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>
66 #include <sys/signalvar.h>
67 #include <sys/socket.h>
68 #include <sys/socketvar.h>
69 #include <sys/sysctl.h>
70 #include <sys/syslog.h>
71 #include <sys/systm.h>
73 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
78 #include <net/route.h>
81 #define TCPSTATES /* for logging */
83 #include <netinet/cc.h>
84 #include <netinet/in.h>
85 #include <netinet/in_pcb.h>
86 #include <netinet/in_systm.h>
87 #include <netinet/in_var.h>
88 #include <netinet/ip.h>
89 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
90 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
91 #include <netinet/ip_var.h>
92 #include <netinet/ip_options.h>
93 #include <netinet/ip6.h>
94 #include <netinet/icmp6.h>
95 #include <netinet6/in6_pcb.h>
96 #include <netinet6/ip6_var.h>
97 #include <netinet6/nd6.h>
98 #include <netinet/tcp_fsm.h>
99 #include <netinet/tcp_seq.h>
100 #include <netinet/tcp_timer.h>
101 #include <netinet/tcp_var.h>
102 #include <netinet6/tcp6_var.h>
103 #include <netinet/tcpip.h>
104 #include <netinet/tcp_syncache.h>
106 #include <netinet/tcp_debug.h>
107 #endif /* TCPDEBUG */
109 #include <netinet/tcp_offload.h>
113 #include <netipsec/ipsec.h>
114 #include <netipsec/ipsec6.h>
117 #include <machine/in_cksum.h>
119 #include <security/mac/mac_framework.h>
121 const int tcprexmtthresh = 3;
123 VNET_DEFINE(struct tcpstat, tcpstat);
124 SYSCTL_VNET_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
125 &VNET_NAME(tcpstat), tcpstat,
126 "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
128 int tcp_log_in_vain = 0;
129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
131 "Log all incoming TCP segments to closed ports");
133 VNET_DEFINE(int, blackhole) = 0;
134 #define V_blackhole VNET(blackhole)
135 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
136 &VNET_NAME(blackhole), 0,
137 "Do not send RST on segments to closed ports");
139 VNET_DEFINE(int, tcp_delack_enabled) = 1;
140 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
141 &VNET_NAME(tcp_delack_enabled), 0,
142 "Delay ACK to try and piggyback it onto a data packet");
144 VNET_DEFINE(int, drop_synfin) = 0;
145 #define V_drop_synfin VNET(drop_synfin)
146 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
147 &VNET_NAME(drop_synfin), 0,
148 "Drop TCP packets with SYN+FIN set");
150 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
151 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
152 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
153 &VNET_NAME(tcp_do_rfc3042), 0,
154 "Enable RFC 3042 (Limited Transmit)");
156 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
157 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
158 &VNET_NAME(tcp_do_rfc3390), 0,
159 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
161 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0,
162 "Experimental TCP extensions");
164 VNET_DEFINE(int, tcp_do_initcwnd10) = 1;
165 SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW,
166 &VNET_NAME(tcp_do_initcwnd10), 0,
167 "Enable RFC 6928 (Increasing initial CWND to 10)");
169 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
170 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW,
171 &VNET_NAME(tcp_do_rfc3465), 0,
172 "Enable RFC 3465 (Appropriate Byte Counting)");
174 VNET_DEFINE(int, tcp_abc_l_var) = 2;
175 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW,
176 &VNET_NAME(tcp_abc_l_var), 2,
177 "Cap the max cwnd increment during slow-start to this number of segments");
179 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
181 VNET_DEFINE(int, tcp_do_ecn) = 0;
182 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW,
183 &VNET_NAME(tcp_do_ecn), 0,
186 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
187 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW,
188 &VNET_NAME(tcp_ecn_maxretries), 0,
189 "Max retries before giving up on ECN");
191 VNET_DEFINE(int, tcp_insecure_rst) = 0;
192 #define V_tcp_insecure_rst VNET(tcp_insecure_rst)
193 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
194 &VNET_NAME(tcp_insecure_rst), 0,
195 "Follow the old (insecure) criteria for accepting RST packets");
197 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
198 #define V_tcp_recvspace VNET(tcp_recvspace)
199 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW,
200 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
202 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
203 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf)
204 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
205 &VNET_NAME(tcp_do_autorcvbuf), 0,
206 "Enable automatic receive buffer sizing");
208 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
209 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc)
210 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
211 &VNET_NAME(tcp_autorcvbuf_inc), 0,
212 "Incrementor step size of automatic receive buffer");
214 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
215 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max)
216 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
217 &VNET_NAME(tcp_autorcvbuf_max), 0,
218 "Max size of automatic receive buffer");
220 VNET_DEFINE(struct inpcbhead, tcb);
221 #define tcb6 tcb /* for KAME src sync over BSD*'s */
222 VNET_DEFINE(struct inpcbinfo, tcbinfo);
224 static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
225 static void tcp_do_segment(struct mbuf *, struct tcphdr *,
226 struct socket *, struct tcpcb *, int, int, uint8_t,
228 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *,
229 struct tcpcb *, int, int);
230 static void tcp_pulloutofband(struct socket *,
231 struct tcphdr *, struct mbuf *, int);
232 static void tcp_xmit_timer(struct tcpcb *, int);
233 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
234 static void inline tcp_fields_to_host(struct tcphdr *);
236 static void inline tcp_fields_to_net(struct tcphdr *);
237 static int inline tcp_signature_verify_input(struct mbuf *, int, int,
238 int, struct tcpopt *, struct tcphdr *, u_int);
240 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
242 static void inline cc_conn_init(struct tcpcb *tp);
243 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
244 static void inline hhook_run_tcp_est_in(struct tcpcb *tp,
245 struct tcphdr *th, struct tcpopt *to);
248 * Kernel module interface for updating tcpstat. The argument is an index
249 * into tcpstat treated as an array of u_long. While this encodes the
250 * general layout of tcpstat into the caller, it doesn't encode its location,
251 * so that future changes to add, for example, per-CPU stats support won't
252 * cause binary compatibility problems for kernel modules.
255 kmod_tcpstat_inc(int statnum)
258 (*((u_long *)&V_tcpstat + statnum))++;
262 * Wrapper for the TCP established input helper hook.
265 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
267 struct tcp_hhook_data hhook_data;
269 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
274 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
280 * CC wrapper hook functions
283 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
285 INP_WLOCK_ASSERT(tp->t_inpcb);
287 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
288 if (tp->snd_cwnd <= tp->snd_wnd)
289 tp->ccv->flags |= CCF_CWND_LIMITED;
291 tp->ccv->flags &= ~CCF_CWND_LIMITED;
293 if (type == CC_ACK) {
294 if (tp->snd_cwnd > tp->snd_ssthresh) {
295 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
296 V_tcp_abc_l_var * tp->t_maxseg);
297 if (tp->t_bytes_acked >= tp->snd_cwnd) {
298 tp->t_bytes_acked -= tp->snd_cwnd;
299 tp->ccv->flags |= CCF_ABC_SENTAWND;
302 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
303 tp->t_bytes_acked = 0;
307 if (CC_ALGO(tp)->ack_received != NULL) {
308 /* XXXLAS: Find a way to live without this */
309 tp->ccv->curack = th->th_ack;
310 CC_ALGO(tp)->ack_received(tp->ccv, type);
315 cc_conn_init(struct tcpcb *tp)
317 struct hc_metrics_lite metrics;
318 struct inpcb *inp = tp->t_inpcb;
321 INP_WLOCK_ASSERT(tp->t_inpcb);
323 tcp_hc_get(&inp->inp_inc, &metrics);
325 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
327 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
328 TCPSTAT_INC(tcps_usedrtt);
329 if (metrics.rmx_rttvar) {
330 tp->t_rttvar = metrics.rmx_rttvar;
331 TCPSTAT_INC(tcps_usedrttvar);
333 /* default variation is +- 1 rtt */
335 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
337 TCPT_RANGESET(tp->t_rxtcur,
338 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
339 tp->t_rttmin, TCPTV_REXMTMAX);
341 if (metrics.rmx_ssthresh) {
343 * There's some sort of gateway or interface
344 * buffer limit on the path. Use this to set
345 * the slow start threshhold, but set the
346 * threshold to no less than 2*mss.
348 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
349 TCPSTAT_INC(tcps_usedssthresh);
353 * Set the initial slow-start flight size.
355 * RFC5681 Section 3.1 specifies the default conservative values.
356 * RFC3390 specifies slightly more aggressive values.
357 * RFC6928 increases it to ten segments.
359 * If a SYN or SYN/ACK was lost and retransmitted, we have to
360 * reduce the initial CWND to one segment as congestion is likely
361 * requiring us to be cautious.
363 if (tp->snd_cwnd == 1)
364 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */
365 else if (V_tcp_do_initcwnd10)
366 tp->snd_cwnd = min(10 * tp->t_maxseg,
367 max(2 * tp->t_maxseg, 14600));
368 else if (V_tcp_do_rfc3390)
369 tp->snd_cwnd = min(4 * tp->t_maxseg,
370 max(2 * tp->t_maxseg, 4380));
372 /* Per RFC5681 Section 3.1 */
373 if (tp->t_maxseg > 2190)
374 tp->snd_cwnd = 2 * tp->t_maxseg;
375 else if (tp->t_maxseg > 1095)
376 tp->snd_cwnd = 3 * tp->t_maxseg;
378 tp->snd_cwnd = 4 * tp->t_maxseg;
381 if (CC_ALGO(tp)->conn_init != NULL)
382 CC_ALGO(tp)->conn_init(tp->ccv);
386 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
388 INP_WLOCK_ASSERT(tp->t_inpcb);
392 if (!IN_FASTRECOVERY(tp->t_flags)) {
393 tp->snd_recover = tp->snd_max;
394 if (tp->t_flags & TF_ECN_PERMIT)
395 tp->t_flags |= TF_ECN_SND_CWR;
399 if (!IN_CONGRECOVERY(tp->t_flags)) {
400 TCPSTAT_INC(tcps_ecn_rcwnd);
401 tp->snd_recover = tp->snd_max;
402 if (tp->t_flags & TF_ECN_PERMIT)
403 tp->t_flags |= TF_ECN_SND_CWR;
408 tp->t_bytes_acked = 0;
409 EXIT_RECOVERY(tp->t_flags);
410 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
411 tp->t_maxseg) * tp->t_maxseg;
412 tp->snd_cwnd = tp->t_maxseg;
415 TCPSTAT_INC(tcps_sndrexmitbad);
416 /* RTO was unnecessary, so reset everything. */
417 tp->snd_cwnd = tp->snd_cwnd_prev;
418 tp->snd_ssthresh = tp->snd_ssthresh_prev;
419 tp->snd_recover = tp->snd_recover_prev;
420 if (tp->t_flags & TF_WASFRECOVERY)
421 ENTER_FASTRECOVERY(tp->t_flags);
422 if (tp->t_flags & TF_WASCRECOVERY)
423 ENTER_CONGRECOVERY(tp->t_flags);
424 tp->snd_nxt = tp->snd_max;
425 tp->t_flags &= ~TF_PREVVALID;
430 if (CC_ALGO(tp)->cong_signal != NULL) {
432 tp->ccv->curack = th->th_ack;
433 CC_ALGO(tp)->cong_signal(tp->ccv, type);
438 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
440 INP_WLOCK_ASSERT(tp->t_inpcb);
442 /* XXXLAS: KASSERT that we're in recovery? */
444 if (CC_ALGO(tp)->post_recovery != NULL) {
445 tp->ccv->curack = th->th_ack;
446 CC_ALGO(tp)->post_recovery(tp->ccv);
448 /* XXXLAS: EXIT_RECOVERY ? */
449 tp->t_bytes_acked = 0;
453 tcp_fields_to_host(struct tcphdr *th)
456 th->th_seq = ntohl(th->th_seq);
457 th->th_ack = ntohl(th->th_ack);
458 th->th_win = ntohs(th->th_win);
459 th->th_urp = ntohs(th->th_urp);
464 tcp_fields_to_net(struct tcphdr *th)
467 th->th_seq = htonl(th->th_seq);
468 th->th_ack = htonl(th->th_ack);
469 th->th_win = htons(th->th_win);
470 th->th_urp = htons(th->th_urp);
474 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
475 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
479 tcp_fields_to_net(th);
480 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
481 tcp_fields_to_host(th);
486 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
488 #define ND6_HINT(tp) \
490 if ((tp) && (tp)->t_inpcb && \
491 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
492 nd6_nud_hint(NULL, NULL, 0); \
499 * Indicate whether this ack should be delayed. We can delay the ack if
500 * - there is no delayed ack timer in progress and
501 * - our last ack wasn't a 0-sized window. We never want to delay
502 * the ack that opens up a 0-sized window and
503 * - delayed acks are enabled or
504 * - this is a half-synchronized T/TCP connection.
505 * - the segment size is not larger than the MSS and LRO wasn't used
508 #define DELAY_ACK(tp, tlen) \
509 ((!tcp_timer_active(tp, TT_DELACK) && \
510 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
511 (tlen <= tp->t_maxopd) && \
512 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
515 * TCP input handling is split into multiple parts:
516 * tcp6_input is a thin wrapper around tcp_input for the extended
517 * ip6_protox[] call format in ip6_input
518 * tcp_input handles primary segment validation, inpcb lookup and
519 * SYN processing on listen sockets
520 * tcp_do_segment processes the ACK and text of the segment for
521 * establishing, established and closing connections
525 tcp6_input(struct mbuf **mp, int *offp, int proto)
527 struct mbuf *m = *mp;
528 struct in6_ifaddr *ia6;
530 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
533 * draft-itojun-ipv6-tcp-to-anycast
534 * better place to put this in?
536 ia6 = ip6_getdstifaddr(m);
537 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
540 ifa_free(&ia6->ia_ifa);
541 ip6 = mtod(m, struct ip6_hdr *);
542 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
543 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
547 ifa_free(&ia6->ia_ifa);
555 tcp_input(struct mbuf *m, int off0)
557 struct tcphdr *th = NULL;
558 struct ip *ip = NULL;
562 struct inpcb *inp = NULL;
563 struct tcpcb *tp = NULL;
564 struct socket *so = NULL;
573 int rstreason = 0; /* For badport_bandlim accounting purposes */
575 uint8_t sig_checked = 0;
578 struct m_tag *fwd_tag = NULL;
580 struct ip6_hdr *ip6 = NULL;
583 const void *ip6 = NULL;
585 struct tcpopt to; /* options in this segment */
586 char *s = NULL; /* address and port logging */
588 #define TI_UNLOCKED 1
593 * The size of tcp_saveipgen must be the size of the max ip header,
596 u_char tcp_saveipgen[IP6_HDR_LEN];
597 struct tcphdr tcp_savetcp;
602 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
606 TCPSTAT_INC(tcps_rcvtotal);
610 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
612 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
613 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
615 TCPSTAT_INC(tcps_rcvshort);
620 ip6 = mtod(m, struct ip6_hdr *);
621 th = (struct tcphdr *)((caddr_t)ip6 + off0);
622 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
623 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
624 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
625 th->th_sum = m->m_pkthdr.csum_data;
627 th->th_sum = in6_cksum_pseudo(ip6, tlen,
628 IPPROTO_TCP, m->m_pkthdr.csum_data);
629 th->th_sum ^= 0xffff;
631 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
633 TCPSTAT_INC(tcps_rcvbadsum);
638 * Be proactive about unspecified IPv6 address in source.
639 * As we use all-zero to indicate unbounded/unconnected pcb,
640 * unspecified IPv6 address can be used to confuse us.
642 * Note that packets with unspecified IPv6 destination is
643 * already dropped in ip6_input.
645 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
651 #if defined(INET) && defined(INET6)
657 * Get IP and TCP header together in first mbuf.
658 * Note: IP leaves IP header in first mbuf.
660 if (off0 > sizeof (struct ip)) {
661 ip_stripoptions(m, (struct mbuf *)0);
662 off0 = sizeof(struct ip);
664 if (m->m_len < sizeof (struct tcpiphdr)) {
665 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
667 TCPSTAT_INC(tcps_rcvshort);
671 ip = mtod(m, struct ip *);
672 ipov = (struct ipovly *)ip;
673 th = (struct tcphdr *)((caddr_t)ip + off0);
676 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
677 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
678 th->th_sum = m->m_pkthdr.csum_data;
680 th->th_sum = in_pseudo(ip->ip_src.s_addr,
682 htonl(m->m_pkthdr.csum_data +
685 th->th_sum ^= 0xffff;
687 ipov->ih_len = (u_short)tlen;
688 ipov->ih_len = htons(ipov->ih_len);
692 * Checksum extended TCP header and data.
694 len = sizeof (struct ip) + tlen;
695 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
696 ipov->ih_len = (u_short)tlen;
697 ipov->ih_len = htons(ipov->ih_len);
698 th->th_sum = in_cksum(m, len);
701 TCPSTAT_INC(tcps_rcvbadsum);
704 /* Re-initialization for later version check */
705 ip->ip_v = IPVERSION;
711 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
713 #if defined(INET) && defined(INET6)
721 * Check that TCP offset makes sense,
722 * pull out TCP options and adjust length. XXX
724 off = th->th_off << 2;
725 if (off < sizeof (struct tcphdr) || off > tlen) {
726 TCPSTAT_INC(tcps_rcvbadoff);
729 tlen -= off; /* tlen is used instead of ti->ti_len */
730 if (off > sizeof (struct tcphdr)) {
733 IP6_EXTHDR_CHECK(m, off0, off, );
734 ip6 = mtod(m, struct ip6_hdr *);
735 th = (struct tcphdr *)((caddr_t)ip6 + off0);
738 #if defined(INET) && defined(INET6)
743 if (m->m_len < sizeof(struct ip) + off) {
744 if ((m = m_pullup(m, sizeof (struct ip) + off))
746 TCPSTAT_INC(tcps_rcvshort);
749 ip = mtod(m, struct ip *);
750 ipov = (struct ipovly *)ip;
751 th = (struct tcphdr *)((caddr_t)ip + off0);
755 optlen = off - sizeof (struct tcphdr);
756 optp = (u_char *)(th + 1);
758 thflags = th->th_flags;
761 * Convert TCP protocol specific fields to host format.
763 tcp_fields_to_host(th);
766 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
768 drop_hdrlen = off0 + off;
771 * Locate pcb for segment; if we're likely to add or remove a
772 * connection then first acquire pcbinfo lock. There are two cases
773 * where we might discover later we need a write lock despite the
774 * flags: ACKs moving a connection out of the syncache, and ACKs for
775 * a connection in TIMEWAIT.
777 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) {
778 INP_INFO_WLOCK(&V_tcbinfo);
779 ti_locked = TI_WLOCKED;
781 ti_locked = TI_UNLOCKED;
785 if (ti_locked == TI_WLOCKED) {
786 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
788 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
793 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
797 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
799 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
802 #if defined(INET) && !defined(INET6)
803 (m->m_flags & M_IP_NEXTHOP)
806 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
809 if (isipv6 && fwd_tag != NULL) {
810 struct sockaddr_in6 *next_hop6;
812 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
814 * Transparently forwarded. Pretend to be the destination.
815 * Already got one like this?
817 inp = in6_pcblookup_mbuf(&V_tcbinfo,
818 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
819 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
822 * It's new. Try to find the ambushing socket.
823 * Because we've rewritten the destination address,
824 * any hardware-generated hash is ignored.
826 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
827 th->th_sport, &next_hop6->sin6_addr,
828 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
829 th->th_dport, INPLOOKUP_WILDCARD |
830 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
832 /* Remove the tag from the packet. We don't need it anymore. */
833 m_tag_delete(m, fwd_tag);
834 m->m_flags &= ~M_IP6_NEXTHOP;
837 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
838 th->th_sport, &ip6->ip6_dst, th->th_dport,
839 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
840 m->m_pkthdr.rcvif, m);
843 #if defined(INET6) && defined(INET)
847 if (fwd_tag != NULL) {
848 struct sockaddr_in *next_hop;
850 next_hop = (struct sockaddr_in *)(fwd_tag+1);
852 * Transparently forwarded. Pretend to be the destination.
853 * already got one like this?
855 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
856 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
857 m->m_pkthdr.rcvif, m);
860 * It's new. Try to find the ambushing socket.
861 * Because we've rewritten the destination address,
862 * any hardware-generated hash is ignored.
864 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
865 th->th_sport, next_hop->sin_addr,
866 next_hop->sin_port ? ntohs(next_hop->sin_port) :
867 th->th_dport, INPLOOKUP_WILDCARD |
868 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
870 /* Remove the tag from the packet. We don't need it anymore. */
871 m_tag_delete(m, fwd_tag);
872 m->m_flags &= ~M_IP_NEXTHOP;
875 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
876 th->th_sport, ip->ip_dst, th->th_dport,
877 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
878 m->m_pkthdr.rcvif, m);
882 * If the INPCB does not exist then all data in the incoming
883 * segment is discarded and an appropriate RST is sent back.
884 * XXX MRT Send RST using which routing table?
888 * Log communication attempts to ports that are not
891 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
892 tcp_log_in_vain == 2) {
893 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
894 log(LOG_INFO, "%s; %s: Connection attempt "
895 "to closed port\n", s, __func__);
898 * When blackholing do not respond with a RST but
899 * completely ignore the segment and drop it.
901 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
905 rstreason = BANDLIM_RST_CLOSEDPORT;
908 INP_WLOCK_ASSERT(inp);
909 if (!(inp->inp_flags & INP_HW_FLOWID)
910 && (m->m_flags & M_FLOWID)
911 && ((inp->inp_socket == NULL)
912 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
913 inp->inp_flags |= INP_HW_FLOWID;
914 inp->inp_flags &= ~INP_SW_FLOWID;
915 inp->inp_flowid = m->m_pkthdr.flowid;
919 if (isipv6 && ipsec6_in_reject(m, inp)) {
920 IPSEC6STAT_INC(in_polvio);
924 if (ipsec4_in_reject(m, inp) != 0) {
925 IPSECSTAT_INC(in_polvio);
931 * Check the minimum TTL for socket.
933 if (inp->inp_ip_minttl != 0) {
935 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
939 if (inp->inp_ip_minttl > ip->ip_ttl)
944 * A previous connection in TIMEWAIT state is supposed to catch stray
945 * or duplicate segments arriving late. If this segment was a
946 * legitimate new connection attempt the old INPCB gets removed and
947 * we can try again to find a listening socket.
949 * At this point, due to earlier optimism, we may hold only an inpcb
950 * lock, and not the inpcbinfo write lock. If so, we need to try to
951 * acquire it, or if that fails, acquire a reference on the inpcb,
952 * drop all locks, acquire a global write lock, and then re-acquire
953 * the inpcb lock. We may at that point discover that another thread
954 * has tried to free the inpcb, in which case we need to loop back
955 * and try to find a new inpcb to deliver to.
957 * XXXRW: It may be time to rethink timewait locking.
960 if (inp->inp_flags & INP_TIMEWAIT) {
961 if (ti_locked == TI_UNLOCKED) {
962 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
965 INP_INFO_WLOCK(&V_tcbinfo);
966 ti_locked = TI_WLOCKED;
968 if (in_pcbrele_wlocked(inp)) {
973 ti_locked = TI_WLOCKED;
975 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
977 if (thflags & TH_SYN)
978 tcp_dooptions(&to, optp, optlen, TO_SYN);
980 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
982 if (tcp_twcheck(inp, &to, th, m, tlen))
984 INP_INFO_WUNLOCK(&V_tcbinfo);
988 * The TCPCB may no longer exist if the connection is winding
989 * down or it is in the CLOSED state. Either way we drop the
990 * segment and send an appropriate response.
993 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
994 rstreason = BANDLIM_RST_CLOSEDPORT;
999 if (tp->t_flags & TF_TOE) {
1000 tcp_offload_input(tp, m);
1001 m = NULL; /* consumed by the TOE driver */
1007 * We've identified a valid inpcb, but it could be that we need an
1008 * inpcbinfo write lock but don't hold it. In this case, attempt to
1009 * acquire using the same strategy as the TIMEWAIT case above. If we
1010 * relock, we have to jump back to 'relocked' as the connection might
1011 * now be in TIMEWAIT.
1014 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0)
1015 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1017 if (tp->t_state != TCPS_ESTABLISHED) {
1018 if (ti_locked == TI_UNLOCKED) {
1019 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
1022 INP_INFO_WLOCK(&V_tcbinfo);
1023 ti_locked = TI_WLOCKED;
1025 if (in_pcbrele_wlocked(inp)) {
1031 ti_locked = TI_WLOCKED;
1033 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1037 INP_WLOCK_ASSERT(inp);
1038 if (mac_inpcb_check_deliver(inp, m))
1041 so = inp->inp_socket;
1042 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1044 if (so->so_options & SO_DEBUG) {
1045 ostate = tp->t_state;
1048 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1051 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1054 #endif /* TCPDEBUG */
1056 * When the socket is accepting connections (the INPCB is in LISTEN
1057 * state) we look into the SYN cache if this is a new connection
1058 * attempt or the completion of a previous one. Because listen
1059 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be
1060 * held in this case.
1062 if (so->so_options & SO_ACCEPTCONN) {
1063 struct in_conninfo inc;
1065 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
1066 "tp not listening", __func__));
1067 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1069 bzero(&inc, sizeof(inc));
1072 inc.inc_flags |= INC_ISIPV6;
1073 inc.inc6_faddr = ip6->ip6_src;
1074 inc.inc6_laddr = ip6->ip6_dst;
1078 inc.inc_faddr = ip->ip_src;
1079 inc.inc_laddr = ip->ip_dst;
1081 inc.inc_fport = th->th_sport;
1082 inc.inc_lport = th->th_dport;
1083 inc.inc_fibnum = so->so_fibnum;
1086 * Check for an existing connection attempt in syncache if
1087 * the flag is only ACK. A successful lookup creates a new
1088 * socket appended to the listen queue in SYN_RECEIVED state.
1090 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1092 * Parse the TCP options here because
1093 * syncookies need access to the reflected
1096 tcp_dooptions(&to, optp, optlen, 0);
1098 * NB: syncache_expand() doesn't unlock
1099 * inp and tcpinfo locks.
1101 if (!syncache_expand(&inc, &to, th, &so, m)) {
1103 * No syncache entry or ACK was not
1104 * for our SYN/ACK. Send a RST.
1105 * NB: syncache did its own logging
1106 * of the failure cause.
1108 rstreason = BANDLIM_RST_OPENPORT;
1113 * We completed the 3-way handshake
1114 * but could not allocate a socket
1115 * either due to memory shortage,
1116 * listen queue length limits or
1117 * global socket limits. Send RST
1118 * or wait and have the remote end
1119 * retransmit the ACK for another
1122 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1123 log(LOG_DEBUG, "%s; %s: Listen socket: "
1124 "Socket allocation failed due to "
1125 "limits or memory shortage, %s\n",
1127 V_tcp_sc_rst_sock_fail ?
1128 "sending RST" : "try again");
1129 if (V_tcp_sc_rst_sock_fail) {
1130 rstreason = BANDLIM_UNLIMITED;
1136 * Socket is created in state SYN_RECEIVED.
1137 * Unlock the listen socket, lock the newly
1138 * created socket and update the tp variable.
1140 INP_WUNLOCK(inp); /* listen socket */
1141 inp = sotoinpcb(so);
1142 INP_WLOCK(inp); /* new connection */
1143 tp = intotcpcb(inp);
1144 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1145 ("%s: ", __func__));
1146 #ifdef TCP_SIGNATURE
1147 if (sig_checked == 0) {
1148 tcp_dooptions(&to, optp, optlen,
1149 (thflags & TH_SYN) ? TO_SYN : 0);
1150 if (!tcp_signature_verify_input(m, off0, tlen,
1151 optlen, &to, th, tp->t_flags)) {
1154 * In SYN_SENT state if it receives an
1155 * RST, it is allowed for further
1158 if ((thflags & TH_RST) == 0 ||
1159 (tp->t_state == TCPS_SYN_SENT) == 0)
1167 * Process the segment and the data it
1168 * contains. tcp_do_segment() consumes
1169 * the mbuf chain and unlocks the inpcb.
1171 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1173 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1177 * Segment flag validation for new connection attempts:
1179 * Our (SYN|ACK) response was rejected.
1180 * Check with syncache and remove entry to prevent
1183 * NB: syncache_chkrst does its own logging of failure
1186 if (thflags & TH_RST) {
1187 syncache_chkrst(&inc, th);
1191 * We can't do anything without SYN.
1193 if ((thflags & TH_SYN) == 0) {
1194 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1195 log(LOG_DEBUG, "%s; %s: Listen socket: "
1196 "SYN is missing, segment ignored\n",
1198 TCPSTAT_INC(tcps_badsyn);
1202 * (SYN|ACK) is bogus on a listen socket.
1204 if (thflags & TH_ACK) {
1205 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1206 log(LOG_DEBUG, "%s; %s: Listen socket: "
1207 "SYN|ACK invalid, segment rejected\n",
1209 syncache_badack(&inc); /* XXX: Not needed! */
1210 TCPSTAT_INC(tcps_badsyn);
1211 rstreason = BANDLIM_RST_OPENPORT;
1215 * If the drop_synfin option is enabled, drop all
1216 * segments with both the SYN and FIN bits set.
1217 * This prevents e.g. nmap from identifying the
1219 * XXX: Poor reasoning. nmap has other methods
1220 * and is constantly refining its stack detection
1222 * XXX: This is a violation of the TCP specification
1223 * and was used by RFC1644.
1225 if ((thflags & TH_FIN) && V_drop_synfin) {
1226 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1227 log(LOG_DEBUG, "%s; %s: Listen socket: "
1228 "SYN|FIN segment ignored (based on "
1229 "sysctl setting)\n", s, __func__);
1230 TCPSTAT_INC(tcps_badsyn);
1234 * Segment's flags are (SYN) or (SYN|FIN).
1236 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1237 * as they do not affect the state of the TCP FSM.
1238 * The data pointed to by TH_URG and th_urp is ignored.
1240 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1241 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1242 KASSERT(thflags & (TH_SYN),
1243 ("%s: Listen socket: TH_SYN not set", __func__));
1246 * If deprecated address is forbidden,
1247 * we do not accept SYN to deprecated interface
1248 * address to prevent any new inbound connection from
1249 * getting established.
1250 * When we do not accept SYN, we send a TCP RST,
1251 * with deprecated source address (instead of dropping
1252 * it). We compromise it as it is much better for peer
1253 * to send a RST, and RST will be the final packet
1256 * If we do not forbid deprecated addresses, we accept
1257 * the SYN packet. RFC2462 does not suggest dropping
1259 * If we decipher RFC2462 5.5.4, it says like this:
1260 * 1. use of deprecated addr with existing
1261 * communication is okay - "SHOULD continue to be
1263 * 2. use of it with new communication:
1264 * (2a) "SHOULD NOT be used if alternate address
1265 * with sufficient scope is available"
1266 * (2b) nothing mentioned otherwise.
1267 * Here we fall into (2b) case as we have no choice in
1268 * our source address selection - we must obey the peer.
1270 * The wording in RFC2462 is confusing, and there are
1271 * multiple description text for deprecated address
1272 * handling - worse, they are not exactly the same.
1273 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1275 if (isipv6 && !V_ip6_use_deprecated) {
1276 struct in6_ifaddr *ia6;
1278 ia6 = ip6_getdstifaddr(m);
1280 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1281 ifa_free(&ia6->ia_ifa);
1282 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1283 log(LOG_DEBUG, "%s; %s: Listen socket: "
1284 "Connection attempt to deprecated "
1285 "IPv6 address rejected\n",
1287 rstreason = BANDLIM_RST_OPENPORT;
1291 ifa_free(&ia6->ia_ifa);
1295 * Basic sanity checks on incoming SYN requests:
1296 * Don't respond if the destination is a link layer
1297 * broadcast according to RFC1122 4.2.3.10, p. 104.
1298 * If it is from this socket it must be forged.
1299 * Don't respond if the source or destination is a
1300 * global or subnet broad- or multicast address.
1301 * Note that it is quite possible to receive unicast
1302 * link-layer packets with a broadcast IP address. Use
1303 * in_broadcast() to find them.
1305 if (m->m_flags & (M_BCAST|M_MCAST)) {
1306 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1307 log(LOG_DEBUG, "%s; %s: Listen socket: "
1308 "Connection attempt from broad- or multicast "
1309 "link layer address ignored\n", s, __func__);
1314 if (th->th_dport == th->th_sport &&
1315 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1316 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1317 log(LOG_DEBUG, "%s; %s: Listen socket: "
1318 "Connection attempt to/from self "
1319 "ignored\n", s, __func__);
1322 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1323 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1324 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1325 log(LOG_DEBUG, "%s; %s: Listen socket: "
1326 "Connection attempt from/to multicast "
1327 "address ignored\n", s, __func__);
1332 #if defined(INET) && defined(INET6)
1337 if (th->th_dport == th->th_sport &&
1338 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1339 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1340 log(LOG_DEBUG, "%s; %s: Listen socket: "
1341 "Connection attempt from/to self "
1342 "ignored\n", s, __func__);
1345 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1346 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1347 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1348 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1349 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1350 log(LOG_DEBUG, "%s; %s: Listen socket: "
1351 "Connection attempt from/to broad- "
1352 "or multicast address ignored\n",
1359 * SYN appears to be valid. Create compressed TCP state
1363 if (so->so_options & SO_DEBUG)
1364 tcp_trace(TA_INPUT, ostate, tp,
1365 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1367 tcp_dooptions(&to, optp, optlen, TO_SYN);
1368 syncache_add(&inc, &to, th, inp, &so, m);
1370 * Entry added to syncache and mbuf consumed.
1371 * Everything already unlocked by syncache_add().
1373 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1375 } else if (tp->t_state == TCPS_LISTEN) {
1377 * When a listen socket is torn down the SO_ACCEPTCONN
1378 * flag is removed first while connections are drained
1379 * from the accept queue in a unlock/lock cycle of the
1380 * ACCEPT_LOCK, opening a race condition allowing a SYN
1381 * attempt go through unhandled.
1386 #ifdef TCP_SIGNATURE
1387 if (sig_checked == 0) {
1388 tcp_dooptions(&to, optp, optlen,
1389 (thflags & TH_SYN) ? TO_SYN : 0);
1390 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
1394 * In SYN_SENT state if it receives an RST, it is
1395 * allowed for further processing.
1397 if ((thflags & TH_RST) == 0 ||
1398 (tp->t_state == TCPS_SYN_SENT) == 0)
1406 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1407 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1408 * the inpcb, and unlocks pcbinfo.
1410 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1411 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1415 if (ti_locked == TI_WLOCKED) {
1416 INP_INFO_WUNLOCK(&V_tcbinfo);
1417 ti_locked = TI_UNLOCKED;
1421 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1422 "ti_locked: %d", __func__, ti_locked));
1423 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1428 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1431 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1432 m = NULL; /* mbuf chain got consumed. */
1436 if (ti_locked == TI_WLOCKED) {
1437 INP_INFO_WUNLOCK(&V_tcbinfo);
1438 ti_locked = TI_UNLOCKED;
1442 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1443 "ti_locked: %d", __func__, ti_locked));
1444 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1452 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1460 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1461 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1464 int thflags, acked, ourfinisacked, needoutput = 0;
1465 int rstreason, todrop, win;
1471 * The size of tcp_saveipgen must be the size of the max ip header,
1474 u_char tcp_saveipgen[IP6_HDR_LEN];
1475 struct tcphdr tcp_savetcp;
1478 thflags = th->th_flags;
1479 tp->sackhint.last_sack_ack = 0;
1482 * If this is either a state-changing packet or current state isn't
1483 * established, we require a write lock on tcbinfo. Otherwise, we
1484 * allow either a read lock or a write lock, as we may have acquired
1485 * a write lock due to a race.
1487 * Require a global write lock for SYN/FIN/RST segments or
1488 * non-established connections; otherwise accept either a read or
1489 * write lock, as we may have conservatively acquired a write lock in
1490 * certain cases in tcp_input() (is this still true?). Currently we
1491 * will never enter with no lock, so we try to drop it quickly in the
1492 * common pure ack/pure data cases.
1494 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1495 tp->t_state != TCPS_ESTABLISHED) {
1496 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
1497 "SYN/FIN/RST/!EST", __func__, ti_locked));
1498 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1501 if (ti_locked == TI_WLOCKED)
1502 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1504 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1505 "ti_locked: %d", __func__, ti_locked));
1506 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1510 INP_WLOCK_ASSERT(tp->t_inpcb);
1511 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1513 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1517 * Segment received on connection.
1518 * Reset idle time and keep-alive timer.
1519 * XXX: This should be done after segment
1520 * validation to ignore broken/spoofed segs.
1522 tp->t_rcvtime = ticks;
1523 if (TCPS_HAVEESTABLISHED(tp->t_state))
1524 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1527 * Unscale the window into a 32-bit value.
1528 * For the SYN_SENT state the scale is zero.
1530 tiwin = th->th_win << tp->snd_scale;
1533 * TCP ECN processing.
1535 if (tp->t_flags & TF_ECN_PERMIT) {
1536 if (thflags & TH_CWR)
1537 tp->t_flags &= ~TF_ECN_SND_ECE;
1538 switch (iptos & IPTOS_ECN_MASK) {
1540 tp->t_flags |= TF_ECN_SND_ECE;
1541 TCPSTAT_INC(tcps_ecn_ce);
1543 case IPTOS_ECN_ECT0:
1544 TCPSTAT_INC(tcps_ecn_ect0);
1546 case IPTOS_ECN_ECT1:
1547 TCPSTAT_INC(tcps_ecn_ect1);
1550 /* Congestion experienced. */
1551 if (thflags & TH_ECE) {
1552 cc_cong_signal(tp, th, CC_ECN);
1557 * Parse options on any incoming segment.
1559 tcp_dooptions(&to, (u_char *)(th + 1),
1560 (th->th_off << 2) - sizeof(struct tcphdr),
1561 (thflags & TH_SYN) ? TO_SYN : 0);
1564 * If echoed timestamp is later than the current time,
1565 * fall back to non RFC1323 RTT calculation. Normalize
1566 * timestamp if syncookies were used when this connection
1569 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1570 to.to_tsecr -= tp->ts_offset;
1571 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1576 * Process options only when we get SYN/ACK back. The SYN case
1577 * for incoming connections is handled in tcp_syncache.
1578 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1579 * or <SYN,ACK>) segment itself is never scaled.
1580 * XXX this is traditional behavior, may need to be cleaned up.
1582 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1583 if ((to.to_flags & TOF_SCALE) &&
1584 (tp->t_flags & TF_REQ_SCALE)) {
1585 tp->t_flags |= TF_RCVD_SCALE;
1586 tp->snd_scale = to.to_wscale;
1589 * Initial send window. It will be updated with
1590 * the next incoming segment to the scaled value.
1592 tp->snd_wnd = th->th_win;
1593 if (to.to_flags & TOF_TS) {
1594 tp->t_flags |= TF_RCVD_TSTMP;
1595 tp->ts_recent = to.to_tsval;
1596 tp->ts_recent_age = tcp_ts_getticks();
1598 if (to.to_flags & TOF_MSS)
1599 tcp_mss(tp, to.to_mss);
1600 if ((tp->t_flags & TF_SACK_PERMIT) &&
1601 (to.to_flags & TOF_SACKPERM) == 0)
1602 tp->t_flags &= ~TF_SACK_PERMIT;
1606 * Header prediction: check for the two common cases
1607 * of a uni-directional data xfer. If the packet has
1608 * no control flags, is in-sequence, the window didn't
1609 * change and we're not retransmitting, it's a
1610 * candidate. If the length is zero and the ack moved
1611 * forward, we're the sender side of the xfer. Just
1612 * free the data acked & wake any higher level process
1613 * that was blocked waiting for space. If the length
1614 * is non-zero and the ack didn't move, we're the
1615 * receiver side. If we're getting packets in-order
1616 * (the reassembly queue is empty), add the data to
1617 * the socket buffer and note that we need a delayed ack.
1618 * Make sure that the hidden state-flags are also off.
1619 * Since we check for TCPS_ESTABLISHED first, it can only
1622 if (tp->t_state == TCPS_ESTABLISHED &&
1623 th->th_seq == tp->rcv_nxt &&
1624 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1625 tp->snd_nxt == tp->snd_max &&
1626 tiwin && tiwin == tp->snd_wnd &&
1627 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1628 LIST_EMPTY(&tp->t_segq) &&
1629 ((to.to_flags & TOF_TS) == 0 ||
1630 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1633 * If last ACK falls within this segment's sequence numbers,
1634 * record the timestamp.
1635 * NOTE that the test is modified according to the latest
1636 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1638 if ((to.to_flags & TOF_TS) != 0 &&
1639 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1640 tp->ts_recent_age = tcp_ts_getticks();
1641 tp->ts_recent = to.to_tsval;
1645 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1646 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1647 !IN_RECOVERY(tp->t_flags) &&
1648 (to.to_flags & TOF_SACK) == 0 &&
1649 TAILQ_EMPTY(&tp->snd_holes)) {
1651 * This is a pure ack for outstanding data.
1653 if (ti_locked == TI_WLOCKED)
1654 INP_INFO_WUNLOCK(&V_tcbinfo);
1655 ti_locked = TI_UNLOCKED;
1657 TCPSTAT_INC(tcps_predack);
1660 * "bad retransmit" recovery.
1662 if (tp->t_rxtshift == 1 &&
1663 tp->t_flags & TF_PREVVALID &&
1664 (int)(ticks - tp->t_badrxtwin) < 0) {
1665 cc_cong_signal(tp, th, CC_RTO_ERR);
1669 * Recalculate the transmit timer / rtt.
1671 * Some boxes send broken timestamp replies
1672 * during the SYN+ACK phase, ignore
1673 * timestamps of 0 or we could calculate a
1674 * huge RTT and blow up the retransmit timer.
1676 if ((to.to_flags & TOF_TS) != 0 &&
1680 t = tcp_ts_getticks() - to.to_tsecr;
1681 if (!tp->t_rttlow || tp->t_rttlow > t)
1684 TCP_TS_TO_TICKS(t) + 1);
1685 } else if (tp->t_rtttime &&
1686 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1687 if (!tp->t_rttlow ||
1688 tp->t_rttlow > ticks - tp->t_rtttime)
1689 tp->t_rttlow = ticks - tp->t_rtttime;
1691 ticks - tp->t_rtttime);
1693 acked = BYTES_THIS_ACK(tp, th);
1695 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1696 hhook_run_tcp_est_in(tp, th, &to);
1698 TCPSTAT_INC(tcps_rcvackpack);
1699 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1700 sbdrop(&so->so_snd, acked);
1701 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1702 SEQ_LEQ(th->th_ack, tp->snd_recover))
1703 tp->snd_recover = th->th_ack - 1;
1706 * Let the congestion control algorithm update
1707 * congestion control related information. This
1708 * typically means increasing the congestion
1711 cc_ack_received(tp, th, CC_ACK);
1713 tp->snd_una = th->th_ack;
1715 * Pull snd_wl2 up to prevent seq wrap relative
1718 tp->snd_wl2 = th->th_ack;
1721 ND6_HINT(tp); /* Some progress has been made. */
1724 * If all outstanding data are acked, stop
1725 * retransmit timer, otherwise restart timer
1726 * using current (possibly backed-off) value.
1727 * If process is waiting for space,
1728 * wakeup/selwakeup/signal. If data
1729 * are ready to send, let tcp_output
1730 * decide between more output or persist.
1733 if (so->so_options & SO_DEBUG)
1734 tcp_trace(TA_INPUT, ostate, tp,
1735 (void *)tcp_saveipgen,
1738 if (tp->snd_una == tp->snd_max)
1739 tcp_timer_activate(tp, TT_REXMT, 0);
1740 else if (!tcp_timer_active(tp, TT_PERSIST))
1741 tcp_timer_activate(tp, TT_REXMT,
1744 if (so->so_snd.sb_cc)
1745 (void) tcp_output(tp);
1748 } else if (th->th_ack == tp->snd_una &&
1749 tlen <= sbspace(&so->so_rcv)) {
1750 int newsize = 0; /* automatic sockbuf scaling */
1753 * This is a pure, in-sequence data packet with
1754 * nothing on the reassembly queue and we have enough
1755 * buffer space to take it.
1757 if (ti_locked == TI_WLOCKED)
1758 INP_INFO_WUNLOCK(&V_tcbinfo);
1759 ti_locked = TI_UNLOCKED;
1761 /* Clean receiver SACK report if present */
1762 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1763 tcp_clean_sackreport(tp);
1764 TCPSTAT_INC(tcps_preddat);
1765 tp->rcv_nxt += tlen;
1767 * Pull snd_wl1 up to prevent seq wrap relative to
1770 tp->snd_wl1 = th->th_seq;
1772 * Pull rcv_up up to prevent seq wrap relative to
1775 tp->rcv_up = tp->rcv_nxt;
1776 TCPSTAT_INC(tcps_rcvpack);
1777 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1778 ND6_HINT(tp); /* Some progress has been made */
1780 if (so->so_options & SO_DEBUG)
1781 tcp_trace(TA_INPUT, ostate, tp,
1782 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1785 * Automatic sizing of receive socket buffer. Often the send
1786 * buffer size is not optimally adjusted to the actual network
1787 * conditions at hand (delay bandwidth product). Setting the
1788 * buffer size too small limits throughput on links with high
1789 * bandwidth and high delay (eg. trans-continental/oceanic links).
1791 * On the receive side the socket buffer memory is only rarely
1792 * used to any significant extent. This allows us to be much
1793 * more aggressive in scaling the receive socket buffer. For
1794 * the case that the buffer space is actually used to a large
1795 * extent and we run out of kernel memory we can simply drop
1796 * the new segments; TCP on the sender will just retransmit it
1797 * later. Setting the buffer size too big may only consume too
1798 * much kernel memory if the application doesn't read() from
1799 * the socket or packet loss or reordering makes use of the
1802 * The criteria to step up the receive buffer one notch are:
1803 * 1. the number of bytes received during the time it takes
1804 * one timestamp to be reflected back to us (the RTT);
1805 * 2. received bytes per RTT is within seven eighth of the
1806 * current socket buffer size;
1807 * 3. receive buffer size has not hit maximal automatic size;
1809 * This algorithm does one step per RTT at most and only if
1810 * we receive a bulk stream w/o packet losses or reorderings.
1811 * Shrinking the buffer during idle times is not necessary as
1812 * it doesn't consume any memory when idle.
1814 * TODO: Only step up if the application is actually serving
1815 * the buffer to better manage the socket buffer resources.
1817 if (V_tcp_do_autorcvbuf &&
1819 (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
1820 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
1821 to.to_tsecr - tp->rfbuf_ts < hz) {
1823 (so->so_rcv.sb_hiwat / 8 * 7) &&
1824 so->so_rcv.sb_hiwat <
1825 V_tcp_autorcvbuf_max) {
1827 min(so->so_rcv.sb_hiwat +
1828 V_tcp_autorcvbuf_inc,
1829 V_tcp_autorcvbuf_max);
1831 /* Start over with next RTT. */
1835 tp->rfbuf_cnt += tlen; /* add up */
1838 /* Add data to socket buffer. */
1839 SOCKBUF_LOCK(&so->so_rcv);
1840 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1844 * Set new socket buffer size.
1845 * Give up when limit is reached.
1848 if (!sbreserve_locked(&so->so_rcv,
1850 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1851 m_adj(m, drop_hdrlen); /* delayed header drop */
1852 sbappendstream_locked(&so->so_rcv, m);
1854 /* NB: sorwakeup_locked() does an implicit unlock. */
1855 sorwakeup_locked(so);
1856 if (DELAY_ACK(tp, tlen)) {
1857 tp->t_flags |= TF_DELACK;
1859 tp->t_flags |= TF_ACKNOW;
1867 * Calculate amount of space in receive window,
1868 * and then do TCP input processing.
1869 * Receive window is amount of space in rcv queue,
1870 * but not less than advertised window.
1872 win = sbspace(&so->so_rcv);
1875 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1877 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1881 switch (tp->t_state) {
1884 * If the state is SYN_RECEIVED:
1885 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1887 case TCPS_SYN_RECEIVED:
1888 if ((thflags & TH_ACK) &&
1889 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1890 SEQ_GT(th->th_ack, tp->snd_max))) {
1891 rstreason = BANDLIM_RST_OPENPORT;
1897 * If the state is SYN_SENT:
1898 * if seg contains an ACK, but not for our SYN, drop the input.
1899 * if seg contains a RST, then drop the connection.
1900 * if seg does not contain SYN, then drop it.
1901 * Otherwise this is an acceptable SYN segment
1902 * initialize tp->rcv_nxt and tp->irs
1903 * if seg contains ack then advance tp->snd_una
1904 * if seg contains an ECE and ECN support is enabled, the stream
1906 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1907 * arrange for segment to be acked (eventually)
1908 * continue processing rest of data/controls, beginning with URG
1911 if ((thflags & TH_ACK) &&
1912 (SEQ_LEQ(th->th_ack, tp->iss) ||
1913 SEQ_GT(th->th_ack, tp->snd_max))) {
1914 rstreason = BANDLIM_UNLIMITED;
1917 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST))
1918 tp = tcp_drop(tp, ECONNREFUSED);
1919 if (thflags & TH_RST)
1921 if (!(thflags & TH_SYN))
1924 tp->irs = th->th_seq;
1926 if (thflags & TH_ACK) {
1927 TCPSTAT_INC(tcps_connects);
1930 mac_socketpeer_set_from_mbuf(m, so);
1932 /* Do window scaling on this connection? */
1933 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1934 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1935 tp->rcv_scale = tp->request_r_scale;
1937 tp->rcv_adv += imin(tp->rcv_wnd,
1938 TCP_MAXWIN << tp->rcv_scale);
1939 tp->snd_una++; /* SYN is acked */
1941 * If there's data, delay ACK; if there's also a FIN
1942 * ACKNOW will be turned on later.
1944 if (DELAY_ACK(tp, tlen) && tlen != 0)
1945 tcp_timer_activate(tp, TT_DELACK,
1948 tp->t_flags |= TF_ACKNOW;
1950 if ((thflags & TH_ECE) && V_tcp_do_ecn) {
1951 tp->t_flags |= TF_ECN_PERMIT;
1952 TCPSTAT_INC(tcps_ecn_shs);
1956 * Received <SYN,ACK> in SYN_SENT[*] state.
1958 * SYN_SENT --> ESTABLISHED
1959 * SYN_SENT* --> FIN_WAIT_1
1961 tp->t_starttime = ticks;
1962 if (tp->t_flags & TF_NEEDFIN) {
1963 tp->t_state = TCPS_FIN_WAIT_1;
1964 tp->t_flags &= ~TF_NEEDFIN;
1967 tp->t_state = TCPS_ESTABLISHED;
1969 tcp_timer_activate(tp, TT_KEEP,
1974 * Received initial SYN in SYN-SENT[*] state =>
1975 * simultaneous open. If segment contains CC option
1976 * and there is a cached CC, apply TAO test.
1977 * If it succeeds, connection is * half-synchronized.
1978 * Otherwise, do 3-way handshake:
1979 * SYN-SENT -> SYN-RECEIVED
1980 * SYN-SENT* -> SYN-RECEIVED*
1981 * If there was no CC option, clear cached CC value.
1983 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1984 tcp_timer_activate(tp, TT_REXMT, 0);
1985 tp->t_state = TCPS_SYN_RECEIVED;
1988 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
1989 "ti_locked %d", __func__, ti_locked));
1990 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1991 INP_WLOCK_ASSERT(tp->t_inpcb);
1994 * Advance th->th_seq to correspond to first data byte.
1995 * If data, trim to stay within window,
1996 * dropping FIN if necessary.
1999 if (tlen > tp->rcv_wnd) {
2000 todrop = tlen - tp->rcv_wnd;
2004 TCPSTAT_INC(tcps_rcvpackafterwin);
2005 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2007 tp->snd_wl1 = th->th_seq - 1;
2008 tp->rcv_up = th->th_seq;
2010 * Client side of transaction: already sent SYN and data.
2011 * If the remote host used T/TCP to validate the SYN,
2012 * our data will be ACK'd; if so, enter normal data segment
2013 * processing in the middle of step 5, ack processing.
2014 * Otherwise, goto step 6.
2016 if (thflags & TH_ACK)
2022 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2023 * do normal processing.
2025 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2029 break; /* continue normal processing */
2033 * States other than LISTEN or SYN_SENT.
2034 * First check the RST flag and sequence number since reset segments
2035 * are exempt from the timestamp and connection count tests. This
2036 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2037 * below which allowed reset segments in half the sequence space
2038 * to fall though and be processed (which gives forged reset
2039 * segments with a random sequence number a 50 percent chance of
2040 * killing a connection).
2041 * Then check timestamp, if present.
2042 * Then check the connection count, if present.
2043 * Then check that at least some bytes of segment are within
2044 * receive window. If segment begins before rcv_nxt,
2045 * drop leading data (and SYN); if nothing left, just ack.
2048 * If the RST bit is set, check the sequence number to see
2049 * if this is a valid reset segment.
2051 * In all states except SYN-SENT, all reset (RST) segments
2052 * are validated by checking their SEQ-fields. A reset is
2053 * valid if its sequence number is in the window.
2054 * Note: this does not take into account delayed ACKs, so
2055 * we should test against last_ack_sent instead of rcv_nxt.
2056 * The sequence number in the reset segment is normally an
2057 * echo of our outgoing acknowlegement numbers, but some hosts
2058 * send a reset with the sequence number at the rightmost edge
2059 * of our receive window, and we have to handle this case.
2060 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
2061 * that brute force RST attacks are possible. To combat this,
2062 * we use a much stricter check while in the ESTABLISHED state,
2063 * only accepting RSTs where the sequence number is equal to
2064 * last_ack_sent. In all other states (the states in which a
2065 * RST is more likely), the more permissive check is used.
2066 * If we have multiple segments in flight, the initial reset
2067 * segment sequence numbers will be to the left of last_ack_sent,
2068 * but they will eventually catch up.
2069 * In any case, it never made sense to trim reset segments to
2070 * fit the receive window since RFC 1122 says:
2071 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
2073 * A TCP SHOULD allow a received RST segment to include data.
2076 * It has been suggested that a RST segment could contain
2077 * ASCII text that encoded and explained the cause of the
2078 * RST. No standard has yet been established for such
2081 * If the reset segment passes the sequence number test examine
2083 * SYN_RECEIVED STATE:
2084 * If passive open, return to LISTEN state.
2085 * If active open, inform user that connection was refused.
2086 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
2087 * Inform user that connection was reset, and close tcb.
2088 * CLOSING, LAST_ACK STATES:
2091 * Drop the segment - see Stevens, vol. 2, p. 964 and
2094 if (thflags & TH_RST) {
2095 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2096 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2097 switch (tp->t_state) {
2099 case TCPS_SYN_RECEIVED:
2100 so->so_error = ECONNREFUSED;
2103 case TCPS_ESTABLISHED:
2104 if (V_tcp_insecure_rst == 0 &&
2105 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) &&
2106 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) &&
2107 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2108 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) {
2109 TCPSTAT_INC(tcps_badrst);
2113 case TCPS_FIN_WAIT_1:
2114 case TCPS_FIN_WAIT_2:
2115 case TCPS_CLOSE_WAIT:
2116 so->so_error = ECONNRESET;
2118 KASSERT(ti_locked == TI_WLOCKED,
2119 ("tcp_do_segment: TH_RST 1 ti_locked %d",
2121 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2123 tp->t_state = TCPS_CLOSED;
2124 TCPSTAT_INC(tcps_drops);
2130 KASSERT(ti_locked == TI_WLOCKED,
2131 ("tcp_do_segment: TH_RST 2 ti_locked %d",
2133 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2143 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2144 * and it's less than ts_recent, drop it.
2146 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2147 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2149 /* Check to see if ts_recent is over 24 days old. */
2150 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2152 * Invalidate ts_recent. If this segment updates
2153 * ts_recent, the age will be reset later and ts_recent
2154 * will get a valid value. If it does not, setting
2155 * ts_recent to zero will at least satisfy the
2156 * requirement that zero be placed in the timestamp
2157 * echo reply when ts_recent isn't valid. The
2158 * age isn't reset until we get a valid ts_recent
2159 * because we don't want out-of-order segments to be
2160 * dropped when ts_recent is old.
2164 TCPSTAT_INC(tcps_rcvduppack);
2165 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2166 TCPSTAT_INC(tcps_pawsdrop);
2174 * In the SYN-RECEIVED state, validate that the packet belongs to
2175 * this connection before trimming the data to fit the receive
2176 * window. Check the sequence number versus IRS since we know
2177 * the sequence numbers haven't wrapped. This is a partial fix
2178 * for the "LAND" DoS attack.
2180 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2181 rstreason = BANDLIM_RST_OPENPORT;
2185 todrop = tp->rcv_nxt - th->th_seq;
2187 if (thflags & TH_SYN) {
2197 * Following if statement from Stevens, vol. 2, p. 960.
2200 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2202 * Any valid FIN must be to the left of the window.
2203 * At this point the FIN must be a duplicate or out
2204 * of sequence; drop it.
2209 * Send an ACK to resynchronize and drop any data.
2210 * But keep on processing for RST or ACK.
2212 tp->t_flags |= TF_ACKNOW;
2214 TCPSTAT_INC(tcps_rcvduppack);
2215 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2217 TCPSTAT_INC(tcps_rcvpartduppack);
2218 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2220 drop_hdrlen += todrop; /* drop from the top afterwards */
2221 th->th_seq += todrop;
2223 if (th->th_urp > todrop)
2224 th->th_urp -= todrop;
2232 * If new data are received on a connection after the
2233 * user processes are gone, then RST the other end.
2235 if ((so->so_state & SS_NOFDREF) &&
2236 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2239 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
2240 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2241 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2243 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
2244 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket "
2245 "was closed, sending RST and removing tcpcb\n",
2246 s, __func__, tcpstates[tp->t_state], tlen);
2250 TCPSTAT_INC(tcps_rcvafterclose);
2251 rstreason = BANDLIM_UNLIMITED;
2256 * If segment ends after window, drop trailing data
2257 * (and PUSH and FIN); if nothing left, just ACK.
2259 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2261 TCPSTAT_INC(tcps_rcvpackafterwin);
2262 if (todrop >= tlen) {
2263 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2265 * If window is closed can only take segments at
2266 * window edge, and have to drop data and PUSH from
2267 * incoming segments. Continue processing, but
2268 * remember to ack. Otherwise, drop segment
2271 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2272 tp->t_flags |= TF_ACKNOW;
2273 TCPSTAT_INC(tcps_rcvwinprobe);
2277 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2280 thflags &= ~(TH_PUSH|TH_FIN);
2284 * If last ACK falls within this segment's sequence numbers,
2285 * record its timestamp.
2287 * 1) That the test incorporates suggestions from the latest
2288 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2289 * 2) That updating only on newer timestamps interferes with
2290 * our earlier PAWS tests, so this check should be solely
2291 * predicated on the sequence space of this segment.
2292 * 3) That we modify the segment boundary check to be
2293 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2294 * instead of RFC1323's
2295 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2296 * This modified check allows us to overcome RFC1323's
2297 * limitations as described in Stevens TCP/IP Illustrated
2298 * Vol. 2 p.869. In such cases, we can still calculate the
2299 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2301 if ((to.to_flags & TOF_TS) != 0 &&
2302 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2303 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2304 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2305 tp->ts_recent_age = tcp_ts_getticks();
2306 tp->ts_recent = to.to_tsval;
2310 * If a SYN is in the window, then this is an
2311 * error and we send an RST and drop the connection.
2313 if (thflags & TH_SYN) {
2314 KASSERT(ti_locked == TI_WLOCKED,
2315 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2316 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2318 tp = tcp_drop(tp, ECONNRESET);
2319 rstreason = BANDLIM_UNLIMITED;
2324 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2325 * flag is on (half-synchronized state), then queue data for
2326 * later processing; else drop segment and return.
2328 if ((thflags & TH_ACK) == 0) {
2329 if (tp->t_state == TCPS_SYN_RECEIVED ||
2330 (tp->t_flags & TF_NEEDSYN))
2332 else if (tp->t_flags & TF_ACKNOW)
2341 switch (tp->t_state) {
2344 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2345 * ESTABLISHED state and continue processing.
2346 * The ACK was checked above.
2348 case TCPS_SYN_RECEIVED:
2350 TCPSTAT_INC(tcps_connects);
2352 /* Do window scaling? */
2353 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2354 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2355 tp->rcv_scale = tp->request_r_scale;
2356 tp->snd_wnd = tiwin;
2360 * SYN-RECEIVED -> ESTABLISHED
2361 * SYN-RECEIVED* -> FIN-WAIT-1
2363 tp->t_starttime = ticks;
2364 if (tp->t_flags & TF_NEEDFIN) {
2365 tp->t_state = TCPS_FIN_WAIT_1;
2366 tp->t_flags &= ~TF_NEEDFIN;
2368 tp->t_state = TCPS_ESTABLISHED;
2370 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2373 * If segment contains data or ACK, will call tcp_reass()
2374 * later; if not, do so now to pass queued data to user.
2376 if (tlen == 0 && (thflags & TH_FIN) == 0)
2377 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2379 tp->snd_wl1 = th->th_seq - 1;
2383 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2384 * ACKs. If the ack is in the range
2385 * tp->snd_una < th->th_ack <= tp->snd_max
2386 * then advance tp->snd_una to th->th_ack and drop
2387 * data from the retransmission queue. If this ACK reflects
2388 * more up to date window information we update our window information.
2390 case TCPS_ESTABLISHED:
2391 case TCPS_FIN_WAIT_1:
2392 case TCPS_FIN_WAIT_2:
2393 case TCPS_CLOSE_WAIT:
2396 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2397 TCPSTAT_INC(tcps_rcvacktoomuch);
2400 if ((tp->t_flags & TF_SACK_PERMIT) &&
2401 ((to.to_flags & TOF_SACK) ||
2402 !TAILQ_EMPTY(&tp->snd_holes)))
2403 tcp_sack_doack(tp, &to, th->th_ack);
2405 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2406 hhook_run_tcp_est_in(tp, th, &to);
2408 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2409 if (tlen == 0 && tiwin == tp->snd_wnd) {
2410 TCPSTAT_INC(tcps_rcvdupack);
2412 * If we have outstanding data (other than
2413 * a window probe), this is a completely
2414 * duplicate ack (ie, window info didn't
2415 * change), the ack is the biggest we've
2416 * seen and we've seen exactly our rexmt
2417 * threshhold of them, assume a packet
2418 * has been dropped and retransmit it.
2419 * Kludge snd_nxt & the congestion
2420 * window so we send only this one
2423 * We know we're losing at the current
2424 * window size so do congestion avoidance
2425 * (set ssthresh to half the current window
2426 * and pull our congestion window back to
2427 * the new ssthresh).
2429 * Dup acks mean that packets have left the
2430 * network (they're now cached at the receiver)
2431 * so bump cwnd by the amount in the receiver
2432 * to keep a constant cwnd packets in the
2435 * When using TCP ECN, notify the peer that
2436 * we reduced the cwnd.
2438 if (!tcp_timer_active(tp, TT_REXMT) ||
2439 th->th_ack != tp->snd_una)
2441 else if (++tp->t_dupacks > tcprexmtthresh ||
2442 IN_FASTRECOVERY(tp->t_flags)) {
2443 cc_ack_received(tp, th, CC_DUPACK);
2444 if ((tp->t_flags & TF_SACK_PERMIT) &&
2445 IN_FASTRECOVERY(tp->t_flags)) {
2449 * Compute the amount of data in flight first.
2450 * We can inject new data into the pipe iff
2451 * we have less than 1/2 the original window's
2452 * worth of data in flight.
2454 awnd = (tp->snd_nxt - tp->snd_fack) +
2455 tp->sackhint.sack_bytes_rexmit;
2456 if (awnd < tp->snd_ssthresh) {
2457 tp->snd_cwnd += tp->t_maxseg;
2458 if (tp->snd_cwnd > tp->snd_ssthresh)
2459 tp->snd_cwnd = tp->snd_ssthresh;
2462 tp->snd_cwnd += tp->t_maxseg;
2463 if ((thflags & TH_FIN) &&
2464 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2466 * If its a fin we need to process
2467 * it to avoid a race where both
2468 * sides enter FIN-WAIT and send FIN|ACK
2473 (void) tcp_output(tp);
2475 } else if (tp->t_dupacks == tcprexmtthresh) {
2476 tcp_seq onxt = tp->snd_nxt;
2479 * If we're doing sack, check to
2480 * see if we're already in sack
2481 * recovery. If we're not doing sack,
2482 * check to see if we're in newreno
2485 if (tp->t_flags & TF_SACK_PERMIT) {
2486 if (IN_FASTRECOVERY(tp->t_flags)) {
2491 if (SEQ_LEQ(th->th_ack,
2497 /* Congestion signal before ack. */
2498 cc_cong_signal(tp, th, CC_NDUPACK);
2499 cc_ack_received(tp, th, CC_DUPACK);
2500 tcp_timer_activate(tp, TT_REXMT, 0);
2502 if (tp->t_flags & TF_SACK_PERMIT) {
2504 tcps_sack_recovery_episode);
2505 tp->sack_newdata = tp->snd_nxt;
2506 tp->snd_cwnd = tp->t_maxseg;
2507 (void) tcp_output(tp);
2510 tp->snd_nxt = th->th_ack;
2511 tp->snd_cwnd = tp->t_maxseg;
2512 if ((thflags & TH_FIN) &&
2513 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2515 * If its a fin we need to process
2516 * it to avoid a race where both
2517 * sides enter FIN-WAIT and send FIN|ACK
2522 (void) tcp_output(tp);
2523 KASSERT(tp->snd_limited <= 2,
2524 ("%s: tp->snd_limited too big",
2526 tp->snd_cwnd = tp->snd_ssthresh +
2528 (tp->t_dupacks - tp->snd_limited);
2529 if (SEQ_GT(onxt, tp->snd_nxt))
2532 } else if (V_tcp_do_rfc3042) {
2533 cc_ack_received(tp, th, CC_DUPACK);
2534 u_long oldcwnd = tp->snd_cwnd;
2535 tcp_seq oldsndmax = tp->snd_max;
2539 KASSERT(tp->t_dupacks == 1 ||
2541 ("%s: dupacks not 1 or 2",
2543 if (tp->t_dupacks == 1)
2544 tp->snd_limited = 0;
2546 (tp->snd_nxt - tp->snd_una) +
2547 (tp->t_dupacks - tp->snd_limited) *
2549 if ((thflags & TH_FIN) &&
2550 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2552 * If its a fin we need to process
2553 * it to avoid a race where both
2554 * sides enter FIN-WAIT and send FIN|ACK
2560 * Only call tcp_output when there
2561 * is new data available to be sent.
2562 * Otherwise we would send pure ACKs.
2564 SOCKBUF_LOCK(&so->so_snd);
2565 avail = so->so_snd.sb_cc -
2566 (tp->snd_nxt - tp->snd_una);
2567 SOCKBUF_UNLOCK(&so->so_snd);
2569 (void) tcp_output(tp);
2570 sent = tp->snd_max - oldsndmax;
2571 if (sent > tp->t_maxseg) {
2572 KASSERT((tp->t_dupacks == 2 &&
2573 tp->snd_limited == 0) ||
2574 (sent == tp->t_maxseg + 1 &&
2575 tp->t_flags & TF_SENTFIN),
2576 ("%s: sent too much",
2578 tp->snd_limited = 2;
2579 } else if (sent > 0)
2581 tp->snd_cwnd = oldcwnd;
2589 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2590 ("%s: th_ack <= snd_una", __func__));
2593 * If the congestion window was inflated to account
2594 * for the other side's cached packets, retract it.
2596 if (IN_FASTRECOVERY(tp->t_flags)) {
2597 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2598 if (tp->t_flags & TF_SACK_PERMIT)
2599 tcp_sack_partialack(tp, th);
2601 tcp_newreno_partial_ack(tp, th);
2603 cc_post_recovery(tp, th);
2607 * If we reach this point, ACK is not a duplicate,
2608 * i.e., it ACKs something we sent.
2610 if (tp->t_flags & TF_NEEDSYN) {
2612 * T/TCP: Connection was half-synchronized, and our
2613 * SYN has been ACK'd (so connection is now fully
2614 * synchronized). Go to non-starred state,
2615 * increment snd_una for ACK of SYN, and check if
2616 * we can do window scaling.
2618 tp->t_flags &= ~TF_NEEDSYN;
2620 /* Do window scaling? */
2621 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2622 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2623 tp->rcv_scale = tp->request_r_scale;
2624 /* Send window already scaled. */
2629 INP_WLOCK_ASSERT(tp->t_inpcb);
2631 acked = BYTES_THIS_ACK(tp, th);
2632 KASSERT(acked >= 0, ("%s: acked unexepectedly negative "
2633 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__,
2634 tp->snd_una, th->th_ack, tp, m));
2635 TCPSTAT_INC(tcps_rcvackpack);
2636 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2639 * If we just performed our first retransmit, and the ACK
2640 * arrives within our recovery window, then it was a mistake
2641 * to do the retransmit in the first place. Recover our
2642 * original cwnd and ssthresh, and proceed to transmit where
2645 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2646 (int)(ticks - tp->t_badrxtwin) < 0)
2647 cc_cong_signal(tp, th, CC_RTO_ERR);
2650 * If we have a timestamp reply, update smoothed
2651 * round trip time. If no timestamp is present but
2652 * transmit timer is running and timed sequence
2653 * number was acked, update smoothed round trip time.
2654 * Since we now have an rtt measurement, cancel the
2655 * timer backoff (cf., Phil Karn's retransmit alg.).
2656 * Recompute the initial retransmit timer.
2658 * Some boxes send broken timestamp replies
2659 * during the SYN+ACK phase, ignore
2660 * timestamps of 0 or we could calculate a
2661 * huge RTT and blow up the retransmit timer.
2663 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2666 t = tcp_ts_getticks() - to.to_tsecr;
2667 if (!tp->t_rttlow || tp->t_rttlow > t)
2669 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2670 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2671 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2672 tp->t_rttlow = ticks - tp->t_rtttime;
2673 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2677 * If all outstanding data is acked, stop retransmit
2678 * timer and remember to restart (more output or persist).
2679 * If there is more data to be acked, restart retransmit
2680 * timer, using current (possibly backed-off) value.
2682 if (th->th_ack == tp->snd_max) {
2683 tcp_timer_activate(tp, TT_REXMT, 0);
2685 } else if (!tcp_timer_active(tp, TT_PERSIST))
2686 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2689 * If no data (only SYN) was ACK'd,
2690 * skip rest of ACK processing.
2696 * Let the congestion control algorithm update congestion
2697 * control related information. This typically means increasing
2698 * the congestion window.
2700 cc_ack_received(tp, th, CC_ACK);
2702 SOCKBUF_LOCK(&so->so_snd);
2703 if (acked > so->so_snd.sb_cc) {
2704 if (tp->snd_wnd >= so->so_snd.sb_cc)
2705 tp->snd_wnd -= so->so_snd.sb_cc;
2708 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
2711 sbdrop_locked(&so->so_snd, acked);
2712 if (tp->snd_wnd >= (u_long) acked)
2713 tp->snd_wnd -= acked;
2718 /* NB: sowwakeup_locked() does an implicit unlock. */
2719 sowwakeup_locked(so);
2720 /* Detect una wraparound. */
2721 if (!IN_RECOVERY(tp->t_flags) &&
2722 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2723 SEQ_LEQ(th->th_ack, tp->snd_recover))
2724 tp->snd_recover = th->th_ack - 1;
2725 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2726 if (IN_RECOVERY(tp->t_flags) &&
2727 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2728 EXIT_RECOVERY(tp->t_flags);
2730 tp->snd_una = th->th_ack;
2731 if (tp->t_flags & TF_SACK_PERMIT) {
2732 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2733 tp->snd_recover = tp->snd_una;
2735 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2736 tp->snd_nxt = tp->snd_una;
2738 switch (tp->t_state) {
2741 * In FIN_WAIT_1 STATE in addition to the processing
2742 * for the ESTABLISHED state if our FIN is now acknowledged
2743 * then enter FIN_WAIT_2.
2745 case TCPS_FIN_WAIT_1:
2746 if (ourfinisacked) {
2748 * If we can't receive any more
2749 * data, then closing user can proceed.
2750 * Starting the timer is contrary to the
2751 * specification, but if we don't get a FIN
2752 * we'll hang forever.
2755 * we should release the tp also, and use a
2758 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2759 soisdisconnected(so);
2760 tcp_timer_activate(tp, TT_2MSL,
2761 (tcp_fast_finwait2_recycle ?
2762 tcp_finwait2_timeout :
2765 tp->t_state = TCPS_FIN_WAIT_2;
2770 * In CLOSING STATE in addition to the processing for
2771 * the ESTABLISHED state if the ACK acknowledges our FIN
2772 * then enter the TIME-WAIT state, otherwise ignore
2776 if (ourfinisacked) {
2777 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2779 INP_INFO_WUNLOCK(&V_tcbinfo);
2786 * In LAST_ACK, we may still be waiting for data to drain
2787 * and/or to be acked, as well as for the ack of our FIN.
2788 * If our FIN is now acknowledged, delete the TCB,
2789 * enter the closed state and return.
2792 if (ourfinisacked) {
2793 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2802 INP_WLOCK_ASSERT(tp->t_inpcb);
2805 * Update window information.
2806 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2808 if ((thflags & TH_ACK) &&
2809 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2810 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2811 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2812 /* keep track of pure window updates */
2814 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2815 TCPSTAT_INC(tcps_rcvwinupd);
2816 tp->snd_wnd = tiwin;
2817 tp->snd_wl1 = th->th_seq;
2818 tp->snd_wl2 = th->th_ack;
2819 if (tp->snd_wnd > tp->max_sndwnd)
2820 tp->max_sndwnd = tp->snd_wnd;
2825 * Process segments with URG.
2827 if ((thflags & TH_URG) && th->th_urp &&
2828 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2830 * This is a kludge, but if we receive and accept
2831 * random urgent pointers, we'll crash in
2832 * soreceive. It's hard to imagine someone
2833 * actually wanting to send this much urgent data.
2835 SOCKBUF_LOCK(&so->so_rcv);
2836 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2837 th->th_urp = 0; /* XXX */
2838 thflags &= ~TH_URG; /* XXX */
2839 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2840 goto dodata; /* XXX */
2843 * If this segment advances the known urgent pointer,
2844 * then mark the data stream. This should not happen
2845 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2846 * a FIN has been received from the remote side.
2847 * In these states we ignore the URG.
2849 * According to RFC961 (Assigned Protocols),
2850 * the urgent pointer points to the last octet
2851 * of urgent data. We continue, however,
2852 * to consider it to indicate the first octet
2853 * of data past the urgent section as the original
2854 * spec states (in one of two places).
2856 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2857 tp->rcv_up = th->th_seq + th->th_urp;
2858 so->so_oobmark = so->so_rcv.sb_cc +
2859 (tp->rcv_up - tp->rcv_nxt) - 1;
2860 if (so->so_oobmark == 0)
2861 so->so_rcv.sb_state |= SBS_RCVATMARK;
2863 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2865 SOCKBUF_UNLOCK(&so->so_rcv);
2867 * Remove out of band data so doesn't get presented to user.
2868 * This can happen independent of advancing the URG pointer,
2869 * but if two URG's are pending at once, some out-of-band
2870 * data may creep in... ick.
2872 if (th->th_urp <= (u_long)tlen &&
2873 !(so->so_options & SO_OOBINLINE)) {
2874 /* hdr drop is delayed */
2875 tcp_pulloutofband(so, th, m, drop_hdrlen);
2879 * If no out of band data is expected,
2880 * pull receive urgent pointer along
2881 * with the receive window.
2883 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2884 tp->rcv_up = tp->rcv_nxt;
2887 INP_WLOCK_ASSERT(tp->t_inpcb);
2890 * Process the segment text, merging it into the TCP sequencing queue,
2891 * and arranging for acknowledgment of receipt if necessary.
2892 * This process logically involves adjusting tp->rcv_wnd as data
2893 * is presented to the user (this happens in tcp_usrreq.c,
2894 * case PRU_RCVD). If a FIN has already been received on this
2895 * connection then we just ignore the text.
2897 if ((tlen || (thflags & TH_FIN)) &&
2898 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2899 tcp_seq save_start = th->th_seq;
2900 m_adj(m, drop_hdrlen); /* delayed header drop */
2902 * Insert segment which includes th into TCP reassembly queue
2903 * with control block tp. Set thflags to whether reassembly now
2904 * includes a segment with FIN. This handles the common case
2905 * inline (segment is the next to be received on an established
2906 * connection, and the queue is empty), avoiding linkage into
2907 * and removal from the queue and repetition of various
2909 * Set DELACK for segments received in order, but ack
2910 * immediately when segments are out of order (so
2911 * fast retransmit can work).
2913 if (th->th_seq == tp->rcv_nxt &&
2914 LIST_EMPTY(&tp->t_segq) &&
2915 TCPS_HAVEESTABLISHED(tp->t_state)) {
2916 if (DELAY_ACK(tp, tlen))
2917 tp->t_flags |= TF_DELACK;
2919 tp->t_flags |= TF_ACKNOW;
2920 tp->rcv_nxt += tlen;
2921 thflags = th->th_flags & TH_FIN;
2922 TCPSTAT_INC(tcps_rcvpack);
2923 TCPSTAT_ADD(tcps_rcvbyte, tlen);
2925 SOCKBUF_LOCK(&so->so_rcv);
2926 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2929 sbappendstream_locked(&so->so_rcv, m);
2930 /* NB: sorwakeup_locked() does an implicit unlock. */
2931 sorwakeup_locked(so);
2934 * XXX: Due to the header drop above "th" is
2935 * theoretically invalid by now. Fortunately
2936 * m_adj() doesn't actually frees any mbufs
2937 * when trimming from the head.
2939 thflags = tcp_reass(tp, th, &tlen, m);
2940 tp->t_flags |= TF_ACKNOW;
2942 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2943 tcp_update_sack_list(tp, save_start, save_start + tlen);
2946 * Note the amount of data that peer has sent into
2947 * our window, in order to estimate the sender's
2951 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2952 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2954 len = so->so_rcv.sb_hiwat;
2962 * If FIN is received ACK the FIN and let the user know
2963 * that the connection is closing.
2965 if (thflags & TH_FIN) {
2966 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2969 * If connection is half-synchronized
2970 * (ie NEEDSYN flag on) then delay ACK,
2971 * so it may be piggybacked when SYN is sent.
2972 * Otherwise, since we received a FIN then no
2973 * more input can be expected, send ACK now.
2975 if (tp->t_flags & TF_NEEDSYN)
2976 tp->t_flags |= TF_DELACK;
2978 tp->t_flags |= TF_ACKNOW;
2981 switch (tp->t_state) {
2984 * In SYN_RECEIVED and ESTABLISHED STATES
2985 * enter the CLOSE_WAIT state.
2987 case TCPS_SYN_RECEIVED:
2988 tp->t_starttime = ticks;
2990 case TCPS_ESTABLISHED:
2991 tp->t_state = TCPS_CLOSE_WAIT;
2995 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2996 * enter the CLOSING state.
2998 case TCPS_FIN_WAIT_1:
2999 tp->t_state = TCPS_CLOSING;
3003 * In FIN_WAIT_2 state enter the TIME_WAIT state,
3004 * starting the time-wait timer, turning off the other
3007 case TCPS_FIN_WAIT_2:
3008 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
3009 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
3010 "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
3014 INP_INFO_WUNLOCK(&V_tcbinfo);
3018 if (ti_locked == TI_WLOCKED)
3019 INP_INFO_WUNLOCK(&V_tcbinfo);
3020 ti_locked = TI_UNLOCKED;
3023 if (so->so_options & SO_DEBUG)
3024 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3029 * Return any desired output.
3031 if (needoutput || (tp->t_flags & TF_ACKNOW))
3032 (void) tcp_output(tp);
3035 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3036 __func__, ti_locked));
3037 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3038 INP_WLOCK_ASSERT(tp->t_inpcb);
3040 if (tp->t_flags & TF_DELACK) {
3041 tp->t_flags &= ~TF_DELACK;
3042 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3044 INP_WUNLOCK(tp->t_inpcb);
3049 * Generate an ACK dropping incoming segment if it occupies
3050 * sequence space, where the ACK reflects our state.
3052 * We can now skip the test for the RST flag since all
3053 * paths to this code happen after packets containing
3054 * RST have been dropped.
3056 * In the SYN-RECEIVED state, don't send an ACK unless the
3057 * segment we received passes the SYN-RECEIVED ACK test.
3058 * If it fails send a RST. This breaks the loop in the
3059 * "LAND" DoS attack, and also prevents an ACK storm
3060 * between two listening ports that have been sent forged
3061 * SYN segments, each with the source address of the other.
3063 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3064 (SEQ_GT(tp->snd_una, th->th_ack) ||
3065 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3066 rstreason = BANDLIM_RST_OPENPORT;
3070 if (so->so_options & SO_DEBUG)
3071 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3074 if (ti_locked == TI_WLOCKED)
3075 INP_INFO_WUNLOCK(&V_tcbinfo);
3076 ti_locked = TI_UNLOCKED;
3078 tp->t_flags |= TF_ACKNOW;
3079 (void) tcp_output(tp);
3080 INP_WUNLOCK(tp->t_inpcb);
3085 if (ti_locked == TI_WLOCKED)
3086 INP_INFO_WUNLOCK(&V_tcbinfo);
3087 ti_locked = TI_UNLOCKED;
3090 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3091 INP_WUNLOCK(tp->t_inpcb);
3093 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3097 if (ti_locked == TI_WLOCKED) {
3098 INP_INFO_WUNLOCK(&V_tcbinfo);
3099 ti_locked = TI_UNLOCKED;
3103 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3107 * Drop space held by incoming segment and return.
3110 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3111 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3115 INP_WUNLOCK(tp->t_inpcb);
3120 * Issue RST and make ACK acceptable to originator of segment.
3121 * The mbuf must still include the original packet header.
3125 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3126 int tlen, int rstreason)
3132 struct ip6_hdr *ip6;
3136 INP_WLOCK_ASSERT(tp->t_inpcb);
3139 /* Don't bother if destination was broadcast/multicast. */
3140 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3143 if (mtod(m, struct ip *)->ip_v == 6) {
3144 ip6 = mtod(m, struct ip6_hdr *);
3145 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3146 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3148 /* IPv6 anycast check is done at tcp6_input() */
3151 #if defined(INET) && defined(INET6)
3156 ip = mtod(m, struct ip *);
3157 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3158 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3159 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3160 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3165 /* Perform bandwidth limiting. */
3166 if (badport_bandlim(rstreason) < 0)
3169 /* tcp_respond consumes the mbuf chain. */
3170 if (th->th_flags & TH_ACK) {
3171 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3172 th->th_ack, TH_RST);
3174 if (th->th_flags & TH_SYN)
3176 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3177 (tcp_seq)0, TH_RST|TH_ACK);
3185 * Parse TCP options and place in tcpopt.
3188 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3193 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3195 if (opt == TCPOPT_EOL)
3197 if (opt == TCPOPT_NOP)
3203 if (optlen < 2 || optlen > cnt)
3208 if (optlen != TCPOLEN_MAXSEG)
3210 if (!(flags & TO_SYN))
3212 to->to_flags |= TOF_MSS;
3213 bcopy((char *)cp + 2,
3214 (char *)&to->to_mss, sizeof(to->to_mss));
3215 to->to_mss = ntohs(to->to_mss);
3218 if (optlen != TCPOLEN_WINDOW)
3220 if (!(flags & TO_SYN))
3222 to->to_flags |= TOF_SCALE;
3223 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3225 case TCPOPT_TIMESTAMP:
3226 if (optlen != TCPOLEN_TIMESTAMP)
3228 to->to_flags |= TOF_TS;
3229 bcopy((char *)cp + 2,
3230 (char *)&to->to_tsval, sizeof(to->to_tsval));
3231 to->to_tsval = ntohl(to->to_tsval);
3232 bcopy((char *)cp + 6,
3233 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3234 to->to_tsecr = ntohl(to->to_tsecr);
3236 #ifdef TCP_SIGNATURE
3238 * XXX In order to reply to a host which has set the
3239 * TCP_SIGNATURE option in its initial SYN, we have to
3240 * record the fact that the option was observed here
3241 * for the syncache code to perform the correct response.
3243 case TCPOPT_SIGNATURE:
3244 if (optlen != TCPOLEN_SIGNATURE)
3246 to->to_flags |= TOF_SIGNATURE;
3247 to->to_signature = cp + 2;
3250 case TCPOPT_SACK_PERMITTED:
3251 if (optlen != TCPOLEN_SACK_PERMITTED)
3253 if (!(flags & TO_SYN))
3257 to->to_flags |= TOF_SACKPERM;
3260 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3264 to->to_flags |= TOF_SACK;
3265 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3266 to->to_sacks = cp + 2;
3267 TCPSTAT_INC(tcps_sack_rcv_blocks);
3276 * Pull out of band byte out of a segment so
3277 * it doesn't appear in the user's data queue.
3278 * It is still reflected in the segment length for
3279 * sequencing purposes.
3282 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3285 int cnt = off + th->th_urp - 1;
3288 if (m->m_len > cnt) {
3289 char *cp = mtod(m, caddr_t) + cnt;
3290 struct tcpcb *tp = sototcpcb(so);
3292 INP_WLOCK_ASSERT(tp->t_inpcb);
3295 tp->t_oobflags |= TCPOOB_HAVEDATA;
3296 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3298 if (m->m_flags & M_PKTHDR)
3307 panic("tcp_pulloutofband");
3311 * Collect new round-trip time estimate
3312 * and update averages and current timeout.
3315 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3319 INP_WLOCK_ASSERT(tp->t_inpcb);
3321 TCPSTAT_INC(tcps_rttupdated);
3323 if (tp->t_srtt != 0) {
3325 * srtt is stored as fixed point with 5 bits after the
3326 * binary point (i.e., scaled by 8). The following magic
3327 * is equivalent to the smoothing algorithm in rfc793 with
3328 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3329 * point). Adjust rtt to origin 0.
3331 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3332 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3334 if ((tp->t_srtt += delta) <= 0)
3338 * We accumulate a smoothed rtt variance (actually, a
3339 * smoothed mean difference), then set the retransmit
3340 * timer to smoothed rtt + 4 times the smoothed variance.
3341 * rttvar is stored as fixed point with 4 bits after the
3342 * binary point (scaled by 16). The following is
3343 * equivalent to rfc793 smoothing with an alpha of .75
3344 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3345 * rfc793's wired-in beta.
3349 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3350 if ((tp->t_rttvar += delta) <= 0)
3352 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3353 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3356 * No rtt measurement yet - use the unsmoothed rtt.
3357 * Set the variance to half the rtt (so our first
3358 * retransmit happens at 3*rtt).
3360 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3361 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3362 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3368 * the retransmit should happen at rtt + 4 * rttvar.
3369 * Because of the way we do the smoothing, srtt and rttvar
3370 * will each average +1/2 tick of bias. When we compute
3371 * the retransmit timer, we want 1/2 tick of rounding and
3372 * 1 extra tick because of +-1/2 tick uncertainty in the
3373 * firing of the timer. The bias will give us exactly the
3374 * 1.5 tick we need. But, because the bias is
3375 * statistical, we have to test that we don't drop below
3376 * the minimum feasible timer (which is 2 ticks).
3378 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3379 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3382 * We received an ack for a packet that wasn't retransmitted;
3383 * it is probably safe to discard any error indications we've
3384 * received recently. This isn't quite right, but close enough
3385 * for now (a route might have failed after we sent a segment,
3386 * and the return path might not be symmetrical).
3388 tp->t_softerror = 0;
3392 * Determine a reasonable value for maxseg size.
3393 * If the route is known, check route for mtu.
3394 * If none, use an mss that can be handled on the outgoing interface
3395 * without forcing IP to fragment. If no route is found, route has no mtu,
3396 * or the destination isn't local, use a default, hopefully conservative
3397 * size (usually 512 or the default IP max size, but no more than the mtu
3398 * of the interface), as we can't discover anything about intervening
3399 * gateways or networks. We also initialize the congestion/slow start
3400 * window to be a single segment if the destination isn't local.
3401 * While looking at the routing entry, we also initialize other path-dependent
3402 * parameters from pre-set or cached values in the routing entry.
3404 * Also take into account the space needed for options that we
3405 * send regularly. Make maxseg shorter by that amount to assure
3406 * that we can send maxseg amount of data even when the options
3407 * are present. Store the upper limit of the length of options plus
3410 * NOTE that this routine is only called when we process an incoming
3411 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3412 * settings are handled in tcp_mssopt().
3415 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3416 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3420 struct inpcb *inp = tp->t_inpcb;
3421 struct hc_metrics_lite metrics;
3424 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3425 size_t min_protoh = isipv6 ?
3426 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3427 sizeof (struct tcpiphdr);
3429 const size_t min_protoh = sizeof(struct tcpiphdr);
3432 INP_WLOCK_ASSERT(tp->t_inpcb);
3434 if (mtuoffer != -1) {
3435 KASSERT(offer == -1, ("%s: conflict", __func__));
3436 offer = mtuoffer - min_protoh;
3443 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3444 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3447 #if defined(INET) && defined(INET6)
3452 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3453 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3458 * No route to sender, stay with default mss and return.
3462 * In case we return early we need to initialize metrics
3463 * to a defined state as tcp_hc_get() would do for us
3464 * if there was no cache hit.
3466 if (metricptr != NULL)
3467 bzero(metricptr, sizeof(struct hc_metrics_lite));
3471 /* What have we got? */
3475 * Offer == 0 means that there was no MSS on the SYN
3476 * segment, in this case we use tcp_mssdflt as
3477 * already assigned to t_maxopd above.
3479 offer = tp->t_maxopd;
3484 * Offer == -1 means that we didn't receive SYN yet.
3490 * Prevent DoS attack with too small MSS. Round up
3491 * to at least minmss.
3493 offer = max(offer, V_tcp_minmss);
3497 * rmx information is now retrieved from tcp_hostcache.
3499 tcp_hc_get(&inp->inp_inc, &metrics);
3500 if (metricptr != NULL)
3501 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3504 * If there's a discovered mtu int tcp hostcache, use it
3505 * else, use the link mtu.
3507 if (metrics.rmx_mtu)
3508 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3512 mss = maxmtu - min_protoh;
3513 if (!V_path_mtu_discovery &&
3514 !in6_localaddr(&inp->in6p_faddr))
3515 mss = min(mss, V_tcp_v6mssdflt);
3518 #if defined(INET) && defined(INET6)
3523 mss = maxmtu - min_protoh;
3524 if (!V_path_mtu_discovery &&
3525 !in_localaddr(inp->inp_faddr))
3526 mss = min(mss, V_tcp_mssdflt);
3530 * XXX - The above conditional (mss = maxmtu - min_protoh)
3531 * probably violates the TCP spec.
3532 * The problem is that, since we don't know the
3533 * other end's MSS, we are supposed to use a conservative
3534 * default. But, if we do that, then MTU discovery will
3535 * never actually take place, because the conservative
3536 * default is much less than the MTUs typically seen
3537 * on the Internet today. For the moment, we'll sweep
3538 * this under the carpet.
3540 * The conservative default might not actually be a problem
3541 * if the only case this occurs is when sending an initial
3542 * SYN with options and data to a host we've never talked
3543 * to before. Then, they will reply with an MSS value which
3544 * will get recorded and the new parameters should get
3545 * recomputed. For Further Study.
3548 mss = min(mss, offer);
3551 * Sanity check: make sure that maxopd will be large
3552 * enough to allow some data on segments even if the
3553 * all the option space is used (40bytes). Otherwise
3554 * funny things may happen in tcp_output.
3559 * maxopd stores the maximum length of data AND options
3560 * in a segment; maxseg is the amount of data in a normal
3561 * segment. We need to store this value (maxopd) apart
3562 * from maxseg, because now every segment carries options
3563 * and thus we normally have somewhat less data in segments.
3568 * origoffer==-1 indicates that no segments were received yet.
3569 * In this case we just guess.
3571 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3573 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3574 mss -= TCPOLEN_TSTAMP_APPA;
3580 tcp_mss(struct tcpcb *tp, int offer)
3586 struct hc_metrics_lite metrics;
3587 struct tcp_ifcap cap;
3589 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3591 bzero(&cap, sizeof(cap));
3592 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3598 * If there's a pipesize, change the socket buffer to that size,
3599 * don't change if sb_hiwat is different than default (then it
3600 * has been changed on purpose with setsockopt).
3601 * Make the socket buffers an integral number of mss units;
3602 * if the mss is larger than the socket buffer, decrease the mss.
3604 so = inp->inp_socket;
3605 SOCKBUF_LOCK(&so->so_snd);
3606 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3607 bufsize = metrics.rmx_sendpipe;
3609 bufsize = so->so_snd.sb_hiwat;
3613 bufsize = roundup(bufsize, mss);
3614 if (bufsize > sb_max)
3616 if (bufsize > so->so_snd.sb_hiwat)
3617 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3619 SOCKBUF_UNLOCK(&so->so_snd);
3622 SOCKBUF_LOCK(&so->so_rcv);
3623 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3624 bufsize = metrics.rmx_recvpipe;
3626 bufsize = so->so_rcv.sb_hiwat;
3627 if (bufsize > mss) {
3628 bufsize = roundup(bufsize, mss);
3629 if (bufsize > sb_max)
3631 if (bufsize > so->so_rcv.sb_hiwat)
3632 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3634 SOCKBUF_UNLOCK(&so->so_rcv);
3636 /* Check the interface for TSO capabilities. */
3637 if (cap.ifcap & CSUM_TSO) {
3638 tp->t_flags |= TF_TSO;
3639 tp->t_tsomax = cap.tsomax;
3640 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3641 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3646 * Determine the MSS option to send on an outgoing SYN.
3649 tcp_mssopt(struct in_conninfo *inc)
3656 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3659 if (inc->inc_flags & INC_ISIPV6) {
3660 mss = V_tcp_v6mssdflt;
3661 maxmtu = tcp_maxmtu6(inc, NULL);
3662 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3665 #if defined(INET) && defined(INET6)
3670 mss = V_tcp_mssdflt;
3671 maxmtu = tcp_maxmtu(inc, NULL);
3672 min_protoh = sizeof(struct tcpiphdr);
3675 #if defined(INET6) || defined(INET)
3676 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3679 if (maxmtu && thcmtu)
3680 mss = min(maxmtu, thcmtu) - min_protoh;
3681 else if (maxmtu || thcmtu)
3682 mss = max(maxmtu, thcmtu) - min_protoh;
3689 * On a partial ack arrives, force the retransmission of the
3690 * next unacknowledged segment. Do not clear tp->t_dupacks.
3691 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3695 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3697 tcp_seq onxt = tp->snd_nxt;
3698 u_long ocwnd = tp->snd_cwnd;
3700 INP_WLOCK_ASSERT(tp->t_inpcb);
3702 tcp_timer_activate(tp, TT_REXMT, 0);
3704 tp->snd_nxt = th->th_ack;
3706 * Set snd_cwnd to one segment beyond acknowledged offset.
3707 * (tp->snd_una has not yet been updated when this function is called.)
3709 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3710 tp->t_flags |= TF_ACKNOW;
3711 (void) tcp_output(tp);
3712 tp->snd_cwnd = ocwnd;
3713 if (SEQ_GT(onxt, tp->snd_nxt))
3716 * Partial window deflation. Relies on fact that tp->snd_una
3719 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3720 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3723 tp->snd_cwnd += tp->t_maxseg;
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