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Add sysctl variable net.inet.tcp.rexmit_initial for setting RTO.Initial

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used by TCP.

Reviewed by:		rrs@, 0mp@
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D19355
This commit is contained in:
Michael Tuexen 2019-03-23 21:36:59 +00:00
parent 557e162fe7
commit 0999766ddf
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=345458
5 changed files with 22 additions and 11 deletions
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5
share/man/man4/tcp.4
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@ -34,7 +34,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd August 6, 2018
.Dd March 23, 2019
.Dt TCP 4
.Os
.Sh NAME
@ -459,7 +459,7 @@ The actual limit applied to a session's reassembly queue will be the lower of
the system-calculated automatic limit and the user-specified
.Va reass.maxqueuelen
limit.
.It Va rexmit_min , rexmit_slop
.It Va rexmit_initial , rexmit_min , rexmit_slop
Adjust the retransmit timer calculation for
.Tn TCP .
The slop is
@ -481,6 +481,7 @@ code.
For this reason, we use 200ms of slop and a near-0
minimum, which gives us an effective minimum of 200ms (similar to
.Tn Linux ) .
The initial value is used before an RTT measurement has been performed.
.It Va initcwnd_segments
Enable the ability to specify initial congestion window in number of segments.
The default value is 10 as suggested by RFC 6928.

7
sys/netinet/tcp_subr.c
View File

@ -1065,6 +1065,9 @@ tcp_init(void)
tcp_keepintvl = TCPTV_KEEPINTVL;
tcp_maxpersistidle = TCPTV_KEEP_IDLE;
tcp_msl = TCPTV_MSL;
tcp_rexmit_initial = TCPTV_RTOBASE;
if (tcp_rexmit_initial < 1)
tcp_rexmit_initial = 1;
tcp_rexmit_min = TCPTV_MIN;
if (tcp_rexmit_min < 1)
tcp_rexmit_min = 1;
@ -1645,9 +1648,9 @@ tcp_newtcpcb(struct inpcb *inp)
* reasonable initial retransmit time.
*/
tp->t_srtt = TCPTV_SRTTBASE;
tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
tp->t_rttvar = ((tcp_rexmit_initial - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
tp->t_rttmin = tcp_rexmit_min;
tp->t_rxtcur = TCPTV_RTOBASE;
tp->t_rxtcur = tcp_rexmit_initial;
tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
tp->t_rcvtime = ticks;

13
sys/netinet/tcp_syncache.c
View File

@ -155,10 +155,10 @@ static int syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
/*
* Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
* 3 retransmits corresponds to a timeout with default values of
* TCPTV_RTOBASE * ( 1 +
* tcp_backoff[1] +
* tcp_backoff[2] +
* tcp_backoff[3]) + 3 * tcp_rexmit_slop,
* tcp_rexmit_initial * ( 1 +
* tcp_backoff[1] +
* tcp_backoff[2] +
* tcp_backoff[3]) + 3 * tcp_rexmit_slop,
* 1000 ms * (1 + 2 + 4 + 8) + 3 * 200 ms = 15600 ms,
* the odds are that the user has given up attempting to connect by then.
*/
@ -424,9 +424,10 @@ syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
int rexmt;
if (sc->sc_rxmits == 0)
rexmt = TCPTV_RTOBASE;
rexmt = tcp_rexmit_initial;
else
TCPT_RANGESET(rexmt, TCPTV_RTOBASE * tcp_backoff[sc->sc_rxmits],
TCPT_RANGESET(rexmt,
tcp_rexmit_initial * tcp_backoff[sc->sc_rxmits],
tcp_rexmit_min, TCPTV_REXMTMAX);
sc->sc_rxttime = ticks + rexmt;
sc->sc_rxmits++;

7
sys/netinet/tcp_timer.c
View File

@ -110,6 +110,11 @@ int tcp_msl;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
int tcp_rexmit_initial;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I",
"Initial Retransmission Timeout");
int tcp_rexmit_min;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
@ -668,7 +673,7 @@ tcp_timer_rexmt(void * xtp)
TCPSTAT_INC(tcps_rexmttimeo);
if ((tp->t_state == TCPS_SYN_SENT) ||
(tp->t_state == TCPS_SYN_RECEIVED))
rexmt = TCPTV_RTOBASE * tcp_backoff[tp->t_rxtshift];
rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift];
else
rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
TCPT_RANGESET(tp->t_rxtcur, rexmt,

1
sys/netinet/tcp_timer.h
View File

@ -194,6 +194,7 @@ 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;