2 * Copyright (c) 1982, 1986, 1988, 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * @(#)tcp_output.c 8.3 (Berkeley) 12/30/93
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/malloc.h>
41 #include <sys/protosw.h>
42 #include <sys/socket.h>
43 #include <sys/socketvar.h>
44 #include <sys/errno.h>
45 #include <sys/queue.h>
47 #include <net/route.h>
49 #include <netinet/in.h>
50 #include <netinet/in_systm.h>
51 #include <netinet/ip.h>
52 #include <netinet/in_pcb.h>
53 #include <netinet/ip_var.h>
54 #include <netinet/tcp.h>
55 #include <netinet/tcp_fsm.h>
56 #include <netinet/tcp_seq.h>
57 #include <netinet/tcp_timer.h>
58 #include <netinet/tcp_var.h>
59 #include <netinet/tcpip.h>
61 #include <netinet/tcp_debug.h>
66 extern struct mbuf
*m_copypack();
69 #define IS_LOOPBACK_ADDR(addr) \
70 ((ntohl(addr) & IN_CLASSA_NET) == (IN_LOOPBACKNET << IN_CLASSA_NSHIFT))
73 * Tcp output routine: figure out what should be sent and send it.
77 register struct tcpcb
*tp
;
79 register struct socket
*so
= tp
->t_inpcb
->inp_socket
;
80 register long len
, win
;
81 int off
, flags
, error
;
82 register struct mbuf
*m
;
83 register struct tcpiphdr
*ti
;
84 u_char opt
[TCP_MAXOLEN
];
85 unsigned optlen
, hdrlen
;
87 struct rmxp_tao
*taop
;
88 struct rmxp_tao tao_noncached
;
90 OS_DbgPrint(OSK_MID_TRACE
,("Called\n"));
93 * Determine length of data that should be transmitted,
94 * and flags that will be used.
95 * If there is some data or critical controls (SYN, RST)
96 * to send, then transmit; otherwise, investigate further.
98 idle
= (tp
->snd_max
== tp
->snd_una
);
99 if (idle
&& tp
->t_idle
>= tp
->t_rxtcur
)
101 * We have been idle for "a while" and no acks are
102 * expected to clock out any data we send --
103 * slow start to get ack "clock" running again.
105 tp
->snd_cwnd
= tp
->t_maxseg
;
107 OS_DbgPrint(OSK_MID_TRACE
,("again:\n"));
109 off
= tp
->snd_nxt
- tp
->snd_una
;
110 win
= min(tp
->snd_wnd
, tp
->snd_cwnd
);
112 flags
= tcp_outflags
[tp
->t_state
];
114 * Get standard flags, and add SYN or FIN if requested by 'hidden'
117 if (tp
->t_flags
& TF_NEEDFIN
)
119 if (tp
->t_flags
& TF_NEEDSYN
)
123 * If in persist timeout with window of 0, send 1 byte.
124 * Otherwise, if window is small but nonzero
125 * and timer expired, we will send what we can
126 * and go to transmit state.
131 * If we still have some data to send, then
132 * clear the FIN bit. Usually this would
133 * happen below when it realizes that we
134 * aren't sending all the data. However,
135 * if we have exactly 1 byte of unset data,
136 * then it won't clear the FIN bit below,
137 * and if we are in persist state, we wind
138 * up sending the packet without recording
139 * that we sent the FIN bit.
141 * We can't just blindly clear the FIN bit,
142 * because if we don't have any more data
143 * to send then the probe will be the FIN
146 if (off
< so
->so_snd
.sb_cc
)
150 tp
->t_timer
[TCPT_PERSIST
] = 0;
155 len
= min(so
->so_snd
.sb_cc
, win
) - off
;
157 if ((taop
= tcp_gettaocache(tp
->t_inpcb
)) == NULL
) {
158 taop
= &tao_noncached
;
159 bzero(taop
, sizeof(*taop
));
163 * Lop off SYN bit if it has already been sent. However, if this
164 * is SYN-SENT state and if segment contains data and if we don't
165 * know that foreign host supports TAO, suppress sending segment.
167 if ((flags
& TH_SYN
) && SEQ_GT(tp
->snd_nxt
, tp
->snd_una
)) {
170 if (len
> 0 && tp
->t_state
== TCPS_SYN_SENT
&&
171 taop
->tao_ccsent
== 0) {
172 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
178 * Be careful not to send data and/or FIN on SYN segments
179 * in cases when no CC option will be sent.
180 * This measure is needed to prevent interoperability problems
181 * with not fully conformant TCP implementations.
183 if ((flags
& TH_SYN
) &&
184 ((tp
->t_flags
& TF_NOOPT
) || !(tp
->t_flags
& TF_REQ_CC
) ||
185 ((flags
& TH_ACK
) && !(tp
->t_flags
& TF_RCVD_CC
)))) {
192 * If FIN has been sent but not acked,
193 * but we haven't been called to retransmit,
194 * len will be -1. Otherwise, window shrank
195 * after we sent into it. If window shrank to 0,
196 * cancel pending retransmit, pull snd_nxt back
197 * to (closed) window, and set the persist timer
198 * if it isn't already going. If the window didn't
199 * close completely, just wait for an ACK.
203 tp
->t_timer
[TCPT_REXMT
] = 0;
205 tp
->snd_nxt
= tp
->snd_una
;
206 if (tp
->t_timer
[TCPT_PERSIST
] == 0)
210 if (len
> tp
->t_maxseg
) {
214 if (SEQ_LT(tp
->snd_nxt
+ len
, tp
->snd_una
+ so
->so_snd
.sb_cc
))
217 win
= sbspace(&so
->so_rcv
);
220 * Sender silly window avoidance. If connection is idle or using
221 * the loopback interface and can send all data, a maximum segment,
222 * at least a maximum default-size segment do it,
223 * or are forced, do it; otherwise don't bother.
224 * If peer's buffer is tiny, then send
225 * when window is at least half open.
226 * If retransmitting (possibly after persist timer forced us
227 * to send into a small window), then must resend.
230 if (len
== tp
->t_maxseg
)
232 if ((idle
|| tp
->t_flags
& TF_NODELAY
||
233 IS_LOOPBACK_ADDR(tp
->t_inpcb
->inp_laddr
.s_addr
)) &&
234 (tp
->t_flags
& TF_NOPUSH
) == 0 &&
235 len
+ off
>= so
->so_snd
.sb_cc
)
239 if (len
>= tp
->max_sndwnd
/ 2 && tp
->max_sndwnd
> 0)
241 if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
))
246 * Compare available window to amount of window
247 * known to peer (as advertised window less
248 * next expected input). If the difference is at least two
249 * max size segments, or at least 50% of the maximum possible
250 * window, then want to send a window update to peer.
254 * "adv" is the amount we can increase the window,
255 * taking into account that we are limited by
256 * TCP_MAXWIN << tp->rcv_scale.
258 long adv
= min(win
, (long)TCP_MAXWIN
<< tp
->rcv_scale
) -
259 (tp
->rcv_adv
- tp
->rcv_nxt
);
261 if (adv
>= (long) (2 * tp
->t_maxseg
))
263 if (2 * adv
>= (long) so
->so_rcv
.sb_hiwat
)
268 * Send if we owe peer an ACK.
270 if (tp
->t_flags
& TF_ACKNOW
)
272 if ((flags
& TH_RST
) ||
273 ((flags
& TH_SYN
) && (tp
->t_flags
& TF_NEEDSYN
) == 0))
275 if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
278 * If our state indicates that FIN should be sent
279 * and we have not yet done so, or we're retransmitting the FIN,
280 * then we need to send.
282 if (flags
& TH_FIN
&&
283 ((tp
->t_flags
& TF_SENTFIN
) == 0 || tp
->snd_nxt
== tp
->snd_una
))
287 * TCP window updates are not reliable, rather a polling protocol
288 * using ``persist'' packets is used to insure receipt of window
289 * updates. The three ``states'' for the output side are:
290 * idle not doing retransmits or persists
291 * persisting to move a small or zero window
292 * (re)transmitting and thereby not persisting
294 * tp->t_timer[TCPT_PERSIST]
295 * is set when we are in persist state.
297 * is set when we are called to send a persist packet.
298 * tp->t_timer[TCPT_REXMT]
299 * is set when we are retransmitting
300 * The output side is idle when both timers are zero.
302 * If send window is too small, there is data to transmit, and no
303 * retransmit or persist is pending, then go to persist state.
304 * If nothing happens soon, send when timer expires:
305 * if window is nonzero, transmit what we can,
306 * otherwise force out a byte.
308 if (so
->so_snd
.sb_cc
&& tp
->t_timer
[TCPT_REXMT
] == 0 &&
309 tp
->t_timer
[TCPT_PERSIST
] == 0) {
315 * No reason to send a segment, just return.
317 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
321 OS_DbgPrint(OSK_MID_TRACE
,("send:\n"));
323 * Before ESTABLISHED, force sending of initial options
324 * unless TCP set not to do any options.
325 * NOTE: we assume that the IP/TCP header plus TCP options
326 * always fit in a single mbuf, leaving room for a maximum
328 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
331 hdrlen
= sizeof (struct tcpiphdr
);
332 if (flags
& TH_SYN
) {
333 tp
->snd_nxt
= tp
->iss
;
334 if ((tp
->t_flags
& TF_NOOPT
) == 0) {
337 opt
[0] = TCPOPT_MAXSEG
;
338 opt
[1] = TCPOLEN_MAXSEG
;
339 mss
= htons((u_short
) tcp_mssopt(tp
));
340 (void)memcpy(opt
+ 2, &mss
, sizeof(mss
));
341 optlen
= TCPOLEN_MAXSEG
;
343 if ((tp
->t_flags
& TF_REQ_SCALE
) &&
344 ((flags
& TH_ACK
) == 0 ||
345 (tp
->t_flags
& TF_RCVD_SCALE
))) {
346 *((u_long
*) (opt
+ optlen
)) = htonl(
348 TCPOPT_WINDOW
<< 16 |
349 TCPOLEN_WINDOW
<< 8 |
350 tp
->request_r_scale
);
357 * Send a timestamp and echo-reply if this is a SYN and our side
358 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
359 * and our peer have sent timestamps in our SYN's.
361 if ((tp
->t_flags
& (TF_REQ_TSTMP
|TF_NOOPT
)) == TF_REQ_TSTMP
&&
362 (flags
& TH_RST
) == 0 &&
363 ((flags
& TH_ACK
) == 0 ||
364 (tp
->t_flags
& TF_RCVD_TSTMP
))) {
365 u_long
*lp
= (u_long
*)(opt
+ optlen
);
367 /* Form timestamp option as shown in appendix A of RFC 1323. */
368 *lp
++ = htonl(TCPOPT_TSTAMP_HDR
);
369 *lp
++ = htonl(tcp_now
);
370 *lp
= htonl(tp
->ts_recent
);
371 optlen
+= TCPOLEN_TSTAMP_APPA
;
375 * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
376 * options are allowed (!TF_NOOPT) and it's not a RST.
378 if ((tp
->t_flags
& (TF_REQ_CC
|TF_NOOPT
)) == TF_REQ_CC
&&
379 (flags
& TH_RST
) == 0) {
380 switch (flags
& (TH_SYN
|TH_ACK
)) {
382 * This is a normal ACK, send CC if we received CC before
386 if (!(tp
->t_flags
& TF_RCVD_CC
))
391 * We can only get here in T/TCP's SYN_SENT* state, when
392 * we're a sending a non-SYN segment without waiting for
393 * the ACK of our SYN. A check above assures that we only
394 * do this if our peer understands T/TCP.
397 opt
[optlen
++] = TCPOPT_NOP
;
398 opt
[optlen
++] = TCPOPT_NOP
;
399 opt
[optlen
++] = TCPOPT_CC
;
400 opt
[optlen
++] = TCPOLEN_CC
;
401 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
407 * This is our initial SYN, check whether we have to use
411 opt
[optlen
++] = TCPOPT_NOP
;
412 opt
[optlen
++] = TCPOPT_NOP
;
413 opt
[optlen
++] = tp
->t_flags
& TF_SENDCCNEW
?
414 TCPOPT_CCNEW
: TCPOPT_CC
;
415 opt
[optlen
++] = TCPOLEN_CC
;
416 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
421 * This is a SYN,ACK; send CC and CC.echo if we received
424 case (TH_SYN
|TH_ACK
):
425 if (tp
->t_flags
& TF_RCVD_CC
) {
426 opt
[optlen
++] = TCPOPT_NOP
;
427 opt
[optlen
++] = TCPOPT_NOP
;
428 opt
[optlen
++] = TCPOPT_CC
;
429 opt
[optlen
++] = TCPOLEN_CC
;
430 *(u_int32_t
*)&opt
[optlen
] =
433 opt
[optlen
++] = TCPOPT_NOP
;
434 opt
[optlen
++] = TCPOPT_NOP
;
435 opt
[optlen
++] = TCPOPT_CCECHO
;
436 opt
[optlen
++] = TCPOLEN_CC
;
437 *(u_int32_t
*)&opt
[optlen
] =
448 * Adjust data length if insertion of options will
449 * bump the packet length beyond the t_maxopd length.
450 * Clear the FIN bit because we cut off the tail of
453 if (len
+ optlen
> tp
->t_maxopd
) {
455 * If there is still more to send, don't close the connection.
458 len
= tp
->t_maxopd
- optlen
;
462 /*#ifdef DIAGNOSTIC*/
463 if (max_linkhdr
+ hdrlen
> MHLEN
)
464 panic("tcphdr too big");
468 * Grab a header mbuf, attaching a copy of data to
469 * be transmitted, and initialize the header from
470 * the template for sends on this connection.
473 if (tp
->t_force
&& len
== 1)
474 tcpstat
.tcps_sndprobe
++;
475 else if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
)) {
476 tcpstat
.tcps_sndrexmitpack
++;
477 tcpstat
.tcps_sndrexmitbyte
+= len
;
479 tcpstat
.tcps_sndpack
++;
480 tcpstat
.tcps_sndbyte
+= len
;
483 if ((m
= m_copypack(so
->so_snd
.sb_mb
, off
,
484 (int)len
, max_linkhdr
+ hdrlen
)) == 0) {
489 * m_copypack left space for our hdr; use it.
494 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
499 m
->m_data
+= max_linkhdr
;
501 /* m is not initialized here ... see below up to line
502 * in_cksum to see how it gets there */
503 if (len
<= MHLEN
- hdrlen
- max_linkhdr
) {
504 m_copydata(so
->so_snd
.sb_mb
, off
, (int) len
,
505 mtod(m
, caddr_t
) + hdrlen
);
508 m
->m_next
= m_copy(so
->so_snd
.sb_mb
, off
, (int) len
);
509 // the buffer is allocated, but not filled with the tcp
510 // header yet, so dumping it here yields garbage...
511 //OskitDumpBuffer(mtod(m, caddr_t), len);
512 if (m
->m_next
== 0) {
520 * If we're sending everything we've got, set PUSH.
521 * (This will keep happy those implementations which only
522 * give data to the user when a buffer fills or
525 if (off
+ len
== so
->so_snd
.sb_cc
)
528 if (tp
->t_flags
& TF_ACKNOW
)
529 tcpstat
.tcps_sndacks
++;
530 else if (flags
& (TH_SYN
|TH_FIN
|TH_RST
))
531 tcpstat
.tcps_sndctrl
++;
532 else if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
533 tcpstat
.tcps_sndurg
++;
535 tcpstat
.tcps_sndwinup
++;
537 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
542 m
->m_data
+= max_linkhdr
;
545 m
->m_pkthdr
.rcvif
= (struct ifnet
*)0;
547 /* This pulls the data ptr from m and start initting it...
548 * before this point, m is empty. */
549 ti
= mtod(m
, struct tcpiphdr
*);
550 if (tp
->t_template
== 0)
552 (void)memcpy(ti
, tp
->t_template
, sizeof (struct tcpiphdr
));
555 * Fill in fields, remembering maximum advertised
556 * window for use in delaying messages about window sizes.
557 * If resending a FIN, be sure not to use a new sequence number.
559 if (flags
& TH_FIN
&& tp
->t_flags
& TF_SENTFIN
&&
560 tp
->snd_nxt
== tp
->snd_max
)
563 * If we are doing retransmissions, then snd_nxt will
564 * not reflect the first unsent octet. For ACK only
565 * packets, we do not want the sequence number of the
566 * retransmitted packet, we want the sequence number
567 * of the next unsent octet. So, if there is no data
568 * (and no SYN or FIN), use snd_max instead of snd_nxt
569 * when filling in ti_seq. But if we are in persist
570 * state, snd_max might reflect one byte beyond the
571 * right edge of the window, so use snd_nxt in that
572 * case, since we know we aren't doing a retransmission.
573 * (retransmit and persist are mutually exclusive...)
575 if (len
|| (flags
& (TH_SYN
|TH_FIN
)) || tp
->t_timer
[TCPT_PERSIST
])
576 ti
->ti_seq
= htonl(tp
->snd_nxt
);
578 ti
->ti_seq
= htonl(tp
->snd_max
);
579 ti
->ti_ack
= htonl(tp
->rcv_nxt
);
582 (void)memcpy(ti
+ 1, opt
, optlen
);
583 ti
->ti_off
= (sizeof (struct tcphdr
) + optlen
) >> 2;
585 ti
->ti_flags
= flags
;
587 * Calculate receive window. Don't shrink window,
588 * but avoid silly window syndrome.
590 if (win
< (long)(so
->so_rcv
.sb_hiwat
/ 4) && win
< (long)tp
->t_maxseg
)
592 if (win
> (long)TCP_MAXWIN
<< tp
->rcv_scale
)
593 win
= (long)TCP_MAXWIN
<< tp
->rcv_scale
;
594 if (win
< (long)(tp
->rcv_adv
- tp
->rcv_nxt
))
595 win
= (long)(tp
->rcv_adv
- tp
->rcv_nxt
);
596 ti
->ti_win
= htons((u_short
) (win
>>tp
->rcv_scale
));
597 if (SEQ_GT(tp
->snd_up
, tp
->snd_nxt
)) {
598 ti
->ti_urp
= htons((u_short
)(tp
->snd_up
- tp
->snd_nxt
));
599 ti
->ti_flags
|= TH_URG
;
602 * If no urgent pointer to send, then we pull
603 * the urgent pointer to the left edge of the send window
604 * so that it doesn't drift into the send window on sequence
607 tp
->snd_up
= tp
->snd_una
; /* drag it along */
610 * Put TCP length in extended header, and then
611 * checksum extended header and data.
614 ti
->ti_len
= htons((u_short
)(sizeof (struct tcphdr
) +
616 ti
->ti_sum
= in_cksum(m
, (int)(hdrlen
+ len
));
619 * In transmit state, time the transmission and arrange for
620 * the retransmit. In persist state, just set snd_max.
622 if (tp
->t_force
== 0 || tp
->t_timer
[TCPT_PERSIST
] == 0) {
623 tcp_seq startseq
= tp
->snd_nxt
;
626 * Advance snd_nxt over sequence space of this segment.
628 if (flags
& (TH_SYN
|TH_FIN
)) {
631 if (flags
& TH_FIN
) {
633 tp
->t_flags
|= TF_SENTFIN
;
637 if (SEQ_GT(tp
->snd_nxt
, tp
->snd_max
)) {
638 tp
->snd_max
= tp
->snd_nxt
;
640 * Time this transmission if not a retransmission and
641 * not currently timing anything.
643 if (tp
->t_rtt
== 0) {
645 tp
->t_rtseq
= startseq
;
646 tcpstat
.tcps_segstimed
++;
651 * Set retransmit timer if not currently set,
652 * and not doing an ack or a keep-alive probe.
653 * Initial value for retransmit timer is smoothed
654 * round-trip time + 2 * round-trip time variance.
655 * Initialize shift counter which is used for backoff
656 * of retransmit time.
658 if (tp
->t_timer
[TCPT_REXMT
] == 0 &&
659 tp
->snd_nxt
!= tp
->snd_una
) {
660 tp
->t_timer
[TCPT_REXMT
] = tp
->t_rxtcur
;
661 if (tp
->t_timer
[TCPT_PERSIST
]) {
662 tp
->t_timer
[TCPT_PERSIST
] = 0;
667 if (SEQ_GT(tp
->snd_nxt
+ len
, tp
->snd_max
))
668 tp
->snd_max
= tp
->snd_nxt
+ len
;
674 if (so
->so_options
& SO_DEBUG
)
675 tcp_trace(TA_OUTPUT
, tp
->t_state
, tp
, ti
, 0);
679 * Fill in IP length and desired time to live and
680 * send to IP level. There should be a better way
681 * to handle ttl and tos; we could keep them in
682 * the template, but need a way to checksum without them.
684 m
->m_pkthdr
.len
= hdrlen
+ len
;
687 error
= tuba_output(m
, tp
);
694 ((struct ip
*)ti
)->ip_len
= m
->m_pkthdr
.len
;
695 ((struct ip
*)ti
)->ip_ttl
= tp
->t_inpcb
->inp_ip
.ip_ttl
; /* XXX */
696 ((struct ip
*)ti
)->ip_tos
= tp
->t_inpcb
->inp_ip
.ip_tos
; /* XXX */
699 * See if we should do MTU discovery. We do it only if the following
701 * 1) we have a valid route to the destination
702 * 2) the MTU is not locked (if it is, then discovery has been
705 if ((rt
= tp
->t_inpcb
->inp_route
.ro_rt
)
706 && rt
->rt_flags
& RTF_UP
707 && !(rt
->rt_rmx
.rmx_locks
& RTV_MTU
)) {
708 ((struct ip
*)ti
)->ip_off
|= IP_DF
;
711 error
= ip_output(m
, tp
->t_inpcb
->inp_options
, &tp
->t_inpcb
->inp_route
,
712 so
->so_options
& SO_DONTROUTE
, 0);
716 if (error
== ENOBUFS
) {
717 tcp_quench(tp
->t_inpcb
, 0);
718 OS_DbgPrint(OSK_MID_TRACE
,("quench 0\n"));
722 if (error
== EMSGSIZE
) {
724 * ip_output() will have already fixed the route
725 * for us. tcp_mtudisc() will, as its last action,
726 * initiate retransmission, so it is important to
729 tcp_mtudisc(tp
->t_inpcb
, 0);
730 OS_DbgPrint(OSK_MID_TRACE
,("mtudisc 0\n"));
734 if ((error
== EHOSTUNREACH
|| error
== ENETDOWN
)
735 && TCPS_HAVERCVDSYN(tp
->t_state
)) {
736 tp
->t_softerror
= error
;
737 OS_DbgPrint(OSK_MID_TRACE
,("softerror %d\n", error
));
740 OS_DbgPrint(OSK_MID_TRACE
,("error %d\n", error
));
743 tcpstat
.tcps_sndtotal
++;
746 * Data sent (as far as we can tell).
747 * If this advertises a larger window than any other segment,
748 * then remember the size of the advertised window.
749 * Any pending ACK has now been sent.
751 if (win
> 0 && SEQ_GT(tp
->rcv_nxt
+win
, tp
->rcv_adv
))
752 tp
->rcv_adv
= tp
->rcv_nxt
+ win
;
753 tp
->last_ack_sent
= tp
->rcv_nxt
;
754 tp
->t_flags
&= ~(TF_ACKNOW
|TF_DELACK
);
757 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
763 register struct tcpcb
*tp
;
765 register int t
= ((tp
->t_srtt
>> 2) + tp
->t_rttvar
) >> 1;
767 if (tp
->t_timer
[TCPT_REXMT
])
768 panic("tcp_output REXMT");
770 * Start/restart persistance timer.
772 TCPT_RANGESET(tp
->t_timer
[TCPT_PERSIST
],
773 t
* tcp_backoff
[tp
->t_rxtshift
],
774 TCPTV_PERSMIN
, TCPTV_PERSMAX
);
775 if (tp
->t_rxtshift
< TCP_MAXRXTSHIFT
)