title: What exactly do the rx-vlan-offload and tx-vlan-offload ethtool options do?
body: <p>The ethtool manpage only gives a nebulous explanation:</p>
  
  <pre><code>   rxvlan on|off
            Specifies whether RX VLAN acceleration should be enabled
  
     txvlan on|off
            Specifies whether TX VLAN acceleration should be enabled
  </code></pre>
  
  <p>What exactly do the options accomplish, assuming you can enable them?</p>