🛂 Check for required permissions

On Linux, checks for the `CAP_NET_ADMIN` capability.
On macOS, checks for root.

tun/src/unix/apple/mod.rs

@@ -6,7 +6,7 @@ use std::io::{IoSlice, Write};
 use std::net::{Ipv4Addr, SocketAddrV4};
 use std::os::fd::{AsRawFd, RawFd};
 use std::{
-    io::{Error, Read},
+    io::{Error},
     mem,
 };