Tone down insignificant discovery error messages (ref #241)

cmd/syncthing/monitor.go

@@ -86,6 +86,7 @@ func monitorMain() {
 			cmd.Process.Kill()
 			<-exit
 			return
+
 		case err = <-exit:
 			if err == nil {
 				// Successfull exit indicates an intentional shutdown
@@ -109,9 +110,6 @@ func copyStderr(stderr io.ReadCloser) {
 	for {
 		line, err := br.ReadString('\n')
 		if err != nil {
-			if err != io.EOF {
-				l.Warnln("stderr:", err)
-			}
 			return
 		}
 
@@ -150,9 +148,6 @@ func copyStdout(stderr io.ReadCloser) {
 	for {
 		line, err := br.ReadString('\n')
 		if err != nil {
-			if err != io.EOF {
-				l.Warnln("stdout:", err)
-			}
 			return
 		}
 

discover/discover.go

@@ -65,7 +65,10 @@ func (d *Discoverer) StartLocal(localPort int, localMCAddr string) {
 	if localPort > 0 {
 		bb, err := beacon.NewBroadcast(localPort)
 		if err != nil {
-			l.Infof("No IPv4 discovery possible (%v)", err)
+			if debug {
+				l.Debugln(err)
+			}
+			l.Infoln("Local discovery over IPv4 unavailable")
 		} else {
 			d.broadcastBeacon = bb
 			go d.recvAnnouncements(bb)
@@ -75,7 +78,10 @@ func (d *Discoverer) StartLocal(localPort int, localMCAddr string) {
 	if len(localMCAddr) > 0 {
 		mb, err := beacon.NewMulticast(localMCAddr)
 		if err != nil {
-			l.Infof("No IPv6 discovery possible (%v)", err)
+			if debug {
+				l.Debugln(err)
+			}
+			l.Infoln("Local discovery over IPv6 unavailable")
 		} else {
 			d.multicastBeacon = mb
 			go d.recvAnnouncements(mb)
@@ -83,7 +89,7 @@ func (d *Discoverer) StartLocal(localPort int, localMCAddr string) {
 	}
 
 	if d.broadcastBeacon == nil && d.multicastBeacon == nil {
-		l.Warnln("No local discovery method available")
+		l.Warnln("Local discovery unavailable")
 	} else {
 		d.localBcastTick = time.Tick(d.localBcastIntv)
 		d.forcedBcastTick = make(chan time.Time)