netdev - Re: [PATCH net v2] rtnetlink: always put ILFA

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Message-ID: <20190513150812.GA18478@bistromath.localdomain>
Date:   Mon, 13 May 2019 17:08:12 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     netdev@...r.kernel.org, Dan Winship <danw@...hat.com>
Subject: Re: [PATCH net v2] rtnetlink: always put ILFA_LINK for links with a
 link-netnsid

2019-05-13, 16:50:51 +0200, Nicolas Dichtel wrote:
> Le 13/05/2019 à 15:47, Sabrina Dubroca a écrit :
> > Currently, nla_put_iflink() doesn't put the IFLA_LINK attribute when
> > iflink == ifindex.
> > 
> > In some cases, a device can be created in a different netns with the
> > same ifindex as its parent. That device will not dump its IFLA_LINK
> > attribute, which can confuse some userspace software that expects it.
> > For example, if the last ifindex created in init_net and foo are both
> > 8, these commands will trigger the issue:
> > 
> >     ip link add parent type dummy                   # ifindex 9
> >     ip link add link parent netns foo type macvlan  # ifindex 9 in ns foo
> > 
> > So, in case a device puts the IFLA_LINK_NETNSID attribute in a dump,
> > always put the IFLA_LINK attribute as well.
> > 
> > Thanks to Dan Winship for analyzing the original OpenShift bug down to
> > the missing netlink attribute.
> > 
> > Analyzed-by: Dan Winship <danw@...hat.com>
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> I would say:
> Fixes: 5e6700b3bf98 ("sit: add support of x-netns")
> 
> Because before this patch, there was no device with an iflink that can be put in
> another netns.

That tells us how far back we might want to backport this fix, but not
which commit introduced the bug. I think Fixes should refer to the
introduction of the faulty code, not to what patch made it visible (if
we can find both).

Thanks,

-- 
Sabrina