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

[Arseniy Krasnov <oxffffaa@gmail.com>]

Hello

On 17.02.2022 15:55, Stefano Garzarella wrote:
> 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.
>
So, rely on current implementation, virtio vsock rx buffers will be allocated with this size from config? And also both peers must negotiate this value(like credit size), to avoid packets drop?


Thank You

> 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
>
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