netdev - Re: [PATCH 1/2] netlink: add NLA

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Message-ID: <847cc635-cb90-821d-5824-07e7f941db75@mojatatu.com>
Date:   Tue, 18 Sep 2018 08:34:53 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        jbenc@...hat.com
Subject: Re: [PATCH 1/2] netlink: add NLA_REJECT policy type

On 2018-09-17 5:38 a.m., Johannes Berg wrote:
> On Thu, 2018-09-13 at 18:58 -0300, Marcelo Ricardo Leitner wrote:
> 

[..]

> 
> So in one case I was thinking of, there are some fields that simply
> cannot be used for input, they're only used for output. > But it may not
> always be obvious to somebody using the API. Thus, I think it makes
> sense to instruct the kernel to reject that, so that whoever gets
> confused has immediate feedback that their usage is wrong. If we ignore
> that, they may not realize their error immediately.
> 
> I think the ethtool case is similar: you can read and write some fields,
> and only read others - but if you try to write the read-only fields
> would you prefer to be told "sorry, this is not possible" vs. it being
> silently ignored? I'd definitely prefer the former.
> 
>> Maybe it would be better to have NLA_IGNORE instead? </idea>
> 
> I don't think so, it doesn't give any feedback to the application author
> that they're doing something wrong.
> 

Maybe time to introduce kernel side access-control flags?
Read/Write permissions for example. Attrs marked as read only
(in the kernel) cannot be written to.


cheers,
jamal