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[dragonfly.git] / sys / netinet / tcp_timer.h
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1 /*
2 * Copyright (c) 1982, 1986, 1993
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
33 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
34 * $FreeBSD: src/sys/netinet/tcp_timer.h,v 1.18.2.1 2002/08/16 22:16:39 dillon Exp $
35 * $DragonFly: src/sys/netinet/tcp_timer.h,v 1.3 2003/08/23 11:18:00 rob Exp $
38 #ifndef _NETINET_TCP_TIMER_H_
39 #define _NETINET_TCP_TIMER_H_
42 * The TCPT_REXMT timer is used to force retransmissions.
43 * The TCP has the TCPT_REXMT timer set whenever segments
44 * have been sent for which ACKs are expected but not yet
45 * received. If an ACK is received which advances tp->snd_una,
46 * then the retransmit timer is cleared (if there are no more
47 * outstanding segments) or reset to the base value (if there
48 * are more ACKs expected). Whenever the retransmit timer goes off,
49 * we retransmit one unacknowledged segment, and do a backoff
50 * on the retransmit timer.
52 * The TCPT_PERSIST timer is used to keep window size information
53 * flowing even if the window goes shut. If all previous transmissions
54 * have been acknowledged (so that there are no retransmissions in progress),
55 * and the window is too small to bother sending anything, then we start
56 * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
57 * we go to transmit state. Otherwise, at intervals send a single byte
58 * into the peer's window to force him to update our window information.
59 * We do this at most as often as TCPT_PERSMIN time intervals,
60 * but no more frequently than the current estimate of round-trip
61 * packet time. The TCPT_PERSIST timer is cleared whenever we receive
62 * a window update from the peer.
64 * The TCPT_KEEP timer is used to keep connections alive. If an
65 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
66 * but not yet established, then we drop the connection. Once the connection
67 * is established, if the connection is idle for TCPTV_KEEP_IDLE time
68 * (and keepalives have been enabled on the socket), we begin to probe
69 * the connection. We force the peer to send us a segment by sending:
70 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
71 * This segment is (deliberately) outside the window, and should elicit
72 * an ack segment in response from the peer. If, despite the TCPT_KEEP
73 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
74 * amount of time probing, then we drop the connection.
78 * Time constants.
80 #define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */
81 #define TCPTV_SRTTBASE 0 /* base roundtrip time;
82 if 0, no idea yet */
83 #define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */
84 #define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */
86 #define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */
87 #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */
89 #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */
90 #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */
91 #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */
92 #define TCPTV_KEEPCNT 8 /* max probes before drop */
95 * TCPTV_MIN represents the minimum allowed retransmit interval. It
96 * is currently one second but will ultimately be reduced to 3 ticks
97 * for algorithmic stability, leaving the 200ms variance to deal with
98 * delayed-acks, protocol overheads. A 1 second minimum badly breaks
99 * throughput on any network faster then a modem that has minor but
100 * continuous packet loss unrelated to congestion, such as on a wireless
101 * network.
103 #define TCPTV_MIN ( hz ) /* minimum allowable value */
104 #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance (200ms) */
105 #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */
107 #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */
109 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */
111 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
113 #define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */
115 #ifdef TCPTIMERS
116 static char *tcptimers[] =
117 { "REXMT", "PERSIST", "KEEP", "2MSL" };
118 #endif
121 * Force a time value to be in a certain range.
123 #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
124 (tv) = (value) + tcp_rexmit_slop; \
125 if ((u_long)(tv) < (u_long)(tvmin)) \
126 (tv) = (tvmin); \
127 else if ((u_long)(tv) > (u_long)(tvmax)) \
128 (tv) = (tvmax); \
129 } while(0)
131 #ifdef _KERNEL
132 extern int tcp_keepinit; /* time to establish connection */
133 extern int tcp_keepidle; /* time before keepalive probes begin */
134 extern int tcp_keepintvl; /* time between keepalive probes */
135 extern int tcp_maxidle; /* time to drop after starting probes */
136 extern int tcp_delacktime; /* time before sending a delayed ACK */
137 extern int tcp_maxpersistidle;
138 extern int tcp_rexmit_min;
139 extern int tcp_rexmit_slop;
140 extern int tcp_msl;
141 extern int tcp_ttl; /* time to live for TCP segs */
142 extern int tcp_backoff[];
144 void tcp_timer_2msl (void *xtp);
145 void tcp_timer_keep (void *xtp);
146 void tcp_timer_persist (void *xtp);
147 void tcp_timer_rexmt (void *xtp);
148 void tcp_timer_delack (void *xtp);
150 #endif /* _KERNEL */
152 #endif /* !_NETINET_TCP_TIMER_H_ */