net/ipv4/netfilter/iptable_filter.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   4  *
   5  * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   6  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/moduleparam.h>
  11 #include <linux/netfilter_ipv4/ip_tables.h>
  12 #include <linux/slab.h>
  13 #include <net/ip.h>
  14
  15 MODULE_LICENSE("GPL");
  16 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  17 MODULE_DESCRIPTION("iptables filter table");
  18
  19 #define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
  20                             (1 << NF_INET_FORWARD) | \
  21                             (1 << NF_INET_LOCAL_OUT))
  22
  23 static const struct xt_table packet_filter = {
  24         .name           = "filter",
  25         .valid_hooks    = FILTER_VALID_HOOKS,
  26         .me             = THIS_MODULE,
  27         .af             = NFPROTO_IPV4,
  28         .priority       = NF_IP_PRI_FILTER,
  29 };
  30
  31 static struct nf_hook_ops *filter_ops __read_mostly;
  32
  33 /* Default to forward because I got too much mail already. */
  34 static bool forward __read_mostly = true;
  35 module_param(forward, bool, 0000);
  36
  37 static int iptable_filter_table_init(struct net *net)
  38 {
  39         struct ipt_replace *repl;
  40         int err;
  41
  42         repl = ipt_alloc_initial_table(&packet_filter);
  43         if (repl == NULL)
  44                 return -ENOMEM;
  45         /* Entry 1 is the FORWARD hook */
  46         ((struct ipt_standard *)repl->entries)[1].target.verdict =
  47                 forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
  48
  49         err = ipt_register_table(net, &packet_filter, repl, filter_ops);
  50         kfree(repl);
  51         return err;
  52 }
  53
  54 static int __net_init iptable_filter_net_init(struct net *net)
  55 {
  56         if (!forward)
  57                 return iptable_filter_table_init(net);
  58
  59         return 0;
  60 }
  61
  62 static void __net_exit iptable_filter_net_pre_exit(struct net *net)
  63 {
  64         ipt_unregister_table_pre_exit(net, "filter");
  65 }
  66
  67 static void __net_exit iptable_filter_net_exit(struct net *net)
  68 {
  69         ipt_unregister_table_exit(net, "filter");
  70 }
  71
  72 static struct pernet_operations iptable_filter_net_ops = {
  73         .init = iptable_filter_net_init,
  74         .pre_exit = iptable_filter_net_pre_exit,
  75         .exit = iptable_filter_net_exit,
  76 };
  77
  78 static int __init iptable_filter_init(void)
  79 {
  80         int ret = xt_register_template(&packet_filter,
  81                                        iptable_filter_table_init);
  82
  83         if (ret < 0)
  84                 return ret;
  85
  86         filter_ops = xt_hook_ops_alloc(&packet_filter, ipt_do_table);
  87         if (IS_ERR(filter_ops)) {
  88                 xt_unregister_template(&packet_filter);
  89                 return PTR_ERR(filter_ops);
  90         }
  91
  92         ret = register_pernet_subsys(&iptable_filter_net_ops);
  93         if (ret < 0) {
  94                 xt_unregister_template(&packet_filter);
  95                 kfree(filter_ops);
  96                 return ret;
  97         }
  98
  99         return 0;
 100 }
 101
 102 static void __exit iptable_filter_fini(void)
 103 {
 104         unregister_pernet_subsys(&iptable_filter_net_ops);
 105         xt_unregister_template(&packet_filter);
 106         kfree(filter_ops);
 107 }
 108
 109 module_init(iptable_filter_init);
 110 module_exit(iptable_filter_fini);