[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: tcp_timer.c,v 1.3 1993/11/25 01:35:18 wollman Exp $
 */

#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"

/*
 * Fast timeout routine for processing delayed acks
 */
void
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.
 */
void
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,
						  (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.
 */
void
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	33	* from: @(#)tcp_timer.c 7.18 (Berkeley) 6/28/90
fde1aeb2	34	* $Id: tcp_timer.c,v 1.3 1993/11/25 01:35:18 wollman Exp $
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
15637ed4 RG	61	/*
	62	* Fast timeout routine for processing delayed acks
	63	*/
4c45483e	64	void
15637ed4 RG	65	tcp_fasttimo()
	66	{
	67	register struct inpcb *inp;
	68	register struct tcpcb *tp;
	69	int s = splnet();
	70
	71	inp = tcb.inp_next;
	72	if (inp)
	73	for (; inp != &tcb; inp = inp->inp_next)
	74	if ((tp = (struct tcpcb *)inp->inp_ppcb) &&
	75	(tp->t_flags & TF_DELACK)) {
	76	tp->t_flags &= ~TF_DELACK;
	77	tp->t_flags \|= TF_ACKNOW;
	78	tcpstat.tcps_delack++;
	79	(void) tcp_output(tp);
	80	}
	81	splx(s);
	82	}
	83
	84	/*
	85	* Tcp protocol timeout routine called every 500 ms.
	86	* Updates the timers in all active tcb's and
	87	* causes finite state machine actions if timers expire.
	88	*/
4c45483e	89	void
15637ed4 RG	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,
fde1aeb2 GW	115	(struct mbuf )i, (struct mbuf )0,
fde1aeb2 GW	116	(struct mbuf *)0);
15637ed4 RG	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	*/
4c45483e	138	void
15637ed4 RG	139	tcp_canceltimers(tp)
	140	struct tcpcb *tp;
	141	{
	142	register int i;
	143
	144	for (i = 0; i < TCPT_NTIMERS; i++)
	145	tp->t_timer[i] = 0;
	146	}
	147
	148	int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
	149	{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
	150
	151	/*
	152	* TCP timer processing.
	153	*/
	154	struct tcpcb *
	155	tcp_timers(tp, timer)
	156	register struct tcpcb *tp;
	157	int timer;
	158	{
	159	register int rexmt;
	160
	161	switch (timer) {
	162
	163	/*
	164	* 2 MSL timeout in shutdown went off. If we're closed but
	165	* still waiting for peer to close and connection has been idle
	166	* too long, or if 2MSL time is up from TIME_WAIT, delete connection
	167	* control block. Otherwise, check again in a bit.
	168	*/
	169	case TCPT_2MSL:
	170	if (tp->t_state != TCPS_TIME_WAIT &&
	171	tp->t_idle <= tcp_maxidle)
	172	tp->t_timer[TCPT_2MSL] = tcp_keepintvl;
	173	else
	174	tp = tcp_close(tp);
	175	break;
	176
	177	/*
	178	* Retransmission timer went off. Message has not
	179	* been acked within retransmit interval. Back off
	180	* to a longer retransmit interval and retransmit one segment.
	181	*/
	182	case TCPT_REXMT:
	183	if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
	184	tp->t_rxtshift = TCP_MAXRXTSHIFT;
	185	tcpstat.tcps_timeoutdrop++;
	186	tp = tcp_drop(tp, tp->t_softerror ?
	187	tp->t_softerror : ETIMEDOUT);
	188	break;
	189	}
	190	tcpstat.tcps_rexmttimeo++;
	191	rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
	192	TCPT_RANGESET(tp->t_rxtcur, rexmt,
	193	tp->t_rttmin, TCPTV_REXMTMAX);
	194	tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
	195	/*
	196	* If losing, let the lower level know and try for
	197	* a better route. Also, if we backed off this far,
	198	* our srtt estimate is probably bogus. Clobber it
	199	* so we'll take the next rtt measurement as our srtt;
	200	* move the current srtt into rttvar to keep the current
	201	* retransmit times until then.
	202	*/
203	if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {
204	in_losing(tp->t_inpcb);
205	tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);
206	tp->t_srtt = 0;
207	}
208	tp->snd_nxt = tp->snd_una;
209	/*
210	* If timing a segment in this window, stop the timer.
211	*/
212	tp->t_rtt = 0;
213	/*
214	* Close the congestion window down to one segment
215	* (we'll open it by one segment for each ack we get).
216	* Since we probably have a window's worth of unacked
217	* data accumulated, this "slow start" keeps us from
218	* dumping all that data as back-to-back packets (which
219	* might overwhelm an intermediate gateway).
220	*
221	* There are two phases to the opening: Initially we
222	* open by one mss on each ack. This makes the window
223	* size increase exponentially with time. If the
224	* window is larger than the path can handle, this
225	* exponential growth results in dropped packet(s)
226	* almost immediately. To get more time between
227	* drops but still "push" the network to take advantage
228	* of improving conditions, we switch from exponential
229	* to linear window opening at some threshhold size.
230	* For a threshhold, we use half the current window
231	* size, truncated to a multiple of the mss.
232	*
233	* (the minimum cwnd that will give us exponential
234	* growth is 2 mss. We don't allow the threshhold
235	* to go below this.)
236	*/
237	{
238	u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
239	if (win < 2)
240	win = 2;
241	tp->snd_cwnd = tp->t_maxseg;
242	tp->snd_ssthresh = win * tp->t_maxseg;
243	tp->t_dupacks = 0;
244	}
245	(void) tcp_output(tp);
246	break;
247
248	/*
249	* Persistance timer into zero window.
250	* Force a byte to be output, if possible.
251	*/
252	case TCPT_PERSIST:
253	tcpstat.tcps_persisttimeo++;
254	tcp_setpersist(tp);
255	tp->t_force = 1;
256	(void) tcp_output(tp);
257	tp->t_force = 0;
258	break;
259
260	/*
261	* Keep-alive timer went off; send something
262	* or drop connection if idle for too long.
263	*/
264	case TCPT_KEEP:
265	tcpstat.tcps_keeptimeo++;
266	if (tp->t_state < TCPS_ESTABLISHED)
267	goto dropit;
268	if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
269	tp->t_state <= TCPS_CLOSE_WAIT) {
270	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)
271	goto dropit;
272	/*
273	* Send a packet designed to force a response
274	* if the peer is up and reachable:
275	* either an ACK if the connection is still alive,
276	* or an RST if the peer has closed the connection
277	* due to timeout or reboot.
278	* Using sequence number tp->snd_una-1
279	* causes the transmitted zero-length segment
280	* to lie outside the receive window;
281	* by the protocol spec, this requires the
282	* correspondent TCP to respond.
283	*/
284	tcpstat.tcps_keepprobe++;
285	#ifdef TCP_COMPAT_42
286	/*
287	* The keepalive packet must have nonzero length
288	* to get a 4.2 host to respond.
289	*/
290	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
291	tp->rcv_nxt - 1, tp->snd_una - 1, 0);
292	#else
293	tcp_respond(tp, tp->t_template, (struct mbuf *)NULL,
294	tp->rcv_nxt, tp->snd_una - 1, 0);
295	#endif
296	tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
297	} else
298	tp->t_timer[TCPT_KEEP] = tcp_keepidle;
299	break;
300	dropit:
301	tcpstat.tcps_keepdrops++;
302	tp = tcp_drop(tp, ETIMEDOUT);
303	break;
304	}
305	return (tp);
306	}