internal void LockedDrainRecvBuffer(PacketFifo toUser)
        {
            DmaMemory mem;
            ulong     controlBits;

            while (rxRingBuffer.Peek(out mem, out controlBits))
            {
                Packet packet = MakePacketFromDescriptor(mem, controlBits);
                toUser.Push(packet);
                rxRingBuffer.Pop();
            }
        }