Added support for slot stealing

Slot stealing is how a traffic slot can be partially or fully "stolen" by a control channel. This patch adds support for that and maintains the stealing status in the tetra_mac_state. This can be used to prevent passing a signalling half slot to the voice decoder.

Change-Id: I01a112e6e74f75401649d358b8f98c6248d2522b
---
M src/lower_mac/tetra_lower_mac.c
M src/tetra_common.h
2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/lower_mac/tetra_lower_mac.c b/src/lower_mac/tetra_lower_mac.c
index 2a2cbbe..907f1dc 100644
--- a/src/lower_mac/tetra_lower_mac.c
+++ b/src/lower_mac/tetra_lower_mac.c
@@ -186,8 +186,14 @@
 	DEBUGP("%s %s type4: %s\n", tbp->name, time_str,
 		osmo_ubit_dump(type4, tbp->type345_bits));
 
+	/* Handle block 1 slot stealing, see clause 19.4.4 */
+	/* Block 1 is stolen if AACH says slot is traffic and burst used training sequence 1 */
+	/* Block 2 is stolen if indicated in stolen block 1 resource len (-2) */
+	if (tms->cur_burst.is_traffic && type == TPSAP_T_NDB && blk_num == BLK_1)
+		tms->cur_burst.blk1_stolen = true;
+
 	/* If this is a traffic channel, dump. */
-	if ((type == TPSAP_T_SCH_F) && tms->cur_burst.is_traffic && tms->dumpdir) {
+	if (tms->cur_burst.is_traffic && (type == TPSAP_T_SCH_F || (blk_num == BLK_2 && !tms->cur_burst.blk2_stolen))) {
 		char fname[PATH_MAX];
 		int16_t block[690];
 		FILE *f;
@@ -229,6 +235,7 @@
 		f = fopen(fname, "a");
 		fprintf(f, "%d\n", tms->ssi);
 		fclose(f);
+		goto out;
 	}
 
 	if (tbp->interleave_a) {
@@ -333,6 +340,7 @@
 		msg->l4h = 0;
 	}
 
+out:
 	talloc_free(msg);
 	talloc_free(ttp);
 }
diff --git a/src/tetra_common.h b/src/tetra_common.h
index dc538d0..3296a3f 100644
--- a/src/tetra_common.h
+++ b/src/tetra_common.h
@@ -3,8 +3,12 @@
 
 #include <stdint.h>
 #include "tetra_mac_pdu.h"
+#include <stdbool.h>
 #include <osmocom/core/linuxlist.h>
 
+#include "tetra_common.h"
+#include "tetra_mac_pdu.h"
+
 #ifdef DEBUG
 #define DEBUGP(x, args...)	printf(x, ## args)
 #else
@@ -46,12 +50,16 @@
 	struct llist_head voice_channels;
 	struct {
 		int is_traffic;
+		bool blk1_stolen;
+		bool blk2_stolen;
 	} cur_burst;
 	struct tetra_si_decoded last_sid;
 
 	char *dumpdir;	/* Where to save traffic channel dump */
 	int ssi;	/* SSI */
 	int tsn;	/* Timeslon number */
+	int usage_marker; /* Usage marker (if addressed)*/
+	int addr_type;
 };
 
 void tetra_mac_state_init(struct tetra_mac_state *tms);

