From bba29a0ee78e6033e886c37af577776156a920af Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Thu, 23 Aug 2018 14:19:16 +0200
Subject: [PATCH] samplefilt: check for non-increasing sample times

Adopt the check from the refclock code to check also samples from NTP.
---
 refclock.c   | 19 ++++++++++---------
 samplefilt.c | 24 +++++++++++++++++++++++-
 samplefilt.h |  2 +-
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/refclock.c b/refclock.c
index 45fb3ab..66224d5 100644
--- a/refclock.c
+++ b/refclock.c
@@ -372,7 +372,7 @@ convert_tai_offset(struct timespec *sample_time, double *offset)
   return 1;
 }
 
-static void
+static int
 accumulate_sample(RCL_Instance instance, struct timespec *sample_time, double offset, double dispersion)
 {
   NTP_Sample sample;
@@ -391,7 +391,7 @@ accumulate_sample(RCL_Instance instance, struct timespec *sample_time, double of
   else
     sample.stratum = instance->stratum;
 
-  SPF_AccumulateSample(instance->filter, &sample);
+  return SPF_AccumulateSample(instance->filter, &sample);
 }
 
 int
@@ -428,7 +428,10 @@ RCL_AddSample(RCL_Instance instance, struct timespec *sample_time, double offset
     return 0;
   }
 
-  accumulate_sample(instance, &cooked_time, offset - correction + instance->offset, dispersion);
+  if (!accumulate_sample(instance, &cooked_time,
+                         offset - correction + instance->offset, dispersion))
+    return 0;
+
   instance->pps_active = 0;
 
   log_sample(instance, &cooked_time, 0, 0, offset, offset - correction + instance->offset, dispersion);
@@ -570,7 +573,9 @@ RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
       return 0;
   }
 
-  accumulate_sample(instance, cooked_time, offset, dispersion);
+  if (!accumulate_sample(instance, cooked_time, offset, dispersion))
+    return 0;
+
   instance->leap_status = leap;
   instance->pps_active = 1;
 
@@ -599,17 +604,13 @@ RCL_GetDriverPoll(RCL_Instance instance)
 static int
 valid_sample_time(RCL_Instance instance, struct timespec *sample_time)
 {
-  NTP_Sample last_sample;
   struct timespec now;
   double diff;
 
   LCL_ReadCookedTime(&now, NULL);
   diff = UTI_DiffTimespecsToDouble(&now, sample_time);
 
-  if (diff < 0.0 || diff > UTI_Log2ToDouble(instance->poll + 1) ||
-      (SPF_GetNumberOfSamples(instance->filter) > 0 &&
-       SPF_GetLastSample(instance->filter, &last_sample) &&
-       UTI_CompareTimespecs(&last_sample.time, sample_time) >= 0)) {
+  if (diff < 0.0 || diff > UTI_Log2ToDouble(instance->poll + 1)) {
     DEBUG_LOG("%s refclock sample time %s not valid age=%.6f",
               UTI_RefidToString(instance->ref_id),
               UTI_TimespecToString(sample_time), diff);
diff --git a/samplefilt.c b/samplefilt.c
index af0b34c..7226963 100644
--- a/samplefilt.c
+++ b/samplefilt.c
@@ -102,9 +102,30 @@ SPF_DestroyInstance(SPF_Instance filter)
 
 /* ================================================== */
 
-void
+/* Check that samples times are strictly increasing */
+
+static int
+check_sample(SPF_Instance filter, NTP_Sample *sample)
+{
+  if (filter->used <= 0)
+    return 1;
+
+  if (UTI_CompareTimespecs(&filter->samples[filter->last].time, &sample->time) >= 0) {
+    DEBUG_LOG("filter non-increasing sample time %s", UTI_TimespecToString(&sample->time));
+    return 0;
+  }
+
+  return 1;
+}
+
+/* ================================================== */
+
+int
 SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample)
 {
+  if (!check_sample(filter, sample))
+      return 0;
+
   filter->index++;
   filter->index %= filter->max_samples;
   filter->last = filter->index;
@@ -116,6 +137,7 @@ SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample)
   DEBUG_LOG("filter sample %d t=%s offset=%.9f peer_disp=%.9f",
             filter->index, UTI_TimespecToString(&sample->time),
             sample->offset, sample->peer_dispersion);
+  return 1;
 }
 
 /* ================================================== */
diff --git a/samplefilt.h b/samplefilt.h
index 03eb939..3b4350a 100644
--- a/samplefilt.h
+++ b/samplefilt.h
@@ -36,7 +36,7 @@ extern SPF_Instance SPF_CreateInstance(int min_samples, int max_samples,
                                        double max_dispersion, double combine_ratio);
 extern void SPF_DestroyInstance(SPF_Instance filter);
 
-extern void SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample);
+extern int SPF_AccumulateSample(SPF_Instance filter, NTP_Sample *sample);
 extern int SPF_GetLastSample(SPF_Instance filter, NTP_Sample *sample);
 extern int SPF_GetNumberOfSamples(SPF_Instance filter);
 extern double SPF_GetAvgSampleDispersion(SPF_Instance filter);