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

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Date:   Wed, 2 Dec 2020 18:18:15 +0200
From:   "Paraschiv, Andra-Irina" <andraprs@...zon.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
CC:     netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        David Duncan <davdunc@...zon.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Alexander Graf <graf@...zon.de>,
        Jorgen Hansen <jhansen@...are.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH net-next v1 0/3] vsock: Add flag field in the vsock
 address



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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