/*
   * net/sched/cls_cgroup.c	Control Group Classifier
   *
   *		This program is free software; you can redistribute it and/or
   *		modify it under the terms of the GNU General Public License
   *		as published by the Free Software Foundation; either version
   *		2 of the License, or (at your option) any later version.
   *
   * Authors:	Thomas Graf <tgraf@suug.ch>
   */
  
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/skbuff.h>
  #include <linux/rcupdate.h>
  #include <net/rtnetlink.h>
  #include <net/pkt_cls.h>
  #include <net/sock.h>
  #include <net/cls_cgroup.h>
  
  struct cls_cgroup_head {
  	u32			handle;
  	struct tcf_exts		exts;
  	struct tcf_ematch_tree	ematches;
  };
  
  static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
  			       struct tcf_result *res)
  {
  	struct cls_cgroup_head *head = tp->root;
  	u32 classid;
  
  	rcu_read_lock();
  	classid = task_cls_state(current)->classid;
  	rcu_read_unlock();
  
  	/*
  	 * Due to the nature of the classifier it is required to ignore all
  	 * packets originating from softirq context as accessing `current'
  	 * would lead to false results.
  	 *
  	 * This test assumes that all callers of dev_queue_xmit() explicitely
  	 * disable bh. Knowing this, it is possible to detect softirq based
  	 * calls by looking at the number of nested bh disable calls because
  	 * softirqs always disables bh.
  	 */
  	if (in_serving_softirq()) {
  		/* If there is an sk_classid we'll use that. */
  		if (!skb->sk)
  			return -1;
  		classid = skb->sk->sk_classid;
  	}
  
  	if (!classid)
  		return -1;
  
  	if (!tcf_em_tree_match(skb, &head->ematches, NULL))
  		return -1;
  
  	res->classid = classid;
  	res->class = 0;
  	return tcf_exts_exec(skb, &head->exts, res);
  }
  
  static unsigned long cls_cgroup_get(struct tcf_proto *tp, u32 handle)
  {
  	return 0UL;
  }
  
  static void cls_cgroup_put(struct tcf_proto *tp, unsigned long f)
  {
  }
  
  static int cls_cgroup_init(struct tcf_proto *tp)
  {
  	return 0;
  }
  
  static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX + 1] = {
  	[TCA_CGROUP_EMATCHES]	= { .type = NLA_NESTED },
  };
  
  static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
  			     struct tcf_proto *tp, unsigned long base,
  			     u32 handle, struct nlattr **tca,
  			     unsigned long *arg)
  {
  	struct nlattr *tb[TCA_CGROUP_MAX + 1];
  	struct cls_cgroup_head *head = tp->root;
  	struct tcf_ematch_tree t;
  	struct tcf_exts e;
  	int err;
  
  	if (!tca[TCA_OPTIONS])
  		return -EINVAL;
  
  	if (head == NULL) {
  		if (!handle)
  			return -EINVAL;
  
  		head = kzalloc(sizeof(*head), GFP_KERNEL);
  		if (head == NULL)
  			return -ENOBUFS;
  
  		tcf_exts_init(&head->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
  		head->handle = handle;
  
  		tcf_tree_lock(tp);
  		tp->root = head;
  		tcf_tree_unlock(tp);
  	}
  
  	if (handle != head->handle)
  		return -ENOENT;
  
  	err = nla_parse_nested(tb, TCA_CGROUP_MAX, tca[TCA_OPTIONS],
  			       cgroup_policy);
  	if (err < 0)
  		return err;
  
  	tcf_exts_init(&e, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
  	err = tcf_exts_validate(net, tp, tb, tca[TCA_RATE], &e);
  	if (err < 0)
  		return err;
  
  	err = tcf_em_tree_validate(tp, tb[TCA_CGROUP_EMATCHES], &t);
  	if (err < 0)
  		return err;
  
  	tcf_exts_change(tp, &head->exts, &e);
  	tcf_em_tree_change(tp, &head->ematches, &t);
  
  	return 0;
  }
  
  static void cls_cgroup_destroy(struct tcf_proto *tp)
  {
  	struct cls_cgroup_head *head = tp->root;
  
  	if (head) {
  		tcf_exts_destroy(tp, &head->exts);
  		tcf_em_tree_destroy(tp, &head->ematches);
  		kfree(head);
  	}
  }
  
  static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg)
  {
  	return -EOPNOTSUPP;
  }
  
  static void cls_cgroup_walk(struct tcf_proto *tp, struct tcf_walker *arg)
  {
  	struct cls_cgroup_head *head = tp->root;
  
  	if (arg->count < arg->skip)
  		goto skip;
  
  	if (arg->fn(tp, (unsigned long) head, arg) < 0) {
  		arg->stop = 1;
  		return;
  	}
  skip:
  	arg->count++;
  }
  
  static int cls_cgroup_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
  			   struct sk_buff *skb, struct tcmsg *t)
  {
  	struct cls_cgroup_head *head = tp->root;
  	unsigned char *b = skb_tail_pointer(skb);
  	struct nlattr *nest;
  
  	t->tcm_handle = head->handle;
  
  	nest = nla_nest_start(skb, TCA_OPTIONS);
  	if (nest == NULL)
  		goto nla_put_failure;
  
  	if (tcf_exts_dump(skb, &head->exts) < 0 ||
  	    tcf_em_tree_dump(skb, &head->ematches, TCA_CGROUP_EMATCHES) < 0)
  		goto nla_put_failure;
  
  	nla_nest_end(skb, nest);
  
  	if (tcf_exts_dump_stats(skb, &head->exts) < 0)
  		goto nla_put_failure;
  
  	return skb->len;
  
  nla_put_failure:
  	nlmsg_trim(skb, b);
  	return -1;
  }
  
  static struct tcf_proto_ops cls_cgroup_ops __read_mostly = {
  	.kind		=	"cgroup",
  	.init		=	cls_cgroup_init,
  	.change		=	cls_cgroup_change,
  	.classify	=	cls_cgroup_classify,
  	.destroy	=	cls_cgroup_destroy,
  	.get		=	cls_cgroup_get,
  	.put		=	cls_cgroup_put,
  	.delete		=	cls_cgroup_delete,
  	.walk		=	cls_cgroup_walk,
  	.dump		=	cls_cgroup_dump,
  	.owner		=	THIS_MODULE,
  };
  
  static int __init init_cgroup_cls(void)
  {
  	return register_tcf_proto_ops(&cls_cgroup_ops);
  }
  
  static void __exit exit_cgroup_cls(void)
  {
  	unregister_tcf_proto_ops(&cls_cgroup_ops);
  }
  
  module_init(init_cgroup_cls);
  module_exit(exit_cgroup_cls);
  MODULE_LICENSE("GPL");