sniffer_ip_header_decode.py

# -*- coding: utf-8 -*-

import socket

import os
import struct
from ctypes import *

# ip addres of listened host
host = '192.168.91.134'

# ip header
class IP(Structure):
    _fields_ = [
        ("ihl",        c_uint8, 4),
        ("version",    c_uint8, 4),
        ("tos",        c_uint8),
        ("len",        c_uint16),
        ("id",         c_uint16),
        ("offset",     c_uint16),
        ("ttl",        c_uint8),
        ("protocol_num", c_uint8),
        ("sum",        c_uint16),
        ("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):
        
        # mapping protocol constant value to name
        self.protocol_map = {1:"ICMP", 6:"TCP", 17:"UDP"}
        
        # transfer to readable ip address
        self.src_address = socket.inet_ntoa(struct.pack("<L", self.src))
        self.dst_address = socket.inet_ntoa(struct.pack("<L", self.dst))
        
        # transfer to readable protocol name
        try:
            self.protocol = self.protocol_map[self.protocol_num]
        except:
            self.protocol = str(self.protocol_num)
            
# handle like last example
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))
# setting to add ip address of listened host
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 packets
        raw_buffer = sniffer.recvfrom(65565)[0]
        
        # create ip structure from first 20 bytes of buffer
        ip_header = IP(raw_buffer[0:20])
        
        # print detected host and protocol
        print "Protocol: %s %s -> %s" % (ip_header.protocol, ip_header.src_address, ip_header.dst_address)
        
# handle Ctrl-C
except KeyboardInterrupt:
    
    # disable promisecasmode if windows
    if os.name == "nt":
        sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)