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

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Message-ID: <20171114063551.GB1890@nanopsycho>
Date:   Tue, 14 Nov 2017 07:35:51 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Cong Wang <xiyou.wangcong@...il.com>
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

Tue, Nov 14, 2017 at 06:51:42AM CET, xiyou.wangcong@...il.com wrote:
>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?

Nope.

>
>> dissapear from underneath the mirred action. You certainly cannot add an
>
>
>It disappears only because we don't display it properly, nothing else.

Okay.

>
>
>> 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.

Okay. What about my question? Should we allow adding an action mirred
pointing to a netdev in another netns? I think it would make sense in
case we consider movement of mirred device legit.