func main() {
defer util.Run()()
var handle *pcap.Handle
var err error
// Set up pcap packet capture
if *fname != "" {
log.Printf("Reading from pcap dump %q", *fname)
handle, err = pcap.OpenOffline(*fname)
} else {
log.Printf("Starting capture on interface %q", *iface)
handle, err = pcap.OpenLive(*iface, int32(*snaplen), true, pcap.BlockForever)
}
if err != nil {
log.Fatal(err)
}
if err := handle.SetBPFFilter(*filter); err != nil {
log.Fatal(err)
}
// Set up assembly
streamFactory := &httpStreamFactory{}
streamPool := tcpassembly.NewStreamPool(streamFactory)
assembler := tcpassembly.NewAssembler(streamPool)
log.Println("reading in packets")
// Read in packets, pass to assembler.
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
packets := packetSource.Packets()
ticker := time.Tick(time.Minute)
for {
select {
case packet := <-packets:
// A nil packet indicates the end of a pcap file.
if packet == nil {
return
}
if *logAllPackets {
log.Println(packet)
}
if packet.NetworkLayer() == nil || packet.TransportLayer() == nil || packet.TransportLayer().LayerType() != layers.LayerTypeTCP {
log.Println("Unusable packet")
continue
}
tcp := packet.TransportLayer().(*layers.TCP)
assembler.AssembleWithTimestamp(packet.NetworkLayer().NetworkFlow(), tcp, packet.Metadata().Timestamp)
case <-ticker:
// Every minute, flush connections that haven't seen activity in the past 2 minutes.
assembler.FlushOlderThan(time.Now().Add(time.Minute * -2))
}
}
}
func (tap *Wiretap) capture(handle *pcap.Handle, channel chan gopacket.Packet) {
defer handle.Close()
src := gopacket.NewPacketSource(handle, handle.LinkType())
src.DecodeOptions = gopacket.NoCopy
for {
packet, err := src.NextPacket()
if err == io.EOF {
return
} else if err == nil {
channel <- packet
}
}
}
//startCapture captures all packets on any interface for an unlimited duration.
//Packets can be filtered by a BPF filter string. (E.g. tcp port 22)
func capture(snaplen int32, quit chan bool, captureReady chan bool, pcapFile string) error {
var handle *pcap.Handle
var err error
if pcapFile != "" {
log.Println("Reading packet loss data from pcap-file:", pcapFile)
handle, err = pcap.OpenOffline(pcapFile)
} else {
//https://godoc.org/code.google.com/p/gopacket/pcap
//This might have been the culprit
//Alternative to try: 250*time.Millisecond
handle, err = pcap.OpenLive("any", snaplen, true, 250*time.Millisecond)
}
if err != nil {
log.Println("Error while start capturing packets", err)
return err
}
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
captureReady <- true
for {
select {
case packet := <-packetSource.Packets():
if packet != nil {
if packet.Layer(layers.LayerTypeIPSecESP) != nil {
putChannel(packet, ipSecChannel)
}
if packet.Layer(layers.LayerTypeICMPv4) != nil {
putChannel(packet, icmpChannel)
}
}
case <-quit:
log.Println("Received quit message, stopping Listener.")
return nil
}
}
}
