2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 2007-2008,2010
5 * Swinburne University of Technology, Melbourne, Australia.
6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
7 * Copyright (c) 2010 The FreeBSD Foundation
8 * Copyright (c) 2010-2011 Juniper Networks, Inc.
11 * Portions of this software were developed at the Centre for Advanced Internet
12 * Architectures, Swinburne University of Technology, by Lawrence Stewart,
13 * James Healy and David Hayes, made possible in part by a grant from the Cisco
14 * University Research Program Fund at Community Foundation Silicon Valley.
16 * Portions of this software were developed at the Centre for Advanced
17 * Internet Architectures, Swinburne University of Technology, Melbourne,
18 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
20 * Portions of this software were developed by Robert N. M. Watson under
21 * contract to Juniper Networks, Inc.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 4. Neither the name of the University nor the names of its contributors
32 * may be used to endorse or promote products derived from this software
33 * without specific prior written permission.
35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
50 #include <sys/cdefs.h>
51 __FBSDID("$FreeBSD$");
53 #include "opt_ipfw.h" /* for ipfw_fwd */
55 #include "opt_inet6.h"
56 #include "opt_ipsec.h"
57 #include "opt_tcpdebug.h"
59 #include <sys/param.h>
60 #include <sys/kernel.h>
61 #include <sys/hhook.h>
62 #include <sys/malloc.h>
64 #include <sys/proc.h> /* for proc0 declaration */
65 #include <sys/protosw.h>
67 #include <sys/signalvar.h>
68 #include <sys/socket.h>
69 #include <sys/socketvar.h>
70 #include <sys/sysctl.h>
71 #include <sys/syslog.h>
72 #include <sys/systm.h>
74 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
79 #include <net/if_var.h>
80 #include <net/route.h>
83 #define TCPSTATES /* for logging */
85 #include <netinet/cc.h>
86 #include <netinet/in.h>
87 #include <netinet/in_kdtrace.h>
88 #include <netinet/in_pcb.h>
89 #include <netinet/in_systm.h>
90 #include <netinet/in_var.h>
91 #include <netinet/ip.h>
92 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
93 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
94 #include <netinet/ip_var.h>
95 #include <netinet/ip_options.h>
96 #include <netinet/ip6.h>
97 #include <netinet/icmp6.h>
98 #include <netinet6/in6_pcb.h>
99 #include <netinet6/ip6_var.h>
100 #include <netinet6/nd6.h>
101 #include <netinet/tcp_fsm.h>
102 #include <netinet/tcp_seq.h>
103 #include <netinet/tcp_timer.h>
104 #include <netinet/tcp_var.h>
105 #include <netinet6/tcp6_var.h>
106 #include <netinet/tcpip.h>
107 #include <netinet/tcp_syncache.h>
109 #include <netinet/tcp_debug.h>
110 #endif /* TCPDEBUG */
112 #include <netinet/tcp_offload.h>
116 #include <netipsec/ipsec.h>
117 #include <netipsec/ipsec6.h>
120 #include <machine/in_cksum.h>
122 #include <security/mac/mac_framework.h>
124 const int tcprexmtthresh = 3;
126 int tcp_log_in_vain = 0;
127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
129 "Log all incoming TCP segments to closed ports");
131 VNET_DEFINE(int, blackhole) = 0;
132 #define V_blackhole VNET(blackhole)
133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW,
134 &VNET_NAME(blackhole), 0,
135 "Do not send RST on segments to closed ports");
137 VNET_DEFINE(int, tcp_delack_enabled) = 1;
138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW,
139 &VNET_NAME(tcp_delack_enabled), 0,
140 "Delay ACK to try and piggyback it onto a data packet");
142 VNET_DEFINE(int, drop_synfin) = 0;
143 #define V_drop_synfin VNET(drop_synfin)
144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW,
145 &VNET_NAME(drop_synfin), 0,
146 "Drop TCP packets with SYN+FIN set");
148 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
149 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW,
151 &VNET_NAME(tcp_do_rfc3042), 0,
152 "Enable RFC 3042 (Limited Transmit)");
154 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW,
156 &VNET_NAME(tcp_do_rfc3390), 0,
157 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
159 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0,
160 "Experimental TCP extensions");
162 VNET_DEFINE(int, tcp_do_initcwnd10) = 1;
163 SYSCTL_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_VNET | CTLFLAG_RW,
164 &VNET_NAME(tcp_do_initcwnd10), 0,
165 "Enable RFC 6928 (Increasing initial CWND to 10)");
167 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW,
169 &VNET_NAME(tcp_do_rfc3465), 0,
170 "Enable RFC 3465 (Appropriate Byte Counting)");
172 VNET_DEFINE(int, tcp_abc_l_var) = 2;
173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW,
174 &VNET_NAME(tcp_abc_l_var), 2,
175 "Cap the max cwnd increment during slow-start to this number of segments");
177 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
179 VNET_DEFINE(int, tcp_do_ecn) = 0;
180 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
181 &VNET_NAME(tcp_do_ecn), 0,
184 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
185 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW,
186 &VNET_NAME(tcp_ecn_maxretries), 0,
187 "Max retries before giving up on ECN");
189 VNET_DEFINE(int, tcp_insecure_syn) = 0;
190 #define V_tcp_insecure_syn VNET(tcp_insecure_syn)
191 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW,
192 &VNET_NAME(tcp_insecure_syn), 0,
193 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets");
195 VNET_DEFINE(int, tcp_insecure_rst) = 0;
196 #define V_tcp_insecure_rst VNET(tcp_insecure_rst)
197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW,
198 &VNET_NAME(tcp_insecure_rst), 0,
199 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets");
201 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
202 #define V_tcp_recvspace VNET(tcp_recvspace)
203 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW,
204 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
206 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
207 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf)
208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
209 &VNET_NAME(tcp_do_autorcvbuf), 0,
210 "Enable automatic receive buffer sizing");
212 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
213 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc)
214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
215 &VNET_NAME(tcp_autorcvbuf_inc), 0,
216 "Incrementor step size of automatic receive buffer");
218 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
219 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max)
220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
221 &VNET_NAME(tcp_autorcvbuf_max), 0,
222 "Max size of automatic receive buffer");
224 VNET_DEFINE(struct inpcbhead, tcb);
225 #define tcb6 tcb /* for KAME src sync over BSD*'s */
226 VNET_DEFINE(struct inpcbinfo, tcbinfo);
228 static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
229 static void tcp_do_segment(struct mbuf *, struct tcphdr *,
230 struct socket *, struct tcpcb *, int, int, uint8_t,
232 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *,
233 struct tcpcb *, int, int);
234 static void tcp_pulloutofband(struct socket *,
235 struct tcphdr *, struct mbuf *, int);
236 static void tcp_xmit_timer(struct tcpcb *, int);
237 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
238 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
240 static void inline cc_conn_init(struct tcpcb *tp);
241 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
242 static void inline hhook_run_tcp_est_in(struct tcpcb *tp,
243 struct tcphdr *th, struct tcpopt *to);
246 * TCP statistics are stored in an "array" of counter(9)s.
248 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
249 VNET_PCPUSTAT_SYSINIT(tcpstat);
250 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
251 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
254 VNET_PCPUSTAT_SYSUNINIT(tcpstat);
257 * Kernel module interface for updating tcpstat. The argument is an index
258 * into tcpstat treated as an array.
261 kmod_tcpstat_inc(int statnum)
264 counter_u64_add(VNET(tcpstat)[statnum], 1);
268 * Wrapper for the TCP established input helper hook.
271 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
273 struct tcp_hhook_data hhook_data;
275 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
280 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
286 * CC wrapper hook functions
289 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
291 INP_WLOCK_ASSERT(tp->t_inpcb);
293 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
294 if (tp->snd_cwnd <= tp->snd_wnd)
295 tp->ccv->flags |= CCF_CWND_LIMITED;
297 tp->ccv->flags &= ~CCF_CWND_LIMITED;
299 if (type == CC_ACK) {
300 if (tp->snd_cwnd > tp->snd_ssthresh) {
301 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
302 V_tcp_abc_l_var * tp->t_maxseg);
303 if (tp->t_bytes_acked >= tp->snd_cwnd) {
304 tp->t_bytes_acked -= tp->snd_cwnd;
305 tp->ccv->flags |= CCF_ABC_SENTAWND;
308 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
309 tp->t_bytes_acked = 0;
313 if (CC_ALGO(tp)->ack_received != NULL) {
314 /* XXXLAS: Find a way to live without this */
315 tp->ccv->curack = th->th_ack;
316 CC_ALGO(tp)->ack_received(tp->ccv, type);
321 cc_conn_init(struct tcpcb *tp)
323 struct hc_metrics_lite metrics;
324 struct inpcb *inp = tp->t_inpcb;
327 INP_WLOCK_ASSERT(tp->t_inpcb);
329 tcp_hc_get(&inp->inp_inc, &metrics);
331 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
333 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
334 TCPSTAT_INC(tcps_usedrtt);
335 if (metrics.rmx_rttvar) {
336 tp->t_rttvar = metrics.rmx_rttvar;
337 TCPSTAT_INC(tcps_usedrttvar);
339 /* default variation is +- 1 rtt */
341 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
343 TCPT_RANGESET(tp->t_rxtcur,
344 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
345 tp->t_rttmin, TCPTV_REXMTMAX);
347 if (metrics.rmx_ssthresh) {
349 * There's some sort of gateway or interface
350 * buffer limit on the path. Use this to set
351 * the slow start threshhold, but set the
352 * threshold to no less than 2*mss.
354 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
355 TCPSTAT_INC(tcps_usedssthresh);
359 * Set the initial slow-start flight size.
361 * RFC5681 Section 3.1 specifies the default conservative values.
362 * RFC3390 specifies slightly more aggressive values.
363 * RFC6928 increases it to ten segments.
365 * If a SYN or SYN/ACK was lost and retransmitted, we have to
366 * reduce the initial CWND to one segment as congestion is likely
367 * requiring us to be cautious.
369 if (tp->snd_cwnd == 1)
370 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */
371 else if (V_tcp_do_initcwnd10)
372 tp->snd_cwnd = min(10 * tp->t_maxseg,
373 max(2 * tp->t_maxseg, 14600));
374 else if (V_tcp_do_rfc3390)
375 tp->snd_cwnd = min(4 * tp->t_maxseg,
376 max(2 * tp->t_maxseg, 4380));
378 /* Per RFC5681 Section 3.1 */
379 if (tp->t_maxseg > 2190)
380 tp->snd_cwnd = 2 * tp->t_maxseg;
381 else if (tp->t_maxseg > 1095)
382 tp->snd_cwnd = 3 * tp->t_maxseg;
384 tp->snd_cwnd = 4 * tp->t_maxseg;
387 if (CC_ALGO(tp)->conn_init != NULL)
388 CC_ALGO(tp)->conn_init(tp->ccv);
392 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
394 INP_WLOCK_ASSERT(tp->t_inpcb);
398 if (!IN_FASTRECOVERY(tp->t_flags)) {
399 tp->snd_recover = tp->snd_max;
400 if (tp->t_flags & TF_ECN_PERMIT)
401 tp->t_flags |= TF_ECN_SND_CWR;
405 if (!IN_CONGRECOVERY(tp->t_flags)) {
406 TCPSTAT_INC(tcps_ecn_rcwnd);
407 tp->snd_recover = tp->snd_max;
408 if (tp->t_flags & TF_ECN_PERMIT)
409 tp->t_flags |= TF_ECN_SND_CWR;
414 tp->t_bytes_acked = 0;
415 EXIT_RECOVERY(tp->t_flags);
416 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
417 tp->t_maxseg) * tp->t_maxseg;
418 tp->snd_cwnd = tp->t_maxseg;
421 TCPSTAT_INC(tcps_sndrexmitbad);
422 /* RTO was unnecessary, so reset everything. */
423 tp->snd_cwnd = tp->snd_cwnd_prev;
424 tp->snd_ssthresh = tp->snd_ssthresh_prev;
425 tp->snd_recover = tp->snd_recover_prev;
426 if (tp->t_flags & TF_WASFRECOVERY)
427 ENTER_FASTRECOVERY(tp->t_flags);
428 if (tp->t_flags & TF_WASCRECOVERY)
429 ENTER_CONGRECOVERY(tp->t_flags);
430 tp->snd_nxt = tp->snd_max;
431 tp->t_flags &= ~TF_PREVVALID;
436 if (CC_ALGO(tp)->cong_signal != NULL) {
438 tp->ccv->curack = th->th_ack;
439 CC_ALGO(tp)->cong_signal(tp->ccv, type);
444 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
446 INP_WLOCK_ASSERT(tp->t_inpcb);
448 /* XXXLAS: KASSERT that we're in recovery? */
450 if (CC_ALGO(tp)->post_recovery != NULL) {
451 tp->ccv->curack = th->th_ack;
452 CC_ALGO(tp)->post_recovery(tp->ccv);
454 /* XXXLAS: EXIT_RECOVERY ? */
455 tp->t_bytes_acked = 0;
460 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
461 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
465 tcp_fields_to_net(th);
466 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
467 tcp_fields_to_host(th);
472 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
474 #define ND6_HINT(tp) \
476 if ((tp) && (tp)->t_inpcb && \
477 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
478 nd6_nud_hint(NULL, NULL, 0); \
485 * Indicate whether this ack should be delayed. We can delay the ack if
486 * following conditions are met:
487 * - There is no delayed ack timer in progress.
488 * - Our last ack wasn't a 0-sized window. We never want to delay
489 * the ack that opens up a 0-sized window.
490 * - LRO wasn't used for this segment. We make sure by checking that the
491 * segment size is not larger than the MSS.
492 * - Delayed acks are enabled or this is a half-synchronized T/TCP
495 #define DELAY_ACK(tp, tlen) \
496 ((!tcp_timer_active(tp, TT_DELACK) && \
497 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
498 (tlen <= tp->t_maxopd) && \
499 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
502 * TCP input handling is split into multiple parts:
503 * tcp6_input is a thin wrapper around tcp_input for the extended
504 * ip6_protox[] call format in ip6_input
505 * tcp_input handles primary segment validation, inpcb lookup and
506 * SYN processing on listen sockets
507 * tcp_do_segment processes the ACK and text of the segment for
508 * establishing, established and closing connections
512 tcp6_input(struct mbuf **mp, int *offp, int proto)
514 struct mbuf *m = *mp;
515 struct in6_ifaddr *ia6;
518 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
521 * draft-itojun-ipv6-tcp-to-anycast
522 * better place to put this in?
524 ip6 = mtod(m, struct ip6_hdr *);
525 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
526 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
529 ifa_free(&ia6->ia_ifa);
530 ip6 = mtod(m, struct ip6_hdr *);
531 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
532 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
533 return (IPPROTO_DONE);
536 ifa_free(&ia6->ia_ifa);
538 return (tcp_input(mp, offp, proto));
543 tcp_input(struct mbuf **mp, int *offp, int proto)
545 struct mbuf *m = *mp;
546 struct tcphdr *th = NULL;
547 struct ip *ip = NULL;
548 struct inpcb *inp = NULL;
549 struct tcpcb *tp = NULL;
550 struct socket *so = NULL;
560 int rstreason = 0; /* For badport_bandlim accounting purposes */
562 uint8_t sig_checked = 0;
565 struct m_tag *fwd_tag = NULL;
567 struct ip6_hdr *ip6 = NULL;
570 const void *ip6 = NULL;
572 struct tcpopt to; /* options in this segment */
573 char *s = NULL; /* address and port logging */
575 #define TI_UNLOCKED 1
580 * The size of tcp_saveipgen must be the size of the max ip header,
583 u_char tcp_saveipgen[IP6_HDR_LEN];
584 struct tcphdr tcp_savetcp;
589 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
596 TCPSTAT_INC(tcps_rcvtotal);
600 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
602 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
603 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
605 TCPSTAT_INC(tcps_rcvshort);
606 return (IPPROTO_DONE);
610 ip6 = mtod(m, struct ip6_hdr *);
611 th = (struct tcphdr *)((caddr_t)ip6 + off0);
612 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
613 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
614 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
615 th->th_sum = m->m_pkthdr.csum_data;
617 th->th_sum = in6_cksum_pseudo(ip6, tlen,
618 IPPROTO_TCP, m->m_pkthdr.csum_data);
619 th->th_sum ^= 0xffff;
621 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
623 TCPSTAT_INC(tcps_rcvbadsum);
628 * Be proactive about unspecified IPv6 address in source.
629 * As we use all-zero to indicate unbounded/unconnected pcb,
630 * unspecified IPv6 address can be used to confuse us.
632 * Note that packets with unspecified IPv6 destination is
633 * already dropped in ip6_input.
635 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
641 #if defined(INET) && defined(INET6)
647 * Get IP and TCP header together in first mbuf.
648 * Note: IP leaves IP header in first mbuf.
650 if (off0 > sizeof (struct ip)) {
652 off0 = sizeof(struct ip);
654 if (m->m_len < sizeof (struct tcpiphdr)) {
655 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
657 TCPSTAT_INC(tcps_rcvshort);
658 return (IPPROTO_DONE);
661 ip = mtod(m, struct ip *);
662 th = (struct tcphdr *)((caddr_t)ip + off0);
663 tlen = ntohs(ip->ip_len) - off0;
665 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
666 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
667 th->th_sum = m->m_pkthdr.csum_data;
669 th->th_sum = in_pseudo(ip->ip_src.s_addr,
671 htonl(m->m_pkthdr.csum_data + tlen +
673 th->th_sum ^= 0xffff;
675 struct ipovly *ipov = (struct ipovly *)ip;
678 * Checksum extended TCP header and data.
681 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
682 ipov->ih_len = htons(tlen);
683 th->th_sum = in_cksum(m, len);
684 /* Reset length for SDT probes. */
685 ip->ip_len = htons(tlen + off0);
689 TCPSTAT_INC(tcps_rcvbadsum);
692 /* Re-initialization for later version check */
693 ip->ip_v = IPVERSION;
699 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
701 #if defined(INET) && defined(INET6)
709 * Check that TCP offset makes sense,
710 * pull out TCP options and adjust length. XXX
712 off = th->th_off << 2;
713 if (off < sizeof (struct tcphdr) || off > tlen) {
714 TCPSTAT_INC(tcps_rcvbadoff);
717 tlen -= off; /* tlen is used instead of ti->ti_len */
718 if (off > sizeof (struct tcphdr)) {
721 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
722 ip6 = mtod(m, struct ip6_hdr *);
723 th = (struct tcphdr *)((caddr_t)ip6 + off0);
726 #if defined(INET) && defined(INET6)
731 if (m->m_len < sizeof(struct ip) + off) {
732 if ((m = m_pullup(m, sizeof (struct ip) + off))
734 TCPSTAT_INC(tcps_rcvshort);
735 return (IPPROTO_DONE);
737 ip = mtod(m, struct ip *);
738 th = (struct tcphdr *)((caddr_t)ip + off0);
742 optlen = off - sizeof (struct tcphdr);
743 optp = (u_char *)(th + 1);
745 thflags = th->th_flags;
748 * Convert TCP protocol specific fields to host format.
750 tcp_fields_to_host(th);
753 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
755 drop_hdrlen = off0 + off;
758 * Locate pcb for segment; if we're likely to add or remove a
759 * connection then first acquire pcbinfo lock. There are three cases
760 * where we might discover later we need a write lock despite the
761 * flags: ACKs moving a connection out of the syncache, ACKs for a
762 * connection in TIMEWAIT and SYNs not targeting a listening socket.
764 if ((thflags & (TH_FIN | TH_RST)) != 0) {
765 INP_INFO_WLOCK(&V_tcbinfo);
766 ti_locked = TI_WLOCKED;
768 ti_locked = TI_UNLOCKED;
771 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
775 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
777 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
780 #if defined(INET) && !defined(INET6)
781 (m->m_flags & M_IP_NEXTHOP)
784 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
788 if (ti_locked == TI_WLOCKED) {
789 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
791 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
795 if (isipv6 && fwd_tag != NULL) {
796 struct sockaddr_in6 *next_hop6;
798 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
800 * Transparently forwarded. Pretend to be the destination.
801 * Already got one like this?
803 inp = in6_pcblookup_mbuf(&V_tcbinfo,
804 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
805 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
808 * It's new. Try to find the ambushing socket.
809 * Because we've rewritten the destination address,
810 * any hardware-generated hash is ignored.
812 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
813 th->th_sport, &next_hop6->sin6_addr,
814 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
815 th->th_dport, INPLOOKUP_WILDCARD |
816 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
819 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
820 th->th_sport, &ip6->ip6_dst, th->th_dport,
821 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
822 m->m_pkthdr.rcvif, m);
825 #if defined(INET6) && defined(INET)
829 if (fwd_tag != NULL) {
830 struct sockaddr_in *next_hop;
832 next_hop = (struct sockaddr_in *)(fwd_tag+1);
834 * Transparently forwarded. Pretend to be the destination.
835 * already got one like this?
837 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
838 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
839 m->m_pkthdr.rcvif, m);
842 * It's new. Try to find the ambushing socket.
843 * Because we've rewritten the destination address,
844 * any hardware-generated hash is ignored.
846 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
847 th->th_sport, next_hop->sin_addr,
848 next_hop->sin_port ? ntohs(next_hop->sin_port) :
849 th->th_dport, INPLOOKUP_WILDCARD |
850 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
853 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
854 th->th_sport, ip->ip_dst, th->th_dport,
855 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
856 m->m_pkthdr.rcvif, m);
860 * If the INPCB does not exist then all data in the incoming
861 * segment is discarded and an appropriate RST is sent back.
862 * XXX MRT Send RST using which routing table?
866 * Log communication attempts to ports that are not
869 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
870 tcp_log_in_vain == 2) {
871 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
872 log(LOG_INFO, "%s; %s: Connection attempt "
873 "to closed port\n", s, __func__);
876 * When blackholing do not respond with a RST but
877 * completely ignore the segment and drop it.
879 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
883 rstreason = BANDLIM_RST_CLOSEDPORT;
886 INP_WLOCK_ASSERT(inp);
887 if (!(inp->inp_flags & INP_HW_FLOWID)
888 && (m->m_flags & M_FLOWID)
889 && ((inp->inp_socket == NULL)
890 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
891 inp->inp_flags |= INP_HW_FLOWID;
892 inp->inp_flags &= ~INP_SW_FLOWID;
893 inp->inp_flowid = m->m_pkthdr.flowid;
894 inp->inp_flowtype = M_HASHTYPE_GET(m);
898 if (isipv6 && ipsec6_in_reject(m, inp)) {
899 IPSEC6STAT_INC(ips_in_polvio);
903 if (ipsec4_in_reject(m, inp) != 0) {
904 IPSECSTAT_INC(ips_in_polvio);
910 * Check the minimum TTL for socket.
912 if (inp->inp_ip_minttl != 0) {
914 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
918 if (inp->inp_ip_minttl > ip->ip_ttl)
923 * A previous connection in TIMEWAIT state is supposed to catch stray
924 * or duplicate segments arriving late. If this segment was a
925 * legitimate new connection attempt, the old INPCB gets removed and
926 * we can try again to find a listening socket.
928 * At this point, due to earlier optimism, we may hold only an inpcb
929 * lock, and not the inpcbinfo write lock. If so, we need to try to
930 * acquire it, or if that fails, acquire a reference on the inpcb,
931 * drop all locks, acquire a global write lock, and then re-acquire
932 * the inpcb lock. We may at that point discover that another thread
933 * has tried to free the inpcb, in which case we need to loop back
934 * and try to find a new inpcb to deliver to.
936 * XXXRW: It may be time to rethink timewait locking.
939 if (inp->inp_flags & INP_TIMEWAIT) {
940 if (ti_locked == TI_UNLOCKED) {
941 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
944 INP_INFO_WLOCK(&V_tcbinfo);
945 ti_locked = TI_WLOCKED;
947 if (in_pcbrele_wlocked(inp)) {
952 ti_locked = TI_WLOCKED;
954 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
956 if (thflags & TH_SYN)
957 tcp_dooptions(&to, optp, optlen, TO_SYN);
959 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
961 if (tcp_twcheck(inp, &to, th, m, tlen))
963 INP_INFO_WUNLOCK(&V_tcbinfo);
964 return (IPPROTO_DONE);
967 * The TCPCB may no longer exist if the connection is winding
968 * down or it is in the CLOSED state. Either way we drop the
969 * segment and send an appropriate response.
972 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
973 rstreason = BANDLIM_RST_CLOSEDPORT;
978 if (tp->t_flags & TF_TOE) {
979 tcp_offload_input(tp, m);
980 m = NULL; /* consumed by the TOE driver */
986 * We've identified a valid inpcb, but it could be that we need an
987 * inpcbinfo write lock but don't hold it. In this case, attempt to
988 * acquire using the same strategy as the TIMEWAIT case above. If we
989 * relock, we have to jump back to 'relocked' as the connection might
990 * now be in TIMEWAIT.
993 if ((thflags & (TH_FIN | TH_RST)) != 0)
994 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
996 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) ||
997 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN)))) {
998 if (ti_locked == TI_UNLOCKED) {
999 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
1002 INP_INFO_WLOCK(&V_tcbinfo);
1003 ti_locked = TI_WLOCKED;
1005 if (in_pcbrele_wlocked(inp)) {
1011 ti_locked = TI_WLOCKED;
1013 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1017 INP_WLOCK_ASSERT(inp);
1018 if (mac_inpcb_check_deliver(inp, m))
1021 so = inp->inp_socket;
1022 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1024 if (so->so_options & SO_DEBUG) {
1025 ostate = tp->t_state;
1028 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1031 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1034 #endif /* TCPDEBUG */
1036 * When the socket is accepting connections (the INPCB is in LISTEN
1037 * state) we look into the SYN cache if this is a new connection
1038 * attempt or the completion of a previous one.
1040 if (so->so_options & SO_ACCEPTCONN) {
1041 struct in_conninfo inc;
1043 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
1044 "tp not listening", __func__));
1045 bzero(&inc, sizeof(inc));
1048 inc.inc_flags |= INC_ISIPV6;
1049 inc.inc6_faddr = ip6->ip6_src;
1050 inc.inc6_laddr = ip6->ip6_dst;
1054 inc.inc_faddr = ip->ip_src;
1055 inc.inc_laddr = ip->ip_dst;
1057 inc.inc_fport = th->th_sport;
1058 inc.inc_lport = th->th_dport;
1059 inc.inc_fibnum = so->so_fibnum;
1062 * Check for an existing connection attempt in syncache if
1063 * the flag is only ACK. A successful lookup creates a new
1064 * socket appended to the listen queue in SYN_RECEIVED state.
1066 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1068 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1070 * Parse the TCP options here because
1071 * syncookies need access to the reflected
1074 tcp_dooptions(&to, optp, optlen, 0);
1076 * NB: syncache_expand() doesn't unlock
1077 * inp and tcpinfo locks.
1079 if (!syncache_expand(&inc, &to, th, &so, m)) {
1081 * No syncache entry or ACK was not
1082 * for our SYN/ACK. Send a RST.
1083 * NB: syncache did its own logging
1084 * of the failure cause.
1086 rstreason = BANDLIM_RST_OPENPORT;
1091 * We completed the 3-way handshake
1092 * but could not allocate a socket
1093 * either due to memory shortage,
1094 * listen queue length limits or
1095 * global socket limits. Send RST
1096 * or wait and have the remote end
1097 * retransmit the ACK for another
1100 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1101 log(LOG_DEBUG, "%s; %s: Listen socket: "
1102 "Socket allocation failed due to "
1103 "limits or memory shortage, %s\n",
1105 V_tcp_sc_rst_sock_fail ?
1106 "sending RST" : "try again");
1107 if (V_tcp_sc_rst_sock_fail) {
1108 rstreason = BANDLIM_UNLIMITED;
1114 * Socket is created in state SYN_RECEIVED.
1115 * Unlock the listen socket, lock the newly
1116 * created socket and update the tp variable.
1118 INP_WUNLOCK(inp); /* listen socket */
1119 inp = sotoinpcb(so);
1120 INP_WLOCK(inp); /* new connection */
1121 tp = intotcpcb(inp);
1122 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1123 ("%s: ", __func__));
1124 #ifdef TCP_SIGNATURE
1125 if (sig_checked == 0) {
1126 tcp_dooptions(&to, optp, optlen,
1127 (thflags & TH_SYN) ? TO_SYN : 0);
1128 if (!tcp_signature_verify_input(m, off0, tlen,
1129 optlen, &to, th, tp->t_flags)) {
1132 * In SYN_SENT state if it receives an
1133 * RST, it is allowed for further
1136 if ((thflags & TH_RST) == 0 ||
1137 (tp->t_state == TCPS_SYN_SENT) == 0)
1145 * Process the segment and the data it
1146 * contains. tcp_do_segment() consumes
1147 * the mbuf chain and unlocks the inpcb.
1149 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1151 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1152 return (IPPROTO_DONE);
1155 * Segment flag validation for new connection attempts:
1157 * Our (SYN|ACK) response was rejected.
1158 * Check with syncache and remove entry to prevent
1161 * NB: syncache_chkrst does its own logging of failure
1164 if (thflags & TH_RST) {
1165 syncache_chkrst(&inc, th);
1169 * We can't do anything without SYN.
1171 if ((thflags & TH_SYN) == 0) {
1172 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1173 log(LOG_DEBUG, "%s; %s: Listen socket: "
1174 "SYN is missing, segment ignored\n",
1176 TCPSTAT_INC(tcps_badsyn);
1180 * (SYN|ACK) is bogus on a listen socket.
1182 if (thflags & TH_ACK) {
1183 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1184 log(LOG_DEBUG, "%s; %s: Listen socket: "
1185 "SYN|ACK invalid, segment rejected\n",
1187 syncache_badack(&inc); /* XXX: Not needed! */
1188 TCPSTAT_INC(tcps_badsyn);
1189 rstreason = BANDLIM_RST_OPENPORT;
1193 * If the drop_synfin option is enabled, drop all
1194 * segments with both the SYN and FIN bits set.
1195 * This prevents e.g. nmap from identifying the
1197 * XXX: Poor reasoning. nmap has other methods
1198 * and is constantly refining its stack detection
1200 * XXX: This is a violation of the TCP specification
1201 * and was used by RFC1644.
1203 if ((thflags & TH_FIN) && V_drop_synfin) {
1204 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1205 log(LOG_DEBUG, "%s; %s: Listen socket: "
1206 "SYN|FIN segment ignored (based on "
1207 "sysctl setting)\n", s, __func__);
1208 TCPSTAT_INC(tcps_badsyn);
1212 * Segment's flags are (SYN) or (SYN|FIN).
1214 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1215 * as they do not affect the state of the TCP FSM.
1216 * The data pointed to by TH_URG and th_urp is ignored.
1218 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1219 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1220 KASSERT(thflags & (TH_SYN),
1221 ("%s: Listen socket: TH_SYN not set", __func__));
1224 * If deprecated address is forbidden,
1225 * we do not accept SYN to deprecated interface
1226 * address to prevent any new inbound connection from
1227 * getting established.
1228 * When we do not accept SYN, we send a TCP RST,
1229 * with deprecated source address (instead of dropping
1230 * it). We compromise it as it is much better for peer
1231 * to send a RST, and RST will be the final packet
1234 * If we do not forbid deprecated addresses, we accept
1235 * the SYN packet. RFC2462 does not suggest dropping
1237 * If we decipher RFC2462 5.5.4, it says like this:
1238 * 1. use of deprecated addr with existing
1239 * communication is okay - "SHOULD continue to be
1241 * 2. use of it with new communication:
1242 * (2a) "SHOULD NOT be used if alternate address
1243 * with sufficient scope is available"
1244 * (2b) nothing mentioned otherwise.
1245 * Here we fall into (2b) case as we have no choice in
1246 * our source address selection - we must obey the peer.
1248 * The wording in RFC2462 is confusing, and there are
1249 * multiple description text for deprecated address
1250 * handling - worse, they are not exactly the same.
1251 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1253 if (isipv6 && !V_ip6_use_deprecated) {
1254 struct in6_ifaddr *ia6;
1256 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
1258 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1259 ifa_free(&ia6->ia_ifa);
1260 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1261 log(LOG_DEBUG, "%s; %s: Listen socket: "
1262 "Connection attempt to deprecated "
1263 "IPv6 address rejected\n",
1265 rstreason = BANDLIM_RST_OPENPORT;
1269 ifa_free(&ia6->ia_ifa);
1273 * Basic sanity checks on incoming SYN requests:
1274 * Don't respond if the destination is a link layer
1275 * broadcast according to RFC1122 4.2.3.10, p. 104.
1276 * If it is from this socket it must be forged.
1277 * Don't respond if the source or destination is a
1278 * global or subnet broad- or multicast address.
1279 * Note that it is quite possible to receive unicast
1280 * link-layer packets with a broadcast IP address. Use
1281 * in_broadcast() to find them.
1283 if (m->m_flags & (M_BCAST|M_MCAST)) {
1284 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1285 log(LOG_DEBUG, "%s; %s: Listen socket: "
1286 "Connection attempt from broad- or multicast "
1287 "link layer address ignored\n", s, __func__);
1292 if (th->th_dport == th->th_sport &&
1293 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1294 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1295 log(LOG_DEBUG, "%s; %s: Listen socket: "
1296 "Connection attempt to/from self "
1297 "ignored\n", s, __func__);
1300 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1301 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1302 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1303 log(LOG_DEBUG, "%s; %s: Listen socket: "
1304 "Connection attempt from/to multicast "
1305 "address ignored\n", s, __func__);
1310 #if defined(INET) && defined(INET6)
1315 if (th->th_dport == th->th_sport &&
1316 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1317 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1318 log(LOG_DEBUG, "%s; %s: Listen socket: "
1319 "Connection attempt from/to self "
1320 "ignored\n", s, __func__);
1323 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1324 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1325 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1326 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1327 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1328 log(LOG_DEBUG, "%s; %s: Listen socket: "
1329 "Connection attempt from/to broad- "
1330 "or multicast address ignored\n",
1337 * SYN appears to be valid. Create compressed TCP state
1341 if (so->so_options & SO_DEBUG)
1342 tcp_trace(TA_INPUT, ostate, tp,
1343 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1345 tcp_dooptions(&to, optp, optlen, TO_SYN);
1346 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL);
1348 * Entry added to syncache and mbuf consumed.
1349 * Only the listen socket is unlocked by syncache_add().
1351 if (ti_locked == TI_WLOCKED) {
1352 INP_INFO_WUNLOCK(&V_tcbinfo);
1353 ti_locked = TI_UNLOCKED;
1355 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1356 return (IPPROTO_DONE);
1357 } else if (tp->t_state == TCPS_LISTEN) {
1359 * When a listen socket is torn down the SO_ACCEPTCONN
1360 * flag is removed first while connections are drained
1361 * from the accept queue in a unlock/lock cycle of the
1362 * ACCEPT_LOCK, opening a race condition allowing a SYN
1363 * attempt go through unhandled.
1368 #ifdef TCP_SIGNATURE
1369 if (sig_checked == 0) {
1370 tcp_dooptions(&to, optp, optlen,
1371 (thflags & TH_SYN) ? TO_SYN : 0);
1372 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
1376 * In SYN_SENT state if it receives an RST, it is
1377 * allowed for further processing.
1379 if ((thflags & TH_RST) == 0 ||
1380 (tp->t_state == TCPS_SYN_SENT) == 0)
1387 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1390 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1391 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1392 * the inpcb, and unlocks pcbinfo.
1394 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1395 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1396 return (IPPROTO_DONE);
1399 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1401 if (ti_locked == TI_WLOCKED) {
1402 INP_INFO_WUNLOCK(&V_tcbinfo);
1403 ti_locked = TI_UNLOCKED;
1407 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1408 "ti_locked: %d", __func__, ti_locked));
1409 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1414 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1417 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1418 m = NULL; /* mbuf chain got consumed. */
1423 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1425 if (ti_locked == TI_WLOCKED) {
1426 INP_INFO_WUNLOCK(&V_tcbinfo);
1427 ti_locked = TI_UNLOCKED;
1431 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1432 "ti_locked: %d", __func__, ti_locked));
1433 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1441 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1446 return (IPPROTO_DONE);
1450 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1451 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1454 int thflags, acked, ourfinisacked, needoutput = 0;
1455 int rstreason, todrop, win;
1458 struct in_conninfo *inc;
1464 * The size of tcp_saveipgen must be the size of the max ip header,
1467 u_char tcp_saveipgen[IP6_HDR_LEN];
1468 struct tcphdr tcp_savetcp;
1471 thflags = th->th_flags;
1472 inc = &tp->t_inpcb->inp_inc;
1473 tp->sackhint.last_sack_ack = 0;
1476 * If this is either a state-changing packet or current state isn't
1477 * established, we require a write lock on tcbinfo. Otherwise, we
1478 * allow the tcbinfo to be in either alocked or unlocked, as the
1479 * caller may have unnecessarily acquired a write lock due to a race.
1481 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1482 tp->t_state != TCPS_ESTABLISHED) {
1483 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
1484 "SYN/FIN/RST/!EST", __func__, ti_locked));
1485 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1488 if (ti_locked == TI_WLOCKED)
1489 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1491 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1492 "ti_locked: %d", __func__, ti_locked));
1493 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1497 INP_WLOCK_ASSERT(tp->t_inpcb);
1498 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1500 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1504 * Segment received on connection.
1505 * Reset idle time and keep-alive timer.
1506 * XXX: This should be done after segment
1507 * validation to ignore broken/spoofed segs.
1509 tp->t_rcvtime = ticks;
1510 if (TCPS_HAVEESTABLISHED(tp->t_state))
1511 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1514 * Unscale the window into a 32-bit value.
1515 * For the SYN_SENT state the scale is zero.
1517 tiwin = th->th_win << tp->snd_scale;
1520 * TCP ECN processing.
1522 if (tp->t_flags & TF_ECN_PERMIT) {
1523 if (thflags & TH_CWR)
1524 tp->t_flags &= ~TF_ECN_SND_ECE;
1525 switch (iptos & IPTOS_ECN_MASK) {
1527 tp->t_flags |= TF_ECN_SND_ECE;
1528 TCPSTAT_INC(tcps_ecn_ce);
1530 case IPTOS_ECN_ECT0:
1531 TCPSTAT_INC(tcps_ecn_ect0);
1533 case IPTOS_ECN_ECT1:
1534 TCPSTAT_INC(tcps_ecn_ect1);
1537 /* Congestion experienced. */
1538 if (thflags & TH_ECE) {
1539 cc_cong_signal(tp, th, CC_ECN);
1544 * Parse options on any incoming segment.
1546 tcp_dooptions(&to, (u_char *)(th + 1),
1547 (th->th_off << 2) - sizeof(struct tcphdr),
1548 (thflags & TH_SYN) ? TO_SYN : 0);
1551 * If echoed timestamp is later than the current time,
1552 * fall back to non RFC1323 RTT calculation. Normalize
1553 * timestamp if syncookies were used when this connection
1556 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1557 to.to_tsecr -= tp->ts_offset;
1558 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1562 * If timestamps were negotiated during SYN/ACK they should
1563 * appear on every segment during this session and vice versa.
1565 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1566 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1567 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1568 "no action\n", s, __func__);
1572 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1573 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1574 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1575 "no action\n", s, __func__);
1581 * Process options only when we get SYN/ACK back. The SYN case
1582 * for incoming connections is handled in tcp_syncache.
1583 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1584 * or <SYN,ACK>) segment itself is never scaled.
1585 * XXX this is traditional behavior, may need to be cleaned up.
1587 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1588 if ((to.to_flags & TOF_SCALE) &&
1589 (tp->t_flags & TF_REQ_SCALE)) {
1590 tp->t_flags |= TF_RCVD_SCALE;
1591 tp->snd_scale = to.to_wscale;
1594 * Initial send window. It will be updated with
1595 * the next incoming segment to the scaled value.
1597 tp->snd_wnd = th->th_win;
1598 if (to.to_flags & TOF_TS) {
1599 tp->t_flags |= TF_RCVD_TSTMP;
1600 tp->ts_recent = to.to_tsval;
1601 tp->ts_recent_age = tcp_ts_getticks();
1603 if (to.to_flags & TOF_MSS)
1604 tcp_mss(tp, to.to_mss);
1605 if ((tp->t_flags & TF_SACK_PERMIT) &&
1606 (to.to_flags & TOF_SACKPERM) == 0)
1607 tp->t_flags &= ~TF_SACK_PERMIT;
1611 * Header prediction: check for the two common cases
1612 * of a uni-directional data xfer. If the packet has
1613 * no control flags, is in-sequence, the window didn't
1614 * change and we're not retransmitting, it's a
1615 * candidate. If the length is zero and the ack moved
1616 * forward, we're the sender side of the xfer. Just
1617 * free the data acked & wake any higher level process
1618 * that was blocked waiting for space. If the length
1619 * is non-zero and the ack didn't move, we're the
1620 * receiver side. If we're getting packets in-order
1621 * (the reassembly queue is empty), add the data to
1622 * the socket buffer and note that we need a delayed ack.
1623 * Make sure that the hidden state-flags are also off.
1624 * Since we check for TCPS_ESTABLISHED first, it can only
1627 if (tp->t_state == TCPS_ESTABLISHED &&
1628 th->th_seq == tp->rcv_nxt &&
1629 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1630 tp->snd_nxt == tp->snd_max &&
1631 tiwin && tiwin == tp->snd_wnd &&
1632 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1633 tp->t_segq == NULL && ((to.to_flags & TOF_TS) == 0 ||
1634 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1637 * If last ACK falls within this segment's sequence numbers,
1638 * record the timestamp.
1639 * NOTE that the test is modified according to the latest
1640 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1642 if ((to.to_flags & TOF_TS) != 0 &&
1643 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1644 tp->ts_recent_age = tcp_ts_getticks();
1645 tp->ts_recent = to.to_tsval;
1649 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1650 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1651 !IN_RECOVERY(tp->t_flags) &&
1652 (to.to_flags & TOF_SACK) == 0 &&
1653 TAILQ_EMPTY(&tp->snd_holes)) {
1655 * This is a pure ack for outstanding data.
1657 if (ti_locked == TI_WLOCKED)
1658 INP_INFO_WUNLOCK(&V_tcbinfo);
1659 ti_locked = TI_UNLOCKED;
1661 TCPSTAT_INC(tcps_predack);
1664 * "bad retransmit" recovery.
1666 if (tp->t_rxtshift == 1 &&
1667 tp->t_flags & TF_PREVVALID &&
1668 (int)(ticks - tp->t_badrxtwin) < 0) {
1669 cc_cong_signal(tp, th, CC_RTO_ERR);
1673 * Recalculate the transmit timer / rtt.
1675 * Some boxes send broken timestamp replies
1676 * during the SYN+ACK phase, ignore
1677 * timestamps of 0 or we could calculate a
1678 * huge RTT and blow up the retransmit timer.
1680 if ((to.to_flags & TOF_TS) != 0 &&
1684 t = tcp_ts_getticks() - to.to_tsecr;
1685 if (!tp->t_rttlow || tp->t_rttlow > t)
1688 TCP_TS_TO_TICKS(t) + 1);
1689 } else if (tp->t_rtttime &&
1690 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1691 if (!tp->t_rttlow ||
1692 tp->t_rttlow > ticks - tp->t_rtttime)
1693 tp->t_rttlow = ticks - tp->t_rtttime;
1695 ticks - tp->t_rtttime);
1697 acked = BYTES_THIS_ACK(tp, th);
1699 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1700 hhook_run_tcp_est_in(tp, th, &to);
1702 TCPSTAT_INC(tcps_rcvackpack);
1703 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1704 sbdrop(&so->so_snd, acked);
1705 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1706 SEQ_LEQ(th->th_ack, tp->snd_recover))
1707 tp->snd_recover = th->th_ack - 1;
1710 * Let the congestion control algorithm update
1711 * congestion control related information. This
1712 * typically means increasing the congestion
1715 cc_ack_received(tp, th, CC_ACK);
1717 tp->snd_una = th->th_ack;
1719 * Pull snd_wl2 up to prevent seq wrap relative
1722 tp->snd_wl2 = th->th_ack;
1725 ND6_HINT(tp); /* Some progress has been made. */
1728 * If all outstanding data are acked, stop
1729 * retransmit timer, otherwise restart timer
1730 * using current (possibly backed-off) value.
1731 * If process is waiting for space,
1732 * wakeup/selwakeup/signal. If data
1733 * are ready to send, let tcp_output
1734 * decide between more output or persist.
1737 if (so->so_options & SO_DEBUG)
1738 tcp_trace(TA_INPUT, ostate, tp,
1739 (void *)tcp_saveipgen,
1742 if (tp->snd_una == tp->snd_max)
1743 tcp_timer_activate(tp, TT_REXMT, 0);
1744 else if (!tcp_timer_active(tp, TT_PERSIST))
1745 tcp_timer_activate(tp, TT_REXMT,
1748 if (sbavail(&so->so_snd))
1749 (void) tcp_output(tp);
1752 } else if (th->th_ack == tp->snd_una &&
1753 tlen <= sbspace(&so->so_rcv)) {
1754 int newsize = 0; /* automatic sockbuf scaling */
1757 * This is a pure, in-sequence data packet with
1758 * nothing on the reassembly queue and we have enough
1759 * buffer space to take it.
1761 if (ti_locked == TI_WLOCKED)
1762 INP_INFO_WUNLOCK(&V_tcbinfo);
1763 ti_locked = TI_UNLOCKED;
1765 /* Clean receiver SACK report if present */
1766 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1767 tcp_clean_sackreport(tp);
1768 TCPSTAT_INC(tcps_preddat);
1769 tp->rcv_nxt += tlen;
1771 * Pull snd_wl1 up to prevent seq wrap relative to
1774 tp->snd_wl1 = th->th_seq;
1776 * Pull rcv_up up to prevent seq wrap relative to
1779 tp->rcv_up = tp->rcv_nxt;
1780 TCPSTAT_INC(tcps_rcvpack);
1781 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1782 ND6_HINT(tp); /* Some progress has been made */
1784 if (so->so_options & SO_DEBUG)
1785 tcp_trace(TA_INPUT, ostate, tp,
1786 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1789 * Automatic sizing of receive socket buffer. Often the send
1790 * buffer size is not optimally adjusted to the actual network
1791 * conditions at hand (delay bandwidth product). Setting the
1792 * buffer size too small limits throughput on links with high
1793 * bandwidth and high delay (eg. trans-continental/oceanic links).
1795 * On the receive side the socket buffer memory is only rarely
1796 * used to any significant extent. This allows us to be much
1797 * more aggressive in scaling the receive socket buffer. For
1798 * the case that the buffer space is actually used to a large
1799 * extent and we run out of kernel memory we can simply drop
1800 * the new segments; TCP on the sender will just retransmit it
1801 * later. Setting the buffer size too big may only consume too
1802 * much kernel memory if the application doesn't read() from
1803 * the socket or packet loss or reordering makes use of the
1806 * The criteria to step up the receive buffer one notch are:
1807 * 1. Application has not set receive buffer size with
1808 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1809 * 2. the number of bytes received during the time it takes
1810 * one timestamp to be reflected back to us (the RTT);
1811 * 3. received bytes per RTT is within seven eighth of the
1812 * current socket buffer size;
1813 * 4. receive buffer size has not hit maximal automatic size;
1815 * This algorithm does one step per RTT at most and only if
1816 * we receive a bulk stream w/o packet losses or reorderings.
1817 * Shrinking the buffer during idle times is not necessary as
1818 * it doesn't consume any memory when idle.
1820 * TODO: Only step up if the application is actually serving
1821 * the buffer to better manage the socket buffer resources.
1823 if (V_tcp_do_autorcvbuf &&
1825 (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
1826 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
1827 to.to_tsecr - tp->rfbuf_ts < hz) {
1829 (so->so_rcv.sb_hiwat / 8 * 7) &&
1830 so->so_rcv.sb_hiwat <
1831 V_tcp_autorcvbuf_max) {
1833 min(so->so_rcv.sb_hiwat +
1834 V_tcp_autorcvbuf_inc,
1835 V_tcp_autorcvbuf_max);
1837 /* Start over with next RTT. */
1841 tp->rfbuf_cnt += tlen; /* add up */
1844 /* Add data to socket buffer. */
1845 SOCKBUF_LOCK(&so->so_rcv);
1846 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1850 * Set new socket buffer size.
1851 * Give up when limit is reached.
1854 if (!sbreserve_locked(&so->so_rcv,
1856 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1857 m_adj(m, drop_hdrlen); /* delayed header drop */
1858 sbappendstream_locked(&so->so_rcv, m);
1860 /* NB: sorwakeup_locked() does an implicit unlock. */
1861 sorwakeup_locked(so);
1862 if (DELAY_ACK(tp, tlen)) {
1863 tp->t_flags |= TF_DELACK;
1865 tp->t_flags |= TF_ACKNOW;
1873 * Calculate amount of space in receive window,
1874 * and then do TCP input processing.
1875 * Receive window is amount of space in rcv queue,
1876 * but not less than advertised window.
1878 win = sbspace(&so->so_rcv);
1881 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1883 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1887 switch (tp->t_state) {
1890 * If the state is SYN_RECEIVED:
1891 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1893 case TCPS_SYN_RECEIVED:
1894 if ((thflags & TH_ACK) &&
1895 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1896 SEQ_GT(th->th_ack, tp->snd_max))) {
1897 rstreason = BANDLIM_RST_OPENPORT;
1903 * If the state is SYN_SENT:
1904 * if seg contains an ACK, but not for our SYN, drop the input.
1905 * if seg contains a RST, then drop the connection.
1906 * if seg does not contain SYN, then drop it.
1907 * Otherwise this is an acceptable SYN segment
1908 * initialize tp->rcv_nxt and tp->irs
1909 * if seg contains ack then advance tp->snd_una
1910 * if seg contains an ECE and ECN support is enabled, the stream
1912 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1913 * arrange for segment to be acked (eventually)
1914 * continue processing rest of data/controls, beginning with URG
1917 if ((thflags & TH_ACK) &&
1918 (SEQ_LEQ(th->th_ack, tp->iss) ||
1919 SEQ_GT(th->th_ack, tp->snd_max))) {
1920 rstreason = BANDLIM_UNLIMITED;
1923 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1924 TCP_PROBE5(connect__refused, NULL, tp,
1925 mtod(m, const char *), tp, th);
1926 tp = tcp_drop(tp, ECONNREFUSED);
1928 if (thflags & TH_RST)
1930 if (!(thflags & TH_SYN))
1933 tp->irs = th->th_seq;
1935 if (thflags & TH_ACK) {
1936 TCPSTAT_INC(tcps_connects);
1939 mac_socketpeer_set_from_mbuf(m, so);
1941 /* Do window scaling on this connection? */
1942 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1943 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1944 tp->rcv_scale = tp->request_r_scale;
1946 tp->rcv_adv += imin(tp->rcv_wnd,
1947 TCP_MAXWIN << tp->rcv_scale);
1948 tp->snd_una++; /* SYN is acked */
1950 * If there's data, delay ACK; if there's also a FIN
1951 * ACKNOW will be turned on later.
1953 if (DELAY_ACK(tp, tlen) && tlen != 0)
1954 tcp_timer_activate(tp, TT_DELACK,
1957 tp->t_flags |= TF_ACKNOW;
1959 if ((thflags & TH_ECE) && V_tcp_do_ecn) {
1960 tp->t_flags |= TF_ECN_PERMIT;
1961 TCPSTAT_INC(tcps_ecn_shs);
1965 * Received <SYN,ACK> in SYN_SENT[*] state.
1967 * SYN_SENT --> ESTABLISHED
1968 * SYN_SENT* --> FIN_WAIT_1
1970 tp->t_starttime = ticks;
1971 if (tp->t_flags & TF_NEEDFIN) {
1972 tcp_state_change(tp, TCPS_FIN_WAIT_1);
1973 tp->t_flags &= ~TF_NEEDFIN;
1976 tcp_state_change(tp, TCPS_ESTABLISHED);
1977 TCP_PROBE5(connect__established, NULL, tp,
1978 mtod(m, const char *), tp, th);
1980 tcp_timer_activate(tp, TT_KEEP,
1985 * Received initial SYN in SYN-SENT[*] state =>
1986 * simultaneous open.
1987 * If it succeeds, connection is * half-synchronized.
1988 * Otherwise, do 3-way handshake:
1989 * SYN-SENT -> SYN-RECEIVED
1990 * SYN-SENT* -> SYN-RECEIVED*
1992 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1993 tcp_timer_activate(tp, TT_REXMT, 0);
1994 tcp_state_change(tp, TCPS_SYN_RECEIVED);
1997 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
1998 "ti_locked %d", __func__, ti_locked));
1999 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2000 INP_WLOCK_ASSERT(tp->t_inpcb);
2003 * Advance th->th_seq to correspond to first data byte.
2004 * If data, trim to stay within window,
2005 * dropping FIN if necessary.
2008 if (tlen > tp->rcv_wnd) {
2009 todrop = tlen - tp->rcv_wnd;
2013 TCPSTAT_INC(tcps_rcvpackafterwin);
2014 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2016 tp->snd_wl1 = th->th_seq - 1;
2017 tp->rcv_up = th->th_seq;
2019 * Client side of transaction: already sent SYN and data.
2020 * If the remote host used T/TCP to validate the SYN,
2021 * our data will be ACK'd; if so, enter normal data segment
2022 * processing in the middle of step 5, ack processing.
2023 * Otherwise, goto step 6.
2025 if (thflags & TH_ACK)
2031 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2032 * do normal processing.
2034 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2038 break; /* continue normal processing */
2042 * States other than LISTEN or SYN_SENT.
2043 * First check the RST flag and sequence number since reset segments
2044 * are exempt from the timestamp and connection count tests. This
2045 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2046 * below which allowed reset segments in half the sequence space
2047 * to fall though and be processed (which gives forged reset
2048 * segments with a random sequence number a 50 percent chance of
2049 * killing a connection).
2050 * Then check timestamp, if present.
2051 * Then check the connection count, if present.
2052 * Then check that at least some bytes of segment are within
2053 * receive window. If segment begins before rcv_nxt,
2054 * drop leading data (and SYN); if nothing left, just ack.
2056 if (thflags & TH_RST) {
2058 * RFC5961 Section 3.2
2060 * - RST drops connection only if SEG.SEQ == RCV.NXT.
2061 * - If RST is in window, we send challenge ACK.
2063 * Note: to take into account delayed ACKs, we should
2064 * test against last_ack_sent instead of rcv_nxt.
2065 * Note 2: we handle special case of closed window, not
2066 * covered by the RFC.
2068 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2069 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
2070 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
2072 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2073 KASSERT(ti_locked == TI_WLOCKED,
2074 ("%s: TH_RST ti_locked %d, th %p tp %p",
2075 __func__, ti_locked, th, tp));
2076 KASSERT(tp->t_state != TCPS_SYN_SENT,
2077 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
2080 if (V_tcp_insecure_rst ||
2081 tp->last_ack_sent == th->th_seq) {
2082 TCPSTAT_INC(tcps_drops);
2083 /* Drop the connection. */
2084 switch (tp->t_state) {
2085 case TCPS_SYN_RECEIVED:
2086 so->so_error = ECONNREFUSED;
2088 case TCPS_ESTABLISHED:
2089 case TCPS_FIN_WAIT_1:
2090 case TCPS_FIN_WAIT_2:
2091 case TCPS_CLOSE_WAIT:
2092 so->so_error = ECONNRESET;
2094 tcp_state_change(tp, TCPS_CLOSED);
2100 TCPSTAT_INC(tcps_badrst);
2101 /* Send challenge ACK. */
2102 tcp_respond(tp, mtod(m, void *), th, m,
2103 tp->rcv_nxt, tp->snd_nxt, TH_ACK);
2104 tp->last_ack_sent = tp->rcv_nxt;
2112 * RFC5961 Section 4.2
2113 * Send challenge ACK for any SYN in synchronized state.
2115 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT) {
2116 KASSERT(ti_locked == TI_WLOCKED,
2117 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2118 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2120 TCPSTAT_INC(tcps_badsyn);
2121 if (V_tcp_insecure_syn &&
2122 SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2123 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2124 tp = tcp_drop(tp, ECONNRESET);
2125 rstreason = BANDLIM_UNLIMITED;
2127 /* Send challenge ACK. */
2128 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
2129 tp->snd_nxt, TH_ACK);
2130 tp->last_ack_sent = tp->rcv_nxt;
2137 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2138 * and it's less than ts_recent, drop it.
2140 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2141 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2143 /* Check to see if ts_recent is over 24 days old. */
2144 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2146 * Invalidate ts_recent. If this segment updates
2147 * ts_recent, the age will be reset later and ts_recent
2148 * will get a valid value. If it does not, setting
2149 * ts_recent to zero will at least satisfy the
2150 * requirement that zero be placed in the timestamp
2151 * echo reply when ts_recent isn't valid. The
2152 * age isn't reset until we get a valid ts_recent
2153 * because we don't want out-of-order segments to be
2154 * dropped when ts_recent is old.
2158 TCPSTAT_INC(tcps_rcvduppack);
2159 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2160 TCPSTAT_INC(tcps_pawsdrop);
2168 * In the SYN-RECEIVED state, validate that the packet belongs to
2169 * this connection before trimming the data to fit the receive
2170 * window. Check the sequence number versus IRS since we know
2171 * the sequence numbers haven't wrapped. This is a partial fix
2172 * for the "LAND" DoS attack.
2174 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2175 rstreason = BANDLIM_RST_OPENPORT;
2179 todrop = tp->rcv_nxt - th->th_seq;
2181 if (thflags & TH_SYN) {
2191 * Following if statement from Stevens, vol. 2, p. 960.
2194 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2196 * Any valid FIN must be to the left of the window.
2197 * At this point the FIN must be a duplicate or out
2198 * of sequence; drop it.
2203 * Send an ACK to resynchronize and drop any data.
2204 * But keep on processing for RST or ACK.
2206 tp->t_flags |= TF_ACKNOW;
2208 TCPSTAT_INC(tcps_rcvduppack);
2209 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2211 TCPSTAT_INC(tcps_rcvpartduppack);
2212 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2214 drop_hdrlen += todrop; /* drop from the top afterwards */
2215 th->th_seq += todrop;
2217 if (th->th_urp > todrop)
2218 th->th_urp -= todrop;
2226 * If new data are received on a connection after the
2227 * user processes are gone, then RST the other end.
2229 if ((so->so_state & SS_NOFDREF) &&
2230 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2231 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
2232 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2233 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2235 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2236 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2237 "after socket was closed, "
2238 "sending RST and removing tcpcb\n",
2239 s, __func__, tcpstates[tp->t_state], tlen);
2243 TCPSTAT_INC(tcps_rcvafterclose);
2244 rstreason = BANDLIM_UNLIMITED;
2249 * If segment ends after window, drop trailing data
2250 * (and PUSH and FIN); if nothing left, just ACK.
2252 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2254 TCPSTAT_INC(tcps_rcvpackafterwin);
2255 if (todrop >= tlen) {
2256 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2258 * If window is closed can only take segments at
2259 * window edge, and have to drop data and PUSH from
2260 * incoming segments. Continue processing, but
2261 * remember to ack. Otherwise, drop segment
2264 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2265 tp->t_flags |= TF_ACKNOW;
2266 TCPSTAT_INC(tcps_rcvwinprobe);
2270 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2273 thflags &= ~(TH_PUSH|TH_FIN);
2277 * If last ACK falls within this segment's sequence numbers,
2278 * record its timestamp.
2280 * 1) That the test incorporates suggestions from the latest
2281 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2282 * 2) That updating only on newer timestamps interferes with
2283 * our earlier PAWS tests, so this check should be solely
2284 * predicated on the sequence space of this segment.
2285 * 3) That we modify the segment boundary check to be
2286 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2287 * instead of RFC1323's
2288 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2289 * This modified check allows us to overcome RFC1323's
2290 * limitations as described in Stevens TCP/IP Illustrated
2291 * Vol. 2 p.869. In such cases, we can still calculate the
2292 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2294 if ((to.to_flags & TOF_TS) != 0 &&
2295 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2296 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2297 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2298 tp->ts_recent_age = tcp_ts_getticks();
2299 tp->ts_recent = to.to_tsval;
2303 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2304 * flag is on (half-synchronized state), then queue data for
2305 * later processing; else drop segment and return.
2307 if ((thflags & TH_ACK) == 0) {
2308 if (tp->t_state == TCPS_SYN_RECEIVED ||
2309 (tp->t_flags & TF_NEEDSYN))
2311 else if (tp->t_flags & TF_ACKNOW)
2320 switch (tp->t_state) {
2323 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2324 * ESTABLISHED state and continue processing.
2325 * The ACK was checked above.
2327 case TCPS_SYN_RECEIVED:
2329 TCPSTAT_INC(tcps_connects);
2331 /* Do window scaling? */
2332 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2333 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2334 tp->rcv_scale = tp->request_r_scale;
2335 tp->snd_wnd = tiwin;
2339 * SYN-RECEIVED -> ESTABLISHED
2340 * SYN-RECEIVED* -> FIN-WAIT-1
2342 tp->t_starttime = ticks;
2343 if (tp->t_flags & TF_NEEDFIN) {
2344 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2345 tp->t_flags &= ~TF_NEEDFIN;
2347 tcp_state_change(tp, TCPS_ESTABLISHED);
2348 TCP_PROBE5(accept__established, NULL, tp,
2349 mtod(m, const char *), tp, th);
2351 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2354 * If segment contains data or ACK, will call tcp_reass()
2355 * later; if not, do so now to pass queued data to user.
2357 if (tlen == 0 && (thflags & TH_FIN) == 0)
2358 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2360 tp->snd_wl1 = th->th_seq - 1;
2364 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2365 * ACKs. If the ack is in the range
2366 * tp->snd_una < th->th_ack <= tp->snd_max
2367 * then advance tp->snd_una to th->th_ack and drop
2368 * data from the retransmission queue. If this ACK reflects
2369 * more up to date window information we update our window information.
2371 case TCPS_ESTABLISHED:
2372 case TCPS_FIN_WAIT_1:
2373 case TCPS_FIN_WAIT_2:
2374 case TCPS_CLOSE_WAIT:
2377 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2378 TCPSTAT_INC(tcps_rcvacktoomuch);
2381 if ((tp->t_flags & TF_SACK_PERMIT) &&
2382 ((to.to_flags & TOF_SACK) ||
2383 !TAILQ_EMPTY(&tp->snd_holes)))
2384 tcp_sack_doack(tp, &to, th->th_ack);
2386 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2387 hhook_run_tcp_est_in(tp, th, &to);
2389 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2390 if (tlen == 0 && tiwin == tp->snd_wnd) {
2392 * If this is the first time we've seen a
2393 * FIN from the remote, this is not a
2394 * duplicate and it needs to be processed
2395 * normally. This happens during a
2396 * simultaneous close.
2398 if ((thflags & TH_FIN) &&
2399 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2403 TCPSTAT_INC(tcps_rcvdupack);
2405 * If we have outstanding data (other than
2406 * a window probe), this is a completely
2407 * duplicate ack (ie, window info didn't
2408 * change and FIN isn't set),
2409 * the ack is the biggest we've
2410 * seen and we've seen exactly our rexmt
2411 * threshhold of them, assume a packet
2412 * has been dropped and retransmit it.
2413 * Kludge snd_nxt & the congestion
2414 * window so we send only this one
2417 * We know we're losing at the current
2418 * window size so do congestion avoidance
2419 * (set ssthresh to half the current window
2420 * and pull our congestion window back to
2421 * the new ssthresh).
2423 * Dup acks mean that packets have left the
2424 * network (they're now cached at the receiver)
2425 * so bump cwnd by the amount in the receiver
2426 * to keep a constant cwnd packets in the
2429 * When using TCP ECN, notify the peer that
2430 * we reduced the cwnd.
2432 if (!tcp_timer_active(tp, TT_REXMT) ||
2433 th->th_ack != tp->snd_una)
2435 else if (++tp->t_dupacks > tcprexmtthresh ||
2436 IN_FASTRECOVERY(tp->t_flags)) {
2437 cc_ack_received(tp, th, CC_DUPACK);
2438 if ((tp->t_flags & TF_SACK_PERMIT) &&
2439 IN_FASTRECOVERY(tp->t_flags)) {
2443 * Compute the amount of data in flight first.
2444 * We can inject new data into the pipe iff
2445 * we have less than 1/2 the original window's
2446 * worth of data in flight.
2448 awnd = (tp->snd_nxt - tp->snd_fack) +
2449 tp->sackhint.sack_bytes_rexmit;
2450 if (awnd < tp->snd_ssthresh) {
2451 tp->snd_cwnd += tp->t_maxseg;
2452 if (tp->snd_cwnd > tp->snd_ssthresh)
2453 tp->snd_cwnd = tp->snd_ssthresh;
2456 tp->snd_cwnd += tp->t_maxseg;
2457 (void) tcp_output(tp);
2459 } else if (tp->t_dupacks == tcprexmtthresh) {
2460 tcp_seq onxt = tp->snd_nxt;
2463 * If we're doing sack, check to
2464 * see if we're already in sack
2465 * recovery. If we're not doing sack,
2466 * check to see if we're in newreno
2469 if (tp->t_flags & TF_SACK_PERMIT) {
2470 if (IN_FASTRECOVERY(tp->t_flags)) {
2475 if (SEQ_LEQ(th->th_ack,
2481 /* Congestion signal before ack. */
2482 cc_cong_signal(tp, th, CC_NDUPACK);
2483 cc_ack_received(tp, th, CC_DUPACK);
2484 tcp_timer_activate(tp, TT_REXMT, 0);
2486 if (tp->t_flags & TF_SACK_PERMIT) {
2488 tcps_sack_recovery_episode);
2489 tp->sack_newdata = tp->snd_nxt;
2490 tp->snd_cwnd = tp->t_maxseg;
2491 (void) tcp_output(tp);
2494 tp->snd_nxt = th->th_ack;
2495 tp->snd_cwnd = tp->t_maxseg;
2496 (void) tcp_output(tp);
2497 KASSERT(tp->snd_limited <= 2,
2498 ("%s: tp->snd_limited too big",
2500 tp->snd_cwnd = tp->snd_ssthresh +
2502 (tp->t_dupacks - tp->snd_limited);
2503 if (SEQ_GT(onxt, tp->snd_nxt))
2506 } else if (V_tcp_do_rfc3042) {
2507 cc_ack_received(tp, th, CC_DUPACK);
2508 u_long oldcwnd = tp->snd_cwnd;
2509 tcp_seq oldsndmax = tp->snd_max;
2513 KASSERT(tp->t_dupacks == 1 ||
2515 ("%s: dupacks not 1 or 2",
2517 if (tp->t_dupacks == 1)
2518 tp->snd_limited = 0;
2520 (tp->snd_nxt - tp->snd_una) +
2521 (tp->t_dupacks - tp->snd_limited) *
2524 * Only call tcp_output when there
2525 * is new data available to be sent.
2526 * Otherwise we would send pure ACKs.
2528 SOCKBUF_LOCK(&so->so_snd);
2529 avail = sbavail(&so->so_snd) -
2530 (tp->snd_nxt - tp->snd_una);
2531 SOCKBUF_UNLOCK(&so->so_snd);
2533 (void) tcp_output(tp);
2534 sent = tp->snd_max - oldsndmax;
2535 if (sent > tp->t_maxseg) {
2536 KASSERT((tp->t_dupacks == 2 &&
2537 tp->snd_limited == 0) ||
2538 (sent == tp->t_maxseg + 1 &&
2539 tp->t_flags & TF_SENTFIN),
2540 ("%s: sent too much",
2542 tp->snd_limited = 2;
2543 } else if (sent > 0)
2545 tp->snd_cwnd = oldcwnd;
2553 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2554 ("%s: th_ack <= snd_una", __func__));
2557 * If the congestion window was inflated to account
2558 * for the other side's cached packets, retract it.
2560 if (IN_FASTRECOVERY(tp->t_flags)) {
2561 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2562 if (tp->t_flags & TF_SACK_PERMIT)
2563 tcp_sack_partialack(tp, th);
2565 tcp_newreno_partial_ack(tp, th);
2567 cc_post_recovery(tp, th);
2571 * If we reach this point, ACK is not a duplicate,
2572 * i.e., it ACKs something we sent.
2574 if (tp->t_flags & TF_NEEDSYN) {
2576 * T/TCP: Connection was half-synchronized, and our
2577 * SYN has been ACK'd (so connection is now fully
2578 * synchronized). Go to non-starred state,
2579 * increment snd_una for ACK of SYN, and check if
2580 * we can do window scaling.
2582 tp->t_flags &= ~TF_NEEDSYN;
2584 /* Do window scaling? */
2585 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2586 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2587 tp->rcv_scale = tp->request_r_scale;
2588 /* Send window already scaled. */
2593 INP_WLOCK_ASSERT(tp->t_inpcb);
2595 acked = BYTES_THIS_ACK(tp, th);
2596 TCPSTAT_INC(tcps_rcvackpack);
2597 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2600 * If we just performed our first retransmit, and the ACK
2601 * arrives within our recovery window, then it was a mistake
2602 * to do the retransmit in the first place. Recover our
2603 * original cwnd and ssthresh, and proceed to transmit where
2606 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2607 (int)(ticks - tp->t_badrxtwin) < 0)
2608 cc_cong_signal(tp, th, CC_RTO_ERR);
2611 * If we have a timestamp reply, update smoothed
2612 * round trip time. If no timestamp is present but
2613 * transmit timer is running and timed sequence
2614 * number was acked, update smoothed round trip time.
2615 * Since we now have an rtt measurement, cancel the
2616 * timer backoff (cf., Phil Karn's retransmit alg.).
2617 * Recompute the initial retransmit timer.
2619 * Some boxes send broken timestamp replies
2620 * during the SYN+ACK phase, ignore
2621 * timestamps of 0 or we could calculate a
2622 * huge RTT and blow up the retransmit timer.
2624 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2627 t = tcp_ts_getticks() - to.to_tsecr;
2628 if (!tp->t_rttlow || tp->t_rttlow > t)
2630 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2631 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2632 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2633 tp->t_rttlow = ticks - tp->t_rtttime;
2634 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2638 * If all outstanding data is acked, stop retransmit
2639 * timer and remember to restart (more output or persist).
2640 * If there is more data to be acked, restart retransmit
2641 * timer, using current (possibly backed-off) value.
2643 if (th->th_ack == tp->snd_max) {
2644 tcp_timer_activate(tp, TT_REXMT, 0);
2646 } else if (!tcp_timer_active(tp, TT_PERSIST))
2647 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2650 * If no data (only SYN) was ACK'd,
2651 * skip rest of ACK processing.
2657 * Let the congestion control algorithm update congestion
2658 * control related information. This typically means increasing
2659 * the congestion window.
2661 cc_ack_received(tp, th, CC_ACK);
2663 SOCKBUF_LOCK(&so->so_snd);
2664 if (acked > sbavail(&so->so_snd)) {
2665 tp->snd_wnd -= sbavail(&so->so_snd);
2666 mfree = sbcut_locked(&so->so_snd,
2667 (int)sbavail(&so->so_snd));
2670 mfree = sbcut_locked(&so->so_snd, acked);
2671 tp->snd_wnd -= acked;
2674 /* NB: sowwakeup_locked() does an implicit unlock. */
2675 sowwakeup_locked(so);
2677 /* Detect una wraparound. */
2678 if (!IN_RECOVERY(tp->t_flags) &&
2679 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2680 SEQ_LEQ(th->th_ack, tp->snd_recover))
2681 tp->snd_recover = th->th_ack - 1;
2682 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2683 if (IN_RECOVERY(tp->t_flags) &&
2684 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2685 EXIT_RECOVERY(tp->t_flags);
2687 tp->snd_una = th->th_ack;
2688 if (tp->t_flags & TF_SACK_PERMIT) {
2689 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2690 tp->snd_recover = tp->snd_una;
2692 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2693 tp->snd_nxt = tp->snd_una;
2695 switch (tp->t_state) {
2698 * In FIN_WAIT_1 STATE in addition to the processing
2699 * for the ESTABLISHED state if our FIN is now acknowledged
2700 * then enter FIN_WAIT_2.
2702 case TCPS_FIN_WAIT_1:
2703 if (ourfinisacked) {
2705 * If we can't receive any more
2706 * data, then closing user can proceed.
2707 * Starting the timer is contrary to the
2708 * specification, but if we don't get a FIN
2709 * we'll hang forever.
2712 * we should release the tp also, and use a
2715 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2716 soisdisconnected(so);
2717 tcp_timer_activate(tp, TT_2MSL,
2718 (tcp_fast_finwait2_recycle ?
2719 tcp_finwait2_timeout :
2722 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2727 * In CLOSING STATE in addition to the processing for
2728 * the ESTABLISHED state if the ACK acknowledges our FIN
2729 * then enter the TIME-WAIT state, otherwise ignore
2733 if (ourfinisacked) {
2734 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2736 INP_INFO_WUNLOCK(&V_tcbinfo);
2743 * In LAST_ACK, we may still be waiting for data to drain
2744 * and/or to be acked, as well as for the ack of our FIN.
2745 * If our FIN is now acknowledged, delete the TCB,
2746 * enter the closed state and return.
2749 if (ourfinisacked) {
2750 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2759 INP_WLOCK_ASSERT(tp->t_inpcb);
2762 * Update window information.
2763 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2765 if ((thflags & TH_ACK) &&
2766 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2767 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2768 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2769 /* keep track of pure window updates */
2771 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2772 TCPSTAT_INC(tcps_rcvwinupd);
2773 tp->snd_wnd = tiwin;
2774 tp->snd_wl1 = th->th_seq;
2775 tp->snd_wl2 = th->th_ack;
2776 if (tp->snd_wnd > tp->max_sndwnd)
2777 tp->max_sndwnd = tp->snd_wnd;
2782 * Process segments with URG.
2784 if ((thflags & TH_URG) && th->th_urp &&
2785 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2787 * This is a kludge, but if we receive and accept
2788 * random urgent pointers, we'll crash in
2789 * soreceive. It's hard to imagine someone
2790 * actually wanting to send this much urgent data.
2792 SOCKBUF_LOCK(&so->so_rcv);
2793 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
2794 th->th_urp = 0; /* XXX */
2795 thflags &= ~TH_URG; /* XXX */
2796 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2797 goto dodata; /* XXX */
2800 * If this segment advances the known urgent pointer,
2801 * then mark the data stream. This should not happen
2802 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2803 * a FIN has been received from the remote side.
2804 * In these states we ignore the URG.
2806 * According to RFC961 (Assigned Protocols),
2807 * the urgent pointer points to the last octet
2808 * of urgent data. We continue, however,
2809 * to consider it to indicate the first octet
2810 * of data past the urgent section as the original
2811 * spec states (in one of two places).
2813 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2814 tp->rcv_up = th->th_seq + th->th_urp;
2815 so->so_oobmark = sbavail(&so->so_rcv) +
2816 (tp->rcv_up - tp->rcv_nxt) - 1;
2817 if (so->so_oobmark == 0)
2818 so->so_rcv.sb_state |= SBS_RCVATMARK;
2820 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2822 SOCKBUF_UNLOCK(&so->so_rcv);
2824 * Remove out of band data so doesn't get presented to user.
2825 * This can happen independent of advancing the URG pointer,
2826 * but if two URG's are pending at once, some out-of-band
2827 * data may creep in... ick.
2829 if (th->th_urp <= (u_long)tlen &&
2830 !(so->so_options & SO_OOBINLINE)) {
2831 /* hdr drop is delayed */
2832 tcp_pulloutofband(so, th, m, drop_hdrlen);
2836 * If no out of band data is expected,
2837 * pull receive urgent pointer along
2838 * with the receive window.
2840 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2841 tp->rcv_up = tp->rcv_nxt;
2844 INP_WLOCK_ASSERT(tp->t_inpcb);
2847 * Process the segment text, merging it into the TCP sequencing queue,
2848 * and arranging for acknowledgment of receipt if necessary.
2849 * This process logically involves adjusting tp->rcv_wnd as data
2850 * is presented to the user (this happens in tcp_usrreq.c,
2851 * case PRU_RCVD). If a FIN has already been received on this
2852 * connection then we just ignore the text.
2854 if ((tlen || (thflags & TH_FIN)) &&
2855 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2856 tcp_seq save_start = th->th_seq;
2857 m_adj(m, drop_hdrlen); /* delayed header drop */
2859 * Insert segment which includes th into TCP reassembly queue
2860 * with control block tp. Set thflags to whether reassembly now
2861 * includes a segment with FIN. This handles the common case
2862 * inline (segment is the next to be received on an established
2863 * connection, and the queue is empty), avoiding linkage into
2864 * and removal from the queue and repetition of various
2866 * Set DELACK for segments received in order, but ack
2867 * immediately when segments are out of order (so
2868 * fast retransmit can work).
2870 if (th->th_seq == tp->rcv_nxt && tp->t_segq == NULL &&
2871 TCPS_HAVEESTABLISHED(tp->t_state)) {
2872 if (DELAY_ACK(tp, tlen))
2873 tp->t_flags |= TF_DELACK;
2875 tp->t_flags |= TF_ACKNOW;
2876 tp->rcv_nxt += tlen;
2877 thflags = th->th_flags & TH_FIN;
2878 TCPSTAT_INC(tcps_rcvpack);
2879 TCPSTAT_ADD(tcps_rcvbyte, tlen);
2881 SOCKBUF_LOCK(&so->so_rcv);
2882 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2885 sbappendstream_locked(&so->so_rcv, m);
2886 /* NB: sorwakeup_locked() does an implicit unlock. */
2887 sorwakeup_locked(so);
2890 * XXX: Due to the header drop above "th" is
2891 * theoretically invalid by now. Fortunately
2892 * m_adj() doesn't actually frees any mbufs
2893 * when trimming from the head.
2895 thflags = tcp_reass(tp, th, &tlen, m);
2896 tp->t_flags |= TF_ACKNOW;
2898 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2899 tcp_update_sack_list(tp, save_start, save_start + tlen);
2902 * Note the amount of data that peer has sent into
2903 * our window, in order to estimate the sender's
2907 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2908 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2910 len = so->so_rcv.sb_hiwat;
2918 * If FIN is received ACK the FIN and let the user know
2919 * that the connection is closing.
2921 if (thflags & TH_FIN) {
2922 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2925 * If connection is half-synchronized
2926 * (ie NEEDSYN flag on) then delay ACK,
2927 * so it may be piggybacked when SYN is sent.
2928 * Otherwise, since we received a FIN then no
2929 * more input can be expected, send ACK now.
2931 if (tp->t_flags & TF_NEEDSYN)
2932 tp->t_flags |= TF_DELACK;
2934 tp->t_flags |= TF_ACKNOW;
2937 switch (tp->t_state) {
2940 * In SYN_RECEIVED and ESTABLISHED STATES
2941 * enter the CLOSE_WAIT state.
2943 case TCPS_SYN_RECEIVED:
2944 tp->t_starttime = ticks;
2946 case TCPS_ESTABLISHED:
2947 tcp_state_change(tp, TCPS_CLOSE_WAIT);
2951 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2952 * enter the CLOSING state.
2954 case TCPS_FIN_WAIT_1:
2955 tcp_state_change(tp, TCPS_CLOSING);
2959 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2960 * starting the time-wait timer, turning off the other
2963 case TCPS_FIN_WAIT_2:
2964 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2965 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
2966 "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
2970 INP_INFO_WUNLOCK(&V_tcbinfo);
2974 if (ti_locked == TI_WLOCKED)
2975 INP_INFO_WUNLOCK(&V_tcbinfo);
2976 ti_locked = TI_UNLOCKED;
2979 if (so->so_options & SO_DEBUG)
2980 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
2985 * Return any desired output.
2987 if (needoutput || (tp->t_flags & TF_ACKNOW))
2988 (void) tcp_output(tp);
2991 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
2992 __func__, ti_locked));
2993 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
2994 INP_WLOCK_ASSERT(tp->t_inpcb);
2996 if (tp->t_flags & TF_DELACK) {
2997 tp->t_flags &= ~TF_DELACK;
2998 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3000 INP_WUNLOCK(tp->t_inpcb);
3005 * Generate an ACK dropping incoming segment if it occupies
3006 * sequence space, where the ACK reflects our state.
3008 * We can now skip the test for the RST flag since all
3009 * paths to this code happen after packets containing
3010 * RST have been dropped.
3012 * In the SYN-RECEIVED state, don't send an ACK unless the
3013 * segment we received passes the SYN-RECEIVED ACK test.
3014 * If it fails send a RST. This breaks the loop in the
3015 * "LAND" DoS attack, and also prevents an ACK storm
3016 * between two listening ports that have been sent forged
3017 * SYN segments, each with the source address of the other.
3019 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3020 (SEQ_GT(tp->snd_una, th->th_ack) ||
3021 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3022 rstreason = BANDLIM_RST_OPENPORT;
3026 if (so->so_options & SO_DEBUG)
3027 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3030 if (ti_locked == TI_WLOCKED)
3031 INP_INFO_WUNLOCK(&V_tcbinfo);
3032 ti_locked = TI_UNLOCKED;
3034 tp->t_flags |= TF_ACKNOW;
3035 (void) tcp_output(tp);
3036 INP_WUNLOCK(tp->t_inpcb);
3041 if (ti_locked == TI_WLOCKED)
3042 INP_INFO_WUNLOCK(&V_tcbinfo);
3043 ti_locked = TI_UNLOCKED;
3046 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3047 INP_WUNLOCK(tp->t_inpcb);
3049 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3053 if (ti_locked == TI_WLOCKED) {
3054 INP_INFO_WUNLOCK(&V_tcbinfo);
3055 ti_locked = TI_UNLOCKED;
3059 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3063 * Drop space held by incoming segment and return.
3066 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3067 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3071 INP_WUNLOCK(tp->t_inpcb);
3076 * Issue RST and make ACK acceptable to originator of segment.
3077 * The mbuf must still include the original packet header.
3081 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3082 int tlen, int rstreason)
3088 struct ip6_hdr *ip6;
3092 INP_WLOCK_ASSERT(tp->t_inpcb);
3095 /* Don't bother if destination was broadcast/multicast. */
3096 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3099 if (mtod(m, struct ip *)->ip_v == 6) {
3100 ip6 = mtod(m, struct ip6_hdr *);
3101 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3102 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3104 /* IPv6 anycast check is done at tcp6_input() */
3107 #if defined(INET) && defined(INET6)
3112 ip = mtod(m, struct ip *);
3113 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3114 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3115 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3116 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3121 /* Perform bandwidth limiting. */
3122 if (badport_bandlim(rstreason) < 0)
3125 /* tcp_respond consumes the mbuf chain. */
3126 if (th->th_flags & TH_ACK) {
3127 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3128 th->th_ack, TH_RST);
3130 if (th->th_flags & TH_SYN)
3132 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3133 (tcp_seq)0, TH_RST|TH_ACK);
3141 * Parse TCP options and place in tcpopt.
3144 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3149 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3151 if (opt == TCPOPT_EOL)
3153 if (opt == TCPOPT_NOP)
3159 if (optlen < 2 || optlen > cnt)
3164 if (optlen != TCPOLEN_MAXSEG)
3166 if (!(flags & TO_SYN))
3168 to->to_flags |= TOF_MSS;
3169 bcopy((char *)cp + 2,
3170 (char *)&to->to_mss, sizeof(to->to_mss));
3171 to->to_mss = ntohs(to->to_mss);
3174 if (optlen != TCPOLEN_WINDOW)
3176 if (!(flags & TO_SYN))
3178 to->to_flags |= TOF_SCALE;
3179 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3181 case TCPOPT_TIMESTAMP:
3182 if (optlen != TCPOLEN_TIMESTAMP)
3184 to->to_flags |= TOF_TS;
3185 bcopy((char *)cp + 2,
3186 (char *)&to->to_tsval, sizeof(to->to_tsval));
3187 to->to_tsval = ntohl(to->to_tsval);
3188 bcopy((char *)cp + 6,
3189 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3190 to->to_tsecr = ntohl(to->to_tsecr);
3192 #ifdef TCP_SIGNATURE
3194 * XXX In order to reply to a host which has set the
3195 * TCP_SIGNATURE option in its initial SYN, we have to
3196 * record the fact that the option was observed here
3197 * for the syncache code to perform the correct response.
3199 case TCPOPT_SIGNATURE:
3200 if (optlen != TCPOLEN_SIGNATURE)
3202 to->to_flags |= TOF_SIGNATURE;
3203 to->to_signature = cp + 2;
3206 case TCPOPT_SACK_PERMITTED:
3207 if (optlen != TCPOLEN_SACK_PERMITTED)
3209 if (!(flags & TO_SYN))
3213 to->to_flags |= TOF_SACKPERM;
3216 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3220 to->to_flags |= TOF_SACK;
3221 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3222 to->to_sacks = cp + 2;
3223 TCPSTAT_INC(tcps_sack_rcv_blocks);
3232 * Pull out of band byte out of a segment so
3233 * it doesn't appear in the user's data queue.
3234 * It is still reflected in the segment length for
3235 * sequencing purposes.
3238 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3241 int cnt = off + th->th_urp - 1;
3244 if (m->m_len > cnt) {
3245 char *cp = mtod(m, caddr_t) + cnt;
3246 struct tcpcb *tp = sototcpcb(so);
3248 INP_WLOCK_ASSERT(tp->t_inpcb);
3251 tp->t_oobflags |= TCPOOB_HAVEDATA;
3252 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3254 if (m->m_flags & M_PKTHDR)
3263 panic("tcp_pulloutofband");
3267 * Collect new round-trip time estimate
3268 * and update averages and current timeout.
3271 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3275 INP_WLOCK_ASSERT(tp->t_inpcb);
3277 TCPSTAT_INC(tcps_rttupdated);
3279 if (tp->t_srtt != 0) {
3281 * srtt is stored as fixed point with 5 bits after the
3282 * binary point (i.e., scaled by 8). The following magic
3283 * is equivalent to the smoothing algorithm in rfc793 with
3284 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3285 * point). Adjust rtt to origin 0.
3287 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3288 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3290 if ((tp->t_srtt += delta) <= 0)
3294 * We accumulate a smoothed rtt variance (actually, a
3295 * smoothed mean difference), then set the retransmit
3296 * timer to smoothed rtt + 4 times the smoothed variance.
3297 * rttvar is stored as fixed point with 4 bits after the
3298 * binary point (scaled by 16). The following is
3299 * equivalent to rfc793 smoothing with an alpha of .75
3300 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3301 * rfc793's wired-in beta.
3305 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3306 if ((tp->t_rttvar += delta) <= 0)
3308 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3309 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3312 * No rtt measurement yet - use the unsmoothed rtt.
3313 * Set the variance to half the rtt (so our first
3314 * retransmit happens at 3*rtt).
3316 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3317 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3318 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3324 * the retransmit should happen at rtt + 4 * rttvar.
3325 * Because of the way we do the smoothing, srtt and rttvar
3326 * will each average +1/2 tick of bias. When we compute
3327 * the retransmit timer, we want 1/2 tick of rounding and
3328 * 1 extra tick because of +-1/2 tick uncertainty in the
3329 * firing of the timer. The bias will give us exactly the
3330 * 1.5 tick we need. But, because the bias is
3331 * statistical, we have to test that we don't drop below
3332 * the minimum feasible timer (which is 2 ticks).
3334 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3335 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3338 * We received an ack for a packet that wasn't retransmitted;
3339 * it is probably safe to discard any error indications we've
3340 * received recently. This isn't quite right, but close enough
3341 * for now (a route might have failed after we sent a segment,
3342 * and the return path might not be symmetrical).
3344 tp->t_softerror = 0;
3348 * Determine a reasonable value for maxseg size.
3349 * If the route is known, check route for mtu.
3350 * If none, use an mss that can be handled on the outgoing interface
3351 * without forcing IP to fragment. If no route is found, route has no mtu,
3352 * or the destination isn't local, use a default, hopefully conservative
3353 * size (usually 512 or the default IP max size, but no more than the mtu
3354 * of the interface), as we can't discover anything about intervening
3355 * gateways or networks. We also initialize the congestion/slow start
3356 * window to be a single segment if the destination isn't local.
3357 * While looking at the routing entry, we also initialize other path-dependent
3358 * parameters from pre-set or cached values in the routing entry.
3360 * Also take into account the space needed for options that we
3361 * send regularly. Make maxseg shorter by that amount to assure
3362 * that we can send maxseg amount of data even when the options
3363 * are present. Store the upper limit of the length of options plus
3366 * NOTE that this routine is only called when we process an incoming
3367 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3368 * settings are handled in tcp_mssopt().
3371 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3372 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3376 struct inpcb *inp = tp->t_inpcb;
3377 struct hc_metrics_lite metrics;
3380 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3381 size_t min_protoh = isipv6 ?
3382 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3383 sizeof (struct tcpiphdr);
3385 const size_t min_protoh = sizeof(struct tcpiphdr);
3388 INP_WLOCK_ASSERT(tp->t_inpcb);
3390 if (mtuoffer != -1) {
3391 KASSERT(offer == -1, ("%s: conflict", __func__));
3392 offer = mtuoffer - min_protoh;
3399 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3400 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3403 #if defined(INET) && defined(INET6)
3408 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3409 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3414 * No route to sender, stay with default mss and return.
3418 * In case we return early we need to initialize metrics
3419 * to a defined state as tcp_hc_get() would do for us
3420 * if there was no cache hit.
3422 if (metricptr != NULL)
3423 bzero(metricptr, sizeof(struct hc_metrics_lite));
3427 /* What have we got? */
3431 * Offer == 0 means that there was no MSS on the SYN
3432 * segment, in this case we use tcp_mssdflt as
3433 * already assigned to t_maxopd above.
3435 offer = tp->t_maxopd;
3440 * Offer == -1 means that we didn't receive SYN yet.
3446 * Prevent DoS attack with too small MSS. Round up
3447 * to at least minmss.
3449 offer = max(offer, V_tcp_minmss);
3453 * rmx information is now retrieved from tcp_hostcache.
3455 tcp_hc_get(&inp->inp_inc, &metrics);
3456 if (metricptr != NULL)
3457 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3460 * If there's a discovered mtu in tcp hostcache, use it.
3461 * Else, use the link mtu.
3463 if (metrics.rmx_mtu)
3464 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3468 mss = maxmtu - min_protoh;
3469 if (!V_path_mtu_discovery &&
3470 !in6_localaddr(&inp->in6p_faddr))
3471 mss = min(mss, V_tcp_v6mssdflt);
3474 #if defined(INET) && defined(INET6)
3479 mss = maxmtu - min_protoh;
3480 if (!V_path_mtu_discovery &&
3481 !in_localaddr(inp->inp_faddr))
3482 mss = min(mss, V_tcp_mssdflt);
3486 * XXX - The above conditional (mss = maxmtu - min_protoh)
3487 * probably violates the TCP spec.
3488 * The problem is that, since we don't know the
3489 * other end's MSS, we are supposed to use a conservative
3490 * default. But, if we do that, then MTU discovery will
3491 * never actually take place, because the conservative
3492 * default is much less than the MTUs typically seen
3493 * on the Internet today. For the moment, we'll sweep
3494 * this under the carpet.
3496 * The conservative default might not actually be a problem
3497 * if the only case this occurs is when sending an initial
3498 * SYN with options and data to a host we've never talked
3499 * to before. Then, they will reply with an MSS value which
3500 * will get recorded and the new parameters should get
3501 * recomputed. For Further Study.
3504 mss = min(mss, offer);
3507 * Sanity check: make sure that maxopd will be large
3508 * enough to allow some data on segments even if the
3509 * all the option space is used (40bytes). Otherwise
3510 * funny things may happen in tcp_output.
3515 * maxopd stores the maximum length of data AND options
3516 * in a segment; maxseg is the amount of data in a normal
3517 * segment. We need to store this value (maxopd) apart
3518 * from maxseg, because now every segment carries options
3519 * and thus we normally have somewhat less data in segments.
3524 * origoffer==-1 indicates that no segments were received yet.
3525 * In this case we just guess.
3527 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3529 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3530 mss -= TCPOLEN_TSTAMP_APPA;
3536 tcp_mss(struct tcpcb *tp, int offer)
3542 struct hc_metrics_lite metrics;
3543 struct tcp_ifcap cap;
3545 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3547 bzero(&cap, sizeof(cap));
3548 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3554 * If there's a pipesize, change the socket buffer to that size,
3555 * don't change if sb_hiwat is different than default (then it
3556 * has been changed on purpose with setsockopt).
3557 * Make the socket buffers an integral number of mss units;
3558 * if the mss is larger than the socket buffer, decrease the mss.
3560 so = inp->inp_socket;
3561 SOCKBUF_LOCK(&so->so_snd);
3562 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3563 bufsize = metrics.rmx_sendpipe;
3565 bufsize = so->so_snd.sb_hiwat;
3569 bufsize = roundup(bufsize, mss);
3570 if (bufsize > sb_max)
3572 if (bufsize > so->so_snd.sb_hiwat)
3573 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3575 SOCKBUF_UNLOCK(&so->so_snd);
3578 SOCKBUF_LOCK(&so->so_rcv);
3579 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3580 bufsize = metrics.rmx_recvpipe;
3582 bufsize = so->so_rcv.sb_hiwat;
3583 if (bufsize > mss) {
3584 bufsize = roundup(bufsize, mss);
3585 if (bufsize > sb_max)
3587 if (bufsize > so->so_rcv.sb_hiwat)
3588 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3590 SOCKBUF_UNLOCK(&so->so_rcv);
3592 /* Check the interface for TSO capabilities. */
3593 if (cap.ifcap & CSUM_TSO) {
3594 tp->t_flags |= TF_TSO;
3595 tp->t_tsomax = cap.tsomax;
3596 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3597 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3602 * Determine the MSS option to send on an outgoing SYN.
3605 tcp_mssopt(struct in_conninfo *inc)
3612 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3615 if (inc->inc_flags & INC_ISIPV6) {
3616 mss = V_tcp_v6mssdflt;
3617 maxmtu = tcp_maxmtu6(inc, NULL);
3618 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3621 #if defined(INET) && defined(INET6)
3626 mss = V_tcp_mssdflt;
3627 maxmtu = tcp_maxmtu(inc, NULL);
3628 min_protoh = sizeof(struct tcpiphdr);
3631 #if defined(INET6) || defined(INET)
3632 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3635 if (maxmtu && thcmtu)
3636 mss = min(maxmtu, thcmtu) - min_protoh;
3637 else if (maxmtu || thcmtu)
3638 mss = max(maxmtu, thcmtu) - min_protoh;
3645 * On a partial ack arrives, force the retransmission of the
3646 * next unacknowledged segment. Do not clear tp->t_dupacks.
3647 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3651 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3653 tcp_seq onxt = tp->snd_nxt;
3654 u_long ocwnd = tp->snd_cwnd;
3656 INP_WLOCK_ASSERT(tp->t_inpcb);
3658 tcp_timer_activate(tp, TT_REXMT, 0);
3660 tp->snd_nxt = th->th_ack;
3662 * Set snd_cwnd to one segment beyond acknowledged offset.
3663 * (tp->snd_una has not yet been updated when this function is called.)
3665 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3666 tp->t_flags |= TF_ACKNOW;
3667 (void) tcp_output(tp);
3668 tp->snd_cwnd = ocwnd;
3669 if (SEQ_GT(onxt, tp->snd_nxt))
3672 * Partial window deflation. Relies on fact that tp->snd_una
3675 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3676 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3679 tp->snd_cwnd += tp->t_maxseg;
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