New features have been added to ef_vi to
allow applications to reuse the result of the hardware packet parsing and filtering
which an X3522 has performed on RX. The new ef_vi_filter_query() will return the ID which the NIC has allocated for a
previously-added filter, which will match the ef_event.rx_ref.filter_id field returned by an ef_vi_poll() call.
Note:
ef_vi will not
always use on-NIC filtering to satisfy a call to
ef_vi_filter_add(), and so ef_vi_filter_query() has the ability to report that no filter ID is
available. Applications should be written to be robust to this scenario.