Annotation of sys/netinet/tcp_timer.h, Revision 1.1.1.1
1.1 nbrk 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_ */
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