Layer 2 Frame Generator (C)

A lightweight C utility to generate and transmit custom Ethernet (Layer 2) frames directly onto the wire using raw sockets. This tool allows for the specification of custom EtherTypes and payloads, making it ideal for network protocol testing and educational purposes.

Features

• Raw Socket Transmission: Bypasses the standard TCP/IP stack to send frames directly.
• Custom EtherType: Easily define your own protocol identifiers.
• Hardware Address Retrieval: Automatically fetches the source MAC address and interface index using ioctl.
• Custom Payloads: Supports arbitrary string or binary payloads.

Prerequisites

• Operating System: Linux (Raw sockets AF_PACKET are Linux-specific).
• Privileges: Root/Sudo access is required to open raw sockets.

Getting Started

1. Configuration

Open l2frame.c and modify the following variables to match your environment:

• interface: The name of your network interface (e.g., eth0, wlan0).
• dst_mac_str: The destination MAC address.
• ethtype: Your custom EtherType (e.g., 0x8888).
• payload: The data you wish to transmit.

2. Compilation

Compile the program using gcc:

gcc l2frame.c -o l2

3. Execution

Run the executable with sudo:

sudo ./l2

Wireshark Verification

To verify the transmission, capture traffic on the specified interface using Wireshark. Filter by your custom EtherType (e.g., eth.type == 0x8888).

Screenshots

Attach your Wireshark capture here to demonstrate the frame structure.

Project Structure

• l2frame.c: Main source code.
• l2: Compiled executable.

License

MIT License