Re: vsock support for communication between guests

[Robert Hoo <robert.hoo.linux@gmail.com>]

On 11/6/2025 10:32 PM, Stefano Garzarella wrote:
> On Fri, Oct 10, 2025 at 09:00:21PM +0800, Robert Hoo wrote:
>> Hi,
>>
>> Does vsock support communication between guests?
>> From man page, and my experiment, seems it doesn't.
>> But why not?
>>
> 
> It depends, vhost-user vsock device, supports it.
> See 
> https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-vsock#sibling-vm-communication
> 
> The vhost-vsock in-kernel device doesn't support it.
> 
> The main problem is that vsock is designed for host<->guest communication, so 
> implementing a guest<->guest communication is possible, but requires more 
> configuration (e.g. some kind of firewall, etc.) and also an extension to the 
> address (see the required
> `.svm_flags = VMADDR_FLAG_TO_HOST` in the link).
> 
> The easy way to do that with vhost-vsock, is to use socat in the host to 
> concatenate 2 VMs (some examples here: 
> https://stefano-garzarella.github.io/posts/2021-01-22-socat-vsock/)
> 
> Cheers,
> Stefano
> 
Nice, thanks Stefano. It sounds ideal for my VM <--> VM communication 
requirement. I'll read the doc carefully later.

BTW, I also found your vsock-bridge 
(https://github.com/stefano-garzarella/vsock-bridge); but seems its last commit 
was 5 yrs ago. It's not recommended, is it?