watcher: do not run initial sync in background

Signed-off-by: Steffen Vogel <post@steffenvogel.de>

etc/wice.yaml

@@ -1,3 +1,4 @@
+# An interval at which wice will periodically check for added, removed or modified WireGuard interfaces.
 watch_interval: 1s
 community: "some-common-password"
 

pkg/core/interface.go

@@ -300,7 +300,7 @@ func NewInterface(wgDev *wgtypes.Device, client *wgctrl.Client) (*Interface, err
 	}
 
 	if i.KernelDevice, err = device.FindDevice(wgDev.Name); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to find kernel device: %w", err)
 	}
 
 	i.logger.Info("Added interface",

pkg/daemon.go

@@ -106,7 +106,13 @@ func (d *Daemon) Run() error {
 
 	signals := util.SetupSignals(util.SigUpdate)
 
-	go d.Watcher.Run()
+	d.logger.Debug("Started initial synchronization")
+	if err := d.Watcher.Sync(); err != nil {
+		d.logger.Fatal("Initial synchronization failed", zap.Error(err))
+	}
+	d.logger.Debug("Finished initial synchronization")
+
+	go d.Watcher.Watch()
 
 out:
 	for {

pkg/watcher/watcher.go

@@ -94,13 +94,7 @@ func (w *Watcher) Close() error {
 	return nil
 }
 
-func (w *Watcher) Run() {
+func (w *Watcher) Watch() {
-	w.logger.Debug("Started initial synchronization")
-	if err := w.Sync(); err != nil {
-		w.logger.Fatal("Initial synchronization failed", zap.Error(err))
-	}
-	w.logger.Debug("Finished initial synchronization")
-
 	if err := w.watchUser(); err != nil {
 		w.logger.Fatal("Failed to watch userspace interfaces", zap.Error(err))
 	}
@@ -111,8 +105,11 @@ func (w *Watcher) Run() {
 	}
 	w.logger.Debug("Started watching for changes of WireGuard kernel devices")
 
-	ticker := time.NewTicker(w.interval)
+	ticker := &time.Ticker{}
-	defer ticker.Stop()
+	if w.interval > 0 {
+		ticker = time.NewTicker(w.interval)
+		defer ticker.Stop()
+	}
 
 out:
 	for {