1 /* $OpenBSD: tcp_timer.h,v 1.19 2022/11/07 11:22:55 yasuoka 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.
40 */
41 #define TCPT_REXMT 0 /* retransmit */
42 #define TCPT_PERSIST 1 /* retransmit persistence */
43 #define TCPT_KEEP 2 /* keep alive */
44 #define TCPT_2MSL 3 /* 2*msl quiet time timer */
45 #define TCPT_REAPER 4 /* delayed cleanup timeout */
46 #define TCPT_DELACK 5 /* delayed ack timeout */
47
48 #define TCPT_NTIMERS 6
49
50 /*
51 * The TCPT_REXMT timer is used to force retransmissions.
52 * The TCP has the TCPT_REXMT timer set whenever segments
53 * have been sent for which ACKs are expected but not yet
54 * received. If an ACK is received which advances tp->snd_una,
55 * then the retransmit timer is cleared (if there are no more
56 * outstanding segments) or reset to the base value (if there
57 * are more ACKs expected). Whenever the retransmit timer goes off,
58 * we retransmit one unacknowledged segment, and do a backoff
59 * on the retransmit timer.
60 *
61 * The TCPT_PERSIST timer is used to keep window size information
62 * flowing even if the window goes shut. If all previous transmissions
63 * have been acknowledged (so that there are no retransmissions in progress),
64 * and the window is too small to bother sending anything, then we start
65 * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
66 * we go to transmit state. Otherwise, at intervals send a single byte
67 * into the peer's window to force him to update our window information.
68 * We do this at most as often as TCPT_PERSMIN time intervals,
69 * but no more frequently than the current estimate of round-trip
70 * packet time. The TCPT_PERSIST timer is cleared whenever we receive
71 * a window update from the peer.
72 *
73 * The TCPT_KEEP timer is used to keep connections alive. If an
74 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
75 * but not yet established, then we drop the connection. Once the connection
76 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
77 * (and keepalives have been enabled on the socket), we begin to probe
78 * the connection. We force the peer to send us a segment by sending:
79 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
80 * This segment is (deliberately) outside the window, and should elicit
81 * an ack segment in response from the peer. If, despite the TCPT_KEEP
82 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
83 * amount of time probing, then we drop the connection.
84 */
85
86 /*
87 * Time constants.
88 */
89 #define TCPTV_MSL 30 /* max seg lifetime (hah!) */
90 #define TCPTV_SRTTBASE 0 /* base roundtrip time;
91 if 0, no idea yet */
92 #define TCPTV_SRTTDFLT TCP_TIME_MSEC(1500) /* assumed RTT if no info */
93
94 #define TCPTV_PERSMIN 5 /* retransmit persistence */
95 #define TCPTV_PERSMAX 60 /* maximum persist interval */
96
97 #define TCPTV_KEEP_INIT 75 /* initial connect keep alive */
98 #define TCPTV_KEEP_IDLE 120*60 /* dflt time before probing */
99 #define TCPTV_KEEPINTVL 75 /* default probe interval */
100 #define TCPTV_KEEPCNT 8 /* max probes before drop */
101
102 #define TCPTV_MIN TCP_TIME(1) /* minimum allowable value */
103 #define TCPTV_REXMTMAX TCP_TIME(64) /* max allowable REXMT value */
104
105 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */
106
107 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
108
109 #define TCP_DELACK_MSECS 200 /* time to delay ACK */
110
111 #ifdef TCPTIMERS
112 const char *tcptimers[TCPT_NTIMERS] =
113 { "REXMT", "PERSIST", "KEEP", "2MSL", "REAPER", "DELACK" };
114 #endif /* TCPTIMERS */
115
116 /*
117 * Init, arm, disarm, and test TCP timers.
118 */
119 #define TCP_TIMER_INIT(tp, timer) \
120 timeout_set_proc(&(tp)->t_timer[(timer)], tcp_timer_funcs[(timer)], tp)
121
122 #define TCP_TIMER_ARM(tp, timer, msecs) \
123 do { \
124 SET((tp)->t_flags, TF_TIMER << (timer)); \
125 timeout_add_msec(&(tp)->t_timer[(timer)], (msecs)); \
126 } while (0)
127
128 #define TCP_TIMER_DISARM(tp, timer) \
129 do { \
130 CLR((tp)->t_flags, TF_TIMER << (timer)); \
131 timeout_del(&(tp)->t_timer[(timer)]); \
132 } while (0)
133
134 #define TCP_TIMER_ISARMED(tp, timer) \
135 ISSET((tp)->t_flags, TF_TIMER << (timer))
136
137 /*
138 * Force a time value to be in a certain range.
139 */
140 #define TCPT_RANGESET(tv, value, tvmin, tvmax) \
141 do { \
142 (tv) = (value); \
143 if ((tv) < (tvmin)) \
144 (tv) = (tvmin); \
145 else if ((tv) > (tvmax)) \
146 (tv) = (tvmax); \
147 } while (/* CONSTCOND */ 0)
148
149 #ifdef _KERNEL
150 typedef void (*tcp_timer_func_t)(void *);
151
152 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
153
154 extern int tcp_delack_msecs; /* delayed ACK timeout in millisecs */
155 extern int tcptv_keep_init;
156 extern int tcp_always_keepalive; /* assume SO_KEEPALIVE is always set */
157 extern int tcp_keepidle; /* time before keepalive probes begin */
158 extern int tcp_keepintvl; /* time between keepalive probes */
159 extern int tcp_maxidle; /* time to drop after starting probes */
160 extern int tcp_ttl; /* time to live for TCP segs */
161 extern int tcp_backoff[];
162
163 void tcp_timer_init(void);
164 #endif /* _KERNEL */
165 #endif /* _NETINET_TCP_TIMER_H_ */
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