Demo1（Find devices）：
package main
import (
"fmt"
"log"
"github.com/google/gopacket/pcap"
)
func main() {
// Find all devices
devices, err := pcap.FindAllDevs()
if err != nil {
log.Fatal(err)
}
// Print device information
fmt.Println("Devices found:")
for _, device := range devices {
fmt.Println("\nName: ", device.Name)
fmt.Println("Description: ", device.Description)
fmt.Println("Devices addresses: ", device.Description)
for _, address := range device.Addresses {
fmt.Println("- IP address: ", address.IP)
fmt.Println("- Subnet mask: ", address.Netmask)
}
}
}
测试结果：
[root@wangjq device]# go run main.go
Devices found:
Name: br0
Description:
Devices addresses:
- IP address: 10.95.149.186
- Subnet mask: ffffffc0
- IP address: fe80:::61ff:fe04:81d3
- Subnet mask: ffffffffffffffff0000000000000000
Name: virbr0
Description:
Devices addresses:
- IP address: 192.168.122.1
- Subnet mask: ffffff00
Name: docker0
Description:
Devices addresses:
- IP address: 172.17.0.1
- Subnet mask: ffff0000
Name: nflog
Description: Linux netfilter log (NFLOG) interface
Devices addresses: Linux netfilter log (NFLOG) interface
Name: nfqueue
Description: Linux netfilter queue (NFQUEUE) interface
Devices addresses: Linux netfilter queue (NFQUEUE) interface
Name: usbmon1
Description: USB bus number
Devices addresses: USB bus number
Name: usbmon2
Description: USB bus number
Devices addresses: USB bus number
Name: ens3
Description:
Devices addresses:
Name: usbmon3
Description: USB bus number
Devices addresses: USB bus number
Name: ens4
Description:
Devices addresses:
- IP address: fe80::7f29:1f32:6a3:2a59
- Subnet mask: ffffffffffffffff0000000000000000
Name: usbmon4
Description: USB bus number
Devices addresses: USB bus number
Name: any
Description: Pseudo-device that captures on all interfaces
Devices addresses: Pseudo-device that captures on all interfaces
Name: lo
Description:
Devices addresses:
- IP address: 127.0.0.1
- Subnet mask: ff000000
- IP address: ::
- Subnet mask: ffffffffffffffffffffffffffffffff
Demo2（Open Device for Live Capture）：
package main
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
"time"
)
var (
device string = "eth0"
snapshot_len int32 =
promiscuous bool = false
err error
timeout time.Duration = * time.Second
handle *pcap.Handle
)
func main() {
// Open device
handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {log.Fatal(err) }
defer handle.Close()
// Use the handle as a packet source to process all packets
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
// Process packet here
fmt.Println(packet)
}
}
测试结果：
PACKET: bytes, truncated, wire length cap length @ -- ::00.069751 + HKT
- Layer ( bytes) = Ethernet {Contents=[....] Payload=[....] SrcMAC=:::3d::f1 DstMAC=:ea:cb:5d:e4:f7 EthernetType=IPv4 Length=}
- Layer ( bytes) = IPv4 {Contents=[....] Payload=[....] Version= IHL= TOS= Length= Id= Flags=DF FragOffset= TTL= Protocol=TCP Checksum= SrcIP=10.95.149.186 DstIP=172.24.46.56 Options=[] Padding=[]}
- Layer ( bytes) = TCP {Contents=[....] Payload=[....] SrcPort=(ssh) DstPort= Seq= Ack= DataOffset= FIN=false SYN=false RST=false PSH=false ACK=true URG=false ECE=false CWR=false NS=false Window= Checksum= Urgent= Options=[] Padding=[]}
- Layer ( bytes) = Payload byte(s)
PACKET: bytes, wire length cap length @ -- ::00.069956 + HKT
- Layer ( bytes) = Ethernet {Contents=[....] Payload=[....] SrcMAC=:ea:cb:5d:e4:f7 DstMAC=:::3d::f1 EthernetType=IPv4 Length=}
- Layer ( bytes) = IPv4 {Contents=[....] Payload=[....] Version= IHL= TOS= Length= Id= Flags=DF FragOffset= TTL= Protocol=TCP Checksum= SrcIP=172.24.46.56 DstIP=10.95.149.186 Options=[] Padding=[]}
- Layer ( bytes) = TCP {Contents=[....] Payload=[] SrcPort= DstPort=(ssh) Seq= Ack= DataOffset= FIN=false SYN=false RST=false PSH=false ACK=true URG=false ECE=false CWR=false NS=false Window= Checksum= Urgent= Options=[] Padding=[]}
Demo3（Write Pcap File）：
package main
import (
"fmt"
"os"
"time"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"github.com/google/gopacket/pcapgo"
)
var (
deviceName string = "eth0"
snapshotLen int32 =
promiscuous bool = false
err error
timeout time.Duration = - * time.Second
handle *pcap.Handle
packetCount int =
)
func main() {
// Open output pcap file and write header
f, _ := os.Create("test.pcap")
w := pcapgo.NewWriter(f)
w.WriteFileHeader(snapshotLen, layers.LinkTypeEthernet)
defer f.Close()
// Open the device for capturing
handle, err = pcap.OpenLive(deviceName, snapshotLen, promiscuous, timeout)
if err != nil {
fmt.Printf("Error opening device %s: %v", deviceName, err)
os.Exit()
}
defer handle.Close()
// Start processing packets
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
// Process packet here
fmt.Println(packet)
w.WritePacket(packet.Metadata().CaptureInfo, packet.Data())
packetCount++
// Only capture 100 and then stop
if packetCount > {
break
}
}
}
Demo4（Open Pcap File）：
package main
// Use tcpdump to create a test file
// tcpdump -w test.pcap
// or use the example above for writing pcap files
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
)
var (
pcapFile string = "test.pcap"
handle *pcap.Handle
err error
)
func main() {
// Open file instead of device
handle, err = pcap.OpenOffline(pcapFile)
if err != nil { log.Fatal(err) }
defer handle.Close()
// Loop through packets in file
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
fmt.Println(packet)
}
}
Demo5（Setting Filters）：
package main
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/pcap"
"log"
"time"
)
var (
device string = "eth0"
snapshot_len int32 =
promiscuous bool = false
err error
timeout time.Duration = * time.Second
handle *pcap.Handle
)
func main() {
// Open device
handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()
// Set filter
var filter string = "tcp and port 80"
err = handle.SetBPFFilter(filter)
if err != nil {
log.Fatal(err)
}
fmt.Println("Only capturing TCP port 80 packets.")
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
// Do something with a packet here.
fmt.Println(packet)
}
}
Demo6（Decoding Packet Layers）：
package main
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"log"
"strings"
"time"
)
var (
device string = "eth0"
snapshotLen int32 =
promiscuous bool = false
err error
timeout time.Duration = * time.Second
handle *pcap.Handle
)
func main() {
// Open device
handle, err = pcap.OpenLive(device, snapshotLen, promiscuous, timeout)
if err != nil {log.Fatal(err) }
defer handle.Close()
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
printPacketInfo(packet)
}
}
func printPacketInfo(packet gopacket.Packet) {
// Let's see if the packet is an ethernet packet
ethernetLayer := packet.Layer(layers.LayerTypeEthernet)
if ethernetLayer != nil {
fmt.Println("Ethernet layer detected.")
ethernetPacket, _ := ethernetLayer.(*layers.Ethernet)
fmt.Println("Source MAC: ", ethernetPacket.SrcMAC)
fmt.Println("Destination MAC: ", ethernetPacket.DstMAC)
// Ethernet type is typically IPv4 but could be ARP or other
fmt.Println("Ethernet type: ", ethernetPacket.EthernetType)
fmt.Println()
}
// Let's see if the packet is IP (even though the ether type told us)
ipLayer := packet.Layer(layers.LayerTypeIPv4)
if ipLayer != nil {
fmt.Println("IPv4 layer detected.")
ip, _ := ipLayer.(*layers.IPv4)
// IP layer variables:
// Version (Either 4 or 6)
// IHL (IP Header Length in 32-bit words)
// TOS, Length, Id, Flags, FragOffset, TTL, Protocol (TCP?),
// Checksum, SrcIP, DstIP
fmt.Printf("From %s to %s\n", ip.SrcIP, ip.DstIP)
fmt.Println("Protocol: ", ip.Protocol)
fmt.Println()
}
// Let's see if the packet is TCP
tcpLayer := packet.Layer(layers.LayerTypeTCP)
if tcpLayer != nil {
fmt.Println("TCP layer detected.")
tcp, _ := tcpLayer.(*layers.TCP)
// TCP layer variables:
// SrcPort, DstPort, Seq, Ack, DataOffset, Window, Checksum, Urgent
// Bool flags: FIN, SYN, RST, PSH, ACK, URG, ECE, CWR, NS
fmt.Printf("From port %d to %d\n", tcp.SrcPort, tcp.DstPort)
fmt.Println("Sequence number: ", tcp.Seq)
fmt.Println()
}
// Iterate over all layers, printing out each layer type
fmt.Println("All packet layers:")
for _, layer := range packet.Layers() {
fmt.Println("- ", layer.LayerType())
}
// When iterating through packet.Layers() above,
// if it lists Payload layer then that is the same as
// this applicationLayer. applicationLayer contains the payload
applicationLayer := packet.ApplicationLayer()
if applicationLayer != nil {
fmt.Println("Application layer/Payload found.")
fmt.Printf("%s\n", applicationLayer.Payload())
// Search for a string inside the payload
if strings.Contains(string(applicationLayer.Payload()), "HTTP") {
fmt.Println("HTTP found!")
}
}
// Check for errors
if err := packet.ErrorLayer(); err != nil {
fmt.Println("Error decoding some part of the packet:", err)
}
}
Demo7（Creating and Sending Packets）：
package main
import (
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"log"
"net"
"time"
)
var (
device string = "eth0"
snapshot_len int32 =
promiscuous bool = false
err error
timeout time.Duration = * time.Second
handle *pcap.Handle
buffer gopacket.SerializeBuffer
options gopacket.SerializeOptions
)
func main() {
// Open device
handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {log.Fatal(err) }
defer handle.Close()
// Send raw bytes over wire
rawBytes := []byte{, , }
err = handle.WritePacketData(rawBytes)
if err != nil {
log.Fatal(err)
}
// Create a properly formed packet, just with
// empty details. Should fill out MAC addresses,
// IP addresses, etc.
buffer = gopacket.NewSerializeBuffer()
gopacket.SerializeLayers(buffer, options,
&layers.Ethernet{},
&layers.IPv4{},
&layers.TCP{},
gopacket.Payload(rawBytes),
)
outgoingPacket := buffer.Bytes()
// Send our packet
err = handle.WritePacketData(outgoingPacket)
if err != nil {
log.Fatal(err)
}
// This time lets fill out some information
ipLayer := &layers.IPv4{
SrcIP: net.IP{, , , },
DstIP: net.IP{, , , },
}
ethernetLayer := &layers.Ethernet{
SrcMAC: net.HardwareAddr{0xFF, 0xAA, 0xFA, 0xAA, 0xFF, 0xAA},
DstMAC: net.HardwareAddr{0xBD, 0xBD, 0xBD, 0xBD, 0xBD, 0xBD},
}
tcpLayer := &layers.TCP{
SrcPort: layers.TCPPort(),
DstPort: layers.TCPPort(),
}
// And create the packet with the layers
buffer = gopacket.NewSerializeBuffer()
gopacket.SerializeLayers(buffer, options,
ethernetLayer,
ipLayer,
tcpLayer,
gopacket.Payload(rawBytes),
)
outgoingPacket = buffer.Bytes()
}
Demo8（More on Creating/Decoding Packets）：
package main
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
)
func main() {
// If we don't have a handle to a device or a file, but we have a bunch
// of raw bytes, we can try to decode them in to packet information
// NewPacket() takes the raw bytes that make up the packet as the first parameter
// The second parameter is the lowest level layer you want to decode. It will
// decode that layer and all layers on top of it. The third layer
// is the type of decoding: default(all at once), lazy(on demand), and NoCopy
// which will not create a copy of the buffer
// Create an packet with ethernet, IP, TCP, and payload layers
// We are creating one we know will be decoded properly but
// your byte source could be anything. If any of the packets
// come back as nil, that means it could not decode it in to
// the proper layer (malformed or incorrect packet type)
payload := []byte{, , }
options := gopacket.SerializeOptions{}
buffer := gopacket.NewSerializeBuffer()
gopacket.SerializeLayers(buffer, options,
&layers.Ethernet{},
&layers.IPv4{},
&layers.TCP{},
gopacket.Payload(payload),
)
rawBytes := buffer.Bytes()
// Decode an ethernet packet
ethPacket :=
gopacket.NewPacket(
rawBytes,
layers.LayerTypeEthernet,
gopacket.Default,
)
// with Lazy decoding it will only decode what it needs when it needs it
// This is not concurrency safe. If using concurrency, use default
ipPacket :=
gopacket.NewPacket(
rawBytes,
layers.LayerTypeIPv4,
gopacket.Lazy,
)
// With the NoCopy option, the underlying slices are referenced
// directly and not copied. If the underlying bytes change so will
// the packet
tcpPacket :=
gopacket.NewPacket(
rawBytes,
layers.LayerTypeTCP,
gopacket.NoCopy,
)
fmt.Println(ethPacket)
fmt.Println(ipPacket)
fmt.Println(tcpPacket)
}
Demo9（Custom Layers）：
package main
import (
"fmt"
"github.com/google/gopacket"
)
// Create custom layer structure
type CustomLayer struct {
// This layer just has two bytes at the front
SomeByte byte
AnotherByte byte
restOfData []byte
}
// Register the layer type so we can use it
// The first argument is an ID. Use negative
// or 2000+ for custom layers. It must be unique
var CustomLayerType = gopacket.RegisterLayerType(
,
gopacket.LayerTypeMetadata{
"CustomLayerType",
gopacket.DecodeFunc(decodeCustomLayer),
},
)
// When we inquire about the type, what type of layer should
// we say it is? We want it to return our custom layer type
func (l CustomLayer) LayerType() gopacket.LayerType {
return CustomLayerType
}
// LayerContents returns the information that our layer
// provides. In this case it is a header layer so
// we return the header information
func (l CustomLayer) LayerContents() []byte {
return []byte{l.SomeByte, l.AnotherByte}
}
// LayerPayload returns the subsequent layer built
// on top of our layer or raw payload
func (l CustomLayer) LayerPayload() []byte {
return l.restOfData
}
// Custom decode function. We can name it whatever we want
// but it should have the same arguments and return value
// When the layer is registered we tell it to use this decode function
func decodeCustomLayer(data []byte, p gopacket.PacketBuilder) error {
// AddLayer appends to the list of layers that the packet has
p.AddLayer(&CustomLayer{data[], data[], data[:]})
// The return value tells the packet what layer to expect
// with the rest of the data. It could be another header layer,
// nothing, or a payload layer.
// nil means this is the last layer. No more decoding
// return nil
// Returning another layer type tells it to decode
// the next layer with that layer's decoder function
// return p.NextDecoder(layers.LayerTypeEthernet)
// Returning payload type means the rest of the data
// is raw payload. It will set the application layer
// contents with the payload
return p.NextDecoder(gopacket.LayerTypePayload)
}
func main() {
// If you create your own encoding and decoding you can essentially
// create your own protocol or implement a protocol that is not
// already defined in the layers package. In our example we are just
// wrapping a normal ethernet packet with our own layer.
// Creating your own protocol is good if you want to create
// some obfuscated binary data type that was difficult for others
// to decode
// Finally, decode your packets:
rawBytes := []byte{0xF0, 0x0F, , , , , }
packet := gopacket.NewPacket(
rawBytes,
CustomLayerType,
gopacket.Default,
)
fmt.Println("Created packet out of raw bytes.")
fmt.Println(packet)
// Decode the packet as our custom layer
customLayer := packet.Layer(CustomLayerType)
if customLayer != nil {
fmt.Println("Packet was successfully decoded with custom layer decoder.")
customLayerContent, _ := customLayer.(*CustomLayer)
// Now we can access the elements of the custom struct
fmt.Println("Payload: ", customLayerContent.LayerPayload())
fmt.Println("SomeByte element:", customLayerContent.SomeByte)
fmt.Println("AnotherByte element:", customLayerContent.AnotherByte)
}
}
Demo10（Decoding Packets Faster）：
package main
import (
"fmt"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
"log"
"time"
)
var (
device string = "eth0"
snapshot_len int32 =
promiscuous bool = false
err error
timeout time.Duration = * time.Second
handle *pcap.Handle
// Will reuse these for each packet
ethLayer layers.Ethernet
ipLayer layers.IPv4
tcpLayer layers.TCP
)
func main() {
// Open device
handle, err = pcap.OpenLive(device, snapshot_len, promiscuous, timeout)
if err != nil {
log.Fatal(err)
}
defer handle.Close()
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
for packet := range packetSource.Packets() {
parser := gopacket.NewDecodingLayerParser(
layers.LayerTypeEthernet,
ðLayer,
&ipLayer,
&tcpLayer,
)
foundLayerTypes := []gopacket.LayerType{}
err := parser.DecodeLayers(packet.Data(), &foundLayerTypes)
if err != nil {
fmt.Println("Trouble decoding layers: ", err)
}
for _, layerType := range foundLayerTypes {
if layerType == layers.LayerTypeIPv4 {
fmt.Println("IPv4: ", ipLayer.SrcIP, "->", ipLayer.DstIP)
}
if layerType == layers.LayerTypeTCP {
fmt.Println("TCP Port: ", tcpLayer.SrcPort, "->", tcpLayer.DstPort)
fmt.Println("TCP SYN:", tcpLayer.SYN, " | ACK:", tcpLayer.ACK)
}
}
}
}