2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 2007-2008,2010
7 * Swinburne University of Technology, Melbourne, Australia.
8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
9 * Copyright (c) 2010 The FreeBSD Foundation
10 * Copyright (c) 2010-2011 Juniper Networks, Inc.
11 * All rights reserved.
13 * Portions of this software were developed at the Centre for Advanced Internet
14 * Architectures, Swinburne University of Technology, by Lawrence Stewart,
15 * James Healy and David Hayes, made possible in part by a grant from the Cisco
16 * University Research Program Fund at Community Foundation Silicon Valley.
18 * Portions of this software were developed at the Centre for Advanced
19 * Internet Architectures, Swinburne University of Technology, Melbourne,
20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
22 * Portions of this software were developed by Robert N. M. Watson under
23 * contract to Juniper Networks, Inc.
25 * Redistribution and use in source and binary forms, with or without
26 * modification, are permitted provided that the following conditions
28 * 1. Redistributions of source code must retain the above copyright
29 * notice, this list of conditions and the following disclaimer.
30 * 2. Redistributions in binary form must reproduce the above copyright
31 * notice, this list of conditions and the following disclaimer in the
32 * documentation and/or other materials provided with the distribution.
33 * 3. Neither the name of the University nor the names of its contributors
34 * may be used to endorse or promote products derived from this software
35 * without specific prior written permission.
37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
52 #include <sys/cdefs.h>
53 __FBSDID("$FreeBSD$");
56 #include "opt_inet6.h"
57 #include "opt_ipsec.h"
58 #include "opt_tcpdebug.h"
60 #include <sys/param.h>
62 #include <sys/kernel.h>
64 #include <sys/hhook.h>
66 #include <sys/malloc.h>
68 #include <sys/proc.h> /* for proc0 declaration */
69 #include <sys/protosw.h>
70 #include <sys/qmath.h>
72 #include <sys/signalvar.h>
73 #include <sys/socket.h>
74 #include <sys/socketvar.h>
75 #include <sys/sysctl.h>
76 #include <sys/syslog.h>
77 #include <sys/systm.h>
78 #include <sys/stats.h>
80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
85 #include <net/if_var.h>
86 #include <net/route.h>
89 #define TCPSTATES /* for logging */
91 #include <netinet/in.h>
92 #include <netinet/in_kdtrace.h>
93 #include <netinet/in_pcb.h>
94 #include <netinet/in_systm.h>
95 #include <netinet/ip.h>
96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
98 #include <netinet/ip_var.h>
99 #include <netinet/ip_options.h>
100 #include <netinet/ip6.h>
101 #include <netinet/icmp6.h>
102 #include <netinet6/in6_pcb.h>
103 #include <netinet6/in6_var.h>
104 #include <netinet6/ip6_var.h>
105 #include <netinet6/nd6.h>
106 #include <netinet/tcp.h>
107 #include <netinet/tcp_fsm.h>
108 #include <netinet/tcp_log_buf.h>
109 #include <netinet/tcp_seq.h>
110 #include <netinet/tcp_timer.h>
111 #include <netinet/tcp_var.h>
112 #include <netinet6/tcp6_var.h>
113 #include <netinet/tcpip.h>
114 #include <netinet/cc/cc.h>
115 #include <netinet/tcp_fastopen.h>
117 #include <netinet/tcp_pcap.h>
119 #include <netinet/tcp_syncache.h>
121 #include <netinet/tcp_debug.h>
122 #endif /* TCPDEBUG */
124 #include <netinet/tcp_offload.h>
127 #include <netipsec/ipsec_support.h>
129 #include <machine/in_cksum.h>
131 #include <security/mac/mac_framework.h>
133 const int tcprexmtthresh = 3;
135 VNET_DEFINE(int, tcp_log_in_vain) = 0;
136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW,
137 &VNET_NAME(tcp_log_in_vain), 0,
138 "Log all incoming TCP segments to closed ports");
140 VNET_DEFINE(int, blackhole) = 0;
141 #define V_blackhole VNET(blackhole)
142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW,
143 &VNET_NAME(blackhole), 0,
144 "Do not send RST on segments to closed ports");
146 VNET_DEFINE(int, tcp_delack_enabled) = 1;
147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW,
148 &VNET_NAME(tcp_delack_enabled), 0,
149 "Delay ACK to try and piggyback it onto a data packet");
151 VNET_DEFINE(int, drop_synfin) = 0;
152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW,
153 &VNET_NAME(drop_synfin), 0,
154 "Drop TCP packets with SYN+FIN set");
156 VNET_DEFINE(int, tcp_do_newcwv) = 0;
157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW,
158 &VNET_NAME(tcp_do_newcwv), 0,
159 "Enable New Congestion Window Validation per RFC7661");
161 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0;
162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW,
163 &VNET_NAME(tcp_do_rfc6675_pipe), 0,
164 "Use calculated pipe/in-flight bytes per RFC 6675");
166 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW,
168 &VNET_NAME(tcp_do_rfc3042), 0,
169 "Enable RFC 3042 (Limited Transmit)");
171 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW,
173 &VNET_NAME(tcp_do_rfc3390), 0,
174 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
176 VNET_DEFINE(int, tcp_initcwnd_segments) = 10;
177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments,
178 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0,
179 "Slow-start flight size (initial congestion window) in number of segments");
181 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW,
183 &VNET_NAME(tcp_do_rfc3465), 0,
184 "Enable RFC 3465 (Appropriate Byte Counting)");
186 VNET_DEFINE(int, tcp_abc_l_var) = 2;
187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW,
188 &VNET_NAME(tcp_abc_l_var), 2,
189 "Cap the max cwnd increment during slow-start to this number of segments");
191 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn,
192 CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
195 VNET_DEFINE(int, tcp_do_ecn) = 2;
196 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
197 &VNET_NAME(tcp_do_ecn), 0,
200 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
201 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW,
202 &VNET_NAME(tcp_ecn_maxretries), 0,
203 "Max retries before giving up on ECN");
205 VNET_DEFINE(int, tcp_insecure_syn) = 0;
206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW,
207 &VNET_NAME(tcp_insecure_syn), 0,
208 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets");
210 VNET_DEFINE(int, tcp_insecure_rst) = 0;
211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW,
212 &VNET_NAME(tcp_insecure_rst), 0,
213 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets");
215 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
216 #define V_tcp_recvspace VNET(tcp_recvspace)
217 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW,
218 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
220 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
222 &VNET_NAME(tcp_do_autorcvbuf), 0,
223 "Enable automatic receive buffer sizing");
225 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
226 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
227 &VNET_NAME(tcp_autorcvbuf_max), 0,
228 "Max size of automatic receive buffer");
230 VNET_DEFINE(struct inpcbhead, tcb);
231 #define tcb6 tcb /* for KAME src sync over BSD*'s */
232 VNET_DEFINE(struct inpcbinfo, tcbinfo);
235 * TCP statistics are stored in an array of counter(9)s, which size matches
236 * size of struct tcpstat. TCP running connection count is a regular array.
238 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
239 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
240 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
241 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]);
242 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD |
243 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES,
244 "TCP connection counts by TCP state");
247 tcp_vnet_init(const void *unused)
250 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK);
251 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK);
253 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY,
254 tcp_vnet_init, NULL);
258 tcp_vnet_uninit(const void *unused)
261 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES);
262 VNET_PCPUSTAT_FREE(tcpstat);
264 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY,
265 tcp_vnet_uninit, NULL);
269 * Kernel module interface for updating tcpstat. The first argument is an index
270 * into tcpstat treated as an array.
273 kmod_tcpstat_add(int statnum, int val)
276 counter_u64_add(VNET(tcpstat)[statnum], val);
281 * Wrapper for the TCP established input helper hook.
284 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
286 struct tcp_hhook_data hhook_data;
288 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
293 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
300 * CC wrapper hook functions
303 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs,
310 INP_WLOCK_ASSERT(tp->t_inpcb);
312 tp->ccv->nsegs = nsegs;
313 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
314 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) ||
315 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) &&
316 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2))))
317 tp->ccv->flags |= CCF_CWND_LIMITED;
319 tp->ccv->flags &= ~CCF_CWND_LIMITED;
321 if (type == CC_ACK) {
323 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF,
324 ((int32_t)tp->snd_cwnd) - tp->snd_wnd);
325 if (!IN_RECOVERY(tp->t_flags))
326 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN,
327 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs));
328 if ((tp->t_flags & TF_GPUTINPROG) &&
329 SEQ_GEQ(th->th_ack, tp->gput_ack)) {
331 * Compute goodput in bits per millisecond.
333 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) /
334 max(1, tcp_ts_getticks() - tp->gput_ts);
335 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT,
338 * XXXLAS: This is a temporary hack, and should be
339 * chained off VOI_TCP_GPUT when stats(9) grows an API
340 * to deal with chained VOIs.
342 if (tp->t_stats_gput_prev > 0)
343 stats_voi_update_abs_s32(tp->t_stats,
345 ((gput - tp->t_stats_gput_prev) * 100) /
346 tp->t_stats_gput_prev);
347 tp->t_flags &= ~TF_GPUTINPROG;
348 tp->t_stats_gput_prev = gput;
351 if (tp->snd_cwnd > tp->snd_ssthresh) {
352 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
353 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp));
354 if (tp->t_bytes_acked >= tp->snd_cwnd) {
355 tp->t_bytes_acked -= tp->snd_cwnd;
356 tp->ccv->flags |= CCF_ABC_SENTAWND;
359 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
360 tp->t_bytes_acked = 0;
364 if (CC_ALGO(tp)->ack_received != NULL) {
365 /* XXXLAS: Find a way to live without this */
366 tp->ccv->curack = th->th_ack;
367 CC_ALGO(tp)->ack_received(tp->ccv, type);
370 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd);
375 cc_conn_init(struct tcpcb *tp)
377 struct hc_metrics_lite metrics;
378 struct inpcb *inp = tp->t_inpcb;
382 INP_WLOCK_ASSERT(tp->t_inpcb);
384 tcp_hc_get(&inp->inp_inc, &metrics);
385 maxseg = tcp_maxseg(tp);
387 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
389 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
390 TCPSTAT_INC(tcps_usedrtt);
391 if (metrics.rmx_rttvar) {
392 tp->t_rttvar = metrics.rmx_rttvar;
393 TCPSTAT_INC(tcps_usedrttvar);
395 /* default variation is +- 1 rtt */
397 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
399 TCPT_RANGESET(tp->t_rxtcur,
400 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
401 tp->t_rttmin, TCPTV_REXMTMAX);
403 if (metrics.rmx_ssthresh) {
405 * There's some sort of gateway or interface
406 * buffer limit on the path. Use this to set
407 * the slow start threshold, but set the
408 * threshold to no less than 2*mss.
410 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh);
411 TCPSTAT_INC(tcps_usedssthresh);
415 * Set the initial slow-start flight size.
417 * If a SYN or SYN/ACK was lost and retransmitted, we have to
418 * reduce the initial CWND to one segment as congestion is likely
419 * requiring us to be cautious.
421 if (tp->snd_cwnd == 1)
422 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */
424 tp->snd_cwnd = tcp_compute_initwnd(maxseg);
426 if (CC_ALGO(tp)->conn_init != NULL)
427 CC_ALGO(tp)->conn_init(tp->ccv);
431 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
435 INP_WLOCK_ASSERT(tp->t_inpcb);
438 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type);
443 if (!IN_FASTRECOVERY(tp->t_flags)) {
444 tp->snd_recover = tp->snd_max;
445 if (tp->t_flags2 & TF2_ECN_PERMIT)
446 tp->t_flags2 |= TF2_ECN_SND_CWR;
450 if (!IN_CONGRECOVERY(tp->t_flags) ||
452 * Allow ECN reaction on ACK to CWR, if
453 * that data segment was also CE marked.
455 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
456 EXIT_CONGRECOVERY(tp->t_flags);
457 TCPSTAT_INC(tcps_ecn_rcwnd);
458 tp->snd_recover = tp->snd_max + 1;
459 if (tp->t_flags2 & TF2_ECN_PERMIT)
460 tp->t_flags2 |= TF2_ECN_SND_CWR;
464 maxseg = tcp_maxseg(tp);
466 tp->t_bytes_acked = 0;
467 EXIT_RECOVERY(tp->t_flags);
468 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
470 tp->snd_cwnd = maxseg;
471 if (tp->t_flags2 & TF2_ECN_PERMIT)
472 tp->t_flags2 |= TF2_ECN_SND_CWR;
475 TCPSTAT_INC(tcps_sndrexmitbad);
476 /* RTO was unnecessary, so reset everything. */
477 tp->snd_cwnd = tp->snd_cwnd_prev;
478 tp->snd_ssthresh = tp->snd_ssthresh_prev;
479 tp->snd_recover = tp->snd_recover_prev;
480 if (tp->t_flags & TF_WASFRECOVERY)
481 ENTER_FASTRECOVERY(tp->t_flags);
482 if (tp->t_flags & TF_WASCRECOVERY)
483 ENTER_CONGRECOVERY(tp->t_flags);
484 tp->snd_nxt = tp->snd_max;
485 tp->t_flags &= ~TF_PREVVALID;
490 if (CC_ALGO(tp)->cong_signal != NULL) {
492 tp->ccv->curack = th->th_ack;
493 CC_ALGO(tp)->cong_signal(tp->ccv, type);
498 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
500 INP_WLOCK_ASSERT(tp->t_inpcb);
502 /* XXXLAS: KASSERT that we're in recovery? */
504 if (CC_ALGO(tp)->post_recovery != NULL) {
505 tp->ccv->curack = th->th_ack;
506 CC_ALGO(tp)->post_recovery(tp->ccv);
508 /* XXXLAS: EXIT_RECOVERY ? */
509 tp->t_bytes_acked = 0;
513 * Indicate whether this ack should be delayed. We can delay the ack if
514 * following conditions are met:
515 * - There is no delayed ack timer in progress.
516 * - Our last ack wasn't a 0-sized window. We never want to delay
517 * the ack that opens up a 0-sized window.
518 * - LRO wasn't used for this segment. We make sure by checking that the
519 * segment size is not larger than the MSS.
521 #define DELAY_ACK(tp, tlen) \
522 ((!tcp_timer_active(tp, TT_DELACK) && \
523 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
524 (tlen <= tp->t_maxseg) && \
525 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
528 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos)
530 INP_WLOCK_ASSERT(tp->t_inpcb);
532 if (CC_ALGO(tp)->ecnpkt_handler != NULL) {
533 switch (iptos & IPTOS_ECN_MASK) {
535 tp->ccv->flags |= CCF_IPHDR_CE;
541 case IPTOS_ECN_NOTECT:
542 tp->ccv->flags &= ~CCF_IPHDR_CE;
546 if (th->th_flags & TH_CWR)
547 tp->ccv->flags |= CCF_TCPHDR_CWR;
549 tp->ccv->flags &= ~CCF_TCPHDR_CWR;
551 CC_ALGO(tp)->ecnpkt_handler(tp->ccv);
553 if (tp->ccv->flags & CCF_ACKNOW) {
554 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
555 tp->t_flags |= TF_ACKNOW;
561 * TCP input handling is split into multiple parts:
562 * tcp6_input is a thin wrapper around tcp_input for the extended
563 * ip6_protox[] call format in ip6_input
564 * tcp_input handles primary segment validation, inpcb lookup and
565 * SYN processing on listen sockets
566 * tcp_do_segment processes the ACK and text of the segment for
567 * establishing, established and closing connections
571 tcp6_input(struct mbuf **mp, int *offp, int proto)
574 struct in6_ifaddr *ia6;
578 if (m->m_len < *offp + sizeof(struct tcphdr)) {
579 m = m_pullup(m, *offp + sizeof(struct tcphdr));
582 TCPSTAT_INC(tcps_rcvshort);
583 return (IPPROTO_DONE);
588 * draft-itojun-ipv6-tcp-to-anycast
589 * better place to put this in?
591 ip6 = mtod(m, struct ip6_hdr *);
592 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
593 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
595 ifa_free(&ia6->ia_ifa);
596 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
597 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
599 return (IPPROTO_DONE);
602 ifa_free(&ia6->ia_ifa);
605 return (tcp_input(mp, offp, proto));
610 tcp_input(struct mbuf **mp, int *offp, int proto)
612 struct mbuf *m = *mp;
613 struct tcphdr *th = NULL;
614 struct ip *ip = NULL;
615 struct inpcb *inp = NULL;
616 struct tcpcb *tp = NULL;
617 struct socket *so = NULL;
628 int rstreason = 0; /* For badport_bandlim accounting purposes */
630 struct m_tag *fwd_tag = NULL;
632 struct ip6_hdr *ip6 = NULL;
635 const void *ip6 = NULL;
637 struct tcpopt to; /* options in this segment */
638 char *s = NULL; /* address and port logging */
641 * The size of tcp_saveipgen must be the size of the max ip header,
644 u_char tcp_saveipgen[IP6_HDR_LEN];
645 struct tcphdr tcp_savetcp;
652 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
659 TCPSTAT_INC(tcps_rcvtotal);
664 ip6 = mtod(m, struct ip6_hdr *);
665 th = (struct tcphdr *)((caddr_t)ip6 + off0);
666 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
667 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
668 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
669 th->th_sum = m->m_pkthdr.csum_data;
671 th->th_sum = in6_cksum_pseudo(ip6, tlen,
672 IPPROTO_TCP, m->m_pkthdr.csum_data);
673 th->th_sum ^= 0xffff;
675 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
677 TCPSTAT_INC(tcps_rcvbadsum);
682 * Be proactive about unspecified IPv6 address in source.
683 * As we use all-zero to indicate unbounded/unconnected pcb,
684 * unspecified IPv6 address can be used to confuse us.
686 * Note that packets with unspecified IPv6 destination is
687 * already dropped in ip6_input.
689 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
693 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
696 #if defined(INET) && defined(INET6)
702 * Get IP and TCP header together in first mbuf.
703 * Note: IP leaves IP header in first mbuf.
705 if (off0 > sizeof (struct ip)) {
707 off0 = sizeof(struct ip);
709 if (m->m_len < sizeof (struct tcpiphdr)) {
710 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
712 TCPSTAT_INC(tcps_rcvshort);
713 return (IPPROTO_DONE);
716 ip = mtod(m, struct ip *);
717 th = (struct tcphdr *)((caddr_t)ip + off0);
718 tlen = ntohs(ip->ip_len) - off0;
721 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
722 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
723 th->th_sum = m->m_pkthdr.csum_data;
725 th->th_sum = in_pseudo(ip->ip_src.s_addr,
727 htonl(m->m_pkthdr.csum_data + tlen +
729 th->th_sum ^= 0xffff;
731 struct ipovly *ipov = (struct ipovly *)ip;
734 * Checksum extended TCP header and data.
738 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
739 ipov->ih_len = htons(tlen);
740 th->th_sum = in_cksum(m, len);
741 /* Reset length for SDT probes. */
742 ip->ip_len = htons(len);
745 /* Re-initialization for later version check */
747 ip->ip_v = IPVERSION;
748 ip->ip_hl = off0 >> 2;
752 TCPSTAT_INC(tcps_rcvbadsum);
759 * Check that TCP offset makes sense,
760 * pull out TCP options and adjust length. XXX
762 off = th->th_off << 2;
763 if (off < sizeof (struct tcphdr) || off > tlen) {
764 TCPSTAT_INC(tcps_rcvbadoff);
767 tlen -= off; /* tlen is used instead of ti->ti_len */
768 if (off > sizeof (struct tcphdr)) {
771 if (m->m_len < off0 + off) {
772 m = m_pullup(m, off0 + off);
774 TCPSTAT_INC(tcps_rcvshort);
775 return (IPPROTO_DONE);
778 ip6 = mtod(m, struct ip6_hdr *);
779 th = (struct tcphdr *)((caddr_t)ip6 + off0);
782 #if defined(INET) && defined(INET6)
787 if (m->m_len < sizeof(struct ip) + off) {
788 if ((m = m_pullup(m, sizeof (struct ip) + off))
790 TCPSTAT_INC(tcps_rcvshort);
791 return (IPPROTO_DONE);
793 ip = mtod(m, struct ip *);
794 th = (struct tcphdr *)((caddr_t)ip + off0);
798 optlen = off - sizeof (struct tcphdr);
799 optp = (u_char *)(th + 1);
801 thflags = th->th_flags;
804 * Convert TCP protocol specific fields to host format.
806 tcp_fields_to_host(th);
809 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
811 drop_hdrlen = off0 + off;
814 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
818 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
820 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
823 #if defined(INET) && !defined(INET6)
824 (m->m_flags & M_IP_NEXTHOP)
827 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
831 if (isipv6 && fwd_tag != NULL) {
832 struct sockaddr_in6 *next_hop6;
834 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
836 * Transparently forwarded. Pretend to be the destination.
837 * Already got one like this?
839 inp = in6_pcblookup_mbuf(&V_tcbinfo,
840 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
841 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
844 * It's new. Try to find the ambushing socket.
845 * Because we've rewritten the destination address,
846 * any hardware-generated hash is ignored.
848 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
849 th->th_sport, &next_hop6->sin6_addr,
850 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
851 th->th_dport, INPLOOKUP_WILDCARD |
852 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
855 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
856 th->th_sport, &ip6->ip6_dst, th->th_dport,
857 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
858 m->m_pkthdr.rcvif, m);
861 #if defined(INET6) && defined(INET)
865 if (fwd_tag != NULL) {
866 struct sockaddr_in *next_hop;
868 next_hop = (struct sockaddr_in *)(fwd_tag+1);
870 * Transparently forwarded. Pretend to be the destination.
871 * already got one like this?
873 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
874 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
875 m->m_pkthdr.rcvif, m);
878 * It's new. Try to find the ambushing socket.
879 * Because we've rewritten the destination address,
880 * any hardware-generated hash is ignored.
882 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
883 th->th_sport, next_hop->sin_addr,
884 next_hop->sin_port ? ntohs(next_hop->sin_port) :
885 th->th_dport, INPLOOKUP_WILDCARD |
886 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
889 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
890 th->th_sport, ip->ip_dst, th->th_dport,
891 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
892 m->m_pkthdr.rcvif, m);
896 * If the INPCB does not exist then all data in the incoming
897 * segment is discarded and an appropriate RST is sent back.
898 * XXX MRT Send RST using which routing table?
902 * Log communication attempts to ports that are not
905 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
906 V_tcp_log_in_vain == 2) {
907 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
908 log(LOG_INFO, "%s; %s: Connection attempt "
909 "to closed port\n", s, __func__);
912 * When blackholing do not respond with a RST but
913 * completely ignore the segment and drop it.
915 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
919 rstreason = BANDLIM_RST_CLOSEDPORT;
922 INP_WLOCK_ASSERT(inp);
924 * While waiting for inp lock during the lookup, another thread
925 * can have dropped the inpcb, in which case we need to loop back
926 * and try to find a new inpcb to deliver to.
928 if (inp->inp_flags & INP_DROPPED) {
933 if ((inp->inp_flowtype == M_HASHTYPE_NONE) &&
934 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) &&
935 ((inp->inp_socket == NULL) ||
936 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
937 inp->inp_flowid = m->m_pkthdr.flowid;
938 inp->inp_flowtype = M_HASHTYPE_GET(m);
940 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
942 if (isipv6 && IPSEC_ENABLED(ipv6) &&
943 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) {
951 if (IPSEC_ENABLED(ipv4) &&
952 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) {
959 * Check the minimum TTL for socket.
961 if (inp->inp_ip_minttl != 0) {
964 if (inp->inp_ip_minttl > ip6->ip6_hlim)
968 if (inp->inp_ip_minttl > ip->ip_ttl)
973 * A previous connection in TIMEWAIT state is supposed to catch stray
974 * or duplicate segments arriving late. If this segment was a
975 * legitimate new connection attempt, the old INPCB gets removed and
976 * we can try again to find a listening socket.
978 * At this point, due to earlier optimism, we may hold only an inpcb
979 * lock, and not the inpcbinfo write lock. If so, we need to try to
980 * acquire it, or if that fails, acquire a reference on the inpcb,
981 * drop all locks, acquire a global write lock, and then re-acquire
982 * the inpcb lock. We may at that point discover that another thread
983 * has tried to free the inpcb, in which case we need to loop back
984 * and try to find a new inpcb to deliver to.
986 * XXXRW: It may be time to rethink timewait locking.
988 if (inp->inp_flags & INP_TIMEWAIT) {
989 if (thflags & TH_SYN)
990 tcp_dooptions(&to, optp, optlen, TO_SYN);
992 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
994 if (tcp_twcheck(inp, &to, th, m, tlen))
996 return (IPPROTO_DONE);
999 * The TCPCB may no longer exist if the connection is winding
1000 * down or it is in the CLOSED state. Either way we drop the
1001 * segment and send an appropriate response.
1003 tp = intotcpcb(inp);
1004 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
1005 rstreason = BANDLIM_RST_CLOSEDPORT;
1010 if (tp->t_flags & TF_TOE) {
1011 tcp_offload_input(tp, m);
1012 m = NULL; /* consumed by the TOE driver */
1018 INP_WLOCK_ASSERT(inp);
1019 if (mac_inpcb_check_deliver(inp, m))
1022 so = inp->inp_socket;
1023 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1025 if (so->so_options & SO_DEBUG) {
1026 ostate = tp->t_state;
1029 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1032 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1035 #endif /* TCPDEBUG */
1037 * When the socket is accepting connections (the INPCB is in LISTEN
1038 * state) we look into the SYN cache if this is a new connection
1039 * attempt or the completion of a previous one.
1041 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN),
1042 ("%s: so accepting but tp %p not listening", __func__, tp));
1043 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) {
1044 struct in_conninfo inc;
1046 bzero(&inc, sizeof(inc));
1049 inc.inc_flags |= INC_ISIPV6;
1050 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU)
1051 inc.inc_flags |= INC_IPV6MINMTU;
1052 inc.inc6_faddr = ip6->ip6_src;
1053 inc.inc6_laddr = ip6->ip6_dst;
1057 inc.inc_faddr = ip->ip_src;
1058 inc.inc_laddr = ip->ip_dst;
1060 inc.inc_fport = th->th_sport;
1061 inc.inc_lport = th->th_dport;
1062 inc.inc_fibnum = so->so_fibnum;
1065 * Check for an existing connection attempt in syncache if
1066 * the flag is only ACK. A successful lookup creates a new
1067 * socket appended to the listen queue in SYN_RECEIVED state.
1069 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1072 * Parse the TCP options here because
1073 * syncookies need access to the reflected
1076 tcp_dooptions(&to, optp, optlen, 0);
1078 * NB: syncache_expand() doesn't unlock
1079 * inp and tcpinfo locks.
1081 rstreason = syncache_expand(&inc, &to, th, &so, m);
1082 if (rstreason < 0) {
1084 * A failing TCP MD5 signature comparison
1085 * must result in the segment being dropped
1086 * and must not produce any response back
1090 } else if (rstreason == 0) {
1092 * No syncache entry or ACK was not
1093 * for our SYN/ACK. Send a RST.
1094 * NB: syncache did its own logging
1095 * of the failure cause.
1097 rstreason = BANDLIM_RST_OPENPORT;
1103 * We completed the 3-way handshake
1104 * but could not allocate a socket
1105 * either due to memory shortage,
1106 * listen queue length limits or
1107 * global socket limits. Send RST
1108 * or wait and have the remote end
1109 * retransmit the ACK for another
1112 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1113 log(LOG_DEBUG, "%s; %s: Listen socket: "
1114 "Socket allocation failed due to "
1115 "limits or memory shortage, %s\n",
1117 V_tcp_sc_rst_sock_fail ?
1118 "sending RST" : "try again");
1119 if (V_tcp_sc_rst_sock_fail) {
1120 rstreason = BANDLIM_UNLIMITED;
1126 * Socket is created in state SYN_RECEIVED.
1127 * Unlock the listen socket, lock the newly
1128 * created socket and update the tp variable.
1130 INP_WUNLOCK(inp); /* listen socket */
1131 inp = sotoinpcb(so);
1133 * New connection inpcb is already locked by
1134 * syncache_expand().
1136 INP_WLOCK_ASSERT(inp);
1137 tp = intotcpcb(inp);
1138 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1139 ("%s: ", __func__));
1141 * Process the segment and the data it
1142 * contains. tcp_do_segment() consumes
1143 * the mbuf chain and unlocks the inpcb.
1145 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1146 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1148 return (IPPROTO_DONE);
1151 * Segment flag validation for new connection attempts:
1153 * Our (SYN|ACK) response was rejected.
1154 * Check with syncache and remove entry to prevent
1157 * NB: syncache_chkrst does its own logging of failure
1160 if (thflags & TH_RST) {
1161 syncache_chkrst(&inc, th, m);
1165 * We can't do anything without SYN.
1167 if ((thflags & TH_SYN) == 0) {
1168 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1169 log(LOG_DEBUG, "%s; %s: Listen socket: "
1170 "SYN is missing, segment ignored\n",
1172 TCPSTAT_INC(tcps_badsyn);
1176 * (SYN|ACK) is bogus on a listen socket.
1178 if (thflags & TH_ACK) {
1179 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1180 log(LOG_DEBUG, "%s; %s: Listen socket: "
1181 "SYN|ACK invalid, segment rejected\n",
1183 syncache_badack(&inc); /* XXX: Not needed! */
1184 TCPSTAT_INC(tcps_badsyn);
1185 rstreason = BANDLIM_RST_OPENPORT;
1189 * If the drop_synfin option is enabled, drop all
1190 * segments with both the SYN and FIN bits set.
1191 * This prevents e.g. nmap from identifying the
1193 * XXX: Poor reasoning. nmap has other methods
1194 * and is constantly refining its stack detection
1196 * XXX: This is a violation of the TCP specification
1197 * and was used by RFC1644.
1199 if ((thflags & TH_FIN) && V_drop_synfin) {
1200 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1201 log(LOG_DEBUG, "%s; %s: Listen socket: "
1202 "SYN|FIN segment ignored (based on "
1203 "sysctl setting)\n", s, __func__);
1204 TCPSTAT_INC(tcps_badsyn);
1208 * Segment's flags are (SYN) or (SYN|FIN).
1210 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1211 * as they do not affect the state of the TCP FSM.
1212 * The data pointed to by TH_URG and th_urp is ignored.
1214 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1215 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1216 KASSERT(thflags & (TH_SYN),
1217 ("%s: Listen socket: TH_SYN not set", __func__));
1220 * If deprecated address is forbidden,
1221 * we do not accept SYN to deprecated interface
1222 * address to prevent any new inbound connection from
1223 * getting established.
1224 * When we do not accept SYN, we send a TCP RST,
1225 * with deprecated source address (instead of dropping
1226 * it). We compromise it as it is much better for peer
1227 * to send a RST, and RST will be the final packet
1230 * If we do not forbid deprecated addresses, we accept
1231 * the SYN packet. RFC2462 does not suggest dropping
1233 * If we decipher RFC2462 5.5.4, it says like this:
1234 * 1. use of deprecated addr with existing
1235 * communication is okay - "SHOULD continue to be
1237 * 2. use of it with new communication:
1238 * (2a) "SHOULD NOT be used if alternate address
1239 * with sufficient scope is available"
1240 * (2b) nothing mentioned otherwise.
1241 * Here we fall into (2b) case as we have no choice in
1242 * our source address selection - we must obey the peer.
1244 * The wording in RFC2462 is confusing, and there are
1245 * multiple description text for deprecated address
1246 * handling - worse, they are not exactly the same.
1247 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1249 if (isipv6 && !V_ip6_use_deprecated) {
1250 struct in6_ifaddr *ia6;
1252 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
1254 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1255 ifa_free(&ia6->ia_ifa);
1256 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1257 log(LOG_DEBUG, "%s; %s: Listen socket: "
1258 "Connection attempt to deprecated "
1259 "IPv6 address rejected\n",
1261 rstreason = BANDLIM_RST_OPENPORT;
1265 ifa_free(&ia6->ia_ifa);
1269 * Basic sanity checks on incoming SYN requests:
1270 * Don't respond if the destination is a link layer
1271 * broadcast according to RFC1122 4.2.3.10, p. 104.
1272 * If it is from this socket it must be forged.
1273 * Don't respond if the source or destination is a
1274 * global or subnet broad- or multicast address.
1275 * Note that it is quite possible to receive unicast
1276 * link-layer packets with a broadcast IP address. Use
1277 * in_broadcast() to find them.
1279 if (m->m_flags & (M_BCAST|M_MCAST)) {
1280 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1281 log(LOG_DEBUG, "%s; %s: Listen socket: "
1282 "Connection attempt from broad- or multicast "
1283 "link layer address ignored\n", s, __func__);
1288 if (th->th_dport == th->th_sport &&
1289 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1290 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1291 log(LOG_DEBUG, "%s; %s: Listen socket: "
1292 "Connection attempt to/from self "
1293 "ignored\n", s, __func__);
1296 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1297 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1298 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1299 log(LOG_DEBUG, "%s; %s: Listen socket: "
1300 "Connection attempt from/to multicast "
1301 "address ignored\n", s, __func__);
1306 #if defined(INET) && defined(INET6)
1311 if (th->th_dport == th->th_sport &&
1312 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1313 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1314 log(LOG_DEBUG, "%s; %s: Listen socket: "
1315 "Connection attempt from/to self "
1316 "ignored\n", s, __func__);
1319 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1320 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1321 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1322 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1323 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1324 log(LOG_DEBUG, "%s; %s: Listen socket: "
1325 "Connection attempt from/to broad- "
1326 "or multicast address ignored\n",
1333 * SYN appears to be valid. Create compressed TCP state
1337 if (so->so_options & SO_DEBUG)
1338 tcp_trace(TA_INPUT, ostate, tp,
1339 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1341 TCP_PROBE3(debug__input, tp, th, m);
1342 tcp_dooptions(&to, optp, optlen, TO_SYN);
1343 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL, iptos))
1344 goto tfo_socket_result;
1347 * Entry added to syncache and mbuf consumed.
1348 * Only the listen socket is unlocked by syncache_add().
1350 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1351 return (IPPROTO_DONE);
1352 } else if (tp->t_state == TCPS_LISTEN) {
1354 * When a listen socket is torn down the SO_ACCEPTCONN
1355 * flag is removed first while connections are drained
1356 * from the accept queue in a unlock/lock cycle of the
1357 * ACCEPT_LOCK, opening a race condition allowing a SYN
1358 * attempt go through unhandled.
1362 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1363 if (tp->t_flags & TF_SIGNATURE) {
1364 tcp_dooptions(&to, optp, optlen, thflags);
1365 if ((to.to_flags & TOF_SIGNATURE) == 0) {
1366 TCPSTAT_INC(tcps_sig_err_nosigopt);
1369 if (!TCPMD5_ENABLED() ||
1370 TCPMD5_INPUT(m, th, to.to_signature) != 0)
1374 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1377 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1378 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1379 * the inpcb, and unlocks pcbinfo.
1381 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos);
1382 return (IPPROTO_DONE);
1385 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1388 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1391 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1392 m = NULL; /* mbuf chain got consumed. */
1397 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1403 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1408 return (IPPROTO_DONE);
1412 * Automatic sizing of receive socket buffer. Often the send
1413 * buffer size is not optimally adjusted to the actual network
1414 * conditions at hand (delay bandwidth product). Setting the
1415 * buffer size too small limits throughput on links with high
1416 * bandwidth and high delay (eg. trans-continental/oceanic links).
1418 * On the receive side the socket buffer memory is only rarely
1419 * used to any significant extent. This allows us to be much
1420 * more aggressive in scaling the receive socket buffer. For
1421 * the case that the buffer space is actually used to a large
1422 * extent and we run out of kernel memory we can simply drop
1423 * the new segments; TCP on the sender will just retransmit it
1424 * later. Setting the buffer size too big may only consume too
1425 * much kernel memory if the application doesn't read() from
1426 * the socket or packet loss or reordering makes use of the
1429 * The criteria to step up the receive buffer one notch are:
1430 * 1. Application has not set receive buffer size with
1431 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1432 * 2. the number of bytes received during 1/2 of an sRTT
1433 * is at least 3/8 of the current socket buffer size.
1434 * 3. receive buffer size has not hit maximal automatic size;
1436 * If all of the criteria are met we increaset the socket buffer
1437 * by a 1/2 (bounded by the max). This allows us to keep ahead
1438 * of slow-start but also makes it so our peer never gets limited
1439 * by our rwnd which we then open up causing a burst.
1441 * This algorithm does two steps per RTT at most and only if
1442 * we receive a bulk stream w/o packet losses or reorderings.
1443 * Shrinking the buffer during idle times is not necessary as
1444 * it doesn't consume any memory when idle.
1446 * TODO: Only step up if the application is actually serving
1447 * the buffer to better manage the socket buffer resources.
1450 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so,
1451 struct tcpcb *tp, int tlen)
1455 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
1456 tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
1457 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) >
1458 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) {
1459 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) &&
1460 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) {
1461 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max);
1463 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize);
1465 /* Start over with next RTT. */
1469 tp->rfbuf_cnt += tlen; /* add up */
1475 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1476 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos)
1478 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed;
1479 int rstreason, todrop, win, incforsyn = 0;
1483 struct in_conninfo *inc;
1490 * The size of tcp_saveipgen must be the size of the max ip header,
1493 u_char tcp_saveipgen[IP6_HDR_LEN];
1494 struct tcphdr tcp_savetcp;
1497 thflags = th->th_flags;
1498 inc = &tp->t_inpcb->inp_inc;
1499 tp->sackhint.last_sack_ack = 0;
1501 nsegs = max(1, m->m_pkthdr.lro_nsegs);
1504 INP_WLOCK_ASSERT(tp->t_inpcb);
1505 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1507 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1511 /* Save segment, if requested. */
1512 tcp_pcap_add(th, m, &(tp->t_inpkts));
1514 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0,
1517 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
1518 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1519 log(LOG_DEBUG, "%s; %s: "
1520 "SYN|FIN segment ignored (based on "
1521 "sysctl setting)\n", s, __func__);
1528 * If a segment with the ACK-bit set arrives in the SYN-SENT state
1529 * check SEQ.ACK first.
1531 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) &&
1532 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) {
1533 rstreason = BANDLIM_UNLIMITED;
1538 * Segment received on connection.
1539 * Reset idle time and keep-alive timer.
1540 * XXX: This should be done after segment
1541 * validation to ignore broken/spoofed segs.
1543 tp->t_rcvtime = ticks;
1546 * Scale up the window into a 32-bit value.
1547 * For the SYN_SENT state the scale is zero.
1549 tiwin = th->th_win << tp->snd_scale;
1551 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin);
1555 * TCP ECN processing.
1557 if (tp->t_flags2 & TF2_ECN_PERMIT) {
1558 if (thflags & TH_CWR) {
1559 tp->t_flags2 &= ~TF2_ECN_SND_ECE;
1560 tp->t_flags |= TF_ACKNOW;
1562 switch (iptos & IPTOS_ECN_MASK) {
1564 tp->t_flags2 |= TF2_ECN_SND_ECE;
1565 TCPSTAT_INC(tcps_ecn_ce);
1567 case IPTOS_ECN_ECT0:
1568 TCPSTAT_INC(tcps_ecn_ect0);
1570 case IPTOS_ECN_ECT1:
1571 TCPSTAT_INC(tcps_ecn_ect1);
1575 /* Process a packet differently from RFC3168. */
1576 cc_ecnpkt_handler(tp, th, iptos);
1578 /* Congestion experienced. */
1579 if (thflags & TH_ECE) {
1580 cc_cong_signal(tp, th, CC_ECN);
1585 * Parse options on any incoming segment.
1587 tcp_dooptions(&to, (u_char *)(th + 1),
1588 (th->th_off << 2) - sizeof(struct tcphdr),
1589 (thflags & TH_SYN) ? TO_SYN : 0);
1591 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1592 if ((tp->t_flags & TF_SIGNATURE) != 0 &&
1593 (to.to_flags & TOF_SIGNATURE) == 0) {
1594 TCPSTAT_INC(tcps_sig_err_sigopt);
1595 /* XXX: should drop? */
1599 * If echoed timestamp is later than the current time,
1600 * fall back to non RFC1323 RTT calculation. Normalize
1601 * timestamp if syncookies were used when this connection
1604 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1605 to.to_tsecr -= tp->ts_offset;
1606 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1608 else if (tp->t_flags & TF_PREVVALID &&
1609 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
1610 cc_cong_signal(tp, th, CC_RTO_ERR);
1613 * Process options only when we get SYN/ACK back. The SYN case
1614 * for incoming connections is handled in tcp_syncache.
1615 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1616 * or <SYN,ACK>) segment itself is never scaled.
1617 * XXX this is traditional behavior, may need to be cleaned up.
1619 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1620 /* Handle parallel SYN for ECN */
1621 if (!(thflags & TH_ACK) &&
1622 ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) &&
1623 ((V_tcp_do_ecn == 1) || (V_tcp_do_ecn == 2))) {
1624 tp->t_flags2 |= TF2_ECN_PERMIT;
1625 tp->t_flags2 |= TF2_ECN_SND_ECE;
1626 TCPSTAT_INC(tcps_ecn_shs);
1628 if ((to.to_flags & TOF_SCALE) &&
1629 (tp->t_flags & TF_REQ_SCALE)) {
1630 tp->t_flags |= TF_RCVD_SCALE;
1631 tp->snd_scale = to.to_wscale;
1633 tp->t_flags &= ~TF_REQ_SCALE;
1635 * Initial send window. It will be updated with
1636 * the next incoming segment to the scaled value.
1638 tp->snd_wnd = th->th_win;
1639 if ((to.to_flags & TOF_TS) &&
1640 (tp->t_flags & TF_REQ_TSTMP)) {
1641 tp->t_flags |= TF_RCVD_TSTMP;
1642 tp->ts_recent = to.to_tsval;
1643 tp->ts_recent_age = tcp_ts_getticks();
1645 tp->t_flags &= ~TF_REQ_TSTMP;
1646 if (to.to_flags & TOF_MSS)
1647 tcp_mss(tp, to.to_mss);
1648 if ((tp->t_flags & TF_SACK_PERMIT) &&
1649 (to.to_flags & TOF_SACKPERM) == 0)
1650 tp->t_flags &= ~TF_SACK_PERMIT;
1651 if (IS_FASTOPEN(tp->t_flags)) {
1652 if (to.to_flags & TOF_FASTOPEN) {
1655 if (to.to_flags & TOF_MSS)
1658 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
1662 tcp_fastopen_update_cache(tp, mss,
1663 to.to_tfo_len, to.to_tfo_cookie);
1665 tcp_fastopen_disable_path(tp);
1670 * If timestamps were negotiated during SYN/ACK they should
1671 * appear on every segment during this session and vice versa.
1673 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1674 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1675 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1676 "no action\n", s, __func__);
1680 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1681 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1682 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1683 "no action\n", s, __func__);
1689 * Header prediction: check for the two common cases
1690 * of a uni-directional data xfer. If the packet has
1691 * no control flags, is in-sequence, the window didn't
1692 * change and we're not retransmitting, it's a
1693 * candidate. If the length is zero and the ack moved
1694 * forward, we're the sender side of the xfer. Just
1695 * free the data acked & wake any higher level process
1696 * that was blocked waiting for space. If the length
1697 * is non-zero and the ack didn't move, we're the
1698 * receiver side. If we're getting packets in-order
1699 * (the reassembly queue is empty), add the data to
1700 * the socket buffer and note that we need a delayed ack.
1701 * Make sure that the hidden state-flags are also off.
1702 * Since we check for TCPS_ESTABLISHED first, it can only
1705 if (tp->t_state == TCPS_ESTABLISHED &&
1706 th->th_seq == tp->rcv_nxt &&
1707 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1708 tp->snd_nxt == tp->snd_max &&
1709 tiwin && tiwin == tp->snd_wnd &&
1710 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1712 ((to.to_flags & TOF_TS) == 0 ||
1713 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1716 * If last ACK falls within this segment's sequence numbers,
1717 * record the timestamp.
1718 * NOTE that the test is modified according to the latest
1719 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1721 if ((to.to_flags & TOF_TS) != 0 &&
1722 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1723 tp->ts_recent_age = tcp_ts_getticks();
1724 tp->ts_recent = to.to_tsval;
1728 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1729 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1730 !IN_RECOVERY(tp->t_flags) &&
1731 (to.to_flags & TOF_SACK) == 0 &&
1732 TAILQ_EMPTY(&tp->snd_holes)) {
1734 * This is a pure ack for outstanding data.
1736 TCPSTAT_INC(tcps_predack);
1739 * "bad retransmit" recovery without timestamps.
1741 if ((to.to_flags & TOF_TS) == 0 &&
1742 tp->t_rxtshift == 1 &&
1743 tp->t_flags & TF_PREVVALID &&
1744 (int)(ticks - tp->t_badrxtwin) < 0) {
1745 cc_cong_signal(tp, th, CC_RTO_ERR);
1749 * Recalculate the transmit timer / rtt.
1751 * Some boxes send broken timestamp replies
1752 * during the SYN+ACK phase, ignore
1753 * timestamps of 0 or we could calculate a
1754 * huge RTT and blow up the retransmit timer.
1756 if ((to.to_flags & TOF_TS) != 0 &&
1760 t = tcp_ts_getticks() - to.to_tsecr;
1761 if (!tp->t_rttlow || tp->t_rttlow > t)
1764 TCP_TS_TO_TICKS(t) + 1);
1765 } else if (tp->t_rtttime &&
1766 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1767 if (!tp->t_rttlow ||
1768 tp->t_rttlow > ticks - tp->t_rtttime)
1769 tp->t_rttlow = ticks - tp->t_rtttime;
1771 ticks - tp->t_rtttime);
1773 acked = BYTES_THIS_ACK(tp, th);
1776 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1777 hhook_run_tcp_est_in(tp, th, &to);
1780 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
1781 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1782 sbdrop(&so->so_snd, acked);
1783 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1784 SEQ_LEQ(th->th_ack, tp->snd_recover))
1785 tp->snd_recover = th->th_ack - 1;
1788 * Let the congestion control algorithm update
1789 * congestion control related information. This
1790 * typically means increasing the congestion
1793 cc_ack_received(tp, th, nsegs, CC_ACK);
1795 tp->snd_una = th->th_ack;
1797 * Pull snd_wl2 up to prevent seq wrap relative
1800 tp->snd_wl2 = th->th_ack;
1805 * If all outstanding data are acked, stop
1806 * retransmit timer, otherwise restart timer
1807 * using current (possibly backed-off) value.
1808 * If process is waiting for space,
1809 * wakeup/selwakeup/signal. If data
1810 * are ready to send, let tcp_output
1811 * decide between more output or persist.
1814 if (so->so_options & SO_DEBUG)
1815 tcp_trace(TA_INPUT, ostate, tp,
1816 (void *)tcp_saveipgen,
1819 TCP_PROBE3(debug__input, tp, th, m);
1820 if (tp->snd_una == tp->snd_max)
1821 tcp_timer_activate(tp, TT_REXMT, 0);
1822 else if (!tcp_timer_active(tp, TT_PERSIST))
1823 tcp_timer_activate(tp, TT_REXMT,
1826 if (sbavail(&so->so_snd))
1827 (void) tp->t_fb->tfb_tcp_output(tp);
1830 } else if (th->th_ack == tp->snd_una &&
1831 tlen <= sbspace(&so->so_rcv)) {
1832 int newsize = 0; /* automatic sockbuf scaling */
1835 * This is a pure, in-sequence data packet with
1836 * nothing on the reassembly queue and we have enough
1837 * buffer space to take it.
1839 /* Clean receiver SACK report if present */
1840 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1841 tcp_clean_sackreport(tp);
1842 TCPSTAT_INC(tcps_preddat);
1843 tp->rcv_nxt += tlen;
1845 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) &&
1846 (tp->t_fbyte_in == 0)) {
1847 tp->t_fbyte_in = ticks;
1848 if (tp->t_fbyte_in == 0)
1850 if (tp->t_fbyte_out && tp->t_fbyte_in)
1851 tp->t_flags2 |= TF2_FBYTES_COMPLETE;
1854 * Pull snd_wl1 up to prevent seq wrap relative to
1857 tp->snd_wl1 = th->th_seq;
1859 * Pull rcv_up up to prevent seq wrap relative to
1862 tp->rcv_up = tp->rcv_nxt;
1863 TCPSTAT_ADD(tcps_rcvpack, nsegs);
1864 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1866 if (so->so_options & SO_DEBUG)
1867 tcp_trace(TA_INPUT, ostate, tp,
1868 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1870 TCP_PROBE3(debug__input, tp, th, m);
1872 newsize = tcp_autorcvbuf(m, th, so, tp, tlen);
1874 /* Add data to socket buffer. */
1875 SOCKBUF_LOCK(&so->so_rcv);
1876 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1880 * Set new socket buffer size.
1881 * Give up when limit is reached.
1884 if (!sbreserve_locked(&so->so_rcv,
1886 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1887 m_adj(m, drop_hdrlen); /* delayed header drop */
1888 sbappendstream_locked(&so->so_rcv, m, 0);
1890 /* NB: sorwakeup_locked() does an implicit unlock. */
1891 sorwakeup_locked(so);
1892 if (DELAY_ACK(tp, tlen)) {
1893 tp->t_flags |= TF_DELACK;
1895 tp->t_flags |= TF_ACKNOW;
1896 tp->t_fb->tfb_tcp_output(tp);
1903 * Calculate amount of space in receive window,
1904 * and then do TCP input processing.
1905 * Receive window is amount of space in rcv queue,
1906 * but not less than advertised window.
1908 win = sbspace(&so->so_rcv);
1911 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1913 switch (tp->t_state) {
1916 * If the state is SYN_RECEIVED:
1917 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1919 case TCPS_SYN_RECEIVED:
1920 if ((thflags & TH_ACK) &&
1921 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1922 SEQ_GT(th->th_ack, tp->snd_max))) {
1923 rstreason = BANDLIM_RST_OPENPORT;
1926 if (IS_FASTOPEN(tp->t_flags)) {
1928 * When a TFO connection is in SYN_RECEIVED, the
1929 * only valid packets are the initial SYN, a
1930 * retransmit/copy of the initial SYN (possibly with
1931 * a subset of the original data), a valid ACK, a
1934 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
1935 rstreason = BANDLIM_RST_OPENPORT;
1937 } else if (thflags & TH_SYN) {
1938 /* non-initial SYN is ignored */
1939 if ((tcp_timer_active(tp, TT_DELACK) ||
1940 tcp_timer_active(tp, TT_REXMT)))
1942 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) {
1949 * If the state is SYN_SENT:
1950 * if seg contains a RST with valid ACK (SEQ.ACK has already
1951 * been verified), then drop the connection.
1952 * if seg contains a RST without an ACK, drop the seg.
1953 * if seg does not contain SYN, then drop the seg.
1954 * Otherwise this is an acceptable SYN segment
1955 * initialize tp->rcv_nxt and tp->irs
1956 * if seg contains ack then advance tp->snd_una
1957 * if seg contains an ECE and ECN support is enabled, the stream
1959 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1960 * arrange for segment to be acked (eventually)
1961 * continue processing rest of data/controls, beginning with URG
1964 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1965 TCP_PROBE5(connect__refused, NULL, tp,
1967 tp = tcp_drop(tp, ECONNREFUSED);
1969 if (thflags & TH_RST)
1971 if (!(thflags & TH_SYN))
1974 tp->irs = th->th_seq;
1976 if (thflags & TH_ACK) {
1977 int tfo_partial_ack = 0;
1979 TCPSTAT_INC(tcps_connects);
1982 mac_socketpeer_set_from_mbuf(m, so);
1984 /* Do window scaling on this connection? */
1985 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1986 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1987 tp->rcv_scale = tp->request_r_scale;
1989 tp->rcv_adv += min(tp->rcv_wnd,
1990 TCP_MAXWIN << tp->rcv_scale);
1991 tp->snd_una++; /* SYN is acked */
1993 * If not all the data that was sent in the TFO SYN
1994 * has been acked, resend the remainder right away.
1996 if (IS_FASTOPEN(tp->t_flags) &&
1997 (tp->snd_una != tp->snd_max)) {
1998 tp->snd_nxt = th->th_ack;
1999 tfo_partial_ack = 1;
2002 * If there's data, delay ACK; if there's also a FIN
2003 * ACKNOW will be turned on later.
2005 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack)
2006 tcp_timer_activate(tp, TT_DELACK,
2009 tp->t_flags |= TF_ACKNOW;
2011 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
2012 (V_tcp_do_ecn == 1)) {
2013 tp->t_flags2 |= TF2_ECN_PERMIT;
2014 TCPSTAT_INC(tcps_ecn_shs);
2018 * Received <SYN,ACK> in SYN_SENT[*] state.
2020 * SYN_SENT --> ESTABLISHED
2021 * SYN_SENT* --> FIN_WAIT_1
2023 tp->t_starttime = ticks;
2024 if (tp->t_flags & TF_NEEDFIN) {
2025 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2026 tp->t_flags &= ~TF_NEEDFIN;
2029 tcp_state_change(tp, TCPS_ESTABLISHED);
2030 TCP_PROBE5(connect__established, NULL, tp,
2033 tcp_timer_activate(tp, TT_KEEP,
2038 * Received initial SYN in SYN-SENT[*] state =>
2039 * simultaneous open.
2040 * If it succeeds, connection is * half-synchronized.
2041 * Otherwise, do 3-way handshake:
2042 * SYN-SENT -> SYN-RECEIVED
2043 * SYN-SENT* -> SYN-RECEIVED*
2045 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
2046 tcp_timer_activate(tp, TT_REXMT, 0);
2047 tcp_state_change(tp, TCPS_SYN_RECEIVED);
2050 INP_WLOCK_ASSERT(tp->t_inpcb);
2053 * Advance th->th_seq to correspond to first data byte.
2054 * If data, trim to stay within window,
2055 * dropping FIN if necessary.
2058 if (tlen > tp->rcv_wnd) {
2059 todrop = tlen - tp->rcv_wnd;
2063 TCPSTAT_INC(tcps_rcvpackafterwin);
2064 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2066 tp->snd_wl1 = th->th_seq - 1;
2067 tp->rcv_up = th->th_seq;
2069 * Client side of transaction: already sent SYN and data.
2070 * If the remote host used T/TCP to validate the SYN,
2071 * our data will be ACK'd; if so, enter normal data segment
2072 * processing in the middle of step 5, ack processing.
2073 * Otherwise, goto step 6.
2075 if (thflags & TH_ACK)
2081 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2082 * do normal processing.
2084 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2088 break; /* continue normal processing */
2092 * States other than LISTEN or SYN_SENT.
2093 * First check the RST flag and sequence number since reset segments
2094 * are exempt from the timestamp and connection count tests. This
2095 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2096 * below which allowed reset segments in half the sequence space
2097 * to fall though and be processed (which gives forged reset
2098 * segments with a random sequence number a 50 percent chance of
2099 * killing a connection).
2100 * Then check timestamp, if present.
2101 * Then check the connection count, if present.
2102 * Then check that at least some bytes of segment are within
2103 * receive window. If segment begins before rcv_nxt,
2104 * drop leading data (and SYN); if nothing left, just ack.
2106 if (thflags & TH_RST) {
2108 * RFC5961 Section 3.2
2110 * - RST drops connection only if SEG.SEQ == RCV.NXT.
2111 * - If RST is in window, we send challenge ACK.
2113 * Note: to take into account delayed ACKs, we should
2114 * test against last_ack_sent instead of rcv_nxt.
2115 * Note 2: we handle special case of closed window, not
2116 * covered by the RFC.
2118 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2119 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
2120 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
2122 KASSERT(tp->t_state != TCPS_SYN_SENT,
2123 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
2126 if (V_tcp_insecure_rst ||
2127 tp->last_ack_sent == th->th_seq) {
2128 TCPSTAT_INC(tcps_drops);
2129 /* Drop the connection. */
2130 switch (tp->t_state) {
2131 case TCPS_SYN_RECEIVED:
2132 so->so_error = ECONNREFUSED;
2134 case TCPS_ESTABLISHED:
2135 case TCPS_FIN_WAIT_1:
2136 case TCPS_FIN_WAIT_2:
2137 case TCPS_CLOSE_WAIT:
2140 so->so_error = ECONNRESET;
2147 TCPSTAT_INC(tcps_badrst);
2148 /* Send challenge ACK. */
2149 tcp_respond(tp, mtod(m, void *), th, m,
2150 tp->rcv_nxt, tp->snd_nxt, TH_ACK);
2151 tp->last_ack_sent = tp->rcv_nxt;
2159 * RFC5961 Section 4.2
2160 * Send challenge ACK for any SYN in synchronized state.
2162 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT &&
2163 tp->t_state != TCPS_SYN_RECEIVED) {
2164 TCPSTAT_INC(tcps_badsyn);
2165 if (V_tcp_insecure_syn &&
2166 SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2167 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2168 tp = tcp_drop(tp, ECONNRESET);
2169 rstreason = BANDLIM_UNLIMITED;
2171 /* Send challenge ACK. */
2172 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
2173 tp->snd_nxt, TH_ACK);
2174 tp->last_ack_sent = tp->rcv_nxt;
2181 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2182 * and it's less than ts_recent, drop it.
2184 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2185 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2187 /* Check to see if ts_recent is over 24 days old. */
2188 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2190 * Invalidate ts_recent. If this segment updates
2191 * ts_recent, the age will be reset later and ts_recent
2192 * will get a valid value. If it does not, setting
2193 * ts_recent to zero will at least satisfy the
2194 * requirement that zero be placed in the timestamp
2195 * echo reply when ts_recent isn't valid. The
2196 * age isn't reset until we get a valid ts_recent
2197 * because we don't want out-of-order segments to be
2198 * dropped when ts_recent is old.
2202 TCPSTAT_INC(tcps_rcvduppack);
2203 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2204 TCPSTAT_INC(tcps_pawsdrop);
2212 * In the SYN-RECEIVED state, validate that the packet belongs to
2213 * this connection before trimming the data to fit the receive
2214 * window. Check the sequence number versus IRS since we know
2215 * the sequence numbers haven't wrapped. This is a partial fix
2216 * for the "LAND" DoS attack.
2218 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2219 rstreason = BANDLIM_RST_OPENPORT;
2223 todrop = tp->rcv_nxt - th->th_seq;
2225 if (thflags & TH_SYN) {
2235 * Following if statement from Stevens, vol. 2, p. 960.
2238 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2240 * Any valid FIN must be to the left of the window.
2241 * At this point the FIN must be a duplicate or out
2242 * of sequence; drop it.
2247 * Send an ACK to resynchronize and drop any data.
2248 * But keep on processing for RST or ACK.
2250 tp->t_flags |= TF_ACKNOW;
2252 TCPSTAT_INC(tcps_rcvduppack);
2253 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2255 TCPSTAT_INC(tcps_rcvpartduppack);
2256 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2259 * DSACK - add SACK block for dropped range
2261 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) {
2262 tcp_update_sack_list(tp, th->th_seq,
2263 th->th_seq + todrop);
2265 * ACK now, as the next in-sequence segment
2266 * will clear the DSACK block again
2268 tp->t_flags |= TF_ACKNOW;
2270 drop_hdrlen += todrop; /* drop from the top afterwards */
2271 th->th_seq += todrop;
2273 if (th->th_urp > todrop)
2274 th->th_urp -= todrop;
2282 * If new data are received on a connection after the
2283 * user processes are gone, then RST the other end.
2285 if ((so->so_state & SS_NOFDREF) &&
2286 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2287 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2288 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2289 "after socket was closed, "
2290 "sending RST and removing tcpcb\n",
2291 s, __func__, tcpstates[tp->t_state], tlen);
2295 TCPSTAT_INC(tcps_rcvafterclose);
2296 rstreason = BANDLIM_UNLIMITED;
2301 * If segment ends after window, drop trailing data
2302 * (and PUSH and FIN); if nothing left, just ACK.
2304 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2306 TCPSTAT_INC(tcps_rcvpackafterwin);
2307 if (todrop >= tlen) {
2308 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2310 * If window is closed can only take segments at
2311 * window edge, and have to drop data and PUSH from
2312 * incoming segments. Continue processing, but
2313 * remember to ack. Otherwise, drop segment
2316 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2317 tp->t_flags |= TF_ACKNOW;
2318 TCPSTAT_INC(tcps_rcvwinprobe);
2322 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2325 thflags &= ~(TH_PUSH|TH_FIN);
2329 * If last ACK falls within this segment's sequence numbers,
2330 * record its timestamp.
2332 * 1) That the test incorporates suggestions from the latest
2333 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2334 * 2) That updating only on newer timestamps interferes with
2335 * our earlier PAWS tests, so this check should be solely
2336 * predicated on the sequence space of this segment.
2337 * 3) That we modify the segment boundary check to be
2338 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2339 * instead of RFC1323's
2340 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2341 * This modified check allows us to overcome RFC1323's
2342 * limitations as described in Stevens TCP/IP Illustrated
2343 * Vol. 2 p.869. In such cases, we can still calculate the
2344 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2346 if ((to.to_flags & TOF_TS) != 0 &&
2347 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2348 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2349 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2350 tp->ts_recent_age = tcp_ts_getticks();
2351 tp->ts_recent = to.to_tsval;
2355 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2356 * flag is on (half-synchronized state), then queue data for
2357 * later processing; else drop segment and return.
2359 if ((thflags & TH_ACK) == 0) {
2360 if (tp->t_state == TCPS_SYN_RECEIVED ||
2361 (tp->t_flags & TF_NEEDSYN)) {
2362 if (tp->t_state == TCPS_SYN_RECEIVED &&
2363 IS_FASTOPEN(tp->t_flags)) {
2364 tp->snd_wnd = tiwin;
2368 } else if (tp->t_flags & TF_ACKNOW)
2377 switch (tp->t_state) {
2380 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2381 * ESTABLISHED state and continue processing.
2382 * The ACK was checked above.
2384 case TCPS_SYN_RECEIVED:
2386 TCPSTAT_INC(tcps_connects);
2388 /* Do window scaling? */
2389 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2390 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2391 tp->rcv_scale = tp->request_r_scale;
2393 tp->snd_wnd = tiwin;
2396 * SYN-RECEIVED -> ESTABLISHED
2397 * SYN-RECEIVED* -> FIN-WAIT-1
2399 tp->t_starttime = ticks;
2400 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
2401 tcp_fastopen_decrement_counter(tp->t_tfo_pending);
2402 tp->t_tfo_pending = NULL;
2404 if (tp->t_flags & TF_NEEDFIN) {
2405 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2406 tp->t_flags &= ~TF_NEEDFIN;
2408 tcp_state_change(tp, TCPS_ESTABLISHED);
2409 TCP_PROBE5(accept__established, NULL, tp,
2412 * TFO connections call cc_conn_init() during SYN
2413 * processing. Calling it again here for such
2414 * connections is not harmless as it would undo the
2415 * snd_cwnd reduction that occurs when a TFO SYN|ACK
2418 if (!IS_FASTOPEN(tp->t_flags))
2420 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2423 * Account for the ACK of our SYN prior to
2424 * regular ACK processing below, except for
2425 * simultaneous SYN, which is handled later.
2427 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN))
2430 * If segment contains data or ACK, will call tcp_reass()
2431 * later; if not, do so now to pass queued data to user.
2433 if (tlen == 0 && (thflags & TH_FIN) == 0)
2434 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0,
2436 tp->snd_wl1 = th->th_seq - 1;
2440 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2441 * ACKs. If the ack is in the range
2442 * tp->snd_una < th->th_ack <= tp->snd_max
2443 * then advance tp->snd_una to th->th_ack and drop
2444 * data from the retransmission queue. If this ACK reflects
2445 * more up to date window information we update our window information.
2447 case TCPS_ESTABLISHED:
2448 case TCPS_FIN_WAIT_1:
2449 case TCPS_FIN_WAIT_2:
2450 case TCPS_CLOSE_WAIT:
2453 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2454 TCPSTAT_INC(tcps_rcvacktoomuch);
2457 if ((tp->t_flags & TF_SACK_PERMIT) &&
2458 ((to.to_flags & TOF_SACK) ||
2459 !TAILQ_EMPTY(&tp->snd_holes)))
2460 sack_changed = tcp_sack_doack(tp, &to, th->th_ack);
2463 * Reset the value so that previous (valid) value
2464 * from the last ack with SACK doesn't get used.
2466 tp->sackhint.sacked_bytes = 0;
2469 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2470 hhook_run_tcp_est_in(tp, th, &to);
2473 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2476 maxseg = tcp_maxseg(tp);
2478 (tiwin == tp->snd_wnd ||
2479 (tp->t_flags & TF_SACK_PERMIT))) {
2481 * If this is the first time we've seen a
2482 * FIN from the remote, this is not a
2483 * duplicate and it needs to be processed
2484 * normally. This happens during a
2485 * simultaneous close.
2487 if ((thflags & TH_FIN) &&
2488 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2492 TCPSTAT_INC(tcps_rcvdupack);
2494 * If we have outstanding data (other than
2495 * a window probe), this is a completely
2496 * duplicate ack (ie, window info didn't
2497 * change and FIN isn't set),
2498 * the ack is the biggest we've
2499 * seen and we've seen exactly our rexmt
2500 * threshold of them, assume a packet
2501 * has been dropped and retransmit it.
2502 * Kludge snd_nxt & the congestion
2503 * window so we send only this one
2506 * We know we're losing at the current
2507 * window size so do congestion avoidance
2508 * (set ssthresh to half the current window
2509 * and pull our congestion window back to
2510 * the new ssthresh).
2512 * Dup acks mean that packets have left the
2513 * network (they're now cached at the receiver)
2514 * so bump cwnd by the amount in the receiver
2515 * to keep a constant cwnd packets in the
2518 * When using TCP ECN, notify the peer that
2519 * we reduced the cwnd.
2522 * Following 2 kinds of acks should not affect
2525 * 2) Acks with SACK but without any new SACK
2526 * information in them. These could result from
2527 * any anomaly in the network like a switch
2528 * duplicating packets or a possible DoS attack.
2530 if (th->th_ack != tp->snd_una ||
2531 ((tp->t_flags & TF_SACK_PERMIT) &&
2534 else if (!tcp_timer_active(tp, TT_REXMT))
2536 else if (++tp->t_dupacks > tcprexmtthresh ||
2537 IN_FASTRECOVERY(tp->t_flags)) {
2538 cc_ack_received(tp, th, nsegs,
2540 if ((tp->t_flags & TF_SACK_PERMIT) &&
2541 IN_FASTRECOVERY(tp->t_flags)) {
2545 * Compute the amount of data in flight first.
2546 * We can inject new data into the pipe iff
2547 * we have less than 1/2 the original window's
2548 * worth of data in flight.
2550 if (V_tcp_do_rfc6675_pipe)
2551 awnd = tcp_compute_pipe(tp);
2553 awnd = (tp->snd_nxt - tp->snd_fack) +
2554 tp->sackhint.sack_bytes_rexmit;
2556 if (awnd < tp->snd_ssthresh) {
2557 tp->snd_cwnd += maxseg;
2558 if (tp->snd_cwnd > tp->snd_ssthresh)
2559 tp->snd_cwnd = tp->snd_ssthresh;
2562 tp->snd_cwnd += maxseg;
2563 (void) tp->t_fb->tfb_tcp_output(tp);
2565 } else if (tp->t_dupacks == tcprexmtthresh) {
2566 tcp_seq onxt = tp->snd_nxt;
2569 * If we're doing sack, check to
2570 * see if we're already in sack
2571 * recovery. If we're not doing sack,
2572 * check to see if we're in newreno
2575 if (tp->t_flags & TF_SACK_PERMIT) {
2576 if (IN_FASTRECOVERY(tp->t_flags)) {
2581 if (SEQ_LEQ(th->th_ack,
2587 /* Congestion signal before ack. */
2588 cc_cong_signal(tp, th, CC_NDUPACK);
2589 cc_ack_received(tp, th, nsegs,
2591 tcp_timer_activate(tp, TT_REXMT, 0);
2593 if (tp->t_flags & TF_SACK_PERMIT) {
2595 tcps_sack_recovery_episode);
2596 tp->snd_recover = tp->snd_nxt;
2597 tp->snd_cwnd = maxseg;
2598 (void) tp->t_fb->tfb_tcp_output(tp);
2601 tp->snd_nxt = th->th_ack;
2602 tp->snd_cwnd = maxseg;
2603 (void) tp->t_fb->tfb_tcp_output(tp);
2604 KASSERT(tp->snd_limited <= 2,
2605 ("%s: tp->snd_limited too big",
2607 tp->snd_cwnd = tp->snd_ssthresh +
2609 (tp->t_dupacks - tp->snd_limited);
2610 if (SEQ_GT(onxt, tp->snd_nxt))
2613 } else if (V_tcp_do_rfc3042) {
2615 * Process first and second duplicate
2616 * ACKs. Each indicates a segment
2617 * leaving the network, creating room
2618 * for more. Make sure we can send a
2619 * packet on reception of each duplicate
2620 * ACK by increasing snd_cwnd by one
2621 * segment. Restore the original
2622 * snd_cwnd after packet transmission.
2624 cc_ack_received(tp, th, nsegs,
2626 uint32_t oldcwnd = tp->snd_cwnd;
2627 tcp_seq oldsndmax = tp->snd_max;
2631 KASSERT(tp->t_dupacks == 1 ||
2633 ("%s: dupacks not 1 or 2",
2635 if (tp->t_dupacks == 1)
2636 tp->snd_limited = 0;
2638 (tp->snd_nxt - tp->snd_una) +
2639 (tp->t_dupacks - tp->snd_limited) *
2642 * Only call tcp_output when there
2643 * is new data available to be sent.
2644 * Otherwise we would send pure ACKs.
2646 SOCKBUF_LOCK(&so->so_snd);
2647 avail = sbavail(&so->so_snd) -
2648 (tp->snd_nxt - tp->snd_una);
2649 SOCKBUF_UNLOCK(&so->so_snd);
2651 (void) tp->t_fb->tfb_tcp_output(tp);
2652 sent = tp->snd_max - oldsndmax;
2653 if (sent > maxseg) {
2654 KASSERT((tp->t_dupacks == 2 &&
2655 tp->snd_limited == 0) ||
2656 (sent == maxseg + 1 &&
2657 tp->t_flags & TF_SENTFIN),
2658 ("%s: sent too much",
2660 tp->snd_limited = 2;
2661 } else if (sent > 0)
2663 tp->snd_cwnd = oldcwnd;
2670 * This ack is advancing the left edge, reset the
2675 * If this ack also has new SACK info, increment the
2676 * counter as per rfc6675. The variable
2677 * sack_changed tracks all changes to the SACK
2678 * scoreboard, including when partial ACKs without
2679 * SACK options are received, and clear the scoreboard
2680 * from the left side. Such partial ACKs should not be
2681 * counted as dupacks here.
2683 if ((tp->t_flags & TF_SACK_PERMIT) &&
2684 (to.to_flags & TOF_SACK) &&
2689 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2690 ("%s: th_ack <= snd_una", __func__));
2693 * If the congestion window was inflated to account
2694 * for the other side's cached packets, retract it.
2696 if (IN_FASTRECOVERY(tp->t_flags)) {
2697 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2698 if (tp->t_flags & TF_SACK_PERMIT)
2699 tcp_sack_partialack(tp, th);
2701 tcp_newreno_partial_ack(tp, th);
2703 cc_post_recovery(tp, th);
2706 * If we reach this point, ACK is not a duplicate,
2707 * i.e., it ACKs something we sent.
2709 if (tp->t_flags & TF_NEEDSYN) {
2711 * T/TCP: Connection was half-synchronized, and our
2712 * SYN has been ACK'd (so connection is now fully
2713 * synchronized). Go to non-starred state,
2714 * increment snd_una for ACK of SYN, and check if
2715 * we can do window scaling.
2717 tp->t_flags &= ~TF_NEEDSYN;
2719 /* Do window scaling? */
2720 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2721 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2722 tp->rcv_scale = tp->request_r_scale;
2723 /* Send window already scaled. */
2728 INP_WLOCK_ASSERT(tp->t_inpcb);
2731 * Adjust for the SYN bit in sequence space,
2732 * but don't account for it in cwnd calculations.
2733 * This is for the SYN_RECEIVED, non-simultaneous
2734 * SYN case. SYN_SENT and simultaneous SYN are
2735 * treated elsewhere.
2739 acked = BYTES_THIS_ACK(tp, th);
2740 KASSERT(acked >= 0, ("%s: acked unexepectedly negative "
2741 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__,
2742 tp->snd_una, th->th_ack, tp, m));
2743 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
2744 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2747 * If we just performed our first retransmit, and the ACK
2748 * arrives within our recovery window, then it was a mistake
2749 * to do the retransmit in the first place. Recover our
2750 * original cwnd and ssthresh, and proceed to transmit where
2753 if (tp->t_rxtshift == 1 &&
2754 tp->t_flags & TF_PREVVALID &&
2756 SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
2757 cc_cong_signal(tp, th, CC_RTO_ERR);
2760 * If we have a timestamp reply, update smoothed
2761 * round trip time. If no timestamp is present but
2762 * transmit timer is running and timed sequence
2763 * number was acked, update smoothed round trip time.
2764 * Since we now have an rtt measurement, cancel the
2765 * timer backoff (cf., Phil Karn's retransmit alg.).
2766 * Recompute the initial retransmit timer.
2768 * Some boxes send broken timestamp replies
2769 * during the SYN+ACK phase, ignore
2770 * timestamps of 0 or we could calculate a
2771 * huge RTT and blow up the retransmit timer.
2773 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2776 t = tcp_ts_getticks() - to.to_tsecr;
2777 if (!tp->t_rttlow || tp->t_rttlow > t)
2779 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2780 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2781 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2782 tp->t_rttlow = ticks - tp->t_rtttime;
2783 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2787 * If all outstanding data is acked, stop retransmit
2788 * timer and remember to restart (more output or persist).
2789 * If there is more data to be acked, restart retransmit
2790 * timer, using current (possibly backed-off) value.
2792 if (th->th_ack == tp->snd_max) {
2793 tcp_timer_activate(tp, TT_REXMT, 0);
2795 } else if (!tcp_timer_active(tp, TT_PERSIST))
2796 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2799 * If no data (only SYN) was ACK'd,
2800 * skip rest of ACK processing.
2806 * Let the congestion control algorithm update congestion
2807 * control related information. This typically means increasing
2808 * the congestion window.
2810 cc_ack_received(tp, th, nsegs, CC_ACK);
2812 SOCKBUF_LOCK(&so->so_snd);
2813 if (acked > sbavail(&so->so_snd)) {
2814 if (tp->snd_wnd >= sbavail(&so->so_snd))
2815 tp->snd_wnd -= sbavail(&so->so_snd);
2818 mfree = sbcut_locked(&so->so_snd,
2819 (int)sbavail(&so->so_snd));
2822 mfree = sbcut_locked(&so->so_snd, acked);
2823 if (tp->snd_wnd >= (uint32_t) acked)
2824 tp->snd_wnd -= acked;
2829 /* NB: sowwakeup_locked() does an implicit unlock. */
2830 sowwakeup_locked(so);
2832 /* Detect una wraparound. */
2833 if (!IN_RECOVERY(tp->t_flags) &&
2834 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2835 SEQ_LEQ(th->th_ack, tp->snd_recover))
2836 tp->snd_recover = th->th_ack - 1;
2837 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2838 if (IN_RECOVERY(tp->t_flags) &&
2839 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2840 EXIT_RECOVERY(tp->t_flags);
2842 tp->snd_una = th->th_ack;
2843 if (tp->t_flags & TF_SACK_PERMIT) {
2844 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2845 tp->snd_recover = tp->snd_una;
2847 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2848 tp->snd_nxt = tp->snd_una;
2850 switch (tp->t_state) {
2853 * In FIN_WAIT_1 STATE in addition to the processing
2854 * for the ESTABLISHED state if our FIN is now acknowledged
2855 * then enter FIN_WAIT_2.
2857 case TCPS_FIN_WAIT_1:
2858 if (ourfinisacked) {
2860 * If we can't receive any more
2861 * data, then closing user can proceed.
2862 * Starting the timer is contrary to the
2863 * specification, but if we don't get a FIN
2864 * we'll hang forever.
2867 * we should release the tp also, and use a
2870 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2871 soisdisconnected(so);
2872 tcp_timer_activate(tp, TT_2MSL,
2873 (tcp_fast_finwait2_recycle ?
2874 tcp_finwait2_timeout :
2877 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2882 * In CLOSING STATE in addition to the processing for
2883 * the ESTABLISHED state if the ACK acknowledges our FIN
2884 * then enter the TIME-WAIT state, otherwise ignore
2888 if (ourfinisacked) {
2896 * In LAST_ACK, we may still be waiting for data to drain
2897 * and/or to be acked, as well as for the ack of our FIN.
2898 * If our FIN is now acknowledged, delete the TCB,
2899 * enter the closed state and return.
2902 if (ourfinisacked) {
2911 INP_WLOCK_ASSERT(tp->t_inpcb);
2914 * Update window information.
2915 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2917 if ((thflags & TH_ACK) &&
2918 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2919 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2920 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2921 /* keep track of pure window updates */
2923 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2924 TCPSTAT_INC(tcps_rcvwinupd);
2925 tp->snd_wnd = tiwin;
2926 tp->snd_wl1 = th->th_seq;
2927 tp->snd_wl2 = th->th_ack;
2928 if (tp->snd_wnd > tp->max_sndwnd)
2929 tp->max_sndwnd = tp->snd_wnd;
2934 * Process segments with URG.
2936 if ((thflags & TH_URG) && th->th_urp &&
2937 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2939 * This is a kludge, but if we receive and accept
2940 * random urgent pointers, we'll crash in
2941 * soreceive. It's hard to imagine someone
2942 * actually wanting to send this much urgent data.
2944 SOCKBUF_LOCK(&so->so_rcv);
2945 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
2946 th->th_urp = 0; /* XXX */
2947 thflags &= ~TH_URG; /* XXX */
2948 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2949 goto dodata; /* XXX */
2952 * If this segment advances the known urgent pointer,
2953 * then mark the data stream. This should not happen
2954 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2955 * a FIN has been received from the remote side.
2956 * In these states we ignore the URG.
2958 * According to RFC961 (Assigned Protocols),
2959 * the urgent pointer points to the last octet
2960 * of urgent data. We continue, however,
2961 * to consider it to indicate the first octet
2962 * of data past the urgent section as the original
2963 * spec states (in one of two places).
2965 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2966 tp->rcv_up = th->th_seq + th->th_urp;
2967 so->so_oobmark = sbavail(&so->so_rcv) +
2968 (tp->rcv_up - tp->rcv_nxt) - 1;
2969 if (so->so_oobmark == 0)
2970 so->so_rcv.sb_state |= SBS_RCVATMARK;
2972 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2974 SOCKBUF_UNLOCK(&so->so_rcv);
2976 * Remove out of band data so doesn't get presented to user.
2977 * This can happen independent of advancing the URG pointer,
2978 * but if two URG's are pending at once, some out-of-band
2979 * data may creep in... ick.
2981 if (th->th_urp <= (uint32_t)tlen &&
2982 !(so->so_options & SO_OOBINLINE)) {
2983 /* hdr drop is delayed */
2984 tcp_pulloutofband(so, th, m, drop_hdrlen);
2988 * If no out of band data is expected,
2989 * pull receive urgent pointer along
2990 * with the receive window.
2992 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2993 tp->rcv_up = tp->rcv_nxt;
2996 INP_WLOCK_ASSERT(tp->t_inpcb);
2999 * Process the segment text, merging it into the TCP sequencing queue,
3000 * and arranging for acknowledgment of receipt if necessary.
3001 * This process logically involves adjusting tp->rcv_wnd as data
3002 * is presented to the user (this happens in tcp_usrreq.c,
3003 * case PRU_RCVD). If a FIN has already been received on this
3004 * connection then we just ignore the text.
3006 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
3007 IS_FASTOPEN(tp->t_flags));
3008 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) &&
3009 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
3010 tcp_seq save_start = th->th_seq;
3011 tcp_seq save_rnxt = tp->rcv_nxt;
3012 int save_tlen = tlen;
3013 m_adj(m, drop_hdrlen); /* delayed header drop */
3015 * Insert segment which includes th into TCP reassembly queue
3016 * with control block tp. Set thflags to whether reassembly now
3017 * includes a segment with FIN. This handles the common case
3018 * inline (segment is the next to be received on an established
3019 * connection, and the queue is empty), avoiding linkage into
3020 * and removal from the queue and repetition of various
3022 * Set DELACK for segments received in order, but ack
3023 * immediately when segments are out of order (so
3024 * fast retransmit can work).
3026 if (th->th_seq == tp->rcv_nxt &&
3028 (TCPS_HAVEESTABLISHED(tp->t_state) ||
3030 if (DELAY_ACK(tp, tlen) || tfo_syn)
3031 tp->t_flags |= TF_DELACK;
3033 tp->t_flags |= TF_ACKNOW;
3034 tp->rcv_nxt += tlen;
3036 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) &&
3037 (tp->t_fbyte_in == 0)) {
3038 tp->t_fbyte_in = ticks;
3039 if (tp->t_fbyte_in == 0)
3041 if (tp->t_fbyte_out && tp->t_fbyte_in)
3042 tp->t_flags2 |= TF2_FBYTES_COMPLETE;
3044 thflags = th->th_flags & TH_FIN;
3045 TCPSTAT_INC(tcps_rcvpack);
3046 TCPSTAT_ADD(tcps_rcvbyte, tlen);
3047 SOCKBUF_LOCK(&so->so_rcv);
3048 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
3051 sbappendstream_locked(&so->so_rcv, m, 0);
3052 /* NB: sorwakeup_locked() does an implicit unlock. */
3053 sorwakeup_locked(so);
3056 * XXX: Due to the header drop above "th" is
3057 * theoretically invalid by now. Fortunately
3058 * m_adj() doesn't actually frees any mbufs
3059 * when trimming from the head.
3061 tcp_seq temp = save_start;
3062 thflags = tcp_reass(tp, th, &temp, &tlen, m);
3063 tp->t_flags |= TF_ACKNOW;
3065 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) {
3066 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) {
3068 * DSACK actually handled in the fastpath
3071 tcp_update_sack_list(tp, save_start,
3072 save_start + save_tlen);
3073 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
3074 if ((tp->rcv_numsacks >= 1) &&
3075 (tp->sackblks[0].end == save_start)) {
3077 * Partial overlap, recorded at todrop
3080 tcp_update_sack_list(tp,
3081 tp->sackblks[0].start,
3082 tp->sackblks[0].end);
3084 tcp_update_dsack_list(tp, save_start,
3085 save_start + save_tlen);
3087 } else if (tlen >= save_tlen) {
3088 /* Update of sackblks. */
3089 tcp_update_dsack_list(tp, save_start,
3090 save_start + save_tlen);
3091 } else if (tlen > 0) {
3092 tcp_update_dsack_list(tp, save_start,
3098 * Note the amount of data that peer has sent into
3099 * our window, in order to estimate the sender's
3103 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
3104 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
3106 len = so->so_rcv.sb_hiwat;
3114 * If FIN is received ACK the FIN and let the user know
3115 * that the connection is closing.
3117 if (thflags & TH_FIN) {
3118 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
3121 * If connection is half-synchronized
3122 * (ie NEEDSYN flag on) then delay ACK,
3123 * so it may be piggybacked when SYN is sent.
3124 * Otherwise, since we received a FIN then no
3125 * more input can be expected, send ACK now.
3127 if (tp->t_flags & TF_NEEDSYN)
3128 tp->t_flags |= TF_DELACK;
3130 tp->t_flags |= TF_ACKNOW;
3133 switch (tp->t_state) {
3136 * In SYN_RECEIVED and ESTABLISHED STATES
3137 * enter the CLOSE_WAIT state.
3139 case TCPS_SYN_RECEIVED:
3140 tp->t_starttime = ticks;
3142 case TCPS_ESTABLISHED:
3143 tcp_state_change(tp, TCPS_CLOSE_WAIT);
3147 * If still in FIN_WAIT_1 STATE FIN has not been acked so
3148 * enter the CLOSING state.
3150 case TCPS_FIN_WAIT_1:
3151 tcp_state_change(tp, TCPS_CLOSING);
3155 * In FIN_WAIT_2 state enter the TIME_WAIT state,
3156 * starting the time-wait timer, turning off the other
3159 case TCPS_FIN_WAIT_2:
3165 if (so->so_options & SO_DEBUG)
3166 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3169 TCP_PROBE3(debug__input, tp, th, m);
3172 * Return any desired output.
3174 if (needoutput || (tp->t_flags & TF_ACKNOW))
3175 (void) tp->t_fb->tfb_tcp_output(tp);
3178 INP_WLOCK_ASSERT(tp->t_inpcb);
3180 if (tp->t_flags & TF_DELACK) {
3181 tp->t_flags &= ~TF_DELACK;
3182 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3184 INP_WUNLOCK(tp->t_inpcb);
3189 * Generate an ACK dropping incoming segment if it occupies
3190 * sequence space, where the ACK reflects our state.
3192 * We can now skip the test for the RST flag since all
3193 * paths to this code happen after packets containing
3194 * RST have been dropped.
3196 * In the SYN-RECEIVED state, don't send an ACK unless the
3197 * segment we received passes the SYN-RECEIVED ACK test.
3198 * If it fails send a RST. This breaks the loop in the
3199 * "LAND" DoS attack, and also prevents an ACK storm
3200 * between two listening ports that have been sent forged
3201 * SYN segments, each with the source address of the other.
3203 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3204 (SEQ_GT(tp->snd_una, th->th_ack) ||
3205 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3206 rstreason = BANDLIM_RST_OPENPORT;
3210 if (so->so_options & SO_DEBUG)
3211 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3214 TCP_PROBE3(debug__input, tp, th, m);
3215 tp->t_flags |= TF_ACKNOW;
3216 (void) tp->t_fb->tfb_tcp_output(tp);
3217 INP_WUNLOCK(tp->t_inpcb);
3223 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3224 INP_WUNLOCK(tp->t_inpcb);
3226 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3231 * Drop space held by incoming segment and return.
3234 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3235 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3238 TCP_PROBE3(debug__input, tp, th, m);
3240 INP_WUNLOCK(tp->t_inpcb);
3245 * Issue RST and make ACK acceptable to originator of segment.
3246 * The mbuf must still include the original packet header.
3250 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3251 int tlen, int rstreason)
3257 struct ip6_hdr *ip6;
3261 INP_WLOCK_ASSERT(tp->t_inpcb);
3264 /* Don't bother if destination was broadcast/multicast. */
3265 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3268 if (mtod(m, struct ip *)->ip_v == 6) {
3269 ip6 = mtod(m, struct ip6_hdr *);
3270 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3271 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3273 /* IPv6 anycast check is done at tcp6_input() */
3276 #if defined(INET) && defined(INET6)
3281 ip = mtod(m, struct ip *);
3282 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3283 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3284 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3285 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3290 /* Perform bandwidth limiting. */
3291 if (badport_bandlim(rstreason) < 0)
3294 /* tcp_respond consumes the mbuf chain. */
3295 if (th->th_flags & TH_ACK) {
3296 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3297 th->th_ack, TH_RST);
3299 if (th->th_flags & TH_SYN)
3301 if (th->th_flags & TH_FIN)
3303 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3304 (tcp_seq)0, TH_RST|TH_ACK);
3312 * Parse TCP options and place in tcpopt.
3315 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3320 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3322 if (opt == TCPOPT_EOL)
3324 if (opt == TCPOPT_NOP)
3330 if (optlen < 2 || optlen > cnt)
3335 if (optlen != TCPOLEN_MAXSEG)
3337 if (!(flags & TO_SYN))
3339 to->to_flags |= TOF_MSS;
3340 bcopy((char *)cp + 2,
3341 (char *)&to->to_mss, sizeof(to->to_mss));
3342 to->to_mss = ntohs(to->to_mss);
3345 if (optlen != TCPOLEN_WINDOW)
3347 if (!(flags & TO_SYN))
3349 to->to_flags |= TOF_SCALE;
3350 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3352 case TCPOPT_TIMESTAMP:
3353 if (optlen != TCPOLEN_TIMESTAMP)
3355 to->to_flags |= TOF_TS;
3356 bcopy((char *)cp + 2,
3357 (char *)&to->to_tsval, sizeof(to->to_tsval));
3358 to->to_tsval = ntohl(to->to_tsval);
3359 bcopy((char *)cp + 6,
3360 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3361 to->to_tsecr = ntohl(to->to_tsecr);
3363 case TCPOPT_SIGNATURE:
3365 * In order to reply to a host which has set the
3366 * TCP_SIGNATURE option in its initial SYN, we have
3367 * to record the fact that the option was observed
3368 * here for the syncache code to perform the correct
3371 if (optlen != TCPOLEN_SIGNATURE)
3373 to->to_flags |= TOF_SIGNATURE;
3374 to->to_signature = cp + 2;
3376 case TCPOPT_SACK_PERMITTED:
3377 if (optlen != TCPOLEN_SACK_PERMITTED)
3379 if (!(flags & TO_SYN))
3383 to->to_flags |= TOF_SACKPERM;
3386 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3390 to->to_flags |= TOF_SACK;
3391 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3392 to->to_sacks = cp + 2;
3393 TCPSTAT_INC(tcps_sack_rcv_blocks);
3395 case TCPOPT_FAST_OPEN:
3397 * Cookie length validation is performed by the
3398 * server side cookie checking code or the client
3399 * side cookie cache update code.
3401 if (!(flags & TO_SYN))
3403 if (!V_tcp_fastopen_client_enable &&
3404 !V_tcp_fastopen_server_enable)
3406 to->to_flags |= TOF_FASTOPEN;
3407 to->to_tfo_len = optlen - 2;
3408 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL;
3417 * Pull out of band byte out of a segment so
3418 * it doesn't appear in the user's data queue.
3419 * It is still reflected in the segment length for
3420 * sequencing purposes.
3423 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3426 int cnt = off + th->th_urp - 1;
3429 if (m->m_len > cnt) {
3430 char *cp = mtod(m, caddr_t) + cnt;
3431 struct tcpcb *tp = sototcpcb(so);
3433 INP_WLOCK_ASSERT(tp->t_inpcb);
3436 tp->t_oobflags |= TCPOOB_HAVEDATA;
3437 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3439 if (m->m_flags & M_PKTHDR)
3448 panic("tcp_pulloutofband");
3452 * Collect new round-trip time estimate
3453 * and update averages and current timeout.
3456 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3460 INP_WLOCK_ASSERT(tp->t_inpcb);
3462 TCPSTAT_INC(tcps_rttupdated);
3465 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT,
3466 imax(0, rtt * 1000 / hz));
3468 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) {
3470 * srtt is stored as fixed point with 5 bits after the
3471 * binary point (i.e., scaled by 8). The following magic
3472 * is equivalent to the smoothing algorithm in rfc793 with
3473 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3474 * point). Adjust rtt to origin 0.
3476 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3477 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3479 if ((tp->t_srtt += delta) <= 0)
3483 * We accumulate a smoothed rtt variance (actually, a
3484 * smoothed mean difference), then set the retransmit
3485 * timer to smoothed rtt + 4 times the smoothed variance.
3486 * rttvar is stored as fixed point with 4 bits after the
3487 * binary point (scaled by 16). The following is
3488 * equivalent to rfc793 smoothing with an alpha of .75
3489 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3490 * rfc793's wired-in beta.
3494 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3495 if ((tp->t_rttvar += delta) <= 0)
3497 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3498 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3501 * No rtt measurement yet - use the unsmoothed rtt.
3502 * Set the variance to half the rtt (so our first
3503 * retransmit happens at 3*rtt).
3505 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3506 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3507 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3513 * the retransmit should happen at rtt + 4 * rttvar.
3514 * Because of the way we do the smoothing, srtt and rttvar
3515 * will each average +1/2 tick of bias. When we compute
3516 * the retransmit timer, we want 1/2 tick of rounding and
3517 * 1 extra tick because of +-1/2 tick uncertainty in the
3518 * firing of the timer. The bias will give us exactly the
3519 * 1.5 tick we need. But, because the bias is
3520 * statistical, we have to test that we don't drop below
3521 * the minimum feasible timer (which is 2 ticks).
3523 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3524 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3527 * We received an ack for a packet that wasn't retransmitted;
3528 * it is probably safe to discard any error indications we've
3529 * received recently. This isn't quite right, but close enough
3530 * for now (a route might have failed after we sent a segment,
3531 * and the return path might not be symmetrical).
3533 tp->t_softerror = 0;
3537 * Determine a reasonable value for maxseg size.
3538 * If the route is known, check route for mtu.
3539 * If none, use an mss that can be handled on the outgoing interface
3540 * without forcing IP to fragment. If no route is found, route has no mtu,
3541 * or the destination isn't local, use a default, hopefully conservative
3542 * size (usually 512 or the default IP max size, but no more than the mtu
3543 * of the interface), as we can't discover anything about intervening
3544 * gateways or networks. We also initialize the congestion/slow start
3545 * window to be a single segment if the destination isn't local.
3546 * While looking at the routing entry, we also initialize other path-dependent
3547 * parameters from pre-set or cached values in the routing entry.
3549 * NOTE that resulting t_maxseg doesn't include space for TCP options or
3550 * IP options, e.g. IPSEC data, since length of this data may vary, and
3551 * thus it is calculated for every segment separately in tcp_output().
3553 * NOTE that this routine is only called when we process an incoming
3554 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3555 * settings are handled in tcp_mssopt().
3558 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3559 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3562 uint32_t maxmtu = 0;
3563 struct inpcb *inp = tp->t_inpcb;
3564 struct hc_metrics_lite metrics;
3566 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3567 size_t min_protoh = isipv6 ?
3568 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3569 sizeof (struct tcpiphdr);
3571 const size_t min_protoh = sizeof(struct tcpiphdr);
3574 INP_WLOCK_ASSERT(tp->t_inpcb);
3576 if (mtuoffer != -1) {
3577 KASSERT(offer == -1, ("%s: conflict", __func__));
3578 offer = mtuoffer - min_protoh;
3584 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3585 tp->t_maxseg = V_tcp_v6mssdflt;
3588 #if defined(INET) && defined(INET6)
3593 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3594 tp->t_maxseg = V_tcp_mssdflt;
3599 * No route to sender, stay with default mss and return.
3603 * In case we return early we need to initialize metrics
3604 * to a defined state as tcp_hc_get() would do for us
3605 * if there was no cache hit.
3607 if (metricptr != NULL)
3608 bzero(metricptr, sizeof(struct hc_metrics_lite));
3612 /* What have we got? */
3616 * Offer == 0 means that there was no MSS on the SYN
3617 * segment, in this case we use tcp_mssdflt as
3618 * already assigned to t_maxseg above.
3620 offer = tp->t_maxseg;
3625 * Offer == -1 means that we didn't receive SYN yet.
3631 * Prevent DoS attack with too small MSS. Round up
3632 * to at least minmss.
3634 offer = max(offer, V_tcp_minmss);
3638 * rmx information is now retrieved from tcp_hostcache.
3640 tcp_hc_get(&inp->inp_inc, &metrics);
3641 if (metricptr != NULL)
3642 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3645 * If there's a discovered mtu in tcp hostcache, use it.
3646 * Else, use the link mtu.
3648 if (metrics.rmx_mtu)
3649 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3653 mss = maxmtu - min_protoh;
3654 if (!V_path_mtu_discovery &&
3655 !in6_localaddr(&inp->in6p_faddr))
3656 mss = min(mss, V_tcp_v6mssdflt);
3659 #if defined(INET) && defined(INET6)
3664 mss = maxmtu - min_protoh;
3665 if (!V_path_mtu_discovery &&
3666 !in_localaddr(inp->inp_faddr))
3667 mss = min(mss, V_tcp_mssdflt);
3671 * XXX - The above conditional (mss = maxmtu - min_protoh)
3672 * probably violates the TCP spec.
3673 * The problem is that, since we don't know the
3674 * other end's MSS, we are supposed to use a conservative
3675 * default. But, if we do that, then MTU discovery will
3676 * never actually take place, because the conservative
3677 * default is much less than the MTUs typically seen
3678 * on the Internet today. For the moment, we'll sweep
3679 * this under the carpet.
3681 * The conservative default might not actually be a problem
3682 * if the only case this occurs is when sending an initial
3683 * SYN with options and data to a host we've never talked
3684 * to before. Then, they will reply with an MSS value which
3685 * will get recorded and the new parameters should get
3686 * recomputed. For Further Study.
3689 mss = min(mss, offer);
3692 * Sanity check: make sure that maxseg will be large
3693 * enough to allow some data on segments even if the
3694 * all the option space is used (40bytes). Otherwise
3695 * funny things may happen in tcp_output.
3697 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3705 tcp_mss(struct tcpcb *tp, int offer)
3711 struct hc_metrics_lite metrics;
3712 struct tcp_ifcap cap;
3714 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3716 bzero(&cap, sizeof(cap));
3717 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3723 * If there's a pipesize, change the socket buffer to that size,
3724 * don't change if sb_hiwat is different than default (then it
3725 * has been changed on purpose with setsockopt).
3726 * Make the socket buffers an integral number of mss units;
3727 * if the mss is larger than the socket buffer, decrease the mss.
3729 so = inp->inp_socket;
3730 SOCKBUF_LOCK(&so->so_snd);
3731 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3732 bufsize = metrics.rmx_sendpipe;
3734 bufsize = so->so_snd.sb_hiwat;
3738 bufsize = roundup(bufsize, mss);
3739 if (bufsize > sb_max)
3741 if (bufsize > so->so_snd.sb_hiwat)
3742 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3744 SOCKBUF_UNLOCK(&so->so_snd);
3746 * Sanity check: make sure that maxseg will be large
3747 * enough to allow some data on segments even if the
3748 * all the option space is used (40bytes). Otherwise
3749 * funny things may happen in tcp_output.
3751 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3753 tp->t_maxseg = max(mss, 64);
3755 SOCKBUF_LOCK(&so->so_rcv);
3756 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3757 bufsize = metrics.rmx_recvpipe;
3759 bufsize = so->so_rcv.sb_hiwat;
3760 if (bufsize > mss) {
3761 bufsize = roundup(bufsize, mss);
3762 if (bufsize > sb_max)
3764 if (bufsize > so->so_rcv.sb_hiwat)
3765 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3767 SOCKBUF_UNLOCK(&so->so_rcv);
3769 /* Check the interface for TSO capabilities. */
3770 if (cap.ifcap & CSUM_TSO) {
3771 tp->t_flags |= TF_TSO;
3772 tp->t_tsomax = cap.tsomax;
3773 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3774 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3779 * Determine the MSS option to send on an outgoing SYN.
3782 tcp_mssopt(struct in_conninfo *inc)
3785 uint32_t thcmtu = 0;
3786 uint32_t maxmtu = 0;
3789 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3792 if (inc->inc_flags & INC_ISIPV6) {
3793 mss = V_tcp_v6mssdflt;
3794 maxmtu = tcp_maxmtu6(inc, NULL);
3795 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3798 #if defined(INET) && defined(INET6)
3803 mss = V_tcp_mssdflt;
3804 maxmtu = tcp_maxmtu(inc, NULL);
3805 min_protoh = sizeof(struct tcpiphdr);
3808 #if defined(INET6) || defined(INET)
3809 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3812 if (maxmtu && thcmtu)
3813 mss = min(maxmtu, thcmtu) - min_protoh;
3814 else if (maxmtu || thcmtu)
3815 mss = max(maxmtu, thcmtu) - min_protoh;
3822 * On a partial ack arrives, force the retransmission of the
3823 * next unacknowledged segment. Do not clear tp->t_dupacks.
3824 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3828 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3830 tcp_seq onxt = tp->snd_nxt;
3831 uint32_t ocwnd = tp->snd_cwnd;
3832 u_int maxseg = tcp_maxseg(tp);
3834 INP_WLOCK_ASSERT(tp->t_inpcb);
3836 tcp_timer_activate(tp, TT_REXMT, 0);
3838 tp->snd_nxt = th->th_ack;
3840 * Set snd_cwnd to one segment beyond acknowledged offset.
3841 * (tp->snd_una has not yet been updated when this function is called.)
3843 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th);
3844 tp->t_flags |= TF_ACKNOW;
3845 (void) tp->t_fb->tfb_tcp_output(tp);
3846 tp->snd_cwnd = ocwnd;
3847 if (SEQ_GT(onxt, tp->snd_nxt))
3850 * Partial window deflation. Relies on fact that tp->snd_una
3853 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3854 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3857 tp->snd_cwnd += maxseg;
3861 tcp_compute_pipe(struct tcpcb *tp)
3863 return (tp->snd_max - tp->snd_una +
3864 tp->sackhint.sack_bytes_rexmit -
3865 tp->sackhint.sacked_bytes);
3869 tcp_compute_initwnd(uint32_t maxseg)
3872 * Calculate the Initial Window, also used as Restart Window
3874 * RFC5681 Section 3.1 specifies the default conservative values.
3875 * RFC3390 specifies slightly more aggressive values.
3876 * RFC6928 increases it to ten segments.
3877 * Support for user specified value for initial flight size.
3879 if (V_tcp_initcwnd_segments)
3880 return min(V_tcp_initcwnd_segments * maxseg,
3881 max(2 * maxseg, V_tcp_initcwnd_segments * 1460));
3882 else if (V_tcp_do_rfc3390)
3883 return min(4 * maxseg, max(2 * maxseg, 4380));
3885 /* Per RFC5681 Section 3.1 */
3887 return (2 * maxseg);
3888 else if (maxseg > 1095)
3889 return (3 * maxseg);
3891 return (4 * maxseg);
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