tests: virtio-9p: add version operation test
[qemu.git] / slirp / tcp_output.c
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. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)tcp_output.c 8.3 (Berkeley) 12/30/93
30 * tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp
31 */
32
33 /*
34 * Changes and additions relating to SLiRP
35 * Copyright (c) 1995 Danny Gasparovski.
36 *
37 * Please read the file COPYRIGHT for the
38 * terms and conditions of the copyright.
39 */
40
41 #include "qemu/osdep.h"
42 #include "slirp.h"
43
44 static const u_char tcp_outflags[TCP_NSTATES] = {
45 TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK,
46 TH_ACK, TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK,
47 TH_FIN|TH_ACK, TH_ACK, TH_ACK,
48 };
49
50
51 #undef MAX_TCPOPTLEN
52 #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */
53
54 /*
55 * Tcp output routine: figure out what should be sent and send it.
56 */
57 int
58 tcp_output(struct tcpcb *tp)
59 {
60 register struct socket *so = tp->t_socket;
61 register long len, win;
62 int off, flags, error;
63 register struct mbuf *m;
64 register struct tcpiphdr *ti, tcpiph_save;
65 struct ip *ip;
66 struct ip6 *ip6;
67 u_char opt[MAX_TCPOPTLEN];
68 unsigned optlen, hdrlen;
69 int idle, sendalot;
70
71 DEBUG_CALL("tcp_output");
72 DEBUG_ARG("tp = %p", tp);
73
74 /*
75 * Determine length of data that should be transmitted,
76 * and flags that will be used.
77 * If there is some data or critical controls (SYN, RST)
78 * to send, then transmit; otherwise, investigate further.
79 */
80 idle = (tp->snd_max == tp->snd_una);
81 if (idle && tp->t_idle >= tp->t_rxtcur)
82 /*
83 * We have been idle for "a while" and no acks are
84 * expected to clock out any data we send --
85 * slow start to get ack "clock" running again.
86 */
87 tp->snd_cwnd = tp->t_maxseg;
88 again:
89 sendalot = 0;
90 off = tp->snd_nxt - tp->snd_una;
91 win = MIN(tp->snd_wnd, tp->snd_cwnd);
92
93 flags = tcp_outflags[tp->t_state];
94
95 DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
96
97 /*
98 * If in persist timeout with window of 0, send 1 byte.
99 * Otherwise, if window is small but nonzero
100 * and timer expired, we will send what we can
101 * and go to transmit state.
102 */
103 if (tp->t_force) {
104 if (win == 0) {
105 /*
106 * If we still have some data to send, then
107 * clear the FIN bit. Usually this would
108 * happen below when it realizes that we
109 * aren't sending all the data. However,
110 * if we have exactly 1 byte of unset data,
111 * then it won't clear the FIN bit below,
112 * and if we are in persist state, we wind
113 * up sending the packet without recording
114 * that we sent the FIN bit.
115 *
116 * We can't just blindly clear the FIN bit,
117 * because if we don't have any more data
118 * to send then the probe will be the FIN
119 * itself.
120 */
121 if (off < so->so_snd.sb_cc)
122 flags &= ~TH_FIN;
123 win = 1;
124 } else {
125 tp->t_timer[TCPT_PERSIST] = 0;
126 tp->t_rxtshift = 0;
127 }
128 }
129
130 len = MIN(so->so_snd.sb_cc, win) - off;
131
132 if (len < 0) {
133 /*
134 * If FIN has been sent but not acked,
135 * but we haven't been called to retransmit,
136 * len will be -1. Otherwise, window shrank
137 * after we sent into it. If window shrank to 0,
138 * cancel pending retransmit and pull snd_nxt
139 * back to (closed) window. We will enter persist
140 * state below. If the window didn't close completely,
141 * just wait for an ACK.
142 */
143 len = 0;
144 if (win == 0) {
145 tp->t_timer[TCPT_REXMT] = 0;
146 tp->snd_nxt = tp->snd_una;
147 }
148 }
149
150 if (len > tp->t_maxseg) {
151 len = tp->t_maxseg;
152 sendalot = 1;
153 }
154 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
155 flags &= ~TH_FIN;
156
157 win = sbspace(&so->so_rcv);
158
159 /*
160 * Sender silly window avoidance. If connection is idle
161 * and can send all data, a maximum segment,
162 * at least a maximum default-size segment do it,
163 * or are forced, do it; otherwise don't bother.
164 * If peer's buffer is tiny, then send
165 * when window is at least half open.
166 * If retransmitting (possibly after persist timer forced us
167 * to send into a small window), then must resend.
168 */
169 if (len) {
170 if (len == tp->t_maxseg)
171 goto send;
172 if ((1 || idle || tp->t_flags & TF_NODELAY) &&
173 len + off >= so->so_snd.sb_cc)
174 goto send;
175 if (tp->t_force)
176 goto send;
177 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
178 goto send;
179 if (SEQ_LT(tp->snd_nxt, tp->snd_max))
180 goto send;
181 }
182
183 /*
184 * Compare available window to amount of window
185 * known to peer (as advertised window less
186 * next expected input). If the difference is at least two
187 * max size segments, or at least 50% of the maximum possible
188 * window, then want to send a window update to peer.
189 */
190 if (win > 0) {
191 /*
192 * "adv" is the amount we can increase the window,
193 * taking into account that we are limited by
194 * TCP_MAXWIN << tp->rcv_scale.
195 */
196 long adv = MIN(win, (long)TCP_MAXWIN << tp->rcv_scale) -
197 (tp->rcv_adv - tp->rcv_nxt);
198
199 if (adv >= (long) (2 * tp->t_maxseg))
200 goto send;
201 if (2 * adv >= (long) so->so_rcv.sb_datalen)
202 goto send;
203 }
204
205 /*
206 * Send if we owe peer an ACK.
207 */
208 if (tp->t_flags & TF_ACKNOW)
209 goto send;
210 if (flags & (TH_SYN|TH_RST))
211 goto send;
212 if (SEQ_GT(tp->snd_up, tp->snd_una))
213 goto send;
214 /*
215 * If our state indicates that FIN should be sent
216 * and we have not yet done so, or we're retransmitting the FIN,
217 * then we need to send.
218 */
219 if (flags & TH_FIN &&
220 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
221 goto send;
222
223 /*
224 * TCP window updates are not reliable, rather a polling protocol
225 * using ``persist'' packets is used to insure receipt of window
226 * updates. The three ``states'' for the output side are:
227 * idle not doing retransmits or persists
228 * persisting to move a small or zero window
229 * (re)transmitting and thereby not persisting
230 *
231 * tp->t_timer[TCPT_PERSIST]
232 * is set when we are in persist state.
233 * tp->t_force
234 * is set when we are called to send a persist packet.
235 * tp->t_timer[TCPT_REXMT]
236 * is set when we are retransmitting
237 * The output side is idle when both timers are zero.
238 *
239 * If send window is too small, there is data to transmit, and no
240 * retransmit or persist is pending, then go to persist state.
241 * If nothing happens soon, send when timer expires:
242 * if window is nonzero, transmit what we can,
243 * otherwise force out a byte.
244 */
245 if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
246 tp->t_timer[TCPT_PERSIST] == 0) {
247 tp->t_rxtshift = 0;
248 tcp_setpersist(tp);
249 }
250
251 /*
252 * No reason to send a segment, just return.
253 */
254 return (0);
255
256 send:
257 /*
258 * Before ESTABLISHED, force sending of initial options
259 * unless TCP set not to do any options.
260 * NOTE: we assume that the IP/TCP header plus TCP options
261 * always fit in a single mbuf, leaving room for a maximum
262 * link header, i.e.
263 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
264 */
265 optlen = 0;
266 hdrlen = sizeof (struct tcpiphdr);
267 if (flags & TH_SYN) {
268 tp->snd_nxt = tp->iss;
269 if ((tp->t_flags & TF_NOOPT) == 0) {
270 uint16_t mss;
271
272 opt[0] = TCPOPT_MAXSEG;
273 opt[1] = 4;
274 mss = htons((uint16_t) tcp_mss(tp, 0));
275 memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss));
276 optlen = 4;
277 }
278 }
279
280 hdrlen += optlen;
281
282 /*
283 * Adjust data length if insertion of options will
284 * bump the packet length beyond the t_maxseg length.
285 */
286 if (len > tp->t_maxseg - optlen) {
287 len = tp->t_maxseg - optlen;
288 sendalot = 1;
289 }
290
291 /*
292 * Grab a header mbuf, attaching a copy of data to
293 * be transmitted, and initialize the header from
294 * the template for sends on this connection.
295 */
296 if (len) {
297 m = m_get(so->slirp);
298 if (m == NULL) {
299 error = 1;
300 goto out;
301 }
302 m->m_data += IF_MAXLINKHDR;
303 m->m_len = hdrlen;
304
305 sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
306 m->m_len += len;
307
308 /*
309 * If we're sending everything we've got, set PUSH.
310 * (This will keep happy those implementations which only
311 * give data to the user when a buffer fills or
312 * a PUSH comes in.)
313 */
314 if (off + len == so->so_snd.sb_cc)
315 flags |= TH_PUSH;
316 } else {
317 m = m_get(so->slirp);
318 if (m == NULL) {
319 error = 1;
320 goto out;
321 }
322 m->m_data += IF_MAXLINKHDR;
323 m->m_len = hdrlen;
324 }
325
326 ti = mtod(m, struct tcpiphdr *);
327
328 memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr));
329
330 /*
331 * Fill in fields, remembering maximum advertised
332 * window for use in delaying messages about window sizes.
333 * If resending a FIN, be sure not to use a new sequence number.
334 */
335 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
336 tp->snd_nxt == tp->snd_max)
337 tp->snd_nxt--;
338 /*
339 * If we are doing retransmissions, then snd_nxt will
340 * not reflect the first unsent octet. For ACK only
341 * packets, we do not want the sequence number of the
342 * retransmitted packet, we want the sequence number
343 * of the next unsent octet. So, if there is no data
344 * (and no SYN or FIN), use snd_max instead of snd_nxt
345 * when filling in ti_seq. But if we are in persist
346 * state, snd_max might reflect one byte beyond the
347 * right edge of the window, so use snd_nxt in that
348 * case, since we know we aren't doing a retransmission.
349 * (retransmit and persist are mutually exclusive...)
350 */
351 if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
352 ti->ti_seq = htonl(tp->snd_nxt);
353 else
354 ti->ti_seq = htonl(tp->snd_max);
355 ti->ti_ack = htonl(tp->rcv_nxt);
356 if (optlen) {
357 memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
358 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
359 }
360 ti->ti_flags = flags;
361 /*
362 * Calculate receive window. Don't shrink window,
363 * but avoid silly window syndrome.
364 */
365 if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg)
366 win = 0;
367 if (win > (long)TCP_MAXWIN << tp->rcv_scale)
368 win = (long)TCP_MAXWIN << tp->rcv_scale;
369 if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
370 win = (long)(tp->rcv_adv - tp->rcv_nxt);
371 ti->ti_win = htons((uint16_t) (win>>tp->rcv_scale));
372
373 if (SEQ_GT(tp->snd_up, tp->snd_una)) {
374 ti->ti_urp = htons((uint16_t)(tp->snd_up - ntohl(ti->ti_seq)));
375 ti->ti_flags |= TH_URG;
376 } else
377 /*
378 * If no urgent pointer to send, then we pull
379 * the urgent pointer to the left edge of the send window
380 * so that it doesn't drift into the send window on sequence
381 * number wraparound.
382 */
383 tp->snd_up = tp->snd_una; /* drag it along */
384
385 /*
386 * Put TCP length in extended header, and then
387 * checksum extended header and data.
388 */
389 if (len + optlen)
390 ti->ti_len = htons((uint16_t)(sizeof (struct tcphdr) +
391 optlen + len));
392 ti->ti_sum = cksum(m, (int)(hdrlen + len));
393
394 /*
395 * In transmit state, time the transmission and arrange for
396 * the retransmit. In persist state, just set snd_max.
397 */
398 if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
399 tcp_seq startseq = tp->snd_nxt;
400
401 /*
402 * Advance snd_nxt over sequence space of this segment.
403 */
404 if (flags & (TH_SYN|TH_FIN)) {
405 if (flags & TH_SYN)
406 tp->snd_nxt++;
407 if (flags & TH_FIN) {
408 tp->snd_nxt++;
409 tp->t_flags |= TF_SENTFIN;
410 }
411 }
412 tp->snd_nxt += len;
413 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
414 tp->snd_max = tp->snd_nxt;
415 /*
416 * Time this transmission if not a retransmission and
417 * not currently timing anything.
418 */
419 if (tp->t_rtt == 0) {
420 tp->t_rtt = 1;
421 tp->t_rtseq = startseq;
422 }
423 }
424
425 /*
426 * Set retransmit timer if not currently set,
427 * and not doing an ack or a keep-alive probe.
428 * Initial value for retransmit timer is smoothed
429 * round-trip time + 2 * round-trip time variance.
430 * Initialize shift counter which is used for backoff
431 * of retransmit time.
432 */
433 if (tp->t_timer[TCPT_REXMT] == 0 &&
434 tp->snd_nxt != tp->snd_una) {
435 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
436 if (tp->t_timer[TCPT_PERSIST]) {
437 tp->t_timer[TCPT_PERSIST] = 0;
438 tp->t_rxtshift = 0;
439 }
440 }
441 } else
442 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
443 tp->snd_max = tp->snd_nxt + len;
444
445 /*
446 * Fill in IP length and desired time to live and
447 * send to IP level. There should be a better way
448 * to handle ttl and tos; we could keep them in
449 * the template, but need a way to checksum without them.
450 */
451 m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
452 tcpiph_save = *mtod(m, struct tcpiphdr *);
453
454 switch (so->so_ffamily) {
455 case AF_INET:
456 m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
457 - sizeof(struct ip);
458 m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
459 - sizeof(struct ip);
460 ip = mtod(m, struct ip *);
461
462 ip->ip_len = m->m_len;
463 ip->ip_dst = tcpiph_save.ti_dst;
464 ip->ip_src = tcpiph_save.ti_src;
465 ip->ip_p = tcpiph_save.ti_pr;
466
467 ip->ip_ttl = IPDEFTTL;
468 ip->ip_tos = so->so_iptos;
469 error = ip_output(so, m);
470 break;
471
472 case AF_INET6:
473 m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
474 - sizeof(struct ip6);
475 m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
476 - sizeof(struct ip6);
477 ip6 = mtod(m, struct ip6 *);
478
479 ip6->ip_pl = tcpiph_save.ti_len;
480 ip6->ip_dst = tcpiph_save.ti_dst6;
481 ip6->ip_src = tcpiph_save.ti_src6;
482 ip6->ip_nh = tcpiph_save.ti_nh6;
483
484 error = ip6_output(so, m, 0);
485 break;
486
487 default:
488 g_assert_not_reached();
489 }
490
491 if (error) {
492 out:
493 return (error);
494 }
495
496 /*
497 * Data sent (as far as we can tell).
498 * If this advertises a larger window than any other segment,
499 * then remember the size of the advertised window.
500 * Any pending ACK has now been sent.
501 */
502 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
503 tp->rcv_adv = tp->rcv_nxt + win;
504 tp->last_ack_sent = tp->rcv_nxt;
505 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
506 if (sendalot)
507 goto again;
508
509 return (0);
510 }
511
512 void
513 tcp_setpersist(struct tcpcb *tp)
514 {
515 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
516
517 /*
518 * Start/restart persistence timer.
519 */
520 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
521 t * tcp_backoff[tp->t_rxtshift],
522 TCPTV_PERSMIN, TCPTV_PERSMAX);
523 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
524 tp->t_rxtshift++;
525 }