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))
  26static int __net_init iptable_filter_table_init(struct net *net);
  27
  28static const struct xt_table packet_filter = {
  29        .name           = "filter",
  30        .valid_hooks    = FILTER_VALID_HOOKS,
  31        .me             = THIS_MODULE,
  32        .af             = NFPROTO_IPV4,
  33        .priority       = NF_IP_PRI_FILTER,
  34        .table_init     = iptable_filter_table_init,
  35};
  36
  37static unsigned int
  38iptable_filter_hook(void *priv, struct sk_buff *skb,
  39                    const struct nf_hook_state *state)
  40{
  41        if (state->hook == 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        return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
  48}
  49
  50static struct nf_hook_ops *filter_ops __read_mostly;
  51
  52/* Default to forward because I got too much mail already. */
  53static bool forward __read_mostly = true;
  54module_param(forward, bool, 0000);
  55
  56static int __net_init iptable_filter_table_init(struct net *net)
  57{
  58        struct ipt_replace *repl;
  59        int err;
  60
  61        if (net->ipv4.iptable_filter)
  62                return 0;
  63
  64        repl = ipt_alloc_initial_table(&packet_filter);
  65        if (repl == NULL)
  66                return -ENOMEM;
  67        /* Entry 1 is the FORWARD hook */
  68        ((struct ipt_standard *)repl->entries)[1].target.verdict =
  69                forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
  70
  71        err = ipt_register_table(net, &packet_filter, repl, filter_ops,
  72                                 &net->ipv4.iptable_filter);
  73        kfree(repl);
  74        return err;
  75}
  76
  77static int __net_init iptable_filter_net_init(struct net *net)
  78{
  79        if (net == &init_net || !forward)
  80                return iptable_filter_table_init(net);
  81
  82        return 0;
  83}
  84
  85static void __net_exit iptable_filter_net_exit(struct net *net)
  86{
  87        if (!net->ipv4.iptable_filter)
  88                return;
  89        ipt_unregister_table(net, net->ipv4.iptable_filter, filter_ops);
  90        net->ipv4.iptable_filter = NULL;
  91}
  92
  93static struct pernet_operations iptable_filter_net_ops = {
  94        .init = iptable_filter_net_init,
  95        .exit = iptable_filter_net_exit,
  96};
  97
  98static int __init iptable_filter_init(void)
  99{
 100        int ret;
 101
 102        filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
 103        if (IS_ERR(filter_ops))
 104                return PTR_ERR(filter_ops);
 105
 106        ret = register_pernet_subsys(&iptable_filter_net_ops);
 107        if (ret < 0)
 108                kfree(filter_ops);
 109
 110        return ret;
 111}
 112
 113static void __exit iptable_filter_fini(void)
 114{
 115        unregister_pernet_subsys(&iptable_filter_net_ops);
 116        kfree(filter_ops);
 117}
 118
 119module_init(iptable_filter_init);
 120module_exit(iptable_filter_fini);
 121