2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
37 * License terms: all terms for the DragonFly license above plus the following:
39 * 4. All advertising materials mentioning features or use of this software
40 * must display the following acknowledgement:
42 * This product includes software developed by Jeffrey M. Hsu
43 * for the DragonFly Project.
45 * This requirement may be waived with permission from Jeffrey Hsu.
46 * This requirement will sunset and may be removed on July 8 2005,
47 * after which the standard DragonFly license (as shown above) will
52 * All advertising materials mentioning features or use of this software
53 * must display the following acknowledgement:
54 * This product includes software developed by Jeffrey M. Hsu.
56 * Copyright (c) 2001 Networks Associates Technologies, Inc.
57 * All rights reserved.
59 * This software was developed for the FreeBSD Project by Jonathan Lemon
60 * and NAI Labs, the Security Research Division of Network Associates, Inc.
61 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
62 * DARPA CHATS research program.
64 * Redistribution and use in source and binary forms, with or without
65 * modification, are permitted provided that the following conditions
67 * 1. Redistributions of source code must retain the above copyright
68 * notice, this list of conditions and the following disclaimer.
69 * 2. Redistributions in binary form must reproduce the above copyright
70 * notice, this list of conditions and the following disclaimer in the
71 * documentation and/or other materials provided with the distribution.
72 * 3. The name of the author may not be used to endorse or promote
73 * products derived from this software without specific prior written
76 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
77 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
78 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
79 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
80 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
81 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
82 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
83 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
84 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
85 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
88 * $FreeBSD: src/sys/netinet/tcp_syncache.c,v 1.5.2.14 2003/02/24 04:02:27 silby Exp $
89 * $DragonFly: src/sys/netinet/tcp_syncache.c,v 1.16 2004/08/08 06:33:24 hsu Exp $
92 #include "opt_inet6.h"
93 #include "opt_ipsec.h"
95 #include <sys/param.h>
96 #include <sys/systm.h>
97 #include <sys/kernel.h>
98 #include <sys/sysctl.h>
99 #include <sys/malloc.h>
100 #include <sys/mbuf.h>
102 #include <sys/proc.h> /* for proc0 declaration */
103 #include <sys/random.h>
104 #include <sys/socket.h>
105 #include <sys/socketvar.h>
106 #include <sys/in_cksum.h>
109 #include <net/route.h>
111 #include <netinet/in.h>
112 #include <netinet/in_systm.h>
113 #include <netinet/ip.h>
114 #include <netinet/in_var.h>
115 #include <netinet/in_pcb.h>
116 #include <netinet/ip_var.h>
117 #include <netinet/ip6.h>
119 #include <netinet/icmp6.h>
120 #include <netinet6/nd6.h>
122 #include <netinet6/ip6_var.h>
123 #include <netinet6/in6_pcb.h>
124 #include <netinet/tcp.h>
125 #include <netinet/tcp_fsm.h>
126 #include <netinet/tcp_seq.h>
127 #include <netinet/tcp_timer.h>
128 #include <netinet/tcp_var.h>
129 #include <netinet6/tcp6_var.h>
132 #include <netinet6/ipsec.h>
134 #include <netinet6/ipsec6.h>
136 #include <netproto/key/key.h>
140 #include <netipsec/ipsec.h>
142 #include <netipsec/ipsec6.h>
144 #include <netipsec/key.h>
146 #endif /*FAST_IPSEC*/
148 #include <vm/vm_zone.h>
150 static int tcp_syncookies = 1;
151 SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
153 "Use TCP SYN cookies if the syncache overflows");
155 static void syncache_drop(struct syncache *, struct syncache_head *);
156 static void syncache_free(struct syncache *);
157 static void syncache_insert(struct syncache *, struct syncache_head *);
158 struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
159 static int syncache_respond(struct syncache *, struct mbuf *);
160 static struct socket *syncache_socket(struct syncache *, struct socket *);
161 static void syncache_timer(void *);
162 static u_int32_t syncookie_generate(struct syncache *);
163 static struct syncache *syncookie_lookup(struct in_conninfo *,
164 struct tcphdr *, struct socket *);
167 * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
168 * 3 retransmits corresponds to a timeout of (1 + 2 + 4 + 8 == 15) seconds,
169 * the odds are that the user has given up attempting to connect by then.
171 #define SYNCACHE_MAXREXMTS 3
173 /* Arbitrary values */
174 #define TCP_SYNCACHE_HASHSIZE 512
175 #define TCP_SYNCACHE_BUCKETLIMIT 30
177 struct tcp_syncache {
178 struct syncache_head *hashbase;
179 struct vm_zone *zone;
187 TAILQ_HEAD(, syncache) timerq[SYNCACHE_MAXREXMTS + 1];
188 struct callout tt_timerq[SYNCACHE_MAXREXMTS + 1];
190 static struct tcp_syncache tcp_syncache;
192 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
194 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RD,
195 &tcp_syncache.bucket_limit, 0, "Per-bucket hash limit for syncache");
197 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RD,
198 &tcp_syncache.cache_limit, 0, "Overall entry limit for syncache");
200 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
201 &tcp_syncache.cache_count, 0, "Current number of entries in syncache");
203 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RD,
204 &tcp_syncache.hashsize, 0, "Size of TCP syncache hashtable");
206 SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
207 &tcp_syncache.rexmt_limit, 0, "Limit on SYN/ACK retransmissions");
209 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
211 #define SYNCACHE_HASH(inc, mask) \
212 ((tcp_syncache.hash_secret ^ \
213 (inc)->inc_faddr.s_addr ^ \
214 ((inc)->inc_faddr.s_addr >> 16) ^ \
215 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
217 #define SYNCACHE_HASH6(inc, mask) \
218 ((tcp_syncache.hash_secret ^ \
219 (inc)->inc6_faddr.s6_addr32[0] ^ \
220 (inc)->inc6_faddr.s6_addr32[3] ^ \
221 (inc)->inc_fport ^ (inc)->inc_lport) & mask)
223 #define ENDPTS_EQ(a, b) ( \
224 (a)->ie_fport == (b)->ie_fport && \
225 (a)->ie_lport == (b)->ie_lport && \
226 (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
227 (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
230 #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
232 #define SYNCACHE_TIMEOUT(sc, slot) do { \
233 sc->sc_rxtslot = slot; \
234 sc->sc_rxttime = ticks + TCPTV_RTOBASE * tcp_backoff[slot]; \
235 TAILQ_INSERT_TAIL(&tcp_syncache.timerq[slot], sc, sc_timerq); \
236 if (!callout_active(&tcp_syncache.tt_timerq[slot])) \
237 callout_reset(&tcp_syncache.tt_timerq[slot], \
238 TCPTV_RTOBASE * tcp_backoff[slot], \
239 syncache_timer, (void *)((intptr_t)slot)); \
243 syncache_free(struct syncache *sc)
247 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
249 const boolean_t isipv6 = FALSE;
253 (void) m_free(sc->sc_ipopts);
255 rt = sc->sc_route6.ro_rt;
257 rt = sc->sc_route.ro_rt;
260 * If this is the only reference to a protocol cloned
261 * route, remove it immediately.
263 if (rt->rt_flags & RTF_WASCLONED &&
264 (sc->sc_flags & SCF_KEEPROUTE) == 0 &&
266 rtrequest(RTM_DELETE, rt_key(rt),
267 rt->rt_gateway, rt_mask(rt),
271 zfree(tcp_syncache.zone, sc);
279 tcp_syncache.cache_count = 0;
280 tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
281 tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
282 tcp_syncache.cache_limit =
283 tcp_syncache.hashsize * tcp_syncache.bucket_limit;
284 tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
285 tcp_syncache.hash_secret = arc4random();
287 TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
288 &tcp_syncache.hashsize);
289 TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
290 &tcp_syncache.cache_limit);
291 TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
292 &tcp_syncache.bucket_limit);
293 if (!powerof2(tcp_syncache.hashsize)) {
294 printf("WARNING: syncache hash size is not a power of 2.\n");
295 tcp_syncache.hashsize = 512; /* safe default */
297 tcp_syncache.hashmask = tcp_syncache.hashsize - 1;
299 /* Allocate the hash table. */
300 MALLOC(tcp_syncache.hashbase, struct syncache_head *,
301 tcp_syncache.hashsize * sizeof(struct syncache_head),
302 M_SYNCACHE, M_WAITOK);
304 /* Initialize the hash buckets. */
305 for (i = 0; i < tcp_syncache.hashsize; i++) {
306 TAILQ_INIT(&tcp_syncache.hashbase[i].sch_bucket);
307 tcp_syncache.hashbase[i].sch_length = 0;
310 /* Initialize the timer queues. */
311 for (i = 0; i <= SYNCACHE_MAXREXMTS; i++) {
312 TAILQ_INIT(&tcp_syncache.timerq[i]);
313 callout_init(&tcp_syncache.tt_timerq[i]);
317 * Allocate the syncache entries. Allow the zone to allocate one
318 * more entry than cache limit, so a new entry can bump out an
321 tcp_syncache.zone = zinit("syncache", sizeof(struct syncache),
322 tcp_syncache.cache_limit, ZONE_INTERRUPT, 0);
323 tcp_syncache.cache_limit -= 1;
327 syncache_insert(sc, sch)
329 struct syncache_head *sch;
331 struct syncache *sc2;
335 * Make sure that we don't overflow the per-bucket
336 * limit or the total cache size limit.
338 if (sch->sch_length >= tcp_syncache.bucket_limit) {
340 * The bucket is full, toss the oldest element.
342 sc2 = TAILQ_FIRST(&sch->sch_bucket);
343 sc2->sc_tp->ts_recent = ticks;
344 syncache_drop(sc2, sch);
345 tcpstat.tcps_sc_bucketoverflow++;
346 } else if (tcp_syncache.cache_count >= tcp_syncache.cache_limit) {
348 * The cache is full. Toss the oldest entry in the
349 * entire cache. This is the front entry in the
350 * first non-empty timer queue with the largest
353 for (i = SYNCACHE_MAXREXMTS; i >= 0; i--) {
354 sc2 = TAILQ_FIRST(&tcp_syncache.timerq[i]);
358 sc2->sc_tp->ts_recent = ticks;
359 syncache_drop(sc2, NULL);
360 tcpstat.tcps_sc_cacheoverflow++;
363 /* Initialize the entry's timer. */
364 SYNCACHE_TIMEOUT(sc, 0);
366 /* Put it into the bucket. */
367 TAILQ_INSERT_TAIL(&sch->sch_bucket, sc, sc_hash);
369 tcp_syncache.cache_count++;
370 tcpstat.tcps_sc_added++;
374 syncache_drop(sc, sch)
376 struct syncache_head *sch;
379 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
381 const boolean_t isipv6 = FALSE;
386 sch = &tcp_syncache.hashbase[
387 SYNCACHE_HASH6(&sc->sc_inc, tcp_syncache.hashmask)];
389 sch = &tcp_syncache.hashbase[
390 SYNCACHE_HASH(&sc->sc_inc, tcp_syncache.hashmask)];
394 TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
396 tcp_syncache.cache_count--;
398 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot], sc, sc_timerq);
399 if (TAILQ_EMPTY(&tcp_syncache.timerq[sc->sc_rxtslot]))
400 callout_stop(&tcp_syncache.tt_timerq[sc->sc_rxtslot]);
406 * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
407 * If we have retransmitted an entry the maximum number of times, expire it.
410 syncache_timer(xslot)
413 intptr_t slot = (intptr_t)xslot;
414 struct syncache *sc, *nsc;
419 if (callout_pending(&tcp_syncache.tt_timerq[slot]) ||
420 !callout_active(&tcp_syncache.tt_timerq[slot])) {
424 callout_deactivate(&tcp_syncache.tt_timerq[slot]);
426 nsc = TAILQ_FIRST(&tcp_syncache.timerq[slot]);
427 while (nsc != NULL) {
428 if (ticks < nsc->sc_rxttime)
431 inp = sc->sc_tp->t_inpcb;
432 if (slot == SYNCACHE_MAXREXMTS ||
433 slot >= tcp_syncache.rexmt_limit ||
434 inp->inp_gencnt != sc->sc_inp_gencnt) {
435 nsc = TAILQ_NEXT(sc, sc_timerq);
436 syncache_drop(sc, NULL);
437 tcpstat.tcps_sc_stale++;
441 * syncache_respond() may call back into the syncache to
442 * to modify another entry, so do not obtain the next
443 * entry on the timer chain until it has completed.
445 (void) syncache_respond(sc, NULL);
446 nsc = TAILQ_NEXT(sc, sc_timerq);
447 tcpstat.tcps_sc_retransmitted++;
448 TAILQ_REMOVE(&tcp_syncache.timerq[slot], sc, sc_timerq);
449 SYNCACHE_TIMEOUT(sc, slot + 1);
452 callout_reset(&tcp_syncache.tt_timerq[slot],
453 nsc->sc_rxttime - ticks, syncache_timer, (void *)(slot));
458 * Find an entry in the syncache.
461 syncache_lookup(inc, schp)
462 struct in_conninfo *inc;
463 struct syncache_head **schp;
466 struct syncache_head *sch;
469 if (inc->inc_isipv6) {
470 sch = &tcp_syncache.hashbase[
471 SYNCACHE_HASH6(inc, tcp_syncache.hashmask)];
473 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
474 if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
479 sch = &tcp_syncache.hashbase[
480 SYNCACHE_HASH(inc, tcp_syncache.hashmask)];
482 TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
484 if (sc->sc_inc.inc_isipv6)
487 if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
495 * This function is called when we get a RST for a
496 * non-existent connection, so that we can see if the
497 * connection is in the syn cache. If it is, zap it.
500 syncache_chkrst(inc, th)
501 struct in_conninfo *inc;
505 struct syncache_head *sch;
507 sc = syncache_lookup(inc, &sch);
511 * If the RST bit is set, check the sequence number to see
512 * if this is a valid reset segment.
514 * In all states except SYN-SENT, all reset (RST) segments
515 * are validated by checking their SEQ-fields. A reset is
516 * valid if its sequence number is in the window.
518 * The sequence number in the reset segment is normally an
519 * echo of our outgoing acknowlegement numbers, but some hosts
520 * send a reset with the sequence number at the rightmost edge
521 * of our receive window, and we have to handle this case.
523 if (SEQ_GEQ(th->th_seq, sc->sc_irs) &&
524 SEQ_LEQ(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
525 syncache_drop(sc, sch);
526 tcpstat.tcps_sc_reset++;
532 struct in_conninfo *inc;
535 struct syncache_head *sch;
537 sc = syncache_lookup(inc, &sch);
539 syncache_drop(sc, sch);
540 tcpstat.tcps_sc_badack++;
545 syncache_unreach(inc, th)
546 struct in_conninfo *inc;
550 struct syncache_head *sch;
552 /* we are called at splnet() here */
553 sc = syncache_lookup(inc, &sch);
557 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
558 if (ntohl(th->th_seq) != sc->sc_iss)
562 * If we've rertransmitted 3 times and this is our second error,
563 * we remove the entry. Otherwise, we allow it to continue on.
564 * This prevents us from incorrectly nuking an entry during a
565 * spurious network outage.
569 if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtslot < 3) {
570 sc->sc_flags |= SCF_UNREACH;
573 syncache_drop(sc, sch);
574 tcpstat.tcps_sc_unreach++;
578 * Build a new TCP socket structure from a syncache entry.
580 static struct socket *
581 syncache_socket(sc, lso)
585 struct inpcb *inp = NULL;
589 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
591 const boolean_t isipv6 = FALSE;
595 * Ok, create the full blown connection, and set things up
596 * as they would have been set up if we had created the
597 * connection when the SYN arrived. If we can't create
598 * the connection, abort it.
600 so = sonewconn(lso, SS_ISCONNECTED);
603 * Drop the connection; we will send a RST if the peer
604 * retransmits the ACK,
606 tcpstat.tcps_listendrop++;
613 * Insert new socket into hash list.
615 inp->inp_inc.inc_isipv6 = sc->sc_inc.inc_isipv6;
617 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
620 inp->inp_vflag &= ~INP_IPV6;
621 inp->inp_vflag |= INP_IPV4;
623 inp->inp_laddr = sc->sc_inc.inc_laddr;
625 inp->inp_lport = sc->sc_inc.inc_lport;
626 if (in_pcbinsporthash(inp) != 0) {
628 * Undo the assignments above if we failed to
629 * put the PCB on the hash lists.
632 inp->in6p_laddr = in6addr_any;
634 inp->inp_laddr.s_addr = INADDR_ANY;
639 /* copy old policy into new socket's */
640 if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
641 printf("syncache_expand: could not copy policy\n");
644 struct inpcb *oinp = sotoinpcb(lso);
645 struct in6_addr laddr6;
646 struct sockaddr_in6 sin6;
648 * Inherit socket options from the listening socket.
649 * Note that in6p_inputopts are not (and should not be)
650 * copied, since it stores previously received options and is
651 * used to detect if each new option is different than the
652 * previous one and hence should be passed to a user.
653 * If we copied in6p_inputopts, a user would not be able to
654 * receive options just after calling the accept system call.
656 inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
657 if (oinp->in6p_outputopts)
658 inp->in6p_outputopts =
659 ip6_copypktopts(oinp->in6p_outputopts, M_INTWAIT);
660 inp->in6p_route = sc->sc_route6;
661 sc->sc_route6.ro_rt = NULL;
663 sin6.sin6_family = AF_INET6;
664 sin6.sin6_len = sizeof sin6;
665 sin6.sin6_addr = sc->sc_inc.inc6_faddr;
666 sin6.sin6_port = sc->sc_inc.inc_fport;
667 sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
668 laddr6 = inp->in6p_laddr;
669 if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
670 inp->in6p_laddr = sc->sc_inc.inc6_laddr;
671 if (in6_pcbconnect(inp, (struct sockaddr *)&sin6, &thread0)) {
672 inp->in6p_laddr = laddr6;
676 struct in_addr laddr;
677 struct sockaddr_in sin;
679 inp->inp_options = ip_srcroute();
680 if (inp->inp_options == NULL) {
681 inp->inp_options = sc->sc_ipopts;
682 sc->sc_ipopts = NULL;
684 inp->inp_route = sc->sc_route;
685 sc->sc_route.ro_rt = NULL;
687 sin.sin_family = AF_INET;
688 sin.sin_len = sizeof sin;
689 sin.sin_addr = sc->sc_inc.inc_faddr;
690 sin.sin_port = sc->sc_inc.inc_fport;
691 bzero(sin.sin_zero, sizeof sin.sin_zero);
692 laddr = inp->inp_laddr;
693 if (inp->inp_laddr.s_addr == INADDR_ANY)
694 inp->inp_laddr = sc->sc_inc.inc_laddr;
695 if (in_pcbconnect(inp, (struct sockaddr *)&sin, &thread0)) {
696 inp->inp_laddr = laddr;
702 tp->t_state = TCPS_SYN_RECEIVED;
703 tp->iss = sc->sc_iss;
704 tp->irs = sc->sc_irs;
707 tp->snd_wl1 = sc->sc_irs;
708 tp->rcv_up = sc->sc_irs + 1;
709 tp->rcv_wnd = sc->sc_wnd;
710 tp->rcv_adv += tp->rcv_wnd;
712 tp->t_flags = sototcpcb(lso)->t_flags & (TF_NOPUSH | TF_NODELAY);
713 if (sc->sc_flags & SCF_NOOPT)
714 tp->t_flags |= TF_NOOPT;
715 if (sc->sc_flags & SCF_WINSCALE) {
716 tp->t_flags |= TF_REQ_SCALE | TF_RCVD_SCALE;
717 tp->requested_s_scale = sc->sc_requested_s_scale;
718 tp->request_r_scale = sc->sc_request_r_scale;
720 if (sc->sc_flags & SCF_TIMESTAMP) {
721 tp->t_flags |= TF_REQ_TSTMP | TF_RCVD_TSTMP;
722 tp->ts_recent = sc->sc_tsrecent;
723 tp->ts_recent_age = ticks;
725 if (sc->sc_flags & SCF_CC) {
727 * Initialization of the tcpcb for transaction;
728 * set SND.WND = SEG.WND,
729 * initialize CCsend and CCrecv.
731 tp->t_flags |= TF_REQ_CC | TF_RCVD_CC;
732 tp->cc_send = sc->sc_cc_send;
733 tp->cc_recv = sc->sc_cc_recv;
736 tcp_mss(tp, sc->sc_peer_mss);
739 * If the SYN,ACK was retransmitted, reset cwnd to 1 segment.
741 if (sc->sc_rxtslot != 0)
742 tp->snd_cwnd = tp->t_maxseg;
743 callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp);
745 tcpstat.tcps_accepts++;
755 * This function gets called when we receive an ACK for a
756 * socket in the LISTEN state. We look up the connection
757 * in the syncache, and if its there, we pull it out of
758 * the cache and turn it into a full-blown connection in
759 * the SYN-RECEIVED state.
762 syncache_expand(inc, th, sop, m)
763 struct in_conninfo *inc;
769 struct syncache_head *sch;
772 sc = syncache_lookup(inc, &sch);
775 * There is no syncache entry, so see if this ACK is
776 * a returning syncookie. To do this, first:
777 * A. See if this socket has had a syncache entry dropped in
778 * the past. We don't want to accept a bogus syncookie
779 * if we've never received a SYN.
780 * B. check that the syncookie is valid. If it is, then
781 * cobble up a fake syncache entry, and return.
785 sc = syncookie_lookup(inc, th, *sop);
789 tcpstat.tcps_sc_recvcookie++;
793 * If seg contains an ACK, but not for our SYN/ACK, send a RST.
795 if (th->th_ack != sc->sc_iss + 1)
798 so = syncache_socket(sc, *sop);
802 /* XXXjlemon check this - is this correct? */
803 (void) tcp_respond(NULL, m, m, th,
804 th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK);
806 m_freem(m); /* XXX only needed for above */
807 tcpstat.tcps_sc_aborted++;
809 sc->sc_flags |= SCF_KEEPROUTE;
810 tcpstat.tcps_sc_completed++;
815 syncache_drop(sc, sch);
821 * Given a LISTEN socket and an inbound SYN request, add
822 * this to the syn cache, and send back a segment:
823 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
826 * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
827 * Doing so would require that we hold onto the data and deliver it
828 * to the application. However, if we are the target of a SYN-flood
829 * DoS attack, an attacker could send data which would eventually
830 * consume all available buffer space if it were ACKed. By not ACKing
831 * the data, we avoid this DoS scenario.
834 syncache_add(inc, to, th, sop, m)
835 struct in_conninfo *inc;
843 struct syncache *sc = NULL;
844 struct syncache_head *sch;
845 struct mbuf *ipopts = NULL;
846 struct rmxp_tao *taop;
853 * Remember the IP options, if any.
856 if (!inc->inc_isipv6)
858 ipopts = ip_srcroute();
861 * See if we already have an entry for this connection.
862 * If we do, resend the SYN,ACK, and reset the retransmit timer.
865 * should the syncache be re-initialized with the contents
866 * of the new SYN here (which may have different options?)
868 sc = syncache_lookup(inc, &sch);
870 tcpstat.tcps_sc_dupsyn++;
873 * If we were remembering a previous source route,
874 * forget it and use the new one we've been given.
877 (void) m_free(sc->sc_ipopts);
878 sc->sc_ipopts = ipopts;
881 * Update timestamp if present.
883 if (sc->sc_flags & SCF_TIMESTAMP)
884 sc->sc_tsrecent = to->to_tsval;
886 * PCB may have changed, pick up new values.
889 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
890 if (syncache_respond(sc, m) == 0) {
891 TAILQ_REMOVE(&tcp_syncache.timerq[sc->sc_rxtslot],
893 SYNCACHE_TIMEOUT(sc, sc->sc_rxtslot);
894 tcpstat.tcps_sndacks++;
895 tcpstat.tcps_sndtotal++;
902 * This allocation is guaranteed to succeed because we
903 * preallocate one more syncache entry than cache_limit.
905 sc = zalloc(tcp_syncache.zone);
908 * Fill in the syncache values.
911 sc->sc_inp_gencnt = tp->t_inpcb->inp_gencnt;
912 sc->sc_ipopts = ipopts;
913 sc->sc_inc.inc_fport = inc->inc_fport;
914 sc->sc_inc.inc_lport = inc->inc_lport;
916 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
917 if (inc->inc_isipv6) {
918 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
919 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
920 sc->sc_route6.ro_rt = NULL;
924 sc->sc_inc.inc_faddr = inc->inc_faddr;
925 sc->sc_inc.inc_laddr = inc->inc_laddr;
926 sc->sc_route.ro_rt = NULL;
928 sc->sc_irs = th->th_seq;
930 sc->sc_peer_mss = to->to_flags & TOF_MSS ? to->to_mss : 0;
932 sc->sc_iss = syncookie_generate(sc);
934 sc->sc_iss = arc4random();
936 /* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN] */
937 win = sbspace(&so->so_rcv);
939 win = imin(win, TCP_MAXWIN);
942 if (tcp_do_rfc1323) {
944 * A timestamp received in a SYN makes
945 * it ok to send timestamp requests and replies.
947 if (to->to_flags & TOF_TS) {
948 sc->sc_tsrecent = to->to_tsval;
949 sc->sc_flags |= SCF_TIMESTAMP;
951 if (to->to_flags & TOF_SCALE) {
954 /* Compute proper scaling value from buffer space */
955 while (wscale < TCP_MAX_WINSHIFT &&
956 (TCP_MAXWIN << wscale) < so->so_rcv.sb_hiwat)
958 sc->sc_request_r_scale = wscale;
959 sc->sc_requested_s_scale = to->to_requested_s_scale;
960 sc->sc_flags |= SCF_WINSCALE;
963 if (tcp_do_rfc1644) {
965 * A CC or CC.new option received in a SYN makes
966 * it ok to send CC in subsequent segments.
968 if (to->to_flags & (TOF_CC | TOF_CCNEW)) {
969 sc->sc_cc_recv = to->to_cc;
970 sc->sc_cc_send = CC_INC(tcp_ccgen);
971 sc->sc_flags |= SCF_CC;
974 if (tp->t_flags & TF_NOOPT)
975 sc->sc_flags = SCF_NOOPT;
979 * We have the option here of not doing TAO (even if the segment
980 * qualifies) and instead fall back to a normal 3WHS via the syncache.
981 * This allows us to apply synflood protection to TAO-qualifying SYNs
982 * also. However, there should be a hueristic to determine when to
983 * do this, and is not present at the moment.
987 * Perform TAO test on incoming CC (SEG.CC) option, if any.
988 * - compare SEG.CC against cached CC from the same host, if any.
989 * - if SEG.CC > chached value, SYN must be new and is accepted
990 * immediately: save new CC in the cache, mark the socket
991 * connected, enter ESTABLISHED state, turn on flag to
992 * send a SYN in the next segment.
993 * A virtual advertised window is set in rcv_adv to
994 * initialize SWS prevention. Then enter normal segment
995 * processing: drop SYN, process data and FIN.
996 * - otherwise do a normal 3-way handshake.
998 taop = tcp_gettaocache(&sc->sc_inc);
999 if ((to->to_flags & TOF_CC) != 0) {
1000 if (((tp->t_flags & TF_NOPUSH) != 0) &&
1001 sc->sc_flags & SCF_CC &&
1002 taop != NULL && taop->tao_cc != 0 &&
1003 CC_GT(to->to_cc, taop->tao_cc)) {
1005 so = syncache_socket(sc, *sop);
1007 sc->sc_flags |= SCF_KEEPROUTE;
1008 taop->tao_cc = to->to_cc;
1012 return (so != NULL);
1016 * No CC option, but maybe CC.NEW: invalidate cached value.
1022 * TAO test failed or there was no CC option,
1023 * do a standard 3-way handshake.
1025 if (syncache_respond(sc, m) == 0) {
1026 syncache_insert(sc, sch);
1027 tcpstat.tcps_sndacks++;
1028 tcpstat.tcps_sndtotal++;
1031 tcpstat.tcps_sc_dropped++;
1038 syncache_respond(sc, m)
1039 struct syncache *sc;
1044 u_int16_t tlen, hlen, mssopt;
1045 struct ip *ip = NULL;
1048 struct ip6_hdr *ip6 = NULL;
1050 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1052 const boolean_t isipv6 = FALSE;
1056 rt = tcp_rtlookup6(&sc->sc_inc);
1058 mssopt = rt->rt_ifp->if_mtu -
1059 (sizeof(struct ip6_hdr) + sizeof(struct tcphdr));
1061 mssopt = tcp_v6mssdflt;
1062 hlen = sizeof(struct ip6_hdr);
1064 rt = tcp_rtlookup(&sc->sc_inc);
1066 mssopt = rt->rt_ifp->if_mtu -
1067 (sizeof(struct ip) + sizeof(struct tcphdr));
1069 mssopt = tcp_mssdflt;
1070 hlen = sizeof(struct ip);
1073 /* Compute the size of the TCP options. */
1074 if (sc->sc_flags & SCF_NOOPT) {
1077 optlen = TCPOLEN_MAXSEG +
1078 ((sc->sc_flags & SCF_WINSCALE) ? 4 : 0) +
1079 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0) +
1080 ((sc->sc_flags & SCF_CC) ? TCPOLEN_CC_APPA * 2 : 0);
1082 tlen = hlen + sizeof(struct tcphdr) + optlen;
1086 * assume that the entire packet will fit in a header mbuf
1088 KASSERT(max_linkhdr + tlen <= MHLEN, ("syncache: mbuf too small"));
1091 * XXX shouldn't this reuse the mbuf if possible ?
1092 * Create the IP+TCP header from scratch.
1097 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
1100 m->m_data += max_linkhdr;
1102 m->m_pkthdr.len = tlen;
1103 m->m_pkthdr.rcvif = NULL;
1106 ip6 = mtod(m, struct ip6_hdr *);
1107 ip6->ip6_vfc = IPV6_VERSION;
1108 ip6->ip6_nxt = IPPROTO_TCP;
1109 ip6->ip6_src = sc->sc_inc.inc6_laddr;
1110 ip6->ip6_dst = sc->sc_inc.inc6_faddr;
1111 ip6->ip6_plen = htons(tlen - hlen);
1112 /* ip6_hlim is set after checksum */
1113 /* ip6_flow = ??? */
1115 th = (struct tcphdr *)(ip6 + 1);
1117 ip = mtod(m, struct ip *);
1118 ip->ip_v = IPVERSION;
1119 ip->ip_hl = sizeof(struct ip) >> 2;
1124 ip->ip_p = IPPROTO_TCP;
1125 ip->ip_src = sc->sc_inc.inc_laddr;
1126 ip->ip_dst = sc->sc_inc.inc_faddr;
1127 ip->ip_ttl = sc->sc_tp->t_inpcb->inp_ip_ttl; /* XXX */
1128 ip->ip_tos = sc->sc_tp->t_inpcb->inp_ip_tos; /* XXX */
1131 * See if we should do MTU discovery. Route lookups are
1132 * expensive, so we will only unset the DF bit if:
1134 * 1) path_mtu_discovery is disabled
1135 * 2) the SCF_UNREACH flag has been set
1137 if (path_mtu_discovery
1138 && ((sc->sc_flags & SCF_UNREACH) == 0)) {
1139 ip->ip_off |= IP_DF;
1142 th = (struct tcphdr *)(ip + 1);
1144 th->th_sport = sc->sc_inc.inc_lport;
1145 th->th_dport = sc->sc_inc.inc_fport;
1147 th->th_seq = htonl(sc->sc_iss);
1148 th->th_ack = htonl(sc->sc_irs + 1);
1149 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1151 th->th_flags = TH_SYN | TH_ACK;
1152 th->th_win = htons(sc->sc_wnd);
1155 /* Tack on the TCP options. */
1158 optp = (u_int8_t *)(th + 1);
1159 *optp++ = TCPOPT_MAXSEG;
1160 *optp++ = TCPOLEN_MAXSEG;
1161 *optp++ = (mssopt >> 8) & 0xff;
1162 *optp++ = mssopt & 0xff;
1164 if (sc->sc_flags & SCF_WINSCALE) {
1165 *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
1166 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
1167 sc->sc_request_r_scale);
1171 if (sc->sc_flags & SCF_TIMESTAMP) {
1172 u_int32_t *lp = (u_int32_t *)(optp);
1174 /* Form timestamp option as shown in appendix A of RFC 1323. */
1175 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
1176 *lp++ = htonl(ticks);
1177 *lp = htonl(sc->sc_tsrecent);
1178 optp += TCPOLEN_TSTAMP_APPA;
1182 * Send CC and CC.echo if we received CC from our peer.
1184 if (sc->sc_flags & SCF_CC) {
1185 u_int32_t *lp = (u_int32_t *)(optp);
1187 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CC));
1188 *lp++ = htonl(sc->sc_cc_send);
1189 *lp++ = htonl(TCPOPT_CC_HDR(TCPOPT_CCECHO));
1190 *lp = htonl(sc->sc_cc_recv);
1191 optp += TCPOLEN_CC_APPA * 2;
1196 struct route_in6 *ro6 = &sc->sc_route6;
1199 th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
1200 ip6->ip6_hlim = in6_selecthlim(NULL,
1201 ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL);
1202 error = ip6_output(m, NULL, ro6, 0, NULL, NULL,
1203 sc->sc_tp->t_inpcb);
1205 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1206 htons(tlen - hlen + IPPROTO_TCP));
1207 m->m_pkthdr.csum_flags = CSUM_TCP;
1208 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1209 error = ip_output(m, sc->sc_ipopts, &sc->sc_route, 0, NULL,
1210 sc->sc_tp->t_inpcb);
1218 * |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|
1220 * | MD5(laddr,faddr,secret,lport,fport) |. . . . . . .|
1222 * (A): peer mss index
1226 * The values below are chosen to minimize the size of the tcp_secret
1227 * table, as well as providing roughly a 16 second lifetime for the cookie.
1230 #define SYNCOOKIE_WNDBITS 5 /* exposed bits for window indexing */
1231 #define SYNCOOKIE_TIMESHIFT 1 /* scale ticks to window time units */
1233 #define SYNCOOKIE_WNDMASK ((1 << SYNCOOKIE_WNDBITS) - 1)
1234 #define SYNCOOKIE_NSECRETS (1 << SYNCOOKIE_WNDBITS)
1235 #define SYNCOOKIE_TIMEOUT \
1236 (hz * (1 << SYNCOOKIE_WNDBITS) / (1 << SYNCOOKIE_TIMESHIFT))
1237 #define SYNCOOKIE_DATAMASK ((3 << SYNCOOKIE_WNDBITS) | SYNCOOKIE_WNDMASK)
1240 u_int32_t ts_secbits[4];
1242 } tcp_secret[SYNCOOKIE_NSECRETS];
1244 static int tcp_msstab[] = { 0, 536, 1460, 8960 };
1246 static MD5_CTX syn_ctx;
1248 #define MD5Add(v) MD5Update(&syn_ctx, (u_char *)&v, sizeof(v))
1251 u_int32_t laddr, faddr;
1252 u_int32_t secbits[4];
1253 u_int16_t lport, fport;
1257 CTASSERT(sizeof(struct md5_add) == 28);
1261 * Consider the problem of a recreated (and retransmitted) cookie. If the
1262 * original SYN was accepted, the connection is established. The second
1263 * SYN is inflight, and if it arrives with an ISN that falls within the
1264 * receive window, the connection is killed.
1266 * However, since cookies have other problems, this may not be worth
1271 syncookie_generate(struct syncache *sc)
1273 u_int32_t md5_buffer[4];
1278 const boolean_t isipv6 = sc->sc_inc.inc_isipv6;
1280 const boolean_t isipv6 = FALSE;
1283 idx = ((ticks << SYNCOOKIE_TIMESHIFT) / hz) & SYNCOOKIE_WNDMASK;
1284 if (tcp_secret[idx].ts_expire < ticks) {
1285 for (i = 0; i < 4; i++)
1286 tcp_secret[idx].ts_secbits[i] = arc4random();
1287 tcp_secret[idx].ts_expire = ticks + SYNCOOKIE_TIMEOUT;
1289 for (data = sizeof(tcp_msstab) / sizeof(int) - 1; data > 0; data--)
1290 if (tcp_msstab[data] <= sc->sc_peer_mss)
1292 data = (data << SYNCOOKIE_WNDBITS) | idx;
1293 data ^= sc->sc_irs; /* peer's iss */
1296 MD5Add(sc->sc_inc.inc6_laddr);
1297 MD5Add(sc->sc_inc.inc6_faddr);
1301 add.laddr = sc->sc_inc.inc_laddr.s_addr;
1302 add.faddr = sc->sc_inc.inc_faddr.s_addr;
1304 add.lport = sc->sc_inc.inc_lport;
1305 add.fport = sc->sc_inc.inc_fport;
1306 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1307 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1308 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1309 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1311 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1312 data ^= (md5_buffer[0] & ~SYNCOOKIE_WNDMASK);
1316 static struct syncache *
1317 syncookie_lookup(inc, th, so)
1318 struct in_conninfo *inc;
1322 u_int32_t md5_buffer[4];
1323 struct syncache *sc;
1328 data = (th->th_ack - 1) ^ (th->th_seq - 1); /* remove ISS */
1329 idx = data & SYNCOOKIE_WNDMASK;
1330 if (tcp_secret[idx].ts_expire < ticks ||
1331 sototcpcb(so)->ts_recent + SYNCOOKIE_TIMEOUT < ticks)
1335 if (inc->inc_isipv6) {
1336 MD5Add(inc->inc6_laddr);
1337 MD5Add(inc->inc6_faddr);
1343 add.laddr = inc->inc_laddr.s_addr;
1344 add.faddr = inc->inc_faddr.s_addr;
1346 add.lport = inc->inc_lport;
1347 add.fport = inc->inc_fport;
1348 add.secbits[0] = tcp_secret[idx].ts_secbits[0];
1349 add.secbits[1] = tcp_secret[idx].ts_secbits[1];
1350 add.secbits[2] = tcp_secret[idx].ts_secbits[2];
1351 add.secbits[3] = tcp_secret[idx].ts_secbits[3];
1353 MD5Final((u_char *)&md5_buffer, &syn_ctx);
1354 data ^= md5_buffer[0];
1355 if ((data & ~SYNCOOKIE_DATAMASK) != 0)
1357 data = data >> SYNCOOKIE_WNDBITS;
1360 * This allocation is guaranteed to succeed because we
1361 * preallocate one more syncache entry than cache_limit.
1363 sc = zalloc(tcp_syncache.zone);
1366 * Fill in the syncache values.
1367 * XXX duplicate code from syncache_add
1369 sc->sc_ipopts = NULL;
1370 sc->sc_inc.inc_fport = inc->inc_fport;
1371 sc->sc_inc.inc_lport = inc->inc_lport;
1373 sc->sc_inc.inc_isipv6 = inc->inc_isipv6;
1374 if (inc->inc_isipv6) {
1375 sc->sc_inc.inc6_faddr = inc->inc6_faddr;
1376 sc->sc_inc.inc6_laddr = inc->inc6_laddr;
1377 sc->sc_route6.ro_rt = NULL;
1381 sc->sc_inc.inc_faddr = inc->inc_faddr;
1382 sc->sc_inc.inc_laddr = inc->inc_laddr;
1383 sc->sc_route.ro_rt = NULL;
1385 sc->sc_irs = th->th_seq - 1;
1386 sc->sc_iss = th->th_ack - 1;
1387 wnd = sbspace(&so->so_rcv);
1389 wnd = imin(wnd, TCP_MAXWIN);
1393 sc->sc_peer_mss = tcp_msstab[data];