release/src-rt-6.x.4708/linux/linux-2.6.36/net/ipv4/netfilter/ipt_MASQUERADE.c

   1 /* Masquerade.  Simple mapping which alters range to a local IP address
   2    (depending on route). */
   3
   4 /* (C) 1999-2001 Paul `Rusty' Russell
   5  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12 #include <linux/types.h>
  13 #include <linux/inetdevice.h>
  14 #include <linux/ip.h>
  15 #include <linux/timer.h>
  16 #include <linux/module.h>
  17 #include <linux/netfilter.h>
  18 #include <net/protocol.h>
  19 #include <net/ip.h>
  20 #include <net/checksum.h>
  21 #include <net/route.h>
  22 #include <net/netfilter/nf_nat_rule.h>
  23 #include <linux/netfilter_ipv4.h>
  24 #include <linux/netfilter/x_tables.h>
  25
  26 MODULE_LICENSE("GPL");
  27 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  28 MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
  29
  30 static int masquerade_tg_check(const struct xt_tgchk_param *par)
  31 {
  32         const struct nf_nat_multi_range_compat *mr = par->targinfo;
  33
  34         if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
  35                 pr_debug("bad MAP_IPS.\n");
  36                 return -EINVAL;
  37         }
  38         if (mr->rangesize != 1) {
  39                 pr_debug("bad rangesize %u\n", mr->rangesize);
  40                 return -EINVAL;
  41         }
  42         return 0;
  43 }
  44
  45 static unsigned int
  46 masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
  47 {
  48         struct nf_conn *ct;
  49         struct nf_conn_nat *nat;
  50         enum ip_conntrack_info ctinfo;
  51         struct nf_nat_range newrange;
  52         const struct nf_nat_multi_range_compat *mr;
  53         const struct rtable *rt;
  54         __be32 newsrc;
  55
  56         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
  57
  58         ct = nf_ct_get(skb, &ctinfo);
  59         nat = nfct_nat(ct);
  60
  61         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
  62                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
  63
  64 #ifdef CONFIG_IP_NF_TARGET_CONE
  65         /* Mark the connection as cone if we have such rule configured */
  66         nat->nat_type |= (skb->nfcache & NFC_IP_CONE_NAT) ? NFC_IP_CONE_NAT:0;
  67 #endif /* CONFIG_IP_NF_TARGET_CONE */
  68         /* Source address is 0.0.0.0 - locally generated packet that is
  69          * probably not supposed to be masqueraded.
  70          */
  71         if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
  72                 return NF_ACCEPT;
  73
  74         mr = par->targinfo;
  75         rt = skb_rtable(skb);
  76         newsrc = inet_select_addr(par->out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
  77         if (!newsrc) {
  78                 pr_info("%s ate my IP address\n", par->out->name);
  79                 return NF_DROP;
  80         }
  81
  82         nat->masq_index = par->out->ifindex;
  83
  84         /* Transfer from original range. */
  85         newrange = ((struct nf_nat_range)
  86                 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
  87                   newsrc, newsrc,
  88                   mr->range[0].min, mr->range[0].max });
  89
  90         /* Hand modified range to generic setup. */
  91         return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_SRC);
  92 }
  93
  94 static int
  95 device_cmp(struct nf_conn *i, void *ifindex)
  96 {
  97         const struct nf_conn_nat *nat = nfct_nat(i);
  98
  99         if (!nat)
 100                 return 0;
 101
 102         return nat->masq_index == (int)(long)ifindex;
 103 }
 104
 105 static int masq_device_event(struct notifier_block *this,
 106                              unsigned long event,
 107                              void *ptr)
 108 {
 109         const struct net_device *dev = ptr;
 110         struct net *net = dev_net(dev);
 111
 112         if (event == NETDEV_DOWN) {
 113                 /* Device was downed.  Search entire table for
 114                    conntracks which were associated with that device,
 115                    and forget them. */
 116                 NF_CT_ASSERT(dev->ifindex != 0);
 117
 118                 nf_ct_iterate_cleanup(net, device_cmp,
 119                                       (void *)(long)dev->ifindex);
 120         }
 121
 122         return NOTIFY_DONE;
 123 }
 124
 125 static int masq_inet_event(struct notifier_block *this,
 126                            unsigned long event,
 127                            void *ptr)
 128 {
 129         struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
 130         return masq_device_event(this, event, dev);
 131 }
 132
 133 static struct notifier_block masq_dev_notifier = {
 134         .notifier_call  = masq_device_event,
 135 };
 136
 137 static struct notifier_block masq_inet_notifier = {
 138         .notifier_call  = masq_inet_event,
 139 };
 140
 141 static struct xt_target masquerade_tg_reg __read_mostly = {
 142         .name           = "MASQUERADE",
 143         .family         = NFPROTO_IPV4,
 144         .target         = masquerade_tg,
 145         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
 146         .table          = "nat",
 147         .hooks          = 1 << NF_INET_POST_ROUTING,
 148         .checkentry     = masquerade_tg_check,
 149         .me             = THIS_MODULE,
 150 };
 151
 152 static int __init masquerade_tg_init(void)
 153 {
 154         int ret;
 155
 156         ret = xt_register_target(&masquerade_tg_reg);
 157
 158         if (ret == 0) {
 159                 /* Register for device down reports */
 160                 register_netdevice_notifier(&masq_dev_notifier);
 161                 /* Register IP address change reports */
 162                 register_inetaddr_notifier(&masq_inet_notifier);
 163         }
 164
 165         return ret;
 166 }
 167
 168 static void __exit masquerade_tg_exit(void)
 169 {
 170         xt_unregister_target(&masquerade_tg_reg);
 171         unregister_netdevice_notifier(&masq_dev_notifier);
 172         unregister_inetaddr_notifier(&masq_inet_notifier);
 173 }
 174
 175 module_init(masquerade_tg_init);
 176 module_exit(masquerade_tg_exit);