rtt.c File Reference

This file contains a data type and functions to help estimate good round trip times for UDP resend timeout values. More...

#include "config.h"
#include "util/rtt.h"
#include "iterator/iterator.h"

Functions
static int	calc_rto (const struct rtt_info *rtt)
	calculate RTO from rtt information
void	rtt_init (struct rtt_info *rtt)
	Initialize RTT estimators.
int	rtt_timeout (const struct rtt_info *rtt)
	Get timeout to use for sending a UDP packet.
int	rtt_unclamped (const struct rtt_info *rtt)
	Get unclamped timeout to use for server selection.
void	rtt_update (struct rtt_info *rtt, int ms)
	Update the statistics with a new roundtrip estimate observation.
void	rtt_lost (struct rtt_info *rtt, int orig)
	Update the statistics with a new timeout expired observation.
int	rtt_notimeout (const struct rtt_info *rtt)
	RTT for valid responses.

Variables
int	RTT_MIN_TIMEOUT = 50
	min retransmit timeout value, in milliseconds
int	RTT_MAX_TIMEOUT = 120000
	max retransmit timeout value, in milliseconds

Detailed Description

This file contains a data type and functions to help estimate good round trip times for UDP resend timeout values.

Function Documentation

rtt_init()

void rtt_init

(

struct rtt_info *

rtt

)

Initialize RTT estimators.

Parameters

rtt	The structure. Caller is responsible for allocation of it.

References calc_rto(), rtt_info::rto, rtt_info::rttvar, rtt_info::srtt, and UNKNOWN_SERVER_NICENESS.

Referenced by data_entry_init(), infra_del_host(), infra_rtt_update(), and rtt_test().

rtt_timeout()

int rtt_timeout

(

const struct rtt_info *

rtt

)

Get timeout to use for sending a UDP packet.

Parameters

rtt	round trip statistics structure.

Returns

: timeout to use in milliseconds. Relative time value.

References rtt_info::rto.

Referenced by infra_host(), and rtt_test().

rtt_unclamped()

int rtt_unclamped

(

const struct rtt_info *

rtt

)

Get unclamped timeout to use for server selection.

Recent timeouts are reflected in the returned value.

Parameters

rtt	round trip statistics structure.

Returns

: value to use in milliseconds.

References calc_rto(), rtt_info::rto, rtt_info::rttvar, and rtt_info::srtt.

Referenced by infra_get_lame_rtt(), and infra_rtt_update().

rtt_update()

void rtt_update	(	struct rtt_info *	rtt,
		int	ms
	)

Update the statistics with a new roundtrip estimate observation.

Parameters

rtt	round trip statistics structure.
ms	estimate of roundtrip time in milliseconds.

References calc_rto(), rtt_info::rto, rtt_info::rttvar, and rtt_info::srtt.

Referenced by infra_rtt_update(), and rtt_test().

rtt_lost()

void rtt_lost	(	struct rtt_info *	rtt,
		int	orig
	)

Update the statistics with a new timeout expired observation.

Parameters

rtt	round trip statistics structure.
orig	original rtt time given for the query that timed out. Used to calculate the maximum responsible backed off time that can reasonably be applied.

References rtt_info::rto, and RTT_MAX_TIMEOUT.

Referenced by infra_rtt_update(), and rtt_test().

rtt_notimeout()

int rtt_notimeout

(

const struct rtt_info *

rtt

)

RTT for valid responses.

Without timeouts.

Parameters

rtt	round trip statistics structure.

Returns

: value in msec.

References calc_rto().

Referenced by dump_infra_host(), infra_get_lame_rtt(), infra_host(), and print_dp_details().