import struct
import socket
class Packet(object):
"""Creates ICMPv4 and v6 packets.
header
two-item sequence containing the type and code of the packet,
respectively.
version
Automatically set to version of protocol being used or None if ambiguous.
data
Contains data of the packet. Can only assign a subclass of basestring
or None.
packet
binary representation of packet.
"""
header_table = {
0 : (0, 4),
#3 : (15, 4), Overlap with ICMPv6
3 : (15, None),
#4 : (0, 4), Deprecated by RFC 1812
5 : (3, 4),
8 : (0, 4),
9 : (0, 4),
10: (0, 4),
11: (1, 4),
12: (1, 4),
13: (0, 4),
14: (0, 4),
15: (0, 4),
16: (0, 4),
17: (0, 4),
18: (0, 4),
1 : (4, 6),
2 : (0, 6),
#3 : (2, 6), Overlap with ICMPv4
#4 : (2, 6), Type of 4 in ICMPv4 is deprecated
4 : (2, None),
128: (0, 6),
129: (0, 6),
130: (0, 6),
131: (0, 6),
132: (0, 6),
133: (0, 6),
134: (0, 6),
135: (0, 6),
136: (0, 6),
137: (0, 6),
}
def _setheader(self, header):
"""Set type, code, and version for the packet."""
if len(header) != 2:
raise ValueError("header data must be in a two-item sequence")
type_, code = header
try:
max_range, version = self.header_table[type_]
except KeyError:
raise ValueError("%s is not a valid type argument" % type_)
else:
if code > max_range:
raise ValueError("%s is not a valid code value for type %s" %\
(type_, code))
self._type, self._code, self._version = type_, code, version
header = property(lambda self: (self._type, self._code), _setheader,
doc="type and code of packet")
version = property(lambda self: self._version,
doc="Protocol version packet is using or None if "
"ambiguous")
def _setdata(self, data):
"""Setter for self.data; will only accept a basestring or None type."""
if not isinstance(data, basestring) and not isinstance(data, type(None)):
raise TypeError("value must be a subclass of basestring or None, "
"not %s" % type(data))
self._data = data
data = property(lambda self: self._data, _setdata,
doc="data contained within the packet")
def __init__(self, header=(None, None), data=None):
"""Set instance attributes if given."""
#XXX: Consider using __slots__
# self._version initialized by setting self.header
self.header = header
self.data = data
def __repr__(self):
return "" % \
(self.version, self.type, self.code, len(self.data))
def create(self):
"""Return a packet."""
# Kept as a separate method instead of rolling into 'packet' property so
# as to allow passing method around without having to define a lambda
# method.
args = [self.header[0], self.header[1], 0]
pack_format = "!BBH"
if self.data:
pack_format += "%ss" % len(self.data)
args.append(self.data)
# ICMPv6 has the IP stack calculate the checksum
# For ambiguous cases, just go ahead and calculate it just in case
if self.version == 4 or not self.version:
args[2] = self._checksum(struct.pack(pack_format, *args))
return struct.pack(pack_format, *args)
packet = property(create,
doc="Complete ICMP packet")
def _checksum(self, checksum_packet):
"""Calculate checksum"""
byte_count = len(checksum_packet)
#XXX: Think there is an error here about odd number of bytes
if byte_count % 2:
odd_byte = ord(checksum_packet[-1])
checksum_packet = checksum_packet[:-1]
else:
odd_byte = 0
two_byte_chunks = struct.unpack("!%sH" % (len(checksum_packet)/2),
checksum_packet)
total = 0
for two_bytes in two_byte_chunks:
total += two_bytes
else:
total += odd_byte
total = (total >> 16) + (total & 0xFFFF)
total += total >> 16
return ~total
def parse(cls, packet):
"""Parse ICMP packet and return an instance of Packet"""
string_len = len(packet) - 4 # Ignore IP header
pack_format = "!BBH"
if string_len:
pack_format += "%ss" % string_len
unpacked_packet = struct.unpack(pack_format, packet)
type, code, checksum = unpacked_packet[:3]
try:
data = unpacked_packet[3]
except IndexError:
data = None
return cls((type, code), data)
parse = classmethod(parse)
def tracert(host, callback, maxTTL=128, icmpData="Yo, what's up?"):
import os
host = socket.gethostbyname(host)
# create socket
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.getprotobyname('icmp'))
pid = os.getpid()
icmp = Packet((8,0))
icmp.data = icmpData
for i in range(1, maxTTL):
# set ttl
s.setsockopt(socket.IPPROTO_IP, socket.IP_TTL, i)
# send icmp packet
s.sendto(icmp.packet, (host, 0))
# receive result
data, address = s.recvfrom(1024)
# parse result icmp packet
result = Packet.parse(data[20:])
# callback
callback(address[0], result)
type, code = result.header
if type == 0:
break
__all__ = [
'tracert',
'Packet'
]
if __name__ == '__main__':
def printIp(address, packet):
print address
tracert(raw_input('Host to trace router:'), printIp)
