GenerateArpReply.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       *
 * Product or its content without express prior written consent of Tetcos is        *
 * prohibited. Ownership and / or any other right relating to the software and all  *
 * intellectual property rights therein shall remain at all times with Tetcos.      *
 
 * Author:   Basamma YB 
 * Date  :    
 ************************************************************************************/
#define _CRT_SECURE_NO_DEPRECATE
#include "main.h"
#include "ARP.h"
/**
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This function is called whenever the NETWORK_IN_EVENT triggred with the control 
packet as REQUEST_PACKET. That is ARP request is received. Then call this
function to generate REPLY_PACKET. Do the following to generate Reply
1.Check for the hardware type, protocol type,MAC address lenth, IP adress length
  are correct matching.
2. Check the Source IP and MAC entry present in the table, if not update the table.
3. Check the packet received device is the destination, if not, dicard the packet,
  else Generate the REPLY_PACKET by updating its MAC address.       
4.Add the control packet to access buffer to farward the packet to next layer.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
int fn_NetSim_Generate_ARP_Reply(NetSim_EVENTDETAILS *pstruEventDetails, struct stru_NetSim_Network *NETWORK)
//_declspec (dllexport) int fn_NetSim_Generate_ARP_Reply()
{
    NETSIM_ID nDeviceId;
    NETSIM_ID nInterfaceId;     
    int nMerge_flag = 0;
    int nType;      
    unsigned int unProtocolId;  
    NETSIM_IPAddress szSrcIPadd;        
    NETSIM_IPAddress szDestIPadd;           
    PNETSIM_MACADDRESS szTargetMAC; 
    
    NetSim_PACKET *pstruTemp_Data;      // NetSim Temp packet to store the packet from the event details    
    NetSim_PACKET *pstruControlPacket;  // NetSim packet To store the ARP packet        
    ARP_PACKET *pstruArpRequestPkt;     // ARP PACKET to store ARP Request pcaket   
    ARP_PACKET *pstruArpReplyPkt;       // ARP PACKET to store ARP Reply pcaket         
    ARP_TABLE  *pstruTableHead,*pstruCurrentTable;  //Type casting Arp Table
    ARP_VARIABLES *pstruArpVariables;   //type casting Arp variables 
 
    //Get the packet from the event 
    pstruTemp_Data =pstruEventDetails->pPacket; 
    pstruControlPacket = pstruEventDetails->pPacket;
    // Get the Arp Packet from the NetworkData of temp packet
    pstruArpRequestPkt = pstruTemp_Data->pstruNetworkData->Packet_NetworkProtocol;
    // Get the device and interface Id from the event
    nInterfaceId = pstruEventDetails->nInterfaceId;
    nDeviceId = pstruEventDetails->nDeviceId;
 
    if(pstruArpRequestPkt->n_ar$hrd != IEEE802)     
        fnNetSimError("Mismatch in ARP Hardware Type");         
    if(pstruArpRequestPkt->usn_ar$hln != HARDWARE_ADDRESS_LENGTH)
        fnNetSimError("Mismatch in ARP Hardware/MAC Adress Length ");   
    if(pstruArpRequestPkt->n_ar$pro != ARP_TO_RESOLVE_IP)
        fnNetSimError("Mismatch in ARP Protocol Type"); 
    unProtocolId = fn_NetSim_Stack_GetNWProtocol(nDeviceId);
    if(unProtocolId == NW_PROTOCOL_IPV4)
    {
        if(pstruArpRequestPkt->usn_ar$pln != IPV4_PROTOCOL_ADDREES_LENGTH)
        fnNetSimError("Mismatch in ARP Protocol IPV4 Adress Length ");
    }
    else
    {
        if(pstruArpRequestPkt->usn_ar$pln != IPV6_PROTOCOL_ADDREES_LENGTH)
        fnNetSimError("Mismatch in ARP Protocol IPV6 Adress Length ");
    }
    // Get the Arp variables from device ipVar
    pstruArpVariables = DEVICE_INTERFACE(nDeviceId,nInterfaceId)->ipVar;    
    pstruTableHead = pstruArpVariables->pstruArpTable;  
    pstruCurrentTable = pstruTableHead; 
    // Get the source IP address from the request packet
    szSrcIPadd = pstruArpRequestPkt->sz_ar$spa;//_strdup(pstruArpRequestPkt->sz_ar$spa);
    // Check the Source entry in the ARP TABLE 
    while(pstruCurrentTable != NULL)
    {
        if(IP_COMPARE(pstruCurrentTable->szIPAddress,szSrcIPadd)== 0)
        {   // set the merge flag if entry exists
            nMerge_flag = 1;            
            break;
        }
        else 
        pstruCurrentTable = pstruCurrentTable->pstruNextEntry;
    }           
    // Source entry not there in the ARP table, update the table.
    if(nMerge_flag == 0)
    {       
        nType = DYNAMIC;
        fn_NetSim_Add_IP_MAC_AddressTo_ARP_Table(&pstruTableHead,pstruArpRequestPkt->sz_ar$spa,pstruArpRequestPkt->sz_ar$sha,nType);  
        pstruArpVariables->pstruArpTable = pstruTableHead;
        nMerge_flag =1;
    }
                /* Generate ARP Reply */    
    // Check for REQUEST, and send the REPLY PACKET 
    if(pstruArpRequestPkt->n_ar$op == ares_opSREQUEST)
    {   
        //Allocate memory for the ARP Reply packet
        pstruArpReplyPkt = fnpAllocateMemory(1,sizeof(ARP_PACKET));                 
        //Swap IP and MAC of source and destinations from the Request packet
        pstruArpReplyPkt->sz_ar$spa = IP_COPY(pstruArpRequestPkt->sz_ar$tpa);
        pstruArpReplyPkt->sz_ar$sha = DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruMACLayer->szMacAddress;
        pstruArpReplyPkt->sz_ar$tpa = IP_COPY(pstruArpRequestPkt->sz_ar$spa);
        pstruArpReplyPkt->sz_ar$tha = pstruArpRequestPkt->sz_ar$sha;
        pstruArpReplyPkt->n_ar$op = ares_opSREPLY; // Set Opcode as REPLY 
        //Set the Ethernet header details
        pstruArpReplyPkt->szDestMac = pstruArpRequestPkt->sz_ar$sha;
        pstruArpReplyPkt->szSrcMac = (DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruMACLayer->szMacAddress);
        pstruArpReplyPkt->nEther_type = ADDRESS_RESOLUTION;      
        //Add other relevent fields 
        pstruArpReplyPkt->n_ar$hrd = IEEE802;                // H/W type
        pstruArpReplyPkt->n_ar$pro = ARP_TO_RESOLVE_IP;      // Protocol type   
        pstruArpReplyPkt->usn_ar$hln = HARDWARE_ADDRESS_LENGTH; // MAC add length in bytes
        // Create netsim packet for NETWORK_LAYER
        pstruControlPacket = fn_NetSim_Packet_CreatePacket(NETWORK_LAYER);
        //Generate the control packet           
        pstruControlPacket->dEventTime = pstruEventDetails->dEventTime;
        add_dest_to_packet(pstruControlPacket, pstruEventDetails->pPacket->nSourceId);
        pstruControlPacket->nPacketType = PacketType_Control;
        pstruControlPacket->nControlDataType = REPLY_PACKET;
        pstruControlPacket->nTransmitterId=pstruEventDetails->nDeviceId;
        pstruControlPacket->nReceiverId = pstruEventDetails->pPacket->nTransmitterId;//0;
        pstruControlPacket->nSourceId = pstruEventDetails->nDeviceId;
        //Update IP address in the packet
        pstruControlPacket->pstruNetworkData->szSourceIP = IP_COPY(DEVICE_NWADDRESS(nDeviceId,nInterfaceId));
        pstruControlPacket->pstruNetworkData->szDestIP = IP_COPY(pstruArpRequestPkt->sz_ar$spa);        
        //Update MAC address in the packet
        pstruControlPacket->pstruMacData->szSourceMac = DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruMACLayer->szMacAddress;
        pstruControlPacket->pstruMacData->szDestMac = pstruArpRequestPkt->sz_ar$sha;                   
        //Update NetworkData packet timings 
        pstruControlPacket->pstruNetworkData->dArrivalTime = pstruEventDetails->dEventTime;
        pstruControlPacket->pstruNetworkData->dEndTime = pstruEventDetails->dEventTime;
        pstruControlPacket->pstruNetworkData->dStartTime = pstruEventDetails->dEventTime;
        pstruControlPacket->nPacketPriority = Priority_High;
        //Add overheads and size to NetworkData of the packet       
        unProtocolId = fn_NetSim_Stack_GetNWProtocol(nDeviceId);
        if(unProtocolId == NW_PROTOCOL_IPV4)
        {           
            pstruArpReplyPkt->usn_ar$pln = IPV4_PROTOCOL_ADDREES_LENGTH; // IP add length in bytes
            pstruControlPacket->pstruNetworkData->dPayload = IPV4_ARP_PACKET_SIZE_WITH_ETH_HEADER;
            pstruControlPacket->pstruNetworkData->dOverhead =IPV4_NETWORK_OVERHEADS;            
        }
        else
        {
            pstruArpReplyPkt->usn_ar$pln = IPV6_PROTOCOL_ADDREES_LENGTH; // IP add length in bytes
            pstruControlPacket->pstruNetworkData->dPayload = IPV6_ARP_PACKET_SIZE_WITH_ETH_HEADER;
            pstruControlPacket->pstruNetworkData->dOverhead = IPV6_NETWORK_OVERHEADS;           
        }
        pstruControlPacket->pstruNetworkData->dPacketSize=pstruControlPacket->pstruNetworkData->dPayload + pstruControlPacket->pstruNetworkData->dOverhead;  
        // Assign Protocol Id
        pstruControlPacket->pstruNetworkData->nNetworkProtocol= NW_PROTOCOL_ARP;        
        // Assign ARP Reply packet to NetworkProtocolPacket
        pstruControlPacket->pstruNetworkData->Packet_NetworkProtocol = pstruArpReplyPkt;
        pstruControlPacket->pstruNextPacket=NULL;   
        
        // Get buffer status
        if(!fn_NetSim_GetBufferStatus(DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruAccessInterface->pstruAccessBuffer))
        {                       
            pstruEventDetails->nSubEventType = 0;           
            pstruEventDetails->dPacketSize = pstruControlPacket->pstruNetworkData->dPacketSize;         
            pstruEventDetails->nProtocolId = fn_NetSim_Stack_GetMacProtocol(nDeviceId,nInterfaceId);                
            pstruEventDetails->nEventType=MAC_OUT_EVENT;
            pstruEventDetails->pPacket =  NULL;                 
            fnpAddEvent( pstruEventDetails);            
        }
        //Add packet to mac buffer
        fn_NetSim_Packet_AddPacketToList(DEVICE_INTERFACE(nDeviceId,nInterfaceId)->pstruAccessInterface->pstruAccessBuffer,pstruControlPacket,0);
        
        // Increment the reply sent count       
        pstruArpVariables->pstruArpMetrics->nArpReplySentCount += 1;
        
        // Write to LogFile 
        szDestIPadd = DEVICE_NWADDRESS(nDeviceId,nInterfaceId);
        szTargetMAC = pstruArpReplyPkt->sz_ar$sha;
        printf("ARP---ARP_ReplySent\tEventTime:%0.3lf\tSrcIP:%s\tMAC_Add:%s\tDestIP:%s \n",
               pstruEventDetails->dEventTime,
               szDestIPadd->str_ip,
               szTargetMAC->szmacaddress,
               szSrcIPadd->str_ip);
 
    }
    else
    {           
        fnNetSimError("Error in ARP REQEUST. This function should never be called");
    }   
    // After sending the reply drop the request packet
    fn_NetSim_Packet_FreePacket(pstruTemp_Data);
    pstruTemp_Data = NULL;
    pstruEventDetails->pPacket = NULL;  
    return 0;
}