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

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 8 Dec 2020 10:00:40 +0100

On Mon, 07 Dec 2020 12:52:22 -0800
John Fastabend <[email-masked]> 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