ReadArpTable.c

/************************************************************************************
* Copyright (C) 2023                                                                *
* TETCOS, Bangalore. India                                                          *
*                                                                                   *
* Tetcos owns the intellectual property rights in the Product and its content.      *
* The copying, redistribution, reselling or publication of any or all of the        *
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* prohibited. Ownership and / or any other right relating to the software and all   *
* intellectual property rights therein shall remain at all times with Tetcos.       *
*                                                                                   *
* This source code is licensed per the NetSim license agreement.                    *
*                                                                                   *
* No portion of this source code may be used as the basis for a derivative work,    *
* or used, for any purpose other than its intended use per the NetSim license       *
* agreement.                                                                        *
*                                                                                   *
* This source code and the algorithms contained within it are confidential trade    *
* secrets of TETCOS and may not be used as the basis for any other software,        *
* hardware, product or service.                                                     *
*                                                                                   *
* Author:    Shashi Kant Suman                                                      *
*                                                                                   *
* ----------------------------------------------------------------------------------*/
 
#define _CRT_SECURE_NO_DEPRECATE
#include "main.h"
#include "ARP.h"
/**
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Function: Read ARP Table
When packet want to transmit the MAC OUT EVENT, the job of Address Resolution Protocol
is to update the destination MAC address in the MAC data of the packet. To do that it 
follows the below steps.
1. Check the destination is in the same LAN. If yes, set the nDestinationId as well as
   DestinationIP from the packet you received. if not,then set the nDestinationId ZERO 
   for the DefaultGateway and the DestinationIP as the GatewayIP.
2. Then check the DestinationIP entry present in the ARP table. If present,
    set the nDestinationPresentFlag.
3  If nDestinationPresentFlag is set (ONE)then update the DestMAc of MACdata of packet
   and forward to MAC layer by keeping the packet in the AccessBuffer of AccessInterface.
4.  If nDestinationPresentFlag is not set and pnArpRequestFlag[nDestinationId](request flag 
    for the destination) is also not set, then buffer the packet and add event by adding 
    subevent type as GENERATE_ARP_REQUEST.
5. If nDestinationPresentFlag is not set pnArpRequestFlag[nDestinationId] is set, then just
    buffer the packet.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
 
static PNETSIM_MACADDRESS read_table(ARP_VARIABLES* arp,NETSIM_IPAddress ip)
{
    ARP_TABLE* table = arp->pstruArpTable;
    while (table)
    {
        if (!IP_COMPARE(table->szIPAddress, ip))
            return table->szMACAddress;
        table = table->pstruNextEntry;
    }
    return NULL;
}
 
int fn_NetSim_Read_ARP_Table()
{
    NETSIM_ID nDeviceId;
    NETSIM_ID nInterfaceId, nDestinationId=0;       
    NETSIM_IPAddress szDestIPadd;
    PNETSIM_MACADDRESS szDestMAC=NULL;  
    int nType;
 
    NetSim_PACKET *pstruTemp_Data;// NetSim Temp packet to store the packet from the event details  
    ARP_TABLE  *pstruTableHead, *pstruCurrentTable; //Type casting ARP table    
    ARP_VARIABLES *pstruArpVariables;//Type casting ARP variables   
 
    // Get packet from the event
    pstruTemp_Data =pstruEventDetails->pPacket; 
 
    // Get the interface and device id from the event
    nInterfaceId = pstruEventDetails->nInterfaceId;
    nDeviceId = pstruEventDetails->nDeviceId;       
    szDestIPadd = pstruTemp_Data->pstruNetworkData->szNextHopIp;
 
    if (isBroadcastIP(szDestIPadd))
    {
        szDestMAC = BROADCAST_MAC;
    }
    else if (isMulticastIP(szDestIPadd))
    {
        szDestMAC = multicastIP_to_Mac(szDestIPadd);
    }
    else
    {
        pstruArpVariables = DEVICE_INTERFACE(nDeviceId, nInterfaceId)->ipVar;
        pstruTableHead = pstruArpVariables->pstruArpTable;
 
        szDestMAC = read_table(pstruArpVariables, szDestIPadd);
    }
 
    // nDestinationId = pstruTemp_Data->nReceiverId; 
    // Corrected to resolve static ARP bug ID 3498 involving multiple applications
    nDestinationId = get_first_dest_from_packet(pstruTemp_Data); 
 
    if(szDestMAC) //Destination MAC present,forward the packet
    {
        //Update the destination and Source MAC address in the MacData of the packet
        pstruTemp_Data->pstruMacData->szDestMac = szDestMAC;
        pstruTemp_Data->pstruMacData->szSourceMac = DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruMACLayer->szMacAddress;
        
        if(!fn_NetSim_GetBufferStatus(DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruAccessInterface->pstruAccessBuffer))
        {
            pstruEventDetails->nProtocolId = fn_NetSim_Stack_GetMacProtocol(nDeviceId,nInterfaceId);
            pstruEventDetails->dEventTime = pstruEventDetails->dEventTime;
            pstruEventDetails->nSubEventType = 0;           
            pstruEventDetails->dPacketSize = pstruTemp_Data->pstruNetworkData->dPacketSize;             
            pstruEventDetails->nEventType=MAC_OUT_EVENT;
            pstruEventDetails->pPacket=NULL;    
            fnpAddEvent( pstruEventDetails);            
        }
        fn_NetSim_Packet_AddPacketToList(DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruAccessInterface->pstruAccessBuffer,pstruTemp_Data,0);
    }   
    /*check the request flag, ZERO for first time, then generate the request,and set the flag. 
    When the flag is ONE, the packets are buffered */   
    else if(pstruArpVariables->pnArpRequestFlag[nDestinationId]== 0)
    {
        /* Buffer the Packet*/          
        fn_NetSim_Add_PacketTo_Buffer(nDeviceId,pstruTemp_Data,szDestIPadd,nInterfaceId);       
        //Increment the buffered pkt count              
        pstruArpVariables->pstruArpMetrics->nPacketsInBuffer += 1;       
        /*Generate ARP Request */
        pstruEventDetails->nSubEventType = GENERATE_ARP_REQUEST;
        fnpAddEvent(pstruEventDetails);
        pstruArpVariables->pnArpRequestFlag[nDestinationId]= 1; 
    }
    else
    {   /* Buffer the Packet*/          
        fn_NetSim_Add_PacketTo_Buffer(nDeviceId,pstruTemp_Data,szDestIPadd,nInterfaceId);
        //Increment the buffered pkt count      
        pstruArpVariables->pstruArpMetrics->nPacketsInBuffer += 1;       
    }   
    
    return 0;
}