NAT.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:    Shashi Kant Suman                                                     *
*                                                                                  *
* ---------------------------------------------------------------------------------*/
#include "main.h"
 
static void add_new_dest(NetSim_PACKET* packet, NETSIM_IPAddress ip)
{
    NetSim_PACKET_NETWORKLAYER* nw = calloc(1, sizeof* nw);
    
    memcpy(nw, packet->pstruNetworkData, sizeof* nw);
    nw->next = packet->pstruNetworkData;
    packet->pstruNetworkData = nw;
 
    nw->szDestIP = ip;
    nw->Packet_NetworkProtocol = NULL;
    nw->Packet_RoutingProtocol = NULL;
}
 
static void remove_dest(NetSim_PACKET* packet)
{
    NetSim_PACKET_NETWORKLAYER* nw = packet->pstruNetworkData;
    NetSim_PACKET_NETWORKLAYER* nnw = nw->next;
    if (nnw)
    {
        void* n = nnw->next;
        void* i = nnw->szDestIP;
        nw->Packet_NetworkProtocol = nnw->Packet_NetworkProtocol;
        nw->Packet_RoutingProtocol = nnw->Packet_RoutingProtocol;
        memcpy(nnw, nw, sizeof* nnw);
        nnw->next = n;
        nnw->szDestIP = i;
        packet->pstruNetworkData = nnw;
        nw->next = NULL;
        free(nw);
    }
}
 
int fn_NetSim_NAT_NetworkOut(NETSIM_ID ndev,NetSim_PACKET* packet)
{
    NETSIM_IPAddress dest = packet->pstruNetworkData->szDestIP;
    NETSIM_ID i;
    NETSIM_IPAddress newDest = NULL;
 
    UINT destCount;
    NETSIM_ID* destList = get_dest_from_packet(packet, &destCount);
 
    if(destCount>1)
        return 1; //Broadcast or Multicast
 
    if (destList[0] == 0)
        return 1; //Broadcast
 
    if (isMulticastIP(dest))
        return 1;
 
    for(i=0;i<DEVICE(ndev)->nNumOfInterface;i++)
    {
        if(DEVICE_INTERFACE(ndev,i+1) && DEVICE_INTERFACE(ndev,i+1)->szAddress)
        {
            NETSIM_IPAddress ip = DEVICE_INTERFACE(ndev,i+1)->szAddress;
            NETSIM_IPAddress mask = DEVICE_INTERFACE(ndev,i+1)->szSubnetMask;
            unsigned int prefix = DEVICE_INTERFACE(ndev,i+1)->prefix_len;
            NETSIM_IPAddress n1,n2;
            if(dest->type != ip->type)
                continue;
            n1=IP_NETWORK_ADDRESS(ip,mask,prefix);
            n2=IP_NETWORK_ADDRESS(dest,mask,prefix);
            if(!IP_COMPARE(n1,n2))
                return 2;
        }
    }
    for(i=0;i<DEVICE(ndev)->nNumOfInterface;i++)
    {
        if(DEVICE_INTERFACE(ndev,i+1) && DEVICE_INTERFACE(ndev,i+1)->szAddress && DEVICE_INTERFACE(ndev,i+1)->szDefaultGateWay)
        {
            newDest = DEVICE_INTERFACE(ndev,i+1)->szDefaultGateWay;
            break;
        }
    }
 
    if (newDest)
    {
        //Set me to default
        add_new_dest(packet, newDest);
    }
    else if (DEVICE_FIRST_PUBLICIP(destList[0]))
    {
        NETSIM_IPAddress pub = DEVICE_FIRST_PUBLICIP(destList[0]);
        if (!IP_COMPARE(pub, dest))
            return -1; // Already public ip is set
 
        for (i = 0; i < DEVICE(ndev)->nNumOfInterface; i++)
        {
            if (DEVICE_INTERFACE(ndev, i + 1) && DEVICE_INTERFACE(ndev, i + 1)->szAddress)
            {
                if (!IP_COMPARE(DEVICE_NWADDRESS(ndev, i + 1), pub))
                    return -1; // I am public ip of dest
            }
        }
 
        //set me to public ip
        add_new_dest(packet, DEVICE_FIRST_PUBLICIP(destList[0]));
    }
    return 0;
}
 
int fn_NetSim_NAT_NetworkIn(NETSIM_ID ndev,NetSim_PACKET* packet)
{
    UINT destCount;
    NETSIM_ID* dest = get_dest_from_packet(packet, &destCount);
    if (destCount > 1)
        return -1; //Broadcast or Multicast
 
    if (ndev == dest[0])
    {
        remove_dest(packet);
        return -2;
    }
 
    if (isBroadcastIP(packet->pstruNetworkData->szDestIP))
        return -3;
 
    if (isMulticastIP(packet->pstruNetworkData->szDestIP))
        return -4;
 
    NETSIM_ID i;
    NETSIM_IPAddress ip = packet->pstruNetworkData->szDestIP;
    bool flag = false;
    for (i = 0; i < DEVICE(ndev)->nNumOfInterface; i++)
    {
        if (DEVICE_INTERFACE(ndev, i + 1) &&
            DEVICE_INTERFACE(ndev, i + 1)->szAddress &&
            !IP_COMPARE(ip, DEVICE_NWADDRESS(ndev, i + 1)))
        {
            flag = true;
            break;
        }
    }
 
    if (flag)
        remove_dest(packet);
 
    return 0;
}