From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Mon, 18 Nov 2024 15:18:40 +0000 (+0100)
Subject: ntp+hwclock: add margin to estimated delay quantiles
X-Git-Tag: 4.7-pre1~69
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c92358e0413a9fcaddb66822eb5b09e2e4089b76;p=thirdparty%2Fchrony.git

ntp+hwclock: add margin to estimated delay quantiles

Extend the interval of accepted delays by half of the quantile minimum
step in both directions to make room for floating-point errors in the
quantile calculation and an error that will be intentionally added in
the next commit.
---

diff --git a/hwclock.c b/hwclock.c
index c662dae3..e2f72e7a 100644
--- a/hwclock.c
+++ b/hwclock.c
@@ -199,8 +199,10 @@ HCL_ProcessReadings(HCL_Instance clock, int n_readings, struct timespec tss[][3]
 
   local_prec = LCL_GetSysPrecisionAsQuantum();
 
-  low_delay = QNT_GetQuantile(clock->delay_quants, QNT_GetMinK(clock->delay_quants));
-  high_delay = QNT_GetQuantile(clock->delay_quants, QNT_GetMaxK(clock->delay_quants));
+  low_delay = QNT_GetQuantile(clock->delay_quants, QNT_GetMinK(clock->delay_quants)) -
+              QNT_GetMinStep(clock->delay_quants) / 2.0;
+  high_delay = QNT_GetQuantile(clock->delay_quants, QNT_GetMaxK(clock->delay_quants)) +
+               QNT_GetMinStep(clock->delay_quants) / 2.0;
   low_delay = MIN(low_delay, high_delay);
   high_delay = MAX(high_delay, low_delay + local_prec);
 
diff --git a/ntp_core.c b/ntp_core.c
index 29654138..e802e183 100644
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -1742,7 +1742,7 @@ check_delay_quant(NCR_Instance inst, double delay)
 
   quant = QNT_GetQuantile(inst->delay_quant, QNT_GetMinK(inst->delay_quant));
 
-  if (delay <= quant)
+  if (delay <= quant + QNT_GetMinStep(inst->delay_quant) / 2.0)
     return 1;
 
   DEBUG_LOG("maxdelayquant: delay=%e quant=%e", delay, quant);