root/net/netfilter/nf_conntrack_helper.c

DEFINITIONS

1. helper_hash
2. __nf_ct_helper_find
3. __nf_conntrack_helper_find_byname
4. nf_ct_helper_ext_add
5. unhelp
6. nf_conntrack_helper_register
7. __nf_conntrack_helper_unregister
8. nf_conntrack_helper_unregister
9. nf_conntrack_helper_init
10. nf_conntrack_helper_fini

/* Helper handling 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/module.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/rculist.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_extend.h>

static DEFINE_MUTEX(nf_ct_helper_mutex);
static struct hlist_head *nf_ct_helper_hash __read_mostly;
static unsigned int nf_ct_helper_hsize __read_mostly;
static unsigned int nf_ct_helper_count __read_mostly;
static int nf_ct_helper_vmalloc;


/* Stupid hash, but collision free for the default registrations of the
 * helpers currently in the kernel. */
static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
{
        return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
                (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
}

struct nf_conntrack_helper *
__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
{
        struct nf_conntrack_helper *helper;
        struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
        struct hlist_node *n;
        unsigned int h;

        if (!nf_ct_helper_count)
                return NULL;

        h = helper_hash(tuple);
        hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
                if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
                        return helper;
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(__nf_ct_helper_find);

struct nf_conntrack_helper *
__nf_conntrack_helper_find_byname(const char *name)
{
        struct nf_conntrack_helper *h;
        struct hlist_node *n;
        unsigned int i;

        for (i = 0; i < nf_ct_helper_hsize; i++) {
                hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
                        if (!strcmp(h->name, name))
                                return h;
                }
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);

struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
{
        struct nf_conn_help *help;

        help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
        if (help)
                INIT_HLIST_HEAD(&help->expectations);
        else
                pr_debug("failed to add helper extension area");
        return help;
}
EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);

static inline int unhelp(struct nf_conntrack_tuple_hash *i,
                         const struct nf_conntrack_helper *me)
{
        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
        struct nf_conn_help *help = nfct_help(ct);

        if (help && help->helper == me) {
                nf_conntrack_event(IPCT_HELPER, ct);
                rcu_assign_pointer(help->helper, NULL);
        }
        return 0;
}

int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
{
        unsigned int h = helper_hash(&me->tuple);

        BUG_ON(me->expect_policy == NULL);
        BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);

        mutex_lock(&nf_ct_helper_mutex);
        hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
        nf_ct_helper_count++;
        mutex_unlock(&nf_ct_helper_mutex);

        return 0;
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);

static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
                                             struct net *net)
{
        struct nf_conntrack_tuple_hash *h;
        struct nf_conntrack_expect *exp;
        const struct hlist_node *n, *next;
        unsigned int i;

        /* Get rid of expectations */
        for (i = 0; i < nf_ct_expect_hsize; i++) {
                hlist_for_each_entry_safe(exp, n, next,
                                          &net->ct.expect_hash[i], hnode) {
                        struct nf_conn_help *help = nfct_help(exp->master);
                        if ((help->helper == me || exp->helper == me) &&
                            del_timer(&exp->timeout)) {
                                nf_ct_unlink_expect(exp);
                                nf_ct_expect_put(exp);
                        }
                }
        }

        /* Get rid of expecteds, set helpers to NULL. */
        hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
                unhelp(h, me);
        for (i = 0; i < nf_conntrack_htable_size; i++) {
                hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
                        unhelp(h, me);
        }
}

void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
{
        struct net *net;

        mutex_lock(&nf_ct_helper_mutex);
        hlist_del_rcu(&me->hnode);
        nf_ct_helper_count--;
        mutex_unlock(&nf_ct_helper_mutex);

        /* Make sure every nothing is still using the helper unless its a
         * connection in the hash.
         */
        synchronize_rcu();

        spin_lock_bh(&nf_conntrack_lock);
        for_each_net(net)
                __nf_conntrack_helper_unregister(me, net);
        spin_unlock_bh(&nf_conntrack_lock);
}
EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);

static struct nf_ct_ext_type helper_extend __read_mostly = {
        .len    = sizeof(struct nf_conn_help),
        .align  = __alignof__(struct nf_conn_help),
        .id     = NF_CT_EXT_HELPER,
};

int nf_conntrack_helper_init(void)
{
        int err;

        nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
        nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
                                                  &nf_ct_helper_vmalloc);
        if (!nf_ct_helper_hash)
                return -ENOMEM;

        err = nf_ct_extend_register(&helper_extend);
        if (err < 0)
                goto err1;

        return 0;

err1:
        nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
                             nf_ct_helper_hsize);
        return err;
}

void nf_conntrack_helper_fini(void)
{
        nf_ct_extend_unregister(&helper_extend);
        nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
                             nf_ct_helper_hsize);
}