5 files changed, 645 insertions, 0 deletions

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index ffe975c..cde56c2 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -655,4 +655,30 @@ struct tc_qfq_stats {
 	__u32 lmax;
 };
 
+/* CODEL */
+
+enum {
+	TCA_CODEL_UNSPEC,
+	TCA_CODEL_TARGET,
+	TCA_CODEL_LIMIT,
+	TCA_CODEL_INTERVAL,
+	TCA_CODEL_ECN,
+	__TCA_CODEL_MAX
+};
+
+#define TCA_CODEL_MAX	(__TCA_CODEL_MAX - 1)
+
+struct tc_codel_xstats {
+	__u32	maxpacket; /* largest packet we've seen so far */
+	__u32	count;	   /* how many drops we've done since the last time we
+			    * entered dropping state
+			    */
+	__u32	lastcount; /* count at entry to dropping state */
+	__u32	ldelay;    /* in-queue delay seen by most recently dequeued packet */
+	__s32	drop_next; /* time to drop next packet */
+	__u32	drop_overlimit; /* number of time max qdisc packet limit was hit */
+	__u32	ecn_mark;  /* number of packets we ECN marked instead of dropped */
+	__u32	dropping;  /* are we in dropping state ? */
+};
+
 #endif
diff --git a/include/net/codel.h b/include/net/codel.h
new file mode 100644
index 0000000..bce2cef
--- /dev/null
+++ b/include/net/codel.h
@@ -0,0 +1,332 @@
+#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
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 75b58f8..fadd252 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -250,6 +250,17 @@ config NET_SCH_QFQ
 
 	  If unsure, say N.
 
+config NET_SCH_CODEL
+	tristate "Controlled Delay AQM (CODEL)"
+	help
+	  Say Y here if you want to use the Controlled Delay (CODEL)
+	  packet scheduling algorithm.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called sch_codel.
+
+	  If unsure, say N.
+
 config NET_SCH_INGRESS
 	tristate "Ingress Qdisc"
 	depends on NET_CLS_ACT
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 8cdf4e2..30fab03 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_NET_SCH_PLUG)	+= sch_plug.o
 obj-$(CONFIG_NET_SCH_MQPRIO)	+= sch_mqprio.o
 obj-$(CONFIG_NET_SCH_CHOKE)	+= sch_choke.o
 obj-$(CONFIG_NET_SCH_QFQ)	+= sch_qfq.o
+obj-$(CONFIG_NET_SCH_CODEL)	+= sch_codel.o
 
 obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
new file mode 100644
index 0000000..b4a1a81
--- /dev/null
+++ b/net/sched/sch_codel.c
@@ -0,0 +1,275 @@
+/*
+ * 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>
+ *
+ *  Implemented on linux by :
+ *  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/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+#include <net/codel.h>
+
+
+#define DEFAULT_CODEL_LIMIT 1000
+
+struct codel_sched_data {
+	struct codel_params	params;
+	struct codel_vars	vars;
+	struct codel_stats	stats;
+	u32			drop_overlimit;
+};
+
+/* This is the specific function called from codel_dequeue()
+ * to dequeue a packet from queue. Note: backlog is handled in
+ * codel, we dont need to reduce it here.
+ */
+static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
+{
+	struct sk_buff *skb = __skb_dequeue(&sch->q);
+
+	prefetch(&skb->end); /* we'll need skb_shinfo() */
+	return skb;
+}
+
+static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
+{
+	struct codel_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb;
+
+	skb = codel_dequeue(sch, &q->params, &q->vars, &q->stats,
+			    dequeue, &sch->qstats.backlog);
+	/* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
+	 * or HTB crashes. Defer it for next round.
+	 */
+	if (q->stats.drop_count && sch->q.qlen) {
+		qdisc_tree_decrease_qlen(sch, q->stats.drop_count);
+		q->stats.drop_count = 0;
+	}
+	if (skb)
+		qdisc_bstats_update(sch, skb);
+	return skb;
+}
+
+static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+	struct codel_sched_data *q;
+
+	if (likely(qdisc_qlen(sch) < sch->limit)) {
+		codel_set_enqueue_time(skb);
+		return qdisc_enqueue_tail(skb, sch);
+	}
+	q = qdisc_priv(sch);
+	q->drop_overlimit++;
+	return qdisc_drop(skb, sch);
+}
+
+static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
+	[TCA_CODEL_TARGET]	= { .type = NLA_U32 },
+	[TCA_CODEL_LIMIT]	= { .type = NLA_U32 },
+	[TCA_CODEL_INTERVAL]	= { .type = NLA_U32 },
+	[TCA_CODEL_ECN]		= { .type = NLA_U32 },
+};
+
+static int codel_change(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct codel_sched_data *q = qdisc_priv(sch);
+	struct nlattr *tb[TCA_CODEL_MAX + 1];
+	unsigned int qlen;
+	int err;
+
+	if (!opt)
+		return -EINVAL;
+
+	err = nla_parse_nested(tb, TCA_CODEL_MAX, opt, codel_policy);
+	if (err < 0)
+		return err;
+
+	sch_tree_lock(sch);
+
+	if (tb[TCA_CODEL_TARGET]) {
+		u32 target = nla_get_u32(tb[TCA_CODEL_TARGET]);
+
+		q->params.target = ((u64)target * NSEC_PER_USEC) >> CODEL_SHIFT;
+	}
+
+	if (tb[TCA_CODEL_INTERVAL]) {
+		u32 interval = nla_get_u32(tb[TCA_CODEL_INTERVAL]);
+
+		q->params.interval = ((u64)interval * NSEC_PER_USEC) >> CODEL_SHIFT;
+	}
+
+	if (tb[TCA_CODEL_LIMIT])
+		sch->limit = nla_get_u32(tb[TCA_CODEL_LIMIT]);
+
+	if (tb[TCA_CODEL_ECN])
+		q->params.ecn = !!nla_get_u32(tb[TCA_CODEL_ECN]);
+
+	qlen = sch->q.qlen;
+	while (sch->q.qlen > sch->limit) {
+		struct sk_buff *skb = __skb_dequeue(&sch->q);
+
+		sch->qstats.backlog -= qdisc_pkt_len(skb);
+		qdisc_drop(skb, sch);
+	}
+	qdisc_tree_decrease_qlen(sch, qlen - sch->q.qlen);
+
+	sch_tree_unlock(sch);
+	return 0;
+}
+
+static int codel_init(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct codel_sched_data *q = qdisc_priv(sch);
+
+	sch->limit = DEFAULT_CODEL_LIMIT;
+
+	codel_params_init(&q->params);
+	codel_vars_init(&q->vars);
+	codel_stats_init(&q->stats);
+
+	if (opt) {
+		int err = codel_change(sch, opt);
+
+		if (err)
+			return err;
+	}
+
+	if (sch->limit >= 1)
+		sch->flags |= TCQ_F_CAN_BYPASS;
+	else
+		sch->flags &= ~TCQ_F_CAN_BYPASS;
+
+	return 0;
+}
+
+static int codel_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct codel_sched_data *q = qdisc_priv(sch);
+	struct nlattr *opts;
+
+	opts = nla_nest_start(skb, TCA_OPTIONS);
+	if (opts == NULL)
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, TCA_CODEL_TARGET,
+			codel_time_to_us(q->params.target)) ||
+	    nla_put_u32(skb, TCA_CODEL_LIMIT,
+			sch->limit) ||
+	    nla_put_u32(skb, TCA_CODEL_INTERVAL,
+			codel_time_to_us(q->params.interval)) ||
+	    nla_put_u32(skb, TCA_CODEL_ECN,
+			q->params.ecn))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, opts);
+
+nla_put_failure:
+	nla_nest_cancel(skb, opts);
+	return -1;
+}
+
+static int codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
+{
+	const struct codel_sched_data *q = qdisc_priv(sch);
+	struct tc_codel_xstats st = {
+		.maxpacket	= q->stats.maxpacket,
+		.count		= q->vars.count,
+		.lastcount	= q->vars.lastcount,
+		.drop_overlimit = q->drop_overlimit,
+		.ldelay		= codel_time_to_us(q->vars.ldelay),
+		.dropping	= q->vars.dropping,
+		.ecn_mark	= q->stats.ecn_mark,
+	};
+
+	if (q->vars.dropping) {
+		codel_tdiff_t delta = q->vars.drop_next - codel_get_time();
+
+		if (delta >= 0)
+			st.drop_next = codel_time_to_us(delta);
+		else
+			st.drop_next = -codel_time_to_us(-delta);
+	}
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static void codel_reset(struct Qdisc *sch)
+{
+	struct codel_sched_data *q = qdisc_priv(sch);
+
+	qdisc_reset_queue(sch);
+	codel_vars_init(&q->vars);
+}
+
+static struct Qdisc_ops codel_qdisc_ops __read_mostly = {
+	.id		=	"codel",
+	.priv_size	=	sizeof(struct codel_sched_data),
+
+	.enqueue	=	codel_qdisc_enqueue,
+	.dequeue	=	codel_qdisc_dequeue,
+	.peek		=	qdisc_peek_dequeued,
+	.init		=	codel_init,
+	.reset		=	codel_reset,
+	.change 	=	codel_change,
+	.dump		=	codel_dump,
+	.dump_stats	=	codel_dump_stats,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init codel_module_init(void)
+{
+	return register_qdisc(&codel_qdisc_ops);
+}
+
+static void __exit codel_module_exit(void)
+{
+	unregister_qdisc(&codel_qdisc_ops);
+}
+
+module_init(codel_module_init)
+module_exit(codel_module_exit)
+
+MODULE_DESCRIPTION("Controlled Delay queue discipline");
+MODULE_AUTHOR("Dave Taht");
+MODULE_AUTHOR("Eric Dumazet");
+MODULE_LICENSE("Dual BSD/GPL");