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
