tcp_output.c@ 15136

Last change on this file since 15136 was 15074, checked in by vboxsync, 16 years ago
slirp: better readability
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Line
1	/*
2	* Copyright (c) 1982, 1986, 1988, 1990, 1993
3	* The Regents of the University of California. All rights reserved.
4	*
5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions
7	* are met:
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.
20	*
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
31	* SUCH DAMAGE.
32	*
33	* @(#)tcp_output.c 8.3 (Berkeley) 12/30/93
34	* tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp
35	*/
36
37	/*
38	* Changes and additions relating to SLiRP
39	* Copyright (c) 1995 Danny Gasparovski.
40	*
41	* Please read the file COPYRIGHT for the
42	* terms and conditions of the copyright.
43	*/
44
45	#include <slirp.h>
46
47	/*
48	* Since this is only used in "stats socket", we give meaning
49	* names instead of the REAL names
50	*/
51	const char * const tcpstates[] =
52	{
53	/* "CLOSED", "LISTEN", "SYN_SENT", "SYN_RCVD", */
54	"REDIRECT", "LISTEN", "SYN_SENT", "SYN_RCVD",
55	"ESTABLISHED", "CLOSE_WAIT", "FIN_WAIT_1", "CLOSING",
56	"LAST_ACK", "FIN_WAIT_2", "TIME_WAIT",
57	};
58
59	static const u_char tcp_outflags[TCP_NSTATES] =
60	{
61	TH_RST\|TH_ACK, 0, TH_SYN, TH_SYN\|TH_ACK,
62	TH_ACK, TH_ACK, TH_FIN\|TH_ACK, TH_FIN\|TH_ACK,
63	TH_FIN\|TH_ACK, TH_ACK, TH_ACK,
64	};
65
66
67	#define MAX_TCPOPTLEN 32 /* max # bytes that go in options */
68
69	/*
70	* Tcp output routine: figure out what should be sent and send it.
71	*/
72	int
73	tcp_output(PNATState pData, register struct tcpcb *tp)
74	{
75	register struct socket *so = tp->t_socket;
76	register long len, win;
77	int off, flags, error;
78	register struct mbuf *m;
79	register struct tcpiphdr *ti;
80	u_char opt[MAX_TCPOPTLEN];
81	unsigned optlen, hdrlen;
82	int idle, sendalot;
83
84	DEBUG_CALL("tcp_output");
85	DEBUG_ARG("tp = %lx", (long )tp);
86
87	/*
88	* Determine length of data that should be transmitted,
89	* and flags that will be used.
90	* If there is some data or critical controls (SYN, RST)
91	* to send, then transmit; otherwise, investigate further.
92	*/
93	idle = (tp->snd_max == tp->snd_una);
94	if (idle && tp->t_idle >= tp->t_rxtcur)
95	/*
96	* We have been idle for "a while" and no acks are
97	* expected to clock out any data we send --
98	* slow start to get ack "clock" running again.
99	*/
100	tp->snd_cwnd = tp->t_maxseg;
101
102	again:
103	sendalot = 0;
104	off = tp->snd_nxt - tp->snd_una;
105	win = min(tp->snd_wnd, tp->snd_cwnd);
106
107	flags = tcp_outflags[tp->t_state];
108
109	DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
110
111	/*
112	* If in persist timeout with window of 0, send 1 byte.
113	* Otherwise, if window is small but nonzero
114	* and timer expired, we will send what we can
115	* and go to transmit state.
116	*/
117	if (tp->t_force)
118	{
119	if (win == 0)
120	{
121	/*
122	* If we still have some data to send, then
123	* clear the FIN bit. Usually this would
124	* happen below when it realizes that we
125	* aren't sending all the data. However,
126	* if we have exactly 1 byte of unset data,
127	* then it won't clear the FIN bit below,
128	* and if we are in persist state, we wind
129	* up sending the packet without recording
130	* that we sent the FIN bit.
131	*
132	* We can't just blindly clear the FIN bit,
133	* because if we don't have any more data
134	* to send then the probe will be the FIN
135	* itself.
136	*/
137	if (off < so->so_snd.sb_cc)
138	flags &= ~TH_FIN;
139	win = 1;
140	}
141	else
142	{
143	tp->t_timer[TCPT_PERSIST] = 0;
144	tp->t_rxtshift = 0;
145	}
146	}
147
148	len = min(so->so_snd.sb_cc, win) - off;
149	if (len < 0)
150	{
151	/*
152	* If FIN has been sent but not acked,
153	* but we haven't been called to retransmit,
154	* len will be -1. Otherwise, window shrank
155	* after we sent into it. If window shrank to 0,
156	* cancel pending retransmit and pull snd_nxt
157	* back to (closed) window. We will enter persist
158	* state below. If the window didn't close completely,
159	* just wait for an ACK.
160	*/
161	len = 0;
162	if (win == 0)
163	{
164	tp->t_timer[TCPT_REXMT] = 0;
165	tp->snd_nxt = tp->snd_una;
166	}
167	}
168	if (len > tp->t_maxseg)
169	{
170	len = tp->t_maxseg;
171	sendalot = 1;
172	}
173	if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
174	flags &= ~TH_FIN;
175
176	win = sbspace(&so->so_rcv);
177
178	/*
179	* Sender silly window avoidance. If connection is idle
180	* and can send all data, a maximum segment,
181	* at least a maximum default-size segment do it,
182	* or are forced, do it; otherwise don't bother.
183	* If peer's buffer is tiny, then send
184	* when window is at least half open.
185	* If retransmitting (possibly after persist timer forced us
186	* to send into a small window), then must resend.
187	*/
188	if (len)
189	{
190	if (len == tp->t_maxseg)
191	goto send;
192	if ((1 \|\| idle \|\| tp->t_flags & TF_NODELAY) &&
193	len + off >= so->so_snd.sb_cc)
194	goto send;
195	if (tp->t_force)
196	goto send;
197	if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
198	goto send;
199	if (SEQ_LT(tp->snd_nxt, tp->snd_max))
200	goto send;
201	}
202
203	/*
204	* Compare available window to amount of window
205	* known to peer (as advertised window less
206	* next expected input). If the difference is at least two
207	* max size segments, or at least 50% of the maximum possible
208	* window, then want to send a window update to peer.
209	*/
210	if (win > 0)
211	{
212	/*
213	* "adv" is the amount we can increase the window,
214	* taking into account that we are limited by
215	* TCP_MAXWIN << tp->rcv_scale.
216	*/
217	long adv = min(win,
218	(long)TCP_MAXWIN << tp->rcv_scale) -
219	(tp->rcv_adv - tp->rcv_nxt);
220
221	if (adv >= (long) (2 * tp->t_maxseg))
222	goto send;
223	if (2 * adv >= (long) so->so_rcv.sb_datalen)
224	goto send;
225	}
226
227	/*
228	* Send if we owe peer an ACK.
229	*/
230	if (tp->t_flags & TF_ACKNOW)
231	goto send;
232	if (flags & (TH_SYN\|TH_RST))
233	goto send;
234	if (SEQ_GT(tp->snd_up, tp->snd_una))
235	goto send;
236	/*
237	* If our state indicates that FIN should be sent
238	* and we have not yet done so, or we're retransmitting the FIN,
239	* then we need to send.
240	*/
241	if ( flags & TH_FIN
242	&& ((tp->t_flags & TF_SENTFIN) == 0 \|\| tp->snd_nxt == tp->snd_una))
243	goto send;
244
245	/*
246	* TCP window updates are not reliable, rather a polling protocol
247	* using ``persist'' packets is used to insure receipt of window
248	* updates. The three ``states'' for the output side are:
249	* idle not doing retransmits or persists
250	* persisting to move a small or zero window
251	* (re)transmitting and thereby not persisting
252	*
253	* tp->t_timer[TCPT_PERSIST]
254	* is set when we are in persist state.
255	* tp->t_force
256	* is set when we are called to send a persist packet.
257	* tp->t_timer[TCPT_REXMT]
258	* is set when we are retransmitting
259	* The output side is idle when both timers are zero.
260	*
261	* If send window is too small, there is data to transmit, and no
262	* retransmit or persist is pending, then go to persist state.
263	* If nothing happens soon, send when timer expires:
264	* if window is nonzero, transmit what we can,
265	* otherwise force out a byte.
266	*/
267	if ( so->so_snd.sb_cc
268	&& tp->t_timer[TCPT_REXMT] == 0
269	&& tp->t_timer[TCPT_PERSIST] == 0)
270	{
271	tp->t_rxtshift = 0;
272	tcp_setpersist(tp);
273	}
274
275	/*
276	* No reason to send a segment, just return.
277	*/
278	tcpstat.tcps_didnuttin++;
279
280	return (0);
281
282	send:
283	/*
284	* Before ESTABLISHED, force sending of initial options
285	* unless TCP set not to do any options.
286	* NOTE: we assume that the IP/TCP header plus TCP options
287	* always fit in a single mbuf, leaving room for a maximum
288	* link header, i.e.
289	* max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
290	*/
291	optlen = 0;
292	hdrlen = sizeof (struct tcpiphdr);
293	if (flags & TH_SYN)
294	{
295	tp->snd_nxt = tp->iss;
296	if ((tp->t_flags & TF_NOOPT) == 0)
297	{
298	u_int16_t mss;
299
300	opt[0] = TCPOPT_MAXSEG;
301	opt[1] = 4;
302	mss = htons((u_int16_t) tcp_mss(pData, tp, 0));
303	memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss));
304	optlen = 4;
305
306	#if 0
307	if ( (tp->t_flags & TF_REQ_SCALE)
308	&& ( (flags & TH_ACK) == 0
309	\|\| (tp->t_flags & TF_RCVD_SCALE)))
310	{
311	((u_int32_t ) (opt + optlen)) = htonl( TCPOPT_NOP << 24
312	\| TCPOPT_WINDOW << 16
313	\| TCPOLEN_WINDOW << 8
314	\| tp->request_r_scale);
315	optlen += 4;
316	}
317	#endif
318	}
319	}
320
321	/*
322	* Send a timestamp and echo-reply if this is a SYN and our side
323	* wants to use timestamps (TF_REQ_TSTMP is set) or both our side
324	* and our peer have sent timestamps in our SYN's.
325	*/
326	#if 0
327	if ( (tp->t_flags & (TF_REQ_TSTMP\|TF_NOOPT)) == TF_REQ_TSTMP
328	&& (flags & TH_RST) == 0
329	&& ( (flags & (TH_SYN\|TH_ACK)) == TH_SYN
330	\|\| (tp->t_flags & TF_RCVD_TSTMP)))
331	{
332	u_int32_t lp = (u_int32_t )(opt + optlen);
333
334	/* Form timestamp option as shown in appendix A of RFC 1323. */
335	*lp++ = htonl(TCPOPT_TSTAMP_HDR);
336	*lp++ = htonl(tcp_now);
337	*lp = htonl(tp->ts_recent);
338	optlen += TCPOLEN_TSTAMP_APPA;
339	}
340	#endif
341	hdrlen += optlen;
342
343	/*
344	* Adjust data length if insertion of options will
345	* bump the packet length beyond the t_maxseg length.
346	*/
347	if (len > tp->t_maxseg - optlen)
348	{
349	len = tp->t_maxseg - optlen;
350	sendalot = 1;
351	}
352
353	/*
354	* Grab a header mbuf, attaching a copy of data to
355	* be transmitted, and initialize the header from
356	* the template for sends on this connection.
357	*/
358	if (len)
359	{
360	if (tp->t_force && len == 1)
361	tcpstat.tcps_sndprobe++;
362	else if (SEQ_LT(tp->snd_nxt, tp->snd_max))
363	{
364	tcpstat.tcps_sndrexmitpack++;
365	tcpstat.tcps_sndrexmitbyte += len;
366	}
367	else
368	{
369	tcpstat.tcps_sndpack++;
370	tcpstat.tcps_sndbyte += len;
371	}
372
373	m = m_get(pData);
374	if (m == NULL)
375	{
376	/* error = ENOBUFS; */
377	error = 1;
378	goto out;
379	}
380	m->m_data += if_maxlinkhdr;
381	m->m_len = hdrlen;
382
383	/*
384	* This will always succeed, since we make sure our mbufs
385	* are big enough to hold one MSS packet + header + ... etc.
386	*/
387	#if 0
388	if (len <= MHLEN - hdrlen - max_linkhdr)
389	{
390	#endif
391	sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
392	m->m_len += len;
393	#if 0
394	}
395	else
396	{
397	m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
398	if (m->m_next == 0)
399	len = 0;
400	}
401	#endif
402	/*
403	* If we're sending everything we've got, set PUSH.
404	* (This will keep happy those implementations which only
405	* give data to the user when a buffer fills or
406	* a PUSH comes in.)
407	*/
408	if (off + len == so->so_snd.sb_cc)
409	flags \|= TH_PUSH;
410	}
411	else
412	{
413	if (tp->t_flags & TF_ACKNOW)
414	tcpstat.tcps_sndacks++;
415	else if (flags & (TH_SYN\|TH_FIN\|TH_RST))
416	tcpstat.tcps_sndctrl++;
417	else if (SEQ_GT(tp->snd_up, tp->snd_una))
418	tcpstat.tcps_sndurg++;
419	else
420	tcpstat.tcps_sndwinup++;
421
422	m = m_get(pData);
423	if (m == NULL)
424	{
425	/* error = ENOBUFS; */
426	error = 1;
427	goto out;
428	}
429	m->m_data += if_maxlinkhdr;
430	m->m_len = hdrlen;
431	}
432
433	ti = mtod(m, struct tcpiphdr *);
434
435	memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr));
436
437	/*
438	* Fill in fields, remembering maximum advertised
439	* window for use in delaying messages about window sizes.
440	* If resending a FIN, be sure not to use a new sequence number.
441	*/
442	if ( flags & TH_FIN
443	&& tp->t_flags & TF_SENTFIN
444	&& tp->snd_nxt == tp->snd_max)
445	tp->snd_nxt--;
446	/*
447	* If we are doing retransmissions, then snd_nxt will
448	* not reflect the first unsent octet. For ACK only
449	* packets, we do not want the sequence number of the
450	* retransmitted packet, we want the sequence number
451	* of the next unsent octet. So, if there is no data
452	* (and no SYN or FIN), use snd_max instead of snd_nxt
453	* when filling in ti_seq. But if we are in persist
454	* state, snd_max might reflect one byte beyond the
455	* right edge of the window, so use snd_nxt in that
456	* case, since we know we aren't doing a retransmission.
457	* (retransmit and persist are mutually exclusive...)
458	*/
459	if (len \|\| (flags & (TH_SYN\|TH_FIN)) \|\| tp->t_timer[TCPT_PERSIST])
460	ti->ti_seq = htonl(tp->snd_nxt);
461	else
462	ti->ti_seq = htonl(tp->snd_max);
463	ti->ti_ack = htonl(tp->rcv_nxt);
464	if (optlen)
465	{
466	memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
467	ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
468	}
469	ti->ti_flags = flags;
470	/*
471	* Calculate receive window. Don't shrink window,
472	* but avoid silly window syndrome.
473	*/
474	if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg)
475	win = 0;
476	if (win > (long)TCP_MAXWIN << tp->rcv_scale)
477	win = (long)TCP_MAXWIN << tp->rcv_scale;
478	if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
479	win = (long)(tp->rcv_adv - tp->rcv_nxt);
480	ti->ti_win = htons((u_int16_t) (win>>tp->rcv_scale));
481
482	#if 0
483	if (SEQ_GT(tp->snd_up, tp->snd_nxt))
484	{
485	ti->ti_urp = htons((u_int16_t)(tp->snd_up - tp->snd_nxt));
486	#else
487	if (SEQ_GT(tp->snd_up, tp->snd_una))
488	{
489	ti->ti_urp = htons((u_int16_t)(tp->snd_up - ntohl(ti->ti_seq)));
490	#endif
491	ti->ti_flags \|= TH_URG;
492	}
493	else
494	/*
495	* If no urgent pointer to send, then we pull
496	* the urgent pointer to the left edge of the send window
497	* so that it doesn't drift into the send window on sequence
498	* number wraparound.
499	*/
500	tp->snd_up = tp->snd_una; /* drag it along */
501
502	/*
503	* Put TCP length in extended header, and then
504	* checksum extended header and data.
505	*/
506	if (len + optlen)
507	ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr)
508	+ optlen + len));
509	ti->ti_sum = cksum(m, (int)(hdrlen + len));
510
511	/*
512	* In transmit state, time the transmission and arrange for
513	* the retransmit. In persist state, just set snd_max.
514	*/
515	if (tp->t_force == 0 \|\| tp->t_timer[TCPT_PERSIST] == 0)
516	{
517	tcp_seq startseq = tp->snd_nxt;
518
519	/*
520	* Advance snd_nxt over sequence space of this segment.
521	*/
522	if (flags & (TH_SYN\|TH_FIN))
523	{
524	if (flags & TH_SYN)
525	tp->snd_nxt++;
526	if (flags & TH_FIN)
527	{
528	tp->snd_nxt++;
529	tp->t_flags \|= TF_SENTFIN;
530	}
531	}
532	tp->snd_nxt += len;
533	if (SEQ_GT(tp->snd_nxt, tp->snd_max))
534	{
535	tp->snd_max = tp->snd_nxt;
536	/*
537	* Time this transmission if not a retransmission and
538	* not currently timing anything.
539	*/
540	if (tp->t_rtt == 0)
541	{
542	tp->t_rtt = 1;
543	tp->t_rtseq = startseq;
544	tcpstat.tcps_segstimed++;
545	}
546	}
547
548	/*
549	* Set retransmit timer if not currently set,
550	* and not doing an ack or a keep-alive probe.
551	* Initial value for retransmit timer is smoothed
552	* round-trip time + 2 * round-trip time variance.
553	* Initialize shift counter which is used for backoff
554	* of retransmit time.
555	*/
556	if ( tp->t_timer[TCPT_REXMT] == 0
557	&& tp->snd_nxt != tp->snd_una)
558	{
559	tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
560	if (tp->t_timer[TCPT_PERSIST])
561	{
562	tp->t_timer[TCPT_PERSIST] = 0;
563	tp->t_rxtshift = 0;
564	}
565	}
566	}
567	else
568	if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
569	tp->snd_max = tp->snd_nxt + len;
570
571	/*
572	* Fill in IP length and desired time to live and
573	* send to IP level. There should be a better way
574	* to handle ttl and tos; we could keep them in
575	* the template, but need a way to checksum without them.
576	*/
577	m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
578
579	{
580	((struct ip *)ti)->ip_len = m->m_len;
581	((struct ip *)ti)->ip_ttl = ip_defttl;
582	((struct ip *)ti)->ip_tos = so->so_iptos;
583
584	/* #if BSD >= 43 */
585	/* Don't do IP options... */
586	#if 0
587	error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
588	so->so_options & SO_DONTROUTE, 0);
589	#endif
590	error = ip_output(pData, so, m);
591
592	#if 0
593	/* #else */
594	error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route,
595	so->so_options & SO_DONTROUTE);
596	/* #endif */
597	#endif
598	}
599	if (error)
600	{
601	out:
602	#if 0
603	if (error == ENOBUFS)
604	{
605	tcp_quench(tp->t_inpcb, 0);
606	return (0);
607	}
608
609	if ( ( error == EHOSTUNREACH
610	\|\| error == ENETDOWN)
611	&& TCPS_HAVERCVDSYN(tp->t_state))
612	{
613	tp->t_softerror = error;
614	return (0);
615	}
616	#endif
617	return (error);
618	}
619	tcpstat.tcps_sndtotal++;
620
621	/*
622	* Data sent (as far as we can tell).
623	* If this advertises a larger window than any other segment,
624	* then remember the size of the advertised window.
625	* Any pending ACK has now been sent.
626	*/
627	if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
628	tp->rcv_adv = tp->rcv_nxt + win;
629	tp->last_ack_sent = tp->rcv_nxt;
630	tp->t_flags &= ~(TF_ACKNOW\|TF_DELACK);
631	if (sendalot)
632	goto again;
633
634	return (0);
635	}
636
637	void
638	tcp_setpersist(struct tcpcb *tp)
639	{
640	int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
641
642	#if 0
643	if (tp->t_timer[TCPT_REXMT])
644	panic("tcp_output REXMT");
645	#endif
646	/*
647	* Start/restart persistence timer.
648	*/
649	TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
650	t * tcp_backoff[tp->t_rxtshift],
651	TCPTV_PERSMIN, TCPTV_PERSMAX);
652	if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
653	tp->t_rxtshift++;
654	}

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source: vbox/trunk/src/VBox/Devices/Network/slirp/tcp_output.c@ 15136

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