From a46401bbb151d8f1e662dc16b612426352138c1e Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sat, 5 May 2018 06:00:38 +0200
Subject: More robust solution to close deadlock

---
 device.go | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

(limited to 'device.go')

diff --git a/device.go b/device.go
index 8b0d2a5..c714b21 100644
--- a/device.go
+++ b/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()
 
-- 
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