text: /*
               LUFA Library
       Copyright (C) Dean Camera, 2009.
                
    dean [at] fourwalledcubicle [dot] com
        www.fourwalledcubicle.com
  */
  
  /*
    Copyright 2009  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  
    Permission to use, copy, modify, and distribute this software
    and its documentation for any purpose and without fee is hereby
    granted, provided that the above copyright notice appear in all
    copies and that both that the copyright notice and this
    permission notice and warranty disclaimer appear in supporting
    documentation, and that the name of the author not be used in
    advertising or publicity pertaining to distribution of the
    software without specific, written prior permission.
  
    The author disclaim all warranties with regard to this
    software, including all implied warranties of merchantability
    and fitness.  In no event shall the author be liable for any
    special, indirect or consequential damages or any damages
    whatsoever resulting from loss of use, data or profits, whether
    in an action of contract, negligence or other tortious action,
    arising out of or in connection with the use or performance of
    this software.
  */
  
  /** \file
   *
   *  Address Resolution Protocol (ARP) packet handling routines. This protocol handles the
   *  conversion of physical MAC addresses to protocol IP addresses between the host and the
   *  device.
   */
   
  #include "ARP.h"
  
  /** Processes an ARP packet inside an Ethernet frame, and writes the appropriate response
   *  to the output Ethernet frame if the host is requesting the IP or MAC address of the
   *  virtual server device on the network.
   *
   *  \param InDataStart   Pointer to the start of the incoming packet's ARP header
   *  \param OutDataStart  Pointer to the start of the outgoing packet's ARP header
   *
   *  \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE otherwise
   */
  int16_t ARP_ProcessARPPacket(void* InDataStart, void* OutDataStart)
  {
  	DecodeARPHeader(InDataStart);
  
  	ARP_Header_t* ARPHeaderIN  = (ARP_Header_t*)InDataStart;
  	ARP_Header_t* ARPHeaderOUT = (ARP_Header_t*)OutDataStart;
  
  	/* Ensure that the ARP request is a IPv4 request packet */
  	if ((SwapEndian_16(ARPHeaderIN->ProtocolType) == ETHERTYPE_IPV4) &&
  	    (SwapEndian_16(ARPHeaderIN->Operation) == ARP_OPERATION_REQUEST))
  	{
  		/* If the ARP packet is requesting the MAC or IP of the virtual webserver, return the response */
  		if (IP_COMPARE(&ARPHeaderIN->TPA, &ServerIPAddress) || 
  		    MAC_COMPARE(&ARPHeaderIN->THA, &ServerMACAddress))
  		{
  			/* Fill out the ARP response header */
  			ARPHeaderOUT->HardwareType = ARPHeaderIN->HardwareType;
  			ARPHeaderOUT->ProtocolType = ARPHeaderIN->ProtocolType;
  			ARPHeaderOUT->HLEN         = ARPHeaderIN->HLEN;
  			ARPHeaderOUT->PLEN         = ARPHeaderIN->PLEN;
  			ARPHeaderOUT->Operation    = SwapEndian_16(ARP_OPERATION_REPLY);
  
  			/* Copy over the sender MAC/IP to the target fields for the response */
  			ARPHeaderOUT->THA = ARPHeaderIN->SHA;
  			ARPHeaderOUT->TPA = ARPHeaderIN->SPA;
  
  			/* Copy over the new sender MAC/IP - MAC and IP addresses of the virtual webserver */
  			ARPHeaderOUT->SHA = ServerMACAddress;
  			ARPHeaderOUT->SPA = ServerIPAddress;
  
  			/* Return the size of the response so far */
  			return sizeof(ARP_Header_t);
  		}
  	}
  	
  	return NO_RESPONSE;
  }
  