edge: Handle EGPRS PACKET DOWNLINK ACK NACK

Currently this message is ignored.

Support decoding and handling of this message. Use a bitvec for the
decoder that just represents a BSN sequence without any encoding
details (first bit -> first BSN). Return the corresponding BSN range
(snsmod(bsn_begin + bits_in_bitvec) = bsn_end), so snsmod(bsn_end-1)
is the last BSN if there is at least 1. If bsn_begin == bsn_end, no
BSNs has been added.

Note that this bitvec is not yet used for RBB handling. It just calls
the old rcvd_dl_ack with a faked (all bits are 1) RBB map.

Sponsored-by: On-Waves ehf

5 files changed, 219 insertions, 0 deletions

diff --git a/src/bts.cpp b/src/bts.cpp
index 18bee665..16961454 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -946,6 +946,123 @@ void gprs_rlcmac_pdch::rcv_control_dl_ack_nack(Packet_Downlink_Ack_Nack_t *ack_n
 	}
 }
 
+void gprs_rlcmac_pdch::rcv_control_egprs_dl_ack_nack(EGPRS_PD_AckNack_t *ack_nack, uint32_t fn)
+{
+	int8_t tfi = 0; /* must be signed */
+	struct gprs_rlcmac_dl_tbf *tbf;
+	struct pcu_l1_meas meas;
+	int rc;
+	int num_blocks;
+	uint8_t bits_data[RLC_EGPRS_MAX_WS/8];
+	char show_bits[RLC_EGPRS_MAX_WS + 1];
+	bitvec bits;
+	int bsn_begin, bsn_end;
+
+	tfi = ack_nack->DOWNLINK_TFI;
+	tbf = bts()->dl_tbf_by_poll_fn(fn, trx_no(), ts_no);
+	if (!tbf) {
+		LOGP(DRLCMAC, LOGL_NOTICE, "EGPRS PACKET DOWNLINK ACK with "
+			"unknown FN=%u TFI=%d (TRX %d TS %d)\n",
+			fn, tfi, trx_no(), ts_no);
+		return;
+	}
+	if (tbf->tfi() != tfi) {
+		LOGP(DRLCMAC, LOGL_NOTICE, "EGPRS PACKET DOWNLINK ACK with "
+			"wrong TFI=%d, ignoring!\n", tfi);
+		return;
+	}
+	tbf->state_flags |= (1 << GPRS_RLCMAC_FLAG_DL_ACK);
+	if ((tbf->state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK))) {
+		tbf->state_flags &= ~(1 << GPRS_RLCMAC_FLAG_TO_DL_ACK);
+		LOGP(DRLCMAC, LOGL_NOTICE, "Recovered EGPRS downlink ack "
+			"for %s\n", tbf_name(tbf));
+	}
+	/* reset N3105 */
+	tbf->n3105 = 0;
+	tbf->stop_t3191();
+	LOGP(DRLCMAC, LOGL_DEBUG,
+		"RX: [PCU <- BTS] %s EGPRS Packet Downlink Ack/Nack\n",
+		tbf_name(tbf));
+	tbf->poll_state = GPRS_RLCMAC_POLL_NONE;
+
+	LOGP(DRLCMAC, LOGL_DEBUG, "EGPRS ACK/NACK: "
+		"ut: %d, final: %d, bow: %d, eow: %d, ssn: %d, have_crbb: %d, "
+		"urbb_len:%d, %p, %p, %d, %d, win: %d-%d, urbb: %s\n",
+		(int)ack_nack->EGPRS_AckNack.UnionType,
+		(int)ack_nack->EGPRS_AckNack.Desc.FINAL_ACK_INDICATION,
+		(int)ack_nack->EGPRS_AckNack.Desc.BEGINNING_OF_WINDOW,
+		(int)ack_nack->EGPRS_AckNack.Desc.END_OF_WINDOW,
+		(int)ack_nack->EGPRS_AckNack.Desc.STARTING_SEQUENCE_NUMBER,
+		(int)ack_nack->EGPRS_AckNack.Desc.Exist_CRBB,
+		(int)ack_nack->EGPRS_AckNack.Desc.URBB_LENGTH,
+		(void *)&ack_nack->EGPRS_AckNack.UnionType,
+		(void *)&ack_nack->EGPRS_AckNack.Desc,
+		(int)offsetof(EGPRS_AckNack_t, Desc),
+		(int)offsetof(EGPRS_AckNack_w_len_t, Desc),
+		tbf->m_window.v_a(),
+		tbf->m_window.v_s(),
+		osmo_hexdump((const uint8_t *)&ack_nack->EGPRS_AckNack.Desc.URBB,
+			sizeof(ack_nack->EGPRS_AckNack.Desc.URBB)));
+
+	bits.data = bits_data;
+	bits.data_len = sizeof(bits_data);
+	bits.cur_bit = 0;
+
+	num_blocks = Decoding::decode_egprs_acknack_bits(
+		&ack_nack->EGPRS_AckNack.Desc, &bits,
+		&bsn_begin, &bsn_end, &tbf->m_window);
+
+	for (int i = 0; i < num_blocks; i++) {
+		show_bits[i] = bitvec_get_bit_pos(&bits, i) ? 'R' : 'I';
+	}
+	show_bits[num_blocks] = 0;
+
+	LOGP(DRLCMAC, LOGL_DEBUG,
+		"EGPRS DL ACK bitmap: BSN %d to %d - 1 (%d blocks): %s\n",
+		bsn_begin, bsn_end, num_blocks, show_bits);
+
+	if (ack_nack->EGPRS_AckNack.Desc.URBB_LENGTH == 0 &&
+		!ack_nack->EGPRS_AckNack.Desc.Exist_CRBB)
+	{
+		/* Everything has been received successfully */
+		/* Fake a GPRS type ack */
+		uint64_t fake_map = -1;
+
+		rc = tbf->rcvd_dl_ack(
+			ack_nack->EGPRS_AckNack.Desc.FINAL_ACK_INDICATION,
+			tbf->m_window.mod_sns(ack_nack->EGPRS_AckNack.Desc.STARTING_SEQUENCE_NUMBER-1),
+			(uint8_t *)&fake_map);
+
+		if (rc == 1) {
+			tbf_free(tbf);
+			return;
+		}
+	}
+
+	/* 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,
+			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;
+	}
+
+	/* get measurements */
+	if (tbf->ms()) {
+		/* TODO: Implement Measurements parsing for EGPRS */
+		/*
+		get_meas(&meas, &ack_nack->Channel_Quality_Report);
+		tbf->ms()->update_l1_meas(&meas);
+		*/
+	}
+}
+
 void gprs_rlcmac_pdch::rcv_resource_request(Packet_Resource_Request_t *request, uint32_t fn)
 {
 	struct gprs_rlcmac_sba *sba;
@@ -1105,6 +1222,9 @@ int gprs_rlcmac_pdch::rcv_control_block(
 	case MT_PACKET_DOWNLINK_ACK_NACK:
 		rcv_control_dl_ack_nack(&ul_control_block->u.Packet_Downlink_Ack_Nack, fn);
 		break;
+	case MT_EGPRS_PACKET_DOWNLINK_ACK_NACK:
+		rcv_control_egprs_dl_ack_nack(&ul_control_block->u.Egprs_Packet_Downlink_Ack_Nack, fn);
+		break;
 	case MT_PACKET_RESOURCE_REQUEST:
 		rcv_resource_request(&ul_control_block->u.Packet_Resource_Request, fn);
 		break;
diff --git a/src/bts.h b/src/bts.h
index 0928f8d7..52154cb2 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -107,6 +107,7 @@ private:
 
 	void rcv_control_ack(Packet_Control_Acknowledgement_t *, uint32_t fn);
 	void rcv_control_dl_ack_nack(Packet_Downlink_Ack_Nack_t *, uint32_t fn);
+	void rcv_control_egprs_dl_ack_nack(EGPRS_PD_AckNack_t *, uint32_t fn);
 	void rcv_resource_request(Packet_Resource_Request_t *t, uint32_t fn);
 	void rcv_measurement_report(Packet_Measurement_Report_t *t, uint32_t fn);
 	gprs_rlcmac_tbf *tbf_from_list_by_tfi(
diff --git a/src/csn1.cpp b/src/csn1.cpp
index 377c50f4..54cc411c 100644
--- a/src/csn1.cpp
+++ b/src/csn1.cpp
@@ -549,6 +549,7 @@ csnStreamDecoder(csnStream_t* ar, const CSN_DESCR* pDescr, bitvec *vector, unsig
 
         csnStreamInit(&arT, bit_offset, length);
         arT.direction = 1;
+        LOGPC(DCSN1, LOGL_NOTICE, "ptr = %p | offset = %d | ", (void *)data, (int)pDescr->offset);
         Status = serialize(&arT, vector, readIndex, pvDATA(data, pDescr->offset));
 
         if (Status >= 0)
diff --git a/src/decoding.cpp b/src/decoding.cpp
index cb1b34d4..f4cd8802 100644
--- a/src/decoding.cpp
+++ b/src/decoding.cpp
@@ -493,3 +493,94 @@ const uint8_t *Decoding::rlc_get_data_aligned(
 	Decoding::rlc_copy_to_aligned_buffer(rlc, data_block_idx, src, buffer);
 	return buffer;
 }
+
+static int handle_final_ack(bitvec *bits, int *bsn_begin, int *bsn_end,
+	gprs_rlc_dl_window *window)
+{
+	int num_blocks, i;
+
+	num_blocks = window->mod_sns(window->v_s() - window->v_a());
+	for (i = 0; i < num_blocks; i++)
+		bitvec_set_bit(bits, ONE);
+
+	*bsn_begin = window->v_a();
+	*bsn_end   = window->mod_sns(*bsn_begin + num_blocks);
+	return num_blocks;
+}
+
+int Decoding::decode_egprs_acknack_bits(const EGPRS_AckNack_Desc_t *desc,
+	bitvec *bits, int *bsn_begin, int *bsn_end, gprs_rlc_dl_window *window)
+{
+	int urbb_len = desc->URBB_LENGTH;
+	int crbb_len = 0;
+	int num_blocks = 0;
+	struct bitvec urbb;
+	int i;
+	bool have_bitmap;
+	int implicitly_acked_blocks;
+	int ssn = desc->STARTING_SEQUENCE_NUMBER;
+
+	if (desc->FINAL_ACK_INDICATION)
+		return handle_final_ack(bits, bsn_begin, bsn_end, window);
+
+	if (desc->Exist_CRBB)
+		crbb_len = desc->CRBB_LENGTH;
+
+	have_bitmap = (urbb_len + crbb_len) > 0;
+
+	/*
+	 * bow & bitmap present:
+	 *   V(A)-> [ 11111...11111 0 SSN-> BBBBB...BBBBB ] (SSN+Nbits) .... V(S)
+	 * bow & not bitmap present:
+	 *   V(A)-> [ 11111...11111 ] . SSN .... V(S)
+	 * not bow & bitmap present:
+	 *   V(A)-> ... [ 0 SSN-> BBBBB...BBBBB ](SSN+N) .... V(S)
+	 * not bow & not bitmap present:
+	 *   V(A)-> ... [] . SSN .... V(S)
+	 */
+
+	if (desc->BEGINNING_OF_WINDOW) {
+		implicitly_acked_blocks = window->mod_sns(ssn - 1 - window->v_a());
+
+		for (i = 0; i < implicitly_acked_blocks; i++)
+			bitvec_set_bit(bits, ONE);
+
+		num_blocks += implicitly_acked_blocks;
+	}
+
+	if (have_bitmap) {
+		/* next bit refers to V(Q) and thus is always zero (and not
+		 * transmitted) */
+		bitvec_set_bit(bits, ZERO);
+		num_blocks += 1;
+
+		if (crbb_len > 0) {
+			int old_len = bits->cur_bit;
+			/*
+			decode_t4_rle(bits, desc->CRBB, desc->CRBB_LENGTH,
+					desc->CRBB_STARTING_COLOR_CODE);
+			 */
+
+			num_blocks += (bits->cur_bit - old_len);
+		}
+
+		urbb.cur_bit = 0;
+		urbb.data = (uint8_t *)desc->URBB;
+		urbb.data_len = sizeof(desc->URBB);
+
+		for (i = urbb_len; i > 0; i--) {
+			/*
+			 * Set bit at the appropriate position (see 3GPP TS
+			 * 44.060 12.3.1)
+			 */
+			int is_ack = bitvec_get_bit_pos(&urbb, i-1);
+			bitvec_set_bit(bits, is_ack == 1 ? ONE : ZERO);
+		}
+		num_blocks += urbb_len;
+	}
+
+	*bsn_begin = window->v_a();
+	*bsn_end   = window->mod_sns(*bsn_begin + num_blocks);
+
+	return num_blocks;
+}
diff --git a/src/decoding.h b/src/decoding.h
index c75b19a1..99cb3187 100644
--- a/src/decoding.h
+++ b/src/decoding.h
@@ -24,6 +24,8 @@
 
 #include <stdint.h>
 
+struct bitvec;
+
 class Decoding {
 public:
 	struct RlcData {
@@ -51,4 +53,8 @@ public:
 		const struct gprs_rlc_data_info *rlc,
 		unsigned int data_block_idx,
 		const uint8_t *src, uint8_t *buffer);
+	static int decode_egprs_acknack_bits(
+		const EGPRS_AckNack_Desc_t *desc,
+		struct bitvec *bits, int *bsn_begin, int *bsn_end,
+		struct gprs_rlc_dl_window *window);
 };