Add an example demonstrating trickle timers
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George Oikonomou
George Oikonomou
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examples/trickle-library/trickle-library.c
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examples/trickle-library/trickle-library.c
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/*
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* Copyright (c) 2012, George Oikonomou - <oikonomou@users.sourceforge.net>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/* Example trickle-based protocol demonstrating the functionality of the
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* trickle (trickle_timer) library (RFC 6206) */
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#include "contiki.h"
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#include "contiki-lib.h"
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#include "contiki-net.h"
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#include "lib/trickle-timer.h"
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#include "dev/leds.h"
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#include "lib/random.h"
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#include <string.h>
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#define DEBUG DEBUG_PRINT
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#include "net/uip-debug.h"
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/* Trickle variables and constants */
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static struct trickle_timer tt;
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#define IMIN 16 /* ticks */
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#define IMAX 10 /* doublings */
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#define REDUNDANCY_CONST 2
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/* Networking */
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#define TRICKLE_PROTO_PORT 30001
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static struct uip_udp_conn *trickle_conn;
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static uip_ipaddr_t ipaddr; /* destination: link-local all-nodes multicast */
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/*
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* For this 'protocol', nodes exchange a token (1 byte) at a frequency
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* governed by trickle. A node detects an inconsistency when it receives a
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* token different than the one it knows.
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* In this case, either:
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* - 'they' have a 'newer' token and we also update our own value, or
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* - 'we' have a 'newer' token, in which case we trigger an inconsistency
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* without updating our value.
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* In this context, 'newer' is defined in serial number arithmetic terms.
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*
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* Every NEW_TOKEN_INTERVAL clock ticks each node will generate a new token
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* with probability 1/NEW_TOKEN_PROB. This is controlled by etimer et.
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*/
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#define NEW_TOKEN_INTERVAL 10 * CLOCK_SECOND
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#define NEW_TOKEN_PROB 0x80
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static uint8_t token;
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static struct etimer et; /* Used to periodically generate inconsistencies */
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/*---------------------------------------------------------------------------*/
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PROCESS(trickle_protocol_process, "Trickle Protocol process");
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AUTOSTART_PROCESSES(&trickle_protocol_process);
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/*---------------------------------------------------------------------------*/
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static void
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tcpip_handler(void)
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{
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leds_on(LEDS_GREEN);
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if(uip_newdata()) {
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PRINTF("At %lu (I=%lu, c=%u): ",
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(unsigned long)clock_time(), (unsigned long)tt.i_cur, tt.c);
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PRINTF("Our token=0x%02x, theirs=0x%02x\n", token,
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((uint8_t *)uip_appdata)[0]);
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if(token == ((uint8_t *)uip_appdata)[0]) {
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PRINTF("Consistent RX\n");
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trickle_timer_consistency(&tt);
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} else {
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if((signed char)(token - ((uint8_t *)uip_appdata)[0]) < 0) {
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PRINTF("Theirs is newer. Update\n");
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token = ((uint8_t *)uip_appdata)[0];
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} else {
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PRINTF("They are behind\n");
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}
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trickle_timer_inconsistency(&tt);
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/*
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* Here tt.ct.etimer.timer.{start + interval} points to time t in the
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* current interval. However, between t and I it points to the interval's
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* end so if you're going to use this, do so with caution.
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*/
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PRINTF("At %lu: Trickle inconsistency. Scheduled TX for %lu\n",
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(unsigned long)clock_time(),
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(unsigned long)(tt.ct.etimer.timer.start +
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tt.ct.etimer.timer.interval));
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}
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}
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leds_off(LEDS_GREEN);
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return;
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}
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/*---------------------------------------------------------------------------*/
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static void
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trickle_tx(void *ptr, uint8_t suppress)
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{
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/* *ptr is a pointer to the trickle_timer that triggered this callback. In
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* his example we know that ptr points to tt. However, we pretend that we did
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* not know (which would be the case if we e.g. had multiple trickle timers)
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* and cast it to a local struct trickle_timer* */
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struct trickle_timer *loc_tt = (struct trickle_timer *)ptr;
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if(suppress == TRICKLE_TIMER_TX_SUPPRESS) {
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return;
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}
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leds_on(LEDS_RED);
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PRINTF("At %lu (I=%lu, c=%u): ",
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(unsigned long)clock_time(), (unsigned long)loc_tt->i_cur,
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loc_tt->c);
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PRINTF("Trickle TX token 0x%02x\n", token);
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/* Instead of changing ->ripaddr around by ourselves, we could have used
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* uip_udp_packet_sendto which would have done it for us. However it puts an
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* extra ~20 bytes on stack and the cc2x3x micros hate it, so we stick with
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* send() */
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/* Destination IP: link-local all-nodes multicast */
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uip_ipaddr_copy(&trickle_conn->ripaddr, &ipaddr);
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uip_udp_packet_send(trickle_conn, &token, sizeof(token));
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/* Restore to 'accept incoming from any IP' */
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uip_create_unspecified(&trickle_conn->ripaddr);
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leds_off(LEDS_RED);
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}
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/*---------------------------------------------------------------------------*/
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PROCESS_THREAD(trickle_protocol_process, ev, data)
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{
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PROCESS_BEGIN();
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PRINTF("Trickle protocol started\n");
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uip_create_linklocal_allnodes_mcast(&ipaddr); /* Store for later */
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trickle_conn = udp_new(NULL, UIP_HTONS(TRICKLE_PROTO_PORT), NULL);
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udp_bind(trickle_conn, UIP_HTONS(TRICKLE_PROTO_PORT));
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PRINTF("Connection: local/remote port %u/%u\n",
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UIP_HTONS(trickle_conn->lport), UIP_HTONS(trickle_conn->rport));
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token = 0;
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trickle_timer_config(&tt, IMIN, IMAX, REDUNDANCY_CONST);
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trickle_timer_set(&tt, trickle_tx, &tt);
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/*
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* At this point trickle is started and is running the first interval. All
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* nodes 'agree' that token == 0. This will change when one of them randomly
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* decides to generate a new one
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*/
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etimer_set(&et, NEW_TOKEN_INTERVAL);
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while(1) {
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PROCESS_YIELD();
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if(ev == tcpip_event) {
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tcpip_handler();
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} else if(etimer_expired(&et)) {
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/* Periodically (and randomly) generate a new token. This will trigger
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* a trickle inconsistency */
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if((random_rand() & NEW_TOKEN_PROB) == 0) {
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token++;
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PRINTF("At %lu: Generating a new token 0x%02x\n",
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(unsigned long)clock_time(), token);
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trickle_timer_reset_event(&tt);
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}
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etimer_set(&et, NEW_TOKEN_INTERVAL);
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}
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}
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PROCESS_END();
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}
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/*---------------------------------------------------------------------------*/
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