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

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Date:   Mon, 13 May 2019 23:46:48 +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, 17:13:36 +0200, Nicolas Dichtel wrote:
> 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.

What about macvlan devices?

>From commit b863ceb7ddce ("[NET]: Add macvlan driver"):

static int macvlan_init(struct net_device *dev)
{
...
        dev->iflink             = lowerdev->ifindex;
...
}

vlan devices also had an iflink assigned since commit ddd7bf9fe4e5.

What am I missing?

-- 
Sabrina