Re: [PATCH 1/2] net: Allow to create links with given ifindex

[Eric Dumazet <eric.dumazet@gmail.com>]

On Mon, 2012-07-30 at 03:49 -0700, Eric W. Biederman wrote:
> Pavel Emelyanov <xemul@parallels.com> writes:
> 
> > Currently the RTM_NEWLINK results in -EOPNOTSUPP if the ifinfomsg->ifi_index
> > is not zero. I propose to allow requesting ifindices on link creation. This
> > is required by the checkpoint-restore to correctly restore a net namespace
> > (i.e. -- a container). The question what to do with pre-created devices such
> > as lo or sit fbdev is open, but for manually created devices this can be 
> > solved by this patch.
> 
> Have you walked through and found the locations where we still rely on
> ifindex being globally unique?
> 
> Last time I was working in this area there were serveral places where
> things were indexed by just the interface index.

Really ? This would be very strange.

AFAIK dev_new_index() is always called, even in the
dev_change_net_namespace() case if there is a conflict.

And dev_new_index() could use a pernet net->ifindex instead of a
shared/static one.