fix panic if derp update is 0 (#2368)

* fix panic if derp update is 0

Fixes #2362

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

* update changelog

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

---------

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

CHANGELOG.md

@@ -17,6 +17,8 @@
   [#2364](https://github.com/juanfont/headscale/pull/2364)
 - Remove invalid routes and add stronger constraints for routes to avoid API panic
   [#2371](https://github.com/juanfont/headscale/pull/2371)
+- Fix panic when `derp.update_frequency` is 0
+  [#2368](https://github.com/juanfont/headscale/pull/2368)
 
 ## 0.24.0 (2025-01-17)
 

hscontrol/app.go

@@ -245,11 +245,11 @@ func (h *Headscale) scheduledTasks(ctx context.Context) {
 
 	lastExpiryCheck := time.Unix(0, 0)
 
-	derpTicker := time.NewTicker(h.cfg.DERP.UpdateFrequency)
-	defer derpTicker.Stop()
-	// If we dont want auto update, just stop the ticker
-	if !h.cfg.DERP.AutoUpdate {
-		derpTicker.Stop()
+	derpTickerChan := make(<-chan time.Time)
+	if h.cfg.DERP.AutoUpdate && h.cfg.DERP.UpdateFrequency != 0 {
+		derpTicker := time.NewTicker(h.cfg.DERP.UpdateFrequency)
+		defer derpTicker.Stop()
+		derpTickerChan = derpTicker.C
 	}
 
 	var extraRecordsUpdate <-chan []tailcfg.DNSRecord
@@ -285,7 +285,7 @@ func (h *Headscale) scheduledTasks(ctx context.Context) {
 				h.nodeNotifier.NotifyAll(ctx, update)
 			}
 
-		case <-derpTicker.C:
+		case <-derpTickerChan:
 			log.Info().Msg("Fetching DERPMap updates")
 			h.DERPMap = derp.GetDERPMap(h.cfg.DERP)
 			if h.cfg.DERP.ServerEnabled && h.cfg.DERP.AutomaticallyAddEmbeddedDerpRegion {