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 #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  */
  62 typedef u32 codel_time_t;
  63 typedef s32 codel_tdiff_t;
  64 #define CODEL_SHIFT 10
  65 #define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
  66
  67 static 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
  90 static 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  */
 106 struct 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  */
 126 struct 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  */
 148 struct 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
 158 typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
 159 typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
 160 typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
 161 typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
 162                                                 void *ctx);
 163
 164 #endif