Switch inbound data cipher.

def set_inbound_cipher(
        self, block_engine, block_size, mac_engine, mac_size, mac_key
    ):
        """
        Switch inbound data cipher.
        """
        self.__block_engine_in = block_engine
        self.__block_size_in = block_size
        self.__mac_engine_in = mac_engine
        self.__mac_size_in = mac_size
        self.__mac_key_in = mac_key
        self.__received_bytes = 0
        self.__received_packets = 0
        self.__received_bytes_overflow = 0
        self.__received_packets_overflow = 0
        # wait until the reset happens in both directions before clearing
        # rekey flag
        self.__init_count |= 2
        if self.__init_count == 3:
            self.__init_count = 0
            self.__need_rekey = False