netdev - Re: [PATCH bpf-next 3/4] libbpf: handle AF_XDP sockets created with XDP

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Message-ID: <8a71dd88-43d0-e1fd-3a08-ecf431e36954@intel.com>
Date:   Tue, 8 Oct 2019 10:05:48 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Sridhar Samudrala <sridhar.samudrala@...el.com>,
        magnus.karlsson@...el.com, netdev@...r.kernel.org,
        bpf@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        maciej.fijalkowski@...el.com, tom.herbert@...el.com
Subject: Re: [PATCH bpf-next 3/4] libbpf: handle AF_XDP sockets created with
 XDP_DIRECT bind flag.

On 2019-10-08 08:16, Sridhar Samudrala wrote:
> Don't allow an AF_XDP socket trying to bind with XDP_DIRECT bind
> flag when a normal XDP program is already attached to the device,
> 
> Don't attach the default XDP program when AF_XDP socket is created
> with XDP_DIRECT bind flag.
>

I'd like this to be default for xsk.c, and if not supported fall back to 
old code.


> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
> ---
>   tools/lib/bpf/xsk.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index d5f4900e5c54..953b479040cd 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -454,6 +454,9 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   		return err;
>   
>   	if (!prog_id) {
> +		if (xsk->config.bind_flags & XDP_DIRECT)
> +			return 0;
> +
>   		err = xsk_create_bpf_maps(xsk);
>   		if (err)
>   			return err;
> @@ -464,6 +467,9 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   			return err;
>   		}
>   	} else {
> +		if (xsk->config.bind_flags & XDP_DIRECT)
> +			return -EEXIST;
> +
>   		xsk->prog_fd = bpf_prog_get_fd_by_id(prog_id);
>   		err = xsk_lookup_bpf_maps(xsk);
>   		if (err) {
>