Resolve "OS upstream failure / wrong default route"

cmd/cli/prog.go

@@ -120,6 +120,7 @@ type prog struct {
 	runningIface              string
 	requiredMultiNICsConfig   bool
 	adDomain                  string
+	runningOnDomainController bool
 
 	selfUninstallMu       sync.Mutex
 	refusedQueryCount     int
@@ -276,6 +277,11 @@ func (p *prog) preRun() {
 
 func (p *prog) postRun() {
 	if !service.Interactive() {
+		if runtime.GOOS == "windows" {
+			isDC, roleInt := isRunningOnDomainController()
+			p.runningOnDomainController = isDC
+			mainLog.Load().Debug().Msgf("running on domain controller: %t, role: %d", p.runningOnDomainController, roleInt)
+		}
 		p.resetDNS(false, false)
 		ns := ctrld.InitializeOsResolver(false)
 		mainLog.Load().Debug().Msgf("initialized OS resolver with nameservers: %v", ns)
@@ -1410,5 +1416,25 @@ func (p *prog) leakOnUpstreamFailure() bool {
 	if router.Name() != "" {
 		return false
 	}
+	// if we are running on ADDC, we should not leak on upstream failure
+	if p.runningOnDomainController {
+		return false
+	}
 	return true
 }
+
+// Domain controller role values from Win32_ComputerSystem
+// https://learn.microsoft.com/en-us/windows/win32/cimwin32prov/win32-computersystem
+const (
+	BackupDomainController  = 4
+	PrimaryDomainController = 5
+)
+
+// isRunningOnDomainController checks if the current machine is a domain controller
+// by querying the DomainRole property from Win32_ComputerSystem via WMI.
+func isRunningOnDomainController() (bool, int) {
+	if runtime.GOOS != "windows" {
+		return false, 0
+	}
+	return isRunningOnDomainControllerWindows()
+}