2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 2007-2008,2010
5 * Swinburne University of Technology, Melbourne, Australia.
6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
7 * Copyright (c) 2010 The FreeBSD Foundation
8 * Copyright (c) 2010-2011 Juniper Networks, Inc.
11 * Portions of this software were developed at the Centre for Advanced Internet
12 * Architectures, Swinburne University of Technology, by Lawrence Stewart,
13 * James Healy and David Hayes, made possible in part by a grant from the Cisco
14 * University Research Program Fund at Community Foundation Silicon Valley.
16 * Portions of this software were developed at the Centre for Advanced
17 * Internet Architectures, Swinburne University of Technology, Melbourne,
18 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
20 * Portions of this software were developed by Robert N. M. Watson under
21 * contract to Juniper Networks, Inc.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 4. Neither the name of the University nor the names of its contributors
32 * may be used to endorse or promote products derived from this software
33 * without specific prior written permission.
35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
50 #include <sys/cdefs.h>
51 __FBSDID("$FreeBSD$");
53 #include "opt_ipfw.h" /* for ipfw_fwd */
55 #include "opt_inet6.h"
56 #include "opt_ipsec.h"
57 #include "opt_tcpdebug.h"
59 #include <sys/param.h>
60 #include <sys/kernel.h>
61 #include <sys/hhook.h>
62 #include <sys/malloc.h>
64 #include <sys/proc.h> /* for proc0 declaration */
65 #include <sys/protosw.h>
67 #include <sys/signalvar.h>
68 #include <sys/socket.h>
69 #include <sys/socketvar.h>
70 #include <sys/sysctl.h>
71 #include <sys/syslog.h>
72 #include <sys/systm.h>
74 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
79 #include <net/if_var.h>
80 #include <net/route.h>
83 #define TCPSTATES /* for logging */
85 #include <netinet/cc.h>
86 #include <netinet/in.h>
87 #include <netinet/in_kdtrace.h>
88 #include <netinet/in_pcb.h>
89 #include <netinet/in_systm.h>
90 #include <netinet/in_var.h>
91 #include <netinet/ip.h>
92 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
93 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
94 #include <netinet/ip_var.h>
95 #include <netinet/ip_options.h>
96 #include <netinet/ip6.h>
97 #include <netinet/icmp6.h>
98 #include <netinet6/in6_pcb.h>
99 #include <netinet6/ip6_var.h>
100 #include <netinet6/nd6.h>
101 #include <netinet/tcp_fsm.h>
102 #include <netinet/tcp_seq.h>
103 #include <netinet/tcp_timer.h>
104 #include <netinet/tcp_var.h>
105 #include <netinet6/tcp6_var.h>
106 #include <netinet/tcpip.h>
107 #include <netinet/tcp_syncache.h>
109 #include <netinet/tcp_debug.h>
110 #endif /* TCPDEBUG */
112 #include <netinet/tcp_offload.h>
116 #include <netipsec/ipsec.h>
117 #include <netipsec/ipsec6.h>
120 #include <machine/in_cksum.h>
122 #include <security/mac/mac_framework.h>
124 const int tcprexmtthresh = 3;
126 int tcp_log_in_vain = 0;
127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
129 "Log all incoming TCP segments to closed ports");
131 VNET_DEFINE(int, blackhole) = 0;
132 #define V_blackhole VNET(blackhole)
133 SYSCTL_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 RFC 6928 (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 cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
234 static void inline cc_conn_init(struct tcpcb *tp);
235 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
236 static void inline hhook_run_tcp_est_in(struct tcpcb *tp,
237 struct tcphdr *th, struct tcpopt *to);
240 * TCP statistics are stored in an "array" of counter(9)s.
242 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
243 VNET_PCPUSTAT_SYSINIT(tcpstat);
244 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
245 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
248 VNET_PCPUSTAT_SYSUNINIT(tcpstat);
251 * Kernel module interface for updating tcpstat. The argument is an index
252 * into tcpstat treated as an array.
255 kmod_tcpstat_inc(int statnum)
258 counter_u64_add(VNET(tcpstat)[statnum], 1);
262 * Wrapper for the TCP established input helper hook.
265 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
267 struct tcp_hhook_data hhook_data;
269 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
274 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
280 * CC wrapper hook functions
283 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
285 INP_WLOCK_ASSERT(tp->t_inpcb);
287 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
288 if (tp->snd_cwnd <= tp->snd_wnd)
289 tp->ccv->flags |= CCF_CWND_LIMITED;
291 tp->ccv->flags &= ~CCF_CWND_LIMITED;
293 if (type == CC_ACK) {
294 if (tp->snd_cwnd > tp->snd_ssthresh) {
295 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
296 V_tcp_abc_l_var * tp->t_maxseg);
297 if (tp->t_bytes_acked >= tp->snd_cwnd) {
298 tp->t_bytes_acked -= tp->snd_cwnd;
299 tp->ccv->flags |= CCF_ABC_SENTAWND;
302 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
303 tp->t_bytes_acked = 0;
307 if (CC_ALGO(tp)->ack_received != NULL) {
308 /* XXXLAS: Find a way to live without this */
309 tp->ccv->curack = th->th_ack;
310 CC_ALGO(tp)->ack_received(tp->ccv, type);
315 cc_conn_init(struct tcpcb *tp)
317 struct hc_metrics_lite metrics;
318 struct inpcb *inp = tp->t_inpcb;
321 INP_WLOCK_ASSERT(tp->t_inpcb);
323 tcp_hc_get(&inp->inp_inc, &metrics);
325 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
327 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
328 TCPSTAT_INC(tcps_usedrtt);
329 if (metrics.rmx_rttvar) {
330 tp->t_rttvar = metrics.rmx_rttvar;
331 TCPSTAT_INC(tcps_usedrttvar);
333 /* default variation is +- 1 rtt */
335 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
337 TCPT_RANGESET(tp->t_rxtcur,
338 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
339 tp->t_rttmin, TCPTV_REXMTMAX);
341 if (metrics.rmx_ssthresh) {
343 * There's some sort of gateway or interface
344 * buffer limit on the path. Use this to set
345 * the slow start threshhold, but set the
346 * threshold to no less than 2*mss.
348 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
349 TCPSTAT_INC(tcps_usedssthresh);
353 * Set the initial slow-start flight size.
355 * RFC5681 Section 3.1 specifies the default conservative values.
356 * RFC3390 specifies slightly more aggressive values.
357 * RFC6928 increases it to ten segments.
359 * If a SYN or SYN/ACK was lost and retransmitted, we have to
360 * reduce the initial CWND to one segment as congestion is likely
361 * requiring us to be cautious.
363 if (tp->snd_cwnd == 1)
364 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */
365 else if (V_tcp_do_initcwnd10)
366 tp->snd_cwnd = min(10 * tp->t_maxseg,
367 max(2 * tp->t_maxseg, 14600));
368 else if (V_tcp_do_rfc3390)
369 tp->snd_cwnd = min(4 * tp->t_maxseg,
370 max(2 * tp->t_maxseg, 4380));
372 /* Per RFC5681 Section 3.1 */
373 if (tp->t_maxseg > 2190)
374 tp->snd_cwnd = 2 * tp->t_maxseg;
375 else if (tp->t_maxseg > 1095)
376 tp->snd_cwnd = 3 * tp->t_maxseg;
378 tp->snd_cwnd = 4 * tp->t_maxseg;
381 if (CC_ALGO(tp)->conn_init != NULL)
382 CC_ALGO(tp)->conn_init(tp->ccv);
386 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
388 INP_WLOCK_ASSERT(tp->t_inpcb);
392 if (!IN_FASTRECOVERY(tp->t_flags)) {
393 tp->snd_recover = tp->snd_max;
394 if (tp->t_flags & TF_ECN_PERMIT)
395 tp->t_flags |= TF_ECN_SND_CWR;
399 if (!IN_CONGRECOVERY(tp->t_flags)) {
400 TCPSTAT_INC(tcps_ecn_rcwnd);
401 tp->snd_recover = tp->snd_max;
402 if (tp->t_flags & TF_ECN_PERMIT)
403 tp->t_flags |= TF_ECN_SND_CWR;
408 tp->t_bytes_acked = 0;
409 EXIT_RECOVERY(tp->t_flags);
410 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
411 tp->t_maxseg) * tp->t_maxseg;
412 tp->snd_cwnd = tp->t_maxseg;
415 TCPSTAT_INC(tcps_sndrexmitbad);
416 /* RTO was unnecessary, so reset everything. */
417 tp->snd_cwnd = tp->snd_cwnd_prev;
418 tp->snd_ssthresh = tp->snd_ssthresh_prev;
419 tp->snd_recover = tp->snd_recover_prev;
420 if (tp->t_flags & TF_WASFRECOVERY)
421 ENTER_FASTRECOVERY(tp->t_flags);
422 if (tp->t_flags & TF_WASCRECOVERY)
423 ENTER_CONGRECOVERY(tp->t_flags);
424 tp->snd_nxt = tp->snd_max;
425 tp->t_flags &= ~TF_PREVVALID;
430 if (CC_ALGO(tp)->cong_signal != NULL) {
432 tp->ccv->curack = th->th_ack;
433 CC_ALGO(tp)->cong_signal(tp->ccv, type);
438 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
440 INP_WLOCK_ASSERT(tp->t_inpcb);
442 /* XXXLAS: KASSERT that we're in recovery? */
444 if (CC_ALGO(tp)->post_recovery != NULL) {
445 tp->ccv->curack = th->th_ack;
446 CC_ALGO(tp)->post_recovery(tp->ccv);
448 /* XXXLAS: EXIT_RECOVERY ? */
449 tp->t_bytes_acked = 0;
454 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
455 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
459 tcp_fields_to_net(th);
460 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
461 tcp_fields_to_host(th);
466 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
468 #define ND6_HINT(tp) \
470 if ((tp) && (tp)->t_inpcb && \
471 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
472 nd6_nud_hint(NULL, NULL, 0); \
479 * Indicate whether this ack should be delayed. We can delay the ack if
480 * following conditions are met:
481 * - There is no delayed ack timer in progress.
482 * - Our last ack wasn't a 0-sized window. We never want to delay
483 * the ack that opens up a 0-sized window.
484 * - LRO wasn't used for this segment. We make sure by checking that the
485 * segment size is not larger than the MSS.
486 * - Delayed acks are enabled or this is a half-synchronized T/TCP
489 #define DELAY_ACK(tp, tlen) \
490 ((!tcp_timer_active(tp, TT_DELACK) && \
491 (tp->t_flags & TF_RXWIN0SENT) == 0) && \
492 (tlen <= tp->t_maxopd) && \
493 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
496 * TCP input handling is split into multiple parts:
497 * tcp6_input is a thin wrapper around tcp_input for the extended
498 * ip6_protox[] call format in ip6_input
499 * tcp_input handles primary segment validation, inpcb lookup and
500 * SYN processing on listen sockets
501 * tcp_do_segment processes the ACK and text of the segment for
502 * establishing, established and closing connections
506 tcp6_input(struct mbuf **mp, int *offp, int proto)
508 struct mbuf *m = *mp;
509 struct in6_ifaddr *ia6;
511 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
514 * draft-itojun-ipv6-tcp-to-anycast
515 * better place to put this in?
517 ia6 = ip6_getdstifaddr(m);
518 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
521 ifa_free(&ia6->ia_ifa);
522 ip6 = mtod(m, struct ip6_hdr *);
523 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
524 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
528 ifa_free(&ia6->ia_ifa);
536 tcp_input(struct mbuf *m, int off0)
538 struct tcphdr *th = NULL;
539 struct ip *ip = NULL;
540 struct inpcb *inp = NULL;
541 struct tcpcb *tp = NULL;
542 struct socket *so = NULL;
551 int rstreason = 0; /* For badport_bandlim accounting purposes */
553 uint8_t sig_checked = 0;
556 struct m_tag *fwd_tag = NULL;
558 struct ip6_hdr *ip6 = NULL;
561 const void *ip6 = NULL;
563 struct tcpopt to; /* options in this segment */
564 char *s = NULL; /* address and port logging */
566 #define TI_UNLOCKED 1
571 * The size of tcp_saveipgen must be the size of the max ip header,
574 u_char tcp_saveipgen[IP6_HDR_LEN];
575 struct tcphdr tcp_savetcp;
580 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
584 TCPSTAT_INC(tcps_rcvtotal);
588 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
590 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
591 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
593 TCPSTAT_INC(tcps_rcvshort);
598 ip6 = mtod(m, struct ip6_hdr *);
599 th = (struct tcphdr *)((caddr_t)ip6 + off0);
600 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
601 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
602 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
603 th->th_sum = m->m_pkthdr.csum_data;
605 th->th_sum = in6_cksum_pseudo(ip6, tlen,
606 IPPROTO_TCP, m->m_pkthdr.csum_data);
607 th->th_sum ^= 0xffff;
609 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
611 TCPSTAT_INC(tcps_rcvbadsum);
616 * Be proactive about unspecified IPv6 address in source.
617 * As we use all-zero to indicate unbounded/unconnected pcb,
618 * unspecified IPv6 address can be used to confuse us.
620 * Note that packets with unspecified IPv6 destination is
621 * already dropped in ip6_input.
623 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
629 #if defined(INET) && defined(INET6)
635 * Get IP and TCP header together in first mbuf.
636 * Note: IP leaves IP header in first mbuf.
638 if (off0 > sizeof (struct ip)) {
640 off0 = sizeof(struct ip);
642 if (m->m_len < sizeof (struct tcpiphdr)) {
643 if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
645 TCPSTAT_INC(tcps_rcvshort);
649 ip = mtod(m, struct ip *);
650 th = (struct tcphdr *)((caddr_t)ip + off0);
651 tlen = ntohs(ip->ip_len) - off0;
653 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
654 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
655 th->th_sum = m->m_pkthdr.csum_data;
657 th->th_sum = in_pseudo(ip->ip_src.s_addr,
659 htonl(m->m_pkthdr.csum_data + tlen +
661 th->th_sum ^= 0xffff;
663 struct ipovly *ipov = (struct ipovly *)ip;
666 * Checksum extended TCP header and data.
669 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
670 ipov->ih_len = htons(tlen);
671 th->th_sum = in_cksum(m, len);
672 /* Reset length for SDT probes. */
673 ip->ip_len = htons(tlen + off0);
677 TCPSTAT_INC(tcps_rcvbadsum);
680 /* Re-initialization for later version check */
681 ip->ip_v = IPVERSION;
687 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
689 #if defined(INET) && defined(INET6)
697 * Check that TCP offset makes sense,
698 * pull out TCP options and adjust length. XXX
700 off = th->th_off << 2;
701 if (off < sizeof (struct tcphdr) || off > tlen) {
702 TCPSTAT_INC(tcps_rcvbadoff);
705 tlen -= off; /* tlen is used instead of ti->ti_len */
706 if (off > sizeof (struct tcphdr)) {
709 IP6_EXTHDR_CHECK(m, off0, off, );
710 ip6 = mtod(m, struct ip6_hdr *);
711 th = (struct tcphdr *)((caddr_t)ip6 + off0);
714 #if defined(INET) && defined(INET6)
719 if (m->m_len < sizeof(struct ip) + off) {
720 if ((m = m_pullup(m, sizeof (struct ip) + off))
722 TCPSTAT_INC(tcps_rcvshort);
725 ip = mtod(m, struct ip *);
726 th = (struct tcphdr *)((caddr_t)ip + off0);
730 optlen = off - sizeof (struct tcphdr);
731 optp = (u_char *)(th + 1);
733 thflags = th->th_flags;
736 * Convert TCP protocol specific fields to host format.
738 tcp_fields_to_host(th);
741 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
743 drop_hdrlen = off0 + off;
746 * Locate pcb for segment; if we're likely to add or remove a
747 * connection then first acquire pcbinfo lock. There are two cases
748 * where we might discover later we need a write lock despite the
749 * flags: ACKs moving a connection out of the syncache, and ACKs for
750 * a connection in TIMEWAIT.
752 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) {
753 INP_INFO_WLOCK(&V_tcbinfo);
754 ti_locked = TI_WLOCKED;
756 ti_locked = TI_UNLOCKED;
759 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
763 (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
765 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
768 #if defined(INET) && !defined(INET6)
769 (m->m_flags & M_IP_NEXTHOP)
772 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
776 if (ti_locked == TI_WLOCKED) {
777 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
779 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
783 if (isipv6 && fwd_tag != NULL) {
784 struct sockaddr_in6 *next_hop6;
786 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
788 * Transparently forwarded. Pretend to be the destination.
789 * Already got one like this?
791 inp = in6_pcblookup_mbuf(&V_tcbinfo,
792 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
793 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
796 * It's new. Try to find the ambushing socket.
797 * Because we've rewritten the destination address,
798 * any hardware-generated hash is ignored.
800 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
801 th->th_sport, &next_hop6->sin6_addr,
802 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
803 th->th_dport, INPLOOKUP_WILDCARD |
804 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
807 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
808 th->th_sport, &ip6->ip6_dst, th->th_dport,
809 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
810 m->m_pkthdr.rcvif, m);
813 #if defined(INET6) && defined(INET)
817 if (fwd_tag != NULL) {
818 struct sockaddr_in *next_hop;
820 next_hop = (struct sockaddr_in *)(fwd_tag+1);
822 * Transparently forwarded. Pretend to be the destination.
823 * already got one like this?
825 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
826 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
827 m->m_pkthdr.rcvif, m);
830 * It's new. Try to find the ambushing socket.
831 * Because we've rewritten the destination address,
832 * any hardware-generated hash is ignored.
834 inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
835 th->th_sport, next_hop->sin_addr,
836 next_hop->sin_port ? ntohs(next_hop->sin_port) :
837 th->th_dport, INPLOOKUP_WILDCARD |
838 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
841 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
842 th->th_sport, ip->ip_dst, th->th_dport,
843 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
844 m->m_pkthdr.rcvif, m);
848 * If the INPCB does not exist then all data in the incoming
849 * segment is discarded and an appropriate RST is sent back.
850 * XXX MRT Send RST using which routing table?
854 * Log communication attempts to ports that are not
857 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
858 tcp_log_in_vain == 2) {
859 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
860 log(LOG_INFO, "%s; %s: Connection attempt "
861 "to closed port\n", s, __func__);
864 * When blackholing do not respond with a RST but
865 * completely ignore the segment and drop it.
867 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
871 rstreason = BANDLIM_RST_CLOSEDPORT;
874 INP_WLOCK_ASSERT(inp);
875 if (!(inp->inp_flags & INP_HW_FLOWID)
876 && (m->m_flags & M_FLOWID)
877 && ((inp->inp_socket == NULL)
878 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
879 inp->inp_flags |= INP_HW_FLOWID;
880 inp->inp_flags &= ~INP_SW_FLOWID;
881 inp->inp_flowid = m->m_pkthdr.flowid;
882 inp->inp_flowtype = M_HASHTYPE_GET(m);
886 if (isipv6 && ipsec6_in_reject(m, inp)) {
887 IPSEC6STAT_INC(ips_in_polvio);
891 if (ipsec4_in_reject(m, inp) != 0) {
892 IPSECSTAT_INC(ips_in_polvio);
898 * Check the minimum TTL for socket.
900 if (inp->inp_ip_minttl != 0) {
902 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
906 if (inp->inp_ip_minttl > ip->ip_ttl)
911 * A previous connection in TIMEWAIT state is supposed to catch stray
912 * or duplicate segments arriving late. If this segment was a
913 * legitimate new connection attempt, the old INPCB gets removed and
914 * we can try again to find a listening socket.
916 * At this point, due to earlier optimism, we may hold only an inpcb
917 * lock, and not the inpcbinfo write lock. If so, we need to try to
918 * acquire it, or if that fails, acquire a reference on the inpcb,
919 * drop all locks, acquire a global write lock, and then re-acquire
920 * the inpcb lock. We may at that point discover that another thread
921 * has tried to free the inpcb, in which case we need to loop back
922 * and try to find a new inpcb to deliver to.
924 * XXXRW: It may be time to rethink timewait locking.
927 if (inp->inp_flags & INP_TIMEWAIT) {
928 if (ti_locked == TI_UNLOCKED) {
929 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
932 INP_INFO_WLOCK(&V_tcbinfo);
933 ti_locked = TI_WLOCKED;
935 if (in_pcbrele_wlocked(inp)) {
940 ti_locked = TI_WLOCKED;
942 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
944 if (thflags & TH_SYN)
945 tcp_dooptions(&to, optp, optlen, TO_SYN);
947 * NB: tcp_twcheck unlocks the INP and frees the mbuf.
949 if (tcp_twcheck(inp, &to, th, m, tlen))
951 INP_INFO_WUNLOCK(&V_tcbinfo);
955 * The TCPCB may no longer exist if the connection is winding
956 * down or it is in the CLOSED state. Either way we drop the
957 * segment and send an appropriate response.
960 if (tp == NULL || tp->t_state == TCPS_CLOSED) {
961 rstreason = BANDLIM_RST_CLOSEDPORT;
966 if (tp->t_flags & TF_TOE) {
967 tcp_offload_input(tp, m);
968 m = NULL; /* consumed by the TOE driver */
974 * We've identified a valid inpcb, but it could be that we need an
975 * inpcbinfo write lock but don't hold it. In this case, attempt to
976 * acquire using the same strategy as the TIMEWAIT case above. If we
977 * relock, we have to jump back to 'relocked' as the connection might
978 * now be in TIMEWAIT.
981 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0)
982 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
984 if (tp->t_state != TCPS_ESTABLISHED) {
985 if (ti_locked == TI_UNLOCKED) {
986 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) {
989 INP_INFO_WLOCK(&V_tcbinfo);
990 ti_locked = TI_WLOCKED;
992 if (in_pcbrele_wlocked(inp)) {
998 ti_locked = TI_WLOCKED;
1000 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1004 INP_WLOCK_ASSERT(inp);
1005 if (mac_inpcb_check_deliver(inp, m))
1008 so = inp->inp_socket;
1009 KASSERT(so != NULL, ("%s: so == NULL", __func__));
1011 if (so->so_options & SO_DEBUG) {
1012 ostate = tp->t_state;
1015 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1018 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1021 #endif /* TCPDEBUG */
1023 * When the socket is accepting connections (the INPCB is in LISTEN
1024 * state) we look into the SYN cache if this is a new connection
1025 * attempt or the completion of a previous one. Because listen
1026 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be
1027 * held in this case.
1029 if (so->so_options & SO_ACCEPTCONN) {
1030 struct in_conninfo inc;
1032 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
1033 "tp not listening", __func__));
1034 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1036 bzero(&inc, sizeof(inc));
1039 inc.inc_flags |= INC_ISIPV6;
1040 inc.inc6_faddr = ip6->ip6_src;
1041 inc.inc6_laddr = ip6->ip6_dst;
1045 inc.inc_faddr = ip->ip_src;
1046 inc.inc_laddr = ip->ip_dst;
1048 inc.inc_fport = th->th_sport;
1049 inc.inc_lport = th->th_dport;
1050 inc.inc_fibnum = so->so_fibnum;
1053 * Check for an existing connection attempt in syncache if
1054 * the flag is only ACK. A successful lookup creates a new
1055 * socket appended to the listen queue in SYN_RECEIVED state.
1057 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1059 * Parse the TCP options here because
1060 * syncookies need access to the reflected
1063 tcp_dooptions(&to, optp, optlen, 0);
1065 * NB: syncache_expand() doesn't unlock
1066 * inp and tcpinfo locks.
1068 if (!syncache_expand(&inc, &to, th, &so, m)) {
1070 * No syncache entry or ACK was not
1071 * for our SYN/ACK. Send a RST.
1072 * NB: syncache did its own logging
1073 * of the failure cause.
1075 rstreason = BANDLIM_RST_OPENPORT;
1080 * We completed the 3-way handshake
1081 * but could not allocate a socket
1082 * either due to memory shortage,
1083 * listen queue length limits or
1084 * global socket limits. Send RST
1085 * or wait and have the remote end
1086 * retransmit the ACK for another
1089 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1090 log(LOG_DEBUG, "%s; %s: Listen socket: "
1091 "Socket allocation failed due to "
1092 "limits or memory shortage, %s\n",
1094 V_tcp_sc_rst_sock_fail ?
1095 "sending RST" : "try again");
1096 if (V_tcp_sc_rst_sock_fail) {
1097 rstreason = BANDLIM_UNLIMITED;
1103 * Socket is created in state SYN_RECEIVED.
1104 * Unlock the listen socket, lock the newly
1105 * created socket and update the tp variable.
1107 INP_WUNLOCK(inp); /* listen socket */
1108 inp = sotoinpcb(so);
1109 INP_WLOCK(inp); /* new connection */
1110 tp = intotcpcb(inp);
1111 KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1112 ("%s: ", __func__));
1113 #ifdef TCP_SIGNATURE
1114 if (sig_checked == 0) {
1115 tcp_dooptions(&to, optp, optlen,
1116 (thflags & TH_SYN) ? TO_SYN : 0);
1117 if (!tcp_signature_verify_input(m, off0, tlen,
1118 optlen, &to, th, tp->t_flags)) {
1121 * In SYN_SENT state if it receives an
1122 * RST, it is allowed for further
1125 if ((thflags & TH_RST) == 0 ||
1126 (tp->t_state == TCPS_SYN_SENT) == 0)
1134 * Process the segment and the data it
1135 * contains. tcp_do_segment() consumes
1136 * the mbuf chain and unlocks the inpcb.
1138 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1140 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1144 * Segment flag validation for new connection attempts:
1146 * Our (SYN|ACK) response was rejected.
1147 * Check with syncache and remove entry to prevent
1150 * NB: syncache_chkrst does its own logging of failure
1153 if (thflags & TH_RST) {
1154 syncache_chkrst(&inc, th);
1158 * We can't do anything without SYN.
1160 if ((thflags & TH_SYN) == 0) {
1161 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1162 log(LOG_DEBUG, "%s; %s: Listen socket: "
1163 "SYN is missing, segment ignored\n",
1165 TCPSTAT_INC(tcps_badsyn);
1169 * (SYN|ACK) is bogus on a listen socket.
1171 if (thflags & TH_ACK) {
1172 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1173 log(LOG_DEBUG, "%s; %s: Listen socket: "
1174 "SYN|ACK invalid, segment rejected\n",
1176 syncache_badack(&inc); /* XXX: Not needed! */
1177 TCPSTAT_INC(tcps_badsyn);
1178 rstreason = BANDLIM_RST_OPENPORT;
1182 * If the drop_synfin option is enabled, drop all
1183 * segments with both the SYN and FIN bits set.
1184 * This prevents e.g. nmap from identifying the
1186 * XXX: Poor reasoning. nmap has other methods
1187 * and is constantly refining its stack detection
1189 * XXX: This is a violation of the TCP specification
1190 * and was used by RFC1644.
1192 if ((thflags & TH_FIN) && V_drop_synfin) {
1193 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1194 log(LOG_DEBUG, "%s; %s: Listen socket: "
1195 "SYN|FIN segment ignored (based on "
1196 "sysctl setting)\n", s, __func__);
1197 TCPSTAT_INC(tcps_badsyn);
1201 * Segment's flags are (SYN) or (SYN|FIN).
1203 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1204 * as they do not affect the state of the TCP FSM.
1205 * The data pointed to by TH_URG and th_urp is ignored.
1207 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1208 ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1209 KASSERT(thflags & (TH_SYN),
1210 ("%s: Listen socket: TH_SYN not set", __func__));
1213 * If deprecated address is forbidden,
1214 * we do not accept SYN to deprecated interface
1215 * address to prevent any new inbound connection from
1216 * getting established.
1217 * When we do not accept SYN, we send a TCP RST,
1218 * with deprecated source address (instead of dropping
1219 * it). We compromise it as it is much better for peer
1220 * to send a RST, and RST will be the final packet
1223 * If we do not forbid deprecated addresses, we accept
1224 * the SYN packet. RFC2462 does not suggest dropping
1226 * If we decipher RFC2462 5.5.4, it says like this:
1227 * 1. use of deprecated addr with existing
1228 * communication is okay - "SHOULD continue to be
1230 * 2. use of it with new communication:
1231 * (2a) "SHOULD NOT be used if alternate address
1232 * with sufficient scope is available"
1233 * (2b) nothing mentioned otherwise.
1234 * Here we fall into (2b) case as we have no choice in
1235 * our source address selection - we must obey the peer.
1237 * The wording in RFC2462 is confusing, and there are
1238 * multiple description text for deprecated address
1239 * handling - worse, they are not exactly the same.
1240 * I believe 5.5.4 is the best one, so we follow 5.5.4.
1242 if (isipv6 && !V_ip6_use_deprecated) {
1243 struct in6_ifaddr *ia6;
1245 ia6 = ip6_getdstifaddr(m);
1247 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1248 ifa_free(&ia6->ia_ifa);
1249 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1250 log(LOG_DEBUG, "%s; %s: Listen socket: "
1251 "Connection attempt to deprecated "
1252 "IPv6 address rejected\n",
1254 rstreason = BANDLIM_RST_OPENPORT;
1258 ifa_free(&ia6->ia_ifa);
1262 * Basic sanity checks on incoming SYN requests:
1263 * Don't respond if the destination is a link layer
1264 * broadcast according to RFC1122 4.2.3.10, p. 104.
1265 * If it is from this socket it must be forged.
1266 * Don't respond if the source or destination is a
1267 * global or subnet broad- or multicast address.
1268 * Note that it is quite possible to receive unicast
1269 * link-layer packets with a broadcast IP address. Use
1270 * in_broadcast() to find them.
1272 if (m->m_flags & (M_BCAST|M_MCAST)) {
1273 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1274 log(LOG_DEBUG, "%s; %s: Listen socket: "
1275 "Connection attempt from broad- or multicast "
1276 "link layer address ignored\n", s, __func__);
1281 if (th->th_dport == th->th_sport &&
1282 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1283 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1284 log(LOG_DEBUG, "%s; %s: Listen socket: "
1285 "Connection attempt to/from self "
1286 "ignored\n", s, __func__);
1289 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1290 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1291 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1292 log(LOG_DEBUG, "%s; %s: Listen socket: "
1293 "Connection attempt from/to multicast "
1294 "address ignored\n", s, __func__);
1299 #if defined(INET) && defined(INET6)
1304 if (th->th_dport == th->th_sport &&
1305 ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1306 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1307 log(LOG_DEBUG, "%s; %s: Listen socket: "
1308 "Connection attempt from/to self "
1309 "ignored\n", s, __func__);
1312 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1313 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1314 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1315 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1316 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1317 log(LOG_DEBUG, "%s; %s: Listen socket: "
1318 "Connection attempt from/to broad- "
1319 "or multicast address ignored\n",
1326 * SYN appears to be valid. Create compressed TCP state
1330 if (so->so_options & SO_DEBUG)
1331 tcp_trace(TA_INPUT, ostate, tp,
1332 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1334 tcp_dooptions(&to, optp, optlen, TO_SYN);
1335 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL);
1337 * Entry added to syncache and mbuf consumed.
1338 * Everything already unlocked by syncache_add().
1340 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1342 } else if (tp->t_state == TCPS_LISTEN) {
1344 * When a listen socket is torn down the SO_ACCEPTCONN
1345 * flag is removed first while connections are drained
1346 * from the accept queue in a unlock/lock cycle of the
1347 * ACCEPT_LOCK, opening a race condition allowing a SYN
1348 * attempt go through unhandled.
1353 #ifdef TCP_SIGNATURE
1354 if (sig_checked == 0) {
1355 tcp_dooptions(&to, optp, optlen,
1356 (thflags & TH_SYN) ? TO_SYN : 0);
1357 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
1361 * In SYN_SENT state if it receives an RST, it is
1362 * allowed for further processing.
1364 if ((thflags & TH_RST) == 0 ||
1365 (tp->t_state == TCPS_SYN_SENT) == 0)
1372 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1375 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1376 * state. tcp_do_segment() always consumes the mbuf chain, unlocks
1377 * the inpcb, and unlocks pcbinfo.
1379 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1380 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1384 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1386 if (ti_locked == TI_WLOCKED) {
1387 INP_INFO_WUNLOCK(&V_tcbinfo);
1388 ti_locked = TI_UNLOCKED;
1392 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1393 "ti_locked: %d", __func__, ti_locked));
1394 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1399 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1402 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1403 m = NULL; /* mbuf chain got consumed. */
1408 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1410 if (ti_locked == TI_WLOCKED) {
1411 INP_INFO_WUNLOCK(&V_tcbinfo);
1412 ti_locked = TI_UNLOCKED;
1416 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1417 "ti_locked: %d", __func__, ti_locked));
1418 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1426 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1434 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1435 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1438 int thflags, acked, ourfinisacked, needoutput = 0;
1439 int rstreason, todrop, win;
1442 struct in_conninfo *inc;
1448 * The size of tcp_saveipgen must be the size of the max ip header,
1451 u_char tcp_saveipgen[IP6_HDR_LEN];
1452 struct tcphdr tcp_savetcp;
1455 thflags = th->th_flags;
1456 inc = &tp->t_inpcb->inp_inc;
1457 tp->sackhint.last_sack_ack = 0;
1460 * If this is either a state-changing packet or current state isn't
1461 * established, we require a write lock on tcbinfo. Otherwise, we
1462 * allow the tcbinfo to be in either alocked or unlocked, as the
1463 * caller may have unnecessarily acquired a write lock due to a race.
1465 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1466 tp->t_state != TCPS_ESTABLISHED) {
1467 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
1468 "SYN/FIN/RST/!EST", __func__, ti_locked));
1469 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1472 if (ti_locked == TI_WLOCKED)
1473 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1475 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1476 "ti_locked: %d", __func__, ti_locked));
1477 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1481 INP_WLOCK_ASSERT(tp->t_inpcb);
1482 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1484 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1488 * Segment received on connection.
1489 * Reset idle time and keep-alive timer.
1490 * XXX: This should be done after segment
1491 * validation to ignore broken/spoofed segs.
1493 tp->t_rcvtime = ticks;
1494 if (TCPS_HAVEESTABLISHED(tp->t_state))
1495 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1498 * Unscale the window into a 32-bit value.
1499 * For the SYN_SENT state the scale is zero.
1501 tiwin = th->th_win << tp->snd_scale;
1504 * TCP ECN processing.
1506 if (tp->t_flags & TF_ECN_PERMIT) {
1507 if (thflags & TH_CWR)
1508 tp->t_flags &= ~TF_ECN_SND_ECE;
1509 switch (iptos & IPTOS_ECN_MASK) {
1511 tp->t_flags |= TF_ECN_SND_ECE;
1512 TCPSTAT_INC(tcps_ecn_ce);
1514 case IPTOS_ECN_ECT0:
1515 TCPSTAT_INC(tcps_ecn_ect0);
1517 case IPTOS_ECN_ECT1:
1518 TCPSTAT_INC(tcps_ecn_ect1);
1521 /* Congestion experienced. */
1522 if (thflags & TH_ECE) {
1523 cc_cong_signal(tp, th, CC_ECN);
1528 * Parse options on any incoming segment.
1530 tcp_dooptions(&to, (u_char *)(th + 1),
1531 (th->th_off << 2) - sizeof(struct tcphdr),
1532 (thflags & TH_SYN) ? TO_SYN : 0);
1535 * If echoed timestamp is later than the current time,
1536 * fall back to non RFC1323 RTT calculation. Normalize
1537 * timestamp if syncookies were used when this connection
1540 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1541 to.to_tsecr -= tp->ts_offset;
1542 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1546 * If timestamps were negotiated during SYN/ACK they should
1547 * appear on every segment during this session and vice versa.
1549 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1550 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1551 log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1552 "no action\n", s, __func__);
1556 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1557 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1558 log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1559 "no action\n", s, __func__);
1565 * Process options only when we get SYN/ACK back. The SYN case
1566 * for incoming connections is handled in tcp_syncache.
1567 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1568 * or <SYN,ACK>) segment itself is never scaled.
1569 * XXX this is traditional behavior, may need to be cleaned up.
1571 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
1572 if ((to.to_flags & TOF_SCALE) &&
1573 (tp->t_flags & TF_REQ_SCALE)) {
1574 tp->t_flags |= TF_RCVD_SCALE;
1575 tp->snd_scale = to.to_wscale;
1578 * Initial send window. It will be updated with
1579 * the next incoming segment to the scaled value.
1581 tp->snd_wnd = th->th_win;
1582 if (to.to_flags & TOF_TS) {
1583 tp->t_flags |= TF_RCVD_TSTMP;
1584 tp->ts_recent = to.to_tsval;
1585 tp->ts_recent_age = tcp_ts_getticks();
1587 if (to.to_flags & TOF_MSS)
1588 tcp_mss(tp, to.to_mss);
1589 if ((tp->t_flags & TF_SACK_PERMIT) &&
1590 (to.to_flags & TOF_SACKPERM) == 0)
1591 tp->t_flags &= ~TF_SACK_PERMIT;
1595 * Header prediction: check for the two common cases
1596 * of a uni-directional data xfer. If the packet has
1597 * no control flags, is in-sequence, the window didn't
1598 * change and we're not retransmitting, it's a
1599 * candidate. If the length is zero and the ack moved
1600 * forward, we're the sender side of the xfer. Just
1601 * free the data acked & wake any higher level process
1602 * that was blocked waiting for space. If the length
1603 * is non-zero and the ack didn't move, we're the
1604 * receiver side. If we're getting packets in-order
1605 * (the reassembly queue is empty), add the data to
1606 * the socket buffer and note that we need a delayed ack.
1607 * Make sure that the hidden state-flags are also off.
1608 * Since we check for TCPS_ESTABLISHED first, it can only
1611 if (tp->t_state == TCPS_ESTABLISHED &&
1612 th->th_seq == tp->rcv_nxt &&
1613 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1614 tp->snd_nxt == tp->snd_max &&
1615 tiwin && tiwin == tp->snd_wnd &&
1616 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1617 tp->t_segq == NULL && ((to.to_flags & TOF_TS) == 0 ||
1618 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1621 * If last ACK falls within this segment's sequence numbers,
1622 * record the timestamp.
1623 * NOTE that the test is modified according to the latest
1624 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1626 if ((to.to_flags & TOF_TS) != 0 &&
1627 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1628 tp->ts_recent_age = tcp_ts_getticks();
1629 tp->ts_recent = to.to_tsval;
1633 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1634 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1635 !IN_RECOVERY(tp->t_flags) &&
1636 (to.to_flags & TOF_SACK) == 0 &&
1637 TAILQ_EMPTY(&tp->snd_holes)) {
1639 * This is a pure ack for outstanding data.
1641 if (ti_locked == TI_WLOCKED)
1642 INP_INFO_WUNLOCK(&V_tcbinfo);
1643 ti_locked = TI_UNLOCKED;
1645 TCPSTAT_INC(tcps_predack);
1648 * "bad retransmit" recovery.
1650 if (tp->t_rxtshift == 1 &&
1651 tp->t_flags & TF_PREVVALID &&
1652 (int)(ticks - tp->t_badrxtwin) < 0) {
1653 cc_cong_signal(tp, th, CC_RTO_ERR);
1657 * Recalculate the transmit timer / rtt.
1659 * Some boxes send broken timestamp replies
1660 * during the SYN+ACK phase, ignore
1661 * timestamps of 0 or we could calculate a
1662 * huge RTT and blow up the retransmit timer.
1664 if ((to.to_flags & TOF_TS) != 0 &&
1668 t = tcp_ts_getticks() - to.to_tsecr;
1669 if (!tp->t_rttlow || tp->t_rttlow > t)
1672 TCP_TS_TO_TICKS(t) + 1);
1673 } else if (tp->t_rtttime &&
1674 SEQ_GT(th->th_ack, tp->t_rtseq)) {
1675 if (!tp->t_rttlow ||
1676 tp->t_rttlow > ticks - tp->t_rtttime)
1677 tp->t_rttlow = ticks - tp->t_rtttime;
1679 ticks - tp->t_rtttime);
1681 acked = BYTES_THIS_ACK(tp, th);
1683 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1684 hhook_run_tcp_est_in(tp, th, &to);
1686 TCPSTAT_INC(tcps_rcvackpack);
1687 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1688 sbdrop(&so->so_snd, acked);
1689 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1690 SEQ_LEQ(th->th_ack, tp->snd_recover))
1691 tp->snd_recover = th->th_ack - 1;
1694 * Let the congestion control algorithm update
1695 * congestion control related information. This
1696 * typically means increasing the congestion
1699 cc_ack_received(tp, th, CC_ACK);
1701 tp->snd_una = th->th_ack;
1703 * Pull snd_wl2 up to prevent seq wrap relative
1706 tp->snd_wl2 = th->th_ack;
1709 ND6_HINT(tp); /* Some progress has been made. */
1712 * If all outstanding data are acked, stop
1713 * retransmit timer, otherwise restart timer
1714 * using current (possibly backed-off) value.
1715 * If process is waiting for space,
1716 * wakeup/selwakeup/signal. If data
1717 * are ready to send, let tcp_output
1718 * decide between more output or persist.
1721 if (so->so_options & SO_DEBUG)
1722 tcp_trace(TA_INPUT, ostate, tp,
1723 (void *)tcp_saveipgen,
1726 if (tp->snd_una == tp->snd_max)
1727 tcp_timer_activate(tp, TT_REXMT, 0);
1728 else if (!tcp_timer_active(tp, TT_PERSIST))
1729 tcp_timer_activate(tp, TT_REXMT,
1732 if (so->so_snd.sb_cc)
1733 (void) tcp_output(tp);
1736 } else if (th->th_ack == tp->snd_una &&
1737 tlen <= sbspace(&so->so_rcv)) {
1738 int newsize = 0; /* automatic sockbuf scaling */
1741 * This is a pure, in-sequence data packet with
1742 * nothing on the reassembly queue and we have enough
1743 * buffer space to take it.
1745 if (ti_locked == TI_WLOCKED)
1746 INP_INFO_WUNLOCK(&V_tcbinfo);
1747 ti_locked = TI_UNLOCKED;
1749 /* Clean receiver SACK report if present */
1750 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1751 tcp_clean_sackreport(tp);
1752 TCPSTAT_INC(tcps_preddat);
1753 tp->rcv_nxt += tlen;
1755 * Pull snd_wl1 up to prevent seq wrap relative to
1758 tp->snd_wl1 = th->th_seq;
1760 * Pull rcv_up up to prevent seq wrap relative to
1763 tp->rcv_up = tp->rcv_nxt;
1764 TCPSTAT_INC(tcps_rcvpack);
1765 TCPSTAT_ADD(tcps_rcvbyte, tlen);
1766 ND6_HINT(tp); /* Some progress has been made */
1768 if (so->so_options & SO_DEBUG)
1769 tcp_trace(TA_INPUT, ostate, tp,
1770 (void *)tcp_saveipgen, &tcp_savetcp, 0);
1773 * Automatic sizing of receive socket buffer. Often the send
1774 * buffer size is not optimally adjusted to the actual network
1775 * conditions at hand (delay bandwidth product). Setting the
1776 * buffer size too small limits throughput on links with high
1777 * bandwidth and high delay (eg. trans-continental/oceanic links).
1779 * On the receive side the socket buffer memory is only rarely
1780 * used to any significant extent. This allows us to be much
1781 * more aggressive in scaling the receive socket buffer. For
1782 * the case that the buffer space is actually used to a large
1783 * extent and we run out of kernel memory we can simply drop
1784 * the new segments; TCP on the sender will just retransmit it
1785 * later. Setting the buffer size too big may only consume too
1786 * much kernel memory if the application doesn't read() from
1787 * the socket or packet loss or reordering makes use of the
1790 * The criteria to step up the receive buffer one notch are:
1791 * 1. the number of bytes received during the time it takes
1792 * one timestamp to be reflected back to us (the RTT);
1793 * 2. received bytes per RTT is within seven eighth of the
1794 * current socket buffer size;
1795 * 3. receive buffer size has not hit maximal automatic size;
1797 * This algorithm does one step per RTT at most and only if
1798 * we receive a bulk stream w/o packet losses or reorderings.
1799 * Shrinking the buffer during idle times is not necessary as
1800 * it doesn't consume any memory when idle.
1802 * TODO: Only step up if the application is actually serving
1803 * the buffer to better manage the socket buffer resources.
1805 if (V_tcp_do_autorcvbuf &&
1807 (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
1808 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
1809 to.to_tsecr - tp->rfbuf_ts < hz) {
1811 (so->so_rcv.sb_hiwat / 8 * 7) &&
1812 so->so_rcv.sb_hiwat <
1813 V_tcp_autorcvbuf_max) {
1815 min(so->so_rcv.sb_hiwat +
1816 V_tcp_autorcvbuf_inc,
1817 V_tcp_autorcvbuf_max);
1819 /* Start over with next RTT. */
1823 tp->rfbuf_cnt += tlen; /* add up */
1826 /* Add data to socket buffer. */
1827 SOCKBUF_LOCK(&so->so_rcv);
1828 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1832 * Set new socket buffer size.
1833 * Give up when limit is reached.
1836 if (!sbreserve_locked(&so->so_rcv,
1838 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1839 m_adj(m, drop_hdrlen); /* delayed header drop */
1840 sbappendstream_locked(&so->so_rcv, m);
1842 /* NB: sorwakeup_locked() does an implicit unlock. */
1843 sorwakeup_locked(so);
1844 if (DELAY_ACK(tp, tlen)) {
1845 tp->t_flags |= TF_DELACK;
1847 tp->t_flags |= TF_ACKNOW;
1855 * Calculate amount of space in receive window,
1856 * and then do TCP input processing.
1857 * Receive window is amount of space in rcv queue,
1858 * but not less than advertised window.
1860 win = sbspace(&so->so_rcv);
1863 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1865 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1869 switch (tp->t_state) {
1872 * If the state is SYN_RECEIVED:
1873 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1875 case TCPS_SYN_RECEIVED:
1876 if ((thflags & TH_ACK) &&
1877 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1878 SEQ_GT(th->th_ack, tp->snd_max))) {
1879 rstreason = BANDLIM_RST_OPENPORT;
1885 * If the state is SYN_SENT:
1886 * if seg contains an ACK, but not for our SYN, drop the input.
1887 * if seg contains a RST, then drop the connection.
1888 * if seg does not contain SYN, then drop it.
1889 * Otherwise this is an acceptable SYN segment
1890 * initialize tp->rcv_nxt and tp->irs
1891 * if seg contains ack then advance tp->snd_una
1892 * if seg contains an ECE and ECN support is enabled, the stream
1894 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1895 * arrange for segment to be acked (eventually)
1896 * continue processing rest of data/controls, beginning with URG
1899 if ((thflags & TH_ACK) &&
1900 (SEQ_LEQ(th->th_ack, tp->iss) ||
1901 SEQ_GT(th->th_ack, tp->snd_max))) {
1902 rstreason = BANDLIM_UNLIMITED;
1905 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1906 TCP_PROBE5(connect__refused, NULL, tp,
1907 mtod(m, const char *), tp, th);
1908 tp = tcp_drop(tp, ECONNREFUSED);
1910 if (thflags & TH_RST)
1912 if (!(thflags & TH_SYN))
1915 tp->irs = th->th_seq;
1917 if (thflags & TH_ACK) {
1918 TCPSTAT_INC(tcps_connects);
1921 mac_socketpeer_set_from_mbuf(m, so);
1923 /* Do window scaling on this connection? */
1924 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1925 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1926 tp->rcv_scale = tp->request_r_scale;
1928 tp->rcv_adv += imin(tp->rcv_wnd,
1929 TCP_MAXWIN << tp->rcv_scale);
1930 tp->snd_una++; /* SYN is acked */
1932 * If there's data, delay ACK; if there's also a FIN
1933 * ACKNOW will be turned on later.
1935 if (DELAY_ACK(tp, tlen) && tlen != 0)
1936 tcp_timer_activate(tp, TT_DELACK,
1939 tp->t_flags |= TF_ACKNOW;
1941 if ((thflags & TH_ECE) && V_tcp_do_ecn) {
1942 tp->t_flags |= TF_ECN_PERMIT;
1943 TCPSTAT_INC(tcps_ecn_shs);
1947 * Received <SYN,ACK> in SYN_SENT[*] state.
1949 * SYN_SENT --> ESTABLISHED
1950 * SYN_SENT* --> FIN_WAIT_1
1952 tp->t_starttime = ticks;
1953 if (tp->t_flags & TF_NEEDFIN) {
1954 tcp_state_change(tp, TCPS_FIN_WAIT_1);
1955 tp->t_flags &= ~TF_NEEDFIN;
1958 tcp_state_change(tp, TCPS_ESTABLISHED);
1959 TCP_PROBE5(connect__established, NULL, tp,
1960 mtod(m, const char *), tp, th);
1962 tcp_timer_activate(tp, TT_KEEP,
1967 * Received initial SYN in SYN-SENT[*] state =>
1968 * simultaneous open.
1969 * If it succeeds, connection is * half-synchronized.
1970 * Otherwise, do 3-way handshake:
1971 * SYN-SENT -> SYN-RECEIVED
1972 * SYN-SENT* -> SYN-RECEIVED*
1974 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
1975 tcp_timer_activate(tp, TT_REXMT, 0);
1976 tcp_state_change(tp, TCPS_SYN_RECEIVED);
1979 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
1980 "ti_locked %d", __func__, ti_locked));
1981 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
1982 INP_WLOCK_ASSERT(tp->t_inpcb);
1985 * Advance th->th_seq to correspond to first data byte.
1986 * If data, trim to stay within window,
1987 * dropping FIN if necessary.
1990 if (tlen > tp->rcv_wnd) {
1991 todrop = tlen - tp->rcv_wnd;
1995 TCPSTAT_INC(tcps_rcvpackafterwin);
1996 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
1998 tp->snd_wl1 = th->th_seq - 1;
1999 tp->rcv_up = th->th_seq;
2001 * Client side of transaction: already sent SYN and data.
2002 * If the remote host used T/TCP to validate the SYN,
2003 * our data will be ACK'd; if so, enter normal data segment
2004 * processing in the middle of step 5, ack processing.
2005 * Otherwise, goto step 6.
2007 if (thflags & TH_ACK)
2013 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2014 * do normal processing.
2016 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
2020 break; /* continue normal processing */
2024 * States other than LISTEN or SYN_SENT.
2025 * First check the RST flag and sequence number since reset segments
2026 * are exempt from the timestamp and connection count tests. This
2027 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2028 * below which allowed reset segments in half the sequence space
2029 * to fall though and be processed (which gives forged reset
2030 * segments with a random sequence number a 50 percent chance of
2031 * killing a connection).
2032 * Then check timestamp, if present.
2033 * Then check the connection count, if present.
2034 * Then check that at least some bytes of segment are within
2035 * receive window. If segment begins before rcv_nxt,
2036 * drop leading data (and SYN); if nothing left, just ack.
2039 * If the RST bit is set, check the sequence number to see
2040 * if this is a valid reset segment.
2042 * In all states except SYN-SENT, all reset (RST) segments
2043 * are validated by checking their SEQ-fields. A reset is
2044 * valid if its sequence number is in the window.
2045 * Note: this does not take into account delayed ACKs, so
2046 * we should test against last_ack_sent instead of rcv_nxt.
2047 * The sequence number in the reset segment is normally an
2048 * echo of our outgoing acknowlegement numbers, but some hosts
2049 * send a reset with the sequence number at the rightmost edge
2050 * of our receive window, and we have to handle this case.
2051 * Note 2: Paul Watson's paper "Slipping in the Window" has shown
2052 * that brute force RST attacks are possible. To combat this,
2053 * we use a much stricter check while in the ESTABLISHED state,
2054 * only accepting RSTs where the sequence number is equal to
2055 * last_ack_sent. In all other states (the states in which a
2056 * RST is more likely), the more permissive check is used.
2057 * If we have multiple segments in flight, the initial reset
2058 * segment sequence numbers will be to the left of last_ack_sent,
2059 * but they will eventually catch up.
2060 * In any case, it never made sense to trim reset segments to
2061 * fit the receive window since RFC 1122 says:
2062 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
2064 * A TCP SHOULD allow a received RST segment to include data.
2067 * It has been suggested that a RST segment could contain
2068 * ASCII text that encoded and explained the cause of the
2069 * RST. No standard has yet been established for such
2072 * If the reset segment passes the sequence number test examine
2074 * SYN_RECEIVED STATE:
2075 * If passive open, return to LISTEN state.
2076 * If active open, inform user that connection was refused.
2077 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
2078 * Inform user that connection was reset, and close tcb.
2079 * CLOSING, LAST_ACK STATES:
2082 * Drop the segment - see Stevens, vol. 2, p. 964 and
2085 if (thflags & TH_RST) {
2086 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2087 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
2088 switch (tp->t_state) {
2090 case TCPS_SYN_RECEIVED:
2091 so->so_error = ECONNREFUSED;
2094 case TCPS_ESTABLISHED:
2095 if (V_tcp_insecure_rst == 0 &&
2096 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) &&
2097 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) &&
2098 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
2099 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) {
2100 TCPSTAT_INC(tcps_badrst);
2104 case TCPS_FIN_WAIT_1:
2105 case TCPS_FIN_WAIT_2:
2106 case TCPS_CLOSE_WAIT:
2107 so->so_error = ECONNRESET;
2109 KASSERT(ti_locked == TI_WLOCKED,
2110 ("tcp_do_segment: TH_RST 1 ti_locked %d",
2112 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2114 tcp_state_change(tp, TCPS_CLOSED);
2115 TCPSTAT_INC(tcps_drops);
2121 KASSERT(ti_locked == TI_WLOCKED,
2122 ("tcp_do_segment: TH_RST 2 ti_locked %d",
2124 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2134 * RFC 1323 PAWS: If we have a timestamp reply on this segment
2135 * and it's less than ts_recent, drop it.
2137 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
2138 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
2140 /* Check to see if ts_recent is over 24 days old. */
2141 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
2143 * Invalidate ts_recent. If this segment updates
2144 * ts_recent, the age will be reset later and ts_recent
2145 * will get a valid value. If it does not, setting
2146 * ts_recent to zero will at least satisfy the
2147 * requirement that zero be placed in the timestamp
2148 * echo reply when ts_recent isn't valid. The
2149 * age isn't reset until we get a valid ts_recent
2150 * because we don't want out-of-order segments to be
2151 * dropped when ts_recent is old.
2155 TCPSTAT_INC(tcps_rcvduppack);
2156 TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
2157 TCPSTAT_INC(tcps_pawsdrop);
2165 * In the SYN-RECEIVED state, validate that the packet belongs to
2166 * this connection before trimming the data to fit the receive
2167 * window. Check the sequence number versus IRS since we know
2168 * the sequence numbers haven't wrapped. This is a partial fix
2169 * for the "LAND" DoS attack.
2171 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
2172 rstreason = BANDLIM_RST_OPENPORT;
2176 todrop = tp->rcv_nxt - th->th_seq;
2179 * If this is a duplicate SYN for our current connection,
2180 * advance over it and pretend and it's not a SYN.
2182 if (thflags & TH_SYN && th->th_seq == tp->irs) {
2192 * Following if statement from Stevens, vol. 2, p. 960.
2195 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
2197 * Any valid FIN must be to the left of the window.
2198 * At this point the FIN must be a duplicate or out
2199 * of sequence; drop it.
2204 * Send an ACK to resynchronize and drop any data.
2205 * But keep on processing for RST or ACK.
2207 tp->t_flags |= TF_ACKNOW;
2209 TCPSTAT_INC(tcps_rcvduppack);
2210 TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
2212 TCPSTAT_INC(tcps_rcvpartduppack);
2213 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
2215 drop_hdrlen += todrop; /* drop from the top afterwards */
2216 th->th_seq += todrop;
2218 if (th->th_urp > todrop)
2219 th->th_urp -= todrop;
2227 * If new data are received on a connection after the
2228 * user processes are gone, then RST the other end.
2230 if ((so->so_state & SS_NOFDREF) &&
2231 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2232 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
2233 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2234 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2236 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2237 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2238 "after socket was closed, "
2239 "sending RST and removing tcpcb\n",
2240 s, __func__, tcpstates[tp->t_state], tlen);
2244 TCPSTAT_INC(tcps_rcvafterclose);
2245 rstreason = BANDLIM_UNLIMITED;
2250 * If segment ends after window, drop trailing data
2251 * (and PUSH and FIN); if nothing left, just ACK.
2253 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2255 TCPSTAT_INC(tcps_rcvpackafterwin);
2256 if (todrop >= tlen) {
2257 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2259 * If window is closed can only take segments at
2260 * window edge, and have to drop data and PUSH from
2261 * incoming segments. Continue processing, but
2262 * remember to ack. Otherwise, drop segment
2265 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2266 tp->t_flags |= TF_ACKNOW;
2267 TCPSTAT_INC(tcps_rcvwinprobe);
2271 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2274 thflags &= ~(TH_PUSH|TH_FIN);
2278 * If last ACK falls within this segment's sequence numbers,
2279 * record its timestamp.
2281 * 1) That the test incorporates suggestions from the latest
2282 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
2283 * 2) That updating only on newer timestamps interferes with
2284 * our earlier PAWS tests, so this check should be solely
2285 * predicated on the sequence space of this segment.
2286 * 3) That we modify the segment boundary check to be
2287 * Last.ACK.Sent <= SEG.SEQ + SEG.Len
2288 * instead of RFC1323's
2289 * Last.ACK.Sent < SEG.SEQ + SEG.Len,
2290 * This modified check allows us to overcome RFC1323's
2291 * limitations as described in Stevens TCP/IP Illustrated
2292 * Vol. 2 p.869. In such cases, we can still calculate the
2293 * RTT correctly when RCV.NXT == Last.ACK.Sent.
2295 if ((to.to_flags & TOF_TS) != 0 &&
2296 SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2297 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2298 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2299 tp->ts_recent_age = tcp_ts_getticks();
2300 tp->ts_recent = to.to_tsval;
2304 * If a SYN is in the window, then this is an
2305 * error and we send an RST and drop the connection.
2307 if (thflags & TH_SYN) {
2308 KASSERT(ti_locked == TI_WLOCKED,
2309 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2310 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2312 tp = tcp_drop(tp, ECONNRESET);
2313 rstreason = BANDLIM_UNLIMITED;
2318 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
2319 * flag is on (half-synchronized state), then queue data for
2320 * later processing; else drop segment and return.
2322 if ((thflags & TH_ACK) == 0) {
2323 if (tp->t_state == TCPS_SYN_RECEIVED ||
2324 (tp->t_flags & TF_NEEDSYN))
2326 else if (tp->t_flags & TF_ACKNOW)
2335 switch (tp->t_state) {
2338 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2339 * ESTABLISHED state and continue processing.
2340 * The ACK was checked above.
2342 case TCPS_SYN_RECEIVED:
2344 TCPSTAT_INC(tcps_connects);
2346 /* Do window scaling? */
2347 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2348 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2349 tp->rcv_scale = tp->request_r_scale;
2350 tp->snd_wnd = tiwin;
2354 * SYN-RECEIVED -> ESTABLISHED
2355 * SYN-RECEIVED* -> FIN-WAIT-1
2357 tp->t_starttime = ticks;
2358 if (tp->t_flags & TF_NEEDFIN) {
2359 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2360 tp->t_flags &= ~TF_NEEDFIN;
2362 tcp_state_change(tp, TCPS_ESTABLISHED);
2363 TCP_PROBE5(accept__established, NULL, tp,
2364 mtod(m, const char *), tp, th);
2366 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2369 * If segment contains data or ACK, will call tcp_reass()
2370 * later; if not, do so now to pass queued data to user.
2372 if (tlen == 0 && (thflags & TH_FIN) == 0)
2373 (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2375 tp->snd_wl1 = th->th_seq - 1;
2379 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2380 * ACKs. If the ack is in the range
2381 * tp->snd_una < th->th_ack <= tp->snd_max
2382 * then advance tp->snd_una to th->th_ack and drop
2383 * data from the retransmission queue. If this ACK reflects
2384 * more up to date window information we update our window information.
2386 case TCPS_ESTABLISHED:
2387 case TCPS_FIN_WAIT_1:
2388 case TCPS_FIN_WAIT_2:
2389 case TCPS_CLOSE_WAIT:
2392 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2393 TCPSTAT_INC(tcps_rcvacktoomuch);
2396 if ((tp->t_flags & TF_SACK_PERMIT) &&
2397 ((to.to_flags & TOF_SACK) ||
2398 !TAILQ_EMPTY(&tp->snd_holes)))
2399 tcp_sack_doack(tp, &to, th->th_ack);
2401 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2402 hhook_run_tcp_est_in(tp, th, &to);
2404 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2405 if (tlen == 0 && tiwin == tp->snd_wnd) {
2407 * If this is the first time we've seen a
2408 * FIN from the remote, this is not a
2409 * duplicate and it needs to be processed
2410 * normally. This happens during a
2411 * simultaneous close.
2413 if ((thflags & TH_FIN) &&
2414 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2418 TCPSTAT_INC(tcps_rcvdupack);
2420 * If we have outstanding data (other than
2421 * a window probe), this is a completely
2422 * duplicate ack (ie, window info didn't
2423 * change and FIN isn't set),
2424 * the ack is the biggest we've
2425 * seen and we've seen exactly our rexmt
2426 * threshhold of them, assume a packet
2427 * has been dropped and retransmit it.
2428 * Kludge snd_nxt & the congestion
2429 * window so we send only this one
2432 * We know we're losing at the current
2433 * window size so do congestion avoidance
2434 * (set ssthresh to half the current window
2435 * and pull our congestion window back to
2436 * the new ssthresh).
2438 * Dup acks mean that packets have left the
2439 * network (they're now cached at the receiver)
2440 * so bump cwnd by the amount in the receiver
2441 * to keep a constant cwnd packets in the
2444 * When using TCP ECN, notify the peer that
2445 * we reduced the cwnd.
2447 if (!tcp_timer_active(tp, TT_REXMT) ||
2448 th->th_ack != tp->snd_una)
2450 else if (++tp->t_dupacks > tcprexmtthresh ||
2451 IN_FASTRECOVERY(tp->t_flags)) {
2452 cc_ack_received(tp, th, CC_DUPACK);
2453 if ((tp->t_flags & TF_SACK_PERMIT) &&
2454 IN_FASTRECOVERY(tp->t_flags)) {
2458 * Compute the amount of data in flight first.
2459 * We can inject new data into the pipe iff
2460 * we have less than 1/2 the original window's
2461 * worth of data in flight.
2463 awnd = (tp->snd_nxt - tp->snd_fack) +
2464 tp->sackhint.sack_bytes_rexmit;
2465 if (awnd < tp->snd_ssthresh) {
2466 tp->snd_cwnd += tp->t_maxseg;
2467 if (tp->snd_cwnd > tp->snd_ssthresh)
2468 tp->snd_cwnd = tp->snd_ssthresh;
2471 tp->snd_cwnd += tp->t_maxseg;
2472 (void) tcp_output(tp);
2474 } else if (tp->t_dupacks == tcprexmtthresh) {
2475 tcp_seq onxt = tp->snd_nxt;
2478 * If we're doing sack, check to
2479 * see if we're already in sack
2480 * recovery. If we're not doing sack,
2481 * check to see if we're in newreno
2484 if (tp->t_flags & TF_SACK_PERMIT) {
2485 if (IN_FASTRECOVERY(tp->t_flags)) {
2490 if (SEQ_LEQ(th->th_ack,
2496 /* Congestion signal before ack. */
2497 cc_cong_signal(tp, th, CC_NDUPACK);
2498 cc_ack_received(tp, th, CC_DUPACK);
2499 tcp_timer_activate(tp, TT_REXMT, 0);
2501 if (tp->t_flags & TF_SACK_PERMIT) {
2503 tcps_sack_recovery_episode);
2504 tp->sack_newdata = tp->snd_nxt;
2505 tp->snd_cwnd = tp->t_maxseg;
2506 (void) tcp_output(tp);
2509 tp->snd_nxt = th->th_ack;
2510 tp->snd_cwnd = tp->t_maxseg;
2511 (void) tcp_output(tp);
2512 KASSERT(tp->snd_limited <= 2,
2513 ("%s: tp->snd_limited too big",
2515 tp->snd_cwnd = tp->snd_ssthresh +
2517 (tp->t_dupacks - tp->snd_limited);
2518 if (SEQ_GT(onxt, tp->snd_nxt))
2521 } else if (V_tcp_do_rfc3042) {
2522 cc_ack_received(tp, th, CC_DUPACK);
2523 u_long oldcwnd = tp->snd_cwnd;
2524 tcp_seq oldsndmax = tp->snd_max;
2528 KASSERT(tp->t_dupacks == 1 ||
2530 ("%s: dupacks not 1 or 2",
2532 if (tp->t_dupacks == 1)
2533 tp->snd_limited = 0;
2535 (tp->snd_nxt - tp->snd_una) +
2536 (tp->t_dupacks - tp->snd_limited) *
2539 * Only call tcp_output when there
2540 * is new data available to be sent.
2541 * Otherwise we would send pure ACKs.
2543 SOCKBUF_LOCK(&so->so_snd);
2544 avail = so->so_snd.sb_cc -
2545 (tp->snd_nxt - tp->snd_una);
2546 SOCKBUF_UNLOCK(&so->so_snd);
2548 (void) tcp_output(tp);
2549 sent = tp->snd_max - oldsndmax;
2550 if (sent > tp->t_maxseg) {
2551 KASSERT((tp->t_dupacks == 2 &&
2552 tp->snd_limited == 0) ||
2553 (sent == tp->t_maxseg + 1 &&
2554 tp->t_flags & TF_SENTFIN),
2555 ("%s: sent too much",
2557 tp->snd_limited = 2;
2558 } else if (sent > 0)
2560 tp->snd_cwnd = oldcwnd;
2568 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2569 ("%s: th_ack <= snd_una", __func__));
2572 * If the congestion window was inflated to account
2573 * for the other side's cached packets, retract it.
2575 if (IN_FASTRECOVERY(tp->t_flags)) {
2576 if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2577 if (tp->t_flags & TF_SACK_PERMIT)
2578 tcp_sack_partialack(tp, th);
2580 tcp_newreno_partial_ack(tp, th);
2582 cc_post_recovery(tp, th);
2586 * If we reach this point, ACK is not a duplicate,
2587 * i.e., it ACKs something we sent.
2589 if (tp->t_flags & TF_NEEDSYN) {
2591 * T/TCP: Connection was half-synchronized, and our
2592 * SYN has been ACK'd (so connection is now fully
2593 * synchronized). Go to non-starred state,
2594 * increment snd_una for ACK of SYN, and check if
2595 * we can do window scaling.
2597 tp->t_flags &= ~TF_NEEDSYN;
2599 /* Do window scaling? */
2600 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2601 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2602 tp->rcv_scale = tp->request_r_scale;
2603 /* Send window already scaled. */
2608 INP_WLOCK_ASSERT(tp->t_inpcb);
2610 acked = BYTES_THIS_ACK(tp, th);
2611 TCPSTAT_INC(tcps_rcvackpack);
2612 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2615 * If we just performed our first retransmit, and the ACK
2616 * arrives within our recovery window, then it was a mistake
2617 * to do the retransmit in the first place. Recover our
2618 * original cwnd and ssthresh, and proceed to transmit where
2621 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2622 (int)(ticks - tp->t_badrxtwin) < 0)
2623 cc_cong_signal(tp, th, CC_RTO_ERR);
2626 * If we have a timestamp reply, update smoothed
2627 * round trip time. If no timestamp is present but
2628 * transmit timer is running and timed sequence
2629 * number was acked, update smoothed round trip time.
2630 * Since we now have an rtt measurement, cancel the
2631 * timer backoff (cf., Phil Karn's retransmit alg.).
2632 * Recompute the initial retransmit timer.
2634 * Some boxes send broken timestamp replies
2635 * during the SYN+ACK phase, ignore
2636 * timestamps of 0 or we could calculate a
2637 * huge RTT and blow up the retransmit timer.
2639 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2642 t = tcp_ts_getticks() - to.to_tsecr;
2643 if (!tp->t_rttlow || tp->t_rttlow > t)
2645 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2646 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2647 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2648 tp->t_rttlow = ticks - tp->t_rtttime;
2649 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2653 * If all outstanding data is acked, stop retransmit
2654 * timer and remember to restart (more output or persist).
2655 * If there is more data to be acked, restart retransmit
2656 * timer, using current (possibly backed-off) value.
2658 if (th->th_ack == tp->snd_max) {
2659 tcp_timer_activate(tp, TT_REXMT, 0);
2661 } else if (!tcp_timer_active(tp, TT_PERSIST))
2662 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2665 * If no data (only SYN) was ACK'd,
2666 * skip rest of ACK processing.
2672 * Let the congestion control algorithm update congestion
2673 * control related information. This typically means increasing
2674 * the congestion window.
2676 cc_ack_received(tp, th, CC_ACK);
2678 SOCKBUF_LOCK(&so->so_snd);
2679 if (acked > so->so_snd.sb_cc) {
2680 tp->snd_wnd -= so->so_snd.sb_cc;
2681 mfree = sbcut_locked(&so->so_snd,
2682 (int)so->so_snd.sb_cc);
2685 mfree = sbcut_locked(&so->so_snd, acked);
2686 tp->snd_wnd -= acked;
2689 /* NB: sowwakeup_locked() does an implicit unlock. */
2690 sowwakeup_locked(so);
2692 /* Detect una wraparound. */
2693 if (!IN_RECOVERY(tp->t_flags) &&
2694 SEQ_GT(tp->snd_una, tp->snd_recover) &&
2695 SEQ_LEQ(th->th_ack, tp->snd_recover))
2696 tp->snd_recover = th->th_ack - 1;
2697 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2698 if (IN_RECOVERY(tp->t_flags) &&
2699 SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2700 EXIT_RECOVERY(tp->t_flags);
2702 tp->snd_una = th->th_ack;
2703 if (tp->t_flags & TF_SACK_PERMIT) {
2704 if (SEQ_GT(tp->snd_una, tp->snd_recover))
2705 tp->snd_recover = tp->snd_una;
2707 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2708 tp->snd_nxt = tp->snd_una;
2710 switch (tp->t_state) {
2713 * In FIN_WAIT_1 STATE in addition to the processing
2714 * for the ESTABLISHED state if our FIN is now acknowledged
2715 * then enter FIN_WAIT_2.
2717 case TCPS_FIN_WAIT_1:
2718 if (ourfinisacked) {
2720 * If we can't receive any more
2721 * data, then closing user can proceed.
2722 * Starting the timer is contrary to the
2723 * specification, but if we don't get a FIN
2724 * we'll hang forever.
2727 * we should release the tp also, and use a
2730 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2731 soisdisconnected(so);
2732 tcp_timer_activate(tp, TT_2MSL,
2733 (tcp_fast_finwait2_recycle ?
2734 tcp_finwait2_timeout :
2737 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2742 * In CLOSING STATE in addition to the processing for
2743 * the ESTABLISHED state if the ACK acknowledges our FIN
2744 * then enter the TIME-WAIT state, otherwise ignore
2748 if (ourfinisacked) {
2749 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2751 INP_INFO_WUNLOCK(&V_tcbinfo);
2758 * In LAST_ACK, we may still be waiting for data to drain
2759 * and/or to be acked, as well as for the ack of our FIN.
2760 * If our FIN is now acknowledged, delete the TCB,
2761 * enter the closed state and return.
2764 if (ourfinisacked) {
2765 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2774 INP_WLOCK_ASSERT(tp->t_inpcb);
2777 * Update window information.
2778 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2780 if ((thflags & TH_ACK) &&
2781 (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2782 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2783 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2784 /* keep track of pure window updates */
2786 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2787 TCPSTAT_INC(tcps_rcvwinupd);
2788 tp->snd_wnd = tiwin;
2789 tp->snd_wl1 = th->th_seq;
2790 tp->snd_wl2 = th->th_ack;
2791 if (tp->snd_wnd > tp->max_sndwnd)
2792 tp->max_sndwnd = tp->snd_wnd;
2797 * Process segments with URG.
2799 if ((thflags & TH_URG) && th->th_urp &&
2800 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2802 * This is a kludge, but if we receive and accept
2803 * random urgent pointers, we'll crash in
2804 * soreceive. It's hard to imagine someone
2805 * actually wanting to send this much urgent data.
2807 SOCKBUF_LOCK(&so->so_rcv);
2808 if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
2809 th->th_urp = 0; /* XXX */
2810 thflags &= ~TH_URG; /* XXX */
2811 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */
2812 goto dodata; /* XXX */
2815 * If this segment advances the known urgent pointer,
2816 * then mark the data stream. This should not happen
2817 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2818 * a FIN has been received from the remote side.
2819 * In these states we ignore the URG.
2821 * According to RFC961 (Assigned Protocols),
2822 * the urgent pointer points to the last octet
2823 * of urgent data. We continue, however,
2824 * to consider it to indicate the first octet
2825 * of data past the urgent section as the original
2826 * spec states (in one of two places).
2828 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2829 tp->rcv_up = th->th_seq + th->th_urp;
2830 so->so_oobmark = so->so_rcv.sb_cc +
2831 (tp->rcv_up - tp->rcv_nxt) - 1;
2832 if (so->so_oobmark == 0)
2833 so->so_rcv.sb_state |= SBS_RCVATMARK;
2835 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2837 SOCKBUF_UNLOCK(&so->so_rcv);
2839 * Remove out of band data so doesn't get presented to user.
2840 * This can happen independent of advancing the URG pointer,
2841 * but if two URG's are pending at once, some out-of-band
2842 * data may creep in... ick.
2844 if (th->th_urp <= (u_long)tlen &&
2845 !(so->so_options & SO_OOBINLINE)) {
2846 /* hdr drop is delayed */
2847 tcp_pulloutofband(so, th, m, drop_hdrlen);
2851 * If no out of band data is expected,
2852 * pull receive urgent pointer along
2853 * with the receive window.
2855 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2856 tp->rcv_up = tp->rcv_nxt;
2859 INP_WLOCK_ASSERT(tp->t_inpcb);
2862 * Process the segment text, merging it into the TCP sequencing queue,
2863 * and arranging for acknowledgment of receipt if necessary.
2864 * This process logically involves adjusting tp->rcv_wnd as data
2865 * is presented to the user (this happens in tcp_usrreq.c,
2866 * case PRU_RCVD). If a FIN has already been received on this
2867 * connection then we just ignore the text.
2869 if ((tlen || (thflags & TH_FIN)) &&
2870 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2871 tcp_seq save_start = th->th_seq;
2872 m_adj(m, drop_hdrlen); /* delayed header drop */
2874 * Insert segment which includes th into TCP reassembly queue
2875 * with control block tp. Set thflags to whether reassembly now
2876 * includes a segment with FIN. This handles the common case
2877 * inline (segment is the next to be received on an established
2878 * connection, and the queue is empty), avoiding linkage into
2879 * and removal from the queue and repetition of various
2881 * Set DELACK for segments received in order, but ack
2882 * immediately when segments are out of order (so
2883 * fast retransmit can work).
2885 if (th->th_seq == tp->rcv_nxt && tp->t_segq == NULL &&
2886 TCPS_HAVEESTABLISHED(tp->t_state)) {
2887 if (DELAY_ACK(tp, tlen))
2888 tp->t_flags |= TF_DELACK;
2890 tp->t_flags |= TF_ACKNOW;
2891 tp->rcv_nxt += tlen;
2892 thflags = th->th_flags & TH_FIN;
2893 TCPSTAT_INC(tcps_rcvpack);
2894 TCPSTAT_ADD(tcps_rcvbyte, tlen);
2896 SOCKBUF_LOCK(&so->so_rcv);
2897 if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2900 sbappendstream_locked(&so->so_rcv, m);
2901 /* NB: sorwakeup_locked() does an implicit unlock. */
2902 sorwakeup_locked(so);
2905 * XXX: Due to the header drop above "th" is
2906 * theoretically invalid by now. Fortunately
2907 * m_adj() doesn't actually frees any mbufs
2908 * when trimming from the head.
2910 thflags = tcp_reass(tp, th, &tlen, m);
2911 tp->t_flags |= TF_ACKNOW;
2913 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2914 tcp_update_sack_list(tp, save_start, save_start + tlen);
2917 * Note the amount of data that peer has sent into
2918 * our window, in order to estimate the sender's
2922 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2923 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2925 len = so->so_rcv.sb_hiwat;
2933 * If FIN is received ACK the FIN and let the user know
2934 * that the connection is closing.
2936 if (thflags & TH_FIN) {
2937 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2940 * If connection is half-synchronized
2941 * (ie NEEDSYN flag on) then delay ACK,
2942 * so it may be piggybacked when SYN is sent.
2943 * Otherwise, since we received a FIN then no
2944 * more input can be expected, send ACK now.
2946 if (tp->t_flags & TF_NEEDSYN)
2947 tp->t_flags |= TF_DELACK;
2949 tp->t_flags |= TF_ACKNOW;
2952 switch (tp->t_state) {
2955 * In SYN_RECEIVED and ESTABLISHED STATES
2956 * enter the CLOSE_WAIT state.
2958 case TCPS_SYN_RECEIVED:
2959 tp->t_starttime = ticks;
2961 case TCPS_ESTABLISHED:
2962 tcp_state_change(tp, TCPS_CLOSE_WAIT);
2966 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2967 * enter the CLOSING state.
2969 case TCPS_FIN_WAIT_1:
2970 tcp_state_change(tp, TCPS_CLOSING);
2974 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2975 * starting the time-wait timer, turning off the other
2978 case TCPS_FIN_WAIT_2:
2979 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
2980 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
2981 "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
2985 INP_INFO_WUNLOCK(&V_tcbinfo);
2989 if (ti_locked == TI_WLOCKED)
2990 INP_INFO_WUNLOCK(&V_tcbinfo);
2991 ti_locked = TI_UNLOCKED;
2994 if (so->so_options & SO_DEBUG)
2995 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3000 * Return any desired output.
3002 if (needoutput || (tp->t_flags & TF_ACKNOW))
3003 (void) tcp_output(tp);
3006 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3007 __func__, ti_locked));
3008 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3009 INP_WLOCK_ASSERT(tp->t_inpcb);
3011 if (tp->t_flags & TF_DELACK) {
3012 tp->t_flags &= ~TF_DELACK;
3013 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3015 INP_WUNLOCK(tp->t_inpcb);
3020 * Generate an ACK dropping incoming segment if it occupies
3021 * sequence space, where the ACK reflects our state.
3023 * We can now skip the test for the RST flag since all
3024 * paths to this code happen after packets containing
3025 * RST have been dropped.
3027 * In the SYN-RECEIVED state, don't send an ACK unless the
3028 * segment we received passes the SYN-RECEIVED ACK test.
3029 * If it fails send a RST. This breaks the loop in the
3030 * "LAND" DoS attack, and also prevents an ACK storm
3031 * between two listening ports that have been sent forged
3032 * SYN segments, each with the source address of the other.
3034 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3035 (SEQ_GT(tp->snd_una, th->th_ack) ||
3036 SEQ_GT(th->th_ack, tp->snd_max)) ) {
3037 rstreason = BANDLIM_RST_OPENPORT;
3041 if (so->so_options & SO_DEBUG)
3042 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3045 if (ti_locked == TI_WLOCKED)
3046 INP_INFO_WUNLOCK(&V_tcbinfo);
3047 ti_locked = TI_UNLOCKED;
3049 tp->t_flags |= TF_ACKNOW;
3050 (void) tcp_output(tp);
3051 INP_WUNLOCK(tp->t_inpcb);
3056 if (ti_locked == TI_WLOCKED)
3057 INP_INFO_WUNLOCK(&V_tcbinfo);
3058 ti_locked = TI_UNLOCKED;
3061 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3062 INP_WUNLOCK(tp->t_inpcb);
3064 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3068 if (ti_locked == TI_WLOCKED) {
3069 INP_INFO_WUNLOCK(&V_tcbinfo);
3070 ti_locked = TI_UNLOCKED;
3074 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3078 * Drop space held by incoming segment and return.
3081 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3082 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3086 INP_WUNLOCK(tp->t_inpcb);
3091 * Issue RST and make ACK acceptable to originator of segment.
3092 * The mbuf must still include the original packet header.
3096 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3097 int tlen, int rstreason)
3103 struct ip6_hdr *ip6;
3107 INP_WLOCK_ASSERT(tp->t_inpcb);
3110 /* Don't bother if destination was broadcast/multicast. */
3111 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3114 if (mtod(m, struct ip *)->ip_v == 6) {
3115 ip6 = mtod(m, struct ip6_hdr *);
3116 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3117 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3119 /* IPv6 anycast check is done at tcp6_input() */
3122 #if defined(INET) && defined(INET6)
3127 ip = mtod(m, struct ip *);
3128 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3129 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3130 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3131 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3136 /* Perform bandwidth limiting. */
3137 if (badport_bandlim(rstreason) < 0)
3140 /* tcp_respond consumes the mbuf chain. */
3141 if (th->th_flags & TH_ACK) {
3142 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3143 th->th_ack, TH_RST);
3145 if (th->th_flags & TH_SYN)
3147 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3148 (tcp_seq)0, TH_RST|TH_ACK);
3156 * Parse TCP options and place in tcpopt.
3159 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3164 for (; cnt > 0; cnt -= optlen, cp += optlen) {
3166 if (opt == TCPOPT_EOL)
3168 if (opt == TCPOPT_NOP)
3174 if (optlen < 2 || optlen > cnt)
3179 if (optlen != TCPOLEN_MAXSEG)
3181 if (!(flags & TO_SYN))
3183 to->to_flags |= TOF_MSS;
3184 bcopy((char *)cp + 2,
3185 (char *)&to->to_mss, sizeof(to->to_mss));
3186 to->to_mss = ntohs(to->to_mss);
3189 if (optlen != TCPOLEN_WINDOW)
3191 if (!(flags & TO_SYN))
3193 to->to_flags |= TOF_SCALE;
3194 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3196 case TCPOPT_TIMESTAMP:
3197 if (optlen != TCPOLEN_TIMESTAMP)
3199 to->to_flags |= TOF_TS;
3200 bcopy((char *)cp + 2,
3201 (char *)&to->to_tsval, sizeof(to->to_tsval));
3202 to->to_tsval = ntohl(to->to_tsval);
3203 bcopy((char *)cp + 6,
3204 (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3205 to->to_tsecr = ntohl(to->to_tsecr);
3207 #ifdef TCP_SIGNATURE
3209 * XXX In order to reply to a host which has set the
3210 * TCP_SIGNATURE option in its initial SYN, we have to
3211 * record the fact that the option was observed here
3212 * for the syncache code to perform the correct response.
3214 case TCPOPT_SIGNATURE:
3215 if (optlen != TCPOLEN_SIGNATURE)
3217 to->to_flags |= TOF_SIGNATURE;
3218 to->to_signature = cp + 2;
3221 case TCPOPT_SACK_PERMITTED:
3222 if (optlen != TCPOLEN_SACK_PERMITTED)
3224 if (!(flags & TO_SYN))
3228 to->to_flags |= TOF_SACKPERM;
3231 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3235 to->to_flags |= TOF_SACK;
3236 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3237 to->to_sacks = cp + 2;
3238 TCPSTAT_INC(tcps_sack_rcv_blocks);
3247 * Pull out of band byte out of a segment so
3248 * it doesn't appear in the user's data queue.
3249 * It is still reflected in the segment length for
3250 * sequencing purposes.
3253 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3256 int cnt = off + th->th_urp - 1;
3259 if (m->m_len > cnt) {
3260 char *cp = mtod(m, caddr_t) + cnt;
3261 struct tcpcb *tp = sototcpcb(so);
3263 INP_WLOCK_ASSERT(tp->t_inpcb);
3266 tp->t_oobflags |= TCPOOB_HAVEDATA;
3267 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3269 if (m->m_flags & M_PKTHDR)
3278 panic("tcp_pulloutofband");
3282 * Collect new round-trip time estimate
3283 * and update averages and current timeout.
3286 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3290 INP_WLOCK_ASSERT(tp->t_inpcb);
3292 TCPSTAT_INC(tcps_rttupdated);
3294 if (tp->t_srtt != 0) {
3296 * srtt is stored as fixed point with 5 bits after the
3297 * binary point (i.e., scaled by 8). The following magic
3298 * is equivalent to the smoothing algorithm in rfc793 with
3299 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3300 * point). Adjust rtt to origin 0.
3302 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3303 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3305 if ((tp->t_srtt += delta) <= 0)
3309 * We accumulate a smoothed rtt variance (actually, a
3310 * smoothed mean difference), then set the retransmit
3311 * timer to smoothed rtt + 4 times the smoothed variance.
3312 * rttvar is stored as fixed point with 4 bits after the
3313 * binary point (scaled by 16). The following is
3314 * equivalent to rfc793 smoothing with an alpha of .75
3315 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
3316 * rfc793's wired-in beta.
3320 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3321 if ((tp->t_rttvar += delta) <= 0)
3323 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3324 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3327 * No rtt measurement yet - use the unsmoothed rtt.
3328 * Set the variance to half the rtt (so our first
3329 * retransmit happens at 3*rtt).
3331 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3332 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3333 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3339 * the retransmit should happen at rtt + 4 * rttvar.
3340 * Because of the way we do the smoothing, srtt and rttvar
3341 * will each average +1/2 tick of bias. When we compute
3342 * the retransmit timer, we want 1/2 tick of rounding and
3343 * 1 extra tick because of +-1/2 tick uncertainty in the
3344 * firing of the timer. The bias will give us exactly the
3345 * 1.5 tick we need. But, because the bias is
3346 * statistical, we have to test that we don't drop below
3347 * the minimum feasible timer (which is 2 ticks).
3349 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3350 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3353 * We received an ack for a packet that wasn't retransmitted;
3354 * it is probably safe to discard any error indications we've
3355 * received recently. This isn't quite right, but close enough
3356 * for now (a route might have failed after we sent a segment,
3357 * and the return path might not be symmetrical).
3359 tp->t_softerror = 0;
3363 * Determine a reasonable value for maxseg size.
3364 * If the route is known, check route for mtu.
3365 * If none, use an mss that can be handled on the outgoing interface
3366 * without forcing IP to fragment. If no route is found, route has no mtu,
3367 * or the destination isn't local, use a default, hopefully conservative
3368 * size (usually 512 or the default IP max size, but no more than the mtu
3369 * of the interface), as we can't discover anything about intervening
3370 * gateways or networks. We also initialize the congestion/slow start
3371 * window to be a single segment if the destination isn't local.
3372 * While looking at the routing entry, we also initialize other path-dependent
3373 * parameters from pre-set or cached values in the routing entry.
3375 * Also take into account the space needed for options that we
3376 * send regularly. Make maxseg shorter by that amount to assure
3377 * that we can send maxseg amount of data even when the options
3378 * are present. Store the upper limit of the length of options plus
3381 * NOTE that this routine is only called when we process an incoming
3382 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3383 * settings are handled in tcp_mssopt().
3386 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3387 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3391 struct inpcb *inp = tp->t_inpcb;
3392 struct hc_metrics_lite metrics;
3395 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3396 size_t min_protoh = isipv6 ?
3397 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3398 sizeof (struct tcpiphdr);
3400 const size_t min_protoh = sizeof(struct tcpiphdr);
3403 INP_WLOCK_ASSERT(tp->t_inpcb);
3405 if (mtuoffer != -1) {
3406 KASSERT(offer == -1, ("%s: conflict", __func__));
3407 offer = mtuoffer - min_protoh;
3414 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3415 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3418 #if defined(INET) && defined(INET6)
3423 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3424 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3429 * No route to sender, stay with default mss and return.
3433 * In case we return early we need to initialize metrics
3434 * to a defined state as tcp_hc_get() would do for us
3435 * if there was no cache hit.
3437 if (metricptr != NULL)
3438 bzero(metricptr, sizeof(struct hc_metrics_lite));
3442 /* What have we got? */
3446 * Offer == 0 means that there was no MSS on the SYN
3447 * segment, in this case we use tcp_mssdflt as
3448 * already assigned to t_maxopd above.
3450 offer = tp->t_maxopd;
3455 * Offer == -1 means that we didn't receive SYN yet.
3461 * Prevent DoS attack with too small MSS. Round up
3462 * to at least minmss.
3464 offer = max(offer, V_tcp_minmss);
3468 * rmx information is now retrieved from tcp_hostcache.
3470 tcp_hc_get(&inp->inp_inc, &metrics);
3471 if (metricptr != NULL)
3472 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3475 * If there's a discovered mtu int tcp hostcache, use it
3476 * else, use the link mtu.
3478 if (metrics.rmx_mtu)
3479 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3483 mss = maxmtu - min_protoh;
3484 if (!V_path_mtu_discovery &&
3485 !in6_localaddr(&inp->in6p_faddr))
3486 mss = min(mss, V_tcp_v6mssdflt);
3489 #if defined(INET) && defined(INET6)
3494 mss = maxmtu - min_protoh;
3495 if (!V_path_mtu_discovery &&
3496 !in_localaddr(inp->inp_faddr))
3497 mss = min(mss, V_tcp_mssdflt);
3501 * XXX - The above conditional (mss = maxmtu - min_protoh)
3502 * probably violates the TCP spec.
3503 * The problem is that, since we don't know the
3504 * other end's MSS, we are supposed to use a conservative
3505 * default. But, if we do that, then MTU discovery will
3506 * never actually take place, because the conservative
3507 * default is much less than the MTUs typically seen
3508 * on the Internet today. For the moment, we'll sweep
3509 * this under the carpet.
3511 * The conservative default might not actually be a problem
3512 * if the only case this occurs is when sending an initial
3513 * SYN with options and data to a host we've never talked
3514 * to before. Then, they will reply with an MSS value which
3515 * will get recorded and the new parameters should get
3516 * recomputed. For Further Study.
3519 mss = min(mss, offer);
3522 * Sanity check: make sure that maxopd will be large
3523 * enough to allow some data on segments even if the
3524 * all the option space is used (40bytes). Otherwise
3525 * funny things may happen in tcp_output.
3530 * maxopd stores the maximum length of data AND options
3531 * in a segment; maxseg is the amount of data in a normal
3532 * segment. We need to store this value (maxopd) apart
3533 * from maxseg, because now every segment carries options
3534 * and thus we normally have somewhat less data in segments.
3539 * origoffer==-1 indicates that no segments were received yet.
3540 * In this case we just guess.
3542 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3544 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3545 mss -= TCPOLEN_TSTAMP_APPA;
3551 tcp_mss(struct tcpcb *tp, int offer)
3557 struct hc_metrics_lite metrics;
3558 struct tcp_ifcap cap;
3560 KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3562 bzero(&cap, sizeof(cap));
3563 tcp_mss_update(tp, offer, -1, &metrics, &cap);
3569 * If there's a pipesize, change the socket buffer to that size,
3570 * don't change if sb_hiwat is different than default (then it
3571 * has been changed on purpose with setsockopt).
3572 * Make the socket buffers an integral number of mss units;
3573 * if the mss is larger than the socket buffer, decrease the mss.
3575 so = inp->inp_socket;
3576 SOCKBUF_LOCK(&so->so_snd);
3577 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3578 bufsize = metrics.rmx_sendpipe;
3580 bufsize = so->so_snd.sb_hiwat;
3584 bufsize = roundup(bufsize, mss);
3585 if (bufsize > sb_max)
3587 if (bufsize > so->so_snd.sb_hiwat)
3588 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3590 SOCKBUF_UNLOCK(&so->so_snd);
3593 SOCKBUF_LOCK(&so->so_rcv);
3594 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3595 bufsize = metrics.rmx_recvpipe;
3597 bufsize = so->so_rcv.sb_hiwat;
3598 if (bufsize > mss) {
3599 bufsize = roundup(bufsize, mss);
3600 if (bufsize > sb_max)
3602 if (bufsize > so->so_rcv.sb_hiwat)
3603 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3605 SOCKBUF_UNLOCK(&so->so_rcv);
3607 /* Check the interface for TSO capabilities. */
3608 if (cap.ifcap & CSUM_TSO) {
3609 tp->t_flags |= TF_TSO;
3610 tp->t_tsomax = cap.tsomax;
3615 * Determine the MSS option to send on an outgoing SYN.
3618 tcp_mssopt(struct in_conninfo *inc)
3625 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3628 if (inc->inc_flags & INC_ISIPV6) {
3629 mss = V_tcp_v6mssdflt;
3630 maxmtu = tcp_maxmtu6(inc, NULL);
3631 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3634 #if defined(INET) && defined(INET6)
3639 mss = V_tcp_mssdflt;
3640 maxmtu = tcp_maxmtu(inc, NULL);
3641 min_protoh = sizeof(struct tcpiphdr);
3644 #if defined(INET6) || defined(INET)
3645 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3648 if (maxmtu && thcmtu)
3649 mss = min(maxmtu, thcmtu) - min_protoh;
3650 else if (maxmtu || thcmtu)
3651 mss = max(maxmtu, thcmtu) - min_protoh;
3658 * On a partial ack arrives, force the retransmission of the
3659 * next unacknowledged segment. Do not clear tp->t_dupacks.
3660 * By setting snd_nxt to ti_ack, this forces retransmission timer to
3664 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3666 tcp_seq onxt = tp->snd_nxt;
3667 u_long ocwnd = tp->snd_cwnd;
3669 INP_WLOCK_ASSERT(tp->t_inpcb);
3671 tcp_timer_activate(tp, TT_REXMT, 0);
3673 tp->snd_nxt = th->th_ack;
3675 * Set snd_cwnd to one segment beyond acknowledged offset.
3676 * (tp->snd_una has not yet been updated when this function is called.)
3678 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3679 tp->t_flags |= TF_ACKNOW;
3680 (void) tcp_output(tp);
3681 tp->snd_cwnd = ocwnd;
3682 if (SEQ_GT(onxt, tp->snd_nxt))
3685 * Partial window deflation. Relies on fact that tp->snd_una
3688 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3689 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3692 tp->snd_cwnd += tp->t_maxseg;
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