Handle packet access reject during EPDAN/PDAN with channel description

When PDAN/EPDAN with channel description is received, PCU will generate the
packet access reject if no resources are present. The encoding is done
based on section 7.1.3.2.1 and 8.1.2.5 of 44.060 version 7.27.0 Release 7.
This patch also includes the test case to validate the generated
packet access reject message.

This patch is integration tested on Osmo-trx setup with Ettus B210 board
and LG F70 MS with some simulation code changes in Osmo-pcu.

Change-Id: I096a3bb44a65533b9e9b091925dd5f70a8696d6

9 files changed, 135 insertions, 12 deletions

diff --git a/src/bts.cpp b/src/bts.cpp
index 4e6b5e96..0668c2da 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1077,16 +1077,23 @@ void gprs_rlcmac_pdch::rcv_control_dl_ack_nack(Packet_Downlink_Ack_Nack_t *ack_n
 	}
 	/* check for channel request */
 	if (ack_nack->Exist_Channel_Request_Description) {
-		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
-			"message, so we provide one:\n");
 
 		/* This call will register the new TBF with the MS on success */
-		tbf_alloc_ul(bts_data(), tbf->trx->trx_no,
+		gprs_rlcmac_ul_tbf *ul_tbf = tbf_alloc_ul(bts_data(),
+			tbf->trx->trx_no,
 			tbf->ms_class(), tbf->ms()->egprs_ms_class(),
 			tbf->tlli(), tbf->ta(), tbf->ms());
 
-		/* schedule uplink assignment */
-		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
+		/* schedule uplink assignment or reject*/
+		if (ul_tbf) {
+			LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
+				"message, so we provide one:\n");
+			tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
+		} else {
+			LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
+				"message, so we pacekt access reject:\n");
+			tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS_REJ;
+		}
 	}
 	/* get measurements */
 	if (tbf->ms()) {
@@ -1179,16 +1186,23 @@ void gprs_rlcmac_pdch::rcv_control_egprs_dl_ack_nack(EGPRS_PD_AckNack_t *ack_nac
 
 	/* check for channel request */
 	if (ack_nack->Exist_ChannelRequestDescription) {
-		LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
-			"message, so we provide one:\n");
 
 		/* This call will register the new TBF with the MS on success */
-		tbf_alloc_ul(bts_data(), tbf->trx->trx_no,
+		gprs_rlcmac_ul_tbf *ul_tbf = tbf_alloc_ul(bts_data(),
+			tbf->trx->trx_no,
 			tbf->ms_class(), tbf->ms()->egprs_ms_class(),
 			tbf->tlli(), tbf->ta(), tbf->ms());
 
-		/* schedule uplink assignment */
-		tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
+		/* schedule uplink assignment or reject*/
+		if (ul_tbf) {
+			LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
+				"message, so we provide one:\n");
+			tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS;
+		} else {
+			LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF in ack "
+				"message, so we send packet access reject:\n");
+			tbf->ul_ass_state = GPRS_RLCMAC_UL_ASS_SEND_ASS_REJ;
+		}
 	}
 
 	/* get measurements */
diff --git a/src/encoding.cpp b/src/encoding.cpp
index ca72b0fb..e5a8605f 100644
--- a/src/encoding.cpp
+++ b/src/encoding.cpp
@@ -1391,3 +1391,28 @@ Encoding::AppendResult Encoding::rlc_data_to_dl_append(
 
 	return AR_NEED_MORE_BLOCKS;
 }
+
+/*
+ * Refer 44.060 version 7.27.0 Release 7
+ * section 7.1.3.2.1 On receipt of a PACKET RESOURCE REQUEST message
+ * 8.1.2.5 Establishment of uplink TBF
+ */
+void Encoding::write_packet_access_reject(
+	bitvec * dest, uint32_t tlli)
+{
+	unsigned wp = 0;
+
+	bitvec_write_field(dest, wp, 0x1, 2);  // Payload Type
+	bitvec_write_field(dest, wp, 0x0, 2);  // Uplink block with TDMA FN
+	bitvec_write_field(dest, wp, 0, 1);  // No Polling Bit
+	bitvec_write_field(dest, wp, 0x0, 3);  // Uplink state flag
+	bitvec_write_field(dest, wp,
+				MT_PACKET_ACCESS_REJECT, 6);  // MESSAGE TYPE
+	bitvec_write_field(dest, wp, 0, 2); // fixed 00
+	bitvec_write_field(dest, wp, 0x0, 1);  //  TLLI / G-RNTI : bit (32)
+	bitvec_write_field(dest, wp, tlli, 32); // CONTENTION_RESOLUTION_TLLI
+	bitvec_write_field(dest, wp, 1, 1);  //  WAIT_INDICATION size in seconds
+	/* TODO: make it configurable */
+	bitvec_write_field(dest, wp, 5, 8);  //  WAIT_INDICATION value
+	bitvec_write_field(dest, wp, 0, 1);  //  WAIT_INDICATION size in seconds
+}
diff --git a/src/encoding.h b/src/encoding.h
index 79dc32dd..6164b891 100644
--- a/src/encoding.h
+++ b/src/encoding.h
@@ -74,6 +74,9 @@ public:
 
 	static void encode_rbb(const char *show_rbb, uint8_t *rbb);
 
+	static void write_packet_access_reject(
+		bitvec * dest, uint32_t tlli);
+
 	static void write_packet_uplink_ack(
 			struct gprs_rlcmac_bts *bts, bitvec * dest,
 			struct gprs_rlcmac_ul_tbf *tbf, bool is_final,
diff --git a/src/gprs_rlcmac_sched.cpp b/src/gprs_rlcmac_sched.cpp
index f4860758..a3723df3 100644
--- a/src/gprs_rlcmac_sched.cpp
+++ b/src/gprs_rlcmac_sched.cpp
@@ -72,7 +72,8 @@ static uint32_t sched_poll(BTS *bts,
 			*poll_tbf = dl_tbf;
 		if (dl_tbf->dl_ass_state == GPRS_RLCMAC_DL_ASS_SEND_ASS)
 			*dl_ass_tbf = dl_tbf;
-		if (dl_tbf->ul_ass_state == GPRS_RLCMAC_UL_ASS_SEND_ASS)
+		if (dl_tbf->ul_ass_state == GPRS_RLCMAC_UL_ASS_SEND_ASS
+		 || dl_tbf->ul_ass_state == GPRS_RLCMAC_UL_ASS_SEND_ASS_REJ)
 			*ul_ass_tbf = dl_tbf;
 	}
 
@@ -137,7 +138,11 @@ static struct msgb *sched_select_ctrl_msg(
 		 */
 
 		if (tbf == ul_ass_tbf && tbf->direction == GPRS_RLCMAC_DL_TBF)
-			msg = ul_ass_tbf->create_ul_ass(fn, ts);
+			if (tbf->ul_ass_state ==
+					GPRS_RLCMAC_UL_ASS_SEND_ASS_REJ)
+				msg = ul_ass_tbf->create_packet_access_reject();
+			else
+				msg = ul_ass_tbf->create_ul_ass(fn, ts);
 		else if (tbf == dl_ass_tbf && tbf->direction == GPRS_RLCMAC_UL_TBF)
 			msg = dl_ass_tbf->create_dl_ass(fn, ts);
 		else if (tbf == ul_ack_tbf)
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 0ac8acee..2d827270 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -1013,6 +1013,29 @@ struct msgb *gprs_rlcmac_tbf::create_dl_ass(uint32_t fn, uint8_t ts)
 	return msg;
 }
 
+struct msgb *gprs_rlcmac_tbf::create_packet_access_reject()
+{
+	struct msgb *msg;
+
+	msg = msgb_alloc(23, "rlcmac_ul_ass_rej");
+
+	bitvec *packet_access_rej = bitvec_alloc(23);
+
+	bitvec_unhex(packet_access_rej,
+		"2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b2b");
+
+	Encoding::write_packet_access_reject(
+		packet_access_rej, tlli());
+
+	bitvec_pack(packet_access_rej, msgb_put(msg, 23));
+
+	bitvec_free(packet_access_rej);
+	ul_ass_state = GPRS_RLCMAC_UL_ASS_NONE;
+
+	return msg;
+
+}
+
 struct msgb *gprs_rlcmac_tbf::create_ul_ass(uint32_t fn, uint8_t ts)
 {
 	struct msgb *msg;
diff --git a/src/tbf.h b/src/tbf.h
index 3205f6e0..e0440535 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -64,6 +64,7 @@ enum gprs_rlcmac_tbf_dl_ass_state {
 enum gprs_rlcmac_tbf_ul_ass_state {
 	GPRS_RLCMAC_UL_ASS_NONE = 0,
 	GPRS_RLCMAC_UL_ASS_SEND_ASS, /* send uplink assignment on next RTS */
+	GPRS_RLCMAC_UL_ASS_SEND_ASS_REJ, /* send assignment reject next RTS */
 	GPRS_RLCMAC_UL_ASS_WAIT_ACK, /* wait for PACKET CONTROL ACK */
 };
 
@@ -103,6 +104,7 @@ struct gprs_rlcmac_tbf {
 
 	struct msgb *create_dl_ass(uint32_t fn, uint8_t ts);
 	struct msgb *create_ul_ass(uint32_t fn, uint8_t ts);
+	struct msgb *create_packet_access_reject();
 
 	GprsMs *ms() const;
 	void set_ms(GprsMs *ms);
diff --git a/tests/tbf/TbfTest.cpp b/tests/tbf/TbfTest.cpp
index 339390b2..213bd125 100644
--- a/tests/tbf/TbfTest.cpp
+++ b/tests/tbf/TbfTest.cpp
@@ -2831,6 +2831,29 @@ const struct log_info debug_log_info = {
 	ARRAY_SIZE(default_categories),
 };
 
+void test_packet_access_rej_epdan()
+{
+	BTS the_bts;
+	uint32_t tlli = 0xffeeddcc;
+
+	printf("=== start %s ===\n", __func__);
+	setup_bts(&the_bts, 4);
+	static gprs_rlcmac_dl_tbf *dl_tbf = tbf_init(&the_bts, 1);
+
+	dl_tbf->update_ms(tlli, GPRS_RLCMAC_DL_TBF);
+
+	struct msgb *msg = dl_tbf->create_packet_access_reject();
+
+	printf("packet reject: %s\n",
+			osmo_hexdump(msg->data, 23));
+
+	OSMO_ASSERT(!strcmp(osmo_hexdump(msg->data, 23),
+			    "40 84 7f f7 6e e6 41 4b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b "));
+	printf("=== end %s ===\n", __func__);
+
+}
+
+
 int main(int argc, char **argv)
 {
 	struct vty_app_info pcu_vty_info = {0};
@@ -2874,6 +2897,7 @@ int main(int argc, char **argv)
 	test_tbf_li_decoding();
 	test_tbf_epdan_out_of_rx_window();
 	test_immediate_assign_rej();
+	test_packet_access_rej_epdan();
 
 	if (getenv("TALLOC_REPORT_FULL"))
 		talloc_report_full(tall_pcu_ctx, stderr);
diff --git a/tests/tbf/TbfTest.err b/tests/tbf/TbfTest.err
index 627cdc30..a6808122 100644
--- a/tests/tbf/TbfTest.err
+++ b/tests/tbf/TbfTest.err
@@ -6846,3 +6846,27 @@ MS requests single block allocation
 No PDCH available.
 No PDCH resource for single block allocation.sending Immediate Assignment Uplink (AGCH) reject
 Sending data request: trx=0 ts=0 sapi=2 arfcn=0 fn=0 block=0 data=4d 06 3a 10 70 8b 29 14 70 8b 29 14 70 8b 29 14 70 8b 29 14 0b 2b 2b 
+Searching for first unallocated TFI: TRX=0
+ Found TFI=0.
+********** TBF starts here **********
+Allocating DL TBF: MS_CLASS=11/11
+Creating MS object, TLLI = 0x00000000
+Modifying MS object, TLLI = 0x00000000, MS class 0 -> 11
+Modifying MS object, TLLI = 0x00000000, EGPRS MS class 0 -> 11
+Slot Allocation (Algorithm A) for class 11
+- Skipping TS 0, because not enabled
+- Skipping TS 1, because not enabled
+- Skipping TS 2, because not enabled
+- Skipping TS 3, because not enabled
+- Skipping TS 5, because not enabled
+- Skipping TS 6, because not enabled
+- Skipping TS 7, because not enabled
+- Assign downlink TS=4 TFI=0
+PDCH(TS 4, TRX 0): Attaching TBF(TFI=0 TLLI=0x00000000 DIR=DL STATE=NULL), 1 TBFs, USFs = 00, TFIs = 00000001.
+- Setting Control TS 4
+Attaching TBF to MS object, TLLI = 0x00000000, TBF = TBF(TFI=0 TLLI=0x00000000 DIR=DL STATE=NULL)
+Allocated TBF(TFI=0 TLLI=0x00000000 DIR=DL STATE=NULL): trx = 0, ul_slots = 10, dl_slots = 10
+Modifying MS object, TLLI = 0x00000000, TA 220 -> 0
+TBF(TFI=0 TLLI=0x00000000 DIR=DL STATE=NULL) 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) append
diff --git a/tests/tbf/TbfTest.ok b/tests/tbf/TbfTest.ok
index f921dfce..dc07fc72 100644
--- a/tests/tbf/TbfTest.ok
+++ b/tests/tbf/TbfTest.ok
@@ -72,3 +72,6 @@ Testing retx for MCS 6 to reseg_mcs 3
 === end test_immediate_assign_rej_multi_block ===
 === start test_immediate_assign_rej_single_block ===
 === end test_immediate_assign_rej_single_block ===
+=== start test_packet_access_rej_epdan ===
+packet reject: 40 84 7f f7 6e e6 41 4b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 
+=== end test_packet_access_rej_epdan ===