On 11/10/2025 7:10 PM, Stefano Garzarella wrote:
On Sun, 9 Nov 2025 at 14:13, Robert Hoo <[email protected]> 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.
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?
Oh, that was just a little exercise I did to learn Rust at the time,
so I'd say no, it's not recommended.
BTW `socat` supports a similar use case, so related to the example in
the vsock-bridge's README, you can do the following:
host$ socat VSOCK-LISTEN:5201 VSOCK-CONNECT:4:5201
vm_cid3$ iperf --vsock -s
vm_cid4$ iperf --vsock -c 2
But yeah, it's not 2 ways like vsock-bridge (i.e. `vm_cid3` can't
connect to `vm_cid4`).
Cheers,
Stefano
Thanks Stefano.
