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
  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 void *matchinfo,
  46       int offset,
  47       unsigned int protoff,
  48       int *hotdrop)
  49 {
  50         const struct xt_helper_info *info = matchinfo;
  51         struct ip_conntrack *ct;
  52         enum ip_conntrack_info ctinfo;
  53         int ret = info->invert;
  54
  55         ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
  56         if (!ct) {
  57                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
  58                 return ret;
  59         }
  60
  61         if (!ct->master) {
  62                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
  63                 return ret;
  64         }
  65
  66         read_lock_bh(&ip_conntrack_lock);
  67         if (!ct->master->helper) {
  68                 DEBUGP("xt_helper: master ct %p has no helper\n",
  69                         exp->expectant);
  70                 goto out_unlock;
  71         }
  72
  73         DEBUGP("master's name = %s , info->name = %s\n",
  74                 ct->master->helper->name, info->name);
  75
  76         if (info->name[0] == '\0')
  77                 ret ^= 1;
  78         else
  79                 ret ^= !strncmp(ct->master->helper->name, info->name,
  80                                 strlen(ct->master->helper->name));
  81 out_unlock:
  82         read_unlock_bh(&ip_conntrack_lock);
  83         return ret;
  84 }
  85
  86 #else /* CONFIG_IP_NF_CONNTRACK */
  87
  88 static int
  89 match(const struct sk_buff *skb,
  90       const struct net_device *in,
  91       const struct net_device *out,
  92       const void *matchinfo,
  93       int offset,
  94       unsigned int protoff,
  95       int *hotdrop)
  96 {
  97         const struct xt_helper_info *info = matchinfo;
  98         struct nf_conn *ct;
  99         enum ip_conntrack_info ctinfo;
 100         int ret = info->invert;
 101
 102         ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
 103         if (!ct) {
 104                 DEBUGP("xt_helper: Eek! invalid conntrack?\n");
 105                 return ret;
 106         }
 107
 108         if (!ct->master) {
 109                 DEBUGP("xt_helper: conntrack %p has no master\n", ct);
 110                 return ret;
 111         }
 112
 113         read_lock_bh(&nf_conntrack_lock);
 114         if (!ct->master->helper) {
 115                 DEBUGP("xt_helper: master ct %p has no helper\n",
 116                         exp->expectant);
 117                 goto out_unlock;
 118         }
 119
 120         DEBUGP("master's name = %s , info->name = %s\n",
 121                 ct->master->helper->name, info->name);
 122
 123         if (info->name[0] == '\0')
 124                 ret ^= 1;
 125         else
 126                 ret ^= !strncmp(ct->master->helper->name, info->name,
 127                                 strlen(ct->master->helper->name));
 128 out_unlock:
 129         read_unlock_bh(&nf_conntrack_lock);
 130         return ret;
 131 }
 132 #endif
 133
 134 static int check(const char *tablename,
 135                  const void *inf,
 136                  void *matchinfo,
 137                  unsigned int matchsize,
 138                  unsigned int hook_mask)
 139 {
 140         struct xt_helper_info *info = matchinfo;
 141
 142         info->name[29] = '\0';
 143
 144         /* verify size */
 145         if (matchsize != XT_ALIGN(sizeof(struct xt_helper_info)))
 146                 return 0;
 147
 148         return 1;
 149 }
 150
 151 static struct xt_match helper_match = {
 152         .name           = "helper",
 153         .match          = &match,
 154         .checkentry     = &check,
 155         .me             = THIS_MODULE,
 156 };
 157 static struct xt_match helper6_match = {
 158         .name           = "helper",
 159         .match          = &match,
 160         .checkentry     = &check,
 161         .me             = THIS_MODULE,
 162 };
 163
 164 static int __init init(void)
 165 {
 166         int ret;
 167         need_conntrack();
 168
 169         ret = xt_register_match(AF_INET, &helper_match);
 170         if (ret < 0)
 171                 return ret;
 172
 173         ret = xt_register_match(AF_INET6, &helper6_match);
 174         if (ret < 0)
 175                 xt_unregister_match(AF_INET, &helper_match);
 176
 177         return ret;
 178 }
 179
 180 static void __exit fini(void)
 181 {
 182         xt_unregister_match(AF_INET, &helper_match);
 183         xt_unregister_match(AF_INET6, &helper6_match);
 184 }
 185
 186 module_init(init);
 187 module_exit(fini);
 188