title: Android 6.0 464XLAT: (AF_INET) IPV4 stack is too slow when using an ipv6 apn
body: <p>I am a developer in charge of maintaining an Android application which one uses native (<code>C/C++</code>) code to establish TCP and UDP sockets.</p>
  
  <p>I am not limited to ipv4 stack only as in code we are handling ipv6 stack too.
  The annoying stuff comes when we are handling with those Android 6.0 devices which ones are sticking with an ipv6 APN..usually an ipv6 APN seems to have the dual stack with some ipv4 routing.</p>
  
  <p>I have noticed that during a such scenario, from our app/client side, there is no way to resolve a remote host-name in an ipv6 address so then we are forced to go with the ipv4 stack which one in presence of the clat/xlat daemon is very slow.</p>
  
  <p>I ve tried to force in any way the host-name resolution in an ipv6 address and to go with the ipv6 stack but there were no way to do that.</p>
  
  <p>I ve read that from ver 4.2 Android is using some clat/xlat daemon to allow ipv4 stack applications do work on ipv6 networks...and I almost sure that this is the cause of the degraded functionality of our sockets.</p>
  
  <p>Has anyone experienced such an issue?</p>
  
  <p>Is there any way to speed up the ipv4 stack in presence of the clat daemon and of an ipv6 apn?</p>
  
  <p>Is there any way to force the ipv6 stack in presence of the clat daemon and of an ipv6 apn?</p>
  
  <p>Thank you so much!</p>