LXR linux/net/ipv4/netfilter/ipt

   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
  24MODULE_LICENSE("GPL");
  25MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  26MODULE_DESCRIPTION("Xtables: Connection redirection to localhost");
  27
  28/* FIXME: Take multiple ranges --RR */
  29static 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
  44static unsigned int
  45redirect_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
  88static 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
  99static int __init redirect_tg_init(void)
 100{
 101        return xt_register_target(&redirect_tg_reg);
 102}
 103
 104static void __exit redirect_tg_exit(void)
 105{
 106        xt_unregister_target(&redirect_tg_reg);
 107}
 108
 109module_init(redirect_tg_init);
 110module_exit(redirect_tg_exit);
 111