netdev - Re: [PATCH net-next] Documentation: xsk: correct the obsolete references and examples

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Message-ID: <aGJ4ohHA3Cs45wCp@boxer>
Date: Mon, 30 Jun 2025 13:44:34 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Jason Xing <kerneljasonxing@...il.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 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

> -
> -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
> 
>