pylibpcap: python module for libpcap

#!/usr/bin/env python2
import pcap
import sys
import string
import time
import socket
import struct
protocols={socket.IPPROTO_TCP:'tcp',
           socket.IPPROTO_UDP:'udp',
           socket.IPPROTO_ICMP:'icmp'}
def decode_ip_packet(s):
  d={}
  d['version']=(ord(s[0]) & 0xf0) >> 4
  d['header_len']=ord(s[0]) & 0x0f
  d['tos']=ord(s[1])
  d['total_len']=socket.ntohs(struct.unpack('H',s[2:4])[0])
  d['id']=socket.ntohs(struct.unpack('H',s[4:6])[0])
  d['flags']=(ord(s[6]) & 0xe0) >> 5
  d['fragment_offset']=socket.ntohs(struct.unpack('H',s[6:8])[0] & 0x1f)
  d['ttl']=ord(s[8])
  d['protocol']=ord(s[9])
  d['checksum']=socket.ntohs(struct.unpack('H',s[10:12])[0])
  d['source_address']=pcap.ntoa(struct.unpack('i',s[12:16])[0])
  d['destination_address']=pcap.ntoa(struct.unpack('i',s[16:20])[0])
  if d['header_len']>5:
    d['options']=s[20:4*(d['header_len']-5)]
  else:
    d['options']=None
  d['data']=s[4*d['header_len']:]
  return d
def dumphex(s):
  bytes = map(lambda x: '%.2x' % x, map(ord, s))
  for i in xrange(0,len(bytes)/16):
    print '    %s' % string.join(bytes[i*16:(i+1)*16],' ')
  print '    %s' % string.join(bytes[(i+1)*16:],' ')
   
def print_packet(pktlen, data, timestamp):
  if not data:
    return
  if data[12:14]=='\x08\x00':
    decoded=decode_ip_packet(data[14:])
    print '\n%s.%f %s > %s' % (time.strftime('%H:%M',
                                    &nbs