linux-kernel - Re: [PATCH bpf-next,v5 1/1] doc: xdp: clarify driver implementation for XDP Rx metadata

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Message-ID: <aHgfhIUvScQ26-zF@mini-arch>
Date: Wed, 16 Jul 2025 14:54:12 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Song Yoong Siang <yoong.siang.song@...el.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next,v5 1/1] doc: xdp: clarify driver implementation
 for XDP Rx metadata

On 07/16, Song Yoong Siang wrote:
> Clarify that drivers must remove device-reserved metadata from the
> data_meta area before passing frames to XDP programs.
> 
> Additionally, expand the explanation of how userspace and BPF programs
> should coordinate the use of METADATA_SIZE, and add a detailed diagram
> to illustrate pointer adjustments and metadata layout.
> 
> Also describe the requirements and constraints enforced by
> bpf_xdp_adjust_meta().
> 
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> ---
> V5:
>   - create a new section called 'Driver implementation' (Stanislav)
>   - reword 'utilize the data_meta area' to 'prepend metadata to received packets' (Jakub)

Thanks!

Acked-by: Stanislav Fomichev <sdf@...ichev.me>