netdev - Re: [PATCH net v3] rtnetlink: always put IFLA

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Message-Id: <20190514.154044.1522144907282124471.davem@davemloft.net>
Date:   Tue, 14 May 2019 15:40:44 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     sd@...asysnail.net
Cc:     netdev@...r.kernel.org, danw@...hat.com, nicolas.dichtel@...nd.com
Subject: Re: [PATCH net v3] rtnetlink: always put IFLA_LINK for links with
 a link-netnsid

From: Sabrina Dubroca <sd@...asysnail.net>
Date: Tue, 14 May 2019 15:12:19 +0200

> 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.
> 
> v2: change Fixes tag, it's been here forever, as Nicolas Dichtel said
>     add Nicolas' ack
> v3: change Fixes tag
>     fix subject typo, spotted by Edward Cree
> 
> Analyzed-by: Dan Winship <danw@...hat.com>
> Fixes: d8a5ec672768 ("[NET]: netlink support for moving devices between network namespaces.")
> Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
> Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>

Applied and queued up for -stable, thank you.