2 * Copyright (c) 2001 McAfee, Inc.
3 * Copyright (c) 2006,2013 Andre Oppermann, Internet Business Solutions AG
6 * This software was developed for the FreeBSD Project by Jonathan Lemon
7 * and McAfee Research, the Security Research Division of McAfee, Inc. under
8 * DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
9 * DARPA CHATS research program. [2001 McAfee, Inc.]
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
37 #include "opt_inet6.h"
38 #include "opt_ipsec.h"
39 #include "opt_pcbgroup.h"
41 #include <sys/param.h>
42 #include <sys/systm.h>
44 #include <sys/refcount.h>
45 #include <sys/kernel.h>
46 #include <sys/sysctl.h>
47 #include <sys/limits.h>
49 #include <sys/mutex.h>
50 #include <sys/malloc.h>
52 #include <sys/proc.h> /* for proc0 declaration */
53 #include <sys/random.h>
54 #include <sys/socket.h>
55 #include <sys/socketvar.h>
56 #include <sys/syslog.h>
57 #include <sys/ucred.h>
60 #include <crypto/siphash/siphash.h>
65 #include <net/if_var.h>
66 #include <net/route.h>
69 #include <netinet/in.h>
70 #include <netinet/in_systm.h>
71 #include <netinet/ip.h>
72 #include <netinet/in_var.h>
73 #include <netinet/in_pcb.h>
74 #include <netinet/ip_var.h>
75 #include <netinet/ip_options.h>
77 #include <netinet/ip6.h>
78 #include <netinet/icmp6.h>
79 #include <netinet6/nd6.h>
80 #include <netinet6/ip6_var.h>
81 #include <netinet6/in6_pcb.h>
83 #include <netinet/tcp.h>
85 #include <netinet/tcp_fastopen.h>
87 #include <netinet/tcp_fsm.h>
88 #include <netinet/tcp_seq.h>
89 #include <netinet/tcp_timer.h>
90 #include <netinet/tcp_var.h>
91 #include <netinet/tcp_syncache.h>
93 #include <netinet6/tcp6_var.h>
96 #include <netinet/toecore.h>
99 #include <netipsec/ipsec_support.h>
101 #include <machine/in_cksum.h>
103 #include <security/mac/mac_framework.h>
105 static VNET_DEFINE(int, tcp_syncookies) = 1;
106 #define V_tcp_syncookies VNET(tcp_syncookies)
107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW,
108 &VNET_NAME(tcp_syncookies), 0,
109 "Use TCP SYN cookies if the syncache overflows");
111 static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
112 #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW,
114 &VNET_NAME(tcp_syncookiesonly), 0,
115 "Use only TCP SYN cookies");
118 #define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
121 static void syncache_drop(struct syncache *, struct syncache_head *);
122 static void syncache_free(struct syncache *);
123 static void syncache_insert(struct syncache *, struct syncache_head *);
124 static int syncache_respond(struct syncache *, struct syncache_head *, int,
125 const struct mbuf *);
126 static struct socket *syncache_socket(struct syncache *, struct socket *,
128 static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
130 static void syncache_timer(void *);
132 static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
133 uint8_t *, uintptr_t);
134 static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
135 static struct syncache
136 *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
137 struct syncache *, struct tcphdr *, struct tcpopt *,
139 static void syncookie_reseed(void *);
141 static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
142 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
147 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
148 * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
149 * the odds are that the user has given up attempting to connect by then.
151 #define SYNCACHE_MAXREXMTS 3
153 /* Arbitrary values */
154 #define TCP_SYNCACHE_HASHSIZE 512
155 #define TCP_SYNCACHE_BUCKETLIMIT 30
157 static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
158 #define V_tcp_syncache VNET(tcp_syncache)
160 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0,
163 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
164 &VNET_NAME(tcp_syncache.bucket_limit), 0,
165 "Per-bucket hash limit for syncache");
167 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
168 &VNET_NAME(tcp_syncache.cache_limit), 0,
169 "Overall entry limit for syncache");
171 SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
172 &VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
174 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
175 &VNET_NAME(tcp_syncache.hashsize), 0,
176 "Size of TCP syncache hashtable");
178 SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_VNET | CTLFLAG_RW,
179 &VNET_NAME(tcp_syncache.rexmt_limit), 0,
180 "Limit on SYN/ACK retransmissions");
182 VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
183 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
184 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
185 "Send reset on socket allocation failure");
187 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
189 #define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
190 #define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
191 #define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
194 * Requires the syncache entry to be already removed from the bucket list.
197 syncache_free(struct syncache *sc)
201 (void) m_free(sc->sc_ipopts);
205 mac_syncache_destroy(&sc->sc_label);
208 uma_zfree(V_tcp_syncache.zone, sc);
216 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
217 V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
218 V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
219 V_tcp_syncache.hash_secret = arc4random();
221 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
222 &V_tcp_syncache.hashsize);
223 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
224 &V_tcp_syncache.bucket_limit);
225 if (!powerof2(V_tcp_syncache.hashsize) ||
226 V_tcp_syncache.hashsize == 0) {
227 printf("WARNING: syncache hash size is not a power of 2.\n");
228 V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
230 V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
233 V_tcp_syncache.cache_limit =
234 V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
235 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
236 &V_tcp_syncache.cache_limit);
238 /* Allocate the hash table. */
239 V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
240 sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
243 V_tcp_syncache.vnet = curvnet;
246 /* Initialize the hash buckets. */
247 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
248 TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
249 mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
251 callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
252 &V_tcp_syncache.hashbase[i].sch_mtx, 0);
253 V_tcp_syncache.hashbase[i].sch_length = 0;
254 V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
257 /* Create the syncache entry zone. */
258 V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
259 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
260 V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
261 V_tcp_syncache.cache_limit);
263 /* Start the SYN cookie reseeder callout. */
264 callout_init(&V_tcp_syncache.secret.reseed, 1);
265 arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
266 arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
267 callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
268 syncookie_reseed, &V_tcp_syncache);
273 syncache_destroy(void)
275 struct syncache_head *sch;
276 struct syncache *sc, *nsc;
280 * Stop the re-seed timer before freeing resources. No need to
281 * possibly schedule it another time.
283 callout_drain(&V_tcp_syncache.secret.reseed);
285 /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
286 for (i = 0; i < V_tcp_syncache.hashsize; i++) {
288 sch = &V_tcp_syncache.hashbase[i];
289 callout_drain(&sch->sch_timer);
292 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
293 syncache_drop(sc, sch);
295 KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
296 ("%s: sch->sch_bucket not empty", __func__));
297 KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
298 __func__, sch->sch_length));
299 mtx_destroy(&sch->sch_mtx);
302 KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
303 ("%s: cache_count not 0", __func__));
305 /* Free the allocated global resources. */
306 uma_zdestroy(V_tcp_syncache.zone);
307 free(V_tcp_syncache.hashbase, M_SYNCACHE);
312 * Inserts a syncache entry into the specified bucket row.
313 * Locks and unlocks the syncache_head autonomously.
316 syncache_insert(struct syncache *sc, struct syncache_head *sch)
318 struct syncache *sc2;
323 * Make sure that we don't overflow the per-bucket limit.
324 * If the bucket is full, toss the oldest element.
326 if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
327 KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
328 ("sch->sch_length incorrect"));
329 sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
330 syncache_drop(sc2, sch);
331 TCPSTAT_INC(tcps_sc_bucketoverflow);
334 /* Put it into the bucket. */
335 TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
339 if (ADDED_BY_TOE(sc)) {
340 struct toedev *tod = sc->sc_tod;
342 tod->tod_syncache_added(tod, sc->sc_todctx);
346 /* Reinitialize the bucket row's timer. */
347 if (sch->sch_length == 1)
348 sch->sch_nextc = ticks + INT_MAX;
349 syncache_timeout(sc, sch, 1);
353 TCPSTATES_INC(TCPS_SYN_RECEIVED);
354 TCPSTAT_INC(tcps_sc_added);
358 * Remove and free entry from syncache bucket row.
359 * Expects locked syncache head.
362 syncache_drop(struct syncache *sc, struct syncache_head *sch)
365 SCH_LOCK_ASSERT(sch);
367 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
368 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
372 if (ADDED_BY_TOE(sc)) {
373 struct toedev *tod = sc->sc_tod;
375 tod->tod_syncache_removed(tod, sc->sc_todctx);
383 * Engage/reengage time on bucket row.
386 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
388 sc->sc_rxttime = ticks +
389 TCPTV_RTOBASE * (tcp_syn_backoff[sc->sc_rxmits]);
391 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
392 sch->sch_nextc = sc->sc_rxttime;
394 callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
395 syncache_timer, (void *)sch);
400 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
401 * If we have retransmitted an entry the maximum number of times, expire it.
402 * One separate timer for each bucket row.
405 syncache_timer(void *xsch)
407 struct syncache_head *sch = (struct syncache_head *)xsch;
408 struct syncache *sc, *nsc;
412 CURVNET_SET(sch->sch_sc->vnet);
414 /* NB: syncache_head has already been locked by the callout. */
415 SCH_LOCK_ASSERT(sch);
418 * In the following cycle we may remove some entries and/or
419 * advance some timeouts, so re-initialize the bucket timer.
421 sch->sch_nextc = tick + INT_MAX;
423 TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
425 * We do not check if the listen socket still exists
426 * and accept the case where the listen socket may be
427 * gone by the time we resend the SYN/ACK. We do
428 * not expect this to happens often. If it does,
429 * then the RST will be sent by the time the remote
430 * host does the SYN/ACK->ACK.
432 if (TSTMP_GT(sc->sc_rxttime, tick)) {
433 if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
434 sch->sch_nextc = sc->sc_rxttime;
437 if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
438 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
439 log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
440 "giving up and removing syncache entry\n",
444 syncache_drop(sc, sch);
445 TCPSTAT_INC(tcps_sc_stale);
448 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
449 log(LOG_DEBUG, "%s; %s: Response timeout, "
450 "retransmitting (%u) SYN|ACK\n",
451 s, __func__, sc->sc_rxmits);
455 syncache_respond(sc, sch, 1, NULL);
456 TCPSTAT_INC(tcps_sc_retransmitted);
457 syncache_timeout(sc, sch, 0);
459 if (!TAILQ_EMPTY(&(sch)->sch_bucket))
460 callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
461 syncache_timer, (void *)(sch));
466 * Find an entry in the syncache.
467 * Returns always with locked syncache_head plus a matching entry or NULL.
469 static struct syncache *
470 syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
473 struct syncache_head *sch;
477 * The hash is built on foreign port + local port + foreign address.
478 * We rely on the fact that struct in_conninfo starts with 16 bits
479 * of foreign port, then 16 bits of local port then followed by 128
480 * bits of foreign address. In case of IPv4 address, the first 3
481 * 32-bit words of the address always are zeroes.
483 hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
484 V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
486 sch = &V_tcp_syncache.hashbase[hash];
490 /* Circle through bucket row to find matching entry. */
491 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
492 if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
493 sizeof(struct in_endpoints)) == 0)
496 return (sc); /* Always returns with locked sch. */
500 * This function is called when we get a RST for a
501 * non-existent connection, so that we can see if the
502 * connection is in the syn cache. If it is, zap it.
505 syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
508 struct syncache_head *sch;
511 sc = syncache_lookup(inc, &sch); /* returns locked sch */
512 SCH_LOCK_ASSERT(sch);
515 * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
516 * See RFC 793 page 65, section SEGMENT ARRIVES.
518 if (th->th_flags & (TH_ACK|TH_SYN|TH_FIN)) {
519 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
520 log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
521 "FIN flag set, segment ignored\n", s, __func__);
522 TCPSTAT_INC(tcps_badrst);
527 * No corresponding connection was found in syncache.
528 * If syncookies are enabled and possibly exclusively
529 * used, or we are under memory pressure, a valid RST
530 * may not find a syncache entry. In that case we're
531 * done and no SYN|ACK retransmissions will happen.
532 * Otherwise the RST was misdirected or spoofed.
535 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
536 log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
537 "syncache entry (possibly syncookie only), "
538 "segment ignored\n", s, __func__);
539 TCPSTAT_INC(tcps_badrst);
544 * If the RST bit is set, check the sequence number to see
545 * if this is a valid reset segment.
547 * In all states except SYN-SENT, all reset (RST) segments
548 * are validated by checking their SEQ-fields. A reset is
549 * valid if its sequence number is in the window.
551 * The sequence number in the reset segment is normally an
552 * echo of our outgoing acknowlegement numbers, but some hosts
553 * send a reset with the sequence number at the rightmost edge
554 * of our receive window, and we have to handle this case.
556 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
557 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
558 syncache_drop(sc, sch);
559 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
560 log(LOG_DEBUG, "%s; %s: Our SYN|ACK was rejected, "
561 "connection attempt aborted by remote endpoint\n",
563 TCPSTAT_INC(tcps_sc_reset);
565 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
566 log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
567 "IRS %u (+WND %u), segment ignored\n",
568 s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
569 TCPSTAT_INC(tcps_badrst);
579 syncache_badack(struct in_conninfo *inc)
582 struct syncache_head *sch;
584 sc = syncache_lookup(inc, &sch); /* returns locked sch */
585 SCH_LOCK_ASSERT(sch);
587 syncache_drop(sc, sch);
588 TCPSTAT_INC(tcps_sc_badack);
594 syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
597 struct syncache_head *sch;
599 sc = syncache_lookup(inc, &sch); /* returns locked sch */
600 SCH_LOCK_ASSERT(sch);
604 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
605 if (ntohl(th->th_seq) != sc->sc_iss)
609 * If we've rertransmitted 3 times and this is our second error,
610 * we remove the entry. Otherwise, we allow it to continue on.
611 * This prevents us from incorrectly nuking an entry during a
612 * spurious network outage.
616 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
617 sc->sc_flags |= SCF_UNREACH;
620 syncache_drop(sc, sch);
621 TCPSTAT_INC(tcps_sc_unreach);
627 * Build a new TCP socket structure from a syncache entry.
629 * On success return the newly created socket with its underlying inp locked.
631 static struct socket *
632 syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
634 struct tcp_function_block *blk;
635 struct inpcb *inp = NULL;
641 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
644 * Ok, create the full blown connection, and set things up
645 * as they would have been set up if we had created the
646 * connection when the SYN arrived. If we can't create
647 * the connection, abort it.
649 so = sonewconn(lso, 0);
652 * Drop the connection; we will either send a RST or
653 * have the peer retransmit its SYN again after its
656 TCPSTAT_INC(tcps_listendrop);
657 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
658 log(LOG_DEBUG, "%s; %s: Socket create failed "
659 "due to limits or memory shortage\n",
666 mac_socketpeer_set_from_mbuf(m, so);
670 inp->inp_inc.inc_fibnum = so->so_fibnum;
673 * Exclusive pcbinfo lock is not required in syncache socket case even
674 * if two inpcb locks can be acquired simultaneously:
675 * - the inpcb in LISTEN state,
676 * - the newly created inp.
678 * In this case, an inp cannot be at same time in LISTEN state and
679 * just created by an accept() call.
681 INP_HASH_WLOCK(&V_tcbinfo);
683 /* Insert new socket into PCB hash list. */
684 inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
686 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
687 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
689 inp->inp_vflag &= ~INP_IPV6;
690 inp->inp_vflag |= INP_IPV4;
692 inp->inp_laddr = sc->sc_inc.inc_laddr;
698 * If there's an mbuf and it has a flowid, then let's initialise the
699 * inp with that particular flowid.
701 if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
702 inp->inp_flowid = m->m_pkthdr.flowid;
703 inp->inp_flowtype = M_HASHTYPE_GET(m);
707 * Install in the reservation hash table for now, but don't yet
708 * install a connection group since the full 4-tuple isn't yet
711 inp->inp_lport = sc->sc_inc.inc_lport;
712 if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
714 * Undo the assignments above if we failed to
715 * put the PCB on the hash lists.
718 if (sc->sc_inc.inc_flags & INC_ISIPV6)
719 inp->in6p_laddr = in6addr_any;
722 inp->inp_laddr.s_addr = INADDR_ANY;
724 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
725 log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
730 INP_HASH_WUNLOCK(&V_tcbinfo);
734 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
735 struct inpcb *oinp = sotoinpcb(lso);
736 struct in6_addr laddr6;
737 struct sockaddr_in6 sin6;
739 * Inherit socket options from the listening socket.
740 * Note that in6p_inputopts are not (and should not be)
741 * copied, since it stores previously received options and is
742 * used to detect if each new option is different than the
743 * previous one and hence should be passed to a user.
744 * If we copied in6p_inputopts, a user would not be able to
745 * receive options just after calling the accept system call.
747 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
748 if (oinp->in6p_outputopts)
749 inp->in6p_outputopts =
750 ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
752 sin6.sin6_family = AF_INET6;
753 sin6.sin6_len = sizeof(sin6);
754 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
755 sin6.sin6_port = sc->sc_inc.inc_fport;
756 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
757 laddr6 = inp->in6p_laddr;
758 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
759 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
760 if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
761 thread0.td_ucred, m)) != 0) {
762 inp->in6p_laddr = laddr6;
763 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
764 log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
769 INP_HASH_WUNLOCK(&V_tcbinfo);
772 /* Override flowlabel from in6_pcbconnect. */
773 inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
774 inp->inp_flow |= sc->sc_flowlabel;
777 #if defined(INET) && defined(INET6)
782 struct in_addr laddr;
783 struct sockaddr_in sin;
785 inp->inp_options = (m) ? ip_srcroute(m) : NULL;
787 if (inp->inp_options == NULL) {
788 inp->inp_options = sc->sc_ipopts;
789 sc->sc_ipopts = NULL;
792 sin.sin_family = AF_INET;
793 sin.sin_len = sizeof(sin);
794 sin.sin_addr = sc->sc_inc.inc_faddr;
795 sin.sin_port = sc->sc_inc.inc_fport;
796 bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
797 laddr = inp->inp_laddr;
798 if (inp->inp_laddr.s_addr == INADDR_ANY)
799 inp->inp_laddr = sc->sc_inc.inc_laddr;
800 if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
801 thread0.td_ucred, m)) != 0) {
802 inp->inp_laddr = laddr;
803 if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
804 log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
809 INP_HASH_WUNLOCK(&V_tcbinfo);
814 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
815 /* Copy old policy into new socket's. */
816 if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
817 printf("syncache_socket: could not copy policy\n");
819 INP_HASH_WUNLOCK(&V_tcbinfo);
821 tcp_state_change(tp, TCPS_SYN_RECEIVED);
822 tp->iss = sc->sc_iss;
823 tp->irs = sc->sc_irs;
826 blk = sototcpcb(lso)->t_fb;
827 if (blk != tp->t_fb) {
829 * Our parents t_fb was not the default,
830 * we need to release our ref on tp->t_fb and
831 * pickup one on the new entry.
833 struct tcp_function_block *rblk;
835 rblk = find_and_ref_tcp_fb(blk);
836 KASSERT(rblk != NULL,
837 ("cannot find blk %p out of syncache?", blk));
838 if (tp->t_fb->tfb_tcp_fb_fini)
839 (*tp->t_fb->tfb_tcp_fb_fini)(tp);
840 refcount_release(&tp->t_fb->tfb_refcnt);
842 if (tp->t_fb->tfb_tcp_fb_init) {
843 (*tp->t_fb->tfb_tcp_fb_init)(tp);
846 tp->snd_wl1 = sc->sc_irs;
847 tp->snd_max = tp->iss + 1;
848 tp->snd_nxt = tp->iss + 1;
849 tp->rcv_up = sc->sc_irs + 1;
850 tp->rcv_wnd = sc->sc_wnd;
851 tp->rcv_adv += tp->rcv_wnd;
852 tp->last_ack_sent = tp->rcv_nxt;
854 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH|TF_NODELAY);
855 if (sc->sc_flags & SCF_NOOPT)
856 tp->t_flags |= TF_NOOPT;
858 if (sc->sc_flags & SCF_WINSCALE) {
859 tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
860 tp->snd_scale = sc->sc_requested_s_scale;
861 tp->request_r_scale = sc->sc_requested_r_scale;
863 if (sc->sc_flags & SCF_TIMESTAMP) {
864 tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
865 tp->ts_recent = sc->sc_tsreflect;
866 tp->ts_recent_age = tcp_ts_getticks();
867 tp->ts_offset = sc->sc_tsoff;
869 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
870 if (sc->sc_flags & SCF_SIGNATURE)
871 tp->t_flags |= TF_SIGNATURE;
873 if (sc->sc_flags & SCF_SACK)
874 tp->t_flags |= TF_SACK_PERMIT;
877 if (sc->sc_flags & SCF_ECN)
878 tp->t_flags |= TF_ECN_PERMIT;
881 * Set up MSS and get cached values from tcp_hostcache.
882 * This might overwrite some of the defaults we just set.
884 tcp_mss(tp, sc->sc_peer_mss);
887 * If the SYN,ACK was retransmitted, indicate that CWND to be
888 * limited to one segment in cc_conn_init().
889 * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
891 if (sc->sc_rxmits > 1)
896 * Allow a TOE driver to install its hooks. Note that we hold the
897 * pcbinfo lock too and that prevents tcp_usr_accept from accepting a
898 * new connection before the TOE driver has done its thing.
900 if (ADDED_BY_TOE(sc)) {
901 struct toedev *tod = sc->sc_tod;
903 tod->tod_offload_socket(tod, sc->sc_todctx, so);
907 * Copy and activate timers.
909 tp->t_keepinit = sototcpcb(lso)->t_keepinit;
910 tp->t_keepidle = sototcpcb(lso)->t_keepidle;
911 tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
912 tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
913 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
915 TCPSTAT_INC(tcps_accepts);
927 * This function gets called when we receive an ACK for a
928 * socket in the LISTEN state. We look up the connection
929 * in the syncache, and if its there, we pull it out of
930 * the cache and turn it into a full-blown connection in
931 * the SYN-RECEIVED state.
933 * On syncache_socket() success the newly created socket
934 * has its underlying inp locked.
937 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
938 struct socket **lsop, struct mbuf *m)
941 struct syncache_head *sch;
946 * Global TCP locks are held because we manipulate the PCB lists
947 * and create a new socket.
949 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
950 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
951 ("%s: can handle only ACK", __func__));
953 sc = syncache_lookup(inc, &sch); /* returns locked sch */
954 SCH_LOCK_ASSERT(sch);
958 * Test code for syncookies comparing the syncache stored
959 * values with the reconstructed values from the cookie.
962 syncookie_cmp(inc, sch, sc, th, to, *lsop);
967 * There is no syncache entry, so see if this ACK is
968 * a returning syncookie. To do this, first:
969 * A. See if this socket has had a syncache entry dropped in
970 * the past. We don't want to accept a bogus syncookie
971 * if we've never received a SYN.
972 * B. check that the syncookie is valid. If it is, then
973 * cobble up a fake syncache entry, and return.
975 if (!V_tcp_syncookies) {
977 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
978 log(LOG_DEBUG, "%s; %s: Spurious ACK, "
979 "segment rejected (syncookies disabled)\n",
983 bzero(&scs, sizeof(scs));
984 sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop);
987 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
988 log(LOG_DEBUG, "%s; %s: Segment failed "
989 "SYNCOOKIE authentication, segment rejected "
990 "(probably spoofed)\n", s, __func__);
993 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
994 /* If received ACK has MD5 signature, check it. */
995 if ((to->to_flags & TOF_SIGNATURE) != 0 &&
996 (!TCPMD5_ENABLED() ||
997 TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
999 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1000 log(LOG_DEBUG, "%s; %s: Segment rejected, "
1001 "MD5 signature doesn't match.\n",
1005 TCPSTAT_INC(tcps_sig_err_sigopt);
1006 return (-1); /* Do not send RST */
1008 #endif /* TCP_SIGNATURE */
1010 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1012 * If listening socket requested TCP digests, check that
1013 * received ACK has signature and it is correct.
1014 * If not, drop the ACK and leave sc entry in th cache,
1015 * because SYN was received with correct signature.
1017 if (sc->sc_flags & SCF_SIGNATURE) {
1018 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1020 TCPSTAT_INC(tcps_sig_err_nosigopt);
1022 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1023 log(LOG_DEBUG, "%s; %s: Segment "
1024 "rejected, MD5 signature wasn't "
1025 "provided.\n", s, __func__);
1028 return (-1); /* Do not send RST */
1030 if (!TCPMD5_ENABLED() ||
1031 TCPMD5_INPUT(m, th, to->to_signature) != 0) {
1032 /* Doesn't match or no SA */
1034 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1035 log(LOG_DEBUG, "%s; %s: Segment "
1036 "rejected, MD5 signature doesn't "
1037 "match.\n", s, __func__);
1040 return (-1); /* Do not send RST */
1043 #endif /* TCP_SIGNATURE */
1045 * Pull out the entry to unlock the bucket row.
1047 * NOTE: We must decrease TCPS_SYN_RECEIVED count here, not
1048 * tcp_state_change(). The tcpcb is not existent at this
1049 * moment. A new one will be allocated via syncache_socket->
1050 * sonewconn->tcp_usr_attach in TCPS_CLOSED state, then
1051 * syncache_socket() will change it to TCPS_SYN_RECEIVED.
1053 TCPSTATES_DEC(TCPS_SYN_RECEIVED);
1054 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
1057 if (ADDED_BY_TOE(sc)) {
1058 struct toedev *tod = sc->sc_tod;
1060 tod->tod_syncache_removed(tod, sc->sc_todctx);
1067 * Segment validation:
1068 * ACK must match our initial sequence number + 1 (the SYN|ACK).
1070 if (th->th_ack != sc->sc_iss + 1) {
1071 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1072 log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
1073 "rejected\n", s, __func__, th->th_ack, sc->sc_iss);
1078 * The SEQ must fall in the window starting at the received
1079 * initial receive sequence number + 1 (the SYN).
1081 if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
1082 SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
1083 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1084 log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
1085 "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
1090 * If timestamps were not negotiated during SYN/ACK they
1091 * must not appear on any segment during this session.
1093 if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
1094 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1095 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1096 "segment rejected\n", s, __func__);
1101 * If timestamps were negotiated during SYN/ACK they should
1102 * appear on every segment during this session.
1103 * XXXAO: This is only informal as there have been unverified
1104 * reports of non-compliants stacks.
1106 if ((sc->sc_flags & SCF_TIMESTAMP) && !(to->to_flags & TOF_TS)) {
1107 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1108 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1109 "no action\n", s, __func__);
1116 * If timestamps were negotiated, the reflected timestamp
1117 * must be equal to what we actually sent in the SYN|ACK
1118 * except in the case of 0. Some boxes are known for sending
1119 * broken timestamp replies during the 3whs (and potentially
1120 * during the connection also).
1122 * Accept the final ACK of 3whs with reflected timestamp of 0
1123 * instead of sending a RST and deleting the syncache entry.
1125 if ((to->to_flags & TOF_TS) && to->to_tsecr &&
1126 to->to_tsecr != sc->sc_ts) {
1127 if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
1128 log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
1129 "segment rejected\n",
1130 s, __func__, to->to_tsecr, sc->sc_ts);
1134 *lsop = syncache_socket(sc, *lsop, m);
1137 TCPSTAT_INC(tcps_sc_aborted);
1139 TCPSTAT_INC(tcps_sc_completed);
1141 /* how do we find the inp for the new socket? */
1146 if (sc != NULL && sc != &scs)
1156 syncache_tfo_expand(struct syncache *sc, struct socket **lsop, struct mbuf *m,
1157 uint64_t response_cookie)
1161 unsigned int *pending_counter;
1164 * Global TCP locks are held because we manipulate the PCB lists
1165 * and create a new socket.
1167 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1169 pending_counter = intotcpcb(sotoinpcb(*lsop))->t_tfo_pending;
1170 *lsop = syncache_socket(sc, *lsop, m);
1171 if (*lsop == NULL) {
1172 TCPSTAT_INC(tcps_sc_aborted);
1173 atomic_subtract_int(pending_counter, 1);
1175 inp = sotoinpcb(*lsop);
1176 tp = intotcpcb(inp);
1177 tp->t_flags |= TF_FASTOPEN;
1178 tp->t_tfo_cookie = response_cookie;
1179 tp->snd_max = tp->iss;
1180 tp->snd_nxt = tp->iss;
1181 tp->t_tfo_pending = pending_counter;
1182 TCPSTAT_INC(tcps_sc_completed);
1185 #endif /* TCP_RFC7413 */
1188 * Given a LISTEN socket and an inbound SYN request, add
1189 * this to the syn cache, and send back a segment:
1190 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
1193 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
1194 * Doing so would require that we hold onto the data and deliver it
1195 * to the application. However, if we are the target of a SYN-flood
1196 * DoS attack, an attacker could send data which would eventually
1197 * consume all available buffer space if it were ACKed. By not ACKing
1198 * the data, we avoid this DoS scenario.
1200 * The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
1201 * cookie is processed, V_tcp_fastopen_enabled set to true, and the
1202 * TCP_FASTOPEN socket option is set. In this case, a new socket is created
1203 * and returned via lsop, the mbuf is not freed so that tcp_input() can
1204 * queue its data to the socket, and 1 is returned to indicate the
1205 * TFO-socket-creation path was taken.
1208 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
1209 struct inpcb *inp, struct socket **lsop, struct mbuf *m, void *tod,
1214 struct syncache *sc = NULL;
1215 struct syncache_head *sch;
1216 struct mbuf *ipopts = NULL;
1218 int win, sb_hiwat, ip_ttl, ip_tos;
1222 int autoflowlabel = 0;
1225 struct label *maclabel;
1227 struct syncache scs;
1230 uint64_t tfo_response_cookie;
1231 int tfo_cookie_valid = 0;
1232 int tfo_response_cookie_valid = 0;
1235 INP_WLOCK_ASSERT(inp); /* listen socket */
1236 KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
1237 ("%s: unexpected tcp flags", __func__));
1240 * Combine all so/tp operations very early to drop the INP lock as
1245 cred = crhold(so->so_cred);
1248 if ((inc->inc_flags & INC_ISIPV6) &&
1249 (inp->inp_flags & IN6P_AUTOFLOWLABEL))
1252 ip_ttl = inp->inp_ip_ttl;
1253 ip_tos = inp->inp_ip_tos;
1254 win = sbspace(&so->so_rcv);
1255 sb_hiwat = so->so_rcv.sb_hiwat;
1256 ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
1259 if (V_tcp_fastopen_enabled && (tp->t_flags & TF_FASTOPEN) &&
1260 (tp->t_tfo_pending != NULL) && (to->to_flags & TOF_FASTOPEN)) {
1262 * Limit the number of pending TFO connections to
1263 * approximately half of the queue limit. This prevents TFO
1264 * SYN floods from starving the service by filling the
1265 * listen queue with bogus TFO connections.
1267 if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
1268 (so->so_qlimit / 2)) {
1271 result = tcp_fastopen_check_cookie(inc,
1272 to->to_tfo_cookie, to->to_tfo_len,
1273 &tfo_response_cookie);
1274 tfo_cookie_valid = (result > 0);
1275 tfo_response_cookie_valid = (result >= 0);
1277 atomic_subtract_int(tp->t_tfo_pending, 1);
1281 /* By the time we drop the lock these should no longer be used. */
1286 if (mac_syncache_init(&maclabel) != 0) {
1290 mac_syncache_create(maclabel, inp);
1293 if (!tfo_cookie_valid)
1298 * Remember the IP options, if any.
1301 if (!(inc->inc_flags & INC_ISIPV6))
1304 ipopts = (m) ? ip_srcroute(m) : NULL;
1309 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1311 * If listening socket requested TCP digests, check that received
1312 * SYN has signature and it is correct. If signature doesn't match
1313 * or TCP_SIGNATURE support isn't enabled, drop the packet.
1315 if (ltflags & TF_SIGNATURE) {
1316 if ((to->to_flags & TOF_SIGNATURE) == 0) {
1317 TCPSTAT_INC(tcps_sig_err_nosigopt);
1320 if (!TCPMD5_ENABLED() ||
1321 TCPMD5_INPUT(m, th, to->to_signature) != 0)
1324 #endif /* TCP_SIGNATURE */
1326 * See if we already have an entry for this connection.
1327 * If we do, resend the SYN,ACK, and reset the retransmit timer.
1329 * XXX: should the syncache be re-initialized with the contents
1330 * of the new SYN here (which may have different options?)
1332 * XXX: We do not check the sequence number to see if this is a
1333 * real retransmit or a new connection attempt. The question is
1334 * how to handle such a case; either ignore it as spoofed, or
1335 * drop the current entry and create a new one?
1337 sc = syncache_lookup(inc, &sch); /* returns locked entry */
1338 SCH_LOCK_ASSERT(sch);
1341 if (tfo_cookie_valid)
1344 TCPSTAT_INC(tcps_sc_dupsyn);
1347 * If we were remembering a previous source route,
1348 * forget it and use the new one we've been given.
1351 (void) m_free(sc->sc_ipopts);
1352 sc->sc_ipopts = ipopts;
1355 * Update timestamp if present.
1357 if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
1358 sc->sc_tsreflect = to->to_tsval;
1360 sc->sc_flags &= ~SCF_TIMESTAMP;
1363 * Since we have already unconditionally allocated label
1364 * storage, free it up. The syncache entry will already
1365 * have an initialized label we can use.
1367 mac_syncache_destroy(&maclabel);
1369 /* Retransmit SYN|ACK and reset retransmit count. */
1370 if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
1371 log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
1372 "resetting timer and retransmitting SYN|ACK\n",
1376 if (syncache_respond(sc, sch, 1, m) == 0) {
1378 syncache_timeout(sc, sch, 1);
1379 TCPSTAT_INC(tcps_sndacks);
1380 TCPSTAT_INC(tcps_sndtotal);
1387 if (tfo_cookie_valid) {
1388 bzero(&scs, sizeof(scs));
1394 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1397 * The zone allocator couldn't provide more entries.
1398 * Treat this as if the cache was full; drop the oldest
1399 * entry and insert the new one.
1401 TCPSTAT_INC(tcps_sc_zonefail);
1402 if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL)
1403 syncache_drop(sc, sch);
1404 sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
1406 if (V_tcp_syncookies) {
1407 bzero(&scs, sizeof(scs));
1412 (void) m_free(ipopts);
1420 if (!tfo_cookie_valid && tfo_response_cookie_valid)
1421 sc->sc_tfo_cookie = &tfo_response_cookie;
1425 * Fill in the syncache values.
1428 sc->sc_label = maclabel;
1432 sc->sc_ipopts = ipopts;
1433 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
1435 if (!(inc->inc_flags & INC_ISIPV6))
1438 sc->sc_ip_tos = ip_tos;
1439 sc->sc_ip_ttl = ip_ttl;
1443 sc->sc_todctx = todctx;
1445 sc->sc_irs = th->th_seq;
1446 sc->sc_iss = arc4random();
1448 sc->sc_flowlabel = 0;
1451 * Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
1452 * win was derived from socket earlier in the function.
1455 win = imin(win, TCP_MAXWIN);
1458 if (V_tcp_do_rfc1323) {
1460 * A timestamp received in a SYN makes
1461 * it ok to send timestamp requests and replies.
1463 if (to->to_flags & TOF_TS) {
1464 sc->sc_tsreflect = to->to_tsval;
1465 sc->sc_ts = tcp_ts_getticks();
1466 sc->sc_flags |= SCF_TIMESTAMP;
1468 if (to->to_flags & TOF_SCALE) {
1472 * Pick the smallest possible scaling factor that
1473 * will still allow us to scale up to sb_max, aka
1474 * kern.ipc.maxsockbuf.
1476 * We do this because there are broken firewalls that
1477 * will corrupt the window scale option, leading to
1478 * the other endpoint believing that our advertised
1479 * window is unscaled. At scale factors larger than
1480 * 5 the unscaled window will drop below 1500 bytes,
1481 * leading to serious problems when traversing these
1484 * With the default maxsockbuf of 256K, a scale factor
1485 * of 3 will be chosen by this algorithm. Those who
1486 * choose a larger maxsockbuf should watch out
1487 * for the compatibility problems mentioned above.
1489 * RFC1323: The Window field in a SYN (i.e., a <SYN>
1490 * or <SYN,ACK>) segment itself is never scaled.
1492 while (wscale < TCP_MAX_WINSHIFT &&
1493 (TCP_MAXWIN << wscale) < sb_max)
1495 sc->sc_requested_r_scale = wscale;
1496 sc->sc_requested_s_scale = to->to_wscale;
1497 sc->sc_flags |= SCF_WINSCALE;
1500 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1502 * If listening socket requested TCP digests, flag this in the
1503 * syncache so that syncache_respond() will do the right thing
1506 if (ltflags & TF_SIGNATURE)
1507 sc->sc_flags |= SCF_SIGNATURE;
1508 #endif /* TCP_SIGNATURE */
1509 if (to->to_flags & TOF_SACKPERM)
1510 sc->sc_flags |= SCF_SACK;
1511 if (to->to_flags & TOF_MSS)
1512 sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
1513 if (ltflags & TF_NOOPT)
1514 sc->sc_flags |= SCF_NOOPT;
1515 if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
1516 sc->sc_flags |= SCF_ECN;
1518 if (V_tcp_syncookies)
1519 sc->sc_iss = syncookie_generate(sch, sc);
1521 if (autoflowlabel) {
1522 if (V_tcp_syncookies)
1523 sc->sc_flowlabel = sc->sc_iss;
1525 sc->sc_flowlabel = ip6_randomflowlabel();
1526 sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
1532 if (tfo_cookie_valid) {
1533 syncache_tfo_expand(sc, lsop, m, tfo_response_cookie);
1534 /* INP_WUNLOCK(inp) will be performed by the called */
1541 * Do a standard 3-way handshake.
1543 if (syncache_respond(sc, sch, 0, m) == 0) {
1544 if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
1546 else if (sc != &scs)
1547 syncache_insert(sc, sch); /* locks and unlocks sch */
1548 TCPSTAT_INC(tcps_sndacks);
1549 TCPSTAT_INC(tcps_sndtotal);
1553 TCPSTAT_INC(tcps_sc_dropped);
1568 mac_syncache_destroy(&maclabel);
1574 * Send SYN|ACK to the peer. Either in response to the peer's SYN,
1575 * i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
1578 syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked,
1579 const struct mbuf *m0)
1581 struct ip *ip = NULL;
1583 struct tcphdr *th = NULL;
1584 int optlen, error = 0; /* Make compiler happy */
1585 u_int16_t hlen, tlen, mssopt;
1588 struct ip6_hdr *ip6 = NULL;
1592 (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
1595 tlen = hlen + sizeof(struct tcphdr);
1597 /* Determine MSS we advertize to other end of connection. */
1598 mssopt = tcp_mssopt(&sc->sc_inc);
1599 if (sc->sc_peer_mss)
1600 mssopt = max( min(sc->sc_peer_mss, mssopt), V_tcp_minmss);
1602 /* XXX: Assume that the entire packet will fit in a header mbuf. */
1603 KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
1604 ("syncache: mbuf too small"));
1606 /* Create the IP+TCP header from scratch. */
1607 m = m_gethdr(M_NOWAIT, MT_DATA);
1611 mac_syncache_create_mbuf(sc->sc_label, m);
1613 m->m_data += max_linkhdr;
1615 m->m_pkthdr.len = tlen;
1616 m->m_pkthdr.rcvif = NULL;
1619 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1620 ip6 = mtod(m, struct ip6_hdr *);
1621 ip6->ip6_vfc = IPV6_VERSION;
1622 ip6->ip6_nxt = IPPROTO_TCP;
1623 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1624 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1625 ip6->ip6_plen = htons(tlen - hlen);
1626 /* ip6_hlim is set after checksum */
1627 ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
1628 ip6->ip6_flow |= sc->sc_flowlabel;
1630 th = (struct tcphdr *)(ip6 + 1);
1633 #if defined(INET6) && defined(INET)
1638 ip = mtod(m, struct ip *);
1639 ip->ip_v = IPVERSION;
1640 ip->ip_hl = sizeof(struct ip) >> 2;
1641 ip->ip_len = htons(tlen);
1645 ip->ip_p = IPPROTO_TCP;
1646 ip->ip_src = sc->sc_inc.inc_laddr;
1647 ip->ip_dst = sc->sc_inc.inc_faddr;
1648 ip->ip_ttl = sc->sc_ip_ttl;
1649 ip->ip_tos = sc->sc_ip_tos;
1652 * See if we should do MTU discovery. Route lookups are
1653 * expensive, so we will only unset the DF bit if:
1655 * 1) path_mtu_discovery is disabled
1656 * 2) the SCF_UNREACH flag has been set
1658 if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
1659 ip->ip_off |= htons(IP_DF);
1661 th = (struct tcphdr *)(ip + 1);
1664 th->th_sport = sc->sc_inc.inc_lport;
1665 th->th_dport = sc->sc_inc.inc_fport;
1667 th->th_seq = htonl(sc->sc_iss);
1668 th->th_ack = htonl(sc->sc_irs + 1);
1669 th->th_off = sizeof(struct tcphdr) >> 2;
1671 th->th_flags = TH_SYN|TH_ACK;
1672 th->th_win = htons(sc->sc_wnd);
1675 if (sc->sc_flags & SCF_ECN) {
1676 th->th_flags |= TH_ECE;
1677 TCPSTAT_INC(tcps_ecn_shs);
1680 /* Tack on the TCP options. */
1681 if ((sc->sc_flags & SCF_NOOPT) == 0) {
1685 to.to_flags = TOF_MSS;
1686 if (sc->sc_flags & SCF_WINSCALE) {
1687 to.to_wscale = sc->sc_requested_r_scale;
1688 to.to_flags |= TOF_SCALE;
1690 if (sc->sc_flags & SCF_TIMESTAMP) {
1691 /* Virgin timestamp or TCP cookie enhanced one. */
1692 to.to_tsval = sc->sc_ts;
1693 to.to_tsecr = sc->sc_tsreflect;
1694 to.to_flags |= TOF_TS;
1696 if (sc->sc_flags & SCF_SACK)
1697 to.to_flags |= TOF_SACKPERM;
1698 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1699 if (sc->sc_flags & SCF_SIGNATURE)
1700 to.to_flags |= TOF_SIGNATURE;
1703 if (sc->sc_tfo_cookie) {
1704 to.to_flags |= TOF_FASTOPEN;
1705 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
1706 to.to_tfo_cookie = sc->sc_tfo_cookie;
1707 /* don't send cookie again when retransmitting response */
1708 sc->sc_tfo_cookie = NULL;
1711 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
1713 /* Adjust headers by option size. */
1714 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1716 m->m_pkthdr.len += optlen;
1718 if (sc->sc_inc.inc_flags & INC_ISIPV6)
1719 ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
1722 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
1723 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1724 if (sc->sc_flags & SCF_SIGNATURE) {
1725 KASSERT(to.to_flags & TOF_SIGNATURE,
1726 ("tcp_addoptions() didn't set tcp_signature"));
1728 /* NOTE: to.to_signature is inside of mbuf */
1729 if (!TCPMD5_ENABLED() ||
1730 TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
1739 M_SETFIB(m, sc->sc_inc.inc_fibnum);
1740 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1742 * If we have peer's SYN and it has a flowid, then let's assign it to
1743 * our SYN|ACK. ip6_output() and ip_output() will not assign flowid
1744 * to SYN|ACK due to lack of inp here.
1746 if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
1747 m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
1748 M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
1751 if (sc->sc_inc.inc_flags & INC_ISIPV6) {
1752 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1753 th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
1755 ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
1757 if (ADDED_BY_TOE(sc)) {
1758 struct toedev *tod = sc->sc_tod;
1760 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1765 error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
1768 #if defined(INET6) && defined(INET)
1773 m->m_pkthdr.csum_flags = CSUM_TCP;
1774 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1775 htons(tlen + optlen - hlen + IPPROTO_TCP));
1777 if (ADDED_BY_TOE(sc)) {
1778 struct toedev *tod = sc->sc_tod;
1780 error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
1785 error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
1792 * The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
1793 * that exceed the capacity of the syncache by avoiding the storage of any
1794 * of the SYNs we receive. Syncookies defend against blind SYN flooding
1795 * attacks where the attacker does not have access to our responses.
1797 * Syncookies encode and include all necessary information about the
1798 * connection setup within the SYN|ACK that we send back. That way we
1799 * can avoid keeping any local state until the ACK to our SYN|ACK returns
1800 * (if ever). Normally the syncache and syncookies are running in parallel
1801 * with the latter taking over when the former is exhausted. When matching
1802 * syncache entry is found the syncookie is ignored.
1804 * The only reliable information persisting the 3WHS is our initial sequence
1805 * number ISS of 32 bits. Syncookies embed a cryptographically sufficient
1806 * strong hash (MAC) value and a few bits of TCP SYN options in the ISS
1807 * of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
1808 * returns and signifies a legitimate connection if it matches the ACK.
1810 * The available space of 32 bits to store the hash and to encode the SYN
1811 * option information is very tight and we should have at least 24 bits for
1812 * the MAC to keep the number of guesses by blind spoofing reasonably high.
1814 * SYN option information we have to encode to fully restore a connection:
1815 * MSS: is imporant to chose an optimal segment size to avoid IP level
1816 * fragmentation along the path. The common MSS values can be encoded
1817 * in a 3-bit table. Uncommon values are captured by the next lower value
1818 * in the table leading to a slight increase in packetization overhead.
1819 * WSCALE: is necessary to allow large windows to be used for high delay-
1820 * bandwidth product links. Not scaling the window when it was initially
1821 * negotiated is bad for performance as lack of scaling further decreases
1822 * the apparent available send window. We only need to encode the WSCALE
1823 * we received from the remote end. Our end can be recalculated at any
1824 * time. The common WSCALE values can be encoded in a 3-bit table.
1825 * Uncommon values are captured by the next lower value in the table
1826 * making us under-estimate the available window size halving our
1827 * theoretically possible maximum throughput for that connection.
1828 * SACK: Greatly assists in packet loss recovery and requires 1 bit.
1829 * TIMESTAMP and SIGNATURE is not encoded because they are permanent options
1830 * that are included in all segments on a connection. We enable them when
1833 * Security of syncookies and attack vectors:
1835 * The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
1836 * together with the gloabl secret to make it unique per connection attempt.
1837 * Thus any change of any of those parameters results in a different MAC output
1838 * in an unpredictable way unless a collision is encountered. 24 bits of the
1839 * MAC are embedded into the ISS.
1841 * To prevent replay attacks two rotating global secrets are updated with a
1842 * new random value every 15 seconds. The life-time of a syncookie is thus
1845 * Vector 1: Attacking the secret. This requires finding a weakness in the
1846 * MAC itself or the way it is used here. The attacker can do a chosen plain
1847 * text attack by varying and testing the all parameters under his control.
1848 * The strength depends on the size and randomness of the secret, and the
1849 * cryptographic security of the MAC function. Due to the constant updating
1850 * of the secret the attacker has at most 29.999 seconds to find the secret
1851 * and launch spoofed connections. After that he has to start all over again.
1853 * Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
1854 * size an average of 4,823 attempts are required for a 50% chance of success
1855 * to spoof a single syncookie (birthday collision paradox). However the
1856 * attacker is blind and doesn't know if one of his attempts succeeded unless
1857 * he has a side channel to interfere success from. A single connection setup
1858 * success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
1859 * This many attempts are required for each one blind spoofed connection. For
1860 * every additional spoofed connection he has to launch another N attempts.
1861 * Thus for a sustained rate 100 spoofed connections per second approximately
1862 * 1,800,000 packets per second would have to be sent.
1864 * NB: The MAC function should be fast so that it doesn't become a CPU
1865 * exhaustion attack vector itself.
1868 * RFC4987 TCP SYN Flooding Attacks and Common Mitigations
1869 * SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
1870 * http://cr.yp.to/syncookies.html (overview)
1871 * http://cr.yp.to/syncookies/archive (details)
1874 * Schematic construction of a syncookie enabled Initial Sequence Number:
1876 * 12345678901234567890123456789012
1877 * |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
1879 * x 24 MAC (truncated)
1880 * W 3 Send Window Scale index
1882 * S 1 SACK permitted
1883 * P 1 Odd/even secret
1887 * Distribution and probability of certain MSS values. Those in between are
1888 * rounded down to the next lower one.
1889 * [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
1890 * .2% .3% 5% 7% 7% 20% 15% 45%
1892 static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
1895 * Distribution and probability of certain WSCALE values. We have to map the
1896 * (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
1897 * bits based on prevalence of certain values. Where we don't have an exact
1898 * match for are rounded down to the next lower one letting us under-estimate
1899 * the true available window. At the moment this would happen only for the
1900 * very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
1901 * and window size). The absence of the WSCALE option (no scaling in either
1902 * direction) is encoded with index zero.
1903 * [WSCALE values histograms, Allman, 2012]
1904 * X 10 10 35 5 6 14 10% by host
1905 * X 11 4 5 5 18 49 3% by connections
1907 static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
1910 * Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
1911 * and good cryptographic properties.
1914 syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
1915 uint8_t *secbits, uintptr_t secmod)
1918 uint32_t siphash[2];
1920 SipHash24_Init(&ctx);
1921 SipHash_SetKey(&ctx, secbits);
1922 switch (inc->inc_flags & INC_ISIPV6) {
1925 SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
1926 SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
1931 SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
1932 SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
1936 SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
1937 SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
1938 SipHash_Update(&ctx, &irs, sizeof(irs));
1939 SipHash_Update(&ctx, &flags, sizeof(flags));
1940 SipHash_Update(&ctx, &secmod, sizeof(secmod));
1941 SipHash_Final((u_int8_t *)&siphash, &ctx);
1943 return (siphash[0] ^ siphash[1]);
1947 syncookie_generate(struct syncache_head *sch, struct syncache *sc)
1949 u_int i, mss, secbit, wscale;
1952 union syncookie cookie;
1954 SCH_LOCK_ASSERT(sch);
1958 /* Map our computed MSS into the 3-bit index. */
1959 mss = min(tcp_mssopt(&sc->sc_inc), max(sc->sc_peer_mss, V_tcp_minmss));
1960 for (i = nitems(tcp_sc_msstab) - 1; tcp_sc_msstab[i] > mss && i > 0;
1963 cookie.flags.mss_idx = i;
1966 * Map the send window scale into the 3-bit index but only if
1967 * the wscale option was received.
1969 if (sc->sc_flags & SCF_WINSCALE) {
1970 wscale = sc->sc_requested_s_scale;
1971 for (i = nitems(tcp_sc_wstab) - 1;
1972 tcp_sc_wstab[i] > wscale && i > 0;
1975 cookie.flags.wscale_idx = i;
1978 /* Can we do SACK? */
1979 if (sc->sc_flags & SCF_SACK)
1980 cookie.flags.sack_ok = 1;
1982 /* Which of the two secrets to use. */
1983 secbit = sch->sch_sc->secret.oddeven & 0x1;
1984 cookie.flags.odd_even = secbit;
1986 secbits = sch->sch_sc->secret.key[secbit];
1987 hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
1991 * Put the flags into the hash and XOR them to get better ISS number
1992 * variance. This doesn't enhance the cryptographic strength and is
1993 * done to prevent the 8 cookie bits from showing up directly on the
1997 iss |= cookie.cookie ^ (hash >> 24);
1999 /* Randomize the timestamp. */
2000 if (sc->sc_flags & SCF_TIMESTAMP) {
2001 sc->sc_ts = arc4random();
2002 sc->sc_tsoff = sc->sc_ts - tcp_ts_getticks();
2005 TCPSTAT_INC(tcps_sc_sendcookie);
2009 static struct syncache *
2010 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
2011 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2017 int wnd, wscale = 0;
2018 union syncookie cookie;
2020 SCH_LOCK_ASSERT(sch);
2023 * Pull information out of SYN-ACK/ACK and revert sequence number
2026 ack = th->th_ack - 1;
2027 seq = th->th_seq - 1;
2030 * Unpack the flags containing enough information to restore the
2033 cookie.cookie = (ack & 0xff) ^ (ack >> 24);
2035 /* Which of the two secrets to use. */
2036 secbits = sch->sch_sc->secret.key[cookie.flags.odd_even];
2038 hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
2040 /* The recomputed hash matches the ACK if this was a genuine cookie. */
2041 if ((ack & ~0xff) != (hash & ~0xff))
2044 /* Fill in the syncache values. */
2046 bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
2047 sc->sc_ipopts = NULL;
2052 switch (inc->inc_flags & INC_ISIPV6) {
2055 sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
2056 sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
2061 if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
2062 sc->sc_flowlabel = sc->sc_iss & IPV6_FLOWLABEL_MASK;
2067 sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
2069 /* We can simply recompute receive window scale we sent earlier. */
2070 while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
2073 /* Only use wscale if it was enabled in the orignal SYN. */
2074 if (cookie.flags.wscale_idx > 0) {
2075 sc->sc_requested_r_scale = wscale;
2076 sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
2077 sc->sc_flags |= SCF_WINSCALE;
2080 wnd = sbspace(&lso->so_rcv);
2082 wnd = imin(wnd, TCP_MAXWIN);
2085 if (cookie.flags.sack_ok)
2086 sc->sc_flags |= SCF_SACK;
2088 if (to->to_flags & TOF_TS) {
2089 sc->sc_flags |= SCF_TIMESTAMP;
2090 sc->sc_tsreflect = to->to_tsval;
2091 sc->sc_ts = to->to_tsecr;
2092 sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
2095 if (to->to_flags & TOF_SIGNATURE)
2096 sc->sc_flags |= SCF_SIGNATURE;
2100 TCPSTAT_INC(tcps_sc_recvcookie);
2106 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
2107 struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
2110 struct syncache scs, *scx;
2113 bzero(&scs, sizeof(scs));
2114 scx = syncookie_lookup(inc, sch, &scs, th, to, lso);
2116 if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
2120 if (sc->sc_peer_mss != scx->sc_peer_mss)
2121 log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
2122 s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
2124 if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
2125 log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
2126 s, __func__, sc->sc_requested_r_scale,
2127 scx->sc_requested_r_scale);
2129 if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
2130 log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
2131 s, __func__, sc->sc_requested_s_scale,
2132 scx->sc_requested_s_scale);
2134 if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
2135 log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
2142 #endif /* INVARIANTS */
2145 syncookie_reseed(void *arg)
2147 struct tcp_syncache *sc = arg;
2152 * Reseeding the secret doesn't have to be protected by a lock.
2153 * It only must be ensured that the new random values are visible
2154 * to all CPUs in a SMP environment. The atomic with release
2155 * semantics ensures that.
2157 secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
2158 secbits = sc->secret.key[secbit];
2159 arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
2160 atomic_add_rel_int(&sc->secret.oddeven, 1);
2162 /* Reschedule ourself. */
2163 callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
2167 * Exports the syncache entries to userland so that netstat can display
2168 * them alongside the other sockets. This function is intended to be
2169 * called only from tcp_pcblist.
2171 * Due to concurrency on an active system, the number of pcbs exported
2172 * may have no relation to max_pcbs. max_pcbs merely indicates the
2173 * amount of space the caller allocated for this function to use.
2176 syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported)
2179 struct syncache *sc;
2180 struct syncache_head *sch;
2181 int count, error, i;
2183 for (count = 0, error = 0, i = 0; i < V_tcp_syncache.hashsize; i++) {
2184 sch = &V_tcp_syncache.hashbase[i];
2186 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
2187 if (count >= max_pcbs) {
2191 if (cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
2193 bzero(&xt, sizeof(xt));
2194 xt.xt_len = sizeof(xt);
2195 if (sc->sc_inc.inc_flags & INC_ISIPV6)
2196 xt.xt_inp.inp_vflag = INP_IPV6;
2198 xt.xt_inp.inp_vflag = INP_IPV4;
2199 bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc, sizeof (struct in_conninfo));
2200 xt.xt_tp.t_inpcb = &xt.xt_inp;
2201 xt.xt_tp.t_state = TCPS_SYN_RECEIVED;
2202 xt.xt_socket.xso_protocol = IPPROTO_TCP;
2203 xt.xt_socket.xso_len = sizeof (struct xsocket);
2204 xt.xt_socket.so_type = SOCK_STREAM;
2205 xt.xt_socket.so_state = SS_ISCONNECTING;
2206 error = SYSCTL_OUT(req, &xt, sizeof xt);
2216 *pcbs_exported = count;