Re: [virtio-comment] vsock: define a maximum size for the packet data

[Stefano Garzarella <sgarzare@redhat.com>]

On Thu, Feb 17, 2022 at 12:31:20PM +0000, Loghin, Laura wrote:
> Hello,
>
> Would it be possible to define a maximum size for the packet data in 
> the spec (for example the one from the Linux driver [1])? We are 
> working on a vsock packet implementation in rust-vmm [2], and we would 
> like to check for some sort of limit for the data packet,
>
> without using the limit from a specific driver implementation. We want 
> to do this so that the driver is not allowed to reserve huge chunks of 
> memory. VMMs might want to reject packets that have bigger data arrays.  
> This limit could probably be defined in the VMM as well, and then 
> propagated/checked where it is needed, but it would be nicer to have 
> one at the spec level.

Yep, I think it is possible, but maybe to limit the memory used in the 
guest, it would be better to add a field in the configuration space to 
define the maximum packet size (like MTU for virtio-net) for each 
device.

At that point we can also add a maximum that seems reasonable. For now I 
think the theoretical maximum is 4GB since the len field is on 32bit, 
obviously not a real limit :-)

Thanks,
Stefano