Re: [PATCH net] net: make dev_xdp_sb_prog_count() see programs attached through a link

[Stanislav Fomichev <sdf.kernel@gmail.com>]

On 09/30, Jakub Kicinski wrote:
> ethtool refuses to enable tcp-data-split on a device running
> a single-buffer XDP program (which can't deal with the payload
> landing in a separate buffer). dev_xdp_sb_prog_count() only looks
> at xdp_state[].prog though, ignoring bpf_link integration.
> Get the prog pointer from dev_xdp_prog(), which will consult both.
> 
> bpf_xdp_link_update() needs a bit of a touch-up, too, since
> ethtool calls dev_xdp_sb_prog_count() with just the instance
> lock (for ops-locked devices) - we now have to make sure the
> link updates happen under that lock.
> 
> Spotted by AI while reviewing the XDP propagation series,
> verified and tested on netdevsim with a C test along these lines:
> 
>   link = bpf_program__attach_xdp(prog, ifindex);
>   system("ethtool -G eth0 tcp-data-split on")
> 
> Fixes: 197258f0ef68 ("net: ethtool: add hds_config member in ethtool_netdev_state")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>