Currently drivers have to check if they already have a umem
installed for a given queue and return an error if so. Make
better use of XDP_QUERY_XSK_UMEM and move this functionality
to the core.
We need to keep rtnl across the calls now.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com> Acked-by: Björn Töpel <bjorn.topel@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>