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

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Message-ID: <681b96abe7ae4_1f6aad294c9@willemb.c.googlers.com.notmuch>
Date: Wed, 07 May 2025 13:21:47 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jesper Dangaard Brouer <hawk@...nel.org>, 
 Zvi Effron <zeffron@...tgames.com>
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Stanislav Fomichev <stfomichev@...il.com>, 
 Jon Kohler <jon@...anix.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, 
 linux-kernel@...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

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.