net/netfilter/xt_helper.c

   1 /* iptables module to match on related connections */
   2 /*
   3  * (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  *   19 Mar 2002 Harald Welte <laforge@gnumonks.org>:
  10  *               - Port to newnat infrastructure
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/netfilter.h>
  16 #if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
  17 #include <linux/netfilter_ipv4/ip_conntrack.h>
  18 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  19 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  20 #else
  21 #include <net/netfilter/nf_conntrack.h>
  22 #include <net/netfilter/nf_conntrack_core.h>
  23 #include <net/netfilter/nf_conntrack_helper.h>
  24 #endif
  25 #include <linux/netfilter/x_tables.h>
  26 #include <linux/netfilter/xt_helper.h>
  27 #include <net/netfilter/nf_conntrack_compat.h>
  28
  29 MODULE_LICENSE("GPL");
  30 MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
  31 MODULE_DESCRIPTION("iptables helper match module");
  32 MODULE_ALIAS("ipt_helper");
  33 MODULE_ALIAS("ip6t_helper");
  34
  35 #if 0
  36 #define DEBUGP printk
  37 #else
  38 #define DEBUGP(format, args...)
  39 #endif
  40
  41 #if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
  42 static int
  43 match(const struct sk_buff *skb,
  44       const struct net_device *in,
  45       const struct net_device *out,
  46       const struct xt_match *match,
  47       const void *matchinfo,
  48       int offset,
  49       unsigned int protoff,
  50       int *hotdrop)
  51 {
  52         const struct xt_helper_info *info = matchinfo;
  53         struct ip_conntrack *ct;
  54         enum ip_conntrack_info ctinfo;
  55         int ret = info->invert;
  56
  57         ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
  58         if (!ct) {
  59                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
  60                 return ret;
  61         }
  62
  63         if (!ct->master) {
  64                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
  65                 return ret;
  66         }
  67
  68         read_lock_bh(&ip_conntrack_lock);
  69         if (!ct->master->helper) {
  70                 DEBUGP("xt_helper: master ct %p has no helper\n",
  71                         exp->expectant);
  72                 goto out_unlock;
  73         }
  74
  75         DEBUGP("master's name = %s , info->name = %s\n",
  76                 ct->master->helper->name, info->name);
  77
  78         if (info->name[0] == '\0')
  79                 ret ^= 1;
  80         else
  81                 ret ^= !strncmp(ct->master->helper->name, info->name,
  82                                 strlen(ct->master->helper->name));
  83 out_unlock:
  84         read_unlock_bh(&ip_conntrack_lock);
  85         return ret;
  86 }
  87
  88 #else /* CONFIG_IP_NF_CONNTRACK */
  89
  90 static int
  91 match(const struct sk_buff *skb,
  92       const struct net_device *in,
  93       const struct net_device *out,
  94       const struct xt_match *match,
  95       const void *matchinfo,
  96       int offset,
  97       unsigned int protoff,
  98       int *hotdrop)
  99 {
 100         const struct xt_helper_info *info = matchinfo;
 101         struct nf_conn *ct;
 102         struct nf_conn_help *master_help;
 103         enum ip_conntrack_info ctinfo;
 104         int ret = info->invert;
 105
 106         ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
 107         if (!ct) {
 108                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
 109                 return ret;
 110         }
 111
 112         if (!ct->master) {
 113                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
 114                 return ret;
 115         }
 116
 117         read_lock_bh(&nf_conntrack_lock);
 118         master_help = nfct_help(ct->master);
 119         if (!master_help || !master_help->helper) {
 120                 DEBUGP("xt_helper: master ct %p has no helper\n",
 121                         exp->expectant);
 122                 goto out_unlock;
 123         }
 124
 125         DEBUGP("master's name = %s , info->name = %s\n",
 126                 ct->master->helper->name, info->name);
 127
 128         if (info->name[0] == '\0')
 129                 ret ^= 1;
 130         else
 131                 ret ^= !strncmp(master_help->helper->name, info->name,
 132                                 strlen(master_help->helper->name));
 133 out_unlock:
 134         read_unlock_bh(&nf_conntrack_lock);
 135         return ret;
 136 }
 137 #endif
 138
 139 static int check(const char *tablename,
 140                  const void *inf,
 141                  const struct xt_match *match,
 142                  void *matchinfo,
 143                  unsigned int hook_mask)
 144 {
 145         struct xt_helper_info *info = matchinfo;
 146
 147         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 148                 printk(KERN_WARNING "can't load conntrack support for "
 149                                     "proto=%d\n", match->family);
 150                 return 0;
 151         }
 152         info->name[29] = '\0';
 153         return 1;
 154 }
 155
 156 static void
 157 destroy(const struct xt_match *match, void *matchinfo)
 158 {
 159         nf_ct_l3proto_module_put(match->family);
 160 }
 161
 162 static struct xt_match xt_helper_match[] = {
 163         {
 164                 .name           = "helper",
 165                 .family         = AF_INET,
 166                 .checkentry     = check,
 167                 .match          = match,
 168                 .destroy        = destroy,
 169                 .matchsize      = sizeof(struct xt_helper_info),
 170                 .me             = THIS_MODULE,
 171         },
 172         {
 173                 .name           = "helper",
 174                 .family         = AF_INET6,
 175                 .checkentry     = check,
 176                 .match          = match,
 177                 .destroy        = destroy,
 178                 .matchsize      = sizeof(struct xt_helper_info),
 179                 .me             = THIS_MODULE,
 180         },
 181 };
 182
 183 static int __init xt_helper_init(void)
 184 {
 185         return xt_register_matches(xt_helper_match,
 186                                    ARRAY_SIZE(xt_helper_match));
 187 }
 188
 189 static void __exit xt_helper_fini(void)
 190 {
 191         xt_unregister_matches(xt_helper_match, ARRAY_SIZE(xt_helper_match));
 192 }
 193
 194 module_init(xt_helper_init);
 195 module_exit(xt_helper_fini);
 196