netdev - Re: [RFC bpf-next v1 0/7] Add kfunc bpf_xdp_pull

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Message-ID: <CAMB2axO1Hb=pNMw8p2Ca+4XfVmDTA+TxbbXaD4G6kxUVEsHERg@mail.gmail.com>
Date: Thu, 4 Sep 2025 10:28:45 -0700
From: Amery Hung <ameryhung@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Nimrod Oren <noren@...dia.com>, bpf@...r.kernel.org, netdev@...r.kernel.org, 
	alexei.starovoitov@...il.com, andrii@...nel.org, daniel@...earbox.net, 
	kuba@...nel.org, martin.lau@...nel.org, mohsin.bashr@...il.com, 
	saeedm@...dia.com, tariqt@...dia.com, mbloch@...dia.com, 
	maciej.fijalkowski@...el.com, kernel-team@...a.com, 
	Dragos Tatulea <dtatulea@...dia.com>
Subject: Re: [RFC bpf-next v1 0/7] Add kfunc bpf_xdp_pull_data

On Fri, Aug 29, 2025 at 11:22 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 8/28/25 6:39 AM, Nimrod Oren wrote:
> > I'm currently working on a series that converts the xdp_native program
> > to use dynptr for accessing header data. If accepted, it should provide
> > better performance, since dynptr can access without copying the data.
>
> The bpf_xdp_adjust_tail is aware of xdp_buff_has_frags. Is there a reason that
> bpf_xdp_adjust_head cannot handle frags also?

I am not aware of reasons that would stop this.

Are you suggesting another way to pop headers? E.g., use
bpf_xdp_adjust_head() to shrink the first frag from the front and call
bpf_xdp_store_bytes() to move the remaining headers