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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20211108134059.738ce863@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 8 Nov 2021 13:40:59 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lorenzo Bianconi <lorenzo@...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?