80#ifdef TCPDEBUG
81#include <netinet/tcp_debug.h>
82#endif
83#ifdef TCP_OFFLOAD
84#include <netinet/tcp_offload.h>
85#endif
86
87#ifdef IPSEC
88#include <netipsec/ipsec.h>
89#endif /*IPSEC*/
90
91#include <machine/in_cksum.h>
92
93#include <security/mac/mac_framework.h>
94
95VNET_DEFINE(int, path_mtu_discovery) = 1;
96SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW,
97 &VNET_NAME(path_mtu_discovery), 1,
98 "Enable Path MTU Discovery");
99
100VNET_DEFINE(int, tcp_do_tso) = 1;
101#define V_tcp_do_tso VNET(tcp_do_tso)
102SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW,
103 &VNET_NAME(tcp_do_tso), 0,
104 "Enable TCP Segmentation Offload");
105
106VNET_DEFINE(int, tcp_sendspace) = 1024*32;
107#define V_tcp_sendspace VNET(tcp_sendspace)
108SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW,
109 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size");
110
111VNET_DEFINE(int, tcp_do_autosndbuf) = 1;
112#define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
113SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
114 &VNET_NAME(tcp_do_autosndbuf), 0,
115 "Enable automatic send buffer sizing");
116
117VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024;
118#define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc)
119SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
120 &VNET_NAME(tcp_autosndbuf_inc), 0,
121 "Incrementor step size of automatic send buffer");
122
123VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024;
124#define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max)
125SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
126 &VNET_NAME(tcp_autosndbuf_max), 0,
127 "Max size of automatic send buffer");
128
129static void inline hhook_run_tcp_est_out(struct tcpcb *tp,
130 struct tcphdr *th, struct tcpopt *to,
131 long len, int tso);
132static void inline cc_after_idle(struct tcpcb *tp);
133
134/*
135 * Wrapper for the TCP established output helper hook.
136 */
137static void inline
138hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th,
139 struct tcpopt *to, long len, int tso)
140{
141 struct tcp_hhook_data hhook_data;
142
143 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) {
144 hhook_data.tp = tp;
145 hhook_data.th = th;
146 hhook_data.to = to;
147 hhook_data.len = len;
148 hhook_data.tso = tso;
149
150 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data,
151 tp->osd);
152 }
153}
154
155/*
156 * CC wrapper hook functions
157 */
158static void inline
159cc_after_idle(struct tcpcb *tp)
160{
161 INP_WLOCK_ASSERT(tp->t_inpcb);
162
163 if (CC_ALGO(tp)->after_idle != NULL)
164 CC_ALGO(tp)->after_idle(tp->ccv);
165}
166
167/*
168 * Tcp output routine: figure out what should be sent and send it.
169 */
170int
171tcp_output(struct tcpcb *tp)
172{
173 struct socket *so = tp->t_inpcb->inp_socket;
174 long len, recwin, sendwin;
175 int off, flags, error = 0; /* Keep compiler happy */
176 struct mbuf *m;
177 struct ip *ip = NULL;
178 struct ipovly *ipov = NULL;
179 struct tcphdr *th;
180 u_char opt[TCP_MAXOLEN];
181 unsigned ipoptlen, optlen, hdrlen;
182#ifdef IPSEC
183 unsigned ipsec_optlen = 0;
184#endif
185 int idle, sendalot;
186 int sack_rxmit, sack_bytes_rxmt;
187 struct sackhole *p;
188 int tso, mtu;
189 struct tcpopt to;
190#if 0
191 int maxburst = TCP_MAXBURST;
192#endif
193#ifdef INET6
194 struct ip6_hdr *ip6 = NULL;
195 int isipv6;
196
197 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
198#endif
199
200 INP_WLOCK_ASSERT(tp->t_inpcb);
201
202#ifdef TCP_OFFLOAD
203 if (tp->t_flags & TF_TOE)
204 return (tcp_offload_output(tp));
205#endif
206
207 /*
208 * Determine length of data that should be transmitted,
209 * and flags that will be used.
210 * If there is some data or critical controls (SYN, RST)
211 * to send, then transmit; otherwise, investigate further.
212 */
213 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
214 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
215 cc_after_idle(tp);
216 tp->t_flags &= ~TF_LASTIDLE;
217 if (idle) {
218 if (tp->t_flags & TF_MORETOCOME) {
219 tp->t_flags |= TF_LASTIDLE;
220 idle = 0;
221 }
222 }
223again:
224 /*
225 * If we've recently taken a timeout, snd_max will be greater than
226 * snd_nxt. There may be SACK information that allows us to avoid
227 * resending already delivered data. Adjust snd_nxt accordingly.
228 */
229 if ((tp->t_flags & TF_SACK_PERMIT) &&
230 SEQ_LT(tp->snd_nxt, tp->snd_max))
231 tcp_sack_adjust(tp);
232 sendalot = 0;
233 tso = 0;
234 mtu = 0;
235 off = tp->snd_nxt - tp->snd_una;
236 sendwin = min(tp->snd_wnd, tp->snd_cwnd);
237
238 flags = tcp_outflags[tp->t_state];
239 /*
240 * Send any SACK-generated retransmissions. If we're explicitly trying
241 * to send out new data (when sendalot is 1), bypass this function.
242 * If we retransmit in fast recovery mode, decrement snd_cwnd, since
243 * we're replacing a (future) new transmission with a retransmission
244 * now, and we previously incremented snd_cwnd in tcp_input().
245 */
246 /*
247 * Still in sack recovery , reset rxmit flag to zero.
248 */
249 sack_rxmit = 0;
250 sack_bytes_rxmt = 0;
251 len = 0;
252 p = NULL;
253 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) &&
254 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
255 long cwin;
256
257 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
258 if (cwin < 0)
259 cwin = 0;
260 /* Do not retransmit SACK segments beyond snd_recover */
261 if (SEQ_GT(p->end, tp->snd_recover)) {
262 /*
263 * (At least) part of sack hole extends beyond
264 * snd_recover. Check to see if we can rexmit data
265 * for this hole.
266 */
267 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) {
268 /*
269 * Can't rexmit any more data for this hole.
270 * That data will be rexmitted in the next
271 * sack recovery episode, when snd_recover
272 * moves past p->rxmit.
273 */
274 p = NULL;
275 goto after_sack_rexmit;
276 } else
277 /* Can rexmit part of the current hole */
278 len = ((long)ulmin(cwin,
279 tp->snd_recover - p->rxmit));
280 } else
281 len = ((long)ulmin(cwin, p->end - p->rxmit));
282 off = p->rxmit - tp->snd_una;
283 KASSERT(off >= 0,("%s: sack block to the left of una : %d",
284 __func__, off));
285 if (len > 0) {
286 sack_rxmit = 1;
287 sendalot = 1;
288 TCPSTAT_INC(tcps_sack_rexmits);
289 TCPSTAT_ADD(tcps_sack_rexmit_bytes,
290 min(len, tp->t_maxseg));
291 }
292 }
293after_sack_rexmit:
294 /*
295 * Get standard flags, and add SYN or FIN if requested by 'hidden'
296 * state flags.
297 */
298 if (tp->t_flags & TF_NEEDFIN)
299 flags |= TH_FIN;
300 if (tp->t_flags & TF_NEEDSYN)
301 flags |= TH_SYN;
302
303 SOCKBUF_LOCK(&so->so_snd);
304 /*
305 * If in persist timeout with window of 0, send 1 byte.
306 * Otherwise, if window is small but nonzero
307 * and timer expired, we will send what we can
308 * and go to transmit state.
309 */
310 if (tp->t_flags & TF_FORCEDATA) {
311 if (sendwin == 0) {
312 /*
313 * If we still have some data to send, then
314 * clear the FIN bit. Usually this would
315 * happen below when it realizes that we
316 * aren't sending all the data. However,
317 * if we have exactly 1 byte of unsent data,
318 * then it won't clear the FIN bit below,
319 * and if we are in persist state, we wind
320 * up sending the packet without recording
321 * that we sent the FIN bit.
322 *
323 * We can't just blindly clear the FIN bit,
324 * because if we don't have any more data
325 * to send then the probe will be the FIN
326 * itself.
327 */
328 if (off < sbused(&so->so_snd))
329 flags &= ~TH_FIN;
330 sendwin = 1;
331 } else {
332 tcp_timer_activate(tp, TT_PERSIST, 0);
333 tp->t_rxtshift = 0;
334 }
335 }
336
337 /*
338 * If snd_nxt == snd_max and we have transmitted a FIN, the
339 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in
340 * a negative length. This can also occur when TCP opens up
341 * its congestion window while receiving additional duplicate
342 * acks after fast-retransmit because TCP will reset snd_nxt
343 * to snd_max after the fast-retransmit.
344 *
345 * In the normal retransmit-FIN-only case, however, snd_nxt will
346 * be set to snd_una, the offset will be 0, and the length may
347 * wind up 0.
348 *
349 * If sack_rxmit is true we are retransmitting from the scoreboard
350 * in which case len is already set.
351 */
352 if (sack_rxmit == 0) {
353 if (sack_bytes_rxmt == 0)
354 len = ((long)ulmin(sbavail(&so->so_snd), sendwin) -
355 off);
356 else {
357 long cwin;
358
359 /*
360 * We are inside of a SACK recovery episode and are
361 * sending new data, having retransmitted all the
362 * data possible in the scoreboard.
363 */
364 len = ((long)ulmin(sbavail(&so->so_snd), tp->snd_wnd) -
365 off);
366 /*
367 * Don't remove this (len > 0) check !
368 * We explicitly check for len > 0 here (although it
369 * isn't really necessary), to work around a gcc
370 * optimization issue - to force gcc to compute
371 * len above. Without this check, the computation
372 * of len is bungled by the optimizer.
373 */
374 if (len > 0) {
375 cwin = tp->snd_cwnd -
376 (tp->snd_nxt - tp->sack_newdata) -
377 sack_bytes_rxmt;
378 if (cwin < 0)
379 cwin = 0;
380 len = lmin(len, cwin);
381 }
382 }
383 }
384
385 /*
386 * Lop off SYN bit if it has already been sent. However, if this
387 * is SYN-SENT state and if segment contains data and if we don't
388 * know that foreign host supports TAO, suppress sending segment.
389 */
390 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
391 if (tp->t_state != TCPS_SYN_RECEIVED)
392 flags &= ~TH_SYN;
393 off--, len++;
394 }
395
396 /*
397 * Be careful not to send data and/or FIN on SYN segments.
398 * This measure is needed to prevent interoperability problems
399 * with not fully conformant TCP implementations.
400 */
401 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) {
402 len = 0;
403 flags &= ~TH_FIN;
404 }
405
406 if (len <= 0) {
407 /*
408 * If FIN has been sent but not acked,
409 * but we haven't been called to retransmit,
410 * len will be < 0. Otherwise, window shrank
411 * after we sent into it. If window shrank to 0,
412 * cancel pending retransmit, pull snd_nxt back
413 * to (closed) window, and set the persist timer
414 * if it isn't already going. If the window didn't
415 * close completely, just wait for an ACK.
416 *
417 * We also do a general check here to ensure that
418 * we will set the persist timer when we have data
419 * to send, but a 0-byte window. This makes sure
420 * the persist timer is set even if the packet
421 * hits one of the "goto send" lines below.
422 */
423 len = 0;
424 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) &&
425 (off < (int) sbavail(&so->so_snd))) {
426 tcp_timer_activate(tp, TT_REXMT, 0);
427 tp->t_rxtshift = 0;
428 tp->snd_nxt = tp->snd_una;
429 if (!tcp_timer_active(tp, TT_PERSIST))
430 tcp_setpersist(tp);
431 }
432 }
433
434 /* len will be >= 0 after this point. */
435 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
436
437 /*
438 * Automatic sizing of send socket buffer. Often the send buffer
439 * size is not optimally adjusted to the actual network conditions
440 * at hand (delay bandwidth product). Setting the buffer size too
441 * small limits throughput on links with high bandwidth and high
442 * delay (eg. trans-continental/oceanic links). Setting the
443 * buffer size too big consumes too much real kernel memory,
444 * especially with many connections on busy servers.
445 *
446 * The criteria to step up the send buffer one notch are:
447 * 1. receive window of remote host is larger than send buffer
448 * (with a fudge factor of 5/4th);
449 * 2. send buffer is filled to 7/8th with data (so we actually
450 * have data to make use of it);
451 * 3. send buffer fill has not hit maximal automatic size;
452 * 4. our send window (slow start and cogestion controlled) is
453 * larger than sent but unacknowledged data in send buffer.
454 *
455 * The remote host receive window scaling factor may limit the
456 * growing of the send buffer before it reaches its allowed
457 * maximum.
458 *
459 * It scales directly with slow start or congestion window
460 * and does at most one step per received ACK. This fast
461 * scaling has the drawback of growing the send buffer beyond
462 * what is strictly necessary to make full use of a given
463 * delay*bandwith product. However testing has shown this not
464 * to be much of an problem. At worst we are trading wasting
465 * of available bandwith (the non-use of it) for wasting some
466 * socket buffer memory.
467 *
468 * TODO: Shrink send buffer during idle periods together
469 * with congestion window. Requires another timer. Has to
470 * wait for upcoming tcp timer rewrite.
471 *
472 * XXXGL: should there be used sbused() or sbavail()?
473 */
474 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) {
475 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat &&
476 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) &&
477 sbused(&so->so_snd) < V_tcp_autosndbuf_max &&
478 sendwin >= (sbused(&so->so_snd) -
479 (tp->snd_nxt - tp->snd_una))) {
480 if (!sbreserve_locked(&so->so_snd,
481 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc,
482 V_tcp_autosndbuf_max), so, curthread))
483 so->so_snd.sb_flags &= ~SB_AUTOSIZE;
484 }
485 }
486
487 /*
488 * Decide if we can use TCP Segmentation Offloading (if supported by
489 * hardware).
490 *
491 * TSO may only be used if we are in a pure bulk sending state. The
492 * presence of TCP-MD5, SACK retransmits, SACK advertizements and
493 * IP options prevent using TSO. With TSO the TCP header is the same
494 * (except for the sequence number) for all generated packets. This
495 * makes it impossible to transmit any options which vary per generated
496 * segment or packet.
497 */
498#ifdef IPSEC
499 /*
500 * Pre-calculate here as we save another lookup into the darknesses
501 * of IPsec that way and can actually decide if TSO is ok.
502 */
503 ipsec_optlen = ipsec_hdrsiz_tcp(tp);
504#endif
505 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
506 ((tp->t_flags & TF_SIGNATURE) == 0) &&
507 tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
508#ifdef IPSEC
509 ipsec_optlen == 0 &&
510#endif
511 tp->t_inpcb->inp_options == NULL &&
512 tp->t_inpcb->in6p_options == NULL)
513 tso = 1;
514
515 if (sack_rxmit) {
516 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd)))
517 flags &= ~TH_FIN;
518 } else {
519 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una +
520 sbused(&so->so_snd)))
521 flags &= ~TH_FIN;
522 }
523
524 recwin = sbspace(&so->so_rcv);
525
526 /*
527 * Sender silly window avoidance. We transmit under the following
528 * conditions when len is non-zero:
529 *
530 * - We have a full segment (or more with TSO)
531 * - This is the last buffer in a write()/send() and we are
532 * either idle or running NODELAY
533 * - we've timed out (e.g. persist timer)
534 * - we have more then 1/2 the maximum send window's worth of
535 * data (receiver may be limited the window size)
536 * - we need to retransmit
537 */
538 if (len) {
539 if (len >= tp->t_maxseg)
540 goto send;
541 /*
542 * NOTE! on localhost connections an 'ack' from the remote
543 * end may occur synchronously with the output and cause
544 * us to flush a buffer queued with moretocome. XXX
545 *
546 * note: the len + off check is almost certainly unnecessary.
547 */
548 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
549 (idle || (tp->t_flags & TF_NODELAY)) &&
550 len + off >= sbavail(&so->so_snd) &&
551 (tp->t_flags & TF_NOPUSH) == 0) {
552 goto send;
553 }
554 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */
555 goto send;
556 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
557 goto send;
558 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
559 goto send;
560 if (sack_rxmit)
561 goto send;
562 }
563
564 /*
565 * Sending of standalone window updates.
566 *
567 * Window updates are important when we close our window due to a
568 * full socket buffer and are opening it again after the application
569 * reads data from it. Once the window has opened again and the
570 * remote end starts to send again the ACK clock takes over and
571 * provides the most current window information.
572 *
573 * We must avoid the silly window syndrome whereas every read
574 * from the receive buffer, no matter how small, causes a window
575 * update to be sent. We also should avoid sending a flurry of
576 * window updates when the socket buffer had queued a lot of data
577 * and the application is doing small reads.
578 *
579 * Prevent a flurry of pointless window updates by only sending
580 * an update when we can increase the advertized window by more
581 * than 1/4th of the socket buffer capacity. When the buffer is
582 * getting full or is very small be more aggressive and send an
583 * update whenever we can increase by two mss sized segments.
584 * In all other situations the ACK's to new incoming data will
585 * carry further window increases.
586 *
587 * Don't send an independent window update if a delayed
588 * ACK is pending (it will get piggy-backed on it) or the
589 * remote side already has done a half-close and won't send
590 * more data. Skip this if the connection is in T/TCP
591 * half-open state.
592 */
593 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) &&
594 !(tp->t_flags & TF_DELACK) &&
595 !TCPS_HAVERCVDFIN(tp->t_state)) {
596 /*
597 * "adv" is the amount we could increase the window,
598 * taking into account that we are limited by
599 * TCP_MAXWIN << tp->rcv_scale.
600 */
601 long adv;
602 int oldwin;
603
604 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale);
605 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) {
606 oldwin = (tp->rcv_adv - tp->rcv_nxt);
607 adv -= oldwin;
608 } else
609 oldwin = 0;
610
611 /*
612 * If the new window size ends up being the same as the old
613 * size when it is scaled, then don't force a window update.
614 */
615 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale)
616 goto dontupdate;
617
618 if (adv >= (long)(2 * tp->t_maxseg) &&
619 (adv >= (long)(so->so_rcv.sb_hiwat / 4) ||
620 recwin <= (long)(so->so_rcv.sb_hiwat / 8) ||
621 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg))
622 goto send;
623 }
624dontupdate:
625
626 /*
627 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
628 * is also a catch-all for the retransmit timer timeout case.
629 */
630 if (tp->t_flags & TF_ACKNOW)
631 goto send;
632 if ((flags & TH_RST) ||
633 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0))
634 goto send;
635 if (SEQ_GT(tp->snd_up, tp->snd_una))
636 goto send;
637 /*
638 * If our state indicates that FIN should be sent
639 * and we have not yet done so, then we need to send.
640 */
641 if (flags & TH_FIN &&
642 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
643 goto send;
644 /*
645 * In SACK, it is possible for tcp_output to fail to send a segment
646 * after the retransmission timer has been turned off. Make sure
647 * that the retransmission timer is set.
648 */
649 if ((tp->t_flags & TF_SACK_PERMIT) &&
650 SEQ_GT(tp->snd_max, tp->snd_una) &&
651 !tcp_timer_active(tp, TT_REXMT) &&
652 !tcp_timer_active(tp, TT_PERSIST)) {
653 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
654 goto just_return;
655 }
656 /*
657 * TCP window updates are not reliable, rather a polling protocol
658 * using ``persist'' packets is used to insure receipt of window
659 * updates. The three ``states'' for the output side are:
660 * idle not doing retransmits or persists
661 * persisting to move a small or zero window
662 * (re)transmitting and thereby not persisting
663 *
664 * tcp_timer_active(tp, TT_PERSIST)
665 * is true when we are in persist state.
666 * (tp->t_flags & TF_FORCEDATA)
667 * is set when we are called to send a persist packet.
668 * tcp_timer_active(tp, TT_REXMT)
669 * is set when we are retransmitting
670 * The output side is idle when both timers are zero.
671 *
672 * If send window is too small, there is data to transmit, and no
673 * retransmit or persist is pending, then go to persist state.
674 * If nothing happens soon, send when timer expires:
675 * if window is nonzero, transmit what we can,
676 * otherwise force out a byte.
677 */
678 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) &&
679 !tcp_timer_active(tp, TT_PERSIST)) {
680 tp->t_rxtshift = 0;
681 tcp_setpersist(tp);
682 }
683
684 /*
685 * No reason to send a segment, just return.
686 */
687just_return:
688 SOCKBUF_UNLOCK(&so->so_snd);
689 return (0);
690
691send:
692 SOCKBUF_LOCK_ASSERT(&so->so_snd);
693 if (len > 0) {
694 if (len >= tp->t_maxseg)
695 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT;
696 else
697 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT;
698 }
699 /*
700 * Before ESTABLISHED, force sending of initial options
701 * unless TCP set not to do any options.
702 * NOTE: we assume that the IP/TCP header plus TCP options
703 * always fit in a single mbuf, leaving room for a maximum
704 * link header, i.e.
705 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
706 */
707 optlen = 0;
708#ifdef INET6
709 if (isipv6)
710 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
711 else
712#endif
713 hdrlen = sizeof (struct tcpiphdr);
714
715 /*
716 * Compute options for segment.
717 * We only have to care about SYN and established connection
718 * segments. Options for SYN-ACK segments are handled in TCP
719 * syncache.
720 */
721 if ((tp->t_flags & TF_NOOPT) == 0) {
722 to.to_flags = 0;
723 /* Maximum segment size. */
724 if (flags & TH_SYN) {
725 tp->snd_nxt = tp->iss;
726 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
727 to.to_flags |= TOF_MSS;
728 }
729 /* Window scaling. */
730 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) {
731 to.to_wscale = tp->request_r_scale;
732 to.to_flags |= TOF_SCALE;
733 }
734 /* Timestamps. */
735 if ((tp->t_flags & TF_RCVD_TSTMP) ||
736 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) {
737 to.to_tsval = tcp_ts_getticks() + tp->ts_offset;
738 to.to_tsecr = tp->ts_recent;
739 to.to_flags |= TOF_TS;
740 /* Set receive buffer autosizing timestamp. */
741 if (tp->rfbuf_ts == 0 &&
742 (so->so_rcv.sb_flags & SB_AUTOSIZE))
743 tp->rfbuf_ts = tcp_ts_getticks();
744 }
745 /* Selective ACK's. */
746 if (tp->t_flags & TF_SACK_PERMIT) {
747 if (flags & TH_SYN)
748 to.to_flags |= TOF_SACKPERM;
749 else if (TCPS_HAVEESTABLISHED(tp->t_state) &&
750 (tp->t_flags & TF_SACK_PERMIT) &&
751 tp->rcv_numsacks > 0) {
752 to.to_flags |= TOF_SACK;
753 to.to_nsacks = tp->rcv_numsacks;
754 to.to_sacks = (u_char *)tp->sackblks;
755 }
756 }
757#ifdef TCP_SIGNATURE
758 /* TCP-MD5 (RFC2385). */
759 if (tp->t_flags & TF_SIGNATURE)
760 to.to_flags |= TOF_SIGNATURE;
761#endif /* TCP_SIGNATURE */
762
763 /* Processing the options. */
764 hdrlen += optlen = tcp_addoptions(&to, opt);
765 }
766
767#ifdef INET6
768 if (isipv6)
769 ipoptlen = ip6_optlen(tp->t_inpcb);
770 else
771#endif
772 if (tp->t_inpcb->inp_options)
773 ipoptlen = tp->t_inpcb->inp_options->m_len -
774 offsetof(struct ipoption, ipopt_list);
775 else
776 ipoptlen = 0;
777#ifdef IPSEC
778 ipoptlen += ipsec_optlen;
779#endif
780
781 /*
782 * Adjust data length if insertion of options will
783 * bump the packet length beyond the t_maxopd length.
784 * Clear the FIN bit because we cut off the tail of
785 * the segment.
786 */
787 if (len + optlen + ipoptlen > tp->t_maxopd) {
788 flags &= ~TH_FIN;
789
790 if (tso) {
791 u_int if_hw_tsomax;
792 u_int if_hw_tsomaxsegcount;
793 u_int if_hw_tsomaxsegsize;
794 struct mbuf *mb;
795 u_int moff;
796 int max_len;
797
798 /* extract TSO information */
799 if_hw_tsomax = tp->t_tsomax;
800 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount;
801 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize;
802
803 /*
804 * Limit a TSO burst to prevent it from
805 * overflowing or exceeding the maximum length
806 * allowed by the network interface:
807 */
808 KASSERT(ipoptlen == 0,
809 ("%s: TSO can't do IP options", __func__));
810
811 /*
812 * Check if we should limit by maximum payload
813 * length:
814 */
815 if (if_hw_tsomax != 0) {
816 /* compute maximum TSO length */
817 max_len = (if_hw_tsomax - hdrlen -
818 max_linkhdr);
819 if (max_len <= 0) {
820 len = 0;
821 } else if (len > max_len) {
822 sendalot = 1;
823 len = max_len;
824 }
825 }
826
827 /*
828 * Check if we should limit by maximum segment
829 * size and count:
830 */
831 if (if_hw_tsomaxsegcount != 0 &&
832 if_hw_tsomaxsegsize != 0) {
833 /*
834 * Subtract one segment for the LINK
835 * and TCP/IP headers mbuf that will
836 * be prepended to this mbuf chain
837 * after the code in this section
838 * limits the number of mbufs in the
839 * chain to if_hw_tsomaxsegcount.
840 */
841 if_hw_tsomaxsegcount -= 1;
842 max_len = 0;
843 mb = sbsndmbuf(&so->so_snd, off, &moff);
844
845 while (mb != NULL && max_len < len) {
846 u_int mlen;
847 u_int frags;
848
849 /*
850 * Get length of mbuf fragment
851 * and how many hardware frags,
852 * rounded up, it would use:
853 */
854 mlen = (mb->m_len - moff);
855 frags = howmany(mlen,
856 if_hw_tsomaxsegsize);
857
858 /* Handle special case: Zero Length Mbuf */
859 if (frags == 0)
860 frags = 1;
861
862 /*
863 * Check if the fragment limit
864 * will be reached or exceeded:
865 */
866 if (frags >= if_hw_tsomaxsegcount) {
867 max_len += min(mlen,
868 if_hw_tsomaxsegcount *
869 if_hw_tsomaxsegsize);
870 break;
871 }
872 max_len += mlen;
873 if_hw_tsomaxsegcount -= frags;
874 moff = 0;
875 mb = mb->m_next;
876 }
877 if (max_len <= 0) {
878 len = 0;
879 } else if (len > max_len) {
880 sendalot = 1;
881 len = max_len;
882 }
883 }
884
885 /*
886 * Prevent the last segment from being
887 * fractional unless the send sockbuf can be
888 * emptied:
889 */
890 max_len = (tp->t_maxopd - optlen);
891 if ((off + len) < sbavail(&so->so_snd)) {
892 moff = len % max_len;
893 if (moff != 0) {
894 len -= moff;
895 sendalot = 1;
896 }
897 }
898
899 /*
900 * In case there are too many small fragments
901 * don't use TSO:
902 */
903 if (len <= max_len) {
904 len = max_len;
905 sendalot = 1;
906 tso = 0;
907 }
908
909 /*
910 * Send the FIN in a separate segment
911 * after the bulk sending is done.
912 * We don't trust the TSO implementations
913 * to clear the FIN flag on all but the
914 * last segment.
915 */
916 if (tp->t_flags & TF_NEEDFIN)
917 sendalot = 1;
918
919 } else {
920 len = tp->t_maxopd - optlen - ipoptlen;
921 sendalot = 1;
922 }
923 } else
924 tso = 0;
925
926 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET,
927 ("%s: len > IP_MAXPACKET", __func__));
928
929/*#ifdef DIAGNOSTIC*/
930#ifdef INET6
931 if (max_linkhdr + hdrlen > MCLBYTES)
932#else
933 if (max_linkhdr + hdrlen > MHLEN)
934#endif
935 panic("tcphdr too big");
936/*#endif*/
937
938 /*
939 * This KASSERT is here to catch edge cases at a well defined place.
940 * Before, those had triggered (random) panic conditions further down.
941 */
942 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__));
943
944 /*
945 * Grab a header mbuf, attaching a copy of data to
946 * be transmitted, and initialize the header from
947 * the template for sends on this connection.
948 */
949 if (len) {
950 struct mbuf *mb;
951 u_int moff;
952
953 if ((tp->t_flags & TF_FORCEDATA) && len == 1)
954 TCPSTAT_INC(tcps_sndprobe);
955 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) {
956 tp->t_sndrexmitpack++;
957 TCPSTAT_INC(tcps_sndrexmitpack);
958 TCPSTAT_ADD(tcps_sndrexmitbyte, len);
959 } else {
960 TCPSTAT_INC(tcps_sndpack);
961 TCPSTAT_ADD(tcps_sndbyte, len);
962 }
963#ifdef INET6
964 if (MHLEN < hdrlen + max_linkhdr)
965 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
966 else
967#endif
968 m = m_gethdr(M_NOWAIT, MT_DATA);
969
970 if (m == NULL) {
971 SOCKBUF_UNLOCK(&so->so_snd);
972 error = ENOBUFS;
973 sack_rxmit = 0;
974 goto out;
975 }
976
977 m->m_data += max_linkhdr;
978 m->m_len = hdrlen;
979
980 /*
981 * Start the m_copy functions from the closest mbuf
982 * to the offset in the socket buffer chain.
983 */
984 mb = sbsndptr(&so->so_snd, off, len, &moff);
985
986 if (len <= MHLEN - hdrlen - max_linkhdr) {
987 m_copydata(mb, moff, (int)len,
988 mtod(m, caddr_t) + hdrlen);
989 m->m_len += len;
990 } else {
991 m->m_next = m_copy(mb, moff, (int)len);
992 if (m->m_next == NULL) {
993 SOCKBUF_UNLOCK(&so->so_snd);
994 (void) m_free(m);
995 error = ENOBUFS;
996 sack_rxmit = 0;
997 goto out;
998 }
999 }
1000
1001 /*
1002 * If we're sending everything we've got, set PUSH.
1003 * (This will keep happy those implementations which only
1004 * give data to the user when a buffer fills or
1005 * a PUSH comes in.)
1006 */
1007 if (off + len == sbused(&so->so_snd))
1008 flags |= TH_PUSH;
1009 SOCKBUF_UNLOCK(&so->so_snd);
1010 } else {
1011 SOCKBUF_UNLOCK(&so->so_snd);
1012 if (tp->t_flags & TF_ACKNOW)
1013 TCPSTAT_INC(tcps_sndacks);
1014 else if (flags & (TH_SYN|TH_FIN|TH_RST))
1015 TCPSTAT_INC(tcps_sndctrl);
1016 else if (SEQ_GT(tp->snd_up, tp->snd_una))
1017 TCPSTAT_INC(tcps_sndurg);
1018 else
1019 TCPSTAT_INC(tcps_sndwinup);
1020
1021 m = m_gethdr(M_NOWAIT, MT_DATA);
1022 if (m == NULL) {
1023 error = ENOBUFS;
1024 sack_rxmit = 0;
1025 goto out;
1026 }
1027#ifdef INET6
1028 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
1029 MHLEN >= hdrlen) {
1030 M_ALIGN(m, hdrlen);
1031 } else
1032#endif
1033 m->m_data += max_linkhdr;
1034 m->m_len = hdrlen;
1035 }
1036 SOCKBUF_UNLOCK_ASSERT(&so->so_snd);
1037 m->m_pkthdr.rcvif = (struct ifnet *)0;
1038#ifdef MAC
1039 mac_inpcb_create_mbuf(tp->t_inpcb, m);
1040#endif
1041#ifdef INET6
1042 if (isipv6) {
1043 ip6 = mtod(m, struct ip6_hdr *);
1044 th = (struct tcphdr *)(ip6 + 1);
1045 tcpip_fillheaders(tp->t_inpcb, ip6, th);
1046 } else
1047#endif /* INET6 */
1048 {
1049 ip = mtod(m, struct ip *);
1050 ipov = (struct ipovly *)ip;
1051 th = (struct tcphdr *)(ip + 1);
1052 tcpip_fillheaders(tp->t_inpcb, ip, th);
1053 }
1054
1055 /*
1056 * Fill in fields, remembering maximum advertised
1057 * window for use in delaying messages about window sizes.
1058 * If resending a FIN, be sure not to use a new sequence number.
1059 */
1060 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1061 tp->snd_nxt == tp->snd_max)
1062 tp->snd_nxt--;
1063 /*
1064 * If we are starting a connection, send ECN setup
1065 * SYN packet. If we are on a retransmit, we may
1066 * resend those bits a number of times as per
1067 * RFC 3168.
1068 */
1069 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) {
1070 if (tp->t_rxtshift >= 1) {
1071 if (tp->t_rxtshift <= V_tcp_ecn_maxretries)
1072 flags |= TH_ECE|TH_CWR;
1073 } else
1074 flags |= TH_ECE|TH_CWR;
1075 }
1076
1077 if (tp->t_state == TCPS_ESTABLISHED &&
1078 (tp->t_flags & TF_ECN_PERMIT)) {
1079 /*
1080 * If the peer has ECN, mark data packets with
1081 * ECN capable transmission (ECT).
1082 * Ignore pure ack packets, retransmissions and window probes.
1083 */
1084 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) &&
1085 !((tp->t_flags & TF_FORCEDATA) && len == 1)) {
1086#ifdef INET6
1087 if (isipv6)
1088 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1089 else
1090#endif
1091 ip->ip_tos |= IPTOS_ECN_ECT0;
1092 TCPSTAT_INC(tcps_ecn_ect0);
1093 }
1094
1095 /*
1096 * Reply with proper ECN notifications.
1097 */
1098 if (tp->t_flags & TF_ECN_SND_CWR) {
1099 flags |= TH_CWR;
1100 tp->t_flags &= ~TF_ECN_SND_CWR;
1101 }
1102 if (tp->t_flags & TF_ECN_SND_ECE)
1103 flags |= TH_ECE;
1104 }
1105
1106 /*
1107 * If we are doing retransmissions, then snd_nxt will
1108 * not reflect the first unsent octet. For ACK only
1109 * packets, we do not want the sequence number of the
1110 * retransmitted packet, we want the sequence number
1111 * of the next unsent octet. So, if there is no data
1112 * (and no SYN or FIN), use snd_max instead of snd_nxt
1113 * when filling in ti_seq. But if we are in persist
1114 * state, snd_max might reflect one byte beyond the
1115 * right edge of the window, so use snd_nxt in that
1116 * case, since we know we aren't doing a retransmission.
1117 * (retransmit and persist are mutually exclusive...)
1118 */
1119 if (sack_rxmit == 0) {
1120 if (len || (flags & (TH_SYN|TH_FIN)) ||
1121 tcp_timer_active(tp, TT_PERSIST))
1122 th->th_seq = htonl(tp->snd_nxt);
1123 else
1124 th->th_seq = htonl(tp->snd_max);
1125 } else {
1126 th->th_seq = htonl(p->rxmit);
1127 p->rxmit += len;
1128 tp->sackhint.sack_bytes_rexmit += len;
1129 }
1130 th->th_ack = htonl(tp->rcv_nxt);
1131 if (optlen) {
1132 bcopy(opt, th + 1, optlen);
1133 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
1134 }
1135 th->th_flags = flags;
1136 /*
1137 * Calculate receive window. Don't shrink window,
1138 * but avoid silly window syndrome.
1139 */
1140 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
1141 recwin < (long)tp->t_maxseg)
1142 recwin = 0;
1143 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
1144 recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
1145 recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
1146 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
1147 recwin = (long)TCP_MAXWIN << tp->rcv_scale;
1148
1149 /*
1150 * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1151 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>
1152 * case is handled in syncache.
1153 */
1154 if (flags & TH_SYN)
1155 th->th_win = htons((u_short)
1156 (min(sbspace(&so->so_rcv), TCP_MAXWIN)));
1157 else
1158 th->th_win = htons((u_short)(recwin >> tp->rcv_scale));
1159
1160 /*
1161 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1162 * a 0 window. This may cause the remote transmitter to stall. This
1163 * flag tells soreceive() to disable delayed acknowledgements when
1164 * draining the buffer. This can occur if the receiver is attempting
1165 * to read more data than can be buffered prior to transmitting on
1166 * the connection.
1167 */
1168 if (th->th_win == 0) {
1169 tp->t_sndzerowin++;
1170 tp->t_flags |= TF_RXWIN0SENT;
1171 } else
1172 tp->t_flags &= ~TF_RXWIN0SENT;
1173 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1174 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1175 th->th_flags |= TH_URG;
1176 } else
1177 /*
1178 * If no urgent pointer to send, then we pull
1179 * the urgent pointer to the left edge of the send window
1180 * so that it doesn't drift into the send window on sequence
1181 * number wraparound.
1182 */
1183 tp->snd_up = tp->snd_una; /* drag it along */
1184
1185#ifdef TCP_SIGNATURE
1186 if (tp->t_flags & TF_SIGNATURE) {
1187 int sigoff = to.to_signature - opt;
1188 tcp_signature_compute(m, 0, len, optlen,
1189 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1190 }
1191#endif
1192
1193 /*
1194 * Put TCP length in extended header, and then
1195 * checksum extended header and data.
1196 */
1197 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1198 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
1199#ifdef INET6
1200 if (isipv6) {
1201 /*
1202 * ip6_plen is not need to be filled now, and will be filled
1203 * in ip6_output.
1204 */
1205 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
1206 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
1207 optlen + len, IPPROTO_TCP, 0);
1208 }
1209#endif
1210#if defined(INET6) && defined(INET)
1211 else
1212#endif
1213#ifdef INET
1214 {
1215 m->m_pkthdr.csum_flags = CSUM_TCP;
1216 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
1217 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
1218
1219 /* IP version must be set here for ipv4/ipv6 checking later */
1220 KASSERT(ip->ip_v == IPVERSION,
1221 ("%s: IP version incorrect: %d", __func__, ip->ip_v));
1222 }
1223#endif
1224
1225 /*
1226 * Enable TSO and specify the size of the segments.
1227 * The TCP pseudo header checksum is always provided.
1228 */
1229 if (tso) {
1230 KASSERT(len > tp->t_maxopd - optlen,
1231 ("%s: len <= tso_segsz", __func__));
1232 m->m_pkthdr.csum_flags |= CSUM_TSO;
1233 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen;
1234 }
1235
1236#ifdef IPSEC
1237 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL),
1238 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u",
1239 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL)));
1240#else
1241 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL),
1242 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u",
1243 __func__, len, hdrlen, ipoptlen, m_length(m, NULL)));
1244#endif
1245
1246 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */
1247 hhook_run_tcp_est_out(tp, th, &to, len, tso);
1248
1249#ifdef TCPDEBUG
1250 /*
1251 * Trace.
1252 */
1253 if (so->so_options & SO_DEBUG) {
1254 u_short save = 0;
1255#ifdef INET6
1256 if (!isipv6)
1257#endif
1258 {
1259 save = ipov->ih_len;
1260 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */);
1261 }
1262 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0);
1263#ifdef INET6
1264 if (!isipv6)
1265#endif
1266 ipov->ih_len = save;
1267 }
1268#endif /* TCPDEBUG */
1269 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
1270
1271 /*
1272 * Fill in IP length and desired time to live and
1273 * send to IP level. There should be a better way
1274 * to handle ttl and tos; we could keep them in
1275 * the template, but need a way to checksum without them.
1276 */
1277 /*
1278 * m->m_pkthdr.len should have been set before checksum calculation,
1279 * because in6_cksum() need it.
1280 */
1281#ifdef INET6
1282 if (isipv6) {
1283 struct route_in6 ro;
1284
1285 bzero(&ro, sizeof(ro));
1286 /*
1287 * we separately set hoplimit for every segment, since the
1288 * user might want to change the value via setsockopt.
1289 * Also, desired default hop limit might be changed via
1290 * Neighbor Discovery.
1291 */
1292 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1293
1294 /*
1295 * Set the packet size here for the benefit of DTrace probes.
1296 * ip6_output() will set it properly; it's supposed to include
1297 * the option header lengths as well.
1298 */
1299 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6));
1300
1301 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss)
1302 tp->t_flags2 |= TF2_PLPMTU_PMTUD;
1303 else
1304 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
1305
1306 if (tp->t_state == TCPS_SYN_SENT)
1307 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th);
1308
1309 TCP_PROBE5(send, NULL, tp, ip6, tp, th);
1310
|
1364 error = ip_output(m, tp->t_inpcb->inp_options, &ro,
1365 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0,
1366 tp->t_inpcb);
1367
1368 if (error == EMSGSIZE && ro.ro_rt != NULL)
1369 mtu = ro.ro_rt->rt_mtu;
1370 RO_RTFREE(&ro);
1371 }
1372#endif /* INET */
1373
1374out:
1375 /*
1376 * In transmit state, time the transmission and arrange for
1377 * the retransmit. In persist state, just set snd_max.
1378 */
1379 if ((tp->t_flags & TF_FORCEDATA) == 0 ||
1380 !tcp_timer_active(tp, TT_PERSIST)) {
1381 tcp_seq startseq = tp->snd_nxt;
1382
1383 /*
1384 * Advance snd_nxt over sequence space of this segment.
1385 */
1386 if (flags & (TH_SYN|TH_FIN)) {
1387 if (flags & TH_SYN)
1388 tp->snd_nxt++;
1389 if (flags & TH_FIN) {
1390 tp->snd_nxt++;
1391 tp->t_flags |= TF_SENTFIN;
1392 }
1393 }
1394 if (sack_rxmit)
1395 goto timer;
1396 tp->snd_nxt += len;
1397 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1398 tp->snd_max = tp->snd_nxt;
1399 /*
1400 * Time this transmission if not a retransmission and
1401 * not currently timing anything.
1402 */
1403 if (tp->t_rtttime == 0) {
1404 tp->t_rtttime = ticks;
1405 tp->t_rtseq = startseq;
1406 TCPSTAT_INC(tcps_segstimed);
1407 }
1408 }
1409
1410 /*
1411 * Set retransmit timer if not currently set,
1412 * and not doing a pure ack or a keep-alive probe.
1413 * Initial value for retransmit timer is smoothed
1414 * round-trip time + 2 * round-trip time variance.
1415 * Initialize shift counter which is used for backoff
1416 * of retransmit time.
1417 */
1418timer:
1419 if (!tcp_timer_active(tp, TT_REXMT) &&
1420 ((sack_rxmit && tp->snd_nxt != tp->snd_max) ||
1421 (tp->snd_nxt != tp->snd_una))) {
1422 if (tcp_timer_active(tp, TT_PERSIST)) {
1423 tcp_timer_activate(tp, TT_PERSIST, 0);
1424 tp->t_rxtshift = 0;
1425 }
1426 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1427 } else if (len == 0 && sbavail(&so->so_snd) &&
1428 !tcp_timer_active(tp, TT_REXMT) &&
1429 !tcp_timer_active(tp, TT_PERSIST)) {
1430 /*
1431 * Avoid a situation where we do not set persist timer
1432 * after a zero window condition. For example:
1433 * 1) A -> B: packet with enough data to fill the window
1434 * 2) B -> A: ACK for #1 + new data (0 window
1435 * advertisement)
1436 * 3) A -> B: ACK for #2, 0 len packet
1437 *
1438 * In this case, A will not activate the persist timer,
1439 * because it chose to send a packet. Unless tcp_output
1440 * is called for some other reason (delayed ack timer,
1441 * another input packet from B, socket syscall), A will
1442 * not send zero window probes.
1443 *
1444 * So, if you send a 0-length packet, but there is data
1445 * in the socket buffer, and neither the rexmt or
1446 * persist timer is already set, then activate the
1447 * persist timer.
1448 */
1449 tp->t_rxtshift = 0;
1450 tcp_setpersist(tp);
1451 }
1452 } else {
1453 /*
1454 * Persist case, update snd_max but since we are in
1455 * persist mode (no window) we do not update snd_nxt.
1456 */
1457 int xlen = len;
1458 if (flags & TH_SYN)
1459 ++xlen;
1460 if (flags & TH_FIN) {
1461 ++xlen;
1462 tp->t_flags |= TF_SENTFIN;
1463 }
1464 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1465 tp->snd_max = tp->snd_nxt + len;
1466 }
1467
1468 if (error) {
1469
1470 /*
1471 * We know that the packet was lost, so back out the
1472 * sequence number advance, if any.
1473 *
1474 * If the error is EPERM the packet got blocked by the
1475 * local firewall. Normally we should terminate the
1476 * connection but the blocking may have been spurious
1477 * due to a firewall reconfiguration cycle. So we treat
1478 * it like a packet loss and let the retransmit timer and
1479 * timeouts do their work over time.
1480 * XXX: It is a POLA question whether calling tcp_drop right
1481 * away would be the really correct behavior instead.
1482 */
1483 if (((tp->t_flags & TF_FORCEDATA) == 0 ||
1484 !tcp_timer_active(tp, TT_PERSIST)) &&
1485 ((flags & TH_SYN) == 0) &&
1486 (error != EPERM)) {
1487 if (sack_rxmit) {
1488 p->rxmit -= len;
1489 tp->sackhint.sack_bytes_rexmit -= len;
1490 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
1491 ("sackhint bytes rtx >= 0"));
1492 } else
1493 tp->snd_nxt -= len;
1494 }
1495 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */
1496 switch (error) {
1497 case EPERM:
1498 tp->t_softerror = error;
1499 return (error);
1500 case ENOBUFS:
1501 if (!tcp_timer_active(tp, TT_REXMT) &&
1502 !tcp_timer_active(tp, TT_PERSIST))
1503 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
1504 tp->snd_cwnd = tp->t_maxseg;
1505 return (0);
1506 case EMSGSIZE:
1507 /*
1508 * For some reason the interface we used initially
1509 * to send segments changed to another or lowered
1510 * its MTU.
1511 * If TSO was active we either got an interface
1512 * without TSO capabilits or TSO was turned off.
1513 * If we obtained mtu from ip_output() then update
1514 * it and try again.
1515 */
1516 if (tso)
1517 tp->t_flags &= ~TF_TSO;
1518 if (mtu != 0) {
1519 tcp_mss_update(tp, -1, mtu, NULL, NULL);
1520 goto again;
1521 }
1522 return (error);
1523 case EHOSTDOWN:
1524 case EHOSTUNREACH:
1525 case ENETDOWN:
1526 case ENETUNREACH:
1527 if (TCPS_HAVERCVDSYN(tp->t_state)) {
1528 tp->t_softerror = error;
1529 return (0);
1530 }
1531 /* FALLTHROUGH */
1532 default:
1533 return (error);
1534 }
1535 }
1536 TCPSTAT_INC(tcps_sndtotal);
1537
1538 /*
1539 * Data sent (as far as we can tell).
1540 * If this advertises a larger window than any other segment,
1541 * then remember the size of the advertised window.
1542 * Any pending ACK has now been sent.
1543 */
1544 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv))
1545 tp->rcv_adv = tp->rcv_nxt + recwin;
1546 tp->last_ack_sent = tp->rcv_nxt;
1547 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK);
1548 if (tcp_timer_active(tp, TT_DELACK))
1549 tcp_timer_activate(tp, TT_DELACK, 0);
1550#if 0
1551 /*
1552 * This completely breaks TCP if newreno is turned on. What happens
1553 * is that if delayed-acks are turned on on the receiver, this code
1554 * on the transmitter effectively destroys the TCP window, forcing
1555 * it to four packets (1.5Kx4 = 6K window).
1556 */
1557 if (sendalot && --maxburst)
1558 goto again;
1559#endif
1560 if (sendalot)
1561 goto again;
1562 return (0);
1563}
1564
1565void
1566tcp_setpersist(struct tcpcb *tp)
1567{
1568 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1569 int tt;
1570
1571 tp->t_flags &= ~TF_PREVVALID;
1572 if (tcp_timer_active(tp, TT_REXMT))
1573 panic("tcp_setpersist: retransmit pending");
1574 /*
1575 * Start/restart persistance timer.
1576 */
1577 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
1578 TCPTV_PERSMIN, TCPTV_PERSMAX);
1579 tcp_timer_activate(tp, TT_PERSIST, tt);
1580 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1581 tp->t_rxtshift++;
1582}
1583
1584/*
1585 * Insert TCP options according to the supplied parameters to the place
1586 * optp in a consistent way. Can handle unaligned destinations.
1587 *
1588 * The order of the option processing is crucial for optimal packing and
1589 * alignment for the scarce option space.
1590 *
1591 * The optimal order for a SYN/SYN-ACK segment is:
1592 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) +
1593 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40.
1594 *
1595 * The SACK options should be last. SACK blocks consume 8*n+2 bytes.
1596 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks).
1597 * At minimum we need 10 bytes (to generate 1 SACK block). If both
1598 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present,
1599 * we only have 10 bytes for SACK options (40 - (12 + 18)).
1600 */
1601int
1602tcp_addoptions(struct tcpopt *to, u_char *optp)
1603{
1604 u_int mask, optlen = 0;
1605
1606 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) {
1607 if ((to->to_flags & mask) != mask)
1608 continue;
1609 if (optlen == TCP_MAXOLEN)
1610 break;
1611 switch (to->to_flags & mask) {
1612 case TOF_MSS:
1613 while (optlen % 4) {
1614 optlen += TCPOLEN_NOP;
1615 *optp++ = TCPOPT_NOP;
1616 }
1617 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG)
1618 continue;
1619 optlen += TCPOLEN_MAXSEG;
1620 *optp++ = TCPOPT_MAXSEG;
1621 *optp++ = TCPOLEN_MAXSEG;
1622 to->to_mss = htons(to->to_mss);
1623 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss));
1624 optp += sizeof(to->to_mss);
1625 break;
1626 case TOF_SCALE:
1627 while (!optlen || optlen % 2 != 1) {
1628 optlen += TCPOLEN_NOP;
1629 *optp++ = TCPOPT_NOP;
1630 }
1631 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW)
1632 continue;
1633 optlen += TCPOLEN_WINDOW;
1634 *optp++ = TCPOPT_WINDOW;
1635 *optp++ = TCPOLEN_WINDOW;
1636 *optp++ = to->to_wscale;
1637 break;
1638 case TOF_SACKPERM:
1639 while (optlen % 2) {
1640 optlen += TCPOLEN_NOP;
1641 *optp++ = TCPOPT_NOP;
1642 }
1643 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED)
1644 continue;
1645 optlen += TCPOLEN_SACK_PERMITTED;
1646 *optp++ = TCPOPT_SACK_PERMITTED;
1647 *optp++ = TCPOLEN_SACK_PERMITTED;
1648 break;
1649 case TOF_TS:
1650 while (!optlen || optlen % 4 != 2) {
1651 optlen += TCPOLEN_NOP;
1652 *optp++ = TCPOPT_NOP;
1653 }
1654 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP)
1655 continue;
1656 optlen += TCPOLEN_TIMESTAMP;
1657 *optp++ = TCPOPT_TIMESTAMP;
1658 *optp++ = TCPOLEN_TIMESTAMP;
1659 to->to_tsval = htonl(to->to_tsval);
1660 to->to_tsecr = htonl(to->to_tsecr);
1661 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval));
1662 optp += sizeof(to->to_tsval);
1663 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr));
1664 optp += sizeof(to->to_tsecr);
1665 break;
1666 case TOF_SIGNATURE:
1667 {
1668 int siglen = TCPOLEN_SIGNATURE - 2;
1669
1670 while (!optlen || optlen % 4 != 2) {
1671 optlen += TCPOLEN_NOP;
1672 *optp++ = TCPOPT_NOP;
1673 }
1674 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE)
1675 continue;
1676 optlen += TCPOLEN_SIGNATURE;
1677 *optp++ = TCPOPT_SIGNATURE;
1678 *optp++ = TCPOLEN_SIGNATURE;
1679 to->to_signature = optp;
1680 while (siglen--)
1681 *optp++ = 0;
1682 break;
1683 }
1684 case TOF_SACK:
1685 {
1686 int sackblks = 0;
1687 struct sackblk *sack = (struct sackblk *)to->to_sacks;
1688 tcp_seq sack_seq;
1689
1690 while (!optlen || optlen % 4 != 2) {
1691 optlen += TCPOLEN_NOP;
1692 *optp++ = TCPOPT_NOP;
1693 }
1694 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK)
1695 continue;
1696 optlen += TCPOLEN_SACKHDR;
1697 *optp++ = TCPOPT_SACK;
1698 sackblks = min(to->to_nsacks,
1699 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK);
1700 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK;
1701 while (sackblks--) {
1702 sack_seq = htonl(sack->start);
1703 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1704 optp += sizeof(sack_seq);
1705 sack_seq = htonl(sack->end);
1706 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq));
1707 optp += sizeof(sack_seq);
1708 optlen += TCPOLEN_SACK;
1709 sack++;
1710 }
1711 TCPSTAT_INC(tcps_sack_send_blocks);
1712 break;
1713 }
1714 default:
1715 panic("%s: unknown TCP option type", __func__);
1716 break;
1717 }
1718 }
1719
1720 /* Terminate and pad TCP options to a 4 byte boundary. */
1721 if (optlen % 4) {
1722 optlen += TCPOLEN_EOL;
1723 *optp++ = TCPOPT_EOL;
1724 }
1725 /*
1726 * According to RFC 793 (STD0007):
1727 * "The content of the header beyond the End-of-Option option
1728 * must be header padding (i.e., zero)."
1729 * and later: "The padding is composed of zeros."
1730 */
1731 while (optlen % 4) {
1732 optlen += TCPOLEN_PAD;
1733 *optp++ = TCPOPT_PAD;
1734 }
1735
1736 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__));
1737 return (optlen);
1738}
|