netdev - Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

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Message-ID: <20201207135433.41172202@carbon>
Date:   Mon, 7 Dec 2020 13:54:33 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>, alardam@...il.com, magnus.karlsson@...el.com,
        bjorn.topel@...el.com, andrii.nakryiko@...il.com, kuba@...nel.org,
        ast@...nel.org, netdev@...r.kernel.org, davem@...emloft.net,
        john.fastabend@...il.com, hawk@...nel.org,
        jonathan.lemon@...il.com, bpf@...r.kernel.org,
        jeffrey.t.kirsher@...el.com, maciejromanfijalkowski@...il.com,
        intel-wired-lan@...ts.osuosl.org,
        Marek Majtyka <marekx.majtyka@...el.com>
Subject: Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

On Fri, 4 Dec 2020 16:21:08 +0100
Daniel Borkmann <daniel@...earbox.net> wrote:

> On 12/4/20 1:46 PM, Maciej Fijalkowski wrote:
> > On Fri, Dec 04, 2020 at 01:18:31PM +0100, Toke Høiland-Jørgensen wrote:  
> >> alardam@...il.com writes:  
> >>> From: Marek Majtyka <marekx.majtyka@...el.com>
> >>>
> >>> Implement support for checking what kind of xdp functionality a netdev
> >>> supports. Previously, there was no way to do this other than to try
> >>> to create an AF_XDP socket on the interface or load an XDP program and see
> >>> if it worked. This commit changes this by adding a new variable which
> >>> describes all xdp supported functions on pretty detailed level:  
> >>
> >> I like the direction this is going! :)

(Me too, don't get discouraged by our nitpicking, keep working on this! :-))

> >>  
> >>>   - aborted
> >>>   - drop
> >>>   - pass
> >>>   - tx  
> 
> I strongly think we should _not_ merge any native XDP driver patchset
> that does not support/implement the above return codes. 

I agree, with above statement.

> Could we instead group them together and call this something like
> XDP_BASE functionality to not give a wrong impression?

I disagree.  I can accept that XDP_BASE include aborted+drop+pass.

I think we need to keep XDP_TX action separate, because I think that
there are use-cases where the we want to disable XDP_TX due to end-user
policy or hardware limitations.

Use-case(1): Cloud-provider want to give customers (running VMs) ability
to load XDP program for DDoS protection (only), but don't want to allow
customer to use XDP_TX (that can implement LB or cheat their VM
isolation policy).

Use-case(2): Disable XDP_TX on a driver to save hardware TX-queue
resources, as the use-case is only DDoS.  Today we have this problem
with the ixgbe hardware, that cannot load XDP programs on systems with
more than 192 CPUs.


> If this is properly documented that these are basic must-have
> _requirements_, then users and driver developers both know what the
> expectations are.

We can still document that XDP_TX is a must-have requirement, when a
driver implements XDP.


> >>>   - redirect  
> >>


-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer