/*
   * net/sched/sch_gred.c	Generic Random Early Detection queue.
   *
   *
   *              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:    J Hadi Salim (hadi@cyberus.ca) 1998-2002
   *
   *             991129: -  Bug fix with grio mode
   *		       - a better sing. AvgQ mode with Grio(WRED)
   *		       - A finer grained VQ dequeue based on sugestion
   *		         from Ren Liu
   *		       - More error checks
   *

   *  For all the glorious comments look at include/net/red.h

   */

  #include <linux/slab.h>

  #include <linux/module.h>

  #include <linux/types.h>
  #include <linux/kernel.h>

  #include <linux/skbuff.h>

  #include <net/pkt_sched.h>

  #include <net/red.h>

  #define GRED_DEF_PRIO (MAX_DPs / 2)

  #define GRED_VQ_MASK (MAX_DPs - 1)

  struct gred_sched_data;
  struct gred_sched;

  struct gred_sched_data {

  	u32		limit;		/* HARD maximal queue length	*/

  	u32		DP;		/* the drop parameters */

  	u32		bytesin;	/* bytes seen on virtualQ so far*/
  	u32		packetsin;	/* packets seen on virtualQ so far*/
  	u32		backlog;	/* bytes on the virtualQ */

  	u8		prio;		/* the prio of this vq */

  	struct red_parms parms;

  	struct red_vars  vars;

  	struct red_stats stats;

  };

  enum {
  	GRED_WRED_MODE = 1,

  	GRED_RIO_MODE,

  };

  struct gred_sched {

  	struct gred_sched_data *tab[MAX_DPs];

  	unsigned long	flags;

  	u32		red_flags;

  	u32 		DPs;
  	u32 		def;

  	struct red_vars wred_set;

  };

  static inline int gred_wred_mode(struct gred_sched *table)
  {
  	return test_bit(GRED_WRED_MODE, &table->flags);
  }
  
  static inline void gred_enable_wred_mode(struct gred_sched *table)
  {
  	__set_bit(GRED_WRED_MODE, &table->flags);
  }
  
  static inline void gred_disable_wred_mode(struct gred_sched *table)
  {
  	__clear_bit(GRED_WRED_MODE, &table->flags);
  }

  static inline int gred_rio_mode(struct gred_sched *table)
  {
  	return test_bit(GRED_RIO_MODE, &table->flags);
  }
  
  static inline void gred_enable_rio_mode(struct gred_sched *table)
  {
  	__set_bit(GRED_RIO_MODE, &table->flags);
  }
  
  static inline void gred_disable_rio_mode(struct gred_sched *table)
  {
  	__clear_bit(GRED_RIO_MODE, &table->flags);
  }

  static inline int gred_wred_mode_check(struct Qdisc *sch)
  {
  	struct gred_sched *table = qdisc_priv(sch);
  	int i;
  
  	/* Really ugly O(n^2) but shouldn't be necessary too frequent. */
  	for (i = 0; i < table->DPs; i++) {
  		struct gred_sched_data *q = table->tab[i];
  		int n;
  
  		if (q == NULL)
  			continue;
  
  		for (n = 0; n < table->DPs; n++)
  			if (table->tab[n] && table->tab[n] != q &&
  			    table->tab[n]->prio == q->prio)
  				return 1;
  	}
  
  	return 0;
  }

  static inline unsigned int gred_backlog(struct gred_sched *table,
  					struct gred_sched_data *q,
  					struct Qdisc *sch)
  {
  	if (gred_wred_mode(table))
  		return sch->qstats.backlog;
  	else
  		return q->backlog;
  }

  static inline u16 tc_index_to_dp(struct sk_buff *skb)
  {
  	return skb->tc_index & GRED_VQ_MASK;
  }

  static inline void gred_load_wred_set(const struct gred_sched *table,

  				      struct gred_sched_data *q)
  {

  	q->vars.qavg = table->wred_set.qavg;
  	q->vars.qidlestart = table->wred_set.qidlestart;

  }
  
  static inline void gred_store_wred_set(struct gred_sched *table,
  				       struct gred_sched_data *q)
  {

  	table->wred_set.qavg = q->vars.qavg;

  }

  static inline int gred_use_ecn(struct gred_sched *t)
  {
  	return t->red_flags & TC_RED_ECN;
  }

  static inline int gred_use_harddrop(struct gred_sched *t)
  {
  	return t->red_flags & TC_RED_HARDDROP;
  }

  static int gred_enqueue(struct sk_buff *skb, struct Qdisc *sch)

  {

  	struct gred_sched_data *q = NULL;
  	struct gred_sched *t = qdisc_priv(sch);

  	unsigned long qavg = 0;

  	u16 dp = tc_index_to_dp(skb);

  	if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {

  		dp = t->def;

  		q = t->tab[dp];
  		if (!q) {

  			/* Pass through packets not assigned to a DP
  			 * if no default DP has been configured. This
  			 * allows for DP flows to be left untouched.
  			 */

  			if (skb_queue_len(&sch->q) < qdisc_dev(sch)->tx_queue_len)

  				return qdisc_enqueue_tail(skb, sch);
  			else
  				goto drop;

  		}

  		/* fix tc_index? --could be controversial but needed for

  		   requeueing */

  		skb->tc_index = (skb->tc_index & ~GRED_VQ_MASK) | dp;

  	}

  	/* sum up all the qaves of prios <= to ours to get the new qave */

  	if (!gred_wred_mode(t) && gred_rio_mode(t)) {

  		int i;
  
  		for (i = 0; i < t->DPs; i++) {
  			if (t->tab[i] && t->tab[i]->prio < q->prio &&

  			    !red_is_idling(&t->tab[i]->vars))
  				qavg += t->tab[i]->vars.qavg;

  		}

  	}
  
  	q->packetsin++;

  	q->bytesin += qdisc_pkt_len(skb);

  	if (gred_wred_mode(t))

  		gred_load_wred_set(t, q);

  	q->vars.qavg = red_calc_qavg(&q->parms,
  				     &q->vars,
  				     gred_backlog(t, q, sch));

  	if (red_is_idling(&q->vars))
  		red_end_of_idle_period(&q->vars);

  	if (gred_wred_mode(t))

  		gred_store_wred_set(t, q);

  	switch (red_action(&q->parms, &q->vars, q->vars.qavg + qavg)) {

  	case RED_DONT_MARK:
  		break;
  
  	case RED_PROB_MARK:
  		sch->qstats.overlimits++;
  		if (!gred_use_ecn(t) || !INET_ECN_set_ce(skb)) {
  			q->stats.prob_drop++;
  			goto congestion_drop;
  		}
  
  		q->stats.prob_mark++;
  		break;
  
  	case RED_HARD_MARK:
  		sch->qstats.overlimits++;
  		if (gred_use_harddrop(t) || !gred_use_ecn(t) ||
  		    !INET_ECN_set_ce(skb)) {
  			q->stats.forced_drop++;
  			goto congestion_drop;
  		}
  		q->stats.forced_mark++;
  		break;

  	}

  	if (q->backlog + qdisc_pkt_len(skb) <= q->limit) {
  		q->backlog += qdisc_pkt_len(skb);

  		return qdisc_enqueue_tail(skb, sch);

  	}

  
  	q->stats.pdrop++;
  drop:

  	return qdisc_drop(skb, sch);

  
  congestion_drop:

  	qdisc_drop(skb, sch);

  	return NET_XMIT_CN;

  }

  static struct sk_buff *gred_dequeue(struct Qdisc *sch)

  {
  	struct sk_buff *skb;

  	struct gred_sched *t = qdisc_priv(sch);

  	skb = qdisc_dequeue_head(sch);

  	if (skb) {

  		struct gred_sched_data *q;

  		u16 dp = tc_index_to_dp(skb);
  
  		if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
  			if (net_ratelimit())

  				pr_warning("GRED: Unable to relocate VQ 0x%x "
  					   "after dequeue, screwing up "
  					   "backlog.
  ", tc_index_to_dp(skb));

  		} else {

  			q->backlog -= qdisc_pkt_len(skb);

  			if (!q->backlog && !gred_wred_mode(t))

  				red_start_of_idle_period(&q->vars);

  		}

  		return skb;
  	}

  	if (gred_wred_mode(t) && !red_is_idling(&t->wred_set))

  		red_start_of_idle_period(&t->wred_set);

  
  	return NULL;
  }

  static unsigned int gred_drop(struct Qdisc *sch)

  {
  	struct sk_buff *skb;

  	struct gred_sched *t = qdisc_priv(sch);

  	skb = qdisc_dequeue_tail(sch);

  	if (skb) {

  		unsigned int len = qdisc_pkt_len(skb);

  		struct gred_sched_data *q;

  		u16 dp = tc_index_to_dp(skb);
  
  		if (dp >= t->DPs || (q = t->tab[dp]) == NULL) {
  			if (net_ratelimit())

  				pr_warning("GRED: Unable to relocate VQ 0x%x "
  					   "while dropping, screwing up "
  					   "backlog.
  ", tc_index_to_dp(skb));

  		} else {

  			q->backlog -= len;

  			q->stats.other++;

  			if (!q->backlog && !gred_wred_mode(t))

  				red_start_of_idle_period(&q->vars);

  		}

  		qdisc_drop(skb, sch);

  		return len;
  	}

  	if (gred_wred_mode(t) && !red_is_idling(&t->wred_set))

  		red_start_of_idle_period(&t->wred_set);

  	return 0;
  
  }

  static void gred_reset(struct Qdisc *sch)

  {
  	int i;

  	struct gred_sched *t = qdisc_priv(sch);

  	qdisc_reset_queue(sch);

  	for (i = 0; i < t->DPs; i++) {

  		struct gred_sched_data *q = t->tab[i];
  
  		if (!q)
  			continue;

  		red_restart(&q->vars);

  		q->backlog = 0;

  	}
  }

  static inline void gred_destroy_vq(struct gred_sched_data *q)
  {
  	kfree(q);
  }

  static inline int gred_change_table_def(struct Qdisc *sch, struct nlattr *dps)

  {
  	struct gred_sched *table = qdisc_priv(sch);

  	struct tc_gred_sopt *sopt;

  	int i;

  	if (dps == NULL)

  		return -EINVAL;

  	sopt = nla_data(dps);

  	if (sopt->DPs > MAX_DPs || sopt->DPs == 0 || sopt->def_DP >= sopt->DPs)
  		return -EINVAL;

  	sch_tree_lock(sch);
  	table->DPs = sopt->DPs;
  	table->def = sopt->def_DP;

  	table->red_flags = sopt->flags;

  	/*
  	 * Every entry point to GRED is synchronized with the above code
  	 * and the DP is checked against DPs, i.e. shadowed VQs can no
  	 * longer be found so we can unlock right here.
  	 */
  	sch_tree_unlock(sch);

  	if (sopt->grio) {
  		gred_enable_rio_mode(table);
  		gred_disable_wred_mode(table);
  		if (gred_wred_mode_check(sch))
  			gred_enable_wred_mode(table);
  	} else {
  		gred_disable_rio_mode(table);
  		gred_disable_wred_mode(table);
  	}
  
  	for (i = table->DPs; i < MAX_DPs; i++) {
  		if (table->tab[i]) {

  			pr_warning("GRED: Warning: Destroying "
  				   "shadowed VQ 0x%x
  ", i);

  			gred_destroy_vq(table->tab[i]);
  			table->tab[i] = NULL;

  		}

  	}

  	return 0;
  }

  static inline int gred_change_vq(struct Qdisc *sch, int dp,

  				 struct tc_gred_qopt *ctl, int prio,

  				 u8 *stab, u32 max_P,
  				 struct gred_sched_data **prealloc)

  {
  	struct gred_sched *table = qdisc_priv(sch);

  	struct gred_sched_data *q = table->tab[dp];

  	if (!q) {
  		table->tab[dp] = q = *prealloc;
  		*prealloc = NULL;
  		if (!q)

  			return -ENOMEM;

  	}

  	q->DP = dp;
  	q->prio = prio;

  	q->limit = ctl->limit;

  
  	if (q->backlog == 0)

  		red_end_of_idle_period(&q->vars);

  
  	red_set_parms(&q->parms,
  		      ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Plog,

  		      ctl->Scell_log, stab, max_P);

  	red_set_vars(&q->vars);

  	return 0;
  }

  static const struct nla_policy gred_policy[TCA_GRED_MAX + 1] = {
  	[TCA_GRED_PARMS]	= { .len = sizeof(struct tc_gred_qopt) },
  	[TCA_GRED_STAB]		= { .len = 256 },
  	[TCA_GRED_DPS]		= { .len = sizeof(struct tc_gred_sopt) },

  	[TCA_GRED_MAX_P]	= { .type = NLA_U32 },

  };

  static int gred_change(struct Qdisc *sch, struct nlattr *opt)

  {
  	struct gred_sched *table = qdisc_priv(sch);

  	struct tc_gred_qopt *ctl;

  	struct nlattr *tb[TCA_GRED_MAX + 1];

  	int err, prio = GRED_DEF_PRIO;

  	u8 *stab;

  	u32 max_P;

  	struct gred_sched_data *prealloc;

  	if (opt == NULL)

  		return -EINVAL;

  	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);

  	if (err < 0)
  		return err;

  	if (tb[TCA_GRED_PARMS] == NULL && tb[TCA_GRED_STAB] == NULL)

  		return gred_change_table_def(sch, opt);

  	if (tb[TCA_GRED_PARMS] == NULL ||

  	    tb[TCA_GRED_STAB] == NULL)

  		return -EINVAL;

  	max_P = tb[TCA_GRED_MAX_P] ? nla_get_u32(tb[TCA_GRED_MAX_P]) : 0;

  	err = -EINVAL;

  	ctl = nla_data(tb[TCA_GRED_PARMS]);
  	stab = nla_data(tb[TCA_GRED_STAB]);

  
  	if (ctl->DP >= table->DPs)

  		goto errout;

  	if (gred_rio_mode(table)) {

  		if (ctl->prio == 0) {
  			int def_prio = GRED_DEF_PRIO;
  
  			if (table->tab[table->def])
  				def_prio = table->tab[table->def]->prio;
  
  			printk(KERN_DEBUG "GRED: DP %u does not have a prio "
  			       "setting default to %d
  ", ctl->DP, def_prio);
  
  			prio = def_prio;
  		} else
  			prio = ctl->prio;

  	}

  	prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);

  	sch_tree_lock(sch);

  	err = gred_change_vq(sch, ctl->DP, ctl, prio, stab, max_P, &prealloc);

  	if (err < 0)
  		goto errout_locked;

  	if (gred_rio_mode(table)) {

  		gred_disable_wred_mode(table);
  		if (gred_wred_mode_check(sch))
  			gred_enable_wred_mode(table);

  	}

  	err = 0;

  errout_locked:
  	sch_tree_unlock(sch);

  	kfree(prealloc);

  errout:
  	return err;

  }

  static int gred_init(struct Qdisc *sch, struct nlattr *opt)

  {

  	struct nlattr *tb[TCA_GRED_MAX + 1];

  	int err;

  	if (opt == NULL)

  		return -EINVAL;

  	err = nla_parse_nested(tb, TCA_GRED_MAX, opt, gred_policy);

  	if (err < 0)
  		return err;

  	if (tb[TCA_GRED_PARMS] || tb[TCA_GRED_STAB])

  		return -EINVAL;

  	return gred_change_table_def(sch, tb[TCA_GRED_DPS]);

  }
  
  static int gred_dump(struct Qdisc *sch, struct sk_buff *skb)
  {

  	struct gred_sched *table = qdisc_priv(sch);

  	struct nlattr *parms, *opts = NULL;

  	int i;

  	u32 max_p[MAX_DPs];

  	struct tc_gred_sopt sopt = {
  		.DPs	= table->DPs,
  		.def_DP	= table->def,
  		.grio	= gred_rio_mode(table),

  		.flags	= table->red_flags,

  	};

  	opts = nla_nest_start(skb, TCA_OPTIONS);
  	if (opts == NULL)
  		goto nla_put_failure;
  	NLA_PUT(skb, TCA_GRED_DPS, sizeof(sopt), &sopt);

  
  	for (i = 0; i < MAX_DPs; i++) {
  		struct gred_sched_data *q = table->tab[i];
  
  		max_p[i] = q ? q->parms.max_P : 0;
  	}
  	NLA_PUT(skb, TCA_GRED_MAX_P, sizeof(max_p), max_p);

  	parms = nla_nest_start(skb, TCA_GRED_PARMS);
  	if (parms == NULL)
  		goto nla_put_failure;

  	for (i = 0; i < MAX_DPs; i++) {
  		struct gred_sched_data *q = table->tab[i];
  		struct tc_gred_qopt opt;

  		memset(&opt, 0, sizeof(opt));

  
  		if (!q) {
  			/* hack -- fix at some point with proper message
  			   This is how we indicate to tc that there is no VQ
  			   at this DP */

  			opt.DP = MAX_DPs + i;
  			goto append_opt;

  		}

  		opt.limit	= q->limit;
  		opt.DP		= q->DP;
  		opt.backlog	= q->backlog;
  		opt.prio	= q->prio;

  		opt.qth_min	= q->parms.qth_min >> q->parms.Wlog;
  		opt.qth_max	= q->parms.qth_max >> q->parms.Wlog;
  		opt.Wlog	= q->parms.Wlog;
  		opt.Plog	= q->parms.Plog;
  		opt.Scell_log	= q->parms.Scell_log;
  		opt.other	= q->stats.other;
  		opt.early	= q->stats.prob_drop;
  		opt.forced	= q->stats.forced_drop;
  		opt.pdrop	= q->stats.pdrop;

  		opt.packets	= q->packetsin;
  		opt.bytesin	= q->bytesin;

  		if (gred_wred_mode(table)) {

  			q->vars.qidlestart =
  				table->tab[table->def]->vars.qidlestart;
  			q->vars.qavg = table->tab[table->def]->vars.qavg;

  		}

  		opt.qave = red_calc_qavg(&q->parms, &q->vars, q->vars.qavg);

  append_opt:

  		if (nla_append(skb, sizeof(opt), &opt) < 0)
  			goto nla_put_failure;

  	}

  	nla_nest_end(skb, parms);

  	return nla_nest_end(skb, opts);

  nla_put_failure:

  	nla_nest_cancel(skb, opts);
  	return -EMSGSIZE;

  }
  
  static void gred_destroy(struct Qdisc *sch)
  {
  	struct gred_sched *table = qdisc_priv(sch);
  	int i;

  	for (i = 0; i < table->DPs; i++) {

  		if (table->tab[i])

  			gred_destroy_vq(table->tab[i]);

  	}
  }

  static struct Qdisc_ops gred_qdisc_ops __read_mostly = {

  	.id		=	"gred",
  	.priv_size	=	sizeof(struct gred_sched),
  	.enqueue	=	gred_enqueue,
  	.dequeue	=	gred_dequeue,

  	.peek		=	qdisc_peek_head,

  	.drop		=	gred_drop,
  	.init		=	gred_init,
  	.reset		=	gred_reset,
  	.destroy	=	gred_destroy,
  	.change		=	gred_change,
  	.dump		=	gred_dump,
  	.owner		=	THIS_MODULE,
  };
  
  static int __init gred_module_init(void)
  {
  	return register_qdisc(&gred_qdisc_ops);
  }

  
  static void __exit gred_module_exit(void)

  {
  	unregister_qdisc(&gred_qdisc_ops);
  }

  module_init(gred_module_init)
  module_exit(gred_module_exit)

  MODULE_LICENSE("GPL");