Only set serveDns if the host is also configured to be a lighthouse. (#433)

dns_server.go

@@ -133,7 +133,7 @@ func getDnsServerAddr(c *Config) string {
 func startDns(l *logrus.Logger, c *Config) {
 	dnsAddr = getDnsServerAddr(c)
 	dnsServer = &dns.Server{Addr: dnsAddr, Net: "udp"}
-	l.Debugf("Starting DNS responder at %s\n", dnsAddr)
+	l.WithField("dnsListener", dnsAddr).Infof("Starting DNS responder")
 	err := dnsServer.ListenAndServe()
 	defer dnsServer.Shutdown()
 	if err != nil {

main.go

@@ -341,7 +341,15 @@ func Main(config *Config, configTest bool, buildVersion string, logger *logrus.L
 	//handshakeMACKey := config.GetString("handshake_mac.key", "")
 	//handshakeAcceptedMACKeys := config.GetStringSlice("handshake_mac.accepted_keys", []string{})
 
-	serveDns := config.GetBool("lighthouse.serve_dns", false)
+	serveDns := false
+	if config.GetBool("lighthouse.serve_dns", false) {
+		if config.GetBool("lighthouse.am_lighthouse", false) {
+			serveDns = true
+		} else {
+			l.Warn("DNS server refusing to run because this host is not a lighthouse.")
+		}
+	}
+
 	checkInterval := config.GetInt("timers.connection_alive_interval", 5)
 	pendingDeletionInterval := config.GetInt("timers.pending_deletion_interval", 10)
 	ifConfig := &InterfaceConfig{