🦀 Rust Traffic Inspector

A Low-Level, User-Space Network Traffic Filter Built from Scratch

"To understand the Web, you have to break it down to the bytes."

This isn't a wrapper around Nginx or a high-level proxy library. This is a manual implementation of a Traffic Inspector using raw TCP streams in Rust. It captures, decodes, and filters HTTP packets at the byte level—all running in user space without sudo.

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⚡ Key Features

🚀 Zero Dependencies (Almost) Built primarily using Rust's standard library (std::net, std::io) 📡 Raw Packet Capture Reads network traffic directly into a 1024-byte stack buffer 🔍 Manual HTTP Decoding Converts raw u8 byte streams into readable text using lossy UTF-8 decoding

🛡️ Active Traffic Control Detects signatures (like ad or banner) and injects custom HTTP 403 Forbidden in real-time 👤 Non-Root Execution Runs entirely in user space (Layer 7) via TcpListener, bypassing raw sockets ⚙️ First Principles Engineering No black boxes—every byte is manually inspected and processed

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🛠️ How It Works

Most ad blockers work as browser extensions. Most firewalls work at the Kernel level. This tool sits in the middle.

┌─────────────┐
│   Client    │
│  (Browser)  │
└──────┬──────┘
       │ HTTP Request
       ▼
┌─────────────────────────────────────┐
│  🦀 Rust Traffic Inspector          │
│  (User Space Proxy)                 │
│                                     │
│  1️⃣ Bind to 127.0.0.1:3000         │
│  2️⃣ Accept TCP connection          │
│  3️⃣ Read 1024 bytes into buffer    │
│  4️⃣ Scan for banned keywords       │
│  5️⃣ Inject 403 OR forward 200      │
└─────────────────────────────────────┘

The Architecture

1. The Listener: Binds to 127.0.0.1:3000 acting as a "Man-in-the-Middle" proxy

2. The Buffer: Grabs the first 1024 bytes of the raw TCP stream (no high-level HTTP parsing)

3. The Inspection:

   • Scans raw text for banned keywords (currently: "ad", "banner")
   • If Clean: Forwards 200 OK response
   • If Dirty: Kills connection with custom 403 FORBIDDEN + 🚫 AD BLOCKED HTML

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🚀 Quick Start

Prerequisites

• Rust and Cargo installed via rustup

Installation

# Clone the repository
git clone https://github.com/OP-88/Rust-ad_blocker.git
cd Rust-ad_blocker

# Run the inspector
cargo run

Expected Output:

🛡️ Traffic Inspector Online at http://127.0.0.1:3000

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🧪 Testing

✅ Clean Traffic

curl http://127.0.0.1:3000/hello

Response:

✅ Traffic Clean

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🚫 Blocked Traffic

curl http://127.0.0.1:3000/banner_ads

Response:

HTTP/1.1 403 Forbidden

<h1>🚫 AD BLOCKED</h1>
<p>This request was flagged by the Traffic Inspector.</p>

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🧠 Why Build This?

I built this as a Capstone project to bridge the gap between:

• High-Level Web Development
• Low-Level Systems Programming

The Challenge:
I initially wanted to write a raw packet sniffer, but raw sockets require root/admin privileges.

The Solution:
By pivoting to a TcpListener architecture, I engineered a User Space Firewall—proving you don't need kernel access to control network traffic if you understand how TCP streams work.

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📚 What You'll Learn

• ✅ How to read raw TCP byte streams in Rust
• ✅ Manual HTTP request parsing (no external crates)
• ✅ Building a Layer 7 proxy without root access
• ✅ Real-time packet inspection and filtering
• ✅ Designing lightweight, dependency-minimal systems

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🔧 Technical Stack

Component	Technology
Language	Rust 🦀
Network Layer	Layer 7 (Application)
Core Libraries	std::net::TcpListener, std::io
Buffer Size	1024 bytes (stack-allocated)
Execution	User space (no sudo required)

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🎯 Roadmap

• Add configurable blocklist (JSON/TOML file)
• Implement regex pattern matching for advanced filtering
• Add HTTPS support with TLS termination
• Create WebUI dashboard for real-time traffic monitoring
• Benchmark performance vs traditional ad blockers

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👤 Author

OP-88

Built with ❤️ for systems programmers who want to understand the Web at the byte level.

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📜 License

Open Source. Use it to learn, break things, and rebuild them better.

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🌟 Like This Project?

If you found this helpful or learned something new:

• ⭐ Star the repository
• 🔄 Fork it and build your own version
• 📢 Share it with fellow Rustaceans

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"Security through understanding, not abstraction."