[unix-history] / sys / 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.
 *
 *	from: @(#)tcp_timer.c	7.18 (Berkeley) 6/28/90
 *	$Id$
 */

#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
15637ed4 RG	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	*
38e82238 RG	33	* from: @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
38e82238 RG	34	* $Id$
15637ed4 RG	35	*/
	36
	37	#include "param.h"
	38	#include "systm.h"
	39	#include "malloc.h"
	40	#include "mbuf.h"
	41	#include "socket.h"
	42	#include "socketvar.h"
	43	#include "protosw.h"
	44	#include "errno.h"
	45
	46	#include "../net/if.h"
	47	#include "../net/route.h"
	48
	49	#include "in.h"
	50	#include "in_systm.h"
	51	#include "ip.h"
	52	#include "in_pcb.h"
	53	#include "ip_var.h"
	54	#include "tcp.h"
	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
	61	int tcp_keepidle = TCPTV_KEEP_IDLE;
	62	int tcp_keepintvl = TCPTV_KEEPINTVL;
	63	int tcp_maxidle;
	64	/*
	65	* Fast timeout routine for processing delayed acks
	66	*/
	67	tcp_fasttimo()
	68	{
	69	register struct inpcb *inp;
	70	register struct tcpcb *tp;
	71	int s = splnet();
	72
	73	inp = tcb.inp_next;
	74	if (inp)
	75	for (; inp != &tcb; inp = inp->inp_next)
	76	if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
	77	(tp->t_flags & TF_DELACK)) {
	78	tp->t_flags &= ~TF_DELACK;
	79	tp->t_flags \|= TF_ACKNOW;
	80	tcpstat.tcps_delack++;
	81	(void) tcp_output(tp);
	82	}
	83	splx(s);
	84	}
	85
	86	/*
	87	* Tcp protocol timeout routine called every 500 ms.
	88	* Updates the timers in all active tcb's and
	89	* causes finite state machine actions if timers expire.
	90	*/
	91	tcp_slowtimo()
	92	{
	93	register struct inpcb ip, ipnxt;
	94	register struct tcpcb *tp;
	95	int s = splnet();
	96	register int i;
	97
	98	tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;
99	/*
100	* Search through tcb's and update active timers.
101	*/
102	ip = tcb.inp_next;
103	if (ip == 0) {
104	splx(s);
105	return;
106	}
107	for (; ip != &tcb; ip = ipnxt) {
108	ipnxt = ip->inp_next;
109	tp = intotcpcb(ip);
110	if (tp == 0)
111	continue;
112	for (i = 0; i < TCPT_NTIMERS; i++) {
113	if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
114	(void) tcp_usrreq(tp->t_inpcb->inp_socket,
115	PRU_SLOWTIMO, (struct mbuf *)0,
116	(struct mbuf )i, (struct mbuf )0);
117	if (ipnxt->inp_prev != ip)
118	goto tpgone;
119	}
120	}
121	tp->t_idle++;
122	if (tp->t_rtt)
123	tp->t_rtt++;
124	tpgone:
125	;
126	}
127	tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
128	#ifdef TCP_COMPAT_42
129	if ((int)tcp_iss < 0)
130	tcp_iss = 0; /* XXX */
131	#endif
132	splx(s);
133	}
134
135	/*
136	* Cancel all timers for TCP tp.
137	*/
138	tcp_canceltimers(tp)
139	struct tcpcb *tp;
140	{
141	register int i;
142
143	for (i = 0; i < TCPT_NTIMERS; i++)
144	tp->t_timer[i] = 0;
145	}
146
147	int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
148	{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
149
150	/*
151	* TCP timer processing.
152	*/
153	struct tcpcb *
154	tcp_timers(tp, timer)
155	register struct tcpcb *tp;
156	int timer;
157	{
158	register int rexmt;
159
160	switch (timer) {
161
162	/*
163	* 2 MSL timeout in shutdown went off. If we're closed but
164	* still waiting for peer to close and connection has been idle
165	* too long, or if 2MSL time is up from TIME_WAIT, delete connection
166	* control block. Otherwise, check again in a bit.
167	*/
168	case TCPT_2MSL:
169	if (tp->t_state != TCPS_TIME_WAIT &&
170	tp->t_idle <= tcp_maxidle)
171	tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
172	else
173	tp = tcp_close(tp);
174	break;
175
176	/*
177	* Retransmission timer went off. Message has not
178	* been acked within retransmit interval. Back off
179	* to a longer retransmit interval and retransmit one segment.
180	*/
181	case TCPT_REXMT:
182	if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
183	tp->t_rxtshift = TCP_MAXRXTSHIFT;
184	tcpstat.tcps_timeoutdrop++;
185	tp = tcp_drop(tp, tp->t_softerror ?
186	tp->t_softerror : ETIMEDOUT);
187	break;
188	}
189	tcpstat.tcps_rexmttimeo++;
190	rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
191	TCPT_RANGESET(tp->t_rxtcur, rexmt,
192	tp->t_rttmin, TCPTV_REXMTMAX);
193	tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
194	/*
195	* If losing, let the lower level know and try for
196	* a better route. Also, if we backed off this far,
197	* our srtt estimate is probably bogus. Clobber it
198	* so we'll take the next rtt measurement as our srtt;
199	* move the current srtt into rttvar to keep the current
200	* retransmit times until then.
201	*/
202	if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
203	in_losing(tp->t_inpcb);
204	tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
205	tp->t_srtt = 0;
206	}
207	tp->snd_nxt = tp->snd_una;
208	/*
209	* If timing a segment in this window, stop the timer.
210	*/
211	tp->t_rtt = 0;
212	/*
213	* Close the congestion window down to one segment
214	* (we'll open it by one segment for each ack we get).
215	* Since we probably have a window's worth of unacked
216	* data accumulated, this "slow start" keeps us from
217	* dumping all that data as back-to-back packets (which
218	* might overwhelm an intermediate gateway).
219	*
220	* There are two phases to the opening: Initially we
221	* open by one mss on each ack. This makes the window
222	* size increase exponentially with time. If the
223	* window is larger than the path can handle, this
224	* exponential growth results in dropped packet(s)
225	* almost immediately. To get more time between
226	* drops but still "push" the network to take advantage
227	* of improving conditions, we switch from exponential
228	* to linear window opening at some threshhold size.
229	* For a threshhold, we use half the current window
230	* size, truncated to a multiple of the mss.
231	*
232	* (the minimum cwnd that will give us exponential
233	* growth is 2 mss. We don't allow the threshhold
234	* to go below this.)
235	*/
236	{
237	u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
238	if (win < 2)
239	win = 2;
240	tp->snd_cwnd = tp->t_maxseg;
241	tp->snd_ssthresh = win * tp->t_maxseg;
242	tp->t_dupacks = 0;
243	}
244	(void) tcp_output(tp);
245	break;
246
247	/*
248	* Persistance timer into zero window.
249	* Force a byte to be output, if possible.
250	*/
251	case TCPT_PERSIST:
252	tcpstat.tcps_persisttimeo++;
253	tcp_setpersist(tp);
254	tp->t_force = 1;
255	(void) tcp_output(tp);
256	tp->t_force = 0;
257	break;
258
259	/*
260	* Keep-alive timer went off; send something
261	* or drop connection if idle for too long.
262	*/
263	case TCPT_KEEP:
264	tcpstat.tcps_keeptimeo++;
265	if (tp->t_state < TCPS_ESTABLISHED)
266	goto dropit;
267	if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
268	tp->t_state <= TCPS_CLOSE_WAIT) {
269	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
270	goto dropit;
271	/*
272	* Send a packet designed to force a response
273	* if the peer is up and reachable:
274	* either an ACK if the connection is still alive,
275	* or an RST if the peer has closed the connection
276	* due to timeout or reboot.
277	* Using sequence number tp->snd_una-1
278	* causes the transmitted zero-length segment
279	* to lie outside the receive window;
280	* by the protocol spec, this requires the
281	* correspondent TCP to respond.
282	*/
283	tcpstat.tcps_keepprobe++;
284	#ifdef TCP_COMPAT_42
285	/*
286	* The keepalive packet must have nonzero length
287	* to get a 4.2 host to respond.
288	*/
289	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
290	tp->rcv_nxt - 1, tp->snd_una - 1, 0);
291	#else
292	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
293	tp->rcv_nxt, tp->snd_una - 1, 0);
294	#endif
295	tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
296	} else
297	tp->t_timer[TCPT_KEEP] = tcp_keepidle;
298	break;
299	dropit:
300	tcpstat.tcps_keepdrops++;
301	tp = tcp_drop(tp, ETIMEDOUT);
302	break;
303	}
304	return (tp);
305	}