Routing packets using Packet Tunnel Provider

Hi!

I am new to Apple app development so please bear with me.

I am trying to design an app that can mimic some of the functionality of iptables routing. The crux of it is I would like to redirect local traffic bound for a specific port to a different port and then redirect any outgoing traffic on that port back to the original port:

outgoing packet bound for IP:1234 -> 127.0.0.1:2345 outgoing packet bound for IP:2345 -> IP:1234

I tried to implement this behavior with a packet tunnel but have not made any substantial progress. Is this the right approach?

Here is my implementation:

private func handleConnection(_ connection: NWConnection) {
    connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) { [weak self] data, context, isComplete, error in
        if let data = data, !data.isEmpty {
            self?.processData(data, from: connection)
        }
        if let error = error {
            print("Connection error: \(error)")
        }
        if isComplete {
            connection.cancel()
        } else {
            self?.handleConnection(connection) // Continue to receive data
        }
    }
    connection.start(queue: .main)
}

private func processData(_ data: Data, from connection: NWConnection) {
    switch connection.endpoint {
    case .hostPort(let host, let port):
        let portNumber = port.rawValue
        let hostDescription = host.debugDescription
        print("Received data from host: \(hostDescription) on port: \(portNumber)")
        
        if portNumber == 1234 {
            // Rule 1: Redirect traffic from port 1234 to 127.0.0.1:2345
            redirectTraffic(data, to: "127.0.0.1", port: 2345)
            print("Redirecting traffic from 1234 to 2345")
        } else if portNumber == 2345 {
            // Rule 2: Redirect traffic from port 2345 to the original IP address but port 1234
            redirectTraffic(data, to: hostDescription, port: 1234)
            print("Redirecting traffic from 2345 back to 1234")
        }
        
    case .service(name: _, type: _, domain: _, interface: _):
        print("Received bonjour service")
    case .unix(path: _):
        print("Received unix domain path")
    case .url(_):
        print("Received url")
    case .opaque(_):
        print("Opaque?")
    @unknown default:
        fatalError("Unknown endpoint type")
    }
}