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From: David Ahern <dsahern@gmail.com>
To: Martynas Pumputis <m@lambda.lt>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Networking <netdev@vger.kernel.org>,
	Hangbin Liu <haliu@redhat.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH iproute2] libbpf: fix attach of prog with multiple sections
Date: Wed, 21 Jul 2021 08:59:19 -0600	[thread overview]
Message-ID: <4f1b5aaa-80e0-5dcc-277e-c098811cc359@gmail.com> (raw)
In-Reply-To: <df3396c3-9a4a-824d-648f-69f4da5bc78b@lambda.lt>

On 7/21/21 8:47 AM, Martynas Pumputis wrote:
>>> diff --git a/lib/bpf_libbpf.c b/lib/bpf_libbpf.c
>>> index d05737a4..f76b90d2 100644
>>> --- a/lib/bpf_libbpf.c
>>> +++ b/lib/bpf_libbpf.c
>>> @@ -267,10 +267,12 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
>>>          }
>>>
>>>          bpf_object__for_each_program(p, obj) {
>>> +               bool prog_to_attach = !prog && cfg->section &&
>>> +                       !strcmp(get_bpf_program__section_name(p),
>>> cfg->section);
>>
>> 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
>> 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.
> 
> It would be interesting to hear thoughts from iproute2 maintainers
> before fixing this.

maintaining backwards compatibility is a core principle for iproute2. If
we know of a libbpf change is going to cause a breakage then it is best
to fix it before any iproute2 release is affected.

  reply	other threads:[~2021-07-21 14:59 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 [this message]
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
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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