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446ccdd08e
Use only one callout structure per tcpcb that is responsible for handling all five TCP timeouts. Use locked version of callout, of course. The callout function tcp_timer_enter() chooses soonest timer and executes it with lock held. Unless the timer reports that the tcpcb has been freed, the callout is rescheduled for next soonest timer, if there is any. With single callout per tcpcb on connection teardown we should be able to fully stop the callout and immediately free it, avoiding use of callout_async_drain(). There is one gotcha here: callout_stop() can actually touch our memory when a rare race condition happens. See comment above tcp_timer_stop(). Synchronous stop of the callout makes tcp_discardcb() the single entry point for tcpcb destructor, merging the tcp_freecb() to the end of the function. While here, also remove lots of lingering checks in the beginning of TCP timer functions. With a locked callout they are unnecessary. While here, clean unused parts of timer KPI for the pluggable TCP stacks. While here, remove TCPDEBUG from tcp_timer.c, as this allows for more simplification of TCP timers. The TCPDEBUG is scheduled for removal. Move the DTrace probes in timers to the beginning of a function, where a tcpcb is always existing. Discussed with: rrs, tuexen, rscheff (the TCP part of the diff) Reviewed by: hselasky, kib, mav (the callout part) Differential revision: https://reviews.freebsd.org/D37321
198 lines
8.7 KiB
C
198 lines
8.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1982, 1986, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_timer.h 8.1 (Berkeley) 6/10/93
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* $FreeBSD$
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*/
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#ifndef _NETINET_TCP_TIMER_H_
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#define _NETINET_TCP_TIMER_H_
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/*
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* The TCPT_REXMT timer is used to force retransmissions.
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* The TCP has the TCPT_REXMT timer set whenever segments
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* have been sent for which ACKs are expected but not yet
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* received. If an ACK is received which advances tp->snd_una,
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* then the retransmit timer is cleared (if there are no more
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* outstanding segments) or reset to the base value (if there
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* are more ACKs expected). Whenever the retransmit timer goes off,
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* we retransmit one unacknowledged segment, and do a backoff
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* on the retransmit timer.
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*
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* The TCPT_PERSIST timer is used to keep window size information
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* flowing even if the window goes shut. If all previous transmissions
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* have been acknowledged (so that there are no retransmissions in progress),
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* and the window is too small to bother sending anything, then we start
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* the TCPT_PERSIST timer. When it expires, if the window is nonzero,
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* we go to transmit state. Otherwise, at intervals send a single byte
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* into the peer's window to force him to update our window information.
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* We do this at most as often as TCPT_PERSMIN time intervals,
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* but no more frequently than the current estimate of round-trip
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* packet time. The TCPT_PERSIST timer is cleared whenever we receive
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* a window update from the peer.
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*
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* The TCPT_KEEP timer is used to keep connections alive. If an
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* connection is idle (no segments received) for TCPTV_KEEP_INIT amount of time,
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* but not yet established, then we drop the connection. Once the connection
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* is established, if the connection is idle for TCPTV_KEEP_IDLE time
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* (and keepalives have been enabled on the socket), we begin to probe
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* the connection. We force the peer to send us a segment by sending:
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* <SEQ=SND.UNA-1><ACK=RCV.NXT><CTL=ACK>
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* This segment is (deliberately) outside the window, and should elicit
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* an ack segment in response from the peer. If, despite the TCPT_KEEP
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* initiated segments we cannot elicit a response from a peer in TCPT_MAXIDLE
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* amount of time probing, then we drop the connection.
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*/
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/*
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* Time constants.
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*/
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#define TCPTV_MSL ( 30*hz) /* max seg lifetime (hah!) */
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#define TCPTV_SRTTBASE 0 /* base roundtrip time;
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if 0, no idea yet */
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#define TCPTV_RTOBASE ( 1*hz) /* assumed RTO if no info */
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#define TCPTV_PERSMIN ( 5*hz) /* minimum persist interval */
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#define TCPTV_PERSMAX ( 60*hz) /* maximum persist interval */
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#define TCPTV_KEEP_INIT ( 75*hz) /* initial connect keepalive */
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#define TCPTV_KEEP_IDLE (120*60*hz) /* dflt time before probing */
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#define TCPTV_KEEPINTVL ( 75*hz) /* default probe interval */
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#define TCPTV_KEEPCNT 8 /* max probes before drop */
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#define TCPTV_MAXUNACKTIME 0 /* max time without making progress */
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#define TCPTV_FINWAIT2_TIMEOUT (60*hz) /* FIN_WAIT_2 timeout if no receiver */
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/*
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* Minimum retransmit timer is 3 ticks, for algorithmic stability.
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* TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with
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* the expected worst-case processing variances by the kernels
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* representing the end points. Such variances do not always show
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* up in the srtt because the timestamp is often calculated at
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* the interface rather then at the TCP layer. This value is
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* typically 50ms. However, it is also possible that delayed
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* acks (typically 100ms) could create issues so we set the slop
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* to 200ms to try to cover it. Note that, properly speaking,
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* delayed-acks should not create a major issue for interactive
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* environments which 'P'ush the last segment, at least as
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* long as implementations do the required 'at least one ack
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* for every two packets' for the non-interactive streaming case.
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* (maybe the RTO calculation should use 2*RTT instead of RTT
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* to handle the ack-every-other-packet case).
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*
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* The prior minimum of 1*hz (1 second) badly breaks throughput on any
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* networks faster then a modem that has minor (e.g. 1%) packet loss.
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*/
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#define TCPTV_MIN ( hz/33 ) /* minimum allowable value */
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#define TCPTV_CPU_VAR ( hz/5 ) /* cpu variance allowed (200ms) */
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#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */
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#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */
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#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
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#define TCPTV_DELACK ( hz/25 ) /* 40ms timeout */
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/*
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* If we exceed this number of retransmits for a single segment, we'll consider
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* the current srtt measurement no longer valid and will recalculate from
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* scratch starting with the next ACK.
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*/
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#define TCP_RTT_INVALIDATE (TCP_MAXRXTSHIFT / 4)
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#ifdef TCPTIMERS
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static const char *tcptimers[] =
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{ "REXMT", "PERSIST", "KEEP", "2MSL", "DELACK" };
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#endif
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/*
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* Force a time value to be in a certain range.
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*/
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#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
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(tv) = (value) + tcp_rexmit_slop; \
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if ((u_long)(tv) < (u_long)(tvmin)) \
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(tv) = (tvmin); \
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if ((u_long)(tv) > (u_long)(tvmax)) \
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(tv) = (tvmax); \
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} while(0)
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#ifdef _KERNEL
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#define TP_KEEPINIT(tp) ((tp)->t_keepinit ? (tp)->t_keepinit : tcp_keepinit)
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#define TP_KEEPIDLE(tp) ((tp)->t_keepidle ? (tp)->t_keepidle : tcp_keepidle)
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#define TP_KEEPINTVL(tp) ((tp)->t_keepintvl ? (tp)->t_keepintvl : tcp_keepintvl)
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#define TP_KEEPCNT(tp) ((tp)->t_keepcnt ? (tp)->t_keepcnt : tcp_keepcnt)
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#define TP_MAXIDLE(tp) (TP_KEEPCNT(tp) * TP_KEEPINTVL(tp))
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#define TP_MAXUNACKTIME(tp) \
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((tp)->t_maxunacktime ? (tp)->t_maxunacktime : tcp_maxunacktime)
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/*
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* Obtain the time until the restransmit timer should fire.
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* This macro ensures the restransmit timer fires at the earlier of the
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* t_rxtcur value or the time the maxunacktime would be exceeded.
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*/
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#define TP_RXTCUR(tp) \
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((TP_MAXUNACKTIME(tp) == 0 || tp->t_acktime == 0) ? tp->t_rxtcur : \
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max(1, min(tp->t_rxtcur, tp->t_acktime + TP_MAXUNACKTIME(tp) - ticks)))
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extern int tcp_persmin; /* minimum persist interval */
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extern int tcp_persmax; /* maximum persist interval */
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extern int tcp_keepinit; /* time to establish connection */
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extern int tcp_keepidle; /* time before keepalive probes begin */
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extern int tcp_keepintvl; /* time between keepalive probes */
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extern int tcp_keepcnt; /* number of keepalives */
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extern int tcp_delacktime; /* time before sending a delayed ACK */
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extern int tcp_maxunacktime; /* max time without making progress */
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extern int tcp_maxpersistidle;
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extern int tcp_rexmit_initial;
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extern int tcp_rexmit_min;
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extern int tcp_rexmit_slop;
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extern int tcp_ttl; /* time to live for TCP segs */
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extern int tcp_backoff[];
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extern int tcp_totbackoff;
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extern int tcp_rexmit_drop_options;
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extern int tcp_finwait2_timeout;
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extern int tcp_fast_finwait2_recycle;
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VNET_DECLARE(int, tcp_always_keepalive);
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#define V_tcp_always_keepalive VNET(tcp_always_keepalive)
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VNET_DECLARE(int, tcp_pmtud_blackhole_detect);
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#define V_tcp_pmtud_blackhole_detect VNET(tcp_pmtud_blackhole_detect)
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VNET_DECLARE(int, tcp_pmtud_blackhole_mss);
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#define V_tcp_pmtud_blackhole_mss VNET(tcp_pmtud_blackhole_mss)
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VNET_DECLARE(int, tcp_v6pmtud_blackhole_mss);
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#define V_tcp_v6pmtud_blackhole_mss VNET(tcp_v6pmtud_blackhole_mss)
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VNET_DECLARE(int, tcp_msl);
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#define V_tcp_msl VNET(tcp_msl)
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#endif /* _KERNEL */
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#endif /* !_NETINET_TCP_TIMER_H_ */
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