netdev - Re: [PATCH net] netlink: don't send unknown nsid

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Message-ID: <20170607183746.GD2658@x240.lan>
Date:   Wed, 7 Jun 2017 16:14:13 -0300
From:   Flavio Leitner <fbl@...close.org>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net] netlink: don't send unknown nsid

On Mon, Jun 05, 2017 at 10:40:24AM +0200, Nicolas Dichtel wrote:
> > Let me ask this instead: How do you think userspace should behave when
> > netnsid allocation fails?
> > 
> There is two ways to assign a nsid:
>  - manually with netlink ('ip netns set'). In this case, the error is reported
>    to userspace via netlink.

OK.

>  - automatically when a x-netns interface is created. The link-nsid is also
>    reported to userspace. If the allocation failed, NETNSA_NSID_NOT_ASSIGNED is
>    reported. And if you were able to create this x-netns interface, it means
>    that you have access to this peer netns, thus you can try to assign the nsid
>    manually.

Does that prevent the interface to be created?

> So, in both cases, userland knows that something went wrong.
> Do you have another scenario in mind?

Let's say the app is restarted, or another monitoring app is executed
with enough perms.  How will it identify the error condition?

-- 
Flavio