Unix domain socket tools

Short descriptions

• udshub.py is a server which creates and listens to a unix socket, and forwards messages sent from one client to all others.
• uds2fd.py connects to a unix domain socket and hands the filedescriptor to a program you specify.
• udschatclient.py is a debugging tool to connect to a unix domain socket and send/receive data.

Guide

This toolset can be used to set up internal networking between QEMU virtual machines without requiring root access on the host.

QEMU allows you to create a virtual NIC for a VM, and connect it to a socket listening on localhost. This setup is not very secure in a multi-user environment where everyone on localhost can then connect to your QEMU internal network.

A safer approach is to connect the virtual NIC to unix domain socket, which can be shielded from other users through filesystem permissions.

To set this up, first start udshub.py:

$ ./udshub.py mysocket

Next, start a QEMU VM through uds2fd.py:

./uds2fd.py 99:mysocket -- kvm -k en-us -localtime -m 256 -drive file=vm.qcow,if=virtio -net socket,fd=99 -net nic,macaddr=00:11:22:33:44:55

This command start your QEMU VM and connects a virtual NIC with the given MAC address to filedescriptor 99, which uds2fd.py has connected to the unix domain socket mysocket. Repeat the command for another VM you wish to connect to the same internal network so both VMs can communicate.