[libvirt] Replace AF_LOCAL with AF_PACKET

Ben Gray ben.r.gray at gmail.com
Fri Jul 31 15:33:34 UTC 2015

Thanks Daniel,

It does indeed work for us, we use both a NAT based network config and 
an Isolated network config.  So far we haven't seen any negative impacts.

For reference this is the very simple patch I did

     --- a/src/util/virnetdev.c    2015-07-31 15:46:58.925705063 +0100
     +++ b/src/util/virnetdev.c    2015-07-31 15:47:13.545901192 +0100
     @@ -40,7 +40,7 @@
      #ifdef __linux__
      # include <linux/sockios.h>
      # include <linux/if_vlan.h>
      #elif defined(HAVE_STRUCT_IFREQ) && defined(AF_LOCAL)

Thanks once again,

> On Fri, Jul 31, 2015 at 03:10:24PM +0100, Ben Gray wrote:
>> Hi,
>>      I've a question on whether it's 'safe' to change the socket type used in
>> virNetxxx calls from AF_PACKET to AF_LOCAL ?
>>      The reason I ask is that we're using libvirt-lxc with a couple of bridge
>> interfaces, and we've found that the socket close call on AF_PACKET type
>> sockets takes between 40ms and 60ms. For our container config there is
>> roughly 12 close calls on AF_PACKET sockets, delaying the start-up of the
>> LXC container by around 450ms.
>>      So a simple fix to speed up our container start-up is to just switch
>> from AF_PACKET to AF_LOCAL sockets.  Hence my question on whether we can
>> safely do this, or is there some reason why AF_PACKET was chosen ?
> AFAIK, there's no particular reason why we chose AF_PACKET - we were
> probably just copying code somewhere else. Looking at the kernel code
> it seems the various ioctls() we do are accepted on any type of socket
> family. So if AF_LOCAL works, I don't see a reason not to change it.
> We should probably test old distro like RHEL5 to be sure there's no
> historical reason for it though.
> Regards,
> Daniel

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