1 /*
2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
4 *
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of The DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 /*
35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. Neither the name of the University nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60 * SUCH DAMAGE.
61 *
62 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95
63 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $
64 */
65
66 #include "opt_inet.h"
67 #include "opt_inet6.h"
68 #include "opt_tcpdebug.h"
69
70 #include <sys/param.h>
71 #include <sys/systm.h>
72 #include <sys/kernel.h>
73 #include <sys/malloc.h> /* for M_NOWAIT */
74 #include <sys/sysctl.h>
75 #include <sys/mbuf.h>
76 #include <sys/domain.h>
77 #include <sys/protosw.h>
78 #include <sys/socket.h>
79 #include <sys/socketvar.h>
80 #include <sys/in_cksum.h>
81 #include <sys/thread.h>
82 #include <sys/globaldata.h>
83
84 #include <net/if.h>
85 #include <net/if_var.h>
86 #include <net/route.h>
87 #include <net/netmsg2.h>
88 #include <net/netisr2.h>
89
90 #include <netinet/in.h>
91 #include <netinet/in_systm.h>
92 #include <netinet/ip.h>
93 #include <netinet/in_pcb.h>
94 #include <netinet/ip_var.h>
95 #include <netinet6/in6_pcb.h>
96 #include <netinet/ip6.h>
97 #include <netinet6/ip6_var.h>
98 #include <netinet/tcp.h>
99 #define TCPOUTFLAGS
100 #include <netinet/tcp_fsm.h>
101 #include <netinet/tcp_seq.h>
102 #include <netinet/tcp_timer.h>
103 #include <netinet/tcp_timer2.h>
104 #include <netinet/tcp_var.h>
105 #include <netinet/tcpip.h>
106 #ifdef TCPDEBUG
107 #include <netinet/tcp_debug.h>
108 #endif
109
110 #ifdef notyet
111 extern struct mbuf *m_copypack();
112 #endif
113
114 int path_mtu_discovery = 1;
115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW,
116 &path_mtu_discovery, 1, "Enable Path MTU Discovery");
117
118 static int avoid_pure_win_update = 1;
119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW,
120 &avoid_pure_win_update, 1, "Avoid pure window updates when possible");
121
122 /*
123 * 1 - enabled for increasing and decreasing the buffer size
124 * 2 - enabled only for increasing the buffer size
125 */
126 int tcp_do_autosndbuf = 1;
127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW,
128 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing");
129
130 int tcp_autosndbuf_inc = 8*1024;
131 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW,
132 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer");
133
134 int tcp_autosndbuf_min = 32768;
135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_min, CTLFLAG_RW,
136 &tcp_autosndbuf_min, 0, "Min size of automatic send buffer");
137
138 int tcp_autosndbuf_max = 2*1024*1024;
139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW,
140 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer");
141
142 int tcp_prio_synack = 1;
143 SYSCTL_INT(_net_inet_tcp, OID_AUTO, prio_synack, CTLFLAG_RW,
144 &tcp_prio_synack, 0, "Prioritize SYN, SYN|ACK and pure ACK");
145
146 static int tcp_idle_cwv = 1;
147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_cwv, CTLFLAG_RW,
148 &tcp_idle_cwv, 0,
149 "Congestion window validation after idle period (part of RFC2861)");
150
151 static int tcp_idle_restart = 1;
152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, idle_restart, CTLFLAG_RW,
153 &tcp_idle_restart, 0, "Reset congestion window after idle period");
154
155 static int tcp_do_tso = 1;
156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW,
157 &tcp_do_tso, 0, "Enable TCP Segmentation Offload (TSO)");
158
159 static int tcp_fairsend = 4;
160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fairsend, CTLFLAG_RW,
161 &tcp_fairsend, 0,
162 "Amount of segments sent before yield to other senders or receivers");
163
164 static void tcp_idle_cwnd_validate(struct tcpcb *);
165
166 static int tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen);
167 static void tcp_output_sched(struct tcpcb *tp);
168
169 /*
170 * Tcp output routine: figure out what should be sent and send it.
171 */
172 int
tcp_output(struct tcpcb * tp)173 tcp_output(struct tcpcb *tp)
174 {
175 struct inpcb * const inp = tp->t_inpcb;
176 struct socket *so = inp->inp_socket;
177 long len, recvwin, sendwin;
178 int nsacked = 0;
179 int off, flags, error = 0;
180 #ifdef TCP_SIGNATURE
181 int sigoff = 0;
182 #endif
183 struct mbuf *m;
184 struct ip *ip;
185 struct tcphdr *th;
186 u_char opt[TCP_MAXOLEN];
187 unsigned int ipoptlen, optlen, hdrlen;
188 int idle;
189 boolean_t sendalot;
190 struct ip6_hdr *ip6;
191 #ifdef INET6
192 const boolean_t isipv6 = INP_ISIPV6(inp);
193 #else
194 const boolean_t isipv6 = FALSE;
195 #endif
196 boolean_t can_tso = FALSE, use_tso;
197 boolean_t report_sack, idle_cwv = FALSE;
198 u_int segsz, tso_hlen, tso_lenmax = 0;
199 int segcnt = 0;
200 boolean_t need_sched = FALSE;
201
202 KKASSERT(so->so_port == &curthread->td_msgport);
203
204 /*
205 * Determine length of data that should be transmitted,
206 * and flags that will be used.
207 * If there is some data or critical controls (SYN, RST)
208 * to send, then transmit; otherwise, investigate further.
209 */
210
211 /*
212 * If we have been idle for a while, the send congestion window
213 * could be no longer representative of the current state of the
214 * link; need to validate congestion window. However, we should
215 * not perform congestion window validation here, since we could
216 * be asked to send pure ACK.
217 */
218 if (tp->snd_max == tp->snd_una &&
219 (ticks - tp->snd_last) >= tp->t_rxtcur && tcp_idle_restart)
220 idle_cwv = TRUE;
221
222 /*
223 * Calculate whether the transmit stream was previously idle
224 * and adjust TF_LASTIDLE for the next time.
225 */
226 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
227 if (idle && (tp->t_flags & TF_MORETOCOME))
228 tp->t_flags |= TF_LASTIDLE;
229 else
230 tp->t_flags &= ~TF_LASTIDLE;
231
232 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
233 !IN_FASTRECOVERY(tp))
234 nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt);
235
236 /*
237 * Find out whether TSO could be used or not
238 *
239 * For TSO capable devices, the following assumptions apply to
240 * the processing of TCP flags:
241 * - If FIN is set on the large TCP segment, the device must set
242 * FIN on the last segment that it creates from the large TCP
243 * segment.
244 * - If PUSH is set on the large TCP segment, the device must set
245 * PUSH on the last segment that it creates from the large TCP
246 * segment.
247 */
248 if (tcp_do_tso
249 #ifdef TCP_SIGNATURE
250 && (tp->t_flags & TF_SIGNATURE) == 0
251 #endif
252 ) {
253 if (!isipv6) {
254 struct rtentry *rt = inp->inp_route.ro_rt;
255
256 if (rt != NULL && (rt->rt_flags & RTF_UP) &&
257 (rt->rt_ifp->if_hwassist & CSUM_TSO)) {
258 can_tso = TRUE;
259 tso_lenmax = rt->rt_ifp->if_tsolen;
260 }
261 }
262 }
263
264 again:
265 m = NULL;
266 ip = NULL;
267 th = NULL;
268 ip6 = NULL;
269
270 if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) ==
271 TF_SACK_PERMITTED &&
272 (!TAILQ_EMPTY(&tp->t_segq) ||
273 tp->reportblk.rblk_start != tp->reportblk.rblk_end))
274 report_sack = TRUE;
275 else
276 report_sack = FALSE;
277
278 /* Make use of SACK information when slow-starting after a RTO. */
279 if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
280 !IN_FASTRECOVERY(tp)) {
281 tcp_seq old_snd_nxt = tp->snd_nxt;
282
283 tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt);
284 nsacked += tp->snd_nxt - old_snd_nxt;
285 }
286
287 sendalot = FALSE;
288 off = tp->snd_nxt - tp->snd_una;
289 sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked);
290 sendwin = min(sendwin, tp->snd_bwnd);
291
292 flags = tcp_outflags[tp->t_state];
293 /*
294 * Get standard flags, and add SYN or FIN if requested by 'hidden'
295 * state flags.
296 */
297 if (tp->t_flags & TF_NEEDFIN)
298 flags |= TH_FIN;
299 if (tp->t_flags & TF_NEEDSYN)
300 flags |= TH_SYN;
301
302 /*
303 * If in persist timeout with window of 0, send 1 byte.
304 * Otherwise, if window is small but nonzero
305 * and timer expired, we will send what we can
306 * and go to transmit state.
307 */
308 if (tp->t_flags & TF_FORCE) {
309 if (sendwin == 0) {
310 /*
311 * If we still have some data to send, then
312 * clear the FIN bit. Usually this would
313 * happen below when it realizes that we
314 * aren't sending all the data. However,
315 * if we have exactly 1 byte of unsent data,
316 * then it won't clear the FIN bit below,
317 * and if we are in persist state, we wind
318 * up sending the packet without recording
319 * that we sent the FIN bit.
320 *
321 * We can't just blindly clear the FIN bit,
322 * because if we don't have any more data
323 * to send then the probe will be the FIN
324 * itself.
325 */
326 if (off < so->so_snd.ssb_cc)
327 flags &= ~TH_FIN;
328 sendwin = 1;
329 } else {
330 tcp_callout_stop(tp, tp->tt_persist);
331 tp->t_rxtshift = 0;
332 }
333 }
334
335 /*
336 * If snd_nxt == snd_max and we have transmitted a FIN, the
337 * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in
338 * a negative length. This can also occur when TCP opens up
339 * its congestion window while receiving additional duplicate
340 * acks after fast-retransmit because TCP will reset snd_nxt
341 * to snd_max after the fast-retransmit.
342 *
343 * A negative length can also occur when we are in the
344 * TCPS_SYN_RECEIVED state due to a simultanious connect where
345 * our SYN has not been acked yet.
346 *
347 * In the normal retransmit-FIN-only case, however, snd_nxt will
348 * be set to snd_una, the offset will be 0, and the length may
349 * wind up 0.
350 */
351 len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off;
352
353 /*
354 * Lop off SYN bit if it has already been sent. However, if this
355 * is SYN-SENT state and if segment contains data, suppress sending
356 * segment (sending the segment would be an option if we still
357 * did TAO and the remote host supported it).
358 */
359 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) {
360 flags &= ~TH_SYN;
361 off--, len++;
362 if (len > 0 && tp->t_state == TCPS_SYN_SENT) {
363 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW);
364 return 0;
365 }
366 }
367
368 /*
369 * Be careful not to send data and/or FIN on SYN segments.
370 * This measure is needed to prevent interoperability problems
371 * with not fully conformant TCP implementations.
372 */
373 if (flags & TH_SYN) {
374 len = 0;
375 flags &= ~TH_FIN;
376 }
377
378 if (len < 0) {
379 /*
380 * A negative len can occur if our FIN has been sent but not
381 * acked, or if we are in a simultanious connect in the
382 * TCPS_SYN_RECEIVED state with our SYN sent but not yet
383 * acked.
384 *
385 * If our window has contracted to 0 in the FIN case
386 * (which can only occur if we have NOT been called to
387 * retransmit as per code a few paragraphs up) then we
388 * want to shift the retransmit timer over to the
389 * persist timer.
390 *
391 * However, if we are in the TCPS_SYN_RECEIVED state
392 * (the SYN case) we will be in a simultanious connect and
393 * the window may be zero degeneratively. In this case we
394 * do not want to shift to the persist timer after the SYN
395 * or the SYN+ACK transmission.
396 */
397 len = 0;
398 if (sendwin == 0 && tp->t_state != TCPS_SYN_RECEIVED) {
399 tcp_callout_stop(tp, tp->tt_rexmt);
400 tp->t_rxtshift = 0;
401 tp->snd_nxt = tp->snd_una;
402 if (!tcp_callout_active(tp, tp->tt_persist))
403 tcp_setpersist(tp);
404 }
405 }
406
407 KASSERT(len >= 0, ("%s: len < 0", __func__));
408 /*
409 * Automatic sizing of send socket buffer. Often the send buffer
410 * size is not optimally adjusted to the actual network conditions
411 * at hand (delay bandwidth product). Setting the buffer size too
412 * small limits throughput on links with high bandwidth and high
413 * delay (eg. trans-continental/oceanic links). Setting the
414 * buffer size too big consumes too much real kernel memory,
415 * especially with many connections on busy servers.
416 *
417 * The criteria to step up the send buffer one notch are:
418 * 1. receive window of remote host is larger than send buffer
419 * (with a fudge factor of 5/4th);
420 * 2. hiwat has not significantly exceeded bwnd (inflight)
421 * (bwnd is a maximal value if inflight is disabled).
422 * 3. send buffer is filled to 7/8th with data (so we actually
423 * have data to make use of it);
424 * 4. hiwat has not hit maximal automatic size;
425 * 5. our send window (slow start and cogestion controlled) is
426 * larger than sent but unacknowledged data in send buffer.
427 *
428 * The remote host receive window scaling factor may limit the
429 * growing of the send buffer before it reaches its allowed
430 * maximum.
431 *
432 * It scales directly with slow start or congestion window
433 * and does at most one step per received ACK. This fast
434 * scaling has the drawback of growing the send buffer beyond
435 * what is strictly necessary to make full use of a given
436 * delay*bandwith product. However testing has shown this not
437 * to be much of an problem. At worst we are trading wasting
438 * of available bandwith (the non-use of it) for wasting some
439 * socket buffer memory.
440 *
441 * The criteria for shrinking the buffer is based solely on
442 * the inflight code (snd_bwnd). If inflight is disabled,
443 * the buffer will not be shrinked. Note that snd_bwnd already
444 * has a fudge factor. Our test adds a little hysteresis.
445 */
446 if (tcp_do_autosndbuf && (so->so_snd.ssb_flags & SSB_AUTOSIZE)) {
447 const int asbinc = tcp_autosndbuf_inc;
448 const int hiwat = so->so_snd.ssb_hiwat;
449 const int lowat = so->so_snd.ssb_lowat;
450 u_long newsize;
451
452 if ((tp->snd_wnd / 4 * 5) >= hiwat &&
453 so->so_snd.ssb_cc >= (hiwat / 8 * 7) &&
454 hiwat < tp->snd_bwnd + hiwat / 10 &&
455 hiwat + asbinc < tcp_autosndbuf_max &&
456 hiwat < (TCP_MAXWIN << tp->snd_scale) &&
457 sendwin >= (so->so_snd.ssb_cc -
458 (tp->snd_nxt - tp->snd_una))) {
459 newsize = ulmin(hiwat + asbinc, tcp_autosndbuf_max);
460 if (!ssb_reserve(&so->so_snd, newsize, so, NULL))
461 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
462 #if 0
463 if (newsize >= (TCP_MAXWIN << tp->snd_scale))
464 atomic_clear_int(&so->so_snd.ssb_flags, SSB_AUTOSIZE);
465 #endif
466 } else if ((long)tp->snd_bwnd <
467 (long)(hiwat * 3 / 4 - lowat - asbinc) &&
468 hiwat > tp->t_maxseg * 2 + asbinc &&
469 hiwat + asbinc >= tcp_autosndbuf_min &&
470 tcp_do_autosndbuf == 1) {
471 newsize = ulmax(hiwat - asbinc, tp->t_maxseg * 2);
472 ssb_reserve(&so->so_snd, newsize, so, NULL);
473 }
474 }
475
476 /*
477 * Don't use TSO, if:
478 * - Congestion window needs validation
479 * - There are SACK blocks to report
480 * - RST or SYN flags is set
481 * - URG will be set
482 *
483 * XXX
484 * Checking for SYN|RST looks overkill, just to be safe than sorry
485 */
486 use_tso = can_tso;
487 if (report_sack || idle_cwv || (flags & (TH_RST | TH_SYN)))
488 use_tso = FALSE;
489 if (use_tso) {
490 tcp_seq ugr_nxt = tp->snd_nxt;
491
492 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) &&
493 tp->snd_nxt == tp->snd_max)
494 --ugr_nxt;
495
496 if (SEQ_GT(tp->snd_up, ugr_nxt))
497 use_tso = FALSE;
498 }
499
500 if (use_tso) {
501 /*
502 * Find out segment size and header length for TSO
503 */
504 error = tcp_tso_getsize(tp, &segsz, &tso_hlen);
505 if (error)
506 use_tso = FALSE;
507 }
508 if (!use_tso) {
509 segsz = tp->t_maxseg;
510 tso_hlen = 0; /* not used */
511 }
512
513 /*
514 * Truncate to the maximum segment length if not TSO, and ensure that
515 * FIN is removed if the length no longer contains the last data byte.
516 */
517 if (len > segsz) {
518 if (!use_tso) {
519 len = segsz;
520 ++segcnt;
521 } else {
522 int nsegs;
523
524 if (__predict_false(tso_lenmax < segsz))
525 tso_lenmax = segsz << 1;
526
527 /*
528 * Truncate TSO transfers to (IP_MAXPACKET - iphlen -
529 * thoff), and make sure that we send equal size
530 * transfers down the stack (rather than big-small-
531 * big-small-...).
532 */
533 len = min(len, tso_lenmax);
534 nsegs = min(len, (IP_MAXPACKET - tso_hlen)) / segsz;
535 KKASSERT(nsegs > 0);
536
537 len = nsegs * segsz;
538
539 if (len <= segsz) {
540 use_tso = FALSE;
541 ++segcnt;
542 } else {
543 segcnt += nsegs;
544 }
545 }
546 sendalot = TRUE;
547 } else {
548 use_tso = FALSE;
549 if (len > 0)
550 ++segcnt;
551 }
552 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc))
553 flags &= ~TH_FIN;
554
555 recvwin = ssb_space(&so->so_rcv);
556
557 /*
558 * Sender silly window avoidance. We transmit under the following
559 * conditions when len is non-zero:
560 *
561 * - We have a full segment
562 * - This is the last buffer in a write()/send() and we are
563 * either idle or running NODELAY
564 * - we've timed out (e.g. persist timer)
565 * - we have more then 1/2 the maximum send window's worth of
566 * data (receiver may be limiting the window size)
567 * - we need to retransmit
568 */
569 if (len) {
570 if (len >= segsz)
571 goto send;
572 /*
573 * NOTE! on localhost connections an 'ack' from the remote
574 * end may occur synchronously with the output and cause
575 * us to flush a buffer queued with moretocome. XXX
576 *
577 * note: the len + off check is almost certainly unnecessary.
578 */
579 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */
580 (idle || (tp->t_flags & TF_NODELAY)) &&
581 len + off >= so->so_snd.ssb_cc &&
582 !(tp->t_flags & TF_NOPUSH)) {
583 goto send;
584 }
585 if (tp->t_flags & TF_FORCE) /* typ. timeout case */
586 goto send;
587 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
588 goto send;
589 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */
590 goto send;
591 if (tp->t_flags & TF_XMITNOW)
592 goto send;
593 }
594
595 /*
596 * Compare available window to amount of window
597 * known to peer (as advertised window less
598 * next expected input). If the difference is at least two
599 * max size segments, or at least 50% of the maximum possible
600 * window, then want to send a window update to peer.
601 */
602 if (recvwin > 0) {
603 /*
604 * "adv" is the amount we can increase the window,
605 * taking into account that we are limited by
606 * TCP_MAXWIN << tp->rcv_scale.
607 */
608 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) -
609 (tp->rcv_adv - tp->rcv_nxt);
610 long hiwat;
611
612 /*
613 * This ack case typically occurs when the user has drained
614 * the TCP socket buffer sufficiently to warrent an ack
615 * containing a 'pure window update'... that is, an ack that
616 * ONLY updates the tcp window.
617 *
618 * It is unclear why we would need to do a pure window update
619 * past 2 segments if we are going to do one at 1/2 the high
620 * water mark anyway, especially since under normal conditions
621 * the user program will drain the socket buffer quickly.
622 * The 2-segment pure window update will often add a large
623 * number of extra, unnecessary acks to the stream.
624 *
625 * avoid_pure_win_update now defaults to 1.
626 */
627 if (avoid_pure_win_update == 0 ||
628 (tp->t_flags & TF_RXRESIZED)) {
629 if (adv >= (long) (2 * segsz)) {
630 goto send;
631 }
632 }
633 hiwat = (long)(TCP_MAXWIN << tp->rcv_scale);
634 if (hiwat > (long)so->so_rcv.ssb_hiwat)
635 hiwat = (long)so->so_rcv.ssb_hiwat;
636 if (adv >= hiwat / 2)
637 goto send;
638 }
639
640 /*
641 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW
642 * is also a catch-all for the retransmit timer timeout case.
643 */
644 if (tp->t_flags & TF_ACKNOW)
645 goto send;
646 if ((flags & TH_RST) ||
647 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN)))
648 goto send;
649 if (SEQ_GT(tp->snd_up, tp->snd_una))
650 goto send;
651 /*
652 * If our state indicates that FIN should be sent
653 * and we have not yet done so, then we need to send.
654 */
655 if ((flags & TH_FIN) &&
656 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una))
657 goto send;
658
659 /*
660 * TCP window updates are not reliable, rather a polling protocol
661 * using ``persist'' packets is used to insure receipt of window
662 * updates. The three ``states'' for the output side are:
663 * idle not doing retransmits or persists
664 * persisting to move a small or zero window
665 * (re)transmitting and thereby not persisting
666 *
667 * tcp_callout_active(tp, tp->tt_persist)
668 * is true when we are in persist state.
669 * The TF_FORCE flag in tp->t_flags
670 * is set when we are called to send a persist packet.
671 * tcp_callout_active(tp, tp->tt_rexmt)
672 * is set when we are retransmitting
673 * The output side is idle when both timers are zero.
674 *
675 * If send window is too small, there is data to transmit, and no
676 * retransmit or persist is pending, then go to persist state.
677 *
678 * If nothing happens soon, send when timer expires:
679 * if window is nonzero, transmit what we can, otherwise force out
680 * a byte.
681 *
682 * Don't try to set the persist state if we are in TCPS_SYN_RECEIVED
683 * with data pending. This situation can occur during a
684 * simultanious connect.
685 */
686 if (so->so_snd.ssb_cc > 0 &&
687 tp->t_state != TCPS_SYN_RECEIVED &&
688 !tcp_callout_active(tp, tp->tt_rexmt) &&
689 !tcp_callout_active(tp, tp->tt_persist)) {
690 tp->t_rxtshift = 0;
691 tcp_setpersist(tp);
692 }
693
694 /*
695 * No reason to send a segment, just return.
696 */
697 tp->t_flags &= ~TF_XMITNOW;
698 return (0);
699
700 send:
701 if (need_sched && len > 0) {
702 tcp_output_sched(tp);
703 return 0;
704 }
705
706 /*
707 * Before ESTABLISHED, force sending of initial options
708 * unless TCP set not to do any options.
709 * NOTE: we assume that the IP/TCP header plus TCP options
710 * always fit in a single mbuf, leaving room for a maximum
711 * link header, i.e.
712 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES
713 */
714 optlen = 0;
715 if (isipv6)
716 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
717 else
718 hdrlen = sizeof(struct tcpiphdr);
719 if (flags & TH_SYN) {
720 tp->snd_nxt = tp->iss;
721 if (!(tp->t_flags & TF_NOOPT)) {
722 u_short mss;
723
724 opt[0] = TCPOPT_MAXSEG;
725 opt[1] = TCPOLEN_MAXSEG;
726 mss = htons((u_short) tcp_mssopt(tp));
727 memcpy(opt + 2, &mss, sizeof mss);
728 optlen = TCPOLEN_MAXSEG;
729
730 if ((tp->t_flags & TF_REQ_SCALE) &&
731 (!(flags & TH_ACK) ||
732 (tp->t_flags & TF_RCVD_SCALE))) {
733 *((u_int32_t *)(opt + optlen)) = htonl(
734 TCPOPT_NOP << 24 |
735 TCPOPT_WINDOW << 16 |
736 TCPOLEN_WINDOW << 8 |
737 tp->request_r_scale);
738 optlen += 4;
739 }
740
741 if ((tcp_do_sack && !(flags & TH_ACK)) ||
742 tp->t_flags & TF_SACK_PERMITTED) {
743 uint32_t *lp = (uint32_t *)(opt + optlen);
744
745 *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED);
746 optlen += TCPOLEN_SACK_PERMITTED_ALIGNED;
747 }
748 }
749 }
750
751 /*
752 * Send a timestamp and echo-reply if this is a SYN and our side
753 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
754 * and our peer have sent timestamps in our SYN's.
755 */
756 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
757 !(flags & TH_RST) &&
758 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) {
759 u_int32_t *lp = (u_int32_t *)(opt + optlen);
760
761 /* Form timestamp option as shown in appendix A of RFC 1323. */
762 *lp++ = htonl(TCPOPT_TSTAMP_HDR);
763 *lp++ = htonl(ticks);
764 *lp = htonl(tp->ts_recent);
765 optlen += TCPOLEN_TSTAMP_APPA;
766 }
767
768 /* Set receive buffer autosizing timestamp. */
769 if (tp->rfbuf_ts == 0 && (so->so_rcv.ssb_flags & SSB_AUTOSIZE))
770 tp->rfbuf_ts = ticks;
771
772 /*
773 * If this is a SACK connection and we have a block to report,
774 * fill in the SACK blocks in the TCP options.
775 */
776 if (report_sack)
777 tcp_sack_fill_report(tp, opt, &optlen);
778
779 #ifdef TCP_SIGNATURE
780 if (tp->t_flags & TF_SIGNATURE) {
781 int i;
782 u_char *bp;
783 /*
784 * Initialize TCP-MD5 option (RFC2385)
785 */
786 bp = (u_char *)opt + optlen;
787 *bp++ = TCPOPT_SIGNATURE;
788 *bp++ = TCPOLEN_SIGNATURE;
789 sigoff = optlen + 2;
790 for (i = 0; i < TCP_SIGLEN; i++)
791 *bp++ = 0;
792 optlen += TCPOLEN_SIGNATURE;
793 /*
794 * Terminate options list and maintain 32-bit alignment.
795 */
796 *bp++ = TCPOPT_NOP;
797 *bp++ = TCPOPT_EOL;
798 optlen += 2;
799 }
800 #endif /* TCP_SIGNATURE */
801 KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options"));
802 hdrlen += optlen;
803
804 if (isipv6) {
805 ipoptlen = ip6_optlen(inp);
806 } else {
807 if (inp->inp_options) {
808 ipoptlen = inp->inp_options->m_len -
809 offsetof(struct ipoption, ipopt_list);
810 } else {
811 ipoptlen = 0;
812 }
813 }
814
815 if (use_tso) {
816 /* TSO segment length must be multiple of segment size */
817 KASSERT(len >= (2 * segsz) && (len % segsz == 0),
818 ("invalid TSO len %ld, segsz %u", len, segsz));
819 } else {
820 KASSERT(len <= segsz,
821 ("invalid len %ld, segsz %u", len, segsz));
822
823 /*
824 * Adjust data length if insertion of options will bump
825 * the packet length beyond the t_maxopd length. Clear
826 * FIN to prevent premature closure since there is still
827 * more data to send after this (now truncated) packet.
828 *
829 * If just the options do not fit we are in a no-win
830 * situation and we treat it as an unreachable host.
831 */
832 if (len + optlen + ipoptlen > tp->t_maxopd) {
833 if (tp->t_maxopd <= optlen + ipoptlen) {
834 static time_t last_optlen_report;
835
836 if (last_optlen_report != time_uptime) {
837 last_optlen_report = time_uptime;
838 kprintf("tcpcb %p: MSS (%d) too "
839 "small to hold options!\n",
840 tp, tp->t_maxopd);
841 }
842 error = EHOSTUNREACH;
843 goto out;
844 } else {
845 flags &= ~TH_FIN;
846 len = tp->t_maxopd - optlen - ipoptlen;
847 sendalot = TRUE;
848 }
849 }
850 }
851
852 #ifdef INET6
853 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big"));
854 #else
855 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big"));
856 #endif
857
858 /*
859 * Grab a header mbuf, attaching a copy of data to
860 * be transmitted, and initialize the header from
861 * the template for sends on this connection.
862 */
863 if (len) {
864 if ((tp->t_flags & TF_FORCE) && len == 1)
865 tcpstat.tcps_sndprobe++;
866 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
867 if (tp->snd_nxt == tp->snd_una)
868 tp->snd_max_rexmt = tp->snd_max;
869 if (nsacked) {
870 tcpstat.tcps_sndsackrtopack++;
871 tcpstat.tcps_sndsackrtobyte += len;
872 }
873 tcpstat.tcps_sndrexmitpack++;
874 tcpstat.tcps_sndrexmitbyte += len;
875 } else {
876 tcpstat.tcps_sndpack++;
877 tcpstat.tcps_sndbyte += len;
878 }
879 if (idle_cwv) {
880 idle_cwv = FALSE;
881 tcp_idle_cwnd_validate(tp);
882 }
883 /* Update last send time after CWV */
884 tp->snd_last = ticks;
885 #ifdef notyet
886 if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len,
887 max_linkhdr + hdrlen)) == NULL) {
888 error = ENOBUFS;
889 goto after_th;
890 }
891 /*
892 * m_copypack left space for our hdr; use it.
893 */
894 m->m_len += hdrlen;
895 m->m_data -= hdrlen;
896 #else
897 #ifndef INET6
898 m = m_gethdr(M_NOWAIT, MT_HEADER);
899 #else
900 m = m_getl(hdrlen + max_linkhdr, M_NOWAIT, MT_HEADER,
901 M_PKTHDR, NULL);
902 #endif
903 if (m == NULL) {
904 error = ENOBUFS;
905 goto after_th;
906 }
907 m->m_data += max_linkhdr;
908 m->m_len = hdrlen;
909 if (len <= MHLEN - hdrlen - max_linkhdr) {
910 m_copydata(so->so_snd.ssb_mb, off, (int) len,
911 mtod(m, caddr_t) + hdrlen);
912 m->m_len += len;
913 } else {
914 m->m_next = m_copym(so->so_snd.ssb_mb, off,
915 (int) len, M_NOWAIT);
916 if (m->m_next == NULL) {
917 m_free(m);
918 m = NULL;
919 error = ENOBUFS;
920 goto after_th;
921 }
922 }
923 #endif
924 /*
925 * If we're sending everything we've got, set PUSH.
926 * (This will keep happy those implementations which only
927 * give data to the user when a buffer fills or
928 * a PUSH comes in.)
929 */
930 if (off + len == so->so_snd.ssb_cc)
931 flags |= TH_PUSH;
932 } else {
933 if (tp->t_flags & TF_ACKNOW)
934 tcpstat.tcps_sndacks++;
935 else if (flags & (TH_SYN | TH_FIN | TH_RST))
936 tcpstat.tcps_sndctrl++;
937 else if (SEQ_GT(tp->snd_up, tp->snd_una))
938 tcpstat.tcps_sndurg++;
939 else
940 tcpstat.tcps_sndwinup++;
941
942 MGETHDR(m, M_NOWAIT, MT_HEADER);
943 if (m == NULL) {
944 error = ENOBUFS;
945 goto after_th;
946 }
947 if (isipv6 &&
948 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN)
949 MH_ALIGN(m, hdrlen);
950 else
951 m->m_data += max_linkhdr;
952 m->m_len = hdrlen;
953
954 /*
955 * Prioritize SYN, SYN|ACK and pure ACK.
956 * Leave FIN and RST as they are.
957 */
958 if (tcp_prio_synack && (flags & (TH_FIN | TH_RST)) == 0)
959 m->m_flags |= M_PRIO;
960 }
961 m->m_pkthdr.rcvif = NULL;
962 if (isipv6) {
963 ip6 = mtod(m, struct ip6_hdr *);
964 th = (struct tcphdr *)(ip6 + 1);
965 tcp_fillheaders(tp, ip6, th, use_tso);
966 } else {
967 ip = mtod(m, struct ip *);
968 th = (struct tcphdr *)(ip + 1);
969 /* this picks up the pseudo header (w/o the length) */
970 tcp_fillheaders(tp, ip, th, use_tso);
971 }
972 after_th:
973 /*
974 * Fill in fields, remembering maximum advertised
975 * window for use in delaying messages about window sizes.
976 * If resending a FIN, be sure not to use a new sequence number.
977 */
978 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
979 tp->snd_nxt == tp->snd_max)
980 tp->snd_nxt--;
981
982 if (th != NULL) {
983 /*
984 * If we are doing retransmissions, then snd_nxt will
985 * not reflect the first unsent octet. For ACK only
986 * packets, we do not want the sequence number of the
987 * retransmitted packet, we want the sequence number
988 * of the next unsent octet. So, if there is no data
989 * (and no SYN or FIN), use snd_max instead of snd_nxt
990 * when filling in ti_seq. But if we are in persist
991 * state, snd_max might reflect one byte beyond the
992 * right edge of the window, so use snd_nxt in that
993 * case, since we know we aren't doing a retransmission.
994 * (retransmit and persist are mutually exclusive...)
995 */
996 if (len || (flags & (TH_SYN|TH_FIN)) ||
997 tcp_callout_active(tp, tp->tt_persist))
998 th->th_seq = htonl(tp->snd_nxt);
999 else
1000 th->th_seq = htonl(tp->snd_max);
1001 th->th_ack = htonl(tp->rcv_nxt);
1002 if (optlen) {
1003 bcopy(opt, th + 1, optlen);
1004 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
1005 }
1006 th->th_flags = flags;
1007 }
1008
1009 /*
1010 * Calculate receive window. Don't shrink window, but avoid
1011 * silly window syndrome by sending a 0 window if the actual
1012 * window is less then one segment.
1013 */
1014 if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) &&
1015 recvwin < (long)segsz)
1016 recvwin = 0;
1017 if (recvwin < (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt))
1018 recvwin = (tcp_seq_diff_t)(tp->rcv_adv - tp->rcv_nxt);
1019 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale)
1020 recvwin = (long)TCP_MAXWIN << tp->rcv_scale;
1021
1022 /*
1023 * Adjust the RXWIN0SENT flag - indicate that we have advertised
1024 * a 0 window. This may cause the remote transmitter to stall. This
1025 * flag tells soreceive() to disable delayed acknowledgements when
1026 * draining the buffer. This can occur if the receiver is attempting
1027 * to read more data then can be buffered prior to transmitting on
1028 * the connection.
1029 */
1030 if (recvwin == 0)
1031 tp->t_flags |= TF_RXWIN0SENT;
1032 else
1033 tp->t_flags &= ~TF_RXWIN0SENT;
1034
1035 if (th != NULL)
1036 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale));
1037
1038 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
1039 KASSERT(!use_tso, ("URG with TSO"));
1040 if (th != NULL) {
1041 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
1042 th->th_flags |= TH_URG;
1043 }
1044 } else {
1045 /*
1046 * If no urgent pointer to send, then we pull
1047 * the urgent pointer to the left edge of the send window
1048 * so that it doesn't drift into the send window on sequence
1049 * number wraparound.
1050 */
1051 tp->snd_up = tp->snd_una; /* drag it along */
1052 }
1053
1054 if (th != NULL) {
1055 #ifdef TCP_SIGNATURE
1056 if (tp->t_flags & TF_SIGNATURE) {
1057 tcpsignature_compute(m, len, optlen,
1058 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND);
1059 }
1060 #endif /* TCP_SIGNATURE */
1061
1062 /*
1063 * Put TCP length in extended header, and then
1064 * checksum extended header and data.
1065 */
1066 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
1067 if (isipv6) {
1068 /*
1069 * ip6_plen is not need to be filled now, and will be
1070 * filled in ip6_output().
1071 */
1072 th->th_sum = in6_cksum(m, IPPROTO_TCP,
1073 sizeof(struct ip6_hdr),
1074 sizeof(struct tcphdr) + optlen + len);
1075 } else {
1076 m->m_pkthdr.csum_thlen = sizeof(struct tcphdr) + optlen;
1077 if (use_tso) {
1078 m->m_pkthdr.csum_flags = CSUM_TSO;
1079 m->m_pkthdr.tso_segsz = segsz;
1080 } else {
1081 m->m_pkthdr.csum_flags = CSUM_TCP;
1082 m->m_pkthdr.csum_data =
1083 offsetof(struct tcphdr, th_sum);
1084 if (len + optlen) {
1085 th->th_sum = in_addword(th->th_sum,
1086 htons((u_short)(optlen + len)));
1087 }
1088 }
1089
1090 /*
1091 * IP version must be set here for ipv4/ipv6 checking
1092 * later
1093 */
1094 KASSERT(ip->ip_v == IPVERSION,
1095 ("%s: IP version incorrect: %d",
1096 __func__, ip->ip_v));
1097 }
1098 }
1099
1100 /*
1101 * In transmit state, time the transmission and arrange for
1102 * the retransmit. In persist state, just set snd_max.
1103 */
1104 if (!(tp->t_flags & TF_FORCE) ||
1105 !tcp_callout_active(tp, tp->tt_persist)) {
1106 tcp_seq startseq = tp->snd_nxt;
1107
1108 /*
1109 * Advance snd_nxt over sequence space of this segment.
1110 */
1111 if (flags & (TH_SYN | TH_FIN)) {
1112 if (flags & TH_SYN)
1113 tp->snd_nxt++;
1114 if (flags & TH_FIN) {
1115 tp->snd_nxt++;
1116 tp->t_flags |= TF_SENTFIN;
1117 }
1118 }
1119 tp->snd_nxt += len;
1120 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
1121 tp->snd_max = tp->snd_nxt;
1122 /*
1123 * Time this transmission if not a retransmission and
1124 * not currently timing anything.
1125 */
1126 if (tp->t_rtttime == 0) {
1127 tp->t_rtttime = ticks;
1128 tp->t_rtseq = startseq;
1129 tcpstat.tcps_segstimed++;
1130 }
1131 }
1132
1133 /*
1134 * Set retransmit timer if not currently set,
1135 * and not doing a pure ack or a keep-alive probe.
1136 * Initial value for retransmit timer is smoothed
1137 * round-trip time + 2 * round-trip time variance.
1138 * Initialize shift counter which is used for backoff
1139 * of retransmit time.
1140 */
1141 if (!tcp_callout_active(tp, tp->tt_rexmt) &&
1142 tp->snd_nxt != tp->snd_una) {
1143 if (tcp_callout_active(tp, tp->tt_persist)) {
1144 tcp_callout_stop(tp, tp->tt_persist);
1145 tp->t_rxtshift = 0;
1146 }
1147 tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur,
1148 tcp_timer_rexmt);
1149 } else if (len == 0 && so->so_snd.ssb_cc &&
1150 tp->t_state > TCPS_SYN_RECEIVED &&
1151 !tcp_callout_active(tp, tp->tt_rexmt) &&
1152 !tcp_callout_active(tp, tp->tt_persist)) {
1153 /*
1154 * Avoid a situation where we do not set persist timer
1155 * after a zero window condition. For example:
1156 * 1) A -> B: packet with enough data to fill the window
1157 * 2) B -> A: ACK for #1 + new data (0 window
1158 * advertisement)
1159 * 3) A -> B: ACK for #2, 0 len packet
1160 *
1161 * In this case, A will not activate the persist timer,
1162 * because it chose to send a packet. Unless tcp_output
1163 * is called for some other reason (delayed ack timer,
1164 * another input packet from B, socket syscall), A will
1165 * not send zero window probes.
1166 *
1167 * So, if you send a 0-length packet, but there is data
1168 * in the socket buffer, and neither the rexmt or
1169 * persist timer is already set, then activate the
1170 * persist timer.
1171 */
1172 tp->t_rxtshift = 0;
1173 tcp_setpersist(tp);
1174 }
1175 } else {
1176 /*
1177 * Persist case, update snd_max but since we are in
1178 * persist mode (no window) we do not update snd_nxt.
1179 */
1180 int xlen = len;
1181 if (flags & TH_SYN)
1182 panic("tcp_output: persist timer to send SYN");
1183 if (flags & TH_FIN) {
1184 ++xlen;
1185 tp->t_flags |= TF_SENTFIN;
1186 }
1187 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max))
1188 tp->snd_max = tp->snd_nxt + xlen;
1189 }
1190
1191 if (th != NULL) {
1192 #ifdef TCPDEBUG
1193 /* Trace. */
1194 if (so->so_options & SO_DEBUG) {
1195 tcp_trace(TA_OUTPUT, tp->t_state, tp,
1196 mtod(m, void *), th, 0);
1197 }
1198 #endif
1199
1200 /*
1201 * Fill in IP length and desired time to live and
1202 * send to IP level. There should be a better way
1203 * to handle ttl and tos; we could keep them in
1204 * the template, but need a way to checksum without them.
1205 */
1206 /*
1207 * m->m_pkthdr.len should have been set before cksum
1208 * calcuration, because in6_cksum() need it.
1209 */
1210 if (isipv6) {
1211 /*
1212 * we separately set hoplimit for every segment,
1213 * since the user might want to change the value
1214 * via setsockopt. Also, desired default hop
1215 * limit might be changed via Neighbor Discovery.
1216 */
1217 ip6->ip6_hlim = in6_selecthlim(inp,
1218 (inp->in6p_route.ro_rt ?
1219 inp->in6p_route.ro_rt->rt_ifp : NULL));
1220
1221 /* TODO: IPv6 IP6TOS_ECT bit on */
1222 error = ip6_output(m, inp->in6p_outputopts,
1223 &inp->in6p_route, (so->so_options & SO_DONTROUTE),
1224 NULL, NULL, inp);
1225 } else {
1226 struct rtentry *rt;
1227
1228 KASSERT(!INP_CHECK_SOCKAF(so, AF_INET6), ("inet6 pcb"));
1229
1230 ip->ip_len = htons(m->m_pkthdr.len);
1231 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */
1232 ip->ip_tos = inp->inp_ip_tos; /* XXX */
1233 /*
1234 * See if we should do MTU discovery.
1235 * We do it only if the following are true:
1236 * 1) we have a valid route to the destination
1237 * 2) the MTU is not locked (if it is,
1238 * then discovery has been disabled)
1239 */
1240 if (path_mtu_discovery &&
1241 (rt = inp->inp_route.ro_rt) &&
1242 (rt->rt_flags & RTF_UP) &&
1243 !(rt->rt_rmx.rmx_locks & RTV_MTU))
1244 {
1245 ip->ip_off |= htons(IP_DF);
1246 }
1247
1248 KASSERT(inp->inp_flags & INP_HASH,
1249 ("inpcb has no hash"));
1250 m_sethash(m, inp->inp_hashval);
1251 error = ip_output(m, inp->inp_options, &inp->inp_route,
1252 (so->so_options & SO_DONTROUTE) |
1253 IP_DEBUGROUTE, NULL, inp);
1254 }
1255 } else {
1256 KASSERT(error != 0, ("no error, but th not set"));
1257 }
1258 if (error) {
1259 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW);
1260
1261 /*
1262 * We know that the packet was lost, so back out the
1263 * sequence number advance, if any.
1264 */
1265 if (!(tp->t_flags & TF_FORCE) ||
1266 !tcp_callout_active(tp, tp->tt_persist)) {
1267 /*
1268 * No need to check for TH_FIN here because
1269 * the TF_SENTFIN flag handles that case.
1270 */
1271 if (!(flags & TH_SYN))
1272 tp->snd_nxt -= len;
1273 }
1274
1275 out:
1276 if (error == ENOBUFS) {
1277 KASSERT((len == 0 && (flags & (TH_SYN | TH_FIN)) == 0) ||
1278 tcp_callout_active(tp, tp->tt_rexmt) ||
1279 tcp_callout_active(tp, tp->tt_persist),
1280 ("neither rexmt nor persist timer is set"));
1281 return (0);
1282 }
1283 if (error == EMSGSIZE) {
1284 /*
1285 * ip_output() will have already fixed the route
1286 * for us. tcp_mtudisc() will, as its last action,
1287 * initiate retransmission, so it is important to
1288 * not do so here.
1289 */
1290 tcp_mtudisc(inp, 0);
1291 return 0;
1292 }
1293 if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1294 TCPS_HAVERCVDSYN(tp->t_state)) {
1295 tp->t_softerror = error;
1296 return (0);
1297 }
1298 return (error);
1299 }
1300 tcpstat.tcps_sndtotal++;
1301
1302 /*
1303 * Data sent (as far as we can tell).
1304 *
1305 * If this advertises a larger window than any other segment,
1306 * then remember the size of the advertised window.
1307 *
1308 * Any pending ACK has now been sent.
1309 */
1310 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) {
1311 tp->rcv_adv = tp->rcv_nxt + recvwin;
1312 tp->t_flags &= ~TF_RXRESIZED;
1313 }
1314 tp->last_ack_sent = tp->rcv_nxt;
1315 tp->t_flags &= ~(TF_ACKNOW | TF_XMITNOW);
1316 if (tcp_delack_enabled)
1317 tcp_callout_stop(tp, tp->tt_delack);
1318 if (sendalot) {
1319 if (tcp_fairsend > 0 && (tp->t_flags & TF_FAIRSEND) &&
1320 segcnt >= tcp_fairsend)
1321 need_sched = TRUE;
1322 goto again;
1323 }
1324 return (0);
1325 }
1326
1327 void
tcp_setpersist(struct tcpcb * tp)1328 tcp_setpersist(struct tcpcb *tp)
1329 {
1330 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
1331 int tt;
1332
1333 if (tp->t_state == TCPS_SYN_SENT ||
1334 tp->t_state == TCPS_SYN_RECEIVED) {
1335 panic("tcp_setpersist: not established yet, current %s",
1336 tp->t_state == TCPS_SYN_SENT ?
1337 "SYN_SENT" : "SYN_RECEIVED");
1338 }
1339
1340 if (tcp_callout_active(tp, tp->tt_rexmt))
1341 panic("tcp_setpersist: retransmit pending");
1342 /*
1343 * Start/restart persistance timer.
1344 */
1345 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN,
1346 TCPTV_PERSMAX);
1347 tcp_callout_reset(tp, tp->tt_persist, tt, tcp_timer_persist);
1348 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1349 tp->t_rxtshift++;
1350 }
1351
1352 static void
tcp_idle_cwnd_validate(struct tcpcb * tp)1353 tcp_idle_cwnd_validate(struct tcpcb *tp)
1354 {
1355 u_long initial_cwnd = tcp_initial_window(tp);
1356 u_long min_cwnd;
1357
1358 tcpstat.tcps_sndidle++;
1359
1360 /* According to RFC5681: RW=min(IW,cwnd) */
1361 min_cwnd = min(tp->snd_cwnd, initial_cwnd);
1362
1363 if (tcp_idle_cwv) {
1364 u_long idle_time, decay_cwnd;
1365
1366 /*
1367 * RFC2861, but only after idle period.
1368 */
1369
1370 /*
1371 * Before the congestion window is reduced, ssthresh
1372 * is set to the maximum of its current value and 3/4
1373 * cwnd. If the sender then has more data to send
1374 * than the decayed cwnd allows, the TCP will slow-
1375 * start (perform exponential increase) at least
1376 * half-way back up to the old value of cwnd.
1377 */
1378 tp->snd_ssthresh = max(tp->snd_ssthresh,
1379 (3 * tp->snd_cwnd) / 4);
1380
1381 /*
1382 * Decay the congestion window by half for every RTT
1383 * that the flow remains inactive.
1384 *
1385 * The difference between our implementation and
1386 * RFC2861 is that we don't allow cwnd to go below
1387 * the value allowed by RFC5681 (min_cwnd).
1388 */
1389 idle_time = ticks - tp->snd_last;
1390 decay_cwnd = tp->snd_cwnd;
1391 while (idle_time >= tp->t_rxtcur &&
1392 decay_cwnd > min_cwnd) {
1393 decay_cwnd >>= 1;
1394 idle_time -= tp->t_rxtcur;
1395 }
1396 tp->snd_cwnd = max(decay_cwnd, min_cwnd);
1397 } else {
1398 /*
1399 * Slow-start from scratch to re-determine the send
1400 * congestion window.
1401 */
1402 tp->snd_cwnd = min_cwnd;
1403 }
1404
1405 /* Restart ABC counting during congestion avoidance */
1406 tp->snd_wacked = 0;
1407 }
1408
1409 static int
tcp_tso_getsize(struct tcpcb * tp,u_int * segsz,u_int * hlen0)1410 tcp_tso_getsize(struct tcpcb *tp, u_int *segsz, u_int *hlen0)
1411 {
1412 struct inpcb * const inp = tp->t_inpcb;
1413 #ifdef INET6
1414 const boolean_t isipv6 = INP_ISIPV6(inp);
1415 #else
1416 const boolean_t isipv6 = FALSE;
1417 #endif
1418 unsigned int ipoptlen, optlen;
1419 u_int hlen;
1420
1421 hlen = sizeof(struct ip) + sizeof(struct tcphdr);
1422
1423 if (isipv6) {
1424 ipoptlen = ip6_optlen(inp);
1425 } else {
1426 if (inp->inp_options) {
1427 ipoptlen = inp->inp_options->m_len -
1428 offsetof(struct ipoption, ipopt_list);
1429 } else {
1430 ipoptlen = 0;
1431 }
1432 }
1433 hlen += ipoptlen;
1434
1435 optlen = 0;
1436 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP &&
1437 (tp->t_flags & TF_RCVD_TSTMP))
1438 optlen += TCPOLEN_TSTAMP_APPA;
1439 hlen += optlen;
1440
1441 if (tp->t_maxopd <= optlen + ipoptlen)
1442 return EHOSTUNREACH;
1443
1444 *segsz = tp->t_maxopd - optlen - ipoptlen;
1445 *hlen0 = hlen;
1446 return 0;
1447 }
1448
1449 static void
tcp_output_sched_handler(netmsg_t nmsg)1450 tcp_output_sched_handler(netmsg_t nmsg)
1451 {
1452 struct tcpcb *tp = nmsg->lmsg.u.ms_resultp;
1453
1454 /* Reply ASAP */
1455 crit_enter();
1456 lwkt_replymsg(&nmsg->lmsg, 0);
1457 crit_exit();
1458
1459 tcp_output_fair(tp);
1460 }
1461
1462 void
tcp_output_init(struct tcpcb * tp)1463 tcp_output_init(struct tcpcb *tp)
1464 {
1465 netmsg_init(tp->tt_sndmore, NULL, &netisr_adone_rport, MSGF_DROPABLE,
1466 tcp_output_sched_handler);
1467 tp->tt_sndmore->lmsg.u.ms_resultp = tp;
1468 }
1469
1470 void
tcp_output_cancel(struct tcpcb * tp)1471 tcp_output_cancel(struct tcpcb *tp)
1472 {
1473 /*
1474 * This message is still pending to be processed;
1475 * drop it. Optimized.
1476 */
1477 crit_enter();
1478 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0) {
1479 lwkt_dropmsg(&tp->tt_sndmore->lmsg);
1480 }
1481 crit_exit();
1482 }
1483
1484 boolean_t
tcp_output_pending(struct tcpcb * tp)1485 tcp_output_pending(struct tcpcb *tp)
1486 {
1487 if ((tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE) == 0)
1488 return TRUE;
1489 else
1490 return FALSE;
1491 }
1492
1493 static void
tcp_output_sched(struct tcpcb * tp)1494 tcp_output_sched(struct tcpcb *tp)
1495 {
1496 crit_enter();
1497 if (tp->tt_sndmore->lmsg.ms_flags & MSGF_DONE)
1498 lwkt_sendmsg(netisr_cpuport(mycpuid), &tp->tt_sndmore->lmsg);
1499 crit_exit();
1500 }
1501
1502 /*
1503 * Fairsend
1504 *
1505 * Yield to other senders or receivers on the same netisr if the current
1506 * TCP stream has sent tcp_fairsend segments and is going to burst more
1507 * segments. Bursting large amount of segements in a single TCP stream
1508 * could delay other senders' segments and receivers' ACKs quite a lot,
1509 * if others segments and ACKs are queued on to the same hardware transmit
1510 * queue; thus cause unfairness between senders and suppress receiving
1511 * performance.
1512 *
1513 * Fairsend should be performed at the places that do not affect segment
1514 * sending during congestion control, e.g.
1515 * - User requested output
1516 * - ACK input triggered output
1517 *
1518 * NOTE:
1519 * For devices that are TSO capable, their TSO aggregation size limit could
1520 * affect fairsend.
1521 */
1522 int
tcp_output_fair(struct tcpcb * tp)1523 tcp_output_fair(struct tcpcb *tp)
1524 {
1525 int ret;
1526
1527 tp->t_flags |= TF_FAIRSEND;
1528 ret = tcp_output(tp);
1529 tp->t_flags &= ~TF_FAIRSEND;
1530
1531 return ret;
1532 }
1533