// writeARP writes an ARP request for each address on our local network to the
// pcap handle.
func writeARP(handle *pcap.Handle, iface *net.Interface, addr *net.IPNet) error {
// Set up all the layers' fields we can.
eth := layers.Ethernet{
SrcMAC: iface.HardwareAddr,
DstMAC: net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
EthernetType: layers.EthernetTypeARP,
}
arp := layers.ARP{
AddrType: layers.LinkTypeEthernet,
Protocol: layers.EthernetTypeIPv4,
HwAddressSize: 6,
ProtAddressSize: 4,
Operation: layers.ARPRequest,
SourceHwAddress: []byte(iface.HardwareAddr),
SourceProtAddress: []byte(addr.IP),
DstHwAddress: []byte{0, 0, 0, 0, 0, 0},
}
// Set up buffer and options for serialization.
buf := gopacket.NewSerializeBuffer()
opts := gopacket.SerializeOptions{
FixLengths: true,
ComputeChecksums: true,
}
// Send one packet for every address.
for _, ip := range ips(addr) {
arp.DstProtAddress = []byte(ip)
gopacket.SerializeLayers(buf, opts, ð, &arp)
if err := handle.WritePacketData(buf.Bytes()); err != nil {
return err
}
}
return nil
}
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 main() {
defer util.Run()()
var handle *pcap.Handle
var err error
if *fname != "" {
if handle, err = pcap.OpenOffline(*fname); err != nil {
log.Fatal("PCAP OpenOffline error:", err)
}
} else {
// This is a little complicated because we want to allow all possible options
// for creating the packet capture handle... instead of all this you can
// just call pcap.OpenLive if you want a simple handle.
inactive, err := pcap.NewInactiveHandle(*iface)
if err != nil {
log.Fatal("could not create: %v", err)
}
defer inactive.CleanUp()
if err = inactive.SetSnapLen(*snaplen); err != nil {
log.Fatal("could not set snap length: %v", err)
} else if err = inactive.SetPromisc(*promisc); err != nil {
log.Fatal("could not set promisc mode: %v", err)
} else if err = inactive.SetTimeout(time.Second); err != nil {
log.Fatal("could not set timeout: %v", err)
}
if *tstype != "" {
if t, err := pcap.TimestampSourceFromString(*tstype); err != nil {
log.Fatalf("Supported timestamp types: %v", inactive.SupportedTimestamps())
} else if err := inactive.SetTimestampSource(t); err != nil {
log.Fatalf("Supported timestamp types: %v", inactive.SupportedTimestamps())
}
}
if handle, err = inactive.Activate(); err != nil {
log.Fatal("PCAP Activate error:", err)
}
defer handle.Close()
if len(flag.Args()) > 0 {
bpffilter := strings.Join(flag.Args(), " ")
fmt.Fprintf(os.Stderr, "Using BPF filter %q\n", bpffilter)
if err = handle.SetBPFFilter(bpffilter); err != nil {
log.Fatal("BPF filter error:", err)
}
}
}
dumpcommand.Run(handle)
}
func tryCapture(iface net.Interface) error {
if iface.Name[:2] == "lo" {
return fmt.Errorf("skipping loopback")
}
var h *pcap.Handle
var err error
switch *mode {
case "basic":
h, err = pcap.OpenLive(iface.Name, 65536, false, time.Second*3)
if err != nil {
return fmt.Errorf("openlive: %v", err)
}
defer h.Close()
case "filtered":
h, err = pcap.OpenLive(iface.Name, 65536, false, time.Second*3)
if err != nil {
return fmt.Errorf("openlive: %v", err)
}
defer h.Close()
if err := h.SetBPFFilter("port 80 or port 443"); err != nil {
return fmt.Errorf("setbpf: %v", err)
}
case "timestamp":
u, err := pcap.NewInactiveHandle(iface.Name)
if err != nil {
return err
}
defer u.CleanUp()
if err = u.SetSnapLen(65536); err != nil {
return err
} else if err = u.SetPromisc(false); err != nil {
return err
} else if err = u.SetTimeout(time.Second * 3); err != nil {
return err
}
sources := u.SupportedTimestamps()
if len(sources) == 0 {
return fmt.Errorf("no supported timestamp sources")
} else if err := u.SetTimestampSource(sources[0]); err != nil {
return fmt.Errorf("settimestampsource(%v): %v", sources[0], err)
} else if h, err = u.Activate(); err != nil {
return fmt.Errorf("could not activate: %v", err)
}
defer h.Close()
default:
panic("Invalid --mode: " + *mode)
}
go generatePackets()
h.ReadPacketData() // Do one dummy read to clear any timeouts.
data, ci, err := h.ReadPacketData()
if err != nil {
return fmt.Errorf("readpacketdata: %v", err)
}
log.Printf("Read packet, %v bytes, CI: %+v", len(data), ci)
return nil
}