/*
   * net/sched/sch_drr.c         Deficit Round Robin scheduler
   *
   * Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
   *
   * 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/slab.h>
  #include <linux/init.h>
  #include <linux/errno.h>
  #include <linux/netdevice.h>
  #include <linux/pkt_sched.h>
  #include <net/sch_generic.h>
  #include <net/pkt_sched.h>
  #include <net/pkt_cls.h>
  
  struct drr_class {
  	struct Qdisc_class_common	common;
  	unsigned int			refcnt;
  	unsigned int			filter_cnt;
  
  	struct gnet_stats_basic_packed		bstats;
  	struct gnet_stats_queue		qstats;
  	struct gnet_stats_rate_est64	rate_est;
  	struct list_head		alist;
  	struct Qdisc			*qdisc;
  
  	u32				quantum;
  	u32				deficit;
  };
  
  struct drr_sched {
  	struct list_head		active;
  	struct tcf_proto		*filter_list;
  	struct Qdisc_class_hash		clhash;
  };
  
  static struct drr_class *drr_find_class(struct Qdisc *sch, u32 classid)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct Qdisc_class_common *clc;
  
  	clc = qdisc_class_find(&q->clhash, classid);
  	if (clc == NULL)
  		return NULL;
  	return container_of(clc, struct drr_class, common);
  }
  
  static void drr_purge_queue(struct drr_class *cl)
  {
  	unsigned int len = cl->qdisc->q.qlen;
  
  	qdisc_reset(cl->qdisc);
  	qdisc_tree_decrease_qlen(cl->qdisc, len);
  }
  
  static const struct nla_policy drr_policy[TCA_DRR_MAX + 1] = {
  	[TCA_DRR_QUANTUM]	= { .type = NLA_U32 },
  };
  
  static int drr_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
  			    struct nlattr **tca, unsigned long *arg)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl = (struct drr_class *)*arg;
  	struct nlattr *opt = tca[TCA_OPTIONS];
  	struct nlattr *tb[TCA_DRR_MAX + 1];
  	u32 quantum;
  	int err;
  
  	if (!opt)
  		return -EINVAL;
  
  	err = nla_parse_nested(tb, TCA_DRR_MAX, opt, drr_policy);
  	if (err < 0)
  		return err;
  
  	if (tb[TCA_DRR_QUANTUM]) {
  		quantum = nla_get_u32(tb[TCA_DRR_QUANTUM]);
  		if (quantum == 0)
  			return -EINVAL;
  	} else
  		quantum = psched_mtu(qdisc_dev(sch));
  
  	if (cl != NULL) {
  		if (tca[TCA_RATE]) {
  			err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
  						    qdisc_root_sleeping_lock(sch),
  						    tca[TCA_RATE]);
  			if (err)
  				return err;
  		}
  
  		sch_tree_lock(sch);
  		if (tb[TCA_DRR_QUANTUM])
  			cl->quantum = quantum;
  		sch_tree_unlock(sch);
  
  		return 0;
  	}
  
  	cl = kzalloc(sizeof(struct drr_class), GFP_KERNEL);
  	if (cl == NULL)
  		return -ENOBUFS;
  
  	cl->refcnt	   = 1;
  	cl->common.classid = classid;
  	cl->quantum	   = quantum;
  	cl->qdisc	   = qdisc_create_dflt(sch->dev_queue,
  					       &pfifo_qdisc_ops, classid);
  	if (cl->qdisc == NULL)
  		cl->qdisc = &noop_qdisc;
  
  	if (tca[TCA_RATE]) {
  		err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
  					    qdisc_root_sleeping_lock(sch),
  					    tca[TCA_RATE]);
  		if (err) {
  			qdisc_destroy(cl->qdisc);
  			kfree(cl);
  			return err;
  		}
  	}
  
  	sch_tree_lock(sch);
  	qdisc_class_hash_insert(&q->clhash, &cl->common);
  	sch_tree_unlock(sch);
  
  	qdisc_class_hash_grow(sch, &q->clhash);
  
  	*arg = (unsigned long)cl;
  	return 0;
  }
  
  static void drr_destroy_class(struct Qdisc *sch, struct drr_class *cl)
  {
  	gen_kill_estimator(&cl->bstats, &cl->rate_est);
  	qdisc_destroy(cl->qdisc);
  	kfree(cl);
  }
  
  static int drr_delete_class(struct Qdisc *sch, unsigned long arg)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	if (cl->filter_cnt > 0)
  		return -EBUSY;
  
  	sch_tree_lock(sch);
  
  	drr_purge_queue(cl);
  	qdisc_class_hash_remove(&q->clhash, &cl->common);
  
  	BUG_ON(--cl->refcnt == 0);
  	/*
  	 * This shouldn't happen: we "hold" one cops->get() when called
  	 * from tc_ctl_tclass; the destroy method is done from cops->put().
  	 */
  
  	sch_tree_unlock(sch);
  	return 0;
  }
  
  static unsigned long drr_get_class(struct Qdisc *sch, u32 classid)
  {
  	struct drr_class *cl = drr_find_class(sch, classid);
  
  	if (cl != NULL)
  		cl->refcnt++;
  
  	return (unsigned long)cl;
  }
  
  static void drr_put_class(struct Qdisc *sch, unsigned long arg)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	if (--cl->refcnt == 0)
  		drr_destroy_class(sch, cl);
  }
  
  static struct tcf_proto **drr_tcf_chain(struct Qdisc *sch, unsigned long cl)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  
  	if (cl)
  		return NULL;
  
  	return &q->filter_list;
  }
  
  static unsigned long drr_bind_tcf(struct Qdisc *sch, unsigned long parent,
  				  u32 classid)
  {
  	struct drr_class *cl = drr_find_class(sch, classid);
  
  	if (cl != NULL)
  		cl->filter_cnt++;
  
  	return (unsigned long)cl;
  }
  
  static void drr_unbind_tcf(struct Qdisc *sch, unsigned long arg)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	cl->filter_cnt--;
  }
  
  static int drr_graft_class(struct Qdisc *sch, unsigned long arg,
  			   struct Qdisc *new, struct Qdisc **old)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	if (new == NULL) {
  		new = qdisc_create_dflt(sch->dev_queue,
  					&pfifo_qdisc_ops, cl->common.classid);
  		if (new == NULL)
  			new = &noop_qdisc;
  	}
  
  	sch_tree_lock(sch);
  	drr_purge_queue(cl);
  	*old = cl->qdisc;
  	cl->qdisc = new;
  	sch_tree_unlock(sch);
  	return 0;
  }
  
  static struct Qdisc *drr_class_leaf(struct Qdisc *sch, unsigned long arg)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	return cl->qdisc;
  }
  
  static void drr_qlen_notify(struct Qdisc *csh, unsigned long arg)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  
  	if (cl->qdisc->q.qlen == 0)
  		list_del(&cl->alist);
  }
  
  static int drr_dump_class(struct Qdisc *sch, unsigned long arg,
  			  struct sk_buff *skb, struct tcmsg *tcm)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  	struct nlattr *nest;
  
  	tcm->tcm_parent	= TC_H_ROOT;
  	tcm->tcm_handle	= cl->common.classid;
  	tcm->tcm_info	= cl->qdisc->handle;
  
  	nest = nla_nest_start(skb, TCA_OPTIONS);
  	if (nest == NULL)
  		goto nla_put_failure;
  	if (nla_put_u32(skb, TCA_DRR_QUANTUM, cl->quantum))
  		goto nla_put_failure;
  	return nla_nest_end(skb, nest);
  
  nla_put_failure:
  	nla_nest_cancel(skb, nest);
  	return -EMSGSIZE;
  }
  
  static int drr_dump_class_stats(struct Qdisc *sch, unsigned long arg,
  				struct gnet_dump *d)
  {
  	struct drr_class *cl = (struct drr_class *)arg;
  	struct tc_drr_stats xstats;
  
  	memset(&xstats, 0, sizeof(xstats));
  	if (cl->qdisc->q.qlen) {
  		xstats.deficit = cl->deficit;
  		cl->qdisc->qstats.qlen = cl->qdisc->q.qlen;
  	}
  
  	if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
  	    gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
  	    gnet_stats_copy_queue(d, &cl->qdisc->qstats) < 0)
  		return -1;
  
  	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
  }
  
  static void drr_walk(struct Qdisc *sch, struct qdisc_walker *arg)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	unsigned int i;
  
  	if (arg->stop)
  		return;
  
  	for (i = 0; i < q->clhash.hashsize; i++) {
  		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
  			if (arg->count < arg->skip) {
  				arg->count++;
  				continue;
  			}
  			if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
  				arg->stop = 1;
  				return;
  			}
  			arg->count++;
  		}
  	}
  }
  
  static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
  				      int *qerr)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	struct tcf_result res;
  	int result;
  
  	if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
  		cl = drr_find_class(sch, skb->priority);
  		if (cl != NULL)
  			return cl;
  	}
  
  	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
  	result = tc_classify(skb, q->filter_list, &res);
  	if (result >= 0) {
  #ifdef CONFIG_NET_CLS_ACT
  		switch (result) {
  		case TC_ACT_QUEUED:
  		case TC_ACT_STOLEN:
  			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
  		case TC_ACT_SHOT:
  			return NULL;
  		}
  #endif
  		cl = (struct drr_class *)res.class;
  		if (cl == NULL)
  			cl = drr_find_class(sch, res.classid);
  		return cl;
  	}
  	return NULL;
  }
  
  static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	int err = 0;
  
  	cl = drr_classify(skb, sch, &err);
  	if (cl == NULL) {
  		if (err & __NET_XMIT_BYPASS)
  			sch->qstats.drops++;
  		kfree_skb(skb);
  		return err;
  	}
  
  	err = qdisc_enqueue(skb, cl->qdisc);
  	if (unlikely(err != NET_XMIT_SUCCESS)) {
  		if (net_xmit_drop_count(err)) {
  			cl->qstats.drops++;
  			sch->qstats.drops++;
  		}
  		return err;
  	}
  
  	if (cl->qdisc->q.qlen == 1) {
  		list_add_tail(&cl->alist, &q->active);
  		cl->deficit = cl->quantum;
  	}
  
  	sch->q.qlen++;
  	return err;
  }
  
  static struct sk_buff *drr_dequeue(struct Qdisc *sch)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	struct sk_buff *skb;
  	unsigned int len;
  
  	if (list_empty(&q->active))
  		goto out;
  	while (1) {
  		cl = list_first_entry(&q->active, struct drr_class, alist);
  		skb = cl->qdisc->ops->peek(cl->qdisc);
  		if (skb == NULL)
  			goto out;
  
  		len = qdisc_pkt_len(skb);
  		if (len <= cl->deficit) {
  			cl->deficit -= len;
  			skb = qdisc_dequeue_peeked(cl->qdisc);
  			if (cl->qdisc->q.qlen == 0)
  				list_del(&cl->alist);
  
  			bstats_update(&cl->bstats, skb);
  			qdisc_bstats_update(sch, skb);
  			sch->q.qlen--;
  			return skb;
  		}
  
  		cl->deficit += cl->quantum;
  		list_move_tail(&cl->alist, &q->active);
  	}
  out:
  	return NULL;
  }
  
  static unsigned int drr_drop(struct Qdisc *sch)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	unsigned int len;
  
  	list_for_each_entry(cl, &q->active, alist) {
  		if (cl->qdisc->ops->drop) {
  			len = cl->qdisc->ops->drop(cl->qdisc);
  			if (len > 0) {
  				sch->q.qlen--;
  				if (cl->qdisc->q.qlen == 0)
  					list_del(&cl->alist);
  				return len;
  			}
  		}
  	}
  	return 0;
  }
  
  static int drr_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	int err;
  
  	err = qdisc_class_hash_init(&q->clhash);
  	if (err < 0)
  		return err;
  	INIT_LIST_HEAD(&q->active);
  	return 0;
  }
  
  static void drr_reset_qdisc(struct Qdisc *sch)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	unsigned int i;
  
  	for (i = 0; i < q->clhash.hashsize; i++) {
  		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
  			if (cl->qdisc->q.qlen)
  				list_del(&cl->alist);
  			qdisc_reset(cl->qdisc);
  		}
  	}
  	sch->q.qlen = 0;
  }
  
  static void drr_destroy_qdisc(struct Qdisc *sch)
  {
  	struct drr_sched *q = qdisc_priv(sch);
  	struct drr_class *cl;
  	struct hlist_node *next;
  	unsigned int i;
  
  	tcf_destroy_chain(&q->filter_list);
  
  	for (i = 0; i < q->clhash.hashsize; i++) {
  		hlist_for_each_entry_safe(cl, next, &q->clhash.hash[i],
  					  common.hnode)
  			drr_destroy_class(sch, cl);
  	}
  	qdisc_class_hash_destroy(&q->clhash);
  }
  
  static const struct Qdisc_class_ops drr_class_ops = {
  	.change		= drr_change_class,
  	.delete		= drr_delete_class,
  	.get		= drr_get_class,
  	.put		= drr_put_class,
  	.tcf_chain	= drr_tcf_chain,
  	.bind_tcf	= drr_bind_tcf,
  	.unbind_tcf	= drr_unbind_tcf,
  	.graft		= drr_graft_class,
  	.leaf		= drr_class_leaf,
  	.qlen_notify	= drr_qlen_notify,
  	.dump		= drr_dump_class,
  	.dump_stats	= drr_dump_class_stats,
  	.walk		= drr_walk,
  };
  
  static struct Qdisc_ops drr_qdisc_ops __read_mostly = {
  	.cl_ops		= &drr_class_ops,
  	.id		= "drr",
  	.priv_size	= sizeof(struct drr_sched),
  	.enqueue	= drr_enqueue,
  	.dequeue	= drr_dequeue,
  	.peek		= qdisc_peek_dequeued,
  	.drop		= drr_drop,
  	.init		= drr_init_qdisc,
  	.reset		= drr_reset_qdisc,
  	.destroy	= drr_destroy_qdisc,
  	.owner		= THIS_MODULE,
  };
  
  static int __init drr_init(void)
  {
  	return register_qdisc(&drr_qdisc_ops);
  }
  
  static void __exit drr_exit(void)
  {
  	unregister_qdisc(&drr_qdisc_ops);
  }
  
  module_init(drr_init);
  module_exit(drr_exit);
  MODULE_LICENSE("GPL");