remote peer address is lost in ctx - always resolves to localhost

[mikeatlas]

Since grpc-gateway creates a HTTP REST service that then subsequently calls a gRPC client, the loopback network hop causes all requests at the gRPC service to appear to originate from ::1 (localhost in IPv6).

Example gRPC service:

func (r *myService) MyRPCEndpoint(
    ctx context.Context, msg *grpcapi.Message) (*grpcapi.Message, error) {
    p, _ := peer.FromContext(ctx)
    remoteAddr := p.Addr.String() // ALWAYS localhost when incoming from grp-gateway :(
        // ... etc
}

It would be nice if X-Forwarded-For (or the newer Forwarded RFC header) were populated with the original external address, but since gRPC is not another HTTP endpoint, we need some other context attribute set such as ProxyRemoteAddr (or whatever) in the forwarded gRPC request.

I may make a PR for this as it's something I need right away, and don't see an obvious workaround.

[mikeatlas]

One way I've found is to inject the HTTP req.RemoteAddr into the ctx:

ctx = metadata.NewContext(ctx, metadata.Pairs("RemoteAddr", req.RemoteAddr))

Then, in the server side gRPC service method:

md, _ := metadata.FromContext(ctx)

// this returns a IP string of "[1.2.3.4:5678]"
remoteAddr := md["remoteaddr"] //  - why the "[ ]" wrap??

So, it's doable, kind of ugly but not terrible on the gRPC server side. Any thoughts?

[mikeatlas]

Pull request attached ✅