osmo-msc: finish msc-sided reset

finish the implementation for msc sided reset, automatically
register connecting BSCs.

Ensure that all sccp connections are cleared when the reset
procedure executes.

6 files changed, 280 insertions, 92 deletions

diff --git a/openbsc/include/openbsc/a_iface.h b/openbsc/include/openbsc/a_iface.h
index b27c3db83..4a9eaf620 100644
--- a/openbsc/include/openbsc/a_iface.h
+++ b/openbsc/include/openbsc/a_iface.h
@@ -18,6 +18,36 @@
  *
  */
 
+#pragma once
+
+#include <openbsc/a_reset.h>
+
+/* A struct to keep a context information about the BSCs we are associated with */
+struct bsc_context {
+	struct llist_head list;
+
+	/* Holds a copy of the sccp address of the BSC,
+	 * this address will become known as soon as
+	 * a remote BSC tries to make a connection or
+	 * sends a RESET request via UNIDATA */
+	struct osmo_sccp_addr bsc_addr;
+
+	/* Holds a copy of the our local MSC address,
+	 * this will be the sccp-address that is associated
+	 * with the A interface */
+	struct osmo_sccp_addr msc_addr;
+
+	/* A pointer to the reset handler FSM, the
+	 * state machine is allocated when the BSC
+	 * is registerd. */
+	struct a_reset_ctx *reset;
+
+	/* A pointer to the sccp_user that is associated
+	 * with the A interface. We need this information
+	 * to send the resets and to send paging requests */
+	struct osmo_sccp_user *sccp_user;
+};
+
 /* Initalize A interface connection between to MSC and BSC */
 int a_init(void *ctx, struct osmo_sccp_instance *sccp, struct gsm_network *network);
 
@@ -34,4 +64,10 @@ 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);
 
-#pragma once
+/* Clear all subscriber connections on a specified BSC
+ * (Helper function for a_iface_bssap.c) */
+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
+ * (Helper function for a_iface_bssap.c) */
+void a_delete_bsc_con(uint32_t conn_id);
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/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 13178ae6c..283b5498c 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -209,8 +209,18 @@ struct gsm_subscriber_connection {
 	} iu;
 
 	struct {
+		/* A pointer to the SCCP user that handles
+		 * the SCCP connections for this subscriber
+		 * connection */
 		struct osmo_sccp_user *scu;
+
+		/* The address of the BSC that is associated
+		 * with this subscirber connection */
 		struct osmo_sccp_addr bsc_addr;
+
+		/* The connection identifier that is used
+		 * to reference the SCCP connection that is
+		 * associated with this subscriber connection */
 		int conn_id;
 	} a;
 };
@@ -482,6 +492,12 @@ struct gsm_network {
 		enum nsap_addr_enc rab_assign_addr_enc;
 	} iu;
 
+	struct {
+		/* A list with the context information about
+		 * all BSCs we have connections with */
+		struct llist_head bscs;
+	} a;
+
 	struct osmo_sccp_instance *sccp;
 };
 
diff --git a/openbsc/src/libcommon-cs/common_cs.c b/openbsc/src/libcommon-cs/common_cs.c
index d94381b4c..ad3fb54b1 100644
--- a/openbsc/src/libcommon-cs/common_cs.c
+++ b/openbsc/src/libcommon-cs/common_cs.c
@@ -79,6 +79,8 @@ struct gsm_network *gsm_network_init(void *ctx,
 
 	net->dyn_ts_allow_tch_f = true;
 
+	INIT_LLIST_HEAD(&net->a.bscs);
+
 	return net;
 }
 
diff --git a/openbsc/src/libmsc/a_iface.c b/openbsc/src/libmsc/a_iface.c
index 869cd7887..dcbb5aad7 100644
--- a/openbsc/src/libmsc/a_iface.c
+++ b/openbsc/src/libmsc/a_iface.c
@@ -37,12 +37,94 @@
 #include <openbsc/mgcpgw_client.h>
 #include <osmocom/core/byteswap.h>
 #include <osmocom/sccp/sccp_types.h>
+#include <openbsc/a_reset.h>
+#include <openbsc/osmo_msc.h>
 
 /* A pointer to the GSM network we work with. By the current paradigm,
  * there can only be one gsm_network per MSC. The pointer is set once
  * 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);
+
+/* 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, &gsm_network->a.bscs, list) {
+		if (memcmp(&bsc_ctx->bsc_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)
 {
@@ -107,9 +189,9 @@ 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;
@@ -117,16 +199,26 @@ 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, &gsm_network->a.bscs, 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->msc_addr),
+			     osmo_sccp_addr_dump(&bsc_ctx->bsc_addr), imsi, tmsi, lac);
+			msg = gsm0808_create_paging(imsi, &tmsi, &cil, NULL);
+			osmo_sccp_tx_unitdata_msg(bsc_ctx->sccp_user,
+						  &bsc_ctx->msc_addr, &bsc_ctx->bsc_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->msc_addr),
+			     osmo_sccp_addr_dump(&bsc_ctx->bsc_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;
 }
@@ -303,24 +395,51 @@ 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)
+/* Callback function: Close all open connections */
+static void a_reset_cb(void *priv)
 {
-	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;
-		}
-	}
+	struct msgb *msg;
+	struct bsc_context *bsc_ctx = (struct bsc_context*) priv;
 
-	LOGP(DMSC, LOGL_ERROR, "The calling BSC (%s) is unknown to this MSC, rejecting...\n",
-	     osmo_sccp_addr_dump(bsc_addr));
-	return false;
+	/* Skip if the A interface is not properly initalized yet */
+	if (!gsm_network)
+		return;
+
+	/* Clear all now orphaned subscriber connections */
+	a_clear_all(bsc_ctx->sccp_user, &bsc_ctx->bsc_addr);
+
+	/* Send reset to the remote BSC */
+	LOGP(DMSC, LOGL_NOTICE, "Sending RESET to BSC %s\n", osmo_sccp_addr_dump(&bsc_ctx->bsc_addr));
+	msg = gsm0808_create_reset();
+	osmo_sccp_tx_unitdata_msg(bsc_ctx->sccp_user, &bsc_ctx->msc_addr,
+				  &bsc_ctx->bsc_addr, msg);
+}
+
+/* Add a new BSC connection to our internal list with known BSCs */
+static void add_bsc(struct osmo_sccp_addr *msc_addr, struct osmo_sccp_addr *bsc_addr, struct osmo_sccp_user *scu)
+{
+	struct bsc_context *bsc_ctx;
+
+	OSMO_ASSERT(bsc_addr);
+	OSMO_ASSERT(msc_addr);
+	OSMO_ASSERT(scu);
+
+	/* Check if we already know this BSC, if yes, skip adding it. */
+	if (get_reset_ctx_by_sccp_addr(bsc_addr))
+		return;
+
+	LOGP(DMSC, LOGL_NOTICE, "Adding new BSC connection for BSC %s...\n", osmo_sccp_addr_dump(bsc_addr));
+
+	/* Generate and fill up a new bsc context */
+	bsc_ctx = talloc_zero(gsm_network, struct bsc_context);
+	OSMO_ASSERT(bsc_ctx);
+	memcpy(&bsc_ctx->bsc_addr, bsc_addr, sizeof(*bsc_addr));
+	memcpy(&bsc_ctx->msc_addr, msc_addr, sizeof(*msc_addr));
+	bsc_ctx->sccp_user = scu;
+	llist_add_tail(&bsc_ctx->list, &gsm_network->a.bscs);
+
+	/* Start reset procedure to make the new connection active */
+	bsc_ctx->reset = a_reset_alloc(bsc_ctx, osmo_sccp_addr_dump(bsc_addr), a_reset_cb, bsc_ctx);
 }
 
 /* Callback function, called by the SSCP stack when data arrives */
@@ -332,15 +451,18 @@ 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):
 		/* Handle inbound connection indication */
+		add_bsc(&scu_prim->u.connect.called_addr, &scu_prim->u.connect.calling_addr, 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;
@@ -353,6 +475,9 @@ 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):
@@ -365,8 +490,10 @@ static int sccp_sap_up(struct osmo_prim_hdr *oph, void *_scu)
 
 	case OSMO_PRIM(OSMO_SCU_PRIM_N_UNITDATA, PRIM_OP_INDICATION):
 		/* Handle inbound UNITDATA */
+		add_bsc(&scu_prim->u.unitdata.called_addr, &scu_prim->u.unitdata.calling_addr, scu);
 		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;
@@ -379,13 +506,46 @@ 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);
+			}
+		}
+	}
+}
+
 /* Initalize A interface connection between to MSC and BSC */
 int a_init(void *ctx, struct osmo_sccp_instance *sccp, struct gsm_network *network)
 {
+	OSMO_ASSERT(sccp);
+	OSMO_ASSERT(network);
+
 	/* FIXME: Remove hardcoded parameters, use parameters in parameter list */
 	LOGP(DMSC, LOGL_NOTICE, "Initalizing SCCP connection to stp...\n");
 
-	gsm_network = network;
+	/* Set GSM network variable, there can only be
+	 * one network by design */
+	if (gsm_network != NULL) {
+		OSMO_ASSERT(gsm_network == network);
+	} else
+		gsm_network = network;
 
 	/* SCCP Protocol stack */
 	osmo_sccp_user_bind(sccp, "OsmoMSC-A", sccp_sap_up, SCCP_SSN_BSSAP);
diff --git a/openbsc/src/libmsc/a_iface_bssap.c b/openbsc/src/libmsc/a_iface_bssap.c
index cdddac7e7..d00ad3f31 100644
--- a/openbsc/src/libmsc/a_iface_bssap.c
+++ b/openbsc/src/libmsc/a_iface_bssap.c
@@ -28,34 +28,35 @@
 #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
  */
 
 /* Allocate a new subscriber connection */
 static struct gsm_subscriber_connection *subscr_conn_allocate_a(struct a_conn_info *a_conn_info,
-								struct gsm_network *network,
+								struct gsm_network *network, struct ue_conn_ctx *ue,
 								uint16_t lac, struct osmo_sccp_user *scu, int conn_id)
 {
 	struct gsm_subscriber_connection *conn;
 
-	LOGP(DMSC, LOGL_NOTICE, "Allocating A-Interface subscriber conn: lac %i, conn_id %i\n", lac, conn_id);
+	LOGP(DMSC, LOGL_NOTICE, "Allocating A-Interface subscriber conn: lac %i, conn_id %i\n", lac, ue->conn_id);
 
-	conn = talloc_zero(network, struct gsm_subscriber_connection);
+	conn = talloc_zero(ue, struct gsm_subscriber_connection);
 	if (!conn)
 		return NULL;
 
 	conn->network = network;
 	conn->via_ran = RAN_GERAN_A;
+	conn->iu.ue_ctx = ue;
+	conn->iu.ue_ctx->rab_assign_addr_enc = network->iu.rab_assign_addr_enc;
 	conn->lac = lac;
 
 	conn->a.conn_id = conn_id;
@@ -92,22 +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
  */
@@ -115,36 +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);
 }
 
@@ -165,6 +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]));
@@ -256,6 +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;
 }
@@ -277,6 +264,7 @@ static int bssmap_rx_l3_compl(struct osmo_sccp_user *scu, struct a_conn_info *a_
 	int rc;
 
 	struct gsm_network *network = a_conn_info->network;
+	struct ue_conn_ctx *ue;
 	struct gsm_subscriber_connection *conn;
 
 	LOGP(DMSC, LOGL_NOTICE, "BSC has completed layer 3 connection (conn_id=%i)\n", a_conn_info->conn_id);
@@ -320,7 +308,8 @@ static int bssmap_rx_l3_compl(struct osmo_sccp_user *scu, struct a_conn_info *a_
 	msg->tail = msg->l3h + TLVP_LEN(&tp, GSM0808_IE_LAYER_3_INFORMATION);
 
 	/* Create new subscriber context */
-	conn = subscr_conn_allocate_a(a_conn_info, network, lac, scu, a_conn_info->conn_id);
+	ue = ue_conn_ctx_alloc(a_conn_info->calling_addr, a_conn_info->conn_id);
+	conn = subscr_conn_allocate_a(a_conn_info, network, ue, lac, scu, a_conn_info->conn_id);
 
 	/* Handover location update to the MSC code */
 	/* msc_compl_l3() takes ownership of dtap_msg
@@ -701,9 +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;
-}