130 lines
5.5 KiB
C
130 lines
5.5 KiB
C
/*
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LUFA Library
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Copyright (C) Dean Camera, 2019.
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dean [at] fourwalledcubicle [dot] com
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www.lufa-lib.org
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*/
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/*
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Copyright 2019 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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Permission to use, copy, modify, distribute, and sell this
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software and its documentation for any purpose is hereby granted
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without fee, provided that the above copyright notice appear in
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all copies and that both that the copyright notice and this
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permission notice and warranty disclaimer appear in supporting
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documentation, and that the name of the author not be used in
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advertising or publicity pertaining to distribution of the
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software without specific, written prior permission.
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The author disclaims all warranties with regard to this
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software, including all implied warranties of merchantability
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and fitness. In no event shall the author be liable for any
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special, indirect or consequential damages or any damages
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whatsoever resulting from loss of use, data or profits, whether
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in an action of contract, negligence or other tortious action,
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arising out of or in connection with the use or performance of
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this software.
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*/
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/** \file
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*
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* Dynamic Host Configuration Protocol (DHCP) packet handling routines. This protocol
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* handles the automatic IP negotiation to the host, so that the host will use the provided
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* IP address given to it by the device.
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*/
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#include "DHCP.h"
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/** Processes a DHCP packet inside an Ethernet frame, and writes the appropriate response
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* to the output Ethernet frame if the host is requesting or accepting an IP address.
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*
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* \param[in] IPHeaderInStart Pointer to the start of the incoming packet's IP header
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* \param[in] DHCPHeaderInStart Pointer to the start of the incoming packet's DHCP header
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* \param[out] DHCPHeaderOutStart Pointer to the start of the outgoing packet's DHCP header
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*
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* \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE otherwise
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*/
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int16_t DHCP_ProcessDHCPPacket(void* IPHeaderInStart,
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void* DHCPHeaderInStart,
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void* DHCPHeaderOutStart)
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{
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IP_Header_t* IPHeaderIN = (IP_Header_t*)IPHeaderInStart;
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DHCP_Header_t* DHCPHeaderIN = (DHCP_Header_t*)DHCPHeaderInStart;
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DHCP_Header_t* DHCPHeaderOUT = (DHCP_Header_t*)DHCPHeaderOutStart;
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uint8_t* DHCPOptionsINStart = ((uint8_t*)DHCPHeaderInStart + sizeof(DHCP_Header_t));
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uint8_t* DHCPOptionsOUTStart = ((uint8_t*)DHCPHeaderOutStart + sizeof(DHCP_Header_t));
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DecodeDHCPHeader(DHCPHeaderInStart);
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/* Zero out the response DHCP packet, as much of it is legacy and left at 0 */
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memset(DHCPHeaderOUT, 0, sizeof(DHCP_Header_t));
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/* Fill out the response DHCP packet */
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DHCPHeaderOUT->HardwareType = DHCPHeaderIN->HardwareType;
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DHCPHeaderOUT->Operation = DHCP_OP_BOOTREPLY;
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DHCPHeaderOUT->HardwareAddressLength = DHCPHeaderIN->HardwareAddressLength;
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DHCPHeaderOUT->Hops = 0;
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DHCPHeaderOUT->TransactionID = DHCPHeaderIN->TransactionID;
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DHCPHeaderOUT->ElapsedSeconds = 0;
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DHCPHeaderOUT->Flags = DHCPHeaderIN->Flags;
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DHCPHeaderOUT->YourIP = ClientIPAddress;
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memmove(&DHCPHeaderOUT->ClientHardwareAddress, &DHCPHeaderIN->ClientHardwareAddress, sizeof(MAC_Address_t));
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DHCPHeaderOUT->Cookie = SwapEndian_32(DHCP_MAGIC_COOKIE);
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/* Alter the incoming IP packet header so that the corrected IP source and destinations are used - this means that
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when the response IP header is generated, it will use the corrected addresses and not the null/broatcast addresses */
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IPHeaderIN->SourceAddress = ClientIPAddress;
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IPHeaderIN->DestinationAddress = ServerIPAddress;
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/* Process the incoming DHCP packet options */
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while (DHCPOptionsINStart[0] != DHCP_OPTION_END)
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{
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/* Find the Message Type DHCP option, to determine the type of DHCP packet */
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if (DHCPOptionsINStart[0] == DHCP_OPTION_MESSAGETYPE)
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{
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if ((DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) || (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_REQUEST))
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{
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/* Fill out the response DHCP packet options for a DHCP OFFER or ACK response */
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*(DHCPOptionsOUTStart++) = DHCP_OPTION_MESSAGETYPE;
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*(DHCPOptionsOUTStart++) = 1;
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*(DHCPOptionsOUTStart++) = (DHCPOptionsINStart[2] == DHCP_MESSAGETYPE_DISCOVER) ? DHCP_MESSAGETYPE_OFFER
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: DHCP_MESSAGETYPE_ACK;
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*(DHCPOptionsOUTStart++) = DHCP_OPTION_SUBNETMASK;
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*(DHCPOptionsOUTStart++) = sizeof(IP_Address_t);
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*(DHCPOptionsOUTStart++) = 0xFF;
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*(DHCPOptionsOUTStart++) = 0xFF;
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*(DHCPOptionsOUTStart++) = 0xFF;
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*(DHCPOptionsOUTStart++) = 0x00;
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*(DHCPOptionsOUTStart++) = DHCP_OPTION_LEASETIME;
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*(DHCPOptionsOUTStart++) = sizeof(uint32_t);
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/* Lease Time 86400s (ONE_DAY) */
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*(DHCPOptionsOUTStart++) = 0x00;
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*(DHCPOptionsOUTStart++) = 0x01;
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*(DHCPOptionsOUTStart++) = 0x51;
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*(DHCPOptionsOUTStart++) = 0x80;
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*(DHCPOptionsOUTStart++) = DHCP_OPTION_DHCPSERVER;
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*(DHCPOptionsOUTStart++) = sizeof(IP_Address_t);
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memcpy(DHCPOptionsOUTStart, &ServerIPAddress, sizeof(IP_Address_t));
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DHCPOptionsOUTStart += sizeof(IP_Address_t);
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*(DHCPOptionsOUTStart++) = DHCP_OPTION_END;
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return (sizeof(DHCP_Header_t) + 18 + sizeof(IP_Address_t));
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}
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}
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/* Go to the next DHCP option - skip one byte if option is a padding byte, else skip the complete option's size */
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DHCPOptionsINStart += ((DHCPOptionsINStart[0] == DHCP_OPTION_PAD) ? 1 : (DHCPOptionsINStart[1] + 2));
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}
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return NO_RESPONSE;
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}
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