nes-proj/os/net/rpl-lite/rpl-mrhof.c
2017-09-29 22:18:48 +02:00

293 lines
10 KiB
C

/*
* Copyright (c) 2010, Swedish Institute of Computer Science.
* All rights reserved.
*
* 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.
* 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. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*
*/
/**
* \addtogroup rpl-lite
* @{
*
* \file
* The Minimum Rank with Hysteresis Objective Function (MRHOF), RFC6719
*
* This implementation uses the estimated number of
* transmissions (ETX) as the additive routing metric,
* and also provides stubs for the energy metric.
*
* \author Joakim Eriksson <joakime@sics.se>, Nicolas Tsiftes <nvt@sics.se>
* Simon Duquennoy <simon.duquennoy@inria.fr>
*/
#include "net/rpl-lite/rpl.h"
#include "net/nbr-table.h"
#include "net/link-stats.h"
/* Log configuration */
#include "sys/log.h"
#define LOG_MODULE "RPL"
#define LOG_LEVEL LOG_LEVEL_RPL
/* RFC6551 and RFC6719 do not mandate the use of a specific formula to
* compute the ETX value. This MRHOF implementation relies on the value
* computed by the link-stats module. It has an optional feature,
* RPL_MRHOF_CONF_SQUARED_ETX, that consists in squaring this value.
* This basically penalizes bad links while preserving the semantics of ETX
* (1 = perfect link, more = worse link). As a result, MRHOF will favor
* good links over short paths. Recommended when reliability is a priority.
* Without this feature, a hop with 50% PRR (ETX=2) is equivalent to two
* perfect hops with 100% PRR (ETX=1+1=2). With this feature, the former
* path obtains ETX=2*2=4 and the former ETX=1*1+1*1=2. */
#ifdef RPL_MRHOF_CONF_SQUARED_ETX
#define RPL_MRHOF_SQUARED_ETX RPL_MRHOF_CONF_SQUARED_ETX
#else /* RPL_MRHOF_CONF_SQUARED_ETX */
#define RPL_MRHOF_SQUARED_ETX 1
#endif /* RPL_MRHOF_CONF_SQUARED_ETX */
/* Configuration parameters of RFC6719. Reject parents that have a higher
* link metric than the following. The default value is 512. */
#define MAX_LINK_METRIC 512 /* Eq ETX of 4 */
/* Reject parents that have a higher path cost than the following. */
#define MAX_PATH_COST 32768 /* Eq path ETX of 256 */
#if !RPL_MRHOF_SQUARED_ETX
/* Hysteresis of MRHOF: the rank must differ more than PARENT_SWITCH_THRESHOLD_DIV
* in order to switch preferred parent. Default in RFC6719: 192, eq ETX of 1.5. */
#define RANK_THRESHOLD 192 /* Eq ETX of 1.5 */
#else /* !RPL_MRHOF_SQUARED_ETX */
#define RANK_THRESHOLD 384 /* Eq ETX of sqrt(3) */
#endif /* !RPL_MRHOF_SQUARED_ETX */
/* Additional, custom hysteresis based on time. If a neighbor was consistently
* better than our preferred parent for at least TIME_THRESHOLD, switch to
* this neighbor regardless of RANK_THRESHOLD. */
#define TIME_THRESHOLD (10 * 60 * CLOCK_SECOND)
/*---------------------------------------------------------------------------*/
static void
reset(void)
{
LOG_INFO("reset MRHOF\n");
}
/*---------------------------------------------------------------------------*/
static uint16_t
nbr_link_metric(rpl_nbr_t *nbr)
{
const struct link_stats *stats = rpl_neighbor_get_link_stats(nbr);
return stats != NULL ? stats->etx : 0xffff;
}
/*---------------------------------------------------------------------------*/
static uint16_t
link_metric_to_rank(uint16_t etx)
{
#if RPL_MRHOF_SQUARED_ETX
uint32_t squared_etx = ((uint32_t)etx * etx) / LINK_STATS_ETX_DIVISOR;
return (uint16_t)MIN(squared_etx, 0xffff);
#else /* RPL_MRHOF_SQUARED_ETX */
return etx;
#endif /* RPL_MRHOF_SQUARED_ETX */
}
/*---------------------------------------------------------------------------*/
static uint16_t
nbr_path_cost(rpl_nbr_t *nbr)
{
uint16_t base;
if(nbr == NULL) {
return 0xffff;
}
#if RPL_WITH_MC
/* Handle the different MC types */
switch(curr_instance.mc.type) {
case RPL_DAG_MC_ETX:
base = nbr->mc.obj.etx;
break;
case RPL_DAG_MC_ENERGY:
base = nbr->mc.obj.energy.energy_est << 8;
break;
default:
base = nbr->rank;
break;
}
#else /* RPL_WITH_MC */
base = nbr->rank;
#endif /* RPL_WITH_MC */
/* path cost upper bound: 0xffff */
return MIN((uint32_t)base + link_metric_to_rank(nbr_link_metric(nbr)), 0xffff);
}
/*---------------------------------------------------------------------------*/
static rpl_rank_t
rank_via_nbr(rpl_nbr_t *nbr)
{
uint16_t min_hoprankinc;
uint16_t path_cost;
if(nbr == NULL) {
return RPL_INFINITE_RANK;
}
min_hoprankinc = curr_instance.min_hoprankinc;
path_cost = nbr_path_cost(nbr);
/* Rank lower-bound: nbr rank + min_hoprankinc */
return MAX(MIN((uint32_t)nbr->rank + min_hoprankinc, RPL_INFINITE_RANK), path_cost);
}
/*---------------------------------------------------------------------------*/
static int
nbr_has_usable_link(rpl_nbr_t *nbr)
{
uint16_t link_metric = nbr_link_metric(nbr);
/* Exclude links with too high link metrics */
return link_metric <= MAX_LINK_METRIC;
}
/*---------------------------------------------------------------------------*/
static int
nbr_is_acceptable_parent(rpl_nbr_t *nbr)
{
uint16_t path_cost = nbr_path_cost(nbr);
/* Exclude links with too high link metrics or path cost (RFC6719, 3.2.2) */
return nbr_has_usable_link(nbr) && path_cost <= MAX_PATH_COST;
}
/*---------------------------------------------------------------------------*/
static int
within_hysteresis(rpl_nbr_t *nbr)
{
uint16_t path_cost = nbr_path_cost(nbr);
uint16_t parent_path_cost = nbr_path_cost(curr_instance.dag.preferred_parent);
int within_rank_hysteresis = path_cost + RANK_THRESHOLD > parent_path_cost;
int within_time_hysteresis = nbr->better_parent_since == 0
|| (clock_time() - nbr->better_parent_since) <= TIME_THRESHOLD;
/* As we want to consider neighbors that are either beyond the rank or time
hystereses, return 1 here iff the neighbor is within both hystereses. */
return within_rank_hysteresis && within_time_hysteresis;
}
/*---------------------------------------------------------------------------*/
static rpl_nbr_t *
best_parent(rpl_nbr_t *nbr1, rpl_nbr_t *nbr2)
{
int nbr1_is_acceptable;
int nbr2_is_acceptable;
nbr1_is_acceptable = nbr1 != NULL && nbr_is_acceptable_parent(nbr1);
nbr2_is_acceptable = nbr2 != NULL && nbr_is_acceptable_parent(nbr2);
if(!nbr1_is_acceptable) {
return nbr2_is_acceptable ? nbr2 : NULL;
}
if(!nbr2_is_acceptable) {
return nbr1_is_acceptable ? nbr1 : NULL;
}
/* Maintain stability of the preferred parent. Switch only if the gain
is greater than RANK_THRESHOLD, or if the neighbor has been better than the
current parent for at more than TIME_THRESHOLD. */
if(nbr1 == curr_instance.dag.preferred_parent && within_hysteresis(nbr2)) {
return nbr1;
}
if(nbr2 == curr_instance.dag.preferred_parent && within_hysteresis(nbr1)) {
return nbr2;
}
return nbr_path_cost(nbr1) < nbr_path_cost(nbr2) ? nbr1 : nbr2;
}
/*---------------------------------------------------------------------------*/
#if !RPL_WITH_MC
static void
update_metric_container(void)
{
curr_instance.mc.type = RPL_DAG_MC_NONE;
}
#else /* RPL_WITH_MC */
static void
update_metric_container(void)
{
uint16_t path_cost;
uint8_t type;
if(!curr_instance.used) {
LOG_WARN("cannot update the metric container when not joined\n");
return;
}
if(curr_instance.dag.rank == ROOT_RANK) {
/* Configure MC at root only, other nodes are auto-configured when joining */
curr_instance.mc.type = RPL_DAG_MC;
curr_instance.mc.flags = 0;
curr_instance.mc.aggr = RPL_DAG_MC_AGGR_ADDITIVE;
curr_instance.mc.prec = 0;
path_cost = curr_instance.dag.rank;
} else {
path_cost = nbr_path_cost(curr_instance.dag.preferred_parent);
}
/* Handle the different MC types */
switch(curr_instance.mc.type) {
case RPL_DAG_MC_NONE:
break;
case RPL_DAG_MC_ETX:
curr_instance.mc.length = sizeof(curr_instance.mc.obj.etx);
curr_instance.mc.obj.etx = path_cost;
break;
case RPL_DAG_MC_ENERGY:
curr_instance.mc.length = sizeof(curr_instance.mc.obj.energy);
if(curr_instance.dag.rank == ROOT_RANK) {
type = RPL_DAG_MC_ENERGY_TYPE_MAINS;
} else {
type = RPL_DAG_MC_ENERGY_TYPE_BATTERY;
}
curr_instance.mc.obj.energy.flags = type << RPL_DAG_MC_ENERGY_TYPE;
/* Energy_est is only one byte, use the least significant byte of the path metric. */
curr_instance.mc.obj.energy.energy_est = path_cost >> 8;
break;
default:
LOG_WARN("MRHOF, non-supported MC %u\n", curr_instance.mc.type);
break;
}
}
#endif /* RPL_WITH_MC */
/*---------------------------------------------------------------------------*/
rpl_of_t rpl_mrhof = {
reset,
nbr_link_metric,
nbr_has_usable_link,
nbr_is_acceptable_parent,
nbr_path_cost,
rank_via_nbr,
best_parent,
update_metric_container,
RPL_OCP_MRHOF
};
/** @}*/