Fix: revert to classic TUN creation (#254)

core/device/tun/tun_wireguard_unix.go

@@ -2,7 +2,15 @@
 
 package tun
 
+import (
+	"golang.zx2c4.com/wireguard/tun"
+)
+
 const (
 	offset     = 4 /* 4 bytes TUN_PI */
 	defaultMTU = 1500
 )
+
+func createTUN(name string, mtu int) (tun.Device, error) {
+	return tun.CreateTUN(name, mtu)
+}