v4.19.13 snapshot.
diff --git a/include/net/netns/unix.h b/include/net/netns/unix.h
new file mode 100644
index 0000000..91a3d7e
--- /dev/null
+++ b/include/net/netns/unix.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Unix network namespace
+ */
+#ifndef __NETNS_UNIX_H__
+#define __NETNS_UNIX_H__
+
+struct ctl_table_header;
+struct netns_unix {
+	int			sysctl_max_dgram_qlen;
+	struct ctl_table_header	*ctl;
+};
+
+#endif /* __NETNS_UNIX_H__ */