/*- * SPDX-License-Identifier: BSD-3-Clause * * 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. */ #ifndef _NETINET_TCP_TIMER_H_ #define _NETINET_TCP_TIMER_H_ #ifdef _KERNEL /* * 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 MSEC_2_TICKS(30000) /* max seg lifetime (hah!) */ #define TCPTV_MSL_LOCAL MSEC_2_TICKS(10) /* max seg lifetime for local comm */ #define TCPTV_SRTTBASE 0 /* base roundtrip time; if 0, no idea yet */ #define TCPTV_RTOBASE MSEC_2_TICKS(1000) /* assumed RTO if no info */ #define TCPTV_PERSMIN MSEC_2_TICKS(5000) /* minimum persist interval */ #define TCPTV_PERSMAX MSEC_2_TICKS(60000) /* maximum persist interval */ #define TCPTV_KEEP_INIT MSEC_2_TICKS(75000) /* initial connect keepalive */ #define TCPTV_KEEP_IDLE MSEC_2_TICKS(120*60*1000) /* dflt time before probing */ #define TCPTV_KEEPINTVL MSEC_2_TICKS(75000) /* default probe interval */ #define TCPTV_KEEPCNT 8 /* max probes before drop */ #define TCPTV_MAXUNACKTIME 0 /* max time without making progress */ #define TCPTV_FINWAIT2_TIMEOUT MSEC_2_TICKS(60000) /* FIN_WAIT_2 timeout if no receiver */ /* * Minimum retransmit timer is 3 ticks, for algorithmic stability. * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with * the expected worst-case processing variances by the kernels * representing the end points. Such variances do not always show * up in the srtt because the timestamp is often calculated at * the interface rather then at the TCP layer. This value is * typically 50ms. However, it is also possible that delayed * acks (typically 100ms) could create issues so we set the slop * to 200ms to try to cover it. Note that, properly speaking, * delayed-acks should not create a major issue for interactive * environments which 'P'ush the last segment, at least as * long as implementations do the required 'at least one ack * for every two packets' for the non-interactive streaming case. * (maybe the RTO calculation should use 2*RTT instead of RTT * to handle the ack-every-other-packet case). * * The prior minimum of 1*hz (1 second) badly breaks throughput on any * networks faster then a modem that has minor (e.g. 1%) packet loss. */ #define TCPTV_MIN MSEC_2_TICKS(30) /* minimum allowable value */ #define TCPTV_CPU_VAR MSEC_2_TICKS(200) /* cpu variance allowed (200ms) */ #define TCPTV_REXMTMAX MSEC_2_TICKS(64000) /* max allowable REXMT value */ #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ #define TCPTV_DELACK MSEC_2_TICKS(40) /* 40ms timeout */ /* * If we exceed this number of retransmits for a single segment, we'll consider * the current srtt measurement no longer valid and will recalculate from * scratch starting with the next ACK. */ #define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4) /* * Force a time value to be in a certain range. */ #define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \ (tv) = (value) + tcp_rexmit_slop; \ if ((u_long)(tv) < (u_long)(tvmin)) \ (tv) = (tvmin); \ if ((u_long)(tv) > (u_long)(tvmax)) \ (tv) = (tvmax); \ } while(0) #define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit) #define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle) #define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl) #define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt) #define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp)) #define TP_MAXUNACKTIME(tp) \ ((tp)->t_maxunacktime ? (tp)->t_maxunacktime : tcp_maxunacktime) /* * Obtain the time until the restransmit timer should fire. * This macro ensures the restransmit timer fires at the earlier of the * t_rxtcur value or the time the maxunacktime would be exceeded. */ #define TP_RXTCUR(tp) \ ((TP_MAXUNACKTIME(tp) == 0 || tp->t_acktime == 0) ? tp->t_rxtcur : \ max(1, min(tp->t_rxtcur, tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks))) extern int tcp_persmin; /* minimum persist interval */ extern int tcp_persmax; /* maximum persist interval */ extern int tcp_keepinit; /* time to establish connection */ extern int tcp_keepidle; /* time before keepalive probes begin */ extern int tcp_keepintvl; /* time between keepalive probes */ extern int tcp_keepcnt; /* number of keepalives */ extern int tcp_delacktime; /* time before sending a delayed ACK */ extern int tcp_maxunacktime; /* max time without making progress */ extern int tcp_maxpersistidle; extern int tcp_rexmit_initial; extern int tcp_rexmit_min; extern int tcp_rexmit_max; extern int tcp_rexmit_slop; extern int tcp_ttl; /* time to live for TCP segs */ extern int tcp_backoff[]; extern int tcp_totbackoff; extern int tcp_rexmit_drop_options; extern int tcp_finwait2_timeout; extern int tcp_fast_finwait2_recycle; VNET_DECLARE(int, tcp_always_keepalive); #define V_tcp_always_keepalive VNET(tcp_always_keepalive) VNET_DECLARE(int, tcp_pmtud_blackhole_detect); #define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect) VNET_DECLARE(int, tcp_pmtud_blackhole_mss); #define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss) VNET_DECLARE(int, tcp_v6pmtud_blackhole_mss); #define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss) VNET_DECLARE(int, tcp_msl); #define V_tcp_msl VNET(tcp_msl) VNET_DECLARE(int, tcp_msl_local); #define V_tcp_msl_local VNET(tcp_msl_local) #endif /* _KERNEL */ #endif /* !_NETINET_TCP_TIMER_H_ */
