config.py 文件源码

def find_reply_from(reply_from: Optional[IPv6Address], interface_name: str,
                        interface_addresses: Iterable[IPv6Address]) -> IPv6Address:
        """
        Find the appropriate reply-from address

        :param reply_from: The reply-from address specified in the configuration, if any
        :param interface_name: The name of the interface for logging purposes
        :param interface_addresses: The list of addresses on the interface
        :return: The reply-from address to use
        """
        if reply_from:
            # Check if this address exists
            if reply_from not in interface_addresses:
                raise ValueError("Reply-from address {addr} does not exist on {intf}".format(
                    addr=reply_from,
                    intf=interface_name
                ))
            return reply_from
        else:
            # Pick the first link-local address
            ll_addresses = [address for address in interface_addresses if address.is_link_local]
            if not ll_addresses:
                raise ValueError("No link-local address found on {intf}".format(
                    intf=interface_name
                ))
            return ll_addresses[0]