Annotation of sys/netinet/tcp_output.c, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: tcp_output.c,v 1.80 2007/06/01 00:52:38 henning Exp $ */
2: /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */
3:
4: /*
5: * Copyright (c) 1982, 1986, 1988, 1990, 1993
6: * The Regents of the University of California. All rights reserved.
7: *
8: * Redistribution and use in source and binary forms, with or without
9: * modification, are permitted provided that the following conditions
10: * are met:
11: * 1. Redistributions of source code must retain the above copyright
12: * notice, this list of conditions and the following disclaimer.
13: * 2. Redistributions in binary form must reproduce the above copyright
14: * notice, this list of conditions and the following disclaimer in the
15: * documentation and/or other materials provided with the distribution.
16: * 3. Neither the name of the University nor the names of its contributors
17: * may be used to endorse or promote products derived from this software
18: * without specific prior written permission.
19: *
20: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30: * SUCH DAMAGE.
31: *
32: * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995
33: *
34: * NRL grants permission for redistribution and use in source and binary
35: * forms, with or without modification, of the software and documentation
36: * created at NRL provided that the following conditions are met:
37: *
38: * 1. Redistributions of source code must retain the above copyright
39: * notice, this list of conditions and the following disclaimer.
40: * 2. Redistributions in binary form must reproduce the above copyright
41: * notice, this list of conditions and the following disclaimer in the
42: * documentation and/or other materials provided with the distribution.
43: * 3. All advertising materials mentioning features or use of this software
44: * must display the following acknowledgements:
45: * This product includes software developed by the University of
46: * California, Berkeley and its contributors.
47: * This product includes software developed at the Information
48: * Technology Division, US Naval Research Laboratory.
49: * 4. Neither the name of the NRL nor the names of its contributors
50: * may be used to endorse or promote products derived from this software
51: * without specific prior written permission.
52: *
53: * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
54: * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
55: * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
56: * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
57: * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
58: * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
59: * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
60: * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
61: * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
62: * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
63: * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
64: *
65: * The views and conclusions contained in the software and documentation
66: * are those of the authors and should not be interpreted as representing
67: * official policies, either expressed or implied, of the US Naval
68: * Research Laboratory (NRL).
69: */
70:
71: #include <sys/param.h>
72: #include <sys/systm.h>
73: #include <sys/mbuf.h>
74: #include <sys/protosw.h>
75: #include <sys/socket.h>
76: #include <sys/socketvar.h>
77: #include <sys/kernel.h>
78:
79: #include <net/route.h>
80: #include <net/if.h>
81:
82: #include <netinet/in.h>
83: #include <netinet/in_systm.h>
84: #include <netinet/ip.h>
85: #include <netinet/in_pcb.h>
86: #include <netinet/ip_var.h>
87: #include <netinet/tcp.h>
88: #define TCPOUTFLAGS
89: #include <netinet/tcp_fsm.h>
90: #include <netinet/tcp_seq.h>
91: #include <netinet/tcp_timer.h>
92: #include <netinet/tcp_var.h>
93: #include <netinet/tcpip.h>
94: #include <netinet/tcp_debug.h>
95:
96: #ifdef INET6
97: #include <netinet6/tcpipv6.h>
98: #include <netinet6/in6_var.h>
99: #endif /* INET6 */
100:
101: #ifdef notyet
102: extern struct mbuf *m_copypack();
103: #endif
104:
105: #ifdef TCP_SACK
106: extern int tcprexmtthresh;
107: #endif
108:
109: #ifdef TCP_SACK
110: #ifdef TCP_SACK_DEBUG
111: void tcp_print_holes(struct tcpcb *tp);
112:
113: void
114: tcp_print_holes(struct tcpcb *tp)
115: {
116: struct sackhole *p = tp->snd_holes;
117: if (p == 0)
118: return;
119: printf("Hole report: start--end dups rxmit\n");
120: while (p) {
121: printf("%x--%x d %d r %x\n", p->start, p->end, p->dups,
122: p->rxmit);
123: p = p->next;
124: }
125: printf("\n");
126: }
127: #endif /* TCP_SACK_DEBUG */
128:
129: /*
130: * Returns pointer to a sackhole if there are any pending retransmissions;
131: * NULL otherwise.
132: */
133: struct sackhole *
134: tcp_sack_output(struct tcpcb *tp)
135: {
136: struct sackhole *p;
137:
138: if (!tp->sack_enable)
139: return (NULL);
140: p = tp->snd_holes;
141: while (p) {
142: #ifndef TCP_FACK
143: if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
144: #else
145: /* In FACK, if p->dups is less than tcprexmtthresh, but
146: * snd_fack advances more than tcprextmtthresh * tp->t_maxseg,
147: * tcp_input() will try fast retransmit. This forces output.
148: */
149: if ((p->dups >= tcprexmtthresh ||
150: tp->t_dupacks == tcprexmtthresh) &&
151: SEQ_LT(p->rxmit, p->end)) {
152: #endif /* TCP_FACK */
153: if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
154: p = p->next;
155: continue;
156: }
157: #ifdef TCP_SACK_DEBUG
158: if (p)
159: tcp_print_holes(tp);
160: #endif
161: return (p);
162: }
163: p = p->next;
164: }
165: return (NULL);
166: }
167:
168: /*
169: * After a timeout, the SACK list may be rebuilt. This SACK information
170: * should be used to avoid retransmitting SACKed data. This function
171: * traverses the SACK list to see if snd_nxt should be moved forward.
172: */
173:
174: void
175: tcp_sack_adjust(struct tcpcb *tp)
176: {
177: struct sackhole *cur = tp->snd_holes;
178: if (cur == NULL)
179: return; /* No holes */
180: if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))
181: return; /* We're already beyond any SACKed blocks */
182: /*
183: * Two cases for which we want to advance snd_nxt:
184: * i) snd_nxt lies between end of one hole and beginning of another
185: * ii) snd_nxt lies between end of last hole and rcv_lastsack
186: */
187: while (cur->next) {
188: if (SEQ_LT(tp->snd_nxt, cur->end))
189: return;
190: if (SEQ_GEQ(tp->snd_nxt, cur->next->start))
191: cur = cur->next;
192: else {
193: tp->snd_nxt = cur->next->start;
194: return;
195: }
196: }
197: if (SEQ_LT(tp->snd_nxt, cur->end))
198: return;
199: tp->snd_nxt = tp->rcv_lastsack;
200: return;
201: }
202: #endif /* TCP_SACK */
203:
204: /*
205: * Tcp output routine: figure out what should be sent and send it.
206: */
207: int
208: tcp_output(tp)
209: struct tcpcb *tp;
210: {
211: struct socket *so = tp->t_inpcb->inp_socket;
212: long len, win, txmaxseg;
213: int off, flags, error;
214: struct mbuf *m;
215: struct tcphdr *th;
216: u_char opt[MAX_TCPOPTLEN];
217: unsigned int optlen, hdrlen, packetlen;
218: int idle, sendalot = 0;
219: #ifdef TCP_SACK
220: int i, sack_rxmit = 0;
221: struct sackhole *p;
222: #endif
223: #if defined(TCP_SACK)
224: int maxburst = TCP_MAXBURST;
225: #endif
226: #ifdef TCP_SIGNATURE
227: unsigned int sigoff;
228: #endif /* TCP_SIGNATURE */
229: #ifdef TCP_ECN
230: int needect;
231: #endif
232:
233: #if defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC)
234: if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE))
235: return (EINVAL);
236: #endif /* defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */
237:
238: /*
239: * Determine length of data that should be transmitted,
240: * and flags that will be used.
241: * If there is some data or critical controls (SYN, RST)
242: * to send, then transmit; otherwise, investigate further.
243: */
244: idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
245: if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur)
246: /*
247: * We have been idle for "a while" and no acks are
248: * expected to clock out any data we send --
249: * slow start to get ack "clock" running again.
250: */
251: tp->snd_cwnd = 2 * tp->t_maxseg;
252:
253: /* remember 'idle' for next invocation of tcp_output */
254: if (idle && soissending(so)) {
255: tp->t_flags |= TF_LASTIDLE;
256: idle = 0;
257: } else
258: tp->t_flags &= ~TF_LASTIDLE;
259:
260: again:
261: #ifdef TCP_SACK
262: /*
263: * If we've recently taken a timeout, snd_max will be greater than
264: * snd_nxt. There may be SACK information that allows us to avoid
265: * resending already delivered data. Adjust snd_nxt accordingly.
266: */
267: if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max))
268: tcp_sack_adjust(tp);
269: #endif
270: off = tp->snd_nxt - tp->snd_una;
271: #if defined(TCP_SACK) && defined(TCP_FACK)
272: /* Normally, sendable data is limited by off < tp->snd_cwnd.
273: * But in FACK, sendable data is limited by snd_awnd < snd_cwnd,
274: * regardless of offset.
275: */
276: if (tp->sack_enable && (tp->t_dupacks > tcprexmtthresh))
277: win = tp->snd_wnd;
278: else
279: #endif
280: win = ulmin(tp->snd_wnd, tp->snd_cwnd);
281:
282: flags = tcp_outflags[tp->t_state];
283:
284: #ifdef TCP_SACK
285: /*
286: * Send any SACK-generated retransmissions. If we're explicitly trying
287: * to send out new data (when sendalot is 1), bypass this function.
288: * If we retransmit in fast recovery mode, decrement snd_cwnd, since
289: * we're replacing a (future) new transmission with a retransmission
290: * now, and we previously incremented snd_cwnd in tcp_input().
291: */
292: if (tp->sack_enable && !sendalot) {
293: if (tp->t_dupacks >= tcprexmtthresh &&
294: (p = tcp_sack_output(tp))) {
295: off = p->rxmit - tp->snd_una;
296: sack_rxmit = 1;
297: #if 0
298: /* Coalesce holes into a single retransmission */
299: #endif
300: len = min(tp->t_maxseg, p->end - p->rxmit);
301: #ifndef TCP_FACK
302: /* in FACK, hold snd_cwnd constant during recovery */
303: if (SEQ_LT(tp->snd_una, tp->snd_last))
304: tp->snd_cwnd -= tp->t_maxseg;
305: #endif
306: }
307: }
308: #endif /* TCP_SACK */
309:
310: sendalot = 0;
311: /*
312: * If in persist timeout with window of 0, send 1 byte.
313: * Otherwise, if window is small but nonzero
314: * and timer expired, we will send what we can
315: * and go to transmit state.
316: */
317: if (tp->t_force) {
318: if (win == 0) {
319: /*
320: * If we still have some data to send, then
321: * clear the FIN bit. Usually this would
322: * happen below when it realizes that we
323: * aren't sending all the data. However,
324: * if we have exactly 1 byte of unset data,
325: * then it won't clear the FIN bit below,
326: * and if we are in persist state, we wind
327: * up sending the packet without recording
328: * that we sent the FIN bit.
329: *
330: * We can't just blindly clear the FIN bit,
331: * because if we don't have any more data
332: * to send then the probe will be the FIN
333: * itself.
334: */
335: if (off < so->so_snd.sb_cc)
336: flags &= ~TH_FIN;
337: win = 1;
338: } else {
339: TCP_TIMER_DISARM(tp, TCPT_PERSIST);
340: tp->t_rxtshift = 0;
341: }
342: }
343:
344: #ifdef TCP_SACK
345: if (!sack_rxmit) {
346: #endif
347: len = ulmin(so->so_snd.sb_cc, win) - off;
348:
349: #if defined(TCP_SACK) && defined(TCP_FACK)
350: /*
351: * If we're in fast recovery (SEQ_GT(tp->snd_last, tp->snd_una)), and
352: * amount of outstanding data (snd_awnd) is >= snd_cwnd, then
353: * do not send data (like zero window conditions)
354: */
355: if (tp->sack_enable && len && SEQ_GT(tp->snd_last, tp->snd_una) &&
356: (tp->snd_awnd >= tp->snd_cwnd))
357: len = 0;
358: #endif /* TCP_FACK */
359: #ifdef TCP_SACK
360: }
361: #endif
362:
363: if (len < 0) {
364: /*
365: * If FIN has been sent but not acked,
366: * but we haven't been called to retransmit,
367: * len will be -1. Otherwise, window shrank
368: * after we sent into it. If window shrank to 0,
369: * cancel pending retransmit, pull snd_nxt back
370: * to (closed) window, and set the persist timer
371: * if it isn't already going. If the window didn't
372: * close completely, just wait for an ACK.
373: */
374: len = 0;
375: if (win == 0) {
376: TCP_TIMER_DISARM(tp, TCPT_REXMT);
377: tp->t_rxtshift = 0;
378: tp->snd_nxt = tp->snd_una;
379: if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
380: tcp_setpersist(tp);
381: }
382: }
383:
384: /*
385: * Never send more than half a buffer full. This insures that we can
386: * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
387: * therefore acks will never be delayed unless we run out of data to
388: * transmit.
389: */
390: txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg);
391:
392: if (len > txmaxseg) {
393: len = txmaxseg;
394: sendalot = 1;
395: }
396: if (off + len < so->so_snd.sb_cc)
397: flags &= ~TH_FIN;
398:
399: win = sbspace(&so->so_rcv);
400:
401: /*
402: * Sender silly window avoidance. If connection is idle
403: * and can send all data, a maximum segment,
404: * at least a maximum default-size segment do it,
405: * or are forced, do it; otherwise don't bother.
406: * If peer's buffer is tiny, then send
407: * when window is at least half open.
408: * If retransmitting (possibly after persist timer forced us
409: * to send into a small window), then must resend.
410: */
411: if (len) {
412: if (len == txmaxseg)
413: goto send;
414: if ((idle || tp->t_flags & TF_NODELAY) &&
415: len + off >= so->so_snd.sb_cc && !soissending(so))
416: goto send;
417: if (tp->t_force)
418: goto send;
419: if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
420: goto send;
421: if (SEQ_LT(tp->snd_nxt, tp->snd_max))
422: goto send;
423: #ifdef TCP_SACK
424: if (sack_rxmit)
425: goto send;
426: #endif
427: }
428:
429: /*
430: * Compare available window to amount of window
431: * known to peer (as advertised window less
432: * next expected input). If the difference is at least two
433: * max size segments, or at least 50% of the maximum possible
434: * window, then want to send a window update to peer.
435: */
436: if (win > 0) {
437: /*
438: * "adv" is the amount we can increase the window,
439: * taking into account that we are limited by
440: * TCP_MAXWIN << tp->rcv_scale.
441: */
442: long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) -
443: (tp->rcv_adv - tp->rcv_nxt);
444:
445: if (adv >= (long) (2 * tp->t_maxseg))
446: goto send;
447: if (2 * adv >= (long) so->so_rcv.sb_hiwat)
448: goto send;
449: }
450:
451: /*
452: * Send if we owe peer an ACK.
453: */
454: if (tp->t_flags & TF_ACKNOW)
455: goto send;
456: if (flags & (TH_SYN|TH_RST))
457: goto send;
458: if (SEQ_GT(tp->snd_up, tp->snd_una))
459: goto send;
460: /*
461: * If our state indicates that FIN should be sent
462: * and we have not yet done so, or we're retransmitting the FIN,
463: * then we need to send.
464: */
465: if (flags & TH_FIN &&
466: ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
467: goto send;
468: #ifdef TCP_SACK
469: /*
470: * In SACK, it is possible for tcp_output to fail to send a segment
471: * after the retransmission timer has been turned off. Make sure
472: * that the retransmission timer is set.
473: */
474: if (SEQ_GT(tp->snd_max, tp->snd_una) &&
475: TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
476: TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
477: TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
478: return (0);
479: }
480: #endif /* TCP_SACK */
481:
482: /*
483: * TCP window updates are not reliable, rather a polling protocol
484: * using ``persist'' packets is used to insure receipt of window
485: * updates. The three ``states'' for the output side are:
486: * idle not doing retransmits or persists
487: * persisting to move a small or zero window
488: * (re)transmitting and thereby not persisting
489: *
490: * tp->t_timer[TCPT_PERSIST]
491: * is set when we are in persist state.
492: * tp->t_force
493: * is set when we are called to send a persist packet.
494: * tp->t_timer[TCPT_REXMT]
495: * is set when we are retransmitting
496: * The output side is idle when both timers are zero.
497: *
498: * If send window is too small, there is data to transmit, and no
499: * retransmit or persist is pending, then go to persist state.
500: * If nothing happens soon, send when timer expires:
501: * if window is nonzero, transmit what we can,
502: * otherwise force out a byte.
503: */
504: if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
505: TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
506: tp->t_rxtshift = 0;
507: tcp_setpersist(tp);
508: }
509:
510: /*
511: * No reason to send a segment, just return.
512: */
513: return (0);
514:
515: send:
516: /*
517: * Before ESTABLISHED, force sending of initial options
518: * unless TCP set not to do any options.
519: * NOTE: we assume that the IP/TCP header plus TCP options
520: * always fit in a single mbuf, leaving room for a maximum
521: * link header, i.e.
522: * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr +
523: * optlen <= MHLEN
524: */
525: optlen = 0;
526:
527: switch (tp->pf) {
528: case 0: /*default to PF_INET*/
529: #ifdef INET
530: case PF_INET:
531: hdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
532: break;
533: #endif /* INET */
534: #ifdef INET6
535: case PF_INET6:
536: hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
537: break;
538: #endif /* INET6 */
539: default:
540: return (EPFNOSUPPORT);
541: }
542:
543: if (flags & TH_SYN) {
544: tp->snd_nxt = tp->iss;
545: if ((tp->t_flags & TF_NOOPT) == 0) {
546: u_int16_t mss;
547:
548: opt[0] = TCPOPT_MAXSEG;
549: opt[1] = 4;
550: mss = htons((u_int16_t) tcp_mss(tp, 0));
551: bcopy((caddr_t)&mss, (caddr_t)(opt + 2), sizeof(mss));
552: optlen = 4;
553:
554: if (flags & TH_ACK)
555: tcp_mss_update(tp);
556: #ifdef TCP_SACK
557: /*
558: * If this is the first SYN of connection (not a SYN
559: * ACK), include SACK_PERMIT_HDR option. If this is a
560: * SYN ACK, include SACK_PERMIT_HDR option if peer has
561: * already done so.
562: */
563: if (tp->sack_enable && ((flags & TH_ACK) == 0 ||
564: (tp->t_flags & TF_SACK_PERMIT))) {
565: *((u_int32_t *) (opt + optlen)) =
566: htonl(TCPOPT_SACK_PERMIT_HDR);
567: optlen += 4;
568: }
569: #endif
570:
571: if ((tp->t_flags & TF_REQ_SCALE) &&
572: ((flags & TH_ACK) == 0 ||
573: (tp->t_flags & TF_RCVD_SCALE))) {
574: *((u_int32_t *) (opt + optlen)) = htonl(
575: TCPOPT_NOP << 24 |
576: TCPOPT_WINDOW << 16 |
577: TCPOLEN_WINDOW << 8 |
578: tp->request_r_scale);
579: optlen += 4;
580: }
581: }
582: }
583:
584: /*
585: * Send a timestamp and echo-reply if this is a SYN and our side
586: * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
587: * and our peer have sent timestamps in our SYN's.
588: */
589: if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
590: (flags & TH_RST) == 0 &&
591: ((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
592: (tp->t_flags & TF_RCVD_TSTMP))) {
593: u_int32_t *lp = (u_int32_t *)(opt + optlen);
594:
595: /* Form timestamp option as shown in appendix A of RFC 1323. */
596: *lp++ = htonl(TCPOPT_TSTAMP_HDR);
597: *lp++ = htonl(tcp_now + tp->ts_modulate);
598: *lp = htonl(tp->ts_recent);
599: optlen += TCPOLEN_TSTAMP_APPA;
600: }
601:
602: #ifdef TCP_SIGNATURE
603: if (tp->t_flags & TF_SIGNATURE) {
604: u_int8_t *bp = (u_int8_t *)(opt + optlen);
605:
606: /* Send signature option */
607: *(bp++) = TCPOPT_SIGNATURE;
608: *(bp++) = TCPOLEN_SIGNATURE;
609: sigoff = optlen + 2;
610:
611: {
612: unsigned int i;
613:
614: for (i = 0; i < 16; i++)
615: *(bp++) = 0;
616: }
617:
618:
619: /* Pad options list to the next 32 bit boundary and
620: * terminate it.
621: */
622: *bp++ = TCPOPT_NOP;
623: *bp++ = TCPOPT_EOL;
624:
625: optlen += TCPOLEN_SIGLEN;
626: }
627: #endif /* TCP_SIGNATURE */
628:
629: #ifdef TCP_SACK
630: /*
631: * Send SACKs if necessary. This should be the last option processed.
632: * Only as many SACKs are sent as are permitted by the maximum options
633: * size. No more than three SACKs are sent.
634: */
635: if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED &&
636: (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT &&
637: tp->rcv_numsacks) {
638: u_int32_t *lp = (u_int32_t *)(opt + optlen);
639: u_int32_t *olp = lp++;
640: int count = 0; /* actual number of SACKs inserted */
641: int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK;
642:
643: tcpstat.tcps_sack_snd_opts++;
644: maxsack = min(maxsack, TCP_MAX_SACK);
645: for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) {
646: struct sackblk sack = tp->sackblks[i];
647: if (sack.start == 0 && sack.end == 0)
648: continue;
649: *lp++ = htonl(sack.start);
650: *lp++ = htonl(sack.end);
651: count++;
652: }
653: *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2));
654: optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */
655: }
656: #endif /* TCP_SACK */
657:
658: #ifdef DIAGNOSTIC
659: if (optlen > MAX_TCPOPTLEN)
660: panic("tcp_output: options too long");
661: #endif /* DIAGNOSTIC */
662:
663: hdrlen += optlen;
664:
665: /*
666: * Adjust data length if insertion of options will
667: * bump the packet length beyond the t_maxopd length.
668: */
669: if (len > tp->t_maxopd - optlen) {
670: len = tp->t_maxopd - optlen;
671: sendalot = 1;
672: flags &= ~TH_FIN;
673: }
674:
675: #ifdef DIAGNOSTIC
676: if (max_linkhdr + hdrlen > MCLBYTES)
677: panic("tcphdr too big");
678: #endif
679:
680: /*
681: * Grab a header mbuf, attaching a copy of data to
682: * be transmitted, and initialize the header from
683: * the template for sends on this connection.
684: */
685: if (len) {
686: if (tp->t_force && len == 1)
687: tcpstat.tcps_sndprobe++;
688: else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
689: tcpstat.tcps_sndrexmitpack++;
690: tcpstat.tcps_sndrexmitbyte += len;
691: } else {
692: tcpstat.tcps_sndpack++;
693: tcpstat.tcps_sndbyte += len;
694: }
695: #ifdef notyet
696: if ((m = m_copypack(so->so_snd.sb_mb, off,
697: (int)len, max_linkhdr + hdrlen)) == 0) {
698: error = ENOBUFS;
699: goto out;
700: }
701: /*
702: * m_copypack left space for our hdr; use it.
703: */
704: m->m_len += hdrlen;
705: m->m_data -= hdrlen;
706: #else
707: MGETHDR(m, M_DONTWAIT, MT_HEADER);
708: if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
709: MCLGET(m, M_DONTWAIT);
710: if ((m->m_flags & M_EXT) == 0) {
711: m_freem(m);
712: m = NULL;
713: }
714: }
715: if (m == NULL) {
716: error = ENOBUFS;
717: goto out;
718: }
719: m->m_data += max_linkhdr;
720: m->m_len = hdrlen;
721: if (len <= M_TRAILINGSPACE(m)) {
722: m_copydata(so->so_snd.sb_mb, off, (int) len,
723: mtod(m, caddr_t) + hdrlen);
724: m->m_len += len;
725: } else {
726: m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
727: if (m->m_next == 0) {
728: (void) m_free(m);
729: error = ENOBUFS;
730: goto out;
731: }
732: }
733: #endif
734: /*
735: * If we're sending everything we've got, set PUSH.
736: * (This will keep happy those implementations which only
737: * give data to the user when a buffer fills or
738: * a PUSH comes in.)
739: */
740: if (off + len == so->so_snd.sb_cc && !soissending(so))
741: flags |= TH_PUSH;
742: } else {
743: if (tp->t_flags & TF_ACKNOW)
744: tcpstat.tcps_sndacks++;
745: else if (flags & (TH_SYN|TH_FIN|TH_RST))
746: tcpstat.tcps_sndctrl++;
747: else if (SEQ_GT(tp->snd_up, tp->snd_una))
748: tcpstat.tcps_sndurg++;
749: else
750: tcpstat.tcps_sndwinup++;
751:
752: MGETHDR(m, M_DONTWAIT, MT_HEADER);
753: if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
754: MCLGET(m, M_DONTWAIT);
755: if ((m->m_flags & M_EXT) == 0) {
756: m_freem(m);
757: m = NULL;
758: }
759: }
760: if (m == NULL) {
761: error = ENOBUFS;
762: goto out;
763: }
764: m->m_data += max_linkhdr;
765: m->m_len = hdrlen;
766: }
767: m->m_pkthdr.rcvif = (struct ifnet *)0;
768: m->m_pkthdr.len = hdrlen + len;
769:
770: if (!tp->t_template)
771: panic("tcp_output");
772: #ifdef DIAGNOSTIC
773: if (tp->t_template->m_len != hdrlen - optlen)
774: panic("tcp_output: template len != hdrlen - optlen");
775: #endif /* DIAGNOSTIC */
776: bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t),
777: tp->t_template->m_len);
778: th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len -
779: sizeof(struct tcphdr));
780:
781: /*
782: * Fill in fields, remembering maximum advertised
783: * window for use in delaying messages about window sizes.
784: * If resending a FIN, be sure not to use a new sequence number.
785: */
786: if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) &&
787: (tp->snd_nxt == tp->snd_max))
788: tp->snd_nxt--;
789: /*
790: * If we are doing retransmissions, then snd_nxt will
791: * not reflect the first unsent octet. For ACK only
792: * packets, we do not want the sequence number of the
793: * retransmitted packet, we want the sequence number
794: * of the next unsent octet. So, if there is no data
795: * (and no SYN or FIN), use snd_max instead of snd_nxt
796: * when filling in ti_seq. But if we are in persist
797: * state, snd_max might reflect one byte beyond the
798: * right edge of the window, so use snd_nxt in that
799: * case, since we know we aren't doing a retransmission.
800: * (retransmit and persist are mutually exclusive...)
801: */
802: if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST))
803: th->th_seq = htonl(tp->snd_nxt);
804: else
805: th->th_seq = htonl(tp->snd_max);
806:
807: #ifdef TCP_SACK
808: if (sack_rxmit) {
809: /*
810: * If sendalot was turned on (due to option stuffing), turn it
811: * off. Properly set th_seq field. Advance the ret'x pointer
812: * by len.
813: */
814: if (sendalot)
815: sendalot = 0;
816: th->th_seq = htonl(p->rxmit);
817: p->rxmit += len;
818: #if defined(TCP_SACK) && defined(TCP_FACK)
819: tp->retran_data += len;
820: #endif /* TCP_FACK */
821: tcpstat.tcps_sack_rexmits++;
822: tcpstat.tcps_sack_rexmit_bytes += len;
823: }
824: #endif /* TCP_SACK */
825:
826: th->th_ack = htonl(tp->rcv_nxt);
827: if (optlen) {
828: bcopy((caddr_t)opt, (caddr_t)(th + 1), optlen);
829: th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
830: }
831: #ifdef TCP_ECN
832: if (tcp_do_ecn) {
833: /*
834: * if we have received congestion experienced segs,
835: * set ECE bit.
836: */
837: if (tp->t_flags & TF_RCVD_CE) {
838: flags |= TH_ECE;
839: tcpstat.tcps_ecn_sndece++;
840: }
841: if (!(tp->t_flags & TF_DISABLE_ECN)) {
842: /*
843: * if this is a SYN seg, set ECE and CWR.
844: * set only ECE for SYN-ACK if peer supports ECN.
845: */
846: if ((flags & (TH_SYN|TH_ACK)) == TH_SYN)
847: flags |= (TH_ECE|TH_CWR);
848: else if ((tp->t_flags & TF_ECN_PERMIT) &&
849: (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK))
850: flags |= TH_ECE;
851: }
852: /*
853: * if we have reduced the congestion window, notify
854: * the peer by setting CWR bit.
855: */
856: if ((tp->t_flags & TF_ECN_PERMIT) &&
857: (tp->t_flags & TF_SEND_CWR)) {
858: flags |= TH_CWR;
859: tp->t_flags &= ~TF_SEND_CWR;
860: tcpstat.tcps_ecn_sndcwr++;
861: }
862: }
863: #endif
864: th->th_flags = flags;
865:
866: /*
867: * Calculate receive window. Don't shrink window,
868: * but avoid silly window syndrome.
869: */
870: if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg)
871: win = 0;
872: if (win > (long)TCP_MAXWIN << tp->rcv_scale)
873: win = (long)TCP_MAXWIN << tp->rcv_scale;
874: if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt))
875: win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt);
876: if (flags & TH_RST)
877: win = 0;
878: th->th_win = htons((u_int16_t) (win>>tp->rcv_scale));
879: if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
880: u_int32_t urp = tp->snd_up - tp->snd_nxt;
881: if (urp > IP_MAXPACKET)
882: urp = IP_MAXPACKET;
883: th->th_urp = htons((u_int16_t)urp);
884: th->th_flags |= TH_URG;
885: } else
886: /*
887: * If no urgent pointer to send, then we pull
888: * the urgent pointer to the left edge of the send window
889: * so that it doesn't drift into the send window on sequence
890: * number wraparound.
891: */
892: tp->snd_up = tp->snd_una; /* drag it along */
893:
894: #ifdef TCP_SIGNATURE
895: if (tp->t_flags & TF_SIGNATURE) {
896: int iphlen;
897: union sockaddr_union src, dst;
898: struct tdb *tdb;
899:
900: bzero(&src, sizeof(union sockaddr_union));
901: bzero(&dst, sizeof(union sockaddr_union));
902:
903: switch (tp->pf) {
904: case 0: /*default to PF_INET*/
905: #ifdef INET
906: case AF_INET:
907: iphlen = sizeof(struct ip);
908: src.sa.sa_len = sizeof(struct sockaddr_in);
909: src.sa.sa_family = AF_INET;
910: src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
911: dst.sa.sa_len = sizeof(struct sockaddr_in);
912: dst.sa.sa_family = AF_INET;
913: dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
914: break;
915: #endif /* INET */
916: #ifdef INET6
917: case AF_INET6:
918: iphlen = sizeof(struct ip6_hdr);
919: src.sa.sa_len = sizeof(struct sockaddr_in6);
920: src.sa.sa_family = AF_INET6;
921: src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
922: dst.sa.sa_len = sizeof(struct sockaddr_in6);
923: dst.sa.sa_family = AF_INET6;
924: dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
925: break;
926: #endif /* INET6 */
927: }
928:
929: /* XXX gettdbbysrcdst() should really be called at spltdb(). */
930: /* XXX this is splsoftnet(), currently they are the same. */
931: tdb = gettdbbysrcdst(0, &src, &dst, IPPROTO_TCP);
932: if (tdb == NULL)
933: return (EPERM);
934:
935: if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0,
936: mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0)
937: return (EINVAL);
938: }
939: #endif /* TCP_SIGNATURE */
940:
941: /*
942: * Put TCP length in extended header, and then
943: * checksum extended header and data.
944: */
945: switch (tp->pf) {
946: case 0: /*default to PF_INET*/
947: #ifdef INET
948: case AF_INET:
949: /* Defer checksumming until later (ip_output() or hardware) */
950: m->m_pkthdr.csum_flags |= M_TCPV4_CSUM_OUT;
951: if (len + optlen)
952: th->th_sum = in_cksum_addword(th->th_sum,
953: htons((u_int16_t)(len + optlen)));
954: break;
955: #endif /* INET */
956: #ifdef INET6
957: case AF_INET6:
958: th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
959: hdrlen - sizeof(struct ip6_hdr) + len);
960: break;
961: #endif /* INET6 */
962: }
963:
964: /*
965: * In transmit state, time the transmission and arrange for
966: * the retransmit. In persist state, just set snd_max.
967: */
968: if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
969: tcp_seq startseq = tp->snd_nxt;
970:
971: /*
972: * Advance snd_nxt over sequence space of this segment.
973: */
974: if (flags & (TH_SYN|TH_FIN)) {
975: if (flags & TH_SYN)
976: tp->snd_nxt++;
977: if (flags & TH_FIN) {
978: tp->snd_nxt++;
979: tp->t_flags |= TF_SENTFIN;
980: }
981: }
982: #ifdef TCP_SACK
983: if (tp->sack_enable) {
984: if (sack_rxmit && (p->rxmit != tp->snd_nxt)) {
985: goto timer;
986: }
987: }
988: #endif
989: tp->snd_nxt += len;
990: if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
991: tp->snd_max = tp->snd_nxt;
992: /*
993: * Time this transmission if not a retransmission and
994: * not currently timing anything.
995: */
996: if (tp->t_rtttime == 0) {
997: tp->t_rtttime = tcp_now;
998: tp->t_rtseq = startseq;
999: tcpstat.tcps_segstimed++;
1000: }
1001: }
1002:
1003: /*
1004: * Set retransmit timer if not currently set,
1005: * and not doing an ack or a keep-alive probe.
1006: * Initial value for retransmit timer is smoothed
1007: * round-trip time + 2 * round-trip time variance.
1008: * Initialize shift counter which is used for backoff
1009: * of retransmit time.
1010: */
1011: #ifdef TCP_SACK
1012: timer:
1013: if (tp->sack_enable && sack_rxmit &&
1014: TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
1015: tp->snd_nxt != tp->snd_max) {
1016: TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
1017: if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
1018: TCP_TIMER_DISARM(tp, TCPT_PERSIST);
1019: tp->t_rxtshift = 0;
1020: }
1021: }
1022: #endif
1023:
1024: if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
1025: tp->snd_nxt != tp->snd_una) {
1026: TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
1027: if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
1028: TCP_TIMER_DISARM(tp, TCPT_PERSIST);
1029: tp->t_rxtshift = 0;
1030: }
1031: }
1032: } else
1033: if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
1034: tp->snd_max = tp->snd_nxt + len;
1035:
1036: /*
1037: * Trace.
1038: */
1039: if (so->so_options & SO_DEBUG)
1040: tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, caddr_t), 0,
1041: len);
1042:
1043: /*
1044: * Fill in IP length and desired time to live and
1045: * send to IP level. There should be a better way
1046: * to handle ttl and tos; we could keep them in
1047: * the template, but need a way to checksum without them.
1048: */
1049:
1050: #ifdef TCP_ECN
1051: /*
1052: * if peer is ECN capable, set the ECT bit in the IP header.
1053: * but don't set ECT for a pure ack, a retransmit or a window probe.
1054: */
1055: needect = 0;
1056: if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) {
1057: if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) ||
1058: (tp->t_force && len == 1)) {
1059: /* don't set ECT */
1060: } else {
1061: needect = 1;
1062: tcpstat.tcps_ecn_sndect++;
1063: }
1064: }
1065: #endif
1066:
1067: switch (tp->pf) {
1068: case 0: /*default to PF_INET*/
1069: #ifdef INET
1070: case AF_INET:
1071: {
1072: struct ip *ip;
1073:
1074: ip = mtod(m, struct ip *);
1075: ip->ip_len = htons(m->m_pkthdr.len);
1076: packetlen = m->m_pkthdr.len;
1077: ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl;
1078: ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos;
1079: #ifdef TCP_ECN
1080: if (needect)
1081: ip->ip_tos |= IPTOS_ECN_ECT0;
1082: #endif
1083: }
1084: error = ip_output(m, tp->t_inpcb->inp_options,
1085: &tp->t_inpcb->inp_route,
1086: (ip_mtudisc ? IP_MTUDISC : 0) |
1087: (so->so_options & SO_DONTROUTE),
1088: (void *)NULL, tp->t_inpcb);
1089: break;
1090: #endif /* INET */
1091: #ifdef INET6
1092: case AF_INET6:
1093: {
1094: struct ip6_hdr *ip6;
1095:
1096: ip6 = mtod(m, struct ip6_hdr *);
1097: ip6->ip6_plen = m->m_pkthdr.len -
1098: sizeof(struct ip6_hdr);
1099: packetlen = m->m_pkthdr.len;
1100: ip6->ip6_nxt = IPPROTO_TCP;
1101: ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL);
1102: #ifdef TCP_ECN
1103: if (needect)
1104: ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20);
1105: #endif
1106: }
1107: error = ip6_output(m, tp->t_inpcb->inp_outputopts6,
1108: &tp->t_inpcb->inp_route6,
1109: (so->so_options & SO_DONTROUTE), NULL, NULL,
1110: tp->t_inpcb);
1111: break;
1112: #endif /* INET6 */
1113: }
1114:
1115: #if defined(TCP_SACK) && defined(TCP_FACK)
1116: /* Update snd_awnd to reflect the new data that was sent. */
1117: tp->snd_awnd = tcp_seq_subtract(tp->snd_max, tp->snd_fack) +
1118: tp->retran_data;
1119: #endif /* defined(TCP_SACK) && defined(TCP_FACK) */
1120:
1121: if (error) {
1122: out:
1123: if (error == ENOBUFS) {
1124: /*
1125: * If the interface queue is full, or IP cannot
1126: * get an mbuf, trigger TCP slow start.
1127: */
1128: tp->snd_cwnd = tp->t_maxseg;
1129: return (0);
1130: }
1131: if (error == EMSGSIZE) {
1132: /*
1133: * ip_output() will have already fixed the route
1134: * for us. tcp_mtudisc() will, as its last action,
1135: * initiate retransmission, so it is important to
1136: * not do so here.
1137: */
1138: tcp_mtudisc(tp->t_inpcb, -1);
1139: return (0);
1140: }
1141: if ((error == EHOSTUNREACH || error == ENETDOWN) &&
1142: TCPS_HAVERCVDSYN(tp->t_state)) {
1143: tp->t_softerror = error;
1144: return (0);
1145: }
1146:
1147: /* Restart the delayed ACK timer, if necessary. */
1148: if (tp->t_flags & TF_DELACK)
1149: TCP_RESTART_DELACK(tp);
1150:
1151: return (error);
1152: }
1153:
1154: if (packetlen > tp->t_pmtud_mtu_sent)
1155: tp->t_pmtud_mtu_sent = packetlen;
1156:
1157: tcpstat.tcps_sndtotal++;
1158: if (tp->t_flags & TF_DELACK)
1159: tcpstat.tcps_delack++;
1160:
1161: /*
1162: * Data sent (as far as we can tell).
1163: * If this advertises a larger window than any other segment,
1164: * then remember the size of the advertised window.
1165: * Any pending ACK has now been sent.
1166: */
1167: if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
1168: tp->rcv_adv = tp->rcv_nxt + win;
1169: tp->last_ack_sent = tp->rcv_nxt;
1170: tp->t_flags &= ~TF_ACKNOW;
1171: TCP_CLEAR_DELACK(tp);
1172: #if defined(TCP_SACK)
1173: if (sendalot && --maxburst)
1174: #else
1175: if (sendalot)
1176: #endif
1177: goto again;
1178: return (0);
1179: }
1180:
1181: void
1182: tcp_setpersist(struct tcpcb *tp)
1183: {
1184: int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT);
1185: int nticks;
1186:
1187: if (TCP_TIMER_ISARMED(tp, TCPT_REXMT))
1188: panic("tcp_output REXMT");
1189: /*
1190: * Start/restart persistance timer.
1191: */
1192: if (t < tp->t_rttmin)
1193: t = tp->t_rttmin;
1194: TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift],
1195: TCPTV_PERSMIN, TCPTV_PERSMAX);
1196: TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks);
1197: if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
1198: tp->t_rxtshift++;
1199: }
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