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#!/usr/bin/env python2
# -*- coding: utf-8 -*-
# TRX Toolkit
# DATA interface message definitions and helpers
#
# (C) 2018 by Vadim Yanitskiy <axilirator@gmail.com>
#
# All Rights Reserved
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
import random
import struct
from gsm_shared import *
class DATAMSG:
# Common message fields
burst = None
fn = None
tn = None
# Common constructor
def __init__(self, fn = None, tn = None, burst = None):
self.burst = burst
self.fn = fn
self.tn = tn
# Generates message specific header
def gen_hdr(self):
raise NotImplementedError
# Parses message specific header
def parse_hdr(self, hdr):
raise NotImplementedError
# Generates message specific burst
def gen_burst(self):
raise NotImplementedError
# Parses message specific burst
def parse_burst(self, burst):
raise NotImplementedError
# Generates a random frame number
def rand_fn(self):
return random.randint(0, GSM_HYPERFRAME)
# Generates a random timeslot number
def rand_tn(self):
return random.randint(0, 7)
# Randomizes the message header
def rand_hdr(self):
self.fn = self.rand_fn()
self.tn = self.rand_tn()
# Generates human-readable header description
def desc_hdr(self):
result = ""
if self.fn is not None:
result += ("fn=%u " % self.fn)
if self.tn is not None:
result += ("tn=%u " % self.tn)
return result
# Converts unsigned soft-bits {254..0} to soft-bits {-127..127}
def usbit2sbit(self, bits):
buf = []
for bit in bits:
if bit == 0xff:
buf.append(-127)
else:
buf.append(127 - bit)
return buf
# Converts soft-bits {-127..127} to unsigned soft-bits {254..0}
def sbit2usbit(self, bits):
buf = []
for bit in bits:
buf.append(127 - bit)
return buf
# Converts soft-bits {-127..127} to bits {1..0}
def sbit2ubit(self, bits):
buf = []
for bit in bits:
buf.append(1 if bit < 0 else 0)
return buf
# Converts bits {1..0} to soft-bits {-127..127}
def ubit2sbit(self, bits):
buf = []
for bit in bits:
buf.append(-127 if bit else 127)
return buf
# Validates the message fields
def validate(self):
if self.burst is None:
return False
if len(self.burst) not in (GSM_BURST_LEN, EDGE_BURST_LEN):
return False
if self.fn is None:
return False
if self.fn < 0 or self.fn > GSM_HYPERFRAME:
return False
if self.tn is None:
return False
if self.tn < 0 or self.tn > 7:
return False
return True
# Generates frame number to bytes
def gen_fn(self, fn):
# Big endian, 4 bytes
return struct.pack(">L", fn)
# Parses frame number from bytes
def parse_fn(self, buf):
# Big endian, 4 bytes
return struct.unpack(">L", buf)[0]
# Generates a TRX DATA message
def gen_msg(self, legacy = False):
# Validate all the fields
if not self.validate():
raise ValueError("Message incomplete or incorrect")
# Allocate an empty byte-array
buf = bytearray()
# Put timeslot index
buf.append(self.tn)
# Put frame number
fn = self.gen_fn(self.fn)
buf += fn
# Generate message specific header part
hdr = self.gen_hdr()
buf += hdr
# Generate burst
buf += self.gen_burst()
# This is a rudiment from (legacy) OpenBTS transceiver,
# some L1 implementations still expect two dummy bytes.
if legacy:
buf += bytearray(2)
return buf
# Parses a TRX DATA message
def parse_msg(self, msg):
# Calculate message length
length = len(msg)
# Check length
if length < (self.HDR_LEN + GSM_BURST_LEN):
raise ValueError("Message is to short")
# Parse both fn and tn
self.fn = self.parse_fn(msg[1:5])
self.tn = msg[0]
# Specific message part
self.parse_hdr(msg)
# Copy burst, skipping header
msg_burst = msg[self.HDR_LEN:]
self.parse_burst(msg_burst)
class DATAMSG_L12TRX(DATAMSG):
# Constants
HDR_LEN = 6
PWR_MIN = 0x00
PWR_MAX = 0xff
# Specific message fields
pwr = None
# Validates the message fields
def validate(self):
# Validate common fields
if not DATAMSG.validate(self):
return False
if self.pwr is None:
return False
if self.pwr < self.PWR_MIN or self.pwr > self.PWR_MAX:
return False
return True
# Generates a random power level
def rand_pwr(self, min = None, max = None):
if min is None:
min = self.PWR_MIN
if max is None:
max = self.PWR_MAX
return random.randint(min, max)
# Randomizes message specific header
def rand_hdr(self):
DATAMSG.rand_hdr(self)
self.pwr = self.rand_pwr()
# Generates human-readable header description
def desc_hdr(self):
# Describe the common part
result = DATAMSG.desc_hdr(self)
if self.pwr is not None:
result += ("pwr=%u " % self.pwr)
# Strip useless whitespace and return
return result.strip()
# Generates message specific header part
def gen_hdr(self):
# Allocate an empty byte-array
buf = bytearray()
# Put power
buf.append(self.pwr)
return buf
# Parses message specific header part
def parse_hdr(self, hdr):
# Parse power level
self.pwr = hdr[5]
# Generates message specific burst
def gen_burst(self):
# Copy burst 'as is'
return bytearray(self.burst)
# Parses message specific burst
def parse_burst(self, burst):
length = len(burst)
# Distinguish between GSM and EDGE
if length >= EDGE_BURST_LEN:
self.burst = list(burst[:EDGE_BURST_LEN])
else:
self.burst = list(burst[:GSM_BURST_LEN])
# Transforms this message to TRX2L1 message
def gen_trx2l1(self):
# Allocate a new message
msg = DATAMSG_TRX2L1(fn = self.fn, tn = self.tn)
# Convert burst bits
if self.burst is not None:
msg.burst = self.ubit2sbit(self.burst)
return msg
class DATAMSG_TRX2L1(DATAMSG):
# Constants
HDR_LEN = 8
RSSI_MIN = -120
RSSI_MAX = -50
# Min and max values of int16_t
TOA256_MIN = -32768
TOA256_MAX = 32767
# Specific message fields
rssi = None
toa256 = None
# Validates the message fields
def validate(self):
# Validate common fields
if not DATAMSG.validate(self):
return False
if self.rssi is None:
return False
if self.rssi < self.RSSI_MIN or self.rssi > self.RSSI_MAX:
return False
if self.toa256 is None:
return False
if self.toa256 < self.TOA256_MIN or self.toa256 > self.TOA256_MAX:
return False
return True
# Generates a random RSSI value
def rand_rssi(self, min = None, max = None):
if min is None:
min = self.RSSI_MIN
if max is None:
max = self.RSSI_MAX
return random.randint(min, max)
# Generates a ToA (Time of Arrival) value
def rand_toa256(self, min = None, max = None):
if min is None:
min = self.TOA256_MIN
if max is None:
max = self.TOA256_MAX
return random.randint(min, max)
# Randomizes message specific header
def rand_hdr(self):
DATAMSG.rand_hdr(self)
self.rssi = self.rand_rssi()
self.toa256 = self.rand_toa256()
# Generates human-readable header description
def desc_hdr(self):
# Describe the common part
result = DATAMSG.desc_hdr(self)
if self.rssi is not None:
result += ("rssi=%d " % self.rssi)
if self.toa256 is not None:
result += ("toa256=%d " % self.toa256)
# Strip useless whitespace and return
return result.strip()
# Generates message specific header part
def gen_hdr(self):
# Allocate an empty byte-array
buf = bytearray()
# Put RSSI
buf.append(-self.rssi)
# Encode ToA (Time of Arrival)
# Big endian, 2 bytes (int32_t)
buf += struct.pack(">h", self.toa256)
return buf
# Parses message specific header part
def parse_hdr(self, hdr):
# Parse RSSI
self.rssi = -(hdr[5])
# Parse ToA (Time of Arrival)
self.toa256 = struct.unpack(">h", hdr[6:8])[0]
# Generates message specific burst
def gen_burst(self):
# Convert soft-bits to unsigned soft-bits
burst_usbits = self.sbit2usbit(self.burst)
# Encode to bytes
return bytearray(burst_usbits)
# Parses message specific burst
def parse_burst(self, burst):
length = len(burst)
# Distinguish between GSM and EDGE
if length >= EDGE_BURST_LEN:
burst_usbits = list(burst[:EDGE_BURST_LEN])
else:
burst_usbits = list(burst[:GSM_BURST_LEN])
# Convert unsigned soft-bits to soft-bits
burst_sbits = self.usbit2sbit(burst_usbits)
# Save
self.burst = burst_sbits
# Transforms this message to L12TRX message
def gen_l12trx(self):
# Allocate a new message
msg = DATAMSG_L12TRX(fn = self.fn, tn = self.tn)
# Convert burst bits
if self.burst is not None:
msg.burst = self.sbit2ubit(self.burst)
return msg
# Regression test
if __name__ == '__main__':
import logging as log
# Configure logging
log.basicConfig(level = log.DEBUG,
format = "[%(levelname)s] %(filename)s:%(lineno)d %(message)s")
# Common reference data
fn = 1024
tn = 0
# Generate two random bursts
burst_l12trx_ref = []
burst_trx2l1_ref = []
for i in range(0, GSM_BURST_LEN):
ubit = random.randint(0, 1)
burst_l12trx_ref.append(ubit)
sbit = random.randint(-127, 127)
burst_trx2l1_ref.append(sbit)
log.info("Generating the reference messages")
# Create messages of both types
msg_l12trx_ref = DATAMSG_L12TRX(fn = fn, tn = tn)
msg_trx2l1_ref = DATAMSG_TRX2L1(fn = fn, tn = tn)
# Fill in message specific fields
msg_trx2l1_ref.rssi = -88
msg_l12trx_ref.pwr = 0x33
msg_trx2l1_ref.toa256 = -256
# Specify the reference bursts
msg_l12trx_ref.burst = burst_l12trx_ref
msg_trx2l1_ref.burst = burst_trx2l1_ref
log.info("Encoding the reference messages")
# Encode DATA messages
l12trx_raw = msg_l12trx_ref.gen_msg()
trx2l1_raw = msg_trx2l1_ref.gen_msg()
# Encode a TRX2L1 message in legacy mode
trx2l1_raw_legacy = msg_trx2l1_ref.gen_msg(legacy = True)
log.info("Parsing generated messages back")
# Parse generated DATA messages
msg_l12trx_dec = DATAMSG_L12TRX()
msg_trx2l1_dec = DATAMSG_TRX2L1()
msg_l12trx_dec.parse_msg(l12trx_raw)
msg_trx2l1_dec.parse_msg(trx2l1_raw)
# Parse generated TRX2L1 message in legacy mode
msg_trx2l1_legacy_dec = DATAMSG_TRX2L1()
msg_trx2l1_legacy_dec.parse_msg(trx2l1_raw_legacy)
log.info("Comparing decoded messages with the reference")
# Compare bursts
assert(msg_l12trx_dec.burst == burst_l12trx_ref)
assert(msg_trx2l1_dec.burst == burst_trx2l1_ref)
assert(msg_trx2l1_legacy_dec.burst == burst_trx2l1_ref)
log.info("Compare bursts: OK")
# Compare both parsed messages with the reference data
assert(msg_l12trx_dec.fn == fn)
assert(msg_trx2l1_dec.fn == fn)
assert(msg_l12trx_dec.tn == tn)
assert(msg_trx2l1_dec.tn == tn)
log.info("Compare FN / TN: OK")
# Compare message specific parts
assert(msg_trx2l1_dec.rssi == msg_trx2l1_ref.rssi)
assert(msg_l12trx_dec.pwr == msg_l12trx_ref.pwr)
assert(msg_trx2l1_dec.toa256 == msg_trx2l1_ref.toa256)
log.info("Compare message specific data: OK")
# Validate header randomization
for i in range(0, 100):
msg_l12trx_ref.rand_hdr()
msg_trx2l1_ref.rand_hdr()
assert(msg_l12trx_ref.validate())
assert(msg_trx2l1_ref.validate())
log.info("Validate header randomization: OK")
# Bit conversation test
usbits_ref = list(range(0, 256))
sbits_ref = list(range(-127, 128))
# Test both usbit2sbit() and sbit2usbit()
sbits = msg_trx2l1_ref.usbit2sbit(usbits_ref)
usbits = msg_trx2l1_ref.sbit2usbit(sbits)
assert(usbits[:255] == usbits_ref[:255])
assert(usbits[255] == 254)
log.info("Check both usbit2sbit() and sbit2usbit(): OK")
# Test both sbit2ubit() and ubit2sbit()
ubits = msg_trx2l1_ref.sbit2ubit(sbits_ref)
assert(ubits == ([1] * 127 + [0] * 128))
sbits = msg_trx2l1_ref.ubit2sbit(ubits)
assert(sbits == ([-127] * 127 + [127] * 128))
log.info("Check both sbit2ubit() and ubit2sbit(): OK")
# Test message transformation
msg_l12trx_dec = msg_trx2l1_ref.gen_l12trx()
msg_trx2l1_dec = msg_l12trx_ref.gen_trx2l1()
assert(msg_l12trx_dec.fn == msg_trx2l1_ref.fn)
assert(msg_l12trx_dec.tn == msg_trx2l1_ref.tn)
assert(msg_trx2l1_dec.fn == msg_l12trx_ref.fn)
assert(msg_trx2l1_dec.tn == msg_l12trx_ref.tn)
assert(msg_l12trx_dec.burst == msg_l12trx_dec.sbit2ubit(burst_trx2l1_ref))
assert(msg_trx2l1_dec.burst == msg_trx2l1_dec.ubit2sbit(burst_l12trx_ref))
log.info("Check L12TRX <-> TRX2L1 type transformations: OK")
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