tcp_timer.h revision 21673
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. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 34 * $FreeBSD: head/sys/netinet/tcp_timer.h 21673 1997-01-14 07:20:47Z jkh $ 35 */ 36 37#ifndef _NETINET_TCP_TIMER_H_ 38#define _NETINET_TCP_TIMER_H_ 39 40/* 41 * Definitions of the TCP timers. These timers are counted 42 * down PR_SLOWHZ times a second. 43 */ 44#define TCPT_NTIMERS 4 45 46#define TCPT_REXMT 0 /* retransmit */ 47#define TCPT_PERSIST 1 /* retransmit persistence */ 48#define TCPT_KEEP 2 /* keep alive */ 49#define TCPT_2MSL 3 /* 2*msl quiet time timer */ 50 51/* 52 * The TCPT_REXMT timer is used to force retransmissions. 53 * The TCP has the TCPT_REXMT timer set whenever segments 54 * have been sent for which ACKs are expected but not yet 55 * received. If an ACK is received which advances tp->snd_una, 56 * then the retransmit timer is cleared (if there are no more 57 * outstanding segments) or reset to the base value (if there 58 * are more ACKs expected). Whenever the retransmit timer goes off, 59 * we retransmit one unacknowledged segment, and do a backoff 60 * on the retransmit timer. 61 * 62 * The TCPT_PERSIST timer is used to keep window size information 63 * flowing even if the window goes shut. If all previous transmissions 64 * have been acknowledged (so that there are no retransmissions in progress), 65 * and the window is too small to bother sending anything, then we start 66 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 67 * we go to transmit state. Otherwise, at intervals send a single byte 68 * into the peer's window to force him to update our window information. 69 * We do this at most as often as TCPT_PERSMIN time intervals, 70 * but no more frequently than the current estimate of round-trip 71 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 72 * a window update from the peer. 73 * 74 * The TCPT_KEEP timer is used to keep connections alive. If an 75 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 76 * but not yet established, then we drop the connection. Once the connection 77 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 78 * (and keepalives have been enabled on the socket), we begin to probe 79 * the connection. We force the peer to send us a segment by sending: 80 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 81 * This segment is (deliberately) outside the window, and should elicit 82 * an ack segment in response from the peer. If, despite the TCPT_KEEP 83 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 84 * amount of time probing, then we drop the connection. 85 */ 86 87/* 88 * Time constants. 89 */ 90#define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ 91#define TCPTV_SRTTBASE 0 /* base roundtrip time; 92 if 0, no idea yet */ 93#define TCPTV_RTOBASE ( 3*PR_SLOWHZ) /* assumed RTO if no info */ 94#define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 95 96#define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistence */ 97#define TCPTV_PERSMAX ( 60*PR_SLOWHZ) /* maximum persist interval */ 98 99#define TCPTV_KEEP_INIT ( 75*PR_SLOWHZ) /* initial connect keep alive */ 100#define TCPTV_KEEP_IDLE (120*60*PR_SLOWHZ) /* dflt time before probing */ 101#define TCPTV_KEEPINTVL ( 75*PR_SLOWHZ) /* default probe interval */ 102#define TCPTV_KEEPCNT 8 /* max probes before drop */ 103 104#define TCPTV_MIN ( 1*PR_SLOWHZ) /* minimum allowable value */ 105#define TCPTV_REXMTMAX ( 64*PR_SLOWHZ) /* max allowable REXMT value */ 106 107#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 108 109#define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 110 111#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 112 113#ifdef TCPTIMERS 114static char *tcptimers[] = 115 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 116#endif 117 118/* 119 * Force a time value to be in a certain range. 120 */ 121#define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 122 (tv) = (value); \ 123 if ((u_long)(tv) < (u_long)(tvmin)) \ 124 (tv) = (tvmin); \ 125 else if ((u_long)(tv) > (u_long)(tvmax)) \ 126 (tv) = (tvmax); \ 127} 128 129#ifdef KERNEL 130extern int tcp_keepinit; /* time to establish connection */ 131extern int tcp_keepidle; /* time before keepalive probes begin */ 132extern int tcp_keepintvl; /* time between keepalive probes */ 133extern int tcp_maxidle; /* time to drop after starting probes */ 134extern int tcp_ttl; /* time to live for TCP segs */ 135extern int tcp_backoff[]; 136#endif 137 138#endif 139