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("$FreeBSD$");
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 #ifdef TCP_OFFLOAD
79 #include <netinet/tcp_offload.h>
80 #endif
81
82 #ifdef IPSEC
83 #include <netipsec/ipsec.h>
84 #endif /*IPSEC*/
85
86 #include <machine/in_cksum.h>
87
88 #include <security/mac/mac_framework.h>
89
90 VNET_DEFINE(int, path_mtu_discovery) = 1;
91 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
92 &VNET_NAME(path_mtu_discovery), 1,
93 "Enable Path MTU Discovery");
94
95 VNET_DEFINE(int, tcp_do_tso) = 1;
96 #define V_tcp_do_tso VNET(tcp_do_tso)
97 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
98 &VNET_NAME(tcp_do_tso), 0,
99 "Enable TCP Segmentation Offload");
100
101 VNET_DEFINE(int, tcp_sendspace) = 1024*32;
102 #define V_tcp_sendspace VNET(tcp_sendspace)
103 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW,
104 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
105
106 VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
107 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
109 &VNET_NAME(tcp_do_autosndbuf), 0,
110 "Enable automatic send buffer sizing");
111
112 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
113 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
114 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
115 &VNET_NAME(tcp_autosndbuf_inc), 0,
116 "Incrementor step size of automatic send buffer");
117
118 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
119 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
120 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
121 &VNET_NAME(tcp_autosndbuf_max), 0,
122 "Max size of automatic send buffer");
123
124 static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
125 struct tcphdr *th, struct tcpopt *to,
126 long len, int tso);
127 static void inline cc_after_idle(struct tcpcb *tp);
128
129 /*
130 * Wrapper for the TCP established ouput helper hook.
131 */
132 static void inline
133 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
134 struct tcpopt *to, long len, int tso)
135 {
136 struct tcp_hhook_data hhook_data;
137
138 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
139 hhook_data.tp = tp;
140 hhook_data.th = th;
141 hhook_data.to = to;
142 hhook_data.len = len;
143 hhook_data.tso = tso;
144
145 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
146 tp->osd);
147 }
148 }
149
150 /*
151 * CC wrapper hook functions
152 */
153 static void inline
154 cc_after_idle(struct tcpcb *tp)
155 {
156 INP_WLOCK_ASSERT(tp->t_inpcb);
157
158 if (CC_ALGO(tp)->after_idle != NULL)
159 CC_ALGO(tp)->after_idle(tp->ccv);
160 }
161
162 /*
163 * Tcp output routine: figure out what should be sent and send it.
164 */
165 int
166 tcp_output(struct tcpcb *tp)
167 {
168 struct socket *so = tp->t_inpcb->inp_socket;
169 long len, recwin, sendwin;
170 int off, flags, error = 0; /* Keep compiler happy */
171 struct mbuf *m;
172 struct ip *ip = NULL;
173 struct ipovly *ipov = NULL;
174 struct tcphdr *th;
175 u_char opt[TCP_MAXOLEN];
176 unsigned ipoptlen, optlen, hdrlen;
177 #ifdef IPSEC
178 unsigned ipsec_optlen = 0;
179 #endif
180 int idle, sendalot;
181 int sack_rxmit, sack_bytes_rxmt;
182 struct sackhole *p;
183 int tso, mtu;
184 struct tcpopt to;
185 #if 0
186 int maxburst = TCP_MAXBURST;
187 #endif
188 #ifdef INET6
189 struct ip6_hdr *ip6 = NULL;
190 int isipv6;
191
192 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
193 #endif
194
195 INP_WLOCK_ASSERT(tp->t_inpcb);
196
197 #ifdef TCP_OFFLOAD
198 if (tp->t_flags & TF_TOE)
199 return (tcp_offload_output(tp));
200 #endif
201
202 /*
203 * Determine length of data that should be transmitted,
204 * and flags that will be used.
205 * If there is some data or critical controls (SYN, RST)
206 * to send, then transmit; otherwise, investigate further.
207 */
208 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
209 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
210 cc_after_idle(tp);
211 tp->t_flags &= ~TF_LASTIDLE;
212 if (idle) {
213 if (tp->t_flags & TF_MORETOCOME) {
214 tp->t_flags |= TF_LASTIDLE;
215 idle = 0;
216 }
217 }
218 again:
219 /*
220 * If we've recently taken a timeout, snd_max will be greater than
221 * snd_nxt. There may be SACK information that allows us to avoid
222 * resending already delivered data. Adjust snd_nxt accordingly.
223 */
224 if ((tp->t_flags & TF_SACK_PERMIT) &&
225 SEQ_LT(tp->snd_nxt, tp->snd_max))
226 tcp_sack_adjust(tp);
227 sendalot = 0;
228 tso = 0;
229 mtu = 0;
230 off = tp->snd_nxt - tp->snd_una;
231 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
232
233 flags = tcp_outflags[tp->t_state];
234 /*
235 * Send any SACK-generated retransmissions. If we're explicitly trying
236 * to send out new data (when sendalot is 1), bypass this function.
237 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
238 * we're replacing a (future) new transmission with a retransmission
239 * now, and we previously incremented snd_cwnd in tcp_input().
240 */
241 /*
242 * Still in sack recovery , reset rxmit flag to zero.
243 */
244 sack_rxmit = 0;
245 sack_bytes_rxmt = 0;
246 len = 0;
247 p = NULL;
248 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
249 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
250 long cwin;
251
252 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
253 if (cwin < 0)
254 cwin = 0;
255 /* Do not retransmit SACK segments beyond snd_recover */
256 if (SEQ_GT(p->end, tp->snd_recover)) {
257 /*
258 * (At least) part of sack hole extends beyond
259 * snd_recover. Check to see if we can rexmit data
260 * for this hole.
261 */
262 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
263 /*
264 * Can't rexmit any more data for this hole.
265 * That data will be rexmitted in the next
266 * sack recovery episode, when snd_recover
267 * moves past p->rxmit.
268 */
269 p = NULL;
270 goto after_sack_rexmit;
271 } else
272 /* Can rexmit part of the current hole */
273 len = ((long)ulmin(cwin,
274 tp->snd_recover - p->rxmit));
275 } else
276 len = ((long)ulmin(cwin, p->end - p->rxmit));
277 off = p->rxmit - tp->snd_una;
278 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
279 __func__, off));
280 if (len > 0) {
281 sack_rxmit = 1;
282 sendalot = 1;
283 TCPSTAT_INC(tcps_sack_rexmits);
284 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
285 min(len, tp->t_maxseg));
286 }
287 }
288 after_sack_rexmit:
289 /*
290 * Get standard flags, and add SYN or FIN if requested by 'hidden'
291 * state flags.
292 */
293 if (tp->t_flags & TF_NEEDFIN)
294 flags |= TH_FIN;
295 if (tp->t_flags & TF_NEEDSYN)
296 flags |= TH_SYN;
297
298 SOCKBUF_LOCK(&so->so_snd);
299 /*
300 * If in persist timeout with window of 0, send 1 byte.
301 * Otherwise, if window is small but nonzero
302 * and timer expired, we will send what we can
303 * and go to transmit state.
304 */
305 if (tp->t_flags & TF_FORCEDATA) {
306 if (sendwin == 0) {
307 /*
308 * If we still have some data to send, then
309 * clear the FIN bit. Usually this would
310 * happen below when it realizes that we
311 * aren't sending all the data. However,
312 * if we have exactly 1 byte of unsent data,
313 * then it won't clear the FIN bit below,
314 * and if we are in persist state, we wind
315 * up sending the packet without recording
316 * that we sent the FIN bit.
317 *
318 * We can't just blindly clear the FIN bit,
319 * because if we don't have any more data
320 * to send then the probe will be the FIN
321 * itself.
322 */
323 if (off < so->so_snd.sb_cc)
324 flags &= ~TH_FIN;
325 sendwin = 1;
326 } else {
327 tcp_timer_activate(tp, TT_PERSIST, 0);
328 tp->t_rxtshift = 0;
329 }
330 }
331
332 /*
333 * If snd_nxt == snd_max and we have transmitted a FIN, the
334 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
335 * a negative length. This can also occur when TCP opens up
336 * its congestion window while receiving additional duplicate
337 * acks after fast-retransmit because TCP will reset snd_nxt
338 * to snd_max after the fast-retransmit.
339 *
340 * In the normal retransmit-FIN-only case, however, snd_nxt will
341 * be set to snd_una, the offset will be 0, and the length may
342 * wind up 0.
343 *
344 * If sack_rxmit is true we are retransmitting from the scoreboard
345 * in which case len is already set.
346 */
347 if (sack_rxmit == 0) {
348 if (sack_bytes_rxmt == 0)
349 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off);
350 else {
351 long cwin;
352
353 /*
354 * We are inside of a SACK recovery episode and are
355 * sending new data, having retransmitted all the
356 * data possible in the scoreboard.
357 */
358 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
359 - off);
360 /*
361 * Don't remove this (len > 0) check !
362 * We explicitly check for len > 0 here (although it
363 * isn't really necessary), to work around a gcc
364 * optimization issue - to force gcc to compute
365 * len above. Without this check, the computation
366 * of len is bungled by the optimizer.
367 */
368 if (len > 0) {
369 cwin = tp->snd_cwnd -
370 (tp->snd_nxt - tp->sack_newdata) -
371 sack_bytes_rxmt;
372 if (cwin < 0)
373 cwin = 0;
374 len = lmin(len, cwin);
375 }
376 }
377 }
378
379 /*
380 * Lop off SYN bit if it has already been sent. However, if this
381 * is SYN-SENT state and if segment contains data and if we don't
382 * know that foreign host supports TAO, suppress sending segment.
383 */
384 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
385 if (tp->t_state != TCPS_SYN_RECEIVED)
386 flags &= ~TH_SYN;
387 off--, len++;
388 }
389
390 /*
391 * Be careful not to send data and/or FIN on SYN segments.
392 * This measure is needed to prevent interoperability problems
393 * with not fully conformant TCP implementations.
394 */
395 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
396 len = 0;
397 flags &= ~TH_FIN;
398 }
399
400 if (len <= 0) {
401 /*
402 * If FIN has been sent but not acked,
403 * but we haven't been called to retransmit,
404 * len will be < 0. Otherwise, window shrank
405 * after we sent into it. If window shrank to 0,
406 * cancel pending retransmit, pull snd_nxt back
407 * to (closed) window, and set the persist timer
408 * if it isn't already going. If the window didn't
409 * close completely, just wait for an ACK.
410 *
411 * We also do a general check here to ensure that
412 * we will set the persist timer when we have data
413 * to send, but a 0-byte window. This makes sure
414 * the persist timer is set even if the packet
415 * hits one of the "goto send" lines below.
416 */
417 len = 0;
418 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
419 (off < (int) so->so_snd.sb_cc)) {
420 tcp_timer_activate(tp, TT_REXMT, 0);
421 tp->t_rxtshift = 0;
422 tp->snd_nxt = tp->snd_una;
423 if (!tcp_timer_active(tp, TT_PERSIST))
424 tcp_setpersist(tp);
425 }
426 }
427
428 /* len will be >= 0 after this point. */
429 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
430
431 /*
432 * Automatic sizing of send socket buffer. Often the send buffer
433 * size is not optimally adjusted to the actual network conditions
434 * at hand (delay bandwidth product). Setting the buffer size too
435 * small limits throughput on links with high bandwidth and high
436 * delay (eg. trans-continental/oceanic links). Setting the
437 * buffer size too big consumes too much real kernel memory,
438 * especially with many connections on busy servers.
439 *
440 * The criteria to step up the send buffer one notch are:
441 * 1. receive window of remote host is larger than send buffer
442 * (with a fudge factor of 5/4th);
443 * 2. send buffer is filled to 7/8th with data (so we actually
444 * have data to make use of it);
445 * 3. send buffer fill has not hit maximal automatic size;
446 * 4. our send window (slow start and cogestion controlled) is
447 * larger than sent but unacknowledged data in send buffer.
448 *
449 * The remote host receive window scaling factor may limit the
450 * growing of the send buffer before it reaches its allowed
451 * maximum.
452 *
453 * It scales directly with slow start or congestion window
454 * and does at most one step per received ACK. This fast
455 * scaling has the drawback of growing the send buffer beyond
456 * what is strictly necessary to make full use of a given
457 * delay*bandwith product. However testing has shown this not
458 * to be much of an problem. At worst we are trading wasting
459 * of available bandwith (the non-use of it) for wasting some
460 * socket buffer memory.
461 *
462 * TODO: Shrink send buffer during idle periods together
463 * with congestion window. Requires another timer. Has to
464 * wait for upcoming tcp timer rewrite.
465 */
466 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
467 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
468 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) &&
469 so->so_snd.sb_cc < V_tcp_autosndbuf_max &&
470 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) {
471 if (!sbreserve_locked(&so->so_snd,
472 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
473 V_tcp_autosndbuf_max), so, curthread))
474 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
475 }
476 }
477
478 /*
479 * Decide if we can use TCP Segmentation Offloading (if supported by
480 * hardware).
481 *
482 * TSO may only be used if we are in a pure bulk sending state. The
483 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
484 * IP options prevent using TSO. With TSO the TCP header is the same
485 * (except for the sequence number) for all generated packets. This
486 * makes it impossible to transmit any options which vary per generated
487 * segment or packet.
488 */
489 #ifdef IPSEC
490 /*
491 * Pre-calculate here as we save another lookup into the darknesses
492 * of IPsec that way and can actually decide if TSO is ok.
493 */
494 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
495 #endif
496 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
497 ((tp->t_flags & TF_SIGNATURE) == 0) &&
498 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
499 #ifdef IPSEC
500 ipsec_optlen == 0 &&
501 #endif
502 tp->t_inpcb->inp_options == NULL &&
503 tp->t_inpcb->in6p_options == NULL)
504 tso = 1;
505
506 if (sack_rxmit) {
507 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
508 flags &= ~TH_FIN;
509 } else {
510 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
511 flags &= ~TH_FIN;
512 }
513
514 recwin = sbspace(&so->so_rcv);
515
516 /*
517 * Sender silly window avoidance. We transmit under the following
518 * conditions when len is non-zero:
519 *
520 * - We have a full segment (or more with TSO)
521 * - This is the last buffer in a write()/send() and we are
522 * either idle or running NODELAY
523 * - we've timed out (e.g. persist timer)
524 * - we have more then 1/2 the maximum send window's worth of
525 * data (receiver may be limited the window size)
526 * - we need to retransmit
527 */
528 if (len) {
529 if (len >= tp->t_maxseg)
530 goto send;
531 /*
532 * NOTE! on localhost connections an 'ack' from the remote
533 * end may occur synchronously with the output and cause
534 * us to flush a buffer queued with moretocome. XXX
535 *
536 * note: the len + off check is almost certainly unnecessary.
537 */
538 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
539 (idle || (tp->t_flags & TF_NODELAY)) &&
540 len + off >= so->so_snd.sb_cc &&
541 (tp->t_flags & TF_NOPUSH) == 0) {
542 goto send;
543 }
544 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
545 goto send;
546 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
547 goto send;
548 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
549 goto send;
550 if (sack_rxmit)
551 goto send;
552 }
553
554 /*
555 * Sending of standalone window updates.
556 *
557 * Window updates are important when we close our window due to a
558 * full socket buffer and are opening it again after the application
559 * reads data from it. Once the window has opened again and the
560 * remote end starts to send again the ACK clock takes over and
561 * provides the most current window information.
562 *
563 * We must avoid the silly window syndrome whereas every read
564 * from the receive buffer, no matter how small, causes a window
565 * update to be sent. We also should avoid sending a flurry of
566 * window updates when the socket buffer had queued a lot of data
567 * and the application is doing small reads.
568 *
569 * Prevent a flurry of pointless window updates by only sending
570 * an update when we can increase the advertized window by more
571 * than 1/4th of the socket buffer capacity. When the buffer is
572 * getting full or is very small be more aggressive and send an
573 * update whenever we can increase by two mss sized segments.
574 * In all other situations the ACK's to new incoming data will
575 * carry further window increases.
576 *
577 * Don't send an independent window update if a delayed
578 * ACK is pending (it will get piggy-backed on it) or the
579 * remote side already has done a half-close and won't send
580 * more data. Skip this if the connection is in T/TCP
581 * half-open state.
582 */
583 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
584 !(tp->t_flags & TF_DELACK) &&
585 !TCPS_HAVERCVDFIN(tp->t_state)) {
586 /*
587 * "adv" is the amount we could increase the window,
588 * taking into account that we are limited by
589 * TCP_MAXWIN << tp->rcv_scale.
590 */
591 long adv;
592 int oldwin;
593
594 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
595 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
596 oldwin = (tp->rcv_adv - tp->rcv_nxt);
597 adv -= oldwin;
598 } else
599 oldwin = 0;
600
601 /*
602 * If the new window size ends up being the same as the old
603 * size when it is scaled, then don't force a window update.
604 */
605 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
606 goto dontupdate;
607
608 if (adv >= (long)(2 * tp->t_maxseg) &&
609 (adv >= (long)(so->so_rcv.sb_hiwat / 4) ||
610 recwin <= (long)(so->so_rcv.sb_hiwat / 8) ||
611 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
612 goto send;
613 }
614 dontupdate:
615
616 /*
617 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
618 * is also a catch-all for the retransmit timer timeout case.
619 */
620 if (tp->t_flags & TF_ACKNOW)
621 goto send;
622 if ((flags & TH_RST) ||
623 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
624 goto send;
625 if (SEQ_GT(tp->snd_up, tp->snd_una))
626 goto send;
627 /*
628 * If our state indicates that FIN should be sent
629 * and we have not yet done so, then we need to send.
630 */
631 if (flags & TH_FIN &&
632 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
633 goto send;
634 /*
635 * In SACK, it is possible for tcp_output to fail to send a segment
636 * after the retransmission timer has been turned off. Make sure
637 * that the retransmission timer is set.
638 */
639 if ((tp->t_flags & TF_SACK_PERMIT) &&
640 SEQ_GT(tp->snd_max, tp->snd_una) &&
641 !tcp_timer_active(tp, TT_REXMT) &&
642 !tcp_timer_active(tp, TT_PERSIST)) {
643 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
644 goto just_return;
645 }
646 /*
647 * TCP window updates are not reliable, rather a polling protocol
648 * using ``persist'' packets is used to insure receipt of window
649 * updates. The three ``states'' for the output side are:
650 * idle not doing retransmits or persists
651 * persisting to move a small or zero window
652 * (re)transmitting and thereby not persisting
653 *
654 * tcp_timer_active(tp, TT_PERSIST)
655 * is true when we are in persist state.
656 * (tp->t_flags & TF_FORCEDATA)
657 * is set when we are called to send a persist packet.
658 * tcp_timer_active(tp, TT_REXMT)
659 * is set when we are retransmitting
660 * The output side is idle when both timers are zero.
661 *
662 * If send window is too small, there is data to transmit, and no
663 * retransmit or persist is pending, then go to persist state.
664 * If nothing happens soon, send when timer expires:
665 * if window is nonzero, transmit what we can,
666 * otherwise force out a byte.
667 */
668 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) &&
669 !tcp_timer_active(tp, TT_PERSIST)) {
670 tp->t_rxtshift = 0;
671 tcp_setpersist(tp);
672 }
673
674 /*
675 * No reason to send a segment, just return.
676 */
677 just_return:
678 SOCKBUF_UNLOCK(&so->so_snd);
679 return (0);
680
681 send:
682 SOCKBUF_LOCK_ASSERT(&so->so_snd);
683 /*
684 * Before ESTABLISHED, force sending of initial options
685 * unless TCP set not to do any options.
686 * NOTE: we assume that the IP/TCP header plus TCP options
687 * always fit in a single mbuf, leaving room for a maximum
688 * link header, i.e.
689 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
690 */
691 optlen = 0;
692 #ifdef INET6
693 if (isipv6)
694 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
695 else
696 #endif
697 hdrlen = sizeof (struct tcpiphdr);
698
699 /*
700 * Compute options for segment.
701 * We only have to care about SYN and established connection
702 * segments. Options for SYN-ACK segments are handled in TCP
703 * syncache.
704 */
705 to.to_flags = 0;
706 if ((tp->t_flags & TF_NOOPT) == 0) {
707 /* Maximum segment size. */
708 if (flags & TH_SYN) {
709 tp->snd_nxt = tp->iss;
710 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
711 to.to_flags |= TOF_MSS;
712 }
713 /* Window scaling. */
714 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
715 to.to_wscale = tp->request_r_scale;
716 to.to_flags |= TOF_SCALE;
717 }
718 /* Timestamps. */
719 if ((tp->t_flags & TF_RCVD_TSTMP) ||
720 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
721 to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
722 to.to_tsecr = tp->ts_recent;
723 to.to_flags |= TOF_TS;
724 /* Set receive buffer autosizing timestamp. */
725 if (tp->rfbuf_ts == 0 &&
726 (so->so_rcv.sb_flags & SB_AUTOSIZE))
727 tp->rfbuf_ts = tcp_ts_getticks();
728 }
729 /* Selective ACK's. */
730 if (tp->t_flags & TF_SACK_PERMIT) {
731 if (flags & TH_SYN)
732 to.to_flags |= TOF_SACKPERM;
733 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
734 (tp->t_flags & TF_SACK_PERMIT) &&
735 tp->rcv_numsacks > 0) {
736 to.to_flags |= TOF_SACK;
737 to.to_nsacks = tp->rcv_numsacks;
738 to.to_sacks = (u_char *)tp->sackblks;
739 }
740 }
741 #ifdef TCP_SIGNATURE
742 /* TCP-MD5 (RFC2385). */
743 if (tp->t_flags & TF_SIGNATURE)
744 to.to_flags |= TOF_SIGNATURE;
745 #endif /* TCP_SIGNATURE */
746
747 /* Processing the options. */
748 hdrlen += optlen = tcp_addoptions(&to, opt);
749 }
750
751 #ifdef INET6
752 if (isipv6)
753 ipoptlen = ip6_optlen(tp->t_inpcb);
754 else
755 #endif
756 if (tp->t_inpcb->inp_options)
757 ipoptlen = tp->t_inpcb->inp_options->m_len -
758 offsetof(struct ipoption, ipopt_list);
759 else
760 ipoptlen = 0;
761 #ifdef IPSEC
762 ipoptlen += ipsec_optlen;
763 #endif
764
765 /*
766 * Adjust data length if insertion of options will
767 * bump the packet length beyond the t_maxopd length.
768 * Clear the FIN bit because we cut off the tail of
769 * the segment.
770 */
771 if (len + optlen + ipoptlen > tp->t_maxopd) {
772 flags &= ~TH_FIN;
773
774 if (tso) {
775 u_int if_hw_tsomax;
776 u_int if_hw_tsomaxsegcount;
777 u_int if_hw_tsomaxsegsize;
778 struct mbuf *mb;
779 u_int moff;
780 int max_len;
781
782 /* extract TSO information */
783 if_hw_tsomax = tp->t_tsomax;
784 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
785 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
786
787 /*
788 * Limit a TSO burst to prevent it from
789 * overflowing or exceeding the maximum length
790 * allowed by the network interface:
791 */
792 KASSERT(ipoptlen == 0,
793 ("%s: TSO can't do IP options", __func__));
794
795 /*
796 * Check if we should limit by maximum payload
797 * length:
798 */
799 if (if_hw_tsomax != 0) {
800 /* compute maximum TSO length */
801 max_len = (if_hw_tsomax - hdrlen -
802 max_linkhdr);
803 if (max_len <= 0) {
804 len = 0;
805 } else if (len > max_len) {
806 sendalot = 1;
807 len = max_len;
808 }
809 }
810
811 /*
812 * Check if we should limit by maximum segment
813 * size and count:
814 */
815 if (if_hw_tsomaxsegcount != 0 &&
816 if_hw_tsomaxsegsize != 0) {
817 /*
818 * Subtract one segment for the LINK
819 * and TCP/IP headers mbuf that will
820 * be prepended to this mbuf chain
821 * after the code in this section
822 * limits the number of mbufs in the
823 * chain to if_hw_tsomaxsegcount.
824 */
825 if_hw_tsomaxsegcount -= 1;
826 max_len = 0;
827 mb = sbsndmbuf(&so->so_snd, off, &moff);
828
829 while (mb != NULL && max_len < len) {
830 u_int mlen;
831 u_int frags;
832
833 /*
834 * Get length of mbuf fragment
835 * and how many hardware frags,
836 * rounded up, it would use:
837 */
838 mlen = (mb->m_len - moff);
839 frags = howmany(mlen,
840 if_hw_tsomaxsegsize);
841
842 /* Handle special case: Zero Length Mbuf */
843 if (frags == 0)
844 frags = 1;
845
846 /*
847 * Check if the fragment limit
848 * will be reached or exceeded:
849 */
850 if (frags >= if_hw_tsomaxsegcount) {
851 max_len += min(mlen,
852 if_hw_tsomaxsegcount *
853 if_hw_tsomaxsegsize);
854 break;
855 }
856 max_len += mlen;
857 if_hw_tsomaxsegcount -= frags;
858 moff = 0;
859 mb = mb->m_next;
860 }
861 if (max_len <= 0) {
862 len = 0;
863 } else if (len > max_len) {
864 sendalot = 1;
865 len = max_len;
866 }
867 }
868
869 /*
870 * Prevent the last segment from being
871 * fractional unless the send sockbuf can be
872 * emptied:
873 */
874 max_len = (tp->t_maxopd - optlen);
875 if ((off + len) < so->so_snd.sb_cc) {
876 moff = len % max_len;
877 if (moff != 0) {
878 len -= moff;
879 sendalot = 1;
880 }
881 }
882
883 /*
884 * In case there are too many small fragments
885 * don't use TSO:
886 */
887 if (len <= max_len) {
888 len = max_len;
889 sendalot = 1;
890 tso = 0;
891 }
892
893 /*
894 * Send the FIN in a separate segment
895 * after the bulk sending is done.
896 * We don't trust the TSO implementations
897 * to clear the FIN flag on all but the
898 * last segment.
899 */
900 if (tp->t_flags & TF_NEEDFIN)
901 sendalot = 1;
902
903 } else {
904 len = tp->t_maxopd - optlen - ipoptlen;
905 sendalot = 1;
906 }
907 } else
908 tso = 0;
909
910 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
911 ("%s: len > IP_MAXPACKET", __func__));
912
913 /*#ifdef DIAGNOSTIC*/
914 #ifdef INET6
915 if (max_linkhdr + hdrlen > MCLBYTES)
916 #else
917 if (max_linkhdr + hdrlen > MHLEN)
918 #endif
919 panic("tcphdr too big");
920 /*#endif*/
921
922 /*
923 * This KASSERT is here to catch edge cases at a well defined place.
924 * Before, those had triggered (random) panic conditions further down.
925 */
926 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
927
928 /*
929 * Grab a header mbuf, attaching a copy of data to
930 * be transmitted, and initialize the header from
931 * the template for sends on this connection.
932 */
933 if (len) {
934 struct mbuf *mb;
935 u_int moff;
936
937 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
938 TCPSTAT_INC(tcps_sndprobe);
939 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
940 tp->t_sndrexmitpack++;
941 TCPSTAT_INC(tcps_sndrexmitpack);
942 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
943 } else {
944 TCPSTAT_INC(tcps_sndpack);
945 TCPSTAT_ADD(tcps_sndbyte, len);
946 }
947 MGETHDR(m, M_DONTWAIT, MT_DATA);
948 if (m == NULL) {
949 SOCKBUF_UNLOCK(&so->so_snd);
950 error = ENOBUFS;
951 goto out;
952 }
953 #ifdef INET6
954 if (MHLEN < hdrlen + max_linkhdr) {
955 MCLGET(m, M_DONTWAIT);
956 if ((m->m_flags & M_EXT) == 0) {
957 SOCKBUF_UNLOCK(&so->so_snd);
958 m_freem(m);
959 error = ENOBUFS;
960 goto out;
961 }
962 }
963 #endif
964 m->m_data += max_linkhdr;
965 m->m_len = hdrlen;
966
967 /*
968 * Start the m_copy functions from the closest mbuf
969 * to the offset in the socket buffer chain.
970 */
971 mb = sbsndptr(&so->so_snd, off, len, &moff);
972
973 if (len <= MHLEN - hdrlen - max_linkhdr) {
974 m_copydata(mb, moff, (int)len,
975 mtod(m, caddr_t) + hdrlen);
976 m->m_len += len;
977 } else {
978 m->m_next = m_copy(mb, moff, (int)len);
979 if (m->m_next == NULL) {
980 SOCKBUF_UNLOCK(&so->so_snd);
981 (void) m_free(m);
982 error = ENOBUFS;
983 goto out;
984 }
985 }
986
987 /*
988 * If we're sending everything we've got, set PUSH.
989 * (This will keep happy those implementations which only
990 * give data to the user when a buffer fills or
991 * a PUSH comes in.)
992 */
993 if (off + len == so->so_snd.sb_cc)
994 flags |= TH_PUSH;
995 SOCKBUF_UNLOCK(&so->so_snd);
996 } else {
997 SOCKBUF_UNLOCK(&so->so_snd);
998 if (tp->t_flags & TF_ACKNOW)
999 TCPSTAT_INC(tcps_sndacks);
1000 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1001 TCPSTAT_INC(tcps_sndctrl);
1002 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1003 TCPSTAT_INC(tcps_sndurg);
1004 else
1005 TCPSTAT_INC(tcps_sndwinup);
1006
1007 MGETHDR(m, M_DONTWAIT, MT_DATA);
1008 if (m == NULL) {
1009 error = ENOBUFS;
1010 goto out;
1011 }
1012 #ifdef INET6
1013 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1014 MHLEN >= hdrlen) {
1015 MH_ALIGN(m, hdrlen);
1016 } else
1017 #endif
1018 m->m_data += max_linkhdr;
1019 m->m_len = hdrlen;
1020 }
1021 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1022 m->m_pkthdr.rcvif = (struct ifnet *)0;
1023 #ifdef MAC
1024 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1025 #endif
1026 #ifdef INET6
1027 if (isipv6) {
1028 ip6 = mtod(m, struct ip6_hdr *);
1029 th = (struct tcphdr *)(ip6 + 1);
1030 tcpip_fillheaders(tp->t_inpcb, ip6, th);
1031 } else
1032 #endif /* INET6 */
1033 {
1034 ip = mtod(m, struct ip *);
1035 ipov = (struct ipovly *)ip;
1036 th = (struct tcphdr *)(ip + 1);
1037 tcpip_fillheaders(tp->t_inpcb, ip, th);
1038 }
1039
1040 /*
1041 * Fill in fields, remembering maximum advertised
1042 * window for use in delaying messages about window sizes.
1043 * If resending a FIN, be sure not to use a new sequence number.
1044 */
1045 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1046 tp->snd_nxt == tp->snd_max)
1047 tp->snd_nxt--;
1048 /*
1049 * If we are starting a connection, send ECN setup
1050 * SYN packet. If we are on a retransmit, we may
1051 * resend those bits a number of times as per
1052 * RFC 3168.
1053 */
1054 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1055 if (tp->t_rxtshift >= 1) {
1056 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
1057 flags |= TH_ECE|TH_CWR;
1058 } else
1059 flags |= TH_ECE|TH_CWR;
1060 }
1061
1062 if (tp->t_state == TCPS_ESTABLISHED &&
1063 (tp->t_flags & TF_ECN_PERMIT)) {
1064 /*
1065 * If the peer has ECN, mark data packets with
1066 * ECN capable transmission (ECT).
1067 * Ignore pure ack packets, retransmissions and window probes.
1068 */
1069 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
1070 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
1071 #ifdef INET6
1072 if (isipv6)
1073 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1074 else
1075 #endif
1076 ip->ip_tos |= IPTOS_ECN_ECT0;
1077 TCPSTAT_INC(tcps_ecn_ect0);
1078 }
1079
1080 /*
1081 * Reply with proper ECN notifications.
1082 */
1083 if (tp->t_flags & TF_ECN_SND_CWR) {
1084 flags |= TH_CWR;
1085 tp->t_flags &= ~TF_ECN_SND_CWR;
1086 }
1087 if (tp->t_flags & TF_ECN_SND_ECE)
1088 flags |= TH_ECE;
1089 }
1090
1091 /*
1092 * If we are doing retransmissions, then snd_nxt will
1093 * not reflect the first unsent octet. For ACK only
1094 * packets, we do not want the sequence number of the
1095 * retransmitted packet, we want the sequence number
1096 * of the next unsent octet. So, if there is no data
1097 * (and no SYN or FIN), use snd_max instead of snd_nxt
1098 * when filling in ti_seq. But if we are in persist
1099 * state, snd_max might reflect one byte beyond the
1100 * right edge of the window, so use snd_nxt in that
1101 * case, since we know we aren't doing a retransmission.
1102 * (retransmit and persist are mutually exclusive...)
1103 */
1104 if (sack_rxmit == 0) {
1105 if (len || (flags & (TH_SYN|TH_FIN)) ||
1106 tcp_timer_active(tp, TT_PERSIST))
1107 th->th_seq = htonl(tp->snd_nxt);
1108 else
1109 th->th_seq = htonl(tp->snd_max);
1110 } else {
1111 th->th_seq = htonl(p->rxmit);
1112 p->rxmit += len;
1113 tp->sackhint.sack_bytes_rexmit += len;
1114 }
1115 th->th_ack = htonl(tp->rcv_nxt);
1116 if (optlen) {
1117 bcopy(opt, th + 1, optlen);
1118 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1119 }
1120 th->th_flags = flags;
1121 /*
1122 * Calculate receive window. Don't shrink window,
1123 * but avoid silly window syndrome.
1124 */
1125 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
1126 recwin < (long)tp->t_maxseg)
1127 recwin = 0;
1128 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1129 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1130 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1131 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1132 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1133
1134 /*
1135 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1136 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1137 * case is handled in syncache.
1138 */
1139 if (flags & TH_SYN)
1140 th->th_win = htons((u_short)
1141 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1142 else
1143 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1144
1145 /*
1146 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1147 * a 0 window. This may cause the remote transmitter to stall. This
1148 * flag tells soreceive() to disable delayed acknowledgements when
1149 * draining the buffer. This can occur if the receiver is attempting
1150 * to read more data than can be buffered prior to transmitting on
1151 * the connection.
1152 */
1153 if (th->th_win == 0) {
1154 tp->t_sndzerowin++;
1155 tp->t_flags |= TF_RXWIN0SENT;
1156 } else
1157 tp->t_flags &= ~TF_RXWIN0SENT;
1158 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1159 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1160 th->th_flags |= TH_URG;
1161 } else
1162 /*
1163 * If no urgent pointer to send, then we pull
1164 * the urgent pointer to the left edge of the send window
1165 * so that it doesn't drift into the send window on sequence
1166 * number wraparound.
1167 */
1168 tp->snd_up = tp->snd_una; /* drag it along */
1169
1170 #ifdef TCP_SIGNATURE
1171 if (to.to_flags & TOF_SIGNATURE) {
1172 int sigoff = to.to_signature - opt;
1173 tcp_signature_compute(m, 0, len, optlen,
1174 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1175 }
1176 #endif
1177
1178 /*
1179 * Put TCP length in extended header, and then
1180 * checksum extended header and data.
1181 */
1182 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1183 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1184 #ifdef INET6
1185 if (isipv6) {
1186 /*
1187 * ip6_plen is not need to be filled now, and will be filled
1188 * in ip6_output.
1189 */
1190 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1191 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1192 optlen + len, IPPROTO_TCP, 0);
1193 }
1194 #endif
1195 #if defined(INET6) && defined(INET)
1196 else
1197 #endif
1198 #ifdef INET
1199 {
1200 m->m_pkthdr.csum_flags = CSUM_TCP;
1201 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1202 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1203
1204 /* IP version must be set here for ipv4/ipv6 checking later */
1205 KASSERT(ip->ip_v == IPVERSION,
1206 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1207 }
1208 #endif
1209
1210 /*
1211 * Enable TSO and specify the size of the segments.
1212 * The TCP pseudo header checksum is always provided.
1213 * XXX: Fixme: This is currently not the case for IPv6.
1214 */
1215 if (tso) {
1216 KASSERT(len > tp->t_maxopd - optlen,
1217 ("%s: len <= tso_segsz", __func__));
1218 m->m_pkthdr.csum_flags |= CSUM_TSO;
1219 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1220 }
1221
1222 #ifdef IPSEC
1223 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1224 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1225 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1226 #else
1227 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1228 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1229 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1230 #endif
1231
1232 /*
1233 * In transmit state, time the transmission and arrange for
1234 * the retransmit. In persist state, just set snd_max.
1235 */
1236 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1237 !tcp_timer_active(tp, TT_PERSIST)) {
1238 tcp_seq startseq = tp->snd_nxt;
1239
1240 /*
1241 * Advance snd_nxt over sequence space of this segment.
1242 */
1243 if (flags & (TH_SYN|TH_FIN)) {
1244 if (flags & TH_SYN)
1245 tp->snd_nxt++;
1246 if (flags & TH_FIN) {
1247 tp->snd_nxt++;
1248 tp->t_flags |= TF_SENTFIN;
1249 }
1250 }
1251 if (sack_rxmit)
1252 goto timer;
1253 tp->snd_nxt += len;
1254 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1255 tp->snd_max = tp->snd_nxt;
1256 /*
1257 * Time this transmission if not a retransmission and
1258 * not currently timing anything.
1259 */
1260 if (tp->t_rtttime == 0) {
1261 tp->t_rtttime = ticks;
1262 tp->t_rtseq = startseq;
1263 TCPSTAT_INC(tcps_segstimed);
1264 }
1265 }
1266
1267 /*
1268 * Set retransmit timer if not currently set,
1269 * and not doing a pure ack or a keep-alive probe.
1270 * Initial value for retransmit timer is smoothed
1271 * round-trip time + 2 * round-trip time variance.
1272 * Initialize shift counter which is used for backoff
1273 * of retransmit time.
1274 */
1275 timer:
1276 if (!tcp_timer_active(tp, TT_REXMT) &&
1277 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1278 (tp->snd_nxt != tp->snd_una))) {
1279 if (tcp_timer_active(tp, TT_PERSIST)) {
1280 tcp_timer_activate(tp, TT_PERSIST, 0);
1281 tp->t_rxtshift = 0;
1282 }
1283 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1284 }
1285 } else {
1286 /*
1287 * Persist case, update snd_max but since we are in
1288 * persist mode (no window) we do not update snd_nxt.
1289 */
1290 int xlen = len;
1291 if (flags & TH_SYN)
1292 ++xlen;
1293 if (flags & TH_FIN) {
1294 ++xlen;
1295 tp->t_flags |= TF_SENTFIN;
1296 }
1297 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1298 tp->snd_max = tp->snd_nxt + len;
1299 }
1300
1301 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1302 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1303
1304 #ifdef TCPDEBUG
1305 /*
1306 * Trace.
1307 */
1308 if (so->so_options & SO_DEBUG) {
1309 u_short save = 0;
1310 #ifdef INET6
1311 if (!isipv6)
1312 #endif
1313 {
1314 save = ipov->ih_len;
1315 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1316 }
1317 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1318 #ifdef INET6
1319 if (!isipv6)
1320 #endif
1321 ipov->ih_len = save;
1322 }
1323 #endif /* TCPDEBUG */
1324
1325 /*
1326 * Fill in IP length and desired time to live and
1327 * send to IP level. There should be a better way
1328 * to handle ttl and tos; we could keep them in
1329 * the template, but need a way to checksum without them.
1330 */
1331 /*
1332 * m->m_pkthdr.len should have been set before cksum calcuration,
1333 * because in6_cksum() need it.
1334 */
1335 #ifdef INET6
1336 if (isipv6) {
1337 struct route_in6 ro;
1338
1339 bzero(&ro, sizeof(ro));
1340 /*
1341 * we separately set hoplimit for every segment, since the
1342 * user might want to change the value via setsockopt.
1343 * Also, desired default hop limit might be changed via
1344 * Neighbor Discovery.
1345 */
1346 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1347
1348 /* TODO: IPv6 IP6TOS_ECT bit on */
1349 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro,
1350 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
1351 NULL, NULL, tp->t_inpcb);
1352
1353 if (error == EMSGSIZE && ro.ro_rt != NULL)
1354 mtu = ro.ro_rt->rt_rmx.rmx_mtu;
1355 RO_RTFREE(&ro);
1356 }
1357 #endif /* INET6 */
1358 #if defined(INET) && defined(INET6)
1359 else
1360 #endif
1361 #ifdef INET
1362 {
1363 struct route ro;
1364
1365 bzero(&ro, sizeof(ro));
1366 ip->ip_len = m->m_pkthdr.len;
1367 #ifdef INET6
1368 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO)
1369 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL);
1370 #endif /* INET6 */
1371 /*
1372 * If we do path MTU discovery, then we set DF on every packet.
1373 * This might not be the best thing to do according to RFC3390
1374 * Section 2. However the tcp hostcache migitates the problem
1375 * so it affects only the first tcp connection with a host.
1376 *
1377 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
1378 */
1379 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss)
1380 ip->ip_off |= IP_DF;
1381
1382 error = ip_output(m, tp->t_inpcb->inp_options, &ro,
1383 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1384 tp->t_inpcb);
1385
1386 if (error == EMSGSIZE && ro.ro_rt != NULL)
1387 mtu = ro.ro_rt->rt_rmx.rmx_mtu;
1388 RO_RTFREE(&ro);
1389 }
1390 #endif /* INET */
1391 if (error) {
1392
1393 /*
1394 * We know that the packet was lost, so back out the
1395 * sequence number advance, if any.
1396 *
1397 * If the error is EPERM the packet got blocked by the
1398 * local firewall. Normally we should terminate the
1399 * connection but the blocking may have been spurious
1400 * due to a firewall reconfiguration cycle. So we treat
1401 * it like a packet loss and let the retransmit timer and
1402 * timeouts do their work over time.
1403 * XXX: It is a POLA question whether calling tcp_drop right
1404 * away would be the really correct behavior instead.
1405 */
1406 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1407 !tcp_timer_active(tp, TT_PERSIST)) &&
1408 ((flags & TH_SYN) == 0) &&
1409 (error != EPERM)) {
1410 if (sack_rxmit) {
1411 p->rxmit -= len;
1412 tp->sackhint.sack_bytes_rexmit -= len;
1413 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1414 ("sackhint bytes rtx >= 0"));
1415 } else
1416 tp->snd_nxt -= len;
1417 }
1418 out:
1419 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1420 switch (error) {
1421 case EPERM:
1422 tp->t_softerror = error;
1423 return (error);
1424 case ENOBUFS:
1425 if (!tcp_timer_active(tp, TT_REXMT) &&
1426 !tcp_timer_active(tp, TT_PERSIST))
1427 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1428 tp->snd_cwnd = tp->t_maxseg;
1429 return (0);
1430 case EMSGSIZE:
1431 /*
1432 * For some reason the interface we used initially
1433 * to send segments changed to another or lowered
1434 * its MTU.
1435 * If TSO was active we either got an interface
1436 * without TSO capabilits or TSO was turned off.
1437 * If we obtained mtu from ip_output() then update
1438 * it and try again.
1439 */
1440 if (tso)
1441 tp->t_flags &= ~TF_TSO;
1442 if (mtu != 0) {
1443 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1444 goto again;
1445 }
1446 return (error);
1447 case EHOSTDOWN:
1448 case EHOSTUNREACH:
1449 case ENETDOWN:
1450 case ENETUNREACH:
1451 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1452 tp->t_softerror = error;
1453 return (0);
1454 }
1455 /* FALLTHROUGH */
1456 default:
1457 return (error);
1458 }
1459 }
1460 TCPSTAT_INC(tcps_sndtotal);
1461
1462 /*
1463 * Data sent (as far as we can tell).
1464 * If this advertises a larger window than any other segment,
1465 * then remember the size of the advertised window.
1466 * Any pending ACK has now been sent.
1467 */
1468 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1469 tp->rcv_adv = tp->rcv_nxt + recwin;
1470 tp->last_ack_sent = tp->rcv_nxt;
1471 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1472 if (tcp_timer_active(tp, TT_DELACK))
1473 tcp_timer_activate(tp, TT_DELACK, 0);
1474 #if 0
1475 /*
1476 * This completely breaks TCP if newreno is turned on. What happens
1477 * is that if delayed-acks are turned on on the receiver, this code
1478 * on the transmitter effectively destroys the TCP window, forcing
1479 * it to four packets (1.5Kx4 = 6K window).
1480 */
1481 if (sendalot && --maxburst)
1482 goto again;
1483 #endif
1484 if (sendalot)
1485 goto again;
1486 return (0);
1487 }
1488
1489 void
1490 tcp_setpersist(struct tcpcb *tp)
1491 {
1492 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1493 int tt;
1494
1495 tp->t_flags &= ~TF_PREVVALID;
1496 if (tcp_timer_active(tp, TT_REXMT))
1497 panic("tcp_setpersist: retransmit pending");
1498 /*
1499 * Start/restart persistance timer.
1500 */
1501 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1502 TCPTV_PERSMIN, TCPTV_PERSMAX);
1503 tcp_timer_activate(tp, TT_PERSIST, tt);
1504 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1505 tp->t_rxtshift++;
1506 }
1507
1508 /*
1509 * Insert TCP options according to the supplied parameters to the place
1510 * optp in a consistent way. Can handle unaligned destinations.
1511 *
1512 * The order of the option processing is crucial for optimal packing and
1513 * alignment for the scarce option space.
1514 *
1515 * The optimal order for a SYN/SYN-ACK segment is:
1516 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1517 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1518 *
1519 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1520 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1521 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1522 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1523 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1524 */
1525 int
1526 tcp_addoptions(struct tcpopt *to, u_char *optp)
1527 {
1528 u_int mask, optlen = 0;
1529
1530 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1531 if ((to->to_flags & mask) != mask)
1532 continue;
1533 if (optlen == TCP_MAXOLEN)
1534 break;
1535 switch (to->to_flags & mask) {
1536 case TOF_MSS:
1537 while (optlen % 4) {
1538 optlen += TCPOLEN_NOP;
1539 *optp++ = TCPOPT_NOP;
1540 }
1541 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1542 continue;
1543 optlen += TCPOLEN_MAXSEG;
1544 *optp++ = TCPOPT_MAXSEG;
1545 *optp++ = TCPOLEN_MAXSEG;
1546 to->to_mss = htons(to->to_mss);
1547 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1548 optp += sizeof(to->to_mss);
1549 break;
1550 case TOF_SCALE:
1551 while (!optlen || optlen % 2 != 1) {
1552 optlen += TCPOLEN_NOP;
1553 *optp++ = TCPOPT_NOP;
1554 }
1555 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1556 continue;
1557 optlen += TCPOLEN_WINDOW;
1558 *optp++ = TCPOPT_WINDOW;
1559 *optp++ = TCPOLEN_WINDOW;
1560 *optp++ = to->to_wscale;
1561 break;
1562 case TOF_SACKPERM:
1563 while (optlen % 2) {
1564 optlen += TCPOLEN_NOP;
1565 *optp++ = TCPOPT_NOP;
1566 }
1567 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1568 continue;
1569 optlen += TCPOLEN_SACK_PERMITTED;
1570 *optp++ = TCPOPT_SACK_PERMITTED;
1571 *optp++ = TCPOLEN_SACK_PERMITTED;
1572 break;
1573 case TOF_TS:
1574 while (!optlen || optlen % 4 != 2) {
1575 optlen += TCPOLEN_NOP;
1576 *optp++ = TCPOPT_NOP;
1577 }
1578 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1579 continue;
1580 optlen += TCPOLEN_TIMESTAMP;
1581 *optp++ = TCPOPT_TIMESTAMP;
1582 *optp++ = TCPOLEN_TIMESTAMP;
1583 to->to_tsval = htonl(to->to_tsval);
1584 to->to_tsecr = htonl(to->to_tsecr);
1585 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1586 optp += sizeof(to->to_tsval);
1587 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1588 optp += sizeof(to->to_tsecr);
1589 break;
1590 #ifdef TCP_SIGNATURE
1591 case TOF_SIGNATURE:
1592 {
1593 int siglen = TCPOLEN_SIGNATURE - 2;
1594
1595 while (!optlen || optlen % 4 != 2) {
1596 optlen += TCPOLEN_NOP;
1597 *optp++ = TCPOPT_NOP;
1598 }
1599 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1600 continue;
1601 optlen += TCPOLEN_SIGNATURE;
1602 *optp++ = TCPOPT_SIGNATURE;
1603 *optp++ = TCPOLEN_SIGNATURE;
1604 to->to_signature = optp;
1605 while (siglen--)
1606 *optp++ = 0;
1607 break;
1608 }
1609 #endif
1610 case TOF_SACK:
1611 {
1612 int sackblks = 0;
1613 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1614 tcp_seq sack_seq;
1615
1616 while (!optlen || optlen % 4 != 2) {
1617 optlen += TCPOLEN_NOP;
1618 *optp++ = TCPOPT_NOP;
1619 }
1620 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1621 continue;
1622 optlen += TCPOLEN_SACKHDR;
1623 *optp++ = TCPOPT_SACK;
1624 sackblks = min(to->to_nsacks,
1625 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1626 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1627 while (sackblks--) {
1628 sack_seq = htonl(sack->start);
1629 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1630 optp += sizeof(sack_seq);
1631 sack_seq = htonl(sack->end);
1632 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1633 optp += sizeof(sack_seq);
1634 optlen += TCPOLEN_SACK;
1635 sack++;
1636 }
1637 TCPSTAT_INC(tcps_sack_send_blocks);
1638 break;
1639 }
1640 default:
1641 panic("%s: unknown TCP option type", __func__);
1642 break;
1643 }
1644 }
1645
1646 /* Terminate and pad TCP options to a 4 byte boundary. */
1647 if (optlen % 4) {
1648 optlen += TCPOLEN_EOL;
1649 *optp++ = TCPOPT_EOL;
1650 }
1651 /*
1652 * According to RFC 793 (STD0007):
1653 * "The content of the header beyond the End-of-Option option
1654 * must be header padding (i.e., zero)."
1655 * and later: "The padding is composed of zeros."
1656 */
1657 while (optlen % 4) {
1658 optlen += TCPOLEN_PAD;
1659 *optp++ = TCPOPT_PAD;
1660 }
1661
1662 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1663 return (optlen);
1664 }
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