bsc: Introduce a local MSC type and forbid it from being selected

openbsc/include/openbsc/osmo_msc_data.h

@@ -35,12 +35,19 @@ struct gsm_audio_support {
                 ver : 7;
 };
 
+enum {
+	MSC_CON_TYPE_NORMAL,
+	MSC_CON_TYPE_LOCAL,
+};
+
 struct osmo_msc_data {
 	struct llist_head entry;
 
 	/* Back pointer */
 	struct gsm_network *network;
 
+	int type;
+
 	/* Connection data */
 	char *bsc_token;
 	int ping_timeout;

openbsc/src/osmo-bsc/osmo_bsc_filter.c

@@ -142,6 +142,8 @@ round_robin:
 	llist_for_each_entry(msc, &bsc->mscs, entry) {
 		if (!msc->msc_con->is_authenticated)
 			continue;
+		if (msc->type != MSC_CON_TYPE_NORMAL)
+			continue;
 
 		/* force round robin by moving it to the end */
 		llist_move_tail(&msc->entry, &bsc->mscs);