/* 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);
}