/* bring the interface up */
  netif_set_up(netif);

  return ERR_OK;
}

/**
 * Start AutoIP client
 *
 * @param netif network interface on which start the AutoIP client
 */
err_t
autoip_start(struct netif *netif)
{
  struct autoip *autoip = netif->autoip;
  err_t result = ERR_OK;

  if(netif_is_up(netif)) {
    netif_set_down(netif);
  }

  /* Set IP-Address, Netmask and Gateway to 0 to make sure that
   * ARP Packets are formed correctly
   */
  netif->ip_addr.addr = 0;
  netif->netmask.addr = 0;
  netif->gw.addr      = 0;

  LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
    ("autoip_start(netif=%p) %c%c%"U16_F"\n", (void*)netif, netif->name[0],
    netif->name[1], (u16_t)netif->num));
  if(autoip == NULL) {
    /* no AutoIP client attached yet? */
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
      ("autoip_start(): starting new AUTOIP client\n"));
    autoip = mem_malloc(sizeof(struct autoip));
    if(autoip == NULL) {
      LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
        ("autoip_start(): could not allocate autoip\n"));
      return ERR_MEM;
    }
    memset( autoip, 0, sizeof(struct autoip));
    /* store this AutoIP client in the netif */
    netif->autoip = autoip;
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_start(): allocated autoip"));
  } else {
    autoip->state = AUTOIP_STATE_OFF;
    autoip->ttw = 0;
    autoip->sent_num = 0;
    memset(&autoip->llipaddr, 0, sizeof(struct ip_addr));
    autoip->lastconflict = 0;
  }

  autoip_create_addr(netif, &(autoip->llipaddr));
  autoip->tried_llipaddr++;
  autoip->state = AUTOIP_STATE_PROBING;
  autoip->sent_num = 0;

  /* time to wait to first probe, this is randomly
   * choosen out of 0 to PROBE_WAIT seconds.
   * compliant to RFC 3927 Section 2.2.1
   */
  autoip->ttw = (u16_t)(LWIP_AUTOIP_RAND(netif) % (PROBE_WAIT * AUTOIP_TICKS_PER_SECOND));

  /*
   * if we tried more then MAX_CONFLICTS we must limit our rate for
   * accquiring and probing address
   * compliant to RFC 3927 Section 2.2.1
   */

  if(autoip->tried_llipaddr > MAX_CONFLICTS) {
    autoip->ttw = RATE_LIMIT_INTERVAL * AUTOIP_TICKS_PER_SECOND;
  }

  return result;
}

/**
 * Stop AutoIP client
 *
 * @param netif network interface on which stop the AutoIP client
 */
err_t
autoip_stop(struct netif *netif)
{
  netif->autoip->state = AUTOIP_STATE_OFF;
  netif_set_down(netif);
  return ERR_OK;
}

/**
 * Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds
 */
void
autoip_tmr()
{
  struct netif *netif = netif_list;
  /* loop through netif's */
  while (netif != NULL) {
    /* only act on AutoIP configured interfaces */
    if (netif->autoip != NULL) {
      if(netif->autoip->lastconflict > 0) {
        netif->autoip->lastconflict--;
      }

      LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
        ("autoip_tmr() AutoIP-State: %"U16_F", ttw=%"U16_F"\n",
        (u16_t)(netif->autoip->state), netif->autoip->ttw));

      switch(netif->autoip->state) {
        case AUTOIP_STATE_PROBING:
          if(netif->autoip->ttw > 0) {
            netif->autoip->ttw--;
          } else {
            if(netif->autoip->sent_num == PROBE_NUM) {
              netif->autoip->state = AUTOIP_STATE_ANNOUNCING;
              netif->autoip->sent_num = 0;
              netif->autoip->ttw = ANNOUNCE_WAIT * AUTOIP_TICKS_PER_SECOND;
            } else {
              etharp_request(netif, &(netif->autoip->llipaddr));
              LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
                ("autoip_tmr() PROBING Sent Probe\n"));
              netif->autoip->sent_num++;
              /* calculate time to wait to next probe */
              netif->autoip->ttw = (u16_t)((LWIP_AUTOIP_RAND(netif) %
                ((PROBE_MAX - PROBE_MIN) * AUTOIP_TICKS_PER_SECOND) ) +
                PROBE_MIN * AUTOIP_TICKS_PER_SECOND);
            }
          }
          break;

        case AUTOIP_STATE_ANNOUNCING:
          if(netif->autoip->ttw > 0) {
            netif->autoip->ttw--;
          } else {
            if(netif->autoip->sent_num == 0) {
             /* We are here the first time, so we waited ANNOUNCE_WAIT seconds
              * Now we can bind to an IP address and use it
              */
              autoip_bind(netif);
            }

            if(netif->autoip->sent_num == ANNOUNCE_NUM) {
              netif->autoip->state = AUTOIP_STATE_BOUND;
              netif->autoip->sent_num = 0;
              netif->autoip->ttw = 0;
            } else {
              autoip_arp_announce(netif);
              LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3,
                ("autoip_tmr() ANNOUNCING Sent Announce\n"));
              netif->autoip->sent_num++;
              netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
            }
          }
          break;
      }
    }
    /* proceed to next network interface */
    netif = netif->next;
  }
}

/**
 * Handles every incoming ARP Packet, called by etharp_arp_input.
 *
 * @param netif network interface to use for autoip processing
 * @param hdr Incoming ARP packet
 */
void
autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr)
{
  LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | 3, ("autoip_arp_reply()\n"));
  if ((netif->autoip != NULL) && (netif->autoip->state != AUTOIP_STATE_OFF)) {
   /* when ip.src == llipaddr && hw.src != netif->hwaddr
    *
    * when probing  ip.dst == llipaddr && hw.src != netif->hwaddr
    * we have a conflict and must solve it
    */
    struct ip_addr sipaddr, dipaddr;
    struct eth_addr netifaddr;
    netifaddr.addr[0] = netif->hwaddr[0];
    netifaddr.addr[1] = netif->hwaddr[1];
    netifaddr.addr[2] = netif->hwaddr[2];
    netifaddr.addr[3] = netif->hwaddr[3];
    netifaddr.addr[4] = netif->hwaddr[4];
    netifaddr.addr[5] = netif->hwaddr[5];

    /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
     * structure packing (not using structure copy which breaks strict-aliasing rules).
     */
    SMEMCPY(&sipaddr, &hdr->sipaddr, sizeof(sipaddr));
    SMEMCPY(&dipaddr, &hdr->dipaddr, sizeof(dipaddr));
      
    if ((netif->autoip->state == AUTOIP_STATE_PROBING) ||
        ((netif->autoip->state == AUTOIP_STATE_ANNOUNCING) &&
         (netif->autoip->sent_num == 0))) {
     /* RFC 3927 Section 2.2.1:
      * from beginning to after ANNOUNCE_WAIT
      * seconds we have a conflict if
      * ip.src == llipaddr OR
      * ip.dst == llipaddr && hw.src != own hwaddr
      */
      if ((ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr)) ||
          (ip_addr_cmp(&dipaddr, &netif->autoip->llipaddr) &&
           !eth_addr_cmp(&netifaddr, &hdr->shwaddr))) {
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
          ("autoip_arp_reply(): Probe Conflict detected\n"));
        autoip_start(netif);
      }
    } else {
     /* RFC 3927 Section 2.5:
      * in any state we have a conflict if
      * ip.src == llipaddr && hw.src != own hwaddr
      */
      if (ip_addr_cmp(&sipaddr, &netif->autoip->llipaddr) &&
          !eth_addr_cmp(&netifaddr, &hdr->shwaddr)) {
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE | 1,
          ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
        autoip_handle_arp_conflict(netif);
      }
    }
  }
}

#endif /* LWIP_AUTOIP */