iptable_filter.c
/*
* This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
*
* Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
* Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/slab.h>
#include <net/ip.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("iptables filter table");
#define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
(1 << NF_INET_FORWARD) | \
(1 << NF_INET_LOCAL_OUT))
static const struct xt_table packet_filter = {
.name = "filter",
.valid_hooks = FILTER_VALID_HOOKS,
.me = THIS_MODULE,
.af = NFPROTO_IPV4,
.priority = NF_IP_PRI_FILTER,
};
static unsigned int
iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
const struct net_device *in, const struct net_device *out,
int (*okfn)(struct sk_buff *))
{
const struct net *net;
if (hook == NF_INET_LOCAL_OUT &&
(skb->len < sizeof(struct iphdr) ||
ip_hdrlen(skb) < sizeof(struct iphdr)))
/* root is playing with raw sockets. */
return NF_ACCEPT;
net = dev_net((in != NULL) ? in : out);
return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
}
static struct nf_hook_ops *filter_ops __read_mostly;
/* Default to forward because I got too much mail already. */
static bool forward = true;
module_param(forward, bool, 0000);
static int __net_init iptable_filter_net_init(struct net *net)
{
struct ipt_replace *repl;
repl = ipt_alloc_initial_table(&packet_filter);
if (repl == NULL)
return -ENOMEM;
/* Entry 1 is the FORWARD hook */
((struct ipt_standard *)repl->entries)[1].target.verdict =
forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
net->ipv4.iptable_filter =
ipt_register_table(net, &packet_filter, repl);
kfree(repl);
return PTR_RET(net->ipv4.iptable_filter);
}
static void __net_exit iptable_filter_net_exit(struct net *net)
{
ipt_unregister_table(net, net->ipv4.iptable_filter);
}
static struct pernet_operations iptable_filter_net_ops = {
.init = iptable_filter_net_init,
.exit = iptable_filter_net_exit,
};
static int __init iptable_filter_init(void)
{
int ret;
ret = register_pernet_subsys(&iptable_filter_net_ops);
if (ret < 0)
return ret;
/* Register hooks */
filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
if (IS_ERR(filter_ops)) {
ret = PTR_ERR(filter_ops);
unregister_pernet_subsys(&iptable_filter_net_ops);
}
return ret;
}
static void __exit iptable_filter_fini(void)
{
xt_hook_unlink(&packet_filter, filter_ops);
unregister_pernet_subsys(&iptable_filter_net_ops);
}
module_init(iptable_filter_init);
module_exit(iptable_filter_fini);