There are some implementations of service that use socket loadbalancing
instead of NAT. These implementations don't need to deal with the
conntrack cleanup, however, they need to cleanup the sockets that are
no longer needed, so the application does not get stuck forever.
This can happen in both TCP or UDP, but since UDP is stateless, the
situation is much complicated because does not have mechanisms like TCP
to detect that socket is no longer needed.
Change-Id: Ic2cfbdf6c8b1f1335e8b5964825dd1fa716fef53
039859b9b7