netdev - Re: [xdp-hints] Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to HW offload hints via BTF

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Message-ID: <7518b0ec-ef27-6cc7-65c2-6d4b956b301a@gmail.com>
Date:   Fri, 7 Oct 2022 09:05:14 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>, sdf@...gle.com
Cc:     brouer@...hat.com, bpf@...r.kernel.org, netdev@...r.kernel.org,
        xdp-hints@...-project.net, larysa.zaremba@...el.com,
        memxor@...il.com, Lorenzo Bianconi <lorenzo@...nel.org>,
        mtahhan@...hat.com,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        dave@...cker.co.uk, Magnus Karlsson <magnus.karlsson@...el.com>,
        bjorn@...nel.org
Subject: Re: [xdp-hints] Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP
 gaining access to HW offload hints via BTF

On 10/6/22 11:47 AM, Jesper Dangaard Brouer wrote:
> 
> 
>> I also feel like xdp_hints_common is
>> a bit distracting. It makes the common case easy and it hides the
>> discussion/complexity about per-device hints. Maybe we can drop this
>> common case at all? Why can't every driver has a custom hints struct?
>> If we agree that naming/size will be the same across them (and review
>> catches/guaranteed that), why do we even care about having common
>> xdp_hints_common struct?
> 
> The xdp_hints_common struct is a stepping stone to making this easily
> consumable from C-code that need to generate SKBs and info for
> virtio_net 'hdr' desc.
> 
> David Ahern have been begging me for years to just add this statically
> to xdp_frame.  I have been reluctant, because I think we can come up
> with a more flexible (less UAPI fixed) way, that both allows kerne-code
> and BPF-prog to access these fields.  I think of this approach as a
> compromise between these two users.
> 

Simple implementation for common - standard - networking features; jump
through hoops to use vendor unique features. Isn't that point of
standardization?

There are multiple use cases where vlans and checksumming requests need
to traverse devices on an XDP redirect.