Re: [PATCH iproute2] libbpf: fix attach of prog with multiple sections

On Thu, Jul 22, 2021 at 09:51:50PM -0700, Andrii Nakryiko wrote:

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This is still problematic, because one section can have multiple BPF
programs. I.e., it's possible two define two or more XDP BPF programs
all with SEC("xdp") and libbpf works just fine with that. I suggest
moving users to specify the program name (i.e., C function name
representing the BPF program). All the xdp_mycustom_suffix namings are

I just propose an implementation as you suggested.

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a hack and will be rejected by libbpf 1.0, so it would be great to get
a head start on fixing this early on.

Thanks for bringing this up. Currently, there is no way to specify a
function name with "tc exec bpf" (only a section name via the "sec" arg). So
probably, we should just add another arg to specify the function name.

How about add a "prog" arg to load specified program name and mark
"sec" as not recommended? To keep backwards compatibility we just load the
first program in the section.

Why not error out if there is more than one program with the same
section name? if there is just one (and thus section name is still
unique) -- then proceed. It seems much less confusing, IMO.

If you and others think it's OK to only support one program each section.
I do no object.

Thanks
Hangbin