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

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On Tue, 20 Sep 2016 10:29:43 +0200 Jesper Dangaard Brouer [off-list ref] wrote:

On Mon, 19 Sep 2016 16:58:58 +0300 Tariq Toukan [off-list ref] wrote:

quoted

+	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"

quoted

+	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)).

quoted

+	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