/*
* Codel - The Controlled-Delay Active Queue Management algorithm.
*
* $FreeBSD$
*
* Copyright (C) 2016 Centre for Advanced Internet Architectures,
* Swinburne University of Technology, Melbourne, Australia.
* Portions of this code were made possible in part by a gift from
* The Comcast Innovation Fund.
* Implemented by Rasool Al-Saadi <ralsaadi@swin.edu.au>
*
* Copyright (C) 2011-2014 Kathleen Nichols <nichols@pollere.com>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* o Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
*
* o 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.
*
* o 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.
*/
#ifndef _IP_DN_AQM_CODEL_H
#define _IP_DN_AQM_CODEL_H
// XXX How to choose MTAG?
#define FIX_POINT_BITS 16
enum {
CODEL_ECN_ENABLED = 1
};
/* Codel parameters */
struct dn_aqm_codel_parms {
aqm_time_t target;
aqm_time_t interval;
uint32_t flags;
};
/* codel status variables */
struct codel_status {
uint32_t count; /* number of dropped pkts since entering drop state */
uint16_t dropping; /* dropping state */
aqm_time_t drop_next_time; /* time for next drop */
aqm_time_t first_above_time; /* time for first ts over target we observed */
uint16_t isqrt; /* last isqrt for control low */
uint16_t maxpkt_size; /* max packet size seen so far */
};
struct mbuf *codel_extract_head(struct dn_queue *, aqm_time_t *);
aqm_time_t control_law(struct codel_status *,
struct dn_aqm_codel_parms *, aqm_time_t );
__inline static struct mbuf *
codel_dodequeue(struct dn_queue *q, aqm_time_t now, uint16_t *ok_to_drop)
{
struct mbuf * m;
struct dn_aqm_codel_parms *cprms;
struct codel_status *cst;
aqm_time_t pkt_ts, sojourn_time;
*ok_to_drop = 0;
m = codel_extract_head(q, &pkt_ts);
cst = q->aqm_status;
if (m == NULL) {
/* queue is empty - we can't be above target */
cst->first_above_time= 0;
return m;
}
cprms = q->fs->aqmcfg;
/* To span a large range of bandwidths, CoDel runs two
* different AQMs in parallel. One is sojourn-time-based
* and takes effect when the time to send an MTU-sized
* packet is less than target. The 1st term of the "if"
* below does this. The other is backlog-based and takes
* effect when the time to send an MTU-sized packet is >=
* target. The goal here is to keep the output link
* utilization high by never allowing the queue to get
* smaller than the amount that arrives in a typical
* interarrival time (MTU-sized packets arriving spaced
* by the amount of time it takes to send such a packet on
* the bottleneck). The 2nd term of the "if" does this.
*/
sojourn_time = now - pkt_ts;
if (sojourn_time < cprms->target || q->ni.len_bytes <= cst->maxpkt_size) {
/* went below - stay below for at least interval */
cst->first_above_time = 0;
} else {
if (cst->first_above_time == 0) {
/* just went above from below. if still above at
* first_above_time, will say it's ok to drop. */
cst->first_above_time = now + cprms->interval;
} else if (now >= cst->first_above_time) {
*ok_to_drop = 1;
}
}
return m;
}
/*
* Dequeue a packet from queue 'q'
*/
__inline static struct mbuf *
codel_dequeue(struct dn_queue *q)
{
struct mbuf *m;
struct dn_aqm_codel_parms *cprms;
struct codel_status *cst;
aqm_time_t now;
uint16_t ok_to_drop;
cst = q->aqm_status;;
cprms = q->fs->aqmcfg;
now = AQM_UNOW;
m = codel_dodequeue(q, now, &ok_to_drop);
if (cst->dropping) {
if (!ok_to_drop) {
/* sojourn time below target - leave dropping state */
cst->dropping = false;
}
/*
* Time for the next drop. Drop current packet and dequeue
* next. If the dequeue doesn't take us out of dropping
* state, 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 (now >= cst->drop_next_time && cst->dropping) {
/* mark the packet */
if (cprms->flags & CODEL_ECN_ENABLED && ecn_mark(m)) {
cst->count++;
/* schedule the next mark. */
cst->drop_next_time = control_law(cst, cprms,
cst->drop_next_time);
return m;
}
/* drop the packet */
update_stats(q, 0, 1);
FREE_PKT(m);
m = codel_dodequeue(q, now, &ok_to_drop);
if (!ok_to_drop) {
/* leave dropping state */
cst->dropping = false;
} else {
cst->count++;
/* schedule the next drop. */
cst->drop_next_time = control_law(cst, cprms,
cst->drop_next_time);
}
}
/* If we get here we're not in dropping state. The 'ok_to_drop'
* return from dodequeue means that the sojourn time has been
* above 'target' for 'interval' so enter dropping state.
*/
} else if (ok_to_drop) {
/* if ECN option is disabled or the packet cannot be marked,
* drop the packet and extract another.
*/
if (!(cprms->flags & CODEL_ECN_ENABLED) || !ecn_mark(m)) {
update_stats(q, 0, 1);
FREE_PKT(m);
m = codel_dodequeue(q, now, &ok_to_drop);
}
cst->dropping = true;
/* If min went above target close to when it last went
* below, assume that the drop rate that controlled the
* queue on the last cycle is a good starting point to
* control it now. ('drop_next' will be at most 'interval'
* later than the time of the last drop so 'now - drop_next'
* is a good approximation of the time from the last drop
* until now.)
*/
cst->count = (cst->count > 2 && ((aqm_stime_t)now -
(aqm_stime_t)cst->drop_next_time) < 8* cprms->interval)?
cst->count - 2 : 1;
/* we don't have to set initial guess for Newton's method isqrt as
* we initilaize isqrt in control_law function when count == 1 */
cst->drop_next_time = control_law(cst, cprms, now);
}
return m;
}
#endif
