1 /* $OpenBSD: tcp_output.c,v 1.134 2022/11/07 11:22:55 yasuoka 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 #include "stoeplitz.h"
73
74 #include <sys/param.h>
75 #include <sys/systm.h>
76 #include <sys/mbuf.h>
77 #include <sys/protosw.h>
78 #include <sys/socket.h>
79 #include <sys/socketvar.h>
80 #include <sys/kernel.h>
81
82 #include <net/if.h>
83 #include <net/route.h>
84 #if NPF > 0
85 #include <net/pfvar.h>
86 #endif
87
88 #include <netinet/in.h>
89 #include <netinet/ip.h>
90 #include <netinet/in_pcb.h>
91 #include <netinet/ip_var.h>
92 #include <netinet/tcp.h>
93 #define TCPOUTFLAGS
94 #include <netinet/tcp_fsm.h>
95 #include <netinet/tcp_seq.h>
96 #include <netinet/tcp_timer.h>
97 #include <netinet/tcp_var.h>
98 #include <netinet/tcp_debug.h>
99
100 #ifdef notyet
101 extern struct mbuf *m_copypack();
102 #endif
103
104 extern int tcprexmtthresh;
105
106 #ifdef TCP_SACK_DEBUG
107 void tcp_print_holes(struct tcpcb *tp);
108
109 void
110 tcp_print_holes(struct tcpcb *tp)
111 {
112 struct sackhole *p = tp->snd_holes;
113 if (p == NULL)
114 return;
115 printf("Hole report: start--end dups rxmit\n");
116 while (p) {
117 printf("%x--%x d %d r %x\n", p->start, p->end, p->dups,
118 p->rxmit);
119 p = p->next;
120 }
121 printf("\n");
122 }
123 #endif /* TCP_SACK_DEBUG */
124
125 /*
126 * Returns pointer to a sackhole if there are any pending retransmissions;
127 * NULL otherwise.
128 */
129 struct sackhole *
130 tcp_sack_output(struct tcpcb *tp)
131 {
132 struct sackhole *p;
133
134 if (!tp->sack_enable)
135 return (NULL);
136 p = tp->snd_holes;
137 while (p) {
138 if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
139 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
140 p = p->next;
141 continue;
142 }
143 #ifdef TCP_SACK_DEBUG
144 if (p)
145 tcp_print_holes(tp);
146 #endif
147 return (p);
148 }
149 p = p->next;
150 }
151 return (NULL);
152 }
153
154 /*
155 * After a timeout, the SACK list may be rebuilt. This SACK information
156 * should be used to avoid retransmitting SACKed data. This function
157 * traverses the SACK list to see if snd_nxt should be moved forward.
158 */
159
160 void
161 tcp_sack_adjust(struct tcpcb *tp)
162 {
163 struct sackhole *cur = tp->snd_holes;
164 if (cur == NULL)
165 return; /* No holes */
166 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))
167 return; /* We're already beyond any SACKed blocks */
168 /*
169 * Two cases for which we want to advance snd_nxt:
170 * i) snd_nxt lies between end of one hole and beginning of another
171 * ii) snd_nxt lies between end of last hole and rcv_lastsack
172 */
173 while (cur->next) {
174 if (SEQ_LT(tp->snd_nxt, cur->end))
175 return;
176 if (SEQ_GEQ(tp->snd_nxt, cur->next->start))
177 cur = cur->next;
178 else {
179 tp->snd_nxt = cur->next->start;
180 return;
181 }
182 }
183 if (SEQ_LT(tp->snd_nxt, cur->end))
184 return;
185 tp->snd_nxt = tp->rcv_lastsack;
186 return;
187 }
188
189 /*
190 * Tcp output routine: figure out what should be sent and send it.
191 */
192 int
193 tcp_output(struct tcpcb *tp)
194 {
195 struct socket *so = tp->t_inpcb->inp_socket;
196 long len, win, txmaxseg;
197 int off, flags, error;
198 struct mbuf *m;
199 struct tcphdr *th;
200 u_int32_t optbuf[howmany(MAX_TCPOPTLEN, sizeof(u_int32_t))];
201 u_char *opt = (u_char *)optbuf;
202 unsigned int optlen, hdrlen, packetlen;
203 int idle, sendalot = 0;
204 int i, sack_rxmit = 0;
205 struct sackhole *p;
206 uint32_t now;
207 #ifdef TCP_SIGNATURE
208 unsigned int sigoff;
209 #endif /* TCP_SIGNATURE */
210 #ifdef TCP_ECN
211 int needect;
212 #endif
213
214 if (tp->t_flags & TF_BLOCKOUTPUT) {
215 tp->t_flags |= TF_NEEDOUTPUT;
216 return (0);
217 } else
218 tp->t_flags &= ~TF_NEEDOUTPUT;
219
220 #if defined(TCP_SIGNATURE) && defined(DIAGNOSTIC)
221 if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE))
222 return (EINVAL);
223 #endif /* defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */
224
225 now = tcp_now();
226
227 /*
228 * Determine length of data that should be transmitted,
229 * and flags that will be used.
230 * If there is some data or critical controls (SYN, RST)
231 * to send, then transmit; otherwise, investigate further.
232 */
233 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
234 if (idle && (now - tp->t_rcvtime) >= tp->t_rxtcur)
235 /*
236 * We have been idle for "a while" and no acks are
237 * expected to clock out any data we send --
238 * slow start to get ack "clock" running again.
239 */
240 tp->snd_cwnd = 2 * tp->t_maxseg;
241
242 /* remember 'idle' for next invocation of tcp_output */
243 if (idle && soissending(so)) {
244 tp->t_flags |= TF_LASTIDLE;
245 idle = 0;
246 } else
247 tp->t_flags &= ~TF_LASTIDLE;
248
249 again:
250 /*
251 * If we've recently taken a timeout, snd_max will be greater than
252 * snd_nxt. There may be SACK information that allows us to avoid
253 * resending already delivered data. Adjust snd_nxt accordingly.
254 */
255 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max))
256 tcp_sack_adjust(tp);
257 off = tp->snd_nxt - tp->snd_una;
258 win = ulmin(tp->snd_wnd, tp->snd_cwnd);
259
260 flags = tcp_outflags[tp->t_state];
261
262 /*
263 * Send any SACK-generated retransmissions. If we're explicitly trying
264 * to send out new data (when sendalot is 1), bypass this function.
265 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
266 * we're replacing a (future) new transmission with a retransmission
267 * now, and we previously incremented snd_cwnd in tcp_input().
268 */
269 if (tp->sack_enable && !sendalot) {
270 if (tp->t_dupacks >= tcprexmtthresh &&
271 (p = tcp_sack_output(tp))) {
272 off = p->rxmit - tp->snd_una;
273 sack_rxmit = 1;
274 /* Coalesce holes into a single retransmission */
275 len = min(tp->t_maxseg, p->end - p->rxmit);
276 if (SEQ_LT(tp->snd_una, tp->snd_last))
277 tp->snd_cwnd -= tp->t_maxseg;
278 }
279 }
280
281 sendalot = 0;
282 /*
283 * If in persist timeout with window of 0, send 1 byte.
284 * Otherwise, if window is small but nonzero
285 * and timer expired, we will send what we can
286 * and go to transmit state.
287 */
288 if (tp->t_force) {
289 if (win == 0) {
290 /*
291 * If we still have some data to send, then
292 * clear the FIN bit. Usually this would
293 * happen below when it realizes that we
294 * aren't sending all the data. However,
295 * if we have exactly 1 byte of unset data,
296 * then it won't clear the FIN bit below,
297 * and if we are in persist state, we wind
298 * up sending the packet without recording
299 * that we sent the FIN bit.
300 *
301 * We can't just blindly clear the FIN bit,
302 * because if we don't have any more data
303 * to send then the probe will be the FIN
304 * itself.
305 */
306 if (off < so->so_snd.sb_cc)
307 flags &= ~TH_FIN;
308 win = 1;
309 } else {
310 TCP_TIMER_DISARM(tp, TCPT_PERSIST);
311 tp->t_rxtshift = 0;
312 }
313 }
314
315 if (!sack_rxmit) {
316 len = ulmin(so->so_snd.sb_cc, win) - off;
317 }
318
319 if (len < 0) {
320 /*
321 * If FIN has been sent but not acked,
322 * but we haven't been called to retransmit,
323 * len will be -1. Otherwise, window shrank
324 * after we sent into it. If window shrank to 0,
325 * cancel pending retransmit, pull snd_nxt back
326 * to (closed) window, and set the persist timer
327 * if it isn't already going. If the window didn't
328 * close completely, just wait for an ACK.
329 */
330 len = 0;
331 if (win == 0) {
332 TCP_TIMER_DISARM(tp, TCPT_REXMT);
333 tp->t_rxtshift = 0;
334 tp->snd_nxt = tp->snd_una;
335 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
336 tcp_setpersist(tp);
337 }
338 }
339
340 /*
341 * Never send more than half a buffer full. This insures that we can
342 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
343 * therefore acks will never be delayed unless we run out of data to
344 * transmit.
345 */
346 txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg);
347
348 if (len > txmaxseg) {
349 len = txmaxseg;
350 sendalot = 1;
351 }
352 if (off + len < so->so_snd.sb_cc)
353 flags &= ~TH_FIN;
354
355 win = sbspace(so, &so->so_rcv);
356
357 /*
358 * Sender silly window avoidance. If connection is idle
359 * and can send all data, a maximum segment,
360 * at least a maximum default-size segment do it,
361 * or are forced, do it; otherwise don't bother.
362 * If peer's buffer is tiny, then send
363 * when window is at least half open.
364 * If retransmitting (possibly after persist timer forced us
365 * to send into a small window), then must resend.
366 */
367 if (len) {
368 if (len == txmaxseg)
369 goto send;
370 if ((idle || (tp->t_flags & TF_NODELAY)) &&
371 len + off >= so->so_snd.sb_cc && !soissending(so) &&
372 (tp->t_flags & TF_NOPUSH) == 0)
373 goto send;
374 if (tp->t_force)
375 goto send;
376 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
377 goto send;
378 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
379 goto send;
380 if (sack_rxmit)
381 goto send;
382 }
383
384 /*
385 * Compare available window to amount of window
386 * known to peer (as advertised window less
387 * next expected input). If the difference is at least two
388 * max size segments, or at least 50% of the maximum possible
389 * window, then want to send a window update to peer.
390 */
391 if (win > 0) {
392 /*
393 * "adv" is the amount we can increase the window,
394 * taking into account that we are limited by
395 * TCP_MAXWIN << tp->rcv_scale.
396 */
397 long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) -
398 (tp->rcv_adv - tp->rcv_nxt);
399
400 if (adv >= (long) (2 * tp->t_maxseg))
401 goto send;
402 if (2 * adv >= (long) so->so_rcv.sb_hiwat)
403 goto send;
404 }
405
406 /*
407 * Send if we owe peer an ACK.
408 */
409 if (tp->t_flags & TF_ACKNOW)
410 goto send;
411 if (flags & (TH_SYN|TH_RST))
412 goto send;
413 if (SEQ_GT(tp->snd_up, tp->snd_una))
414 goto send;
415 /*
416 * If our state indicates that FIN should be sent
417 * and we have not yet done so, or we're retransmitting the FIN,
418 * then we need to send.
419 */
420 if (flags & TH_FIN &&
421 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
422 goto send;
423 /*
424 * In SACK, it is possible for tcp_output to fail to send a segment
425 * after the retransmission timer has been turned off. Make sure
426 * that the retransmission timer is set.
427 */
428 if (SEQ_GT(tp->snd_max, tp->snd_una) &&
429 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
430 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
431 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
432 return (0);
433 }
434
435 /*
436 * TCP window updates are not reliable, rather a polling protocol
437 * using ``persist'' packets is used to insure receipt of window
438 * updates. The three ``states'' for the output side are:
439 * idle not doing retransmits or persists
440 * persisting to move a small or zero window
441 * (re)transmitting and thereby not persisting
442 *
443 * tp->t_timer[TCPT_PERSIST]
444 * is set when we are in persist state.
445 * tp->t_force
446 * is set when we are called to send a persist packet.
447 * tp->t_timer[TCPT_REXMT]
448 * is set when we are retransmitting
449 * The output side is idle when both timers are zero.
450 *
451 * If send window is too small, there is data to transmit, and no
452 * retransmit or persist is pending, then go to persist state.
453 * If nothing happens soon, send when timer expires:
454 * if window is nonzero, transmit what we can,
455 * otherwise force out a byte.
456 */
457 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
458 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
459 tp->t_rxtshift = 0;
460 tcp_setpersist(tp);
461 }
462
463 /*
464 * No reason to send a segment, just return.
465 */
466 return (0);
467
468 send:
469 /*
470 * Before ESTABLISHED, force sending of initial options
471 * unless TCP set not to do any options.
472 * NOTE: we assume that the IP/TCP header plus TCP options
473 * always fit in a single mbuf, leaving room for a maximum
474 * link header, i.e.
475 * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr +
476 * optlen <= MHLEN
477 */
478 optlen = 0;
479
480 switch (tp->pf) {
481 case 0: /*default to PF_INET*/
482 case PF_INET:
483 hdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
484 break;
485 #ifdef INET6
486 case PF_INET6:
487 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
488 break;
489 #endif /* INET6 */
490 default:
491 return (EPFNOSUPPORT);
492 }
493
494 if (flags & TH_SYN) {
495 tp->snd_nxt = tp->iss;
496 if ((tp->t_flags & TF_NOOPT) == 0) {
497 u_int16_t mss;
498
499 opt[0] = TCPOPT_MAXSEG;
500 opt[1] = 4;
501 mss = htons((u_int16_t) tcp_mss(tp, 0));
502 memcpy(opt + 2, &mss, sizeof(mss));
503 optlen = 4;
504
505 if (flags & TH_ACK)
506 tcp_mss_update(tp);
507 /*
508 * If this is the first SYN of connection (not a SYN
509 * ACK), include SACK_PERMIT_HDR option. If this is a
510 * SYN ACK, include SACK_PERMIT_HDR option if peer has
511 * already done so.
512 */
513 if (tp->sack_enable && ((flags & TH_ACK) == 0 ||
514 (tp->t_flags & TF_SACK_PERMIT))) {
515 *((u_int32_t *) (opt + optlen)) =
516 htonl(TCPOPT_SACK_PERMIT_HDR);
517 optlen += 4;
518 }
519 if ((tp->t_flags & TF_REQ_SCALE) &&
520 ((flags & TH_ACK) == 0 ||
521 (tp->t_flags & TF_RCVD_SCALE))) {
522 *((u_int32_t *) (opt + optlen)) = htonl(
523 TCPOPT_NOP << 24 |
524 TCPOPT_WINDOW << 16 |
525 TCPOLEN_WINDOW << 8 |
526 tp->request_r_scale);
527 optlen += 4;
528 }
529 }
530 }
531
532 /*
533 * Send a timestamp and echo-reply if this is a SYN and our side
534 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
535 * and our peer have sent timestamps in our SYN's.
536 */
537 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
538 (flags & TH_RST) == 0 &&
539 ((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
540 (tp->t_flags & TF_RCVD_TSTMP))) {
541 u_int32_t *lp = (u_int32_t *)(opt + optlen);
542
543 /* Form timestamp option as shown in appendix A of RFC 1323. */
544 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
545 *lp++ = htonl(now + tp->ts_modulate);
546 *lp = htonl(tp->ts_recent);
547 optlen += TCPOLEN_TSTAMP_APPA;
548 }
549 /* Set receive buffer autosizing timestamp. */
550 if (tp->rfbuf_ts == 0) {
551 tp->rfbuf_ts = now;
552 tp->rfbuf_cnt = 0;
553 }
554
555 #ifdef TCP_SIGNATURE
556 if (tp->t_flags & TF_SIGNATURE) {
557 u_int8_t *bp = (u_int8_t *)(opt + optlen);
558
559 /* Send signature option */
560 *(bp++) = TCPOPT_SIGNATURE;
561 *(bp++) = TCPOLEN_SIGNATURE;
562 sigoff = optlen + 2;
563
564 {
565 unsigned int i;
566
567 for (i = 0; i < 16; i++)
568 *(bp++) = 0;
569 }
570
571
572 /* Pad options list to the next 32 bit boundary and
573 * terminate it.
574 */
575 *bp++ = TCPOPT_NOP;
576 *bp++ = TCPOPT_NOP;
577
578 optlen += TCPOLEN_SIGLEN;
579 }
580 #endif /* TCP_SIGNATURE */
581
582 /*
583 * Send SACKs if necessary. This should be the last option processed.
584 * Only as many SACKs are sent as are permitted by the maximum options
585 * size. No more than three SACKs are sent.
586 */
587 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED &&
588 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT &&
589 tp->rcv_numsacks) {
590 u_int32_t *lp = (u_int32_t *)(opt + optlen);
591 u_int32_t *olp = lp++;
592 int count = 0; /* actual number of SACKs inserted */
593 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK;
594
595 tcpstat_inc(tcps_sack_snd_opts);
596 maxsack = min(maxsack, TCP_MAX_SACK);
597 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) {
598 struct sackblk sack = tp->sackblks[i];
599 if (sack.start == 0 && sack.end == 0)
600 continue;
601 *lp++ = htonl(sack.start);
602 *lp++ = htonl(sack.end);
603 count++;
604 }
605 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2));
606 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */
607 }
608
609 #ifdef DIAGNOSTIC
610 if (optlen > MAX_TCPOPTLEN)
611 panic("tcp_output: options too long");
612 #endif /* DIAGNOSTIC */
613
614 hdrlen += optlen;
615
616 /*
617 * Adjust data length if insertion of options will
618 * bump the packet length beyond the t_maxopd length.
619 */
620 if (len > tp->t_maxopd - optlen) {
621 len = tp->t_maxopd - optlen;
622 sendalot = 1;
623 flags &= ~TH_FIN;
624 }
625
626 #ifdef DIAGNOSTIC
627 if (max_linkhdr + hdrlen > MCLBYTES)
628 panic("tcphdr too big");
629 #endif
630
631 /*
632 * Grab a header mbuf, attaching a copy of data to
633 * be transmitted, and initialize the header from
634 * the template for sends on this connection.
635 */
636 if (len) {
637 if (tp->t_force && len == 1)
638 tcpstat_inc(tcps_sndprobe);
639 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
640 tcpstat_pkt(tcps_sndrexmitpack, tcps_sndrexmitbyte,
641 len);
642 tp->t_sndrexmitpack++;
643 } else {
644 tcpstat_pkt(tcps_sndpack, tcps_sndbyte, len);
645 }
646 #ifdef notyet
647 if ((m = m_copypack(so->so_snd.sb_mb, off,
648 (int)len, max_linkhdr + hdrlen)) == 0) {
649 error = ENOBUFS;
650 goto out;
651 }
652 /*
653 * m_copypack left space for our hdr; use it.
654 */
655 m->m_len += hdrlen;
656 m->m_data -= hdrlen;
657 #else
658 MGETHDR(m, M_DONTWAIT, MT_HEADER);
659 if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
660 MCLGET(m, M_DONTWAIT);
661 if ((m->m_flags & M_EXT) == 0) {
662 m_freem(m);
663 m = NULL;
664 }
665 }
666 if (m == NULL) {
667 error = ENOBUFS;
668 goto out;
669 }
670 m->m_data += max_linkhdr;
671 m->m_len = hdrlen;
672 if (len <= m_trailingspace(m)) {
673 m_copydata(so->so_snd.sb_mb, off, (int) len,
674 mtod(m, caddr_t) + hdrlen);
675 m->m_len += len;
676 } else {
677 m->m_next = m_copym(so->so_snd.sb_mb, off, (int) len,
678 M_NOWAIT);
679 if (m->m_next == 0) {
680 (void) m_free(m);
681 error = ENOBUFS;
682 goto out;
683 }
684 }
685 if (so->so_snd.sb_mb->m_flags & M_PKTHDR)
686 m->m_pkthdr.ph_loopcnt =
687 so->so_snd.sb_mb->m_pkthdr.ph_loopcnt;
688 #endif
689 /*
690 * If we're sending everything we've got, set PUSH.
691 * (This will keep happy those implementations which only
692 * give data to the user when a buffer fills or
693 * a PUSH comes in.)
694 */
695 if (off + len == so->so_snd.sb_cc && !soissending(so))
696 flags |= TH_PUSH;
697 tp->t_sndtime = now;
698 } else {
699 if (tp->t_flags & TF_ACKNOW)
700 tcpstat_inc(tcps_sndacks);
701 else if (flags & (TH_SYN|TH_FIN|TH_RST))
702 tcpstat_inc(tcps_sndctrl);
703 else if (SEQ_GT(tp->snd_up, tp->snd_una))
704 tcpstat_inc(tcps_sndurg);
705 else
706 tcpstat_inc(tcps_sndwinup);
707
708 MGETHDR(m, M_DONTWAIT, MT_HEADER);
709 if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
710 MCLGET(m, M_DONTWAIT);
711 if ((m->m_flags & M_EXT) == 0) {
712 m_freem(m);
713 m = NULL;
714 }
715 }
716 if (m == NULL) {
717 error = ENOBUFS;
718 goto out;
719 }
720 m->m_data += max_linkhdr;
721 m->m_len = hdrlen;
722 }
723 m->m_pkthdr.ph_ifidx = 0;
724 m->m_pkthdr.len = hdrlen + len;
725
726 if (!tp->t_template)
727 panic("tcp_output");
728 #ifdef DIAGNOSTIC
729 if (tp->t_template->m_len != hdrlen - optlen)
730 panic("tcp_output: template len != hdrlen - optlen");
731 #endif /* DIAGNOSTIC */
732 memcpy(mtod(m, caddr_t), mtod(tp->t_template, caddr_t),
733 tp->t_template->m_len);
734 th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len -
735 sizeof(struct tcphdr));
736
737 /*
738 * Fill in fields, remembering maximum advertised
739 * window for use in delaying messages about window sizes.
740 * If resending a FIN, be sure not to use a new sequence number.
741 */
742 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) &&
743 (tp->snd_nxt == tp->snd_max))
744 tp->snd_nxt--;
745 /*
746 * If we are doing retransmissions, then snd_nxt will
747 * not reflect the first unsent octet. For ACK only
748 * packets, we do not want the sequence number of the
749 * retransmitted packet, we want the sequence number
750 * of the next unsent octet. So, if there is no data
751 * (and no SYN or FIN), use snd_max instead of snd_nxt
752 * when filling in ti_seq. But if we are in persist
753 * state, snd_max might reflect one byte beyond the
754 * right edge of the window, so use snd_nxt in that
755 * case, since we know we aren't doing a retransmission.
756 * (retransmit and persist are mutually exclusive...)
757 */
758 if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST))
759 th->th_seq = htonl(tp->snd_nxt);
760 else
761 th->th_seq = htonl(tp->snd_max);
762
763 if (sack_rxmit) {
764 /*
765 * If sendalot was turned on (due to option stuffing), turn it
766 * off. Properly set th_seq field. Advance the ret'x pointer
767 * by len.
768 */
769 if (sendalot)
770 sendalot = 0;
771 th->th_seq = htonl(p->rxmit);
772 p->rxmit += len;
773 tcpstat_pkt(tcps_sack_rexmits, tcps_sack_rexmit_bytes, len);
774 }
775
776 th->th_ack = htonl(tp->rcv_nxt);
777 if (optlen) {
778 memcpy(th + 1, opt, optlen);
779 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
780 }
781 #ifdef TCP_ECN
782 if (tcp_do_ecn) {
783 /*
784 * if we have received congestion experienced segs,
785 * set ECE bit.
786 */
787 if (tp->t_flags & TF_RCVD_CE) {
788 flags |= TH_ECE;
789 tcpstat_inc(tcps_ecn_sndece);
790 }
791 if (!(tp->t_flags & TF_DISABLE_ECN)) {
792 /*
793 * if this is a SYN seg, set ECE and CWR.
794 * set only ECE for SYN-ACK if peer supports ECN.
795 */
796 if ((flags & (TH_SYN|TH_ACK)) == TH_SYN)
797 flags |= (TH_ECE|TH_CWR);
798 else if ((tp->t_flags & TF_ECN_PERMIT) &&
799 (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK))
800 flags |= TH_ECE;
801 }
802 /*
803 * if we have reduced the congestion window, notify
804 * the peer by setting CWR bit.
805 */
806 if ((tp->t_flags & TF_ECN_PERMIT) &&
807 (tp->t_flags & TF_SEND_CWR)) {
808 flags |= TH_CWR;
809 tp->t_flags &= ~TF_SEND_CWR;
810 tcpstat_inc(tcps_ecn_sndcwr);
811 }
812 }
813 #endif
814 th->th_flags = flags;
815
816 /*
817 * Calculate receive window. Don't shrink window,
818 * but avoid silly window syndrome.
819 */
820 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg)
821 win = 0;
822 if (win > (long)TCP_MAXWIN << tp->rcv_scale)
823 win = (long)TCP_MAXWIN << tp->rcv_scale;
824 if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt))
825 win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt);
826 if (flags & TH_RST)
827 win = 0;
828 th->th_win = htons((u_int16_t) (win>>tp->rcv_scale));
829 if (th->th_win == 0)
830 tp->t_sndzerowin++;
831 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
832 u_int32_t urp = tp->snd_up - tp->snd_nxt;
833 if (urp > IP_MAXPACKET)
834 urp = IP_MAXPACKET;
835 th->th_urp = htons((u_int16_t)urp);
836 th->th_flags |= TH_URG;
837 } else
838 /*
839 * If no urgent pointer to send, then we pull
840 * the urgent pointer to the left edge of the send window
841 * so that it doesn't drift into the send window on sequence
842 * number wraparound.
843 */
844 tp->snd_up = tp->snd_una; /* drag it along */
845
846 #ifdef TCP_SIGNATURE
847 if (tp->t_flags & TF_SIGNATURE) {
848 int iphlen;
849 union sockaddr_union src, dst;
850 struct tdb *tdb;
851
852 bzero(&src, sizeof(union sockaddr_union));
853 bzero(&dst, sizeof(union sockaddr_union));
854
855 switch (tp->pf) {
856 case 0: /*default to PF_INET*/
857 case AF_INET:
858 iphlen = sizeof(struct ip);
859 src.sa.sa_len = sizeof(struct sockaddr_in);
860 src.sa.sa_family = AF_INET;
861 src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
862 dst.sa.sa_len = sizeof(struct sockaddr_in);
863 dst.sa.sa_family = AF_INET;
864 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
865 break;
866 #ifdef INET6
867 case AF_INET6:
868 iphlen = sizeof(struct ip6_hdr);
869 src.sa.sa_len = sizeof(struct sockaddr_in6);
870 src.sa.sa_family = AF_INET6;
871 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
872 dst.sa.sa_len = sizeof(struct sockaddr_in6);
873 dst.sa.sa_family = AF_INET6;
874 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
875 break;
876 #endif /* INET6 */
877 }
878
879 tdb = gettdbbysrcdst(rtable_l2(tp->t_inpcb->inp_rtableid),
880 0, &src, &dst, IPPROTO_TCP);
881 if (tdb == NULL) {
882 m_freem(m);
883 return (EPERM);
884 }
885
886 if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0,
887 mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) {
888 m_freem(m);
889 tdb_unref(tdb);
890 return (EINVAL);
891 }
892 tdb_unref(tdb);
893 }
894 #endif /* TCP_SIGNATURE */
895
896 /* Defer checksumming until later (ip_output() or hardware) */
897 m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT;
898
899 /*
900 * In transmit state, time the transmission and arrange for
901 * the retransmit. In persist state, just set snd_max.
902 */
903 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
904 tcp_seq startseq = tp->snd_nxt;
905
906 /*
907 * Advance snd_nxt over sequence space of this segment.
908 */
909 if (flags & (TH_SYN|TH_FIN)) {
910 if (flags & TH_SYN)
911 tp->snd_nxt++;
912 if (flags & TH_FIN) {
913 tp->snd_nxt++;
914 tp->t_flags |= TF_SENTFIN;
915 }
916 }
917 if (tp->sack_enable) {
918 if (sack_rxmit && (p->rxmit != tp->snd_nxt)) {
919 goto timer;
920 }
921 }
922 tp->snd_nxt += len;
923 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
924 tp->snd_max = tp->snd_nxt;
925 /*
926 * Time this transmission if not a retransmission and
927 * not currently timing anything.
928 */
929 if (tp->t_rtttime == 0) {
930 tp->t_rtttime = now;
931 tp->t_rtseq = startseq;
932 tcpstat_inc(tcps_segstimed);
933 }
934 }
935
936 /*
937 * Set retransmit timer if not currently set,
938 * and not doing an ack or a keep-alive probe.
939 * Initial value for retransmit timer is smoothed
940 * round-trip time + 2 * round-trip time variance.
941 * Initialize shift counter which is used for backoff
942 * of retransmit time.
943 */
944 timer:
945 if (tp->sack_enable && sack_rxmit &&
946 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
947 tp->snd_nxt != tp->snd_max) {
948 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
949 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
950 TCP_TIMER_DISARM(tp, TCPT_PERSIST);
951 tp->t_rxtshift = 0;
952 }
953 }
954
955 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
956 tp->snd_nxt != tp->snd_una) {
957 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
958 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
959 TCP_TIMER_DISARM(tp, TCPT_PERSIST);
960 tp->t_rxtshift = 0;
961 }
962 }
963
964 if (len == 0 && so->so_snd.sb_cc &&
965 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
966 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
967 /*
968 * Avoid a situation where we do not set persist timer
969 * after a zero window condition. For example:
970 * 1) A -> B: packet with enough data to fill the window
971 * 2) B -> A: ACK for #1 + new data (0 window
972 * advertisement)
973 * 3) A -> B: ACK for #2, 0 len packet
974 *
975 * In this case, A will not activate the persist timer,
976 * because it chose to send a packet. Unless tcp_output
977 * is called for some other reason (delayed ack timer,
978 * another input packet from B, socket syscall), A will
979 * not send zero window probes.
980 *
981 * So, if you send a 0-length packet, but there is data
982 * in the socket buffer, and neither the rexmt or
983 * persist timer is already set, then activate the
984 * persist timer.
985 */
986 tp->t_rxtshift = 0;
987 tcp_setpersist(tp);
988 }
989 } else
990 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
991 tp->snd_max = tp->snd_nxt + len;
992
993 tcp_update_sndspace(tp);
994
995 /*
996 * Trace.
997 */
998 if (so->so_options & SO_DEBUG)
999 tcp_trace(TA_OUTPUT, tp->t_state, tp, tp, mtod(m, caddr_t), 0,
1000 len);
1001
1002 /*
1003 * Fill in IP length and desired time to live and
1004 * send to IP level. There should be a better way
1005 * to handle ttl and tos; we could keep them in
1006 * the template, but need a way to checksum without them.
1007 */
1008
1009 #ifdef TCP_ECN
1010 /*
1011 * if peer is ECN capable, set the ECT bit in the IP header.
1012 * but don't set ECT for a pure ack, a retransmit or a window probe.
1013 */
1014 needect = 0;
1015 if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) {
1016 if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) ||
1017 (tp->t_force && len == 1)) {
1018 /* don't set ECT */
1019 } else {
1020 needect = 1;
1021 tcpstat_inc(tcps_ecn_sndect);
1022 }
1023 }
1024 #endif
1025
1026 /* force routing table */
1027 m->m_pkthdr.ph_rtableid = tp->t_inpcb->inp_rtableid;
1028
1029 #if NPF > 0
1030 pf_mbuf_link_inpcb(m, tp->t_inpcb);
1031 #endif
1032
1033 switch (tp->pf) {
1034 case 0: /*default to PF_INET*/
1035 case AF_INET:
1036 {
1037 struct ip *ip;
1038
1039 ip = mtod(m, struct ip *);
1040 ip->ip_len = htons(m->m_pkthdr.len);
1041 packetlen = m->m_pkthdr.len;
1042 ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl;
1043 ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos;
1044 #ifdef TCP_ECN
1045 if (needect)
1046 ip->ip_tos |= IPTOS_ECN_ECT0;
1047 #endif
1048 }
1049 #if NSTOEPLITZ > 0
1050 m->m_pkthdr.ph_flowid = tp->t_inpcb->inp_flowid;
1051 SET(m->m_pkthdr.csum_flags, M_FLOWID);
1052 #endif
1053 error = ip_output(m, tp->t_inpcb->inp_options,
1054 &tp->t_inpcb->inp_route,
1055 (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp->t_inpcb, 0);
1056 break;
1057 #ifdef INET6
1058 case AF_INET6:
1059 {
1060 struct ip6_hdr *ip6;
1061
1062 ip6 = mtod(m, struct ip6_hdr *);
1063 ip6->ip6_plen = m->m_pkthdr.len -
1064 sizeof(struct ip6_hdr);
1065 packetlen = m->m_pkthdr.len;
1066 ip6->ip6_nxt = IPPROTO_TCP;
1067 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb);
1068 #ifdef TCP_ECN
1069 if (needect)
1070 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1071 #endif
1072 }
1073 error = ip6_output(m, tp->t_inpcb->inp_outputopts6,
1074 &tp->t_inpcb->inp_route6,
1075 0, NULL, tp->t_inpcb);
1076 break;
1077 #endif /* INET6 */
1078 }
1079
1080 if (error) {
1081 out:
1082 if (error == ENOBUFS) {
1083 /*
1084 * If the interface queue is full, or IP cannot
1085 * get an mbuf, trigger TCP slow start.
1086 */
1087 tp->snd_cwnd = tp->t_maxseg;
1088 return (0);
1089 }
1090 if (error == EMSGSIZE) {
1091 /*
1092 * ip_output() will have already fixed the route
1093 * for us. tcp_mtudisc() will, as its last action,
1094 * initiate retransmission, so it is important to
1095 * not do so here.
1096 */
1097 tcp_mtudisc(tp->t_inpcb, -1);
1098 return (0);
1099 }
1100 if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1101 TCPS_HAVERCVDSYN(tp->t_state)) {
1102 tp->t_softerror = error;
1103 return (0);
1104 }
1105
1106 /* Restart the delayed ACK timer, if necessary. */
1107 if (TCP_TIMER_ISARMED(tp, TCPT_DELACK))
1108 TCP_TIMER_ARM(tp, TCPT_DELACK, tcp_delack_msecs);
1109
1110 return (error);
1111 }
1112
1113 if (packetlen > tp->t_pmtud_mtu_sent)
1114 tp->t_pmtud_mtu_sent = packetlen;
1115
1116 tcpstat_inc(tcps_sndtotal);
1117 if (TCP_TIMER_ISARMED(tp, TCPT_DELACK))
1118 tcpstat_inc(tcps_delack);
1119
1120 /*
1121 * Data sent (as far as we can tell).
1122 * If this advertises a larger window than any other segment,
1123 * then remember the size of the advertised window.
1124 * Any pending ACK has now been sent.
1125 */
1126 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
1127 tp->rcv_adv = tp->rcv_nxt + win;
1128 tp->last_ack_sent = tp->rcv_nxt;
1129 tp->t_sndacktime = now;
1130 tp->t_flags &= ~TF_ACKNOW;
1131 TCP_TIMER_DISARM(tp, TCPT_DELACK);
1132 if (sendalot)
1133 goto again;
1134 return (0);
1135 }
1136
1137 void
1138 tcp_setpersist(struct tcpcb *tp)
1139 {
1140 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT);
1141 int msec;
1142
1143 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT))
1144 panic("tcp_output REXMT");
1145 /*
1146 * Start/restart persistence timer.
1147 */
1148 if (t < tp->t_rttmin)
1149 t = tp->t_rttmin;
1150 TCPT_RANGESET(msec, t * tcp_backoff[tp->t_rxtshift],
1151 TCPTV_PERSMIN, TCPTV_PERSMAX);
1152 TCP_TIMER_ARM(tp, TCPT_PERSIST, msec);
1153 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1154 tp->t_rxtshift++;
1155 }
Cache object: 364a2453299f687d37a81af320fc4446
|