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

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Message-ID: <20201208100040.0d57742a@carbon>
Date:   Tue, 8 Dec 2020 10:00:40 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     brouer@...hat.com, Daniel Borkmann <daniel@...earbox.net>,
        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,
        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 Mon, 07 Dec 2020 12:52:22 -0800
John Fastabend <john.fastabend@...il.com> wrote:

> > 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).  
> 
> Not following. What interface do they want to allow loading on? If its
> the VM interface then I don't see how it matters. From outside the
> VM there should be no way to discover if its done in VM or in tc or
> some other stack.
> 
> If its doing some onloading/offloading I would assume they need to
> ensure the isolation, etc. is still maintained because you can't
> let one VMs program work on other VMs packets safely.
> 
> So what did I miss, above doesn't make sense to me.

The Cloud-provider want to load customer provided BPF-code on the
physical Host-OS NIC (that support XDP).  The customer can get access
to a web-interface where they can write or upload their BPF-prog.

As multiple customers can upload BPF-progs, the Cloud-provider have to
write a BPF-prog dispatcher that runs these multiple program.  This
could be done via BPF tail-calls, or via Toke's libxdp[1], or via
devmap XDP-progs per egress port.

The Cloud-provider don't fully trust customers BPF-prog.   They already
pre-filtered traffic to the given VM, so they can allow customers
freedom to see traffic and do XDP_PASS and XDP_DROP.  They
administratively (via ethtool) want to disable the XDP_REDIRECT and
XDP_TX driver feature, as it can be used for violation their VM
isolation policy between customers.

Is the use-case more clear now?

[1] https://github.com/xdp-project/xdp-tools/tree/master/lib/libxdp
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer