fix: fixing pcap handles w/r ops synchronization here and there (ref #88)

modules/dhcp6_spoof.go

@@ -32,6 +32,7 @@ type DHCP6Spoofer struct {
 	Domains       []string
 	RawDomains    []byte
 	waitGroup     *sync.WaitGroup
+	pktSourceChan chan gopacket.Packet
 }
 
 func NewDHCP6Spoofer(s *session.Session) *DHCP6Spoofer {
@@ -360,13 +361,12 @@ func (s *DHCP6Spoofer) Start() error {
 	}
 
 	return s.SetRunning(true, func() {
-		defer s.Handle.Close()
-
 		s.waitGroup.Add(1)
 		defer s.waitGroup.Done()
 
 		src := gopacket.NewPacketSource(s.Handle, s.Handle.LinkType())
-		for packet := range src.Packets() {
+		s.pktSourceChan = src.Packets()
+		for packet := range s.pktSourceChan {
 			if s.Running() == false {
 				break
 			}
@@ -378,6 +378,7 @@ func (s *DHCP6Spoofer) Start() error {
 
 func (s *DHCP6Spoofer) Stop() error {
 	return s.SetRunning(false, func() {
+		s.pktSourceChan <- nil
 		s.Handle.Close()
 		s.waitGroup.Wait()
 	})

modules/dns_spoof.go

@@ -24,6 +24,7 @@ type DNSSpoofer struct {
 	Address       net.IP
 	All           bool
 	waitGroup     *sync.WaitGroup
+	pktSourceChan chan gopacket.Packet
 }
 
 func NewDNSSpoofer(s *session.Session) *DNSSpoofer {
@@ -273,10 +274,9 @@ func (s *DNSSpoofer) Start() error {
 		s.waitGroup.Add(1)
 		defer s.waitGroup.Done()
 
-		defer s.Handle.Close()
-
 		src := gopacket.NewPacketSource(s.Handle, s.Handle.LinkType())
-		for packet := range src.Packets() {
+		s.pktSourceChan = src.Packets()
+		for packet := range s.pktSourceChan {
 			if s.Running() == false {
 				break
 			}
@@ -288,6 +288,7 @@ func (s *DNSSpoofer) Start() error {
 
 func (s *DNSSpoofer) Stop() error {
 	return s.SetRunning(false, func() {
+		s.pktSourceChan <- nil
 		s.Handle.Close()
 		s.waitGroup.Wait()
 	})

modules/net_sniff.go

@@ -16,6 +16,7 @@ type Sniffer struct {
 	session.SessionModule
 	Stats         *SnifferStats
 	Ctx           *SnifferContext
+	pktSourceChan chan gopacket.Packet
 }
 
 func NewSniffer(s *session.Session) *Sniffer {
@@ -148,7 +149,8 @@ func (s *Sniffer) Start() error {
 		s.Stats = NewSnifferStats()
 
 		src := gopacket.NewPacketSource(s.Ctx.Handle, s.Ctx.Handle.LinkType())
-		for packet := range src.Packets() {
+		s.pktSourceChan = src.Packets()
+		for packet := range s.pktSourceChan {
 			if s.Running() == false {
 				break
 			}
@@ -183,6 +185,7 @@ func (s *Sniffer) Start() error {
 
 func (s *Sniffer) Stop() error {
 	return s.SetRunning(false, func() {
+		s.pktSourceChan <- nil
 		s.Ctx.Close()
 	})
 }

packets/queue.go

@@ -47,6 +47,8 @@ type Queue struct {
 	iface      *network.Endpoint
 	handle     *pcap.Handle
 	source     *gopacket.PacketSource
+	srcChannel chan gopacket.Packet
+	writes     *sync.WaitGroup
 	pktCb      PacketCallback
 	active     bool
 }
@@ -57,6 +59,7 @@ func NewQueue(iface *network.Endpoint) (q *Queue, err error) {
 		Traffic:    make(map[string]*Traffic),
 		Activities: make(chan Activity),
 
+		writes: &sync.WaitGroup{},
 		iface:  iface,
 		active: !iface.IsMonitor(),
 		pktCb:  nil,
@@ -68,6 +71,7 @@ func NewQueue(iface *network.Endpoint) (q *Queue, err error) {
 		}
 
 		q.source = gopacket.NewPacketSource(q.handle, q.handle.LinkType())
+		q.srcChannel = q.source.Packets()
 		go q.worker()
 	}
 
@@ -138,7 +142,7 @@ func (q *Queue) trackActivity(eth *layers.Ethernet, ip4 *layers.IPv4, address ne
 }
 
 func (q *Queue) worker() {
-	for pkt := range q.source.Packets() {
+	for pkt := range q.srcChannel {
 		if q.active == false {
 			return
 		}
@@ -192,6 +196,9 @@ func (q *Queue) Send(raw []byte) error {
 		return fmt.Errorf("Packet queue is not active.")
 	}
 
+	q.writes.Add(1)
+	defer q.writes.Done()
+
 	if err := q.handle.WritePacketData(raw); err != nil {
 		q.Stats.Lock()
 		q.Stats.Errors++
@@ -211,7 +218,11 @@ func (q *Queue) Stop() {
 	defer q.Unlock()
 
 	if q.active == true {
-		q.handle.Close()
+		// wait for write operations to be completed
+		q.writes.Wait()
+		// signal the main loop to exit and close the handle
 		q.active = false
+		q.srcChannel <- nil
+		q.handle.Close()
 	}
 }