From 92f847483200a63193d55418381e685621b24e5c Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 31 Mar 2019 10:17:11 +0200
Subject: [PATCH] wintun: add more retry loops

---
 tun/tun_windows.go                  | 17 ++++--------
 tun/wintun/registryhacks_windows.go | 42 +++++++++++++++++++++++++++++
 tun/wintun/wintun_windows.go        | 27 +++++++------------
 3 files changed, 56 insertions(+), 30 deletions(-)
 create mode 100644 tun/wintun/registryhacks_windows.go

diff --git a/tun/tun_windows.go b/tun/tun_windows.go
index 9428373..948f08d 100644
--- a/tun/tun_windows.go
+++ b/tun/tun_windows.go
@@ -75,18 +75,11 @@ func CreateTUN(ifname string) (TUNDevice, error) {
 		return nil, err
 	}
 
-	go func() {
-		retries := retryTimeout * retryRate
-		for {
-			err := wt.SetInterfaceName(ifname)
-			if err != nil && retries > 0 {
-				time.Sleep(time.Second / retryRate)
-				retries--
-				continue
-			}
-			return
-		}
-	}()
+	err = wt.SetInterfaceName(ifname)
+	if err != nil {
+		wt.DeleteInterface(0)
+		return nil, err
+	}
 
 	err = wt.FlushInterface()
 	if err != nil {
diff --git a/tun/wintun/registryhacks_windows.go b/tun/wintun/registryhacks_windows.go
new file mode 100644
index 0000000..62a629a
--- /dev/null
+++ b/tun/wintun/registryhacks_windows.go
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package wintun
+
+import (
+	"golang.org/x/sys/windows/registry"
+	"time"
+)
+
+const (
+	numRetries = 25
+	retryTimeout = 100 * time.Millisecond
+)
+
+func registryOpenKeyRetry(k registry.Key, path string, access uint32) (key registry.Key, err error) {
+	for i := 0; i < numRetries; i++ {
+		key, err = registry.OpenKey(k, path, access)
+		if err == nil {
+			break
+		}
+		if i != numRetries - 1 {
+			time.Sleep(retryTimeout)
+		}
+	}
+	return
+}
+
+func keyGetStringValueRetry(k registry.Key, name string) (val string, valtype uint32, err error) {
+	for i := 0; i < numRetries; i++ {
+		val, valtype, err = k.GetStringValue(name)
+		if err == nil {
+			break
+		}
+		if i != numRetries - 1 {
+			time.Sleep(retryTimeout)
+		}
+	}
+	return
+}
diff --git a/tun/wintun/wintun_windows.go b/tun/wintun/wintun_windows.go
index ba94b11..77e83a0 100644
--- a/tun/wintun/wintun_windows.go
+++ b/tun/wintun/wintun_windows.go
@@ -48,22 +48,14 @@ func MakeWintun(deviceInfoSet setupapi.DevInfo, deviceInfoData *setupapi.DevInfo
 	var valueStr string
 	var valueType uint32
 
-	//TODO: Figure out a way to not need to loop like this.
-	for i := 0; i < 30; i++ {
-		// Read the NetCfgInstanceId value.
-		valueStr, valueType, err = key.GetStringValue("NetCfgInstanceId")
-		if err != nil {
-			time.Sleep(time.Millisecond * 100)
-			continue
-		}
-		if valueType != registry.SZ {
-			return nil, fmt.Errorf("NetCfgInstanceId registry value is not REG_SZ (expected: %v, provided: %v)", registry.SZ, valueType)
-		}
-		break
-	}
+	// Read the NetCfgInstanceId value.
+	valueStr, valueType, err = keyGetStringValueRetry(key, "NetCfgInstanceId")
 	if err != nil {
 		return nil, errors.New("RegQueryStringValue(\"NetCfgInstanceId\") failed: " + err.Error())
 	}
+	if valueType != registry.SZ {
+		return nil, fmt.Errorf("NetCfgInstanceId registry value is not REG_SZ (expected: %v, provided: %v)", registry.SZ, valueType)
+	}
 
 	// Convert to windows.GUID.
 	ifid, err := guid.FromString(valueStr)
@@ -117,7 +109,6 @@ func GetInterface(ifname string, hwndParent uintptr) (*Wintun, error) {
 	// "foobar" would cause conflict with "FooBar".
 	ifname = strings.ToLower(ifname)
 
-	// Iterate.
 	for index := 0; ; index++ {
 		// Get the device from the list. Should anything be wrong with this device, continue with next.
 		deviceData, err := devInfoList.EnumDeviceInfo(index)
@@ -174,7 +165,7 @@ func GetInterface(ifname string, hwndParent uintptr) (*Wintun, error) {
 			}
 
 			// This interface is not using Wintun driver.
-			return wintun, errors.New("Foreign network interface with the same name exists")
+			return nil, errors.New("Foreign network interface with the same name exists")
 		}
 	}
 
@@ -444,7 +435,7 @@ func checkReboot(deviceInfoSet setupapi.DevInfo, deviceInfoData *setupapi.DevInf
 // GetInterfaceName returns network interface name.
 //
 func (wintun *Wintun) GetInterfaceName() (string, error) {
-	key, err := registry.OpenKey(registry.LOCAL_MACHINE, wintun.GetNetRegKeyName(), registry.QUERY_VALUE)
+	key, err := registryOpenKeyRetry(registry.LOCAL_MACHINE, wintun.GetNetRegKeyName(), registry.QUERY_VALUE)
 	if err != nil {
 		return "", errors.New("Network-specific registry key open failed: " + err.Error())
 	}
@@ -458,7 +449,7 @@ func (wintun *Wintun) GetInterfaceName() (string, error) {
 // SetInterfaceName sets network interface name.
 //
 func (wintun *Wintun) SetInterfaceName(ifname string) error {
-	key, err := registry.OpenKey(registry.LOCAL_MACHINE, wintun.GetNetRegKeyName(), registry.SET_VALUE)
+	key, err := registryOpenKeyRetry(registry.LOCAL_MACHINE, wintun.GetNetRegKeyName(), registry.SET_VALUE)
 	if err != nil {
 		return errors.New("Network-specific registry key open failed: " + err.Error())
 	}
@@ -483,7 +474,7 @@ func (wintun *Wintun) GetNetRegKeyName() string {
 //
 func getRegStringValue(key registry.Key, name string) (string, error) {
 	// Read string value.
-	value, valueType, err := key.GetStringValue(name)
+	value, valueType, err := keyGetStringValueRetry(key, name)
 	if err != nil {
 		return "", err
 	}