IPv4 ICMP

Simple ICMP (Ping) with Golang

2 min readJan 21, 2024

Tujuan: nge-ping 100 ribu IP aktif.

Get Umar Rudi’s stories in your inbox

Join Medium for free to get updates from this writer.

Remember me for faster sign in

Strategi: respon server tidak perlu dibaca dari layer aplikasi. Cukup dari layer network. (Pakai sudo ngrep “” “icmp” di terminal lain). Supaya kode aplikasinya bisa pendek. Ketika pendek, untuk scaling ke 100k jadi mudah.

package main

import (
 "fmt"
 "net"
 "os"
)

func main() {

 destAddr, _ := net.ResolveIPAddr("ip", os.Args[1])

 conn, _ := net.DialIP("ip4:icmp", nil, destAddr)
 defer conn.Close()

 message := "Hello" 
 data := []byte(message)

 icmpPacket := make([]byte, 8+len(data)) // icmpPacket langsung diisi nol (byte) semua sepanjang 8 
 icmpPacket[0] = byte(8)

 copy(icmpPacket[8:], data)

 // checksum := calculateChecksum(icmpPacket)
 icmpPacket[2] = 212 // byte(checksum >> 8)
 icmpPacket[3] = 45  // byte(checksum & 0xff)

 conn.Write(icmpPacket)

}

Angka 212 dan 45 didapat dari fungsi calculateChecksum. Sesuai panjang message.

Impelementasi fungsi calculateChecksum

func calculateChecksum(data []byte) uint16 {
 sum := 0
 for i := 0; i < len(data)-1; i += 2 {
  sum += int(data[i])<<8 | int(data[i+1])
 }
 if len(data)%2 != 0 {
  sum += int(data[len(data)-1]) << 8
 }
 sum = (sum >> 16) + (sum & 0xffff)
 sum += sum >> 16
 return uint16(^sum)
}

Output:

➜  dev sudo ngrep "" "icmp"
interface: wlp3s0 (192.168.177.0/255.255.255.0)
filter: ( icmp ) and ((ip || ip6) || (vlan && (ip || ip6)))

#
I 192.168.177.38 -> 142.251.12.102 8:0 #37
  ....Hello                                                                                                                                                                                  
#
I 142.251.12.102 -> 192.168.177.38 0:0 #38
  ....Hello