codel: split into multiple files

It was impossible to include codel.h for the
purpose of having access to codel_params or
codel_vars structure definitions and using them
for embedding in other more complex structures.

This splits allows codel.h itself to be treated
like any other header file while codel_qdisc.h and
codel_impl.h contain function definitions with
logic that was previously in codel.h.

This copies over copyrights and doesn't involve
code changes other than adding a few additional
include directives to net/sched/sch*codel.c.

Signed-off-by: Michal Kazior <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/codel.h

···
 	 ((s32)((a) - (b)) >= 0))
 #define codel_time_before_eq(a, b)	codel_time_after_eq(b, a)
 
-/* 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);
···
 
 #define CODEL_DISABLED_THRESHOLD INT_MAX
 
-static void codel_params_init(struct codel_params *params)
-{
-	params->interval = MS2TIME(100);
-	params->target = MS2TIME(5);
-	params->ce_threshold = CODEL_DISABLED_THRESHOLD;
-	params->ecn = false;
-}
-
-static void codel_vars_init(struct codel_vars *vars)
-{
-	memset(vars, 0, sizeof(*vars));
-}
-
-static void codel_stats_init(struct codel_stats *stats)
-{
-	stats->maxpacket = 0;
-}
-
-/*
- * http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
- * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
- *
- * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
- */
-static void codel_Newton_step(struct codel_vars *vars)
-{
-	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
-	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
-	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);
-
-	val >>= 2; /* avoid overflow in following multiply */
-	val = (val * invsqrt) >> (32 - 2 + 1);
-
-	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
-}
-
-/*
- * CoDel control_law is t + interval/sqrt(count)
- * We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
- * both sqrt() and divide operation.
- */
-static codel_time_t codel_control_law(codel_time_t t,
-				      codel_time_t interval,
-				      u32 rec_inv_sqrt)
-{
-	return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
-}
-
 typedef u32 (*codel_skb_len_t)(const struct sk_buff *skb);
 typedef codel_time_t (*codel_skb_time_t)(const struct sk_buff *skb);
 typedef void (*codel_skb_drop_t)(struct sk_buff *skb, void *ctx);
 typedef struct sk_buff * (*codel_skb_dequeue_t)(struct codel_vars *vars,
 						void *ctx);
 
-static bool codel_should_drop(const struct sk_buff *skb,
-			      void *ctx,
-			      struct codel_vars *vars,
-			      struct codel_params *params,
-			      struct codel_stats *stats,
-			      codel_skb_len_t skb_len_func,
-			      codel_skb_time_t skb_time_func,
-			      u32 *backlog,
-			      codel_time_t now)
-{
-	bool ok_to_drop;
-	u32 skb_len;
-
-	if (!skb) {
-		vars->first_above_time = 0;
-		return false;
-	}
-
-	skb_len = skb_len_func(skb);
-	vars->ldelay = now - skb_time_func(skb);
-
-	if (unlikely(skb_len > stats->maxpacket))
-		stats->maxpacket = skb_len;
-
-	if (codel_time_before(vars->ldelay, params->target) ||
-	    *backlog <= params->mtu) {
-		/* 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;
-}
-
-static struct sk_buff *codel_dequeue(void *ctx,
-				     u32 *backlog,
-				     struct codel_params *params,
-				     struct codel_vars *vars,
-				     struct codel_stats *stats,
-				     codel_skb_len_t skb_len_func,
-				     codel_skb_time_t skb_time_func,
-				     codel_skb_drop_t drop_func,
-				     codel_skb_dequeue_t dequeue_func)
-{
-	struct sk_buff *skb = dequeue_func(vars, ctx);
-	codel_time_t now;
-	bool drop;
-
-	if (!skb) {
-		vars->dropping = false;
-		return skb;
-	}
-	now = codel_get_time();
-	drop = codel_should_drop(skb, ctx, vars, params, stats,
-				 skb_len_func, skb_time_func, backlog, 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)) {
-				vars->count++; /* dont care of possible wrap
-						* since there is no more divide
-						*/
-				codel_Newton_step(vars);
-				if (params->ecn && INET_ECN_set_ce(skb)) {
-					stats->ecn_mark++;
-					vars->drop_next =
-						codel_control_law(vars->drop_next,
-								  params->interval,
-								  vars->rec_inv_sqrt);
-					goto end;
-				}
-				stats->drop_len += skb_len_func(skb);
-				drop_func(skb, ctx);
-				stats->drop_count++;
-				skb = dequeue_func(vars, ctx);
-				if (!codel_should_drop(skb, ctx,
-						       vars, params, stats,
-						       skb_len_func,
-						       skb_time_func,
-						       backlog, 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->rec_inv_sqrt);
-				}
-			}
-		}
-	} else if (drop) {
-		u32 delta;
-
-		if (params->ecn && INET_ECN_set_ce(skb)) {
-			stats->ecn_mark++;
-		} else {
-			stats->drop_len += skb_len_func(skb);
-			drop_func(skb, ctx);
-			stats->drop_count++;
-
-			skb = dequeue_func(vars, ctx);
-			drop = codel_should_drop(skb, ctx, vars, params,
-						 stats, skb_len_func,
-						 skb_time_func, backlog, 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.
-		 */
-		delta = vars->count - vars->lastcount;
-		if (delta > 1 &&
-		    codel_time_before(now - vars->drop_next,
-				      16 * params->interval)) {
-			vars->count = delta;
-			/* we dont care if rec_inv_sqrt approximation
-			 * is not very precise :
-			 * Next Newton steps will correct it quadratically.
-			 */
-			codel_Newton_step(vars);
-		} else {
-			vars->count = 1;
-			vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
-		}
-		vars->lastcount = vars->count;
-		vars->drop_next = codel_control_law(now, params->interval,
-						    vars->rec_inv_sqrt);
-	}
-end:
-	if (skb && codel_time_after(vars->ldelay, params->ce_threshold) &&
-	    INET_ECN_set_ce(skb))
-		stats->ce_mark++;
-	return skb;
-}
 #endif

include/net/codel_impl.h

···
+#ifndef __NET_SCHED_CODEL_IMPL_H
+#define __NET_SCHED_CODEL_IMPL_H
+
+/*
+ * Codel - The Controlled-Delay Active Queue Management algorithm
+ *
+ *  Copyright (C) 2011-2012 Kathleen Nichols <[e-mail]>
+ *  Copyright (C) 2011-2012 Van Jacobson <[e-mail]>
+ *  Copyright (C) 2012 Michael D. Taht <[e-mail]>
+ *  Copyright (C) 2012,2015 Eric Dumazet <[e-mail]>
+ *
+ * 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.
+ *
+ */
+
+/* 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
+ */
+
+static void codel_params_init(struct codel_params *params)
+{
+	params->interval = MS2TIME(100);
+	params->target = MS2TIME(5);
+	params->ce_threshold = CODEL_DISABLED_THRESHOLD;
+	params->ecn = false;
+}
+
+static void codel_vars_init(struct codel_vars *vars)
+{
+	memset(vars, 0, sizeof(*vars));
+}
+
+static void codel_stats_init(struct codel_stats *stats)
+{
+	stats->maxpacket = 0;
+}
+
+/*
+ * http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots
+ * new_invsqrt = (invsqrt / 2) * (3 - count * invsqrt^2)
+ *
+ * Here, invsqrt is a fixed point number (< 1.0), 32bit mantissa, aka Q0.32
+ */
+static void codel_Newton_step(struct codel_vars *vars)
+{
+	u32 invsqrt = ((u32)vars->rec_inv_sqrt) << REC_INV_SQRT_SHIFT;
+	u32 invsqrt2 = ((u64)invsqrt * invsqrt) >> 32;
+	u64 val = (3LL << 32) - ((u64)vars->count * invsqrt2);
+
+	val >>= 2; /* avoid overflow in following multiply */
+	val = (val * invsqrt) >> (32 - 2 + 1);
+
+	vars->rec_inv_sqrt = val >> REC_INV_SQRT_SHIFT;
+}
+
+/*
+ * CoDel control_law is t + interval/sqrt(count)
+ * We maintain in rec_inv_sqrt the reciprocal value of sqrt(count) to avoid
+ * both sqrt() and divide operation.
+ */
+static codel_time_t codel_control_law(codel_time_t t,
+				      codel_time_t interval,
+				      u32 rec_inv_sqrt)
+{
+	return t + reciprocal_scale(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT);
+}
+
+static bool codel_should_drop(const struct sk_buff *skb,
+			      void *ctx,
+			      struct codel_vars *vars,
+			      struct codel_params *params,
+			      struct codel_stats *stats,
+			      codel_skb_len_t skb_len_func,
+			      codel_skb_time_t skb_time_func,
+			      u32 *backlog,
+			      codel_time_t now)
+{
+	bool ok_to_drop;
+	u32 skb_len;
+
+	if (!skb) {
+		vars->first_above_time = 0;
+		return false;
+	}
+
+	skb_len = skb_len_func(skb);
+	vars->ldelay = now - skb_time_func(skb);
+
+	if (unlikely(skb_len > stats->maxpacket))
+		stats->maxpacket = skb_len;
+
+	if (codel_time_before(vars->ldelay, params->target) ||
+	    *backlog <= params->mtu) {
+		/* 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;
+}
+
+static struct sk_buff *codel_dequeue(void *ctx,
+				     u32 *backlog,
+				     struct codel_params *params,
+				     struct codel_vars *vars,
+				     struct codel_stats *stats,
+				     codel_skb_len_t skb_len_func,
+				     codel_skb_time_t skb_time_func,
+				     codel_skb_drop_t drop_func,
+				     codel_skb_dequeue_t dequeue_func)
+{
+	struct sk_buff *skb = dequeue_func(vars, ctx);
+	codel_time_t now;
+	bool drop;
+
+	if (!skb) {
+		vars->dropping = false;
+		return skb;
+	}
+	now = codel_get_time();
+	drop = codel_should_drop(skb, ctx, vars, params, stats,
+				 skb_len_func, skb_time_func, backlog, 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)) {
+				vars->count++; /* dont care of possible wrap
+						* since there is no more divide
+						*/
+				codel_Newton_step(vars);
+				if (params->ecn && INET_ECN_set_ce(skb)) {
+					stats->ecn_mark++;
+					vars->drop_next =
+						codel_control_law(vars->drop_next,
+								  params->interval,
+								  vars->rec_inv_sqrt);
+					goto end;
+				}
+				stats->drop_len += skb_len_func(skb);
+				drop_func(skb, ctx);
+				stats->drop_count++;
+				skb = dequeue_func(vars, ctx);
+				if (!codel_should_drop(skb, ctx,
+						       vars, params, stats,
+						       skb_len_func,
+						       skb_time_func,
+						       backlog, 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->rec_inv_sqrt);
+				}
+			}
+		}
+	} else if (drop) {
+		u32 delta;
+
+		if (params->ecn && INET_ECN_set_ce(skb)) {
+			stats->ecn_mark++;
+		} else {
+			stats->drop_len += skb_len_func(skb);
+			drop_func(skb, ctx);
+			stats->drop_count++;
+
+			skb = dequeue_func(vars, ctx);
+			drop = codel_should_drop(skb, ctx, vars, params,
+						 stats, skb_len_func,
+						 skb_time_func, backlog, 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.
+		 */
+		delta = vars->count - vars->lastcount;
+		if (delta > 1 &&
+		    codel_time_before(now - vars->drop_next,
+				      16 * params->interval)) {
+			vars->count = delta;
+			/* we dont care if rec_inv_sqrt approximation
+			 * is not very precise :
+			 * Next Newton steps will correct it quadratically.
+			 */
+			codel_Newton_step(vars);
+		} else {
+			vars->count = 1;
+			vars->rec_inv_sqrt = ~0U >> REC_INV_SQRT_SHIFT;
+		}
+		vars->lastcount = vars->count;
+		vars->drop_next = codel_control_law(now, params->interval,
+						    vars->rec_inv_sqrt);
+	}
+end:
+	if (skb && codel_time_after(vars->ldelay, params->ce_threshold) &&
+	    INET_ECN_set_ce(skb))
+		stats->ce_mark++;
+	return skb;
+}
+
+#endif

include/net/codel_qdisc.h

···
+#ifndef __NET_SCHED_CODEL_QDISC_H
+#define __NET_SCHED_CODEL_QDISC_H
+
+/*
+ * Codel - The Controlled-Delay Active Queue Management algorithm
+ *
+ *  Copyright (C) 2011-2012 Kathleen Nichols <[e-mail]>
+ *  Copyright (C) 2011-2012 Van Jacobson <[e-mail]>
+ *  Copyright (C) 2012 Michael D. Taht <[e-mail]>
+ *  Copyright (C) 2012,2015 Eric Dumazet <[e-mail]>
+ *
+ * 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.
+ *
+ */
+
+/* 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
+ */
+
+/* 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();
+}
+
+#endif

net/sched/sch_codel.c

···
 #include <linux/prefetch.h>
 #include <net/pkt_sched.h>
 #include <net/codel.h>
+#include <net/codel_impl.h>
+#include <net/codel_qdisc.h>
 
 
 #define DEFAULT_CODEL_LIMIT 1000

net/sched/sch_fq_codel.c

···
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
 #include <net/codel.h>
+#include <net/codel_impl.h>
+#include <net/codel_qdisc.h>
 
 /*	Fair Queue CoDel.
  *