/* $OpenBSD: tcp_timer.h,v 1.28 2025/12/31 03:47:04 jsg Exp $ */ /* $NetBSD: tcp_timer.h,v 1.6 1995/03/26 20:32:37 jtc Exp $ */ /* * Copyright (c) 1982, 1986, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 */ #ifndef _NETINET_TCP_TIMER_H_ #define _NETINET_TCP_TIMER_H_ /* * Definitions of the TCP timers. */ #define TCPT_REXMT 0 /* retransmit */ #define TCPT_PERSIST 1 /* retransmit persistence */ #define TCPT_KEEP 2 /* keep alive */ #define TCPT_2MSL 3 /* 2*msl quiet time timer */ #define TCPT_DELACK 4 /* delayed ack timeout */ #define TCPT_NTIMERS 5 /* * The TCPT_REXMT timer is used to force retransmissions. * The TCP has the TCPT_REXMT timer set whenever segments * have been sent for which ACKs are expected but not yet * received. If an ACK is received which advances tp->snd_una, * then the retransmit timer is cleared (if there are no more * outstanding segments) or reset to the base value (if there * are more ACKs expected). Whenever the retransmit timer goes off, * we retransmit one unacknowledged segment, and do a backoff * on the retransmit timer. * * The TCPT_PERSIST timer is used to keep window size information * flowing even if the window goes shut. If all previous transmissions * have been acknowledged (so that there are no retransmissions in progress), * and the window is too small to bother sending anything, then we start * the TCPT_PERSIST timer. When it expires, if the window is nonzero, * we go to transmit state. Otherwise, at intervals send a single byte * into the peer's window to force him to update our window information. * We do this at most as often as TCPT_PERSMIN time intervals, * but no more frequently than the current estimate of round-trip * packet time. The TCPT_PERSIST timer is cleared whenever we receive * a window update from the peer. * * The TCPT_KEEP timer is used to keep connections alive. If an * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, * but not yet established, then we drop the connection. Once the connection * is established, if the connection is idle for TCPTV_KEEP_IDLE time * (and keepalives have been enabled on the socket), we begin to probe * the connection. We force the peer to send us a segment by sending: * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> * This segment is (deliberately) outside the window, and should elicit * an ack segment in response from the peer. If, despite the TCPT_KEEP * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE * amount of time probing, then we drop the connection. */ /* * Time constants. */ #define TCPTV_MSL TCP_TIME(30) /* max seg lifetime (hah!) */ #define TCPTV_SRTTBASE 0 /* base roundtrip time; if 0, no idea yet */ #define TCPTV_SRTTDFLT TCP_TIME(3) /* assumed RTT if no info */ #define TCPTV_PERSMIN TCP_TIME(5) /* retransmit persistence */ #define TCPTV_PERSMAX TCP_TIME(60) /* maximum persist interval */ #define TCPTV_KEEPINIT TCP_TIME(75) /* initial connect keep alive */ #define TCPTV_KEEPIDLE TCP_TIME(120*60) /* dflt time before probing */ #define TCPTV_KEEPINTVL TCP_TIME(75) /* default probe interval */ #define TCPTV_KEEPCNT 8 /* max probes before drop */ #define TCPTV_MIN TCP_TIME(1) /* minimum allowable value */ #define TCPTV_REXMTMAX TCP_TIME(64) /* max allowable REXMT value */ #define TCP_LINGERTIME 120 /* linger at most 2 minutes */ #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ #define TCP_DELACK_MSECS 200 /* time to delay ACK */ #ifdef TCPTIMERS const char *tcptimers[TCPT_NTIMERS] = { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; #endif /* TCPTIMERS */ /* * Init, arm, disarm, and test TCP timers. */ #define TCP_TIMER_INIT(tp, timer) \ timeout_set_flags(&(tp)->t_timer[(timer)], \ tcp_timer_funcs[(timer)], (tp)->t_inpcb, \ KCLOCK_NONE, TIMEOUT_PROC | TIMEOUT_MPSAFE) #define TCP_TIMER_ARM(tp, timer, msecs) \ do { \ SET((tp)->t_flags, TF_TIMER << (timer)); \ if (timeout_add_msec(&(tp)->t_timer[(timer)], (msecs))) \ in_pcbref((tp)->t_inpcb); \ } while (0) #define TCP_TIMER_DISARM(tp, timer) \ do { \ CLR((tp)->t_flags, TF_TIMER << (timer)); \ if (timeout_del(&(tp)->t_timer[(timer)])) \ in_pcbunref((tp)->t_inpcb); \ } while (0) #define TCP_TIMER_ISARMED(tp, timer) \ ISSET((tp)->t_flags, TF_TIMER << (timer)) /* * Force a time value to be in a certain range. */ #define TCPT_RANGESET(tv, value, tvmin, tvmax) \ do { \ (tv) = (value); \ if ((tv) < (tvmin)) \ (tv) = (tvmin); \ else if ((tv) > (tvmax)) \ (tv) = (tvmax); \ } while (/* CONSTCOND */ 0) #ifdef _KERNEL typedef void (*tcp_timer_func_t)(void *); extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS]; extern int tcp_delack_msecs; /* [I] delayed ACK timeout in millisecs */ extern int tcp_always_keepalive;/* [a] assume SO_KEEPALIVE always set */ extern int tcp_keepinit; /* [a] time to keep alive initial SYN packet */ extern int tcp_keepidle; /* [a] time before keepalive probes begin */ extern int tcp_keepintvl; /* [a] time between keepalive probes */ extern int tcp_keepinit_sec; /* [a] copy of above in seconds for sysctl */ extern int tcp_keepidle_sec; /* [a] copy of above in seconds for sysctl */ extern int tcp_keepintvl_sec; /* [a] copy of above in seconds for sysctl */ extern const int tcp_backoff[]; #endif /* _KERNEL */ #endif /* _NETINET_TCP_TIMER_H_ */
