1 /*-
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD: releng/7.4/sys/netinet/tcp_output.c 211871 2010-08-27 10:16:32Z andre $");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
38 #include "opt_mac.h"
39 #include "opt_tcpdebug.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/domain.h>
44 #include <sys/kernel.h>
45 #include <sys/lock.h>
46 #include <sys/mbuf.h>
47 #include <sys/mutex.h>
48 #include <sys/protosw.h>
49 #include <sys/socket.h>
50 #include <sys/socketvar.h>
51 #include <sys/sysctl.h>
52
53 #include <net/route.h>
54
55 #include <netinet/in.h>
56 #include <netinet/in_systm.h>
57 #include <netinet/ip.h>
58 #include <netinet/in_pcb.h>
59 #include <netinet/ip_var.h>
60 #include <netinet/ip_options.h>
61 #ifdef INET6
62 #include <netinet6/in6_pcb.h>
63 #include <netinet/ip6.h>
64 #include <netinet6/ip6_var.h>
65 #endif
66 #include <netinet/tcp.h>
67 #define TCPOUTFLAGS
68 #include <netinet/tcp_fsm.h>
69 #include <netinet/tcp_seq.h>
70 #include <netinet/tcp_timer.h>
71 #include <netinet/tcp_var.h>
72 #include <netinet/tcpip.h>
73 #ifdef TCPDEBUG
74 #include <netinet/tcp_debug.h>
75 #endif
76
77 #ifdef IPSEC
78 #include <netipsec/ipsec.h>
79 #endif /*IPSEC*/
80
81 #include <machine/in_cksum.h>
82
83 #include <security/mac/mac_framework.h>
84
85 #ifdef notyet
86 extern struct mbuf *m_copypack();
87 #endif
88
89 int path_mtu_discovery = 1;
90 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
91 &path_mtu_discovery, 1, "Enable Path MTU Discovery");
92
93 int ss_fltsz = 1;
94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW,
95 &ss_fltsz, 1, "Slow start flight size");
96
97 int ss_fltsz_local = 4;
98 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW,
99 &ss_fltsz_local, 1, "Slow start flight size for local networks");
100
101 int tcp_do_newreno = 1;
102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW,
103 &tcp_do_newreno, 0, "Enable NewReno Algorithms");
104
105 int tcp_do_tso = 1;
106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
107 &tcp_do_tso, 0, "Enable TCP Segmentation Offload");
108
109 int tcp_do_autosndbuf = 1;
110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
111 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing");
112
113 int tcp_autosndbuf_inc = 8*1024;
114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
115 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer");
116
117 int tcp_autosndbuf_max = 256*1024;
118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
119 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer");
120
121
122 /*
123 * Tcp output routine: figure out what should be sent and send it.
124 */
125 int
126 tcp_output(struct tcpcb *tp)
127 {
128 struct socket *so = tp->t_inpcb->inp_socket;
129 long len, recwin, sendwin;
130 int off, flags, error, rw;
131 struct mbuf *m;
132 struct ip *ip = NULL;
133 struct ipovly *ipov = NULL;
134 struct tcphdr *th;
135 u_char opt[TCP_MAXOLEN];
136 unsigned ipoptlen, optlen, hdrlen;
137 #ifdef IPSEC
138 unsigned ipsec_optlen = 0;
139 #endif
140 int idle, sendalot;
141 int sack_rxmit, sack_bytes_rxmt;
142 struct sackhole *p;
143 int tso;
144 struct tcpopt to;
145 #if 0
146 int maxburst = TCP_MAXBURST;
147 #endif
148 #ifdef INET6
149 struct ip6_hdr *ip6 = NULL;
150 int isipv6;
151
152 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
153 #endif
154
155 INP_WLOCK_ASSERT(tp->t_inpcb);
156
157 /*
158 * Determine length of data that should be transmitted,
159 * and flags that will be used.
160 * If there is some data or critical controls (SYN, RST)
161 * to send, then transmit; otherwise, investigate further.
162 */
163 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
164 if (idle && (ticks - (int)tp->t_rcvtime) >= tp->t_rxtcur) {
165 /*
166 * If we've been idle for more than one retransmit
167 * timeout the old congestion window is no longer
168 * current and we have to reduce it to the restart
169 * window before we can transmit again.
170 *
171 * The restart window is the initial window or the last
172 * CWND, whichever is smaller.
173 *
174 * This is done to prevent us from flooding the path with
175 * a full CWND at wirespeed, overloading router and switch
176 * buffers along the way.
177 *
178 * See RFC5681 Section 4.1. "Restarting Idle Connections".
179 */
180 if (tcp_do_rfc3390)
181 rw = min(4 * tp->t_maxseg,
182 max(2 * tp->t_maxseg, 4380));
183 #ifdef INET6
184 else if ((isipv6 ? in6_localaddr(&tp->t_inpcb->in6p_faddr) :
185 in_localaddr(tp->t_inpcb->inp_faddr)))
186 #else
187 else if (in_localaddr(tp->t_inpcb->inp_faddr))
188 #endif
189 rw = ss_fltsz_local * tp->t_maxseg;
190 else
191 rw = ss_fltsz * tp->t_maxseg;
192
193 tp->snd_cwnd = min(rw, tp->snd_cwnd);
194 }
195 tp->t_flags &= ~TF_LASTIDLE;
196 if (idle) {
197 if (tp->t_flags & TF_MORETOCOME) {
198 tp->t_flags |= TF_LASTIDLE;
199 idle = 0;
200 }
201 }
202 again:
203 /*
204 * If we've recently taken a timeout, snd_max will be greater than
205 * snd_nxt. There may be SACK information that allows us to avoid
206 * resending already delivered data. Adjust snd_nxt accordingly.
207 */
208 if ((tp->t_flags & TF_SACK_PERMIT) &&
209 SEQ_LT(tp->snd_nxt, tp->snd_max))
210 tcp_sack_adjust(tp);
211 sendalot = 0;
212 tso = 0;
213 off = tp->snd_nxt - tp->snd_una;
214 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
215 sendwin = min(sendwin, tp->snd_bwnd);
216
217 flags = tcp_outflags[tp->t_state];
218 /*
219 * Send any SACK-generated retransmissions. If we're explicitly trying
220 * to send out new data (when sendalot is 1), bypass this function.
221 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
222 * we're replacing a (future) new transmission with a retransmission
223 * now, and we previously incremented snd_cwnd in tcp_input().
224 */
225 /*
226 * Still in sack recovery , reset rxmit flag to zero.
227 */
228 sack_rxmit = 0;
229 sack_bytes_rxmt = 0;
230 len = 0;
231 p = NULL;
232 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) &&
233 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
234 long cwin;
235
236 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
237 if (cwin < 0)
238 cwin = 0;
239 /* Do not retransmit SACK segments beyond snd_recover */
240 if (SEQ_GT(p->end, tp->snd_recover)) {
241 /*
242 * (At least) part of sack hole extends beyond
243 * snd_recover. Check to see if we can rexmit data
244 * for this hole.
245 */
246 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
247 /*
248 * Can't rexmit any more data for this hole.
249 * That data will be rexmitted in the next
250 * sack recovery episode, when snd_recover
251 * moves past p->rxmit.
252 */
253 p = NULL;
254 goto after_sack_rexmit;
255 } else
256 /* Can rexmit part of the current hole */
257 len = ((long)ulmin(cwin,
258 tp->snd_recover - p->rxmit));
259 } else
260 len = ((long)ulmin(cwin, p->end - p->rxmit));
261 off = p->rxmit - tp->snd_una;
262 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
263 __func__, off));
264 if (len > 0) {
265 sack_rxmit = 1;
266 sendalot = 1;
267 tcpstat.tcps_sack_rexmits++;
268 tcpstat.tcps_sack_rexmit_bytes +=
269 min(len, tp->t_maxseg);
270 }
271 }
272 after_sack_rexmit:
273 /*
274 * Get standard flags, and add SYN or FIN if requested by 'hidden'
275 * state flags.
276 */
277 if (tp->t_flags & TF_NEEDFIN)
278 flags |= TH_FIN;
279 if (tp->t_flags & TF_NEEDSYN)
280 flags |= TH_SYN;
281
282 SOCKBUF_LOCK(&so->so_snd);
283 /*
284 * If in persist timeout with window of 0, send 1 byte.
285 * Otherwise, if window is small but nonzero
286 * and timer expired, we will send what we can
287 * and go to transmit state.
288 */
289 if (tp->t_flags & TF_FORCEDATA) {
290 if (sendwin == 0) {
291 /*
292 * If we still have some data to send, then
293 * clear the FIN bit. Usually this would
294 * happen below when it realizes that we
295 * aren't sending all the data. However,
296 * if we have exactly 1 byte of unsent data,
297 * then it won't clear the FIN bit below,
298 * and if we are in persist state, we wind
299 * up sending the packet without recording
300 * that we sent the FIN bit.
301 *
302 * We can't just blindly clear the FIN bit,
303 * because if we don't have any more data
304 * to send then the probe will be the FIN
305 * itself.
306 */
307 if (off < so->so_snd.sb_cc)
308 flags &= ~TH_FIN;
309 sendwin = 1;
310 } else {
311 tcp_timer_activate(tp, TT_PERSIST, 0);
312 tp->t_rxtshift = 0;
313 }
314 }
315
316 /*
317 * If snd_nxt == snd_max and we have transmitted a FIN, the
318 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
319 * a negative length. This can also occur when TCP opens up
320 * its congestion window while receiving additional duplicate
321 * acks after fast-retransmit because TCP will reset snd_nxt
322 * to snd_max after the fast-retransmit.
323 *
324 * In the normal retransmit-FIN-only case, however, snd_nxt will
325 * be set to snd_una, the offset will be 0, and the length may
326 * wind up 0.
327 *
328 * If sack_rxmit is true we are retransmitting from the scoreboard
329 * in which case len is already set.
330 */
331 if (sack_rxmit == 0) {
332 if (sack_bytes_rxmt == 0)
333 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off);
334 else {
335 long cwin;
336
337 /*
338 * We are inside of a SACK recovery episode and are
339 * sending new data, having retransmitted all the
340 * data possible in the scoreboard.
341 */
342 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
343 - off);
344 /*
345 * Don't remove this (len > 0) check !
346 * We explicitly check for len > 0 here (although it
347 * isn't really necessary), to work around a gcc
348 * optimization issue - to force gcc to compute
349 * len above. Without this check, the computation
350 * of len is bungled by the optimizer.
351 */
352 if (len > 0) {
353 cwin = tp->snd_cwnd -
354 (tp->snd_nxt - tp->sack_newdata) -
355 sack_bytes_rxmt;
356 if (cwin < 0)
357 cwin = 0;
358 len = lmin(len, cwin);
359 }
360 }
361 }
362
363 /*
364 * Lop off SYN bit if it has already been sent. However, if this
365 * is SYN-SENT state and if segment contains data and if we don't
366 * know that foreign host supports TAO, suppress sending segment.
367 */
368 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
369 if (tp->t_state != TCPS_SYN_RECEIVED)
370 flags &= ~TH_SYN;
371 off--, len++;
372 }
373
374 /*
375 * Be careful not to send data and/or FIN on SYN segments.
376 * This measure is needed to prevent interoperability problems
377 * with not fully conformant TCP implementations.
378 */
379 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
380 len = 0;
381 flags &= ~TH_FIN;
382 }
383
384 if (len < 0) {
385 /*
386 * If FIN has been sent but not acked,
387 * but we haven't been called to retransmit,
388 * len will be < 0. Otherwise, window shrank
389 * after we sent into it. If window shrank to 0,
390 * cancel pending retransmit, pull snd_nxt back
391 * to (closed) window, and set the persist timer
392 * if it isn't already going. If the window didn't
393 * close completely, just wait for an ACK.
394 */
395 len = 0;
396 if (sendwin == 0) {
397 tcp_timer_activate(tp, TT_REXMT, 0);
398 tp->t_rxtshift = 0;
399 tp->snd_nxt = tp->snd_una;
400 if (!tcp_timer_active(tp, TT_PERSIST))
401 tcp_setpersist(tp);
402 }
403 }
404
405 /* len will be >= 0 after this point. */
406 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
407
408 /*
409 * Automatic sizing of send socket buffer. Often the send buffer
410 * size is not optimally adjusted to the actual network conditions
411 * at hand (delay bandwidth product). Setting the buffer size too
412 * small limits throughput on links with high bandwidth and high
413 * delay (eg. trans-continental/oceanic links). Setting the
414 * buffer size too big consumes too much real kernel memory,
415 * especially with many connections on busy servers.
416 *
417 * The criteria to step up the send buffer one notch are:
418 * 1. receive window of remote host is larger than send buffer
419 * (with a fudge factor of 5/4th);
420 * 2. send buffer is filled to 7/8th with data (so we actually
421 * have data to make use of it);
422 * 3. send buffer fill has not hit maximal automatic size;
423 * 4. our send window (slow start and cogestion controlled) is
424 * larger than sent but unacknowledged data in send buffer.
425 *
426 * The remote host receive window scaling factor may limit the
427 * growing of the send buffer before it reaches its allowed
428 * maximum.
429 *
430 * It scales directly with slow start or congestion window
431 * and does at most one step per received ACK. This fast
432 * scaling has the drawback of growing the send buffer beyond
433 * what is strictly necessary to make full use of a given
434 * delay*bandwith product. However testing has shown this not
435 * to be much of an problem. At worst we are trading wasting
436 * of available bandwith (the non-use of it) for wasting some
437 * socket buffer memory.
438 *
439 * TODO: Shrink send buffer during idle periods together
440 * with congestion window. Requires another timer. Has to
441 * wait for upcoming tcp timer rewrite.
442 */
443 if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
444 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
445 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
446 so->so_snd.sb_cc < tcp_autosndbuf_max &&
447 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
448 if (!sbreserve_locked(&so->so_snd,
449 min(so->so_snd.sb_hiwat + tcp_autosndbuf_inc,
450 tcp_autosndbuf_max), so, curthread))
451 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
452 }
453 }
454
455 /*
456 * Truncate to the maximum segment length or enable TCP Segmentation
457 * Offloading (if supported by hardware) and ensure that FIN is removed
458 * if the length no longer contains the last data byte.
459 *
460 * TSO may only be used if we are in a pure bulk sending state. The
461 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
462 * IP options prevent using TSO. With TSO the TCP header is the same
463 * (except for the sequence number) for all generated packets. This
464 * makes it impossible to transmit any options which vary per generated
465 * segment or packet.
466 *
467 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and
468 * removal of FIN (if not already catched here) are handled later after
469 * the exact length of the TCP options are known.
470 */
471 #ifdef IPSEC
472 /*
473 * Pre-calculate here as we save another lookup into the darknesses
474 * of IPsec that way and can actually decide if TSO is ok.
475 */
476 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
477 #endif
478 if (len > tp->t_maxseg) {
479 if ((tp->t_flags & TF_TSO) && tcp_do_tso &&
480 ((tp->t_flags & TF_SIGNATURE) == 0) &&
481 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
482 tp->t_inpcb->inp_options == NULL &&
483 tp->t_inpcb->in6p_options == NULL
484 #ifdef IPSEC
485 && ipsec_optlen == 0
486 #endif
487 ) {
488 tso = 1;
489 } else {
490 len = tp->t_maxseg;
491 sendalot = 1;
492 }
493 }
494
495 if (sack_rxmit) {
496 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
497 flags &= ~TH_FIN;
498 } else {
499 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
500 flags &= ~TH_FIN;
501 }
502
503 recwin = sbspace(&so->so_rcv);
504
505 /*
506 * Sender silly window avoidance. We transmit under the following
507 * conditions when len is non-zero:
508 *
509 * - We have a full segment (or more with TSO)
510 * - This is the last buffer in a write()/send() and we are
511 * either idle or running NODELAY
512 * - we've timed out (e.g. persist timer)
513 * - we have more then 1/2 the maximum send window's worth of
514 * data (receiver may be limited the window size)
515 * - we need to retransmit
516 */
517 if (len) {
518 if (len >= tp->t_maxseg)
519 goto send;
520 /*
521 * NOTE! on localhost connections an 'ack' from the remote
522 * end may occur synchronously with the output and cause
523 * us to flush a buffer queued with moretocome. XXX
524 *
525 * note: the len + off check is almost certainly unnecessary.
526 */
527 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
528 (idle || (tp->t_flags & TF_NODELAY)) &&
529 len + off >= so->so_snd.sb_cc &&
530 (tp->t_flags & TF_NOPUSH) == 0) {
531 goto send;
532 }
533 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
534 goto send;
535 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
536 goto send;
537 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
538 goto send;
539 if (sack_rxmit)
540 goto send;
541 }
542
543 /*
544 * Compare available window to amount of window
545 * known to peer (as advertised window less
546 * next expected input). If the difference is at least two
547 * max size segments, or at least 50% of the maximum possible
548 * window, then want to send a window update to peer.
549 * Skip this if the connection is in T/TCP half-open state.
550 * Don't send pure window updates when the peer has closed
551 * the connection and won't ever send more data.
552 */
553 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
554 !TCPS_HAVERCVDFIN(tp->t_state)) {
555 /*
556 * "adv" is the amount we can increase the window,
557 * taking into account that we are limited by
558 * TCP_MAXWIN << tp->rcv_scale.
559 */
560 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) -
561 (tp->rcv_adv - tp->rcv_nxt);
562
563 if (adv >= (long) (2 * tp->t_maxseg))
564 goto send;
565 if (2 * adv >= (long) so->so_rcv.sb_hiwat)
566 goto send;
567 }
568
569 /*
570 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
571 * is also a catch-all for the retransmit timer timeout case.
572 */
573 if (tp->t_flags & TF_ACKNOW)
574 goto send;
575 if ((flags & TH_RST) ||
576 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
577 goto send;
578 if (SEQ_GT(tp->snd_up, tp->snd_una))
579 goto send;
580 /*
581 * If our state indicates that FIN should be sent
582 * and we have not yet done so, then we need to send.
583 */
584 if (flags & TH_FIN &&
585 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
586 goto send;
587 /*
588 * In SACK, it is possible for tcp_output to fail to send a segment
589 * after the retransmission timer has been turned off. Make sure
590 * that the retransmission timer is set.
591 */
592 if ((tp->t_flags & TF_SACK_PERMIT) &&
593 SEQ_GT(tp->snd_max, tp->snd_una) &&
594 !tcp_timer_active(tp, TT_REXMT) &&
595 !tcp_timer_active(tp, TT_PERSIST)) {
596 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
597 goto just_return;
598 }
599 /*
600 * TCP window updates are not reliable, rather a polling protocol
601 * using ``persist'' packets is used to insure receipt of window
602 * updates. The three ``states'' for the output side are:
603 * idle not doing retransmits or persists
604 * persisting to move a small or zero window
605 * (re)transmitting and thereby not persisting
606 *
607 * tcp_timer_active(tp, TT_PERSIST)
608 * is true when we are in persist state.
609 * (tp->t_flags & TF_FORCEDATA)
610 * is set when we are called to send a persist packet.
611 * tcp_timer_active(tp, TT_REXMT)
612 * is set when we are retransmitting
613 * The output side is idle when both timers are zero.
614 *
615 * If send window is too small, there is data to transmit, and no
616 * retransmit or persist is pending, then go to persist state.
617 * If nothing happens soon, send when timer expires:
618 * if window is nonzero, transmit what we can,
619 * otherwise force out a byte.
620 */
621 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) &&
622 !tcp_timer_active(tp, TT_PERSIST)) {
623 tp->t_rxtshift = 0;
624 tcp_setpersist(tp);
625 }
626
627 /*
628 * No reason to send a segment, just return.
629 */
630 just_return:
631 SOCKBUF_UNLOCK(&so->so_snd);
632 return (0);
633
634 send:
635 SOCKBUF_LOCK_ASSERT(&so->so_snd);
636 /*
637 * Before ESTABLISHED, force sending of initial options
638 * unless TCP set not to do any options.
639 * NOTE: we assume that the IP/TCP header plus TCP options
640 * always fit in a single mbuf, leaving room for a maximum
641 * link header, i.e.
642 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
643 */
644 optlen = 0;
645 #ifdef INET6
646 if (isipv6)
647 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
648 else
649 #endif
650 hdrlen = sizeof (struct tcpiphdr);
651
652 /*
653 * Compute options for segment.
654 * We only have to care about SYN and established connection
655 * segments. Options for SYN-ACK segments are handled in TCP
656 * syncache.
657 */
658 if ((tp->t_flags & TF_NOOPT) == 0) {
659 to.to_flags = 0;
660 /* Maximum segment size. */
661 if (flags & TH_SYN) {
662 tp->snd_nxt = tp->iss;
663 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
664 to.to_flags |= TOF_MSS;
665 }
666 /* Window scaling. */
667 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
668 to.to_wscale = tp->request_r_scale;
669 to.to_flags |= TOF_SCALE;
670 }
671 /* Timestamps. */
672 if ((tp->t_flags & TF_RCVD_TSTMP) ||
673 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
674 to.to_tsval = ticks + tp->ts_offset;
675 to.to_tsecr = tp->ts_recent;
676 to.to_flags |= TOF_TS;
677 /* Set receive buffer autosizing timestamp. */
678 if (tp->rfbuf_ts == 0 &&
679 (so->so_rcv.sb_flags & SB_AUTOSIZE))
680 tp->rfbuf_ts = ticks;
681 }
682 /* Selective ACK's. */
683 if (tp->t_flags & TF_SACK_PERMIT) {
684 if (flags & TH_SYN)
685 to.to_flags |= TOF_SACKPERM;
686 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
687 (tp->t_flags & TF_SACK_PERMIT) &&
688 tp->rcv_numsacks > 0) {
689 to.to_flags |= TOF_SACK;
690 to.to_nsacks = tp->rcv_numsacks;
691 to.to_sacks = (u_char *)tp->sackblks;
692 }
693 }
694 #ifdef TCP_SIGNATURE
695 /* TCP-MD5 (RFC2385). */
696 if (tp->t_flags & TF_SIGNATURE)
697 to.to_flags |= TOF_SIGNATURE;
698 #endif /* TCP_SIGNATURE */
699
700 /* Processing the options. */
701 hdrlen += optlen = tcp_addoptions(&to, opt);
702 }
703
704 #ifdef INET6
705 if (isipv6)
706 ipoptlen = ip6_optlen(tp->t_inpcb);
707 else
708 #endif
709 if (tp->t_inpcb->inp_options)
710 ipoptlen = tp->t_inpcb->inp_options->m_len -
711 offsetof(struct ipoption, ipopt_list);
712 else
713 ipoptlen = 0;
714 #ifdef IPSEC
715 ipoptlen += ipsec_optlen;
716 #endif
717
718 /*
719 * Adjust data length if insertion of options will
720 * bump the packet length beyond the t_maxopd length.
721 * Clear the FIN bit because we cut off the tail of
722 * the segment.
723 *
724 * When doing TSO limit a burst to TCP_MAXWIN minus the
725 * IP, TCP and Options length to keep ip->ip_len from
726 * overflowing. Prevent the last segment from being
727 * fractional thus making them all equal sized and set
728 * the flag to continue sending. TSO is disabled when
729 * IP options or IPSEC are present.
730 */
731 if (len + optlen + ipoptlen > tp->t_maxopd) {
732 flags &= ~TH_FIN;
733 if (tso) {
734 if (len > TCP_MAXWIN - hdrlen - optlen) {
735 len = TCP_MAXWIN - hdrlen - optlen;
736 len = len - (len % (tp->t_maxopd - optlen));
737 sendalot = 1;
738 } else if (tp->t_flags & TF_NEEDFIN)
739 sendalot = 1;
740 } else {
741 len = tp->t_maxopd - optlen - ipoptlen;
742 sendalot = 1;
743 }
744 }
745
746 /*#ifdef DIAGNOSTIC*/
747 #ifdef INET6
748 if (max_linkhdr + hdrlen > MCLBYTES)
749 #else
750 if (max_linkhdr + hdrlen > MHLEN)
751 #endif
752 panic("tcphdr too big");
753 /*#endif*/
754
755 /*
756 * This KASSERT is here to catch edge cases at a well defined place.
757 * Before, those had triggered (random) panic conditions further down.
758 */
759 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
760
761 /*
762 * Grab a header mbuf, attaching a copy of data to
763 * be transmitted, and initialize the header from
764 * the template for sends on this connection.
765 */
766 if (len) {
767 struct mbuf *mb;
768 u_int moff;
769
770 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
771 tcpstat.tcps_sndprobe++;
772 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
773 tcpstat.tcps_sndrexmitpack++;
774 tcpstat.tcps_sndrexmitbyte += len;
775 } else {
776 tcpstat.tcps_sndpack++;
777 tcpstat.tcps_sndbyte += len;
778 }
779 #ifdef notyet
780 if ((m = m_copypack(so->so_snd.sb_mb, off,
781 (int)len, max_linkhdr + hdrlen)) == 0) {
782 SOCKBUF_UNLOCK(&so->so_snd);
783 error = ENOBUFS;
784 goto out;
785 }
786 /*
787 * m_copypack left space for our hdr; use it.
788 */
789 m->m_len += hdrlen;
790 m->m_data -= hdrlen;
791 #else
792 MGETHDR(m, M_DONTWAIT, MT_DATA);
793 if (m == NULL) {
794 SOCKBUF_UNLOCK(&so->so_snd);
795 error = ENOBUFS;
796 goto out;
797 }
798 #ifdef INET6
799 if (MHLEN < hdrlen + max_linkhdr) {
800 MCLGET(m, M_DONTWAIT);
801 if ((m->m_flags & M_EXT) == 0) {
802 SOCKBUF_UNLOCK(&so->so_snd);
803 m_freem(m);
804 error = ENOBUFS;
805 goto out;
806 }
807 }
808 #endif
809 m->m_data += max_linkhdr;
810 m->m_len = hdrlen;
811
812 /*
813 * Start the m_copy functions from the closest mbuf
814 * to the offset in the socket buffer chain.
815 */
816 mb = sbsndptr(&so->so_snd, off, len, &moff);
817
818 if (len <= MHLEN - hdrlen - max_linkhdr) {
819 m_copydata(mb, moff, (int)len,
820 mtod(m, caddr_t) + hdrlen);
821 m->m_len += len;
822 } else {
823 m->m_next = m_copy(mb, moff, (int)len);
824 if (m->m_next == NULL) {
825 SOCKBUF_UNLOCK(&so->so_snd);
826 (void) m_free(m);
827 error = ENOBUFS;
828 goto out;
829 }
830 }
831 #endif
832 /*
833 * If we're sending everything we've got, set PUSH.
834 * (This will keep happy those implementations which only
835 * give data to the user when a buffer fills or
836 * a PUSH comes in.)
837 */
838 if (off + len == so->so_snd.sb_cc)
839 flags |= TH_PUSH;
840 SOCKBUF_UNLOCK(&so->so_snd);
841 } else {
842 SOCKBUF_UNLOCK(&so->so_snd);
843 if (tp->t_flags & TF_ACKNOW)
844 tcpstat.tcps_sndacks++;
845 else if (flags & (TH_SYN|TH_FIN|TH_RST))
846 tcpstat.tcps_sndctrl++;
847 else if (SEQ_GT(tp->snd_up, tp->snd_una))
848 tcpstat.tcps_sndurg++;
849 else
850 tcpstat.tcps_sndwinup++;
851
852 MGETHDR(m, M_DONTWAIT, MT_DATA);
853 if (m == NULL) {
854 error = ENOBUFS;
855 goto out;
856 }
857 #ifdef INET6
858 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
859 MHLEN >= hdrlen) {
860 MH_ALIGN(m, hdrlen);
861 } else
862 #endif
863 m->m_data += max_linkhdr;
864 m->m_len = hdrlen;
865 }
866 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
867 m->m_pkthdr.rcvif = (struct ifnet *)0;
868 #ifdef MAC
869 mac_create_mbuf_from_inpcb(tp->t_inpcb, m);
870 #endif
871 #ifdef INET6
872 if (isipv6) {
873 ip6 = mtod(m, struct ip6_hdr *);
874 th = (struct tcphdr *)(ip6 + 1);
875 tcpip_fillheaders(tp->t_inpcb, ip6, th);
876 } else
877 #endif /* INET6 */
878 {
879 ip = mtod(m, struct ip *);
880 ipov = (struct ipovly *)ip;
881 th = (struct tcphdr *)(ip + 1);
882 tcpip_fillheaders(tp->t_inpcb, ip, th);
883 }
884
885 /*
886 * Fill in fields, remembering maximum advertised
887 * window for use in delaying messages about window sizes.
888 * If resending a FIN, be sure not to use a new sequence number.
889 */
890 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
891 tp->snd_nxt == tp->snd_max)
892 tp->snd_nxt--;
893 /*
894 * If we are doing retransmissions, then snd_nxt will
895 * not reflect the first unsent octet. For ACK only
896 * packets, we do not want the sequence number of the
897 * retransmitted packet, we want the sequence number
898 * of the next unsent octet. So, if there is no data
899 * (and no SYN or FIN), use snd_max instead of snd_nxt
900 * when filling in ti_seq. But if we are in persist
901 * state, snd_max might reflect one byte beyond the
902 * right edge of the window, so use snd_nxt in that
903 * case, since we know we aren't doing a retransmission.
904 * (retransmit and persist are mutually exclusive...)
905 */
906 if (sack_rxmit == 0) {
907 if (len || (flags & (TH_SYN|TH_FIN)) ||
908 tcp_timer_active(tp, TT_PERSIST))
909 th->th_seq = htonl(tp->snd_nxt);
910 else
911 th->th_seq = htonl(tp->snd_max);
912 } else {
913 th->th_seq = htonl(p->rxmit);
914 p->rxmit += len;
915 tp->sackhint.sack_bytes_rexmit += len;
916 }
917 th->th_ack = htonl(tp->rcv_nxt);
918 if (optlen) {
919 bcopy(opt, th + 1, optlen);
920 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
921 }
922 th->th_flags = flags;
923 /*
924 * Calculate receive window. Don't shrink window,
925 * but avoid silly window syndrome.
926 */
927 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
928 recwin < (long)tp->t_maxseg)
929 recwin = 0;
930 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
931 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
932 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
933 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
934
935 /*
936 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
937 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
938 * case is handled in syncache.
939 */
940 if (flags & TH_SYN)
941 th->th_win = htons((u_short)
942 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
943 else
944 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
945
946 /*
947 * Adjust the RXWIN0SENT flag - indicate that we have advertised
948 * a 0 window. This may cause the remote transmitter to stall. This
949 * flag tells soreceive() to disable delayed acknowledgements when
950 * draining the buffer. This can occur if the receiver is attempting
951 * to read more data then can be buffered prior to transmitting on
952 * the connection.
953 */
954 if (th->th_win == 0)
955 tp->t_flags |= TF_RXWIN0SENT;
956 else
957 tp->t_flags &= ~TF_RXWIN0SENT;
958 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
959 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
960 th->th_flags |= TH_URG;
961 } else
962 /*
963 * If no urgent pointer to send, then we pull
964 * the urgent pointer to the left edge of the send window
965 * so that it doesn't drift into the send window on sequence
966 * number wraparound.
967 */
968 tp->snd_up = tp->snd_una; /* drag it along */
969
970 #ifdef TCP_SIGNATURE
971 if (tp->t_flags & TF_SIGNATURE) {
972 int sigoff = to.to_signature - opt;
973 tcp_signature_compute(m, 0, len, optlen,
974 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
975 }
976 #endif
977
978 /*
979 * Put TCP length in extended header, and then
980 * checksum extended header and data.
981 */
982 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
983 #ifdef INET6
984 if (isipv6)
985 /*
986 * ip6_plen is not need to be filled now, and will be filled
987 * in ip6_output.
988 */
989 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
990 sizeof(struct tcphdr) + optlen + len);
991 else
992 #endif /* INET6 */
993 {
994 m->m_pkthdr.csum_flags = CSUM_TCP;
995 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
996 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
997 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
998
999 /* IP version must be set here for ipv4/ipv6 checking later */
1000 KASSERT(ip->ip_v == IPVERSION,
1001 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1002 }
1003
1004 /*
1005 * Enable TSO and specify the size of the segments.
1006 * The TCP pseudo header checksum is always provided.
1007 * XXX: Fixme: This is currently not the case for IPv6.
1008 */
1009 if (tso) {
1010 KASSERT(len > tp->t_maxopd - optlen,
1011 ("%s: len <= tso_segsz", __func__));
1012 m->m_pkthdr.csum_flags |= CSUM_TSO;
1013 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1014 }
1015
1016 /*
1017 * In transmit state, time the transmission and arrange for
1018 * the retransmit. In persist state, just set snd_max.
1019 */
1020 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1021 !tcp_timer_active(tp, TT_PERSIST)) {
1022 tcp_seq startseq = tp->snd_nxt;
1023
1024 /*
1025 * Advance snd_nxt over sequence space of this segment.
1026 */
1027 if (flags & (TH_SYN|TH_FIN)) {
1028 if (flags & TH_SYN)
1029 tp->snd_nxt++;
1030 if (flags & TH_FIN) {
1031 tp->snd_nxt++;
1032 tp->t_flags |= TF_SENTFIN;
1033 }
1034 }
1035 if (sack_rxmit)
1036 goto timer;
1037 tp->snd_nxt += len;
1038 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1039 tp->snd_max = tp->snd_nxt;
1040 /*
1041 * Time this transmission if not a retransmission and
1042 * not currently timing anything.
1043 */
1044 if (tp->t_rtttime == 0) {
1045 tp->t_rtttime = ticks;
1046 tp->t_rtseq = startseq;
1047 tcpstat.tcps_segstimed++;
1048 }
1049 }
1050
1051 /*
1052 * Set retransmit timer if not currently set,
1053 * and not doing a pure ack or a keep-alive probe.
1054 * Initial value for retransmit timer is smoothed
1055 * round-trip time + 2 * round-trip time variance.
1056 * Initialize shift counter which is used for backoff
1057 * of retransmit time.
1058 */
1059 timer:
1060 if (!tcp_timer_active(tp, TT_REXMT) &&
1061 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1062 (tp->snd_nxt != tp->snd_una))) {
1063 if (tcp_timer_active(tp, TT_PERSIST)) {
1064 tcp_timer_activate(tp, TT_PERSIST, 0);
1065 tp->t_rxtshift = 0;
1066 }
1067 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1068 }
1069 } else {
1070 /*
1071 * Persist case, update snd_max but since we are in
1072 * persist mode (no window) we do not update snd_nxt.
1073 */
1074 int xlen = len;
1075 if (flags & TH_SYN)
1076 ++xlen;
1077 if (flags & TH_FIN) {
1078 ++xlen;
1079 tp->t_flags |= TF_SENTFIN;
1080 }
1081 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1082 tp->snd_max = tp->snd_nxt + len;
1083 }
1084
1085 #ifdef TCPDEBUG
1086 /*
1087 * Trace.
1088 */
1089 if (so->so_options & SO_DEBUG) {
1090 u_short save = 0;
1091 #ifdef INET6
1092 if (!isipv6)
1093 #endif
1094 {
1095 save = ipov->ih_len;
1096 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1097 }
1098 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1099 #ifdef INET6
1100 if (!isipv6)
1101 #endif
1102 ipov->ih_len = save;
1103 }
1104 #endif
1105
1106 /*
1107 * Fill in IP length and desired time to live and
1108 * send to IP level. There should be a better way
1109 * to handle ttl and tos; we could keep them in
1110 * the template, but need a way to checksum without them.
1111 */
1112 /*
1113 * m->m_pkthdr.len should have been set before cksum calcuration,
1114 * because in6_cksum() need it.
1115 */
1116 #ifdef INET6
1117 if (isipv6) {
1118 /*
1119 * we separately set hoplimit for every segment, since the
1120 * user might want to change the value via setsockopt.
1121 * Also, desired default hop limit might be changed via
1122 * Neighbor Discovery.
1123 */
1124 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1125
1126 /* TODO: IPv6 IP6TOS_ECT bit on */
1127 error = ip6_output(m,
1128 tp->t_inpcb->in6p_outputopts, NULL,
1129 ((so->so_options & SO_DONTROUTE) ?
1130 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb);
1131 } else
1132 #endif /* INET6 */
1133 {
1134 ip->ip_len = m->m_pkthdr.len;
1135 #ifdef INET6
1136 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1137 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1138 #endif /* INET6 */
1139 /*
1140 * If we do path MTU discovery, then we set DF on every packet.
1141 * This might not be the best thing to do according to RFC3390
1142 * Section 2. However the tcp hostcache migitates the problem
1143 * so it affects only the first tcp connection with a host.
1144 *
1145 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1146 */
1147 if (path_mtu_discovery && tp->t_maxopd > tcp_minmss)
1148 ip->ip_off |= IP_DF;
1149
1150 error = ip_output(m, tp->t_inpcb->inp_options, NULL,
1151 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1152 tp->t_inpcb);
1153 }
1154 if (error) {
1155
1156 /*
1157 * We know that the packet was lost, so back out the
1158 * sequence number advance, if any.
1159 *
1160 * If the error is EPERM the packet got blocked by the
1161 * local firewall. Normally we should terminate the
1162 * connection but the blocking may have been spurious
1163 * due to a firewall reconfiguration cycle. So we treat
1164 * it like a packet loss and let the retransmit timer and
1165 * timeouts do their work over time.
1166 * XXX: It is a POLA question whether calling tcp_drop right
1167 * away would be the really correct behavior instead.
1168 */
1169 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1170 !tcp_timer_active(tp, TT_PERSIST)) &&
1171 ((flags & TH_SYN) == 0) &&
1172 (error != EPERM)) {
1173 if (sack_rxmit) {
1174 p->rxmit -= len;
1175 tp->sackhint.sack_bytes_rexmit -= len;
1176 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1177 ("sackhint bytes rtx >= 0"));
1178 } else
1179 tp->snd_nxt -= len;
1180 }
1181 out:
1182 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1183 switch (error) {
1184 case EPERM:
1185 tp->t_softerror = error;
1186 return (error);
1187 case ENOBUFS:
1188 if (!tcp_timer_active(tp, TT_REXMT) &&
1189 !tcp_timer_active(tp, TT_PERSIST))
1190 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1191 tp->snd_cwnd = tp->t_maxseg;
1192 return (0);
1193 case EMSGSIZE:
1194 /*
1195 * For some reason the interface we used initially
1196 * to send segments changed to another or lowered
1197 * its MTU.
1198 *
1199 * tcp_mtudisc() will find out the new MTU and as
1200 * its last action, initiate retransmission, so it
1201 * is important to not do so here.
1202 *
1203 * If TSO was active we either got an interface
1204 * without TSO capabilits or TSO was turned off.
1205 * Disable it for this connection as too and
1206 * immediatly retry with MSS sized segments generated
1207 * by this function.
1208 */
1209 if (tso)
1210 tp->t_flags &= ~TF_TSO;
1211 tcp_mtudisc(tp->t_inpcb, 0);
1212 return (0);
1213 case EHOSTDOWN:
1214 case EHOSTUNREACH:
1215 case ENETDOWN:
1216 case ENETUNREACH:
1217 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1218 tp->t_softerror = error;
1219 return (0);
1220 }
1221 /* FALLTHROUGH */
1222 default:
1223 return (error);
1224 }
1225 }
1226 tcpstat.tcps_sndtotal++;
1227
1228 /*
1229 * Data sent (as far as we can tell).
1230 * If this advertises a larger window than any other segment,
1231 * then remember the size of the advertised window.
1232 * Any pending ACK has now been sent.
1233 */
1234 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1235 tp->rcv_adv = tp->rcv_nxt + recwin;
1236 tp->last_ack_sent = tp->rcv_nxt;
1237 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1238 if (tcp_timer_active(tp, TT_DELACK))
1239 tcp_timer_activate(tp, TT_DELACK, 0);
1240 #if 0
1241 /*
1242 * This completely breaks TCP if newreno is turned on. What happens
1243 * is that if delayed-acks are turned on on the receiver, this code
1244 * on the transmitter effectively destroys the TCP window, forcing
1245 * it to four packets (1.5Kx4 = 6K window).
1246 */
1247 if (sendalot && (!tcp_do_newreno || --maxburst))
1248 goto again;
1249 #endif
1250 if (sendalot)
1251 goto again;
1252 return (0);
1253 }
1254
1255 void
1256 tcp_setpersist(struct tcpcb *tp)
1257 {
1258 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1259 int tt;
1260
1261 if (tcp_timer_active(tp, TT_REXMT))
1262 panic("tcp_setpersist: retransmit pending");
1263 /*
1264 * Start/restart persistance timer.
1265 */
1266 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1267 TCPTV_PERSMIN, TCPTV_PERSMAX);
1268 tcp_timer_activate(tp, TT_PERSIST, tt);
1269 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1270 tp->t_rxtshift++;
1271 }
1272
1273 /*
1274 * Insert TCP options according to the supplied parameters to the place
1275 * optp in a consistent way. Can handle unaligned destinations.
1276 *
1277 * The order of the option processing is crucial for optimal packing and
1278 * alignment for the scarce option space.
1279 *
1280 * The optimal order for a SYN/SYN-ACK segment is:
1281 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1282 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1283 *
1284 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1285 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1286 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1287 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1288 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1289 */
1290 int
1291 tcp_addoptions(struct tcpopt *to, u_char *optp)
1292 {
1293 u_int mask, optlen = 0;
1294
1295 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1296 if ((to->to_flags & mask) != mask)
1297 continue;
1298 if (optlen == TCP_MAXOLEN)
1299 break;
1300 switch (to->to_flags & mask) {
1301 case TOF_MSS:
1302 while (optlen % 4) {
1303 optlen += TCPOLEN_NOP;
1304 *optp++ = TCPOPT_NOP;
1305 }
1306 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1307 continue;
1308 optlen += TCPOLEN_MAXSEG;
1309 *optp++ = TCPOPT_MAXSEG;
1310 *optp++ = TCPOLEN_MAXSEG;
1311 to->to_mss = htons(to->to_mss);
1312 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1313 optp += sizeof(to->to_mss);
1314 break;
1315 case TOF_SCALE:
1316 while (!optlen || optlen % 2 != 1) {
1317 optlen += TCPOLEN_NOP;
1318 *optp++ = TCPOPT_NOP;
1319 }
1320 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1321 continue;
1322 optlen += TCPOLEN_WINDOW;
1323 *optp++ = TCPOPT_WINDOW;
1324 *optp++ = TCPOLEN_WINDOW;
1325 *optp++ = to->to_wscale;
1326 break;
1327 case TOF_SACKPERM:
1328 while (optlen % 2) {
1329 optlen += TCPOLEN_NOP;
1330 *optp++ = TCPOPT_NOP;
1331 }
1332 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1333 continue;
1334 optlen += TCPOLEN_SACK_PERMITTED;
1335 *optp++ = TCPOPT_SACK_PERMITTED;
1336 *optp++ = TCPOLEN_SACK_PERMITTED;
1337 break;
1338 case TOF_TS:
1339 while (!optlen || optlen % 4 != 2) {
1340 optlen += TCPOLEN_NOP;
1341 *optp++ = TCPOPT_NOP;
1342 }
1343 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1344 continue;
1345 optlen += TCPOLEN_TIMESTAMP;
1346 *optp++ = TCPOPT_TIMESTAMP;
1347 *optp++ = TCPOLEN_TIMESTAMP;
1348 to->to_tsval = htonl(to->to_tsval);
1349 to->to_tsecr = htonl(to->to_tsecr);
1350 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1351 optp += sizeof(to->to_tsval);
1352 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1353 optp += sizeof(to->to_tsecr);
1354 break;
1355 case TOF_SIGNATURE:
1356 {
1357 int siglen = TCPOLEN_SIGNATURE - 2;
1358
1359 while (!optlen || optlen % 4 != 2) {
1360 optlen += TCPOLEN_NOP;
1361 *optp++ = TCPOPT_NOP;
1362 }
1363 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1364 continue;
1365 optlen += TCPOLEN_SIGNATURE;
1366 *optp++ = TCPOPT_SIGNATURE;
1367 *optp++ = TCPOLEN_SIGNATURE;
1368 to->to_signature = optp;
1369 while (siglen--)
1370 *optp++ = 0;
1371 break;
1372 }
1373 case TOF_SACK:
1374 {
1375 int sackblks = 0;
1376 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1377 tcp_seq sack_seq;
1378
1379 while (!optlen || optlen % 4 != 2) {
1380 optlen += TCPOLEN_NOP;
1381 *optp++ = TCPOPT_NOP;
1382 }
1383 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1384 continue;
1385 optlen += TCPOLEN_SACKHDR;
1386 *optp++ = TCPOPT_SACK;
1387 sackblks = min(to->to_nsacks,
1388 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1389 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1390 while (sackblks--) {
1391 sack_seq = htonl(sack->start);
1392 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1393 optp += sizeof(sack_seq);
1394 sack_seq = htonl(sack->end);
1395 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1396 optp += sizeof(sack_seq);
1397 optlen += TCPOLEN_SACK;
1398 sack++;
1399 }
1400 tcpstat.tcps_sack_send_blocks++;
1401 break;
1402 }
1403 default:
1404 panic("%s: unknown TCP option type", __func__);
1405 break;
1406 }
1407 }
1408
1409 /* Terminate and pad TCP options to a 4 byte boundary. */
1410 if (optlen % 4) {
1411 optlen += TCPOLEN_EOL;
1412 *optp++ = TCPOPT_EOL;
1413 }
1414 /*
1415 * According to RFC 793 (STD0007):
1416 * "The content of the header beyond the End-of-Option option
1417 * must be header padding (i.e., zero)."
1418 * and later: "The padding is composed of zeros."
1419 */
1420 while (optlen % 4) {
1421 optlen += TCPOLEN_PAD;
1422 *optp++ = TCPOPT_PAD;
1423 }
1424
1425 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1426 return (optlen);
1427 }
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