CORE Developer's Guide

Overview

The CORE source consists of several programming languages for historical reasons. Current development focuses on the Python modules and daemon. Here is a brief description of the source directories.

Directory	Description
daemon	Python CORE daemon/gui code that handles receiving API calls and creating containers
docs	Markdown Documentation currently hosted on GitHub
man	Template files for creating man pages for various CORE command line utilities
netns	C program for creating CORE containers

Getting started

To setup CORE for develop we will leverage to automated install script.

Clone CORE Repo

cd ~/Documents
git clone https://github.com/coreemu/core.git
cd core
git checkout develop

Install the Development Environment

This command will automatically install system dependencies, clone and build OSPF-MDR, build CORE, setup the CORE poetry environment, and install pre-commit hooks. You can refer to the install docs for issues related to different distributions.

./install -d

pre-commit

pre-commit hooks help automate running tools to check modified code. Every time a commit is made python utilities will be ran to check validity of code, potentially failing and backing out the commit. These changes are currently mandated as part of the current CI, so add the changes and commit again.

Running CORE

You can now run core as you normally would, or leverage some of the invoke tasks to conveniently run tests, etc.

# run core-daemon
sudo core-daemon

# run gui
core-gui

# run mocked unit tests
cd <CORE_REPO>
inv test-mock

Linux Network Namespace Commands

Linux network namespace containers are often managed using the Linux Container Tools or lxc-tools package. The lxc-tools website is available here http://lxc.sourceforge.net/ for more information. CORE does not use these management utilities, but includes its own set of tools for instantiating and configuring network namespace containers. This section describes these tools.

vnoded

The vnoded daemon is the program used to create a new namespace, and listen on a control channel for commands that may instantiate other processes. This daemon runs as PID 1 in the container. It is launched automatically by the CORE daemon. The control channel is a UNIX domain socket usually named /tmp/pycore.23098/n3, for node 3 running on CORE session 23098, for example. Root privileges are required for creating a new namespace.

vcmd

The vcmd program is used to connect to the vnoded daemon in a Linux network namespace, for running commands in the namespace. The CORE daemon uses the same channel for setting up a node and running processes within it. This program has two required arguments, the control channel name, and the command line to be run within the namespace. This command does not need to run with root privileges.

When you double-click on a node in a running emulation, CORE will open a shell window for that node using a command such as:

gnome-terminal -e vcmd -c /tmp/pycore.50160/n1 -- bash

Similarly, the IPv4 routes Observer Widget will run a command to display the routing table using a command such as:

vcmd -c /tmp/pycore.50160/n1 -- /sbin/ip -4 ro

core-cleanup script

A script named core-cleanup is provided to clean up any running CORE emulations. It will attempt to kill any remaining vnoded processes, kill any EMANE processes, remove the :file:/tmp/pycore.* session directories, and remove any bridges or nftables rules. With a -d option, it will also kill any running CORE daemon.

netns command

The netns command is not used by CORE directly. This utility can be used to run a command in a new network namespace for testing purposes. It does not open a control channel for receiving further commands.

Other Useful Commands

Here are some other Linux commands that are useful for managing the Linux network namespace emulation.

# view the Linux bridging setup
ip link show type bridge
# view the netem rules used for applying link effects
tc qdisc show
# view the rules that make the wireless LAN work
nft list ruleset