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