netdev - Re: [PATCH net-next v5 1/4] net/sched: user-space can't set unknown tcfa

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Message-ID: <b5721ac431ce9d621ea9e4a0c04de8d26dc9f558.camel@redhat.com>
Date:   Mon, 30 Jul 2018 18:41:36 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>, netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Daniel Borkmann <daniel@...earbox.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Eyal Birger <eyal.birger@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next v5 1/4] net/sched: user-space can't set unknown
 tcfa_action values

On Mon, 2018-07-30 at 10:03 -0400, Jamal Hadi Salim wrote:
> On 30/07/18 08:30 AM, Paolo Abeni wrote:
> >   	}
> >   
> > +	if (!tcf_action_valid(a->tcfa_action)) {
> > +		NL_SET_ERR_MSG(extack, "invalid action value, using TC_ACT_UNSPEC instead");
> > +		a->tcfa_action = TC_ACT_UNSPEC;
> > +	}
> > +
> >   	return a;
> >   
> 
> 
> I think it would make a lot more sense to just reject the entry than
> changing it underneath the user to a default value. Least element of
> suprise.

I fear that would break existing (bad) users ?!? This way, such users
are notified they are doing something uncorrect, but still continue to
work.

The patch can be changed to reject bad actions, if there is agreement,
but it would not look as the safest way to me.

Thanks,

Paolo