merged with fixes

internal/transport/metadata.go

@@ -0,0 +1,28 @@
+// Package transport holds neutral transport metadata shared across the
+// protocol/edge boundary and the RPC business layer. It must not import any
+// business package (internal/rpc, internal/app, ...), so that mtprotoedge can
+// produce transport facts without depending on the RPC implementation.
+package transport
+
+import "context"
+
+type ctxKey int
+
+const (
+	clientIPKey ctxKey = iota
+)
+
+// WithClientIP records the client remote IP as neutral transport metadata.
+// An empty ip is ignored.
+func WithClientIP(ctx context.Context, ip string) context.Context {
+	if ip == "" {
+		return ctx
+	}
+	return context.WithValue(ctx, clientIPKey, ip)
+}
+
+// ClientIPFrom returns the client remote IP carried in ctx, if set.
+func ClientIPFrom(ctx context.Context) (string, bool) {
+	v, ok := ctx.Value(clientIPKey).(string)
+	return v, ok && v != ""
+}