From: Jason A. Donenfeld <Jason@zx2c4.com>
Date: Fri, 20 Apr 2018 03:30:22 +0000 (+0200)
Subject: Check for correct first nibble
X-Git-Tag: 0.0.20180514~52
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5c256affdecc50ecf485b7ad54986ebb17e783a;p=thirdparty%2Fwireguard-go.git

Check for correct first nibble

The code before assumed that the flow label was always zero.
---

diff --git a/tun_linux.go b/tun_linux.go
index a37b727..1abc86f 100644
--- a/tun_linux.go
+++ b/tun_linux.go
@@ -273,7 +273,7 @@ func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
 		buff[0] = 0x00
 		buff[1] = 0x00
 
-		if buff[4] == ipv6.Version<<4 {
+		if buff[4]>>4 == ipv6.Version {
 			buff[2] = 0x86
 			buff[3] = 0xdd
 		} else {