netdev - Re: Problem with iflink in netns

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Message-ID: <20140513130554.2e452af8@nehalam.linuxnetplumber.net>
Date:	Tue, 13 May 2014 13:05:54 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Cong Wang <cwang@...pensource.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Problem with iflink in netns

On Tue, 13 May 2014 11:20:58 -0700
Cong Wang <cwang@...pensource.com> wrote:

> On Tue, May 13, 2014 at 8:39 AM, Stephen Hemminger
> <stephen@...workplumber.org> wrote:
> > There have been a couple of bugzilla reports already about cases where a macvlan
> > or vlan is moved into another namespace. In these cases the parent device ifindex (iflink)
> > is no longer valid.
> >
> >
> > Normally it is not a big issue, until another device is created using the ifindex
> > of the parent
> >
> > Does anyone have a suggested fix? Marking iflink as 0 won't work then the devices no
> > longer appear as slaves. Another possibility would be to make block creation of device
> > where ifindex matches existing iflink of other devices; but this would slow down device
> > creation.
> >
> 
> I have a pending fix which converts ->iflink to a pointer to struct net_device,
> this is a suggested fix from Ben. And so, when the lower device is not
> in the same
> namespace with the upper device, we should not display the iflink information.
> 
> I will send it soon.

That won't solve the problem.
 1. a pointer increase size of netns and requires refcount
 2. iflink is still exposed in kernel user API and has to be set
    otherwise the device is falsely reported.
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