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8ae0e4b4 | 1 | /* |
0880b18e | 2 | * Copyright (c) 1982, 1986 Regents of the University of California. |
2b6b6284 | 3 | * All rights reserved. |
8ae0e4b4 | 4 | * |
2b6b6284 | 5 | * Redistribution and use in source and binary forms are permitted |
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6 | * provided that the above copyright notice and this paragraph are |
7 | * duplicated in all such forms and that any documentation, | |
8 | * advertising materials, and other materials related to such | |
9 | * distribution and use acknowledge that the software was developed | |
10 | * by the University of California, Berkeley. The name of the | |
11 | * University may not be used to endorse or promote products derived | |
12 | * from this software without specific prior written permission. | |
13 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
15 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
2b6b6284 | 16 | * |
d0461c72 | 17 | * @(#)tcp_timer.h 7.7 (Berkeley) %G% |
8ae0e4b4 | 18 | */ |
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19 | |
20 | /* | |
21 | * Definitions of the TCP timers. These timers are counted | |
22 | * down PR_SLOWHZ times a second. | |
23 | */ | |
2f9fe2d6 | 24 | #define TCPT_NTIMERS 4 |
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25 | |
26 | #define TCPT_REXMT 0 /* retransmit */ | |
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27 | #define TCPT_PERSIST 1 /* retransmit persistance */ |
28 | #define TCPT_KEEP 2 /* keep alive */ | |
29 | #define TCPT_2MSL 3 /* 2*msl quiet time timer */ | |
30 | ||
31 | /* | |
32 | * The TCPT_REXMT timer is used to force retransmissions. | |
33 | * The TCP has the TCPT_REXMT timer set whenever segments | |
34 | * have been sent for which ACKs are expected but not yet | |
35 | * received. If an ACK is received which advances tp->snd_una, | |
36 | * then the retransmit timer is cleared (if there are no more | |
37 | * outstanding segments) or reset to the base value (if there | |
38 | * are more ACKs expected). Whenever the retransmit timer goes off, | |
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39 | * we retransmit one unacknowledged segment, and do a backoff |
40 | * on the retransmit timer. | |
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41 | * |
42 | * The TCPT_PERSIST timer is used to keep window size information | |
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43 | * flowing even if the window goes shut. If all previous transmissions |
44 | * have been acknowledged (so that there are no retransmissions in progress), | |
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45 | * and the window is too small to bother sending anything, then we start |
46 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero, | |
47 | * we go to transmit state. Otherwise, at intervals send a single byte | |
48 | * into the peer's window to force him to update our window information. | |
49 | * We do this at most as often as TCPT_PERSMIN time intervals, | |
50 | * but no more frequently than the current estimate of round-trip | |
51 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive | |
52 | * a window update from the peer. | |
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53 | * |
54 | * The TCPT_KEEP timer is used to keep connections alive. If an | |
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55 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, |
56 | * but not yet established, then we drop the connection. Once the connection | |
57 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time | |
58 | * (and keepalives have been enabled on the socket), we begin to probe | |
59 | * the connection. We force the peer to send us a segment by sending: | |
405c9168 BJ |
60 | * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> |
61 | * This segment is (deliberately) outside the window, and should elicit | |
62 | * an ack segment in response from the peer. If, despite the TCPT_KEEP | |
63 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE | |
8a36cf82 | 64 | * amount of time probing, then we drop the connection. |
405c9168 | 65 | */ |
1c4a70b8 | 66 | |
d0461c72 | 67 | #define TCP_TTL 60 /* default time to live for TCP segs */ |
1c4a70b8 | 68 | /* |
405c9168 | 69 | * Time constants. |
1c4a70b8 | 70 | */ |
8a36cf82 | 71 | #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ |
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72 | #define TCPTV_SRTTBASE 0 /* base roundtrip time; |
73 | if 0, no idea yet */ | |
6a4fd140 | 74 | #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ |
e8355345 | 75 | |
405c9168 | 76 | #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ |
7cc62c26 | 77 | #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ |
1c4a70b8 | 78 | |
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79 | #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ |
80 | #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ | |
81 | #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ | |
82 | #define TCPTV_KEEPCNT 8 /* max probes before drop */ | |
1c4a70b8 | 83 | |
405c9168 | 84 | #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ |
7cc62c26 | 85 | #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ |
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86 | |
87 | #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ | |
1c4a70b8 | 88 | |
6209c5c4 | 89 | #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ |
fd5dc5f0 | 90 | |
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91 | #ifdef TCPTIMERS |
92 | char *tcptimers[] = | |
2f9fe2d6 | 93 | { "REXMT", "PERSIST", "KEEP", "2MSL" }; |
1c4a70b8 | 94 | #endif |
405c9168 | 95 | |
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96 | /* |
97 | * Force a time value to be in a certain range. | |
98 | */ | |
4aed14e3 | 99 | #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ |
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100 | (tv) = (value); \ |
101 | if ((tv) < (tvmin)) \ | |
102 | (tv) = (tvmin); \ | |
7cc62c26 | 103 | else if ((tv) > (tvmax)) \ |
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104 | (tv) = (tvmax); \ |
105 | } | |
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106 | |
107 | #ifdef KERNEL | |
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108 | extern int tcp_keepidle; /* time before keepalive probes begin */ |
109 | extern int tcp_keepintvl; /* time between keepalive probes */ | |
110 | extern int tcp_maxidle; /* time to drop after starting probes */ | |
111 | extern int tcp_ttl; /* time to live for TCP segs */ | |
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112 | extern int tcp_backoff[]; |
113 | #endif |