nmap with Golang

nmap.go

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"internal/config"

	"github.com/Ullaakut/nmap/v3"
)

// viewAndLogActiveDevices retrieves and logs all active devices in the network
func viewAndLogActiveDevices(cfg *config.Config) error {
	// Create a context with a 5-minute timeout
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
	defer cancel()

	// Create a new nmap scanner with target subnet and options
	scanner, err := nmap.NewScanner(
		ctx,
		nmap.WithTargets(cfg.NetworkSubnet),     // e.g. "192.4.1.0/24"
		nmap.WithCustomDNSServers(cfg.RouterIP), // --dns-servers
		nmap.WithPingScan(),                     // -sn
		nmap.WithPrivileged(),                   // run as privileged user
	)
	if err != nil {
		return fmt.Errorf("error creating nmap scanner: %v", err)
	}

	// Run the scan
	result, warnings, err := scanner.Run()
	if len(*warnings) > 0 {
		log.Printf("Scan completed with warnings: %v\n", *warnings)
	}
	if err != nil {
		return fmt.Errorf("error running nmap scan: %v", err)
	}

	// Log active devices
	log.Println("Active devices in the network:")
	activeCount := 0
	for _, host := range result.Hosts {
		// Skip hosts that are not up, don't have addresses, or don't have hostnames
		if len(host.Addresses) == 0 || host.Status.State != "up" || len(host.Hostnames) == 0 {
			continue
		}

		hostname := host.Hostnames[0].Name
		if hostname == "" {
			continue
		}

		// Get IP and MAC addresses
		var ip, mac string
		for _, addr := range host.Addresses {
			if addr.AddrType == "ipv4" {
				ip = addr.Addr
			} else if addr.AddrType == "mac" {
				mac = addr.Addr
			}
		}

		// Log device information
		log.Printf("- Name: %s, MAC: %s, IP: %s\n", hostname, mac, ip)
		activeCount++
	}

	log.Printf("Total active devices: %d\n", activeCount)
	log.Printf("Total hosts scanned: %d\n", len(result.Hosts))

	return nil
}

func main() {
	cfg, err := config.Load()
	if err != nil {
		log.Fatalf("Failed to load config: %v", err)
	}

	err = viewAndLogActiveDevices(cfg)
	if err != nil {
		log.Fatalf("Failed to view and log active devices: %v", err)
	}
}