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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
  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(const char *name, u16 l3num, u8 protonum)
  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                             h->tuple.src.l3num == l3num &&
  78                             h->tuple.dst.protonum == protonum)
  79                                 return h;
  80                 }
  81         }
  82         return NULL;
  83 }
  84 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
  85
  86 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  87 {
  88         struct nf_conn_help *help;
  89
  90         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  91         if (help)
  92                 INIT_HLIST_HEAD(&help->expectations);
  93         else
  94                 pr_debug("failed to add helper extension area");
  95         return help;
  96 }
  97 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  98
  99 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 100                               gfp_t flags)
 101 {
 102         struct nf_conntrack_helper *helper = NULL;
 103         struct nf_conn_help *help;
 104         int ret = 0;
 105
 106         if (tmpl != NULL) {
 107                 help = nfct_help(tmpl);
 108                 if (help != NULL)
 109                         helper = help->helper;
 110         }
 111
 112         help = nfct_help(ct);
 113         if (helper == NULL)
 114                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 115         if (helper == NULL) {
 116                 if (help)
 117                         rcu_assign_pointer(help->helper, NULL);
 118                 goto out;
 119         }
 120
 121         if (help == NULL) {
 122                 help = nf_ct_helper_ext_add(ct, flags);
 123                 if (help == NULL) {
 124                         ret = -ENOMEM;
 125                         goto out;
 126                 }
 127         } else {
 128                 memset(&help->help, 0, sizeof(help->help));
 129         }
 130
 131         rcu_assign_pointer(help->helper, helper);
 132 out:
 133         return ret;
 134 }
 135 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 136
 137 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 138                          const struct nf_conntrack_helper *me)
 139 {
 140         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 141         struct nf_conn_help *help = nfct_help(ct);
 142
 143         if (help && help->helper == me) {
 144                 nf_conntrack_event(IPCT_HELPER, ct);
 145                 rcu_assign_pointer(help->helper, NULL);
 146         }
 147         return 0;
 148 }
 149
 150 void nf_ct_helper_destroy(struct nf_conn *ct)
 151 {
 152         struct nf_conn_help *help = nfct_help(ct);
 153         struct nf_conntrack_helper *helper;
 154
 155         if (help) {
 156                 rcu_read_lock();
 157                 helper = rcu_dereference(help->helper);
 158                 if (helper && helper->destroy)
 159                         helper->destroy(ct);
 160                 rcu_read_unlock();
 161         }
 162 }
 163
 164 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 165 {
 166         unsigned int h = helper_hash(&me->tuple);
 167
 168         BUG_ON(me->expect_policy == NULL);
 169         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 170         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 171
 172         mutex_lock(&nf_ct_helper_mutex);
 173         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 174         nf_ct_helper_count++;
 175         mutex_unlock(&nf_ct_helper_mutex);
 176
 177         return 0;
 178 }
 179 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 180
 181 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 182                                              struct net *net)
 183 {
 184         struct nf_conntrack_tuple_hash *h;
 185         struct nf_conntrack_expect *exp;
 186         const struct hlist_node *n, *next;
 187         const struct hlist_nulls_node *nn;
 188         unsigned int i;
 189
 190         /* Get rid of expectations */
 191         for (i = 0; i < nf_ct_expect_hsize; i++) {
 192                 hlist_for_each_entry_safe(exp, n, next,
 193                                           &net->ct.expect_hash[i], hnode) {
 194                         struct nf_conn_help *help = nfct_help(exp->master);
 195                         if ((help->helper == me || exp->helper == me) &&
 196                             del_timer(&exp->timeout)) {
 197                                 nf_ct_unlink_expect(exp);
 198                                 nf_ct_expect_put(exp);
 199                         }
 200                 }
 201         }
 202
 203         /* Get rid of expecteds, set helpers to NULL. */
 204         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 205                 unhelp(h, me);
 206         for (i = 0; i < nf_conntrack_htable_size; i++) {
 207                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 208                         unhelp(h, me);
 209         }
 210 }
 211
 212 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 213 {
 214         struct net *net;
 215
 216         mutex_lock(&nf_ct_helper_mutex);
 217         hlist_del_rcu(&me->hnode);
 218         nf_ct_helper_count--;
 219         mutex_unlock(&nf_ct_helper_mutex);
 220
 221         /* Make sure every nothing is still using the helper unless its a
 222          * connection in the hash.
 223          */
 224         synchronize_rcu();
 225
 226         rtnl_lock();
 227         spin_lock_bh(&nf_conntrack_lock);
 228         for_each_net(net)
 229                 __nf_conntrack_helper_unregister(me, net);
 230         spin_unlock_bh(&nf_conntrack_lock);
 231         rtnl_unlock();
 232 }
 233 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 234
 235 static struct nf_ct_ext_type helper_extend __read_mostly = {
 236         .len    = sizeof(struct nf_conn_help),
 237         .align  = __alignof__(struct nf_conn_help),
 238         .id     = NF_CT_EXT_HELPER,
 239 };
 240
 241 int nf_conntrack_helper_init(void)
 242 {
 243         int err;
 244
 245         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 246         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 247                                                   &nf_ct_helper_vmalloc, 0);
 248         if (!nf_ct_helper_hash)
 249                 return -ENOMEM;
 250
 251         err = nf_ct_extend_register(&helper_extend);
 252         if (err < 0)
 253                 goto err1;
 254
 255         return 0;
 256
 257 err1:
 258         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 259                              nf_ct_helper_hsize);
 260         return err;
 261 }
 262
 263 void nf_conntrack_helper_fini(void)
 264 {
 265         nf_ct_extend_unregister(&helper_extend);
 266         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 267                              nf_ct_helper_hsize);
 268 }