bsc: Add the osmo_bsc_grace from the on-waves/bsc-master branch

The grace code will decide if a given connection is allowed to
be made or if it is going to be rejected. For active connections
it is going to send a USSD message.
diff --git a/openbsc/src/bsc/osmo_bsc_grace.c b/openbsc/src/bsc/osmo_bsc_grace.c
new file mode 100644
index 0000000..89f05f4
--- /dev/null
+++ b/openbsc/src/bsc/osmo_bsc_grace.c
@@ -0,0 +1,108 @@
+/*
+ * (C) 2010 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010 by On-Waves
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <openbsc/osmo_bsc_grace.h>
+#include <openbsc/osmo_bsc_rf.h>
+#include <openbsc/osmo_msc_data.h>
+#include <openbsc/gsm_04_80.h>
+#include <openbsc/signal.h>
+
+int bsc_grace_allow_new_connection(struct gsm_network *network)
+{
+	if (!network->msc_data->rf_ctl)
+		return 1;
+	return network->msc_data->rf_ctl->policy == S_RF_ON;
+}
+
+static int handle_sub(struct gsm_lchan *lchan, const char *text)
+{
+	struct gsm_subscriber_connection *conn;
+
+	/* only send it to TCH */
+	if (lchan->type != GSM_LCHAN_TCH_H && lchan->type != GSM_LCHAN_TCH_F)
+		return -1;
+
+	/* only send on the primary channel */
+	conn = lchan->conn;
+	if (!conn)
+		return -1;
+
+	if (conn->lchan != lchan)
+		return -1;
+
+	/* only when active */
+	if (lchan->state != LCHAN_S_ACTIVE)
+		return -1;
+
+	gsm0480_send_ussdNotify(conn, 0, text);
+	gsm0480_send_releaseComplete(conn);
+
+	return 0;
+}
+
+/*
+ * The place to handle the grace mode. Right now we will send
+ * USSD messages to the subscriber, in the future we might start
+ * a timer to have different modes for the grace period.
+ */
+static int handle_grace(struct gsm_network *network)
+{
+	int ts_nr, lchan_nr;
+	struct gsm_bts *bts;
+	struct gsm_bts_trx *trx;
+
+	if (!network->msc_data->ussd_grace_txt)
+		return 0;
+
+	llist_for_each_entry(bts, &network->bts_list, list) {
+		llist_for_each_entry(trx, &bts->trx_list, list) {
+			for (ts_nr = 0; ts_nr < TRX_NR_TS; ++ts_nr) {
+				struct gsm_bts_trx_ts *ts = &trx->ts[ts_nr];
+				for (lchan_nr = 0; lchan_nr < TS_MAX_LCHAN; ++lchan_nr) {
+					handle_sub(&ts->lchan[lchan_nr],
+						   network->msc_data->ussd_grace_txt);
+				}
+			}
+		}
+	}
+	return 0;
+}
+
+static int handle_rf_signal(unsigned int subsys, unsigned int signal,
+			    void *handler_data, void *signal_data)
+{
+	struct rf_signal_data *sig;
+
+	if (subsys != SS_RF)
+		return -1;
+
+	sig = signal_data;
+
+	if (signal == S_RF_GRACE)
+		handle_grace(sig->net);
+
+	return 0;
+}
+
+static __attribute__((constructor)) void on_dso_load_grace(void)
+{
+	register_signal_handler(SS_RF, handle_rf_signal, NULL);
+}