netdev - Re: Fw: [Bug 66691] New: iproute2: macvlan: Wrong root device shown if in different netns

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Date:	Mon, 16 Dec 2013 15:01:33 +0400
From:	Pavel Emelyanov <xemul@...allels.com>
To:	Helmut Schaa <helmut.schaa@...glemail.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Stephen Hemminger <stephen@...workplumber.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Fw: [Bug 66691] New: iproute2: macvlan: Wrong root device shown
 if in different netns

On 12/16/2013 02:47 PM, Helmut Schaa wrote:
> On Mon, Dec 16, 2013 at 11:41 AM, Pavel Emelyanov <xemul@...allels.com> wrote:
>> On 12/16/2013 02:38 PM, Helmut Schaa wrote:
>>> On Fri, Dec 6, 2013 at 9:05 PM, Stephen Hemminger
>>> <stephen@...workplumber.org> wrote:
>>>> This isn't a iproute2 bug, it is only reporting what the kernel tells it
>>>
>>> But iproute2 assumes that the ifindex is unique within all net
>>> namespaces. This isn't true anymore
>>> after commit aa79e66eee5d525e2fcbd2a5fcb87ae3dd4aa9e9 "net: Make
>>> ifindex generation
>>> per-net namespace".
>>>
>>> However, in order to do the right thing iproute2 would have to know
>>> the ifindex of the
>>> link device _and_ its associated netns.
>>>
>>> Not sure how to deal with that ...
>>
>> Helmut, what would you expect to see from "ip netns exec myns ip link"
>> in case there were no device with ifindex 2 in the myns netns?
> 
> No idea, maybe something like "mac0@...nown" would be enough to express
> that the link dev is not available within this netns.

Actually, I think the problem is deeper. For example, we have a veth device
driver, the devices of that kind always exist in pairs, and one device typically
sits in one namespaces, while the other device -- in another namespace.

Right now, given one veth device, there's no way to find out where its peer is.
This creates certain difficulties for the checkpoint-restore project (CRIU)
I'm working on.

Let me add Eric in a loop to ask for his thoughts about the issue.

> My point was that it is confusing to show a clearly wrong link device.

I totally agree.

> Helmut

Thanks,
Pavel
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