Line data Source code
1 : /* $OpenBSD: tcp_output.c,v 1.126 2018/09/13 19:53:58 bluhm Exp $ */
2 : /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */
3 :
4 : /*
5 : * Copyright (c) 1982, 1986, 1988, 1990, 1993
6 : * The Regents of the University of California. All rights reserved.
7 : *
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 University nor the names of its contributors
17 : * may be used to endorse or promote products derived from this software
18 : * without specific prior written permission.
19 : *
20 : * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 : * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 : * SUCH DAMAGE.
31 : *
32 : * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995
33 : *
34 : * NRL grants permission for redistribution and use in source and binary
35 : * forms, with or without modification, of the software and documentation
36 : * created at NRL provided that the following conditions are met:
37 : *
38 : * 1. Redistributions of source code must retain the above copyright
39 : * notice, this list of conditions and the following disclaimer.
40 : * 2. Redistributions in binary form must reproduce the above copyright
41 : * notice, this list of conditions and the following disclaimer in the
42 : * documentation and/or other materials provided with the distribution.
43 : * 3. All advertising materials mentioning features or use of this software
44 : * must display the following acknowledgements:
45 : * This product includes software developed by the University of
46 : * California, Berkeley and its contributors.
47 : * This product includes software developed at the Information
48 : * Technology Division, US Naval Research Laboratory.
49 : * 4. Neither the name of the NRL nor the names of its contributors
50 : * may be used to endorse or promote products derived from this software
51 : * without specific prior written permission.
52 : *
53 : * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
54 : * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
55 : * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
56 : * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
57 : * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
58 : * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
59 : * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
60 : * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
61 : * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
62 : * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
63 : * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
64 : *
65 : * The views and conclusions contained in the software and documentation
66 : * are those of the authors and should not be interpreted as representing
67 : * official policies, either expressed or implied, of the US Naval
68 : * Research Laboratory (NRL).
69 : */
70 :
71 : #include "pf.h"
72 :
73 : #include <sys/param.h>
74 : #include <sys/systm.h>
75 : #include <sys/mbuf.h>
76 : #include <sys/protosw.h>
77 : #include <sys/socket.h>
78 : #include <sys/socketvar.h>
79 : #include <sys/kernel.h>
80 :
81 : #include <net/if.h>
82 : #include <net/route.h>
83 : #if NPF > 0
84 : #include <net/pfvar.h>
85 : #endif
86 :
87 : #include <netinet/in.h>
88 : #include <netinet/ip.h>
89 : #include <netinet/in_pcb.h>
90 : #include <netinet/ip_var.h>
91 : #include <netinet/tcp.h>
92 : #define TCPOUTFLAGS
93 : #include <netinet/tcp_fsm.h>
94 : #include <netinet/tcp_seq.h>
95 : #include <netinet/tcp_timer.h>
96 : #include <netinet/tcp_var.h>
97 : #include <netinet/tcp_debug.h>
98 :
99 : #ifdef notyet
100 : extern struct mbuf *m_copypack();
101 : #endif
102 :
103 : extern int tcprexmtthresh;
104 :
105 : #ifdef TCP_SACK_DEBUG
106 : void tcp_print_holes(struct tcpcb *tp);
107 :
108 : void
109 : tcp_print_holes(struct tcpcb *tp)
110 : {
111 : struct sackhole *p = tp->snd_holes;
112 : if (p == NULL)
113 : return;
114 : printf("Hole report: start--end dups rxmit\n");
115 : while (p) {
116 : printf("%x--%x d %d r %x\n", p->start, p->end, p->dups,
117 : p->rxmit);
118 : p = p->next;
119 : }
120 : printf("\n");
121 : }
122 : #endif /* TCP_SACK_DEBUG */
123 :
124 : /*
125 : * Returns pointer to a sackhole if there are any pending retransmissions;
126 : * NULL otherwise.
127 : */
128 : struct sackhole *
129 0 : tcp_sack_output(struct tcpcb *tp)
130 : {
131 : struct sackhole *p;
132 :
133 0 : if (!tp->sack_enable)
134 0 : return (NULL);
135 0 : p = tp->snd_holes;
136 0 : while (p) {
137 0 : if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
138 0 : if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
139 0 : p = p->next;
140 0 : continue;
141 : }
142 : #ifdef TCP_SACK_DEBUG
143 : if (p)
144 : tcp_print_holes(tp);
145 : #endif
146 0 : return (p);
147 : }
148 0 : p = p->next;
149 : }
150 0 : return (NULL);
151 0 : }
152 :
153 : /*
154 : * After a timeout, the SACK list may be rebuilt. This SACK information
155 : * should be used to avoid retransmitting SACKed data. This function
156 : * traverses the SACK list to see if snd_nxt should be moved forward.
157 : */
158 :
159 : void
160 0 : tcp_sack_adjust(struct tcpcb *tp)
161 : {
162 0 : struct sackhole *cur = tp->snd_holes;
163 0 : if (cur == NULL)
164 0 : return; /* No holes */
165 0 : if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))
166 0 : return; /* We're already beyond any SACKed blocks */
167 : /*
168 : * Two cases for which we want to advance snd_nxt:
169 : * i) snd_nxt lies between end of one hole and beginning of another
170 : * ii) snd_nxt lies between end of last hole and rcv_lastsack
171 : */
172 0 : while (cur->next) {
173 0 : if (SEQ_LT(tp->snd_nxt, cur->end))
174 0 : return;
175 0 : if (SEQ_GEQ(tp->snd_nxt, cur->next->start))
176 : cur = cur->next;
177 : else {
178 0 : tp->snd_nxt = cur->next->start;
179 0 : return;
180 : }
181 : }
182 0 : if (SEQ_LT(tp->snd_nxt, cur->end))
183 0 : return;
184 0 : tp->snd_nxt = tp->rcv_lastsack;
185 0 : return;
186 0 : }
187 :
188 : /*
189 : * Tcp output routine: figure out what should be sent and send it.
190 : */
191 : int
192 0 : tcp_output(struct tcpcb *tp)
193 : {
194 0 : struct socket *so = tp->t_inpcb->inp_socket;
195 : long len, win, txmaxseg;
196 : int off, flags, error;
197 : struct mbuf *m;
198 : struct tcphdr *th;
199 0 : u_int32_t optbuf[howmany(MAX_TCPOPTLEN, sizeof(u_int32_t))];
200 0 : u_char *opt = (u_char *)optbuf;
201 : unsigned int optlen, hdrlen, packetlen;
202 : int idle, sendalot = 0;
203 : int i, sack_rxmit = 0;
204 : struct sackhole *p;
205 : int maxburst = TCP_MAXBURST;
206 : #ifdef TCP_SIGNATURE
207 : unsigned int sigoff;
208 : #endif /* TCP_SIGNATURE */
209 : #ifdef TCP_ECN
210 : int needect;
211 : #endif
212 :
213 0 : if (tp->t_flags & TF_BLOCKOUTPUT) {
214 0 : tp->t_flags |= TF_NEEDOUTPUT;
215 0 : return (0);
216 : } else
217 0 : tp->t_flags &= ~TF_NEEDOUTPUT;
218 :
219 : #if defined(TCP_SIGNATURE) && defined(DIAGNOSTIC)
220 0 : if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE))
221 0 : return (EINVAL);
222 : #endif /* defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */
223 :
224 : /*
225 : * Determine length of data that should be transmitted,
226 : * and flags that will be used.
227 : * If there is some data or critical controls (SYN, RST)
228 : * to send, then transmit; otherwise, investigate further.
229 : */
230 0 : idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
231 0 : if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur)
232 : /*
233 : * We have been idle for "a while" and no acks are
234 : * expected to clock out any data we send --
235 : * slow start to get ack "clock" running again.
236 : */
237 0 : tp->snd_cwnd = 2 * tp->t_maxseg;
238 :
239 : /* remember 'idle' for next invocation of tcp_output */
240 0 : if (idle && soissending(so)) {
241 0 : tp->t_flags |= TF_LASTIDLE;
242 : idle = 0;
243 0 : } else
244 0 : tp->t_flags &= ~TF_LASTIDLE;
245 :
246 : again:
247 : /*
248 : * If we've recently taken a timeout, snd_max will be greater than
249 : * snd_nxt. There may be SACK information that allows us to avoid
250 : * resending already delivered data. Adjust snd_nxt accordingly.
251 : */
252 0 : if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max))
253 0 : tcp_sack_adjust(tp);
254 0 : off = tp->snd_nxt - tp->snd_una;
255 0 : win = ulmin(tp->snd_wnd, tp->snd_cwnd);
256 :
257 0 : flags = tcp_outflags[tp->t_state];
258 :
259 : /*
260 : * Send any SACK-generated retransmissions. If we're explicitly trying
261 : * to send out new data (when sendalot is 1), bypass this function.
262 : * If we retransmit in fast recovery mode, decrement snd_cwnd, since
263 : * we're replacing a (future) new transmission with a retransmission
264 : * now, and we previously incremented snd_cwnd in tcp_input().
265 : */
266 0 : if (tp->sack_enable && !sendalot) {
267 0 : if (tp->t_dupacks >= tcprexmtthresh &&
268 0 : (p = tcp_sack_output(tp))) {
269 0 : off = p->rxmit - tp->snd_una;
270 : sack_rxmit = 1;
271 : /* Coalesce holes into a single retransmission */
272 0 : len = min(tp->t_maxseg, p->end - p->rxmit);
273 0 : if (SEQ_LT(tp->snd_una, tp->snd_last))
274 0 : tp->snd_cwnd -= tp->t_maxseg;
275 : }
276 : }
277 :
278 : sendalot = 0;
279 : /*
280 : * If in persist timeout with window of 0, send 1 byte.
281 : * Otherwise, if window is small but nonzero
282 : * and timer expired, we will send what we can
283 : * and go to transmit state.
284 : */
285 0 : if (tp->t_force) {
286 0 : if (win == 0) {
287 : /*
288 : * If we still have some data to send, then
289 : * clear the FIN bit. Usually this would
290 : * happen below when it realizes that we
291 : * aren't sending all the data. However,
292 : * if we have exactly 1 byte of unset data,
293 : * then it won't clear the FIN bit below,
294 : * and if we are in persist state, we wind
295 : * up sending the packet without recording
296 : * that we sent the FIN bit.
297 : *
298 : * We can't just blindly clear the FIN bit,
299 : * because if we don't have any more data
300 : * to send then the probe will be the FIN
301 : * itself.
302 : */
303 0 : if (off < so->so_snd.sb_cc)
304 0 : flags &= ~TH_FIN;
305 : win = 1;
306 0 : } else {
307 0 : TCP_TIMER_DISARM(tp, TCPT_PERSIST);
308 0 : tp->t_rxtshift = 0;
309 : }
310 : }
311 :
312 0 : if (!sack_rxmit) {
313 0 : len = ulmin(so->so_snd.sb_cc, win) - off;
314 0 : }
315 :
316 0 : if (len < 0) {
317 : /*
318 : * If FIN has been sent but not acked,
319 : * but we haven't been called to retransmit,
320 : * len will be -1. Otherwise, window shrank
321 : * after we sent into it. If window shrank to 0,
322 : * cancel pending retransmit, pull snd_nxt back
323 : * to (closed) window, and set the persist timer
324 : * if it isn't already going. If the window didn't
325 : * close completely, just wait for an ACK.
326 : */
327 : len = 0;
328 0 : if (win == 0) {
329 0 : TCP_TIMER_DISARM(tp, TCPT_REXMT);
330 0 : tp->t_rxtshift = 0;
331 0 : tp->snd_nxt = tp->snd_una;
332 0 : if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
333 0 : tcp_setpersist(tp);
334 : }
335 : }
336 :
337 : /*
338 : * Never send more than half a buffer full. This insures that we can
339 : * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
340 : * therefore acks will never be delayed unless we run out of data to
341 : * transmit.
342 : */
343 0 : txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg);
344 :
345 0 : if (len > txmaxseg) {
346 : len = txmaxseg;
347 : sendalot = 1;
348 0 : }
349 0 : if (off + len < so->so_snd.sb_cc)
350 0 : flags &= ~TH_FIN;
351 :
352 0 : win = sbspace(so, &so->so_rcv);
353 :
354 : /*
355 : * Sender silly window avoidance. If connection is idle
356 : * and can send all data, a maximum segment,
357 : * at least a maximum default-size segment do it,
358 : * or are forced, do it; otherwise don't bother.
359 : * If peer's buffer is tiny, then send
360 : * when window is at least half open.
361 : * If retransmitting (possibly after persist timer forced us
362 : * to send into a small window), then must resend.
363 : */
364 0 : if (len) {
365 0 : if (len == txmaxseg)
366 : goto send;
367 0 : if ((idle || (tp->t_flags & TF_NODELAY)) &&
368 0 : len + off >= so->so_snd.sb_cc && !soissending(so) &&
369 0 : (tp->t_flags & TF_NOPUSH) == 0)
370 : goto send;
371 0 : if (tp->t_force)
372 : goto send;
373 0 : if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
374 : goto send;
375 0 : if (SEQ_LT(tp->snd_nxt, tp->snd_max))
376 : goto send;
377 : if (sack_rxmit)
378 : goto send;
379 : }
380 :
381 : /*
382 : * Compare available window to amount of window
383 : * known to peer (as advertised window less
384 : * next expected input). If the difference is at least two
385 : * max size segments, or at least 50% of the maximum possible
386 : * window, then want to send a window update to peer.
387 : */
388 0 : if (win > 0) {
389 : /*
390 : * "adv" is the amount we can increase the window,
391 : * taking into account that we are limited by
392 : * TCP_MAXWIN << tp->rcv_scale.
393 : */
394 0 : long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) -
395 0 : (tp->rcv_adv - tp->rcv_nxt);
396 :
397 0 : if (adv >= (long) (2 * tp->t_maxseg))
398 0 : goto send;
399 0 : if (2 * adv >= (long) so->so_rcv.sb_hiwat)
400 0 : goto send;
401 0 : }
402 :
403 : /*
404 : * Send if we owe peer an ACK.
405 : */
406 0 : if (tp->t_flags & TF_ACKNOW)
407 : goto send;
408 0 : if (flags & (TH_SYN|TH_RST))
409 : goto send;
410 0 : if (SEQ_GT(tp->snd_up, tp->snd_una))
411 : goto send;
412 : /*
413 : * If our state indicates that FIN should be sent
414 : * and we have not yet done so, or we're retransmitting the FIN,
415 : * then we need to send.
416 : */
417 0 : if (flags & TH_FIN &&
418 0 : ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
419 : goto send;
420 : /*
421 : * In SACK, it is possible for tcp_output to fail to send a segment
422 : * after the retransmission timer has been turned off. Make sure
423 : * that the retransmission timer is set.
424 : */
425 0 : if (SEQ_GT(tp->snd_max, tp->snd_una) &&
426 0 : TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
427 0 : TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
428 0 : TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
429 0 : return (0);
430 : }
431 :
432 : /*
433 : * TCP window updates are not reliable, rather a polling protocol
434 : * using ``persist'' packets is used to insure receipt of window
435 : * updates. The three ``states'' for the output side are:
436 : * idle not doing retransmits or persists
437 : * persisting to move a small or zero window
438 : * (re)transmitting and thereby not persisting
439 : *
440 : * tp->t_timer[TCPT_PERSIST]
441 : * is set when we are in persist state.
442 : * tp->t_force
443 : * is set when we are called to send a persist packet.
444 : * tp->t_timer[TCPT_REXMT]
445 : * is set when we are retransmitting
446 : * The output side is idle when both timers are zero.
447 : *
448 : * If send window is too small, there is data to transmit, and no
449 : * retransmit or persist is pending, then go to persist state.
450 : * If nothing happens soon, send when timer expires:
451 : * if window is nonzero, transmit what we can,
452 : * otherwise force out a byte.
453 : */
454 0 : if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
455 0 : TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
456 0 : tp->t_rxtshift = 0;
457 0 : tcp_setpersist(tp);
458 0 : }
459 :
460 : /*
461 : * No reason to send a segment, just return.
462 : */
463 0 : return (0);
464 :
465 : send:
466 : /*
467 : * Before ESTABLISHED, force sending of initial options
468 : * unless TCP set not to do any options.
469 : * NOTE: we assume that the IP/TCP header plus TCP options
470 : * always fit in a single mbuf, leaving room for a maximum
471 : * link header, i.e.
472 : * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr +
473 : * optlen <= MHLEN
474 : */
475 : optlen = 0;
476 :
477 0 : switch (tp->pf) {
478 : case 0: /*default to PF_INET*/
479 : case PF_INET:
480 : hdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
481 0 : break;
482 : #ifdef INET6
483 : case PF_INET6:
484 : hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
485 0 : break;
486 : #endif /* INET6 */
487 : default:
488 0 : return (EPFNOSUPPORT);
489 : }
490 :
491 0 : if (flags & TH_SYN) {
492 0 : tp->snd_nxt = tp->iss;
493 0 : if ((tp->t_flags & TF_NOOPT) == 0) {
494 : u_int16_t mss;
495 :
496 0 : opt[0] = TCPOPT_MAXSEG;
497 0 : opt[1] = 4;
498 0 : mss = htons((u_int16_t) tcp_mss(tp, 0));
499 0 : memcpy(opt + 2, &mss, sizeof(mss));
500 : optlen = 4;
501 :
502 0 : if (flags & TH_ACK)
503 0 : tcp_mss_update(tp);
504 : /*
505 : * If this is the first SYN of connection (not a SYN
506 : * ACK), include SACK_PERMIT_HDR option. If this is a
507 : * SYN ACK, include SACK_PERMIT_HDR option if peer has
508 : * already done so.
509 : */
510 0 : if (tp->sack_enable && ((flags & TH_ACK) == 0 ||
511 0 : (tp->t_flags & TF_SACK_PERMIT))) {
512 0 : *((u_int32_t *) (opt + optlen)) =
513 : htonl(TCPOPT_SACK_PERMIT_HDR);
514 : optlen += 4;
515 0 : }
516 0 : if ((tp->t_flags & TF_REQ_SCALE) &&
517 0 : ((flags & TH_ACK) == 0 ||
518 0 : (tp->t_flags & TF_RCVD_SCALE))) {
519 0 : *((u_int32_t *) (opt + optlen)) = htonl(
520 : TCPOPT_NOP << 24 |
521 : TCPOPT_WINDOW << 16 |
522 : TCPOLEN_WINDOW << 8 |
523 : tp->request_r_scale);
524 0 : optlen += 4;
525 0 : }
526 0 : }
527 : }
528 :
529 : /*
530 : * Send a timestamp and echo-reply if this is a SYN and our side
531 : * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
532 : * and our peer have sent timestamps in our SYN's.
533 : */
534 0 : if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
535 0 : (flags & TH_RST) == 0 &&
536 0 : ((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
537 0 : (tp->t_flags & TF_RCVD_TSTMP))) {
538 0 : u_int32_t *lp = (u_int32_t *)(opt + optlen);
539 :
540 : /* Form timestamp option as shown in appendix A of RFC 1323. */
541 0 : *lp++ = htonl(TCPOPT_TSTAMP_HDR);
542 0 : *lp++ = htonl(tcp_now + tp->ts_modulate);
543 0 : *lp = htonl(tp->ts_recent);
544 0 : optlen += TCPOLEN_TSTAMP_APPA;
545 :
546 : /* Set receive buffer autosizing timestamp. */
547 0 : if (tp->rfbuf_ts == 0)
548 0 : tp->rfbuf_ts = tcp_now;
549 :
550 0 : }
551 :
552 : #ifdef TCP_SIGNATURE
553 0 : if (tp->t_flags & TF_SIGNATURE) {
554 0 : u_int8_t *bp = (u_int8_t *)(opt + optlen);
555 :
556 : /* Send signature option */
557 0 : *(bp++) = TCPOPT_SIGNATURE;
558 0 : *(bp++) = TCPOLEN_SIGNATURE;
559 0 : sigoff = optlen + 2;
560 :
561 : {
562 : unsigned int i;
563 :
564 0 : for (i = 0; i < 16; i++)
565 0 : *(bp++) = 0;
566 : }
567 :
568 :
569 : /* Pad options list to the next 32 bit boundary and
570 : * terminate it.
571 : */
572 0 : *bp++ = TCPOPT_NOP;
573 0 : *bp++ = TCPOPT_NOP;
574 :
575 0 : optlen += TCPOLEN_SIGLEN;
576 0 : }
577 : #endif /* TCP_SIGNATURE */
578 :
579 : /*
580 : * Send SACKs if necessary. This should be the last option processed.
581 : * Only as many SACKs are sent as are permitted by the maximum options
582 : * size. No more than three SACKs are sent.
583 : */
584 0 : if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED &&
585 0 : (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT &&
586 0 : tp->rcv_numsacks) {
587 0 : u_int32_t *lp = (u_int32_t *)(opt + optlen);
588 0 : u_int32_t *olp = lp++;
589 : int count = 0; /* actual number of SACKs inserted */
590 0 : int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK;
591 :
592 0 : tcpstat_inc(tcps_sack_snd_opts);
593 0 : maxsack = min(maxsack, TCP_MAX_SACK);
594 0 : for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) {
595 0 : struct sackblk sack = tp->sackblks[i];
596 0 : if (sack.start == 0 && sack.end == 0)
597 0 : continue;
598 0 : *lp++ = htonl(sack.start);
599 0 : *lp++ = htonl(sack.end);
600 0 : count++;
601 0 : }
602 0 : *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2));
603 0 : optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */
604 0 : }
605 :
606 : #ifdef DIAGNOSTIC
607 0 : if (optlen > MAX_TCPOPTLEN)
608 0 : panic("tcp_output: options too long");
609 : #endif /* DIAGNOSTIC */
610 :
611 0 : hdrlen += optlen;
612 :
613 : /*
614 : * Adjust data length if insertion of options will
615 : * bump the packet length beyond the t_maxopd length.
616 : */
617 0 : if (len > tp->t_maxopd - optlen) {
618 : len = tp->t_maxopd - optlen;
619 : sendalot = 1;
620 0 : flags &= ~TH_FIN;
621 0 : }
622 :
623 : #ifdef DIAGNOSTIC
624 0 : if (max_linkhdr + hdrlen > MCLBYTES)
625 0 : panic("tcphdr too big");
626 : #endif
627 :
628 : /*
629 : * Grab a header mbuf, attaching a copy of data to
630 : * be transmitted, and initialize the header from
631 : * the template for sends on this connection.
632 : */
633 0 : if (len) {
634 0 : if (tp->t_force && len == 1)
635 0 : tcpstat_inc(tcps_sndprobe);
636 0 : else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
637 0 : tcpstat_pkt(tcps_sndrexmitpack, tcps_sndrexmitbyte,
638 : len);
639 0 : } else {
640 0 : tcpstat_pkt(tcps_sndpack, tcps_sndbyte, len);
641 : }
642 : #ifdef notyet
643 : if ((m = m_copypack(so->so_snd.sb_mb, off,
644 : (int)len, max_linkhdr + hdrlen)) == 0) {
645 : error = ENOBUFS;
646 : goto out;
647 : }
648 : /*
649 : * m_copypack left space for our hdr; use it.
650 : */
651 : m->m_len += hdrlen;
652 : m->m_data -= hdrlen;
653 : #else
654 0 : MGETHDR(m, M_DONTWAIT, MT_HEADER);
655 0 : if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
656 0 : MCLGET(m, M_DONTWAIT);
657 0 : if ((m->m_flags & M_EXT) == 0) {
658 0 : m_freem(m);
659 : m = NULL;
660 0 : }
661 : }
662 0 : if (m == NULL) {
663 : error = ENOBUFS;
664 0 : goto out;
665 : }
666 0 : m->m_data += max_linkhdr;
667 0 : m->m_len = hdrlen;
668 0 : if (len <= M_TRAILINGSPACE(m)) {
669 0 : m_copydata(so->so_snd.sb_mb, off, (int) len,
670 0 : mtod(m, caddr_t) + hdrlen);
671 0 : m->m_len += len;
672 0 : } else {
673 0 : m->m_next = m_copym(so->so_snd.sb_mb, off, (int) len,
674 : M_NOWAIT);
675 0 : if (m->m_next == 0) {
676 0 : (void) m_free(m);
677 : error = ENOBUFS;
678 0 : goto out;
679 : }
680 : }
681 0 : if (so->so_snd.sb_mb->m_flags & M_PKTHDR)
682 0 : m->m_pkthdr.ph_loopcnt =
683 0 : so->so_snd.sb_mb->m_pkthdr.ph_loopcnt;
684 : #endif
685 : /*
686 : * If we're sending everything we've got, set PUSH.
687 : * (This will keep happy those implementations which only
688 : * give data to the user when a buffer fills or
689 : * a PUSH comes in.)
690 : */
691 0 : if (off + len == so->so_snd.sb_cc && !soissending(so))
692 0 : flags |= TH_PUSH;
693 : } else {
694 0 : if (tp->t_flags & TF_ACKNOW)
695 0 : tcpstat_inc(tcps_sndacks);
696 0 : else if (flags & (TH_SYN|TH_FIN|TH_RST))
697 0 : tcpstat_inc(tcps_sndctrl);
698 0 : else if (SEQ_GT(tp->snd_up, tp->snd_una))
699 0 : tcpstat_inc(tcps_sndurg);
700 : else
701 0 : tcpstat_inc(tcps_sndwinup);
702 :
703 0 : MGETHDR(m, M_DONTWAIT, MT_HEADER);
704 0 : if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
705 0 : MCLGET(m, M_DONTWAIT);
706 0 : if ((m->m_flags & M_EXT) == 0) {
707 0 : m_freem(m);
708 : m = NULL;
709 0 : }
710 : }
711 0 : if (m == NULL) {
712 : error = ENOBUFS;
713 0 : goto out;
714 : }
715 0 : m->m_data += max_linkhdr;
716 0 : m->m_len = hdrlen;
717 : }
718 0 : m->m_pkthdr.ph_ifidx = 0;
719 0 : m->m_pkthdr.len = hdrlen + len;
720 :
721 0 : if (!tp->t_template)
722 0 : panic("tcp_output");
723 : #ifdef DIAGNOSTIC
724 0 : if (tp->t_template->m_len != hdrlen - optlen)
725 0 : panic("tcp_output: template len != hdrlen - optlen");
726 : #endif /* DIAGNOSTIC */
727 0 : memcpy(mtod(m, caddr_t), mtod(tp->t_template, caddr_t),
728 : tp->t_template->m_len);
729 0 : th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len -
730 : sizeof(struct tcphdr));
731 :
732 : /*
733 : * Fill in fields, remembering maximum advertised
734 : * window for use in delaying messages about window sizes.
735 : * If resending a FIN, be sure not to use a new sequence number.
736 : */
737 0 : if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) &&
738 0 : (tp->snd_nxt == tp->snd_max))
739 0 : tp->snd_nxt--;
740 : /*
741 : * If we are doing retransmissions, then snd_nxt will
742 : * not reflect the first unsent octet. For ACK only
743 : * packets, we do not want the sequence number of the
744 : * retransmitted packet, we want the sequence number
745 : * of the next unsent octet. So, if there is no data
746 : * (and no SYN or FIN), use snd_max instead of snd_nxt
747 : * when filling in ti_seq. But if we are in persist
748 : * state, snd_max might reflect one byte beyond the
749 : * right edge of the window, so use snd_nxt in that
750 : * case, since we know we aren't doing a retransmission.
751 : * (retransmit and persist are mutually exclusive...)
752 : */
753 0 : if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST))
754 0 : th->th_seq = htonl(tp->snd_nxt);
755 : else
756 0 : th->th_seq = htonl(tp->snd_max);
757 :
758 0 : if (sack_rxmit) {
759 : /*
760 : * If sendalot was turned on (due to option stuffing), turn it
761 : * off. Properly set th_seq field. Advance the ret'x pointer
762 : * by len.
763 : */
764 0 : if (sendalot)
765 0 : sendalot = 0;
766 0 : th->th_seq = htonl(p->rxmit);
767 0 : p->rxmit += len;
768 0 : tcpstat_pkt(tcps_sack_rexmits, tcps_sack_rexmit_bytes, len);
769 0 : }
770 :
771 0 : th->th_ack = htonl(tp->rcv_nxt);
772 0 : if (optlen) {
773 0 : memcpy(th + 1, opt, optlen);
774 0 : th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
775 0 : }
776 : #ifdef TCP_ECN
777 0 : if (tcp_do_ecn) {
778 : /*
779 : * if we have received congestion experienced segs,
780 : * set ECE bit.
781 : */
782 0 : if (tp->t_flags & TF_RCVD_CE) {
783 0 : flags |= TH_ECE;
784 0 : tcpstat_inc(tcps_ecn_sndece);
785 0 : }
786 0 : if (!(tp->t_flags & TF_DISABLE_ECN)) {
787 : /*
788 : * if this is a SYN seg, set ECE and CWR.
789 : * set only ECE for SYN-ACK if peer supports ECN.
790 : */
791 0 : if ((flags & (TH_SYN|TH_ACK)) == TH_SYN)
792 0 : flags |= (TH_ECE|TH_CWR);
793 0 : else if ((tp->t_flags & TF_ECN_PERMIT) &&
794 0 : (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK))
795 0 : flags |= TH_ECE;
796 : }
797 : /*
798 : * if we have reduced the congestion window, notify
799 : * the peer by setting CWR bit.
800 : */
801 0 : if ((tp->t_flags & TF_ECN_PERMIT) &&
802 0 : (tp->t_flags & TF_SEND_CWR)) {
803 0 : flags |= TH_CWR;
804 0 : tp->t_flags &= ~TF_SEND_CWR;
805 0 : tcpstat_inc(tcps_ecn_sndcwr);
806 0 : }
807 : }
808 : #endif
809 0 : th->th_flags = flags;
810 :
811 : /*
812 : * Calculate receive window. Don't shrink window,
813 : * but avoid silly window syndrome.
814 : */
815 0 : if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg)
816 0 : win = 0;
817 0 : if (win > (long)TCP_MAXWIN << tp->rcv_scale)
818 0 : win = (long)TCP_MAXWIN << tp->rcv_scale;
819 0 : if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt))
820 0 : win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt);
821 0 : if (flags & TH_RST)
822 0 : win = 0;
823 0 : th->th_win = htons((u_int16_t) (win>>tp->rcv_scale));
824 0 : if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
825 : u_int32_t urp = tp->snd_up - tp->snd_nxt;
826 0 : if (urp > IP_MAXPACKET)
827 : urp = IP_MAXPACKET;
828 0 : th->th_urp = htons((u_int16_t)urp);
829 0 : th->th_flags |= TH_URG;
830 0 : } else
831 : /*
832 : * If no urgent pointer to send, then we pull
833 : * the urgent pointer to the left edge of the send window
834 : * so that it doesn't drift into the send window on sequence
835 : * number wraparound.
836 : */
837 0 : tp->snd_up = tp->snd_una; /* drag it along */
838 :
839 : #ifdef TCP_SIGNATURE
840 0 : if (tp->t_flags & TF_SIGNATURE) {
841 : int iphlen;
842 0 : union sockaddr_union src, dst;
843 : struct tdb *tdb;
844 :
845 0 : bzero(&src, sizeof(union sockaddr_union));
846 0 : bzero(&dst, sizeof(union sockaddr_union));
847 :
848 0 : switch (tp->pf) {
849 : case 0: /*default to PF_INET*/
850 : case AF_INET:
851 : iphlen = sizeof(struct ip);
852 0 : src.sa.sa_len = sizeof(struct sockaddr_in);
853 0 : src.sa.sa_family = AF_INET;
854 0 : src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
855 0 : dst.sa.sa_len = sizeof(struct sockaddr_in);
856 0 : dst.sa.sa_family = AF_INET;
857 0 : dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
858 0 : break;
859 : #ifdef INET6
860 : case AF_INET6:
861 : iphlen = sizeof(struct ip6_hdr);
862 0 : src.sa.sa_len = sizeof(struct sockaddr_in6);
863 0 : src.sa.sa_family = AF_INET6;
864 0 : src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
865 0 : dst.sa.sa_len = sizeof(struct sockaddr_in6);
866 0 : dst.sa.sa_family = AF_INET6;
867 0 : dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
868 0 : break;
869 : #endif /* INET6 */
870 : }
871 :
872 0 : tdb = gettdbbysrcdst(rtable_l2(tp->t_inpcb->inp_rtableid),
873 : 0, &src, &dst, IPPROTO_TCP);
874 0 : if (tdb == NULL) {
875 0 : m_freem(m);
876 0 : return (EPERM);
877 : }
878 :
879 0 : if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0,
880 0 : mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) {
881 0 : m_freem(m);
882 0 : return (EINVAL);
883 : }
884 0 : }
885 : #endif /* TCP_SIGNATURE */
886 :
887 : /* Defer checksumming until later (ip_output() or hardware) */
888 0 : m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT;
889 :
890 : /*
891 : * In transmit state, time the transmission and arrange for
892 : * the retransmit. In persist state, just set snd_max.
893 : */
894 0 : if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
895 0 : tcp_seq startseq = tp->snd_nxt;
896 :
897 : /*
898 : * Advance snd_nxt over sequence space of this segment.
899 : */
900 0 : if (flags & (TH_SYN|TH_FIN)) {
901 0 : if (flags & TH_SYN)
902 0 : tp->snd_nxt++;
903 0 : if (flags & TH_FIN) {
904 0 : tp->snd_nxt++;
905 0 : tp->t_flags |= TF_SENTFIN;
906 0 : }
907 : }
908 0 : if (tp->sack_enable) {
909 0 : if (sack_rxmit && (p->rxmit != tp->snd_nxt)) {
910 : goto timer;
911 : }
912 : }
913 0 : tp->snd_nxt += len;
914 0 : if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
915 0 : tp->snd_max = tp->snd_nxt;
916 : /*
917 : * Time this transmission if not a retransmission and
918 : * not currently timing anything.
919 : */
920 0 : if (tp->t_rtttime == 0) {
921 0 : tp->t_rtttime = tcp_now;
922 0 : tp->t_rtseq = startseq;
923 0 : tcpstat_inc(tcps_segstimed);
924 0 : }
925 : }
926 :
927 : /*
928 : * Set retransmit timer if not currently set,
929 : * and not doing an ack or a keep-alive probe.
930 : * Initial value for retransmit timer is smoothed
931 : * round-trip time + 2 * round-trip time variance.
932 : * Initialize shift counter which is used for backoff
933 : * of retransmit time.
934 : */
935 : timer:
936 0 : if (tp->sack_enable && sack_rxmit &&
937 0 : TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
938 0 : tp->snd_nxt != tp->snd_max) {
939 0 : TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
940 0 : if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
941 0 : TCP_TIMER_DISARM(tp, TCPT_PERSIST);
942 0 : tp->t_rxtshift = 0;
943 0 : }
944 : }
945 :
946 0 : if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
947 0 : tp->snd_nxt != tp->snd_una) {
948 0 : TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
949 0 : if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
950 0 : TCP_TIMER_DISARM(tp, TCPT_PERSIST);
951 0 : tp->t_rxtshift = 0;
952 0 : }
953 : }
954 :
955 0 : if (len == 0 && so->so_snd.sb_cc &&
956 0 : TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
957 0 : TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
958 : /*
959 : * Avoid a situation where we do not set persist timer
960 : * after a zero window condition. For example:
961 : * 1) A -> B: packet with enough data to fill the window
962 : * 2) B -> A: ACK for #1 + new data (0 window
963 : * advertisement)
964 : * 3) A -> B: ACK for #2, 0 len packet
965 : *
966 : * In this case, A will not activate the persist timer,
967 : * because it chose to send a packet. Unless tcp_output
968 : * is called for some other reason (delayed ack timer,
969 : * another input packet from B, socket syscall), A will
970 : * not send zero window probes.
971 : *
972 : * So, if you send a 0-length packet, but there is data
973 : * in the socket buffer, and neither the rexmt or
974 : * persist timer is already set, then activate the
975 : * persist timer.
976 : */
977 0 : tp->t_rxtshift = 0;
978 0 : tcp_setpersist(tp);
979 0 : }
980 0 : } else
981 0 : if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
982 0 : tp->snd_max = tp->snd_nxt + len;
983 :
984 0 : tcp_update_sndspace(tp);
985 :
986 : /*
987 : * Trace.
988 : */
989 0 : if (so->so_options & SO_DEBUG)
990 0 : tcp_trace(TA_OUTPUT, tp->t_state, tp, tp, mtod(m, caddr_t), 0,
991 0 : len);
992 :
993 : /*
994 : * Fill in IP length and desired time to live and
995 : * send to IP level. There should be a better way
996 : * to handle ttl and tos; we could keep them in
997 : * the template, but need a way to checksum without them.
998 : */
999 :
1000 : #ifdef TCP_ECN
1001 : /*
1002 : * if peer is ECN capable, set the ECT bit in the IP header.
1003 : * but don't set ECT for a pure ack, a retransmit or a window probe.
1004 : */
1005 : needect = 0;
1006 0 : if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) {
1007 0 : if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) ||
1008 0 : (tp->t_force && len == 1)) {
1009 : /* don't set ECT */
1010 : } else {
1011 : needect = 1;
1012 0 : tcpstat_inc(tcps_ecn_sndect);
1013 : }
1014 : }
1015 : #endif
1016 :
1017 : /* force routing table */
1018 0 : m->m_pkthdr.ph_rtableid = tp->t_inpcb->inp_rtableid;
1019 :
1020 : #if NPF > 0
1021 0 : pf_mbuf_link_inpcb(m, tp->t_inpcb);
1022 : #endif
1023 :
1024 0 : switch (tp->pf) {
1025 : case 0: /*default to PF_INET*/
1026 : case AF_INET:
1027 : {
1028 : struct ip *ip;
1029 :
1030 0 : ip = mtod(m, struct ip *);
1031 0 : ip->ip_len = htons(m->m_pkthdr.len);
1032 0 : packetlen = m->m_pkthdr.len;
1033 0 : ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl;
1034 0 : ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos;
1035 : #ifdef TCP_ECN
1036 0 : if (needect)
1037 0 : ip->ip_tos |= IPTOS_ECN_ECT0;
1038 : #endif
1039 : }
1040 0 : error = ip_output(m, tp->t_inpcb->inp_options,
1041 0 : &tp->t_inpcb->inp_route,
1042 0 : (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp->t_inpcb, 0);
1043 0 : break;
1044 : #ifdef INET6
1045 : case AF_INET6:
1046 : {
1047 : struct ip6_hdr *ip6;
1048 :
1049 0 : ip6 = mtod(m, struct ip6_hdr *);
1050 0 : ip6->ip6_plen = m->m_pkthdr.len -
1051 : sizeof(struct ip6_hdr);
1052 0 : packetlen = m->m_pkthdr.len;
1053 0 : ip6->ip6_nxt = IPPROTO_TCP;
1054 0 : ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb);
1055 : #ifdef TCP_ECN
1056 0 : if (needect)
1057 0 : ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1058 : #endif
1059 : }
1060 0 : error = ip6_output(m, tp->t_inpcb->inp_outputopts6,
1061 0 : &tp->t_inpcb->inp_route6,
1062 : 0, NULL, tp->t_inpcb);
1063 0 : break;
1064 : #endif /* INET6 */
1065 : }
1066 :
1067 0 : if (error) {
1068 : out:
1069 0 : if (error == ENOBUFS) {
1070 : /*
1071 : * If the interface queue is full, or IP cannot
1072 : * get an mbuf, trigger TCP slow start.
1073 : */
1074 0 : tp->snd_cwnd = tp->t_maxseg;
1075 0 : return (0);
1076 : }
1077 0 : if (error == EMSGSIZE) {
1078 : /*
1079 : * ip_output() will have already fixed the route
1080 : * for us. tcp_mtudisc() will, as its last action,
1081 : * initiate retransmission, so it is important to
1082 : * not do so here.
1083 : */
1084 0 : tcp_mtudisc(tp->t_inpcb, -1);
1085 0 : return (0);
1086 : }
1087 0 : if (error == EACCES) /* translate pf(4) error for userland */
1088 0 : error = EHOSTUNREACH;
1089 0 : if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1090 0 : TCPS_HAVERCVDSYN(tp->t_state)) {
1091 0 : tp->t_softerror = error;
1092 0 : return (0);
1093 : }
1094 :
1095 : /* Restart the delayed ACK timer, if necessary. */
1096 0 : if (TCP_TIMER_ISARMED(tp, TCPT_DELACK))
1097 0 : TCP_TIMER_ARM_MSEC(tp, TCPT_DELACK, tcp_delack_msecs);
1098 :
1099 0 : return (error);
1100 : }
1101 :
1102 0 : if (packetlen > tp->t_pmtud_mtu_sent)
1103 0 : tp->t_pmtud_mtu_sent = packetlen;
1104 :
1105 0 : tcpstat_inc(tcps_sndtotal);
1106 0 : if (TCP_TIMER_ISARMED(tp, TCPT_DELACK))
1107 0 : tcpstat_inc(tcps_delack);
1108 :
1109 : /*
1110 : * Data sent (as far as we can tell).
1111 : * If this advertises a larger window than any other segment,
1112 : * then remember the size of the advertised window.
1113 : * Any pending ACK has now been sent.
1114 : */
1115 0 : if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
1116 0 : tp->rcv_adv = tp->rcv_nxt + win;
1117 0 : tp->last_ack_sent = tp->rcv_nxt;
1118 0 : tp->t_flags &= ~TF_ACKNOW;
1119 0 : TCP_TIMER_DISARM(tp, TCPT_DELACK);
1120 0 : if (sendalot && --maxburst)
1121 0 : goto again;
1122 0 : return (0);
1123 0 : }
1124 :
1125 : void
1126 0 : tcp_setpersist(struct tcpcb *tp)
1127 : {
1128 0 : int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT);
1129 : int nticks;
1130 :
1131 0 : if (TCP_TIMER_ISARMED(tp, TCPT_REXMT))
1132 0 : panic("tcp_output REXMT");
1133 : /*
1134 : * Start/restart persistence timer.
1135 : */
1136 0 : if (t < tp->t_rttmin)
1137 0 : t = tp->t_rttmin;
1138 0 : TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift],
1139 : TCPTV_PERSMIN, TCPTV_PERSMAX);
1140 0 : TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks);
1141 0 : if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1142 0 : tp->t_rxtshift++;
1143 0 : }
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