text: /**
   * @file
   * AutoIP Automatic LinkLocal IP Configuration
   *
   */
  
  /*
   *
   * Copyright (c) 2007 Dominik Spies <kontakt@dspies.de>
   * 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. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
   *
   * Author: Dominik Spies <kontakt@dspies.de>
   *
   * This is a AutoIP implementation for the lwIP TCP/IP stack. It aims to conform
   * with RFC 3927.
   *
   *
   * Please coordinate changes and requests with Dominik Spies
   * <kontakt@dspies.de>
   */
  
  /*******************************************************************************
   * USAGE:
   * 
   * define LWIP_AUTOIP 1  in your lwipopts.h
   * 
   * If you don't use tcpip.c (so, don't call, you don't call tcpip_init):
   * - First, call autoip_init().
   * - call autoip_tmr() all AUTOIP_TMR_INTERVAL msces,
   *   that should be defined in autoip.h.
   *   I recommend a value of 100. The value must divide 1000 with a remainder almost 0.
   *   Possible values are 1000, 500, 333, 250, 200, 166, 142, 125, 111, 100 ....
   *
   * Without DHCP:
   * - Call autoip_start() after netif_add().
   * 
   * With DHCP:
   * - define LWIP_DHCP_AUTOIP_COOP 1 in your lwipopts.h.
   * - Configure your DHCP Client.
   *
   */
  
  #include "lwip/opt.h"
  
  #if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
  
  #include "lwip/mem.h"
  #include "lwip/udp.h"
  #include "lwip/ip_addr.h"
  #include "lwip/netif.h"
  #include "lwip/autoip.h"
  #include "netif/etharp.h"
  
  #include <stdlib.h>
  #include <string.h>
  
  /* 169.254.0.0 */
  #define AUTOIP_NET         0xA9FE0000
  /* 169.254.1.0 */
  #define AUTOIP_RANGE_START (AUTOIP_NET | 0x0100)
  /* 169.254.254.255 */
  #define AUTOIP_RANGE_END   (AUTOIP_NET | 0xFEFF)
  
  
  /** Pseudo random macro based on netif informations.
   * You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
  #ifndef LWIP_AUTOIP_RAND
  #define LWIP_AUTOIP_RAND(netif) ( (((u32_t)((netif->hwaddr[5]) & 0xff) << 24) | \
                                     ((u32_t)((netif->hwaddr[3]) & 0xff) << 16) | \
                                     ((u32_t)((netif->hwaddr[2]) & 0xff) << 8) | \
                                     ((u32_t)((netif->hwaddr[4]) & 0xff))) + \
                                     (netif->autoip?netif->autoip->tried_llipaddr:0))
  #endif /* LWIP_AUTOIP_RAND */
  
  /**
   * Macro that generates the initial IP address to be tried by AUTOIP.
   * If you want to override this, define it to something else in lwipopts.h.
   */
  #ifndef LWIP_AUTOIP_CREATE_SEED_ADDR
  #define LWIP_AUTOIP_CREATE_SEED_ADDR(netif) \
    htonl(AUTOIP_RANGE_START + ((u32_t)(((u8_t)(netif->hwaddr[4])) | \
                   ((u32_t)((u8_t)(netif->hwaddr[5]))) << 8)))
  #endif /* LWIP_AUTOIP_CREATE_SEED_ADDR */
  
  /* static functions */
  static void autoip_handle_arp_conflict(struct netif *netif);
  
  /* creates a pseudo random LL IP-Address for a network interface */
  static void autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr);
  
  /* sends an ARP probe */
  static err_t autoip_arp_probe(struct netif *netif);
  
  /* sends an ARP announce */
  static err_t autoip_arp_announce(struct netif *netif);
  
  /* configure interface for use with current LL IP-Address */
  static err_t autoip_bind(struct netif *netif);
  
  /* start sending probes for llipaddr */
  static void autoip_start_probing(struct netif *netif);
  
  /**
   * Initialize this module
   */
  void
  autoip_init(void)
  {
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE, ("autoip_init()\n"));
  }
  
  /** Set a statically allocated struct autoip to work with.
   * Using this prevents autoip_start to allocate it using mem_malloc.
   *
   * @param netif the netif for which to set the struct autoip
   * @param dhcp (uninitialised) dhcp struct allocated by the application
   */
  void
  autoip_set_struct(struct netif *netif, struct autoip *autoip)
  {
    LWIP_ASSERT("netif != NULL", netif != NULL);
    LWIP_ASSERT("autoip != NULL", autoip != NULL);
    LWIP_ASSERT("netif already has a struct autoip set", netif->autoip == NULL);
  
    /* clear data structure */
    os_memset(autoip, 0, sizeof(struct autoip));
    /* autoip->state = AUTOIP_STATE_OFF; */
    netif->autoip = autoip;
  }
  
  /** Restart AutoIP client and check the next address (conflict detected)
   *
   * @param netif The netif under AutoIP control
   */
  static void
  autoip_restart(struct netif *netif)
  {
    netif->autoip->tried_llipaddr++;
    autoip_start(netif);
  }
  
  /**
   * Handle a IP address conflict after an ARP conflict detection
   */
  static void
  autoip_handle_arp_conflict(struct netif *netif)
  {
    /* Somehow detect if we are defending or retreating */
    unsigned char defend = 1; /* tbd */
  
    if(defend) {
      if(netif->autoip->lastconflict > 0) {
        /* retreat, there was a conflicting ARP in the last
         * DEFEND_INTERVAL seconds
         */
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
          ("autoip_handle_arp_conflict(): we are defending, but in DEFEND_INTERVAL, retreating\n"));
  
        /* TODO: close all TCP sessions */
        autoip_restart(netif);
      } else {
        LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
          ("autoip_handle_arp_conflict(): we are defend, send ARP Announce\n"));
        autoip_arp_announce(netif);
        netif->autoip->lastconflict = DEFEND_INTERVAL * AUTOIP_TICKS_PER_SECOND;
      }
    } else {
      LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
        ("autoip_handle_arp_conflict(): we do not defend, retreating\n"));
      /* TODO: close all TCP sessions */
      autoip_restart(netif);
    }
  }
  
  /**
   * Create an IP-Address out of range 169.254.1.0 to 169.254.254.255
   *
   * @param netif network interface on which create the IP-Address
   * @param ipaddr ip address to initialize
   */
  static void
  autoip_create_addr(struct netif *netif, ip_addr_t *ipaddr)
  {
    /* Here we create an IP-Address out of range 169.254.1.0 to 169.254.254.255
     * compliant to RFC 3927 Section 2.1
     * We have 254 * 256 possibilities */
  
    u32_t addr = ntohl(LWIP_AUTOIP_CREATE_SEED_ADDR(netif));
    addr += netif->autoip->tried_llipaddr;
    addr = AUTOIP_NET | (addr & 0xffff);
    /* Now, 169.254.0.0 <= addr <= 169.254.255.255 */ 
  
    if (addr < AUTOIP_RANGE_START) {
      addr += AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
    }
    if (addr > AUTOIP_RANGE_END) {
      addr -= AUTOIP_RANGE_END - AUTOIP_RANGE_START + 1;
    }
    LWIP_ASSERT("AUTOIP address not in range", (addr >= AUTOIP_RANGE_START) &&
      (addr <= AUTOIP_RANGE_END));
    ip4_addr_set_u32(ipaddr, htonl(addr));
    
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
      ("autoip_create_addr(): tried_llipaddr=%"U16_F", %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
      (u16_t)(netif->autoip->tried_llipaddr), ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr),
      ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
  }
  
  /**
   * Sends an ARP probe from a network interface
   *
   * @param netif network interface used to send the probe
   */
  static err_t
  autoip_arp_probe(struct netif *netif)
  {
    return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
      (struct eth_addr *)netif->hwaddr, IP_ADDR_ANY, &ethzero,
      &netif->autoip->llipaddr, ARP_REQUEST);
  }
  
  /**
   * Sends an ARP announce from a network interface
   *
   * @param netif network interface used to send the announce
   */
  static err_t
  autoip_arp_announce(struct netif *netif)
  {
    return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
      (struct eth_addr *)netif->hwaddr, &netif->autoip->llipaddr, &ethzero,
      &netif->autoip->llipaddr, ARP_REQUEST);
  }
  
  /**
   * Configure interface for use with current LL IP-Address
   *
   * @param netif network interface to configure with current LL IP-Address
   */
  static err_t
  autoip_bind(struct netif *netif)
  {
    struct autoip *autoip = netif->autoip;
    ip_addr_t sn_mask, gw_addr;
  
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
      ("autoip_bind(netif=%p) %c%c%"U16_F" %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
      (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num,
      ip4_addr1_16(&autoip->llipaddr), ip4_addr2_16(&autoip->llipaddr),
      ip4_addr3_16(&autoip->llipaddr), ip4_addr4_16(&autoip->llipaddr)));
  
    IP4_ADDR(&sn_mask, 255, 255, 0, 0);
    IP4_ADDR(&gw_addr, 0, 0, 0, 0);
  
    netif_set_ipaddr(netif, &autoip->llipaddr);
    netif_set_netmask(netif, &sn_mask);
    netif_set_gw(netif, &gw_addr);  
  
    /* 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
     */
    ip_addr_set_zero(&netif->ip_addr);
    ip_addr_set_zero(&netif->netmask);
    ip_addr_set_zero(&netif->gw);
  
    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 = (struct 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;
      }
      os_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;
      ip_addr_set_zero(&autoip->llipaddr);
      autoip->lastconflict = 0;
    }
  
    autoip_create_addr(netif, &(autoip->llipaddr));
    autoip_start_probing(netif);
  
    return result;
  }
  
  static void
  autoip_start_probing(struct netif *netif)
  {
    struct autoip *autoip = netif->autoip;
  
    autoip->state = AUTOIP_STATE_PROBING;
    autoip->sent_num = 0;
    LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
       ("autoip_start_probing(): changing state to PROBING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
        ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
        ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
  
    /* 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;
    }
  }
  
  /**
   * Handle a possible change in the network configuration.
   *
   * If there is an AutoIP address configured, take the interface down
   * and begin probing with the same address.
   */
  void
  autoip_network_changed(struct netif *netif)
  {
    if (netif->autoip && netif->autoip->state != AUTOIP_STATE_OFF) {
      netif_set_down(netif);
      autoip_start_probing(netif);
    }
  }
  
  /**
   * 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;
                LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                   ("autoip_tmr(): changing state to ANNOUNCING: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
                    ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
                    ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
              } else {
                autoip_arp_probe(netif);
                LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                  ("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 calls netif_set_up. This triggers a gratuitous ARP
                * which counts as an announcement.
                */
                autoip_bind(netif);
              } else {
                autoip_arp_announce(netif);
                LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE,
                  ("autoip_tmr() ANNOUNCING Sent Announce\n"));
              }
              netif->autoip->ttw = ANNOUNCE_INTERVAL * AUTOIP_TICKS_PER_SECOND;
              netif->autoip->sent_num++;
  
              if(netif->autoip->sent_num >= ANNOUNCE_NUM) {
                  netif->autoip->state = AUTOIP_STATE_BOUND;
                  netif->autoip->sent_num = 0;
                  netif->autoip->ttw = 0;
                   LWIP_DEBUGF(AUTOIP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE,
                      ("autoip_tmr(): changing state to BOUND: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
                       ip4_addr1_16(&netif->autoip->llipaddr), ip4_addr2_16(&netif->autoip->llipaddr),
                       ip4_addr3_16(&netif->autoip->llipaddr), ip4_addr4_16(&netif->autoip->llipaddr)));
              }
            }
            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, ("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
      */
      ip_addr_t sipaddr, dipaddr;
      struct eth_addr netifaddr;
      ETHADDR16_COPY(netifaddr.addr, netif->hwaddr);
  
      /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
       * structure packing (not using structure copy which breaks strict-aliasing rules).
       */
      IPADDR2_COPY(&sipaddr, &hdr->sipaddr);
      IPADDR2_COPY(&dipaddr, &hdr->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 | LWIP_DBG_LEVEL_WARNING,
            ("autoip_arp_reply(): Probe Conflict detected\n"));
          autoip_restart(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 | LWIP_DBG_LEVEL_WARNING,
            ("autoip_arp_reply(): Conflicting ARP-Packet detected\n"));
          autoip_handle_arp_conflict(netif);
        }
      }
    }
  }
  
  #endif /* LWIP_AUTOIP */
  