Adds reverse dns lookup option

README.md

@@ -70,6 +70,9 @@ sudo go-lanscan --targets 192.22.22.1,192.168.1.1-192.168.1.50,192.56.42.1/24
 # include vendor look-ups on mac addresses (scan will be a little slower)
 sudo go-lanscan --vendor
 
+# include reverse dns lookup for hostnames
+sudo go-lanscan --hostnames
+
 # update static database used for vendor lookups
 # static file is located at ~/.config/go-lanscan/oui.txt
 sudo go-lanscan update-vendors
@@ -215,5 +218,24 @@ queries against this file. The file is stored at `~/.config/go-lanscan/oui.txt`
   option(arpScanner)
 ```
 
+- Perform reverse dns lookup to find hostnames for found devices
+
+```go
+  arpScanner := scanner.NewArpScanner(
+    targets,
+    netInfo,
+    arpResults,
+    arpDone,
+    scanner.WithHostnames(true)
+  )
+
+  // or
+  arpScanner.IncludeHostnames(true)
+
+  // or
+  option := scanner.WithHostnames(true)
+  option(arpScanner)
+```
+
 [golang]:  https://go.dev/doc/install
 [libpcap]: https://github.com/the-tcpdump-group/libpcap

examples/arp/arpscan.go

@@ -38,6 +38,7 @@ func main() {
 		userNet,
 		scanner.WithIdleTimeout(time.Second*time.Duration(idleTimeout)),
 		scanner.WithVendorInfo(vendorRepo),
+		scanner.WithHostnames(true),
 	)
 
 	go func() {

internal/cli/root.go

@@ -27,6 +27,7 @@ func printConfiguration(
 	listenPort uint16,
 	timing string,
 	vendorInfo,
+	hostNames,
 	printJSON,
 	arpOnly,
 	progress bool,
@@ -76,6 +77,11 @@ func printConfiguration(
 		vendorInfo,
 	})
 
+	configTable.AppendRow(table.Row{
+		"hostNames",
+		hostNames,
+	})
+
 	configTable.AppendRow(table.Row{
 		"json",
 		printJSON,
@@ -114,6 +120,7 @@ func Root(
 	var ifaceName string
 	var targets []string
 	var vendorInfo bool
+	var hostNames bool
 	var arpOnly bool
 	var outFile string
 
@@ -160,6 +167,10 @@ func Root(
 				coreScanner.IncludeVendorInfo(vendorRepo)
 			}
 
+			if hostNames {
+				coreScanner.IncludeHostNames(true)
+			}
+
 			timingDuration, err := time.ParseDuration(timing)
 
 			if err != nil {
@@ -197,6 +208,7 @@ func Root(
 					listenPort,
 					timing,
 					vendorInfo,
+					hostNames,
 					printJSON,
 					arpOnly,
 					!progressDisabled,
@@ -219,6 +231,7 @@ func Root(
 	cmd.Flags().StringSliceVarP(&targets, "targets", "t", []string{userNet.Cidr()}, "set targets for scanning")
 	cmd.Flags().StringVar(&outFile, "out-file", "", "outputs final report to file")
 	cmd.Flags().BoolVar(&vendorInfo, "vendor", false, "include vendor info (takes a little longer)")
+	cmd.Flags().BoolVar(&hostNames, "hostnames", false, "perform reverse dns lookup for hostnames")
 
 	cmd.AddCommand(newVersion())
 	cmd.AddCommand(newUpdateVendors(vendorRepo))

internal/core/core.go

@@ -24,6 +24,7 @@ import (
 type DeviceResult struct {
 	IP        net.IP           `json:"ip"`
 	MAC       net.HardwareAddr `json:"mac"`
+	Hostname  string           `json:"hostname"`
 	Vendor    string           `json:"vendor"`
 	Status    scanner.Status   `json:"status"`
 	OpenPorts []scanner.Port   `json:"openPorts"`
@@ -34,12 +35,14 @@ func (r *DeviceResult) Serializable() interface{} {
 	return struct {
 		IP        string         `json:"ip"`
 		MAC       string         `json:"mac"`
+		Hostname  string         `json:"hostname"`
 		Vendor    string         `json:"vendor"`
 		Status    string         `json:"status"`
 		OpenPorts []scanner.Port `json:"openPorts"`
 	}{
 		IP:        r.IP.String(),
 		MAC:       r.MAC.String(),
+		Hostname:  r.Hostname,
 		Vendor:    r.Vendor,
 		Status:    string(r.Status),
 		OpenPorts: r.OpenPorts,
@@ -217,6 +220,7 @@ func (c *Core) processArpResult(result *scanner.ArpScanResult) {
 			IP:        result.IP,
 			MAC:       result.MAC,
 			Status:    scanner.StatusOnline,
+			Hostname:  result.Hostname,
 			Vendor:    result.Vendor,
 			OpenPorts: []scanner.Port{},
 		})
@@ -277,10 +281,10 @@ func (c *Core) printArpResults() {
 
 	var arpTable = table.NewWriter()
 	arpTable.SetOutputMirror(os.Stdout)
-	arpTable.AppendHeader(table.Row{"IP", "MAC", "VENDOR"})
+	arpTable.AppendHeader(table.Row{"IP", "MAC", "HOSTNAME", "VENDOR"})
 
 	for _, t := range c.results.Devices {
-		arpTable.AppendRow(table.Row{t.IP.String(), t.MAC.String(), t.Vendor})
+		arpTable.AppendRow(table.Row{t.IP.String(), t.MAC.String(), t.Hostname, t.Vendor})
 	}
 
 	output := arpTable.Render()
@@ -319,7 +323,7 @@ func (c *Core) printSynResults() {
 
 	var synTable = table.NewWriter()
 	synTable.SetOutputMirror(os.Stdout)
-	synTable.AppendHeader(table.Row{"IP", "MAC", "VENDOR", "STATUS", "OPEN PORTS"})
+	synTable.AppendHeader(table.Row{"IP", "MAC", "HOSTNAME", "VENDOR", "STATUS", "OPEN PORTS"})
 
 	for _, r := range c.results.Devices {
 		openPorts := []string{}
@@ -331,6 +335,7 @@ func (c *Core) printSynResults() {
 		synTable.AppendRow(table.Row{
 			r.IP.String(),
 			r.MAC.String(),
+			r.Hostname,
 			r.Vendor,
 			r.Status,
 			openPorts,

internal/core/core_test.go

@@ -21,10 +21,11 @@ func TestDeviceResult(t *testing.T) {
 	t.Run("is serializable", func(st *testing.T) {
 		mac, _ := net.ParseMAC("00:00:00:00:00:00")
 		result := &core.DeviceResult{
-			IP:     net.ParseIP("127.0.0.1"),
-			MAC:    mac,
-			Vendor: "unknown",
-			Status: scanner.StatusOnline,
+			IP:       net.ParseIP("127.0.0.1"),
+			MAC:      mac,
+			Hostname: "unknown",
+			Vendor:   "unknown",
+			Status:   scanner.StatusOnline,
 			OpenPorts: []scanner.Port{
 				{
 					ID:      22,

pkg/scanner/arpscan.go

@@ -4,6 +4,7 @@ package scanner
 
 import (
 	"bytes"
+	"fmt"
 	"net"
 	"sync"
 	"time"
@@ -32,6 +33,7 @@ type ArpScanner struct {
 	timing           time.Duration
 	idleTimeout      time.Duration
 	vendorRepo       oui.VendorRepo
+	hostNamesEnables bool
 	scanningMux      *sync.RWMutex
 	packetSentAtMux  *sync.RWMutex
 	debug            logger.DebugLogger
@@ -139,7 +141,9 @@ func (s *ArpScanner) Scan() error {
 // Stop stops the scanner
 func (s *ArpScanner) Stop() {
 	if s.cancel != nil {
-		close(s.cancel)
+		go func() {
+			s.cancel <- struct{}{}
+		}()
 	}
 
 	if s.handle != nil {
@@ -164,6 +168,11 @@ func (s *ArpScanner) SetIdleTimeout(duration time.Duration) {
 	s.idleTimeout = duration
 }
 
+// IncludeHostNames sets whether reverse dns look up is performed to find hostname
+func (s *ArpScanner) IncludeHostNames(v bool) {
+	s.hostNamesEnables = v
+}
+
 // IncludeVendorInfo sets whether or not to include vendor info in the scan
 func (s *ArpScanner) IncludeVendorInfo(repo oui.VendorRepo) {
 	s.vendorRepo = repo
@@ -316,9 +325,10 @@ func (s *ArpScanner) writePacketData(ip net.IP) error {
 
 func (s *ArpScanner) processResult(ip net.IP, mac net.HardwareAddr) {
 	arpResult := &ArpScanResult{
-		IP:     ip,
-		MAC:    mac,
-		Vendor: "unknown",
+		IP:       ip,
+		MAC:      mac,
+		Hostname: "unknown",
+		Vendor:   "unknown",
 	}
 
 	if s.vendorRepo != nil {
@@ -329,6 +339,16 @@ func (s *ArpScanner) processResult(ip net.IP, mac net.HardwareAddr) {
 		}
 	}
 
+	if s.hostNamesEnables {
+		fmt.Printf("performing reverse dns lookup for %s\n", ip.String())
+		addr, err := net.LookupAddr(ip.String())
+		fmt.Printf("reverse dns lookup err: %v\n", err)
+		if err == nil && len(addr) > 0 {
+			fmt.Printf("results for reverse dns lookup on %s: addr: %s\n", ip.String(), addr[0])
+			arpResult.Hostname = addr[0]
+		}
+	}
+
 	go func() {
 		s.resultChan <- &ScanResult{
 			Type:    ARPResult,

pkg/scanner/fullscan.go

@@ -139,7 +139,9 @@ func (s *FullScanner) Scan() error {
 // Stop stops the scanner
 func (s *FullScanner) Stop() {
 	if s.cancel != nil {
-		close(s.cancel)
+		go func() {
+			s.cancel <- struct{}{}
+		}()
 	}
 
 	if s.arpScanner != nil {
@@ -171,6 +173,12 @@ func (s *FullScanner) SetIdleTimeout(d time.Duration) {
 	s.synScanner.SetIdleTimeout(d)
 }
 
+// IncludeHostNames sets whether reverse dns look up is performed to find hostname
+func (s *FullScanner) IncludeHostNames(v bool) {
+	s.arpScanner.IncludeHostNames(v)
+	s.synScanner.IncludeHostNames(v)
+}
+
 // IncludeVendorInfo sets whether or not to include vendor info when scanning
 func (s *FullScanner) IncludeVendorInfo(repo oui.VendorRepo) {
 	s.arpScanner.IncludeVendorInfo(repo)

pkg/scanner/options.go

@@ -41,6 +41,13 @@ func WithVendorInfo(repo oui.VendorRepo) Option {
 	}
 }
 
+// WithHostnames sets whether or not to perform reverse dns lookup
+func WithHostnames(v bool) Option {
+	return func(s Scanner) {
+		s.IncludeHostNames(v)
+	}
+}
+
 // WithPacketCapture sets the packet capture implementation for the scanner
 func WithPacketCapture(cap PacketCapture) Option {
 	return func(s Scanner) {

pkg/scanner/options_test.go

@@ -35,6 +35,7 @@ func TestOptions(t *testing.T) {
 			scanner.WithPacketCapture(testPacketCapture),
 			scanner.WithRequestNotifications(requestNotifier),
 			scanner.WithVendorInfo(vendorRepo),
+			scanner.WithHostnames(true),
 		)
 
 		scanner.NewFullScanner(
@@ -47,6 +48,7 @@ func TestOptions(t *testing.T) {
 			scanner.WithPacketCapture(testPacketCapture),
 			scanner.WithRequestNotifications(requestNotifier),
 			scanner.WithVendorInfo(vendorRepo),
+			scanner.WithHostnames(true),
 		)
 
 		scanner.NewSynScanner(
@@ -59,6 +61,7 @@ func TestOptions(t *testing.T) {
 			scanner.WithPacketCapture(testPacketCapture),
 			scanner.WithRequestNotifications(requestNotifier),
 			scanner.WithVendorInfo(vendorRepo),
+			scanner.WithHostnames(true),
 		)
 	})
 }

pkg/scanner/synscan.go

@@ -54,6 +54,7 @@ func NewSynScanner(
 	options ...Option,
 ) *SynScanner {
 	scanner := &SynScanner{
+		cancel:           make(chan struct{}),
 		targets:          targets,
 		networkInfo:      networkInfo,
 		cap:              &defaultPacketCapture{},
@@ -168,7 +169,9 @@ func (s *SynScanner) Scan() error {
 // Stop stops the scanner
 func (s *SynScanner) Stop() {
 	if s.cancel != nil {
-		close(s.cancel)
+		go func() {
+			s.cancel <- struct{}{}
+		}()
 	}
 
 	if s.handle != nil {
@@ -193,6 +196,11 @@ func (s *SynScanner) SetIdleTimeout(duration time.Duration) {
 	s.idleTimeout = duration
 }
 
+// IncludeHostNames sets whether reverse dns look up is performed to find hostname
+func (s *SynScanner) IncludeHostNames(v bool) {
+	// nothing to do
+}
+
 // IncludeVendorInfo N/A for SYN scanner but here to satisfy Scanner interface
 func (s *SynScanner) IncludeVendorInfo(_ oui.VendorRepo) {
 	// nothing to do