release/src-rt-6.x/linux/linux-2.6/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
  30 static __read_mostly LIST_HEAD(helpers);
  31
  32 struct nf_conntrack_helper *
  33 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  34 {
  35         struct nf_conntrack_helper *h;
  36
  37         list_for_each_entry(h, &helpers, list) {
  38                 if (nf_ct_tuple_mask_cmp(tuple, &h->tuple, &h->mask))
  39                         return h;
  40         }
  41         return NULL;
  42 }
  43
  44 struct nf_conntrack_helper *
  45 nf_ct_helper_find_get( const struct nf_conntrack_tuple *tuple)
  46 {
  47         struct nf_conntrack_helper *helper;
  48
  49         /* need nf_conntrack_lock to assure that helper exists until
  50          * try_module_get() is called */
  51         read_lock_bh(&nf_conntrack_lock);
  52
  53         helper = __nf_ct_helper_find(tuple);
  54         if (helper) {
  55                 /* need to increase module usage count to assure helper will
  56                  * not go away while the caller is e.g. busy putting a
  57                  * conntrack in the hash that uses the helper */
  58                 if (!try_module_get(helper->me))
  59                         helper = NULL;
  60         }
  61
  62         read_unlock_bh(&nf_conntrack_lock);
  63
  64         return helper;
  65 }
  66 EXPORT_SYMBOL_GPL(nf_ct_helper_find_get);
  67
  68 void nf_ct_helper_put(struct nf_conntrack_helper *helper)
  69 {
  70         module_put(helper->me);
  71 }
  72 EXPORT_SYMBOL_GPL(nf_ct_helper_put);
  73
  74 struct nf_conntrack_helper *
  75 __nf_conntrack_helper_find_byname(const char *name)
  76 {
  77         struct nf_conntrack_helper *h;
  78
  79         list_for_each_entry(h, &helpers, list) {
  80                 if (!strcmp(h->name, name))
  81                         return h;
  82         }
  83
  84         return NULL;
  85 }
  86 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  87
  88 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  89                          const struct nf_conntrack_helper *me)
  90 {
  91         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
  92         struct nf_conn_help *help = nfct_help(ct);
  93
  94         if (help && help->helper == me) {
  95                 nf_conntrack_event(IPCT_HELPER, ct);
  96                 rcu_assign_pointer(help->helper, NULL);
  97         }
  98         return 0;
  99 }
 100
 101 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 102 {
 103         int size, ret;
 104
 105         BUG_ON(me->expect_policy == NULL);
 106         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 107
 108         size = ALIGN(sizeof(struct nf_conn), __alignof__(struct nf_conn_help)) +
 109                sizeof(struct nf_conn_help);
 110         ret = nf_conntrack_register_cache(NF_CT_F_HELP, "nf_conntrack:help",
 111                                           size);
 112         if (ret < 0) {
 113                 printk(KERN_ERR "nf_conntrack_helper_register: Unable to create slab cache for conntracks\n");
 114                 return ret;
 115         }
 116         write_lock_bh(&nf_conntrack_lock);
 117         list_add(&me->list, &helpers);
 118         write_unlock_bh(&nf_conntrack_lock);
 119
 120         return 0;
 121 }
 122 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 123
 124 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 125 {
 126         unsigned int i;
 127         struct nf_conntrack_tuple_hash *h;
 128         struct nf_conntrack_expect *exp, *tmp;
 129
 130         /* Need write lock here, to delete helper. */
 131         write_lock_bh(&nf_conntrack_lock);
 132         list_del(&me->list);
 133
 134         /* Get rid of expectations */
 135         list_for_each_entry_safe(exp, tmp, &nf_conntrack_expect_list, list) {
 136                 struct nf_conn_help *help = nfct_help(exp->master);
 137                 if ((help->helper == me || exp->helper == me) &&
 138                     del_timer(&exp->timeout)) {
 139                         nf_ct_unlink_expect(exp);
 140                         nf_conntrack_expect_put(exp);
 141                 }
 142         }
 143
 144         /* Get rid of expecteds, set helpers to NULL. */
 145         list_for_each_entry(h, &unconfirmed, list)
 146                 unhelp(h, me);
 147         for (i = 0; i < nf_conntrack_htable_size; i++) {
 148                 list_for_each_entry(h, &nf_conntrack_hash[i], list)
 149                         unhelp(h, me);
 150         }
 151         write_unlock_bh(&nf_conntrack_lock);
 152
 153         /* Someone could be still looking at the helper in a bh. */
 154         synchronize_net();
 155 }
 156 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);