Update TUN creation

experimental/libbox/tun_darwin.go

@@ -0,0 +1,34 @@
+package libbox
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// kanged from wireauard-apple
+
+const utunControlName = "com.apple.net.utun_control"
+
+func GetTunnelFileDescriptor() int32 {
+	ctlInfo := &unix.CtlInfo{}
+	copy(ctlInfo.Name[:], utunControlName)
+	for fd := 0; fd < 1024; fd++ {
+		addr, err := unix.Getpeername(fd)
+		if err != nil {
+			continue
+		}
+		addrCTL, loaded := addr.(*unix.SockaddrCtl)
+		if !loaded {
+			continue
+		}
+		if ctlInfo.Id == 0 {
+			err = unix.IoctlCtlInfo(fd, ctlInfo)
+			if err != nil {
+				continue
+			}
+		}
+		if addrCTL.ID == ctlInfo.Id {
+			return int32(fd)
+		}
+	}
+	return -1
+}