fix / clarify rsl dtap cache

In certain situations like handover or assignment, DTAP must not go out via RSL
directly but is cached to be submitted later. Make sure that all RSL DTAP
sending adheres to this:

gscon_submit_rsl_dtap() is the new "public" API to request an RSL DTAP to be
sent. Depending on the gscon's state, this ends up in the cache or is sent
directly. When caching, there is no way to tell whether sending will succeed or
not, so semantically it does not make sense to even return a result code. Just
return void. Change all "public" callers to gscon_submit_rsl_dtap().

Merge gsm0808_submit_dtap() and submit_dtap() guts to gsm0808_send_rsl_dtap(),
static in bsc_subscr_conn_fsm.c: directly send DTAP, assume a conn->lchan to be
present, or otherwise trigger a BSSMAP Clear Request.

The static submit_dtap() becomes a thin convenience wrapper.

Move ho_dtap_cache* functions to bsc_subscr_conn_fsm.c and rename to
gscon_dtap_cache_* -- they are not only for handover, also for assignment.

Function gsm0808_submit_dtap() m
Introduce function gscon_submit_rsl_dtap()

Change-Id: I6ffd7aa641c8905292c769400048c96aa0949585

6 files changed, 175 insertions, 158 deletions

diff --git a/src/osmo-bsc/bsc_api.c b/src/osmo-bsc/bsc_api.c
index 4cf11a466..35e697769 100644
--- a/src/osmo-bsc/bsc_api.c
+++ b/src/osmo-bsc/bsc_api.c
@@ -33,6 +33,7 @@
 #include <osmocom/bsc/bsc_subscriber.h>
 #include <osmocom/bsc/penalty_timers.h>
 #include <osmocom/bsc/osmo_bsc_sigtran.h>
+#include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 
 #include <osmocom/gsm/protocol/gsm_08_08.h>
 #include <osmocom/gsm/gsm48.h>
@@ -41,10 +42,6 @@
 
 #define GSM0808_T10_VALUE    6, 0
 
-#define HO_DTAP_CACHE_MSGB_CB_LINK_ID 0
-#define HO_DTAP_CACHE_MSGB_CB_ALLOW_SACCH 1
-
-static void rll_ind_cb(struct gsm_lchan *, uint8_t, void *, enum bsc_rllr_ind);
 static void handle_release(struct gsm_subscriber_connection *conn, struct  gsm_lchan *lchan);
 static void handle_chan_ack(struct gsm_subscriber_connection *conn, struct  gsm_lchan *lchan);
 static void handle_chan_nack(struct gsm_subscriber_connection *conn, struct  gsm_lchan *lchan);
@@ -116,97 +113,6 @@ static int handle_new_assignment(struct gsm_subscriber_connection *conn, int cha
 	return 0;
 }
 
-static void ho_dtap_cache_add(struct gsm_subscriber_connection *conn, struct msgb *msg,
-			      int link_id, bool allow_sacch)
-{
-	if (conn->ho_dtap_cache_len >= 23) {
-		LOGP(DHO, LOGL_ERROR, "%s: Cannot cache more DTAP messages,"
-		     " already reached sane maximum of %u cached messages\n",
-		     bsc_subscr_name(conn->bsub), conn->ho_dtap_cache_len);
-		msgb_free(msg);
-		return;
-	}
-	conn->ho_dtap_cache_len ++;
-	LOGP(DHO, LOGL_DEBUG, "%s: Caching DTAP message during ho/ass (%u)\n",
-	     bsc_subscr_name(conn->bsub), conn->ho_dtap_cache_len);
-	msg->cb[HO_DTAP_CACHE_MSGB_CB_LINK_ID] = (unsigned long)link_id;
-	msg->cb[HO_DTAP_CACHE_MSGB_CB_ALLOW_SACCH] = allow_sacch ? 1 : 0;
-	msgb_enqueue(&conn->ho_dtap_cache, msg);
-}
-
-void ho_dtap_cache_flush(struct gsm_subscriber_connection *conn, int send)
-{
-	struct msgb *msg;
-	unsigned int flushed_count = 0;
-
-	if (conn->secondary_lchan || conn->ho) {
-		LOGP(DHO, LOGL_ERROR, "%s: Cannot send cached DTAP messages, handover/assignment is still ongoing\n",
-		     bsc_subscr_name(conn->bsub));
-		send = 0;
-	}
-
-	while ((msg = msgb_dequeue(&conn->ho_dtap_cache))) {
-		conn->ho_dtap_cache_len --;
-		flushed_count ++;
-		if (send) {
-			int link_id = (int)msg->cb[HO_DTAP_CACHE_MSGB_CB_LINK_ID];
-			bool allow_sacch = !!msg->cb[HO_DTAP_CACHE_MSGB_CB_ALLOW_SACCH];
-			LOGP(DHO, LOGL_DEBUG, "%s: Sending cached DTAP message after handover/assignment (%u/%u)\n",
-			     bsc_subscr_name(conn->bsub), flushed_count, conn->ho_dtap_cache_len);
-			gsm0808_submit_dtap(conn, msg, link_id, allow_sacch);
-		} else
-			msgb_free(msg);
-	}
-}
-
-/*! \brief process incoming 08.08 DTAP from MSC (send via BTS to MS) */
-int gsm0808_submit_dtap(struct gsm_subscriber_connection *conn,
-			struct msgb *msg, int link_id, int allow_sacch)
-{
-	uint8_t sapi;
-
-
-	if (!conn->lchan) {
-		LOGP(DMSC, LOGL_ERROR,
-		     "%s Called submit dtap without an lchan.\n",
-		     bsc_subscr_name(conn->bsub));
-		msgb_free(msg);
-		return -1;
-	}
-
-	/* buffer message during assignment / handover */
-	if (conn->secondary_lchan || conn->ho) {
-		ho_dtap_cache_add(conn, msg, link_id, !! allow_sacch);
-		return 0;
-	}
-
-	sapi = link_id & 0x7;
-	msg->lchan = conn->lchan;
-	msg->dst = msg->lchan->ts->trx->rsl_link;
-
-	/* If we are on a TCH and need to submit a SMS (on SAPI=3) we need to use the SACH */
-	if (allow_sacch && sapi != 0) {
-		if (conn->lchan->type == GSM_LCHAN_TCH_F || conn->lchan->type == GSM_LCHAN_TCH_H)
-			link_id |= 0x40;
-	}
-
-	msg->l3h = msg->data;
-	/* is requested SAPI already up? */
-	if (conn->lchan->sapis[sapi] == LCHAN_SAPI_UNUSED) {
-		/* Establish L2 for additional SAPI */
-		OBSC_LINKID_CB(msg) = link_id;
-		if (rll_establish(msg->lchan, sapi, rll_ind_cb, msg) != 0) {
-			msgb_free(msg);
-			bsc_sapi_n_reject(conn, link_id);
-			return -1;
-		}
-		return 0;
-	} else {
-		/* Directly forward via RLL/RSL to BTS */
-		return rsl_data_request(msg, link_id);
-	}
-}
-
 /*
  * \brief Check if the given channel is compatible with the mode/fullrate
  */
@@ -316,7 +222,7 @@ static void handle_ass_compl(struct gsm_subscriber_connection *conn,
 		/* FIXME: release old channel */
 
 		/* send pending messages, if any */
-		ho_dtap_cache_flush(conn, 1);
+		gscon_dtap_queue_flush(conn, 1);
 
 		return;
 	}
@@ -332,7 +238,7 @@ static void handle_ass_compl(struct gsm_subscriber_connection *conn,
 	conn->secondary_lchan = NULL;
 
 	/* send pending messages, if any */
-	ho_dtap_cache_flush(conn, 1);
+	gscon_dtap_queue_flush(conn, 1);
 
 	if (is_ipaccess_bts(conn_get_bts(conn)) && conn->lchan->tch_mode != GSM48_CMODE_SIGN)
 		rsl_ipacc_crcx(conn->lchan);
@@ -359,7 +265,7 @@ static void handle_ass_fail(struct gsm_subscriber_connection *conn,
 		/* FIXME: release allocated new channel */
 
 		/* send pending messages, if any */
-		ho_dtap_cache_flush(conn, 1);
+		gscon_dtap_queue_flush(conn, 1);
 
 		return;
 	}
@@ -377,7 +283,7 @@ static void handle_ass_fail(struct gsm_subscriber_connection *conn,
 	}
 
 	/* send pending messages, if any */
-	ho_dtap_cache_flush(conn, 1);
+	gscon_dtap_queue_flush(conn, 1);
 
 	gh = msgb_l3(msg);
 	if (msgb_l3len(msg) - sizeof(*gh) != 1) {
@@ -443,7 +349,7 @@ static void handle_rr_ho_compl(struct msgb *msg)
 	/* FIXME: release old channel */
 
 	/* send pending messages, if any */
-	ho_dtap_cache_flush(msg->lchan->conn, 1);
+	gscon_dtap_queue_flush(msg->lchan->conn, 1);
 }
 
 /* Chapter 9.1.17 Handover Failure */
@@ -465,7 +371,7 @@ static void handle_rr_ho_fail(struct msgb *msg)
 	/* FIXME: release allocated new channel */
 
 	/* send pending messages, if any */
-	ho_dtap_cache_flush(msg->lchan->conn, 1);
+	gscon_dtap_queue_flush(msg->lchan->conn, 1);
 }
 
 
@@ -643,31 +549,6 @@ int gsm0808_clear(struct gsm_subscriber_connection *conn)
 	return 0;
 }
 
-static void rll_ind_cb(struct gsm_lchan *lchan, uint8_t link_id, void *_data, enum bsc_rllr_ind rllr_ind)
-{
-	struct msgb *msg = _data;
-
-	/*
-	 * There seems to be a small window that the RLL timer can
-	 * fire after a lchan_release call and before the S_CHALLOC_FREED
-	 * is called. Check if a conn is set before proceeding.
-	 */
-	if (!lchan->conn)
-		return;
-
-	switch (rllr_ind) {
-	case BSC_RLLR_IND_EST_CONF:
-		rsl_data_request(msg, OBSC_LINKID_CB(msg));
-		break;
-	case BSC_RLLR_IND_REL_IND:
-	case BSC_RLLR_IND_ERR_IND:
-	case BSC_RLLR_IND_TIMEOUT:
-		bsc_sapi_n_reject(lchan->conn, OBSC_LINKID_CB(msg));
-		msgb_free(msg);
-		break;
-	}
-}
-
 static int bsc_handle_lchan_signal(unsigned int subsys, unsigned int signal,
 				   void *handler_data, void *signal_data)
 {
diff --git a/src/osmo-bsc/bsc_init.c b/src/osmo-bsc/bsc_init.c
index 1fe484761..641b6db4b 100644
--- a/src/osmo-bsc/bsc_init.c
+++ b/src/osmo-bsc/bsc_init.c
@@ -35,6 +35,7 @@
 #include <osmocom/bsc/bsc_msc_data.h>
 #include <osmocom/bsc/handover_cfg.h>
 #include <osmocom/bsc/gsm_04_08_utils.h>
+#include <osmocom/bsc/neighbor_ident.h>
 
 #include <time.h>
 #include <limits.h>
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index 66cdbbafc..32492707c 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -34,6 +34,8 @@
 #include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 #include <osmocom/bsc/osmo_bsc.h>
 #include <osmocom/bsc/penalty_timers.h>
+#include <osmocom/bsc/bsc_rll.h>
+#include <osmocom/bsc/abis_rsl.h>
 #include <osmocom/mgcp_client/mgcp_client_fsm.h>
 #include <osmocom/core/byteswap.h>
 
@@ -145,6 +147,16 @@ void bsc_subscr_pick_codec(struct mgcp_conn_peer *conn_peer, struct gsm_subscrib
 	}
 }
 
+/* forward MT DTAP from BSSAP side to RSL side */
+static inline void submit_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg,
+			       struct osmo_fsm_inst *fi)
+{
+	OSMO_ASSERT(fi);
+	OSMO_ASSERT(msg);
+	OSMO_ASSERT(conn);
+	gscon_submit_rsl_dtap(conn, msg, OBSC_LINKID_CB(msg), 1);
+}
+
 /* Send data SCCP message through SCCP connection. All sigtran messages
  * that are send from this FSM must use this function. Never use
  * osmo_bsc_sigtran_send() directly since this would defeat the checks
@@ -256,26 +268,6 @@ static void send_ass_compl(struct gsm_lchan *lchan, struct osmo_fsm_inst *fi, bo
 	sigtran_send(conn, resp, fi);
 }
 
-/* forward MT DTAP from BSSAP side to RSL side */
-static void submit_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg, struct osmo_fsm_inst *fi)
-{
-	int rc;
-	struct msgb *resp = NULL;
-
-	OSMO_ASSERT(fi);
-	OSMO_ASSERT(msg);
-	OSMO_ASSERT(conn);
-
-	rc = gsm0808_submit_dtap(conn, msg, OBSC_LINKID_CB(msg), 1);
-	if (rc != 0) {
-		LOGPFSML(fi, LOGL_ERROR, "Tx BSSMAP CLEAR REQUEST to MSC\n");
-		resp = gsm0808_create_clear_rqst(GSM0808_CAUSE_EQUIPMENT_FAILURE);
-		sigtran_send(conn, resp, fi);
-		osmo_fsm_inst_state_chg(fi, ST_ACTIVE, 0, 0);
-		return;
-	}
-}
-
 /* forward MO DTAP from RSL side to BSSAP side */
 static void forward_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg, struct osmo_fsm_inst *fi)
 {
@@ -1005,8 +997,6 @@ static void gscon_fsm_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *d
 	}
 }
 
-void ho_dtap_cache_flush(struct gsm_subscriber_connection *conn, int send);
-
 static void gscon_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cause)
 {
 	struct gsm_subscriber_connection *conn = fi->priv;
@@ -1037,7 +1027,7 @@ static void gscon_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause cau
 	}
 
 	/* drop pending messages */
-	ho_dtap_cache_flush(conn, 0);
+	gscon_dtap_queue_flush(conn, 0);
 
 	penalty_timers_free(&conn->hodec2.penalty_timers);
 
@@ -1130,7 +1120,7 @@ struct gsm_subscriber_connection *bsc_subscr_con_allocate(struct gsm_network *ne
 		return NULL;
 
 	conn->network = net;
-	INIT_LLIST_HEAD(&conn->ho_dtap_cache);
+	INIT_LLIST_HEAD(&conn->dtap_queue);
 	/* BTW, penalty timers will be initialized on-demand. */
 	conn->sccp.conn_id = -1;
 
@@ -1155,3 +1145,143 @@ struct gsm_subscriber_connection *bsc_subscr_con_allocate(struct gsm_network *ne
 	llist_add_tail(&conn->entry, &net->subscr_conns);
 	return conn;
 }
+
+static void gsm0808_send_rsl_dtap(struct gsm_subscriber_connection *conn,
+				  struct msgb *msg, int link_id, int allow_sacch);
+
+#define GSCON_DTAP_QUEUE_MSGB_CB_LINK_ID 0
+#define GSCON_DTAP_QUEUE_MSGB_CB_ALLOW_SACCH 1
+
+static void gscon_dtap_queue_add(struct gsm_subscriber_connection *conn, struct msgb *msg,
+				 int link_id, bool allow_sacch)
+{
+	if (conn->dtap_queue_len >= 8) {
+		LOGP(DMSC, LOGL_ERROR, "%s: Cannot queue more DTAP messages,"
+		     " already reached sane maximum of %u queued messages\n",
+		     bsc_subscr_name(conn->bsub), conn->dtap_queue_len);
+		msgb_free(msg);
+		return;
+	}
+	conn->dtap_queue_len ++;
+	LOGP(DMSC, LOGL_DEBUG, "%s: Queueing DTAP message during handover/assignment (%u)\n",
+	     bsc_subscr_name(conn->bsub), conn->dtap_queue_len);
+	msg->cb[GSCON_DTAP_QUEUE_MSGB_CB_LINK_ID] = (unsigned long)link_id;
+	msg->cb[GSCON_DTAP_QUEUE_MSGB_CB_ALLOW_SACCH] = allow_sacch ? 1 : 0;
+	msgb_enqueue(&conn->dtap_queue, msg);
+}
+
+void gscon_dtap_queue_flush(struct gsm_subscriber_connection *conn, int send)
+{
+	struct msgb *msg;
+	unsigned int flushed_count = 0;
+
+	if (conn->secondary_lchan || conn->ho) {
+		LOGP(DMSC, LOGL_ERROR, "%s: Cannot send queued DTAP messages, handover/assignment is still ongoing\n",
+		     bsc_subscr_name(conn->bsub));
+		send = 0;
+	}
+
+	while ((msg = msgb_dequeue(&conn->dtap_queue))) {
+		conn->dtap_queue_len --;
+		flushed_count ++;
+		if (send) {
+			int link_id = (int)msg->cb[GSCON_DTAP_QUEUE_MSGB_CB_LINK_ID];
+			bool allow_sacch = !!msg->cb[GSCON_DTAP_QUEUE_MSGB_CB_ALLOW_SACCH];
+			LOGP(DMSC, LOGL_DEBUG, "%s: Sending queued DTAP message after handover/assignment (%u/%u)\n",
+			     bsc_subscr_name(conn->bsub), flushed_count, conn->dtap_queue_len);
+			gsm0808_send_rsl_dtap(conn, msg, link_id, allow_sacch);
+		} else
+			msgb_free(msg);
+	}
+}
+
+static void rll_ind_cb(struct gsm_lchan *lchan, uint8_t link_id, void *_data, enum bsc_rllr_ind rllr_ind)
+{
+	struct msgb *msg = _data;
+
+	/*
+	 * There seems to be a small window that the RLL timer can
+	 * fire after a lchan_release call and before the S_CHALLOC_FREED
+	 * is called. Check if a conn is set before proceeding.
+	 */
+	if (!lchan->conn)
+		return;
+
+	switch (rllr_ind) {
+	case BSC_RLLR_IND_EST_CONF:
+		rsl_data_request(msg, OBSC_LINKID_CB(msg));
+		break;
+	case BSC_RLLR_IND_REL_IND:
+	case BSC_RLLR_IND_ERR_IND:
+	case BSC_RLLR_IND_TIMEOUT:
+		bsc_sapi_n_reject(lchan->conn, OBSC_LINKID_CB(msg));
+		msgb_free(msg);
+		break;
+	}
+}
+
+/*! \brief process incoming 08.08 DTAP from MSC (send via BTS to MS) */
+static void gsm0808_send_rsl_dtap(struct gsm_subscriber_connection *conn,
+				  struct msgb *msg, int link_id, int allow_sacch)
+{
+	uint8_t sapi;
+	int rc;
+	struct msgb *resp = NULL;
+
+	if (!conn->lchan) {
+		LOGP(DMSC, LOGL_ERROR,
+		     "%s Called submit dtap without an lchan.\n",
+		     bsc_subscr_name(conn->bsub));
+		msgb_free(msg);
+		rc = -EINVAL;
+		goto failed_to_send;
+	}
+
+	sapi = link_id & 0x7;
+	msg->lchan = conn->lchan;
+	msg->dst = msg->lchan->ts->trx->rsl_link;
+
+	/* If we are on a TCH and need to submit a SMS (on SAPI=3) we need to use the SACH */
+	if (allow_sacch && sapi != 0) {
+		if (conn->lchan->type == GSM_LCHAN_TCH_F || conn->lchan->type == GSM_LCHAN_TCH_H)
+			link_id |= 0x40;
+	}
+
+	msg->l3h = msg->data;
+	/* is requested SAPI already up? */
+	if (conn->lchan->sapis[sapi] == LCHAN_SAPI_UNUSED) {
+		/* Establish L2 for additional SAPI */
+		OBSC_LINKID_CB(msg) = link_id;
+		rc = rll_establish(msg->lchan, sapi, rll_ind_cb, msg);
+		if (rc) {
+			msgb_free(msg);
+			bsc_sapi_n_reject(conn, link_id);
+			goto failed_to_send;
+		}
+		return;
+	} else {
+		/* Directly forward via RLL/RSL to BTS */
+		rc = rsl_data_request(msg, link_id);
+		if (rc)
+			goto failed_to_send;
+	}
+	return;
+
+failed_to_send:
+	LOGPFSML(conn->fi, LOGL_ERROR, "Tx BSSMAP CLEAR REQUEST to MSC\n");
+	resp = gsm0808_create_clear_rqst(GSM0808_CAUSE_EQUIPMENT_FAILURE);
+	sigtran_send(conn, resp, conn->fi);
+	osmo_fsm_inst_state_chg(conn->fi, ST_ACTIVE, 0, 0);
+}
+
+void gscon_submit_rsl_dtap(struct gsm_subscriber_connection *conn,
+			   struct msgb *msg, int link_id, int allow_sacch)
+{
+	/* buffer message during assignment / handover */
+	if (conn->secondary_lchan || conn->ho) {
+		gscon_dtap_queue_add(conn, msg, link_id, !! allow_sacch);
+		return;
+	}
+
+	gsm0808_send_rsl_dtap(conn, msg, link_id, allow_sacch);
+}
diff --git a/src/osmo-bsc/gsm_04_08_utils.c b/src/osmo-bsc/gsm_04_08_utils.c
index e9aeb550f..c54850081 100644
--- a/src/osmo-bsc/gsm_04_08_utils.c
+++ b/src/osmo-bsc/gsm_04_08_utils.c
@@ -34,7 +34,7 @@
 #include <osmocom/bsc/debug.h>
 #include <osmocom/bsc/paging.h>
 #include <osmocom/bsc/signal.h>
-#include <osmocom/bsc/bsc_api.h>
+#include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 #include <osmocom/bsc/gsm_04_08_utils.h>
 
 /* should ip.access BTS use direct RTP streams between each other (1),
@@ -600,7 +600,8 @@ int gsm48_tx_mm_serv_ack(struct gsm_subscriber_connection *conn)
 
 	DEBUGP(DMM, "-> CM SERVICE ACK\n");
 
-	return gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
+	return 0;
 }
 
 /* 9.2.6 CM service reject */
@@ -617,7 +618,8 @@ int gsm48_tx_mm_serv_rej(struct gsm_subscriber_connection *conn,
 
 	DEBUGP(DMM, "-> CM SERVICE Reject cause: %d\n", value);
 
-	return gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
+	return 0;
 }
 
 /* 9.1.29 RR Status */
@@ -644,7 +646,8 @@ int gsm48_tx_rr_status(struct gsm_subscriber_connection *conn, uint8_t cause)
 	struct msgb *msg = gsm48_create_rr_status(cause);
 	if (!msg)
 		return -1;
-	return gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
+	return 0;
 }
 
 struct msgb *gsm48_create_mm_serv_rej(enum gsm48_reject_value value)
diff --git a/src/osmo-bsc/gsm_04_80_utils.c b/src/osmo-bsc/gsm_04_80_utils.c
index d67f3c568..8de1262e9 100644
--- a/src/osmo-bsc/gsm_04_80_utils.c
+++ b/src/osmo-bsc/gsm_04_80_utils.c
@@ -20,7 +20,7 @@
  */
 
 #include <osmocom/gsm/gsm0480.h>
-#include <osmocom/bsc/bsc_api.h>
+#include <osmocom/bsc/bsc_subscr_conn_fsm.h>
 
 int bsc_send_ussd_notify(struct gsm_subscriber_connection *conn, int level,
 			 const char *text)
@@ -28,7 +28,8 @@ int bsc_send_ussd_notify(struct gsm_subscriber_connection *conn, int level,
 	struct msgb *msg = gsm0480_create_ussd_notify(level, text);
 	if (!msg)
 		return -1;
-	return gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
+	return 0;
 }
 
 int bsc_send_ussd_release_complete(struct gsm_subscriber_connection *conn)
@@ -36,5 +37,6 @@ int bsc_send_ussd_release_complete(struct gsm_subscriber_connection *conn)
 	struct msgb *msg = gsm0480_create_ussd_release_complete();
 	if (!msg)
 		return -1;
-	return gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
+	return 0;
 }
diff --git a/src/osmo-bsc/osmo_bsc_api.c b/src/osmo-bsc/osmo_bsc_api.c
index a86b4f99e..d409c9350 100644
--- a/src/osmo-bsc/osmo_bsc_api.c
+++ b/src/osmo-bsc/osmo_bsc_api.c
@@ -86,7 +86,7 @@ static void bsc_maybe_lu_reject(struct gsm_subscriber_connection *conn, int con_
 	}
 
 	msg->lchan = conn->lchan;
-	gsm0808_submit_dtap(conn, msg, 0, 0);
+	gscon_submit_rsl_dtap(conn, msg, 0, 0);
 }
 
 static int bsc_filter_initial(struct osmo_bsc_data *bsc,