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oxidebpf

oxidebpf is a permissive licensed Rust library for managing eBPF programs.

Motivation

The motivation behind oxidebpf is to create a permissive licensed Rust library for managing long-running eBPF programs that operate in as many environments as possible. Doing this required breaking some pre-set patterns on how eBPF applications are developed and deployed. We wanted to be able to easily deploy an eBPF solution that worked on as many distributions as possible; without forcing the user to have a tool-chain present. Users typically just want a product to do the thing - without a bunch of additional setup or maintenance. This library helped us realize that goal - and we are sharing it openly.

Initially this library meets our current eBPF requirements, so its not a fully flushed out eBPF implementation. Contributions are very much welcome, and we will slowly be adding to the feature list over time.

Goals

We want oxidebpf to meet the following goals.

  • Permissive licensed with no GPL dependencies.
  • Support custom CO-RE eBPF
  • Run eBPF programs on Linux 4.4+
  • Written in pure Rust, or as close to pure Rust as possible.
  • Minimal dependencies, pull in the bare minimum set of dependencies required to achieve our desired functionality.

Requirements

A set of Linux environments are provided for building and testing, with dependencies listed in their bootstrap.sh scripts. In general, you will want:

$ sudo apt-get install build-essential clang llvm libclang-dev linux-tools-oem \
  linux-tools-(kernel version)-generic

Additionally, you will need cargo installed. The cargo-with package is recommended for debugging and testing. It allows you to trace BPF calls during tests by running cargo with "strace -vfe bpf" -- test.

Getting Started

Here's some quick steps to get you started right away.

  1. Add oxidebpf to your Cargo.toml, if you wish to use perfmaps you should also add crossbeam-channel.
  2. Use the ProgramBlueprint to load your compiled eBPF object file with maps and programs.
  3. Create a Program for each program you intend to load, with options set.
  4. Create a ProgramVersion with your programs. You may create multiple ProgramVersions, representing different sets of programs. For example, programs intended to run on different kernel versions.
  5. Create a ProgramGroup.
  6. Give the ProgramGroup your ProgramVersions and ProgramBlueprint, and tell it to start loading. It will attempt each ProgramVersion in order until one successfully loads on the current kernel. If it cannot load any program version, it will return an error composed of the underlying errors for each ProgramVersion.
let program = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
    .join("test")
    .join(format!("test_program_{}", std::env::consts::ARCH));
let program_blueprint =
    ProgramBlueprint::new(&std::fs::read(program).expect("Could not open file"), None)
        .expect("Could not open test object file");
let mut program_group = ProgramGroup::new();
let (tx, rx) = crossbeam_channel::bounded(1024);

program_group.load(
    program_blueprint,
    vec![ProgramVersion::new(vec![
        Program::new(
            "test_program_map_update",
            vec!["do_mount"],
        )
        .syscall(true),
        Program::new("test_program", vec!["do_mount"]).syscall(true),
    ])],
    || (tx, PerfBufferSize::Total(4096))),
).expect("Could not load programs");

// read from rx any events from a perfmap in the loaded program version

Note: this expects the presence of a test_program_[arch] binary in a test subfolder of your project, where [arch] is the architecture of your system.

Building

The project includes several Vagrantfiles which are set up to build and test the library.

$ cd vagrant/ubuntu_20.04
$ vagrant up
$ vagrant ssh
$ cd oxidebpf
$ cargo build

If you want to build locally, check the bootstrap.sh file for the Vagrantfile most similar to your system. This file will include build and test dependencies for the distribution.

Testing

  1. Run docker-compose run --rm test-builder from the test/ directory to build the BPF test application. For additional options for RHEL builds, see test/README.md.
  2. Run tests with cargo test. To trace BPF syscalls as they occur, run the tests with cargo with "strace -fe bpf" -- test (depends on cargo-with, included in vagrant bootstrap by default).

Note: some tests will require root privileges to pass. Other tests require a single-threaded context to pass. To test consistently, try running: sudo -E /path/to/your/.cargo/bin/cargo test -- --test-threads=1. For convenience, you can alias this as alias scargo="sudo -E $HOME/.cargo/bin/cargo" and run tests with scargo test -- --test-threads=.

Features

Metrics

oxidebpf has a (disabled by default) feature called metrics. When enabled it will use the metrics crate to propagate internal metrics related to the ebpf maps. These are the metrics that oxidebpf currently reports on:

  • perfmap.unread_size_pct: A histogram of how much of the perfmap buffer has not been read. This is emitted right after polling the perf map file descriptors but before reading from them. This is only emitted by perfmaps that woke up during the epoll, if a perfmap never gets data then it will not report by this metric. The map name and cpu are reported as labels. A describe_histogram! is also emitted for this metric to tell reporters that this is a percentage unit. This can be used to set up histogram buckets.

  • perfmap.buffer_size_kb: A gauge of how much memory (in KB) is being allocated for the data portion of the perfmap buffer. Note that an extra page is always allocated for metadata. This is emitted immediately prior to the creation of the map. The map name is reported as a label.

  • perfmap.num_buffers: A gauge of how many buffers are being allocated for a perfmap. This is also the number of online cpus that oxidebpf detected. This is emitted immediately prior to the creation of the perf map. The map name is reported as a label.

  • perfmap.channel.full: A counter of how many times we tried to send a dropped message across the user provided channel for perfmaps but failed due to it being full. The map name is reported as a label.

Adding or removing metrics will not be considered a breaking change at this point but we may reconsider this decision in the future as we stabilize what metrics seem the most useful

Dependencies

~6–16MB
~179K SLoC