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ntp: allow TX-only HW timestamping by default

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If no rxfilter is specified in the hwtimestamp directive and the NIC
doesn't support the all or ntp filter, enable TX-only HW timestamping
with the none filter.
This commit is contained in:
Miroslav Lichvar
2017-08-23 11:33:37 +02:00
parent 3e93068c43
commit aee42fada8
4 changed files with 42 additions and 25 deletions
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35
doc/chrony.conf.adoc
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@@ -1886,11 +1886,12 @@ be enabled by the *xleave* option in the <<server,*server*>> or the
This directive is supported on Linux 3.19 and newer. The NIC must support HW
timestamping, which can be verified with the *ethtool -T* command. The list of
capabilities should include _SOF_TIMESTAMPING_RAW_HARDWARE_,
_SOF_TIMESTAMPING_TX_HARDWARE_, _SOF_TIMESTAMPING_RX_HARDWARE_, and the receive
filters should include _HWTSTAMP_FILTER_ALL_ or _HWTSTAMP_FILTER_NTP_ALL_. When
*chronyd* is running, no other process (e.g. a PTP daemon) should be working
with the NIC clock. HW timestamping of packets received from bridged and bonded
interfaces is supported on Linux 4.13 and newer.
_SOF_TIMESTAMPING_TX_HARDWARE_, and _SOF_TIMESTAMPING_RX_HARDWARE_. Receive
filter _HWTSTAMP_FILTER_ALL_, or _HWTSTAMP_FILTER_NTP_ALL_, is necessary for
timestamping of received packets. Timestamping of packets received from bridged
and bonded interfaces is supported on Linux 4.13 and newer. When *chronyd* is
running, no other process (e.g. a PTP daemon) should be working with the NIC
clock.
+
If the kernel supports software timestamping, it will be enabled for all
interfaces. The source of timestamps (i.e. hardware, kernel, or daemon) is
@@ -1925,15 +1926,21 @@ is 0.
Some hardware can precisely cross timestamp the NIC clock with the system
clock. This option disables the use of the cross timestamping.
*rxfilter* _filter_:::
This option selects the receive timestamping filter. Possible values are:
_all_, _ntp_, and _none_. The default value is _ntp_, which enables
timestamping of NTP packets (_HWTSTAMP_FILTER_NTP_ALL_) if it is supported, or
timestamping of all packets (_HWTSTAMP_FILTER_ALL_). Setting *rxfilter* to
_all_ forces timestamping of all packets, which can be useful when the NIC
supports both filters and NTP packets are received from or on a non-standard
UDP port (e.g. specified by the *port* directive). Setting *rxfilter* to _none_
disables receive HW timestamping and allows transmit HW timestamping to be
enabled when the NIC supports only PTP-specific receive filters.
This option selects the receive timestamping filter. The _filter_ can be one of
the following:
_all_::::
Enables timestamping of all received packets.
_ntp_::::
Enables timestamping of received NTP packets.
_none_::::
Disables timestamping of received packets.
:::
The most specific filter for timestamping NTP packets which is supported by the
NIC is selected by default. Some NICs can timestamp only PTP packets, which
limits the selection to the _none_ filter. Forcing timestamping of all packets
with the _all_ filter when the NIC supports both _all_ and _ntp_ filters can be
useful when packets are received from or on a non-standard UDP port (e.g.
specified by the *port* directive).
::
+
Examples of the directive are: