netdev - Re: [PATCH net-next 7/8] net/mlx5e: XDP TX forwarding support

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Message-ID: <20160920133300.144037fd@redhat.com>
Date:   Tue, 20 Sep 2016 13:33:00 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     brouer@...hat.com, "David S. Miller" <davem@...emloft.net>,
        netdev@...r.kernel.org, Eran Ben Elisha <eranbe@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Rana Shahout <ranas@...lanox.com>
Subject: Re: [PATCH net-next 7/8] net/mlx5e: XDP TX forwarding support


Resending, email didn't reach the list (used wrong sender email)

On Tue, 20 Sep 2016 10:29:43 +0200 Jesper Dangaard Brouer <netdev@...uer.com> wrote:

> On Mon, 19 Sep 2016 16:58:58 +0300 Tariq Toukan <tariqt@...lanox.com> wrote:
> 
> > +	act = bpf_prog_run_xdp(prog, &xdp);
> > +	switch (act) {
> > +	case XDP_PASS:
> > +		return false;
> > +	case XDP_TX:
> > +		consumed = mlx5e_xmit_xdp_frame(&rq->channel->xdp_sq, di,
> > +						MLX5_RX_HEADROOM,
> > +						len);
> > +		rq->stats.xdp_tx += consumed;
> > +		return consumed;
> > +	default:
> > +		bpf_warn_invalid_xdp_action(act);
> > +		return false;  
> 
> This looks wrong.  According to the specification[1] and comment in the
> code /include/uapi/linux/bpf.h: "Unknown return codes will result in
> packet drop"
> 
> > +	case XDP_ABORTED:  
> 
> It is not clearly defined, but I believe XDP_ABORTED should also result
> in a warning (calling bpf_warn_invalid_xdp_action(act)).
> 
> 
> > +	case XDP_DROP:
> > +		rq->stats.xdp_drop++;
> > +		mlx5e_page_release(rq, di, true);
> > +		return true;
> > +	}  
> 
> 
> I've started documenting XDP[2], as this patch clearly shows there is a
> need to have a specification, given already the second driver
> supporting XDP gets these details wrong.
> 
> [1] https://prototype-kernel.readthedocs.io/en/latest/networking/XDP/implementation/xdp_actions.html#xdp-aborted
> 
> [2] https://prototype-kernel.readthedocs.io/en/latest/networking/XDP/index.html
> 

-- 
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