5f51c9267ed846bdb42b720806817319cc05adce
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.
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23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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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
;
93 OS_DbgPrint(OSK_MID_TRACE
,("Called\n"));
96 * Determine length of data that should be transmitted,
97 * and flags that will be used.
98 * If there is some data or critical controls (SYN, RST)
99 * to send, then transmit; otherwise, investigate further.
101 idle
= (tp
->snd_max
== tp
->snd_una
);
102 if (idle
&& tp
->t_idle
>= tp
->t_rxtcur
)
104 * We have been idle for "a while" and no acks are
105 * expected to clock out any data we send --
106 * slow start to get ack "clock" running again.
108 tp
->snd_cwnd
= tp
->t_maxseg
;
110 OS_DbgPrint(OSK_MID_TRACE
,("again:\n"));
112 off
= tp
->snd_nxt
- tp
->snd_una
;
113 win
= min(tp
->snd_wnd
, tp
->snd_cwnd
);
115 flags
= tcp_outflags
[tp
->t_state
];
117 * Get standard flags, and add SYN or FIN if requested by 'hidden'
120 if (tp
->t_flags
& TF_NEEDFIN
)
122 if (tp
->t_flags
& TF_NEEDSYN
)
126 * If in persist timeout with window of 0, send 1 byte.
127 * Otherwise, if window is small but nonzero
128 * and timer expired, we will send what we can
129 * and go to transmit state.
134 * If we still have some data to send, then
135 * clear the FIN bit. Usually this would
136 * happen below when it realizes that we
137 * aren't sending all the data. However,
138 * if we have exactly 1 byte of unset data,
139 * then it won't clear the FIN bit below,
140 * and if we are in persist state, we wind
141 * up sending the packet without recording
142 * that we sent the FIN bit.
144 * We can't just blindly clear the FIN bit,
145 * because if we don't have any more data
146 * to send then the probe will be the FIN
149 if (off
< so
->so_snd
.sb_cc
)
153 tp
->t_timer
[TCPT_PERSIST
] = 0;
158 len
= min(so
->so_snd
.sb_cc
, win
) - off
;
160 if ((taop
= tcp_gettaocache(tp
->t_inpcb
)) == NULL
) {
161 taop
= &tao_noncached
;
162 bzero(taop
, sizeof(*taop
));
166 * Lop off SYN bit if it has already been sent. However, if this
167 * is SYN-SENT state and if segment contains data and if we don't
168 * know that foreign host supports TAO, suppress sending segment.
170 if ((flags
& TH_SYN
) && SEQ_GT(tp
->snd_nxt
, tp
->snd_una
)) {
173 if (len
> 0 && tp
->t_state
== TCPS_SYN_SENT
&&
174 taop
->tao_ccsent
== 0) {
175 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
181 * Be careful not to send data and/or FIN on SYN segments
182 * in cases when no CC option will be sent.
183 * This measure is needed to prevent interoperability problems
184 * with not fully conformant TCP implementations.
186 if ((flags
& TH_SYN
) &&
187 ((tp
->t_flags
& TF_NOOPT
) || !(tp
->t_flags
& TF_REQ_CC
) ||
188 ((flags
& TH_ACK
) && !(tp
->t_flags
& TF_RCVD_CC
)))) {
195 * If FIN has been sent but not acked,
196 * but we haven't been called to retransmit,
197 * len will be -1. Otherwise, window shrank
198 * after we sent into it. If window shrank to 0,
199 * cancel pending retransmit, pull snd_nxt back
200 * to (closed) window, and set the persist timer
201 * if it isn't already going. If the window didn't
202 * close completely, just wait for an ACK.
206 tp
->t_timer
[TCPT_REXMT
] = 0;
208 tp
->snd_nxt
= tp
->snd_una
;
209 if (tp
->t_timer
[TCPT_PERSIST
] == 0)
213 if (len
> tp
->t_maxseg
) {
217 if (SEQ_LT(tp
->snd_nxt
+ len
, tp
->snd_una
+ so
->so_snd
.sb_cc
))
220 win
= sbspace(&so
->so_rcv
);
223 * Sender silly window avoidance. If connection is idle or using
224 * the loopback interface and can send all data, a maximum segment,
225 * at least a maximum default-size segment do it,
226 * or are forced, do it; otherwise don't bother.
227 * If peer's buffer is tiny, then send
228 * when window is at least half open.
229 * If retransmitting (possibly after persist timer forced us
230 * to send into a small window), then must resend.
233 if (len
== tp
->t_maxseg
)
235 if ((idle
|| tp
->t_flags
& TF_NODELAY
||
236 IS_LOOPBACK_ADDR(tp
->t_inpcb
->inp_laddr
.s_addr
)) &&
237 (tp
->t_flags
& TF_NOPUSH
) == 0 &&
238 len
+ off
>= so
->so_snd
.sb_cc
)
242 if (len
>= tp
->max_sndwnd
/ 2 && tp
->max_sndwnd
> 0)
244 if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
))
249 * Compare available window to amount of window
250 * known to peer (as advertised window less
251 * next expected input). If the difference is at least two
252 * max size segments, or at least 50% of the maximum possible
253 * window, then want to send a window update to peer.
257 * "adv" is the amount we can increase the window,
258 * taking into account that we are limited by
259 * TCP_MAXWIN << tp->rcv_scale.
261 long adv
= min(win
, (long)TCP_MAXWIN
<< tp
->rcv_scale
) -
262 (tp
->rcv_adv
- tp
->rcv_nxt
);
264 if (adv
>= (long) (2 * tp
->t_maxseg
))
266 if (2 * adv
>= (long) so
->so_rcv
.sb_hiwat
)
271 * Send if we owe peer an ACK.
273 if (tp
->t_flags
& TF_ACKNOW
)
275 if ((flags
& TH_RST
) ||
276 ((flags
& TH_SYN
) && (tp
->t_flags
& TF_NEEDSYN
) == 0))
278 if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
281 * If our state indicates that FIN should be sent
282 * and we have not yet done so, or we're retransmitting the FIN,
283 * then we need to send.
285 if (flags
& TH_FIN
&&
286 ((tp
->t_flags
& TF_SENTFIN
) == 0 || tp
->snd_nxt
== tp
->snd_una
))
290 * TCP window updates are not reliable, rather a polling protocol
291 * using ``persist'' packets is used to insure receipt of window
292 * updates. The three ``states'' for the output side are:
293 * idle not doing retransmits or persists
294 * persisting to move a small or zero window
295 * (re)transmitting and thereby not persisting
297 * tp->t_timer[TCPT_PERSIST]
298 * is set when we are in persist state.
300 * is set when we are called to send a persist packet.
301 * tp->t_timer[TCPT_REXMT]
302 * is set when we are retransmitting
303 * The output side is idle when both timers are zero.
305 * If send window is too small, there is data to transmit, and no
306 * retransmit or persist is pending, then go to persist state.
307 * If nothing happens soon, send when timer expires:
308 * if window is nonzero, transmit what we can,
309 * otherwise force out a byte.
311 if (so
->so_snd
.sb_cc
&& tp
->t_timer
[TCPT_REXMT
] == 0 &&
312 tp
->t_timer
[TCPT_PERSIST
] == 0) {
318 * No reason to send a segment, just return.
320 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
324 OS_DbgPrint(OSK_MID_TRACE
,("send:\n"));
326 * Before ESTABLISHED, force sending of initial options
327 * unless TCP set not to do any options.
328 * NOTE: we assume that the IP/TCP header plus TCP options
329 * always fit in a single mbuf, leaving room for a maximum
331 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
334 hdrlen
= sizeof (struct tcpiphdr
);
335 if (flags
& TH_SYN
) {
336 tp
->snd_nxt
= tp
->iss
;
337 if ((tp
->t_flags
& TF_NOOPT
) == 0) {
340 opt
[0] = TCPOPT_MAXSEG
;
341 opt
[1] = TCPOLEN_MAXSEG
;
342 mss
= htons((u_short
) tcp_mssopt(tp
));
343 (void)memcpy(opt
+ 2, &mss
, sizeof(mss
));
344 optlen
= TCPOLEN_MAXSEG
;
346 if ((tp
->t_flags
& TF_REQ_SCALE
) &&
347 ((flags
& TH_ACK
) == 0 ||
348 (tp
->t_flags
& TF_RCVD_SCALE
))) {
349 *((u_long
*) (opt
+ optlen
)) = htonl(
351 TCPOPT_WINDOW
<< 16 |
352 TCPOLEN_WINDOW
<< 8 |
353 tp
->request_r_scale
);
360 * Send a timestamp and echo-reply if this is a SYN and our side
361 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
362 * and our peer have sent timestamps in our SYN's.
364 if ((tp
->t_flags
& (TF_REQ_TSTMP
|TF_NOOPT
)) == TF_REQ_TSTMP
&&
365 (flags
& TH_RST
) == 0 &&
366 ((flags
& TH_ACK
) == 0 ||
367 (tp
->t_flags
& TF_RCVD_TSTMP
))) {
368 u_long
*lp
= (u_long
*)(opt
+ optlen
);
370 /* Form timestamp option as shown in appendix A of RFC 1323. */
371 *lp
++ = htonl(TCPOPT_TSTAMP_HDR
);
372 *lp
++ = htonl(tcp_now
);
373 *lp
= htonl(tp
->ts_recent
);
374 optlen
+= TCPOLEN_TSTAMP_APPA
;
378 * Send `CC-family' options if our side wants to use them (TF_REQ_CC),
379 * options are allowed (!TF_NOOPT) and it's not a RST.
381 if ((tp
->t_flags
& (TF_REQ_CC
|TF_NOOPT
)) == TF_REQ_CC
&&
382 (flags
& TH_RST
) == 0) {
383 switch (flags
& (TH_SYN
|TH_ACK
)) {
385 * This is a normal ACK, send CC if we received CC before
389 if (!(tp
->t_flags
& TF_RCVD_CC
))
394 * We can only get here in T/TCP's SYN_SENT* state, when
395 * we're a sending a non-SYN segment without waiting for
396 * the ACK of our SYN. A check above assures that we only
397 * do this if our peer understands T/TCP.
400 opt
[optlen
++] = TCPOPT_NOP
;
401 opt
[optlen
++] = TCPOPT_NOP
;
402 opt
[optlen
++] = TCPOPT_CC
;
403 opt
[optlen
++] = TCPOLEN_CC
;
404 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
410 * This is our initial SYN, check whether we have to use
415 opt
[optlen
++] = TCPOPT_NOP
;
416 opt
[optlen
++] = TCPOPT_NOP
;
417 opt
[optlen
++] = tp
->t_flags
& TF_SENDCCNEW
?
418 TCPOPT_CCNEW
: TCPOPT_CC
;
419 opt
[optlen
++] = TCPOLEN_CC
;
420 *(u_int32_t
*)&opt
[optlen
] = htonl(tp
->cc_send
);
426 * This is a SYN,ACK; send CC and CC.echo if we received
429 case (TH_SYN
|TH_ACK
):
430 if (tp
->t_flags
& TF_RCVD_CC
) {
431 opt
[optlen
++] = TCPOPT_NOP
;
432 opt
[optlen
++] = TCPOPT_NOP
;
433 opt
[optlen
++] = TCPOPT_CC
;
434 opt
[optlen
++] = TCPOLEN_CC
;
435 *(u_int32_t
*)&opt
[optlen
] =
438 opt
[optlen
++] = TCPOPT_NOP
;
439 opt
[optlen
++] = TCPOPT_NOP
;
440 opt
[optlen
++] = TCPOPT_CCECHO
;
441 opt
[optlen
++] = TCPOLEN_CC
;
442 *(u_int32_t
*)&opt
[optlen
] =
453 * Adjust data length if insertion of options will
454 * bump the packet length beyond the t_maxopd length.
455 * Clear the FIN bit because we cut off the tail of
458 if (len
+ optlen
> tp
->t_maxopd
) {
460 * If there is still more to send, don't close the connection.
463 len
= tp
->t_maxopd
- optlen
;
467 /*#ifdef DIAGNOSTIC*/
468 if (max_linkhdr
+ hdrlen
> MHLEN
)
469 panic("tcphdr too big");
473 * Grab a header mbuf, attaching a copy of data to
474 * be transmitted, and initialize the header from
475 * the template for sends on this connection.
478 if (tp
->t_force
&& len
== 1)
479 tcpstat
.tcps_sndprobe
++;
480 else if (SEQ_LT(tp
->snd_nxt
, tp
->snd_max
)) {
481 tcpstat
.tcps_sndrexmitpack
++;
482 tcpstat
.tcps_sndrexmitbyte
+= len
;
484 tcpstat
.tcps_sndpack
++;
485 tcpstat
.tcps_sndbyte
+= len
;
488 if ((m
= m_copypack(so
->so_snd
.sb_mb
, off
,
489 (int)len
, max_linkhdr
+ hdrlen
)) == 0) {
494 * m_copypack left space for our hdr; use it.
499 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
504 m
->m_data
+= max_linkhdr
;
506 /* m is not initialized here ... see below up to line
507 * in_cksum to see how it gets there */
508 if (len
<= MHLEN
- hdrlen
- max_linkhdr
) {
509 m_copydata(so
->so_snd
.sb_mb
, off
, (int) len
,
510 mtod(m
, caddr_t
) + hdrlen
);
513 m
->m_next
= m_copy(so
->so_snd
.sb_mb
, off
, (int) len
);
514 // the buffer is allocated, but not filled with the tcp
515 // header yet, so dumping it here yields garbage...
516 //OskitDumpBuffer(mtod(m, caddr_t), len);
517 if (m
->m_next
== 0) {
525 * If we're sending everything we've got, set PUSH.
526 * (This will keep happy those implementations which only
527 * give data to the user when a buffer fills or
530 if (off
+ len
== so
->so_snd
.sb_cc
)
533 if (tp
->t_flags
& TF_ACKNOW
)
534 tcpstat
.tcps_sndacks
++;
535 else if (flags
& (TH_SYN
|TH_FIN
|TH_RST
))
536 tcpstat
.tcps_sndctrl
++;
537 else if (SEQ_GT(tp
->snd_up
, tp
->snd_una
))
538 tcpstat
.tcps_sndurg
++;
540 tcpstat
.tcps_sndwinup
++;
542 MGETHDR(m
, M_DONTWAIT
, MT_HEADER
);
547 m
->m_data
+= max_linkhdr
;
550 m
->m_pkthdr
.rcvif
= (struct ifnet
*)0;
552 /* This pulls the data ptr from m and start initting it...
553 * before this point, m is empty. */
554 ti
= mtod(m
, struct tcpiphdr
*);
555 if (tp
->t_template
== 0)
557 (void)memcpy(ti
, tp
->t_template
, sizeof (struct tcpiphdr
));
560 * Fill in fields, remembering maximum advertised
561 * window for use in delaying messages about window sizes.
562 * If resending a FIN, be sure not to use a new sequence number.
564 if (flags
& TH_FIN
&& tp
->t_flags
& TF_SENTFIN
&&
565 tp
->snd_nxt
== tp
->snd_max
)
568 * If we are doing retransmissions, then snd_nxt will
569 * not reflect the first unsent octet. For ACK only
570 * packets, we do not want the sequence number of the
571 * retransmitted packet, we want the sequence number
572 * of the next unsent octet. So, if there is no data
573 * (and no SYN or FIN), use snd_max instead of snd_nxt
574 * when filling in ti_seq. But if we are in persist
575 * state, snd_max might reflect one byte beyond the
576 * right edge of the window, so use snd_nxt in that
577 * case, since we know we aren't doing a retransmission.
578 * (retransmit and persist are mutually exclusive...)
580 if (len
|| (flags
& (TH_SYN
|TH_FIN
)) || tp
->t_timer
[TCPT_PERSIST
])
581 ti
->ti_seq
= htonl(tp
->snd_nxt
);
583 ti
->ti_seq
= htonl(tp
->snd_max
);
584 ti
->ti_ack
= htonl(tp
->rcv_nxt
);
587 (void)memcpy(ti
+ 1, opt
, optlen
);
588 ti
->ti_off
= (sizeof (struct tcphdr
) + optlen
) >> 2;
590 ti
->ti_flags
= flags
;
592 * Calculate receive window. Don't shrink window,
593 * but avoid silly window syndrome.
595 if (win
< (long)(so
->so_rcv
.sb_hiwat
/ 4) && win
< (long)tp
->t_maxseg
)
597 if (win
> (long)TCP_MAXWIN
<< tp
->rcv_scale
)
598 win
= (long)TCP_MAXWIN
<< tp
->rcv_scale
;
599 if (win
< (long)(tp
->rcv_adv
- tp
->rcv_nxt
))
600 win
= (long)(tp
->rcv_adv
- tp
->rcv_nxt
);
601 ti
->ti_win
= htons((u_short
) (win
>>tp
->rcv_scale
));
602 if (SEQ_GT(tp
->snd_up
, tp
->snd_nxt
)) {
603 ti
->ti_urp
= htons((u_short
)(tp
->snd_up
- tp
->snd_nxt
));
604 ti
->ti_flags
|= TH_URG
;
607 * If no urgent pointer to send, then we pull
608 * the urgent pointer to the left edge of the send window
609 * so that it doesn't drift into the send window on sequence
612 tp
->snd_up
= tp
->snd_una
; /* drag it along */
615 * Put TCP length in extended header, and then
616 * checksum extended header and data.
619 ti
->ti_len
= htons((u_short
)(sizeof (struct tcphdr
) +
621 ti
->ti_sum
= in_cksum(m
, (int)(hdrlen
+ len
));
624 * In transmit state, time the transmission and arrange for
625 * the retransmit. In persist state, just set snd_max.
627 if (tp
->t_force
== 0 || tp
->t_timer
[TCPT_PERSIST
] == 0) {
628 tcp_seq startseq
= tp
->snd_nxt
;
631 * Advance snd_nxt over sequence space of this segment.
633 if (flags
& (TH_SYN
|TH_FIN
)) {
636 if (flags
& TH_FIN
) {
638 tp
->t_flags
|= TF_SENTFIN
;
642 if (SEQ_GT(tp
->snd_nxt
, tp
->snd_max
)) {
643 tp
->snd_max
= tp
->snd_nxt
;
645 * Time this transmission if not a retransmission and
646 * not currently timing anything.
648 if (tp
->t_rtt
== 0) {
650 tp
->t_rtseq
= startseq
;
651 tcpstat
.tcps_segstimed
++;
656 * Set retransmit timer if not currently set,
657 * and not doing an ack or a keep-alive probe.
658 * Initial value for retransmit timer is smoothed
659 * round-trip time + 2 * round-trip time variance.
660 * Initialize shift counter which is used for backoff
661 * of retransmit time.
663 if (tp
->t_timer
[TCPT_REXMT
] == 0 &&
664 tp
->snd_nxt
!= tp
->snd_una
) {
665 tp
->t_timer
[TCPT_REXMT
] = tp
->t_rxtcur
;
666 if (tp
->t_timer
[TCPT_PERSIST
]) {
667 tp
->t_timer
[TCPT_PERSIST
] = 0;
672 if (SEQ_GT(tp
->snd_nxt
+ len
, tp
->snd_max
))
673 tp
->snd_max
= tp
->snd_nxt
+ len
;
679 if (so
->so_options
& SO_DEBUG
)
680 tcp_trace(TA_OUTPUT
, tp
->t_state
, tp
, ti
, 0);
684 * Fill in IP length and desired time to live and
685 * send to IP level. There should be a better way
686 * to handle ttl and tos; we could keep them in
687 * the template, but need a way to checksum without them.
689 m
->m_pkthdr
.len
= hdrlen
+ len
;
692 error
= tuba_output(m
, tp
);
699 ((struct ip
*)ti
)->ip_len
= m
->m_pkthdr
.len
;
700 ((struct ip
*)ti
)->ip_ttl
= tp
->t_inpcb
->inp_ip
.ip_ttl
; /* XXX */
701 ((struct ip
*)ti
)->ip_tos
= tp
->t_inpcb
->inp_ip
.ip_tos
; /* XXX */
704 * See if we should do MTU discovery. We do it only if the following
706 * 1) we have a valid route to the destination
707 * 2) the MTU is not locked (if it is, then discovery has been
710 if ((rt
= tp
->t_inpcb
->inp_route
.ro_rt
)
711 && rt
->rt_flags
& RTF_UP
712 && !(rt
->rt_rmx
.rmx_locks
& RTV_MTU
)) {
713 ((struct ip
*)ti
)->ip_off
|= IP_DF
;
717 * XXX: It seems that osktittcp expects that packets are
718 * synchronously processed. The current implementation feeds
719 * oskittcp with the packets asynchronously. That's not a
720 * problem normally when the packets are transfered over
721 * network, but it starts to be a problem when it comes to
723 * The ACK bits are set in tcp_input which calls tcp_output and
724 * expects them to be cleared before further processing.
725 * Instead tcp_output calls ip_output which produces a packet
726 * and ends up in tcp_input and we're stuck in infinite loop.
727 * Normally the flags are masked out at the end of this function
728 * and the incomming packets are processed then, but since
729 * currently the loopback packet is delivered during the
730 * ip_output call, the function end is never reached...
733 tp
->t_flags
&= ~(TF_ACKNOW
|TF_DELACK
);
735 error
= ip_output(m
, tp
->t_inpcb
->inp_options
, &tp
->t_inpcb
->inp_route
,
736 so
->so_options
& SO_DONTROUTE
, 0);
738 /* We allocated m, so we are responsible for freeing it. If the mbuf
739 contains a pointer to an external datablock, we (or rather, m_copy)
740 didn't allocate it but pointed it to the data to send. So we have
741 to cheat a little bit and keep M_FREE from freeing the external
744 m
->m_flags
&= ~M_EXT
;
752 if (error
== ENOBUFS
) {
753 tcp_quench(tp
->t_inpcb
, 0);
754 OS_DbgPrint(OSK_MID_TRACE
,("quench 0\n"));
758 if (error
== EMSGSIZE
) {
760 * ip_output() will have already fixed the route
761 * for us. tcp_mtudisc() will, as its last action,
762 * initiate retransmission, so it is important to
765 tcp_mtudisc(tp
->t_inpcb
, 0);
766 OS_DbgPrint(OSK_MID_TRACE
,("mtudisc 0\n"));
770 if ((error
== EHOSTUNREACH
|| error
== ENETDOWN
)
771 && TCPS_HAVERCVDSYN(tp
->t_state
)) {
772 tp
->t_softerror
= error
;
773 OS_DbgPrint(OSK_MID_TRACE
,("softerror %d\n", error
));
776 OS_DbgPrint(OSK_MID_TRACE
,("error %d\n", error
));
779 tcpstat
.tcps_sndtotal
++;
782 * Data sent (as far as we can tell).
783 * If this advertises a larger window than any other segment,
784 * then remember the size of the advertised window.
785 * Any pending ACK has now been sent.
787 if (win
> 0 && SEQ_GT(tp
->rcv_nxt
+win
, tp
->rcv_adv
))
788 tp
->rcv_adv
= tp
->rcv_nxt
+ win
;
789 tp
->last_ack_sent
= tp
->rcv_nxt
;
790 tp
->t_flags
&= ~(TF_ACKNOW
|TF_DELACK
);
793 OS_DbgPrint(OSK_MID_TRACE
,("leaving 0\n"));
799 register struct tcpcb
*tp
;
801 register int t
= ((tp
->t_srtt
>> 2) + tp
->t_rttvar
) >> 1;
803 if (tp
->t_timer
[TCPT_REXMT
])
804 panic("tcp_output REXMT");
806 * Start/restart persistance timer.
808 TCPT_RANGESET(tp
->t_timer
[TCPT_PERSIST
],
809 t
* tcp_backoff
[tp
->t_rxtshift
],
810 TCPTV_PERSMIN
, TCPTV_PERSMAX
);
811 if (tp
->t_rxtshift
< TCP_MAXRXTSHIFT
)