tcp: Don't allow persist timer if TCP connection is not established yet
[dragonfly.git] / sys / netinet / tcp_output.c
CommitLineData
984263bc 1/*
86e10434 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved.
66d6c637 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
f23061d4 4 *
66d6c637
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5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
f23061d4 7 *
66d6c637
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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.
f23061d4 19 *
66d6c637
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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
34/*
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35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 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_output.c 8.4 (Berkeley) 5/24/95
67 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $
6d49aa6f 68 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.34 2007/04/22 01:13:14 dillon Exp $
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69 */
70
b1992928 71#include "opt_inet.h"
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72#include "opt_inet6.h"
73#include "opt_ipsec.h"
74#include "opt_tcpdebug.h"
75
76#include <sys/param.h>
77#include <sys/systm.h>
78#include <sys/kernel.h>
79#include <sys/sysctl.h>
80#include <sys/mbuf.h>
81#include <sys/domain.h>
82#include <sys/protosw.h>
83#include <sys/socket.h>
84#include <sys/socketvar.h>
3f9db7f8 85#include <sys/in_cksum.h>
2b57d013
MD
86#include <sys/thread.h>
87#include <sys/globaldata.h>
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88
89#include <net/route.h>
90
91#include <netinet/in.h>
92#include <netinet/in_systm.h>
93#include <netinet/ip.h>
94#include <netinet/in_pcb.h>
95#include <netinet/ip_var.h>
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96#include <netinet6/in6_pcb.h>
97#include <netinet/ip6.h>
98#include <netinet6/ip6_var.h>
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99#include <netinet/tcp.h>
100#define TCPOUTFLAGS
101#include <netinet/tcp_fsm.h>
102#include <netinet/tcp_seq.h>
103#include <netinet/tcp_timer.h>
a48c5dd5 104#include <netinet/tcp_timer2.h>
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105#include <netinet/tcp_var.h>
106#include <netinet/tcpip.h>
107#ifdef TCPDEBUG
108#include <netinet/tcp_debug.h>
109#endif
110
111#ifdef IPSEC
112#include <netinet6/ipsec.h>
113#endif /*IPSEC*/
114
115#ifdef FAST_IPSEC
bf844ffa 116#include <netproto/ipsec/ipsec.h>
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117#define IPSEC
118#endif /*FAST_IPSEC*/
119
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120#ifdef notyet
121extern struct mbuf *m_copypack();
122#endif
123
dcc39f86 124int path_mtu_discovery = 0;
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125SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
126 &path_mtu_discovery, 1, "Enable Path MTU Discovery");
127
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128static int avoid_pure_win_update = 1;
129SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW,
130 &avoid_pure_win_update, 1, "Avoid pure window updates when possible");
131
5b0b9fa5
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132int tcp_do_autosndbuf = 1;
133SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
134 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing");
135
136int tcp_autosndbuf_inc = 8*1024;
137SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
138 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer");
139
46e92930 140int tcp_autosndbuf_max = 2*1024*1024;
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141SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
142 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer");
143
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144/*
145 * Tcp output routine: figure out what should be sent and send it.
146 */
147int
f3f70f0d 148tcp_output(struct tcpcb *tp)
984263bc 149{
0770aa24
JH
150 struct inpcb * const inp = tp->t_inpcb;
151 struct socket *so = inp->inp_socket;
c53f07a5 152 long len, recvwin, sendwin;
9a5b142f 153 int nsacked = 0;
984263bc 154 int off, flags, error;
b1992928
MD
155#ifdef TCP_SIGNATURE
156 int sigoff = 0;
157#endif
2256ba69 158 struct mbuf *m;
984263bc 159 struct ip *ip = NULL;
2256ba69 160 struct ipovly *ipov = NULL;
2256ba69 161 struct tcphdr *th;
984263bc 162 u_char opt[TCP_MAXOLEN];
91489f6b 163 unsigned int ipoptlen, optlen, hdrlen;
61896e3c
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164 int idle;
165 boolean_t sendalot;
0770aa24 166 struct ip6_hdr *ip6 = NULL;
984263bc 167#ifdef INET6
0770aa24
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168 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
169#else
170 const boolean_t isipv6 = FALSE;
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171#endif
172
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173 KKASSERT(so->so_port == &curthread->td_msgport);
174
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175 /*
176 * Determine length of data that should be transmitted,
177 * and flags that will be used.
178 * If there is some data or critical controls (SYN, RST)
179 * to send, then transmit; otherwise, investigate further.
180 */
8d573eef
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181
182 /*
183 * If we have been idle for a while, the send congestion window
184 * could be no longer representative of the current state of the link.
185 * So unless we are expecting more acks to come in, slow-start from
186 * scratch to re-determine the send congestion window.
187 */
188 if (tp->snd_max == tp->snd_una &&
76d7f185 189 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) {
8d573eef
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190 if (tcp_do_rfc3390) {
191 int initial_cwnd =
192 min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380));
193
194 tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd);
195 } else {
196 tp->snd_cwnd = tp->t_maxseg;
197 }
8acdb67c 198 tp->snd_wacked = 0;
984263bc 199 }
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200
201 /*
202 * Calculate whether the transmit stream was previously idle
203 * and adjust TF_LASTIDLE for the next time.
204 */
08525cf0
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205 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
206 if (idle && (tp->t_flags & TF_MORETOCOME))
207 tp->t_flags |= TF_LASTIDLE;
208 else
209 tp->t_flags &= ~TF_LASTIDLE;
79a80d9f 210
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211 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
212 !IN_FASTRECOVERY(tp))
213 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt);
214
984263bc 215again:
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216 /* Make use of SACK information when slow-starting after a RTO. */
217 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
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218 !IN_FASTRECOVERY(tp)) {
219 tcp_seq old_snd_nxt = tp->snd_nxt;
220
91489f6b 221 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt);
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222 nsacked += tp->snd_nxt - old_snd_nxt;
223 }
91489f6b 224
61896e3c 225 sendalot = FALSE;
984263bc 226 off = tp->snd_nxt - tp->snd_una;
9a5b142f 227 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked);
c53f07a5 228 sendwin = min(sendwin, tp->snd_bwnd);
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229
230 flags = tcp_outflags[tp->t_state];
231 /*
232 * Get standard flags, and add SYN or FIN if requested by 'hidden'
233 * state flags.
234 */
235 if (tp->t_flags & TF_NEEDFIN)
236 flags |= TH_FIN;
237 if (tp->t_flags & TF_NEEDSYN)
238 flags |= TH_SYN;
239
240 /*
241 * If in persist timeout with window of 0, send 1 byte.
242 * Otherwise, if window is small but nonzero
243 * and timer expired, we will send what we can
244 * and go to transmit state.
245 */
c1d3b892 246 if (tp->t_flags & TF_FORCE) {
c53f07a5 247 if (sendwin == 0) {
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248 /*
249 * If we still have some data to send, then
250 * clear the FIN bit. Usually this would
251 * happen below when it realizes that we
252 * aren't sending all the data. However,
253 * if we have exactly 1 byte of unsent data,
254 * then it won't clear the FIN bit below,
255 * and if we are in persist state, we wind
256 * up sending the packet without recording
257 * that we sent the FIN bit.
258 *
259 * We can't just blindly clear the FIN bit,
260 * because if we don't have any more data
261 * to send then the probe will be the FIN
262 * itself.
263 */
6d49aa6f 264 if (off < so->so_snd.ssb_cc)
984263bc 265 flags &= ~TH_FIN;
c53f07a5 266 sendwin = 1;
984263bc 267 } else {
a48c5dd5 268 tcp_callout_stop(tp, tp->tt_persist);
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269 tp->t_rxtshift = 0;
270 }
271 }
272
273 /*
0770aa24 274 * If snd_nxt == snd_max and we have transmitted a FIN, the
6d49aa6f 275 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in
c53f07a5 276 * a negative length. This can also occur when TCP opens up
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277 * its congestion window while receiving additional duplicate
278 * acks after fast-retransmit because TCP will reset snd_nxt
279 * to snd_max after the fast-retransmit.
280 *
281 * In the normal retransmit-FIN-only case, however, snd_nxt will
282 * be set to snd_una, the offset will be 0, and the length may
283 * wind up 0.
284 */
6d49aa6f 285 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off;
984263bc 286
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287 /*
288 * Lop off SYN bit if it has already been sent. However, if this
27b8aee3
AE
289 * is SYN-SENT state and if segment contains data, suppress sending
290 * segment (sending the segment would be an option if we still
291 * did TAO and the remote host supported it).
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292 */
293 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
294 flags &= ~TH_SYN;
295 off--, len++;
27b8aee3 296 if (len > 0 && tp->t_state == TCPS_SYN_SENT)
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297 return 0;
298 }
299
300 /*
27b8aee3 301 * Be careful not to send data and/or FIN on SYN segments.
984263bc
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302 * This measure is needed to prevent interoperability problems
303 * with not fully conformant TCP implementations.
304 */
27b8aee3 305 if (flags & TH_SYN) {
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306 len = 0;
307 flags &= ~TH_FIN;
308 }
309
310 if (len < 0) {
311 /*
312 * If FIN has been sent but not acked,
313 * but we haven't been called to retransmit,
314 * len will be < 0. Otherwise, window shrank
315 * after we sent into it. If window shrank to 0,
316 * cancel pending retransmit, pull snd_nxt back
317 * to (closed) window, and set the persist timer
318 * if it isn't already going. If the window didn't
319 * close completely, just wait for an ACK.
320 */
321 len = 0;
c53f07a5 322 if (sendwin == 0) {
a48c5dd5 323 tcp_callout_stop(tp, tp->tt_rexmt);
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324 tp->t_rxtshift = 0;
325 tp->snd_nxt = tp->snd_una;
a48c5dd5 326 if (!tcp_callout_active(tp, tp->tt_persist))
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MD
327 tcp_setpersist(tp);
328 }
329 }
330
5b0b9fa5 331 KASSERT(len >= 0, ("%s: len < 0", __func__));
984263bc 332 /*
5b0b9fa5
PA
333 * Automatic sizing of send socket buffer. Often the send buffer
334 * size is not optimally adjusted to the actual network conditions
335 * at hand (delay bandwidth product). Setting the buffer size too
336 * small limits throughput on links with high bandwidth and high
337 * delay (eg. trans-continental/oceanic links). Setting the
338 * buffer size too big consumes too much real kernel memory,
339 * especially with many connections on busy servers.
340 *
341 * The criteria to step up the send buffer one notch are:
342 * 1. receive window of remote host is larger than send buffer
343 * (with a fudge factor of 5/4th);
344 * 2. send buffer is filled to 7/8th with data (so we actually
345 * have data to make use of it);
346 * 3. send buffer fill has not hit maximal automatic size;
347 * 4. our send window (slow start and cogestion controlled) is
348 * larger than sent but unacknowledged data in send buffer.
349 *
350 * The remote host receive window scaling factor may limit the
351 * growing of the send buffer before it reaches its allowed
352 * maximum.
353 *
354 * It scales directly with slow start or congestion window
355 * and does at most one step per received ACK. This fast
356 * scaling has the drawback of growing the send buffer beyond
357 * what is strictly necessary to make full use of a given
358 * delay*bandwith product. However testing has shown this not
359 * to be much of an problem. At worst we are trading wasting
360 * of available bandwith (the non-use of it) for wasting some
361 * socket buffer memory.
362 *
363 * TODO: Shrink send buffer during idle periods together
364 * with congestion window. Requires another timer. Has to
365 * wait for upcoming tcp timer rewrite.
366 */
367 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) {
368 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat &&
369 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) &&
370 so->so_snd.ssb_cc < tcp_autosndbuf_max &&
371 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) {
46e92930
MD
372 u_long newsize;
373
374 newsize = ulmin(so->so_snd.ssb_hiwat +
375 tcp_autosndbuf_inc,
376 tcp_autosndbuf_max);
377 if (!ssb_reserve(&so->so_snd, newsize, so, NULL))
14343ad3 378 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
46e92930 379 if (newsize >= (TCP_MAXWIN << tp->snd_scale))
14343ad3 380 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
5b0b9fa5
PA
381 }
382 }
383
384 /*
385 * Truncate to the maximum segment length and ensure that FIN is
386 * removed if the length no longer contains the last data byte.
984263bc
MD
387 */
388 if (len > tp->t_maxseg) {
389 len = tp->t_maxseg;
61896e3c 390 sendalot = TRUE;
984263bc 391 }
6d49aa6f 392 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc))
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393 flags &= ~TH_FIN;
394
6d49aa6f 395 recvwin = ssb_space(&so->so_rcv);
984263bc
MD
396
397 /*
398 * Sender silly window avoidance. We transmit under the following
399 * conditions when len is non-zero:
400 *
401 * - We have a full segment
402 * - This is the last buffer in a write()/send() and we are
403 * either idle or running NODELAY
404 * - we've timed out (e.g. persist timer)
405 * - we have more then 1/2 the maximum send window's worth of
653eb2c0 406 * data (receiver may be limiting the window size)
984263bc
MD
407 * - we need to retransmit
408 */
409 if (len) {
410 if (len == tp->t_maxseg)
411 goto send;
412 /*
413 * NOTE! on localhost connections an 'ack' from the remote
414 * end may occur synchronously with the output and cause
415 * us to flush a buffer queued with moretocome. XXX
416 *
417 * note: the len + off check is almost certainly unnecessary.
418 */
419 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
420 (idle || (tp->t_flags & TF_NODELAY)) &&
6d49aa6f 421 len + off >= so->so_snd.ssb_cc &&
0770aa24 422 !(tp->t_flags & TF_NOPUSH)) {
984263bc
MD
423 goto send;
424 }
c1d3b892 425 if (tp->t_flags & TF_FORCE) /* typ. timeout case */
984263bc
MD
426 goto send;
427 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
428 goto send;
429 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
430 goto send;
431 }
432
433 /*
434 * Compare available window to amount of window
435 * known to peer (as advertised window less
436 * next expected input). If the difference is at least two
437 * max size segments, or at least 50% of the maximum possible
438 * window, then want to send a window update to peer.
439 */
c53f07a5 440 if (recvwin > 0) {
984263bc
MD
441 /*
442 * "adv" is the amount we can increase the window,
443 * taking into account that we are limited by
444 * TCP_MAXWIN << tp->rcv_scale.
445 */
c53f07a5 446 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) -
984263bc 447 (tp->rcv_adv - tp->rcv_nxt);
46e92930 448 long hiwat;
984263bc 449
ddb2e271
MD
450 /*
451 * This ack case typically occurs when the user has drained
452 * the TCP socket buffer sufficiently to warrent an ack
453 * containing a 'pure window update'... that is, an ack that
454 * ONLY updates the tcp window.
455 *
456 * It is unclear why we would need to do a pure window update
457 * past 2 segments if we are going to do one at 1/2 the high
458 * water mark anyway, especially since under normal conditions
f23061d4 459 * the user program will drain the socket buffer quickly.
ddb2e271
MD
460 * The 2-segment pure window update will often add a large
461 * number of extra, unnecessary acks to the stream.
462 *
463 * avoid_pure_win_update now defaults to 1.
464 */
46e92930
MD
465 if (avoid_pure_win_update == 0 ||
466 (tp->t_flags & TF_RXRESIZED)) {
467 if (adv >= (long) (2 * tp->t_maxseg)) {
ddb2e271 468 goto send;
46e92930 469 }
ddb2e271 470 }
46e92930
MD
471 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale);
472 if (hiwat > (long)so->so_rcv.ssb_hiwat)
473 hiwat = (long)so->so_rcv.ssb_hiwat;
474 if (adv >= hiwat / 2)
984263bc
MD
475 goto send;
476 }
477
478 /*
479 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
480 * is also a catch-all for the retransmit timer timeout case.
481 */
482 if (tp->t_flags & TF_ACKNOW)
483 goto send;
484 if ((flags & TH_RST) ||
0770aa24 485 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN)))
984263bc
MD
486 goto send;
487 if (SEQ_GT(tp->snd_up, tp->snd_una))
488 goto send;
489 /*
490 * If our state indicates that FIN should be sent
491 * and we have not yet done so, then we need to send.
492 */
493 if (flags & TH_FIN &&
0770aa24 494 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una))
984263bc
MD
495 goto send;
496
497 /*
498 * TCP window updates are not reliable, rather a polling protocol
499 * using ``persist'' packets is used to insure receipt of window
500 * updates. The three ``states'' for the output side are:
501 * idle not doing retransmits or persists
502 * persisting to move a small or zero window
503 * (re)transmitting and thereby not persisting
504 *
a48c5dd5 505 * tcp_callout_active(tp, tp->tt_persist)
984263bc 506 * is true when we are in persist state.
c1d3b892 507 * The TF_FORCE flag in tp->t_flags
984263bc 508 * is set when we are called to send a persist packet.
a48c5dd5 509 * tcp_callout_active(tp, tp->tt_rexmt)
984263bc
MD
510 * is set when we are retransmitting
511 * The output side is idle when both timers are zero.
512 *
513 * If send window is too small, there is data to transmit, and no
514 * retransmit or persist is pending, then go to persist state.
515 * If nothing happens soon, send when timer expires:
516 * if window is nonzero, transmit what we can,
517 * otherwise force out a byte.
518 */
6d49aa6f 519 if (so->so_snd.ssb_cc > 0 &&
a48c5dd5
SZ
520 !tcp_callout_active(tp, tp->tt_rexmt) &&
521 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
522 tp->t_rxtshift = 0;
523 tcp_setpersist(tp);
524 }
525
526 /*
527 * No reason to send a segment, just return.
528 */
529 return (0);
530
531send:
532 /*
533 * Before ESTABLISHED, force sending of initial options
534 * unless TCP set not to do any options.
535 * NOTE: we assume that the IP/TCP header plus TCP options
536 * always fit in a single mbuf, leaving room for a maximum
537 * link header, i.e.
79a80d9f 538 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES
984263bc
MD
539 */
540 optlen = 0;
984263bc 541 if (isipv6)
79a80d9f 542 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
984263bc 543 else
79a80d9f 544 hdrlen = sizeof(struct tcpiphdr);
984263bc
MD
545 if (flags & TH_SYN) {
546 tp->snd_nxt = tp->iss;
0770aa24 547 if (!(tp->t_flags & TF_NOOPT)) {
984263bc
MD
548 u_short mss;
549
550 opt[0] = TCPOPT_MAXSEG;
551 opt[1] = TCPOLEN_MAXSEG;
552 mss = htons((u_short) tcp_mssopt(tp));
f23061d4 553 memcpy(opt + 2, &mss, sizeof mss);
984263bc
MD
554 optlen = TCPOLEN_MAXSEG;
555
556 if ((tp->t_flags & TF_REQ_SCALE) &&
0770aa24
JH
557 (!(flags & TH_ACK) ||
558 (tp->t_flags & TF_RCVD_SCALE))) {
984263bc
MD
559 *((u_int32_t *)(opt + optlen)) = htonl(
560 TCPOPT_NOP << 24 |
561 TCPOPT_WINDOW << 16 |
562 TCPOLEN_WINDOW << 8 |
563 tp->request_r_scale);
564 optlen += 4;
565 }
91489f6b
JH
566
567 if ((tcp_do_sack && !(flags & TH_ACK)) ||
568 tp->t_flags & TF_SACK_PERMITTED) {
569 uint32_t *lp = (uint32_t *)(opt + optlen);
570
571 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
572 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED;
573 }
984263bc 574 }
0770aa24 575 }
984263bc 576
0770aa24 577 /*
984263bc
MD
578 * Send a timestamp and echo-reply if this is a SYN and our side
579 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
580 * and our peer have sent timestamps in our SYN's.
0770aa24 581 */
61896e3c 582 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
0770aa24
JH
583 !(flags & TH_RST) &&
584 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) {
984263bc
MD
585 u_int32_t *lp = (u_int32_t *)(opt + optlen);
586
0770aa24
JH
587 /* Form timestamp option as shown in appendix A of RFC 1323. */
588 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
589 *lp++ = htonl(ticks);
590 *lp = htonl(tp->ts_recent);
591 optlen += TCPOLEN_TSTAMP_APPA;
592 }
984263bc 593
5b0b9fa5
PA
594 /* Set receive buffer autosizing timestamp. */
595 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE))
596 tp->rfbuf_ts = ticks;
597
0770aa24 598 /*
91489f6b
JH
599 * If this is a SACK connection and we have a block to report,
600 * fill in the SACK blocks in the TCP options.
601 */
602 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) ==
603 TF_SACK_PERMITTED &&
604 (!LIST_EMPTY(&tp->t_segq) ||
605 tp->reportblk.rblk_start != tp->reportblk.rblk_end))
606 tcp_sack_fill_report(tp, opt, &optlen);
607
b1992928
MD
608#ifdef TCP_SIGNATURE
609 if (tp->t_flags & TF_SIGNATURE) {
610 int i;
611 u_char *bp;
612 /*
613 * Initialize TCP-MD5 option (RFC2385)
614 */
615 bp = (u_char *)opt + optlen;
616 *bp++ = TCPOPT_SIGNATURE;
617 *bp++ = TCPOLEN_SIGNATURE;
618 sigoff = optlen + 2;
619 for (i = 0; i < TCP_SIGLEN; i++)
620 *bp++ = 0;
621 optlen += TCPOLEN_SIGNATURE;
622 /*
623 * Terminate options list and maintain 32-bit alignment.
624 */
625 *bp++ = TCPOPT_NOP;
626 *bp++ = TCPOPT_EOL;
627 optlen += 2;
628 }
629#endif /* TCP_SIGNATURE */
91489f6b 630 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options"));
0770aa24 631 hdrlen += optlen;
984263bc 632
61896e3c 633 if (isipv6) {
0770aa24 634 ipoptlen = ip6_optlen(inp);
61896e3c 635 } else {
0770aa24
JH
636 if (inp->inp_options) {
637 ipoptlen = inp->inp_options->m_len -
638 offsetof(struct ipoption, ipopt_list);
639 } else {
640 ipoptlen = 0;
641 }
984263bc 642 }
984263bc
MD
643#ifdef IPSEC
644 ipoptlen += ipsec_hdrsiz_tcp(tp);
645#endif
646
647 /*
45f20ce7
MD
648 * Adjust data length if insertion of options will bump the packet
649 * length beyond the t_maxopd length. Clear FIN to prevent premature
650 * closure since there is still more data to send after this (now
651 * truncated) packet.
652 *
653 * If just the options do not fit we are in a no-win situation and
654 * we treat it as an unreachable host.
984263bc
MD
655 */
656 if (len + optlen + ipoptlen > tp->t_maxopd) {
45f20ce7
MD
657 if (tp->t_maxopd <= optlen + ipoptlen) {
658 static time_t last_optlen_report;
659
660 if (last_optlen_report != time_second) {
661 last_optlen_report = time_second;
a6ec04bc 662 kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd);
45f20ce7
MD
663 }
664 error = EHOSTUNREACH;
665 goto out;
666 } else {
667 flags &= ~TH_FIN;
668 len = tp->t_maxopd - optlen - ipoptlen;
669 sendalot = TRUE;
670 }
984263bc
MD
671 }
672
984263bc 673#ifdef INET6
0770aa24 674 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big"));
984263bc 675#else
0770aa24 676 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big"));
984263bc 677#endif
984263bc
MD
678
679 /*
680 * Grab a header mbuf, attaching a copy of data to
681 * be transmitted, and initialize the header from
682 * the template for sends on this connection.
683 */
684 if (len) {
c1d3b892 685 if ((tp->t_flags & TF_FORCE) && len == 1)
984263bc
MD
686 tcpstat.tcps_sndprobe++;
687 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
91489f6b
JH
688 if (tp->snd_nxt == tp->snd_una)
689 tp->snd_max_rexmt = tp->snd_max;
984263bc
MD
690 tcpstat.tcps_sndrexmitpack++;
691 tcpstat.tcps_sndrexmitbyte += len;
692 } else {
693 tcpstat.tcps_sndpack++;
694 tcpstat.tcps_sndbyte += len;
695 }
696#ifdef notyet
6d49aa6f 697 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len,
61896e3c 698 max_linkhdr + hdrlen)) == NULL) {
984263bc
MD
699 error = ENOBUFS;
700 goto out;
701 }
702 /*
703 * m_copypack left space for our hdr; use it.
704 */
705 m->m_len += hdrlen;
706 m->m_data -= hdrlen;
707#else
50503f0f
JH
708#ifndef INET6
709 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
710#else
711 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER,
712 M_PKTHDR, NULL);
713#endif
984263bc
MD
714 if (m == NULL) {
715 error = ENOBUFS;
716 goto out;
717 }
984263bc
MD
718 m->m_data += max_linkhdr;
719 m->m_len = hdrlen;
720 if (len <= MHLEN - hdrlen - max_linkhdr) {
6d49aa6f 721 m_copydata(so->so_snd.ssb_mb, off, (int) len,
984263bc
MD
722 mtod(m, caddr_t) + hdrlen);
723 m->m_len += len;
724 } else {
6d49aa6f 725 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len);
61896e3c 726 if (m->m_next == NULL) {
f23061d4 727 m_free(m);
984263bc
MD
728 error = ENOBUFS;
729 goto out;
730 }
731 }
732#endif
733 /*
734 * If we're sending everything we've got, set PUSH.
735 * (This will keep happy those implementations which only
736 * give data to the user when a buffer fills or
737 * a PUSH comes in.)
738 */
6d49aa6f 739 if (off + len == so->so_snd.ssb_cc)
984263bc
MD
740 flags |= TH_PUSH;
741 } else {
742 if (tp->t_flags & TF_ACKNOW)
743 tcpstat.tcps_sndacks++;
61896e3c 744 else if (flags & (TH_SYN | TH_FIN | TH_RST))
984263bc
MD
745 tcpstat.tcps_sndctrl++;
746 else if (SEQ_GT(tp->snd_up, tp->snd_una))
747 tcpstat.tcps_sndurg++;
748 else
749 tcpstat.tcps_sndwinup++;
750
74f1caca 751 MGETHDR(m, MB_DONTWAIT, MT_HEADER);
984263bc
MD
752 if (m == NULL) {
753 error = ENOBUFS;
754 goto out;
755 }
0770aa24
JH
756 if (isipv6 &&
757 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN)
984263bc 758 MH_ALIGN(m, hdrlen);
0770aa24
JH
759 else
760 m->m_data += max_linkhdr;
984263bc
MD
761 m->m_len = hdrlen;
762 }
60233e58 763 m->m_pkthdr.rcvif = NULL;
984263bc
MD
764 if (isipv6) {
765 ip6 = mtod(m, struct ip6_hdr *);
766 th = (struct tcphdr *)(ip6 + 1);
767 tcp_fillheaders(tp, ip6, th);
0770aa24
JH
768 } else {
769 ip = mtod(m, struct ip *);
770 ipov = (struct ipovly *)ip;
771 th = (struct tcphdr *)(ip + 1);
772 /* this picks up the pseudo header (w/o the length) */
773 tcp_fillheaders(tp, ip, th);
774 }
984263bc
MD
775
776 /*
777 * Fill in fields, remembering maximum advertised
778 * window for use in delaying messages about window sizes.
779 * If resending a FIN, be sure not to use a new sequence number.
780 */
781 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
782 tp->snd_nxt == tp->snd_max)
783 tp->snd_nxt--;
784 /*
785 * If we are doing retransmissions, then snd_nxt will
786 * not reflect the first unsent octet. For ACK only
787 * packets, we do not want the sequence number of the
788 * retransmitted packet, we want the sequence number
789 * of the next unsent octet. So, if there is no data
790 * (and no SYN or FIN), use snd_max instead of snd_nxt
791 * when filling in ti_seq. But if we are in persist
792 * state, snd_max might reflect one byte beyond the
793 * right edge of the window, so use snd_nxt in that
794 * case, since we know we aren't doing a retransmission.
795 * (retransmit and persist are mutually exclusive...)
796 */
a48c5dd5
SZ
797 if (len || (flags & (TH_SYN|TH_FIN)) ||
798 tcp_callout_active(tp, tp->tt_persist))
984263bc
MD
799 th->th_seq = htonl(tp->snd_nxt);
800 else
801 th->th_seq = htonl(tp->snd_max);
802 th->th_ack = htonl(tp->rcv_nxt);
803 if (optlen) {
804 bcopy(opt, th + 1, optlen);
79a80d9f 805 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
984263bc
MD
806 }
807 th->th_flags = flags;
46e92930 808
984263bc 809 /*
46e92930
MD
810 * Calculate receive window. Don't shrink window, but avoid
811 * silly window syndrome by sending a 0 window if the actual
812 * window is less then one segment.
984263bc 813 */
6d49aa6f 814 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) &&
c53f07a5
JH
815 recvwin < (long)tp->t_maxseg)
816 recvwin = 0;
55126001
MD
817 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt))
818 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt);
c53f07a5
JH
819 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale)
820 recvwin = (long)TCP_MAXWIN << tp->rcv_scale;
821 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale));
984263bc
MD
822
823 /*
824 * Adjust the RXWIN0SENT flag - indicate that we have advertised
825 * a 0 window. This may cause the remote transmitter to stall. This
826 * flag tells soreceive() to disable delayed acknowledgements when
827 * draining the buffer. This can occur if the receiver is attempting
828 * to read more data then can be buffered prior to transmitting on
829 * the connection.
830 */
c53f07a5 831 if (recvwin == 0)
984263bc
MD
832 tp->t_flags |= TF_RXWIN0SENT;
833 else
834 tp->t_flags &= ~TF_RXWIN0SENT;
835
836 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
837 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
838 th->th_flags |= TH_URG;
79a80d9f 839 } else {
984263bc
MD
840 /*
841 * If no urgent pointer to send, then we pull
842 * the urgent pointer to the left edge of the send window
843 * so that it doesn't drift into the send window on sequence
844 * number wraparound.
845 */
846 tp->snd_up = tp->snd_una; /* drag it along */
79a80d9f 847 }
984263bc 848
b1992928
MD
849#ifdef TCP_SIGNATURE
850 if (tp->t_flags & TF_SIGNATURE)
851 tcpsignature_compute(m, len, optlen,
852 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
853#endif /* TCP_SIGNATURE */
854
984263bc
MD
855 /*
856 * Put TCP length in extended header, and then
857 * checksum extended header and data.
858 */
859 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
0770aa24 860 if (isipv6) {
984263bc
MD
861 /*
862 * ip6_plen is not need to be filled now, and will be filled
5fe66e68 863 * in ip6_output().
984263bc
MD
864 */
865 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
866 sizeof(struct tcphdr) + optlen + len);
0770aa24
JH
867 } else {
868 m->m_pkthdr.csum_flags = CSUM_TCP;
869 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
870 if (len + optlen)
871 th->th_sum = in_addword(th->th_sum,
872 htons((u_short)(optlen + len)));
873
874 /* IP version must be set here for ipv4/ipv6 checking later */
875 KASSERT(ip->ip_v == IPVERSION,
876 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
877 }
984263bc
MD
878
879 /*
880 * In transmit state, time the transmission and arrange for
881 * the retransmit. In persist state, just set snd_max.
882 */
a48c5dd5
SZ
883 if (!(tp->t_flags & TF_FORCE) ||
884 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
885 tcp_seq startseq = tp->snd_nxt;
886
887 /*
888 * Advance snd_nxt over sequence space of this segment.
889 */
61896e3c 890 if (flags & (TH_SYN | TH_FIN)) {
984263bc
MD
891 if (flags & TH_SYN)
892 tp->snd_nxt++;
893 if (flags & TH_FIN) {
894 tp->snd_nxt++;
895 tp->t_flags |= TF_SENTFIN;
896 }
897 }
898 tp->snd_nxt += len;
899 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
900 tp->snd_max = tp->snd_nxt;
901 /*
902 * Time this transmission if not a retransmission and
903 * not currently timing anything.
904 */
905 if (tp->t_rtttime == 0) {
906 tp->t_rtttime = ticks;
907 tp->t_rtseq = startseq;
908 tcpstat.tcps_segstimed++;
909 }
910 }
911
912 /*
913 * Set retransmit timer if not currently set,
914 * and not doing a pure ack or a keep-alive probe.
915 * Initial value for retransmit timer is smoothed
916 * round-trip time + 2 * round-trip time variance.
917 * Initialize shift counter which is used for backoff
918 * of retransmit time.
919 */
a48c5dd5 920 if (!tcp_callout_active(tp, tp->tt_rexmt) &&
984263bc 921 tp->snd_nxt != tp->snd_una) {
a48c5dd5
SZ
922 if (tcp_callout_active(tp, tp->tt_persist)) {
923 tcp_callout_stop(tp, tp->tt_persist);
984263bc
MD
924 tp->t_rxtshift = 0;
925 }
a48c5dd5
SZ
926 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
927 tcp_timer_rexmt);
984263bc
MD
928 }
929 } else {
930 /*
931 * Persist case, update snd_max but since we are in
932 * persist mode (no window) we do not update snd_nxt.
933 */
934 int xlen = len;
935 if (flags & TH_SYN)
94603b1b 936 panic("tcp_output: persist timer to send SYN\n");
984263bc
MD
937 if (flags & TH_FIN) {
938 ++xlen;
939 tp->t_flags |= TF_SENTFIN;
940 }
941 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
942 tp->snd_max = tp->snd_nxt + xlen;
943 }
944
945#ifdef TCPDEBUG
946 /*
947 * Trace.
948 */
949 if (so->so_options & SO_DEBUG)
950 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
951#endif
952
953 /*
954 * Fill in IP length and desired time to live and
955 * send to IP level. There should be a better way
956 * to handle ttl and tos; we could keep them in
957 * the template, but need a way to checksum without them.
958 */
959 /*
960 * m->m_pkthdr.len should have been set before cksum calcuration,
961 * because in6_cksum() need it.
962 */
984263bc
MD
963 if (isipv6) {
964 /*
965 * we separately set hoplimit for every segment, since the
966 * user might want to change the value via setsockopt.
967 * Also, desired default hop limit might be changed via
968 * Neighbor Discovery.
969 */
0770aa24
JH
970 ip6->ip6_hlim = in6_selecthlim(inp,
971 (inp->in6p_route.ro_rt ?
972 inp->in6p_route.ro_rt->rt_ifp : NULL));
984263bc
MD
973
974 /* TODO: IPv6 IP6TOS_ECT bit on */
0770aa24 975 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route,
5fe66e68
JH
976 (so->so_options & SO_DONTROUTE), NULL, NULL,
977 inp);
0770aa24
JH
978 } else {
979 struct rtentry *rt;
980 ip->ip_len = m->m_pkthdr.len;
984263bc 981#ifdef INET6
0770aa24
JH
982 if (INP_CHECK_SOCKAF(so, AF_INET6))
983 ip->ip_ttl = in6_selecthlim(inp,
984 (inp->in6p_route.ro_rt ?
985 inp->in6p_route.ro_rt->rt_ifp : NULL));
986 else
987#endif
988 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
989
990 ip->ip_tos = inp->inp_ip_tos; /* XXX */
991 /*
992 * See if we should do MTU discovery.
993 * We do it only if the following are true:
994 * 1) we have a valid route to the destination
995 * 2) the MTU is not locked (if it is,
996 * then discovery has been disabled)
997 */
998 if (path_mtu_discovery &&
999 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) &&
1000 !(rt->rt_rmx.rmx_locks & RTV_MTU))
1001 ip->ip_off |= IP_DF;
1002
1003 error = ip_output(m, inp->inp_options, &inp->inp_route,
1dbb3516
SZ
1004 (so->so_options & SO_DONTROUTE) |
1005 IP_DEBUGROUTE, NULL, inp);
0770aa24 1006 }
984263bc
MD
1007 if (error) {
1008
1009 /*
1010 * We know that the packet was lost, so back out the
1011 * sequence number advance, if any.
1012 */
c1d3b892 1013 if (!(tp->t_flags & TF_FORCE) ||
a48c5dd5 1014 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
1015 /*
1016 * No need to check for TH_FIN here because
1017 * the TF_SENTFIN flag handles that case.
1018 */
0770aa24 1019 if (!(flags & TH_SYN))
984263bc
MD
1020 tp->snd_nxt -= len;
1021 }
1022
1023out:
1024 if (error == ENOBUFS) {
ea8bd01a
JH
1025 /*
1026 * If we can't send, make sure there is something
1027 * to get us going again later. Persist state
1028 * is not necessarily right, but it is close enough.
1029 */
a48c5dd5
SZ
1030 if (!tcp_callout_active(tp, tp->tt_rexmt) &&
1031 !tcp_callout_active(tp, tp->tt_persist)) {
ea8bd01a
JH
1032 tp->t_rxtshift = 0;
1033 tcp_setpersist(tp);
1034 }
0770aa24 1035 tcp_quench(inp, 0);
984263bc
MD
1036 return (0);
1037 }
1038 if (error == EMSGSIZE) {
1039 /*
1040 * ip_output() will have already fixed the route
1041 * for us. tcp_mtudisc() will, as its last action,
1042 * initiate retransmission, so it is important to
1043 * not do so here.
1044 */
0770aa24 1045 tcp_mtudisc(inp, 0);
984263bc
MD
1046 return 0;
1047 }
0770aa24
JH
1048 if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1049 TCPS_HAVERCVDSYN(tp->t_state)) {
984263bc
MD
1050 tp->t_softerror = error;
1051 return (0);
1052 }
1053 return (error);
1054 }
1055 tcpstat.tcps_sndtotal++;
1056
1057 /*
1058 * Data sent (as far as we can tell).
46e92930 1059 *
984263bc
MD
1060 * If this advertises a larger window than any other segment,
1061 * then remember the size of the advertised window.
46e92930 1062 *
984263bc
MD
1063 * Any pending ACK has now been sent.
1064 */
46e92930 1065 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) {
c53f07a5 1066 tp->rcv_adv = tp->rcv_nxt + recvwin;
46e92930
MD
1067 tp->t_flags &= ~TF_RXRESIZED;
1068 }
984263bc
MD
1069 tp->last_ack_sent = tp->rcv_nxt;
1070 tp->t_flags &= ~TF_ACKNOW;
1071 if (tcp_delack_enabled)
a48c5dd5 1072 tcp_callout_stop(tp, tp->tt_delack);
984263bc
MD
1073 if (sendalot)
1074 goto again;
1075 return (0);
1076}
1077
1078void
f3f70f0d 1079tcp_setpersist(struct tcpcb *tp)
984263bc
MD
1080{
1081 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1082 int tt;
1083
94603b1b
SZ
1084 if (tp->t_state < TCPS_ESTABLISHED)
1085 panic("tcp_setpersist: not established yet\n");
1086
a48c5dd5 1087 if (tcp_callout_active(tp, tp->tt_rexmt))
984263bc
MD
1088 panic("tcp_setpersist: retransmit pending");
1089 /*
1090 * Start/restart persistance timer.
1091 */
5fe66e68
JH
1092 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN,
1093 TCPTV_PERSMAX);
a48c5dd5 1094 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist);
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MD
1095 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1096 tp->t_rxtshift++;
1097}