sslh VS cmux

That already has a (brutal) solution now - sslh https://www.rutschle.net/tech/sslh/README.html - the current version is more sophisticated, but it was originally just a perl script that would send the connection to sshd or the https web server, based on regex matching on an initial string (and I probably timing out and going to sshd if it didn't see one? Something like that, I haven't dug out the old code to check.)

Maybe something like https://github.com/yrutschle/sslh would work? Although it will probably break mobile client as well.

I think you're looking for sslh.

However, there is a hacky tool that should fit your use case, you could try that: https://www.rutschle.net/tech/sslh/README.html

I haven’t tried it but have a look here. TBH I didn’t even know sslh supported UDP!

There is a "known" package that already does this: https://github.com/soheilhy/cmux

Is there a library written in Rust providing comparable functionality to the cmux golang package?

> cmux is a generic Go library to multiplex connections based on their payload. Using cmux, you can serve gRPC, SSH, HTTPS, HTTP, Go RPC, and pretty much any other protocol on the same TCP listener.

https://github.com/soheilhy/cmux

cmux is one way to achieve it. I've used h2c with the grpc server's ServeHTTP handler, although that is marked as experimental.

If you need more from gRPC, you may get stuck with Cloud Run. Cloud Run has a limitation that you need to serve all traffic on one port. In general, you can either use cmux or the experimental gRPC-go ServeHTTP interface. However, if you want streaming gRPC requests, you have to enable end-to-end HTTP/2 on your Cloud Run service. Unfortunately, I haven't found a way to mux both the gRPC server and a regular HTTP/2 server on the same port (I filed an issue with cmux)