IP.c

/*
             LUFA Library
     Copyright (C) Dean Camera, 2011.

  dean [at] fourwalledcubicle [dot] com
           www.lufa-lib.org
*/

/*
  Copyright 2011  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 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
 *
 *  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] FrameIN        Pointer to the incoming Ethernet frame information structure
 *  \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(Ethernet_Frame_Info_t* const FrameIN,
                           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(FrameIN,
			                                 &((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;
}