1/* $NetBSD: tcp_timer.h,v 1.29 2018/01/19 07:53:01 ozaki-r 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 *
21 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
23 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
24 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
25 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
26 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
27 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
29 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
30 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31 * POSSIBILITY OF SUCH DAMAGE.
32 */
33
34/*
35 * Copyright (c) 1982, 1986, 1993
36 * The Regents of the University of California. All rights reserved.
37 *
38 * Redistribution and use in source and binary forms, with or without
39 * modification, are permitted provided that the following conditions
40 * are met:
41 * 1. Redistributions of source code must retain the above copyright
42 * notice, this list of conditions and the following disclaimer.
43 * 2. Redistributions in binary form must reproduce the above copyright
44 * notice, this list of conditions and the following disclaimer in the
45 * documentation and/or other materials provided with the distribution.
46 * 3. Neither the name of the University nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60 * SUCH DAMAGE.
61 *
62 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
63 */
64
65#ifndef _NETINET_TCP_TIMER_H_
66#define _NETINET_TCP_TIMER_H_
67
68/*
69 * Definitions of the TCP timers. These timers are counted
70 * down PR_SLOWHZ times a second.
71 */
72#define TCPT_NTIMERS 4
73
74#define TCPT_REXMT 0 /* retransmit */
75#define TCPT_PERSIST 1 /* retransmit persistance */
76#define TCPT_KEEP 2 /* keep alive */
77#define TCPT_2MSL 3 /* 2*msl quiet time timer */
78
79/*
80 * The TCPT_REXMT timer is used to force retransmissions.
81 * The TCP has the TCPT_REXMT timer set whenever segments
82 * have been sent for which ACKs are expected but not yet
83 * received. If an ACK is received which advances tp->snd_una,
84 * then the retransmit timer is cleared (if there are no more
85 * outstanding segments) or reset to the base value (if there
86 * are more ACKs expected). Whenever the retransmit timer goes off,
87 * we retransmit one unacknowledged segment, and do a backoff
88 * on the retransmit timer.
89 *
90 * The TCPT_PERSIST timer is used to keep window size information
91 * flowing even if the window goes shut. If all previous transmissions
92 * have been acknowledged (so that there are no retransmissions in progress),
93 * and the window is too small to bother sending anything, then we start
94 * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
95 * we go to transmit state. Otherwise, at intervals send a single byte
96 * into the peer's window to force him to update our window information.
97 * We do this at most as often as TCPT_PERSMIN time intervals,
98 * but no more frequently than the current estimate of round-trip
99 * packet time. The TCPT_PERSIST timer is cleared whenever we receive
100 * a window update from the peer.
101 *
102 * The TCPT_KEEP timer is used to keep connections alive. If an
103 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
104 * but not yet established, then we drop the connection. Once the connection
105 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
106 * (and keepalives have been enabled on the socket), we begin to probe
107 * the connection. We force the peer to send us a segment by sending:
108 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
109 * This segment is (deliberately) outside the window, and should elicit
110 * an ack segment in response from the peer. If, despite the TCPT_KEEP
111 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
112 * amount of time probing, then we drop the connection.
113 */
114
115/*
116 * Time constants.
117 * All TCPTV_* constants are in units of slow ticks (typically 500 ms).
118 */
119#define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */
120#define TCPTV_SRTTBASE 0 /* base roundtrip time;
121 if 0, no idea yet */
122#define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */
123
124#define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */
125#define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
126
127#define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */
128#define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */
129#define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */
130#define TCPTV_KEEPCNT 8 /* max probes before drop */
131
132#define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */
133#define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */
134
135#define TCP_LINGERTIME 120 /* linger at most 2 minutes */
136
137#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
138
139/* Acks are delayed for 1 second; constant is in fast ticks. */
140#define TCP_DELACK_TICKS (hz / PR_FASTHZ) /* time to delay ACK */
141
142#ifdef TCPTIMERS
143const char *tcptimers[] =
144 { "REXMT", "PERSIST", "KEEP", "2MSL" };
145#endif
146
147/*
148 * Init, arm, disarm, and test TCP timers.
149 */
150#define TCP_TIMER_INIT(tp, timer) \
151 callout_setfunc(&(tp)->t_timer[(timer)], \
152 tcp_timer_funcs[(timer)], (tp))
153
154/*
155 * nticks is given in units of slow timeouts,
156 * typically 500 ms (with PR_SLOWHZ at 2).
157 */
158#define TCP_TIMER_ARM(tp, timer, nticks) \
159 callout_schedule(&(tp)->t_timer[(timer)], \
160 (nticks) * (hz / PR_SLOWHZ))
161
162#define TCP_TIMER_DISARM(tp, timer) \
163 callout_stop(&(tp)->t_timer[(timer)])
164
165#define TCP_TIMER_ISARMED(tp, timer) \
166 callout_active(&(tp)->t_timer[(timer)])
167
168/*
169 * Force a time value to be in a certain range.
170 */
171#define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
172 (tv) = (value); \
173 if ((tv) < (tvmin)) \
174 (tv) = (tvmin); \
175 if ((tv) > (tvmax)) \
176 (tv) = (tvmax); \
177}
178
179#ifdef _KERNEL
180typedef void (*tcp_timer_func_t)(void *);
181
182extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
183
184extern u_int tcp_keepinit; /* time before initial connection times out */
185extern u_int tcp_keepidle; /* time before keepalive probes begin */
186extern u_int tcp_keepintvl; /* time between keepalive probes */
187extern u_int tcp_keepcnt; /* number of keepalives, 0=infty */
188extern int tcp_maxpersistidle; /* max idle time in persist */
189extern int tcp_ttl; /* time to live for TCP segs */
190extern const int tcp_backoff[];
191
192void tcp_timer_init(void);
193void tcp_slowtimo_init(void);
194#endif
195
196#endif /* !_NETINET_TCP_TIMER_H_ */
197