Features/VirtioVsock

virtio-vsock is a host/guest communications device. It allows applications in the guest and host to communicate. This can be used to implement hypervisor services and guest agents (like qemu-guest-agent or SPICE vdagent).

Unlike virtio-serial, virtio-vsock supports the POSIX Sockets API so existing networking applications require minimal modification. The Sockets API allows N:1 connections so multiple clients can connect to a server simultaneously.

The device has an address assigned automatically so no configuration is required inside the guest.

Sockets are created with the AF_VSOCK address family. The SOCK_STREAM socket type is currently implemented.

Code

Virtio specification: HTML or virtio.git
Linux kernel: stefanha's linux.git
QEMU: stefanha's qemu.git
netcat-like utility: nc-vsock

Quickstart

QEMU:

 $ git clone -b vsock https://github.com/stefanha/qemu
 $ cd qemu
 $ ./configure --target-list=x86_64-softmmu
 $ make

Linux:

 $ git clone -b vsock https://github.com/stefanha/linux
 $ cd linux
 $ cp /boot/config-$(uname -r) .config
 $ make menuconfig # select CONFIG_VHOST_VSOCK=m and CONFIG_VIRTIO_VSOCKETS=m
 $ make install modules_install

To use vhost_vsock.ko you must boot into the new host kernel and modprobe vhost_vsock.

The guest should also use the kernel so that modprobe virtio_transport can load the vsock guest driver.

For details on host and guest boot, see go.sh. Use nc-vsock 2 1234 inside the guest to connect to vsock port 1234 on the host. Use nc-vsock -l 1234 on the host to listen on that port.

Testing

The vhost-vsock-test qtest replays packets from a JSON file and verifies that the expected reply is received.

The JSON test file format is described in a README.

 $ cd qemu
 $ make -j4
 $ make tests/vhost-vsock-test
 $ sudo QTEST_QEMU_BINARY=x86_64-softmmu/qemu-system-x86_64 QTEST_QEMU_IMG=qemu-img MALLOC_PERTURB_=${MALLOC_PERTURB_:-$((RANDOM % 255 + 1))} gtester -k --verbose -m=quick tests/vhost-vsock-test -o /dev/stderr

Create and edit test cases in tests/vhost-vsock-test-data/*.json.

Links

KVM Forum 2015 presentation: virtio-vsock: Zero-configuration host/guest communication (pdf)
Connectathon 2016 presentation: NFS over virtio-vsock: Host/guest file sharing for virtual machines (pdf)