On Thu, Aug 25, 2022 at 5:06 PM Kuniyuki Iwashima <kuniyu@xxxxxxxxxx> wrote:
>
> This patch adds a new init function for pernet_operations, init2().
Why ?
This seems not really needed...
TCP ops->init can trivially reach the parent net_ns if needed,
because the current process is the one doing the creation of a new net_ns.
>
> 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@xxxxxxxxxx>
> ---
> 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 an error comes here, while ops->init() was a success, we probably
leave things in a bad state (memory leak ?)
> 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
>
