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Linux/include/net/codel.h

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  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
165 

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