1 /* $OpenBSD: tcp_timer.h,v 1.26 2025/01/16 11:59:20 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_DELACK 4 /* delayed ack timeout */ 46 47 #define TCPT_NTIMERS 5 48 49 /* 50 * The TCPT_REXMT timer is used to force retransmissions. 51 * The TCP has the TCPT_REXMT timer set whenever segments 52 * have been sent for which ACKs are expected but not yet 53 * received. If an ACK is received which advances tp->snd_una, 54 * then the retransmit timer is cleared (if there are no more 55 * outstanding segments) or reset to the base value (if there 56 * are more ACKs expected). Whenever the retransmit timer goes off, 57 * we retransmit one unacknowledged segment, and do a backoff 58 * on the retransmit timer. 59 * 60 * The TCPT_PERSIST timer is used to keep window size information 61 * flowing even if the window goes shut. If all previous transmissions 62 * have been acknowledged (so that there are no retransmissions in progress), 63 * and the window is too small to bother sending anything, then we start 64 * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 65 * we go to transmit state. Otherwise, at intervals send a single byte 66 * into the peer's window to force him to update our window information. 67 * We do this at most as often as TCPT_PERSMIN time intervals, 68 * but no more frequently than the current estimate of round-trip 69 * packet time. The TCPT_PERSIST timer is cleared whenever we receive 70 * a window update from the peer. 71 * 72 * The TCPT_KEEP timer is used to keep connections alive. If an 73 * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 74 * but not yet established, then we drop the connection. Once the connection 75 * is established, if the connection is idle for TCPTV_KEEP_IDLE time 76 * (and keepalives have been enabled on the socket), we begin to probe 77 * the connection. We force the peer to send us a segment by sending: 78 * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 79 * This segment is (deliberately) outside the window, and should elicit 80 * an ack segment in response from the peer. If, despite the TCPT_KEEP 81 * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 82 * amount of time probing, then we drop the connection. 83 */ 84 85 /* 86 * Time constants. 87 */ 88 #define TCPTV_MSL TCP_TIME(30) /* max seg lifetime (hah!) */ 89 #define TCPTV_SRTTBASE 0 /* base roundtrip time; 90 if 0, no idea yet */ 91 #define TCPTV_SRTTDFLT TCP_TIME(3) /* assumed RTT if no info */ 92 93 #define TCPTV_PERSMIN TCP_TIME(5) /* retransmit persistence */ 94 #define TCPTV_PERSMAX TCP_TIME(60) /* maximum persist interval */ 95 96 #define TCPTV_KEEPINIT TCP_TIME(75) /* initial connect keep alive */ 97 #define TCPTV_KEEPIDLE TCP_TIME(120*60) /* dflt time before probing */ 98 #define TCPTV_KEEPINTVL TCP_TIME(75) /* default probe interval */ 99 #define TCPTV_KEEPCNT 8 /* max probes before drop */ 100 101 #define TCPTV_MIN TCP_TIME(1) /* minimum allowable value */ 102 #define TCPTV_REXMTMAX TCP_TIME(64) /* max allowable REXMT value */ 103 104 #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 105 106 #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 107 108 #define TCP_DELACK_MSECS 200 /* time to delay ACK */ 109 110 #ifdef TCPTIMERS 111 const char *tcptimers[TCPT_NTIMERS] = 112 { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; 113 #endif /* TCPTIMERS */ 114 115 /* 116 * Init, arm, disarm, and test TCP timers. 117 */ 118 #define TCP_TIMER_INIT(tp, timer) \ 119 timeout_set_flags(&(tp)->t_timer[(timer)], \ 120 tcp_timer_funcs[(timer)], (tp)->t_inpcb, \ 121 KCLOCK_NONE, TIMEOUT_PROC | TIMEOUT_MPSAFE) 122 123 #define TCP_TIMER_ARM(tp, timer, msecs) \ 124 do { \ 125 SET((tp)->t_flags, TF_TIMER << (timer)); \ 126 if (timeout_add_msec(&(tp)->t_timer[(timer)], (msecs))) \ 127 in_pcbref((tp)->t_inpcb); \ 128 } while (0) 129 130 #define TCP_TIMER_DISARM(tp, timer) \ 131 do { \ 132 CLR((tp)->t_flags, TF_TIMER << (timer)); \ 133 if (timeout_del(&(tp)->t_timer[(timer)])) \ 134 in_pcbunref((tp)->t_inpcb); \ 135 } while (0) 136 137 #define TCP_TIMER_ISARMED(tp, timer) \ 138 ISSET((tp)->t_flags, TF_TIMER << (timer)) 139 140 /* 141 * Force a time value to be in a certain range. 142 */ 143 #define TCPT_RANGESET(tv, value, tvmin, tvmax) \ 144 do { \ 145 (tv) = (value); \ 146 if ((tv) < (tvmin)) \ 147 (tv) = (tvmin); \ 148 else if ((tv) > (tvmax)) \ 149 (tv) = (tvmax); \ 150 } while (/* CONSTCOND */ 0) 151 152 #ifdef _KERNEL 153 typedef void (*tcp_timer_func_t)(void *); 154 155 extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS]; 156 157 extern int tcp_delack_msecs; /* [I] delayed ACK timeout in millisecs */ 158 extern int tcp_always_keepalive;/* [a] assume SO_KEEPALIVE always set */ 159 extern int tcp_keepinit; /* [a] time to keep alive initial SYN packet */ 160 extern int tcp_keepidle; /* [a] time before keepalive probes begin */ 161 extern int tcp_keepintvl; /* [a] time between keepalive probes */ 162 extern int tcp_keepinit_sec; /* [a] copy of above in seconds for sysctl */ 163 extern int tcp_keepidle_sec; /* [a] copy of above in seconds for sysctl */ 164 extern int tcp_keepintvl_sec; /* [a] copy of above in seconds for sysctl */ 165 extern int tcp_ttl; /* time to live for TCP segs */ 166 extern const int tcp_backoff[]; 167 168 void tcp_timer_reaper(void *); 169 170 #endif /* _KERNEL */ 171 #endif /* _NETINET_TCP_TIMER_H_ */ 172