diff --git a/include/osmocom/hlr/proxy_broken_link_cache.h b/include/osmocom/hlr/proxy_broken_link_cache.h
new file mode 100644
index 0000000..9467a9b
--- /dev/null
+++ b/include/osmocom/hlr/proxy_broken_link_cache.h
@@ -0,0 +1,37 @@
+/* Copyright 2020 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.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/>.
+ *
+ */
+
+/* If a subscriber from a remote site has successfully attached at this local site, and the link to the subscriber's
+ * home HLR has succeeded, this will try to bridge the time of temporary link failure to that home HLR.
+ * Tasks to take over from the unreachable home HLR:
+ * - Resend known auth tuples on OSMO_GSUP_MSGT_SEND_AUTH_INFO_REQUEST.
+ * - ...?
+ *
+ *
+ */
+
+/* Data stored per subscriber */
+struct proxy_broken_link_cache {
+	struct osmo_auth_vector auth_vectors[OSMO_GSUP_MAX_NUM_AUTH_INFO];
+	size_t num_auth_vectors;
+
+	timestamp_t last_update;
+};