decode_icmp

import socket
import sys
import os
import struct
from ctypes import *

# host to listen on
host = "192.168.43.162"

# our IP header
class IP(Structure):
    _fields_ = [
        ("ihl",    c_ubyte, 4),
        ("version", c_ubyte, 4),
        ("tos",  c_ubyte),
        ("len",c_ushort),
        ("id",  c_ushort),
        ("offset", c_ushort),
        ("ttl",c_ubyte),
        ("protocol_num",c_ubyte),
        ("sum",  c_ushort),
        ("src",  c_uint32),
        ("dst",  c_uint32)
    ]

    def __new__(self, socket_buffer=None):
        return self.from_buffer_copy(socket_buffer)
    def __init__(self, socket_buffer=None):
        # map protocol constants to their names
        self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}

        # human readable IP addresses
        self.src_address = socket.inet_ntoa(struct.pack("@I",self.src))
        self.dst_address = socket.inet_ntoa(struct.pack("@I",self.dst))

        # human readable protocol
        try:
            self.protocol = self.protocol_map[self.protocol_num]
        except:
            self.protocol = str(self.protocol_num)

class ICMP(Structure):
    _fields_ = [
        ("type", c_ubyte),
        ("code", c_ubyte),
        ("checksum", c_ushort),
        ("unused", c_ushort),
        ("next_hop_mtu", c_ushort)
    ]

    def __new__(self, socket_buffer):
        return self.from_buffer_copy(socket_buffer)
    def __init__(self, socket_buffer):
        pass

socket_protocol = socket.IPPROTO_ICMP
sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)
sniffer.bind((host, 0))
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

try:
    while True:
        # read in a packet
        raw_buffer = sniffer.recvfrom(65565)[0]

         # create an IP header from the first 20 bytes of the buffer
        ip_header = IP(raw_buffer[:20])

        header_length = ip_header.ihl * 4
        data = raw_buffer[header_length:]

        # print out the protocol that was detected and the hosts
        print(f"Protocol: {ip_header.protocol}, {ip_header.src_address} -> {ip_header.dst_address} ")

        # if it's ICMP, we want it
        if ip_header.protocol == "ICMP":
            # calculate where our ICMP packet starts
            offset = ip_header.ihl * 4
            #buf = raw_buffer[offset:offset + sizeof(ICMP)]
            buf = data[:sizeof(ICMP)]

            # create our ICMP structure
            icmp_header = ICMP(buf)

            print(f"ICMP -> Type:{icmp_header.type}, Code:{icmp_header.code}" )
            print()

# handle CTRL-C
except KeyboardInterrupt:
    sys.exit(1)