libbpf missing set_link_xdp_fd ?

libbpf missing set_link_xdp_fd ?

[Eric Leblond]

Hello,

bpf_load is implementing the set_link_xdp_fd() function and it seems
this function is not available in libbpf.

Should it be the case or should it be part of another library ?

BR,
-- 
Eric Leblond <eric@regit.org>
Blog: https://home.regit.org/

Re: libbpf missing set_link_xdp_fd ?

[Jesper Dangaard Brouer]

On Sun, 24 Sep 2017 20:07:11 +0200
Eric Leblond <eric@regit.org> wrote:

> Hello,
> 
> bpf_load is implementing the set_link_xdp_fd() function and it seems
> this function is not available in libbpf.

I also ran into this problem, when I wanted to switch my XDP programs
into using tools/lib/bpf/.

E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763

> Should it be the case or should it be part of another library ?

I'm not sure... maybe Alexei, Daniel or Wang have an opinion?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer

Re: libbpf missing set_link_xdp_fd ?

[Daniel Borkmann]

On 09/25/2017 11:25 AM, Jesper Dangaard Brouer wrote:
> On Sun, 24 Sep 2017 20:07:11 +0200
> Eric Leblond <eric@regit.org> wrote:
>
>> Hello,
>>
>> bpf_load is implementing the set_link_xdp_fd() function and it seems
>> this function is not available in libbpf.
>
> I also ran into this problem, when I wanted to switch my XDP programs
> into using tools/lib/bpf/.

Right.

> E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763
>
>> Should it be the case or should it be part of another library ?
>
> I'm not sure... maybe Alexei, Daniel or Wang have an opinion?

It seems that none of the actual attach infra is handled in
tools/lib/bpf/, meaning neither attaching the fd to kprobes/
uprobes/tracepoints nor tc or xdp, so adding a special case
only for xdp into the lib feels that we probably might be better
off putting this either into its own mini lib on top of that,
or as a small helper included in the samples / selftests and
the like where its needed.

Best,
Daniel

Re: libbpf missing set_link_xdp_fd ?

[Daniel Borkmann]

On 09/25/2017 11:41 AM, Daniel Borkmann wrote:
> On 09/25/2017 11:25 AM, Jesper Dangaard Brouer wrote:
>> On Sun, 24 Sep 2017 20:07:11 +0200
>> Eric Leblond <eric@regit.org> wrote:
>>
>>> Hello,
>>>
>>> bpf_load is implementing the set_link_xdp_fd() function and it seems
>>> this function is not available in libbpf.
>>
>> I also ran into this problem, when I wanted to switch my XDP programs
>> into using tools/lib/bpf/.
>
> Right.
>
>> E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763
>>
>>> Should it be the case or should it be part of another library ?
>>
>> I'm not sure... maybe Alexei, Daniel or Wang have an opinion?
>
> It seems that none of the actual attach infra is handled in
> tools/lib/bpf/, meaning neither attaching the fd to kprobes/
> uprobes/tracepoints nor tc or xdp, so adding a special case
> only for xdp into the lib feels that we probably might be better
> off putting this either into its own mini lib on top of that,

That could potentially go to tools/lib/xdp/, probably would be
the best option.

> or as a small helper included in the samples / selftests and
> the like where its needed.
>
> Best,
> Daniel

Re: libbpf missing set_link_xdp_fd ?

[Alexei Starovoitov]

On Mon, Sep 25, 2017 at 01:02:04PM +0200, Daniel Borkmann wrote:
> On 09/25/2017 11:41 AM, Daniel Borkmann wrote:
> > On 09/25/2017 11:25 AM, Jesper Dangaard Brouer wrote:
> > > On Sun, 24 Sep 2017 20:07:11 +0200
> > > Eric Leblond <eric@regit.org> wrote:
> > > 
> > > > Hello,
> > > > 
> > > > bpf_load is implementing the set_link_xdp_fd() function and it seems
> > > > this function is not available in libbpf.
> > > 
> > > I also ran into this problem, when I wanted to switch my XDP programs
> > > into using tools/lib/bpf/.
> > 
> > Right.
> > 
> > > E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763
> > > 
> > > > Should it be the case or should it be part of another library ?
> > > 
> > > I'm not sure... maybe Alexei, Daniel or Wang have an opinion?
> > 
> > It seems that none of the actual attach infra is handled in
> > tools/lib/bpf/, meaning neither attaching the fd to kprobes/
> > uprobes/tracepoints nor tc or xdp, so adding a special case
> > only for xdp into the lib feels that we probably might be better
> > off putting this either into its own mini lib on top of that,
> 
> That could potentially go to tools/lib/xdp/, probably would be
> the best option.

I'm afraid it may spiral out of control.
If we create such dirs, we'd need one for xdp, tc, cgroup, tracepoint, kprobe.
Differentiating the libraries by type of attach point is imo too fine grained.

Why not to put everything into toos/lib/bpf ?
New file for netlink stuff is easy enough and we can gatekeep it with
some knob in the Makefile, so perf build won't need to include it.

Re: libbpf missing set_link_xdp_fd ?

[Daniel Borkmann]

On 09/25/2017 06:01 PM, Alexei Starovoitov wrote:
> On Mon, Sep 25, 2017 at 01:02:04PM +0200, Daniel Borkmann wrote:
>> On 09/25/2017 11:41 AM, Daniel Borkmann wrote:
>>> On 09/25/2017 11:25 AM, Jesper Dangaard Brouer wrote:
>>>> On Sun, 24 Sep 2017 20:07:11 +0200
>>>> Eric Leblond <eric@regit.org> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> bpf_load is implementing the set_link_xdp_fd() function and it seems
>>>>> this function is not available in libbpf.
>>>>
>>>> I also ran into this problem, when I wanted to switch my XDP programs
>>>> into using tools/lib/bpf/.
>>>
>>> Right.
>>>
>>>> E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763
>>>>
>>>>> Should it be the case or should it be part of another library ?
>>>>
>>>> I'm not sure... maybe Alexei, Daniel or Wang have an opinion?
>>>
>>> It seems that none of the actual attach infra is handled in
>>> tools/lib/bpf/, meaning neither attaching the fd to kprobes/
>>> uprobes/tracepoints nor tc or xdp, so adding a special case
>>> only for xdp into the lib feels that we probably might be better
>>> off putting this either into its own mini lib on top of that,
>>
>> That could potentially go to tools/lib/xdp/, probably would be
>> the best option.
>
> I'm afraid it may spiral out of control.
> If we create such dirs, we'd need one for xdp, tc, cgroup, tracepoint, kprobe.
> Differentiating the libraries by type of attach point is imo too fine grained.
>
> Why not to put everything into toos/lib/bpf ?
> New file for netlink stuff is easy enough and we can gatekeep it with
> some knob in the Makefile, so perf build won't need to include it.

Personally, I don't really have a strong opinion on that. This could
probably be made a bit modular for each attach handler with the option
to compile some of them out if not desired, so could work as well.

Re: libbpf missing set_link_xdp_fd ?

[Wangnan (F)]

On 2017/9/25 17:25, Jesper Dangaard Brouer wrote:
> On Sun, 24 Sep 2017 20:07:11 +0200
> Eric Leblond <eric@regit.org> wrote:
>
>> Hello,
>>
>> bpf_load is implementing the set_link_xdp_fd() function and it seems
>> this function is not available in libbpf.
> I also ran into this problem, when I wanted to switch my XDP programs
> into using tools/lib/bpf/.
>
> E.g.: https://github.com/netoptimizer/prototype-kernel/commit/5397e596c30416763
>
>> Should it be the case or should it be part of another library ?
> I'm not sure... maybe Alexei, Daniel or Wang have an opinion?
>

tools/lib/bpf is aiming at provide a better way to parse bpf object file,
load bpf program and maps. It doesn't operate link layer. set_link_xdp_fd()
and other socket and link related functions are better to be implement
separately. Two choices: 1. Move them into a library in samples/bpf.
2. make libbpf support XDP. The second choice looks good, but I'm
not familiar with XDP API and don't know how to give a good abstraction.

In my opinion it should be part of another library.

Thank you.