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
  24 #include <net/netfilter/nf_conntrack.h>
  25 #include <net/netfilter/nf_conntrack_l3proto.h>
  26 #include <net/netfilter/nf_conntrack_l4proto.h>
  27 #include <net/netfilter/nf_conntrack_helper.h>
  28 #include <net/netfilter/nf_conntrack_core.h>
  29 #include <net/netfilter/nf_conntrack_extend.h>
  30
  31 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  32 static unsigned int nf_ct_helper_hsize __read_mostly;
  33 static unsigned int nf_ct_helper_count __read_mostly;
  34 static int nf_ct_helper_vmalloc;
  35
  36
  37 /* Stupid hash, but collision free for the default registrations of the
  38  * helpers currently in the kernel. */
  39 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  40 {
  41         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  42                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  43 }
  44
  45 struct nf_conntrack_helper *
  46 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  47 {
  48         struct nf_conntrack_helper *helper;
  49         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  50         struct hlist_node *n;
  51         unsigned int h;
  52
  53         if (!nf_ct_helper_count)
  54                 return NULL;
  55
  56         h = helper_hash(tuple);
  57         hlist_for_each_entry(helper, n, &nf_ct_helper_hash[h], hnode) {
  58                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  59                         return helper;
  60         }
  61         return NULL;
  62 }
  63
  64 struct nf_conntrack_helper *
  65 nf_ct_helper_find_get(const struct nf_conntrack_tuple *tuple)
  66 {
  67         struct nf_conntrack_helper *helper;
  68
  69         /* need nf_conntrack_lock to assure that helper exists until
  70          * try_module_get() is called */
  71         read_lock_bh(&nf_conntrack_lock);
  72
  73         helper = __nf_ct_helper_find(tuple);
  74         if (helper) {
  75                 /* need to increase module usage count to assure helper will
  76                  * not go away while the caller is e.g. busy putting a
  77                  * conntrack in the hash that uses the helper */
  78                 if (!try_module_get(helper->me))
  79                         helper = NULL;
  80         }
  81
  82         read_unlock_bh(&nf_conntrack_lock);
  83
  84         return helper;
  85 }
  86 EXPORT_SYMBOL_GPL(nf_ct_helper_find_get);
  87
  88 void nf_ct_helper_put(struct nf_conntrack_helper *helper)
  89 {
  90         module_put(helper->me);
  91 }
  92 EXPORT_SYMBOL_GPL(nf_ct_helper_put);
  93
  94 struct nf_conntrack_helper *
  95 __nf_conntrack_helper_find_byname(const char *name)
  96 {
  97         struct nf_conntrack_helper *h;
  98         struct hlist_node *n;
  99         unsigned int i;
 100
 101         for (i = 0; i < nf_ct_helper_hsize; i++) {
 102                 hlist_for_each_entry(h, n, &nf_ct_helper_hash[i], hnode) {
 103                         if (!strcmp(h->name, name))
 104                                 return h;
 105                 }
 106         }
 107         return NULL;
 108 }
 109 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
 110
 111 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 112 {
 113         struct nf_conn_help *help;
 114
 115         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
 116         if (help)
 117                 INIT_HLIST_HEAD(&help->expectations);
 118         else
 119                 pr_debug("failed to add helper extension area");
 120         return help;
 121 }
 122 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 123
 124 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 125                          const struct nf_conntrack_helper *me)
 126 {
 127         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 128         struct nf_conn_help *help = nfct_help(ct);
 129
 130         if (help && help->helper == me) {
 131                 nf_conntrack_event(IPCT_HELPER, ct);
 132                 rcu_assign_pointer(help->helper, NULL);
 133         }
 134         return 0;
 135 }
 136
 137 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 138 {
 139         unsigned int h = helper_hash(&me->tuple);
 140
 141         BUG_ON(me->timeout == 0);
 142
 143         write_lock_bh(&nf_conntrack_lock);
 144         hlist_add_head(&me->hnode, &nf_ct_helper_hash[h]);
 145         nf_ct_helper_count++;
 146         write_unlock_bh(&nf_conntrack_lock);
 147
 148         return 0;
 149 }
 150 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 151
 152 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 153 {
 154         struct nf_conntrack_tuple_hash *h;
 155         struct nf_conntrack_expect *exp;
 156         struct hlist_node *n, *next;
 157         unsigned int i;
 158
 159         /* Need write lock here, to delete helper. */
 160         write_lock_bh(&nf_conntrack_lock);
 161         hlist_del(&me->hnode);
 162         nf_ct_helper_count--;
 163
 164         /* Get rid of expectations */
 165         for (i = 0; i < nf_ct_expect_hsize; i++) {
 166                 hlist_for_each_entry_safe(exp, n, next,
 167                                           &nf_ct_expect_hash[i], hnode) {
 168                         struct nf_conn_help *help = nfct_help(exp->master);
 169                         if ((help->helper == me || exp->helper == me) &&
 170                             del_timer(&exp->timeout)) {
 171                                 nf_ct_unlink_expect(exp);
 172                                 nf_ct_expect_put(exp);
 173                         }
 174                 }
 175         }
 176
 177         /* Get rid of expecteds, set helpers to NULL. */
 178         hlist_for_each_entry(h, n, &unconfirmed, hnode)
 179                 unhelp(h, me);
 180         for (i = 0; i < nf_conntrack_htable_size; i++) {
 181                 hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
 182                         unhelp(h, me);
 183         }
 184         write_unlock_bh(&nf_conntrack_lock);
 185
 186         /* Someone could be still looking at the helper in a bh. */
 187         synchronize_net();
 188 }
 189 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 190
 191 static struct nf_ct_ext_type helper_extend __read_mostly = {
 192         .len    = sizeof(struct nf_conn_help),
 193         .align  = __alignof__(struct nf_conn_help),
 194         .id     = NF_CT_EXT_HELPER,
 195 };
 196
 197 int nf_conntrack_helper_init(void)
 198 {
 199         int err;
 200
 201         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 202         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 203                                                   &nf_ct_helper_vmalloc);
 204         if (!nf_ct_helper_hash)
 205                 return -ENOMEM;
 206
 207         err = nf_ct_extend_register(&helper_extend);
 208         if (err < 0)
 209                 goto err1;
 210
 211         return 0;
 212
 213 err1:
 214         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 215                              nf_ct_helper_hsize);
 216         return err;
 217 }
 218
 219 void nf_conntrack_helper_fini(void)
 220 {
 221         nf_ct_extend_unregister(&helper_extend);
 222         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 223                              nf_ct_helper_hsize);
 224 }