Subject: Re: [PATCH bpf-next v3 12/16] libbpf: Add support for SK_LOOKUP program type

From: Jakub Sitnicki <[email-masked]>
Date: Thu, 09 Jul 2020 17:51:42 +0200

On Thu, Jul 09, 2020 at 06:23 AM CEST, Andrii Nakryiko wrote:
> On Thu, Jul 2, 2020 at 2:25 AM Jakub Sitnicki <[email-masked]> wrote:
>>
>> Make libbpf aware of the newly added program type, and assign it a
>> section name.
>>
>> Signed-off-by: Jakub Sitnicki <[email-masked]>
>> ---
>>
>> Notes:
>>     v3:
>>     - Move new libbpf symbols to version 0.1.0.
>>     - Set expected_attach_type in probe_load for new prog type.
>>
>>     v2:
>>     - Add new libbpf symbols to version 0.0.9. (Andrii)
>>
>>  tools/lib/bpf/libbpf.c        | 3 +++
>>  tools/lib/bpf/libbpf.h        | 2 ++
>>  tools/lib/bpf/libbpf.map      | 2 ++
>>  tools/lib/bpf/libbpf_probes.c | 3 +++
>>  4 files changed, 10 insertions(+)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 4ea7f4f1a691..ddcbb5dd78df 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -6793,6 +6793,7 @@ BPF_PROG_TYPE_FNS(perf_event, BPF_PROG_TYPE_PERF_EVENT);
>>  BPF_PROG_TYPE_FNS(tracing, BPF_PROG_TYPE_TRACING);
>>  BPF_PROG_TYPE_FNS(struct_ops, BPF_PROG_TYPE_STRUCT_OPS);
>>  BPF_PROG_TYPE_FNS(extension, BPF_PROG_TYPE_EXT);
>> +BPF_PROG_TYPE_FNS(sk_lookup, BPF_PROG_TYPE_SK_LOOKUP);
>>
>>  enum bpf_attach_type
>>  bpf_program__get_expected_attach_type(struct bpf_program *prog)
>> @@ -6969,6 +6970,8 @@ static const struct bpf_sec_def section_defs[] = {
>>         BPF_EAPROG_SEC("cgroup/setsockopt",     BPF_PROG_TYPE_CGROUP_SOCKOPT,
>>                                                 BPF_CGROUP_SETSOCKOPT),
>>         BPF_PROG_SEC("struct_ops",              BPF_PROG_TYPE_STRUCT_OPS),
>> +       BPF_EAPROG_SEC("sk_lookup",             BPF_PROG_TYPE_SK_LOOKUP,
>> +                                               BPF_SK_LOOKUP),
>
> So it's a BPF_PROG_TYPE_SK_LOOKUP with attach type BPF_SK_LOOKUP. What
> other potential attach types could there be for
> BPF_PROG_TYPE_SK_LOOKUP? How the section name will look like in that
> case?

BPF_PROG_TYPE_SK_LOOKUP won't have any other attach types that I can
forsee. There is a single attach type shared by tcp4, tcp6, udp4, and
udp6 hook points. If we hook it up in the future say to sctp, I expect
the same attach point will be reused.

>
>>  };
>>
>>  #undef BPF_PROG_SEC_IMPL
>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
>> index 2335971ed0bd..c2272132e929 100644
>> --- a/tools/lib/bpf/libbpf.h
>> +++ b/tools/lib/bpf/libbpf.h
>> @@ -350,6 +350,7 @@ LIBBPF_API int bpf_program__set_perf_event(struct bpf_program *prog);
>>  LIBBPF_API int bpf_program__set_tracing(struct bpf_program *prog);
>>  LIBBPF_API int bpf_program__set_struct_ops(struct bpf_program *prog);
>>  LIBBPF_API int bpf_program__set_extension(struct bpf_program *prog);
>> +LIBBPF_API int bpf_program__set_sk_lookup(struct bpf_program *prog);
>>
>>  LIBBPF_API enum bpf_prog_type bpf_program__get_type(struct bpf_program *prog);
>>  LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
>> @@ -377,6 +378,7 @@ LIBBPF_API bool bpf_program__is_perf_event(const struct bpf_program *prog);
>>  LIBBPF_API bool bpf_program__is_tracing(const struct bpf_program *prog);
>>  LIBBPF_API bool bpf_program__is_struct_ops(const struct bpf_program *prog);
>>  LIBBPF_API bool bpf_program__is_extension(const struct bpf_program *prog);
>> +LIBBPF_API bool bpf_program__is_sk_lookup(const struct bpf_program *prog);
>>
>>  /*
>>   * No need for __attribute__((packed)), all members of 'bpf_map_def'
>> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
>> index 6544d2cd1ed6..04b99f63a45c 100644
>> --- a/tools/lib/bpf/libbpf.map
>> +++ b/tools/lib/bpf/libbpf.map
>> @@ -287,5 +287,7 @@ LIBBPF_0.1.0 {
>>                 bpf_map__type;
>>                 bpf_map__value_size;
>>                 bpf_program__autoload;
>> +               bpf_program__is_sk_lookup;
>>                 bpf_program__set_autoload;
>> +               bpf_program__set_sk_lookup;
>>  } LIBBPF_0.0.9;
>> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
>> index 10cd8d1891f5..5a3d3f078408 100644
>> --- a/tools/lib/bpf/libbpf_probes.c
>> +++ b/tools/lib/bpf/libbpf_probes.c
>> @@ -78,6 +78,9 @@ probe_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns,
>>         case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
>>                 xattr.expected_attach_type = BPF_CGROUP_INET4_CONNECT;
>>                 break;
>> +       case BPF_PROG_TYPE_SK_LOOKUP:
>> +               xattr.expected_attach_type = BPF_SK_LOOKUP;
>> +               break;
>>         case BPF_PROG_TYPE_KPROBE:
>>                 xattr.kern_version = get_kernel_version();
>>                 break;
>> --
>> 2.25.4
>>