add LocalAddr to peer.Peer client side

[rittneje]

Use case(s) - what problem will this feature solve?

We want to be able to log the local address in addition to the remote address from our server-side interceptors to aid in debugging.

Proposed Solution

Add LocalAddr net.Addr to peer.Peer.

Alternatives Considered

This information could also be made available via some other context attribute. It doesn't really matter as long as there is a way to get it.

Additional Context

This was already added to the Java implementation several years ago. grpc/grpc-java#4906

[mingdaoy]

hi @ginayeh, I'd like to take a stab at this. Could you assign it to me?

[arvindbr8]

@mingdaoy -- sorry about that. seems like we already have had @prestonvasquez with a fix in flight for it #6702.

Please use this filter to look for issues that are marked "Help wanted" and currently are unassigned.

[CarlosRDomin]

I've been playing with master now that #6716 has been merged and it's great to have access to the local address from server code, kudos @zasweq! However, there's also useful applications of retrieving the local port a client is using (e.g. to correlate it with prometheus metrics that we expose using the client address as a label). Not sure if this was intentional, but I noticed that #6702 exposed the LocalAddr in http2Client.getPeer (see here), while #6716 only updates http2_server.go.

Would it be possible to cherry-pick that one line from #6702? I modified the code locally and can confirm that's all that's needed for client code to retrieve local port through peer.FromContext(stream.Context()). I'd even be happy to contribute with a tiny MR if needed.

Thanks!

[zasweq]

Oh sure, we cna keep this open and try to add that. I will update the title accordingly.