/*-
* 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:
* <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 ( 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);
void tcp_timer_discard(void *);
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_ */
