https://github.com/adithaker/xdp_sfu

🖲️Selective Forwarding Unit Implementation using XDP and TC hooks
https://github.com/adithaker/xdp_sfu

c ebpf ebpf-tc ebpf-xdp linux-kernel rtp-streaming webrtc wireshark

Last synced: 3 days ago
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🖲️Selective Forwarding Unit Implementation using XDP and TC hooks

• Host: GitHub
• URL: https://github.com/adithaker/xdp_sfu
• Owner: ADIthaker
• Created: 2024-12-17T22:57:17.000Z (21 days ago)
• Default Branch: master
• Last Pushed: 2025-01-04T10:28:00.000Z (4 days ago)
• Last Synced: 2025-01-04T11:35:14.737Z (4 days ago)
• Topics: c, ebpf, ebpf-tc, ebpf-xdp, linux-kernel, rtp-streaming, webrtc, wireshark
• Language: C
• Homepage:
• Size: 2.54 MB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Implementing SFU in XDP

## Overview

This project explores implementing a Selective Forwarding Unit (SFU) for video conferencing using **XDP (eXpress Data Path)** and **Traffic Control (TC)** in the Linux kernel. By leveraging **eBPF (Extended Berkeley Packet Filter)** technology, the project aims to enhance the performance of packet processing by bypassing the traditional Linux networking stack.

## Motivation

- **Video Conferencing Challenges**:  

  SFU servers process and forward media streams, but they face inefficiencies due to the need to traverse the entire Linux stack.

- **eBPF Advantages**:  

  eBPF programs can run at the driver level, improving packet processing speed.

- **Goals**:  

  - Enable forwarding packets with flexibility in quality and format.  

  - Optimize performance for multi-participant video conferencing.  

## About XDP and TC

- **XDP**:  

  A high-performance framework for packet processing at the link layer.  

  - **Advantages**: Fast and efficient.  

  - **Limitations**: Limited memory and restricted packet access.

  

- **TC**:  

  Operates within the Linux network stack, allowing full packet modification.  

  - **Advantages**: Packet cloning and extended manipulation capabilities.  

  - **Limitations**: Slower than XDP.

## About SFU

An SFU is a specialized network architecture for video conferencing that:  

- Receives all participant streams.  

- Processes and forwards streams based on participants' needs.  

- Utilizes RTP (Real-time Transport Protocol) for media streams and control packets (e.g., SDP, RTCP, ICE).

## Progress

- Implemented SFU for 2 participants using XDP and TC.

- eBPF maps used to store participant IPs and ports.

- Scapy scripts created to generate RTP packets for testing.

- Utilized tools for debugging and analysis:

  - `bpf_printk` for tracing.

  - `llvm-objdump` for compiler inspection.

  - `tcpdump` and `xdpdump` for packet monitoring.

  - `bpftool` for map visualization.

## Challenges

- **XDP Limitations**:  

  - Restricted stack memory (512 bytes).  

  - Single packet in/out framework.  

- **TC Limitations**:  

  - Slower than XDP.  

- **Documentation Gaps**:  

  - Sparse resources for pointer arithmetic and data types.  

- **Control Plane Integration**:  

  - Requires application-layer modifications via AF_XDP sockets.  

- **Debugging**:  

  - Minimal support for meaningful debug outputs.

## Resources

1. [Supercharge WebRTC with eBPF/XDP (T. Lévai et al., 2023)](https://doi.org/10.1145/3609021.3609296)

2. [XDP Project - Tutorials](https://github.com/xdp-project/xdp-tutorial)

3. [Debugging XDP Packet Issues](https://fedepaol.github.io/blog/2023/09/11/xdp-ate-my-packets-and-how-i-debugged-it)

4. [WebRTC for the Curious](https://webrtcforthecurious.com)

## Setup dependencies

Before you can start completing step in this tutorial, you will need to

install a few dependencies on your system. These are described in

[setup](./setup_dependencies.org).

### Runnning the programs

 - XDP:

    ```

    # /sfu/sfu

    make

    ./xdp-loader load -m skb lo xdp_prog_kern.o -p /sys/fs/bpf/lo -vv   # load bpf with pin path to map to loopback

    ./xdp-loader unload lo --all                                        # unload program

    ./xdp-loader clean lo                                               # clean all links

    # Debugging/Outpu

    xdpdump -i lo --rx-capture exit

    cat /sys/kernel/debug/tracing/trace-pipe

    ```

 - TC:

    ```

    # /sfu/sfu

    clang -O2 -emit-llvm -g -c tc_prog_kern.c -o- | llc -march=bpf -mcpu=probe -filetype=obj tc_prog_kern.o

    tc qdisc add dev lo clsact                               # create a qdisc

    tc filter add dev lo ingress bpf da obj tc_prog_kern.o   # load bpf 

    tc qdisc del dev lo clsact                               # remove bpf chain

    # Debugging/Output

    tcpdump -i lo 

    cat /sys/kernel/debug/tracing/trace-pipe

    ```