p2p: restore default discovery

p2p/server.go

@@ -45,12 +45,6 @@ import (
 const (
 	defaultDialTimeout = 15 * time.Second
 
-	// This is the fairness knob for the discovery mixer. When looking for peers, we'll
-	// wait this long for a single source of candidates before moving on and trying other
-	// sources. Currently there is only one source at the Server level, so this has no effect.
-	// Check the fairMox tineout in the Backend for the actual timeout.
-	discmixTimeout = 100 * time.Millisecond
-
 	// Connectivity defaults.
 	defaultMaxPendingPeers = 50
 	defaultDialRatio       = 3
@@ -448,7 +442,9 @@ func (srv *Server) setupLocalNode() error {
 }
 
 func (srv *Server) setupDiscovery() error {
-	srv.discmix = enode.NewFairMix(discmixTimeout)
+	// Set up the discovery source mixer. Here, we don't care about the
+	// fairness of the mix, it's just for putting the
+	srv.discmix = enode.NewFairMix(0)
 
 	// Don't listen on UDP endpoint if DHT is disabled.
 	if srv.NoDiscovery {
@@ -506,6 +502,19 @@ func (srv *Server) setupDiscovery() error {
 			added[proto.Name] = true
 		}
 	}
+
+	// Set up default non-protocol-specific discovery feeds if no protocol
+	// has configured discovery.
+	if len(added) == 0 {
+		if srv.discv4 != nil {
+			it := srv.discv4.RandomNodes()
+			srv.discmix.AddSource(enode.WithSourceName("discv4-default", it))
+		}
+		if srv.discv5 != nil {
+			it := srv.discv5.RandomNodes()
+			srv.discmix.AddSource(enode.WithSourceName("discv5-default", it))
+		}
+	}
 	return nil
 }