Re: [PATCH bpf-next v2 2/8] libbpf: Add a helper for retrieving a prog via index
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2019-01-23 10:41:18
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?
quoted hunk ↗ jump to hunk
Signed-off-by: Maciej Fijalkowski <redacted> Reviewed-by: Jakub Kicinski <redacted> --- 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;