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/random.h>
  19 #include <linux/err.h>
  20 #include <linux/kernel.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rculist.h>
  23 #include <linux/rtnetlink.h>
  24
  25 #include <net/netfilter/nf_conntrack.h>
  26 #include <net/netfilter/nf_conntrack_l3proto.h>
  27 #include <net/netfilter/nf_conntrack_l4proto.h>
  28 #include <net/netfilter/nf_conntrack_helper.h>
  29 #include <net/netfilter/nf_conntrack_core.h>
  30 #include <net/netfilter/nf_conntrack_extend.h>
  31
  32 static DEFINE_MUTEX(nf_ct_helper_mutex);
  33 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  34 static unsigned int nf_ct_helper_hsize __read_mostly;
  35 static unsigned int nf_ct_helper_count __read_mostly;
  36 static int nf_ct_helper_vmalloc;
  37
  38
  39 /* Stupid hash, but collision free for the default registrations of the
  40  * helpers currently in the kernel. */
  41 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  42 {
  43         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  44                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  45 }
  46
  47 static struct nf_conntrack_helper *
  48 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  49 {
  50         struct nf_conntrack_helper *helper;
  51         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  52         struct hlist_node *n;
  53         unsigned int h;
  54
  55         if (!nf_ct_helper_count)
  56                 return NULL;
  57
  58         h = helper_hash(tuple);
  59         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
  60                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  61                         return helper;
  62         }
  63         return NULL;
  64 }
  65
  66 struct nf_conntrack_helper *
  67 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
  68 {
  69         struct nf_conntrack_helper *h;
  70         struct hlist_node *n;
  71         unsigned int i;
  72
  73         for (i = 0; i < nf_ct_helper_hsize; i++) {
  74                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  75                         if (!strcmp(h->name, name) &&
  76                             h->tuple.src.l3num == l3num &&
  77                             h->tuple.dst.protonum == protonum)
  78                                 return h;
  79                 }
  80         }
  81         return NULL;
  82 }
  83 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
  84
  85 struct nf_conntrack_helper *
  86 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
  87 {
  88         struct nf_conntrack_helper *h;
  89
  90         h = __nf_conntrack_helper_find(name, l3num, protonum);
  91 #ifdef CONFIG_MODULES
  92         if (h == NULL) {
  93                 if (request_module("nfct-helper-%s", name) == 0)
  94                         h = __nf_conntrack_helper_find(name, l3num, protonum);
  95         }
  96 #endif
  97         if (h != NULL && !try_module_get(h->me))
  98                 h = NULL;
  99
 100         return h;
 101 }
 102 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 103
 104 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 105 {
 106         struct nf_conn_help *help;
 107
 108         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
 109         if (help)
 110                 INIT_HLIST_HEAD(&help->expectations);
 111         else
 112                 pr_debug("failed to add helper extension area");
 113         return help;
 114 }
 115 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 116
 117 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 118                               gfp_t flags)
 119 {
 120         struct nf_conntrack_helper *helper = NULL;
 121         struct nf_conn_help *help;
 122         int ret = 0;
 123
 124         if (tmpl != NULL) {
 125                 help = nfct_help(tmpl);
 126                 if (help != NULL)
 127                         helper = help->helper;
 128         }
 129
 130         help = nfct_help(ct);
 131         if (helper == NULL)
 132                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 133         if (helper == NULL) {
 134                 if (help)
 135                         rcu_assign_pointer(help->helper, NULL);
 136                 goto out;
 137         }
 138
 139         if (help == NULL) {
 140                 help = nf_ct_helper_ext_add(ct, flags);
 141                 if (help == NULL) {
 142                         ret = -ENOMEM;
 143                         goto out;
 144                 }
 145         } else {
 146                 memset(&help->help, 0, sizeof(help->help));
 147         }
 148
 149         rcu_assign_pointer(help->helper, helper);
 150 out:
 151         return ret;
 152 }
 153 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 154
 155 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 156                          const struct nf_conntrack_helper *me)
 157 {
 158         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 159         struct nf_conn_help *help = nfct_help(ct);
 160
 161         if (help && help->helper == me) {
 162                 nf_conntrack_event(IPCT_HELPER, ct);
 163                 rcu_assign_pointer(help->helper, NULL);
 164         }
 165         return 0;
 166 }
 167
 168 void nf_ct_helper_destroy(struct nf_conn *ct)
 169 {
 170         struct nf_conn_help *help = nfct_help(ct);
 171         struct nf_conntrack_helper *helper;
 172
 173         if (help) {
 174                 rcu_read_lock();
 175                 helper = rcu_dereference(help->helper);
 176                 if (helper && helper->destroy)
 177                         helper->destroy(ct);
 178                 rcu_read_unlock();
 179         }
 180 }
 181
 182 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 183 {
 184         unsigned int h = helper_hash(&me->tuple);
 185
 186         BUG_ON(me->expect_policy == NULL);
 187         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 188         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 189
 190         mutex_lock(&nf_ct_helper_mutex);
 191         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 192         nf_ct_helper_count++;
 193         mutex_unlock(&nf_ct_helper_mutex);
 194
 195         return 0;
 196 }
 197 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 198
 199 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 200                                              struct net *net)
 201 {
 202         struct nf_conntrack_tuple_hash *h;
 203         struct nf_conntrack_expect *exp;
 204         const struct hlist_node *n, *next;
 205         const struct hlist_nulls_node *nn;
 206         unsigned int i;
 207
 208         /* Get rid of expectations */
 209         for (i = 0; i < nf_ct_expect_hsize; i++) {
 210                 hlist_for_each_entry_safe(exp, n, next,
 211                                           &net->ct.expect_hash[i], hnode) {
 212                         struct nf_conn_help *help = nfct_help(exp->master);
 213                         if ((help->helper == me || exp->helper == me) &&
 214                             del_timer(&exp->timeout)) {
 215                                 nf_ct_unlink_expect(exp);
 216                                 nf_ct_expect_put(exp);
 217                         }
 218                 }
 219         }
 220
 221         /* Get rid of expecteds, set helpers to NULL. */
 222         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 223                 unhelp(h, me);
 224         for (i = 0; i < net->ct.htable_size; i++) {
 225                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 226                         unhelp(h, me);
 227         }
 228 }
 229
 230 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 231 {
 232         struct net *net;
 233
 234         mutex_lock(&nf_ct_helper_mutex);
 235         hlist_del_rcu(&me->hnode);
 236         nf_ct_helper_count--;
 237         mutex_unlock(&nf_ct_helper_mutex);
 238
 239         /* Make sure every nothing is still using the helper unless its a
 240          * connection in the hash.
 241          */
 242         synchronize_rcu();
 243
 244         rtnl_lock();
 245         spin_lock_bh(&nf_conntrack_lock);
 246         for_each_net(net)
 247                 __nf_conntrack_helper_unregister(me, net);
 248         spin_unlock_bh(&nf_conntrack_lock);
 249         rtnl_unlock();
 250 }
 251 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 252
 253 static struct nf_ct_ext_type helper_extend __read_mostly = {
 254         .len    = sizeof(struct nf_conn_help),
 255         .align  = __alignof__(struct nf_conn_help),
 256         .id     = NF_CT_EXT_HELPER,
 257 };
 258
 259 int nf_conntrack_helper_init(void)
 260 {
 261         int err;
 262
 263         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 264         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 265                                                   &nf_ct_helper_vmalloc, 0);
 266         if (!nf_ct_helper_hash)
 267                 return -ENOMEM;
 268
 269         err = nf_ct_extend_register(&helper_extend);
 270         if (err < 0)
 271                 goto err1;
 272
 273         return 0;
 274
 275 err1:
 276         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 277                              nf_ct_helper_hsize);
 278         return err;
 279 }
 280
 281 void nf_conntrack_helper_fini(void)
 282 {
 283         nf_ct_extend_unregister(&helper_extend);
 284         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 285                              nf_ct_helper_hsize);
 286 }