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1.1 root 1: /*
2: * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California.
3: * 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: *
1.1.1.2 ! root 33: * from: @(#)tcp_output.c 7.22 (Berkeley) 8/31/90
! 34: * tcp_output.c,v 1.3 1993/05/22 11:42:42 cgd Exp
1.1 root 35: */
36:
37: #include "param.h"
38: #include "systm.h"
39: #include "malloc.h"
40: #include "mbuf.h"
41: #include "protosw.h"
42: #include "socket.h"
43: #include "socketvar.h"
44: #include "errno.h"
45:
46: #include "../net/route.h"
47:
48: #include "in.h"
49: #include "in_systm.h"
50: #include "ip.h"
51: #include "in_pcb.h"
52: #include "ip_var.h"
53: #include "tcp.h"
54: #define TCPOUTFLAGS
55: #include "tcp_fsm.h"
56: #include "tcp_seq.h"
57: #include "tcp_timer.h"
58: #include "tcp_var.h"
59: #include "tcpip.h"
60: #include "tcp_debug.h"
61:
62: #ifdef notyet
63: extern struct mbuf *m_copypack();
64: #endif
65:
66: /*
67: * Initial options.
68: */
69: u_char tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, };
70:
71: /*
72: * Tcp output routine: figure out what should be sent and send it.
73: */
74: tcp_output(tp)
75: register struct tcpcb *tp;
76: {
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;
83: unsigned optlen, hdrlen;
84: int idle, sendalot;
85:
86: /*
87: * Determine length of data that should be transmitted,
88: * and flags that will be used.
89: * If there is some data or critical controls (SYN, RST)
90: * to send, then transmit; otherwise, investigate further.
91: */
92: idle = (tp->snd_max == tp->snd_una);
93: if (idle && tp->t_idle >= tp->t_rxtcur)
94: /*
95: * We have been idle for "a while" and no acks are
96: * expected to clock out any data we send --
97: * slow start to get ack "clock" running again.
98: */
99: tp->snd_cwnd = tp->t_maxseg;
100: again:
101: sendalot = 0;
102: off = tp->snd_nxt - tp->snd_una;
103: win = min(tp->snd_wnd, tp->snd_cwnd);
104:
105: /*
106: * If in persist timeout with window of 0, send 1 byte.
107: * Otherwise, if window is small but nonzero
108: * and timer expired, we will send what we can
109: * and go to transmit state.
110: */
111: if (tp->t_force) {
112: if (win == 0)
113: win = 1;
114: else {
115: tp->t_timer[TCPT_PERSIST] = 0;
116: tp->t_rxtshift = 0;
117: }
118: }
119:
120: flags = tcp_outflags[tp->t_state];
121: len = min(so->so_snd.sb_cc, win) - off;
122:
123: if (len < 0) {
124: /*
125: * If FIN has been sent but not acked,
126: * but we haven't been called to retransmit,
127: * len will be -1. Otherwise, window shrank
128: * after we sent into it. If window shrank to 0,
129: * cancel pending retransmit and pull snd_nxt
130: * back to (closed) window. We will enter persist
131: * state below. If the window didn't close completely,
132: * just wait for an ACK.
133: */
134: len = 0;
135: if (win == 0) {
136: tp->t_timer[TCPT_REXMT] = 0;
137: tp->snd_nxt = tp->snd_una;
138: }
139: }
140: if (len > tp->t_maxseg) {
141: len = tp->t_maxseg;
142: sendalot = 1;
143: }
144: if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
145: flags &= ~TH_FIN;
146:
147: win = sbspace(&so->so_rcv);
148:
149: /*
150: * Sender silly window avoidance. If connection is idle
151: * and can send all data, a maximum segment,
152: * at least a maximum default-size segment do it,
153: * or are forced, do it; otherwise don't bother.
154: * If peer's buffer is tiny, then send
155: * when window is at least half open.
156: * If retransmitting (possibly after persist timer forced us
157: * to send into a small window), then must resend.
158: */
159: if (len) {
160: if (len == tp->t_maxseg)
161: goto send;
162: if ((idle || tp->t_flags & TF_NODELAY) &&
163: len + off >= so->so_snd.sb_cc)
164: goto send;
165: if (tp->t_force)
166: goto send;
167: if (len >= tp->max_sndwnd / 2)
168: goto send;
169: if (SEQ_LT(tp->snd_nxt, tp->snd_max))
170: goto send;
171: }
172:
173: /*
174: * Compare available window to amount of window
175: * known to peer (as advertised window less
176: * next expected input). If the difference is at least two
177: * max size segments, or at least 50% of the maximum possible
178: * window, then want to send a window update to peer.
179: */
180: if (win > 0) {
181: long adv = win - (tp->rcv_adv - tp->rcv_nxt);
182:
183: if (adv >= (long) (2 * tp->t_maxseg))
184: goto send;
185: if (2 * adv >= (long) so->so_rcv.sb_hiwat)
186: goto send;
187: }
188:
189: /*
190: * Send if we owe peer an ACK.
191: */
192: if (tp->t_flags & TF_ACKNOW)
193: goto send;
194: if (flags & (TH_SYN|TH_RST))
195: goto send;
196: if (SEQ_GT(tp->snd_up, tp->snd_una))
197: goto send;
198: /*
199: * If our state indicates that FIN should be sent
200: * and we have not yet done so, or we're retransmitting the FIN,
201: * then we need to send.
202: */
203: if (flags & TH_FIN &&
204: ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
205: goto send;
206:
207: /*
208: * TCP window updates are not reliable, rather a polling protocol
209: * using ``persist'' packets is used to insure receipt of window
210: * updates. The three ``states'' for the output side are:
211: * idle not doing retransmits or persists
212: * persisting to move a small or zero window
213: * (re)transmitting and thereby not persisting
214: *
215: * tp->t_timer[TCPT_PERSIST]
216: * is set when we are in persist state.
217: * tp->t_force
218: * is set when we are called to send a persist packet.
219: * tp->t_timer[TCPT_REXMT]
220: * is set when we are retransmitting
221: * The output side is idle when both timers are zero.
222: *
223: * If send window is too small, there is data to transmit, and no
224: * retransmit or persist is pending, then go to persist state.
225: * If nothing happens soon, send when timer expires:
226: * if window is nonzero, transmit what we can,
227: * otherwise force out a byte.
228: */
229: if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
230: tp->t_timer[TCPT_PERSIST] == 0) {
231: tp->t_rxtshift = 0;
232: tcp_setpersist(tp);
233: }
234:
235: /*
236: * No reason to send a segment, just return.
237: */
238: return (0);
239:
240: send:
241: /*
242: * Before ESTABLISHED, force sending of initial options
243: * unless TCP set not to do any options.
244: * NOTE: we assume that the IP/TCP header plus TCP options
245: * always fit in a single mbuf, leaving room for a maximum
246: * link header, i.e.
247: * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
248: */
249: optlen = 0;
250: hdrlen = sizeof (struct tcpiphdr);
251: if (flags & TH_SYN && (tp->t_flags & TF_NOOPT) == 0) {
252: opt = tcp_initopt;
253: optlen = sizeof (tcp_initopt);
254: hdrlen += sizeof (tcp_initopt);
255: *(u_short *)(opt + 2) = htons((u_short) tcp_mss(tp, 0));
256: #ifdef DIAGNOSTIC
257: if (max_linkhdr + hdrlen > MHLEN)
258: panic("tcphdr too big");
259: #endif
260: }
261:
262: /*
263: * Grab a header mbuf, attaching a copy of data to
264: * be transmitted, and initialize the header from
265: * the template for sends on this connection.
266: */
267: if (len) {
268: if (tp->t_force && len == 1)
269: tcpstat.tcps_sndprobe++;
270: else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
271: tcpstat.tcps_sndrexmitpack++;
272: tcpstat.tcps_sndrexmitbyte += len;
273: } else {
274: tcpstat.tcps_sndpack++;
275: tcpstat.tcps_sndbyte += len;
276: }
277: #ifdef notyet
278: if ((m = m_copypack(so->so_snd.sb_mb, off,
279: (int)len, max_linkhdr + hdrlen)) == 0) {
280: error = ENOBUFS;
281: goto out;
282: }
283: /*
284: * m_copypack left space for our hdr; use it.
285: */
286: m->m_len += hdrlen;
287: m->m_data -= hdrlen;
288: #else
289: MGETHDR(m, M_DONTWAIT, MT_HEADER);
290: if (m == NULL) {
291: error = ENOBUFS;
292: goto out;
293: }
294: m->m_data += max_linkhdr;
295: m->m_len = hdrlen;
296: if (len <= MHLEN - hdrlen - max_linkhdr) {
297: m_copydata(so->so_snd.sb_mb, off, (int) len,
298: mtod(m, caddr_t) + hdrlen);
299: m->m_len += len;
300: } else {
301: m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
302: if (m->m_next == 0)
303: len = 0;
304: }
305: #endif
306: /*
307: * If we're sending everything we've got, set PUSH.
308: * (This will keep happy those implementations which only
309: * give data to the user when a buffer fills or
310: * a PUSH comes in.)
311: */
312: if (off + len == so->so_snd.sb_cc)
313: flags |= TH_PUSH;
314: } else {
315: if (tp->t_flags & TF_ACKNOW)
316: tcpstat.tcps_sndacks++;
317: else if (flags & (TH_SYN|TH_FIN|TH_RST))
318: tcpstat.tcps_sndctrl++;
319: else if (SEQ_GT(tp->snd_up, tp->snd_una))
320: tcpstat.tcps_sndurg++;
321: else
322: tcpstat.tcps_sndwinup++;
323:
324: MGETHDR(m, M_DONTWAIT, MT_HEADER);
325: if (m == NULL) {
326: error = ENOBUFS;
327: goto out;
328: }
329: m->m_data += max_linkhdr;
330: m->m_len = hdrlen;
331: }
332: m->m_pkthdr.rcvif = (struct ifnet *)0;
333: ti = mtod(m, struct tcpiphdr *);
334: if (tp->t_template == 0)
335: panic("tcp_output");
336: bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr));
337:
338: /*
339: * Fill in fields, remembering maximum advertised
340: * window for use in delaying messages about window sizes.
341: * If resending a FIN, be sure not to use a new sequence number.
342: */
343: if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
344: tp->snd_nxt == tp->snd_max)
345: tp->snd_nxt--;
346: ti->ti_seq = htonl(tp->snd_nxt);
347: ti->ti_ack = htonl(tp->rcv_nxt);
348: if (optlen) {
349: bcopy((caddr_t)opt, (caddr_t)(ti + 1), optlen);
350: ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
351: }
352: ti->ti_flags = flags;
353: /*
354: * Calculate receive window. Don't shrink window,
355: * but avoid silly window syndrome.
356: */
357: if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg)
358: win = 0;
359: if (win > TCP_MAXWIN)
360: win = TCP_MAXWIN;
361: if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
362: win = (long)(tp->rcv_adv - tp->rcv_nxt);
363: ti->ti_win = htons((u_short)win);
364: if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
365: ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));
366: ti->ti_flags |= TH_URG;
367: } else
368: /*
369: * If no urgent pointer to send, then we pull
370: * the urgent pointer to the left edge of the send window
371: * so that it doesn't drift into the send window on sequence
372: * number wraparound.
373: */
374: tp->snd_up = tp->snd_una; /* drag it along */
375:
376: /*
377: * Put TCP length in extended header, and then
378: * checksum extended header and data.
379: */
380: if (len + optlen)
381: ti->ti_len = htons((u_short)(sizeof (struct tcphdr) +
382: optlen + len));
383: ti->ti_sum = in_cksum(m, (int)(hdrlen + len));
384:
385: /*
386: * In transmit state, time the transmission and arrange for
387: * the retransmit. In persist state, just set snd_max.
388: */
389: if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
390: tcp_seq startseq = tp->snd_nxt;
391:
392: /*
393: * Advance snd_nxt over sequence space of this segment.
394: */
395: if (flags & (TH_SYN|TH_FIN)) {
396: if (flags & TH_SYN)
397: tp->snd_nxt++;
398: if (flags & TH_FIN) {
399: tp->snd_nxt++;
400: tp->t_flags |= TF_SENTFIN;
401: }
402: }
403: tp->snd_nxt += len;
404: if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
405: tp->snd_max = tp->snd_nxt;
406: /*
407: * Time this transmission if not a retransmission and
408: * not currently timing anything.
409: */
410: if (tp->t_rtt == 0) {
411: tp->t_rtt = 1;
412: tp->t_rtseq = startseq;
413: tcpstat.tcps_segstimed++;
414: }
415: }
416:
417: /*
418: * Set retransmit timer if not currently set,
419: * and not doing an ack or a keep-alive probe.
420: * Initial value for retransmit timer is smoothed
421: * round-trip time + 2 * round-trip time variance.
422: * Initialize shift counter which is used for backoff
423: * of retransmit time.
424: */
425: if (tp->t_timer[TCPT_REXMT] == 0 &&
426: tp->snd_nxt != tp->snd_una) {
427: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
428: if (tp->t_timer[TCPT_PERSIST]) {
429: tp->t_timer[TCPT_PERSIST] = 0;
430: tp->t_rxtshift = 0;
431: }
432: }
433: } else
434: if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
435: tp->snd_max = tp->snd_nxt + len;
436:
437: /*
438: * Trace.
439: */
440: if (so->so_options & SO_DEBUG)
441: tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0);
442:
443: /*
444: * Fill in IP length and desired time to live and
445: * send to IP level. There should be a better way
446: * to handle ttl and tos; we could keep them in
447: * the template, but need a way to checksum without them.
448: */
449: m->m_pkthdr.len = hdrlen + len;
450: ((struct ip *)ti)->ip_len = m->m_pkthdr.len;
451: ((struct ip *)ti)->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; /* XXX */
452: ((struct ip *)ti)->ip_tos = tp->t_inpcb->inp_ip.ip_tos; /* XXX */
453: #if BSD >= 43
454: error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
455: so->so_options & SO_DONTROUTE);
456: #else
457: error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route,
458: so->so_options & SO_DONTROUTE);
459: #endif
460: if (error) {
461: out:
462: if (error == ENOBUFS) {
463: tcp_quench(tp->t_inpcb);
464: return (0);
465: }
466: if ((error == EHOSTUNREACH || error == ENETDOWN)
467: && TCPS_HAVERCVDSYN(tp->t_state)) {
468: tp->t_softerror = error;
469: return (0);
470: }
471: return (error);
472: }
473: tcpstat.tcps_sndtotal++;
474:
475: /*
476: * Data sent (as far as we can tell).
477: * If this advertises a larger window than any other segment,
478: * then remember the size of the advertised window.
479: * Any pending ACK has now been sent.
480: */
481: if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
482: tp->rcv_adv = tp->rcv_nxt + win;
483: tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
484: if (sendalot)
485: goto again;
486: return (0);
487: }
488:
489: tcp_setpersist(tp)
490: register struct tcpcb *tp;
491: {
492: register t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
493:
494: if (tp->t_timer[TCPT_REXMT])
495: panic("tcp_output REXMT");
496: /*
497: * Start/restart persistance timer.
498: */
499: TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
500: t * tcp_backoff[tp->t_rxtshift],
501: TCPTV_PERSMIN, TCPTV_PERSMAX);
502: if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
503: tp->t_rxtshift++;
504: }
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