Building a Simple IPv4-related API Using Flask

In today's interconnected world, IP addresses and networks are critical components that facilitate communication between devices. Understanding and manipulating IP addresses programmatically can be quite useful. To help you do just that, I'll walk you through building a Flask-based API that performs some useful IPv4-related functions.

What We Will Cover

1. Validating an IPv4 address
2. Obtaining the network and broadcast addresses of a CIDR block
3. Checking if two IP addresses are in the same subnet

Prerequisites

• Python installed on your machine
• Basic understanding of Flask and RESTful APIs
• pip install Flask to install Flask if you haven't already

API Endpoints

1. Validating an IPv4 Address

The first endpoint we'll create validates an IPv4 address.

• Endpoint: /validate_ipv4
• Method: GET
• Parameters: ip (the IP address to validate)

2. Getting Network Information

The second endpoint provides the network and broadcast addresses of a given CIDR block.

• Endpoint: /network_info
• Method: GET
• Parameters: cidr (the CIDR block)

3. Checking if Two IP Addresses are in the Same Subnet

The third endpoint checks if two given IP addresses fall within the same CIDR block.

• Endpoint: /same_subnet
• Method: GET
• Parameters: ip1, ip2 (the IP addresses to check), cidr (the CIDR block)

Code Implementation

from flask import Flask, request, jsonify
from ipaddress import ip_address, ip_network

app = Flask(__name__)

@app.route("/validate_ipv4", methods=["GET"])
def validate_ipv4():
    ip = request.args.get("ip")
    try:
        ip_address(ip)
        return jsonify({"valid": True})
    except ValueError:
        return jsonify({"valid": False}), 400

@app.route("/network_info", methods=["GET"])
def network_info():
    cidr = request.args.get("cidr")
    try:
        network = ip_network(cidr, strict=False)
        return jsonify({"network_address": str(network.network_address), "broadcast_address": str(network.broadcast_address)})
    except ValueError:
        return jsonify({"error": "Invalid CIDR"}), 400

@app.route("/same_subnet", methods=["GET"])
def same_subnet():
    ip1 = request.args.get("ip1")
    ip2 = request.args.get("ip2")
    cidr = request.args.get("cidr")
    try:
        network = ip_network(cidr, strict=False)
        return jsonify({"same_subnet": ip_address(ip1) in network and ip_address(ip2) in network})
    except ValueError:
        return jsonify({"error": "Invalid IP or CIDR"}), 400

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5000)
    

Running the API

1. Save the code to a file named app.py.
2. Open your terminal and run python app.py.
3. The API will be accessible at http://localhost:5000.

Testing the API

Here's how to test each endpoint:

• Validating IPv4: Navigate to http://localhost:5000/validate_ipv4?ip=192.168.1.1.
• Network Info: Navigate to http://localhost:5000/network_info?cidr=192.168.1.0/24.
• Same Subnet: Navigate to http://localhost:5000/same_subnet?ip1=192.168.1.1&ip2=192.168.1.2&cidr=192.168.1.0/24.

And that's it! You now have a working API for IPv4-related tasks. This is a simple example, but you can easily extend it to include more advanced features and functionalities. Happy coding!