#ifndef __NET_SCHED_CODEL_H
#define __NET_SCHED_CODEL_H
/*
* Codel - The Controlled-Delay Active Queue Management algorithm
*
* Copyright (C) 2011-2012 Kathleen Nichols <nichols@pollere.com>
* Copyright (C) 2011-2012 Van Jacobson <van@pollere.net>
* Copyright (C) 2012 Michael D. Taht <dave.taht@bufferbloat.net>
* Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The names of the authors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* Alternatively, provided that this notice is retained in full, this
* software may be distributed under the terms of the GNU General
* Public License ("GPL") version 2, in which case the provisions of the
* GPL apply INSTEAD OF those given above.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
*/
#include <linux/types.h>
#include <linux/ktime.h>
#include <linux/skbuff.h>
#include <net/pkt_sched.h>
#include <net/inet_ecn.h>
/* Controlling Queue Delay (CoDel) algorithm
* =========================================
* Source : Kathleen Nichols and Van Jacobson
* http://queue.acm.org/detail.cfm?id=2209336
*
* Implemented on linux by Dave Taht and Eric Dumazet
*/
/* CoDel uses a 1024 nsec clock, encoded in u32
* This gives a range of 2199 seconds, because of signed compares
*/
typedef u32 codel_time_t;
typedef s32 codel_tdiff_t;
#define CODEL_SHIFT 10
#define MS2TIME(a) ((a * NSEC_PER_MSEC) >> CODEL_SHIFT)
static inline codel_time_t codel_get_time(void)
{
u64 ns = ktime_to_ns(ktime_get());
return ns >> CODEL_SHIFT;
}
#define codel_time_after(a, b) ((s32)(a) - (s32)(b) > 0)
#define codel_time_after_eq(a, b) ((s32)(a) - (s32)(b) >= 0)
#define codel_time_before(a, b) ((s32)(a) - (s32)(b) < 0)
#define codel_time_before_eq(a, b) ((s32)(a) - (s32)(b) <= 0)
/* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
struct codel_skb_cb {
codel_time_t enqueue_time;
};
static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)
{
qdisc_cb_private_validate(skb, sizeof(struct codel_skb_cb));
return (struct codel_skb_cb *)qdisc_skb_cb(skb)->data;
}
static codel_time_t codel_get_enqueue_time(const struct sk_buff *skb)
{
return get_codel_cb(skb)->enqueue_time;
}
static void codel_set_enqueue_time(struct sk_buff *skb)
{
get_codel_cb(skb)->enqueue_time = codel_get_time();
}
static inline u32 codel_time_to_us(codel_time_t val)
{
u64 valns = ((u64)val << CODEL_SHIFT);
do_div(valns, NSEC_PER_USEC);
return (u32)valns;
}
/**
* struct codel_params - contains codel parameters
* @target: target queue size (in time units)
* @interval: width of moving time window
* @ecn: is Explicit Congestion Notification enabled
*/
struct codel_params {
codel_time_t target;
codel_time_t interval;
bool ecn;
};
/**
* struct codel_vars - contains codel variables
* @count: how many drops we've done since the last time we
* entered dropping state
* @lastcount: count at entry to dropping state
* @dropping: set to true if in dropping state
* @first_above_time: when we went (or will go) continuously above target
* for interval
* @drop_next: time to drop next packet, or when we dropped last
* @ldelay: sojourn time of last dequeued packet
*/
struct codel_vars {
u32 count;
u32 lastcount;
bool dropping;
codel_time_t first_above_time;
codel_time_t drop_next;
codel_time_t ldelay;
};
/**
* struct codel_stats - contains codel shared variables and stats
* @maxpacket: largest packet we've seen so far
* @drop_count: temp count of dropped packets in dequeue()
* ecn_mark: number of packets we ECN marked instead of dropping
*/
struct codel_stats {
u32 maxpacket;
u32 drop_count;
u32 ecn_mark;
};
static void codel_params_init(struct codel_params *params)
{
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
params->ecn = false;
}
static void codel_vars_init(struct codel_vars *vars)
{
vars->drop_next = 0;
vars->first_above_time = 0;
vars->dropping = false; /* exit dropping state */
vars->count = 0;
vars->lastcount = 0;
}
static void codel_stats_init(struct codel_stats *stats)
{
stats->maxpacket = 256;
}
/* return interval/sqrt(x) with good precision
* relies on int_sqrt(unsigned long x) kernel implementation
*/
static u32 codel_inv_sqrt(u32 _interval, u32 _x)
{
u64 interval = _interval;
unsigned long x = _x;
/* Scale operands for max precision */
#if BITS_PER_LONG == 64
x <<= 32; /* On 64bit arches, we can prescale x by 32bits */
interval <<= 16;
#endif
while (x < (1UL << (BITS_PER_LONG - 2))) {
x <<= 2;
interval <<= 1;
}
do_div(interval, int_sqrt(x));
return (u32)interval;
}
static codel_time_t codel_control_law(codel_time_t t,
codel_time_t interval,
u32 count)
{
return t + codel_inv_sqrt(interval, count);
}
static bool codel_should_drop(struct sk_buff *skb,
unsigned int *backlog,
struct codel_vars *vars,
struct codel_params *params,
struct codel_stats *stats,
codel_time_t now)
{
bool ok_to_drop;
if (!skb) {
vars->first_above_time = 0;
return false;
}
vars->ldelay = now - codel_get_enqueue_time(skb);
*backlog -= qdisc_pkt_len(skb);
if (unlikely(qdisc_pkt_len(skb) > stats->maxpacket))
stats->maxpacket = qdisc_pkt_len(skb);
if (codel_time_before(vars->ldelay, params->target) ||
*backlog <= stats->maxpacket) {
/* went below - stay below for at least interval */
vars->first_above_time = 0;
return false;
}
ok_to_drop = false;
if (vars->first_above_time == 0) {
/* just went above from below. If we stay above
* for at least interval we'll say it's ok to drop
*/
vars->first_above_time = now + params->interval;
} else if (codel_time_after(now, vars->first_above_time)) {
ok_to_drop = true;
}
return ok_to_drop;
}
typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
struct Qdisc *sch);
static struct sk_buff *codel_dequeue(struct Qdisc *sch,
struct codel_params *params,
struct codel_vars *vars,
struct codel_stats *stats,
codel_skb_dequeue_t dequeue_func,
u32 *backlog)
{
struct sk_buff *skb = dequeue_func(vars, sch);
codel_time_t now;
bool drop;
if (!skb) {
vars->dropping = false;
return skb;
}
now = codel_get_time();
drop = codel_should_drop(skb, backlog, vars, params, stats, now);
if (vars->dropping) {
if (!drop) {
/* sojourn time below target - leave dropping state */
vars->dropping = false;
} else if (codel_time_after_eq(now, vars->drop_next)) {
/* It's time for the next drop. Drop the current
* packet and dequeue the next. The dequeue might
* take us out of dropping state.
* If not, schedule the next drop.
* A large backlog might result in drop rates so high
* that the next drop should happen now,
* hence the while loop.
*/
while (vars->dropping &&
codel_time_after_eq(now, vars->drop_next)) {
if (++vars->count == 0) /* avoid zero divides */
vars->count = ~0U;
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->count);
goto end;
}
qdisc_drop(skb, sch);
stats->drop_count++;
skb = dequeue_func(vars, sch);
if (!codel_should_drop(skb, backlog,
vars, params, stats, now)) {
/* leave dropping state */
vars->dropping = false;
} else {
/* and schedule the next drop */
vars->drop_next =
codel_control_law(vars->drop_next,
params->interval,
vars->count);
}
}
}
} else if (drop) {
if (params->ecn && INET_ECN_set_ce(skb)) {
stats->ecn_mark++;
} else {
qdisc_drop(skb, sch);
stats->drop_count++;
skb = dequeue_func(vars, sch);
drop = codel_should_drop(skb, backlog, vars, params,
stats, now);
}
vars->dropping = true;
/* if min went above target close to when we last went below it
* assume that the drop rate that controlled the queue on the
* last cycle is a good starting point to control it now.
*/
if (codel_time_before(now - vars->drop_next,
16 * params->interval)) {
vars->count = (vars->count - vars->lastcount) | 1;
} else {
vars->count = 1;
}
vars->lastcount = vars->count;
vars->drop_next = codel_control_law(now, params->interval,
vars->count);
}
end:
return skb;
}
#endif
