/*
   * NETLINK      Kernel-user communication protocol.
   *

   * 		Authors:	Alan Cox <alan@lxorguk.ukuu.org.uk>

   * 				Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   *
   *		This program is free software; you can redistribute it and/or
   *		modify it under the terms of the GNU General Public License
   *		as published by the Free Software Foundation; either version
   *		2 of the License, or (at your option) any later version.

   *

   * Tue Jun 26 14:36:48 MEST 2001 Herbert "herp" Rosmanith
   *                               added netlink_proto_exit
   * Tue Jan 22 18:32:44 BRST 2002 Arnaldo C. de Melo <acme@conectiva.com.br>
   * 				 use nlk_sk, as sk->protinfo is on a diet 8)

   * Fri Jul 22 19:51:12 MEST 2005 Harald Welte <laforge@gnumonks.org>
   * 				 - inc module use count of module that owns
   * 				   the kernel socket in case userspace opens
   * 				   socket of same protocol
   * 				 - remove all module support, since netlink is
   * 				   mandatory if CONFIG_NET=y these days

   */

  #include <linux/module.h>

  #include <linux/capability.h>

  #include <linux/kernel.h>
  #include <linux/init.h>

  #include <linux/signal.h>
  #include <linux/sched.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/stat.h>
  #include <linux/socket.h>
  #include <linux/un.h>
  #include <linux/fcntl.h>
  #include <linux/termios.h>
  #include <linux/sockios.h>
  #include <linux/net.h>
  #include <linux/fs.h>
  #include <linux/slab.h>
  #include <asm/uaccess.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/rtnetlink.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>

  #include <linux/notifier.h>
  #include <linux/security.h>
  #include <linux/jhash.h>
  #include <linux/jiffies.h>
  #include <linux/random.h>
  #include <linux/bitops.h>
  #include <linux/mm.h>
  #include <linux/types.h>

  #include <linux/audit.h>

  #include <linux/mutex.h>

  #include <net/net_namespace.h>

  #include <net/sock.h>
  #include <net/scm.h>

  #include <net/netlink.h>

  #define NLGRPSZ(x)	(ALIGN(x, sizeof(unsigned long) * 8) / 8)

  #define NLGRPLONGS(x)	(NLGRPSZ(x)/sizeof(unsigned long))

  
  struct netlink_sock {
  	/* struct sock has to be the first member of netlink_sock */
  	struct sock		sk;
  	u32			pid;

  	u32			dst_pid;

  	u32			dst_group;

  	u32			flags;
  	u32			subscriptions;
  	u32			ngroups;
  	unsigned long		*groups;

  	unsigned long		state;
  	wait_queue_head_t	wait;
  	struct netlink_callback	*cb;

  	struct mutex		*cb_mutex;
  	struct mutex		cb_def_mutex;

  	void			(*netlink_rcv)(struct sk_buff *skb);

  	struct module		*module;

  };

  struct listeners {
  	struct rcu_head		rcu;
  	unsigned long		masks[0];

  };

  #define NETLINK_KERNEL_SOCKET	0x1

  #define NETLINK_RECV_PKTINFO	0x2

  #define NETLINK_BROADCAST_SEND_ERROR	0x4

  #define NETLINK_RECV_NO_ENOBUFS	0x8

  static inline struct netlink_sock *nlk_sk(struct sock *sk)
  {

  	return container_of(sk, struct netlink_sock, sk);

  }

  static inline int netlink_is_kernel(struct sock *sk)

  {
  	return nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET;
  }

  struct nl_pid_hash {
  	struct hlist_head *table;
  	unsigned long rehash_time;
  
  	unsigned int mask;
  	unsigned int shift;
  
  	unsigned int entries;
  	unsigned int max_shift;
  
  	u32 rnd;
  };
  
  struct netlink_table {
  	struct nl_pid_hash hash;
  	struct hlist_head mc_list;

  	struct listeners __rcu *listeners;

  	unsigned int nl_nonroot;

  	unsigned int groups;

  	struct mutex *cb_mutex;

  	struct module *module;

  	int registered;

  };
  
  static struct netlink_table *nl_table;
  
  static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);
  
  static int netlink_dump(struct sock *sk);
  static void netlink_destroy_callback(struct netlink_callback *cb);
  
  static DEFINE_RWLOCK(nl_table_lock);
  static atomic_t nl_table_users = ATOMIC_INIT(0);

  static ATOMIC_NOTIFIER_HEAD(netlink_chain);

  static inline u32 netlink_group_mask(u32 group)

  {
  	return group ? 1 << (group - 1) : 0;
  }

  static inline struct hlist_head *nl_pid_hashfn(struct nl_pid_hash *hash, u32 pid)

  {
  	return &hash->table[jhash_1word(pid, hash->rnd) & hash->mask];
  }
  
  static void netlink_sock_destruct(struct sock *sk)
  {

  	struct netlink_sock *nlk = nlk_sk(sk);

  	if (nlk->cb) {
  		if (nlk->cb->done)
  			nlk->cb->done(nlk->cb);
  		netlink_destroy_callback(nlk->cb);
  	}

  	skb_queue_purge(&sk->sk_receive_queue);
  
  	if (!sock_flag(sk, SOCK_DEAD)) {

  		printk(KERN_ERR "Freeing alive netlink socket %p
  ", sk);

  		return;
  	}

  
  	WARN_ON(atomic_read(&sk->sk_rmem_alloc));
  	WARN_ON(atomic_read(&sk->sk_wmem_alloc));
  	WARN_ON(nlk_sk(sk)->groups);

  }

  /* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
   * SMP. Look, when several writers sleep and reader wakes them up, all but one

   * immediately hit write lock and grab all the cpus. Exclusive sleep solves
   * this, _but_ remember, it adds useless work on UP machines.
   */

  void netlink_table_grab(void)

  	__acquires(nl_table_lock)

  {

  	might_sleep();

  	write_lock_irq(&nl_table_lock);

  
  	if (atomic_read(&nl_table_users)) {
  		DECLARE_WAITQUEUE(wait, current);
  
  		add_wait_queue_exclusive(&nl_table_wait, &wait);

  		for (;;) {

  			set_current_state(TASK_UNINTERRUPTIBLE);
  			if (atomic_read(&nl_table_users) == 0)
  				break;

  			write_unlock_irq(&nl_table_lock);

  			schedule();

  			write_lock_irq(&nl_table_lock);

  		}
  
  		__set_current_state(TASK_RUNNING);
  		remove_wait_queue(&nl_table_wait, &wait);
  	}
  }

  void netlink_table_ungrab(void)

  	__releases(nl_table_lock)

  {

  	write_unlock_irq(&nl_table_lock);

  	wake_up(&nl_table_wait);
  }

  static inline void

  netlink_lock_table(void)
  {
  	/* read_lock() synchronizes us to netlink_table_grab */
  
  	read_lock(&nl_table_lock);
  	atomic_inc(&nl_table_users);
  	read_unlock(&nl_table_lock);
  }

  static inline void

  netlink_unlock_table(void)
  {
  	if (atomic_dec_and_test(&nl_table_users))
  		wake_up(&nl_table_wait);
  }

  static struct sock *netlink_lookup(struct net *net, int protocol, u32 pid)

  {
  	struct nl_pid_hash *hash = &nl_table[protocol].hash;
  	struct hlist_head *head;
  	struct sock *sk;
  	struct hlist_node *node;
  
  	read_lock(&nl_table_lock);
  	head = nl_pid_hashfn(hash, pid);
  	sk_for_each(sk, node, head) {

  		if (net_eq(sock_net(sk), net) && (nlk_sk(sk)->pid == pid)) {

  			sock_hold(sk);
  			goto found;
  		}
  	}
  	sk = NULL;
  found:
  	read_unlock(&nl_table_lock);
  	return sk;
  }

  static struct hlist_head *nl_pid_hash_zalloc(size_t size)

  {
  	if (size <= PAGE_SIZE)

  		return kzalloc(size, GFP_ATOMIC);

  	else
  		return (struct hlist_head *)

  			__get_free_pages(GFP_ATOMIC | __GFP_ZERO,
  					 get_order(size));

  }

  static void nl_pid_hash_free(struct hlist_head *table, size_t size)

  {
  	if (size <= PAGE_SIZE)
  		kfree(table);
  	else
  		free_pages((unsigned long)table, get_order(size));
  }
  
  static int nl_pid_hash_rehash(struct nl_pid_hash *hash, int grow)
  {
  	unsigned int omask, mask, shift;
  	size_t osize, size;
  	struct hlist_head *otable, *table;
  	int i;
  
  	omask = mask = hash->mask;
  	osize = size = (mask + 1) * sizeof(*table);
  	shift = hash->shift;
  
  	if (grow) {
  		if (++shift > hash->max_shift)
  			return 0;
  		mask = mask * 2 + 1;
  		size *= 2;
  	}

  	table = nl_pid_hash_zalloc(size);

  	if (!table)
  		return 0;

  	otable = hash->table;
  	hash->table = table;
  	hash->mask = mask;
  	hash->shift = shift;
  	get_random_bytes(&hash->rnd, sizeof(hash->rnd));
  
  	for (i = 0; i <= omask; i++) {
  		struct sock *sk;
  		struct hlist_node *node, *tmp;
  
  		sk_for_each_safe(sk, node, tmp, &otable[i])
  			__sk_add_node(sk, nl_pid_hashfn(hash, nlk_sk(sk)->pid));
  	}
  
  	nl_pid_hash_free(otable, osize);
  	hash->rehash_time = jiffies + 10 * 60 * HZ;
  	return 1;
  }
  
  static inline int nl_pid_hash_dilute(struct nl_pid_hash *hash, int len)
  {
  	int avg = hash->entries >> hash->shift;
  
  	if (unlikely(avg > 1) && nl_pid_hash_rehash(hash, 1))
  		return 1;
  
  	if (unlikely(len > avg) && time_after(jiffies, hash->rehash_time)) {
  		nl_pid_hash_rehash(hash, 0);
  		return 1;
  	}
  
  	return 0;
  }

  static const struct proto_ops netlink_ops;

  static void
  netlink_update_listeners(struct sock *sk)
  {
  	struct netlink_table *tbl = &nl_table[sk->sk_protocol];
  	struct hlist_node *node;
  	unsigned long mask;
  	unsigned int i;

  	for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {

  		mask = 0;

  		sk_for_each_bound(sk, node, &tbl->mc_list) {
  			if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
  				mask |= nlk_sk(sk)->groups[i];
  		}

  		tbl->listeners->masks[i] = mask;

  	}
  	/* this function is only called with the netlink table "grabbed", which
  	 * makes sure updates are visible before bind or setsockopt return. */
  }

  static int netlink_insert(struct sock *sk, struct net *net, u32 pid)

  {
  	struct nl_pid_hash *hash = &nl_table[sk->sk_protocol].hash;
  	struct hlist_head *head;
  	int err = -EADDRINUSE;
  	struct sock *osk;
  	struct hlist_node *node;
  	int len;
  
  	netlink_table_grab();
  	head = nl_pid_hashfn(hash, pid);
  	len = 0;
  	sk_for_each(osk, node, head) {

  		if (net_eq(sock_net(osk), net) && (nlk_sk(osk)->pid == pid))

  			break;
  		len++;
  	}
  	if (node)
  		goto err;
  
  	err = -EBUSY;
  	if (nlk_sk(sk)->pid)
  		goto err;
  
  	err = -ENOMEM;
  	if (BITS_PER_LONG > 32 && unlikely(hash->entries >= UINT_MAX))
  		goto err;
  
  	if (len && nl_pid_hash_dilute(hash, len))
  		head = nl_pid_hashfn(hash, pid);
  	hash->entries++;
  	nlk_sk(sk)->pid = pid;
  	sk_add_node(sk, head);
  	err = 0;
  
  err:
  	netlink_table_ungrab();
  	return err;
  }
  
  static void netlink_remove(struct sock *sk)
  {
  	netlink_table_grab();

  	if (sk_del_node_init(sk))
  		nl_table[sk->sk_protocol].hash.entries--;

  	if (nlk_sk(sk)->subscriptions)

  		__sk_del_bind_node(sk);
  	netlink_table_ungrab();
  }
  
  static struct proto netlink_proto = {
  	.name	  = "NETLINK",
  	.owner	  = THIS_MODULE,
  	.obj_size = sizeof(struct netlink_sock),
  };

  static int __netlink_create(struct net *net, struct socket *sock,
  			    struct mutex *cb_mutex, int protocol)

  {
  	struct sock *sk;
  	struct netlink_sock *nlk;

  
  	sock->ops = &netlink_ops;

  	sk = sk_alloc(net, PF_NETLINK, GFP_KERNEL, &netlink_proto);

  	if (!sk)
  		return -ENOMEM;
  
  	sock_init_data(sock, sk);
  
  	nlk = nlk_sk(sk);

  	if (cb_mutex)
  		nlk->cb_mutex = cb_mutex;
  	else {
  		nlk->cb_mutex = &nlk->cb_def_mutex;
  		mutex_init(nlk->cb_mutex);
  	}

  	init_waitqueue_head(&nlk->wait);
  
  	sk->sk_destruct = netlink_sock_destruct;
  	sk->sk_protocol = protocol;
  	return 0;
  }

  static int netlink_create(struct net *net, struct socket *sock, int protocol,
  			  int kern)

  {
  	struct module *module = NULL;

  	struct mutex *cb_mutex;

  	struct netlink_sock *nlk;

  	int err = 0;

  
  	sock->state = SS_UNCONNECTED;
  
  	if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
  		return -ESOCKTNOSUPPORT;

  	if (protocol < 0 || protocol >= MAX_LINKS)

  		return -EPROTONOSUPPORT;

  	netlink_lock_table();

  #ifdef CONFIG_MODULES

  	if (!nl_table[protocol].registered) {

  		netlink_unlock_table();

  		request_module("net-pf-%d-proto-%d", PF_NETLINK, protocol);

  		netlink_lock_table();

  	}

  #endif
  	if (nl_table[protocol].registered &&
  	    try_module_get(nl_table[protocol].module))
  		module = nl_table[protocol].module;

  	else
  		err = -EPROTONOSUPPORT;

  	cb_mutex = nl_table[protocol].cb_mutex;

  	netlink_unlock_table();

  	if (err < 0)
  		goto out;

  	err = __netlink_create(net, sock, cb_mutex, protocol);
  	if (err < 0)

  		goto out_module;

  	local_bh_disable();

  	sock_prot_inuse_add(net, &netlink_proto, 1);

  	local_bh_enable();

  	nlk = nlk_sk(sock->sk);

  	nlk->module = module;

  out:
  	return err;

  out_module:
  	module_put(module);
  	goto out;

  }
  
  static int netlink_release(struct socket *sock)
  {
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk;
  
  	if (!sk)
  		return 0;
  
  	netlink_remove(sk);

  	sock_orphan(sk);

  	nlk = nlk_sk(sk);

  	/*
  	 * OK. Socket is unlinked, any packets that arrive now
  	 * will be purged.
  	 */

  	sock->sk = NULL;
  	wake_up_interruptible_all(&nlk->wait);
  
  	skb_queue_purge(&sk->sk_write_queue);

  	if (nlk->pid) {

  		struct netlink_notify n = {

  						.net = sock_net(sk),

  						.protocol = sk->sk_protocol,
  						.pid = nlk->pid,
  					  };

  		atomic_notifier_call_chain(&netlink_chain,
  				NETLINK_URELEASE, &n);

  	}

  	module_put(nlk->module);

  	netlink_table_grab();

  	if (netlink_is_kernel(sk)) {

  		BUG_ON(nl_table[sk->sk_protocol].registered == 0);
  		if (--nl_table[sk->sk_protocol].registered == 0) {
  			kfree(nl_table[sk->sk_protocol].listeners);
  			nl_table[sk->sk_protocol].module = NULL;
  			nl_table[sk->sk_protocol].registered = 0;
  		}

  	} else if (nlk->subscriptions)
  		netlink_update_listeners(sk);
  	netlink_table_ungrab();

  	kfree(nlk->groups);
  	nlk->groups = NULL;

  	local_bh_disable();

  	sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);

  	local_bh_enable();

  	sock_put(sk);
  	return 0;
  }
  
  static int netlink_autobind(struct socket *sock)
  {
  	struct sock *sk = sock->sk;

  	struct net *net = sock_net(sk);

  	struct nl_pid_hash *hash = &nl_table[sk->sk_protocol].hash;
  	struct hlist_head *head;
  	struct sock *osk;
  	struct hlist_node *node;

  	s32 pid = task_tgid_vnr(current);

  	int err;
  	static s32 rover = -4097;
  
  retry:
  	cond_resched();
  	netlink_table_grab();
  	head = nl_pid_hashfn(hash, pid);
  	sk_for_each(osk, node, head) {

  		if (!net_eq(sock_net(osk), net))

  			continue;

  		if (nlk_sk(osk)->pid == pid) {
  			/* Bind collision, search negative pid values. */
  			pid = rover--;
  			if (rover > -4097)
  				rover = -4097;
  			netlink_table_ungrab();
  			goto retry;
  		}
  	}
  	netlink_table_ungrab();

  	err = netlink_insert(sk, net, pid);

  	if (err == -EADDRINUSE)
  		goto retry;

  
  	/* If 2 threads race to autobind, that is fine.  */
  	if (err == -EBUSY)
  		err = 0;
  
  	return err;

  }

  static inline int netlink_capable(const struct socket *sock, unsigned int flag)

  {

  	return (nl_table[sock->sk->sk_protocol].nl_nonroot & flag) ||
  	       capable(CAP_NET_ADMIN);

  }

  static void
  netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions)
  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  
  	if (nlk->subscriptions && !subscriptions)
  		__sk_del_bind_node(sk);
  	else if (!nlk->subscriptions && subscriptions)
  		sk_add_bind_node(sk, &nl_table[sk->sk_protocol].mc_list);
  	nlk->subscriptions = subscriptions;
  }

  static int netlink_realloc_groups(struct sock *sk)

  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  	unsigned int groups;

  	unsigned long *new_groups;

  	int err = 0;

  	netlink_table_grab();

  	groups = nl_table[sk->sk_protocol].groups;

  	if (!nl_table[sk->sk_protocol].registered) {

  		err = -ENOENT;

  		goto out_unlock;
  	}

  	if (nlk->ngroups >= groups)
  		goto out_unlock;

  	new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_ATOMIC);
  	if (new_groups == NULL) {
  		err = -ENOMEM;
  		goto out_unlock;
  	}

  	memset((char *)new_groups + NLGRPSZ(nlk->ngroups), 0,

  	       NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));
  
  	nlk->groups = new_groups;

  	nlk->ngroups = groups;

   out_unlock:
  	netlink_table_ungrab();
  	return err;

  }

  static int netlink_bind(struct socket *sock, struct sockaddr *addr,
  			int addr_len)

  {
  	struct sock *sk = sock->sk;

  	struct net *net = sock_net(sk);

  	struct netlink_sock *nlk = nlk_sk(sk);
  	struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
  	int err;

  	if (nladdr->nl_family != AF_NETLINK)
  		return -EINVAL;
  
  	/* Only superuser is allowed to listen multicasts */

  	if (nladdr->nl_groups) {
  		if (!netlink_capable(sock, NL_NONROOT_RECV))
  			return -EPERM;

  		err = netlink_realloc_groups(sk);
  		if (err)
  			return err;

  	}

  
  	if (nlk->pid) {
  		if (nladdr->nl_pid != nlk->pid)
  			return -EINVAL;
  	} else {
  		err = nladdr->nl_pid ?

  			netlink_insert(sk, net, nladdr->nl_pid) :

  			netlink_autobind(sock);
  		if (err)
  			return err;
  	}

  	if (!nladdr->nl_groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))

  		return 0;
  
  	netlink_table_grab();

  	netlink_update_subscriptions(sk, nlk->subscriptions +

  					 hweight32(nladdr->nl_groups) -
  					 hweight32(nlk->groups[0]));
  	nlk->groups[0] = (nlk->groups[0] & ~0xffffffffUL) | nladdr->nl_groups;

  	netlink_update_listeners(sk);

  	netlink_table_ungrab();
  
  	return 0;
  }
  
  static int netlink_connect(struct socket *sock, struct sockaddr *addr,
  			   int alen, int flags)
  {
  	int err = 0;
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);

  	struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;

  	if (alen < sizeof(addr->sa_family))
  		return -EINVAL;

  	if (addr->sa_family == AF_UNSPEC) {
  		sk->sk_state	= NETLINK_UNCONNECTED;
  		nlk->dst_pid	= 0;

  		nlk->dst_group  = 0;

  		return 0;
  	}
  	if (addr->sa_family != AF_NETLINK)
  		return -EINVAL;
  
  	/* Only superuser is allowed to send multicasts */
  	if (nladdr->nl_groups && !netlink_capable(sock, NL_NONROOT_SEND))
  		return -EPERM;
  
  	if (!nlk->pid)
  		err = netlink_autobind(sock);
  
  	if (err == 0) {
  		sk->sk_state	= NETLINK_CONNECTED;
  		nlk->dst_pid 	= nladdr->nl_pid;

  		nlk->dst_group  = ffs(nladdr->nl_groups);

  	}
  
  	return err;
  }

  static int netlink_getname(struct socket *sock, struct sockaddr *addr,
  			   int *addr_len, int peer)

  {
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);

  	DECLARE_SOCKADDR(struct sockaddr_nl *, nladdr, addr);

  	nladdr->nl_family = AF_NETLINK;
  	nladdr->nl_pad = 0;
  	*addr_len = sizeof(*nladdr);
  
  	if (peer) {
  		nladdr->nl_pid = nlk->dst_pid;

  		nladdr->nl_groups = netlink_group_mask(nlk->dst_group);

  	} else {
  		nladdr->nl_pid = nlk->pid;

  		nladdr->nl_groups = nlk->groups ? nlk->groups[0] : 0;

  	}
  	return 0;
  }
  
  static void netlink_overrun(struct sock *sk)
  {

  	struct netlink_sock *nlk = nlk_sk(sk);
  
  	if (!(nlk->flags & NETLINK_RECV_NO_ENOBUFS)) {
  		if (!test_and_set_bit(0, &nlk_sk(sk)->state)) {
  			sk->sk_err = ENOBUFS;
  			sk->sk_error_report(sk);
  		}

  	}

  	atomic_inc(&sk->sk_drops);

  }
  
  static struct sock *netlink_getsockbypid(struct sock *ssk, u32 pid)
  {

  	struct sock *sock;
  	struct netlink_sock *nlk;

  	sock = netlink_lookup(sock_net(ssk), ssk->sk_protocol, pid);

  	if (!sock)
  		return ERR_PTR(-ECONNREFUSED);
  
  	/* Don't bother queuing skb if kernel socket has no input function */
  	nlk = nlk_sk(sock);

  	if (sock->sk_state == NETLINK_CONNECTED &&
  	    nlk->dst_pid != nlk_sk(ssk)->pid) {

  		sock_put(sock);
  		return ERR_PTR(-ECONNREFUSED);
  	}
  	return sock;
  }
  
  struct sock *netlink_getsockbyfilp(struct file *filp)
  {

  	struct inode *inode = filp->f_path.dentry->d_inode;

  	struct sock *sock;
  
  	if (!S_ISSOCK(inode->i_mode))
  		return ERR_PTR(-ENOTSOCK);
  
  	sock = SOCKET_I(inode)->sk;
  	if (sock->sk_family != AF_NETLINK)
  		return ERR_PTR(-EINVAL);
  
  	sock_hold(sock);
  	return sock;
  }
  
  /*
   * Attach a skb to a netlink socket.
   * The caller must hold a reference to the destination socket. On error, the
   * reference is dropped. The skb is not send to the destination, just all
   * all error checks are performed and memory in the queue is reserved.
   * Return values:
   * < 0: error. skb freed, reference to sock dropped.
   * 0: continue
   * 1: repeat lookup - reference dropped while waiting for socket memory.
   */

  int netlink_attachskb(struct sock *sk, struct sk_buff *skb,

  		      long *timeo, struct sock *ssk)

  {
  	struct netlink_sock *nlk;
  
  	nlk = nlk_sk(sk);
  
  	if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
  	    test_bit(0, &nlk->state)) {
  		DECLARE_WAITQUEUE(wait, current);

  		if (!*timeo) {

  			if (!ssk || netlink_is_kernel(ssk))

  				netlink_overrun(sk);
  			sock_put(sk);
  			kfree_skb(skb);
  			return -EAGAIN;
  		}
  
  		__set_current_state(TASK_INTERRUPTIBLE);
  		add_wait_queue(&nlk->wait, &wait);
  
  		if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
  		     test_bit(0, &nlk->state)) &&
  		    !sock_flag(sk, SOCK_DEAD))

  			*timeo = schedule_timeout(*timeo);

  
  		__set_current_state(TASK_RUNNING);
  		remove_wait_queue(&nlk->wait, &wait);
  		sock_put(sk);
  
  		if (signal_pending(current)) {
  			kfree_skb(skb);

  			return sock_intr_errno(*timeo);

  		}
  		return 1;
  	}
  	skb_set_owner_r(skb, sk);
  	return 0;
  }

  int netlink_sendskb(struct sock *sk, struct sk_buff *skb)

  {

  	int len = skb->len;

  	skb_queue_tail(&sk->sk_receive_queue, skb);
  	sk->sk_data_ready(sk, len);
  	sock_put(sk);
  	return len;
  }
  
  void netlink_detachskb(struct sock *sk, struct sk_buff *skb)
  {
  	kfree_skb(skb);
  	sock_put(sk);
  }

  static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)

  {
  	int delta;
  
  	skb_orphan(skb);

  	delta = skb->end - skb->tail;

  	if (delta * 2 < skb->truesize)
  		return skb;
  
  	if (skb_shared(skb)) {
  		struct sk_buff *nskb = skb_clone(skb, allocation);
  		if (!nskb)
  			return skb;
  		kfree_skb(skb);
  		skb = nskb;
  	}
  
  	if (!pskb_expand_head(skb, 0, -delta, allocation))
  		skb->truesize -= delta;
  
  	return skb;
  }

  static void netlink_rcv_wake(struct sock *sk)

  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  
  	if (skb_queue_empty(&sk->sk_receive_queue))
  		clear_bit(0, &nlk->state);
  	if (!test_bit(0, &nlk->state))
  		wake_up_interruptible(&nlk->wait);
  }

  static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb)

  {
  	int ret;
  	struct netlink_sock *nlk = nlk_sk(sk);
  
  	ret = -ECONNREFUSED;
  	if (nlk->netlink_rcv != NULL) {
  		ret = skb->len;
  		skb_set_owner_r(skb, sk);
  		nlk->netlink_rcv(skb);
  	}
  	kfree_skb(skb);
  	sock_put(sk);
  	return ret;
  }
  
  int netlink_unicast(struct sock *ssk, struct sk_buff *skb,
  		    u32 pid, int nonblock)

  {
  	struct sock *sk;
  	int err;
  	long timeo;
  
  	skb = netlink_trim(skb, gfp_any());
  
  	timeo = sock_sndtimeo(ssk, nonblock);
  retry:
  	sk = netlink_getsockbypid(ssk, pid);
  	if (IS_ERR(sk)) {
  		kfree_skb(skb);
  		return PTR_ERR(sk);
  	}

  	if (netlink_is_kernel(sk))
  		return netlink_unicast_kernel(sk, skb);

  	if (sk_filter(sk, skb)) {

  		err = skb->len;

  		kfree_skb(skb);
  		sock_put(sk);
  		return err;
  	}

  	err = netlink_attachskb(sk, skb, &timeo, ssk);

  	if (err == 1)
  		goto retry;
  	if (err)
  		return err;

  	return netlink_sendskb(sk, skb);

  }

  EXPORT_SYMBOL(netlink_unicast);

  int netlink_has_listeners(struct sock *sk, unsigned int group)
  {
  	int res = 0;

  	struct listeners *listeners;

  	BUG_ON(!netlink_is_kernel(sk));

  
  	rcu_read_lock();
  	listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);

  	if (group - 1 < nl_table[sk->sk_protocol].groups)

  		res = test_bit(group - 1, listeners->masks);

  
  	rcu_read_unlock();

  	return res;
  }
  EXPORT_SYMBOL_GPL(netlink_has_listeners);

  static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)

  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  
  	if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
  	    !test_bit(0, &nlk->state)) {
  		skb_set_owner_r(skb, sk);
  		skb_queue_tail(&sk->sk_receive_queue, skb);
  		sk->sk_data_ready(sk, skb->len);

  		return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);

  	}
  	return -1;
  }
  
  struct netlink_broadcast_data {
  	struct sock *exclude_sk;

  	struct net *net;

  	u32 pid;
  	u32 group;
  	int failure;

  	int delivery_failure;

  	int congested;
  	int delivered;

  	gfp_t allocation;

  	struct sk_buff *skb, *skb2;

  	int (*tx_filter)(struct sock *dsk, struct sk_buff *skb, void *data);
  	void *tx_data;

  };

  static int do_one_broadcast(struct sock *sk,

  				   struct netlink_broadcast_data *p)
  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  	int val;
  
  	if (p->exclude_sk == sk)
  		goto out;

  	if (nlk->pid == p->pid || p->group - 1 >= nlk->ngroups ||
  	    !test_bit(p->group - 1, nlk->groups))

  		goto out;

  	if (!net_eq(sock_net(sk), p->net))

  		goto out;

  	if (p->failure) {
  		netlink_overrun(sk);
  		goto out;
  	}
  
  	sock_hold(sk);
  	if (p->skb2 == NULL) {

  		if (skb_shared(p->skb)) {

  			p->skb2 = skb_clone(p->skb, p->allocation);
  		} else {

  			p->skb2 = skb_get(p->skb);
  			/*
  			 * skb ownership may have been set when
  			 * delivered to a previous socket.
  			 */
  			skb_orphan(p->skb2);

  		}
  	}
  	if (p->skb2 == NULL) {
  		netlink_overrun(sk);
  		/* Clone failed. Notify ALL listeners. */
  		p->failure = 1;

  		if (nlk->flags & NETLINK_BROADCAST_SEND_ERROR)
  			p->delivery_failure = 1;

  	} else if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
  		kfree_skb(p->skb2);
  		p->skb2 = NULL;

  	} else if (sk_filter(sk, p->skb2)) {
  		kfree_skb(p->skb2);
  		p->skb2 = NULL;

  	} else if ((val = netlink_broadcast_deliver(sk, p->skb2)) < 0) {
  		netlink_overrun(sk);

  		if (nlk->flags & NETLINK_BROADCAST_SEND_ERROR)
  			p->delivery_failure = 1;

  	} else {
  		p->congested |= val;
  		p->delivered = 1;
  		p->skb2 = NULL;
  	}
  	sock_put(sk);
  
  out:
  	return 0;
  }

  int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 pid,
  	u32 group, gfp_t allocation,
  	int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
  	void *filter_data)

  {

  	struct net *net = sock_net(ssk);

  	struct netlink_broadcast_data info;
  	struct hlist_node *node;
  	struct sock *sk;
  
  	skb = netlink_trim(skb, allocation);
  
  	info.exclude_sk = ssk;

  	info.net = net;

  	info.pid = pid;
  	info.group = group;
  	info.failure = 0;

  	info.delivery_failure = 0;

  	info.congested = 0;
  	info.delivered = 0;
  	info.allocation = allocation;
  	info.skb = skb;
  	info.skb2 = NULL;

  	info.tx_filter = filter;
  	info.tx_data = filter_data;

  
  	/* While we sleep in clone, do not allow to change socket list */
  
  	netlink_lock_table();
  
  	sk_for_each_bound(sk, node, &nl_table[ssk->sk_protocol].mc_list)
  		do_one_broadcast(sk, &info);

  	consume_skb(skb);

  	netlink_unlock_table();

  	if (info.delivery_failure) {
  		kfree_skb(info.skb2);

  		return -ENOBUFS;

  	} else
  		consume_skb(info.skb2);

  	if (info.delivered) {
  		if (info.congested && (allocation & __GFP_WAIT))
  			yield();
  		return 0;
  	}

  	return -ESRCH;
  }

  EXPORT_SYMBOL(netlink_broadcast_filtered);
  
  int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 pid,
  		      u32 group, gfp_t allocation)
  {
  	return netlink_broadcast_filtered(ssk, skb, pid, group, allocation,
  		NULL, NULL);
  }

  EXPORT_SYMBOL(netlink_broadcast);

  
  struct netlink_set_err_data {
  	struct sock *exclude_sk;
  	u32 pid;
  	u32 group;
  	int code;
  };

  static int do_one_set_err(struct sock *sk, struct netlink_set_err_data *p)

  {
  	struct netlink_sock *nlk = nlk_sk(sk);

  	int ret = 0;

  
  	if (sk == p->exclude_sk)
  		goto out;

  	if (!net_eq(sock_net(sk), sock_net(p->exclude_sk)))

  		goto out;

  	if (nlk->pid == p->pid || p->group - 1 >= nlk->ngroups ||
  	    !test_bit(p->group - 1, nlk->groups))

  		goto out;

  	if (p->code == ENOBUFS && nlk->flags & NETLINK_RECV_NO_ENOBUFS) {
  		ret = 1;
  		goto out;
  	}

  	sk->sk_err = p->code;
  	sk->sk_error_report(sk);
  out:

  	return ret;

  }

  /**
   * netlink_set_err - report error to broadcast listeners
   * @ssk: the kernel netlink socket, as returned by netlink_kernel_create()
   * @pid: the PID of a process that we want to skip (if any)
   * @groups: the broadcast group that will notice the error
   * @code: error code, must be negative (as usual in kernelspace)

   *
   * This function returns the number of broadcast listeners that have set the
   * NETLINK_RECV_NO_ENOBUFS socket option.

   */

  int netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)

  {
  	struct netlink_set_err_data info;
  	struct hlist_node *node;
  	struct sock *sk;

  	int ret = 0;

  
  	info.exclude_sk = ssk;
  	info.pid = pid;
  	info.group = group;

  	/* sk->sk_err wants a positive error value */
  	info.code = -code;

  
  	read_lock(&nl_table_lock);
  
  	sk_for_each_bound(sk, node, &nl_table[ssk->sk_protocol].mc_list)

  		ret += do_one_set_err(sk, &info);

  
  	read_unlock(&nl_table_lock);

  	return ret;

  }

  EXPORT_SYMBOL(netlink_set_err);

  /* must be called with netlink table grabbed */
  static void netlink_update_socket_mc(struct netlink_sock *nlk,
  				     unsigned int group,
  				     int is_new)
  {
  	int old, new = !!is_new, subscriptions;
  
  	old = test_bit(group - 1, nlk->groups);
  	subscriptions = nlk->subscriptions - old + new;
  	if (new)
  		__set_bit(group - 1, nlk->groups);
  	else
  		__clear_bit(group - 1, nlk->groups);
  	netlink_update_subscriptions(&nlk->sk, subscriptions);
  	netlink_update_listeners(&nlk->sk);
  }

  static int netlink_setsockopt(struct socket *sock, int level, int optname,

  			      char __user *optval, unsigned int optlen)

  {
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);

  	unsigned int val = 0;
  	int err;

  
  	if (level != SOL_NETLINK)
  		return -ENOPROTOOPT;
  
  	if (optlen >= sizeof(int) &&

  	    get_user(val, (unsigned int __user *)optval))

  		return -EFAULT;
  
  	switch (optname) {
  	case NETLINK_PKTINFO:
  		if (val)
  			nlk->flags |= NETLINK_RECV_PKTINFO;
  		else
  			nlk->flags &= ~NETLINK_RECV_PKTINFO;
  		err = 0;
  		break;
  	case NETLINK_ADD_MEMBERSHIP:
  	case NETLINK_DROP_MEMBERSHIP: {

  		if (!netlink_capable(sock, NL_NONROOT_RECV))
  			return -EPERM;

  		err = netlink_realloc_groups(sk);
  		if (err)
  			return err;

  		if (!val || val - 1 >= nlk->ngroups)
  			return -EINVAL;
  		netlink_table_grab();

  		netlink_update_socket_mc(nlk, val,
  					 optname == NETLINK_ADD_MEMBERSHIP);

  		netlink_table_ungrab();
  		err = 0;
  		break;
  	}

  	case NETLINK_BROADCAST_ERROR:
  		if (val)
  			nlk->flags |= NETLINK_BROADCAST_SEND_ERROR;
  		else
  			nlk->flags &= ~NETLINK_BROADCAST_SEND_ERROR;
  		err = 0;
  		break;

  	case NETLINK_NO_ENOBUFS:
  		if (val) {
  			nlk->flags |= NETLINK_RECV_NO_ENOBUFS;
  			clear_bit(0, &nlk->state);
  			wake_up_interruptible(&nlk->wait);
  		} else
  			nlk->flags &= ~NETLINK_RECV_NO_ENOBUFS;
  		err = 0;
  		break;

  	default:
  		err = -ENOPROTOOPT;
  	}
  	return err;
  }
  
  static int netlink_getsockopt(struct socket *sock, int level, int optname,

  			      char __user *optval, int __user *optlen)

  {
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);
  	int len, val, err;
  
  	if (level != SOL_NETLINK)
  		return -ENOPROTOOPT;
  
  	if (get_user(len, optlen))
  		return -EFAULT;
  	if (len < 0)
  		return -EINVAL;
  
  	switch (optname) {
  	case NETLINK_PKTINFO:
  		if (len < sizeof(int))
  			return -EINVAL;
  		len = sizeof(int);
  		val = nlk->flags & NETLINK_RECV_PKTINFO ? 1 : 0;

  		if (put_user(len, optlen) ||
  		    put_user(val, optval))
  			return -EFAULT;

  		err = 0;
  		break;

  	case NETLINK_BROADCAST_ERROR:
  		if (len < sizeof(int))
  			return -EINVAL;
  		len = sizeof(int);
  		val = nlk->flags & NETLINK_BROADCAST_SEND_ERROR ? 1 : 0;
  		if (put_user(len, optlen) ||
  		    put_user(val, optval))
  			return -EFAULT;
  		err = 0;
  		break;

  	case NETLINK_NO_ENOBUFS:
  		if (len < sizeof(int))
  			return -EINVAL;
  		len = sizeof(int);
  		val = nlk->flags & NETLINK_RECV_NO_ENOBUFS ? 1 : 0;
  		if (put_user(len, optlen) ||
  		    put_user(val, optval))
  			return -EFAULT;
  		err = 0;
  		break;

  	default:
  		err = -ENOPROTOOPT;
  	}
  	return err;
  }
  
  static void netlink_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
  {
  	struct nl_pktinfo info;
  
  	info.group = NETLINK_CB(skb).dst_group;
  	put_cmsg(msg, SOL_NETLINK, NETLINK_PKTINFO, sizeof(info), &info);
  }

  static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
  			   struct msghdr *msg, size_t len)
  {
  	struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);

  	struct sockaddr_nl *addr = msg->msg_name;

  	u32 dst_pid;

  	u32 dst_group;

  	struct sk_buff *skb;
  	int err;
  	struct scm_cookie scm;
  
  	if (msg->msg_flags&MSG_OOB)
  		return -EOPNOTSUPP;

  	if (NULL == siocb->scm)

  		siocb->scm = &scm;

  	err = scm_send(sock, msg, siocb->scm);
  	if (err < 0)
  		return err;
  
  	if (msg->msg_namelen) {

  		err = -EINVAL;

  		if (addr->nl_family != AF_NETLINK)

  			goto out;

  		dst_pid = addr->nl_pid;

  		dst_group = ffs(addr->nl_groups);

  		err =  -EPERM;

  		if (dst_group && !netlink_capable(sock, NL_NONROOT_SEND))

  			goto out;

  	} else {
  		dst_pid = nlk->dst_pid;

  		dst_group = nlk->dst_group;

  	}
  
  	if (!nlk->pid) {
  		err = netlink_autobind(sock);
  		if (err)
  			goto out;
  	}
  
  	err = -EMSGSIZE;
  	if (len > sk->sk_sndbuf - 32)
  		goto out;
  	err = -ENOBUFS;

  	skb = alloc_skb(len, GFP_KERNEL);

  	if (skb == NULL)

  		goto out;
  
  	NETLINK_CB(skb).pid	= nlk->pid;

  	NETLINK_CB(skb).dst_group = dst_group;

  	memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));

  	err = -EFAULT;

  	if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {

  		kfree_skb(skb);
  		goto out;
  	}
  
  	err = security_netlink_send(sk, skb);
  	if (err) {
  		kfree_skb(skb);
  		goto out;
  	}

  	if (dst_group) {

  		atomic_inc(&skb->users);

  		netlink_broadcast(sk, skb, dst_pid, dst_group, GFP_KERNEL);

  	}
  	err = netlink_unicast(sk, skb, dst_pid, msg->msg_flags&MSG_DONTWAIT);
  
  out:

  	scm_destroy(siocb->scm);

  	return err;
  }
  
  static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
  			   struct msghdr *msg, size_t len,
  			   int flags)
  {
  	struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
  	struct scm_cookie scm;
  	struct sock *sk = sock->sk;
  	struct netlink_sock *nlk = nlk_sk(sk);
  	int noblock = flags&MSG_DONTWAIT;
  	size_t copied;

  	struct sk_buff *skb, *data_skb;

  	int err, ret;

  
  	if (flags&MSG_OOB)
  		return -EOPNOTSUPP;
  
  	copied = 0;

  	skb = skb_recv_datagram(sk, flags, noblock, &err);
  	if (skb == NULL)

  		goto out;

  	data_skb = skb;

  #ifdef CONFIG_COMPAT_NETLINK_MESSAGES
  	if (unlikely(skb_shinfo(skb)->frag_list)) {

  		/*

  		 * If this skb has a frag_list, then here that means that we
  		 * will have to use the frag_list skb's data for compat tasks
  		 * and the regular skb's data for normal (non-compat) tasks.

  		 *

  		 * If we need to send the compat skb, assign it to the
  		 * 'data_skb' variable so that it will be used below for data
  		 * copying. We keep 'skb' for everything else, including
  		 * freeing both later.

  		 */

  		if (flags & MSG_CMSG_COMPAT)
  			data_skb = skb_shinfo(skb)->frag_list;

  	}
  #endif

  	msg->msg_namelen = 0;

  	copied = data_skb->len;

  	if (len < copied) {
  		msg->msg_flags |= MSG_TRUNC;
  		copied = len;
  	}

  	skb_reset_transport_header(data_skb);
  	err = skb_copy_datagram_iovec(data_skb, 0, msg->msg_iov, copied);

  
  	if (msg->msg_name) {

  		struct sockaddr_nl *addr = (struct sockaddr_nl *)msg->msg_name;

  		addr->nl_family = AF_NETLINK;
  		addr->nl_pad    = 0;
  		addr->nl_pid	= NETLINK_CB(skb).pid;

  		addr->nl_groups	= netlink_group_mask(NETLINK_CB(skb).dst_group);

  		msg->msg_namelen = sizeof(*addr);
  	}

  	if (nlk->flags & NETLINK_RECV_PKTINFO)
  		netlink_cmsg_recv_pktinfo(msg, skb);

  	if (NULL == siocb->scm) {
  		memset(&scm, 0, sizeof(scm));
  		siocb->scm = &scm;
  	}
  	siocb->scm->creds = *NETLINK_CREDS(skb);

  	if (flags & MSG_TRUNC)

  		copied = data_skb->len;

  	skb_free_datagram(sk, skb);

  	if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
  		ret = netlink_dump(sk);
  		if (ret) {
  			sk->sk_err = ret;
  			sk->sk_error_report(sk);
  		}
  	}

  
  	scm_recv(sock, msg, siocb->scm, flags);

  out:
  	netlink_rcv_wake(sk);
  	return err ? : copied;
  }
  
  static void netlink_data_ready(struct sock *sk, int len)
  {

  	BUG();

  }
  
  /*

   *	We export these functions to other modules. They provide a

   *	complete set of kernel non-blocking support for message
   *	queueing.
   */
  
  struct sock *

  netlink_kernel_create(struct net *net, int unit, unsigned int groups,

  		      void (*input)(struct sk_buff *skb),

  		      struct mutex *cb_mutex, struct module *module)

  {
  	struct socket *sock;
  	struct sock *sk;

  	struct netlink_sock *nlk;

  	struct listeners *listeners = NULL;

  	BUG_ON(!nl_table);

  	if (unit < 0 || unit >= MAX_LINKS)

  		return NULL;
  
  	if (sock_create_lite(PF_NETLINK, SOCK_DGRAM, unit, &sock))
  		return NULL;

  	/*
  	 * We have to just have a reference on the net from sk, but don't
  	 * get_net it. Besides, we cannot get and then put the net here.
  	 * So we create one inside init_net and the move it to net.
  	 */
  
  	if (__netlink_create(&init_net, sock, cb_mutex, unit) < 0)
  		goto out_sock_release_nosk;
  
  	sk = sock->sk;

  	sk_change_net(sk, net);

  	if (groups < 32)
  		groups = 32;

  	listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);

  	if (!listeners)
  		goto out_sock_release;

  	sk->sk_data_ready = netlink_data_ready;
  	if (input)

  		nlk_sk(sk)->netlink_rcv = input;

  	if (netlink_insert(sk, net, 0))

  		goto out_sock_release;

  	nlk = nlk_sk(sk);
  	nlk->flags |= NETLINK_KERNEL_SOCKET;

  	netlink_table_grab();

  	if (!nl_table[unit].registered) {
  		nl_table[unit].groups = groups;

  		rcu_assign_pointer(nl_table[unit].listeners, listeners);

  		nl_table[unit].cb_mutex = cb_mutex;
  		nl_table[unit].module = module;
  		nl_table[unit].registered = 1;

  	} else {
  		kfree(listeners);

  		nl_table[unit].registered++;

  	}

  	netlink_table_ungrab();

  	return sk;

  out_sock_release:

  	kfree(listeners);

  	netlink_kernel_release(sk);

  	return NULL;
  
  out_sock_release_nosk:

  	sock_release(sock);

  	return NULL;

  }

  EXPORT_SYMBOL(netlink_kernel_create);

  
  void
  netlink_kernel_release(struct sock *sk)
  {

  	sk_release_kernel(sk);

  }
  EXPORT_SYMBOL(netlink_kernel_release);

  int __netlink_change_ngroups(struct sock *sk, unsigned int groups)

  {

  	struct listeners *new, *old;

  	struct netlink_table *tbl = &nl_table[sk->sk_protocol];

  
  	if (groups < 32)
  		groups = 32;

  	if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {

  		new = kzalloc(sizeof(*new) + NLGRPSZ(groups), GFP_ATOMIC);
  		if (!new)

  			return -ENOMEM;

  		old = rcu_dereference_protected(tbl->listeners, 1);

  		memcpy(new->masks, old->masks, NLGRPSZ(tbl->groups));
  		rcu_assign_pointer(tbl->listeners, new);

  		kfree_rcu(old, rcu);

  	}
  	tbl->groups = groups;

  	return 0;
  }
  
  /**
   * netlink_change_ngroups - change number of multicast groups
   *
   * This changes the number of multicast groups that are available
   * on a certain netlink family. Note that it is not possible to
   * change the number of groups to below 32. Also note that it does
   * not implicitly call netlink_clear_multicast_users() when the
   * number of groups is reduced.
   *
   * @sk: The kernel netlink socket, as returned by netlink_kernel_create().
   * @groups: The new number of groups.
   */
  int netlink_change_ngroups(struct sock *sk, unsigned int groups)
  {
  	int err;
  
  	netlink_table_grab();
  	err = __netlink_change_ngroups(sk, groups);

  	netlink_table_ungrab();

  	return err;
  }

  void __netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
  {
  	struct sock *sk;
  	struct hlist_node *node;
  	struct netlink_table *tbl = &nl_table[ksk->sk_protocol];
  
  	sk_for_each_bound(sk, node, &tbl->mc_list)
  		netlink_update_socket_mc(nlk_sk(sk), group, 0);
  }

  /**
   * netlink_clear_multicast_users - kick off multicast listeners
   *
   * This function removes all listeners from the given group.
   * @ksk: The kernel netlink socket, as returned by
   *	netlink_kernel_create().
   * @group: The multicast group to clear.
   */
  void netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
  {

  	netlink_table_grab();

  	__netlink_clear_multicast_users(ksk, group);

  	netlink_table_ungrab();
  }

  void netlink_set_nonroot(int protocol, unsigned int flags)

  {
  	if ((unsigned int)protocol < MAX_LINKS)

  		nl_table[protocol].nl_nonroot = flags;

  }

  EXPORT_SYMBOL(netlink_set_nonroot);

  
  static void netlink_destroy_callback(struct netlink_callback *cb)
  {

  	kfree_skb(cb->skb);

  	kfree(cb);
  }
  
  /*
   * It looks a bit ugly.
   * It would be better to create kernel thread.
   */
  
  static int netlink_dump(struct sock *sk)
  {
  	struct netlink_sock *nlk = nlk_sk(sk);
  	struct netlink_callback *cb;

  	struct sk_buff *skb = NULL;

  	struct nlmsghdr *nlh;

  	int len, err = -ENOBUFS;

  	int alloc_size;

  	mutex_lock(nlk->cb_mutex);

  
  	cb = nlk->cb;
  	if (cb == NULL) {

  		err = -EINVAL;
  		goto errout_skb;

  	}

  	alloc_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
  
  	skb = sock_rmalloc(sk, alloc_size, 0, GFP_KERNEL);
  	if (!skb)

  		goto errout_skb;

  	len = cb->dump(skb, cb);
  
  	if (len > 0) {

  		mutex_unlock(nlk->cb_mutex);

  
  		if (sk_filter(sk, skb))
  			kfree_skb(skb);
  		else {
  			skb_queue_tail(&sk->sk_receive_queue, skb);
  			sk->sk_data_ready(sk, skb->len);
  		}

  		return 0;
  	}

  	nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(len), NLM_F_MULTI);
  	if (!nlh)
  		goto errout_skb;

  	nl_dump_check_consistent(cb, nlh);

  	memcpy(nlmsg_data(nlh), &len, sizeof(len));

  	if (sk_filter(sk, skb))
  		kfree_skb(skb);
  	else {
  		skb_queue_tail(&sk->sk_receive_queue, skb);
  		sk->sk_data_ready(sk, skb->len);
  	}

  	if (cb->done)
  		cb->done(cb);

  	nlk->cb = NULL;

  	mutex_unlock(nlk->cb_mutex);

  
  	netlink_destroy_callback(cb);

  	return 0;

  errout_skb:

  	mutex_unlock(nlk->cb_mutex);

  	kfree_skb(skb);

  	return err;

  }
  
  int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,

  		       const struct nlmsghdr *nlh,

  		       int (*dump)(struct sk_buff *skb,
  				   struct netlink_callback *),

  		       int (*done)(struct netlink_callback *),
  		       u16 min_dump_alloc)

  {
  	struct netlink_callback *cb;
  	struct sock *sk;
  	struct netlink_sock *nlk;

  	int ret;

  	cb = kzalloc(sizeof(*cb), GFP_KERNEL);

  	if (cb == NULL)
  		return -ENOBUFS;

  	cb->dump = dump;
  	cb->done = done;
  	cb->nlh = nlh;

  	cb->min_dump_alloc = min_dump_alloc;

  	atomic_inc(&skb->users);
  	cb->skb = skb;

  	sk = netlink_lookup(sock_net(ssk), ssk->sk_protocol, NETLINK_CB(skb).pid);

  	if (sk == NULL) {
  		netlink_destroy_callback(cb);
  		return -ECONNREFUSED;
  	}
  	nlk = nlk_sk(sk);

  	/* A dump is in progress... */

  	mutex_lock(nlk->cb_mutex);

  	if (nlk->cb) {

  		mutex_unlock(nlk->cb_mutex);

  		netlink_destroy_callback(cb);
  		sock_put(sk);
  		return -EBUSY;
  	}
  	nlk->cb = cb;

  	mutex_unlock(nlk->cb_mutex);

  	ret = netlink_dump(sk);

  	sock_put(sk);

  	if (ret)
  		return ret;

  	/* We successfully started a dump, by returning -EINTR we
  	 * signal not to send ACK even if it was requested.
  	 */
  	return -EINTR;

  }

  EXPORT_SYMBOL(netlink_dump_start);

  
  void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
  {
  	struct sk_buff *skb;
  	struct nlmsghdr *rep;
  	struct nlmsgerr *errmsg;

  	size_t payload = sizeof(*errmsg);

  	/* error messages get the original request appened */
  	if (err)
  		payload += nlmsg_len(nlh);

  	skb = nlmsg_new(payload, GFP_KERNEL);

  	if (!skb) {
  		struct sock *sk;

  		sk = netlink_lookup(sock_net(in_skb->sk),

  				    in_skb->sk->sk_protocol,

  				    NETLINK_CB(in_skb).pid);
  		if (sk) {
  			sk->sk_err = ENOBUFS;
  			sk->sk_error_report(sk);
  			sock_put(sk);
  		}
  		return;
  	}
  
  	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,

  			  NLMSG_ERROR, payload, 0);

  	errmsg = nlmsg_data(rep);

  	errmsg->error = err;

  	memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(*nlh));

  	netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).pid, MSG_DONTWAIT);
  }

  EXPORT_SYMBOL(netlink_ack);

  int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,

  						     struct nlmsghdr *))

  {

  	struct nlmsghdr *nlh;
  	int err;
  
  	while (skb->len >= nlmsg_total_size(0)) {

  		int msglen;

  		nlh = nlmsg_hdr(skb);

  		err = 0;

  		if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)

  			return 0;

  		/* Only requests are handled by the kernel */
  		if (!(nlh->nlmsg_flags & NLM_F_REQUEST))

  			goto ack;

  
  		/* Skip control messages */
  		if (nlh->nlmsg_type < NLMSG_MIN_TYPE)

  			goto ack;

  		err = cb(skb, nlh);

  		if (err == -EINTR)
  			goto skip;
  
  ack:

  		if (nlh->nlmsg_flags & NLM_F_ACK || err)

  			netlink_ack(skb, nlh, err);

  skip:

  		msglen = NLMSG_ALIGN(nlh->nlmsg_len);

  		if (msglen > skb->len)
  			msglen = skb->len;
  		skb_pull(skb, msglen);

  	}
  
  	return 0;
  }

  EXPORT_SYMBOL(netlink_rcv_skb);

  
  /**

   * nlmsg_notify - send a notification netlink message
   * @sk: netlink socket to use
   * @skb: notification message
   * @pid: destination netlink pid for reports or 0
   * @group: destination multicast group or 0
   * @report: 1 to report back, 0 to disable
   * @flags: allocation flags
   */
  int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 pid,
  		 unsigned int group, int report, gfp_t flags)
  {
  	int err = 0;
  
  	if (group) {
  		int exclude_pid = 0;
  
  		if (report) {
  			atomic_inc(&skb->users);
  			exclude_pid = pid;
  		}

  		/* errors reported via destination sk->sk_err, but propagate
  		 * delivery errors if NETLINK_BROADCAST_ERROR flag is set */
  		err = nlmsg_multicast(sk, skb, exclude_pid, group, flags);

  	}

  	if (report) {
  		int err2;
  
  		err2 = nlmsg_unicast(sk, skb, pid);
  		if (!err || err == -ESRCH)
  			err = err2;
  	}

  
  	return err;
  }

  EXPORT_SYMBOL(nlmsg_notify);

  #ifdef CONFIG_PROC_FS
  struct nl_seq_iter {

  	struct seq_net_private p;

  	int link;
  	int hash_idx;
  };
  
  static struct sock *netlink_seq_socket_idx(struct seq_file *seq, loff_t pos)
  {
  	struct nl_seq_iter *iter = seq->private;
  	int i, j;
  	struct sock *s;
  	struct hlist_node *node;
  	loff_t off = 0;

  	for (i = 0; i < MAX_LINKS; i++) {