On Fri, 22 Oct 2021 at 17:56, Maxim Mikityanskiy [off-list ref] wrote:

tcp_time_stamp_raw() uses ktime_get_ns(), while bpf_ktime_get_ns() uses
ktime_get_mono_fast_ns(). Is it fine to use ktime_get_mono_fast_ns()
instead of ktime_get_ns()? I'm a bit worried about this note in
Documentation/core-api/timekeeping.rst:

 > most drivers should never call them,
 > since the time is allowed to jump under certain conditions.

That depends on what happens when the timestamp is "off". Since you're
sending this value over the network I doubt that the two methods will
show a difference.

Lorenz

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