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immediate_assignment_catcher.py
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immediate_assignment_catcher.py
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#!/usr/bin/python
# -*- coding: utf-8 -*-
# Author: Oros
# 2016/10/06
# License : CC0 1.0 Universal
"""
Display SDCCH, Subchannel, Timeslot, HoppingChannel, ARFCN
"""
from scapy.all import sniff
from optparse import OptionParser
def find_assignment(x):
"""
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00
0010 00 43 b1 be 40 00 40 11 8a e9 7f 00 00 01 7f 00
0020 00 01 b9 11 12 79 00 2f fe 42 02 04 01 00 00 00
0030 e6 00 00 08 d4 7a 02 00 06 00 2d 06 3f 10 0e 03
0040 df 7b a3 71 01 00 ce 01 81 59 d7 2b 2b 2b 2b 2b
0050 2b
Dedicated mode or TBF
0000 10
0001 .... = Dedicated mode or TBF: This message assigns an uplink TBF or is the second message of two in a two-message assignment of an uplink or downlink TBF (1)
Packet Channel Description
0000 0e 03 df
0000 1... = Channel Type: 1
.... .110 = Timeslot: 6
000. .... = Training Sequence: 0
.... .0.. = Spare: 0x00
.... ..11 1101 1111 = Single channel ARFCN: 991
Dedicated mode or TBF
0000 30
0011 .... = Dedicated mode or TBF: This message assigns a downlink TBF to the mobile station identified in the IA Rest Octets IE (3)
GSMTAP 81 (CCCH) (RR) Immediate Assignment
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00
0010 00 43 07 02 40 00 40 11 35 a6 7f 00 00 01 7f 00
0020 00 01 b7 29 12 79 00 2f fe 42 02 04 01 00 00 00
0030 e6 00 00 16 ab ce 02 00 07 00 2d 06 3f 03 41 c0
0040 09 00 03 b1 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
0050 2b
0x3e = 0x41
0100 0... = SDCCH/8 + SACCH/C8 or CBCH (SDCCH/8): 8
Subchannel: 0
.... .001 = Timeslot: 1
0x3f = 0xc0
110. .... = Training Sequence: 6
...0 .... = Hopping Channel: No
..00 .... = Spare: 0x00
0x40 = 0x09
Single channel ARFCN: 9
0 1 2 3 4 5 6 7 8 9 a b c d e f
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00
0010 00 43 c8 7f 40 00 40 11 74 28 7f 00 00 01 7f 00
0020 00 01 9c c8 12 79 00 2f fe 42 02 04 01 00 00 00
0030 e4 00 00 09 0a e7 02 00 08 00 2d 06 3f 00 41 03
0040 df 92 f4 2a 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
0050 2b
Dedicated mode or TBF
0000 00
0000 .... = Dedicated mode or TBF: This message assigns a dedicated mode resource (0)
Channel Description
0000 41 03 df
0100 0... = SDCCH/8 + SACCH/C8 or CBCH (SDCCH/8): 8
Subchannel: 0
.... .001 = Timeslot: 1
000. .... = Training Sequence: 0
...0 .... = Hopping Channel: No
..00 .... = Spare: 0x00
Single channel ARFCN: 991
79
0111 1... = SDCCH/8 + SACCH/C8 or CBCH (SDCCH/8): 15
Subchannel: 7
.... .001 = Timeslot: 1
ARFCN calcul :
https://en.wikipedia.org/wiki/ARFCN
http://www.telecomabc.com/a/arfcn.html
http://niviuk.free.fr/gsm_band.php
"""
p=str(x)
if ord(p[0x36]) != 0x1: # Channel Type != BCCH (0)
if ord(p[0x3c]) == 0x3f: # Message Type: Immediate Assignment
if ord(p[0x3d]) >> 4 == 0: # 0000 .... = Dedicated mode or TBF: This message assigns a dedicated mode resource (0)
sdcch=ord(p[0x3e]) >> 3 # 0100 0... = SDCCH/8 + SACCH/C8 or CBCH (SDCCH/8): 8
subchannel=ord(p[0x3e])
timeslot=ord(p[0x3e]) & 0x07 # .... .001 = Timeslot: 1
hopping_channel="yes" if (ord(p[0x3f]) >> 4) & 1 == 1 else "no" # ...0 .... = Hopping Channel: No
arfcn=(ord(p[0x3f]) & 0x03)*256 + ord(p[0x40]) # .... ..11 1101 1111 = Single channel ARFCN: 991
print("{}\t; {}\t\t; {}\t\t; {}\t\t\t; {}".format(sdcch, subchannel, timeslot, hopping_channel, arfcn))
else:
# Dedicated mode or TBF: This message assigns an uplink TBF or is the second message of two in a two-message assignment of an uplink or downlink TBF (1)
sdcch="-"
subchannel="-"
timeslot=ord(p[0x3e]) & 0x07 # .... .001 = Timeslot: 1
hopping_channel="-"
arfcn=(ord(p[0x3f]) & 0x03)*256 + ord(p[0x40]) # .... ..11 1101 1111 = Single channel ARFCN: 991
print("{}\t; {}\t\t; {}\t\t; {}\t\t\t; {}".format(sdcch, subchannel, timeslot, hopping_channel, arfcn))
pass
parser = OptionParser(usage="%prog: [options]")
parser.add_option("-i", "--iface", dest="iface", default="lo", help="Interface (default : lo)")
parser.add_option("-p", "--port", dest="port", default="4729", type="int", help="Port (default : 4729)")
(options, args) = parser.parse_args()
print("SDCCH\t; Subchannel\t; Timeslot\t; HoppingChannel\t; ARFCN")
sniff(iface=options.iface, filter="port {} and not icmp and udp".format(options.port), prn=find_assignment, store=0)