text: /**
   * @file
   * Address Resolution Protocol module for IP over Ethernet
   *
   * Functionally, ARP is divided into two parts. The first maps an IP address
   * to a physical address when sending a packet, and the second part answers
   * requests from other machines for our physical address.
   *
   * This implementation complies with RFC 826 (Ethernet ARP). It supports
   * Gratuitious ARP from RFC3220 (IP Mobility Support for IPv4) section 4.6
   * if an interface calls etharp_gratuitous(our_netif) upon address change.
   */
  
  /*
   * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
   * Copyright (c) 2003-2004 Leon Woestenberg <leon.woestenberg@axon.tv>
   * Copyright (c) 2003-2004 Axon Digital Design B.V., The Netherlands.
   * 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.
   *
   * This file is part of the lwIP TCP/IP stack.
   *
   */
   
  #include "lwip/opt.h"
  
  #if LWIP_ARP || LWIP_ETHERNET
  
  #include "lwip/ip_addr.h"
  #include "lwip/def.h"
  #include "lwip/ip.h"
  #include "lwip/stats.h"
  #include "lwip/snmp.h"
  #include "lwip/dhcp.h"
  #include "lwip/autoip.h"
  #include "netif/etharp.h"
  #include "ipv6/lwip/ip6.h"
  
  #if PPPOE_SUPPORT
  #include "netif/ppp_oe.h"
  #endif /* PPPOE_SUPPORT */
  
  #include <string.h>
  #include <wificonf.h>
  
  const struct eth_addr ethbroadcast = {{0xff,0xff,0xff,0xff,0xff,0xff}};
  const struct eth_addr ethzero = {{0,0,0,0,0,0}};
  
  /** The 24-bit IANA multicast OUI is 01-00-5e: */
  #define LL_MULTICAST_ADDR_0 0x01
  #define LL_MULTICAST_ADDR_1 0x00
  #define LL_MULTICAST_ADDR_2 0x5e
  
  #if LWIP_ARP /* don't build if not configured for use in lwipopts.h */
  
  /** the time an ARP entry stays valid after its last update,
   *  for ARP_TMR_INTERVAL = 5000, this is
   *  (240 * 5) seconds = 20 minutes.
   */
  #define ARP_MAXAGE              240
  /** Re-request a used ARP entry 1 minute before it would expire to prevent
   *  breaking a steadily used connection because the ARP entry timed out. */
  #define ARP_AGE_REREQUEST_USED  (ARP_MAXAGE - 12)
  
  /** the time an ARP entry stays pending after first request,
   *  for ARP_TMR_INTERVAL = 5000, this is
   *  (2 * 5) seconds = 10 seconds.
   * 
   *  @internal Keep this number at least 2, otherwise it might
   *  run out instantly if the timeout occurs directly after a request.
   */
  #define ARP_MAXPENDING 2
  
  #define HWTYPE_ETHERNET 1
  
  enum etharp_state {
    ETHARP_STATE_EMPTY = 0,
    ETHARP_STATE_PENDING,
    ETHARP_STATE_STABLE,
    ETHARP_STATE_STABLE_REREQUESTING
  #if ETHARP_SUPPORT_STATIC_ENTRIES
    ,ETHARP_STATE_STATIC
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
  };
  
  struct etharp_entry {
  #if ARP_QUEUEING
    /** Pointer to queue of pending outgoing packets on this ARP entry. */
    struct etharp_q_entry *q;
  #else /* ARP_QUEUEING */
    /** Pointer to a single pending outgoing packet on this ARP entry. */
    struct pbuf *q;
  #endif /* ARP_QUEUEING */
    ip_addr_t ipaddr;
    struct netif *netif;
    struct eth_addr ethaddr;
    u8_t state;
    u8_t ctime;
  };
  
  static struct etharp_entry arp_table[ARP_TABLE_SIZE];
  
  #if !LWIP_NETIF_HWADDRHINT
  static u8_t etharp_cached_entry;
  #endif /* !LWIP_NETIF_HWADDRHINT */
  
  /** Try hard to create a new entry - we want the IP address to appear in
      the cache (even if this means removing an active entry or so). */
  #define ETHARP_FLAG_TRY_HARD     1
  #define ETHARP_FLAG_FIND_ONLY    2
  #if ETHARP_SUPPORT_STATIC_ENTRIES
  #define ETHARP_FLAG_STATIC_ENTRY 4
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
  
  #if LWIP_NETIF_HWADDRHINT
  #define ETHARP_SET_HINT(netif, hint)  if (((netif) != NULL) && ((netif)->addr_hint != NULL))  \
                                        *((netif)->addr_hint) = (hint);
  #else /* LWIP_NETIF_HWADDRHINT */
  #define ETHARP_SET_HINT(netif, hint)  (etharp_cached_entry = (hint))
  #endif /* LWIP_NETIF_HWADDRHINT */
  
  #if ARP_PROXY
  proxy_arp_hook_fn proxy_arp_hook;
  #endif /* ARP_PROXY */
  
  /* Some checks, instead of etharp_init(): */
  #if (LWIP_ARP && (ARP_TABLE_SIZE > 0x7f))
    #error "ARP_TABLE_SIZE must fit in an s8_t, you have to reduce it in your lwipopts.h"
  #endif
  
  static err_t etharp_send_ip(struct netif *netif, struct pbuf *p, struct eth_addr *src, struct eth_addr *dst) ATTRIBUTE_SECTION_FAST;
  static err_t etharp_output_to_arp_index(struct netif *netif, struct pbuf *q, u8_t arp_idx) ATTRIBUTE_SECTION_FAST;
  
  #if ARP_QUEUEING
  /**
   * Free a complete queue of etharp entries
   *
   * @param q a qeueue of etharp_q_entry's to free
   */
  static void
  free_etharp_q(struct etharp_q_entry *q)
  {
    struct etharp_q_entry *r;
    LWIP_ASSERT("q != NULL", q != NULL);
    LWIP_ASSERT("q->p != NULL", q->p != NULL);
    while (q) {
      r = q;
      q = q->next;
      LWIP_ASSERT("r->p != NULL", (r->p != NULL));
      pbuf_free(r->p);
      memp_free(MEMP_ARP_QUEUE, r);
    }
  }
  #else /* ARP_QUEUEING */
  
  /** Compatibility define: free the queued pbuf */
  #define free_etharp_q(q) pbuf_free(q)
  
  #endif /* ARP_QUEUEING */
  
  /** Clean up ARP table entries */
  static void
  etharp_free_entry(int i)
  {
    /* remove from SNMP ARP index tree */
    snmp_delete_arpidx_tree(arp_table[i].netif, &arp_table[i].ipaddr);
    /* and empty packet queue */
    if (arp_table[i].q != NULL) {
      /* remove all queued packets */
      LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_free_entry: freeing entry %"U16_F", packet queue %p.\r\n", (u16_t)i, (void *)(arp_table[i].q)));
      free_etharp_q(arp_table[i].q);
      arp_table[i].q = NULL;
    }
    /* recycle entry for re-use */
    arp_table[i].state = ETHARP_STATE_EMPTY;
  #ifdef LWIP_DEBUG
    /* for debugging, clean out the complete entry */
    arp_table[i].ctime = 0;
    arp_table[i].netif = NULL;
    ip_addr_set_zero(&arp_table[i].ipaddr);
    arp_table[i].ethaddr = ethzero;
  #endif /* LWIP_DEBUG */
  }
  
  /**
   * Clears expired entries in the ARP table.
   *
   * This function should be called every ETHARP_TMR_INTERVAL milliseconds (5 seconds),
   * in order to expire entries in the ARP table.
   */
  void
  etharp_tmr(void)
  {
    u8_t i;
  
    LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer\r\n"));
    /* remove expired entries from the ARP table */
    for (i = 0; i < ARP_TABLE_SIZE; ++i) {
      u8_t state = arp_table[i].state;
      if (state != ETHARP_STATE_EMPTY
  #if ETHARP_SUPPORT_STATIC_ENTRIES
        && (state != ETHARP_STATE_STATIC)
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
        ) {
        arp_table[i].ctime++;
        if ((arp_table[i].ctime >= ARP_MAXAGE) ||
            ((arp_table[i].state == ETHARP_STATE_PENDING)  &&
             (arp_table[i].ctime >= ARP_MAXPENDING))) {
          /* pending or stable entry has become old! */
          LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired %s entry %"U16_F".\r\n",
               arp_table[i].state >= ETHARP_STATE_STABLE ? "stable" : "pending", (u16_t)i));
          /* clean up entries that have just been expired */
          etharp_free_entry(i);
        }
        else if (arp_table[i].state == ETHARP_STATE_STABLE_REREQUESTING) {
          /* Reset state to stable, so that the next transmitted packet will
             re-send an ARP request. */
          arp_table[i].state = ETHARP_STATE_STABLE;
        }
  #if ARP_QUEUEING
        /* still pending entry? (not expired) */
        if (arp_table[i].state == ETHARP_STATE_PENDING) {
          /* resend an ARP query here? */
        }
  #endif /* ARP_QUEUEING */
      }
    }
  }
  
  /**
   * Search the ARP table for a matching.
   * 
   * If an MAC address is given, return a pending or stable ARP entry that matches
   * the address. 
   *  
   * @param eth_addr MAC address to find in ARP cache.
   * @return The ARP entry index that matched, 
   */
  static s8_t
  etharp_find_entry_by_mac(struct eth_addr *ethaddr)
  {
      u8 j;  
  
      if(ethaddr != NULL)
      {
          for (j = 0; j < ARP_TABLE_SIZE; ++j) 
          {
              if (ethaddr && eth_addr_cmp(ethaddr, &arp_table[j].ethaddr)) 
              {
                  return j;
              }
          }
      }
      return -1;
  }
  
  
  
  /**
   * Search the ARP table for a matching or new entry.
   * 
   * If an IP address is given, return a pending or stable ARP entry that matches
   * the address. If no match is found, create a new entry with this address set,
   * but in state ETHARP_EMPTY. The caller must check and possibly change the
   * state of the returned entry.
   * 
   * If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY.
   * 
   * In all cases, attempt to create new entries from an empty entry. If no
   * empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle
   * old entries. Heuristic choose the least important entry for recycling.
   *
   * @param ipaddr IP address to find in ARP cache, or to add if not found.
   * @param flags @see definition of ETHARP_FLAG_*
   * @param netif netif related to this address (used for NETIF_HWADDRHINT)
   *  
   * @return The ARP entry index that matched or is created, ERR_MEM if no
   * entry is found or could be recycled.
   */
  static s8_t
  etharp_find_entry(struct netif *netif, ip_addr_t *ipaddr, u8_t flags)
  {
    s8_t old_pending = ARP_TABLE_SIZE, old_stable = ARP_TABLE_SIZE;
    s8_t empty = ARP_TABLE_SIZE;
    u8_t i = 0, age_pending = 0, age_stable = 0;
    /* oldest entry with packets on queue */
    s8_t old_queue = ARP_TABLE_SIZE;
    /* its age */
    u8_t age_queue = 0;
  
    /**
     * a) do a search through the cache, remember candidates
     * b) select candidate entry
     * c) create new entry
     */
  
    /* a) in a single search sweep, do all of this
     * 1) remember the first empty entry (if any)
     * 2) remember the oldest stable entry (if any)
     * 3) remember the oldest pending entry without queued packets (if any)
     * 4) remember the oldest pending entry with queued packets (if any)
     * 5) search for a matching IP entry, either pending or stable
     *    until 5 matches, or all entries are searched for.
     */
  
    for (i = 0; i < ARP_TABLE_SIZE; ++i) {
      u8_t state = arp_table[i].state;
      /* no empty entry found yet and now we do find one? */
      if ((empty == ARP_TABLE_SIZE) && (state == ETHARP_STATE_EMPTY)) {
        LWIP_DEBUGF(ETHARP_DEBUG, ("etharp_find_entry: found empty entry %"U16_F"\r\n", (u16_t)i));
        /* remember first empty entry */
        empty = i;
      } else if (state != ETHARP_STATE_EMPTY) {
        LWIP_ASSERT("state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE",
          state == ETHARP_STATE_PENDING || state >= ETHARP_STATE_STABLE);
        /* if given, does IP address match IP address in ARP entry? */
        if (ipaddr && ip_addr_cmp(ipaddr, &arp_table[i].ipaddr) && (netif == arp_table[i].netif)) {
          LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: found matching entry %"U16_F"\r\n", (u16_t)i));
          /* found exact IP address match, simply bail out */
          return i;
        }
        /* pending entry? */
        if (state == ETHARP_STATE_PENDING) {
          /* pending with queued packets? */
          if (arp_table[i].q != NULL) {
            if (arp_table[i].ctime >= age_queue) {
              old_queue = i;
              age_queue = arp_table[i].ctime;
            }
          } else
          /* pending without queued packets? */
          {
            if (arp_table[i].ctime >= age_pending) {
              old_pending = i;
              age_pending = arp_table[i].ctime;
            }
          }
        /* stable entry? */
        } else if (state >= ETHARP_STATE_STABLE) {
  #if ETHARP_SUPPORT_STATIC_ENTRIES
          /* don't record old_stable for static entries since they never expire */
          if (state < ETHARP_STATE_STATIC)
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
          {
            /* remember entry with oldest stable entry in oldest, its age in maxtime */
            if (arp_table[i].ctime >= age_stable) {
              old_stable = i;
              age_stable = arp_table[i].ctime;
            }
          }
        }
      }
    }
    /* { we have no match } => try to create a new entry */
     
    /* don't create new entry, only search? */
    if (((flags & ETHARP_FLAG_FIND_ONLY) != 0) ||
        /* or no empty entry found and not allowed to recycle? */
        ((empty == ARP_TABLE_SIZE) && ((flags & ETHARP_FLAG_TRY_HARD) == 0))) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty entry found and not allowed to recycle\r\n"));
      return (s8_t)ERR_MEM;
    }
    
    /* b) choose the least destructive entry to recycle:
     * 1) empty entry
     * 2) oldest stable entry
     * 3) oldest pending entry without queued packets
     * 4) oldest pending entry with queued packets
     * 
     * { ETHARP_FLAG_TRY_HARD is set at this point }
     */ 
  
    /* 1) empty entry available? */
    if (empty < ARP_TABLE_SIZE) {
      i = empty;
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting empty entry %"U16_F"\r\n", (u16_t)i));
    } else {
      /* 2) found recyclable stable entry? */
      if (old_stable < ARP_TABLE_SIZE) {
        /* recycle oldest stable*/
        i = old_stable;
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest stable entry %"U16_F"\r\n", (u16_t)i));
        /* no queued packets should exist on stable entries */
        LWIP_ASSERT("arp_table[i].q == NULL", arp_table[i].q == NULL);
      /* 3) found recyclable pending entry without queued packets? */
      } else if (old_pending < ARP_TABLE_SIZE) {
        /* recycle oldest pending */
        i = old_pending;
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %"U16_F" (without queue)\r\n", (u16_t)i));
      /* 4) found recyclable pending entry with queued packets? */
      } else if (old_queue < ARP_TABLE_SIZE) {
        /* recycle oldest pending (queued packets are free in etharp_free_entry) */
        i = old_queue;
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: selecting oldest pending entry %"U16_F", freeing packet queue %p\r\n", (u16_t)i, (void *)(arp_table[i].q)));
        /* no empty or recyclable entries found */
      } else {
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_find_entry: no empty or recyclable entries found\r\n"));
        return (s8_t)ERR_MEM;
      }
  
      /* { empty or recyclable entry found } */
      LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
      etharp_free_entry(i);
    }
  
    LWIP_ASSERT("i < ARP_TABLE_SIZE", i < ARP_TABLE_SIZE);
    LWIP_ASSERT("arp_table[i].state == ETHARP_STATE_EMPTY",
      arp_table[i].state == ETHARP_STATE_EMPTY);
  
    /* IP address given? */
    if (ipaddr != NULL) {
      /* set IP address */
      ip_addr_copy(arp_table[i].ipaddr, *ipaddr);
      arp_table[i].netif = netif;
    }
    arp_table[i].ctime = 0;
    return (err_t)i;
  }
  
  /**
   * Send an IP packet on the network using netif->linkoutput
   * The ethernet header is filled in before sending.
   *
   * @params netif the lwIP network interface on which to send the packet
   * @params p the packet to send, p->payload pointing to the (uninitialized) ethernet header
   * @params src the source MAC address to be copied into the ethernet header
   * @params dst the destination MAC address to be copied into the ethernet header
   * @return ERR_OK if the packet was sent, any other err_t on failure
   */
  static err_t
  etharp_send_ip(struct netif *netif, struct pbuf *p, struct eth_addr *src, struct eth_addr *dst)
  {
    struct eth_hdr *ethhdr = (struct eth_hdr *)p->payload;
  
    LWIP_ASSERT("netif->hwaddr_len must be the same as ETHARP_HWADDR_LEN for etharp!",
                (netif->hwaddr_len == ETHARP_HWADDR_LEN));
    ETHADDR32_COPY((void*)&ethhdr->dest, (void*)dst);
    ETHADDR16_COPY((void*)&ethhdr->src, (void*)src);
    ethhdr->type = PP_HTONS(ETHTYPE_IP);
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_send_ip: sending packet %p\r\n", (void *)p));
    /* send the packet */
    return netif->linkoutput(netif, p);
  }
  
  /**
   * Update (or insert) a IP/MAC address pair in the ARP cache.
   *
   * If a pending entry is resolved, any queued packets will be sent
   * at this point.
   * 
   * @param netif netif related to this entry (used for NETIF_ADDRHINT)
   * @param ipaddr IP address of the inserted ARP entry.
   * @param ethaddr Ethernet address of the inserted ARP entry.
   * @param flags @see definition of ETHARP_FLAG_*
   *
   * @return
   * - ERR_OK Succesfully updated ARP cache.
   * - ERR_MEM If we could not add a new ARP entry when ETHARP_FLAG_TRY_HARD was set.
   * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
   *
   * @see pbuf_free()
   */
  static err_t
  etharp_update_arp_entry(struct netif *netif, ip_addr_t *ipaddr, struct eth_addr *ethaddr, u8_t flags)
  {
    s8_t i;
    LWIP_ASSERT("netif->hwaddr_len == ETHARP_HWADDR_LEN", netif->hwaddr_len == ETHARP_HWADDR_LEN);
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F" - %02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F"\r\n",
      ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
      ethaddr->addr[0], ethaddr->addr[1], ethaddr->addr[2],
      ethaddr->addr[3], ethaddr->addr[4], ethaddr->addr[5]));
    /* non-unicast address? */
    if (ip_addr_isany(ipaddr) ||
        ip_addr_isbroadcast(ipaddr, netif) ||
        ip_addr_ismulticast(ipaddr)) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: will not add non-unicast IP address to ARP cache\r\n"));
      return ERR_ARG;
    }
    /* find or create ARP entry */
    i = etharp_find_entry(netif, ipaddr, flags);
    /* bail out if no entry could be found */
    if (i < 0) {
      return (err_t)i;
    }
  
  #if ETHARP_SUPPORT_STATIC_ENTRIES
    if (flags & ETHARP_FLAG_STATIC_ENTRY) {
      /* record static type */
      arp_table[i].state = ETHARP_STATE_STATIC;
    } else
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
    {
      /* mark it stable */
      arp_table[i].state = ETHARP_STATE_STABLE;
    }
  
    /* record network interface */
    //arp_table[i].netif = netif;
    /* insert in SNMP ARP index tree */
    snmp_insert_arpidx_tree(netif, &arp_table[i].ipaddr);
  
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_update_arp_entry: updating stable entry %"S16_F"\r\n", (s16_t)i));
    /* update address */
    ETHADDR32_COPY((void*)&arp_table[i].ethaddr, (void*)ethaddr);
    /* reset time stamp */
    arp_table[i].ctime = 0;
    /* this is where we will send out queued packets! */
  #if ARP_QUEUEING
    while (arp_table[i].q != NULL) {
      struct pbuf *p;
      /* remember remainder of queue */
      struct etharp_q_entry *q = arp_table[i].q;
      /* pop first item off the queue */
      arp_table[i].q = q->next;
      /* get the packet pointer */
      p = q->p;
      /* now queue entry can be freed */
      memp_free(MEMP_ARP_QUEUE, q);
  #else /* ARP_QUEUEING */
    if (arp_table[i].q != NULL) {
      struct pbuf *p = arp_table[i].q;
      arp_table[i].q = NULL;
  #endif /* ARP_QUEUEING */
      /* send the queued IP packet */
      etharp_send_ip(netif, p, (struct eth_addr*)(netif->hwaddr), ethaddr);
      /* free the queued IP packet */
      pbuf_free(p);
    }
    return ERR_OK;
  }
  
  #if ETHARP_SUPPORT_STATIC_ENTRIES
  /** Add a new static entry to the ARP table. If an entry exists for the
   * specified IP address, this entry is overwritten.
   * If packets are queued for the specified IP address, they are sent out.
   *
   * @param ipaddr IP address for the new static entry
   * @param ethaddr ethernet address for the new static entry
   * @return @see return values of etharp_add_static_entry
   */
  err_t
  etharp_add_static_entry(ip_addr_t *ipaddr, struct eth_addr *ethaddr)
  {
    struct netif *netif;
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_add_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F" - %02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F":%02"X16_F"\r\n",
      ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr),
      ethaddr->addr[0], ethaddr->addr[1], ethaddr->addr[2],
      ethaddr->addr[3], ethaddr->addr[4], ethaddr->addr[5]));
  
    netif = ip_route(IPADDR_ANY, ipaddr);
    if (netif == NULL) {
      return ERR_RTE;
    }
  
    return etharp_update_arp_entry(netif, ipaddr, ethaddr, ETHARP_FLAG_TRY_HARD | ETHARP_FLAG_STATIC_ENTRY);
  }
  
  /** Remove a static entry from the ARP table previously added with a call to
   * etharp_add_static_entry.
   *
   * @param ipaddr IP address of the static entry to remove
   * @return ERR_OK: entry removed
   *         ERR_MEM: entry wasn't found
   *         ERR_ARG: entry wasn't a static entry but a dynamic one
   */
  err_t
  etharp_remove_static_entry(ip_addr_t *ipaddr)
  {
    s8_t i;
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_remove_static_entry: %"U16_F".%"U16_F".%"U16_F".%"U16_F"\r\n",
      ip4_addr1_16(ipaddr), ip4_addr2_16(ipaddr), ip4_addr3_16(ipaddr), ip4_addr4_16(ipaddr)));
  
    /* find or create ARP entry */
    i = etharp_find_entry(ipaddr, ETHARP_FLAG_FIND_ONLY);
    /* bail out if no entry could be found */
    if (i < 0) {
      return (err_t)i;
    }
  
    if (arp_table[i].state != ETHARP_STATE_STATIC) {
      /* entry wasn't a static entry, cannot remove it */
      return ERR_ARG;
    }
    /* entry found, free it */
    etharp_free_entry(i);
    return ERR_OK;
  }
  #endif /* ETHARP_SUPPORT_STATIC_ENTRIES */
  
  /**
   * Remove all ARP table entries of the specified netif.
   *
   * @param netif points to a network interface
   */
  void etharp_cleanup_netif(struct netif *netif)
  {
    u8_t i;
  
    for (i = 0; i < ARP_TABLE_SIZE; ++i) {
      u8_t state = arp_table[i].state;
      if ((state != ETHARP_STATE_EMPTY) && (arp_table[i].netif == netif)) {
        etharp_free_entry(i);
      }
    }
  }
  
  /**
   * Finds (stable) ethernet/IP address pair from ARP table
   * using interface and MAC address index.
   * @note the addresses in the ARP table are in network order!
   *
   * @param netif points to interface index
   * @param eth_addr points to the (network order) MAC address index
   * @param eth_ret points to return MAC pointer
   * @param ip_ret points to return IP pointer
   * @return table index if found, -1 otherwise
   */
  s8_t etharp_find_addr_by_mac(struct netif *netif, struct eth_addr *ethaddr,
           struct eth_addr **eth_ret, ip_addr_t **ip_ret)
  {
      s8_t i;
  
      LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",eth_ret != NULL && ip_ret != NULL);
  
      LWIP_UNUSED_ARG(netif);
  
      i = etharp_find_entry_by_mac(ethaddr);
  
      if((i >= 0) && (arp_table[i].state >= ETHARP_STATE_STABLE)) 
      {
          *eth_ret = &arp_table[i].ethaddr;
          *ip_ret  = &arp_table[i].ipaddr;
          return i;
      }
      return -1;
  }
  
  
  /**
   * Finds (stable) ethernet/IP address pair from ARP table
   * using interface and IP address index.
   * @note the addresses in the ARP table are in network order!
   *
   * @param netif points to interface index
   * @param ipaddr points to the (network order) IP address index
   * @param eth_ret points to return pointer
   * @param ip_ret points to return pointer
   * @return table index if found, -1 otherwise
   */
  s8_t
  etharp_find_addr(struct netif *netif, ip_addr_t *ipaddr,
           struct eth_addr **eth_ret, ip_addr_t **ip_ret)
  {
    s8_t i;
  
    LWIP_ASSERT("eth_ret != NULL && ip_ret != NULL",
      eth_ret != NULL && ip_ret != NULL);
  
    LWIP_UNUSED_ARG(netif);
  
    i = etharp_find_entry(netif, ipaddr, ETHARP_FLAG_FIND_ONLY);
    if((i >= 0) && (arp_table[i].state >= ETHARP_STATE_STABLE)) {
        *eth_ret = &arp_table[i].ethaddr;
        *ip_ret = &arp_table[i].ipaddr;
        return i;
    }
    return -1;
  }
  
  #if ETHARP_TRUST_IP_MAC
  /**
   * Updates the ARP table using the given IP packet.
   *
   * Uses the incoming IP packet's source address to update the
   * ARP cache for the local network. The function does not alter
   * or free the packet. This function must be called before the
   * packet p is passed to the IP layer.
   *
   * @param netif The lwIP network interface on which the IP packet pbuf arrived.
   * @param p The IP packet that arrived on netif.
   *
   * @return NULL
   *
   * @see pbuf_free()
   */
  static void
  etharp_ip_input(struct netif *netif, struct pbuf *p)
  {
    struct eth_hdr *ethhdr;
    struct ip_hdr *iphdr;
    ip_addr_t iphdr_src;
    LWIP_ERROR("netif != NULL", (netif != NULL), return;);
  
    /* Only insert an entry if the source IP address of the
       incoming IP packet comes from a host on the local network. */
    ethhdr = (struct eth_hdr *)p->payload;
    iphdr = (struct ip_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR);
  #if ETHARP_SUPPORT_VLAN
    if (ethhdr->type == PP_HTONS(ETHTYPE_VLAN)) {
      iphdr = (struct ip_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR);
    }
  #endif /* ETHARP_SUPPORT_VLAN */
  
    ip_addr_copy(iphdr_src, iphdr->src);
  
    /* source is not on the local network? */
    if (!ip_addr_netcmp(&iphdr_src, &(netif->ip_addr), &(netif->netmask))) {
      /* do nothing */
      return;
    }
  
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_ip_input: updating ETHARP table.\r\n"));
    /* update the source IP address in the cache, if present */
    /* @todo We could use ETHARP_FLAG_TRY_HARD if we think we are going to talk
     * back soon (for example, if the destination IP address is ours. */
    etharp_update_arp_entry(netif, &iphdr_src, &(ethhdr->src), ETHARP_FLAG_FIND_ONLY);
  }
  #endif /* ETHARP_TRUST_IP_MAC */
  
  /**
   * Responds to ARP requests to us. Upon ARP replies to us, add entry to cache  
   * send out queued IP packets. Updates cache with snooped address pairs.
   *
   * Should be called for incoming ARP packets. The pbuf in the argument
   * is freed by this function.
   *
   * @param netif The lwIP network interface on which the ARP packet pbuf arrived.
   * @param ethaddr Ethernet address of netif.
   * @param p The ARP packet that arrived on netif. Is freed by this function.
   *
   * @return NULL
   *
   * @see pbuf_free()
   */
  static void
  etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr, struct pbuf *p)
  {
    struct etharp_hdr *hdr;
    struct eth_hdr *ethhdr;
    /* these are aligned properly, whereas the ARP header fields might not be */
    ip_addr_t sipaddr, dipaddr;
    u8_t for_us;
  #if ARP_PROXY
    u8_t proxy;
  #endif
  #if LWIP_AUTOIP
    const u8_t * ethdst_hwaddr;
  #endif /* LWIP_AUTOIP */
  
  
  
    LWIP_ERROR("netif != NULL", (netif != NULL), return;);
  
    /* drop short ARP packets: we have to check for p->len instead of p->tot_len here
       since a struct etharp_hdr is pointed to p->payload, so it musn't be chained! */
    if (p->len < SIZEOF_ETHARP_PACKET) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
        ("etharp_arp_input: packet dropped, too short (%"S16_F"/%"S16_F")\r\n", p->tot_len,
        (s16_t)SIZEOF_ETHARP_PACKET));
      ETHARP_STATS_INC(etharp.lenerr);
      ETHARP_STATS_INC(etharp.drop);
      pbuf_free(p);
      return;
    }
  
    ethhdr = (struct eth_hdr *)p->payload;
    hdr = (struct etharp_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR);
  
  #if 0
  	if( (0==hdr->sipaddr.addrw[0]) && (0==hdr->sipaddr.addrw[1])){
  		printf("<%s>%d #####source-ip-addr zero #####\n",__func__,__LINE__);
  		pbuf_free(p);
  		return;
  	}
  #endif
  
  
    
  #if ETHARP_SUPPORT_VLAN
    if (ethhdr->type == PP_HTONS(ETHTYPE_VLAN)) {
      hdr = (struct etharp_hdr *)(((u8_t*)ethhdr) + SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR);
    }
  #endif /* ETHARP_SUPPORT_VLAN */
  
    /* RFC 826 "Packet Reception": */
    if ((hdr->hwtype != PP_HTONS(HWTYPE_ETHERNET)) ||
        (hdr->hwlen != ETHARP_HWADDR_LEN) ||
        (hdr->protolen != sizeof(ip_addr_t)) ||
        (hdr->proto != PP_HTONS(ETHTYPE_IP)))  {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
        ("etharp_arp_input: packet dropped, wrong hw type, hwlen, proto, protolen or ethernet type (%"U16_F"/%"U16_F"/%"U16_F"/%"U16_F")\r\n",
        hdr->hwtype, hdr->hwlen, hdr->proto, hdr->protolen));
      ETHARP_STATS_INC(etharp.proterr);
      ETHARP_STATS_INC(etharp.drop);
      pbuf_free(p);
  	LWIP_DEBUGF(ETHARP_DEBUG,("After-etharp_input:arp_table[0]=%d",arp_table[0].state));
      return;
    }
    ETHARP_STATS_INC(etharp.recv);
  
  #if LWIP_AUTOIP
    /* We have to check if a host already has configured our random
     * created link local address and continously check if there is
     * a host with this IP-address so we can detect collisions */
    autoip_arp_reply(netif, hdr);
  #endif /* LWIP_AUTOIP */
  
    /* 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((void*)&sipaddr, (void*)&hdr->sipaddr);
    IPADDR2_COPY((void*)&dipaddr, (void*)&hdr->dipaddr);
  
    /* this interface is not configured? */
    if (ip_addr_isany(&netif->ip_addr)) {
      for_us = 0;
    } else {
      /* ARP packet directed to us? */
      for_us = (u8_t)ip_addr_cmp(&dipaddr, &(netif->ip_addr));
  #if ARP_PROXY
      if (!for_us
  	&& hdr->opcode == PP_HTONS(ARP_REQUEST)
  	&& proxy_arp_hook != NULL
  	&& (*proxy_arp_hook)(netif, &dipaddr))
      {
  	for_us = proxy = 1;
      }
      else {
  	proxy = 0;
      }
  #endif /* ARP_PROXY */
    }
  
    /* ARP message directed to us?
        -> add IP address in ARP cache; assume requester wants to talk to us,
           can result in directly sending the queued packets for this host.
       ARP message not directed to us?
        ->  update the source IP address in the cache, if present */
    etharp_update_arp_entry(netif, &sipaddr, &(hdr->shwaddr),
                     for_us ? ETHARP_FLAG_TRY_HARD : ETHARP_FLAG_FIND_ONLY);
  
    /* now act on the message itself */
    switch (hdr->opcode) {
    /* ARP request? */
    case PP_HTONS(ARP_REQUEST):
      /* ARP request. If it asked for our address, we send out a
       * reply. In any case, we time-stamp any existing ARP entry,
       * and possiby send out an IP packet that was queued on it. */
  
      LWIP_DEBUGF (ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: incoming ARP request\r\n"));
      /* ARP request for our address? */
      if (for_us) {
  
  #if !ARP_PROXY
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: replying to ARP request for our IP address\r\n"));
  #else
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE,
                    ("etharp_arp_input: replying to ARP request %s\r\n",
                     proxy ? "as proxy" : "for our IP address"));
  #endif
        /* Re-use pbuf to send ARP reply.
           Since we are re-using an existing pbuf, we can't call etharp_raw since
           that would allocate a new pbuf. */
        hdr->opcode = htons(ARP_REPLY);
  
        IPADDR2_COPY((void*)&hdr->dipaddr, (void*)&hdr->sipaddr);
        IPADDR2_COPY((void*)&hdr->sipaddr, (void*)&netif->ip_addr);
  
        LWIP_ASSERT("netif->hwaddr_len must be the same as ETHARP_HWADDR_LEN for etharp!",
                    (netif->hwaddr_len == ETHARP_HWADDR_LEN));
  #if LWIP_AUTOIP
        /* If we are using Link-Local, all ARP packets that contain a Link-Local
         * 'sender IP address' MUST be sent using link-layer broadcast instead of
         * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
        ethdst_hwaddr = ip_addr_islinklocal(&netif->ip_addr) ? (u8_t*)(ethbroadcast.addr) : (u8_t*)hdr->shwaddr.addr;
  #endif /* LWIP_AUTOIP */
  
        ETHADDR16_COPY((void*)&hdr->dhwaddr, (void*)&hdr->shwaddr);
  #if LWIP_AUTOIP
        ETHADDR16_COPY((void*)&ethhdr->dest, (void*)ethdst_hwaddr);
  #else  /* LWIP_AUTOIP */
        ETHADDR16_COPY((void*)&ethhdr->dest, (void*)&hdr->shwaddr);
  #endif /* LWIP_AUTOIP */
        ETHADDR16_COPY((void*)&hdr->shwaddr, (void*)ethaddr);
        ETHADDR16_COPY((void*)&ethhdr->src, (void*)ethaddr);
  
        /* hwtype, hwaddr_len, proto, protolen and the type in the ethernet header
           are already correct, we tested that before */
  
        /* return ARP reply */
        netif->linkoutput(netif, p);
      /* we are not configured? */
      } else if (ip_addr_isany(&netif->ip_addr)) {
        /* { for_us == 0 and netif->ip_addr.addr == 0 } */
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: we are unconfigured, ARP request ignored.\r\n"));
      /* request was not directed to us */
      } else {
        /* { for_us == 0 and netif->ip_addr.addr != 0 } */
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: ARP request was not for us.\r\n"));
      }
      break;
    case PP_HTONS(ARP_REPLY):
      /* ARP reply. We already updated the ARP cache earlier. */
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: incoming ARP reply\r\n"));
  #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
      /* DHCP wants to know about ARP replies from any host with an
       * IP address also offered to us by the DHCP server. We do not
       * want to take a duplicate IP address on a single network.
       * @todo How should we handle redundant (fail-over) interfaces? */
      dhcp_arp_reply(netif, &sipaddr);
  #endif /* (LWIP_DHCP && DHCP_DOES_ARP_CHECK) */
      break;
    default:
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_arp_input: ARP unknown opcode type %"S16_F"\r\n", htons(hdr->opcode)));
      ETHARP_STATS_INC(etharp.err);
      break;
    }
    /* free ARP packet */
    pbuf_free(p);
  }
  
  /** Just a small helper function that sends a pbuf to an ethernet address
   * in the arp_table specified by the index 'arp_idx'.
   */
  static err_t
  etharp_output_to_arp_index(struct netif *netif, struct pbuf *q, u8_t arp_idx)
  {
    LWIP_ASSERT("arp_table[arp_idx].state >= ETHARP_STATE_STABLE",
                arp_table[arp_idx].state >= ETHARP_STATE_STABLE);
    /* if arp table entry is about to expire: re-request it,
       but only if its state is ETHARP_STATE_STABLE to prevent flooding the
       network with ARP requests if this address is used frequently. */
    if ((arp_table[arp_idx].state == ETHARP_STATE_STABLE) && 
        (arp_table[arp_idx].ctime >= ARP_AGE_REREQUEST_USED)) {
      if (etharp_request(netif, &arp_table[arp_idx].ipaddr) == ERR_OK) {
        arp_table[arp_idx].state = ETHARP_STATE_STABLE_REREQUESTING;
      }
    }
    
    return etharp_send_ip(netif, q, (struct eth_addr*)(netif->hwaddr),
      &arp_table[arp_idx].ethaddr);
  }
  
  /**
   * Resolve and fill-in Ethernet address header for outgoing IP packet.
   *
   * For IP multicast and broadcast, corresponding Ethernet addresses
   * are selected and the packet is transmitted on the link.
   *
   * For unicast addresses, the packet is submitted to etharp_query(). In
   * case the IP address is outside the local network, the IP address of
   * the gateway is used.
   *
   * @param netif The lwIP network interface which the IP packet will be sent on.
   * @param q The pbuf(s) containing the IP packet to be sent.
   * @param ipaddr The IP address of the packet destination.
   *
   * @return
   * - ERR_RTE No route to destination (no gateway to external networks),
   * or the return type of either etharp_query() or etharp_send_ip().
   */
  err_t
  etharp_output(struct netif *netif, struct pbuf *q, ip_addr_t *ipaddr)
  {
    struct eth_addr *dest;
    struct eth_addr mcastaddr;
    ip_addr_t *dst_addr = ipaddr;
  
    LWIP_ASSERT("netif != NULL", netif != NULL);
    LWIP_ASSERT("q != NULL", q != NULL);
    LWIP_ASSERT("ipaddr != NULL", ipaddr != NULL);
  
    /* make room for Ethernet header - should not fail */
    if (pbuf_header(q, sizeof(struct eth_hdr)) != 0) {
      /* bail out */
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
        ("etharp_output: could not allocate room for header.\r\n"));
      LINK_STATS_INC(link.lenerr);
      return ERR_BUF;
    }
  
  #if CONFIG_MEMP_DEBUG
      PBUF_DBG_FLAGS(q, PBUF_DBG_FLAG_ARP);
  #endif
  
    /* assume unresolved Ethernet address */
    dest = NULL;
    /* Determine on destination hardware address. Broadcasts and multicasts
     * are special, other IP addresses are looked up in the ARP table. */
  
    /* broadcast destination IP address? */
    if (ip_addr_isbroadcast(ipaddr, netif)) {
      /* broadcast on Ethernet also */
      dest = (struct eth_addr *)&ethbroadcast;
    /* multicast destination IP address? */
    } else if (ip_addr_ismulticast(ipaddr)) {
      /* Hash IP multicast address to MAC address.*/
      mcastaddr.addr[0] = LL_MULTICAST_ADDR_0;
      mcastaddr.addr[1] = LL_MULTICAST_ADDR_1;
      mcastaddr.addr[2] = LL_MULTICAST_ADDR_2;
      mcastaddr.addr[3] = ip4_addr2(ipaddr) & 0x7f;
      mcastaddr.addr[4] = ip4_addr3(ipaddr);
      mcastaddr.addr[5] = ip4_addr4(ipaddr);
      /* destination Ethernet address is multicast */
      dest = &mcastaddr;
    /* unicast destination IP address? */
    } else {
      s8_t i;
      /* outside local network? if so, this can neither be a global broadcast nor
         a subnet broadcast. */
      if (!ip_addr_netcmp(ipaddr, &(netif->ip_addr), &(netif->netmask)) &&
          !ip_addr_islinklocal(ipaddr)) {
  #if LWIP_AUTOIP
        struct ip_hdr *iphdr = (struct ip_hdr*)((u8_t*)q->payload +
          sizeof(struct eth_hdr));
        /* According to RFC 3297, chapter 2.6.2 (Forwarding Rules), a packet with
           a link-local source address must always be "directly to its destination
           on the same physical link. The host MUST NOT send the packet to any
           router for forwarding". */
        if (!ip_addr_islinklocal(&iphdr->src))
  #endif /* LWIP_AUTOIP */
        {
          /* interface has default gateway? */
          if (!ip_addr_isany(&netif->gw)) {
            /* send to hardware address of default gateway IP address */
            dst_addr = &(netif->gw);
          /* no default gateway available */
          } else {
            /* no route to destination error (default gateway missing) */
            return ERR_RTE;
          }
        }
      }
  #if LWIP_NETIF_HWADDRHINT
      if (netif->addr_hint != NULL) {
        /* per-pcb cached entry was given */
        u8_t etharp_cached_entry = *(netif->addr_hint);
        if (etharp_cached_entry < ARP_TABLE_SIZE) {
  #endif /* LWIP_NETIF_HWADDRHINT */
          if ((arp_table[etharp_cached_entry].state >= ETHARP_STATE_STABLE) &&
              (ip_addr_cmp(dst_addr, &arp_table[etharp_cached_entry].ipaddr))) {
            /* the per-pcb-cached entry is stable and the right one! */
            ETHARP_STATS_INC(etharp.cachehit);
            return etharp_output_to_arp_index(netif, q, etharp_cached_entry);
          }
  #if LWIP_NETIF_HWADDRHINT
        }
      }
  #endif /* LWIP_NETIF_HWADDRHINT */
  
      /* find stable entry: do this here since this is a critical path for
         throughput and etharp_find_entry() is kind of slow */
      for (i = 0; i < ARP_TABLE_SIZE; i++) {
        if ((arp_table[i].state >= ETHARP_STATE_STABLE) &&
            (ip_addr_cmp(dst_addr, &arp_table[i].ipaddr))) {
          /* found an existing, stable entry */
          ETHARP_SET_HINT(netif, i);
          return etharp_output_to_arp_index(netif, q, i);
        }
      }
      /* no stable entry found, use the (slower) query function:
         queue on destination Ethernet address belonging to ipaddr */
      return etharp_query(netif, dst_addr, q);
    }
  
    /* continuation for multicast/broadcast destinations */
    /* obtain source Ethernet address of the given interface */
    /* send packet directly on the link */
    return etharp_send_ip(netif, q, (struct eth_addr*)(netif->hwaddr), dest);
  }
  
  /**
   * Send an ARP request for the given IP address and/or queue a packet.
   *
   * If the IP address was not yet in the cache, a pending ARP cache entry
   * is added and an ARP request is sent for the given address. The packet
   * is queued on this entry.
   *
   * If the IP address was already pending in the cache, a new ARP request
   * is sent for the given address. The packet is queued on this entry.
   *
   * If the IP address was already stable in the cache, and a packet is
   * given, it is directly sent and no ARP request is sent out. 
   * 
   * If the IP address was already stable in the cache, and no packet is
   * given, an ARP request is sent out.
   * 
   * @param netif The lwIP network interface on which ipaddr
   * must be queried for.
   * @param ipaddr The IP address to be resolved.
   * @param q If non-NULL, a pbuf that must be delivered to the IP address.
   * q is not freed by this function.
   *
   * @note q must only be ONE packet, not a packet queue!
   *
   * @return
   * - ERR_BUF Could not make room for Ethernet header.
   * - ERR_MEM Hardware address unknown, and no more ARP entries available
   *   to query for address or queue the packet.
   * - ERR_MEM Could not queue packet due to memory shortage.
   * - ERR_RTE No route to destination (no gateway to external networks).
   * - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
   *
   */
  err_t
  etharp_query(struct netif *netif, ip_addr_t *ipaddr, struct pbuf *q)
  {
    struct eth_addr * srcaddr = (struct eth_addr *)netif->hwaddr;
    err_t result = ERR_MEM;
    s8_t i; /* ARP entry index */
  
    /* non-unicast address? */
    if (ip_addr_isbroadcast(ipaddr, netif) ||
        ip_addr_ismulticast(ipaddr) ||
        ip_addr_isany(ipaddr)) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: will not add non-unicast IP address to ARP cache\r\n"));
      return ERR_ARG;
    }
  
    /* find entry in ARP cache, ask to create entry if queueing packet */
    i = etharp_find_entry(netif, ipaddr, ETHARP_FLAG_TRY_HARD);
  
    /* could not find or create entry? */
    if (i < 0) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not create ARP entry\r\n"));
      if (q) {
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: packet dropped\r\n"));
        ETHARP_STATS_INC(etharp.memerr);
      }
      return (err_t)i;
    }
  
    /* mark a fresh entry as pending (we just sent a request) */
    if (arp_table[i].state == ETHARP_STATE_EMPTY) {
      arp_table[i].state = ETHARP_STATE_PENDING;
    }
  
    /* { i is either a STABLE or (new or existing) PENDING entry } */
    LWIP_ASSERT("arp_table[i].state == PENDING or STABLE",
    ((arp_table[i].state == ETHARP_STATE_PENDING) ||
     (arp_table[i].state >= ETHARP_STATE_STABLE)));
  
    /* do we have a pending entry? or an implicit query request? */
    if ((arp_table[i].state == ETHARP_STATE_PENDING) || (q == NULL)) {
      /* try to resolve it; send out ARP request */
      result = etharp_request(netif, ipaddr);
      if (result != ERR_OK) {
        /* ARP request couldn't be sent */
        /* We don't re-send arp request in etharp_tmr, but we still queue packets,
           since this failure could be temporary, and the next packet calling
           etharp_query again could lead to sending the queued packets. */
      }
      if (q == NULL) {
        return result;
      }
    }
  
    /* packet given? */
    LWIP_ASSERT("q != NULL", q != NULL);
    /* stable entry? */
    if (arp_table[i].state >= ETHARP_STATE_STABLE) {
      /* we have a valid IP->Ethernet address mapping */
      ETHARP_SET_HINT(netif, i);
      /* send the packet */
      result = etharp_send_ip(netif, q, srcaddr, &(arp_table[i].ethaddr));
    /* pending entry? (either just created or already pending */
    } else if (arp_table[i].state == ETHARP_STATE_PENDING) {
      /* entry is still pending, queue the given packet 'q' */
      struct pbuf *p;
      int copy_needed = 0;
      /* IF q includes a PBUF_REF, PBUF_POOL or PBUF_RAM, we have no choice but
       * to copy the whole queue into a new PBUF_RAM (see bug #11400) 
       * PBUF_ROMs can be left as they are, since ROM must not get changed. */
      p = q;
      while (p) {
        LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
        if(p->type != PBUF_ROM) {
          copy_needed = 1;
          break;
        }
        p = p->next;
      }
      if(copy_needed) {
        /* copy the whole packet into new pbufs */
        p = pbuf_alloc(PBUF_RAW, p->tot_len, PBUF_RAM);
        if(p != NULL) {
          if (pbuf_copy(p, q) != ERR_OK) {
            pbuf_free(p);
            p = NULL;
          }
        }
      } else {
        /* referencing the old pbuf is enough */
        p = q;
        pbuf_ref(p);
      }
      /* packet could be taken over? */
      if (p != NULL) {
        /* queue packet ... */
  #if ARP_QUEUEING
        struct etharp_q_entry *new_entry;
        /* allocate a new arp queue entry */
        new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
        if (new_entry != NULL) {
          new_entry->next = 0;
          new_entry->p = p;
          if(arp_table[i].q != NULL) {
            /* queue was already existent, append the new entry to the end */
            struct etharp_q_entry *r;
            r = arp_table[i].q;
            while (r->next != NULL) {
              r = r->next;
            }
            r->next = new_entry;
          } else {
            /* queue did not exist, first item in queue */
            
            arp_table[i].q = new_entry;
          }
          LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\r\n", (void *)q, (s16_t)i));
          result = ERR_OK;
        } else {
          /* the pool MEMP_ARP_QUEUE is empty */
          pbuf_free(p);
          LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not queue a copy of PBUF_REF packet %p (out of memory)\r\n", (void *)q));
          result = ERR_MEM;
        }
  #else /* ARP_QUEUEING */
        /* always queue one packet per ARP request only, freeing a previously queued packet */
        if (arp_table[i].q != NULL) {
          LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: dropped previously queued packet %p for ARP entry %"S16_F"\r\n", (void *)q, (s16_t)i));
          pbuf_free(arp_table[i].q);
        }
        arp_table[i].q = p;
        result = ERR_OK;
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\r\n", (void *)q, (s16_t)i));
  #endif /* ARP_QUEUEING */
      } else {
        ETHARP_STATS_INC(etharp.memerr);
        LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: could not queue a copy of PBUF_REF packet %p (out of memory)\r\n", (void *)q));
        result = ERR_MEM;
      }
    }
    return result;
  }
  
  /**
   * Send a raw ARP packet (opcode and all addresses can be modified)
   *
   * @param netif the lwip network interface on which to send the ARP packet
   * @param ethsrc_addr the source MAC address for the ethernet header
   * @param ethdst_addr the destination MAC address for the ethernet header
   * @param hwsrc_addr the source MAC address for the ARP protocol header
   * @param ipsrc_addr the source IP address for the ARP protocol header
   * @param hwdst_addr the destination MAC address for the ARP protocol header
   * @param ipdst_addr the destination IP address for the ARP protocol header
   * @param opcode the type of the ARP packet
   * @return ERR_OK if the ARP packet has been sent
   *         ERR_MEM if the ARP packet couldn't be allocated
   *         any other err_t on failure
   */
  #if !LWIP_AUTOIP
  static
  #endif /* LWIP_AUTOIP */
  err_t
  etharp_raw(struct netif *netif, const struct eth_addr *ethsrc_addr,
             const struct eth_addr *ethdst_addr,
             const struct eth_addr *hwsrc_addr, const ip_addr_t *ipsrc_addr,
             const struct eth_addr *hwdst_addr, const ip_addr_t *ipdst_addr,
             const u16_t opcode)
  {
    struct pbuf *p;
    err_t result = ERR_OK;
    struct eth_hdr *ethhdr;
    struct etharp_hdr *hdr;
  #if LWIP_AUTOIP
    const u8_t * ethdst_hwaddr;
  #endif /* LWIP_AUTOIP */
  
    LWIP_ASSERT("netif != NULL", netif != NULL);
  
    /* allocate a pbuf for the outgoing ARP request packet */
    p = pbuf_alloc(PBUF_RAW, SIZEOF_ETHARP_PACKET, PBUF_RAM);
    /* could allocate a pbuf for an ARP request? */
    if (p == NULL) {
      LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
        ("etharp_raw: could not allocate pbuf for ARP request.\r\n"));
      ETHARP_STATS_INC(etharp.memerr);
      return ERR_MEM;
    }
    LWIP_ASSERT("check that first pbuf can hold struct etharp_hdr",
                (p->len >= SIZEOF_ETHARP_PACKET));
  
    ethhdr = (struct eth_hdr *)p->payload;
    hdr = (struct etharp_hdr *)((u8_t*)ethhdr + SIZEOF_ETH_HDR);
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_raw: sending raw ARP packet.\r\n"));
    hdr->opcode = htons(opcode);
  
    LWIP_ASSERT("netif->hwaddr_len must be the same as ETHARP_HWADDR_LEN for etharp!",
                (netif->hwaddr_len == ETHARP_HWADDR_LEN));
  #if LWIP_AUTOIP
    /* If we are using Link-Local, all ARP packets that contain a Link-Local
     * 'sender IP address' MUST be sent using link-layer broadcast instead of
     * link-layer unicast. (See RFC3927 Section 2.5, last paragraph) */
    ethdst_hwaddr = ip_addr_islinklocal(ipsrc_addr) ? (u8_t*)(ethbroadcast.addr) : (u8_t*)ethdst_addr->addr;
  #endif /* LWIP_AUTOIP */
    /* Write the ARP MAC-Addresses */
    ETHADDR16_COPY((void*)&hdr->shwaddr, (void*)hwsrc_addr);
    ETHADDR16_COPY((void*)&hdr->dhwaddr, (void*)hwdst_addr);
    /* Write the Ethernet MAC-Addresses */
  #if LWIP_AUTOIP
    ETHADDR16_COPY((void*)&ethhdr->dest, (void*)ethdst_hwaddr);
  #else  /* LWIP_AUTOIP */
    ETHADDR16_COPY((void*)&ethhdr->dest, (void*)ethdst_addr);
  #endif /* LWIP_AUTOIP */
    ETHADDR16_COPY((void*)&ethhdr->src, (void*)ethsrc_addr);
    /* Copy struct ip_addr2 to aligned ip_addr, to support compilers without
     * structure packing. */ 
    IPADDR2_COPY((void*)&hdr->sipaddr, (void*)ipsrc_addr);
    IPADDR2_COPY((void*)&hdr->dipaddr, (void*)ipdst_addr);
  
    hdr->hwtype = PP_HTONS(HWTYPE_ETHERNET);
    hdr->proto = PP_HTONS(ETHTYPE_IP);
    /* set hwlen and protolen */
    hdr->hwlen = ETHARP_HWADDR_LEN;
    hdr->protolen = sizeof(ip_addr_t);
  
    ethhdr->type = PP_HTONS(ETHTYPE_ARP);
    /* send ARP query */
    result = netif->linkoutput(netif, p);
    ETHARP_STATS_INC(etharp.xmit);
    /* free ARP query packet */
    pbuf_free(p);
    p = NULL;
    /* could not allocate pbuf for ARP request */
  
    return result;
  }
  
  s8_t etharp_unicast (u8 *dst_mac, ip_addr_t *ipaddr)
  {    
      struct netif *netif = netif_list;
      
      //ip_addr_t ipaddr;    
      //if (etharp_getip ((struct eth_addr *)dst_mac, &ipaddr))
      //    return -1;
      
      while (netif != NULL) {
        /* only act on et0 interface */
        if (!STRCMP(netif->name, IF0_NAME)) {      
          LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_request: sending ARP *unicast* request.\r\n"));
          return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, (struct eth_addr *)dst_mac,
                              (struct eth_addr *)netif->hwaddr, &netif->ip_addr, &ethzero,
                              ipaddr, ARP_REQUEST);
        }
        /* proceed to next network interface */
        netif = netif->next;
      }
  
      return -1;    
  }
  
  /**
   * Send an ARP request packet asking for ipaddr.
   *
   * @param netif the lwip network interface on which to send the request
   * @param ipaddr the IP address for which to ask
   * @return ERR_OK if the request has been sent
   *         ERR_MEM if the ARP packet couldn't be allocated
   *         any other err_t on failure
   */
  err_t
  etharp_request(struct netif *netif, ip_addr_t *ipaddr)
  {
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_request: sending ARP request.\r\n"));
    return etharp_raw(netif, (struct eth_addr *)netif->hwaddr, &ethbroadcast,
                      (struct eth_addr *)netif->hwaddr, &netif->ip_addr, &ethzero,
                      ipaddr, ARP_REQUEST);
  }
  #endif /* LWIP_ARP */
  
  /**
   * Process received ethernet frames. Using this function instead of directly
   * calling ip_input and passing ARP frames through etharp in ethernetif_input,
   * the ARP cache is protected from concurrent access.
   *
   * @param p the recevied packet, p->payload pointing to the ethernet header
   * @param netif the network interface on which the packet was received
   */
  err_t
  ethernet_input(struct pbuf *p, struct netif *netif)
  {
    struct eth_hdr* ethhdr;
    u16_t type;
  #if LWIP_ARP || ETHARP_SUPPORT_VLAN
    s16_t ip_hdr_offset = SIZEOF_ETH_HDR;
  #endif /* LWIP_ARP || ETHARP_SUPPORT_VLAN */
  
  #if CONFIG_MEMP_DEBUG
    PBUF_DBG_FLAGS(p, PBUF_DBG_FLAG_ARP);
  #endif
  
    if (p->len <= SIZEOF_ETH_HDR) {
      /* a packet with only an ethernet header (or less) is not valid for us */
      ETHARP_STATS_INC(etharp.proterr);
      ETHARP_STATS_INC(etharp.drop);
      goto free_and_return;
    }
  
    /* points to packet payload, which starts with an Ethernet header */
    ethhdr = (struct eth_hdr *)p->payload;
    LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE,
      ("ethernet_input: dest:%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F", src:%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F", type:%"X16_F"\r\n",
       (unsigned)ethhdr->dest.addr[0], (unsigned)ethhdr->dest.addr[1], (unsigned)ethhdr->dest.addr[2],
       (unsigned)ethhdr->dest.addr[3], (unsigned)ethhdr->dest.addr[4], (unsigned)ethhdr->dest.addr[5],
       (unsigned)ethhdr->src.addr[0], (unsigned)ethhdr->src.addr[1], (unsigned)ethhdr->src.addr[2],
       (unsigned)ethhdr->src.addr[3], (unsigned)ethhdr->src.addr[4], (unsigned)ethhdr->src.addr[5],
       (unsigned)htons(ethhdr->type)));
  
    type = ethhdr->type;
  #if ETHARP_SUPPORT_VLAN
    if (type == PP_HTONS(ETHTYPE_VLAN)) {
      struct eth_vlan_hdr *vlan = (struct eth_vlan_hdr*)(((char*)ethhdr) + SIZEOF_ETH_HDR);
      if (p->len <= SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR) {
        /* a packet with only an ethernet/vlan header (or less) is not valid for us */
        ETHARP_STATS_INC(etharp.proterr);
        ETHARP_STATS_INC(etharp.drop);
        goto free_and_return;
      }
  #if defined(ETHARP_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK_FN) /* if not, allow all VLANs */
  #ifdef ETHARP_VLAN_CHECK_FN
      if (!ETHARP_VLAN_CHECK_FN(ethhdr, vlan)) {
  #elif defined(ETHARP_VLAN_CHECK)
      if (VLAN_ID(vlan) != ETHARP_VLAN_CHECK) {
  #endif
        /* silently ignore this packet: not for our VLAN */
        pbuf_free(p);
        return ERR_OK;
      }
  #endif /* defined(ETHARP_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK_FN) */
      type = vlan->tpid;
      ip_hdr_offset = SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR;
    }
  #endif /* ETHARP_SUPPORT_VLAN */
  
  #if LWIP_ARP_FILTER_NETIF
    netif = LWIP_ARP_FILTER_NETIF_FN(p, netif, htons(type));
  #endif /* LWIP_ARP_FILTER_NETIF*/
  
    if (ethhdr->dest.addr[0] & 1) {
      /* this might be a multicast or broadcast packet */
      if (ethhdr->dest.addr[0] == LL_MULTICAST_ADDR_0) {
        if ((ethhdr->dest.addr[1] == LL_MULTICAST_ADDR_1) &&
            (ethhdr->dest.addr[2] == LL_MULTICAST_ADDR_2)) {
          /* mark the pbuf as link-layer multicast */
          p->flags |= PBUF_FLAG_LLMCAST;
        }
      } else if (eth_addr_cmp(&ethhdr->dest, &ethbroadcast)) {
        /* mark the pbuf as link-layer broadcast */
        p->flags |= PBUF_FLAG_LLBCAST;
      }
    }
  
    switch (type) {
  #if LWIP_ARP
      /* IP packet? */
      case PP_HTONS(ETHTYPE_IP):
        if (!(netif->flags & NETIF_FLAG_ETHARP)) {
          goto free_and_return;
        }
  #if ETHARP_TRUST_IP_MAC
        /* update ARP table */
        etharp_ip_input(netif, p);
  #endif /* ETHARP_TRUST_IP_MAC */
        /* skip Ethernet header */
        if(pbuf_header(p, -ip_hdr_offset)) {
          LWIP_ASSERT("Can't move over header in packet", 0);
          goto free_and_return;
        } else {
          /* pass to IP layer */
          ip_input(p, netif);
        }
        break;
        
      case PP_HTONS(ETHTYPE_ARP):
        if (!(netif->flags & NETIF_FLAG_ETHARP)) {
          goto free_and_return;
        }
        /* pass p to ARP module */
        etharp_arp_input(netif, (struct eth_addr*)(netif->hwaddr), p);
        break;
  #endif /* LWIP_ARP */
  #if PPPOE_SUPPORT
      case PP_HTONS(ETHTYPE_PPPOEDISC): /* PPP Over Ethernet Discovery Stage */
        pppoe_disc_input(netif, p);
        break;
  
      case PP_HTONS(ETHTYPE_PPPOE): /* PPP Over Ethernet Session Stage */
        pppoe_data_input(netif, p);
        break;
  #endif /* PPPOE_SUPPORT */
  
  #if LWIP_IPV6
      case PP_HTONS(ETHTYPE_IPV6): /* IPv6 */
        /* skip Ethernet header */
        if(pbuf_header(p, -(s16_t)SIZEOF_ETH_HDR)) {
          LWIP_ASSERT("Can't move over header in packet", 0);
          goto free_and_return;
        } else {
          /* pass to IPv6 layer */
          ip6_input(p, netif);
        }
        break;
  #endif /* LWIP_IPV6 */
  
      default:
        ETHARP_STATS_INC(etharp.proterr);
        ETHARP_STATS_INC(etharp.drop);
        goto free_and_return;
    }
  
    /* This means the pbuf is freed or consumed,
       so the caller doesn't have to free it again */
    return ERR_OK;
  
  free_and_return:
    pbuf_free(p);
    return ERR_OK;
  }
    
  void etharp_show_all_entry()
  {
      u8 j;  
  
      for (j = 0; j < ARP_TABLE_SIZE; ++j) 
      {
          if ((arp_table[j].state != ETHARP_STATE_PENDING) && (arp_table[j].state != ETHARP_STATE_EMPTY))
          {
              LOG_PRINTF("%d.%d.%d.%d - %02X:%02X:%02X:%02X:%02X:%02X\n\r",
                         ip4_addr1_16(&arp_table[j].ipaddr), ip4_addr2_16(&arp_table[j].ipaddr), ip4_addr3_16(&arp_table[j].ipaddr), ip4_addr4_16(&arp_table[j].ipaddr),
                         arp_table[j].ethaddr.addr[0], arp_table[j].ethaddr.addr[1], arp_table[j].ethaddr.addr[2], arp_table[j].ethaddr.addr[3], arp_table[j].ethaddr.addr[4], arp_table[j].ethaddr.addr[5]);
          }
      }
      
  }
   
  #endif /* LWIP_ARP || LWIP_ETHERNET */
  