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From: Hangbin Liu <haliu@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Martynas Pumputis <m@lambda.lt>,
	Networking <netdev@vger.kernel.org>,
	Stephen Hemminger <stephen@networkplumber.org>,
	David Ahern <dsahern@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH iproute2] libbpf: fix attach of prog with multiple sections
Date: Sat, 24 Jul 2021 16:12:39 +0800	[thread overview]
Message-ID: <YPvLd5BiH7FHtyIp@Laptop-X1> (raw)
In-Reply-To: <CAEf4BzYayFVz4SVw3RpmTd-9w01bkA58NQ_QH4S8gLDDUsVPHA@mail.gmail.com>

On Fri, Jul 23, 2021 at 09:09:01AM -0700, Andrii Nakryiko wrote:
> On Fri, Jul 23, 2021 at 12:55 AM Hangbin Liu <haliu@redhat.com> wrote:
> >
> > 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.
> >
> 
> I'm not sure we are on the same page. I'll try to summarize what I
> understood and you guys can decide for yourself what you want to do.
> 
> So I like your idea of introducing "prog" arg that will expect BPF
> program name (i.e., C function name). In that case the name is always
> unique. For existing "sec" arg, for backwards compatibility, I'd keep
> it working, but when "sec" is used I'd check that the match is unique
> (i.e., there is only one BPF program within the specified section). If
> not and there are more than one matching BPF programs, that's a hard
> error, because otherwise you essentially randomly pick one BPF program
> out of a few.

Cool, we are in the same page now.

Thanks
Hangbin


  reply	other threads:[~2021-07-24  8:13 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05 12:43 Martynas Pumputis
2021-07-06  2:44 ` Hangbin Liu
2021-07-20 20:27 ` Andrii Nakryiko
2021-07-21 14:47   ` Martynas Pumputis
2021-07-21 14:59     ` David Ahern
2021-07-21 15:27       ` Martynas Pumputis
2021-07-23  4:01         ` Andrii Nakryiko
2021-07-23  4:41     ` Hangbin Liu
2021-07-23  4:51       ` Andrii Nakryiko
2021-07-23  7:55         ` Hangbin Liu
2021-07-23 16:09           ` Andrii Nakryiko
2021-07-24  8:12             ` Hangbin Liu [this message]
2021-07-24  0:12         ` David Ahern
2021-07-24  0:25           ` Andrii Nakryiko
2021-07-26 13:58             ` David Ahern
2021-07-26 15:13               ` Andrii Nakryiko
2021-07-27  2:51                 ` David Ahern
2021-07-27 19:05                   ` Andrii Nakryiko

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