Re: [PATCH net-next v1 0/3] vsock: Add flag field in the vsock address

[Paraschiv, Andra-Irina]

On 02/12/2020 15:37, Stefano Garzarella wrote:
> Hi Andra,
>
> On Tue, Dec 01, 2020 at 05:25:02PM +0200, Andra Paraschiv wrote:
> > vsock enables communication between virtual machines and the host 
> > they are
> > running on. Nested VMs can be setup to use vsock channels, as the multi
> > transport support has been available in the mainline since the v5.5 
> > Linux kernel
> > has been released.
> >
> > Implicitly, if no host->guest vsock transport is loaded, all the 
> > vsock packets
> > are forwarded to the host. This behavior can be used to setup 
> > communication
> > channels between sibling VMs that are running on the same host. One 
> > example can
> > be the vsock channels that can be established within AWS Nitro Enclaves
> > (see Documentation/virt/ne_overview.rst).
> >
> > To be able to explicitly mark a connection as being used for a 
> > certain use case,
> > add a flag field in the vsock address data structure. The 
> > "svm_reserved1" field
> > has been repurposed to be the flag field. The value of the flag will 
> > then be
> > taken into consideration when the vsock transport is assigned.
> >
> > This way can distinguish between nested VMs / local communication and 
> > sibling
> > VMs use cases. And can also setup one or more types of communication 
> > at the same
> > time.
>
> Another thing worth mentioning is that for now it is not supported in
> vhost-vsock, since we are discarding every packet not addressed to the
> host.

Right, thanks for the follow-up.

> What we should do would be:
> - add a new IOCTL to vhost-vsock to enable sibling communication, by
>   default I'd like to leave it disabled
>
> - allow sibling forwarding only if both guests have sibling
>   communication enabled and we should implement some kind of filtering
>   or network namespace support to allow the communication only between a
>   subset of VMs
>
>
> Do you have plans to work on it?

Nope, not yet. But I can take some time in the second part of December / 
beginning of January for this. And we can catch up in the meantime if 
there is something blocking or more clarifications are needed to make it 
work.

Thanks,
Andra

> Otherwise I put it in my to-do list and hope I have time to do it (maybe
> next month).
>
> Thanks,
> Stefano




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