sniffer_ip_header_decode.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Tue Jun 23 10:43:01 2020

@author: edoardottt
"""

import socket

import os
import struct
from ctypes import *

# host to listen on 
host = "192.168.0.181"

# 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 adresses
        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)
            
# check the OS
if os.name == "nt":
    socket_protocol = socket.IPPROTO_IP
else:
    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)

if os.name == "nt":
    sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

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

# handle CTRL + C
except KeyboardInterrupt:
    
    # if we're using Windows, turn off promiscuous mode
    if os.name == "nt":
        sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)