netdev - Re: [PATCH net-next] net-loopback: allow lo dev initial state to be controlled

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Date:   Mon, 16 Nov 2020 12:17:11 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Mahesh Bandewar (महेश बंडेवार) " <maheshb@...gle.com>
Cc:     Jian Yang <jianyang.kernel@...il.com>,
        David Miller <davem@...emloft.net>,
        linux-netdev <netdev@...r.kernel.org>,
        Jian Yang <jianyang@...gle.com>
Subject: Re: [PATCH net-next] net-loopback: allow lo dev initial state to be
 controlled

On Mon, 16 Nov 2020 12:02:48 -0800 Mahesh Bandewar (महेश बंडेवार) wrote:
> On Sat, Nov 14, 2020 at 10:17 AM Jakub Kicinski <kuba@...nel.org> wrote:
> > On Wed, 11 Nov 2020 12:43:08 -0800 Jian Yang wrote:  
> > > From: Mahesh Bandewar <maheshb@...gle.com>
> > >
> > > Traditionally loopback devices comes up with initial state as DOWN for
> > > any new network-namespace. This would mean that anyone needing this
> > > device (which is mostly true except sandboxes where networking in not
> > > needed at all), would have to bring this UP by issuing something like
> > > 'ip link set lo up' which can be avoided if the initial state can be set
> > > as UP. Also ICMP error propagation needs loopback to be UP.
> > >
> > > The default value for this sysctl is set to ZERO which will preserve the
> > > backward compatible behavior for the root-netns while changing the
> > > sysctl will only alter the behavior of the newer network namespaces.  
>
> > Any reason why the new sysctl itself is not per netns?
> >  
> Making it per netns would not be very useful since its effect is only
> during netns creation.

I must be confused. Are all namespaces spawned off init_net, not the
current netns the process is in?