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;
584 int rstreason = 0; /* For badport_bandlim accounting purposes */
586 struct m_tag *fwd_tag = NULL;
587 struct epoch_tracker et;
589 struct ip6_hdr *ip6 = NULL;
592 const void *ip6 = NULL;
594 struct tcpopt to; /* options in this segment */
595 char *s = NULL; /* address and port logging */
599 * The size of tcp_saveipgen must be the size of the max ip header,
602 u_char tcp_saveipgen[IP6_HDR_LEN];
603 struct tcphdr tcp_savetcp;
608 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
615 TCPSTAT_INC(tcps_rcvtotal);
619 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
621 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
622 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
624 TCPSTAT_INC(tcps_rcvshort);
625 return (IPPROTO_DONE);
629 ip6 = mtod(m, struct ip6_hdr *);
630 th = (struct tcphdr *)((caddr_t)ip6 + off0);
631 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
632 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
633 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
634 th->th_sum = m->m_pkthdr.csum_data;
636 th->th_sum = in6_cksum_pseudo(ip6, tlen,
637 IPPROTO_TCP, m->m_pkthdr.csum_data);
638 th->th_sum ^= 0xffff;
640 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
642 TCPSTAT_INC(tcps_rcvbadsum);
647 * Be proactive about unspecified IPv6 address in source.
648 * As we use all-zero to indicate unbounded/unconnected pcb,
649 * unspecified IPv6 address can be used to confuse us.
651 * Note that packets with unspecified IPv6 destination is
652 * already dropped in ip6_input.
654 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
658 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
661 #if defined(INET) && defined(INET6)
667 * Get IP and TCP header together in first mbuf.
668 * Note: IP leaves IP header in first mbuf.
670 if (off0 > sizeof (struct ip)) {
672 off0 = sizeof(struct ip);
674 if (m->m_len < sizeof (struct tcpiphdr)) {
675 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
677 TCPSTAT_INC(tcps_rcvshort);
678 return (IPPROTO_DONE);
681 ip = mtod(m, struct ip *);
682 th = (struct tcphdr *)((caddr_t)ip + off0);
683 tlen = ntohs(ip->ip_len) - off0;
686 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
687 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
688 th->th_sum = m->m_pkthdr.csum_data;
690 th->th_sum = in_pseudo(ip->ip_src.s_addr,
692 htonl(m->m_pkthdr.csum_data + tlen +
694 th->th_sum ^= 0xffff;
696 struct ipovly *ipov = (struct ipovly *)ip;
699 * Checksum extended TCP header and data.
703 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
704 ipov->ih_len = htons(tlen);
705 th->th_sum = in_cksum(m, len);
706 /* Reset length for SDT probes. */
707 ip->ip_len = htons(len);
710 /* Re-initialization for later version check */
712 ip->ip_v = IPVERSION;
713 ip->ip_hl = off0 >> 2;
717 TCPSTAT_INC(tcps_rcvbadsum);
724 * Check that TCP offset makes sense,
725 * pull out TCP options and adjust length. XXX
727 off = th->th_off << 2;
728 if (off < sizeof (struct tcphdr) || off > tlen) {
729 TCPSTAT_INC(tcps_rcvbadoff);
732 tlen -= off; /* tlen is used instead of ti->ti_len */
733 if (off > sizeof (struct tcphdr)) {
736 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
737 ip6 = mtod(m, struct ip6_hdr *);
738 th = (struct tcphdr *)((caddr_t)ip6 + off0);
741 #if defined(INET) && defined(INET6)
746 if (m->m_len < sizeof(struct ip) + off) {
747 if ((m = m_pullup(m, sizeof (struct ip) + off))
749 TCPSTAT_INC(tcps_rcvshort);
750 return (IPPROTO_DONE);
752 ip = mtod(m, struct ip *);
753 th = (struct tcphdr *)((caddr_t)ip + off0);
757 optlen = off - sizeof (struct tcphdr);
758 optp = (u_char *)(th + 1);
760 thflags = th->th_flags;
763 * Convert TCP protocol specific fields to host format.
765 tcp_fields_to_host(th);
768 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
770 drop_hdrlen = off0 + off;
773 * Locate pcb for segment; if we're likely to add or remove a
774 * connection then first acquire pcbinfo lock. There are three cases
775 * where we might discover later we need a write lock despite the
776 * flags: ACKs moving a connection out of the syncache, ACKs for a
777 * connection in TIMEWAIT and SYNs not targeting a listening socket.
779 if ((thflags & (TH_FIN | TH_RST)) != 0) {
780 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
781 ti_locked = TI_RLOCKED;
783 ti_locked = TI_UNLOCKED;
786 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
790 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
792 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
795 #if defined(INET) && !defined(INET6)
796 (m->m_flags & M_IP_NEXTHOP)
799 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
803 if (ti_locked == TI_RLOCKED) {
804 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
806 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
810 if (isipv6 && fwd_tag != NULL) {
811 struct sockaddr_in6 *next_hop6;
813 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
815 * Transparently forwarded. Pretend to be the destination.
816 * Already got one like this?
818 inp = in6_pcblookup_mbuf(&V_tcbinfo,
819 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
820 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
823 * It's new. Try to find the ambushing socket.
824 * Because we've rewritten the destination address,
825 * any hardware-generated hash is ignored.
827 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
828 th->th_sport, &next_hop6->sin6_addr,
829 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
830 th->th_dport, INPLOOKUP_WILDCARD |
831 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
834 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
835 th->th_sport, &ip6->ip6_dst, th->th_dport,
836 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
837 m->m_pkthdr.rcvif, m);
840 #if defined(INET6) && defined(INET)
844 if (fwd_tag != NULL) {
845 struct sockaddr_in *next_hop;
847 next_hop = (struct sockaddr_in *)(fwd_tag+1);
849 * Transparently forwarded. Pretend to be the destination.
850 * already got one like this?
852 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
853 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
854 m->m_pkthdr.rcvif, m);
857 * It's new. Try to find the ambushing socket.
858 * Because we've rewritten the destination address,
859 * any hardware-generated hash is ignored.
861 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
862 th->th_sport, next_hop->sin_addr,
863 next_hop->sin_port ? ntohs(next_hop->sin_port) :
864 th->th_dport, INPLOOKUP_WILDCARD |
865 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
868 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
869 th->th_sport, ip->ip_dst, th->th_dport,
870 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
871 m->m_pkthdr.rcvif, m);
875 * If the INPCB does not exist then all data in the incoming
876 * segment is discarded and an appropriate RST is sent back.
877 * XXX MRT Send RST using which routing table?
881 * Log communication attempts to ports that are not
884 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
885 tcp_log_in_vain == 2) {
886 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
887 log(LOG_INFO, "%s; %s: Connection attempt "
888 "to closed port\n", s, __func__);
891 * When blackholing do not respond with a RST but
892 * completely ignore the segment and drop it.
894 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
898 rstreason = BANDLIM_RST_CLOSEDPORT;
901 INP_WLOCK_ASSERT(inp);
903 * While waiting for inp lock during the lookup, another thread
904 * can have dropped the inpcb, in which case we need to loop back
905 * and try to find a new inpcb to deliver to.
907 if (inp->inp_flags & INP_DROPPED) {
912 if ((inp->inp_flowtype == M_HASHTYPE_NONE) &&
913 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) &&
914 ((inp->inp_socket == NULL) ||
915 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
916 inp->inp_flowid = m->m_pkthdr.flowid;
917 inp->inp_flowtype = M_HASHTYPE_GET(m);
919 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
921 if (isipv6 && IPSEC_ENABLED(ipv6) &&
922 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) {
930 if (IPSEC_ENABLED(ipv4) &&
931 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) {
938 * Check the minimum TTL for socket.
940 if (inp->inp_ip_minttl != 0) {
943 if (inp->inp_ip_minttl > ip6->ip6_hlim)
947 if (inp->inp_ip_minttl > ip->ip_ttl)
952 * A previous connection in TIMEWAIT state is supposed to catch stray
953 * or duplicate segments arriving late. If this segment was a
954 * legitimate new connection attempt, the old INPCB gets removed and
955 * we can try again to find a listening socket.
957 * At this point, due to earlier optimism, we may hold only an inpcb
958 * lock, and not the inpcbinfo write lock. If so, we need to try to
959 * acquire it, or if that fails, acquire a reference on the inpcb,
960 * drop all locks, acquire a global write lock, and then re-acquire
961 * the inpcb lock. We may at that point discover that another thread
962 * has tried to free the inpcb, in which case we need to loop back
963 * and try to find a new inpcb to deliver to.
965 * XXXRW: It may be time to rethink timewait locking.
967 if (inp->inp_flags & INP_TIMEWAIT) {
968 if (ti_locked == TI_UNLOCKED) {
969 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
970 ti_locked = TI_RLOCKED;
972 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
974 if (thflags & TH_SYN)
975 tcp_dooptions(&to, optp, optlen, TO_SYN);
977 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
979 if (tcp_twcheck(inp, &to, th, m, tlen))
981 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
982 return (IPPROTO_DONE);
985 * The TCPCB may no longer exist if the connection is winding
986 * down or it is in the CLOSED state. Either way we drop the
987 * segment and send an appropriate response.
990 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
991 rstreason = BANDLIM_RST_CLOSEDPORT;
996 if (tp->t_flags & TF_TOE) {
997 tcp_offload_input(tp, m);
998 m = NULL; /* consumed by the TOE driver */
1004 * We've identified a valid inpcb, but it could be that we need an
1005 * inpcbinfo write lock but don't hold it. In this case, attempt to
1006 * acquire using the same strategy as the TIMEWAIT case above. If we
1007 * relock, we have to jump back to 'relocked' as the connection might
1008 * now be in TIMEWAIT.
1011 if ((thflags & (TH_FIN | TH_RST)) != 0)
1012 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1014 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) ||
1015 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) &&
1016 !IS_FASTOPEN(tp->t_flags)))) {
1017 if (ti_locked == TI_UNLOCKED) {
1018 INP_INFO_RLOCK_ET(&V_tcbinfo, et);
1019 ti_locked = TI_RLOCKED;
1021 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1025 INP_WLOCK_ASSERT(inp);
1026 if (mac_inpcb_check_deliver(inp, m))
1029 so = inp->inp_socket;
1030 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1032 if (so->so_options & SO_DEBUG) {
1033 ostate = tp->t_state;
1036 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1039 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1042 #endif /* TCPDEBUG */
1044 * When the socket is accepting connections (the INPCB is in LISTEN
1045 * state) we look into the SYN cache if this is a new connection
1046 * attempt or the completion of a previous one.
1048 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN),
1049 ("%s: so accepting but tp %p not listening", __func__, tp));
1050 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) {
1051 struct in_conninfo inc;
1053 bzero(&inc, sizeof(inc));
1056 inc.inc_flags |= INC_ISIPV6;
1057 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU)
1058 inc.inc_flags |= INC_IPV6MINMTU;
1059 inc.inc6_faddr = ip6->ip6_src;
1060 inc.inc6_laddr = ip6->ip6_dst;
1064 inc.inc_faddr = ip->ip_src;
1065 inc.inc_laddr = ip->ip_dst;
1067 inc.inc_fport = th->th_sport;
1068 inc.inc_lport = th->th_dport;
1069 inc.inc_fibnum = so->so_fibnum;
1072 * Check for an existing connection attempt in syncache if
1073 * the flag is only ACK. A successful lookup creates a new
1074 * socket appended to the listen queue in SYN_RECEIVED state.
1076 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1078 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1080 * Parse the TCP options here because
1081 * syncookies need access to the reflected
1084 tcp_dooptions(&to, optp, optlen, 0);
1086 * NB: syncache_expand() doesn't unlock
1087 * inp and tcpinfo locks.
1089 rstreason = syncache_expand(&inc, &to, th, &so, m);
1090 if (rstreason < 0) {
1092 * A failing TCP MD5 signature comparison
1093 * must result in the segment being dropped
1094 * and must not produce any response back
1098 } else if (rstreason == 0) {
1100 * No syncache entry or ACK was not
1101 * for our SYN/ACK. Send a RST.
1102 * NB: syncache did its own logging
1103 * of the failure cause.
1105 rstreason = BANDLIM_RST_OPENPORT;
1111 * We completed the 3-way handshake
1112 * but could not allocate a socket
1113 * either due to memory shortage,
1114 * listen queue length limits or
1115 * global socket limits. Send RST
1116 * or wait and have the remote end
1117 * retransmit the ACK for another
1120 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1121 log(LOG_DEBUG, "%s; %s: Listen socket: "
1122 "Socket allocation failed due to "
1123 "limits or memory shortage, %s\n",
1125 V_tcp_sc_rst_sock_fail ?
1126 "sending RST" : "try again");
1127 if (V_tcp_sc_rst_sock_fail) {
1128 rstreason = BANDLIM_UNLIMITED;
1134 * Socket is created in state SYN_RECEIVED.
1135 * Unlock the listen socket, lock the newly
1136 * created socket and update the tp variable.
1138 INP_WUNLOCK(inp); /* listen socket */
1139 inp = sotoinpcb(so);
1141 * New connection inpcb is already locked by
1142 * syncache_expand().
1144 INP_WLOCK_ASSERT(inp);
1145 tp = intotcpcb(inp);
1146 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1147 ("%s: ", __func__));
1149 * Process the segment and the data it
1150 * contains. tcp_do_segment() consumes
1151 * the mbuf chain and unlocks the inpcb.
1153 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1154 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1156 if (ti_locked == TI_RLOCKED)
1157 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
1158 return (IPPROTO_DONE);
1161 * Segment flag validation for new connection attempts:
1163 * Our (SYN|ACK) response was rejected.
1164 * Check with syncache and remove entry to prevent
1167 * NB: syncache_chkrst does its own logging of failure
1170 if (thflags & TH_RST) {
1171 syncache_chkrst(&inc, th, m);
1175 * We can't do anything without SYN.
1177 if ((thflags & TH_SYN) == 0) {
1178 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1179 log(LOG_DEBUG, "%s; %s: Listen socket: "
1180 "SYN is missing, segment ignored\n",
1182 TCPSTAT_INC(tcps_badsyn);
1186 * (SYN|ACK) is bogus on a listen socket.
1188 if (thflags & TH_ACK) {
1189 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1190 log(LOG_DEBUG, "%s; %s: Listen socket: "
1191 "SYN|ACK invalid, segment rejected\n",
1193 syncache_badack(&inc); /* XXX: Not needed! */
1194 TCPSTAT_INC(tcps_badsyn);
1195 rstreason = BANDLIM_RST_OPENPORT;
1199 * If the drop_synfin option is enabled, drop all
1200 * segments with both the SYN and FIN bits set.
1201 * This prevents e.g. nmap from identifying the
1203 * XXX: Poor reasoning. nmap has other methods
1204 * and is constantly refining its stack detection
1206 * XXX: This is a violation of the TCP specification
1207 * and was used by RFC1644.
1209 if ((thflags & TH_FIN) && V_drop_synfin) {
1210 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1211 log(LOG_DEBUG, "%s; %s: Listen socket: "
1212 "SYN|FIN segment ignored (based on "
1213 "sysctl setting)\n", s, __func__);
1214 TCPSTAT_INC(tcps_badsyn);
1218 * Segment's flags are (SYN) or (SYN|FIN).
1220 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1221 * as they do not affect the state of the TCP FSM.
1222 * The data pointed to by TH_URG and th_urp is ignored.
1224 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1225 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1226 KASSERT(thflags & (TH_SYN),
1227 ("%s: Listen socket: TH_SYN not set", __func__));
1230 * If deprecated address is forbidden,
1231 * we do not accept SYN to deprecated interface
1232 * address to prevent any new inbound connection from
1233 * getting established.
1234 * When we do not accept SYN, we send a TCP RST,
1235 * with deprecated source address (instead of dropping
1236 * it). We compromise it as it is much better for peer
1237 * to send a RST, and RST will be the final packet
1240 * If we do not forbid deprecated addresses, we accept
1241 * the SYN packet. RFC2462 does not suggest dropping
1243 * If we decipher RFC2462 5.5.4, it says like this:
1244 * 1. use of deprecated addr with existing
1245 * communication is okay - "SHOULD continue to be
1247 * 2. use of it with new communication:
1248 * (2a) "SHOULD NOT be used if alternate address
1249 * with sufficient scope is available"
1250 * (2b) nothing mentioned otherwise.
1251 * Here we fall into (2b) case as we have no choice in
1252 * our source address selection - we must obey the peer.
1254 * The wording in RFC2462 is confusing, and there are
1255 * multiple description text for deprecated address
1256 * handling - worse, they are not exactly the same.
1257 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1259 if (isipv6 && !V_ip6_use_deprecated) {
1260 struct in6_ifaddr *ia6;
1262 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
1264 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1265 ifa_free(&ia6->ia_ifa);
1266 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1267 log(LOG_DEBUG, "%s; %s: Listen socket: "
1268 "Connection attempt to deprecated "
1269 "IPv6 address rejected\n",
1271 rstreason = BANDLIM_RST_OPENPORT;
1275 ifa_free(&ia6->ia_ifa);
1279 * Basic sanity checks on incoming SYN requests:
1280 * Don't respond if the destination is a link layer
1281 * broadcast according to RFC1122 4.2.3.10, p. 104.
1282 * If it is from this socket it must be forged.
1283 * Don't respond if the source or destination is a
1284 * global or subnet broad- or multicast address.
1285 * Note that it is quite possible to receive unicast
1286 * link-layer packets with a broadcast IP address. Use
1287 * in_broadcast() to find them.
1289 if (m->m_flags & (M_BCAST|M_MCAST)) {
1290 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1291 log(LOG_DEBUG, "%s; %s: Listen socket: "
1292 "Connection attempt from broad- or multicast "
1293 "link layer address ignored\n", s, __func__);
1298 if (th->th_dport == th->th_sport &&
1299 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1300 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1301 log(LOG_DEBUG, "%s; %s: Listen socket: "
1302 "Connection attempt to/from self "
1303 "ignored\n", s, __func__);
1306 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1307 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1308 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1309 log(LOG_DEBUG, "%s; %s: Listen socket: "
1310 "Connection attempt from/to multicast "
1311 "address ignored\n", s, __func__);
1316 #if defined(INET) && defined(INET6)
1321 if (th->th_dport == th->th_sport &&
1322 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1323 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1324 log(LOG_DEBUG, "%s; %s: Listen socket: "
1325 "Connection attempt from/to self "
1326 "ignored\n", s, __func__);
1329 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1330 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1331 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1332 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1333 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1334 log(LOG_DEBUG, "%s; %s: Listen socket: "
1335 "Connection attempt from/to broad- "
1336 "or multicast address ignored\n",
1343 * SYN appears to be valid. Create compressed TCP state
1347 if (so->so_options & SO_DEBUG)
1348 tcp_trace(TA_INPUT, ostate, tp,
1349 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1351 TCP_PROBE3(debug__input, tp, th, m);
1352 tcp_dooptions(&to, optp, optlen, TO_SYN);
1353 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL))
1354 goto tfo_socket_result;
1357 * Entry added to syncache and mbuf consumed.
1358 * Only the listen socket is unlocked by syncache_add().
1360 if (ti_locked == TI_RLOCKED) {
1361 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
1362 ti_locked = TI_UNLOCKED;
1364 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1365 return (IPPROTO_DONE);
1366 } else if (tp->t_state == TCPS_LISTEN) {
1368 * When a listen socket is torn down the SO_ACCEPTCONN
1369 * flag is removed first while connections are drained
1370 * from the accept queue in a unlock/lock cycle of the
1371 * ACCEPT_LOCK, opening a race condition allowing a SYN
1372 * attempt go through unhandled.
1376 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1377 if (tp->t_flags & TF_SIGNATURE) {
1378 tcp_dooptions(&to, optp, optlen, thflags);
1379 if ((to.to_flags & TOF_SIGNATURE) == 0) {
1380 TCPSTAT_INC(tcps_sig_err_nosigopt);
1383 if (!TCPMD5_ENABLED() ||
1384 TCPMD5_INPUT(m, th, to.to_signature) != 0)
1388 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1391 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1392 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1393 * the inpcb, and unlocks pcbinfo.
1395 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos);
1396 if (ti_locked == TI_RLOCKED)
1397 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
1398 return (IPPROTO_DONE);
1401 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1403 if (ti_locked == TI_RLOCKED) {
1404 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
1405 ti_locked = TI_UNLOCKED;
1409 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1410 "ti_locked: %d", __func__, ti_locked));
1411 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1416 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1419 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1420 m = NULL; /* mbuf chain got consumed. */
1425 TCP_PROBE5(receive, NULL, tp, m, tp, th);
1427 if (ti_locked == TI_RLOCKED) {
1428 INP_INFO_RUNLOCK_ET(&V_tcbinfo, et);
1429 ti_locked = TI_UNLOCKED;
1433 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1434 "ti_locked: %d", __func__, ti_locked));
1435 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1443 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo);
1448 return (IPPROTO_DONE);
1452 * Automatic sizing of receive socket buffer. Often the send
1453 * buffer size is not optimally adjusted to the actual network
1454 * conditions at hand (delay bandwidth product). Setting the
1455 * buffer size too small limits throughput on links with high
1456 * bandwidth and high delay (eg. trans-continental/oceanic links).
1458 * On the receive side the socket buffer memory is only rarely
1459 * used to any significant extent. This allows us to be much
1460 * more aggressive in scaling the receive socket buffer. For
1461 * the case that the buffer space is actually used to a large
1462 * extent and we run out of kernel memory we can simply drop
1463 * the new segments; TCP on the sender will just retransmit it
1464 * later. Setting the buffer size too big may only consume too
1465 * much kernel memory if the application doesn't read() from
1466 * the socket or packet loss or reordering makes use of the
1469 * The criteria to step up the receive buffer one notch are:
1470 * 1. Application has not set receive buffer size with
1471 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1472 * 2. the number of bytes received during the time it takes
1473 * one timestamp to be reflected back to us (the RTT);
1474 * 3. received bytes per RTT is within seven eighth of the
1475 * current socket buffer size;
1476 * 4. receive buffer size has not hit maximal automatic size;
1478 * This algorithm does one step per RTT at most and only if
1479 * we receive a bulk stream w/o packet losses or reorderings.
1480 * Shrinking the buffer during idle times is not necessary as
1481 * it doesn't consume any memory when idle.
1483 * TODO: Only step up if the application is actually serving
1484 * the buffer to better manage the socket buffer resources.
1487 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so,
1488 struct tcpcb *tp, int tlen)
1492 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) &&
1493 tp->t_srtt != 0 && tp->rfbuf_ts != 0 &&
1494 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) >
1495 (tp->t_srtt >> TCP_RTT_SHIFT)) {
1496 if (tp->rfbuf_cnt > (so->so_rcv.sb_hiwat / 8 * 7) &&
1497 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) {
1498 newsize = min(so->so_rcv.sb_hiwat +
1499 V_tcp_autorcvbuf_inc, V_tcp_autorcvbuf_max);
1501 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize);
1503 /* Start over with next RTT. */
1507 tp->rfbuf_cnt += tlen; /* add up */
1513 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1514 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos)
1516 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed;
1517 int rstreason, todrop, win;
1521 struct in_conninfo *inc;
1528 * The size of tcp_saveipgen must be the size of the max ip header,
1531 u_char tcp_saveipgen[IP6_HDR_LEN];
1532 struct tcphdr tcp_savetcp;
1535 thflags = th->th_flags;
1536 inc = &tp->t_inpcb->inp_inc;
1537 tp->sackhint.last_sack_ack = 0;
1539 nsegs = max(1, m->m_pkthdr.lro_nsegs);
1541 * If this is either a state-changing packet or current state isn't
1542 * established, we require a write lock on tcbinfo. Otherwise, we
1543 * allow the tcbinfo to be in either alocked or unlocked, as the
1544 * caller may have unnecessarily acquired a write lock due to a race.
1546 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1547 tp->t_state != TCPS_ESTABLISHED) {
1548 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1550 INP_WLOCK_ASSERT(tp->t_inpcb);
1551 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1553 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1557 /* Save segment, if requested. */
1558 tcp_pcap_add(th, m, &(tp->t_inpkts));
1560 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0,
1563 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
1564 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1565 log(LOG_DEBUG, "%s; %s: "
1566 "SYN|FIN segment ignored (based on "
1567 "sysctl setting)\n", s, __func__);
1574 * If a segment with the ACK-bit set arrives in the SYN-SENT state
1575 * check SEQ.ACK first.
1577 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) &&
1578 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) {
1579 rstreason = BANDLIM_UNLIMITED;
1584 * Segment received on connection.
1585 * Reset idle time and keep-alive timer.
1586 * XXX: This should be done after segment
1587 * validation to ignore broken/spoofed segs.
1589 tp->t_rcvtime = ticks;
1592 * Scale up the window into a 32-bit value.
1593 * For the SYN_SENT state the scale is zero.
1595 tiwin = th->th_win << tp->snd_scale;
1598 * TCP ECN processing.
1600 if (tp->t_flags & TF_ECN_PERMIT) {
1601 if (thflags & TH_CWR)
1602 tp->t_flags &= ~TF_ECN_SND_ECE;
1603 switch (iptos & IPTOS_ECN_MASK) {
1605 tp->t_flags |= TF_ECN_SND_ECE;
1606 TCPSTAT_INC(tcps_ecn_ce);
1608 case IPTOS_ECN_ECT0:
1609 TCPSTAT_INC(tcps_ecn_ect0);
1611 case IPTOS_ECN_ECT1:
1612 TCPSTAT_INC(tcps_ecn_ect1);
1616 /* Process a packet differently from RFC3168. */
1617 cc_ecnpkt_handler(tp, th, iptos);
1619 /* Congestion experienced. */
1620 if (thflags & TH_ECE) {
1621 cc_cong_signal(tp, th, CC_ECN);
1626 * Parse options on any incoming segment.
1628 tcp_dooptions(&to, (u_char *)(th + 1),
1629 (th->th_off << 2) - sizeof(struct tcphdr),
1630 (thflags & TH_SYN) ? TO_SYN : 0);
1632 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
1633 if ((tp->t_flags & TF_SIGNATURE) != 0 &&
1634 (to.to_flags & TOF_SIGNATURE) == 0) {
1635 TCPSTAT_INC(tcps_sig_err_sigopt);
1636 /* XXX: should drop? */
1640 * If echoed timestamp is later than the current time,
1641 * fall back to non RFC1323 RTT calculation. Normalize
1642 * timestamp if syncookies were used when this connection
1645 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1646 to.to_tsecr -= tp->ts_offset;
1647 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1649 else if (tp->t_flags & TF_PREVVALID &&
1650 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
1651 cc_cong_signal(tp, th, CC_RTO_ERR);
1654 * Process options only when we get SYN/ACK back. The SYN case
1655 * for incoming connections is handled in tcp_syncache.
1656 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1657 * or <SYN,ACK>) segment itself is never scaled.
1658 * XXX this is traditional behavior, may need to be cleaned up.
1660 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1661 if ((to.to_flags & TOF_SCALE) &&
1662 (tp->t_flags & TF_REQ_SCALE)) {
1663 tp->t_flags |= TF_RCVD_SCALE;
1664 tp->snd_scale = to.to_wscale;
1667 * Initial send window. It will be updated with
1668 * the next incoming segment to the scaled value.
1670 tp->snd_wnd = th->th_win;
1671 if (to.to_flags & TOF_TS) {
1672 tp->t_flags |= TF_RCVD_TSTMP;
1673 tp->ts_recent = to.to_tsval;
1674 tp->ts_recent_age = tcp_ts_getticks();
1676 if (to.to_flags & TOF_MSS)
1677 tcp_mss(tp, to.to_mss);
1678 if ((tp->t_flags & TF_SACK_PERMIT) &&
1679 (to.to_flags & TOF_SACKPERM) == 0)
1680 tp->t_flags &= ~TF_SACK_PERMIT;
1681 if (IS_FASTOPEN(tp->t_flags)) {
1682 if (to.to_flags & TOF_FASTOPEN) {
1685 if (to.to_flags & TOF_MSS)
1688 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
1692 tcp_fastopen_update_cache(tp, mss,
1693 to.to_tfo_len, to.to_tfo_cookie);
1695 tcp_fastopen_disable_path(tp);
1700 * If timestamps were negotiated during SYN/ACK they should
1701 * appear on every segment during this session and vice versa.
1703 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1704 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1705 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1706 "no action\n", s, __func__);
1710 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1711 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1712 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1713 "no action\n", s, __func__);
1719 * Header prediction: check for the two common cases
1720 * of a uni-directional data xfer. If the packet has
1721 * no control flags, is in-sequence, the window didn't
1722 * change and we're not retransmitting, it's a
1723 * candidate. If the length is zero and the ack moved
1724 * forward, we're the sender side of the xfer. Just
1725 * free the data acked & wake any higher level process
1726 * that was blocked waiting for space. If the length
1727 * is non-zero and the ack didn't move, we're the
1728 * receiver side. If we're getting packets in-order
1729 * (the reassembly queue is empty), add the data to
1730 * the socket buffer and note that we need a delayed ack.
1731 * Make sure that the hidden state-flags are also off.
1732 * Since we check for TCPS_ESTABLISHED first, it can only
1735 if (tp->t_state == TCPS_ESTABLISHED &&
1736 th->th_seq == tp->rcv_nxt &&
1737 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1738 tp->snd_nxt == tp->snd_max &&
1739 tiwin && tiwin == tp->snd_wnd &&
1740 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1742 ((to.to_flags & TOF_TS) == 0 ||
1743 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1746 * If last ACK falls within this segment's sequence numbers,
1747 * record the timestamp.
1748 * NOTE that the test is modified according to the latest
1749 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1751 if ((to.to_flags & TOF_TS) != 0 &&
1752 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1753 tp->ts_recent_age = tcp_ts_getticks();
1754 tp->ts_recent = to.to_tsval;
1758 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1759 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1760 !IN_RECOVERY(tp->t_flags) &&
1761 (to.to_flags & TOF_SACK) == 0 &&
1762 TAILQ_EMPTY(&tp->snd_holes)) {
1764 * This is a pure ack for outstanding data.
1766 TCPSTAT_INC(tcps_predack);
1769 * "bad retransmit" recovery without timestamps.
1771 if ((to.to_flags & TOF_TS) == 0 &&
1772 tp->t_rxtshift == 1 &&
1773 tp->t_flags & TF_PREVVALID &&
1774 (int)(ticks - tp->t_badrxtwin) < 0) {
1775 cc_cong_signal(tp, th, CC_RTO_ERR);
1779 * Recalculate the transmit timer / rtt.
1781 * Some boxes send broken timestamp replies
1782 * during the SYN+ACK phase, ignore
1783 * timestamps of 0 or we could calculate a
1784 * huge RTT and blow up the retransmit timer.
1786 if ((to.to_flags & TOF_TS) != 0 &&
1790 t = tcp_ts_getticks() - to.to_tsecr;
1791 if (!tp->t_rttlow || tp->t_rttlow > t)
1794 TCP_TS_TO_TICKS(t) + 1);
1795 } else if (tp->t_rtttime &&
1796 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1797 if (!tp->t_rttlow ||
1798 tp->t_rttlow > ticks - tp->t_rtttime)
1799 tp->t_rttlow = ticks - tp->t_rtttime;
1801 ticks - tp->t_rtttime);
1803 acked = BYTES_THIS_ACK(tp, th);
1806 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1807 hhook_run_tcp_est_in(tp, th, &to);
1810 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
1811 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1812 sbdrop(&so->so_snd, acked);
1813 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1814 SEQ_LEQ(th->th_ack, tp->snd_recover))
1815 tp->snd_recover = th->th_ack - 1;
1818 * Let the congestion control algorithm update
1819 * congestion control related information. This
1820 * typically means increasing the congestion
1823 cc_ack_received(tp, th, nsegs, CC_ACK);
1825 tp->snd_una = th->th_ack;
1827 * Pull snd_wl2 up to prevent seq wrap relative
1830 tp->snd_wl2 = th->th_ack;
1835 * If all outstanding data are acked, stop
1836 * retransmit timer, otherwise restart timer
1837 * using current (possibly backed-off) value.
1838 * If process is waiting for space,
1839 * wakeup/selwakeup/signal. If data
1840 * are ready to send, let tcp_output
1841 * decide between more output or persist.
1844 if (so->so_options & SO_DEBUG)
1845 tcp_trace(TA_INPUT, ostate, tp,
1846 (void *)tcp_saveipgen,
1849 TCP_PROBE3(debug__input, tp, th, m);
1850 if (tp->snd_una == tp->snd_max)
1851 tcp_timer_activate(tp, TT_REXMT, 0);
1852 else if (!tcp_timer_active(tp, TT_PERSIST))
1853 tcp_timer_activate(tp, TT_REXMT,
1856 if (sbavail(&so->so_snd))
1857 (void) tp->t_fb->tfb_tcp_output(tp);
1860 } else if (th->th_ack == tp->snd_una &&
1861 tlen <= sbspace(&so->so_rcv)) {
1862 int newsize = 0; /* automatic sockbuf scaling */
1865 * This is a pure, in-sequence data packet with
1866 * nothing on the reassembly queue and we have enough
1867 * buffer space to take it.
1869 /* Clean receiver SACK report if present */
1870 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1871 tcp_clean_sackreport(tp);
1872 TCPSTAT_INC(tcps_preddat);
1873 tp->rcv_nxt += tlen;
1875 * Pull snd_wl1 up to prevent seq wrap relative to
1878 tp->snd_wl1 = th->th_seq;
1880 * Pull rcv_up up to prevent seq wrap relative to
1883 tp->rcv_up = tp->rcv_nxt;
1884 TCPSTAT_ADD(tcps_rcvpack, nsegs);
1885 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1887 if (so->so_options & SO_DEBUG)
1888 tcp_trace(TA_INPUT, ostate, tp,
1889 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1891 TCP_PROBE3(debug__input, tp, th, m);
1893 newsize = tcp_autorcvbuf(m, th, so, tp, tlen);
1895 /* Add data to socket buffer. */
1896 SOCKBUF_LOCK(&so->so_rcv);
1897 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1901 * Set new socket buffer size.
1902 * Give up when limit is reached.
1905 if (!sbreserve_locked(&so->so_rcv,
1907 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1908 m_adj(m, drop_hdrlen); /* delayed header drop */
1909 sbappendstream_locked(&so->so_rcv, m, 0);
1911 /* NB: sorwakeup_locked() does an implicit unlock. */
1912 sorwakeup_locked(so);
1913 if (DELAY_ACK(tp, tlen)) {
1914 tp->t_flags |= TF_DELACK;
1916 tp->t_flags |= TF_ACKNOW;
1917 tp->t_fb->tfb_tcp_output(tp);
1924 * Calculate amount of space in receive window,
1925 * and then do TCP input processing.
1926 * Receive window is amount of space in rcv queue,
1927 * but not less than advertised window.
1929 win = sbspace(&so->so_rcv);
1932 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1934 switch (tp->t_state) {
1937 * If the state is SYN_RECEIVED:
1938 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1940 case TCPS_SYN_RECEIVED:
1941 if ((thflags & TH_ACK) &&
1942 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1943 SEQ_GT(th->th_ack, tp->snd_max))) {
1944 rstreason = BANDLIM_RST_OPENPORT;
1947 if (IS_FASTOPEN(tp->t_flags)) {
1949 * When a TFO connection is in SYN_RECEIVED, the
1950 * only valid packets are the initial SYN, a
1951 * retransmit/copy of the initial SYN (possibly with
1952 * a subset of the original data), a valid ACK, a
1955 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
1956 rstreason = BANDLIM_RST_OPENPORT;
1958 } else if (thflags & TH_SYN) {
1959 /* non-initial SYN is ignored */
1960 if ((tcp_timer_active(tp, TT_DELACK) ||
1961 tcp_timer_active(tp, TT_REXMT)))
1963 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) {
1970 * If the state is SYN_SENT:
1971 * if seg contains a RST with valid ACK (SEQ.ACK has already
1972 * been verified), then drop the connection.
1973 * if seg contains a RST without an ACK, drop the seg.
1974 * if seg does not contain SYN, then drop the seg.
1975 * Otherwise this is an acceptable SYN segment
1976 * initialize tp->rcv_nxt and tp->irs
1977 * if seg contains ack then advance tp->snd_una
1978 * if seg contains an ECE and ECN support is enabled, the stream
1980 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1981 * arrange for segment to be acked (eventually)
1982 * continue processing rest of data/controls, beginning with URG
1985 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1986 TCP_PROBE5(connect__refused, NULL, tp,
1988 tp = tcp_drop(tp, ECONNREFUSED);
1990 if (thflags & TH_RST)
1992 if (!(thflags & TH_SYN))
1995 tp->irs = th->th_seq;
1997 if (thflags & TH_ACK) {
1998 int tfo_partial_ack = 0;
2000 TCPSTAT_INC(tcps_connects);
2003 mac_socketpeer_set_from_mbuf(m, so);
2005 /* Do window scaling on this connection? */
2006 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2007 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2008 tp->rcv_scale = tp->request_r_scale;
2010 tp->rcv_adv += min(tp->rcv_wnd,
2011 TCP_MAXWIN << tp->rcv_scale);
2012 tp->snd_una++; /* SYN is acked */
2014 * If not all the data that was sent in the TFO SYN
2015 * has been acked, resend the remainder right away.
2017 if (IS_FASTOPEN(tp->t_flags) &&
2018 (tp->snd_una != tp->snd_max)) {
2019 tp->snd_nxt = th->th_ack;
2020 tfo_partial_ack = 1;
2023 * If there's data, delay ACK; if there's also a FIN
2024 * ACKNOW will be turned on later.
2026 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack)
2027 tcp_timer_activate(tp, TT_DELACK,
2030 tp->t_flags |= TF_ACKNOW;
2032 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
2034 tp->t_flags |= TF_ECN_PERMIT;
2035 TCPSTAT_INC(tcps_ecn_shs);
2039 * Received <SYN,ACK> in SYN_SENT[*] state.
2041 * SYN_SENT --> ESTABLISHED
2042 * SYN_SENT* --> FIN_WAIT_1
2044 tp->t_starttime = ticks;
2045 if (tp->t_flags & TF_NEEDFIN) {
2046 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2047 tp->t_flags &= ~TF_NEEDFIN;
2050 tcp_state_change(tp, TCPS_ESTABLISHED);
2051 TCP_PROBE5(connect__established, NULL, tp,
2054 tcp_timer_activate(tp, TT_KEEP,
2059 * Received initial SYN in SYN-SENT[*] state =>
2060 * simultaneous open.
2061 * If it succeeds, connection is * half-synchronized.
2062 * Otherwise, do 3-way handshake:
2063 * SYN-SENT -> SYN-RECEIVED
2064 * SYN-SENT* -> SYN-RECEIVED*
2066 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
2067 tcp_timer_activate(tp, TT_REXMT, 0);
2068 tcp_state_change(tp, TCPS_SYN_RECEIVED);
2071 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2072 INP_WLOCK_ASSERT(tp->t_inpcb);
2075 * Advance th->th_seq to correspond to first data byte.
2076 * If data, trim to stay within window,
2077 * dropping FIN if necessary.
2080 if (tlen > tp->rcv_wnd) {
2081 todrop = tlen - tp->rcv_wnd;
2085 TCPSTAT_INC(tcps_rcvpackafterwin);
2086 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2088 tp->snd_wl1 = th->th_seq - 1;
2089 tp->rcv_up = th->th_seq;
2091 * Client side of transaction: already sent SYN and data.
2092 * If the remote host used T/TCP to validate the SYN,
2093 * our data will be ACK'd; if so, enter normal data segment
2094 * processing in the middle of step 5, ack processing.
2095 * Otherwise, goto step 6.
2097 if (thflags & TH_ACK)
2103 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2104 * do normal processing.
2106 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2110 break; /* continue normal processing */
2114 * States other than LISTEN or SYN_SENT.
2115 * First check the RST flag and sequence number since reset segments
2116 * are exempt from the timestamp and connection count tests. This
2117 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2118 * below which allowed reset segments in half the sequence space
2119 * to fall though and be processed (which gives forged reset
2120 * segments with a random sequence number a 50 percent chance of
2121 * killing a connection).
2122 * Then check timestamp, if present.
2123 * Then check the connection count, if present.
2124 * Then check that at least some bytes of segment are within
2125 * receive window. If segment begins before rcv_nxt,
2126 * drop leading data (and SYN); if nothing left, just ack.
2128 if (thflags & TH_RST) {
2130 * RFC5961 Section 3.2
2132 * - RST drops connection only if SEG.SEQ == RCV.NXT.
2133 * - If RST is in window, we send challenge ACK.
2135 * Note: to take into account delayed ACKs, we should
2136 * test against last_ack_sent instead of rcv_nxt.
2137 * Note 2: we handle special case of closed window, not
2138 * covered by the RFC.
2140 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2141 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
2142 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
2144 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2145 KASSERT(tp->t_state != TCPS_SYN_SENT,
2146 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
2149 if (V_tcp_insecure_rst ||
2150 tp->last_ack_sent == th->th_seq) {
2151 TCPSTAT_INC(tcps_drops);
2152 /* Drop the connection. */
2153 switch (tp->t_state) {
2154 case TCPS_SYN_RECEIVED:
2155 so->so_error = ECONNREFUSED;
2157 case TCPS_ESTABLISHED:
2158 case TCPS_FIN_WAIT_1:
2159 case TCPS_FIN_WAIT_2:
2160 case TCPS_CLOSE_WAIT:
2163 so->so_error = ECONNRESET;
2170 TCPSTAT_INC(tcps_badrst);
2171 /* Send challenge ACK. */
2172 tcp_respond(tp, mtod(m, void *), th, m,
2173 tp->rcv_nxt, tp->snd_nxt, TH_ACK);
2174 tp->last_ack_sent = tp->rcv_nxt;
2182 * RFC5961 Section 4.2
2183 * Send challenge ACK for any SYN in synchronized state.
2185 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT &&
2186 tp->t_state != TCPS_SYN_RECEIVED) {
2187 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2189 TCPSTAT_INC(tcps_badsyn);
2190 if (V_tcp_insecure_syn &&
2191 SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2192 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2193 tp = tcp_drop(tp, ECONNRESET);
2194 rstreason = BANDLIM_UNLIMITED;
2196 /* Send challenge ACK. */
2197 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
2198 tp->snd_nxt, TH_ACK);
2199 tp->last_ack_sent = tp->rcv_nxt;
2206 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2207 * and it's less than ts_recent, drop it.
2209 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2210 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2212 /* Check to see if ts_recent is over 24 days old. */
2213 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2215 * Invalidate ts_recent. If this segment updates
2216 * ts_recent, the age will be reset later and ts_recent
2217 * will get a valid value. If it does not, setting
2218 * ts_recent to zero will at least satisfy the
2219 * requirement that zero be placed in the timestamp
2220 * echo reply when ts_recent isn't valid. The
2221 * age isn't reset until we get a valid ts_recent
2222 * because we don't want out-of-order segments to be
2223 * dropped when ts_recent is old.
2227 TCPSTAT_INC(tcps_rcvduppack);
2228 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2229 TCPSTAT_INC(tcps_pawsdrop);
2237 * In the SYN-RECEIVED state, validate that the packet belongs to
2238 * this connection before trimming the data to fit the receive
2239 * window. Check the sequence number versus IRS since we know
2240 * the sequence numbers haven't wrapped. This is a partial fix
2241 * for the "LAND" DoS attack.
2243 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2244 rstreason = BANDLIM_RST_OPENPORT;
2248 todrop = tp->rcv_nxt - th->th_seq;
2250 if (thflags & TH_SYN) {
2260 * Following if statement from Stevens, vol. 2, p. 960.
2263 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2265 * Any valid FIN must be to the left of the window.
2266 * At this point the FIN must be a duplicate or out
2267 * of sequence; drop it.
2272 * Send an ACK to resynchronize and drop any data.
2273 * But keep on processing for RST or ACK.
2275 tp->t_flags |= TF_ACKNOW;
2277 TCPSTAT_INC(tcps_rcvduppack);
2278 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2280 TCPSTAT_INC(tcps_rcvpartduppack);
2281 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2284 * DSACK - add SACK block for dropped range
2286 if (tp->t_flags & TF_SACK_PERMIT) {
2287 tcp_update_sack_list(tp, th->th_seq,
2288 th->th_seq + todrop);
2290 * ACK now, as the next in-sequence segment
2291 * will clear the DSACK block again
2293 tp->t_flags |= TF_ACKNOW;
2295 drop_hdrlen += todrop; /* drop from the top afterwards */
2296 th->th_seq += todrop;
2298 if (th->th_urp > todrop)
2299 th->th_urp -= todrop;
2307 * If new data are received on a connection after the
2308 * user processes are gone, then RST the other end.
2310 if ((so->so_state & SS_NOFDREF) &&
2311 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2312 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2314 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2315 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2316 "after socket was closed, "
2317 "sending RST and removing tcpcb\n",
2318 s, __func__, tcpstates[tp->t_state], tlen);
2322 TCPSTAT_INC(tcps_rcvafterclose);
2323 rstreason = BANDLIM_UNLIMITED;
2328 * If segment ends after window, drop trailing data
2329 * (and PUSH and FIN); if nothing left, just ACK.
2331 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2333 TCPSTAT_INC(tcps_rcvpackafterwin);
2334 if (todrop >= tlen) {
2335 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2337 * If window is closed can only take segments at
2338 * window edge, and have to drop data and PUSH from
2339 * incoming segments. Continue processing, but
2340 * remember to ack. Otherwise, drop segment
2343 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2344 tp->t_flags |= TF_ACKNOW;
2345 TCPSTAT_INC(tcps_rcvwinprobe);
2349 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2352 thflags &= ~(TH_PUSH|TH_FIN);
2356 * If last ACK falls within this segment's sequence numbers,
2357 * record its timestamp.
2359 * 1) That the test incorporates suggestions from the latest
2360 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2361 * 2) That updating only on newer timestamps interferes with
2362 * our earlier PAWS tests, so this check should be solely
2363 * predicated on the sequence space of this segment.
2364 * 3) That we modify the segment boundary check to be
2365 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2366 * instead of RFC1323's
2367 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2368 * This modified check allows us to overcome RFC1323's
2369 * limitations as described in Stevens TCP/IP Illustrated
2370 * Vol. 2 p.869. In such cases, we can still calculate the
2371 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2373 if ((to.to_flags & TOF_TS) != 0 &&
2374 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2375 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2376 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2377 tp->ts_recent_age = tcp_ts_getticks();
2378 tp->ts_recent = to.to_tsval;
2382 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2383 * flag is on (half-synchronized state), then queue data for
2384 * later processing; else drop segment and return.
2386 if ((thflags & TH_ACK) == 0) {
2387 if (tp->t_state == TCPS_SYN_RECEIVED ||
2388 (tp->t_flags & TF_NEEDSYN)) {
2389 if (tp->t_state == TCPS_SYN_RECEIVED &&
2390 IS_FASTOPEN(tp->t_flags)) {
2391 tp->snd_wnd = tiwin;
2395 } else if (tp->t_flags & TF_ACKNOW)
2404 switch (tp->t_state) {
2407 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2408 * ESTABLISHED state and continue processing.
2409 * The ACK was checked above.
2411 case TCPS_SYN_RECEIVED:
2413 TCPSTAT_INC(tcps_connects);
2415 /* Do window scaling? */
2416 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2417 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2418 tp->rcv_scale = tp->request_r_scale;
2420 tp->snd_wnd = tiwin;
2423 * SYN-RECEIVED -> ESTABLISHED
2424 * SYN-RECEIVED* -> FIN-WAIT-1
2426 tp->t_starttime = ticks;
2427 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
2428 tcp_fastopen_decrement_counter(tp->t_tfo_pending);
2429 tp->t_tfo_pending = NULL;
2432 * Account for the ACK of our SYN prior to
2433 * regular ACK processing below.
2437 if (tp->t_flags & TF_NEEDFIN) {
2438 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2439 tp->t_flags &= ~TF_NEEDFIN;
2441 tcp_state_change(tp, TCPS_ESTABLISHED);
2442 TCP_PROBE5(accept__established, NULL, tp,
2445 * TFO connections call cc_conn_init() during SYN
2446 * processing. Calling it again here for such
2447 * connections is not harmless as it would undo the
2448 * snd_cwnd reduction that occurs when a TFO SYN|ACK
2451 if (!IS_FASTOPEN(tp->t_flags))
2453 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2456 * If segment contains data or ACK, will call tcp_reass()
2457 * later; if not, do so now to pass queued data to user.
2459 if (tlen == 0 && (thflags & TH_FIN) == 0)
2460 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0,
2462 tp->snd_wl1 = th->th_seq - 1;
2466 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2467 * ACKs. If the ack is in the range
2468 * tp->snd_una < th->th_ack <= tp->snd_max
2469 * then advance tp->snd_una to th->th_ack and drop
2470 * data from the retransmission queue. If this ACK reflects
2471 * more up to date window information we update our window information.
2473 case TCPS_ESTABLISHED:
2474 case TCPS_FIN_WAIT_1:
2475 case TCPS_FIN_WAIT_2:
2476 case TCPS_CLOSE_WAIT:
2479 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2480 TCPSTAT_INC(tcps_rcvacktoomuch);
2483 if ((tp->t_flags & TF_SACK_PERMIT) &&
2484 ((to.to_flags & TOF_SACK) ||
2485 !TAILQ_EMPTY(&tp->snd_holes)))
2486 sack_changed = tcp_sack_doack(tp, &to, th->th_ack);
2489 * Reset the value so that previous (valid) value
2490 * from the last ack with SACK doesn't get used.
2492 tp->sackhint.sacked_bytes = 0;
2495 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2496 hhook_run_tcp_est_in(tp, th, &to);
2499 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2502 maxseg = tcp_maxseg(tp);
2504 (tiwin == tp->snd_wnd ||
2505 (tp->t_flags & TF_SACK_PERMIT))) {
2507 * If this is the first time we've seen a
2508 * FIN from the remote, this is not a
2509 * duplicate and it needs to be processed
2510 * normally. This happens during a
2511 * simultaneous close.
2513 if ((thflags & TH_FIN) &&
2514 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2518 TCPSTAT_INC(tcps_rcvdupack);
2520 * If we have outstanding data (other than
2521 * a window probe), this is a completely
2522 * duplicate ack (ie, window info didn't
2523 * change and FIN isn't set),
2524 * the ack is the biggest we've
2525 * seen and we've seen exactly our rexmt
2526 * threshold of them, assume a packet
2527 * has been dropped and retransmit it.
2528 * Kludge snd_nxt & the congestion
2529 * window so we send only this one
2532 * We know we're losing at the current
2533 * window size so do congestion avoidance
2534 * (set ssthresh to half the current window
2535 * and pull our congestion window back to
2536 * the new ssthresh).
2538 * Dup acks mean that packets have left the
2539 * network (they're now cached at the receiver)
2540 * so bump cwnd by the amount in the receiver
2541 * to keep a constant cwnd packets in the
2544 * When using TCP ECN, notify the peer that
2545 * we reduced the cwnd.
2548 * Following 2 kinds of acks should not affect
2551 * 2) Acks with SACK but without any new SACK
2552 * information in them. These could result from
2553 * any anomaly in the network like a switch
2554 * duplicating packets or a possible DoS attack.
2556 if (th->th_ack != tp->snd_una ||
2557 ((tp->t_flags & TF_SACK_PERMIT) &&
2560 else if (!tcp_timer_active(tp, TT_REXMT))
2562 else if (++tp->t_dupacks > tcprexmtthresh ||
2563 IN_FASTRECOVERY(tp->t_flags)) {
2564 cc_ack_received(tp, th, nsegs,
2566 if ((tp->t_flags & TF_SACK_PERMIT) &&
2567 IN_FASTRECOVERY(tp->t_flags)) {
2571 * Compute the amount of data in flight first.
2572 * We can inject new data into the pipe iff
2573 * we have less than 1/2 the original window's
2574 * worth of data in flight.
2576 if (V_tcp_do_rfc6675_pipe)
2577 awnd = tcp_compute_pipe(tp);
2579 awnd = (tp->snd_nxt - tp->snd_fack) +
2580 tp->sackhint.sack_bytes_rexmit;
2582 if (awnd < tp->snd_ssthresh) {
2583 tp->snd_cwnd += maxseg;
2584 if (tp->snd_cwnd > tp->snd_ssthresh)
2585 tp->snd_cwnd = tp->snd_ssthresh;
2588 tp->snd_cwnd += maxseg;
2589 (void) tp->t_fb->tfb_tcp_output(tp);
2591 } else if (tp->t_dupacks == tcprexmtthresh) {
2592 tcp_seq onxt = tp->snd_nxt;
2595 * If we're doing sack, check to
2596 * see if we're already in sack
2597 * recovery. If we're not doing sack,
2598 * check to see if we're in newreno
2601 if (tp->t_flags & TF_SACK_PERMIT) {
2602 if (IN_FASTRECOVERY(tp->t_flags)) {
2607 if (SEQ_LEQ(th->th_ack,
2613 /* Congestion signal before ack. */
2614 cc_cong_signal(tp, th, CC_NDUPACK);
2615 cc_ack_received(tp, th, nsegs,
2617 tcp_timer_activate(tp, TT_REXMT, 0);
2619 if (tp->t_flags & TF_SACK_PERMIT) {
2621 tcps_sack_recovery_episode);
2622 tp->sack_newdata = tp->snd_nxt;
2623 tp->snd_cwnd = maxseg;
2624 (void) tp->t_fb->tfb_tcp_output(tp);
2627 tp->snd_nxt = th->th_ack;
2628 tp->snd_cwnd = maxseg;
2629 (void) tp->t_fb->tfb_tcp_output(tp);
2630 KASSERT(tp->snd_limited <= 2,
2631 ("%s: tp->snd_limited too big",
2633 tp->snd_cwnd = tp->snd_ssthresh +
2635 (tp->t_dupacks - tp->snd_limited);
2636 if (SEQ_GT(onxt, tp->snd_nxt))
2639 } else if (V_tcp_do_rfc3042) {
2641 * Process first and second duplicate
2642 * ACKs. Each indicates a segment
2643 * leaving the network, creating room
2644 * for more. Make sure we can send a
2645 * packet on reception of each duplicate
2646 * ACK by increasing snd_cwnd by one
2647 * segment. Restore the original
2648 * snd_cwnd after packet transmission.
2650 cc_ack_received(tp, th, nsegs,
2652 uint32_t oldcwnd = tp->snd_cwnd;
2653 tcp_seq oldsndmax = tp->snd_max;
2657 KASSERT(tp->t_dupacks == 1 ||
2659 ("%s: dupacks not 1 or 2",
2661 if (tp->t_dupacks == 1)
2662 tp->snd_limited = 0;
2664 (tp->snd_nxt - tp->snd_una) +
2665 (tp->t_dupacks - tp->snd_limited) *
2668 * Only call tcp_output when there
2669 * is new data available to be sent.
2670 * Otherwise we would send pure ACKs.
2672 SOCKBUF_LOCK(&so->so_snd);
2673 avail = sbavail(&so->so_snd) -
2674 (tp->snd_nxt - tp->snd_una);
2675 SOCKBUF_UNLOCK(&so->so_snd);
2677 (void) tp->t_fb->tfb_tcp_output(tp);
2678 sent = tp->snd_max - oldsndmax;
2679 if (sent > maxseg) {
2680 KASSERT((tp->t_dupacks == 2 &&
2681 tp->snd_limited == 0) ||
2682 (sent == maxseg + 1 &&
2683 tp->t_flags & TF_SENTFIN),
2684 ("%s: sent too much",
2686 tp->snd_limited = 2;
2687 } else if (sent > 0)
2689 tp->snd_cwnd = oldcwnd;
2696 * This ack is advancing the left edge, reset the
2701 * If this ack also has new SACK info, increment the
2702 * counter as per rfc6675.
2704 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed)
2708 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2709 ("%s: th_ack <= snd_una", __func__));
2712 * If the congestion window was inflated to account
2713 * for the other side's cached packets, retract it.
2715 if (IN_FASTRECOVERY(tp->t_flags)) {
2716 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2717 if (tp->t_flags & TF_SACK_PERMIT)
2718 tcp_sack_partialack(tp, th);
2720 tcp_newreno_partial_ack(tp, th);
2722 cc_post_recovery(tp, th);
2725 * If we reach this point, ACK is not a duplicate,
2726 * i.e., it ACKs something we sent.
2728 if (tp->t_flags & TF_NEEDSYN) {
2730 * T/TCP: Connection was half-synchronized, and our
2731 * SYN has been ACK'd (so connection is now fully
2732 * synchronized). Go to non-starred state,
2733 * increment snd_una for ACK of SYN, and check if
2734 * we can do window scaling.
2736 tp->t_flags &= ~TF_NEEDSYN;
2738 /* Do window scaling? */
2739 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2740 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2741 tp->rcv_scale = tp->request_r_scale;
2742 /* Send window already scaled. */
2747 INP_WLOCK_ASSERT(tp->t_inpcb);
2749 acked = BYTES_THIS_ACK(tp, th);
2750 KASSERT(acked >= 0, ("%s: acked unexepectedly negative "
2751 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__,
2752 tp->snd_una, th->th_ack, tp, m));
2753 TCPSTAT_ADD(tcps_rcvackpack, nsegs);
2754 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2757 * If we just performed our first retransmit, and the ACK
2758 * arrives within our recovery window, then it was a mistake
2759 * to do the retransmit in the first place. Recover our
2760 * original cwnd and ssthresh, and proceed to transmit where
2763 if (tp->t_rxtshift == 1 &&
2764 tp->t_flags & TF_PREVVALID &&
2766 SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
2767 cc_cong_signal(tp, th, CC_RTO_ERR);
2770 * If we have a timestamp reply, update smoothed
2771 * round trip time. If no timestamp is present but
2772 * transmit timer is running and timed sequence
2773 * number was acked, update smoothed round trip time.
2774 * Since we now have an rtt measurement, cancel the
2775 * timer backoff (cf., Phil Karn's retransmit alg.).
2776 * Recompute the initial retransmit timer.
2778 * Some boxes send broken timestamp replies
2779 * during the SYN+ACK phase, ignore
2780 * timestamps of 0 or we could calculate a
2781 * huge RTT and blow up the retransmit timer.
2783 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2786 t = tcp_ts_getticks() - to.to_tsecr;
2787 if (!tp->t_rttlow || tp->t_rttlow > t)
2789 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2790 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2791 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2792 tp->t_rttlow = ticks - tp->t_rtttime;
2793 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2797 * If all outstanding data is acked, stop retransmit
2798 * timer and remember to restart (more output or persist).
2799 * If there is more data to be acked, restart retransmit
2800 * timer, using current (possibly backed-off) value.
2802 if (th->th_ack == tp->snd_max) {
2803 tcp_timer_activate(tp, TT_REXMT, 0);
2805 } else if (!tcp_timer_active(tp, TT_PERSIST))
2806 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2809 * If no data (only SYN) was ACK'd,
2810 * skip rest of ACK processing.
2816 * Let the congestion control algorithm update congestion
2817 * control related information. This typically means increasing
2818 * the congestion window.
2820 cc_ack_received(tp, th, nsegs, CC_ACK);
2822 SOCKBUF_LOCK(&so->so_snd);
2823 if (acked > sbavail(&so->so_snd)) {
2824 if (tp->snd_wnd >= sbavail(&so->so_snd))
2825 tp->snd_wnd -= sbavail(&so->so_snd);
2828 mfree = sbcut_locked(&so->so_snd,
2829 (int)sbavail(&so->so_snd));
2832 mfree = sbcut_locked(&so->so_snd, acked);
2833 if (tp->snd_wnd >= (uint32_t) acked)
2834 tp->snd_wnd -= acked;
2839 /* NB: sowwakeup_locked() does an implicit unlock. */
2840 sowwakeup_locked(so);
2842 /* Detect una wraparound. */
2843 if (!IN_RECOVERY(tp->t_flags) &&
2844 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2845 SEQ_LEQ(th->th_ack, tp->snd_recover))
2846 tp->snd_recover = th->th_ack - 1;
2847 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2848 if (IN_RECOVERY(tp->t_flags) &&
2849 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2850 EXIT_RECOVERY(tp->t_flags);
2852 tp->snd_una = th->th_ack;
2853 if (tp->t_flags & TF_SACK_PERMIT) {
2854 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2855 tp->snd_recover = tp->snd_una;
2857 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2858 tp->snd_nxt = tp->snd_una;
2860 switch (tp->t_state) {
2863 * In FIN_WAIT_1 STATE in addition to the processing
2864 * for the ESTABLISHED state if our FIN is now acknowledged
2865 * then enter FIN_WAIT_2.
2867 case TCPS_FIN_WAIT_1:
2868 if (ourfinisacked) {
2870 * If we can't receive any more
2871 * data, then closing user can proceed.
2872 * Starting the timer is contrary to the
2873 * specification, but if we don't get a FIN
2874 * we'll hang forever.
2877 * we should release the tp also, and use a
2880 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2881 soisdisconnected(so);
2882 tcp_timer_activate(tp, TT_2MSL,
2883 (tcp_fast_finwait2_recycle ?
2884 tcp_finwait2_timeout :
2887 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2892 * In CLOSING STATE in addition to the processing for
2893 * the ESTABLISHED state if the ACK acknowledges our FIN
2894 * then enter the TIME-WAIT state, otherwise ignore
2898 if (ourfinisacked) {
2899 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2907 * In LAST_ACK, we may still be waiting for data to drain
2908 * and/or to be acked, as well as for the ack of our FIN.
2909 * If our FIN is now acknowledged, delete the TCB,
2910 * enter the closed state and return.
2913 if (ourfinisacked) {
2914 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2923 INP_WLOCK_ASSERT(tp->t_inpcb);
2926 * Update window information.
2927 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2929 if ((thflags & TH_ACK) &&
2930 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2931 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2932 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2933 /* keep track of pure window updates */
2935 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2936 TCPSTAT_INC(tcps_rcvwinupd);
2937 tp->snd_wnd = tiwin;
2938 tp->snd_wl1 = th->th_seq;
2939 tp->snd_wl2 = th->th_ack;
2940 if (tp->snd_wnd > tp->max_sndwnd)
2941 tp->max_sndwnd = tp->snd_wnd;
2946 * Process segments with URG.
2948 if ((thflags & TH_URG) && th->th_urp &&
2949 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2951 * This is a kludge, but if we receive and accept
2952 * random urgent pointers, we'll crash in
2953 * soreceive. It's hard to imagine someone
2954 * actually wanting to send this much urgent data.
2956 SOCKBUF_LOCK(&so->so_rcv);
2957 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
2958 th->th_urp = 0; /* XXX */
2959 thflags &= ~TH_URG; /* XXX */
2960 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2961 goto dodata; /* XXX */
2964 * If this segment advances the known urgent pointer,
2965 * then mark the data stream. This should not happen
2966 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2967 * a FIN has been received from the remote side.
2968 * In these states we ignore the URG.
2970 * According to RFC961 (Assigned Protocols),
2971 * the urgent pointer points to the last octet
2972 * of urgent data. We continue, however,
2973 * to consider it to indicate the first octet
2974 * of data past the urgent section as the original
2975 * spec states (in one of two places).
2977 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2978 tp->rcv_up = th->th_seq + th->th_urp;
2979 so->so_oobmark = sbavail(&so->so_rcv) +
2980 (tp->rcv_up - tp->rcv_nxt) - 1;
2981 if (so->so_oobmark == 0)
2982 so->so_rcv.sb_state |= SBS_RCVATMARK;
2984 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2986 SOCKBUF_UNLOCK(&so->so_rcv);
2988 * Remove out of band data so doesn't get presented to user.
2989 * This can happen independent of advancing the URG pointer,
2990 * but if two URG's are pending at once, some out-of-band
2991 * data may creep in... ick.
2993 if (th->th_urp <= (uint32_t)tlen &&
2994 !(so->so_options & SO_OOBINLINE)) {
2995 /* hdr drop is delayed */
2996 tcp_pulloutofband(so, th, m, drop_hdrlen);
3000 * If no out of band data is expected,
3001 * pull receive urgent pointer along
3002 * with the receive window.
3004 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
3005 tp->rcv_up = tp->rcv_nxt;
3008 INP_WLOCK_ASSERT(tp->t_inpcb);
3011 * Process the segment text, merging it into the TCP sequencing queue,
3012 * and arranging for acknowledgment of receipt if necessary.
3013 * This process logically involves adjusting tp->rcv_wnd as data
3014 * is presented to the user (this happens in tcp_usrreq.c,
3015 * case PRU_RCVD). If a FIN has already been received on this
3016 * connection then we just ignore the text.
3018 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
3019 IS_FASTOPEN(tp->t_flags));
3020 if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
3021 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
3022 tcp_seq save_start = th->th_seq;
3023 tcp_seq save_rnxt = tp->rcv_nxt;
3024 int save_tlen = tlen;
3025 m_adj(m, drop_hdrlen); /* delayed header drop */
3027 * Insert segment which includes th into TCP reassembly queue
3028 * with control block tp. Set thflags to whether reassembly now
3029 * includes a segment with FIN. This handles the common case
3030 * inline (segment is the next to be received on an established
3031 * connection, and the queue is empty), avoiding linkage into
3032 * and removal from the queue and repetition of various
3034 * Set DELACK for segments received in order, but ack
3035 * immediately when segments are out of order (so
3036 * fast retransmit can work).
3038 if (th->th_seq == tp->rcv_nxt &&
3040 (TCPS_HAVEESTABLISHED(tp->t_state) ||
3042 if (DELAY_ACK(tp, tlen) || tfo_syn)
3043 tp->t_flags |= TF_DELACK;
3045 tp->t_flags |= TF_ACKNOW;
3046 tp->rcv_nxt += tlen;
3047 thflags = th->th_flags & TH_FIN;
3048 TCPSTAT_INC(tcps_rcvpack);
3049 TCPSTAT_ADD(tcps_rcvbyte, tlen);
3050 SOCKBUF_LOCK(&so->so_rcv);
3051 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
3054 sbappendstream_locked(&so->so_rcv, m, 0);
3055 /* NB: sorwakeup_locked() does an implicit unlock. */
3056 sorwakeup_locked(so);
3059 * XXX: Due to the header drop above "th" is
3060 * theoretically invalid by now. Fortunately
3061 * m_adj() doesn't actually frees any mbufs
3062 * when trimming from the head.
3064 tcp_seq temp = save_start;
3065 thflags = tcp_reass(tp, th, &temp, &tlen, m);
3066 tp->t_flags |= TF_ACKNOW;
3068 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) {
3069 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) {
3071 * DSACK actually handled in the fastpath
3074 tcp_update_sack_list(tp, save_start,
3075 save_start + save_tlen);
3076 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
3077 if ((tp->rcv_numsacks >= 1) &&
3078 (tp->sackblks[0].end == save_start)) {
3080 * Partial overlap, recorded at todrop
3083 tcp_update_sack_list(tp,
3084 tp->sackblks[0].start,
3085 tp->sackblks[0].end);
3087 tcp_update_dsack_list(tp, save_start,
3088 save_start + save_tlen);
3090 } else if (tlen >= save_tlen) {
3091 /* Update of sackblks. */
3092 tcp_update_dsack_list(tp, save_start,
3093 save_start + save_tlen);
3094 } else if (tlen > 0) {
3095 tcp_update_dsack_list(tp, save_start,
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);
3170 if (so->so_options & SO_DEBUG)
3171 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3174 TCP_PROBE3(debug__input, tp, th, m);
3177 * Return any desired output.
3179 if (needoutput || (tp->t_flags & TF_ACKNOW))
3180 (void) tp->t_fb->tfb_tcp_output(tp);
3183 INP_WLOCK_ASSERT(tp->t_inpcb);
3185 if (tp->t_flags & TF_DELACK) {
3186 tp->t_flags &= ~TF_DELACK;
3187 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3189 INP_WUNLOCK(tp->t_inpcb);
3194 * Generate an ACK dropping incoming segment if it occupies
3195 * sequence space, where the ACK reflects our state.
3197 * We can now skip the test for the RST flag since all
3198 * paths to this code happen after packets containing
3199 * RST have been dropped.
3201 * In the SYN-RECEIVED state, don't send an ACK unless the
3202 * segment we received passes the SYN-RECEIVED ACK test.
3203 * If it fails send a RST. This breaks the loop in the
3204 * "LAND" DoS attack, and also prevents an ACK storm
3205 * between two listening ports that have been sent forged
3206 * SYN segments, each with the source address of the other.
3208 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3209 (SEQ_GT(tp->snd_una, th->th_ack) ||
3210 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3211 rstreason = BANDLIM_RST_OPENPORT;
3215 if (so->so_options & SO_DEBUG)
3216 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3219 TCP_PROBE3(debug__input, tp, th, m);
3220 tp->t_flags |= TF_ACKNOW;
3221 (void) tp->t_fb->tfb_tcp_output(tp);
3222 INP_WUNLOCK(tp->t_inpcb);
3228 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3229 INP_WUNLOCK(tp->t_inpcb);
3231 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3236 * Drop space held by incoming segment and return.
3239 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3240 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3243 TCP_PROBE3(debug__input, tp, th, m);
3245 INP_WUNLOCK(tp->t_inpcb);
3250 * Issue RST and make ACK acceptable to originator of segment.
3251 * The mbuf must still include the original packet header.
3255 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3256 int tlen, int rstreason)
3262 struct ip6_hdr *ip6;
3266 INP_WLOCK_ASSERT(tp->t_inpcb);
3269 /* Don't bother if destination was broadcast/multicast. */
3270 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3273 if (mtod(m, struct ip *)->ip_v == 6) {
3274 ip6 = mtod(m, struct ip6_hdr *);
3275 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3276 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3278 /* IPv6 anycast check is done at tcp6_input() */
3281 #if defined(INET) && defined(INET6)
3286 ip = mtod(m, struct ip *);
3287 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3288 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3289 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3290 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3295 /* Perform bandwidth limiting. */
3296 if (badport_bandlim(rstreason) < 0)
3299 /* tcp_respond consumes the mbuf chain. */
3300 if (th->th_flags & TH_ACK) {
3301 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3302 th->th_ack, TH_RST);
3304 if (th->th_flags & TH_SYN)
3306 if (th->th_flags & TH_FIN)
3308 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3309 (tcp_seq)0, TH_RST|TH_ACK);
3317 * Parse TCP options and place in tcpopt.
3320 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3325 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3327 if (opt == TCPOPT_EOL)
3329 if (opt == TCPOPT_NOP)
3335 if (optlen < 2 || optlen > cnt)
3340 if (optlen != TCPOLEN_MAXSEG)
3342 if (!(flags & TO_SYN))
3344 to->to_flags |= TOF_MSS;
3345 bcopy((char *)cp + 2,
3346 (char *)&to->to_mss, sizeof(to->to_mss));
3347 to->to_mss = ntohs(to->to_mss);
3350 if (optlen != TCPOLEN_WINDOW)
3352 if (!(flags & TO_SYN))
3354 to->to_flags |= TOF_SCALE;
3355 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3357 case TCPOPT_TIMESTAMP:
3358 if (optlen != TCPOLEN_TIMESTAMP)
3360 to->to_flags |= TOF_TS;
3361 bcopy((char *)cp + 2,
3362 (char *)&to->to_tsval, sizeof(to->to_tsval));
3363 to->to_tsval = ntohl(to->to_tsval);
3364 bcopy((char *)cp + 6,
3365 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3366 to->to_tsecr = ntohl(to->to_tsecr);
3368 case TCPOPT_SIGNATURE:
3370 * In order to reply to a host which has set the
3371 * TCP_SIGNATURE option in its initial SYN, we have
3372 * to record the fact that the option was observed
3373 * here for the syncache code to perform the correct
3376 if (optlen != TCPOLEN_SIGNATURE)
3378 to->to_flags |= TOF_SIGNATURE;
3379 to->to_signature = cp + 2;
3381 case TCPOPT_SACK_PERMITTED:
3382 if (optlen != TCPOLEN_SACK_PERMITTED)
3384 if (!(flags & TO_SYN))
3388 to->to_flags |= TOF_SACKPERM;
3391 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3395 to->to_flags |= TOF_SACK;
3396 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3397 to->to_sacks = cp + 2;
3398 TCPSTAT_INC(tcps_sack_rcv_blocks);
3400 case TCPOPT_FAST_OPEN:
3402 * Cookie length validation is performed by the
3403 * server side cookie checking code or the client
3404 * side cookie cache update code.
3406 if (!(flags & TO_SYN))
3408 if (!V_tcp_fastopen_client_enable &&
3409 !V_tcp_fastopen_server_enable)
3411 to->to_flags |= TOF_FASTOPEN;
3412 to->to_tfo_len = optlen - 2;
3413 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL;
3422 * Pull out of band byte out of a segment so
3423 * it doesn't appear in the user's data queue.
3424 * It is still reflected in the segment length for
3425 * sequencing purposes.
3428 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3431 int cnt = off + th->th_urp - 1;
3434 if (m->m_len > cnt) {
3435 char *cp = mtod(m, caddr_t) + cnt;
3436 struct tcpcb *tp = sototcpcb(so);
3438 INP_WLOCK_ASSERT(tp->t_inpcb);
3441 tp->t_oobflags |= TCPOOB_HAVEDATA;
3442 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3444 if (m->m_flags & M_PKTHDR)
3453 panic("tcp_pulloutofband");
3457 * Collect new round-trip time estimate
3458 * and update averages and current timeout.
3461 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3465 INP_WLOCK_ASSERT(tp->t_inpcb);
3467 TCPSTAT_INC(tcps_rttupdated);
3469 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) {
3471 * srtt is stored as fixed point with 5 bits after the
3472 * binary point (i.e., scaled by 8). The following magic
3473 * is equivalent to the smoothing algorithm in rfc793 with
3474 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3475 * point). Adjust rtt to origin 0.
3477 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3478 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3480 if ((tp->t_srtt += delta) <= 0)
3484 * We accumulate a smoothed rtt variance (actually, a
3485 * smoothed mean difference), then set the retransmit
3486 * timer to smoothed rtt + 4 times the smoothed variance.
3487 * rttvar is stored as fixed point with 4 bits after the
3488 * binary point (scaled by 16). The following is
3489 * equivalent to rfc793 smoothing with an alpha of .75
3490 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3491 * rfc793's wired-in beta.
3495 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3496 if ((tp->t_rttvar += delta) <= 0)
3498 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3499 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3502 * No rtt measurement yet - use the unsmoothed rtt.
3503 * Set the variance to half the rtt (so our first
3504 * retransmit happens at 3*rtt).
3506 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3507 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3508 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3514 * the retransmit should happen at rtt + 4 * rttvar.
3515 * Because of the way we do the smoothing, srtt and rttvar
3516 * will each average +1/2 tick of bias. When we compute
3517 * the retransmit timer, we want 1/2 tick of rounding and
3518 * 1 extra tick because of +-1/2 tick uncertainty in the
3519 * firing of the timer. The bias will give us exactly the
3520 * 1.5 tick we need. But, because the bias is
3521 * statistical, we have to test that we don't drop below
3522 * the minimum feasible timer (which is 2 ticks).
3524 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3525 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3528 * We received an ack for a packet that wasn't retransmitted;
3529 * it is probably safe to discard any error indications we've
3530 * received recently. This isn't quite right, but close enough
3531 * for now (a route might have failed after we sent a segment,
3532 * and the return path might not be symmetrical).
3534 tp->t_softerror = 0;
3538 * Determine a reasonable value for maxseg size.
3539 * If the route is known, check route for mtu.
3540 * If none, use an mss that can be handled on the outgoing interface
3541 * without forcing IP to fragment. If no route is found, route has no mtu,
3542 * or the destination isn't local, use a default, hopefully conservative
3543 * size (usually 512 or the default IP max size, but no more than the mtu
3544 * of the interface), as we can't discover anything about intervening
3545 * gateways or networks. We also initialize the congestion/slow start
3546 * window to be a single segment if the destination isn't local.
3547 * While looking at the routing entry, we also initialize other path-dependent
3548 * parameters from pre-set or cached values in the routing entry.
3550 * NOTE that resulting t_maxseg doesn't include space for TCP options or
3551 * IP options, e.g. IPSEC data, since length of this data may vary, and
3552 * thus it is calculated for every segment separately in tcp_output().
3554 * NOTE that this routine is only called when we process an incoming
3555 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3556 * settings are handled in tcp_mssopt().
3559 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3560 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3563 uint32_t maxmtu = 0;
3564 struct inpcb *inp = tp->t_inpcb;
3565 struct hc_metrics_lite metrics;
3567 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3568 size_t min_protoh = isipv6 ?
3569 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3570 sizeof (struct tcpiphdr);
3572 const size_t min_protoh = sizeof(struct tcpiphdr);
3575 INP_WLOCK_ASSERT(tp->t_inpcb);
3577 if (mtuoffer != -1) {
3578 KASSERT(offer == -1, ("%s: conflict", __func__));
3579 offer = mtuoffer - min_protoh;
3585 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3586 tp->t_maxseg = V_tcp_v6mssdflt;
3589 #if defined(INET) && defined(INET6)
3594 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3595 tp->t_maxseg = V_tcp_mssdflt;
3600 * No route to sender, stay with default mss and return.
3604 * In case we return early we need to initialize metrics
3605 * to a defined state as tcp_hc_get() would do for us
3606 * if there was no cache hit.
3608 if (metricptr != NULL)
3609 bzero(metricptr, sizeof(struct hc_metrics_lite));
3613 /* What have we got? */
3617 * Offer == 0 means that there was no MSS on the SYN
3618 * segment, in this case we use tcp_mssdflt as
3619 * already assigned to t_maxseg above.
3621 offer = tp->t_maxseg;
3626 * Offer == -1 means that we didn't receive SYN yet.
3632 * Prevent DoS attack with too small MSS. Round up
3633 * to at least minmss.
3635 offer = max(offer, V_tcp_minmss);
3639 * rmx information is now retrieved from tcp_hostcache.
3641 tcp_hc_get(&inp->inp_inc, &metrics);
3642 if (metricptr != NULL)
3643 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3646 * If there's a discovered mtu in tcp hostcache, use it.
3647 * Else, use the link mtu.
3649 if (metrics.rmx_mtu)
3650 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3654 mss = maxmtu - min_protoh;
3655 if (!V_path_mtu_discovery &&
3656 !in6_localaddr(&inp->in6p_faddr))
3657 mss = min(mss, V_tcp_v6mssdflt);
3660 #if defined(INET) && defined(INET6)
3665 mss = maxmtu - min_protoh;
3666 if (!V_path_mtu_discovery &&
3667 !in_localaddr(inp->inp_faddr))
3668 mss = min(mss, V_tcp_mssdflt);
3672 * XXX - The above conditional (mss = maxmtu - min_protoh)
3673 * probably violates the TCP spec.
3674 * The problem is that, since we don't know the
3675 * other end's MSS, we are supposed to use a conservative
3676 * default. But, if we do that, then MTU discovery will
3677 * never actually take place, because the conservative
3678 * default is much less than the MTUs typically seen
3679 * on the Internet today. For the moment, we'll sweep
3680 * this under the carpet.
3682 * The conservative default might not actually be a problem
3683 * if the only case this occurs is when sending an initial
3684 * SYN with options and data to a host we've never talked
3685 * to before. Then, they will reply with an MSS value which
3686 * will get recorded and the new parameters should get
3687 * recomputed. For Further Study.
3690 mss = min(mss, offer);
3693 * Sanity check: make sure that maxseg will be large
3694 * enough to allow some data on segments even if the
3695 * all the option space is used (40bytes). Otherwise
3696 * funny things may happen in tcp_output.
3698 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3706 tcp_mss(struct tcpcb *tp, int offer)
3712 struct hc_metrics_lite metrics;
3713 struct tcp_ifcap cap;
3715 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3717 bzero(&cap, sizeof(cap));
3718 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3724 * If there's a pipesize, change the socket buffer to that size,
3725 * don't change if sb_hiwat is different than default (then it
3726 * has been changed on purpose with setsockopt).
3727 * Make the socket buffers an integral number of mss units;
3728 * if the mss is larger than the socket buffer, decrease the mss.
3730 so = inp->inp_socket;
3731 SOCKBUF_LOCK(&so->so_snd);
3732 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3733 bufsize = metrics.rmx_sendpipe;
3735 bufsize = so->so_snd.sb_hiwat;
3739 bufsize = roundup(bufsize, mss);
3740 if (bufsize > sb_max)
3742 if (bufsize > so->so_snd.sb_hiwat)
3743 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3745 SOCKBUF_UNLOCK(&so->so_snd);
3747 * Sanity check: make sure that maxseg will be large
3748 * enough to allow some data on segments even if the
3749 * all the option space is used (40bytes). Otherwise
3750 * funny things may happen in tcp_output.
3752 * XXXGL: shouldn't we reserve space for IP/IPv6 options?
3754 tp->t_maxseg = max(mss, 64);
3756 SOCKBUF_LOCK(&so->so_rcv);
3757 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3758 bufsize = metrics.rmx_recvpipe;
3760 bufsize = so->so_rcv.sb_hiwat;
3761 if (bufsize > mss) {
3762 bufsize = roundup(bufsize, mss);
3763 if (bufsize > sb_max)
3765 if (bufsize > so->so_rcv.sb_hiwat)
3766 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3768 SOCKBUF_UNLOCK(&so->so_rcv);
3770 /* Check the interface for TSO capabilities. */
3771 if (cap.ifcap & CSUM_TSO) {
3772 tp->t_flags |= TF_TSO;
3773 tp->t_tsomax = cap.tsomax;
3774 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3775 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3780 * Determine the MSS option to send on an outgoing SYN.
3783 tcp_mssopt(struct in_conninfo *inc)
3786 uint32_t thcmtu = 0;
3787 uint32_t maxmtu = 0;
3790 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3793 if (inc->inc_flags & INC_ISIPV6) {
3794 mss = V_tcp_v6mssdflt;
3795 maxmtu = tcp_maxmtu6(inc, NULL);
3796 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3799 #if defined(INET) && defined(INET6)
3804 mss = V_tcp_mssdflt;
3805 maxmtu = tcp_maxmtu(inc, NULL);
3806 min_protoh = sizeof(struct tcpiphdr);
3809 #if defined(INET6) || defined(INET)
3810 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3813 if (maxmtu && thcmtu)
3814 mss = min(maxmtu, thcmtu) - min_protoh;
3815 else if (maxmtu || thcmtu)
3816 mss = max(maxmtu, thcmtu) - min_protoh;
3823 * On a partial ack arrives, force the retransmission of the
3824 * next unacknowledged segment. Do not clear tp->t_dupacks.
3825 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3829 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3831 tcp_seq onxt = tp->snd_nxt;
3832 uint32_t ocwnd = tp->snd_cwnd;
3833 u_int maxseg = tcp_maxseg(tp);
3835 INP_WLOCK_ASSERT(tp->t_inpcb);
3837 tcp_timer_activate(tp, TT_REXMT, 0);
3839 tp->snd_nxt = th->th_ack;
3841 * Set snd_cwnd to one segment beyond acknowledged offset.
3842 * (tp->snd_una has not yet been updated when this function is called.)
3844 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th);
3845 tp->t_flags |= TF_ACKNOW;
3846 (void) tp->t_fb->tfb_tcp_output(tp);
3847 tp->snd_cwnd = ocwnd;
3848 if (SEQ_GT(onxt, tp->snd_nxt))
3851 * Partial window deflation. Relies on fact that tp->snd_una
3854 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3855 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3858 tp->snd_cwnd += maxseg;
3862 tcp_compute_pipe(struct tcpcb *tp)
3864 return (tp->snd_max - tp->snd_una +
3865 tp->sackhint.sack_bytes_rexmit -
3866 tp->sackhint.sacked_bytes);
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