eth, metrics, p2p: prepare metrics and net packets to eth/62

p2p/metrics.go

@@ -38,8 +38,14 @@ type meteredConn struct {
 }
 
 // newMeteredConn creates a new metered connection, also bumping the ingress or
-// egress connection meter.
+// egress connection meter. If the metrics system is disabled, this function
+// returns the original object.
 func newMeteredConn(conn net.Conn, ingress bool) net.Conn {
+	// Short circuit if metrics are disabled
+	if !metrics.Enabled {
+		return conn
+	}
+	// Otherwise bump the connection counters and wrap the connection
 	if ingress {
 		ingressConnectMeter.Mark(1)
 	} else {