net/core/net_namespace.c - kernel/msm-4.9 - Gitiles

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/workqueue.h>
 #include <linux/rtnetlink.h>
 #include <linux/cache.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/idr.h>
 #include <linux/rculist.h>
 #include <linux/nsproxy.h>
 #include <linux/proc_fs.h>
 #include <linux/file.h>
 #include <linux/export.h>
 #include <linux/user_namespace.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>

 /*
  *	Our network namespace constructor/destructor lists
  */

 static LIST_HEAD(pernet_list);
 static struct list_head *first_device = &pernet_list;
 static DEFINE_MUTEX(net_mutex);

 LIST_HEAD(net_namespace_list);
 EXPORT_SYMBOL_GPL(net_namespace_list);

 struct net init_net = {
 	.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
 };
 EXPORT_SYMBOL(init_net);

 #define INITIAL_NET_GEN_PTRS	13 /* +1 for len +2 for rcu_head */

 static unsigned int max_gen_ptrs = INITIAL_NET_GEN_PTRS;

 static struct net_generic *net_alloc_generic(void)
 {
 	struct net_generic *ng;
 	size_t generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);

 	ng = kzalloc(generic_size, GFP_KERNEL);
 	if (ng)
 		ng->len = max_gen_ptrs;

 	return ng;
 }

 static int net_assign_generic(struct net *net, int id, void *data)
 {
 	struct net_generic *ng, *old_ng;

 	BUG_ON(!mutex_is_locked(&net_mutex));
 	BUG_ON(id == 0);

 	old_ng = rcu_dereference_protected(net->gen,
 					   lockdep_is_held(&net_mutex));
 	ng = old_ng;
 	if (old_ng->len >= id)
 		goto assign;

 	ng = net_alloc_generic();
 	if (ng == NULL)
 		return -ENOMEM;

 	/*
 	 * Some synchronisation notes:
 	 *
 	 * The net_generic explores the net->gen array inside rcu
 	 * read section. Besides once set the net->gen->ptr[x]
 	 * pointer never changes (see rules in netns/generic.h).
 	 *
 	 * That said, we simply duplicate this array and schedule
 	 * the old copy for kfree after a grace period.
 	 */

 	memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));

 	rcu_assign_pointer(net->gen, ng);
 	kfree_rcu(old_ng, rcu);
 assign:
 	ng->ptr[id - 1] = data;
 	return 0;
 }

 static int ops_init(const struct pernet_operations *ops, struct net *net)
 {
 	int err = -ENOMEM;
 	void *data = NULL;

 	if (ops->id && ops->size) {
 		data = kzalloc(ops->size, GFP_KERNEL);
 		if (!data)
 			goto out;

 		err = net_assign_generic(net, *ops->id, data);
 		if (err)
 			goto cleanup;
 	}
 	err = 0;
 	if (ops->init)
 		err = ops->init(net);
 	if (!err)
 		return 0;

 cleanup:
 	kfree(data);

 out:
 	return err;
 }

 static void ops_free(const struct pernet_operations *ops, struct net *net)
 {
 	if (ops->id && ops->size) {
 		int id = *ops->id;
 		kfree(net_generic(net, id));
 	}
 }

 static void ops_exit_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
 	struct net *net;
 	if (ops->exit) {
 		list_for_each_entry(net, net_exit_list, exit_list)
 			ops->exit(net);
 	}
 	if (ops->exit_batch)
 		ops->exit_batch(net_exit_list);
 }

 static void ops_free_list(const struct pernet_operations *ops,
 			  struct list_head *net_exit_list)
 {
 	struct net *net;
 	if (ops->size && ops->id) {
 		list_for_each_entry(net, net_exit_list, exit_list)
 			ops_free(ops, net);
 	}
 }

 /*
  * setup_net runs the initializers for the network namespace object.
  */
 static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
 {
 	/* Must be called with net_mutex held */
 	const struct pernet_operations *ops, *saved_ops;
 	int error = 0;
 	LIST_HEAD(net_exit_list);

 	atomic_set(&net->count, 1);
 	atomic_set(&net->passive, 1);
 	net->dev_base_seq = 1;
 	net->user_ns = user_ns;

 #ifdef NETNS_REFCNT_DEBUG
 	atomic_set(&net->use_count, 0);
 #endif

 	list_for_each_entry(ops, &pernet_list, list) {
 		error = ops_init(ops, net);
 		if (error < 0)
 			goto out_undo;
 	}
 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_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;
 }


 #ifdef CONFIG_NET_NS
 static struct kmem_cache *net_cachep;
 static struct workqueue_struct *netns_wq;

 static struct net *net_alloc(void)
 {
 	struct net *net = NULL;
 	struct net_generic *ng;

 	ng = net_alloc_generic();
 	if (!ng)
 		goto out;

 	net = kmem_cache_zalloc(net_cachep, GFP_KERNEL);
 	if (!net)
 		goto out_free;

 	rcu_assign_pointer(net->gen, ng);
 out:
 	return net;

 out_free:
 	kfree(ng);
 	goto out;
 }

 static void net_free(struct net *net)
 {
 #ifdef NETNS_REFCNT_DEBUG
 	if (unlikely(atomic_read(&net->use_count) != 0)) {
 		pr_emerg("network namespace not free! Usage: %d\n",
 			 atomic_read(&net->use_count));
 		return;
 	}
 #endif
 	kfree(net->gen);
 	kmem_cache_free(net_cachep, net);
 }

 void net_drop_ns(void *p)
 {
 	struct net *ns = p;
 	if (ns && atomic_dec_and_test(&ns->passive))
 		net_free(ns);
 }

 struct net *copy_net_ns(unsigned long flags,
 			struct user_namespace *user_ns, struct net *old_net)
 {
 	struct net *net;
 	int rv;

 	if (!(flags & CLONE_NEWNET))
 		return get_net(old_net);

 	net = net_alloc();
 	if (!net)
 		return ERR_PTR(-ENOMEM);

 	get_user_ns(user_ns);

 	mutex_lock(&net_mutex);
 	rv = setup_net(net, user_ns);
 	if (rv == 0) {
 		rtnl_lock();
 		list_add_tail_rcu(&net->list, &net_namespace_list);
 		rtnl_unlock();
 	}
 	mutex_unlock(&net_mutex);
 	if (rv < 0) {
 		put_user_ns(user_ns);
 		net_drop_ns(net);
 		return ERR_PTR(rv);
 	}
 	return net;
 }

 static DEFINE_SPINLOCK(cleanup_list_lock);
 static LIST_HEAD(cleanup_list);  /* Must hold cleanup_list_lock to touch */

 static void cleanup_net(struct work_struct *work)
 {
 	const struct pernet_operations *ops;
 	struct net *net, *tmp;
 	LIST_HEAD(net_kill_list);
 	LIST_HEAD(net_exit_list);

 	/* Atomically snapshot the list of namespaces to cleanup */
 	spin_lock_irq(&cleanup_list_lock);
 	list_replace_init(&cleanup_list, &net_kill_list);
 	spin_unlock_irq(&cleanup_list_lock);

 	mutex_lock(&net_mutex);

 	/* Don't let anyone else find us. */
 	rtnl_lock();
 	list_for_each_entry(net, &net_kill_list, cleanup_list) {
 		list_del_rcu(&net->list);
 		list_add_tail(&net->exit_list, &net_exit_list);
 	}
 	rtnl_unlock();

 	/*
 	 * Another CPU might be rcu-iterating the list, wait for it.
 	 * This needs to be before calling the exit() notifiers, so
 	 * the rcu_barrier() below isn't sufficient alone.
 	 */
 	synchronize_rcu();

 	/* Run all of the network namespace exit methods */
 	list_for_each_entry_reverse(ops, &pernet_list, list)
 		ops_exit_list(ops, &net_exit_list);

 	/* Free the net generic variables */
 	list_for_each_entry_reverse(ops, &pernet_list, list)
 		ops_free_list(ops, &net_exit_list);

 	mutex_unlock(&net_mutex);

 	/* Ensure there are no outstanding rcu callbacks using this
 	 * network namespace.
 	 */
 	rcu_barrier();

 	/* Finally it is safe to free my network namespace structure */
 	list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
 		list_del_init(&net->exit_list);
 		put_user_ns(net->user_ns);
 		net_drop_ns(net);
 	}
 }
 static DECLARE_WORK(net_cleanup_work, cleanup_net);

 void __put_net(struct net *net)
 {
 	/* Cleanup the network namespace in process context */
 	unsigned long flags;

 	spin_lock_irqsave(&cleanup_list_lock, flags);
 	list_add(&net->cleanup_list, &cleanup_list);
 	spin_unlock_irqrestore(&cleanup_list_lock, flags);

 	queue_work(netns_wq, &net_cleanup_work);
 }
 EXPORT_SYMBOL_GPL(__put_net);

 struct net *get_net_ns_by_fd(int fd)
 {
 	struct proc_inode *ei;
 	struct file *file;
 	struct net *net;

 	file = proc_ns_fget(fd);
 	if (IS_ERR(file))
 		return ERR_CAST(file);

 	ei = PROC_I(file_inode(file));
 	if (ei->ns_ops == &netns_operations)
 		net = get_net(ei->ns);
 	else
 		net = ERR_PTR(-EINVAL);

 	fput(file);
 	return net;
 }

 #else
 struct net *get_net_ns_by_fd(int fd)
 {
 	return ERR_PTR(-EINVAL);
 }
 #endif

 struct net *get_net_ns_by_pid(pid_t pid)
 {
 	struct task_struct *tsk;
 	struct net *net;

 	/* Lookup the network namespace */
 	net = ERR_PTR(-ESRCH);
 	rcu_read_lock();
 	tsk = find_task_by_vpid(pid);
 	if (tsk) {
 		struct nsproxy *nsproxy;
 		nsproxy = task_nsproxy(tsk);
 		if (nsproxy)
 			net = get_net(nsproxy->net_ns);
 	}
 	rcu_read_unlock();
 	return net;
 }
 EXPORT_SYMBOL_GPL(get_net_ns_by_pid);

 static __net_init int net_ns_net_init(struct net *net)
 {
 	return proc_alloc_inum(&net->proc_inum);
 }

 static __net_exit void net_ns_net_exit(struct net *net)
 {
 	proc_free_inum(net->proc_inum);
 }

 static struct pernet_operations __net_initdata net_ns_ops = {
 	.init = net_ns_net_init,
 	.exit = net_ns_net_exit,
 };

 static int __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, 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);

 	mutex_lock(&net_mutex);
 	if (setup_net(&init_net, &init_user_ns))
 		panic("Could not setup the initial network namespace");

 	rtnl_lock();
 	list_add_tail_rcu(&init_net.list, &net_namespace_list);
 	rtnl_unlock();

 	mutex_unlock(&net_mutex);

 	register_pernet_subsys(&net_ns_ops);

 	return 0;
 }

 pure_initcall(net_ns_init);

 #ifdef CONFIG_NET_NS
 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
 	struct net *net;
 	int error;
 	LIST_HEAD(net_exit_list);

 	list_add_tail(&ops->list, list);
 	if (ops->init || (ops->id && ops->size)) {
 		for_each_net(net) {
 			error = ops_init(ops, net);
 			if (error)
 				goto out_undo;
 			list_add_tail(&net->exit_list, &net_exit_list);
 		}
 	}
 	return 0;

 out_undo:
 	/* If I have an error cleanup all namespaces I initialized */
 	list_del(&ops->list);
 	ops_exit_list(ops, &net_exit_list);
 	ops_free_list(ops, &net_exit_list);
 	return error;
 }

 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
 	struct net *net;
 	LIST_HEAD(net_exit_list);

 	list_del(&ops->list);
 	for_each_net(net)
 		list_add_tail(&net->exit_list, &net_exit_list);
 	ops_exit_list(ops, &net_exit_list);
 	ops_free_list(ops, &net_exit_list);
 }

 #else

 static int __register_pernet_operations(struct list_head *list,
 					struct pernet_operations *ops)
 {
 	return ops_init(ops, &init_net);
 }

 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
 	LIST_HEAD(net_exit_list);
 	list_add(&init_net.exit_list, &net_exit_list);
 	ops_exit_list(ops, &net_exit_list);
 	ops_free_list(ops, &net_exit_list);
 }

 #endif /* CONFIG_NET_NS */

 static DEFINE_IDA(net_generic_ids);

 static int register_pernet_operations(struct list_head *list,
 				      struct pernet_operations *ops)
 {
 	int error;

 	if (ops->id) {
 again:
 		error = ida_get_new_above(&net_generic_ids, 1, ops->id);
 		if (error < 0) {
 			if (error == -EAGAIN) {
 				ida_pre_get(&net_generic_ids, GFP_KERNEL);
 				goto again;
 			}
 			return error;
 		}
 		max_gen_ptrs = max_t(unsigned int, max_gen_ptrs, *ops->id);
 	}
 	error = __register_pernet_operations(list, ops);
 	if (error) {
 		rcu_barrier();
 		if (ops->id)
 			ida_remove(&net_generic_ids, *ops->id);
 	}

 	return error;
 }

 static void unregister_pernet_operations(struct pernet_operations *ops)
 {

 	__unregister_pernet_operations(ops);
 	rcu_barrier();
 	if (ops->id)
 		ida_remove(&net_generic_ids, *ops->id);
 }

 /**
  *      register_pernet_subsys - register a network namespace subsystem
  *	@ops:  pernet operations structure for the subsystem
  *
  *	Register a subsystem which has init and exit functions
  *	that are called when network namespaces are created and
  *	destroyed respectively.
  *
  *	When registered all network namespace init functions are
  *	called for every existing network namespace.  Allowing kernel
  *	modules to have a race free view of the set of network namespaces.
  *
  *	When a new network namespace is created all of the init
  *	methods are called in the order in which they were registered.
  *
  *	When a network namespace is destroyed all of the exit methods
  *	are called in the reverse of the order with which they were
  *	registered.
  */
 int register_pernet_subsys(struct pernet_operations *ops)
 {
 	int error;
 	mutex_lock(&net_mutex);
 	error =  register_pernet_operations(first_device, ops);
 	mutex_unlock(&net_mutex);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_subsys);

 /**
  *      unregister_pernet_subsys - unregister a network namespace subsystem
  *	@ops: pernet operations structure to manipulate
  *
  *	Remove the pernet operations structure from the list to be
  *	used when network namespaces are created or destroyed.  In
  *	addition run the exit method for all existing network
  *	namespaces.
  */
 void unregister_pernet_subsys(struct pernet_operations *ops)
 {
 	mutex_lock(&net_mutex);
 	unregister_pernet_operations(ops);
 	mutex_unlock(&net_mutex);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_subsys);

 /**
  *      register_pernet_device - register a network namespace device
  *	@ops:  pernet operations structure for the subsystem
  *
  *	Register a device which has init and exit functions
  *	that are called when network namespaces are created and
  *	destroyed respectively.
  *
  *	When registered all network namespace init functions are
  *	called for every existing network namespace.  Allowing kernel
  *	modules to have a race free view of the set of network namespaces.
  *
  *	When a new network namespace is created all of the init
  *	methods are called in the order in which they were registered.
  *
  *	When a network namespace is destroyed all of the exit methods
  *	are called in the reverse of the order with which they were
  *	registered.
  */
 int register_pernet_device(struct pernet_operations *ops)
 {
 	int error;
 	mutex_lock(&net_mutex);
 	error = register_pernet_operations(&pernet_list, ops);
 	if (!error && (first_device == &pernet_list))
 		first_device = &ops->list;
 	mutex_unlock(&net_mutex);
 	return error;
 }
 EXPORT_SYMBOL_GPL(register_pernet_device);

 /**
  *      unregister_pernet_device - unregister a network namespace netdevice
  *	@ops: pernet operations structure to manipulate
  *
  *	Remove the pernet operations structure from the list to be
  *	used when network namespaces are created or destroyed.  In
  *	addition run the exit method for all existing network
  *	namespaces.
  */
 void unregister_pernet_device(struct pernet_operations *ops)
 {
 	mutex_lock(&net_mutex);
 	if (&ops->list == first_device)
 		first_device = first_device->next;
 	unregister_pernet_operations(ops);
 	mutex_unlock(&net_mutex);
 }
 EXPORT_SYMBOL_GPL(unregister_pernet_device);

 #ifdef CONFIG_NET_NS
 static void *netns_get(struct task_struct *task)
 {
 	struct net *net = NULL;
 	struct nsproxy *nsproxy;

 	rcu_read_lock();
 	nsproxy = task_nsproxy(task);
 	if (nsproxy)
 		net = get_net(nsproxy->net_ns);
 	rcu_read_unlock();

 	return net;
 }

 static void netns_put(void *ns)
 {
 	put_net(ns);
 }

 static int netns_install(struct nsproxy *nsproxy, void *ns)
 {
 	struct net *net = ns;

 	if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) ||
 	    !nsown_capable(CAP_SYS_ADMIN))
 		return -EPERM;

 	put_net(nsproxy->net_ns);
 	nsproxy->net_ns = get_net(net);
 	return 0;
 }

 static unsigned int netns_inum(void *ns)
 {
 	struct net *net = ns;
 	return net->proc_inum;
 }

 const struct proc_ns_operations netns_operations = {
 	.name		= "net",
 	.type		= CLONE_NEWNET,
 	.get		= netns_get,
 	.put		= netns_put,
 	.install	= netns_install,
 	.inum		= netns_inum,
 };
 #endif
	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/workqueue.h>
	#include <linux/rtnetlink.h>
	#include <linux/cache.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <linux/delay.h>
	#include <linux/sched.h>
	#include <linux/idr.h>
	#include <linux/rculist.h>
	#include <linux/nsproxy.h>
	#include <linux/proc_fs.h>
	#include <linux/file.h>
	#include <linux/export.h>
	#include <linux/user_namespace.h>
	#include <net/net_namespace.h>
	#include <net/netns/generic.h>

	/*
	* Our network namespace constructor/destructor lists
	*/

	static LIST_HEAD(pernet_list);
	static struct list_head *first_device = &pernet_list;
	static DEFINE_MUTEX(net_mutex);

	LIST_HEAD(net_namespace_list);
	EXPORT_SYMBOL_GPL(net_namespace_list);

	struct net init_net = {
	.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
	};
	EXPORT_SYMBOL(init_net);

	#define INITIAL_NET_GEN_PTRS 13 /* +1 for len +2 for rcu_head */

	static unsigned int max_gen_ptrs = INITIAL_NET_GEN_PTRS;

	static struct net_generic *net_alloc_generic(void)
	{
	struct net_generic *ng;
	size_t generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);

	ng = kzalloc(generic_size, GFP_KERNEL);
	if (ng)
	ng->len = max_gen_ptrs;

	return ng;
	}

	static int net_assign_generic(struct net net, int id, void data)
	{
	struct net_generic ng, old_ng;

	BUG_ON(!mutex_is_locked(&net_mutex));
	BUG_ON(id == 0);

	old_ng = rcu_dereference_protected(net->gen,
	lockdep_is_held(&net_mutex));
	ng = old_ng;
	if (old_ng->len >= id)
	goto assign;

	ng = net_alloc_generic();
	if (ng == NULL)
	return -ENOMEM;

	/*
	* Some synchronisation notes:
	*
	* The net_generic explores the net->gen array inside rcu
	* read section. Besides once set the net->gen->ptr[x]
	* pointer never changes (see rules in netns/generic.h).
	*
	* That said, we simply duplicate this array and schedule
	* the old copy for kfree after a grace period.
	*/

	memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*));

	rcu_assign_pointer(net->gen, ng);
	kfree_rcu(old_ng, rcu);
	assign:
	ng->ptr[id - 1] = data;
	return 0;
	}

	static int ops_init(const struct pernet_operations ops, struct net net)
	{
	int err = -ENOMEM;
	void *data = NULL;

	if (ops->id && ops->size) {
	data = kzalloc(ops->size, GFP_KERNEL);
	if (!data)
	goto out;

	err = net_assign_generic(net, *ops->id, data);
	if (err)
	goto cleanup;
	}
	err = 0;
	if (ops->init)
	err = ops->init(net);
	if (!err)
	return 0;

	cleanup:
	kfree(data);

	out:
	return err;
	}

	static void ops_free(const struct pernet_operations ops, struct net net)
	{
	if (ops->id && ops->size) {
	int id = *ops->id;
	kfree(net_generic(net, id));
	}
	}

	static void ops_exit_list(const struct pernet_operations *ops,
	struct list_head *net_exit_list)
	{
	struct net *net;
	if (ops->exit) {
	list_for_each_entry(net, net_exit_list, exit_list)
	ops->exit(net);
	}
	if (ops->exit_batch)
	ops->exit_batch(net_exit_list);
	}

	static void ops_free_list(const struct pernet_operations *ops,
	struct list_head *net_exit_list)
	{
	struct net *net;
	if (ops->size && ops->id) {
	list_for_each_entry(net, net_exit_list, exit_list)
	ops_free(ops, net);
	}
	}

	/*
	* setup_net runs the initializers for the network namespace object.
	*/
	static __net_init int setup_net(struct net net, struct user_namespace user_ns)
	{
	/* Must be called with net_mutex held */
	const struct pernet_operations ops, saved_ops;
	int error = 0;
	LIST_HEAD(net_exit_list);

	atomic_set(&net->count, 1);
	atomic_set(&net->passive, 1);
	net->dev_base_seq = 1;
	net->user_ns = user_ns;

	#ifdef NETNS_REFCNT_DEBUG
	atomic_set(&net->use_count, 0);
	#endif

	list_for_each_entry(ops, &pernet_list, list) {
	error = ops_init(ops, net);
	if (error < 0)
	goto out_undo;
	}
	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_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;
	}


	#ifdef CONFIG_NET_NS
	static struct kmem_cache *net_cachep;
	static struct workqueue_struct *netns_wq;

	static struct net *net_alloc(void)
	{
	struct net *net = NULL;
	struct net_generic *ng;

	ng = net_alloc_generic();
	if (!ng)
	goto out;

	net = kmem_cache_zalloc(net_cachep, GFP_KERNEL);
	if (!net)
	goto out_free;

	rcu_assign_pointer(net->gen, ng);
	out:
	return net;

	out_free:
	kfree(ng);
	goto out;
	}

	static void net_free(struct net *net)
	{
	#ifdef NETNS_REFCNT_DEBUG
	if (unlikely(atomic_read(&net->use_count) != 0)) {
	pr_emerg("network namespace not free! Usage: %d\n",
	atomic_read(&net->use_count));
	return;
	}
	#endif
	kfree(net->gen);
	kmem_cache_free(net_cachep, net);
	}

	void net_drop_ns(void *p)
	{
	struct net *ns = p;
	if (ns && atomic_dec_and_test(&ns->passive))
	net_free(ns);
	}

	struct net *copy_net_ns(unsigned long flags,
	struct user_namespace user_ns, struct net old_net)
	{
	struct net *net;
	int rv;

	if (!(flags & CLONE_NEWNET))
	return get_net(old_net);

	net = net_alloc();
	if (!net)
	return ERR_PTR(-ENOMEM);

	get_user_ns(user_ns);

	mutex_lock(&net_mutex);
	rv = setup_net(net, user_ns);
	if (rv == 0) {
	rtnl_lock();
	list_add_tail_rcu(&net->list, &net_namespace_list);
	rtnl_unlock();
	}
	mutex_unlock(&net_mutex);
	if (rv < 0) {
	put_user_ns(user_ns);
	net_drop_ns(net);
	return ERR_PTR(rv);
	}
	return net;
	}

	static DEFINE_SPINLOCK(cleanup_list_lock);
	static LIST_HEAD(cleanup_list); /* Must hold cleanup_list_lock to touch */

	static void cleanup_net(struct work_struct *work)
	{
	const struct pernet_operations *ops;
	struct net net, tmp;
	LIST_HEAD(net_kill_list);
	LIST_HEAD(net_exit_list);

	/* Atomically snapshot the list of namespaces to cleanup */
	spin_lock_irq(&cleanup_list_lock);
	list_replace_init(&cleanup_list, &net_kill_list);
	spin_unlock_irq(&cleanup_list_lock);

	mutex_lock(&net_mutex);

	/* Don't let anyone else find us. */
	rtnl_lock();
	list_for_each_entry(net, &net_kill_list, cleanup_list) {
	list_del_rcu(&net->list);
	list_add_tail(&net->exit_list, &net_exit_list);
	}
	rtnl_unlock();

	/*
	* Another CPU might be rcu-iterating the list, wait for it.
	* This needs to be before calling the exit() notifiers, so
	* the rcu_barrier() below isn't sufficient alone.
	*/
	synchronize_rcu();

	/* Run all of the network namespace exit methods */
	list_for_each_entry_reverse(ops, &pernet_list, list)
	ops_exit_list(ops, &net_exit_list);

	/* Free the net generic variables */
	list_for_each_entry_reverse(ops, &pernet_list, list)
	ops_free_list(ops, &net_exit_list);

	mutex_unlock(&net_mutex);

	/* Ensure there are no outstanding rcu callbacks using this
	* network namespace.
	*/
	rcu_barrier();

	/* Finally it is safe to free my network namespace structure */
	list_for_each_entry_safe(net, tmp, &net_exit_list, exit_list) {
	list_del_init(&net->exit_list);
	put_user_ns(net->user_ns);
	net_drop_ns(net);
	}
	}
	static DECLARE_WORK(net_cleanup_work, cleanup_net);

	void __put_net(struct net *net)
	{
	/* Cleanup the network namespace in process context */
	unsigned long flags;

	spin_lock_irqsave(&cleanup_list_lock, flags);
	list_add(&net->cleanup_list, &cleanup_list);
	spin_unlock_irqrestore(&cleanup_list_lock, flags);

	queue_work(netns_wq, &net_cleanup_work);
	}
	EXPORT_SYMBOL_GPL(__put_net);

	struct net *get_net_ns_by_fd(int fd)
	{
	struct proc_inode *ei;
	struct file *file;
	struct net *net;

	file = proc_ns_fget(fd);
	if (IS_ERR(file))
	return ERR_CAST(file);

	ei = PROC_I(file_inode(file));
	if (ei->ns_ops == &netns_operations)
	net = get_net(ei->ns);
	else
	net = ERR_PTR(-EINVAL);

	fput(file);
	return net;
	}

	#else
	struct net *get_net_ns_by_fd(int fd)
	{
	return ERR_PTR(-EINVAL);
	}
	#endif

	struct net *get_net_ns_by_pid(pid_t pid)
	{
	struct task_struct *tsk;
	struct net *net;

	/* Lookup the network namespace */
	net = ERR_PTR(-ESRCH);
	rcu_read_lock();
	tsk = find_task_by_vpid(pid);
	if (tsk) {
	struct nsproxy *nsproxy;
	nsproxy = task_nsproxy(tsk);
	if (nsproxy)
	net = get_net(nsproxy->net_ns);
	}
	rcu_read_unlock();
	return net;
	}
	EXPORT_SYMBOL_GPL(get_net_ns_by_pid);

	static __net_init int net_ns_net_init(struct net *net)
	{
	return proc_alloc_inum(&net->proc_inum);
	}

	static __net_exit void net_ns_net_exit(struct net *net)
	{
	proc_free_inum(net->proc_inum);
	}

	static struct pernet_operations __net_initdata net_ns_ops = {
	.init = net_ns_net_init,
	.exit = net_ns_net_exit,
	};

	static int __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, 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);

	mutex_lock(&net_mutex);
	if (setup_net(&init_net, &init_user_ns))
	panic("Could not setup the initial network namespace");

	rtnl_lock();
	list_add_tail_rcu(&init_net.list, &net_namespace_list);
	rtnl_unlock();

	mutex_unlock(&net_mutex);

	register_pernet_subsys(&net_ns_ops);

	return 0;
	}

	pure_initcall(net_ns_init);

	#ifdef CONFIG_NET_NS
	static int __register_pernet_operations(struct list_head *list,
	struct pernet_operations *ops)
	{
	struct net *net;
	int error;
	LIST_HEAD(net_exit_list);

	list_add_tail(&ops->list, list);
	if (ops->init \|\| (ops->id && ops->size)) {
	for_each_net(net) {
	error = ops_init(ops, net);
	if (error)
	goto out_undo;
	list_add_tail(&net->exit_list, &net_exit_list);
	}
	}
	return 0;

	out_undo:
	/* If I have an error cleanup all namespaces I initialized */
	list_del(&ops->list);
	ops_exit_list(ops, &net_exit_list);
	ops_free_list(ops, &net_exit_list);
	return error;
	}

	static void __unregister_pernet_operations(struct pernet_operations *ops)
	{
	struct net *net;
	LIST_HEAD(net_exit_list);

	list_del(&ops->list);
	for_each_net(net)
	list_add_tail(&net->exit_list, &net_exit_list);
	ops_exit_list(ops, &net_exit_list);
	ops_free_list(ops, &net_exit_list);
	}

	#else

	static int __register_pernet_operations(struct list_head *list,
	struct pernet_operations *ops)
	{
	return ops_init(ops, &init_net);
	}

	static void __unregister_pernet_operations(struct pernet_operations *ops)
	{
	LIST_HEAD(net_exit_list);
	list_add(&init_net.exit_list, &net_exit_list);
	ops_exit_list(ops, &net_exit_list);
	ops_free_list(ops, &net_exit_list);
	}

	#endif /* CONFIG_NET_NS */

	static DEFINE_IDA(net_generic_ids);

	static int register_pernet_operations(struct list_head *list,
	struct pernet_operations *ops)
	{
	int error;

	if (ops->id) {
	again:
	error = ida_get_new_above(&net_generic_ids, 1, ops->id);
	if (error < 0) {
	if (error == -EAGAIN) {
	ida_pre_get(&net_generic_ids, GFP_KERNEL);
	goto again;
	}
	return error;
	}
	max_gen_ptrs = max_t(unsigned int, max_gen_ptrs, *ops->id);
	}
	error = __register_pernet_operations(list, ops);
	if (error) {
	rcu_barrier();
	if (ops->id)
	ida_remove(&net_generic_ids, *ops->id);
	}

	return error;
	}

	static void unregister_pernet_operations(struct pernet_operations *ops)
	{

	__unregister_pernet_operations(ops);
	rcu_barrier();
	if (ops->id)
	ida_remove(&net_generic_ids, *ops->id);
	}

	/**
	* register_pernet_subsys - register a network namespace subsystem
	* @ops: pernet operations structure for the subsystem
	*
	* Register a subsystem which has init and exit functions
	* that are called when network namespaces are created and
	* destroyed respectively.
	*
	* When registered all network namespace init functions are
	* called for every existing network namespace. Allowing kernel
	* modules to have a race free view of the set of network namespaces.
	*
	* When a new network namespace is created all of the init
	* methods are called in the order in which they were registered.
	*
	* When a network namespace is destroyed all of the exit methods
	* are called in the reverse of the order with which they were
	* registered.
	*/
	int register_pernet_subsys(struct pernet_operations *ops)
	{
	int error;
	mutex_lock(&net_mutex);
	error = register_pernet_operations(first_device, ops);
	mutex_unlock(&net_mutex);
	return error;
	}
	EXPORT_SYMBOL_GPL(register_pernet_subsys);

	/**
	* unregister_pernet_subsys - unregister a network namespace subsystem
	* @ops: pernet operations structure to manipulate
	*
	* Remove the pernet operations structure from the list to be
	* used when network namespaces are created or destroyed. In
	* addition run the exit method for all existing network
	* namespaces.
	*/
	void unregister_pernet_subsys(struct pernet_operations *ops)
	{
	mutex_lock(&net_mutex);
	unregister_pernet_operations(ops);
	mutex_unlock(&net_mutex);
	}
	EXPORT_SYMBOL_GPL(unregister_pernet_subsys);

	/**
	* register_pernet_device - register a network namespace device
	* @ops: pernet operations structure for the subsystem
	*
	* Register a device which has init and exit functions
	* that are called when network namespaces are created and
	* destroyed respectively.
	*
	* When registered all network namespace init functions are
	* called for every existing network namespace. Allowing kernel
	* modules to have a race free view of the set of network namespaces.
	*
	* When a new network namespace is created all of the init
	* methods are called in the order in which they were registered.
	*
	* When a network namespace is destroyed all of the exit methods
	* are called in the reverse of the order with which they were
	* registered.
	*/
	int register_pernet_device(struct pernet_operations *ops)
	{
	int error;
	mutex_lock(&net_mutex);
	error = register_pernet_operations(&pernet_list, ops);
	if (!error && (first_device == &pernet_list))
	first_device = &ops->list;
	mutex_unlock(&net_mutex);
	return error;
	}
	EXPORT_SYMBOL_GPL(register_pernet_device);

	/**
	* unregister_pernet_device - unregister a network namespace netdevice
	* @ops: pernet operations structure to manipulate
	*
	* Remove the pernet operations structure from the list to be
	* used when network namespaces are created or destroyed. In
	* addition run the exit method for all existing network
	* namespaces.
	*/
	void unregister_pernet_device(struct pernet_operations *ops)
	{
	mutex_lock(&net_mutex);
	if (&ops->list == first_device)
	first_device = first_device->next;
	unregister_pernet_operations(ops);
	mutex_unlock(&net_mutex);
	}
	EXPORT_SYMBOL_GPL(unregister_pernet_device);

	#ifdef CONFIG_NET_NS
	static void netns_get(struct task_struct task)
	{
	struct net *net = NULL;
	struct nsproxy *nsproxy;

	rcu_read_lock();
	nsproxy = task_nsproxy(task);
	if (nsproxy)
	net = get_net(nsproxy->net_ns);
	rcu_read_unlock();

	return net;
	}

	static void netns_put(void *ns)
	{
	put_net(ns);
	}

	static int netns_install(struct nsproxy nsproxy, void ns)
	{
	struct net *net = ns;

	if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) \|\|
	!nsown_capable(CAP_SYS_ADMIN))
	return -EPERM;

	put_net(nsproxy->net_ns);
	nsproxy->net_ns = get_net(net);
	return 0;
	}

	static unsigned int netns_inum(void *ns)
	{
	struct net *net = ns;
	return net->proc_inum;
	}

	const struct proc_ns_operations netns_operations = {
	.name = "net",
	.type = CLONE_NEWNET,
	.get = netns_get,
	.put = netns_put,
	.install = netns_install,
	.inum = netns_inum,
	};
	#endif