linux-kernel - Re: [PATCH net-next v3] xdp: Add helpers for head length, headroom, and metadata length

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Message-ID: <B4F050C6-610F-4D04-88D7-7EF581DA7DF1@nutanix.com>
Date: Wed, 7 May 2025 17:47:39 +0000
From: Jon Kohler <jon@...anix.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC: Jesper Dangaard Brouer <hawk@...nel.org>,
        Zvi Effron
	<zeffron@...tgames.com>,
        Stanislav Fomichev <stfomichev@...il.com>,
        Jason
 Wang <jasowang@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>,
        "David S.
 Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Alexei
 Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John
 Fastabend <john.fastabend@...il.com>,
        Simon Horman <horms@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Jacob Keller
	<jacob.e.keller@...el.com>
Subject: Re: [PATCH net-next v3] xdp: Add helpers for head length, headroom,
 and metadata length



> On May 7, 2025, at 1:21 PM, Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
> 
> !-------------------------------------------------------------------|
>  CAUTION: External Email
> 
> |-------------------------------------------------------------------!
> 
> Jesper Dangaard Brouer wrote:
>> 
>> 
>> On 07/05/2025 19.02, Zvi Effron wrote:
>>> On Wed, May 7, 2025 at 9:37 AM Jesper Dangaard Brouer <hawk@...nel.org> wrote:
>>>> 
>>>> 
>>>> 
>>>> On 07/05/2025 15.29, Willem de Bruijn wrote:
>>>>> Stanislav Fomichev wrote:
>>>>>> On 05/06, Jon Kohler wrote:
>>>>>>> Introduce new XDP helpers:
>>>>>>> - xdp_headlen: Similar to skb_headlen
>>>> 
>>>> I really dislike xdp_headlen(). This "headlen" originates from an SKB
>>>> implementation detail, that I don't think we should carry over into XDP
>>>> land.
>>>> We need to come up with something that isn't easily mis-read as the
>>>> header-length.
>>> 
>>> ... snip ...
>>> 
>>>>>> + * xdp_headlen - Calculate the length of the data in an XDP buffer
>>> 
>>> How about xdp_datalen()?
>> 
>> Yes, I like xdp_datalen() :-)
> 
> This is confusing in that it is the inverse of skb->data_len:
> which is exactly the part of the data not in the skb head.
> 
> There is value in consistent naming. I've never confused headlen
> with header len.
> 
> But if diverging, at least let's choose something not
> associated with skbs with a different meaning.

Brainstorming a few options:
- xdp_head_datalen() ?
- xdp_base_datalen() ?
- xdp_base_headlen() ?
- xdp_buff_datalen() ?
- xdp_buff_headlen() ?
- xdp_datalen() ? (ZivE, JesperB)
- xdp_headlen() ? (WillemB, JonK, StanislavF, JacobK, DanielB)