linux-kernel - Re: [PATCH bpf-next] samples/bpf: Fix sockex3: missing BPF prog type

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Date:   Thu, 3 Nov 2022 11:38:02 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Rong Tao <rtoax@...mail.com>
Cc:     andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, haoluo@...gle.com, john.fastabend@...il.com,
        jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org,
        martin.lau@...ux.dev, rongtao@...tc.cn, sdf@...gle.com,
        song@...nel.org, yhs@...com
Subject: Re: [PATCH bpf-next] samples/bpf: Fix sockex3: missing BPF prog type

On Sat, Oct 29, 2022 at 12:53 AM Rong Tao <rtoax@...mail.com> wrote:
>
> From: Rong Tao <rongtao@...tc.cn>
>
> since commit 450b167fb9be("libbpf: clean up SEC() handling"),
> sec_def_matches() does not recognize "socket/xxx" as "socket", therefore,
> the BPF program type is not recognized, set "socket/xxx" to SOCKET_FILTER
> solves this error.
>
>  $ cd samples/bpf
>  $ sudo ./sockex3
>  libbpf: prog 'bpf_func_PARSE_IP': missing BPF prog type, check ELF section name 'socket/3'
>  libbpf: prog 'bpf_func_PARSE_IP': failed to load: -22
>  libbpf: failed to load object './sockex3_kern.o'
>  ERROR: loading BPF object file failed
>
> Signed-off-by: Rong Tao <rongtao@...tc.cn>
> ---

You need to do changes like this:

diff --git a/samples/bpf/sockex3_kern.c b/samples/bpf/sockex3_kern.c
index b363503357e5..db6a93e7ec53 100644
--- a/samples/bpf/sockex3_kern.c
+++ b/samples/bpf/sockex3_kern.c
@@ -17,7 +17,7 @@
 #define IP_MF          0x2000
 #define IP_OFFSET      0x1FFF

-#define PROG(F) SEC("socket/"__stringify(F)) int bpf_func_##F
+#define PROG(F) SEC("socket_filter") int bpf_func_##F

 struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
@@ -279,7 +279,7 @@ PROG(PARSE_MPLS)(struct __sk_buff *skb)
        return 0;
 }

-SEC("socket/0")
+SEC("socket_filter")
 int main_prog(struct __sk_buff *skb)
 {
        __u32 nhoff = ETH_HLEN;


Why fixing up after the fact at runtime, if you can just make those
BPF programs conform to libbpf rules?



>  samples/bpf/sockex3_user.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/samples/bpf/sockex3_user.c b/samples/bpf/sockex3_user.c
> index cd6fa79df900..dc79c17ad195 100644
> --- a/samples/bpf/sockex3_user.c
> +++ b/samples/bpf/sockex3_user.c
> @@ -39,6 +39,9 @@ int main(int argc, char **argv)
>                 return 0;
>         }
>
> +       bpf_object__for_each_program(prog, obj)
> +               bpf_program__set_type(prog, BPF_PROG_TYPE_SOCKET_FILTER);
> +
>         /* load BPF program */
>         if (bpf_object__load(obj)) {
>                 fprintf(stderr, "ERROR: loading BPF object file failed\n");
> --
> 2.31.1
>