On 14 Aug 2019, at 7:34, Maxim Mikityanskiy wrote:
> Don't uninstall an XDP program when none is installed, and don't install
> an XDP program that has the same ID as the one already installed.
>
> dev_change_xdp_fd doesn't perform any checks in case it uninstalls an
> XDP program. It means that the driver's ndo_bpf can be called with
> XDP_SETUP_PROG asking to set it to NULL even if it's already NULL. This
> case happens if the user runs `ip link set eth0 xdp off` when there is
> no XDP program attached.
>
> The symmetrical case is possible when the user tries to set the program
> that is already set.
>
> The drivers typically perform some heavy operations on XDP_SETUP_PROG,
> so they all have to handle these cases internally to return early if
> they happen. This patch puts this check into the kernel code, so that
> all drivers will benefit from it.
>
> Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
Acked-by: Jonathan Lemon <jonathan.le...@gmail.com>
