tcp: Aggregate the mbuf in sosendtcp() a little bit
[dragonfly.git] / sys / netinet / tcp_input.c
CommitLineData
984263bc 1/*
66d6c637
JH
2 * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved.
95b22adf 4 *
66d6c637
JH
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
95b22adf 7 *
66d6c637
JH
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
95b22adf 19 *
66d6c637
JH
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
66d6c637 34/*
984263bc
MD
35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. All advertising materials mentioning features or use of this software
47 * must display the following acknowledgement:
48 * This product includes software developed by the University of
49 * California, Berkeley and its contributors.
50 * 4. Neither the name of the University nor the names of its contributors
51 * may be used to endorse or promote products derived from this software
52 * without specific prior written permission.
53 *
54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
64 * SUCH DAMAGE.
65 *
66 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $
5de23090 68 * $DragonFly: src/sys/netinet/tcp_input.c,v 1.68 2008/08/22 09:14:17 sephe Exp $
984263bc
MD
69 */
70
71#include "opt_ipfw.h" /* for ipfw_fwd */
b1992928 72#include "opt_inet.h"
984263bc
MD
73#include "opt_inet6.h"
74#include "opt_ipsec.h"
75#include "opt_tcpdebug.h"
76#include "opt_tcp_input.h"
77
78#include <sys/param.h>
79#include <sys/systm.h>
80#include <sys/kernel.h>
81#include <sys/sysctl.h>
82#include <sys/malloc.h>
83#include <sys/mbuf.h>
84#include <sys/proc.h> /* for proc0 declaration */
85#include <sys/protosw.h>
86#include <sys/socket.h>
87#include <sys/socketvar.h>
88#include <sys/syslog.h>
3f9db7f8 89#include <sys/in_cksum.h>
984263bc 90
6cef7136
MD
91#include <sys/socketvar2.h>
92
984263bc 93#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
a00138cb 94#include <machine/stdarg.h>
984263bc
MD
95
96#include <net/if.h>
97#include <net/route.h>
98
99#include <netinet/in.h>
100#include <netinet/in_systm.h>
101#include <netinet/ip.h>
95b22adf 102#include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */
984263bc 103#include <netinet/in_var.h>
95b22adf 104#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
984263bc
MD
105#include <netinet/in_pcb.h>
106#include <netinet/ip_var.h>
107#include <netinet/ip6.h>
108#include <netinet/icmp6.h>
109#include <netinet6/nd6.h>
110#include <netinet6/ip6_var.h>
111#include <netinet6/in6_pcb.h>
112#include <netinet/tcp.h>
113#include <netinet/tcp_fsm.h>
114#include <netinet/tcp_seq.h>
115#include <netinet/tcp_timer.h>
a48c5dd5 116#include <netinet/tcp_timer2.h>
984263bc
MD
117#include <netinet/tcp_var.h>
118#include <netinet6/tcp6_var.h>
119#include <netinet/tcpip.h>
95b22adf 120
984263bc
MD
121#ifdef TCPDEBUG
122#include <netinet/tcp_debug.h>
123
95b22adf 124u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */
984263bc 125struct tcphdr tcp_savetcp;
95b22adf 126#endif
984263bc
MD
127
128#ifdef FAST_IPSEC
bf844ffa
JH
129#include <netproto/ipsec/ipsec.h>
130#include <netproto/ipsec/ipsec6.h>
984263bc
MD
131#endif
132
133#ifdef IPSEC
134#include <netinet6/ipsec.h>
135#include <netinet6/ipsec6.h>
d2438d69 136#include <netproto/key/key.h>
95b22adf 137#endif
984263bc 138
984263bc
MD
139MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry");
140
984263bc 141static int log_in_vain = 0;
d24ce1dc 142SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
984263bc
MD
143 &log_in_vain, 0, "Log all incoming TCP connections");
144
145static int blackhole = 0;
146SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
147 &blackhole, 0, "Do not send RST when dropping refused connections");
148
149int tcp_delack_enabled = 1;
d24ce1dc
JH
150SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
151 &tcp_delack_enabled, 0,
984263bc
MD
152 "Delay ACK to try and piggyback it onto a data packet");
153
154#ifdef TCP_DROP_SYNFIN
155static int drop_synfin = 0;
156SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
157 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
158#endif
159
33abdd1c
MD
160static int tcp_do_limitedtransmit = 1;
161SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW,
162 &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)");
163
91489f6b 164static int tcp_do_early_retransmit = 1;
8819433a
JH
165SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW,
166 &tcp_do_early_retransmit, 0, "Early retransmit");
167
8acdb67c 168int tcp_aggregate_acks = 1;
72b37eeb
MD
169SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW,
170 &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack");
171
8d573eef 172int tcp_do_rfc3390 = 1;
4b52d5ee
JH
173SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
174 &tcp_do_rfc3390, 0,
175 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
176
efd4b327
JH
177static int tcp_do_eifel_detect = 1;
178SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW,
179 &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)");
180
8acdb67c
JH
181static int tcp_do_abc = 1;
182SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW,
183 &tcp_do_abc, 0,
184 "TCP Appropriate Byte Counting (RFC 3465)");
185
91489f6b
JH
186/*
187 * Define as tunable for easy testing with SACK on and off.
188 * Warning: do not change setting in the middle of an existing active TCP flow,
189 * else strange things might happen to that flow.
190 */
6e5bbdda 191int tcp_do_sack = 1;
91489f6b
JH
192SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW,
193 &tcp_do_sack, 0, "Enable SACK Algorithms");
194
195int tcp_do_smartsack = 1;
196SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW,
197 &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms");
198
3edf7c37
RG
199SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
200 "TCP Segment Reassembly Queue");
201
202int tcp_reass_maxseg = 0;
203SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD,
204 &tcp_reass_maxseg, 0,
205 "Global maximum number of TCP Segments in Reassembly Queue");
206
207int tcp_reass_qsize = 0;
208SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
209 &tcp_reass_qsize, 0,
210 "Global number of TCP Segments currently in Reassembly Queue");
211
212static int tcp_reass_overflows = 0;
213SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
214 &tcp_reass_overflows, 0,
215 "Global number of TCP Segment Reassembly Queue Overflows");
216
5b0b9fa5
PA
217int tcp_do_autorcvbuf = 1;
218SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
219 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing");
220
221int tcp_autorcvbuf_inc = 16*1024;
222SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
223 &tcp_autorcvbuf_inc, 0,
224 "Incrementor step size of automatic receive buffer");
225
46e92930 226int tcp_autorcvbuf_max = 2*1024*1024;
5b0b9fa5
PA
227SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
228 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer");
229
c16aca65
SZ
230int tcp_sosnd_agglim = 2;
231SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosnd_agglim, CTLFLAG_RW,
232 &tcp_sosnd_agglim, 0, "TCP sosend mbuf aggregation limit");
5b0b9fa5 233
95b22adf 234static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t);
984263bc
MD
235static void tcp_pulloutofband(struct socket *,
236 struct tcphdr *, struct mbuf *, int);
237static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
238 struct mbuf *);
239static void tcp_xmit_timer(struct tcpcb *, int);
91489f6b
JH
240static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int);
241static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *);
984263bc
MD
242
243/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
244#ifdef INET6
245#define ND6_HINT(tp) \
246do { \
247 if ((tp) && (tp)->t_inpcb && \
61896e3c 248 ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \
984263bc
MD
249 (tp)->t_inpcb->in6p_route.ro_rt) \
250 nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \
251} while (0)
252#else
253#define ND6_HINT(tp)
254#endif
255
256/*
257 * Indicate whether this ack should be delayed. We can delay the ack if
258 * - delayed acks are enabled and
259 * - there is no delayed ack timer in progress and
260 * - our last ack wasn't a 0-sized window. We never want to delay
261 * the ack that opens up a 0-sized window.
262 */
263#define DELAY_ACK(tp) \
a48c5dd5 264 (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \
61896e3c 265 !(tp->t_flags & TF_RXWIN0SENT))
984263bc 266
df9d7670
JH
267#define acceptable_window_update(tp, th, tiwin) \
268 (SEQ_LT(tp->snd_wl1, th->th_seq) || \
269 (tp->snd_wl1 == th->th_seq && \
270 (SEQ_LT(tp->snd_wl2, th->th_ack) || \
271 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))
272
984263bc 273static int
95b22adf 274tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
984263bc
MD
275{
276 struct tseg_qent *q;
277 struct tseg_qent *p = NULL;
984263bc
MD
278 struct tseg_qent *te;
279 struct socket *so = tp->t_inpcb->inp_socket;
280 int flags;
281
282 /*
61896e3c 283 * Call with th == NULL after become established to
984263bc
MD
284 * force pre-ESTABLISHED data up to user socket.
285 */
61896e3c 286 if (th == NULL)
984263bc
MD
287 goto present;
288
3edf7c37
RG
289 /*
290 * Limit the number of segments in the reassembly queue to prevent
291 * holding on to too many segments (and thus running out of mbufs).
292 * Make sure to let the missing segment through which caused this
293 * queue. Always keep one global queue entry spare to be able to
294 * process the missing segment.
295 */
296 if (th->th_seq != tp->rcv_nxt &&
297 tcp_reass_qsize + 1 >= tcp_reass_maxseg) {
298 tcp_reass_overflows++;
299 tcpstat.tcps_rcvmemdrop++;
300 m_freem(m);
91489f6b
JH
301 /* no SACK block to report */
302 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
3edf7c37
RG
303 return (0);
304 }
305
ba4e3dbe 306 /* Allocate a new queue entry. */
984263bc 307 MALLOC(te, struct tseg_qent *, sizeof(struct tseg_qent), M_TSEGQ,
ba4e3dbe 308 M_INTWAIT | M_NULLOK);
984263bc
MD
309 if (te == NULL) {
310 tcpstat.tcps_rcvmemdrop++;
311 m_freem(m);
91489f6b
JH
312 /* no SACK block to report */
313 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
984263bc
MD
314 return (0);
315 }
2d23a8be 316 atomic_add_int(&tcp_reass_qsize, 1);
984263bc
MD
317
318 /*
319 * Find a segment which begins after this one does.
320 */
321 LIST_FOREACH(q, &tp->t_segq, tqe_q) {
322 if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
323 break;
324 p = q;
325 }
326
327 /*
328 * If there is a preceding segment, it may provide some of
329 * our data already. If so, drop the data from the incoming
330 * segment. If it provides all of our data, drop us.
331 */
332 if (p != NULL) {
76cf5e41 333 tcp_seq_diff_t i;
91489f6b 334
984263bc
MD
335 /* conversion to int (in i) handles seq wraparound */
336 i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
91489f6b
JH
337 if (i > 0) { /* overlaps preceding segment */
338 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
339 /* enclosing block starts w/ preceding segment */
340 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
984263bc 341 if (i >= *tlenp) {
91489f6b
JH
342 /* preceding encloses incoming segment */
343 tp->encloseblk.rblk_end = p->tqe_th->th_seq +
344 p->tqe_len;
984263bc
MD
345 tcpstat.tcps_rcvduppack++;
346 tcpstat.tcps_rcvdupbyte += *tlenp;
347 m_freem(m);
efda3bd0 348 kfree(te, M_TSEGQ);
2d23a8be 349 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
350 /*
351 * Try to present any queued data
352 * at the left window edge to the user.
353 * This is needed after the 3-WHS
354 * completes.
355 */
356 goto present; /* ??? */
357 }
358 m_adj(m, i);
359 *tlenp -= i;
360 th->th_seq += i;
91489f6b
JH
361 /* incoming segment end is enclosing block end */
362 tp->encloseblk.rblk_end = th->th_seq + *tlenp +
363 ((th->th_flags & TH_FIN) != 0);
364 /* trim end of reported D-SACK block */
365 tp->reportblk.rblk_end = th->th_seq;
984263bc
MD
366 }
367 }
368 tcpstat.tcps_rcvoopack++;
369 tcpstat.tcps_rcvoobyte += *tlenp;
370
371 /*
372 * While we overlap succeeding segments trim them or,
373 * if they are completely covered, dequeue them.
374 */
375 while (q) {
76cf5e41 376 tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
91489f6b
JH
377 tcp_seq qend = q->tqe_th->th_seq + q->tqe_len;
378 struct tseg_qent *nq;
379
984263bc
MD
380 if (i <= 0)
381 break;
91489f6b
JH
382 if (!(tp->t_flags & TF_DUPSEG)) { /* first time through */
383 tp->t_flags |= (TF_DUPSEG | TF_ENCLOSESEG);
384 tp->encloseblk = tp->reportblk;
385 /* report trailing duplicate D-SACK segment */
386 tp->reportblk.rblk_start = q->tqe_th->th_seq;
387 }
388 if ((tp->t_flags & TF_ENCLOSESEG) &&
389 SEQ_GT(qend, tp->encloseblk.rblk_end)) {
390 /* extend enclosing block if one exists */
391 tp->encloseblk.rblk_end = qend;
392 }
984263bc
MD
393 if (i < q->tqe_len) {
394 q->tqe_th->th_seq += i;
395 q->tqe_len -= i;
396 m_adj(q->tqe_m, i);
397 break;
398 }
399
400 nq = LIST_NEXT(q, tqe_q);
401 LIST_REMOVE(q, tqe_q);
402 m_freem(q->tqe_m);
efda3bd0 403 kfree(q, M_TSEGQ);
2d23a8be 404 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
405 q = nq;
406 }
407
408 /* Insert the new segment queue entry into place. */
409 te->tqe_m = m;
410 te->tqe_th = th;
411 te->tqe_len = *tlenp;
412
91489f6b
JH
413 /* check if can coalesce with following segment */
414 if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) {
415 tcp_seq tend = te->tqe_th->th_seq + te->tqe_len;
416
417 te->tqe_len += q->tqe_len;
a174690a 418 if (q->tqe_th->th_flags & TH_FIN)
f16f8cc3 419 te->tqe_th->th_flags |= TH_FIN;
91489f6b
JH
420 m_cat(te->tqe_m, q->tqe_m);
421 tp->encloseblk.rblk_end = tend;
422 /*
423 * When not reporting a duplicate segment, use
424 * the larger enclosing block as the SACK block.
425 */
426 if (!(tp->t_flags & TF_DUPSEG))
427 tp->reportblk.rblk_end = tend;
428 LIST_REMOVE(q, tqe_q);
efda3bd0 429 kfree(q, M_TSEGQ);
2d23a8be 430 atomic_add_int(&tcp_reass_qsize, -1);
91489f6b
JH
431 }
432
984263bc
MD
433 if (p == NULL) {
434 LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
435 } else {
91489f6b
JH
436 /* check if can coalesce with preceding segment */
437 if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) {
a174690a
JH
438 p->tqe_len += te->tqe_len;
439 m_cat(p->tqe_m, te->tqe_m);
91489f6b
JH
440 tp->encloseblk.rblk_start = p->tqe_th->th_seq;
441 /*
442 * When not reporting a duplicate segment, use
443 * the larger enclosing block as the SACK block.
444 */
445 if (!(tp->t_flags & TF_DUPSEG))
446 tp->reportblk.rblk_start = p->tqe_th->th_seq;
efda3bd0 447 kfree(te, M_TSEGQ);
2d23a8be
MD
448 atomic_add_int(&tcp_reass_qsize, -1);
449 } else {
91489f6b 450 LIST_INSERT_AFTER(p, te, tqe_q);
2d23a8be 451 }
984263bc
MD
452 }
453
454present:
455 /*
456 * Present data to user, advancing rcv_nxt through
457 * completed sequence space.
458 */
459 if (!TCPS_HAVEESTABLISHED(tp->t_state))
460 return (0);
461 q = LIST_FIRST(&tp->t_segq);
61896e3c 462 if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt)
984263bc 463 return (0);
91489f6b
JH
464 tp->rcv_nxt += q->tqe_len;
465 if (!(tp->t_flags & TF_DUPSEG)) {
466 /* no SACK block to report since ACK advanced */
467 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
468 }
469 /* no enclosing block to report since ACK advanced */
470 tp->t_flags &= ~TF_ENCLOSESEG;
471 flags = q->tqe_th->th_flags & TH_FIN;
472 LIST_REMOVE(q, tqe_q);
473 KASSERT(LIST_EMPTY(&tp->t_segq) ||
474 LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt,
475 ("segment not coalesced"));
6cef7136 476 if (so->so_state & SS_CANTRCVMORE) {
91489f6b 477 m_freem(q->tqe_m);
6cef7136
MD
478 } else {
479 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 480 ssb_appendstream(&so->so_rcv, q->tqe_m);
6cef7136
MD
481 lwkt_reltoken(&so->so_rcv.ssb_token);
482 }
efda3bd0 483 kfree(q, M_TSEGQ);
2d23a8be 484 atomic_add_int(&tcp_reass_qsize, -1);
984263bc
MD
485 ND6_HINT(tp);
486 sorwakeup(so);
487 return (flags);
488}
489
490/*
491 * TCP input routine, follows pages 65-76 of the
492 * protocol specification dated September, 1981 very closely.
493 */
494#ifdef INET6
495int
95b22adf 496tcp6_input(struct mbuf **mp, int *offp, int proto)
984263bc 497{
2256ba69 498 struct mbuf *m = *mp;
984263bc
MD
499 struct in6_ifaddr *ia6;
500
501 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
502
503 /*
504 * draft-itojun-ipv6-tcp-to-anycast
505 * better place to put this in?
506 */
507 ia6 = ip6_getdstifaddr(m);
d24ce1dc 508 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
984263bc
MD
509 struct ip6_hdr *ip6;
510
511 ip6 = mtod(m, struct ip6_hdr *);
512 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
f23061d4 513 offsetof(struct ip6_hdr, ip6_dst));
d24ce1dc 514 return (IPPROTO_DONE);
984263bc
MD
515 }
516
002c1265 517 tcp_input(mp, offp, proto);
d24ce1dc 518 return (IPPROTO_DONE);
984263bc
MD
519}
520#endif
521
002c1265
MD
522int
523tcp_input(struct mbuf **mp, int *offp, int proto)
984263bc 524{
002c1265 525 int off0;
2256ba69
RG
526 struct tcphdr *th;
527 struct ip *ip = NULL;
528 struct ipovly *ipov;
529 struct inpcb *inp = NULL;
984263bc
MD
530 u_char *optp = NULL;
531 int optlen = 0;
b1992928
MD
532 int tlen, off;
533 int len = 0;
984263bc 534 int drop_hdrlen;
2256ba69
RG
535 struct tcpcb *tp = NULL;
536 int thflags;
984263bc 537 struct socket *so = 0;
61896e3c
JH
538 int todrop, acked;
539 boolean_t ourfinisacked, needoutput = FALSE;
984263bc 540 u_long tiwin;
61896e3c 541 int recvwin;
984263bc 542 struct tcpopt to; /* options in this segment */
984263bc
MD
543 struct sockaddr_in *next_hop = NULL;
544 int rstreason; /* For badport_bandlim accounting purposes */
d371a63a 545 int cpu;
984263bc 546 struct ip6_hdr *ip6 = NULL;
002c1265 547 struct mbuf *m;
984263bc 548#ifdef INET6
d24ce1dc 549 boolean_t isipv6;
984263bc 550#else
d24ce1dc 551 const boolean_t isipv6 = FALSE;
984263bc
MD
552#endif
553#ifdef TCPDEBUG
554 short ostate = 0;
555#endif
556
002c1265
MD
557 off0 = *offp;
558 m = *mp;
559 *mp = NULL;
a00138cb 560
d24ce1dc
JH
561 tcpstat.tcps_rcvtotal++;
562
5de23090
SZ
563 if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) {
564 struct m_tag *mtag;
565
566 mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
567 KKASSERT(mtag != NULL);
568 next_hop = m_tag_data(mtag);
984263bc 569 }
d24ce1dc 570
984263bc 571#ifdef INET6
d24ce1dc 572 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE;
984263bc 573#endif
984263bc
MD
574
575 if (isipv6) {
576 /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */
577 ip6 = mtod(m, struct ip6_hdr *);
407e896e 578 tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0;
984263bc
MD
579 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
580 tcpstat.tcps_rcvbadsum++;
581 goto drop;
582 }
583 th = (struct tcphdr *)((caddr_t)ip6 + off0);
584
585 /*
586 * Be proactive about unspecified IPv6 address in source.
587 * As we use all-zero to indicate unbounded/unconnected pcb,
588 * unspecified IPv6 address can be used to confuse us.
589 *
590 * Note that packets with unspecified IPv6 destination is
591 * already dropped in ip6_input.
592 */
593 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
594 /* XXX stat */
595 goto drop;
596 }
597 } else {
598 /*
599 * Get IP and TCP header together in first mbuf.
600 * Note: IP leaves IP header in first mbuf.
601 */
602 if (off0 > sizeof(struct ip)) {
bddf0751 603 ip_stripoptions(m);
984263bc
MD
604 off0 = sizeof(struct ip);
605 }
55d829f8
JH
606 /* already checked and pulled up in ip_demux() */
607 KASSERT(m->m_len >= sizeof(struct tcpiphdr),
61896e3c 608 ("TCP header not in one mbuf: m->m_len %d", m->m_len));
984263bc
MD
609 ip = mtod(m, struct ip *);
610 ipov = (struct ipovly *)ip;
611 th = (struct tcphdr *)((caddr_t)ip + off0);
612 tlen = ip->ip_len;
613
614 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
615 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
616 th->th_sum = m->m_pkthdr.csum_data;
617 else
618 th->th_sum = in_pseudo(ip->ip_src.s_addr,
619 ip->ip_dst.s_addr,
620 htonl(m->m_pkthdr.csum_data +
621 ip->ip_len +
622 IPPROTO_TCP));
623 th->th_sum ^= 0xffff;
624 } else {
625 /*
626 * Checksum extended TCP header and data.
627 */
628 len = sizeof(struct ip) + tlen;
407e896e 629 bzero(ipov->ih_x1, sizeof ipov->ih_x1);
984263bc
MD
630 ipov->ih_len = (u_short)tlen;
631 ipov->ih_len = htons(ipov->ih_len);
632 th->th_sum = in_cksum(m, len);
633 }
634 if (th->th_sum) {
635 tcpstat.tcps_rcvbadsum++;
636 goto drop;
637 }
638#ifdef INET6
639 /* Re-initialization for later version check */
640 ip->ip_v = IPVERSION;
641#endif
642 }
643
644 /*
645 * Check that TCP offset makes sense,
646 * pull out TCP options and adjust length. XXX
647 */
648 off = th->th_off << 2;
55d829f8
JH
649 /* already checked and pulled up in ip_demux() */
650 KASSERT(off >= sizeof(struct tcphdr) && off <= tlen,
61896e3c 651 ("bad TCP data offset %d (tlen %d)", off, tlen));
984263bc
MD
652 tlen -= off; /* tlen is used instead of ti->ti_len */
653 if (off > sizeof(struct tcphdr)) {
654 if (isipv6) {
002c1265 655 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
984263bc
MD
656 ip6 = mtod(m, struct ip6_hdr *);
657 th = (struct tcphdr *)((caddr_t)ip6 + off0);
658 } else {
55d829f8
JH
659 /* already pulled up in ip_demux() */
660 KASSERT(m->m_len >= sizeof(struct ip) + off,
61896e3c
JH
661 ("TCP header and options not in one mbuf: "
662 "m_len %d, off %d", m->m_len, off));
984263bc
MD
663 }
664 optlen = off - sizeof(struct tcphdr);
665 optp = (u_char *)(th + 1);
666 }
667 thflags = th->th_flags;
668
669#ifdef TCP_DROP_SYNFIN
670 /*
671 * If the drop_synfin option is enabled, drop all packets with
672 * both the SYN and FIN bits set. This prevents e.g. nmap from
673 * identifying the TCP/IP stack.
674 *
675 * This is a violation of the TCP specification.
676 */
61896e3c 677 if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN))
984263bc
MD
678 goto drop;
679#endif
680
681 /*
682 * Convert TCP protocol specific fields to host format.
683 */
684 th->th_seq = ntohl(th->th_seq);
685 th->th_ack = ntohl(th->th_ack);
686 th->th_win = ntohs(th->th_win);
687 th->th_urp = ntohs(th->th_urp);
688
689 /*
d24ce1dc 690 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options,
984263bc
MD
691 * until after ip6_savecontrol() is called and before other functions
692 * which don't want those proto headers.
693 * Because ip6_savecontrol() is going to parse the mbuf to
694 * search for data to be passed up to user-land, it wants mbuf
695 * parameters to be unchanged.
696 * XXX: the call of ip6_savecontrol() has been obsoleted based on
697 * latest version of the advanced API (20020110).
698 */
699 drop_hdrlen = off0 + off;
700
701 /*
702 * Locate pcb for segment.
703 */
704findpcb:
705 /* IPFIREWALL_FORWARD section */
d24ce1dc 706 if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */
984263bc
MD
707 /*
708 * Transparently forwarded. Pretend to be the destination.
d24ce1dc 709 * already got one like this?
984263bc 710 */
6ca1a1cd 711 cpu = mycpu->gd_cpuid;
6ca1a1cd 712 inp = in_pcblookup_hash(&tcbinfo[cpu],
d371a63a 713 ip->ip_src, th->th_sport,
984263bc
MD
714 ip->ip_dst, th->th_dport,
715 0, m->m_pkthdr.rcvif);
716 if (!inp) {
83be63fe
JH
717 /*
718 * It's new. Try to find the ambushing socket.
719 */
720
721 /*
722 * The rest of the ipfw code stores the port in
723 * host order. XXX
724 * (The IP address is still in network order.)
725 */
726 in_port_t dport = next_hop->sin_port ?
727 htons(next_hop->sin_port) :
728 th->th_dport;
729
d371a63a 730 cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport,
83be63fe 731 next_hop->sin_addr.s_addr, dport);
d371a63a 732 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc 733 ip->ip_src, th->th_sport,
83be63fe 734 next_hop->sin_addr, dport,
984263bc
MD
735 1, m->m_pkthdr.rcvif);
736 }
737 } else {
6ca1a1cd 738 if (isipv6) {
d371a63a 739 inp = in6_pcblookup_hash(&tcbinfo[0],
984263bc
MD
740 &ip6->ip6_src, th->th_sport,
741 &ip6->ip6_dst, th->th_dport,
742 1, m->m_pkthdr.rcvif);
6ca1a1cd 743 } else {
6ca1a1cd 744 cpu = mycpu->gd_cpuid;
6ca1a1cd 745 inp = in_pcblookup_hash(&tcbinfo[cpu],
984263bc
MD
746 ip->ip_src, th->th_sport,
747 ip->ip_dst, th->th_dport,
748 1, m->m_pkthdr.rcvif);
6ca1a1cd 749 }
984263bc 750 }
984263bc
MD
751
752 /*
753 * If the state is CLOSED (i.e., TCB does not exist) then
754 * all data in the incoming segment is discarded.
755 * If the TCB exists but is in CLOSED state, it is embryonic,
756 * but should either do a listen or a connect soon.
757 */
758 if (inp == NULL) {
759 if (log_in_vain) {
760#ifdef INET6
761 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
762#else
1141eb20
JH
763 char dbuf[sizeof "aaa.bbb.ccc.ddd"];
764 char sbuf[sizeof "aaa.bbb.ccc.ddd"];
984263bc
MD
765#endif
766 if (isipv6) {
767 strcpy(dbuf, "[");
984263bc 768 strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
984263bc 769 strcat(dbuf, "]");
95b22adf
JH
770 strcpy(sbuf, "[");
771 strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
984263bc
MD
772 strcat(sbuf, "]");
773 } else {
774 strcpy(dbuf, inet_ntoa(ip->ip_dst));
775 strcpy(sbuf, inet_ntoa(ip->ip_src));
776 }
777 switch (log_in_vain) {
778 case 1:
61896e3c 779 if (!(thflags & TH_SYN))
984263bc
MD
780 break;
781 case 2:
782 log(LOG_INFO,
783 "Connection attempt to TCP %s:%d "
784 "from %s:%d flags:0x%02x\n",
785 dbuf, ntohs(th->th_dport), sbuf,
786 ntohs(th->th_sport), thflags);
787 break;
788 default:
789 break;
790 }
791 }
d24ce1dc 792 if (blackhole) {
984263bc
MD
793 switch (blackhole) {
794 case 1:
795 if (thflags & TH_SYN)
796 goto drop;
797 break;
798 case 2:
799 goto drop;
800 default:
801 goto drop;
802 }
803 }
804 rstreason = BANDLIM_RST_CLOSEDPORT;
805 goto dropwithreset;
806 }
61896e3c
JH
807
808#ifdef IPSEC
809 if (isipv6) {
810 if (ipsec6_in_reject_so(m, inp->inp_socket)) {
811 ipsec6stat.in_polvio++;
812 goto drop;
813 }
814 } else {
815 if (ipsec4_in_reject_so(m, inp->inp_socket)) {
816 ipsecstat.in_polvio++;
817 goto drop;
818 }
819 }
820#endif
821#ifdef FAST_IPSEC
822 if (isipv6) {
823 if (ipsec6_in_reject(m, inp))
824 goto drop;
825 } else {
826 if (ipsec4_in_reject(m, inp))
827 goto drop;
828 }
829#endif
95926362
MD
830 /* Check the minimum TTL for socket. */
831#ifdef INET6
832 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl)
833 goto drop;
834#endif
61896e3c 835
984263bc
MD
836 tp = intotcpcb(inp);
837 if (tp == NULL) {
838 rstreason = BANDLIM_RST_CLOSEDPORT;
839 goto dropwithreset;
840 }
eb594563 841 if (tp->t_state <= TCPS_CLOSED)
984263bc
MD
842 goto drop;
843
844 /* Unscale the window into a 32-bit value. */
95b22adf 845 if (!(thflags & TH_SYN))
984263bc
MD
846 tiwin = th->th_win << tp->snd_scale;
847 else
848 tiwin = th->th_win;
849
850 so = inp->inp_socket;
47654766 851
984263bc 852#ifdef TCPDEBUG
47654766
JH
853 if (so->so_options & SO_DEBUG) {
854 ostate = tp->t_state;
855 if (isipv6)
95b22adf 856 bcopy(ip6, tcp_saveipgen, sizeof(*ip6));
47654766 857 else
95b22adf 858 bcopy(ip, tcp_saveipgen, sizeof(*ip));
47654766
JH
859 tcp_savetcp = *th;
860 }
984263bc 861#endif
47654766 862
407e896e 863 bzero(&to, sizeof to);
d24ce1dc 864
47654766
JH
865 if (so->so_options & SO_ACCEPTCONN) {
866 struct in_conninfo inc;
867
984263bc 868#ifdef INET6
d24ce1dc 869 inc.inc_isipv6 = (isipv6 == TRUE);
984263bc
MD
870#endif
871 if (isipv6) {
872 inc.inc6_faddr = ip6->ip6_src;
873 inc.inc6_laddr = ip6->ip6_dst;
874 inc.inc6_route.ro_rt = NULL; /* XXX */
875 } else {
876 inc.inc_faddr = ip->ip_src;
877 inc.inc_laddr = ip->ip_dst;
878 inc.inc_route.ro_rt = NULL; /* XXX */
879 }
880 inc.inc_fport = th->th_sport;
881 inc.inc_lport = th->th_dport;
882
61896e3c
JH
883 /*
884 * If the state is LISTEN then ignore segment if it contains
984263bc
MD
885 * a RST. If the segment contains an ACK then it is bad and
886 * send a RST. If it does not contain a SYN then it is not
887 * interesting; drop it.
888 *
889 * If the state is SYN_RECEIVED (syncache) and seg contains
890 * an ACK, but not for our SYN/ACK, send a RST. If the seg
891 * contains a RST, check the sequence number to see if it
892 * is a valid reset segment.
893 */
61896e3c
JH
894 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) {
895 if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) {
984263bc
MD
896 if (!syncache_expand(&inc, th, &so, m)) {
897 /*
898 * No syncache entry, or ACK was not
899 * for our SYN/ACK. Send a RST.
900 */
901 tcpstat.tcps_badsyn++;
902 rstreason = BANDLIM_RST_OPENPORT;
903 goto dropwithreset;
904 }
2d23a8be
MD
905
906 /*
907 * Could not complete 3-way handshake,
908 * connection is being closed down, and
909 * syncache will free mbuf.
910 */
984263bc 911 if (so == NULL)
002c1265 912 return(IPPROTO_DONE);
2d23a8be
MD
913
914 /*
915 * We must be in the correct protocol thread
916 * for this connection.
917 */
918 KKASSERT(so->so_port == &curthread->td_msgport);
919
984263bc
MD
920 /*
921 * Socket is created in state SYN_RECEIVED.
922 * Continue processing segment.
923 */
ed894f8c 924 inp = so->so_pcb;
984263bc
MD
925 tp = intotcpcb(inp);
926 /*
927 * This is what would have happened in
928 * tcp_output() when the SYN,ACK was sent.
929 */
930 tp->snd_up = tp->snd_una;
931 tp->snd_max = tp->snd_nxt = tp->iss + 1;
932 tp->last_ack_sent = tp->rcv_nxt;
933/*
934 * XXX possible bug - it doesn't appear that tp->snd_wnd is unscaled
935 * until the _second_ ACK is received:
936 * rcv SYN (set wscale opts) --> send SYN/ACK, set snd_wnd = window.
937 * rcv ACK, calculate tiwin --> process SYN_RECEIVED, determine wscale,
61896e3c 938 * move to ESTAB, set snd_wnd to tiwin.
d24ce1dc 939 */
984263bc
MD
940 tp->snd_wnd = tiwin; /* unscaled */
941 goto after_listen;
942 }
943 if (thflags & TH_RST) {
944 syncache_chkrst(&inc, th);
945 goto drop;
946 }
947 if (thflags & TH_ACK) {
948 syncache_badack(&inc);
949 tcpstat.tcps_badsyn++;
950 rstreason = BANDLIM_RST_OPENPORT;
951 goto dropwithreset;
952 }
953 goto drop;
954 }
955
956 /*
61896e3c 957 * Segment's flags are (SYN) or (SYN | FIN).
984263bc
MD
958 */
959#ifdef INET6
960 /*
961 * If deprecated address is forbidden,
962 * we do not accept SYN to deprecated interface
963 * address to prevent any new inbound connection from
964 * getting established.
965 * When we do not accept SYN, we send a TCP RST,
966 * with deprecated source address (instead of dropping
967 * it). We compromise it as it is much better for peer
968 * to send a RST, and RST will be the final packet
969 * for the exchange.
970 *
971 * If we do not forbid deprecated addresses, we accept
972 * the SYN packet. RFC2462 does not suggest dropping
973 * SYN in this case.
974 * If we decipher RFC2462 5.5.4, it says like this:
975 * 1. use of deprecated addr with existing
976 * communication is okay - "SHOULD continue to be
977 * used"
978 * 2. use of it with new communication:
979 * (2a) "SHOULD NOT be used if alternate address
61896e3c 980 * with sufficient scope is available"
984263bc
MD
981 * (2b) nothing mentioned otherwise.
982 * Here we fall into (2b) case as we have no choice in
983 * our source address selection - we must obey the peer.
984 *
985 * The wording in RFC2462 is confusing, and there are
986 * multiple description text for deprecated address
987 * handling - worse, they are not exactly the same.
988 * I believe 5.5.4 is the best one, so we follow 5.5.4.
989 */
990 if (isipv6 && !ip6_use_deprecated) {
991 struct in6_ifaddr *ia6;
992
993 if ((ia6 = ip6_getdstifaddr(m)) &&
994 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
995 tp = NULL;
996 rstreason = BANDLIM_RST_OPENPORT;
997 goto dropwithreset;
998 }
999 }
1000#endif
1001 /*
1002 * If it is from this socket, drop it, it must be forged.
1003 * Don't bother responding if the destination was a broadcast.
1004 */
1005 if (th->th_dport == th->th_sport) {
1006 if (isipv6) {
1007 if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
1008 &ip6->ip6_src))
1009 goto drop;
1010 } else {
1011 if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
1012 goto drop;
1013 }
1014 }
1015 /*
1016 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
1017 *
1018 * Note that it is quite possible to receive unicast
1019 * link-layer packets with a broadcast IP address. Use
1020 * in_broadcast() to find them.
1021 */
61896e3c 1022 if (m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
1023 goto drop;
1024 if (isipv6) {
1025 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1026 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
1027 goto drop;
1028 } else {
1029 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1030 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1031 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1032 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
1033 goto drop;
1034 }
1035 /*
1036 * SYN appears to be valid; create compressed TCP state
1037 * for syncache, or perform t/tcp connection.
1038 */
1039 if (so->so_qlen <= so->so_qlimit) {
95b22adf 1040 tcp_dooptions(&to, optp, optlen, TRUE);
984263bc
MD
1041 if (!syncache_add(&inc, &to, th, &so, m))
1042 goto drop;
2d23a8be
MD
1043
1044 /*
1045 * Entry added to syncache, mbuf used to
1046 * send SYN,ACK packet.
1047 */
984263bc 1048 if (so == NULL)
002c1265 1049 return(IPPROTO_DONE);
2d23a8be
MD
1050
1051 /*
1052 * We must be in the correct protocol thread for
1053 * this connection.
1054 */
1055 KKASSERT(so->so_port == &curthread->td_msgport);
1056
ed894f8c 1057 inp = so->so_pcb;
984263bc
MD
1058 tp = intotcpcb(inp);
1059 tp->snd_wnd = tiwin;
1060 tp->t_starttime = ticks;
1061 tp->t_state = TCPS_ESTABLISHED;
1062
1063 /*
1064 * If there is a FIN, or if there is data and the
1065 * connection is local, then delay SYN,ACK(SYN) in
1066 * the hope of piggy-backing it on a response
1067 * segment. Otherwise must send ACK now in case
1068 * the other side is slow starting.
1069 */
1070 if (DELAY_ACK(tp) &&
1071 ((thflags & TH_FIN) ||
1072 (tlen != 0 &&
1073 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
1074 (!isipv6 && in_localaddr(inp->inp_faddr)))))) {
a48c5dd5
SZ
1075 tcp_callout_reset(tp, tp->tt_delack,
1076 tcp_delacktime, tcp_timer_delack);
984263bc 1077 tp->t_flags |= TF_NEEDSYN;
a48c5dd5 1078 } else {
984263bc 1079 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
a48c5dd5 1080 }
984263bc
MD
1081
1082 tcpstat.tcps_connects++;
1083 soisconnected(so);
1084 goto trimthenstep6;
1085 }
1086 goto drop;
1087 }
984263bc 1088
2d23a8be
MD
1089after_listen:
1090 /*
1091 * Should not happen - syncache should pick up these connections.
1092 *
1093 * Once we are past handling listen sockets we must be in the
1094 * correct protocol processing thread.
1095 */
61896e3c 1096 KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state"));
2d23a8be 1097 KKASSERT(so->so_port == &curthread->td_msgport);
984263bc 1098
5b0b9fa5
PA
1099 /*
1100 * This is the second part of the MSS DoS prevention code (after
1101 * minmss on the sending side) and it deals with too many too small
1102 * tcp packets in a too short timeframe (1 second).
1103 *
153d34ac
MD
1104 * XXX Removed. This code was crap. It does not scale to network
1105 * speed, and default values break NFS. Gone.
5b0b9fa5 1106 */
153d34ac 1107 /* REMOVED */
5b0b9fa5 1108
984263bc
MD
1109 /*
1110 * Segment received on connection.
efca2b8e
MD
1111 *
1112 * Reset idle time and keep-alive timer. Don't waste time if less
0ecd93f9 1113 * then a second has elapsed.
984263bc 1114 */
0ecd93f9
MD
1115 if ((int)(ticks - tp->t_rcvtime) > hz)
1116 tcp_timer_keep_activity(tp, thflags);
984263bc
MD
1117
1118 /*
1119 * Process options.
1120 * XXX this is tradtitional behavior, may need to be cleaned up.
1121 */
95b22adf 1122 tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0);
ad0af98b 1123 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
984263bc
MD
1124 if (to.to_flags & TOF_SCALE) {
1125 tp->t_flags |= TF_RCVD_SCALE;
1126 tp->requested_s_scale = to.to_requested_s_scale;
1127 }
1128 if (to.to_flags & TOF_TS) {
1129 tp->t_flags |= TF_RCVD_TSTMP;
1130 tp->ts_recent = to.to_tsval;
1131 tp->ts_recent_age = ticks;
1132 }
984263bc
MD
1133 if (to.to_flags & TOF_MSS)
1134 tcp_mss(tp, to.to_mss);
91489f6b
JH
1135 /*
1136 * Only set the TF_SACK_PERMITTED per-connection flag
1137 * if we got a SACK_PERMITTED option from the other side
1138 * and the global tcp_do_sack variable is true.
1139 */
1140 if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED))
1141 tp->t_flags |= TF_SACK_PERMITTED;
984263bc
MD
1142 }
1143
1144 /*
1145 * Header prediction: check for the two common cases
1146 * of a uni-directional data xfer. If the packet has
1147 * no control flags, is in-sequence, the window didn't
1148 * change and we're not retransmitting, it's a
1149 * candidate. If the length is zero and the ack moved
1150 * forward, we're the sender side of the xfer. Just
1151 * free the data acked & wake any higher level process
1152 * that was blocked waiting for space. If the length
1153 * is non-zero and the ack didn't move, we're the
1154 * receiver side. If we're getting packets in-order
1155 * (the reassembly queue is empty), add the data to
1156 * the socket buffer and note that we need a delayed ack.
1157 * Make sure that the hidden state-flags are also off.
1158 * Since we check for TCPS_ESTABLISHED above, it can only
1159 * be TH_NEEDSYN.
1160 */
1161 if (tp->t_state == TCPS_ESTABLISHED &&
1162 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
61896e3c
JH
1163 !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) &&
1164 (!(to.to_flags & TOF_TS) ||
984263bc 1165 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
984263bc 1166 th->th_seq == tp->rcv_nxt &&
984263bc
MD
1167 tp->snd_nxt == tp->snd_max) {
1168
1169 /*
1170 * If last ACK falls within this segment's sequence numbers,
1171 * record the timestamp.
1172 * NOTE that the test is modified according to the latest
1173 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1174 */
61896e3c 1175 if ((to.to_flags & TOF_TS) &&
984263bc
MD
1176 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1177 tp->ts_recent_age = ticks;
1178 tp->ts_recent = to.to_tsval;
1179 }
1180
1181 if (tlen == 0) {
1182 if (SEQ_GT(th->th_ack, tp->snd_una) &&
1183 SEQ_LEQ(th->th_ack, tp->snd_max) &&
1184 tp->snd_cwnd >= tp->snd_wnd &&
95b22adf 1185 !IN_FASTRECOVERY(tp)) {
984263bc 1186 /*
be23faf1 1187 * This is a pure ack for outstanding data.
984263bc
MD
1188 */
1189 ++tcpstat.tcps_predack;
1190 /*
1191 * "bad retransmit" recovery
bfdb979e
JH
1192 *
1193 * If Eifel detection applies, then
1194 * it is deterministic, so use it
1195 * unconditionally over the old heuristic.
1196 * Otherwise, fall back to the old heuristic.
984263bc 1197 */
bfdb979e
JH
1198 if (tcp_do_eifel_detect &&
1199 (to.to_flags & TOF_TS) && to.to_tsecr &&
1200 (tp->t_flags & TF_FIRSTACCACK)) {
1201 /* Eifel detection applicable. */
1202 if (to.to_tsecr < tp->t_rexmtTS) {
1203 tcp_revert_congestion_state(tp);
1204 ++tcpstat.tcps_eifeldetected;
1205 }
1206 } else if (tp->t_rxtshift == 1 &&
1207 ticks < tp->t_badrxtwin) {
1208 tcp_revert_congestion_state(tp);
1209 ++tcpstat.tcps_rttdetected;
984263bc 1210 }
8819433a
JH
1211 tp->t_flags &= ~(TF_FIRSTACCACK |
1212 TF_FASTREXMT | TF_EARLYREXMT);
984263bc
MD
1213 /*
1214 * Recalculate the retransmit timer / rtt.
1215 *
d24ce1dc 1216 * Some machines (certain windows boxes)
984263bc
MD
1217 * send broken timestamp replies during the
1218 * SYN+ACK phase, ignore timestamps of 0.
1219 */
95b22adf 1220 if ((to.to_flags & TOF_TS) && to.to_tsecr) {
984263bc 1221 tcp_xmit_timer(tp,
95b22adf 1222 ticks - to.to_tsecr + 1);
984263bc 1223 } else if (tp->t_rtttime &&
95b22adf 1224 SEQ_GT(th->th_ack, tp->t_rtseq)) {
984263bc
MD
1225 tcp_xmit_timer(tp,
1226 ticks - tp->t_rtttime);
1227 }
1228 tcp_xmit_bandwidth_limit(tp, th->th_ack);
1229 acked = th->th_ack - tp->snd_una;
1230 tcpstat.tcps_rcvackpack++;
1231 tcpstat.tcps_rcvackbyte += acked;
6d49aa6f 1232 sbdrop(&so->so_snd.sb, acked);
cfb3f3f4 1233 tp->snd_recover = th->th_ack - 1;
9845754e 1234 tp->snd_una = th->th_ack;
984263bc 1235 tp->t_dupacks = 0;
df9d7670
JH
1236 /*
1237 * Update window information.
1238 */
1239 if (tiwin != tp->snd_wnd &&
1240 acceptable_window_update(tp, th, tiwin)) {
1241 /* keep track of pure window updates */
1242 if (tp->snd_wl2 == th->th_ack &&
1243 tiwin > tp->snd_wnd)
1244 tcpstat.tcps_rcvwinupd++;
1245 tp->snd_wnd = tiwin;
1246 tp->snd_wl1 = th->th_seq;
1247 tp->snd_wl2 = th->th_ack;
1248 if (tp->snd_wnd > tp->max_sndwnd)
1249 tp->max_sndwnd = tp->snd_wnd;
1250 }
984263bc
MD
1251 m_freem(m);
1252 ND6_HINT(tp); /* some progress has been done */
984263bc
MD
1253 /*
1254 * If all outstanding data are acked, stop
1255 * retransmit timer, otherwise restart timer
1256 * using current (possibly backed-off) value.
1257 * If process is waiting for space,
1258 * wakeup/selwakeup/signal. If data
1259 * are ready to send, let tcp_output
1260 * decide between more output or persist.
1261 */
a48c5dd5
SZ
1262 if (tp->snd_una == tp->snd_max) {
1263 tcp_callout_stop(tp, tp->tt_rexmt);
1264 } else if (!tcp_callout_active(tp,
1265 tp->tt_persist)) {
1266 tcp_callout_reset(tp, tp->tt_rexmt,
1267 tp->t_rxtcur, tcp_timer_rexmt);
1268 }
984263bc 1269 sowwakeup(so);
6d49aa6f 1270 if (so->so_snd.ssb_cc > 0)
f23061d4 1271 tcp_output(tp);
002c1265 1272 return(IPPROTO_DONE);
984263bc 1273 }
df9d7670
JH
1274 } else if (tiwin == tp->snd_wnd &&
1275 th->th_ack == tp->snd_una &&
984263bc 1276 LIST_EMPTY(&tp->t_segq) &&
6d49aa6f 1277 tlen <= ssb_space(&so->so_rcv)) {
46e92930 1278 u_long newsize = 0; /* automatic sockbuf scaling */
984263bc 1279 /*
be23faf1 1280 * This is a pure, in-sequence data packet
984263bc
MD
1281 * with nothing on the reassembly queue and
1282 * we have enough buffer space to take it.
1283 */
1284 ++tcpstat.tcps_preddat;
1285 tp->rcv_nxt += tlen;
1286 tcpstat.tcps_rcvpack++;
1287 tcpstat.tcps_rcvbyte += tlen;
1288 ND6_HINT(tp); /* some progress has been done */
5b0b9fa5
PA
1289 /*
1290 * Automatic sizing of receive socket buffer. Often the send
1291 * buffer size is not optimally adjusted to the actual network
1292 * conditions at hand (delay bandwidth product). Setting the
1293 * buffer size too small limits throughput on links with high
1294 * bandwidth and high delay (eg. trans-continental/oceanic links).
1295 *
1296 * On the receive side the socket buffer memory is only rarely
1297 * used to any significant extent. This allows us to be much
1298 * more aggressive in scaling the receive socket buffer. For
1299 * the case that the buffer space is actually used to a large
1300 * extent and we run out of kernel memory we can simply drop
1301 * the new segments; TCP on the sender will just retransmit it
1302 * later. Setting the buffer size too big may only consume too
1303 * much kernel memory if the application doesn't read() from
1304 * the socket or packet loss or reordering makes use of the
1305 * reassembly queue.
1306 *
1307 * The criteria to step up the receive buffer one notch are:
1308 * 1. the number of bytes received during the time it takes
1309 * one timestamp to be reflected back to us (the RTT);
1310 * 2. received bytes per RTT is within seven eighth of the
1311 * current socket buffer size;
1312 * 3. receive buffer size has not hit maximal automatic size;
1313 *
1314 * This algorithm does one step per RTT at most and only if
1315 * we receive a bulk stream w/o packet losses or reorderings.
1316 * Shrinking the buffer during idle times is not necessary as
1317 * it doesn't consume any memory when idle.
1318 *
1319 * TODO: Only step up if the application is actually serving
1320 * the buffer to better manage the socket buffer resources.
1321 */
1322 if (tcp_do_autorcvbuf &&
1323 to.to_tsecr &&
1324 (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) {
1325 if (to.to_tsecr > tp->rfbuf_ts &&
1326 to.to_tsecr - tp->rfbuf_ts < hz) {
1327 if (tp->rfbuf_cnt >
1328 (so->so_rcv.ssb_hiwat / 8 * 7) &&
1329 so->so_rcv.ssb_hiwat <
1330 tcp_autorcvbuf_max) {
1331 newsize =
46e92930
MD
1332 ulmin(so->so_rcv.ssb_hiwat +
1333 tcp_autorcvbuf_inc,
1334 tcp_autorcvbuf_max);
5b0b9fa5
PA
1335 }
1336 /* Start over with next RTT. */
1337 tp->rfbuf_ts = 0;
1338 tp->rfbuf_cnt = 0;
1339 } else
1340 tp->rfbuf_cnt += tlen; /* add up */
1341 }
984263bc
MD
1342 /*
1343 * Add data to socket buffer.
1344 */
1345 if (so->so_state & SS_CANTRCVMORE) {
1346 m_freem(m);
1347 } else {
5b0b9fa5 1348 /*
46e92930
MD
1349 * Set new socket buffer size, give up when
1350 * limit is reached.
1351 *
1352 * Adjusting the size can mess up ACK
1353 * sequencing when pure window updates are
1354 * being avoided (which is the default),
1355 * so force an ack.
5b0b9fa5 1356 */
6cef7136 1357 lwkt_gettoken(&so->so_rcv.ssb_token);
46e92930
MD
1358 if (newsize) {
1359 tp->t_flags |= TF_RXRESIZED;
5b0b9fa5 1360 if (!ssb_reserve(&so->so_rcv, newsize,
46e92930 1361 so, NULL)) {
14343ad3 1362 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
46e92930
MD
1363 }
1364 if (newsize >=
1365 (TCP_MAXWIN << tp->rcv_scale)) {
14343ad3 1366 atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE);
46e92930
MD
1367 }
1368 }
09cf73e0 1369 m_adj(m, drop_hdrlen); /* delayed header drop */
6d49aa6f 1370 ssb_appendstream(&so->so_rcv, m);
6cef7136 1371 lwkt_reltoken(&so->so_rcv.ssb_token);
984263bc
MD
1372 }
1373 sorwakeup(so);
2b1ce38a
MD
1374 /*
1375 * This code is responsible for most of the ACKs
1376 * the TCP stack sends back after receiving a data
1377 * packet. Note that the DELAY_ACK check fails if
1378 * the delack timer is already running, which results
1379 * in an ack being sent every other packet (which is
1380 * what we want).
72b37eeb
MD
1381 *
1382 * We then further aggregate acks by not actually
1383 * sending one until the protocol thread has completed
1384 * processing the current backlog of packets. This
1385 * does not delay the ack any further, but allows us
1386 * to take advantage of the packet aggregation that
1387 * high speed NICs do (usually blocks of 8-10 packets)
1388 * to send a single ack rather then four or five acks,
1389 * greatly reducing the ack rate, the return channel
1390 * bandwidth, and the protocol overhead on both ends.
1391 *
1392 * Since this also has the effect of slowing down
1393 * the exponential slow-start ramp-up, systems with
1394 * very large bandwidth-delay products might want
1395 * to turn the feature off.
2b1ce38a 1396 */
984263bc 1397 if (DELAY_ACK(tp)) {
a48c5dd5
SZ
1398 tcp_callout_reset(tp, tp->tt_delack,
1399 tcp_delacktime, tcp_timer_delack);
72b37eeb 1400 } else if (tcp_aggregate_acks) {
984263bc 1401 tp->t_flags |= TF_ACKNOW;
61896e3c 1402 if (!(tp->t_flags & TF_ONOUTPUTQ)) {
2b1ce38a
MD
1403 tp->t_flags |= TF_ONOUTPUTQ;
1404 tp->tt_cpu = mycpu->gd_cpuid;
1405 TAILQ_INSERT_TAIL(
1406 &tcpcbackq[tp->tt_cpu],
1407 tp, t_outputq);
1408 }
72b37eeb
MD
1409 } else {
1410 tp->t_flags |= TF_ACKNOW;
1411 tcp_output(tp);
984263bc 1412 }
002c1265 1413 return(IPPROTO_DONE);
984263bc
MD
1414 }
1415 }
1416
1417 /*
1418 * Calculate amount of space in receive window,
1419 * and then do TCP input processing.
1420 * Receive window is amount of space in rcv queue,
1421 * but not less than advertised window.
1422 */
6d49aa6f 1423 recvwin = ssb_space(&so->so_rcv);
61896e3c
JH
1424 if (recvwin < 0)
1425 recvwin = 0;
1426 tp->rcv_wnd = imax(recvwin, (int)(tp->rcv_adv - tp->rcv_nxt));
984263bc 1427
5b0b9fa5
PA
1428 /* Reset receive buffer auto scaling when not in bulk receive mode. */
1429 tp->rfbuf_ts = 0;
1430 tp->rfbuf_cnt = 0;
1431
984263bc 1432 switch (tp->t_state) {
984263bc
MD
1433 /*
1434 * If the state is SYN_RECEIVED:
1435 * if seg contains an ACK, but not for our SYN/ACK, send a RST.
1436 */
1437 case TCPS_SYN_RECEIVED:
1438 if ((thflags & TH_ACK) &&
1439 (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1440 SEQ_GT(th->th_ack, tp->snd_max))) {
1441 rstreason = BANDLIM_RST_OPENPORT;
1442 goto dropwithreset;
1443 }
1444 break;
1445
1446 /*
1447 * If the state is SYN_SENT:
1448 * if seg contains an ACK, but not for our SYN, drop the input.
1449 * if seg contains a RST, then drop the connection.
1450 * if seg does not contain SYN, then drop it.
1451 * Otherwise this is an acceptable SYN segment
1452 * initialize tp->rcv_nxt and tp->irs
1453 * if seg contains ack then advance tp->snd_una
1454 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1455 * arrange for segment to be acked (eventually)
1456 * continue processing rest of data/controls, beginning with URG
1457 */
1458 case TCPS_SYN_SENT:
984263bc
MD
1459 if ((thflags & TH_ACK) &&
1460 (SEQ_LEQ(th->th_ack, tp->iss) ||
1461 SEQ_GT(th->th_ack, tp->snd_max))) {
27b8aee3
AE
1462 rstreason = BANDLIM_UNLIMITED;
1463 goto dropwithreset;
984263bc
MD
1464 }
1465 if (thflags & TH_RST) {
1466 if (thflags & TH_ACK)
1467 tp = tcp_drop(tp, ECONNREFUSED);
1468 goto drop;
1469 }
61896e3c 1470 if (!(thflags & TH_SYN))
984263bc
MD
1471 goto drop;
1472 tp->snd_wnd = th->th_win; /* initial send window */
984263bc
MD
1473
1474 tp->irs = th->th_seq;
1475 tcp_rcvseqinit(tp);
1476 if (thflags & TH_ACK) {
27b8aee3 1477 /* Our SYN was acked. */
984263bc
MD
1478 tcpstat.tcps_connects++;
1479 soisconnected(so);
1480 /* Do window scaling on this connection? */
61896e3c 1481 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1482 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1483 tp->snd_scale = tp->requested_s_scale;
1484 tp->rcv_scale = tp->request_r_scale;
1485 }
984263bc
MD
1486 tp->rcv_adv += tp->rcv_wnd;
1487 tp->snd_una++; /* SYN is acked */
a48c5dd5 1488 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
1489 /*
1490 * If there's data, delay ACK; if there's also a FIN
1491 * ACKNOW will be turned on later.
1492 */
a48c5dd5
SZ
1493 if (DELAY_ACK(tp) && tlen != 0) {
1494 tcp_callout_reset(tp, tp->tt_delack,
1495 tcp_delacktime, tcp_timer_delack);
1496 } else {
984263bc 1497 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1498 }
984263bc
MD
1499 /*
1500 * Received <SYN,ACK> in SYN_SENT[*] state.
1501 * Transitions:
1502 * SYN_SENT --> ESTABLISHED
1503 * SYN_SENT* --> FIN_WAIT_1
1504 */
1505 tp->t_starttime = ticks;
1506 if (tp->t_flags & TF_NEEDFIN) {
1507 tp->t_state = TCPS_FIN_WAIT_1;
1508 tp->t_flags &= ~TF_NEEDFIN;
1509 thflags &= ~TH_SYN;
1510 } else {
1511 tp->t_state = TCPS_ESTABLISHED;
2a0c7c52
MD
1512 tcp_callout_reset(tp, tp->tt_keep,
1513 tcp_getkeepidle(tp),
1514 tcp_timer_keep);
984263bc
MD
1515 }
1516 } else {
1517 /*
95b22adf 1518 * Received initial SYN in SYN-SENT[*] state =>
27b8aee3
AE
1519 * simultaneous open.
1520 * Do 3-way handshake:
61896e3c
JH
1521 * SYN-SENT -> SYN-RECEIVED
1522 * SYN-SENT* -> SYN-RECEIVED*
95b22adf 1523 */
984263bc 1524 tp->t_flags |= TF_ACKNOW;
a48c5dd5 1525 tcp_callout_stop(tp, tp->tt_rexmt);
27b8aee3 1526 tp->t_state = TCPS_SYN_RECEIVED;
984263bc
MD
1527 }
1528
1529trimthenstep6:
1530 /*
1531 * Advance th->th_seq to correspond to first data byte.
1532 * If data, trim to stay within window,
1533 * dropping FIN if necessary.
1534 */
1535 th->th_seq++;
1536 if (tlen > tp->rcv_wnd) {
1537 todrop = tlen - tp->rcv_wnd;
1538 m_adj(m, -todrop);
1539 tlen = tp->rcv_wnd;
1540 thflags &= ~TH_FIN;
1541 tcpstat.tcps_rcvpackafterwin++;
1542 tcpstat.tcps_rcvbyteafterwin += todrop;
1543 }
1544 tp->snd_wl1 = th->th_seq - 1;
1545 tp->rcv_up = th->th_seq;
1546 /*
1547 * Client side of transaction: already sent SYN and data.
1548 * If the remote host used T/TCP to validate the SYN,
1549 * our data will be ACK'd; if so, enter normal data segment
1550 * processing in the middle of step 5, ack processing.
1551 * Otherwise, goto step 6.
1552 */
95b22adf 1553 if (thflags & TH_ACK)
984263bc
MD
1554 goto process_ACK;
1555
1556 goto step6;
1557
1558 /*
1559 * If the state is LAST_ACK or CLOSING or TIME_WAIT:
27b8aee3 1560 * do normal processing (we no longer bother with T/TCP).
984263bc
MD
1561 */
1562 case TCPS_LAST_ACK:
1563 case TCPS_CLOSING:
1564 case TCPS_TIME_WAIT:
95b22adf 1565 break; /* continue normal processing */
984263bc
MD
1566 }
1567
1568 /*
1569 * States other than LISTEN or SYN_SENT.
1570 * First check the RST flag and sequence number since reset segments
1571 * are exempt from the timestamp and connection count tests. This
1572 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
1573 * below which allowed reset segments in half the sequence space
1574 * to fall though and be processed (which gives forged reset
1575 * segments with a random sequence number a 50 percent chance of
1576 * killing a connection).
1577 * Then check timestamp, if present.
1578 * Then check the connection count, if present.
1579 * Then check that at least some bytes of segment are within
1580 * receive window. If segment begins before rcv_nxt,
1581 * drop leading data (and SYN); if nothing left, just ack.
1582 *
1583 *
1584 * If the RST bit is set, check the sequence number to see
1585 * if this is a valid reset segment.
1586 * RFC 793 page 37:
1587 * In all states except SYN-SENT, all reset (RST) segments
1588 * are validated by checking their SEQ-fields. A reset is
1589 * valid if its sequence number is in the window.
1590 * Note: this does not take into account delayed ACKs, so
1591 * we should test against last_ack_sent instead of rcv_nxt.
1592 * The sequence number in the reset segment is normally an
91489f6b 1593 * echo of our outgoing acknowledgement numbers, but some hosts
984263bc
MD
1594 * send a reset with the sequence number at the rightmost edge
1595 * of our receive window, and we have to handle this case.
1596 * If we have multiple segments in flight, the intial reset
1597 * segment sequence numbers will be to the left of last_ack_sent,
1598 * but they will eventually catch up.
1599 * In any case, it never made sense to trim reset segments to
1600 * fit the receive window since RFC 1122 says:
1601 * 4.2.2.12 RST Segment: RFC-793 Section 3.4
1602 *
1603 * A TCP SHOULD allow a received RST segment to include data.
1604 *
1605 * DISCUSSION
61896e3c
JH
1606 * It has been suggested that a RST segment could contain
1607 * ASCII text that encoded and explained the cause of the
91489f6b 1608 * RST. No standard has yet been established for such
61896e3c 1609 * data.
984263bc
MD
1610 *
1611 * If the reset segment passes the sequence number test examine
1612 * the state:
1613 * SYN_RECEIVED STATE:
1614 * If passive open, return to LISTEN state.
1615 * If active open, inform user that connection was refused.
1616 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES:
1617 * Inform user that connection was reset, and close tcb.
1618 * CLOSING, LAST_ACK STATES:
1619 * Close the tcb.
1620 * TIME_WAIT STATE:
1621 * Drop the segment - see Stevens, vol. 2, p. 964 and
61896e3c 1622 * RFC 1337.
984263bc
MD
1623 */
1624 if (thflags & TH_RST) {
1625 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
d4dbb5be 1626 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
984263bc
MD
1627 switch (tp->t_state) {
1628
1629 case TCPS_SYN_RECEIVED:
1630 so->so_error = ECONNREFUSED;
1631 goto close;
1632
1633 case TCPS_ESTABLISHED:
1634 case TCPS_FIN_WAIT_1:
1635 case TCPS_FIN_WAIT_2:
1636 case TCPS_CLOSE_WAIT:
1637 so->so_error = ECONNRESET;
1638 close:
1639 tp->t_state = TCPS_CLOSED;
1640 tcpstat.tcps_drops++;
1641 tp = tcp_close(tp);
1642 break;
1643
1644 case TCPS_CLOSING:
1645 case TCPS_LAST_ACK:
1646 tp = tcp_close(tp);
1647 break;
1648
1649 case TCPS_TIME_WAIT:
1650 break;
1651 }
1652 }
1653 goto drop;
1654 }
1655
1656 /*
1657 * RFC 1323 PAWS: If we have a timestamp reply on this segment
1658 * and it's less than ts_recent, drop it.
1659 */
61896e3c 1660 if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 &&
984263bc
MD
1661 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
1662
1663 /* Check to see if ts_recent is over 24 days old. */
1664 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) {
1665 /*
1666 * Invalidate ts_recent. If this segment updates
1667 * ts_recent, the age will be reset later and ts_recent
1668 * will get a valid value. If it does not, setting
1669 * ts_recent to zero will at least satisfy the
1670 * requirement that zero be placed in the timestamp
1671 * echo reply when ts_recent isn't valid. The
1672 * age isn't reset until we get a valid ts_recent
1673 * because we don't want out-of-order segments to be
1674 * dropped when ts_recent is old.
1675 */
1676 tp->ts_recent = 0;
1677 } else {
1678 tcpstat.tcps_rcvduppack++;
1679 tcpstat.tcps_rcvdupbyte += tlen;
1680 tcpstat.tcps_pawsdrop++;
1681 if (tlen)
1682 goto dropafterack;
1683 goto drop;
1684 }
1685 }
1686
984263bc
MD
1687 /*
1688 * In the SYN-RECEIVED state, validate that the packet belongs to
1689 * this connection before trimming the data to fit the receive
1690 * window. Check the sequence number versus IRS since we know
1691 * the sequence numbers haven't wrapped. This is a partial fix
1692 * for the "LAND" DoS attack.
1693 */
1694 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
1695 rstreason = BANDLIM_RST_OPENPORT;
1696 goto dropwithreset;
1697 }
1698
1699 todrop = tp->rcv_nxt - th->th_seq;
1700 if (todrop > 0) {
91489f6b
JH
1701 if (TCP_DO_SACK(tp)) {
1702 /* Report duplicate segment at head of packet. */
1703 tp->reportblk.rblk_start = th->th_seq;
1704 tp->reportblk.rblk_end = th->th_seq + tlen;
1705 if (thflags & TH_FIN)
1706 ++tp->reportblk.rblk_end;
1707 if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt))
1708 tp->reportblk.rblk_end = tp->rcv_nxt;
1709 tp->t_flags |= (TF_DUPSEG | TF_SACKLEFT | TF_ACKNOW);
1710 }
984263bc
MD
1711 if (thflags & TH_SYN) {
1712 thflags &= ~TH_SYN;
1713 th->th_seq++;
1714 if (th->th_urp > 1)
1715 th->th_urp--;
1716 else
1717 thflags &= ~TH_URG;
1718 todrop--;
1719 }
1720 /*
1721 * Following if statement from Stevens, vol. 2, p. 960.
1722 */
61896e3c
JH
1723 if (todrop > tlen ||
1724 (todrop == tlen && !(thflags & TH_FIN))) {
984263bc
MD
1725 /*
1726 * Any valid FIN must be to the left of the window.
1727 * At this point the FIN must be a duplicate or out
1728 * of sequence; drop it.
1729 */
1730 thflags &= ~TH_FIN;
1731
1732 /*
1733 * Send an ACK to resynchronize and drop any data.
1734 * But keep on processing for RST or ACK.
1735 */
1736 tp->t_flags |= TF_ACKNOW;
1737 todrop = tlen;
1738 tcpstat.tcps_rcvduppack++;
1739 tcpstat.tcps_rcvdupbyte += todrop;
1740 } else {
1741 tcpstat.tcps_rcvpartduppack++;
1742 tcpstat.tcps_rcvpartdupbyte += todrop;
1743 }
1744 drop_hdrlen += todrop; /* drop from the top afterwards */
1745 th->th_seq += todrop;
1746 tlen -= todrop;
1747 if (th->th_urp > todrop)
1748 th->th_urp -= todrop;
1749 else {
1750 thflags &= ~TH_URG;
1751 th->th_urp = 0;
1752 }
1753 }
1754
1755 /*
1756 * If new data are received on a connection after the
1757 * user processes are gone, then RST the other end.
1758 */
1759 if ((so->so_state & SS_NOFDREF) &&
1760 tp->t_state > TCPS_CLOSE_WAIT && tlen) {
1761 tp = tcp_close(tp);
1762 tcpstat.tcps_rcvafterclose++;
1763 rstreason = BANDLIM_UNLIMITED;
1764 goto dropwithreset;
1765 }
1766
1767 /*
1768 * If segment ends after window, drop trailing data
1769 * (and PUSH and FIN); if nothing left, just ACK.
1770 */
61896e3c 1771 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
984263bc
MD
1772 if (todrop > 0) {
1773 tcpstat.tcps_rcvpackafterwin++;
1774 if (todrop >= tlen) {
1775 tcpstat.tcps_rcvbyteafterwin += tlen;
1776 /*
1777 * If a new connection request is received
1778 * while in TIME_WAIT, drop the old connection
1779 * and start over if the sequence numbers
1780 * are above the previous ones.
1781 */
1782 if (thflags & TH_SYN &&
1783 tp->t_state == TCPS_TIME_WAIT &&
1784 SEQ_GT(th->th_seq, tp->rcv_nxt)) {
1785 tp = tcp_close(tp);
1786 goto findpcb;
1787 }
1788 /*
1789 * If window is closed can only take segments at
1790 * window edge, and have to drop data and PUSH from
1791 * incoming segments. Continue processing, but
1792 * remember to ack. Otherwise, drop segment
1793 * and ack.
1794 */
1795 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
1796 tp->t_flags |= TF_ACKNOW;
1797 tcpstat.tcps_rcvwinprobe++;
1798 } else
1799 goto dropafterack;
1800 } else
1801 tcpstat.tcps_rcvbyteafterwin += todrop;
1802 m_adj(m, -todrop);
1803 tlen -= todrop;
61896e3c 1804 thflags &= ~(TH_PUSH | TH_FIN);
984263bc
MD
1805 }
1806
1807 /*
1808 * If last ACK falls within this segment's sequence numbers,
1809 * record its timestamp.
ad0af98b
ND
1810 * NOTE:
1811 * 1) That the test incorporates suggestions from the latest
1812 * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1813 * 2) That updating only on newer timestamps interferes with
1814 * our earlier PAWS tests, so this check should be solely
1815 * predicated on the sequence space of this segment.
1816 * 3) That we modify the segment boundary check to be
1817 * Last.ACK.Sent <= SEG.SEQ + SEG.LEN
1818 * instead of RFC1323's
1819 * Last.ACK.Sent < SEG.SEQ + SEG.LEN,
1820 * This modified check allows us to overcome RFC1323's
1821 * limitations as described in Stevens TCP/IP Illustrated
1822 * Vol. 2 p.869. In such cases, we can still calculate the
1823 * RTT correctly when RCV.NXT == Last.ACK.Sent.
984263bc 1824 */
ad0af98b
ND
1825 if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
1826 SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen
1827 + ((thflags & TH_SYN) != 0)
1828 + ((thflags & TH_FIN) != 0)))) {
984263bc
MD
1829 tp->ts_recent_age = ticks;
1830 tp->ts_recent = to.to_tsval;
1831 }
1832
1833 /*
1834 * If a SYN is in the window, then this is an
1835 * error and we send an RST and drop the connection.
1836 */
1837 if (thflags & TH_SYN) {
1838 tp = tcp_drop(tp, ECONNRESET);
1839 rstreason = BANDLIM_UNLIMITED;
1840 goto dropwithreset;
1841 }
1842
1843 /*
1844 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
1845 * flag is on (half-synchronized state), then queue data for
1846 * later processing; else drop segment and return.
1847 */
61896e3c 1848 if (!(thflags & TH_ACK)) {
984263bc
MD
1849 if (tp->t_state == TCPS_SYN_RECEIVED ||
1850 (tp->t_flags & TF_NEEDSYN))
1851 goto step6;
1852 else
1853 goto drop;
1854 }
1855
1856 /*
1857 * Ack processing.
1858 */
1859 switch (tp->t_state) {
984263bc 1860 /*
91489f6b 1861 * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter
984263bc
MD
1862 * ESTABLISHED state and continue processing.
1863 * The ACK was checked above.
1864 */
1865 case TCPS_SYN_RECEIVED:
1866
1867 tcpstat.tcps_connects++;
1868 soisconnected(so);
1869 /* Do window scaling? */
61896e3c 1870 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
b5572302 1871 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
1872 tp->snd_scale = tp->requested_s_scale;
1873 tp->rcv_scale = tp->request_r_scale;
1874 }
984263bc
MD
1875 /*
1876 * Make transitions:
1877 * SYN-RECEIVED -> ESTABLISHED
1878 * SYN-RECEIVED* -> FIN-WAIT-1
1879 */
1880 tp->t_starttime = ticks;
1881 if (tp->t_flags & TF_NEEDFIN) {
1882 tp->t_state = TCPS_FIN_WAIT_1;
1883 tp->t_flags &= ~TF_NEEDFIN;
1884 } else {
1885 tp->t_state = TCPS_ESTABLISHED;
2a0c7c52
MD
1886 tcp_callout_reset(tp, tp->tt_keep,
1887 tcp_getkeepidle(tp),
1888 tcp_timer_keep);
984263bc
MD
1889 }
1890 /*
1891 * If segment contains data or ACK, will call tcp_reass()
1892 * later; if not, do so now to pass queued data to user.
1893 */
61896e3c 1894 if (tlen == 0 && !(thflags & TH_FIN))
f23061d4 1895 tcp_reass(tp, NULL, NULL, NULL);
984263bc
MD
1896 /* fall into ... */
1897
1898 /*
1899 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1900 * ACKs. If the ack is in the range
1901 * tp->snd_una < th->th_ack <= tp->snd_max
1902 * then advance tp->snd_una to th->th_ack and drop
1903 * data from the retransmission queue. If this ACK reflects
1904 * more up to date window information we update our window information.
1905 */
1906 case TCPS_ESTABLISHED:
1907 case TCPS_FIN_WAIT_1:
1908 case TCPS_FIN_WAIT_2:
1909 case TCPS_CLOSE_WAIT:
1910 case TCPS_CLOSING:
1911 case TCPS_LAST_ACK:
1912 case TCPS_TIME_WAIT:
1913
1914 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
91489f6b
JH
1915 if (TCP_DO_SACK(tp))
1916 tcp_sack_update_scoreboard(tp, &to);
95b22adf
JH
1917 if (tlen != 0 || tiwin != tp->snd_wnd) {
1918 tp->t_dupacks = 0;
1919 break;
1920 }
1921 tcpstat.tcps_rcvdupack++;
a48c5dd5 1922 if (!tcp_callout_active(tp, tp->tt_rexmt) ||
91489f6b
JH
1923 th->th_ack != tp->snd_una) {
1924 tp->t_dupacks = 0;
1925 break;
1926 }
95b22adf 1927 /*
91489f6b 1928 * We have outstanding data (other than
95b22adf
JH
1929 * a window probe), this is a completely
1930 * duplicate ack (ie, window info didn't
1931 * change), the ack is the biggest we've
1932 * seen and we've seen exactly our rexmt
91489f6b 1933 * threshhold of them, so assume a packet
95b22adf
JH
1934 * has been dropped and retransmit it.
1935 * Kludge snd_nxt & the congestion
1936 * window so we send only this one
1937 * packet.
95b22adf 1938 */
91489f6b
JH
1939 if (IN_FASTRECOVERY(tp)) {
1940 if (TCP_DO_SACK(tp)) {
1941 /* No artifical cwnd inflation. */
1942 tcp_sack_rexmt(tp, th);
1943 } else {
1944 /*
1945 * Dup acks mean that packets
1946 * have left the network
1947 * (they're now cached at the
1948 * receiver) so bump cwnd by
1949 * the amount in the receiver
1950 * to keep a constant cwnd
1951 * packets in the network.
1952 */
1953 tp->snd_cwnd += tp->t_maxseg;
f23061d4 1954 tcp_output(tp);
91489f6b
JH
1955 }
1956 } else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
95b22adf
JH
1957 tp->t_dupacks = 0;
1958 break;
95b22adf 1959 } else if (++tp->t_dupacks == tcprexmtthresh) {
91489f6b 1960 tcp_seq old_snd_nxt;
95b22adf
JH
1961 u_int win;
1962
8819433a 1963fastretransmit:
95b22adf
JH
1964 if (tcp_do_eifel_detect &&
1965 (tp->t_flags & TF_RCVD_TSTMP)) {
1966 tcp_save_congestion_state(tp);
1967 tp->t_flags |= TF_FASTREXMT;
1968 }
91489f6b
JH
1969 /*
1970 * We know we're losing at the current
1971 * window size, so do congestion avoidance:
1972 * set ssthresh to half the current window
1973 * and pull our congestion window back to the
1974 * new ssthresh.
1975 */
95b22adf
JH
1976 win = min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1977 tp->t_maxseg;
1978 if (win < 2)
1979 win = 2;
1980 tp->snd_ssthresh = win * tp->t_maxseg;
1981 ENTER_FASTRECOVERY(tp);
1982 tp->snd_recover = tp->snd_max;
a48c5dd5 1983 tcp_callout_stop(tp, tp->tt_rexmt);
95b22adf 1984 tp->t_rtttime = 0;
91489f6b 1985 old_snd_nxt = tp->snd_nxt;
95b22adf
JH
1986 tp->snd_nxt = th->th_ack;
1987 tp->snd_cwnd = tp->t_maxseg;
f23061d4 1988 tcp_output(tp);
95b22adf 1989 ++tcpstat.tcps_sndfastrexmit;
91489f6b
JH
1990 tp->snd_cwnd = tp->snd_ssthresh;
1991 tp->rexmt_high = tp->snd_nxt;
1992 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
1993 tp->snd_nxt = old_snd_nxt;
95b22adf
JH
1994 KASSERT(tp->snd_limited <= 2,
1995 ("tp->snd_limited too big"));
91489f6b
JH
1996 if (TCP_DO_SACK(tp))
1997 tcp_sack_rexmt(tp, th);
1998 else
1999 tp->snd_cwnd += tp->t_maxseg *
2000 (tp->t_dupacks - tp->snd_limited);
95b22adf
JH
2001 } else if (tcp_do_limitedtransmit) {
2002 u_long oldcwnd = tp->snd_cwnd;
2003 tcp_seq oldsndmax = tp->snd_max;
9e707f76 2004 tcp_seq oldsndnxt = tp->snd_nxt;
95b22adf
JH
2005 /* outstanding data */
2006 uint32_t ownd = tp->snd_max - tp->snd_una;
2007 u_int sent;
ca94b4a6 2008
8819433a
JH
2009#define iceildiv(n, d) (((n)+(d)-1) / (d))
2010
95b22adf
JH
2011 KASSERT(tp->t_dupacks == 1 ||
2012 tp->t_dupacks == 2,
2013 ("dupacks not 1 or 2"));
2014 if (tp->t_dupacks == 1)
2015 tp->snd_limited = 0;
9e707f76 2016 tp->snd_nxt = tp->snd_max;
95b22adf
JH
2017 tp->snd_cwnd = ownd +
2018 (tp->t_dupacks - tp->snd_limited) *
2019 tp->t_maxseg;
f23061d4 2020 tcp_output(tp);
98cb2337
MD
2021
2022 /*
2023 * Other acks may have been processed,
2024 * snd_nxt cannot be reset to a value less
2025 * then snd_una.
2026 */
2027 if (SEQ_LT(oldsndnxt, oldsndmax)) {
2028 if (SEQ_GT(oldsndnxt, tp->snd_una))
6d08465d 2029 tp->snd_nxt = oldsndnxt;
98cb2337
MD
2030 else
2031 tp->snd_nxt = tp->snd_una;
2032 }
95b22adf
JH
2033 tp->snd_cwnd = oldcwnd;
2034 sent = tp->snd_max - oldsndmax;
2035 if (sent > tp->t_maxseg) {
2036 KASSERT((tp->t_dupacks == 2 &&
2037 tp->snd_limited == 0) ||
2038 (sent == tp->t_maxseg + 1 &&
2039 tp->t_flags & TF_SENTFIN),
2040 ("sent too much"));
2041 KASSERT(sent <= tp->t_maxseg * 2,
2042 ("sent too many segments"));
2043 tp->snd_limited = 2;
2044 tcpstat.tcps_sndlimited += 2;
2045 } else if (sent > 0) {
2046 ++tp->snd_limited;
2047 ++tcpstat.tcps_sndlimited;
2048 } else if (tcp_do_early_retransmit &&
2049 (tcp_do_eifel_detect &&
2050 (tp->t_flags & TF_RCVD_TSTMP)) &&
91489f6b 2051 ownd < 4 * tp->t_maxseg &&
95b22adf 2052 tp->t_dupacks + 1 >=
91489f6b
JH
2053 iceildiv(ownd, tp->t_maxseg) &&
2054 (!TCP_DO_SACK(tp) ||
f23061d4 2055 ownd <= tp->t_maxseg ||
91489f6b 2056 tcp_sack_has_sacked(&tp->scb,
f23061d4 2057 ownd - tp->t_maxseg))) {
95b22adf
JH
2058 ++tcpstat.tcps_sndearlyrexmit;
2059 tp->t_flags |= TF_EARLYREXMT;
2060 goto fastretransmit;
984263bc 2061 }
95b22adf
JH
2062 }
2063 goto drop;
984263bc
MD
2064 }
2065
2066 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una"));
984263bc
MD
2067 tp->t_dupacks = 0;
2068 if (SEQ_GT(th->th_ack, tp->snd_max)) {
5a274421
JH
2069 /*
2070 * Detected optimistic ACK attack.
2071 * Force slow-start to de-synchronize attack.
2072 */
2073 tp->snd_cwnd = tp->t_maxseg;
8acdb67c 2074 tp->snd_wacked = 0;
5a274421 2075
984263bc
MD
2076 tcpstat.tcps_rcvacktoomuch++;
2077 goto dropafterack;
2078 }
2079 /*
2080 * If we reach this point, ACK is not a duplicate,
2081 * i.e., it ACKs something we sent.
2082 */
2083 if (tp->t_flags & TF_NEEDSYN) {
2084 /*
2085 * T/TCP: Connection was half-synchronized, and our
2086 * SYN has been ACK'd (so connection is now fully
2087 * synchronized). Go to non-starred state,
2088 * increment snd_una for ACK of SYN, and check if
2089 * we can do window scaling.
2090 */
2091 tp->t_flags &= ~TF_NEEDSYN;
2092 tp->snd_una++;
2093 /* Do window scaling? */
61896e3c
JH
2094 if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
2095 (TF_RCVD_SCALE | TF_REQ_SCALE)) {
984263bc
MD
2096 tp->snd_scale = tp->requested_s_scale;
2097 tp->rcv_scale = tp->request_r_scale;
2098 }
2099 }
2100
2101process_ACK:
2102 acked = th->th_ack - tp->snd_una;
2103 tcpstat.tcps_rcvackpack++;
2104 tcpstat.tcps_rcvackbyte += acked;
2105
b5572302 2106 if (tcp_do_eifel_detect && acked > 0 &&
95b22adf 2107 (to.to_flags & TOF_TS) && (to.to_tsecr != 0) &&
bfdb979e
JH
2108 (tp->t_flags & TF_FIRSTACCACK)) {
2109 /* Eifel detection applicable. */
2110 if (to.to_tsecr < tp->t_rexmtTS) {
bfdb979e 2111 ++tcpstat.tcps_eifeldetected;
8819433a
JH
2112 tcp_revert_congestion_state(tp);
2113 if (tp->t_rxtshift == 1 &&
2114 ticks >= tp->t_badrxtwin)
2115 ++tcpstat.tcps_rttcantdetect;
bfdb979e
JH
2116 }
2117 } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) {
b5572302
JH
2118 /*
2119 * If we just performed our first retransmit,
2120 * and the ACK arrives within our recovery window,
2121 * then it was a mistake to do the retransmit
91489f6b 2122 * in the first place. Recover our original cwnd
b5572302
JH
2123 * and ssthresh, and proceed to transmit where we
2124 * left off.
2125 */
bfdb979e
JH
2126 tcp_revert_congestion_state(tp);
2127 ++tcpstat.tcps_rttdetected;
984263bc
MD
2128 }
2129
2130 /*
2131 * If we have a timestamp reply, update smoothed
2132 * round trip time. If no timestamp is present but
2133 * transmit timer is running and timed sequence
2134 * number was acked, update smoothed round trip time.
2135 * Since we now have an rtt measurement, cancel the
2136 * timer backoff (cf., Phil Karn's retransmit alg.).
2137 * Recompute the initial retransmit timer.
2138 *
2139 * Some machines (certain windows boxes) send broken
d24ce1dc 2140 * timestamp replies during the SYN+ACK phase, ignore
984263bc
MD
2141 * timestamps of 0.
2142 */
95b22adf 2143 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0))
984263bc 2144 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
95b22adf 2145 else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
984263bc 2146 tcp_xmit_timer(tp, ticks - tp->t_rtttime);
984263bc
MD
2147 tcp_xmit_bandwidth_limit(tp, th->th_ack);
2148
984263bc
MD
2149 /*
2150 * If no data (only SYN) was ACK'd,
2151 * skip rest of ACK processing.
2152 */
2153 if (acked == 0)
2154 goto step6;
2155
efd4b327 2156 /* Stop looking for an acceptable ACK since one was received. */
8819433a 2157 tp->t_flags &= ~(TF_FIRSTACCACK | TF_FASTREXMT | TF_EARLYREXMT);
efd4b327 2158
6d49aa6f
MD
2159 if (acked > so->so_snd.ssb_cc) {
2160 tp->snd_wnd -= so->so_snd.ssb_cc;
2161 sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc);
61896e3c 2162 ourfinisacked = TRUE;
984263bc 2163 } else {
6d49aa6f 2164 sbdrop(&so->so_snd.sb, acked);
984263bc 2165 tp->snd_wnd -= acked;
61896e3c 2166 ourfinisacked = FALSE;
984263bc
MD
2167 }
2168 sowwakeup(so);
91489f6b
JH
2169
2170 /*
2171 * Update window information.
2172 * Don't look at window if no ACK:
2173 * TAC's send garbage on first SYN.
2174 */
2175 if (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2176 (tp->snd_wl1 == th->th_seq &&
2177 (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2178 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)))) {
2179 /* keep track of pure window updates */
2180 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2181 tiwin > tp->snd_wnd)
2182 tcpstat.tcps_rcvwinupd++;
2183 tp->snd_wnd = tiwin;
2184 tp->snd_wl1 = th->th_seq;
2185 tp->snd_wl2 = th->th_ack;
2186 if (tp->snd_wnd > tp->max_sndwnd)
2187 tp->max_sndwnd = tp->snd_wnd;
2188 needoutput = TRUE;
2189 }
2190
2191 tp->snd_una = th->th_ack;
2192 if (TCP_DO_SACK(tp))
2193 tcp_sack_update_scoreboard(tp, &to);
95b22adf 2194 if (IN_FASTRECOVERY(tp)) {
91489f6b 2195 if (SEQ_GEQ(th->th_ack, tp->snd_recover)) {
95b22adf 2196 EXIT_FASTRECOVERY(tp);
91489f6b
JH
2197 needoutput = TRUE;
2198 /*
2199 * If the congestion window was inflated
2200 * to account for the other side's
2201 * cached packets, retract it.
8acdb67c
JH
2202 */
2203 if (!TCP_DO_SACK(tp))
2204 tp->snd_cwnd = tp->snd_ssthresh;
2205
2206 /*
91489f6b
JH
2207 * Window inflation should have left us
2208 * with approximately snd_ssthresh outstanding
2209 * data. But, in case we would be inclined
2210 * to send a burst, better do it using
2211 * slow start.
2212 */
91489f6b
JH
2213 if (SEQ_GT(th->th_ack + tp->snd_cwnd,
2214 tp->snd_max + 2 * tp->t_maxseg))
2215 tp->snd_cwnd =
2216 (tp->snd_max - tp->snd_una) +
2217 2 * tp->t_maxseg;
8acdb67c
JH
2218
2219 tp->snd_wacked = 0;
91489f6b
JH
2220 } else {
2221 if (TCP_DO_SACK(tp)) {
2222 tp->snd_max_rexmt = tp->snd_max;
2223 tcp_sack_rexmt(tp, th);
2224 } else {
2225 tcp_newreno_partial_ack(tp, th, acked);
2226 }
2227 needoutput = FALSE;
2228 }
95b22adf 2229 } else {
91489f6b 2230 /*
8acdb67c
JH
2231 * Open the congestion window. When in slow-start,
2232 * open exponentially: maxseg per packet. Otherwise,
2233 * open linearly: maxseg per window.
91489f6b 2234 */
8acdb67c
JH
2235 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2236 u_int abc_sslimit =
2237 (SEQ_LT(tp->snd_nxt, tp->snd_max) ?
2238 tp->t_maxseg : 2 * tp->t_maxseg);
2239
2240 /* slow-start */
2241 tp->snd_cwnd += tcp_do_abc ?
2242 min(acked, abc_sslimit) : tp->t_maxseg;
2243 } else {
2244 /* linear increase */
2245 tp->snd_wacked += tcp_do_abc ? acked :
2246 tp->t_maxseg;
2247 if (tp->snd_wacked >= tp->snd_cwnd) {
2248 tp->snd_wacked -= tp->snd_cwnd;
2249 tp->snd_cwnd += tp->t_maxseg;
2250 }
2251 }
2252 tp->snd_cwnd = min(tp->snd_cwnd,
2253 TCP_MAXWIN << tp->snd_scale);
95b22adf 2254 tp->snd_recover = th->th_ack - 1;
cfb3f3f4 2255 }
984263bc
MD
2256 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2257 tp->snd_nxt = tp->snd_una;
2258
91489f6b
JH
2259 /*
2260 * If all outstanding data is acked, stop retransmit
2261 * timer and remember to restart (more output or persist).
2262 * If there is more data to be acked, restart retransmit
2263 * timer, using current (possibly backed-off) value.
2264 */
2265 if (th->th_ack == tp->snd_max) {
a48c5dd5 2266 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b 2267 needoutput = TRUE;
a48c5dd5
SZ
2268 } else if (!tcp_callout_active(tp, tp->tt_persist)) {
2269 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
2270 tcp_timer_rexmt);
2271 }
91489f6b 2272
984263bc 2273 switch (tp->t_state) {
984263bc
MD
2274 /*
2275 * In FIN_WAIT_1 STATE in addition to the processing
2276 * for the ESTABLISHED state if our FIN is now acknowledged
2277 * then enter FIN_WAIT_2.
2278 */
2279 case TCPS_FIN_WAIT_1:
2280 if (ourfinisacked) {
2281 /*
2282 * If we can't receive any more
2283 * data, then closing user can proceed.
2284 * Starting the timer is contrary to the
2285 * specification, but if we don't get a FIN
2286 * we'll hang forever.
2287 */
2288 if (so->so_state & SS_CANTRCVMORE) {
2289 soisdisconnected(so);
a48c5dd5 2290 tcp_callout_reset(tp, tp->tt_2msl,
5d61ded3 2291 tp->t_maxidle, tcp_timer_2msl);
984263bc
MD
2292 }
2293 tp->t_state = TCPS_FIN_WAIT_2;
2294 }
2295 break;
2296
95b22adf 2297 /*
984263bc
MD
2298 * In CLOSING STATE in addition to the processing for
2299 * the ESTABLISHED state if the ACK acknowledges our FIN
2300 * then enter the TIME-WAIT state, otherwise ignore
2301 * the segment.
2302 */
2303 case TCPS_CLOSING:
2304 if (ourfinisacked) {
2305 tp->t_state = TCPS_TIME_WAIT;
2306 tcp_canceltimers(tp);
27b8aee3 2307 tcp_callout_reset(tp, tp->tt_2msl,
a48c5dd5 2308 2 * tcp_msl, tcp_timer_2msl);
984263bc
MD
2309 soisdisconnected(so);
2310 }
2311 break;
2312
2313 /*
2314 * In LAST_ACK, we may still be waiting for data to drain
2315 * and/or to be acked, as well as for the ack of our FIN.
2316 * If our FIN is now acknowledged, delete the TCB,
2317 * enter the closed state and return.
2318 */
2319 case TCPS_LAST_ACK:
2320 if (ourfinisacked) {
2321 tp = tcp_close(tp);
2322 goto drop;
2323 }
2324 break;
2325
2326 /*
2327 * In TIME_WAIT state the only thing that should arrive
2328 * is a retransmission of the remote FIN. Acknowledge
2329 * it and restart the finack timer.
2330 */
2331 case TCPS_TIME_WAIT:
a48c5dd5
SZ
2332 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2333 tcp_timer_2msl);
984263bc
MD
2334 goto dropafterack;
2335 }
2336 }
2337
2338step6:
2339 /*
2340 * Update window information.
2341 * Don't look at window if no ACK: TAC's send garbage on first SYN.
2342 */
2343 if ((thflags & TH_ACK) &&
df9d7670 2344 acceptable_window_update(tp, th, tiwin)) {
984263bc 2345 /* keep track of pure window updates */
b5572302
JH
2346 if (tlen == 0 && tp->snd_wl2 == th->th_ack &&
2347 tiwin > tp->snd_wnd)
984263bc
MD
2348 tcpstat.tcps_rcvwinupd++;
2349 tp->snd_wnd = tiwin;
2350 tp->snd_wl1 = th->th_seq;
2351 tp->snd_wl2 = th->th_ack;
2352 if (tp->snd_wnd > tp->max_sndwnd)
2353 tp->max_sndwnd = tp->snd_wnd;
61896e3c 2354 needoutput = TRUE;
984263bc
MD
2355 }
2356
2357 /*
2358 * Process segments with URG.
2359 */
2360 if ((thflags & TH_URG) && th->th_urp &&
95b22adf 2361 !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2362 /*
2363 * This is a kludge, but if we receive and accept
2364 * random urgent pointers, we'll crash in
2365 * soreceive. It's hard to imagine someone
2366 * actually wanting to send this much urgent data.
2367 */
6d49aa6f 2368 if (th->th_urp + so->so_rcv.ssb_cc > sb_max) {
984263bc
MD
2369 th->th_urp = 0; /* XXX */
2370 thflags &= ~TH_URG; /* XXX */
2371 goto dodata; /* XXX */
2372 }
2373 /*
2374 * If this segment advances the known urgent pointer,
2375 * then mark the data stream. This should not happen
2376 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2377 * a FIN has been received from the remote side.
2378 * In these states we ignore the URG.
2379 *
2380 * According to RFC961 (Assigned Protocols),
2381 * the urgent pointer points to the last octet
2382 * of urgent data. We continue, however,
2383 * to consider it to indicate the first octet
2384 * of data past the urgent section as the original
2385 * spec states (in one of two places).
2386 */
61896e3c 2387 if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) {
984263bc 2388 tp->rcv_up = th->th_seq + th->th_urp;
6d49aa6f 2389 so->so_oobmark = so->so_rcv.ssb_cc +
984263bc
MD
2390 (tp->rcv_up - tp->rcv_nxt) - 1;
2391 if (so->so_oobmark == 0)
6cef7136 2392 sosetstate(so, SS_RCVATMARK);
984263bc
MD
2393 sohasoutofband(so);
2394 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2395 }
2396 /*
2397 * Remove out of band data so doesn't get presented to user.
2398 * This can happen independent of advancing the URG pointer,
2399 * but if two URG's are pending at once, some out-of-band
2400 * data may creep in... ick.
2401 */
61896e3c
JH
2402 if (th->th_urp <= (u_long)tlen &&
2403 !(so->so_options & SO_OOBINLINE)) {
2404 /* hdr drop is delayed */
2405 tcp_pulloutofband(so, th, m, drop_hdrlen);
2406 }
984263bc
MD
2407 } else {
2408 /*
2409 * If no out of band data is expected,
2410 * pull receive urgent pointer along
2411 * with the receive window.
2412 */
2413 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2414 tp->rcv_up = tp->rcv_nxt;
2415 }
984263bc 2416
61896e3c 2417dodata: /* XXX */
984263bc
MD
2418 /*
2419 * Process the segment text, merging it into the TCP sequencing queue,
2420 * and arranging for acknowledgment of receipt if necessary.
2421 * This process logically involves adjusting tp->rcv_wnd as data
2422 * is presented to the user (this happens in tcp_usrreq.c,
2423 * case PRU_RCVD). If a FIN has already been received on this
2424 * connection then we just ignore the text.
2425 */
95b22adf 2426 if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2427 m_adj(m, drop_hdrlen); /* delayed header drop */
2428 /*
2429 * Insert segment which includes th into TCP reassembly queue
2430 * with control block tp. Set thflags to whether reassembly now
2431 * includes a segment with FIN. This handles the common case
2432 * inline (segment is the next to be received on an established
2433 * connection, and the queue is empty), avoiding linkage into
2434 * and removal from the queue and repetition of various
2435 * conversions.
2436 * Set DELACK for segments received in order, but ack
2437 * immediately when segments are out of order (so
2438 * fast retransmit can work).
2439 */
2440 if (th->th_seq == tp->rcv_nxt &&
2441 LIST_EMPTY(&tp->t_segq) &&
2442 TCPS_HAVEESTABLISHED(tp->t_state)) {
a48c5dd5
SZ
2443 if (DELAY_ACK(tp)) {
2444 tcp_callout_reset(tp, tp->tt_delack,
2445 tcp_delacktime, tcp_timer_delack);
2446 } else {
984263bc 2447 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2448 }
984263bc
MD
2449 tp->rcv_nxt += tlen;
2450 thflags = th->th_flags & TH_FIN;
2451 tcpstat.tcps_rcvpack++;
2452 tcpstat.tcps_rcvbyte += tlen;
2453 ND6_HINT(tp);
6cef7136 2454 if (so->so_state & SS_CANTRCVMORE) {
984263bc 2455 m_freem(m);
6cef7136
MD
2456 } else {
2457 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 2458 ssb_appendstream(&so->so_rcv, m);
6cef7136
MD
2459 lwkt_reltoken(&so->so_rcv.ssb_token);
2460 }
984263bc
MD
2461 sorwakeup(so);
2462 } else {
91489f6b
JH
2463 if (!(tp->t_flags & TF_DUPSEG)) {
2464 /* Initialize SACK report block. */
2465 tp->reportblk.rblk_start = th->th_seq;
2466 tp->reportblk.rblk_end = th->th_seq + tlen +
2467 ((thflags & TH_FIN) != 0);
2468 }
984263bc
MD
2469 thflags = tcp_reass(tp, th, &tlen, m);
2470 tp->t_flags |= TF_ACKNOW;
2471 }
2472
2473 /*
2474 * Note the amount of data that peer has sent into
2475 * our window, in order to estimate the sender's
2476 * buffer size.
2477 */
6d49aa6f 2478 len = so->so_rcv.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
984263bc
MD
2479 } else {
2480 m_freem(m);
2481 thflags &= ~TH_FIN;
2482 }
2483
2484 /*
2485 * If FIN is received ACK the FIN and let the user know
2486 * that the connection is closing.
2487 */
2488 if (thflags & TH_FIN) {
95b22adf 2489 if (!TCPS_HAVERCVDFIN(tp->t_state)) {
984263bc
MD
2490 socantrcvmore(so);
2491 /*
2492 * If connection is half-synchronized
2493 * (ie NEEDSYN flag on) then delay ACK,
2494 * so it may be piggybacked when SYN is sent.
2495 * Otherwise, since we received a FIN then no
2496 * more input can be expected, send ACK now.
2497 */
a48c5dd5
SZ
2498 if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) {
2499 tcp_callout_reset(tp, tp->tt_delack,
2500 tcp_delacktime, tcp_timer_delack);
2501 } else {
984263bc 2502 tp->t_flags |= TF_ACKNOW;
a48c5dd5 2503 }
984263bc
MD
2504 tp->rcv_nxt++;
2505 }
984263bc 2506
61896e3c 2507 switch (tp->t_state) {
95b22adf 2508 /*
984263bc
MD
2509 * In SYN_RECEIVED and ESTABLISHED STATES
2510 * enter the CLOSE_WAIT state.
2511 */
2512 case TCPS_SYN_RECEIVED:
2513 tp->t_starttime = ticks;
2514 /*FALLTHROUGH*/
2515 case TCPS_ESTABLISHED:
2516 tp->t_state = TCPS_CLOSE_WAIT;
2517 break;
2518
95b22adf 2519 /*
984263bc
MD
2520 * If still in FIN_WAIT_1 STATE FIN has not been acked so
2521 * enter the CLOSING state.
2522 */
2523 case TCPS_FIN_WAIT_1:
2524 tp->t_state = TCPS_CLOSING;
2525 break;
2526
95b22adf 2527 /*
984263bc
MD
2528 * In FIN_WAIT_2 state enter the TIME_WAIT state,
2529 * starting the time-wait timer, turning off the other
2530 * standard timers.
2531 */
2532 case TCPS_FIN_WAIT_2:
2533 tp->t_state = TCPS_TIME_WAIT;
2534 tcp_canceltimers(tp);
27b8aee3 2535 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
a48c5dd5 2536 tcp_timer_2msl);
984263bc
MD
2537 soisdisconnected(so);
2538 break;
2539
2540 /*
2541 * In TIME_WAIT state restart the 2 MSL time_wait timer.
2542 */
2543 case TCPS_TIME_WAIT:
a48c5dd5
SZ
2544 tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_msl,
2545 tcp_timer_2msl);
984263bc
MD
2546 break;
2547 }
2548 }
61896e3c 2549
984263bc
MD
2550#ifdef TCPDEBUG
2551 if (so->so_options & SO_DEBUG)
f23061d4 2552 tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2553#endif
2554
2555 /*
2556 * Return any desired output.
2557 */
2558 if (needoutput || (tp->t_flags & TF_ACKNOW))
f23061d4 2559 tcp_output(tp);
002c1265 2560 return(IPPROTO_DONE);
984263bc
MD
2561
2562dropafterack:
2563 /*
2564 * Generate an ACK dropping incoming segment if it occupies
2565 * sequence space, where the ACK reflects our state.
2566 *
2567 * We can now skip the test for the RST flag since all
2568 * paths to this code happen after packets containing
2569 * RST have been dropped.
2570 *
2571 * In the SYN-RECEIVED state, don't send an ACK unless the
2572 * segment we received passes the SYN-RECEIVED ACK test.
2573 * If it fails send a RST. This breaks the loop in the
2574 * "LAND" DoS attack, and also prevents an ACK storm
2575 * between two listening ports that have been sent forged
2576 * SYN segments, each with the source address of the other.
2577 */
2578 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
2579 (SEQ_GT(tp->snd_una, th->th_ack) ||
2580 SEQ_GT(th->th_ack, tp->snd_max)) ) {
2581 rstreason = BANDLIM_RST_OPENPORT;
2582 goto dropwithreset;
2583 }
2584#ifdef TCPDEBUG
2585 if (so->so_options & SO_DEBUG)
f23061d4 2586 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2587#endif
2588 m_freem(m);
2589 tp->t_flags |= TF_ACKNOW;
f23061d4 2590 tcp_output(tp);
002c1265 2591 return(IPPROTO_DONE);
984263bc
MD
2592
2593dropwithreset:
2594 /*
2595 * Generate a RST, dropping incoming segment.
2596 * Make ACK acceptable to originator of segment.
2597 * Don't bother to respond if destination was broadcast/multicast.
2598 */
61896e3c 2599 if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST))
984263bc
MD
2600 goto drop;
2601 if (isipv6) {
2602 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
2603 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
2604 goto drop;
2605 } else {
2606 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
2607 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
95b22adf
JH
2608 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
2609 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
984263bc
MD
2610 goto drop;
2611 }
2612 /* IPv6 anycast check is done at tcp6_input() */
2613
2614 /*
2615 * Perform bandwidth limiting.
2616 */
2617#ifdef ICMP_BANDLIM
2618 if (badport_bandlim(rstreason) < 0)
2619 goto drop;
2620#endif
2621
2622#ifdef TCPDEBUG
2623 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2624 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2625#endif
2626 if (thflags & TH_ACK)
2627 /* mtod() below is safe as long as hdr dropping is delayed */
2628 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
2629 TH_RST);
2630 else {
2631 if (thflags & TH_SYN)
2632 tlen++;
2633 /* mtod() below is safe as long as hdr dropping is delayed */
61896e3c
JH
2634 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen,
2635 (tcp_seq)0, TH_RST | TH_ACK);
984263bc 2636 }
002c1265 2637 return(IPPROTO_DONE);
984263bc
MD
2638
2639drop:
2640 /*
2641 * Drop space held by incoming segment and return.
2642 */
2643#ifdef TCPDEBUG
2644 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
f23061d4 2645 tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0);
984263bc
MD
2646#endif
2647 m_freem(m);
002c1265 2648 return(IPPROTO_DONE);
984263bc
MD
2649}
2650
2651/*
2652 * Parse TCP options and place in tcpopt.
2653 */
2654static void
95b22adf 2655tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn)
984263bc 2656{
91489f6b 2657 int opt, optlen, i;
984263bc
MD
2658
2659 to->to_flags = 0;
2660 for (; cnt > 0; cnt -= optlen, cp += optlen) {
2661 opt = cp[0];
2662 if (opt == TCPOPT_EOL)
2663 break;
2664 if (opt == TCPOPT_NOP)
2665 optlen = 1;
2666 else {
2667 if (cnt < 2)
2668 break;
2669 optlen = cp[1];
2670 if (optlen < 2 || optlen > cnt)
2671 break;
2672 }
2673 switch (opt) {
2674 case TCPOPT_MAXSEG:
2675 if (optlen != TCPOLEN_MAXSEG)
2676 continue;
2677 if (!is_syn)
2678 continue;
2679 to->to_flags |= TOF_MSS;
407e896e 2680 bcopy(cp + 2, &to->to_mss, sizeof to->to_mss);
984263bc
MD
2681 to->to_mss = ntohs(to->to_mss);
2682 break;
2683 case TCPOPT_WINDOW:
2684 if (optlen != TCPOLEN_WINDOW)
2685 continue;
95b22adf 2686 if (!is_syn)
984263bc
MD
2687 continue;
2688 to->to_flags |= TOF_SCALE;
2689 to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
2690 break;
2691 case TCPOPT_TIMESTAMP:
2692 if (optlen != TCPOLEN_TIMESTAMP)
2693 continue;
2694 to->to_flags |= TOF_TS;
407e896e 2695 bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval);
984263bc 2696 to->to_tsval = ntohl(to->to_tsval);
407e896e 2697 bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr);
984263bc 2698 to->to_tsecr = ntohl(to->to_tsecr);
ad0af98b
ND
2699 /*
2700 * If echoed timestamp is later than the current time,
2701 * fall back to non RFC1323 RTT calculation.
2702 */
2703 if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks))
2704 to->to_tsecr = 0;
984263bc 2705 break;
91489f6b
JH
2706 case TCPOPT_SACK_PERMITTED:
2707 if (optlen != TCPOLEN_SACK_PERMITTED)
2708 continue;
2709 if (!is_syn)
2710 continue;
2711 to->to_flags |= TOF_SACK_PERMITTED;
2712 break;
2713 case TCPOPT_SACK:
2714 if ((optlen - 2) & 0x07) /* not multiple of 8 */
2715 continue;
2716 to->to_nsackblocks = (optlen - 2) / 8;
2717 to->to_sackblocks = (struct raw_sackblock *) (cp + 2);
2718 to->to_flags |= TOF_SACK;
2719 for (i = 0; i < to->to_nsackblocks; i++) {
2720 struct raw_sackblock *r = &to->to_sackblocks[i];
2721
2722 r->rblk_start = ntohl(r->rblk_start);
2723 r->rblk_end = ntohl(r->rblk_end);
2724 }
2725 break;
b1992928
MD
2726#ifdef TCP_SIGNATURE
2727 /*
2728 * XXX In order to reply to a host which has set the
2729 * TCP_SIGNATURE option in its initial SYN, we have to
2730 * record the fact that the option was observed here
2731 * for the syncache code to perform the correct response.
2732 */
2733 case TCPOPT_SIGNATURE:
2734 if (optlen != TCPOLEN_SIGNATURE)
2735 continue;
2736 to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN);
2737 break;
2738#endif /* TCP_SIGNATURE */
984263bc
MD
2739 default:
2740 continue;
2741 }
2742 }
2743}
2744
2745/*
2746 * Pull out of band byte out of a segment so
2747 * it doesn't appear in the user's data queue.
2748 * It is still reflected in the segment length for
2749 * sequencing purposes.
95b22adf 2750 * "off" is the delayed to be dropped hdrlen.
984263bc
MD
2751 */
2752static void
95b22adf 2753tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, int off)
984263bc
MD
2754{
2755 int cnt = off + th->th_urp - 1;
2756
2757 while (cnt >= 0) {
2758 if (m->m_len > cnt) {
2759 char *cp = mtod(m, caddr_t) + cnt;
2760 struct tcpcb *tp = sototcpcb(so);
2761
2762 tp->t_iobc = *cp;
2763 tp->t_oobflags |= TCPOOB_HAVEDATA;
95b22adf 2764 bcopy(cp + 1, cp, m->m_len - cnt - 1);
984263bc
MD
2765 m->m_len--;
2766 if (m->m_flags & M_PKTHDR)
2767 m->m_pkthdr.len--;
2768 return;
2769 }
2770 cnt -= m->m_len;
2771 m = m->m_next;
2772 if (m == 0)
2773 break;
2774 }
2775 panic("tcp_pulloutofband");
2776}
2777
2778/*
2779 * Collect new round-trip time estimate
2780 * and update averages and current timeout.
2781 */
2782static void
95b22adf 2783tcp_xmit_timer(struct tcpcb *tp, int rtt)
984263bc 2784{
2256ba69 2785 int delta;
984263bc
MD
2786
2787 tcpstat.tcps_rttupdated++;
2788 tp->t_rttupdated++;
2789 if (tp->t_srtt != 0) {
2790 /*
2791 * srtt is stored as fixed point with 5 bits after the
2792 * binary point (i.e., scaled by 8). The following magic
2793 * is equivalent to the smoothing algorithm in rfc793 with
2794 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
2795 * point). Adjust rtt to origin 0.
2796 */
2797 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
2798 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
2799
2800 if ((tp->t_srtt += delta) <= 0)
2801 tp->t_srtt = 1;
2802
2803 /*
2804 * We accumulate a smoothed rtt variance (actually, a
2805 * smoothed mean difference), then set the retransmit
2806 * timer to smoothed rtt + 4 times the smoothed variance.
2807 * rttvar is stored as fixed point with 4 bits after the
2808 * binary point (scaled by 16). The following is
2809 * equivalent to rfc793 smoothing with an alpha of .75
2810 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
2811 * rfc793's wired-in beta.
2812 */
2813 if (delta < 0)
2814 delta = -delta;
2815 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
2816 if ((tp->t_rttvar += delta) <= 0)
2817 tp->t_rttvar = 1;
2818 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
2819 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2820 } else {
2821 /*
2822 * No rtt measurement yet - use the unsmoothed rtt.
2823 * Set the variance to half the rtt (so our first
2824 * retransmit happens at 3*rtt).
2825 */
2826 tp->t_srtt = rtt << TCP_RTT_SHIFT;
2827 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
2828 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
2829 }
2830 tp->t_rtttime = 0;
2831 tp->t_rxtshift = 0;
2832
2833 /*
2834 * the retransmit should happen at rtt + 4 * rttvar.
2835 * Because of the way we do the smoothing, srtt and rttvar
2836 * will each average +1/2 tick of bias. When we compute
2837 * the retransmit timer, we want 1/2 tick of rounding and
2838 * 1 extra tick because of +-1/2 tick uncertainty in the
2839 * firing of the timer. The bias will give us exactly the
2840 * 1.5 tick we need. But, because the bias is
2841 * statistical, we have to test that we don't drop below
2842 * the minimum feasible timer (which is 2 ticks).
2843 */
2844 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
2845 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
2846
2847 /*
2848 * We received an ack for a packet that wasn't retransmitted;
2849 * it is probably safe to discard any error indications we've
2850 * received recently. This isn't quite right, but close enough
2851 * for now (a route might have failed after we sent a segment,
2852 * and the return path might not be symmetrical).
2853 */
2854 tp->t_softerror = 0;
2855}
2856
2857/*
2858 * Determine a reasonable value for maxseg size.
2859 * If the route is known, check route for mtu.
2860 * If none, use an mss that can be handled on the outgoing
2861 * interface without forcing IP to fragment; if bigger than
2862 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
2863 * to utilize large mbufs. If no route is found, route has no mtu,
2864 * or the destination isn't local, use a default, hopefully conservative
2865 * size (usually 512 or the default IP max size, but no more than the mtu
2866 * of the interface), as we can't discover anything about intervening
2867 * gateways or networks. We also initialize the congestion/slow start
2868 * window to be a single segment if the destination isn't local.
2869 * While looking at the routing entry, we also initialize other path-dependent
2870 * parameters from pre-set or cached values in the routing entry.
2871 *
2872 * Also take into account the space needed for options that we
2873 * send regularly. Make maxseg shorter by that amount to assure
2874 * that we can send maxseg amount of data even when the options
2875 * are present. Store the upper limit of the length of options plus
2876 * data in maxopd.
2877 *
2878 * NOTE that this routine is only called when we process an incoming
2879 * segment, for outgoing segments only tcp_mssopt is called.
984263bc
MD
2880 */
2881void
95b22adf 2882tcp_mss(struct tcpcb *tp, int offer)
984263bc 2883{
2256ba69 2884 struct rtentry *rt;
984263bc 2885 struct ifnet *ifp;
2256ba69 2886 int rtt, mss;
984263bc
MD
2887 u_long bufsize;
2888 struct inpcb *inp = tp->t_inpcb;
2889 struct socket *so;
984263bc 2890#ifdef INET6
d24ce1dc 2891 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
2892 size_t min_protoh = isipv6 ?
2893 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
2894 sizeof(struct tcpiphdr);
2895#else
d24ce1dc 2896 const boolean_t isipv6 = FALSE;
984263bc
MD
2897 const size_t min_protoh = sizeof(struct tcpiphdr);
2898#endif
2899
2900 if (isipv6)
2901 rt = tcp_rtlookup6(&inp->inp_inc);
2902 else
2903 rt = tcp_rtlookup(&inp->inp_inc);
2904 if (rt == NULL) {
2905 tp->t_maxopd = tp->t_maxseg =
d24ce1dc 2906 (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
984263bc
MD
2907 return;
2908 }
2909 ifp = rt->rt_ifp;
2910 so = inp->inp_socket;
2911
984263bc
MD
2912 /*
2913 * Offer == 0 means that there was no MSS on the SYN segment,
b235ad6d
MD
2914 * in this case we use either the interface mtu or tcp_mssdflt.
2915 *
2916 * An offer which is too large will be cut down later.
984263bc 2917 */
5b0b9fa5 2918 if (offer == 0) {
b235ad6d
MD
2919 if (isipv6) {
2920 if (in6_localaddr(&inp->in6p_faddr)) {
2921 offer = ND_IFINFO(rt->rt_ifp)->linkmtu -
2922 min_protoh;
2923 } else {
2924 offer = tcp_v6mssdflt;
2925 }
2926 } else {
2927 if (in_localaddr(inp->inp_faddr))
2928 offer = ifp->if_mtu - min_protoh;
2929 else
2930 offer = tcp_mssdflt;
2931 }
5b0b9fa5 2932 }
b235ad6d
MD
2933
2934 /*
2935 * Prevent DoS attack with too small MSS. Round up
2936 * to at least minmss.
2937 *
2938 * Sanity check: make sure that maxopd will be large
2939 * enough to allow some data on segments even is the
2940 * all the option space is used (40bytes). Otherwise
2941 * funny things may happen in tcp_output.
2942 */
2943 offer = max(offer, tcp_minmss);
2944 offer = max(offer, 64);
2945
27b8aee3 2946 rt->rt_rmx.rmx_mssopt = offer;
984263bc
MD
2947
2948 /*
2949 * While we're here, check if there's an initial rtt
2950 * or rttvar. Convert from the route-table units
2951 * to scaled multiples of the slow timeout timer.
2952 */
2953 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
2954 /*
2955 * XXX the lock bit for RTT indicates that the value
2956 * is also a minimum value; this is subject to time.
2957 */
2958 if (rt->rt_rmx.rmx_locks & RTV_RTT)
2959 tp->t_rttmin = rtt / (RTM_RTTUNIT / hz);
2960 tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
2961 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
2962 tcpstat.tcps_usedrtt++;
2963 if (rt->rt_rmx.rmx_rttvar) {
2964 tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
2965 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
2966 tcpstat.tcps_usedrttvar++;
2967 } else {
2968 /* default variation is +- 1 rtt */
2969 tp->t_rttvar =
2970 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
2971 }
2972 TCPT_RANGESET(tp->t_rxtcur,
2973 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
2974 tp->t_rttmin, TCPTV_REXMTMAX);
2975 }
b235ad6d 2976
984263bc
MD
2977 /*
2978 * if there's an mtu associated with the route, use it
b235ad6d
MD
2979 * else, use the link mtu. Take the smaller of mss or offer
2980 * as our final mss.
984263bc 2981 */
b235ad6d 2982 if (rt->rt_rmx.rmx_mtu) {
984263bc 2983 mss = rt->rt_rmx.rmx_mtu - min_protoh;
b235ad6d
MD
2984 } else {
2985 if (isipv6)
698ac46c 2986 mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh;
b235ad6d 2987 else
984263bc 2988 mss = ifp->if_mtu - min_protoh;
984263bc
MD
2989 }
2990 mss = min(mss, offer);
b235ad6d 2991
984263bc
MD
2992 /*
2993 * maxopd stores the maximum length of data AND options
2994 * in a segment; maxseg is the amount of data in a normal
2995 * segment. We need to store this value (maxopd) apart
2996 * from maxseg, because now every segment carries options
2997 * and thus we normally have somewhat less data in segments.
2998 */
2999 tp->t_maxopd = mss;
3000
61896e3c 3001 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
27b8aee3 3002 ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
984263bc 3003 mss -= TCPOLEN_TSTAMP_APPA;
984263bc
MD
3004
3005#if (MCLBYTES & (MCLBYTES - 1)) == 0
3006 if (mss > MCLBYTES)
3007 mss &= ~(MCLBYTES-1);
3008#else
3009 if (mss > MCLBYTES)
3010 mss = mss / MCLBYTES * MCLBYTES;
3011#endif
3012 /*
3013 * If there's a pipesize, change the socket buffer
3014 * to that size. Make the socket buffers an integral
3015 * number of mss units; if the mss is larger than
3016 * the socket buffer, decrease the mss.
3017 */
3018#ifdef RTV_SPIPE
3019 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0)
3020#endif
6d49aa6f 3021 bufsize = so->so_snd.ssb_hiwat;
984263bc
MD
3022 if (bufsize < mss)
3023 mss = bufsize;
3024 else {
3025 bufsize = roundup(bufsize, mss);
3026 if (bufsize > sb_max)
3027 bufsize = sb_max;
6d49aa6f
MD
3028 if (bufsize > so->so_snd.ssb_hiwat)
3029 ssb_reserve(&so->so_snd, bufsize, so, NULL);
984263bc
MD
3030 }
3031 tp->t_maxseg = mss;
3032
3033#ifdef RTV_RPIPE
3034 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0)
3035#endif
6d49aa6f 3036 bufsize = so->so_rcv.ssb_hiwat;
984263bc
MD
3037 if (bufsize > mss) {
3038 bufsize = roundup(bufsize, mss);
3039 if (bufsize > sb_max)
3040 bufsize = sb_max;
6cef7136
MD
3041 if (bufsize > so->so_rcv.ssb_hiwat) {
3042 lwkt_gettoken(&so->so_rcv.ssb_token);
6d49aa6f 3043 ssb_reserve(&so->so_rcv, bufsize, so, NULL);
6cef7136
MD
3044 lwkt_reltoken(&so->so_rcv.ssb_token);
3045 }
984263bc
MD
3046 }
3047
3048 /*
3049 * Set the slow-start flight size depending on whether this
3050 * is a local network or not.
3051 */
4b52d5ee
JH
3052 if (tcp_do_rfc3390)
3053 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
4b52d5ee 3054 else
cd149066 3055 tp->snd_cwnd = mss;
984263bc
MD
3056
3057 if (rt->rt_rmx.rmx_ssthresh) {
3058 /*
3059 * There's some sort of gateway or interface
3060 * buffer limit on the path. Use this to set
3061 * the slow start threshhold, but set the
3062 * threshold to no less than 2*mss.
3063 */
3064 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
3065 tcpstat.tcps_usedssthresh++;
3066 }
3067}
3068
3069/*
3070 * Determine the MSS option to send on an outgoing SYN.
3071 */
3072int
95b22adf 3073tcp_mssopt(struct tcpcb *tp)
984263bc
MD
3074{
3075 struct rtentry *rt;
3076#ifdef INET6
d24ce1dc
JH
3077 boolean_t isipv6 =
3078 ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE);
984263bc
MD
3079 int min_protoh = isipv6 ?
3080 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
3081 sizeof(struct tcpiphdr);
3082#else
d24ce1dc 3083 const boolean_t isipv6 = FALSE;
984263bc
MD
3084 const size_t min_protoh = sizeof(struct tcpiphdr);
3085#endif
3086
3087 if (isipv6)
3088 rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc);
3089 else
3090 rt = tcp_rtlookup(&tp->t_inpcb->inp_inc);
3091 if (rt == NULL)
3092 return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt);
3093
3094 return (rt->rt_ifp->if_mtu - min_protoh);
3095}
3096
984263bc
MD
3097/*
3098 * When a partial ack arrives, force the retransmission of the
91489f6b
JH
3099 * next unacknowledged segment. Do not exit Fast Recovery.
3100 *
3101 * Implement the Slow-but-Steady variant of NewReno by restarting the
3102 * the retransmission timer. Turn it off here so it can be restarted
3103 * later in tcp_output().
984263bc
MD
3104 */
3105static void
91489f6b 3106tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked)
984263bc 3107{
91489f6b
JH
3108 tcp_seq old_snd_nxt = tp->snd_nxt;
3109 u_long ocwnd = tp->snd_cwnd;
984263bc 3110
a48c5dd5 3111 tcp_callout_stop(tp, tp->tt_rexmt);
984263bc
MD
3112 tp->t_rtttime = 0;
3113 tp->snd_nxt = th->th_ack;
91489f6b
JH
3114 /* Set snd_cwnd to one segment beyond acknowledged offset. */
3115 tp->snd_cwnd = tp->t_maxseg;
984263bc 3116 tp->t_flags |= TF_ACKNOW;
f23061d4 3117 tcp_output(tp);
91489f6b
JH
3118 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3119 tp->snd_nxt = old_snd_nxt;
3120 /* partial window deflation */
68947d12
ND
3121 if (ocwnd > acked)
3122 tp->snd_cwnd = ocwnd - acked + tp->t_maxseg;
3123 else
3124 tp->snd_cwnd = tp->t_maxseg;
91489f6b
JH
3125}
3126
3127/*
3128 * In contrast to the Slow-but-Steady NewReno variant,
3129 * we do not reset the retransmission timer for SACK retransmissions,
3130 * except when retransmitting snd_una.
3131 */
3132static void
3133tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th)
3134{
3135 uint32_t pipe, seglen;
3136 tcp_seq nextrexmt;
3137 boolean_t lostdup;
3138 tcp_seq old_snd_nxt = tp->snd_nxt;
3139 u_long ocwnd = tp->snd_cwnd;
3140 int nseg = 0; /* consecutive new segments */
3141#define MAXBURST 4 /* limit burst of new packets on partial ack */
3142
3143 tp->t_rtttime = 0;
3144 pipe = tcp_sack_compute_pipe(tp);
3145 while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg &&
3146 (!tcp_do_smartsack || nseg < MAXBURST) &&
3147 tcp_sack_nextseg(tp, &nextrexmt, &seglen, &lostdup)) {
3148 uint32_t sent;
3149 tcp_seq old_snd_max;
3150 int error;
3151
98cb2337
MD
3152 if (nextrexmt == tp->snd_max)
3153 ++nseg;
91489f6b
JH
3154 tp->snd_nxt = nextrexmt;
3155 tp->snd_cwnd = nextrexmt - tp->snd_una + seglen;
3156 old_snd_max = tp->snd_max;
3157 if (nextrexmt == tp->snd_una)
a48c5dd5 3158 tcp_callout_stop(tp, tp->tt_rexmt);
91489f6b
JH
3159 error = tcp_output(tp);
3160 if (error != 0)
3161 break;
3162 sent = tp->snd_nxt - nextrexmt;
3163 if (sent <= 0)
3164 break;
3165 if (!lostdup)
3166 pipe += sent;
3167 tcpstat.tcps_sndsackpack++;
3168 tcpstat.tcps_sndsackbyte += sent;
3169 if (SEQ_LT(nextrexmt, old_snd_max) &&
3170 SEQ_LT(tp->rexmt_high, tp->snd_nxt))
3171 tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max);
3172 }
3173 if (SEQ_GT(old_snd_nxt, tp->snd_nxt))
3174 tp->snd_nxt = old_snd_nxt;
984263bc 3175 tp->snd_cwnd = ocwnd;
984263bc 3176}
0ecd93f9
MD
3177
3178/*
3179 * Reset idle time and keep-alive timer, typically called when a valid
3180 * tcp packet is received but may also be called when FASTKEEP is set
3181 * to prevent the previous long-timeout from calculating to a drop.
3182 *
3183 * Only update t_rcvtime for non-SYN packets.
3184 *
3185 * Handle the case where one side thinks the connection is established
3186 * but the other side has, say, rebooted without cleaning out the
3187 * connection. The SYNs could be construed as an attack and wind
3188 * up ignored, but in case it isn't an attack we can validate the
3189 * connection by forcing a keepalive.
3190 */
3191void
3192tcp_timer_keep_activity(struct tcpcb *tp, int thflags)
3193{
3194 if (TCPS_HAVEESTABLISHED(tp->t_state)) {
3195 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) {
3196 tp->t_flags |= TF_KEEPALIVE;
3197 tcp_callout_reset(tp, tp->tt_keep, hz / 2,
3198 tcp_timer_keep);
3199 } else {
3200 tp->t_rcvtime = ticks;
3201 tp->t_flags &= ~TF_KEEPALIVE;
3202 tcp_callout_reset(tp, tp->tt_keep,
3203 tcp_getkeepidle(tp),
3204 tcp_timer_keep);
3205 }
3206 }
3207}