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) 2002-2006 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 #ifdef CONFIG_NF_NAT_NEEDED
  22 #include <net/netfilter/nf_nat_rule.h>
  23 #else
  24 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  25 #endif
  26
  27 MODULE_LICENSE("GPL");
  28 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  29 MODULE_DESCRIPTION("iptables REDIRECT target module");
  30
  31 #if 0
  32 #define DEBUGP printk
  33 #else
  34 #define DEBUGP(format, args...)
  35 #endif
  36
  37 /* FIXME: Take multiple ranges --RR */
  38 static int
  39 redirect_check(const char *tablename,
  40                const void *e,
  41                const struct xt_target *target,
  42                void *targinfo,
  43                unsigned int hook_mask)
  44 {
  45         const struct ip_nat_multi_range_compat *mr = targinfo;
  46
  47         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  48                 DEBUGP("redirect_check: bad MAP_IPS.\n");
  49                 return 0;
  50         }
  51         if (mr->rangesize != 1) {
  52                 DEBUGP("redirect_check: bad rangesize %u.\n", mr->rangesize);
  53                 return 0;
  54         }
  55         return 1;
  56 }
  57
  58 static unsigned int
  59 redirect_target(struct sk_buff **pskb,
  60                 const struct net_device *in,
  61                 const struct net_device *out,
  62                 unsigned int hooknum,
  63                 const struct xt_target *target,
  64                 const void *targinfo)
  65 {
  66         struct ip_conntrack *ct;
  67         enum ip_conntrack_info ctinfo;
  68         __be32 newdst;
  69         const struct ip_nat_multi_range_compat *mr = targinfo;
  70         struct ip_nat_range newrange;
  71
  72         IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
  73                      || hooknum == NF_IP_LOCAL_OUT);
  74
  75         ct = ip_conntrack_get(*pskb, &ctinfo);
  76         IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  77
  78         /* Local packets: make them go to loopback */
  79         if (hooknum == NF_IP_LOCAL_OUT)
  80                 newdst = htonl(0x7F000001);
  81         else {
  82                 struct in_device *indev;
  83                 struct in_ifaddr *ifa;
  84
  85                 newdst = 0;
  86
  87                 rcu_read_lock();
  88                 indev = __in_dev_get_rcu((*pskb)->dev);
  89                 if (indev && (ifa = indev->ifa_list))
  90                         newdst = ifa->ifa_local;
  91                 rcu_read_unlock();
  92
  93                 if (!newdst)
  94                         return NF_DROP;
  95         }
  96
  97         /* Transfer from original range. */
  98         newrange = ((struct ip_nat_range)
  99                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
 100                   newdst, newdst,
 101                   mr->range[0].min, mr->range[0].max });
 102
 103         /* Hand modified range to generic setup. */
 104         return ip_nat_setup_info(ct, &newrange, hooknum);
 105 }
 106
 107 static struct ipt_target redirect_reg = {
 108         .name           = "REDIRECT",
 109         .target         = redirect_target,
 110         .targetsize     = sizeof(struct ip_nat_multi_range_compat),
 111         .table          = "nat",
 112         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 113         .checkentry     = redirect_check,
 114         .me             = THIS_MODULE,
 115 };
 116
 117 static int __init ipt_redirect_init(void)
 118 {
 119         return ipt_register_target(&redirect_reg);
 120 }
 121
 122 static void __exit ipt_redirect_fini(void)
 123 {
 124         ipt_unregister_target(&redirect_reg);
 125 }
 126
 127 module_init(ipt_redirect_init);
 128 module_exit(ipt_redirect_fini);