mDNS: emit `ToSwarm::NewExternalAddrOfPeer`

[thomaseizinger]

Description

With #4371 merged, we have the foundation of #4302 implemented.

libp2p-mdns needs to be extended to emit this new event whenever it discovers a new address via mDNS.

Motivation

Other behaviours should be able to learn the addresses discovered by mDNS.

Current Implementation

Only mDNS knows about its discovered addresses.

Are you planning to do it yourself in a pull request ?

No

[1010adigupta]

would like to work on this

[justcode740]

would like to take this one once previous one time out. @thomaseizinger , unsure the policy here.

[thomaseizinger]

Feel free to start! :)

I've not heard from @1010adigupta so far.

[justcode740]

Feel free to start! :)

I've not heard from @1010adigupta so far.

ah, ok, just afraid there's some duplicated work done.

[1010adigupta]

You can go for it, I got busy with some other stuff, didn't got time for this :)

[justcode740]

@thomaseizinger hey i have a question, isn't the mDNS service already inform Swarm when a new peer discovered? https://github.com/libp2p/rust-libp2p/blob/master/protocols/mdns/src/behaviour.rs#L351, what need to change here?

[thomaseizinger]

It emits an mDNS specific event that the user has to react to manually. The idea of the new event is that it is shared with other behaviours.