Getting Started with eBPF: Concepts, Examples, and Security Considerations

Understanding eBPF from These Examples

eBPF (Extended Berkeley Packet Filter) is a Linux kernel technology that extends the classic BPF packet‑filtering mechanism with a richer instruction set, JIT compilation, maps, and safety verification, enabling use cases such as performance analysis, security auditing, and application tracing.

eBPF Basics

Originally created in 1992 for packet filtering, classic BPF was integrated into Linux in 1997. In early 2014, Alexei Starovoitov implemented eBPF, adding advanced features that broaden its applicability beyond networking.

How eBPF Works

eBPF inserts a virtual machine into the kernel that can safely execute restricted programs. These programs run at specific hook points, triggered by kernel events, network traffic, or user‑space probes, allowing filtering, modification, and monitoring of system behavior.

USDT Example

USDT (Userland Statically Defined Tracing) provides static trace points in user‑space programs. The following bpftrace script monitors Erlang garbage‑collection events:

usdt:beam.smp:gcminorstart{ @start[srt(arg0)] = nsecs; }
usdt:beam.smp:gcminorend{ @usecs = hist((nsecs - @start[str(arg0)]) / 1000); delete(@start[str(arg0)]); }
END{ clear(@start); }

The script records start timestamps, computes durations, stores them in a histogram, and cleans up after each GC cycle.

Uprobes Introduction

When USDT points are unavailable, uprobes can dynamically insert probes at arbitrary user‑space function entry and exit points, enabling debugging, performance analysis, and security auditing by executing custom handlers.

Traffic Control (TC) Hooks

TC is a Linux kernel subsystem for network traffic shaping. TC hooks allow eBPF programs to be attached to various points in the traffic‑control pipeline, such as queueing disciplines, enabling low‑overhead request‑flow tracing without modifying application code.

Security Considerations

Loading eBPF programs typically requires elevated privileges (e.g., root or CAP_EBPF). The kernel verifier checks programs for memory safety, termination guarantees, and restricted API usage, ensuring that eBPF code cannot compromise kernel stability.

Notable Open‑Source eBPF Projects

Katran – a high‑performance L4 load balancer from Facebook.

Cilium – provides eBPF‑based networking, security, and observability for Kubernetes.

BCC – a toolkit that simplifies writing eBPF programs with C, Python, and Lua bindings.

bmc‑cache – uses eBPF to accelerate Memcached throughput.

For further learning, refer to the eBPF technical blog at https://www.ebpf.top/.