net/ipv4/netfilter/ipt_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 #include <linux/netfilter_ipv4/ip_conntrack.h>
  17 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  18 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  19 #include <linux/netfilter_ipv4/ip_tables.h>
  20 #include <linux/netfilter_ipv4/ipt_helper.h>
  21
  22 MODULE_LICENSE("GPL");
  23 MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
  24 MODULE_DESCRIPTION("iptables helper match module");
  25
  26 #if 0
  27 #define DEBUGP printk
  28 #else
  29 #define DEBUGP(format, args...)
  30 #endif
  31
  32 static int
  33 match(const struct sk_buff *skb,
  34       const struct net_device *in,
  35       const struct net_device *out,
  36       const void *matchinfo,
  37       int offset,
  38       int *hotdrop)
  39 {
  40         const struct ipt_helper_info *info = matchinfo;
  41         struct ip_conntrack *ct;
  42         enum ip_conntrack_info ctinfo;
  43         int ret = info->invert;
  44
  45         ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
  46         if (!ct) {
  47                 DEBUGP("ipt_helper: Eek! invalid conntrack?\n");
  48                 return ret;
  49         }
  50
  51         if (!ct->master) {
  52                 DEBUGP("ipt_helper: conntrack %p has no master\n", ct);
  53                 return ret;
  54         }
  55
  56         READ_LOCK(&ip_conntrack_lock);
  57         if (!ct->master->helper) {
  58                 DEBUGP("ipt_helper: master ct %p has no helper\n",
  59                         exp->expectant);
  60                 goto out_unlock;
  61         }
  62
  63         DEBUGP("master's name = %s , info->name = %s\n",
  64                 ct->master->helper->name, info->name);
  65
  66         if (info->name[0] == '\0')
  67                 ret ^= 1;
  68         else
  69                 ret ^= !strncmp(ct->master->helper->name, info->name,
  70                                 strlen(ct->master->helper->name));
  71 out_unlock:
  72         READ_UNLOCK(&ip_conntrack_lock);
  73         return ret;
  74 }
  75
  76 static int check(const char *tablename,
  77                  const struct ipt_ip *ip,
  78                  void *matchinfo,
  79                  unsigned int matchsize,
  80                  unsigned int hook_mask)
  81 {
  82         struct ipt_helper_info *info = matchinfo;
  83
  84         info->name[29] = '\0';
  85
  86         /* verify size */
  87         if (matchsize != IPT_ALIGN(sizeof(struct ipt_helper_info)))
  88                 return 0;
  89
  90         return 1;
  91 }
  92
  93 static struct ipt_match helper_match = {
  94         .name           = "helper",
  95         .match          = &match,
  96         .checkentry     = &check,
  97         .me             = THIS_MODULE,
  98 };
  99
 100 static int __init init(void)
 101 {
 102         need_ip_conntrack();
 103         return ipt_register_match(&helper_match);
 104 }
 105
 106 static void __exit fini(void)
 107 {
 108         ipt_unregister_match(&helper_match);
 109 }
 110
 111 module_init(init);
 112 module_exit(fini);
 113