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Message-ID: <91d162e0-3d15-c1d8-1e80-8d0a4f561540@iogearbox.net> Date: Wed, 23 Jan 2019 11:41:11 +0100 From: Daniel Borkmann <daniel@...earbox.net> To: Maciej Fijalkowski <maciejromanfijalkowski@...il.com>, ast@...nel.org Cc: netdev@...r.kernel.org, jakub.kicinski@...ronome.com, brouer@...hat.com Subject: Re: [PATCH bpf-next v2 2/8] libbpf: Add a helper for retrieving a prog via index 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 <maciejromanfijalkowski@...il.com> > Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.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; >
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