netdev - Re: [PATCH RFC v4 bpf-next 08/11] tun: Support xdp in the Tx path for skb

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Date:   Tue, 3 Mar 2020 11:46:19 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        prashantbhole.linux@...il.com, jasowang@...hat.com,
        toke@...hat.com, mst@...hat.com, toshiaki.makita1@...il.com,
        daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
        dsahern@...il.com, David Ahern <dahern@...italocean.com>,
        brouer@...hat.com
Subject: Re: [PATCH RFC v4 bpf-next 08/11] tun: Support xdp in the Tx path
 for skb

On Wed, 26 Feb 2020 20:20:10 -0700
David Ahern <dsahern@...nel.org> wrote:

> +static u32 tun_do_xdp_tx_generic(struct tun_struct *tun,
> +				 struct net_device *dev,
> +				 struct sk_buff *skb)
> +{
> +	struct bpf_prog *xdp_prog;
> +	u32 act = XDP_PASS;
> +
> +	xdp_prog = rcu_dereference(tun->xdp_egress_prog);
> +	if (xdp_prog) {
> +		struct xdp_txq_info txq = { .dev = dev };
> +		struct xdp_buff xdp;
> +
> +		skb = tun_prepare_xdp_skb(skb);
> +		if (!skb) {
> +			act = XDP_DROP;
> +			goto out;
> +		}
> +
> +		xdp.txq = &txq;
> +
> +		act = do_xdp_generic_core(skb, &xdp, xdp_prog);
> +		switch (act) {
> +		case XDP_TX:    /* for Tx path, XDP_TX == XDP_PASS */
> +			act = XDP_PASS;
> +			break;
> +		case XDP_PASS:
> +			break;
> +		case XDP_REDIRECT:
> +			/* fall through */
> +		default:
> +			bpf_warn_invalid_xdp_action(act);
> +			/* fall through */
> +		case XDP_ABORTED:
> +			trace_xdp_exception(tun->dev, xdp_prog, act);

Hmm, don't we need to extend the trace_xdp_exception() to give users a
hint that this happened on the TX/egress path?

> +			/* fall through */
> +		case XDP_DROP:
> +			break;
> +		}
> +	}
> +
> +out:
> +	return act;
> +}


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