Assume MTU if not available from BlueZ

blefs/fs.go

@@ -199,7 +199,13 @@ func decode(data []byte, vals ...interface{}) error {
 // to send in a packet. Subtracting 20 ensures that the MTU
 // is never exceeded.
 func (blefs *FS) maxData() uint16 {
-	return blefs.transferChar.Properties.MTU - 20
+	mtu := blefs.transferChar.Properties.MTU
+	// If MTU is zero, the current version of BlueZ likely
+	// doesn't support the MTU property, so assume 256.
+	if mtu == 0 {
+		mtu = 256
+	}
+	return mtu - 20
 }
 
 // padding returns a slice of len amount of 0x00.