reset: fixup for reset

We now perform the reset procedure on both sides. Also both sides
will clear now their open SCCP connections.

8 files changed, 245 insertions, 127 deletions

diff --git a/openbsc/include/openbsc/a_iface.h b/openbsc/include/openbsc/a_iface.h
index 483ffa47f..34dfca67a 100644
--- a/openbsc/include/openbsc/a_iface.h
+++ b/openbsc/include/openbsc/a_iface.h
@@ -35,4 +35,10 @@ int a_iface_tx_paging(const char *imsi, uint32_t tmsi, uint16_t lac);
 /* Send assignment request via A-interface */
 int a_iface_tx_assignment(struct gsm_trans *trans);
 
+/* Clear all subscriber connections on a specified BSC */
+void a_clear_all(struct osmo_sccp_user *scu, struct osmo_sccp_addr *bsc_addr);
+
+/* Delete info of a closed connection from the active connection list */
+void a_delete_bsc_con(uint32_t conn_id);
+
 #pragma once
diff --git a/openbsc/include/openbsc/a_iface_bssap.h b/openbsc/include/openbsc/a_iface_bssap.h
index 211bcf2d9..f0a2187ef 100644
--- a/openbsc/include/openbsc/a_iface_bssap.h
+++ b/openbsc/include/openbsc/a_iface_bssap.h
@@ -28,16 +28,9 @@
 struct a_conn_info {
 	struct osmo_sccp_addr *called_addr;
 	struct osmo_sccp_addr *calling_addr;
-	int conn_id;
+	uint32_t conn_id;
 	struct gsm_network *network;
-};
-
-/* A structure to pack BSC calling addresses into a list */
-struct a_bsc_addr {
-	struct llist_head list;
-	struct osmo_sccp_addr called_addr;
-	struct osmo_sccp_addr calling_addr;
-	struct osmo_sccp_user *scu;
+	struct a_reset_ctx *reset;
 };
 
 /* Receive incoming connection less data messages via sccp */
@@ -46,5 +39,3 @@ void sccp_rx_udt(struct osmo_sccp_user *scu, struct a_conn_info *a_conn_info, st
 /* Receive incoming connection oriented data messages via sccp */
 int sccp_rx_dt(struct osmo_sccp_user *scu, struct a_conn_info *a_conn_info, struct msgb *msg);
 
-/* Get a list with all known BSCs */
-struct llist_head *get_bsc_addr_list(void);
diff --git a/openbsc/include/openbsc/bsc_msc.h b/openbsc/include/openbsc/bsc_msc.h
index a7c881b84..35b8654d5 100644
--- a/openbsc/include/openbsc/bsc_msc.h
+++ b/openbsc/include/openbsc/bsc_msc.h
@@ -62,8 +62,6 @@ struct bsc_msc_connection {
 	struct osmo_sccp_addr g_calling_addr;
 	struct osmo_sccp_addr g_called_addr;
 	struct a_reset_ctx reset;
-
-	int conn_id_counter;
 };
 
 struct bsc_msc_connection *bsc_msc_create(void *ctx, struct llist_head *dest);
diff --git a/openbsc/src/libcommon-cs/a_reset.c b/openbsc/src/libcommon-cs/a_reset.c
index 94d215562..7eebb152d 100644
--- a/openbsc/src/libcommon-cs/a_reset.c
+++ b/openbsc/src/libcommon-cs/a_reset.c
@@ -158,7 +158,10 @@ void a_reset_ack_confirm(struct a_reset_ctx *reset)
 /* Report a failed connection */
 void a_reset_conn_fail(struct a_reset_ctx *reset)
 {
-	OSMO_ASSERT(reset);
+	/* If no reset context is supplied, just drop the info */
+	if (!reset)
+		return;
+
 	OSMO_ASSERT(reset->fsm);
 
 	osmo_fsm_inst_dispatch(reset->fsm, EV_N_DISCONNECT, reset);
@@ -167,7 +170,10 @@ void a_reset_conn_fail(struct a_reset_ctx *reset)
 /* Report a successful connection */
 void a_reset_conn_success(struct a_reset_ctx *reset)
 {
-	OSMO_ASSERT(reset);
+	/* If no reset context is supplied, just drop the info */
+	if (!reset)
+		return;
+
 	OSMO_ASSERT(reset->fsm);
 
 	osmo_fsm_inst_dispatch(reset->fsm, EV_N_CONNECT, reset);
@@ -176,9 +182,12 @@ void a_reset_conn_success(struct a_reset_ctx *reset)
 /* Check if we have a connection to a specified msc */
 bool a_reset_conn_ready(struct a_reset_ctx *reset)
 {
-	OSMO_ASSERT(reset);
-	OSMO_ASSERT(reset->fsm);
+	/* If no reset context is supplied, we assume that
+	 * the connection can't be ready! */
+	if (!reset)
+		return false;
 
+	OSMO_ASSERT(reset->fsm);
 	if (reset->fsm->state == ST_CONN)
 		return true;
 
diff --git a/openbsc/src/libmsc/a_iface.c b/openbsc/src/libmsc/a_iface.c
index 85fabe5ed..d4b73080b 100644
--- a/openbsc/src/libmsc/a_iface.c
+++ b/openbsc/src/libmsc/a_iface.c
@@ -38,6 +38,7 @@
 #include <osmocom/core/byteswap.h>
 #include <osmocom/sccp/sccp_types.h>
 #include <openbsc/a_reset.h>
+#include <openbsc/osmo_msc.h>
 
 #define SSN_BSSAP	254	/* SCCP_SSN_BSSAP */
 #define SENDER_PC	1	/* Our local point code */
@@ -47,15 +48,99 @@
  * when calling a_init() */
 static struct gsm_network *gsm_network = NULL;
 
+/* A struct to track currently active connections. We need that information
+ * to handle failure sitautions. In case of a problem, we must know which
+ * connections are currently open and which BSC is responsible. We also need
+ * the data to perform our connection checks (a_reset). All other logic will
+ * look at the connection ids and addresses that are supplied by the
+ * primitives */
+struct bsc_conn {
+	struct llist_head list;
+	struct osmo_sccp_addr called_addr;	/* BSC (remote) */
+	struct osmo_sccp_addr calling_addr;	/* MSC (local) */
+	uint32_t conn_id;			/* Connection identifier */
+};
+
+/* Internal list with connections we currently maintain. This
+ * list is of type struct bsc_conn (see above) */
+static LLIST_HEAD(active_connections);
+
+/* Context information about the BSC, will be used only internally in this
+ * file to manage the BSCs we are associated with */
 struct bsc_context {
 	struct llist_head list;
-	struct a_reset_ctx reset;
-	struct osmo_sccp_addr addr;
+	struct a_reset_ctx reset;		/* Reset FSM (one per BSC) */
+	struct osmo_sccp_addr called_addr;	/* BSC (remote) */
+	struct osmo_sccp_addr calling_addr;	/* MSC (local) */
+	struct osmo_sccp_user *sccp_user;	/* SCCP user (the same for all) */
 };
 
+/* List with BSCs we are associated with. This list is of type
+ * struct bsc_context (see above) */
 static LLIST_HEAD(bsc_context_list);
 
+/* Record info of a new active connection in the active connection list */
+static void record_bsc_con(void *ctx, struct osmo_sccp_addr *called_addr, struct osmo_sccp_addr *calling_addr,
+			   uint32_t conn_id)
+{
+	struct bsc_conn *conn;
+
+	conn = talloc_zero(ctx, struct bsc_conn);
+	OSMO_ASSERT(conn);
+
+	memcpy(&conn->called_addr, called_addr, sizeof(*called_addr));
+	memcpy(&conn->calling_addr, calling_addr, sizeof(*calling_addr));
+	conn->conn_id = conn_id;
+
+	llist_add_tail(&conn->list, &active_connections);
+}
+
+/* Delete info of a closed connection from the active connection list */
+void a_delete_bsc_con(uint32_t conn_id)
+{
+	struct bsc_conn *conn;
+	struct bsc_conn *conn_temp;
+
+	llist_for_each_entry_safe(conn, conn_temp, &active_connections, list) {
+		if (conn->conn_id == conn_id) {
+			llist_del(&conn->list);
+			talloc_free(conn);
+		}
+	}
+}
+
+/* Check if a specified connection id has an active SCCP connection */
+static bool check_connection_active(uint32_t conn_id)
+{
+	struct bsc_conn *conn;
 
+	/* Find the address for the current connection id */
+	llist_for_each_entry(conn, &active_connections, list) {
+		if (conn->conn_id == conn_id) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/* Get the reset context for a specifiec calling (BSC) address */
+static struct a_reset_ctx *get_reset_ctx_by_sccp_addr(struct osmo_sccp_addr *addr)
+{
+	struct bsc_context *bsc_ctx;
+
+	if (!addr)
+		return NULL;
+
+	llist_for_each_entry(bsc_ctx, &bsc_context_list, list) {
+		if (memcmp(&bsc_ctx->called_addr, addr, sizeof(*addr)) == 0)
+			return &bsc_ctx->reset;
+	}
+
+	LOGP(DMSC, LOGL_ERROR, "The calling BSC (%s) is unknown to this MSC ...\n",
+	     osmo_sccp_addr_dump(addr));
+	return NULL;
+}
 
 /* Send DTAP message via A-interface */
 int a_iface_tx_dtap(struct msgb *msg)
@@ -121,9 +206,9 @@ int a_iface_tx_cipher_mode(struct gsm_subscriber_connection *conn,
 /* Page a subscriber via A-interface */
 int a_iface_tx_paging(const char *imsi, uint32_t tmsi, uint16_t lac)
 {
-	struct a_bsc_addr *addr;
-	struct llist_head *bsc_addr_list = get_bsc_addr_list();
+	struct bsc_context *bsc_ctx;
 	struct gsm0808_cell_id_list cil;
+	struct msgb *msg;
 	int page_count = 0;
 
 	cil.id_discr = CELL_IDENT_LAC;
@@ -131,16 +216,26 @@ int a_iface_tx_paging(const char *imsi, uint32_t tmsi, uint16_t lac)
 	cil.id_list_len = 1;
 
 	/* Deliver paging request to all known BSCs */
-	llist_for_each_entry(addr, bsc_addr_list, list) {
-		LOGP(DMSC, LOGL_DEBUG, "Passing paging message from MSC to BSC %s (imsi=%s, tmsi=0x%08x, lac=%u)\n",
-		     osmo_sccp_addr_dump(&addr->calling_addr), imsi, tmsi, lac);
-		osmo_sccp_tx_unitdata_msg(addr->scu, &addr->called_addr, &addr->calling_addr,
-					  gsm0808_create_paging(imsi, &tmsi, &cil, NULL));
-		page_count++;
+	llist_for_each_entry(bsc_ctx, &bsc_context_list, list) {
+		if (a_reset_conn_ready(&bsc_ctx->reset)) {
+			LOGP(DMSC, LOGL_DEBUG,
+			     "Passing paging message from MSC %s to BSC %s (imsi=%s, tmsi=0x%08x, lac=%u)\n",
+			     osmo_sccp_addr_dump(&bsc_ctx->calling_addr),
+			     osmo_sccp_addr_dump(&bsc_ctx->called_addr), imsi, tmsi, lac);
+			msg = gsm0808_create_paging(imsi, &tmsi, &cil, NULL);
+			osmo_sccp_tx_unitdata_msg(bsc_ctx->sccp_user,
+						  &bsc_ctx->calling_addr, &bsc_ctx->called_addr, msg);
+			page_count++;
+		} else {
+			LOGP(DMSC, LOGL_DEBUG,
+			     "Connection down, dropping paging from MSC %s to BSC %s (imsi=%s, tmsi=0x%08x, lac=%u)\n",
+			     osmo_sccp_addr_dump(&bsc_ctx->calling_addr),
+			     osmo_sccp_addr_dump(&bsc_ctx->called_addr), imsi, tmsi, lac);
+		}
 	}
 
 	if (page_count <= 0)
-		LOGP(DMSC, LOGL_ERROR, "Could not deliver paging because no BSC is available!\n");
+		LOGP(DMSC, LOGL_ERROR, "Could not deliver paging because none of the associated BSCs is available!\n");
 
 	return page_count;
 }
@@ -317,26 +412,6 @@ int a_iface_tx_assignment(struct gsm_trans *trans)
 	return osmo_sccp_tx_data_msg(conn->a.scu, conn->a.conn_id, msg);
 }
 
-/* Check if we already know this BSC from a successfuly executed reset procedure. */
-static bool test_bsc_known(struct osmo_sccp_addr *bsc_addr)
-{
-	struct a_bsc_addr *addr;
-	struct llist_head *bsc_addr_list = get_bsc_addr_list();
-
-	/* Check if the given address is  */
-	llist_for_each_entry(addr, bsc_addr_list, list) {
-		if (memcmp(&addr->calling_addr, bsc_addr, sizeof(*bsc_addr)) == 0) {
-			LOGP(DMSC, LOGL_ERROR, "The calling BSC (%s) is known by this MSC, proceeding...\n",
-			     osmo_sccp_addr_dump(bsc_addr));
-			return true;
-		}
-	}
-
-	LOGP(DMSC, LOGL_ERROR, "The calling BSC (%s) is unknown to this MSC, rejecting...\n",
-	     osmo_sccp_addr_dump(bsc_addr));
-	return false;
-}
-
 /* Callback function, called by the SSCP stack when data arrives */
 static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 {
@@ -346,6 +421,7 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 	struct a_conn_info a_conn_info;
 	memset(&a_conn_info, 0, sizeof(a_conn_info));
 	a_conn_info.network = gsm_network;
+	a_conn_info.reset = NULL;
 
 	switch (OSMO_PRIM_HDR(&scu_prim->oph)) {
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_CONNECT, PRIM_OP_INDICATION):
@@ -353,8 +429,9 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 		a_conn_info.conn_id = scu_prim->u.connect.conn_id;
 		a_conn_info.called_addr = &scu_prim->u.connect.called_addr;
 		a_conn_info.calling_addr = &scu_prim->u.connect.calling_addr;
+		a_conn_info.reset = get_reset_ctx_by_sccp_addr(&scu_prim->u.unitdata.calling_addr);
 
-		if (test_bsc_known(a_conn_info.calling_addr) == false) {
+		if (a_reset_conn_ready(a_conn_info.reset) == false) {
 			rc = osmo_sccp_tx_disconn(scu, a_conn_info.conn_id, a_conn_info.called_addr,
 						  SCCP_RETURN_CAUSE_UNQUALIFIED);
 			break;
@@ -367,6 +444,8 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 			rc = sccp_rx_dt(scu, &a_conn_info, oph->msg);
 		} else
 			LOGP(DMSC, LOGL_DEBUG, "N-CONNECT.ind(%u)\n", scu_prim->u.connect.conn_id);
+
+		record_bsc_con(scu, &scu_prim->u.connect.calling_addr, &scu_prim->u.connect.called_addr, scu_prim->u.connect.conn_id);
 		break;
 
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_DATA, PRIM_OP_INDICATION):
@@ -381,6 +460,8 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 		/* Handle inbound UNITDATA */
 		a_conn_info.called_addr = &scu_prim->u.unitdata.called_addr;
 		a_conn_info.calling_addr = &scu_prim->u.unitdata.calling_addr;
+		a_conn_info.reset = get_reset_ctx_by_sccp_addr(&scu_prim->u.unitdata.calling_addr);
+
 		DEBUGP(DMSC, "N-UNITDATA.ind(%s)\n", osmo_hexdump(msgb_l2(oph->msg), msgb_l2len(oph->msg)));
 		sccp_rx_udt(scu, &a_conn_info, oph->msg);
 		break;
@@ -393,15 +474,43 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 	return rc;
 }
 
+/* Clear all subscriber connections on a specified BSC */
+void a_clear_all(struct osmo_sccp_user *scu, struct osmo_sccp_addr *bsc_addr)
+{
+	struct gsm_subscriber_connection *conn;
+	struct gsm_subscriber_connection *conn_temp;
+	struct gsm_network *network = gsm_network;
+
+	llist_for_each_entry_safe(conn, conn_temp, &network->subscr_conns, entry) {
+		/* Clear only A connections and connections that actually
+		 * belong to the specified BSC */
+		if (conn->via_ran == RAN_GERAN_A
+		    && memcmp(bsc_addr, &conn->a.bsc_addr, sizeof(conn->a.bsc_addr)) == 0) {
+			LOGP(DMSC, LOGL_NOTICE, "Dropping orphaned subscriber connection (conn_id %i)\n", conn->a.conn_id);
+			msc_clear_request(conn, GSM48_CC_CAUSE_SWITCH_CONG);
+
+			/* If there is still an SCCP connection active, remove it now */
+			if (check_connection_active(conn->a.conn_id)) {
+				osmo_sccp_tx_disconn(scu, conn->a.conn_id, bsc_addr, SCCP_RELEASE_CAUSE_END_USER_ORIGINATED);
+				a_delete_bsc_con(conn->a.conn_id);
+			}
+		}
+	}
+}
+
 /* Callback function: Close all open connections */
 static void a_reset_cb(void *priv)
 {
 	struct msgb *msg;
-	struct osmo_sccp_addr *addr = (struct osmo_sccp_addr*) priv;
-	LOGP(DMSC, LOGL_NOTICE, "Sending RESET to BSC %s\n", osmo_sccp_addr_dump(addr));
+	struct bsc_context *bsc_ctx = (struct bsc_context*) priv;
+
+	/* Clear all now orphaned subscriber connections */
+	a_clear_all(bsc_ctx->sccp_user, &bsc_ctx->called_addr);
+
+	LOGP(DMSC, LOGL_NOTICE, "Sending RESET to BSC %s\n", osmo_sccp_addr_dump(&bsc_ctx->called_addr));
 	msg = gsm0808_create_reset();
-//	osmo_sccp_tx_unitdata_msg(msc->msc_con->sccp_user, &msc->msc_con->g_calling_addr,
-//				  &msc->msc_con->g_called_addr, msg);
+	osmo_sccp_tx_unitdata_msg(bsc_ctx->sccp_user, &bsc_ctx->calling_addr,
+				  &bsc_ctx->called_addr, msg);
 }
 
 /* Initalize A interface connection between to MSC and BSC */
@@ -410,31 +519,37 @@ int a_init(void *ctx, const char *name, uint32_t local_pc,
 {
 	/* FIXME: Remove hardcoded parameters, use parameters in parameter list */
 	struct osmo_sccp_instance *sccp;
+	struct osmo_sccp_user *scu;
+	struct bsc_context *bsc_ctx;
 
 	LOGP(DMSC, LOGL_NOTICE, "Initalizing SCCP connection to stp...\n");
 
 	gsm_network = network;
 	osmo_ss7_init();
 
+	/* SCCP Protocol stack */
+	sccp =
+	    osmo_sccp_simple_client(NULL, "osmo-msc", SENDER_PC, OSMO_SS7_ASP_PROT_M3UA, 0, NULL, M3UA_PORT,
+				    "127.0.0.1");
+	scu = osmo_sccp_user_bind(sccp, "osmo-msc", sccp_sap_up, SSN_BSSAP);
+
 	/* Add some BSCs to the context list */
-	/* FIXME: Make this configurable */
-	struct bsc_context *bsc_ctx;
+	/* FIXME: Make this configurable (VTY!) */
 	bsc_ctx = talloc_zero(NULL, struct bsc_context);
-	bsc_ctx->reset.priv = &bsc_ctx->addr;
+	bsc_ctx->reset.priv = bsc_ctx;
 	bsc_ctx->reset.cb = a_reset_cb;
 	llist_add_tail(&bsc_ctx->list, &bsc_context_list);
-	bsc_ctx->addr.presence = OSMO_SCCP_ADDR_T_SSN | OSMO_SCCP_ADDR_T_PC;
-	bsc_ctx->addr.ssn = SCCP_SSN_BSSAP;
-	bsc_ctx->addr.ri = OSMO_SCCP_RI_SSN_PC;
-	bsc_ctx->addr.pc = 1;
+	bsc_ctx->called_addr.presence = OSMO_SCCP_ADDR_T_SSN | OSMO_SCCP_ADDR_T_PC;
+	bsc_ctx->called_addr.ssn = SCCP_SSN_BSSAP;
+	bsc_ctx->called_addr.ri = OSMO_SCCP_RI_SSN_PC;
+	bsc_ctx->called_addr.pc = 23;
+	bsc_ctx->calling_addr.presence = OSMO_SCCP_ADDR_T_SSN | OSMO_SCCP_ADDR_T_PC;
+	bsc_ctx->calling_addr.ssn = SCCP_SSN_BSSAP;
+	bsc_ctx->calling_addr.ri = OSMO_SCCP_RI_SSN_PC;
+	bsc_ctx->calling_addr.pc = 1;
+	bsc_ctx->sccp_user = scu;
 	bsc_ctx = NULL;
 
-	/* SCCP Protocol stack */
-	sccp =
-	    osmo_sccp_simple_client(NULL, "osmo-msc", SENDER_PC, OSMO_SS7_ASP_PROT_M3UA, 0, NULL, M3UA_PORT,
-				    "127.0.0.1");
-	osmo_sccp_user_bind(sccp, "osmo-msc", sccp_sap_up, SSN_BSSAP);
-
 	/* Start reset procedure for all BSC connections */
 	llist_for_each_entry(bsc_ctx, &bsc_context_list, list) {
 		a_reset_start(&bsc_ctx->reset);
diff --git a/openbsc/src/libmsc/a_iface_bssap.c b/openbsc/src/libmsc/a_iface_bssap.c
index b1fd11a03..f2201bb9a 100644
--- a/openbsc/src/libmsc/a_iface_bssap.c
+++ b/openbsc/src/libmsc/a_iface_bssap.c
@@ -28,15 +28,14 @@
 #include <openbsc/debug.h>
 #include <openbsc/gsm_data.h>
 #include <openbsc/a_iface_bssap.h>
+#include <openbsc/a_iface.h>
 #include <openbsc/iu.h>
 #include <openbsc/osmo_msc.h>
 #include <osmocom/core/byteswap.h>
+#include <openbsc/a_reset.h>
 
 #define IP_V4_ADDR_LEN 4
 
-/* Addresses of all BSCs which have been registered to this MSC */
-static LLIST_HEAD(bsc_addr_list);
-
 /*
  * Helper functions to lookup and allocate subscribers
  */
@@ -94,22 +93,6 @@ struct gsm_subscriber_connection *subscr_conn_lookup_a(struct gsm_network *netwo
 	return NULL;
 }
 
-/* Clear oprphand subscriber connections (called by bssmap_rx_reset()) */
-static void subscr_conn_clear_all(struct a_conn_info *a_conn_info)
-{
-	struct gsm_subscriber_connection *conn;
-	struct gsm_subscriber_connection *conn_temp;
-	struct gsm_network *network = a_conn_info->network;
-
-	llist_for_each_entry_safe(conn, conn_temp, &network->subscr_conns, entry) {
-		if (conn->via_ran == RAN_GERAN_A
-		    && memcmp(a_conn_info->calling_addr, &conn->a.bsc_addr, sizeof(conn->a.bsc_addr)) == 0) {
-			LOGP(DMSC, LOGL_NOTICE, "Dropping old subscriber connection (conn_id %i)\n", conn->a.conn_id);
-			msc_clear_request(conn, GSM48_CC_CAUSE_SWITCH_CONG);
-		}
-	}
-}
-
 /*
  * BSSMAP handling for UNITDATA
  */
@@ -117,36 +100,32 @@ static void subscr_conn_clear_all(struct a_conn_info *a_conn_info)
 /* Endpoint to handle BSSMAP reset */
 static void bssmap_rx_reset(struct osmo_sccp_user *scu, struct a_conn_info *a_conn_info, struct msgb *msg)
 {
-	struct a_bsc_addr *addr;
-	struct a_bsc_addr *known_addr;
-	bool addr_unknown = true;
-
-	LOGP(DMSC, LOGL_NOTICE, "Rx RESET from BSC %s\n", osmo_sccp_addr_dump(a_conn_info->calling_addr));
+	LOGP(DMSC, LOGL_NOTICE, "Rx RESET from BSC %s, sending RESET ACK\n", osmo_sccp_addr_dump(a_conn_info->calling_addr));
 	osmo_sccp_tx_unitdata_msg(scu, a_conn_info->called_addr, a_conn_info->calling_addr, gsm0808_create_reset_ack());
 
 	/* Make sure all orphand subscriber connections will be cleard */
-	subscr_conn_clear_all(a_conn_info);
-
-	/* Check if we know this BSC already, if yes, refresh its item */
-	llist_for_each_entry(known_addr, &bsc_addr_list, list) {
-		if (memcmp(&known_addr->calling_addr, a_conn_info->calling_addr, sizeof(*a_conn_info->calling_addr)) ==
-		    0) {
-			LOGP(DMSC, LOGL_NOTICE, "This BSC is already known to this MSC, refreshing its list item\n");
-			llist_del(&known_addr->list);
-			talloc_free(known_addr);
-			addr_unknown = false;
-			break;
-		}
+	a_clear_all(scu, a_conn_info->calling_addr);
+
+	msgb_free(msg);
+}
+
+/* Endpoint to handle BSSMAP reset acknowlegement */
+static void bssmap_rx_reset_ack(struct osmo_sccp_user *scu, struct a_conn_info *a_conn_info, struct msgb *msg)
+{
+	if (a_conn_info->reset == NULL) {
+		LOGP(DMSC, LOGL_ERROR, "Received RESET ACK from an unknown BSC %s, ignoring...\n",
+		     osmo_sccp_addr_dump(a_conn_info->calling_addr));
+		goto fail;
 	}
-	if (addr_unknown)
-		LOGP(DMSC, LOGL_NOTICE, "This BSC is not known to this MSC yet, adding it to list\n");
 
-	addr = talloc_zero(NULL, struct a_bsc_addr);
-	memcpy(&addr->calling_addr, a_conn_info->calling_addr, sizeof(addr->calling_addr));
-	memcpy(&addr->called_addr, a_conn_info->called_addr, sizeof(addr->called_addr));
-	addr->scu = scu;
-	llist_add(&addr->list, &bsc_addr_list);
+	LOGP(DMSC, LOGL_NOTICE, "Received RESET ACK from BSC %s\n",
+	     osmo_sccp_addr_dump(a_conn_info->calling_addr));
+
+	/* Confirm that we managed to get the reset ack message
+	 * towards the connection reset logic */
+	a_reset_ack_confirm(a_conn_info->reset);
 
+fail:
 	msgb_free(msg);
 }
 
@@ -167,6 +146,9 @@ static void bssmap_rcvmsg_udt(struct osmo_sccp_user *scu, struct a_conn_info *a_
 	case BSS_MAP_MSG_RESET:
 		bssmap_rx_reset(scu, a_conn_info, msg);
 		break;
+	case BSS_MAP_MSG_RESET_ACKNOWLEDGE:
+		bssmap_rx_reset_ack(scu, a_conn_info, msg);
+		break;
 	default:
 		LOGP(DMSC, LOGL_NOTICE, "Unimplemented message format: %s -- message discarded!\n",
 		     gsm0808_bssmap_name(msg->l3h[0]));
@@ -258,6 +240,9 @@ static int bssmap_rx_clear_complete(struct osmo_sccp_user *scu, struct a_conn_in
 	rc = osmo_sccp_tx_disconn(scu, a_conn_info->conn_id,
 				  a_conn_info->called_addr, SCCP_RELEASE_CAUSE_END_USER_ORIGINATED);
 
+	/* Remove the record from the list with active connections. */
+	a_delete_bsc_con(a_conn_info->conn_id);
+
 	msgb_free(msg);
 	return rc;
 }
@@ -705,9 +690,3 @@ int sccp_rx_dt(struct osmo_sccp_user *scu, struct a_conn_info *a_conn_info, stru
 
 	return -EINVAL;
 }
-
-/* Get a list with all known BSCs */
-struct llist_head *get_bsc_addr_list(void)
-{
-	return &bsc_addr_list;
-}
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_bssap.c b/openbsc/src/osmo-bsc/osmo_bsc_bssap.c
index afa81b0e5..38725a0b8 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_bssap.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_bssap.c
@@ -194,7 +194,7 @@ static int match_codec_pref(int *full_rate, enum gsm48_chan_mode *chan_mode,
 static int bssmap_handle_reset_ack(struct bsc_msc_data *msc,
 				   struct msgb *msg, unsigned int length)
 {
-	LOGP(DMSC, LOGL_NOTICE, "Reset ACK from MSC No.: %i\n", msc->nr);
+	LOGP(DMSC, LOGL_NOTICE, "RESET ACK from MSC No.: %i\n", msc->nr);
 
 	/* Inform the FSM that controls the RESET/RESET-ACK procedure
 	 * that we have successfully received the reset-ack message */
@@ -207,7 +207,7 @@ static int bssmap_handle_reset_ack(struct bsc_msc_data *msc,
 static int bssmap_handle_reset(struct bsc_msc_data *msc,
 			       struct msgb *msg, unsigned int length)
 {
-	LOGP(DMSC, LOGL_NOTICE, "Reset from MSC No.: %i\n", msc->nr);
+	LOGP(DMSC, LOGL_NOTICE, "RESET from MSC No.: %i\n", msc->nr);
 
 	/* Instruct the bsc to close all open sigtran connections and to
 	 * close all active channels on the BTS side as well */
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
index 80dac828d..8364d2aad 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -41,8 +41,15 @@ static struct llist_head *msc_list;
 #define RESET_INTERVAL 1	/* sek */
 #define SCCP_MSG_MAXSIZE 1024
 
+/* Internal list with connections we currently maintain. This 
+ * list is of type struct osmo_bsc_sccp_con */
 static LLIST_HEAD(active_connections);
 
+/* The SCCP stack will not assign connection IDs to us automatically, we
+ * will do this ourselves using a counter variable, that counts one up
+ * for every new connection */
+static uint32_t conn_id_counter;
+
 /* Helper function to Check if the given connection id is already assigned */
 static struct osmo_bsc_sccp_con *get_bsc_conn_by_conn_id(int conn_id)
 {
@@ -60,14 +67,14 @@ static struct osmo_bsc_sccp_con *get_bsc_conn_by_conn_id(int conn_id)
 /* Pick a free connection id */
 static int pick_free_conn_id(struct bsc_msc_data *msc)
 {
-	int conn_id = msc->msc_con->conn_id_counter;
+	int conn_id = conn_id_counter;
 	int i;
 
 	for (i = 0; i < 0xFFFFFF; i++) {
 		conn_id++;
 		conn_id &= 0xFFFFFF;
 		if (get_bsc_conn_by_conn_id(conn_id) == false) {
-			msc->msc_con->conn_id_counter = conn_id;
+			conn_id_counter = conn_id;
 			return conn_id;
 		}
 	}
@@ -89,13 +96,12 @@ static void osmo_bsc_sigtran_tx_reset(struct bsc_msc_data *msc)
 void osmo_bsc_sigtran_tx_reset_ack(struct bsc_msc_data *msc)
 {
 	struct msgb *msg;
-	LOGP(DMSC, LOGL_NOTICE, "Sending RESET RACK to MSC No.: %i\n", msc->nr);
+	LOGP(DMSC, LOGL_NOTICE, "Sending RESET ACK to MSC No.: %i\n", msc->nr);
 	msg = gsm0808_create_reset_ack();
 	osmo_sccp_tx_unitdata_msg(msc->msc_con->sccp_user, &msc->msc_con->g_calling_addr,
 				  &msc->msc_con->g_called_addr, msg);
 }
 
-
 /* Find an MSC by its sigtran point code */
 static struct bsc_msc_data *get_msc_by_addr(struct osmo_sccp_addr *calling_addr)
 {
@@ -367,12 +373,24 @@ void osmo_bsc_sigtran_reset(struct bsc_msc_data *msc)
 
 	/* Close all open connections */
 	llist_for_each_entry_safe(conn, conn_temp, &active_connections, entry) {
-		if (conn->conn)
-			gsm0808_clear(conn->conn);
-		bsc_notify_msc_lost(conn);
-		osmo_bsc_sigtran_del_conn(conn);
+
+		/* We only may close connections which actually belong to this
+		 * MSC. All other open connections are left untouched */
+		if (conn->msc == msc) {
+			/* Notify active connection users via USSD that the MSC is down */
+			bsc_notify_msc_lost(conn);
+
+			/* Take down all occopied RF channels */
+			if (conn->conn)
+				gsm0808_clear(conn->conn);
+
+			/* Disconnect all Sigtran connections */
+			osmo_sccp_tx_disconn(msc->msc_con->sccp_user, conn->conn_id, &msc->msc_con->g_calling_addr, 0);
+
+			/* Delete subscriber connection */
+			osmo_bsc_sigtran_del_conn(conn);
+		}
 	}
-	msc->msc_con->conn_id_counter = 0;
 }
 
 /* Callback function: Close all open connections */
@@ -380,7 +398,7 @@ static void osmo_bsc_sigtran_reset_cb(void *priv)
 {
 	struct bsc_msc_data *msc = (struct bsc_msc_data*) priv;
 
-	/* Shut down all ongoint traffic */
+	/* Shut down all ongoing traffic */
 	osmo_bsc_sigtran_reset(msc);
 
 	/* Send reset to MSC */
@@ -400,6 +418,8 @@ int osmo_bsc_sigtran_init(struct llist_head *mscs)
 
 	msc_list = mscs;
 
+	conn_id_counter = 0;
+
 	llist_for_each_entry(msc, msc_list, entry) {
 		snprintf(msc_name, sizeof(msc_name), "MSC No.: %u", msc->nr);
 		LOGP(DMSC, LOGL_NOTICE, "Initalizing SCCP connection to %s\n", msc_name);