async-pcap

async-pcap is a Rust library that provides an asynchronous wrapper around pcap packet captures. It allows you to capture network packets in a non-blocking, async context using Tokio. Internally, it spawns a dedicated thread to poll packets and delivers them via an asynchronous channel.

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Features

• Async-friendly wrapper around pcap::Capture<Active>.
• Returns owned packet data (Vec<u8>) with packet metadata.
• Safe to use in multi-threaded Tokio contexts.
• Simple API: AsyncCapture::new() and next_packet().await.

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Usage

use async_pcap::{AsyncCapture, Capture, Device};
use tokio::runtime::Runtime;

fn main() {
    let rt = Runtime::new().unwrap();

    rt.block_on(async {
        // Open the network device
        let device = Device::lookup().unwrap().unwrap();
        let cap = Capture::from_device(device)
            .unwrap()
            .promisc(true)
            .snaplen(65535)
            .timeout(500)
            .immediate_mode(true)
            .open()
            .unwrap();

        // Create the async capture and handle
        let (async_cap, handle) = AsyncCapture::new(cap);

        // Clone the handle to stop from another task
        let handle_clone = handle.clone();

        // Spawn a task to stop capture after 5 seconds
        tokio::spawn(async move {
            tokio::time::sleep(std::time::Duration::from_secs(5)).await;
            handle_clone.stop(); // This sends the Stop signal
            println!("Capture stopped from another task");
        });

        // Read packets asynchronously
        while let Some(packet) = async_cap.next_packet().await {
            match packet {
                Ok(packet) => {
                    println!("Packet: {}", packet.data.len());
                }
                Err(e) => {
                    println!("{e}");
                }
            }
        }

        println!("Capture loop exited cleanly");
    });
}

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Notes

• AsyncCapture internally spawns a dedicated thread for polling packets.
• Uses a Tokio Mutex and UnboundedReceiver for async packet delivery.
• Suitable for async network monitoring applications.

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