does fly.io guarantee same UDP IPv4 return address for NAT traversal

Questions / Help
1

Hi everyone,

I need to implement an aoo (audio over osc) server on fly.io. Does Fly guarantee UDP reply traffic on a dedicated IPv4 egresses from the same IP that received the request? I’m seeing replies come from a different public IP than the one my UDP packet was sent to, which breaks NAT traversal for any client behind a standard home router.

Thank you!

2

You need to bind to fly-global-services in order for Linux to send return traffic from the right address. See docs for an explanation for why. We’re working on removing some of these quirks with UDP-on-fly hopefully in the not so distant future.