Merge branch 'net-dst_metadata-fix-df-flag-extraction-on-tunnel-rx'

Ilya Maximets says:

====================
net: dst_metadata: fix DF flag extraction on tunnel rx

Two patches here, first fixes the issue where tunnel core doesn't
actually extract DF bit from the outer IP header, even though both
OVS and TC flower allow matching on it.  More details in the commit
message.

The second is a selftest for openvswitch that reproduces the issue,
but also just adds some basic coverage for the tunnel metadata
extraction and related openvswitch uAPI.
====================

Link: https://patch.msgid.link/20250909165440.229890-1-i.maximets@ovn.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>