This example expands on the print_packets example. It checks for ICMP packets and displays the ICMP contents.
Code Excerpt
# 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_addr(eth.src), mac_addr(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))
Example Output
Timestamp: 2013-05-30 22:45:17.283187 Ethernet Frame: 60:33:4b:13:c5:58 02:1a:11:f0:c8:3b 2048 IP: 192.168.43.9 -> 8.8.8.8 (len=84 ttl=64 DF=0 MF=0 offset=0) ICMP: type:8 code:0 checksum:48051 data: Echo(id=55099, data='Q\xa7\xd6}\x00\x04Q\xe4\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./01234567') Timestamp: 2013-05-30 22:45:17.775391 Ethernet Frame: 02:1a:11:f0:c8:3b 60:33:4b:13:c5:58 2048 IP: 8.8.8.8 -> 192.168.43.9 (len=84 ttl=40 DF=0 MF=0 offset=0) ICMP: type:0 code:0 checksum:50099 data: Echo(id=55099, data='Q\xa7\xd6}\x00\x04Q\xe4\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./01234567') ...
Set full code at: https://github.com/kbandla/dpkt/blob/master/examples/print_icmp.py