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 const struct xt_table nf_nat_ipv4_table = {
  22         .name           = "nat",
  23         .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
  24                           (1 << NF_INET_POST_ROUTING) |
  25                           (1 << NF_INET_LOCAL_OUT) |
  26                           (1 << NF_INET_LOCAL_IN),
  27         .me             = THIS_MODULE,
  28         .af             = NFPROTO_IPV4,
  29 };
  30
  31 static unsigned int iptable_nat_do_chain(const struct nf_hook_ops *ops,
  32                                          struct sk_buff *skb,
  33                                          const struct nf_hook_state *state,
  34                                          struct nf_conn *ct)
  35 {
  36         return ipt_do_table(skb, ops->hooknum, state,
  37                             state->net->ipv4.nat_table);
  38 }
  39
  40 static unsigned int iptable_nat_ipv4_fn(const struct nf_hook_ops *ops,
  41                                         struct sk_buff *skb,
  42                                         const struct nf_hook_state *state)
  43 {
  44         return nf_nat_ipv4_fn(ops, skb, state, iptable_nat_do_chain);
  45 }
  46
  47 static unsigned int iptable_nat_ipv4_in(const struct nf_hook_ops *ops,
  48                                         struct sk_buff *skb,
  49                                         const struct nf_hook_state *state)
  50 {
  51         return nf_nat_ipv4_in(ops, skb, state, iptable_nat_do_chain);
  52 }
  53
  54 static unsigned int iptable_nat_ipv4_out(const struct nf_hook_ops *ops,
  55                                          struct sk_buff *skb,
  56                                          const struct nf_hook_state *state)
  57 {
  58         return nf_nat_ipv4_out(ops, skb, state, iptable_nat_do_chain);
  59 }
  60
  61 static unsigned int iptable_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
  62                                               struct sk_buff *skb,
  63                                               const struct nf_hook_state *state)
  64 {
  65         return nf_nat_ipv4_local_fn(ops, skb, state, iptable_nat_do_chain);
  66 }
  67
  68 static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
  69         /* Before packet filtering, change destination */
  70         {
  71                 .hook           = iptable_nat_ipv4_in,
  72                 .owner          = THIS_MODULE,
  73                 .pf             = NFPROTO_IPV4,
  74                 .hooknum        = NF_INET_PRE_ROUTING,
  75                 .priority       = NF_IP_PRI_NAT_DST,
  76         },
  77         /* After packet filtering, change source */
  78         {
  79                 .hook           = iptable_nat_ipv4_out,
  80                 .owner          = THIS_MODULE,
  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                 .owner          = THIS_MODULE,
  89                 .pf             = NFPROTO_IPV4,
  90                 .hooknum        = NF_INET_LOCAL_OUT,
  91                 .priority       = NF_IP_PRI_NAT_DST,
  92         },
  93         /* After packet filtering, change source */
  94         {
  95                 .hook           = iptable_nat_ipv4_fn,
  96                 .owner          = THIS_MODULE,
  97                 .pf             = NFPROTO_IPV4,
  98                 .hooknum        = NF_INET_LOCAL_IN,
  99                 .priority       = NF_IP_PRI_NAT_SRC,
 100         },
 101 };
 102
 103 static int __net_init iptable_nat_net_init(struct net *net)
 104 {
 105         struct ipt_replace *repl;
 106
 107         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 108         if (repl == NULL)
 109                 return -ENOMEM;
 110         net->ipv4.nat_table = ipt_register_table(net, &nf_nat_ipv4_table, repl);
 111         kfree(repl);
 112         return PTR_ERR_OR_ZERO(net->ipv4.nat_table);
 113 }
 114
 115 static void __net_exit iptable_nat_net_exit(struct net *net)
 116 {
 117         ipt_unregister_table(net, net->ipv4.nat_table);
 118 }
 119
 120 static struct pernet_operations iptable_nat_net_ops = {
 121         .init   = iptable_nat_net_init,
 122         .exit   = iptable_nat_net_exit,
 123 };
 124
 125 static int __init iptable_nat_init(void)
 126 {
 127         int err;
 128
 129         err = register_pernet_subsys(&iptable_nat_net_ops);
 130         if (err < 0)
 131                 goto err1;
 132
 133         err = nf_register_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 134         if (err < 0)
 135                 goto err2;
 136         return 0;
 137
 138 err2:
 139         unregister_pernet_subsys(&iptable_nat_net_ops);
 140 err1:
 141         return err;
 142 }
 143
 144 static void __exit iptable_nat_exit(void)
 145 {
 146         nf_unregister_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 147         unregister_pernet_subsys(&iptable_nat_net_ops);
 148 }
 149
 150 module_init(iptable_nat_init);
 151 module_exit(iptable_nat_exit);
 152
 153 MODULE_LICENSE("GPL");