/*
   * Xtables module to match the process control group.
   *
   * Might be used to implement individual "per-application" firewall
   * policies in contrast to global policies based on control groups.
   * Matching is based upon processes tagged to net_cls' classid marker.
   *
   * (C) 2013 Daniel Borkmann <dborkman@redhat.com>
   *
   * 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/skbuff.h>
  #include <linux/module.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter/xt_cgroup.h>
  #include <net/sock.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
  MODULE_DESCRIPTION("Xtables: process control group matching");
  MODULE_ALIAS("ipt_cgroup");
  MODULE_ALIAS("ip6t_cgroup");
  
  static int cgroup_mt_check(const struct xt_mtchk_param *par)
  {
  	struct xt_cgroup_info *info = par->matchinfo;
  
  	if (info->invert & ~1)
  		return -EINVAL;

  	return 0;

  }
  
  static bool
  cgroup_mt(const struct sk_buff *skb, struct xt_action_param *par)
  {
  	const struct xt_cgroup_info *info = par->matchinfo;
  
  	if (skb->sk == NULL)
  		return false;
  
  	return (info->id == skb->sk->sk_classid) ^ info->invert;
  }
  
  static struct xt_match cgroup_mt_reg __read_mostly = {
  	.name       = "cgroup",
  	.revision   = 0,
  	.family     = NFPROTO_UNSPEC,
  	.checkentry = cgroup_mt_check,
  	.match      = cgroup_mt,
  	.matchsize  = sizeof(struct xt_cgroup_info),
  	.me         = THIS_MODULE,
  	.hooks      = (1 << NF_INET_LOCAL_OUT) |

  		      (1 << NF_INET_POST_ROUTING) |
  		      (1 << NF_INET_LOCAL_IN),

  };
  
  static int __init cgroup_mt_init(void)
  {
  	return xt_register_match(&cgroup_mt_reg);
  }
  
  static void __exit cgroup_mt_exit(void)
  {
  	xt_unregister_match(&cgroup_mt_reg);
  }
  
  module_init(cgroup_mt_init);
  module_exit(cgroup_mt_exit);