1 /* $NetBSD: tcp_timer.h,v 1.10 1998/09/10 10:47:00 mouse Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 36 */ 37 38 #ifndef _NETINET_TCP_TIMER_H_ 39 #define _NETINET_TCP_TIMER_H_ 40 41 /* 42 * Definitions of the TCP timers. These timers are counted 43 * down PR_SLOWHZ times a second. 44 */ 45 #define TCPT_NTIMERS 4 46 47 #define TCPT_REXMT 0 /* retransmit */ 48 #define TCPT_PERSIST 1 /* retransmit persistance */ 49 #define TCPT_KEEP 2 /* keep alive */ 50 #define TCPT_2MSL 3 /* 2*msl quiet time timer */ 51 52 /* 53 * The TCPT_REXMT timer is used to force retransmissions. 54 * The TCP has the TCPT_REXMT timer set whenever segments 55 * have been sent for which ACKs are expected but not yet 56 * received. If an ACK is received which advances tp->snd_una, 57 * then the retransmit timer is cleared (if there are no more 58 * outstanding segments) or reset to the base value (if there 59 * are more ACKs expected). Whenever the retransmit timer goes off, 60 * we retransmit one unacknowledged segment, and do a backoff 61 * on the retransmit timer. 62 * 63 * The TCPT_PERSIST timer is used to keep window size information 64 * flowing even if the window goes shut. If all previous transmissions 65 * have been acknowledged (so that there are no retransmissions in progress), 66 * and the window is too small to bother sending anything, then we start 67 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 68 * we go to transmit state. Otherwise, at intervals send a single byte 69 * into the peer's window to force him to update our window information. 70 * We do this at most as often as TCPT_PERSMIN time intervals, 71 * but no more frequently than the current estimate of round-trip 72 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 73 * a window update from the peer. 74 * 75 * The TCPT_KEEP timer is used to keep connections alive. If an 76 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 77 * but not yet established, then we drop the connection. Once the connection 78 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 79 * (and keepalives have been enabled on the socket), we begin to probe 80 * the connection. We force the peer to send us a segment by sending: 81 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 82 * This segment is (deliberately) outside the window, and should elicit 83 * an ack segment in response from the peer. If, despite the TCPT_KEEP 84 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 85 * amount of time probing, then we drop the connection. 86 */ 87 88 /* 89 * Time constants. 90 */ 91 #define TCPTV_MSL ( 30*PR_SLOWHZ) /* max seg lifetime (hah!) */ 92 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 93 if 0, no idea yet */ 94 #define TCPTV_SRTTDFLT ( 3*PR_SLOWHZ) /* assumed RTT if no info */ 95 96 #define TCPTV_PERSMIN ( 5*PR_SLOWHZ) /* retransmit persistance */ 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 TCP_LINGERTIME 120 /* linger at most 2 minutes */ 108 109 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 110 111 #ifdef TCPTIMERS 112 char *tcptimers[] = 113 { "REXMT", "PERSIST", "KEEP", "2MSL" }; 114 #endif 115 116 /* 117 * Arm, disarm, and test TCP timers. 118 */ 119 #define TCP_TIMER_ARM(tp, timer, nticks) \ 120 PRT_SLOW_ARM((tp)->t_timer[(timer)], (nticks)) 121 122 #define TCP_TIMER_DISARM(tp, timer) \ 123 PRT_SLOW_DISARM((tp)->t_timer[(timer)]) 124 125 #define TCP_TIMER_ISARMED(tp, timer) \ 126 PRT_SLOW_ISARMED((tp)->t_timer[(timer)]) 127 128 #define TCP_TIMER_ISEXPIRED(tp, timer) \ 129 PRT_SLOW_ISEXPIRED((tp)->t_timer[(timer)]) 130 131 /* 132 * Force a time value to be in a certain range. 133 */ 134 #define TCPT_RANGESET(tv, value, tvmin, tvmax) { \ 135 (tv) = (value); \ 136 if ((tv) < (tvmin)) \ 137 (tv) = (tvmin); \ 138 else if ((tv) > (tvmax)) \ 139 (tv) = (tvmax); \ 140 } 141 142 #ifdef _KERNEL 143 extern int tcp_keepidle; /* time before keepalive probes begin */ 144 extern int tcp_keepintvl; /* time between keepalive probes */ 145 extern int tcp_keepcnt; /* number of keepalives, 0=infty */ 146 extern int tcp_maxidle; /* time to drop after starting probes */ 147 extern int tcp_ttl; /* time to live for TCP segs */ 148 extern int tcp_backoff[]; 149 #endif 150 151 #endif /* _NETINET_TCP_TIMER_H_ */ 152