Use proper naming for GSM TS 09.11 implementation

During a long time, we had both file and symbol names, actually
related to Supplementary Services, with the 'ussd' abbreviation.
This is not absolutely wrong, but isn't correct at the same time.

USSD is a kind of Supplementary Services, this is only a part
of them. There are also 'structured' Supplementary Services,
which can be call related or call independent.

The "Signalling interworking for supplementary services" is
defined by GSM TS 09.11, and this is exactly what MSC should
implement. Let's use the specification number for naming, as
we do e.g. in the GSM 04.11 (SMS) implementation.

Change-Id: Ic1eaceddb58132318e4e941be542da34b8ebefe1

1 files changed, 159 insertions, 0 deletions

diff --git a/src/libmsc/gsm_09_11.c b/src/libmsc/gsm_09_11.c
new file mode 100644
index 000000000..8f7e54fac
--- /dev/null
+++ b/src/libmsc/gsm_09_11.c
@@ -0,0 +1,159 @@
+/* (C) 2008-2009 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2008, 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2009 by Mike Haben <michael.haben@btinternet.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/**
+ * MSC-specific handling of call independent Supplementary
+ * Services messages (NC_SS) according to GSM TS 09.11
+ * "Signalling interworking for supplementary services".
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include <osmocom/msc/gsm_04_80.h>
+#include <osmocom/msc/gsm_subscriber.h>
+#include <osmocom/msc/debug.h>
+#include <osmocom/msc/osmo_msc.h>
+#include <osmocom/msc/vlr.h>
+#include <osmocom/msc/gsm_04_08.h>
+#include <osmocom/msc/transaction.h>
+
+/* FIXME: choose a proper range */
+static uint32_t new_callref = 0x20000001;
+
+/* Declarations of USSD strings to be recognised */
+const char USSD_TEXT_OWN_NUMBER[] = "*#100#";
+
+/* A network-specific handler function */
+static int send_own_number(struct gsm_subscriber_connection *conn,
+			   const struct ss_request *req)
+{
+	char *own_number = conn->vsub->msisdn;
+	char response_string[GSM_EXTENSION_LENGTH + 20];
+
+	DEBUGP(DMM, "%s: MSISDN = %s\n", vlr_subscr_name(conn->vsub),
+	       own_number);
+
+	/* Need trailing CR as EOT character */
+	snprintf(response_string, sizeof(response_string), "Your extension is %s\r", own_number);
+	return gsm0480_send_ussd_response(conn, response_string, req);
+}
+
+/* Entry point for call independent MO SS messages */
+int gsm0911_rcv_nc_ss(struct gsm_subscriber_connection *conn, struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+	struct gsm_trans *trans;
+	struct ss_request req;
+	uint8_t pdisc, tid;
+	uint8_t msg_type;
+	int rc;
+
+	pdisc = gsm48_hdr_pdisc(gh);
+	msg_type = gsm48_hdr_msg_type(gh);
+	tid = gsm48_hdr_trans_id_flip_ti(gh);
+
+	/* Associate logging messages with this subscriber */
+	log_set_context(LOG_CTX_VLR_SUBSCR, conn->vsub);
+
+	DEBUGP(DMM, "Received SS/USSD data (trans_id=%x, msg_type=%s)\n",
+		tid, gsm48_pdisc_msgtype_name(pdisc, msg_type));
+
+	/* Reuse existing transaction, or create a new one */
+	trans = trans_find_by_id(conn, pdisc, tid);
+	if (!trans) {
+		/**
+		 * According to GSM TS 04.80, section 2.4.2 "Register
+		 * (mobile station to network direction)", the REGISTER
+		 * message is sent by the mobile station to the network
+		 * to assign a new transaction identifier for call independent
+		 * supplementary service control and to request or acknowledge
+		 * a supplementary service.
+		 */
+		if (msg_type != GSM0480_MTYPE_REGISTER) {
+			LOGP(DMM, LOGL_ERROR, "Unexpected message (msg_type=%s), "
+				"transaction is not allocated yet\n",
+				gsm48_pdisc_msgtype_name(pdisc, msg_type));
+			gsm0480_send_ussd_reject(conn, &req,
+				GSM_0480_PROBLEM_CODE_TAG_GENERAL,
+				GSM_0480_GEN_PROB_CODE_UNRECOGNISED);
+			return -EINVAL;
+		}
+
+		DEBUGP(DMM, " -> (new transaction)\n");
+		trans = trans_alloc(conn->network, conn->vsub,
+			pdisc, tid, new_callref++);
+		if (!trans) {
+			DEBUGP(DMM, " -> No memory for trans\n");
+			gsm0480_send_ussd_return_error(conn, &req,
+				GSM0480_ERR_CODE_SYSTEM_FAILURE);
+			return -ENOMEM;
+		}
+
+		trans->conn = msc_subscr_conn_get(conn, MSC_CONN_USE_TRANS_NC_SS);
+		trans->dlci = OMSC_LINKID_CB(msg);
+		cm_service_request_concludes(conn, msg);
+	}
+
+	memset(&req, 0, sizeof(req));
+	rc = gsm0480_decode_ss_request(gh, msgb_l3len(msg), &req);
+	if (!rc) {
+		LOGP(DMM, LOGL_ERROR, "SS/USSD message parsing error, "
+			"rejecting request...\n");
+		gsm0480_send_ussd_reject(conn, &req, GSM_0480_PROBLEM_CODE_TAG_GENERAL,
+			GSM_0480_GEN_PROB_CODE_UNRECOGNISED);
+		/* The GSM 04.80 API uses inverted codes (0 means error) */
+		return -EPROTO;
+	}
+
+	/* Interrogation or releaseComplete? */
+	if (req.ussd_text[0] == '\0' || req.ussd_text[0] == 0xFF) {
+		if (req.ss_code > 0) {
+			/* Assume interrogateSS or modification of it and reject */
+			return gsm0480_send_ussd_return_error(conn, &req,
+				GSM0480_ERR_CODE_ILLEGAL_SS_OPERATION);
+		}
+		/* Still assuming a Release-Complete and returning */
+		return 0;
+	}
+
+	msc_subscr_conn_communicating(conn);
+	if (!strcmp(USSD_TEXT_OWN_NUMBER, (const char *)req.ussd_text)) {
+		DEBUGP(DMM, "USSD: Own number requested\n");
+		rc = send_own_number(conn, &req);
+	} else {
+		DEBUGP(DMM, "Unhandled USSD %s\n", req.ussd_text);
+		rc = gsm0480_send_ussd_return_error(conn, &req,
+			GSM0480_ERR_CODE_UNEXPECTED_DATA_VALUE);
+	}
+
+	/**
+	 * TODO: as we only handle *#100# for now, and always
+	 * respond with RELEASE COMPLETE, let's manually free
+	 * the transaction here, until the external interface
+	 * is implemented.
+	 */
+	trans_free(trans);
+
+	return rc;
+}