diff --git a/inc/uapi/hf/socket.h b/inc/uapi/hf/socket.h
new file mode 100644
index 0000000..26d6432
--- /dev/null
+++ b/inc/uapi/hf/socket.h
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2019 The Hafnium Authors.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * 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 General Public License for more details.
+ */
+
+#pragma once
+
+#include <linux/socket.h>
+
+#include <hf/spci.h>
+
+/* TODO: Reusing AF_ECONET for now as it's otherwise unused. */
+#define AF_HF AF_ECONET
+#define PF_HF AF_HF
+
+/*
+ * Address of a Hafnium socket
+ */
+struct hf_sockaddr {
+	__kernel_sa_family_t family;
+	spci_vm_id_t vm_id;
+	uint64_t port;
+};