backport-include/net/codel.h - vendor/opensource/backports - Git at Google

 #include <linux/version.h>
 #include <linux/pkt_sched.h>

 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,5,0)) || (defined(TCA_CODEL_MAX) && !defined(COMPAT_CODEL_BACKPORT))
 #include_next <net/codel.h>
 #else

 #ifndef __NET_SCHED_CODEL_H
 #define __NET_SCHED_CODEL_H

 /*
  * Codel - The Controlled-Delay Active Queue Management algorithm
  *
  *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
  *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
  *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
  *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions, and the following disclaimer,
  *    without modification.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  * 3. The names of the authors may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * Alternatively, provided that this notice is retained in full, this
  * software may be distributed under the terms of the GNU General
  * Public License ("GPL") version 2, in which case the provisions of the
  * GPL apply INSTEAD OF those given above.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  * DAMAGE.
  *
  */

 #include <linux/types.h>
 #include <linux/ktime.h>
 #include <linux/skbuff.h>
 #include <net/pkt_sched.h>
 #include <net/inet_ecn.h>
 #include <linux/reciprocal_div.h>

 /* Controlling Queue Delay (CoDel) algorithm
  * =========================================
  * Source : Kathleen Nichols and Van Jacobson
  * http://queue.acm.org/detail.cfm?id=2209336
  *
  * Implemented on linux by Dave Taht and Eric Dumazet
  */


 /* CoDel uses a 1024 nsec clock, encoded in u32
  * This gives a range of 2199 seconds, because of signed compares
  */
 typedef u32 codel_time_t;
 typedef s32 codel_tdiff_t;
 #define CODEL_SHIFT 10
 #define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)

 static inline codel_time_t codel_get_time(void)
 {
 	u64 ns = ktime_to_ns(ktime_get());

 	return ns >> CODEL_SHIFT;
 }

 #define codel_time_after(a, b)		((s32)(a) - (s32)(b) > 0)
 #define codel_time_after_eq(a, b)	((s32)(a) - (s32)(b) >= 0)
 #define codel_time_before(a, b)		((s32)(a) - (s32)(b) < 0)
 #define codel_time_before_eq(a, b)	((s32)(a) - (s32)(b) <= 0)

 /* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
 struct codel_skb_cb {
 	codel_time_t enqueue_time;
 };

 static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)
 {
 	qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
 	return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
 }

 static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
 {
 	return get_codel_cb(skb)->enqueue_time;
 }

 static void codel_set_enqueue_time(struct sk_buff *skb)
 {
 	get_codel_cb(skb)->enqueue_time = codel_get_time();
 }

 static inline u32 codel_time_to_us(codel_time_t val)
 {
 	u64 valns = ((u64)val << CODEL_SHIFT);

 	do_div(valns, NSEC_PER_USEC);
 	return (u32)valns;
 }

 /**
  * struct codel_params - contains codel parameters
  * @target:	target queue size (in time units)
  * @interval:	width of moving time window
  * @ecn:	is Explicit Congestion Notification enabled
  */
 struct codel_params {
 	codel_time_t	target;
 	codel_time_t	interval;
 	bool		ecn;
 };

 /**
  * struct codel_vars - contains codel variables
  * @count:		how many drops we've done since the last time we
  *			entered dropping state
  * @lastcount:		count at entry to dropping state
  * @dropping:		set to true if in dropping state
  * @rec_inv_sqrt:	reciprocal value of sqrt(count) >> 1
  * @first_above_time:	when we went (or will go) continuously above target
  *			for interval
  * @drop_next:		time to drop next packet, or when we dropped last
  * @ldelay:		sojourn time of last dequeued packet
  */
 struct codel_vars {
 	u32		count;
 	u32		lastcount;
 	bool		dropping;
 	u16		rec_inv_sqrt;
 	codel_time_t	first_above_time;
 	codel_time_t	drop_next;
 	codel_time_t	ldelay;
 };

 #define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
 /* needed shift to get a Q0.32 number from rec_inv_sqrt */
 #define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)

 /**
  * struct codel_stats - contains codel shared variables and stats
  * @maxpacket:	largest packet we've seen so far
  * @drop_count:	temp count of dropped packets in dequeue()
  * ecn_mark:	number of packets we ECN marked instead of dropping
  */
 struct codel_stats {
 	u32		maxpacket;
 	u32		drop_count;
 	u32		ecn_mark;
 };

 static void codel_params_init(struct codel_params *params)
 {
 	params->interval = MS2TIME(100);
 	params->target = MS2TIME(5);
 	params->ecn = false;
 }

 static void codel_vars_init(struct codel_vars *vars)
 {
 	memset(vars, 0, sizeof(*vars));
 }

 static void codel_stats_init(struct codel_stats *stats)
 {
 	stats->maxpacket = 256;
 }

 /*
  * http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
  * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
  *
  * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
  */
 static void codel_Newton_step(struct codel_vars *vars)
 {
 	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
 	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
 	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);

 	val >>= 2; /* avoid overflow in following multiply */
 	val = (val * invsqrt) >> (32 - 2 + 1);

 	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
 }

 /*
  * CoDel control_law is t + interval/sqrt(count)
  * We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
  * both sqrt() and divide operation.
  */
 static codel_time_t codel_control_law(codel_time_t t,
 				      codel_time_t interval,
 				      u32 rec_inv_sqrt)
 {
 	return t + reciprocal_divide(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
 }


 static bool codel_should_drop(const struct sk_buff *skb,
 			      struct Qdisc *sch,
 			      struct codel_vars *vars,
 			      struct codel_params *params,
 			      struct codel_stats *stats,
 			      codel_time_t now)
 {
 	bool ok_to_drop;

 	if (!skb) {
 		vars->first_above_time = 0;
 		return false;
 	}

 	vars->ldelay = now - codel_get_enqueue_time(skb);
 	sch->qstats.backlog -= qdisc_pkt_len(skb);

 	if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
 		stats->maxpacket = qdisc_pkt_len(skb);

 	if (codel_time_before(vars->ldelay, params->target) ||
 	    sch->qstats.backlog <= stats->maxpacket) {
 		/* went below - stay below for at least interval */
 		vars->first_above_time = 0;
 		return false;
 	}
 	ok_to_drop = false;
 	if (vars->first_above_time == 0) {
 		/* just went above from below. If we stay above
 		 * for at least interval we'll say it's ok to drop
 		 */
 		vars->first_above_time = now + params->interval;
 	} else if (codel_time_after(now, vars->first_above_time)) {
 		ok_to_drop = true;
 	}
 	return ok_to_drop;
 }

 typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
 						struct Qdisc *sch);

 static struct sk_buff *codel_dequeue(struct Qdisc *sch,
 				     struct codel_params *params,
 				     struct codel_vars *vars,
 				     struct codel_stats *stats,
 				     codel_skb_dequeue_t dequeue_func)
 {
 	struct sk_buff *skb = dequeue_func(vars, sch);
 	codel_time_t now;
 	bool drop;

 	if (!skb) {
 		vars->dropping = false;
 		return skb;
 	}
 	now = codel_get_time();
 	drop = codel_should_drop(skb, sch, vars, params, stats, now);
 	if (vars->dropping) {
 		if (!drop) {
 			/* sojourn time below target - leave dropping state */
 			vars->dropping = false;
 		} else if (codel_time_after_eq(now, vars->drop_next)) {
 			/* It's time for the next drop. Drop the current
 			 * packet and dequeue the next. The dequeue might
 			 * take us out of dropping state.
 			 * If not, schedule the next drop.
 			 * A large backlog might result in drop rates so high
 			 * that the next drop should happen now,
 			 * hence the while loop.
 			 */
 			while (vars->dropping &&
 			       codel_time_after_eq(now, vars->drop_next)) {
 				vars->count++; /* dont care of possible wrap
 						* since there is no more divide
 						*/
 				codel_Newton_step(vars);
 				if (params->ecn && INET_ECN_set_ce(skb)) {
 					stats->ecn_mark++;
 					vars->drop_next =
 						codel_control_law(vars->drop_next,
 								  params->interval,
 								  vars->rec_inv_sqrt);
 					goto end;
 				}
 				qdisc_drop(skb, sch);
 				stats->drop_count++;
 				skb = dequeue_func(vars, sch);
 				if (!codel_should_drop(skb, sch,
 						       vars, params, stats, now)) {
 					/* leave dropping state */
 					vars->dropping = false;
 				} else {
 					/* and schedule the next drop */
 					vars->drop_next =
 						codel_control_law(vars->drop_next,
 								  params->interval,
 								  vars->rec_inv_sqrt);
 				}
 			}
 		}
 	} else if (drop) {
 		if (params->ecn && INET_ECN_set_ce(skb)) {
 			stats->ecn_mark++;
 		} else {
 			qdisc_drop(skb, sch);
 			stats->drop_count++;

 			skb = dequeue_func(vars, sch);
 			drop = codel_should_drop(skb, sch, vars, params,
 						 stats, now);
 		}
 		vars->dropping = true;
 		/* if min went above target close to when we last went below it
 		 * assume that the drop rate that controlled the queue on the
 		 * last cycle is a good starting point to control it now.
 		 */
 		if (codel_time_before(now - vars->drop_next,
 				      16 * params->interval)) {
 			vars->count = (vars->count - vars->lastcount) | 1;
 			/* we dont care if rec_inv_sqrt approximation
 			 * is not very precise :
 			 * Next Newton steps will correct it quadratically.
 			 */
 			codel_Newton_step(vars);
 		} else {
 			vars->count = 1;
 			vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
 		}
 		vars->lastcount = vars->count;
 		vars->drop_next = codel_control_law(now, params->interval,
 						    vars->rec_inv_sqrt);
 	}
 end:
 	return skb;
 }
 #endif
 #endif
	#include <linux/version.h>
	#include <linux/pkt_sched.h>

	#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,5,0)) \|\| (defined(TCA_CODEL_MAX) && !defined(COMPAT_CODEL_BACKPORT))
	#include_next <net/codel.h>
	#else

	#ifndef __NET_SCHED_CODEL_H
	#define __NET_SCHED_CODEL_H

	/*
	* Codel - The Controlled-Delay Active Queue Management algorithm
	*
	* Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
	* Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
	* Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
	* Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions, and the following disclaimer,
	* without modification.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. The names of the authors may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* Alternatively, provided that this notice is retained in full, this
	* software may be distributed under the terms of the GNU General
	* Public License ("GPL") version 2, in which case the provisions of the
	* GPL apply INSTEAD OF those given above.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
	* DAMAGE.
	*
	*/

	#include <linux/types.h>
	#include <linux/ktime.h>
	#include <linux/skbuff.h>
	#include <net/pkt_sched.h>
	#include <net/inet_ecn.h>
	#include <linux/reciprocal_div.h>

	/* Controlling Queue Delay (CoDel) algorithm
	* =========================================
	* Source : Kathleen Nichols and Van Jacobson
	* http://queue.acm.org/detail.cfm?id=2209336
	*
	* Implemented on linux by Dave Taht and Eric Dumazet
	*/


	/* CoDel uses a 1024 nsec clock, encoded in u32
	* This gives a range of 2199 seconds, because of signed compares
	*/
	typedef u32 codel_time_t;
	typedef s32 codel_tdiff_t;
	#define CODEL_SHIFT 10
	#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)

	static inline codel_time_t codel_get_time(void)
	{
	u64 ns = ktime_to_ns(ktime_get());

	return ns >> CODEL_SHIFT;
	}

	#define codel_time_after(a, b) ((s32)(a) - (s32)(b) > 0)
	#define codel_time_after_eq(a, b) ((s32)(a) - (s32)(b) >= 0)
	#define codel_time_before(a, b) ((s32)(a) - (s32)(b) < 0)
	#define codel_time_before_eq(a, b) ((s32)(a) - (s32)(b) <= 0)

	/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
	struct codel_skb_cb {
	codel_time_t enqueue_time;
	};

	static struct codel_skb_cb get_codel_cb(const struct sk_buff skb)
	{
	qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
	return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
	}

	static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
	{
	return get_codel_cb(skb)->enqueue_time;
	}

	static void codel_set_enqueue_time(struct sk_buff *skb)
	{
	get_codel_cb(skb)->enqueue_time = codel_get_time();
	}

	static inline u32 codel_time_to_us(codel_time_t val)
	{
	u64 valns = ((u64)val << CODEL_SHIFT);

	do_div(valns, NSEC_PER_USEC);
	return (u32)valns;
	}

	/**
	* struct codel_params - contains codel parameters
	* @target: target queue size (in time units)
	* @interval: width of moving time window
	* @ecn: is Explicit Congestion Notification enabled
	*/
	struct codel_params {
	codel_time_t target;
	codel_time_t interval;
	bool ecn;
	};

	/**
	* struct codel_vars - contains codel variables
	* @count: how many drops we've done since the last time we
	* entered dropping state
	* @lastcount: count at entry to dropping state
	* @dropping: set to true if in dropping state
	* @rec_inv_sqrt: reciprocal value of sqrt(count) >> 1
	* @first_above_time: when we went (or will go) continuously above target
	* for interval
	* @drop_next: time to drop next packet, or when we dropped last
	* @ldelay: sojourn time of last dequeued packet
	*/
	struct codel_vars {
	u32 count;
	u32 lastcount;
	bool dropping;
	u16 rec_inv_sqrt;
	codel_time_t first_above_time;
	codel_time_t drop_next;
	codel_time_t ldelay;
	};

	#define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
	/* needed shift to get a Q0.32 number from rec_inv_sqrt */
	#define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)

	/**
	* struct codel_stats - contains codel shared variables and stats
	* @maxpacket: largest packet we've seen so far
	* @drop_count: temp count of dropped packets in dequeue()
	* ecn_mark: number of packets we ECN marked instead of dropping
	*/
	struct codel_stats {
	u32 maxpacket;
	u32 drop_count;
	u32 ecn_mark;
	};

	static void codel_params_init(struct codel_params *params)
	{
	params->interval = MS2TIME(100);
	params->target = MS2TIME(5);
	params->ecn = false;
	}

	static void codel_vars_init(struct codel_vars *vars)
	{
	memset(vars, 0, sizeof(*vars));
	}

	static void codel_stats_init(struct codel_stats *stats)
	{
	stats->maxpacket = 256;
	}

	/*
	* http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
	* new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
	*
	* Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
	*/
	static void codel_Newton_step(struct codel_vars *vars)
	{
	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);

	val >>= 2; /* avoid overflow in following multiply */
	val = (val * invsqrt) >> (32 - 2 + 1);

	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
	}

	/*
	* CoDel control_law is t + interval/sqrt(count)
	* We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
	* both sqrt() and divide operation.
	*/
	static codel_time_t codel_control_law(codel_time_t t,
	codel_time_t interval,
	u32 rec_inv_sqrt)
	{
	return t + reciprocal_divide(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
	}


	static bool codel_should_drop(const struct sk_buff *skb,
	struct Qdisc *sch,
	struct codel_vars *vars,
	struct codel_params *params,
	struct codel_stats *stats,
	codel_time_t now)
	{
	bool ok_to_drop;

	if (!skb) {
	vars->first_above_time = 0;
	return false;
	}

	vars->ldelay = now - codel_get_enqueue_time(skb);
	sch->qstats.backlog -= qdisc_pkt_len(skb);

	if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
	stats->maxpacket = qdisc_pkt_len(skb);

	if (codel_time_before(vars->ldelay, params->target) \|\|
	sch->qstats.backlog <= stats->maxpacket) {
	/* went below - stay below for at least interval */
	vars->first_above_time = 0;
	return false;
	}
	ok_to_drop = false;
	if (vars->first_above_time == 0) {
	/* just went above from below. If we stay above
	* for at least interval we'll say it's ok to drop
	*/
	vars->first_above_time = now + params->interval;
	} else if (codel_time_after(now, vars->first_above_time)) {
	ok_to_drop = true;
	}
	return ok_to_drop;
	}

	typedef struct sk_buff * (codel_skb_dequeue_t)(struct codel_vars vars,
	struct Qdisc *sch);

	static struct sk_buff codel_dequeue(struct Qdisc sch,
	struct codel_params *params,
	struct codel_vars *vars,
	struct codel_stats *stats,
	codel_skb_dequeue_t dequeue_func)
	{
	struct sk_buff *skb = dequeue_func(vars, sch);
	codel_time_t now;
	bool drop;

	if (!skb) {
	vars->dropping = false;
	return skb;
	}
	now = codel_get_time();
	drop = codel_should_drop(skb, sch, vars, params, stats, now);
	if (vars->dropping) {
	if (!drop) {
	/* sojourn time below target - leave dropping state */
	vars->dropping = false;
	} else if (codel_time_after_eq(now, vars->drop_next)) {
	/* It's time for the next drop. Drop the current
	* packet and dequeue the next. The dequeue might
	* take us out of dropping state.
	* If not, schedule the next drop.
	* A large backlog might result in drop rates so high
	* that the next drop should happen now,
	* hence the while loop.
	*/
	while (vars->dropping &&
	codel_time_after_eq(now, vars->drop_next)) {
	vars->count++; /* dont care of possible wrap
	* since there is no more divide
	*/
	codel_Newton_step(vars);
	if (params->ecn && INET_ECN_set_ce(skb)) {
	stats->ecn_mark++;
	vars->drop_next =
	codel_control_law(vars->drop_next,
	params->interval,
	vars->rec_inv_sqrt);
	goto end;
	}
	qdisc_drop(skb, sch);
	stats->drop_count++;
	skb = dequeue_func(vars, sch);
	if (!codel_should_drop(skb, sch,
	vars, params, stats, now)) {
	/* leave dropping state */
	vars->dropping = false;
	} else {
	/* and schedule the next drop */
	vars->drop_next =
	codel_control_law(vars->drop_next,
	params->interval,
	vars->rec_inv_sqrt);
	}
	}
	}
	} else if (drop) {
	if (params->ecn && INET_ECN_set_ce(skb)) {
	stats->ecn_mark++;
	} else {
	qdisc_drop(skb, sch);
	stats->drop_count++;

	skb = dequeue_func(vars, sch);
	drop = codel_should_drop(skb, sch, vars, params,
	stats, now);
	}
	vars->dropping = true;
	/* if min went above target close to when we last went below it
	* assume that the drop rate that controlled the queue on the
	* last cycle is a good starting point to control it now.
	*/
	if (codel_time_before(now - vars->drop_next,
	16 * params->interval)) {
	vars->count = (vars->count - vars->lastcount) \| 1;
	/* we dont care if rec_inv_sqrt approximation
	* is not very precise :
	* Next Newton steps will correct it quadratically.
	*/
	codel_Newton_step(vars);
	} else {
	vars->count = 1;
	vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
	}
	vars->lastcount = vars->count;
	vars->drop_next = codel_control_law(now, params->interval,
	vars->rec_inv_sqrt);
	}
	end:
	return skb;
	}
	#endif
	#endif