xref: /netbsd-src/sys/netinet/tcp_timer.h (revision d48f14661dda8638fee055ba15d35bdfb29b9fa8)
1 /*	$NetBSD: tcp_timer.h,v 1.23 2005/12/10 23:36:23 elad Exp $	*/
2 
3 /*-
4  * Copyright (c) 2001, 2005 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Jason R. Thorpe of Wasabi Systems, Inc.
9  * This code is derived from software contributed to The NetBSD Foundation
10  * by Charles M. Hannum.
11  *
12  * Redistribution and use in source and binary forms, with or without
13  * modification, are permitted provided that the following conditions
14  * are met:
15  * 1. Redistributions of source code must retain the above copyright
16  *    notice, this list of conditions and the following disclaimer.
17  * 2. Redistributions in binary form must reproduce the above copyright
18  *    notice, this list of conditions and the following disclaimer in the
19  *    documentation and/or other materials provided with the distribution.
20  * 3. All advertising materials mentioning features or use of this software
21  *    must display the following acknowledgement:
22  *	This product includes software developed by the NetBSD
23  *	Foundation, Inc. and its contributors.
24  * 4. Neither the name of The NetBSD Foundation nor the names of its
25  *    contributors may be used to endorse or promote products derived
26  *    from this software without specific prior written permission.
27  *
28  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
29  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
30  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
31  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
32  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
34  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
35  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
36  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
37  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38  * POSSIBILITY OF SUCH DAMAGE.
39  */
40 
41 /*
42  * Copyright (c) 1982, 1986, 1993
43  *	The Regents of the University of California.  All rights reserved.
44  *
45  * Redistribution and use in source and binary forms, with or without
46  * modification, are permitted provided that the following conditions
47  * are met:
48  * 1. Redistributions of source code must retain the above copyright
49  *    notice, this list of conditions and the following disclaimer.
50  * 2. Redistributions in binary form must reproduce the above copyright
51  *    notice, this list of conditions and the following disclaimer in the
52  *    documentation and/or other materials provided with the distribution.
53  * 3. Neither the name of the University nor the names of its contributors
54  *    may be used to endorse or promote products derived from this software
55  *    without specific prior written permission.
56  *
57  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
58  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
59  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
60  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
61  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
62  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
63  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
64  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
65  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
66  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
67  * SUCH DAMAGE.
68  *
69  *	@(#)tcp_timer.h	8.1 (Berkeley) 6/10/93
70  */
71 
72 #ifndef _NETINET_TCP_TIMER_H_
73 #define _NETINET_TCP_TIMER_H_
74 
75 /*
76  * Definitions of the TCP timers.  These timers are counted
77  * down PR_SLOWHZ times a second.
78  */
79 #define	TCPT_NTIMERS	4
80 
81 #define	TCPT_REXMT	0		/* retransmit */
82 #define	TCPT_PERSIST	1		/* retransmit persistance */
83 #define	TCPT_KEEP	2		/* keep alive */
84 #define	TCPT_2MSL	3		/* 2*msl quiet time timer */
85 
86 /*
87  * The TCPT_REXMT timer is used to force retransmissions.
88  * The TCP has the TCPT_REXMT timer set whenever segments
89  * have been sent for which ACKs are expected but not yet
90  * received.  If an ACK is received which advances tp->snd_una,
91  * then the retransmit timer is cleared (if there are no more
92  * outstanding segments) or reset to the base value (if there
93  * are more ACKs expected).  Whenever the retransmit timer goes off,
94  * we retransmit one unacknowledged segment, and do a backoff
95  * on the retransmit timer.
96  *
97  * The TCPT_PERSIST timer is used to keep window size information
98  * flowing even if the window goes shut.  If all previous transmissions
99  * have been acknowledged (so that there are no retransmissions in progress),
100  * and the window is too small to bother sending anything, then we start
101  * the TCPT_PERSIST timer.  When it expires, if the window is nonzero,
102  * we go to transmit state.  Otherwise, at intervals send a single byte
103  * into the peer's window to force him to update our window information.
104  * We do this at most as often as TCPT_PERSMIN time intervals,
105  * but no more frequently than the current estimate of round-trip
106  * packet time.  The TCPT_PERSIST timer is cleared whenever we receive
107  * a window update from the peer.
108  *
109  * The TCPT_KEEP timer is used to keep connections alive.  If an
110  * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
111  * but not yet established, then we drop the connection.  Once the connection
112  * is established, if the connection is idle for TCPTV_KEEP_IDLE time
113  * (and keepalives have been enabled on the socket), we begin to probe
114  * the connection.  We force the peer to send us a segment by sending:
115  *	<SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
116  * This segment is (deliberately) outside the window, and should elicit
117  * an ack segment in response from the peer.  If, despite the TCPT_KEEP
118  * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
119  * amount of time probing, then we drop the connection.
120  */
121 
122 /*
123  * Time constants.
124  */
125 #define	TCPTV_MSL	( 30*PR_SLOWHZ)		/* max seg lifetime (hah!) */
126 #define	TCPTV_SRTTBASE	0			/* base roundtrip time;
127 						   if 0, no idea yet */
128 #define	TCPTV_SRTTDFLT	(  3*PR_SLOWHZ)		/* assumed RTT if no info */
129 
130 #define	TCPTV_PERSMIN	(  5*PR_SLOWHZ)		/* retransmit persistance */
131 #define	TCPTV_PERSMAX	( 60*PR_SLOWHZ)		/* maximum persist interval */
132 
133 #define	TCPTV_KEEP_INIT	( 75*PR_SLOWHZ)		/* initial connect keep alive */
134 #define	TCPTV_KEEP_IDLE	(120*60*PR_SLOWHZ)	/* dflt time before probing */
135 #define	TCPTV_KEEPINTVL	( 75*PR_SLOWHZ)		/* default probe interval */
136 #define	TCPTV_KEEPCNT	8			/* max probes before drop */
137 
138 #define	TCPTV_MIN	(  1*PR_SLOWHZ)		/* minimum allowable value */
139 #define	TCPTV_REXMTMAX	( 64*PR_SLOWHZ)		/* max allowable REXMT value */
140 
141 #define	TCP_LINGERTIME	120			/* linger at most 2 minutes */
142 
143 #define	TCP_MAXRXTSHIFT	12			/* maximum retransmits */
144 
145 #define	TCP_DELACK_TICKS (hz / PR_FASTHZ)	/* time to delay ACK */
146 
147 #ifdef	TCPTIMERS
148 const char *tcptimers[] =
149     { "REXMT", "PERSIST", "KEEP", "2MSL" };
150 #endif
151 
152 /*
153  * Init, arm, disarm, and test TCP timers.
154  */
155 #define	TCP_TIMER_INIT(tp, timer)					\
156 	callout_setfunc(&(tp)->t_timer[(timer)],			\
157 	    tcp_timer_funcs[(timer)], (tp))
158 
159 #define	TCP_TIMER_ARM(tp, timer, nticks)				\
160 	callout_schedule(&(tp)->t_timer[(timer)],			\
161 	    (nticks) * (hz / PR_SLOWHZ))
162 
163 #define	TCP_TIMER_DISARM(tp, timer)					\
164 	callout_stop(&(tp)->t_timer[(timer)])
165 
166 #define	TCP_TIMER_ISARMED(tp, timer)					\
167 	callout_active(&(tp)->t_timer[(timer)])
168 
169 /*
170  * Force a time value to be in a certain range.
171  */
172 #define	TCPT_RANGESET(tv, value, tvmin, tvmax) { \
173 	(tv) = (value); \
174 	if ((tv) < (tvmin)) \
175 		(tv) = (tvmin); \
176 	else if ((tv) > (tvmax)) \
177 		(tv) = (tvmax); \
178 }
179 
180 #ifdef _KERNEL
181 typedef void (*tcp_timer_func_t)(void *);
182 
183 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
184 
185 extern int tcp_keepidle;		/* time before keepalive probes begin */
186 extern int tcp_keepintvl;		/* time between keepalive probes */
187 extern int tcp_keepcnt;			/* number of keepalives, 0=infty */
188 extern int tcp_maxpersistidle;		/* max idle time in persist */
189 extern int tcp_maxidle;			/* time to drop after starting probes */
190 extern int tcp_ttl;			/* time to live for TCP segs */
191 extern const int tcp_backoff[];
192 
193 void	tcp_timer_init(void);
194 #endif
195 
196 #endif /* !_NETINET_TCP_TIMER_H_ */
197