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   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
  28 MODULE_LICENSE("GPL");
  29 MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
  30 MODULE_DESCRIPTION("iptables helper match module");
  31 MODULE_ALIAS("ipt_helper");
  32 MODULE_ALIAS("ip6t_helper");
  33
  34 #if 0
  35 #define DEBUGP printk
  36 #else
  37 #define DEBUGP(format, args...)
  38 #endif
  39
  40 #if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
  41 static int
  42 match(const struct sk_buff *skb,
  43       const struct net_device *in,
  44       const struct net_device *out,
  45       const struct xt_match *match,
  46       const void *matchinfo,
  47       int offset,
  48       unsigned int protoff,
  49       int *hotdrop)
  50 {
  51         const struct xt_helper_info *info = matchinfo;
  52         struct ip_conntrack *ct;
  53         enum ip_conntrack_info ctinfo;
  54         int ret = info->invert;
  55
  56         ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
  57         if (!ct) {
  58                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
  59                 return ret;
  60         }
  61
  62         if (!ct->master) {
  63                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
  64                 return ret;
  65         }
  66
  67         read_lock_bh(&ip_conntrack_lock);
  68         if (!ct->master->helper) {
  69                 DEBUGP("xt_helper: master ct %p has no helper\n",
  70                         exp->expectant);
  71                 goto out_unlock;
  72         }
  73
  74         DEBUGP("master's name = %s , info->name = %s\n",
  75                 ct->master->helper->name, info->name);
  76
  77         if (info->name[0] == '\0')
  78                 ret ^= 1;
  79         else
  80                 ret ^= !strncmp(ct->master->helper->name, info->name,
  81                                 strlen(ct->master->helper->name));
  82 out_unlock:
  83         read_unlock_bh(&ip_conntrack_lock);
  84         return ret;
  85 }
  86
  87 #else /* CONFIG_IP_NF_CONNTRACK */
  88
  89 static int
  90 match(const struct sk_buff *skb,
  91       const struct net_device *in,
  92       const struct net_device *out,
  93       const struct xt_match *match,
  94       const void *matchinfo,
  95       int offset,
  96       unsigned int protoff,
  97       int *hotdrop)
  98 {
  99         const struct xt_helper_info *info = matchinfo;
 100         struct nf_conn *ct;
 101         struct nf_conn_help *master_help;
 102         enum ip_conntrack_info ctinfo;
 103         int ret = info->invert;
 104
 105         ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
 106         if (!ct) {
 107                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
 108                 return ret;
 109         }
 110
 111         if (!ct->master) {
 112                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
 113                 return ret;
 114         }
 115
 116         read_lock_bh(&nf_conntrack_lock);
 117         master_help = nfct_help(ct->master);
 118         if (!master_help || !master_help->helper) {
 119                 DEBUGP("xt_helper: master ct %p has no helper\n",
 120                         exp->expectant);
 121                 goto out_unlock;
 122         }
 123
 124         DEBUGP("master's name = %s , info->name = %s\n",
 125                 ct->master->helper->name, info->name);
 126
 127         if (info->name[0] == '\0')
 128                 ret ^= 1;
 129         else
 130                 ret ^= !strncmp(master_help->helper->name, info->name,
 131                                 strlen(master_help->helper->name));
 132 out_unlock:
 133         read_unlock_bh(&nf_conntrack_lock);
 134         return ret;
 135 }
 136 #endif
 137
 138 static int check(const char *tablename,
 139                  const void *inf,
 140                  const struct xt_match *match,
 141                  void *matchinfo,
 142                  unsigned int matchsize,
 143                  unsigned int hook_mask)
 144 {
 145         struct xt_helper_info *info = matchinfo;
 146
 147 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 148         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 149                 printk(KERN_WARNING "can't load nf_conntrack support for "
 150                                     "proto=%d\n", match->family);
 151                 return 0;
 152         }
 153 #endif
 154         info->name[29] = '\0';
 155         return 1;
 156 }
 157
 158 static void
 159 destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
 160 {
 161 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 162         nf_ct_l3proto_module_put(match->family);
 163 #endif
 164 }
 165
 166 static struct xt_match xt_helper_match[] = {
 167         {
 168                 .name           = "helper",
 169                 .family         = AF_INET,
 170                 .checkentry     = check,
 171                 .match          = match,
 172                 .destroy        = destroy,
 173                 .matchsize      = sizeof(struct xt_helper_info),
 174                 .me             = THIS_MODULE,
 175         },
 176         {
 177                 .name           = "helper",
 178                 .family         = AF_INET6,
 179                 .checkentry     = check,
 180                 .match          = match,
 181                 .destroy        = destroy,
 182                 .matchsize      = sizeof(struct xt_helper_info),
 183                 .me             = THIS_MODULE,
 184         },
 185 };
 186
 187 static int __init xt_helper_init(void)
 188 {
 189         need_conntrack();
 190         return xt_register_matches(xt_helper_match,
 191                                    ARRAY_SIZE(xt_helper_match));
 192 }
 193
 194 static void __exit xt_helper_fini(void)
 195 {
 196         xt_unregister_matches(xt_helper_match, ARRAY_SIZE(xt_helper_match));
 197 }
 198
 199 module_init(xt_helper_init);
 200 module_exit(xt_helper_fini);
 201