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

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Message-ID: <20171114051752.GA1890@nanopsycho>
Date:   Tue, 14 Nov 2017 06:17:52 +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

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
dissapear from underneath the mirred action. You certainly cannot add an
action mirred with device from another net namespace. So should we allow
that?