/* $NetBSD: tcp_syncache.c,v 1.6 2022/11/04 09:01:53 ozaki-r Exp $ */ /* * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. * All rights reserved. * * 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. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE PROJECT 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 PROJECT 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. */ /* * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 * * NRL grants permission for redistribution and use in source and binary * forms, with or without modification, of the software and documentation * created at NRL 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. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgements: * This product includes software developed by the University of * California, Berkeley and its contributors. * This product includes software developed at the Information * Technology Division, US Naval Research Laboratory. * 4. Neither the name of the NRL nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL 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 NRL 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. * * The views and conclusions contained in the software and documentation * are those of the authors and should not be interpreted as representing * official policies, either expressed or implied, of the US Naval * Research Laboratory (NRL). */ /*- * Copyright (c) 1997, 1998, 1999, 2001, 2005, 2006, * 2011 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Coyote Point Systems, Inc. * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation * Facility, NASA Ames Research Center. * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum. * This code is derived from software contributed to The NetBSD Foundation * by Rui Paulo. * * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 * The Regents of the University of California. All rights reserved. * * 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. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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. * * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 */ /* * TODO list for SYN cache stuff: * * Find room for a "state" field, which is needed to keep a * compressed state for TIME_WAIT TCBs. It's been noted already * that this is fairly important for very high-volume web and * mail servers, which use a large number of short-lived * connections. */ #include __KERNEL_RCSID(0, "$NetBSD: tcp_syncache.c,v 1.6 2022/11/04 09:01:53 ozaki-r Exp $"); #ifdef _KERNEL_OPT #include "opt_inet.h" #include "opt_ipsec.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include /* for lwp0 */ #include #include #include #include #include #include #include #ifdef INET6 #include #include #include #include #endif #include #include #include #include #include #include #include #ifdef TCP_SIGNATURE #ifdef IPSEC #include #include #ifdef INET6 #include #endif #endif /* IPSEC*/ #endif static void syn_cache_timer(void *); static struct syn_cache * syn_cache_lookup(const struct sockaddr *, const struct sockaddr *, struct syn_cache_head **); static int syn_cache_respond(struct syn_cache *); /* syn hash parameters */ #define TCP_SYN_HASH_SIZE 293 #define TCP_SYN_BUCKET_SIZE 35 static int tcp_syn_cache_size = TCP_SYN_HASH_SIZE; int tcp_syn_cache_limit = TCP_SYN_HASH_SIZE*TCP_SYN_BUCKET_SIZE; int tcp_syn_bucket_limit = 3*TCP_SYN_BUCKET_SIZE; static struct syn_cache_head tcp_syn_cache[TCP_SYN_HASH_SIZE]; /* * TCP compressed state engine. Currently used to hold compressed * state for SYN_RECEIVED. */ u_long syn_cache_count; static u_int32_t syn_hash1, syn_hash2; #define SYN_HASH(sa, sp, dp) \ ((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \ ((u_int32_t)(sp)))^syn_hash2))) #ifndef INET6 #define SYN_HASHALL(hash, src, dst) \ do { \ hash = SYN_HASH(&((const struct sockaddr_in *)(src))->sin_addr, \ ((const struct sockaddr_in *)(src))->sin_port, \ ((const struct sockaddr_in *)(dst))->sin_port); \ } while (/*CONSTCOND*/ 0) #else #define SYN_HASH6(sa, sp, dp) \ ((((sa)->s6_addr32[0] ^ (sa)->s6_addr32[3] ^ syn_hash1) * \ (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp)))^syn_hash2)) \ & 0x7fffffff) #define SYN_HASHALL(hash, src, dst) \ do { \ switch ((src)->sa_family) { \ case AF_INET: \ hash = SYN_HASH(&((const struct sockaddr_in *)(src))->sin_addr, \ ((const struct sockaddr_in *)(src))->sin_port, \ ((const struct sockaddr_in *)(dst))->sin_port); \ break; \ case AF_INET6: \ hash = SYN_HASH6(&((const struct sockaddr_in6 *)(src))->sin6_addr, \ ((const struct sockaddr_in6 *)(src))->sin6_port, \ ((const struct sockaddr_in6 *)(dst))->sin6_port); \ break; \ default: \ hash = 0; \ } \ } while (/*CONSTCOND*/0) #endif /* INET6 */ static struct pool syn_cache_pool; /* * We don't estimate RTT with SYNs, so each packet starts with the default * RTT and each timer step has a fixed timeout value. */ static inline void syn_cache_timer_arm(struct syn_cache *sc) { TCPT_RANGESET(sc->sc_rxtcur, TCPTV_SRTTDFLT * tcp_backoff[sc->sc_rxtshift], TCPTV_MIN, TCPTV_REXMTMAX); callout_reset(&sc->sc_timer, sc->sc_rxtcur * (hz / PR_SLOWHZ), syn_cache_timer, sc); } #define SYN_CACHE_TIMESTAMP(sc) (tcp_now - (sc)->sc_timebase) static inline void syn_cache_rm(struct syn_cache *sc) { TAILQ_REMOVE(&tcp_syn_cache[sc->sc_bucketidx].sch_bucket, sc, sc_bucketq); sc->sc_tp = NULL; LIST_REMOVE(sc, sc_tpq); tcp_syn_cache[sc->sc_bucketidx].sch_length--; callout_stop(&sc->sc_timer); syn_cache_count--; } static inline void syn_cache_put(struct syn_cache *sc) { if (sc->sc_ipopts) (void) m_free(sc->sc_ipopts); rtcache_free(&sc->sc_route); sc->sc_flags |= SCF_DEAD; if (!callout_invoking(&sc->sc_timer)) callout_schedule(&(sc)->sc_timer, 1); } void syn_cache_init(void) { int i; pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, 0, 0, "synpl", NULL, IPL_SOFTNET); /* Initialize the hash buckets. */ for (i = 0; i < tcp_syn_cache_size; i++) TAILQ_INIT(&tcp_syn_cache[i].sch_bucket); } void syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp) { struct syn_cache_head *scp; struct syn_cache *sc2; int s; /* * If there are no entries in the hash table, reinitialize * the hash secrets. */ if (syn_cache_count == 0) { syn_hash1 = cprng_fast32(); syn_hash2 = cprng_fast32(); } SYN_HASHALL(sc->sc_hash, &sc->sc_src.sa, &sc->sc_dst.sa); sc->sc_bucketidx = sc->sc_hash % tcp_syn_cache_size; scp = &tcp_syn_cache[sc->sc_bucketidx]; /* * Make sure that we don't overflow the per-bucket * limit or the total cache size limit. */ s = splsoftnet(); if (scp->sch_length >= tcp_syn_bucket_limit) { TCP_STATINC(TCP_STAT_SC_BUCKETOVERFLOW); /* * The bucket is full. Toss the oldest element in the * bucket. This will be the first entry in the bucket. */ sc2 = TAILQ_FIRST(&scp->sch_bucket); #ifdef DIAGNOSTIC /* * This should never happen; we should always find an * entry in our bucket. */ if (sc2 == NULL) panic("syn_cache_insert: bucketoverflow: impossible"); #endif syn_cache_rm(sc2); syn_cache_put(sc2); /* calls pool_put but see spl above */ } else if (syn_cache_count >= tcp_syn_cache_limit) { struct syn_cache_head *scp2, *sce; TCP_STATINC(TCP_STAT_SC_OVERFLOWED); /* * The cache is full. Toss the oldest entry in the * first non-empty bucket we can find. * * XXX We would really like to toss the oldest * entry in the cache, but we hope that this * condition doesn't happen very often. */ scp2 = scp; if (TAILQ_EMPTY(&scp2->sch_bucket)) { sce = &tcp_syn_cache[tcp_syn_cache_size]; for (++scp2; scp2 != scp; scp2++) { if (scp2 >= sce) scp2 = &tcp_syn_cache[0]; if (! TAILQ_EMPTY(&scp2->sch_bucket)) break; } #ifdef DIAGNOSTIC /* * This should never happen; we should always find a * non-empty bucket. */ if (scp2 == scp) panic("syn_cache_insert: cacheoverflow: " "impossible"); #endif } sc2 = TAILQ_FIRST(&scp2->sch_bucket); syn_cache_rm(sc2); syn_cache_put(sc2); /* calls pool_put but see spl above */ } /* * Initialize the entry's timer. */ sc->sc_rxttot = 0; sc->sc_rxtshift = 0; syn_cache_timer_arm(sc); /* Link it from tcpcb entry */ LIST_INSERT_HEAD(&tp->t_sc, sc, sc_tpq); /* Put it into the bucket. */ TAILQ_INSERT_TAIL(&scp->sch_bucket, sc, sc_bucketq); scp->sch_length++; syn_cache_count++; TCP_STATINC(TCP_STAT_SC_ADDED); splx(s); } /* * 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 * that entry. */ static void syn_cache_timer(void *arg) { struct syn_cache *sc = arg; mutex_enter(softnet_lock); KERNEL_LOCK(1, NULL); callout_ack(&sc->sc_timer); if (__predict_false(sc->sc_flags & SCF_DEAD)) { TCP_STATINC(TCP_STAT_SC_DELAYED_FREE); goto free; } if (__predict_false(sc->sc_rxtshift == TCP_MAXRXTSHIFT)) { /* Drop it -- too many retransmissions. */ goto dropit; } /* * Compute the total amount of time this entry has * been on a queue. If this entry has been on longer * than the keep alive timer would allow, expire it. */ sc->sc_rxttot += sc->sc_rxtcur; if (sc->sc_rxttot >= MIN(tcp_keepinit, TCP_TIMER_MAXTICKS)) goto dropit; TCP_STATINC(TCP_STAT_SC_RETRANSMITTED); (void)syn_cache_respond(sc); /* Advance the timer back-off. */ sc->sc_rxtshift++; syn_cache_timer_arm(sc); goto out; dropit: TCP_STATINC(TCP_STAT_SC_TIMED_OUT); syn_cache_rm(sc); if (sc->sc_ipopts) (void) m_free(sc->sc_ipopts); rtcache_free(&sc->sc_route); free: callout_destroy(&sc->sc_timer); pool_put(&syn_cache_pool, sc); out: KERNEL_UNLOCK_ONE(NULL); mutex_exit(softnet_lock); } /* * Remove syn cache created by the specified tcb entry, * because this does not make sense to keep them * (if there's no tcb entry, syn cache entry will never be used) */ void syn_cache_cleanup(struct tcpcb *tp) { struct syn_cache *sc, *nsc; int s; s = splsoftnet(); for (sc = LIST_FIRST(&tp->t_sc); sc != NULL; sc = nsc) { nsc = LIST_NEXT(sc, sc_tpq); #ifdef DIAGNOSTIC if (sc->sc_tp != tp) panic("invalid sc_tp in syn_cache_cleanup"); #endif syn_cache_rm(sc); syn_cache_put(sc); /* calls pool_put but see spl above */ } /* just for safety */ LIST_INIT(&tp->t_sc); splx(s); } /* * Find an entry in the syn cache. */ static struct syn_cache * syn_cache_lookup(const struct sockaddr *src, const struct sockaddr *dst, struct syn_cache_head **headp) { struct syn_cache *sc; struct syn_cache_head *scp; u_int32_t hash; int s; SYN_HASHALL(hash, src, dst); scp = &tcp_syn_cache[hash % tcp_syn_cache_size]; *headp = scp; s = splsoftnet(); for (sc = TAILQ_FIRST(&scp->sch_bucket); sc != NULL; sc = TAILQ_NEXT(sc, sc_bucketq)) { if (sc->sc_hash != hash) continue; if (!memcmp(&sc->sc_src, src, src->sa_len) && !memcmp(&sc->sc_dst, dst, dst->sa_len)) { splx(s); return (sc); } } splx(s); 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 syn cache, and if it's * there, we pull it out of the cache and turn it into a full-blown * connection in the SYN-RECEIVED state. * * The return values may not be immediately obvious, and their effects * can be subtle, so here they are: * * NULL SYN was not found in cache; caller should drop the * packet and send an RST. * * -1 We were unable to create the new connection, and are * aborting it. An ACK,RST is being sent to the peer * (unless we got screwey sequence numbers; see below), * because the 3-way handshake has been completed. Caller * should not free the mbuf, since we may be using it. If * we are not, we will free it. * * Otherwise, the return value is a pointer to the new socket * associated with the connection. */ struct socket * syn_cache_get(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, struct socket *so, struct mbuf *m) { struct syn_cache *sc; struct syn_cache_head *scp; struct inpcb *inp = NULL; struct tcpcb *tp; int s; struct socket *oso; s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); return NULL; } /* * Verify the sequence and ack numbers. Try getting the correct * response again. */ if ((th->th_ack != sc->sc_iss + 1) || SEQ_LEQ(th->th_seq, sc->sc_irs) || SEQ_GT(th->th_seq, sc->sc_irs + 1 + sc->sc_win)) { m_freem(m); (void)syn_cache_respond(sc); splx(s); return ((struct socket *)(-1)); } /* Remove this cache entry */ syn_cache_rm(sc); splx(s); /* * 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. */ /* * inp still has the OLD in_pcb stuff, set the * v6-related flags on the new guy, too. This is * done particularly for the case where an AF_INET6 * socket is bound only to a port, and a v4 connection * comes in on that port. * we also copy the flowinfo from the original pcb * to the new one. */ oso = so; so = sonewconn(so, true); if (so == NULL) goto resetandabort; inp = sotoinpcb(so); switch (src->sa_family) { case AF_INET: if (inp->inp_af == AF_INET) { in4p_laddr(inp) = ((struct sockaddr_in *)dst)->sin_addr; inp->inp_lport = ((struct sockaddr_in *)dst)->sin_port; inp->inp_options = ip_srcroute(m); inpcb_set_state(inp, INP_BOUND); if (inp->inp_options == NULL) { inp->inp_options = sc->sc_ipopts; sc->sc_ipopts = NULL; } } #ifdef INET6 else if (inp->inp_af == AF_INET6) { /* IPv4 packet to AF_INET6 socket */ memset(&in6p_laddr(inp), 0, sizeof(in6p_laddr(inp))); in6p_laddr(inp).s6_addr16[5] = htons(0xffff); bcopy(&((struct sockaddr_in *)dst)->sin_addr, &in6p_laddr(inp).s6_addr32[3], sizeof(((struct sockaddr_in *)dst)->sin_addr)); inp->inp_lport = ((struct sockaddr_in *)dst)->sin_port; intotcpcb(inp)->t_family = AF_INET; if (sotoinpcb(oso)->inp_flags & IN6P_IPV6_V6ONLY) inp->inp_flags |= IN6P_IPV6_V6ONLY; else inp->inp_flags &= ~IN6P_IPV6_V6ONLY; inpcb_set_state(inp, INP_BOUND); } #endif break; #ifdef INET6 case AF_INET6: if (inp->inp_af == AF_INET6) { in6p_laddr(inp) = ((struct sockaddr_in6 *)dst)->sin6_addr; inp->inp_lport = ((struct sockaddr_in6 *)dst)->sin6_port; inpcb_set_state(inp, INP_BOUND); } break; #endif } #ifdef INET6 if (inp && intotcpcb(inp)->t_family == AF_INET6 && sotoinpcb(oso)) { struct inpcb *oinp = sotoinpcb(oso); /* inherit socket options from the listening socket */ inp->inp_flags |= (oinp->inp_flags & IN6P_CONTROLOPTS); if (inp->inp_flags & IN6P_CONTROLOPTS) { m_freem(inp->inp_options); inp->inp_options = NULL; } ip6_savecontrol(inp, &inp->inp_options, mtod(m, struct ip6_hdr *), m); } #endif /* * Give the new socket our cached route reference. */ rtcache_copy(&inp->inp_route, &sc->sc_route); rtcache_free(&sc->sc_route); if (inp->inp_af == AF_INET) { struct sockaddr_in sin; memcpy(&sin, src, src->sa_len); if (inpcb_connect(inp, &sin, &lwp0)) { goto resetandabort; } } #ifdef INET6 else if (inp->inp_af == AF_INET6) { struct sockaddr_in6 sin6; memcpy(&sin6, src, src->sa_len); if (src->sa_family == AF_INET) { /* IPv4 packet to AF_INET6 socket */ in6_sin_2_v4mapsin6((struct sockaddr_in *)src, &sin6); } if (in6pcb_connect(inp, &sin6, NULL)) { goto resetandabort; } } #endif else { goto resetandabort; } tp = intotcpcb(inp); tp->t_flags = sototcpcb(oso)->t_flags & TF_NODELAY; if (sc->sc_request_r_scale != 15) { tp->requested_s_scale = sc->sc_requested_s_scale; tp->request_r_scale = sc->sc_request_r_scale; tp->snd_scale = sc->sc_requested_s_scale; tp->rcv_scale = sc->sc_request_r_scale; tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; } if (sc->sc_flags & SCF_TIMESTAMP) tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; tp->ts_timebase = sc->sc_timebase; tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ so = NULL; m_freem(m); goto abort; } tp->iss = sc->sc_iss; tp->irs = sc->sc_irs; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->t_state = TCPS_SYN_RECEIVED; TCP_TIMER_ARM(tp, TCPT_KEEP, tp->t_keepinit); TCP_STATINC(TCP_STAT_ACCEPTS); if ((sc->sc_flags & SCF_SACK_PERMIT) && tcp_do_sack) tp->t_flags |= TF_WILL_SACK; if ((sc->sc_flags & SCF_ECN_PERMIT) && tcp_do_ecn) tp->t_flags |= TF_ECN_PERMIT; #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) tp->t_flags |= TF_SIGNATURE; #endif /* Initialize tp->t_ourmss before we deal with the peer's! */ tp->t_ourmss = sc->sc_ourmaxseg; tcp_mss_from_peer(tp, sc->sc_peermaxseg); /* * Initialize the initial congestion window. If we * had to retransmit the SYN,ACK, we must initialize cwnd * to 1 segment (i.e. the Loss Window). */ if (sc->sc_rxtshift) tp->snd_cwnd = tp->t_peermss; else { int ss = tcp_init_win; if (inp->inp_af == AF_INET && in_localaddr(in4p_faddr(inp))) ss = tcp_init_win_local; #ifdef INET6 else if (inp->inp_af == AF_INET6 && in6_localaddr(&in6p_faddr(inp))) ss = tcp_init_win_local; #endif tp->snd_cwnd = TCP_INITIAL_WINDOW(ss, tp->t_peermss); } tcp_rmx_rtt(tp); tp->snd_wl1 = sc->sc_irs; tp->rcv_up = sc->sc_irs + 1; /* * This is what would have happened in tcp_output() when * the SYN,ACK was sent. */ tp->snd_up = tp->snd_una; tp->snd_max = tp->snd_nxt = tp->iss+1; TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); if (sc->sc_win > 0 && SEQ_GT(tp->rcv_nxt + sc->sc_win, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + sc->sc_win; tp->last_ack_sent = tp->rcv_nxt; tp->t_partialacks = -1; tp->t_dupacks = 0; TCP_STATINC(TCP_STAT_SC_COMPLETED); s = splsoftnet(); syn_cache_put(sc); splx(s); return so; resetandabort: (void)tcp_respond(NULL, m, m, th, (tcp_seq)0, th->th_ack, TH_RST); abort: if (so != NULL) { (void) soqremque(so, 1); (void) soabort(so); mutex_enter(softnet_lock); } s = splsoftnet(); syn_cache_put(sc); splx(s); TCP_STATINC(TCP_STAT_SC_ABORTED); return ((struct socket *)(-1)); } /* * 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 syn_cache_reset(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th) { struct syn_cache *sc; struct syn_cache_head *scp; int s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); return; } if (SEQ_LT(th->th_seq, sc->sc_irs) || SEQ_GT(th->th_seq, sc->sc_irs+1)) { splx(s); return; } syn_cache_rm(sc); TCP_STATINC(TCP_STAT_SC_RESET); syn_cache_put(sc); /* calls pool_put but see spl above */ splx(s); } void syn_cache_unreach(const struct sockaddr *src, const struct sockaddr *dst, struct tcphdr *th) { struct syn_cache *sc; struct syn_cache_head *scp; int s; s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); return; } /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ if (ntohl(th->th_seq) != sc->sc_iss) { splx(s); return; } /* * If we've retransmitted 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_rxtshift < 3) { sc->sc_flags |= SCF_UNREACH; splx(s); return; } syn_cache_rm(sc); TCP_STATINC(TCP_STAT_SC_UNREACH); syn_cache_put(sc); /* calls pool_put but see spl above */ splx(s); } /* * Given a LISTEN socket and an inbound SYN request, add this to the syn * cache, and send back a segment: * * 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. */ int syn_cache_add(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, unsigned int toff, struct socket *so, struct mbuf *m, u_char *optp, int optlen, struct tcp_opt_info *oi) { struct tcpcb tb, *tp; long win; struct syn_cache *sc; struct syn_cache_head *scp; struct mbuf *ipopts; int s; tp = sototcpcb(so); /* * Initialize some local state. */ win = sbspace(&so->so_rcv); if (win > TCP_MAXWIN) win = TCP_MAXWIN; #ifdef TCP_SIGNATURE if (optp || (tp->t_flags & TF_SIGNATURE)) #else if (optp) #endif { tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; #ifdef TCP_SIGNATURE tb.t_flags |= (tp->t_flags & TF_SIGNATURE); #endif tb.t_state = TCPS_LISTEN; if (tcp_dooptions(&tb, optp, optlen, th, m, toff, oi) < 0) return 0; } else tb.t_flags = 0; switch (src->sa_family) { case AF_INET: /* Remember the IP options, if any. */ ipopts = ip_srcroute(m); break; default: ipopts = NULL; } /* * See if we already have an entry for this connection. * If we do, resend the SYN,ACK. We do not count this * as a retransmission (XXX though maybe we should). */ if ((sc = syn_cache_lookup(src, dst, &scp)) != NULL) { TCP_STATINC(TCP_STAT_SC_DUPESYN); 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; } sc->sc_timestamp = tb.ts_recent; m_freem(m); if (syn_cache_respond(sc) == 0) { uint64_t *tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_SNDACKS]++; tcps[TCP_STAT_SNDTOTAL]++; TCP_STAT_PUTREF(); } return 1; } s = splsoftnet(); sc = pool_get(&syn_cache_pool, PR_NOWAIT); splx(s); if (sc == NULL) { if (ipopts) (void)m_free(ipopts); return 0; } /* * Fill in the cache, and put the necessary IP and TCP * options into the reply. */ memset(sc, 0, sizeof(struct syn_cache)); callout_init(&sc->sc_timer, CALLOUT_MPSAFE); memcpy(&sc->sc_src, src, src->sa_len); memcpy(&sc->sc_dst, dst, dst->sa_len); sc->sc_flags = 0; sc->sc_ipopts = ipopts; sc->sc_irs = th->th_seq; switch (src->sa_family) { case AF_INET: { struct sockaddr_in *srcin = (void *)src; struct sockaddr_in *dstin = (void *)dst; sc->sc_iss = tcp_new_iss1(&dstin->sin_addr, &srcin->sin_addr, dstin->sin_port, srcin->sin_port, sizeof(dstin->sin_addr)); break; } #ifdef INET6 case AF_INET6: { struct sockaddr_in6 *srcin6 = (void *)src; struct sockaddr_in6 *dstin6 = (void *)dst; sc->sc_iss = tcp_new_iss1(&dstin6->sin6_addr, &srcin6->sin6_addr, dstin6->sin6_port, srcin6->sin6_port, sizeof(dstin6->sin6_addr)); break; } #endif } sc->sc_peermaxseg = oi->maxseg; sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ? m_get_rcvif_NOMPSAFE(m) : NULL, sc->sc_src.sa.sa_family); sc->sc_win = win; sc->sc_timebase = tcp_now - 1; /* see tcp_newtcpcb() */ sc->sc_timestamp = tb.ts_recent; if ((tb.t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP)) == (TF_REQ_TSTMP|TF_RCVD_TSTMP)) sc->sc_flags |= SCF_TIMESTAMP; if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { sc->sc_requested_s_scale = tb.requested_s_scale; sc->sc_request_r_scale = 0; /* * Pick the smallest possible scaling factor that * will still allow us to scale up to sb_max. * * 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 sbmax of 256K, a scale factor * of 3 will be chosen by this algorithm. Those who * choose a larger sbmax should watch out * for the compatibility problems mentioned above. * * RFC1323: The Window field in a SYN (i.e., a * or ) segment itself is never scaled. */ while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << sc->sc_request_r_scale) < sb_max) sc->sc_request_r_scale++; } else { sc->sc_requested_s_scale = 15; sc->sc_request_r_scale = 15; } if ((tb.t_flags & TF_SACK_PERMIT) && tcp_do_sack) sc->sc_flags |= SCF_SACK_PERMIT; /* * ECN setup packet received. */ if ((th->th_flags & (TH_ECE|TH_CWR)) && tcp_do_ecn) sc->sc_flags |= SCF_ECN_PERMIT; #ifdef TCP_SIGNATURE if (tb.t_flags & TF_SIGNATURE) sc->sc_flags |= SCF_SIGNATURE; #endif sc->sc_tp = tp; m_freem(m); if (syn_cache_respond(sc) == 0) { uint64_t *tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_SNDACKS]++; tcps[TCP_STAT_SNDTOTAL]++; TCP_STAT_PUTREF(); syn_cache_insert(sc, tp); } else { s = splsoftnet(); /* * syn_cache_put() will try to schedule the timer, so * we need to initialize it */ syn_cache_timer_arm(sc); syn_cache_put(sc); splx(s); TCP_STATINC(TCP_STAT_SC_DROPPED); } return 1; } /* * syn_cache_respond: (re)send SYN+ACK. * * Returns 0 on success. */ static int syn_cache_respond(struct syn_cache *sc) { #ifdef INET6 struct rtentry *rt = NULL; #endif struct route *ro; u_int8_t *optp; int optlen, error; u_int16_t tlen; struct ip *ip = NULL; #ifdef INET6 struct ip6_hdr *ip6 = NULL; #endif struct tcpcb *tp; struct tcphdr *th; struct mbuf *m; u_int hlen; #ifdef TCP_SIGNATURE struct secasvar *sav = NULL; u_int8_t *sigp = NULL; #endif ro = &sc->sc_route; switch (sc->sc_src.sa.sa_family) { case AF_INET: hlen = sizeof(struct ip); break; #ifdef INET6 case AF_INET6: hlen = sizeof(struct ip6_hdr); break; #endif default: return EAFNOSUPPORT; } /* Worst case scenario, since we don't know the option size yet. */ tlen = hlen + sizeof(struct tcphdr) + MAX_TCPOPTLEN; KASSERT(max_linkhdr + tlen <= MCLBYTES); /* * Create the IP+TCP header from scratch. */ MGETHDR(m, M_DONTWAIT, MT_DATA); if (m && (max_linkhdr + tlen) > MHLEN) { MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); m = NULL; } } if (m == NULL) return ENOBUFS; MCLAIM(m, &tcp_tx_mowner); tp = sc->sc_tp; /* Fixup the mbuf. */ m->m_data += max_linkhdr; m_reset_rcvif(m); memset(mtod(m, void *), 0, tlen); switch (sc->sc_src.sa.sa_family) { case AF_INET: ip = mtod(m, struct ip *); ip->ip_v = 4; ip->ip_dst = sc->sc_src.sin.sin_addr; ip->ip_src = sc->sc_dst.sin.sin_addr; ip->ip_p = IPPROTO_TCP; th = (struct tcphdr *)(ip + 1); th->th_dport = sc->sc_src.sin.sin_port; th->th_sport = sc->sc_dst.sin.sin_port; break; #ifdef INET6 case AF_INET6: ip6 = mtod(m, struct ip6_hdr *); ip6->ip6_vfc = IPV6_VERSION; ip6->ip6_dst = sc->sc_src.sin6.sin6_addr; ip6->ip6_src = sc->sc_dst.sin6.sin6_addr; ip6->ip6_nxt = IPPROTO_TCP; /* ip6_plen will be updated in ip6_output() */ th = (struct tcphdr *)(ip6 + 1); th->th_dport = sc->sc_src.sin6.sin6_port; th->th_sport = sc->sc_dst.sin6.sin6_port; break; #endif default: panic("%s: impossible (1)", __func__); } th->th_seq = htonl(sc->sc_iss); th->th_ack = htonl(sc->sc_irs + 1); th->th_flags = TH_SYN|TH_ACK; th->th_win = htons(sc->sc_win); /* th_x2, th_sum, th_urp already 0 from memset */ /* Tack on the TCP options. */ optp = (u_int8_t *)(th + 1); optlen = 0; *optp++ = TCPOPT_MAXSEG; *optp++ = TCPOLEN_MAXSEG; *optp++ = (sc->sc_ourmaxseg >> 8) & 0xff; *optp++ = sc->sc_ourmaxseg & 0xff; optlen += TCPOLEN_MAXSEG; if (sc->sc_request_r_scale != 15) { *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | sc->sc_request_r_scale); optp += TCPOLEN_WINDOW + TCPOLEN_NOP; optlen += TCPOLEN_WINDOW + TCPOLEN_NOP; } if (sc->sc_flags & SCF_SACK_PERMIT) { /* Let the peer know that we will SACK. */ *optp++ = TCPOPT_SACK_PERMITTED; *optp++ = TCPOLEN_SACK_PERMITTED; optlen += TCPOLEN_SACK_PERMITTED; } if (sc->sc_flags & SCF_TIMESTAMP) { while (optlen % 4 != 2) { optlen += TCPOLEN_NOP; *optp++ = TCPOPT_NOP; } *optp++ = TCPOPT_TIMESTAMP; *optp++ = TCPOLEN_TIMESTAMP; u_int32_t *lp = (u_int32_t *)(optp); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(SYN_CACHE_TIMESTAMP(sc)); *lp = htonl(sc->sc_timestamp); optp += TCPOLEN_TIMESTAMP - 2; optlen += TCPOLEN_TIMESTAMP; } #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) { sav = tcp_signature_getsav(m); if (sav == NULL) { m_freem(m); return EPERM; } *optp++ = TCPOPT_SIGNATURE; *optp++ = TCPOLEN_SIGNATURE; sigp = optp; memset(optp, 0, TCP_SIGLEN); optp += TCP_SIGLEN; optlen += TCPOLEN_SIGNATURE; } #endif /* * Terminate and pad TCP options to a 4 byte boundary. * * According to RFC793: "The content of the header beyond the * End-of-Option option must be header padding (i.e., zero)." * And later: "The padding is composed of zeros." */ if (optlen % 4) { optlen += TCPOLEN_EOL; *optp++ = TCPOPT_EOL; } while (optlen % 4) { optlen += TCPOLEN_PAD; *optp++ = TCPOPT_PAD; } /* Compute the actual values now that we've added the options. */ tlen = hlen + sizeof(struct tcphdr) + optlen; m->m_len = m->m_pkthdr.len = tlen; th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; #ifdef TCP_SIGNATURE if (sav) { (void)tcp_signature(m, th, hlen, sav, sigp); key_sa_recordxfer(sav, m); KEY_SA_UNREF(&sav); } #endif /* * Send ECN SYN-ACK setup packet. * Routes can be asymmetric, so, even if we receive a packet * with ECE and CWR set, we must not assume no one will block * the ECE packet we are about to send. */ if ((sc->sc_flags & SCF_ECN_PERMIT) && tp && SEQ_GEQ(tp->snd_nxt, tp->snd_max)) { th->th_flags |= TH_ECE; TCP_STATINC(TCP_STAT_ECN_SHS); /* * draft-ietf-tcpm-ecnsyn-00.txt * * "[...] a TCP node MAY respond to an ECN-setup * SYN packet by setting ECT in the responding * ECN-setup SYN/ACK packet, indicating to routers * that the SYN/ACK packet is ECN-Capable. * This allows a congested router along the path * to mark the packet instead of dropping the * packet as an indication of congestion." * * "[...] There can be a great benefit in setting * an ECN-capable codepoint in SYN/ACK packets [...] * Congestion is most likely to occur in * the server-to-client direction. As a result, * setting an ECN-capable codepoint in SYN/ACK * packets can reduce the occurrence of three-second * retransmit timeouts resulting from the drop * of SYN/ACK packets." * * Page 4 and 6, January 2006. */ switch (sc->sc_src.sa.sa_family) { case AF_INET: ip->ip_tos |= IPTOS_ECN_ECT0; break; #ifdef INET6 case AF_INET6: ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); break; #endif } TCP_STATINC(TCP_STAT_ECN_ECT); } /* * Compute the packet's checksum. * * Fill in some straggling IP bits. Note the stack expects * ip_len to be in host order, for convenience. */ switch (sc->sc_src.sa.sa_family) { case AF_INET: ip->ip_len = htons(tlen - hlen); th->th_sum = 0; th->th_sum = in4_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); ip->ip_len = htons(tlen); ip->ip_ttl = ip_defttl; /* XXX tos? */ break; #ifdef INET6 case AF_INET6: ip6->ip6_plen = htons(tlen - hlen); th->th_sum = 0; th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); ip6->ip6_vfc &= ~IPV6_VERSION_MASK; ip6->ip6_vfc |= IPV6_VERSION; ip6->ip6_plen = htons(tlen - hlen); /* ip6_hlim will be initialized afterwards */ /* XXX flowlabel? */ break; #endif } /* XXX use IPsec policy on listening socket, on SYN ACK */ tp = sc->sc_tp; switch (sc->sc_src.sa.sa_family) { case AF_INET: error = ip_output(m, sc->sc_ipopts, ro, (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp ? tp->t_inpcb : NULL); break; #ifdef INET6 case AF_INET6: ip6->ip6_hlim = in6pcb_selecthlim(NULL, (rt = rtcache_validate(ro)) != NULL ? rt->rt_ifp : NULL); rtcache_unref(rt, ro); error = ip6_output(m, NULL /*XXX*/, ro, 0, NULL, tp ? tp->t_inpcb : NULL, NULL); break; #endif default: panic("%s: impossible (2)", __func__); } return error; }