Merge pull request #608 from ngc0202/master

Return tuntap err instead of unwrap

src/phy/sys/tuntap_interface.rs

@@ -103,7 +103,7 @@ impl TunTapInterfaceDesc {
                 buffer.len(),
             );
             if len == -1 {
-                Err(io::Error::last_os_error()).unwrap()
+                return Err(io::Error::last_os_error());
             }
             Ok(len as usize)
         }