tcp_timer.h revision 92723
1262569Simp/* 2262569Simp * Copyright (c) 1982, 1986, 1993 3262569Simp * The Regents of the University of California. All rights reserved. 4262569Simp * 5262569Simp * Redistribution and use in source and binary forms, with or without 6262569Simp * modification, are permitted provided that the following conditions 7262569Simp * are met: 8262569Simp * 1. Redistributions of source code must retain the above copyright 9262569Simp * notice, this list of conditions and the following disclaimer. 10262569Simp * 2. Redistributions in binary form must reproduce the above copyright 11262569Simp * notice, this list of conditions and the following disclaimer in the 12262569Simp * documentation and/or other materials provided with the distribution. 13262569Simp * 3. All advertising materials mentioning features or use of this software 14262569Simp * must display the following acknowledgement: 15262569Simp * This product includes software developed by the University of 16262569Simp * California, Berkeley and its contributors. 17262569Simp * 4. Neither the name of the University nor the names of its contributors 18262569Simp * may be used to endorse or promote products derived from this software 19262569Simp * without specific prior written permission. 20262569Simp * 21262569Simp * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22262569Simp * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23262569Simp * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24262569Simp * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25262569Simp * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26262569Simp * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27262569Simp * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28262569Simp * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29262569Simp * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30262569Simp * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31262569Simp * SUCH DAMAGE. 32262569Simp * 33262569Simp * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 34262569Simp * $FreeBSD: head/sys/netinet/tcp_timer.h 92723 2002-03-19 21:25:46Z alfred $ 35262569Simp */ 36262569Simp 37262569Simp#ifndef _NETINET_TCP_TIMER_H_ 38262569Simp#define _NETINET_TCP_TIMER_H_ 39262569Simp 40262569Simp/* 41262569Simp * The TCPT_REXMT timer is used to force retransmissions. 42262569Simp * The TCP has the TCPT_REXMT timer set whenever segments 43262569Simp * have been sent for which ACKs are expected but not yet 44262569Simp * received. If an ACK is received which advances tp->snd_una, 45270864Simp * then the retransmit timer is cleared (if there are no more 46270864Simp * outstanding segments) or reset to the base value (if there 47270864Simp * are more ACKs expected). Whenever the retransmit timer goes off, 48270864Simp * we retransmit one unacknowledged segment, and do a backoff 49270864Simp * on the retransmit timer. 50270864Simp * 51270864Simp * The TCPT_PERSIST timer is used to keep window size information 52270864Simp * flowing even if the window goes shut. If all previous transmissions 53270864Simp * have been acknowledged (so that there are no retransmissions in progress), 54262569Simp * and the window is too small to bother sending anything, then we start 55262569Simp * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 56262569Simp * we go to transmit state. Otherwise, at intervals send a single byte 57262569Simp * into the peer's window to force him to update our window information. 58262569Simp * We do this at most as often as TCPT_PERSMIN time intervals, 59262569Simp * but no more frequently than the current estimate of round-trip 60279385Simp * packet time. The TCPT_PERSIST timer is cleared whenever we receive 61279385Simp * a window update from the peer. 62279385Simp * 63270864Simp * The TCPT_KEEP timer is used to keep connections alive. If an 64270864Simp * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 65262569Simp * but not yet established, then we drop the connection. Once the connection 66262569Simp * is established, if the connection is idle for TCPTV_KEEP_IDLE time 67262569Simp * (and keepalives have been enabled on the socket), we begin to probe 68262569Simp * the connection. We force the peer to send us a segment by sending: 69262569Simp * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 70 * This segment is (deliberately) outside the window, and should elicit 71 * an ack segment in response from the peer. If, despite the TCPT_KEEP 72 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 73 * amount of time probing, then we drop the connection. 74 */ 75 76/* 77 * Time constants. 78 */ 79#define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 80#define TCPTV_SRTTBASE 0 /* base roundtrip time; 81 if 0, no idea yet */ 82#define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */ 83#define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */ 84 85#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 86#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 87 88#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 89#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 90#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 91#define TCPTV_KEEPCNT 8 /* max probes before drop */ 92 93#define TCPTV_MIN ( 1*hz) /* minimum allowable value */ 94#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 95 96#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 97 98#define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 99 100#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 101 102#define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */ 103 104#ifdef TCPTIMERS 105static char *tcptimers[] = 106 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 107#endif 108 109/* 110 * Force a time value to be in a certain range. 111 */ 112#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 113 (tv) = (value); \ 114 if ((u_long)(tv) < (u_long)(tvmin)) \ 115 (tv) = (tvmin); \ 116 else if ((u_long)(tv) > (u_long)(tvmax)) \ 117 (tv) = (tvmax); \ 118} while(0) 119 120#ifdef _KERNEL 121extern int tcp_keepinit; /* time to establish connection */ 122extern int tcp_keepidle; /* time before keepalive probes begin */ 123extern int tcp_keepintvl; /* time between keepalive probes */ 124extern int tcp_maxidle; /* time to drop after starting probes */ 125extern int tcp_delacktime; /* time before sending a delayed ACK */ 126extern int tcp_maxpersistidle; 127extern int tcp_msl; 128extern int tcp_ttl; /* time to live for TCP segs */ 129extern int tcp_backoff[]; 130 131void tcp_timer_2msl(void *xtp); 132void tcp_timer_keep(void *xtp); 133void tcp_timer_persist(void *xtp); 134void tcp_timer_rexmt(void *xtp); 135void tcp_timer_delack(void *xtp); 136 137#endif /* _KERNEL */ 138 139#endif /* !_NETINET_TCP_TIMER_H_ */ 140