* By the time we drop the lock these should no longer be used. */
1303 if (mac_syncache_init(&maclabel) != 0) {
1307 mac_syncache_create(maclabel, inp);
1310 if (!tfo_cookie_valid)
1315 * Remember the IP options, if any.
1318 if (!(inc->inc_flags & INC_ISIPV6))
1321 ipopts = (m) ? ip_srcroute(m) : NULL;
1326 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1328 * If listening socket requested TCP digests, check that received
1329 * SYN has signature and it is correct. If signature doesn't match
1330 * or TCP_SIGNATURE support isn't enabled, drop the packet.
1332 if (ltflags & TF_SIGNATURE) {
1333 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1334 TCPSTAT_INC(tcps_sig_err_nosigopt);
1337 if (!TCPMD5_ENABLED() ||
1338 TCPMD5_INPUT(m, th, to->to_signature) != 0)
1341 #endif /* TCP_SIGNATURE */
1343 * See if we already have an entry for this connection.
1344 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1346 * XXX: should the syncache be re-initialized with the contents
1347 * of the new SYN here (which may have different options?)
1349 * XXX: We do not check the sequence number to see if this is a
1350 * real retransmit or a new connection attempt. The question is
1351 * how to handle such a case; either ignore it as spoofed, or
1352 * drop the current entry and create a new one?
1354 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1355 SCH_LOCK_ASSERT(sch);
1358 if (tfo_cookie_valid)
1361 TCPSTAT_INC(tcps_sc_dupsyn);
1364 * If we were remembering a previous source route,
1365 * forget it and use the new one we've been given.
1368 (void) m_free(sc->sc_ipopts);
1369 sc->sc_ipopts = ipopts;
1372 * Update timestamp if present.
1374 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1375 sc->sc_tsreflect = to->to_tsval;
1377 sc->sc_flags &= ~SCF_TIMESTAMP;
1380 * Since we have already unconditionally allocated label
1381 * storage, free it up. The syncache entry will already
1382 * have an initialized label we can use.
1384 mac_syncache_destroy(&maclabel);
1386 /* Retransmit SYN|ACK and reset retransmit count. */
1387 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1388 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1389 "resetting timer and retransmitting SYN|ACK\n",
1393 if (syncache_respond(sc, sch, 1, m) == 0) {
1395 syncache_timeout(sc, sch, 1);
1396 TCPSTAT_INC(tcps_sndacks);
1397 TCPSTAT_INC(tcps_sndtotal);
1404 if (tfo_cookie_valid) {
1405 bzero(&scs, sizeof(scs));
1411 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1414 * The zone allocator couldn't provide more entries.
1415 * Treat this as if the cache was full; drop the oldest
1416 * entry and insert the new one.
1418 TCPSTAT_INC(tcps_sc_zonefail);
1419 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) {
1420 sch->sch_last_overflow = time_uptime;
1421 syncache_drop(sc, sch);
1423 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1425 if (V_tcp_syncookies) {
1426 bzero(&scs, sizeof(scs));
1431 (void) m_free(ipopts);
1439 if (!tfo_cookie_valid && tfo_response_cookie_valid)
1440 sc->sc_tfo_cookie = &tfo_response_cookie;
1444 * Fill in the syncache values.
1447 sc->sc_label = maclabel;
1451 sc->sc_ipopts = ipopts;
1452 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1454 if (!(inc->inc_flags & INC_ISIPV6))
1457 sc->sc_ip_tos = ip_tos;
1458 sc->sc_ip_ttl = ip_ttl;
1462 sc->sc_todctx = todctx;
1464 sc->sc_irs = th->th_seq;
1465 sc->sc_iss = arc4random();
1467 sc->sc_flowlabel = 0;
1470 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1471 * win was derived from socket earlier in the function.
1474 win = imin(win, TCP_MAXWIN);
1477 if (V_tcp_do_rfc1323) {
1479 * A timestamp received in a SYN makes
1480 * it ok to send timestamp requests and replies.
1482 if (to->to_flags & TOF_TS) {
1483 sc->sc_tsreflect = to->to_tsval;
1484 sc->sc_ts = tcp_ts_getticks();
1485 sc->sc_flags |= SCF_TIMESTAMP;
1487 if (to->to_flags & TOF_SCALE) {
1491 * Pick the smallest possible scaling factor that
1492 * will still allow us to scale up to sb_max, aka
1493 * kern.ipc.maxsockbuf.
1495 * We do this because there are broken firewalls that
1496 * will corrupt the window scale option, leading to
1497 * the other endpoint believing that our advertised
1498 * window is unscaled. At scale factors larger than
1499 * 5 the unscaled window will drop below 1500 bytes,
1500 * leading to serious problems when traversing these
1503 * With the default maxsockbuf of 256K, a scale factor
1504 * of 3 will be chosen by this algorithm. Those who
1505 * choose a larger maxsockbuf should watch out
1506 * for the compatibility problems mentioned above.
1508 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1509 * or <SYN,ACK>) segment itself is never scaled.
1511 while (wscale < TCP_MAX_WINSHIFT &&
1512 (TCP_MAXWIN << wscale) < sb_max)
1514 sc->sc_requested_r_scale = wscale;
1515 sc->sc_requested_s_scale = to->to_wscale;
1516 sc->sc_flags |= SCF_WINSCALE;
1519 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1521 * If listening socket requested TCP digests, flag this in the
1522 * syncache so that syncache_respond() will do the right thing
1525 if (ltflags & TF_SIGNATURE)
1526 sc->sc_flags |= SCF_SIGNATURE;
1527 #endif /* TCP_SIGNATURE */
1528 if (to->to_flags & TOF_SACKPERM)
1529 sc->sc_flags |= SCF_SACK;
1530 if (to->to_flags & TOF_MSS)
1531 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1532 if (ltflags & TF_NOOPT)
1533 sc->sc_flags |= SCF_NOOPT;
1534 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1535 sc->sc_flags |= SCF_ECN;
1537 if (V_tcp_syncookies)
1538 sc->sc_iss = syncookie_generate(sch, sc);
1540 if (autoflowlabel) {
1541 if (V_tcp_syncookies)
1542 sc->sc_flowlabel = sc->sc_iss;
1544 sc->sc_flowlabel = ip6_randomflowlabel();
1545 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
1551 if (tfo_cookie_valid) {
1552 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie);
1553 /* INP_WUNLOCK(inp) will be performed by the called */
1560 * Do a standard 3-way handshake.
1562 if (syncache_respond(sc, sch, 0, m) == 0) {
1563 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1565 else if (sc != &scs)
1566 syncache_insert(sc, sch); /* locks and unlocks sch */
1567 TCPSTAT_INC(tcps_sndacks);
1568 TCPSTAT_INC(tcps_sndtotal);
1572 TCPSTAT_INC(tcps_sc_dropped);
1587 mac_syncache_destroy(&maclabel);
1593 * Send SYN|ACK to the peer. Either in response to the peer's SYN,
1594 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
1597 syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked,
1598 const struct mbuf *m0)
1600 struct ip *ip = NULL;
1602 struct tcphdr *th = NULL;
1603 int optlen, error = 0; /* Make compiler happy */
1604 u_int16_t hlen, tlen, mssopt;
1607 struct ip6_hdr *ip6 = NULL;
1611 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1614 tlen = hlen + sizeof(struct tcphdr);
1616 /* Determine MSS we advertize to other end of connection. */
1617 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss);
1619 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1620 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1621 ("syncache: mbuf too small"));
1623 /* Create the IP+TCP header from scratch. */
1624 m = m_gethdr(M_NOWAIT, MT_DATA);
1628 mac_syncache_create_mbuf(sc->sc_label, m);
1630 m->m_data += max_linkhdr;
1632 m->m_pkthdr.len = tlen;
1633 m->m_pkthdr.rcvif = NULL;
1636 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1637 ip6 = mtod(m, struct ip6_hdr *);
1638 ip6->ip6_vfc = IPV6_VERSION;
1639 ip6->ip6_nxt = IPPROTO_TCP;
1640 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1641 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1642 ip6->ip6_plen = htons(tlen - hlen);
1643 /* ip6_hlim is set after checksum */
1644 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1645 ip6->ip6_flow |= sc->sc_flowlabel;
1647 th = (struct tcphdr *)(ip6 + 1);
1650 #if defined(INET6) && defined(INET)
1655 ip = mtod(m, struct ip *);
1656 ip->ip_v = IPVERSION;
1657 ip->ip_hl = sizeof(struct ip) >> 2;
1658 ip->ip_len = htons(tlen);
1662 ip->ip_p = IPPROTO_TCP;
1663 ip->ip_src = sc->sc_inc.inc_laddr;
1664 ip->ip_dst = sc->sc_inc.inc_faddr;
1665 ip->ip_ttl = sc->sc_ip_ttl;
1666 ip->ip_tos = sc->sc_ip_tos;
1669 * See if we should do MTU discovery. Route lookups are
1670 * expensive, so we will only unset the DF bit if:
1672 * 1) path_mtu_discovery is disabled
1673 * 2) the SCF_UNREACH flag has been set
1675 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1676 ip->ip_off |= htons(IP_DF);
1678 th = (struct tcphdr *)(ip + 1);
1681 th->th_sport = sc->sc_inc.inc_lport;
1682 th->th_dport = sc->sc_inc.inc_fport;
1684 th->th_seq = htonl(sc->sc_iss);
1685 th->th_ack = htonl(sc->sc_irs + 1);
1686 th->th_off = sizeof(struct tcphdr) >> 2;
1688 th->th_flags = TH_SYN|TH_ACK;
1689 th->th_win = htons(sc->sc_wnd);
1692 if (sc->sc_flags & SCF_ECN) {
1693 th->th_flags |= TH_ECE;
1694 TCPSTAT_INC(tcps_ecn_shs);
1697 /* Tack on the TCP options. */
1698 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1702 to.to_flags = TOF_MSS;
1703 if (sc->sc_flags & SCF_WINSCALE) {
1704 to.to_wscale = sc->sc_requested_r_scale;
1705 to.to_flags |= TOF_SCALE;
1707 if (sc->sc_flags & SCF_TIMESTAMP) {
1708 /* Virgin timestamp or TCP cookie enhanced one. */
1709 to.to_tsval = sc->sc_ts;
1710 to.to_tsecr = sc->sc_tsreflect;
1711 to.to_flags |= TOF_TS;
1713 if (sc->sc_flags & SCF_SACK)
1714 to.to_flags |= TOF_SACKPERM;
1715 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1716 if (sc->sc_flags & SCF_SIGNATURE)
1717 to.to_flags |= TOF_SIGNATURE;
1720 if (sc->sc_tfo_cookie) {
1721 to.to_flags |= TOF_FASTOPEN;
1722 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
1723 to.to_tfo_cookie = sc->sc_tfo_cookie;
1724 /* don't send cookie again when retransmitting response */
1725 sc->sc_tfo_cookie = NULL;
1728 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1730 /* Adjust headers by option size. */
1731 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1733 m->m_pkthdr.len += optlen;
1735 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1736 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1739 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
1740 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1741 if (sc->sc_flags & SCF_SIGNATURE) {
1742 KASSERT(to.to_flags & TOF_SIGNATURE,
1743 ("tcp_addoptions() didn't set tcp_signature"));
1745 /* NOTE: to.to_signature is inside of mbuf */
1746 if (!TCPMD5_ENABLED() ||
1747 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
1756 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1757 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1759 * If we have peer's SYN and it has a flowid, then let's assign it to
1760 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid
1761 * to SYN|ACK due to lack of inp here.
1763 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
1764 m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
1765 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
1768 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1769 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1770 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1772 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1774 if (ADDED_BY_TOE(sc)) {
1775 struct toedev *tod = sc->sc_tod;
1777 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1782 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1785 #if defined(INET6) && defined(INET)
1790 m->m_pkthdr.csum_flags = CSUM_TCP;
1791 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1792 htons(tlen + optlen - hlen + IPPROTO_TCP));
1794 if (ADDED_BY_TOE(sc)) {
1795 struct toedev *tod = sc->sc_tod;
1797 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1802 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1809 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
1810 * that exceed the capacity of the syncache by avoiding the storage of any
1811 * of the SYNs we receive. Syncookies defend against blind SYN flooding
1812 * attacks where the attacker does not have access to our responses.
1814 * Syncookies encode and include all necessary information about the
1815 * connection setup within the SYN|ACK that we send back. That way we
1816 * can avoid keeping any local state until the ACK to our SYN|ACK returns
1817 * (if ever). Normally the syncache and syncookies are running in parallel
1818 * with the latter taking over when the former is exhausted. When matching
1819 * syncache entry is found the syncookie is ignored.
1821 * The only reliable information persisting the 3WHS is our initial sequence
1822 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient
1823 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS
1824 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
1825 * returns and signifies a legitimate connection if it matches the ACK.
1827 * The available space of 32 bits to store the hash and to encode the SYN
1828 * option information is very tight and we should have at least 24 bits for
1829 * the MAC to keep the number of guesses by blind spoofing reasonably high.
1831 * SYN option information we have to encode to fully restore a connection:
1832 * MSS: is imporant to chose an optimal segment size to avoid IP level
1833 * fragmentation along the path. The common MSS values can be encoded
1834 * in a 3-bit table. Uncommon values are captured by the next lower value
1835 * in the table leading to a slight increase in packetization overhead.
1836 * WSCALE: is necessary to allow large windows to be used for high delay-
1837 * bandwidth product links. Not scaling the window when it was initially
1838 * negotiated is bad for performance as lack of scaling further decreases
1839 * the apparent available send window. We only need to encode the WSCALE
1840 * we received from the remote end. Our end can be recalculated at any
1841 * time. The common WSCALE values can be encoded in a 3-bit table.
1842 * Uncommon values are captured by the next lower value in the table
1843 * making us under-estimate the available window size halving our
1844 * theoretically possible maximum throughput for that connection.
1845 * SACK: Greatly assists in packet loss recovery and requires 1 bit.
1846 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options
1847 * that are included in all segments on a connection. We enable them when
1850 * Security of syncookies and attack vectors:
1852 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
1853 * together with the gloabl secret to make it unique per connection attempt.
1854 * Thus any change of any of those parameters results in a different MAC output
1855 * in an unpredictable way unless a collision is encountered. 24 bits of the
1856 * MAC are embedded into the ISS.
1858 * To prevent replay attacks two rotating global secrets are updated with a
1859 * new random value every 15 seconds. The life-time of a syncookie is thus
1862 * Vector 1: Attacking the secret. This requires finding a weakness in the
1863 * MAC itself or the way it is used here. The attacker can do a chosen plain
1864 * text attack by varying and testing the all parameters under his control.
1865 * The strength depends on the size and randomness of the secret, and the
1866 * cryptographic security of the MAC function. Due to the constant updating
1867 * of the secret the attacker has at most 29.999 seconds to find the secret
1868 * and launch spoofed connections. After that he has to start all over again.
1870 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
1871 * size an average of 4,823 attempts are required for a 50% chance of success
1872 * to spoof a single syncookie (birthday collision paradox). However the
1873 * attacker is blind and doesn't know if one of his attempts succeeded unless
1874 * he has a side channel to interfere success from. A single connection setup
1875 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
1876 * This many attempts are required for each one blind spoofed connection. For
1877 * every additional spoofed connection he has to launch another N attempts.
1878 * Thus for a sustained rate 100 spoofed connections per second approximately
1879 * 1,800,000 packets per second would have to be sent.
1881 * NB: The MAC function should be fast so that it doesn't become a CPU
1882 * exhaustion attack vector itself.
1885 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations
1886 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
1887 * http://cr.yp.to/syncookies.html (overview)
1888 * http://cr.yp.to/syncookies/archive (details)
1891 * Schematic construction of a syncookie enabled Initial Sequence Number:
1893 * 12345678901234567890123456789012
1894 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
1896 * x 24 MAC (truncated)
1897 * W 3 Send Window Scale index
1899 * S 1 SACK permitted
1900 * P 1 Odd/even secret
1904 * Distribution and probability of certain MSS values. Those in between are
1905 * rounded down to the next lower one.
1906 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
1907 * .2% .3% 5% 7% 7% 20% 15% 45%
1909 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
1912 * Distribution and probability of certain WSCALE values. We have to map the
1913 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
1914 * bits based on prevalence of certain values. Where we don't have an exact
1915 * match for are rounded down to the next lower one letting us under-estimate
1916 * the true available window. At the moment this would happen only for the
1917 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
1918 * and window size). The absence of the WSCALE option (no scaling in either
1919 * direction) is encoded with index zero.
1920 * [WSCALE values histograms, Allman, 2012]
1921 * X 10 10 35 5 6 14 10% by host
1922 * X 11 4 5 5 18 49 3% by connections
1924 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
1927 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
1928 * and good cryptographic properties.
1931 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
1932 uint8_t *secbits, uintptr_t secmod)
1935 uint32_t siphash[2];
1937 SipHash24_Init(&ctx);
1938 SipHash_SetKey(&ctx, secbits);
1939 switch (inc->inc_flags & INC_ISIPV6) {
1942 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
1943 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
1948 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
1949 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
1953 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
1954 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
1955 SipHash_Update(&ctx, &irs, sizeof(irs));
1956 SipHash_Update(&ctx, &flags, sizeof(flags));
1957 SipHash_Update(&ctx, &secmod, sizeof(secmod));
1958 SipHash_Final((u_int8_t *)&siphash, &ctx);
1960 return (siphash[0] ^ siphash[1]);
1964 syncookie_generate(struct syncache_head *sch, struct syncache *sc)
1966 u_int i, secbit, wscale;
1969 union syncookie cookie;
1971 SCH_LOCK_ASSERT(sch);
1975 /* Map our computed MSS into the 3-bit index. */
1976 for (i = nitems(tcp_sc_msstab) - 1;
1977 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0;
1980 cookie.flags.mss_idx = i;
1983 * Map the send window scale into the 3-bit index but only if
1984 * the wscale option was received.
1986 if (sc->sc_flags & SCF_WINSCALE) {
1987 wscale = sc->sc_requested_s_scale;
1988 for (i = nitems(tcp_sc_wstab) - 1;
1989 tcp_sc_wstab[i] > wscale && i > 0;
1992 cookie.flags.wscale_idx = i;
1995 /* Can we do SACK? */
1996 if (sc->sc_flags & SCF_SACK)
1997 cookie.flags.sack_ok = 1;
1999 /* Which of the two secrets to use. */
2000 secbit = sch->sch_sc->secret.oddeven & 0x1;
2001 cookie.flags.odd_even = secbit;
2003 secbits = sch->sch_sc->secret.key[secbit];
2004 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
2008 * Put the flags into the hash and XOR them to get better ISS number
2009 * variance. This doesn't enhance the cryptographic strength and is
2010 * done to prevent the 8 cookie bits from showing up directly on the
2014 iss |= cookie.cookie ^ (hash >> 24);
2016 /* Randomize the timestamp. */
2017 if (sc->sc_flags & SCF_TIMESTAMP) {
2018 sc->sc_ts = arc4random();
2019 sc->sc_tsoff = sc->sc_ts - tcp_ts_getticks();
2022 TCPSTAT_INC(tcps_sc_sendcookie);
2026 static struct syncache *
2027 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
2028 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2034 int wnd, wscale = 0;
2035 union syncookie cookie;
2037 SCH_LOCK_ASSERT(sch);
2040 * Pull information out of SYN-ACK/ACK and revert sequence number
2043 ack = th->th_ack - 1;
2044 seq = th->th_seq - 1;
2047 * Unpack the flags containing enough information to restore the
2050 cookie.cookie = (ack & 0xff) ^ (ack >> 24);
2052 /* Which of the two secrets to use. */
2053 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even];
2055 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
2057 /* The recomputed hash matches the ACK if this was a genuine cookie. */
2058 if ((ack & ~0xff) != (hash & ~0xff))
2061 /* Fill in the syncache values. */
2063 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
2064 sc->sc_ipopts = NULL;
2069 switch (inc->inc_flags & INC_ISIPV6) {
2072 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
2073 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
2078 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
2079 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK;
2084 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
2086 /* We can simply recompute receive window scale we sent earlier. */
2087 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
2090 /* Only use wscale if it was enabled in the orignal SYN. */
2091 if (cookie.flags.wscale_idx > 0) {
2092 sc->sc_requested_r_scale = wscale;
2093 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
2094 sc->sc_flags |= SCF_WINSCALE;
2097 wnd = sbspace(&lso->so_rcv);
2099 wnd = imin(wnd, TCP_MAXWIN);
2102 if (cookie.flags.sack_ok)
2103 sc->sc_flags |= SCF_SACK;
2105 if (to->to_flags & TOF_TS) {
2106 sc->sc_flags |= SCF_TIMESTAMP;
2107 sc->sc_tsreflect = to->to_tsval;
2108 sc->sc_ts = to->to_tsecr;
2109 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
2112 if (to->to_flags & TOF_SIGNATURE)
2113 sc->sc_flags |= SCF_SIGNATURE;
2117 TCPSTAT_INC(tcps_sc_recvcookie);
2123 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
2124 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2127 struct syncache scs, *scx;
2130 bzero(&scs, sizeof(scs));
2131 scx = syncookie_lookup(inc, sch, &scs, th, to, lso);
2133 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
2137 if (sc->sc_peer_mss != scx->sc_peer_mss)
2138 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
2139 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
2141 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
2142 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
2143 s, __func__, sc->sc_requested_r_scale,
2144 scx->sc_requested_r_scale);
2146 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
2147 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
2148 s, __func__, sc->sc_requested_s_scale,
2149 scx->sc_requested_s_scale);
2151 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
2152 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
2159 #endif /* INVARIANTS */
2162 syncookie_reseed(void *arg)
2164 struct tcp_syncache *sc = arg;
2169 * Reseeding the secret doesn't have to be protected by a lock.
2170 * It only must be ensured that the new random values are visible
2171 * to all CPUs in a SMP environment. The atomic with release
2172 * semantics ensures that.
2174 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
2175 secbits = sc->secret.key[secbit];
2176 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
2177 atomic_add_rel_int(&sc->secret.oddeven, 1);
2179 /* Reschedule ourself. */
2180 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
2184 * Exports the syncache entries to userland so that netstat can display
2185 * them alongside the other sockets. This function is intended to be
2186 * called only from tcp_pcblist.
2188 * Due to concurrency on an active system, the number of pcbs exported
2189 * may have no relation to max_pcbs. max_pcbs merely indicates the
2190 * amount of space the caller allocated for this function to use.
2193 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
2196 struct syncache *sc;
2197 struct syncache_head *sch;
2198 int count, error, i;
2200 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
2201 sch = &V_tcp_syncache.hashbase[i];
2203 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
2204 if (count >= max_pcbs) {
2208 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
2210 bzero(&xt, sizeof(xt));
2211 xt.xt_len = sizeof(xt);
2212 if (sc->sc_inc.inc_flags & INC_ISIPV6)
2213 xt.xt_inp.inp_vflag = INP_IPV6;
2215 xt.xt_inp.inp_vflag = INP_IPV4;
2216 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
2217 xt.xt_tp.t_inpcb = &xt.xt_inp;
2218 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
2219 xt.xt_socket.xso_protocol = IPPROTO_TCP;
2220 xt.xt_socket.xso_len = sizeof (struct xsocket);
2221 xt.xt_socket.so_type = SOCK_STREAM;
2222 xt.xt_socket.so_state = SS_ISCONNECTING;
2223 error = SYSCTL_OUT(req, &xt, sizeof xt);
2233 *pcbs_exported = count;