diff --git a/src/hlr_ussd.h b/src/hlr_ussd.h
index 433a7f2..d1b9fe0 100644
--- a/src/hlr_ussd.h
+++ b/src/hlr_ussd.h
@@ -5,11 +5,15 @@
 
 struct osmo_gsup_conn;
 
-struct hlr_euse_route {
-	/* hlr_euse.routes */
+struct hlr_ussd_route {
+	/* g_hlr.routes */
 	struct llist_head list;
-	struct hlr_euse *euse;
 	const char *prefix;
+	bool is_external;
+	union {
+		struct hlr_euse *euse;
+		const struct hlr_iuse *iuse;
+	} u;
 };
 
 struct hlr_euse {
@@ -20,21 +24,34 @@
 	const char *name;
 	/* human-readable description */
 	const char *description;
-	/* list of hlr_euse_route */
-	struct llist_head routes;
 
 	/* GSUP connection to the EUSE, if any */
 	struct osmo_gsup_conn *conn;
 };
 
-
 struct hlr_euse *euse_find(struct hlr *hlr, const char *name);
 struct hlr_euse *euse_alloc(struct hlr *hlr, const char *name);
 void euse_del(struct hlr_euse *euse);
 
-struct hlr_euse_route *euse_route_find(struct hlr_euse *euse, const char *prefix);
-struct hlr_euse_route *euse_route_prefix_alloc(struct hlr_euse *euse, const char *prefix);
-void euse_route_del(struct hlr_euse_route *rt);
+const struct hlr_iuse *iuse_find(const char *name);
+
+struct hlr_ussd_route *ussd_route_find_prefix(struct hlr *hlr, const char *prefix);
+struct hlr_ussd_route *ussd_route_prefix_alloc_int(struct hlr *hlr, const char *prefix,
+						   const struct hlr_iuse *iuse);
+struct hlr_ussd_route *ussd_route_prefix_alloc_ext(struct hlr *hlr, const char *prefix,
+						   struct hlr_euse *euse);
+void ussd_route_del(struct hlr_ussd_route *rt);
 
 int rx_proc_ss_req(struct osmo_gsup_conn *conn, const struct osmo_gsup_message *gsup);
 int rx_proc_ss_error(struct osmo_gsup_conn *conn, const struct osmo_gsup_message *gsup);
+
+struct ss_session;
+struct ss_request;
+
+/* Internal USSD Handler */
+struct hlr_iuse {
+	const char *name;
+	/* call-back to be called for any incoming USSD messages for this IUSE */
+	int (*handle_ussd)(struct osmo_gsup_conn *conn, struct ss_session *ss,
+			   const struct osmo_gsup_message *gsup, const struct ss_request *req);
+};