v4.19.13 snapshot.
diff --git a/include/net/netns/generic.h b/include/net/netns/generic.h
new file mode 100644
index 0000000..8a1ab47
--- /dev/null
+++ b/include/net/netns/generic.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * generic net pointers
+ */
+
+#ifndef __NET_GENERIC_H__
+#define __NET_GENERIC_H__
+
+#include <linux/bug.h>
+#include <linux/rcupdate.h>
+
+/*
+ * Generic net pointers are to be used by modules to put some private
+ * stuff on the struct net without explicit struct net modification
+ *
+ * The rules are simple:
+ * 1. set pernet_operations->id. After register_pernet_device you
+ * will have the id of your private pointer.
+ * 2. set pernet_operations->size to have the code allocate and free
+ * a private structure pointed to from struct net.
+ * 3. do not change this pointer while the net is alive;
+ * 4. do not try to have any private reference on the net_generic object.
+ *
+ * After accomplishing all of the above, the private pointer can be
+ * accessed with the net_generic() call.
+ */
+
+struct net_generic {
+ union {
+ struct {
+ unsigned int len;
+ struct rcu_head rcu;
+ } s;
+
+ void *ptr[0];
+ };
+};
+
+static inline void *net_generic(const struct net *net, unsigned int id)
+{
+ struct net_generic *ng;
+ void *ptr;
+
+ rcu_read_lock();
+ ng = rcu_dereference(net->gen);
+ ptr = ng->ptr[id];
+ rcu_read_unlock();
+
+ return ptr;
+}
+#endif