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main.go
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main.go
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// Package main is the example of gopacket.Packet
package main
import (
"fmt"
"log"
"os"
"os/signal"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
)
var (
appLog = log.New(os.Stderr, "", 0)
)
func main() {
if err := run(); err != nil {
appLog.Panic(err)
}
}
func run() error {
const (
device = "lo"
filter = "tcp port 22222"
snapshotLen = int32(128)
promiscuous = false
)
// --------------------------------------
// Open capture handle
// --------------------------------------
var (
handle *pcap.Handle
err error
)
handle, err = pcap.OpenLive(device, snapshotLen, promiscuous, pcap.BlockForever)
if err != nil {
return fmt.Errorf("error open handle: %w", err)
}
defer handle.Close()
// --------------------------------------
// Apply capture filter (optional)
// --------------------------------------
if filter != "" {
err = handle.SetBPFFilter(filter)
if err != nil {
return fmt.Errorf("error apply filter: %w", err)
}
}
// --------------------------------------
// Set signal handler
// --------------------------------------
var (
sigCh = make(chan os.Signal, 1)
)
signal.Notify(sigCh, os.Interrupt)
// --------------------------------------
// Make packet source and display.
// --------------------------------------
var (
dataSource gopacket.PacketDataSource = handle
decoder gopacket.Decoder = handle.LinkType()
packetSource *gopacket.PacketSource = gopacket.NewPacketSource(dataSource, decoder)
packetCh <-chan gopacket.Packet = packetSource.Packets()
)
LOOP:
for {
select {
case <-sigCh:
break LOOP
case p, ok := <-packetCh:
if !ok {
break LOOP
}
see(p)
}
}
return nil
}
func see(p gopacket.Packet) {
// ダンプ出力(各レイヤー毎の詳細も見れる)
//appLog.Printf("[Dump] %v", p.Dump())
// データ (各レイヤー毎のフルパケットデータが見れる)
//appLog.Printf("[Data] %v", p.Data())
appLog.Println("------------------------------")
{
appLog.Printf("[Capture Length] %v", p.Metadata().CaptureLength)
ipLayer := p.Layer(layers.LayerTypeIPv4)
if ipLayer != nil {
ipv4, ok := ipLayer.(*layers.IPv4)
if ok {
appLog.Printf("[Src ] %v", ipv4.SrcIP)
appLog.Printf("[Dst ] %v", ipv4.DstIP)
appLog.Printf("[Protocol ] %v", ipv4.Protocol)
}
}
tcpLayer := p.Layer(layers.LayerTypeTCP)
if tcpLayer != nil {
tcp, ok := tcpLayer.(*layers.TCP)
if ok {
appLog.Printf("[SRC PORT ] %v", tcp.SrcPort)
appLog.Printf("[DST PORT ] %v", tcp.DstPort)
appLog.Println("[TCP FLAGS ]")
appLog.Printf(">>> SYN=%v", tcp.SYN)
appLog.Printf(">>> ACK=%v", tcp.ACK)
appLog.Printf(">>> PSH=%v", tcp.PSH)
appLog.Printf(">>> RST=%v", tcp.RST)
appLog.Printf(">>> FIN=%v", tcp.FIN)
}
}
appLayer := p.ApplicationLayer()
if appLayer != nil {
payload := appLayer.Payload()
if payload != nil {
appLog.Printf("[Payload ] %v", payload)
}
}
}
appLog.Println("------------------------------")
}