ipv6_pmtu.c

00001 /**
00002  * @file ipv6_pmtu.c
00003  * @brief Path MTU Discovery for IPv6
00004  *
00005  * @section License
00006  *
00007  * Copyright (C) 2010-2017 Oryx Embedded SARL. All rights reserved.
00008  *
00009  * This file is part of CycloneTCP Open.
00010  *
00011  * This program is free software; you can redistribute it and/or
00012  * modify it under the terms of the GNU General Public License
00013  * as published by the Free Software Foundation; either version 2
00014  * of the License, or (at your option) any later version.
00015  *
00016  * This program is distributed in the hope that it will be useful,
00017  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00018  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00019  * GNU General Public License for more details.
00020  *
00021  * You should have received a copy of the GNU General Public License
00022  * along with this program; if not, write to the Free Software Foundation,
00023  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
00024  *
00025  * @author Oryx Embedded SARL (www.oryx-embedded.com)
00026  * @version 1.7.6
00027  **/
00028 
00029 //Switch to the appropriate trace level
00030 #define TRACE_LEVEL IPV6_TRACE_LEVEL
00031 
00032 //Dependencies
00033 #include "core/net.h"
00034 #include "core/ip.h"
00035 #include "ipv6/ipv6.h"
00036 #include "ipv6/ipv6_pmtu.h"
00037 #include "ipv6/ndp.h"
00038 #include "ipv6/ndp_cache.h"
00039 #include "debug.h"
00040 
00041 //Check TCP/IP stack configuration
00042 #if (IPV6_SUPPORT == ENABLED && IPV6_PMTU_SUPPORT == ENABLED)
00043 
00044 
00045 /**
00046  * @brief Retrieve the PMTU for the specified path
00047  * @param[in] interface Underlying network interface
00048  * @param[in] destAddr Destination IPv6 address
00049  * @return PMTU value
00050  **/
00051 
00052 size_t ipv6GetPathMtu(NetInterface *interface, const Ipv6Addr *destAddr)
00053 {
00054    size_t pathMtu;
00055 
00056 #if (NDP_SUPPORT == ENABLED)
00057    NdpDestCacheEntry *entry;
00058 
00059    //Search the Destination Cache for the specified IPv6 address
00060    entry = ndpFindDestCacheEntry(interface, destAddr);
00061 
00062    //Check whether a matching entry has been found in the Destination Cache
00063    if(entry != NULL)
00064    {
00065       //Use the existing PMTU estimate
00066       pathMtu = entry->pathMtu;
00067    }
00068    else
00069    {
00070       //If no entry exists in the Destination Cache, the PMTU value for
00071       //the path is assumed to be the MTU of the first-hop link
00072       pathMtu = interface->ipv6Context.linkMtu;
00073    }
00074 #else
00075    //The PMTU value for the path is assumed to be the MTU of the first-hop link
00076    pathMtu = interface->ipv6Context.linkMtu;
00077 #endif
00078 
00079    //Return the PMTU value
00080    return pathMtu;
00081 }
00082 
00083 
00084 /**
00085  * @brief Update the PMTU for the specified path
00086  * @param[in] interface Underlying network interface
00087  * @param[in] destAddr Destination IPv6 address
00088  * @param[in] tentativePathMtu Tentative PMTU value
00089  **/
00090 
00091 void ipv6UpdatePathMtu(NetInterface *interface,
00092    const Ipv6Addr *destAddr, size_t tentativePathMtu)
00093 {
00094 #if (NDP_SUPPORT == ENABLED)
00095    NdpDestCacheEntry *entry;
00096 
00097    //The destination address from the original packet is used to determine
00098    //which path the message applies to
00099    entry = ndpFindDestCacheEntry(interface, destAddr);
00100 
00101    //Check whether a matching entry has been found in the Destination Cache
00102    if(entry != NULL)
00103    {
00104       //Compare the tentative PMTU to the existing PMTU
00105       if(tentativePathMtu < entry->pathMtu)
00106       {
00107          //If the tentative PMTU is less than the existing PMTU estimate,
00108          //the tentative PMTU replaces the existing PMTU
00109          entry->pathMtu = tentativePathMtu;
00110       }
00111    }
00112 #endif
00113 }
00114 
00115 #endif
00116