[service] Fix module failure when dll is missing

service/firewall/interception/dnsmonitor/etwlink_windows.go

@@ -14,7 +14,7 @@ import (
 )
 
 type ETWSession struct {
-	i integration.ETWFunctions
+	i *integration.ETWFunctions
 
 	shutdownGuard atomic.Bool
 	shutdownMutex sync.Mutex
@@ -23,7 +23,10 @@ type ETWSession struct {
 }
 
 // NewSession creates new ETW event listener and initilizes it. This is a low level interface, make sure to call DestorySession when you are done using it.
-func NewSession(etwInterface integration.ETWFunctions, callback func(domain string, result string)) (*ETWSession, error) {
+func NewSession(etwInterface *integration.ETWFunctions, callback func(domain string, result string)) (*ETWSession, error) {
+	if etwInterface == nil {
+		return nil, fmt.Errorf("etw interface was nil")
+	}
 	etwSession := &ETWSession{
 		i: etwInterface,
 	}
@@ -47,7 +50,7 @@ func NewSession(etwInterface integration.ETWFunctions, callback func(domain stri
 	// Initialize session.
 	err := etwSession.i.InitializeSession(etwSession.state)
 	if err != nil {
-		return nil, fmt.Errorf("failed to initialzie session: %q", err)
+		return nil, fmt.Errorf("failed to initialize session: %q", err)
 	}
 
 	return etwSession, nil

service/firewall/interception/dnsmonitor/eventlistener_windows.go

@@ -23,19 +23,32 @@ func newListener(module *DNSMonitor) (*Listener, error) {
 	ResolverInfo.Source = resolver.ServerSourceETW
 
 	listener := &Listener{}
-	var err error
 	// Initialize new dns event session.
+	err := initializeSessions(module, listener)
+	if err != nil {
+		// Listen for event if the dll has been loaded
+		module.instance.OSIntegration().OnInitializedEvent.AddCallback("loader-listener", func(wc *mgr.WorkerCtx, s struct{}) (cancel bool, err error) {
+			err = initializeSessions(module, listener)
+			if err != nil {
+				return false, err
+			}
+			return true, nil
+		})
+	}
+	return listener, nil
+}
+
+func initializeSessions(module *DNSMonitor, listener *Listener) error {
+	var err error
 	listener.etw, err = NewSession(module.instance.OSIntegration().GetETWInterface(), listener.processEvent)
 	if err != nil {
-		return nil, err
+		return err
 	}
-
-	// Start listening for events.
+	// Start listener
 	module.mgr.Go("etw-dns-event-listener", func(w *mgr.WorkerCtx) error {
 		return listener.etw.StartTrace()
 	})
-
-	return listener, nil
+	return nil
 }
 
 func (l *Listener) flush() error {