kernel/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         struct net *net = nf_ct_net(ct);
  37
  38         return ipt_do_table(skb, ops->hooknum, state, net->ipv4.nat_table);
  39 }
  40
  41 static unsigned int iptable_nat_ipv4_fn(const struct nf_hook_ops *ops,
  42                                         struct sk_buff *skb,
  43                                         const struct nf_hook_state *state)
  44 {
  45         return nf_nat_ipv4_fn(ops, skb, state, iptable_nat_do_chain);
  46 }
  47
  48 static unsigned int iptable_nat_ipv4_in(const struct nf_hook_ops *ops,
  49                                         struct sk_buff *skb,
  50                                         const struct nf_hook_state *state)
  51 {
  52         return nf_nat_ipv4_in(ops, skb, state, iptable_nat_do_chain);
  53 }
  54
  55 static unsigned int iptable_nat_ipv4_out(const struct nf_hook_ops *ops,
  56                                          struct sk_buff *skb,
  57                                          const struct nf_hook_state *state)
  58 {
  59         return nf_nat_ipv4_out(ops, skb, state, iptable_nat_do_chain);
  60 }
  61
  62 static unsigned int iptable_nat_ipv4_local_fn(const struct nf_hook_ops *ops,
  63                                               struct sk_buff *skb,
  64                                               const struct nf_hook_state *state)
  65 {
  66         return nf_nat_ipv4_local_fn(ops, skb, state, iptable_nat_do_chain);
  67 }
  68
  69 static struct nf_hook_ops nf_nat_ipv4_ops[] __read_mostly = {
  70         /* Before packet filtering, change destination */
  71         {
  72                 .hook           = iptable_nat_ipv4_in,
  73                 .owner          = THIS_MODULE,
  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                 .owner          = THIS_MODULE,
  82                 .pf             = NFPROTO_IPV4,
  83                 .hooknum        = NF_INET_POST_ROUTING,
  84                 .priority       = NF_IP_PRI_NAT_SRC,
  85         },
  86         /* Before packet filtering, change destination */
  87         {
  88                 .hook           = iptable_nat_ipv4_local_fn,
  89                 .owner          = THIS_MODULE,
  90                 .pf             = NFPROTO_IPV4,
  91                 .hooknum        = NF_INET_LOCAL_OUT,
  92                 .priority       = NF_IP_PRI_NAT_DST,
  93         },
  94         /* After packet filtering, change source */
  95         {
  96                 .hook           = iptable_nat_ipv4_fn,
  97                 .owner          = THIS_MODULE,
  98                 .pf             = NFPROTO_IPV4,
  99                 .hooknum        = NF_INET_LOCAL_IN,
 100                 .priority       = NF_IP_PRI_NAT_SRC,
 101         },
 102 };
 103
 104 static int __net_init iptable_nat_net_init(struct net *net)
 105 {
 106         struct ipt_replace *repl;
 107
 108         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 109         if (repl == NULL)
 110                 return -ENOMEM;
 111         net->ipv4.nat_table = ipt_register_table(net, &nf_nat_ipv4_table, repl);
 112         kfree(repl);
 113         return PTR_ERR_OR_ZERO(net->ipv4.nat_table);
 114 }
 115
 116 static void __net_exit iptable_nat_net_exit(struct net *net)
 117 {
 118         ipt_unregister_table(net, net->ipv4.nat_table);
 119 }
 120
 121 static struct pernet_operations iptable_nat_net_ops = {
 122         .init   = iptable_nat_net_init,
 123         .exit   = iptable_nat_net_exit,
 124 };
 125
 126 static int __init iptable_nat_init(void)
 127 {
 128         int err;
 129
 130         err = register_pernet_subsys(&iptable_nat_net_ops);
 131         if (err < 0)
 132                 goto err1;
 133
 134         err = nf_register_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 135         if (err < 0)
 136                 goto err2;
 137         return 0;
 138
 139 err2:
 140         unregister_pernet_subsys(&iptable_nat_net_ops);
 141 err1:
 142         return err;
 143 }
 144
 145 static void __exit iptable_nat_exit(void)
 146 {
 147         nf_unregister_hooks(nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 148         unregister_pernet_subsys(&iptable_nat_net_ops);
 149 }
 150
 151 module_init(iptable_nat_init);
 152 module_exit(iptable_nat_exit);
 153
 154 MODULE_LICENSE("GPL");