net_ns_init

void __init net_ns_init(void)
{
	struct net_generic *ng;

#ifdef CONFIG_NET_NS
	net_cachep = kmem_cache_create("net_namespace", sizeof(struct net),
					SMP_CACHE_BYTES,
					SLAB_PANIC|SLAB_ACCOUNT, NULL);

	/* Create workqueue for cleanup */
	netns_wq = create_singlethread_workqueue("netns");
	if (!netns_wq)
		panic("Could not create netns workq");
#endif

	ng = net_alloc_generic();
	if (!ng)
		panic("Could not allocate generic netns");

	rcu_assign_pointer(init_net.gen, ng);

#ifdef CONFIG_KEYS
	init_net.key_domain = &init_net_key_domain;
#endif
	down_write(&pernet_ops_rwsem);
	preinit_net(&init_net);
	if (setup_net(&init_net, &init_user_ns))
		panic("Could not setup the initial network namespace");

	init_net_initialized = true;
	up_write(&pernet_ops_rwsem);

	if (register_pernet_subsys(&net_ns_ops))
		panic("Could not register network namespace subsystems");

	rtnl_register(PF_UNSPEC, RTM_NEWNSID, rtnl_net_newid, NULL,
		      RTNL_FLAG_DOIT_UNLOCKED);
	rtnl_register(PF_UNSPEC, RTM_GETNSID, rtnl_net_getid, rtnl_net_dumpid,
		      RTNL_FLAG_DOIT_UNLOCKED);
}

static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
{
	/* Must be called with pernet_ops_rwsem held */
	const struct pernet_operations *ops, *saved_ops;
	int error = 0;
	LIST_HEAD(net_exit_list);

	refcount_set(&net->ns.count, 1);
	ref_tracker_dir_init(&net->refcnt_tracker, 128, "net refcnt");

	refcount_set(&net->passive, 1);
	get_random_bytes(&net->hash_mix, sizeof(u32));
	preempt_disable();
	net->net_cookie = gen_cookie_next(&net_cookie);
	preempt_enable();
	net->dev_base_seq = 1;
	net->user_ns = user_ns;
	idr_init(&net->netns_ids);
	spin_lock_init(&net->nsid_lock);
	mutex_init(&net->ipv4.ra_mutex);

	list_for_each_entry(ops, &pernet_list, list) {
		error = ops_init(ops, net);
		if (error < 0)
			goto out_undo;
	}
	down_write(&net_rwsem);
	list_add_tail_rcu(&net->list, &net_namespace_list);
	up_write(&net_rwsem);
out:
	return error;

out_undo:
	/* Walk through the list backwards calling the exit functions
	 * for the pernet modules whose init functions did not fail.
	 */
	list_add(&net->exit_list, &net_exit_list);
	saved_ops = ops;
	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
		ops_pre_exit_list(ops, &net_exit_list);

	synchronize_rcu();

	ops = saved_ops;
	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
		ops_exit_list(ops, &net_exit_list);

	ops = saved_ops;
	list_for_each_entry_continue_reverse(ops, &pernet_list, list)
		ops_free_list(ops, &net_exit_list);

	rcu_barrier();
	goto out;
}