fix: RX goroutine cleanup

internal/lldp/rx.go

@@ -87,23 +87,25 @@ func (l *LLDP) setUpCapture() error {
 	return nil
 }
 
-func (l *LLDP) doCapture(logger *zerolog.Logger, rxCtx context.Context) {
-	defer func() {
-		l.mu.Lock()
-		l.rxRunning = false
-		l.mu.Unlock()
-
-		logger.Info().Msg("RX goroutine finished")
-
-		l.rxWaitGroup.Done()
-	}()
-
+func (l *LLDP) doCapture(logger *zerolog.Logger) {
 	l.rxWaitGroup.Add(1)
+	defer l.rxWaitGroup.Done()
 
 	// TODO: use a channel to handle the packets
 	// PacketSource.Packets() is not reliable and can cause panics and the upstream hasn't fixed it yet
-	for rxCtx.Err() == nil {
+	for {
+		// check if the context is done before blocking call
+		select {
+		case <-l.rxCtx.Done():
+			logger.Info().Msg("RX context cancelled")
+			return
+		default:
+		}
+
+		logger.Trace().Msg("waiting for next packet")
 		packet, err := l.pktSourceRx.NextPacket()
+		logger.Trace().Interface("packet", packet).Err(err).Msg("got next packet")
+
 		if err != nil {
 			logger.Error().
 				Err(err).
@@ -152,9 +154,7 @@ func (l *LLDP) startCapture() error {
 	l.rxCtx, l.rxCancel = context.WithCancel(context.Background())
 	l.rxRunning = true
 
-	// Capture context in closure
-	rxCtx := l.rxCtx
-	go l.doCapture(&logger, rxCtx)
+	go l.doCapture(&logger)
 
 	return nil
 }
@@ -363,11 +363,25 @@ func (l *LLDP) stopCapture() error {
 		logger.Info().Msg("cancelled RX context, waiting for goroutine to finish")
 	}
 
+	// stop the TPacketRx
+	go func() {
+		if l.tPacketRx == nil {
+			return
+		}
+
+		// write an empty packet to the TPacketRx to interrupt the blocking read
+		// it's a shitty workaround until https://github.com/google/gopacket/pull/777 is merged,
+		// or we have a better solution, see https://github.com/google/gopacket/issues/1064
+		l.tPacketRx.WritePacketData([]byte{})
+	}()
+
 	// wait for the goroutine to finish
 	start := time.Now()
 	l.rxWaitGroup.Wait()
 	logger.Info().Dur("duration", time.Since(start)).Msg("RX goroutine finished")
 
+	l.rxRunning = false
+
 	if l.tPacketRx != nil {
 		logger.Info().Msg("closing TPacketRx")
 		l.tPacketRx.Close()