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1.1 root 1: /*
2: * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
3: *
4: * @APPLE_LICENSE_HEADER_START@
5: *
6: * Portions Copyright (c) 1999 Apple Computer, Inc. All Rights
7: * Reserved. This file contains Original Code and/or Modifications of
8: * Original Code as defined in and that are subject to the Apple Public
9: * Source License Version 1.1 (the "License"). You may not use this file
10: * except in compliance with the License. Please obtain a copy of the
11: * License at http://www.apple.com/publicsource and read it before using
12: * this file.
13: *
14: * The Original Code and all software distributed under the License are
15: * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
16: * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
17: * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
18: * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
19: * License for the specific language governing rights and limitations
20: * under the License.
21: *
22: * @APPLE_LICENSE_HEADER_END@
23: */
24:
25: /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
26: /*
27: * Copyright (c) 1982, 1986, 1993
28: * The Regents of the University of California. All rights reserved.
29: *
30: * Redistribution and use in source and binary forms, with or without
31: * modification, are permitted provided that the following conditions
32: * are met:
33: * 1. Redistributions of source code must retain the above copyright
34: * notice, this list of conditions and the following disclaimer.
35: * 2. Redistributions in binary form must reproduce the above copyright
36: * notice, this list of conditions and the following disclaimer in the
37: * documentation and/or other materials provided with the distribution.
38: * 3. All advertising materials mentioning features or use of this software
39: * must display the following acknowledgement:
40: * This product includes software developed by the University of
41: * California, Berkeley and its contributors.
42: * 4. Neither the name of the University nor the names of its contributors
43: * may be used to endorse or promote products derived from this software
44: * without specific prior written permission.
45: *
46: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
47: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
48: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
49: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
50: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
51: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
52: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
53: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
54: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
55: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
56: * SUCH DAMAGE.
57: *
58: * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
59: */
60:
61: /*
62: * Definitions of the TCP timers. These timers are counted
63: * down PR_SLOWHZ times a second.
64: */
65: #define TCPT_NTIMERS 4
66:
67: #define TCPT_REXMT 0 /* retransmit */
68: #define TCPT_PERSIST 1 /* retransmit persistance */
69: #define TCPT_KEEP 2 /* keep alive */
70: #define TCPT_2MSL 3 /* 2*msl quiet time timer */
71:
72: /*
73: * The TCPT_REXMT timer is used to force retransmissions.
74: * The TCP has the TCPT_REXMT timer set whenever segments
75: * have been sent for which ACKs are expected but not yet
76: * received. If an ACK is received which advances tp->snd_una,
77: * then the retransmit timer is cleared (if there are no more
78: * outstanding segments) or reset to the base value (if there
79: * are more ACKs expected). Whenever the retransmit timer goes off,
80: * we retransmit one unacknowledged segment, and do a backoff
81: * on the retransmit timer.
82: *
83: * The TCPT_PERSIST timer is used to keep window size information
84: * flowing even if the window goes shut. If all previous transmissions
85: * have been acknowledged (so that there are no retransmissions in progress),
86: * and the window is too small to bother sending anything, then we start
87: * the TCPT_PERSIST timer. When it expires, if the window is nonzero,
88: * we go to transmit state. Otherwise, at intervals send a single byte
89: * into the peer's window to force him to update our window information.
90: * We do this at most as often as TCPT_PERSMIN time intervals,
91: * but no more frequently than the current estimate of round-trip
92: * packet time. The TCPT_PERSIST timer is cleared whenever we receive
93: * a window update from the peer.
94: *
95: * The TCPT_KEEP timer is used to keep connections alive. If an
96: * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
97: * but not yet established, then we drop the connection. Once the connection
98: * is established, if the connection is idle for TCPTV_KEEP_IDLE time
99: * (and keepalives have been enabled on the socket), we begin to probe
100: * the connection. We force the peer to send us a segment by sending:
101: * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
102: * This segment is (deliberately) outside the window, and should elicit
103: * an ack segment in response from the peer. If, despite the TCPT_KEEP
104: * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
105: * amount of time probing, then we drop the connection.
106: */
107:
108: /*
109: * Time constants.
110: */
111: #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */
112: #define TCPTV_SRTTBASE 0 /* base roundtrip time;
113: if 0, no idea yet */
114: #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */
115:
116: #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */
117: #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */
118:
119: #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */
120: #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */
121: #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */
122: #define TCPTV_KEEPCNT 8 /* max probes before drop */
123:
124: #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */
125: #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */
126:
127: #define TCP_LINGERTIME 120 /* linger at most 2 minutes */
128:
129: #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
130:
131: #ifdef TCPTIMERS
132: char *tcptimers[] =
133: { "REXMT", "PERSIST", "KEEP", "2MSL" };
134: #endif
135:
136: /*
137: * Force a time value to be in a certain range.
138: */
139: #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \
140: (tv) = (value); \
141: if ((tv) < (tvmin)) \
142: (tv) = (tvmin); \
143: else if ((tv) > (tvmax)) \
144: (tv) = (tvmax); \
145: }
146:
147: #ifdef _KERNEL
148: extern int tcp_keepidle; /* time before keepalive probes begin */
149: extern int tcp_keepintvl; /* time between keepalive probes */
150: extern int tcp_maxidle; /* time to drop after starting probes */
151: extern int tcp_ttl; /* time to live for TCP segs */
152: extern int tcp_backoff[];
153: #endif
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