[PATCH] net/mlx5: document IP fragment matching limitations

[Bing Zhao]

Hi,
@Stephen Hemminger, we don't know other NICs behavior. If all NICs behave the same, maybe the limitation can be considered to move to the common part.

> -----Original Message-----
> From: Dariusz Sosnowski <dsosnowski at nvidia.com>
> Sent: Friday, July 18, 2025 7:52 PM
> To: Slava Ovsiienko <viacheslavo at nvidia.com>; Bing Zhao
> <bingz at nvidia.com>; Ori Kam <orika at nvidia.com>; Suanming Mou
> <suanmingm at nvidia.com>; Matan Azrad <matan at nvidia.com>
> Cc: dev at dpdk.org; NBU-Contact-Thomas Monjalon (EXTERNAL)
> <thomas at monjalon.net>; Raslan Darawsheh <rasland at nvidia.com>
> Subject: [PATCH] net/mlx5: document IP fragment matching limitations
> 
> NVIDIA NICs do not support matching on packet headers appearing after IP
> header if the received packet is an IP fragment.
> This patch updates the relevant documentation.
> 
> Bugzilla ID: 1417
> 
> Signed-off-by: Dariusz Sosnowski <dsosnowski at nvidia.com>
> ---
> Depends-on: series-35735 ("rework mlx5 guide")
> 
> FYI - I added Bugzilla ticket ID just for reference.
> Patch does not resolve the issue, just adds missing documentation for
> existing limitation.
> 
>  doc/guides/nics/mlx5.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index
> f29408eace..f58fea106a 100644
> --- a/doc/guides/nics/mlx5.rst
> +++ b/doc/guides/nics/mlx5.rst
> @@ -3305,6 +3305,13 @@ Limitations
> 
>  #. IP-in-IP is not supported with :ref:`HW steering <mlx5_hws>`.
> 
> +#. Matching on packet headers appearing after an IP header is not
> supported
> +   if that packet is an IP fragment:
> +
> +   - For example: If a flow rule with pattern matching on L4 header
> contents is created,
> +     and the first IP fragment is received,
> +     then this IP fragment will miss on that flow rule.
> +
> 
>  .. _mlx5_nat64:
> 
> --
> 2.39.5


Acked-by: Bing Zhao <bingz at nvidia.com>

Thanks