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("iptables REDIRECT target module");
  27
  28/* FIXME: Take multiple ranges --RR */
  29static bool
  30redirect_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
  49static unsigned int
  50redirect_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
  98static 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
 109static int __init ipt_redirect_init(void)
 110{
 111        return xt_register_target(&redirect_reg);
 112}
 113
 114static void __exit ipt_redirect_fini(void)
 115{
 116        xt_unregister_target(&redirect_reg);
 117}
 118
 119module_init(ipt_redirect_init);
 120module_exit(ipt_redirect_fini);
 121