osd-contiki/examples/trickle-library/trickle-library.c

/*
 * Copyright (c) 2012, George Oikonomou - <oikonomou@users.sourceforge.net>
 * 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 copyright holder 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 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 HOLDER 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.
 */

/* Example trickle-based protocol demonstrating the functionality of the
 * trickle (trickle_timer) library (RFC 6206) */
#include "contiki.h"
#include "contiki-lib.h"
#include "contiki-net.h"

#include "lib/trickle-timer.h"
#include "dev/leds.h"
#include "lib/random.h"

#include <string.h>

#define DEBUG DEBUG_PRINT
#include "net/uip-debug.h"

/* Trickle variables and constants */
static struct trickle_timer tt;

#define IMIN               16   /* ticks */
#define IMAX               10   /* doublings */
#define REDUNDANCY_CONST    2

/* Networking */
#define TRICKLE_PROTO_PORT 30001
static struct uip_udp_conn *trickle_conn;
static uip_ipaddr_t ipaddr;     /* destination: link-local all-nodes multicast */

/*
 * For this 'protocol', nodes exchange a token (1 byte) at a frequency
 * governed by trickle. A node detects an inconsistency when it receives a
 * token different than the one it knows.
 * In this case, either:
 * - 'they' have a 'newer' token and we also update our own value, or
 * - 'we' have a 'newer' token, in which case we trigger an inconsistency
 *   without updating our value.
 * In this context, 'newer' is defined in serial number arithmetic terms.
 *
 * Every NEW_TOKEN_INTERVAL clock ticks each node will generate a new token
 * with probability 1/NEW_TOKEN_PROB. This is controlled by etimer et.
 */
#define NEW_TOKEN_INTERVAL  10 * CLOCK_SECOND
#define NEW_TOKEN_PROB      0x80
static uint8_t token;
static struct etimer et; /* Used to periodically generate inconsistencies */
/*---------------------------------------------------------------------------*/
PROCESS(trickle_protocol_process, "Trickle Protocol process");
AUTOSTART_PROCESSES(&trickle_protocol_process);
/*---------------------------------------------------------------------------*/
static void
tcpip_handler(void)
{
  leds_on(LEDS_GREEN);
  if(uip_newdata()) {
    PRINTF("At %lu (I=%lu, c=%u): ",
           (unsigned long)clock_time(), (unsigned long)tt.i_cur, tt.c);
    PRINTF("Our token=0x%02x, theirs=0x%02x\n", token,
           ((uint8_t *)uip_appdata)[0]);
    if(token == ((uint8_t *)uip_appdata)[0]) {
      PRINTF("Consistent RX\n");
      trickle_timer_consistency(&tt);
    } else {
      if((signed char)(token - ((uint8_t *)uip_appdata)[0]) < 0) {
        PRINTF("Theirs is newer. Update\n");
        token = ((uint8_t *)uip_appdata)[0];
      } else {
        PRINTF("They are behind\n");
      }
      trickle_timer_inconsistency(&tt);

      /*
       * Here tt.ct.etimer.timer.{start + interval} points to time t in the
       * current interval. However, between t and I it points to the interval's
       * end so if you're going to use this, do so with caution.
       */
      PRINTF("At %lu: Trickle inconsistency. Scheduled TX for %lu\n",
             (unsigned long)clock_time(),
             (unsigned long)(tt.ct.etimer.timer.start +
                             tt.ct.etimer.timer.interval));
    }
  }
  leds_off(LEDS_GREEN);
  return;
}
/*---------------------------------------------------------------------------*/
static void
trickle_tx(void *ptr, uint8_t suppress)
{
  /* *ptr is a pointer to the trickle_timer that triggered this callback. In
   * his example we know that ptr points to tt. However, we pretend that we did
   * not know (which would be the case if we e.g. had multiple trickle timers)
   * and cast it to a local struct trickle_timer* */
  struct trickle_timer *loc_tt = (struct trickle_timer *)ptr;

  if(suppress == TRICKLE_TIMER_TX_SUPPRESS) {
    return;
  }

  leds_on(LEDS_RED);

  PRINTF("At %lu (I=%lu, c=%u): ",
         (unsigned long)clock_time(), (unsigned long)loc_tt->i_cur,
         loc_tt->c);
  PRINTF("Trickle TX token 0x%02x\n", token);

  /* Instead of changing ->ripaddr around by ourselves, we could have used
   * uip_udp_packet_sendto which would have done it for us. However it puts an
   * extra ~20 bytes on stack and the cc2x3x micros hate it, so we stick with
   * send() */

  /* Destination IP: link-local all-nodes multicast */
  uip_ipaddr_copy(&trickle_conn->ripaddr, &ipaddr);
  uip_udp_packet_send(trickle_conn, &token, sizeof(token));

  /* Restore to 'accept incoming from any IP' */
  uip_create_unspecified(&trickle_conn->ripaddr);

  leds_off(LEDS_RED);
}
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(trickle_protocol_process, ev, data)
{
  PROCESS_BEGIN();

  PRINTF("Trickle protocol started\n");

  uip_create_linklocal_allnodes_mcast(&ipaddr); /* Store for later */

  trickle_conn = udp_new(NULL, UIP_HTONS(TRICKLE_PROTO_PORT), NULL);
  udp_bind(trickle_conn, UIP_HTONS(TRICKLE_PROTO_PORT));

  PRINTF("Connection: local/remote port %u/%u\n",
         UIP_HTONS(trickle_conn->lport), UIP_HTONS(trickle_conn->rport));

  token = 0;

  trickle_timer_config(&tt, IMIN, IMAX, REDUNDANCY_CONST);
  trickle_timer_set(&tt, trickle_tx, &tt);
  /*
   * At this point trickle is started and is running the first interval. All
   * nodes 'agree' that token == 0. This will change when one of them randomly
   * decides to generate a new one
   */
  etimer_set(&et, NEW_TOKEN_INTERVAL);

  while(1) {
    PROCESS_YIELD();
    if(ev == tcpip_event) {
      tcpip_handler();
    } else if(etimer_expired(&et)) {
      /* Periodically (and randomly) generate a new token. This will trigger
       * a trickle inconsistency */
      if((random_rand() & NEW_TOKEN_PROB) == 0) {
        token++;
        PRINTF("At %lu: Generating a new token 0x%02x\n",
               (unsigned long)clock_time(), token);
        trickle_timer_reset_event(&tt);
      }
      etimer_set(&et, NEW_TOKEN_INTERVAL);
    }
  }
  PROCESS_END();
}
/*---------------------------------------------------------------------------*/