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