netdev - Re: [PATCH v10 04/12] rtnl: add option for setting link xdp prog

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Date:	Wed, 20 Jul 2016 10:38:49 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Brenden Blanco <bblanco@...mgrid.com>, davem@...emloft.net,
	netdev@...r.kernel.org
CC:	Jamal Hadi Salim <jhs@...atatu.com>,
	Saeed Mahameed <saeedm@....mellanox.co.il>,
	Martin KaFai Lau <kafai@...com>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Ari Saha <as754m@....com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Or Gerlitz <gerlitz.or@...il.com>, john.fastabend@...il.com,
	hannes@...essinduktion.org, Thomas Graf <tgraf@...g.ch>,
	Tom Herbert <tom@...bertland.com>,
	Tariq Toukan <ttoukan.linux@...il.com>
Subject: Re: [PATCH v10 04/12] rtnl: add option for setting link xdp prog

On 07/19/2016 09:16 PM, Brenden Blanco wrote:
> Sets the bpf program represented by fd as an early filter in the rx path
> of the netdev. The fd must have been created as BPF_PROG_TYPE_XDP.
> Providing a negative value as fd clears the program. Getting the fd back
> via rtnl is not possible, therefore reading of this value merely
> provides a bool whether the program is valid on the link or not.
>
> Signed-off-by: Brenden Blanco <bblanco@...mgrid.com>
[...]
> @@ -2054,6 +2101,23 @@ static int do_setlink(const struct sk_buff *skb,
>   		status |= DO_SETLINK_NOTIFY;
>   	}
>
> +	if (tb[IFLA_XDP]) {
> +		struct nlattr *xdp[IFLA_XDP_MAX + 1];
> +
> +		err = nla_parse_nested(xdp, IFLA_XDP_MAX, tb[IFLA_XDP],
> +				       ifla_xdp_policy);
> +		if (err < 0)
> +			goto errout;
> +
> +		if (xdp[IFLA_XDP_FD]) {
> +			err = dev_change_xdp_fd(dev,
> +						nla_get_s32(xdp[IFLA_XDP_FD]));
> +			if (err)
> +				goto errout;
> +			status |= DO_SETLINK_NOTIFY;
> +		}

For the setlink case IFLA_XDP_ATTACHED has no meaning currently, so I'd
suggest it would be good to be strict and still add a:

		/* Only used in rtnl_fill_ifinfo currently. */
		if (xdp[IFLA_XDP_ATTACHED]) {
			err = -EINVAL;
			goto errout;
		}

> +	}
> +
>   errout:
>   	if (status & DO_SETLINK_MODIFIED) {
>   		if (status & DO_SETLINK_NOTIFY)
>