Skip tun tokio test without tun access

tun/tests/tokio.rs

@@ -1,10 +1,27 @@
 #[cfg(all(feature = "tokio", not(target_os = "windows")))]
-use std::net::Ipv4Addr;
+use std::{
+    io::ErrorKind,
+    net::Ipv4Addr,
+};
+
+#[cfg(all(feature = "tokio", not(target_os = "windows")))]
+fn open_test_tun() -> Option<tun::TunInterface> {
+    match tun::TunInterface::new() {
+        Ok(tun) => Some(tun),
+        Err(error) if matches!(error.kind(), ErrorKind::NotFound | ErrorKind::PermissionDenied) => {
+            eprintln!("skipping test: {}", error);
+            None
+        }
+        Err(error) => panic!("failed to create tun interface: {error}"),
+    }
+}
 
 #[tokio::test]
 #[cfg(all(feature = "tokio", not(target_os = "windows")))]
 async fn test_create() {
-    let tun = tun::TunInterface::new().unwrap();
+    let Some(tun) = open_test_tun() else {
+        return;
+    };
     let _ = tun::tokio::TunInterface::new(tun).unwrap();
 }
 
@@ -12,7 +29,9 @@ async fn test_create() {
 #[ignore = "requires interactivity"]
 #[cfg(all(feature = "tokio", not(target_os = "windows")))]
 async fn test_write() {
-    let tun = tun::TunInterface::new().unwrap();
+    let Some(tun) = open_test_tun() else {
+        return;
+    };
     tun.set_ipv4_addr(Ipv4Addr::from([192, 168, 1, 10]))
         .unwrap();
     let async_tun = tun::tokio::TunInterface::new(tun).unwrap();