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

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Message-Id: <20190513.091930.1863448800331209213.davem@davemloft.net>
Date:   Mon, 13 May 2019 09:19:30 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     nicolas.dichtel@...nd.com
Cc:     sd@...asysnail.net, netdev@...r.kernel.org, danw@...hat.com
Subject: Re: [PATCH net v2] rtnetlink: always put ILFA_LINK for links with
 a link-netnsid

From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
Date: Mon, 13 May 2019 16:50:51 +0200

> 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.

I kind of agree.

What's important for people is knowing at what point they need to backport a
fix in order to actually fix a real problem.

Sabrina, please adjust the Fixes tag, thank you.