/* 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 * * Dynamic Host Configuration Protocol (DHCP) packet handling routines. This protocol * handles the automatic IP negotiation to the host, so that the host will use the provided * IP address given to it by the device. */ #include "DHCP.h" /** Processes a DHCP packet inside an Ethernet frame, and writes the appropriate response * to the output Ethernet frame if the host is requesting or accepting an IP address. * * \param IPHeaderInStart Pointer to the start of the incomming packet's IP header * \param DHCPHeaderInStart Pointer to the start of the incomming packet's DHCP header * \param DHCPHeaderOutStart Pointer to the start of the outgoing packet's DHCP header * * \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE otherwise */ int16_t DHCP_ProcessDHCPPacket(void* IPHeaderInStart, void* DHCPHeaderInStart, void* DHCPHeaderOutStart) { IP_Header_t* IPHeaderIN = (IP_Header_t*)IPHeaderInStart; DHCP_Header_t* DHCPHeaderIN = (DHCP_Header_t*)DHCPHeaderInStart; DHCP_Header_t* DHCPHeaderOUT = (DHCP_Header_t*)DHCPHeaderOutStart; uint8_t* DHCPOptionsINStart = (uint8_t*)(DHCPHeaderInStart + sizeof(DHCP_Header_t)); uint8_t* DHCPOptionsOUTStart = (uint8_t*)(DHCPHeaderOutStart + sizeof(DHCP_Header_t)); DecodeDHCPHeader(DHCPHeaderInStart); /* Zero out the response DHCP packet, as much of it legacy and left at 0 */ memset(DHCPHeaderOUT, 0, sizeof(DHCP_Header_t)); /* Fill out the response DHCP packet */ DHCPHeaderOUT->HardwareType = DHCPHeaderIN->HardwareType; DHCPHeaderOUT->Operation = DHCP_OP_BOOTREPLY; DHCPHeaderOUT->HardwareAddressLength = DHCPHeaderIN->HardwareAddressLength; DHCPHeaderOUT->Hops = 0; DHCPHeaderOUT->TransactionID = DHCPHeaderIN->TransactionID; DHCPHeaderOUT->ElapsedSeconds = 0; DHCPHeaderOUT->Flags = DHCPHeaderIN->Flags; DHCPHeaderOUT->YourIP = ClientIPAddress; memcpy(&DHCPHeaderOUT->ClientHardwareAddress, &DHCPHeaderIN->ClientHardwareAddress, sizeof(MAC_Address_t)); DHCPHeaderOUT->Cookie = SwapEndian_32(DHCP_MAGIC_COOKIE); /* Alter the incomming IP packet header so that the corrected IP source and destinations are used - this means that when the response IP header is generated, it will use the corrected addresses and not the null/broatcast addresses */ IPHeaderIN->SourceAddress = ClientIPAddress; IPHeaderIN->DestinationAddress = ServerIPAddress; /* Process the incomming DHCP packet options */ while (DHCPOptionsINStart[0] != DHCP_OPTION_END) { /* Find the Message Type DHCP option, to determine the type of DHCP packet */ if (DHCPOptionsINStart[0] == DHCP_OPTION_MESSAGETYPE) { if ((DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) || (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_REQUEST)) { /* Fill out the response DHCP packet options for a DHCP OFFER or ACK response */ *(DHCPOptionsOUTStart++) = DHCP_OPTION_MESSAGETYPE; *(DHCPOptionsOUTStart++) = 1; *(DHCPOptionsOUTStart++) = (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) ? DHCP_MESSAGETYPE_OFFER : DHCP_MESSAGETYPE_ACK; *(DHCPOptionsOUTStart++) = DHCP_OPTION_SUBNETMASK; *(DHCPOptionsOUTStart++) = 4; *(DHCPOptionsOUTStart++) = 0xFF; *(DHCPOptionsOUTStart++) = 0xFF; *(DHCPOptionsOUTStart++) = 0xFF; *(DHCPOptionsOUTStart++) = 0x00; *(DHCPOptionsOUTStart++) = DHCP_OPTION_DHCPSERVER; *(DHCPOptionsOUTStart++) = sizeof(IP_Address_t); memcpy(DHCPOptionsOUTStart, &ServerIPAddress, sizeof(IP_Address_t)); DHCPOptionsOUTStart += sizeof(IP_Address_t); *(DHCPOptionsOUTStart++) = DHCP_OPTION_END; return (sizeof(DHCP_Header_t) + 12 + sizeof(IP_Address_t)); } } /* Go to the next DHCP option - skip one byte if option is a padding byte, else skip the complete option's size */ DHCPOptionsINStart += ((DHCPOptionsINStart[0] == DHCP_OPTION_PAD) ? 1 : (DHCPOptionsINStart[1] + 2)); } return NO_RESPONSE; }