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 hook_mask)
  40 {
  41         const struct ip_nat_multi_range_compat *mr = targinfo;
  42
  43         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  44                 DEBUGP("redirect_check: bad MAP_IPS.\n");
  45                 return 0;
  46         }
  47         if (mr->rangesize != 1) {
  48                 DEBUGP("redirect_check: bad rangesize %u.\n", mr->rangesize);
  49                 return 0;
  50         }
  51         return 1;
  52 }
  53
  54 static unsigned int
  55 redirect_target(struct sk_buff **pskb,
  56                 const struct net_device *in,
  57                 const struct net_device *out,
  58                 unsigned int hooknum,
  59                 const struct xt_target *target,
  60                 const void *targinfo)
  61 {
  62         struct ip_conntrack *ct;
  63         enum ip_conntrack_info ctinfo;
  64         u_int32_t newdst;
  65         const struct ip_nat_multi_range_compat *mr = targinfo;
  66         struct ip_nat_range newrange;
  67
  68         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
  69                      || hooknum == NF_IP_LOCAL_OUT);
  70
  71         ct = ip_conntrack_get(*pskb, &ctinfo);
  72         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  73
  74         /* Local packets: make them go to loopback */
  75         if (hooknum == NF_IP_LOCAL_OUT)
  76                 newdst = htonl(0x7F000001);
  77         else {
  78                 struct in_device *indev;
  79                 struct in_ifaddr *ifa;
  80
  81                 newdst = 0;
  82
  83                 rcu_read_lock();
  84                 indev = __in_dev_get_rcu((*pskb)->dev);
  85                 if (indev && (ifa = indev->ifa_list))
  86                         newdst = ifa->ifa_local;
  87                 rcu_read_unlock();
  88
  89                 if (!newdst)
  90                         return NF_DROP;
  91         }
  92
  93         /* Transfer from original range. */
  94         newrange = ((struct ip_nat_range)
  95                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  96                   newdst, newdst,
  97                   mr->range[0].min, mr->range[0].max });
  98
  99         /* Hand modified range to generic setup. */
 100         return ip_nat_setup_info(ct, &newrange, hooknum);
 101 }
 102
 103 static struct ipt_target redirect_reg = {
 104         .name           = "REDIRECT",
 105         .target         = redirect_target,
 106         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 107         .table          = "nat",
 108         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 109         .checkentry     = redirect_check,
 110         .me             = THIS_MODULE,
 111 };
 112
 113 static int __init ipt_redirect_init(void)
 114 {
 115         return ipt_register_target(&redirect_reg);
 116 }
 117
 118 static void __exit ipt_redirect_fini(void)
 119 {
 120         ipt_unregister_target(&redirect_reg);
 121 }
 122
 123 module_init(ipt_redirect_init);
 124 module_exit(ipt_redirect_fini);