diff --git a/src/Makefile.am b/src/Makefile.am
index 093db8e..94575ad 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -53,6 +53,9 @@
 	hlr_vty_subscr.c \
 	gsup_send.c \
 	hlr_ussd.c \
+	proxy.c \
+	dgsm.c \
+	remote_hlr.c \
 	lu_fsm.c \
 	timestamp.c \
 	mslookup_server.c \
diff --git a/src/dgsm.c b/src/dgsm.c
new file mode 100644
index 0000000..57012c8
--- /dev/null
+++ b/src/dgsm.c
@@ -0,0 +1,247 @@
+/* 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 <errno.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/mslookup/mslookup_client.h>
+#include <osmocom/mslookup/mslookup_client_mdns.h>
+#include <osmocom/gsupclient/gsup_client.h>
+#include <osmocom/gsupclient/gsup_peer_id.h>
+#include <osmocom/hlr/logging.h>
+#include <osmocom/hlr/hlr.h>
+#include <osmocom/hlr/db.h>
+#include <osmocom/hlr/gsup_router.h>
+#include <osmocom/hlr/gsup_server.h>
+#include <osmocom/hlr/dgsm.h>
+#include <osmocom/hlr/proxy.h>
+#include <osmocom/hlr/remote_hlr.h>
+#include <osmocom/hlr/mslookup_server.h>
+#include <osmocom/hlr/mslookup_server_mdns.h>
+#include <osmocom/hlr/dgsm.h>
+
+void *dgsm_ctx = NULL;
+
+static void resolve_hlr_result_cb(struct osmo_mslookup_client *client,
+				  uint32_t request_handle,
+				  const struct osmo_mslookup_query *query,
+				  const struct osmo_mslookup_result *result)
+{
+	struct proxy *proxy = g_hlr->gs->proxy;
+	struct proxy_subscr proxy_subscr;
+	const struct osmo_sockaddr_str *remote_hlr_addr;
+
+	/* A remote HLR is answering back, indicating that it is the home HLR for a given IMSI.
+	 * There should be a mostly empty proxy entry for that IMSI.
+	 * Add the remote address data in the proxy. */
+	if (query->id.type != OSMO_MSLOOKUP_ID_IMSI) {
+		LOGP(DDGSM, LOGL_ERROR, "Expected IMSI ID type in mslookup query+result: %s\n",
+		     osmo_mslookup_result_name_c(OTC_SELECT, query, result));
+		return;
+	}
+
+	if (result->rc != OSMO_MSLOOKUP_RC_RESULT) {
+		LOG_DGSM(query->id.imsi, LOGL_ERROR, "Failed to resolve remote HLR: %s\n",
+			 osmo_mslookup_result_name_c(OTC_SELECT, query, result));
+		proxy_subscr_del(proxy, query->id.imsi);
+		return;
+	}
+
+	if (osmo_sockaddr_str_is_nonzero(&result->host_v4))
+		remote_hlr_addr = &result->host_v4;
+	else if (osmo_sockaddr_str_is_nonzero(&result->host_v6))
+		remote_hlr_addr = &result->host_v6;
+	else {
+		LOG_DGSM(query->id.imsi, LOGL_ERROR, "Invalid address for remote HLR: %s\n",
+			 osmo_mslookup_result_name_c(OTC_SELECT, query, result));
+		proxy_subscr_del(proxy, query->id.imsi);
+		return;
+	}
+
+	if (proxy_subscr_get_by_imsi(&proxy_subscr, proxy, query->id.imsi)) {
+		LOG_DGSM(query->id.imsi, LOGL_ERROR, "No proxy entry for mslookup result: %s\n",
+			 osmo_mslookup_result_name_c(OTC_SELECT, query, result));
+		return;
+	}
+
+	proxy_subscr_remote_hlr_resolved(proxy, &proxy_subscr, remote_hlr_addr);
+}
+
+/* Return true when the message has been handled by D-GSM. */
+bool dgsm_check_forward_gsup_msg(struct osmo_gsup_req *req)
+{
+	struct proxy_subscr proxy_subscr;
+	struct proxy *proxy = g_hlr->gs->proxy;
+	struct osmo_mslookup_query query;
+	struct osmo_mslookup_query_handling handling;
+	uint32_t request_handle;
+
+	/* If the IMSI is known in the local HLR, then we won't proxy. */
+	if (db_subscr_exists_by_imsi(g_hlr->dbc, req->gsup.imsi) == 0)
+		return false;
+
+	/* Are we already forwarding this IMSI to a remote HLR? */
+	if (proxy_subscr_get_by_imsi(&proxy_subscr, proxy, req->gsup.imsi) == 0) {
+		proxy_subscr_forward_to_remote_hlr(proxy, &proxy_subscr, req);
+		return true;
+	}
+
+	/* The IMSI is not known locally, so we want to proxy to a remote HLR, but no proxy entry exists yet. We need to
+	 * look up the subscriber in remote HLRs via D-GSM mslookup, forward GSUP and reply once a result is back from
+	 * there.  Defer message and kick off MS lookup. */
+
+	/* Add a proxy entry without a remote address to indicate that we are busy querying for a remote HLR. */
+	proxy_subscr = (struct proxy_subscr){};
+	OSMO_STRLCPY_ARRAY(proxy_subscr.imsi, req->gsup.imsi);
+	if (proxy_subscr_create_or_update(proxy, &proxy_subscr)) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Failed to create proxy entry\n");
+		return true;
+	}
+
+	/* Is a fixed gateway proxy configured? */
+	if (osmo_sockaddr_str_is_nonzero(&g_hlr->mslookup.client.gsup_gateway_proxy)) {
+		proxy_subscr_remote_hlr_resolved(proxy, &proxy_subscr, &g_hlr->mslookup.client.gsup_gateway_proxy);
+
+		/* Proxy database modified, update info */
+		if (proxy_subscr_get_by_imsi(&proxy_subscr, proxy, req->gsup.imsi)) {
+			osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Internal proxy error\n");
+			return true;
+		}
+
+		proxy_subscr_forward_to_remote_hlr(proxy, &proxy_subscr, req);
+		return true;
+	}
+
+	/* Kick off an mslookup for the remote HLR?  This check could be up first on the top, but do it only now so that
+	 * if the mslookup client disconnected, we still continue to service open proxy entries. */
+	if (!osmo_mslookup_client_active(g_hlr->mslookup.client.client)) {
+		LOG_GSUP_REQ(req, LOGL_DEBUG, "mslookup client not running, cannot query remote home HLR\n");
+		return false;
+	}
+
+	/* First spool message, then kick off mslookup. If the proxy denies this message type, then don't do anything. */
+	if (proxy_subscr_forward_to_remote_hlr(proxy, &proxy_subscr, req)) {
+		/* If the proxy denied forwarding, an error response was already generated. */
+		return true;
+	}
+
+	query = (struct osmo_mslookup_query){
+		.id = {
+			.type = OSMO_MSLOOKUP_ID_IMSI,
+		},
+	};
+	OSMO_STRLCPY_ARRAY(query.id.imsi, req->gsup.imsi);
+	OSMO_STRLCPY_ARRAY(query.service, OSMO_MSLOOKUP_SERVICE_HLR_GSUP);
+	handling = (struct osmo_mslookup_query_handling){
+		.min_wait_milliseconds = g_hlr->mslookup.client.result_timeout_milliseconds,
+		.result_cb = resolve_hlr_result_cb,
+	};
+	request_handle = osmo_mslookup_client_request(g_hlr->mslookup.client.client, &query, &handling);
+	if (!request_handle) {
+		LOG_DGSM(req->gsup.imsi, LOGL_ERROR, "Error dispatching mslookup query for home HLR: %s\n",
+			 osmo_mslookup_result_name_c(OTC_SELECT, &query, NULL));
+		proxy_subscr_del(proxy, req->gsup.imsi);
+		/* mslookup seems to not be working. Try handling it locally. */
+		return false;
+	}
+
+	return true;
+}
+
+void dgsm_init(void *ctx)
+{
+	dgsm_ctx = talloc_named_const(ctx, 0, "dgsm");
+	INIT_LLIST_HEAD(&g_hlr->mslookup.server.local_site_services);
+
+	g_hlr->mslookup.server.local_attach_max_age = 60 * 60;
+
+	g_hlr->mslookup.client.result_timeout_milliseconds = 2000;
+
+	g_hlr->gsup_unit_name.unit_name = "HLR";
+	g_hlr->gsup_unit_name.serno = "unnamed-HLR";
+	g_hlr->gsup_unit_name.swversion = PACKAGE_NAME "-" PACKAGE_VERSION;
+
+	osmo_sockaddr_str_from_str(&g_hlr->mslookup.server.mdns.bind_addr,
+				   OSMO_MSLOOKUP_MDNS_IP4, OSMO_MSLOOKUP_MDNS_PORT);
+	osmo_sockaddr_str_from_str(&g_hlr->mslookup.client.mdns.query_addr,
+				   OSMO_MSLOOKUP_MDNS_IP4, OSMO_MSLOOKUP_MDNS_PORT);
+}
+
+void dgsm_start(void *ctx)
+{
+	g_hlr->mslookup.client.client = osmo_mslookup_client_new(dgsm_ctx);
+	OSMO_ASSERT(g_hlr->mslookup.client.client);
+	g_hlr->mslookup.allow_startup = true;
+	mslookup_server_mdns_config_apply();
+	dgsm_mdns_client_config_apply();
+}
+
+void dgsm_stop()
+{
+	g_hlr->mslookup.allow_startup = false;
+	mslookup_server_mdns_config_apply();
+	dgsm_mdns_client_config_apply();
+}
+
+void dgsm_mdns_client_config_apply(void)
+{
+	/* Check whether to start/stop/restart mDNS client */
+	const struct osmo_sockaddr_str *current_bind_addr;
+	const char *current_domain_suffix;
+	current_bind_addr = osmo_mslookup_client_method_mdns_get_bind_addr(g_hlr->mslookup.client.mdns.running);
+	current_domain_suffix = osmo_mslookup_client_method_mdns_get_domain_suffix(g_hlr->mslookup.client.mdns.running);
+
+	bool should_run = g_hlr->mslookup.allow_startup
+		&& g_hlr->mslookup.client.enable && g_hlr->mslookup.client.mdns.enable;
+
+	bool should_stop = g_hlr->mslookup.client.mdns.running &&
+		(!should_run
+		 || osmo_sockaddr_str_cmp(&g_hlr->mslookup.client.mdns.query_addr,
+					  current_bind_addr)
+		 || strcmp(g_hlr->mslookup.client.mdns.domain_suffix,
+			   current_domain_suffix));
+
+	if (should_stop) {
+		osmo_mslookup_client_method_del(g_hlr->mslookup.client.client, g_hlr->mslookup.client.mdns.running);
+		g_hlr->mslookup.client.mdns.running = NULL;
+		LOGP(DDGSM, LOGL_NOTICE, "Stopped mslookup mDNS client\n");
+	}
+
+	if (should_run && !g_hlr->mslookup.client.mdns.running) {
+		g_hlr->mslookup.client.mdns.running =
+			osmo_mslookup_client_add_mdns(g_hlr->mslookup.client.client,
+						      g_hlr->mslookup.client.mdns.query_addr.ip,
+						      g_hlr->mslookup.client.mdns.query_addr.port,
+						      -1,
+						      g_hlr->mslookup.client.mdns.domain_suffix);
+		if (!g_hlr->mslookup.client.mdns.running)
+			LOGP(DDGSM, LOGL_ERROR, "Failed to start mslookup mDNS client with target "
+			     OSMO_SOCKADDR_STR_FMT "\n",
+			     OSMO_SOCKADDR_STR_FMT_ARGS(&g_hlr->mslookup.client.mdns.query_addr));
+		else
+			LOGP(DDGSM, LOGL_NOTICE, "Started mslookup mDNS client, sending mDNS requests to multicast "
+			     OSMO_SOCKADDR_STR_FMT "\n",
+			     OSMO_SOCKADDR_STR_FMT_ARGS(&g_hlr->mslookup.client.mdns.query_addr));
+	}
+
+	if (g_hlr->mslookup.client.enable && osmo_sockaddr_str_is_nonzero(&g_hlr->mslookup.client.gsup_gateway_proxy))
+			LOGP(DDGSM, LOGL_NOTICE,
+			     "mslookup client: all GSUP requests for unknown IMSIs will be forwarded to"
+			     " gateway-proxy " OSMO_SOCKADDR_STR_FMT "\n",
+			     OSMO_SOCKADDR_STR_FMT_ARGS(&g_hlr->mslookup.client.gsup_gateway_proxy));
+}
diff --git a/src/dgsm_vty.c b/src/dgsm_vty.c
index 83c6820..277fc54 100644
--- a/src/dgsm_vty.c
+++ b/src/dgsm_vty.c
@@ -61,6 +61,26 @@
 	return CMD_SUCCESS;
 }
 
+static int mslookup_client_mdns_to(struct vty *vty, int argc, const char **argv)
+{
+	const char *ip_str = argc > 0? argv[0] : g_hlr->mslookup.client.mdns.query_addr.ip;
+	const char *port_str = argc > 1? argv[1] : NULL;
+	uint16_t port_nr = port_str ? atoi(port_str) : g_hlr->mslookup.client.mdns.query_addr.port;
+	struct osmo_sockaddr_str addr;
+	if (osmo_sockaddr_str_from_str(&addr, ip_str, port_nr)
+	    || !osmo_sockaddr_str_is_nonzero(&addr)) {
+		vty_out(vty, "%% mslookup client: Invalid mDNS target address: %s %u%s",
+			ip_str, port_nr, VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	g_hlr->mslookup.client.mdns.query_addr = addr;
+	g_hlr->mslookup.client.mdns.enable = true;
+	g_hlr->mslookup.client.enable = true;
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
 #define MDNS_STR "Multicast DNS related configuration\n"
 #define MDNS_IP46_STR "multicast IPv4 address like " OSMO_MSLOOKUP_MDNS_IP4 \
 			" or IPv6 address like " OSMO_MSLOOKUP_MDNS_IP6 "\n"
@@ -71,6 +91,44 @@
 #define IP46_STR "IPv4 address like 1.2.3.4 or IPv6 address like a:b:c:d::1\n"
 #define PORT_STR "Service-specific port number\n"
 
+DEFUN(cfg_mslookup_mdns,
+      cfg_mslookup_mdns_cmd,
+      "mdns bind [IP] [<1-65535>]",
+      MDNS_STR
+      "Convenience shortcut: enable and configure both server and client for mDNS mslookup\n"
+      MDNS_IP46_STR MDNS_PORT_STR)
+{
+	int rc1 = mslookup_server_mdns_bind(vty, argc, argv);
+	int rc2 = mslookup_client_mdns_to(vty, argc, argv);
+	if (rc1 != CMD_SUCCESS)
+		return rc1;
+	return rc2;
+}
+
+DEFUN(cfg_mslookup_mdns_domain_suffix,
+      cfg_mslookup_mdns_domain_suffix_cmd,
+      "mdns domain-suffix DOMAIN_SUFFIX",
+      MDNS_STR MDNS_DOMAIN_SUFFIX_STR MDNS_DOMAIN_SUFFIX_STR)
+{
+	osmo_talloc_replace_string(g_hlr, &g_hlr->mslookup.server.mdns.domain_suffix, argv[0]);
+	osmo_talloc_replace_string(g_hlr, &g_hlr->mslookup.client.mdns.domain_suffix, argv[0]);
+	mslookup_server_mdns_config_apply();
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_no_mdns,
+      cfg_mslookup_no_mdns_cmd,
+      "no mdns bind",
+      NO_STR "Disable both server and client for mDNS mslookup\n")
+{
+	g_hlr->mslookup.server.mdns.enable = false;
+	g_hlr->mslookup.client.mdns.enable = false;
+	mslookup_server_mdns_config_apply();
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
 struct cmd_node mslookup_server_node = {
 	MSLOOKUP_SERVER_NODE,
 	"%s(config-mslookup-server)# ",
@@ -265,6 +323,81 @@
 	return CMD_SUCCESS;
 }
 
+struct cmd_node mslookup_client_node = {
+	MSLOOKUP_CLIENT_NODE,
+	"%s(config-mslookup-client)# ",
+	1,
+};
+
+DEFUN(cfg_mslookup_client,
+      cfg_mslookup_client_cmd,
+      "client",
+      "Enable and configure Distributed GSM mslookup client")
+{
+	vty->node = MSLOOKUP_CLIENT_NODE;
+	g_hlr->mslookup.client.enable = true;
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_no_client,
+      cfg_mslookup_no_client_cmd,
+      "no client",
+      NO_STR "Disable Distributed GSM mslookup client")
+{
+	g_hlr->mslookup.client.enable = false;
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_client_timeout,
+      cfg_mslookup_client_timeout_cmd,
+      "timeout <1-100000>",
+      "How long should the mslookup client wait for remote responses before evaluating received results\n"
+      "timeout in milliseconds\n")
+{
+	uint32_t val = atol(argv[0]);
+	g_hlr->mslookup.client.result_timeout_milliseconds = val;
+	return CMD_SUCCESS;
+}
+
+#define EXIT_HINT() \
+	if (vty->type != VTY_FILE) \
+		vty_out(vty, "%% 'exit' this node to apply changes%s", VTY_NEWLINE)
+
+
+DEFUN(cfg_mslookup_client_mdns_bind,
+      cfg_mslookup_client_mdns_bind_cmd,
+      "mdns bind [IP] [<1-65535>]",
+      MDNS_STR
+      "Enable mDNS client, and configure multicast address to send mDNS mslookup requests to\n"
+      MDNS_IP46_STR MDNS_PORT_STR)
+{
+	return mslookup_client_mdns_to(vty, argc, argv);
+}
+
+DEFUN(cfg_mslookup_client_mdns_domain_suffix,
+      cfg_mslookup_client_mdns_domain_suffix_cmd,
+      "mdns domain-suffix DOMAIN_SUFFIX",
+      MDNS_STR
+      MDNS_DOMAIN_SUFFIX_STR
+      MDNS_DOMAIN_SUFFIX_STR)
+{
+	osmo_talloc_replace_string(g_hlr, &g_hlr->mslookup.client.mdns.domain_suffix, argv[0]);
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_client_no_mdns_bind,
+      cfg_mslookup_client_no_mdns_bind_cmd,
+      "no mdns bind",
+      NO_STR "Disable mDNS client, do not query remote services by mDNS\n")
+{
+	g_hlr->mslookup.client.mdns.enable = false;
+	dgsm_mdns_client_config_apply();
+	return CMD_SUCCESS;
+}
+
 void config_write_msc_services(struct vty *vty, const char *indent, struct mslookup_server_msc_cfg *msc)
 {
 	struct mslookup_service_host *e;
@@ -282,7 +415,8 @@
 int config_write_mslookup(struct vty *vty)
 {
 	if (!g_hlr->mslookup.server.enable
-	    && llist_empty(&g_hlr->mslookup.server.local_site_services))
+	    && llist_empty(&g_hlr->mslookup.server.local_site_services)
+	    && !g_hlr->mslookup.client.enable)
 		return CMD_SUCCESS;
 
 	vty_out(vty, "mslookup%s", VTY_NEWLINE);
@@ -322,6 +456,57 @@
 			vty_out(vty, " no server%s", VTY_NEWLINE);
 	}
 
+	if (g_hlr->mslookup.client.enable) {
+		vty_out(vty, " client%s", VTY_NEWLINE);
+
+		if (osmo_sockaddr_str_is_nonzero(&g_hlr->mslookup.client.gsup_gateway_proxy))
+			vty_out(vty, "  gateway-proxy %s %u%s",
+				g_hlr->mslookup.client.gsup_gateway_proxy.ip,
+				g_hlr->mslookup.client.gsup_gateway_proxy.port,
+				VTY_NEWLINE);
+
+		if (g_hlr->mslookup.client.mdns.enable
+		    && osmo_sockaddr_str_is_nonzero(&g_hlr->mslookup.client.mdns.query_addr))
+			vty_out(vty, "  mdns bind %s %u%s",
+				g_hlr->mslookup.client.mdns.query_addr.ip,
+				g_hlr->mslookup.client.mdns.query_addr.port,
+				VTY_NEWLINE);
+		if (strcmp(g_hlr->mslookup.client.mdns.domain_suffix, OSMO_MDNS_DOMAIN_SUFFIX_DEFAULT))
+			vty_out(vty, "  mdns domain-suffix %s%s",
+				g_hlr->mslookup.client.mdns.domain_suffix,
+				VTY_NEWLINE);
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_client_gateway_proxy,
+      cfg_mslookup_client_gateway_proxy_cmd,
+      "gateway-proxy IP [<1-65535>]",
+      "Configure a fixed IP address to send all GSUP requests for unknown IMSIs to, without invoking a lookup for IMSI\n"
+      "IP address of the remote HLR\n" "GSUP port number (omit for default " OSMO_STRINGIFY_VAL(OSMO_GSUP_PORT) ")\n")
+{
+	const char *ip_str = argv[0];
+	const char *port_str = argc > 1 ? argv[1] : NULL;
+	struct osmo_sockaddr_str addr;
+
+	if (osmo_sockaddr_str_from_str(&addr, ip_str, port_str ? atoi(port_str) : OSMO_GSUP_PORT)
+	    || !osmo_sockaddr_str_is_nonzero(&addr)) {
+		vty_out(vty, "%% mslookup client: Invalid address for gateway-proxy: %s %s%s",
+			ip_str, port_str ? : "", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	g_hlr->mslookup.client.gsup_gateway_proxy = addr;
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_mslookup_client_no_gateway_proxy,
+      cfg_mslookup_client_no_gateway_proxy_cmd,
+      "no gateway-proxy",
+      NO_STR "Disable gateway proxy for GSUP with unknown IMSIs\n")
+{
+	g_hlr->mslookup.client.gsup_gateway_proxy = (struct osmo_sockaddr_str){};
 	return CMD_SUCCESS;
 }
 
@@ -361,6 +546,9 @@
 	install_element(CONFIG_NODE, &cfg_mslookup_cmd);
 
 	install_node(&mslookup_node, config_write_mslookup);
+	install_element(MSLOOKUP_NODE, &cfg_mslookup_mdns_cmd);
+	install_element(MSLOOKUP_NODE, &cfg_mslookup_mdns_domain_suffix_cmd);
+	install_element(MSLOOKUP_NODE, &cfg_mslookup_no_mdns_cmd);
 	install_element(MSLOOKUP_NODE, &cfg_mslookup_server_cmd);
 	install_element(MSLOOKUP_NODE, &cfg_mslookup_no_server_cmd);
 
@@ -378,5 +566,15 @@
 	install_element(MSLOOKUP_SERVER_MSC_NODE, &cfg_mslookup_server_msc_no_service_cmd);
 	install_element(MSLOOKUP_SERVER_MSC_NODE, &cfg_mslookup_server_msc_no_service_addr_cmd);
 
+	install_element(MSLOOKUP_NODE, &cfg_mslookup_client_cmd);
+	install_element(MSLOOKUP_NODE, &cfg_mslookup_no_client_cmd);
+	install_node(&mslookup_client_node, NULL);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_timeout_cmd);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_mdns_bind_cmd);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_mdns_domain_suffix_cmd);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_no_mdns_bind_cmd);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_gateway_proxy_cmd);
+	install_element(MSLOOKUP_CLIENT_NODE, &cfg_mslookup_client_no_gateway_proxy_cmd);
+
 	install_element_ve(&do_mslookup_show_services_cmd);
 }
diff --git a/src/gsup_server.c b/src/gsup_server.c
index effbdb0..35ad4e4 100644
--- a/src/gsup_server.c
+++ b/src/gsup_server.c
@@ -502,3 +502,39 @@
 
 	return 0;
 }
+
+int osmo_gsup_forward_to_local_peer(struct osmo_gsup_server *server, const struct osmo_gsup_peer_id *to_peer,
+				    struct osmo_gsup_req *req, struct osmo_gsup_message *modified_gsup)
+{
+	int rc;
+	/* To forward to a remote entity (HLR, SMSC,...), we need to indicate the original source name in the Source
+	 * Name IE to make sure the reply can be routed back. Store the sender in gsup->source_name -- the remote entity
+	 * is required to return this as gsup->destination_name so that the reply gets routed to the original sender. */
+	struct osmo_gsup_message forward = *(modified_gsup? : &req->gsup);
+
+	if (req->source_name.type != OSMO_GSUP_PEER_ID_IPA_NAME) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Unsupported GSUP peer id type: %s",
+					  osmo_gsup_peer_id_type_name(req->source_name.type));
+		rc = -ENOTSUP;
+		goto routing_error;
+	}
+	forward.source_name = req->source_name.ipa_name.val;
+	forward.source_name_len = req->source_name.ipa_name.len;
+
+	if (to_peer->type != OSMO_GSUP_PEER_ID_IPA_NAME) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Unsupported GSUP peer id type: %s",
+					  osmo_gsup_peer_id_type_name(to_peer->type));
+		rc = -ENOTSUP;
+		goto routing_error;
+	}
+	LOG_GSUP_REQ(req, LOGL_INFO, "Forwarding to %s\n", osmo_gsup_peer_id_to_str(to_peer));
+	rc = osmo_gsup_enc_send_to_ipa_name(server, &to_peer->ipa_name, &forward);
+	if (rc)
+		goto routing_error;
+	osmo_gsup_req_free(req);
+	return 0;
+
+routing_error:
+	osmo_gsup_req_respond_msgt(req, OSMO_GSUP_MSGT_ROUTING_ERROR, true);
+	return rc;
+}
diff --git a/src/hlr.c b/src/hlr.c
index 70bd2a5..fee0920 100644
--- a/src/hlr.c
+++ b/src/hlr.c
@@ -36,6 +36,7 @@
 #include <osmocom/gsm/gsm48_ie.h>
 #include <osmocom/gsm/gsm_utils.h>
 #include <osmocom/gsm/gsm23003.h>
+#include <osmocom/mslookup/mslookup_client.h>
 
 #include <osmocom/gsupclient/gsup_peer_id.h>
 #include <osmocom/hlr/db.h>
@@ -47,6 +48,8 @@
 #include <osmocom/hlr/rand.h>
 #include <osmocom/hlr/hlr_vty.h>
 #include <osmocom/hlr/hlr_ussd.h>
+#include <osmocom/hlr/dgsm.h>
+#include <osmocom/hlr/proxy.h>
 #include <osmocom/hlr/lu_fsm.h>
 #include <osmocom/mslookup/mdns.h>
 
@@ -500,6 +503,16 @@
 		}
 	}
 
+	/* Distributed GSM: check whether to proxy for / lookup a remote HLR.
+	 * It would require less database hits to do this only if a local-only operation fails with "unknown IMSI", but
+	 * it becomes semantically easier if we do this once-off ahead of time. */
+	if (osmo_mslookup_client_active(g_hlr->mslookup.client.client)
+	    || osmo_sockaddr_str_is_nonzero(&g_hlr->mslookup.client.gsup_gateway_proxy)) {
+		if (dgsm_check_forward_gsup_msg(req))
+			return 0;
+	}
+
+	/* HLR related messages that are handled at this HLR instance */
 	switch (req->gsup.message_type) {
 	/* requests sent to us */
 	case OSMO_GSUP_MSGT_SEND_AUTH_INFO_REQUEST:
@@ -699,6 +712,7 @@
 	INIT_LLIST_HEAD(&g_hlr->mslookup.server.local_site_services);
 	g_hlr->db_file_path = talloc_strdup(g_hlr, HLR_DEFAULT_DB_FILE_PATH);
 	g_hlr->mslookup.server.mdns.domain_suffix = talloc_strdup(g_hlr, OSMO_MDNS_DOMAIN_SUFFIX_DEFAULT);
+	g_hlr->mslookup.client.mdns.domain_suffix = talloc_strdup(g_hlr, OSMO_MDNS_DOMAIN_SUFFIX_DEFAULT);
 
 	/* Init default (call independent) SS session guard timeout value */
 	g_hlr->ncss_guard_timeout = NCSS_GUARD_TIMEOUT_DEFAULT;
@@ -709,6 +723,9 @@
 		exit(1);
 	}
 
+	/* Set up llists and objects, startup is happening from VTY commands. */
+	dgsm_init(hlr_ctx);
+
 	osmo_stats_init(hlr_ctx);
 	vty_init(&vty_info);
 	ctrl_vty_init(hlr_ctx);
@@ -764,10 +781,13 @@
 		LOGP(DMAIN, LOGL_FATAL, "Error starting GSUP server\n");
 		exit(1);
 	}
+	proxy_init(g_hlr->gs);
 
 	g_hlr->ctrl_bind_addr = ctrl_vty_get_bind_addr();
 	g_hlr->ctrl = hlr_controlif_setup(g_hlr);
 
+	dgsm_start(hlr_ctx);
+
 	osmo_init_ignore_signals();
 	signal(SIGINT, &signal_hdlr);
 	signal(SIGTERM, &signal_hdlr);
@@ -784,6 +804,7 @@
 	while (!quit)
 		osmo_select_main_ctx(0);
 
+	dgsm_stop();
 
 	osmo_gsup_server_destroy(g_hlr->gs);
 	db_close(g_hlr->dbc);
diff --git a/src/hlr_vty.c b/src/hlr_vty.c
index 6701cd9..e959be8 100644
--- a/src/hlr_vty.c
+++ b/src/hlr_vty.c
@@ -146,6 +146,24 @@
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_hlr_gsup_ipa_name,
+      cfg_hlr_gsup_ipa_name_cmd,
+      "ipa-name NAME",
+      "Set the IPA name of this HLR, for proxying to remote HLRs\n"
+      "A globally unique name for this HLR. For example: PLMN + redundancy server number: HLR-901-70-0. "
+      "This name is used for GSUP routing and must be set if multiple HLRs interconnect (e.g. mslookup "
+      "for Distributed GSM).\n")
+{
+	if (vty->type != VTY_FILE) {
+		vty_out(vty, "gsup/ipa-name: The GSUP IPA name cannot be changed at run-time; "
+			"It can only be set in the configuraton file.%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	g_hlr->gsup_unit_name.serno = talloc_strdup(g_hlr, argv[0]);
+	return CMD_SUCCESS;
+}
+
 /***********************************************************************
  * USSD Entity
  ***********************************************************************/
@@ -444,6 +462,7 @@
 	install_node(&gsup_node, config_write_hlr_gsup);
 
 	install_element(GSUP_NODE, &cfg_hlr_gsup_bind_ip_cmd);
+	install_element(GSUP_NODE, &cfg_hlr_gsup_ipa_name_cmd);
 
 	install_element(HLR_NODE, &cfg_database_cmd);
 
diff --git a/src/logging.c b/src/logging.c
index 15ef596..eab0510 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -37,6 +37,12 @@
 		.color = "\033[1;33m",
 		.enabled = 1, .loglevel = LOGL_NOTICE,
 	},
+	[DDGSM] = {
+		.name = "DDGSM",
+		.description = "Distributed GSM: MS lookup and proxy",
+		.color = "\033[1;35m",
+		.enabled = 1, .loglevel = LOGL_NOTICE,
+	},
 };
 
 const struct log_info hlr_log_info = {
diff --git a/src/mslookup_server.c b/src/mslookup_server.c
index 9c4dc58..885adf8 100644
--- a/src/mslookup_server.c
+++ b/src/mslookup_server.c
@@ -27,6 +27,7 @@
 #include <osmocom/hlr/db.h>
 #include <osmocom/hlr/timestamp.h>
 #include <osmocom/hlr/mslookup_server.h>
+#include <osmocom/hlr/proxy.h>
 
 static const struct osmo_mslookup_result not_found = {
 		.rc = OSMO_MSLOOKUP_RC_NOT_FOUND,
@@ -294,13 +295,84 @@
 	return true;
 }
 
-static bool subscriber_has_done_lu_here(const struct osmo_mslookup_query *query,
-					uint32_t *lu_age_p,
-					struct osmo_ipa_name *local_msc_name)
+
+/* Determine whether the subscriber with the given ID has routed a Location Updating via this HLR as first hop. Return
+ * true if it is attached at a local VLR, and we are serving as proxy for a remote home HLR.
+ */
+static bool subscriber_has_done_lu_here_proxy(const struct osmo_mslookup_query *query,
+					      uint32_t *lu_age,
+					      struct osmo_ipa_name *local_msc_name,
+					      struct proxy_subscr *ret_proxy_subscr)
+{
+	struct proxy_subscr proxy_subscr;
+	uint32_t age;
+	int rc;
+
+	/* See the local HLR record. If the subscriber is "at home" in this HLR and is also currently located here, we
+	 * will find a valid location updating and no vlr_via_proxy entry. */
+	switch (query->id.type) {
+	case OSMO_MSLOOKUP_ID_IMSI:
+		rc = proxy_subscr_get_by_imsi(&proxy_subscr, g_hlr->gs->proxy, query->id.imsi);
+		break;
+	case OSMO_MSLOOKUP_ID_MSISDN:
+		rc = proxy_subscr_get_by_msisdn(&proxy_subscr, g_hlr->gs->proxy, query->id.msisdn);
+		break;
+	default:
+		LOGP(DDGSM, LOGL_ERROR, "%s: unknown ID type\n",
+		     osmo_mslookup_result_name_c(OTC_SELECT, query, NULL));
+		return false;
+	}
+
+	if (rc) {
+		LOGP(DDGSM, LOGL_DEBUG, "%s: does not exist in GSUP proxy\n",
+		     osmo_mslookup_result_name_c(OTC_SELECT, query, NULL));
+		return false;
+	}
+
+	/* We only need to care about CS LU, since only CS services need D-GSM routing. */
+	if (!timestamp_age(&proxy_subscr.cs.last_lu, &age)
+	    || age > g_hlr->mslookup.server.local_attach_max_age) {
+		LOGP(DDGSM, LOGL_ERROR,
+		     "%s: last attach was at local VLR (proxying for remote HLR), but too long ago: %us > %us\n",
+		     osmo_mslookup_result_name_c(OTC_SELECT, query, NULL),
+		     age, g_hlr->mslookup.server.local_attach_max_age);
+		return false;
+	}
+
+	if (proxy_subscr.cs.vlr_via_proxy.len) {
+		LOGP(DDGSM, LOGL_DEBUG, "%s: last attach is not at local VLR, but at VLR '%s' via proxy '%s'\n",
+		     osmo_mslookup_result_name_c(OTC_SELECT, query, NULL),
+		     osmo_ipa_name_to_str(&proxy_subscr.cs.vlr_name),
+		     osmo_ipa_name_to_str(&proxy_subscr.cs.vlr_via_proxy));
+		return false;
+	}
+
+	*lu_age = age;
+	*local_msc_name = proxy_subscr.cs.vlr_name;
+	LOGP(DDGSM, LOGL_DEBUG, "%s: attached %u seconds ago at local VLR %s; proxying for remote HLR "
+	     OSMO_SOCKADDR_STR_FMT "\n",
+	     osmo_mslookup_result_name_c(OTC_SELECT, query, NULL),
+	     age, osmo_ipa_name_to_str(local_msc_name),
+	     OSMO_SOCKADDR_STR_FMT_ARGS(&proxy_subscr.remote_hlr_addr));
+
+	if (ret_proxy_subscr)
+		*ret_proxy_subscr = proxy_subscr;
+	return true;
+}
+
+bool subscriber_has_done_lu_here(const struct osmo_mslookup_query *query,
+				 uint32_t *lu_age_p, struct osmo_ipa_name *local_msc_name,
+				 char *ret_imsi, size_t ret_imsi_len)
 {
 	bool attached_here;
 	uint32_t lu_age = 0;
 	struct osmo_ipa_name msc_name = {};
+	bool attached_here_proxy;
+	uint32_t proxy_lu_age = 0;
+	struct osmo_ipa_name proxy_msc_name = {};
+	struct proxy_subscr proxy_subscr;
+	struct hlr_subscriber db_subscr;
+
 
 	/* First ask the local HLR db, but if the local proxy record indicates a more recent LU, use that instead.
 	 * For all usual cases, only one of these will reflect a LU, even if a subscriber had more than one home HLR:
@@ -310,9 +382,20 @@
 	 * the local HLR database, there might occur a situation where both reflect a LU. So, to be safe against all
 	 * situations, compare the two entries.
 	 */
-	attached_here = subscriber_has_done_lu_here_hlr(query, &lu_age, &msc_name, NULL);
+	attached_here = subscriber_has_done_lu_here_hlr(query, &lu_age, &msc_name, &db_subscr);
+	attached_here_proxy = subscriber_has_done_lu_here_proxy(query, &proxy_lu_age, &proxy_msc_name, &proxy_subscr);
 
-	/* Future: If proxy has a younger lu, replace. */
+	/* If proxy has a younger lu, replace. */
+	if (attached_here_proxy && (!attached_here || (proxy_lu_age < lu_age))) {
+		attached_here = true;
+		lu_age = proxy_lu_age;
+		msc_name = proxy_msc_name;
+		if (ret_imsi)
+			osmo_strlcpy(ret_imsi, proxy_subscr.imsi, ret_imsi_len);
+	} else if (attached_here) {
+		if (ret_imsi)
+			osmo_strlcpy(ret_imsi, db_subscr.imsi, ret_imsi_len);
+	}
 
 	if (attached_here && !msc_name.len) {
 		LOGP(DMSLOOKUP, LOGL_ERROR, "%s: attached here, but no VLR name known\n",
@@ -349,7 +432,7 @@
 	/* All other service types: answer when the subscriber has done a LU that is either listed in the local HLR or
 	 * in the GSUP proxy database: i.e. if the subscriber has done a Location Updating at an VLR belonging to this
 	 * HLR. Respond with whichever services are configured in the osmo-hlr.cfg. */
-	if (!subscriber_has_done_lu_here(query, &age, &msc_name)) {
+	if (!subscriber_has_done_lu_here(query, &age, &msc_name, NULL, 0)) {
 		*result = not_found;
 		return;
 	}
diff --git a/src/proxy.c b/src/proxy.c
new file mode 100644
index 0000000..b9cd313
--- /dev/null
+++ b/src/proxy.c
@@ -0,0 +1,554 @@
+/* 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 <string.h>
+#include <talloc.h>
+#include <errno.h>
+#include <inttypes.h>
+
+#include <osmocom/core/timer.h>
+#include <osmocom/gsm/gsup.h>
+#include <osmocom/gsm/gsm23003.h>
+#include <osmocom/gsm/gsm48_ie.h>
+#include <osmocom/gsupclient/gsup_client.h>
+#include <osmocom/gsupclient/gsup_req.h>
+
+#include <osmocom/hlr/logging.h>
+#include <osmocom/hlr/proxy.h>
+#include <osmocom/hlr/remote_hlr.h>
+#include <osmocom/hlr/gsup_server.h>
+#include <osmocom/hlr/gsup_router.h>
+
+#define LOG_PROXY_SUBSCR(proxy_subscr, level, fmt, args...) \
+	LOGP(DDGSM, level, "(Proxy IMSI-%s MSISDN-%s HLR-" OSMO_SOCKADDR_STR_FMT ") " fmt, \
+	     ((proxy_subscr) && *(proxy_subscr)->imsi)? (proxy_subscr)->imsi : "?", \
+	     ((proxy_subscr) && *(proxy_subscr)->msisdn)? (proxy_subscr)->msisdn : "?", \
+	     OSMO_SOCKADDR_STR_FMT_ARGS((proxy_subscr)? &(proxy_subscr)->remote_hlr_addr : NULL), \
+	     ##args)
+
+#define LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup_msg, level, fmt, args...) \
+		     LOG_PROXY_SUBSCR(proxy_subscr, level, "%s: " fmt, \
+				      (gsup_msg) ? osmo_gsup_message_type_name((gsup_msg)->message_type) : "NULL", \
+				      ##args)
+
+/* The proxy subscriber database.
+ * Why have a separate struct to add an llist_head entry?
+ * This is to keep the option open to store the proxy data in the database instead, without any visible effect outside
+ * of proxy.c. */
+struct proxy_subscr_listentry {
+	struct llist_head entry;
+	timestamp_t last_update;
+	struct proxy_subscr data;
+};
+
+struct proxy_pending_gsup_req {
+	struct llist_head entry;
+	struct osmo_gsup_req *req;
+	timestamp_t received_at;
+};
+
+/* Defer a GSUP message until we know a remote HLR to proxy to.
+ * Where to send this GSUP message is indicated by its IMSI: as soon as an MS lookup has yielded the IMSI's home HLR,
+ * that's where the message should go. */
+static void proxy_deferred_gsup_req_add(struct proxy *proxy, struct osmo_gsup_req *req)
+{
+	struct proxy_pending_gsup_req *m;
+
+	m = talloc_zero(proxy, struct proxy_pending_gsup_req);
+	OSMO_ASSERT(m);
+	m->req = req;
+	timestamp_update(&m->received_at);
+	llist_add_tail(&m->entry, &proxy->pending_gsup_reqs);
+}
+
+static void proxy_pending_req_remote_hlr_connect_result(struct osmo_gsup_req *req, struct remote_hlr *remote_hlr)
+{
+	if (!remote_hlr || !remote_hlr_is_up(remote_hlr)) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_IMSI_UNKNOWN, "Proxy: Failed to connect to home HLR");
+		return;
+	}
+
+	remote_hlr_gsup_forward_to_remote_hlr(remote_hlr, req, NULL);
+}
+
+static bool proxy_deferred_gsup_req_waiting(struct proxy *proxy, const char *imsi)
+{
+	struct proxy_pending_gsup_req *p;
+	OSMO_ASSERT(imsi);
+
+	llist_for_each_entry(p, &proxy->pending_gsup_reqs, entry) {
+		if (strcmp(p->req->gsup.imsi, imsi))
+			continue;
+		return true;
+	}
+	return false;
+}
+
+/* Result of looking for remote HLR. If it failed, pass remote_hlr as NULL. On failure, the remote_hlr may be passed
+ * NULL. */
+static void proxy_deferred_gsup_req_pop(struct proxy *proxy, const char *imsi, struct remote_hlr *remote_hlr)
+{
+	struct proxy_pending_gsup_req *p, *n;
+	OSMO_ASSERT(imsi);
+
+	llist_for_each_entry_safe(p, n, &proxy->pending_gsup_reqs, entry) {
+		if (strcmp(p->req->gsup.imsi, imsi))
+			continue;
+
+		proxy_pending_req_remote_hlr_connect_result(p->req, remote_hlr);
+		p->req = NULL;
+		llist_del(&p->entry);
+		talloc_free(p);
+	}
+}
+
+static bool proxy_subscr_matches_imsi(const struct proxy_subscr *proxy_subscr, const char *imsi)
+{
+	if (!proxy_subscr || !imsi)
+		return false;
+	return strcmp(proxy_subscr->imsi, imsi) == 0;
+}
+
+static bool proxy_subscr_matches_msisdn(const struct proxy_subscr *proxy_subscr, const char *msisdn)
+{
+	if (!proxy_subscr || !msisdn)
+		return false;
+	return strcmp(proxy_subscr->msisdn, msisdn) == 0;
+}
+
+static struct proxy_subscr_listentry *_proxy_get_by_imsi(struct proxy *proxy, const char *imsi)
+{
+	struct proxy_subscr_listentry *e;
+	if (!proxy)
+		return NULL;
+	llist_for_each_entry(e, &proxy->subscr_list, entry) {
+		if (proxy_subscr_matches_imsi(&e->data, imsi))
+			return e;
+	}
+	return NULL;
+}
+
+static struct proxy_subscr_listentry *_proxy_get_by_msisdn(struct proxy *proxy, const char *msisdn)
+{
+	struct proxy_subscr_listentry *e;
+	if (!proxy)
+		return NULL;
+	llist_for_each_entry(e, &proxy->subscr_list, entry) {
+		if (proxy_subscr_matches_msisdn(&e->data, msisdn))
+			return e;
+	}
+	return NULL;
+}
+
+int proxy_subscr_get_by_imsi(struct proxy_subscr *dst, struct proxy *proxy, const char *imsi)
+{
+	struct proxy_subscr_listentry *e = _proxy_get_by_imsi(proxy, imsi);
+	if (!e)
+		return -ENOENT;
+	*dst = e->data;
+	return 0;
+}
+
+int proxy_subscr_get_by_msisdn(struct proxy_subscr *dst, struct proxy *proxy, const char *msisdn)
+{
+	struct proxy_subscr_listentry *e = _proxy_get_by_msisdn(proxy, msisdn);
+	if (!e)
+		return -ENOENT;
+	*dst = e->data;
+	return 0;
+}
+
+int proxy_subscr_create_or_update(struct proxy *proxy, const struct proxy_subscr *proxy_subscr)
+{
+	struct proxy_subscr_listentry *e = _proxy_get_by_imsi(proxy, proxy_subscr->imsi);
+	if (!e) {
+		/* Does not exist yet */
+		e = talloc_zero(proxy, struct proxy_subscr_listentry);
+		llist_add(&e->entry, &proxy->subscr_list);
+	}
+	e->data = *proxy_subscr;
+	timestamp_update(&e->last_update);
+	return 0;
+}
+
+int _proxy_subscr_del(struct proxy_subscr_listentry *e)
+{
+	llist_del(&e->entry);
+	return 0;
+}
+
+int proxy_subscr_del(struct proxy *proxy, const char *imsi)
+{
+	struct proxy_subscr_listentry *e;
+	proxy_deferred_gsup_req_pop(proxy, imsi, NULL);
+	e = _proxy_get_by_imsi(proxy, imsi);
+	if (!e)
+		return -ENOENT;
+	return _proxy_subscr_del(e);
+}
+
+/* Discard stale proxy entries. */
+static void proxy_cleanup(void *proxy_v)
+{
+	struct proxy *proxy = proxy_v;
+	struct proxy_subscr_listentry *e, *n;
+	uint32_t age;
+	llist_for_each_entry_safe(e, n, &proxy->subscr_list, entry) {
+		if (!timestamp_age(&e->last_update, &age))
+			LOGP(DDGSM, LOGL_ERROR, "Invalid timestamp, deleting proxy entry\n");
+		else if (age <= proxy->fresh_time)
+			continue;
+		LOG_PROXY_SUBSCR(&e->data, LOGL_INFO, "proxy entry timed out, deleting\n");
+		_proxy_subscr_del(e);
+	}
+	if (proxy->gc_period)
+		osmo_timer_schedule(&proxy->gc_timer, proxy->gc_period, 0);
+	else
+		LOGP(DDGSM, LOGL_NOTICE, "Proxy cleanup is switched off (gc_period == 0)\n");
+}
+
+void proxy_set_gc_period(struct proxy *proxy, uint32_t gc_period)
+{
+	proxy->gc_period = gc_period;
+	proxy_cleanup(proxy);
+}
+
+void proxy_init(struct osmo_gsup_server *gsup_server_to_vlr)
+{
+	OSMO_ASSERT(!gsup_server_to_vlr->proxy);
+	struct proxy *proxy = talloc_zero(gsup_server_to_vlr, struct proxy);
+	*proxy = (struct proxy){
+		.gsup_server_to_vlr = gsup_server_to_vlr,
+		.fresh_time = 60*60,
+		.gc_period = 60,
+	};
+	INIT_LLIST_HEAD(&proxy->subscr_list);
+	INIT_LLIST_HEAD(&proxy->pending_gsup_reqs);
+
+	osmo_timer_setup(&proxy->gc_timer, proxy_cleanup, proxy);
+	/* Invoke to trigger the first timer schedule */
+	proxy_set_gc_period(proxy, proxy->gc_period);
+	gsup_server_to_vlr->proxy = proxy;
+}
+
+void proxy_del(struct proxy *proxy)
+{
+	osmo_timer_del(&proxy->gc_timer);
+	talloc_free(proxy);
+}
+
+/* All GSUP messages sent to the remote HLR pass through this function, to modify the subscriber state or disallow
+ * sending the message. Return 0 to allow sending the message. */
+static int proxy_acknowledge_gsup_to_remote_hlr(struct proxy *proxy, const struct proxy_subscr *proxy_subscr,
+						const struct osmo_gsup_req *req)
+{
+	struct proxy_subscr proxy_subscr_new = *proxy_subscr;
+	bool ps;
+	bool cs;
+	int rc;
+
+	if (req->source_name.type != OSMO_GSUP_PEER_ID_IPA_NAME) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, LOGL_ERROR,
+				     "Unsupported GSUP peer id type: %s\n",
+				     osmo_gsup_peer_id_type_name(req->source_name.type));
+		return -ENOTSUP;
+	}
+
+	switch (req->gsup.message_type) {
+
+	case OSMO_GSUP_MSGT_UPDATE_LOCATION_REQUEST:
+		/* Store the CS and PS VLR name in vlr_name_preliminary to later update the right {cs,ps} LU timestamp
+		 * when receiving an OSMO_GSUP_MSGT_UPDATE_LOCATION_RESULT. Store in vlr_name_preliminary so that in
+		 * case the LU fails, we keep the vlr_name intact. */
+		switch (req->gsup.cn_domain) {
+		case OSMO_GSUP_CN_DOMAIN_CS:
+			proxy_subscr_new.cs.vlr_name_preliminary = req->source_name.ipa_name;
+			break;
+		case OSMO_GSUP_CN_DOMAIN_PS:
+			proxy_subscr_new.ps.vlr_name_preliminary = req->source_name.ipa_name;
+			break;
+		default:
+			break;
+		}
+
+		ps = cs = false;
+		if (osmo_ipa_name_cmp(&proxy_subscr_new.cs.vlr_name_preliminary, &proxy_subscr->cs.vlr_name_preliminary))
+			cs = true;
+		if (osmo_ipa_name_cmp(&proxy_subscr_new.ps.vlr_name_preliminary, &proxy_subscr->ps.vlr_name_preliminary))
+			ps = true;
+
+		if (!(cs || ps)) {
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, LOGL_DEBUG, "VLR names remain unchanged\n");
+			break;
+		}
+
+		rc = proxy_subscr_create_or_update(proxy, &proxy_subscr_new);
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, rc ? LOGL_ERROR : LOGL_INFO,
+				     "%s: preliminary VLR name for%s%s to %s\n",
+				     rc ? "failed to update" : "updated",
+				     cs ? " CS" : "", ps ? " PS" : "",
+				     osmo_gsup_peer_id_to_str(&req->source_name));
+		break;
+	/* TODO: delete proxy entry in case of a Purge Request? */
+	default:
+		break;
+	}
+	return 0;
+}
+
+/* All GSUP messages received from the remote HLR to be sent to a local MSC pass through this function, to modify the
+ * subscriber state or disallow sending the message. Return 0 to allow sending the message.
+ * The local MSC shall be indicated by gsup.destination_name. */
+static int proxy_acknowledge_gsup_from_remote_hlr(struct proxy *proxy, const struct proxy_subscr *proxy_subscr,
+						  const struct osmo_gsup_message *gsup,
+						  struct remote_hlr *from_remote_hlr,
+						  const struct osmo_ipa_name *destination,
+						  const struct osmo_ipa_name *via_peer)
+{
+	struct proxy_subscr proxy_subscr_new = *proxy_subscr;
+	bool ps;
+	bool cs;
+	bool vlr_name_changed_cs = false;
+	bool vlr_name_changed_ps = false;
+	int rc;
+	struct osmo_ipa_name via_proxy = {};
+	if (osmo_ipa_name_cmp(via_peer, destination))
+		via_proxy = *via_peer;
+
+	switch (gsup->message_type) {
+	case OSMO_GSUP_MSGT_INSERT_DATA_REQUEST:
+		/* Remember the MSISDN of the subscriber. This does not need to be a preliminary record, because when
+		 * the HLR tells us about subscriber data, it is definitive info and there is no ambiguity (like there
+		 * would be with failed LU attempts from various sources). */
+		if (!gsup->msisdn_enc_len)
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_DEBUG, "No MSISDN in this Insert Data Request\n");
+		else if (gsm48_decode_bcd_number2(proxy_subscr_new.msisdn, sizeof(proxy_subscr_new.msisdn),
+						  gsup->msisdn_enc, gsup->msisdn_enc_len, 0))
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR, "Failed to decode MSISDN\n");
+		else if (!osmo_msisdn_str_valid(proxy_subscr_new.msisdn))
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR, "invalid MSISDN: %s\n",
+					     osmo_quote_str_c(OTC_SELECT, proxy_subscr_new.msisdn, -1));
+		else if (!strcmp(proxy_subscr->msisdn, proxy_subscr_new.msisdn))
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_DEBUG, "already have MSISDN = %s\n",
+					     proxy_subscr_new.msisdn);
+		else if (proxy_subscr_create_or_update(proxy, &proxy_subscr_new))
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR, "failed to update MSISDN to %s\n",
+					     proxy_subscr_new.msisdn);
+		else
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_INFO, "stored MSISDN=%s\n",
+					     proxy_subscr_new.msisdn);
+		break;
+
+	case OSMO_GSUP_MSGT_UPDATE_LOCATION_RESULT:
+		/* Update the Location Updating timestamp */
+		cs = ps = false;
+		if (!osmo_ipa_name_cmp(destination, &proxy_subscr->cs.vlr_name_preliminary)) {
+			timestamp_update(&proxy_subscr_new.cs.last_lu);
+			proxy_subscr_new.cs.vlr_name_preliminary = (struct osmo_ipa_name){};
+			vlr_name_changed_cs =
+				osmo_ipa_name_cmp(&proxy_subscr->cs.vlr_name, destination)
+				|| osmo_ipa_name_cmp(&proxy_subscr->cs.vlr_via_proxy, &via_proxy);
+			proxy_subscr_new.cs.vlr_name = *destination;
+			proxy_subscr_new.cs.vlr_via_proxy = via_proxy;
+			cs = true;
+		}
+		if (!osmo_ipa_name_cmp(destination, &proxy_subscr->ps.vlr_name_preliminary)) {
+			timestamp_update(&proxy_subscr_new.ps.last_lu);
+			proxy_subscr_new.ps.vlr_name_preliminary = (struct osmo_ipa_name){};
+			proxy_subscr_new.ps.vlr_name = *destination;
+			vlr_name_changed_ps =
+				osmo_ipa_name_cmp(&proxy_subscr->ps.vlr_name, destination)
+				|| osmo_ipa_name_cmp(&proxy_subscr->ps.vlr_via_proxy, &via_proxy);
+			proxy_subscr_new.ps.vlr_via_proxy = via_proxy;
+			ps = true;
+		}
+		if (!(cs || ps)) {
+			LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR,
+					     "destination is neither CS nor PS VLR: %s\n",
+					     osmo_ipa_name_to_str(destination));
+			return GMM_CAUSE_PROTO_ERR_UNSPEC;
+		}
+		rc = proxy_subscr_create_or_update(proxy, &proxy_subscr_new);
+
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, rc ? LOGL_ERROR : LOGL_INFO,
+				     "%s LU: timestamp for%s%s%s%s%s%s%s%s%s%s\n",
+				     rc ? "failed to update" : "updated",
+				     cs ? " CS" : "", ps ? " PS" : "",
+				     vlr_name_changed_cs? ", CS VLR=" : "",
+				     vlr_name_changed_cs? osmo_ipa_name_to_str(&proxy_subscr_new.cs.vlr_name) : "",
+				     proxy_subscr_new.cs.vlr_via_proxy.len ? " via proxy " : "",
+				     proxy_subscr_new.cs.vlr_via_proxy.len ?
+					     osmo_ipa_name_to_str(&proxy_subscr_new.cs.vlr_via_proxy) : "",
+				     vlr_name_changed_ps? ", PS VLR=" : "",
+				     vlr_name_changed_ps? osmo_ipa_name_to_str(&proxy_subscr_new.ps.vlr_name) : "",
+				     proxy_subscr_new.ps.vlr_via_proxy.len ? " via proxy " : "",
+				     proxy_subscr_new.ps.vlr_via_proxy.len ?
+					     osmo_ipa_name_to_str(&proxy_subscr_new.ps.vlr_via_proxy) : ""
+				    );
+		break;
+
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static void proxy_remote_hlr_connect_result_cb(const struct osmo_sockaddr_str *addr, struct remote_hlr *remote_hlr,
+					       void *data)
+{
+	struct proxy *proxy = data;
+	struct proxy_subscr_listentry *e;
+	if (!proxy)
+		return;
+	llist_for_each_entry(e, &proxy->subscr_list, entry) {
+		if (!osmo_sockaddr_str_cmp(addr, &e->data.remote_hlr_addr)) {
+			proxy_deferred_gsup_req_pop(proxy, e->data.imsi, remote_hlr);
+		}
+	}
+}
+
+/* Store the remote HLR's GSUP address for this proxy subscriber.
+ * This can be set before the remote_hlr is connected, or after.
+ * And, this can be set before the gsup_req has been queued for this HLR, or after.
+ */
+void proxy_subscr_remote_hlr_resolved(struct proxy *proxy, const struct proxy_subscr *proxy_subscr,
+				      const struct osmo_sockaddr_str *remote_hlr_addr)
+{
+	struct proxy_subscr proxy_subscr_new;
+
+	if (osmo_sockaddr_str_is_nonzero(&proxy_subscr->remote_hlr_addr)) {
+		if (!osmo_sockaddr_str_cmp(remote_hlr_addr, &proxy_subscr->remote_hlr_addr)) {
+			/* Already have this remote address */
+			return;
+		} else {
+			LOG_PROXY_SUBSCR(proxy_subscr, LOGL_NOTICE,
+					 "Remote HLR address changes to " OSMO_SOCKADDR_STR_FMT "\n",
+					 OSMO_SOCKADDR_STR_FMT_ARGS(remote_hlr_addr));
+		}
+	}
+
+	/* Store the address. Make a copy to modify. */
+	proxy_subscr_new = *proxy_subscr;
+	proxy_subscr = &proxy_subscr_new;
+	proxy_subscr_new.remote_hlr_addr = *remote_hlr_addr;
+
+	if (proxy_subscr_create_or_update(proxy, proxy_subscr)) {
+		LOG_PROXY_SUBSCR(proxy_subscr, LOGL_ERROR, "Failed to store proxy entry for remote HLR\n");
+		/* If no remote HLR is known for the IMSI, the proxy entry is pointless. */
+		proxy_subscr_del(proxy, proxy_subscr->imsi);
+		return;
+	}
+	LOG_PROXY_SUBSCR(proxy_subscr, LOGL_DEBUG, "Remote HLR resolved, stored address\n");
+
+	/* If any messages for this HLR are already spooled, connect now. Otherwise wait for
+	 * proxy_subscr_forward_to_remote_hlr() to connect then. */
+	if (proxy_deferred_gsup_req_waiting(proxy, proxy_subscr->imsi))
+		remote_hlr_get_or_connect(&proxy_subscr->remote_hlr_addr, true,
+					  proxy_remote_hlr_connect_result_cb, proxy);
+}
+
+int proxy_subscr_forward_to_remote_hlr(struct proxy *proxy, const struct proxy_subscr *proxy_subscr, struct osmo_gsup_req *req)
+{
+	struct remote_hlr *remote_hlr;
+	int rc;
+
+	rc = proxy_acknowledge_gsup_to_remote_hlr(proxy, proxy_subscr, req);
+	if (rc) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_PROTO_ERR_UNSPEC, "Proxy does not allow this message");
+		return rc;
+	}
+
+	if (!osmo_sockaddr_str_is_nonzero(&proxy_subscr->remote_hlr_addr)) {
+		/* We don't know the remote target yet. Still waiting for an MS lookup response, which will end up
+		 * calling proxy_subscr_remote_hlr_resolved(). See dgsm.c. */
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, LOGL_DEBUG, "deferring until remote HLR is known\n");
+		proxy_deferred_gsup_req_add(proxy, req);
+		return 0;
+	}
+
+	if (!osmo_gsup_peer_id_is_empty(&req->via_proxy)) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, LOGL_INFO, "VLR->HLR: forwarding from %s via proxy %s\n",
+				     osmo_gsup_peer_id_to_str(&req->source_name),
+				     osmo_gsup_peer_id_to_str(&req->via_proxy));
+	} else {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, &req->gsup, LOGL_INFO, "VLR->HLR: forwarding from %s\n",
+				     osmo_gsup_peer_id_to_str(&req->source_name));
+	}
+
+	/* We could always store in the defer queue and empty the queue if the connection is already up.
+	 * Slight optimisation: if the remote_hlr is already up and running, skip the defer queue.
+	 * First ask for an existing remote_hlr. */
+	remote_hlr = remote_hlr_get_or_connect(&proxy_subscr->remote_hlr_addr, false, NULL, NULL);
+	if (remote_hlr && remote_hlr_is_up(remote_hlr)) {
+		proxy_pending_req_remote_hlr_connect_result(req, remote_hlr);
+		return 0;
+	}
+
+	/* Not existing or not up. Defer req and ask to be notified when it is up.
+	 * If the remote_hlr exists but is not connected yet, there should actually already be a pending
+	 * proxy_remote_hlr_connect_result_cb queued, but it doesn't hurt to do that more often. */
+	proxy_deferred_gsup_req_add(proxy, req);
+	remote_hlr_get_or_connect(&proxy_subscr->remote_hlr_addr, true,
+				  proxy_remote_hlr_connect_result_cb, proxy);
+	return 0;
+}
+
+int proxy_subscr_forward_to_vlr(struct proxy *proxy, const struct proxy_subscr *proxy_subscr,
+				const struct osmo_gsup_message *gsup, struct remote_hlr *from_remote_hlr)
+{
+	struct osmo_ipa_name destination;
+	struct osmo_gsup_conn *vlr_conn;
+	struct msgb *msg;
+
+	if (osmo_ipa_name_set(&destination, gsup->destination_name, gsup->destination_name_len)) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR,
+				     "no valid Destination Name IE, cannot route to VLR.\n");
+		return GMM_CAUSE_INV_MAND_INFO;
+	}
+
+	/* Route to MSC/SGSN that we're proxying for */
+	vlr_conn = gsup_route_find_by_ipa_name(proxy->gsup_server_to_vlr, &destination);
+	if (!vlr_conn) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR,
+				     "Destination VLR unreachable: %s\n", osmo_ipa_name_to_str(&destination));
+		return GMM_CAUSE_MSC_TEMP_NOTREACH;
+	}
+
+	if (proxy_acknowledge_gsup_from_remote_hlr(proxy, proxy_subscr, gsup, from_remote_hlr, &destination,
+						   &vlr_conn->peer_name)) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR,
+				     "Proxy does not allow forwarding this message\n");
+		return GMM_CAUSE_PROTO_ERR_UNSPEC;
+	}
+
+	msg = osmo_gsup_msgb_alloc("GSUP proxy to VLR");
+	if (osmo_gsup_encode(msg, gsup)) {
+		LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_ERROR,
+				     "Failed to re-encode GSUP message, cannot forward\n");
+		return GMM_CAUSE_INV_MAND_INFO;
+	}
+
+	LOG_PROXY_SUBSCR_MSG(proxy_subscr, gsup, LOGL_INFO, "VLR<-HLR: forwarding to %s%s%s\n",
+			     osmo_ipa_name_to_str(&destination),
+			     osmo_ipa_name_cmp(&destination, &vlr_conn->peer_name) ? " via " : "",
+			     osmo_ipa_name_cmp(&destination, &vlr_conn->peer_name) ?
+						       osmo_ipa_name_to_str(&vlr_conn->peer_name) : "");
+	return osmo_gsup_conn_send(vlr_conn, msg);
+}
diff --git a/src/remote_hlr.c b/src/remote_hlr.c
new file mode 100644
index 0000000..e2e7d47
--- /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_GSUP_PEER_ID_IPA_NAME) {
+		osmo_gsup_req_respond_err(req, GMM_CAUSE_NET_FAIL, "Unsupported GSUP peer id type: %s",
+					  osmo_gsup_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);
+}