title: Calling OpenConnect VPN client in docker container shows TUNSETIFF failed: Operation not permitted
body: <p>I'm calling openconnect inside an ubuntu based docker container. It successfully connects to the server and prompt for my password, but then</p>
  
  <pre><code>Got CONNECT response: HTTP/1.1 200 OK
  CSTP connected. DPD 30, Keepalive 20
  TUNSETIFF failed: Operation not permitted
  </code></pre>
  
  <p>I search for the TUNSETIFF word and every answer is about the command not running in sudo, but I am already root inside the container. What else can go wrong?</p>