/*- * 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. * * @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93 * $FreeBSD$ */ #ifndef _NETINET_TCP_TIMER_H_ #define _NETINET_TCP_TIMER_H_ /* * 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: * * 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 ( 30*hz) /* max seg lifetime (hah!) */ #define TCPTV_SRTTBASE 0 /* base roundtrip time; if 0, no idea yet */ #define TCPTV_RTOBASE ( 1*hz) /* assumed RTO if no info */ #define TCPTV_PERSMIN ( 5*hz) /* minimum persist interval */ #define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */ #define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */ #define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */ #define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */ #define TCPTV_KEEPCNT 8 /* max probes before drop */ #define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* 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 ( hz/33 ) /* minimum allowable value */ #define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */ #define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */ #define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */ #define TCP_MAXRXTSHIFT 12 /* maximum retransmits */ #define TCPTV_DELACK ( hz/25 ) /* 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) #ifdef TCPTIMERS static const char *tcptimers[] = { "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" }; #endif /* * 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) #ifdef _KERNEL struct xtcp_timer; struct tcp_timer { struct callout tt_rexmt; /* retransmit timer */ struct callout tt_persist; /* retransmit persistence */ struct callout tt_keep; /* keepalive */ struct callout tt_2msl; /* 2*msl TIME_WAIT timer */ struct callout tt_delack; /* delayed ACK timer */ uint32_t tt_flags; /* Timers flags */ uint32_t tt_draincnt; /* Count being drained */ }; /* * Flags for the tt_flags field. */ #define TT_DELACK 0x0001 #define TT_REXMT 0x0002 #define TT_PERSIST 0x0004 #define TT_KEEP 0x0008 #define TT_2MSL 0x0010 #define TT_MASK (TT_DELACK|TT_REXMT|TT_PERSIST|TT_KEEP|TT_2MSL) /* * Suspend flags - used when suspending a timer * from ever running again. */ #define TT_DELACK_SUS 0x0100 #define TT_REXMT_SUS 0x0200 #define TT_PERSIST_SUS 0x0400 #define TT_KEEP_SUS 0x0800 #define TT_2MSL_SUS 0x1000 #define TT_STOPPED 0x00010000 #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)) 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_maxpersistidle; extern int tcp_rexmit_initial; extern int tcp_rexmit_min; extern int tcp_rexmit_slop; extern int tcp_msl; 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) void tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp); void tcp_timer_init(void); void tcp_timer_2msl(void *xtp); struct tcptw * tcp_tw_2msl_scan(int reuse); /* XXX temporary? */ void tcp_timer_keep(void *xtp); void tcp_timer_persist(void *xtp); void tcp_timer_rexmt(void *xtp); void tcp_timer_delack(void *xtp); #endif /* _KERNEL */ #endif /* !_NETINET_TCP_TIMER_H_ */