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 DEFINE_MUTEX(nf_ct_helper_mutex);
  32 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  33 static unsigned int nf_ct_helper_hsize __read_mostly;
  34 static unsigned int nf_ct_helper_count __read_mostly;
  35 static int nf_ct_helper_vmalloc;
  36
  37
  38 /* Stupid hash, but collision free for the default registrations of the
  39  * helpers currently in the kernel. */
  40 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  41 {
  42         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  43                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  44 }
  45
  46 struct nf_conntrack_helper *
  47 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  48 {
  49         struct nf_conntrack_helper *helper;
  50         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  51         struct hlist_node *n;
  52         unsigned int h;
  53
  54         if (!nf_ct_helper_count)
  55                 return NULL;
  56
  57         h = helper_hash(tuple);
  58         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
  59                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  60                         return helper;
  61         }
  62         return NULL;
  63 }
  64 EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
  65
  66 struct nf_conntrack_helper *
  67 __nf_conntrack_helper_find_byname(const char *name)
  68 {
  69         struct nf_conntrack_helper *h;
  70         struct hlist_node *n;
  71         unsigned int i;
  72
  73         for (i = 0; i < nf_ct_helper_hsize; i++) {
  74                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  75                         if (!strcmp(h->name, name))
  76                                 return h;
  77                 }
  78         }
  79         return NULL;
  80 }
  81 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
  82
  83 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
  84 {
  85         struct nf_conn_help *help;
  86
  87         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
  88         if (help)
  89                 INIT_HLIST_HEAD(&help->expectations);
  90         else
  91                 pr_debug("failed to add helper extension area");
  92         return help;
  93 }
  94 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
  95
  96 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
  97                          const struct nf_conntrack_helper *me)
  98 {
  99         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 100         struct nf_conn_help *help = nfct_help(ct);
 101
 102         if (help && help->helper == me) {
 103                 nf_conntrack_event(IPCT_HELPER, ct);
 104                 rcu_assign_pointer(help->helper, NULL);
 105         }
 106         return 0;
 107 }
 108
 109 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 110 {
 111         unsigned int h = helper_hash(&me->tuple);
 112
 113         BUG_ON(me->timeout == 0);
 114
 115         mutex_lock(&nf_ct_helper_mutex);
 116         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 117         nf_ct_helper_count++;
 118         mutex_unlock(&nf_ct_helper_mutex);
 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         struct nf_conntrack_tuple_hash *h;
 127         struct nf_conntrack_expect *exp;
 128         struct hlist_node *n, *next;
 129         unsigned int i;
 130
 131         mutex_lock(&nf_ct_helper_mutex);
 132         hlist_del_rcu(&me->hnode);
 133         nf_ct_helper_count--;
 134         mutex_unlock(&nf_ct_helper_mutex);
 135
 136         /* Make sure every nothing is still using the helper unless its a
 137          * connection in the hash.
 138          */
 139         synchronize_rcu();
 140
 141         spin_lock_bh(&nf_conntrack_lock);
 142
 143         /* Get rid of expectations */
 144         for (i = 0; i < nf_ct_expect_hsize; i++) {
 145                 hlist_for_each_entry_safe(exp, n, next,
 146                                           &nf_ct_expect_hash[i], hnode) {
 147                         struct nf_conn_help *help = nfct_help(exp->master);
 148                         if ((help->helper == me || exp->helper == me) &&
 149                             del_timer(&exp->timeout)) {
 150                                 nf_ct_unlink_expect(exp);
 151                                 nf_ct_expect_put(exp);
 152                         }
 153                 }
 154         }
 155
 156         /* Get rid of expecteds, set helpers to NULL. */
 157         hlist_for_each_entry(h, n, &unconfirmed, hnode)
 158                 unhelp(h, me);
 159         for (i = 0; i < nf_conntrack_htable_size; i++) {
 160                 hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
 161                         unhelp(h, me);
 162         }
 163         spin_unlock_bh(&nf_conntrack_lock);
 164 }
 165 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 166
 167 static struct nf_ct_ext_type helper_extend __read_mostly = {
 168         .len    = sizeof(struct nf_conn_help),
 169         .align  = __alignof__(struct nf_conn_help),
 170         .id     = NF_CT_EXT_HELPER,
 171 };
 172
 173 int nf_conntrack_helper_init(void)
 174 {
 175         int err;
 176
 177         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 178         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
 179                                                   &nf_ct_helper_vmalloc);
 180         if (!nf_ct_helper_hash)
 181                 return -ENOMEM;
 182
 183         err = nf_ct_extend_register(&helper_extend);
 184         if (err < 0)
 185                 goto err1;
 186
 187         return 0;
 188
 189 err1:
 190         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 191                              nf_ct_helper_hsize);
 192         return err;
 193 }
 194
 195 void nf_conntrack_helper_fini(void)
 196 {
 197         nf_ct_extend_unregister(&helper_extend);
 198         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
 199                              nf_ct_helper_hsize);
 200 }