LLC_XID_NULL_CLASS_2
llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 0);
llc_pdu_init_as_xid_cmd(skb, LLC_XID_NULL_CLASS_2, 0);
llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);