From c69d02664924e11ffc5e6728638216a26b81c4ce Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 18 Jun 2019 16:08:28 +0200
Subject: tun: windows: never retry open on Windows 10

---
 tun/tun_windows.go | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

(limited to 'tun/tun_windows.go')

diff --git a/tun/tun_windows.go b/tun/tun_windows.go
index b88129d..05fc3df 100644
--- a/tun/tun_windows.go
+++ b/tun/tun_windows.go
@@ -55,6 +55,15 @@ func packetAlign(size uint32) uint32 {
 	return (size + (packetExchangeAlignment - 1)) &^ (packetExchangeAlignment - 1)
 }
 
+var shouldRetryOpen = windows.RtlGetVersion().MajorVersion < 10
+
+func maybeRetry(x int) int {
+	if shouldRetryOpen {
+		return x
+	}
+	return 0
+}
+
 //
 // CreateTUN creates a Wintun adapter with the given name. Should a Wintun
 // adapter with the same name exist, it is reused.
@@ -104,7 +113,7 @@ func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID) (Dev
 }
 
 func (tun *NativeTun) openTUN() error {
-	retries := retryTimeout * retryRate
+	retries := maybeRetry(retryTimeout * retryRate)
 	if tun.close {
 		return os.ErrClosed
 	}
@@ -238,7 +247,7 @@ func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
 	default:
 	}
 
-	retries := 1000
+	retries := maybeRetry(1000)
 	for {
 		if tun.rdBuff.offset+packetExchangeAlignment <= tun.rdBuff.avail {
 			// Get packet from the exchange buffer.
@@ -302,7 +311,7 @@ func (tun *NativeTun) Flush() error {
 		tun.wrBuff.packetNum = 0
 		tun.wrBuff.offset = 0
 	}()
-	retries := 1000
+	retries := maybeRetry(1000)
 
 	for {
 		// Get TUN data pipe.
-- 
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