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("iptables REDIRECT target module");
  27
  28 /* FIXME: Take multiple ranges --RR */
  29 static bool
  30 redirect_check(const char *tablename,
  31                const void *e,
  32                const struct xt_target *target,
  33                void *targinfo,
  34                unsigned int hook_mask)
  35 {
  36         const struct nf_nat_multi_range_compat *mr = targinfo;
  37
  38         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  39                 pr_debug("redirect_check: bad MAP_IPS.\n");
  40                 return false;
  41         }
  42         if (mr->rangesize != 1) {
  43                 pr_debug("redirect_check: bad rangesize %u.\n", mr->rangesize);
  44                 return false;
  45         }
  46         return true;
  47 }
  48
  49 static unsigned int
  50 redirect_target(struct sk_buff *skb,
  51                 const struct net_device *in,
  52                 const struct net_device *out,
  53                 unsigned int hooknum,
  54                 const struct xt_target *target,
  55                 const void *targinfo)
  56 {
  57         struct nf_conn *ct;
  58         enum ip_conntrack_info ctinfo;
  59         __be32 newdst;
  60         const struct nf_nat_multi_range_compat *mr = targinfo;
  61         struct nf_nat_range newrange;
  62
  63         NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING
  64                      || hooknum == NF_IP_LOCAL_OUT);
  65
  66         ct = nf_ct_get(skb, &ctinfo);
  67         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  68
  69         /* Local packets: make them go to loopback */
  70         if (hooknum == NF_IP_LOCAL_OUT)
  71                 newdst = htonl(0x7F000001);
  72         else {
  73                 struct in_device *indev;
  74                 struct in_ifaddr *ifa;
  75
  76                 newdst = 0;
  77
  78                 rcu_read_lock();
  79                 indev = __in_dev_get_rcu(skb->dev);
  80                 if (indev && (ifa = indev->ifa_list))
  81                         newdst = ifa->ifa_local;
  82                 rcu_read_unlock();
  83
  84                 if (!newdst)
  85                         return NF_DROP;
  86         }
  87
  88         /* Transfer from original range. */
  89         newrange = ((struct nf_nat_range)
  90                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  91                   newdst, newdst,
  92                   mr->range[0].min, mr->range[0].max });
  93
  94         /* Hand modified range to generic setup. */
  95         return nf_nat_setup_info(ct, &newrange, hooknum);
  96 }
  97
  98 static struct xt_target redirect_reg __read_mostly = {
  99         .name           = "REDIRECT",
 100         .family         = AF_INET,
 101         .target         = redirect_target,
 102         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 103         .table          = "nat",
 104         .hooks          = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT),
 105         .checkentry     = redirect_check,
 106         .me             = THIS_MODULE,
 107 };
 108
 109 static int __init ipt_redirect_init(void)
 110 {
 111         return xt_register_target(&redirect_reg);
 112 }
 113
 114 static void __exit ipt_redirect_fini(void)
 115 {
 116         xt_unregister_target(&redirect_reg);
 117 }
 118
 119 module_init(ipt_redirect_init);
 120 module_exit(ipt_redirect_fini);