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                                          struct nf_conn *ct)
  38 {
  39         return ipt_do_table(skb, state, state->net->ipv4.nat_table);
  40 }
  41
  42 static unsigned int iptable_nat_ipv4_fn(void *priv,
  43                                         struct sk_buff *skb,
  44                                         const struct nf_hook_state *state)
  45 {
  46         return nf_nat_ipv4_fn(priv, skb, state, iptable_nat_do_chain);
  47 }
  48
  49 static unsigned int iptable_nat_ipv4_in(void *priv,
  50                                         struct sk_buff *skb,
  51                                         const struct nf_hook_state *state)
  52 {
  53         return nf_nat_ipv4_in(priv, skb, state, iptable_nat_do_chain);
  54 }
  55
  56 static unsigned int iptable_nat_ipv4_out(void *priv,
  57                                          struct sk_buff *skb,
  58                                          const struct nf_hook_state *state)
  59 {
  60         return nf_nat_ipv4_out(priv, skb, state, iptable_nat_do_chain);
  61 }
  62
  63 static unsigned int iptable_nat_ipv4_local_fn(void *priv,
  64                                               struct sk_buff *skb,
  65                                               const struct nf_hook_state *state)
  66 {
  67         return nf_nat_ipv4_local_fn(priv, skb, state, iptable_nat_do_chain);
  68 }
  69
  70 static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
  71         /* Before packet filtering, change destination */
  72         {
  73                 .hook           = iptable_nat_ipv4_in,
  74                 .pf             = NFPROTO_IPV4,
  75                 .hooknum        = NF_INET_PRE_ROUTING,
  76                 .priority       = NF_IP_PRI_NAT_DST,
  77         },
  78         /* After packet filtering, change source */
  79         {
  80                 .hook           = iptable_nat_ipv4_out,
  81                 .pf             = NFPROTO_IPV4,
  82                 .hooknum        = NF_INET_POST_ROUTING,
  83                 .priority       = NF_IP_PRI_NAT_SRC,
  84         },
  85         /* Before packet filtering, change destination */
  86         {
  87                 .hook           = iptable_nat_ipv4_local_fn,
  88                 .pf             = NFPROTO_IPV4,
  89                 .hooknum        = NF_INET_LOCAL_OUT,
  90                 .priority       = NF_IP_PRI_NAT_DST,
  91         },
  92         /* After packet filtering, change source */
  93         {
  94                 .hook           = iptable_nat_ipv4_fn,
  95                 .pf             = NFPROTO_IPV4,
  96                 .hooknum        = NF_INET_LOCAL_IN,
  97                 .priority       = NF_IP_PRI_NAT_SRC,
  98         },
  99 };
 100
 101 static int __net_init iptable_nat_table_init(struct net *net)
 102 {
 103         struct ipt_replace *repl;
 104         int ret;
 105
 106         if (net->ipv4.nat_table)
 107                 return 0;
 108
 109         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 110         if (repl == NULL)
 111                 return -ENOMEM;
 112         ret = ipt_register_table(net, &nf_nat_ipv4_table, repl,
 113                                  nf_nat_ipv4_ops, &net->ipv4.nat_table);
 114         kfree(repl);
 115         return ret;
 116 }
 117
 118 static void __net_exit iptable_nat_net_exit(struct net *net)
 119 {
 120         if (!net->ipv4.nat_table)
 121                 return;
 122         ipt_unregister_table(net, net->ipv4.nat_table, nf_nat_ipv4_ops);
 123         net->ipv4.nat_table = NULL;
 124 }
 125
 126 static struct pernet_operations iptable_nat_net_ops = {
 127         .exit   = iptable_nat_net_exit,
 128 };
 129
 130 static int __init iptable_nat_init(void)
 131 {
 132         int ret = register_pernet_subsys(&iptable_nat_net_ops);
 133
 134         if (ret)
 135                 return ret;
 136
 137         ret = iptable_nat_table_init(&init_net);
 138         if (ret)
 139                 unregister_pernet_subsys(&iptable_nat_net_ops);
 140         return ret;
 141 }
 142
 143 static void __exit iptable_nat_exit(void)
 144 {
 145         unregister_pernet_subsys(&iptable_nat_net_ops);
 146 }
 147
 148 module_init(iptable_nat_init);
 149 module_exit(iptable_nat_exit);
 150
 151 MODULE_LICENSE("GPL");