/bsd/sys/netinet/tcp_syncache.cc
C++ | 1750 lines | 1158 code | 174 blank | 418 comment | 212 complexity | 0264deb65c3ea759d6e4f2f951bf58c8 MD5 | raw file
Possible License(s): BSD-3-Clause, 0BSD, MPL-2.0-no-copyleft-exception
Large files files are truncated, but you can click here to view the full file
- /*-
- * Copyright (c) 2001 McAfee, Inc.
- * Copyright (c) 2006 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.
- *
- * 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 <bsd/porting/netport.h>
- #include <bsd/porting/uma_stub.h>
- #include <bsd/porting/sync_stub.h>
- #include <bsd/sys/sys/libkern.h>
- #include <bsd/sys/sys/param.h>
- #include <bsd/sys/sys/limits.h>
- #include <bsd/sys/sys/mbuf.h>
- #include <bsd/sys/sys/md5.h>
- #include <bsd/sys/sys/socket.h>
- #include <bsd/sys/sys/socketvar.h>
- #include <bsd/sys/net/if.h>
- #include <bsd/sys/net/route.h>
- #include <bsd/sys/net/vnet.h>
- #include <bsd/sys/netinet/in.h>
- #include <bsd/sys/netinet/in_systm.h>
- #include <bsd/sys/netinet/ip.h>
- #include <bsd/sys/netinet/in_var.h>
- #include <bsd/sys/netinet/in_pcb.h>
- #include <bsd/sys/netinet/ip_var.h>
- #include <bsd/sys/netinet/ip_options.h>
- #ifdef INET6
- #include <bsd/sys/netinet/ip6.h>
- #include <bsd/sys/netinet/icmp6.h>
- #include <bsd/sys/netinet6/nd6.h>
- #include <bsd/sys/netinet6/ip6_var.h>
- #include <bsd/sys/netinet6/in6_pcb.h>
- #endif
- #include <bsd/sys/netinet/tcp.h>
- #include <bsd/sys/netinet/tcp_fsm.h>
- #include <bsd/sys/netinet/tcp_seq.h>
- #include <bsd/sys/netinet/tcp_timer.h>
- #include <bsd/sys/netinet/tcp_var.h>
- #include <bsd/sys/netinet/tcp_syncache.h>
- #ifdef INET6
- #include <bsd/sys/netinet6/tcp6_var.h>
- #endif
- #ifdef IPSEC
- #include <bsd/sys/netipsec/ipsec.h>
- #ifdef INET6
- #include <bsd/sys/netipsec/ipsec6.h>
- #endif
- #include <bsd/sys/netipsec/key.h>
- #endif /*IPSEC*/
- #include <machine/in_cksum.h>
- #include <functional>
- static VNET_DEFINE(int, tcp_syncookies) = 1;
- #define V_tcp_syncookies VNET(tcp_syncookies)
- SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies, CTLFLAG_RW,
- &VNET_NAME(tcp_syncookies), 0,
- "Use TCP SYN cookies if the syncache overflows");
- static VNET_DEFINE(int, tcp_syncookiesonly) = 0;
- #define V_tcp_syncookiesonly VNET(tcp_syncookiesonly)
- SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, syncookies_only, CTLFLAG_RW,
- &VNET_NAME(tcp_syncookiesonly), 0,
- "Use only TCP SYN cookies");
- #ifdef TCP_OFFLOAD_DISABLE
- #define TOEPCB_ISSET(sc) (0)
- #else
- #define TOEPCB_ISSET(sc) ((sc)->sc_toepcb != 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 *);
- struct syncache *syncache_lookup(struct in_conninfo *, struct syncache_head **);
- static int syncache_respond(struct syncache *);
- 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(struct syncache_head *sch, serial_timer_task& timer);
- static void syncookie_generate(struct syncache_head *, struct syncache *,
- u_int32_t *);
- static struct syncache
- *syncookie_lookup(struct in_conninfo *, struct syncache_head *,
- struct syncache *, struct tcpopt *, struct tcphdr *, struct socket *);
- /*
- * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
- * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
- * 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
- static VNET_DEFINE(struct tcp_syncache, tcp_syncache);
- #define V_tcp_syncache VNET(tcp_syncache)
- SYSCTL_NODE(_net_inet_tcp, OID_AUTO, syncache, CTLFLAG_RW, 0, "TCP SYN cache");
- SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, bucketlimit, CTLFLAG_RDTUN,
- &VNET_NAME(tcp_syncache.bucket_limit), 0,
- "Per-bucket hash limit for syncache");
- SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, cachelimit, CTLFLAG_RDTUN,
- &VNET_NAME(tcp_syncache.cache_limit), 0,
- "Overall entry limit for syncache");
- SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, count, CTLFLAG_RD,
- &VNET_NAME(tcp_syncache.cache_count), 0,
- "Current number of entries in syncache");
- SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, hashsize, CTLFLAG_RDTUN,
- &VNET_NAME(tcp_syncache.hashsize), 0,
- "Size of TCP syncache hashtable");
- SYSCTL_VNET_UINT(_net_inet_tcp_syncache, OID_AUTO, rexmtlimit, CTLFLAG_RW,
- &VNET_NAME(tcp_syncache.rexmt_limit), 0,
- "Limit on SYN/ACK retransmissions");
- VNET_DEFINE(int, tcp_sc_rst_sock_fail) = 0; // match Linux behavior
- SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
- CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
- "Send reset on socket allocation failure");
- MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
- #define SYNCACHE_HASH(inc, mask) \
- ((V_tcp_syncache.hash_secret ^ \
- (inc)->inc_faddr.s_addr ^ \
- ((inc)->inc_faddr.s_addr >> 16) ^ \
- (inc)->inc_fport ^ (inc)->inc_lport) & mask)
- #define SYNCACHE_HASH6(inc, mask) \
- ((V_tcp_syncache.hash_secret ^ \
- (inc)->inc6_faddr.s6_addr32[0] ^ \
- (inc)->inc6_faddr.s6_addr32[3] ^ \
- (inc)->inc_fport ^ (inc)->inc_lport) & mask)
- #define ENDPTS_EQ(a, b) ( \
- (a)->ie_fport == (b)->ie_fport && \
- (a)->ie_lport == (b)->ie_lport && \
- (a)->ie_faddr.s_addr == (b)->ie_faddr.s_addr && \
- (a)->ie_laddr.s_addr == (b)->ie_laddr.s_addr \
- )
- #define ENDPTS6_EQ(a, b) (memcmp(a, b, sizeof(*a)) == 0)
- #define SCH_LOCK(sch) mutex_lock(&(sch)->sch_mtx)
- #define SCH_UNLOCK(sch) mutex_unlock(&(sch)->sch_mtx)
- #define SCH_LOCK_ASSERT(sch) assert(mutex_owned(&(sch)->sch_mtx))
- /*
- * 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);
- #ifdef MAC
- mac_syncache_destroy(&sc->sc_label);
- #endif
- uma_zfree(V_tcp_syncache.zone, sc);
- }
- syncache_head::syncache_head()
- : sch_timer(sch_mtx, std::bind(syncache_timer, this, std::placeholders::_1))
- {
- #ifdef VIMAGE
- sch_vnet = curvnet;
- #endif
- TAILQ_INIT(&sch_bucket);
- }
- void syncache_init(void)
- {
- V_tcp_syncache.cache_count = 0;
- 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 = new syncache_head[V_tcp_syncache.hashsize];
- /* Create the syncache entry zone. */V_tcp_syncache.zone = uma_zcreate(
- "syncache", sizeof(struct syncache), NULL, NULL, NULL, NULL,
- UMA_ALIGN_PTR, 0);
- uma_zone_set_max(V_tcp_syncache.zone, V_tcp_syncache.cache_limit);
- }
- #ifdef VIMAGE
- void
- syncache_destroy(void)
- {
- struct syncache_head *sch;
- struct syncache *sc, *nsc;
- int i;
- /* Cleanup hash buckets: stop timers, free entries, destroy locks. */
- for (i = 0; i < V_tcp_syncache.hashsize; i++) {
- sch = &V_tcp_syncache.hashbase[i];
- sch->sch_timer.cancel_sync();
- 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));
- }
- KASSERT(V_tcp_syncache.cache_count == 0, ("%s: cache_count %d not 0",
- __func__, V_tcp_syncache.cache_count));
- /* Free the allocated global resources. */
- uma_zdestroy(V_tcp_syncache.zone);
- delete[] V_tcp_syncache.hashbase;
- }
- #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"));
- sc2 = TAILQ_LAST(&sch->sch_bucket, sch_head);
- syncache_drop(sc2, sch);
- TCPSTAT_INC(tcps_sc_bucketoverflow);
- }
- /* Put it into the bucket. */
- TAILQ_INSERT_HEAD(&sch->sch_bucket, sc, sc_hash);
- sch->sch_length++;
- /* Reinitialize the bucket row's timer. */
- if (sch->sch_length == 1)
- sch->sch_nextc = bsd_ticks + INT_MAX;
- syncache_timeout(sc, sch, 1);
- SCH_UNLOCK(sch);
- V_tcp_syncache.cache_count++;
- 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);
- TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
- sch->sch_length--;
- syncache_free(sc);
- V_tcp_syncache.cache_count--;
- }
- /*
- * Engage/reengage time on bucket row.
- */
- static void syncache_timeout(struct syncache *sc, struct syncache_head *sch,
- int docallout)
- {
- sc->sc_rxttime = bsd_ticks + TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
- sc->sc_rxmits++;
- if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
- sch->sch_nextc = sc->sc_rxttime;
- if (docallout) {
- reschedule(sch->sch_timer, sch->sch_nextc - bsd_ticks);
- }
- }
- }
- /*
- * 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(struct syncache_head *sch, serial_timer_task& timer)
- {
- struct syncache *sc, *nsc;
- int tick = bsd_ticks;
- char *s;
- CURVNET_SET(sch->sch_vnet);
- SCOPE_LOCK(sch->sch_mtx);
- if (!timer.try_fire()) {
- return;
- }
- /*
- * 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;
- TAILQ_FOREACH_SAFE(sc, &sch->sch_bucket, sc_hash, nsc)
- {
- /*
- * 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_syncache.rexmt_limit) {
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: Retransmits exhausted, "
- "giving up and removing syncache entry\n", s, __func__);
- free(s);
- }
- syncache_drop(sc, sch);
- TCPSTAT_INC(tcps_sc_stale);
- continue;
- }
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: Response timeout, "
- "retransmitting (%u) SYN|ACK\n", s, __func__, sc->sc_rxmits);
- free(s);
- }
- (void)syncache_respond(sc);
- TCPSTAT_INC(tcps_sc_retransmitted);
- syncache_timeout(sc, sch, 0);
- }
- if (!TAILQ_EMPTY(&(sch)->sch_bucket)) {
- reschedule(timer, (sch)->sch_nextc - tick);
- }
- CURVNET_RESTORE();
- }
- /*
- * Find an entry in the syncache.
- * Returns always with locked syncache_head plus a matching entry or NULL.
- */
- struct syncache *
- syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
- {
- struct syncache *sc;
- struct syncache_head *sch;
- #ifdef INET6
- if (inc->inc_flags & INC_ISIPV6) {
- sch = &V_tcp_syncache.hashbase[
- SYNCACHE_HASH6(inc, V_tcp_syncache.hashmask)];
- *schp = sch;
- SCH_LOCK(sch);
- /* Circle through bucket row to find matching entry. */
- TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash) {
- if (ENDPTS6_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
- return (sc);
- }
- } else
- #endif
- {
- sch =
- &V_tcp_syncache.hashbase[SYNCACHE_HASH(inc, V_tcp_syncache.hashmask)];
- *schp = sch;
- SCH_LOCK(sch);
- /* Circle through bucket row to find matching entry. */
- TAILQ_FOREACH(sc, &sch->sch_bucket, sc_hash)
- {
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6)
- continue;
- #endif
- if (ENDPTS_EQ(&inc->inc_ie, &sc->sc_inc.inc_ie))
- return (sc);
- }
- }
- SCH_LOCK_ASSERT(*schp);
- return (NULL ); /* 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.
- */
- void syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th)
- {
- struct syncache *sc;
- struct syncache_head *sch;
- char *s = NULL;
- sc = syncache_lookup(inc, &sch); /* returns locked sch */
- SCH_LOCK_ASSERT(sch);
- /*
- * Any RST to our SYN|ACK must not carry ACK, SYN or FIN flags.
- * See RFC 793 page 65, section SEGMENT ARRIVES.
- */
- if (th->th_flags & (TH_ACK | TH_SYN | TH_FIN)) {
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: Spurious RST with ACK, SYN or "
- "FIN flag set, segment ignored\n", s, __func__);
- TCPSTAT_INC(tcps_badrst);
- goto done;
- }
- /*
- * 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 )))
- bsd_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;
- }
- /*
- * 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.
- *
- * The sequence number in the reset segment is normally an
- * echo of our outgoing acknowlegement numbers, but some hosts
- * send a reset with the sequence number at the rightmost edge
- * of our receive window, and we have to handle this case.
- */
- if (th->th_seq >= sc->sc_irs
- && th->th_seq <= sc->sc_irs + sc->sc_wnd) {
- syncache_drop(sc, sch);
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_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 {
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: RST with invalid SEQ %u != "
- "IRS %u (+WND %u), segment ignored\n",
- s, __func__, th->th_seq, sc->sc_irs, sc->sc_wnd);
- TCPSTAT_INC(tcps_badrst);
- }
- done: if (s != NULL )
- free(s);
- SCH_UNLOCK(sch);
- }
- void syncache_badack(struct in_conninfo *inc)
- {
- struct syncache *sc;
- struct syncache_head *sch;
- sc = syncache_lookup(inc, &sch); /* returns locked sch */
- SCH_LOCK_ASSERT(sch);
- if (sc != NULL ) {
- syncache_drop(sc, sch);
- TCPSTAT_INC(tcps_sc_badack);
- }
- SCH_UNLOCK(sch);
- }
- void syncache_unreach(struct in_conninfo *inc, struct tcphdr *th)
- {
- struct syncache *sc;
- struct syncache_head *sch;
- sc = syncache_lookup(inc, &sch); /* returns locked sch */
- SCH_LOCK_ASSERT(sch);
- if (sc == NULL )
- goto done;
- /* If the sequence number != sc_iss, then it's a bogus ICMP msg */
- if (ntohl(th->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.
- */
- 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;
- INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
- /*
- * 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 we can't create
- * the connection, abort it.
- */
- so = sonewconn(lso, 0);
- if (so == NULL ) {
- /*
- * Drop the connection; we will either send a RST or
- * have the peer retransmit its SYN again after its
- * RTO and try again.
- */
- TCPSTAT_INC(tcps_listendrop);
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: Socket create failed "
- "due to limits or memory shortage\n", s, __func__);
- free(s);
- }
- goto abort2;
- }
- #ifdef MAC
- mac_socketpeer_set_from_mbuf(m, so);
- #endif
- inp = sotoinpcb(so);
- inp->inp_inc.inc_fibnum = so->so_fibnum;
- INP_LOCK(inp);
- INP_HASH_WLOCK(&V_tcbinfo);
- /* Insert new socket into PCB hash list. */
- inp->inp_inc.inc_flags = sc->sc_inc.inc_flags;
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6) {
- inp->in6p_laddr = sc->sc_inc.inc6_laddr;
- } else {
- inp->inp_vflag &= ~INP_IPV6;
- inp->inp_vflag |= INP_IPV4;
- #endif
- inp->inp_laddr = sc->sc_inc.inc_laddr;
- #ifdef INET6
- }
- #endif
- /*
- * Install in the reservation hash table for now, but don't yet
- * install a connection group since the full 4-tuple isn't yet
- * configured.
- */
- inp->inp_lport = sc->sc_inc.inc_lport;
- if ((error = in_pcbinshash(inp)) != 0) {
- /*
- * Undo the assignments above if we failed to
- * put the PCB on the hash lists.
- */
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6)
- inp->in6p_laddr = in6addr_any;
- else
- #endif
- inp->inp_laddr.s_addr = INADDR_ANY;
- inp->inp_lport = 0;
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
- "with error %i\n", s, __func__, error);
- free(s);
- }
- INP_HASH_WUNLOCK(&V_tcbinfo);
- goto abort;
- }
- #ifdef IPSEC
- /* Copy old policy into new socket's. */
- if (ipsec_copy_policy(sotoinpcb(lso)->inp_sp, inp->inp_sp))
- printf("syncache_socket: could not copy policy\n");
- #endif
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6) {
- struct inpcb *oinp = sotoinpcb(lso);
- struct in6_addr laddr6;
- struct bsd_sockaddr_in6 sin6;
- /*
- * 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);
- 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;
- laddr6 = inp->in6p_laddr;
- if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
- inp->in6p_laddr = sc->sc_inc.inc6_laddr;
- if ((error = in6_pcbconnect_mbuf(inp, (struct bsd_sockaddr *)&sin6,
- thread0.td_ucred, m)) != 0) {
- inp->in6p_laddr = laddr6;
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
- bsd_log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
- "with error %i\n",
- s, __func__, error);
- free(s);
- }
- INP_HASH_WUNLOCK(&V_tcbinfo);
- 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 in_addr laddr;
- struct bsd_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));
- laddr = inp->inp_laddr;
- if (inp->inp_laddr.s_addr == INADDR_ANY)
- inp->inp_laddr = sc->sc_inc.inc_laddr;
- if ((error = in_pcbconnect_mbuf(inp, (struct bsd_sockaddr *)&sin, 0, m))
- != 0) {
- inp->inp_laddr = laddr;
- if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
- "with error %i\n", s, __func__, error);
- free(s);
- }
- INP_HASH_WUNLOCK(&V_tcbinfo);
- goto abort;
- }
- }
- #endif /* INET */
- INP_HASH_WUNLOCK(&V_tcbinfo);
- tp = intotcpcb(inp);
- tp->set_state(TCPS_SYN_RECEIVED);
- tp->iss = sc->sc_iss;
- tp->irs = sc->sc_irs;
- 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_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;
- }
- #ifdef 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;
- }
- if (sc->sc_flags & SCF_ECN)
- tp->t_flags |= TF_ECN_PERMIT;
- /*
- * 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, reset cwnd to 1 segment.
- * NB: sc_rxmits counts all SYN,ACK transmits, not just retransmits.
- */
- if (sc->sc_rxmits > 1)
- tp->snd_cwnd = tp->t_maxseg;
- /*
- * Copy and activate timers.
- */
- 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));
- INP_UNLOCK(inp);
- SOCK_LOCK(so);
- soisconnected(so);
- TCPSTAT_INC(tcps_accepts);
- return (so);
- abort: INP_UNLOCK(inp);
- abort2: if (so != NULL )
- soabort(so);
- return (NULL );
- }
- static void
- syncache_remove_and_free(struct syncache_head *sch, struct syncache *sc)
- {
- SCH_LOCK_ASSERT(sch);
- TAILQ_REMOVE(&sch->sch_bucket, sc, sc_hash);
- sch->sch_length--;
- V_tcp_syncache.cache_count--;
- SCH_UNLOCK(sch);
- syncache_free(sc);
- }
- /*
- * 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.
- */
- int syncache_expand(struct in_conninfo *inc, struct tcpopt *to,
- struct tcphdr *th, struct socket **lsop, struct mbuf *m)
- {
- struct syncache *sc;
- struct syncache_head *sch;
- struct syncache scs;
- char *s;
- /*
- * Global TCP locks are held because we manipulate the PCB lists
- * and create a new socket.
- */
- INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
- KASSERT((th->th_flags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK,
- ("%s: can handle only ACK", __func__));
- sc = syncache_lookup(inc, &sch); /* returns locked sch */
- SCH_LOCK_ASSERT(sch);
- if (sc == NULL ) {
- /*
- * There is no syncache entry, so see if this ACK is
- * a returning syncookie. To do this, first:
- * A. See if this socket has had a syncache entry dropped in
- * the past. We don't want to accept a bogus syncookie
- * if we've never received a SYN.
- * B. check that the syncookie is valid. If it is, then
- * cobble up a fake syncache entry, and return.
- */
- if (!V_tcp_syncookies) {
- SCH_UNLOCK(sch);
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: Spurious ACK, "
- "segment rejected (syncookies disabled)\n", s, __func__);
- goto failed;
- }
- bzero(&scs, sizeof(scs));
- sc = syncookie_lookup(inc, sch, &scs, to, th, *lsop);
- SCH_UNLOCK(sch);
- if (sc == NULL ) {
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: Segment failed "
- "SYNCOOKIE authentication, segment rejected "
- "(probably spoofed)\n", s, __func__);
- goto failed;
- }
- }
- /*
- * Segment validation:
- * ACK must match our initial sequence number + 1 (the SYN|ACK).
- */
- if (th->th_ack != sc->sc_iss + 1 && !TOEPCB_ISSET(sc)) {
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_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 ((th->th_seq <= sc->sc_irs
- || th->th_seq > sc->sc_irs + sc->sc_wnd) &&
- !TOEPCB_ISSET(sc)){
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: SEQ %u != IRS+1 %u, segment "
- "rejected\n", s, __func__, th->th_seq, sc->sc_irs);
- goto failed;
- }
- if (!(sc->sc_flags & SCF_TIMESTAMP) && (to->to_flags & TOF_TS)) {
- if ((s = tcp_log_addrs(inc, th, NULL, NULL )))
- bsd_log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
- "segment rejected\n", s, __func__);
- goto failed;
- }
- /*
- * If timestamps were negotiated the reflected timestamp
- * must be equal to what we actually sent in the SYN|ACK.
- */
- if ((to->to_flags & TOF_TS) && to->to_tsecr != sc->sc_ts&&
- !TOEPCB_ISSET(sc)) {if
- ( (s = tcp_log_addrs(inc, th, NULL, NULL)))
- bsd_log(LOG_DEBUG, "%s; %s: TSECR %u != TS %u, "
- "segment rejected\n",
- s, __func__, to->to_tsecr, sc->sc_ts);
- goto failed;
- }
- *lsop = syncache_socket(sc, *lsop, m);
- if (*lsop == NULL) {
- TCPSTAT_INC(tcps_sc_aborted);
- } else {
- TCPSTAT_INC(tcps_sc_completed);
- if (sc != &scs) {
- syncache_remove_and_free(sch, sc);
- }
- }
- return (1);
- failed:
- if (sc != NULL && sc != &scs) {
- syncache_remove_and_free(sch, sc);
- }
- if (s != NULL )
- free(s);
- *lsop = NULL;
- return (0);
- }
- /*
- * 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.
- */
- static void _syncache_add(struct in_conninfo *inc, struct tcpopt *to,
- struct tcphdr *th, struct inpcb *inp, struct socket **lsop, struct mbuf *m,
- struct toe_usrreqs *tu, void *toepcb)
- {
- struct tcpcb *tp;
- struct socket *so;
- struct syncache *sc = NULL;
- struct syncache_head *sch;
- struct mbuf *ipopts = NULL;
- u_int32_t flowtmp;
- u_int ltflags;
- int win, sb_hiwat, ip_ttl, ip_tos;
- char *s;
- #ifdef INET6
- int autoflowlabel = 0;
- #endif
- #ifdef MAC
- struct label *maclabel;
- #endif
- struct syncache scs;
- INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
- INP_LOCK_ASSERT(inp); /* listen socket */
- KASSERT((th->th_flags & (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.
- */
- so = *lsop;
- tp = sototcpcb(so);
- #ifdef INET6
- if ((inc->inc_flags & INC_ISIPV6) &&
- (inp->inp_flags & IN6P_AUTOFLOWLABEL))
- autoflowlabel = 1;
- #endif
- ip_ttl = inp->inp_ip_ttl;
- ip_tos = inp->inp_ip_tos;
- win = sbspace(&so->so_rcv);
- sb_hiwat = so->so_rcv.sb_hiwat;
- ltflags = (tp->t_flags & (TF_NOOPT | TF_SIGNATURE));
- /* By the time we drop the lock these should no longer be used. */
- so = NULL;
- tp = NULL;
- #ifdef MAC
- if (mac_syncache_init(&maclabel) != 0) {
- INP_UNLOCK(inp);
- INP_INFO_WUNLOCK(&V_tcbinfo);
- goto done;
- } else
- mac_syncache_create(maclabel, inp);
- #endif
- INP_UNLOCK(inp);
- INP_INFO_WUNLOCK(&V_tcbinfo);
- /*
- * 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
- /*
- * 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?
- */
- sc = syncache_lookup(inc, &sch); /* returns locked entry */
- SCH_LOCK_ASSERT(sch);
- if (sc != NULL ) {
- 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;
- #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
- /* Retransmit SYN|ACK and reset retransmit count. */
- if ((s = tcp_log_addrs(&sc->sc_inc, th, NULL, NULL ))) {
- bsd_log(LOG_DEBUG, "%s; %s: Received duplicate SYN, "
- "resetting timer and retransmitting SYN|ACK\n", s, __func__);
- free(s);
- }
- if (!TOEPCB_ISSET(sc) && syncache_respond(sc) == 0) {
- sc->sc_rxmits = 0;
- syncache_timeout(sc, sch, 1);
- TCPSTAT_INC(tcps_sndacks);
- TCPSTAT_INC(tcps_sndtotal);
- }
- SCH_UNLOCK(sch);
- goto done;
- }
- sc = (syncache *)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)
- syncache_drop(sc, sch);
- sc = (syncache *)uma_zalloc(V_tcp_syncache.zone, M_NOWAIT | M_ZERO);
- if (sc == NULL ) {
- if (V_tcp_syncookies) {
- bzero(&scs, sizeof(scs));
- sc = &scs;
- } else {
- SCH_UNLOCK(sch);
- if (ipopts)
- (void)m_free(ipopts);
- goto done;
- }
- }
- }
- /*
- * Fill in the syncache values.
- */
- #ifdef MAC
- sc->sc_label = maclabel;
- #endif
- sc->sc_ipopts = ipopts;
- bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
- #ifdef INET6
- if (!(inc->inc_flags & INC_ISIPV6))
- #endif
- {
- sc->sc_ip_tos = ip_tos;
- sc->sc_ip_ttl = ip_ttl;
- }
- #ifndef TCP_OFFLOAD_DISABLE
- sc->sc_tu = tu;
- sc->sc_toepcb = toepcb;
- #endif
- sc->sc_irs = th->th_seq;
- sc->sc_iss = tcp_seq(arc4random());
- 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) {
- /*
- * A timestamp received in a SYN makes
- * it ok to send timestamp requests and replies.
- */
- if (to->to_flags & TOF_TS) {
- sc->sc_tsreflect = to->to_tsval;
- sc->sc_ts = tcp_ts_getticks();
- sc->sc_flags |= SCF_TIMESTAMP;
- }
- if (to->to_flags & TOF_SCALE) {
- 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 compatiblity 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;
- }
- }
- #ifdef TCP_SIGNATURE
- /*
- * If listening socket requested TCP digests, and received SYN
- * contains the option, flag this in the syncache so that
- * syncache_respond() will do the right thing with the SYN+ACK.
- * XXX: Currently we always record the option by default and will
- * attempt to use it in syncache_respond().
- */
- if (to->to_flags & TOF_SIGNATURE || ltflags & TF_SIGNATURE)
- sc->sc_flags |= SCF_SIGNATURE;
- #endif
- 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;
- if ((th->th_flags & (TH_ECE | TH_CWR)) && V_tcp_do_ecn)
- sc->sc_flags |= SCF_ECN;
- if (V_tcp_syncookies) {
- syncookie_generate(sch, sc, &flowtmp);
- #ifdef INET6
- if (autoflowlabel)
- sc->sc_flowlabel = flowtmp;
- #endif
- } else {
- #ifdef INET6
- if (autoflowlabel)
- sc->sc_flowlabel =
- (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
- #endif
- }
- SCH_UNLOCK(sch);
- /*
- * Do a standard 3-way handshake.
- */
- if (TOEPCB_ISSET(sc) || syncache_respond(sc) == 0) {
- if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
- syncache_free(sc);
- else 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);
- }
- done:
- #ifdef MAC
- if (sc == &scs)
- mac_syncache_destroy(&maclabel);
- #endif
- if (m) {
- *lsop = NULL;
- m_freem(m);
- }
- }
- static int syncache_respond(struct syncache *sc)
- {
- struct ip *ip = NULL;
- struct mbuf *m;
- struct tcphdr *th = NULL;
- int optlen, error = 0; /* Make compiler happy */
- u_int16_t hlen, tlen, mssopt;
- struct tcpopt to;
- #ifdef INET6
- struct ip6_hdr *ip6 = NULL;
- #endif
- hlen =
- #ifdef INET6
- (sc->sc_inc.inc_flags & INC_ISIPV6) ? sizeof(struct ip6_hdr) :
- #endif
- sizeof(struct ip);
- tlen = hlen + sizeof(struct tcphdr);
- /* Determine MSS we advertize to other end of connection. */
- mssopt = tcp_mssopt(&sc->sc_inc);
- if (sc->sc_peer_mss)
- mssopt = bsd_max(bsd_min(sc->sc_peer_mss, 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"));
- /* Create the IP+TCP header from scratch. */
- m = m_gethdr(M_DONTWAIT, MT_DATA);
- if (m == NULL )
- return (ENOBUFS);
- #ifdef MAC
- mac_syncache_create_mbuf(sc->sc_label, m);
- #endif
- m->m_hdr.mh_data += max_linkhdr;
- m->m_hdr.mh_len = tlen;
- m->M_dat.MH.MH_pkthdr.len = tlen;
- m->M_dat.MH.MH_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_nxt = IPPROTO_TCP;
- 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 */
- ip6->ip6_flow &= ~IPV6_FLOWLABEL_MASK;
- ip6->ip6_flow |= sc->sc_flowlabel;
- th = (struct tcphdr *)(ip6 + 1);
- }
- #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 = tlen;
- ip->ip_id = 0;
- ip->ip_off = 0;
- ip->ip_sum = 0;
- ip->ip_p = IPPROTO_TCP;
- 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 |= IP_DF;
- th = (struct tcphdr *)(ip + 1);
- }
- #endif /* INET */
- th->th_sport = sc->sc_inc.inc_lport;
- th->th_dport = sc->sc_inc.inc_fport;
- th->th_seq = htonl(sc->sc_iss);
- th->th_ack = htonl(sc->sc_irs + 1);
- th->th_off = sizeof(struct tcphdr) >> 2;
- th->th_x2 = 0;
- th->th_flags = TH_SYN | TH_ACK;
- th->th_win = htons(sc->sc_wnd);
- th->th_urp = 0;
- if (sc->sc_flags & SCF_ECN) {
- th->th_flags |= TH_ECE;
- TCPSTAT_INC(tcps_ecn_shs);
- }
- /* Tack on the TCP options. */
- if ((sc->sc_flags & SCF_NOOPT) == 0) {
- to.to_flags = 0;
- 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_TIMESTAMP) {
- /* Virgin timestamp or TCP cookie enhanced one. */
- to.to_tsval = sc->sc_ts;
- to.to_tsecr = sc->sc_tsreflect;
- to.to_flags |= TOF_TS;
- }
- if (sc->sc_flags & SCF_SACK)
- to.to_flags |= TOF_SACKPERM;
- #ifdef TCP_SIGNATURE
- if (sc->sc_flags & SCF_SIGNATURE)
- to.to_flags |= TOF_SIGNATURE;
- #endif
- optlen = tcp_addoptions(&to, (u_char *)(th + 1));
- /* Adjust headers by option size. */
- th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
- m->m_hdr.mh_len += optlen;
- m->M_dat.MH.MH_pkthdr.len += optlen;
- #ifdef TCP_SIGNATURE
- if (sc->sc_flags & SCF_SIGNATURE)
- tcp_signature_compute(m, 0, 0, optlen,
- to.to_signature, IPSEC_DIR_OUTBOUND);
- #endif
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6)
- ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) + optlen);
- else
- #endif
- ip->ip_len += optlen;
- } else
- optlen = 0;
- M_SETFIB(m, sc->sc_inc.inc_fibnum);
- m->M_dat.MH.MH_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
- #ifdef INET6
- if (sc->sc_inc.inc_flags & INC_ISIPV6) {
- m->M_dat.MH.MH_pkthdr.csum_flags = CSUM_TCP_IPV6;
- th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
- IPPROTO_TCP, 0);
- ip6->ip6_hlim = in6_selecthlim(NULL, NULL);
- error = ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL);
- }
- #endif
- #if defined(INET6) && defined(INET)
- else
- #endif
- #ifdef INET
- {
- m->M_dat.MH.MH_pkthdr.csum_flags = CSUM_TCP;
- th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
- htons(tlen + optlen - hlen + IPPROTO_TCP));
- error = ip_output(m, sc->sc_ipopts, NULL, 0, NULL, NULL );
- }
- #endif
- return (error);
- }
- void syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
- struct inpcb *inp, struct socket **lsop, struct mbuf *m)
- {
- _syncache_add(inc, to, th, inp, lsop, m, NULL, NULL );
- }
- /*
- * The purpose of SYN cookies is to avoid keeping track of all SYN's we
- * receive and to be able to handle SYN floods from bogus source addresses
- * (where we will never receive any reply). SYN floods try to exhaust all
- * our memory and available slots in the SYN cache table to cause a denial
- * of service to legitimate users of the local host.
- *
- * The idea of SYN cookies is to encode and include all necessary information
- * about the connection setup state within the SYN-ACK we send back and thus
- * to get along without keeping any local state until the ACK to the SYN-ACK
- * arrives (if ever). Everything we need to know should be available from
- * the information we encoded in the SYN-ACK.
- *
- * More information about the theory behind SYN cookies and its first
- * discussion and specification can be found at:
- * http://cr.yp.to/syncookies.html (overview)
- * http://cr.yp.to/syncookies/archive (gory details)
- *
- * This implementation extends the orginal idea and first implementation
- * of FreeBSD by using not only the initial sequence number field to store
- * information but also the timestamp field if present. This way we can
- * keep track of the entire state we need to know to recreate the session in
- * its original form. Almost all TCP speakers implement RFC1323 timestamps
- * these days. For those that do not we still have to live with the known
- * shortcomings of the ISN only SYN cookies.
- *
- * Cookie layers:
- *
- * Initial sequence number we send:
- * 31|................................|0
- * DDDDDDDDDDDDDDDDDDDDDDDDDMMMRRRP
- * D = MD5 Digest (first dword)
- * M = MSS index
- * R = Rotation of secret
- * P = Odd or Even secret
- *
- * The MD5 Digest is computed with over following parameters:
- * a) randomly rotated secret
- * b) struct in_conninfo containing the remote/local ip/port (IPv4&IPv6)
- * c) the received initial sequence number from remote host
- * d) the rotation offset and odd/even bit
- *
- * Timestamp we send:
- * 31|................................|0
- * DDDDDDDDDDDDDDDDDDDDDDSSSSRRRRA5
- * D = MD5 Digest (third dword) (only as filler)
- * S = Requested send window scale
- * R = Requested receive window scale
- * A = SACK allowed
- * 5 = TCP-MD5 enabled (not implemented yet)
- * XORed with MD5 Digest (forth dword)
- *
- * The timestamp isn't cryptographically secure and doesn't need to be.
- * The double use of the MD5 digest dwords ties it to a specific remote/
- * local host/port, remote initial sequence number and our local time
- * limited secret. A received timestamp is reverted (XORed) and then
- * the contained MD5 dword is compared to the computed one to ensure the
- * timestamp belongs to the SYN-ACK we sent. The other parameters may
- * have been tampered with but this isn't different from supplying bogus
- * values in the SYN in the first place.
- *
- * Some problems with SYN cookies remain however:
- * Consider the problem of a recreated (and retransmitted) cookie. If the
- * original SYN was accepted, the connection is established. The second
- * SYN is inflight, and if it arrives with an ISN that falls within the
- * receive window, the connection is killed.
- *
- * Notes:
- * A heuristic to determine when to accept syn cookies is not necessary.
- * An ACK flood would cause the syncookie verification to be attempted,
- * but a SYN flood causes syncookies to be generated. Both are of equal
- * cost, so there's no point in trying to optimize the ACK flood case.
- * Also, if you don't process certain ACKs for some reason, then all someone
- * would have to do is launch a SYN and ACK flood at the same time, which
- * would stop cookie verification and defeat the entire purpose of syncookies.
- */
- static int tcp_sc_msstab[] =
- { 0, 256, 468, 536, 996, 1452, 1460, 8960 };
- static void syncookie_generate(struct syncache_head *sch, struct syncache *sc,
- u_int32_t *flowlabel)
- {
- MD5_CTX ctx;
- u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
- u_int32_t data;
- u_int32_t *secbits;
- u_int off, pmss, mss;
- int i;
- SCH_LOCK_ASSERT(sch);
- /* Which of the two secrets to use. */
- secbits = sch->sch_oddeven ? sch->sch_secbits_odd : sch->sch_secbits_even;
- /* Reseed secret if too old. */
- if (sch->sch_reseed < time_uptime) {
- sch->sch_oddeven = sch->sch_oddeven ? 0 : 1; /* toggle */
- secbits =
- sch->sch_oddeven ? sch->sch_secbits_odd : sch->sch_secbits_even;
- for (i = 0; i < SYNCOOKIE_SECRET_SIZE; i++)
- secbits[i] = arc4random();
- sch->sch_reseed = time_uptime + SYNCOOKIE_LIFETIME;
- }
- /* Secret rotation offset. */
- off = sc->sc_iss.raw() & 0x7; /* iss was randomized before */
- /* Maximum segment size calculation. */
- pmss = bsd_max(bsd_min(sc->sc_peer_mss, tcp_mssopt(&sc->sc_inc)), V_tcp_minmss);
- for (mss = sizeof(tcp_sc_msstab) / sizeof(int) - 1; mss > 0; mss--)
- if (tcp_sc_msstab[mss] <= pmss)
- break;
- /* Fold parameters and MD5 digest into the ISN we will send. */
- data = sch->sch_oddeven;/* odd or even secret, 1 bit */
- data |= off << 1; /* secret offset, derived from iss, 3 bits */
- data |= mss << 4; /* mss, 3 bits */
- MD5Init(&ctx);
- MD5Update(&ctx, ((u_int8_t *)secbits) + off,
- SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
- MD5Update(&ctx, secbits, off);
- MD5Update(&ctx, &sc->sc_inc, sizeof(sc->sc_inc));
- MD5Update(&ctx, &sc->sc_irs, sizeof(sc->sc_irs));
- MD5Update(&ctx, &data, sizeof(data));
- MD5Final((u_int8_t *)&md5_buffer, &ctx);
- data |= (md5_buffer[0] << 7);
- sc->sc_iss = tcp_seq(data);
- #ifdef INET6
- *flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
- #endif
- /* Additional parameters are stored in the timestamp if present. */
- if (sc->sc_flags & SCF_TIMESTAMP) {
- data = ((sc->sc_flags & SCF_SIGNATURE) ? 1 : 0); /* TCP-MD5, 1 bit */
- data |= ((sc->sc_flags & SCF_SACK) ? 1 : 0) << 1; /* SACK, 1 bit */
- data |= sc->sc_requested_s_scale << 2; /* SWIN scale, 4 bits */
- data |= sc->sc_requested_r_scale << 6; /* RWIN scale, 4 bits */
- data |= md5_buffer[2] << 10; /* more digest bits */
- data ^= md5_buffer[3];
- sc->sc_ts = data;
- sc->sc_tsoff = data - tcp_ts_getticks(); /* after XOR */
- }
- TCPSTAT_INC(tcps_sc_sendcookie);
- }
- static struct syncache *
- syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
- struct syncache *sc, struct tcpopt *to, struct tcphdr *th,
- struct socket *so)
- {
- MD5_CTX ctx;
- u_int32_t md5_buffer[MD5_DIGEST_LENGTH / sizeof(u_int32_t)];
- u_int32_t data = 0;
- u_int32_t *secbits;
- u_int32_t ack, seq;
- int off, mss, wnd, flags;
- SCH_LOCK_ASSERT(sch);
- /*
- * Pull information out of SYN-ACK/ACK and
- * revert sequence number advances.
- */
- ack = th->th_ack.raw() - 1;
- seq = th->th_seq.raw() - 1;
- off = (ack >> 1) & 0x7;
- mss = (ack >> 4) & 0x7;
- flags = ack & 0x7f;
- /* Which of the two secrets to use. */
- secbits = (flags & 0x1) ? sch->sch_secbits_odd : sch->sch_secbits_even;
- /*
- * The secret wasn't updated for the lifetime of a syncookie,
- * so this SYN-ACK/ACK is either too old (replay) or totally bogus.
- */
- if (sch->sch_reseed + SYNCOOKIE_LIFETIME < time_uptime) {
- return (NULL );
- }
- /* Recompute the digest so we can compare it. */
- MD5Init(&ctx);
- MD5Update(&ctx, ((u_int8_t *)secbits) + off,
- SYNCOOKIE_SECRET_SIZE * sizeof(*secbits) - off);
- MD5Update(&ctx, secbits, off);
- MD5Update(&ctx, inc, sizeof(*inc));
- MD5Update(&ctx, &seq, sizeof(seq));
- MD5Update(&ctx, &flags, sizeof(flags));
- MD5Final((u_int8_t *)&md5_buffer, &ctx);
- /* Does the digest part of or ACK'ed ISS match? */
- if ((ack & (~0x7f)) != (md5_buffer[0] << 7))
- return (NULL );
- /* Does the digest part of our reflected timestamp match? */
- if (to->to_flags & TOF_TS) {
- data = md5_buffer[3] ^ to->to_tsecr;
- if ((data & (~0x3ff)) != (md5_buffer[2] << 10))
- return (NULL );
- }
- /* Fill in the syncache values. */
- bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
- sc->sc_ipopts = NULL;
- sc->sc_irs = tcp_seq(seq);
- sc->sc_iss = tcp_seq(ack);
- #ifdef INET6
- if (inc->inc_flags & INC_ISIPV6) {
- if (sotoinpcb(so)->inp_flags & IN6P_AUTOFLOWLABEL)
- sc->sc_flowlabel = md5_buffer[1] & IPV6_FLOWLABEL_MASK;
- } else
- #endif
- {
- sc->sc_ip_ttl = sotoinpcb(so) ->inp_ip_ttl;
- sc->sc_ip_tos = sotoinpcb(so) ->inp_ip_tos;
- }
- /* Additional parameters that were encoded in the timestamp. */
- if (data) {
- sc->sc_flags |= SCF_TIMESTAMP;
- sc->sc_tsreflect = to->to_tsval;
- sc->sc_ts = to->to_tsecr;
- sc->sc_tsoff = to->to_tsecr - tcp_ts_getticks();
- sc->sc_flags |= (data & 0x1) ? SCF_SIGNATURE : 0;
- sc->sc_flags |= ((data >> 1) & 0x1) ? SCF_SACK : 0;
- sc->sc_requested_s_scale = bsd_min((data >> 2) & 0xf, TCP_MAX_WINSHIFT);
- sc->sc_requested_r_scale = bsd_min((data >> 6) & 0xf, TCP_MAX_WINSHIFT);
- if (sc->sc_requested_s_scale || sc->sc_requested_r_scale)
- sc->sc_flags |= SCF_WINSCALE;
- } else
- sc->sc_flags |= SCF_NOOPT;
- wnd = sbspace(&so->so_rcv);
- wnd = imax(wnd, 0);
- wnd = imin(wnd, TCP_MAXWIN);
- sc->sc_wnd = wnd;
- sc->sc_rxmits = 0;
- sc->sc_peer_mss = tcp_sc_msstab[mss];
- TCPSTAT_INC(tcps_…
Large files files are truncated, but you can click here to view the full file