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");
117 static VNET_DEFINE(int, functions_inherit_listen_socket_stack) = 1;
118 #define V_functions_inherit_listen_socket_stack \
119 VNET(functions_inherit_listen_socket_stack)
120 SYSCTL_INT(_net_inet_tcp, OID_AUTO, functions_inherit_listen_socket_stack,
121 CTLFLAG_VNET | CTLFLAG_RW,
122 &VNET_NAME(functions_inherit_listen_socket_stack), 0,
123 "Inherit listen socket's stack");
126 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
129 static void syncache_drop(struct syncache *, struct syncache_head *);
130 static void syncache_free(struct syncache *);
131 static void syncache_insert(struct syncache *, struct syncache_head *);
132 static int syncache_respond(struct syncache *, struct syncache_head *, int,
133 const struct mbuf *);
134 static struct socket *syncache_socket(struct syncache *, struct socket *,
136 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
138 static void syncache_timer(void *);
140 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
141 uint8_t *, uintptr_t);
142 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
143 static struct syncache
144 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
145 struct syncache *, struct tcphdr *, struct tcpopt *,
147 static void syncookie_reseed(void *);
149 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
150 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
155 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
156 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
157 * the odds are that the user has given up attempting to connect by then.
159 #define SYNCACHE_MAXREXMTS 3
161 /* Arbitrary values */
162 #define TCP_SYNCACHE_HASHSIZE 512
163 #define TCP_SYNCACHE_BUCKETLIMIT 30
165 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
166 #define V_tcp_syncache VNET(tcp_syncache)
168 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0,
171 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
172 &VNET_NAME(tcp_syncache.bucket_limit), 0,
173 "Per-bucket hash limit for syncache");
175 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
176 &VNET_NAME(tcp_syncache.cache_limit), 0,
177 "Overall entry limit for syncache");
179 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
180 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
182 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
183 &VNET_NAME(tcp_syncache.hashsize), 0,
184 "Size of TCP syncache hashtable");
186 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_VNET | CTLFLAG_RW,
187 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
188 "Limit on SYN/ACK retransmissions");
190 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
191 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
192 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
193 "Send reset on socket allocation failure");
195 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
197 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
198 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
199 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
202 * Requires the syncache entry to be already removed from the bucket list.
205 syncache_free(struct syncache *sc)
209 (void) m_free(sc->sc_ipopts);
213 mac_syncache_destroy(&sc->sc_label);
216 uma_zfree(V_tcp_syncache.zone, sc);
224 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
225 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
226 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
227 V_tcp_syncache.hash_secret = arc4random();
229 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
230 &V_tcp_syncache.hashsize);
231 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
232 &V_tcp_syncache.bucket_limit);
233 if (!powerof2(V_tcp_syncache.hashsize) ||
234 V_tcp_syncache.hashsize == 0) {
235 printf("WARNING: syncache hash size is not a power of 2.\n");
236 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
238 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
241 V_tcp_syncache.cache_limit =
242 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
243 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
244 &V_tcp_syncache.cache_limit);
246 /* Allocate the hash table. */
247 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
248 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
251 V_tcp_syncache.vnet = curvnet;
254 /* Initialize the hash buckets. */
255 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
256 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
257 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
259 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
260 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
261 V_tcp_syncache.hashbase[i].sch_length = 0;
262 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
265 /* Create the syncache entry zone. */
266 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
267 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
268 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
269 V_tcp_syncache.cache_limit);
271 /* Start the SYN cookie reseeder callout. */
272 callout_init(&V_tcp_syncache.secret.reseed, 1);
273 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
274 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
275 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
276 syncookie_reseed, &V_tcp_syncache);
281 syncache_destroy(void)
283 struct syncache_head *sch;
284 struct syncache *sc, *nsc;
288 * Stop the re-seed timer before freeing resources. No need to
289 * possibly schedule it another time.
291 callout_drain(&V_tcp_syncache.secret.reseed);
293 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
294 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
296 sch = &V_tcp_syncache.hashbase[i];
297 callout_drain(&sch->sch_timer);
300 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
301 syncache_drop(sc, sch);
303 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
304 ("%s: sch->sch_bucket not empty", __func__));
305 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
306 __func__, sch->sch_length));
307 mtx_destroy(&sch->sch_mtx);
310 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
311 ("%s: cache_count not 0", __func__));
313 /* Free the allocated global resources. */
314 uma_zdestroy(V_tcp_syncache.zone);
315 free(V_tcp_syncache.hashbase, M_SYNCACHE);
320 * Inserts a syncache entry into the specified bucket row.
321 * Locks and unlocks the syncache_head autonomously.
324 syncache_insert(struct syncache *sc, struct syncache_head *sch)
326 struct syncache *sc2;
331 * Make sure that we don't overflow the per-bucket limit.
332 * If the bucket is full, toss the oldest element.
334 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
335 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
336 ("sch->sch_length incorrect"));
337 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
338 syncache_drop(sc2, sch);
339 TCPSTAT_INC(tcps_sc_bucketoverflow);
342 /* Put it into the bucket. */
343 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
347 if (ADDED_BY_TOE(sc)) {
348 struct toedev *tod = sc->sc_tod;
350 tod->tod_syncache_added(tod, sc->sc_todctx);
354 /* Reinitialize the bucket row's timer. */
355 if (sch->sch_length == 1)
356 sch->sch_nextc = ticks + INT_MAX;
357 syncache_timeout(sc, sch, 1);
361 TCPSTATES_INC(TCPS_SYN_RECEIVED);
362 TCPSTAT_INC(tcps_sc_added);
366 * Remove and free entry from syncache bucket row.
367 * Expects locked syncache head.
370 syncache_drop(struct syncache *sc, struct syncache_head *sch)
373 SCH_LOCK_ASSERT(sch);
375 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
376 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
380 if (ADDED_BY_TOE(sc)) {
381 struct toedev *tod = sc->sc_tod;
383 tod->tod_syncache_removed(tod, sc->sc_todctx);
391 * Engage/reengage time on bucket row.
394 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
396 sc->sc_rxttime = ticks +
397 TCPTV_RTOBASE * (tcp_syn_backoff[sc->sc_rxmits]);
399 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
400 sch->sch_nextc = sc->sc_rxttime;
402 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
403 syncache_timer, (void *)sch);
408 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
409 * If we have retransmitted an entry the maximum number of times, expire it.
410 * One separate timer for each bucket row.
413 syncache_timer(void *xsch)
415 struct syncache_head *sch = (struct syncache_head *)xsch;
416 struct syncache *sc, *nsc;
420 CURVNET_SET(sch->sch_sc->vnet);
422 /* NB: syncache_head has already been locked by the callout. */
423 SCH_LOCK_ASSERT(sch);
426 * In the following cycle we may remove some entries and/or
427 * advance some timeouts, so re-initialize the bucket timer.
429 sch->sch_nextc = tick + INT_MAX;
431 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
433 * We do not check if the listen socket still exists
434 * and accept the case where the listen socket may be
435 * gone by the time we resend the SYN/ACK. We do
436 * not expect this to happens often. If it does,
437 * then the RST will be sent by the time the remote
438 * host does the SYN/ACK->ACK.
440 if (TSTMP_GT(sc->sc_rxttime, tick)) {
441 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
442 sch->sch_nextc = sc->sc_rxttime;
445 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
446 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
447 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
448 "giving up and removing syncache entry\n",
452 syncache_drop(sc, sch);
453 TCPSTAT_INC(tcps_sc_stale);
456 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
457 log(LOG_DEBUG, "%s; %s: Response timeout, "
458 "retransmitting (%u) SYN|ACK\n",
459 s, __func__, sc->sc_rxmits);
463 syncache_respond(sc, sch, 1, NULL);
464 TCPSTAT_INC(tcps_sc_retransmitted);
465 syncache_timeout(sc, sch, 0);
467 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
468 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
469 syncache_timer, (void *)(sch));
474 * Find an entry in the syncache.
475 * Returns always with locked syncache_head plus a matching entry or NULL.
477 static struct syncache *
478 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
481 struct syncache_head *sch;
485 * The hash is built on foreign port + local port + foreign address.
486 * We rely on the fact that struct in_conninfo starts with 16 bits
487 * of foreign port, then 16 bits of local port then followed by 128
488 * bits of foreign address. In case of IPv4 address, the first 3
489 * 32-bit words of the address always are zeroes.
491 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
492 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
494 sch = &V_tcp_syncache.hashbase[hash];
498 /* Circle through bucket row to find matching entry. */
499 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
500 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
501 sizeof(struct in_endpoints)) == 0)
504 return (sc); /* Always returns with locked sch. */
508 * This function is called when we get a RST for a
509 * non-existent connection, so that we can see if the
510 * connection is in the syn cache. If it is, zap it.
513 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
516 struct syncache_head *sch;
519 sc = syncache_lookup(inc, &sch); /* returns locked sch */
520 SCH_LOCK_ASSERT(sch);
523 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
524 * See RFC 793 page 65, section SEGMENT ARRIVES.
526 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
527 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
528 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
529 "FIN flag set, segment ignored\n", s, __func__);
530 TCPSTAT_INC(tcps_badrst);
535 * No corresponding connection was found in syncache.
536 * If syncookies are enabled and possibly exclusively
537 * used, or we are under memory pressure, a valid RST
538 * may not find a syncache entry. In that case we're
539 * done and no SYN|ACK retransmissions will happen.
540 * Otherwise the RST was misdirected or spoofed.
543 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
544 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
545 "syncache entry (possibly syncookie only), "
546 "segment ignored\n", s, __func__);
547 TCPSTAT_INC(tcps_badrst);
552 * If the RST bit is set, check the sequence number to see
553 * if this is a valid reset segment.
555 * In all states except SYN-SENT, all reset (RST) segments
556 * are validated by checking their SEQ-fields. A reset is
557 * valid if its sequence number is in the window.
559 * The sequence number in the reset segment is normally an
560 * echo of our outgoing acknowlegement numbers, but some hosts
561 * send a reset with the sequence number at the rightmost edge
562 * of our receive window, and we have to handle this case.
564 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
565 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
566 syncache_drop(sc, sch);
567 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
568 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
569 "connection attempt aborted by remote endpoint\n",
571 TCPSTAT_INC(tcps_sc_reset);
573 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
574 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
575 "IRS %u (+WND %u), segment ignored\n",
576 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
577 TCPSTAT_INC(tcps_badrst);
587 syncache_badack(struct in_conninfo *inc)
590 struct syncache_head *sch;
592 sc = syncache_lookup(inc, &sch); /* returns locked sch */
593 SCH_LOCK_ASSERT(sch);
595 syncache_drop(sc, sch);
596 TCPSTAT_INC(tcps_sc_badack);
602 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
605 struct syncache_head *sch;
607 sc = syncache_lookup(inc, &sch); /* returns locked sch */
608 SCH_LOCK_ASSERT(sch);
612 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
613 if (ntohl(th->th_seq) != sc->sc_iss)
617 * If we've rertransmitted 3 times and this is our second error,
618 * we remove the entry. Otherwise, we allow it to continue on.
619 * This prevents us from incorrectly nuking an entry during a
620 * spurious network outage.
624 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
625 sc->sc_flags |= SCF_UNREACH;
628 syncache_drop(sc, sch);
629 TCPSTAT_INC(tcps_sc_unreach);
635 * Build a new TCP socket structure from a syncache entry.
637 * On success return the newly created socket with its underlying inp locked.
639 static struct socket *
640 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
642 struct tcp_function_block *blk;
643 struct inpcb *inp = NULL;
649 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
652 * Ok, create the full blown connection, and set things up
653 * as they would have been set up if we had created the
654 * connection when the SYN arrived. If we can't create
655 * the connection, abort it.
657 so = sonewconn(lso, 0);
660 * Drop the connection; we will either send a RST or
661 * have the peer retransmit its SYN again after its
664 TCPSTAT_INC(tcps_listendrop);
665 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
666 log(LOG_DEBUG, "%s; %s: Socket create failed "
667 "due to limits or memory shortage\n",
674 mac_socketpeer_set_from_mbuf(m, so);
678 inp->inp_inc.inc_fibnum = so->so_fibnum;
681 * Exclusive pcbinfo lock is not required in syncache socket case even
682 * if two inpcb locks can be acquired simultaneously:
683 * - the inpcb in LISTEN state,
684 * - the newly created inp.
686 * In this case, an inp cannot be at same time in LISTEN state and
687 * just created by an accept() call.
689 INP_HASH_WLOCK(&V_tcbinfo);
691 /* Insert new socket into PCB hash list. */
692 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
694 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
695 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
697 inp->inp_vflag &= ~INP_IPV6;
698 inp->inp_vflag |= INP_IPV4;
700 inp->inp_laddr = sc->sc_inc.inc_laddr;
706 * If there's an mbuf and it has a flowid, then let's initialise the
707 * inp with that particular flowid.
709 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
710 inp->inp_flowid = m->m_pkthdr.flowid;
711 inp->inp_flowtype = M_HASHTYPE_GET(m);
715 * Install in the reservation hash table for now, but don't yet
716 * install a connection group since the full 4-tuple isn't yet
719 inp->inp_lport = sc->sc_inc.inc_lport;
720 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
722 * Undo the assignments above if we failed to
723 * put the PCB on the hash lists.
726 if (sc->sc_inc.inc_flags & INC_ISIPV6)
727 inp->in6p_laddr = in6addr_any;
730 inp->inp_laddr.s_addr = INADDR_ANY;
732 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
733 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
738 INP_HASH_WUNLOCK(&V_tcbinfo);
742 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
743 struct inpcb *oinp = sotoinpcb(lso);
744 struct in6_addr laddr6;
745 struct sockaddr_in6 sin6;
747 * Inherit socket options from the listening socket.
748 * Note that in6p_inputopts are not (and should not be)
749 * copied, since it stores previously received options and is
750 * used to detect if each new option is different than the
751 * previous one and hence should be passed to a user.
752 * If we copied in6p_inputopts, a user would not be able to
753 * receive options just after calling the accept system call.
755 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
756 if (oinp->in6p_outputopts)
757 inp->in6p_outputopts =
758 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
760 sin6.sin6_family = AF_INET6;
761 sin6.sin6_len = sizeof(sin6);
762 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
763 sin6.sin6_port = sc->sc_inc.inc_fport;
764 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
765 laddr6 = inp->in6p_laddr;
766 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
767 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
768 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
769 thread0.td_ucred, m)) != 0) {
770 inp->in6p_laddr = laddr6;
771 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
772 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
777 INP_HASH_WUNLOCK(&V_tcbinfo);
780 /* Override flowlabel from in6_pcbconnect. */
781 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
782 inp->inp_flow |= sc->sc_flowlabel;
785 #if defined(INET) && defined(INET6)
790 struct in_addr laddr;
791 struct sockaddr_in sin;
793 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
795 if (inp->inp_options == NULL) {
796 inp->inp_options = sc->sc_ipopts;
797 sc->sc_ipopts = NULL;
800 sin.sin_family = AF_INET;
801 sin.sin_len = sizeof(sin);
802 sin.sin_addr = sc->sc_inc.inc_faddr;
803 sin.sin_port = sc->sc_inc.inc_fport;
804 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
805 laddr = inp->inp_laddr;
806 if (inp->inp_laddr.s_addr == INADDR_ANY)
807 inp->inp_laddr = sc->sc_inc.inc_laddr;
808 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
809 thread0.td_ucred, m)) != 0) {
810 inp->inp_laddr = laddr;
811 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
812 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
817 INP_HASH_WUNLOCK(&V_tcbinfo);
822 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
823 /* Copy old policy into new socket's. */
824 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
825 printf("syncache_socket: could not copy policy\n");
827 INP_HASH_WUNLOCK(&V_tcbinfo);
829 tcp_state_change(tp, TCPS_SYN_RECEIVED);
830 tp->iss = sc->sc_iss;
831 tp->irs = sc->sc_irs;
834 blk = sototcpcb(lso)->t_fb;
835 if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) {
837 * Our parents t_fb was not the default,
838 * we need to release our ref on tp->t_fb and
839 * pickup one on the new entry.
841 struct tcp_function_block *rblk;
843 rblk = find_and_ref_tcp_fb(blk);
844 KASSERT(rblk != NULL,
845 ("cannot find blk %p out of syncache?", blk));
846 if (tp->t_fb->tfb_tcp_fb_fini)
847 (*tp->t_fb->tfb_tcp_fb_fini)(tp, 0);
848 refcount_release(&tp->t_fb->tfb_refcnt);
850 if (tp->t_fb->tfb_tcp_fb_init) {
851 (*tp->t_fb->tfb_tcp_fb_init)(tp);
854 tp->snd_wl1 = sc->sc_irs;
855 tp->snd_max = tp->iss + 1;
856 tp->snd_nxt = tp->iss + 1;
857 tp->rcv_up = sc->sc_irs + 1;
858 tp->rcv_wnd = sc->sc_wnd;
859 tp->rcv_adv += tp->rcv_wnd;
860 tp->last_ack_sent = tp->rcv_nxt;
862 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
863 if (sc->sc_flags & SCF_NOOPT)
864 tp->t_flags |= TF_NOOPT;
866 if (sc->sc_flags & SCF_WINSCALE) {
867 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
868 tp->snd_scale = sc->sc_requested_s_scale;
869 tp->request_r_scale = sc->sc_requested_r_scale;
871 if (sc->sc_flags & SCF_TIMESTAMP) {
872 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
873 tp->ts_recent = sc->sc_tsreflect;
874 tp->ts_recent_age = tcp_ts_getticks();
875 tp->ts_offset = sc->sc_tsoff;
877 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
878 if (sc->sc_flags & SCF_SIGNATURE)
879 tp->t_flags |= TF_SIGNATURE;
881 if (sc->sc_flags & SCF_SACK)
882 tp->t_flags |= TF_SACK_PERMIT;
885 if (sc->sc_flags & SCF_ECN)
886 tp->t_flags |= TF_ECN_PERMIT;
889 * Set up MSS and get cached values from tcp_hostcache.
890 * This might overwrite some of the defaults we just set.
892 tcp_mss(tp, sc->sc_peer_mss);
895 * If the SYN,ACK was retransmitted, indicate that CWND to be
896 * limited to one segment in cc_conn_init().
897 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
899 if (sc->sc_rxmits > 1)
904 * Allow a TOE driver to install its hooks. Note that we hold the
905 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
906 * new connection before the TOE driver has done its thing.
908 if (ADDED_BY_TOE(sc)) {
909 struct toedev *tod = sc->sc_tod;
911 tod->tod_offload_socket(tod, sc->sc_todctx, so);
915 * Copy and activate timers.
917 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
918 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
919 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
920 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
921 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
923 TCPSTAT_INC(tcps_accepts);
935 * This function gets called when we receive an ACK for a
936 * socket in the LISTEN state. We look up the connection
937 * in the syncache, and if its there, we pull it out of
938 * the cache and turn it into a full-blown connection in
939 * the SYN-RECEIVED state.
941 * On syncache_socket() success the newly created socket
942 * has its underlying inp locked.
945 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
946 struct socket **lsop, struct mbuf *m)
949 struct syncache_head *sch;
954 * Global TCP locks are held because we manipulate the PCB lists
955 * and create a new socket.
957 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
958 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
959 ("%s: can handle only ACK", __func__));
961 sc = syncache_lookup(inc, &sch); /* returns locked sch */
962 SCH_LOCK_ASSERT(sch);
966 * Test code for syncookies comparing the syncache stored
967 * values with the reconstructed values from the cookie.
970 syncookie_cmp(inc, sch, sc, th, to, *lsop);
975 * There is no syncache entry, so see if this ACK is
976 * a returning syncookie. To do this, first:
977 * A. See if this socket has had a syncache entry dropped in
978 * the past. We don't want to accept a bogus syncookie
979 * if we've never received a SYN.
980 * B. 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 bzero(&scs, sizeof(scs));
992 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop);
995 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
996 log(LOG_DEBUG, "%s; %s: Segment failed "
997 "SYNCOOKIE authentication, segment rejected "
998 "(probably spoofed)\n", s, __func__);
1001 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1002 /* If received ACK has MD5 signature, check it. */
1003 if ((to->to_flags & TOF_SIGNATURE) != 0 &&
1004 (!TCPMD5_ENABLED() ||
1005 TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
1007 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1008 log(LOG_DEBUG, "%s; %s: Segment rejected, "
1009 "MD5 signature doesn't match.\n",
1013 TCPSTAT_INC(tcps_sig_err_sigopt);
1014 return (-1); /* Do not send RST */
1016 #endif /* TCP_SIGNATURE */
1018 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1020 * If listening socket requested TCP digests, check that
1021 * received ACK has signature and it is correct.
1022 * If not, drop the ACK and leave sc entry in th cache,
1023 * because SYN was received with correct signature.
1025 if (sc->sc_flags & SCF_SIGNATURE) {
1026 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1028 TCPSTAT_INC(tcps_sig_err_nosigopt);
1030 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1031 log(LOG_DEBUG, "%s; %s: Segment "
1032 "rejected, MD5 signature wasn't "
1033 "provided.\n", s, __func__);
1036 return (-1); /* Do not send RST */
1038 if (!TCPMD5_ENABLED() ||
1039 TCPMD5_INPUT(m, th, to->to_signature) != 0) {
1040 /* Doesn't match or no SA */
1042 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1043 log(LOG_DEBUG, "%s; %s: Segment "
1044 "rejected, MD5 signature doesn't "
1045 "match.\n", s, __func__);
1048 return (-1); /* Do not send RST */
1051 #endif /* TCP_SIGNATURE */
1053 * Pull out the entry to unlock the bucket row.
1055 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
1056 * tcp_state_change(). The tcpcb is not existent at this
1057 * moment. A new one will be allocated via syncache_socket->
1058 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then
1059 * syncache_socket() will change it to TCPS_SYN_RECEIVED.
1061 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
1062 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
1065 if (ADDED_BY_TOE(sc)) {
1066 struct toedev *tod = sc->sc_tod;
1068 tod->tod_syncache_removed(tod, sc->sc_todctx);
1075 * Segment validation:
1076 * ACK must match our initial sequence number + 1 (the SYN|ACK).
1078 if (th->th_ack != sc->sc_iss + 1) {
1079 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1080 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
1081 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
1086 * The SEQ must fall in the window starting at the received
1087 * initial receive sequence number + 1 (the SYN).
1089 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
1090 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
1091 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1092 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
1093 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
1098 * If timestamps were not negotiated during SYN/ACK they
1099 * must not appear on any segment during this session.
1101 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
1102 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1103 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1104 "segment rejected\n", s, __func__);
1109 * If timestamps were negotiated during SYN/ACK they should
1110 * appear on every segment during this session.
1111 * XXXAO: This is only informal as there have been unverified
1112 * reports of non-compliants stacks.
1114 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
1115 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1116 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1117 "no action\n", s, __func__);
1124 * If timestamps were negotiated, the reflected timestamp
1125 * must be equal to what we actually sent in the SYN|ACK
1126 * except in the case of 0. Some boxes are known for sending
1127 * broken timestamp replies during the 3whs (and potentially
1128 * during the connection also).
1130 * Accept the final ACK of 3whs with reflected timestamp of 0
1131 * instead of sending a RST and deleting the syncache entry.
1133 if ((to->to_flags & TOF_TS) && to->to_tsecr &&
1134 to->to_tsecr != sc->sc_ts) {
1135 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1136 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
1137 "segment rejected\n",
1138 s, __func__, to->to_tsecr, sc->sc_ts);
1142 *lsop = syncache_socket(sc, *lsop, m);
1145 TCPSTAT_INC(tcps_sc_aborted);
1147 TCPSTAT_INC(tcps_sc_completed);
1149 /* how do we find the inp for the new socket? */
1154 if (sc != NULL && sc != &scs)
1164 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m,
1165 uint64_t response_cookie)
1169 unsigned int *pending_counter;
1172 * Global TCP locks are held because we manipulate the PCB lists
1173 * and create a new socket.
1175 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1177 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending;
1178 *lsop = syncache_socket(sc, *lsop, m);
1179 if (*lsop == NULL) {
1180 TCPSTAT_INC(tcps_sc_aborted);
1181 atomic_subtract_int(pending_counter, 1);
1183 inp = sotoinpcb(*lsop);
1184 tp = intotcpcb(inp);
1185 tp->t_flags |= TF_FASTOPEN;
1186 tp->t_tfo_cookie = response_cookie;
1187 tp->snd_max = tp->iss;
1188 tp->snd_nxt = tp->iss;
1189 tp->t_tfo_pending = pending_counter;
1190 TCPSTAT_INC(tcps_sc_completed);
1193 #endif /* TCP_RFC7413 */
1196 * Given a LISTEN socket and an inbound SYN request, add
1197 * this to the syn cache, and send back a segment:
1198 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1201 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1202 * Doing so would require that we hold onto the data and deliver it
1203 * to the application. However, if we are the target of a SYN-flood
1204 * DoS attack, an attacker could send data which would eventually
1205 * consume all available buffer space if it were ACKed. By not ACKing
1206 * the data, we avoid this DoS scenario.
1208 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
1209 * cookie is processed and a new socket is created. In this case, any data
1210 * accompanying the SYN will be queued to the socket by tcp_input() and will
1211 * be ACKed either when the application sends response data or the delayed
1212 * ACK timer expires, whichever comes first.
1215 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1216 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod,
1221 struct syncache *sc = NULL;
1222 struct syncache_head *sch;
1223 struct mbuf *ipopts = NULL;
1225 int win, ip_ttl, ip_tos;
1229 int autoflowlabel = 0;
1232 struct label *maclabel;
1234 struct syncache scs;
1237 uint64_t tfo_response_cookie;
1238 unsigned int *tfo_pending = NULL;
1239 int tfo_cookie_valid = 0;
1240 int tfo_response_cookie_valid = 0;
1243 INP_WLOCK_ASSERT(inp); /* listen socket */
1244 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1245 ("%s: unexpected tcp flags", __func__));
1248 * Combine all so/tp operations very early to drop the INP lock as
1253 cred = crhold(so->so_cred);
1256 if ((inc->inc_flags & INC_ISIPV6) &&
1257 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1260 ip_ttl = inp->inp_ip_ttl;
1261 ip_tos = inp->inp_ip_tos;
1262 win = sbspace(&so->so_rcv);
1263 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1266 if (V_tcp_fastopen_enabled && IS_FASTOPEN(tp->t_flags) &&
1267 (tp->t_tfo_pending != NULL) && (to->to_flags & TOF_FASTOPEN)) {
1269 * Limit the number of pending TFO connections to
1270 * approximately half of the queue limit. This prevents TFO
1271 * SYN floods from starving the service by filling the
1272 * listen queue with bogus TFO connections.
1274 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
1275 (so->so_qlimit / 2)) {
1278 result = tcp_fastopen_check_cookie(inc,
1279 to->to_tfo_cookie, to->to_tfo_len,
1280 &tfo_response_cookie);
1281 tfo_cookie_valid = (result > 0);
1282 tfo_response_cookie_valid = (result >= 0);
1286 * Remember the TFO pending counter as it will have to be
1287 * decremented below if we don't make it to syncache_tfo_expand().
1289 tfo_pending = tp->t_tfo_pending;
1293 /* By the time we drop the lock these should no longer be used. */
1298 if (mac_syncache_init(&maclabel) != 0) {
1302 mac_syncache_create(maclabel, inp);
1305 if (!tfo_cookie_valid)
1310 * Remember the IP options, if any.
1313 if (!(inc->inc_flags & INC_ISIPV6))
1316 ipopts = (m) ? ip_srcroute(m) : NULL;
1321 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1323 * If listening socket requested TCP digests, check that received
1324 * SYN has signature and it is correct. If signature doesn't match
1325 * or TCP_SIGNATURE support isn't enabled, drop the packet.
1327 if (ltflags & TF_SIGNATURE) {
1328 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1329 TCPSTAT_INC(tcps_sig_err_nosigopt);
1332 if (!TCPMD5_ENABLED() ||
1333 TCPMD5_INPUT(m, th, to->to_signature) != 0)
1336 #endif /* TCP_SIGNATURE */
1338 * See if we already have an entry for this connection.
1339 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1341 * XXX: should the syncache be re-initialized with the contents
1342 * of the new SYN here (which may have different options?)
1344 * XXX: We do not check the sequence number to see if this is a
1345 * real retransmit or a new connection attempt. The question is
1346 * how to handle such a case; either ignore it as spoofed, or
1347 * drop the current entry and create a new one?
1349 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1350 SCH_LOCK_ASSERT(sch);
1353 if (tfo_cookie_valid)
1356 TCPSTAT_INC(tcps_sc_dupsyn);
1359 * If we were remembering a previous source route,
1360 * forget it and use the new one we've been given.
1363 (void) m_free(sc->sc_ipopts);
1364 sc->sc_ipopts = ipopts;
1367 * Update timestamp if present.
1369 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1370 sc->sc_tsreflect = to->to_tsval;
1372 sc->sc_flags &= ~SCF_TIMESTAMP;
1375 * Since we have already unconditionally allocated label
1376 * storage, free it up. The syncache entry will already
1377 * have an initialized label we can use.
1379 mac_syncache_destroy(&maclabel);
1381 /* Retransmit SYN|ACK and reset retransmit count. */
1382 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1383 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1384 "resetting timer and retransmitting SYN|ACK\n",
1388 if (syncache_respond(sc, sch, 1, m) == 0) {
1390 syncache_timeout(sc, sch, 1);
1391 TCPSTAT_INC(tcps_sndacks);
1392 TCPSTAT_INC(tcps_sndtotal);
1399 if (tfo_cookie_valid) {
1400 bzero(&scs, sizeof(scs));
1406 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1409 * The zone allocator couldn't provide more entries.
1410 * Treat this as if the cache was full; drop the oldest
1411 * entry and insert the new one.
1413 TCPSTAT_INC(tcps_sc_zonefail);
1414 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1415 syncache_drop(sc, sch);
1416 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1418 if (V_tcp_syncookies) {
1419 bzero(&scs, sizeof(scs));
1424 (void) m_free(ipopts);
1432 if (!tfo_cookie_valid && tfo_response_cookie_valid)
1433 sc->sc_tfo_cookie = &tfo_response_cookie;
1437 * Fill in the syncache values.
1440 sc->sc_label = maclabel;
1444 sc->sc_ipopts = ipopts;
1445 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1447 if (!(inc->inc_flags & INC_ISIPV6))
1450 sc->sc_ip_tos = ip_tos;
1451 sc->sc_ip_ttl = ip_ttl;
1455 sc->sc_todctx = todctx;
1457 sc->sc_irs = th->th_seq;
1458 sc->sc_iss = arc4random();
1460 sc->sc_flowlabel = 0;
1463 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1464 * win was derived from socket earlier in the function.
1467 win = imin(win, TCP_MAXWIN);
1470 if (V_tcp_do_rfc1323) {
1472 * A timestamp received in a SYN makes
1473 * it ok to send timestamp requests and replies.
1475 if (to->to_flags & TOF_TS) {
1476 sc->sc_tsreflect = to->to_tsval;
1477 sc->sc_ts = tcp_ts_getticks();
1478 sc->sc_flags |= SCF_TIMESTAMP;
1480 if (to->to_flags & TOF_SCALE) {
1484 * Pick the smallest possible scaling factor that
1485 * will still allow us to scale up to sb_max, aka
1486 * kern.ipc.maxsockbuf.
1488 * We do this because there are broken firewalls that
1489 * will corrupt the window scale option, leading to
1490 * the other endpoint believing that our advertised
1491 * window is unscaled. At scale factors larger than
1492 * 5 the unscaled window will drop below 1500 bytes,
1493 * leading to serious problems when traversing these
1496 * With the default maxsockbuf of 256K, a scale factor
1497 * of 3 will be chosen by this algorithm. Those who
1498 * choose a larger maxsockbuf should watch out
1499 * for the compatibility problems mentioned above.
1501 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1502 * or <SYN,ACK>) segment itself is never scaled.
1504 while (wscale < TCP_MAX_WINSHIFT &&
1505 (TCP_MAXWIN << wscale) < sb_max)
1507 sc->sc_requested_r_scale = wscale;
1508 sc->sc_requested_s_scale = to->to_wscale;
1509 sc->sc_flags |= SCF_WINSCALE;
1512 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1514 * If listening socket requested TCP digests, flag this in the
1515 * syncache so that syncache_respond() will do the right thing
1518 if (ltflags & TF_SIGNATURE)
1519 sc->sc_flags |= SCF_SIGNATURE;
1520 #endif /* TCP_SIGNATURE */
1521 if (to->to_flags & TOF_SACKPERM)
1522 sc->sc_flags |= SCF_SACK;
1523 if (to->to_flags & TOF_MSS)
1524 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1525 if (ltflags & TF_NOOPT)
1526 sc->sc_flags |= SCF_NOOPT;
1527 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1528 sc->sc_flags |= SCF_ECN;
1530 if (V_tcp_syncookies)
1531 sc->sc_iss = syncookie_generate(sch, sc);
1533 if (autoflowlabel) {
1534 if (V_tcp_syncookies)
1535 sc->sc_flowlabel = sc->sc_iss;
1537 sc->sc_flowlabel = ip6_randomflowlabel();
1538 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
1544 if (tfo_cookie_valid) {
1545 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie);
1546 /* INP_WUNLOCK(inp) will be performed by the caller */
1553 * Do a standard 3-way handshake.
1555 if (syncache_respond(sc, sch, 0, m) == 0) {
1556 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1558 else if (sc != &scs)
1559 syncache_insert(sc, sch); /* locks and unlocks sch */
1560 TCPSTAT_INC(tcps_sndacks);
1561 TCPSTAT_INC(tcps_sndtotal);
1565 TCPSTAT_INC(tcps_sc_dropped);
1575 * If tfo_pending is not NULL here, then a TFO SYN that did not
1576 * result in a new socket was processed and the associated pending
1577 * counter has not yet been decremented. All such TFO processing paths
1578 * transit this point.
1580 if (tfo_pending != NULL)
1581 tcp_fastopen_decrement_counter(tfo_pending);
1589 mac_syncache_destroy(&maclabel);
1595 * Send SYN|ACK to the peer. Either in response to the peer's SYN,
1596 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
1599 syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked,
1600 const struct mbuf *m0)
1602 struct ip *ip = NULL;
1604 struct tcphdr *th = NULL;
1605 int optlen, error = 0; /* Make compiler happy */
1606 u_int16_t hlen, tlen, mssopt;
1609 struct ip6_hdr *ip6 = NULL;
1613 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1616 tlen = hlen + sizeof(struct tcphdr);
1618 /* Determine MSS we advertize to other end of connection. */
1619 mssopt = tcp_mssopt(&sc->sc_inc);
1620 if (sc->sc_peer_mss)
1621 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1623 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1624 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1625 ("syncache: mbuf too small"));
1627 /* Create the IP+TCP header from scratch. */
1628 m = m_gethdr(M_NOWAIT, MT_DATA);
1632 mac_syncache_create_mbuf(sc->sc_label, m);
1634 m->m_data += max_linkhdr;
1636 m->m_pkthdr.len = tlen;
1637 m->m_pkthdr.rcvif = NULL;
1640 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1641 ip6 = mtod(m, struct ip6_hdr *);
1642 ip6->ip6_vfc = IPV6_VERSION;
1643 ip6->ip6_nxt = IPPROTO_TCP;
1644 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1645 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1646 ip6->ip6_plen = htons(tlen - hlen);
1647 /* ip6_hlim is set after checksum */
1648 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1649 ip6->ip6_flow |= sc->sc_flowlabel;
1651 th = (struct tcphdr *)(ip6 + 1);
1654 #if defined(INET6) && defined(INET)
1659 ip = mtod(m, struct ip *);
1660 ip->ip_v = IPVERSION;
1661 ip->ip_hl = sizeof(struct ip) >> 2;
1662 ip->ip_len = htons(tlen);
1666 ip->ip_p = IPPROTO_TCP;
1667 ip->ip_src = sc->sc_inc.inc_laddr;
1668 ip->ip_dst = sc->sc_inc.inc_faddr;
1669 ip->ip_ttl = sc->sc_ip_ttl;
1670 ip->ip_tos = sc->sc_ip_tos;
1673 * See if we should do MTU discovery. Route lookups are
1674 * expensive, so we will only unset the DF bit if:
1676 * 1) path_mtu_discovery is disabled
1677 * 2) the SCF_UNREACH flag has been set
1679 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1680 ip->ip_off |= htons(IP_DF);
1682 th = (struct tcphdr *)(ip + 1);
1685 th->th_sport = sc->sc_inc.inc_lport;
1686 th->th_dport = sc->sc_inc.inc_fport;
1688 th->th_seq = htonl(sc->sc_iss);
1689 th->th_ack = htonl(sc->sc_irs + 1);
1690 th->th_off = sizeof(struct tcphdr) >> 2;
1692 th->th_flags = TH_SYN|TH_ACK;
1693 th->th_win = htons(sc->sc_wnd);
1696 if (sc->sc_flags & SCF_ECN) {
1697 th->th_flags |= TH_ECE;
1698 TCPSTAT_INC(tcps_ecn_shs);
1701 /* Tack on the TCP options. */
1702 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1706 to.to_flags = TOF_MSS;
1707 if (sc->sc_flags & SCF_WINSCALE) {
1708 to.to_wscale = sc->sc_requested_r_scale;
1709 to.to_flags |= TOF_SCALE;
1711 if (sc->sc_flags & SCF_TIMESTAMP) {
1712 /* Virgin timestamp or TCP cookie enhanced one. */
1713 to.to_tsval = sc->sc_ts;
1714 to.to_tsecr = sc->sc_tsreflect;
1715 to.to_flags |= TOF_TS;
1717 if (sc->sc_flags & SCF_SACK)
1718 to.to_flags |= TOF_SACKPERM;
1719 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1720 if (sc->sc_flags & SCF_SIGNATURE)
1721 to.to_flags |= TOF_SIGNATURE;
1724 if (sc->sc_tfo_cookie) {
1725 to.to_flags |= TOF_FASTOPEN;
1726 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
1727 to.to_tfo_cookie = sc->sc_tfo_cookie;
1728 /* don't send cookie again when retransmitting response */
1729 sc->sc_tfo_cookie = NULL;
1732 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1734 /* Adjust headers by option size. */
1735 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1737 m->m_pkthdr.len += optlen;
1739 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1740 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1743 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
1744 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1745 if (sc->sc_flags & SCF_SIGNATURE) {
1746 KASSERT(to.to_flags & TOF_SIGNATURE,
1747 ("tcp_addoptions() didn't set tcp_signature"));
1749 /* NOTE: to.to_signature is inside of mbuf */
1750 if (!TCPMD5_ENABLED() ||
1751 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
1760 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1761 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1763 * If we have peer's SYN and it has a flowid, then let's assign it to
1764 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid
1765 * to SYN|ACK due to lack of inp here.
1767 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
1768 m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
1769 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
1772 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1773 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1774 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1776 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1778 if (ADDED_BY_TOE(sc)) {
1779 struct toedev *tod = sc->sc_tod;
1781 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1786 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1789 #if defined(INET6) && defined(INET)
1794 m->m_pkthdr.csum_flags = CSUM_TCP;
1795 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1796 htons(tlen + optlen - hlen + IPPROTO_TCP));
1798 if (ADDED_BY_TOE(sc)) {
1799 struct toedev *tod = sc->sc_tod;
1801 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1806 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1813 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
1814 * that exceed the capacity of the syncache by avoiding the storage of any
1815 * of the SYNs we receive. Syncookies defend against blind SYN flooding
1816 * attacks where the attacker does not have access to our responses.
1818 * Syncookies encode and include all necessary information about the
1819 * connection setup within the SYN|ACK that we send back. That way we
1820 * can avoid keeping any local state until the ACK to our SYN|ACK returns
1821 * (if ever). Normally the syncache and syncookies are running in parallel
1822 * with the latter taking over when the former is exhausted. When matching
1823 * syncache entry is found the syncookie is ignored.
1825 * The only reliable information persisting the 3WHS is our initial sequence
1826 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient
1827 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS
1828 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
1829 * returns and signifies a legitimate connection if it matches the ACK.
1831 * The available space of 32 bits to store the hash and to encode the SYN
1832 * option information is very tight and we should have at least 24 bits for
1833 * the MAC to keep the number of guesses by blind spoofing reasonably high.
1835 * SYN option information we have to encode to fully restore a connection:
1836 * MSS: is imporant to chose an optimal segment size to avoid IP level
1837 * fragmentation along the path. The common MSS values can be encoded
1838 * in a 3-bit table. Uncommon values are captured by the next lower value
1839 * in the table leading to a slight increase in packetization overhead.
1840 * WSCALE: is necessary to allow large windows to be used for high delay-
1841 * bandwidth product links. Not scaling the window when it was initially
1842 * negotiated is bad for performance as lack of scaling further decreases
1843 * the apparent available send window. We only need to encode the WSCALE
1844 * we received from the remote end. Our end can be recalculated at any
1845 * time. The common WSCALE values can be encoded in a 3-bit table.
1846 * Uncommon values are captured by the next lower value in the table
1847 * making us under-estimate the available window size halving our
1848 * theoretically possible maximum throughput for that connection.
1849 * SACK: Greatly assists in packet loss recovery and requires 1 bit.
1850 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options
1851 * that are included in all segments on a connection. We enable them when
1854 * Security of syncookies and attack vectors:
1856 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
1857 * together with the gloabl secret to make it unique per connection attempt.
1858 * Thus any change of any of those parameters results in a different MAC output
1859 * in an unpredictable way unless a collision is encountered. 24 bits of the
1860 * MAC are embedded into the ISS.
1862 * To prevent replay attacks two rotating global secrets are updated with a
1863 * new random value every 15 seconds. The life-time of a syncookie is thus
1866 * Vector 1: Attacking the secret. This requires finding a weakness in the
1867 * MAC itself or the way it is used here. The attacker can do a chosen plain
1868 * text attack by varying and testing the all parameters under his control.
1869 * The strength depends on the size and randomness of the secret, and the
1870 * cryptographic security of the MAC function. Due to the constant updating
1871 * of the secret the attacker has at most 29.999 seconds to find the secret
1872 * and launch spoofed connections. After that he has to start all over again.
1874 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
1875 * size an average of 4,823 attempts are required for a 50% chance of success
1876 * to spoof a single syncookie (birthday collision paradox). However the
1877 * attacker is blind and doesn't know if one of his attempts succeeded unless
1878 * he has a side channel to interfere success from. A single connection setup
1879 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
1880 * This many attempts are required for each one blind spoofed connection. For
1881 * every additional spoofed connection he has to launch another N attempts.
1882 * Thus for a sustained rate 100 spoofed connections per second approximately
1883 * 1,800,000 packets per second would have to be sent.
1885 * NB: The MAC function should be fast so that it doesn't become a CPU
1886 * exhaustion attack vector itself.
1889 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations
1890 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
1891 * http://cr.yp.to/syncookies.html (overview)
1892 * http://cr.yp.to/syncookies/archive (details)
1895 * Schematic construction of a syncookie enabled Initial Sequence Number:
1897 * 12345678901234567890123456789012
1898 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
1900 * x 24 MAC (truncated)
1901 * W 3 Send Window Scale index
1903 * S 1 SACK permitted
1904 * P 1 Odd/even secret
1908 * Distribution and probability of certain MSS values. Those in between are
1909 * rounded down to the next lower one.
1910 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
1911 * .2% .3% 5% 7% 7% 20% 15% 45%
1913 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
1916 * Distribution and probability of certain WSCALE values. We have to map the
1917 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
1918 * bits based on prevalence of certain values. Where we don't have an exact
1919 * match for are rounded down to the next lower one letting us under-estimate
1920 * the true available window. At the moment this would happen only for the
1921 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
1922 * and window size). The absence of the WSCALE option (no scaling in either
1923 * direction) is encoded with index zero.
1924 * [WSCALE values histograms, Allman, 2012]
1925 * X 10 10 35 5 6 14 10% by host
1926 * X 11 4 5 5 18 49 3% by connections
1928 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
1931 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
1932 * and good cryptographic properties.
1935 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
1936 uint8_t *secbits, uintptr_t secmod)
1939 uint32_t siphash[2];
1941 SipHash24_Init(&ctx);
1942 SipHash_SetKey(&ctx, secbits);
1943 switch (inc->inc_flags & INC_ISIPV6) {
1946 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
1947 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
1952 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
1953 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
1957 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
1958 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
1959 SipHash_Update(&ctx, &irs, sizeof(irs));
1960 SipHash_Update(&ctx, &flags, sizeof(flags));
1961 SipHash_Update(&ctx, &secmod, sizeof(secmod));
1962 SipHash_Final((u_int8_t *)&siphash, &ctx);
1964 return (siphash[0] ^ siphash[1]);
1968 syncookie_generate(struct syncache_head *sch, struct syncache *sc)
1970 u_int i, mss, secbit, wscale;
1973 union syncookie cookie;
1975 SCH_LOCK_ASSERT(sch);
1979 /* Map our computed MSS into the 3-bit index. */
1980 mss = min(tcp_mssopt(&sc->sc_inc), max(sc->sc_peer_mss, V_tcp_minmss));
1981 for (i = nitems(tcp_sc_msstab) - 1; tcp_sc_msstab[i] > mss && i > 0;
1984 cookie.flags.mss_idx = i;
1987 * Map the send window scale into the 3-bit index but only if
1988 * the wscale option was received.
1990 if (sc->sc_flags & SCF_WINSCALE) {
1991 wscale = sc->sc_requested_s_scale;
1992 for (i = nitems(tcp_sc_wstab) - 1;
1993 tcp_sc_wstab[i] > wscale && i > 0;
1996 cookie.flags.wscale_idx = i;
1999 /* Can we do SACK? */
2000 if (sc->sc_flags & SCF_SACK)
2001 cookie.flags.sack_ok = 1;
2003 /* Which of the two secrets to use. */
2004 secbit = sch->sch_sc->secret.oddeven & 0x1;
2005 cookie.flags.odd_even = secbit;
2007 secbits = sch->sch_sc->secret.key[secbit];
2008 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
2012 * Put the flags into the hash and XOR them to get better ISS number
2013 * variance. This doesn't enhance the cryptographic strength and is
2014 * done to prevent the 8 cookie bits from showing up directly on the
2018 iss |= cookie.cookie ^ (hash >> 24);
2020 /* Randomize the timestamp. */
2021 if (sc->sc_flags & SCF_TIMESTAMP) {
2022 sc->sc_ts = arc4random();
2023 sc->sc_tsoff = sc->sc_ts - tcp_ts_getticks();
2026 TCPSTAT_INC(tcps_sc_sendcookie);
2030 static struct syncache *
2031 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
2032 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2038 int wnd, wscale = 0;
2039 union syncookie cookie;
2041 SCH_LOCK_ASSERT(sch);
2044 * Pull information out of SYN-ACK/ACK and revert sequence number
2047 ack = th->th_ack - 1;
2048 seq = th->th_seq - 1;
2051 * Unpack the flags containing enough information to restore the
2054 cookie.cookie = (ack & 0xff) ^ (ack >> 24);
2056 /* Which of the two secrets to use. */
2057 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even];
2059 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
2061 /* The recomputed hash matches the ACK if this was a genuine cookie. */
2062 if ((ack & ~0xff) != (hash & ~0xff))
2065 /* Fill in the syncache values. */
2067 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
2068 sc->sc_ipopts = NULL;
2073 switch (inc->inc_flags & INC_ISIPV6) {
2076 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
2077 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
2082 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
2083 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK;
2088 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
2090 /* We can simply recompute receive window scale we sent earlier. */
2091 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
2094 /* Only use wscale if it was enabled in the orignal SYN. */
2095 if (cookie.flags.wscale_idx > 0) {
2096 sc->sc_requested_r_scale = wscale;
2097 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
2098 sc->sc_flags |= SCF_WINSCALE;
2101 wnd = sbspace(&lso->so_rcv);
2103 wnd = imin(wnd, TCP_MAXWIN);
2106 if (cookie.flags.sack_ok)
2107 sc->sc_flags |= SCF_SACK;
2109 if (to->to_flags & TOF_TS) {
2110 sc->sc_flags |= SCF_TIMESTAMP;
2111 sc->sc_tsreflect = to->to_tsval;
2112 sc->sc_ts = to->to_tsecr;
2113 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
2116 if (to->to_flags & TOF_SIGNATURE)
2117 sc->sc_flags |= SCF_SIGNATURE;
2121 TCPSTAT_INC(tcps_sc_recvcookie);
2127 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
2128 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2131 struct syncache scs, *scx;
2134 bzero(&scs, sizeof(scs));
2135 scx = syncookie_lookup(inc, sch, &scs, th, to, lso);
2137 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
2141 if (sc->sc_peer_mss != scx->sc_peer_mss)
2142 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
2143 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
2145 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
2146 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
2147 s, __func__, sc->sc_requested_r_scale,
2148 scx->sc_requested_r_scale);
2150 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
2151 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
2152 s, __func__, sc->sc_requested_s_scale,
2153 scx->sc_requested_s_scale);
2155 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
2156 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
2163 #endif /* INVARIANTS */
2166 syncookie_reseed(void *arg)
2168 struct tcp_syncache *sc = arg;
2173 * Reseeding the secret doesn't have to be protected by a lock.
2174 * It only must be ensured that the new random values are visible
2175 * to all CPUs in a SMP environment. The atomic with release
2176 * semantics ensures that.
2178 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
2179 secbits = sc->secret.key[secbit];
2180 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
2181 atomic_add_rel_int(&sc->secret.oddeven, 1);
2183 /* Reschedule ourself. */
2184 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
2188 * Exports the syncache entries to userland so that netstat can display
2189 * them alongside the other sockets. This function is intended to be
2190 * called only from tcp_pcblist.
2192 * Due to concurrency on an active system, the number of pcbs exported
2193 * may have no relation to max_pcbs. max_pcbs merely indicates the
2194 * amount of space the caller allocated for this function to use.
2197 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
2200 struct syncache *sc;
2201 struct syncache_head *sch;
2202 int count, error, i;
2204 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
2205 sch = &V_tcp_syncache.hashbase[i];
2207 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
2208 if (count >= max_pcbs) {
2212 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
2214 bzero(&xt, sizeof(xt));
2215 xt.xt_len = sizeof(xt);
2216 if (sc->sc_inc.inc_flags & INC_ISIPV6)
2217 xt.xt_inp.inp_vflag = INP_IPV6;
2219 xt.xt_inp.inp_vflag = INP_IPV4;
2220 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
2221 xt.xt_tp.t_inpcb = &xt.xt_inp;
2222 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
2223 xt.xt_socket.xso_protocol = IPPROTO_TCP;
2224 xt.xt_socket.xso_len = sizeof (struct xsocket);
2225 xt.xt_socket.so_type = SOCK_STREAM;
2226 xt.xt_socket.so_state = SS_ISCONNECTING;
2227 error = SYSCTL_OUT(req, &xt, sizeof xt);
2237 *pcbs_exported = count;