net/ipv4/netfilter/iptable_nat.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   3  * (C) 2011 Patrick McHardy <kaber@trash.net>
   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/module.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/netfilter_ipv4.h>
  13 #include <linux/netfilter_ipv4/ip_tables.h>
  14 #include <linux/ip.h>
  15 #include <net/ip.h>
  16
  17 #include <net/netfilter/nf_nat.h>
  18 #include <net/netfilter/nf_nat_core.h>
  19 #include <net/netfilter/nf_nat_l3proto.h>
  20
  21 static int __net_init iptable_nat_table_init(struct net *net);
  22
  23 static const struct xt_table nf_nat_ipv4_table = {
  24         .name           = "nat",
  25         .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
  26                           (1 << NF_INET_POST_ROUTING) |
  27                           (1 << NF_INET_LOCAL_OUT) |
  28                           (1 << NF_INET_LOCAL_IN),
  29         .me             = THIS_MODULE,
  30         .af             = NFPROTO_IPV4,
  31         .table_init     = iptable_nat_table_init,
  32 };
  33
  34 static unsigned int iptable_nat_do_chain(void *priv,
  35                                          struct sk_buff *skb,
  36                                          const struct nf_hook_state *state)
  37 {
  38         return ipt_do_table(skb, state, state->net->ipv4.nat_table);
  39 }
  40
  41 static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
  42         {
  43                 .hook           = iptable_nat_do_chain,
  44                 .pf             = NFPROTO_IPV4,
  45                 .hooknum        = NF_INET_PRE_ROUTING,
  46                 .priority       = NF_IP_PRI_NAT_DST,
  47         },
  48         {
  49                 .hook           = iptable_nat_do_chain,
  50                 .pf             = NFPROTO_IPV4,
  51                 .hooknum        = NF_INET_POST_ROUTING,
  52                 .priority       = NF_IP_PRI_NAT_SRC,
  53         },
  54         {
  55                 .hook           = iptable_nat_do_chain,
  56                 .pf             = NFPROTO_IPV4,
  57                 .hooknum        = NF_INET_LOCAL_OUT,
  58                 .priority       = NF_IP_PRI_NAT_DST,
  59         },
  60         {
  61                 .hook           = iptable_nat_do_chain,
  62                 .pf             = NFPROTO_IPV4,
  63                 .hooknum        = NF_INET_LOCAL_IN,
  64                 .priority       = NF_IP_PRI_NAT_SRC,
  65         },
  66 };
  67
  68 static int ipt_nat_register_lookups(struct net *net)
  69 {
  70         int i, ret;
  71
  72         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
  73                 ret = nf_nat_l3proto_ipv4_register_fn(net, &nf_nat_ipv4_ops[i]);
  74                 if (ret) {
  75                         while (i)
  76                                 nf_nat_l3proto_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[--i]);
  77
  78                         return ret;
  79                 }
  80         }
  81
  82         return 0;
  83 }
  84
  85 static void ipt_nat_unregister_lookups(struct net *net)
  86 {
  87         int i;
  88
  89         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
  90                 nf_nat_l3proto_ipv4_unregister_fn(net, &nf_nat_ipv4_ops[i]);
  91 }
  92
  93 static int __net_init iptable_nat_table_init(struct net *net)
  94 {
  95         struct ipt_replace *repl;
  96         int ret;
  97
  98         if (net->ipv4.nat_table)
  99                 return 0;
 100
 101         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 102         if (repl == NULL)
 103                 return -ENOMEM;
 104         ret = ipt_register_table(net, &nf_nat_ipv4_table, repl,
 105                                  NULL, &net->ipv4.nat_table);
 106         if (ret < 0) {
 107                 kfree(repl);
 108                 return ret;
 109         }
 110
 111         ret = ipt_nat_register_lookups(net);
 112         if (ret < 0) {
 113                 ipt_unregister_table(net, net->ipv4.nat_table, NULL);
 114                 net->ipv4.nat_table = NULL;
 115         }
 116
 117         kfree(repl);
 118         return ret;
 119 }
 120
 121 static void __net_exit iptable_nat_net_exit(struct net *net)
 122 {
 123         if (!net->ipv4.nat_table)
 124                 return;
 125         ipt_nat_unregister_lookups(net);
 126         ipt_unregister_table(net, net->ipv4.nat_table, NULL);
 127         net->ipv4.nat_table = NULL;
 128 }
 129
 130 static struct pernet_operations iptable_nat_net_ops = {
 131         .exit   = iptable_nat_net_exit,
 132 };
 133
 134 static int __init iptable_nat_init(void)
 135 {
 136         int ret = register_pernet_subsys(&iptable_nat_net_ops);
 137
 138         if (ret)
 139                 return ret;
 140
 141         ret = iptable_nat_table_init(&init_net);
 142         if (ret)
 143                 unregister_pernet_subsys(&iptable_nat_net_ops);
 144         return ret;
 145 }
 146
 147 static void __exit iptable_nat_exit(void)
 148 {
 149         unregister_pernet_subsys(&iptable_nat_net_ops);
 150 }
 151
 152 module_init(iptable_nat_init);
 153 module_exit(iptable_nat_exit);
 154
 155 MODULE_LICENSE("GPL");