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 __read_mostly LIST_HEAD(helpers);
  32
  33 struct nf_conntrack_helper *
  34 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  35 {
  36         struct nf_conntrack_helper *h;
  37         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  38
  39         list_for_each_entry(h, &helpers, list) {
  40                 if (nf_ct_tuple_src_mask_cmp(tuple, &h->tuple, &mask))
  41                         return h;
  42         }
  43         return NULL;
  44 }
  45
  46 struct nf_conntrack_helper *
  47 nf_ct_helper_find_get( const struct nf_conntrack_tuple *tuple)
  48 {
  49         struct nf_conntrack_helper *helper;
  50
  51         /* need nf_conntrack_lock to assure that helper exists until
  52          * try_module_get() is called */
  53         read_lock_bh(&nf_conntrack_lock);
  54
  55         helper = __nf_ct_helper_find(tuple);
  56         if (helper) {
  57                 /* need to increase module usage count to assure helper will
  58                  * not go away while the caller is e.g. busy putting a
  59                  * conntrack in the hash that uses the helper */
  60                 if (!try_module_get(helper->me))
  61                         helper = NULL;
  62         }
  63
  64         read_unlock_bh(&nf_conntrack_lock);
  65
  66         return helper;
  67 }
  68 EXPORT_SYMBOL_GPL(nf_ct_helper_find_get);
  69
  70 void nf_ct_helper_put(struct nf_conntrack_helper *helper)
  71 {
  72         module_put(helper->me);
  73 }
  74 EXPORT_SYMBOL_GPL(nf_ct_helper_put);
  75
  76 struct nf_conntrack_helper *
  77 __nf_conntrack_helper_find_byname(const char *name)
  78 {
  79         struct nf_conntrack_helper *h;
  80
  81         list_for_each_entry(h, &helpers, list) {
  82                 if (!strcmp(h->name, name))
  83                         return h;
  84         }
  85
  86         return NULL;
  87 }
  88 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  89
  90 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  91                          const struct nf_conntrack_helper *me)
  92 {
  93         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
  94         struct nf_conn_help *help = nfct_help(ct);
  95
  96         if (help && help->helper == me) {
  97                 nf_conntrack_event(IPCT_HELPER, ct);
  98                 rcu_assign_pointer(help->helper, NULL);
  99         }
 100         return 0;
 101 }
 102
 103 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 104 {
 105         BUG_ON(me->timeout == 0);
 106
 107         write_lock_bh(&nf_conntrack_lock);
 108         list_add(&me->list, &helpers);
 109         write_unlock_bh(&nf_conntrack_lock);
 110
 111         return 0;
 112 }
 113 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 114
 115 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 116 {
 117         unsigned int i;
 118         struct nf_conntrack_tuple_hash *h;
 119         struct nf_conntrack_expect *exp, *tmp;
 120         struct hlist_node *n;
 121
 122         /* Need write lock here, to delete helper. */
 123         write_lock_bh(&nf_conntrack_lock);
 124         list_del(&me->list);
 125
 126         /* Get rid of expectations */
 127         list_for_each_entry_safe(exp, tmp, &nf_ct_expect_list, list) {
 128                 struct nf_conn_help *help = nfct_help(exp->master);
 129                 if ((help->helper == me || exp->helper == me) &&
 130                     del_timer(&exp->timeout)) {
 131                         nf_ct_unlink_expect(exp);
 132                         nf_ct_expect_put(exp);
 133                 }
 134         }
 135
 136         /* Get rid of expecteds, set helpers to NULL. */
 137         hlist_for_each_entry(h, n, &unconfirmed, hnode)
 138                 unhelp(h, me);
 139         for (i = 0; i < nf_conntrack_htable_size; i++) {
 140                 hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
 141                         unhelp(h, me);
 142         }
 143         write_unlock_bh(&nf_conntrack_lock);
 144
 145         /* Someone could be still looking at the helper in a bh. */
 146         synchronize_net();
 147 }
 148 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 149
 150 static struct nf_ct_ext_type helper_extend __read_mostly = {
 151         .len    = sizeof(struct nf_conn_help),
 152         .align  = __alignof__(struct nf_conn_help),
 153         .id     = NF_CT_EXT_HELPER,
 154 };
 155
 156 int nf_conntrack_helper_init()
 157 {
 158         return nf_ct_extend_register(&helper_extend);
 159 }
 160
 161 void nf_conntrack_helper_fini()
 162 {
 163         nf_ct_extend_unregister(&helper_extend);
 164 }