diff --git a/src/remote_hlr.c b/src/remote_hlr.c
new file mode 100644
index 0000000..00bfbb1
--- /dev/null
+++ b/src/remote_hlr.c
@@ -0,0 +1,252 @@
+/* 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/>.
+ *
+ */
+
+#include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
+#include <osmocom/gsm/gsup.h>
+#include <osmocom/gsm/gsm23003.h>
+#include <osmocom/abis/ipa.h>
+#include <osmocom/gsupclient/gsup_client.h>
+#include <osmocom/hlr/logging.h>
+#include <osmocom/hlr/hlr.h>
+#include <osmocom/hlr/gsup_server.h>
+#include <osmocom/hlr/gsup_router.h>
+#include <osmocom/hlr/remote_hlr.h>
+#include <osmocom/hlr/proxy.h>
+
+static LLIST_HEAD(remote_hlrs);
+
+static void remote_hlr_err_reply(struct remote_hlr *rh, const struct osmo_gsup_message *gsup_orig,
+				 enum gsm48_gmm_cause cause)
+{
+	struct osmo_gsup_message gsup_reply;
+
+	/* No need to answer if we couldn't parse an ERROR message type, only REQUESTs need an error reply. */
+	if (!OSMO_GSUP_IS_MSGT_REQUEST(gsup_orig->message_type))
+		return;
+
+	gsup_reply = (struct osmo_gsup_message){
+		.cause = cause,
+		.message_type = OSMO_GSUP_TO_MSGT_ERROR(gsup_orig->message_type),
+		.message_class = gsup_orig->message_class,
+
+		/* RP-Message-Reference is mandatory for SM Service */
+		.sm_rp_mr = gsup_orig->sm_rp_mr,
+	};
+
+	OSMO_STRLCPY_ARRAY(gsup_reply.imsi, gsup_orig->imsi);
+
+	/* For SS/USSD, it's important to keep both session state and ID IEs */
+	if (gsup_orig->session_state != OSMO_GSUP_SESSION_STATE_NONE) {
+		gsup_reply.session_state = OSMO_GSUP_SESSION_STATE_END;
+		gsup_reply.session_id = gsup_orig->session_id;
+	}
+
+	if (osmo_gsup_client_enc_send(rh->gsupc, &gsup_reply))
+		LOGP(DLGSUP, LOGL_ERROR, "Failed to send Error reply (imsi=%s)\n",
+		     osmo_quote_str(gsup_orig->imsi, -1));
+}
+
+/* We are receiving a GSUP message from a remote HLR to go back to a local MSC.
+ * The local MSC shall be indicated by gsup.destination_name. */
+static int remote_hlr_rx(struct osmo_gsup_client *gsupc, struct msgb *msg)
+{
+	struct remote_hlr *rh = gsupc->data;
+	struct proxy_subscr proxy_subscr;
+	struct osmo_gsup_message gsup;
+	int rc;
+
+	rc = osmo_gsup_decode(msgb_l2(msg), msgb_l2len(msg), &gsup);
+	if (rc < 0) {
+		LOG_REMOTE_HLR(rh, LOGL_ERROR, "Failed to decode GSUP message: '%s' (%d) [ %s]\n",
+			       get_value_string(gsm48_gmm_cause_names, -rc),
+			       -rc, osmo_hexdump(msg->data, msg->len));
+		return rc;
+	}
+
+	if (!osmo_imsi_str_valid(gsup.imsi)) {
+		LOG_REMOTE_HLR_MSG(rh, &gsup, LOGL_ERROR, "Invalid IMSI\n");
+		remote_hlr_err_reply(rh, &gsup, GMM_CAUSE_INV_MAND_INFO);
+		return -GMM_CAUSE_INV_MAND_INFO;
+	}
+
+	if (proxy_subscr_get_by_imsi(&proxy_subscr, g_hlr->gs->proxy, gsup.imsi)) {
+		LOG_REMOTE_HLR_MSG(rh, &gsup, LOGL_ERROR, "No proxy entry for this IMSI\n");
+		remote_hlr_err_reply(rh, &gsup, GMM_CAUSE_NET_FAIL);
+		return -GMM_CAUSE_NET_FAIL;
+	}
+
+	rc = proxy_subscr_forward_to_vlr(g_hlr->gs->proxy, &proxy_subscr, &gsup, rh);
+	if (rc) {
+		LOG_REMOTE_HLR_MSG(rh, &gsup, LOGL_ERROR, "Failed to forward GSUP message towards VLR\n");
+		remote_hlr_err_reply(rh, &gsup, GMM_CAUSE_NET_FAIL);
+		return -GMM_CAUSE_NET_FAIL;
+	}
+	return 0;
+}
+
+struct remote_hlr_pending_up {
+	struct llist_head entry;
+	remote_hlr_connect_result_cb_t connect_result_cb;
+	void *data;
+};
+
+static bool remote_hlr_up_down(struct osmo_gsup_client *gsupc, bool up)
+{
+	struct remote_hlr *remote_hlr = gsupc->data;
+	struct remote_hlr_pending_up *p, *n;
+	if (!up) {
+		LOG_REMOTE_HLR(remote_hlr, LOGL_NOTICE, "link to remote HLR is down, removing GSUP client\n");
+		remote_hlr_destroy(remote_hlr);
+		return false;
+	}
+
+	LOG_REMOTE_HLR(remote_hlr, LOGL_NOTICE, "link up\n");
+	llist_for_each_entry_safe(p, n, &remote_hlr->pending_up_callbacks, entry) {
+		if (p->connect_result_cb)
+			p->connect_result_cb(&remote_hlr->addr, remote_hlr, p->data);
+		llist_del(&p->entry);
+	}
+	return true;
+}
+
+bool remote_hlr_is_up(struct remote_hlr *remote_hlr)
+{
+	return remote_hlr && remote_hlr->gsupc && remote_hlr->gsupc->is_connected;
+}
+
+struct remote_hlr *remote_hlr_get_or_connect(const struct osmo_sockaddr_str *addr, bool connect,
+					     remote_hlr_connect_result_cb_t connect_result_cb, void *data)
+{
+	struct remote_hlr *rh = NULL;
+	struct remote_hlr *rh_i;
+	struct osmo_gsup_client_config cfg;
+
+	llist_for_each_entry(rh_i, &remote_hlrs, entry) {
+		if (!osmo_sockaddr_str_cmp(&rh_i->addr, addr)) {
+			rh = rh_i;
+			break;
+		}
+	}
+
+	if (rh)
+		goto add_result_cb;
+
+	if (!connect) {
+		if (connect_result_cb)
+			connect_result_cb(addr, NULL, data);
+		return NULL;
+	}
+
+	/* Doesn't exist yet, create a GSUP client to remote HLR. */
+	cfg = (struct osmo_gsup_client_config){
+		.ipa_dev = &g_hlr->gsup_unit_name,
+		.ip_addr = addr->ip,
+		.tcp_port = addr->port,
+		.oapc_config = NULL,
+		.read_cb = remote_hlr_rx,
+		.up_down_cb = remote_hlr_up_down,
+		.data = rh,
+	};
+	rh = talloc_zero(dgsm_ctx, struct remote_hlr);
+	OSMO_ASSERT(rh);
+	*rh = (struct remote_hlr){
+		.addr = *addr,
+		.gsupc = osmo_gsup_client_create3(rh, &cfg),
+	};
+	INIT_LLIST_HEAD(&rh->pending_up_callbacks);
+	if (!rh->gsupc) {
+		LOGP(DDGSM, LOGL_ERROR,
+		     "Failed to establish connection to remote HLR " OSMO_SOCKADDR_STR_FMT "\n",
+		     OSMO_SOCKADDR_STR_FMT_ARGS(addr));
+		talloc_free(rh);
+		if (connect_result_cb)
+			connect_result_cb(addr, NULL, data);
+		return NULL;
+	}
+
+	rh->gsupc->data = rh;
+	llist_add(&rh->entry, &remote_hlrs);
+
+add_result_cb:
+	if (connect_result_cb) {
+		if (remote_hlr_is_up(rh)) {
+			connect_result_cb(addr, rh, data);
+		} else {
+			struct remote_hlr_pending_up *p;
+			p = talloc_zero(rh, struct remote_hlr_pending_up);
+			OSMO_ASSERT(p);
+			p->connect_result_cb = connect_result_cb;
+			p->data = data;
+			llist_add_tail(&p->entry, &rh->pending_up_callbacks);
+		}
+	}
+	return rh;
+}
+
+void remote_hlr_destroy(struct remote_hlr *remote_hlr)
+{
+	osmo_gsup_client_destroy(remote_hlr->gsupc);
+	remote_hlr->gsupc = NULL;
+	llist_del(&remote_hlr->entry);
+	talloc_free(remote_hlr);
+}
+
+/* This function takes ownership of the msg, do not free it after passing to this function. */
+int remote_hlr_msgb_send(struct remote_hlr *remote_hlr, struct msgb *msg)
+{
+	int rc = osmo_gsup_client_send(remote_hlr->gsupc, msg);
+	if (rc) {
+		LOGP(DDGSM, LOGL_ERROR, "Failed to send GSUP message to " OSMO_SOCKADDR_STR_FMT "\n",
+		     OSMO_SOCKADDR_STR_FMT_ARGS(&remote_hlr->addr));
+	}
+	return rc;
+}
+
+/* A GSUP message was received from the MS/MSC side, forward it to the remote HLR. */
+void remote_hlr_gsup_forward_to_remote_hlr(struct remote_hlr *remote_hlr, struct osmo_gsup_req *req,
+					   struct osmo_gsup_message *modified_gsup)
+{
+	int rc;
+	struct msgb *msg;
+	/* To forward to a remote HLR, we need to indicate the source MSC's name in the Source Name IE to make sure the
+	 * reply can be routed back. Store the sender MSC in gsup->source_name -- the remote HLR is required to return
+	 * this as gsup->destination_name so that the reply gets routed to the original MSC. */
+	struct osmo_gsup_message forward;
+	if (modified_gsup)
+		forward = *modified_gsup;
+	else
+		forward = req->gsup;
+
+	if (req->source_name.type != OSMO_CNI_PEER_ID_IPA_NAME) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Unsupported GSUP peer id type: %s",
+					  osmo_cni_peer_id_type_name(req->source_name.type));
+		return;
+	}
+	forward.source_name = req->source_name.ipa_name.val;
+	forward.source_name_len = req->source_name.ipa_name.len;
+
+	msg = osmo_gsup_msgb_alloc("GSUP proxy to remote HLR");
+	rc = osmo_gsup_encode(msg, &forward);
+	if (rc) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Failed to encode GSUP message for forwarding");
+		return;
+	}
+	remote_hlr_msgb_send(remote_hlr, msg);
+	osmo_gsup_req_free(req);
+}