Re: [virtio-dev] RE: [PATCH v9] virtio-net: support inner header hash

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 22, 2023 at 03:03:32PM +0800, Heng Qi wrote:
> 
> 
> 在 2023/2/22 下午2:21, Michael S. Tsirkin 写道:
> > On Wed, Feb 22, 2023 at 10:34:39AM +0800, Heng Qi wrote:
> > > > The user will figure out how to mitigate when such QoS is not available. Either to run in best-effort mode or mitigate differently.
> > > Yes, our cloud security and cloud network team will configure and use inner
> > > hash on dpdk.
> > Sounds good. More practical for dpdk than Linux.
> > Is there a chance that when the interface is close
> > to be final, but before the vote, you post a patch to the dpdk list and
> > get some acks from the maintainers, cc virtio-dev. This way we won't
> > merge something that will then go unused?
> > That would be best - do you have a prototype?
> 
> Not yet, dpdk and the business team are waiting for our virtio
> specification, and
> they have stated as a business team that their implementation on dpdk will
> not necessarily be open sourced to the community.😅

Ugh so no open source implementations at all :(


> > 
> > > In fact I discussed with them the security issues between
> > > tunnels,
> > > and I will quote their solutions to tunnel attacks below, but this is a
> > > problem between the tunnels, not the introduction of inner hash.
> > > I don't think we need to focus too much on this, but I'll do my best to
> > > describe the security issues between tunnels in v10.
> > > 
> > > "
> > > This is not a problem with the inner hash, it is a general problem with the
> > > outer hash.
> > > I communicated with our people who are doing cloud security (they are also
> > > one of the demanders of inner hash),
> > > and it is a common problem for one tunnel to attack another tunnel.
> > > 
> > > For example, there is a tunnel t1; a tunnel t2; a tunnel endpoint VTEP0, and
> > > the vni id of t1 is id1, and the vni id of v2 is id2; a VM.
> > > 
> > > At this time, regardless of the inner hash or the outer hash, the traffic of
> > > tunnel t1 and tunnel t2 will reach the VM through VTEP0 (whether it is a
> > > single queue or multiple queues),
> > > and may be placed on the same queue to cause queue overflow.
> > Do note (and explain in spec?) that with just an outer hash and RSS it
> > is possible to configure the tunnels to use distict queues. Impossible
> > with this interface but arguably only works for a small number of
> > tunnels anyway.
> > 
> > > # Solutions:
> > More like mitigations.
> 
> Yes, you are right.
> 
> > 
> > > 1. Some current forwarding tools such as DPDK have good forwarding
> > > performance, and it is difficult to fill up the queue;
> > Oh that's a good point. If driver is generally faster than the device
> > and queues stay away from filling up there's no DoS.
> > I'd add this to the spec.
> 
> Ok.
> 
> > 
> > > 2. or switch the attack traffic to the attack clusters;
> > What is that?
> 
> This is done by the monitoring part outside the tunnel, which is also an
> important mitigation method they mentioned
> to prevent DoS between tunnels. For example, the monitoring part cuts off,
> limits or redirects the abnormal traffic of the tunnel.

This has to be outside the device though right?
Before traffic arrives at the device.

> > 
> > > 3. or connect the traffic of different tunnels to different network card
> > > ports or network devices.
> > Not sure how this is relevant. These a distinct outer MAC - with this
> > why do we need a tunnel?
> > 
> > > 4..
> > > "