Network Analysis in Rust: Capturing and Analyzing Network Traffic with Pcap and Pnet

Network analysis is critical for monitoring, securing, and diagnosing network infrastructure, and Rust is becoming an increasingly popular choice for developers to build network tools due to its performance and memory safety.

In this article, we'll explore how to use pcap and pnet in Rust to read PCAP files, capture live network traffic, and briefly discuss high-performance packet capture using PF_RING.

Reading PCAP files using pcap

The pcap library allows you to read files captured from the network, commonly known as PCAP (Packet Capture), which contains traces of network traffic. This step is essential for analyzing network events or debugging.

Simple example of reading packets from a file:

 use pcap::Capture; fn main() { let mut cap = Capture::from_file("example.pcap").unwrap(); while let Ok(packet) = cap.next() { println!("Packet : {:?}", packet); } }

Fine-grained packet capture and analysis using pnet

The pnet crate allows working with lower-level network packets in Rust. Unlike pcap, it provides a more detailed API for manipulating packet headers, protocols, and accessing network cards through system libraries.

Pnet embeds the operating system's raw sockets into the crate:

 use pnet::datalink::{self, Channel::Ethernet}; fn main() { let interfaces = datalink::interfaces(); let interface = interfaces.into_iter() .find(|iface| iface.is_up() && !iface.is_loopback()) .expect("No suitable interface found."); let (_, mut rx) = match datalink::channel(&interface, Default::default()) { Ok(Ethernet(tx, rx)) => (tx, rx), Ok(_) => panic!("Unhandled channel type."), Err(e) => panic!("An error occurred: {}", e), }; loop { match rx.next() { Ok(packet) => println!("Packet : {:?}", packet), Err(e) => eprintln!("An error occurred while reading: {}", e), } } }

Using pnet and libc to access the network card

To efficiently capture and filter packets, pnet can interact directly with system libraries. On Windows, this is done via Npcap (a fork of WinPcap), and on Linux via raw sockets and Berkeley Packet Filter (BPF). libc is often used to access these system-level features.

picture

Pnet uses system calls to access network drivers through libraries such as libc.

For environments that require high performance, PF_RING can be used to optimize capture by directly accessing the network card.

Summarize

Rust provides a variety of powerful tools for network analysis and capture, and pcap and pnet provide features suitable for different abstraction levels. For the capture and detailed analysis of network data and the need for high performance, pnet and PF_RING are particularly suitable.