diff --git a/src/gsupclient/gsup_client.c b/src/gsupclient/gsup_client.c
new file mode 100644
index 0000000..761e8bd
--- /dev/null
+++ b/src/gsupclient/gsup_client.c
@@ -0,0 +1,345 @@
+/* Generic Subscriber Update Protocol client */
+
+/* (C) 2014-2016 by Sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Jacob Erlbeck
+ * Author: Neels Hofmeyr
+ *
+ * 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 <osmocom/gsupclient/gsup_client.h>
+
+#include <osmocom/abis/ipa.h>
+#include <osmocom/gsm/oap_client.h>
+#include <osmocom/gsm/protocol/ipaccess.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+
+#include <errno.h>
+#include <string.h>
+
+static void start_test_procedure(struct gsup_client *gsupc);
+
+static void gsup_client_send_ping(struct gsup_client *gsupc)
+{
+	struct msgb *msg = gsup_client_msgb_alloc();
+
+	msg->l2h = msgb_put(msg, 1);
+	msg->l2h[0] = IPAC_MSGT_PING;
+	ipa_msg_push_header(msg, IPAC_PROTO_IPACCESS);
+	ipa_client_conn_send(gsupc->link, msg);
+}
+
+static int gsup_client_connect(struct gsup_client *gsupc)
+{
+	int rc;
+
+	if (gsupc->is_connected)
+		return 0;
+
+	if (osmo_timer_pending(&gsupc->connect_timer)) {
+		LOGP(DLGSUP, LOGL_DEBUG,
+		     "GSUP connect: connect timer already running\n");
+		osmo_timer_del(&gsupc->connect_timer);
+	}
+
+	if (osmo_timer_pending(&gsupc->ping_timer)) {
+		LOGP(DLGSUP, LOGL_DEBUG,
+		     "GSUP connect: ping timer already running\n");
+		osmo_timer_del(&gsupc->ping_timer);
+	}
+
+	if (ipa_client_conn_clear_queue(gsupc->link) > 0)
+		LOGP(DLGSUP, LOGL_DEBUG, "GSUP connect: discarded stored messages\n");
+
+	rc = ipa_client_conn_open(gsupc->link);
+
+	if (rc >= 0) {
+		LOGP(DLGSUP, LOGL_NOTICE, "GSUP connecting to %s:%d\n",
+		     gsupc->link->addr, gsupc->link->port);
+		return 0;
+	}
+
+	LOGP(DLGSUP, LOGL_ERROR, "GSUP failed to connect to %s:%d: %s\n",
+	     gsupc->link->addr, gsupc->link->port, strerror(-rc));
+
+	if (rc == -EBADF || rc == -ENOTSOCK || rc == -EAFNOSUPPORT ||
+	    rc == -EINVAL)
+		return rc;
+
+	osmo_timer_schedule(&gsupc->connect_timer,
+			    GSUP_CLIENT_RECONNECT_INTERVAL, 0);
+
+	LOGP(DLGSUP, LOGL_INFO, "Scheduled timer to retry GSUP connect to %s:%d\n",
+	     gsupc->link->addr, gsupc->link->port);
+
+	return 0;
+}
+
+static void connect_timer_cb(void *gsupc_)
+{
+	struct gsup_client *gsupc = gsupc_;
+
+	if (gsupc->is_connected)
+		return;
+
+	gsup_client_connect(gsupc);
+}
+
+static void client_send(struct gsup_client *gsupc, int proto_ext,
+			struct msgb *msg_tx)
+{
+	ipa_prepend_header_ext(msg_tx, proto_ext);
+	ipa_msg_push_header(msg_tx, IPAC_PROTO_OSMO);
+	ipa_client_conn_send(gsupc->link, msg_tx);
+	/* msg_tx is now queued and will be freed. */
+}
+
+static void gsup_client_oap_register(struct gsup_client *gsupc)
+{
+	struct msgb *msg_tx;
+	int rc;
+	rc = osmo_oap_client_register(&gsupc->oap_state, &msg_tx);
+
+	if ((rc < 0) || (!msg_tx)) {
+		LOGP(DLGSUP, LOGL_ERROR, "GSUP OAP set up, but cannot register.\n");
+		return;
+	}
+
+	client_send(gsupc, IPAC_PROTO_EXT_OAP, msg_tx);
+}
+
+static void gsup_client_updown_cb(struct ipa_client_conn *link, int up)
+{
+	struct gsup_client *gsupc = link->data;
+
+	LOGP(DLGSUP, LOGL_INFO, "GSUP link to %s:%d %s\n",
+		     link->addr, link->port, up ? "UP" : "DOWN");
+
+	gsupc->is_connected = up;
+
+	if (up) {
+		start_test_procedure(gsupc);
+
+		if (gsupc->oap_state.state == OSMO_OAP_INITIALIZED)
+			gsup_client_oap_register(gsupc);
+
+		osmo_timer_del(&gsupc->connect_timer);
+	} else {
+		osmo_timer_del(&gsupc->ping_timer);
+
+		osmo_timer_schedule(&gsupc->connect_timer,
+				    GSUP_CLIENT_RECONNECT_INTERVAL, 0);
+	}
+}
+
+static int gsup_client_oap_handle(struct gsup_client *gsupc, struct msgb *msg_rx)
+{
+	int rc;
+	struct msgb *msg_tx;
+
+	/* If the oap_state is disabled, this will reject the messages. */
+	rc = osmo_oap_client_handle(&gsupc->oap_state, msg_rx, &msg_tx);
+	msgb_free(msg_rx);
+	if (rc < 0)
+		return rc;
+
+	if (msg_tx)
+		client_send(gsupc, IPAC_PROTO_EXT_OAP, msg_tx);
+
+	return 0;
+}
+
+static int gsup_client_read_cb(struct ipa_client_conn *link, struct msgb *msg)
+{
+	struct ipaccess_head *hh = (struct ipaccess_head *) msg->data;
+	struct ipaccess_head_ext *he = (struct ipaccess_head_ext *) msgb_l2(msg);
+	struct gsup_client *gsupc = (struct gsup_client *)link->data;
+	int rc;
+	struct ipaccess_unit ipa_dev = {
+		/* see gsup_client_create() on const vs non-const */
+		.unit_name = (char*)gsupc->unit_name,
+	};
+
+	OSMO_ASSERT(ipa_dev.unit_name);
+
+	msg->l2h = &hh->data[0];
+
+	rc = ipaccess_bts_handle_ccm(link, &ipa_dev, msg);
+
+	if (rc < 0) {
+		LOGP(DLGSUP, LOGL_NOTICE,
+		     "GSUP received an invalid IPA/CCM message from %s:%d\n",
+		     link->addr, link->port);
+		/* Link has been closed */
+		gsupc->is_connected = 0;
+		msgb_free(msg);
+		return -1;
+	}
+
+	if (rc == 1) {
+		uint8_t msg_type = *(msg->l2h);
+		/* CCM message */
+		if (msg_type == IPAC_MSGT_PONG) {
+			LOGP(DLGSUP, LOGL_DEBUG, "GSUP receiving PONG\n");
+			gsupc->got_ipa_pong = 1;
+		}
+
+		msgb_free(msg);
+		return 0;
+	}
+
+	if (hh->proto != IPAC_PROTO_OSMO)
+		goto invalid;
+
+	if (!he || msgb_l2len(msg) < sizeof(*he))
+		goto invalid;
+
+	msg->l2h = &he->data[0];
+
+	if (he->proto == IPAC_PROTO_EXT_GSUP) {
+		OSMO_ASSERT(gsupc->read_cb != NULL);
+		gsupc->read_cb(gsupc, msg);
+		/* expecting read_cb() to free msg */
+	} else if (he->proto == IPAC_PROTO_EXT_OAP) {
+		return gsup_client_oap_handle(gsupc, msg);
+		/* gsup_client_oap_handle frees msg */
+	} else
+		goto invalid;
+
+	return 0;
+
+invalid:
+	LOGP(DLGSUP, LOGL_NOTICE,
+	     "GSUP received an invalid IPA message from %s:%d, size = %d\n",
+	     link->addr, link->port, msgb_length(msg));
+
+	msgb_free(msg);
+	return -1;
+}
+
+static void ping_timer_cb(void *gsupc_)
+{
+	struct gsup_client *gsupc = gsupc_;
+
+	LOGP(DLGSUP, LOGL_INFO, "GSUP ping callback (%s, %s PONG)\n",
+	     gsupc->is_connected ? "connected" : "not connected",
+	     gsupc->got_ipa_pong ? "got" : "didn't get");
+
+	if (gsupc->got_ipa_pong) {
+		start_test_procedure(gsupc);
+		return;
+	}
+
+	LOGP(DLGSUP, LOGL_NOTICE, "GSUP ping timed out, reconnecting\n");
+	ipa_client_conn_close(gsupc->link);
+	gsupc->is_connected = 0;
+
+	gsup_client_connect(gsupc);
+}
+
+static void start_test_procedure(struct gsup_client *gsupc)
+{
+	osmo_timer_setup(&gsupc->ping_timer, ping_timer_cb, gsupc);
+
+	gsupc->got_ipa_pong = 0;
+	osmo_timer_schedule(&gsupc->ping_timer, GSUP_CLIENT_PING_INTERVAL, 0);
+	LOGP(DLGSUP, LOGL_DEBUG, "GSUP sending PING\n");
+	gsup_client_send_ping(gsupc);
+}
+
+struct gsup_client *gsup_client_create(void *talloc_ctx,
+				       const char *unit_name,
+				       const char *ip_addr,
+				       unsigned int tcp_port,
+				       gsup_client_read_cb_t read_cb,
+				       struct osmo_oap_client_config *oapc_config)
+{
+	struct gsup_client *gsupc;
+	int rc;
+
+	gsupc = talloc_zero(talloc_ctx, struct gsup_client);
+	OSMO_ASSERT(gsupc);
+
+	/* struct ipaccess_unit has a non-const unit_name, so let's copy to be
+	 * able to have a non-const unit_name here as well. To not taint the
+	 * public gsup_client API, let's store it in a const char* anyway. */
+	gsupc->unit_name = talloc_strdup(gsupc, unit_name);
+	OSMO_ASSERT(gsupc->unit_name);
+
+	/* a NULL oapc_config will mark oap_state disabled. */
+	rc = osmo_oap_client_init(oapc_config, &gsupc->oap_state);
+	if (rc != 0)
+		goto failed;
+
+	gsupc->link = ipa_client_conn_create(gsupc,
+					     /* no e1inp */ NULL,
+					     0,
+					     ip_addr, tcp_port,
+					     gsup_client_updown_cb,
+					     gsup_client_read_cb,
+					     /* default write_cb */ NULL,
+					     gsupc);
+	if (!gsupc->link)
+		goto failed;
+
+	osmo_timer_setup(&gsupc->connect_timer, connect_timer_cb, gsupc);
+
+	rc = gsup_client_connect(gsupc);
+
+	if (rc < 0)
+		goto failed;
+
+	gsupc->read_cb = read_cb;
+
+	return gsupc;
+
+failed:
+	gsup_client_destroy(gsupc);
+	return NULL;
+}
+
+void gsup_client_destroy(struct gsup_client *gsupc)
+{
+	osmo_timer_del(&gsupc->connect_timer);
+	osmo_timer_del(&gsupc->ping_timer);
+
+	if (gsupc->link) {
+		ipa_client_conn_close(gsupc->link);
+		ipa_client_conn_destroy(gsupc->link);
+		gsupc->link = NULL;
+	}
+	talloc_free(gsupc);
+}
+
+int gsup_client_send(struct gsup_client *gsupc, struct msgb *msg)
+{
+	if (!gsupc || !gsupc->is_connected) {
+		LOGP(DLGSUP, LOGL_ERROR, "GSUP not connected, unable to send %s\n", msgb_hexdump(msg));
+		msgb_free(msg);
+		return -ENOTCONN;
+	}
+
+	client_send(gsupc, IPAC_PROTO_EXT_GSUP, msg);
+
+	return 0;
+}
+
+struct msgb *gsup_client_msgb_alloc(void)
+{
+	return msgb_alloc_headroom(4000, 64, __func__);
+}