From af611b5842a6d107d1668cd4f5d6d6c8b3079c1c Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Thu, 2 Dec 2021 10:56:26 +0100
Subject: [PATCH] ntp: limit total monotonic offset correction

In addition to the 16s limit in per-response change in the monotonic
offset, don't allow the total accumulated offset injected in sourcestats
to be larger than 16 seconds.
---
 ntp_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ntp_core.c b/ntp_core.c
index 6c3ba76..f259f6a 100644
--- a/ntp_core.c
+++ b/ntp_core.c
@@ -1660,11 +1660,11 @@ process_sample(NCR_Instance inst, NTP_Sample *sample)
 
   error_in_estimate = fabs(-sample->offset - estimated_offset);
 
-  if (inst->mono_doffset != 0.0) {
+  if (inst->mono_doffset != 0.0 && fabs(inst->mono_doffset) <= MAX_MONO_DOFFSET) {
     DEBUG_LOG("Monotonic correction offset=%.9f", inst->mono_doffset);
     SST_CorrectOffset(SRC_GetSourcestats(inst->source), inst->mono_doffset);
-    inst->mono_doffset = 0.0;
   }
+  inst->mono_doffset = 0.0;
 
   SRC_AccumulateSample(inst->source, sample);
   SRC_SelectSource(inst->source);