diff --git a/include/osmocom/gsupclient/gsup_req.h b/include/osmocom/gsupclient/gsup_req.h
new file mode 100644
index 0000000..c61483b
--- /dev/null
+++ b/include/osmocom/gsupclient/gsup_req.h
@@ -0,0 +1,119 @@
+/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <osmocom/gsm/gsup.h>
+#include <osmocom/gsupclient/ipa_name.h>
+
+struct osmo_gsup_req;
+
+#define LOG_GSUP_REQ_CAT_SRC(req, subsys, level, file, line, fmt, args...) \
+	LOGPSRC(subsys, level, file, line, "GSUP %u: %s: IMSI-%s %s: " fmt, \
+		(req) ? (req)->nr : 0, \
+		(req) ? osmo_ipa_name_to_str(&(req)->source_name) : "NULL", \
+		(req) ? (req)->gsup.imsi : "NULL", \
+		(req) ? osmo_gsup_message_type_name((req)->gsup.message_type) : "NULL", \
+		##args)
+#define LOG_GSUP_REQ_CAT(req, subsys, level, fmt, args...) \
+	LOG_GSUP_REQ_CAT_SRC(req, subsys, level, __FILE__, __LINE__, fmt, ##args)
+
+#define LOG_GSUP_REQ_SRC(req, level, file, line, fmt, args...) \
+	LOG_GSUP_REQ_CAT_SRC(req, DLGSUP, level, file, line, fmt, ##args)
+
+#define LOG_GSUP_REQ(req, level, fmt, args...) \
+	LOG_GSUP_REQ_SRC(req, level, __FILE__, __LINE__, fmt, ##args)
+
+typedef void (*osmo_gsup_req_send_response_t)(struct osmo_gsup_req *req, struct osmo_gsup_message *response);
+
+/* Keep track of an incoming request, to route back a response when it is ready.
+ * Particularly, a GSUP response to a request must contain various bits of information that need to be copied from the
+ * request for proxy/routing to work and for session states to remain valid. That is the main reason why (almost) all
+ * GSUP request/response should go through an osmo_gsup_req, even if it is handled synchronously.
+ */
+struct osmo_gsup_req {
+	/* The incoming GSUP message in decoded form. */
+	const struct osmo_gsup_message gsup;
+
+	/* Decoding result code. If decoding failed, this will be != 0. */
+	int decode_rc;
+
+	/* The ultimate source of this message: the source_name form the GSUP message, or, if not present, then the
+	 * immediate GSUP peer. GSUP messages going via a proxy reflect the initial source in the source_name.
+	 * This source_name is implicitly added to the routes for the conn the message was received on. */
+	struct osmo_ipa_name source_name;
+
+	/* If the source_name is not an immediate GSUP peer, this is set to the closest intermediate peer between here
+	 * and source_name. */
+	struct osmo_ipa_name via_proxy;
+
+	/* Identify this request by number, for logging. */
+	unsigned int nr;
+
+	/* osmo_gsup_req can be used by both gsup_server and gsup_client. The individual method of actually sending a
+	 * GSUP message is provided by this callback. */
+	osmo_gsup_req_send_response_t send_response_cb;
+
+	/* User supplied data pointer, may be used to provide context to send_response_cb(). */
+	void *cb_data;
+
+	/* List entry that can be used to keep a list of osmo_gsup_req instances; not used directly by osmo_gsup_req.c,
+	 * it is up to using implementations to keep a list. If this is non-NULL, osmo_gsup_req_free() calls
+	 * llist_del() on this. */
+	struct llist_head entry;
+
+	/* A decoded GSUP message still points into the received msgb. For a decoded osmo_gsup_message to remain valid,
+	 * we also need to keep the msgb. */
+	struct msgb *msg;
+};
+
+struct osmo_gsup_req *osmo_gsup_req_new(void *ctx, const struct osmo_ipa_name *from_peer, struct msgb *msg,
+					osmo_gsup_req_send_response_t send_response_cb, void *cb_data,
+					struct llist_head *add_to_list);
+void osmo_gsup_req_free(struct osmo_gsup_req *req);
+
+/*! See _osmo_gsup_req_respond() for details.
+ * Call _osmo_gsup_req_respond(), passing the caller's source file and line for logging. */
+#define osmo_gsup_req_respond(REQ, RESPONSE, ERROR, FINAL_RESPONSE) \
+	_osmo_gsup_req_respond(REQ, RESPONSE, ERROR, FINAL_RESPONSE, __FILE__, __LINE__)
+int _osmo_gsup_req_respond(struct osmo_gsup_req *req, struct osmo_gsup_message *response,
+			   bool error, bool final_response, const char *file, int line);
+
+/*! See _osmo_gsup_req_respond_msgt() for details.
+ * Call _osmo_gsup_req_respond_msgt(), passing the caller's source file and line for logging. */
+#define osmo_gsup_req_respond_msgt(REQ, MESSAGE_TYPE, FINAL_RESPONSE) \
+	_osmo_gsup_req_respond_msgt(REQ, MESSAGE_TYPE, FINAL_RESPONSE, __FILE__, __LINE__)
+int _osmo_gsup_req_respond_msgt(struct osmo_gsup_req *req, enum osmo_gsup_message_type message_type,
+				bool final_response, const char *file, int line);
+
+/*! See _osmo_gsup_req_respond_err() for details.
+ * Log an error message, and call _osmo_gsup_req_respond_err(), passing the caller's source file and line for logging.
+ */
+#define osmo_gsup_req_respond_err(REQ, CAUSE, FMT, args...) do { \
+		LOG_GSUP_REQ(REQ, LOGL_ERROR, "%s: " FMT "\n", \
+			     get_value_string(gsm48_gmm_cause_names, CAUSE), ##args); \
+		_osmo_gsup_req_respond_err(REQ, CAUSE, __FILE__, __LINE__); \
+	} while(0)
+void _osmo_gsup_req_respond_err(struct osmo_gsup_req *req, enum gsm48_gmm_cause cause,
+				const char *file, int line);
+
+int osmo_gsup_make_response(struct osmo_gsup_message *reply,
+			    const struct osmo_gsup_message *rx, bool error, bool final_response);
+
+size_t osmo_gsup_message_to_str_buf(char *buf, size_t bufsize, const struct osmo_gsup_message *msg);
+char *osmo_gsup_message_to_str_c(void *ctx, const struct osmo_gsup_message *msg);
diff --git a/include/osmocom/gsupclient/ipa_name.h b/include/osmocom/gsupclient/ipa_name.h
new file mode 100644
index 0000000..73cd1fb
--- /dev/null
+++ b/include/osmocom/gsupclient/ipa_name.h
@@ -0,0 +1,38 @@
+/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include <unistd.h>
+#include <stdint.h>
+
+/*! IPA Name: Arbitrary length blob, not necessarily zero-terminated.
+ * In osmo-hlr, struct hlr_subscriber is mostly used as static reference and cannot serve as talloc context, which is
+ * why this is also implemented as a fixed-maximum-size buffer instead of a talloc'd arbitrary sized buffer.
+ * NOTE: The length of val may be extended in the future if it becomes necessary.
+ * At the time of writing, this holds IPA unit name strings of very limited length.
+ */
+struct osmo_ipa_name {
+	size_t len;
+	uint8_t val[128];
+};
+
+int osmo_ipa_name_set(struct osmo_ipa_name *ipa_name, const uint8_t *val, size_t len);
+int osmo_ipa_name_set_str(struct osmo_ipa_name *ipa_name, const char *str_fmt, ...);
+int osmo_ipa_name_cmp(const struct osmo_ipa_name *a, const struct osmo_ipa_name *b);
+const char *osmo_ipa_name_to_str_c(void *ctx, const struct osmo_ipa_name *ipa_name);
+const char *osmo_ipa_name_to_str(const struct osmo_ipa_name *ipa_name);
diff --git a/include/osmocom/hlr/Makefile.am b/include/osmocom/hlr/Makefile.am
index 77a8764..532fa5d 100644
--- a/include/osmocom/hlr/Makefile.am
+++ b/include/osmocom/hlr/Makefile.am
@@ -9,6 +9,6 @@
 	hlr_vty.h \
 	hlr_vty_subscr.h \
 	logging.h \
-	luop.h \
+	lu_fsm.h \
 	rand.h \
 	$(NULL)
diff --git a/include/osmocom/hlr/db.h b/include/osmocom/hlr/db.h
index c927099..5c627be 100644
--- a/include/osmocom/hlr/db.h
+++ b/include/osmocom/hlr/db.h
@@ -3,6 +3,8 @@
 #include <stdbool.h>
 #include <sqlite3.h>
 
+#include <osmocom/gsupclient/ipa_name.h>
+
 struct hlr;
 
 enum stmt_idx {
@@ -151,13 +153,12 @@
 int db_subscr_get_by_imei(struct db_context *dbc, const char *imei, struct hlr_subscriber *subscr);
 int db_subscr_nam(struct db_context *dbc, const char *imsi, bool nam_val, bool is_ps);
 int db_subscr_lu(struct db_context *dbc, int64_t subscr_id,
-		 const char *vlr_or_sgsn_number, bool is_ps);
+		 const struct osmo_ipa_name *vlr_name, bool is_ps,
+		 const struct osmo_ipa_name *via_proxy);
 
 int db_subscr_purge(struct db_context *dbc, const char *by_imsi,
 		    bool purge_val, bool is_ps);
 
-int hlr_subscr_nam(struct hlr *hlr, struct hlr_subscriber *subscr, bool nam_val, bool is_ps);
-
 /*! Call sqlite3_column_text() and copy result to a char[].
  * \param[out] buf  A char[] used as sizeof() arg(!) and osmo_strlcpy() target.
  * \param[in] stmt  An sqlite3_stmt*.
@@ -168,3 +169,14 @@
 		const char *_txt = (const char *) sqlite3_column_text(stmt, idx); \
 		osmo_strlcpy(buf, _txt, sizeof(buf)); \
 	} while (0)
+
+/*! Call sqlite3_column_text() and copy result to a struct osmo_ipa_name.
+ * \param[out] ipa_name  A struct osmo_ipa_name* to write to.
+ * \param[in] stmt  An sqlite3_stmt*.
+ * \param[in] idx  Index in stmt's returned columns.
+ */
+#define copy_sqlite3_text_to_ipa_name(ipa_name, stmt, idx) \
+	do { \
+		const char *_txt = (const char *) sqlite3_column_text(stmt, idx); \
+		osmo_ipa_name_set_str(ipa_name, _txt); \
+	} while (0)
diff --git a/include/osmocom/hlr/gsup_router.h b/include/osmocom/hlr/gsup_router.h
index 0fc10d0..ee12a2b 100644
--- a/include/osmocom/hlr/gsup_router.h
+++ b/include/osmocom/hlr/gsup_router.h
@@ -3,6 +3,8 @@
 #include <stdint.h>
 #include <osmocom/hlr/gsup_server.h>
 
+struct osmo_ipa_name;
+
 struct gsup_route {
 	struct llist_head list;
 
@@ -12,10 +14,12 @@
 
 struct osmo_gsup_conn *gsup_route_find(struct osmo_gsup_server *gs,
 					const uint8_t *addr, size_t addrlen);
+struct osmo_gsup_conn *gsup_route_find_by_ipa_name(struct osmo_gsup_server *gs, const struct osmo_ipa_name *ipa_name);
 
 struct gsup_route *gsup_route_find_by_conn(const struct osmo_gsup_conn *conn);
 
 /* add a new route for the given address to the given conn */
+int gsup_route_add_ipa_name(struct osmo_gsup_conn *conn, const struct osmo_ipa_name *ipa_name);
 int gsup_route_add(struct osmo_gsup_conn *conn, const uint8_t *addr, size_t addrlen);
 
 /* delete all routes for the given connection */
@@ -24,3 +28,6 @@
 int osmo_gsup_addr_send(struct osmo_gsup_server *gs,
 			const uint8_t *addr, size_t addrlen,
 			struct msgb *msg);
+int osmo_gsup_send_to_ipa_name(struct osmo_gsup_server *gs, const struct osmo_ipa_name *ipa_name, struct msgb *msg);
+int osmo_gsup_enc_send_to_ipa_name(struct osmo_gsup_server *gs, const struct osmo_ipa_name *ipa_name,
+			  const struct osmo_gsup_message *gsup);
diff --git a/include/osmocom/hlr/gsup_server.h b/include/osmocom/hlr/gsup_server.h
index 14f5013..149971a 100644
--- a/include/osmocom/hlr/gsup_server.h
+++ b/include/osmocom/hlr/gsup_server.h
@@ -5,6 +5,8 @@
 #include <osmocom/abis/ipa.h>
 #include <osmocom/abis/ipaccess.h>
 #include <osmocom/gsm/gsup.h>
+#include <osmocom/gsupclient/ipa_name.h>
+#include <osmocom/gsupclient/gsup_req.h>
 
 #ifndef OSMO_GSUP_MAX_CALLED_PARTY_BCD_LEN
 #define OSMO_GSUP_MAX_CALLED_PARTY_BCD_LEN	43 /* TS 24.008 10.5.4.7 */
@@ -22,9 +24,6 @@
 	/* list of osmo_gsup_conn */
 	struct llist_head clients;
 
-	/* lu_operations list */
-	struct llist_head *luop;
-
 	struct ipa_server_link *link;
 	osmo_gsup_read_cb_t read_cb;
 	struct llist_head routes;
@@ -45,10 +44,15 @@
 	/* Set when Location Update is received: */
 	bool supports_cs; /* client supports OSMO_GSUP_CN_DOMAIN_CS */
 	bool supports_ps; /* client supports OSMO_GSUP_CN_DOMAIN_PS */
+
+	/* The IPA unit name received on this link. Routes with more unit names serviced by this link may exist in
+	 * osmo_gsup_server->routes, but this is the name the immediate peer identified as in the IPA handshake. */
+	struct osmo_ipa_name peer_name;
 };
 
 struct msgb *osmo_gsup_msgb_alloc(const char *label);
 
+struct osmo_gsup_req *osmo_gsup_conn_rx(struct osmo_gsup_conn *conn, struct msgb *msg);
 int osmo_gsup_conn_send(struct osmo_gsup_conn *conn, struct msgb *msg);
 int osmo_gsup_conn_ccm_get(const struct osmo_gsup_conn *clnt, uint8_t **addr,
 			   uint8_t tag);
@@ -57,7 +61,6 @@
 						 const char *ip_addr,
 						 uint16_t tcp_port,
 						 osmo_gsup_read_cb_t read_cb,
-						 struct llist_head *lu_op_lst,
 						 void *priv);
 
 void osmo_gsup_server_destroy(struct osmo_gsup_server *gsups);
diff --git a/include/osmocom/hlr/hlr.h b/include/osmocom/hlr/hlr.h
index 0564518..5885600 100644
--- a/include/osmocom/hlr/hlr.h
+++ b/include/osmocom/hlr/hlr.h
@@ -24,10 +24,16 @@
 
 #include <stdbool.h>
 #include <osmocom/core/linuxlist.h>
+#include <osmocom/gsm/ipa.h>
+#include <osmocom/core/tdef.h>
 
 #define HLR_DEFAULT_DB_FILE_PATH "hlr.db"
 
 struct hlr_euse;
+struct osmo_gsup_conn;
+enum osmo_gsup_message_type;
+
+extern struct osmo_tdef g_hlr_tdefs[];
 
 struct hlr {
 	/* GSUP server pointer */
@@ -43,6 +49,7 @@
 
 	/* Local bind addr */
 	char *gsup_bind_addr;
+	struct ipaccess_unit gsup_unit_name;
 
 	struct llist_head euse_list;
 	struct hlr_euse *euse_default;
@@ -67,3 +74,4 @@
 struct hlr_subscriber;
 
 void osmo_hlr_subscriber_update_notify(struct hlr_subscriber *subscr);
+int hlr_subscr_nam(struct hlr *hlr, struct hlr_subscriber *subscr, bool nam_val, bool is_ps);
diff --git a/include/osmocom/hlr/hlr_ussd.h b/include/osmocom/hlr/hlr_ussd.h
index 08e810e..8b2e837 100644
--- a/include/osmocom/hlr/hlr_ussd.h
+++ b/include/osmocom/hlr/hlr_ussd.h
@@ -46,8 +46,8 @@
 						   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);
+void rx_proc_ss_req(struct osmo_gsup_req *req);
+void rx_proc_ss_error(struct osmo_gsup_req *req);
 
 struct ss_session;
 struct ss_request;
@@ -56,6 +56,5 @@
 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);
+	int (*handle_ussd)(struct ss_session *ss, const struct osmo_gsup_message *gsup, const struct ss_request *req);
 };
diff --git a/include/osmocom/hlr/logging.h b/include/osmocom/hlr/logging.h
index 83f1acd..4e0a25c 100644
--- a/include/osmocom/hlr/logging.h
+++ b/include/osmocom/hlr/logging.h
@@ -9,6 +9,7 @@
 	DAUC,
 	DSS,
 	DMSLOOKUP,
+	DLU,
 };
 
 extern const struct log_info hlr_log_info;
diff --git a/include/osmocom/hlr/lu_fsm.h b/include/osmocom/hlr/lu_fsm.h
new file mode 100644
index 0000000..2440185
--- /dev/null
+++ b/include/osmocom/hlr/lu_fsm.h
@@ -0,0 +1,22 @@
+/* Copyright 2019 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * 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/>.
+ *
+ */
+
+#pragma once
+
+void lu_rx_gsup(struct osmo_gsup_req *req);
diff --git a/include/osmocom/hlr/luop.h b/include/osmocom/hlr/luop.h
deleted file mode 100644
index 77a1dec..0000000
--- a/include/osmocom/hlr/luop.h
+++ /dev/null
@@ -1,81 +0,0 @@
-/* OsmoHLR TX/RX lu operations */
-
-/* (C) 2017 sysmocom s.f.m.c. GmbH <info@sysmocom.de>
- * All Rights Reserved
- *
- * Author: Harald Welte <laforge@gnumonks.org>
- *
- * 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/>.
- *
- */
-
-#pragma once
-
-#include <stdbool.h>
-
-#include <osmocom/core/timer.h>
-#include <osmocom/gsm/gsup.h>
-
-#include <osmocom/hlr/db.h>
-#include <osmocom/hlr/gsup_server.h>
-
-#define CANCEL_TIMEOUT_SECS	30
-#define ISD_TIMEOUT_SECS	30
-
-enum lu_state {
-	LU_S_NULL,
-	LU_S_LU_RECEIVED,
-	LU_S_CANCEL_SENT,
-	LU_S_CANCEL_ACK_RECEIVED,
-	LU_S_ISD_SENT,
-	LU_S_ISD_ACK_RECEIVED,
-	LU_S_COMPLETE,
-};
-
-extern const struct value_string lu_state_names[];
-
-struct lu_operation {
-	/*! entry in global list of location update operations */
-	struct llist_head list;
-	/*! to which gsup_server do we belong */
-	struct osmo_gsup_server *gsup_server;
-	/*! state of the location update */
-	enum lu_state state;
-	/*! CS (false) or PS (true) Location Update? */
-	bool is_ps;
-	/*! currently running timer */
-	struct osmo_timer_list timer;
-
-	/*! subscriber related to this operation */
-	struct hlr_subscriber subscr;
-	/*! peer VLR/SGSN starting the request */
-	uint8_t *peer;
-};
-
-
-struct lu_operation *lu_op_alloc(struct osmo_gsup_server *srv);
-struct lu_operation *lu_op_alloc_conn(struct osmo_gsup_conn *conn);
-void lu_op_statechg(struct lu_operation *luop, enum lu_state new_state);
-bool lu_op_fill_subscr(struct lu_operation *luop, struct db_context *dbc,
-		       const char *imsi);
-struct lu_operation *lu_op_by_imsi(const char *imsi,
-				   const struct llist_head *lst);
-
-void lu_op_tx_error(struct lu_operation *luop, enum gsm48_gmm_cause cause);
-void lu_op_tx_ack(struct lu_operation *luop);
-void lu_op_tx_cancel_old(struct lu_operation *luop);
-void lu_op_tx_insert_subscr_data(struct lu_operation *luop);
-void lu_op_tx_del_subscr_data(struct lu_operation *luop);
-
-void lu_op_free(struct lu_operation *luop);