1#ifndef __NET_SCHED_CODEL_H
  2#define __NET_SCHED_CODEL_H
  3
  4/*
  5 * Codel - The Controlled-Delay Active Queue Management algorithm
  6 *
  7 *  Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
  8 *  Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
  9 *  Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
 10 *  Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
 11 *
 12 * Redistribution and use in source and binary forms, with or without
 13 * modification, are permitted provided that the following conditions
 14 * are met:
 15 * 1. Redistributions of source code must retain the above copyright
 16 *    notice, this list of conditions, and the following disclaimer,
 17 *    without modification.
 18 * 2. Redistributions in binary form must reproduce the above copyright
 19 *    notice, this list of conditions and the following disclaimer in the
 20 *    documentation and/or other materials provided with the distribution.
 21 * 3. The names of the authors may not be used to endorse or promote products
 22 *    derived from this software without specific prior written permission.
 23 *
 24 * Alternatively, provided that this notice is retained in full, this
 25 * software may be distributed under the terms of the GNU General
 26 * Public License ("GPL") version 2, in which case the provisions of the
 27 * GPL apply INSTEAD OF those given above.
 28 *
 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 40 * DAMAGE.
 41 *
 42 */
 43
 44#include <linux/types.h>
 45#include <linux/ktime.h>
 46#include <linux/skbuff.h>
 47
 48/* Controlling Queue Delay (CoDel) algorithm
 49 * =========================================
 50 * Source : Kathleen Nichols and Van Jacobson
 51 * http://queue.acm.org/detail.cfm?id=2209336
 52 *
 53 * Implemented on linux by Dave Taht and Eric Dumazet
 54 */
 55
 56
 57/* CoDel uses a 1024 nsec clock, encoded in u32
 58 * This gives a range of 2199 seconds, because of signed compares
 59 */
 60typedef u32 codel_time_t;
 61typedef s32 codel_tdiff_t;
 62#define CODEL_SHIFT 10
 63#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
 64
 65static inline codel_time_t codel_get_time(void)
 66{
 67	u64 ns = ktime_get_ns();
 68
 69	return ns >> CODEL_SHIFT;
 70}
 71
 72/* Dealing with timer wrapping, according to RFC 1982, as desc in wikipedia:
 73 *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
 74 * codel_time_after(a,b) returns true if the time a is after time b.
 75 */
 76#define codel_time_after(a, b)						\
 77	(typecheck(codel_time_t, a) &&					\
 78	 typecheck(codel_time_t, b) &&					\
 79	 ((s32)((a) - (b)) > 0))
 80#define codel_time_before(a, b) 	codel_time_after(b, a)
 81
 82#define codel_time_after_eq(a, b)					\
 83	(typecheck(codel_time_t, a) &&					\
 84	 typecheck(codel_time_t, b) &&					\
 85	 ((s32)((a) - (b)) >= 0))
 86#define codel_time_before_eq(a, b)	codel_time_after_eq(b, a)
 87
 88static inline u32 codel_time_to_us(codel_time_t val)
 89{
 90	u64 valns = ((u64)val << CODEL_SHIFT);
 91
 92	do_div(valns, NSEC_PER_USEC);
 93	return (u32)valns;
 94}
 95
 96/**
 97 * struct codel_params - contains codel parameters
 98 * @target:	target queue size (in time units)
 99 * @ce_threshold:  threshold for marking packets with ECN CE
100 * @interval:	width of moving time window
101 * @mtu:	device mtu, or minimal queue backlog in bytes.
102 * @ecn:	is Explicit Congestion Notification enabled
103 * @ce_threshold_selector: apply ce_threshold to packets matching this value
104 *                         in the diffserv/ECN byte of the IP header
105 * @ce_threshold_mask: mask to apply to ce_threshold_selector comparison
106 */
107struct codel_params {
108	codel_time_t	target;
109	codel_time_t	ce_threshold;
110	codel_time_t	interval;
111	u32		mtu;
112	bool		ecn;
113	u8		ce_threshold_selector;
114	u8		ce_threshold_mask;
115};
116
117/**
118 * struct codel_vars - contains codel variables
119 * @count:		how many drops we've done since the last time we
120 *			entered dropping state
121 * @lastcount:		count at entry to dropping state
122 * @dropping:		set to true if in dropping state
123 * @rec_inv_sqrt:	reciprocal value of sqrt(count) >> 1
124 * @first_above_time:	when we went (or will go) continuously above target
125 *			for interval
126 * @drop_next:		time to drop next packet, or when we dropped last
127 * @ldelay:		sojourn time of last dequeued packet
128 */
129struct codel_vars {
130	u32		count;
131	u32		lastcount;
132	bool		dropping;
133	u16		rec_inv_sqrt;
134	codel_time_t	first_above_time;
135	codel_time_t	drop_next;
136	codel_time_t	ldelay;
137};
138
139#define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
140/* needed shift to get a Q0.32 number from rec_inv_sqrt */
141#define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
142
143/**
144 * struct codel_stats - contains codel shared variables and stats
145 * @maxpacket:	largest packet we've seen so far
146 * @drop_count:	temp count of dropped packets in dequeue()
147 * @drop_len:	bytes of dropped packets in dequeue()
148 * @ecn_mark:	number of packets we ECN marked instead of dropping
149 * @ce_mark:	number of packets CE marked because sojourn time was above ce_threshold
150 */
151struct codel_stats {
152	u32		maxpacket;
153	u32		drop_count;
154	u32		drop_len;
155	u32		ecn_mark;
156	u32		ce_mark;
157};
158
159#define CODEL_DISABLED_THRESHOLD INT_MAX
160
161typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
162typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
163typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
164typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
165						void *ctx);
166
167#endif