More robust solution to close deadlock

device.go

@@ -13,6 +13,10 @@ import (
 	"time"
 )
 
+const (
+	DeviceRoutineNumberPerCPU = 3
+)
+
 type Device struct {
 	isUp     AtomicBool // device is (going) up
 	isClosed AtomicBool // device is closed? (acting as guard)
@@ -21,6 +25,7 @@ type Device struct {
 	// synchronized resources (locks acquired in order)
 
 	state struct {
+		stopping sync.WaitGroup
 		mutex    sync.Mutex
 		changing AtomicBool
 		current  bool
@@ -306,7 +311,9 @@ func NewDevice(tun TUNDevice, logger *Logger) *Device {
 
 	// start workers
 
-	for i := 0; i < runtime.NumCPU(); i += 1 {
+	cpus := runtime.NumCPU()
+	device.state.stopping.Add(DeviceRoutineNumberPerCPU * cpus)
+	for i := 0; i < cpus; i += 1 {
 		go device.RoutineEncryption()
 		go device.RoutineDecryption()
 		go device.RoutineHandshake()
@@ -360,6 +367,25 @@ func (device *Device) RemoveAllPeers() {
 	device.peers.keyMap = make(map[NoisePublicKey]*Peer)
 }
 
+func (device *Device) FlushPacketQueues() {
+	for {
+		select {
+		case elem, ok := <-device.queue.decryption:
+			if ok {
+				elem.Drop()
+			}
+		case elem, ok := <-device.queue.encryption:
+			if ok {
+				elem.Drop()
+			}
+		case <-device.queue.handshake:
+		default:
+			return
+		}
+	}
+
+}
+
 func (device *Device) Close() {
 	if device.isClosed.Swap(true) {
 		return
@@ -376,6 +402,9 @@ func (device *Device) Close() {
 
 	device.signal.stop.Broadcast()
 
+	device.state.stopping.Wait()
+	device.FlushPacketQueues()
+
 	device.RemoveAllPeers()
 	device.rate.limiter.Close()
 

receive.go

@@ -238,17 +238,7 @@ func (device *Device) RoutineDecryption() {
 
 	logDebug := device.log.Debug
 	defer func() {
-		for {
+		device.state.stopping.Done()
-			select {
-			case elem, ok := <-device.queue.decryption:
-				if ok {
-					elem.Drop()
-				}
-			default:
-				goto out
-			}
-		}
-		out:
 		logDebug.Println("Routine: decryption worker - stopped")
 	}()
 	logDebug.Println("Routine: decryption worker - started")
@@ -314,14 +304,7 @@ func (device *Device) RoutineHandshake() {
 	logDebug := device.log.Debug
 
 	defer func() {
-		for {
+		device.state.stopping.Done()
-			select {
-			case <-device.queue.handshake:
-			default:
-				goto out
-			}
-		}
-		out:
 		logDebug.Println("Routine: handshake worker - stopped")
 	}()
 

send.go

@@ -274,17 +274,7 @@ func (device *Device) RoutineEncryption() {
 	logDebug := device.log.Debug
 
 	defer func() {
-		for {
+		device.state.stopping.Done()
-			select {
-			case elem, ok := <-device.queue.encryption:
-				if ok {
-					elem.Drop()
-				}
-			default:
-				goto out
-			}
-		}
-		out:
 		logDebug.Println("Routine: encryption worker - stopped")
 	}()