netdev - Re: [RFC net-next 3/6] net: xdp: make the stack take care of the tear down

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Date:   Fri, 24 Nov 2017 19:28:48 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        alexei.starovoitov@...il.com, jiri@...nulli.us,
        Saeed Mahameed <saeedm@...lanox.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Ariel Elior <Ariel.Elior@...ium.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [RFC net-next 3/6] net: xdp: make the stack take care of the
 tear down

On Sat, 25 Nov 2017 00:24:50 +0100, Daniel Borkmann wrote:
> > +static void dev_xdp_uninstall(struct net_device *dev)
> > +{
> > +	struct netdev_bpf xdp;
> > +	bpf_op_t ndo_bpf;  
> 
> Can you add a comment here stating that generic XDP does not
> need to be handled since we drop the prog from free_netdev()?
> Potentially we could also drop the generic one from here, that
> way we'd make no difference and have a dev_xdp_install() and
> one dev_xdp_uninstall() for all kind of attach types. Given
> generic XDP should simulate native XDP anyway, probably better
> to just do that.

I will move the freeing of generic XDP here and add a simple test to
the last patch.  Thanks!

> > +	ndo_bpf = dev->netdev_ops->ndo_bpf;
> > +	if (!ndo_bpf)
> > +		return;
> > +
> > +	__dev_xdp_query(dev, ndo_bpf, &xdp);
> > +	if (xdp.prog_attached == XDP_ATTACHED_NONE)
> > +		return;
> > +
> > +	/* Program removal should always succeed */
> > +	WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags, NULL));
> > +}