mirror of
https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
synced 2024-11-22 22:01:05 +01:00
0a05ea1f56
While processing the ECN flags of an incoming packet, incorrectly cleared all other syncache flags. Reported by: tuexen Reviewed By: tuexen, #transport Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D46694
2553 lines
74 KiB
C
2553 lines
74 KiB
C
/*-
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*
|
|
* Copyright (c) 2001 McAfee, Inc.
|
|
* Copyright (c) 2006,2013 Andre Oppermann, Internet Business Solutions AG
|
|
* All rights reserved.
|
|
*
|
|
* This software was developed for the FreeBSD Project by Jonathan Lemon
|
|
* and McAfee Research, the Security Research Division of McAfee, Inc. under
|
|
* DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
|
|
* DARPA CHATS research program. [2001 McAfee, Inc.]
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
#include "opt_inet.h"
|
|
#include "opt_inet6.h"
|
|
#include "opt_ipsec.h"
|
|
|
|
#include <sys/param.h>
|
|
#include <sys/systm.h>
|
|
#include <sys/hash.h>
|
|
#include <sys/refcount.h>
|
|
#include <sys/kernel.h>
|
|
#include <sys/sysctl.h>
|
|
#include <sys/limits.h>
|
|
#include <sys/lock.h>
|
|
#include <sys/mutex.h>
|
|
#include <sys/malloc.h>
|
|
#include <sys/mbuf.h>
|
|
#include <sys/proc.h> /* for proc0 declaration */
|
|
#include <sys/random.h>
|
|
#include <sys/socket.h>
|
|
#include <sys/socketvar.h>
|
|
#include <sys/syslog.h>
|
|
#include <sys/ucred.h>
|
|
|
|
#include <sys/md5.h>
|
|
#include <crypto/siphash/siphash.h>
|
|
|
|
#include <vm/uma.h>
|
|
|
|
#include <net/if.h>
|
|
#include <net/if_var.h>
|
|
#include <net/route.h>
|
|
#include <net/vnet.h>
|
|
|
|
#include <netinet/in.h>
|
|
#include <netinet/in_kdtrace.h>
|
|
#include <netinet/in_systm.h>
|
|
#include <netinet/ip.h>
|
|
#include <netinet/in_var.h>
|
|
#include <netinet/in_pcb.h>
|
|
#include <netinet/ip_var.h>
|
|
#include <netinet/ip_options.h>
|
|
#ifdef INET6
|
|
#include <netinet/ip6.h>
|
|
#include <netinet/icmp6.h>
|
|
#include <netinet6/nd6.h>
|
|
#include <netinet6/ip6_var.h>
|
|
#include <netinet6/in6_pcb.h>
|
|
#endif
|
|
#include <netinet/tcp.h>
|
|
#include <netinet/tcp_fastopen.h>
|
|
#include <netinet/tcp_fsm.h>
|
|
#include <netinet/tcp_seq.h>
|
|
#include <netinet/tcp_timer.h>
|
|
#include <netinet/tcp_var.h>
|
|
#include <netinet/tcp_syncache.h>
|
|
#include <netinet/tcp_ecn.h>
|
|
#ifdef TCP_BLACKBOX
|
|
#include <netinet/tcp_log_buf.h>
|
|
#endif
|
|
#ifdef TCP_OFFLOAD
|
|
#include <netinet/toecore.h>
|
|
#endif
|
|
#include <netinet/udp.h>
|
|
|
|
#include <netipsec/ipsec_support.h>
|
|
|
|
#include <machine/in_cksum.h>
|
|
|
|
#include <security/mac/mac_framework.h>
|
|
|
|
VNET_DEFINE_STATIC(int, tcp_syncookies) = 1;
|
|
#define V_tcp_syncookies VNET(tcp_syncookies)
|
|
SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_VNET | CTLFLAG_RW,
|
|
&VNET_NAME(tcp_syncookies), 0,
|
|
"Use TCP SYN cookies if the syncache overflows");
|
|
|
|
VNET_DEFINE_STATIC(int, tcp_syncookiesonly) = 0;
|
|
#define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
|
|
SYSCTL_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_VNET | CTLFLAG_RW,
|
|
&VNET_NAME(tcp_syncookiesonly), 0,
|
|
"Use only TCP SYN cookies");
|
|
|
|
#ifdef TCP_OFFLOAD
|
|
#define ADDED_BY_TOE(sc) ((sc)->sc_tod != NULL)
|
|
#endif
|
|
|
|
static void syncache_drop(struct syncache *, struct syncache_head *);
|
|
static void syncache_free(struct syncache *);
|
|
static void syncache_insert(struct syncache *, struct syncache_head *);
|
|
static int syncache_respond(struct syncache *, const struct mbuf *, int);
|
|
static struct socket *syncache_socket(struct syncache *, struct socket *,
|
|
struct mbuf *m);
|
|
static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
|
|
int docallout);
|
|
static void syncache_timer(void *);
|
|
|
|
static uint32_t syncookie_mac(struct in_conninfo *, tcp_seq, uint8_t,
|
|
uint8_t *, uintptr_t);
|
|
static tcp_seq syncookie_generate(struct syncache_head *, struct syncache *);
|
|
static struct syncache
|
|
*syncookie_lookup(struct in_conninfo *, struct syncache_head *,
|
|
struct syncache *, struct tcphdr *, struct tcpopt *,
|
|
struct socket *, uint16_t);
|
|
static void syncache_pause(struct in_conninfo *);
|
|
static void syncache_unpause(void *);
|
|
static void syncookie_reseed(void *);
|
|
#ifdef INVARIANTS
|
|
static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
|
|
struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
|
|
struct socket *lso, uint16_t port);
|
|
#endif
|
|
|
|
/*
|
|
* Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
|
|
* 3 retransmits corresponds to a timeout with default values of
|
|
* tcp_rexmit_initial * ( 1 +
|
|
* tcp_backoff[1] +
|
|
* tcp_backoff[2] +
|
|
* tcp_backoff[3]) + 3 * tcp_rexmit_slop,
|
|
* 1000 ms * (1 + 2 + 4 + 8) + 3 * 200 ms = 15600 ms,
|
|
* the odds are that the user has given up attempting to connect by then.
|
|
*/
|
|
#define SYNCACHE_MAXREXMTS 3
|
|
|
|
/* Arbitrary values */
|
|
#define TCP_SYNCACHE_HASHSIZE 512
|
|
#define TCP_SYNCACHE_BUCKETLIMIT 30
|
|
|
|
VNET_DEFINE_STATIC(struct tcp_syncache, tcp_syncache);
|
|
#define V_tcp_syncache VNET(tcp_syncache)
|
|
|
|
static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache,
|
|
CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
|
|
"TCP SYN cache");
|
|
|
|
SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
|
|
&VNET_NAME(tcp_syncache.bucket_limit), 0,
|
|
"Per-bucket hash limit for syncache");
|
|
|
|
SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN,
|
|
&VNET_NAME(tcp_syncache.cache_limit), 0,
|
|
"Overall entry limit for syncache");
|
|
|
|
SYSCTL_UMA_CUR(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_VNET,
|
|
&VNET_NAME(tcp_syncache.zone), "Current number of entries in syncache");
|
|
|
|
SYSCTL_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_VNET | CTLFLAG_RDTUN,
|
|
&VNET_NAME(tcp_syncache.hashsize), 0,
|
|
"Size of TCP syncache hashtable");
|
|
|
|
SYSCTL_BOOL(_net_inet_tcp_syncache, OID_AUTO, see_other, CTLFLAG_VNET |
|
|
CTLFLAG_RW, &VNET_NAME(tcp_syncache.see_other), 0,
|
|
"All syncache(4) entries are visible, ignoring UID/GID, jail(2) "
|
|
"and mac(4) checks");
|
|
|
|
static int
|
|
sysctl_net_inet_tcp_syncache_rexmtlimit_check(SYSCTL_HANDLER_ARGS)
|
|
{
|
|
int error;
|
|
u_int new;
|
|
|
|
new = V_tcp_syncache.rexmt_limit;
|
|
error = sysctl_handle_int(oidp, &new, 0, req);
|
|
if ((error == 0) && (req->newptr != NULL)) {
|
|
if (new > TCP_MAXRXTSHIFT)
|
|
error = EINVAL;
|
|
else
|
|
V_tcp_syncache.rexmt_limit = new;
|
|
}
|
|
return (error);
|
|
}
|
|
|
|
SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit,
|
|
CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
|
|
&VNET_NAME(tcp_syncache.rexmt_limit), 0,
|
|
sysctl_net_inet_tcp_syncache_rexmtlimit_check, "IU",
|
|
"Limit on SYN/ACK retransmissions");
|
|
|
|
VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 1;
|
|
SYSCTL_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
|
|
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
|
|
"Send reset on socket allocation failure");
|
|
|
|
static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
|
|
|
|
#define SCH_LOCK(sch) mtx_lock(&(sch)->sch_mtx)
|
|
#define SCH_UNLOCK(sch) mtx_unlock(&(sch)->sch_mtx)
|
|
#define SCH_LOCK_ASSERT(sch) mtx_assert(&(sch)->sch_mtx, MA_OWNED)
|
|
|
|
/*
|
|
* Requires the syncache entry to be already removed from the bucket list.
|
|
*/
|
|
static void
|
|
syncache_free(struct syncache *sc)
|
|
{
|
|
|
|
if (sc->sc_ipopts)
|
|
(void) m_free(sc->sc_ipopts);
|
|
if (sc->sc_cred)
|
|
crfree(sc->sc_cred);
|
|
#ifdef MAC
|
|
mac_syncache_destroy(&sc->sc_label);
|
|
#endif
|
|
|
|
uma_zfree(V_tcp_syncache.zone, sc);
|
|
}
|
|
|
|
void
|
|
syncache_init(void)
|
|
{
|
|
int i;
|
|
|
|
V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
|
|
V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
|
|
V_tcp_syncache.rexmt_limit = SYNCACHE_MAXREXMTS;
|
|
V_tcp_syncache.hash_secret = arc4random();
|
|
|
|
TUNABLE_INT_FETCH("net.inet.tcp.syncache.hashsize",
|
|
&V_tcp_syncache.hashsize);
|
|
TUNABLE_INT_FETCH("net.inet.tcp.syncache.bucketlimit",
|
|
&V_tcp_syncache.bucket_limit);
|
|
if (!powerof2(V_tcp_syncache.hashsize) ||
|
|
V_tcp_syncache.hashsize == 0) {
|
|
printf("WARNING: syncache hash size is not a power of 2.\n");
|
|
V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
|
|
}
|
|
V_tcp_syncache.hashmask = V_tcp_syncache.hashsize - 1;
|
|
|
|
/* Set limits. */
|
|
V_tcp_syncache.cache_limit =
|
|
V_tcp_syncache.hashsize * V_tcp_syncache.bucket_limit;
|
|
TUNABLE_INT_FETCH("net.inet.tcp.syncache.cachelimit",
|
|
&V_tcp_syncache.cache_limit);
|
|
|
|
/* Allocate the hash table. */
|
|
V_tcp_syncache.hashbase = malloc(V_tcp_syncache.hashsize *
|
|
sizeof(struct syncache_head), M_SYNCACHE, M_WAITOK | M_ZERO);
|
|
|
|
#ifdef VIMAGE
|
|
V_tcp_syncache.vnet = curvnet;
|
|
#endif
|
|
|
|
/* Initialize the hash buckets. */
|
|
for (i = 0; i < V_tcp_syncache.hashsize; i++) {
|
|
TAILQ_INIT(&V_tcp_syncache.hashbase[i].sch_bucket);
|
|
mtx_init(&V_tcp_syncache.hashbase[i].sch_mtx, "tcp_sc_head",
|
|
NULL, MTX_DEF);
|
|
callout_init_mtx(&V_tcp_syncache.hashbase[i].sch_timer,
|
|
&V_tcp_syncache.hashbase[i].sch_mtx, 0);
|
|
V_tcp_syncache.hashbase[i].sch_length = 0;
|
|
V_tcp_syncache.hashbase[i].sch_sc = &V_tcp_syncache;
|
|
V_tcp_syncache.hashbase[i].sch_last_overflow =
|
|
-(SYNCOOKIE_LIFETIME + 1);
|
|
}
|
|
|
|
/* Create the syncache entry zone. */
|
|
V_tcp_syncache.zone = uma_zcreate("syncache", sizeof(struct syncache),
|
|
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
|
|
V_tcp_syncache.cache_limit = uma_zone_set_max(V_tcp_syncache.zone,
|
|
V_tcp_syncache.cache_limit);
|
|
|
|
/* Start the SYN cookie reseeder callout. */
|
|
callout_init(&V_tcp_syncache.secret.reseed, 1);
|
|
arc4rand(V_tcp_syncache.secret.key[0], SYNCOOKIE_SECRET_SIZE, 0);
|
|
arc4rand(V_tcp_syncache.secret.key[1], SYNCOOKIE_SECRET_SIZE, 0);
|
|
callout_reset(&V_tcp_syncache.secret.reseed, SYNCOOKIE_LIFETIME * hz,
|
|
syncookie_reseed, &V_tcp_syncache);
|
|
|
|
/* Initialize the pause machinery. */
|
|
mtx_init(&V_tcp_syncache.pause_mtx, "tcp_sc_pause", NULL, MTX_DEF);
|
|
callout_init_mtx(&V_tcp_syncache.pause_co, &V_tcp_syncache.pause_mtx,
|
|
0);
|
|
V_tcp_syncache.pause_until = time_uptime - TCP_SYNCACHE_PAUSE_TIME;
|
|
V_tcp_syncache.pause_backoff = 0;
|
|
V_tcp_syncache.paused = false;
|
|
}
|
|
|
|
#ifdef VIMAGE
|
|
void
|
|
syncache_destroy(void)
|
|
{
|
|
struct syncache_head *sch;
|
|
struct syncache *sc, *nsc;
|
|
int i;
|
|
|
|
/*
|
|
* Stop the re-seed timer before freeing resources. No need to
|
|
* possibly schedule it another time.
|
|
*/
|
|
callout_drain(&V_tcp_syncache.secret.reseed);
|
|
|
|
/* Stop the SYN cache pause callout. */
|
|
mtx_lock(&V_tcp_syncache.pause_mtx);
|
|
if (callout_stop(&V_tcp_syncache.pause_co) == 0) {
|
|
mtx_unlock(&V_tcp_syncache.pause_mtx);
|
|
callout_drain(&V_tcp_syncache.pause_co);
|
|
} else
|
|
mtx_unlock(&V_tcp_syncache.pause_mtx);
|
|
|
|
/* Cleanup hash buckets: stop timers, free entries, destroy locks. */
|
|
for (i = 0; i < V_tcp_syncache.hashsize; i++) {
|
|
sch = &V_tcp_syncache.hashbase[i];
|
|
callout_drain(&sch->sch_timer);
|
|
|
|
SCH_LOCK(sch);
|
|
TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
|
|
syncache_drop(sc, sch);
|
|
SCH_UNLOCK(sch);
|
|
KASSERT(TAILQ_EMPTY(&sch->sch_bucket),
|
|
("%s: sch->sch_bucket not empty", __func__));
|
|
KASSERT(sch->sch_length == 0, ("%s: sch->sch_length %d not 0",
|
|
__func__, sch->sch_length));
|
|
mtx_destroy(&sch->sch_mtx);
|
|
}
|
|
|
|
KASSERT(uma_zone_get_cur(V_tcp_syncache.zone) == 0,
|
|
("%s: cache_count not 0", __func__));
|
|
|
|
/* Free the allocated global resources. */
|
|
uma_zdestroy(V_tcp_syncache.zone);
|
|
free(V_tcp_syncache.hashbase, M_SYNCACHE);
|
|
mtx_destroy(&V_tcp_syncache.pause_mtx);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Inserts a syncache entry into the specified bucket row.
|
|
* Locks and unlocks the syncache_head autonomously.
|
|
*/
|
|
static void
|
|
syncache_insert(struct syncache *sc, struct syncache_head *sch)
|
|
{
|
|
struct syncache *sc2;
|
|
|
|
SCH_LOCK(sch);
|
|
|
|
/*
|
|
* Make sure that we don't overflow the per-bucket limit.
|
|
* If the bucket is full, toss the oldest element.
|
|
*/
|
|
if (sch->sch_length >= V_tcp_syncache.bucket_limit) {
|
|
KASSERT(!TAILQ_EMPTY(&sch->sch_bucket),
|
|
("sch->sch_length incorrect"));
|
|
syncache_pause(&sc->sc_inc);
|
|
sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
|
|
sch->sch_last_overflow = time_uptime;
|
|
syncache_drop(sc2, sch);
|
|
}
|
|
|
|
/* Put it into the bucket. */
|
|
TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
|
|
sch->sch_length++;
|
|
|
|
#ifdef TCP_OFFLOAD
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
tod->tod_syncache_added(tod, sc->sc_todctx);
|
|
}
|
|
#endif
|
|
|
|
/* Reinitialize the bucket row's timer. */
|
|
if (sch->sch_length == 1)
|
|
sch->sch_nextc = ticks + INT_MAX;
|
|
syncache_timeout(sc, sch, 1);
|
|
|
|
SCH_UNLOCK(sch);
|
|
|
|
TCPSTATES_INC(TCPS_SYN_RECEIVED);
|
|
TCPSTAT_INC(tcps_sc_added);
|
|
}
|
|
|
|
/*
|
|
* Remove and free entry from syncache bucket row.
|
|
* Expects locked syncache head.
|
|
*/
|
|
static void
|
|
syncache_drop(struct syncache *sc, struct syncache_head *sch)
|
|
{
|
|
|
|
SCH_LOCK_ASSERT(sch);
|
|
|
|
TCPSTATES_DEC(TCPS_SYN_RECEIVED);
|
|
TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
|
|
sch->sch_length--;
|
|
|
|
#ifdef TCP_OFFLOAD
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
tod->tod_syncache_removed(tod, sc->sc_todctx);
|
|
}
|
|
#endif
|
|
|
|
syncache_free(sc);
|
|
}
|
|
|
|
/*
|
|
* Engage/reengage time on bucket row.
|
|
*/
|
|
static void
|
|
syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
|
|
{
|
|
int rexmt;
|
|
|
|
if (sc->sc_rxmits == 0)
|
|
rexmt = tcp_rexmit_initial;
|
|
else
|
|
TCPT_RANGESET(rexmt,
|
|
tcp_rexmit_initial * tcp_backoff[sc->sc_rxmits],
|
|
tcp_rexmit_min, TCPTV_REXMTMAX);
|
|
sc->sc_rxttime = ticks + rexmt;
|
|
sc->sc_rxmits++;
|
|
if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
|
|
sch->sch_nextc = sc->sc_rxttime;
|
|
if (docallout)
|
|
callout_reset(&sch->sch_timer, sch->sch_nextc - ticks,
|
|
syncache_timer, (void *)sch);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
|
|
* If we have retransmitted an entry the maximum number of times, expire it.
|
|
* One separate timer for each bucket row.
|
|
*/
|
|
static void
|
|
syncache_timer(void *xsch)
|
|
{
|
|
struct syncache_head *sch = (struct syncache_head *)xsch;
|
|
struct syncache *sc, *nsc;
|
|
struct epoch_tracker et;
|
|
int tick = ticks;
|
|
char *s;
|
|
bool paused;
|
|
|
|
CURVNET_SET(sch->sch_sc->vnet);
|
|
|
|
/* NB: syncache_head has already been locked by the callout. */
|
|
SCH_LOCK_ASSERT(sch);
|
|
|
|
/*
|
|
* In the following cycle we may remove some entries and/or
|
|
* advance some timeouts, so re-initialize the bucket timer.
|
|
*/
|
|
sch->sch_nextc = tick + INT_MAX;
|
|
|
|
/*
|
|
* If we have paused processing, unconditionally remove
|
|
* all syncache entries.
|
|
*/
|
|
mtx_lock(&V_tcp_syncache.pause_mtx);
|
|
paused = V_tcp_syncache.paused;
|
|
mtx_unlock(&V_tcp_syncache.pause_mtx);
|
|
|
|
TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc) {
|
|
if (paused) {
|
|
syncache_drop(sc, sch);
|
|
continue;
|
|
}
|
|
/*
|
|
* We do not check if the listen socket still exists
|
|
* and accept the case where the listen socket may be
|
|
* gone by the time we resend the SYN/ACK. We do
|
|
* not expect this to happens often. If it does,
|
|
* then the RST will be sent by the time the remote
|
|
* host does the SYN/ACK->ACK.
|
|
*/
|
|
if (TSTMP_GT(sc->sc_rxttime, tick)) {
|
|
if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc))
|
|
sch->sch_nextc = sc->sc_rxttime;
|
|
continue;
|
|
}
|
|
if (sc->sc_rxmits > V_tcp_ecn_maxretries) {
|
|
sc->sc_flags &= ~SCF_ECN_MASK;
|
|
}
|
|
if (sc->sc_rxmits > V_tcp_syncache.rexmt_limit) {
|
|
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
|
|
"giving up and removing syncache entry\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_stale);
|
|
continue;
|
|
}
|
|
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Response timeout, "
|
|
"retransmitting (%u) SYN|ACK\n",
|
|
s, __func__, sc->sc_rxmits);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
|
|
NET_EPOCH_ENTER(et);
|
|
if (syncache_respond(sc, NULL, TH_SYN|TH_ACK) == 0) {
|
|
syncache_timeout(sc, sch, 0);
|
|
TCPSTAT_INC(tcps_sndacks);
|
|
TCPSTAT_INC(tcps_sndtotal);
|
|
TCPSTAT_INC(tcps_sc_retransmitted);
|
|
} else {
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_dropped);
|
|
}
|
|
NET_EPOCH_EXIT(et);
|
|
}
|
|
if (!TAILQ_EMPTY(&(sch)->sch_bucket))
|
|
callout_reset(&(sch)->sch_timer, (sch)->sch_nextc - tick,
|
|
syncache_timer, (void *)(sch));
|
|
CURVNET_RESTORE();
|
|
}
|
|
|
|
/*
|
|
* Returns true if the system is only using cookies at the moment.
|
|
* This could be due to a sysadmin decision to only use cookies, or it
|
|
* could be due to the system detecting an attack.
|
|
*/
|
|
static inline bool
|
|
syncache_cookiesonly(void)
|
|
{
|
|
|
|
return (V_tcp_syncookies && (V_tcp_syncache.paused ||
|
|
V_tcp_syncookiesonly));
|
|
}
|
|
|
|
/*
|
|
* Find the hash bucket for the given connection.
|
|
*/
|
|
static struct syncache_head *
|
|
syncache_hashbucket(struct in_conninfo *inc)
|
|
{
|
|
uint32_t hash;
|
|
|
|
/*
|
|
* The hash is built on foreign port + local port + foreign address.
|
|
* We rely on the fact that struct in_conninfo starts with 16 bits
|
|
* of foreign port, then 16 bits of local port then followed by 128
|
|
* bits of foreign address. In case of IPv4 address, the first 3
|
|
* 32-bit words of the address always are zeroes.
|
|
*/
|
|
hash = jenkins_hash32((uint32_t *)&inc->inc_ie, 5,
|
|
V_tcp_syncache.hash_secret) & V_tcp_syncache.hashmask;
|
|
|
|
return (&V_tcp_syncache.hashbase[hash]);
|
|
}
|
|
|
|
/*
|
|
* Find an entry in the syncache.
|
|
* Returns always with locked syncache_head plus a matching entry or NULL.
|
|
*/
|
|
static struct syncache *
|
|
syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
|
|
{
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
|
|
*schp = sch = syncache_hashbucket(inc);
|
|
SCH_LOCK(sch);
|
|
|
|
/* Circle through bucket row to find matching entry. */
|
|
TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
|
|
if (bcmp(&inc->inc_ie, &sc->sc_inc.inc_ie,
|
|
sizeof(struct in_endpoints)) == 0)
|
|
break;
|
|
|
|
return (sc); /* Always returns with locked sch. */
|
|
}
|
|
|
|
/*
|
|
* This function is called when we get a RST for a
|
|
* non-existent connection, so that we can see if the
|
|
* connection is in the syn cache. If it is, zap it.
|
|
* If required send a challenge ACK.
|
|
*/
|
|
void
|
|
syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m,
|
|
uint16_t port)
|
|
{
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
char *s = NULL;
|
|
|
|
if (syncache_cookiesonly())
|
|
return;
|
|
sc = syncache_lookup(inc, &sch); /* returns locked sch */
|
|
SCH_LOCK_ASSERT(sch);
|
|
|
|
/*
|
|
* No corresponding connection was found in syncache.
|
|
* If syncookies are enabled and possibly exclusively
|
|
* used, or we are under memory pressure, a valid RST
|
|
* may not find a syncache entry. In that case we're
|
|
* done and no SYN|ACK retransmissions will happen.
|
|
* Otherwise the RST was misdirected or spoofed.
|
|
*/
|
|
if (sc == NULL) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: Spurious RST without matching "
|
|
"syncache entry (possibly syncookie only), "
|
|
"segment ignored\n", s, __func__);
|
|
TCPSTAT_INC(tcps_badrst);
|
|
goto done;
|
|
}
|
|
|
|
/* The remote UDP encaps port does not match. */
|
|
if (sc->sc_port != port) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: Spurious RST with matching "
|
|
"syncache entry but non-matching UDP encaps port, "
|
|
"segment ignored\n", s, __func__);
|
|
TCPSTAT_INC(tcps_badrst);
|
|
goto done;
|
|
}
|
|
|
|
/*
|
|
* If the RST bit is set, check the sequence number to see
|
|
* if this is a valid reset segment.
|
|
*
|
|
* RFC 793 page 37:
|
|
* In all states except SYN-SENT, all reset (RST) segments
|
|
* are validated by checking their SEQ-fields. A reset is
|
|
* valid if its sequence number is in the window.
|
|
*
|
|
* RFC 793 page 69:
|
|
* There are four cases for the acceptability test for an incoming
|
|
* segment:
|
|
*
|
|
* Segment Receive Test
|
|
* Length Window
|
|
* ------- ------- -------------------------------------------
|
|
* 0 0 SEG.SEQ = RCV.NXT
|
|
* 0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
|
|
* >0 0 not acceptable
|
|
* >0 >0 RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
|
|
* or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND
|
|
*
|
|
* Note that when receiving a SYN segment in the LISTEN state,
|
|
* IRS is set to SEG.SEQ and RCV.NXT is set to SEG.SEQ+1, as
|
|
* described in RFC 793, page 66.
|
|
*/
|
|
if ((SEQ_GEQ(th->th_seq, sc->sc_irs + 1) &&
|
|
SEQ_LT(th->th_seq, sc->sc_irs + 1 + sc->sc_wnd)) ||
|
|
(sc->sc_wnd == 0 && th->th_seq == sc->sc_irs + 1)) {
|
|
if (V_tcp_insecure_rst ||
|
|
th->th_seq == sc->sc_irs + 1) {
|
|
syncache_drop(sc, sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG,
|
|
"%s; %s: Our SYN|ACK was rejected, "
|
|
"connection attempt aborted by remote "
|
|
"endpoint\n",
|
|
s, __func__);
|
|
TCPSTAT_INC(tcps_sc_reset);
|
|
} else {
|
|
TCPSTAT_INC(tcps_badrst);
|
|
/* Send challenge ACK. */
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: RST with invalid "
|
|
" SEQ %u != NXT %u (+WND %u), "
|
|
"sending challenge ACK\n",
|
|
s, __func__,
|
|
th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
|
|
if (syncache_respond(sc, m, TH_ACK) == 0) {
|
|
TCPSTAT_INC(tcps_sndacks);
|
|
TCPSTAT_INC(tcps_sndtotal);
|
|
} else {
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_dropped);
|
|
}
|
|
}
|
|
} else {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
|
|
"NXT %u (+WND %u), segment ignored\n",
|
|
s, __func__,
|
|
th->th_seq, sc->sc_irs + 1, sc->sc_wnd);
|
|
TCPSTAT_INC(tcps_badrst);
|
|
}
|
|
|
|
done:
|
|
if (s != NULL)
|
|
free(s, M_TCPLOG);
|
|
SCH_UNLOCK(sch);
|
|
}
|
|
|
|
void
|
|
syncache_badack(struct in_conninfo *inc, uint16_t port)
|
|
{
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
|
|
if (syncache_cookiesonly())
|
|
return;
|
|
sc = syncache_lookup(inc, &sch); /* returns locked sch */
|
|
SCH_LOCK_ASSERT(sch);
|
|
if ((sc != NULL) && (sc->sc_port == port)) {
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_badack);
|
|
}
|
|
SCH_UNLOCK(sch);
|
|
}
|
|
|
|
void
|
|
syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq, uint16_t port)
|
|
{
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
|
|
if (syncache_cookiesonly())
|
|
return;
|
|
sc = syncache_lookup(inc, &sch); /* returns locked sch */
|
|
SCH_LOCK_ASSERT(sch);
|
|
if (sc == NULL)
|
|
goto done;
|
|
|
|
/* If the port != sc_port, then it's a bogus ICMP msg */
|
|
if (port != sc->sc_port)
|
|
goto done;
|
|
|
|
/* If the sequence number != sc_iss, then it's a bogus ICMP msg */
|
|
if (ntohl(th_seq) != sc->sc_iss)
|
|
goto done;
|
|
|
|
/*
|
|
* If we've rertransmitted 3 times and this is our second error,
|
|
* we remove the entry. Otherwise, we allow it to continue on.
|
|
* This prevents us from incorrectly nuking an entry during a
|
|
* spurious network outage.
|
|
*
|
|
* See tcp_notify().
|
|
*/
|
|
if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxmits < 3 + 1) {
|
|
sc->sc_flags |= SCF_UNREACH;
|
|
goto done;
|
|
}
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_unreach);
|
|
done:
|
|
SCH_UNLOCK(sch);
|
|
}
|
|
|
|
/*
|
|
* Build a new TCP socket structure from a syncache entry.
|
|
*
|
|
* On success return the newly created socket with its underlying inp locked.
|
|
*/
|
|
static struct socket *
|
|
syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
|
|
{
|
|
struct inpcb *inp = NULL;
|
|
struct socket *so;
|
|
struct tcpcb *tp;
|
|
int error;
|
|
char *s;
|
|
|
|
NET_EPOCH_ASSERT();
|
|
|
|
/*
|
|
* Ok, create the full blown connection, and set things up
|
|
* as they would have been set up if we had created the
|
|
* connection when the SYN arrived.
|
|
*/
|
|
if ((so = solisten_clone(lso)) == NULL)
|
|
goto allocfail;
|
|
#ifdef MAC
|
|
mac_socketpeer_set_from_mbuf(m, so);
|
|
#endif
|
|
error = in_pcballoc(so, &V_tcbinfo);
|
|
if (error) {
|
|
sodealloc(so);
|
|
goto allocfail;
|
|
}
|
|
inp = sotoinpcb(so);
|
|
if ((tp = tcp_newtcpcb(inp, sototcpcb(lso))) == NULL) {
|
|
in_pcbfree(inp);
|
|
sodealloc(so);
|
|
goto allocfail;
|
|
}
|
|
inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
|
|
#ifdef INET6
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6) {
|
|
inp->inp_vflag &= ~INP_IPV4;
|
|
inp->inp_vflag |= INP_IPV6;
|
|
inp->in6p_laddr = sc->sc_inc.inc6_laddr;
|
|
} else {
|
|
inp->inp_vflag &= ~INP_IPV6;
|
|
inp->inp_vflag |= INP_IPV4;
|
|
#endif
|
|
inp->inp_ip_ttl = sc->sc_ip_ttl;
|
|
inp->inp_ip_tos = sc->sc_ip_tos;
|
|
inp->inp_laddr = sc->sc_inc.inc_laddr;
|
|
#ifdef INET6
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* If there's an mbuf and it has a flowid, then let's initialise the
|
|
* inp with that particular flowid.
|
|
*/
|
|
if (m != NULL && M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
|
|
inp->inp_flowid = m->m_pkthdr.flowid;
|
|
inp->inp_flowtype = M_HASHTYPE_GET(m);
|
|
#ifdef NUMA
|
|
inp->inp_numa_domain = m->m_pkthdr.numa_domain;
|
|
#endif
|
|
}
|
|
|
|
inp->inp_lport = sc->sc_inc.inc_lport;
|
|
#ifdef INET6
|
|
if (inp->inp_vflag & INP_IPV6PROTO) {
|
|
struct inpcb *oinp = sotoinpcb(lso);
|
|
|
|
/*
|
|
* Inherit socket options from the listening socket.
|
|
* Note that in6p_inputopts are not (and should not be)
|
|
* copied, since it stores previously received options and is
|
|
* used to detect if each new option is different than the
|
|
* previous one and hence should be passed to a user.
|
|
* If we copied in6p_inputopts, a user would not be able to
|
|
* receive options just after calling the accept system call.
|
|
*/
|
|
inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS;
|
|
if (oinp->in6p_outputopts)
|
|
inp->in6p_outputopts =
|
|
ip6_copypktopts(oinp->in6p_outputopts, M_NOWAIT);
|
|
inp->in6p_hops = oinp->in6p_hops;
|
|
}
|
|
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6) {
|
|
struct sockaddr_in6 sin6;
|
|
|
|
sin6.sin6_family = AF_INET6;
|
|
sin6.sin6_len = sizeof(sin6);
|
|
sin6.sin6_addr = sc->sc_inc.inc6_faddr;
|
|
sin6.sin6_port = sc->sc_inc.inc_fport;
|
|
sin6.sin6_flowinfo = sin6.sin6_scope_id = 0;
|
|
INP_HASH_WLOCK(&V_tcbinfo);
|
|
error = in6_pcbconnect(inp, &sin6, thread0.td_ucred, false);
|
|
INP_HASH_WUNLOCK(&V_tcbinfo);
|
|
if (error != 0)
|
|
goto abort;
|
|
/* Override flowlabel from in6_pcbconnect. */
|
|
inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
|
|
inp->inp_flow |= sc->sc_flowlabel;
|
|
}
|
|
#endif /* INET6 */
|
|
#if defined(INET) && defined(INET6)
|
|
else
|
|
#endif
|
|
#ifdef INET
|
|
{
|
|
struct sockaddr_in sin;
|
|
|
|
inp->inp_options = (m) ? ip_srcroute(m) : NULL;
|
|
|
|
if (inp->inp_options == NULL) {
|
|
inp->inp_options = sc->sc_ipopts;
|
|
sc->sc_ipopts = NULL;
|
|
}
|
|
|
|
sin.sin_family = AF_INET;
|
|
sin.sin_len = sizeof(sin);
|
|
sin.sin_addr = sc->sc_inc.inc_faddr;
|
|
sin.sin_port = sc->sc_inc.inc_fport;
|
|
bzero((caddr_t)sin.sin_zero, sizeof(sin.sin_zero));
|
|
INP_HASH_WLOCK(&V_tcbinfo);
|
|
error = in_pcbconnect(inp, &sin, thread0.td_ucred, false);
|
|
INP_HASH_WUNLOCK(&V_tcbinfo);
|
|
if (error != 0)
|
|
goto abort;
|
|
}
|
|
#endif /* INET */
|
|
#if defined(IPSEC) || defined(IPSEC_SUPPORT)
|
|
/* Copy old policy into new socket's. */
|
|
if (ipsec_copy_pcbpolicy(sotoinpcb(lso), inp) != 0)
|
|
printf("syncache_socket: could not copy policy\n");
|
|
#endif
|
|
tp->t_state = TCPS_SYN_RECEIVED;
|
|
tp->iss = sc->sc_iss;
|
|
tp->irs = sc->sc_irs;
|
|
tp->t_port = sc->sc_port;
|
|
tcp_rcvseqinit(tp);
|
|
tcp_sendseqinit(tp);
|
|
tp->snd_wl1 = sc->sc_irs;
|
|
tp->snd_max = tp->iss + 1;
|
|
tp->snd_nxt = tp->iss + 1;
|
|
tp->rcv_up = sc->sc_irs + 1;
|
|
tp->rcv_wnd = sc->sc_wnd;
|
|
tp->rcv_adv += tp->rcv_wnd;
|
|
tp->last_ack_sent = tp->rcv_nxt;
|
|
|
|
tp->t_flags = sototcpcb(lso)->t_flags &
|
|
(TF_LRD|TF_NOPUSH|TF_NODELAY);
|
|
if (sc->sc_flags & SCF_NOOPT)
|
|
tp->t_flags |= TF_NOOPT;
|
|
else {
|
|
if (sc->sc_flags & SCF_WINSCALE) {
|
|
tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
|
|
tp->snd_scale = sc->sc_requested_s_scale;
|
|
tp->request_r_scale = sc->sc_requested_r_scale;
|
|
}
|
|
if (sc->sc_flags & SCF_TIMESTAMP) {
|
|
tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
|
|
tp->ts_recent = sc->sc_tsreflect;
|
|
tp->ts_recent_age = tcp_ts_getticks();
|
|
tp->ts_offset = sc->sc_tsoff;
|
|
}
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
if (sc->sc_flags & SCF_SIGNATURE)
|
|
tp->t_flags |= TF_SIGNATURE;
|
|
#endif
|
|
if (sc->sc_flags & SCF_SACK)
|
|
tp->t_flags |= TF_SACK_PERMIT;
|
|
}
|
|
|
|
tcp_ecn_syncache_socket(tp, sc);
|
|
|
|
/*
|
|
* Set up MSS and get cached values from tcp_hostcache.
|
|
* This might overwrite some of the defaults we just set.
|
|
*/
|
|
tcp_mss(tp, sc->sc_peer_mss);
|
|
|
|
/*
|
|
* If the SYN,ACK was retransmitted, indicate that CWND to be
|
|
* limited to one segment in cc_conn_init().
|
|
* NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
|
|
*/
|
|
if (sc->sc_rxmits > 1)
|
|
tp->snd_cwnd = 1;
|
|
|
|
#ifdef TCP_OFFLOAD
|
|
/*
|
|
* Allow a TOE driver to install its hooks. Note that we hold the
|
|
* pcbinfo lock too and that prevents tcp_usr_accept from accepting a
|
|
* new connection before the TOE driver has done its thing.
|
|
*/
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
tod->tod_offload_socket(tod, sc->sc_todctx, so);
|
|
}
|
|
#endif
|
|
#ifdef TCP_BLACKBOX
|
|
/*
|
|
* Inherit the log state from the listening socket, if
|
|
* - the log state of the listening socket is not off and
|
|
* - the listening socket was not auto selected from all sessions and
|
|
* - a log id is not set on the listening socket.
|
|
* This avoids inheriting a log state which was automatically set.
|
|
*/
|
|
if ((tcp_get_bblog_state(sototcpcb(lso)) != TCP_LOG_STATE_OFF) &&
|
|
((sototcpcb(lso)->t_flags2 & TF2_LOG_AUTO) == 0) &&
|
|
(sototcpcb(lso)->t_lib == NULL)) {
|
|
tcp_log_state_change(tp, tcp_get_bblog_state(sototcpcb(lso)));
|
|
}
|
|
#endif
|
|
/*
|
|
* Copy and activate timers.
|
|
*/
|
|
tp->t_maxunacktime = sototcpcb(lso)->t_maxunacktime;
|
|
tp->t_keepinit = sototcpcb(lso)->t_keepinit;
|
|
tp->t_keepidle = sototcpcb(lso)->t_keepidle;
|
|
tp->t_keepintvl = sototcpcb(lso)->t_keepintvl;
|
|
tp->t_keepcnt = sototcpcb(lso)->t_keepcnt;
|
|
tcp_timer_activate(tp, TT_KEEP, TP_KEEPINIT(tp));
|
|
|
|
TCPSTAT_INC(tcps_accepts);
|
|
TCP_PROBE6(state__change, NULL, tp, NULL, tp, NULL, TCPS_LISTEN);
|
|
|
|
if (!solisten_enqueue(so, SS_ISCONNECTED))
|
|
tp->t_flags |= TF_SONOTCONN;
|
|
/* Can we inherit anything from the listener? */
|
|
if (tp->t_fb->tfb_inherit != NULL) {
|
|
(*tp->t_fb->tfb_inherit)(tp, sotoinpcb(lso));
|
|
}
|
|
return (so);
|
|
|
|
allocfail:
|
|
/*
|
|
* Drop the connection; we will either send a RST or have the peer
|
|
* retransmit its SYN again after its RTO and try again.
|
|
*/
|
|
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Socket create failed "
|
|
"due to limits or memory shortage\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
TCPSTAT_INC(tcps_listendrop);
|
|
return (NULL);
|
|
|
|
abort:
|
|
tcp_discardcb(tp);
|
|
in_pcbfree(inp);
|
|
sodealloc(so);
|
|
if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: in%s_pcbconnect failed with error %i\n",
|
|
s, __func__, (sc->sc_inc.inc_flags & INC_ISIPV6) ? "6" : "",
|
|
error);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
TCPSTAT_INC(tcps_listendrop);
|
|
return (NULL);
|
|
}
|
|
|
|
/*
|
|
* This function gets called when we receive an ACK for a
|
|
* socket in the LISTEN state. We look up the connection
|
|
* in the syncache, and if its there, we pull it out of
|
|
* the cache and turn it into a full-blown connection in
|
|
* the SYN-RECEIVED state.
|
|
*
|
|
* On syncache_socket() success the newly created socket
|
|
* has its underlying inp locked.
|
|
*/
|
|
int
|
|
syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
|
|
struct socket **lsop, struct mbuf *m, uint16_t port)
|
|
{
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
struct syncache scs;
|
|
char *s;
|
|
bool locked;
|
|
|
|
NET_EPOCH_ASSERT();
|
|
KASSERT((tcp_get_flags(th) & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
|
|
("%s: can handle only ACK", __func__));
|
|
|
|
if (syncache_cookiesonly()) {
|
|
sc = NULL;
|
|
sch = syncache_hashbucket(inc);
|
|
locked = false;
|
|
} else {
|
|
sc = syncache_lookup(inc, &sch); /* returns locked sch */
|
|
locked = true;
|
|
SCH_LOCK_ASSERT(sch);
|
|
}
|
|
|
|
#ifdef INVARIANTS
|
|
/*
|
|
* Test code for syncookies comparing the syncache stored
|
|
* values with the reconstructed values from the cookie.
|
|
*/
|
|
if (sc != NULL)
|
|
syncookie_cmp(inc, sch, sc, th, to, *lsop, port);
|
|
#endif
|
|
|
|
if (sc == NULL) {
|
|
/*
|
|
* There is no syncache entry, so see if this ACK is
|
|
* a returning syncookie. To do this, first:
|
|
* A. Check if syncookies are used in case of syncache
|
|
* overflows
|
|
* B. See if this socket has had a syncache entry dropped in
|
|
* the recent past. We don't want to accept a bogus
|
|
* syncookie if we've never received a SYN or accept it
|
|
* twice.
|
|
* C. check that the syncookie is valid. If it is, then
|
|
* cobble up a fake syncache entry, and return.
|
|
*/
|
|
if (locked && !V_tcp_syncookies) {
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: Spurious ACK, "
|
|
"segment rejected (syncookies disabled)\n",
|
|
s, __func__);
|
|
goto failed;
|
|
}
|
|
if (locked && !V_tcp_syncookiesonly &&
|
|
sch->sch_last_overflow < time_uptime - SYNCOOKIE_LIFETIME) {
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: Spurious ACK, "
|
|
"segment rejected (no syncache entry)\n",
|
|
s, __func__);
|
|
goto failed;
|
|
}
|
|
bzero(&scs, sizeof(scs));
|
|
sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop, port);
|
|
if (locked)
|
|
SCH_UNLOCK(sch);
|
|
if (sc == NULL) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: Segment failed "
|
|
"SYNCOOKIE authentication, segment rejected "
|
|
"(probably spoofed)\n", s, __func__);
|
|
goto failed;
|
|
}
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
/* If received ACK has MD5 signature, check it. */
|
|
if ((to->to_flags & TOF_SIGNATURE) != 0 &&
|
|
(!TCPMD5_ENABLED() ||
|
|
TCPMD5_INPUT(m, th, to->to_signature) != 0)) {
|
|
/* Drop the ACK. */
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Segment rejected, "
|
|
"MD5 signature doesn't match.\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
TCPSTAT_INC(tcps_sig_err_sigopt);
|
|
return (-1); /* Do not send RST */
|
|
}
|
|
#endif /* TCP_SIGNATURE */
|
|
TCPSTATES_INC(TCPS_SYN_RECEIVED);
|
|
} else {
|
|
if (sc->sc_port != port) {
|
|
SCH_UNLOCK(sch);
|
|
return (0);
|
|
}
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
/*
|
|
* If listening socket requested TCP digests, check that
|
|
* received ACK has signature and it is correct.
|
|
* If not, drop the ACK and leave sc entry in th cache,
|
|
* because SYN was received with correct signature.
|
|
*/
|
|
if (sc->sc_flags & SCF_SIGNATURE) {
|
|
if ((to->to_flags & TOF_SIGNATURE) == 0) {
|
|
/* No signature */
|
|
TCPSTAT_INC(tcps_sig_err_nosigopt);
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Segment "
|
|
"rejected, MD5 signature wasn't "
|
|
"provided.\n", s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
return (-1); /* Do not send RST */
|
|
}
|
|
if (!TCPMD5_ENABLED() ||
|
|
TCPMD5_INPUT(m, th, to->to_signature) != 0) {
|
|
/* Doesn't match or no SA */
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Segment "
|
|
"rejected, MD5 signature doesn't "
|
|
"match.\n", s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
return (-1); /* Do not send RST */
|
|
}
|
|
}
|
|
#endif /* TCP_SIGNATURE */
|
|
|
|
/*
|
|
* RFC 7323 PAWS: If we have a timestamp on this segment and
|
|
* it's less than ts_recent, drop it.
|
|
* XXXMT: RFC 7323 also requires to send an ACK.
|
|
* In tcp_input.c this is only done for TCP segments
|
|
* with user data, so be consistent here and just drop
|
|
* the segment.
|
|
*/
|
|
if (sc->sc_flags & SCF_TIMESTAMP && to->to_flags & TOF_TS &&
|
|
TSTMP_LT(to->to_tsval, sc->sc_tsreflect)) {
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG,
|
|
"%s; %s: SEG.TSval %u < TS.Recent %u, "
|
|
"segment dropped\n", s, __func__,
|
|
to->to_tsval, sc->sc_tsreflect);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
return (-1); /* Do not send RST */
|
|
}
|
|
|
|
/*
|
|
* If timestamps were not negotiated during SYN/ACK and a
|
|
* segment with a timestamp is received, ignore the
|
|
* timestamp and process the packet normally.
|
|
* See section 3.2 of RFC 7323.
|
|
*/
|
|
if (!(sc->sc_flags & SCF_TIMESTAMP) &&
|
|
(to->to_flags & TOF_TS)) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Timestamp not "
|
|
"expected, segment processed normally\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
s = NULL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If timestamps were negotiated during SYN/ACK and a
|
|
* segment without a timestamp is received, silently drop
|
|
* the segment, unless the missing timestamps are tolerated.
|
|
* See section 3.2 of RFC 7323.
|
|
*/
|
|
if ((sc->sc_flags & SCF_TIMESTAMP) &&
|
|
!(to->to_flags & TOF_TS)) {
|
|
if (V_tcp_tolerate_missing_ts) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG,
|
|
"%s; %s: Timestamp missing, "
|
|
"segment processed normally\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
} else {
|
|
SCH_UNLOCK(sch);
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG,
|
|
"%s; %s: Timestamp missing, "
|
|
"segment silently dropped\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
return (-1); /* Do not send RST */
|
|
}
|
|
}
|
|
TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
|
|
sch->sch_length--;
|
|
#ifdef TCP_OFFLOAD
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
tod->tod_syncache_removed(tod, sc->sc_todctx);
|
|
}
|
|
#endif
|
|
SCH_UNLOCK(sch);
|
|
}
|
|
|
|
/*
|
|
* Segment validation:
|
|
* ACK must match our initial sequence number + 1 (the SYN|ACK).
|
|
*/
|
|
if (th->th_ack != sc->sc_iss + 1) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: ACK %u != ISS+1 %u, segment "
|
|
"rejected\n", s, __func__, th->th_ack, sc->sc_iss);
|
|
goto failed;
|
|
}
|
|
|
|
/*
|
|
* The SEQ must fall in the window starting at the received
|
|
* initial receive sequence number + 1 (the SYN).
|
|
*/
|
|
if (SEQ_LEQ(th->th_seq, sc->sc_irs) ||
|
|
SEQ_GT(th->th_seq, sc->sc_irs + sc->sc_wnd)) {
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
|
|
log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
|
|
"rejected\n", s, __func__, th->th_seq, sc->sc_irs);
|
|
goto failed;
|
|
}
|
|
|
|
*lsop = syncache_socket(sc, *lsop, m);
|
|
|
|
if (__predict_false(*lsop == NULL)) {
|
|
TCPSTAT_INC(tcps_sc_aborted);
|
|
TCPSTATES_DEC(TCPS_SYN_RECEIVED);
|
|
} else
|
|
TCPSTAT_INC(tcps_sc_completed);
|
|
|
|
/* how do we find the inp for the new socket? */
|
|
if (sc != &scs)
|
|
syncache_free(sc);
|
|
return (1);
|
|
failed:
|
|
if (sc != NULL) {
|
|
TCPSTATES_DEC(TCPS_SYN_RECEIVED);
|
|
if (sc != &scs)
|
|
syncache_free(sc);
|
|
}
|
|
if (s != NULL)
|
|
free(s, M_TCPLOG);
|
|
*lsop = NULL;
|
|
return (0);
|
|
}
|
|
|
|
static struct socket *
|
|
syncache_tfo_expand(struct syncache *sc, struct socket *lso, struct mbuf *m,
|
|
uint64_t response_cookie)
|
|
{
|
|
struct inpcb *inp;
|
|
struct tcpcb *tp;
|
|
unsigned int *pending_counter;
|
|
struct socket *so;
|
|
|
|
NET_EPOCH_ASSERT();
|
|
|
|
pending_counter = intotcpcb(sotoinpcb(lso))->t_tfo_pending;
|
|
so = syncache_socket(sc, lso, m);
|
|
if (so == NULL) {
|
|
TCPSTAT_INC(tcps_sc_aborted);
|
|
atomic_subtract_int(pending_counter, 1);
|
|
} else {
|
|
soisconnected(so);
|
|
inp = sotoinpcb(so);
|
|
tp = intotcpcb(inp);
|
|
tp->t_flags |= TF_FASTOPEN;
|
|
tp->t_tfo_cookie.server = response_cookie;
|
|
tp->snd_max = tp->iss;
|
|
tp->snd_nxt = tp->iss;
|
|
tp->t_tfo_pending = pending_counter;
|
|
TCPSTATES_INC(TCPS_SYN_RECEIVED);
|
|
TCPSTAT_INC(tcps_sc_completed);
|
|
}
|
|
|
|
return (so);
|
|
}
|
|
|
|
/*
|
|
* Given a LISTEN socket and an inbound SYN request, add
|
|
* this to the syn cache, and send back a segment:
|
|
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
|
|
* to the source.
|
|
*
|
|
* IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
|
|
* Doing so would require that we hold onto the data and deliver it
|
|
* to the application. However, if we are the target of a SYN-flood
|
|
* DoS attack, an attacker could send data which would eventually
|
|
* consume all available buffer space if it were ACKed. By not ACKing
|
|
* the data, we avoid this DoS scenario.
|
|
*
|
|
* The exception to the above is when a SYN with a valid TCP Fast Open (TFO)
|
|
* cookie is processed and a new socket is created. In this case, any data
|
|
* accompanying the SYN will be queued to the socket by tcp_input() and will
|
|
* be ACKed either when the application sends response data or the delayed
|
|
* ACK timer expires, whichever comes first.
|
|
*/
|
|
struct socket *
|
|
syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
|
|
struct inpcb *inp, struct socket *so, struct mbuf *m, void *tod,
|
|
void *todctx, uint8_t iptos, uint16_t port)
|
|
{
|
|
struct tcpcb *tp;
|
|
struct socket *rv = NULL;
|
|
struct syncache *sc = NULL;
|
|
struct syncache_head *sch;
|
|
struct mbuf *ipopts = NULL;
|
|
u_int ltflags;
|
|
int win, ip_ttl, ip_tos;
|
|
char *s;
|
|
#ifdef INET6
|
|
int autoflowlabel = 0;
|
|
#endif
|
|
#ifdef MAC
|
|
struct label *maclabel;
|
|
#endif
|
|
struct syncache scs;
|
|
struct ucred *cred;
|
|
uint64_t tfo_response_cookie;
|
|
unsigned int *tfo_pending = NULL;
|
|
int tfo_cookie_valid = 0;
|
|
int tfo_response_cookie_valid = 0;
|
|
bool locked;
|
|
|
|
INP_RLOCK_ASSERT(inp); /* listen socket */
|
|
KASSERT((tcp_get_flags(th) & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN,
|
|
("%s: unexpected tcp flags", __func__));
|
|
|
|
/*
|
|
* Combine all so/tp operations very early to drop the INP lock as
|
|
* soon as possible.
|
|
*/
|
|
KASSERT(SOLISTENING(so), ("%s: %p not listening", __func__, so));
|
|
tp = sototcpcb(so);
|
|
cred = V_tcp_syncache.see_other ? NULL : crhold(so->so_cred);
|
|
|
|
#ifdef INET6
|
|
if (inc->inc_flags & INC_ISIPV6) {
|
|
if (inp->inp_flags & IN6P_AUTOFLOWLABEL) {
|
|
autoflowlabel = 1;
|
|
}
|
|
ip_ttl = in6_selecthlim(inp, NULL);
|
|
if ((inp->in6p_outputopts == NULL) ||
|
|
(inp->in6p_outputopts->ip6po_tclass == -1)) {
|
|
ip_tos = 0;
|
|
} else {
|
|
ip_tos = inp->in6p_outputopts->ip6po_tclass;
|
|
}
|
|
}
|
|
#endif
|
|
#if defined(INET6) && defined(INET)
|
|
else
|
|
#endif
|
|
#ifdef INET
|
|
{
|
|
ip_ttl = inp->inp_ip_ttl;
|
|
ip_tos = inp->inp_ip_tos;
|
|
}
|
|
#endif
|
|
win = so->sol_sbrcv_hiwat;
|
|
ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
|
|
|
|
if (V_tcp_fastopen_server_enable && (tp->t_flags & TF_FASTOPEN) &&
|
|
(tp->t_tfo_pending != NULL) &&
|
|
(to->to_flags & TOF_FASTOPEN)) {
|
|
/*
|
|
* Limit the number of pending TFO connections to
|
|
* approximately half of the queue limit. This prevents TFO
|
|
* SYN floods from starving the service by filling the
|
|
* listen queue with bogus TFO connections.
|
|
*/
|
|
if (atomic_fetchadd_int(tp->t_tfo_pending, 1) <=
|
|
(so->sol_qlimit / 2)) {
|
|
int result;
|
|
|
|
result = tcp_fastopen_check_cookie(inc,
|
|
to->to_tfo_cookie, to->to_tfo_len,
|
|
&tfo_response_cookie);
|
|
tfo_cookie_valid = (result > 0);
|
|
tfo_response_cookie_valid = (result >= 0);
|
|
}
|
|
|
|
/*
|
|
* Remember the TFO pending counter as it will have to be
|
|
* decremented below if we don't make it to syncache_tfo_expand().
|
|
*/
|
|
tfo_pending = tp->t_tfo_pending;
|
|
}
|
|
|
|
#ifdef MAC
|
|
if (mac_syncache_init(&maclabel) != 0) {
|
|
INP_RUNLOCK(inp);
|
|
goto done;
|
|
} else
|
|
mac_syncache_create(maclabel, inp);
|
|
#endif
|
|
if (!tfo_cookie_valid)
|
|
INP_RUNLOCK(inp);
|
|
|
|
/*
|
|
* Remember the IP options, if any.
|
|
*/
|
|
#ifdef INET6
|
|
if (!(inc->inc_flags & INC_ISIPV6))
|
|
#endif
|
|
#ifdef INET
|
|
ipopts = (m) ? ip_srcroute(m) : NULL;
|
|
#else
|
|
ipopts = NULL;
|
|
#endif
|
|
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
/*
|
|
* When the socket is TCP-MD5 enabled check that,
|
|
* - a signed packet is valid
|
|
* - a non-signed packet does not have a security association
|
|
*
|
|
* If a signed packet fails validation or a non-signed packet has a
|
|
* security association, the packet will be dropped.
|
|
*/
|
|
if (ltflags & TF_SIGNATURE) {
|
|
if (to->to_flags & TOF_SIGNATURE) {
|
|
if (!TCPMD5_ENABLED() ||
|
|
TCPMD5_INPUT(m, th, to->to_signature) != 0)
|
|
goto done;
|
|
} else {
|
|
if (TCPMD5_ENABLED() &&
|
|
TCPMD5_INPUT(m, NULL, NULL) != ENOENT)
|
|
goto done;
|
|
}
|
|
} else if (to->to_flags & TOF_SIGNATURE)
|
|
goto done;
|
|
#endif /* TCP_SIGNATURE */
|
|
/*
|
|
* See if we already have an entry for this connection.
|
|
* If we do, resend the SYN,ACK, and reset the retransmit timer.
|
|
*
|
|
* XXX: should the syncache be re-initialized with the contents
|
|
* of the new SYN here (which may have different options?)
|
|
*
|
|
* XXX: We do not check the sequence number to see if this is a
|
|
* real retransmit or a new connection attempt. The question is
|
|
* how to handle such a case; either ignore it as spoofed, or
|
|
* drop the current entry and create a new one?
|
|
*/
|
|
if (syncache_cookiesonly()) {
|
|
sc = NULL;
|
|
sch = syncache_hashbucket(inc);
|
|
locked = false;
|
|
} else {
|
|
sc = syncache_lookup(inc, &sch); /* returns locked sch */
|
|
locked = true;
|
|
SCH_LOCK_ASSERT(sch);
|
|
}
|
|
if (sc != NULL) {
|
|
if (tfo_cookie_valid)
|
|
INP_RUNLOCK(inp);
|
|
TCPSTAT_INC(tcps_sc_dupsyn);
|
|
if (ipopts) {
|
|
/*
|
|
* If we were remembering a previous source route,
|
|
* forget it and use the new one we've been given.
|
|
*/
|
|
if (sc->sc_ipopts)
|
|
(void) m_free(sc->sc_ipopts);
|
|
sc->sc_ipopts = ipopts;
|
|
}
|
|
/*
|
|
* Update timestamp if present.
|
|
*/
|
|
if ((sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS))
|
|
sc->sc_tsreflect = to->to_tsval;
|
|
else
|
|
sc->sc_flags &= ~SCF_TIMESTAMP;
|
|
/*
|
|
* Adjust ECN response if needed, e.g. different
|
|
* IP ECN field, or a fallback by the remote host.
|
|
*/
|
|
if (sc->sc_flags & SCF_ECN_MASK) {
|
|
sc->sc_flags &= ~SCF_ECN_MASK;
|
|
sc->sc_flags |= tcp_ecn_syncache_add(tcp_get_flags(th), iptos);
|
|
}
|
|
#ifdef MAC
|
|
/*
|
|
* Since we have already unconditionally allocated label
|
|
* storage, free it up. The syncache entry will already
|
|
* have an initialized label we can use.
|
|
*/
|
|
mac_syncache_destroy(&maclabel);
|
|
#endif
|
|
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
|
|
/* Retransmit SYN|ACK and reset retransmit count. */
|
|
if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL))) {
|
|
log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
|
|
"resetting timer and retransmitting SYN|ACK\n",
|
|
s, __func__);
|
|
free(s, M_TCPLOG);
|
|
}
|
|
if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) {
|
|
sc->sc_rxmits = 0;
|
|
syncache_timeout(sc, sch, 1);
|
|
TCPSTAT_INC(tcps_sndacks);
|
|
TCPSTAT_INC(tcps_sndtotal);
|
|
} else {
|
|
syncache_drop(sc, sch);
|
|
TCPSTAT_INC(tcps_sc_dropped);
|
|
}
|
|
SCH_UNLOCK(sch);
|
|
goto donenoprobe;
|
|
}
|
|
|
|
if (tfo_cookie_valid) {
|
|
bzero(&scs, sizeof(scs));
|
|
sc = &scs;
|
|
goto skip_alloc;
|
|
}
|
|
|
|
/*
|
|
* Skip allocating a syncache entry if we are just going to discard
|
|
* it later.
|
|
*/
|
|
if (!locked) {
|
|
bzero(&scs, sizeof(scs));
|
|
sc = &scs;
|
|
} else
|
|
sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
|
|
if (sc == NULL) {
|
|
/*
|
|
* The zone allocator couldn't provide more entries.
|
|
* Treat this as if the cache was full; drop the oldest
|
|
* entry and insert the new one.
|
|
*/
|
|
TCPSTAT_INC(tcps_sc_zonefail);
|
|
if ((sc = TAILQ_LAST(&sch->sch_bucket, sch_head)) != NULL) {
|
|
sch->sch_last_overflow = time_uptime;
|
|
syncache_drop(sc, sch);
|
|
syncache_pause(inc);
|
|
}
|
|
sc = uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
|
|
if (sc == NULL) {
|
|
if (V_tcp_syncookies) {
|
|
bzero(&scs, sizeof(scs));
|
|
sc = &scs;
|
|
} else {
|
|
KASSERT(locked,
|
|
("%s: bucket unexpectedly unlocked",
|
|
__func__));
|
|
SCH_UNLOCK(sch);
|
|
if (ipopts)
|
|
(void) m_free(ipopts);
|
|
goto done;
|
|
}
|
|
}
|
|
}
|
|
|
|
skip_alloc:
|
|
if (!tfo_cookie_valid && tfo_response_cookie_valid)
|
|
sc->sc_tfo_cookie = &tfo_response_cookie;
|
|
|
|
/*
|
|
* Fill in the syncache values.
|
|
*/
|
|
#ifdef MAC
|
|
sc->sc_label = maclabel;
|
|
#endif
|
|
sc->sc_cred = cred;
|
|
sc->sc_port = port;
|
|
cred = NULL;
|
|
sc->sc_ipopts = ipopts;
|
|
bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
|
|
sc->sc_ip_tos = ip_tos;
|
|
sc->sc_ip_ttl = ip_ttl;
|
|
#ifdef TCP_OFFLOAD
|
|
sc->sc_tod = tod;
|
|
sc->sc_todctx = todctx;
|
|
#endif
|
|
sc->sc_irs = th->th_seq;
|
|
sc->sc_flags = 0;
|
|
sc->sc_flowlabel = 0;
|
|
|
|
/*
|
|
* Initial receive window: clip sbspace to [0 .. TCP_MAXWIN].
|
|
* win was derived from socket earlier in the function.
|
|
*/
|
|
win = imax(win, 0);
|
|
win = imin(win, TCP_MAXWIN);
|
|
sc->sc_wnd = win;
|
|
|
|
if (V_tcp_do_rfc1323 &&
|
|
!(ltflags & TF_NOOPT)) {
|
|
/*
|
|
* A timestamp received in a SYN makes
|
|
* it ok to send timestamp requests and replies.
|
|
*/
|
|
if ((to->to_flags & TOF_TS) && (V_tcp_do_rfc1323 != 2)) {
|
|
sc->sc_tsreflect = to->to_tsval;
|
|
sc->sc_flags |= SCF_TIMESTAMP;
|
|
sc->sc_tsoff = tcp_new_ts_offset(inc);
|
|
}
|
|
if ((to->to_flags & TOF_SCALE) && (V_tcp_do_rfc1323 != 3)) {
|
|
int wscale = 0;
|
|
|
|
/*
|
|
* Pick the smallest possible scaling factor that
|
|
* will still allow us to scale up to sb_max, aka
|
|
* kern.ipc.maxsockbuf.
|
|
*
|
|
* We do this because there are broken firewalls that
|
|
* will corrupt the window scale option, leading to
|
|
* the other endpoint believing that our advertised
|
|
* window is unscaled. At scale factors larger than
|
|
* 5 the unscaled window will drop below 1500 bytes,
|
|
* leading to serious problems when traversing these
|
|
* broken firewalls.
|
|
*
|
|
* With the default maxsockbuf of 256K, a scale factor
|
|
* of 3 will be chosen by this algorithm. Those who
|
|
* choose a larger maxsockbuf should watch out
|
|
* for the compatibility problems mentioned above.
|
|
*
|
|
* RFC1323: The Window field in a SYN (i.e., a <SYN>
|
|
* or <SYN,ACK>) segment itself is never scaled.
|
|
*/
|
|
while (wscale < TCP_MAX_WINSHIFT &&
|
|
(TCP_MAXWIN << wscale) < sb_max)
|
|
wscale++;
|
|
sc->sc_requested_r_scale = wscale;
|
|
sc->sc_requested_s_scale = to->to_wscale;
|
|
sc->sc_flags |= SCF_WINSCALE;
|
|
}
|
|
}
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
/*
|
|
* If incoming packet has an MD5 signature, flag this in the
|
|
* syncache so that syncache_respond() will do the right thing
|
|
* with the SYN+ACK.
|
|
*/
|
|
if (to->to_flags & TOF_SIGNATURE)
|
|
sc->sc_flags |= SCF_SIGNATURE;
|
|
#endif /* TCP_SIGNATURE */
|
|
if (to->to_flags & TOF_SACKPERM)
|
|
sc->sc_flags |= SCF_SACK;
|
|
if (to->to_flags & TOF_MSS)
|
|
sc->sc_peer_mss = to->to_mss; /* peer mss may be zero */
|
|
if (ltflags & TF_NOOPT)
|
|
sc->sc_flags |= SCF_NOOPT;
|
|
/* ECN Handshake */
|
|
if (V_tcp_do_ecn && (tp->t_flags2 & TF2_CANNOT_DO_ECN) == 0)
|
|
sc->sc_flags |= tcp_ecn_syncache_add(tcp_get_flags(th), iptos);
|
|
|
|
if (V_tcp_syncookies)
|
|
sc->sc_iss = syncookie_generate(sch, sc);
|
|
else
|
|
sc->sc_iss = arc4random();
|
|
#ifdef INET6
|
|
if (autoflowlabel) {
|
|
if (V_tcp_syncookies)
|
|
sc->sc_flowlabel = sc->sc_iss;
|
|
else
|
|
sc->sc_flowlabel = ip6_randomflowlabel();
|
|
sc->sc_flowlabel = htonl(sc->sc_flowlabel) & IPV6_FLOWLABEL_MASK;
|
|
}
|
|
#endif
|
|
if (locked)
|
|
SCH_UNLOCK(sch);
|
|
|
|
if (tfo_cookie_valid) {
|
|
rv = syncache_tfo_expand(sc, so, m, tfo_response_cookie);
|
|
/* INP_RUNLOCK(inp) will be performed by the caller */
|
|
goto tfo_expanded;
|
|
}
|
|
|
|
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
|
|
/*
|
|
* Do a standard 3-way handshake.
|
|
*/
|
|
if (syncache_respond(sc, m, TH_SYN|TH_ACK) == 0) {
|
|
if (sc != &scs)
|
|
syncache_insert(sc, sch); /* locks and unlocks sch */
|
|
TCPSTAT_INC(tcps_sndacks);
|
|
TCPSTAT_INC(tcps_sndtotal);
|
|
} else {
|
|
if (sc != &scs)
|
|
syncache_free(sc);
|
|
TCPSTAT_INC(tcps_sc_dropped);
|
|
}
|
|
goto donenoprobe;
|
|
|
|
done:
|
|
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
|
|
donenoprobe:
|
|
if (m)
|
|
m_freem(m);
|
|
/*
|
|
* If tfo_pending is not NULL here, then a TFO SYN that did not
|
|
* result in a new socket was processed and the associated pending
|
|
* counter has not yet been decremented. All such TFO processing paths
|
|
* transit this point.
|
|
*/
|
|
if (tfo_pending != NULL)
|
|
tcp_fastopen_decrement_counter(tfo_pending);
|
|
|
|
tfo_expanded:
|
|
if (cred != NULL)
|
|
crfree(cred);
|
|
#ifdef MAC
|
|
if (sc == &scs)
|
|
mac_syncache_destroy(&maclabel);
|
|
#endif
|
|
return (rv);
|
|
}
|
|
|
|
/*
|
|
* Send SYN|ACK or ACK to the peer. Either in response to a peer's segment,
|
|
* i.e. m0 != NULL, or upon 3WHS ACK timeout, i.e. m0 == NULL.
|
|
*/
|
|
static int
|
|
syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
|
|
{
|
|
struct ip *ip = NULL;
|
|
struct mbuf *m;
|
|
struct tcphdr *th = NULL;
|
|
struct udphdr *udp = NULL;
|
|
int optlen, error = 0; /* Make compiler happy */
|
|
u_int16_t hlen, tlen, mssopt, ulen;
|
|
struct tcpopt to;
|
|
#ifdef INET6
|
|
struct ip6_hdr *ip6 = NULL;
|
|
#endif
|
|
|
|
NET_EPOCH_ASSERT();
|
|
|
|
hlen =
|
|
#ifdef INET6
|
|
(sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
|
|
#endif
|
|
sizeof(struct ip);
|
|
tlen = hlen + sizeof(struct tcphdr);
|
|
if (sc->sc_port) {
|
|
tlen += sizeof(struct udphdr);
|
|
}
|
|
/* Determine MSS we advertize to other end of connection. */
|
|
mssopt = tcp_mssopt(&sc->sc_inc);
|
|
if (sc->sc_port)
|
|
mssopt -= V_tcp_udp_tunneling_overhead;
|
|
mssopt = max(mssopt, V_tcp_minmss);
|
|
|
|
/* XXX: Assume that the entire packet will fit in a header mbuf. */
|
|
KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
|
|
("syncache: mbuf too small: hlen %u, sc_port %u, max_linkhdr %d + "
|
|
"tlen %d + TCP_MAXOLEN %ju <= MHLEN %d", hlen, sc->sc_port,
|
|
max_linkhdr, tlen, (uintmax_t)TCP_MAXOLEN, MHLEN));
|
|
|
|
/* Create the IP+TCP header from scratch. */
|
|
m = m_gethdr(M_NOWAIT, MT_DATA);
|
|
if (m == NULL)
|
|
return (ENOBUFS);
|
|
#ifdef MAC
|
|
mac_syncache_create_mbuf(sc->sc_label, m);
|
|
#endif
|
|
m->m_data += max_linkhdr;
|
|
m->m_len = tlen;
|
|
m->m_pkthdr.len = tlen;
|
|
m->m_pkthdr.rcvif = NULL;
|
|
|
|
#ifdef INET6
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6) {
|
|
ip6 = mtod(m, struct ip6_hdr *);
|
|
ip6->ip6_vfc = IPV6_VERSION;
|
|
ip6->ip6_src = sc->sc_inc.inc6_laddr;
|
|
ip6->ip6_dst = sc->sc_inc.inc6_faddr;
|
|
ip6->ip6_plen = htons(tlen - hlen);
|
|
/* ip6_hlim is set after checksum */
|
|
/* Zero out traffic class and flow label. */
|
|
ip6->ip6_flow &= ~IPV6_FLOWINFO_MASK;
|
|
ip6->ip6_flow |= sc->sc_flowlabel;
|
|
if (sc->sc_port != 0) {
|
|
ip6->ip6_nxt = IPPROTO_UDP;
|
|
udp = (struct udphdr *)(ip6 + 1);
|
|
udp->uh_sport = htons(V_tcp_udp_tunneling_port);
|
|
udp->uh_dport = sc->sc_port;
|
|
ulen = (tlen - sizeof(struct ip6_hdr));
|
|
th = (struct tcphdr *)(udp + 1);
|
|
} else {
|
|
ip6->ip6_nxt = IPPROTO_TCP;
|
|
th = (struct tcphdr *)(ip6 + 1);
|
|
}
|
|
ip6->ip6_flow |= htonl(sc->sc_ip_tos << IPV6_FLOWLABEL_LEN);
|
|
}
|
|
#endif
|
|
#if defined(INET6) && defined(INET)
|
|
else
|
|
#endif
|
|
#ifdef INET
|
|
{
|
|
ip = mtod(m, struct ip *);
|
|
ip->ip_v = IPVERSION;
|
|
ip->ip_hl = sizeof(struct ip) >> 2;
|
|
ip->ip_len = htons(tlen);
|
|
ip->ip_id = 0;
|
|
ip->ip_off = 0;
|
|
ip->ip_sum = 0;
|
|
ip->ip_src = sc->sc_inc.inc_laddr;
|
|
ip->ip_dst = sc->sc_inc.inc_faddr;
|
|
ip->ip_ttl = sc->sc_ip_ttl;
|
|
ip->ip_tos = sc->sc_ip_tos;
|
|
|
|
/*
|
|
* See if we should do MTU discovery. Route lookups are
|
|
* expensive, so we will only unset the DF bit if:
|
|
*
|
|
* 1) path_mtu_discovery is disabled
|
|
* 2) the SCF_UNREACH flag has been set
|
|
*/
|
|
if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
|
|
ip->ip_off |= htons(IP_DF);
|
|
if (sc->sc_port == 0) {
|
|
ip->ip_p = IPPROTO_TCP;
|
|
th = (struct tcphdr *)(ip + 1);
|
|
} else {
|
|
ip->ip_p = IPPROTO_UDP;
|
|
udp = (struct udphdr *)(ip + 1);
|
|
udp->uh_sport = htons(V_tcp_udp_tunneling_port);
|
|
udp->uh_dport = sc->sc_port;
|
|
ulen = (tlen - sizeof(struct ip));
|
|
th = (struct tcphdr *)(udp + 1);
|
|
}
|
|
}
|
|
#endif /* INET */
|
|
th->th_sport = sc->sc_inc.inc_lport;
|
|
th->th_dport = sc->sc_inc.inc_fport;
|
|
|
|
if (flags & TH_SYN)
|
|
th->th_seq = htonl(sc->sc_iss);
|
|
else
|
|
th->th_seq = htonl(sc->sc_iss + 1);
|
|
th->th_ack = htonl(sc->sc_irs + 1);
|
|
th->th_off = sizeof(struct tcphdr) >> 2;
|
|
th->th_win = htons(sc->sc_wnd);
|
|
th->th_urp = 0;
|
|
|
|
flags = tcp_ecn_syncache_respond(flags, sc);
|
|
tcp_set_flags(th, flags);
|
|
|
|
/* Tack on the TCP options. */
|
|
if ((sc->sc_flags & SCF_NOOPT) == 0) {
|
|
to.to_flags = 0;
|
|
|
|
if (flags & TH_SYN) {
|
|
to.to_mss = mssopt;
|
|
to.to_flags = TOF_MSS;
|
|
if (sc->sc_flags & SCF_WINSCALE) {
|
|
to.to_wscale = sc->sc_requested_r_scale;
|
|
to.to_flags |= TOF_SCALE;
|
|
}
|
|
if (sc->sc_flags & SCF_SACK)
|
|
to.to_flags |= TOF_SACKPERM;
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
if (sc->sc_flags & SCF_SIGNATURE)
|
|
to.to_flags |= TOF_SIGNATURE;
|
|
#endif
|
|
if (sc->sc_tfo_cookie) {
|
|
to.to_flags |= TOF_FASTOPEN;
|
|
to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN;
|
|
to.to_tfo_cookie = sc->sc_tfo_cookie;
|
|
/* don't send cookie again when retransmitting response */
|
|
sc->sc_tfo_cookie = NULL;
|
|
}
|
|
}
|
|
if (sc->sc_flags & SCF_TIMESTAMP) {
|
|
to.to_tsval = sc->sc_tsoff + tcp_ts_getticks();
|
|
to.to_tsecr = sc->sc_tsreflect;
|
|
to.to_flags |= TOF_TS;
|
|
}
|
|
optlen = tcp_addoptions(&to, (u_char *)(th + 1));
|
|
|
|
/* Adjust headers by option size. */
|
|
th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
|
|
m->m_len += optlen;
|
|
m->m_pkthdr.len += optlen;
|
|
#ifdef INET6
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6)
|
|
ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
|
|
else
|
|
#endif
|
|
ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
|
|
#if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
|
|
if (sc->sc_flags & SCF_SIGNATURE) {
|
|
KASSERT(to.to_flags & TOF_SIGNATURE,
|
|
("tcp_addoptions() didn't set tcp_signature"));
|
|
|
|
/* NOTE: to.to_signature is inside of mbuf */
|
|
if (!TCPMD5_ENABLED() ||
|
|
TCPMD5_OUTPUT(m, th, to.to_signature) != 0) {
|
|
m_freem(m);
|
|
return (EACCES);
|
|
}
|
|
}
|
|
#endif
|
|
} else
|
|
optlen = 0;
|
|
|
|
if (udp) {
|
|
ulen += optlen;
|
|
udp->uh_ulen = htons(ulen);
|
|
}
|
|
M_SETFIB(m, sc->sc_inc.inc_fibnum);
|
|
/*
|
|
* If we have peer's SYN and it has a flowid, then let's assign it to
|
|
* our SYN|ACK. ip6_output() and ip_output() will not assign flowid
|
|
* to SYN|ACK due to lack of inp here.
|
|
*/
|
|
if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
|
|
m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
|
|
M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
|
|
}
|
|
#ifdef INET6
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6) {
|
|
if (sc->sc_port) {
|
|
m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
|
|
m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
|
|
udp->uh_sum = in6_cksum_pseudo(ip6, ulen,
|
|
IPPROTO_UDP, 0);
|
|
th->th_sum = htons(0);
|
|
} else {
|
|
m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
|
|
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
|
|
th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
|
|
IPPROTO_TCP, 0);
|
|
}
|
|
ip6->ip6_hlim = sc->sc_ip_ttl;
|
|
#ifdef TCP_OFFLOAD
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
|
|
|
|
return (error);
|
|
}
|
|
#endif
|
|
TCP_PROBE5(send, NULL, NULL, ip6, NULL, th);
|
|
error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
|
|
}
|
|
#endif
|
|
#if defined(INET6) && defined(INET)
|
|
else
|
|
#endif
|
|
#ifdef INET
|
|
{
|
|
if (sc->sc_port) {
|
|
m->m_pkthdr.csum_flags = CSUM_UDP;
|
|
m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
|
|
udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
|
|
ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
|
|
th->th_sum = htons(0);
|
|
} else {
|
|
m->m_pkthdr.csum_flags = CSUM_TCP;
|
|
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
|
|
th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
|
|
htons(tlen + optlen - hlen + IPPROTO_TCP));
|
|
}
|
|
#ifdef TCP_OFFLOAD
|
|
if (ADDED_BY_TOE(sc)) {
|
|
struct toedev *tod = sc->sc_tod;
|
|
|
|
error = tod->tod_syncache_respond(tod, sc->sc_todctx, m);
|
|
|
|
return (error);
|
|
}
|
|
#endif
|
|
TCP_PROBE5(send, NULL, NULL, ip, NULL, th);
|
|
error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL);
|
|
}
|
|
#endif
|
|
return (error);
|
|
}
|
|
|
|
/*
|
|
* The purpose of syncookies is to handle spoofed SYN flooding DoS attacks
|
|
* that exceed the capacity of the syncache by avoiding the storage of any
|
|
* of the SYNs we receive. Syncookies defend against blind SYN flooding
|
|
* attacks where the attacker does not have access to our responses.
|
|
*
|
|
* Syncookies encode and include all necessary information about the
|
|
* connection setup within the SYN|ACK that we send back. That way we
|
|
* can avoid keeping any local state until the ACK to our SYN|ACK returns
|
|
* (if ever). Normally the syncache and syncookies are running in parallel
|
|
* with the latter taking over when the former is exhausted. When matching
|
|
* syncache entry is found the syncookie is ignored.
|
|
*
|
|
* The only reliable information persisting the 3WHS is our initial sequence
|
|
* number ISS of 32 bits. Syncookies embed a cryptographically sufficient
|
|
* strong hash (MAC) value and a few bits of TCP SYN options in the ISS
|
|
* of our SYN|ACK. The MAC can be recomputed when the ACK to our SYN|ACK
|
|
* returns and signifies a legitimate connection if it matches the ACK.
|
|
*
|
|
* The available space of 32 bits to store the hash and to encode the SYN
|
|
* option information is very tight and we should have at least 24 bits for
|
|
* the MAC to keep the number of guesses by blind spoofing reasonably high.
|
|
*
|
|
* SYN option information we have to encode to fully restore a connection:
|
|
* MSS: is imporant to chose an optimal segment size to avoid IP level
|
|
* fragmentation along the path. The common MSS values can be encoded
|
|
* in a 3-bit table. Uncommon values are captured by the next lower value
|
|
* in the table leading to a slight increase in packetization overhead.
|
|
* WSCALE: is necessary to allow large windows to be used for high delay-
|
|
* bandwidth product links. Not scaling the window when it was initially
|
|
* negotiated is bad for performance as lack of scaling further decreases
|
|
* the apparent available send window. We only need to encode the WSCALE
|
|
* we received from the remote end. Our end can be recalculated at any
|
|
* time. The common WSCALE values can be encoded in a 3-bit table.
|
|
* Uncommon values are captured by the next lower value in the table
|
|
* making us under-estimate the available window size halving our
|
|
* theoretically possible maximum throughput for that connection.
|
|
* SACK: Greatly assists in packet loss recovery and requires 1 bit.
|
|
* TIMESTAMP and SIGNATURE is not encoded because they are permanent options
|
|
* that are included in all segments on a connection. We enable them when
|
|
* the ACK has them.
|
|
*
|
|
* Security of syncookies and attack vectors:
|
|
*
|
|
* The MAC is computed over (faddr||laddr||fport||lport||irs||flags||secmod)
|
|
* together with the gloabl secret to make it unique per connection attempt.
|
|
* Thus any change of any of those parameters results in a different MAC output
|
|
* in an unpredictable way unless a collision is encountered. 24 bits of the
|
|
* MAC are embedded into the ISS.
|
|
*
|
|
* To prevent replay attacks two rotating global secrets are updated with a
|
|
* new random value every 15 seconds. The life-time of a syncookie is thus
|
|
* 15-30 seconds.
|
|
*
|
|
* Vector 1: Attacking the secret. This requires finding a weakness in the
|
|
* MAC itself or the way it is used here. The attacker can do a chosen plain
|
|
* text attack by varying and testing the all parameters under his control.
|
|
* The strength depends on the size and randomness of the secret, and the
|
|
* cryptographic security of the MAC function. Due to the constant updating
|
|
* of the secret the attacker has at most 29.999 seconds to find the secret
|
|
* and launch spoofed connections. After that he has to start all over again.
|
|
*
|
|
* Vector 2: Collision attack on the MAC of a single ACK. With a 24 bit MAC
|
|
* size an average of 4,823 attempts are required for a 50% chance of success
|
|
* to spoof a single syncookie (birthday collision paradox). However the
|
|
* attacker is blind and doesn't know if one of his attempts succeeded unless
|
|
* he has a side channel to interfere success from. A single connection setup
|
|
* success average of 90% requires 8,790 packets, 99.99% requires 17,578 packets.
|
|
* This many attempts are required for each one blind spoofed connection. For
|
|
* every additional spoofed connection he has to launch another N attempts.
|
|
* Thus for a sustained rate 100 spoofed connections per second approximately
|
|
* 1,800,000 packets per second would have to be sent.
|
|
*
|
|
* NB: The MAC function should be fast so that it doesn't become a CPU
|
|
* exhaustion attack vector itself.
|
|
*
|
|
* References:
|
|
* RFC4987 TCP SYN Flooding Attacks and Common Mitigations
|
|
* SYN cookies were first proposed by cryptographer Dan J. Bernstein in 1996
|
|
* http://cr.yp.to/syncookies.html (overview)
|
|
* http://cr.yp.to/syncookies/archive (details)
|
|
*
|
|
*
|
|
* Schematic construction of a syncookie enabled Initial Sequence Number:
|
|
* 0 1 2 3
|
|
* 12345678901234567890123456789012
|
|
* |xxxxxxxxxxxxxxxxxxxxxxxxWWWMMMSP|
|
|
*
|
|
* x 24 MAC (truncated)
|
|
* W 3 Send Window Scale index
|
|
* M 3 MSS index
|
|
* S 1 SACK permitted
|
|
* P 1 Odd/even secret
|
|
*/
|
|
|
|
/*
|
|
* Distribution and probability of certain MSS values. Those in between are
|
|
* rounded down to the next lower one.
|
|
* [An Analysis of TCP Maximum Segment Sizes, S. Alcock and R. Nelson, 2011]
|
|
* .2% .3% 5% 7% 7% 20% 15% 45%
|
|
*/
|
|
static int tcp_sc_msstab[] = { 216, 536, 1200, 1360, 1400, 1440, 1452, 1460 };
|
|
|
|
/*
|
|
* Distribution and probability of certain WSCALE values. We have to map the
|
|
* (send) window scale (shift) option with a range of 0-14 from 4 bits into 3
|
|
* bits based on prevalence of certain values. Where we don't have an exact
|
|
* match for are rounded down to the next lower one letting us under-estimate
|
|
* the true available window. At the moment this would happen only for the
|
|
* very uncommon values 3, 5 and those above 8 (more than 16MB socket buffer
|
|
* and window size). The absence of the WSCALE option (no scaling in either
|
|
* direction) is encoded with index zero.
|
|
* [WSCALE values histograms, Allman, 2012]
|
|
* X 10 10 35 5 6 14 10% by host
|
|
* X 11 4 5 5 18 49 3% by connections
|
|
*/
|
|
static int tcp_sc_wstab[] = { 0, 0, 1, 2, 4, 6, 7, 8 };
|
|
|
|
/*
|
|
* Compute the MAC for the SYN cookie. SIPHASH-2-4 is chosen for its speed
|
|
* and good cryptographic properties.
|
|
*/
|
|
static uint32_t
|
|
syncookie_mac(struct in_conninfo *inc, tcp_seq irs, uint8_t flags,
|
|
uint8_t *secbits, uintptr_t secmod)
|
|
{
|
|
SIPHASH_CTX ctx;
|
|
uint32_t siphash[2];
|
|
|
|
SipHash24_Init(&ctx);
|
|
SipHash_SetKey(&ctx, secbits);
|
|
switch (inc->inc_flags & INC_ISIPV6) {
|
|
#ifdef INET
|
|
case 0:
|
|
SipHash_Update(&ctx, &inc->inc_faddr, sizeof(inc->inc_faddr));
|
|
SipHash_Update(&ctx, &inc->inc_laddr, sizeof(inc->inc_laddr));
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case INC_ISIPV6:
|
|
SipHash_Update(&ctx, &inc->inc6_faddr, sizeof(inc->inc6_faddr));
|
|
SipHash_Update(&ctx, &inc->inc6_laddr, sizeof(inc->inc6_laddr));
|
|
break;
|
|
#endif
|
|
}
|
|
SipHash_Update(&ctx, &inc->inc_fport, sizeof(inc->inc_fport));
|
|
SipHash_Update(&ctx, &inc->inc_lport, sizeof(inc->inc_lport));
|
|
SipHash_Update(&ctx, &irs, sizeof(irs));
|
|
SipHash_Update(&ctx, &flags, sizeof(flags));
|
|
SipHash_Update(&ctx, &secmod, sizeof(secmod));
|
|
SipHash_Final((u_int8_t *)&siphash, &ctx);
|
|
|
|
return (siphash[0] ^ siphash[1]);
|
|
}
|
|
|
|
static tcp_seq
|
|
syncookie_generate(struct syncache_head *sch, struct syncache *sc)
|
|
{
|
|
u_int i, secbit, wscale;
|
|
uint32_t iss, hash;
|
|
uint8_t *secbits;
|
|
union syncookie cookie;
|
|
|
|
cookie.cookie = 0;
|
|
|
|
/* Map our computed MSS into the 3-bit index. */
|
|
for (i = nitems(tcp_sc_msstab) - 1;
|
|
tcp_sc_msstab[i] > sc->sc_peer_mss && i > 0;
|
|
i--)
|
|
;
|
|
cookie.flags.mss_idx = i;
|
|
|
|
/*
|
|
* Map the send window scale into the 3-bit index but only if
|
|
* the wscale option was received.
|
|
*/
|
|
if (sc->sc_flags & SCF_WINSCALE) {
|
|
wscale = sc->sc_requested_s_scale;
|
|
for (i = nitems(tcp_sc_wstab) - 1;
|
|
tcp_sc_wstab[i] > wscale && i > 0;
|
|
i--)
|
|
;
|
|
cookie.flags.wscale_idx = i;
|
|
}
|
|
|
|
/* Can we do SACK? */
|
|
if (sc->sc_flags & SCF_SACK)
|
|
cookie.flags.sack_ok = 1;
|
|
|
|
/* Which of the two secrets to use. */
|
|
secbit = V_tcp_syncache.secret.oddeven & 0x1;
|
|
cookie.flags.odd_even = secbit;
|
|
|
|
secbits = V_tcp_syncache.secret.key[secbit];
|
|
hash = syncookie_mac(&sc->sc_inc, sc->sc_irs, cookie.cookie, secbits,
|
|
(uintptr_t)sch);
|
|
|
|
/*
|
|
* Put the flags into the hash and XOR them to get better ISS number
|
|
* variance. This doesn't enhance the cryptographic strength and is
|
|
* done to prevent the 8 cookie bits from showing up directly on the
|
|
* wire.
|
|
*/
|
|
iss = hash & ~0xff;
|
|
iss |= cookie.cookie ^ (hash >> 24);
|
|
|
|
TCPSTAT_INC(tcps_sc_sendcookie);
|
|
return (iss);
|
|
}
|
|
|
|
static struct syncache *
|
|
syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
|
|
struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
|
|
struct socket *lso, uint16_t port)
|
|
{
|
|
uint32_t hash;
|
|
uint8_t *secbits;
|
|
tcp_seq ack, seq;
|
|
int wnd, wscale = 0;
|
|
union syncookie cookie;
|
|
|
|
/*
|
|
* Pull information out of SYN-ACK/ACK and revert sequence number
|
|
* advances.
|
|
*/
|
|
ack = th->th_ack - 1;
|
|
seq = th->th_seq - 1;
|
|
|
|
/*
|
|
* Unpack the flags containing enough information to restore the
|
|
* connection.
|
|
*/
|
|
cookie.cookie = (ack & 0xff) ^ (ack >> 24);
|
|
|
|
/* Which of the two secrets to use. */
|
|
secbits = V_tcp_syncache.secret.key[cookie.flags.odd_even];
|
|
|
|
hash = syncookie_mac(inc, seq, cookie.cookie, secbits, (uintptr_t)sch);
|
|
|
|
/* The recomputed hash matches the ACK if this was a genuine cookie. */
|
|
if ((ack & ~0xff) != (hash & ~0xff))
|
|
return (NULL);
|
|
|
|
/* Fill in the syncache values. */
|
|
sc->sc_flags = 0;
|
|
bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
|
|
sc->sc_ipopts = NULL;
|
|
|
|
sc->sc_irs = seq;
|
|
sc->sc_iss = ack;
|
|
|
|
switch (inc->inc_flags & INC_ISIPV6) {
|
|
#ifdef INET
|
|
case 0:
|
|
sc->sc_ip_ttl = sotoinpcb(lso)->inp_ip_ttl;
|
|
sc->sc_ip_tos = sotoinpcb(lso)->inp_ip_tos;
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case INC_ISIPV6:
|
|
if (sotoinpcb(lso)->inp_flags & IN6P_AUTOFLOWLABEL)
|
|
sc->sc_flowlabel =
|
|
htonl(sc->sc_iss) & IPV6_FLOWLABEL_MASK;
|
|
break;
|
|
#endif
|
|
}
|
|
|
|
sc->sc_peer_mss = tcp_sc_msstab[cookie.flags.mss_idx];
|
|
|
|
/* We can simply recompute receive window scale we sent earlier. */
|
|
while (wscale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << wscale) < sb_max)
|
|
wscale++;
|
|
|
|
/* Only use wscale if it was enabled in the orignal SYN. */
|
|
if (cookie.flags.wscale_idx > 0) {
|
|
sc->sc_requested_r_scale = wscale;
|
|
sc->sc_requested_s_scale = tcp_sc_wstab[cookie.flags.wscale_idx];
|
|
sc->sc_flags |= SCF_WINSCALE;
|
|
}
|
|
|
|
wnd = lso->sol_sbrcv_hiwat;
|
|
wnd = imax(wnd, 0);
|
|
wnd = imin(wnd, TCP_MAXWIN);
|
|
sc->sc_wnd = wnd;
|
|
|
|
if (cookie.flags.sack_ok)
|
|
sc->sc_flags |= SCF_SACK;
|
|
|
|
if (to->to_flags & TOF_TS) {
|
|
sc->sc_flags |= SCF_TIMESTAMP;
|
|
sc->sc_tsreflect = to->to_tsval;
|
|
sc->sc_tsoff = tcp_new_ts_offset(inc);
|
|
}
|
|
|
|
if (to->to_flags & TOF_SIGNATURE)
|
|
sc->sc_flags |= SCF_SIGNATURE;
|
|
|
|
sc->sc_rxmits = 0;
|
|
|
|
sc->sc_port = port;
|
|
|
|
TCPSTAT_INC(tcps_sc_recvcookie);
|
|
return (sc);
|
|
}
|
|
|
|
#ifdef INVARIANTS
|
|
static int
|
|
syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
|
|
struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
|
|
struct socket *lso, uint16_t port)
|
|
{
|
|
struct syncache scs, *scx;
|
|
char *s;
|
|
|
|
bzero(&scs, sizeof(scs));
|
|
scx = syncookie_lookup(inc, sch, &scs, th, to, lso, port);
|
|
|
|
if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
|
|
return (0);
|
|
|
|
if (scx != NULL) {
|
|
if (sc->sc_peer_mss != scx->sc_peer_mss)
|
|
log(LOG_DEBUG, "%s; %s: mss different %i vs %i\n",
|
|
s, __func__, sc->sc_peer_mss, scx->sc_peer_mss);
|
|
|
|
if (sc->sc_requested_r_scale != scx->sc_requested_r_scale)
|
|
log(LOG_DEBUG, "%s; %s: rwscale different %i vs %i\n",
|
|
s, __func__, sc->sc_requested_r_scale,
|
|
scx->sc_requested_r_scale);
|
|
|
|
if (sc->sc_requested_s_scale != scx->sc_requested_s_scale)
|
|
log(LOG_DEBUG, "%s; %s: swscale different %i vs %i\n",
|
|
s, __func__, sc->sc_requested_s_scale,
|
|
scx->sc_requested_s_scale);
|
|
|
|
if ((sc->sc_flags & SCF_SACK) != (scx->sc_flags & SCF_SACK))
|
|
log(LOG_DEBUG, "%s; %s: SACK different\n", s, __func__);
|
|
}
|
|
|
|
if (s != NULL)
|
|
free(s, M_TCPLOG);
|
|
return (0);
|
|
}
|
|
#endif /* INVARIANTS */
|
|
|
|
static void
|
|
syncookie_reseed(void *arg)
|
|
{
|
|
struct tcp_syncache *sc = arg;
|
|
uint8_t *secbits;
|
|
int secbit;
|
|
|
|
/*
|
|
* Reseeding the secret doesn't have to be protected by a lock.
|
|
* It only must be ensured that the new random values are visible
|
|
* to all CPUs in a SMP environment. The atomic with release
|
|
* semantics ensures that.
|
|
*/
|
|
secbit = (sc->secret.oddeven & 0x1) ? 0 : 1;
|
|
secbits = sc->secret.key[secbit];
|
|
arc4rand(secbits, SYNCOOKIE_SECRET_SIZE, 0);
|
|
atomic_add_rel_int(&sc->secret.oddeven, 1);
|
|
|
|
/* Reschedule ourself. */
|
|
callout_schedule(&sc->secret.reseed, SYNCOOKIE_LIFETIME * hz);
|
|
}
|
|
|
|
/*
|
|
* We have overflowed a bucket. Let's pause dealing with the syncache.
|
|
* This function will increment the bucketoverflow statistics appropriately
|
|
* (once per pause when pausing is enabled; otherwise, once per overflow).
|
|
*/
|
|
static void
|
|
syncache_pause(struct in_conninfo *inc)
|
|
{
|
|
time_t delta;
|
|
const char *s;
|
|
|
|
/* XXX:
|
|
* 2. Add sysctl read here so we don't get the benefit of this
|
|
* change without the new sysctl.
|
|
*/
|
|
|
|
/*
|
|
* Try an unlocked read. If we already know that another thread
|
|
* has activated the feature, there is no need to proceed.
|
|
*/
|
|
if (V_tcp_syncache.paused)
|
|
return;
|
|
|
|
/* Are cookied enabled? If not, we can't pause. */
|
|
if (!V_tcp_syncookies) {
|
|
TCPSTAT_INC(tcps_sc_bucketoverflow);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* We may be the first thread to find an overflow. Get the lock
|
|
* and evaluate if we need to take action.
|
|
*/
|
|
mtx_lock(&V_tcp_syncache.pause_mtx);
|
|
if (V_tcp_syncache.paused) {
|
|
mtx_unlock(&V_tcp_syncache.pause_mtx);
|
|
return;
|
|
}
|
|
|
|
/* Activate protection. */
|
|
V_tcp_syncache.paused = true;
|
|
TCPSTAT_INC(tcps_sc_bucketoverflow);
|
|
|
|
/*
|
|
* Determine the last backoff time. If we are seeing a re-newed
|
|
* attack within that same time after last reactivating the syncache,
|
|
* consider it an extension of the same attack.
|
|
*/
|
|
delta = TCP_SYNCACHE_PAUSE_TIME << V_tcp_syncache.pause_backoff;
|
|
if (V_tcp_syncache.pause_until + delta - time_uptime > 0) {
|
|
if (V_tcp_syncache.pause_backoff < TCP_SYNCACHE_MAX_BACKOFF) {
|
|
delta <<= 1;
|
|
V_tcp_syncache.pause_backoff++;
|
|
}
|
|
} else {
|
|
delta = TCP_SYNCACHE_PAUSE_TIME;
|
|
V_tcp_syncache.pause_backoff = 0;
|
|
}
|
|
|
|
/* Log a warning, including IP addresses, if able. */
|
|
if (inc != NULL)
|
|
s = tcp_log_addrs(inc, NULL, NULL, NULL);
|
|
else
|
|
s = (const char *)NULL;
|
|
log(LOG_WARNING, "TCP syncache overflow detected; using syncookies for "
|
|
"the next %lld seconds%s%s%s\n", (long long)delta,
|
|
(s != NULL) ? " (last SYN: " : "", (s != NULL) ? s : "",
|
|
(s != NULL) ? ")" : "");
|
|
free(__DECONST(void *, s), M_TCPLOG);
|
|
|
|
/* Use the calculated delta to set a new pause time. */
|
|
V_tcp_syncache.pause_until = time_uptime + delta;
|
|
callout_reset(&V_tcp_syncache.pause_co, delta * hz, syncache_unpause,
|
|
&V_tcp_syncache);
|
|
mtx_unlock(&V_tcp_syncache.pause_mtx);
|
|
}
|
|
|
|
/* Evaluate whether we need to unpause. */
|
|
static void
|
|
syncache_unpause(void *arg)
|
|
{
|
|
struct tcp_syncache *sc;
|
|
time_t delta;
|
|
|
|
sc = arg;
|
|
mtx_assert(&sc->pause_mtx, MA_OWNED | MA_NOTRECURSED);
|
|
callout_deactivate(&sc->pause_co);
|
|
|
|
/*
|
|
* Check to make sure we are not running early. If the pause
|
|
* time has expired, then deactivate the protection.
|
|
*/
|
|
if ((delta = sc->pause_until - time_uptime) > 0)
|
|
callout_schedule(&sc->pause_co, delta * hz);
|
|
else
|
|
sc->paused = false;
|
|
}
|
|
|
|
/*
|
|
* Exports the syncache entries to userland so that netstat can display
|
|
* them alongside the other sockets. This function is intended to be
|
|
* called only from tcp_pcblist.
|
|
*
|
|
* Due to concurrency on an active system, the number of pcbs exported
|
|
* may have no relation to max_pcbs. max_pcbs merely indicates the
|
|
* amount of space the caller allocated for this function to use.
|
|
*/
|
|
int
|
|
syncache_pcblist(struct sysctl_req *req)
|
|
{
|
|
struct xtcpcb xt;
|
|
struct syncache *sc;
|
|
struct syncache_head *sch;
|
|
int error, i;
|
|
|
|
bzero(&xt, sizeof(xt));
|
|
xt.xt_len = sizeof(xt);
|
|
xt.t_state = TCPS_SYN_RECEIVED;
|
|
xt.xt_inp.xi_socket.xso_protocol = IPPROTO_TCP;
|
|
xt.xt_inp.xi_socket.xso_len = sizeof (struct xsocket);
|
|
xt.xt_inp.xi_socket.so_type = SOCK_STREAM;
|
|
xt.xt_inp.xi_socket.so_state = SS_ISCONNECTING;
|
|
|
|
for (i = 0; i < V_tcp_syncache.hashsize; i++) {
|
|
sch = &V_tcp_syncache.hashbase[i];
|
|
SCH_LOCK(sch);
|
|
TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
|
|
if (sc->sc_cred != NULL &&
|
|
cr_cansee(req->td->td_ucred, sc->sc_cred) != 0)
|
|
continue;
|
|
if (sc->sc_inc.inc_flags & INC_ISIPV6)
|
|
xt.xt_inp.inp_vflag = INP_IPV6;
|
|
else
|
|
xt.xt_inp.inp_vflag = INP_IPV4;
|
|
xt.xt_encaps_port = sc->sc_port;
|
|
bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc,
|
|
sizeof (struct in_conninfo));
|
|
error = SYSCTL_OUT(req, &xt, sizeof xt);
|
|
if (error) {
|
|
SCH_UNLOCK(sch);
|
|
return (0);
|
|
}
|
|
}
|
|
SCH_UNLOCK(sch);
|
|
}
|
|
|
|
return (0);
|
|
}
|