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1.1 root 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.
1.1.1.3 ! root 13: * 3. Neither the name of the University nor the names of its contributors
1.1 root 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.
1.1.1.2 root 36: *
37: * Please read the file COPYRIGHT for the
1.1 root 38: * terms and conditions of the copyright.
39: */
40:
41: #include <slirp.h>
42:
43: /*
44: * Since this is only used in "stats socket", we give meaning
45: * names instead of the REAL names
46: */
1.1.1.2 root 47: const char * const tcpstates[] = {
1.1 root 48: /* "CLOSED", "LISTEN", "SYN_SENT", "SYN_RCVD", */
49: "REDIRECT", "LISTEN", "SYN_SENT", "SYN_RCVD",
50: "ESTABLISHED", "CLOSE_WAIT", "FIN_WAIT_1", "CLOSING",
51: "LAST_ACK", "FIN_WAIT_2", "TIME_WAIT",
52: };
53:
1.1.1.2 root 54: static const u_char tcp_outflags[TCP_NSTATES] = {
1.1 root 55: TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK,
1.1.1.2 root 56: TH_ACK, TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK,
1.1 root 57: TH_FIN|TH_ACK, TH_ACK, TH_ACK,
58: };
59:
60:
61: #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */
62:
63: /*
64: * Tcp output routine: figure out what should be sent and send it.
65: */
66: int
67: tcp_output(tp)
68: register struct tcpcb *tp;
69: {
70: register struct socket *so = tp->t_socket;
71: register long len, win;
72: int off, flags, error;
73: register struct mbuf *m;
74: register struct tcpiphdr *ti;
75: u_char opt[MAX_TCPOPTLEN];
76: unsigned optlen, hdrlen;
77: int idle, sendalot;
1.1.1.2 root 78:
1.1 root 79: DEBUG_CALL("tcp_output");
80: DEBUG_ARG("tp = %lx", (long )tp);
1.1.1.2 root 81:
1.1 root 82: /*
83: * Determine length of data that should be transmitted,
84: * and flags that will be used.
85: * If there is some data or critical controls (SYN, RST)
86: * to send, then transmit; otherwise, investigate further.
87: */
88: idle = (tp->snd_max == tp->snd_una);
89: if (idle && tp->t_idle >= tp->t_rxtcur)
90: /*
91: * We have been idle for "a while" and no acks are
92: * expected to clock out any data we send --
93: * slow start to get ack "clock" running again.
94: */
95: tp->snd_cwnd = tp->t_maxseg;
96: again:
97: sendalot = 0;
98: off = tp->snd_nxt - tp->snd_una;
99: win = min(tp->snd_wnd, tp->snd_cwnd);
100:
101: flags = tcp_outflags[tp->t_state];
1.1.1.2 root 102:
1.1 root 103: DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
1.1.1.2 root 104:
1.1 root 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: /*
114: * If we still have some data to send, then
115: * clear the FIN bit. Usually this would
116: * happen below when it realizes that we
117: * aren't sending all the data. However,
118: * if we have exactly 1 byte of unset data,
119: * then it won't clear the FIN bit below,
120: * and if we are in persist state, we wind
121: * up sending the packet without recording
122: * that we sent the FIN bit.
123: *
124: * We can't just blindly clear the FIN bit,
125: * because if we don't have any more data
126: * to send then the probe will be the FIN
127: * itself.
128: */
129: if (off < so->so_snd.sb_cc)
130: flags &= ~TH_FIN;
131: win = 1;
132: } else {
133: tp->t_timer[TCPT_PERSIST] = 0;
134: tp->t_rxtshift = 0;
135: }
136: }
137:
138: len = min(so->so_snd.sb_cc, win) - off;
139:
140: if (len < 0) {
141: /*
142: * If FIN has been sent but not acked,
143: * but we haven't been called to retransmit,
144: * len will be -1. Otherwise, window shrank
145: * after we sent into it. If window shrank to 0,
146: * cancel pending retransmit and pull snd_nxt
147: * back to (closed) window. We will enter persist
148: * state below. If the window didn't close completely,
149: * just wait for an ACK.
150: */
151: len = 0;
152: if (win == 0) {
153: tp->t_timer[TCPT_REXMT] = 0;
154: tp->snd_nxt = tp->snd_una;
155: }
156: }
1.1.1.2 root 157:
1.1 root 158: if (len > tp->t_maxseg) {
159: len = tp->t_maxseg;
160: sendalot = 1;
161: }
162: if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
163: flags &= ~TH_FIN;
164:
165: win = sbspace(&so->so_rcv);
166:
167: /*
168: * Sender silly window avoidance. If connection is idle
169: * and can send all data, a maximum segment,
170: * at least a maximum default-size segment do it,
171: * or are forced, do it; otherwise don't bother.
172: * If peer's buffer is tiny, then send
173: * when window is at least half open.
174: * If retransmitting (possibly after persist timer forced us
175: * to send into a small window), then must resend.
176: */
177: if (len) {
178: if (len == tp->t_maxseg)
179: goto send;
180: if ((1 || idle || tp->t_flags & TF_NODELAY) &&
181: len + off >= so->so_snd.sb_cc)
182: goto send;
183: if (tp->t_force)
184: goto send;
185: if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
186: goto send;
187: if (SEQ_LT(tp->snd_nxt, tp->snd_max))
188: goto send;
189: }
190:
191: /*
192: * Compare available window to amount of window
193: * known to peer (as advertised window less
194: * next expected input). If the difference is at least two
195: * max size segments, or at least 50% of the maximum possible
196: * window, then want to send a window update to peer.
197: */
198: if (win > 0) {
1.1.1.2 root 199: /*
1.1 root 200: * "adv" is the amount we can increase the window,
201: * taking into account that we are limited by
202: * TCP_MAXWIN << tp->rcv_scale.
203: */
204: long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
205: (tp->rcv_adv - tp->rcv_nxt);
206:
207: if (adv >= (long) (2 * tp->t_maxseg))
208: goto send;
209: if (2 * adv >= (long) so->so_rcv.sb_datalen)
210: goto send;
211: }
212:
213: /*
214: * Send if we owe peer an ACK.
215: */
216: if (tp->t_flags & TF_ACKNOW)
217: goto send;
218: if (flags & (TH_SYN|TH_RST))
219: goto send;
220: if (SEQ_GT(tp->snd_up, tp->snd_una))
221: goto send;
222: /*
223: * If our state indicates that FIN should be sent
224: * and we have not yet done so, or we're retransmitting the FIN,
225: * then we need to send.
226: */
227: if (flags & TH_FIN &&
228: ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
229: goto send;
230:
231: /*
232: * TCP window updates are not reliable, rather a polling protocol
233: * using ``persist'' packets is used to insure receipt of window
234: * updates. The three ``states'' for the output side are:
235: * idle not doing retransmits or persists
236: * persisting to move a small or zero window
237: * (re)transmitting and thereby not persisting
238: *
239: * tp->t_timer[TCPT_PERSIST]
240: * is set when we are in persist state.
241: * tp->t_force
242: * is set when we are called to send a persist packet.
243: * tp->t_timer[TCPT_REXMT]
244: * is set when we are retransmitting
245: * The output side is idle when both timers are zero.
246: *
247: * If send window is too small, there is data to transmit, and no
248: * retransmit or persist is pending, then go to persist state.
249: * If nothing happens soon, send when timer expires:
250: * if window is nonzero, transmit what we can,
251: * otherwise force out a byte.
252: */
253: if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
254: tp->t_timer[TCPT_PERSIST] == 0) {
255: tp->t_rxtshift = 0;
256: tcp_setpersist(tp);
257: }
258:
259: /*
260: * No reason to send a segment, just return.
261: */
1.1.1.2 root 262: STAT(tcpstat.tcps_didnuttin++);
263:
1.1 root 264: return (0);
265:
266: send:
267: /*
268: * Before ESTABLISHED, force sending of initial options
269: * unless TCP set not to do any options.
270: * NOTE: we assume that the IP/TCP header plus TCP options
271: * always fit in a single mbuf, leaving room for a maximum
272: * link header, i.e.
273: * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
274: */
275: optlen = 0;
276: hdrlen = sizeof (struct tcpiphdr);
277: if (flags & TH_SYN) {
278: tp->snd_nxt = tp->iss;
279: if ((tp->t_flags & TF_NOOPT) == 0) {
280: u_int16_t mss;
281:
282: opt[0] = TCPOPT_MAXSEG;
283: opt[1] = 4;
284: mss = htons((u_int16_t) tcp_mss(tp, 0));
285: memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss));
286: optlen = 4;
287:
288: /* if ((tp->t_flags & TF_REQ_SCALE) &&
289: * ((flags & TH_ACK) == 0 ||
290: * (tp->t_flags & TF_RCVD_SCALE))) {
291: * *((u_int32_t *) (opt + optlen)) = htonl(
292: * TCPOPT_NOP << 24 |
293: * TCPOPT_WINDOW << 16 |
294: * TCPOLEN_WINDOW << 8 |
295: * tp->request_r_scale);
296: * optlen += 4;
297: * }
298: */
299: }
300: }
1.1.1.2 root 301:
1.1 root 302: /*
1.1.1.2 root 303: * Send a timestamp and echo-reply if this is a SYN and our side
1.1 root 304: * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
305: * and our peer have sent timestamps in our SYN's.
306: */
307: /* if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
308: * (flags & TH_RST) == 0 &&
309: * ((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
310: * (tp->t_flags & TF_RCVD_TSTMP))) {
311: * u_int32_t *lp = (u_int32_t *)(opt + optlen);
312: *
313: * / * Form timestamp option as shown in appendix A of RFC 1323. * /
314: * *lp++ = htonl(TCPOPT_TSTAMP_HDR);
315: * *lp++ = htonl(tcp_now);
316: * *lp = htonl(tp->ts_recent);
317: * optlen += TCPOLEN_TSTAMP_APPA;
318: * }
319: */
320: hdrlen += optlen;
1.1.1.2 root 321:
1.1 root 322: /*
323: * Adjust data length if insertion of options will
324: * bump the packet length beyond the t_maxseg length.
325: */
326: if (len > tp->t_maxseg - optlen) {
327: len = tp->t_maxseg - optlen;
328: sendalot = 1;
329: }
330:
331: /*
332: * Grab a header mbuf, attaching a copy of data to
333: * be transmitted, and initialize the header from
334: * the template for sends on this connection.
335: */
336: if (len) {
337: if (tp->t_force && len == 1)
1.1.1.2 root 338: STAT(tcpstat.tcps_sndprobe++);
1.1 root 339: else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
1.1.1.2 root 340: STAT(tcpstat.tcps_sndrexmitpack++);
341: STAT(tcpstat.tcps_sndrexmitbyte += len);
1.1 root 342: } else {
1.1.1.2 root 343: STAT(tcpstat.tcps_sndpack++);
344: STAT(tcpstat.tcps_sndbyte += len);
1.1 root 345: }
346:
347: m = m_get();
348: if (m == NULL) {
349: /* error = ENOBUFS; */
350: error = 1;
351: goto out;
352: }
1.1.1.2 root 353: m->m_data += IF_MAXLINKHDR;
1.1 root 354: m->m_len = hdrlen;
1.1.1.2 root 355:
356: /*
1.1 root 357: * This will always succeed, since we make sure our mbufs
358: * are big enough to hold one MSS packet + header + ... etc.
359: */
360: /* if (len <= MHLEN - hdrlen - max_linkhdr) { */
361:
362: sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
363: m->m_len += len;
364:
365: /* } else {
366: * m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
367: * if (m->m_next == 0)
368: * len = 0;
369: * }
370: */
371: /*
372: * If we're sending everything we've got, set PUSH.
373: * (This will keep happy those implementations which only
374: * give data to the user when a buffer fills or
375: * a PUSH comes in.)
376: */
377: if (off + len == so->so_snd.sb_cc)
378: flags |= TH_PUSH;
379: } else {
380: if (tp->t_flags & TF_ACKNOW)
1.1.1.2 root 381: STAT(tcpstat.tcps_sndacks++);
1.1 root 382: else if (flags & (TH_SYN|TH_FIN|TH_RST))
1.1.1.2 root 383: STAT(tcpstat.tcps_sndctrl++);
1.1 root 384: else if (SEQ_GT(tp->snd_up, tp->snd_una))
1.1.1.2 root 385: STAT(tcpstat.tcps_sndurg++);
1.1 root 386: else
1.1.1.2 root 387: STAT(tcpstat.tcps_sndwinup++);
1.1 root 388:
389: m = m_get();
390: if (m == NULL) {
391: /* error = ENOBUFS; */
392: error = 1;
393: goto out;
394: }
1.1.1.2 root 395: m->m_data += IF_MAXLINKHDR;
1.1 root 396: m->m_len = hdrlen;
397: }
398:
399: ti = mtod(m, struct tcpiphdr *);
1.1.1.2 root 400:
1.1 root 401: memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr));
402:
403: /*
404: * Fill in fields, remembering maximum advertised
405: * window for use in delaying messages about window sizes.
406: * If resending a FIN, be sure not to use a new sequence number.
407: */
1.1.1.2 root 408: if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
1.1 root 409: tp->snd_nxt == tp->snd_max)
410: tp->snd_nxt--;
411: /*
412: * If we are doing retransmissions, then snd_nxt will
413: * not reflect the first unsent octet. For ACK only
414: * packets, we do not want the sequence number of the
415: * retransmitted packet, we want the sequence number
416: * of the next unsent octet. So, if there is no data
417: * (and no SYN or FIN), use snd_max instead of snd_nxt
418: * when filling in ti_seq. But if we are in persist
419: * state, snd_max might reflect one byte beyond the
420: * right edge of the window, so use snd_nxt in that
421: * case, since we know we aren't doing a retransmission.
422: * (retransmit and persist are mutually exclusive...)
423: */
424: if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
425: ti->ti_seq = htonl(tp->snd_nxt);
426: else
427: ti->ti_seq = htonl(tp->snd_max);
428: ti->ti_ack = htonl(tp->rcv_nxt);
429: if (optlen) {
430: memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
431: ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
432: }
433: ti->ti_flags = flags;
434: /*
435: * Calculate receive window. Don't shrink window,
436: * but avoid silly window syndrome.
437: */
438: if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg)
439: win = 0;
440: if (win > (long)TCP_MAXWIN << tp->rcv_scale)
441: win = (long)TCP_MAXWIN << tp->rcv_scale;
442: if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
443: win = (long)(tp->rcv_adv - tp->rcv_nxt);
444: ti->ti_win = htons((u_int16_t) (win>>tp->rcv_scale));
1.1.1.2 root 445:
1.1 root 446: if (SEQ_GT(tp->snd_up, tp->snd_una)) {
447: ti->ti_urp = htons((u_int16_t)(tp->snd_up - ntohl(ti->ti_seq)));
1.1.1.2 root 448: #ifdef notdef
1.1 root 449: if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
450: ti->ti_urp = htons((u_int16_t)(tp->snd_up - tp->snd_nxt));
451: #endif
452: ti->ti_flags |= TH_URG;
453: } else
454: /*
455: * If no urgent pointer to send, then we pull
456: * the urgent pointer to the left edge of the send window
457: * so that it doesn't drift into the send window on sequence
458: * number wraparound.
459: */
460: tp->snd_up = tp->snd_una; /* drag it along */
461:
462: /*
463: * Put TCP length in extended header, and then
464: * checksum extended header and data.
465: */
466: if (len + optlen)
467: ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) +
468: optlen + len));
469: ti->ti_sum = cksum(m, (int)(hdrlen + len));
470:
471: /*
472: * In transmit state, time the transmission and arrange for
473: * the retransmit. In persist state, just set snd_max.
474: */
475: if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
476: tcp_seq startseq = tp->snd_nxt;
477:
478: /*
479: * Advance snd_nxt over sequence space of this segment.
480: */
481: if (flags & (TH_SYN|TH_FIN)) {
482: if (flags & TH_SYN)
483: tp->snd_nxt++;
484: if (flags & TH_FIN) {
485: tp->snd_nxt++;
486: tp->t_flags |= TF_SENTFIN;
487: }
488: }
489: tp->snd_nxt += len;
490: if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
491: tp->snd_max = tp->snd_nxt;
492: /*
493: * Time this transmission if not a retransmission and
494: * not currently timing anything.
495: */
496: if (tp->t_rtt == 0) {
497: tp->t_rtt = 1;
498: tp->t_rtseq = startseq;
1.1.1.2 root 499: STAT(tcpstat.tcps_segstimed++);
1.1 root 500: }
501: }
502:
503: /*
504: * Set retransmit timer if not currently set,
505: * and not doing an ack or a keep-alive probe.
506: * Initial value for retransmit timer is smoothed
507: * round-trip time + 2 * round-trip time variance.
508: * Initialize shift counter which is used for backoff
509: * of retransmit time.
510: */
511: if (tp->t_timer[TCPT_REXMT] == 0 &&
512: tp->snd_nxt != tp->snd_una) {
513: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
514: if (tp->t_timer[TCPT_PERSIST]) {
515: tp->t_timer[TCPT_PERSIST] = 0;
516: tp->t_rxtshift = 0;
517: }
518: }
519: } else
520: if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
521: tp->snd_max = tp->snd_nxt + len;
522:
523: /*
524: * Fill in IP length and desired time to live and
525: * send to IP level. There should be a better way
526: * to handle ttl and tos; we could keep them in
527: * the template, but need a way to checksum without them.
528: */
529: m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
1.1.1.2 root 530:
1.1 root 531: {
1.1.1.2 root 532:
1.1 root 533: ((struct ip *)ti)->ip_len = m->m_len;
534:
1.1.1.2 root 535: ((struct ip *)ti)->ip_ttl = IPDEFTTL;
1.1 root 536: ((struct ip *)ti)->ip_tos = so->so_iptos;
1.1.1.2 root 537:
1.1 root 538: /* #if BSD >= 43 */
539: /* Don't do IP options... */
540: /* error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
541: * so->so_options & SO_DONTROUTE, 0);
542: */
543: error = ip_output(so, m);
544:
545: /* #else
1.1.1.2 root 546: * error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route,
1.1 root 547: * so->so_options & SO_DONTROUTE);
548: * #endif
549: */
550: }
551: if (error) {
552: out:
553: /* if (error == ENOBUFS) {
554: * tcp_quench(tp->t_inpcb, 0);
555: * return (0);
556: * }
557: */
558: /* if ((error == EHOSTUNREACH || error == ENETDOWN)
559: * && TCPS_HAVERCVDSYN(tp->t_state)) {
560: * tp->t_softerror = error;
561: * return (0);
562: * }
563: */
564: return (error);
565: }
1.1.1.2 root 566: STAT(tcpstat.tcps_sndtotal++);
1.1 root 567:
568: /*
569: * Data sent (as far as we can tell).
570: * If this advertises a larger window than any other segment,
571: * then remember the size of the advertised window.
572: * Any pending ACK has now been sent.
573: */
574: if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
575: tp->rcv_adv = tp->rcv_nxt + win;
576: tp->last_ack_sent = tp->rcv_nxt;
577: tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
578: if (sendalot)
579: goto again;
580:
581: return (0);
582: }
583:
584: void
585: tcp_setpersist(tp)
586: register struct tcpcb *tp;
587: {
588: int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
589:
590: /* if (tp->t_timer[TCPT_REXMT])
591: * panic("tcp_output REXMT");
592: */
593: /*
594: * Start/restart persistence timer.
595: */
596: TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
597: t * tcp_backoff[tp->t_rxtshift],
598: TCPTV_PERSMIN, TCPTV_PERSMAX);
599: if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
600: tp->t_rxtshift++;
601: }
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