c4a184bdc4
be in ticks "for algorithm stability" when originally committed, it turns out that it has a significant impact in timing out connections. When we changed HZ from 100 to 1000, this had a big effect on reducing the time before dropping connections. To demonstrate, boot with kern.hz=100. ssh to a box on local ethernet and establish a reliable round-trip-time (ie: type a few commands). Then unplug the ethernet and press a key. Time how long it takes to drop the connection. The old behavior (with hz=100) caused the connection to typically drop between 90 and 110 seconds of getting no response. Now boot with kern.hz=1000 (default). The same test causes the ssh session to drop after just 9-10 seconds. This is a big deal on a wifi connection. With kern.hz=1000, change sysctl net.inet.tcp.rexmit_min from 3 to 30. Note how it behaves the same as when HZ was 100. Also, note that when booting with hz=100, net.inet.tcp.rexmit_min *used* to be 30. This commit changes TCPTV_MIN to be scaled with hz. rexmit_min should always be about 30. If you set hz to Really Slow(TM), there is a safety feature to prevent a value of 0 being used. This may be revised in the future, but for the time being, it restores the old, pre-hz=1000 behavior, which is significantly less annoying. As a workaround, to avoid rebooting or rebuilding a kernel, you can run "sysctl net.inet.tcp.rexmit_min=30" and add "net.inet.tcp.rexmit_min=30" to /etc/sysctl.conf. This is safe to run from 6.0 onwards. Approved by: re (rwatson) Reviewed by: andre, silby
182 lines
7.5 KiB
C
182 lines
7.5 KiB
C
/*-
|
|
* 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.
|
|
* 4. 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 ( 3*hz) /* assumed RTO if no info */
|
|
#define TCPTV_SRTTDFLT ( 3*hz) /* assumed RTT if no info */
|
|
|
|
#define TCPTV_PERSMIN ( 5*hz) /* retransmit persistence */
|
|
#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_INFLIGHT_RTTTHRESH (10*hz/1000) /* below which inflight
|
|
disengages, in msec */
|
|
|
|
#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_LINGERTIME 120 /* linger at most 2 minutes */
|
|
|
|
#define TCP_MAXRXTSHIFT 12 /* maximum retransmits */
|
|
|
|
#define TCPTV_DELACK (hz / PR_FASTHZ / 2) /* 100ms timeout */
|
|
|
|
#ifdef TCPTIMERS
|
|
static const char *tcptimers[] =
|
|
{ "REXMT", "PERSIST", "KEEP", "2MSL" };
|
|
#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 tcp_timer {
|
|
struct callout tt_timer;
|
|
int tt_nextc; /* next callout time in time_uptime */
|
|
int tt_active; /* engaged callouts */
|
|
#define TT_DELACK 0x01
|
|
#define TT_REXMT 0x02
|
|
#define TT_PERSIST 0x04
|
|
#define TT_KEEP 0x08
|
|
#define TT_2MSL 0x10
|
|
int tt_delack;
|
|
int tt_rexmt;
|
|
int tt_persist;
|
|
int tt_keep;
|
|
int tt_2msl;
|
|
};
|
|
|
|
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_maxidle; /* time to drop after starting probes */
|
|
extern int tcp_delacktime; /* time before sending a delayed ACK */
|
|
extern int tcp_maxpersistidle;
|
|
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_finwait2_timeout;
|
|
extern int tcp_fast_finwait2_recycle;
|
|
|
|
void tcp_timer_init(void);
|
|
struct tcptw *
|
|
tcp_tw_2msl_scan(int _reuse); /* XXX temporary */
|
|
|
|
#endif /* _KERNEL */
|
|
|
|
#endif /* !_NETINET_TCP_TIMER_H_ */
|