systemd-networkd

Overview

This repository contains all the necessary source files to build the executable systemd-networkd on Ubuntu.

I created this repository only for learning purpose. The entire systemd codebase is sort of large and I could get lost easily when I was only interested in the source code of systemd-networkd. So I spent time and moved the systemd-networkd-related files here and made them compile. Therefore, the code in this repository belongs to the original systemd authors and is under the same license as the original systemd code. See their systemd/README for the license.

How to build

• 1). cd in the root directory of this repository.
• 2). ./install-deps.sh to install the build dependencies.
  • Note I only tested this script on my machine so it may not install all the needed dependencies on your machine.
• 3). ./configure to generate the build folder.
  • a). If you want to add more C flags, define the environment variable CFLAGS/CXXFLAGS before running configure. For example, export CFLAGS=-rdynamic. See configure for more details.
• 4). make to build the code.
  • a). If you want to display the actual gcc command line for debugging, define the environment variable NINJA_VERBOSE before running make. For example, export NINJA_VERBOSE=1. See Makefile for more details.
• 5). When the build is done, the executable systemd-networkd can be found under the build folder.

Debug environment setup & build

To make debugging easier, I added some supportive files and scripts:

• debug-env contains the files that set up a debugging environment to play with the locally built systemd-networkd.
• debug-env.sh is the script that installs/removes the debugging environment.
• debug-build.sh is the script that, after the debugging environment is set up, build the code and restart systemd-networkd.service.

Enable debug logging

Set the environment variable SYSTEMD_LOG_LEVEL=debug before running systemd-networkd.

If you replace the real systemd-networkd with the version you built by yourself, enabling debugging logs can also be done by dropping the following systemd-networkd configuration file as /etc/systemd/system/systemd-networkd.service.d/10-debug.conf, followed by systemctl restart systemd-networkd.service:

[Service]
Environment=SYSTEMD_LOG_LEVEL=debug

Entry point

The entry point (i.e., the main function) is in src/network/networkd.c.