net/netfilter/nf_conntrack_helper.c

   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
  33 static DEFINE_MUTEX(nf_ct_helper_mutex);
  34 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  35 static unsigned int nf_ct_helper_hsize __read_mostly;
  36 static unsigned int nf_ct_helper_count __read_mostly;
  37 static 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. */
  42 static 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
  48 static struct 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 }
  66
  67 struct nf_conntrack_helper *
  68 __nf_conntrack_helper_find_byname(const char *name)
  69 {
  70         struct nf_conntrack_helper *h;
  71         struct hlist_node *n;
  72         unsigned int i;
  73
  74         for (i = 0; i < nf_ct_helper_hsize; i++) {
  75                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  76                         if (!strcmp(h->name, name))
  77                                 return h;
  78                 }
  79         }
  80         return NULL;
  81 }
  82 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  83
  84 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  85 {
  86         struct nf_conn_help *help;
  87
  88         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  89         if (help)
  90                 INIT_HLIST_HEAD(&help->expectations);
  91         else
  92                 pr_debug("failed to add helper extension area");
  93         return help;
  94 }
  95 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  96
  97 int __nf_ct_try_assign_helper(struct nf_conn *ct, gfp_t flags)
  98 {
  99         int ret = 0;
 100         struct nf_conntrack_helper *helper;
 101         struct nf_conn_help *help = nfct_help(ct);
 102
 103         helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 104         if (helper == NULL) {
 105                 if (help)
 106                         rcu_assign_pointer(help->helper, NULL);
 107                 goto out;
 108         }
 109
 110         if (help == NULL) {
 111                 help = nf_ct_helper_ext_add(ct, flags);
 112                 if (help == NULL) {
 113                         ret = -ENOMEM;
 114                         goto out;
 115                 }
 116         } else {
 117                 memset(&help->help, 0, sizeof(help->help));
 118         }
 119
 120         rcu_assign_pointer(help->helper, helper);
 121 out:
 122         return ret;
 123 }
 124 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 125
 126 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 127                          const struct nf_conntrack_helper *me)
 128 {
 129         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 130         struct nf_conn_help *help = nfct_help(ct);
 131
 132         if (help && help->helper == me) {
 133                 nf_conntrack_event(IPCT_HELPER, ct);
 134                 rcu_assign_pointer(help->helper, NULL);
 135         }
 136         return 0;
 137 }
 138
 139 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 140 {
 141         unsigned int h = helper_hash(&me->tuple);
 142
 143         BUG_ON(me->expect_policy == NULL);
 144         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 145         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 146
 147         mutex_lock(&nf_ct_helper_mutex);
 148         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 149         nf_ct_helper_count++;
 150         mutex_unlock(&nf_ct_helper_mutex);
 151
 152         return 0;
 153 }
 154 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 155
 156 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 157                                              struct net *net)
 158 {
 159         struct nf_conntrack_tuple_hash *h;
 160         struct nf_conntrack_expect *exp;
 161         const struct hlist_node *n, *next;
 162         const struct hlist_nulls_node *nn;
 163         unsigned int i;
 164
 165         /* Get rid of expectations */
 166         for (i = 0; i < nf_ct_expect_hsize; i++) {
 167                 hlist_for_each_entry_safe(exp, n, next,
 168                                           &net->ct.expect_hash[i], hnode) {
 169                         struct nf_conn_help *help = nfct_help(exp->master);
 170                         if ((help->helper == me || exp->helper == me) &&
 171                             del_timer(&exp->timeout)) {
 172                                 nf_ct_unlink_expect(exp);
 173                                 nf_ct_expect_put(exp);
 174                         }
 175                 }
 176         }
 177
 178         /* Get rid of expecteds, set helpers to NULL. */
 179         hlist_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 180                 unhelp(h, me);
 181         for (i = 0; i < nf_conntrack_htable_size; i++) {
 182                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 183                         unhelp(h, me);
 184         }
 185 }
 186
 187 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 188 {
 189         struct net *net;
 190
 191         mutex_lock(&nf_ct_helper_mutex);
 192         hlist_del_rcu(&me->hnode);
 193         nf_ct_helper_count--;
 194         mutex_unlock(&nf_ct_helper_mutex);
 195
 196         /* Make sure every nothing is still using the helper unless its a
 197          * connection in the hash.
 198          */
 199         synchronize_rcu();
 200
 201         rtnl_lock();
 202         spin_lock_bh(&nf_conntrack_lock);
 203         for_each_net(net)
 204                 __nf_conntrack_helper_unregister(me, net);
 205         spin_unlock_bh(&nf_conntrack_lock);
 206         rtnl_unlock();
 207 }
 208 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 209
 210 static struct nf_ct_ext_type helper_extend __read_mostly = {
 211         .len    = sizeof(struct nf_conn_help),
 212         .align  = __alignof__(struct nf_conn_help),
 213         .id     = NF_CT_EXT_HELPER,
 214 };
 215
 216 int nf_conntrack_helper_init(void)
 217 {
 218         int err;
 219
 220         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 221         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 222                                                   &nf_ct_helper_vmalloc, 0);
 223         if (!nf_ct_helper_hash)
 224                 return -ENOMEM;
 225
 226         err = nf_ct_extend_register(&helper_extend);
 227         if (err < 0)
 228                 goto err1;
 229
 230         return 0;
 231
 232 err1:
 233         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 234                              nf_ct_helper_hsize);
 235         return err;
 236 }
 237
 238 void nf_conntrack_helper_fini(void)
 239 {
 240         nf_ct_extend_unregister(&helper_extend);
 241         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 242                              nf_ct_helper_hsize);
 243 }