eBPF! This blog breaks down “Learning eBPF” in simple terms, assuming you’re completely new to programming and Linux concepts. Don’t worry if you don’t know C, Go, or Python yet – we’ll explain everything step by step.

What is eBPF?

eBPF stands for extended Berkeley Packet Filter. Think of it as a way to write small programs that run inside the Linux operating system’s core (called the “kernel”) safely and efficiently.

A Simple Analogy

Imagine your computer’s operating system is like a building:

• Regular programs run in the “apartments” (user space) – they can’t directly access the building’s core systems
• The kernel is like the building’s “control room” – it manages everything (memory, network, files, etc.)
• eBPF is like having a safe, monitored way to add small “helper scripts” to the control room without rebuilding the entire building

eBPF’s Roots: The Berkeley Packet Filter (BPF)

What Was BPF?

BPF (Berkeley Packet Filter) was created in the early 1990s. It was designed to:

• Filter network packets efficiently
• Run small programs directly in the kernel
• Avoid copying data between user space and kernel space (which is slow)

Why Was This Important?

Before BPF, if you wanted to analyze network traffic, you had to:

1. Copy ALL network packets from the kernel to your program
2. Filter them in your program
3. This was very slow and inefficient

BPF allowed you to filter packets INSIDE the kernel, so only the packets you cared about were copied to your program. This was much faster!

From BPF to eBPF

What Changed?

eBPF (the “e” stands for “extended”) evolved from BPF to become much more powerful:

1. More Program Types: Not just network filtering, but also:
   • Tracing system calls
   • Monitoring security events
   • Observing application behavior
   • And much more!
2. Better Safety: eBPF programs are verified before they run to ensure they’re safe
3. More Helper Functions: More things you can do from eBPF programs
4. Better Performance: Optimized for modern hardware

Key Difference

• BPF: Mainly for network packet filtering
• eBPF: A general-purpose platform for many different use cases

The Evolution of eBPF to Production Systems

Timeline of eBPF Development

1. 2014: eBPF was introduced to the Linux kernel
2. 2015-2016: Tools like BCC (BPF Compiler Collection) made eBPF easier to use
3. 2017-2018: Major projects started using eBPF:
   • Cilium: For networking and security in Kubernetes
   • Falco: For security monitoring
   • BCC tools: For system observability
4. 2019-Present: eBPF became mainstream in cloud-native environments

Why Did It Become Popular?

• Performance: Much faster than traditional approaches
• Safety: Programs are verified before running
• Flexibility: Can be loaded/unloaded without rebooting
• No Kernel Recompilation: Don’t need to rebuild the entire kernel

Naming Is HardWhy the Confusion?

You might see different names:

• BPF: The original name (still used sometimes)
• eBPF: Extended BPF (the modern version)
• cBPF: Classic BPF (the old version)

In practice: When people say “BPF” today, they usually mean “eBPF”. The book uses “eBPF” to be clear.

The Linux Kernel

What Is the Linux Kernel?

The kernel is the core of the Linux operating system. It’s like the “brain” that:

• Manages hardware (CPU, memory, disk, network)
• Provides services to programs
• Controls security and permissions
• Handles system calls (requests from programs)

User Space vs Kernel Space

Think of your computer as having two “zones”:

1. User Space (where your programs run):
   • Your web browser
   • Your text editor
   • Your applications
   • These programs can’t directly access hardware
2. Kernel Space (the core of the OS):
   • Manages hardware directly
   • Controls system resources
   • Handles security
   • eBPF programs run here!

Why This Matters

• Programs in user space are “sandboxed” – they can’t crash the system
• Kernel space has full power – mistakes here can crash the entire computer
• eBPF programs run in kernel space BUT are verified to be safe before running

Adding New Functionality to the Kernel

The Traditional Problem

If you wanted to add new functionality to Linux, you had two options:

Option 1: Modify the Kernel Source Code

• Pros: Full control
• Cons:
  • Need to recompile the entire kernel (takes hours)
  • Need to reboot the computer
  • Your changes might break other things
  • Hard to distribute (everyone needs your custom kernel)

Option 2: Kernel Modules

• Pros: Can load/unload without rebooting
• Cons:
  • Still need to compile for specific kernel versions
  • Can crash the system if buggy
  • Hard to verify safety
  • Complex to write

The eBPF Solution

eBPF provides a third option:

• ✅ Load programs dynamically (no reboot needed)
• ✅ Verified for safety before running
• ✅ Portable across kernel versions
• ✅ Can’t crash the system (verifier prevents dangerous code)
• ✅ Easy to write and distribute

Kernel Modules

What Are Kernel Modules?

Kernel modules are pieces of code that can be loaded into the kernel at runtime. They’re like “plugins” for the kernel.

Example Use Case

If you wanted to add support for a new network card:

• Write a kernel module
• Load it into the kernel
• Your new network card works!
• Limitations of Kernel Modules

1. Safety: Can crash the entire system if buggy
2. Complexity: Hard to write correctly
3. Portability: Need different versions for different kernel versions
4. Verification: No automatic safety checks

Dynamic Loading of eBPF Programs

What Does “Dynamic Loading” Mean?

Dynamic loading means you can:

• Load an eBPF program into the kernel while the system is running
• Unload it when you don’t need it anymore
• No reboot required!

Why Is This Amazing?

Imagine you want to monitor network traffic:

• Old way: Modify kernel, recompile, reboot (hours of work)
• eBPF way: Write program, load it, start monitoring (seconds!)
• Real-World Example

# Load an eBPF program to monitor network packets
# (Don't worry about understanding this yet - we'll learn it later!)
sudo ./monitor-network

# When done, just stop the program - it unloads automatically

High Performance of eBPF Programs

Why Are eBPF Programs Fast?

1. Runs in Kernel Space: No need to copy data to user space
2. JIT Compilation: Programs are compiled to machine code for maximum speed
3. Efficient Data Structures: Uses optimized maps and buffers
4. No Context Switching: Stays in kernel space

Performance Comparison

Traditional approach:

Network Packet → Kernel → Copy to User Space → Your Program → Process → Copy Back

(Slow! Multiple copies and context switches)

eBPF approach:

Network Packet → eBPF Program (in kernel) → Process → Done

(Fast! Everything happens in kernel space)Real Numbers

• eBPF can process millions of packets per second
• Traditional approaches: thousands of packets per second
• 100-1000x faster in many cases!

eBPF in Cloud Native Environments

What Is “Cloud Native”?

Cloud native refers to applications designed to run in cloud environments (like Kubernetes, Docker, etc.). These environments have:

• Many containers running
• Complex networking between containers
• Need for observability (monitoring, logging, tracing)
• Security requirements

Why eBPF Is Perfect for Cloud Native

1. Networking

• Cilium: Uses eBPF for Kubernetes networking
• Handles millions of network connections
• Provides security policies
• Load balancing

2. Observability

• Monitor what’s happening in containers
• Track system calls
• Measure performance
• Debug issues

3. Security

• Falco: Uses eBPF for security monitoring
• Detect suspicious behavior
• Enforce security policies
• Monitor file access, network connections, etc.

The Sidecar Model (Old Way)

Traditional approach used “sidecars” – separate containers that:

• Intercept network traffic
• Add overhead
• Use more resources
• Are slower

eBPF Model (New Way)

eBPF programs:

• Run directly in the kernel
• No separate containers needed
• Lower overhead
• Much faster

Summary

Key Takeaways

1. eBPF = Extended Berkeley Packet Filter
   • A way to write safe programs that run in the Linux kernel
2. Evolution: Started as BPF (network filtering) → Became eBPF (general-purpose platform)
3. Why It Matters:
   • ✅ Safe (verified before running)
   • ✅ Fast (runs in kernel space)
   • ✅ Flexible (load/unload without reboot)
   • ✅ Portable (works across kernel versions)
4. Use Cases:
   • Networking (Cilium)
   • Security (Falco, Tetragon)
   • Observability (monitoring, tracing)
   • Performance analysis
5. Perfect for Cloud Native:
   • Used in Kubernetes
   • Powers modern infrastructure tools
   • Enables new capabilities

Common Questions for Beginners

Q: Do I need to know C to learn eBPF?

A: Not initially! You can start with tools like bpftrace which use a simpler syntax. But learning C will help you understand eBPF programs better.

Q: Can eBPF programs crash my computer?

A: The eBPF verifier checks programs before they run to prevent crashes. However, you should still be careful and test on non-production systems first.

Q: Do I need root/admin access?

A: Yes, loading eBPF programs requires root/administrator privileges because they run in the kernel.

Q: Can I use eBPF on Windows or Mac?

A: eBPF is primarily for Linux. However, there are some experimental ports for Windows. Mac doesn’t support eBPF natively.

Q: Is eBPF hard to learn?

A: It has a learning curve, but the book breaks it down step by step. Start simple and build up gradually!