cilium / cilium

Understanding Cilium's BPF Programming

Scenario: A developer wants to understand the basics of Cilium’s BPF (Berkeley Packet Filter) programming for network policy enforcement. In this guide, we will explore the concepts, documentation, and codebase of Cilium’s BPF implementation.

  1. Understanding BPF and its role in Cilium

BPF (Berkeley Packet Filter) is a powerful technology that allows developers to write and run custom programs in the Linux kernel. Cilium, an open-source project for securing and observing microservices, uses BPF extensively for network policy enforcement.

  1. Getting started with Cilium’s BPF programming

To get started with Cilium’s BPF programming, you can refer to the following resources:

  1. Exploring Cilium’s BPF codebase

Cilium’s BPF codebase is located in the bpf directory of the Cilium repository. Some key directories and files include:

  • bpf/complexity-tests/: Contains BPF test programs for complexity analysis.
  • bpf/custom/: Contains custom BPF programs.
  • bpf/include/: Contains BPF header files.
  • bpf/lib/: Contains BPF helper libraries.
  • bpf/tests/: Contains BPF test programs.
  • bpf/COPYING: Contains the BPF license.
  • bpf/LICENSE.BSD-2-Clause: Contains the BSD-2-Clause license.
  • bpf/LICENSE.GPL-2.0: Contains the GPL-2.0 license.
  • bpf/Makefile: Build file for BPF programs.
  • bpf/Makefile.bpf: Makefile for building BPF programs.
  • Various BPF program files, such as bpf_network.c, bpf_sock.c, etc.
  1. Testing your understanding

To test your understanding of Cilium’s BPF programming, you can try the following:

  • Write and test a simple BPF program for network policy enforcement using Cilium’s documentation and codebase as a reference.
  • Experiment with different BPF programs in the bpf/tests/ directory and understand their functionality.
  • Contribute to Cilium’s BPF codebase by fixing bugs, adding features, or writing new BPF programs.
  1. Additional resources