On Fri, 07 Jul 2017 10:37:12 -0700
John Fastabend <[email protected]> wrote:
> Device map (devmap) is a BPF map, primarily useful for networking
> applications, that uses a key to lookup a reference to a netdevice.
>
> The map provides a clean way for BPF programs to build virtual port
> to physical port maps. Additionally, it provides a scoping function
> for the redirect action itself allowing multiple optimizations. Future
> patches will leverage the map to provide batching at the XDP layer.
>
> Another optimization/feature, that is not yet implemented, would be
> to support multiple netdevices per key to support efficient multicast
> and broadcast support.
[...]
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 74ea96e..06073ba 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -1294,6 +1294,14 @@ static int check_map_func_compatibility(struct bpf_map
> *map, int func_id)
> func_id != BPF_FUNC_current_task_under_cgroup)
> goto error;
> break;
> + /* devmap returns a pointer to a live net_device ifindex that we cannot
> + * allow to be modified from bpf side. So do not allow lookup elemnts
^^^^^^^
Spelling of elements
> + * for now.
> + */
> + case BPF_MAP_TYPE_DEVMAP:
> + if (func_id == BPF_FUNC_map_lookup_elem)
> + goto error;
> + break;
Reviewer notice this limitation from the bpf_prog side.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
