On 01/21/2019 10:10 AM, Maciej Fijalkowski wrote:
> xdp_redirect_cpu has a 6 different XDP programs that can be attached to
> network interface. This sample has a option --prognum that allows user
> for specifying which particular program from a given set will be
> attached to network interface.
> In order to make it easier when converting the mentioned sample to
> libbpf usage, add a function to libbpf that will return program's fd for
> a given index.
>
> Note that there is already a bpf_object__find_prog_by_idx, which could
> be exported and might be used for that purpose, but it operates on the
> number of ELF section and here we need an index from a programs array
> within the bpf_object.
Series in general looks good to me. Few minor comments, mainly in relation
to the need for libbpf extensions.
Would it not be a better interface to the user to instead choose the prog
based on section name and then retrieve it via
bpf_object__find_program_by_title()
instead of prognum (which feels less user friendly) at least?
> Signed-off-by: Maciej Fijalkowski <maciejromanfijalkow...@gmail.com>
> Reviewed-by: Jakub Kicinski <jakub.kicin...@netronome.com>
> ---
> tools/lib/bpf/libbpf.c | 8 ++++++++
> tools/lib/bpf/libbpf.h | 3 +++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 12 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index dc838bea403f..21c84d0f6128 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -935,6 +935,14 @@ static int bpf_object__elf_collect(struct bpf_object
> *obj, int flags)
> return err;
> }
>
> +int
> +bpf_object__get_prog_fd_by_num(struct bpf_object *obj, int idx)
> +{
> + if (idx >= 0 && idx < obj->nr_programs)
> + return bpf_program__fd(&obj->programs[idx]);
> + return -ENOENT;
> +}
> +
> static struct bpf_program *
> bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx)
> {
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 7f10d36abdde..ca1b381cb3ad 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -95,6 +95,9 @@ LIBBPF_API int bpf_object__btf_fd(const struct bpf_object
> *obj);
> LIBBPF_API struct bpf_program *
> bpf_object__find_program_by_title(struct bpf_object *obj, const char *title);
>
> +LIBBPF_API int
> +bpf_object__get_prog_fd_by_num(struct bpf_object *obj, int idx);
> +
> LIBBPF_API struct bpf_object *bpf_object__next(struct bpf_object *prev);
> #define bpf_object__for_each_safe(pos, tmp) \
> for ((pos) = bpf_object__next(NULL), \
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 7c59e4f64082..871d2fc07150 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -127,4 +127,5 @@ LIBBPF_0.0.1 {
> LIBBPF_0.0.2 {
> global:
> bpf_object__find_map_fd_by_name;
> + bpf_object__get_prog_fd_by_num;
> } LIBBPF_0.0.1;
>
