Demos/Device/RNDISEthernet/Lib/DHCP.c

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2009.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6       www.fourwalledcubicle.com
   7 */
   8
   9 /*
  10   Copyright 2009  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  11
  12   Permission to use, copy, modify, and distribute this software
  13   and its documentation for any purpose and without fee is hereby
  14   granted, provided that the above copyright notice appear in all
  15   copies and that both that the copyright notice and this
  16   permission notice and warranty disclaimer appear in supporting
  17   documentation, and that the name of the author not be used in
  18   advertising or publicity pertaining to distribution of the
  19   software without specific, written prior permission.
  20
  21   The author disclaim all warranties with regard to this
  22   software, including all implied warranties of merchantability
  23   and fitness.  In no event shall the author be liable for any
  24   special, indirect or consequential damages or any damages
  25   whatsoever resulting from loss of use, data or profits, whether
  26   in an action of contract, negligence or other tortious action,
  27   arising out of or in connection with the use or performance of
  28   this software.
  29 */
  30
  31 /** \file
  32  *
  33  *  Dynamic Host Configuration Protocol (DHCP) packet handling routines. This protocol
  34  *  handles the automatic IP negotiation to the host, so that the host will use the provided
  35  *  IP address given to it by the device.
  36  */
  37
  38 #include "DHCP.h"
  39
  40 /** Processes a DHCP packet inside an Ethernet frame, and writes the appropriate response
  41  *  to the output Ethernet frame if the host is requesting or accepting an IP address.
  42  *
  43  *  \param IPHeaderInStart     Pointer to the start of the incoming packet's IP header
  44  *  \param DHCPHeaderInStart   Pointer to the start of the incoming packet's DHCP header
  45  *  \param DHCPHeaderOutStart  Pointer to the start of the outgoing packet's DHCP header
  46  *
  47  *  \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE otherwise
  48  */
  49 int16_t DHCP_ProcessDHCPPacket(void* IPHeaderInStart, void* DHCPHeaderInStart, void* DHCPHeaderOutStart)
  50 {
  51         IP_Header_t*   IPHeaderIN    = (IP_Header_t*)IPHeaderInStart;
  52         DHCP_Header_t* DHCPHeaderIN  = (DHCP_Header_t*)DHCPHeaderInStart;
  53         DHCP_Header_t* DHCPHeaderOUT = (DHCP_Header_t*)DHCPHeaderOutStart;
  54
  55         uint8_t* DHCPOptionsINStart  = (uint8_t*)(DHCPHeaderInStart  + sizeof(DHCP_Header_t));
  56         uint8_t* DHCPOptionsOUTStart = (uint8_t*)(DHCPHeaderOutStart + sizeof(DHCP_Header_t));
  57
  58         DecodeDHCPHeader(DHCPHeaderInStart);
  59
  60         /* Zero out the response DHCP packet, as much of it legacy and left at 0 */
  61         memset(DHCPHeaderOUT, 0, sizeof(DHCP_Header_t));
  62
  63         /* Fill out the response DHCP packet */
  64         DHCPHeaderOUT->HardwareType          = DHCPHeaderIN->HardwareType;
  65         DHCPHeaderOUT->Operation             = DHCP_OP_BOOTREPLY;
  66         DHCPHeaderOUT->HardwareAddressLength = DHCPHeaderIN->HardwareAddressLength;
  67         DHCPHeaderOUT->Hops                  = 0;
  68         DHCPHeaderOUT->TransactionID         = DHCPHeaderIN->TransactionID;
  69         DHCPHeaderOUT->ElapsedSeconds        = 0;
  70         DHCPHeaderOUT->Flags                 = DHCPHeaderIN->Flags;
  71         DHCPHeaderOUT->YourIP                = ClientIPAddress;
  72         memcpy(&DHCPHeaderOUT->ClientHardwareAddress, &DHCPHeaderIN->ClientHardwareAddress, sizeof(MAC_Address_t));
  73         DHCPHeaderOUT->Cookie                = SwapEndian_32(DHCP_MAGIC_COOKIE);
  74
  75         /* Alter the incoming IP packet header so that the corrected IP source and destinations are used - this means that
  76            when the response IP header is generated, it will use the corrected addresses and not the null/broatcast addresses */
  77         IPHeaderIN->SourceAddress      = ClientIPAddress;
  78         IPHeaderIN->DestinationAddress = ServerIPAddress;
  79
  80         /* Process the incoming DHCP packet options */
  81         while (DHCPOptionsINStart[0] != DHCP_OPTION_END)
  82         {
  83                 /* Find the Message Type DHCP option, to determine the type of DHCP packet */
  84                 if (DHCPOptionsINStart[0] == DHCP_OPTION_MESSAGETYPE)
  85                 {
  86                         if ((DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) || (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_REQUEST))
  87                         {
  88                                 /* Fill out the response DHCP packet options for a DHCP OFFER or ACK response */
  89
  90                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_MESSAGETYPE;
  91                                 *(DHCPOptionsOUTStart++) = 1;
  92                                 *(DHCPOptionsOUTStart++) = (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) ? DHCP_MESSAGETYPE_OFFER
  93                                                                                                                                                                                                 : DHCP_MESSAGETYPE_ACK;
  94
  95                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_SUBNETMASK;
  96                                 *(DHCPOptionsOUTStart++) = 4;
  97                                 *(DHCPOptionsOUTStart++) = 0xFF;
  98                                 *(DHCPOptionsOUTStart++) = 0xFF;
  99                                 *(DHCPOptionsOUTStart++) = 0xFF;
 100                                 *(DHCPOptionsOUTStart++) = 0x00;
 101
 102                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_DHCPSERVER;
 103                                 *(DHCPOptionsOUTStart++) = sizeof(IP_Address_t);
 104                                 memcpy(DHCPOptionsOUTStart, &ServerIPAddress, sizeof(IP_Address_t));
 105                                 DHCPOptionsOUTStart     += sizeof(IP_Address_t);
 106
 107                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_END;
 108
 109                                 return (sizeof(DHCP_Header_t) + 12 + sizeof(IP_Address_t));
 110                         }
 111                 }
 112
 113                 /* Go to the next DHCP option - skip one byte if option is a padding byte, else skip the complete option's size */
 114                 DHCPOptionsINStart += ((DHCPOptionsINStart[0] == DHCP_OPTION_PAD) ? 1 : (DHCPOptionsINStart[1] + 2));
 115         }
 116
 117         return NO_RESPONSE;
 118 }