CORE Developer's Guide
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.
|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|
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.
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.
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.
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.
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
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.
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