Applications that request kernel tx timestamps with SO_TIMESTAMPING
read timestamps as recvmsg() ancillary data. The response is defined
implicitly as timespec[3].
1) define struct scm_timestamping explicitly and
2) add support for new tstamp types. On tx, scm_timestamping always
accompanies a sock_extended_err. Define previously unused field
ee_info to signal the type of ts[0]. Introduce SCM_TSTAMP_SND to
define the existing behavior.
The reception path is not modified. On rx, no struct similar to
sock_extended_err is passed along with SCM_TIMESTAMPING.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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