gap/linux: update implementation for GAP to allow for calling adv.Con…

…figure()

followed by adv.Start() followed by adv.Stop() multiple times. This is required
in order to update advertising ServiceData.

Signed-off-by: deadprogram <[email protected]>

gap_linux.go

@@ -28,6 +28,7 @@ type Advertisement struct {
 	adapter    *Adapter
 	properties *prop.Properties
 	path       dbus.ObjectPath
+	started    bool
 }
 
 // DefaultAdvertisement returns the default advertisement instance but does not
@@ -45,8 +46,8 @@ func (a *Adapter) DefaultAdvertisement() *Advertisement {
 //
 // On Linux with BlueZ, it is not possible to set the advertisement interval.
 func (a *Advertisement) Configure(options AdvertisementOptions) error {
-	if a.properties != nil {
-		panic("todo: configure advertisement a second time")
+	if a.started {
+		panic("cannot configure advertisement that is already started")
 	}
 
 	var serviceUUIDs []string
@@ -110,6 +111,7 @@ func (a *Advertisement) Start() error {
 	if err != nil {
 		return fmt.Errorf("bluetooth: could not start advertisement: %w", err)
 	}
+	a.started = true
 	return nil
 }
 
@@ -122,6 +124,7 @@ func (a *Advertisement) Stop() error {
 		}
 		return fmt.Errorf("bluetooth: could not stop advertisement: %w", err)
 	}
+	a.started = false
 	return nil
 }