print_packets.py

import dpkt
from dpkt.compat import compat_ord
import socket




def mac_addr(address):
    """Convert a MAC address to a readable/printable string
       Args:
           address (str): a MAC address in hex form (e.g. '\x01\x02\x03\x04\x05\x06')
       Returns:
           str: Printable/readable MAC address
    """
    return ':'.join('%02x' % compat_ord(b) for b in address)


def inet_to_str(inet):
    """Convert inet object to a string
        Args:
            inet (inet struct): inet network address
        Returns:
            str: Printable/readable IP address
    """
    # First try ipv4 and then ipv6
    try:
        return socket.inet_ntop(socket.AF_INET, inet)
    except ValueError:
        return socket.inet_ntop(socket.AF_INET6, inet)

def print_packets(pcap):
    """Print out information about each packet in a pcap
       Args:
           pcap: dpkt pcap reader object (dpkt.pcap.Reader)
    """
    # For each packet in the pcap process the contents
    for timestamp, buf in pcap:

        # Print out the timestamp in UTC
        print('Timestamp: ', str(datetime.datetime.utcfromtimestamp(timestamp)))

        # Unpack the Ethernet frame (mac src/dst, ethertype)
        eth = dpkt.ethernet.Ethernet(buf)
        print('Ethernet Frame: ', mac_addr(eth.src), mac_addr(eth.dst), eth.type)

        # Make sure the Ethernet data contains an IP packet
        if not isinstance(eth.data, dpkt.ip.IP):
            print('Non IP Packet type not supported %s\n' % eth.data.__class__.__name__)
            continue

        # Now unpack the data within the Ethernet frame (the IP packet)
        # Pulling out src, dst, length, fragment info, TTL, and Protocol
        ip = eth.data

        # Pull out fragment information (flags and offset all packed into off field, so use bitmasks)
        do_not_fragment = bool(ip.off & dpkt.ip.IP_DF)
        more_fragments = bool(ip.off & dpkt.ip.IP_MF)
        fragment_offset = ip.off & dpkt.ip.IP_OFFMASK

        # Print out the info
        print('IP: %s -> %s   (len=%d ttl=%d DF=%d MF=%d offset=%d)\n' % \
              (inet_to_str(ip.src), inet_to_str(ip.dst), ip.len, ip.ttl, do_not_fragment, more_fragments, fragment_offset))


def test():
    """Open up a test pcap file and print out the packets"""
    with open('data/http.pcap', 'rb') as f:
        pcap = dpkt.pcap.Reader(f)
        print_packets(pcap)