#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) 2012,2015 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>
  
  /* 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_get_ns();

  
  	return ns >> CODEL_SHIFT;
  }

  /* Dealing with timer wrapping, according to RFC 1982, as desc in wikipedia:
   *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
   * codel_time_after(a,b) returns true if the time a is after time b.
   */
  #define codel_time_after(a, b)						\
  	(typecheck(codel_time_t, a) &&					\
  	 typecheck(codel_time_t, b) &&					\
  	 ((s32)((a) - (b)) > 0))
  #define codel_time_before(a, b) 	codel_time_after(b, a)
  
  #define codel_time_after_eq(a, b)					\
  	(typecheck(codel_time_t, a) &&					\
  	 typecheck(codel_time_t, b) &&					\
  	 ((s32)((a) - (b)) >= 0))
  #define codel_time_before_eq(a, b)	codel_time_after_eq(b, a)

  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)

   * @ce_threshold:  threshold for marking packets with ECN CE

   * @interval:	width of moving time window

   * @mtu:	device mtu, or minimal queue backlog in bytes.

   * @ecn:	is Explicit Congestion Notification enabled
   */
  struct codel_params {
  	codel_time_t	target;

  	codel_time_t	ce_threshold;

  	codel_time_t	interval;

  	u32		mtu;

  	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()

   * @drop_len:	bytes of dropped packets in dequeue()

   * ecn_mark:	number of packets we ECN marked instead of dropping

   * ce_mark:	number of packets CE marked because sojourn time was above ce_threshold

   */
  struct codel_stats {
  	u32		maxpacket;
  	u32		drop_count;

  	u32		drop_len;

  	u32		ecn_mark;

  	u32		ce_mark;

  };

  #define CODEL_DISABLED_THRESHOLD INT_MAX

  typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
  typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
  typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
  typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
  						void *ctx);

  #endif