netdev - Re: [PATCH bpf-next v3 2/6] net: tun: enable transfer of XDP metadata to skb

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Message-ID: <CACGkMEt72ZwDQUUDPUrxiEJQLTWBQ25pP0wCO-FrZ2tZDj7itA@mail.gmail.com>
Date: Wed, 26 Feb 2025 13:59:10 +0800
From: Jason Wang <jasowang@...hat.com>
To: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, willemdebruijn.kernel@...il.com, 
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, andrii@...nel.org, eddyz87@...il.com, 
	mykolal@...com, ast@...nel.org, daniel@...earbox.net, martin.lau@...ux.dev, 
	song@...nel.org, yonghong.song@...ux.dev, john.fastabend@...il.com, 
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, 
	shuah@...nel.org, hawk@...nel.org
Subject: Re: [PATCH bpf-next v3 2/6] net: tun: enable transfer of XDP metadata
 to skb

On Mon, Feb 24, 2025 at 11:29 PM Marcus Wichelmann
<marcus.wichelmann@...zner-cloud.de> wrote:
>
> When the XDP metadata area was used, it is expected that the same
> metadata can also be accessed from TC, as can be read in the description
> of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
> not yet implemented.
>
> To make this work, the skb that is being built on XDP_PASS should know
> of the current size of the metadata area. This is ensured by adding
> calls to skb_metadata_set. For the tun_xdp_one code path, an additional
> check is necessary to handle the case where the externally initialized
> xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).
>
> More information about this feature can be found in the commit message
> of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").
>
> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks