Re: [PATCH bpf-next 1/2] bpf: Add support for {set|get} socket options from setsockopt BPF

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Mon, Aug 16, 2021 at 4:17 PM Prankur gupta <prankgup@fb.com> wrote:
>
> Add logic to call bpf_setsockopt and bpf_getsockopt from
> setsockopt BPF programs.
> Example use case, when the user sets the IPV6_TCLASS socket option
> we would also like to change the tcp-cc for that socket.
> We don't have any use case for calling bpf_setsockopt from
> supposedly read-only sys_getsockopti, so it is made available to
> BPF_CGROUP_SETSOCKOPT only.
>
> Signed-off-by: Prankur gupta <prankgup@fb.com>
> ---
>  kernel/bpf/cgroup.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index a1dedba4c174..9c92eff9af95 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -1873,6 +1873,14 @@ cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 return &bpf_sk_storage_get_proto;
>         case BPF_FUNC_sk_storage_delete:
>                 return &bpf_sk_storage_delete_proto;
> +       case BPF_FUNC_setsockopt:
> +               if (prog->expected_attach_type == BPF_CGROUP_SETSOCKOPT)
> +                       return &bpf_sk_setsockopt_proto;
> +               return NULL;
> +       case BPF_FUNC_getsockopt:
> +               if (prog->expected_attach_type == BPF_CGROUP_SETSOCKOPT)
> +                       return &bpf_sk_getsockopt_proto;

Is there any problem enabling bpf_getsockopt() for
BPF_CGROUP_GETSOCKOPT program type?

> +               return NULL;
>  #endif
>  #ifdef CONFIG_INET
>         case BPF_FUNC_tcp_sock:
> --
> 2.30.2
>