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dlnaprox
This program is a DLNA proxy. It proxies UDP multicast packets to and from the specified networks. These two networks are knowns as the inner and the outer network. The basic assumption is that the inner network can send normal IP requests to the outer network, but not visa versa. For example, a Docker container on a bridged docker network can only be accessed through forwarded ports. However, if it sends a request to an address on the same network as the host system, by default, the other host is reachable. This program forwards multicast broadcasts to 239.255.255.250:1900 to the other network. Since the spec says that responses to the broadcast should sent to port that originated it. So we keep a map of sockets so we can correctly proxy these responses.
Usage
dlnaprox -i 172.17.0.0/16 -o 192.168.0.0/24