edge: Work-around to not use MCS-6 with padding

Currently single BSN blocks of size 68 (a single unit from MCS-8)
are put into a MCS-6 block with padding according to TS 44.060
Annex J. Unfortunately, these packets are ignored by the E71. This
might be related to the currently incorrect usage of the puncturing
schemes and the RSB bit (the puncturing schemes are not updated and
the RBS flag is never set).

Avoid downgrading from MCS-8 to MCS-6 if there is no second block
available. Send the block twice instead.

Sponsored-by: On-Waves ehf

2 files changed, 12 insertions, 6 deletions

diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 6d4209f1..7540d1b3 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -609,8 +609,12 @@ struct msgb *gprs_rlcmac_dl_tbf::create_dl_acked_block(
 		num_bsns += 1;
 	}
 
-	if (num_bsns == 1)
-		cs.decToSingleBlock(&need_padding);
+	if (num_bsns == 1) {
+		/* TODO: remove the conditional when MCS-6 padding isn't
+		 * failing to be decoded by MEs anymore */
+		if (cs != GprsCodingScheme(GprsCodingScheme::MCS8))
+			cs.decToSingleBlock(&need_padding);
+	}
 
 	gprs_rlc_data_info_init_dl(&rlc, cs, need_padding);
 
diff --git a/tests/tbf/TbfTest.err b/tests/tbf/TbfTest.err
index e0027386..77966595 100644
--- a/tests/tbf/TbfTest.err
+++ b/tests/tbf/TbfTest.err
@@ -4886,10 +4886,11 @@ Complete DL frame for TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)len=56
 data block (BSN 0, MCS-8): 14 71 01 01 01 01 01 01 01 01 01 01 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
 - Restarting at BSN 0, because all blocks have been transmitted (FLOW).
 - Copying data unit 0 (BSN 0)
+- Copying data unit 1 (BSN 0)
 - Scheduling Ack/Nack polling, because is was requested explicitly (e.g. first final block sent).
 Polling is already scheduled for TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)
-msg block (BSN 0, MCS-6, padded): 07 00 00 04 00 00 00 00 00 00 45 5c 40 40 40 40 40 40 40 40 40 c0 10 70 c0 ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca 0a 
-Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=4 block=1 data=07 00 00 04 00 00 00 00 00 00 45 5c 40 40 40 40 40 40 40 40 40 c0 10 70 c0 ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca 0a 
+msg block (BSN 0, MCS-8): 07 00 00 00 60 50 c4 05 04 04 04 04 04 04 04 04 04 0c 01 07 ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac 40 11 17 10 10 10 10 10 10 10 10 10 30 04 1c b0 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 02 
+Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=4 block=1 data=07 00 00 00 60 50 c4 05 04 04 04 04 04 04 04 04 04 0c 01 07 ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac 40 11 17 10 10 10 10 10 10 10 10 10 30 04 1c b0 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 02 
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) append
 Received RTS for PDCH: TRX=0 TS=4 FN=8 block_nr=2 scheduling free USF for polling at FN=13 of TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)
 Scheduling data message at RTS for DL TFI=0 (TRX=0, TS=4) prio=3
@@ -4959,10 +4960,11 @@ Complete DL frame for TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)len=30
 data block (BSN 8, MCS-8): 48 3d 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
 - Restarting at BSN 0, because all blocks have been transmitted (FLOW).
 - Copying data unit 0 (BSN 8)
+- Copying data unit 1 (BSN 8)
 - Scheduling Ack/Nack polling, because is was requested explicitly (e.g. first final block sent).
 Polling is already scheduled for TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)
-msg block (BSN 8, MCS-6, padded): 07 00 02 04 00 00 00 00 00 00 52 4f 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 c0 10 70 c0 ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca 0a 
-Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=26 block=6 data=07 00 02 04 00 00 00 00 00 00 52 4f 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 c0 10 70 c0 ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca ca 0a 
+msg block (BSN 8, MCS-8): 07 00 02 00 60 20 f5 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 0c 01 07 ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac 80 d4 13 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 30 04 1c b0 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 02 
+Sending data request: trx=0 ts=4 sapi=5 arfcn=0 fn=26 block=6 data=07 00 02 00 60 20 f5 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 04 0c 01 07 ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac ac 80 d4 13 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 30 04 1c b0 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 02 
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 - Final ACK received.
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) changes state from FLOW to WAIT RELEASE