text: #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/fs.h>
  #include <linux/proc_ns.h>
  #include <linux/file.h>
  #include <linux/export.h>
  #include <linux/user_namespace.h>
  #include <linux/net_namespace.h>
  #include <linux/sched/task.h>
  
  #include <net/sock.h>
  #include <net/netlink.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;
  DEFINE_MUTEX(net_mutex);
  
  LIST_HEAD(net_namespace_list);
  EXPORT_SYMBOL_GPL(net_namespace_list);
  
  struct net init_net = {
  	.count		= ATOMIC_INIT(1),
  	.dev_base_head	= LIST_HEAD_INIT(init_net.dev_base_head),
  };
  EXPORT_SYMBOL(init_net);
  
  static bool init_net_initialized;
  
  #define MIN_PERNET_OPS_ID	\
  	((sizeof(struct net_generic) + sizeof(void *) - 1) / sizeof(void *))
  
  #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;
  	unsigned int generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);
  
  	ng = kzalloc(generic_size, GFP_KERNEL);
  	if (ng)
  		ng->s.len = max_gen_ptrs;
  
  	return ng;
  }
  
  static int net_assign_generic(struct net *net, unsigned int id, void *data)
  {
  	struct net_generic *ng, *old_ng;
  
  	BUG_ON(!mutex_is_locked(&net_mutex));
  	BUG_ON(id < MIN_PERNET_OPS_ID);
  
  	old_ng = rcu_dereference_protected(net->gen,
  					   lockdep_is_held(&net_mutex));
  	if (old_ng->s.len > id) {
  		old_ng->ptr[id] = data;
  		return 0;
  	}
  
  	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[MIN_PERNET_OPS_ID], &old_ng->ptr[MIN_PERNET_OPS_ID],
  	       (old_ng->s.len - MIN_PERNET_OPS_ID) * sizeof(void *));
  	ng->ptr[id] = data;
  
  	rcu_assign_pointer(net->gen, ng);
  	kfree_rcu(old_ng, s.rcu);
  	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) {
  		kfree(net_generic(net, *ops->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);
  	}
  }
  
  /* should be called with nsid_lock held */
  static int alloc_netid(struct net *net, struct net *peer, int reqid)
  {
  	int min = 0, max = 0;
  
  	if (reqid >= 0) {
  		min = reqid;
  		max = reqid + 1;
  	}
  
  	return idr_alloc(&net->netns_ids, peer, min, max, GFP_ATOMIC);
  }
  
  /* This function is used by idr_for_each(). If net is equal to peer, the
   * function returns the id so that idr_for_each() stops. Because we cannot
   * returns the id 0 (idr_for_each() will not stop), we return the magic value
   * NET_ID_ZERO (-1) for it.
   */
  #define NET_ID_ZERO -1
  static int net_eq_idr(int id, void *net, void *peer)
  {
  	if (net_eq(net, peer))
  		return id ? : NET_ID_ZERO;
  	return 0;
  }
  
  /* Should be called with nsid_lock held. If a new id is assigned, the bool alloc
   * is set to true, thus the caller knows that the new id must be notified via
   * rtnl.
   */
  static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)
  {
  	int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);
  	bool alloc_it = *alloc;
  
  	*alloc = false;
  
  	/* Magic value for id 0. */
  	if (id == NET_ID_ZERO)
  		return 0;
  	if (id > 0)
  		return id;
  
  	if (alloc_it) {
  		id = alloc_netid(net, peer, -1);
  		*alloc = true;
  		return id >= 0 ? id : NETNSA_NSID_NOT_ASSIGNED;
  	}
  
  	return NETNSA_NSID_NOT_ASSIGNED;
  }
  
  /* should be called with nsid_lock held */
  static int __peernet2id(struct net *net, struct net *peer)
  {
  	bool no = false;
  
  	return __peernet2id_alloc(net, peer, &no);
  }
  
  static void rtnl_net_notifyid(struct net *net, int cmd, int id);
  /* This function returns the id of a peer netns. If no id is assigned, one will
   * be allocated and returned.
   */
  int peernet2id_alloc(struct net *net, struct net *peer)
  {
  	bool alloc;
  	int id;
  
  	if (atomic_read(&net->count) == 0)
  		return NETNSA_NSID_NOT_ASSIGNED;
  	spin_lock_bh(&net->nsid_lock);
  	alloc = atomic_read(&peer->count) == 0 ? false : true;
  	id = __peernet2id_alloc(net, peer, &alloc);
  	spin_unlock_bh(&net->nsid_lock);
  	if (alloc && id >= 0)
  		rtnl_net_notifyid(net, RTM_NEWNSID, id);
  	return id;
  }
  EXPORT_SYMBOL_GPL(peernet2id_alloc);
  
  /* This function returns, if assigned, the id of a peer netns. */
  int peernet2id(struct net *net, struct net *peer)
  {
  	int id;
  
  	spin_lock_bh(&net->nsid_lock);
  	id = __peernet2id(net, peer);
  	spin_unlock_bh(&net->nsid_lock);
  	return id;
  }
  EXPORT_SYMBOL(peernet2id);
  
  /* This function returns true is the peer netns has an id assigned into the
   * current netns.
   */
  bool peernet_has_id(struct net *net, struct net *peer)
  {
  	return peernet2id(net, peer) >= 0;
  }
  
  struct net *get_net_ns_by_id(struct net *net, int id)
  {
  	struct net *peer;
  
  	if (id < 0)
  		return NULL;
  
  	rcu_read_lock();
  	spin_lock_bh(&net->nsid_lock);
  	peer = idr_find(&net->netns_ids, id);
  	if (peer)
  		get_net(peer);
  	spin_unlock_bh(&net->nsid_lock);
  	rcu_read_unlock();
  
  	return peer;
  }
  
  /*
   * 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);
  	refcount_set(&net->passive, 1);
  	net->dev_base_seq = 1;
  	net->user_ns = user_ns;
  	idr_init(&net->netns_ids);
  	spin_lock_init(&net->nsid_lock);
  
  	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;
  }
  
  static int __net_init net_defaults_init_net(struct net *net)
  {
  	net->core.sysctl_somaxconn = SOMAXCONN;
  	return 0;
  }
  
  static struct pernet_operations net_defaults_ops = {
  	.init = net_defaults_init_net,
  };
  
  static __init int net_defaults_init(void)
  {
  	if (register_pernet_subsys(&net_defaults_ops))
  		panic("Cannot initialize net default settings");
  
  	return 0;
  }
  
  core_initcall(net_defaults_init);
  
  #ifdef CONFIG_NET_NS
  static struct ucounts *inc_net_namespaces(struct user_namespace *ns)
  {
  	return inc_ucount(ns, current_euid(), UCOUNT_NET_NAMESPACES);
  }
  
  static void dec_net_namespaces(struct ucounts *ucounts)
  {
  	dec_ucount(ucounts, UCOUNT_NET_NAMESPACES);
  }
  
  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)
  {
  	kfree(rcu_access_pointer(net->gen));
  	kmem_cache_free(net_cachep, net);
  }
  
  void net_drop_ns(void *p)
  {
  	struct net *ns = p;
  	if (ns && refcount_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 ucounts *ucounts;
  	struct net *net;
  	int rv;
  
  	if (!(flags & CLONE_NEWNET))
  		return get_net(old_net);
  
  	ucounts = inc_net_namespaces(user_ns);
  	if (!ucounts)
  		return ERR_PTR(-ENOSPC);
  
  	net = net_alloc();
  	if (!net) {
  		dec_net_namespaces(ucounts);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	get_user_ns(user_ns);
  
  	rv = mutex_lock_killable(&net_mutex);
  	if (rv < 0) {
  		net_free(net);
  		dec_net_namespaces(ucounts);
  		put_user_ns(user_ns);
  		return ERR_PTR(rv);
  	}
  
  	net->ucounts = ucounts;
  	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) {
  		dec_net_namespaces(ucounts);
  		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;
  	struct 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);
  		for_each_net(tmp) {
  			int id;
  
  			spin_lock_bh(&tmp->nsid_lock);
  			id = __peernet2id(tmp, net);
  			if (id >= 0)
  				idr_remove(&tmp->netns_ids, id);
  			spin_unlock_bh(&tmp->nsid_lock);
  			if (id >= 0)
  				rtnl_net_notifyid(tmp, RTM_DELNSID, id);
  		}
  		spin_lock_bh(&net->nsid_lock);
  		idr_destroy(&net->netns_ids);
  		spin_unlock_bh(&net->nsid_lock);
  
  	}
  	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);
  		dec_net_namespaces(net->ucounts);
  		put_user_ns(net->user_ns);
  		net_drop_ns(net);
  	}
  }
  
  /**
   * net_ns_barrier - wait until concurrent net_cleanup_work is done
   *
   * cleanup_net runs from work queue and will first remove namespaces
   * from the global list, then run net exit functions.
   *
   * Call this in module exit path to make sure that all netns
   * ->exit ops have been invoked before the function is removed.
   */
  void net_ns_barrier(void)
  {
  	mutex_lock(&net_mutex);
  	mutex_unlock(&net_mutex);
  }
  EXPORT_SYMBOL(net_ns_barrier);
  
  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 file *file;
  	struct ns_common *ns;
  	struct net *net;
  
  	file = proc_ns_fget(fd);
  	if (IS_ERR(file))
  		return ERR_CAST(file);
  
  	ns = get_proc_ns(file_inode(file));
  	if (ns->ops == &netns_operations)
  		net = get_net(container_of(ns, struct net, 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
  EXPORT_SYMBOL_GPL(get_net_ns_by_fd);
  
  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;
  		task_lock(tsk);
  		nsproxy = tsk->nsproxy;
  		if (nsproxy)
  			net = get_net(nsproxy->net_ns);
  		task_unlock(tsk);
  	}
  	rcu_read_unlock();
  	return net;
  }
  EXPORT_SYMBOL_GPL(get_net_ns_by_pid);
  
  static __net_init int net_ns_net_init(struct net *net)
  {
  #ifdef CONFIG_NET_NS
  	net->ns.ops = &netns_operations;
  #endif
  	return ns_alloc_inum(&net->ns);
  }
  
  static __net_exit void net_ns_net_exit(struct net *net)
  {
  	ns_free_inum(&net->ns);
  }
  
  static struct pernet_operations __net_initdata net_ns_ops = {
  	.init = net_ns_net_init,
  	.exit = net_ns_net_exit,
  };
  
  static const struct nla_policy rtnl_net_policy[NETNSA_MAX + 1] = {
  	[NETNSA_NONE]		= { .type = NLA_UNSPEC },
  	[NETNSA_NSID]		= { .type = NLA_S32 },
  	[NETNSA_PID]		= { .type = NLA_U32 },
  	[NETNSA_FD]		= { .type = NLA_U32 },
  };
  
  static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh,
  			  struct netlink_ext_ack *extack)
  {
  	struct net *net = sock_net(skb->sk);
  	struct nlattr *tb[NETNSA_MAX + 1];
  	struct nlattr *nla;
  	struct net *peer;
  	int nsid, err;
  
  	err = nlmsg_parse(nlh, sizeof(struct rtgenmsg), tb, NETNSA_MAX,
  			  rtnl_net_policy, extack);
  	if (err < 0)
  		return err;
  	if (!tb[NETNSA_NSID]) {
  		NL_SET_ERR_MSG(extack, "nsid is missing");
  		return -EINVAL;
  	}
  	nsid = nla_get_s32(tb[NETNSA_NSID]);
  
  	if (tb[NETNSA_PID]) {
  		peer = get_net_ns_by_pid(nla_get_u32(tb[NETNSA_PID]));
  		nla = tb[NETNSA_PID];
  	} else if (tb[NETNSA_FD]) {
  		peer = get_net_ns_by_fd(nla_get_u32(tb[NETNSA_FD]));
  		nla = tb[NETNSA_FD];
  	} else {
  		NL_SET_ERR_MSG(extack, "Peer netns reference is missing");
  		return -EINVAL;
  	}
  	if (IS_ERR(peer)) {
  		NL_SET_BAD_ATTR(extack, nla);
  		NL_SET_ERR_MSG(extack, "Peer netns reference is invalid");
  		return PTR_ERR(peer);
  	}
  
  	spin_lock_bh(&net->nsid_lock);
  	if (__peernet2id(net, peer) >= 0) {
  		spin_unlock_bh(&net->nsid_lock);
  		err = -EEXIST;
  		NL_SET_BAD_ATTR(extack, nla);
  		NL_SET_ERR_MSG(extack,
  			       "Peer netns already has a nsid assigned");
  		goto out;
  	}
  
  	err = alloc_netid(net, peer, nsid);
  	spin_unlock_bh(&net->nsid_lock);
  	if (err >= 0) {
  		rtnl_net_notifyid(net, RTM_NEWNSID, err);
  		err = 0;
  	} else if (err == -ENOSPC && nsid >= 0) {
  		err = -EEXIST;
  		NL_SET_BAD_ATTR(extack, tb[NETNSA_NSID]);
  		NL_SET_ERR_MSG(extack, "The specified nsid is already used");
  	}
  out:
  	put_net(peer);
  	return err;
  }
  
  static int rtnl_net_get_size(void)
  {
  	return NLMSG_ALIGN(sizeof(struct rtgenmsg))
  	       + nla_total_size(sizeof(s32)) /* NETNSA_NSID */
  	       ;
  }
  
  static int rtnl_net_fill(struct sk_buff *skb, u32 portid, u32 seq, int flags,
  			 int cmd, struct net *net, int nsid)
  {
  	struct nlmsghdr *nlh;
  	struct rtgenmsg *rth;
  
  	nlh = nlmsg_put(skb, portid, seq, cmd, sizeof(*rth), flags);
  	if (!nlh)
  		return -EMSGSIZE;
  
  	rth = nlmsg_data(nlh);
  	rth->rtgen_family = AF_UNSPEC;
  
  	if (nla_put_s32(skb, NETNSA_NSID, nsid))
  		goto nla_put_failure;
  
  	nlmsg_end(skb, nlh);
  	return 0;
  
  nla_put_failure:
  	nlmsg_cancel(skb, nlh);
  	return -EMSGSIZE;
  }
  
  static int rtnl_net_getid(struct sk_buff *skb, struct nlmsghdr *nlh,
  			  struct netlink_ext_ack *extack)
  {
  	struct net *net = sock_net(skb->sk);
  	struct nlattr *tb[NETNSA_MAX + 1];
  	struct nlattr *nla;
  	struct sk_buff *msg;
  	struct net *peer;
  	int err, id;
  
  	err = nlmsg_parse(nlh, sizeof(struct rtgenmsg), tb, NETNSA_MAX,
  			  rtnl_net_policy, extack);
  	if (err < 0)
  		return err;
  	if (tb[NETNSA_PID]) {
  		peer = get_net_ns_by_pid(nla_get_u32(tb[NETNSA_PID]));
  		nla = tb[NETNSA_PID];
  	} else if (tb[NETNSA_FD]) {
  		peer = get_net_ns_by_fd(nla_get_u32(tb[NETNSA_FD]));
  		nla = tb[NETNSA_FD];
  	} else {
  		NL_SET_ERR_MSG(extack, "Peer netns reference is missing");
  		return -EINVAL;
  	}
  
  	if (IS_ERR(peer)) {
  		NL_SET_BAD_ATTR(extack, nla);
  		NL_SET_ERR_MSG(extack, "Peer netns reference is invalid");
  		return PTR_ERR(peer);
  	}
  
  	msg = nlmsg_new(rtnl_net_get_size(), GFP_KERNEL);
  	if (!msg) {
  		err = -ENOMEM;
  		goto out;
  	}
  
  	id = peernet2id(net, peer);
  	err = rtnl_net_fill(msg, NETLINK_CB(skb).portid, nlh->nlmsg_seq, 0,
  			    RTM_NEWNSID, net, id);
  	if (err < 0)
  		goto err_out;
  
  	err = rtnl_unicast(msg, net, NETLINK_CB(skb).portid);
  	goto out;
  
  err_out:
  	nlmsg_free(msg);
  out:
  	put_net(peer);
  	return err;
  }
  
  struct rtnl_net_dump_cb {
  	struct net *net;
  	struct sk_buff *skb;
  	struct netlink_callback *cb;
  	int idx;
  	int s_idx;
  };
  
  static int rtnl_net_dumpid_one(int id, void *peer, void *data)
  {
  	struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
  	int ret;
  
  	if (net_cb->idx < net_cb->s_idx)
  		goto cont;
  
  	ret = rtnl_net_fill(net_cb->skb, NETLINK_CB(net_cb->cb->skb).portid,
  			    net_cb->cb->nlh->nlmsg_seq, NLM_F_MULTI,
  			    RTM_NEWNSID, net_cb->net, id);
  	if (ret < 0)
  		return ret;
  
  cont:
  	net_cb->idx++;
  	return 0;
  }
  
  static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb)
  {
  	struct net *net = sock_net(skb->sk);
  	struct rtnl_net_dump_cb net_cb = {
  		.net = net,
  		.skb = skb,
  		.cb = cb,
  		.idx = 0,
  		.s_idx = cb->args[0],
  	};
  
  	spin_lock_bh(&net->nsid_lock);
  	idr_for_each(&net->netns_ids, rtnl_net_dumpid_one, &net_cb);
  	spin_unlock_bh(&net->nsid_lock);
  
  	cb->args[0] = net_cb.idx;
  	return skb->len;
  }
  
  static void rtnl_net_notifyid(struct net *net, int cmd, int id)
  {
  	struct sk_buff *msg;
  	int err = -ENOMEM;
  
  	msg = nlmsg_new(rtnl_net_get_size(), GFP_KERNEL);
  	if (!msg)
  		goto out;
  
  	err = rtnl_net_fill(msg, 0, 0, 0, cmd, net, id);
  	if (err < 0)
  		goto err_out;
  
  	rtnl_notify(msg, net, 0, RTNLGRP_NSID, NULL, 0);
  	return;
  
  err_out:
  	nlmsg_free(msg);
  out:
  	rtnl_set_sk_err(net, RTNLGRP_NSID, err);
  }
  
  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");
  
  	init_net_initialized = true;
  
  	rtnl_lock();
  	list_add_tail_rcu(&init_net.list, &net_namespace_list);
  	rtnl_unlock();
  
  	mutex_unlock(&net_mutex);
  
  	register_pernet_subsys(&net_ns_ops);
  
  	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);
  
  	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)
  {
  	if (!init_net_initialized) {
  		list_add_tail(&ops->list, list);
  		return 0;
  	}
  
  	return ops_init(ops, &init_net);
  }
  
  static void __unregister_pernet_operations(struct pernet_operations *ops)
  {
  	if (!init_net_initialized) {
  		list_del(&ops->list);
  	} else {
  		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, MIN_PERNET_OPS_ID, ops->id);
  		if (error < 0) {
  			if (error == -EAGAIN) {
  				ida_pre_get(&net_generic_ids, GFP_KERNEL);
  				goto again;
  			}
  			return error;
  		}
  		max_gen_ptrs = max(max_gen_ptrs, *ops->id + 1);
  	}
  	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 struct ns_common *netns_get(struct task_struct *task)
  {
  	struct net *net = NULL;
  	struct nsproxy *nsproxy;
  
  	task_lock(task);
  	nsproxy = task->nsproxy;
  	if (nsproxy)
  		net = get_net(nsproxy->net_ns);
  	task_unlock(task);
  
  	return net ? &net->ns : NULL;
  }
  
  static inline struct net *to_net_ns(struct ns_common *ns)
  {
  	return container_of(ns, struct net, ns);
  }
  
  static void netns_put(struct ns_common *ns)
  {
  	put_net(to_net_ns(ns));
  }
  
  static int netns_install(struct nsproxy *nsproxy, struct ns_common *ns)
  {
  	struct net *net = to_net_ns(ns);
  
  	if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) ||
  	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
  		return -EPERM;
  
  	put_net(nsproxy->net_ns);
  	nsproxy->net_ns = get_net(net);
  	return 0;
  }
  
  static struct user_namespace *netns_owner(struct ns_common *ns)
  {
  	return to_net_ns(ns)->user_ns;
  }
  
  const struct proc_ns_operations netns_operations = {
  	.name		= "net",
  	.type		= CLONE_NEWNET,
  	.get		= netns_get,
  	.put		= netns_put,
  	.install	= netns_install,
  	.owner		= netns_owner,
  };
  #endif
  