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1.1 root 1: /*
2: * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
3: *
4: * @APPLE_LICENSE_HEADER_START@
5: *
6: * The contents of this file constitute Original Code as defined in and
7: * are subject to the Apple Public Source License Version 1.1 (the
8: * "License"). You may not use this file except in compliance with the
9: * License. Please obtain a copy of the License at
10: * http://www.apple.com/publicsource and read it before using this file.
11: *
12: * This Original Code and all software distributed under the License are
13: * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
14: * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
15: * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
16: * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
17: * License for the specific language governing rights and limitations
18: * under the License.
19: *
20: * @APPLE_LICENSE_HEADER_END@
21: */
22: /*
23: * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
24: * The Regents of the University of California. All rights reserved.
25: *
26: * Redistribution and use in source and binary forms, with or without
27: * modification, are permitted provided that the following conditions
28: * are met:
29: * 1. Redistributions of source code must retain the above copyright
30: * notice, this list of conditions and the following disclaimer.
31: * 2. Redistributions in binary form must reproduce the above copyright
32: * notice, this list of conditions and the following disclaimer in the
33: * documentation and/or other materials provided with the distribution.
34: * 3. All advertising materials mentioning features or use of this software
35: * must display the following acknowledgement:
36: * This product includes software developed by the University of
37: * California, Berkeley and its contributors.
38: * 4. Neither the name of the University nor the names of its contributors
39: * may be used to endorse or promote products derived from this software
40: * without specific prior written permission.
41: *
42: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
43: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
44: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
45: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
46: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
47: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
48: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
49: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
50: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
51: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52: * SUCH DAMAGE.
53: *
54: * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95
55: */
56:
57: #if ISFB31
58: #include "opt_compat.h"
59: #include "opt_tcpdebug.h"
60: #endif
61:
62: #include <sys/param.h>
63: #include <sys/systm.h>
64: #include <sys/kernel.h>
65: #include <sys/sysctl.h>
66: #include <sys/socket.h>
67: #include <sys/socketvar.h>
68: #include <sys/protosw.h>
69:
70: #include <kern/cpu_number.h> /* before tcp_seq.h, for tcp_random18() */
71:
72: #include <net/route.h>
73:
74: #include <netinet/in.h>
75: #include <netinet/in_systm.h>
76: #include <netinet/in_pcb.h>
77: #include <netinet/ip_var.h>
78: #include <netinet/tcp.h>
79: #include <netinet/tcp_fsm.h>
80: #include <netinet/tcp_seq.h>
81: #include <netinet/tcp_timer.h>
82: #include <netinet/tcp_var.h>
83: #include <netinet/tcpip.h>
84: #if TCPDEBUG
85: #include <netinet/tcp_debug.h>
86: #endif
87:
88: int tcp_keepinit = TCPTV_KEEP_INIT;
89: SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit,
90: CTLFLAG_RW, &tcp_keepinit , 0, "");
91:
92: int tcp_keepidle = TCPTV_KEEP_IDLE;
93: SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle,
94: CTLFLAG_RW, &tcp_keepidle , 0, "");
95:
96: static int tcp_keepintvl = TCPTV_KEEPINTVL;
97: SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl,
98: CTLFLAG_RW, &tcp_keepintvl , 0, "");
99:
100: static int always_keepalive = 0;
101: SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive,
102: CTLFLAG_RW, &always_keepalive , 0, "");
103:
104: static int tcp_keepcnt = TCPTV_KEEPCNT;
105: /* max idle probes */
106: static int tcp_maxpersistidle = TCPTV_KEEP_IDLE;
107: /* max idle time in persist */
108: int tcp_maxidle;
109:
110: /*
111: * Fast timeout routine for processing delayed acks
112: */
113: void
114: tcp_fasttimo()
115: {
116: register struct inpcb *inp;
117: register struct tcpcb *tp;
118: int s;
119:
120: if (tcp_delack_enabled) {
121: s = splnet();
122: for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {
123: if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
124: (tp->t_flags & TF_DELACK)) {
125: tp->t_flags &= ~TF_DELACK;
126: tp->t_flags |= TF_ACKNOW;
127: tcpstat.tcps_delack++;
128: (void) tcp_output(tp);
129: }
130: }
131: splx(s);
132: }
133: }
134:
135: /*
136: * Tcp protocol timeout routine called every 500 ms.
137: * Updates the timers in all active tcb's and
138: * causes finite state machine actions if timers expire.
139: */
140: void
141: tcp_slowtimo()
142: {
143: register struct inpcb *ip, *ipnxt;
144: register struct tcpcb *tp;
145: register int i;
146: int s;
147: #if TCPDEBUG
148: int ostate;
149: #endif
150:
151: s = splnet();
152:
153: tcp_maxidle = tcp_keepcnt * tcp_keepintvl;
154:
155: ip = tcb.lh_first;
156: if (ip == NULL) {
157: splx(s);
158: return;
159: }
160: /*
161: * Search through tcb's and update active timers.
162: */
163: for (; ip != NULL; ip = ipnxt) {
164: ipnxt = ip->inp_list.le_next;
165: tp = intotcpcb(ip);
166: if (tp == 0 || tp->t_state == TCPS_LISTEN)
167: continue;
168: for (i = 0; i < TCPT_NTIMERS; i++) {
169: if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
170: #if TCPDEBUG
171: ostate = tp->t_state;
172: #endif
173: tp = tcp_timers(tp, i);
174: if (tp == NULL)
175: goto tpgone;
176: #if TCPDEBUG
177: if (tp->t_inpcb->inp_socket->so_options
178: & SO_DEBUG)
179: tcp_trace(TA_USER, ostate, tp,
180: (struct tcpiphdr *)0,
181: PRU_SLOWTIMO);
182: #endif
183: }
184: }
185: tp->t_idle++;
186: tp->t_duration++;
187: if (tp->t_rtt)
188: tp->t_rtt++;
189: tpgone:
190: ;
191: }
192: tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
193: #if TCP_COMPAT_42
194: if ((int)tcp_iss < 0)
195: tcp_iss = TCP_ISSINCR; /* XXX */
196: #endif
197: tcp_now++; /* for timestamps */
198: splx(s);
199: }
200:
201: /*
202: * Cancel all timers for TCP tp.
203: */
204: void
205: tcp_canceltimers(tp)
206: struct tcpcb *tp;
207: {
208: register int i;
209:
210: for (i = 0; i < TCPT_NTIMERS; i++)
211: tp->t_timer[i] = 0;
212: }
213:
214: int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
215: { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
216:
217: static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
218:
219: /*
220: * TCP timer processing.
221: */
222: struct tcpcb *
223: tcp_timers(tp, timer)
224: register struct tcpcb *tp;
225: int timer;
226: {
227: register int rexmt;
228: struct socket *so_tmp;
229:
230: switch (timer) {
231:
232: /*
233: * 2 MSL timeout in shutdown went off. If we're closed but
234: * still waiting for peer to close and connection has been idle
235: * too long, or if 2MSL time is up from TIME_WAIT, delete connection
236: * control block. Otherwise, check again in a bit.
237: */
238: case TCPT_2MSL:
239: if (tp->t_state != TCPS_TIME_WAIT &&
240: tp->t_idle <= tcp_maxidle)
241: tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
242: else
243: tp = tcp_close(tp);
244: break;
245:
246: /*
247: * Retransmission timer went off. Message has not
248: * been acked within retransmit interval. Back off
249: * to a longer retransmit interval and retransmit one segment.
250: */
251: case TCPT_REXMT:
252: if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
253: tp->t_rxtshift = TCP_MAXRXTSHIFT;
254: tcpstat.tcps_timeoutdrop++;
255: so_tmp = tp->t_inpcb->inp_socket;
256: tp = tcp_drop(tp, tp->t_softerror ?
257: tp->t_softerror : ETIMEDOUT);
258: postevent(so_tmp, 0, EV_TIMEOUT);
259: break;
260: }
261: tcpstat.tcps_rexmttimeo++;
262: rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
263: TCPT_RANGESET(tp->t_rxtcur, rexmt,
264: tp->t_rttmin, TCPTV_REXMTMAX);
265: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
266: /*
267: * If losing, let the lower level know and try for
268: * a better route. Also, if we backed off this far,
269: * our srtt estimate is probably bogus. Clobber it
270: * so we'll take the next rtt measurement as our srtt;
271: * move the current srtt into rttvar to keep the current
272: * retransmit times until then.
273: */
274: if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
275: in_losing(tp->t_inpcb);
276: tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
277: tp->t_srtt = 0;
278: }
279: tp->snd_nxt = tp->snd_una;
280: /*
281: * Force a segment to be sent.
282: */
283: tp->t_flags |= TF_ACKNOW;
284: /*
285: * If timing a segment in this window, stop the timer.
286: */
287: tp->t_rtt = 0;
288: /*
289: * Close the congestion window down to one segment
290: * (we'll open it by one segment for each ack we get).
291: * Since we probably have a window's worth of unacked
292: * data accumulated, this "slow start" keeps us from
293: * dumping all that data as back-to-back packets (which
294: * might overwhelm an intermediate gateway).
295: *
296: * There are two phases to the opening: Initially we
297: * open by one mss on each ack. This makes the window
298: * size increase exponentially with time. If the
299: * window is larger than the path can handle, this
300: * exponential growth results in dropped packet(s)
301: * almost immediately. To get more time between
302: * drops but still "push" the network to take advantage
303: * of improving conditions, we switch from exponential
304: * to linear window opening at some threshhold size.
305: * For a threshhold, we use half the current window
306: * size, truncated to a multiple of the mss.
307: *
308: * (the minimum cwnd that will give us exponential
309: * growth is 2 mss. We don't allow the threshhold
310: * to go below this.)
311: */
312: {
313: u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
314: if (win < 2)
315: win = 2;
316: tp->snd_cwnd = tp->t_maxseg;
317: tp->snd_ssthresh = win * tp->t_maxseg;
318: tp->t_dupacks = 0;
319: }
320: (void) tcp_output(tp);
321: break;
322:
323: /*
324: * Persistance timer into zero window.
325: * Force a byte to be output, if possible.
326: */
327: case TCPT_PERSIST:
328: tcpstat.tcps_persisttimeo++;
329: /*
330: * Hack: if the peer is dead/unreachable, we do not
331: * time out if the window is closed. After a full
332: * backoff, drop the connection if the idle time
333: * (no responses to probes) reaches the maximum
334: * backoff that we would use if retransmitting.
335: */
336: if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
337: (tp->t_idle >= tcp_maxpersistidle ||
338: tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
339: tcpstat.tcps_persistdrop++;
340: so_tmp = tp->t_inpcb->inp_socket;
341: tp = tcp_drop(tp, ETIMEDOUT);
342: postevent(so_tmp, 0, EV_TIMEOUT);
343: break;
344: }
345: tcp_setpersist(tp);
346: tp->t_force = 1;
347: (void) tcp_output(tp);
348: tp->t_force = 0;
349: break;
350:
351: /*
352: * Keep-alive timer went off; send something
353: * or drop connection if idle for too long.
354: */
355: case TCPT_KEEP:
356: tcpstat.tcps_keeptimeo++;
357: if (tp->t_state < TCPS_ESTABLISHED)
358: goto dropit;
359: if ((always_keepalive ||
360: tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) &&
361: tp->t_state <= TCPS_CLOSING) {
362: if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
363: goto dropit;
364: /*
365: * Send a packet designed to force a response
366: * if the peer is up and reachable:
367: * either an ACK if the connection is still alive,
368: * or an RST if the peer has closed the connection
369: * due to timeout or reboot.
370: * Using sequence number tp->snd_una-1
371: * causes the transmitted zero-length segment
372: * to lie outside the receive window;
373: * by the protocol spec, this requires the
374: * correspondent TCP to respond.
375: */
376: tcpstat.tcps_keepprobe++;
377: #if TCP_COMPAT_42
378: /*
379: * The keepalive packet must have nonzero length
380: * to get a 4.2 host to respond.
381: */
382: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
383: tp->rcv_nxt - 1, tp->snd_una - 1, 0);
384: #else
385: tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
386: tp->rcv_nxt, tp->snd_una - 1, 0);
387: #endif
388: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
389: } else
390: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
391: break;
392: dropit:
393: tcpstat.tcps_keepdrops++;
394: so_tmp = tp->t_inpcb->inp_socket;
395: tp = tcp_drop(tp, ETIMEDOUT);
396: postevent(so_tmp, 0, EV_TIMEOUT);
397: break;
398: }
399: return (tp);
400: }
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