Added an option for passing a seed for mac generation. (#21)

* Added an option for passing a seed for mac generation.

* Better option message

* Changes for linter.  Some annoying.  Some reasonable.

* Missed a spot

Co-authored-by: ipchama <[email protected]>

Author: ipchama

cmd/dhcpv4.go

@@ -28,6 +28,7 @@ func prepareCmd(cmd *cobra.Command) *cobra.Command {
 	cmd.Flags().Int("rps", 0, "Max number of packets per second. 0 == unlimited.")
 	cmd.Flags().Int("maxlife", 0, "How long to run. 0 == forever")
 	cmd.Flags().Int("mac-count", 1, "Total number of MAC addresses to use. If the 'mac' option is used, mac-count - number of mac will be used to pad with additional pre-generated MAC addresses.")
+	cmd.Flags().Int64("mac-seed", 0, "Optional seed to use for generating MAC addresses.  This is mainly for when you want the same 'random' MACs every time.")
 	cmd.Flags().StringArray("mac", []string{}, "Optionally specified MAC address to be used for requesting leases. Can be used multiple times.")
 
 	cmd.Flags().Int("stats-rate", 5, "How frequently to update stat calculations. (seconds).")
@@ -125,10 +126,12 @@ func arp(n string, l netlink.Link, i net.IP) (net.HardwareAddr, error) {
 	}
 	buf := gopacket.NewSerializeBuffer()
 
-	gopacket.SerializeLayers(buf, goPacketSerializeOpts,
+	if err := gopacket.SerializeLayers(buf, goPacketSerializeOpts,
 		ethernetLayer,
 		arpLayer,
-	)
+	); err != nil {
+		panic(err)
+	}
 
 	s.AddPayload(buf.Bytes())
 
@@ -157,7 +160,7 @@ func arp(n string, l netlink.Link, i net.IP) (net.HardwareAddr, error) {
 	wg.Wait()
 
 	if !ok {
-		return nil, errors.New("Failed to get ARP response for default gateway probe during init.")
+		return nil, errors.New("failed to get ARP response for default gateway probe during init")
 	}
 
 	return gwMac, nil
@@ -187,6 +190,7 @@ func init() {
 			options.RequestsPerSecond = getVal(cmd.Flags().GetInt("rps")).(int)
 			options.MaxLifetime = getVal(cmd.Flags().GetInt("maxlife")).(int)
 			options.MacCount = getVal(cmd.Flags().GetInt("mac-count")).(int)
+			options.MacSeed = getVal(cmd.Flags().GetInt64("mac-seed")).(int64)
 			options.SpecifiedMacs = getVal(cmd.Flags().GetStringArray("mac")).([]string)
 
 			if options.MacCount <= 0 && len(options.SpecifiedMacs) == 0 {

config/dhcpv4.go

@@ -29,6 +29,7 @@ type DhcpV4Options struct {
 
 	MacCount      int
 	SpecifiedMacs []string
+	MacSeed       int64
 
 	StatsRate int
 }

generator/dhcpv4.go

@@ -63,7 +63,7 @@ func (g *GeneratorV4) DeInit() error {
 
 func (g *GeneratorV4) Stop() error {
 	g.finishChannel <- struct{}{}
-	_, _ = <-g.doneChannel
+	<-g.doneChannel
 	return nil
 }
 
@@ -177,30 +177,31 @@ func (g *GeneratorV4) Run() {
 	sent := 0
 
 	start := time.Now()
-	time.Sleep(1)
+	time.Sleep(1 * time.Nanosecond)
 
 	mRps := g.options.RequestsPerSecond
 
 	var t time.Time
 	var elapsed float64
 	var rps int
 
+	var err error
 	g.addLog("Finished generating MACs and preparing packet headers.")
 
 	for g.options.MaxLifetime == 0 || int(elapsed) <= g.options.MaxLifetime {
 
 		select {
-		case _, _ = <-g.finishChannel:
+		case <-g.finishChannel:
 			close(g.doneChannel)
 			return
 		default:
 		}
 
 		select {
-		case mRps, _ = <-g.rpsChannel:
+		case mRps = <-g.rpsChannel:
 			sent = 0
 			start = time.Now()
-			time.Sleep(1)
+			time.Sleep(1 * time.Nanosecond) // Being explict...
 		default:
 		}
 
@@ -218,15 +219,20 @@ func (g *GeneratorV4) Run() {
 
 		//ethernetLayer.SrcMAC = macs[i]
 
+		// I refuse to even assign to _ ...
+		// skipcq
 		udpLayer.SetNetworkLayerForChecksum(ipLayer)
 
 		buf := gopacket.NewSerializeBuffer()
-		gopacket.SerializeLayers(buf, opts,
+		if err = gopacket.SerializeLayers(buf, opts,
 			ethernetLayer,
 			ipLayer,
 			udpLayer,
 			outDhcpLayer,
-		)
+		); err != nil {
+			g.addError(err)
+			continue
+		}
 
 		if g.sendPayload(buf.Bytes()) {
 			g.addStat(stats.DiscoverSentStat)
@@ -242,7 +248,14 @@ func (g *GeneratorV4) Run() {
 }
 
 func (g *GeneratorV4) generateMacList() []net.HardwareAddr {
-	nS := rand.NewSource(time.Now().Unix())
+
+	seed := g.options.MacSeed
+
+	if seed == 0 {
+		seed = time.Now().Unix()
+	}
+
+	nS := rand.NewSource(seed)
 	nRand := rand.New(nS)
 
 	macs := make([]net.HardwareAddr, 0)