arp_cache.c

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/**
 * @file arp_cache.c
 * @brief ARP cache management
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2024 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneTCP Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @section Description
 *
 * Address Resolution Protocol is used to determine the hardware address of
 * a specific host when only its IPv4 address is known. Refer to RFC 826
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.4.4
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL ARP_TRACE_LEVEL
 
//Dependencies
#include "core/net.h"
#include "ipv4/arp_cache.h"
#include "ipv4/ipv4_misc.h"
#include "debug.h"
 
//Check TCP/IP stack configuration
#if (IPV4_SUPPORT == ENABLED && ETH_SUPPORT == ENABLED)
 
 
/**
 * @brief Update ARP cache entry state
 * @param[in] entry Pointer to a ARP cache entry
 * @param[in] newState New state to switch to
 **/
 
void arpChangeState(ArpCacheEntry *entry, ArpState newState)
{
#if defined(ARP_CHANGE_STATE_HOOK)
   ARP_CHANGE_STATE_HOOK(entry, newState);
#endif
 
   //Save current time
   entry->timestamp = osGetSystemTime();
   //Switch to the new state
   entry->state = newState;
}
 
 
/**
 * @brief Create a new entry in the ARP cache
 * @param[in] interface Underlying network interface
 * @return Pointer to the newly created entry
 **/
 
ArpCacheEntry *arpCreateEntry(NetInterface *interface)
{
   uint_t i;
   systime_t time;
   ArpCacheEntry *entry;
   ArpCacheEntry *oldestEntry;
 
   //Get current time
   time = osGetSystemTime();
 
   //Keep track of the oldest entry
   oldestEntry = NULL;
 
   //Loop through ARP cache entries
   for(i = 0; i < ARP_CACHE_SIZE; i++)
   {
      //Point to the current entry
      entry = &interface->arpCache[i];
 
      //Check the state of the ARP entry
      if(entry->state == ARP_STATE_NONE)
      {
         //Initialize ARP entry
         osMemset(entry, 0, sizeof(ArpCacheEntry));
 
         //Return a pointer to the ARP entry
         return entry;
      }
      else if(entry->state == ARP_STATE_PERMANENT)
      {
         //Static ARP entries are never updated
      }
      else
      {
         //Keep track of the oldest entry in the table
         if(oldestEntry == NULL)
         {
            oldestEntry = entry;
         }
         else if(entry->state == ARP_STATE_STALE &&
            oldestEntry->state != ARP_STATE_STALE)
         {
            oldestEntry = entry;
         }
         else if(entry->state != ARP_STATE_STALE &&
            oldestEntry->state == ARP_STATE_STALE)
         {
         }
         else if((time - entry->timestamp) > (time - oldestEntry->timestamp))
         {
            oldestEntry = entry;
         }
         else
         {
         }
      }
   }
 
   //Any entry available in the ARP cache?
   if(oldestEntry != NULL)
   {
      //Drop any pending packets
      arpFlushQueuedPackets(interface, oldestEntry);
      //The oldest entry is removed whenever the table runs out of space
      arpChangeState(oldestEntry, ARP_STATE_NONE);
      //Initialize ARP entry
      osMemset(oldestEntry, 0, sizeof(ArpCacheEntry));
   }
 
   //Return a pointer to the ARP entry
   return oldestEntry;
}
 
 
/**
 * @brief Search the ARP cache for a given IPv4 address
 * @param[in] interface Underlying network interface
 * @param[in] ipAddr IPv4 address
 * @return A pointer to the matching ARP entry is returned. NULL is returned
 *   if the specified IPv4 address could not be found in ARP cache
 **/
 
ArpCacheEntry *arpFindEntry(NetInterface *interface, Ipv4Addr ipAddr)
{
   uint_t i;
   ArpCacheEntry *entry;
 
   //Loop through ARP cache entries
   for(i = 0; i < ARP_CACHE_SIZE; i++)
   {
      //Point to the current entry
      entry = &interface->arpCache[i];
 
      //Check whether the entry is currently in use
      if(entry->state != ARP_STATE_NONE)
      {
         //Current entry matches the specified address?
         if(entry->ipAddr == ipAddr)
         {
            return entry;
         }
      }
   }
 
   //No matching entry in ARP cache
   return NULL;
}
 
 
/**
 * @brief Flush ARP cache
 * @param[in] interface Underlying network interface
 **/
 
void arpFlushCache(NetInterface *interface)
{
   uint_t i;
   ArpCacheEntry *entry;
 
   //Loop through ARP cache entries
   for(i = 0; i < ARP_CACHE_SIZE; i++)
   {
      //Point to the current entry
      entry = &interface->arpCache[i];
 
      //Check the state of the ARP entry
      if(entry->state == ARP_STATE_PERMANENT)
      {
         //Static ARP entries are never updated
      }
      else
      {
         //Drop packets that are waiting for address resolution
         arpFlushQueuedPackets(interface, entry);
 
         //Delete ARP entry
         arpChangeState(entry, ARP_STATE_NONE);
      }
   }
}
 
 
/**
 * @brief Send packets that are waiting for address resolution
 * @param[in] interface Underlying network interface
 * @param[in] entry Pointer to a ARP cache entry
 **/
 
void arpSendQueuedPackets(NetInterface *interface, ArpCacheEntry *entry)
{
   uint_t i;
   size_t length;
   ArpQueueItem *item;
 
   //Check the state of the ARP entry
   if(entry->state == ARP_STATE_INCOMPLETE)
   {
      //Loop through the queued packets
      for(i = 0; i < entry->queueSize; i++)
      {
         //Point to the current queue item
         item = &entry->queue[i];
 
         //Retrieve the length of the IPv4 packet
         length = netBufferGetLength(item->buffer) - item->offset;
         //Update IP statistics
         ipv4UpdateOutStats(interface, entry->ipAddr, length);
 
         //Send the IPv4 packet
         ethSendFrame(interface, &entry->macAddr, ETH_TYPE_IPV4, item->buffer,
            item->offset, &item->ancillary);
 
         //Release memory buffer
         netBufferFree(item->buffer);
      }
   }
 
   //The queue is now empty
   entry->queueSize = 0;
}
 
 
/**
 * @brief Flush packet queue
 * @param[in] interface Underlying network interface
 * @param[in] entry Pointer to a ARP cache entry
 **/
 
void arpFlushQueuedPackets(NetInterface *interface, ArpCacheEntry *entry)
{
   uint_t i;
 
   //Check the state of the ARP entry
   if(entry->state == ARP_STATE_INCOMPLETE)
   {
      //Drop packets that are waiting for address resolution
      for(i = 0; i < entry->queueSize; i++)
      {
         //Release memory buffer
         netBufferFree(entry->queue[i].buffer);
      }
   }
 
   //The queue is now empty
   entry->queueSize = 0;
}
 
#endif