[PATCH v1 net-next 04/13] net: Introduce init2() for pernet_operations.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

This patch adds a new init function for pernet_operations, init2().

We call each init2() during clone() or unshare() only, where we can
access the parent netns for a child netns creation.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/net_namespace.h |  3 +++
 net/core/net_namespace.c    | 18 +++++++++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 8c3587d5c308..3ca426649756 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -410,6 +410,8 @@ struct pernet_operations {
 	 * from register_pernet_subsys(), unregister_pernet_subsys()
 	 * register_pernet_device() and unregister_pernet_device().
 	 *
+	 * init2() is called during clone() or unshare() only.
+	 *
 	 * Exit methods using blocking RCU primitives, such as
 	 * synchronize_rcu(), should be implemented via exit_batch.
 	 * Then, destruction of a group of net requires single
@@ -422,6 +424,7 @@ struct pernet_operations {
 	 * the calls.
 	 */
 	int (*init)(struct net *net);
+	int (*init2)(struct net *net, struct net *old_net);
 	void (*pre_exit)(struct net *net);
 	void (*exit)(struct net *net);
 	void (*exit_batch)(struct list_head *net_exit_list);
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 6b9f19122ec1..b120ff97d9f5 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -116,7 +116,8 @@ static int net_assign_generic(struct net *net, unsigned int id, void *data)
 	return 0;
 }
 
-static int ops_init(const struct pernet_operations *ops, struct net *net)
+static int ops_init(const struct pernet_operations *ops,
+		    struct net *net, struct net *old_net)
 {
 	int err = -ENOMEM;
 	void *data = NULL;
@@ -133,6 +134,8 @@ static int ops_init(const struct pernet_operations *ops, struct net *net)
 	err = 0;
 	if (ops->init)
 		err = ops->init(net);
+	if (!err && ops->init2 && old_net)
+		err = ops->init2(net, old_net);
 	if (!err)
 		return 0;
 
@@ -301,7 +304,8 @@ EXPORT_SYMBOL_GPL(get_net_ns_by_id);
 /*
  * setup_net runs the initializers for the network namespace object.
  */
-static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
+static __net_init int setup_net(struct net *net, struct net *old_net,
+				struct user_namespace *user_ns)
 {
 	/* Must be called with pernet_ops_rwsem held */
 	const struct pernet_operations *ops, *saved_ops;
@@ -323,7 +327,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 	mutex_init(&net->ipv4.ra_mutex);
 
 	list_for_each_entry(ops, &pernet_list, list) {
-		error = ops_init(ops, net);
+		error = ops_init(ops, net, old_net);
 		if (error < 0)
 			goto out_undo;
 	}
@@ -469,7 +473,7 @@ struct net *copy_net_ns(unsigned long flags,
 	if (rv < 0)
 		goto put_userns;
 
-	rv = setup_net(net, user_ns);
+	rv = setup_net(net, old_net, user_ns);
 
 	up_read(&pernet_ops_rwsem);
 
@@ -1107,7 +1111,7 @@ void __init net_ns_init(void)
 	init_net.key_domain = &init_net_key_domain;
 #endif
 	down_write(&pernet_ops_rwsem);
-	if (setup_net(&init_net, &init_user_ns))
+	if (setup_net(&init_net, NULL, &init_user_ns))
 		panic("Could not setup the initial network namespace");
 
 	init_net_initialized = true;
@@ -1148,7 +1152,7 @@ static int __register_pernet_operations(struct list_head *list,
 
 			memcg = mem_cgroup_or_root(get_mem_cgroup_from_obj(net));
 			old = set_active_memcg(memcg);
-			error = ops_init(ops, net);
+			error = ops_init(ops, net, NULL);
 			set_active_memcg(old);
 			mem_cgroup_put(memcg);
 			if (error)
@@ -1188,7 +1192,7 @@ static int __register_pernet_operations(struct list_head *list,
 		return 0;
 	}
 
-	return ops_init(ops, &init_net);
+	return ops_init(ops, &init_net, NULL);
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
-- 
2.30.2