gopacket 是golang语言使用的网络数据抓取和分析的工具包。
本文简单介绍如何使用gopacket进行网络抓包。
下载gopacket
# go get git@github.com:google/gopacket.git
Demo
代码中，抓取与端口3306相关的数据，也就是mysql通信数据。
package main
import(
"fmt"
"net"
"strings"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/google/gopacket/pcap"
)
func main() {
fmt.Println("packet start...")
deviceName := "eth0"
snapLen := int32(65535)
port := uint16(3306)
filter := getFilter(port)
fmt.Printf("device:%v, snapLen:%v, port:%v\n", deviceName, snapLen, port)
fmt.Println("filter:", filter)
//打开网络接口，抓取在线数据
handle, err := pcap.OpenLive(deviceName, snapLen, true, pcap.BlockForever)
if err != nil {
fmt.Printf("pcap open live failed: %v", err)
return
}
// 设置过滤器
if err := handle.SetBPFFilter(filter); err != nil {
fmt.Printf("set bpf filter failed: %v", err)
return
}
defer handle.Close()
// 抓包
packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
packetSource.NoCopy = true
for packet := range packetSource.Packets() {
if packet.NetworkLayer() == nil || packet.TransportLayer() == nil || packet.TransportLayer().LayerType() != layers.LayerTypeTCP {
fmt.Println("unexpected packet")
continue
}
fmt.Printf("packet:%v\n",packet)
// tcp 层
tcp := packet.TransportLayer().(*layers.TCP)
fmt.Printf("tcp:%v\n", tcp)
// tcp payload，也即是tcp传输的数据
fmt.Printf("tcp payload:%v\n", tcp.Payload)
}
}
//定义过滤器
func getFilter(port uint16) string {
filter := fmt.Sprintf("tcp and ((src port %v) or (dst port %v))", port, port)
return filter
}
抓取到的数据包
packet start...
device:lo0, snapLen:65535, port:3306
filter: tcp and ((src port 3306) or (dst port 3306))
packet:PACKET: 75 bytes, wire length 75 cap length 75 @ 2018-10-20 11:13:00.106452 +0800 CST
- Layer 1 (04 bytes) = Loopback {Contents=[2, 0, 0, 0] Payload=[..71..] Family=IPv4}
- Layer 2 (20 bytes) = IPv4 {Contents=[..20..] Payload=[..51..] Version=4 IHL=5 TOS=0 Length=71 Id=0 Flags=DF FragOffset=0 TTL=64 Protocol=TCP Checksum=0 SrcIP=172.16.1.103 DstIP=172.16.1.103 Options=[] Padding=[]}
- Layer 3 (32 bytes) = TCP {Contents=[..32..] Payload=[..19..] SrcPort=50351 DstPort=3306(mysql) Seq=110592366 Ack=3116315438 DataOffset=8 FIN=false SYN=false RST=false PSH=true ACK=true URG=false ECE=false CWR=false NS=false Window=12753 Checksum=23336 Urgent=0 Options=[TCPOption(NOP:), TCPOption(NOP:), TCPOption(Timestamps:1064185591/1064170040 0x3f6e2ef73f6df238)] Padding=[]}
- Layer 4 (19 bytes) = Payload 19 byte(s)
tcp:&{{[196 175 12 234 6 151 129 110 185 191 51 46 128 24 49 209 91 40 0 0 1 1 8 10 63 110 46 247 63 109 242 56] [15 0 0 0 3 115 104 111 119 32 100 97 116 97 98 97 115 101 115]} 50351 3306(mysql) 110592366 3116315438 8 false false false true true false false false false 12753 23336 0 [196 175] [12 234] [TCPOption(NOP:) TCPOption(NOP:) TCPOption(Timestamps:1064185591/1064170040 0x3f6e2ef73f6df238)] [] [{1 1 []} {1 1 []} {8 10 [63 110 46 247 63 109 242 56]} {0 0 []}] {<nil>}}
tcp payload:[15 0 0 0 3 115 104 111 119 32 100 97 116 97 98 97 115 101 115]
。。。
对抓取到的mysql数据感兴趣的同学，可以参考Mysql 通信协议抓包分析
参考
github
https://github.com/google/gopacket
文档godoc
https://godoc.org/github.com/google/gopacket
go抓包分析demo
https://blog.lab99.org/post/golang-2017-09-23-video-packet-capture-analysis-with-go.html
Just try, don't shy.
