Commit | Line | Data |
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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 | * |
dbf0c423 | 5 | * %sccs.include.redist.c% |
2b6b6284 | 6 | * |
aef18e52 | 7 | * @(#)tcp_timer.h 7.9 (Berkeley) %G% |
8ae0e4b4 | 8 | */ |
1c4a70b8 BJ |
9 | |
10 | /* | |
11 | * Definitions of the TCP timers. These timers are counted | |
12 | * down PR_SLOWHZ times a second. | |
13 | */ | |
2f9fe2d6 | 14 | #define TCPT_NTIMERS 4 |
1c4a70b8 BJ |
15 | |
16 | #define TCPT_REXMT 0 /* retransmit */ | |
405c9168 BJ |
17 | #define TCPT_PERSIST 1 /* retransmit persistance */ |
18 | #define TCPT_KEEP 2 /* keep alive */ | |
19 | #define TCPT_2MSL 3 /* 2*msl quiet time timer */ | |
20 | ||
21 | /* | |
22 | * The TCPT_REXMT timer is used to force retransmissions. | |
23 | * The TCP has the TCPT_REXMT timer set whenever segments | |
24 | * have been sent for which ACKs are expected but not yet | |
25 | * received. If an ACK is received which advances tp->snd_una, | |
26 | * then the retransmit timer is cleared (if there are no more | |
27 | * outstanding segments) or reset to the base value (if there | |
28 | * are more ACKs expected). Whenever the retransmit timer goes off, | |
6209c5c4 MK |
29 | * we retransmit one unacknowledged segment, and do a backoff |
30 | * on the retransmit timer. | |
405c9168 BJ |
31 | * |
32 | * The TCPT_PERSIST timer is used to keep window size information | |
bc8e4818 BJ |
33 | * flowing even if the window goes shut. If all previous transmissions |
34 | * have been acknowledged (so that there are no retransmissions in progress), | |
6209c5c4 MK |
35 | * and the window is too small to bother sending anything, then we start |
36 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero, | |
37 | * we go to transmit state. Otherwise, at intervals send a single byte | |
38 | * into the peer's window to force him to update our window information. | |
39 | * We do this at most as often as TCPT_PERSMIN time intervals, | |
40 | * but no more frequently than the current estimate of round-trip | |
41 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive | |
42 | * a window update from the peer. | |
405c9168 BJ |
43 | * |
44 | * The TCPT_KEEP timer is used to keep connections alive. If an | |
8a36cf82 MK |
45 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, |
46 | * but not yet established, then we drop the connection. Once the connection | |
47 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time | |
48 | * (and keepalives have been enabled on the socket), we begin to probe | |
49 | * the connection. We force the peer to send us a segment by sending: | |
405c9168 BJ |
50 | * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> |
51 | * This segment is (deliberately) outside the window, and should elicit | |
52 | * an ack segment in response from the peer. If, despite the TCPT_KEEP | |
53 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE | |
8a36cf82 | 54 | * amount of time probing, then we drop the connection. |
405c9168 | 55 | */ |
1c4a70b8 | 56 | |
1c4a70b8 | 57 | /* |
405c9168 | 58 | * Time constants. |
1c4a70b8 | 59 | */ |
8a36cf82 | 60 | #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ |
7668259e MK |
61 | #define TCPTV_SRTTBASE 0 /* base roundtrip time; |
62 | if 0, no idea yet */ | |
6a4fd140 | 63 | #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ |
e8355345 | 64 | |
405c9168 | 65 | #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ |
7cc62c26 | 66 | #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ |
1c4a70b8 | 67 | |
8a36cf82 MK |
68 | #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ |
69 | #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ | |
70 | #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ | |
71 | #define TCPTV_KEEPCNT 8 /* max probes before drop */ | |
1c4a70b8 | 72 | |
405c9168 | 73 | #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ |
7cc62c26 | 74 | #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ |
8e65fd66 BJ |
75 | |
76 | #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ | |
1c4a70b8 | 77 | |
6209c5c4 | 78 | #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ |
fd5dc5f0 | 79 | |
1c4a70b8 BJ |
80 | #ifdef TCPTIMERS |
81 | char *tcptimers[] = | |
2f9fe2d6 | 82 | { "REXMT", "PERSIST", "KEEP", "2MSL" }; |
1c4a70b8 | 83 | #endif |
405c9168 | 84 | |
405c9168 BJ |
85 | /* |
86 | * Force a time value to be in a certain range. | |
87 | */ | |
4aed14e3 | 88 | #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ |
405c9168 BJ |
89 | (tv) = (value); \ |
90 | if ((tv) < (tvmin)) \ | |
91 | (tv) = (tvmin); \ | |
7cc62c26 | 92 | else if ((tv) > (tvmax)) \ |
4aed14e3 BJ |
93 | (tv) = (tvmax); \ |
94 | } | |
7cc62c26 MK |
95 | |
96 | #ifdef KERNEL | |
8a36cf82 MK |
97 | extern int tcp_keepidle; /* time before keepalive probes begin */ |
98 | extern int tcp_keepintvl; /* time between keepalive probes */ | |
99 | extern int tcp_maxidle; /* time to drop after starting probes */ | |
100 | extern int tcp_ttl; /* time to live for TCP segs */ | |
7cc62c26 MK |
101 | extern int tcp_backoff[]; |
102 | #endif |