fix modifier usage

pkg/ebpf/manager.go

@@ -91,6 +91,14 @@ type ModifierAfterInit interface {
 	AfterInit(*manager.Manager, names.ModuleName, *manager.Options) error
 }
 
+// ModifierPreStart is a sub-interface of Modifier that exposes an PreStart method
+type ModifierPreStart interface {
+	Modifier
+
+	// PreStart is called before the ebpf.Manager.Start call
+	PreStart(*manager.Manager, names.ModuleName) error
+}
+
 // ModifierBeforeStop is a sub-interface of Modifier that exposes a BeforeStop method
 type ModifierBeforeStop interface {
 	Modifier
@@ -169,39 +177,14 @@ func (m *Manager) Stop(cleanupType manager.MapCleanupType) error {
 	return errors.Join(errs, err)
 }
 
-type modifierPreStart interface {
-	PreStart() error
-}
-
 // Start is a wrapper around ebpf-manager.Manager.Start
 func (m *Manager) Start() error {
-	for _, mod := range m.EnabledModifiers {
-		if ps, ok := mod.(modifierPreStart); ok {
-			if err := ps.PreStart(); err != nil {
-				return fmt.Errorf("prestart %s manager modifier: %w", mod, err)
-			}
-		}
-	}
-	return m.Manager.Start()
-}
-
-type modifierAfterStop interface {
-	AfterStop(manager.MapCleanupType) error
-}
-
-// Stop is a wrapper around ebpf-manager.Manager.Stop
-func (m *Manager) Stop(ct manager.MapCleanupType) error {
-	if err := m.Manager.Stop(ct); err != nil {
+	err := runModifiersOfType(m.EnabledModifiers, "PreStart", func(mod ModifierPreStart) error {
+		return mod.PreStart(m.Manager, m.Name)
+	})
+	if err != nil {
 		return err
 	}
 
-	for _, mod := range m.EnabledModifiers {
-		if as, ok := mod.(modifierAfterStop); ok {
-			if err := as.AfterStop(ct); err != nil {
-				return fmt.Errorf("afterstop %s manager modifier: %w", mod, err)
-			}
-		}
-	}
-
-	return nil
+	return m.Manager.Start()
 }

pkg/ebpf/perf/event.go

@@ -35,8 +35,9 @@ type Flusher interface {
 	Flush()
 }
 
-// compile time check to ensure this satisfies the Modifier interface
-var _ ddebpf.Modifier = (*EventHandler)(nil)
+// compile time check to ensure this satisfies the Modifier* interfaces
+var _ ddebpf.ModifierPreStart = (*EventHandler)(nil)
+var _ ddebpf.ModifierAfterStop = (*EventHandler)(nil)
 
 // EventHandler abstracts consuming data from a perf buffer or ring buffer (depending on availability and options).
 // It handles upgrading maps from a ring buffer if desired, and unmarshalling into the desired data type.
@@ -295,19 +296,14 @@ func (e *EventHandler) setupRingbufferWakeupConstant(mgrOpts *manager.Options) {
 	}
 }
 
-// AfterInit implements the Modifier interface
-func (e *EventHandler) AfterInit(_ *manager.Manager, _ names.ModuleName, _ *manager.Options) error {
-	return nil
-}
-
-// PreStart implements the Modifier interface
-func (e *EventHandler) PreStart() error {
+// PreStart implements the ModifierPreStart interface
+func (e *EventHandler) PreStart(_ *manager.Manager, _ names.ModuleName) error {
 	go e.readLoop()
 	return nil
 }
 
-// AfterStop implements the Modifier interface
-func (e *EventHandler) AfterStop(_ manager.MapCleanupType) error {
+// AfterStop implements the ModifierAfterStop interface
+func (e *EventHandler) AfterStop(_ *manager.Manager, _ names.ModuleName, _ manager.MapCleanupType) error {
 	if e.perfChan != nil {
 		close(e.perfChan)
 	}