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
 15MODULE_LICENSE("GPL");
 16MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
 17MODULE_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
 23static 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
 31static struct nf_hook_ops *filter_ops __read_mostly;
 32
 33/* Default to forward because I got too much mail already. */
 34static bool forward __read_mostly = true;
 35module_param(forward, bool, 0000);
 36
 37static 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
 54static 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
 62static void __net_exit iptable_filter_net_pre_exit(struct net *net)
 63{
 64	ipt_unregister_table_pre_exit(net, "filter");
 65}
 66
 67static void __net_exit iptable_filter_net_exit(struct net *net)
 68{
 69	ipt_unregister_table_exit(net, "filter");
 70}
 71
 72static 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
 78static 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
102static 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
109module_init(iptable_filter_init);
110module_exit(iptable_filter_fini);