tap: keeping only an fd around after jailing...

is not a correct option for making use of /dev/net/tun.
We need to obtain an fd everytime we create a tap interface.

Signed-off-by: Diana Popa <[email protected]>

Author: dianpopa

net_util/src/tap.rs

@@ -63,19 +63,13 @@ impl Tap {
     pub fn open_named(if_name: &str) -> Result<Tap> {
         let terminated_if_name = build_terminated_if_name(if_name)?;
 
-        let fd = if ::data_model::FIRECRACKER_IS_JAILED.load(::std::sync::atomic::Ordering::Relaxed)
-        {
-            // This is the /dev/net/tun fd inherited from the jailer.
-            ::jailer::DEV_NET_TUN_FD
-        } else {
-            unsafe {
-                // Open calls are safe because we give a constant nul-terminated
-                // string and verify the result.
-                libc::open(
-                    b"/dev/net/tun\0".as_ptr() as *const c_char,
-                    libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
-                )
-            }
+        let fd = unsafe {
+            // Open calls are safe because we give a constant null-terminated
+            // string and verify the result.
+            libc::open(
+                b"/dev/net/tun\0".as_ptr() as *const c_char,
+                libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
+            )
         };
         if fd < 0 {
             return Err(Error::OpenTun(IoError::last_os_error()));