[unix-history] / usr / src / sys.386bsd / netinet / tcp_timer.c

/*
 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)tcp_timer.c	7.18 (Berkeley) 6/28/90
 */

#include "param.h"
#include "systm.h"
#include "malloc.h"
#include "mbuf.h"
#include "socket.h"
#include "socketvar.h"
#include "protosw.h"
#include "errno.h"

#include "../net/if.h"
#include "../net/route.h"

#include "in.h"
#include "in_systm.h"
#include "ip.h"
#include "in_pcb.h"
#include "ip_var.h"
#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "tcpip.h"

int	tcp_keepidle = TCPTV_KEEP_IDLE;
int	tcp_keepintvl = TCPTV_KEEPINTVL;
int	tcp_maxidle;
/*
 * Fast timeout routine for processing delayed acks
 */
tcp_fasttimo()
{
	register struct inpcb *inp;
	register struct tcpcb *tp;
	int s = splnet();

	inp = tcb.inp_next;
	if (inp)
	for (; inp != &tcb; inp = inp->inp_next)
		if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
		    (tp->t_flags & TF_DELACK)) {
			tp->t_flags &= ~TF_DELACK;
			tp->t_flags |= TF_ACKNOW;
			tcpstat.tcps_delack++;
			(void) tcp_output(tp);
		}
	splx(s);
}

/*
 * Tcp protocol timeout routine called every 500 ms.
 * Updates the timers in all active tcb's and
 * causes finite state machine actions if timers expire.
 */
tcp_slowtimo()
{
	register struct inpcb *ip, *ipnxt;
	register struct tcpcb *tp;
	int s = splnet();
	register int i;

	tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
	/*
	 * Search through tcb's and update active timers.
	 */
	ip = tcb.inp_next;
	if (ip == 0) {
		splx(s);
		return;
	}
	for (; ip != &tcb; ip = ipnxt) {
		ipnxt = ip->inp_next;
		tp = intotcpcb(ip);
		if (tp == 0)
			continue;
		for (i = 0; i < TCPT_NTIMERS; i++) {
			if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
				(void) tcp_usrreq(tp->t_inpcb->inp_socket,
				    PRU_SLOWTIMO, (struct mbuf *)0,
				    (struct mbuf *)i, (struct mbuf *)0);
				if (ipnxt->inp_prev != ip)
					goto tpgone;
			}
		}
		tp->t_idle++;
		if (tp->t_rtt)
			tp->t_rtt++;
tpgone:
		;
	}
	tcp_iss += TCP_ISSINCR/PR_SLOWHZ;		/* increment iss */
#ifdef TCP_COMPAT_42
	if ((int)tcp_iss < 0)
		tcp_iss = 0;				/* XXX */
#endif
	splx(s);
}

/*
 * Cancel all timers for TCP tp.
 */
tcp_canceltimers(tp)
	struct tcpcb *tp;
{
	register int i;

	for (i = 0; i < TCPT_NTIMERS; i++)
		tp->t_timer[i] = 0;
}

int	tcp_backoff[TCP_MAXRXTSHIFT + 1] =
    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };

/*
 * TCP timer processing.
 */
struct tcpcb *
tcp_timers(tp, timer)
	register struct tcpcb *tp;
	int timer;
{
	register int rexmt;

	switch (timer) {

	/*
	 * 2 MSL timeout in shutdown went off.  If we're closed but
	 * still waiting for peer to close and connection has been idle
	 * too long, or if 2MSL time is up from TIME_WAIT, delete connection
	 * control block.  Otherwise, check again in a bit.
	 */
	case TCPT_2MSL:
		if (tp->t_state != TCPS_TIME_WAIT &&
		    tp->t_idle <= tcp_maxidle)
			tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
		else
			tp = tcp_close(tp);
		break;

	/*
	 * Retransmission timer went off.  Message has not
	 * been acked within retransmit interval.  Back off
	 * to a longer retransmit interval and retransmit one segment.
	 */
	case TCPT_REXMT:
		if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
			tp->t_rxtshift = TCP_MAXRXTSHIFT;
			tcpstat.tcps_timeoutdrop++;
			tp = tcp_drop(tp, tp->t_softerror ?
			    tp->t_softerror : ETIMEDOUT);
			break;
		}
		tcpstat.tcps_rexmttimeo++;
		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
		TCPT_RANGESET(tp->t_rxtcur, rexmt,
		    tp->t_rttmin, TCPTV_REXMTMAX);
		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
		/*
		 * If losing, let the lower level know and try for
		 * a better route.  Also, if we backed off this far,
		 * our srtt estimate is probably bogus.  Clobber it
		 * so we'll take the next rtt measurement as our srtt;
		 * move the current srtt into rttvar to keep the current
		 * retransmit times until then.
		 */
		if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
			in_losing(tp->t_inpcb);
			tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
			tp->t_srtt = 0;
		}
		tp->snd_nxt = tp->snd_una;
		/*
		 * If timing a segment in this window, stop the timer.
		 */
		tp->t_rtt = 0;
		/*
		 * Close the congestion window down to one segment
		 * (we'll open it by one segment for each ack we get).
		 * Since we probably have a window's worth of unacked
		 * data accumulated, this "slow start" keeps us from
		 * dumping all that data as back-to-back packets (which
		 * might overwhelm an intermediate gateway).
		 *
		 * There are two phases to the opening: Initially we
		 * open by one mss on each ack.  This makes the window
		 * size increase exponentially with time.  If the
		 * window is larger than the path can handle, this
		 * exponential growth results in dropped packet(s)
		 * almost immediately.  To get more time between 
		 * drops but still "push" the network to take advantage
		 * of improving conditions, we switch from exponential
		 * to linear window opening at some threshhold size.
		 * For a threshhold, we use half the current window
		 * size, truncated to a multiple of the mss.
		 *
		 * (the minimum cwnd that will give us exponential
		 * growth is 2 mss.  We don't allow the threshhold
		 * to go below this.)
		 */
		{
		u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
		if (win < 2)
			win = 2;
		tp->snd_cwnd = tp->t_maxseg;
		tp->snd_ssthresh = win * tp->t_maxseg;
		tp->t_dupacks = 0;
		}
		(void) tcp_output(tp);
		break;

	/*
	 * Persistance timer into zero window.
	 * Force a byte to be output, if possible.
	 */
	case TCPT_PERSIST:
		tcpstat.tcps_persisttimeo++;
		tcp_setpersist(tp);
		tp->t_force = 1;
		(void) tcp_output(tp);
		tp->t_force = 0;
		break;

	/*
	 * Keep-alive timer went off; send something
	 * or drop connection if idle for too long.
	 */
	case TCPT_KEEP:
		tcpstat.tcps_keeptimeo++;
		if (tp->t_state < TCPS_ESTABLISHED)
			goto dropit;
		if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
		    tp->t_state <= TCPS_CLOSE_WAIT) {
		    	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
				goto dropit;
			/*
			 * Send a packet designed to force a response
			 * if the peer is up and reachable:
			 * either an ACK if the connection is still alive,
			 * or an RST if the peer has closed the connection
			 * due to timeout or reboot.
			 * Using sequence number tp->snd_una-1
			 * causes the transmitted zero-length segment
			 * to lie outside the receive window;
			 * by the protocol spec, this requires the
			 * correspondent TCP to respond.
			 */
			tcpstat.tcps_keepprobe++;
#ifdef TCP_COMPAT_42
			/*
			 * The keepalive packet must have nonzero length
			 * to get a 4.2 host to respond.
			 */
			tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
			    tp->rcv_nxt - 1, tp->snd_una - 1, 0);
#else
			tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
			    tp->rcv_nxt, tp->snd_una - 1, 0);
#endif
			tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
		} else
			tp->t_timer[TCPT_KEEP] = tcp_keepidle;
		break;
	dropit:
		tcpstat.tcps_keepdrops++;
		tp = tcp_drop(tp, ETIMEDOUT);
		break;
	}
	return (tp);
}
Commit	Line	Data
b688fc87 WJ	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	*
	33	* @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
	34	*/
	35
	36	#include "param.h"
	37	#include "systm.h"
	38	#include "malloc.h"
	39	#include "mbuf.h"
	40	#include "socket.h"
	41	#include "socketvar.h"
	42	#include "protosw.h"
	43	#include "errno.h"
	44
	45	#include "../net/if.h"
	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	#include "tcp_fsm.h"
	55	#include "tcp_seq.h"
	56	#include "tcp_timer.h"
	57	#include "tcp_var.h"
	58	#include "tcpip.h"
	59
	60	int tcp_keepidle = TCPTV_KEEP_IDLE;
	61	int tcp_keepintvl = TCPTV_KEEPINTVL;
	62	int tcp_maxidle;
	63	/*
	64	* Fast timeout routine for processing delayed acks
65	*/
66	tcp_fasttimo()
67	{
68	register struct inpcb *inp;
69	register struct tcpcb *tp;
70	int s = splnet();
71
72	inp = tcb.inp_next;
73	if (inp)
74	for (; inp != &tcb; inp = inp->inp_next)
75	if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
76	(tp->t_flags & TF_DELACK)) {
77	tp->t_flags &= ~TF_DELACK;
78	tp->t_flags \|= TF_ACKNOW;
79	tcpstat.tcps_delack++;
80	(void) tcp_output(tp);
81	}
82	splx(s);
83	}
84
85	/*
86	* Tcp protocol timeout routine called every 500 ms.
87	* Updates the timers in all active tcb's and
88	* causes finite state machine actions if timers expire.
89	*/
90	tcp_slowtimo()
91	{
92	register struct inpcb ip, ipnxt;
93	register struct tcpcb *tp;
94	int s = splnet();
95	register int i;
96
97	tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
98	/*
99	* Search through tcb's and update active timers.
100	*/
101	ip = tcb.inp_next;
102	if (ip == 0) {
103	splx(s);
104	return;
105	}
106	for (; ip != &tcb; ip = ipnxt) {
107	ipnxt = ip->inp_next;
108	tp = intotcpcb(ip);
109	if (tp == 0)
110	continue;
111	for (i = 0; i < TCPT_NTIMERS; i++) {
112	if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
113	(void) tcp_usrreq(tp->t_inpcb->inp_socket,
114	PRU_SLOWTIMO, (struct mbuf *)0,
115	(struct mbuf )i, (struct mbuf )0);
116	if (ipnxt->inp_prev != ip)
117	goto tpgone;
118	}
119	}
120	tp->t_idle++;
121	if (tp->t_rtt)
122	tp->t_rtt++;
123	tpgone:
124	;
125	}
126	tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
127	#ifdef TCP_COMPAT_42
128	if ((int)tcp_iss < 0)
129	tcp_iss = 0; /* XXX */
130	#endif
131	splx(s);
132	}
133
134	/*
135	* Cancel all timers for TCP tp.
136	*/
137	tcp_canceltimers(tp)
138	struct tcpcb *tp;
139	{
140	register int i;
141
142	for (i = 0; i < TCPT_NTIMERS; i++)
143	tp->t_timer[i] = 0;
144	}
145
146	int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
147	{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
148
149	/*
150	* TCP timer processing.
151	*/
152	struct tcpcb *
153	tcp_timers(tp, timer)
154	register struct tcpcb *tp;
155	int timer;
156	{
157	register int rexmt;
158
159	switch (timer) {
160
161	/*
162	* 2 MSL timeout in shutdown went off. If we're closed but
163	* still waiting for peer to close and connection has been idle
164	* too long, or if 2MSL time is up from TIME_WAIT, delete connection
165	* control block. Otherwise, check again in a bit.
166	*/
167	case TCPT_2MSL:
168	if (tp->t_state != TCPS_TIME_WAIT &&
169	tp->t_idle <= tcp_maxidle)
170	tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
171	else
172	tp = tcp_close(tp);
173	break;
174
175	/*
176	* Retransmission timer went off. Message has not
177	* been acked within retransmit interval. Back off
178	* to a longer retransmit interval and retransmit one segment.
179	*/
180	case TCPT_REXMT:
181	if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
182	tp->t_rxtshift = TCP_MAXRXTSHIFT;
183	tcpstat.tcps_timeoutdrop++;
184	tp = tcp_drop(tp, tp->t_softerror ?
185	tp->t_softerror : ETIMEDOUT);
186	break;
187	}
188	tcpstat.tcps_rexmttimeo++;
189	rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
190	TCPT_RANGESET(tp->t_rxtcur, rexmt,
191	tp->t_rttmin, TCPTV_REXMTMAX);
192	tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
193	/*
194	* If losing, let the lower level know and try for
195	* a better route. Also, if we backed off this far,
196	* our srtt estimate is probably bogus. Clobber it
197	* so we'll take the next rtt measurement as our srtt;
198	* move the current srtt into rttvar to keep the current
199	* retransmit times until then.
200	*/
201	if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
202	in_losing(tp->t_inpcb);
203	tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
204	tp->t_srtt = 0;
205	}
206	tp->snd_nxt = tp->snd_una;
207	/*
208	* If timing a segment in this window, stop the timer.
209	*/
210	tp->t_rtt = 0;
211	/*
212	* Close the congestion window down to one segment
213	* (we'll open it by one segment for each ack we get).
214	* Since we probably have a window's worth of unacked
215	* data accumulated, this "slow start" keeps us from
216	* dumping all that data as back-to-back packets (which
217	* might overwhelm an intermediate gateway).
218	*
219	* There are two phases to the opening: Initially we
220	* open by one mss on each ack. This makes the window
221	* size increase exponentially with time. If the
222	* window is larger than the path can handle, this
223	* exponential growth results in dropped packet(s)
224	* almost immediately. To get more time between
225	* drops but still "push" the network to take advantage
226	* of improving conditions, we switch from exponential
227	* to linear window opening at some threshhold size.
228	* For a threshhold, we use half the current window
229	* size, truncated to a multiple of the mss.
230	*
231	* (the minimum cwnd that will give us exponential
232	* growth is 2 mss. We don't allow the threshhold
233	* to go below this.)
234	*/
235	{
236	u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
237	if (win < 2)
238	win = 2;
239	tp->snd_cwnd = tp->t_maxseg;
240	tp->snd_ssthresh = win * tp->t_maxseg;
241	tp->t_dupacks = 0;
242	}
243	(void) tcp_output(tp);
244	break;
245
246	/*
247	* Persistance timer into zero window.
248	* Force a byte to be output, if possible.
249	*/
250	case TCPT_PERSIST:
251	tcpstat.tcps_persisttimeo++;
252	tcp_setpersist(tp);
253	tp->t_force = 1;
254	(void) tcp_output(tp);
255	tp->t_force = 0;
256	break;
257
258	/*
259	* Keep-alive timer went off; send something
260	* or drop connection if idle for too long.
261	*/
262	case TCPT_KEEP:
263	tcpstat.tcps_keeptimeo++;
264	if (tp->t_state < TCPS_ESTABLISHED)
265	goto dropit;
266	if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
267	tp->t_state <= TCPS_CLOSE_WAIT) {
268	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
269	goto dropit;
270	/*
271	* Send a packet designed to force a response
272	* if the peer is up and reachable:
273	* either an ACK if the connection is still alive,
274	* or an RST if the peer has closed the connection
275	* due to timeout or reboot.
276	* Using sequence number tp->snd_una-1
277	* causes the transmitted zero-length segment
278	* to lie outside the receive window;
279	* by the protocol spec, this requires the
280	* correspondent TCP to respond.
281	*/
282	tcpstat.tcps_keepprobe++;
283	#ifdef TCP_COMPAT_42
284	/*
285	* The keepalive packet must have nonzero length
286	* to get a 4.2 host to respond.
287	*/
288	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
289	tp->rcv_nxt - 1, tp->snd_una - 1, 0);
290	#else
291	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
292	tp->rcv_nxt, tp->snd_una - 1, 0);
293	#endif
294	tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
295	} else
296	tp->t_timer[TCPT_KEEP] = tcp_keepidle;
297	break;
298	dropit:
299	tcpstat.tcps_keepdrops++;
300	tp = tcp_drop(tp, ETIMEDOUT);
301	break;
302	}
303	return (tp);
304	}