Re: [Xen-devel] PATCH: default number of netloop devices to number of network devices

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

The loopback device is deprecated in xen-unstable (not needed any more) and
this isn't really critical enough for 3.1.2.

 -- Keir

On 25/10/07 19:38, "Eric Schwartz" <eric.schwartz@xxxxxx> wrote:

> Right now, unless specifically overridden, loopback_init() in
> drivers/xen/netback/loopback.c creates 4 netloop devices.  If your
> default network device is eth4 or higher, you're out of luck creating a
> xenbrN device with /etc/xen/scripts/network-bridge unless you explicitly
> set netloop.nloopbacks to something higher.  This patch attempts to set
> a more reasonable default: the number of network devices that exist, as
> reported by dev_get_by_index().
> 
> This isn't a perfect solution-- in particular, there will generally be a
> few more devices than there are physical network devices, but looking
> around and consulting with Paul Moore (netlabel maintainer), there
> doesn't seem to be a good way to tell real network devices from pseudo
> ones.  My initial attempt at a patch checked tmp->name for whether it
> began with 'eth', but it's completely reasonable to have network devices
> named anything-- an old laptop used to have its wireless interface named
> 'ath0', for instance, and another used 'wlan0'.  So while this approach
> may waste a little bit of memory, at module load time, we can ensure
> that no matter how many devices you have in your system, at least at
> boot time, you can create that many xenbrN devices.
> 
> Signed-off-by: Eric Schwartz <eric.schwartz@xxxxxx>
> 
> -=Eric
> --- linux-2.6.18.ia64/drivers/xen/netback/loopback.c.old 2007-10-25
> 13:05:30.716516696 -0400
> +++ linux-2.6.18.ia64/drivers/xen/netback/loopback.c 2007-10-25
> 14:14:07.835744809 -0400
> @@ -298,9 +298,18 @@
>  static int __init loopback_init(void)
>  {
> int i, err = 0;
> + struct net_device *tmp;
>  
> - if (nloopbacks == -1)
> -  nloopbacks = is_initial_xendomain() ? 4 : 0;
> + if (nloopbacks == -1) {
> +  nloopbacks = 0;
> +
> +  if (is_initial_xendomain()) {
> +   for(i = 1; tmp = dev_get_by_index(i); i++) {
> +    nloopbacks++;
> +    dev_put(tmp);
> +   } 
> +  } 
> + }
>  
> for (i = 0; i < nloopbacks; i++)
> if ((err = make_loopback(i)) != 0)
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