From de7ecc571b9ea81d5cad97e339e84f8084352741 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Fri, 4 May 2018 21:11:38 +0200
Subject: [PATCH] tun: allow darwin to auto assign names

---
 main.go       | 22 +++++++++++++++-------
 tun_darwin.go |  8 +++++---
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/main.go b/main.go
index 41231bf..8562bf6 100644
--- a/main.go
+++ b/main.go
@@ -115,13 +115,6 @@ func main() {
 		return LogLevelInfo
 	}()
 
-	logger := NewLogger(
-		logLevel,
-		fmt.Sprintf("(%s) ", interfaceName),
-	)
-
-	logger.Debug.Println("Debug log enabled")
-
 	// open TUN device (or use supplied fd)
 
 	tun, err := func() (TUNDevice, error) {
@@ -141,6 +134,21 @@ func main() {
 		return CreateTUNFromFile(file)
 	}()
 
+	if err == nil {
+		realInterfaceName, err2 := tun.Name()
+		if err2 == nil {
+			interfaceName = realInterfaceName
+		}
+	}
+
+	logger := NewLogger(
+		logLevel,
+		fmt.Sprintf("(%s) ", interfaceName),
+	)
+
+	logger.Debug.Println("Debug log enabled")
+
+
 	if err != nil {
 		logger.Error.Println("Failed to create TUN device:", err)
 		os.Exit(ExitSetupFailed)
diff --git a/tun_darwin.go b/tun_darwin.go
index a03347f..4d9b06d 100644
--- a/tun_darwin.go
+++ b/tun_darwin.go
@@ -46,9 +46,11 @@ var sockaddrCtlSize uintptr = 32
 
 func CreateTUN(name string) (TUNDevice, error) {
 	ifIndex := -1
-	fmt.Sscanf(name, "utun%d", &ifIndex)
-	if ifIndex < 0 {
-		return nil, fmt.Errorf("error parsing interface name %s, must be utun[0-9]+", name)
+	if (name != "utun") {
+		fmt.Sscanf(name, "utun%d", &ifIndex)
+		if ifIndex < 0 {
+			return nil, fmt.Errorf("Interface name must be utun[0-9]*")
+		}
 	}
 
 	fd, err := unix.Socket(unix.AF_SYSTEM, unix.SOCK_DGRAM, 2)