libmnl limitation...
From: David Miller <davem@davemloft.net>
Date: 2011-02-20 21:40:51
Unfortunately, libmnl only allows setting socket options that are of SOL_NETLINK. This precludes setting socket options such as SO_ATTACH_FILTER which need to be of level SOL_SOCKET. It seems to be a mistake to have hard-coded the socket level instead of simply letting the user specify it :-/