text: /*
               LUFA Library
       Copyright (C) Dean Camera, 2015.
  
    dean [at] fourwalledcubicle [dot] com
             www.lufa-lib.org
  */
  
  /*
    Copyright 2015  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  
    Permission to use, copy, modify, distribute, and sell this
    software and its documentation for any purpose is hereby granted
    without fee, 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 disclaims 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
   *
   *  Internet Protocol (IP) packet handling routines. This protocol handles IP packets from the
   *  host which typically encapsulate other protocols such as ICMP, UDP and TCP.
   */
  
  #include "IP.h"
  
  /** Processes an IP packet inside an Ethernet frame, and writes the appropriate response
   *  to the output Ethernet frame if one is created by a sub-protocol handler.
   *
   *  \param[in] InDataStart    Pointer to the start of the incoming packet's IP header
   *  \param[out] OutDataStart  Pointer to the start of the outgoing packet's IP header
   *
   *  \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE if no
   *           response was generated, NO_PROCESS if the packet processing was deferred until the
   *           next Ethernet packet handler iteration
   */
  int16_t IP_ProcessIPPacket(void* InDataStart,
                             void* OutDataStart)
  {
  	DecodeIPHeader(InDataStart);
  
  	IP_Header_t* IPHeaderIN  = (IP_Header_t*)InDataStart;
  	IP_Header_t* IPHeaderOUT = (IP_Header_t*)OutDataStart;
  
  	/* Header length is specified in number of longs in the packet header, convert to bytes */
  	uint16_t HeaderLengthBytes = (IPHeaderIN->HeaderLength * sizeof(uint32_t));
  
  	int16_t  RetSize = NO_RESPONSE;
  
  	/* Check to ensure the IP packet is addressed to the virtual webserver's IP or the broadcast IP address */
  	if (!(IP_COMPARE(&IPHeaderIN->DestinationAddress, &ServerIPAddress)) &&
  	    !(IP_COMPARE(&IPHeaderIN->DestinationAddress, &BroadcastIPAddress)))
  	{
  		return NO_RESPONSE;
  	}
  
  	/* Pass off the IP payload to the appropriate protocol processing routine */
  	switch (IPHeaderIN->Protocol)
  	{
  		case PROTOCOL_ICMP:
  			RetSize = ICMP_ProcessICMPPacket(&((uint8_t*)InDataStart)[HeaderLengthBytes],
  			                                 &((uint8_t*)OutDataStart)[sizeof(IP_Header_t)]);
  			break;
  		case PROTOCOL_TCP:
  			RetSize = TCP_ProcessTCPPacket(InDataStart,
  			                               &((uint8_t*)InDataStart)[HeaderLengthBytes],
  			                               &((uint8_t*)OutDataStart)[sizeof(IP_Header_t)]);
  			break;
  		case PROTOCOL_UDP:
  			RetSize = UDP_ProcessUDPPacket(InDataStart,
  			                               &((uint8_t*)InDataStart)[HeaderLengthBytes],
  			                               &((uint8_t*)OutDataStart)[sizeof(IP_Header_t)]);
  			break;
  	}
  
  	/* Check to see if the protocol processing routine has filled out a response */
  	if (RetSize > 0)
  	{
  		/* Fill out the response IP packet header */
  		IPHeaderOUT->TotalLength        = SwapEndian_16(sizeof(IP_Header_t) + RetSize);
  		IPHeaderOUT->TypeOfService      = 0;
  		IPHeaderOUT->HeaderLength       = (sizeof(IP_Header_t) / sizeof(uint32_t));
  		IPHeaderOUT->Version            = 4;
  		IPHeaderOUT->Flags              = 0;
  		IPHeaderOUT->FragmentOffset     = 0;
  		IPHeaderOUT->Identification     = 0;
  		IPHeaderOUT->HeaderChecksum     = 0;
  		IPHeaderOUT->Protocol           = IPHeaderIN->Protocol;
  		IPHeaderOUT->TTL                = DEFAULT_TTL;
  		IPHeaderOUT->SourceAddress      = IPHeaderIN->DestinationAddress;
  		IPHeaderOUT->DestinationAddress = IPHeaderIN->SourceAddress;
  
  		IPHeaderOUT->HeaderChecksum     = Ethernet_Checksum16(IPHeaderOUT, sizeof(IP_Header_t));
  
  		/* Return the size of the response so far */
  		return (sizeof(IP_Header_t) + RetSize);
  	}
  
  	return RetSize;
  }
  
  