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fixeria gerrit-no-reply at lists.osmocom.orgfixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmocom-bb/+/14576
Change subject: trx_toolkit/data_msg.py: implement header version coding
......................................................................
trx_toolkit/data_msg.py: implement header version coding
Change-Id: Idb0377d66290eb9c15d6998a5806a84fa2e5dd02
Related: OS#4006
---
M src/target/trx_toolkit/data_msg.py
1 file changed, 92 insertions(+), 15 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/76/14576/1
diff --git a/src/target/trx_toolkit/data_msg.py b/src/target/trx_toolkit/data_msg.py
index 9ad19f6..669c9d2 100644
--- a/src/target/trx_toolkit/data_msg.py
+++ b/src/target/trx_toolkit/data_msg.py
@@ -4,7 +4,7 @@
# TRX Toolkit
# DATA interface message definitions and helpers
#
-# (C) 2018 by Vadim Yanitskiy <axilirator at gmail.com>
+# (C) 2018-2019 by Vadim Yanitskiy <axilirator at gmail.com>
#
# All Rights Reserved
#
@@ -49,20 +49,53 @@
parent of both DATAMSG_L12TRX and DATAMSG_TRX2L2 (see below),
and has the following fields:
- +--------------+-------------------+
- | TN (1 octet) | FN (4 octets, BE) |
- +--------------+-------------------+
+ +-----------------+----------------+-------------------+
+ | VER (1/2 octet) | TN (1/2 octet) | FN (4 octets, BE) |
+ +-----------------+----------------+-------------------+
where:
- - TN is TDMA time-slot number (1 octet), and
+ - VER is the header version indicator (1/2 octet MSB),
+ - TN is TDMA time-slot number (1/2 octet LSB), and
- FN is TDMA frame number (4 octets, big endian).
+ == Header version indication
+
+ It may be necessary to extend the message specific header
+ with more information. Since this is not a TLV-based
+ protocol, we need to include the header format version.
+
+ +-----------------+------------------------+
+ | 7 6 5 4 3 2 1 0 | bit numbers |
+ +-----------------+------------------------+
+ | X X X X . . . . | header version (0..15) |
+ +-----------------+------------------------+
+ | . . . . . X X X | TDMA TN (0..7) |
+ +-----------------+------------------------+
+ | . . . . X . . . | RESERVED (0) |
+ +-----------------+------------------------+
+
+ Instead of prepending an additional byte, it was decided
+ to use bits 4..7 of the first octet, which are always
+ zero-initialized due to the value range of TDMA TN. This
+ would prevent Wireshark from misinterpreting the message
+ header version (e.g. 0x01) as TDMA TN.
+
+ The reserved bit number 3 can be used in the future to extend
+ the TDMA TN range to (0..15), in case anybody would need
+ to transfer UMTS bursts.
+
+ The legacy header version (0x00) is assumed as the default.
+
"""
+ # NOTE: up to 15 (0x0f) versions can be encoded
+ known_versions = [0x00, 0x01]
+
# Common constructor
- def __init__(self, fn = None, tn = None, burst = None):
+ def __init__(self, fn = None, tn = None, burst = None, ver = 0):
self.burst = burst
+ self.ver = ver
self.fn = fn
self.tn = tn
@@ -99,6 +132,9 @@
def desc_hdr(self):
result = ""
+ if self.ver > 0:
+ result += ("ver=%u " % self.ver)
+
if self.fn is not None:
result += ("fn=%u " % self.fn)
@@ -148,6 +184,9 @@
# Validates the message fields
def validate(self):
+ if not self.ver in self.known_versions:
+ return False
+
if self.burst is None:
return False
@@ -177,10 +216,10 @@
# Allocate an empty byte-array
buf = bytearray()
- # Put timeslot index
- buf.append(self.tn)
+ # Put version (4 bits) and TDMA TN (3 bits)
+ buf.append((self.ver << 4) | (self.tn & 0x07))
- # Put frame number (4 octets, BE)
+ # Put TDMA FN (4 octets, BE)
buf += struct.pack(">L", self.fn)
# Generate message specific header part
@@ -206,9 +245,12 @@
if length < (self.HDR_LEN + GSM_BURST_LEN):
raise ValueError("Message is to short")
- # Parse both fn and tn
+ # Parse version and TDMA TN
+ self.ver = (msg[0] >> 4)
+ self.tn = (msg[0] & 0x07)
+
+ # Parse TDMA FN
self.fn = struct.unpack(">L", msg[1:5])[0]
- self.tn = msg[0]
# Specific message part
self.parse_hdr(msg)
@@ -316,9 +358,9 @@
self.burst = list(burst[:GSM_BURST_LEN])
# Transforms this message to TRX2L1 message
- def gen_trx2l1(self):
+ def gen_trx2l1(self, ver = 0):
# Allocate a new message
- msg = DATAMSG_TRX2L1(fn = self.fn, tn = self.tn)
+ msg = DATAMSG_TRX2L1(fn = self.fn, tn = self.tn, ver = ver)
# Convert burst bits
if self.burst is not None:
@@ -477,9 +519,9 @@
self.burst = burst_sbits
# Transforms this message to L12TRX message
- def gen_l12trx(self):
+ def gen_l12trx(self, ver = 0):
# Allocate a new message
- msg = DATAMSG_L12TRX(fn = self.fn, tn = self.tn)
+ msg = DATAMSG_L12TRX(fn = self.fn, tn = self.tn, ver = ver)
# Convert burst bits
if self.burst is not None:
@@ -602,3 +644,38 @@
assert(msg_trx2l1_dec.burst == msg_trx2l1_dec.ubit2sbit(burst_l12trx_ref))
log.info("Check L12TRX <-> TRX2L1 type transformations: OK")
+
+ # Test header version coding
+ # TODO: verify transformations with different versions
+ for ver in DATAMSG.known_versions:
+ # Create messages of both types
+ msg_l12trx = DATAMSG_L12TRX(burst = burst_l12trx_ref, ver = ver)
+ msg_trx2l1 = DATAMSG_TRX2L1(burst = burst_trx2l1_ref, ver = ver)
+
+ # Randomize message specific headers
+ msg_l12trx.rand_hdr()
+ msg_trx2l1.rand_hdr()
+
+ # Encode DATA messages
+ msg_l12trx_enc = msg_l12trx.gen_msg()
+ msg_trx2l1_enc = msg_trx2l1.gen_msg()
+
+ # Parse generated DATA messages
+ msg_l12trx_dec = DATAMSG_L12TRX()
+ msg_trx2l1_dec = DATAMSG_TRX2L1()
+ msg_l12trx_dec.parse_msg(msg_l12trx_enc)
+ msg_trx2l1_dec.parse_msg(msg_trx2l1_enc)
+
+ # Match the header version
+ assert(msg_l12trx_dec.ver == ver)
+ assert(msg_trx2l1_dec.ver == ver)
+
+ # Match common TDMA fields
+ assert(msg_l12trx_dec.tn == msg_l12trx.tn)
+ assert(msg_trx2l1_dec.fn == msg_trx2l1.fn)
+
+ # Compare bursts
+ assert(msg_l12trx_dec.burst == msg_l12trx.burst)
+ assert(msg_trx2l1_dec.burst == msg_trx2l1.burst)
+
+ log.info("Check header version %u coding: OK" % ver)
--
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Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-Change-Id: Idb0377d66290eb9c15d6998a5806a84fa2e5dd02
Gerrit-Change-Number: 14576
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <axilirator at gmail.com>
Gerrit-MessageType: newchange
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