netdev - Re: [PATCH v17 bpf-next 12/23] bpf: add multi-buff support to the bpf_xdp_adjust

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Date:   Tue, 9 Nov 2021 22:58:11 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com, davem@...emloft.net, ast@...nel.org,
        daniel@...earbox.net, shayagr@...zon.com, john.fastabend@...il.com,
        dsahern@...nel.org, brouer@...hat.com, echaudro@...hat.com,
        jasowang@...hat.com, alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com
Subject: Re: [PATCH v17 bpf-next 12/23] bpf: add multi-buff support to the
 bpf_xdp_adjust_tail() API

> On Mon, 8 Nov 2021 20:06:39 +0100 Lorenzo Bianconi wrote:
> > > Not sure I get what the issue is with this either? But having a test
> > > that can be run to validate this on hardware would be great in any case,
> > > I suppose - we've been discussing more general "compliance tests" for
> > > XDP before...  
> > 
> > what about option 2? We can add a frag_size field to rxq [0] that is set by
> > the driver initializing the xdp_buff. frag_size set to 0 means we can use
> > all the buffer.
> 
> So 0 would mean xdp->frame_sz can be used for extending frags?
> 
> I was expecting that we'd used rxq->frag_size in place of xdp->frame_sz.
> 
> For devices doing payload packing we will not be able to extend the
> last frag at all. Wouldn't it be better to keep 0 for the case where
> extending is not allowed?

ack, I am fine with it. I will integrate it in v18. Thanks.

Regards,
Lorenzo

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