kernel - Fix improper persist state in tcp
[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>
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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
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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
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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;
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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
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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 */
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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 *
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281 * A negative length can also occur when we are in the
282 * TCPS_SYN_RECEIVED state due to a simultanious connect where
283 * our SYN has not been acked yet.
284 *
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285 * In the normal retransmit-FIN-only case, however, snd_nxt will
286 * be set to snd_una, the offset will be 0, and the length may
287 * wind up 0.
288 */
6d49aa6f 289 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off;
984263bc 290
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291 /*
292 * Lop off SYN bit if it has already been sent. However, if this
27b8aee3
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293 * is SYN-SENT state and if segment contains data, suppress sending
294 * segment (sending the segment would be an option if we still
295 * did TAO and the remote host supported it).
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296 */
297 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
298 flags &= ~TH_SYN;
299 off--, len++;
27b8aee3 300 if (len > 0 && tp->t_state == TCPS_SYN_SENT)
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301 return 0;
302 }
303
304 /*
27b8aee3 305 * Be careful not to send data and/or FIN on SYN segments.
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306 * This measure is needed to prevent interoperability problems
307 * with not fully conformant TCP implementations.
308 */
27b8aee3 309 if (flags & TH_SYN) {
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310 len = 0;
311 flags &= ~TH_FIN;
312 }
313
314 if (len < 0) {
315 /*
55696211
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316 * A negative len can occur if our FIN has been sent but not
317 * acked, or if we are in a simultanious connect in the
318 * TCPS_SYN_RECEIVED state with our SYN sent but not yet
319 * acked.
320 *
321 * If our window has contracted to 0 in the FIN case
322 * (which can only occur if we have NOT been called to
323 * retransmit as per code a few paragraphs up) then we
324 * want to shift the retransmit timer over to the
325 * persist timer.
326 *
327 * However, if we are in the TCPS_SYN_RECEIVED state
328 * (the SYN case) we will be in a simultanious connect and
329 * the window may be zero degeneratively. In this case we
330 * do not want to shift to the persist timer after the SYN
331 * or the SYN+ACK transmission.
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332 */
333 len = 0;
55696211 334 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) {
a48c5dd5 335 tcp_callout_stop(tp, tp->tt_rexmt);
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336 tp->t_rxtshift = 0;
337 tp->snd_nxt = tp->snd_una;
a48c5dd5 338 if (!tcp_callout_active(tp, tp->tt_persist))
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MD
339 tcp_setpersist(tp);
340 }
341 }
342
5b0b9fa5 343 KASSERT(len >= 0, ("%s: len < 0", __func__));
984263bc 344 /*
5b0b9fa5
PA
345 * Automatic sizing of send socket buffer. Often the send buffer
346 * size is not optimally adjusted to the actual network conditions
347 * at hand (delay bandwidth product). Setting the buffer size too
348 * small limits throughput on links with high bandwidth and high
349 * delay (eg. trans-continental/oceanic links). Setting the
350 * buffer size too big consumes too much real kernel memory,
351 * especially with many connections on busy servers.
352 *
353 * The criteria to step up the send buffer one notch are:
354 * 1. receive window of remote host is larger than send buffer
355 * (with a fudge factor of 5/4th);
356 * 2. send buffer is filled to 7/8th with data (so we actually
357 * have data to make use of it);
358 * 3. send buffer fill has not hit maximal automatic size;
359 * 4. our send window (slow start and cogestion controlled) is
360 * larger than sent but unacknowledged data in send buffer.
361 *
362 * The remote host receive window scaling factor may limit the
363 * growing of the send buffer before it reaches its allowed
364 * maximum.
365 *
366 * It scales directly with slow start or congestion window
367 * and does at most one step per received ACK. This fast
368 * scaling has the drawback of growing the send buffer beyond
369 * what is strictly necessary to make full use of a given
370 * delay*bandwith product. However testing has shown this not
371 * to be much of an problem. At worst we are trading wasting
372 * of available bandwith (the non-use of it) for wasting some
373 * socket buffer memory.
374 *
375 * TODO: Shrink send buffer during idle periods together
376 * with congestion window. Requires another timer. Has to
377 * wait for upcoming tcp timer rewrite.
378 */
379 if (tcp_do_autosndbuf && so->so_snd.ssb_flags & SSB_AUTOSIZE) {
380 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.ssb_hiwat &&
381 so->so_snd.ssb_cc >= (so->so_snd.ssb_hiwat / 8 * 7) &&
382 so->so_snd.ssb_cc < tcp_autosndbuf_max &&
383 sendwin >= (so->so_snd.ssb_cc - (tp->snd_nxt - tp->snd_una))) {
46e92930
MD
384 u_long newsize;
385
386 newsize = ulmin(so->so_snd.ssb_hiwat +
387 tcp_autosndbuf_inc,
388 tcp_autosndbuf_max);
389 if (!ssb_reserve(&so->so_snd, newsize, so, NULL))
14343ad3 390 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
46e92930 391 if (newsize >= (TCP_MAXWIN << tp->snd_scale))
14343ad3 392 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
5b0b9fa5
PA
393 }
394 }
395
396 /*
397 * Truncate to the maximum segment length and ensure that FIN is
398 * removed if the length no longer contains the last data byte.
984263bc
MD
399 */
400 if (len > tp->t_maxseg) {
401 len = tp->t_maxseg;
61896e3c 402 sendalot = TRUE;
984263bc 403 }
6d49aa6f 404 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc))
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405 flags &= ~TH_FIN;
406
6d49aa6f 407 recvwin = ssb_space(&so->so_rcv);
984263bc
MD
408
409 /*
410 * Sender silly window avoidance. We transmit under the following
411 * conditions when len is non-zero:
412 *
413 * - We have a full segment
414 * - This is the last buffer in a write()/send() and we are
415 * either idle or running NODELAY
416 * - we've timed out (e.g. persist timer)
417 * - we have more then 1/2 the maximum send window's worth of
653eb2c0 418 * data (receiver may be limiting the window size)
984263bc
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419 * - we need to retransmit
420 */
421 if (len) {
422 if (len == tp->t_maxseg)
423 goto send;
424 /*
425 * NOTE! on localhost connections an 'ack' from the remote
426 * end may occur synchronously with the output and cause
427 * us to flush a buffer queued with moretocome. XXX
428 *
429 * note: the len + off check is almost certainly unnecessary.
430 */
431 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
432 (idle || (tp->t_flags & TF_NODELAY)) &&
6d49aa6f 433 len + off >= so->so_snd.ssb_cc &&
0770aa24 434 !(tp->t_flags & TF_NOPUSH)) {
984263bc
MD
435 goto send;
436 }
c1d3b892 437 if (tp->t_flags & TF_FORCE) /* typ. timeout case */
984263bc
MD
438 goto send;
439 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
440 goto send;
441 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
442 goto send;
443 }
444
445 /*
446 * Compare available window to amount of window
447 * known to peer (as advertised window less
448 * next expected input). If the difference is at least two
449 * max size segments, or at least 50% of the maximum possible
450 * window, then want to send a window update to peer.
451 */
c53f07a5 452 if (recvwin > 0) {
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453 /*
454 * "adv" is the amount we can increase the window,
455 * taking into account that we are limited by
456 * TCP_MAXWIN << tp->rcv_scale.
457 */
c53f07a5 458 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) -
984263bc 459 (tp->rcv_adv - tp->rcv_nxt);
46e92930 460 long hiwat;
984263bc 461
ddb2e271
MD
462 /*
463 * This ack case typically occurs when the user has drained
464 * the TCP socket buffer sufficiently to warrent an ack
465 * containing a 'pure window update'... that is, an ack that
466 * ONLY updates the tcp window.
467 *
468 * It is unclear why we would need to do a pure window update
469 * past 2 segments if we are going to do one at 1/2 the high
470 * water mark anyway, especially since under normal conditions
f23061d4 471 * the user program will drain the socket buffer quickly.
ddb2e271
MD
472 * The 2-segment pure window update will often add a large
473 * number of extra, unnecessary acks to the stream.
474 *
475 * avoid_pure_win_update now defaults to 1.
476 */
46e92930
MD
477 if (avoid_pure_win_update == 0 ||
478 (tp->t_flags & TF_RXRESIZED)) {
479 if (adv >= (long) (2 * tp->t_maxseg)) {
ddb2e271 480 goto send;
46e92930 481 }
ddb2e271 482 }
46e92930
MD
483 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale);
484 if (hiwat > (long)so->so_rcv.ssb_hiwat)
485 hiwat = (long)so->so_rcv.ssb_hiwat;
486 if (adv >= hiwat / 2)
984263bc
MD
487 goto send;
488 }
489
490 /*
491 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
492 * is also a catch-all for the retransmit timer timeout case.
493 */
494 if (tp->t_flags & TF_ACKNOW)
495 goto send;
496 if ((flags & TH_RST) ||
0770aa24 497 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN)))
984263bc
MD
498 goto send;
499 if (SEQ_GT(tp->snd_up, tp->snd_una))
500 goto send;
501 /*
502 * If our state indicates that FIN should be sent
503 * and we have not yet done so, then we need to send.
504 */
505 if (flags & TH_FIN &&
0770aa24 506 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una))
984263bc
MD
507 goto send;
508
509 /*
510 * TCP window updates are not reliable, rather a polling protocol
511 * using ``persist'' packets is used to insure receipt of window
512 * updates. The three ``states'' for the output side are:
513 * idle not doing retransmits or persists
514 * persisting to move a small or zero window
515 * (re)transmitting and thereby not persisting
516 *
a48c5dd5 517 * tcp_callout_active(tp, tp->tt_persist)
984263bc 518 * is true when we are in persist state.
c1d3b892 519 * The TF_FORCE flag in tp->t_flags
984263bc 520 * is set when we are called to send a persist packet.
a48c5dd5 521 * tcp_callout_active(tp, tp->tt_rexmt)
984263bc
MD
522 * is set when we are retransmitting
523 * The output side is idle when both timers are zero.
524 *
525 * If send window is too small, there is data to transmit, and no
526 * retransmit or persist is pending, then go to persist state.
527 * If nothing happens soon, send when timer expires:
528 * if window is nonzero, transmit what we can,
529 * otherwise force out a byte.
530 */
6d49aa6f 531 if (so->so_snd.ssb_cc > 0 &&
a48c5dd5
SZ
532 !tcp_callout_active(tp, tp->tt_rexmt) &&
533 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
534 tp->t_rxtshift = 0;
535 tcp_setpersist(tp);
536 }
537
538 /*
539 * No reason to send a segment, just return.
540 */
541 return (0);
542
543send:
544 /*
545 * Before ESTABLISHED, force sending of initial options
546 * unless TCP set not to do any options.
547 * NOTE: we assume that the IP/TCP header plus TCP options
548 * always fit in a single mbuf, leaving room for a maximum
549 * link header, i.e.
79a80d9f 550 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES
984263bc
MD
551 */
552 optlen = 0;
984263bc 553 if (isipv6)
79a80d9f 554 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
984263bc 555 else
79a80d9f 556 hdrlen = sizeof(struct tcpiphdr);
984263bc
MD
557 if (flags & TH_SYN) {
558 tp->snd_nxt = tp->iss;
0770aa24 559 if (!(tp->t_flags & TF_NOOPT)) {
984263bc
MD
560 u_short mss;
561
562 opt[0] = TCPOPT_MAXSEG;
563 opt[1] = TCPOLEN_MAXSEG;
564 mss = htons((u_short) tcp_mssopt(tp));
f23061d4 565 memcpy(opt + 2, &mss, sizeof mss);
984263bc
MD
566 optlen = TCPOLEN_MAXSEG;
567
568 if ((tp->t_flags & TF_REQ_SCALE) &&
0770aa24
JH
569 (!(flags & TH_ACK) ||
570 (tp->t_flags & TF_RCVD_SCALE))) {
984263bc
MD
571 *((u_int32_t *)(opt + optlen)) = htonl(
572 TCPOPT_NOP << 24 |
573 TCPOPT_WINDOW << 16 |
574 TCPOLEN_WINDOW << 8 |
575 tp->request_r_scale);
576 optlen += 4;
577 }
91489f6b
JH
578
579 if ((tcp_do_sack && !(flags & TH_ACK)) ||
580 tp->t_flags & TF_SACK_PERMITTED) {
581 uint32_t *lp = (uint32_t *)(opt + optlen);
582
583 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
584 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED;
585 }
984263bc 586 }
0770aa24 587 }
984263bc 588
0770aa24 589 /*
984263bc
MD
590 * Send a timestamp and echo-reply if this is a SYN and our side
591 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
592 * and our peer have sent timestamps in our SYN's.
0770aa24 593 */
61896e3c 594 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
0770aa24
JH
595 !(flags & TH_RST) &&
596 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) {
984263bc
MD
597 u_int32_t *lp = (u_int32_t *)(opt + optlen);
598
0770aa24
JH
599 /* Form timestamp option as shown in appendix A of RFC 1323. */
600 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
601 *lp++ = htonl(ticks);
602 *lp = htonl(tp->ts_recent);
603 optlen += TCPOLEN_TSTAMP_APPA;
604 }
984263bc 605
5b0b9fa5
PA
606 /* Set receive buffer autosizing timestamp. */
607 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE))
608 tp->rfbuf_ts = ticks;
609
0770aa24 610 /*
91489f6b
JH
611 * If this is a SACK connection and we have a block to report,
612 * fill in the SACK blocks in the TCP options.
613 */
614 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) ==
615 TF_SACK_PERMITTED &&
616 (!LIST_EMPTY(&tp->t_segq) ||
617 tp->reportblk.rblk_start != tp->reportblk.rblk_end))
618 tcp_sack_fill_report(tp, opt, &optlen);
619
b1992928
MD
620#ifdef TCP_SIGNATURE
621 if (tp->t_flags & TF_SIGNATURE) {
622 int i;
623 u_char *bp;
624 /*
625 * Initialize TCP-MD5 option (RFC2385)
626 */
627 bp = (u_char *)opt + optlen;
628 *bp++ = TCPOPT_SIGNATURE;
629 *bp++ = TCPOLEN_SIGNATURE;
630 sigoff = optlen + 2;
631 for (i = 0; i < TCP_SIGLEN; i++)
632 *bp++ = 0;
633 optlen += TCPOLEN_SIGNATURE;
634 /*
635 * Terminate options list and maintain 32-bit alignment.
636 */
637 *bp++ = TCPOPT_NOP;
638 *bp++ = TCPOPT_EOL;
639 optlen += 2;
640 }
641#endif /* TCP_SIGNATURE */
91489f6b 642 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options"));
0770aa24 643 hdrlen += optlen;
984263bc 644
61896e3c 645 if (isipv6) {
0770aa24 646 ipoptlen = ip6_optlen(inp);
61896e3c 647 } else {
0770aa24
JH
648 if (inp->inp_options) {
649 ipoptlen = inp->inp_options->m_len -
650 offsetof(struct ipoption, ipopt_list);
651 } else {
652 ipoptlen = 0;
653 }
984263bc 654 }
984263bc
MD
655#ifdef IPSEC
656 ipoptlen += ipsec_hdrsiz_tcp(tp);
657#endif
658
659 /*
45f20ce7
MD
660 * Adjust data length if insertion of options will bump the packet
661 * length beyond the t_maxopd length. Clear FIN to prevent premature
662 * closure since there is still more data to send after this (now
663 * truncated) packet.
664 *
665 * If just the options do not fit we are in a no-win situation and
666 * we treat it as an unreachable host.
984263bc
MD
667 */
668 if (len + optlen + ipoptlen > tp->t_maxopd) {
45f20ce7
MD
669 if (tp->t_maxopd <= optlen + ipoptlen) {
670 static time_t last_optlen_report;
671
672 if (last_optlen_report != time_second) {
673 last_optlen_report = time_second;
a6ec04bc 674 kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd);
45f20ce7
MD
675 }
676 error = EHOSTUNREACH;
677 goto out;
678 } else {
679 flags &= ~TH_FIN;
680 len = tp->t_maxopd - optlen - ipoptlen;
681 sendalot = TRUE;
682 }
984263bc
MD
683 }
684
984263bc 685#ifdef INET6
0770aa24 686 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big"));
984263bc 687#else
0770aa24 688 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big"));
984263bc 689#endif
984263bc
MD
690
691 /*
692 * Grab a header mbuf, attaching a copy of data to
693 * be transmitted, and initialize the header from
694 * the template for sends on this connection.
695 */
696 if (len) {
c1d3b892 697 if ((tp->t_flags & TF_FORCE) && len == 1)
984263bc
MD
698 tcpstat.tcps_sndprobe++;
699 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
91489f6b
JH
700 if (tp->snd_nxt == tp->snd_una)
701 tp->snd_max_rexmt = tp->snd_max;
984263bc
MD
702 tcpstat.tcps_sndrexmitpack++;
703 tcpstat.tcps_sndrexmitbyte += len;
704 } else {
705 tcpstat.tcps_sndpack++;
706 tcpstat.tcps_sndbyte += len;
707 }
708#ifdef notyet
6d49aa6f 709 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len,
61896e3c 710 max_linkhdr + hdrlen)) == NULL) {
984263bc
MD
711 error = ENOBUFS;
712 goto out;
713 }
714 /*
715 * m_copypack left space for our hdr; use it.
716 */
717 m->m_len += hdrlen;
718 m->m_data -= hdrlen;
719#else
50503f0f
JH
720#ifndef INET6
721 m = m_gethdr(MB_DONTWAIT, MT_HEADER);
722#else
723 m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER,
724 M_PKTHDR, NULL);
725#endif
984263bc
MD
726 if (m == NULL) {
727 error = ENOBUFS;
728 goto out;
729 }
984263bc
MD
730 m->m_data += max_linkhdr;
731 m->m_len = hdrlen;
732 if (len <= MHLEN - hdrlen - max_linkhdr) {
6d49aa6f 733 m_copydata(so->so_snd.ssb_mb, off, (int) len,
984263bc
MD
734 mtod(m, caddr_t) + hdrlen);
735 m->m_len += len;
736 } else {
6d49aa6f 737 m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len);
61896e3c 738 if (m->m_next == NULL) {
f23061d4 739 m_free(m);
984263bc
MD
740 error = ENOBUFS;
741 goto out;
742 }
743 }
744#endif
745 /*
746 * If we're sending everything we've got, set PUSH.
747 * (This will keep happy those implementations which only
748 * give data to the user when a buffer fills or
749 * a PUSH comes in.)
750 */
6d49aa6f 751 if (off + len == so->so_snd.ssb_cc)
984263bc
MD
752 flags |= TH_PUSH;
753 } else {
754 if (tp->t_flags & TF_ACKNOW)
755 tcpstat.tcps_sndacks++;
61896e3c 756 else if (flags & (TH_SYN | TH_FIN | TH_RST))
984263bc
MD
757 tcpstat.tcps_sndctrl++;
758 else if (SEQ_GT(tp->snd_up, tp->snd_una))
759 tcpstat.tcps_sndurg++;
760 else
761 tcpstat.tcps_sndwinup++;
762
74f1caca 763 MGETHDR(m, MB_DONTWAIT, MT_HEADER);
984263bc
MD
764 if (m == NULL) {
765 error = ENOBUFS;
766 goto out;
767 }
0770aa24
JH
768 if (isipv6 &&
769 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN)
984263bc 770 MH_ALIGN(m, hdrlen);
0770aa24
JH
771 else
772 m->m_data += max_linkhdr;
984263bc
MD
773 m->m_len = hdrlen;
774 }
60233e58 775 m->m_pkthdr.rcvif = NULL;
984263bc
MD
776 if (isipv6) {
777 ip6 = mtod(m, struct ip6_hdr *);
778 th = (struct tcphdr *)(ip6 + 1);
779 tcp_fillheaders(tp, ip6, th);
0770aa24
JH
780 } else {
781 ip = mtod(m, struct ip *);
782 ipov = (struct ipovly *)ip;
783 th = (struct tcphdr *)(ip + 1);
784 /* this picks up the pseudo header (w/o the length) */
785 tcp_fillheaders(tp, ip, th);
786 }
984263bc
MD
787
788 /*
789 * Fill in fields, remembering maximum advertised
790 * window for use in delaying messages about window sizes.
791 * If resending a FIN, be sure not to use a new sequence number.
792 */
793 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
794 tp->snd_nxt == tp->snd_max)
795 tp->snd_nxt--;
796 /*
797 * If we are doing retransmissions, then snd_nxt will
798 * not reflect the first unsent octet. For ACK only
799 * packets, we do not want the sequence number of the
800 * retransmitted packet, we want the sequence number
801 * of the next unsent octet. So, if there is no data
802 * (and no SYN or FIN), use snd_max instead of snd_nxt
803 * when filling in ti_seq. But if we are in persist
804 * state, snd_max might reflect one byte beyond the
805 * right edge of the window, so use snd_nxt in that
806 * case, since we know we aren't doing a retransmission.
807 * (retransmit and persist are mutually exclusive...)
808 */
a48c5dd5
SZ
809 if (len || (flags & (TH_SYN|TH_FIN)) ||
810 tcp_callout_active(tp, tp->tt_persist))
984263bc
MD
811 th->th_seq = htonl(tp->snd_nxt);
812 else
813 th->th_seq = htonl(tp->snd_max);
814 th->th_ack = htonl(tp->rcv_nxt);
815 if (optlen) {
816 bcopy(opt, th + 1, optlen);
79a80d9f 817 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
984263bc
MD
818 }
819 th->th_flags = flags;
46e92930 820
984263bc 821 /*
46e92930
MD
822 * Calculate receive window. Don't shrink window, but avoid
823 * silly window syndrome by sending a 0 window if the actual
824 * window is less then one segment.
984263bc 825 */
6d49aa6f 826 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) &&
c53f07a5
JH
827 recvwin < (long)tp->t_maxseg)
828 recvwin = 0;
55126001
MD
829 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt))
830 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt);
c53f07a5
JH
831 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale)
832 recvwin = (long)TCP_MAXWIN << tp->rcv_scale;
833 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale));
984263bc
MD
834
835 /*
836 * Adjust the RXWIN0SENT flag - indicate that we have advertised
837 * a 0 window. This may cause the remote transmitter to stall. This
838 * flag tells soreceive() to disable delayed acknowledgements when
839 * draining the buffer. This can occur if the receiver is attempting
840 * to read more data then can be buffered prior to transmitting on
841 * the connection.
842 */
c53f07a5 843 if (recvwin == 0)
984263bc
MD
844 tp->t_flags |= TF_RXWIN0SENT;
845 else
846 tp->t_flags &= ~TF_RXWIN0SENT;
847
848 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
849 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
850 th->th_flags |= TH_URG;
79a80d9f 851 } else {
984263bc
MD
852 /*
853 * If no urgent pointer to send, then we pull
854 * the urgent pointer to the left edge of the send window
855 * so that it doesn't drift into the send window on sequence
856 * number wraparound.
857 */
858 tp->snd_up = tp->snd_una; /* drag it along */
79a80d9f 859 }
984263bc 860
b1992928
MD
861#ifdef TCP_SIGNATURE
862 if (tp->t_flags & TF_SIGNATURE)
863 tcpsignature_compute(m, len, optlen,
864 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
865#endif /* TCP_SIGNATURE */
866
984263bc
MD
867 /*
868 * Put TCP length in extended header, and then
869 * checksum extended header and data.
870 */
871 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
0770aa24 872 if (isipv6) {
984263bc
MD
873 /*
874 * ip6_plen is not need to be filled now, and will be filled
5fe66e68 875 * in ip6_output().
984263bc
MD
876 */
877 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
878 sizeof(struct tcphdr) + optlen + len);
0770aa24
JH
879 } else {
880 m->m_pkthdr.csum_flags = CSUM_TCP;
881 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
882 if (len + optlen)
883 th->th_sum = in_addword(th->th_sum,
884 htons((u_short)(optlen + len)));
885
886 /* IP version must be set here for ipv4/ipv6 checking later */
887 KASSERT(ip->ip_v == IPVERSION,
888 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
889 }
984263bc
MD
890
891 /*
892 * In transmit state, time the transmission and arrange for
893 * the retransmit. In persist state, just set snd_max.
894 */
a48c5dd5
SZ
895 if (!(tp->t_flags & TF_FORCE) ||
896 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
897 tcp_seq startseq = tp->snd_nxt;
898
899 /*
900 * Advance snd_nxt over sequence space of this segment.
901 */
61896e3c 902 if (flags & (TH_SYN | TH_FIN)) {
984263bc
MD
903 if (flags & TH_SYN)
904 tp->snd_nxt++;
905 if (flags & TH_FIN) {
906 tp->snd_nxt++;
907 tp->t_flags |= TF_SENTFIN;
908 }
909 }
910 tp->snd_nxt += len;
911 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
912 tp->snd_max = tp->snd_nxt;
913 /*
914 * Time this transmission if not a retransmission and
915 * not currently timing anything.
916 */
917 if (tp->t_rtttime == 0) {
918 tp->t_rtttime = ticks;
919 tp->t_rtseq = startseq;
920 tcpstat.tcps_segstimed++;
921 }
922 }
923
924 /*
925 * Set retransmit timer if not currently set,
926 * and not doing a pure ack or a keep-alive probe.
927 * Initial value for retransmit timer is smoothed
928 * round-trip time + 2 * round-trip time variance.
929 * Initialize shift counter which is used for backoff
930 * of retransmit time.
931 */
a48c5dd5 932 if (!tcp_callout_active(tp, tp->tt_rexmt) &&
984263bc 933 tp->snd_nxt != tp->snd_una) {
a48c5dd5
SZ
934 if (tcp_callout_active(tp, tp->tt_persist)) {
935 tcp_callout_stop(tp, tp->tt_persist);
984263bc
MD
936 tp->t_rxtshift = 0;
937 }
a48c5dd5
SZ
938 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
939 tcp_timer_rexmt);
984263bc
MD
940 }
941 } else {
942 /*
943 * Persist case, update snd_max but since we are in
944 * persist mode (no window) we do not update snd_nxt.
945 */
946 int xlen = len;
947 if (flags & TH_SYN)
94603b1b 948 panic("tcp_output: persist timer to send SYN\n");
984263bc
MD
949 if (flags & TH_FIN) {
950 ++xlen;
951 tp->t_flags |= TF_SENTFIN;
952 }
953 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
954 tp->snd_max = tp->snd_nxt + xlen;
955 }
956
957#ifdef TCPDEBUG
958 /*
959 * Trace.
960 */
961 if (so->so_options & SO_DEBUG)
962 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
963#endif
964
965 /*
966 * Fill in IP length and desired time to live and
967 * send to IP level. There should be a better way
968 * to handle ttl and tos; we could keep them in
969 * the template, but need a way to checksum without them.
970 */
971 /*
972 * m->m_pkthdr.len should have been set before cksum calcuration,
973 * because in6_cksum() need it.
974 */
984263bc
MD
975 if (isipv6) {
976 /*
977 * we separately set hoplimit for every segment, since the
978 * user might want to change the value via setsockopt.
979 * Also, desired default hop limit might be changed via
980 * Neighbor Discovery.
981 */
0770aa24
JH
982 ip6->ip6_hlim = in6_selecthlim(inp,
983 (inp->in6p_route.ro_rt ?
984 inp->in6p_route.ro_rt->rt_ifp : NULL));
984263bc
MD
985
986 /* TODO: IPv6 IP6TOS_ECT bit on */
0770aa24 987 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route,
5fe66e68
JH
988 (so->so_options & SO_DONTROUTE), NULL, NULL,
989 inp);
0770aa24
JH
990 } else {
991 struct rtentry *rt;
992 ip->ip_len = m->m_pkthdr.len;
984263bc 993#ifdef INET6
0770aa24
JH
994 if (INP_CHECK_SOCKAF(so, AF_INET6))
995 ip->ip_ttl = in6_selecthlim(inp,
996 (inp->in6p_route.ro_rt ?
997 inp->in6p_route.ro_rt->rt_ifp : NULL));
998 else
999#endif
1000 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
1001
1002 ip->ip_tos = inp->inp_ip_tos; /* XXX */
1003 /*
1004 * See if we should do MTU discovery.
1005 * We do it only if the following are true:
1006 * 1) we have a valid route to the destination
1007 * 2) the MTU is not locked (if it is,
1008 * then discovery has been disabled)
1009 */
1010 if (path_mtu_discovery &&
1011 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) &&
1012 !(rt->rt_rmx.rmx_locks & RTV_MTU))
1013 ip->ip_off |= IP_DF;
1014
1015 error = ip_output(m, inp->inp_options, &inp->inp_route,
1dbb3516
SZ
1016 (so->so_options & SO_DONTROUTE) |
1017 IP_DEBUGROUTE, NULL, inp);
0770aa24 1018 }
984263bc
MD
1019 if (error) {
1020
1021 /*
1022 * We know that the packet was lost, so back out the
1023 * sequence number advance, if any.
1024 */
c1d3b892 1025 if (!(tp->t_flags & TF_FORCE) ||
a48c5dd5 1026 !tcp_callout_active(tp, tp->tt_persist)) {
984263bc
MD
1027 /*
1028 * No need to check for TH_FIN here because
1029 * the TF_SENTFIN flag handles that case.
1030 */
0770aa24 1031 if (!(flags & TH_SYN))
984263bc
MD
1032 tp->snd_nxt -= len;
1033 }
1034
1035out:
1036 if (error == ENOBUFS) {
ea8bd01a
JH
1037 /*
1038 * If we can't send, make sure there is something
1039 * to get us going again later. Persist state
1040 * is not necessarily right, but it is close enough.
1041 */
a48c5dd5
SZ
1042 if (!tcp_callout_active(tp, tp->tt_rexmt) &&
1043 !tcp_callout_active(tp, tp->tt_persist)) {
ea8bd01a
JH
1044 tp->t_rxtshift = 0;
1045 tcp_setpersist(tp);
1046 }
0770aa24 1047 tcp_quench(inp, 0);
984263bc
MD
1048 return (0);
1049 }
1050 if (error == EMSGSIZE) {
1051 /*
1052 * ip_output() will have already fixed the route
1053 * for us. tcp_mtudisc() will, as its last action,
1054 * initiate retransmission, so it is important to
1055 * not do so here.
1056 */
0770aa24 1057 tcp_mtudisc(inp, 0);
984263bc
MD
1058 return 0;
1059 }
0770aa24
JH
1060 if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1061 TCPS_HAVERCVDSYN(tp->t_state)) {
984263bc
MD
1062 tp->t_softerror = error;
1063 return (0);
1064 }
1065 return (error);
1066 }
1067 tcpstat.tcps_sndtotal++;
1068
1069 /*
1070 * Data sent (as far as we can tell).
46e92930 1071 *
984263bc
MD
1072 * If this advertises a larger window than any other segment,
1073 * then remember the size of the advertised window.
46e92930 1074 *
984263bc
MD
1075 * Any pending ACK has now been sent.
1076 */
46e92930 1077 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) {
c53f07a5 1078 tp->rcv_adv = tp->rcv_nxt + recvwin;
46e92930
MD
1079 tp->t_flags &= ~TF_RXRESIZED;
1080 }
984263bc
MD
1081 tp->last_ack_sent = tp->rcv_nxt;
1082 tp->t_flags &= ~TF_ACKNOW;
1083 if (tcp_delack_enabled)
a48c5dd5 1084 tcp_callout_stop(tp, tp->tt_delack);
984263bc
MD
1085 if (sendalot)
1086 goto again;
1087 return (0);
1088}
1089
1090void
f3f70f0d 1091tcp_setpersist(struct tcpcb *tp)
984263bc
MD
1092{
1093 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1094 int tt;
1095
c529614e
SZ
1096 if (tp->t_state == TCPS_SYN_SENT ||
1097 tp->t_state == TCPS_SYN_RECEIVED) {
1098 panic("tcp_setpersist: not established yet, current %s\n",
1099 tp->t_state == TCPS_SYN_SENT ?
1100 "SYN_SENT" : "SYN_RECEIVED");
1101 }
94603b1b 1102
a48c5dd5 1103 if (tcp_callout_active(tp, tp->tt_rexmt))
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MD
1104 panic("tcp_setpersist: retransmit pending");
1105 /*
1106 * Start/restart persistance timer.
1107 */
5fe66e68
JH
1108 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN,
1109 TCPTV_PERSMAX);
a48c5dd5 1110 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist);
984263bc
MD
1111 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1112 tp->t_rxtshift++;
1113}