ipv6_pmtu.c

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/**
 * @file ipv6_pmtu.c
 * @brief Path MTU Discovery for IPv6
 *
 * @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.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.4.0
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL IPV6_TRACE_LEVEL
 
//Dependencies
#include "core/net.h"
#include "core/ip.h"
#include "ipv6/ipv6.h"
#include "ipv6/ipv6_pmtu.h"
#include "ipv6/ndp.h"
#include "ipv6/ndp_cache.h"
#include "debug.h"
 
//Check TCP/IP stack configuration
#if (IPV6_SUPPORT == ENABLED && IPV6_PMTU_SUPPORT == ENABLED)
 
 
/**
 * @brief Retrieve the PMTU for the specified path
 * @param[in] interface Underlying network interface
 * @param[in] destAddr Destination IPv6 address
 * @return PMTU value
 **/
 
size_t ipv6GetPathMtu(NetInterface *interface, const Ipv6Addr *destAddr)
{
   size_t pathMtu;
 
#if (NDP_SUPPORT == ENABLED)
   NdpDestCacheEntry *entry;
 
   //Search the Destination Cache for the specified IPv6 address
   entry = ndpFindDestCacheEntry(interface, destAddr);
 
   //Check whether a matching entry has been found in the Destination Cache
   if(entry != NULL)
   {
      //Use the existing PMTU estimate
      pathMtu = entry->pathMtu;
   }
   else
   {
      //If no entry exists in the Destination Cache, the PMTU value for
      //the path is assumed to be the MTU of the first-hop link
      pathMtu = interface->ipv6Context.linkMtu;
   }
#else
   //The PMTU value for the path is assumed to be the MTU of the first-hop link
   pathMtu = interface->ipv6Context.linkMtu;
#endif
 
   //Return the PMTU value
   return pathMtu;
}
 
 
/**
 * @brief Update the PMTU for the specified path
 * @param[in] interface Underlying network interface
 * @param[in] destAddr Destination IPv6 address
 * @param[in] tentativePathMtu Tentative PMTU value
 **/
 
void ipv6UpdatePathMtu(NetInterface *interface,
   const Ipv6Addr *destAddr, size_t tentativePathMtu)
{
#if (NDP_SUPPORT == ENABLED)
   NdpDestCacheEntry *entry;
 
   //The destination address from the original packet is used to determine
   //which path the message applies to
   entry = ndpFindDestCacheEntry(interface, destAddr);
 
   //Check whether a matching entry has been found in the Destination Cache
   if(entry != NULL)
   {
      //Compare the tentative PMTU to the existing PMTU
      if(tentativePathMtu < entry->pathMtu)
      {
         //If the tentative PMTU is less than the existing PMTU estimate,
         //the tentative PMTU replaces the existing PMTU
         entry->pathMtu = tentativePathMtu;
      }
   }
#endif
}
 
#endif