UDP port forwarding doesn't seem to work with IPv6. I verified it does work with IPv4.

Reproduction steps (e.g. with https://gist.github.com/tuxmartin/e64d2132061ffef7e031 and modified to work with Python3 by changing the prints and MESSAGE to have b prefix)

1. UDP port forward with coder cli: coder port-forward <workspace> --udp 5005
2. Run server inside the coder workspace
3. Run client locally with AF_INET6 and UDP_IP=::1 or localhost: doesn't work (with Wireshark I can see it's using IPv6)
4. Run client locally with AF_INET and UDP_IP=127.0.0.1 or localhost: works (with Wireshark I can see it's using IPv4)