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Work In Progress

This software is still under development and should be considered experimental. It is currently developed for x86-64 and has not been built or tested for ARM targets.

VSOCK module for Xen/Argo

vsock(7) is an address family to facilitate communication between virtual machines. Argo is an interdomain communication mechanism for Xen.

This module implements Argo primitives under the Vsock address family to allow socket communication between Xen domains.

Getting started

Linux module

Building vsock_argo_transport will require your Linux kernel headers. It can be built as an out-of-tree module. A convenience Makefile is provided:

 $ make -C module

The module itself will require VSock support in the kernel:

 $ zgrep CONFIG_VSOCKETS /proc/config.gz
CONFIG_VSOCKETS=m
CONFIG_VSOCKETS_DIAG=m
 $ sudo modprobe vsock

It is possible that another VSock transport driver was already loaded, you will need to remove it, e.g:

 $ lsmod | grep vsock
vmw_vsock_vmci_transport    32768  0
vmw_vmci               77824  1 vmw_vsock_vmci_transport
vsock                  40960  1 vmw_vsock_vmci_transport
 $ sudo rmmod vmw_vsock_vmci_transport

Then load the module and confirm the operation succeeded.

 $ sudo insmod module/vsock_argo_transport.ko
 $ dmesg -H | grep argo
[  +0.000017] vsock_argo_transport registered.

Test client

A test netcat like utility is provided to simplify send and receive operation using VSock datagram over Argo, the tool is call hatch and roughly follows the netcat usage.

Ship cargo, packets, are usualy passed through a hatch, hence the name... Since Argo is an old mythological ship.

It builds using autotools:

 $ cd test/hatch
 $ autoreconf -i
 $ mkdir dist ; ./configure --prefix=$(pwd)/dist
 ...
 $ make install
 $ ./dist/bin/hatch -h
Basic usage:
        hatch domid port
        hatch -r -p local_port
Options:
        -r, --recv      receive mode, wait for incoming packets.
        -p, --port      set local port number.
        -D              enable debug output on stderr.

Testing

Argo was released with Xen 4.12.0, but is still experimental feature. You will likely need to rebuild Xen to enable argo and change its cmdline. I recommend following the way your distribution packages Xen (PKGBUILD, sbuild, etc) and amend with the changes described below. The following is only provided as an example:

 $ git clone git://xenbits.xen.org/xen.git
 $ cd xen
 $ git checkout -b stable-4.12 origin/stable-4.12
 $ echo 'CONFIG_ARGO=y' >> xen/.config
 $ PYTHON=/usr/bin/python2 ./configure --prefix=/usr --sbindir=/usr/bin --with-sysconfig-leaf-dir=conf.d --with-rundir=/run --enable-systemd--with-extra-qemuu-configure-args="--disable-bluez --disable-gtk --disable-vte --disable-werror --disable-virglrenderer --disable-libnfs --disable-glusterfs --disable-numa --disable-smartcard --disable-fdt --enable-spice --enable-usb-redir --with-sdlabi=1.2"
 $ yes "" | make XEN_CONFIG_EXPERT=y -C xen oldconfig
 $ make XEN_CONFIG_EXPERT=y LANG=C PYTHON=python2 dist

Install and configure the previously built Xen to suit your distribution. This is beyond the scope of this document.

Add argo=true,mac-permissive=1 to your Xen cmdline and reboot on the freshly built Xen with Argo support.

You will need at least 1 Xen guest, other than dom0, to test vsock_argo_transport.ko. No guest specific guest configuration is required, e.g:

type = "pvh"
kernel="/var/lib/machines/vm0/boot/vmlinuz-linux"
ramdisk="/var/lib/machines/vm0/boot/initramfs-linux.img"
root="/dev/xvda"
extra="earlyprintk=xen console=tty0 console=hvc0,115200n8 rw quiet"
name = "vm0.pvh"
memory = 512
maxmem = 512
vcpus = 2
vfb = [ "type=vfb, vnc=1, vnclisten=0.0.0.0, vncdisplay=1" ]
vif = [ 'mac=00:16:3e:01:01:01, bridge=br0' ]
disk = [ '/dev/vg0/vm0,raw,xvda,rw' ]

Start and log into the guest to load vsock_argo_transport.ko. hatch can be used as netcat using the domain-id as address and a port.

user@dom0 $ hatch -r -p 1234 > /tmp/file
 ^C
user@dom0 $ md5sum file
b061b7954fbcb8b17cc7e2e8a5754269  file
user@vm0 $ md5sum file
b061b7954fbcb8b17cc7e2e8a5754269  file
user@vm0 $ hatch 0 1234 < file