1 | /* SPDX-License-Identifier: BSD-3-Clause */ |
2 | /* |
3 | * Copyright (c) 1982, 1986, 1993 |
4 | * The Regents of the University of California. All rights reserved. |
5 | * |
6 | * Redistribution and use in source and binary forms, with or without |
7 | * modification, are permitted provided that the following conditions |
8 | * are met: |
9 | * 1. Redistributions of source code must retain the above copyright |
10 | * notice, this list of conditions and the following disclaimer. |
11 | * 2. Redistributions in binary form must reproduce the above copyright |
12 | * notice, this list of conditions and the following disclaimer in the |
13 | * documentation and/or other materials provided with the distribution. |
14 | * 3. Neither the name of the University nor the names of its contributors |
15 | * may be used to endorse or promote products derived from this software |
16 | * without specific prior written permission. |
17 | * |
18 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
19 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
20 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
21 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
22 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
23 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
24 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
25 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
26 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
27 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
28 | * SUCH DAMAGE. |
29 | * |
30 | * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 |
31 | * tcp_timer.h,v 1.4 1994/08/21 05:27:38 paul Exp |
32 | */ |
33 | |
34 | #ifndef TCP_TIMER_H |
35 | #define TCP_TIMER_H |
36 | |
37 | /* |
38 | * Definitions of the TCP timers. These timers are counted |
39 | * down PR_SLOWHZ times a second. |
40 | */ |
41 | #define TCPT_NTIMERS 4 |
42 | |
43 | #define TCPT_REXMT 0 /* retransmit */ |
44 | #define TCPT_PERSIST 1 /* retransmit persistence */ |
45 | #define TCPT_KEEP 2 /* keep alive */ |
46 | #define TCPT_2MSL 3 /* 2*msl quiet time timer */ |
47 | |
48 | /* |
49 | * The TCPT_REXMT timer is used to force retransmissions. |
50 | * The TCP has the TCPT_REXMT timer set whenever segments |
51 | * have been sent for which ACKs are expected but not yet |
52 | * received. If an ACK is received which advances tp->snd_una, |
53 | * then the retransmit timer is cleared (if there are no more |
54 | * outstanding segments) or reset to the base value (if there |
55 | * are more ACKs expected). Whenever the retransmit timer goes off, |
56 | * we retransmit one unacknowledged segment, and do a backoff |
57 | * on the retransmit timer. |
58 | * |
59 | * The TCPT_PERSIST timer is used to keep window size information |
60 | * flowing even if the window goes shut. If all previous transmissions |
61 | * have been acknowledged (so that there are no retransmissions in progress), |
62 | * and the window is too small to bother sending anything, then we start |
63 | * the TCPT_PERSIST timer. When it expires, if the window is nonzero, |
64 | * we go to transmit state. Otherwise, at intervals send a single byte |
65 | * into the peer's window to force him to update our window information. |
66 | * We do this at most as often as TCPT_PERSMIN time intervals, |
67 | * but no more frequently than the current estimate of round-trip |
68 | * packet time. The TCPT_PERSIST timer is cleared whenever we receive |
69 | * a window update from the peer. |
70 | * |
71 | * The TCPT_KEEP timer is used to keep connections alive. If an |
72 | * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, |
73 | * but not yet established, then we drop the connection. Once the connection |
74 | * is established, if the connection is idle for TCPTV_KEEP_IDLE time |
75 | * (and keepalives have been enabled on the socket), we begin to probe |
76 | * the connection. We force the peer to send us a segment by sending: |
77 | * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> |
78 | * This segment is (deliberately) outside the window, and should elicit |
79 | * an ack segment in response from the peer. If, despite the TCPT_KEEP |
80 | * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE |
81 | * amount of time probing, then we drop the connection. |
82 | */ |
83 | |
84 | /* |
85 | * Time constants. |
86 | */ |
87 | #define TCPTV_MSL (5 * PR_SLOWHZ) /* max seg lifetime (hah!) */ |
88 | |
89 | #define TCPTV_SRTTBASE \ |
90 | 0 /* base roundtrip time; \ |
91 | if 0, no idea yet */ |
92 | #define TCPTV_SRTTDFLT (3 * PR_SLOWHZ) /* assumed RTT if no info */ |
93 | |
94 | #define TCPTV_PERSMIN (5 * PR_SLOWHZ) /* retransmit persistence */ |
95 | #define TCPTV_PERSMAX (60 * PR_SLOWHZ) /* maximum persist interval */ |
96 | |
97 | #define TCPTV_KEEP_INIT (75 * PR_SLOWHZ) /* initial connect keep alive */ |
98 | #define TCPTV_KEEP_IDLE (120 * 60 * PR_SLOWHZ) /* dflt time before probing */ |
99 | #define TCPTV_KEEPINTVL (75 * PR_SLOWHZ) /* default probe interval */ |
100 | #define TCPTV_KEEPCNT 8 /* max probes before drop */ |
101 | |
102 | #define TCPTV_MIN (1 * PR_SLOWHZ) /* minimum allowable value */ |
103 | #define TCPTV_REXMTMAX (12 * PR_SLOWHZ) /* max allowable REXMT value */ |
104 | |
105 | #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ |
106 | |
107 | #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ |
108 | |
109 | |
110 | /* |
111 | * Force a time value to be in a certain range. |
112 | */ |
113 | #define TCPT_RANGESET(tv, value, tvmin, tvmax) \ |
114 | { \ |
115 | (tv) = (value); \ |
116 | if ((tv) < (tvmin)) \ |
117 | (tv) = (tvmin); \ |
118 | else if ((tv) > (tvmax)) \ |
119 | (tv) = (tvmax); \ |
120 | } |
121 | |
122 | extern const int tcp_backoff[]; |
123 | |
124 | struct tcpcb; |
125 | |
126 | void tcp_fasttimo(Slirp *); |
127 | void tcp_slowtimo(Slirp *); |
128 | void tcp_canceltimers(struct tcpcb *); |
129 | |
130 | #endif |
131 | |