title: error: ‘LIBNET_ERR_FATAL’ with libnet
body: <p>I write a demo with libnet, but get an error when call the function:</p>
  
  <pre><code>libnet_error(LIBNET_ERR_FATAL, "libnet_open_link_interface: %s\n", errbuf);
  </code></pre>
  
  <p>The error is "error: ‘LIBNET_ERR_FATAL’ undeclared (first use in this function)".</p>
  
  <p>my gcc command is: "gcc demo.c <code>libnet-config --defines --cflags --libs</code>", and run on ubuntu.</p>
  
  <p>I want to know who got the same error before ?</p>