Message-ID: <CAL+tcoA6if=S3592=V503vo_BFxEJ1FgOdDA+SGOrNWtuAQuTg@mail.gmail.com>
Date: Mon, 30 Jun 2025 19:50:48 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, bjorn@...nel.org, magnus.karlsson@...el.com, 
	jonathan.lemon@...il.com, sdf@...ichev.me, ast@...nel.org, 
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com, joe@...a.to, 
	willemdebruijn.kernel@...il.com, bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next] Documentation: xsk: correct the obsolete
 references and examples

On Mon, Jun 30, 2025 at 7:44 PM Maciej Fijalkowski
<maciej.fijalkowski@...el.com> wrote:
>
> On Sat, Jun 28, 2025 at 08:08:40PM +0800, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > The modified lines are mainly related to the following commits[1][2]
> > which remove those tests and examples. Since samples/bpf has been
> > deprecated, we can refer to more examples that are easily searched
> > in the various xdp-projects.
> >
> > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=f36600634
> > [2]: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=cfb5a2dbf14
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> >  Documentation/networking/af_xdp.rst | 45 ++++++++---------------------
> >  1 file changed, 12 insertions(+), 33 deletions(-)
> >
> > diff --git a/Documentation/networking/af_xdp.rst b/Documentation/networking/af_xdp.rst
> > index dceeb0d763aa..37711619e89e 100644
> > --- a/Documentation/networking/af_xdp.rst
> > +++ b/Documentation/networking/af_xdp.rst
> > @@ -209,13 +209,10 @@ Libbpf
> >
> >  Libbpf is a helper library for eBPF and XDP that makes using these
> >  technologies a lot simpler. It also contains specific helper functions
> > -in tools/lib/bpf/xsk.h for facilitating the use of AF_XDP. It
> > -contains two types of functions: those that can be used to make the
> > -setup of AF_XDP socket easier and ones that can be used in the data
> > -plane to access the rings safely and quickly. To see an example on how
> > -to use this API, please take a look at the sample application in
> > -samples/bpf/xdpsock_usr.c which uses libbpf for both setup and data
> > -plane operations.
> > +in ./tools/testing/selftests/bpf/xsk.h for facilitating the use of
> > +AF_XDP. It contains two types of functions: those that can be used to
> > +make the setup of AF_XDP socket easier and ones that can be used in the
> > +data plane to access the rings safely and quickly.
> >
> >  We recommend that you use this library unless you have become a power
> >  user. It will make your program a lot simpler.
> > @@ -372,8 +369,7 @@ needs to explicitly notify the kernel to send any packets put on the
> >  TX ring. This can be accomplished either by a poll() call, as in the
> >  RX path, or by calling sendto().
> >
> > -An example of how to use this flag can be found in
> > -samples/bpf/xdpsock_user.c. An example with the use of libbpf helpers
> > +An example with the use of libbpf helpers
> >  would look like this for the TX path:
> >
> >  .. code-block:: c
> > @@ -551,10 +547,9 @@ Usage
> >
> >  In order to use AF_XDP sockets two parts are needed. The
> >  user-space application and the XDP program. For a complete setup and
> > -usage example, please refer to the sample application. The user-space
> > -side is xdpsock_user.c and the XDP side is part of libbpf.
> > +usage example, please refer to the xdp-project.
> >
> > -The XDP code sample included in tools/lib/bpf/xsk.c is the following:
> > +The XDP code sample is the following:
> >
> >  .. code-block:: c
> >
> > @@ -753,27 +748,11 @@ to facilitate extending a zero-copy driver with multi-buffer support.
> >  Sample application
> >  ==================
> >
> > -There is a xdpsock benchmarking/test application included that
> > -demonstrates how to use AF_XDP sockets with private UMEMs. Say that
> > -you would like your UDP traffic from port 4242 to end up in queue 16,
> > -that we will enable AF_XDP on. Here, we use ethtool for this::
> > -
> > -      ethtool -N p3p2 rx-flow-hash udp4 fn
> > -      ethtool -N p3p2 flow-type udp4 src-port 4242 dst-port 4242 \
> > -          action 16
> > -
> > -Running the rxdrop benchmark in XDP_DRV mode can then be done
> > -using::
> > -
> > -      samples/bpf/xdpsock -i p3p2 -q 16 -r -N
> > -
> > -For XDP_SKB mode, use the switch "-S" instead of "-N" and all options
> > -can be displayed with "-h", as usual.
>
> Hi Jason,
>
> these commands above should be kept as-is imho and we should point users
> to new xdpsock's location:
>
> https://github.com/xdp-project/bpf-examples/tree/main/AF_XDP-example

I thought we'd better not refer to an external link that might be
unreliable in the future. It turns out I was wrong.

No problem. I will revise them because for now it's still working well.

Thanks,
Jason

>
> > -
> > -This sample application uses libbpf to make the setup and usage of
> > -AF_XDP simpler. If you want to know how the raw uapi of AF_XDP is
> > -really used to make something more advanced, take a look at the libbpf
> > -code in tools/lib/bpf/xsk.[ch].
> > +Xdpsock benchmarking/test application can be found through googling
> > +the various xdp-project repositories connected to libxdp. If you want
> > +to know how the raw uapi of AF_XDP is really used to make something
> > +more advanced, take a look at the libbpf code in
> > +tools/testing/selftests/bpf/xsk.[ch].
> >
> >  FAQ
> >  =======
> > --
> > 2.41.3
> >
> >

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