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source: vbox/trunk/src/VBox/Devices/Network/slirp/tcp_output.c@ 22013

Last change on this file since 22013 was 22013, checked in by vboxsync, 15 years ago

NAT: clearing (removing non-libalias code)

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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 */
51const 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
59static 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 */
72int
73tcp_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
102again:
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
282send:
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 Assert(m->m_len == (hdrlen + len));
578 m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
579
580 {
581 ((struct ip *)ti)->ip_len = m->m_len;
582 ((struct ip *)ti)->ip_ttl = ip_defttl;
583 ((struct ip *)ti)->ip_tos = so->so_iptos;
584
585 /* #if BSD >= 43 */
586 /* Don't do IP options... */
587#if 0
588 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
589 so->so_options & SO_DONTROUTE, 0);
590#endif
591#ifdef VBOX_WITH_NAT_SERVICE
592 {
593 struct ethhdr *eh0, *eh;
594 eh = (struct ethhdr *)m->m_dat;
595
596 if (so->so_m != NULL)
597 {
598 eh0 = (struct ethhdr *)so->so_m->m_dat;
599 memcpy(eh->h_source, eh0->h_source, ETH_ALEN);
600 }
601 }
602#endif
603 if(so->so_la != NULL)
604 m->m_la = so->so_la;
605 error = ip_output(pData, so, m);
606
607#if 0
608/* #else */
609 error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route,
610 so->so_options & SO_DONTROUTE);
611/* #endif */
612#endif
613 }
614 if (error)
615 {
616out:
617#if 0
618 if (error == ENOBUFS)
619 {
620 tcp_quench(tp->t_inpcb, 0);
621 return (0);
622 }
623
624 if ( ( error == EHOSTUNREACH
625 || error == ENETDOWN)
626 && TCPS_HAVERCVDSYN(tp->t_state))
627 {
628 tp->t_softerror = error;
629 return (0);
630 }
631#endif
632 return (error);
633 }
634 tcpstat.tcps_sndtotal++;
635
636 /*
637 * Data sent (as far as we can tell).
638 * If this advertises a larger window than any other segment,
639 * then remember the size of the advertised window.
640 * Any pending ACK has now been sent.
641 */
642 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
643 tp->rcv_adv = tp->rcv_nxt + win;
644 tp->last_ack_sent = tp->rcv_nxt;
645 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
646 if (sendalot)
647 goto again;
648
649 return (0);
650}
651
652void
653tcp_setpersist(struct tcpcb *tp)
654{
655 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
656
657#if 0
658 if (tp->t_timer[TCPT_REXMT])
659 panic("tcp_output REXMT");
660#endif
661 /*
662 * Start/restart persistence timer.
663 */
664 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
665 t * tcp_backoff[tp->t_rxtshift],
666 TCPTV_PERSMIN, TCPTV_PERSMAX);
667 if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
668 tp->t_rxtshift++;
669}
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