LXR linux/include/net/codel.h

   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
 168