text: /*
   * 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.
   * 
   */
  
  #include <linux/config.h>
  #include <linux/module.h>
  
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/major.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/malloc.h>
  #include <asm/uaccess.h>
  #include <linux/skbuff.h>
  #include <linux/netdevice.h>
  #include <linux/netlink.h>
  #include <linux/proc_fs.h>
  #include <linux/smp_lock.h>
  #include <net/sock.h>
  #include <net/scm.h>
  
  #define Nprintk(a...)
  
  #if defined(CONFIG_NETLINK_DEV) || defined(CONFIG_NETLINK_DEV_MODULE)
  #define NL_EMULATE_DEV
  #endif
  
  #define BUG_TRAP(x) if (!(x)) { printk("Assertion (" #x ") failed at " __FILE__ "(%d):" __FUNCTION__ "\n", __LINE__); }
  
  struct netlink_opt
  {
  	u32			pid;
  	unsigned		groups;
  	u32			dst_pid;
  	unsigned		dst_groups;
  	unsigned long		state;
  	int			(*handler)(int unit, struct sk_buff *skb);
  	wait_queue_head_t	wait;
  	struct netlink_callback	*cb;
  	spinlock_t		cb_lock;
  	void			(*data_ready)(struct sock *sk, int bytes);
  };
  
  static struct sock *nl_table[MAX_LINKS];
  static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);
  
  #ifdef NL_EMULATE_DEV
  static struct socket *netlink_kernel[MAX_LINKS];
  #endif
  
  static int netlink_dump(struct sock *sk);
  static void netlink_destroy_callback(struct netlink_callback *cb);
  
  atomic_t netlink_sock_nr;
  
  static rwlock_t nl_table_lock = RW_LOCK_UNLOCKED;
  static atomic_t nl_table_users = ATOMIC_INIT(0);
  
  static void netlink_sock_destruct(struct sock *sk)
  {
  	skb_queue_purge(&sk->receive_queue);
  
  	if (!sk->dead) {
  		printk("Freeing alive netlink socket %p\n", sk);
  		return;
  	}
  	BUG_TRAP(atomic_read(&sk->rmem_alloc)==0);
  	BUG_TRAP(atomic_read(&sk->wmem_alloc)==0);
  	BUG_TRAP(sk->protinfo.af_netlink->cb==NULL);
  
  	kfree(sk->protinfo.af_netlink);
  
  	atomic_dec(&netlink_sock_nr);
  #ifdef NETLINK_REFCNT_DEBUG
  	printk(KERN_DEBUG "NETLINK %p released, %d are still alive\n", sk, atomic_read(&netlink_sock_nr));
  #endif
  }
  
  /* 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 sock *sk;
  
  	read_lock(&nl_table_lock);
  	for (sk=nl_table[protocol]; sk; sk=sk->next) {
  		if (sk->protinfo.af_netlink->pid == pid) {
  			sock_hold(sk);
  			read_unlock(&nl_table_lock);
  			return sk;
  		}
  	}
  
  	read_unlock(&nl_table_lock);
  	return NULL;
  }
  
  extern struct proto_ops netlink_ops;
  
  static int netlink_insert(struct sock *sk, u32 pid)
  {
  	int err = -EADDRINUSE;
  	struct sock *osk;
  
  	netlink_table_grab();
  	for (osk=nl_table[sk->protocol]; osk; osk=osk->next) {
  		if (osk->protinfo.af_netlink->pid == pid)
  			break;
  	}
  	if (osk == NULL) {
  		err = -EBUSY;
  		if (sk->protinfo.af_netlink->pid == 0) {
  			sk->protinfo.af_netlink->pid = pid;
  			sk->next = nl_table[sk->protocol];
  			nl_table[sk->protocol] = sk;
  			sock_hold(sk);
  			err = 0;
  		}
  	}
  	netlink_table_ungrab();
  	return err;
  }
  
  static void netlink_remove(struct sock *sk)
  {
  	struct sock **skp;
  
  	netlink_table_grab();
  	for (skp = &nl_table[sk->protocol]; *skp; skp = &((*skp)->next)) {
  		if (*skp == sk) {
  			*skp = sk->next;
  			__sock_put(sk);
  			break;
  		}
  	}
  	netlink_table_ungrab();
  }
  
  static int netlink_create(struct socket *sock, int protocol)
  {
  	struct sock *sk;
  
  	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, 1);
  	if (!sk)
  		return -ENOMEM;
  
  	sock_init_data(sock,sk);
  
  	sk->protinfo.af_netlink = kmalloc(sizeof(struct netlink_opt), GFP_KERNEL);
  	if (sk->protinfo.af_netlink == NULL) {
  		sk_free(sk);
  		return -ENOMEM;
  	}
  	memset(sk->protinfo.af_netlink, 0, sizeof(struct netlink_opt));
  
  	spin_lock_init(&sk->protinfo.af_netlink->cb_lock);
  	init_waitqueue_head(&sk->protinfo.af_netlink->wait);
  	sk->destruct = netlink_sock_destruct;
  	atomic_inc(&netlink_sock_nr);
  
  	sk->protocol=protocol;
  	return 0;
  }
  
  static int netlink_release(struct socket *sock)
  {
  	struct sock *sk = sock->sk;
  
  	if (!sk)
  		return 0;
  
  	netlink_remove(sk);
  
  	spin_lock(&sk->protinfo.af_netlink->cb_lock);
  	if (sk->protinfo.af_netlink->cb) {
  		sk->protinfo.af_netlink->cb->done(sk->protinfo.af_netlink->cb);
  		netlink_destroy_callback(sk->protinfo.af_netlink->cb);
  		sk->protinfo.af_netlink->cb = NULL;
  		__sock_put(sk);
  	}
  	spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  
  	/* OK. Socket is unlinked, and, therefore,
  	   no new packets will arrive */
  
  	sock_orphan(sk);
  	sock->sk = NULL;
  	wake_up_interruptible_all(&sk->protinfo.af_netlink->wait);
  
  	skb_queue_purge(&sk->write_queue);
  
  	sock_put(sk);
  	return 0;
  }
  
  static int netlink_autobind(struct socket *sock)
  {
  	struct sock *sk = sock->sk;
  	struct sock *osk;
  	s32 pid = current->pid;
  	int err;
  
  retry:
  	netlink_table_grab();
  	for (osk=nl_table[sk->protocol]; osk; osk=osk->next) {
  		if (osk->protinfo.af_netlink->pid == pid) {
  			/* Bind collision, search negative pid values. */
  			if (pid > 0)
  				pid = -4096;
  			pid--;
  			netlink_table_ungrab();
  			goto retry;
  		}
  	}
  	netlink_table_ungrab();
  
  	err = netlink_insert(sk, pid);
  	if (err == -EADDRINUSE)
  		goto retry;
  	sk->protinfo.af_netlink->groups = 0;
  	return 0;
  }
  
  static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
  {
  	struct sock *sk = sock->sk;
  	int err;
  	struct sockaddr_nl *nladdr=(struct sockaddr_nl *)addr;
  	
  	if (nladdr->nl_family != AF_NETLINK)
  		return -EINVAL;
  
  	/* Only superuser is allowed to listen multicasts */
  	if (nladdr->nl_groups && !capable(CAP_NET_ADMIN))
  		return -EPERM;
  
  	if (sk->protinfo.af_netlink->pid) {
  		if (nladdr->nl_pid != sk->protinfo.af_netlink->pid)
  			return -EINVAL;
  		sk->protinfo.af_netlink->groups = nladdr->nl_groups;
  		return 0;
  	}
  
  	if (nladdr->nl_pid == 0) {
  		err = netlink_autobind(sock);
  		if (err == 0)
  			sk->protinfo.af_netlink->groups = nladdr->nl_groups;
  		return err;
  	}
  
  	err = netlink_insert(sk, nladdr->nl_pid);
  	if (err == 0)
  		sk->protinfo.af_netlink->groups = nladdr->nl_groups;
  	return err;
  }
  
  static int netlink_connect(struct socket *sock, struct sockaddr *addr,
  			   int alen, int flags)
  {
  	int err = 0;
  	struct sock *sk = sock->sk;
  	struct sockaddr_nl *nladdr=(struct sockaddr_nl*)addr;
  
  	if (addr->sa_family == AF_UNSPEC) {
  		sk->protinfo.af_netlink->dst_pid = 0;
  		sk->protinfo.af_netlink->dst_groups = 0;
  		return 0;
  	}
  	if (addr->sa_family != AF_NETLINK)
  		return -EINVAL;
  
  	/* Only superuser is allowed to send multicasts */
  	if (nladdr->nl_groups && !capable(CAP_NET_ADMIN))
  		return -EPERM;
  
  	if (!sk->protinfo.af_netlink->pid)
  		err = netlink_autobind(sock);
  
  	if (err == 0) {
  		sk->protinfo.af_netlink->dst_pid = nladdr->nl_pid;
  		sk->protinfo.af_netlink->dst_groups = nladdr->nl_groups;
  	}
  
  	return 0;
  }
  
  static int netlink_getname(struct socket *sock, struct sockaddr *addr, int *addr_len, int peer)
  {
  	struct sock *sk = sock->sk;
  	struct sockaddr_nl *nladdr=(struct sockaddr_nl *)addr;
  	
  	nladdr->nl_family = AF_NETLINK;
  	*addr_len = sizeof(*nladdr);
  
  	if (peer) {
  		nladdr->nl_pid = sk->protinfo.af_netlink->dst_pid;
  		nladdr->nl_groups = sk->protinfo.af_netlink->dst_groups;
  	} else {
  		nladdr->nl_pid = sk->protinfo.af_netlink->pid;
  		nladdr->nl_groups = sk->protinfo.af_netlink->groups;
  	}
  	return 0;
  }
  
  static void netlink_overrun(struct sock *sk)
  {
  	if (!test_and_set_bit(0, &sk->protinfo.af_netlink->state)) {
  		sk->err = ENOBUFS;
  		sk->error_report(sk);
  	}
  }
  
  int netlink_unicast(struct sock *ssk, struct sk_buff *skb, u32 pid, int nonblock)
  {
  	struct sock *sk;
  	int len = skb->len;
  	int protocol = ssk->protocol;
  	long timeo;
          DECLARE_WAITQUEUE(wait, current);
  
  	timeo = sock_sndtimeo(ssk, nonblock);
  
  retry:
  	sk = netlink_lookup(protocol, pid);
  	if (sk == NULL)
  		goto no_dst;
  
  #ifdef NL_EMULATE_DEV
  	if (sk->protinfo.af_netlink->handler) {
  		skb_orphan(skb);
  		len = sk->protinfo.af_netlink->handler(protocol, skb);
  		sock_put(sk);
  		return len;
  	}
  #endif
  
  	if (atomic_read(&sk->rmem_alloc) > sk->rcvbuf ||
  	    test_bit(0, &sk->protinfo.af_netlink->state)) {
  		if (!timeo) {
  			if (ssk->protinfo.af_netlink->pid == 0)
  				netlink_overrun(sk);
  			sock_put(sk);
  			kfree_skb(skb);
  			return -EAGAIN;
  		}
  
  		__set_current_state(TASK_INTERRUPTIBLE);
  		add_wait_queue(&sk->protinfo.af_netlink->wait, &wait);
  
  		if ((atomic_read(&sk->rmem_alloc) > sk->rcvbuf ||
  		    test_bit(0, &sk->protinfo.af_netlink->state)) &&
  		    !sk->dead)
  			timeo = schedule_timeout(timeo);
  
  		__set_current_state(TASK_RUNNING);
  		remove_wait_queue(&sk->protinfo.af_netlink->wait, &wait);
  		sock_put(sk);
  
  		if (signal_pending(current)) {
  			kfree_skb(skb);
  			return sock_intr_errno(timeo);
  		}
  		goto retry;
  	}
  
  	skb_orphan(skb);
  	skb_set_owner_r(skb, sk);
  	skb_queue_tail(&sk->receive_queue, skb);
  	sk->data_ready(sk, len);
  	sock_put(sk);
  	return len;
  
  no_dst:
  	kfree_skb(skb);
  	return -ECONNREFUSED;
  }
  
  static __inline__ int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
  {
  #ifdef NL_EMULATE_DEV
  	if (sk->protinfo.af_netlink->handler) {
  		skb_orphan(skb);
  		sk->protinfo.af_netlink->handler(sk->protocol, skb);
  		return 0;
  	} else
  #endif
  	if (atomic_read(&sk->rmem_alloc) <= sk->rcvbuf &&
  	    !test_bit(0, &sk->protinfo.af_netlink->state)) {
                  skb_orphan(skb);
  		skb_set_owner_r(skb, sk);
  		skb_queue_tail(&sk->receive_queue, skb);
  		sk->data_ready(sk, skb->len);
  		return 0;
  	}
  	return -1;
  }
  
  void netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 pid,
  		       u32 group, int allocation)
  {
  	struct sock *sk;
  	struct sk_buff *skb2 = NULL;
  	int protocol = ssk->protocol;
  	int failure = 0;
  
  	/* While we sleep in clone, do not allow to change socket list */
  
  	netlink_lock_table();
  
  	for (sk = nl_table[protocol]; sk; sk = sk->next) {
  		if (ssk == sk)
  			continue;
  
  		if (sk->protinfo.af_netlink->pid == pid ||
  		    !(sk->protinfo.af_netlink->groups&group))
  			continue;
  
  		if (failure) {
  			netlink_overrun(sk);
  			continue;
  		}
  
  		sock_hold(sk);
  		if (skb2 == NULL) {
  			if (atomic_read(&skb->users) != 1) {
  				skb2 = skb_clone(skb, allocation);
  			} else {
  				skb2 = skb;
  				atomic_inc(&skb->users);
  			}
  		}
  		if (skb2 == NULL) {
  			netlink_overrun(sk);
  			/* Clone failed. Notify ALL listeners. */
  			failure = 1;
  		} else if (netlink_broadcast_deliver(sk, skb2)) {
  			netlink_overrun(sk);
  		} else
  			skb2 = NULL;
  		sock_put(sk);
  	}
  
  	netlink_unlock_table();
  
  	if (skb2)
  		kfree_skb(skb2);
  	kfree_skb(skb);
  }
  
  void netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
  {
  	struct sock *sk;
  	int protocol = ssk->protocol;
  
  	read_lock(&nl_table_lock);
  	for (sk = nl_table[protocol]; sk; sk = sk->next) {
  		if (ssk == sk)
  			continue;
  
  		if (sk->protinfo.af_netlink->pid == pid ||
  		    !(sk->protinfo.af_netlink->groups&group))
  			continue;
  
  		sk->err = code;
  		sk->error_report(sk);
  	}
  	read_unlock(&nl_table_lock);
  }
  
  static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, int len,
  			   struct scm_cookie *scm)
  {
  	struct sock *sk = sock->sk;
  	struct sockaddr_nl *addr=msg->msg_name;
  	u32 dst_pid;
  	u32 dst_groups;
  	struct sk_buff *skb;
  	int err;
  
  	if (msg->msg_flags&MSG_OOB)
  		return -EOPNOTSUPP;
  
  	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 && !capable(CAP_NET_ADMIN))
  			return -EPERM;
  	} else {
  		dst_pid = sk->protinfo.af_netlink->dst_pid;
  		dst_groups = sk->protinfo.af_netlink->dst_groups;
  	}
  
  	if (!sk->protinfo.af_netlink->pid) {
  		err = netlink_autobind(sock);
  		if (err)
  			goto out;
  	}
  
  	err = -EMSGSIZE;
  	if ((unsigned)len > sk->sndbuf-32)
  		goto out;
  	err = -ENOBUFS;
  	skb = alloc_skb(len, GFP_KERNEL);
  	if (skb==NULL)
  		goto out;
  
  	NETLINK_CB(skb).pid = sk->protinfo.af_netlink->pid;
  	NETLINK_CB(skb).groups = sk->protinfo.af_netlink->groups;
  	NETLINK_CB(skb).dst_pid = dst_pid;
  	NETLINK_CB(skb).dst_groups = dst_groups;
  	memcpy(NETLINK_CREDS(skb), &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)
  	 */
  	NETLINK_CB(skb).eff_cap = current->cap_effective;
  
  	err = -EFAULT;
  	if (memcpy_fromiovec(skb_put(skb,len), msg->msg_iov, len)) {
  		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 socket *sock, struct msghdr *msg, int len,
  			   int flags, struct scm_cookie *scm)
  {
  	struct sock *sk = sock->sk;
  	int noblock = flags&MSG_DONTWAIT;
  	int 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_pid	= NETLINK_CB(skb).pid;
  		addr->nl_groups	= NETLINK_CB(skb).dst_groups;
  		msg->msg_namelen = sizeof(*addr);
  	}
  
  	scm->creds = *NETLINK_CREDS(skb);
  	skb_free_datagram(sk, skb);
  
  	if (sk->protinfo.af_netlink->cb
  	    && atomic_read(&sk->rmem_alloc) <= sk->rcvbuf/2)
  		netlink_dump(sk);
  
  out:
  	if (skb_queue_len(&sk->receive_queue) <= sk->rcvbuf/2) {
  		if (skb_queue_len(&sk->receive_queue) == 0)
  			clear_bit(0, &sk->protinfo.af_netlink->state);
  		if (!test_bit(0, &sk->protinfo.af_netlink->state))
  			wake_up_interruptible(&sk->protinfo.af_netlink->wait);
  	}
  	return err ? : copied;
  }
  
  void netlink_data_ready(struct sock *sk, int len)
  {
  	if (sk->protinfo.af_netlink->data_ready)
  		sk->protinfo.af_netlink->data_ready(sk, len);
  
  	if (skb_queue_len(&sk->receive_queue) <= sk->rcvbuf/2) {
  		if (skb_queue_len(&sk->receive_queue) == 0)
  			clear_bit(0, &sk->protinfo.af_netlink->state);
  		if (!test_bit(0, &sk->protinfo.af_netlink->state))
  			wake_up_interruptible(&sk->protinfo.af_netlink->wait);
  	}
  }
  
  /*
   *	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(int unit, void (*input)(struct sock *sk, int len))
  {
  	struct socket *sock;
  	struct sock *sk;
  
  	if (unit<0 || unit>=MAX_LINKS)
  		return NULL;
  
  	if (!(sock = sock_alloc())) 
  		return NULL;
  
  	sock->type = SOCK_RAW;
  
  	if (netlink_create(sock, unit) < 0) {
  		sock_release(sock);
  		return NULL;
  	}
  	sk = sock->sk;
  	sk->data_ready = netlink_data_ready;
  	if (input)
  		sk->protinfo.af_netlink->data_ready = input;
  
  	netlink_insert(sk, 0);
  	return sk;
  }
  
  static void netlink_destroy_callback(struct netlink_callback *cb)
  {
  	if (cb->skb)
  		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_callback *cb;
  	struct sk_buff *skb;
  	struct nlmsghdr *nlh;
  	int len;
  	
  	skb = sock_rmalloc(sk, NLMSG_GOODSIZE, 0, GFP_KERNEL);
  	if (!skb)
  		return -ENOBUFS;
  
  	spin_lock(&sk->protinfo.af_netlink->cb_lock);
  
  	cb = sk->protinfo.af_netlink->cb;
  	if (cb == NULL) {
  		spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  		kfree_skb(skb);
  		return -EINVAL;
  	}
  
  	len = cb->dump(skb, cb);
  
  	if (len > 0) {
  		spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  		skb_queue_tail(&sk->receive_queue, skb);
  		sk->data_ready(sk, len);
  		return 0;
  	}
  
  	nlh = __nlmsg_put(skb, NETLINK_CB(cb->skb).pid, cb->nlh->nlmsg_seq, NLMSG_DONE, sizeof(int));
  	nlh->nlmsg_flags |= NLM_F_MULTI;
  	memcpy(NLMSG_DATA(nlh), &len, sizeof(len));
  	skb_queue_tail(&sk->receive_queue, skb);
  	sk->data_ready(sk, skb->len);
  
  	cb->done(cb);
  	sk->protinfo.af_netlink->cb = NULL;
  	spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  
  	netlink_destroy_callback(cb);
  	sock_put(sk);
  	return 0;
  }
  
  int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
  		       struct nlmsghdr *nlh,
  		       int (*dump)(struct sk_buff *skb, struct netlink_callback*),
  		       int (*done)(struct netlink_callback*))
  {
  	struct netlink_callback *cb;
  	struct sock *sk;
  
  	cb = kmalloc(sizeof(*cb), GFP_KERNEL);
  	if (cb == NULL)
  		return -ENOBUFS;
  
  	memset(cb, 0, sizeof(*cb));
  	cb->dump = dump;
  	cb->done = done;
  	cb->nlh = nlh;
  	atomic_inc(&skb->users);
  	cb->skb = skb;
  
  	sk = netlink_lookup(ssk->protocol, NETLINK_CB(skb).pid);
  	if (sk == NULL) {
  		netlink_destroy_callback(cb);
  		return -ECONNREFUSED;
  	}
  	/* A dump is in progress... */
  	spin_lock(&sk->protinfo.af_netlink->cb_lock);
  	if (sk->protinfo.af_netlink->cb) {
  		spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  		netlink_destroy_callback(cb);
  		sock_put(sk);
  		return -EBUSY;
  	}
  	sk->protinfo.af_netlink->cb = cb;
  	spin_unlock(&sk->protinfo.af_netlink->cb_lock);
  
  	netlink_dump(sk);
  	return 0;
  }
  
  void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
  {
  	struct sk_buff *skb;
  	struct nlmsghdr *rep;
  	struct nlmsgerr *errmsg;
  	int size;
  
  	if (err == 0)
  		size = NLMSG_SPACE(sizeof(struct nlmsgerr));
  	else
  		size = NLMSG_SPACE(4 + NLMSG_ALIGN(nlh->nlmsg_len));
  
  	skb = alloc_skb(size, GFP_KERNEL);
  	if (!skb)
  		return;
  
  	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,
  			  NLMSG_ERROR, sizeof(struct nlmsgerr));
  	errmsg = NLMSG_DATA(rep);
  	errmsg->error = err;
  	memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(struct nlmsghdr));
  	netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).pid, MSG_DONTWAIT);
  }
  
  
  #ifdef NL_EMULATE_DEV
  
  static rwlock_t nl_emu_lock = RW_LOCK_UNLOCKED;
  
  /*
   *	Backward compatibility.
   */	
   
  int netlink_attach(int unit, int (*function)(int, struct sk_buff *skb))
  {
  	struct sock *sk = netlink_kernel_create(unit, NULL);
  	if (sk == NULL)
  		return -ENOBUFS;
  	sk->protinfo.af_netlink->handler = function;
  	write_lock_bh(&nl_emu_lock);
  	netlink_kernel[unit] = sk->socket;
  	write_unlock_bh(&nl_emu_lock);
  	return 0;
  }
  
  void netlink_detach(int unit)
  {
  	struct socket *sock;
  
  	write_lock_bh(&nl_emu_lock);
  	sock = netlink_kernel[unit];
  	netlink_kernel[unit] = NULL;
  	write_unlock_bh(&nl_emu_lock);
  
  	sock_release(sock);
  }
  
  int netlink_post(int unit, struct sk_buff *skb)
  {
  	struct socket *sock;
  
  	read_lock(&nl_emu_lock);
  	sock = netlink_kernel[unit];
  	if (sock) {
  		struct sock *sk = sock->sk;
  		memset(skb->cb, 0, sizeof(skb->cb));
  		sock_hold(sk);
  		read_unlock(&nl_emu_lock);
  
  		netlink_broadcast(sk, skb, 0, ~0, GFP_ATOMIC);
  
  		sock_put(sk);
  		return 0;
  	}
  	read_unlock(&nl_emu_lock);
  	return -EUNATCH;
  }
  
  #endif
  
  
  #ifdef CONFIG_PROC_FS
  static int netlink_read_proc(char *buffer, char **start, off_t offset,
  			     int length, int *eof, void *data)
  {
  	off_t pos=0;
  	off_t begin=0;
  	int len=0;
  	int i;
  	struct sock *s;
  	
  	len+= sprintf(buffer,"sk       Eth Pid    Groups   "
  		      "Rmem     Wmem     Dump     Locks\n");
  	
  	for (i=0; i<MAX_LINKS; i++) {
  		read_lock(&nl_table_lock);
  		for (s = nl_table[i]; s; s = s->next) {
  			len+=sprintf(buffer+len,"%p %-3d %-6d %08x %-8d %-8d %p %d",
  				     s,
  				     s->protocol,
  				     s->protinfo.af_netlink->pid,
  				     s->protinfo.af_netlink->groups,
  				     atomic_read(&s->rmem_alloc),
  				     atomic_read(&s->wmem_alloc),
  				     s->protinfo.af_netlink->cb,
  				     atomic_read(&s->refcnt)
  				     );
  
  			buffer[len++]='\n';
  		
  			pos=begin+len;
  			if(pos<offset) {
  				len=0;
  				begin=pos;
  			}
  			if(pos>offset+length) {
  				read_unlock(&nl_table_lock);
  				goto done;
  			}
  		}
  		read_unlock(&nl_table_lock);
  	}
  	*eof = 1;
  
  done:
  	*start=buffer+(offset-begin);
  	len-=(offset-begin);
  	if(len>length)
  		len=length;
  	if(len<0)
  		len=0;
  	return len;
  }
  #endif
  
  struct proto_ops netlink_ops = {
  	family:		PF_NETLINK,
  
  	release:	netlink_release,
  	bind:		netlink_bind,
  	connect:	netlink_connect,
  	socketpair:	sock_no_socketpair,
  	accept:		sock_no_accept,
  	getname:	netlink_getname,
  	poll:		datagram_poll,
  	ioctl:		sock_no_ioctl,
  	listen:		sock_no_listen,
  	shutdown:	sock_no_shutdown,
  	setsockopt:	sock_no_setsockopt,
  	getsockopt:	sock_no_getsockopt,
  	sendmsg:	netlink_sendmsg,
  	recvmsg:	netlink_recvmsg,
  	mmap:		sock_no_mmap,
  };
  
  struct net_proto_family netlink_family_ops = {
  	PF_NETLINK,
  	netlink_create
  };
  
  static int __init netlink_proto_init(void)
  {
  	struct sk_buff *dummy_skb;
  
  	if (sizeof(struct netlink_skb_parms) > sizeof(dummy_skb->cb)) {
  		printk(KERN_CRIT "netlink_init: panic\n");
  		return -1;
  	}
  	sock_register(&netlink_family_ops);
  #ifdef CONFIG_PROC_FS
  	create_proc_read_entry("net/netlink", 0, 0, netlink_read_proc, NULL);
  #endif
  	return 0;
  }
  
  module_init(netlink_proto_init);
  