// processor is a worker that decodes packets and passes on to Account and Log.
func (c *Capture) processor(num int, packetsCh <-chan gopacket.Packet) {
log.Printf("processor %d: starting", num)
buffer := c.nextBuffer()
defer func() {
// TODO: Save a checkpoint.
if c.Log != nil {
c.Log(buffer)
}
}()
var (
eth layers.Ethernet
ip4 layers.IPv4
ip6 layers.IPv6
tcp layers.TCP
udp layers.UDP
dns layers.DNS
payload gopacket.Payload
)
parser := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet, ð, &ip4, &ip6, &tcp, &udp, &dns, &payload)
for packet := range packetsCh {
var decoded []gopacket.LayerType
if err := parser.DecodeLayers(packet.Data(), &decoded); err != nil {
log.Printf("processor %d: %v", num, err)
}
m := packet.Metadata()
b := Metadata{
Timestamp: m.Timestamp,
Size: uint64(m.Length),
}
for _, layerType := range decoded {
switch layerType {
case layers.LayerTypeIPv6:
b.SrcIP, b.DstIP = ip6.SrcIP, ip6.DstIP
b.SrcName, b.DstName = c.revDNS.names(local(b.SrcIP, b.DstIP), ip6.NetworkFlow())
b.V6 = true
case layers.LayerTypeIPv4:
b.SrcIP, b.DstIP = ip4.SrcIP, ip4.DstIP
b.SrcName, b.DstName = c.revDNS.names(local(b.SrcIP, b.DstIP), ip4.NetworkFlow())
case layers.LayerTypeTCP:
b.SrcPort, b.DstPort = uint16(tcp.SrcPort), uint16(tcp.DstPort)
case layers.LayerTypeUDP:
b.SrcPort, b.DstPort = uint16(udp.SrcPort), uint16(udp.DstPort)
case layers.LayerTypeDNS:
// Add DNS answers to reverse DNS map.
// The "src" is the host who did the query, but answers are replies, so "src" = dst.
// Should be here only after b.DstIP is set.
c.revDNS.add(b.DstIP, &dns)
}
}
c.Account(&b)
if c.Log != nil {
buffer = append(buffer, b)
if len(buffer) >= c.BufferSize {
go c.logBuffer(buffer)
buffer = c.nextBuffer()
}
}
}
log.Printf("processor %d: stopping", num)
}
func main() {
defer util.Run()()
var handle *pcap.Handle
var err error
flushDuration, err := time.ParseDuration(*flushAfter)
if err != nil {
log.Fatal("invalid flush duration: ", *flushAfter)
}
// log.Printf("starting capture on interface %q", *iface)
// // Set up pcap packet capture
// handle, err := pcap.OpenLive(*iface, int32(*snaplen), true, flushDuration/2)
// if err != nil {
// log.Fatal("error opening pcap handle: ", err)
// }
// Set up pcap packet capture
if *fname != "" {
log.Printf("Reading from pcap dump %q", *fname)
handle, err = pcap.OpenOffline(*fname)
} else {
log.Fatalln("Error: pcap file name is required!")
// 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("error setting BPF filter: ", err)
}
// Set up assembly
streamFactory := &statsStreamFactory{}
streamPool := tcpassembly.NewStreamPool(streamFactory)
assembler := tcpassembly.NewAssembler(streamPool)
assembler.MaxBufferedPagesPerConnection = *bufferedPerConnection
assembler.MaxBufferedPagesTotal = *bufferedTotal
log.Println("reading in packets")
// We use a DecodingLayerParser here instead of a simpler PacketSource.
// This approach should be measurably faster, but is also more rigid.
// PacketSource will handle any known type of packet safely and easily,
// but DecodingLayerParser will only handle those packet types we
// specifically pass in. This trade-off can be quite useful, though, in
// high-throughput situations.
var eth layers.Ethernet
var dot1q layers.Dot1Q
var ip4 layers.IPv4
var ip6 layers.IPv6
var ip6extensions layers.IPv6ExtensionSkipper
var tcp layers.TCP
var payload gopacket.Payload
parser := gopacket.NewDecodingLayerParser(layers.LayerTypeEthernet,
ð, &dot1q, &ip4, &ip6, &ip6extensions, &tcp, &payload)
decoded := make([]gopacket.LayerType, 0, 4)
nextFlush := time.Now().Add(flushDuration / 2)
var byteCount int64
start := time.Now()
loop:
for ; *packetCount != 0; *packetCount-- {
// Check to see if we should flush the streams we have
// that haven't seen any new data in a while. Note we set a
// timeout on our PCAP handle, so this should happen even if we
// never see packet data.
if time.Now().After(nextFlush) {
stats, _ := handle.Stats()
log.Printf("flushing all streams that haven't seen packets in the last 2 minutes, pcap stats: %+v", stats)
assembler.FlushOlderThan(time.Now().Add(flushDuration))
nextFlush = time.Now().Add(flushDuration / 2)
}
// To speed things up, we're also using the ZeroCopy method for
// reading packet data. This method is faster than the normal
// ReadPacketData, but the returned bytes in 'data' are
// invalidated by any subsequent ZeroCopyReadPacketData call.
// Note that tcpassembly is entirely compatible with this packet
// reading method. This is another trade-off which might be
// appropriate for high-throughput sniffing: it avoids a packet
// copy, but its cost is much more careful handling of the
// resulting byte slice.
data, ci, err := handle.ZeroCopyReadPacketData()
if err != nil {
log.Printf("error getting packet: %v", err)
break loop // continue
}
err = parser.DecodeLayers(data, &decoded)
if err != nil {
log.Printf("error decoding packet: %v", err)
continue
}
if *logAllPackets {
log.Printf("decoded the following layers: %v", decoded)
}
byteCount += int64(len(data))
// Find either the IPv4 or IPv6 address to use as our network
// layer.
foundNetLayer := false
var netFlow gopacket.Flow
for _, typ := range decoded {
switch typ {
case layers.LayerTypeIPv4:
netFlow = ip4.NetworkFlow()
foundNetLayer = true
case layers.LayerTypeIPv6:
netFlow = ip6.NetworkFlow()
foundNetLayer = true
case layers.LayerTypeTCP:
if foundNetLayer {
assembler.AssembleWithTimestamp(netFlow, &tcp, ci.Timestamp)
} else {
log.Println("could not find IPv4 or IPv6 layer, inoring")
}
continue loop
}
}
log.Println("could not find TCP layer")
}
assembler.FlushAll()
log.Printf("processed %d bytes in %v", byteCount, time.Since(start))
}
