What exactly do the rx-vlan-offload and tx-vlan-offload ethtool options do?
<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>