tetragon: handle test events sequentially

The test infrastructure that monitors the ring buffers and handles
events during tests does not mirror how tetragon does this in
production. When monitoring events for real, we have an event cache
channel that the ring buffer monitors write to, and the event handler
reads from. This means that events are handled sequentially.

In the test infrastructure, the ring buffer monitors handle the events
directly, resulting in two events able to be handle concurrently, which
causes problems. This commit introduces an event cache to the test
infrastructure and uses that to handle events sequentially, avoiding the
problem.

Signed-off-by: Kevin Sheldrake <[email protected]>

Author: kevsecurity

pkg/testutils/perfring/perfring.go

@@ -100,83 +100,77 @@ func ProcessEvents(t *testing.T, ctx context.Context, eventFn EventFn, wgStarted
 
 	wgStarted.Done()
 
-	errChan := make(chan error)
+	errChan := make(chan error, 2)
 	defer close(errChan)
 
-	complChan := make(chan bool)
+	complChan := make(chan bool, 2)
 	defer close(complChan)
 
+	// Create an events queue that both the ring buffers can send to.
+	// This means we can handle the events sequentially by reading from the
+	// queue, avoiding issues of handling events concurrently.
+	type testEvent struct {
+		RawSample    *[]byte
+		ComplChecker *testsensor.CompletionChecker
+		Ctx          context.Context
+		CancelFunc   context.CancelFunc
+	}
+
+	eventsQueue := make(chan *testEvent, 65536) // arbitrary size for tests
+
 	var wg sync.WaitGroup
 	wg.Add(1)
+	ctxPerfRing, cancelPerfRing := context.WithCancel(ctx)
 	defer wg.Wait()
 
 	go func() {
 		defer wg.Done()
 
 		complChecker := testsensor.NewCompletionChecker()
 
-		for ctx.Err() == nil {
+		for ctxPerfRing.Err() == nil {
 
 			record, err := perfReader.Read()
 			if err != nil {
-				if ctx.Err() == nil && !errors.Is(err, os.ErrClosed) {
+				if ctxPerfRing.Err() == nil && !errors.Is(err, os.ErrClosed) {
 					errChan <- fmt.Errorf("error reading perfring data: %w", err)
 				}
 				break
 			}
 
-			if len(record.RawSample) > 0 {
-				_, events, handlerErr := observer.HandlePerfData(record.RawSample)
-				if handlerErr != nil {
-					errChan <- fmt.Errorf("error handling perfring data: %w", handlerErr)
-					break
-				}
-				err = loopEvents(events, eventFn, complChecker)
-				if err != nil {
-					errChan <- fmt.Errorf("error loop event function returned: %w", err)
-					break
-				}
+			if complChecker.Done() || ctxPerfRing.Err() != nil {
+				break
 			}
 
-			if complChecker.Done() {
-				complChan <- true
-				break
+			if len(record.RawSample) > 0 {
+				eventsQueue <- &testEvent{&record.RawSample, complChecker, ctxPerfRing, cancelPerfRing}
 			}
 		}
 	}()
 
 	if useBPFRingBuffer {
 		// Service the BPF ring buffer.
+		ctxBPFRing, cancelBPFRing := context.WithCancel(ctx)
 		wg.Go(func() {
 
 			complChecker := testsensor.NewCompletionChecker()
 
-			for ctx.Err() == nil {
+			for ctxBPFRing.Err() == nil {
 
 				record, err := ringBufReader.Read()
 				if err != nil {
-					if ctx.Err() == nil && !errors.Is(err, os.ErrClosed) {
+					if ctxBPFRing.Err() == nil && !errors.Is(err, os.ErrClosed) {
 						errChan <- fmt.Errorf("error reading ringbuf data: %w", err)
 					}
 					break
 				}
 
-				if len(record.RawSample) > 0 {
-					_, events, handlerErr := observer.HandlePerfData(record.RawSample)
-					if handlerErr != nil {
-						errChan <- fmt.Errorf("error handling ringbuf data: %w", handlerErr)
-						break
-					}
-					err = loopEvents(events, eventFn, complChecker)
-					if err != nil {
-						errChan <- fmt.Errorf("error loop event function returned: %w", err)
-						break
-					}
+				if complChecker.Done() || ctxBPFRing.Err() != nil {
+					break
 				}
 
-				if complChecker.Done() {
-					complChan <- true
-					break
+				if len(record.RawSample) > 0 {
+					eventsQueue <- &testEvent{&record.RawSample, complChecker, ctxBPFRing, cancelBPFRing}
 				}
 			}
 		})
@@ -189,6 +183,21 @@ func ProcessEvents(t *testing.T, ctx context.Context, eventFn EventFn, wgStarted
 	}
 	for {
 		select {
+		case event := <-eventsQueue:
+			_, events, handlerErr := observer.HandlePerfData(*event.RawSample)
+			if handlerErr != nil {
+				errChan <- fmt.Errorf("error handling ringbuf data: %w", handlerErr)
+				break
+			}
+			err = loopEvents(events, eventFn, event.ComplChecker)
+			if err != nil {
+				errChan <- fmt.Errorf("error loop event function returned: %w", err)
+				break
+			}
+			if event.ComplChecker.Done() && event.Ctx.Err() == nil {
+				event.CancelFunc()
+				complChan <- true
+			}
 		case err := <-errChan:
 			t.Fatal(err)
 		case <-complChan: