I'm trying to build something wherein I can redirect all traffic from a given application to a specified network interface. As an example use case, because I'm stuck with DSL for the time being, I don't want to saturate my line uploading every day things like dropbox or whatnot, so I want to be able to say, all traffic from dropbox should go through the wifi/personal hotspot. I can do this somewhat with squidproxy and specifying each application to go through that proxy -- but that relies on the app even allowing that kind of configuration and it's more work than I think it needs to be.
As an example of the same concept but for audio, see SoundSource by https://rogueamoeba.com/
With soundsource you can direct audio per application to any interface. I want to do the same, but for network traffic. Bonus I can get granular enough to direct outgoing and incoming to different devices on the same app.
But this is an area of systems programming I always felt the least accessible and I'm not really sure where to start reading.
First, I guess I should ask, is this even possible with macos/darwin at this time? I know in linux I could just namespace each application, but as far as I know, macos lacks that kind of functionality.
Cheers