rlcmac: Implement Tx of DL ACK/NACK

Measurement related functionality is not yet implemented and hence the
related fields cannot be filled in yet.

Related: OS#5500
Change-Id: I6ae2df07929fb6c4733e87b18cebe75a6f24f520
---
M include/osmocom/gprs/rlcmac/rlcmac_enc.h
M include/osmocom/gprs/rlcmac/tbf_dl.h
M src/rlcmac/rlcmac_enc.c
M src/rlcmac/sched.c
M src/rlcmac/tbf_dl.c
M tests/rlcmac/rlcmac_prim_test.err
M tests/rlcmac/rlcmac_prim_test.ok
7 files changed, 114 insertions(+), 4 deletions(-)

diff --git a/include/osmocom/gprs/rlcmac/rlcmac_enc.h b/include/osmocom/gprs/rlcmac/rlcmac_enc.h
index d091d53..1a0f586 100644
--- a/include/osmocom/gprs/rlcmac/rlcmac_enc.h
+++ b/include/osmocom/gprs/rlcmac/rlcmac_enc.h
@@ -46,3 +46,5 @@
 void gprs_rlcmac_enc_prepare_pkt_ul_dummy_block(RlcMacUplink_t *block, uint32_t tlli);
 
 void gprs_rlcmac_enc_prepare_pkt_resource_req(RlcMacUplink_t *block, struct gprs_rlcmac_ul_tbf *ul_tbf, enum gprs_rlcmac_access_type acc_type);
+
+void gprs_rlcmac_enc_prepare_pkt_downlink_ack_nack(RlcMacUplink_t *block, const struct gprs_rlcmac_dl_tbf *dl_tbf);
diff --git a/include/osmocom/gprs/rlcmac/tbf_dl.h b/include/osmocom/gprs/rlcmac/tbf_dl.h
index facae81..f398c0a 100644
--- a/include/osmocom/gprs/rlcmac/tbf_dl.h
+++ b/include/osmocom/gprs/rlcmac/tbf_dl.h
@@ -40,6 +40,8 @@
 
 int gprs_rlcmac_dl_tbf_configure_l1ctl(struct gprs_rlcmac_dl_tbf *dl_tbf);
 
+struct msgb *gprs_rlcmac_dl_tbf_create_pkt_dl_ack_nack(const struct gprs_rlcmac_dl_tbf *dl_tbf);
+
 int gprs_rlcmac_dl_tbf_rcv_data_block(struct gprs_rlcmac_dl_tbf *dl_tbf,
 				      const struct gprs_rlcmac_rlc_data_info *rlc,
 				      uint8_t *data, uint32_t fn, uint8_t ts_nr);
diff --git a/src/rlcmac/rlcmac_enc.c b/src/rlcmac/rlcmac_enc.c
index e1ea990..1f1ebc3 100644
--- a/src/rlcmac/rlcmac_enc.c
+++ b/src/rlcmac/rlcmac_enc.c
@@ -24,6 +24,8 @@
 #include <osmocom/gprs/rlcmac/csn1_defs.h>
 #include <osmocom/gprs/rlcmac/rlcmac_enc.h>
 #include <osmocom/gprs/rlcmac/gre.h>
+#include <osmocom/gprs/rlcmac/tbf_dl.h>
+#include <osmocom/gprs/rlcmac/rlc_window_dl.h>
 #include <osmocom/gprs/rlcmac/tbf_ul.h>
 
 int gprs_rlcmac_rlc_write_ul_data_header(const struct gprs_rlcmac_rlc_data_info *rlc, uint8_t *data)
@@ -352,3 +354,59 @@
 	req->Exist_AdditionsR99 = 0;
 	/* TODO: no req->AdditionsR99 yet */
 }
+
+static void gprs_rlcmac_enc_prepare_pkt_ack_nack_desc_gprs(Ack_Nack_Description_t *ack_desc, const struct gprs_rlcmac_dl_tbf *dl_tbf)
+{
+	struct bitvec bv = {
+		.data = &ack_desc->RECEIVED_BLOCK_BITMAP[0],
+		.data_len = sizeof(ack_desc->RECEIVED_BLOCK_BITMAP),
+	};
+	char rbb[65];
+
+	gprs_rlcmac_rlc_dl_window_update_rbb(dl_tbf->dlw, rbb);
+	rbb[64] = 0;
+	LOGPTBFDL(dl_tbf, LOGL_DEBUG, "- V(N): \"%s\" R=Received I=Invalid\n", rbb);
+
+	ack_desc->FINAL_ACK_INDICATION = (gprs_rlcmac_tbf_dl_state(dl_tbf) == GPRS_RLCMAC_TBF_DL_ST_FINISHED);
+	ack_desc->STARTING_SEQUENCE_NUMBER = gprs_rlcmac_rlc_dl_window_ssn(dl_tbf->dlw);
+	for (int i = 0; i < 64; i++) {
+		/* Set bit at the appropriate position (see 3GPP TS 44.060 9.1.8.1) */
+		bool is_ack = (rbb[i] == 'R');
+		bitvec_set_bit(&bv, is_ack == 1 ? ONE : ZERO);
+	}
+}
+
+/* Channel Quality Report struct, TS 44.060 Table 11.2.6. */
+static void gprs_rlcmac_enc_prepare_channel_quality_report(Channel_Quality_Report_t *cqr, const struct gprs_rlcmac_dl_tbf *dl_tbf)
+{
+	/* TODO: fill cqr from info stored probably in the gre object. */
+}
+
+void gprs_rlcmac_enc_prepare_pkt_downlink_ack_nack(RlcMacUplink_t *block, const struct gprs_rlcmac_dl_tbf *dl_tbf)
+{
+	Packet_Downlink_Ack_Nack_t *ack = &block->u.Packet_Downlink_Ack_Nack;
+	struct gprs_rlcmac_entity *gre = dl_tbf->tbf.gre;
+
+	memset(block, 0, sizeof(*block));
+	ack->MESSAGE_TYPE = OSMO_GPRS_RLCMAC_UL_MSGT_PACKET_RESOURCE_REQUEST;
+	ack->PayloadType = GPRS_RLCMAC_PT_CONTROL_BLOCK;
+	ack->R = 0; /* MS sent channel request message once */
+
+	ack->DOWNLINK_TFI = dl_tbf->cur_alloc.dl_tfi;
+	gprs_rlcmac_enc_prepare_pkt_ack_nack_desc_gprs(&ack->Ack_Nack_Description, dl_tbf);
+
+	/* Channel Request Description */
+	if (gre->ul_tbf && gprs_rlcmac_tbf_ul_ass_pending(gre->ul_tbf)) {
+		Channel_Request_Description_t *chan_req = &ack->Channel_Request_Description;
+		ack->Exist_Channel_Request_Description = 1;
+		chan_req->PEAK_THROUGHPUT_CLASS = 0; /* TODO */
+		chan_req->RADIO_PRIORITY = 0; /* TODO */
+		chan_req->RLC_MODE = GPRS_RLCMAC_RLC_MODE_ACKNOWLEDGED;
+		chan_req->LLC_PDU_TYPE = GPRS_RLCMAC_LLC_PDU_TYPE_ACKNOWLEDGED;
+		chan_req->RLC_OCTET_COUNT = 0; /* TODO */
+	} else {
+		ack->Exist_Channel_Request_Description = 0;
+	}
+
+	gprs_rlcmac_enc_prepare_channel_quality_report(&ack->Channel_Quality_Report, dl_tbf);
+}
diff --git a/src/rlcmac/sched.c b/src/rlcmac/sched.c
index f229b7a..6a31f83 100644
--- a/src/rlcmac/sched.c
+++ b/src/rlcmac/sched.c
@@ -150,7 +150,7 @@
 	if (tbfs->poll_dl_ack_final_ack) {
 		LOGRLCMAC(LOGL_DEBUG, "(ts=%u,fn=%u,usf=%u) Tx DL ACK/NACK FinalAck=1\n",
 			  bi->ts, bi->fn, bi->usf);
-		msg = NULL; /* TODO: generate DL ACK/NACK ctrl block */
+		msg = gprs_rlcmac_dl_tbf_create_pkt_dl_ack_nack(tbfs->poll_dl_ack_final_ack);
 		if (msg)
 			return msg;
 	}
@@ -167,7 +167,7 @@
 	if (tbfs->poll_dl_ack) {
 		LOGRLCMAC(LOGL_DEBUG, "(ts=%u,fn=%u,usf=%u) Tx DL ACK/NACK\n",
 			  bi->ts, bi->fn, bi->usf);
-		msg = NULL; /* TODO: generate DL ACK/NACK ctrl block */
+		msg = gprs_rlcmac_dl_tbf_create_pkt_dl_ack_nack(tbfs->poll_dl_ack);
 		if (msg)
 			return msg;
 	}
diff --git a/src/rlcmac/tbf_dl.c b/src/rlcmac/tbf_dl.c
index da9b871..49f8187 100644
--- a/src/rlcmac/tbf_dl.c
+++ b/src/rlcmac/tbf_dl.c
@@ -24,6 +24,7 @@
 #include <osmocom/gprs/rlcmac/gre.h>
 #include <osmocom/gprs/rlcmac/rlc_window_dl.h>
 #include <osmocom/gprs/rlcmac/rlcmac_dec.h>
+#include <osmocom/gprs/rlcmac/rlcmac_enc.h>
 #include <osmocom/gprs/rlcmac/pdch_ul_controller.h>
 
 struct gprs_rlcmac_dl_tbf *gprs_rlcmac_dl_tbf_alloc(struct gprs_rlcmac_entity *gre)
@@ -105,6 +106,40 @@
 	return gprs_rlcmac_prim_call_down_cb(rlcmac_prim);
 }
 
+struct msgb *gprs_rlcmac_dl_tbf_create_pkt_dl_ack_nack(const struct gprs_rlcmac_dl_tbf *dl_tbf)
+{
+	struct msgb *msg;
+	struct bitvec bv;
+	RlcMacUplink_t ul_block;
+	int rc;
+
+	OSMO_ASSERT(dl_tbf);
+
+	msg = msgb_alloc(GSM_MACBLOCK_LEN, "pkt_dl_ack_nack");
+	if (!msg)
+		return NULL;
+
+	/* Initialize a bit vector that uses allocated msgb as the data buffer. */
+	bv = (struct bitvec){
+		.data = msgb_put(msg, GSM_MACBLOCK_LEN),
+		.data_len = GSM_MACBLOCK_LEN,
+	};
+	bitvec_unhex(&bv, GPRS_RLCMAC_DUMMY_VEC);
+
+	gprs_rlcmac_enc_prepare_pkt_downlink_ack_nack(&ul_block, dl_tbf);
+	rc = osmo_gprs_rlcmac_encode_uplink(&bv, &ul_block);
+	if (rc < 0) {
+		LOGPTBFDL(dl_tbf, LOGL_ERROR, "Encoding of Packet Downlink ACK/NACK failed (%d)\n", rc);
+		goto free_ret;
+	}
+
+	return msg;
+
+free_ret:
+	msgb_free(msg);
+	return NULL;
+}
+
 /*
  * Store received block data in LLC message(s) and forward to SGSN
  * if complete.
diff --git a/tests/rlcmac/rlcmac_prim_test.err b/tests/rlcmac/rlcmac_prim_test.err
index 2d1b804..d4c8250 100644
--- a/tests/rlcmac/rlcmac_prim_test.err
+++ b/tests/rlcmac/rlcmac_prim_test.err
@@ -54,5 +54,4 @@
 DLGLOBAL DEBUG Register POLL (TS=7 FN=21, reason=DL_ACK)
 DLGLOBAL INFO Rx from lower layers: L1CTL-PDCH_RTS.indication
 DLGLOBAL DEBUG (ts=7,fn=21,usf=0) Tx DL ACK/NACK FinalAck=1
-DLGLOBAL DEBUG (ts=7,fn=21,usf=0) No Uplink TBF available to transmit RLC/MAC Ul Data Block
-DLGLOBAL DEBUG (ts=7,fn=21,usf=0) No Uplink TBF available to transmit RLC/MAC Ul Dummy Ctrl Block
+DLGLOBAL DEBUG TBF(DL:NR-0:TLLI-00000001) - V(N): "IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIR" R=Received I=Invalid
diff --git a/tests/rlcmac/rlcmac_prim_test.ok b/tests/rlcmac/rlcmac_prim_test.ok
index 49b02b9..7823636 100644
--- a/tests/rlcmac/rlcmac_prim_test.ok
+++ b/tests/rlcmac/rlcmac_prim_test.ok
@@ -6,4 +6,5 @@
 === test_dl_tbf_ccch_assign start ===
 test_rlcmac_prim_down_cb(): Rx L1CTL-CFG_DL_TBF.request dl_tbf_nr=0 dl_slotmask=0x80 dl_tfi=0
 test_rlcmac_prim_up_cb(): Rx GRR-UNITDATA.indication TLLI=0x00000001 ll=[43 c0 01 2b 2b 2b ]
+test_rlcmac_prim_down_cb(): Rx L1CTL-PDCH_DATA.request fn=21 ts=7 data_len=23 data=[40 14 00 00 00 00 00 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b ]
 === test_dl_tbf_ccch_assign end ===

