On Mon, May 25, 2020 at 11:46:19PM -0500, Dan Drown wrote:
> This adds the "disablerxadjust" config option to hwtimestamp.  This uses RX
> timestamps at the 1588 point (after SFD/before ethernet header) instead of
> the NTP point (after ethernet CRC).  At 1G, this changes the timestamp (and
> RTT) by 752ns.  To be symmetrical, you'd want this enabled on both the NTP
> server and client.

What is the use case for this option? Is it meant for testing or
debugging?

As NTP doesn't rely on HW support in switches/routers, it needs to
shift the timestamping point to the end of the packet to minimize the
error when the server and client are connected to the network with
different link speeds. If you know the link speed, you could use the
rxcomp option to make the adjustment manually.

If there is a good use case, please try to find a shorter name, update
also the documentation, and submit it as a git patch.

-- 
Miroslav Lichvar


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