af_netlink.c 31 KB
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/*
 * NETLINK      Kernel-user communication protocol.
 *
 * 		Authors:	Alan Cox <alan@redhat.com>
 * 				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)
 *
 */

#include <linux/config.h>
#include <linux/module.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/smp_lock.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>
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#include <linux/audit.h>

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

#define Nprintk(a...)

struct netlink_sock {
	/* struct sock has to be the first member of netlink_sock */
	struct sock		sk;
	u32			pid;
	unsigned int		groups;
	u32			dst_pid;
	unsigned int		dst_groups;
	unsigned long		state;
	wait_queue_head_t	wait;
	struct netlink_callback	*cb;
	spinlock_t		cb_lock;
	void			(*data_ready)(struct sock *sk, int bytes);
};

static inline struct netlink_sock *nlk_sk(struct sock *sk)
{
	return (struct netlink_sock *)sk;
}

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;
	unsigned int nl_nonroot;
};

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 struct notifier_block *netlink_chain;

static 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)
{
	skb_queue_purge(&sk->sk_receive_queue);

	if (!sock_flag(sk, SOCK_DEAD)) {
		printk("Freeing alive netlink socket %p\n", sk);
		return;
	}
	BUG_TRAP(!atomic_read(&sk->sk_rmem_alloc));
	BUG_TRAP(!atomic_read(&sk->sk_wmem_alloc));
	BUG_TRAP(!nlk_sk(sk)->cb);
}

/* 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.
 */

static void netlink_table_grab(void)
{
	write_lock_bh(&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_bh(&nl_table_lock);
			schedule();
			write_lock_bh(&nl_table_lock);
		}

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

static __inline__ void netlink_table_ungrab(void)
{
	write_unlock_bh(&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 __inline__ struct sock *netlink_lookup(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 (nlk_sk(sk)->pid == pid) {
			sock_hold(sk);
			goto found;
		}
	}
	sk = NULL;
found:
	read_unlock(&nl_table_lock);
	return sk;
}

static inline struct hlist_head *nl_pid_hash_alloc(size_t size)
{
	if (size <= PAGE_SIZE)
		return kmalloc(size, GFP_ATOMIC);
	else
		return (struct hlist_head *)
			__get_free_pages(GFP_ATOMIC, get_order(size));
}

static inline 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_alloc(size);
	if (!table)
		return 0;

	memset(table, 0, size);
	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 struct proto_ops netlink_ops;

static int netlink_insert(struct sock *sk, 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 (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();
	nl_table[sk->sk_protocol].hash.entries--;
	sk_del_node_init(sk);
	if (nlk_sk(sk)->groups)
		__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 socket *sock, int protocol)
{
	struct sock *sk;
	struct netlink_sock *nlk;

	sock->state = SS_UNCONNECTED;

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

	if (protocol<0 || protocol >= MAX_LINKS)
		return -EPROTONOSUPPORT;

	sock->ops = &netlink_ops;

	sk = sk_alloc(PF_NETLINK, GFP_KERNEL, &netlink_proto, 1);
	if (!sk)
		return -ENOMEM;

	sock_init_data(sock, sk);

	nlk = nlk_sk(sk);

	spin_lock_init(&nlk->cb_lock);
	init_waitqueue_head(&nlk->wait);
	sk->sk_destruct = netlink_sock_destruct;

	sk->sk_protocol = protocol;
	return 0;
}

static int netlink_release(struct socket *sock)
{
	struct sock *sk = sock->sk;
	struct netlink_sock *nlk;

	if (!sk)
		return 0;

	netlink_remove(sk);
	nlk = nlk_sk(sk);

	spin_lock(&nlk->cb_lock);
	if (nlk->cb) {
		nlk->cb->done(nlk->cb);
		netlink_destroy_callback(nlk->cb);
		nlk->cb = NULL;
	}
	spin_unlock(&nlk->cb_lock);

	/* OK. Socket is unlinked, and, therefore,
	   no new packets will arrive */

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

	skb_queue_purge(&sk->sk_write_queue);

	if (nlk->pid && !nlk->groups) {
		struct netlink_notify n = {
						.protocol = sk->sk_protocol,
						.pid = nlk->pid,
					  };
		notifier_call_chain(&netlink_chain, NETLINK_URELEASE, &n);
	}	
	
	sock_put(sk);
	return 0;
}

static int netlink_autobind(struct socket *sock)
{
	struct sock *sk = sock->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 = current->pid;
	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 (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, pid);
	if (err == -EADDRINUSE)
		goto retry;
	return 0;
}

static inline int netlink_capable(struct socket *sock, unsigned int flag) 
{ 
	return (nl_table[sock->sk->sk_protocol].nl_nonroot & flag) ||
	       capable(CAP_NET_ADMIN);
} 

static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
{
	struct sock *sk = sock->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 && !netlink_capable(sock, NL_NONROOT_RECV))
		return -EPERM;

	if (nlk->pid) {
		if (nladdr->nl_pid != nlk->pid)
			return -EINVAL;
	} else {
		err = nladdr->nl_pid ?
			netlink_insert(sk, nladdr->nl_pid) :
			netlink_autobind(sock);
		if (err)
			return err;
	}

	if (!nladdr->nl_groups && !nlk->groups)
		return 0;

	netlink_table_grab();
	if (nlk->groups && !nladdr->nl_groups)
		__sk_del_bind_node(sk);
	else if (!nlk->groups && nladdr->nl_groups)
		sk_add_bind_node(sk, &nl_table[sk->sk_protocol].mc_list);
	nlk->groups = nladdr->nl_groups;
	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 (addr->sa_family == AF_UNSPEC) {
		sk->sk_state	= NETLINK_UNCONNECTED;
		nlk->dst_pid	= 0;
		nlk->dst_groups = 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_groups = 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);
	struct sockaddr_nl *nladdr=(struct sockaddr_nl *)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 = nlk->dst_groups;
	} else {
		nladdr->nl_pid = nlk->pid;
		nladdr->nl_groups = nlk->groups;
	}
	return 0;
}

static void netlink_overrun(struct sock *sk)
{
	if (!test_and_set_bit(0, &nlk_sk(sk)->state)) {
		sk->sk_err = ENOBUFS;
		sk->sk_error_report(sk);
	}
}

static struct sock *netlink_getsockbypid(struct sock *ssk, u32 pid)
{
	int protocol = ssk->sk_protocol;
	struct sock *sock;
	struct netlink_sock *nlk;

	sock = netlink_lookup(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 ((nlk->pid == 0 && !nlk->data_ready) ||
	    (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_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, int nonblock, long timeo)
{
	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 (!nlk->pid)
				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 protocol)
{
	struct netlink_sock *nlk;
	int len = skb->len;

	nlk = nlk_sk(sk);

	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 inline struct sk_buff *netlink_trim(struct sk_buff *skb, int 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;
}

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);
	}
	err = netlink_attachskb(sk, skb, nonblock, timeo);
	if (err == 1)
		goto retry;
	if (err)
		return err;

	return netlink_sendskb(sk, skb, ssk->sk_protocol);
}

static __inline__ 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;
	}
	return -1;
}

struct netlink_broadcast_data {
	struct sock *exclude_sk;
	u32 pid;
	u32 group;
	int failure;
	int congested;
	int delivered;
	int allocation;
	struct sk_buff *skb, *skb2;
};

static inline 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 || !(nlk->groups & p->group))
		goto out;

	if (p->failure) {
		netlink_overrun(sk);
		goto out;
	}

	sock_hold(sk);
	if (p->skb2 == NULL) {
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		if (skb_shared(p->skb)) {
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			p->skb2 = skb_clone(p->skb, p->allocation);
		} else {
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			p->skb2 = skb_get(p->skb);
			/*
			 * skb ownership may have been set when
			 * delivered to a previous socket.
			 */
			skb_orphan(p->skb2);
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		}
	}
	if (p->skb2 == NULL) {
		netlink_overrun(sk);
		/* Clone failed. Notify ALL listeners. */
		p->failure = 1;
	} else if ((val = netlink_broadcast_deliver(sk, p->skb2)) < 0) {
		netlink_overrun(sk);
	} else {
		p->congested |= val;
		p->delivered = 1;
		p->skb2 = NULL;
	}
	sock_put(sk);

out:
	return 0;
}

int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 pid,
		      u32 group, int allocation)
{
	struct netlink_broadcast_data info;
	struct hlist_node *node;
	struct sock *sk;

	skb = netlink_trim(skb, allocation);

	info.exclude_sk = ssk;
	info.pid = pid;
	info.group = group;
	info.failure = 0;
	info.congested = 0;
	info.delivered = 0;
	info.allocation = allocation;
	info.skb = skb;
	info.skb2 = NULL;

	/* 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);

	netlink_unlock_table();

	if (info.skb2)
		kfree_skb(info.skb2);
	kfree_skb(skb);

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

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

static inline int do_one_set_err(struct sock *sk,
				 struct netlink_set_err_data *p)
{
	struct netlink_sock *nlk = nlk_sk(sk);

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

	if (nlk->pid == p->pid || !(nlk->groups & p->group))
		goto out;

	sk->sk_err = p->code;
	sk->sk_error_report(sk);
out:
	return 0;
}

void 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;

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

	read_lock(&nl_table_lock);

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

	read_unlock(&nl_table_lock);
}

static inline void netlink_rcv_wake(struct sock *sk)
{
	struct netlink_sock *nlk = nlk_sk(sk);

	if (!skb_queue_len(&sk->sk_receive_queue))
		clear_bit(0, &nlk->state);
	if (!test_bit(0, &nlk->state))
		wake_up_interruptible(&nlk->wait);
}

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_groups;
	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) {
		if (addr->nl_family != AF_NETLINK)
			return -EINVAL;
		dst_pid = addr->nl_pid;
		dst_groups = addr->nl_groups;
		if (dst_groups && !netlink_capable(sock, NL_NONROOT_SEND))
			return -EPERM;
	} else {
		dst_pid = nlk->dst_pid;
		dst_groups = nlk->dst_groups;
	}

	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).groups	= nlk->groups;
	NETLINK_CB(skb).dst_pid = dst_pid;
	NETLINK_CB(skb).dst_groups = dst_groups;
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	NETLINK_CB(skb).loginuid = audit_get_loginuid(current->audit_context);
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	memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));

	/* What can I do? Netlink is asynchronous, so that
	   we will have to save current capabilities to
	   check them, when this message will be delivered
	   to corresponding kernel module.   --ANK (980802)
	 */

	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_groups) {
		atomic_inc(&skb->users);
		netlink_broadcast(sk, skb, dst_pid, dst_groups, GFP_KERNEL);
	}
	err = netlink_unicast(sk, skb, dst_pid, msg->msg_flags&MSG_DONTWAIT);

out:
	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;
	int err;

	if (flags&MSG_OOB)
		return -EOPNOTSUPP;

	copied = 0;

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

	msg->msg_namelen = 0;

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

	skb->h.raw = skb->data;
	err = skb_copy_datagram_iovec(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_CB(skb).dst_groups;
		msg->msg_namelen = sizeof(*addr);
	}

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

	if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2)
		netlink_dump(sk);

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

out:
	netlink_rcv_wake(sk);
	return err ? : copied;
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