Re: [RFC PATCH bpf-next 3/5] libbpf: Add link support for BPF_PROG_TYPE_SK_MSG

[Yonghong Song <yonghong.song@linux.dev>]

On 3/8/24 5:01 PM, Andrii Nakryiko wrote:
> On Tue, Mar 5, 2024 at 12:22 PM Yonghong Song <yonghong.song@linux.dev> wrote:
>> Introduce a libbpf API bpf_program__attach_sk_msg() which allows
>> user to get a bpf_link. The API makes auto-deletion easier and
>> also allows user space application easier as link based APIs
>> are used for all programs.
>>
>> Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
>> ---
>>   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 97b573516675..b3982bb3f979 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -149,6 +149,7 @@ static const char * const link_type_name[] = {
>>          [BPF_LINK_TYPE_TCX]                     = "tcx",
>>          [BPF_LINK_TYPE_UPROBE_MULTI]            = "uprobe_multi",
>>          [BPF_LINK_TYPE_NETKIT]                  = "netkit",
>> +       [BPF_LINK_TYPE_SK_MSG]                  = "sk_msg",
>>   };
>>
>>   static const char * const map_type_name[] = {
>> @@ -12280,6 +12281,13 @@ bpf_program__attach_netkit(const struct bpf_program *prog, int ifindex,
>>          return bpf_program_attach_fd(prog, ifindex, "netkit", &link_create_opts);
>>   }
>>
>> +struct bpf_link *
>> +bpf_program__attach_sk_msg(const struct bpf_program *prog, int map_fd,
>> +                          enum bpf_attach_type attach_type)
> Why do we need to allow users to override attach_type? Why can't it
> come from bpf_program's expected attach type?

The interface is similar to previously used bpf_prog_attach(), but you are
right that this may not be needed. Let me double check.

>
>> +{
>> +       return __bpf_program_attach_fd(prog, map_fd, attach_type, "sk_msg", NULL);
>> +}
>> +
>>   struct bpf_link *bpf_program__attach_freplace(const struct bpf_program *prog,
>>                                                int target_fd,
>>                                                const char *attach_func_name)
>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
>> index 5723cbbfcc41..c8448f05e8d6 100644
>> --- a/tools/lib/bpf/libbpf.h
>> +++ b/tools/lib/bpf/libbpf.h
>> @@ -786,6 +786,9 @@ bpf_program__attach_netns(const struct bpf_program *prog, int netns_fd);
>>   LIBBPF_API struct bpf_link *
>>   bpf_program__attach_xdp(const struct bpf_program *prog, int ifindex);
>>   LIBBPF_API struct bpf_link *
>> +bpf_program__attach_sk_msg(const struct bpf_program *prog, int map_fd,
>> +                          enum bpf_attach_type attach_type);
>> +LIBBPF_API struct bpf_link *
>>   bpf_program__attach_freplace(const struct bpf_program *prog,
>>                               int target_fd, const char *attach_func_name);
>>
>> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
>> index 86804fd90dd1..c59986c6dbc5 100644
>> --- a/tools/lib/bpf/libbpf.map
>> +++ b/tools/lib/bpf/libbpf.map
>> @@ -410,6 +410,7 @@ LIBBPF_1.3.0 {
>>
>>   LIBBPF_1.4.0 {
>>          global:
>> +               bpf_program__attach_sk_msg;
>>                  bpf_token_create;
>>                  btf__new_split;
>>                  btf_ext__raw_data;
>> --
>> 2.43.0
>>