codel_impl.h | Explore in Territory

#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 <[email protected]>
 *  Copyright (C) 2011-2012 Van Jacobson <[email protected]>
 *  Copyright (C) 2012 Michael D. Taht <[email protected]>
 *  Copyright (C) 2012,2015 Eric Dumazet <[email protected]>
 *
 * 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
 */

#include <net/inet_ecn.h>

static void codel_params_init(struct codel_params *params)
{ … }

static void codel_vars_init(struct codel_vars *vars)
{ … }

static void codel_stats_init(struct codel_stats *stats)
{ … }

/*
 * 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)
{ … }

/*
 * 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)
{ … }

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)
{ … }

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)
{ … }

#endif
linux/include/net/codel_impl.h
