2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2001 McAfee, Inc.
5 * Copyright (c) 2006,2013 Andre Oppermann, Internet Business Solutions AG
8 * This software was developed for the FreeBSD Project by Jonathan Lemon
9 * and McAfee Research, the Security Research Division of McAfee, Inc. under
10 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
11 * DARPA CHATS research program. [2001 McAfee, Inc.]
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
39 #include "opt_inet6.h"
40 #include "opt_ipsec.h"
41 #include "opt_pcbgroup.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
46 #include <sys/refcount.h>
47 #include <sys/kernel.h>
48 #include <sys/sysctl.h>
49 #include <sys/limits.h>
51 #include <sys/mutex.h>
52 #include <sys/malloc.h>
54 #include <sys/proc.h> /* for proc0 declaration */
55 #include <sys/random.h>
56 #include <sys/socket.h>
57 #include <sys/socketvar.h>
58 #include <sys/syslog.h>
59 #include <sys/ucred.h>
62 #include <crypto/siphash/siphash.h>
67 #include <net/if_var.h>
68 #include <net/route.h>
71 #include <netinet/in.h>
72 #include <netinet/in_systm.h>
73 #include <netinet/ip.h>
74 #include <netinet/in_var.h>
75 #include <netinet/in_pcb.h>
76 #include <netinet/ip_var.h>
77 #include <netinet/ip_options.h>
79 #include <netinet/ip6.h>
80 #include <netinet/icmp6.h>
81 #include <netinet6/nd6.h>
82 #include <netinet6/ip6_var.h>
83 #include <netinet6/in6_pcb.h>
85 #include <netinet/tcp.h>
87 #include <netinet/tcp_fastopen.h>
89 #include <netinet/tcp_fsm.h>
90 #include <netinet/tcp_seq.h>
91 #include <netinet/tcp_timer.h>
92 #include <netinet/tcp_var.h>
93 #include <netinet/tcp_syncache.h>
95 #include <netinet6/tcp6_var.h>
98 #include <netinet/toecore.h>
101 #include <netipsec/ipsec_support.h>
103 #include <machine/in_cksum.h>
105 #include <security/mac/mac_framework.h>
107 static VNET_DEFINE(int, tcp_syncookies) = 1;
108 #define V_tcp_syncookies VNET(tcp_syncookies)
109 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW,
110 &VNET_NAME(tcp_syncookies), 0,
111 "Use TCP SYN cookies if the syncache overflows");
113 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
114 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW,
116 &VNET_NAME(tcp_syncookiesonly), 0,
117 "Use only TCP SYN cookies");
119 static VNET_DEFINE(int, functions_inherit_listen_socket_stack) = 1;
120 #define V_functions_inherit_listen_socket_stack \
121 VNET(functions_inherit_listen_socket_stack)
122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, functions_inherit_listen_socket_stack,
123 CTLFLAG_VNET | CTLFLAG_RW,
124 &VNET_NAME(functions_inherit_listen_socket_stack), 0,
125 "Inherit listen socket's stack");
128 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
131 static void syncache_drop(struct syncache *, struct syncache_head *);
132 static void syncache_free(struct syncache *);
133 static void syncache_insert(struct syncache *, struct syncache_head *);
134 static int syncache_respond(struct syncache *, struct syncache_head *, int,
135 const struct mbuf *);
136 static struct socket *syncache_socket(struct syncache *, struct socket *,
138 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
140 static void syncache_timer(void *);
142 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
143 uint8_t *, uintptr_t);
144 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
145 static struct syncache
146 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
147 struct syncache *, struct tcphdr *, struct tcpopt *,
149 static void syncookie_reseed(void *);
151 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
152 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
157 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
158 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
159 * the odds are that the user has given up attempting to connect by then.
161 #define SYNCACHE_MAXREXMTS 3
163 /* Arbitrary values */
164 #define TCP_SYNCACHE_HASHSIZE 512
165 #define TCP_SYNCACHE_BUCKETLIMIT 30
167 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
168 #define V_tcp_syncache VNET(tcp_syncache)
170 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0,
173 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
174 &VNET_NAME(tcp_syncache.bucket_limit), 0,
175 "Per-bucket hash limit for syncache");
177 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
178 &VNET_NAME(tcp_syncache.cache_limit), 0,
179 "Overall entry limit for syncache");
181 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
182 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
184 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
185 &VNET_NAME(tcp_syncache.hashsize), 0,
186 "Size of TCP syncache hashtable");
188 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_VNET | CTLFLAG_RW,
189 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
190 "Limit on SYN/ACK retransmissions");
192 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
193 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
194 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
195 "Send reset on socket allocation failure");
197 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
199 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
200 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
201 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
204 * Requires the syncache entry to be already removed from the bucket list.
207 syncache_free(struct syncache *sc)
211 (void) m_free(sc->sc_ipopts);
215 mac_syncache_destroy(&sc->sc_label);
218 uma_zfree(V_tcp_syncache.zone, sc);
226 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
227 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
228 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
229 V_tcp_syncache.hash_secret = arc4random();
231 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
232 &V_tcp_syncache.hashsize);
233 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
234 &V_tcp_syncache.bucket_limit);
235 if (!powerof2(V_tcp_syncache.hashsize) ||
236 V_tcp_syncache.hashsize == 0) {
237 printf("WARNING: syncache hash size is not a power of 2.\n");
238 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
240 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
243 V_tcp_syncache.cache_limit =
244 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
245 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
246 &V_tcp_syncache.cache_limit);
248 /* Allocate the hash table. */
249 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
250 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
253 V_tcp_syncache.vnet = curvnet;
256 /* Initialize the hash buckets. */
257 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
258 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
259 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
261 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
262 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
263 V_tcp_syncache.hashbase[i].sch_length = 0;
264 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
265 V_tcp_syncache.hashbase[i].sch_last_overflow =
266 -(SYNCOOKIE_LIFETIME + 1);
269 /* Create the syncache entry zone. */
270 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
271 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
272 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
273 V_tcp_syncache.cache_limit);
275 /* Start the SYN cookie reseeder callout. */
276 callout_init(&V_tcp_syncache.secret.reseed, 1);
277 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
278 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
279 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
280 syncookie_reseed, &V_tcp_syncache);
285 syncache_destroy(void)
287 struct syncache_head *sch;
288 struct syncache *sc, *nsc;
292 * Stop the re-seed timer before freeing resources. No need to
293 * possibly schedule it another time.
295 callout_drain(&V_tcp_syncache.secret.reseed);
297 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
298 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
300 sch = &V_tcp_syncache.hashbase[i];
301 callout_drain(&sch->sch_timer);
304 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
305 syncache_drop(sc, sch);
307 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
308 ("%s: sch->sch_bucket not empty", __func__));
309 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
310 __func__, sch->sch_length));
311 mtx_destroy(&sch->sch_mtx);
314 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
315 ("%s: cache_count not 0", __func__));
317 /* Free the allocated global resources. */
318 uma_zdestroy(V_tcp_syncache.zone);
319 free(V_tcp_syncache.hashbase, M_SYNCACHE);
324 * Inserts a syncache entry into the specified bucket row.
325 * Locks and unlocks the syncache_head autonomously.
328 syncache_insert(struct syncache *sc, struct syncache_head *sch)
330 struct syncache *sc2;
335 * Make sure that we don't overflow the per-bucket limit.
336 * If the bucket is full, toss the oldest element.
338 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
339 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
340 ("sch->sch_length incorrect"));
341 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
342 sch->sch_last_overflow = time_uptime;
343 syncache_drop(sc2, sch);
344 TCPSTAT_INC(tcps_sc_bucketoverflow);
347 /* Put it into the bucket. */
348 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
352 if (ADDED_BY_TOE(sc)) {
353 struct toedev *tod = sc->sc_tod;
355 tod->tod_syncache_added(tod, sc->sc_todctx);
359 /* Reinitialize the bucket row's timer. */
360 if (sch->sch_length == 1)
361 sch->sch_nextc = ticks + INT_MAX;
362 syncache_timeout(sc, sch, 1);
366 TCPSTATES_INC(TCPS_SYN_RECEIVED);
367 TCPSTAT_INC(tcps_sc_added);
371 * Remove and free entry from syncache bucket row.
372 * Expects locked syncache head.
375 syncache_drop(struct syncache *sc, struct syncache_head *sch)
378 SCH_LOCK_ASSERT(sch);
380 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
381 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
385 if (ADDED_BY_TOE(sc)) {
386 struct toedev *tod = sc->sc_tod;
388 tod->tod_syncache_removed(tod, sc->sc_todctx);
396 * Engage/reengage time on bucket row.
399 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
401 sc->sc_rxttime = ticks +
402 TCPTV_RTOBASE * (tcp_syn_backoff[sc->sc_rxmits]);
404 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
405 sch->sch_nextc = sc->sc_rxttime;
407 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
408 syncache_timer, (void *)sch);
413 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
414 * If we have retransmitted an entry the maximum number of times, expire it.
415 * One separate timer for each bucket row.
418 syncache_timer(void *xsch)
420 struct syncache_head *sch = (struct syncache_head *)xsch;
421 struct syncache *sc, *nsc;
425 CURVNET_SET(sch->sch_sc->vnet);
427 /* NB: syncache_head has already been locked by the callout. */
428 SCH_LOCK_ASSERT(sch);
431 * In the following cycle we may remove some entries and/or
432 * advance some timeouts, so re-initialize the bucket timer.
434 sch->sch_nextc = tick + INT_MAX;
436 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
438 * We do not check if the listen socket still exists
439 * and accept the case where the listen socket may be
440 * gone by the time we resend the SYN/ACK. We do
441 * not expect this to happens often. If it does,
442 * then the RST will be sent by the time the remote
443 * host does the SYN/ACK->ACK.
445 if (TSTMP_GT(sc->sc_rxttime, tick)) {
446 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
447 sch->sch_nextc = sc->sc_rxttime;
450 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
451 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
452 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
453 "giving up and removing syncache entry\n",
457 syncache_drop(sc, sch);
458 TCPSTAT_INC(tcps_sc_stale);
461 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
462 log(LOG_DEBUG, "%s; %s: Response timeout, "
463 "retransmitting (%u) SYN|ACK\n",
464 s, __func__, sc->sc_rxmits);
468 syncache_respond(sc, sch, 1, NULL);
469 TCPSTAT_INC(tcps_sc_retransmitted);
470 syncache_timeout(sc, sch, 0);
472 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
473 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
474 syncache_timer, (void *)(sch));
479 * Find an entry in the syncache.
480 * Returns always with locked syncache_head plus a matching entry or NULL.
482 static struct syncache *
483 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
486 struct syncache_head *sch;
490 * The hash is built on foreign port + local port + foreign address.
491 * We rely on the fact that struct in_conninfo starts with 16 bits
492 * of foreign port, then 16 bits of local port then followed by 128
493 * bits of foreign address. In case of IPv4 address, the first 3
494 * 32-bit words of the address always are zeroes.
496 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
497 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
499 sch = &V_tcp_syncache.hashbase[hash];
503 /* Circle through bucket row to find matching entry. */
504 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
505 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
506 sizeof(struct in_endpoints)) == 0)
509 return (sc); /* Always returns with locked sch. */
513 * This function is called when we get a RST for a
514 * non-existent connection, so that we can see if the
515 * connection is in the syn cache. If it is, zap it.
518 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
521 struct syncache_head *sch;
524 sc = syncache_lookup(inc, &sch); /* returns locked sch */
525 SCH_LOCK_ASSERT(sch);
528 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
529 * See RFC 793 page 65, section SEGMENT ARRIVES.
531 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
532 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
533 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
534 "FIN flag set, segment ignored\n", s, __func__);
535 TCPSTAT_INC(tcps_badrst);
540 * No corresponding connection was found in syncache.
541 * If syncookies are enabled and possibly exclusively
542 * used, or we are under memory pressure, a valid RST
543 * may not find a syncache entry. In that case we're
544 * done and no SYN|ACK retransmissions will happen.
545 * Otherwise the RST was misdirected or spoofed.
548 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
549 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
550 "syncache entry (possibly syncookie only), "
551 "segment ignored\n", s, __func__);
552 TCPSTAT_INC(tcps_badrst);
557 * If the RST bit is set, check the sequence number to see
558 * if this is a valid reset segment.
560 * In all states except SYN-SENT, all reset (RST) segments
561 * are validated by checking their SEQ-fields. A reset is
562 * valid if its sequence number is in the window.
564 * The sequence number in the reset segment is normally an
565 * echo of our outgoing acknowlegement numbers, but some hosts
566 * send a reset with the sequence number at the rightmost edge
567 * of our receive window, and we have to handle this case.
569 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
570 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
571 syncache_drop(sc, sch);
572 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
573 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
574 "connection attempt aborted by remote endpoint\n",
576 TCPSTAT_INC(tcps_sc_reset);
578 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
579 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
580 "IRS %u (+WND %u), segment ignored\n",
581 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
582 TCPSTAT_INC(tcps_badrst);
592 syncache_badack(struct in_conninfo *inc)
595 struct syncache_head *sch;
597 sc = syncache_lookup(inc, &sch); /* returns locked sch */
598 SCH_LOCK_ASSERT(sch);
600 syncache_drop(sc, sch);
601 TCPSTAT_INC(tcps_sc_badack);
607 syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq)
610 struct syncache_head *sch;
612 sc = syncache_lookup(inc, &sch); /* returns locked sch */
613 SCH_LOCK_ASSERT(sch);
617 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
618 if (ntohl(th_seq) != sc->sc_iss)
622 * If we've rertransmitted 3 times and this is our second error,
623 * we remove the entry. Otherwise, we allow it to continue on.
624 * This prevents us from incorrectly nuking an entry during a
625 * spurious network outage.
629 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
630 sc->sc_flags |= SCF_UNREACH;
633 syncache_drop(sc, sch);
634 TCPSTAT_INC(tcps_sc_unreach);
640 * Build a new TCP socket structure from a syncache entry.
642 * On success return the newly created socket with its underlying inp locked.
644 static struct socket *
645 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
647 struct tcp_function_block *blk;
648 struct inpcb *inp = NULL;
654 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
657 * Ok, create the full blown connection, and set things up
658 * as they would have been set up if we had created the
659 * connection when the SYN arrived. If we can't create
660 * the connection, abort it.
662 so = sonewconn(lso, 0);
665 * Drop the connection; we will either send a RST or
666 * have the peer retransmit its SYN again after its
669 TCPSTAT_INC(tcps_listendrop);
670 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
671 log(LOG_DEBUG, "%s; %s: Socket create failed "
672 "due to limits or memory shortage\n",
679 mac_socketpeer_set_from_mbuf(m, so);
683 inp->inp_inc.inc_fibnum = so->so_fibnum;
686 * Exclusive pcbinfo lock is not required in syncache socket case even
687 * if two inpcb locks can be acquired simultaneously:
688 * - the inpcb in LISTEN state,
689 * - the newly created inp.
691 * In this case, an inp cannot be at same time in LISTEN state and
692 * just created by an accept() call.
694 INP_HASH_WLOCK(&V_tcbinfo);
696 /* Insert new socket into PCB hash list. */
697 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
699 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
700 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
702 inp->inp_vflag &= ~INP_IPV6;
703 inp->inp_vflag |= INP_IPV4;
705 inp->inp_laddr = sc->sc_inc.inc_laddr;
711 * If there's an mbuf and it has a flowid, then let's initialise the
712 * inp with that particular flowid.
714 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
715 inp->inp_flowid = m->m_pkthdr.flowid;
716 inp->inp_flowtype = M_HASHTYPE_GET(m);
720 * Install in the reservation hash table for now, but don't yet
721 * install a connection group since the full 4-tuple isn't yet
724 inp->inp_lport = sc->sc_inc.inc_lport;
725 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
727 * Undo the assignments above if we failed to
728 * put the PCB on the hash lists.
731 if (sc->sc_inc.inc_flags & INC_ISIPV6)
732 inp->in6p_laddr = in6addr_any;
735 inp->inp_laddr.s_addr = INADDR_ANY;
737 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
738 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
743 INP_HASH_WUNLOCK(&V_tcbinfo);
747 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
748 struct inpcb *oinp = sotoinpcb(lso);
749 struct in6_addr laddr6;
750 struct sockaddr_in6 sin6;
752 * Inherit socket options from the listening socket.
753 * Note that in6p_inputopts are not (and should not be)
754 * copied, since it stores previously received options and is
755 * used to detect if each new option is different than the
756 * previous one and hence should be passed to a user.
757 * If we copied in6p_inputopts, a user would not be able to
758 * receive options just after calling the accept system call.
760 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
761 if (oinp->in6p_outputopts)
762 inp->in6p_outputopts =
763 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
765 sin6.sin6_family = AF_INET6;
766 sin6.sin6_len = sizeof(sin6);
767 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
768 sin6.sin6_port = sc->sc_inc.inc_fport;
769 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
770 laddr6 = inp->in6p_laddr;
771 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
772 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
773 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
774 thread0.td_ucred, m)) != 0) {
775 inp->in6p_laddr = laddr6;
776 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
777 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
782 INP_HASH_WUNLOCK(&V_tcbinfo);
785 /* Override flowlabel from in6_pcbconnect. */
786 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
787 inp->inp_flow |= sc->sc_flowlabel;
790 #if defined(INET) && defined(INET6)
795 struct in_addr laddr;
796 struct sockaddr_in sin;
798 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
800 if (inp->inp_options == NULL) {
801 inp->inp_options = sc->sc_ipopts;
802 sc->sc_ipopts = NULL;
805 sin.sin_family = AF_INET;
806 sin.sin_len = sizeof(sin);
807 sin.sin_addr = sc->sc_inc.inc_faddr;
808 sin.sin_port = sc->sc_inc.inc_fport;
809 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
810 laddr = inp->inp_laddr;
811 if (inp->inp_laddr.s_addr == INADDR_ANY)
812 inp->inp_laddr = sc->sc_inc.inc_laddr;
813 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
814 thread0.td_ucred, m)) != 0) {
815 inp->inp_laddr = laddr;
816 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
817 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
822 INP_HASH_WUNLOCK(&V_tcbinfo);
827 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
828 /* Copy old policy into new socket's. */
829 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
830 printf("syncache_socket: could not copy policy\n");
832 INP_HASH_WUNLOCK(&V_tcbinfo);
834 tcp_state_change(tp, TCPS_SYN_RECEIVED);
835 tp->iss = sc->sc_iss;
836 tp->irs = sc->sc_irs;
839 blk = sototcpcb(lso)->t_fb;
840 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) {
842 * Our parents t_fb was not the default,
843 * we need to release our ref on tp->t_fb and
844 * pickup one on the new entry.
846 struct tcp_function_block *rblk;
848 rblk = find_and_ref_tcp_fb(blk);
849 KASSERT(rblk != NULL,
850 ("cannot find blk %p out of syncache?", blk));
851 if (tp->t_fb->tfb_tcp_fb_fini)
852 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0);
853 refcount_release(&tp->t_fb->tfb_refcnt);
855 if (tp->t_fb->tfb_tcp_fb_init) {
856 (*tp->t_fb->tfb_tcp_fb_init)(tp);
859 tp->snd_wl1 = sc->sc_irs;
860 tp->snd_max = tp->iss + 1;
861 tp->snd_nxt = tp->iss + 1;
862 tp->rcv_up = sc->sc_irs + 1;
863 tp->rcv_wnd = sc->sc_wnd;
864 tp->rcv_adv += tp->rcv_wnd;
865 tp->last_ack_sent = tp->rcv_nxt;
867 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
868 if (sc->sc_flags & SCF_NOOPT)
869 tp->t_flags |= TF_NOOPT;
871 if (sc->sc_flags & SCF_WINSCALE) {
872 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
873 tp->snd_scale = sc->sc_requested_s_scale;
874 tp->request_r_scale = sc->sc_requested_r_scale;
876 if (sc->sc_flags & SCF_TIMESTAMP) {
877 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
878 tp->ts_recent = sc->sc_tsreflect;
879 tp->ts_recent_age = tcp_ts_getticks();
880 tp->ts_offset = sc->sc_tsoff;
882 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
883 if (sc->sc_flags & SCF_SIGNATURE)
884 tp->t_flags |= TF_SIGNATURE;
886 if (sc->sc_flags & SCF_SACK)
887 tp->t_flags |= TF_SACK_PERMIT;
890 if (sc->sc_flags & SCF_ECN)
891 tp->t_flags |= TF_ECN_PERMIT;
894 * Set up MSS and get cached values from tcp_hostcache.
895 * This might overwrite some of the defaults we just set.
897 tcp_mss(tp, sc->sc_peer_mss);
900 * If the SYN,ACK was retransmitted, indicate that CWND to be
901 * limited to one segment in cc_conn_init().
902 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
904 if (sc->sc_rxmits > 1)
909 * Allow a TOE driver to install its hooks. Note that we hold the
910 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
911 * new connection before the TOE driver has done its thing.
913 if (ADDED_BY_TOE(sc)) {
914 struct toedev *tod = sc->sc_tod;
916 tod->tod_offload_socket(tod, sc->sc_todctx, so);
920 * Copy and activate timers.
922 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
923 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
924 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
925 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
926 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
928 TCPSTAT_INC(tcps_accepts);
940 * This function gets called when we receive an ACK for a
941 * socket in the LISTEN state. We look up the connection
942 * in the syncache, and if its there, we pull it out of
943 * the cache and turn it into a full-blown connection in
944 * the SYN-RECEIVED state.
946 * On syncache_socket() success the newly created socket
947 * has its underlying inp locked.
950 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
951 struct socket **lsop, struct mbuf *m)
954 struct syncache_head *sch;
959 * Global TCP locks are held because we manipulate the PCB lists
960 * and create a new socket.
962 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
963 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
964 ("%s: can handle only ACK", __func__));
966 sc = syncache_lookup(inc, &sch); /* returns locked sch */
967 SCH_LOCK_ASSERT(sch);
971 * Test code for syncookies comparing the syncache stored
972 * values with the reconstructed values from the cookie.
975 syncookie_cmp(inc, sch, sc, th, to, *lsop);
980 * There is no syncache entry, so see if this ACK is
981 * a returning syncookie. To do this, first:
982 * A. Check if syncookies are used in case of syncache
984 * B. See if this socket has had a syncache entry dropped in
985 * the recent past. We don't want to accept a bogus
986 * syncookie if we've never received a SYN or accept it
988 * C. check that the syncookie is valid. If it is, then
989 * cobble up a fake syncache entry, and return.
991 if (!V_tcp_syncookies) {
993 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
994 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
995 "segment rejected (syncookies disabled)\n",
999 if (!V_tcp_syncookiesonly &&
1000 sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) {
1002 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1003 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
1004 "segment rejected (no syncache entry)\n",
1008 bzero(&scs, sizeof(scs));
1009 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop);
1012 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1013 log(LOG_DEBUG, "%s; %s: Segment failed "
1014 "SYNCOOKIE authentication, segment rejected "
1015 "(probably spoofed)\n", s, __func__);
1018 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1019 /* If received ACK has MD5 signature, check it. */
1020 if ((to->to_flags & TOF_SIGNATURE) != 0 &&
1021 (!TCPMD5_ENABLED() ||
1022 TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
1024 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1025 log(LOG_DEBUG, "%s; %s: Segment rejected, "
1026 "MD5 signature doesn't match.\n",
1030 TCPSTAT_INC(tcps_sig_err_sigopt);
1031 return (-1); /* Do not send RST */
1033 #endif /* TCP_SIGNATURE */
1035 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1037 * If listening socket requested TCP digests, check that
1038 * received ACK has signature and it is correct.
1039 * If not, drop the ACK and leave sc entry in th cache,
1040 * because SYN was received with correct signature.
1042 if (sc->sc_flags & SCF_SIGNATURE) {
1043 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1045 TCPSTAT_INC(tcps_sig_err_nosigopt);
1047 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1048 log(LOG_DEBUG, "%s; %s: Segment "
1049 "rejected, MD5 signature wasn't "
1050 "provided.\n", s, __func__);
1053 return (-1); /* Do not send RST */
1055 if (!TCPMD5_ENABLED() ||
1056 TCPMD5_INPUT(m, th, to->to_signature) != 0) {
1057 /* Doesn't match or no SA */
1059 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1060 log(LOG_DEBUG, "%s; %s: Segment "
1061 "rejected, MD5 signature doesn't "
1062 "match.\n", s, __func__);
1065 return (-1); /* Do not send RST */
1068 #endif /* TCP_SIGNATURE */
1070 * Pull out the entry to unlock the bucket row.
1072 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
1073 * tcp_state_change(). The tcpcb is not existent at this
1074 * moment. A new one will be allocated via syncache_socket->
1075 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then
1076 * syncache_socket() will change it to TCPS_SYN_RECEIVED.
1078 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
1079 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
1082 if (ADDED_BY_TOE(sc)) {
1083 struct toedev *tod = sc->sc_tod;
1085 tod->tod_syncache_removed(tod, sc->sc_todctx);
1092 * Segment validation:
1093 * ACK must match our initial sequence number + 1 (the SYN|ACK).
1095 if (th->th_ack != sc->sc_iss + 1) {
1096 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1097 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
1098 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
1103 * The SEQ must fall in the window starting at the received
1104 * initial receive sequence number + 1 (the SYN).
1106 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
1107 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
1108 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1109 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
1110 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
1115 * If timestamps were not negotiated during SYN/ACK they
1116 * must not appear on any segment during this session.
1118 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
1119 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1120 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1121 "segment rejected\n", s, __func__);
1126 * If timestamps were negotiated during SYN/ACK they should
1127 * appear on every segment during this session.
1128 * XXXAO: This is only informal as there have been unverified
1129 * reports of non-compliants stacks.
1131 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
1132 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1133 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1134 "no action\n", s, __func__);
1141 * If timestamps were negotiated, the reflected timestamp
1142 * must be equal to what we actually sent in the SYN|ACK
1143 * except in the case of 0. Some boxes are known for sending
1144 * broken timestamp replies during the 3whs (and potentially
1145 * during the connection also).
1147 * Accept the final ACK of 3whs with reflected timestamp of 0
1148 * instead of sending a RST and deleting the syncache entry.
1150 if ((to->to_flags & TOF_TS) && to->to_tsecr &&
1151 to->to_tsecr != sc->sc_ts) {
1152 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1153 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
1154 "segment rejected\n",
1155 s, __func__, to->to_tsecr, sc->sc_ts);
1159 *lsop = syncache_socket(sc, *lsop, m);
1162 TCPSTAT_INC(tcps_sc_aborted);
1164 TCPSTAT_INC(tcps_sc_completed);
1166 /* how do we find the inp for the new socket? */
1171 if (sc != NULL && sc != &scs)
1181 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m,
1182 uint64_t response_cookie)
1186 unsigned int *pending_counter;
1189 * Global TCP locks are held because we manipulate the PCB lists
1190 * and create a new socket.
1192 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1194 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending;
1195 *lsop = syncache_socket(sc, *lsop, m);
1196 if (*lsop == NULL) {
1197 TCPSTAT_INC(tcps_sc_aborted);
1198 atomic_subtract_int(pending_counter, 1);
1200 soisconnected(*lsop);
1201 inp = sotoinpcb(*lsop);
1202 tp = intotcpcb(inp);
1203 tp->t_flags |= TF_FASTOPEN;
1204 tp->t_tfo_cookie = response_cookie;
1205 tp->snd_max = tp->iss;
1206 tp->snd_nxt = tp->iss;
1207 tp->t_tfo_pending = pending_counter;
1208 TCPSTAT_INC(tcps_sc_completed);
1211 #endif /* TCP_RFC7413 */
1214 * Given a LISTEN socket and an inbound SYN request, add
1215 * this to the syn cache, and send back a segment:
1216 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1219 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1220 * Doing so would require that we hold onto the data and deliver it
1221 * to the application. However, if we are the target of a SYN-flood
1222 * DoS attack, an attacker could send data which would eventually
1223 * consume all available buffer space if it were ACKed. By not ACKing
1224 * the data, we avoid this DoS scenario.
1226 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
1227 * cookie is processed and a new socket is created. In this case, any data
1228 * accompanying the SYN will be queued to the socket by tcp_input() and will
1229 * be ACKed either when the application sends response data or the delayed
1230 * ACK timer expires, whichever comes first.
1233 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1234 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod,
1239 struct syncache *sc = NULL;
1240 struct syncache_head *sch;
1241 struct mbuf *ipopts = NULL;
1243 int win, ip_ttl, ip_tos;
1247 int autoflowlabel = 0;
1250 struct label *maclabel;
1252 struct syncache scs;
1255 uint64_t tfo_response_cookie;
1256 unsigned int *tfo_pending = NULL;
1257 int tfo_cookie_valid = 0;
1258 int tfo_response_cookie_valid = 0;
1261 INP_WLOCK_ASSERT(inp); /* listen socket */
1262 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1263 ("%s: unexpected tcp flags", __func__));
1266 * Combine all so/tp operations very early to drop the INP lock as
1270 KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so));
1272 cred = crhold(so->so_cred);
1275 if ((inc->inc_flags & INC_ISIPV6) &&
1276 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1279 ip_ttl = inp->inp_ip_ttl;
1280 ip_tos = inp->inp_ip_tos;
1281 win = so->sol_sbrcv_hiwat;
1282 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1285 if (V_tcp_fastopen_enabled && IS_FASTOPEN(tp->t_flags) &&
1286 (tp->t_tfo_pending != NULL) && (to->to_flags & TOF_FASTOPEN)) {
1288 * Limit the number of pending TFO connections to
1289 * approximately half of the queue limit. This prevents TFO
1290 * SYN floods from starving the service by filling the
1291 * listen queue with bogus TFO connections.
1293 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
1294 (so->sol_qlimit / 2)) {
1297 result = tcp_fastopen_check_cookie(inc,
1298 to->to_tfo_cookie, to->to_tfo_len,
1299 &tfo_response_cookie);
1300 tfo_cookie_valid = (result > 0);
1301 tfo_response_cookie_valid = (result >= 0);
1305 * Remember the TFO pending counter as it will have to be
1306 * decremented below if we don't make it to syncache_tfo_expand().
1308 tfo_pending = tp->t_tfo_pending;
1312 /* By the time we drop the lock these should no longer be used. */
1317 if (mac_syncache_init(&maclabel) != 0) {
1321 mac_syncache_create(maclabel, inp);
1324 if (!tfo_cookie_valid)
1329 * Remember the IP options, if any.
1332 if (!(inc->inc_flags & INC_ISIPV6))
1335 ipopts = (m) ? ip_srcroute(m) : NULL;
1340 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1342 * If listening socket requested TCP digests, check that received
1343 * SYN has signature and it is correct. If signature doesn't match
1344 * or TCP_SIGNATURE support isn't enabled, drop the packet.
1346 if (ltflags & TF_SIGNATURE) {
1347 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1348 TCPSTAT_INC(tcps_sig_err_nosigopt);
1351 if (!TCPMD5_ENABLED() ||
1352 TCPMD5_INPUT(m, th, to->to_signature) != 0)
1355 #endif /* TCP_SIGNATURE */
1357 * See if we already have an entry for this connection.
1358 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1360 * XXX: should the syncache be re-initialized with the contents
1361 * of the new SYN here (which may have different options?)
1363 * XXX: We do not check the sequence number to see if this is a
1364 * real retransmit or a new connection attempt. The question is
1365 * how to handle such a case; either ignore it as spoofed, or
1366 * drop the current entry and create a new one?
1368 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1369 SCH_LOCK_ASSERT(sch);
1372 if (tfo_cookie_valid)
1375 TCPSTAT_INC(tcps_sc_dupsyn);
1378 * If we were remembering a previous source route,
1379 * forget it and use the new one we've been given.
1382 (void) m_free(sc->sc_ipopts);
1383 sc->sc_ipopts = ipopts;
1386 * Update timestamp if present.
1388 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1389 sc->sc_tsreflect = to->to_tsval;
1391 sc->sc_flags &= ~SCF_TIMESTAMP;
1394 * Since we have already unconditionally allocated label
1395 * storage, free it up. The syncache entry will already
1396 * have an initialized label we can use.
1398 mac_syncache_destroy(&maclabel);
1400 /* Retransmit SYN|ACK and reset retransmit count. */
1401 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1402 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1403 "resetting timer and retransmitting SYN|ACK\n",
1407 if (syncache_respond(sc, sch, 1, m) == 0) {
1409 syncache_timeout(sc, sch, 1);
1410 TCPSTAT_INC(tcps_sndacks);
1411 TCPSTAT_INC(tcps_sndtotal);
1418 if (tfo_cookie_valid) {
1419 bzero(&scs, sizeof(scs));
1425 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1428 * The zone allocator couldn't provide more entries.
1429 * Treat this as if the cache was full; drop the oldest
1430 * entry and insert the new one.
1432 TCPSTAT_INC(tcps_sc_zonefail);
1433 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) {
1434 sch->sch_last_overflow = time_uptime;
1435 syncache_drop(sc, sch);
1437 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1439 if (V_tcp_syncookies) {
1440 bzero(&scs, sizeof(scs));
1445 (void) m_free(ipopts);
1453 if (!tfo_cookie_valid && tfo_response_cookie_valid)
1454 sc->sc_tfo_cookie = &tfo_response_cookie;
1458 * Fill in the syncache values.
1461 sc->sc_label = maclabel;
1465 sc->sc_ipopts = ipopts;
1466 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1468 if (!(inc->inc_flags & INC_ISIPV6))
1471 sc->sc_ip_tos = ip_tos;
1472 sc->sc_ip_ttl = ip_ttl;
1476 sc->sc_todctx = todctx;
1478 sc->sc_irs = th->th_seq;
1479 sc->sc_iss = arc4random();
1481 sc->sc_flowlabel = 0;
1484 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1485 * win was derived from socket earlier in the function.
1488 win = imin(win, TCP_MAXWIN);
1491 if (V_tcp_do_rfc1323) {
1493 * A timestamp received in a SYN makes
1494 * it ok to send timestamp requests and replies.
1496 if (to->to_flags & TOF_TS) {
1497 sc->sc_tsreflect = to->to_tsval;
1498 sc->sc_ts = tcp_ts_getticks();
1499 sc->sc_flags |= SCF_TIMESTAMP;
1501 if (to->to_flags & TOF_SCALE) {
1505 * Pick the smallest possible scaling factor that
1506 * will still allow us to scale up to sb_max, aka
1507 * kern.ipc.maxsockbuf.
1509 * We do this because there are broken firewalls that
1510 * will corrupt the window scale option, leading to
1511 * the other endpoint believing that our advertised
1512 * window is unscaled. At scale factors larger than
1513 * 5 the unscaled window will drop below 1500 bytes,
1514 * leading to serious problems when traversing these
1517 * With the default maxsockbuf of 256K, a scale factor
1518 * of 3 will be chosen by this algorithm. Those who
1519 * choose a larger maxsockbuf should watch out
1520 * for the compatibility problems mentioned above.
1522 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1523 * or <SYN,ACK>) segment itself is never scaled.
1525 while (wscale < TCP_MAX_WINSHIFT &&
1526 (TCP_MAXWIN << wscale) < sb_max)
1528 sc->sc_requested_r_scale = wscale;
1529 sc->sc_requested_s_scale = to->to_wscale;
1530 sc->sc_flags |= SCF_WINSCALE;
1533 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1535 * If listening socket requested TCP digests, flag this in the
1536 * syncache so that syncache_respond() will do the right thing
1539 if (ltflags & TF_SIGNATURE)
1540 sc->sc_flags |= SCF_SIGNATURE;
1541 #endif /* TCP_SIGNATURE */
1542 if (to->to_flags & TOF_SACKPERM)
1543 sc->sc_flags |= SCF_SACK;
1544 if (to->to_flags & TOF_MSS)
1545 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1546 if (ltflags & TF_NOOPT)
1547 sc->sc_flags |= SCF_NOOPT;
1548 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1549 sc->sc_flags |= SCF_ECN;
1551 if (V_tcp_syncookies)
1552 sc->sc_iss = syncookie_generate(sch, sc);
1554 if (autoflowlabel) {
1555 if (V_tcp_syncookies)
1556 sc->sc_flowlabel = sc->sc_iss;
1558 sc->sc_flowlabel = ip6_randomflowlabel();
1559 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
1565 if (tfo_cookie_valid) {
1566 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie);
1567 /* INP_WUNLOCK(inp) will be performed by the caller */
1574 * Do a standard 3-way handshake.
1576 if (syncache_respond(sc, sch, 0, m) == 0) {
1577 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1579 else if (sc != &scs)
1580 syncache_insert(sc, sch); /* locks and unlocks sch */
1581 TCPSTAT_INC(tcps_sndacks);
1582 TCPSTAT_INC(tcps_sndtotal);
1586 TCPSTAT_INC(tcps_sc_dropped);
1596 * If tfo_pending is not NULL here, then a TFO SYN that did not
1597 * result in a new socket was processed and the associated pending
1598 * counter has not yet been decremented. All such TFO processing paths
1599 * transit this point.
1601 if (tfo_pending != NULL)
1602 tcp_fastopen_decrement_counter(tfo_pending);
1610 mac_syncache_destroy(&maclabel);
1616 * Send SYN|ACK to the peer. Either in response to the peer's SYN,
1617 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
1620 syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked,
1621 const struct mbuf *m0)
1623 struct ip *ip = NULL;
1625 struct tcphdr *th = NULL;
1626 int optlen, error = 0; /* Make compiler happy */
1627 u_int16_t hlen, tlen, mssopt;
1630 struct ip6_hdr *ip6 = NULL;
1634 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1637 tlen = hlen + sizeof(struct tcphdr);
1639 /* Determine MSS we advertize to other end of connection. */
1640 mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss);
1642 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1643 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1644 ("syncache: mbuf too small"));
1646 /* Create the IP+TCP header from scratch. */
1647 m = m_gethdr(M_NOWAIT, MT_DATA);
1651 mac_syncache_create_mbuf(sc->sc_label, m);
1653 m->m_data += max_linkhdr;
1655 m->m_pkthdr.len = tlen;
1656 m->m_pkthdr.rcvif = NULL;
1659 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1660 ip6 = mtod(m, struct ip6_hdr *);
1661 ip6->ip6_vfc = IPV6_VERSION;
1662 ip6->ip6_nxt = IPPROTO_TCP;
1663 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1664 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1665 ip6->ip6_plen = htons(tlen - hlen);
1666 /* ip6_hlim is set after checksum */
1667 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1668 ip6->ip6_flow |= sc->sc_flowlabel;
1670 th = (struct tcphdr *)(ip6 + 1);
1673 #if defined(INET6) && defined(INET)
1678 ip = mtod(m, struct ip *);
1679 ip->ip_v = IPVERSION;
1680 ip->ip_hl = sizeof(struct ip) >> 2;
1681 ip->ip_len = htons(tlen);
1685 ip->ip_p = IPPROTO_TCP;
1686 ip->ip_src = sc->sc_inc.inc_laddr;
1687 ip->ip_dst = sc->sc_inc.inc_faddr;
1688 ip->ip_ttl = sc->sc_ip_ttl;
1689 ip->ip_tos = sc->sc_ip_tos;
1692 * See if we should do MTU discovery. Route lookups are
1693 * expensive, so we will only unset the DF bit if:
1695 * 1) path_mtu_discovery is disabled
1696 * 2) the SCF_UNREACH flag has been set
1698 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1699 ip->ip_off |= htons(IP_DF);
1701 th = (struct tcphdr *)(ip + 1);
1704 th->th_sport = sc->sc_inc.inc_lport;
1705 th->th_dport = sc->sc_inc.inc_fport;
1707 th->th_seq = htonl(sc->sc_iss);
1708 th->th_ack = htonl(sc->sc_irs + 1);
1709 th->th_off = sizeof(struct tcphdr) >> 2;
1711 th->th_flags = TH_SYN|TH_ACK;
1712 th->th_win = htons(sc->sc_wnd);
1715 if (sc->sc_flags & SCF_ECN) {
1716 th->th_flags |= TH_ECE;
1717 TCPSTAT_INC(tcps_ecn_shs);
1720 /* Tack on the TCP options. */
1721 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1725 to.to_flags = TOF_MSS;
1726 if (sc->sc_flags & SCF_WINSCALE) {
1727 to.to_wscale = sc->sc_requested_r_scale;
1728 to.to_flags |= TOF_SCALE;
1730 if (sc->sc_flags & SCF_TIMESTAMP) {
1731 /* Virgin timestamp or TCP cookie enhanced one. */
1732 to.to_tsval = sc->sc_ts;
1733 to.to_tsecr = sc->sc_tsreflect;
1734 to.to_flags |= TOF_TS;
1736 if (sc->sc_flags & SCF_SACK)
1737 to.to_flags |= TOF_SACKPERM;
1738 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1739 if (sc->sc_flags & SCF_SIGNATURE)
1740 to.to_flags |= TOF_SIGNATURE;
1743 if (sc->sc_tfo_cookie) {
1744 to.to_flags |= TOF_FASTOPEN;
1745 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
1746 to.to_tfo_cookie = sc->sc_tfo_cookie;
1747 /* don't send cookie again when retransmitting response */
1748 sc->sc_tfo_cookie = NULL;
1751 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1753 /* Adjust headers by option size. */
1754 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1756 m->m_pkthdr.len += optlen;
1758 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1759 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1762 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
1763 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1764 if (sc->sc_flags & SCF_SIGNATURE) {
1765 KASSERT(to.to_flags & TOF_SIGNATURE,
1766 ("tcp_addoptions() didn't set tcp_signature"));
1768 /* NOTE: to.to_signature is inside of mbuf */
1769 if (!TCPMD5_ENABLED() ||
1770 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
1779 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1780 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1782 * If we have peer's SYN and it has a flowid, then let's assign it to
1783 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid
1784 * to SYN|ACK due to lack of inp here.
1786 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
1787 m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
1788 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
1791 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1792 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1793 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1795 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1797 if (ADDED_BY_TOE(sc)) {
1798 struct toedev *tod = sc->sc_tod;
1800 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1805 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1808 #if defined(INET6) && defined(INET)
1813 m->m_pkthdr.csum_flags = CSUM_TCP;
1814 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1815 htons(tlen + optlen - hlen + IPPROTO_TCP));
1817 if (ADDED_BY_TOE(sc)) {
1818 struct toedev *tod = sc->sc_tod;
1820 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1825 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1832 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
1833 * that exceed the capacity of the syncache by avoiding the storage of any
1834 * of the SYNs we receive. Syncookies defend against blind SYN flooding
1835 * attacks where the attacker does not have access to our responses.
1837 * Syncookies encode and include all necessary information about the
1838 * connection setup within the SYN|ACK that we send back. That way we
1839 * can avoid keeping any local state until the ACK to our SYN|ACK returns
1840 * (if ever). Normally the syncache and syncookies are running in parallel
1841 * with the latter taking over when the former is exhausted. When matching
1842 * syncache entry is found the syncookie is ignored.
1844 * The only reliable information persisting the 3WHS is our initial sequence
1845 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient
1846 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS
1847 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
1848 * returns and signifies a legitimate connection if it matches the ACK.
1850 * The available space of 32 bits to store the hash and to encode the SYN
1851 * option information is very tight and we should have at least 24 bits for
1852 * the MAC to keep the number of guesses by blind spoofing reasonably high.
1854 * SYN option information we have to encode to fully restore a connection:
1855 * MSS: is imporant to chose an optimal segment size to avoid IP level
1856 * fragmentation along the path. The common MSS values can be encoded
1857 * in a 3-bit table. Uncommon values are captured by the next lower value
1858 * in the table leading to a slight increase in packetization overhead.
1859 * WSCALE: is necessary to allow large windows to be used for high delay-
1860 * bandwidth product links. Not scaling the window when it was initially
1861 * negotiated is bad for performance as lack of scaling further decreases
1862 * the apparent available send window. We only need to encode the WSCALE
1863 * we received from the remote end. Our end can be recalculated at any
1864 * time. The common WSCALE values can be encoded in a 3-bit table.
1865 * Uncommon values are captured by the next lower value in the table
1866 * making us under-estimate the available window size halving our
1867 * theoretically possible maximum throughput for that connection.
1868 * SACK: Greatly assists in packet loss recovery and requires 1 bit.
1869 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options
1870 * that are included in all segments on a connection. We enable them when
1873 * Security of syncookies and attack vectors:
1875 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
1876 * together with the gloabl secret to make it unique per connection attempt.
1877 * Thus any change of any of those parameters results in a different MAC output
1878 * in an unpredictable way unless a collision is encountered. 24 bits of the
1879 * MAC are embedded into the ISS.
1881 * To prevent replay attacks two rotating global secrets are updated with a
1882 * new random value every 15 seconds. The life-time of a syncookie is thus
1885 * Vector 1: Attacking the secret. This requires finding a weakness in the
1886 * MAC itself or the way it is used here. The attacker can do a chosen plain
1887 * text attack by varying and testing the all parameters under his control.
1888 * The strength depends on the size and randomness of the secret, and the
1889 * cryptographic security of the MAC function. Due to the constant updating
1890 * of the secret the attacker has at most 29.999 seconds to find the secret
1891 * and launch spoofed connections. After that he has to start all over again.
1893 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
1894 * size an average of 4,823 attempts are required for a 50% chance of success
1895 * to spoof a single syncookie (birthday collision paradox). However the
1896 * attacker is blind and doesn't know if one of his attempts succeeded unless
1897 * he has a side channel to interfere success from. A single connection setup
1898 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
1899 * This many attempts are required for each one blind spoofed connection. For
1900 * every additional spoofed connection he has to launch another N attempts.
1901 * Thus for a sustained rate 100 spoofed connections per second approximately
1902 * 1,800,000 packets per second would have to be sent.
1904 * NB: The MAC function should be fast so that it doesn't become a CPU
1905 * exhaustion attack vector itself.
1908 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations
1909 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
1910 * http://cr.yp.to/syncookies.html (overview)
1911 * http://cr.yp.to/syncookies/archive (details)
1914 * Schematic construction of a syncookie enabled Initial Sequence Number:
1916 * 12345678901234567890123456789012
1917 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
1919 * x 24 MAC (truncated)
1920 * W 3 Send Window Scale index
1922 * S 1 SACK permitted
1923 * P 1 Odd/even secret
1927 * Distribution and probability of certain MSS values. Those in between are
1928 * rounded down to the next lower one.
1929 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
1930 * .2% .3% 5% 7% 7% 20% 15% 45%
1932 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
1935 * Distribution and probability of certain WSCALE values. We have to map the
1936 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
1937 * bits based on prevalence of certain values. Where we don't have an exact
1938 * match for are rounded down to the next lower one letting us under-estimate
1939 * the true available window. At the moment this would happen only for the
1940 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
1941 * and window size). The absence of the WSCALE option (no scaling in either
1942 * direction) is encoded with index zero.
1943 * [WSCALE values histograms, Allman, 2012]
1944 * X 10 10 35 5 6 14 10% by host
1945 * X 11 4 5 5 18 49 3% by connections
1947 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
1950 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
1951 * and good cryptographic properties.
1954 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
1955 uint8_t *secbits, uintptr_t secmod)
1958 uint32_t siphash[2];
1960 SipHash24_Init(&ctx);
1961 SipHash_SetKey(&ctx, secbits);
1962 switch (inc->inc_flags & INC_ISIPV6) {
1965 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
1966 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
1971 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
1972 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
1976 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
1977 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
1978 SipHash_Update(&ctx, &irs, sizeof(irs));
1979 SipHash_Update(&ctx, &flags, sizeof(flags));
1980 SipHash_Update(&ctx, &secmod, sizeof(secmod));
1981 SipHash_Final((u_int8_t *)&siphash, &ctx);
1983 return (siphash[0] ^ siphash[1]);
1987 syncookie_generate(struct syncache_head *sch, struct syncache *sc)
1989 u_int i, secbit, wscale;
1992 union syncookie cookie;
1994 SCH_LOCK_ASSERT(sch);
1998 /* Map our computed MSS into the 3-bit index. */
1999 for (i = nitems(tcp_sc_msstab) - 1;
2000 tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0;
2003 cookie.flags.mss_idx = i;
2006 * Map the send window scale into the 3-bit index but only if
2007 * the wscale option was received.
2009 if (sc->sc_flags & SCF_WINSCALE) {
2010 wscale = sc->sc_requested_s_scale;
2011 for (i = nitems(tcp_sc_wstab) - 1;
2012 tcp_sc_wstab[i] > wscale && i > 0;
2015 cookie.flags.wscale_idx = i;
2018 /* Can we do SACK? */
2019 if (sc->sc_flags & SCF_SACK)
2020 cookie.flags.sack_ok = 1;
2022 /* Which of the two secrets to use. */
2023 secbit = sch->sch_sc->secret.oddeven & 0x1;
2024 cookie.flags.odd_even = secbit;
2026 secbits = sch->sch_sc->secret.key[secbit];
2027 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
2031 * Put the flags into the hash and XOR them to get better ISS number
2032 * variance. This doesn't enhance the cryptographic strength and is
2033 * done to prevent the 8 cookie bits from showing up directly on the
2037 iss |= cookie.cookie ^ (hash >> 24);
2039 /* Randomize the timestamp. */
2040 if (sc->sc_flags & SCF_TIMESTAMP) {
2041 sc->sc_ts = arc4random();
2042 sc->sc_tsoff = sc->sc_ts - tcp_ts_getticks();
2045 TCPSTAT_INC(tcps_sc_sendcookie);
2049 static struct syncache *
2050 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
2051 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2057 int wnd, wscale = 0;
2058 union syncookie cookie;
2060 SCH_LOCK_ASSERT(sch);
2063 * Pull information out of SYN-ACK/ACK and revert sequence number
2066 ack = th->th_ack - 1;
2067 seq = th->th_seq - 1;
2070 * Unpack the flags containing enough information to restore the
2073 cookie.cookie = (ack & 0xff) ^ (ack >> 24);
2075 /* Which of the two secrets to use. */
2076 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even];
2078 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
2080 /* The recomputed hash matches the ACK if this was a genuine cookie. */
2081 if ((ack & ~0xff) != (hash & ~0xff))
2084 /* Fill in the syncache values. */
2086 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
2087 sc->sc_ipopts = NULL;
2092 switch (inc->inc_flags & INC_ISIPV6) {
2095 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
2096 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
2101 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
2102 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK;
2107 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
2109 /* We can simply recompute receive window scale we sent earlier. */
2110 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
2113 /* Only use wscale if it was enabled in the orignal SYN. */
2114 if (cookie.flags.wscale_idx > 0) {
2115 sc->sc_requested_r_scale = wscale;
2116 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
2117 sc->sc_flags |= SCF_WINSCALE;
2120 wnd = lso->sol_sbrcv_hiwat;
2122 wnd = imin(wnd, TCP_MAXWIN);
2125 if (cookie.flags.sack_ok)
2126 sc->sc_flags |= SCF_SACK;
2128 if (to->to_flags & TOF_TS) {
2129 sc->sc_flags |= SCF_TIMESTAMP;
2130 sc->sc_tsreflect = to->to_tsval;
2131 sc->sc_ts = to->to_tsecr;
2132 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
2135 if (to->to_flags & TOF_SIGNATURE)
2136 sc->sc_flags |= SCF_SIGNATURE;
2140 TCPSTAT_INC(tcps_sc_recvcookie);
2146 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
2147 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2150 struct syncache scs, *scx;
2153 bzero(&scs, sizeof(scs));
2154 scx = syncookie_lookup(inc, sch, &scs, th, to, lso);
2156 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
2160 if (sc->sc_peer_mss != scx->sc_peer_mss)
2161 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
2162 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
2164 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
2165 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
2166 s, __func__, sc->sc_requested_r_scale,
2167 scx->sc_requested_r_scale);
2169 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
2170 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
2171 s, __func__, sc->sc_requested_s_scale,
2172 scx->sc_requested_s_scale);
2174 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
2175 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
2182 #endif /* INVARIANTS */
2185 syncookie_reseed(void *arg)
2187 struct tcp_syncache *sc = arg;
2192 * Reseeding the secret doesn't have to be protected by a lock.
2193 * It only must be ensured that the new random values are visible
2194 * to all CPUs in a SMP environment. The atomic with release
2195 * semantics ensures that.
2197 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
2198 secbits = sc->secret.key[secbit];
2199 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
2200 atomic_add_rel_int(&sc->secret.oddeven, 1);
2202 /* Reschedule ourself. */
2203 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
2207 * Exports the syncache entries to userland so that netstat can display
2208 * them alongside the other sockets. This function is intended to be
2209 * called only from tcp_pcblist.
2211 * Due to concurrency on an active system, the number of pcbs exported
2212 * may have no relation to max_pcbs. max_pcbs merely indicates the
2213 * amount of space the caller allocated for this function to use.
2216 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
2219 struct syncache *sc;
2220 struct syncache_head *sch;
2221 int count, error, i;
2223 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
2224 sch = &V_tcp_syncache.hashbase[i];
2226 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
2227 if (count >= max_pcbs) {
2231 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
2233 bzero(&xt, sizeof(xt));
2234 xt.xt_len = sizeof(xt);
2235 if (sc->sc_inc.inc_flags & INC_ISIPV6)
2236 xt.xt_inp.inp_vflag = INP_IPV6;
2238 xt.xt_inp.inp_vflag = INP_IPV4;
2239 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc,
2240 sizeof (struct in_conninfo));
2241 xt.t_state = TCPS_SYN_RECEIVED;
2242 xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP;
2243 xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket);
2244 xt.xt_inp.xi_socket.so_type = SOCK_STREAM;
2245 xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING;
2246 error = SYSCTL_OUT(req, &xt, sizeof xt);
2256 *pcbs_exported = count;