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 #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 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 EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
  67
  68 struct nf_conntrack_helper *
  69 __nf_conntrack_helper_find_byname(const char *name)
  70 {
  71         struct nf_conntrack_helper *h;
  72         struct hlist_node *n;
  73         unsigned int i;
  74
  75         for (i = 0; i < nf_ct_helper_hsize; i++) {
  76                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  77                         if (!strcmp(h->name, name))
  78                                 return h;
  79                 }
  80         }
  81         return NULL;
  82 }
  83 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  84
  85 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  86 {
  87         struct nf_conn_help *help;
  88
  89         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  90         if (help)
  91                 INIT_HLIST_HEAD(&help->expectations);
  92         else
  93                 pr_debug("failed to add helper extension area");
  94         return help;
  95 }
  96 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  97
  98 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  99                          const struct nf_conntrack_helper *me)
 100 {
 101         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 102         struct nf_conn_help *help = nfct_help(ct);
 103
 104         if (help && help->helper == me) {
 105                 nf_conntrack_event(IPCT_HELPER, ct);
 106                 rcu_assign_pointer(help->helper, NULL);
 107         }
 108         return 0;
 109 }
 110
 111 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 112 {
 113         unsigned int h = helper_hash(&me->tuple);
 114
 115         BUG_ON(me->expect_policy == NULL);
 116         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 117
 118         mutex_lock(&nf_ct_helper_mutex);
 119         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 120         nf_ct_helper_count++;
 121         mutex_unlock(&nf_ct_helper_mutex);
 122
 123         return 0;
 124 }
 125 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 126
 127 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 128                                              struct net *net)
 129 {
 130         struct nf_conntrack_tuple_hash *h;
 131         struct nf_conntrack_expect *exp;
 132         const struct hlist_node *n, *next;
 133         unsigned int i;
 134
 135         /* Get rid of expectations */
 136         for (i = 0; i < nf_ct_expect_hsize; i++) {
 137                 hlist_for_each_entry_safe(exp, n, next,
 138                                           &net->ct.expect_hash[i], hnode) {
 139                         struct nf_conn_help *help = nfct_help(exp->master);
 140                         if ((help->helper == me || exp->helper == me) &&
 141                             del_timer(&exp->timeout)) {
 142                                 nf_ct_unlink_expect(exp);
 143                                 nf_ct_expect_put(exp);
 144                         }
 145                 }
 146         }
 147
 148         /* Get rid of expecteds, set helpers to NULL. */
 149         hlist_for_each_entry(h, n, &net->ct.unconfirmed, hnode)
 150                 unhelp(h, me);
 151         for (i = 0; i < nf_conntrack_htable_size; i++) {
 152                 hlist_for_each_entry(h, n, &net->ct.hash[i], hnode)
 153                         unhelp(h, me);
 154         }
 155 }
 156
 157 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 158 {
 159         struct net *net;
 160
 161         mutex_lock(&nf_ct_helper_mutex);
 162         hlist_del_rcu(&me->hnode);
 163         nf_ct_helper_count--;
 164         mutex_unlock(&nf_ct_helper_mutex);
 165
 166         /* Make sure every nothing is still using the helper unless its a
 167          * connection in the hash.
 168          */
 169         synchronize_rcu();
 170
 171         rtnl_lock();
 172         spin_lock_bh(&nf_conntrack_lock);
 173         for_each_net(net)
 174                 __nf_conntrack_helper_unregister(me, net);
 175         spin_unlock_bh(&nf_conntrack_lock);
 176         rtnl_unlock();
 177 }
 178 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 179
 180 static struct nf_ct_ext_type helper_extend __read_mostly = {
 181         .len    = sizeof(struct nf_conn_help),
 182         .align  = __alignof__(struct nf_conn_help),
 183         .id     = NF_CT_EXT_HELPER,
 184 };
 185
 186 int nf_conntrack_helper_init(void)
 187 {
 188         int err;
 189
 190         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 191         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 192                                                   &nf_ct_helper_vmalloc);
 193         if (!nf_ct_helper_hash)
 194                 return -ENOMEM;
 195
 196         err = nf_ct_extend_register(&helper_extend);
 197         if (err < 0)
 198                 goto err1;
 199
 200         return 0;
 201
 202 err1:
 203         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 204                              nf_ct_helper_hsize);
 205         return err;
 206 }
 207
 208 void nf_conntrack_helper_fini(void)
 209 {
 210         nf_ct_extend_unregister(&helper_extend);
 211         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 212                              nf_ct_helper_hsize);
 213 }