feat: use static buffer, context for cancellation, and functional arguments

[jaredallard]

What this PR does: This PR fixes the issues found in https://github.com/omrikiei/ktunnel/issues/24, and some struggles I ran into when trying to use this as a library with my own project. The main highlights are:

• Uses context for cancellation in both the client and server.
• Uses a single static buffer on the session, and then reads in chunks from each side for TCP listeners instead of a dynamically resized buffer. Right now the limit is around 3MB, which is below the 4MB limit.
• Uses functional args for configuration to allow for easier updates to these interfaces
• Allows the user to pass their own logger, with the default being a logrus logger that uses ioutil.Discard as the out.
• Few misc adjustments around handling TCP client connections, closing, and etc.

What's left?

This is what is keeping this in draft currently:

• [ ] Update everything in cmd/ to support the new functional args interface, and pass in a logger.
• [ ] A quick once over to make sure I didn't miss anything, I did this incrementally, and a lot of times was pushing just to be able to build a docker image 😆

Notes for my reviewer: I'm happy to split this into chunks, if that's wanted!

[jaredallard]

Tested this out and it seems like there is issues with concurrent connections, going to need to fix this :sob:

[omrikiei]

Tested this out and it seems like there is issues with concurrent connections, going to need to fix this 😭

Could you elaborate? what are you seeing?

[jaredallard]

@omrikiei It looks like when two connections, or more, are made at once something is getting deadlocked.

I moved my project to ssh tunneling to remove this for now, and I'm pretty sure I actually fixed this but deleted the code on accident. I need to re-do this sometime soon. It might be a bit though, now that I stopped using this.

Maybe it makes sense to have this project also be using ssh tunneling?

[omrikiei]

Ill see if I'm able to reproduce and troubleshoot it