1/* $OpenBSD: tcp_timer.h,v 1.21 2024/01/29 22:47:13 bluhm 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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 33 */ 34 35#ifndef _NETINET_TCP_TIMER_H_ 36#define _NETINET_TCP_TIMER_H_ 37 38/* 39 * Definitions of the TCP timers. 40 */ 41#define TCPT_REXMT 0 /* retransmit */ 42#define TCPT_PERSIST 1 /* retransmit persistence */ 43#define TCPT_KEEP 2 /* keep alive */ 44#define TCPT_2MSL 3 /* 2*msl quiet time timer */ 45#define TCPT_REAPER 4 /* delayed cleanup timeout */ 46#define TCPT_DELACK 5 /* delayed ack timeout */ 47 48#define TCPT_NTIMERS 6 49 50/* 51 * The TCPT_REXMT timer is used to force retransmissions. 52 * The TCP has the TCPT_REXMT timer set whenever segments 53 * have been sent for which ACKs are expected but not yet 54 * received. If an ACK is received which advances tp->snd_una, 55 * then the retransmit timer is cleared (if there are no more 56 * outstanding segments) or reset to the base value (if there 57 * are more ACKs expected). Whenever the retransmit timer goes off, 58 * we retransmit one unacknowledged segment, and do a backoff 59 * on the retransmit timer. 60 * 61 * The TCPT_PERSIST timer is used to keep window size information 62 * flowing even if the window goes shut. If all previous transmissions 63 * have been acknowledged (so that there are no retransmissions in progress), 64 * and the window is too small to bother sending anything, then we start 65 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 66 * we go to transmit state. Otherwise, at intervals send a single byte 67 * into the peer's window to force him to update our window information. 68 * We do this at most as often as TCPT_PERSMIN time intervals, 69 * but no more frequently than the current estimate of round-trip 70 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 71 * a window update from the peer. 72 * 73 * The TCPT_KEEP timer is used to keep connections alive. If an 74 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 75 * but not yet established, then we drop the connection. Once the connection 76 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 77 * (and keepalives have been enabled on the socket), we begin to probe 78 * the connection. We force the peer to send us a segment by sending: 79 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 80 * This segment is (deliberately) outside the window, and should elicit 81 * an ack segment in response from the peer. If, despite the TCPT_KEEP 82 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 83 * amount of time probing, then we drop the connection. 84 */ 85 86/* 87 * Time constants. 88 */ 89#define TCPTV_MSL TCP_TIME(30) /* max seg lifetime (hah!) */ 90#define TCPTV_SRTTBASE 0 /* base roundtrip time; 91 if 0, no idea yet */ 92#define TCPTV_SRTTDFLT TCP_TIME(3) /* assumed RTT if no info */ 93 94#define TCPTV_PERSMIN TCP_TIME(5) /* retransmit persistence */ 95#define TCPTV_PERSMAX TCP_TIME(60) /* maximum persist interval */ 96 97#define TCPTV_KEEP_INIT TCP_TIME(75) /* initial connect keep alive */ 98#define TCPTV_KEEP_IDLE TCP_TIME(120*60) /* dflt time before probing */ 99#define TCPTV_KEEPINTVL TCP_TIME(75) /* default probe interval */ 100#define TCPTV_KEEPCNT 8 /* max probes before drop */ 101 102#define TCPTV_MIN TCP_TIME(1) /* minimum allowable value */ 103#define TCPTV_REXMTMAX TCP_TIME(64) /* max allowable REXMT value */ 104 105#define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 106 107#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 108 109#define TCP_DELACK_MSECS 200 /* time to delay ACK */ 110 111#ifdef TCPTIMERS 112const char *tcptimers[TCPT_NTIMERS] = 113 { "REXMT", "PERSIST", "KEEP", "2MSL", "REAPER", "DELACK" }; 114#endif /* TCPTIMERS */ 115 116/* 117 * Init, arm, disarm, and test TCP timers. 118 */ 119#define TCP_TIMER_INIT(tp, timer) \ 120 timeout_set_flags(&(tp)->t_timer[(timer)], \ 121 tcp_timer_funcs[(timer)], tp, KCLOCK_NONE, \ 122 TIMEOUT_PROC | TIMEOUT_MPSAFE) 123 124#define TCP_TIMER_ARM(tp, timer, msecs) \ 125do { \ 126 SET((tp)->t_flags, TF_TIMER << (timer)); \ 127 timeout_add_msec(&(tp)->t_timer[(timer)], (msecs)); \ 128} while (0) 129 130#define TCP_TIMER_DISARM(tp, timer) \ 131do { \ 132 CLR((tp)->t_flags, TF_TIMER << (timer)); \ 133 timeout_del(&(tp)->t_timer[(timer)]); \ 134} while (0) 135 136#define TCP_TIMER_ISARMED(tp, timer) \ 137 ISSET((tp)->t_flags, TF_TIMER << (timer)) 138 139/* 140 * Force a time value to be in a certain range. 141 */ 142#define TCPT_RANGESET(tv, value, tvmin, tvmax) \ 143do { \ 144 (tv) = (value); \ 145 if ((tv) < (tvmin)) \ 146 (tv) = (tvmin); \ 147 else if ((tv) > (tvmax)) \ 148 (tv) = (tvmax); \ 149} while (/* CONSTCOND */ 0) 150 151#ifdef _KERNEL 152typedef void (*tcp_timer_func_t)(void *); 153 154extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS]; 155 156extern int tcp_delack_msecs; /* delayed ACK timeout in millisecs */ 157extern int tcptv_keep_init; 158extern int tcp_always_keepalive; /* assume SO_KEEPALIVE is always set */ 159extern int tcp_keepidle; /* time before keepalive probes begin */ 160extern int tcp_keepintvl; /* time between keepalive probes */ 161extern int tcp_maxidle; /* time to drop after starting probes */ 162extern int tcp_ttl; /* time to live for TCP segs */ 163extern int tcp_backoff[]; 164 165void tcp_timer_init(void); 166#endif /* _KERNEL */ 167#endif /* _NETINET_TCP_TIMER_H_ */ 168