Internships/ProjectIdeas/VsockSiblingCommunication

Sibling VM communication in vhost-user-vsock

Summary: Extend the existing vhost-user-vsock Rust application to support sibling VM communication

During GSoC 2021, we developed vhost-user-vsock application in Rust. It leveraged the vhost-user protocol to emulate a virtio-vsock device in an external process. It provides the hybrid VSOCK interface over AF_UNIX introduced by Firecracker.

The current implementation supports a single virtual machine (VM) per process instance. The idea of this project is to extend the vhost-user-vsock crate available in the rust-vmm/vhost-device workspace to support multiple VMs per instance and allow communication between sibling VMs.

vsock is usually used as a communication channel between the host and the guest running in a VM. Recently it has been proposed to extend vsock to also allow communication between VMs running on the same host (sibling VMs).

Usually struct sockaddr_vm { .svm_cid = 42, .svm_port = 1234 } address inside a VM is used to communicate with a nested VM, but a new flag is recently added to allow sibling VM communication. So by setting .svm_flags = VMADDR_FLAG_TO_HOST, the connection will be forwarded to the host, allowing communication with the sibling VM that has CID 42 (if the device supports it).

AF_VSOCK in Linux already supports it, but the vhost-user-vsock application still does not support it, so we want to extend it.

This project will allow you to learn more about the virtio-vsock specification, rust-vmm crates, and vhost-user protocol to interface with QEMU.

This work will be done in Rust, but we may need to patch the virtio-vsock driver or the AF_VSOCK core in Linux if we will find some issues.

Goals:

• Understand how a virtio-vsock device works
• Refactor vhost-user-vsock code to allow multiple virtio-vsock device instances
• Extend the vhost-user-vsock CLI to define sibling VMs
• Implement sibling VM communication
• (optional) Support adding new VMs at runtime

Links:

• vsock info and issues
• virtio-vsock QEMU wiki page
• vhost-user-vsock application
• vhost-user-vsock project @ GSoC 2021
• Firecracker's hybrid VSOCK
• vhost-user protocol
• VMADDR_FLAG_TO_HOST flag support in Linux

Details:

• Project size: 350 hours
• Skill level: intermediate (knowledge of Rust and virtualization)
• Language: Rust
• Mentors: Stefano Garzarella <sgarzare@redhat.com>, German Maglione <gmaglione@redhat.com>
  • IRC: sgarzare / Matrix: @sgarzare:matrix.org
• Suggested by: Stefano Garzarella <sgarzare@redhat.com>