NETOBSERV-2077: switch to syncMap to handle concurrency issues (#537)

Signed-off-by: Mohamed Mahmoud <mmahmoud@redhat.com>
(cherry picked from commit 6feda50)

pkg/ifaces/watcher.go

@@ -20,6 +20,8 @@ const (
 	netnsVolume = "/var/run/netns"
 )
 
+var log = logrus.WithField("component", "ifaces.Watcher")
+
 // Watcher uses system's netlink to get real-time information events about network interfaces'
 // addition or removal.
 type Watcher struct {
@@ -31,7 +33,7 @@ type Watcher struct {
 	linkSubscriberAt func(ns netns.NsHandle, ch chan<- netlink.LinkUpdate, done <-chan struct{}) error
 	mutex            *sync.Mutex
 	netnsWatcher     *fsnotify.Watcher
-	nsDone           map[string]chan struct{}
+	nsDone           sync.Map
 }
 
 func NewWatcher(bufLen int) *Watcher {
@@ -42,19 +44,19 @@ func NewWatcher(bufLen int) *Watcher {
 		linkSubscriberAt: netlink.LinkSubscribeAt,
 		mutex:            &sync.Mutex{},
 		netnsWatcher:     &fsnotify.Watcher{},
-		nsDone:           make(map[string]chan struct{}),
+		nsDone:           sync.Map{},
 	}
 }
 
 func (w *Watcher) Subscribe(ctx context.Context) (<-chan Event, error) {
 	out := make(chan Event, w.bufLen)
 	netns, err := getNetNS()
 	if err != nil {
-		w.nsDone[""] = make(chan struct{})
+		w.nsDone.Store("", make(chan struct{}))
 		go w.sendUpdates(ctx, "", out)
 	} else {
 		for _, n := range netns {
-			w.nsDone[n] = make(chan struct{})
+			w.nsDone.Store(n, make(chan struct{}))
 			go w.sendUpdates(ctx, n, out)
 		}
 	}
@@ -66,11 +68,13 @@ func (w *Watcher) Subscribe(ctx context.Context) (<-chan Event, error) {
 func (w *Watcher) sendUpdates(ctx context.Context, ns string, out chan Event) {
 	var netnsHandle netns.NsHandle
 	var err error
-	log := logrus.WithField("component", "ifaces.Watcher")
-	doneChan := w.nsDone[ns]
+	ch, ok := w.nsDone.Load(ns)
+	if !ok {
+		log.WithError(err).Warnf("netns %s not found in netns map", ns)
+		return
+	}
+	doneChan := ch.(chan struct{})
 	defer func() {
-		close(doneChan)
-		delete(w.nsDone, ns)
 		if netnsHandle.IsOpen() {
 			netnsHandle.Close()
 		}
@@ -181,9 +185,41 @@ func getNetNS() ([]string, error) {
 	return netns, nil
 }
 
+func (w *Watcher) handleEvent(ctx context.Context, event fsnotify.Event, out chan Event) {
+	ns := filepath.Base(event.Name)
+
+	switch {
+	case event.Op&fsnotify.Create == fsnotify.Create:
+		log.WithField("netns", ns).Debug("netns create notification")
+		w.createNamespace(ctx, ns, out)
+	case event.Op&fsnotify.Remove == fsnotify.Remove:
+		log.WithField("netns", ns).Debug("netns delete notification")
+		w.deleteNamespace(ns)
+	}
+}
+
+func (w *Watcher) createNamespace(ctx context.Context, ns string, out chan Event) {
+	if ch, ok := w.nsDone.Load(ns); ok {
+		log.WithField("netns", ns).Debug("netns channel already exists, deleting it")
+		close(ch.(chan struct{}))
+		w.nsDone.Delete(ns)
+	}
+
+	w.nsDone.Store(ns, make(chan struct{}))
+	go w.sendUpdates(ctx, ns, out)
+}
+
+func (w *Watcher) deleteNamespace(ns string) {
+	if ch, ok := w.nsDone.Load(ns); ok {
+		close(ch.(chan struct{}))
+		w.nsDone.Delete(ns)
+	} else {
+		log.WithField("netns", ns).Debug("netns delete but no channel exists")
+	}
+}
+
 func (w *Watcher) netnsNotify(ctx context.Context, out chan Event) {
 	var err error
-	log := logrus.WithField("component", "ifaces.Watcher")
 
 	w.netnsWatcher, err = fsnotify.NewWatcher()
 	if err != nil {
@@ -198,25 +234,7 @@ func (w *Watcher) netnsNotify(ctx context.Context, out chan Event) {
 				if !ok {
 					return
 				}
-				if event.Op&fsnotify.Create == fsnotify.Create {
-					ns := filepath.Base(event.Name)
-					log.WithField("netns", ns).Debug("netns create notification")
-					if _, ok := w.nsDone[ns]; ok {
-						log.WithField("netns", ns).Debug("netns channel already exists, delete it")
-						delete(w.nsDone, ns)
-					}
-					w.nsDone[ns] = make(chan struct{})
-					go w.sendUpdates(ctx, ns, out)
-				}
-				if event.Op&fsnotify.Remove == fsnotify.Remove {
-					ns := filepath.Base(event.Name)
-					log.WithField("netns", ns).Debug("netns delete notification")
-					if _, ok := w.nsDone[ns]; ok {
-						w.nsDone[ns] <- struct{}{}
-					} else {
-						log.WithField("netns", ns).Debug("netns delete but there is no channel to send events to")
-					}
-				}
+				w.handleEvent(ctx, event, out)
 			case err, ok := <-w.netnsWatcher.Errors:
 				if !ok {
 					return