nf_conntrack_ecache.c

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/* Event cache for netfilter. */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <[email protected]>
 * (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 <linux/export.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);

/* deliver cached events and clear cache entry - must be called with locally
 * disabled softirqs */
void nf_ct_deliver_cached_events(struct nf_conn *ct)
{
    struct net *net = nf_ct_net(ct);
    unsigned long events, missed;
    struct nf_ct_event_notifier *notify;
    struct nf_conntrack_ecache *e;
    struct nf_ct_event item;
    int ret;

    rcu_read_lock();
    notify = rcu_dereference(net->ct.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)
        goto out_unlock;

    /* 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. */
    missed = e->missed;

    if (!((events | missed) & e->ctmask))
        goto out_unlock;

    item.ct = ct;
    item.portid = 0;
    item.report = 0;

    ret = notify->fcn(events | missed, &item);

    if (likely(ret >= 0 && !missed))
        goto out_unlock;

    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 net *net,
                   struct nf_ct_event_notifier *new)
{
    int ret;
    struct nf_ct_event_notifier *notify;

    mutex_lock(&nf_ct_ecache_mutex);
    notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
                       lockdep_is_held(&nf_ct_ecache_mutex));
    if (notify != NULL) {
        ret = -EBUSY;
        goto out_unlock;
    }
    rcu_assign_pointer(net->ct.nf_conntrack_event_cb, new);
    ret = 0;

out_unlock:
    mutex_unlock(&nf_ct_ecache_mutex);
    return ret;
}
EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);

void nf_conntrack_unregister_notifier(struct net *net,
                      struct nf_ct_event_notifier *new)
{
    struct nf_ct_event_notifier *notify;

    mutex_lock(&nf_ct_ecache_mutex);
    notify = rcu_dereference_protected(net->ct.nf_conntrack_event_cb,
                       lockdep_is_held(&nf_ct_ecache_mutex));
    BUG_ON(notify != new);
    RCU_INIT_POINTER(net->ct.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 net *net,
                   struct nf_exp_event_notifier *new)
{
    int ret;
    struct nf_exp_event_notifier *notify;

    mutex_lock(&nf_ct_ecache_mutex);
    notify = rcu_dereference_protected(net->ct.nf_expect_event_cb,
                       lockdep_is_held(&nf_ct_ecache_mutex));
    if (notify != NULL) {
        ret = -EBUSY;
        goto out_unlock;
    }
    rcu_assign_pointer(net->ct.nf_expect_event_cb, new);
    ret = 0;

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 net *net,
                      struct nf_exp_event_notifier *new)
{
    struct nf_exp_event_notifier *notify;

    mutex_lock(&nf_ct_ecache_mutex);
    notify = rcu_dereference_protected(net->ct.nf_expect_event_cb,
                       lockdep_is_held(&nf_ct_ecache_mutex));
    BUG_ON(notify != new);
    RCU_INIT_POINTER(net->ct.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(net, "net/netfilter", 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);
}