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

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Date:   Mon, 13 May 2019 17:13:36 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Sabrina Dubroca <sd@...asysnail.net>
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

Le 13/05/2019 à 17:08, Sabrina Dubroca a écrit :
> 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).
No sure to follow you. The problem you describe cannot happen before commit
5e6700b3bf98, so there cannot be a "faulty" patch before that commit.
Anyway, both commits are very old, so it doesn't matter.


Thank you,
Nicolas