Demos/Device/LowLevel/RNDISEthernet/Lib/DHCP.c

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2012.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6            www.lufa-lib.org
   7 */
   8
   9 /*
  10   Copyright 2012  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  11
  12   Permission to use, copy, modify, distribute, and sell this
  13   software and its documentation for any purpose is hereby granted
  14   without fee, provided that the above copyright notice appear in
  15   all 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[in] IPHeaderInStart      Pointer to the start of the incoming packet's IP header
  44  *  \param[in] DHCPHeaderInStart    Pointer to the start of the incoming packet's DHCP header
  45  *  \param[out] 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,
  50                                void* DHCPHeaderInStart,
  51                                void* DHCPHeaderOutStart)
  52 {
  53         IP_Header_t*   IPHeaderIN    = (IP_Header_t*)IPHeaderInStart;
  54         DHCP_Header_t* DHCPHeaderIN  = (DHCP_Header_t*)DHCPHeaderInStart;
  55         DHCP_Header_t* DHCPHeaderOUT = (DHCP_Header_t*)DHCPHeaderOutStart;
  56
  57         uint8_t* DHCPOptionsINStart  = (uint8_t*)(DHCPHeaderInStart  + sizeof(DHCP_Header_t));
  58         uint8_t* DHCPOptionsOUTStart = (uint8_t*)(DHCPHeaderOutStart + sizeof(DHCP_Header_t));
  59
  60         DecodeDHCPHeader(DHCPHeaderInStart);
  61
  62         /* Zero out the response DHCP packet, as much of it is legacy and left at 0 */
  63         memset(DHCPHeaderOUT, 0, sizeof(DHCP_Header_t));
  64
  65         /* Fill out the response DHCP packet */
  66         DHCPHeaderOUT->HardwareType          = DHCPHeaderIN->HardwareType;
  67         DHCPHeaderOUT->Operation             = DHCP_OP_BOOTREPLY;
  68         DHCPHeaderOUT->HardwareAddressLength = DHCPHeaderIN->HardwareAddressLength;
  69         DHCPHeaderOUT->Hops                  = 0;
  70         DHCPHeaderOUT->TransactionID         = DHCPHeaderIN->TransactionID;
  71         DHCPHeaderOUT->ElapsedSeconds        = 0;
  72         DHCPHeaderOUT->Flags                 = DHCPHeaderIN->Flags;
  73         DHCPHeaderOUT->YourIP                = ClientIPAddress;
  74         memmove(&DHCPHeaderOUT->ClientHardwareAddress, &DHCPHeaderIN->ClientHardwareAddress, sizeof(MAC_Address_t));
  75         DHCPHeaderOUT->Cookie                = SwapEndian_32(DHCP_MAGIC_COOKIE);
  76
  77         /* Alter the incoming IP packet header so that the corrected IP source and destinations are used - this means that
  78            when the response IP header is generated, it will use the corrected addresses and not the null/broatcast addresses */
  79         IPHeaderIN->SourceAddress      = ClientIPAddress;
  80         IPHeaderIN->DestinationAddress = ServerIPAddress;
  81
  82         /* Process the incoming DHCP packet options */
  83         while (DHCPOptionsINStart[0] != DHCP_OPTION_END)
  84         {
  85                 /* Find the Message Type DHCP option, to determine the type of DHCP packet */
  86                 if (DHCPOptionsINStart[0] == DHCP_OPTION_MESSAGETYPE)
  87                 {
  88                         if ((DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) || (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_REQUEST))
  89                         {
  90                                 /* Fill out the response DHCP packet options for a DHCP OFFER or ACK response */
  91
  92                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_MESSAGETYPE;
  93                                 *(DHCPOptionsOUTStart++) = 1;
  94                                 *(DHCPOptionsOUTStart++) = (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) ? DHCP_MESSAGETYPE_OFFER
  95                                                                                                                                                                                                 : DHCP_MESSAGETYPE_ACK;
  96
  97                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_SUBNETMASK;
  98                                 *(DHCPOptionsOUTStart++) = 4;
  99                                 *(DHCPOptionsOUTStart++) = 0xFF;
 100                                 *(DHCPOptionsOUTStart++) = 0xFF;
 101                                 *(DHCPOptionsOUTStart++) = 0xFF;
 102                                 *(DHCPOptionsOUTStart++) = 0x00;
 103
 104                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_DHCPSERVER;
 105                                 *(DHCPOptionsOUTStart++) = sizeof(IP_Address_t);
 106                                 memcpy(DHCPOptionsOUTStart, &ServerIPAddress, sizeof(IP_Address_t));
 107                                 DHCPOptionsOUTStart     += sizeof(IP_Address_t);
 108
 109                                 *(DHCPOptionsOUTStart++) = DHCP_OPTION_END;
 110
 111                                 return (sizeof(DHCP_Header_t) + 12 + sizeof(IP_Address_t));
 112                         }
 113                 }
 114
 115                 /* Go to the next DHCP option - skip one byte if option is a padding byte, else skip the complete option's size */
 116                 DHCPOptionsINStart += ((DHCPOptionsINStart[0] == DHCP_OPTION_PAD) ? 1 : (DHCPOptionsINStart[1] + 2));
 117         }
 118
 119         return NO_RESPONSE;
 120 }
 121