Re: [PATCH net-next 3/4] bpf: devmap: implement devmap prog execution for generic XDP

Toke Høiland-Jørgensen
2021-06-21T15:50:40Z

Kumar Kartikeya Dwivedi <memxor@gmail.com> writes:

> This lifts the restriction on running devmap BPF progs in generic
> redirect mode. To match native XDP behavior, it is invoked right before
> generic_xdp_tx is called, and only supports XDP_PASS/XDP_ABORTED/
> XDP_DROP actions.
>
> We also return 0 even if devmap program drops the packet, as
> semantically redirect has already succeeded and the devmap prog is the
> last point before TX of the packet to device where it can deliver a
> verdict on the packet.
>
> This also means it must take care of freeing the skb, as
> xdp_do_generic_redirect callers only do that in case an error is
> returned.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
> kernel/bpf/devmap.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 2a75e6c2d27d..db3ed8b20c8c 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -322,7 +322,8 @@ bool dev_map_can_have_prog(struct bpf_map *map)
> {
> if ((map->map_type == BPF_MAP_TYPE_DEVMAP ||
> map->map_type == BPF_MAP_TYPE_DEVMAP_HASH) &&
> - map->value_size != offsetofend(struct bpf_devmap_val, ifindex))
> + map->value_size != offsetofend(struct bpf_devmap_val, ifindex) &&
> + map->value_size != offsetofend(struct bpf_devmap_val, bpf_prog.fd))
> return true;

With this you've basically removed the need for the check that calls
this, so why not just get rid of it entirely? Same thing for cpumap,
instead of updating cpu_map_prog_allowed(), just get rid of it...

-Toke