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

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Date:   Tue, 14 Nov 2017 10:53:51 -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 10:35 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>
> 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.

I don't think it is possible to add an action pointing to any netdev in
other netns in current code base, you just can't find it.

Moving a netdev after linking it to an action is different, if you want to
argue this using above question. Because we allow other "linking"
netdev to be moved too, like a tunnel device on top of a physical
one (this is why we have netnsid).

The "linking" of a mirred action might not be as strong as a tunnel
device "linking", but the idea is pretty much similar, I don't see
anything fundamentally wrong.