nes-proj/core/net/nbr-table.c

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/*
* Copyright (c) 2013, Swedish Institute of Computer Science
* Copyright (c) 2010, Vrije Universiteit Brussel
* 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.
*
*
* Authors: Simon Duquennoy <simonduq@sics.se>
* Joris Borms <joris.borms@vub.ac.be>
*/
#include "contiki.h"
#include <stddef.h>
#include <string.h>
#include "lib/memb.h"
#include "lib/list.h"
#include "net/nbr-table.h"
/* List of link-layer addresses of the neighbors, used as key in the tables */
typedef struct nbr_table_key {
struct nbr_table_key *next;
rimeaddr_t lladdr;
} nbr_table_key_t;
/* For each neighbor, a map of the tables that use the neighbor.
* As we are using uint8_t, we have a maximum of 8 tables in the system */
static uint8_t used_map[NBR_TABLE_MAX_NEIGHBORS];
/* For each neighbor, a map of the tables that lock the neighbor */
static uint8_t locked_map[NBR_TABLE_MAX_NEIGHBORS];
/* The maximum number of tables */
#define MAX_NUM_TABLES 8
/* A list of pointers to tables in use */
static struct nbr_table *all_tables[MAX_NUM_TABLES];
/* The current number of tables */
static unsigned num_tables;
/* The neighbor address table */
MEMB(neighbor_addr_mem, nbr_table_key_t, NBR_TABLE_MAX_NEIGHBORS);
LIST(nbr_table_keys);
/*---------------------------------------------------------------------------*/
/* Get a key from a neighbor index */
static nbr_table_key_t *
key_from_index(int index)
{
return index != -1 ? &((nbr_table_key_t *)neighbor_addr_mem.mem)[index] : NULL;
}
/*---------------------------------------------------------------------------*/
/* Get an item from its neighbor index */
static nbr_table_item_t *
item_from_index(nbr_table_t *table, int index)
{
return table != NULL && index != -1 ? (char *)table->data + index * table->item_size : NULL;
}
/*---------------------------------------------------------------------------*/
/* Get the neighbor index of an item */
static int
index_from_key(nbr_table_key_t *key)
{
return key != NULL ? key - (nbr_table_key_t *)neighbor_addr_mem.mem : -1;
}
/*---------------------------------------------------------------------------*/
/* Get the neighbor index of an item */
static int
index_from_item(nbr_table_t *table, const nbr_table_item_t *item)
{
return table != NULL && item != NULL ? ((int)((char *)item - (char *)table->data)) / table->item_size : -1;
}
/*---------------------------------------------------------------------------*/
/* Get an item from its key */
static nbr_table_item_t *
item_from_key(nbr_table_t *table, nbr_table_key_t *key)
{
return item_from_index(table, index_from_key(key));
}
/*---------------------------------------------------------------------------*/
/* Get the key af an item */
static nbr_table_key_t *
key_from_item(nbr_table_t *table, const nbr_table_item_t *item)
{
return key_from_index(index_from_item(table, item));
}
/*---------------------------------------------------------------------------*/
/* Get the index of a neighbor from its link-layer address */
static int
index_from_lladdr(const rimeaddr_t *lladdr)
{
nbr_table_key_t *key;
/* Allow lladdr-free insertion, useful e.g. for IPv6 ND.
* Only one such entry is possible at a time, indexed by rimeaddr_null. */
if(lladdr == NULL) {
lladdr = &rimeaddr_null;
}
key = list_head(nbr_table_keys);
while(key != NULL) {
if(lladdr && rimeaddr_cmp(lladdr, &key->lladdr)) {
return index_from_key(key);
}
key = list_item_next(key);
}
return -1;
}
/*---------------------------------------------------------------------------*/
/* Get bit from "used" or "locked" bitmap */
static int
nbr_get_bit(uint8_t *bitmap, nbr_table_t *table, nbr_table_item_t *item)
{
int item_index = index_from_item(table, item);
if(table != NULL && item_index != -1) {
return (bitmap[item_index] & (1 << table->index)) != 0;
} else {
return 0;
}
return 0;
}
/*---------------------------------------------------------------------------*/
/* Set bit in "used" or "locked" bitmap */
static int
nbr_set_bit(uint8_t *bitmap, nbr_table_t *table, nbr_table_item_t *item, int value)
{
int item_index = index_from_item(table, item);
if(table != NULL && item_index != -1) {
if(value) {
bitmap[item_index] |= 1 << table->index;
} else {
bitmap[item_index] &= ~(1 << table->index);
}
return 1;
} else {
return 0;
}
return 0;
}
/*---------------------------------------------------------------------------*/
static nbr_table_key_t *
nbr_table_allocate(void)
{
nbr_table_key_t *key;
int least_used_count = 0;
nbr_table_key_t *least_used_key = NULL;
key = memb_alloc(&neighbor_addr_mem);
if(key != NULL) {
return key;
} else { /* No more space, try to free a neighbor.
* The replacement policy is the following: remove neighbor that is:
* (1) not locked
* (2) used by fewest tables
* (3) oldest (the list is ordered by insertion time)
* */
/* Get item from first key */
key = list_head(nbr_table_keys);
while(key != NULL) {
int item_index = index_from_key(key);
int locked = locked_map[item_index];
/* Never delete a locked item */
if(!locked) {
int used = used_map[item_index];
int used_count = 0;
/* Count how many tables are using this item */
while(used != 0) {
if((used & 1) == 1) {
used_count++;
}
used >>= 1;
}
/* Find least used item */
if(least_used_key == NULL || used_count < least_used_count) {
least_used_key = key;
least_used_count = used_count;
if(used_count == 0) { /* We won't find any least used item */
break;
}
}
}
key = list_item_next(key);
}
if(least_used_key == NULL) {
/* We haven't found any unlocked item, allocation fails */
return NULL;
} else {
/* Reuse least used item */
int i;
for(i = 0; i<MAX_NUM_TABLES; i++) {
if(all_tables[i] != NULL && all_tables[i]->callback != NULL) {
/* Call table callback for each table that uses this item */
nbr_table_item_t *removed_item = item_from_key(all_tables[i], least_used_key);
if(nbr_get_bit(used_map, all_tables[i], removed_item) == 1) {
all_tables[i]->callback(removed_item);
}
}
}
/* Empty used map */
used_map[index_from_key(least_used_key)] = 0;
/* Remove neighbor from list */
list_remove(nbr_table_keys, least_used_key);
/* Return associated key */
return least_used_key;
}
}
}
/*---------------------------------------------------------------------------*/
/* Register a new neighbor table. To be used at initialization by modules
* using a neighbor table */
int
nbr_table_register(nbr_table_t *table, nbr_table_callback *callback)
{
if(num_tables < MAX_NUM_TABLES) {
table->index = num_tables++;
table->callback = callback;
all_tables[table->index] = table;
return 1;
} else {
/* Maximum number of tables exceeded */
return 0;
}
}
/*---------------------------------------------------------------------------*/
/* Returns the first item of the current table */
nbr_table_item_t *
nbr_table_head(nbr_table_t *table)
{
/* Get item from first key */
nbr_table_item_t *item = item_from_key(table, list_head(nbr_table_keys));
/* Item is the first neighbor, now check is it is in the current table */
if(nbr_get_bit(used_map, table, item)) {
return item;
} else {
return nbr_table_next(table, item);
}
}
/*---------------------------------------------------------------------------*/
/* Iterates over the current table */
nbr_table_item_t *
nbr_table_next(nbr_table_t *table, nbr_table_item_t *item)
{
do {
void *key = key_from_item(table, item);
key = list_item_next(key);
/* Loop until the next item is in the current table */
item = item_from_key(table, key);
} while(item && !nbr_get_bit(used_map, table, item));
return item;
}
/*---------------------------------------------------------------------------*/
/* Add a neighbor indexed with its link-layer address */
nbr_table_item_t *
nbr_table_add_lladdr(nbr_table_t *table, const rimeaddr_t *lladdr)
{
int index;
nbr_table_item_t *item;
nbr_table_key_t *key;
/* Allow lladdr-free insertion, useful e.g. for IPv6 ND.
* Only one such entry is possible at a time, indexed by rimeaddr_null. */
if(lladdr == NULL) {
lladdr = &rimeaddr_null;
}
if((index = index_from_lladdr(lladdr)) == -1) {
/* Neighbor not yet in table, let's try to allocate one */
key = nbr_table_allocate();
/* No space available for new entry */
if(key == NULL) {
return NULL;
}
/* Add neighbor to list */
list_add(nbr_table_keys, key);
/* Get index from newly allocated neighbor */
index = index_from_key(key);
/* Set link-layer address */
rimeaddr_copy(&key->lladdr, lladdr);
}
/* Get item in the current table */
item = item_from_index(table, index);
/* Initialize item data and set "used" bit */
memset(item, 0, table->item_size);
nbr_set_bit(used_map, table, item, 1);
return item;
}
/*---------------------------------------------------------------------------*/
/* Get an item from its link-layer address */
void *
nbr_table_get_from_lladdr(nbr_table_t *table, const rimeaddr_t *lladdr)
{
void *item = item_from_index(table, index_from_lladdr(lladdr));
return nbr_get_bit(used_map, table, item) ? item : NULL;
}
/*---------------------------------------------------------------------------*/
/* Removes a neighbor from the current table (unset "used" bit) */
int
nbr_table_remove(nbr_table_t *table, void *item)
{
int ret = nbr_set_bit(used_map, table, item, 0);
nbr_set_bit(locked_map, table, item, 0);
return ret;
}
/*---------------------------------------------------------------------------*/
/* Lock a neighbor for the current table (set "locked" bit) */
int
nbr_table_lock(nbr_table_t *table, void *item)
{
return nbr_set_bit(locked_map, table, item, 1);
}
/*---------------------------------------------------------------------------*/
/* Release the lock on a neighbor for the current table (unset "locked" bit) */
int
nbr_table_unlock(nbr_table_t *table, void *item)
{
return nbr_set_bit(locked_map, table, item, 0);
}
/*---------------------------------------------------------------------------*/
/* Get link-layer address of an item */
rimeaddr_t *
nbr_table_get_lladdr(nbr_table_t *table, const void *item)
{
nbr_table_key_t *key = key_from_item(table, item);
return key != NULL ? &key->lladdr : NULL;
}