On 11/11/2025 12:20 AM, Bobby Eshleman wrote:
On Sun, Nov 09, 2025 at 09:13:13PM +0800, Robert Hoo wrote:
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.
Though not as convenient as socat, VSOCK also supports sockmap which can
do this in-kernel (bpf), there are a few test cases for this in
selftests/bpf.
Best,
Bobby
Nice to know this, thanks Bobby. It a good idea. I'll look into the selftests
for reference.
