How eBPF Works
Understanding Hooks, Maps, and the eBPF Architecture.
eBPF
What is eBPF?
Understanding eBPF
Imagine your computer’s Operating System is a high-security office building. Inside this building is the Kernel—the staff that manages the locks, the electricity, and the filing cabinets.
For decades, if you wanted to change how the building worked (like adding a new security camera), you had to convince the owners to do a massive renovation, which took years.
eBPF changes that. It is a technology that allows you to run “mini-apps” inside that high-security office safely and instantly, without changing the building’s structure.
1. The Core Concept:
eBPF (Extended Berkeley Packet Filter) allows you to execute custom code inside the Linux Kernel. It is often called the “JavaScript for Hardware” because, just as JavaScript allows you to change how a website behaves without redesigning the browser, eBPF lets you change how the system behaves without restarting it.
Why is it a big deal?
- Speed: It runs at the heart of the computer (the Kernel).
- Safety: It uses a Verifier—a strict inspector that ensures your code won’t crash the computer or steal data.
- Visibility: It can see everything happening on your system in real-time.
2. The Three Pillars of eBPF
To understand how eBPF works, you only need to know three things:
| Pillar | Analogy | Technical Role |
|---|---|---|
| Hooks | The “Sensors” | Triggers that wake up your program when an event happens (e.g., a file opens). |
| Maps | The “Notebook” | A shared storage space where the Kernel and your apps can exchange data. |
| Helpers | The “Vending Machine” | A set of safe functions the Kernel provides so you don’t have to do things manually. |
3. How a Program is “Born”
- Write: You write a small program (usually in C, Go, or Python).
- Verify: The Kernel’s Verifier checks the code for safety.
- Compile: The JIT (Just-In-Time) Compiler turns it into super-fast machine code.
- Attach: The program “hooks” onto a part of the system and starts monitoring or filtering data.
4. Real-World Use Cases
What do people actually use eBPF for?
- High-Speed Networking: Dropping “bad” data packets (DDoS attacks) before they even reach your apps.
- Deep Security: Watching if a suspicious program is trying to access your private passwords.
- Observability: Creating real-time “dashboards” that show exactly which part of your computer is running slow.