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 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 EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
  66
  67 struct nf_conntrack_helper *
  68 __nf_conntrack_helper_find_byname(const char *name)
  69 {
  70         struct nf_conntrack_helper *h;
  71         struct hlist_node *n;
  72         unsigned int i;
  73
  74         for (i = 0; i < nf_ct_helper_hsize; i++) {
  75                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  76                         if (!strcmp(h->name, name))
  77                                 return h;
  78                 }
  79         }
  80         return NULL;
  81 }
  82 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  83
  84 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  85 {
  86         struct nf_conn_help *help;
  87
  88         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  89         if (help)
  90                 INIT_HLIST_HEAD(&help->expectations);
  91         else
  92                 pr_debug("failed to add helper extension area");
  93         return help;
  94 }
  95 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  96
  97 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  98                          const struct nf_conntrack_helper *me)
  99 {
 100         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 101         struct nf_conn_help *help = nfct_help(ct);
 102
 103         if (help && help->helper == me) {
 104                 nf_conntrack_event(IPCT_HELPER, ct);
 105                 rcu_assign_pointer(help->helper, NULL);
 106         }
 107         return 0;
 108 }
 109
 110 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 111 {
 112         unsigned int h = helper_hash(&me->tuple);
 113
 114         BUG_ON(me->expect_policy == NULL);
 115         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 116
 117         mutex_lock(&nf_ct_helper_mutex);
 118         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 119         nf_ct_helper_count++;
 120         mutex_unlock(&nf_ct_helper_mutex);
 121
 122         return 0;
 123 }
 124 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 125
 126 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 127 {
 128         struct nf_conntrack_tuple_hash *h;
 129         struct nf_conntrack_expect *exp;
 130         const struct hlist_node *n, *next;
 131         unsigned int i;
 132
 133         mutex_lock(&nf_ct_helper_mutex);
 134         hlist_del_rcu(&me->hnode);
 135         nf_ct_helper_count--;
 136         mutex_unlock(&nf_ct_helper_mutex);
 137
 138         /* Make sure every nothing is still using the helper unless its a
 139          * connection in the hash.
 140          */
 141         synchronize_rcu();
 142
 143         spin_lock_bh(&nf_conntrack_lock);
 144
 145         /* Get rid of expectations */
 146         for (i = 0; i < nf_ct_expect_hsize; i++) {
 147                 hlist_for_each_entry_safe(exp, n, next,
 148                                           &nf_ct_expect_hash[i], hnode) {
 149                         struct nf_conn_help *help = nfct_help(exp->master);
 150                         if ((help->helper == me || exp->helper == me) &&
 151                             del_timer(&exp->timeout)) {
 152                                 nf_ct_unlink_expect(exp);
 153                                 nf_ct_expect_put(exp);
 154                         }
 155                 }
 156         }
 157
 158         /* Get rid of expecteds, set helpers to NULL. */
 159         hlist_for_each_entry(h, n, &unconfirmed, hnode)
 160                 unhelp(h, me);
 161         for (i = 0; i < nf_conntrack_htable_size; i++) {
 162                 hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
 163                         unhelp(h, me);
 164         }
 165         spin_unlock_bh(&nf_conntrack_lock);
 166 }
 167 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 168
 169 static struct nf_ct_ext_type helper_extend __read_mostly = {
 170         .len    = sizeof(struct nf_conn_help),
 171         .align  = __alignof__(struct nf_conn_help),
 172         .id     = NF_CT_EXT_HELPER,
 173 };
 174
 175 int nf_conntrack_helper_init(void)
 176 {
 177         int err;
 178
 179         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 180         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 181                                                   &nf_ct_helper_vmalloc);
 182         if (!nf_ct_helper_hash)
 183                 return -ENOMEM;
 184
 185         err = nf_ct_extend_register(&helper_extend);
 186         if (err < 0)
 187                 goto err1;
 188
 189         return 0;
 190
 191 err1:
 192         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 193                              nf_ct_helper_hsize);
 194         return err;
 195 }
 196
 197 void nf_conntrack_helper_fini(void)
 198 {
 199         nf_ct_extend_unregister(&helper_extend);
 200         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 201                              nf_ct_helper_hsize);
 202 }