diff --git a/include/openbsc/Makefile.am b/include/openbsc/Makefile.am
index 2740a5d..532328c 100644
--- a/include/openbsc/Makefile.am
+++ b/include/openbsc/Makefile.am
@@ -84,6 +84,7 @@
 	trau_mux.h \
 	trau_upqueue.h \
 	ussd.h \
+	vlr.h \
 	vty.h \
 	v42bis.h \
 	v42bis_private.h \
diff --git a/include/openbsc/debug.h b/include/openbsc/debug.h
index 8a4247b..3feb7c3 100644
--- a/include/openbsc/debug.h
+++ b/include/openbsc/debug.h
@@ -38,12 +38,8 @@
 	DSUA,
 	DV42BIS,
 	DPCU,
+	DVLR,
 	Debug_LastEntry,
 };
 
-struct gsm_subscriber;
-
-void log_set_filter_vlr_subscr(struct log_target *target,
-			       struct gsm_subscriber *vlr_subscr);
-
 extern const struct log_info log_info;
diff --git a/include/openbsc/iu.h b/include/openbsc/iu.h
index f973ac1..8cf830e 100644
--- a/include/openbsc/iu.h
+++ b/include/openbsc/iu.h
@@ -22,9 +22,6 @@
 	IU_EVENT_SECURITY_MODE_COMPLETE,
 	IU_EVENT_IU_RELEASE, /* An actual Iu Release message was received */
 	IU_EVENT_LINK_INVALIDATED, /* A SUA link was lost or closed down */
-	/* FIXME: maybe IU_EVENT_IU_RELEASE and IU_EVENT_LINK_INVALIDATED
-	 * should be combined to one generic event that simply means the
-	 * ue_conn_ctx should no longer be used, for whatever reason. */
 };
 
 extern const struct value_string iu_event_type_names[];
@@ -35,7 +32,6 @@
 
 /* Implementations of iu_recv_cb_t shall find the ue_conn_ctx in msg->dst. */
 typedef int (* iu_recv_cb_t )(struct msgb *msg, struct gprs_ra_id *ra_id,
-			      /* TODO "gprs_" in generic CS+PS domain ^ */
 			      uint16_t *sai);
 
 typedef int (* iu_event_cb_t )(struct ue_conn_ctx *ue_ctx,
diff --git a/include/openbsc/vlr.h b/include/openbsc/vlr.h
new file mode 100644
index 0000000..90e3d7a
--- /dev/null
+++ b/include/openbsc/vlr.h
@@ -0,0 +1,413 @@
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/fsm.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
+#include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
+#include <osmocom/gsm/gsm23003.h>
+#include <openbsc/gsm_data.h>
+// for GSM_NAME_LENGTH
+#include <openbsc/gsm_subscriber.h>
+
+/* from 3s to 10s */
+#define GSM_29002_TIMER_S	10
+/* from 15s to 30s */
+#define GSM_29002_TIMER_M	30
+/* from 1min to 10min */
+#define GSM_29002_TIMER_ML	(10*60)
+/* from 28h to 38h */
+#define GSM_29002_TIMER_L	(32*60*60)
+
+
+/* VLR subscriber authentication state */
+enum vlr_subscr_auth_state {
+	/* subscriber needs to be autenticated */
+	VLR_SUB_AS_NEEDS_AUTH,
+	/* waiting for AuthInfo from HLR/AUC */
+	VLR_SUB_AS_NEEDS_AUTH_WAIT_AI,
+	/* waiting for response from subscriber */
+	VLR_SUB_AS_WAIT_RESP,
+	/* successfully authenticated */
+	VLR_SUB_AS_AUTHENTICATED,
+	/* subscriber needs re-sync */
+	VLR_SUB_AS_NEEDS_RESYNC,
+	/* waiting for AuthInfo with ReSync */
+	VLR_SUB_AS_NEEDS_AUTH_WAIT_SAI_RESYNC,
+	/* waiting for response from subscr, resync case */
+	VLR_SUB_AS_WAIT_RESP_RESYNC,
+	/* waiting for IMSI from subscriber */
+	VLR_SUB_AS_WAIT_ID_IMSI,
+	/* authentication has failed */
+	VLR_SUB_AS_AUTH_FAILED,
+};
+
+enum vlr_lu_event {
+	VLR_ULA_E_UPDATE_LA,	/* Initial trigger (LU from MS) */
+	VLR_ULA_E_SEND_ID_ACK,	/* Result of Send-ID from PVLR */
+	VLR_ULA_E_SEND_ID_NACK,	/* Result of Send-ID from PVLR */
+	VLR_ULA_E_AUTH_RES,	/* Result of auth procedure */
+	VLR_ULA_E_CIPH_RES,	/* Result of Ciphering Mode Command */
+	VLR_ULA_E_ID_IMSI,	/* IMSI recieved from MS */
+	VLR_ULA_E_ID_IMEI,	/* IMEI received from MS */
+	VLR_ULA_E_ID_IMEISV,	/* IMEISV received from MS */
+	VLR_ULA_E_HLR_LU_RES,	/* HLR UpdateLocation result */
+	VLR_ULA_E_UPD_HLR_COMPL,/* UpdatE_HLR_VLR result */
+	VLR_ULA_E_LU_COMPL_SUCCESS,/* Location_Update_Completion_VLR result */
+	VLR_ULA_E_LU_COMPL_FAILURE,/* Location_Update_Completion_VLR result */
+	VLR_ULA_E_NEW_TMSI_ACK,	/* TMSI Reallocation Complete */
+};
+
+enum vlr_ciph_result_cause {
+	VLR_CIPH_REJECT, /* ? */
+	VLR_CIPH_COMPL,
+};
+
+struct vlr_ciph_result {
+	enum vlr_ciph_result_cause cause;
+	const char *imeisv;
+};
+
+enum vlr_subscr_security_context {
+	VLR_SEC_CTX_NONE,
+	VLR_SEC_CTX_GSM,
+	VLR_SEC_CTX_UMTS,
+};
+
+enum vlr_lu_type {
+	VLR_LU_TYPE_PERIODIC,
+	VLR_LU_TYPE_IMSI_ATTACH,
+	VLR_LU_TYPE_REGULAR,
+};
+
+#define OSMO_LBUF_DECL(name, xlen)		\
+	struct {				\
+		uint8_t buf[xlen];		\
+		size_t len;			\
+	} name
+
+struct sgsn_mm_ctx;
+struct vlr_instance;
+
+/* The VLR subscriber is the part of the GSM subscriber state in VLR (CS) or
+ * SGSN (PS), particularly while interacting with the HLR via GSUP */
+struct vlr_subscr {
+	struct llist_head list;
+	struct vlr_instance *vlr;
+
+	/* TODO either populate from HLR or drop this completely? */
+	long long unsigned int id;
+
+	/* Data from HLR */				/* 3GPP TS 23.008 */
+	/* Always use vlr_subscr_set_imsi() to write to imsi[] */
+	char imsi[GSM23003_IMSI_MAX_DIGITS+1];		/* 2.1.1.1 */
+	char msisdn[GSM_EXTENSION_LENGTH+1];		/* 2.1.2 */
+	char name[GSM_NAME_LENGTH+1];			/* proprietary */
+	OSMO_LBUF_DECL(hlr, 16);			/* 2.4.7 */
+	uint32_t periodic_lu_timer;			/* 2.4.24 */
+	uint32_t age_indicator;				/* 2.17.1 */
+
+	/* Authentication Data */
+	struct gsm_auth_tuple auth_tuples[5];		/* 2.3.1-2.3.4 */
+	struct gsm_auth_tuple *last_tuple;
+	enum vlr_subscr_security_context sec_ctx;
+
+	/* Data local to VLR is below */
+	uint32_t tmsi;					/* 2.1.4 */
+	/* Newly allocated TMSI that was not yet acked by MS */
+	uint32_t tmsi_new;
+
+	/* some redundancy in information below? */
+	struct osmo_cell_global_id cgi;			/* 2.4.16 */
+	uint16_t lac;					/* 2.4.2 */
+
+	char imeisv[GSM23003_IMEISV_NUM_DIGITS+1];	/* 2.2.3 */
+	char imei[GSM23003_IMEISV_NUM_DIGITS+1];	/* 2.1.9 */
+	bool imsi_detached_flag;			/* 2.7.1 */
+	bool conf_by_radio_contact_ind;			/* 2.7.4.1 */
+	bool sub_dataconf_by_hlr_ind;			/* 2.7.4.2 */
+	bool loc_conf_in_hlr_ind;			/* 2.7.4.3 */
+	bool dormant_ind;				/* 2.7.8 */
+	bool cancel_loc_rx;				/* 2.7.8A */
+	bool ms_not_reachable_flag;			/* 2.10.2 (MNRF) */
+	bool la_allowed;
+
+	int use_count;
+	time_t expire_lu;	/* FIXME: overlap with periodic_lu_timer/age_indicator */
+
+	struct osmo_fsm_inst *lu_fsm;
+	struct osmo_fsm_inst *auth_fsm;
+	struct osmo_fsm_inst *proc_arq_fsm;
+
+	bool lu_complete;
+
+	void *msc_conn_ref;
+
+	/* PS (SGSN) specific parts */
+	struct {
+		struct llist_head pdp_list;
+		uint8_t rac;
+		uint8_t sac;
+		struct gprs_mm_ctx *mmctx;
+	} ps;
+	/* CS (NITB/CSCN) specific parts */
+	struct {
+		/* pending requests */
+		bool is_paging;
+		struct llist_head requests;
+	} cs;
+};
+
+enum vlr_proc_arq_result;
+
+enum vlr_ciph {
+	VLR_CIPH_NONE, /*< A5/0, no encryption */
+	VLR_CIPH_A5_1, /*< A5/1, encryption */
+	VLR_CIPH_A5_2, /*< A5/2, deprecated export-grade encryption */
+	VLR_CIPH_A5_3, /*< A5/3, 'new secure' encryption */
+};
+
+struct vlr_ops {
+	/* encode + transmit an AUTH REQ towards the MS.
+	 * \param[in] at  auth tuple providing rand, key_seq and autn.
+	 * \param[in] send_autn  True to send AUTN, for r99 UMTS auth.
+	 */
+	int (*tx_auth_req)(void *msc_conn_ref, struct gsm_auth_tuple *at,
+			   bool send_autn);
+	/* encode + transmit an AUTH REJECT towards the MS */
+	int (*tx_auth_rej)(void *msc_conn_ref);
+
+	/* encode + transmit an IDENTITY REQUEST towards the MS */
+	int (*tx_id_req)(void *msc_conn_ref, uint8_t mi_type);
+
+	int (*tx_lu_acc)(void *msc_conn_ref, uint32_t send_tmsi);
+	int (*tx_lu_rej)(void *msc_conn_ref, uint8_t cause);
+	int (*tx_cm_serv_acc)(void *msc_conn_ref);
+	int (*tx_cm_serv_rej)(void *msc_conn_ref, enum vlr_proc_arq_result result);
+
+	int (*set_ciph_mode)(void *msc_conn_ref, enum vlr_ciph ciph_mode,
+			     bool retrieve_imeisv);
+
+	/* notify MSC/SGSN that the subscriber data in VLR has been updated */
+	void (*subscr_update)(struct vlr_subscr *vsub);
+	/* notify MSC/SGSN that the given subscriber has been associated
+	 * with this msc_conn_ref */
+	void (*subscr_assoc)(void *msc_conn_ref, struct vlr_subscr *vsub);
+};
+
+enum vlr_timer {
+	VLR_T_3250,
+	VLR_T_3260,
+	VLR_T_3270,
+	_NUM_VLR_TIMERS
+};
+
+/* An instance of the VLR codebase */
+struct vlr_instance {
+	struct llist_head subscribers;
+	struct llist_head operations;
+	struct gsup_client *gsup_client;
+	struct vlr_ops ops;
+	struct {
+		bool retrieve_imeisv;
+		bool assign_tmsi;
+		bool check_imei_rqd;
+		int auth_tuple_max_use_count;
+		bool auth_reuse_old_sets_on_error;
+		bool parq_retrieve_imsi;
+		bool is_ps;
+		uint32_t timer[_NUM_VLR_TIMERS];
+	} cfg;
+	/* A free-form pointer for use by the caller */
+	void *user_ctx;
+};
+
+extern const struct value_string vlr_ciph_names[];
+static inline const char *vlr_ciph_name(enum vlr_ciph val)
+{
+	return get_value_string(vlr_ciph_names, val);
+}
+
+/* Location Updating request */
+struct osmo_fsm_inst *
+vlr_loc_update(struct osmo_fsm_inst *parent,
+	       uint32_t parent_event_success,
+	       uint32_t parent_event_failure,
+	       void *parent_event_data,
+	       struct vlr_instance *vlr, void *msc_conn_ref,
+	       enum vlr_lu_type type, uint32_t tmsi, const char *imsi,
+	       const struct osmo_location_area_id *old_lai,
+	       const struct osmo_location_area_id *new_lai,
+	       bool authentication_required,
+	       enum vlr_ciph ciphering_required,
+	       bool is_r99, bool is_utran,
+	       bool assign_tmsi);
+
+void vlr_loc_update_conn_timeout(struct osmo_fsm_inst *fi);
+
+/* tell the VLR that the subscriber connection is gone */
+int vlr_subscr_disconnected(struct vlr_subscr *vsub);
+
+int vlr_subscr_rx_id_resp(struct vlr_subscr *vsub, const uint8_t *mi, size_t mi_len);
+int vlr_subscr_rx_auth_resp(struct vlr_subscr *vsub, bool is_r99, bool is_utran,
+			    const uint8_t *res, uint8_t res_len);
+int vlr_subscr_rx_auth_fail(struct vlr_subscr *vsub, const uint8_t *auts);
+int vlr_subscr_tx_auth_fail_rep(struct vlr_subscr *vsub);
+void vlr_subscr_rx_ciph_res(struct vlr_subscr *vsub, struct vlr_ciph_result *res);
+int vlr_subscr_rx_tmsi_reall_compl(struct vlr_subscr *vsub);
+int vlr_subscr_rx_imsi_detach(struct vlr_subscr *vsub);
+void vlr_subscr_conn_timeout(struct vlr_subscr *vsub);
+
+struct vlr_instance *vlr_alloc(void *ctx, const struct vlr_ops *ops);
+int vlr_start(const char *gsup_unit_name, struct vlr_instance *vlr,
+	      const char *gsup_server_addr_str, uint16_t gsup_server_port);
+
+/* internal use only */
+
+struct osmo_fsm_inst *sub_pres_vlr_fsm_start(struct osmo_fsm_inst *parent,
+					     struct vlr_subscr *vsub,
+					     uint32_t term_event);
+struct osmo_fsm_inst *
+upd_hlr_vlr_proc_start(struct osmo_fsm_inst *parent,
+		       struct vlr_subscr *vsub,
+		       uint32_t parent_event);
+
+struct osmo_fsm_inst *
+lu_compl_vlr_proc_start(struct osmo_fsm_inst *parent,
+			struct vlr_subscr *vsub,
+			void *msc_conn_ref,
+			uint32_t parent_event_success,
+			uint32_t parent_event_failure);
+
+
+const char *vlr_subscr_name(struct vlr_subscr *vsub);
+const char *vlr_subscr_msisdn_or_name(struct vlr_subscr *vsub);
+
+#define vlr_subscr_find_by_imsi(vlr, imsi) \
+	_vlr_subscr_find_by_imsi(vlr, imsi, __BASE_FILE__, __LINE__)
+#define vlr_subscr_find_or_create_by_imsi(vlr, imsi, created) \
+	_vlr_subscr_find_or_create_by_imsi(vlr, imsi, created, \
+					   __BASE_FILE__, __LINE__)
+
+#define vlr_subscr_find_by_tmsi(vlr, tmsi) \
+	_vlr_subscr_find_by_tmsi(vlr, tmsi, __BASE_FILE__, __LINE__)
+#define vlr_subscr_find_or_create_by_tmsi(vlr, tmsi, created) \
+	_vlr_subscr_find_or_create_by_tmsi(vlr, tmsi, created, \
+					   __BASE_FILE__, __LINE__)
+
+#define vlr_subscr_find_by_msisdn(vlr, msisdn) \
+	_vlr_subscr_find_by_msisdn(vlr, msisdn, __BASE_FILE__, __LINE__)
+
+struct vlr_subscr *_vlr_subscr_find_by_imsi(struct vlr_instance *vlr,
+					    const char *imsi,
+					    const char *file, int line);
+struct vlr_subscr *_vlr_subscr_find_or_create_by_imsi(struct vlr_instance *vlr,
+						      const char *imsi,
+						      bool *created,
+						      const char *file,
+						      int line);
+
+struct vlr_subscr *_vlr_subscr_find_by_tmsi(struct vlr_instance *vlr,
+					    uint32_t tmsi,
+					    const char *file, int line);
+struct vlr_subscr *_vlr_subscr_find_or_create_by_tmsi(struct vlr_instance *vlr,
+						      uint32_t tmsi,
+						      bool *created,
+						      const char *file,
+						      int line);
+
+struct vlr_subscr *_vlr_subscr_find_by_msisdn(struct vlr_instance *vlr,
+					      const char *msisdn,
+					      const char *file, int line);
+
+#define vlr_subscr_get(sub) _vlr_subscr_get(sub, __BASE_FILE__, __LINE__)
+#define vlr_subscr_put(sub) _vlr_subscr_put(sub, __BASE_FILE__, __LINE__)
+struct vlr_subscr *_vlr_subscr_get(struct vlr_subscr *sub, const char *file, int line);
+struct vlr_subscr *_vlr_subscr_put(struct vlr_subscr *sub, const char *file, int line);
+
+struct vlr_subscr *vlr_subscr_alloc(struct vlr_instance *vlr);
+void vlr_subscr_free(struct vlr_subscr *vsub);
+int vlr_subscr_alloc_tmsi(struct vlr_subscr *vsub);
+
+void vlr_subscr_set_imsi(struct vlr_subscr *vsub, const char *imsi);
+void vlr_subscr_set_imei(struct vlr_subscr *vsub, const char *imei);
+void vlr_subscr_set_imeisv(struct vlr_subscr *vsub, const char *imeisv);
+void vlr_subscr_set_msisdn(struct vlr_subscr *vsub, const char *msisdn);
+
+bool vlr_subscr_matches_imsi(struct vlr_subscr *vsub, const char *imsi);
+bool vlr_subscr_matches_tmsi(struct vlr_subscr *vsub, uint32_t tmsi);
+bool vlr_subscr_matches_msisdn(struct vlr_subscr *vsub, const char *msisdn);
+bool vlr_subscr_matches_imei(struct vlr_subscr *vsub, const char *imei);
+
+uint32_t vlr_timer(struct vlr_instance *vlr, uint32_t timer);
+
+int vlr_subscr_changed(struct vlr_subscr *vsub);
+int vlr_subscr_purge(struct vlr_subscr *vsub);
+void vlr_subscr_cancel(struct vlr_subscr *vsub, enum gsm48_gmm_cause cause);
+
+
+/* Process Acccess Request FSM */
+
+enum vlr_proc_arq_result {
+	VLR_PR_ARQ_RES_NONE,
+	VLR_PR_ARQ_RES_SYSTEM_FAILURE,
+	VLR_PR_ARQ_RES_ILLEGAL_SUBSCR,
+	VLR_PR_ARQ_RES_UNIDENT_SUBSCR,
+	VLR_PR_ARQ_RES_ROAMING_NOTALLOWED,
+	VLR_PR_ARQ_RES_ILLEGAL_EQUIP,
+	VLR_PR_ARQ_RES_UNKNOWN_ERROR,
+	VLR_PR_ARQ_RES_TIMEOUT,
+	VLR_PR_ARQ_RES_PASSED,
+};
+
+extern const struct value_string vlr_proc_arq_result_names[];
+static inline const char *vlr_proc_arq_result_name(enum vlr_proc_arq_result res)
+{
+	return get_value_string(vlr_proc_arq_result_names, res);
+}
+
+enum proc_arq_vlr_event {
+	PR_ARQ_E_START,
+	PR_ARQ_E_ID_IMSI,
+	PR_ARQ_E_AUTH_RES,
+	PR_ARQ_E_CIPH_RES,
+	PR_ARQ_E_UPD_LOC_RES,
+	PR_ARQ_E_TRACE_RES,
+	PR_ARQ_E_IMEI_RES,
+	PR_ARQ_E_PRES_RES,
+	PR_ARQ_E_TMSI_ACK,
+};
+
+enum vlr_parq_type {
+	VLR_PR_ARQ_T_INVALID = 0, /* to guard against unset vars */
+	VLR_PR_ARQ_T_CM_SERV_REQ,
+	VLR_PR_ARQ_T_PAGING_RESP,
+	/* FIXME: differentiate between services of 24.008 10.5.3.3 */
+};
+
+/* Process Access Request (CM SERV REQ / PAGING RESP) */
+void
+vlr_proc_acc_req(struct osmo_fsm_inst *parent,
+		 uint32_t parent_event_success,
+		 uint32_t parent_event_failure,
+		 void *parent_event_data,
+		 struct vlr_instance *vlr, void *msc_conn_ref,
+		 enum vlr_parq_type type, const uint8_t *mi_lv,
+		 const struct osmo_location_area_id *lai,
+		 bool authentication_required,
+		 enum vlr_ciph ciphering_required,
+		 bool is_r99, bool is_utran);
+
+void vlr_parq_conn_timeout(struct osmo_fsm_inst *fi);
+
+void vlr_parq_fsm_init(void);
+
+int vlr_set_ciph_mode(struct vlr_instance *vlr,
+		      struct osmo_fsm_inst *fi,
+		      void *msc_conn_ref,
+		      enum vlr_ciph ciph_mode,
+		      bool retrieve_imeisv);
+
+void log_set_filter_vlr_subscr(struct log_target *target,
+			       struct vlr_subscr *vlr_subscr);