transparent udp proxy

[Mark Felder]

I'm not sure if this is what you're looking for, but perhaps the
solution is in net/samplicator ?

>From the project's website:

This simple program listens for UDP datagrams on a network port, and
sends copies of these datagrams on to a set of destinations. Optionally,
it can perform sampling, i.e. rather than forwarding every packet,
forward only 1 in N. Another option is that it can "spoof" the IP source
address, so that the copies appear to come from the original source,
rather than the relay. Currently only supports IPv4.