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