net/ipv4/netfilter/iptable_nat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2006 Netfilter Core Team <[email protected]>
   4  * (C) 2011 Patrick McHardy <[email protected]>
   5  */
   6
   7 #include <linux/module.h>
   8 #include <linux/netfilter.h>
   9 #include <linux/netfilter_ipv4.h>
  10 #include <linux/netfilter_ipv4/ip_tables.h>
  11 #include <linux/ip.h>
  12 #include <net/ip.h>
  13
  14 #include <net/netfilter/nf_nat.h>
  15
  16 struct iptable_nat_pernet {
  17         struct nf_hook_ops *nf_nat_ops;
  18 };
  19
  20 static unsigned int iptable_nat_net_id __read_mostly;
  21
  22 static const struct xt_table nf_nat_ipv4_table = {
  23         .name           = "nat",
  24         .valid_hooks    = (1 << NF_INET_PRE_ROUTING) |
  25                           (1 << NF_INET_POST_ROUTING) |
  26                           (1 << NF_INET_LOCAL_OUT) |
  27                           (1 << NF_INET_LOCAL_IN),
  28         .me             = THIS_MODULE,
  29         .af             = NFPROTO_IPV4,
  30 };
  31
  32 static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
  33         {
  34                 .hook           = ipt_do_table,
  35                 .pf             = NFPROTO_IPV4,
  36                 .hooknum        = NF_INET_PRE_ROUTING,
  37                 .priority       = NF_IP_PRI_NAT_DST,
  38         },
  39         {
  40                 .hook           = ipt_do_table,
  41                 .pf             = NFPROTO_IPV4,
  42                 .hooknum        = NF_INET_POST_ROUTING,
  43                 .priority       = NF_IP_PRI_NAT_SRC,
  44         },
  45         {
  46                 .hook           = ipt_do_table,
  47                 .pf             = NFPROTO_IPV4,
  48                 .hooknum        = NF_INET_LOCAL_OUT,
  49                 .priority       = NF_IP_PRI_NAT_DST,
  50         },
  51         {
  52                 .hook           = ipt_do_table,
  53                 .pf             = NFPROTO_IPV4,
  54                 .hooknum        = NF_INET_LOCAL_IN,
  55                 .priority       = NF_IP_PRI_NAT_SRC,
  56         },
  57 };
  58
  59 static int ipt_nat_register_lookups(struct net *net)
  60 {
  61         struct iptable_nat_pernet *xt_nat_net;
  62         struct nf_hook_ops *ops;
  63         struct xt_table *table;
  64         int i, ret;
  65
  66         xt_nat_net = net_generic(net, iptable_nat_net_id);
  67         table = xt_find_table(net, NFPROTO_IPV4, "nat");
  68         if (WARN_ON_ONCE(!table))
  69                 return -ENOENT;
  70
  71         ops = kmemdup(nf_nat_ipv4_ops, sizeof(nf_nat_ipv4_ops), GFP_KERNEL);
  72         if (!ops)
  73                 return -ENOMEM;
  74
  75         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
  76                 ops[i].priv = table;
  77                 ret = nf_nat_ipv4_register_fn(net, &ops[i]);
  78                 if (ret) {
  79                         while (i)
  80                                 nf_nat_ipv4_unregister_fn(net, &ops[--i]);
  81
  82                         kfree(ops);
  83                         return ret;
  84                 }
  85         }
  86
  87         xt_nat_net->nf_nat_ops = ops;
  88         return 0;
  89 }
  90
  91 static void ipt_nat_unregister_lookups(struct net *net)
  92 {
  93         struct iptable_nat_pernet *xt_nat_net = net_generic(net, iptable_nat_net_id);
  94         struct nf_hook_ops *ops = xt_nat_net->nf_nat_ops;
  95         int i;
  96
  97         if (!ops)
  98                 return;
  99
 100         for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
 101                 nf_nat_ipv4_unregister_fn(net, &ops[i]);
 102
 103         kfree(ops);
 104 }
 105
 106 static int iptable_nat_table_init(struct net *net)
 107 {
 108         struct ipt_replace *repl;
 109         int ret;
 110
 111         repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
 112         if (repl == NULL)
 113                 return -ENOMEM;
 114
 115         ret = ipt_register_table(net, &nf_nat_ipv4_table, repl, NULL);
 116         if (ret < 0) {
 117                 kfree(repl);
 118                 return ret;
 119         }
 120
 121         ret = ipt_nat_register_lookups(net);
 122         if (ret < 0)
 123                 ipt_unregister_table_exit(net, "nat");
 124
 125         kfree(repl);
 126         return ret;
 127 }
 128
 129 static void __net_exit iptable_nat_net_pre_exit(struct net *net)
 130 {
 131         ipt_nat_unregister_lookups(net);
 132 }
 133
 134 static void __net_exit iptable_nat_net_exit(struct net *net)
 135 {
 136         ipt_unregister_table_exit(net, "nat");
 137 }
 138
 139 static struct pernet_operations iptable_nat_net_ops = {
 140         .pre_exit = iptable_nat_net_pre_exit,
 141         .exit   = iptable_nat_net_exit,
 142         .id     = &iptable_nat_net_id,
 143         .size   = sizeof(struct iptable_nat_pernet),
 144 };
 145
 146 static int __init iptable_nat_init(void)
 147 {
 148         int ret;
 149
 150         /* net->gen->ptr[iptable_nat_net_id] must be allocated
 151          * before calling iptable_nat_table_init().
 152          */
 153         ret = register_pernet_subsys(&iptable_nat_net_ops);
 154         if (ret < 0)
 155                 return ret;
 156
 157         ret = xt_register_template(&nf_nat_ipv4_table,
 158                                    iptable_nat_table_init);
 159         if (ret < 0)
 160                 unregister_pernet_subsys(&iptable_nat_net_ops);
 161
 162         return ret;
 163 }
 164
 165 static void __exit iptable_nat_exit(void)
 166 {
 167         xt_unregister_template(&nf_nat_ipv4_table);
 168         unregister_pernet_subsys(&iptable_nat_net_ops);
 169 }
 170
 171 module_init(iptable_nat_init);
 172 module_exit(iptable_nat_exit);
 173
 174 MODULE_LICENSE("GPL");
 175 MODULE_DESCRIPTION("iptables legacy nat table");