By UATeam in rust —

Rust eBPF Example: Building Efficient Observability Tools with Rust

eBPF (extended Berkeley Packet Filter) is a powerful Linux kernel technology that allows you to run sandboxed programs in the kernel space. It is widely used for observability, networking, and security. Rust, with its safety and performance, is an excellent choice for developing eBPF applications.

This guide demonstrates how to create a basic eBPF program in Rust, focusing on practical use cases and examples.

What Is eBPF?

eBPF allows developers to run custom programs in the Linux kernel without modifying it. These programs are:

  • Safe: Sandbox environment ensures they cannot crash the kernel.
  • Efficient: Runs at kernel speed with minimal overhead.
  • Flexible: Used for tasks like monitoring, tracing, and networking.

Why Use Rust for eBPF Development?

  1. Safety: Rust’s strong type system and memory safety prevent bugs.
  2. Performance: Rust compiles to highly efficient machine code, ideal for kernel-level operations.
  3. eBPF Ecosystem: Rust libraries like aya simplify writing and deploying eBPF programs.

Setting Up Rust for eBPF Development

1. Install Rust

Install Rust using rustup:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

2. Add eBPF Development Tools

Install the necessary dependencies for eBPF development:

sudo apt-get install -y clang llvm libelf-dev libbpf-dev

3. Create a New Rust Project

Create a new project for your eBPF application:

cargo new rust_ebpf_example
cd rust_ebpf_example

4. Add Dependencies

Add the aya crate to Cargo.toml for eBPF support:

[dependencies]
aya = "0.12"

Creating a Basic eBPF Program

This example demonstrates how to write a simple eBPF program that tracks system calls.

1. Write the eBPF Program

Create a new directory src-ebpf/ and add a file tracepoint.bpf.rs:

#![no_std]
#![no_main]

use aya_bpf::{macros::tracepoint, programs::TracePointContext};
use aya_log_ebpf::info;

#[tracepoint(name = "syscall_enter")]
pub fn syscall_enter(ctx: TracePointContext) -> u32 {
    match unsafe { try_syscall_enter(ctx) } {
        Ok(ret) => ret,
        Err(_) => 1,
    }
}

unsafe fn try_syscall_enter(ctx: TracePointContext) -> Result<u32, u32> {
    info!(&ctx, "System call entered");
    Ok(0)
}

2. Build the eBPF Program

To build the eBPF program, use the bpf-linker tool. Add the following build script:

build.rs:

use std::process::Command;

fn main() {
    println!("cargo:rerun-if-changed=src-ebpf/tracepoint.bpf.rs");

    Command::new("cargo")
        .args(&[
            "+nightly",
            "build",
            "--target",
            "bpf",
            "--release",
            "-p",
            "tracepoint",
        ])
        .status()
        .unwrap();
}

3. Write the User-Space Application

Replace src/main.rs with:

use aya::programs::TracePoint;
use aya::{Bpf, BpfLoader};
use std::convert::TryInto;
use tokio::signal;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    // Load the compiled eBPF program
    let mut bpf = Bpf::load_file("target/bpf/release/tracepoint")?;
    
    // Attach the tracepoint to the syscall_enter event
    let program: &mut TracePoint = bpf.program_mut("syscall_enter").unwrap().try_into()?;
    program.load()?;
    program.attach("syscalls", "sys_enter")?;

    println!("eBPF program attached. Press Ctrl+C to exit.");

    // Wait for the user to terminate the program
    signal::ctrl_c().await?;
    Ok(())
}

Testing the eBPF Program

1. Build and Run the Application

Build the project:

cargo build

Run the user-space application:

sudo target/debug/rust_ebpf_example

2. Trigger a System Call

Open a new terminal and run a command like ls or cat. You should see logs from the eBPF program indicating that a system call was intercepted.

Enhancing the Example

  1. Monitor Specific System Calls:
    • Filter events by syscall ID.
  2. Attach to Other Hooks:
    • Use other hook types like XDP, kprobe, or uprobe for different use cases.
  3. Export Metrics:
    • Export metrics using perf maps or user-space logging.
  4. Integrate with Grafana:
    • Visualize collected data in real time.

Best Practices for eBPF Development

  1. Keep Programs Minimal:
    • Minimize eBPF logic to avoid performance penalties.
  2. Use Verified Libraries:
    • Use libraries like aya or libbpf to simplify development.
  3. Test on Staging Systems:
    • Always test eBPF programs in a controlled environment before deploying to production.

Conclusion

Rust and eBPF together offer a powerful way to build efficient, safe observability and security tools. By following this guide, you can start writing eBPF programs in Rust for use cases like tracing, monitoring, and networking. With Rust’s performance and safety guarantees, you can create reliable kernel-level applications. Start exploring eBPF with Rust today!