Re: [Xen-devel] RFC: XenSock brainstorming

[Stefano Stabellini <stefano@xxxxxxxxxxx>]

On Thu, 23 Jun 2016, David Vrabel wrote:
> On 06/06/16 10:33, Stefano Stabellini wrote:
> > # Goals
> > 
> > The goal of the protocol is to provide networking capabilities to any
> > guests, with the following added benefits:
> > 
> > * guest networking should work out of the box with VPNs, wireless
> >   networks and any other complex network configurations in Dom0
> > 
> > * guest services should listen on ports bound directly to Dom0 IP
> >   addresses, fitting naturally in a Docker based workflow, where guests
> >   are Docker containers
> > 
> > * Dom0 should have full visibility on the guest behavior and should be
> >   able to perform inexpensive filtering and manipulation of guest calls
> > 
> > * XenSock should provide excellent performance. Unoptimized early code
> >   reaches 22 Gbit/sec TCP single stream and scales to 60 Gbit/sec with 3
> >   streams.
> 
> I think it looks a bit odd to isolate the workload into a VM and then
> blow a hole in the isolation by providing a "fat" RPC interface directly
> to the privileged dom0 kernel.

It might look odd but this is exactly the goal of the project. The vast
majority of the syscalls will be run entirely within the VM. The ones
that are allowed to reach dom0 are only very few, less then 10 today in
fact. It is a big win from a security perspective compared to
containers. And it is a big win compared to VMs in terms of performance.
In my last test I reached 84 gbit/sec with 4 tcp streams.

Monitoring the behavior of the guest becomes extremely cheap and easy as
one can just keep track of the syscalls forwarded to dom0. It would be
trivial to figure out if your NGINX container unexpectedly tried to open
port 22 for example. One would have to employ complex firewall rules or
VM introspection to do this otherwise. In addition one can still use all
the traditional filtering techniques for these syscalls in dom0, such as
seccomp.

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