Re: [PATCH] socket: don't clear SOCK_TSTAMP_NEW when SO_TIMESTAMPNS is disabled

[Greg KH <greg@kroah.com>]

On Tue, Oct 27, 2020 at 06:15:26PM +0100, Christian Eggers wrote:
> [ Upstream commit 4e3bbb33e6f36e4b05be1b1b9b02e3dd5aaa3e69 ]
> 
> SOCK_TSTAMP_NEW (timespec64 instead of timespec) is also used for
> hardware time stamps (configured via SO_TIMESTAMPING_NEW).
> 
> User space (ptp4l) first configures hardware time stamping via
> SO_TIMESTAMPING_NEW which sets SOCK_TSTAMP_NEW. In the next step, ptp4l
> disables SO_TIMESTAMPNS(_NEW) (software time stamps), but this must not
> switch hardware time stamps back to "32 bit mode".
> 
> This problem happens on 32 bit platforms were the libc has already
> switched to struct timespec64 (from SO_TIMExxx_OLD to SO_TIMExxx_NEW
> socket options). ptp4l complains with "missing timestamp on transmitted
> peer delay request" because the wrong format is received (and
> discarded).
> 
> Fixes: 887feae36aee ("socket: Add SO_TIMESTAMP[NS]_NEW")
> Signed-off-by: Christian Eggers <ceggers@arri.de>
> Acked-by: Willem de Bruijn <willemb@google.com>
> Acked-by: Deepa Dinamani <deepa.kernel@gmail.com>
> ---
> Hi Greg,
> 
> I just got your E-mail(s) that this patch has been applied to 5.8 and 5.9.
> This is a back port for the same problem on 5.4. It does the same as the
> upstream patch, only the affected code is at another position here. Please
> decide yourself whether the Acked-by: tags (from the upstream patch) should
> be kept or removed.
> 
> This back port is only required for 5.4, older kernels like 4.19 are not
> affected.
> 
> regards
> Christian

Now queued up, thanks.

greg k-h