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

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Message-ID: <20160920175753.0dccd9de@redhat.com>
Date:   Tue, 20 Sep 2016 17:57:53 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Tariq Toukan <ttoukan.linux@...il.com>,
        Tariq Toukan <tariqt@...lanox.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>, brouer@...hat.com
Subject: Re: [PATCH net-next 7/8] net/mlx5e: XDP TX forwarding support

On Tue, 20 Sep 2016 08:40:37 -0700
Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> On Tue, Sep 20, 2016 at 03:53:10PM +0300, Tariq Toukan wrote:
> > >>>+	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)).  
> > I'll add this.  
> 
> Certainly NOT.
> XDP_ABORTED is an exception case when program does divide by zero.
> It should NOT do bpf_warn. It must drop the packet.
> We discussed it several months ago.
> See mlx4/en_rx.c for canonical implementation.

It was certainly not documented, and my memory fails me.

Please explain why a eBPF program error (div by zero) must be a silent drop?

-- 
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