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// @Title sysIcmp.go
// @Description Build an icmp packet with sys/unix
// @Author Sunny Tsai
// @Update 2023-09-27
package packet
import (
"log"
"net"
"golang.org/x/sys/unix"
)
// @title Icmp
// @description Build an icmp packet with sys/unix
// @auth Sunny Tsai Time(2023/09/27)
// @param targetIP string send to target ip address
// @return error error
func Icmp(targetIP string) error {
srcIP := "0.0.0.0"
// build socket
fd, err := unix.Socket(unix.AF_INET, unix.SOCK_RAW, unix.IPPROTO_ICMP)
if err != nil {
log.Fatal(err)
}
defer unix.Close(fd)
localAddr := &unix.SockaddrInet4{}
copy(localAddr.Addr[:], net.ParseIP(srcIP).To4())
err = unix.Bind(fd, localAddr)
if err != nil {
log.Fatal(err)
}
// set message
message := []byte("")
remoteAddr := &unix.SockaddrInet4{}
copy(remoteAddr.Addr[:], net.ParseIP(targetIP).To4())
sendIcmpTo(fd, message, remoteAddr)
return nil
}
// @title sendIcmpTo
// @description Send ICMP packet to target
// @auth Sunny Tsai Time(2023/09/27)
// @param fd int socket fd
// @param message []byte message
// @param remoteAddr *unix.SockaddrInet4 remote address
func sendIcmpTo(fd int, message []byte, remoteAddr *unix.SockaddrInet4) {
icmpPacket := append([]byte{8, 0, 0, 0, 0, 0, 0, 0}, message...) // ICMP类型8表示Echo Request
// 计算并设置校验和
checksum := calculateChecksum(icmpPacket)
icmpPacket[2] = byte(checksum >> 8)
icmpPacket[3] = byte(checksum)
_ = unix.Sendto(fd, icmpPacket, 0, remoteAddr)
}
// @title calculateChecksum
// @description Calculate the checksum for ICMP packet
// @auth Sunny Tsai Time(2023/09/27)
// @param data []byte ICMP packet data
// @return uint16 checksum value
func calculateChecksum(data []byte) uint16 {
sum := uint32(0)
// Sum all 16-bit words
for i := 0; i < len(data)-1; i += 2 {
sum += uint32(data[i+1])<<8 + uint32(data[i])
}
// Add carry if any
if len(data)%2 != 0 {
sum += uint32(data[len(data)-1]) << 8
}
// Fold sum to 16 bits
for (sum >> 16) > 0 {
sum = (sum & 0xFFFF) + (sum >> 16)
}
// Take one's complement
checksum := ^uint16(sum)
return checksum
}
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