cmd/tailscale: only refresh VPN tunnel if configuration changed

This used to work, but a later ChromeOS workaround closed and cleared the last
configuration before comparing it with the new.

Fixes tailscale/tailscale#966

Signed-off-by: Elias Naur <mail@eliasnaur.com>

cmd/tailscale/backend.go

@@ -142,6 +142,10 @@ func (b *backend) setCfg(cfg *router.Config) error {
 }
 
 func (b *backend) updateTUN(service jni.Object, cfg *router.Config) error {
+	if reflect.DeepEqual(cfg, b.lastCfg) {
+		return nil
+	}
+
 	// Close previous tunnel(s).
 	// This is necessary for ChromeOS, native Android devices
 	// seem to handle seamless handover between tunnels correctly.
@@ -150,9 +154,6 @@ func (b *backend) updateTUN(service jni.Object, cfg *router.Config) error {
 	// the closing on ChromeOS.
 	b.CloseTUNs()
 
-	if reflect.DeepEqual(cfg, b.lastCfg) {
-		return nil
-	}
 	if len(cfg.LocalAddrs) == 0 {
 		return nil
 	}