func benchmarkLayerDecode(source *BufferPacketSource, assemble bool) {
var tcp layers.TCP
var ip layers.IPv4
var eth layers.Ethernet
var udp layers.UDP
var icmp layers.ICMPv4
var payload gopacket.Payload
parser := gopacket.NewDecodingLayerParser(
layers.LayerTypeEthernet,
ð, &ip, &icmp, &tcp, &udp, &payload)
pool := tcpassembly.NewStreamPool(&streamFactory{})
assembler := tcpassembly.NewAssembler(pool)
var decoded []gopacket.LayerType
start := time.Now()
packets, decodedlayers, assembled := 0, 0, 0
for {
packets++
data, ci, err := source.ReadPacketData()
if err == io.EOF {
break
} else if err != nil {
fmt.Println("Error reading packet: ", err)
continue
}
err = parser.DecodeLayers(data, &decoded)
for _, typ := range decoded {
decodedlayers++
if typ == layers.LayerTypeTCP && assemble {
assembled++
assembler.AssembleWithTimestamp(ip.NetworkFlow(), &tcp, ci.Timestamp)
}
}
}
if assemble {
assembler.FlushAll()
}
duration := time.Since(start)
fmt.Printf("\tRead in %d packets in %v, decoded %v layers, assembled %v packets: %v per packet\n", packets, duration, decodedlayers, assembled, duration/time.Duration(packets))
}
func main() {
flag.Parse()
log.Printf("starting capture on interface %q", *iface)
// Set up pcap packet capture
handle, err := pcap.OpenLive(*iface, int32(*snaplen), true, time.Minute)
if err != nil {
log.Fatal("error opening pcap handle: ", 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)
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(time.Minute)
loop:
for {
// 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(-time.Minute * 2))
nextFlush = time.Now().Add(time.Minute)
}
// 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, _, err := handle.ZeroCopyReadPacketData()
if err != nil {
log.Printf("error getting packet: %v", err)
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)
}
// 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.Assemble(netFlow, &tcp)
} else {
log.Println("could not find IPv4 or IPv6 layer, inoring")
}
continue loop
}
}
log.Println("could not find TCP layer")
}
}