EGPRS: fix for EPDAN out of window

Fix alignment of EPDAN outside the RLC transmit window,
according to section 9.1.8.2.4 in 44.060 version 7.27.0 Release 7.
The specification explains that a bit within the uncompressed bitmap
whose corresponding BSN is not within the transmit window shall be
ignored. Without this fix PCU was dropping the EPDAN message and not
updating the status of BSNs which are inside the RLC window. This patch
updates the status of the BSNs which are inside the window and ignores
the remaining bits.

Related: OS#1789

Change-Id: Id07d178970f168f5389016c1eea31eb6b82057b6

4 files changed, 134 insertions, 37 deletions

diff --git a/src/rlc.cpp b/src/rlc.cpp
index ee2635aa..2bffccb8 100644
--- a/src/rlc.cpp
+++ b/src/rlc.cpp
@@ -105,7 +105,9 @@ void gprs_rlc_dl_window::update(BTS *bts, const struct bitvec *rbb,
 			uint16_t first_bsn, uint16_t *lost,
 			uint16_t *received)
 {
-	unsigned num_blocks = rbb->cur_bit;
+	unsigned dist = distance();
+	unsigned num_blocks = rbb->cur_bit > dist
+				? dist : rbb->cur_bit;
 	unsigned bsn;
 
 	/* first_bsn is in range V(A)..V(S) */
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index c89cd03a..f6836f8b 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -847,6 +847,11 @@ int gprs_rlcmac_dl_tbf::analyse_errors(char *show_rbb, uint8_t ssn,
 	unsigned received_packets = 0, lost_packets = 0;
 	unsigned num_blocks = strlen(show_rbb);
 
+	unsigned distance = m_window.distance();
+
+	num_blocks = num_blocks > distance
+				? distance : num_blocks;
+
 	/* SSN - 1 is in range V(A)..V(S)-1 */
 	for (unsigned int bitpos = 0; bitpos < num_blocks; bitpos++) {
 		bool is_received;
@@ -919,13 +924,15 @@ int gprs_rlcmac_dl_tbf::analyse_errors(char *show_rbb, uint8_t ssn,
 int gprs_rlcmac_dl_tbf::update_window(unsigned first_bsn,
 	const struct bitvec *rbb)
 {
-	int16_t dist; /* must be signed */
+	unsigned dist;
 	uint16_t lost = 0, received = 0;
 	char show_v_b[RLC_MAX_SNS + 1];
 	char show_rbb[RLC_MAX_SNS + 1];
 	int error_rate;
 	struct ana_result ana_res;
-	unsigned num_blocks = rbb->cur_bit;
+	dist = m_window.distance();
+	unsigned num_blocks = rbb->cur_bit > dist
+				? dist : rbb->cur_bit;
 	unsigned behind_last_bsn = m_window.mod_sns(first_bsn + num_blocks);
 
 	Decoding::extract_rbb(rbb, show_rbb);
@@ -934,25 +941,6 @@ int gprs_rlcmac_dl_tbf::update_window(unsigned first_bsn,
 		"(BSN=%d)  R=ACK I=NACK\n", first_bsn,
 		show_rbb, m_window.mod_sns(behind_last_bsn - 1));
 
-	/* apply received array to receive state (first_bsn..behind_last_bsn-1) */
-	if (num_blocks > 0) {
-		/* calculate distance of ssn from V(S) */
-		dist = m_window.mod_sns(m_window.v_s() - behind_last_bsn);
-		/* check if distance is less than distance V(A)..V(S) */
-		if (dist >= m_window.distance()) {
-			/* this might happpen, if the downlink assignment
-			 * was not received by ms and the ack refers
-			 * to previous TBF
-			 * FIXME: we should implement polling for
-			 * control ack!
-			 * TODO: check whether this FIXME still makes sense
-			 */
-			LOGP(DRLCMACDL, LOGL_NOTICE, "- ack range is out of "
-				"V(A)..V(S) range %s Free TBF!\n", tbf_name(this));
-			return 1; /* indicate to free TBF */
-		}
-	}
-
 	error_rate = analyse_errors(show_rbb, behind_last_bsn, &ana_res);
 
 	if (bts_data()->cs_adj_enabled && ms())
diff --git a/tests/tbf/TbfTest.cpp b/tests/tbf/TbfTest.cpp
index 8fb8bfe9..cc483926 100644
--- a/tests/tbf/TbfTest.cpp
+++ b/tests/tbf/TbfTest.cpp
@@ -2101,17 +2101,11 @@ static void test_tbf_epdan_out_of_rx_window(void)
 	dl_tbf->rcvd_dl_ack(
 		ack_nack->EGPRS_AckNack.Desc.FINAL_ACK_INDICATION,
 		bsn_begin, &bits);
-	/*
-	 * TODO:status of BSN:1176,1177 shall be invalid
-	 * status of BSN:1286,1287 shall be acked.
-	 * both condition fails because of existing bug. Which shall be
-	 * fixed in subsequent commit
-	 */
 
-	OSMO_ASSERT(prlcmvb->is_unacked(1176));
-	OSMO_ASSERT(prlcmvb->is_unacked(1177));
-	OSMO_ASSERT(prlcmvb->is_unacked(1286));
-	OSMO_ASSERT(prlcmvb->is_unacked(1287));
+	OSMO_ASSERT(prlcmvb->is_invalid(1176));
+	OSMO_ASSERT(prlcmvb->is_invalid(1177));
+	OSMO_ASSERT(prlcmvb->is_acked(1286));
+	OSMO_ASSERT(prlcmvb->is_acked(1287));
 
 	bitvec_free(block);
 	tbf_free(dl_tbf);
diff --git a/tests/tbf/TbfTest.err b/tests/tbf/TbfTest.err
index f8e65034..fc3a1134 100644
--- a/tests/tbf/TbfTest.err
+++ b/tests/tbf/TbfTest.err
@@ -446,7 +446,7 @@ msg block (BSN 20, CS-1): 07 00 28 0a 41 c6 c7 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b
 Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=91 block=9 data=07 00 28 0a 41 c6 c7 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) downlink acknowledge
 - ack:  (BSN=85)"RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR"(BSN=20)  R=ACK I=NACK
-TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) DL analysis, range=0:21, lost=0, recv=21, skipped=0, bsn=127, info='RRRRRRRRRRRRRRRRRRRRR$..........................................'
+TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) DL analysis, range=0:21, lost=0, recv=21, skipped=0, bsn=0, info='RRRRRRRRRRRRRRRRRRRRR...........................................'
 - got ack for BSN=20
 - got ack for BSN=19
 - got ack for BSN=18
@@ -485,7 +485,7 @@ msg block (BSN 21, CS-1): 07 00 2a 4d 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
 Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=95 block=10 data=07 00 2a 4d 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) downlink acknowledge
 - ack:  (BSN=86)"RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR"(BSN=21)  R=ACK I=NACK
-TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) DL analysis, range=21:22, lost=0, recv=1, skipped=0, bsn=20, info='R$..............................................................'
+TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW) DL analysis, range=21:22, lost=0, recv=1, skipped=0, bsn=21, info='R...............................................................'
 - got ack for BSN=21
 - V(B): (V(A)=22)""(V(S)-1=21)  A=Acked N=Nacked U=Unacked X=Resend-Unacked I=Invalid
 Scheduling data message at RTS for DL TFI=0 (TRX=0, TS=4) prio=4
@@ -6504,9 +6504,122 @@ Modifying MS object, TLLI = 0x00000000, TA 220 -> 0
 TBF(TFI=0 TLLI=0x00000000 DIR=DL STATE=NULL EGPRS) changes state from NULL to FLOW
 The MS object cannot fully confirm an unexpected TLLI: 0xffeeddcc, partly confirmed
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
-- ack:  (BSN=1176)"RRRRRRRRRRIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIRRRIRRRRRRRRRRRRRRRRRRRRRRRRRRI"(BSN=1288)  R=ACK I=NACK
-- ack range is out of V(A)..V(S) range TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Free TBF!
-DL packet loss of IMSI= / TLLI=0xffeeddcc: 100%
+- ack:  (BSN=1176)"RRRRRRRRRRIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIRRRIRRRRRRRRRRRRRRRRRRRRRRRRRRI"(BSN=1287)  R=ACK I=NACK
+TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=1176:1288, lost=73, recv=39, skipped=0, bsn=1944, info='RRRRRRRRRRRRRRRRRRRRRRRRRRLRRRLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLRRRRRRRRRR................................................................................................................................................................................................................................................................................................................................................................................'
+- got ack for BSN=1176
+- got ack for BSN=1177
+- got ack for BSN=1178
+- got ack for BSN=1179
+- got ack for BSN=1180
+- got ack for BSN=1181
+- got ack for BSN=1182
+- got ack for BSN=1183
+- got ack for BSN=1184
+- got ack for BSN=1185
+- got NACK for BSN=1186
+- got NACK for BSN=1187
+- got NACK for BSN=1188
+- got NACK for BSN=1189
+- got NACK for BSN=1190
+- got NACK for BSN=1191
+- got NACK for BSN=1192
+- got NACK for BSN=1193
+- got NACK for BSN=1194
+- got NACK for BSN=1195
+- got NACK for BSN=1196
+- got NACK for BSN=1197
+- got NACK for BSN=1198
+- got NACK for BSN=1199
+- got NACK for BSN=1200
+- got NACK for BSN=1201
+- got NACK for BSN=1202
+- got NACK for BSN=1203
+- got NACK for BSN=1204
+- got NACK for BSN=1205
+- got NACK for BSN=1206
+- got NACK for BSN=1207
+- got NACK for BSN=1208
+- got NACK for BSN=1209
+- got NACK for BSN=1210
+- got NACK for BSN=1211
+- got NACK for BSN=1212
+- got NACK for BSN=1213
+- got NACK for BSN=1214
+- got NACK for BSN=1215
+- got NACK for BSN=1216
+- got NACK for BSN=1217
+- got NACK for BSN=1218
+- got NACK for BSN=1219
+- got NACK for BSN=1220
+- got NACK for BSN=1221
+- got NACK for BSN=1222
+- got NACK for BSN=1223
+- got NACK for BSN=1224
+- got NACK for BSN=1225
+- got NACK for BSN=1226
+- got NACK for BSN=1227
+- got NACK for BSN=1228
+- got NACK for BSN=1229
+- got NACK for BSN=1230
+- got NACK for BSN=1231
+- got NACK for BSN=1232
+- got NACK for BSN=1233
+- got NACK for BSN=1234
+- got NACK for BSN=1235
+- got NACK for BSN=1236
+- got NACK for BSN=1237
+- got NACK for BSN=1238
+- got NACK for BSN=1239
+- got NACK for BSN=1240
+- got NACK for BSN=1241
+- got NACK for BSN=1242
+- got NACK for BSN=1243
+- got NACK for BSN=1244
+- got NACK for BSN=1245
+- got NACK for BSN=1246
+- got NACK for BSN=1247
+- got NACK for BSN=1248
+- got NACK for BSN=1249
+- got NACK for BSN=1250
+- got NACK for BSN=1251
+- got NACK for BSN=1252
+- got NACK for BSN=1253
+- got NACK for BSN=1254
+- got NACK for BSN=1255
+- got NACK for BSN=1256
+- got NACK for BSN=1257
+- got ack for BSN=1258
+- got ack for BSN=1259
+- got ack for BSN=1260
+- got NACK for BSN=1261
+- got ack for BSN=1262
+- got ack for BSN=1263
+- got ack for BSN=1264
+- got ack for BSN=1265
+- got ack for BSN=1266
+- got ack for BSN=1267
+- got ack for BSN=1268
+- got ack for BSN=1269
+- got ack for BSN=1270
+- got ack for BSN=1271
+- got ack for BSN=1272
+- got ack for BSN=1273
+- got ack for BSN=1274
+- got ack for BSN=1275
+- got ack for BSN=1276
+- got ack for BSN=1277
+- got ack for BSN=1278
+- got ack for BSN=1279
+- got ack for BSN=1280
+- got ack for BSN=1281
+- got ack for BSN=1282
+- got ack for BSN=1283
+- got ack for BSN=1284
+- got ack for BSN=1285
+- got ack for BSN=1286
+- got ack for BSN=1287
+- V(B): (V(A)=1186)"NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNAAANAAAAAAAAAAAAAAAAAAAAAAAAAA"(V(S)-1=1287)  A=Acked N=Nacked U=Unacked X=Resend-Unacked I=Invalid
+DL packet loss of IMSI= / TLLI=0xffeeddcc: 78%
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) changes state from FLOW to RELEASING
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=RELEASING EGPRS) free
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=RELEASING EGPRS) Software error: Pending downlink assignment. This may not happen, because the assignment message never gets transmitted. Please be sure not to free in this state. PLEASE FIX!