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

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Message-ID: <YPp17yOht8W+Kaqy@Laptop-X1>
Date:   Fri, 23 Jul 2021 15:55:27 +0800
From:   Hangbin Liu <haliu@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Martynas Pumputis <m@...bda.lt>,
        Networking <netdev@...r.kernel.org>,
        Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH iproute2] libbpf: fix attach of prog with multiple
 sections

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

> > > > 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