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>
61 #include <sys/kernel.h>
63 #include <sys/hhook.h>
65 #include <sys/malloc.h>
67 #include <sys/proc.h> /* for proc0 declaration */
68 #include <sys/protosw.h>
70 #include <sys/signalvar.h>
71 #include <sys/socket.h>
72 #include <sys/socketvar.h>
73 #include <sys/sysctl.h>
74 #include <sys/syslog.h>
75 #include <sys/systm.h>
77 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
82 #include <net/if_var.h>
83 #include <net/route.h>
86 #define TCPSTATES /* for logging */
88 #include <netinet/in.h>
89 #include <netinet/in_kdtrace.h>
90 #include <netinet/in_pcb.h>
91 #include <netinet/in_systm.h>
92 #include <netinet/ip.h>
93 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
94 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
95 #include <netinet/ip_var.h>
96 #include <netinet/ip_options.h>
97 #include <netinet/ip6.h>
98 #include <netinet/icmp6.h>
99 #include <netinet6/in6_pcb.h>
100 #include <netinet6/in6_var.h>
101 #include <netinet6/ip6_var.h>
102 #include <netinet6/nd6.h>
103 #include <netinet/tcp.h>
104 #include <netinet/tcp_fsm.h>
105 #include <netinet/tcp_log_buf.h>
106 #include <netinet/tcp_seq.h>
107 #include <netinet/tcp_timer.h>
108 #include <netinet/tcp_var.h>
109 #include <netinet6/tcp6_var.h>
110 #include <netinet/tcpip.h>
111 #include <netinet/cc/cc.h>
112 #include <netinet/tcp_fastopen.h>
114 #include <netinet/tcp_pcap.h>
116 #include <netinet/tcp_syncache.h>
118 #include <netinet/tcp_debug.h>
119 #endif /* TCPDEBUG */
121 #include <netinet/tcp_offload.h>
124 #include <netipsec/ipsec_support.h>
126 #include <machine/in_cksum.h>
128 #include <security/mac/mac_framework.h>
130 const int tcprexmtthresh = 3;
132 int tcp_log_in_vain = 0;
133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
135 "Log all incoming TCP segments to closed ports");
137 VNET_DEFINE(int, blackhole) = 0;
138 #define V_blackhole VNET(blackhole)
139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW,
140 &VNET_NAME(blackhole), 0,
141 "Do not send RST on segments to closed ports");
143 VNET_DEFINE(int, tcp_delack_enabled) = 1;
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW,
145 &VNET_NAME(tcp_delack_enabled), 0,
146 "Delay ACK to try and piggyback it onto a data packet");
148 VNET_DEFINE(int, drop_synfin) = 0;
149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW,
150 &VNET_NAME(drop_synfin), 0,
151 "Drop TCP packets with SYN+FIN set");
153 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0;
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW,
155 &VNET_NAME(tcp_do_rfc6675_pipe), 0,
156 "Use calculated pipe/in-flight bytes per RFC 6675");
158 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
159 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW,
160 &VNET_NAME(tcp_do_rfc3042), 0,
161 "Enable RFC 3042 (Limited Transmit)");
163 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW,
165 &VNET_NAME(tcp_do_rfc3390), 0,
166 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
168 VNET_DEFINE(int, tcp_initcwnd_segments) = 10;
169 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments,
170 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0,
171 "Slow-start flight size (initial congestion window) in number of segments");
173 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
174 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW,
175 &VNET_NAME(tcp_do_rfc3465), 0,
176 "Enable RFC 3465 (Appropriate Byte Counting)");
178 VNET_DEFINE(int, tcp_abc_l_var) = 2;
179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW,
180 &VNET_NAME(tcp_abc_l_var), 2,
181 "Cap the max cwnd increment during slow-start to this number of segments");
183 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
185 VNET_DEFINE(int, tcp_do_ecn) = 2;
186 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
187 &VNET_NAME(tcp_do_ecn), 0,
190 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
191 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW,
192 &VNET_NAME(tcp_ecn_maxretries), 0,
193 "Max retries before giving up on ECN");
195 VNET_DEFINE(int, tcp_insecure_syn) = 0;
196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW,
197 &VNET_NAME(tcp_insecure_syn), 0,
198 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets");
200 VNET_DEFINE(int, tcp_insecure_rst) = 0;
201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW,
202 &VNET_NAME(tcp_insecure_rst), 0,
203 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets");
205 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
206 #define V_tcp_recvspace VNET(tcp_recvspace)
207 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW,
208 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
210 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
212 &VNET_NAME(tcp_do_autorcvbuf), 0,
213 "Enable automatic receive buffer sizing");
215 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
217 &VNET_NAME(tcp_autorcvbuf_inc), 0,
218 "Incrementor step size of automatic receive buffer");
220 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
222 &VNET_NAME(tcp_autorcvbuf_max), 0,
223 "Max size of automatic receive buffer");
225 VNET_DEFINE(struct inpcbhead, tcb);
226 #define tcb6 tcb /* for KAME src sync over BSD*'s */
227 VNET_DEFINE(struct inpcbinfo, tcbinfo);
230 * TCP statistics are stored in an array of counter(9)s, which size matches
231 * size of struct tcpstat. TCP running connection count is a regular array.
233 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
234 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
235 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
236 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]);
237 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD |
238 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES,
239 "TCP connection counts by TCP state");
242 tcp_vnet_init(const void *unused)
245 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK);
246 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK);
248 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY,
249 tcp_vnet_init, NULL);
253 tcp_vnet_uninit(const void *unused)
256 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES);
257 VNET_PCPUSTAT_FREE(tcpstat);
259 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY,
260 tcp_vnet_uninit, NULL);
264 * Kernel module interface for updating tcpstat. The argument is an index
265 * into tcpstat treated as an array.
268 kmod_tcpstat_inc(int statnum)
271 counter_u64_add(VNET(tcpstat)[statnum], 1);
276 * Wrapper for the TCP established input helper hook.
279 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
281 struct tcp_hhook_data hhook_data;
283 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
288 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
295 * CC wrapper hook functions
298 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs,
301 INP_WLOCK_ASSERT(tp->t_inpcb);
303 tp->ccv->nsegs = nsegs;
304 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
305 if (tp->snd_cwnd <= tp->snd_wnd)
306 tp->ccv->flags |= CCF_CWND_LIMITED;
308 tp->ccv->flags &= ~CCF_CWND_LIMITED;
310 if (type == CC_ACK) {
311 if (tp->snd_cwnd > tp->snd_ssthresh) {
312 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
313 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp));
314 if (tp->t_bytes_acked >= tp->snd_cwnd) {
315 tp->t_bytes_acked -= tp->snd_cwnd;
316 tp->ccv->flags |= CCF_ABC_SENTAWND;
319 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
320 tp->t_bytes_acked = 0;
324 if (CC_ALGO(tp)->ack_received != NULL) {
325 /* XXXLAS: Find a way to live without this */
326 tp->ccv->curack = th->th_ack;
327 CC_ALGO(tp)->ack_received(tp->ccv, type);
332 cc_conn_init(struct tcpcb *tp)
334 struct hc_metrics_lite metrics;
335 struct inpcb *inp = tp->t_inpcb;
339 INP_WLOCK_ASSERT(tp->t_inpcb);
341 tcp_hc_get(&inp->inp_inc, &metrics);
342 maxseg = tcp_maxseg(tp);
344 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
346 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
347 TCPSTAT_INC(tcps_usedrtt);
348 if (metrics.rmx_rttvar) {
349 tp->t_rttvar = metrics.rmx_rttvar;
350 TCPSTAT_INC(tcps_usedrttvar);
352 /* default variation is +- 1 rtt */
354 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
356 TCPT_RANGESET(tp->t_rxtcur,
357 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
358 tp->t_rttmin, TCPTV_REXMTMAX);
360 if (metrics.rmx_ssthresh) {
362 * There's some sort of gateway or interface
363 * buffer limit on the path. Use this to set
364 * the slow start threshold, but set the
365 * threshold to no less than 2*mss.
367 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh);
368 TCPSTAT_INC(tcps_usedssthresh);
372 * Set the initial slow-start flight size.
374 * RFC5681 Section 3.1 specifies the default conservative values.
375 * RFC3390 specifies slightly more aggressive values.
376 * RFC6928 increases it to ten segments.
377 * Support for user specified value for initial flight size.
379 * If a SYN or SYN/ACK was lost and retransmitted, we have to
380 * reduce the initial CWND to one segment as congestion is likely
381 * requiring us to be cautious.
383 if (tp->snd_cwnd == 1)
384 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */
385 else if (V_tcp_initcwnd_segments)
386 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg,
387 max(2 * maxseg, V_tcp_initcwnd_segments * 1460));
388 else if (V_tcp_do_rfc3390)
389 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380));
391 /* Per RFC5681 Section 3.1 */
393 tp->snd_cwnd = 2 * maxseg;
394 else if (maxseg > 1095)
395 tp->snd_cwnd = 3 * maxseg;
397 tp->snd_cwnd = 4 * maxseg;
400 if (CC_ALGO(tp)->conn_init != NULL)
401 CC_ALGO(tp)->conn_init(tp->ccv);
405 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
409 INP_WLOCK_ASSERT(tp->t_inpcb);
413 if (!IN_FASTRECOVERY(tp->t_flags)) {
414 tp->snd_recover = tp->snd_max;
415 if (tp->t_flags & TF_ECN_PERMIT)
416 tp->t_flags |= TF_ECN_SND_CWR;
420 if (!IN_CONGRECOVERY(tp->t_flags)) {
421 TCPSTAT_INC(tcps_ecn_rcwnd);
422 tp->snd_recover = tp->snd_max;
423 if (tp->t_flags & TF_ECN_PERMIT)
424 tp->t_flags |= TF_ECN_SND_CWR;
428 maxseg = tcp_maxseg(tp);
430 tp->t_bytes_acked = 0;
431 EXIT_RECOVERY(tp->t_flags);
432 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
434 tp->snd_cwnd = maxseg;
437 TCPSTAT_INC(tcps_sndrexmitbad);
438 /* RTO was unnecessary, so reset everything. */
439 tp->snd_cwnd = tp->snd_cwnd_prev;
440 tp->snd_ssthresh = tp->snd_ssthresh_prev;
441 tp->snd_recover = tp->snd_recover_prev;
442 if (tp->t_flags & TF_WASFRECOVERY)
443 ENTER_FASTRECOVERY(tp->t_flags);
444 if (tp->t_flags & TF_WASCRECOVERY)
445 ENTER_CONGRECOVERY(tp->t_flags);
446 tp->snd_nxt = tp->snd_max;
447 tp->t_flags &= ~TF_PREVVALID;
452 if (CC_ALGO(tp)->cong_signal != NULL) {
454 tp->ccv->curack = th->th_ack;
455 CC_ALGO(tp)->cong_signal(tp->ccv, type);
460 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
462 INP_WLOCK_ASSERT(tp->t_inpcb);
464 /* XXXLAS: KASSERT that we're in recovery? */
466 if (CC_ALGO(tp)->post_recovery != NULL) {
467 tp->ccv->curack = th->th_ack;
468 CC_ALGO(tp)->post_recovery(tp->ccv);
470 /* XXXLAS: EXIT_RECOVERY ? */
471 tp->t_bytes_acked = 0;
475 * Indicate whether this ack should be delayed. We can delay the ack if
476 * following conditions are met:
477 * - There is no delayed ack timer in progress.
478 * - Our last ack wasn't a 0-sized window. We never want to delay
479 * the ack that opens up a 0-sized window.
480 * - LRO wasn't used for this segment. We make sure by checking that the
481 * segment size is not larger than the MSS.
483 #define DELAY_ACK(tp, tlen) \
484 ((!tcp_timer_active(tp, TT_DELACK) && \
485 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
486 (tlen <= tp->t_maxseg) && \
487 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
490 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos)
492 INP_WLOCK_ASSERT(tp->t_inpcb);
494 if (CC_ALGO(tp)->ecnpkt_handler != NULL) {
495 switch (iptos & IPTOS_ECN_MASK) {
497 tp->ccv->flags |= CCF_IPHDR_CE;
500 tp->ccv->flags &= ~CCF_IPHDR_CE;
503 tp->ccv->flags &= ~CCF_IPHDR_CE;
507 if (th->th_flags & TH_CWR)
508 tp->ccv->flags |= CCF_TCPHDR_CWR;
510 tp->ccv->flags &= ~CCF_TCPHDR_CWR;
512 if (tp->t_flags & TF_DELACK)
513 tp->ccv->flags |= CCF_DELACK;
515 tp->ccv->flags &= ~CCF_DELACK;
517 CC_ALGO(tp)->ecnpkt_handler(tp->ccv);
519 if (tp->ccv->flags & CCF_ACKNOW)
520 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
525 * TCP input handling is split into multiple parts:
526 * tcp6_input is a thin wrapper around tcp_input for the extended
527 * ip6_protox[] call format in ip6_input
528 * tcp_input handles primary segment validation, inpcb lookup and
529 * SYN processing on listen sockets
530 * tcp_do_segment processes the ACK and text of the segment for
531 * establishing, established and closing connections
535 tcp6_input(struct mbuf **mp, int *offp, int proto)
537 struct mbuf *m = *mp;
538 struct in6_ifaddr *ia6;
541 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
544 * draft-itojun-ipv6-tcp-to-anycast
545 * better place to put this in?
547 ip6 = mtod(m, struct ip6_hdr *);
548 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
549 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
552 ifa_free(&ia6->ia_ifa);
553 ip6 = mtod(m, struct ip6_hdr *);
554 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
555 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
556 return (IPPROTO_DONE);
559 ifa_free(&ia6->ia_ifa);
561 return (tcp_input(mp, offp, proto));
566 tcp_input(struct mbuf **mp, int *offp, int proto)
568 struct mbuf *m = *mp;
569 struct tcphdr *th = NULL;
570 struct ip *ip = NULL;
571 struct inpcb *inp = NULL;
572 struct tcpcb *tp = NULL;
573 struct socket *so = NULL;
583 int rstreason = 0; /* For badport_bandlim accounting purposes */
585 struct m_tag *fwd_tag = NULL;
587 struct ip6_hdr *ip6 = NULL;
590 const void *ip6 = NULL;
592 struct tcpopt to; /* options in this segment */
593 char *s = NULL; /* address and port logging */
597 * The size of tcp_saveipgen must be the size of the max ip header,
600 u_char tcp_saveipgen[IP6_HDR_LEN];
601 struct tcphdr tcp_savetcp;
606 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
613 TCPSTAT_INC(tcps_rcvtotal);
617 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
619 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
620 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
622 TCPSTAT_INC(tcps_rcvshort);
623 return (IPPROTO_DONE);
627 ip6 = mtod(m, struct ip6_hdr *);
628 th = (struct tcphdr *)((caddr_t)ip6 + off0);
629 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
630 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
631 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
632 th->th_sum = m->m_pkthdr.csum_data;
634 th->th_sum = in6_cksum_pseudo(ip6, tlen,
635 IPPROTO_TCP, m->m_pkthdr.csum_data);
636 th->th_sum ^= 0xffff;
638 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
640 TCPSTAT_INC(tcps_rcvbadsum);
645 * Be proactive about unspecified IPv6 address in source.
646 * As we use all-zero to indicate unbounded/unconnected pcb,
647 * unspecified IPv6 address can be used to confuse us.
649 * Note that packets with unspecified IPv6 destination is
650 * already dropped in ip6_input.
652 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
656 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
659 #if defined(INET) && defined(INET6)
665 * Get IP and TCP header together in first mbuf.
666 * Note: IP leaves IP header in first mbuf.
668 if (off0 > sizeof (struct ip)) {
670 off0 = sizeof(struct ip);
672 if (m->m_len < sizeof (struct tcpiphdr)) {
673 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
675 TCPSTAT_INC(tcps_rcvshort);
676 return (IPPROTO_DONE);
679 ip = mtod(m, struct ip *);
680 th = (struct tcphdr *)((caddr_t)ip + off0);
681 tlen = ntohs(ip->ip_len) - off0;
684 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
685 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
686 th->th_sum = m->m_pkthdr.csum_data;
688 th->th_sum = in_pseudo(ip->ip_src.s_addr,
690 htonl(m->m_pkthdr.csum_data + tlen +
692 th->th_sum ^= 0xffff;
694 struct ipovly *ipov = (struct ipovly *)ip;
697 * Checksum extended TCP header and data.
700 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
701 ipov->ih_len = htons(tlen);
702 th->th_sum = in_cksum(m, len);
703 /* Reset length for SDT probes. */
704 ip->ip_len = htons(len);
707 /* Re-initialization for later version check */
708 ip->ip_v = IPVERSION;
709 ip->ip_hl = off0 >> 2;
713 TCPSTAT_INC(tcps_rcvbadsum);
720 * Check that TCP offset makes sense,
721 * pull out TCP options and adjust length. XXX
723 off = th->th_off << 2;
724 if (off < sizeof (struct tcphdr) || off > tlen) {
725 TCPSTAT_INC(tcps_rcvbadoff);
728 tlen -= off; /* tlen is used instead of ti->ti_len */
729 if (off > sizeof (struct tcphdr)) {
732 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
733 ip6 = mtod(m, struct ip6_hdr *);
734 th = (struct tcphdr *)((caddr_t)ip6 + off0);
737 #if defined(INET) && defined(INET6)
742 if (m->m_len < sizeof(struct ip) + off) {
743 if ((m = m_pullup(m, sizeof (struct ip) + off))
745 TCPSTAT_INC(tcps_rcvshort);
746 return (IPPROTO_DONE);
748 ip = mtod(m, struct ip *);
749 th = (struct tcphdr *)((caddr_t)ip + off0);
753 optlen = off - sizeof (struct tcphdr);
754 optp = (u_char *)(th + 1);
756 thflags = th->th_flags;
759 * Convert TCP protocol specific fields to host format.
761 tcp_fields_to_host(th);
764 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
766 drop_hdrlen = off0 + off;
769 * Locate pcb for segment; if we're likely to add or remove a
770 * connection then first acquire pcbinfo lock. There are three cases
771 * where we might discover later we need a write lock despite the
772 * flags: ACKs moving a connection out of the syncache, ACKs for a
773 * connection in TIMEWAIT and SYNs not targeting a listening socket.
775 if ((thflags & (TH_FIN | TH_RST)) != 0) {
776 INP_INFO_RLOCK(&V_tcbinfo);
777 ti_locked = TI_RLOCKED;
779 ti_locked = TI_UNLOCKED;
782 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
786 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
788 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
791 #if defined(INET) && !defined(INET6)
792 (m->m_flags & M_IP_NEXTHOP)
795 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
799 if (ti_locked == TI_RLOCKED) {
800 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
802 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
806 if (isipv6 && fwd_tag != NULL) {
807 struct sockaddr_in6 *next_hop6;
809 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
811 * Transparently forwarded. Pretend to be the destination.
812 * Already got one like this?
814 inp = in6_pcblookup_mbuf(&V_tcbinfo,
815 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
816 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
819 * It's new. Try to find the ambushing socket.
820 * Because we've rewritten the destination address,
821 * any hardware-generated hash is ignored.
823 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
824 th->th_sport, &next_hop6->sin6_addr,
825 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
826 th->th_dport, INPLOOKUP_WILDCARD |
827 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
830 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
831 th->th_sport, &ip6->ip6_dst, th->th_dport,
832 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
833 m->m_pkthdr.rcvif, m);
836 #if defined(INET6) && defined(INET)
840 if (fwd_tag != NULL) {
841 struct sockaddr_in *next_hop;
843 next_hop = (struct sockaddr_in *)(fwd_tag+1);
845 * Transparently forwarded. Pretend to be the destination.
846 * already got one like this?
848 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
849 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
850 m->m_pkthdr.rcvif, m);
853 * It's new. Try to find the ambushing socket.
854 * Because we've rewritten the destination address,
855 * any hardware-generated hash is ignored.
857 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
858 th->th_sport, next_hop->sin_addr,
859 next_hop->sin_port ? ntohs(next_hop->sin_port) :
860 th->th_dport, INPLOOKUP_WILDCARD |
861 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
864 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
865 th->th_sport, ip->ip_dst, th->th_dport,
866 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
867 m->m_pkthdr.rcvif, m);
871 * If the INPCB does not exist then all data in the incoming
872 * segment is discarded and an appropriate RST is sent back.
873 * XXX MRT Send RST using which routing table?
877 * Log communication attempts to ports that are not
880 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
881 tcp_log_in_vain == 2) {
882 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
883 log(LOG_INFO, "%s; %s: Connection attempt "
884 "to closed port\n", s, __func__);
887 * When blackholing do not respond with a RST but
888 * completely ignore the segment and drop it.
890 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
894 rstreason = BANDLIM_RST_CLOSEDPORT;
897 INP_WLOCK_ASSERT(inp);
899 * While waiting for inp lock during the lookup, another thread
900 * can have dropped the inpcb, in which case we need to loop back
901 * and try to find a new inpcb to deliver to.
903 if (inp->inp_flags & INP_DROPPED) {
908 if ((inp->inp_flowtype == M_HASHTYPE_NONE) &&
909 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) &&
910 ((inp->inp_socket == NULL) ||
911 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
912 inp->inp_flowid = m->m_pkthdr.flowid;
913 inp->inp_flowtype = M_HASHTYPE_GET(m);
915 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
917 if (isipv6 && IPSEC_ENABLED(ipv6) &&
918 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) {
926 if (IPSEC_ENABLED(ipv4) &&
927 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) {
934 * Check the minimum TTL for socket.
936 if (inp->inp_ip_minttl != 0) {
939 if (inp->inp_ip_minttl > ip6->ip6_hlim)
943 if (inp->inp_ip_minttl > ip->ip_ttl)
948 * A previous connection in TIMEWAIT state is supposed to catch stray
949 * or duplicate segments arriving late. If this segment was a
950 * legitimate new connection attempt, the old INPCB gets removed and
951 * we can try again to find a listening socket.
953 * At this point, due to earlier optimism, we may hold only an inpcb
954 * lock, and not the inpcbinfo write lock. If so, we need to try to
955 * acquire it, or if that fails, acquire a reference on the inpcb,
956 * drop all locks, acquire a global write lock, and then re-acquire
957 * the inpcb lock. We may at that point discover that another thread
958 * has tried to free the inpcb, in which case we need to loop back
959 * and try to find a new inpcb to deliver to.
961 * XXXRW: It may be time to rethink timewait locking.
964 if (inp->inp_flags & INP_TIMEWAIT) {
965 if (ti_locked == TI_UNLOCKED) {
966 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) {
969 INP_INFO_RLOCK(&V_tcbinfo);
970 ti_locked = TI_RLOCKED;
972 if (in_pcbrele_wlocked(inp)) {
975 } else if (inp->inp_flags & INP_DROPPED) {
981 ti_locked = TI_RLOCKED;
983 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
985 if (thflags & TH_SYN)
986 tcp_dooptions(&to, optp, optlen, TO_SYN);
988 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
990 if (tcp_twcheck(inp, &to, th, m, tlen))
992 INP_INFO_RUNLOCK(&V_tcbinfo);
993 return (IPPROTO_DONE);
996 * The TCPCB may no longer exist if the connection is winding
997 * down or it is in the CLOSED state. Either way we drop the
998 * segment and send an appropriate response.
1000 tp = intotcpcb(inp);
1001 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
1002 rstreason = BANDLIM_RST_CLOSEDPORT;
1007 if (tp->t_flags & TF_TOE) {
1008 tcp_offload_input(tp, m);
1009 m = NULL; /* consumed by the TOE driver */
1015 * We've identified a valid inpcb, but it could be that we need an
1016 * inpcbinfo write lock but don't hold it. In this case, attempt to
1017 * acquire using the same strategy as the TIMEWAIT case above. If we
1018 * relock, we have to jump back to 'relocked' as the connection might
1019 * now be in TIMEWAIT.
1022 if ((thflags & (TH_FIN | TH_RST)) != 0)
1023 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1025 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) ||
1026 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) &&
1027 !IS_FASTOPEN(tp->t_flags)))) {
1028 if (ti_locked == TI_UNLOCKED) {
1029 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) {
1032 INP_INFO_RLOCK(&V_tcbinfo);
1033 ti_locked = TI_RLOCKED;
1035 if (in_pcbrele_wlocked(inp)) {
1038 } else if (inp->inp_flags & INP_DROPPED) {
1045 ti_locked = TI_RLOCKED;
1047 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1051 INP_WLOCK_ASSERT(inp);
1052 if (mac_inpcb_check_deliver(inp, m))
1055 so = inp->inp_socket;
1056 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1058 if (so->so_options & SO_DEBUG) {
1059 ostate = tp->t_state;
1062 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1065 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1068 #endif /* TCPDEBUG */
1070 * When the socket is accepting connections (the INPCB is in LISTEN
1071 * state) we look into the SYN cache if this is a new connection
1072 * attempt or the completion of a previous one.
1074 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN),
1075 ("%s: so accepting but tp %p not listening", __func__, tp));
1076 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) {
1077 struct in_conninfo inc;
1079 bzero(&inc, sizeof(inc));
1082 inc.inc_flags |= INC_ISIPV6;
1083 inc.inc6_faddr = ip6->ip6_src;
1084 inc.inc6_laddr = ip6->ip6_dst;
1088 inc.inc_faddr = ip->ip_src;
1089 inc.inc_laddr = ip->ip_dst;
1091 inc.inc_fport = th->th_sport;
1092 inc.inc_lport = th->th_dport;
1093 inc.inc_fibnum = so->so_fibnum;
1096 * Check for an existing connection attempt in syncache if
1097 * the flag is only ACK. A successful lookup creates a new
1098 * socket appended to the listen queue in SYN_RECEIVED state.
1100 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1102 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1104 * Parse the TCP options here because
1105 * syncookies need access to the reflected
1108 tcp_dooptions(&to, optp, optlen, 0);
1110 * NB: syncache_expand() doesn't unlock
1111 * inp and tcpinfo locks.
1113 rstreason = syncache_expand(&inc, &to, th, &so, m);
1114 if (rstreason < 0) {
1116 * A failing TCP MD5 signature comparison
1117 * must result in the segment being dropped
1118 * and must not produce any response back
1122 } else if (rstreason == 0) {
1124 * No syncache entry or ACK was not
1125 * for our SYN/ACK. Send a RST.
1126 * NB: syncache did its own logging
1127 * of the failure cause.
1129 rstreason = BANDLIM_RST_OPENPORT;
1135 * We completed the 3-way handshake
1136 * but could not allocate a socket
1137 * either due to memory shortage,
1138 * listen queue length limits or
1139 * global socket limits. Send RST
1140 * or wait and have the remote end
1141 * retransmit the ACK for another
1144 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1145 log(LOG_DEBUG, "%s; %s: Listen socket: "
1146 "Socket allocation failed due to "
1147 "limits or memory shortage, %s\n",
1149 V_tcp_sc_rst_sock_fail ?
1150 "sending RST" : "try again");
1151 if (V_tcp_sc_rst_sock_fail) {
1152 rstreason = BANDLIM_UNLIMITED;
1158 * Socket is created in state SYN_RECEIVED.
1159 * Unlock the listen socket, lock the newly
1160 * created socket and update the tp variable.
1162 INP_WUNLOCK(inp); /* listen socket */
1163 inp = sotoinpcb(so);
1165 * New connection inpcb is already locked by
1166 * syncache_expand().
1168 INP_WLOCK_ASSERT(inp);
1169 tp = intotcpcb(inp);
1170 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1171 ("%s: ", __func__));
1173 * Process the segment and the data it
1174 * contains. tcp_do_segment() consumes
1175 * the mbuf chain and unlocks the inpcb.
1177 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1179 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1180 return (IPPROTO_DONE);
1183 * Segment flag validation for new connection attempts:
1185 * Our (SYN|ACK) response was rejected.
1186 * Check with syncache and remove entry to prevent
1189 * NB: syncache_chkrst does its own logging of failure
1192 if (thflags & TH_RST) {
1193 syncache_chkrst(&inc, th);
1197 * We can't do anything without SYN.
1199 if ((thflags & TH_SYN) == 0) {
1200 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1201 log(LOG_DEBUG, "%s; %s: Listen socket: "
1202 "SYN is missing, segment ignored\n",
1204 TCPSTAT_INC(tcps_badsyn);
1208 * (SYN|ACK) is bogus on a listen socket.
1210 if (thflags & TH_ACK) {
1211 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1212 log(LOG_DEBUG, "%s; %s: Listen socket: "
1213 "SYN|ACK invalid, segment rejected\n",
1215 syncache_badack(&inc); /* XXX: Not needed! */
1216 TCPSTAT_INC(tcps_badsyn);
1217 rstreason = BANDLIM_RST_OPENPORT;
1221 * If the drop_synfin option is enabled, drop all
1222 * segments with both the SYN and FIN bits set.
1223 * This prevents e.g. nmap from identifying the
1225 * XXX: Poor reasoning. nmap has other methods
1226 * and is constantly refining its stack detection
1228 * XXX: This is a violation of the TCP specification
1229 * and was used by RFC1644.
1231 if ((thflags & TH_FIN) && V_drop_synfin) {
1232 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1233 log(LOG_DEBUG, "%s; %s: Listen socket: "
1234 "SYN|FIN segment ignored (based on "
1235 "sysctl setting)\n", s, __func__);
1236 TCPSTAT_INC(tcps_badsyn);
1240 * Segment's flags are (SYN) or (SYN|FIN).
1242 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1243 * as they do not affect the state of the TCP FSM.
1244 * The data pointed to by TH_URG and th_urp is ignored.
1246 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1247 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1248 KASSERT(thflags & (TH_SYN),
1249 ("%s: Listen socket: TH_SYN not set", __func__));
1252 * If deprecated address is forbidden,
1253 * we do not accept SYN to deprecated interface
1254 * address to prevent any new inbound connection from
1255 * getting established.
1256 * When we do not accept SYN, we send a TCP RST,
1257 * with deprecated source address (instead of dropping
1258 * it). We compromise it as it is much better for peer
1259 * to send a RST, and RST will be the final packet
1262 * If we do not forbid deprecated addresses, we accept
1263 * the SYN packet. RFC2462 does not suggest dropping
1265 * If we decipher RFC2462 5.5.4, it says like this:
1266 * 1. use of deprecated addr with existing
1267 * communication is okay - "SHOULD continue to be
1269 * 2. use of it with new communication:
1270 * (2a) "SHOULD NOT be used if alternate address
1271 * with sufficient scope is available"
1272 * (2b) nothing mentioned otherwise.
1273 * Here we fall into (2b) case as we have no choice in
1274 * our source address selection - we must obey the peer.
1276 * The wording in RFC2462 is confusing, and there are
1277 * multiple description text for deprecated address
1278 * handling - worse, they are not exactly the same.
1279 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1281 if (isipv6 && !V_ip6_use_deprecated) {
1282 struct in6_ifaddr *ia6;
1284 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
1286 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1287 ifa_free(&ia6->ia_ifa);
1288 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1289 log(LOG_DEBUG, "%s; %s: Listen socket: "
1290 "Connection attempt to deprecated "
1291 "IPv6 address rejected\n",
1293 rstreason = BANDLIM_RST_OPENPORT;
1297 ifa_free(&ia6->ia_ifa);
1301 * Basic sanity checks on incoming SYN requests:
1302 * Don't respond if the destination is a link layer
1303 * broadcast according to RFC1122 4.2.3.10, p. 104.
1304 * If it is from this socket it must be forged.
1305 * Don't respond if the source or destination is a
1306 * global or subnet broad- or multicast address.
1307 * Note that it is quite possible to receive unicast
1308 * link-layer packets with a broadcast IP address. Use
1309 * in_broadcast() to find them.
1311 if (m->m_flags & (M_BCAST|M_MCAST)) {
1312 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1313 log(LOG_DEBUG, "%s; %s: Listen socket: "
1314 "Connection attempt from broad- or multicast "
1315 "link layer address ignored\n", s, __func__);
1320 if (th->th_dport == th->th_sport &&
1321 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1322 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1323 log(LOG_DEBUG, "%s; %s: Listen socket: "
1324 "Connection attempt to/from self "
1325 "ignored\n", s, __func__);
1328 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1329 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1330 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1331 log(LOG_DEBUG, "%s; %s: Listen socket: "
1332 "Connection attempt from/to multicast "
1333 "address ignored\n", s, __func__);
1338 #if defined(INET) && defined(INET6)
1343 if (th->th_dport == th->th_sport &&
1344 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1345 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1346 log(LOG_DEBUG, "%s; %s: Listen socket: "
1347 "Connection attempt from/to self "
1348 "ignored\n", s, __func__);
1351 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1352 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1353 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1354 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1355 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1356 log(LOG_DEBUG, "%s; %s: Listen socket: "
1357 "Connection attempt from/to broad- "
1358 "or multicast address ignored\n",
1365 * SYN appears to be valid. Create compressed TCP state
1369 if (so->so_options & SO_DEBUG)
1370 tcp_trace(TA_INPUT, ostate, tp,
1371 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1373 TCP_PROBE3(debug__input, tp, th, m);
1374 tcp_dooptions(&to, optp, optlen, TO_SYN);
1375 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL))
1376 goto tfo_socket_result;
1379 * Entry added to syncache and mbuf consumed.
1380 * Only the listen socket is unlocked by syncache_add().
1382 if (ti_locked == TI_RLOCKED) {
1383 INP_INFO_RUNLOCK(&V_tcbinfo);
1384 ti_locked = TI_UNLOCKED;
1386 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1387 return (IPPROTO_DONE);
1388 } else if (tp->t_state == TCPS_LISTEN) {
1390 * When a listen socket is torn down the SO_ACCEPTCONN
1391 * flag is removed first while connections are drained
1392 * from the accept queue in a unlock/lock cycle of the
1393 * ACCEPT_LOCK, opening a race condition allowing a SYN
1394 * attempt go through unhandled.
1398 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1399 if (tp->t_flags & TF_SIGNATURE) {
1400 tcp_dooptions(&to, optp, optlen, thflags);
1401 if ((to.to_flags & TOF_SIGNATURE) == 0) {
1402 TCPSTAT_INC(tcps_sig_err_nosigopt);
1405 if (!TCPMD5_ENABLED() ||
1406 TCPMD5_INPUT(m, th, to.to_signature) != 0)
1410 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1413 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1414 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1415 * the inpcb, and unlocks pcbinfo.
1417 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1418 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1419 return (IPPROTO_DONE);
1422 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1424 if (ti_locked == TI_RLOCKED) {
1425 INP_INFO_RUNLOCK(&V_tcbinfo);
1426 ti_locked = TI_UNLOCKED;
1430 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1431 "ti_locked: %d", __func__, ti_locked));
1432 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1437 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1440 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1441 m = NULL; /* mbuf chain got consumed. */
1446 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1448 if (ti_locked == TI_RLOCKED) {
1449 INP_INFO_RUNLOCK(&V_tcbinfo);
1450 ti_locked = TI_UNLOCKED;
1454 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1455 "ti_locked: %d", __func__, ti_locked));
1456 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1464 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1469 return (IPPROTO_DONE);
1473 * Automatic sizing of receive socket buffer. Often the send
1474 * buffer size is not optimally adjusted to the actual network
1475 * conditions at hand (delay bandwidth product). Setting the
1476 * buffer size too small limits throughput on links with high
1477 * bandwidth and high delay (eg. trans-continental/oceanic links).
1479 * On the receive side the socket buffer memory is only rarely
1480 * used to any significant extent. This allows us to be much
1481 * more aggressive in scaling the receive socket buffer. For
1482 * the case that the buffer space is actually used to a large
1483 * extent and we run out of kernel memory we can simply drop
1484 * the new segments; TCP on the sender will just retransmit it
1485 * later. Setting the buffer size too big may only consume too
1486 * much kernel memory if the application doesn't read() from
1487 * the socket or packet loss or reordering makes use of the
1490 * The criteria to step up the receive buffer one notch are:
1491 * 1. Application has not set receive buffer size with
1492 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1493 * 2. the number of bytes received during the time it takes
1494 * one timestamp to be reflected back to us (the RTT);
1495 * 3. received bytes per RTT is within seven eighth of the
1496 * current socket buffer size;
1497 * 4. receive buffer size has not hit maximal automatic size;
1499 * This algorithm does one step per RTT at most and only if
1500 * we receive a bulk stream w/o packet losses or reorderings.
1501 * Shrinking the buffer during idle times is not necessary as
1502 * it doesn't consume any memory when idle.
1504 * TODO: Only step up if the application is actually serving
1505 * the buffer to better manage the socket buffer resources.
1508 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so,
1509 struct tcpcb *tp, int tlen)
1513 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
1514 tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
1515 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) >
1516 (tp->t_srtt >> TCP_RTT_SHIFT)) {
1517 if (tp->rfbuf_cnt > (so->so_rcv.sb_hiwat / 8 * 7) &&
1518 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) {
1519 newsize = min(so->so_rcv.sb_hiwat +
1520 V_tcp_autorcvbuf_inc, V_tcp_autorcvbuf_max);
1522 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize);
1524 /* Start over with next RTT. */
1528 tp->rfbuf_cnt += tlen; /* add up */
1535 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1536 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1539 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed;
1540 int rstreason, todrop, win;
1544 struct in_conninfo *inc;
1551 * The size of tcp_saveipgen must be the size of the max ip header,
1554 u_char tcp_saveipgen[IP6_HDR_LEN];
1555 struct tcphdr tcp_savetcp;
1558 thflags = th->th_flags;
1559 inc = &tp->t_inpcb->inp_inc;
1560 tp->sackhint.last_sack_ack = 0;
1562 nsegs = max(1, m->m_pkthdr.lro_nsegs);
1565 * If this is either a state-changing packet or current state isn't
1566 * established, we require a write lock on tcbinfo. Otherwise, we
1567 * allow the tcbinfo to be in either alocked or unlocked, as the
1568 * caller may have unnecessarily acquired a write lock due to a race.
1570 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1571 tp->t_state != TCPS_ESTABLISHED) {
1572 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for "
1573 "SYN/FIN/RST/!EST", __func__, ti_locked));
1574 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1577 if (ti_locked == TI_RLOCKED)
1578 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1580 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1581 "ti_locked: %d", __func__, ti_locked));
1582 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1586 INP_WLOCK_ASSERT(tp->t_inpcb);
1587 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1589 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1593 /* Save segment, if requested. */
1594 tcp_pcap_add(th, m, &(tp->t_inpkts));
1596 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0,
1599 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
1600 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1601 log(LOG_DEBUG, "%s; %s: "
1602 "SYN|FIN segment ignored (based on "
1603 "sysctl setting)\n", s, __func__);
1610 * If a segment with the ACK-bit set arrives in the SYN-SENT state
1611 * check SEQ.ACK first.
1613 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) &&
1614 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) {
1615 rstreason = BANDLIM_UNLIMITED;
1620 * Segment received on connection.
1621 * Reset idle time and keep-alive timer.
1622 * XXX: This should be done after segment
1623 * validation to ignore broken/spoofed segs.
1625 tp->t_rcvtime = ticks;
1628 * Scale up the window into a 32-bit value.
1629 * For the SYN_SENT state the scale is zero.
1631 tiwin = th->th_win << tp->snd_scale;
1634 * TCP ECN processing.
1636 if (tp->t_flags & TF_ECN_PERMIT) {
1637 if (thflags & TH_CWR)
1638 tp->t_flags &= ~TF_ECN_SND_ECE;
1639 switch (iptos & IPTOS_ECN_MASK) {
1641 tp->t_flags |= TF_ECN_SND_ECE;
1642 TCPSTAT_INC(tcps_ecn_ce);
1644 case IPTOS_ECN_ECT0:
1645 TCPSTAT_INC(tcps_ecn_ect0);
1647 case IPTOS_ECN_ECT1:
1648 TCPSTAT_INC(tcps_ecn_ect1);
1652 /* Process a packet differently from RFC3168. */
1653 cc_ecnpkt_handler(tp, th, iptos);
1655 /* Congestion experienced. */
1656 if (thflags & TH_ECE) {
1657 cc_cong_signal(tp, th, CC_ECN);
1662 * Parse options on any incoming segment.
1664 tcp_dooptions(&to, (u_char *)(th + 1),
1665 (th->th_off << 2) - sizeof(struct tcphdr),
1666 (thflags & TH_SYN) ? TO_SYN : 0);
1668 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1669 if ((tp->t_flags & TF_SIGNATURE) != 0 &&
1670 (to.to_flags & TOF_SIGNATURE) == 0) {
1671 TCPSTAT_INC(tcps_sig_err_sigopt);
1672 /* XXX: should drop? */
1676 * If echoed timestamp is later than the current time,
1677 * fall back to non RFC1323 RTT calculation. Normalize
1678 * timestamp if syncookies were used when this connection
1681 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1682 to.to_tsecr -= tp->ts_offset;
1683 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1685 else if (tp->t_flags & TF_PREVVALID &&
1686 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
1687 cc_cong_signal(tp, th, CC_RTO_ERR);
1690 * Process options only when we get SYN/ACK back. The SYN case
1691 * for incoming connections is handled in tcp_syncache.
1692 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1693 * or <SYN,ACK>) segment itself is never scaled.
1694 * XXX this is traditional behavior, may need to be cleaned up.
1696 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1697 if ((to.to_flags & TOF_SCALE) &&
1698 (tp->t_flags & TF_REQ_SCALE)) {
1699 tp->t_flags |= TF_RCVD_SCALE;
1700 tp->snd_scale = to.to_wscale;
1703 * Initial send window. It will be updated with
1704 * the next incoming segment to the scaled value.
1706 tp->snd_wnd = th->th_win;
1707 if (to.to_flags & TOF_TS) {
1708 tp->t_flags |= TF_RCVD_TSTMP;
1709 tp->ts_recent = to.to_tsval;
1710 tp->ts_recent_age = tcp_ts_getticks();
1712 if (to.to_flags & TOF_MSS)
1713 tcp_mss(tp, to.to_mss);
1714 if ((tp->t_flags & TF_SACK_PERMIT) &&
1715 (to.to_flags & TOF_SACKPERM) == 0)
1716 tp->t_flags &= ~TF_SACK_PERMIT;
1717 if (IS_FASTOPEN(tp->t_flags)) {
1718 if (to.to_flags & TOF_FASTOPEN)
1719 tcp_fastopen_update_cache(tp, to.to_mss,
1720 to.to_tfo_len, to.to_tfo_cookie);
1722 tcp_fastopen_disable_path(tp);
1727 * If timestamps were negotiated during SYN/ACK they should
1728 * appear on every segment during this session and vice versa.
1730 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1731 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1732 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1733 "no action\n", s, __func__);
1737 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1738 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1739 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1740 "no action\n", s, __func__);
1746 * Header prediction: check for the two common cases
1747 * of a uni-directional data xfer. If the packet has
1748 * no control flags, is in-sequence, the window didn't
1749 * change and we're not retransmitting, it's a
1750 * candidate. If the length is zero and the ack moved
1751 * forward, we're the sender side of the xfer. Just
1752 * free the data acked & wake any higher level process
1753 * that was blocked waiting for space. If the length
1754 * is non-zero and the ack didn't move, we're the
1755 * receiver side. If we're getting packets in-order
1756 * (the reassembly queue is empty), add the data to
1757 * the socket buffer and note that we need a delayed ack.
1758 * Make sure that the hidden state-flags are also off.
1759 * Since we check for TCPS_ESTABLISHED first, it can only
1762 if (tp->t_state == TCPS_ESTABLISHED &&
1763 th->th_seq == tp->rcv_nxt &&
1764 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1765 tp->snd_nxt == tp->snd_max &&
1766 tiwin && tiwin == tp->snd_wnd &&
1767 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1768 LIST_EMPTY(&tp->t_segq) &&
1769 ((to.to_flags & TOF_TS) == 0 ||
1770 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1773 * If last ACK falls within this segment's sequence numbers,
1774 * record the timestamp.
1775 * NOTE that the test is modified according to the latest
1776 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1778 if ((to.to_flags & TOF_TS) != 0 &&
1779 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1780 tp->ts_recent_age = tcp_ts_getticks();
1781 tp->ts_recent = to.to_tsval;
1785 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1786 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1787 !IN_RECOVERY(tp->t_flags) &&
1788 (to.to_flags & TOF_SACK) == 0 &&
1789 TAILQ_EMPTY(&tp->snd_holes)) {
1791 * This is a pure ack for outstanding data.
1793 if (ti_locked == TI_RLOCKED)
1794 INP_INFO_RUNLOCK(&V_tcbinfo);
1795 ti_locked = TI_UNLOCKED;
1797 TCPSTAT_INC(tcps_predack);
1800 * "bad retransmit" recovery without timestamps.
1802 if ((to.to_flags & TOF_TS) == 0 &&
1803 tp->t_rxtshift == 1 &&
1804 tp->t_flags & TF_PREVVALID &&
1805 (int)(ticks - tp->t_badrxtwin) < 0) {
1806 cc_cong_signal(tp, th, CC_RTO_ERR);
1810 * Recalculate the transmit timer / rtt.
1812 * Some boxes send broken timestamp replies
1813 * during the SYN+ACK phase, ignore
1814 * timestamps of 0 or we could calculate a
1815 * huge RTT and blow up the retransmit timer.
1817 if ((to.to_flags & TOF_TS) != 0 &&
1821 t = tcp_ts_getticks() - to.to_tsecr;
1822 if (!tp->t_rttlow || tp->t_rttlow > t)
1825 TCP_TS_TO_TICKS(t) + 1);
1826 } else if (tp->t_rtttime &&
1827 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1828 if (!tp->t_rttlow ||
1829 tp->t_rttlow > ticks - tp->t_rtttime)
1830 tp->t_rttlow = ticks - tp->t_rtttime;
1832 ticks - tp->t_rtttime);
1834 acked = BYTES_THIS_ACK(tp, th);
1837 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1838 hhook_run_tcp_est_in(tp, th, &to);
1841 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
1842 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1843 sbdrop(&so->so_snd, acked);
1844 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1845 SEQ_LEQ(th->th_ack, tp->snd_recover))
1846 tp->snd_recover = th->th_ack - 1;
1849 * Let the congestion control algorithm update
1850 * congestion control related information. This
1851 * typically means increasing the congestion
1854 cc_ack_received(tp, th, nsegs, CC_ACK);
1856 tp->snd_una = th->th_ack;
1858 * Pull snd_wl2 up to prevent seq wrap relative
1861 tp->snd_wl2 = th->th_ack;
1866 * If all outstanding data are acked, stop
1867 * retransmit timer, otherwise restart timer
1868 * using current (possibly backed-off) value.
1869 * If process is waiting for space,
1870 * wakeup/selwakeup/signal. If data
1871 * are ready to send, let tcp_output
1872 * decide between more output or persist.
1875 if (so->so_options & SO_DEBUG)
1876 tcp_trace(TA_INPUT, ostate, tp,
1877 (void *)tcp_saveipgen,
1880 TCP_PROBE3(debug__input, tp, th, m);
1881 if (tp->snd_una == tp->snd_max)
1882 tcp_timer_activate(tp, TT_REXMT, 0);
1883 else if (!tcp_timer_active(tp, TT_PERSIST))
1884 tcp_timer_activate(tp, TT_REXMT,
1887 if (sbavail(&so->so_snd))
1888 (void) tp->t_fb->tfb_tcp_output(tp);
1891 } else if (th->th_ack == tp->snd_una &&
1892 tlen <= sbspace(&so->so_rcv)) {
1893 int newsize = 0; /* automatic sockbuf scaling */
1896 * This is a pure, in-sequence data packet with
1897 * nothing on the reassembly queue and we have enough
1898 * buffer space to take it.
1900 if (ti_locked == TI_RLOCKED)
1901 INP_INFO_RUNLOCK(&V_tcbinfo);
1902 ti_locked = TI_UNLOCKED;
1904 /* Clean receiver SACK report if present */
1905 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1906 tcp_clean_sackreport(tp);
1907 TCPSTAT_INC(tcps_preddat);
1908 tp->rcv_nxt += tlen;
1910 * Pull snd_wl1 up to prevent seq wrap relative to
1913 tp->snd_wl1 = th->th_seq;
1915 * Pull rcv_up up to prevent seq wrap relative to
1918 tp->rcv_up = tp->rcv_nxt;
1919 TCPSTAT_ADD(tcps_rcvpack, nsegs);
1920 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1922 if (so->so_options & SO_DEBUG)
1923 tcp_trace(TA_INPUT, ostate, tp,
1924 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1926 TCP_PROBE3(debug__input, tp, th, m);
1928 newsize = tcp_autorcvbuf(m, th, so, tp, tlen);
1930 /* Add data to socket buffer. */
1931 SOCKBUF_LOCK(&so->so_rcv);
1932 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1936 * Set new socket buffer size.
1937 * Give up when limit is reached.
1940 if (!sbreserve_locked(&so->so_rcv,
1942 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1943 m_adj(m, drop_hdrlen); /* delayed header drop */
1944 sbappendstream_locked(&so->so_rcv, m, 0);
1946 /* NB: sorwakeup_locked() does an implicit unlock. */
1947 sorwakeup_locked(so);
1948 if (DELAY_ACK(tp, tlen)) {
1949 tp->t_flags |= TF_DELACK;
1951 tp->t_flags |= TF_ACKNOW;
1952 tp->t_fb->tfb_tcp_output(tp);
1959 * Calculate amount of space in receive window,
1960 * and then do TCP input processing.
1961 * Receive window is amount of space in rcv queue,
1962 * but not less than advertised window.
1964 win = sbspace(&so->so_rcv);
1967 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1969 switch (tp->t_state) {
1972 * If the state is SYN_RECEIVED:
1973 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1975 case TCPS_SYN_RECEIVED:
1976 if ((thflags & TH_ACK) &&
1977 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1978 SEQ_GT(th->th_ack, tp->snd_max))) {
1979 rstreason = BANDLIM_RST_OPENPORT;
1982 if (IS_FASTOPEN(tp->t_flags)) {
1984 * When a TFO connection is in SYN_RECEIVED, the
1985 * only valid packets are the initial SYN, a
1986 * retransmit/copy of the initial SYN (possibly with
1987 * a subset of the original data), a valid ACK, a
1990 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
1991 rstreason = BANDLIM_RST_OPENPORT;
1993 } else if (thflags & TH_SYN) {
1994 /* non-initial SYN is ignored */
1995 if ((tcp_timer_active(tp, TT_DELACK) ||
1996 tcp_timer_active(tp, TT_REXMT)))
1998 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) {
2005 * If the state is SYN_SENT:
2006 * if seg contains a RST with valid ACK (SEQ.ACK has already
2007 * been verified), then drop the connection.
2008 * if seg contains a RST without an ACK, drop the seg.
2009 * if seg does not contain SYN, then drop the seg.
2010 * Otherwise this is an acceptable SYN segment
2011 * initialize tp->rcv_nxt and tp->irs
2012 * if seg contains ack then advance tp->snd_una
2013 * if seg contains an ECE and ECN support is enabled, the stream
2015 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
2016 * arrange for segment to be acked (eventually)
2017 * continue processing rest of data/controls, beginning with URG
2020 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
2021 TCP_PROBE5(connect__refused, NULL, tp,
2023 tp = tcp_drop(tp, ECONNREFUSED);
2025 if (thflags & TH_RST)
2027 if (!(thflags & TH_SYN))
2030 tp->irs = th->th_seq;
2032 if (thflags & TH_ACK) {
2033 int tfo_partial_ack = 0;
2035 TCPSTAT_INC(tcps_connects);
2038 mac_socketpeer_set_from_mbuf(m, so);
2040 /* Do window scaling on this connection? */
2041 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2042 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2043 tp->rcv_scale = tp->request_r_scale;
2045 tp->rcv_adv += min(tp->rcv_wnd,
2046 TCP_MAXWIN << tp->rcv_scale);
2047 tp->snd_una++; /* SYN is acked */
2049 * If not all the data that was sent in the TFO SYN
2050 * has been acked, resend the remainder right away.
2052 if (IS_FASTOPEN(tp->t_flags) &&
2053 (tp->snd_una != tp->snd_max)) {
2054 tp->snd_nxt = th->th_ack;
2055 tfo_partial_ack = 1;
2058 * If there's data, delay ACK; if there's also a FIN
2059 * ACKNOW will be turned on later.
2061 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack)
2062 tcp_timer_activate(tp, TT_DELACK,
2065 tp->t_flags |= TF_ACKNOW;
2067 if ((thflags & TH_ECE) && V_tcp_do_ecn) {
2068 tp->t_flags |= TF_ECN_PERMIT;
2069 TCPSTAT_INC(tcps_ecn_shs);
2073 * Received <SYN,ACK> in SYN_SENT[*] state.
2075 * SYN_SENT --> ESTABLISHED
2076 * SYN_SENT* --> FIN_WAIT_1
2078 tp->t_starttime = ticks;
2079 if (tp->t_flags & TF_NEEDFIN) {
2080 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2081 tp->t_flags &= ~TF_NEEDFIN;
2084 tcp_state_change(tp, TCPS_ESTABLISHED);
2085 TCP_PROBE5(connect__established, NULL, tp,
2088 tcp_timer_activate(tp, TT_KEEP,
2093 * Received initial SYN in SYN-SENT[*] state =>
2094 * simultaneous open.
2095 * If it succeeds, connection is * half-synchronized.
2096 * Otherwise, do 3-way handshake:
2097 * SYN-SENT -> SYN-RECEIVED
2098 * SYN-SENT* -> SYN-RECEIVED*
2100 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
2101 tcp_timer_activate(tp, TT_REXMT, 0);
2102 tcp_state_change(tp, TCPS_SYN_RECEIVED);
2105 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: "
2106 "ti_locked %d", __func__, ti_locked));
2107 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2108 INP_WLOCK_ASSERT(tp->t_inpcb);
2111 * Advance th->th_seq to correspond to first data byte.
2112 * If data, trim to stay within window,
2113 * dropping FIN if necessary.
2116 if (tlen > tp->rcv_wnd) {
2117 todrop = tlen - tp->rcv_wnd;
2121 TCPSTAT_INC(tcps_rcvpackafterwin);
2122 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2124 tp->snd_wl1 = th->th_seq - 1;
2125 tp->rcv_up = th->th_seq;
2127 * Client side of transaction: already sent SYN and data.
2128 * If the remote host used T/TCP to validate the SYN,
2129 * our data will be ACK'd; if so, enter normal data segment
2130 * processing in the middle of step 5, ack processing.
2131 * Otherwise, goto step 6.
2133 if (thflags & TH_ACK)
2139 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2140 * do normal processing.
2142 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2146 break; /* continue normal processing */
2150 * States other than LISTEN or SYN_SENT.
2151 * First check the RST flag and sequence number since reset segments
2152 * are exempt from the timestamp and connection count tests. This
2153 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2154 * below which allowed reset segments in half the sequence space
2155 * to fall though and be processed (which gives forged reset
2156 * segments with a random sequence number a 50 percent chance of
2157 * killing a connection).
2158 * Then check timestamp, if present.
2159 * Then check the connection count, if present.
2160 * Then check that at least some bytes of segment are within
2161 * receive window. If segment begins before rcv_nxt,
2162 * drop leading data (and SYN); if nothing left, just ack.
2164 if (thflags & TH_RST) {
2166 * RFC5961 Section 3.2
2168 * - RST drops connection only if SEG.SEQ == RCV.NXT.
2169 * - If RST is in window, we send challenge ACK.
2171 * Note: to take into account delayed ACKs, we should
2172 * test against last_ack_sent instead of rcv_nxt.
2173 * Note 2: we handle special case of closed window, not
2174 * covered by the RFC.
2176 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2177 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
2178 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
2180 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2181 KASSERT(ti_locked == TI_RLOCKED,
2182 ("%s: TH_RST ti_locked %d, th %p tp %p",
2183 __func__, ti_locked, th, tp));
2184 KASSERT(tp->t_state != TCPS_SYN_SENT,
2185 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
2188 if (V_tcp_insecure_rst ||
2189 tp->last_ack_sent == th->th_seq) {
2190 TCPSTAT_INC(tcps_drops);
2191 /* Drop the connection. */
2192 switch (tp->t_state) {
2193 case TCPS_SYN_RECEIVED:
2194 so->so_error = ECONNREFUSED;
2196 case TCPS_ESTABLISHED:
2197 case TCPS_FIN_WAIT_1:
2198 case TCPS_FIN_WAIT_2:
2199 case TCPS_CLOSE_WAIT:
2202 so->so_error = ECONNRESET;
2209 TCPSTAT_INC(tcps_badrst);
2210 /* Send challenge ACK. */
2211 tcp_respond(tp, mtod(m, void *), th, m,
2212 tp->rcv_nxt, tp->snd_nxt, TH_ACK);
2213 tp->last_ack_sent = tp->rcv_nxt;
2221 * RFC5961 Section 4.2
2222 * Send challenge ACK for any SYN in synchronized state.
2224 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT &&
2225 tp->t_state != TCPS_SYN_RECEIVED) {
2226 KASSERT(ti_locked == TI_RLOCKED,
2227 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2228 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2230 TCPSTAT_INC(tcps_badsyn);
2231 if (V_tcp_insecure_syn &&
2232 SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2233 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2234 tp = tcp_drop(tp, ECONNRESET);
2235 rstreason = BANDLIM_UNLIMITED;
2237 /* Send challenge ACK. */
2238 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
2239 tp->snd_nxt, TH_ACK);
2240 tp->last_ack_sent = tp->rcv_nxt;
2247 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2248 * and it's less than ts_recent, drop it.
2250 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2251 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2253 /* Check to see if ts_recent is over 24 days old. */
2254 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2256 * Invalidate ts_recent. If this segment updates
2257 * ts_recent, the age will be reset later and ts_recent
2258 * will get a valid value. If it does not, setting
2259 * ts_recent to zero will at least satisfy the
2260 * requirement that zero be placed in the timestamp
2261 * echo reply when ts_recent isn't valid. The
2262 * age isn't reset until we get a valid ts_recent
2263 * because we don't want out-of-order segments to be
2264 * dropped when ts_recent is old.
2268 TCPSTAT_INC(tcps_rcvduppack);
2269 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2270 TCPSTAT_INC(tcps_pawsdrop);
2278 * In the SYN-RECEIVED state, validate that the packet belongs to
2279 * this connection before trimming the data to fit the receive
2280 * window. Check the sequence number versus IRS since we know
2281 * the sequence numbers haven't wrapped. This is a partial fix
2282 * for the "LAND" DoS attack.
2284 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2285 rstreason = BANDLIM_RST_OPENPORT;
2289 todrop = tp->rcv_nxt - th->th_seq;
2291 if (thflags & TH_SYN) {
2301 * Following if statement from Stevens, vol. 2, p. 960.
2304 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2306 * Any valid FIN must be to the left of the window.
2307 * At this point the FIN must be a duplicate or out
2308 * of sequence; drop it.
2313 * Send an ACK to resynchronize and drop any data.
2314 * But keep on processing for RST or ACK.
2316 tp->t_flags |= TF_ACKNOW;
2318 TCPSTAT_INC(tcps_rcvduppack);
2319 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2321 TCPSTAT_INC(tcps_rcvpartduppack);
2322 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2324 drop_hdrlen += todrop; /* drop from the top afterwards */
2325 th->th_seq += todrop;
2327 if (th->th_urp > todrop)
2328 th->th_urp -= todrop;
2336 * If new data are received on a connection after the
2337 * user processes are gone, then RST the other end.
2339 if ((so->so_state & SS_NOFDREF) &&
2340 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2341 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && "
2342 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2343 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2345 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2346 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2347 "after socket was closed, "
2348 "sending RST and removing tcpcb\n",
2349 s, __func__, tcpstates[tp->t_state], tlen);
2353 TCPSTAT_INC(tcps_rcvafterclose);
2354 rstreason = BANDLIM_UNLIMITED;
2359 * If segment ends after window, drop trailing data
2360 * (and PUSH and FIN); if nothing left, just ACK.
2362 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2364 TCPSTAT_INC(tcps_rcvpackafterwin);
2365 if (todrop >= tlen) {
2366 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2368 * If window is closed can only take segments at
2369 * window edge, and have to drop data and PUSH from
2370 * incoming segments. Continue processing, but
2371 * remember to ack. Otherwise, drop segment
2374 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2375 tp->t_flags |= TF_ACKNOW;
2376 TCPSTAT_INC(tcps_rcvwinprobe);
2380 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2383 thflags &= ~(TH_PUSH|TH_FIN);
2387 * If last ACK falls within this segment's sequence numbers,
2388 * record its timestamp.
2390 * 1) That the test incorporates suggestions from the latest
2391 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2392 * 2) That updating only on newer timestamps interferes with
2393 * our earlier PAWS tests, so this check should be solely
2394 * predicated on the sequence space of this segment.
2395 * 3) That we modify the segment boundary check to be
2396 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2397 * instead of RFC1323's
2398 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2399 * This modified check allows us to overcome RFC1323's
2400 * limitations as described in Stevens TCP/IP Illustrated
2401 * Vol. 2 p.869. In such cases, we can still calculate the
2402 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2404 if ((to.to_flags & TOF_TS) != 0 &&
2405 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2406 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2407 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2408 tp->ts_recent_age = tcp_ts_getticks();
2409 tp->ts_recent = to.to_tsval;
2413 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2414 * flag is on (half-synchronized state), then queue data for
2415 * later processing; else drop segment and return.
2417 if ((thflags & TH_ACK) == 0) {
2418 if (tp->t_state == TCPS_SYN_RECEIVED ||
2419 (tp->t_flags & TF_NEEDSYN)) {
2420 if (tp->t_state == TCPS_SYN_RECEIVED &&
2421 IS_FASTOPEN(tp->t_flags)) {
2422 tp->snd_wnd = tiwin;
2426 } else if (tp->t_flags & TF_ACKNOW)
2435 switch (tp->t_state) {
2438 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2439 * ESTABLISHED state and continue processing.
2440 * The ACK was checked above.
2442 case TCPS_SYN_RECEIVED:
2444 TCPSTAT_INC(tcps_connects);
2446 /* Do window scaling? */
2447 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2448 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2449 tp->rcv_scale = tp->request_r_scale;
2450 tp->snd_wnd = tiwin;
2454 * SYN-RECEIVED -> ESTABLISHED
2455 * SYN-RECEIVED* -> FIN-WAIT-1
2457 tp->t_starttime = ticks;
2458 if (tp->t_flags & TF_NEEDFIN) {
2459 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2460 tp->t_flags &= ~TF_NEEDFIN;
2462 tcp_state_change(tp, TCPS_ESTABLISHED);
2463 TCP_PROBE5(accept__established, NULL, tp,
2465 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
2466 tcp_fastopen_decrement_counter(tp->t_tfo_pending);
2467 tp->t_tfo_pending = NULL;
2470 * Account for the ACK of our SYN prior to
2471 * regular ACK processing below.
2476 * TFO connections call cc_conn_init() during SYN
2477 * processing. Calling it again here for such
2478 * connections is not harmless as it would undo the
2479 * snd_cwnd reduction that occurs when a TFO SYN|ACK
2482 if (!IS_FASTOPEN(tp->t_flags))
2484 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2487 * If segment contains data or ACK, will call tcp_reass()
2488 * later; if not, do so now to pass queued data to user.
2490 if (tlen == 0 && (thflags & TH_FIN) == 0)
2491 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2493 tp->snd_wl1 = th->th_seq - 1;
2497 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2498 * ACKs. If the ack is in the range
2499 * tp->snd_una < th->th_ack <= tp->snd_max
2500 * then advance tp->snd_una to th->th_ack and drop
2501 * data from the retransmission queue. If this ACK reflects
2502 * more up to date window information we update our window information.
2504 case TCPS_ESTABLISHED:
2505 case TCPS_FIN_WAIT_1:
2506 case TCPS_FIN_WAIT_2:
2507 case TCPS_CLOSE_WAIT:
2510 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2511 TCPSTAT_INC(tcps_rcvacktoomuch);
2514 if ((tp->t_flags & TF_SACK_PERMIT) &&
2515 ((to.to_flags & TOF_SACK) ||
2516 !TAILQ_EMPTY(&tp->snd_holes)))
2517 sack_changed = tcp_sack_doack(tp, &to, th->th_ack);
2520 * Reset the value so that previous (valid) value
2521 * from the last ack with SACK doesn't get used.
2523 tp->sackhint.sacked_bytes = 0;
2526 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2527 hhook_run_tcp_est_in(tp, th, &to);
2530 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2533 maxseg = tcp_maxseg(tp);
2535 (tiwin == tp->snd_wnd ||
2536 (tp->t_flags & TF_SACK_PERMIT))) {
2538 * If this is the first time we've seen a
2539 * FIN from the remote, this is not a
2540 * duplicate and it needs to be processed
2541 * normally. This happens during a
2542 * simultaneous close.
2544 if ((thflags & TH_FIN) &&
2545 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2549 TCPSTAT_INC(tcps_rcvdupack);
2551 * If we have outstanding data (other than
2552 * a window probe), this is a completely
2553 * duplicate ack (ie, window info didn't
2554 * change and FIN isn't set),
2555 * the ack is the biggest we've
2556 * seen and we've seen exactly our rexmt
2557 * threshold of them, assume a packet
2558 * has been dropped and retransmit it.
2559 * Kludge snd_nxt & the congestion
2560 * window so we send only this one
2563 * We know we're losing at the current
2564 * window size so do congestion avoidance
2565 * (set ssthresh to half the current window
2566 * and pull our congestion window back to
2567 * the new ssthresh).
2569 * Dup acks mean that packets have left the
2570 * network (they're now cached at the receiver)
2571 * so bump cwnd by the amount in the receiver
2572 * to keep a constant cwnd packets in the
2575 * When using TCP ECN, notify the peer that
2576 * we reduced the cwnd.
2579 * Following 2 kinds of acks should not affect
2582 * 2) Acks with SACK but without any new SACK
2583 * information in them. These could result from
2584 * any anomaly in the network like a switch
2585 * duplicating packets or a possible DoS attack.
2587 if (th->th_ack != tp->snd_una ||
2588 ((tp->t_flags & TF_SACK_PERMIT) &&
2591 else if (!tcp_timer_active(tp, TT_REXMT))
2593 else if (++tp->t_dupacks > tcprexmtthresh ||
2594 IN_FASTRECOVERY(tp->t_flags)) {
2595 cc_ack_received(tp, th, nsegs,
2597 if ((tp->t_flags & TF_SACK_PERMIT) &&
2598 IN_FASTRECOVERY(tp->t_flags)) {
2602 * Compute the amount of data in flight first.
2603 * We can inject new data into the pipe iff
2604 * we have less than 1/2 the original window's
2605 * worth of data in flight.
2607 if (V_tcp_do_rfc6675_pipe)
2608 awnd = tcp_compute_pipe(tp);
2610 awnd = (tp->snd_nxt - tp->snd_fack) +
2611 tp->sackhint.sack_bytes_rexmit;
2613 if (awnd < tp->snd_ssthresh) {
2614 tp->snd_cwnd += maxseg;
2615 if (tp->snd_cwnd > tp->snd_ssthresh)
2616 tp->snd_cwnd = tp->snd_ssthresh;
2619 tp->snd_cwnd += maxseg;
2620 (void) tp->t_fb->tfb_tcp_output(tp);
2622 } else if (tp->t_dupacks == tcprexmtthresh) {
2623 tcp_seq onxt = tp->snd_nxt;
2626 * If we're doing sack, check to
2627 * see if we're already in sack
2628 * recovery. If we're not doing sack,
2629 * check to see if we're in newreno
2632 if (tp->t_flags & TF_SACK_PERMIT) {
2633 if (IN_FASTRECOVERY(tp->t_flags)) {
2638 if (SEQ_LEQ(th->th_ack,
2644 /* Congestion signal before ack. */
2645 cc_cong_signal(tp, th, CC_NDUPACK);
2646 cc_ack_received(tp, th, nsegs,
2648 tcp_timer_activate(tp, TT_REXMT, 0);
2650 if (tp->t_flags & TF_SACK_PERMIT) {
2652 tcps_sack_recovery_episode);
2653 tp->sack_newdata = tp->snd_nxt;
2654 tp->snd_cwnd = maxseg;
2655 (void) tp->t_fb->tfb_tcp_output(tp);
2658 tp->snd_nxt = th->th_ack;
2659 tp->snd_cwnd = maxseg;
2660 (void) tp->t_fb->tfb_tcp_output(tp);
2661 KASSERT(tp->snd_limited <= 2,
2662 ("%s: tp->snd_limited too big",
2664 tp->snd_cwnd = tp->snd_ssthresh +
2666 (tp->t_dupacks - tp->snd_limited);
2667 if (SEQ_GT(onxt, tp->snd_nxt))
2670 } else if (V_tcp_do_rfc3042) {
2672 * Process first and second duplicate
2673 * ACKs. Each indicates a segment
2674 * leaving the network, creating room
2675 * for more. Make sure we can send a
2676 * packet on reception of each duplicate
2677 * ACK by increasing snd_cwnd by one
2678 * segment. Restore the original
2679 * snd_cwnd after packet transmission.
2681 cc_ack_received(tp, th, nsegs,
2683 uint32_t oldcwnd = tp->snd_cwnd;
2684 tcp_seq oldsndmax = tp->snd_max;
2688 KASSERT(tp->t_dupacks == 1 ||
2690 ("%s: dupacks not 1 or 2",
2692 if (tp->t_dupacks == 1)
2693 tp->snd_limited = 0;
2695 (tp->snd_nxt - tp->snd_una) +
2696 (tp->t_dupacks - tp->snd_limited) *
2699 * Only call tcp_output when there
2700 * is new data available to be sent.
2701 * Otherwise we would send pure ACKs.
2703 SOCKBUF_LOCK(&so->so_snd);
2704 avail = sbavail(&so->so_snd) -
2705 (tp->snd_nxt - tp->snd_una);
2706 SOCKBUF_UNLOCK(&so->so_snd);
2708 (void) tp->t_fb->tfb_tcp_output(tp);
2709 sent = tp->snd_max - oldsndmax;
2710 if (sent > maxseg) {
2711 KASSERT((tp->t_dupacks == 2 &&
2712 tp->snd_limited == 0) ||
2713 (sent == maxseg + 1 &&
2714 tp->t_flags & TF_SENTFIN),
2715 ("%s: sent too much",
2717 tp->snd_limited = 2;
2718 } else if (sent > 0)
2720 tp->snd_cwnd = oldcwnd;
2727 * This ack is advancing the left edge, reset the
2732 * If this ack also has new SACK info, increment the
2733 * counter as per rfc6675.
2735 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed)
2739 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2740 ("%s: th_ack <= snd_una", __func__));
2743 * If the congestion window was inflated to account
2744 * for the other side's cached packets, retract it.
2746 if (IN_FASTRECOVERY(tp->t_flags)) {
2747 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2748 if (tp->t_flags & TF_SACK_PERMIT)
2749 tcp_sack_partialack(tp, th);
2751 tcp_newreno_partial_ack(tp, th);
2753 cc_post_recovery(tp, th);
2756 * If we reach this point, ACK is not a duplicate,
2757 * i.e., it ACKs something we sent.
2759 if (tp->t_flags & TF_NEEDSYN) {
2761 * T/TCP: Connection was half-synchronized, and our
2762 * SYN has been ACK'd (so connection is now fully
2763 * synchronized). Go to non-starred state,
2764 * increment snd_una for ACK of SYN, and check if
2765 * we can do window scaling.
2767 tp->t_flags &= ~TF_NEEDSYN;
2769 /* Do window scaling? */
2770 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2771 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2772 tp->rcv_scale = tp->request_r_scale;
2773 /* Send window already scaled. */
2778 INP_WLOCK_ASSERT(tp->t_inpcb);
2780 acked = BYTES_THIS_ACK(tp, th);
2781 KASSERT(acked >= 0, ("%s: acked unexepectedly negative "
2782 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__,
2783 tp->snd_una, th->th_ack, tp, m));
2784 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
2785 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2788 * If we just performed our first retransmit, and the ACK
2789 * arrives within our recovery window, then it was a mistake
2790 * to do the retransmit in the first place. Recover our
2791 * original cwnd and ssthresh, and proceed to transmit where
2794 if (tp->t_rxtshift == 1 &&
2795 tp->t_flags & TF_PREVVALID &&
2797 SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
2798 cc_cong_signal(tp, th, CC_RTO_ERR);
2801 * If we have a timestamp reply, update smoothed
2802 * round trip time. If no timestamp is present but
2803 * transmit timer is running and timed sequence
2804 * number was acked, update smoothed round trip time.
2805 * Since we now have an rtt measurement, cancel the
2806 * timer backoff (cf., Phil Karn's retransmit alg.).
2807 * Recompute the initial retransmit timer.
2809 * Some boxes send broken timestamp replies
2810 * during the SYN+ACK phase, ignore
2811 * timestamps of 0 or we could calculate a
2812 * huge RTT and blow up the retransmit timer.
2814 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2817 t = tcp_ts_getticks() - to.to_tsecr;
2818 if (!tp->t_rttlow || tp->t_rttlow > t)
2820 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2821 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2822 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2823 tp->t_rttlow = ticks - tp->t_rtttime;
2824 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2828 * If all outstanding data is acked, stop retransmit
2829 * timer and remember to restart (more output or persist).
2830 * If there is more data to be acked, restart retransmit
2831 * timer, using current (possibly backed-off) value.
2833 if (th->th_ack == tp->snd_max) {
2834 tcp_timer_activate(tp, TT_REXMT, 0);
2836 } else if (!tcp_timer_active(tp, TT_PERSIST))
2837 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2840 * If no data (only SYN) was ACK'd,
2841 * skip rest of ACK processing.
2847 * Let the congestion control algorithm update congestion
2848 * control related information. This typically means increasing
2849 * the congestion window.
2851 cc_ack_received(tp, th, nsegs, CC_ACK);
2853 SOCKBUF_LOCK(&so->so_snd);
2854 if (acked > sbavail(&so->so_snd)) {
2855 if (tp->snd_wnd >= sbavail(&so->so_snd))
2856 tp->snd_wnd -= sbavail(&so->so_snd);
2859 mfree = sbcut_locked(&so->so_snd,
2860 (int)sbavail(&so->so_snd));
2863 mfree = sbcut_locked(&so->so_snd, acked);
2864 if (tp->snd_wnd >= (uint32_t) acked)
2865 tp->snd_wnd -= acked;
2870 /* NB: sowwakeup_locked() does an implicit unlock. */
2871 sowwakeup_locked(so);
2873 /* Detect una wraparound. */
2874 if (!IN_RECOVERY(tp->t_flags) &&
2875 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2876 SEQ_LEQ(th->th_ack, tp->snd_recover))
2877 tp->snd_recover = th->th_ack - 1;
2878 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2879 if (IN_RECOVERY(tp->t_flags) &&
2880 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2881 EXIT_RECOVERY(tp->t_flags);
2883 tp->snd_una = th->th_ack;
2884 if (tp->t_flags & TF_SACK_PERMIT) {
2885 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2886 tp->snd_recover = tp->snd_una;
2888 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2889 tp->snd_nxt = tp->snd_una;
2891 switch (tp->t_state) {
2894 * In FIN_WAIT_1 STATE in addition to the processing
2895 * for the ESTABLISHED state if our FIN is now acknowledged
2896 * then enter FIN_WAIT_2.
2898 case TCPS_FIN_WAIT_1:
2899 if (ourfinisacked) {
2901 * If we can't receive any more
2902 * data, then closing user can proceed.
2903 * Starting the timer is contrary to the
2904 * specification, but if we don't get a FIN
2905 * we'll hang forever.
2908 * we should release the tp also, and use a
2911 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2912 soisdisconnected(so);
2913 tcp_timer_activate(tp, TT_2MSL,
2914 (tcp_fast_finwait2_recycle ?
2915 tcp_finwait2_timeout :
2918 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2923 * In CLOSING STATE in addition to the processing for
2924 * the ESTABLISHED state if the ACK acknowledges our FIN
2925 * then enter the TIME-WAIT state, otherwise ignore
2929 if (ourfinisacked) {
2930 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2932 INP_INFO_RUNLOCK(&V_tcbinfo);
2939 * In LAST_ACK, we may still be waiting for data to drain
2940 * and/or to be acked, as well as for the ack of our FIN.
2941 * If our FIN is now acknowledged, delete the TCB,
2942 * enter the closed state and return.
2945 if (ourfinisacked) {
2946 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2955 INP_WLOCK_ASSERT(tp->t_inpcb);
2958 * Update window information.
2959 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2961 if ((thflags & TH_ACK) &&
2962 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2963 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2964 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2965 /* keep track of pure window updates */
2967 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2968 TCPSTAT_INC(tcps_rcvwinupd);
2969 tp->snd_wnd = tiwin;
2970 tp->snd_wl1 = th->th_seq;
2971 tp->snd_wl2 = th->th_ack;
2972 if (tp->snd_wnd > tp->max_sndwnd)
2973 tp->max_sndwnd = tp->snd_wnd;
2978 * Process segments with URG.
2980 if ((thflags & TH_URG) && th->th_urp &&
2981 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2983 * This is a kludge, but if we receive and accept
2984 * random urgent pointers, we'll crash in
2985 * soreceive. It's hard to imagine someone
2986 * actually wanting to send this much urgent data.
2988 SOCKBUF_LOCK(&so->so_rcv);
2989 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
2990 th->th_urp = 0; /* XXX */
2991 thflags &= ~TH_URG; /* XXX */
2992 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2993 goto dodata; /* XXX */
2996 * If this segment advances the known urgent pointer,
2997 * then mark the data stream. This should not happen
2998 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2999 * a FIN has been received from the remote side.
3000 * In these states we ignore the URG.
3002 * According to RFC961 (Assigned Protocols),
3003 * the urgent pointer points to the last octet
3004 * of urgent data. We continue, however,
3005 * to consider it to indicate the first octet
3006 * of data past the urgent section as the original
3007 * spec states (in one of two places).
3009 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
3010 tp->rcv_up = th->th_seq + th->th_urp;
3011 so->so_oobmark = sbavail(&so->so_rcv) +
3012 (tp->rcv_up - tp->rcv_nxt) - 1;
3013 if (so->so_oobmark == 0)
3014 so->so_rcv.sb_state |= SBS_RCVATMARK;
3016 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
3018 SOCKBUF_UNLOCK(&so->so_rcv);
3020 * Remove out of band data so doesn't get presented to user.
3021 * This can happen independent of advancing the URG pointer,
3022 * but if two URG's are pending at once, some out-of-band
3023 * data may creep in... ick.
3025 if (th->th_urp <= (uint32_t)tlen &&
3026 !(so->so_options & SO_OOBINLINE)) {
3027 /* hdr drop is delayed */
3028 tcp_pulloutofband(so, th, m, drop_hdrlen);
3032 * If no out of band data is expected,
3033 * pull receive urgent pointer along
3034 * with the receive window.
3036 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
3037 tp->rcv_up = tp->rcv_nxt;
3040 INP_WLOCK_ASSERT(tp->t_inpcb);
3043 * Process the segment text, merging it into the TCP sequencing queue,
3044 * and arranging for acknowledgment of receipt if necessary.
3045 * This process logically involves adjusting tp->rcv_wnd as data
3046 * is presented to the user (this happens in tcp_usrreq.c,
3047 * case PRU_RCVD). If a FIN has already been received on this
3048 * connection then we just ignore the text.
3050 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
3051 IS_FASTOPEN(tp->t_flags));
3052 if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
3053 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
3054 tcp_seq save_start = th->th_seq;
3055 m_adj(m, drop_hdrlen); /* delayed header drop */
3057 * Insert segment which includes th into TCP reassembly queue
3058 * with control block tp. Set thflags to whether reassembly now
3059 * includes a segment with FIN. This handles the common case
3060 * inline (segment is the next to be received on an established
3061 * connection, and the queue is empty), avoiding linkage into
3062 * and removal from the queue and repetition of various
3064 * Set DELACK for segments received in order, but ack
3065 * immediately when segments are out of order (so
3066 * fast retransmit can work).
3068 if (th->th_seq == tp->rcv_nxt &&
3069 LIST_EMPTY(&tp->t_segq) &&
3070 (TCPS_HAVEESTABLISHED(tp->t_state) ||
3072 if (DELAY_ACK(tp, tlen) || tfo_syn)
3073 tp->t_flags |= TF_DELACK;
3075 tp->t_flags |= TF_ACKNOW;
3076 tp->rcv_nxt += tlen;
3077 thflags = th->th_flags & TH_FIN;
3078 TCPSTAT_INC(tcps_rcvpack);
3079 TCPSTAT_ADD(tcps_rcvbyte, tlen);
3080 SOCKBUF_LOCK(&so->so_rcv);
3081 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
3084 sbappendstream_locked(&so->so_rcv, m, 0);
3085 /* NB: sorwakeup_locked() does an implicit unlock. */
3086 sorwakeup_locked(so);
3089 * XXX: Due to the header drop above "th" is
3090 * theoretically invalid by now. Fortunately
3091 * m_adj() doesn't actually frees any mbufs
3092 * when trimming from the head.
3094 thflags = tcp_reass(tp, th, &tlen, m);
3095 tp->t_flags |= TF_ACKNOW;
3097 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
3098 tcp_update_sack_list(tp, save_start, save_start + tlen);
3101 * Note the amount of data that peer has sent into
3102 * our window, in order to estimate the sender's
3106 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
3107 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
3109 len = so->so_rcv.sb_hiwat;
3117 * If FIN is received ACK the FIN and let the user know
3118 * that the connection is closing.
3120 if (thflags & TH_FIN) {
3121 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
3124 * If connection is half-synchronized
3125 * (ie NEEDSYN flag on) then delay ACK,
3126 * so it may be piggybacked when SYN is sent.
3127 * Otherwise, since we received a FIN then no
3128 * more input can be expected, send ACK now.
3130 if (tp->t_flags & TF_NEEDSYN)
3131 tp->t_flags |= TF_DELACK;
3133 tp->t_flags |= TF_ACKNOW;
3136 switch (tp->t_state) {
3139 * In SYN_RECEIVED and ESTABLISHED STATES
3140 * enter the CLOSE_WAIT state.
3142 case TCPS_SYN_RECEIVED:
3143 tp->t_starttime = ticks;
3145 case TCPS_ESTABLISHED:
3146 tcp_state_change(tp, TCPS_CLOSE_WAIT);
3150 * If still in FIN_WAIT_1 STATE FIN has not been acked so
3151 * enter the CLOSING state.
3153 case TCPS_FIN_WAIT_1:
3154 tcp_state_change(tp, TCPS_CLOSING);
3158 * In FIN_WAIT_2 state enter the TIME_WAIT state,
3159 * starting the time-wait timer, turning off the other
3162 case TCPS_FIN_WAIT_2:
3163 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
3164 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata "
3165 "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
3169 INP_INFO_RUNLOCK(&V_tcbinfo);
3173 if (ti_locked == TI_RLOCKED)
3174 INP_INFO_RUNLOCK(&V_tcbinfo);
3175 ti_locked = TI_UNLOCKED;
3178 if (so->so_options & SO_DEBUG)
3179 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3182 TCP_PROBE3(debug__input, tp, th, m);
3185 * Return any desired output.
3187 if (needoutput || (tp->t_flags & TF_ACKNOW))
3188 (void) tp->t_fb->tfb_tcp_output(tp);
3191 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3192 __func__, ti_locked));
3193 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3194 INP_WLOCK_ASSERT(tp->t_inpcb);
3196 if (tp->t_flags & TF_DELACK) {
3197 tp->t_flags &= ~TF_DELACK;
3198 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3200 INP_WUNLOCK(tp->t_inpcb);
3205 * Generate an ACK dropping incoming segment if it occupies
3206 * sequence space, where the ACK reflects our state.
3208 * We can now skip the test for the RST flag since all
3209 * paths to this code happen after packets containing
3210 * RST have been dropped.
3212 * In the SYN-RECEIVED state, don't send an ACK unless the
3213 * segment we received passes the SYN-RECEIVED ACK test.
3214 * If it fails send a RST. This breaks the loop in the
3215 * "LAND" DoS attack, and also prevents an ACK storm
3216 * between two listening ports that have been sent forged
3217 * SYN segments, each with the source address of the other.
3219 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3220 (SEQ_GT(tp->snd_una, th->th_ack) ||
3221 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3222 rstreason = BANDLIM_RST_OPENPORT;
3226 if (so->so_options & SO_DEBUG)
3227 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3230 TCP_PROBE3(debug__input, tp, th, m);
3231 if (ti_locked == TI_RLOCKED)
3232 INP_INFO_RUNLOCK(&V_tcbinfo);
3233 ti_locked = TI_UNLOCKED;
3235 tp->t_flags |= TF_ACKNOW;
3236 (void) tp->t_fb->tfb_tcp_output(tp);
3237 INP_WUNLOCK(tp->t_inpcb);
3242 if (ti_locked == TI_RLOCKED)
3243 INP_INFO_RUNLOCK(&V_tcbinfo);
3244 ti_locked = TI_UNLOCKED;
3247 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3248 INP_WUNLOCK(tp->t_inpcb);
3250 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3254 if (ti_locked == TI_RLOCKED) {
3255 INP_INFO_RUNLOCK(&V_tcbinfo);
3256 ti_locked = TI_UNLOCKED;
3260 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3264 * Drop space held by incoming segment and return.
3267 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3268 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3271 TCP_PROBE3(debug__input, tp, th, m);
3273 INP_WUNLOCK(tp->t_inpcb);
3278 * Issue RST and make ACK acceptable to originator of segment.
3279 * The mbuf must still include the original packet header.
3283 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3284 int tlen, int rstreason)
3290 struct ip6_hdr *ip6;
3294 INP_WLOCK_ASSERT(tp->t_inpcb);
3297 /* Don't bother if destination was broadcast/multicast. */
3298 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3301 if (mtod(m, struct ip *)->ip_v == 6) {
3302 ip6 = mtod(m, struct ip6_hdr *);
3303 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3304 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3306 /* IPv6 anycast check is done at tcp6_input() */
3309 #if defined(INET) && defined(INET6)
3314 ip = mtod(m, struct ip *);
3315 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3316 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3317 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3318 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3323 /* Perform bandwidth limiting. */
3324 if (badport_bandlim(rstreason) < 0)
3327 /* tcp_respond consumes the mbuf chain. */
3328 if (th->th_flags & TH_ACK) {
3329 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3330 th->th_ack, TH_RST);
3332 if (th->th_flags & TH_SYN)
3334 if (th->th_flags & TH_FIN)
3336 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3337 (tcp_seq)0, TH_RST|TH_ACK);
3345 * Parse TCP options and place in tcpopt.
3348 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3353 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3355 if (opt == TCPOPT_EOL)
3357 if (opt == TCPOPT_NOP)
3363 if (optlen < 2 || optlen > cnt)
3368 if (optlen != TCPOLEN_MAXSEG)
3370 if (!(flags & TO_SYN))
3372 to->to_flags |= TOF_MSS;
3373 bcopy((char *)cp + 2,
3374 (char *)&to->to_mss, sizeof(to->to_mss));
3375 to->to_mss = ntohs(to->to_mss);
3378 if (optlen != TCPOLEN_WINDOW)
3380 if (!(flags & TO_SYN))
3382 to->to_flags |= TOF_SCALE;
3383 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3385 case TCPOPT_TIMESTAMP:
3386 if (optlen != TCPOLEN_TIMESTAMP)
3388 to->to_flags |= TOF_TS;
3389 bcopy((char *)cp + 2,
3390 (char *)&to->to_tsval, sizeof(to->to_tsval));
3391 to->to_tsval = ntohl(to->to_tsval);
3392 bcopy((char *)cp + 6,
3393 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3394 to->to_tsecr = ntohl(to->to_tsecr);
3396 case TCPOPT_SIGNATURE:
3398 * In order to reply to a host which has set the
3399 * TCP_SIGNATURE option in its initial SYN, we have
3400 * to record the fact that the option was observed
3401 * here for the syncache code to perform the correct
3404 if (optlen != TCPOLEN_SIGNATURE)
3406 to->to_flags |= TOF_SIGNATURE;
3407 to->to_signature = cp + 2;
3409 case TCPOPT_SACK_PERMITTED:
3410 if (optlen != TCPOLEN_SACK_PERMITTED)
3412 if (!(flags & TO_SYN))
3416 to->to_flags |= TOF_SACKPERM;
3419 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3423 to->to_flags |= TOF_SACK;
3424 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3425 to->to_sacks = cp + 2;
3426 TCPSTAT_INC(tcps_sack_rcv_blocks);
3428 case TCPOPT_FAST_OPEN:
3430 * Cookie length validation is performed by the
3431 * server side cookie checking code or the client
3432 * side cookie cache update code.
3434 if (!(flags & TO_SYN))
3436 if (!V_tcp_fastopen_client_enable &&
3437 !V_tcp_fastopen_server_enable)
3439 to->to_flags |= TOF_FASTOPEN;
3440 to->to_tfo_len = optlen - 2;
3441 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL;
3450 * Pull out of band byte out of a segment so
3451 * it doesn't appear in the user's data queue.
3452 * It is still reflected in the segment length for
3453 * sequencing purposes.
3456 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3459 int cnt = off + th->th_urp - 1;
3462 if (m->m_len > cnt) {
3463 char *cp = mtod(m, caddr_t) + cnt;
3464 struct tcpcb *tp = sototcpcb(so);
3466 INP_WLOCK_ASSERT(tp->t_inpcb);
3469 tp->t_oobflags |= TCPOOB_HAVEDATA;
3470 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3472 if (m->m_flags & M_PKTHDR)
3481 panic("tcp_pulloutofband");
3485 * Collect new round-trip time estimate
3486 * and update averages and current timeout.
3489 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3493 INP_WLOCK_ASSERT(tp->t_inpcb);
3495 TCPSTAT_INC(tcps_rttupdated);
3497 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) {
3499 * srtt is stored as fixed point with 5 bits after the
3500 * binary point (i.e., scaled by 8). The following magic
3501 * is equivalent to the smoothing algorithm in rfc793 with
3502 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3503 * point). Adjust rtt to origin 0.
3505 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3506 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3508 if ((tp->t_srtt += delta) <= 0)
3512 * We accumulate a smoothed rtt variance (actually, a
3513 * smoothed mean difference), then set the retransmit
3514 * timer to smoothed rtt + 4 times the smoothed variance.
3515 * rttvar is stored as fixed point with 4 bits after the
3516 * binary point (scaled by 16). The following is
3517 * equivalent to rfc793 smoothing with an alpha of .75
3518 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3519 * rfc793's wired-in beta.
3523 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3524 if ((tp->t_rttvar += delta) <= 0)
3526 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3527 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3530 * No rtt measurement yet - use the unsmoothed rtt.
3531 * Set the variance to half the rtt (so our first
3532 * retransmit happens at 3*rtt).
3534 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3535 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3536 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3542 * the retransmit should happen at rtt + 4 * rttvar.
3543 * Because of the way we do the smoothing, srtt and rttvar
3544 * will each average +1/2 tick of bias. When we compute
3545 * the retransmit timer, we want 1/2 tick of rounding and
3546 * 1 extra tick because of +-1/2 tick uncertainty in the
3547 * firing of the timer. The bias will give us exactly the
3548 * 1.5 tick we need. But, because the bias is
3549 * statistical, we have to test that we don't drop below
3550 * the minimum feasible timer (which is 2 ticks).
3552 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3553 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3556 * We received an ack for a packet that wasn't retransmitted;
3557 * it is probably safe to discard any error indications we've
3558 * received recently. This isn't quite right, but close enough
3559 * for now (a route might have failed after we sent a segment,
3560 * and the return path might not be symmetrical).
3562 tp->t_softerror = 0;
3566 * Determine a reasonable value for maxseg size.
3567 * If the route is known, check route for mtu.
3568 * If none, use an mss that can be handled on the outgoing interface
3569 * without forcing IP to fragment. If no route is found, route has no mtu,
3570 * or the destination isn't local, use a default, hopefully conservative
3571 * size (usually 512 or the default IP max size, but no more than the mtu
3572 * of the interface), as we can't discover anything about intervening
3573 * gateways or networks. We also initialize the congestion/slow start
3574 * window to be a single segment if the destination isn't local.
3575 * While looking at the routing entry, we also initialize other path-dependent
3576 * parameters from pre-set or cached values in the routing entry.
3578 * NOTE that resulting t_maxseg doesn't include space for TCP options or
3579 * IP options, e.g. IPSEC data, since length of this data may vary, and
3580 * thus it is calculated for every segment separately in tcp_output().
3582 * NOTE that this routine is only called when we process an incoming
3583 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3584 * settings are handled in tcp_mssopt().
3587 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3588 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3591 uint32_t maxmtu = 0;
3592 struct inpcb *inp = tp->t_inpcb;
3593 struct hc_metrics_lite metrics;
3595 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3596 size_t min_protoh = isipv6 ?
3597 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3598 sizeof (struct tcpiphdr);
3600 const size_t min_protoh = sizeof(struct tcpiphdr);
3603 INP_WLOCK_ASSERT(tp->t_inpcb);
3605 if (mtuoffer != -1) {
3606 KASSERT(offer == -1, ("%s: conflict", __func__));
3607 offer = mtuoffer - min_protoh;
3613 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3614 tp->t_maxseg = V_tcp_v6mssdflt;
3617 #if defined(INET) && defined(INET6)
3622 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3623 tp->t_maxseg = V_tcp_mssdflt;
3628 * No route to sender, stay with default mss and return.
3632 * In case we return early we need to initialize metrics
3633 * to a defined state as tcp_hc_get() would do for us
3634 * if there was no cache hit.
3636 if (metricptr != NULL)
3637 bzero(metricptr, sizeof(struct hc_metrics_lite));
3641 /* What have we got? */
3645 * Offer == 0 means that there was no MSS on the SYN
3646 * segment, in this case we use tcp_mssdflt as
3647 * already assigned to t_maxseg above.
3649 offer = tp->t_maxseg;
3654 * Offer == -1 means that we didn't receive SYN yet.
3660 * Prevent DoS attack with too small MSS. Round up
3661 * to at least minmss.
3663 offer = max(offer, V_tcp_minmss);
3667 * rmx information is now retrieved from tcp_hostcache.
3669 tcp_hc_get(&inp->inp_inc, &metrics);
3670 if (metricptr != NULL)
3671 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3674 * If there's a discovered mtu in tcp hostcache, use it.
3675 * Else, use the link mtu.
3677 if (metrics.rmx_mtu)
3678 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3682 mss = maxmtu - min_protoh;
3683 if (!V_path_mtu_discovery &&
3684 !in6_localaddr(&inp->in6p_faddr))
3685 mss = min(mss, V_tcp_v6mssdflt);
3688 #if defined(INET) && defined(INET6)
3693 mss = maxmtu - min_protoh;
3694 if (!V_path_mtu_discovery &&
3695 !in_localaddr(inp->inp_faddr))
3696 mss = min(mss, V_tcp_mssdflt);
3700 * XXX - The above conditional (mss = maxmtu - min_protoh)
3701 * probably violates the TCP spec.
3702 * The problem is that, since we don't know the
3703 * other end's MSS, we are supposed to use a conservative
3704 * default. But, if we do that, then MTU discovery will
3705 * never actually take place, because the conservative
3706 * default is much less than the MTUs typically seen
3707 * on the Internet today. For the moment, we'll sweep
3708 * this under the carpet.
3710 * The conservative default might not actually be a problem
3711 * if the only case this occurs is when sending an initial
3712 * SYN with options and data to a host we've never talked
3713 * to before. Then, they will reply with an MSS value which
3714 * will get recorded and the new parameters should get
3715 * recomputed. For Further Study.
3718 mss = min(mss, offer);
3721 * Sanity check: make sure that maxseg will be large
3722 * enough to allow some data on segments even if the
3723 * all the option space is used (40bytes). Otherwise
3724 * funny things may happen in tcp_output.
3726 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3734 tcp_mss(struct tcpcb *tp, int offer)
3740 struct hc_metrics_lite metrics;
3741 struct tcp_ifcap cap;
3743 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3745 bzero(&cap, sizeof(cap));
3746 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3752 * If there's a pipesize, change the socket buffer to that size,
3753 * don't change if sb_hiwat is different than default (then it
3754 * has been changed on purpose with setsockopt).
3755 * Make the socket buffers an integral number of mss units;
3756 * if the mss is larger than the socket buffer, decrease the mss.
3758 so = inp->inp_socket;
3759 SOCKBUF_LOCK(&so->so_snd);
3760 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3761 bufsize = metrics.rmx_sendpipe;
3763 bufsize = so->so_snd.sb_hiwat;
3767 bufsize = roundup(bufsize, mss);
3768 if (bufsize > sb_max)
3770 if (bufsize > so->so_snd.sb_hiwat)
3771 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3773 SOCKBUF_UNLOCK(&so->so_snd);
3775 * Sanity check: make sure that maxseg will be large
3776 * enough to allow some data on segments even if the
3777 * all the option space is used (40bytes). Otherwise
3778 * funny things may happen in tcp_output.
3780 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3782 tp->t_maxseg = max(mss, 64);
3784 SOCKBUF_LOCK(&so->so_rcv);
3785 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3786 bufsize = metrics.rmx_recvpipe;
3788 bufsize = so->so_rcv.sb_hiwat;
3789 if (bufsize > mss) {
3790 bufsize = roundup(bufsize, mss);
3791 if (bufsize > sb_max)
3793 if (bufsize > so->so_rcv.sb_hiwat)
3794 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3796 SOCKBUF_UNLOCK(&so->so_rcv);
3798 /* Check the interface for TSO capabilities. */
3799 if (cap.ifcap & CSUM_TSO) {
3800 tp->t_flags |= TF_TSO;
3801 tp->t_tsomax = cap.tsomax;
3802 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3803 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3808 * Determine the MSS option to send on an outgoing SYN.
3811 tcp_mssopt(struct in_conninfo *inc)
3814 uint32_t thcmtu = 0;
3815 uint32_t maxmtu = 0;
3818 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3821 if (inc->inc_flags & INC_ISIPV6) {
3822 mss = V_tcp_v6mssdflt;
3823 maxmtu = tcp_maxmtu6(inc, NULL);
3824 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3827 #if defined(INET) && defined(INET6)
3832 mss = V_tcp_mssdflt;
3833 maxmtu = tcp_maxmtu(inc, NULL);
3834 min_protoh = sizeof(struct tcpiphdr);
3837 #if defined(INET6) || defined(INET)
3838 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3841 if (maxmtu && thcmtu)
3842 mss = min(maxmtu, thcmtu) - min_protoh;
3843 else if (maxmtu || thcmtu)
3844 mss = max(maxmtu, thcmtu) - min_protoh;
3851 * On a partial ack arrives, force the retransmission of the
3852 * next unacknowledged segment. Do not clear tp->t_dupacks.
3853 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3857 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3859 tcp_seq onxt = tp->snd_nxt;
3860 uint32_t ocwnd = tp->snd_cwnd;
3861 u_int maxseg = tcp_maxseg(tp);
3863 INP_WLOCK_ASSERT(tp->t_inpcb);
3865 tcp_timer_activate(tp, TT_REXMT, 0);
3867 tp->snd_nxt = th->th_ack;
3869 * Set snd_cwnd to one segment beyond acknowledged offset.
3870 * (tp->snd_una has not yet been updated when this function is called.)
3872 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th);
3873 tp->t_flags |= TF_ACKNOW;
3874 (void) tp->t_fb->tfb_tcp_output(tp);
3875 tp->snd_cwnd = ocwnd;
3876 if (SEQ_GT(onxt, tp->snd_nxt))
3879 * Partial window deflation. Relies on fact that tp->snd_una
3882 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3883 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3886 tp->snd_cwnd += maxseg;
3890 tcp_compute_pipe(struct tcpcb *tp)
3892 return (tp->snd_max - tp->snd_una +
3893 tp->sackhint.sack_bytes_rexmit -
3894 tp->sackhint.sacked_bytes);