Subject: Re: [PATCH net-next v2] samples/bpf: fixup some tools to be able to support xdp multibuffer

From: Jakub Kicinski <[email-masked]>
Date: Tue, 3 Jan 2023 17:21:53 -0800

On Tue, 03 Jan 2023 16:19:49 +0100 Toke Høiland-Jørgensen wrote:
> Hmm, good question! I don't think we've ever explicitly documented any
> assumptions one way or the other. My own mental model has certainly
> always assumed the first frag would continue to be the same size as in
> non-multi-buf packets.

Interesting! :) My mental model was closer to GRO by frags 
so the linear part would have no data, just headers.

A random datapoint is that bpf_xdp_adjust_head() seems 
to enforce that there is at least ETH_HLEN.