don't drop PHC samples with zero delay

chrony-phcdelay.patch

@@ -0,0 +1,33 @@
+commit abb09418b16993ecd8289dd459dff91701f4f971
+Author: Miroslav Lichvar <mlichvar@redhat.com>
+Date:   Wed Apr 19 12:20:14 2017 +0200
+
+    sys_linux: don't drop PHC samples with zero delay
+    
+    When processing data from the PTP_SYS_OFFSET ioctl, the sample is
+    dropped when an interval between two consecutive readings of the system
+    clock is negative or zero, assuming the clock has been stepped between
+    the two readings.
+    
+    With a real PHC the interval is normally expected to be at least a
+    microsecond, but with a virtual PHC and a low-resolution system clock
+    it's possible to get two readings with the same system time. Modify the
+    check to drop only samples with a negative delay.
+
+diff --git a/sys_linux.c b/sys_linux.c
+index c06112a..649afb0 100644
+--- a/sys_linux.c
++++ b/sys_linux.c
+@@ -705,9 +705,11 @@ get_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
+     phc_tss[i] = ts2;
+     delays[i] = UTI_DiffTimespecsToDouble(&ts3, &ts1);
+ 
+-    if (delays[i] <= 0.0)
++    if (delays[i] < 0.0) {
+       /* Step in the middle of a PHC reading? */
++      DEBUG_LOG(LOGF_SysLinux, "Bad PTP_SYS_OFFSET sample delay=%e", delays[i]);
+       return 0;
++    }
+ 
+     if (!i || delays[i] < min_delay)
+       min_delay = delays[i];

chrony.spec

@@ -23,6 +23,8 @@ Source10:       https://github.com/mlichvar/clknetsim/archive/%{clknetsim_ver}/c
 Patch1:         chrony-service-helper.patch
 # fix seccomp filter for new glibc
 Patch2:         chrony-seccomp.patch
+# don't drop PHC samples with zero delay
+Patch3:         chrony-phcdelay.patch
 
 BuildRequires:  libcap-devel libedit-devel nss-devel pps-tools-devel
 %ifarch %{ix86} x86_64 %{arm} aarch64 mipsel mips64el ppc64 ppc64le s390 s390x
@@ -60,6 +62,7 @@ clocks, system real-time clock or manual input as time references.
 %{?gitpatch:%patch0 -p1}
 %patch1 -p1 -b .service-helper
 %patch2 -p1 -b .seccomp
+%patch3 -p1 -b .phcdelay
 
 %{?gitpatch: echo %{version}-%{gitpatch} > version.txt}