-
Notifications
You must be signed in to change notification settings - Fork 0
/
traceroute.py
201 lines (163 loc) · 7.8 KB
/
traceroute.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
#!/usr/bin/env/python3
""" Traceroute Python implementation almost from scratch.
Before the script is run, the following constant have to be set:
INTERFACE, SRC_IP, DEST_IP, SRC_MAC
UDP Header according to RFC 768 :
0 7 8 15 16 23 24 31
+--------+--------+--------+--------+
| Source | Destination |
| Port | Port |
+--------+--------+--------+--------+
| | |
| Length | Checksum |
+--------+--------+--------+--------+
| |
| data octets ... |
+-----------------------------------+
IP header
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
"""
import socket
import struct
import sys
from time import time
from arp import get_target_mac, mac_to_byte
# Network environment settings for ARP request.
INTERFACE = None # 'wlan0'
SRC_IP = None # '192.168.1.192'
DEST_IP = None # '192.168.1.1'
SRC_MAC = None # '11:aa:6d:24:01:68'
DEST_MAC = 0 if not INTERFACE else get_target_mac(DEST_IP, SRC_IP, SRC_MAC, INTERFACE) # ARP req
def get_checksum(data):
"""Checksum for UDP, IP and ICMP packages. The checksum field is the 16-bit
one's complement of the one's complement sum of all 16-bit words in the header.
"""
if len(data) % 2 == 1:
data += b'\x00'
checksum = sum(data[i] << 8 | data[i + 1] for i in range(0, len(data), 2))
while checksum >> 16:
# If shifting right by 16 places returns a result other than 0,
# it means we've got more than 16bit number. So, according to RFC
# specification we mask only the 16 bits and carry anything what's left
# by adding it to the result.
checksum = (checksum & 0xffff) + (checksum >> 16)
# Finally, switch bits by xoring with 0xffff.
return checksum ^ 0xffff
def ethernet_construct():
"""Constructs ethernet header"""
eth_dest_mac = mac_to_byte(DEST_MAC)
eth_src_mac = mac_to_byte(SRC_MAC)
eth_type = 0x0800 # IP
return struct.pack('>6s6sH', eth_dest_mac, eth_src_mac, eth_type)
def udp_construct(src_ip, dest_ip, udp_port=33434, udp_mes=b'@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_'):
"""Returns UDP packet."""
src_port = 0 # (2B) when it's not used then set to 0.
# Set non-existent port number to get ICMP(3) - „destination port unreachable” in return.
dest_port = udp_port # (2B)
data = udp_mes
data_len = len(data)
udp_len = 8 + data_len # (2B) Min 8 bytes (header), max 65527 bytes.
# udp_checksum = 0
# Udp checksum (2B) not only needs UDP fields, but also requires pseudo header built
# on parts of IP protocol: source ip, destination ip and protocol id.
# That's the reason for these 3 fields below, which are not part of UDP, but IP.
udp_protocol = 17 # (1B) UDP
src_ip = socket.inet_aton(src_ip)
dest_ip = socket.inet_aton(dest_ip)
ip_part = struct.pack('>4s4sBBH', dest_ip, src_ip, 0, udp_protocol, udp_len)
udp_part = struct.pack('>HHH{}s'.format(data_len), src_port, dest_port, udp_len, data)
udp_checksum = get_checksum(ip_part + udp_part)
udp_pkt = struct.pack('>HHHH{}s'.format(data_len),
src_port, dest_port, udp_len, udp_checksum, data)
return udp_pkt
class IpPacket:
"""get_pkt public instance method returns IP packet."""
def __init__(self, src_ip, target_ip, data_len, proto=17):
"""All IP protocol fields. TTL is passed by the get_pkt method. """
self.ver = 4 # IPv4 (4 bits field)
# in 32 bit words. 32 Bit is 4 Bytes, so 20B header length is 20/4 = 5.
self.head_len = 5 # (4 bits field)
# Join version and head_len together into 1 byte value.
self.ver_head_byte = self.ver << 4 | self.head_len
self.tos = 0 # (1B)
self.pkt_len = 20 + data_len # (2B) len of full IP pkt, header + data (UDP in this case)
self.ident = 0 # (16b)
self.flags = 0b010 # (3b), unused, DF, MF
self.offset = 0 # (13b)
self.flags_offset = (self.flags << 13 | self.offset) & 0xffff
# self.ttl = 1
self.proto_id = proto # (1B) 17 for UDP
self.ip_checksum = 0 # (2B)
self.src_ip = socket.inet_aton(src_ip)
self.dest_ip = socket.inet_aton(target_ip) # (32b)
def _ip_struct(self, ttl, chsum): # ttl is added by this method (1B)
pkt = struct.pack('>BBHHHBBH4s4s',
self.ver_head_byte, self.tos, self.pkt_len, self.ident,
self.flags_offset, ttl, self.proto_id, chsum, self.src_ip, self.dest_ip)
return pkt
def get_pkt(self, ttl):
"""Packet is constructed twice. For checksum computation and as a final packet."""
pkt = self._ip_struct(ttl, self.ip_checksum)
ip_checksum = get_checksum(pkt)
pkt = self._ip_struct(ttl, ip_checksum)
return pkt
def traceroute(url, hops):
"""Takes url and number of max ttl (hops parameter).
Output: ICMP type and code, rtt (ms), hop_time (ms) and route IP as raw address (no DNS name).
Hop_time returns time between current and previous node. A packet may fly through the network
via different paths in each run or may wait in a queue for a while.
That's why hop_time can sometimes take negative value and rtt of the next run can be smaller
than the previous one.
"""
sock = socket.socket(socket.PF_PACKET, socket.SOCK_RAW)
sock.bind((INTERFACE, 0x800))
dest_ip = socket.gethostbyname(url)
print('Traceroute to: %s (%s), %s hops max.\n' % (url, dest_ip, hops))
ether = ethernet_construct()
udp = udp_construct(SRC_IP, dest_ip)
ip = IpPacket(SRC_IP, dest_ip, len(udp))
last_rtt = 0
for i in range(1, hops + 1):
frame = ether + ip.get_pkt(i) + udp
try:
start = time()
sock.send(frame)
while True:
resp = sock.recv(1024)
sock.settimeout(2)
if resp[23] == 1: # looking for ICMP packets.
break
rtt = round((time() - start) * 1000, 3)
hop_time = round(rtt - last_rtt, 3)
last_rtt = rtt
except socket.timeout:
print('{:<2} * * *'.format(i))
continue
target_ip = socket.inet_ntoa(resp[26:30])
icmp_type = resp[34]
icmp_code = resp[35]
# TODO DNS resolver for target_ip for more informative output.
print('{:<2} type/code={}/{}, rtt={:<8} hop_time={:<8} route IP: {}'
.format(i, icmp_type, icmp_code, rtt, hop_time, target_ip))
if icmp_type == 3:
break
if __name__ == "__main__":
if not (INTERFACE and SRC_IP and DEST_IP and SRC_MAC):
print("Constant variables have to be set before running the script.\n"
"These are: INTERFACE, SRC_IP, DEST_IP and SRC_MAC.")
sys.exit(0)
traceroute(sys.argv[-1], 20)