netdev - Re: [patch net] net: forbid netdev used by mirred tc act from being moved to another netns

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Date:   Mon, 13 Nov 2017 21:51:42 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        tcharding <me@...in.cc>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [patch net] net: forbid netdev used by mirred tc act from being
 moved to another netns

On Mon, Nov 13, 2017 at 9:17 PM, Jiri Pirko <jiri@...nulli.us> wrote:
> Mon, Nov 13, 2017 at 08:53:57PM CET, xiyou.wangcong@...il.com wrote:
>>On Mon, Nov 13, 2017 at 6:05 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>>> From: Jiri Pirko <jiri@...lanox.com>
>>>
>>> Currently, user may choose to move device that is used by mirred action
>>> to another network namespace. That is wrong as the action still remains
>>> in the original namespace and references non-existing ifindex.
>>
>>It is a pure display issue, the action itself should function well
>>because we only use ifindex to lookup netdevice once and
>>we save the netdevice pointer in action.
>>
>>If you really want to fix it, just tell iprout2 to display netnsid together
>>with ifindex.
>
> It is not only display issue. I think it is wrong to let a netdevice

What's wrong with it? Is it mis-functioning?

> dissapear from underneath the mirred action. You certainly cannot add an


It disappears only because we don't display it properly, nothing else.


> action mirred with device from another net namespace. So should we allow
> that?

On the other hand why linking a device to mirred action prevents it
from moving to another netns? Also, device can be moved back too.

I don't see anything wrong with it except displaying it.