netdev - Re: [PATCH net 1/3] net/sched: act_pedit: fix action bind logic

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Date:   Sat, 25 Feb 2023 17:15:00 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Pedro Tammela <pctammela@...atatu.com>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, amir@...ai.me,
        dcaratti@...hat.com, willemb@...gle.com, ozsh@...dia.com,
        paulb@...dia.com
Subject: Re: [PATCH net 1/3] net/sched: act_pedit: fix action bind logic

On Sat, Feb 25, 2023 at 10:38:31AM -0300, Pedro Tammela wrote:
> On 25/02/2023 10:08, Simon Horman wrote:
> > On Fri, Feb 24, 2023 at 12:00:56PM -0300, Pedro Tammela wrote:
> > > The TC architecture allows filters and actions to be created independently.
> > > In filters the user can reference action objects using:
> > > tc action add action pedit ... index 1
> > > tc filter add ... action pedit index 1
> > > 
> > > In the current code for act_pedit this is broken as it checks netlink
> > > attributes for create/update before actually checking if we are binding to an
> > > existing action.
> > > 
> > > tdc results:
> > > 1..69
> > 
> > ...
> > 
> > Hi Pedro,
> > 
> > Thanks for running the tests :)
> > 
> > I think this patch looks good - though I am still digesting it.
> > But I do wonder if you considered adding a test for this condition.
> 
> Yes, they are in my backlog to post when net-next reopens.

Excellent, thanks.

> > Also, what is the failure mode?
> 
> When referencing actions via its indexes on filters there would be three
> outcomes:
> 1 - Action binds to filter (expected)
> 2 - Action fails netlink parsing in kernel
> 3 - Action fails parsing in iproute2
> 
> I also posted complementary iproute2 patches.
> 
> > 
> > If it is that user's can't bind actions to filters,  but the kernel behaves
> > correctly with configurations it accepts. If so, then perhaps this is more
> > of a feature than a fix.
> 
> I would argue it's a fix...
> 
> > OTOH, perhaps it's a regression wrt the oldest of
> > the two patches references below.
> 
> ...because filters and actions are completely separate TC objects.
> There shouldn't be actions that can be created independently but can't be
> really used.

I agree that shouldn't be the case.
For me that doesn't make it a bug, but I don't feel strongly about it.

In any case, I'm now happy with this patch.

Reviewed-by: Simon Horman <simon.horman@...igine.com>

...