Add function to update TRAU muxer after assignment or handover

E1 based BTS use TRAU muxer to decode TRAU frames. After changing
channel from one timeslot to another (due to handover or assignment),
the TRAU muxer must be updated. The call reference of the call is
disconnected from the old channel and connected to the new channel.

openbsc/include/openbsc/gsm_data.h

@@ -382,6 +382,20 @@ static inline int is_nokia_bts(struct gsm_bts *bts)
 	return 0;
 }
 
+static inline int is_e1_bts(struct gsm_bts *bts)
+{
+	switch (bts->type) {
+	case GSM_BTS_TYPE_BS11:
+	case GSM_BTS_TYPE_RBS2000:
+	case GSM_BTS_TYPE_NOKIA_SITE:
+		return 1;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
 enum gsm_auth_policy gsm_auth_policy_parse(const char *arg);
 const char *gsm_auth_policy_name(enum gsm_auth_policy policy);
 

openbsc/include/openbsc/trau_mux.h

@@ -51,6 +51,9 @@ int trau_recv_lchan(struct gsm_lchan *lchan, uint32_t callref);
 /* send trau from application */
 int trau_send_frame(struct gsm_lchan *lchan, struct gsm_data_frame *frame);
 
+/* switch trau muxer to new lchan */
+int switch_trau_mux(struct gsm_lchan *old_lchan, struct gsm_lchan *new_lchan);
+
 /* callback invoked if we receive TRAU frames */
 int subch_cb(struct subch_demux *dmx, int ch, uint8_t *data, int len, void *_priv);
 

openbsc/src/libbsc/bsc_api.c

@@ -31,6 +31,7 @@
 #include <openbsc/handover.h>
 #include <openbsc/debug.h>
 #include <openbsc/gsm_04_08.h>
+#include <openbsc/trau_mux.h>
 
 #include <osmocom/gsm/protocol/gsm_08_08.h>
 
@@ -419,6 +420,10 @@ static void handle_ass_compl(struct gsm_subscriber_connection *conn,
 		return;
 	}
 
+	/* switch TRAU muxer for E1 based BTS from one channel to another */
+	if (is_e1_bts(conn->bts))
+		switch_trau_mux(conn->lchan, conn->secondary_lchan);
+
 	/* swap channels */
 	osmo_timer_del(&conn->T10);
 

openbsc/src/libbsc/handover_logic.c

@@ -39,6 +39,7 @@
 #include <openbsc/signal.h>
 #include <osmocom/core/talloc.h>
 #include <openbsc/transaction.h>
+#include <openbsc/trau_mux.h>
 
 struct bsc_handover {
 	struct llist_head list;
@@ -264,6 +265,10 @@ static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
 
 	osmo_timer_del(&ho->T3103);
 
+	/* switch TRAU muxer for E1 based BTS from one channel to another */
+	if (is_e1_bts(new_lchan->conn->bts))
+		switch_trau_mux(ho->old_lchan, new_lchan);
+
 	/* Replace the ho lchan with the primary one */
 	if (ho->old_lchan != new_lchan->conn->lchan)
 		LOGP(DHO, LOGL_ERROR, "Primary lchan changed during handover.\n");
@@ -278,8 +283,6 @@ static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
 	rsl_lchan_set_state(ho->old_lchan, LCHAN_S_INACTIVE);
 	lchan_release(ho->old_lchan, 0, RSL_REL_LOCAL_END);
 
-	/* do something to re-route the actual speech frames ! */
-
 	llist_del(&ho->list);
 	talloc_free(ho);
 

openbsc/src/libmsc/gsm_04_08.c

@@ -1648,6 +1648,9 @@ static int tch_recv_mncc(struct gsm_network *net, uint32_t callref, int enable)
 	lchan = trans->conn->lchan;
 	bts = lchan->ts->trx->bts;
 
+	/* store receive state */
+	trans->tch_recv = enable;
+
 	switch (bts->type) {
 	case GSM_BTS_TYPE_NANOBTS:
 	case GSM_BTS_TYPE_OSMO_SYSMO:
@@ -1655,10 +1658,12 @@ static int tch_recv_mncc(struct gsm_network *net, uint32_t callref, int enable)
 			LOGP(DCC, LOGL_ERROR, "Error: RTP proxy is disabled\n");
 			return -EINVAL;
 		}
-		/* in case, we don't have a RTP socket yet, we note this
-		 * in the transaction and try later */
+		/* In case, we don't have a RTP socket to the BTS yet, the BTS
+		 * will not be connected to our RTP proxy and the socket will
+		 * not be assigned to the application interface. This method
+		 * will be called again, once the audio socket is created and
+		 * connected. */
 		if (!lchan->abis_ip.rtp_socket) {
-			trans->tch_recv = enable;
 			DEBUGP(DCC, "queue tch_recv_mncc request (%d)\n", enable);
 			return 0;
 		}
@@ -1677,6 +1682,14 @@ static int tch_recv_mncc(struct gsm_network *net, uint32_t callref, int enable)
 	case GSM_BTS_TYPE_BS11:
 	case GSM_BTS_TYPE_RBS2000:
 	case GSM_BTS_TYPE_NOKIA_SITE:
+		/* In case we don't have a TCH with correct mode, the TRAU muxer
+		 * will not be asigned to the application interface. This is
+		 * performed by switch_trau_mux() after successful handover or
+		 * assignment. */
+		if (lchan->tch_mode == GSM48_CMODE_SIGN) {
+			DEBUGP(DCC, "queue tch_recv_mncc request (%d)\n", enable);
+			return 0;
+		}
 		if (enable)
 			return trau_recv_lchan(lchan, callref);
 		return trau_mux_unmap(NULL, callref);

openbsc/src/libtrau/trau_mux.c

@@ -31,6 +31,7 @@
 #include <osmocom/core/talloc.h>
 #include <openbsc/trau_upqueue.h>
 #include <osmocom/core/crcgen.h>
+#include <openbsc/transaction.h>
 
 /* this corresponds to the bit-lengths of the individual codec
  * parameters as indicated in Table 1.1 of TS 06.10 */
@@ -518,3 +519,20 @@ int trau_send_frame(struct gsm_lchan *lchan, struct gsm_data_frame *frame)
 	return subchan_mux_enqueue(mx, dst_e1_ss->e1_ts_ss, trau_bits_out,
 				   TRAU_FRAME_BITS);
 }
+
+/* switch trau muxer to new lchan */
+int switch_trau_mux(struct gsm_lchan *old_lchan, struct gsm_lchan *new_lchan)
+{
+	struct gsm_network *net = old_lchan->ts->trx->bts->network;
+	struct gsm_trans *trans;
+
+	/* look up transaction with TCH frame receive enabled */
+	llist_for_each_entry(trans, &net->trans_list, entry) {
+		if (trans->conn && trans->conn->lchan == old_lchan && trans->tch_recv) {
+			/* switch */
+			trau_recv_lchan(new_lchan, trans->callref);
+		}
+	}
+
+	return 0;
+}