bsc: Select a MSC in a round-robin fashion

Select a MSC, add it to the back of the list after we have
selected it.

1 files changed, 28 insertions, 1 deletions

diff --git a/openbsc/src/osmo-bsc/osmo_bsc_api.c b/openbsc/src/osmo-bsc/osmo_bsc_api.c
index 04305c20f..8fa17e6ba 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_api.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_api.c
@@ -81,6 +81,25 @@ static void bsc_cipher_mode_compl(struct gsm_subscriber_connection *conn,
 	queue_msg_or_return(resp);
 }
 
+static struct osmo_msc_data *find_msc(struct gsm_subscriber_connection *conn,
+				      struct msgb *msg)
+{
+	struct osmo_bsc_data *bsc;
+	struct osmo_msc_data *msc;
+
+	bsc = conn->bts->network->bsc_data;
+	llist_for_each_entry(msc, &bsc->mscs, entry) {
+		if (!msc->msc_con->is_authenticated)
+			continue;
+
+		/* force round robin by moving it to the end */
+		llist_move_tail(&msc->entry, &bsc->mscs);
+		return msc;
+	}
+
+	return NULL;
+}
+
 /*
  * Instruct to reserve data for a new connectiom, create the complete
  * layer three message, send it to open the connection.
@@ -89,13 +108,21 @@ static int bsc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg
 			uint16_t chosen_channel)
 {
 	struct msgb *resp;
+	struct osmo_msc_data *msc;
 	uint16_t network_code;
 	uint16_t country_code;
 
 	LOGP(DMSC, LOGL_INFO, "Tx MSC COMPL L3\n");
 
+	/* find the MSC link we want to use */
+	msc = find_msc(conn, msg);
+	if (!msc) {
+		LOGP(DMSC, LOGL_ERROR, "Failed to find a MSC for a connection.\n");
+		return -1;
+	}
+
 	/* allocate resource for a new connection */
-	if (bsc_create_new_connection(conn) != 0)
+	if (bsc_create_new_connection(conn, msc) != 0)
 		return BSC_API_CONN_POL_REJECT;
 
 	network_code = get_network_code_for_msc(conn->sccp_con->msc);