1 /* $OpenBSD: tcp_timer.h,v 1.4 2001/06/09 07:03:43 angelos Exp $ */ 2 /* $NetBSD: tcp_timer.h,v 1.6 1995/03/26 20:32:37 jtc Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 37 */ 38 39 #ifndef _NETINET_TCP_TIMER_H_ 40 #define _NETINET_TCP_TIMER_H_ 41 42 /* 43 * Definitions of the TCP timers. These timers are counted 44 * down PR_SLOWHZ times a second. 45 */ 46 #define TCPT_NTIMERS 4 47 48 #define TCPT_REXMT 0 /* retransmit */ 49 #define TCPT_PERSIST 1 /* retransmit persistance */ 50 #define TCPT_KEEP 2 /* keep alive */ 51 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 52 53 /* 54 * The TCPT_REXMT timer is used to force retransmissions. 55 * The TCP has the TCPT_REXMT timer set whenever segments 56 * have been sent for which ACKs are expected but not yet 57 * received. If an ACK is received which advances tp->snd_una, 58 * then the retransmit timer is cleared (if there are no more 59 * outstanding segments) or reset to the base value (if there 60 * are more ACKs expected). Whenever the retransmit timer goes off, 61 * we retransmit one unacknowledged segment, and do a backoff 62 * on the retransmit timer. 63 * 64 * The TCPT_PERSIST timer is used to keep window size information 65 * flowing even if the window goes shut. If all previous transmissions 66 * have been acknowledged (so that there are no retransmissions in progress), 67 * and the window is too small to bother sending anything, then we start 68 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 69 * we go to transmit state. Otherwise, at intervals send a single byte 70 * into the peer's window to force him to update our window information. 71 * We do this at most as often as TCPT_PERSMIN time intervals, 72 * but no more frequently than the current estimate of round-trip 73 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 74 * a window update from the peer. 75 * 76 * The TCPT_KEEP timer is used to keep connections alive. If an 77 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 78 * but not yet established, then we drop the connection. Once the connection 79 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 80 * (and keepalives have been enabled on the socket), we begin to probe 81 * the connection. We force the peer to send us a segment by sending: 82 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 83 * This segment is (deliberately) outside the window, and should elicit 84 * an ack segment in response from the peer. If, despite the TCPT_KEEP 85 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 86 * amount of time probing, then we drop the connection. 87 */ 88 89 /* 90 * Time constants. 91 */ 92 #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ 93 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 94 if 0, no idea yet */ 95 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 96 97 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ 98 #define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 99 100 #define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ 101 #define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ 102 #define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ 103 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 104 105 #define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 106 #define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ 107 108 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 109 110 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 111 112 #ifdef TCPTIMERS 113 char *tcptimers[] = 114 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 115 #endif /* TCPTIMERS */ 116 117 /* 118 * Force a time value to be in a certain range. 119 */ 120 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 121 (tv) = (value); \ 122 if ((tv) < (tvmin)) \ 123 (tv) = (tvmin); \ 124 else if ((tv) > (tvmax)) \ 125 (tv) = (tvmax); \ 126 } 127 128 #ifdef _KERNEL 129 extern int tcptv_keep_init; 130 extern int tcp_keepidle; /* time before keepalive probes begin */ 131 extern int tcp_keepintvl; /* time between keepalive probes */ 132 extern int tcp_maxidle; /* time to drop after starting probes */ 133 extern int tcp_ttl; /* time to live for TCP segs */ 134 extern int tcp_backoff[]; 135 #endif /* _KERNEL */ 136 #endif /* _NETINET_TCP_TIMER_H_ */ 137