tcp_timer.h revision 287304
177298Sobrien/*- 277298Sobrien * Copyright (c) 1982, 1986, 1993 378828Sobrien * The Regents of the University of California. All rights reserved. 477298Sobrien * 577298Sobrien * Redistribution and use in source and binary forms, with or without 677298Sobrien * modification, are permitted provided that the following conditions 777298Sobrien * are met: 877298Sobrien * 1. Redistributions of source code must retain the above copyright 977298Sobrien * notice, this list of conditions and the following disclaimer. 1077298Sobrien * 2. Redistributions in binary form must reproduce the above copyright 1177298Sobrien * notice, this list of conditions and the following disclaimer in the 1277298Sobrien * documentation and/or other materials provided with the distribution. 1377298Sobrien * 4. Neither the name of the University nor the names of its contributors 1477298Sobrien * may be used to endorse or promote products derived from this software 1577298Sobrien * without specific prior written permission. 1677298Sobrien * 1777298Sobrien * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 1877298Sobrien * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19218822Sdim * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 2077298Sobrien * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 2177298Sobrien * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 2277298Sobrien * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 2377298Sobrien * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 2477298Sobrien * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 2577298Sobrien * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 2677298Sobrien * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 2777298Sobrien * SUCH DAMAGE. 2877298Sobrien * 2977298Sobrien * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 30218822Sdim * $FreeBSD: head/sys/netinet/tcp_timer.h 287304 2015-08-30 13:44:39Z jch $ 31218822Sdim */ 3277298Sobrien 3377298Sobrien#ifndef _NETINET_TCP_TIMER_H_ 3477298Sobrien#define _NETINET_TCP_TIMER_H_ 3577298Sobrien 3677298Sobrien/* 3777298Sobrien * The TCPT_REXMT timer is used to force retransmissions. 3877298Sobrien * The TCP has the TCPT_REXMT timer set whenever segments 3977298Sobrien * have been sent for which ACKs are expected but not yet 4077298Sobrien * received. If an ACK is received which advances tp->snd_una, 4177298Sobrien * then the retransmit timer is cleared (if there are no more 42218822Sdim * outstanding segments) or reset to the base value (if there 4377298Sobrien * are more ACKs expected). Whenever the retransmit timer goes off, 4477298Sobrien * we retransmit one unacknowledged segment, and do a backoff 4577298Sobrien * on the retransmit timer. 4677298Sobrien * 4777298Sobrien * The TCPT_PERSIST timer is used to keep window size information 4877298Sobrien * flowing even if the window goes shut. If all previous transmissions 4977298Sobrien * have been acknowledged (so that there are no retransmissions in progress), 5077298Sobrien * and the window is too small to bother sending anything, then we start 5177298Sobrien * the TCPT_PERSIST timer. When it expires, if the window is nonzero, 5277298Sobrien * we go to transmit state. Otherwise, at intervals send a single byte 5377298Sobrien * into the peer's window to force him to update our window information. 5477298Sobrien * We do this at most as often as TCPT_PERSMIN time intervals, 5577298Sobrien * but no more frequently than the current estimate of round-trip 5677298Sobrien * packet time. The TCPT_PERSIST timer is cleared whenever we receive 5777298Sobrien * a window update from the peer. 5877298Sobrien * 5977298Sobrien * The TCPT_KEEP timer is used to keep connections alive. If an 6077298Sobrien * connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time, 6177298Sobrien * but not yet established, then we drop the connection. Once the connection 6277298Sobrien * is established, if the connection is idle for TCPTV_KEEP_IDLE time 6377298Sobrien * (and keepalives have been enabled on the socket), we begin to probe 6477298Sobrien * the connection. We force the peer to send us a segment by sending: 6577298Sobrien * <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK> 6677298Sobrien * This segment is (deliberately) outside the window, and should elicit 6777298Sobrien * an ack segment in response from the peer. If, despite the TCPT_KEEP 6877298Sobrien * initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE 6977298Sobrien * amount of time probing, then we drop the connection. 70218822Sdim */ 71218822Sdim 72218822Sdim/* 7377298Sobrien * Time constants. 7477298Sobrien */ 7577298Sobrien#define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */ 7677298Sobrien#define TCPTV_SRTTBASE 0 /* base roundtrip time; 7777298Sobrien if 0, no idea yet */ 7877298Sobrien#define TCPTV_RTOBASE ( 3*hz) /* assumed RTO if no info */ 7977298Sobrien 8077298Sobrien#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */ 8177298Sobrien#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ 8277298Sobrien 8377298Sobrien#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ 8477298Sobrien#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ 85218822Sdim#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ 8677298Sobrien#define TCPTV_KEEPCNT 8 /* max probes before drop */ 8777298Sobrien 8877298Sobrien#define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */ 8977298Sobrien 9077298Sobrien/* 9177298Sobrien * Minimum retransmit timer is 3 ticks, for algorithmic stability. 9277298Sobrien * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with 9377298Sobrien * the expected worst-case processing variances by the kernels 9477298Sobrien * representing the end points. Such variances do not always show 95218822Sdim * up in the srtt because the timestamp is often calculated at 9677298Sobrien * the interface rather then at the TCP layer. This value is 9777298Sobrien * typically 50ms. However, it is also possible that delayed 9877298Sobrien * acks (typically 100ms) could create issues so we set the slop 9977298Sobrien * to 200ms to try to cover it. Note that, properly speaking, 10077298Sobrien * delayed-acks should not create a major issue for interactive 101218822Sdim * environments which 'P'ush the last segment, at least as 102218822Sdim * long as implementations do the required 'at least one ack 10377298Sobrien * for every two packets' for the non-interactive streaming case. 10477298Sobrien * (maybe the RTO calculation should use 2*RTT instead of RTT 10577298Sobrien * to handle the ack-every-other-packet case). 10677298Sobrien * 10777298Sobrien * The prior minimum of 1*hz (1 second) badly breaks throughput on any 108218822Sdim * networks faster then a modem that has minor (e.g. 1%) packet loss. 109218822Sdim */ 11077298Sobrien#define TCPTV_MIN ( hz/33 ) /* minimum allowable value */ 11177298Sobrien#define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ 11277298Sobrien#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ 11377298Sobrien 11477298Sobrien#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ 11577298Sobrien 11677298Sobrien#define TCP_LINGERTIME 120 /* linger at most 2 minutes */ 11777298Sobrien 118218822Sdim#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ 11977298Sobrien 12077298Sobrien#define TCPTV_DELACK ( hz/10 ) /* 100ms timeout */ 12177298Sobrien 12277298Sobrien#ifdef TCPTIMERS 12377298Sobrienstatic const char *tcptimers[] = 12477298Sobrien { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; 12577298Sobrien#endif 12677298Sobrien 127218822Sdim/* 12877298Sobrien * Force a time value to be in a certain range. 12977298Sobrien */ 13077298Sobrien#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ 13177298Sobrien (tv) = (value) + tcp_rexmit_slop; \ 13277298Sobrien if ((u_long)(tv) < (u_long)(tvmin)) \ 133218822Sdim (tv) = (tvmin); \ 13477298Sobrien if ((u_long)(tv) > (u_long)(tvmax)) \ 13577298Sobrien (tv) = (tvmax); \ 13677298Sobrien} while(0) 13777298Sobrien 13877298Sobrien#ifdef _KERNEL 139218822Sdim 14077298Sobrienstruct xtcp_timer; 14177298Sobrien 142struct tcp_timer { 143 struct callout tt_rexmt; /* retransmit timer */ 144 struct callout tt_persist; /* retransmit persistence */ 145 struct callout tt_keep; /* keepalive */ 146 struct callout tt_2msl; /* 2*msl TIME_WAIT timer */ 147 struct callout tt_delack; /* delayed ACK timer */ 148 uint32_t tt_flags; /* Timers flags */ 149 uint32_t tt_spare; /* TDB */ 150}; 151 152/* 153 * Flags for the tt_flags field. 154 */ 155#define TT_DELACK 0x0001 156#define TT_REXMT 0x0002 157#define TT_PERSIST 0x0004 158#define TT_KEEP 0x0008 159#define TT_2MSL 0x0010 160#define TT_MASK (TT_DELACK|TT_REXMT|TT_PERSIST|TT_KEEP|TT_2MSL) 161 162#define TT_DELACK_RST 0x0100 163#define TT_REXMT_RST 0x0200 164#define TT_PERSIST_RST 0x0400 165#define TT_KEEP_RST 0x0800 166#define TT_2MSL_RST 0x1000 167 168#define TT_STOPPED 0x00010000 169 170#define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit) 171#define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle) 172#define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl) 173#define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt) 174#define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) 175 176extern int tcp_keepinit; /* time to establish connection */ 177extern int tcp_keepidle; /* time before keepalive probes begin */ 178extern int tcp_keepintvl; /* time between keepalive probes */ 179extern int tcp_keepcnt; /* number of keepalives */ 180extern int tcp_delacktime; /* time before sending a delayed ACK */ 181extern int tcp_maxpersistidle; 182extern int tcp_rexmit_min; 183extern int tcp_rexmit_slop; 184extern int tcp_msl; 185extern int tcp_ttl; /* time to live for TCP segs */ 186extern int tcp_backoff[]; 187extern int tcp_syn_backoff[]; 188 189extern int tcp_finwait2_timeout; 190extern int tcp_fast_finwait2_recycle; 191 192void tcp_timer_init(void); 193void tcp_timer_2msl(void *xtp); 194struct tcptw * 195 tcp_tw_2msl_scan(int reuse); /* XXX temporary? */ 196void tcp_timer_keep(void *xtp); 197void tcp_timer_persist(void *xtp); 198void tcp_timer_rexmt(void *xtp); 199void tcp_timer_delack(void *xtp); 200void tcp_timer_2msl_discard(void *xtp); 201void tcp_timer_keep_discard(void *xtp); 202void tcp_timer_persist_discard(void *xtp); 203void tcp_timer_rexmt_discard(void *xtp); 204void tcp_timer_delack_discard(void *xtp); 205void tcp_timer_to_xtimer(struct tcpcb *tp, struct tcp_timer *timer, 206 struct xtcp_timer *xtimer); 207 208#endif /* _KERNEL */ 209 210#endif /* !_NETINET_TCP_TIMER_H_ */ 211