From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Re: RFC: bring UP 'lo' by default after creating new netns
Date: Thu, 29 Jun 2017 20:08:58 -0500
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Cc: Eric Dumazet <edumazet@google.com>, adobriyan@gmail.com,
        David Miller <davem@davemloft.net>, xiyou.wangcong@gmail.com,
        linux-netdev <netdev@vger.kernel.org>
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        (Mahesh Bandewar's message of "Thu, 29 Jun 2017 16:57:39 -0700")
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"Mahesh Bandewar (महेश बंडेवार)" <maheshb@google.com> writes:

> Creation of new network namespace is almost always followed up by
> bringing up the loopback device.
>
>         ip netns add foo
>         ip -netns foo link set lo up
>
> I'm not sure if there are any consequences of bringing the device UP
> at the creation of network-namespace.

Hard coded in net/core/net_namespace.c:copy_net_ns is definitely the
wrong place in the code for something like this.  If this lives anywhere
it should live in driver/net/loopback.c, or possibly in
net/core/dev.c:net_dev_init.

If we want this we want to match what we do when we the primary network
namespace.  Just so that there are no unneeded surprises with network
namespaces.

Eric