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/9.0/sys/netinet/tcp_output.c 225169 2011-08-25 09:20:13Z bz $");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_ipsec.h"
38 #include "opt_tcpdebug.h"
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/domain.h>
43 #include <sys/hhook.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/if.h>
54 #include <net/route.h>
55 #include <net/vnet.h>
56
57 #include <netinet/cc.h>
58 #include <netinet/in.h>
59 #include <netinet/in_systm.h>
60 #include <netinet/ip.h>
61 #include <netinet/in_pcb.h>
62 #include <netinet/ip_var.h>
63 #include <netinet/ip_options.h>
64 #ifdef INET6
65 #include <netinet6/in6_pcb.h>
66 #include <netinet/ip6.h>
67 #include <netinet6/ip6_var.h>
68 #endif
69 #define TCPOUTFLAGS
70 #include <netinet/tcp_fsm.h>
71 #include <netinet/tcp_seq.h>
72 #include <netinet/tcp_timer.h>
73 #include <netinet/tcp_var.h>
74 #include <netinet/tcpip.h>
75 #ifdef TCPDEBUG
76 #include <netinet/tcp_debug.h>
77 #endif
78
79 #ifdef IPSEC
80 #include <netipsec/ipsec.h>
81 #endif /*IPSEC*/
82
83 #include <machine/in_cksum.h>
84
85 #include <security/mac/mac_framework.h>
86
87 VNET_DEFINE(int, path_mtu_discovery) = 1;
88 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
89 &VNET_NAME(path_mtu_discovery), 1,
90 "Enable Path MTU Discovery");
91
92 VNET_DEFINE(int, ss_fltsz) = 1;
93 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW,
94 &VNET_NAME(ss_fltsz), 1,
95 "Slow start flight size");
96
97 VNET_DEFINE(int, ss_fltsz_local) = 4;
98 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize,
99 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1,
100 "Slow start flight size for local networks");
101
102 VNET_DEFINE(int, tcp_do_tso) = 1;
103 #define V_tcp_do_tso VNET(tcp_do_tso)
104 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
105 &VNET_NAME(tcp_do_tso), 0,
106 "Enable TCP Segmentation Offload");
107
108 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
109 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
110 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
111 &VNET_NAME(tcp_do_autosndbuf), 0,
112 "Enable automatic send buffer sizing");
113
114 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
115 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
116 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
117 &VNET_NAME(tcp_autosndbuf_inc), 0,
118 "Incrementor step size of automatic send buffer");
119
120 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
121 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
122 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
123 &VNET_NAME(tcp_autosndbuf_max), 0,
124 "Max size of automatic send buffer");
125
126 static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
127 struct tcphdr *th, struct tcpopt *to,
128 long len, int tso);
129 static void inline cc_after_idle(struct tcpcb *tp);
130
131 /*
132 * Wrapper for the TCP established ouput helper hook.
133 */
134 static void inline
135 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
136 struct tcpopt *to, long len, int tso)
137 {
138 struct tcp_hhook_data hhook_data;
139
140 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
141 hhook_data.tp = tp;
142 hhook_data.th = th;
143 hhook_data.to = to;
144 hhook_data.len = len;
145 hhook_data.tso = tso;
146
147 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
148 tp->osd);
149 }
150 }
151
152 /*
153 * CC wrapper hook functions
154 */
155 static void inline
156 cc_after_idle(struct tcpcb *tp)
157 {
158 INP_WLOCK_ASSERT(tp->t_inpcb);
159
160 if (CC_ALGO(tp)->after_idle != NULL)
161 CC_ALGO(tp)->after_idle(tp->ccv);
162 }
163
164 /*
165 * Tcp output routine: figure out what should be sent and send it.
166 */
167 int
168 tcp_output(struct tcpcb *tp)
169 {
170 struct socket *so = tp->t_inpcb->inp_socket;
171 long len, recwin, sendwin;
172 int off, flags, error = 0; /* Keep compiler happy */
173 struct mbuf *m;
174 struct ip *ip = NULL;
175 struct ipovly *ipov = NULL;
176 struct tcphdr *th;
177 u_char opt[TCP_MAXOLEN];
178 unsigned ipoptlen, optlen, hdrlen;
179 #ifdef IPSEC
180 unsigned ipsec_optlen = 0;
181 #endif
182 int idle, sendalot;
183 int sack_rxmit, sack_bytes_rxmt;
184 struct sackhole *p;
185 int tso;
186 struct tcpopt to;
187 #if 0
188 int maxburst = TCP_MAXBURST;
189 #endif
190 #ifdef INET6
191 struct ip6_hdr *ip6 = NULL;
192 int isipv6;
193
194 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
195 #endif
196
197 INP_WLOCK_ASSERT(tp->t_inpcb);
198
199 /*
200 * Determine length of data that should be transmitted,
201 * and flags that will be used.
202 * If there is some data or critical controls (SYN, RST)
203 * to send, then transmit; otherwise, investigate further.
204 */
205 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
206 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
207 cc_after_idle(tp);
208 tp->t_flags &= ~TF_LASTIDLE;
209 if (idle) {
210 if (tp->t_flags & TF_MORETOCOME) {
211 tp->t_flags |= TF_LASTIDLE;
212 idle = 0;
213 }
214 }
215 again:
216 /*
217 * If we've recently taken a timeout, snd_max will be greater than
218 * snd_nxt. There may be SACK information that allows us to avoid
219 * resending already delivered data. Adjust snd_nxt accordingly.
220 */
221 if ((tp->t_flags & TF_SACK_PERMIT) &&
222 SEQ_LT(tp->snd_nxt, tp->snd_max))
223 tcp_sack_adjust(tp);
224 sendalot = 0;
225 tso = 0;
226 off = tp->snd_nxt - tp->snd_una;
227 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
228
229 flags = tcp_outflags[tp->t_state];
230 /*
231 * Send any SACK-generated retransmissions. If we're explicitly trying
232 * to send out new data (when sendalot is 1), bypass this function.
233 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
234 * we're replacing a (future) new transmission with a retransmission
235 * now, and we previously incremented snd_cwnd in tcp_input().
236 */
237 /*
238 * Still in sack recovery , reset rxmit flag to zero.
239 */
240 sack_rxmit = 0;
241 sack_bytes_rxmt = 0;
242 len = 0;
243 p = NULL;
244 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
245 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
246 long cwin;
247
248 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
249 if (cwin < 0)
250 cwin = 0;
251 /* Do not retransmit SACK segments beyond snd_recover */
252 if (SEQ_GT(p->end, tp->snd_recover)) {
253 /*
254 * (At least) part of sack hole extends beyond
255 * snd_recover. Check to see if we can rexmit data
256 * for this hole.
257 */
258 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
259 /*
260 * Can't rexmit any more data for this hole.
261 * That data will be rexmitted in the next
262 * sack recovery episode, when snd_recover
263 * moves past p->rxmit.
264 */
265 p = NULL;
266 goto after_sack_rexmit;
267 } else
268 /* Can rexmit part of the current hole */
269 len = ((long)ulmin(cwin,
270 tp->snd_recover - p->rxmit));
271 } else
272 len = ((long)ulmin(cwin, p->end - p->rxmit));
273 off = p->rxmit - tp->snd_una;
274 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
275 __func__, off));
276 if (len > 0) {
277 sack_rxmit = 1;
278 sendalot = 1;
279 TCPSTAT_INC(tcps_sack_rexmits);
280 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
281 min(len, tp->t_maxseg));
282 }
283 }
284 after_sack_rexmit:
285 /*
286 * Get standard flags, and add SYN or FIN if requested by 'hidden'
287 * state flags.
288 */
289 if (tp->t_flags & TF_NEEDFIN)
290 flags |= TH_FIN;
291 if (tp->t_flags & TF_NEEDSYN)
292 flags |= TH_SYN;
293
294 SOCKBUF_LOCK(&so->so_snd);
295 /*
296 * If in persist timeout with window of 0, send 1 byte.
297 * Otherwise, if window is small but nonzero
298 * and timer expired, we will send what we can
299 * and go to transmit state.
300 */
301 if (tp->t_flags & TF_FORCEDATA) {
302 if (sendwin == 0) {
303 /*
304 * If we still have some data to send, then
305 * clear the FIN bit. Usually this would
306 * happen below when it realizes that we
307 * aren't sending all the data. However,
308 * if we have exactly 1 byte of unsent data,
309 * then it won't clear the FIN bit below,
310 * and if we are in persist state, we wind
311 * up sending the packet without recording
312 * that we sent the FIN bit.
313 *
314 * We can't just blindly clear the FIN bit,
315 * because if we don't have any more data
316 * to send then the probe will be the FIN
317 * itself.
318 */
319 if (off < so->so_snd.sb_cc)
320 flags &= ~TH_FIN;
321 sendwin = 1;
322 } else {
323 tcp_timer_activate(tp, TT_PERSIST, 0);
324 tp->t_rxtshift = 0;
325 }
326 }
327
328 /*
329 * If snd_nxt == snd_max and we have transmitted a FIN, the
330 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
331 * a negative length. This can also occur when TCP opens up
332 * its congestion window while receiving additional duplicate
333 * acks after fast-retransmit because TCP will reset snd_nxt
334 * to snd_max after the fast-retransmit.
335 *
336 * In the normal retransmit-FIN-only case, however, snd_nxt will
337 * be set to snd_una, the offset will be 0, and the length may
338 * wind up 0.
339 *
340 * If sack_rxmit is true we are retransmitting from the scoreboard
341 * in which case len is already set.
342 */
343 if (sack_rxmit == 0) {
344 if (sack_bytes_rxmt == 0)
345 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off);
346 else {
347 long cwin;
348
349 /*
350 * We are inside of a SACK recovery episode and are
351 * sending new data, having retransmitted all the
352 * data possible in the scoreboard.
353 */
354 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
355 - off);
356 /*
357 * Don't remove this (len > 0) check !
358 * We explicitly check for len > 0 here (although it
359 * isn't really necessary), to work around a gcc
360 * optimization issue - to force gcc to compute
361 * len above. Without this check, the computation
362 * of len is bungled by the optimizer.
363 */
364 if (len > 0) {
365 cwin = tp->snd_cwnd -
366 (tp->snd_nxt - tp->sack_newdata) -
367 sack_bytes_rxmt;
368 if (cwin < 0)
369 cwin = 0;
370 len = lmin(len, cwin);
371 }
372 }
373 }
374
375 /*
376 * Lop off SYN bit if it has already been sent. However, if this
377 * is SYN-SENT state and if segment contains data and if we don't
378 * know that foreign host supports TAO, suppress sending segment.
379 */
380 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
381 if (tp->t_state != TCPS_SYN_RECEIVED)
382 flags &= ~TH_SYN;
383 off--, len++;
384 }
385
386 /*
387 * Be careful not to send data and/or FIN on SYN segments.
388 * This measure is needed to prevent interoperability problems
389 * with not fully conformant TCP implementations.
390 */
391 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
392 len = 0;
393 flags &= ~TH_FIN;
394 }
395
396 if (len < 0) {
397 /*
398 * If FIN has been sent but not acked,
399 * but we haven't been called to retransmit,
400 * len will be < 0. Otherwise, window shrank
401 * after we sent into it. If window shrank to 0,
402 * cancel pending retransmit, pull snd_nxt back
403 * to (closed) window, and set the persist timer
404 * if it isn't already going. If the window didn't
405 * close completely, just wait for an ACK.
406 */
407 len = 0;
408 if (sendwin == 0) {
409 tcp_timer_activate(tp, TT_REXMT, 0);
410 tp->t_rxtshift = 0;
411 tp->snd_nxt = tp->snd_una;
412 if (!tcp_timer_active(tp, TT_PERSIST))
413 tcp_setpersist(tp);
414 }
415 }
416
417 /* len will be >= 0 after this point. */
418 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
419
420 /*
421 * Automatic sizing of send socket buffer. Often the send buffer
422 * size is not optimally adjusted to the actual network conditions
423 * at hand (delay bandwidth product). Setting the buffer size too
424 * small limits throughput on links with high bandwidth and high
425 * delay (eg. trans-continental/oceanic links). Setting the
426 * buffer size too big consumes too much real kernel memory,
427 * especially with many connections on busy servers.
428 *
429 * The criteria to step up the send buffer one notch are:
430 * 1. receive window of remote host is larger than send buffer
431 * (with a fudge factor of 5/4th);
432 * 2. send buffer is filled to 7/8th with data (so we actually
433 * have data to make use of it);
434 * 3. send buffer fill has not hit maximal automatic size;
435 * 4. our send window (slow start and cogestion controlled) is
436 * larger than sent but unacknowledged data in send buffer.
437 *
438 * The remote host receive window scaling factor may limit the
439 * growing of the send buffer before it reaches its allowed
440 * maximum.
441 *
442 * It scales directly with slow start or congestion window
443 * and does at most one step per received ACK. This fast
444 * scaling has the drawback of growing the send buffer beyond
445 * what is strictly necessary to make full use of a given
446 * delay*bandwith product. However testing has shown this not
447 * to be much of an problem. At worst we are trading wasting
448 * of available bandwith (the non-use of it) for wasting some
449 * socket buffer memory.
450 *
451 * TODO: Shrink send buffer during idle periods together
452 * with congestion window. Requires another timer. Has to
453 * wait for upcoming tcp timer rewrite.
454 */
455 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
456 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
457 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
458 so->so_snd.sb_cc < V_tcp_autosndbuf_max &&
459 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
460 if (!sbreserve_locked(&so->so_snd,
461 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
462 V_tcp_autosndbuf_max), so, curthread))
463 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
464 }
465 }
466
467 /*
468 * Decide if we can use TCP Segmentation Offloading (if supported by
469 * hardware).
470 *
471 * TSO may only be used if we are in a pure bulk sending state. The
472 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
473 * IP options prevent using TSO. With TSO the TCP header is the same
474 * (except for the sequence number) for all generated packets. This
475 * makes it impossible to transmit any options which vary per generated
476 * segment or packet.
477 */
478 #ifdef IPSEC
479 /*
480 * Pre-calculate here as we save another lookup into the darknesses
481 * of IPsec that way and can actually decide if TSO is ok.
482 */
483 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
484 #endif
485 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
486 ((tp->t_flags & TF_SIGNATURE) == 0) &&
487 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
488 #ifdef IPSEC
489 ipsec_optlen == 0 &&
490 #endif
491 tp->t_inpcb->inp_options == NULL &&
492 tp->t_inpcb->in6p_options == NULL)
493 tso = 1;
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;
561 int oldwin;
562
563 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
564 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
565 oldwin = (tp->rcv_adv - tp->rcv_nxt);
566 adv -= oldwin;
567 } else
568 oldwin = 0;
569
570 /*
571 * If the new window size ends up being the same as the old
572 * size when it is scaled, then don't force a window update.
573 */
574 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
575 goto dontupdate;
576 if (adv >= (long) (2 * tp->t_maxseg))
577 goto send;
578 if (2 * adv >= (long) so->so_rcv.sb_hiwat)
579 goto send;
580 }
581 dontupdate:
582
583 /*
584 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
585 * is also a catch-all for the retransmit timer timeout case.
586 */
587 if (tp->t_flags & TF_ACKNOW)
588 goto send;
589 if ((flags & TH_RST) ||
590 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
591 goto send;
592 if (SEQ_GT(tp->snd_up, tp->snd_una))
593 goto send;
594 /*
595 * If our state indicates that FIN should be sent
596 * and we have not yet done so, then we need to send.
597 */
598 if (flags & TH_FIN &&
599 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
600 goto send;
601 /*
602 * In SACK, it is possible for tcp_output to fail to send a segment
603 * after the retransmission timer has been turned off. Make sure
604 * that the retransmission timer is set.
605 */
606 if ((tp->t_flags & TF_SACK_PERMIT) &&
607 SEQ_GT(tp->snd_max, tp->snd_una) &&
608 !tcp_timer_active(tp, TT_REXMT) &&
609 !tcp_timer_active(tp, TT_PERSIST)) {
610 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
611 goto just_return;
612 }
613 /*
614 * TCP window updates are not reliable, rather a polling protocol
615 * using ``persist'' packets is used to insure receipt of window
616 * updates. The three ``states'' for the output side are:
617 * idle not doing retransmits or persists
618 * persisting to move a small or zero window
619 * (re)transmitting and thereby not persisting
620 *
621 * tcp_timer_active(tp, TT_PERSIST)
622 * is true when we are in persist state.
623 * (tp->t_flags & TF_FORCEDATA)
624 * is set when we are called to send a persist packet.
625 * tcp_timer_active(tp, TT_REXMT)
626 * is set when we are retransmitting
627 * The output side is idle when both timers are zero.
628 *
629 * If send window is too small, there is data to transmit, and no
630 * retransmit or persist is pending, then go to persist state.
631 * If nothing happens soon, send when timer expires:
632 * if window is nonzero, transmit what we can,
633 * otherwise force out a byte.
634 */
635 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) &&
636 !tcp_timer_active(tp, TT_PERSIST)) {
637 tp->t_rxtshift = 0;
638 tcp_setpersist(tp);
639 }
640
641 /*
642 * No reason to send a segment, just return.
643 */
644 just_return:
645 SOCKBUF_UNLOCK(&so->so_snd);
646 return (0);
647
648 send:
649 SOCKBUF_LOCK_ASSERT(&so->so_snd);
650 /*
651 * Before ESTABLISHED, force sending of initial options
652 * unless TCP set not to do any options.
653 * NOTE: we assume that the IP/TCP header plus TCP options
654 * always fit in a single mbuf, leaving room for a maximum
655 * link header, i.e.
656 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
657 */
658 optlen = 0;
659 #ifdef INET6
660 if (isipv6)
661 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
662 else
663 #endif
664 hdrlen = sizeof (struct tcpiphdr);
665
666 /*
667 * Compute options for segment.
668 * We only have to care about SYN and established connection
669 * segments. Options for SYN-ACK segments are handled in TCP
670 * syncache.
671 */
672 if ((tp->t_flags & TF_NOOPT) == 0) {
673 to.to_flags = 0;
674 /* Maximum segment size. */
675 if (flags & TH_SYN) {
676 tp->snd_nxt = tp->iss;
677 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
678 to.to_flags |= TOF_MSS;
679 }
680 /* Window scaling. */
681 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
682 to.to_wscale = tp->request_r_scale;
683 to.to_flags |= TOF_SCALE;
684 }
685 /* Timestamps. */
686 if ((tp->t_flags & TF_RCVD_TSTMP) ||
687 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
688 to.to_tsval = ticks + tp->ts_offset;
689 to.to_tsecr = tp->ts_recent;
690 to.to_flags |= TOF_TS;
691 /* Set receive buffer autosizing timestamp. */
692 if (tp->rfbuf_ts == 0 &&
693 (so->so_rcv.sb_flags & SB_AUTOSIZE))
694 tp->rfbuf_ts = ticks;
695 }
696 /* Selective ACK's. */
697 if (tp->t_flags & TF_SACK_PERMIT) {
698 if (flags & TH_SYN)
699 to.to_flags |= TOF_SACKPERM;
700 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
701 (tp->t_flags & TF_SACK_PERMIT) &&
702 tp->rcv_numsacks > 0) {
703 to.to_flags |= TOF_SACK;
704 to.to_nsacks = tp->rcv_numsacks;
705 to.to_sacks = (u_char *)tp->sackblks;
706 }
707 }
708 #ifdef TCP_SIGNATURE
709 /* TCP-MD5 (RFC2385). */
710 if (tp->t_flags & TF_SIGNATURE)
711 to.to_flags |= TOF_SIGNATURE;
712 #endif /* TCP_SIGNATURE */
713
714 /* Processing the options. */
715 hdrlen += optlen = tcp_addoptions(&to, opt);
716 }
717
718 #ifdef INET6
719 if (isipv6)
720 ipoptlen = ip6_optlen(tp->t_inpcb);
721 else
722 #endif
723 if (tp->t_inpcb->inp_options)
724 ipoptlen = tp->t_inpcb->inp_options->m_len -
725 offsetof(struct ipoption, ipopt_list);
726 else
727 ipoptlen = 0;
728 #ifdef IPSEC
729 ipoptlen += ipsec_optlen;
730 #endif
731
732 /*
733 * Adjust data length if insertion of options will
734 * bump the packet length beyond the t_maxopd length.
735 * Clear the FIN bit because we cut off the tail of
736 * the segment.
737 */
738 if (len + optlen + ipoptlen > tp->t_maxopd) {
739 flags &= ~TH_FIN;
740
741 if (tso) {
742 KASSERT(ipoptlen == 0,
743 ("%s: TSO can't do IP options", __func__));
744
745 /*
746 * Limit a burst to IP_MAXPACKET minus IP,
747 * TCP and options length to keep ip->ip_len
748 * from overflowing.
749 */
750 if (len > IP_MAXPACKET - hdrlen) {
751 len = IP_MAXPACKET - hdrlen;
752 sendalot = 1;
753 }
754
755 /*
756 * Prevent the last segment from being
757 * fractional unless the send sockbuf can
758 * be emptied.
759 */
760 if (sendalot && off + len < so->so_snd.sb_cc) {
761 len -= len % (tp->t_maxopd - optlen);
762 sendalot = 1;
763 }
764
765 /*
766 * Send the FIN in a separate segment
767 * after the bulk sending is done.
768 * We don't trust the TSO implementations
769 * to clear the FIN flag on all but the
770 * last segment.
771 */
772 if (tp->t_flags & TF_NEEDFIN)
773 sendalot = 1;
774
775 } else {
776 len = tp->t_maxopd - optlen - ipoptlen;
777 sendalot = 1;
778 }
779 } else
780 tso = 0;
781
782 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
783 ("%s: len > IP_MAXPACKET", __func__));
784
785 /*#ifdef DIAGNOSTIC*/
786 #ifdef INET6
787 if (max_linkhdr + hdrlen > MCLBYTES)
788 #else
789 if (max_linkhdr + hdrlen > MHLEN)
790 #endif
791 panic("tcphdr too big");
792 /*#endif*/
793
794 /*
795 * This KASSERT is here to catch edge cases at a well defined place.
796 * Before, those had triggered (random) panic conditions further down.
797 */
798 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
799
800 /*
801 * Grab a header mbuf, attaching a copy of data to
802 * be transmitted, and initialize the header from
803 * the template for sends on this connection.
804 */
805 if (len) {
806 struct mbuf *mb;
807 u_int moff;
808
809 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
810 TCPSTAT_INC(tcps_sndprobe);
811 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
812 tp->t_sndrexmitpack++;
813 TCPSTAT_INC(tcps_sndrexmitpack);
814 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
815 } else {
816 TCPSTAT_INC(tcps_sndpack);
817 TCPSTAT_ADD(tcps_sndbyte, len);
818 }
819 MGETHDR(m, M_DONTWAIT, MT_DATA);
820 if (m == NULL) {
821 SOCKBUF_UNLOCK(&so->so_snd);
822 error = ENOBUFS;
823 goto out;
824 }
825 #ifdef INET6
826 if (MHLEN < hdrlen + max_linkhdr) {
827 MCLGET(m, M_DONTWAIT);
828 if ((m->m_flags & M_EXT) == 0) {
829 SOCKBUF_UNLOCK(&so->so_snd);
830 m_freem(m);
831 error = ENOBUFS;
832 goto out;
833 }
834 }
835 #endif
836 m->m_data += max_linkhdr;
837 m->m_len = hdrlen;
838
839 /*
840 * Start the m_copy functions from the closest mbuf
841 * to the offset in the socket buffer chain.
842 */
843 mb = sbsndptr(&so->so_snd, off, len, &moff);
844
845 if (len <= MHLEN - hdrlen - max_linkhdr) {
846 m_copydata(mb, moff, (int)len,
847 mtod(m, caddr_t) + hdrlen);
848 m->m_len += len;
849 } else {
850 m->m_next = m_copy(mb, moff, (int)len);
851 if (m->m_next == NULL) {
852 SOCKBUF_UNLOCK(&so->so_snd);
853 (void) m_free(m);
854 error = ENOBUFS;
855 goto out;
856 }
857 }
858
859 /*
860 * If we're sending everything we've got, set PUSH.
861 * (This will keep happy those implementations which only
862 * give data to the user when a buffer fills or
863 * a PUSH comes in.)
864 */
865 if (off + len == so->so_snd.sb_cc)
866 flags |= TH_PUSH;
867 SOCKBUF_UNLOCK(&so->so_snd);
868 } else {
869 SOCKBUF_UNLOCK(&so->so_snd);
870 if (tp->t_flags & TF_ACKNOW)
871 TCPSTAT_INC(tcps_sndacks);
872 else if (flags & (TH_SYN|TH_FIN|TH_RST))
873 TCPSTAT_INC(tcps_sndctrl);
874 else if (SEQ_GT(tp->snd_up, tp->snd_una))
875 TCPSTAT_INC(tcps_sndurg);
876 else
877 TCPSTAT_INC(tcps_sndwinup);
878
879 MGETHDR(m, M_DONTWAIT, MT_DATA);
880 if (m == NULL) {
881 error = ENOBUFS;
882 goto out;
883 }
884 #ifdef INET6
885 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
886 MHLEN >= hdrlen) {
887 MH_ALIGN(m, hdrlen);
888 } else
889 #endif
890 m->m_data += max_linkhdr;
891 m->m_len = hdrlen;
892 }
893 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
894 m->m_pkthdr.rcvif = (struct ifnet *)0;
895 #ifdef MAC
896 mac_inpcb_create_mbuf(tp->t_inpcb, m);
897 #endif
898 #ifdef INET6
899 if (isipv6) {
900 ip6 = mtod(m, struct ip6_hdr *);
901 th = (struct tcphdr *)(ip6 + 1);
902 tcpip_fillheaders(tp->t_inpcb, ip6, th);
903 } else
904 #endif /* INET6 */
905 {
906 ip = mtod(m, struct ip *);
907 ipov = (struct ipovly *)ip;
908 th = (struct tcphdr *)(ip + 1);
909 tcpip_fillheaders(tp->t_inpcb, ip, th);
910 }
911
912 /*
913 * Fill in fields, remembering maximum advertised
914 * window for use in delaying messages about window sizes.
915 * If resending a FIN, be sure not to use a new sequence number.
916 */
917 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
918 tp->snd_nxt == tp->snd_max)
919 tp->snd_nxt--;
920 /*
921 * If we are starting a connection, send ECN setup
922 * SYN packet. If we are on a retransmit, we may
923 * resend those bits a number of times as per
924 * RFC 3168.
925 */
926 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
927 if (tp->t_rxtshift >= 1) {
928 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
929 flags |= TH_ECE|TH_CWR;
930 } else
931 flags |= TH_ECE|TH_CWR;
932 }
933
934 if (tp->t_state == TCPS_ESTABLISHED &&
935 (tp->t_flags & TF_ECN_PERMIT)) {
936 /*
937 * If the peer has ECN, mark data packets with
938 * ECN capable transmission (ECT).
939 * Ignore pure ack packets, retransmissions and window probes.
940 */
941 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
942 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
943 #ifdef INET6
944 if (isipv6)
945 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
946 else
947 #endif
948 ip->ip_tos |= IPTOS_ECN_ECT0;
949 TCPSTAT_INC(tcps_ecn_ect0);
950 }
951
952 /*
953 * Reply with proper ECN notifications.
954 */
955 if (tp->t_flags & TF_ECN_SND_CWR) {
956 flags |= TH_CWR;
957 tp->t_flags &= ~TF_ECN_SND_CWR;
958 }
959 if (tp->t_flags & TF_ECN_SND_ECE)
960 flags |= TH_ECE;
961 }
962
963 /*
964 * If we are doing retransmissions, then snd_nxt will
965 * not reflect the first unsent octet. For ACK only
966 * packets, we do not want the sequence number of the
967 * retransmitted packet, we want the sequence number
968 * of the next unsent octet. So, if there is no data
969 * (and no SYN or FIN), use snd_max instead of snd_nxt
970 * when filling in ti_seq. But if we are in persist
971 * state, snd_max might reflect one byte beyond the
972 * right edge of the window, so use snd_nxt in that
973 * case, since we know we aren't doing a retransmission.
974 * (retransmit and persist are mutually exclusive...)
975 */
976 if (sack_rxmit == 0) {
977 if (len || (flags & (TH_SYN|TH_FIN)) ||
978 tcp_timer_active(tp, TT_PERSIST))
979 th->th_seq = htonl(tp->snd_nxt);
980 else
981 th->th_seq = htonl(tp->snd_max);
982 } else {
983 th->th_seq = htonl(p->rxmit);
984 p->rxmit += len;
985 tp->sackhint.sack_bytes_rexmit += len;
986 }
987 th->th_ack = htonl(tp->rcv_nxt);
988 if (optlen) {
989 bcopy(opt, th + 1, optlen);
990 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
991 }
992 th->th_flags = flags;
993 /*
994 * Calculate receive window. Don't shrink window,
995 * but avoid silly window syndrome.
996 */
997 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
998 recwin < (long)tp->t_maxseg)
999 recwin = 0;
1000 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1001 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1002 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1003 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1004 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1005
1006 /*
1007 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1008 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1009 * case is handled in syncache.
1010 */
1011 if (flags & TH_SYN)
1012 th->th_win = htons((u_short)
1013 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1014 else
1015 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1016
1017 /*
1018 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1019 * a 0 window. This may cause the remote transmitter to stall. This
1020 * flag tells soreceive() to disable delayed acknowledgements when
1021 * draining the buffer. This can occur if the receiver is attempting
1022 * to read more data than can be buffered prior to transmitting on
1023 * the connection.
1024 */
1025 if (th->th_win == 0) {
1026 tp->t_sndzerowin++;
1027 tp->t_flags |= TF_RXWIN0SENT;
1028 } else
1029 tp->t_flags &= ~TF_RXWIN0SENT;
1030 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1031 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1032 th->th_flags |= TH_URG;
1033 } else
1034 /*
1035 * If no urgent pointer to send, then we pull
1036 * the urgent pointer to the left edge of the send window
1037 * so that it doesn't drift into the send window on sequence
1038 * number wraparound.
1039 */
1040 tp->snd_up = tp->snd_una; /* drag it along */
1041
1042 #ifdef TCP_SIGNATURE
1043 if (tp->t_flags & TF_SIGNATURE) {
1044 int sigoff = to.to_signature - opt;
1045 tcp_signature_compute(m, 0, len, optlen,
1046 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1047 }
1048 #endif
1049
1050 /*
1051 * Put TCP length in extended header, and then
1052 * checksum extended header and data.
1053 */
1054 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1055 #ifdef INET6
1056 if (isipv6)
1057 /*
1058 * ip6_plen is not need to be filled now, and will be filled
1059 * in ip6_output.
1060 */
1061 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
1062 sizeof(struct tcphdr) + optlen + len);
1063 else
1064 #endif /* INET6 */
1065 {
1066 m->m_pkthdr.csum_flags = CSUM_TCP;
1067 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1068 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1069 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1070
1071 /* IP version must be set here for ipv4/ipv6 checking later */
1072 KASSERT(ip->ip_v == IPVERSION,
1073 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1074 }
1075
1076 /*
1077 * Enable TSO and specify the size of the segments.
1078 * The TCP pseudo header checksum is always provided.
1079 * XXX: Fixme: This is currently not the case for IPv6.
1080 */
1081 if (tso) {
1082 KASSERT(len > tp->t_maxopd - optlen,
1083 ("%s: len <= tso_segsz", __func__));
1084 m->m_pkthdr.csum_flags |= CSUM_TSO;
1085 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1086 }
1087
1088 #ifdef IPSEC
1089 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1090 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1091 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1092 #else
1093 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1094 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1095 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1096 #endif
1097
1098 /*
1099 * In transmit state, time the transmission and arrange for
1100 * the retransmit. In persist state, just set snd_max.
1101 */
1102 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1103 !tcp_timer_active(tp, TT_PERSIST)) {
1104 tcp_seq startseq = tp->snd_nxt;
1105
1106 /*
1107 * Advance snd_nxt over sequence space of this segment.
1108 */
1109 if (flags & (TH_SYN|TH_FIN)) {
1110 if (flags & TH_SYN)
1111 tp->snd_nxt++;
1112 if (flags & TH_FIN) {
1113 tp->snd_nxt++;
1114 tp->t_flags |= TF_SENTFIN;
1115 }
1116 }
1117 if (sack_rxmit)
1118 goto timer;
1119 tp->snd_nxt += len;
1120 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1121 tp->snd_max = tp->snd_nxt;
1122 /*
1123 * Time this transmission if not a retransmission and
1124 * not currently timing anything.
1125 */
1126 if (tp->t_rtttime == 0) {
1127 tp->t_rtttime = ticks;
1128 tp->t_rtseq = startseq;
1129 TCPSTAT_INC(tcps_segstimed);
1130 }
1131 }
1132
1133 /*
1134 * Set retransmit timer if not currently set,
1135 * and not doing a pure ack or a keep-alive probe.
1136 * Initial value for retransmit timer is smoothed
1137 * round-trip time + 2 * round-trip time variance.
1138 * Initialize shift counter which is used for backoff
1139 * of retransmit time.
1140 */
1141 timer:
1142 if (!tcp_timer_active(tp, TT_REXMT) &&
1143 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1144 (tp->snd_nxt != tp->snd_una))) {
1145 if (tcp_timer_active(tp, TT_PERSIST)) {
1146 tcp_timer_activate(tp, TT_PERSIST, 0);
1147 tp->t_rxtshift = 0;
1148 }
1149 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1150 }
1151 } else {
1152 /*
1153 * Persist case, update snd_max but since we are in
1154 * persist mode (no window) we do not update snd_nxt.
1155 */
1156 int xlen = len;
1157 if (flags & TH_SYN)
1158 ++xlen;
1159 if (flags & TH_FIN) {
1160 ++xlen;
1161 tp->t_flags |= TF_SENTFIN;
1162 }
1163 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1164 tp->snd_max = tp->snd_nxt + len;
1165 }
1166
1167 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1168 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1169
1170 #ifdef TCPDEBUG
1171 /*
1172 * Trace.
1173 */
1174 if (so->so_options & SO_DEBUG) {
1175 u_short save = 0;
1176 #ifdef INET6
1177 if (!isipv6)
1178 #endif
1179 {
1180 save = ipov->ih_len;
1181 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1182 }
1183 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1184 #ifdef INET6
1185 if (!isipv6)
1186 #endif
1187 ipov->ih_len = save;
1188 }
1189 #endif /* TCPDEBUG */
1190
1191 /*
1192 * Fill in IP length and desired time to live and
1193 * send to IP level. There should be a better way
1194 * to handle ttl and tos; we could keep them in
1195 * the template, but need a way to checksum without them.
1196 */
1197 /*
1198 * m->m_pkthdr.len should have been set before cksum calcuration,
1199 * because in6_cksum() need it.
1200 */
1201 #ifdef INET6
1202 if (isipv6) {
1203 /*
1204 * we separately set hoplimit for every segment, since the
1205 * user might want to change the value via setsockopt.
1206 * Also, desired default hop limit might be changed via
1207 * Neighbor Discovery.
1208 */
1209 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1210
1211 /* TODO: IPv6 IP6TOS_ECT bit on */
1212 error = ip6_output(m,
1213 tp->t_inpcb->in6p_outputopts, NULL,
1214 ((so->so_options & SO_DONTROUTE) ?
1215 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb);
1216 }
1217 #endif /* INET6 */
1218 #if defined(INET) && defined(INET6)
1219 else
1220 #endif
1221 #ifdef INET
1222 {
1223 ip->ip_len = m->m_pkthdr.len;
1224 #ifdef INET6
1225 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1226 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1227 #endif /* INET6 */
1228 /*
1229 * If we do path MTU discovery, then we set DF on every packet.
1230 * This might not be the best thing to do according to RFC3390
1231 * Section 2. However the tcp hostcache migitates the problem
1232 * so it affects only the first tcp connection with a host.
1233 *
1234 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1235 */
1236 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss)
1237 ip->ip_off |= IP_DF;
1238
1239 error = ip_output(m, tp->t_inpcb->inp_options, NULL,
1240 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1241 tp->t_inpcb);
1242 }
1243 #endif /* INET */
1244 if (error) {
1245
1246 /*
1247 * We know that the packet was lost, so back out the
1248 * sequence number advance, if any.
1249 *
1250 * If the error is EPERM the packet got blocked by the
1251 * local firewall. Normally we should terminate the
1252 * connection but the blocking may have been spurious
1253 * due to a firewall reconfiguration cycle. So we treat
1254 * it like a packet loss and let the retransmit timer and
1255 * timeouts do their work over time.
1256 * XXX: It is a POLA question whether calling tcp_drop right
1257 * away would be the really correct behavior instead.
1258 */
1259 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1260 !tcp_timer_active(tp, TT_PERSIST)) &&
1261 ((flags & TH_SYN) == 0) &&
1262 (error != EPERM)) {
1263 if (sack_rxmit) {
1264 p->rxmit -= len;
1265 tp->sackhint.sack_bytes_rexmit -= len;
1266 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1267 ("sackhint bytes rtx >= 0"));
1268 } else
1269 tp->snd_nxt -= len;
1270 }
1271 out:
1272 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1273 switch (error) {
1274 case EPERM:
1275 tp->t_softerror = error;
1276 return (error);
1277 case ENOBUFS:
1278 if (!tcp_timer_active(tp, TT_REXMT) &&
1279 !tcp_timer_active(tp, TT_PERSIST))
1280 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1281 tp->snd_cwnd = tp->t_maxseg;
1282 return (0);
1283 case EMSGSIZE:
1284 /*
1285 * For some reason the interface we used initially
1286 * to send segments changed to another or lowered
1287 * its MTU.
1288 *
1289 * tcp_mtudisc() will find out the new MTU and as
1290 * its last action, initiate retransmission, so it
1291 * is important to not do so here.
1292 *
1293 * If TSO was active we either got an interface
1294 * without TSO capabilits or TSO was turned off.
1295 * Disable it for this connection as too and
1296 * immediatly retry with MSS sized segments generated
1297 * by this function.
1298 */
1299 if (tso)
1300 tp->t_flags &= ~TF_TSO;
1301 tcp_mtudisc(tp->t_inpcb, 0);
1302 return (0);
1303 case EHOSTDOWN:
1304 case EHOSTUNREACH:
1305 case ENETDOWN:
1306 case ENETUNREACH:
1307 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1308 tp->t_softerror = error;
1309 return (0);
1310 }
1311 /* FALLTHROUGH */
1312 default:
1313 return (error);
1314 }
1315 }
1316 TCPSTAT_INC(tcps_sndtotal);
1317
1318 /*
1319 * Data sent (as far as we can tell).
1320 * If this advertises a larger window than any other segment,
1321 * then remember the size of the advertised window.
1322 * Any pending ACK has now been sent.
1323 */
1324 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1325 tp->rcv_adv = tp->rcv_nxt + recwin;
1326 tp->last_ack_sent = tp->rcv_nxt;
1327 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1328 if (tcp_timer_active(tp, TT_DELACK))
1329 tcp_timer_activate(tp, TT_DELACK, 0);
1330 #if 0
1331 /*
1332 * This completely breaks TCP if newreno is turned on. What happens
1333 * is that if delayed-acks are turned on on the receiver, this code
1334 * on the transmitter effectively destroys the TCP window, forcing
1335 * it to four packets (1.5Kx4 = 6K window).
1336 */
1337 if (sendalot && --maxburst)
1338 goto again;
1339 #endif
1340 if (sendalot)
1341 goto again;
1342 return (0);
1343 }
1344
1345 void
1346 tcp_setpersist(struct tcpcb *tp)
1347 {
1348 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1349 int tt;
1350
1351 tp->t_flags &= ~TF_PREVVALID;
1352 if (tcp_timer_active(tp, TT_REXMT))
1353 panic("tcp_setpersist: retransmit pending");
1354 /*
1355 * Start/restart persistance timer.
1356 */
1357 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1358 TCPTV_PERSMIN, TCPTV_PERSMAX);
1359 tcp_timer_activate(tp, TT_PERSIST, tt);
1360 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1361 tp->t_rxtshift++;
1362 }
1363
1364 /*
1365 * Insert TCP options according to the supplied parameters to the place
1366 * optp in a consistent way. Can handle unaligned destinations.
1367 *
1368 * The order of the option processing is crucial for optimal packing and
1369 * alignment for the scarce option space.
1370 *
1371 * The optimal order for a SYN/SYN-ACK segment is:
1372 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1373 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1374 *
1375 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1376 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1377 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1378 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1379 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1380 */
1381 int
1382 tcp_addoptions(struct tcpopt *to, u_char *optp)
1383 {
1384 u_int mask, optlen = 0;
1385
1386 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1387 if ((to->to_flags & mask) != mask)
1388 continue;
1389 if (optlen == TCP_MAXOLEN)
1390 break;
1391 switch (to->to_flags & mask) {
1392 case TOF_MSS:
1393 while (optlen % 4) {
1394 optlen += TCPOLEN_NOP;
1395 *optp++ = TCPOPT_NOP;
1396 }
1397 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1398 continue;
1399 optlen += TCPOLEN_MAXSEG;
1400 *optp++ = TCPOPT_MAXSEG;
1401 *optp++ = TCPOLEN_MAXSEG;
1402 to->to_mss = htons(to->to_mss);
1403 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1404 optp += sizeof(to->to_mss);
1405 break;
1406 case TOF_SCALE:
1407 while (!optlen || optlen % 2 != 1) {
1408 optlen += TCPOLEN_NOP;
1409 *optp++ = TCPOPT_NOP;
1410 }
1411 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1412 continue;
1413 optlen += TCPOLEN_WINDOW;
1414 *optp++ = TCPOPT_WINDOW;
1415 *optp++ = TCPOLEN_WINDOW;
1416 *optp++ = to->to_wscale;
1417 break;
1418 case TOF_SACKPERM:
1419 while (optlen % 2) {
1420 optlen += TCPOLEN_NOP;
1421 *optp++ = TCPOPT_NOP;
1422 }
1423 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1424 continue;
1425 optlen += TCPOLEN_SACK_PERMITTED;
1426 *optp++ = TCPOPT_SACK_PERMITTED;
1427 *optp++ = TCPOLEN_SACK_PERMITTED;
1428 break;
1429 case TOF_TS:
1430 while (!optlen || optlen % 4 != 2) {
1431 optlen += TCPOLEN_NOP;
1432 *optp++ = TCPOPT_NOP;
1433 }
1434 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1435 continue;
1436 optlen += TCPOLEN_TIMESTAMP;
1437 *optp++ = TCPOPT_TIMESTAMP;
1438 *optp++ = TCPOLEN_TIMESTAMP;
1439 to->to_tsval = htonl(to->to_tsval);
1440 to->to_tsecr = htonl(to->to_tsecr);
1441 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1442 optp += sizeof(to->to_tsval);
1443 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1444 optp += sizeof(to->to_tsecr);
1445 break;
1446 case TOF_SIGNATURE:
1447 {
1448 int siglen = TCPOLEN_SIGNATURE - 2;
1449
1450 while (!optlen || optlen % 4 != 2) {
1451 optlen += TCPOLEN_NOP;
1452 *optp++ = TCPOPT_NOP;
1453 }
1454 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1455 continue;
1456 optlen += TCPOLEN_SIGNATURE;
1457 *optp++ = TCPOPT_SIGNATURE;
1458 *optp++ = TCPOLEN_SIGNATURE;
1459 to->to_signature = optp;
1460 while (siglen--)
1461 *optp++ = 0;
1462 break;
1463 }
1464 case TOF_SACK:
1465 {
1466 int sackblks = 0;
1467 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1468 tcp_seq sack_seq;
1469
1470 while (!optlen || optlen % 4 != 2) {
1471 optlen += TCPOLEN_NOP;
1472 *optp++ = TCPOPT_NOP;
1473 }
1474 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1475 continue;
1476 optlen += TCPOLEN_SACKHDR;
1477 *optp++ = TCPOPT_SACK;
1478 sackblks = min(to->to_nsacks,
1479 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1480 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1481 while (sackblks--) {
1482 sack_seq = htonl(sack->start);
1483 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1484 optp += sizeof(sack_seq);
1485 sack_seq = htonl(sack->end);
1486 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1487 optp += sizeof(sack_seq);
1488 optlen += TCPOLEN_SACK;
1489 sack++;
1490 }
1491 TCPSTAT_INC(tcps_sack_send_blocks);
1492 break;
1493 }
1494 default:
1495 panic("%s: unknown TCP option type", __func__);
1496 break;
1497 }
1498 }
1499
1500 /* Terminate and pad TCP options to a 4 byte boundary. */
1501 if (optlen % 4) {
1502 optlen += TCPOLEN_EOL;
1503 *optp++ = TCPOPT_EOL;
1504 }
1505 /*
1506 * According to RFC 793 (STD0007):
1507 * "The content of the header beyond the End-of-Option option
1508 * must be header padding (i.e., zero)."
1509 * and later: "The padding is composed of zeros."
1510 */
1511 while (optlen % 4) {
1512 optlen += TCPOLEN_PAD;
1513 *optp++ = TCPOPT_PAD;
1514 }
1515
1516 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1517 return (optlen);
1518 }
Cache object: 01c04d9877b2f564f7d8a4932ad2f6df
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