[chrony-users] Synchronizing PHCs in addition to system clock

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In my use case I use tcpdump and other tools to capture and record network traffic.. This traffic is stored with a attached hardware timestamp form the NIC PHCs. I want these timestamps to be synchronized as close as possible to UTC.

In some data centers I have access to PTP and can easily synchronize all clocks on each servers to UTC. In some data centers I need to use NTP and chrony.

The problem is that chrony only synchronizes the system clock to NTP, not the rest of the PHC in the server. I use https://github.com/exablaze-oss/exanic-software/blob/master/util/exanic-clock-sync.c to synchronize the NIC PHCs to the system clock. I also use chrony hardware timestamping.. This causes a synchronization loop that can potentially lead to oscillations. If I use the default min/max poll intervals I see no oscillations in practice. This is probably because exanic-clock-sync servo runs at much higher frequency (~10s).

When I decrease the chrony poll interval I end up with oscillations.

Are there any plans for making chrony also synchronize the NIC PHCs? It seems to me that NIC PHCs are become more prevalent and the only way to reliably synchronize them to the system clock is to have the system wide clock servo (NTP or chrony) perform that task.


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