text: /* Event cache for netfilter. */
  
  /* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/types.h>
  #include <linux/netfilter.h>
  #include <linux/skbuff.h>
  #include <linux/vmalloc.h>
  #include <linux/stddef.h>
  #include <linux/err.h>
  #include <linux/percpu.h>
  #include <linux/kernel.h>
  #include <linux/netdevice.h>
  #include <linux/slab.h>
  
  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_conntrack_core.h>
  #include <net/netfilter/nf_conntrack_extend.h>
  
  static DEFINE_MUTEX(nf_ct_ecache_mutex);
  
  struct nf_ct_event_notifier *nf_conntrack_event_cb __read_mostly;
  EXPORT_SYMBOL_GPL(nf_conntrack_event_cb);
  
  struct nf_exp_event_notifier *nf_expect_event_cb __read_mostly;
  EXPORT_SYMBOL_GPL(nf_expect_event_cb);
  
  /* deliver cached events and clear cache entry - must be called with locally
   * disabled softirqs */
  void nf_ct_deliver_cached_events(struct nf_conn *ct)
  {
  	unsigned long events;
  	struct nf_ct_event_notifier *notify;
  	struct nf_conntrack_ecache *e;
  
  	rcu_read_lock();
  	notify = rcu_dereference(nf_conntrack_event_cb);
  	if (notify == NULL)
  		goto out_unlock;
  
  	e = nf_ct_ecache_find(ct);
  	if (e == NULL)
  		goto out_unlock;
  
  	events = xchg(&e->cache, 0);
  
  	if (nf_ct_is_confirmed(ct) && !nf_ct_is_dying(ct) && events) {
  		struct nf_ct_event item = {
  			.ct	= ct,
  			.pid	= 0,
  			.report	= 0
  		};
  		int ret;
  		/* We make a copy of the missed event cache without taking
  		 * the lock, thus we may send missed events twice. However,
  		 * this does not harm and it happens very rarely. */
  		unsigned long missed = e->missed;
  
  		ret = notify->fcn(events | missed, &item);
  		if (unlikely(ret < 0 || missed)) {
  			spin_lock_bh(&ct->lock);
  			if (ret < 0)
  				e->missed |= events;
  			else
  				e->missed &= ~missed;
  			spin_unlock_bh(&ct->lock);
  		} 
  	}
  
  out_unlock:
  	rcu_read_unlock();
  }
  EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
  
  int nf_conntrack_register_notifier(struct nf_ct_event_notifier *new)
  {
  	int ret = 0;
  	struct nf_ct_event_notifier *notify;
  
  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(nf_conntrack_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
  	if (notify != NULL) {
  		ret = -EBUSY;
  		goto out_unlock;
  	}
  	rcu_assign_pointer(nf_conntrack_event_cb, new);
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  
  out_unlock:
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);
  
  void nf_conntrack_unregister_notifier(struct nf_ct_event_notifier *new)
  {
  	struct nf_ct_event_notifier *notify;
  
  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(nf_conntrack_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
  	BUG_ON(notify != new);
  	rcu_assign_pointer(nf_conntrack_event_cb, NULL);
  	mutex_unlock(&nf_ct_ecache_mutex);
  }
  EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
  
  int nf_ct_expect_register_notifier(struct nf_exp_event_notifier *new)
  {
  	int ret = 0;
  	struct nf_exp_event_notifier *notify;
  
  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(nf_expect_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
  	if (notify != NULL) {
  		ret = -EBUSY;
  		goto out_unlock;
  	}
  	rcu_assign_pointer(nf_expect_event_cb, new);
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  
  out_unlock:
  	mutex_unlock(&nf_ct_ecache_mutex);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(nf_ct_expect_register_notifier);
  
  void nf_ct_expect_unregister_notifier(struct nf_exp_event_notifier *new)
  {
  	struct nf_exp_event_notifier *notify;
  
  	mutex_lock(&nf_ct_ecache_mutex);
  	notify = rcu_dereference_protected(nf_expect_event_cb,
  					   lockdep_is_held(&nf_ct_ecache_mutex));
  	BUG_ON(notify != new);
  	rcu_assign_pointer(nf_expect_event_cb, NULL);
  	mutex_unlock(&nf_ct_ecache_mutex);
  }
  EXPORT_SYMBOL_GPL(nf_ct_expect_unregister_notifier);
  
  #define NF_CT_EVENTS_DEFAULT 1
  static int nf_ct_events __read_mostly = NF_CT_EVENTS_DEFAULT;
  static int nf_ct_events_retry_timeout __read_mostly = 15*HZ;
  
  #ifdef CONFIG_SYSCTL
  static struct ctl_table event_sysctl_table[] = {
  	{
  		.procname	= "nf_conntrack_events",
  		.data		= &init_net.ct.sysctl_events,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec,
  	},
  	{
  		.procname	= "nf_conntrack_events_retry_timeout",
  		.data		= &init_net.ct.sysctl_events_retry_timeout,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_jiffies,
  	},
  	{}
  };
  #endif /* CONFIG_SYSCTL */
  
  static struct nf_ct_ext_type event_extend __read_mostly = {
  	.len	= sizeof(struct nf_conntrack_ecache),
  	.align	= __alignof__(struct nf_conntrack_ecache),
  	.id	= NF_CT_EXT_ECACHE,
  };
  
  #ifdef CONFIG_SYSCTL
  static int nf_conntrack_event_init_sysctl(struct net *net)
  {
  	struct ctl_table *table;
  
  	table = kmemdup(event_sysctl_table, sizeof(event_sysctl_table),
  			GFP_KERNEL);
  	if (!table)
  		goto out;
  
  	table[0].data = &net->ct.sysctl_events;
  	table[1].data = &net->ct.sysctl_events_retry_timeout;
  
  	net->ct.event_sysctl_header =
  		register_net_sysctl_table(net,
  					  nf_net_netfilter_sysctl_path, table);
  	if (!net->ct.event_sysctl_header) {
  		printk(KERN_ERR "nf_ct_event: can't register to sysctl.\n");
  		goto out_register;
  	}
  	return 0;
  
  out_register:
  	kfree(table);
  out:
  	return -ENOMEM;
  }
  
  static void nf_conntrack_event_fini_sysctl(struct net *net)
  {
  	struct ctl_table *table;
  
  	table = net->ct.event_sysctl_header->ctl_table_arg;
  	unregister_net_sysctl_table(net->ct.event_sysctl_header);
  	kfree(table);
  }
  #else
  static int nf_conntrack_event_init_sysctl(struct net *net)
  {
  	return 0;
  }
  
  static void nf_conntrack_event_fini_sysctl(struct net *net)
  {
  }
  #endif /* CONFIG_SYSCTL */
  
  int nf_conntrack_ecache_init(struct net *net)
  {
  	int ret;
  
  	net->ct.sysctl_events = nf_ct_events;
  	net->ct.sysctl_events_retry_timeout = nf_ct_events_retry_timeout;
  
  	if (net_eq(net, &init_net)) {
  		ret = nf_ct_extend_register(&event_extend);
  		if (ret < 0) {
  			printk(KERN_ERR "nf_ct_event: Unable to register "
  					"event extension.\n");
  			goto out_extend_register;
  		}
  	}
  
  	ret = nf_conntrack_event_init_sysctl(net);
  	if (ret < 0)
  		goto out_sysctl;
  
  	return 0;
  
  out_sysctl:
  	if (net_eq(net, &init_net))
  		nf_ct_extend_unregister(&event_extend);
  out_extend_register:
  	return ret;
  }
  
  void nf_conntrack_ecache_fini(struct net *net)
  {
  	nf_conntrack_event_fini_sysctl(net);
  	if (net_eq(net, &init_net))
  		nf_ct_extend_unregister(&event_extend);
  }
  