Switch mdns library

[Stebalien]

Either (a) switch to a fork or, even better, switch to https://github.com/grandcat/zeroconf. The current library is unmaintained and has at least one data race (and parts of it are incomprehensible).

[Stebalien]

Also needs to fix:

• Hostname squatting: mdns is squating on host hostname #176
• Try to be smarter about polling: Why poll? js-libp2p-mdns#70

[Stebalien]

Closing in favor of #623.

[kpp]

Why not switch to https://github.com/hashicorp/mdns ? https://github.com/whyrusleeping/mdns is a fork of https://github.com/hashicorp/mdns and https://github.com/hashicorp/mdns fixed some data races.

[Stebalien]

We've fixed all the ones fixed upstream.

[kpp]

Where?

[Stebalien]

whyrusleeping/mdns@9d49aa4

Looking at a diff between the two versions, it looks like the only remaining change we need is the ability to turn off (or redirect) logging. We should probably upstream that and then get off the fork (eventually).

[kpp]

whyrusleeping/mdns@9d49aa4

Mutex is a bad solution because of:

$ go vet
# github.com/whyrusleeping/mdns
./client.go:165:41: call of logf copies lock value: github.com/whyrusleeping/mdns.client contains sync.Mutex

Looking at a diff between the two versions, it looks like the only remaining change we need is the ability to turn off (or redirect) logging.

What do you mean? I am new to go

[Stebalien]

Mutex is a bad solution because of:

That's just a really stupid debug line. It shouldn't be copying the client. Fix in whyrusleeping/mdns#8.

What do you mean? I am new to go

This version supports suppressing log output (error/info messages to standard error) and the upstream version doesn't.