new: implemented syn.scan module (closes #67)

packets/queue.go

@@ -32,8 +32,10 @@ type Stats struct {
 	Errors      uint64
 }
 
+type PacketCallback func(pkt gopacket.Packet)
+
 type Queue struct {
-	sync.Mutex
+	sync.RWMutex
 
 	Activities chan Activity `json:"-"`
 
@@ -44,6 +46,7 @@ type Queue struct {
 	iface  *network.Endpoint
 	handle *pcap.Handle
 	source *gopacket.PacketSource
+	pktCb  PacketCallback
 	active bool
 }
 
@@ -55,6 +58,7 @@ func NewQueue(iface *network.Endpoint) (q *Queue, err error) {
 
 		iface:  iface,
 		active: !iface.IsMonitor(),
+		pktCb:  nil,
 	}
 
 	if q.active == true {
@@ -69,6 +73,21 @@ func NewQueue(iface *network.Endpoint) (q *Queue, err error) {
 	return
 }
 
+func (q *Queue) OnPacket(cb PacketCallback) {
+	q.Lock()
+	defer q.Unlock()
+	q.pktCb = cb
+}
+
+func (q *Queue) onPacketCallback(pkt gopacket.Packet) {
+	q.RLock()
+	defer q.RUnlock()
+
+	if q.pktCb != nil {
+		q.pktCb(pkt)
+	}
+}
+
 func (q *Queue) trackProtocols(pkt gopacket.Packet) {
 	// gather protocols stats
 	pktLayers := pkt.Layers()
@@ -130,6 +149,8 @@ func (q *Queue) worker() {
 		atomic.AddUint64(&q.Stats.PktReceived, 1)
 		atomic.AddUint64(&q.Stats.Received, pktSize)
 
+		q.onPacketCallback(pkt)
+
 		// decode eth and ipv4 layers
 		leth := pkt.Layer(layers.LayerTypeEthernet)
 		lip4 := pkt.Layer(layers.LayerTypeIPv4)

packets/tcp.go

@@ -0,0 +1,29 @@
+package packets
+
+import (
+	"github.com/google/gopacket/layers"
+	"net"
+)
+
+func NewTCPSyn(from net.IP, from_hw net.HardwareAddr, to net.IP, to_hw net.HardwareAddr, srcPort int, dstPort int) (error, []byte) {
+	eth := layers.Ethernet{
+		SrcMAC:       from_hw,
+		DstMAC:       to_hw,
+		EthernetType: layers.EthernetTypeIPv4,
+	}
+	ip4 := layers.IPv4{
+		Protocol: layers.IPProtocolTCP,
+		Version:  4,
+		TTL:      64,
+		SrcIP:    from,
+		DstIP:    to,
+	}
+	tcp := layers.TCP{
+		SrcPort: layers.TCPPort(srcPort),
+		DstPort: layers.TCPPort(dstPort),
+		SYN:     true,
+	}
+	tcp.SetNetworkLayerForChecksum(&ip4)
+
+	return Serialize(&eth, &ip4, &tcp)
+}