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ntp: add options for compensating HW timestamping errors

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Miroslav Lichvar
2017-01-05 16:37:28 +01:00
parent 8efec1d640
commit cacbe9976f
5 changed files with 108 additions and 36 deletions
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19
doc/chrony.conf.adoc
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@@ -1776,7 +1776,7 @@ sendmail binary.
=== Miscellaneous
[[hwtimestamp]]*hwtimestamp* _interface_::
[[hwtimestamp]]*hwtimestamp* _interface_ [_option_]...::
This directive enables hardware timestamping of NTP packets sent to and
received from the specified network interface. The network interface controller
(NIC) uses its own clock to accurately timestamp the actual transmissions and
@@ -1807,10 +1807,25 @@ and the <<chronyc.adoc#ntpdata,*ntpdata*>> report in *chronyc*.
If the specified interface is _*_, *chronyd* will try to enable HW timestamping
on all available interfaces.
+
An example of the directive is:
The *hwtimestamp* directive has the following options:
+
*txcomp* _compensation_:::
This option specifies the difference in seconds between the actual transmission
time at the physical layer and the reported transmit timestamp. This value will
be added to transmit timestamps obtained from the NIC. The default value is 0.
*rxcomp* _compensation_:::
This option specifies the difference in seconds between the reported receive
timestamp and the actual reception time at the physical layer. This value will
be subtracted from receive timestamps obtained from the NIC. The default value
is 0.
::
+
Examples of the directive are:
+
----
hwtimestamp eth0
hwtimestamp eth1 txcomp 300e-9 rxcomp 645e-9
hwtimestamp *
----
[[include]]*include* _pattern_::