netdev - Re: [PATCH v6 01/12] bpf: add XDP prog type for early driver filter

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Date:	Mon, 11 Jul 2016 15:53:46 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	Brenden Blanco <bblanco@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Martin KaFai Lau <kafai@...com>, Ari Saha <as754m@....com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Or Gerlitz <gerlitz.or@...il.com>,
	john fastabend <john.fastabend@...il.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Thomas Graf <tgraf@...g.ch>,
	Daniel Borkmann <daniel@...earbox.net>, brouer@...hat.com
Subject: Re: [PATCH v6 01/12] bpf: add XDP prog type for early driver filter

On Sun, 10 Jul 2016 16:04:16 -0500
Tom Herbert <tom@...bertland.com> wrote:

> > +/* User return codes for XDP prog type.
> > + * A valid XDP program must return one of these defined values. All other
> > + * return codes are reserved for future use. Unknown return codes will result
> > + * in driver-dependent behavior.
> > + */
> > +enum xdp_action {
> > +       XDP_DROP,
> > +       XDP_PASS,  
> 
> I think that we should be able to distinguish an abort in BPF program
> from a normal programmatic drop. e.g.:
> 
> enum xdp_action {
>       XDP_ABORTED = 0,
>       XDP_DROP,
>       XDP_PASS,
> };

I agree.  And maybe we can re-use the bpf_warn_invalid_xdp_action() call
to keep the branch/jump-table as simple as possible, handling the
distinguishing on the slow path.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer