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(const struct nf_hook_ops *ops, struct sk_buff *skb,
  37                    const struct nf_hook_state *state)
  38{
  39        const struct net *net;
  40
  41        if (ops->hooknum == NF_INET_LOCAL_OUT &&
  42            (skb->len < sizeof(struct iphdr) ||
  43             ip_hdrlen(skb) < sizeof(struct iphdr)))
  44                /* root is playing with raw sockets. */
  45                return NF_ACCEPT;
  46
  47        net = dev_net(state->in ? state->in : state->out);
  48        return ipt_do_table(skb, ops->hooknum, state, net->ipv4.iptable_filter);
  49}
  50
  51static struct nf_hook_ops *filter_ops __read_mostly;
  52
  53/* Default to forward because I got too much mail already. */
  54static bool forward = true;
  55module_param(forward, bool, 0000);
  56
  57static int __net_init iptable_filter_net_init(struct net *net)
  58{
  59        struct ipt_replace *repl;
  60
  61        repl = ipt_alloc_initial_table(&packet_filter);
  62        if (repl == NULL)
  63                return -ENOMEM;
  64        /* Entry 1 is the FORWARD hook */
  65        ((struct ipt_standard *)repl->entries)[1].target.verdict =
  66                forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
  67
  68        net->ipv4.iptable_filter =
  69                ipt_register_table(net, &packet_filter, repl);
  70        kfree(repl);
  71        return PTR_ERR_OR_ZERO(net->ipv4.iptable_filter);
  72}
  73
  74static void __net_exit iptable_filter_net_exit(struct net *net)
  75{
  76        ipt_unregister_table(net, net->ipv4.iptable_filter);
  77}
  78
  79static struct pernet_operations iptable_filter_net_ops = {
  80        .init = iptable_filter_net_init,
  81        .exit = iptable_filter_net_exit,
  82};
  83
  84static int __init iptable_filter_init(void)
  85{
  86        int ret;
  87
  88        ret = register_pernet_subsys(&iptable_filter_net_ops);
  89        if (ret < 0)
  90                return ret;
  91
  92        /* Register hooks */
  93        filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
  94        if (IS_ERR(filter_ops)) {
  95                ret = PTR_ERR(filter_ops);
  96                unregister_pernet_subsys(&iptable_filter_net_ops);
  97        }
  98
  99        return ret;
 100}
 101
 102static void __exit iptable_filter_fini(void)
 103{
 104        xt_hook_unlink(&packet_filter, filter_ops);
 105        unregister_pernet_subsys(&iptable_filter_net_ops);
 106}
 107
 108module_init(iptable_filter_init);
 109module_exit(iptable_filter_fini);
 110