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#include <net/pkt_sched.h>
48#include <net/inet_ecn.h>
49
50/* Controlling Queue Delay (CoDel) algorithm
51 * =========================================
52 * Source : Kathleen Nichols and Van Jacobson
53 * http://queue.acm.org/detail.cfm?id=2209336
54 *
55 * Implemented on linux by Dave Taht and Eric Dumazet
56 */
57
58
59/* CoDel uses a 1024 nsec clock, encoded in u32
60 * This gives a range of 2199 seconds, because of signed compares
61 */
62typedef u32 codel_time_t;
63typedef s32 codel_tdiff_t;
64#define CODEL_SHIFT 10
65#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
66
67static inline codel_time_t codel_get_time(void)
68{
69 u64 ns = ktime_get_ns();
70
71 return ns >> CODEL_SHIFT;
72}
73
74/* Dealing with timer wrapping, according to RFC 1982, as desc in wikipedia:
75 * https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
76 * codel_time_after(a,b) returns true if the time a is after time b.
77 */
78#define codel_time_after(a, b) \
79 (typecheck(codel_time_t, a) && \
80 typecheck(codel_time_t, b) && \
81 ((s32)((a) - (b)) > 0))
82#define codel_time_before(a, b) codel_time_after(b, a)
83
84#define codel_time_after_eq(a, b) \
85 (typecheck(codel_time_t, a) && \
86 typecheck(codel_time_t, b) && \
87 ((s32)((a) - (b)) >= 0))
88#define codel_time_before_eq(a, b) codel_time_after_eq(b, a)
89
90static inline u32 codel_time_to_us(codel_time_t val)
91{
92 u64 valns = ((u64)val << CODEL_SHIFT);
93
94 do_div(valns, NSEC_PER_USEC);
95 return (u32)valns;
96}
97
98/**
99 * struct codel_params - contains codel parameters
100 * @target: target queue size (in time units)
101 * @ce_threshold: threshold for marking packets with ECN CE
102 * @interval: width of moving time window
103 * @mtu: device mtu, or minimal queue backlog in bytes.
104 * @ecn: is Explicit Congestion Notification enabled
105 */
106struct codel_params {
107 codel_time_t target;
108 codel_time_t ce_threshold;
109 codel_time_t interval;
110 u32 mtu;
111 bool ecn;
112};
113
114/**
115 * struct codel_vars - contains codel variables
116 * @count: how many drops we've done since the last time we
117 * entered dropping state
118 * @lastcount: count at entry to dropping state
119 * @dropping: set to true if in dropping state
120 * @rec_inv_sqrt: reciprocal value of sqrt(count) >> 1
121 * @first_above_time: when we went (or will go) continuously above target
122 * for interval
123 * @drop_next: time to drop next packet, or when we dropped last
124 * @ldelay: sojourn time of last dequeued packet
125 */
126struct codel_vars {
127 u32 count;
128 u32 lastcount;
129 bool dropping;
130 u16 rec_inv_sqrt;
131 codel_time_t first_above_time;
132 codel_time_t drop_next;
133 codel_time_t ldelay;
134};
135
136#define REC_INV_SQRT_BITS (8 * sizeof(u16)) /* or sizeof_in_bits(rec_inv_sqrt) */
137/* needed shift to get a Q0.32 number from rec_inv_sqrt */
138#define REC_INV_SQRT_SHIFT (32 - REC_INV_SQRT_BITS)
139
140/**
141 * struct codel_stats - contains codel shared variables and stats
142 * @maxpacket: largest packet we've seen so far
143 * @drop_count: temp count of dropped packets in dequeue()
144 * @drop_len: bytes of dropped packets in dequeue()
145 * ecn_mark: number of packets we ECN marked instead of dropping
146 * ce_mark: number of packets CE marked because sojourn time was above ce_threshold
147 */
148struct codel_stats {
149 u32 maxpacket;
150 u32 drop_count;
151 u32 drop_len;
152 u32 ecn_mark;
153 u32 ce_mark;
154};
155
156#define CODEL_DISABLED_THRESHOLD INT_MAX
157
158typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
159typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
160typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
161typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
162 void *ctx);
163
164#endif
165