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

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Message-ID: <20180626233302.GU19565@plex.lan>
Date:   Tue, 26 Jun 2018 20:33:02 -0300
From:   Flavio Leitner <fbl@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.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 03:47:31PM -0700, Cong Wang wrote:
> On Tue, Jun 26, 2018 at 3:03 PM Flavio Leitner <fbl@...hat.com> wrote:
> >
> > On Tue, Jun 26, 2018 at 02:48:47PM -0700, Cong Wang wrote:
> > > On Mon, Jun 25, 2018 at 11:41 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
> > > > When a packet is attached to a socket, we should keep the association as much as possible.
> > >
> > > As much as possible within one stack, I agree. I still don't understand
> > > why we should keep it across the stack boundary.
> > >
> > > > Only when a new association needs to be done, skb_orphan() needs to be called.
> > > >
> > > > Doing this skb_orphan() too soon breaks back pressure in general, this is bad, since a socket
> > > > can evades SO_SNDBUF limits.
> > >
> > > Right before leaving the stack is not too soon, it is the latest
> > > actually, for veth case.
> >
> > Depends on how you view things - it's the same host/stack sharing the
> > same resources, so why should we not keep it?
> 
> Because stacks are supposed to be independent, netdevices are
> isolated, iptables and route tables too. This is how netns is designed
> from the beginning. The trend today is actually more isolation instead
> of more sharing, given the popularity of containers.

It is still isolated, the sk carries the netns info and it is
orphaned when it re-enters the stack.

-- 
Flavio