kernel/2.6.29.6-aldebaran-rt/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 redirect_tg_check(const struct xt_tgchk_param *par)
  30 {
  31         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  32
  33         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  34                 pr_debug("redirect_check: bad MAP_IPS.\n");
  35                 return false;
  36         }
  37         if (mr->rangesize != 1) {
  38                 pr_debug("redirect_check: bad rangesize %u.\n", mr->rangesize);
  39                 return false;
  40         }
  41         return true;
  42 }
  43
  44 static unsigned int
  45 redirect_tg(struct sk_buff *skb, const struct xt_target_param *par)
  46 {
  47         struct nf_conn *ct;
  48         enum ip_conntrack_info ctinfo;
  49         __be32 newdst;
  50         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  51         struct nf_nat_range newrange;
  52
  53         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
  54                      par->hooknum == NF_INET_LOCAL_OUT);
  55
  56         ct = nf_ct_get(skb, &ctinfo);
  57         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
  58
  59         /* Local packets: make them go to loopback */
  60         if (par->hooknum == NF_INET_LOCAL_OUT)
  61                 newdst = htonl(0x7F000001);
  62         else {
  63                 struct in_device *indev;
  64                 struct in_ifaddr *ifa;
  65
  66                 newdst = 0;
  67
  68                 rcu_read_lock();
  69                 indev = __in_dev_get_rcu(skb->dev);
  70                 if (indev && (ifa = indev->ifa_list))
  71                         newdst = ifa->ifa_local;
  72                 rcu_read_unlock();
  73
  74                 if (!newdst)
  75                         return NF_DROP;
  76         }
  77
  78         /* Transfer from original range. */
  79         newrange = ((struct nf_nat_range)
  80                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  81                   newdst, newdst,
  82                   mr->range[0].min, mr->range[0].max });
  83
  84         /* Hand modified range to generic setup. */
  85         return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_DST);
  86 }
  87
  88 static struct xt_target redirect_tg_reg __read_mostly = {
  89         .name           = "REDIRECT",
  90         .family         = NFPROTO_IPV4,
  91         .target         = redirect_tg,
  92         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
  93         .table          = "nat",
  94         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
  95         .checkentry     = redirect_tg_check,
  96         .me             = THIS_MODULE,
  97 };
  98
  99 static int __init redirect_tg_init(void)
 100 {
 101         return xt_register_target(&redirect_tg_reg);
 102 }
 103
 104 static void __exit redirect_tg_exit(void)
 105 {
 106         xt_unregister_target(&redirect_tg_reg);
 107 }
 108
 109 module_init(redirect_tg_init);
 110 module_exit(redirect_tg_exit);