SO_REUSEPORT should supersede SO_REUSEADDR

[rahulghangas]

If my understanding is correct, SO_REUSEPORT will be the desired behaviour 99.9% of the time. In control_unix.go, for the following code

                err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
		if err != nil {
			return
		}

		err = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1)
		if err != nil {
			return
		}

instead of setting (or trying to) both options, it should be a try/fail-safe scenario. We should try to set SO_REUSEPORT and if that fails, try to set SO_REUSEADDR. The current approach seems a bit redundant. Imo, it should look something like this,

		if err := unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEPORT, 1); err == nil { 
			return
		}
                unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)

[aarshkshah1992]

@rahulghangas

It depends on the underlying OS:

https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ

The TLDR is set both to ensure everything works as expected. A relevant snippet from that answer is:

There is not much more to say about SO_REUSEPORT other than that it was added later than SO_REUSEADDR, that's why you will not find it in many socket implementations of other systems, which "forked" the BSD code before this option was added, and that there was no way to bind two sockets to exactly the same socket address in BSD prior to this option.

[rahulghangas]

Hey, thanks for the reply.

I do understand that SO_REUSEPORT doesn't exist on some systems, which is why I suggested trying to set it and then setting SO_REUSEADDR if it errors out.