LXR linux/net/ipv4/netfilter/iptable

   1/*
   2 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   3 *
   4 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   5 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/moduleparam.h>
  15#include <linux/netfilter_ipv4/ip_tables.h>
  16#include <linux/slab.h>
  17#include <net/ip.h>
  18
  19MODULE_LICENSE("GPL");
  20MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  21MODULE_DESCRIPTION("iptables filter table");
  22
  23#define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
  24                            (1 << NF_INET_FORWARD) | \
  25                            (1 << NF_INET_LOCAL_OUT))
  26
  27static const struct xt_table packet_filter = {
  28        .name           = "filter",
  29        .valid_hooks    = FILTER_VALID_HOOKS,
  30        .me             = THIS_MODULE,
  31        .af             = NFPROTO_IPV4,
  32        .priority       = NF_IP_PRI_FILTER,
  33};
  34
  35static unsigned int
  36iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
  37                    const struct net_device *in, const struct net_device *out,
  38                    int (*okfn)(struct sk_buff *))
  39{
  40        const struct net *net;
  41
  42        if (hook == NF_INET_LOCAL_OUT &&
  43            (skb->len < sizeof(struct iphdr) ||
  44             ip_hdrlen(skb) < sizeof(struct iphdr)))
  45                /* root is playing with raw sockets. */
  46                return NF_ACCEPT;
  47
  48        net = dev_net((in != NULL) ? in : out);
  49        return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
  50}
  51
  52static struct nf_hook_ops *filter_ops __read_mostly;
  53
  54/* Default to forward because I got too much mail already. */
  55static bool forward = true;
  56module_param(forward, bool, 0000);
  57
  58static int __net_init iptable_filter_net_init(struct net *net)
  59{
  60        struct ipt_replace *repl;
  61
  62        repl = ipt_alloc_initial_table(&packet_filter);
  63        if (repl == NULL)
  64                return -ENOMEM;
  65        /* Entry 1 is the FORWARD hook */
  66        ((struct ipt_standard *)repl->entries)[1].target.verdict =
  67                forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
  68
  69        net->ipv4.iptable_filter =
  70                ipt_register_table(net, &packet_filter, repl);
  71        kfree(repl);
  72        return PTR_RET(net->ipv4.iptable_filter);
  73}
  74
  75static void __net_exit iptable_filter_net_exit(struct net *net)
  76{
  77        ipt_unregister_table(net, net->ipv4.iptable_filter);
  78}
  79
  80static struct pernet_operations iptable_filter_net_ops = {
  81        .init = iptable_filter_net_init,
  82        .exit = iptable_filter_net_exit,
  83};
  84
  85static int __init iptable_filter_init(void)
  86{
  87        int ret;
  88
  89        ret = register_pernet_subsys(&iptable_filter_net_ops);
  90        if (ret < 0)
  91                return ret;
  92
  93        /* Register hooks */
  94        filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
  95        if (IS_ERR(filter_ops)) {
  96                ret = PTR_ERR(filter_ops);
  97                unregister_pernet_subsys(&iptable_filter_net_ops);
  98        }
  99
 100        return ret;
 101}
 102
 103static void __exit iptable_filter_fini(void)
 104{
 105        xt_hook_unlink(&packet_filter, filter_ops);
 106        unregister_pernet_subsys(&iptable_filter_net_ops);
 107}
 108
 109module_init(iptable_filter_init);
 110module_exit(iptable_filter_fini);
 111