linux/net/netfilter/nf_conntrack_helper.c
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   1/* Helper handling for netfilter. */
   2
   3/* (C) 1999-2001 Paul `Rusty' Russell
   4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 */
  11
  12#include <linux/types.h>
  13#include <linux/netfilter.h>
  14#include <linux/module.h>
  15#include <linux/skbuff.h>
  16#include <linux/vmalloc.h>
  17#include <linux/stddef.h>
  18#include <linux/slab.h>
  19#include <linux/random.h>
  20#include <linux/err.h>
  21#include <linux/kernel.h>
  22#include <linux/netdevice.h>
  23#include <linux/rculist.h>
  24#include <linux/rtnetlink.h>
  25
  26#include <net/netfilter/nf_conntrack.h>
  27#include <net/netfilter/nf_conntrack_l3proto.h>
  28#include <net/netfilter/nf_conntrack_l4proto.h>
  29#include <net/netfilter/nf_conntrack_helper.h>
  30#include <net/netfilter/nf_conntrack_core.h>
  31#include <net/netfilter/nf_conntrack_extend.h>
  32
  33static DEFINE_MUTEX(nf_ct_helper_mutex);
  34static struct hlist_head *nf_ct_helper_hash __read_mostly;
  35static unsigned int nf_ct_helper_hsize __read_mostly;
  36static unsigned int nf_ct_helper_count __read_mostly;
  37static int nf_ct_helper_vmalloc;
  38
  39
  40/* Stupid hash, but collision free for the default registrations of the
  41 * helpers currently in the kernel. */
  42static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  43{
  44        return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  45                (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  46}
  47
  48struct nf_conntrack_helper *
  49__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  50{
  51        struct nf_conntrack_helper *helper;
  52        struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  53        struct hlist_node *n;
  54        unsigned int h;
  55
  56        if (!nf_ct_helper_count)
  57                return NULL;
  58
  59        h = helper_hash(tuple);
  60        hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
  61                if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  62                        return helper;
  63        }
  64        return NULL;
  65}
  66EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
  67
  68struct nf_conntrack_helper *
  69__nf_conntrack_helper_find_byname(const char *name)
  70{
  71        struct nf_conntrack_helper *h;
  72        struct hlist_node *n;
  73        unsigned int i;
  74
  75        for (i = 0; i < nf_ct_helper_hsize; i++) {
  76                hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  77                        if (!strcmp(h->name, name))
  78                                return h;
  79                }
  80        }
  81        return NULL;
  82}
  83EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  84
  85struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  86{
  87        struct nf_conn_help *help;
  88
  89        help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  90        if (help)
  91                INIT_HLIST_HEAD(&help->expectations);
  92        else
  93                pr_debug("failed to add helper extension area");
  94        return help;
  95}
  96EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  97
  98static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  99                         const struct nf_conntrack_helper *me)
 100{
 101        struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 102        struct nf_conn_help *help = nfct_help(ct);
 103
 104        if (help && help->helper == me) {
 105                nf_conntrack_event(IPCT_HELPER, ct);
 106                rcu_assign_pointer(help->helper, NULL);
 107        }
 108        return 0;
 109}
 110
 111int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 112{
 113        unsigned int h = helper_hash(&me->tuple);
 114
 115        BUG_ON(me->expect_policy == NULL);
 116        BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 117
 118        mutex_lock(&nf_ct_helper_mutex);
 119        hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 120        nf_ct_helper_count++;
 121        mutex_unlock(&nf_ct_helper_mutex);
 122
 123        return 0;
 124}
 125EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 126
 127static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 128                                             struct net *net)
 129{
 130        struct nf_conntrack_tuple_hash *h;
 131        struct nf_conntrack_expect *exp;
 132        const struct hlist_node *n, *next;
 133        unsigned int i;
 134
 135        /* Get rid of expectations */
 136        for (i = 0; i < nf_ct_expect_hsize; i++) {
 137                hlist_for_each_entry_safe(exp, n, next,
 138                                          &net->ct.expect_hash[i], hnode) {
 139                        struct nf_conn_help *help = nfct_help(exp->master);
 140                        if ((help->helper == me || exp->helper == me) &&
 141                            del_timer(&exp->timeout)) {
 142                                nf_ct_unlink_expect(exp);
 143                                nf_ct_expect_put(exp);
 144                        }
 145                }
 146        }
 147
 148        /* Get rid of expecteds, set helpers to NULL. */
 149        hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
 150                unhelp(h, me);
 151        for (i = 0; i < nf_conntrack_htable_size; i++) {
 152                hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
 153                        unhelp(h, me);
 154        }
 155}
 156
 157void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 158{
 159        struct net *net;
 160
 161        mutex_lock(&nf_ct_helper_mutex);
 162        hlist_del_rcu(&me->hnode);
 163        nf_ct_helper_count--;
 164        mutex_unlock(&nf_ct_helper_mutex);
 165
 166        /* Make sure every nothing is still using the helper unless its a
 167         * connection in the hash.
 168         */
 169        synchronize_rcu();
 170
 171        rtnl_lock();
 172        spin_lock_bh(&nf_conntrack_lock);
 173        for_each_net(net)
 174                __nf_conntrack_helper_unregister(me, net);
 175        spin_unlock_bh(&nf_conntrack_lock);
 176        rtnl_unlock();
 177}
 178EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 179
 180static struct nf_ct_ext_type helper_extend __read_mostly = {
 181        .len    = sizeof(struct nf_conn_help),
 182        .align  = __alignof__(struct nf_conn_help),
 183        .id     = NF_CT_EXT_HELPER,
 184};
 185
 186int nf_conntrack_helper_init(void)
 187{
 188        int err;
 189
 190        nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 191        nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 192                                                  &nf_ct_helper_vmalloc);
 193        if (!nf_ct_helper_hash)
 194                return -ENOMEM;
 195
 196        err = nf_ct_extend_register(&helper_extend);
 197        if (err < 0)
 198                goto err1;
 199
 200        return 0;
 201
 202err1:
 203        nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 204                             nf_ct_helper_hsize);
 205        return err;
 206}
 207
 208void nf_conntrack_helper_fini(void)
 209{
 210        nf_ct_extend_unregister(&helper_extend);
 211        nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 212                             nf_ct_helper_hsize);
 213}
 214