diff --git a/src/Makefile.am b/src/Makefile.am
index ea5023d..646fd34 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -30,6 +30,7 @@
 	ctrl.h \
 	hlr_vty.h \
 	hlr_vty_subscr.h \
+	hlr_ss_ussd.h \
 	db_bootstrap.h \
 	$(NULL)
 
@@ -53,6 +54,7 @@
 	hlr_vty.c \
 	hlr_vty_subscr.c \
 	gsup_send.c \
+	hlr_ss_ussd.c \
 	$(NULL)
 
 osmo_hlr_LDADD = \
diff --git a/src/hlr.c b/src/hlr.c
index 41566be..fb05973 100644
--- a/src/hlr.c
+++ b/src/hlr.c
@@ -42,6 +42,7 @@
 #include "rand.h"
 #include "luop.h"
 #include "hlr_vty.h"
+#include "hlr_ss_ussd.h"
 
 static struct hlr *g_hlr;
 
@@ -533,6 +534,7 @@
 	case SIGINT:
 		LOGP(DMAIN, LOGL_NOTICE, "Terminating due to SIGINT\n");
 		osmo_gsup_server_destroy(g_hlr->gs);
+		hlr_usse_clean_up(g_hlr);
 		db_close(g_hlr->dbc);
 		log_fini();
 		talloc_report_full(hlr_ctx, stderr);
@@ -569,6 +571,9 @@
 
 	g_hlr = talloc_zero(hlr_ctx, struct hlr);
 
+	INIT_LLIST_HEAD(&g_hlr->usse_list);
+	g_hlr->usse_default = NULL;
+
 	rc = osmo_init_logging2(hlr_ctx, &hlr_log_info);
 	if (rc < 0) {
 		fprintf(stderr, "Error initializing logging\n");
diff --git a/src/hlr.h b/src/hlr.h
index 368a052..d9bdc87 100644
--- a/src/hlr.h
+++ b/src/hlr.h
@@ -23,6 +23,9 @@
 #pragma once
 
 #include <stdbool.h>
+#include <osmocom/core/linuxlist.h>
+
+struct hlr_usse;
 
 struct hlr {
 	/* GSUP server pointer */
@@ -37,6 +40,10 @@
 
 	/* Local bind addr */
 	char *gsup_bind_addr;
+
+	/* SS/USSD processing entities */
+	struct llist_head usse_list;
+	struct hlr_usse *usse_default;
 };
 
 struct hlr_subscriber;
diff --git a/src/hlr_ss_ussd.c b/src/hlr_ss_ussd.c
new file mode 100644
index 0000000..027b33f
--- /dev/null
+++ b/src/hlr_ss_ussd.c
@@ -0,0 +1,129 @@
+/* Supplementary Services signalling implementation */
+
+/* (C) 2018 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2018 by Vadim Yanitskiy <axilirator@gmail.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/>.
+ *
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/linuxlist.h>
+
+#include "hlr.h"
+#include "hlr_ss_ussd.h"
+
+struct hlr_usse *hlr_usse_find(struct hlr *hlr, const char *name)
+{
+	struct hlr_usse *usse;
+
+	llist_for_each_entry(usse, &hlr->usse_list, list) {
+		if (!strcmp(usse->name, name))
+			return usse;
+	}
+
+	return NULL;
+}
+
+struct hlr_usse *hlr_usse_alloc(struct hlr *hlr, const char *name)
+{
+	struct hlr_usse *usse;
+
+	usse = hlr_usse_find(hlr, name);
+	if (usse)
+		return NULL;
+
+	usse = talloc(hlr, struct hlr_usse);
+	usse->name = talloc_strdup(usse, name);
+	usse->description = NULL;
+	usse->hlr = hlr;
+
+	INIT_LLIST_HEAD(&usse->patterns);
+	llist_add_tail(&usse->list, &hlr->usse_list);
+
+	return usse;
+}
+
+void hlr_usse_del(struct hlr_usse *usse)
+{
+	struct hlr_usse_pattern *pt, *_pt;
+
+	/* Release linked patterns */
+	llist_for_each_entry_safe(pt, _pt, &usse->patterns, list)
+		hlr_usse_pattern_del(pt);
+
+	/* Unlink from the HLR's USSE list */
+	llist_del(&usse->list);
+
+	/* Release memory */
+	talloc_free(usse);
+}
+
+struct hlr_usse_pattern *hlr_usse_pattern_find(struct hlr_usse *usse,
+	enum hlr_usse_pattern_type type, const char *pattern)
+{
+	struct hlr_usse_pattern *pt;
+
+	llist_for_each_entry(pt, &usse->patterns, list) {
+		if (pt->type != type)
+			continue;
+		if (strcmp(pt->pattern, pattern))
+			continue;
+
+		return pt;
+	}
+
+	return NULL;
+}
+
+struct hlr_usse_pattern *hlr_usse_pattern_add(struct hlr_usse *usse,
+	enum hlr_usse_pattern_type type, const char *pattern)
+{
+	struct hlr_usse_pattern *pt;
+
+	pt = hlr_usse_pattern_find(usse, type, pattern);
+	if (pt)
+		return NULL;
+
+	pt = talloc(usse, struct hlr_usse_pattern);
+	pt->pattern = talloc_strdup(pt, pattern);
+	pt->rsp_fmt = NULL;
+	pt->type = type;
+	pt->usse = usse;
+
+	llist_add_tail(&pt->list, &usse->patterns);
+	return pt;
+}
+
+void hlr_usse_pattern_del(struct hlr_usse_pattern *pt)
+{
+	/* Unlink from the USSE's list */
+	llist_del(&pt->list);
+
+	/* Release memory */
+	talloc_free(pt);
+}
+
+void hlr_usse_clean_up(struct hlr *hlr)
+{
+	struct hlr_usse *usse, *_usse;
+
+	llist_for_each_entry_safe(usse, _usse, &hlr->usse_list, list)
+		hlr_usse_del(usse);
+}
diff --git a/src/hlr_ss_ussd.h b/src/hlr_ss_ussd.h
new file mode 100644
index 0000000..68becd3
--- /dev/null
+++ b/src/hlr_ss_ussd.h
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/gsm/gsm0480.h>
+
+/* Represents a single USSE (either the internal, or an external) */
+struct hlr_usse {
+	/* list in the per-HLR list of USSEs */
+	struct llist_head list;
+	/* back-pointer to the HLR instance */
+	struct hlr *hlr;
+	/* human-readable description */
+	const char *description;
+	/* name (must match the IPA ID tag) */
+	const char *name;
+	/* list of USSD-code matching patterns */
+	struct llist_head patterns;
+};
+
+/* Matching pattern types sorted by priority */
+enum hlr_usse_pattern_type {
+	HLR_USSE_PATTERN_CODE = 0, /* higher priority */
+	HLR_USSE_PATTERN_REGEXP,
+	HLR_USSE_PATTERN_PREFIX,
+};
+
+/* Represents a USSD-code matching pattern */
+struct hlr_usse_pattern {
+	/* link to the parent USSE */
+	struct llist_head list;
+	/* back-pointer to the parent USSE */
+	struct hlr_usse *usse;
+	/* Patter type, e.g. code, regexp or prefix */
+	enum hlr_usse_pattern_type type;
+	/* Mathing pattern, e.g. '*110*' for prefix */
+	const char *pattern;
+	/* Response format string, e.g. 'Your MSISDN is %m' */
+	char *rsp_fmt;
+};
+
+struct hlr_usse *hlr_usse_find(struct hlr *hlr, const char *name);
+struct hlr_usse *hlr_usse_alloc(struct hlr *hlr, const char *name);
+void hlr_usse_del(struct hlr_usse *usse);
+
+struct hlr_usse_pattern *hlr_usse_pattern_find(struct hlr_usse *usse,
+	enum hlr_usse_pattern_type type, const char *pattern);
+struct hlr_usse_pattern *hlr_usse_pattern_add(struct hlr_usse *usse,
+	enum hlr_usse_pattern_type type, const char *pattern);
+void hlr_usse_pattern_del(struct hlr_usse_pattern *pt);
+
+void hlr_usse_clean_up(struct hlr *hlr);
diff --git a/src/hlr_vty.c b/src/hlr_vty.c
index ecc2f5c..4e8e60b 100644
--- a/src/hlr_vty.c
+++ b/src/hlr_vty.c
@@ -3,6 +3,7 @@
 /* (C) 2016 sysmocom s.f.m.c. GmbH <info@sysmocom.de>
  * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
  * (C) 2018 Harald Welte <laforge@gnumonks.org>
+ * (C) 2018 by Vadim Yanitskiy <axilirator@gmail.com>
  *
  * All Rights Reserved
  *
@@ -29,6 +30,7 @@
 #include <osmocom/abis/ipa.h>
 
 #include "hlr_vty.h"
+#include "hlr_ss_ussd.h"
 #include "hlr_vty_subscr.h"
 #include "gsup_server.h"
 
@@ -94,7 +96,7 @@
 
 DEFUN(show_gsup_conn, show_gsup_conn_cmd,
 	"show gsup-connections",
-	SHOW_STR "GSUP Connections from VLRs, SGSNs, EUSEs\n")
+	SHOW_STR "GSUP Connections from VLRs, SGSNs, EUSSEs\n")
 {
 	struct osmo_gsup_server *gs = g_hlr->gs;
 	struct osmo_gsup_conn *conn;
@@ -119,12 +121,290 @@
 	return CMD_SUCCESS;
 }
 
+/***********************************************************************
+ * Unstructured Supplementary Services processing Entity configuration
+ ***********************************************************************/
+
+static struct cmd_node iusse_node = {
+	IUSSE_NODE,
+	"%s(config-hlr-iusse)# ",
+	1,
+};
+
+static struct cmd_node eusse_node = {
+	EUSSE_NODE,
+	"%s(config-hlr-eusse)# ",
+	1,
+};
+
+#define VTY_USSE_NAME_DESC \
+	"Internal USSD processing Entity\n" \
+	"Alphanumeric name of an External USSE\n"
+
+DEFUN(cfg_usse, cfg_usse_cmd,
+	"usse (internal|NAME)",
+	"Configure a particular USSE (USSD processing Entity)\n"
+	VTY_USSE_NAME_DESC)
+{
+	const char *name = argv[0];
+	struct hlr_usse *usse;
+
+	usse = hlr_usse_find(g_hlr, name);
+	if (!usse) {
+		usse = hlr_usse_alloc(g_hlr, name);
+		if (!usse)
+			return CMD_WARNING;
+	}
+
+	vty->index_sub = &usse->description;
+	vty->index = usse;
+
+	/* IUSSE or EUSSE? */
+	if (!strcmp(usse->name, "internal"))
+		vty->node = IUSSE_NODE;
+	else
+		vty->node = EUSSE_NODE;
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_no_usse, cfg_no_usse_cmd,
+	"no usse (internal|NAME)",
+	NO_STR "Remove a particular USSE (USSD processing Entity)\n"
+	VTY_USSE_NAME_DESC)
+{
+	const char *name = argv[0];
+	struct hlr_usse *usse;
+
+	usse = hlr_usse_find(g_hlr, name);
+	if (!usse) {
+		vty_out(vty, "%% Cannot remove non-existent "
+			"USSE '%s'%s", name, VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	if (g_hlr->usse_default == usse) {
+		vty_out(vty, "%% Cannot remove USSE '%s', "
+			"it is the default route%s", name, VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	hlr_usse_del(usse);
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_usse_default, cfg_usse_default_cmd,
+	"usse-default (internal|NAME)",
+	"Default USSD processing Entity\n"
+	VTY_USSE_NAME_DESC)
+{
+	const char *name = argv[0];
+	struct hlr_usse *usse;
+
+	usse = hlr_usse_find(g_hlr, name);
+	if (!usse) {
+		vty_out(vty, "%% Cannot find USSE '%s'%s", name, VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	if (g_hlr->usse_default == usse) {
+		vty_out(vty, "%% USSE '%s' is already "
+			"used by default%s", usse->name, VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	g_hlr->usse_default = usse;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_no_usse_default, cfg_no_usse_default_cmd,
+	"no usse-default",
+	NO_STR "No default USSD processing Entity "
+	"(drop all unmatched requests)\n")
+{
+	g_hlr->usse_default = NULL;
+	return CMD_SUCCESS;
+}
+
+#define VTY_USSE_PATTERN_CMD \
+	"pattern (code|regexp|prefix) PATTERN"
+
+#define VTY_USSE_PATTERN_DESC \
+	"Match USSD-request codes by exact value (e.g. '*#100#')\n" \
+	"Match USSD-request codes by regular expression (e.g. '^\\*[5-7]+'\\*)\n" \
+	"Match USSD-request codes by prefix (e.g. '*#' or '*110*')\n" \
+	"Matching pattern\n"
+
+static int _cfg_usse_pattern(struct vty *vty, int argc, const char **argv)
+{
+	struct hlr_usse *usse = vty->index;
+	enum hlr_usse_pattern_type type;
+	struct hlr_usse_pattern *pt;
+	bool is_iusse;
+
+	/* Determine which kind of matching pattern required */
+	switch (argv[0][0]) {
+	case 'c':
+		type = HLR_USSE_PATTERN_CODE;
+		break;
+	case 'r':
+		type = HLR_USSE_PATTERN_REGEXP;
+		break;
+	case 'p':
+		type = HLR_USSE_PATTERN_PREFIX;
+		break;
+	default:
+		/* Shouldn't happen, but let's make sure */
+		return CMD_WARNING;
+	}
+
+	/* IUSSE or EUSSE? */
+	is_iusse = !strcmp(usse->name, "internal");
+
+	/* Attempt to find pattern */
+	pt = hlr_usse_pattern_find(usse, type, argv[1]);
+	if (pt && !is_iusse) {
+		/* Response modification is only actual for IUSSE */
+		vty_out(vty, "%% Pattern already exists!%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	/* Allocate if required */
+	if (!pt) {
+		pt = hlr_usse_pattern_add(usse, type, argv[1]);
+		if (!pt) {
+			vty_out(vty, "%% Cannot add pattern '%s' of type '%s'%s",
+				argv[1], argv[0], VTY_NEWLINE);
+			return CMD_WARNING;
+		}
+	}
+
+	/* Response string for IUSSE */
+	if (is_iusse) {
+		if (pt->rsp_fmt)
+			talloc_free(pt->rsp_fmt);
+		pt->rsp_fmt = talloc_strdup(pt, argv_concat(argv, argc, 2));
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_iusse_pattern, cfg_iusse_pattern_cmd,
+	VTY_USSE_PATTERN_CMD " response .RESPONSE",
+	"Add or modify a USSD-code matching pattern\n"
+	VTY_USSE_PATTERN_DESC
+	"Response format string (e.g. 'Your MSISDN is %m')\n")
+{
+	return _cfg_usse_pattern(vty, argc, argv);
+}
+
+DEFUN(cfg_eusse_pattern, cfg_eusse_pattern_cmd,
+	VTY_USSE_PATTERN_CMD,
+	"Add a new USSD-code matching pattern\n"
+	VTY_USSE_PATTERN_DESC)
+{
+	return _cfg_usse_pattern(vty, argc, argv);
+}
+
+DEFUN(cfg_usse_no_pattern, cfg_usse_no_pattern_cmd,
+	"no " VTY_USSE_PATTERN_CMD,
+	NO_STR "Remove an existing USSD-code matching pattern\n"
+	VTY_USSE_PATTERN_DESC)
+{
+	struct hlr_usse *usse = vty->index;
+	enum hlr_usse_pattern_type type;
+	struct hlr_usse_pattern *pt;
+
+	/* Determine which kind of matching pattern required */
+	switch (argv[0][0]) {
+	case 'c':
+		type = HLR_USSE_PATTERN_CODE;
+		break;
+	case 'r':
+		type = HLR_USSE_PATTERN_REGEXP;
+		break;
+	case 'p':
+		type = HLR_USSE_PATTERN_PREFIX;
+		break;
+	default:
+		/* Shouldn't happen, but let's make sure */
+		return CMD_WARNING;
+	}
+
+	pt = hlr_usse_pattern_find(usse, type, argv[1]);
+	if (!pt) {
+		vty_out(vty, "%% Cannot remove non-existent pattern '%s' "
+			"of type '%s'%s", argv[1], argv[0], VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	hlr_usse_pattern_del(pt);
+	return CMD_SUCCESS;
+}
+
+static void dump_one_usse(struct vty *vty, struct hlr_usse *usse)
+{
+	struct hlr_usse_pattern *pt;
+	const char *pt_type;
+
+	vty_out(vty, " usse %s%s", usse->name, VTY_NEWLINE);
+	// FIXME: what about usse->description?
+
+	llist_for_each_entry(pt, &usse->patterns, list) {
+		/* Stringify pattern type */
+		switch (pt->type) {
+		case HLR_USSE_PATTERN_CODE:
+			pt_type = "code";
+			break;
+		case HLR_USSE_PATTERN_REGEXP:
+			pt_type = "regexp";
+			break;
+		case HLR_USSE_PATTERN_PREFIX:
+			pt_type = "prefix";
+			break;
+		default:
+			/* Should not happen */
+			OSMO_ASSERT(0);
+		}
+
+		if (pt->rsp_fmt != NULL)
+			vty_out(vty, "  pattern %s %s response %s%s", pt_type,
+				pt->pattern, pt->rsp_fmt, VTY_NEWLINE);
+		else
+			vty_out(vty, "  pattern %s %s%s", pt_type,
+				pt->pattern, VTY_NEWLINE);
+	}
+}
+
+static int config_write_usse(struct vty *vty)
+{
+	struct hlr_usse *usse;
+
+	if (g_hlr->usse_default == NULL)
+		vty_out(vty, " no usse-default%s", VTY_NEWLINE);
+	else
+		vty_out(vty, " usse-default %s%s",
+			g_hlr->usse_default->name, VTY_NEWLINE);
+
+	llist_for_each_entry(usse, &g_hlr->usse_list, list)
+		dump_one_usse(vty, usse);
+
+	return CMD_SUCCESS;
+}
+
+/***********************************************************************
+ * Common Code
+ ***********************************************************************/
+
 int hlr_vty_go_parent(struct vty *vty)
 {
 	switch (vty->node) {
 	case GSUP_NODE:
+	case IUSSE_NODE:
+	case EUSSE_NODE:
 		vty->node = HLR_NODE;
 		vty->index = NULL;
+		vty->index_sub = NULL;
 		break;
 	default:
 	case HLR_NODE:
@@ -169,5 +449,16 @@
 
 	install_element(GSUP_NODE, &cfg_hlr_gsup_bind_ip_cmd);
 
+	install_element(HLR_NODE, &cfg_usse_cmd);
+	install_element(HLR_NODE, &cfg_no_usse_cmd);
+	install_element(HLR_NODE, &cfg_usse_default_cmd);
+	install_element(HLR_NODE, &cfg_no_usse_default_cmd);
+	install_node(&eusse_node, config_write_usse);
+	install_element(EUSSE_NODE, &cfg_eusse_pattern_cmd);
+	install_element(EUSSE_NODE, &cfg_usse_no_pattern_cmd);
+	install_node(&iusse_node, NULL);
+	install_element(IUSSE_NODE, &cfg_iusse_pattern_cmd);
+	install_element(IUSSE_NODE, &cfg_usse_no_pattern_cmd);
+
 	hlr_vty_subscriber_init(hlr);
 }
diff --git a/src/hlr_vty.h b/src/hlr_vty.h
index cd2ff73..411077a 100644
--- a/src/hlr_vty.h
+++ b/src/hlr_vty.h
@@ -30,6 +30,8 @@
 enum hlr_vty_node {
 	HLR_NODE = _LAST_OSMOVTY_NODE + 1,
 	GSUP_NODE,
+	IUSSE_NODE,
+	EUSSE_NODE,
 };
 
 int hlr_vty_is_config_node(struct vty *vty, int node);