mscsplit: getting grips on header scopes

openbsc/include/openbsc/Makefile.am

@@ -19,7 +19,7 @@ noinst_HEADERS = abis_nm.h abis_rsl.h db.h gsm_04_08.h gsm_data.h \
 		 gprs_gsup_client.h bsc_msg_filter.h \
 		 oap.h oap_messages.h \
 		 gtphub.h \
-		 iu.h iu_cs.h \
+		 msc_ifaces.h iu.h iu_cs.h \
 		 common.h
 
 openbsc_HEADERS = gsm_04_08.h meas_rep.h bsc_api.h

openbsc/include/openbsc/iu_cs.h

@@ -6,5 +6,3 @@ struct gsm_subscriber_connection *subscr_conn_allocate_iu(struct gsm_network *ne
 							  uint8_t link_id,
 							  uint32_t conn_id);
 
-int iucs_submit_dtap(struct gsm_subscriber_connection *conn,
-		     struct msgb *msg);

openbsc/include/openbsc/msc_ifaces.h

@@ -9,28 +9,55 @@
  * 2G will use the A-interface,
  * 3G aka UMTS will use the Iu-interface (for the MSC, it's IuCS).
  *
- * Below callback structures allows linking parts of the MSC code without
+ * Below callback structures allow linking parts of the MSC code without
  * having to include entire infrastructures of external libraries. For example,
  * a unit test does not need to link against external ASN1 libraries if it is
  * never going to encode actual outgoing messages. It is up to each building
- * scope to plug real world functions or to have mere dummy implementations. */
+ * scope to plug real world functions or to have mere dummy implementations.
+ *
+ * For example, for msc_tx_foo(ifaces, conn, msg), depending on
+ * conn->via_iface, either ifaces->a.tx() or ifaces.iu_cs.tx() is called to
+ * dispatch the msg.
+ *
+ * To replace the default dummy implementations, a user would do the likes of:
+ *
+ *   int my_iu_cs_tx(...)
+ *   {
+ *           ...
+ *   }
+ *
+ *   int main(void)
+ *   {
+ *           global_msc_ifaces->network = my_network;
+ *           global_msc_ifaces->iu_cs.tx = my_iu_cs_tx;
+ *           ...
+ *   }
+ *
+ * (or use readily available implementations like iu_tx() from libiu)
+ */
 
-extern struct {
+struct msc_ifaces {
+
+	/* global gsm_network to lookup BSC|RNC connections etc. */
+	struct gsm_network *network;
 
 	struct {
 		/* libmsc calls this to send out messages to an A-interface */
 		int (*tx)(struct msgb *msg, uint8_t sapi);
+		/* TODO: I don't understand sapi yet, may not apply to A-iface */
 	} a;
 
 	struct {
 		/* libmsc calls this to send out messages to an Iu-interface */
 		int (*tx)(struct msgb *msg, uint8_t sapi);
+		/* TODO: I don't understand sapi yet */
 	} iu_cs;
 
-} msc_ifaces;
+};
+
+extern struct msc_ifaces *global_msc_ifaces;
 
 
+int msc_tx_dtap(struct gsm_subscriber_connection *conn,
+		struct msgb *msg);
 
-/* Depending on conn->via_iface (A or IuCS), submit msg to the proper link api. */
-extern int msc_submit_dtap(struct gsm_subscriber_connection *conn,
-			   struct msgb *msg);

openbsc/src/libbsc/bsc_api.c

@@ -242,6 +242,8 @@ static int handle_new_assignment(struct gsm_subscriber_connection *conn, int cha
 
 /* Allocate a subscriber connection for A-interface link. For Iu-CS see
  * subscr_con_allocate_iu(). */
+/* TODO this shall move to libmsc, behind an actual A-interface, and lchan will
+ * not be involved. */
 struct gsm_subscriber_connection *subscr_con_allocate(struct gsm_lchan *lchan)
 {
 	struct gsm_subscriber_connection *conn;

openbsc/src/libmsc/Makefile.am

@@ -21,7 +21,7 @@ libmsc_a_SOURCES =	auth.c \
 			vty_interface_layer3.c \
 			transaction.c \
 			osmo_msc.c ctrl_commands.c meas_feed.c \
-			msc_api.c iu_cs.c
+			msc_api.c msc_ifaces.c iu_cs.c
 
 if BUILD_SMPP
 noinst_HEADERS += smpp_smsc.h

openbsc/src/libmsc/iu_cs.c

@@ -109,11 +109,3 @@ int gsm0408_rcvmsg_iucs(struct gsm_network *network, struct msgb *msg)
 }
 
 
-int iucs_submit_dtap(struct gsm_subscriber_connection *conn,
-		     struct msgb *msg)
-{
-	OSMO_ASSERT(conn->via_iface == IFACE_IU);
-	msg->dst = conn->iu.ue_ctx;
-	return iu_tx(msg, 0);
-}
-

openbsc/src/libmsc/msc_api.c

@@ -0,0 +1,51 @@
+/* Implementations for receiving or sending MM|CC|... messages from/to the
+ * BSC|RNC direction, regardless of which particular external interface is
+ * actually involved (A or IuCS). */
+
+/* (C) 2016 by sysmocom s.m.f.c GmbH <info@sysmocom.de>
+ *
+ * Based on parts of osmo_msc.c:
+ * (C) 2010,2013 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 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/>.
+ */
+
+#include <openbsc/msc_api.h>
+#include <openbsc/gsm_data.h>
+
+int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg,
+		 uint16_t chosen_channel)
+{
+	gsm0408_new_conn(conn);
+	gsm0408_dispatch(conn, msg);
+
+	/*
+	 * If this is a silent call we want the channel to remain open as long as
+	 * possible and this is why we accept this connection regardless of any
+	 * pending transaction or ongoing operation.
+	 */
+	if (conn->silent_call)
+		return MSC_CONN_ACCEPT;
+	if (conn->loc_operation || conn->sec_operation || conn->anch_operation)
+		return MSC_CONN_ACCEPT;
+	if (trans_has_conn(conn))
+		return MSC_CONN_ACCEPT;
+
+	LOGP(DRR, LOGL_INFO, "MSC Complete L3: Rejecting connection.\n");
+	return MSC_CONN_REJECT;
+}
+

openbsc/src/libmsc/msc_api.h

@@ -2,9 +2,22 @@
 
 /* These functions receive or send MM|CC|... messages from/to the BSC|RNC
  * direction, while they are not concerned with which particular external
- * interface is actually involved (A or IuCS). */
+ * interface is actually involved (A or IuCS).
+ *
+ * For the interface specific decisions see msc_iface.[hc] */
 
-/* receive a Level 3 Complete message */
+#include <stdint.h>
+
+struct gsm_subscriber_connection;
+struct msgb;
+
+enum {
+	MSC_CONN_ACCEPT = 0,
+	MSC_CONN_REJECT = 1,
+};
+
+/* receive a Level 3 Complete message and return MSC_CONN_ACCEPT or
+ * MSC_CONN_REJECT */
 int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg,
 		 uint16_t chosen_channel);
 /* TODO: is chosen_channel NITB legacy? */

openbsc/src/libmsc/msc_ifaces.c

@@ -1,4 +1,4 @@
-/* MSC decisions which interface to send messages out on. */
+/* Implementation for MSC decisions which interface to send messages out on. */
 
 /* (C) 2016 by sysmocom s.m.f.c GmbH <info@sysmocom.de>
  *
@@ -16,35 +16,63 @@
  *
  * 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/>.
- *
  */
 
 #include <osmocom/core/logging.h>
 
 #include <openbsc/debug.h>
 #include <openbsc/gsm_data.h>
-#include <openbsc/iu_cs.h>
+#include <openbsc/msc_ifaces.h>
 
-#include "msc_api.h"
+static int tx_dummy_a(struct msgb *msg, uint8_t sapi)
+{
+	LOGP(DMSC, LOGL_ERROR,
+	     "attempt to send message via uninitialized A-interface\n");
+	return -1
+}
 
-int msc_submit_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg)
+static int tx_dummy_iu_cs(struct msgb *msg, uint8_t sapi)
+{
+	LOGP(DMSC, LOGL_ERROR,
+	     "attempt to send message via uninitialized IuCS-interface\n");
+	return -1
+}
+
+struct msc_ifaces *global_msc_ifaces = {
+	.a = {
+		.tx = tx_dummy_a,
+	},
+	.iu_cs = {
+		.tx = tx_dummy_iu_cs,
+	}
+};
+
+
+static int msc_tx(struct msc_ifaces *ifaces,
+		  struct gsm_subscriber_connection *conn,
+		  struct msgb *msg)
 {
 	switch (conn->via_iface) {
 	case IFACE_A:
-		//return gsm0808_submit_dtap(conn, msg, link_id, allow_sacch);
-		LOGP(DMSC, LOGL_ERROR,
-		     "submit dtap: A-interface not implemented\n");
-		return -1;
+		/* TODO: msg->dst = <A-iface token> */
+		return ifaces->a.tx(msg, 0);
 
 	case IFACE_IUCS:
-		return iucs_submit_dtap(conn, msg);
+		msg->dst = conn->iu.ue_ctx;
+		return ifaces->iu_cs.tx(msg, 0);
 
 	default:
 		LOGP(DMSC, LOGL_ERROR,
-		     "submit dtap: conn->via_iface invalid (%d)\n",
+		     "msc_tx(): conn->via_iface invalid (%d)\n",
 		     conn->via_iface);
 		return -1;
 	}
 }
 
 
+int msc_tx_dtap(struct gsm_subscriber_connection *conn,
+		struct msgb *msg)
+{
+	msc_tx(global_msc_ifaces, conn, msg);
+}
+

openbsc/src/libmsc/osmo_msc.c

@@ -26,6 +26,7 @@
 #include <openbsc/transaction.h>
 #include <openbsc/db.h>
 
+#include <openbsc/msc_api.h>
 #include <openbsc/gsm_04_11.h>
 
 static void msc_sapi_n_reject(struct gsm_subscriber_connection *conn, int dlci)
@@ -42,28 +43,6 @@ static int msc_clear_request(struct gsm_subscriber_connection *conn, uint32_t ca
 	return 1;
 }
 
-int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg,
-		 uint16_t chosen_channel)
-{
-	gsm0408_new_conn(conn);
-	gsm0408_dispatch(conn, msg);
-
-	/*
-	 * If this is a silent call we want the channel to remain open as long as
-	 * possible and this is why we accept this connection regardless of any
-	 * pending transaction or ongoing operation.
-	 */
-	if (conn->silent_call)
-		return BSC_API_CONN_POL_ACCEPT;
-	if (conn->loc_operation || conn->sec_operation || conn->anch_operation)
-		return BSC_API_CONN_POL_ACCEPT;
-	if (trans_has_conn(conn))
-		return BSC_API_CONN_POL_ACCEPT;
-
-	LOGP(DRR, LOGL_INFO, "MSC Complete L3: Rejecting connection.\n");
-	return BSC_API_CONN_POL_REJECT;
-}
-
 static void msc_dtap(struct gsm_subscriber_connection *conn, uint8_t link_id, struct msgb *msg)
 {
 	gsm0408_dispatch(conn, msg);