libmsc: Add a function to return a unique ID of the subscriber conn

The ID will include the type of connection (GERAN_A, UTRAN_IU) followed
by the SCCP conn_id.
This can be used for the fsm instance ID before we know the IMSI.

Change-Id: I4b875772e3994ad3458ee60dbf880604486d9afd

include/osmocom/msc/osmo_msc.h

@@ -54,6 +54,7 @@ enum msc_compl_l3_rc {
 	MSC_CONN_REJECT = 1,
 };
 
+char *msc_subscr_conn_get_conn_id(struct gsm_subscriber_connection *conn);
 int msc_create_conn_fsm(struct gsm_subscriber_connection *conn, const char *id);
 
 int msc_vlr_alloc(struct gsm_network *net);

src/libmsc/subscr_conn.c

@@ -31,6 +31,7 @@
 #include <osmocom/msc/transaction.h>
 #include <osmocom/msc/signal.h>
 #include <osmocom/msc/a_iface.h>
+#include <osmocom/msc/iucs.h>
 
 #define SUBSCR_CONN_TIMEOUT 5 /* seconds */
 
@@ -303,6 +304,25 @@ static struct osmo_fsm subscr_conn_fsm = {
 	.timer_cb = subscr_conn_fsm_timeout,
 };
 
+char *msc_subscr_conn_get_conn_id(struct gsm_subscriber_connection *conn)
+{
+	char *id;
+
+	switch (conn->via_ran) {
+	case RAN_GERAN_A:
+		id = talloc_asprintf(conn, "GERAN_A-%08x", conn->a.conn_id);
+		break;
+	case RAN_UTRAN_IU:
+		id = talloc_asprintf(conn, "UTRAN_IU-%08x", iu_get_conn_id(conn->iu.ue_ctx));
+		break;
+	default:
+		LOGP(DMM, LOGL_ERROR, "RAN of conn %p unknown!\n", conn);
+		return NULL;
+	}
+
+	return id;
+}
+
 int msc_create_conn_fsm(struct gsm_subscriber_connection *conn, const char *id)
 {
 	struct osmo_fsm_inst *fi;