dabbad: add missing socket filter header file.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabba: add missing socket filter header file.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabba: tell if a socket filter is attached.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>