netdev - Re: [PATCH net-next] net: preserve sock reference when scrubbing the skb.

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Message-ID: <CAM_iQpUnyVHPb96TTNeNo0Ydu9D9s4HqVMwr-YX822euSPXngw@mail.gmail.com>
Date:   Wed, 27 Jun 2018 11:59:59 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Flavio Leitner <fbl@...hat.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        David Miller <davem@...emloft.net>,
        Florian Westphal <fw@...len.de>,
        NetFilter <netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH net-next] net: preserve sock reference when scrubbing the skb.

On Tue, Jun 26, 2018 at 7:35 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
>
> On 06/26/2018 05:44 PM, Cong Wang wrote:
>
> > With this, a netns could totally throttle a TCP socket in a different
> > netns by holding the packets infinitely (e.g. putting them in a loop).
> > This is where the isolation breaks.
> >
>
> That is fine, really. Admin error -> Working as intended.

The point is never it is an error or not, the point is one netns could
influence another one with this change.

>
> The current scrubbing is simply wrong, not documented, and added by someone
> who had absolutely not intended all the side effects.
>

IIRC, this skb_orphan() was introduced much earlier than TSQ, probably
from the beginning of veth.

Leaving the stack should be effectively equivalent to leaving the host,
from the view of network isolation.