net/ipv4/netfilter/ipt_REDIRECT.c

   1 /* Redirect.  Simple mapping which alters dst to a local IP address. */
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   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
  10 #include <linux/types.h>
  11 #include <linux/ip.h>
  12 #include <linux/timer.h>
  13 #include <linux/module.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netdevice.h>
  16 #include <linux/if.h>
  17 #include <linux/inetdevice.h>
  18 #include <net/protocol.h>
  19 #include <net/checksum.h>
  20 #include <linux/netfilter_ipv4.h>
  21 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  25 MODULE_DESCRIPTION("iptables REDIRECT target module");
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(format, args...)
  31 #endif
  32
  33 /* FIXME: Take multiple ranges --RR */
  34 static int
  35 redirect_check(const char *tablename,
  36                const void *e,
  37                const struct xt_target *target,
  38                void *targinfo,
  39                unsigned int targinfosize,
  40                unsigned int hook_mask)
  41 {
  42         const struct ip_nat_multi_range_compat *mr = targinfo;
  43
  44         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  45                 DEBUGP("redirect_check: bad MAP_IPS.\n");
  46                 return 0;
  47         }
  48         if (mr->rangesize != 1) {
  49                 DEBUGP("redirect_check: bad rangesize %u.\n", mr->rangesize);
  50                 return 0;
  51         }
  52         return 1;
  53 }
  54
  55 static unsigned int
  56 redirect_target(struct sk_buff **pskb,
  57                 const struct net_device *in,
  58                 const struct net_device *out,
  59                 unsigned int hooknum,
  60                 const struct xt_target *target,
  61                 const void *targinfo,
  62                 void *userinfo)
  63 {
  64         struct ip_conntrack *ct;
  65         enum ip_conntrack_info ctinfo;
  66         u_int32_t newdst;
  67         const struct ip_nat_multi_range_compat *mr = targinfo;
  68         struct ip_nat_range newrange;
  69
  70         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
  71                      || hooknum == NF_IP_LOCAL_OUT);
  72
  73         ct = ip_conntrack_get(*pskb, &ctinfo);
  74         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  75
  76         /* Local packets: make them go to loopback */
  77         if (hooknum == NF_IP_LOCAL_OUT)
  78                 newdst = htonl(0x7F000001);
  79         else {
  80                 struct in_device *indev;
  81                 struct in_ifaddr *ifa;
  82
  83                 newdst = 0;
  84
  85                 rcu_read_lock();
  86                 indev = __in_dev_get_rcu((*pskb)->dev);
  87                 if (indev && (ifa = indev->ifa_list))
  88                         newdst = ifa->ifa_local;
  89                 rcu_read_unlock();
  90
  91                 if (!newdst)
  92                         return NF_DROP;
  93         }
  94
  95         /* Transfer from original range. */
  96         newrange = ((struct ip_nat_range)
  97                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  98                   newdst, newdst,
  99                   mr->range[0].min, mr->range[0].max });
 100
 101         /* Hand modified range to generic setup. */
 102         return ip_nat_setup_info(ct, &newrange, hooknum);
 103 }
 104
 105 static struct ipt_target redirect_reg = {
 106         .name           = "REDIRECT",
 107         .target         = redirect_target,
 108         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 109         .table          = "nat",
 110         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 111         .checkentry     = redirect_check,
 112         .me             = THIS_MODULE,
 113 };
 114
 115 static int __init init(void)
 116 {
 117         return ipt_register_target(&redirect_reg);
 118 }
 119
 120 static void __exit fini(void)
 121 {
 122         ipt_unregister_target(&redirect_reg);
 123 }
 124
 125 module_init(init);
 126 module_exit(fini);