From c432e062ea3239bf541afc25f14f0e69d074b5c2 Mon Sep 17 00:00:00 2001
From: Pau Espin Pedrol <pespin@sysmocom.de>
Date: Tue, 11 May 2021 13:17:31 +0200
Subject: [PATCH] encoding: Encode TA in UL ACK/NACK if available

Change-Id: I3b060ee16aeac5f5d9b314b6bc46383f5e9c44c3
---
 src/encoding.cpp      | 21 +++++++++++++++++++--
 tests/tbf/TbfTest.cpp |  8 ++++----
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/encoding.cpp b/src/encoding.cpp
index 22da6abc..0a4050fa 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -897,7 +897,15 @@ static void write_packet_uplink_ack_gprs(
 		bitvec_write_field(dest, &wp, 0, 1); // 0: don't have CONTENTION_RESOLUTION_TLLI
 	}
 
-	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Packet Timing Advance
+	if (gsm48_ta_is_valid(tbf->ta())) {
+		bitvec_write_field(dest, &wp, 1, 1); // 1: have Packet Timing Advance IE (TS 44.060 12.12)
+		bitvec_write_field(dest, &wp, 1, 1); // 1: have TIMING_ADVANCE_VALUE
+		bitvec_write_field(dest, &wp, tbf->ta(), 6); // TIMING_ADVANCE_VALUE
+		bitvec_write_field(dest, &wp, 0, 1); // 0: don't have TIMING_ADVANCE_INDEX
+	} else {
+		bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Packet Timing Advance
+	}
+
 	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Power Control Parameters
 	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Extension Bits
 	bitvec_write_field(dest, &wp, 0, 1); // fixed 0
@@ -1085,7 +1093,16 @@ static void write_packet_uplink_ack_egprs(
 	}
 
 	bitvec_write_field(dest, &wp, 1, 1); // TBF_EST (enabled)
-	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Packet Timing Advance
+
+	if (gsm48_ta_is_valid(tbf->ta())) {
+		bitvec_write_field(dest, &wp, 1, 1); // 1: have Packet Timing Advance IE (TS 44.060 12.12)
+		bitvec_write_field(dest, &wp, 1, 1); // 1: have TIMING_ADVANCE_VALUE
+		bitvec_write_field(dest, &wp, tbf->ta(), 6); // TIMING_ADVANCE_VALUE
+		bitvec_write_field(dest, &wp, 0, 1); // 0: don't have TIMING_ADVANCE_INDEX
+	} else {
+		bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Packet Timing Advance
+	}
+
 	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Packet Extended Timing Advance
 	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Power Control Parameters
 	bitvec_write_field(dest, &wp, 0, 1); // 0: don't have Extension Bits
diff --git a/tests/tbf/TbfTest.cpp b/tests/tbf/TbfTest.cpp
index e0fd9ccd..18a0a37d 100644
--- a/tests/tbf/TbfTest.cpp
+++ b/tests/tbf/TbfTest.cpp
@@ -794,8 +794,8 @@ static gprs_rlcmac_ul_tbf *puan_urbb_len_issue(struct gprs_rlcmac_bts *bts,
 
 	struct msgb *msg1 = ul_tbf->create_ul_ack(*fn, ts_no);
 
-	static uint8_t exp1[] = { 0x40, 0x24, 0x01, 0x0b, 0x3e, 0x24, 0x46, 0x68, 0x90, 0x87, 0xb0, 0x06,
-				  0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b
+	static uint8_t exp1[] = { 0x40, 0x24, 0x01, 0x0b, 0x3e, 0x24, 0x46, 0x68, 0x9c, 0x70, 0x87, 0xb0,
+				  0x06, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b
 	};
 
 	if (!msgb_eq_data_print(msg1, exp1, GSM_MACBLOCK_LEN)) {
@@ -821,8 +821,8 @@ static gprs_rlcmac_ul_tbf *puan_urbb_len_issue(struct gprs_rlcmac_bts *bts,
 
 	msg1 = ul_tbf->create_ul_ack(*fn, ts_no);
 
-	static uint8_t exp2[] = { 0x40, 0x24, 0x01, 0x0b, 0x3e, 0x24, 0x46, 0x68, 0x90, 0x88, 0xb0, 0x06, 0x8b,
-				  0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b
+	static uint8_t exp2[] = { 0x40, 0x24, 0x01, 0x0b, 0x3e, 0x24, 0x46, 0x68, 0x9c, 0x70, 0x88, 0xb0,
+				  0x06, 0x8b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b
 	};
 
 	if (!msgb_eq_data_print(msg1, exp2, GSM_MACBLOCK_LEN)) {