1 /* $OpenBSD: tcp_timer.h,v 1.10 2003/06/02 23:28:15 millert Exp $ */
2 /* $NetBSD: tcp_timer.h,v 1.6 1995/03/26 20:32:37 jtc Exp $ */
3
4 /*
5 * Copyright (c) 1982, 1986, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
33 */
34
35 #ifndef _NETINET_TCP_TIMER_H_
36 #define _NETINET_TCP_TIMER_H_
37
38 /*
39 * Definitions of the TCP timers. These timers are counted
40 * down PR_SLOWHZ times a second.
41 */
42 #define TCPT_NTIMERS 4
43
44 #define TCPT_REXMT 0 /* retransmit */
45 #define TCPT_PERSIST 1 /* retransmit persistance */
46 #define TCPT_KEEP 2 /* keep alive */
47 #define TCPT_2MSL 3 /* 2*msl quiet time timer */
48
49 /*
50 * The TCPT_REXMT timer is used to force retransmissions.
51 * The TCP has the TCPT_REXMT timer set whenever segments
52 * have been sent for which ACKs are expected but not yet
53 * received. If an ACK is received which advances tp->snd_una,
54 * then the retransmit timer is cleared (if there are no more
55 * outstanding segments) or reset to the base value (if there
56 * are more ACKs expected). Whenever the retransmit timer goes off,
57 * we retransmit one unacknowledged segment, and do a backoff
58 * on the retransmit timer.
59 *
60 * The TCPT_PERSIST timer is used to keep window size information
61 * flowing even if the window goes shut. If all previous transmissions
62 * have been acknowledged (so that there are no retransmissions in progress),
63 * and the window is too small to bother sending anything, then we start
64 * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
65 * we go to transmit state. Otherwise, at intervals send a single byte
66 * into the peer's window to force him to update our window information.
67 * We do this at most as often as TCPT_PERSMIN time intervals,
68 * but no more frequently than the current estimate of round-trip
69 * packet time. The TCPT_PERSIST timer is cleared whenever we receive
70 * a window update from the peer.
71 *
72 * The TCPT_KEEP timer is used to keep connections alive. If an
73 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
74 * but not yet established, then we drop the connection. Once the connection
75 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
76 * (and keepalives have been enabled on the socket), we begin to probe
77 * the connection. We force the peer to send us a segment by sending:
78 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
79 * This segment is (deliberately) outside the window, and should elicit
80 * an ack segment in response from the peer. If, despite the TCPT_KEEP
81 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
82 * amount of time probing, then we drop the connection.
83 */
84
85 /*
86 * Time constants.
87 */
88 #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */
89 #define TCPTV_SRTTBASE 0 /* base roundtrip time;
90 if 0, no idea yet */
91 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */
92
93 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */
94 #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
95
96 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */
97 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */
98 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */
99 #define TCPTV_KEEPCNT 8 /* max probes before drop */
100
101 #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */
102 #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */
103
104 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */
105
106 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
107
108 #define TCP_DELACK_TICKS (hz / PR_FASTHZ) /* time to delay ACK */
109
110 #ifdef TCPTIMERS
111 const char *tcptimers[] =
112 { "REXMT", "PERSIST", "KEEP", "2MSL" };
113 #endif /* TCPTIMERS */
114
115 /*
116 * Init, arm, disarm, and test TCP timers.
117 */
118 #define TCP_TIMER_INIT(tp, timer) \
119 timeout_set(&(tp)->t_timer[(timer)], tcp_timer_funcs[(timer)], tp)
120
121 #define TCP_TIMER_ARM(tp, timer, nticks) \
122 timeout_add(&(tp)->t_timer[(timer)], (nticks) * (hz / PR_SLOWHZ))
123
124 #define TCP_TIMER_DISARM(tp, timer) \
125 timeout_del(&(tp)->t_timer[(timer)])
126
127 #define TCP_TIMER_ISARMED(tp, timer) \
128 timeout_pending(&(tp)->t_timer[(timer)])
129
130 /*
131 * Force a time value to be in a certain range.
132 */
133 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
134 (tv) = (value); \
135 if ((tv) < (tvmin)) \
136 (tv) = (tvmin); \
137 else if ((tv) > (tvmax)) \
138 (tv) = (tvmax); \
139 }
140
141 #ifdef _KERNEL
142 typedef void (*tcp_timer_func_t)(void *);
143
144 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
145
146 extern int tcptv_keep_init;
147 extern int tcp_keepidle; /* time before keepalive probes begin */
148 extern int tcp_keepintvl; /* time between keepalive probes */
149 extern int tcp_maxidle; /* time to drop after starting probes */
150 extern int tcp_ttl; /* time to live for TCP segs */
151 extern int tcp_backoff[];
152
153 void tcp_timer_init(void);
154 #endif /* _KERNEL */
155 #endif /* _NETINET_TCP_TIMER_H_ */