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();
71 * Tcp output routine: figure out what should be sent and send it.
75 register struct tcpcb
*tp
;
77 register struct socket
*so
= tp
->t_inpcb
->inp_socket
;
78 register long len
, win
;
79 int off
, flags
, error
;
80 register struct mbuf
*m
;
81 register struct tcpiphdr
*ti
;
82 u_char opt
[TCP_MAXOLEN
];
83 unsigned optlen
, hdrlen
;
85 struct rmxp_tao
*taop
;
86 struct rmxp_tao tao_noncached
;
88 OS_DbgPrint(OSK_MID_TRACE
,("Called\n"));
91 * Determine length of data that should be transmitted,
92 * and flags that will be used.
93 * If there is some data or critical controls (SYN, RST)
94 * to send, then transmit; otherwise, investigate further.
96 idle
= (tp
->snd_max
== tp
->snd_una
);
97 if (idle
&& tp
->t_idle
>= tp
->t_rxtcur
)
99 * We have been idle for "a while" and no acks are
100 * expected to clock out any data we send --
101 * slow start to get ack "clock" running again.
103 tp
->snd_cwnd
= tp
->t_maxseg
;
105 OS_DbgPrint(OSK_MID_TRACE
,("again:\n"));
107 off
= tp
->snd_nxt
- tp
->snd_una
;
108 win
= min(tp
->snd_wnd
, tp
->snd_cwnd
);
110 flags
= tcp_outflags
[tp
->t_state
];
112 * Get standard flags, and add SYN or FIN if requested by 'hidden'
115 if (tp
->t_flags
& TF_NEEDFIN
)
117 if (tp
->t_flags
& TF_NEEDSYN
)
121 * If in persist timeout with window of 0, send 1 byte.
122 * Otherwise, if window is small but nonzero
123 * and timer expired, we will send what we can
124 * and go to transmit state.
129 * If we still have some data to send, then
130 * clear the FIN bit. Usually this would
131 * happen below when it realizes that we
132 * aren't sending all the data. However,
133 * if we have exactly 1 byte of unset data,
134 * then it won't clear the FIN bit below,
135 * and if we are in persist state, we wind
136 * up sending the packet without recording
137 * that we sent the FIN bit.
139 * We can't just blindly clear the FIN bit,
140 * because if we don't have any more data
141 * to send then the probe will be the FIN
144 if (off
< so
->so_snd
.sb_cc
)
148 tp
->t_timer
[TCPT_PERSIST
] = 0;
153 len
= min(so
->so_snd
.sb_cc
, win
) - off
;
155 if ((taop
= tcp_gettaocache(tp
->t_inpcb
)) == NULL
) {
156 taop
= &tao_noncached
;
157 bzero(taop
, sizeof(*taop
));
161 * Lop off SYN bit if it has already been sent. However, if this
162 * is SYN-SENT state and if segment contains data and if we don't
163 * know that foreign host supports TAO, suppress sending segment.
165 if ((flags
& TH_SYN
) && SEQ_GT(tp
->snd_nxt
, tp
->snd_una
)) {
168 if (len
> 0 && tp
->t_state
== TCPS_SYN_SENT
&&
169 taop
->tao_ccsent
== 0) {
170 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
176 * Be careful not to send data and/or FIN on SYN segments
177 * in cases when no CC option will be sent.
178 * This measure is needed to prevent interoperability problems
179 * with not fully conformant TCP implementations.
181 if ((flags
& TH_SYN
) &&
182 ((tp
->t_flags
& TF_NOOPT
) || !(tp
->t_flags
& TF_REQ_CC
) ||
183 ((flags
& TH_ACK
) && !(tp
->t_flags
& TF_RCVD_CC
)))) {
190 * If FIN has been sent but not acked,
191 * but we haven't been called to retransmit,
192 * len will be -1. Otherwise, window shrank
193 * after we sent into it. If window shrank to 0,
194 * cancel pending retransmit, pull snd_nxt back
195 * to (closed) window, and set the persist timer
196 * if it isn't already going. If the window didn't
197 * close completely, just wait for an ACK.
201 tp
->t_timer
[TCPT_REXMT
] = 0;
203 tp
->snd_nxt
= tp
->snd_una
;
204 if (tp
->t_timer
[TCPT_PERSIST
] == 0)
208 if (len
> tp
->t_maxseg
) {
212 if (SEQ_LT(tp
->snd_nxt
+ len
, tp
->snd_una
+ so
->so_snd
.sb_cc
))
215 win
= sbspace(&so
->so_rcv
);
218 * Sender silly window avoidance. If connection is idle
219 * and can send all data, a maximum segment,
220 * at least a maximum default-size segment do it,
221 * or are forced, do it; otherwise don't bother.
222 * If peer's buffer is tiny, then send
223 * when window is at least half open.
224 * If retransmitting (possibly after persist timer forced us
225 * to send into a small window), then must resend.
228 if (len
== tp
->t_maxseg
)
230 if ((idle
|| tp
->t_flags
& TF_NODELAY
) &&
231 (tp
->t_flags
& TF_NOPUSH
) == 0 &&
232 len
+ off
>= so
->so_snd
.sb_cc
)
236 if (len
>= tp
->max_sndwnd
/ 2 && tp
->max_sndwnd
> 0)
238 if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
))
243 * Compare available window to amount of window
244 * known to peer (as advertised window less
245 * next expected input). If the difference is at least two
246 * max size segments, or at least 50% of the maximum possible
247 * window, then want to send a window update to peer.
251 * "adv" is the amount we can increase the window,
252 * taking into account that we are limited by
253 * TCP_MAXWIN << tp->rcv_scale.
255 long adv
= min(win
, (long)TCP_MAXWIN
<< tp
->rcv_scale
) -
256 (tp
->rcv_adv
- tp
->rcv_nxt
);
258 if (adv
>= (long) (2 * tp
->t_maxseg
))
260 if (2 * adv
>= (long) so
->so_rcv
.sb_hiwat
)
265 * Send if we owe peer an ACK.
267 if (tp
->t_flags
& TF_ACKNOW
)
269 if ((flags
& TH_RST
) ||
270 ((flags
& TH_SYN
) && (tp
->t_flags
& TF_NEEDSYN
) == 0))
272 if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
275 * If our state indicates that FIN should be sent
276 * and we have not yet done so, or we're retransmitting the FIN,
277 * then we need to send.
279 if (flags
& TH_FIN
&&
280 ((tp
->t_flags
& TF_SENTFIN
) == 0 || tp
->snd_nxt
== tp
->snd_una
))
284 * TCP window updates are not reliable, rather a polling protocol
285 * using ``persist'' packets is used to insure receipt of window
286 * updates. The three ``states'' for the output side are:
287 * idle not doing retransmits or persists
288 * persisting to move a small or zero window
289 * (re)transmitting and thereby not persisting
291 * tp->t_timer[TCPT_PERSIST]
292 * is set when we are in persist state.
294 * is set when we are called to send a persist packet.
295 * tp->t_timer[TCPT_REXMT]
296 * is set when we are retransmitting
297 * The output side is idle when both timers are zero.
299 * If send window is too small, there is data to transmit, and no
300 * retransmit or persist is pending, then go to persist state.
301 * If nothing happens soon, send when timer expires:
302 * if window is nonzero, transmit what we can,
303 * otherwise force out a byte.
305 if (so
->so_snd
.sb_cc
&& tp
->t_timer
[TCPT_REXMT
] == 0 &&
306 tp
->t_timer
[TCPT_PERSIST
] == 0) {
312 * No reason to send a segment, just return.
314 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
318 OS_DbgPrint(OSK_MID_TRACE
,("send:\n"));
320 * Before ESTABLISHED, force sending of initial options
321 * unless TCP set not to do any options.
322 * NOTE: we assume that the IP/TCP header plus TCP options
323 * always fit in a single mbuf, leaving room for a maximum
325 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
328 hdrlen
= sizeof (struct tcpiphdr
);
329 if (flags
& TH_SYN
) {
330 tp
->snd_nxt
= tp
->iss
;
331 if ((tp
->t_flags
& TF_NOOPT
) == 0) {
334 opt
[0] = TCPOPT_MAXSEG
;
335 opt
[1] = TCPOLEN_MAXSEG
;
336 mss
= htons((u_short
) tcp_mssopt(tp
));
337 (void)memcpy(opt
+ 2, &mss
, sizeof(mss
));
338 optlen
= TCPOLEN_MAXSEG
;
340 if ((tp
->t_flags
& TF_REQ_SCALE
) &&
341 ((flags
& TH_ACK
) == 0 ||
342 (tp
->t_flags
& TF_RCVD_SCALE
))) {
343 *((u_long
*) (opt
+ optlen
)) = htonl(
345 TCPOPT_WINDOW
<< 16 |
346 TCPOLEN_WINDOW
<< 8 |
347 tp
->request_r_scale
);
354 * Send a timestamp and echo-reply if this is a SYN and our side
355 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
356 * and our peer have sent timestamps in our SYN's.
358 if ((tp
->t_flags
& (TF_REQ_TSTMP
|TF_NOOPT
)) == TF_REQ_TSTMP
&&
359 (flags
& TH_RST
) == 0 &&
360 ((flags
& TH_ACK
) == 0 ||
361 (tp
->t_flags
& TF_RCVD_TSTMP
))) {
362 u_long
*lp
= (u_long
*)(opt
+ optlen
);
364 /* Form timestamp option as shown in appendix A of RFC 1323. */
365 *lp
++ = htonl(TCPOPT_TSTAMP_HDR
);
366 *lp
++ = htonl(tcp_now
);
367 *lp
= htonl(tp
->ts_recent
);
368 optlen
+= TCPOLEN_TSTAMP_APPA
;
372 * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
373 * options are allowed (!TF_NOOPT) and it's not a RST.
375 if ((tp
->t_flags
& (TF_REQ_CC
|TF_NOOPT
)) == TF_REQ_CC
&&
376 (flags
& TH_RST
) == 0) {
377 switch (flags
& (TH_SYN
|TH_ACK
)) {
379 * This is a normal ACK, send CC if we received CC before
383 if (!(tp
->t_flags
& TF_RCVD_CC
))
388 * We can only get here in T/TCP's SYN_SENT* state, when
389 * we're a sending a non-SYN segment without waiting for
390 * the ACK of our SYN. A check above assures that we only
391 * do this if our peer understands T/TCP.
394 opt
[optlen
++] = TCPOPT_NOP
;
395 opt
[optlen
++] = TCPOPT_NOP
;
396 opt
[optlen
++] = TCPOPT_CC
;
397 opt
[optlen
++] = TCPOLEN_CC
;
398 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
404 * This is our initial SYN, check whether we have to use
409 opt
[optlen
++] = TCPOPT_NOP
;
410 opt
[optlen
++] = TCPOPT_NOP
;
411 opt
[optlen
++] = tp
->t_flags
& TF_SENDCCNEW
?
412 TCPOPT_CCNEW
: TCPOPT_CC
;
413 opt
[optlen
++] = TCPOLEN_CC
;
414 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
420 * This is a SYN,ACK; send CC and CC.echo if we received
423 case (TH_SYN
|TH_ACK
):
424 if (tp
->t_flags
& TF_RCVD_CC
) {
425 opt
[optlen
++] = TCPOPT_NOP
;
426 opt
[optlen
++] = TCPOPT_NOP
;
427 opt
[optlen
++] = TCPOPT_CC
;
428 opt
[optlen
++] = TCPOLEN_CC
;
429 *(u_int32_t
*)&opt
[optlen
] =
432 opt
[optlen
++] = TCPOPT_NOP
;
433 opt
[optlen
++] = TCPOPT_NOP
;
434 opt
[optlen
++] = TCPOPT_CCECHO
;
435 opt
[optlen
++] = TCPOLEN_CC
;
436 *(u_int32_t
*)&opt
[optlen
] =
447 * Adjust data length if insertion of options will
448 * bump the packet length beyond the t_maxopd length.
449 * Clear the FIN bit because we cut off the tail of
452 if (len
+ optlen
> tp
->t_maxopd
) {
454 * If there is still more to send, don't close the connection.
457 len
= tp
->t_maxopd
- optlen
;
461 /*#ifdef DIAGNOSTIC*/
462 if (max_linkhdr
+ hdrlen
> MHLEN
)
463 panic("tcphdr too big");
467 * Grab a header mbuf, attaching a copy of data to
468 * be transmitted, and initialize the header from
469 * the template for sends on this connection.
472 if (tp
->t_force
&& len
== 1)
473 tcpstat
.tcps_sndprobe
++;
474 else if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
)) {
475 tcpstat
.tcps_sndrexmitpack
++;
476 tcpstat
.tcps_sndrexmitbyte
+= len
;
478 tcpstat
.tcps_sndpack
++;
479 tcpstat
.tcps_sndbyte
+= len
;
482 if ((m
= m_copypack(so
->so_snd
.sb_mb
, off
,
483 (int)len
, max_linkhdr
+ hdrlen
)) == 0) {
488 * m_copypack left space for our hdr; use it.
493 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
498 m
->m_data
+= max_linkhdr
;
500 /* m is not initialized here ... see below up to line
501 * in_cksum to see how it gets there */
502 if (len
<= MHLEN
- hdrlen
- max_linkhdr
) {
503 m_copydata(so
->so_snd
.sb_mb
, off
, (int) len
,
504 mtod(m
, caddr_t
) + hdrlen
);
507 m
->m_next
= m_copy(so
->so_snd
.sb_mb
, off
, (int) len
);
508 // the buffer is allocated, but not filled with the tcp
509 // header yet, so dumping it here yields garbage...
510 //OskitDumpBuffer(mtod(m, caddr_t), len);
511 if (m
->m_next
== 0) {
519 * If we're sending everything we've got, set PUSH.
520 * (This will keep happy those implementations which only
521 * give data to the user when a buffer fills or
524 if (off
+ len
== so
->so_snd
.sb_cc
)
527 if (tp
->t_flags
& TF_ACKNOW
)
528 tcpstat
.tcps_sndacks
++;
529 else if (flags
& (TH_SYN
|TH_FIN
|TH_RST
))
530 tcpstat
.tcps_sndctrl
++;
531 else if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
532 tcpstat
.tcps_sndurg
++;
534 tcpstat
.tcps_sndwinup
++;
536 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
541 m
->m_data
+= max_linkhdr
;
544 m
->m_pkthdr
.rcvif
= (struct ifnet
*)0;
546 /* This pulls the data ptr from m and start initting it...
547 * before this point, m is empty. */
548 ti
= mtod(m
, struct tcpiphdr
*);
549 if (tp
->t_template
== 0)
551 (void)memcpy(ti
, tp
->t_template
, sizeof (struct tcpiphdr
));
554 * Fill in fields, remembering maximum advertised
555 * window for use in delaying messages about window sizes.
556 * If resending a FIN, be sure not to use a new sequence number.
558 if (flags
& TH_FIN
&& tp
->t_flags
& TF_SENTFIN
&&
559 tp
->snd_nxt
== tp
->snd_max
)
562 * If we are doing retransmissions, then snd_nxt will
563 * not reflect the first unsent octet. For ACK only
564 * packets, we do not want the sequence number of the
565 * retransmitted packet, we want the sequence number
566 * of the next unsent octet. So, if there is no data
567 * (and no SYN or FIN), use snd_max instead of snd_nxt
568 * when filling in ti_seq. But if we are in persist
569 * state, snd_max might reflect one byte beyond the
570 * right edge of the window, so use snd_nxt in that
571 * case, since we know we aren't doing a retransmission.
572 * (retransmit and persist are mutually exclusive...)
574 if (len
|| (flags
& (TH_SYN
|TH_FIN
)) || tp
->t_timer
[TCPT_PERSIST
])
575 ti
->ti_seq
= htonl(tp
->snd_nxt
);
577 ti
->ti_seq
= htonl(tp
->snd_max
);
578 ti
->ti_ack
= htonl(tp
->rcv_nxt
);
581 (void)memcpy(ti
+ 1, opt
, optlen
);
582 ti
->ti_off
= (sizeof (struct tcphdr
) + optlen
) >> 2;
584 ti
->ti_flags
= flags
;
586 * Calculate receive window. Don't shrink window,
587 * but avoid silly window syndrome.
589 if (win
< (long)(so
->so_rcv
.sb_hiwat
/ 4) && win
< (long)tp
->t_maxseg
)
591 if (win
> (long)TCP_MAXWIN
<< tp
->rcv_scale
)
592 win
= (long)TCP_MAXWIN
<< tp
->rcv_scale
;
593 if (win
< (long)(tp
->rcv_adv
- tp
->rcv_nxt
))
594 win
= (long)(tp
->rcv_adv
- tp
->rcv_nxt
);
595 ti
->ti_win
= htons((u_short
) (win
>>tp
->rcv_scale
));
596 if (SEQ_GT(tp
->snd_up
, tp
->snd_nxt
)) {
597 ti
->ti_urp
= htons((u_short
)(tp
->snd_up
- tp
->snd_nxt
));
598 ti
->ti_flags
|= TH_URG
;
601 * If no urgent pointer to send, then we pull
602 * the urgent pointer to the left edge of the send window
603 * so that it doesn't drift into the send window on sequence
606 tp
->snd_up
= tp
->snd_una
; /* drag it along */
609 * Put TCP length in extended header, and then
610 * checksum extended header and data.
613 ti
->ti_len
= htons((u_short
)(sizeof (struct tcphdr
) +
615 ti
->ti_sum
= in_cksum(m
, (int)(hdrlen
+ len
));
618 * In transmit state, time the transmission and arrange for
619 * the retransmit. In persist state, just set snd_max.
621 if (tp
->t_force
== 0 || tp
->t_timer
[TCPT_PERSIST
] == 0) {
622 tcp_seq startseq
= tp
->snd_nxt
;
625 * Advance snd_nxt over sequence space of this segment.
627 if (flags
& (TH_SYN
|TH_FIN
)) {
630 if (flags
& TH_FIN
) {
632 tp
->t_flags
|= TF_SENTFIN
;
636 if (SEQ_GT(tp
->snd_nxt
, tp
->snd_max
)) {
637 tp
->snd_max
= tp
->snd_nxt
;
639 * Time this transmission if not a retransmission and
640 * not currently timing anything.
642 if (tp
->t_rtt
== 0) {
644 tp
->t_rtseq
= startseq
;
645 tcpstat
.tcps_segstimed
++;
650 * Set retransmit timer if not currently set,
651 * and not doing an ack or a keep-alive probe.
652 * Initial value for retransmit timer is smoothed
653 * round-trip time + 2 * round-trip time variance.
654 * Initialize shift counter which is used for backoff
655 * of retransmit time.
657 if (tp
->t_timer
[TCPT_REXMT
] == 0 &&
658 tp
->snd_nxt
!= tp
->snd_una
) {
659 tp
->t_timer
[TCPT_REXMT
] = tp
->t_rxtcur
;
660 if (tp
->t_timer
[TCPT_PERSIST
]) {
661 tp
->t_timer
[TCPT_PERSIST
] = 0;
666 if (SEQ_GT(tp
->snd_nxt
+ len
, tp
->snd_max
))
667 tp
->snd_max
= tp
->snd_nxt
+ len
;
673 if (so
->so_options
& SO_DEBUG
)
674 tcp_trace(TA_OUTPUT
, tp
->t_state
, tp
, ti
, 0);
678 * Fill in IP length and desired time to live and
679 * send to IP level. There should be a better way
680 * to handle ttl and tos; we could keep them in
681 * the template, but need a way to checksum without them.
683 m
->m_pkthdr
.len
= hdrlen
+ len
;
686 error
= tuba_output(m
, tp
);
693 ((struct ip
*)ti
)->ip_len
= m
->m_pkthdr
.len
;
694 ((struct ip
*)ti
)->ip_ttl
= tp
->t_inpcb
->inp_ip
.ip_ttl
; /* XXX */
695 ((struct ip
*)ti
)->ip_tos
= tp
->t_inpcb
->inp_ip
.ip_tos
; /* XXX */
698 * See if we should do MTU discovery. We do it only if the following
700 * 1) we have a valid route to the destination
701 * 2) the MTU is not locked (if it is, then discovery has been
704 if ((rt
= tp
->t_inpcb
->inp_route
.ro_rt
)
705 && rt
->rt_flags
& RTF_UP
706 && !(rt
->rt_rmx
.rmx_locks
& RTV_MTU
)) {
707 ((struct ip
*)ti
)->ip_off
|= IP_DF
;
711 * XXX: It seems that osktittcp expects that packets are
712 * synchronously processed. The current implementation feeds
713 * oskittcp with the packets asynchronously. That's not a
714 * problem normally when the packets are transfered over
715 * network, but it starts to be a problem when it comes to
717 * The ACK bits are set in tcp_input which calls tcp_output and
718 * expects them to be cleared before further processing.
719 * Instead tcp_output calls ip_output which produces a packet
720 * and ends up in tcp_input and we're stuck in infinite loop.
721 * Normally the flags are masked out at the end of this function
722 * and the incomming packets are processed then, but since
723 * currently the loopback packet is delivered during the
724 * ip_output call, the function end is never reached...
727 tp
->t_flags
&= ~(TF_ACKNOW
|TF_DELACK
);
729 error
= ip_output(m
, tp
->t_inpcb
->inp_options
, &tp
->t_inpcb
->inp_route
,
730 so
->so_options
& SO_DONTROUTE
, 0);
734 if (error
== ENOBUFS
) {
735 tcp_quench(tp
->t_inpcb
, 0);
736 OS_DbgPrint(OSK_MID_TRACE
,("quench 0\n"));
740 if (error
== EMSGSIZE
) {
742 * ip_output() will have already fixed the route
743 * for us. tcp_mtudisc() will, as its last action,
744 * initiate retransmission, so it is important to
747 tcp_mtudisc(tp
->t_inpcb
, 0);
748 OS_DbgPrint(OSK_MID_TRACE
,("mtudisc 0\n"));
752 if ((error
== EHOSTUNREACH
|| error
== ENETDOWN
)
753 && TCPS_HAVERCVDSYN(tp
->t_state
)) {
754 tp
->t_softerror
= error
;
755 OS_DbgPrint(OSK_MID_TRACE
,("softerror %d\n", error
));
758 OS_DbgPrint(OSK_MID_TRACE
,("error %d\n", error
));
761 tcpstat
.tcps_sndtotal
++;
764 * Data sent (as far as we can tell).
765 * If this advertises a larger window than any other segment,
766 * then remember the size of the advertised window.
767 * Any pending ACK has now been sent.
769 if (win
> 0 && SEQ_GT(tp
->rcv_nxt
+win
, tp
->rcv_adv
))
770 tp
->rcv_adv
= tp
->rcv_nxt
+ win
;
771 tp
->last_ack_sent
= tp
->rcv_nxt
;
772 tp
->t_flags
&= ~(TF_ACKNOW
|TF_DELACK
);
775 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
781 register struct tcpcb
*tp
;
783 register t
= ((tp
->t_srtt
>> 2) + tp
->t_rttvar
) >> 1;
785 if (tp
->t_timer
[TCPT_REXMT
])
786 panic("tcp_output REXMT");
788 * Start/restart persistance timer.
790 TCPT_RANGESET(tp
->t_timer
[TCPT_PERSIST
],
791 t
* tcp_backoff
[tp
->t_rxtshift
],
792 TCPTV_PERSMIN
, TCPTV_PERSMAX
);
793 if (tp
->t_rxtshift
< TCP_MAXRXTSHIFT
)