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_kdtrace.h"
58 #include "opt_tcpdebug.h"
60 #include <sys/param.h>
61 #include <sys/kernel.h>
62 #include <sys/hhook.h>
63 #include <sys/malloc.h>
65 #include <sys/proc.h> /* for proc0 declaration */
66 #include <sys/protosw.h>
68 #include <sys/signalvar.h>
69 #include <sys/socket.h>
70 #include <sys/socketvar.h>
71 #include <sys/sysctl.h>
72 #include <sys/syslog.h>
73 #include <sys/systm.h>
75 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
80 #include <net/route.h>
83 #define TCPSTATES /* for logging */
85 #include <netinet/cc.h>
86 #include <netinet/in.h>
87 #include <netinet/in_kdtrace.h>
88 #include <netinet/in_pcb.h>
89 #include <netinet/in_systm.h>
90 #include <netinet/in_var.h>
91 #include <netinet/ip.h>
92 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
93 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
94 #include <netinet/ip_var.h>
95 #include <netinet/ip_options.h>
96 #include <netinet/ip6.h>
97 #include <netinet/icmp6.h>
98 #include <netinet6/in6_pcb.h>
99 #include <netinet6/ip6_var.h>
100 #include <netinet6/nd6.h>
101 #include <netinet/tcp_fsm.h>
102 #include <netinet/tcp_seq.h>
103 #include <netinet/tcp_timer.h>
104 #include <netinet/tcp_var.h>
105 #include <netinet6/tcp6_var.h>
106 #include <netinet/tcpip.h>
107 #include <netinet/tcp_syncache.h>
109 #include <netinet/tcp_debug.h>
110 #endif /* TCPDEBUG */
112 #include <netinet/tcp_offload.h>
116 #include <netipsec/ipsec.h>
117 #include <netipsec/ipsec6.h>
120 #include <machine/in_cksum.h>
122 #include <security/mac/mac_framework.h>
124 const int tcprexmtthresh = 3;
126 int tcp_log_in_vain = 0;
127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
129 "Log all incoming TCP segments to closed ports");
131 VNET_DEFINE(int, blackhole) = 0;
132 #define V_blackhole VNET(blackhole)
133 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
134 &VNET_NAME(blackhole), 0,
135 "Do not send RST on segments to closed ports");
137 VNET_DEFINE(int, tcp_delack_enabled) = 1;
138 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
139 &VNET_NAME(tcp_delack_enabled), 0,
140 "Delay ACK to try and piggyback it onto a data packet");
142 VNET_DEFINE(int, drop_synfin) = 0;
143 #define V_drop_synfin VNET(drop_synfin)
144 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
145 &VNET_NAME(drop_synfin), 0,
146 "Drop TCP packets with SYN+FIN set");
148 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
149 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
150 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
151 &VNET_NAME(tcp_do_rfc3042), 0,
152 "Enable RFC 3042 (Limited Transmit)");
154 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
155 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
156 &VNET_NAME(tcp_do_rfc3390), 0,
157 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
159 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0,
160 "Experimental TCP extensions");
162 VNET_DEFINE(int, tcp_do_initcwnd10) = 1;
163 SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW,
164 &VNET_NAME(tcp_do_initcwnd10), 0,
165 "Enable draft-ietf-tcpm-initcwnd-05 (Increasing initial CWND to 10)");
167 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
168 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW,
169 &VNET_NAME(tcp_do_rfc3465), 0,
170 "Enable RFC 3465 (Appropriate Byte Counting)");
172 VNET_DEFINE(int, tcp_abc_l_var) = 2;
173 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW,
174 &VNET_NAME(tcp_abc_l_var), 2,
175 "Cap the max cwnd increment during slow-start to this number of segments");
177 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
179 VNET_DEFINE(int, tcp_do_ecn) = 0;
180 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW,
181 &VNET_NAME(tcp_do_ecn), 0,
184 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
185 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW,
186 &VNET_NAME(tcp_ecn_maxretries), 0,
187 "Max retries before giving up on ECN");
189 VNET_DEFINE(int, tcp_insecure_rst) = 0;
190 #define V_tcp_insecure_rst VNET(tcp_insecure_rst)
191 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
192 &VNET_NAME(tcp_insecure_rst), 0,
193 "Follow the old (insecure) criteria for accepting RST packets");
195 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
196 #define V_tcp_recvspace VNET(tcp_recvspace)
197 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW,
198 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
200 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
201 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf)
202 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
203 &VNET_NAME(tcp_do_autorcvbuf), 0,
204 "Enable automatic receive buffer sizing");
206 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
207 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc)
208 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
209 &VNET_NAME(tcp_autorcvbuf_inc), 0,
210 "Incrementor step size of automatic receive buffer");
212 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
213 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max)
214 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
215 &VNET_NAME(tcp_autorcvbuf_max), 0,
216 "Max size of automatic receive buffer");
218 VNET_DEFINE(struct inpcbhead, tcb);
219 #define tcb6 tcb /* for KAME src sync over BSD*'s */
220 VNET_DEFINE(struct inpcbinfo, tcbinfo);
222 static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
223 static void tcp_do_segment(struct mbuf *, struct tcphdr *,
224 struct socket *, struct tcpcb *, int, int, uint8_t,
226 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *,
227 struct tcpcb *, int, int);
228 static void tcp_pulloutofband(struct socket *,
229 struct tcphdr *, struct mbuf *, int);
230 static void tcp_xmit_timer(struct tcpcb *, int);
231 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
232 static void inline tcp_fields_to_host(struct tcphdr *);
234 static void inline tcp_fields_to_net(struct tcphdr *);
235 static int inline tcp_signature_verify_input(struct mbuf *, int, int,
236 int, struct tcpopt *, struct tcphdr *, u_int);
238 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
240 static void inline cc_conn_init(struct tcpcb *tp);
241 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
242 static void inline hhook_run_tcp_est_in(struct tcpcb *tp,
243 struct tcphdr *th, struct tcpopt *to);
246 * TCP statistics are stored in an "array" of counter(9)s.
248 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
249 VNET_PCPUSTAT_SYSINIT(tcpstat);
250 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
251 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
254 VNET_PCPUSTAT_SYSUNINIT(tcpstat);
257 * Kernel module interface for updating tcpstat. The argument is an index
258 * into tcpstat treated as an array.
261 kmod_tcpstat_inc(int statnum)
264 counter_u64_add(VNET(tcpstat)[statnum], 1);
268 * Wrapper for the TCP established input helper hook.
271 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
273 struct tcp_hhook_data hhook_data;
275 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
280 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
286 * CC wrapper hook functions
289 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
291 INP_WLOCK_ASSERT(tp->t_inpcb);
293 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
294 if (tp->snd_cwnd <= tp->snd_wnd)
295 tp->ccv->flags |= CCF_CWND_LIMITED;
297 tp->ccv->flags &= ~CCF_CWND_LIMITED;
299 if (type == CC_ACK) {
300 if (tp->snd_cwnd > tp->snd_ssthresh) {
301 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
302 V_tcp_abc_l_var * tp->t_maxseg);
303 if (tp->t_bytes_acked >= tp->snd_cwnd) {
304 tp->t_bytes_acked -= tp->snd_cwnd;
305 tp->ccv->flags |= CCF_ABC_SENTAWND;
308 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
309 tp->t_bytes_acked = 0;
313 if (CC_ALGO(tp)->ack_received != NULL) {
314 /* XXXLAS: Find a way to live without this */
315 tp->ccv->curack = th->th_ack;
316 CC_ALGO(tp)->ack_received(tp->ccv, type);
321 cc_conn_init(struct tcpcb *tp)
323 struct hc_metrics_lite metrics;
324 struct inpcb *inp = tp->t_inpcb;
327 INP_WLOCK_ASSERT(tp->t_inpcb);
329 tcp_hc_get(&inp->inp_inc, &metrics);
331 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
333 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
334 TCPSTAT_INC(tcps_usedrtt);
335 if (metrics.rmx_rttvar) {
336 tp->t_rttvar = metrics.rmx_rttvar;
337 TCPSTAT_INC(tcps_usedrttvar);
339 /* default variation is +- 1 rtt */
341 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
343 TCPT_RANGESET(tp->t_rxtcur,
344 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
345 tp->t_rttmin, TCPTV_REXMTMAX);
347 if (metrics.rmx_ssthresh) {
349 * There's some sort of gateway or interface
350 * buffer limit on the path. Use this to set
351 * the slow start threshhold, but set the
352 * threshold to no less than 2*mss.
354 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
355 TCPSTAT_INC(tcps_usedssthresh);
359 * Set the initial slow-start flight size.
361 * RFC5681 Section 3.1 specifies the default conservative values.
362 * RFC3390 specifies slightly more aggressive values.
363 * Draft-ietf-tcpm-initcwnd-05 increases it to ten segments.
365 * If a SYN or SYN/ACK was lost and retransmitted, we have to
366 * reduce the initial CWND to one segment as congestion is likely
367 * requiring us to be cautious.
369 if (tp->snd_cwnd == 1)
370 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */
371 else if (V_tcp_do_initcwnd10)
372 tp->snd_cwnd = min(10 * tp->t_maxseg,
373 max(2 * tp->t_maxseg, 14600));
374 else if (V_tcp_do_rfc3390)
375 tp->snd_cwnd = min(4 * tp->t_maxseg,
376 max(2 * tp->t_maxseg, 4380));
378 /* Per RFC5681 Section 3.1 */
379 if (tp->t_maxseg > 2190)
380 tp->snd_cwnd = 2 * tp->t_maxseg;
381 else if (tp->t_maxseg > 1095)
382 tp->snd_cwnd = 3 * tp->t_maxseg;
384 tp->snd_cwnd = 4 * tp->t_maxseg;
387 if (CC_ALGO(tp)->conn_init != NULL)
388 CC_ALGO(tp)->conn_init(tp->ccv);
392 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
394 INP_WLOCK_ASSERT(tp->t_inpcb);
398 if (!IN_FASTRECOVERY(tp->t_flags)) {
399 tp->snd_recover = tp->snd_max;
400 if (tp->t_flags & TF_ECN_PERMIT)
401 tp->t_flags |= TF_ECN_SND_CWR;
405 if (!IN_CONGRECOVERY(tp->t_flags)) {
406 TCPSTAT_INC(tcps_ecn_rcwnd);
407 tp->snd_recover = tp->snd_max;
408 if (tp->t_flags & TF_ECN_PERMIT)
409 tp->t_flags |= TF_ECN_SND_CWR;
414 tp->t_bytes_acked = 0;
415 EXIT_RECOVERY(tp->t_flags);
416 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
417 tp->t_maxseg) * tp->t_maxseg;
418 tp->snd_cwnd = tp->t_maxseg;
421 TCPSTAT_INC(tcps_sndrexmitbad);
422 /* RTO was unnecessary, so reset everything. */
423 tp->snd_cwnd = tp->snd_cwnd_prev;
424 tp->snd_ssthresh = tp->snd_ssthresh_prev;
425 tp->snd_recover = tp->snd_recover_prev;
426 if (tp->t_flags & TF_WASFRECOVERY)
427 ENTER_FASTRECOVERY(tp->t_flags);
428 if (tp->t_flags & TF_WASCRECOVERY)
429 ENTER_CONGRECOVERY(tp->t_flags);
430 tp->snd_nxt = tp->snd_max;
431 tp->t_flags &= ~TF_PREVVALID;
436 if (CC_ALGO(tp)->cong_signal != NULL) {
438 tp->ccv->curack = th->th_ack;
439 CC_ALGO(tp)->cong_signal(tp->ccv, type);
444 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
446 INP_WLOCK_ASSERT(tp->t_inpcb);
448 /* XXXLAS: KASSERT that we're in recovery? */
450 if (CC_ALGO(tp)->post_recovery != NULL) {
451 tp->ccv->curack = th->th_ack;
452 CC_ALGO(tp)->post_recovery(tp->ccv);
454 /* XXXLAS: EXIT_RECOVERY ? */
455 tp->t_bytes_acked = 0;
459 tcp_fields_to_host(struct tcphdr *th)
462 th->th_seq = ntohl(th->th_seq);
463 th->th_ack = ntohl(th->th_ack);
464 th->th_win = ntohs(th->th_win);
465 th->th_urp = ntohs(th->th_urp);
470 tcp_fields_to_net(struct tcphdr *th)
473 th->th_seq = htonl(th->th_seq);
474 th->th_ack = htonl(th->th_ack);
475 th->th_win = htons(th->th_win);
476 th->th_urp = htons(th->th_urp);
480 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
481 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
485 tcp_fields_to_net(th);
486 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
487 tcp_fields_to_host(th);
492 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
494 #define ND6_HINT(tp) \
496 if ((tp) && (tp)->t_inpcb && \
497 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
498 nd6_nud_hint(NULL, NULL, 0); \
505 * Indicate whether this ack should be delayed. We can delay the ack if
506 * - there is no delayed ack timer in progress and
507 * - our last ack wasn't a 0-sized window. We never want to delay
508 * the ack that opens up a 0-sized window and
509 * - delayed acks are enabled or
510 * - this is a half-synchronized T/TCP connection.
512 #define DELAY_ACK(tp) \
513 ((!tcp_timer_active(tp, TT_DELACK) && \
514 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
515 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
518 * TCP input handling is split into multiple parts:
519 * tcp6_input is a thin wrapper around tcp_input for the extended
520 * ip6_protox[] call format in ip6_input
521 * tcp_input handles primary segment validation, inpcb lookup and
522 * SYN processing on listen sockets
523 * tcp_do_segment processes the ACK and text of the segment for
524 * establishing, established and closing connections
528 tcp6_input(struct mbuf **mp, int *offp, int proto)
530 struct mbuf *m = *mp;
531 struct in6_ifaddr *ia6;
533 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
536 * draft-itojun-ipv6-tcp-to-anycast
537 * better place to put this in?
539 ia6 = ip6_getdstifaddr(m);
540 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
543 ifa_free(&ia6->ia_ifa);
544 ip6 = mtod(m, struct ip6_hdr *);
545 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
546 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
550 ifa_free(&ia6->ia_ifa);
558 tcp_input(struct mbuf *m, int off0)
560 struct tcphdr *th = NULL;
561 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)) {
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 th = (struct tcphdr *)((caddr_t)ip + off0);
673 tlen = ntohs(ip->ip_len) - off0;
675 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
676 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
677 th->th_sum = m->m_pkthdr.csum_data;
679 th->th_sum = in_pseudo(ip->ip_src.s_addr,
681 htonl(m->m_pkthdr.csum_data + tlen +
683 th->th_sum ^= 0xffff;
685 struct ipovly *ipov = (struct ipovly *)ip;
688 * Checksum extended TCP header and data.
691 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
692 ipov->ih_len = htons(tlen);
693 th->th_sum = in_cksum(m, len);
694 /* Reset length for SDT probes. */
695 ip->ip_len = htons(tlen + off0);
699 TCPSTAT_INC(tcps_rcvbadsum);
702 /* Re-initialization for later version check */
703 ip->ip_v = IPVERSION;
709 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
711 #if defined(INET) && defined(INET6)
719 * Check that TCP offset makes sense,
720 * pull out TCP options and adjust length. XXX
722 off = th->th_off << 2;
723 if (off < sizeof (struct tcphdr) || off > tlen) {
724 TCPSTAT_INC(tcps_rcvbadoff);
727 tlen -= off; /* tlen is used instead of ti->ti_len */
728 if (off > sizeof (struct tcphdr)) {
731 IP6_EXTHDR_CHECK(m, off0, off, );
732 ip6 = mtod(m, struct ip6_hdr *);
733 th = (struct tcphdr *)((caddr_t)ip6 + off0);
736 #if defined(INET) && defined(INET6)
741 if (m->m_len < sizeof(struct ip) + off) {
742 if ((m = m_pullup(m, sizeof (struct ip) + off))
744 TCPSTAT_INC(tcps_rcvshort);
747 ip = mtod(m, struct ip *);
748 th = (struct tcphdr *)((caddr_t)ip + off0);
752 optlen = off - sizeof (struct tcphdr);
753 optp = (u_char *)(th + 1);
755 thflags = th->th_flags;
758 * Convert TCP protocol specific fields to host format.
760 tcp_fields_to_host(th);
763 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
765 drop_hdrlen = off0 + off;
768 * Locate pcb for segment; if we're likely to add or remove a
769 * connection then first acquire pcbinfo lock. There are two cases
770 * where we might discover later we need a write lock despite the
771 * flags: ACKs moving a connection out of the syncache, and ACKs for
772 * a connection in TIMEWAIT.
774 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) {
775 INP_INFO_WLOCK(&V_tcbinfo);
776 ti_locked = TI_WLOCKED;
778 ti_locked = TI_UNLOCKED;
781 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
785 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
787 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
790 #if defined(INET) && !defined(INET6)
791 (m->m_flags & M_IP_NEXTHOP)
794 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
798 if (ti_locked == TI_WLOCKED) {
799 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
801 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
805 if (isipv6 && fwd_tag != NULL) {
806 struct sockaddr_in6 *next_hop6;
808 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
810 * Transparently forwarded. Pretend to be the destination.
811 * Already got one like this?
813 inp = in6_pcblookup_mbuf(&V_tcbinfo,
814 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
815 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
818 * It's new. Try to find the ambushing socket.
819 * Because we've rewritten the destination address,
820 * any hardware-generated hash is ignored.
822 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
823 th->th_sport, &next_hop6->sin6_addr,
824 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
825 th->th_dport, INPLOOKUP_WILDCARD |
826 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
829 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
830 th->th_sport, &ip6->ip6_dst, th->th_dport,
831 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
832 m->m_pkthdr.rcvif, m);
835 #if defined(INET6) && defined(INET)
839 if (fwd_tag != NULL) {
840 struct sockaddr_in *next_hop;
842 next_hop = (struct sockaddr_in *)(fwd_tag+1);
844 * Transparently forwarded. Pretend to be the destination.
845 * already got one like this?
847 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
848 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
849 m->m_pkthdr.rcvif, m);
852 * It's new. Try to find the ambushing socket.
853 * Because we've rewritten the destination address,
854 * any hardware-generated hash is ignored.
856 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
857 th->th_sport, next_hop->sin_addr,
858 next_hop->sin_port ? ntohs(next_hop->sin_port) :
859 th->th_dport, INPLOOKUP_WILDCARD |
860 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
863 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
864 th->th_sport, ip->ip_dst, th->th_dport,
865 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
866 m->m_pkthdr.rcvif, m);
870 * If the INPCB does not exist then all data in the incoming
871 * segment is discarded and an appropriate RST is sent back.
872 * XXX MRT Send RST using which routing table?
876 * Log communication attempts to ports that are not
879 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
880 tcp_log_in_vain == 2) {
881 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
882 log(LOG_INFO, "%s; %s: Connection attempt "
883 "to closed port\n", s, __func__);
886 * When blackholing do not respond with a RST but
887 * completely ignore the segment and drop it.
889 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
893 rstreason = BANDLIM_RST_CLOSEDPORT;
896 INP_WLOCK_ASSERT(inp);
897 if (!(inp->inp_flags & INP_HW_FLOWID)
898 && (m->m_flags & M_FLOWID)
899 && ((inp->inp_socket == NULL)
900 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
901 inp->inp_flags |= INP_HW_FLOWID;
902 inp->inp_flags &= ~INP_SW_FLOWID;
903 inp->inp_flowid = m->m_pkthdr.flowid;
907 if (isipv6 && ipsec6_in_reject(m, inp)) {
908 IPSEC6STAT_INC(ips_in_polvio);
912 if (ipsec4_in_reject(m, inp) != 0) {
913 IPSECSTAT_INC(ips_in_polvio);
919 * Check the minimum TTL for socket.
921 if (inp->inp_ip_minttl != 0) {
923 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
927 if (inp->inp_ip_minttl > ip->ip_ttl)
932 * A previous connection in TIMEWAIT state is supposed to catch stray
933 * or duplicate segments arriving late. If this segment was a
934 * legitimate new connection attempt, the old INPCB gets removed and
935 * we can try again to find a listening socket.
937 * At this point, due to earlier optimism, we may hold only an inpcb
938 * lock, and not the inpcbinfo write lock. If so, we need to try to
939 * acquire it, or if that fails, acquire a reference on the inpcb,
940 * drop all locks, acquire a global write lock, and then re-acquire
941 * the inpcb lock. We may at that point discover that another thread
942 * has tried to free the inpcb, in which case we need to loop back
943 * and try to find a new inpcb to deliver to.
945 * XXXRW: It may be time to rethink timewait locking.
948 if (inp->inp_flags & INP_TIMEWAIT) {
949 if (ti_locked == TI_UNLOCKED) {
950 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
953 INP_INFO_WLOCK(&V_tcbinfo);
954 ti_locked = TI_WLOCKED;
956 if (in_pcbrele_wlocked(inp)) {
961 ti_locked = TI_WLOCKED;
963 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
965 if (thflags & TH_SYN)
966 tcp_dooptions(&to, optp, optlen, TO_SYN);
968 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
970 if (tcp_twcheck(inp, &to, th, m, tlen))
972 INP_INFO_WUNLOCK(&V_tcbinfo);
976 * The TCPCB may no longer exist if the connection is winding
977 * down or it is in the CLOSED state. Either way we drop the
978 * segment and send an appropriate response.
981 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
982 rstreason = BANDLIM_RST_CLOSEDPORT;
987 if (tp->t_flags & TF_TOE) {
988 tcp_offload_input(tp, m);
989 m = NULL; /* consumed by the TOE driver */
995 * We've identified a valid inpcb, but it could be that we need an
996 * inpcbinfo write lock but don't hold it. In this case, attempt to
997 * acquire using the same strategy as the TIMEWAIT case above. If we
998 * relock, we have to jump back to 'relocked' as the connection might
999 * now be in TIMEWAIT.
1002 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0)
1003 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1005 if (tp->t_state != TCPS_ESTABLISHED) {
1006 if (ti_locked == TI_UNLOCKED) {
1007 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
1010 INP_INFO_WLOCK(&V_tcbinfo);
1011 ti_locked = TI_WLOCKED;
1013 if (in_pcbrele_wlocked(inp)) {
1019 ti_locked = TI_WLOCKED;
1021 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1025 INP_WLOCK_ASSERT(inp);
1026 if (mac_inpcb_check_deliver(inp, m))
1029 so = inp->inp_socket;
1030 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1032 if (so->so_options & SO_DEBUG) {
1033 ostate = tp->t_state;
1036 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1039 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1042 #endif /* TCPDEBUG */
1044 * When the socket is accepting connections (the INPCB is in LISTEN
1045 * state) we look into the SYN cache if this is a new connection
1046 * attempt or the completion of a previous one. Because listen
1047 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be
1048 * held in this case.
1050 if (so->so_options & SO_ACCEPTCONN) {
1051 struct in_conninfo inc;
1053 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
1054 "tp not listening", __func__));
1055 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1057 bzero(&inc, sizeof(inc));
1060 inc.inc_flags |= INC_ISIPV6;
1061 inc.inc6_faddr = ip6->ip6_src;
1062 inc.inc6_laddr = ip6->ip6_dst;
1066 inc.inc_faddr = ip->ip_src;
1067 inc.inc_laddr = ip->ip_dst;
1069 inc.inc_fport = th->th_sport;
1070 inc.inc_lport = th->th_dport;
1071 inc.inc_fibnum = so->so_fibnum;
1074 * Check for an existing connection attempt in syncache if
1075 * the flag is only ACK. A successful lookup creates a new
1076 * socket appended to the listen queue in SYN_RECEIVED state.
1078 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1080 * Parse the TCP options here because
1081 * syncookies need access to the reflected
1084 tcp_dooptions(&to, optp, optlen, 0);
1086 * NB: syncache_expand() doesn't unlock
1087 * inp and tcpinfo locks.
1089 if (!syncache_expand(&inc, &to, th, &so, m)) {
1091 * No syncache entry or ACK was not
1092 * for our SYN/ACK. Send a RST.
1093 * NB: syncache did its own logging
1094 * of the failure cause.
1096 rstreason = BANDLIM_RST_OPENPORT;
1101 * We completed the 3-way handshake
1102 * but could not allocate a socket
1103 * either due to memory shortage,
1104 * listen queue length limits or
1105 * global socket limits. Send RST
1106 * or wait and have the remote end
1107 * retransmit the ACK for another
1110 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1111 log(LOG_DEBUG, "%s; %s: Listen socket: "
1112 "Socket allocation failed due to "
1113 "limits or memory shortage, %s\n",
1115 V_tcp_sc_rst_sock_fail ?
1116 "sending RST" : "try again");
1117 if (V_tcp_sc_rst_sock_fail) {
1118 rstreason = BANDLIM_UNLIMITED;
1124 * Socket is created in state SYN_RECEIVED.
1125 * Unlock the listen socket, lock the newly
1126 * created socket and update the tp variable.
1128 INP_WUNLOCK(inp); /* listen socket */
1129 inp = sotoinpcb(so);
1130 INP_WLOCK(inp); /* new connection */
1131 tp = intotcpcb(inp);
1132 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1133 ("%s: ", __func__));
1134 #ifdef TCP_SIGNATURE
1135 if (sig_checked == 0) {
1136 tcp_dooptions(&to, optp, optlen,
1137 (thflags & TH_SYN) ? TO_SYN : 0);
1138 if (!tcp_signature_verify_input(m, off0, tlen,
1139 optlen, &to, th, tp->t_flags)) {
1142 * In SYN_SENT state if it receives an
1143 * RST, it is allowed for further
1146 if ((thflags & TH_RST) == 0 ||
1147 (tp->t_state == TCPS_SYN_SENT) == 0)
1155 * Process the segment and the data it
1156 * contains. tcp_do_segment() consumes
1157 * the mbuf chain and unlocks the inpcb.
1159 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1161 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1165 * Segment flag validation for new connection attempts:
1167 * Our (SYN|ACK) response was rejected.
1168 * Check with syncache and remove entry to prevent
1171 * NB: syncache_chkrst does its own logging of failure
1174 if (thflags & TH_RST) {
1175 syncache_chkrst(&inc, th);
1179 * We can't do anything without SYN.
1181 if ((thflags & TH_SYN) == 0) {
1182 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1183 log(LOG_DEBUG, "%s; %s: Listen socket: "
1184 "SYN is missing, segment ignored\n",
1186 TCPSTAT_INC(tcps_badsyn);
1190 * (SYN|ACK) is bogus on a listen socket.
1192 if (thflags & TH_ACK) {
1193 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1194 log(LOG_DEBUG, "%s; %s: Listen socket: "
1195 "SYN|ACK invalid, segment rejected\n",
1197 syncache_badack(&inc); /* XXX: Not needed! */
1198 TCPSTAT_INC(tcps_badsyn);
1199 rstreason = BANDLIM_RST_OPENPORT;
1203 * If the drop_synfin option is enabled, drop all
1204 * segments with both the SYN and FIN bits set.
1205 * This prevents e.g. nmap from identifying the
1207 * XXX: Poor reasoning. nmap has other methods
1208 * and is constantly refining its stack detection
1210 * XXX: This is a violation of the TCP specification
1211 * and was used by RFC1644.
1213 if ((thflags & TH_FIN) && V_drop_synfin) {
1214 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1215 log(LOG_DEBUG, "%s; %s: Listen socket: "
1216 "SYN|FIN segment ignored (based on "
1217 "sysctl setting)\n", s, __func__);
1218 TCPSTAT_INC(tcps_badsyn);
1222 * Segment's flags are (SYN) or (SYN|FIN).
1224 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1225 * as they do not affect the state of the TCP FSM.
1226 * The data pointed to by TH_URG and th_urp is ignored.
1228 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1229 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1230 KASSERT(thflags & (TH_SYN),
1231 ("%s: Listen socket: TH_SYN not set", __func__));
1234 * If deprecated address is forbidden,
1235 * we do not accept SYN to deprecated interface
1236 * address to prevent any new inbound connection from
1237 * getting established.
1238 * When we do not accept SYN, we send a TCP RST,
1239 * with deprecated source address (instead of dropping
1240 * it). We compromise it as it is much better for peer
1241 * to send a RST, and RST will be the final packet
1244 * If we do not forbid deprecated addresses, we accept
1245 * the SYN packet. RFC2462 does not suggest dropping
1247 * If we decipher RFC2462 5.5.4, it says like this:
1248 * 1. use of deprecated addr with existing
1249 * communication is okay - "SHOULD continue to be
1251 * 2. use of it with new communication:
1252 * (2a) "SHOULD NOT be used if alternate address
1253 * with sufficient scope is available"
1254 * (2b) nothing mentioned otherwise.
1255 * Here we fall into (2b) case as we have no choice in
1256 * our source address selection - we must obey the peer.
1258 * The wording in RFC2462 is confusing, and there are
1259 * multiple description text for deprecated address
1260 * handling - worse, they are not exactly the same.
1261 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1263 if (isipv6 && !V_ip6_use_deprecated) {
1264 struct in6_ifaddr *ia6;
1266 ia6 = ip6_getdstifaddr(m);
1268 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1269 ifa_free(&ia6->ia_ifa);
1270 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1271 log(LOG_DEBUG, "%s; %s: Listen socket: "
1272 "Connection attempt to deprecated "
1273 "IPv6 address rejected\n",
1275 rstreason = BANDLIM_RST_OPENPORT;
1279 ifa_free(&ia6->ia_ifa);
1283 * Basic sanity checks on incoming SYN requests:
1284 * Don't respond if the destination is a link layer
1285 * broadcast according to RFC1122 4.2.3.10, p. 104.
1286 * If it is from this socket it must be forged.
1287 * Don't respond if the source or destination is a
1288 * global or subnet broad- or multicast address.
1289 * Note that it is quite possible to receive unicast
1290 * link-layer packets with a broadcast IP address. Use
1291 * in_broadcast() to find them.
1293 if (m->m_flags & (M_BCAST|M_MCAST)) {
1294 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1295 log(LOG_DEBUG, "%s; %s: Listen socket: "
1296 "Connection attempt from broad- or multicast "
1297 "link layer address ignored\n", s, __func__);
1302 if (th->th_dport == th->th_sport &&
1303 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1304 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1305 log(LOG_DEBUG, "%s; %s: Listen socket: "
1306 "Connection attempt to/from self "
1307 "ignored\n", s, __func__);
1310 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1311 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1312 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1313 log(LOG_DEBUG, "%s; %s: Listen socket: "
1314 "Connection attempt from/to multicast "
1315 "address ignored\n", s, __func__);
1320 #if defined(INET) && defined(INET6)
1325 if (th->th_dport == th->th_sport &&
1326 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1327 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1328 log(LOG_DEBUG, "%s; %s: Listen socket: "
1329 "Connection attempt from/to self "
1330 "ignored\n", s, __func__);
1333 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1334 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1335 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1336 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1337 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1338 log(LOG_DEBUG, "%s; %s: Listen socket: "
1339 "Connection attempt from/to broad- "
1340 "or multicast address ignored\n",
1347 * SYN appears to be valid. Create compressed TCP state
1351 if (so->so_options & SO_DEBUG)
1352 tcp_trace(TA_INPUT, ostate, tp,
1353 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1355 tcp_dooptions(&to, optp, optlen, TO_SYN);
1356 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL);
1358 * Entry added to syncache and mbuf consumed.
1359 * Everything already unlocked by syncache_add().
1361 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1363 } else if (tp->t_state == TCPS_LISTEN) {
1365 * When a listen socket is torn down the SO_ACCEPTCONN
1366 * flag is removed first while connections are drained
1367 * from the accept queue in a unlock/lock cycle of the
1368 * ACCEPT_LOCK, opening a race condition allowing a SYN
1369 * attempt go through unhandled.
1374 #ifdef TCP_SIGNATURE
1375 if (sig_checked == 0) {
1376 tcp_dooptions(&to, optp, optlen,
1377 (thflags & TH_SYN) ? TO_SYN : 0);
1378 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
1382 * In SYN_SENT state if it receives an RST, it is
1383 * allowed for further processing.
1385 if ((thflags & TH_RST) == 0 ||
1386 (tp->t_state == TCPS_SYN_SENT) == 0)
1393 TCP_PROBE5(receive, NULL, tp, m->m_data, tp, th);
1396 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1397 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1398 * the inpcb, and unlocks pcbinfo.
1400 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1401 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1405 TCP_PROBE5(receive, NULL, tp, m->m_data, tp, th);
1407 if (ti_locked == TI_WLOCKED) {
1408 INP_INFO_WUNLOCK(&V_tcbinfo);
1409 ti_locked = TI_UNLOCKED;
1413 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1414 "ti_locked: %d", __func__, ti_locked));
1415 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1420 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1423 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1424 m = NULL; /* mbuf chain got consumed. */
1429 TCP_PROBE5(receive, NULL, tp, m->m_data, tp, th);
1431 if (ti_locked == TI_WLOCKED) {
1432 INP_INFO_WUNLOCK(&V_tcbinfo);
1433 ti_locked = TI_UNLOCKED;
1437 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1438 "ti_locked: %d", __func__, ti_locked));
1439 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1447 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1455 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1456 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1459 int thflags, acked, ourfinisacked, needoutput = 0;
1460 int rstreason, todrop, win;
1463 struct in_conninfo *inc;
1469 * The size of tcp_saveipgen must be the size of the max ip header,
1472 u_char tcp_saveipgen[IP6_HDR_LEN];
1473 struct tcphdr tcp_savetcp;
1476 thflags = th->th_flags;
1477 inc = &tp->t_inpcb->inp_inc;
1478 tp->sackhint.last_sack_ack = 0;
1481 * If this is either a state-changing packet or current state isn't
1482 * established, we require a write lock on tcbinfo. Otherwise, we
1483 * allow the tcbinfo to be in either alocked or unlocked, as the
1484 * caller may have unnecessarily acquired a write lock due to a race.
1486 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1487 tp->t_state != TCPS_ESTABLISHED) {
1488 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
1489 "SYN/FIN/RST/!EST", __func__, ti_locked));
1490 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1493 if (ti_locked == TI_WLOCKED)
1494 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1496 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1497 "ti_locked: %d", __func__, ti_locked));
1498 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1502 INP_WLOCK_ASSERT(tp->t_inpcb);
1503 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1505 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1509 * Segment received on connection.
1510 * Reset idle time and keep-alive timer.
1511 * XXX: This should be done after segment
1512 * validation to ignore broken/spoofed segs.
1514 tp->t_rcvtime = ticks;
1515 if (TCPS_HAVEESTABLISHED(tp->t_state))
1516 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1519 * Unscale the window into a 32-bit value.
1520 * For the SYN_SENT state the scale is zero.
1522 tiwin = th->th_win << tp->snd_scale;
1525 * TCP ECN processing.
1527 if (tp->t_flags & TF_ECN_PERMIT) {
1528 if (thflags & TH_CWR)
1529 tp->t_flags &= ~TF_ECN_SND_ECE;
1530 switch (iptos & IPTOS_ECN_MASK) {
1532 tp->t_flags |= TF_ECN_SND_ECE;
1533 TCPSTAT_INC(tcps_ecn_ce);
1535 case IPTOS_ECN_ECT0:
1536 TCPSTAT_INC(tcps_ecn_ect0);
1538 case IPTOS_ECN_ECT1:
1539 TCPSTAT_INC(tcps_ecn_ect1);
1542 /* Congestion experienced. */
1543 if (thflags & TH_ECE) {
1544 cc_cong_signal(tp, th, CC_ECN);
1549 * Parse options on any incoming segment.
1551 tcp_dooptions(&to, (u_char *)(th + 1),
1552 (th->th_off << 2) - sizeof(struct tcphdr),
1553 (thflags & TH_SYN) ? TO_SYN : 0);
1556 * If echoed timestamp is later than the current time,
1557 * fall back to non RFC1323 RTT calculation. Normalize
1558 * timestamp if syncookies were used when this connection
1561 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1562 to.to_tsecr -= tp->ts_offset;
1563 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1567 * If timestamps were negotiated during SYN/ACK they should
1568 * appear on every segment during this session and vice versa.
1570 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1571 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1572 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1573 "no action\n", s, __func__);
1577 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1578 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1579 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1580 "no action\n", s, __func__);
1586 * Process options only when we get SYN/ACK back. The SYN case
1587 * for incoming connections is handled in tcp_syncache.
1588 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1589 * or <SYN,ACK>) segment itself is never scaled.
1590 * XXX this is traditional behavior, may need to be cleaned up.
1592 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1593 if ((to.to_flags & TOF_SCALE) &&
1594 (tp->t_flags & TF_REQ_SCALE)) {
1595 tp->t_flags |= TF_RCVD_SCALE;
1596 tp->snd_scale = to.to_wscale;
1599 * Initial send window. It will be updated with
1600 * the next incoming segment to the scaled value.
1602 tp->snd_wnd = th->th_win;
1603 if (to.to_flags & TOF_TS) {
1604 tp->t_flags |= TF_RCVD_TSTMP;
1605 tp->ts_recent = to.to_tsval;
1606 tp->ts_recent_age = tcp_ts_getticks();
1608 if (to.to_flags & TOF_MSS)
1609 tcp_mss(tp, to.to_mss);
1610 if ((tp->t_flags & TF_SACK_PERMIT) &&
1611 (to.to_flags & TOF_SACKPERM) == 0)
1612 tp->t_flags &= ~TF_SACK_PERMIT;
1616 * Header prediction: check for the two common cases
1617 * of a uni-directional data xfer. If the packet has
1618 * no control flags, is in-sequence, the window didn't
1619 * change and we're not retransmitting, it's a
1620 * candidate. If the length is zero and the ack moved
1621 * forward, we're the sender side of the xfer. Just
1622 * free the data acked & wake any higher level process
1623 * that was blocked waiting for space. If the length
1624 * is non-zero and the ack didn't move, we're the
1625 * receiver side. If we're getting packets in-order
1626 * (the reassembly queue is empty), add the data to
1627 * the socket buffer and note that we need a delayed ack.
1628 * Make sure that the hidden state-flags are also off.
1629 * Since we check for TCPS_ESTABLISHED first, it can only
1632 if (tp->t_state == TCPS_ESTABLISHED &&
1633 th->th_seq == tp->rcv_nxt &&
1634 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1635 tp->snd_nxt == tp->snd_max &&
1636 tiwin && tiwin == tp->snd_wnd &&
1637 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1638 LIST_EMPTY(&tp->t_segq) &&
1639 ((to.to_flags & TOF_TS) == 0 ||
1640 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1643 * If last ACK falls within this segment's sequence numbers,
1644 * record the timestamp.
1645 * NOTE that the test is modified according to the latest
1646 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1648 if ((to.to_flags & TOF_TS) != 0 &&
1649 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1650 tp->ts_recent_age = tcp_ts_getticks();
1651 tp->ts_recent = to.to_tsval;
1655 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1656 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1657 !IN_RECOVERY(tp->t_flags) &&
1658 (to.to_flags & TOF_SACK) == 0 &&
1659 TAILQ_EMPTY(&tp->snd_holes)) {
1661 * This is a pure ack for outstanding data.
1663 if (ti_locked == TI_WLOCKED)
1664 INP_INFO_WUNLOCK(&V_tcbinfo);
1665 ti_locked = TI_UNLOCKED;
1667 TCPSTAT_INC(tcps_predack);
1670 * "bad retransmit" recovery.
1672 if (tp->t_rxtshift == 1 &&
1673 tp->t_flags & TF_PREVVALID &&
1674 (int)(ticks - tp->t_badrxtwin) < 0) {
1675 cc_cong_signal(tp, th, CC_RTO_ERR);
1679 * Recalculate the transmit timer / rtt.
1681 * Some boxes send broken timestamp replies
1682 * during the SYN+ACK phase, ignore
1683 * timestamps of 0 or we could calculate a
1684 * huge RTT and blow up the retransmit timer.
1686 if ((to.to_flags & TOF_TS) != 0 &&
1690 t = tcp_ts_getticks() - to.to_tsecr;
1691 if (!tp->t_rttlow || tp->t_rttlow > t)
1694 TCP_TS_TO_TICKS(t) + 1);
1695 } else if (tp->t_rtttime &&
1696 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1697 if (!tp->t_rttlow ||
1698 tp->t_rttlow > ticks - tp->t_rtttime)
1699 tp->t_rttlow = ticks - tp->t_rtttime;
1701 ticks - tp->t_rtttime);
1703 acked = BYTES_THIS_ACK(tp, th);
1705 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1706 hhook_run_tcp_est_in(tp, th, &to);
1708 TCPSTAT_INC(tcps_rcvackpack);
1709 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1710 sbdrop(&so->so_snd, acked);
1711 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1712 SEQ_LEQ(th->th_ack, tp->snd_recover))
1713 tp->snd_recover = th->th_ack - 1;
1716 * Let the congestion control algorithm update
1717 * congestion control related information. This
1718 * typically means increasing the congestion
1721 cc_ack_received(tp, th, CC_ACK);
1723 tp->snd_una = th->th_ack;
1725 * Pull snd_wl2 up to prevent seq wrap relative
1728 tp->snd_wl2 = th->th_ack;
1731 ND6_HINT(tp); /* Some progress has been made. */
1734 * If all outstanding data are acked, stop
1735 * retransmit timer, otherwise restart timer
1736 * using current (possibly backed-off) value.
1737 * If process is waiting for space,
1738 * wakeup/selwakeup/signal. If data
1739 * are ready to send, let tcp_output
1740 * decide between more output or persist.
1743 if (so->so_options & SO_DEBUG)
1744 tcp_trace(TA_INPUT, ostate, tp,
1745 (void *)tcp_saveipgen,
1748 if (tp->snd_una == tp->snd_max)
1749 tcp_timer_activate(tp, TT_REXMT, 0);
1750 else if (!tcp_timer_active(tp, TT_PERSIST))
1751 tcp_timer_activate(tp, TT_REXMT,
1754 if (so->so_snd.sb_cc)
1755 (void) tcp_output(tp);
1758 } else if (th->th_ack == tp->snd_una &&
1759 tlen <= sbspace(&so->so_rcv)) {
1760 int newsize = 0; /* automatic sockbuf scaling */
1763 * This is a pure, in-sequence data packet with
1764 * nothing on the reassembly queue and we have enough
1765 * buffer space to take it.
1767 if (ti_locked == TI_WLOCKED)
1768 INP_INFO_WUNLOCK(&V_tcbinfo);
1769 ti_locked = TI_UNLOCKED;
1771 /* Clean receiver SACK report if present */
1772 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1773 tcp_clean_sackreport(tp);
1774 TCPSTAT_INC(tcps_preddat);
1775 tp->rcv_nxt += tlen;
1777 * Pull snd_wl1 up to prevent seq wrap relative to
1780 tp->snd_wl1 = th->th_seq;
1782 * Pull rcv_up up to prevent seq wrap relative to
1785 tp->rcv_up = tp->rcv_nxt;
1786 TCPSTAT_INC(tcps_rcvpack);
1787 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1788 ND6_HINT(tp); /* Some progress has been made */
1790 if (so->so_options & SO_DEBUG)
1791 tcp_trace(TA_INPUT, ostate, tp,
1792 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1795 * Automatic sizing of receive socket buffer. Often the send
1796 * buffer size is not optimally adjusted to the actual network
1797 * conditions at hand (delay bandwidth product). Setting the
1798 * buffer size too small limits throughput on links with high
1799 * bandwidth and high delay (eg. trans-continental/oceanic links).
1801 * On the receive side the socket buffer memory is only rarely
1802 * used to any significant extent. This allows us to be much
1803 * more aggressive in scaling the receive socket buffer. For
1804 * the case that the buffer space is actually used to a large
1805 * extent and we run out of kernel memory we can simply drop
1806 * the new segments; TCP on the sender will just retransmit it
1807 * later. Setting the buffer size too big may only consume too
1808 * much kernel memory if the application doesn't read() from
1809 * the socket or packet loss or reordering makes use of the
1812 * The criteria to step up the receive buffer one notch are:
1813 * 1. the number of bytes received during the time it takes
1814 * one timestamp to be reflected back to us (the RTT);
1815 * 2. received bytes per RTT is within seven eighth of the
1816 * current socket buffer size;
1817 * 3. receive buffer size has not hit maximal automatic size;
1819 * This algorithm does one step per RTT at most and only if
1820 * we receive a bulk stream w/o packet losses or reorderings.
1821 * Shrinking the buffer during idle times is not necessary as
1822 * it doesn't consume any memory when idle.
1824 * TODO: Only step up if the application is actually serving
1825 * the buffer to better manage the socket buffer resources.
1827 if (V_tcp_do_autorcvbuf &&
1829 (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
1830 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
1831 to.to_tsecr - tp->rfbuf_ts < hz) {
1833 (so->so_rcv.sb_hiwat / 8 * 7) &&
1834 so->so_rcv.sb_hiwat <
1835 V_tcp_autorcvbuf_max) {
1837 min(so->so_rcv.sb_hiwat +
1838 V_tcp_autorcvbuf_inc,
1839 V_tcp_autorcvbuf_max);
1841 /* Start over with next RTT. */
1845 tp->rfbuf_cnt += tlen; /* add up */
1848 /* Add data to socket buffer. */
1849 SOCKBUF_LOCK(&so->so_rcv);
1850 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1854 * Set new socket buffer size.
1855 * Give up when limit is reached.
1858 if (!sbreserve_locked(&so->so_rcv,
1860 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1861 m_adj(m, drop_hdrlen); /* delayed header drop */
1862 sbappendstream_locked(&so->so_rcv, m);
1864 /* NB: sorwakeup_locked() does an implicit unlock. */
1865 sorwakeup_locked(so);
1866 if (DELAY_ACK(tp)) {
1867 tp->t_flags |= TF_DELACK;
1869 tp->t_flags |= TF_ACKNOW;
1877 * Calculate amount of space in receive window,
1878 * and then do TCP input processing.
1879 * Receive window is amount of space in rcv queue,
1880 * but not less than advertised window.
1882 win = sbspace(&so->so_rcv);
1885 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1887 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1891 switch (tp->t_state) {
1894 * If the state is SYN_RECEIVED:
1895 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1897 case TCPS_SYN_RECEIVED:
1898 if ((thflags & TH_ACK) &&
1899 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1900 SEQ_GT(th->th_ack, tp->snd_max))) {
1901 rstreason = BANDLIM_RST_OPENPORT;
1907 * If the state is SYN_SENT:
1908 * if seg contains an ACK, but not for our SYN, drop the input.
1909 * if seg contains a RST, then drop the connection.
1910 * if seg does not contain SYN, then drop it.
1911 * Otherwise this is an acceptable SYN segment
1912 * initialize tp->rcv_nxt and tp->irs
1913 * if seg contains ack then advance tp->snd_una
1914 * if seg contains an ECE and ECN support is enabled, the stream
1916 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1917 * arrange for segment to be acked (eventually)
1918 * continue processing rest of data/controls, beginning with URG
1921 if ((thflags & TH_ACK) &&
1922 (SEQ_LEQ(th->th_ack, tp->iss) ||
1923 SEQ_GT(th->th_ack, tp->snd_max))) {
1924 rstreason = BANDLIM_UNLIMITED;
1927 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1928 TCP_PROBE5(connect_refused, NULL, tp, m->m_data, tp,
1930 tp = tcp_drop(tp, ECONNREFUSED);
1932 if (thflags & TH_RST)
1934 if (!(thflags & TH_SYN))
1937 tp->irs = th->th_seq;
1939 if (thflags & TH_ACK) {
1940 TCPSTAT_INC(tcps_connects);
1943 mac_socketpeer_set_from_mbuf(m, so);
1945 /* Do window scaling on this connection? */
1946 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1947 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1948 tp->rcv_scale = tp->request_r_scale;
1950 tp->rcv_adv += imin(tp->rcv_wnd,
1951 TCP_MAXWIN << tp->rcv_scale);
1952 tp->snd_una++; /* SYN is acked */
1954 * If there's data, delay ACK; if there's also a FIN
1955 * ACKNOW will be turned on later.
1957 if (DELAY_ACK(tp) && tlen != 0)
1958 tcp_timer_activate(tp, TT_DELACK,
1961 tp->t_flags |= TF_ACKNOW;
1963 if ((thflags & TH_ECE) && V_tcp_do_ecn) {
1964 tp->t_flags |= TF_ECN_PERMIT;
1965 TCPSTAT_INC(tcps_ecn_shs);
1969 * Received <SYN,ACK> in SYN_SENT[*] state.
1971 * SYN_SENT --> ESTABLISHED
1972 * SYN_SENT* --> FIN_WAIT_1
1974 tp->t_starttime = ticks;
1975 if (tp->t_flags & TF_NEEDFIN) {
1976 tcp_state_change(tp, TCPS_FIN_WAIT_1);
1977 tp->t_flags &= ~TF_NEEDFIN;
1980 tcp_state_change(tp, TCPS_ESTABLISHED);
1981 TCP_PROBE5(connect_established, NULL, tp,
1984 tcp_timer_activate(tp, TT_KEEP,
1989 * Received initial SYN in SYN-SENT[*] state =>
1990 * simultaneous open. If segment contains CC option
1991 * and there is a cached CC, apply TAO test.
1992 * If it succeeds, connection is * half-synchronized.
1993 * Otherwise, do 3-way handshake:
1994 * SYN-SENT -> SYN-RECEIVED
1995 * SYN-SENT* -> SYN-RECEIVED*
1996 * If there was no CC option, clear cached CC value.
1998 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1999 tcp_timer_activate(tp, TT_REXMT, 0);
2000 tcp_state_change(tp, TCPS_SYN_RECEIVED);
2003 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
2004 "ti_locked %d", __func__, ti_locked));
2005 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2006 INP_WLOCK_ASSERT(tp->t_inpcb);
2009 * Advance th->th_seq to correspond to first data byte.
2010 * If data, trim to stay within window,
2011 * dropping FIN if necessary.
2014 if (tlen > tp->rcv_wnd) {
2015 todrop = tlen - tp->rcv_wnd;
2019 TCPSTAT_INC(tcps_rcvpackafterwin);
2020 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2022 tp->snd_wl1 = th->th_seq - 1;
2023 tp->rcv_up = th->th_seq;
2025 * Client side of transaction: already sent SYN and data.
2026 * If the remote host used T/TCP to validate the SYN,
2027 * our data will be ACK'd; if so, enter normal data segment
2028 * processing in the middle of step 5, ack processing.
2029 * Otherwise, goto step 6.
2031 if (thflags & TH_ACK)
2037 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2038 * do normal processing.
2040 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2044 break; /* continue normal processing */
2048 * States other than LISTEN or SYN_SENT.
2049 * First check the RST flag and sequence number since reset segments
2050 * are exempt from the timestamp and connection count tests. This
2051 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2052 * below which allowed reset segments in half the sequence space
2053 * to fall though and be processed (which gives forged reset
2054 * segments with a random sequence number a 50 percent chance of
2055 * killing a connection).
2056 * Then check timestamp, if present.
2057 * Then check the connection count, if present.
2058 * Then check that at least some bytes of segment are within
2059 * receive window. If segment begins before rcv_nxt,
2060 * drop leading data (and SYN); if nothing left, just ack.
2063 * If the RST bit is set, check the sequence number to see
2064 * if this is a valid reset segment.
2066 * In all states except SYN-SENT, all reset (RST) segments
2067 * are validated by checking their SEQ-fields. A reset is
2068 * valid if its sequence number is in the window.
2069 * Note: this does not take into account delayed ACKs, so
2070 * we should test against last_ack_sent instead of rcv_nxt.
2071 * The sequence number in the reset segment is normally an
2072 * echo of our outgoing acknowlegement numbers, but some hosts
2073 * send a reset with the sequence number at the rightmost edge
2074 * of our receive window, and we have to handle this case.
2075 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
2076 * that brute force RST attacks are possible. To combat this,
2077 * we use a much stricter check while in the ESTABLISHED state,
2078 * only accepting RSTs where the sequence number is equal to
2079 * last_ack_sent. In all other states (the states in which a
2080 * RST is more likely), the more permissive check is used.
2081 * If we have multiple segments in flight, the initial reset
2082 * segment sequence numbers will be to the left of last_ack_sent,
2083 * but they will eventually catch up.
2084 * In any case, it never made sense to trim reset segments to
2085 * fit the receive window since RFC 1122 says:
2086 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
2088 * A TCP SHOULD allow a received RST segment to include data.
2091 * It has been suggested that a RST segment could contain
2092 * ASCII text that encoded and explained the cause of the
2093 * RST. No standard has yet been established for such
2096 * If the reset segment passes the sequence number test examine
2098 * SYN_RECEIVED STATE:
2099 * If passive open, return to LISTEN state.
2100 * If active open, inform user that connection was refused.
2101 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
2102 * Inform user that connection was reset, and close tcb.
2103 * CLOSING, LAST_ACK STATES:
2106 * Drop the segment - see Stevens, vol. 2, p. 964 and
2109 if (thflags & TH_RST) {
2110 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2111 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2112 switch (tp->t_state) {
2114 case TCPS_SYN_RECEIVED:
2115 so->so_error = ECONNREFUSED;
2118 case TCPS_ESTABLISHED:
2119 if (V_tcp_insecure_rst == 0 &&
2120 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) &&
2121 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) &&
2122 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2123 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) {
2124 TCPSTAT_INC(tcps_badrst);
2128 case TCPS_FIN_WAIT_1:
2129 case TCPS_FIN_WAIT_2:
2130 case TCPS_CLOSE_WAIT:
2131 so->so_error = ECONNRESET;
2133 KASSERT(ti_locked == TI_WLOCKED,
2134 ("tcp_do_segment: TH_RST 1 ti_locked %d",
2136 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2138 tcp_state_change(tp, TCPS_CLOSED);
2139 TCPSTAT_INC(tcps_drops);
2145 KASSERT(ti_locked == TI_WLOCKED,
2146 ("tcp_do_segment: TH_RST 2 ti_locked %d",
2148 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2158 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2159 * and it's less than ts_recent, drop it.
2161 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2162 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2164 /* Check to see if ts_recent is over 24 days old. */
2165 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2167 * Invalidate ts_recent. If this segment updates
2168 * ts_recent, the age will be reset later and ts_recent
2169 * will get a valid value. If it does not, setting
2170 * ts_recent to zero will at least satisfy the
2171 * requirement that zero be placed in the timestamp
2172 * echo reply when ts_recent isn't valid. The
2173 * age isn't reset until we get a valid ts_recent
2174 * because we don't want out-of-order segments to be
2175 * dropped when ts_recent is old.
2179 TCPSTAT_INC(tcps_rcvduppack);
2180 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2181 TCPSTAT_INC(tcps_pawsdrop);
2189 * In the SYN-RECEIVED state, validate that the packet belongs to
2190 * this connection before trimming the data to fit the receive
2191 * window. Check the sequence number versus IRS since we know
2192 * the sequence numbers haven't wrapped. This is a partial fix
2193 * for the "LAND" DoS attack.
2195 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2196 rstreason = BANDLIM_RST_OPENPORT;
2200 todrop = tp->rcv_nxt - th->th_seq;
2203 * If this is a duplicate SYN for our current connection,
2204 * advance over it and pretend and it's not a SYN.
2206 if (thflags & TH_SYN && th->th_seq == tp->irs) {
2216 * Following if statement from Stevens, vol. 2, p. 960.
2219 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2221 * Any valid FIN must be to the left of the window.
2222 * At this point the FIN must be a duplicate or out
2223 * of sequence; drop it.
2228 * Send an ACK to resynchronize and drop any data.
2229 * But keep on processing for RST or ACK.
2231 tp->t_flags |= TF_ACKNOW;
2233 TCPSTAT_INC(tcps_rcvduppack);
2234 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2236 TCPSTAT_INC(tcps_rcvpartduppack);
2237 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2239 drop_hdrlen += todrop; /* drop from the top afterwards */
2240 th->th_seq += todrop;
2242 if (th->th_urp > todrop)
2243 th->th_urp -= todrop;
2251 * If new data are received on a connection after the
2252 * user processes are gone, then RST the other end.
2254 if ((so->so_state & SS_NOFDREF) &&
2255 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2256 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
2257 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2258 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2260 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2261 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2262 "after socket was closed, "
2263 "sending RST and removing tcpcb\n",
2264 s, __func__, tcpstates[tp->t_state], tlen);
2268 TCPSTAT_INC(tcps_rcvafterclose);
2269 rstreason = BANDLIM_UNLIMITED;
2274 * If segment ends after window, drop trailing data
2275 * (and PUSH and FIN); if nothing left, just ACK.
2277 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2279 TCPSTAT_INC(tcps_rcvpackafterwin);
2280 if (todrop >= tlen) {
2281 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2283 * If window is closed can only take segments at
2284 * window edge, and have to drop data and PUSH from
2285 * incoming segments. Continue processing, but
2286 * remember to ack. Otherwise, drop segment
2289 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2290 tp->t_flags |= TF_ACKNOW;
2291 TCPSTAT_INC(tcps_rcvwinprobe);
2295 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2298 thflags &= ~(TH_PUSH|TH_FIN);
2302 * If last ACK falls within this segment's sequence numbers,
2303 * record its timestamp.
2305 * 1) That the test incorporates suggestions from the latest
2306 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2307 * 2) That updating only on newer timestamps interferes with
2308 * our earlier PAWS tests, so this check should be solely
2309 * predicated on the sequence space of this segment.
2310 * 3) That we modify the segment boundary check to be
2311 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2312 * instead of RFC1323's
2313 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2314 * This modified check allows us to overcome RFC1323's
2315 * limitations as described in Stevens TCP/IP Illustrated
2316 * Vol. 2 p.869. In such cases, we can still calculate the
2317 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2319 if ((to.to_flags & TOF_TS) != 0 &&
2320 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2321 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2322 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2323 tp->ts_recent_age = tcp_ts_getticks();
2324 tp->ts_recent = to.to_tsval;
2328 * If a SYN is in the window, then this is an
2329 * error and we send an RST and drop the connection.
2331 if (thflags & TH_SYN) {
2332 KASSERT(ti_locked == TI_WLOCKED,
2333 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2334 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2336 tp = tcp_drop(tp, ECONNRESET);
2337 rstreason = BANDLIM_UNLIMITED;
2342 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2343 * flag is on (half-synchronized state), then queue data for
2344 * later processing; else drop segment and return.
2346 if ((thflags & TH_ACK) == 0) {
2347 if (tp->t_state == TCPS_SYN_RECEIVED ||
2348 (tp->t_flags & TF_NEEDSYN))
2350 else if (tp->t_flags & TF_ACKNOW)
2359 switch (tp->t_state) {
2362 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2363 * ESTABLISHED state and continue processing.
2364 * The ACK was checked above.
2366 case TCPS_SYN_RECEIVED:
2368 TCPSTAT_INC(tcps_connects);
2370 /* Do window scaling? */
2371 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2372 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2373 tp->rcv_scale = tp->request_r_scale;
2374 tp->snd_wnd = tiwin;
2378 * SYN-RECEIVED -> ESTABLISHED
2379 * SYN-RECEIVED* -> FIN-WAIT-1
2381 tp->t_starttime = ticks;
2382 if (tp->t_flags & TF_NEEDFIN) {
2383 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2384 tp->t_flags &= ~TF_NEEDFIN;
2386 tcp_state_change(tp, TCPS_ESTABLISHED);
2387 TCP_PROBE5(accept_established, NULL, tp, m->m_data, tp,
2390 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2393 * If segment contains data or ACK, will call tcp_reass()
2394 * later; if not, do so now to pass queued data to user.
2396 if (tlen == 0 && (thflags & TH_FIN) == 0)
2397 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2399 tp->snd_wl1 = th->th_seq - 1;
2403 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2404 * ACKs. If the ack is in the range
2405 * tp->snd_una < th->th_ack <= tp->snd_max
2406 * then advance tp->snd_una to th->th_ack and drop
2407 * data from the retransmission queue. If this ACK reflects
2408 * more up to date window information we update our window information.
2410 case TCPS_ESTABLISHED:
2411 case TCPS_FIN_WAIT_1:
2412 case TCPS_FIN_WAIT_2:
2413 case TCPS_CLOSE_WAIT:
2416 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2417 TCPSTAT_INC(tcps_rcvacktoomuch);
2420 if ((tp->t_flags & TF_SACK_PERMIT) &&
2421 ((to.to_flags & TOF_SACK) ||
2422 !TAILQ_EMPTY(&tp->snd_holes)))
2423 tcp_sack_doack(tp, &to, th->th_ack);
2425 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2426 hhook_run_tcp_est_in(tp, th, &to);
2428 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2429 if (tlen == 0 && tiwin == tp->snd_wnd) {
2430 TCPSTAT_INC(tcps_rcvdupack);
2432 * If we have outstanding data (other than
2433 * a window probe), this is a completely
2434 * duplicate ack (ie, window info didn't
2435 * change), the ack is the biggest we've
2436 * seen and we've seen exactly our rexmt
2437 * threshhold of them, assume a packet
2438 * has been dropped and retransmit it.
2439 * Kludge snd_nxt & the congestion
2440 * window so we send only this one
2443 * We know we're losing at the current
2444 * window size so do congestion avoidance
2445 * (set ssthresh to half the current window
2446 * and pull our congestion window back to
2447 * the new ssthresh).
2449 * Dup acks mean that packets have left the
2450 * network (they're now cached at the receiver)
2451 * so bump cwnd by the amount in the receiver
2452 * to keep a constant cwnd packets in the
2455 * When using TCP ECN, notify the peer that
2456 * we reduced the cwnd.
2458 if (!tcp_timer_active(tp, TT_REXMT) ||
2459 th->th_ack != tp->snd_una)
2461 else if (++tp->t_dupacks > tcprexmtthresh ||
2462 IN_FASTRECOVERY(tp->t_flags)) {
2463 cc_ack_received(tp, th, CC_DUPACK);
2464 if ((tp->t_flags & TF_SACK_PERMIT) &&
2465 IN_FASTRECOVERY(tp->t_flags)) {
2469 * Compute the amount of data in flight first.
2470 * We can inject new data into the pipe iff
2471 * we have less than 1/2 the original window's
2472 * worth of data in flight.
2474 awnd = (tp->snd_nxt - tp->snd_fack) +
2475 tp->sackhint.sack_bytes_rexmit;
2476 if (awnd < tp->snd_ssthresh) {
2477 tp->snd_cwnd += tp->t_maxseg;
2478 if (tp->snd_cwnd > tp->snd_ssthresh)
2479 tp->snd_cwnd = tp->snd_ssthresh;
2482 tp->snd_cwnd += tp->t_maxseg;
2483 if ((thflags & TH_FIN) &&
2484 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2486 * If its a fin we need to process
2487 * it to avoid a race where both
2488 * sides enter FIN-WAIT and send FIN|ACK
2493 (void) tcp_output(tp);
2495 } else if (tp->t_dupacks == tcprexmtthresh) {
2496 tcp_seq onxt = tp->snd_nxt;
2499 * If we're doing sack, check to
2500 * see if we're already in sack
2501 * recovery. If we're not doing sack,
2502 * check to see if we're in newreno
2505 if (tp->t_flags & TF_SACK_PERMIT) {
2506 if (IN_FASTRECOVERY(tp->t_flags)) {
2511 if (SEQ_LEQ(th->th_ack,
2517 /* Congestion signal before ack. */
2518 cc_cong_signal(tp, th, CC_NDUPACK);
2519 cc_ack_received(tp, th, CC_DUPACK);
2520 tcp_timer_activate(tp, TT_REXMT, 0);
2522 if (tp->t_flags & TF_SACK_PERMIT) {
2524 tcps_sack_recovery_episode);
2525 tp->sack_newdata = tp->snd_nxt;
2526 tp->snd_cwnd = tp->t_maxseg;
2527 (void) tcp_output(tp);
2530 tp->snd_nxt = th->th_ack;
2531 tp->snd_cwnd = tp->t_maxseg;
2532 if ((thflags & TH_FIN) &&
2533 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2535 * If its a fin we need to process
2536 * it to avoid a race where both
2537 * sides enter FIN-WAIT and send FIN|ACK
2542 (void) tcp_output(tp);
2543 KASSERT(tp->snd_limited <= 2,
2544 ("%s: tp->snd_limited too big",
2546 tp->snd_cwnd = tp->snd_ssthresh +
2548 (tp->t_dupacks - tp->snd_limited);
2549 if (SEQ_GT(onxt, tp->snd_nxt))
2552 } else if (V_tcp_do_rfc3042) {
2553 cc_ack_received(tp, th, CC_DUPACK);
2554 u_long oldcwnd = tp->snd_cwnd;
2555 tcp_seq oldsndmax = tp->snd_max;
2559 KASSERT(tp->t_dupacks == 1 ||
2561 ("%s: dupacks not 1 or 2",
2563 if (tp->t_dupacks == 1)
2564 tp->snd_limited = 0;
2566 (tp->snd_nxt - tp->snd_una) +
2567 (tp->t_dupacks - tp->snd_limited) *
2569 if ((thflags & TH_FIN) &&
2570 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2572 * If its a fin we need to process
2573 * it to avoid a race where both
2574 * sides enter FIN-WAIT and send FIN|ACK
2580 * Only call tcp_output when there
2581 * is new data available to be sent.
2582 * Otherwise we would send pure ACKs.
2584 SOCKBUF_LOCK(&so->so_snd);
2585 avail = so->so_snd.sb_cc -
2586 (tp->snd_nxt - tp->snd_una);
2587 SOCKBUF_UNLOCK(&so->so_snd);
2589 (void) tcp_output(tp);
2590 sent = tp->snd_max - oldsndmax;
2591 if (sent > tp->t_maxseg) {
2592 KASSERT((tp->t_dupacks == 2 &&
2593 tp->snd_limited == 0) ||
2594 (sent == tp->t_maxseg + 1 &&
2595 tp->t_flags & TF_SENTFIN),
2596 ("%s: sent too much",
2598 tp->snd_limited = 2;
2599 } else if (sent > 0)
2601 tp->snd_cwnd = oldcwnd;
2609 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2610 ("%s: th_ack <= snd_una", __func__));
2613 * If the congestion window was inflated to account
2614 * for the other side's cached packets, retract it.
2616 if (IN_FASTRECOVERY(tp->t_flags)) {
2617 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2618 if (tp->t_flags & TF_SACK_PERMIT)
2619 tcp_sack_partialack(tp, th);
2621 tcp_newreno_partial_ack(tp, th);
2623 cc_post_recovery(tp, th);
2627 * If we reach this point, ACK is not a duplicate,
2628 * i.e., it ACKs something we sent.
2630 if (tp->t_flags & TF_NEEDSYN) {
2632 * T/TCP: Connection was half-synchronized, and our
2633 * SYN has been ACK'd (so connection is now fully
2634 * synchronized). Go to non-starred state,
2635 * increment snd_una for ACK of SYN, and check if
2636 * we can do window scaling.
2638 tp->t_flags &= ~TF_NEEDSYN;
2640 /* Do window scaling? */
2641 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2642 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2643 tp->rcv_scale = tp->request_r_scale;
2644 /* Send window already scaled. */
2649 INP_WLOCK_ASSERT(tp->t_inpcb);
2651 acked = BYTES_THIS_ACK(tp, th);
2652 TCPSTAT_INC(tcps_rcvackpack);
2653 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2656 * If we just performed our first retransmit, and the ACK
2657 * arrives within our recovery window, then it was a mistake
2658 * to do the retransmit in the first place. Recover our
2659 * original cwnd and ssthresh, and proceed to transmit where
2662 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2663 (int)(ticks - tp->t_badrxtwin) < 0)
2664 cc_cong_signal(tp, th, CC_RTO_ERR);
2667 * If we have a timestamp reply, update smoothed
2668 * round trip time. If no timestamp is present but
2669 * transmit timer is running and timed sequence
2670 * number was acked, update smoothed round trip time.
2671 * Since we now have an rtt measurement, cancel the
2672 * timer backoff (cf., Phil Karn's retransmit alg.).
2673 * Recompute the initial retransmit timer.
2675 * Some boxes send broken timestamp replies
2676 * during the SYN+ACK phase, ignore
2677 * timestamps of 0 or we could calculate a
2678 * huge RTT and blow up the retransmit timer.
2680 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2683 t = tcp_ts_getticks() - to.to_tsecr;
2684 if (!tp->t_rttlow || tp->t_rttlow > t)
2686 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2687 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2688 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2689 tp->t_rttlow = ticks - tp->t_rtttime;
2690 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2694 * If all outstanding data is acked, stop retransmit
2695 * timer and remember to restart (more output or persist).
2696 * If there is more data to be acked, restart retransmit
2697 * timer, using current (possibly backed-off) value.
2699 if (th->th_ack == tp->snd_max) {
2700 tcp_timer_activate(tp, TT_REXMT, 0);
2702 } else if (!tcp_timer_active(tp, TT_PERSIST))
2703 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2706 * If no data (only SYN) was ACK'd,
2707 * skip rest of ACK processing.
2713 * Let the congestion control algorithm update congestion
2714 * control related information. This typically means increasing
2715 * the congestion window.
2717 cc_ack_received(tp, th, CC_ACK);
2719 SOCKBUF_LOCK(&so->so_snd);
2720 if (acked > so->so_snd.sb_cc) {
2721 tp->snd_wnd -= so->so_snd.sb_cc;
2722 mfree = sbcut_locked(&so->so_snd,
2723 (int)so->so_snd.sb_cc);
2726 mfree = sbcut_locked(&so->so_snd, acked);
2727 tp->snd_wnd -= acked;
2730 /* NB: sowwakeup_locked() does an implicit unlock. */
2731 sowwakeup_locked(so);
2733 /* Detect una wraparound. */
2734 if (!IN_RECOVERY(tp->t_flags) &&
2735 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2736 SEQ_LEQ(th->th_ack, tp->snd_recover))
2737 tp->snd_recover = th->th_ack - 1;
2738 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2739 if (IN_RECOVERY(tp->t_flags) &&
2740 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2741 EXIT_RECOVERY(tp->t_flags);
2743 tp->snd_una = th->th_ack;
2744 if (tp->t_flags & TF_SACK_PERMIT) {
2745 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2746 tp->snd_recover = tp->snd_una;
2748 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2749 tp->snd_nxt = tp->snd_una;
2751 switch (tp->t_state) {
2754 * In FIN_WAIT_1 STATE in addition to the processing
2755 * for the ESTABLISHED state if our FIN is now acknowledged
2756 * then enter FIN_WAIT_2.
2758 case TCPS_FIN_WAIT_1:
2759 if (ourfinisacked) {
2761 * If we can't receive any more
2762 * data, then closing user can proceed.
2763 * Starting the timer is contrary to the
2764 * specification, but if we don't get a FIN
2765 * we'll hang forever.
2768 * we should release the tp also, and use a
2771 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2772 soisdisconnected(so);
2773 tcp_timer_activate(tp, TT_2MSL,
2774 (tcp_fast_finwait2_recycle ?
2775 tcp_finwait2_timeout :
2778 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2783 * In CLOSING STATE in addition to the processing for
2784 * the ESTABLISHED state if the ACK acknowledges our FIN
2785 * then enter the TIME-WAIT state, otherwise ignore
2789 if (ourfinisacked) {
2790 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2792 INP_INFO_WUNLOCK(&V_tcbinfo);
2799 * In LAST_ACK, we may still be waiting for data to drain
2800 * and/or to be acked, as well as for the ack of our FIN.
2801 * If our FIN is now acknowledged, delete the TCB,
2802 * enter the closed state and return.
2805 if (ourfinisacked) {
2806 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2815 INP_WLOCK_ASSERT(tp->t_inpcb);
2818 * Update window information.
2819 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2821 if ((thflags & TH_ACK) &&
2822 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2823 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2824 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2825 /* keep track of pure window updates */
2827 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2828 TCPSTAT_INC(tcps_rcvwinupd);
2829 tp->snd_wnd = tiwin;
2830 tp->snd_wl1 = th->th_seq;
2831 tp->snd_wl2 = th->th_ack;
2832 if (tp->snd_wnd > tp->max_sndwnd)
2833 tp->max_sndwnd = tp->snd_wnd;
2838 * Process segments with URG.
2840 if ((thflags & TH_URG) && th->th_urp &&
2841 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2843 * This is a kludge, but if we receive and accept
2844 * random urgent pointers, we'll crash in
2845 * soreceive. It's hard to imagine someone
2846 * actually wanting to send this much urgent data.
2848 SOCKBUF_LOCK(&so->so_rcv);
2849 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2850 th->th_urp = 0; /* XXX */
2851 thflags &= ~TH_URG; /* XXX */
2852 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2853 goto dodata; /* XXX */
2856 * If this segment advances the known urgent pointer,
2857 * then mark the data stream. This should not happen
2858 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2859 * a FIN has been received from the remote side.
2860 * In these states we ignore the URG.
2862 * According to RFC961 (Assigned Protocols),
2863 * the urgent pointer points to the last octet
2864 * of urgent data. We continue, however,
2865 * to consider it to indicate the first octet
2866 * of data past the urgent section as the original
2867 * spec states (in one of two places).
2869 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2870 tp->rcv_up = th->th_seq + th->th_urp;
2871 so->so_oobmark = so->so_rcv.sb_cc +
2872 (tp->rcv_up - tp->rcv_nxt) - 1;
2873 if (so->so_oobmark == 0)
2874 so->so_rcv.sb_state |= SBS_RCVATMARK;
2876 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2878 SOCKBUF_UNLOCK(&so->so_rcv);
2880 * Remove out of band data so doesn't get presented to user.
2881 * This can happen independent of advancing the URG pointer,
2882 * but if two URG's are pending at once, some out-of-band
2883 * data may creep in... ick.
2885 if (th->th_urp <= (u_long)tlen &&
2886 !(so->so_options & SO_OOBINLINE)) {
2887 /* hdr drop is delayed */
2888 tcp_pulloutofband(so, th, m, drop_hdrlen);
2892 * If no out of band data is expected,
2893 * pull receive urgent pointer along
2894 * with the receive window.
2896 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2897 tp->rcv_up = tp->rcv_nxt;
2900 INP_WLOCK_ASSERT(tp->t_inpcb);
2903 * Process the segment text, merging it into the TCP sequencing queue,
2904 * and arranging for acknowledgment of receipt if necessary.
2905 * This process logically involves adjusting tp->rcv_wnd as data
2906 * is presented to the user (this happens in tcp_usrreq.c,
2907 * case PRU_RCVD). If a FIN has already been received on this
2908 * connection then we just ignore the text.
2910 if ((tlen || (thflags & TH_FIN)) &&
2911 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2912 tcp_seq save_start = th->th_seq;
2913 m_adj(m, drop_hdrlen); /* delayed header drop */
2915 * Insert segment which includes th into TCP reassembly queue
2916 * with control block tp. Set thflags to whether reassembly now
2917 * includes a segment with FIN. This handles the common case
2918 * inline (segment is the next to be received on an established
2919 * connection, and the queue is empty), avoiding linkage into
2920 * and removal from the queue and repetition of various
2922 * Set DELACK for segments received in order, but ack
2923 * immediately when segments are out of order (so
2924 * fast retransmit can work).
2926 if (th->th_seq == tp->rcv_nxt &&
2927 LIST_EMPTY(&tp->t_segq) &&
2928 TCPS_HAVEESTABLISHED(tp->t_state)) {
2930 tp->t_flags |= TF_DELACK;
2932 tp->t_flags |= TF_ACKNOW;
2933 tp->rcv_nxt += tlen;
2934 thflags = th->th_flags & TH_FIN;
2935 TCPSTAT_INC(tcps_rcvpack);
2936 TCPSTAT_ADD(tcps_rcvbyte, tlen);
2938 SOCKBUF_LOCK(&so->so_rcv);
2939 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2942 sbappendstream_locked(&so->so_rcv, m);
2943 /* NB: sorwakeup_locked() does an implicit unlock. */
2944 sorwakeup_locked(so);
2947 * XXX: Due to the header drop above "th" is
2948 * theoretically invalid by now. Fortunately
2949 * m_adj() doesn't actually frees any mbufs
2950 * when trimming from the head.
2952 thflags = tcp_reass(tp, th, &tlen, m);
2953 tp->t_flags |= TF_ACKNOW;
2955 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2956 tcp_update_sack_list(tp, save_start, save_start + tlen);
2959 * Note the amount of data that peer has sent into
2960 * our window, in order to estimate the sender's
2964 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2965 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2967 len = so->so_rcv.sb_hiwat;
2975 * If FIN is received ACK the FIN and let the user know
2976 * that the connection is closing.
2978 if (thflags & TH_FIN) {
2979 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2982 * If connection is half-synchronized
2983 * (ie NEEDSYN flag on) then delay ACK,
2984 * so it may be piggybacked when SYN is sent.
2985 * Otherwise, since we received a FIN then no
2986 * more input can be expected, send ACK now.
2988 if (tp->t_flags & TF_NEEDSYN)
2989 tp->t_flags |= TF_DELACK;
2991 tp->t_flags |= TF_ACKNOW;
2994 switch (tp->t_state) {
2997 * In SYN_RECEIVED and ESTABLISHED STATES
2998 * enter the CLOSE_WAIT state.
3000 case TCPS_SYN_RECEIVED:
3001 tp->t_starttime = ticks;
3003 case TCPS_ESTABLISHED:
3004 tcp_state_change(tp, TCPS_CLOSE_WAIT);
3008 * If still in FIN_WAIT_1 STATE FIN has not been acked so
3009 * enter the CLOSING state.
3011 case TCPS_FIN_WAIT_1:
3012 tcp_state_change(tp, TCPS_CLOSING);
3016 * In FIN_WAIT_2 state enter the TIME_WAIT state,
3017 * starting the time-wait timer, turning off the other
3020 case TCPS_FIN_WAIT_2:
3021 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
3022 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
3023 "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
3027 INP_INFO_WUNLOCK(&V_tcbinfo);
3031 if (ti_locked == TI_WLOCKED)
3032 INP_INFO_WUNLOCK(&V_tcbinfo);
3033 ti_locked = TI_UNLOCKED;
3036 if (so->so_options & SO_DEBUG)
3037 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3042 * Return any desired output.
3044 if (needoutput || (tp->t_flags & TF_ACKNOW))
3045 (void) tcp_output(tp);
3048 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3049 __func__, ti_locked));
3050 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3051 INP_WLOCK_ASSERT(tp->t_inpcb);
3053 if (tp->t_flags & TF_DELACK) {
3054 tp->t_flags &= ~TF_DELACK;
3055 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3057 INP_WUNLOCK(tp->t_inpcb);
3062 * Generate an ACK dropping incoming segment if it occupies
3063 * sequence space, where the ACK reflects our state.
3065 * We can now skip the test for the RST flag since all
3066 * paths to this code happen after packets containing
3067 * RST have been dropped.
3069 * In the SYN-RECEIVED state, don't send an ACK unless the
3070 * segment we received passes the SYN-RECEIVED ACK test.
3071 * If it fails send a RST. This breaks the loop in the
3072 * "LAND" DoS attack, and also prevents an ACK storm
3073 * between two listening ports that have been sent forged
3074 * SYN segments, each with the source address of the other.
3076 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3077 (SEQ_GT(tp->snd_una, th->th_ack) ||
3078 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3079 rstreason = BANDLIM_RST_OPENPORT;
3083 if (so->so_options & SO_DEBUG)
3084 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3087 if (ti_locked == TI_WLOCKED)
3088 INP_INFO_WUNLOCK(&V_tcbinfo);
3089 ti_locked = TI_UNLOCKED;
3091 tp->t_flags |= TF_ACKNOW;
3092 (void) tcp_output(tp);
3093 INP_WUNLOCK(tp->t_inpcb);
3098 if (ti_locked == TI_WLOCKED)
3099 INP_INFO_WUNLOCK(&V_tcbinfo);
3100 ti_locked = TI_UNLOCKED;
3103 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3104 INP_WUNLOCK(tp->t_inpcb);
3106 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3110 if (ti_locked == TI_WLOCKED) {
3111 INP_INFO_WUNLOCK(&V_tcbinfo);
3112 ti_locked = TI_UNLOCKED;
3116 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3120 * Drop space held by incoming segment and return.
3123 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3124 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3128 INP_WUNLOCK(tp->t_inpcb);
3133 * Issue RST and make ACK acceptable to originator of segment.
3134 * The mbuf must still include the original packet header.
3138 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3139 int tlen, int rstreason)
3145 struct ip6_hdr *ip6;
3149 INP_WLOCK_ASSERT(tp->t_inpcb);
3152 /* Don't bother if destination was broadcast/multicast. */
3153 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3156 if (mtod(m, struct ip *)->ip_v == 6) {
3157 ip6 = mtod(m, struct ip6_hdr *);
3158 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3159 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3161 /* IPv6 anycast check is done at tcp6_input() */
3164 #if defined(INET) && defined(INET6)
3169 ip = mtod(m, struct ip *);
3170 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3171 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3172 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3173 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3178 /* Perform bandwidth limiting. */
3179 if (badport_bandlim(rstreason) < 0)
3182 /* tcp_respond consumes the mbuf chain. */
3183 if (th->th_flags & TH_ACK) {
3184 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3185 th->th_ack, TH_RST);
3187 if (th->th_flags & TH_SYN)
3189 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3190 (tcp_seq)0, TH_RST|TH_ACK);
3198 * Parse TCP options and place in tcpopt.
3201 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3206 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3208 if (opt == TCPOPT_EOL)
3210 if (opt == TCPOPT_NOP)
3216 if (optlen < 2 || optlen > cnt)
3221 if (optlen != TCPOLEN_MAXSEG)
3223 if (!(flags & TO_SYN))
3225 to->to_flags |= TOF_MSS;
3226 bcopy((char *)cp + 2,
3227 (char *)&to->to_mss, sizeof(to->to_mss));
3228 to->to_mss = ntohs(to->to_mss);
3231 if (optlen != TCPOLEN_WINDOW)
3233 if (!(flags & TO_SYN))
3235 to->to_flags |= TOF_SCALE;
3236 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3238 case TCPOPT_TIMESTAMP:
3239 if (optlen != TCPOLEN_TIMESTAMP)
3241 to->to_flags |= TOF_TS;
3242 bcopy((char *)cp + 2,
3243 (char *)&to->to_tsval, sizeof(to->to_tsval));
3244 to->to_tsval = ntohl(to->to_tsval);
3245 bcopy((char *)cp + 6,
3246 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3247 to->to_tsecr = ntohl(to->to_tsecr);
3249 #ifdef TCP_SIGNATURE
3251 * XXX In order to reply to a host which has set the
3252 * TCP_SIGNATURE option in its initial SYN, we have to
3253 * record the fact that the option was observed here
3254 * for the syncache code to perform the correct response.
3256 case TCPOPT_SIGNATURE:
3257 if (optlen != TCPOLEN_SIGNATURE)
3259 to->to_flags |= TOF_SIGNATURE;
3260 to->to_signature = cp + 2;
3263 case TCPOPT_SACK_PERMITTED:
3264 if (optlen != TCPOLEN_SACK_PERMITTED)
3266 if (!(flags & TO_SYN))
3270 to->to_flags |= TOF_SACKPERM;
3273 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3277 to->to_flags |= TOF_SACK;
3278 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3279 to->to_sacks = cp + 2;
3280 TCPSTAT_INC(tcps_sack_rcv_blocks);
3289 * Pull out of band byte out of a segment so
3290 * it doesn't appear in the user's data queue.
3291 * It is still reflected in the segment length for
3292 * sequencing purposes.
3295 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3298 int cnt = off + th->th_urp - 1;
3301 if (m->m_len > cnt) {
3302 char *cp = mtod(m, caddr_t) + cnt;
3303 struct tcpcb *tp = sototcpcb(so);
3305 INP_WLOCK_ASSERT(tp->t_inpcb);
3308 tp->t_oobflags |= TCPOOB_HAVEDATA;
3309 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3311 if (m->m_flags & M_PKTHDR)
3320 panic("tcp_pulloutofband");
3324 * Collect new round-trip time estimate
3325 * and update averages and current timeout.
3328 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3332 INP_WLOCK_ASSERT(tp->t_inpcb);
3334 TCPSTAT_INC(tcps_rttupdated);
3336 if (tp->t_srtt != 0) {
3338 * srtt is stored as fixed point with 5 bits after the
3339 * binary point (i.e., scaled by 8). The following magic
3340 * is equivalent to the smoothing algorithm in rfc793 with
3341 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3342 * point). Adjust rtt to origin 0.
3344 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3345 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3347 if ((tp->t_srtt += delta) <= 0)
3351 * We accumulate a smoothed rtt variance (actually, a
3352 * smoothed mean difference), then set the retransmit
3353 * timer to smoothed rtt + 4 times the smoothed variance.
3354 * rttvar is stored as fixed point with 4 bits after the
3355 * binary point (scaled by 16). The following is
3356 * equivalent to rfc793 smoothing with an alpha of .75
3357 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3358 * rfc793's wired-in beta.
3362 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3363 if ((tp->t_rttvar += delta) <= 0)
3365 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3366 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3369 * No rtt measurement yet - use the unsmoothed rtt.
3370 * Set the variance to half the rtt (so our first
3371 * retransmit happens at 3*rtt).
3373 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3374 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3375 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3381 * the retransmit should happen at rtt + 4 * rttvar.
3382 * Because of the way we do the smoothing, srtt and rttvar
3383 * will each average +1/2 tick of bias. When we compute
3384 * the retransmit timer, we want 1/2 tick of rounding and
3385 * 1 extra tick because of +-1/2 tick uncertainty in the
3386 * firing of the timer. The bias will give us exactly the
3387 * 1.5 tick we need. But, because the bias is
3388 * statistical, we have to test that we don't drop below
3389 * the minimum feasible timer (which is 2 ticks).
3391 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3392 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3395 * We received an ack for a packet that wasn't retransmitted;
3396 * it is probably safe to discard any error indications we've
3397 * received recently. This isn't quite right, but close enough
3398 * for now (a route might have failed after we sent a segment,
3399 * and the return path might not be symmetrical).
3401 tp->t_softerror = 0;
3405 * Determine a reasonable value for maxseg size.
3406 * If the route is known, check route for mtu.
3407 * If none, use an mss that can be handled on the outgoing interface
3408 * without forcing IP to fragment. If no route is found, route has no mtu,
3409 * or the destination isn't local, use a default, hopefully conservative
3410 * size (usually 512 or the default IP max size, but no more than the mtu
3411 * of the interface), as we can't discover anything about intervening
3412 * gateways or networks. We also initialize the congestion/slow start
3413 * window to be a single segment if the destination isn't local.
3414 * While looking at the routing entry, we also initialize other path-dependent
3415 * parameters from pre-set or cached values in the routing entry.
3417 * Also take into account the space needed for options that we
3418 * send regularly. Make maxseg shorter by that amount to assure
3419 * that we can send maxseg amount of data even when the options
3420 * are present. Store the upper limit of the length of options plus
3423 * NOTE that this routine is only called when we process an incoming
3424 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3425 * settings are handled in tcp_mssopt().
3428 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3429 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3433 struct inpcb *inp = tp->t_inpcb;
3434 struct hc_metrics_lite metrics;
3437 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3438 size_t min_protoh = isipv6 ?
3439 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3440 sizeof (struct tcpiphdr);
3442 const size_t min_protoh = sizeof(struct tcpiphdr);
3445 INP_WLOCK_ASSERT(tp->t_inpcb);
3447 if (mtuoffer != -1) {
3448 KASSERT(offer == -1, ("%s: conflict", __func__));
3449 offer = mtuoffer - min_protoh;
3456 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3457 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3460 #if defined(INET) && defined(INET6)
3465 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3466 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3471 * No route to sender, stay with default mss and return.
3475 * In case we return early we need to initialize metrics
3476 * to a defined state as tcp_hc_get() would do for us
3477 * if there was no cache hit.
3479 if (metricptr != NULL)
3480 bzero(metricptr, sizeof(struct hc_metrics_lite));
3484 /* What have we got? */
3488 * Offer == 0 means that there was no MSS on the SYN
3489 * segment, in this case we use tcp_mssdflt as
3490 * already assigned to t_maxopd above.
3492 offer = tp->t_maxopd;
3497 * Offer == -1 means that we didn't receive SYN yet.
3503 * Prevent DoS attack with too small MSS. Round up
3504 * to at least minmss.
3506 offer = max(offer, V_tcp_minmss);
3510 * rmx information is now retrieved from tcp_hostcache.
3512 tcp_hc_get(&inp->inp_inc, &metrics);
3513 if (metricptr != NULL)
3514 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3517 * If there's a discovered mtu int tcp hostcache, use it
3518 * else, use the link mtu.
3520 if (metrics.rmx_mtu)
3521 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3525 mss = maxmtu - min_protoh;
3526 if (!V_path_mtu_discovery &&
3527 !in6_localaddr(&inp->in6p_faddr))
3528 mss = min(mss, V_tcp_v6mssdflt);
3531 #if defined(INET) && defined(INET6)
3536 mss = maxmtu - min_protoh;
3537 if (!V_path_mtu_discovery &&
3538 !in_localaddr(inp->inp_faddr))
3539 mss = min(mss, V_tcp_mssdflt);
3543 * XXX - The above conditional (mss = maxmtu - min_protoh)
3544 * probably violates the TCP spec.
3545 * The problem is that, since we don't know the
3546 * other end's MSS, we are supposed to use a conservative
3547 * default. But, if we do that, then MTU discovery will
3548 * never actually take place, because the conservative
3549 * default is much less than the MTUs typically seen
3550 * on the Internet today. For the moment, we'll sweep
3551 * this under the carpet.
3553 * The conservative default might not actually be a problem
3554 * if the only case this occurs is when sending an initial
3555 * SYN with options and data to a host we've never talked
3556 * to before. Then, they will reply with an MSS value which
3557 * will get recorded and the new parameters should get
3558 * recomputed. For Further Study.
3561 mss = min(mss, offer);
3564 * Sanity check: make sure that maxopd will be large
3565 * enough to allow some data on segments even if the
3566 * all the option space is used (40bytes). Otherwise
3567 * funny things may happen in tcp_output.
3572 * maxopd stores the maximum length of data AND options
3573 * in a segment; maxseg is the amount of data in a normal
3574 * segment. We need to store this value (maxopd) apart
3575 * from maxseg, because now every segment carries options
3576 * and thus we normally have somewhat less data in segments.
3581 * origoffer==-1 indicates that no segments were received yet.
3582 * In this case we just guess.
3584 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3586 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3587 mss -= TCPOLEN_TSTAMP_APPA;
3593 tcp_mss(struct tcpcb *tp, int offer)
3599 struct hc_metrics_lite metrics;
3600 struct tcp_ifcap cap;
3602 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3604 bzero(&cap, sizeof(cap));
3605 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3611 * If there's a pipesize, change the socket buffer to that size,
3612 * don't change if sb_hiwat is different than default (then it
3613 * has been changed on purpose with setsockopt).
3614 * Make the socket buffers an integral number of mss units;
3615 * if the mss is larger than the socket buffer, decrease the mss.
3617 so = inp->inp_socket;
3618 SOCKBUF_LOCK(&so->so_snd);
3619 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3620 bufsize = metrics.rmx_sendpipe;
3622 bufsize = so->so_snd.sb_hiwat;
3626 bufsize = roundup(bufsize, mss);
3627 if (bufsize > sb_max)
3629 if (bufsize > so->so_snd.sb_hiwat)
3630 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3632 SOCKBUF_UNLOCK(&so->so_snd);
3635 SOCKBUF_LOCK(&so->so_rcv);
3636 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3637 bufsize = metrics.rmx_recvpipe;
3639 bufsize = so->so_rcv.sb_hiwat;
3640 if (bufsize > mss) {
3641 bufsize = roundup(bufsize, mss);
3642 if (bufsize > sb_max)
3644 if (bufsize > so->so_rcv.sb_hiwat)
3645 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3647 SOCKBUF_UNLOCK(&so->so_rcv);
3649 /* Check the interface for TSO capabilities. */
3650 if (cap.ifcap & CSUM_TSO) {
3651 tp->t_flags |= TF_TSO;
3652 tp->t_tsomax = cap.tsomax;
3657 * Determine the MSS option to send on an outgoing SYN.
3660 tcp_mssopt(struct in_conninfo *inc)
3667 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3670 if (inc->inc_flags & INC_ISIPV6) {
3671 mss = V_tcp_v6mssdflt;
3672 maxmtu = tcp_maxmtu6(inc, NULL);
3673 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3676 #if defined(INET) && defined(INET6)
3681 mss = V_tcp_mssdflt;
3682 maxmtu = tcp_maxmtu(inc, NULL);
3683 min_protoh = sizeof(struct tcpiphdr);
3686 #if defined(INET6) || defined(INET)
3687 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3690 if (maxmtu && thcmtu)
3691 mss = min(maxmtu, thcmtu) - min_protoh;
3692 else if (maxmtu || thcmtu)
3693 mss = max(maxmtu, thcmtu) - min_protoh;
3700 * On a partial ack arrives, force the retransmission of the
3701 * next unacknowledged segment. Do not clear tp->t_dupacks.
3702 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3706 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3708 tcp_seq onxt = tp->snd_nxt;
3709 u_long ocwnd = tp->snd_cwnd;
3711 INP_WLOCK_ASSERT(tp->t_inpcb);
3713 tcp_timer_activate(tp, TT_REXMT, 0);
3715 tp->snd_nxt = th->th_ack;
3717 * Set snd_cwnd to one segment beyond acknowledged offset.
3718 * (tp->snd_una has not yet been updated when this function is called.)
3720 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3721 tp->t_flags |= TF_ACKNOW;
3722 (void) tcp_output(tp);
3723 tp->snd_cwnd = ocwnd;
3724 if (SEQ_GT(onxt, tp->snd_nxt))
3727 * Partial window deflation. Relies on fact that tp->snd_una
3730 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3731 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3734 tp->snd_cwnd += tp->t_maxseg;
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