text: /*
   * 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>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  MODULE_DESCRIPTION("iptables filter table");
  
  #define FILTER_VALID_HOOKS ((1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | (1 << NF_IP_LOCAL_OUT))
  
  static struct
  {
  	struct ipt_replace repl;
  	struct ipt_standard entries[3];
  	struct ipt_error term;
  } initial_table __initdata
  = { { "filter", FILTER_VALID_HOOKS, 4,
        sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
        { [NF_IP_LOCAL_IN] = 0,
  	[NF_IP_FORWARD] = sizeof(struct ipt_standard),
  	[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
        { [NF_IP_LOCAL_IN] = 0,
  	[NF_IP_FORWARD] = sizeof(struct ipt_standard),
  	[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2 },
        0, NULL, { } },
      {
  	    /* LOCAL_IN */
  	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  		0,
  		sizeof(struct ipt_entry),
  		sizeof(struct ipt_standard),
  		0, { 0, 0 }, { } },
  	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  		-NF_ACCEPT - 1 } },
  	    /* FORWARD */
  	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  		0,
  		sizeof(struct ipt_entry),
  		sizeof(struct ipt_standard),
  		0, { 0, 0 }, { } },
  	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  		-NF_ACCEPT - 1 } },
  	    /* LOCAL_OUT */
  	    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  		0,
  		sizeof(struct ipt_entry),
  		sizeof(struct ipt_standard),
  		0, { 0, 0 }, { } },
  	      { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },
  		-NF_ACCEPT - 1 } }
      },
      /* ERROR */
      { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },
  	0,
  	sizeof(struct ipt_entry),
  	sizeof(struct ipt_error),
  	0, { 0, 0 }, { } },
        { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },
  	  { } },
  	"ERROR"
        }
      }
  };
  
  static struct xt_table packet_filter = {
  	.name		= "filter",
  	.valid_hooks	= FILTER_VALID_HOOKS,
  	.lock		= RW_LOCK_UNLOCKED,
  	.me		= THIS_MODULE,
  	.af		= AF_INET,
  };
  
  /* The work comes in here from netfilter.c. */
  static unsigned int
  ipt_hook(unsigned int hook,
  	 struct sk_buff **pskb,
  	 const struct net_device *in,
  	 const struct net_device *out,
  	 int (*okfn)(struct sk_buff *))
  {
  	return ipt_do_table(pskb, hook, in, out, &packet_filter);
  }
  
  static unsigned int
  ipt_local_out_hook(unsigned int hook,
  		   struct sk_buff **pskb,
  		   const struct net_device *in,
  		   const struct net_device *out,
  		   int (*okfn)(struct sk_buff *))
  {
  	/* root is playing with raw sockets. */
  	if ((*pskb)->len < sizeof(struct iphdr)
  	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
  		if (net_ratelimit())
  			printk("ipt_hook: happy cracking.\n");
  		return NF_ACCEPT;
  	}
  
  	return ipt_do_table(pskb, hook, in, out, &packet_filter);
  }
  
  static struct nf_hook_ops ipt_ops[] = {
  	{
  		.hook		= ipt_hook,
  		.owner		= THIS_MODULE,
  		.pf		= PF_INET,
  		.hooknum	= NF_IP_LOCAL_IN,
  		.priority	= NF_IP_PRI_FILTER,
  	},
  	{
  		.hook		= ipt_hook,
  		.owner		= THIS_MODULE,
  		.pf		= PF_INET,
  		.hooknum	= NF_IP_FORWARD,
  		.priority	= NF_IP_PRI_FILTER,
  	},
  	{
  		.hook		= ipt_local_out_hook,
  		.owner		= THIS_MODULE,
  		.pf		= PF_INET,
  		.hooknum	= NF_IP_LOCAL_OUT,
  		.priority	= NF_IP_PRI_FILTER,
  	},
  };
  
  /* Default to forward because I got too much mail already. */
  static int forward = NF_ACCEPT;
  module_param(forward, bool, 0000);
  
  static int __init iptable_filter_init(void)
  {
  	int ret;
  
  	if (forward < 0 || forward > NF_MAX_VERDICT) {
  		printk("iptables forward must be 0 or 1\n");
  		return -EINVAL;
  	}
  
  	/* Entry 1 is the FORWARD hook */
  	initial_table.entries[1].target.verdict = -forward - 1;
  
  	/* Register table */
  	ret = ipt_register_table(&packet_filter, &initial_table.repl);
  	if (ret < 0)
  		return ret;
  
  	/* Register hooks */
  	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
  	if (ret < 0)
  		goto cleanup_table;
  
  	return ret;
  
   cleanup_table:
  	ipt_unregister_table(&packet_filter);
  	return ret;
  }
  
  static void __exit iptable_filter_fini(void)
  {
  	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
  	ipt_unregister_table(&packet_filter);
  }
  
  module_init(iptable_filter_init);
  module_exit(iptable_filter_fini);
  