| #!/usr/bin/env python |
| """ |
| This example expands on the print_packets example. It checks for ICMP packets and displays the ICMP contents. |
| """ |
| import dpkt |
| import datetime |
| from dpkt.utils import mac_to_str, inet_to_str |
| |
| |
| def print_icmp(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: |
| |
| # Unpack the Ethernet frame (mac src/dst, ethertype) |
| eth = dpkt.ethernet.Ethernet(buf) |
| |
| # 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 grab the data within the Ethernet frame (the IP packet) |
| ip = eth.data |
| |
| # Now check if this is an ICMP packet |
| if isinstance(ip.data, dpkt.icmp.ICMP): |
| icmp = ip.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('Timestamp: ', str(datetime.datetime.utcfromtimestamp(timestamp))) |
| print('Ethernet Frame: ', mac_to_str(eth.src), mac_to_str(eth.dst), eth.type) |
| print('IP: %s -> %s (len=%d ttl=%d DF=%d MF=%d offset=%d)' % |
| (inet_to_str(ip.src), inet_to_str(ip.dst), ip.len, ip.ttl, |
| do_not_fragment, more_fragments, fragment_offset)) |
| print('ICMP: type:%d code:%d checksum:%d data: %s\n' % |
| (icmp.type, icmp.code, icmp.sum, repr(icmp.data))) |
| |
| |
| def test(): |
| """Open up a test pcap file and print out the packets""" |
| with open('data/dns_icmp.pcap', 'rb') as f: |
| pcap = dpkt.pcap.Reader(f) |
| print_icmp(pcap) |
| |
| |
| if __name__ == '__main__': |
| test() |