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sourcestats: move maxdelaydevratio test to ntp_core

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Instead of giving NTP-specific data to sourcestats in order to perform
the test, provide a function to get all data needed for the test in
ntp_core. While at it, improve the naming of variables.
This commit is contained in:
Miroslav Lichvar 2017-08-25 12:29:13 +02:00
parent 7ffee73524
commit 51fe80ad95
3 changed files with 53 additions and 35 deletions
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40
ntp_core.c
View file

@ -1325,6 +1325,43 @@ check_packet_auth(NTP_Packet *pkt, int length,
/* ================================================== */
static int
check_delay_dev_ratio(NCR_Instance inst, SST_Stats stats,
struct timespec *sample_time, double offset, double delay)
{
double last_sample_ago, predicted_offset, min_delay, skew, std_dev;
double delta, max_delta, error_in_estimate;
if (!SST_GetDelayTestData(stats, sample_time, &last_sample_ago,
&predicted_offset, &min_delay, &skew, &std_dev))
return 1;
/* Require that the ratio of the increase in delay from the minimum to the
standard deviation is less than max_delay_dev_ratio. In the allowed
increase in delay include also dispersion. */
max_delta = std_dev * inst->max_delay_dev_ratio +
last_sample_ago * (skew + LCL_GetMaxClockError());
delta = (delay - min_delay) / 2.0;
if (delta <= max_delta)
return 1;
error_in_estimate = offset + predicted_offset;
/* Before we decide to drop the sample, make sure the difference between
measured offset and predicted offset is not significantly larger than
the increase in delay */
if (fabs(error_in_estimate) - delta > max_delta)
return 1;
DEBUG_LOG("maxdelaydevratio: error=%e delay=%e delta=%e max_delta=%e",
error_in_estimate, delay, delta, max_delta);
return 0;
}
/* ================================================== */
static int
receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
NTP_Local_Timestamp *rx_ts, NTP_Packet *message, int length)
@ -1554,8 +1591,7 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
in the register is less than an administrator-defined value or the
difference between measured offset and predicted offset is larger than
the increase in delay */
testC = SST_IsGoodSample(stats, -offset, delay, inst->max_delay_dev_ratio,
LCL_GetMaxClockError(), &sample_time);
testC = check_delay_dev_ratio(inst, stats, &sample_time, offset, delay);
/* Test D requires that the remote peer is not synchronised to us to
prevent a synchronisation loop */

42
sourcestats.c
View file

@ -813,39 +813,21 @@ SST_MinRoundTripDelay(SST_Stats inst)
/* ================================================== */
int
SST_IsGoodSample(SST_Stats inst, double offset, double delay,
double max_delay_dev_ratio, double clock_error, struct timespec *when)
SST_GetDelayTestData(SST_Stats inst, struct timespec *sample_time,
double *last_sample_ago, double *predicted_offset,
double *min_delay, double *skew, double *std_dev)
{
double elapsed, allowed_increase, delay_increase;
if (inst->n_samples < 6)
return 1;
elapsed = UTI_DiffTimespecsToDouble(when, &inst->offset_time);
/* Require that the ratio of the increase in delay from the minimum to the
standard deviation is less than max_delay_dev_ratio. In the allowed
increase in delay include also skew and clock_error. */
allowed_increase = inst->std_dev * max_delay_dev_ratio +
elapsed * (inst->skew + clock_error);
delay_increase = (delay - SST_MinRoundTripDelay(inst)) / 2.0;
if (delay_increase < allowed_increase)
return 1;
offset -= inst->estimated_offset + elapsed * inst->estimated_frequency;
/* Before we decide to drop the sample, make sure the difference between
measured offset and predicted offset is not significantly larger than
the increase in delay */
if (fabs(offset) - delay_increase > allowed_increase)
return 1;
DEBUG_LOG("Bad sample: offset=%f delay=%f incr_delay=%f allowed=%f",
offset, delay, delay_increase, allowed_increase);
return 0;
*last_sample_ago = UTI_DiffTimespecsToDouble(sample_time, &inst->offset_time);
*predicted_offset = inst->estimated_offset +
*last_sample_ago * inst->estimated_frequency;
*min_delay = SST_MinRoundTripDelay(inst);
*skew = inst->skew;
*std_dev = inst->std_dev;
return 1;
}
/* ================================================== */

8
sourcestats.h
View file

@ -126,10 +126,10 @@ extern double SST_PredictOffset(SST_Stats inst, struct timespec *when);
/* Find the minimum round trip delay in the register */
extern double SST_MinRoundTripDelay(SST_Stats inst);
/* This routine determines if a new sample is good enough that it should be
accumulated */
extern int SST_IsGoodSample(SST_Stats inst, double offset, double delay,
double max_delay_dev_ratio, double clock_error, struct timespec *when);
/* Get data needed for testing NTP delay */
extern int SST_GetDelayTestData(SST_Stats inst, struct timespec *sample_time,
double *last_sample_ago, double *predicted_offset,
double *min_delay, double *skew, double *std_dev);
extern void SST_SaveToFile(SST_Stats inst, FILE *out);