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 #include <net/netfilter/nf_nat_rule.h>
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  26 MODULE_DESCRIPTION("Xtables: Connection redirection to localhost");
  27
  28 /* FIXME: Take multiple ranges --RR */
  29 static bool
  30 redirect_tg_check(const char *tablename, const void *e,
  31                   const struct xt_target *target, void *targinfo,
  32                   unsigned int hook_mask)
  33 {
  34         const struct nf_nat_multi_range_compat *mr = targinfo;
  35
  36         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  37                 pr_debug("redirect_check: bad MAP_IPS.\n");
  38                 return false;
  39         }
  40         if (mr->rangesize != 1) {
  41                 pr_debug("redirect_check: bad rangesize %u.\n", mr->rangesize);
  42                 return false;
  43         }
  44         return true;
  45 }
  46
  47 static unsigned int
  48 redirect_tg(struct sk_buff *skb, const struct net_device *in,
  49             const struct net_device *out, unsigned int hooknum,
  50             const struct xt_target *target, const void *targinfo)
  51 {
  52         struct nf_conn *ct;
  53         enum ip_conntrack_info ctinfo;
  54         __be32 newdst;
  55         const struct nf_nat_multi_range_compat *mr = targinfo;
  56         struct nf_nat_range newrange;
  57
  58         NF_CT_ASSERT(hooknum == NF_INET_PRE_ROUTING
  59                      || hooknum == NF_INET_LOCAL_OUT);
  60
  61         ct = nf_ct_get(skb, &ctinfo);
  62         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  63
  64         /* Local packets: make them go to loopback */
  65         if (hooknum == NF_INET_LOCAL_OUT)
  66                 newdst = htonl(0x7F000001);
  67         else {
  68                 struct in_device *indev;
  69                 struct in_ifaddr *ifa;
  70
  71                 newdst = 0;
  72
  73                 rcu_read_lock();
  74                 indev = __in_dev_get_rcu(skb->dev);
  75                 if (indev && (ifa = indev->ifa_list))
  76                         newdst = ifa->ifa_local;
  77                 rcu_read_unlock();
  78
  79                 if (!newdst)
  80                         return NF_DROP;
  81         }
  82
  83         /* Transfer from original range. */
  84         newrange = ((struct nf_nat_range)
  85                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  86                   newdst, newdst,
  87                   mr->range[0].min, mr->range[0].max });
  88
  89         /* Hand modified range to generic setup. */
  90         return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_DST);
  91 }
  92
  93 static struct xt_target redirect_tg_reg __read_mostly = {
  94         .name           = "REDIRECT",
  95         .family         = AF_INET,
  96         .target         = redirect_tg,
  97         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
  98         .table          = "nat",
  99         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
 100         .checkentry     = redirect_tg_check,
 101         .me             = THIS_MODULE,
 102 };
 103
 104 static int __init redirect_tg_init(void)
 105 {
 106         return xt_register_target(&redirect_tg_reg);
 107 }
 108
 109 static void __exit redirect_tg_exit(void)
 110 {
 111         xt_unregister_target(&redirect_tg_reg);
 112 }
 113
 114 module_init(redirect_tg_init);
 115 module_exit(redirect_tg_exit);