text: /*
   * FreeRTOS+TCP V2.0.10
   * Copyright (C) 2017 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   *
   * http://aws.amazon.com/freertos
   * http://www.FreeRTOS.org
   */
  
  /* Standard includes. */
  #include <stdint.h>
  
  /* FreeRTOS includes. */
  #include "FreeRTOS.h"
  #include "task.h"
  #include "queue.h"
  #include "list.h"
  #include "semphr.h"
  
  /* FreeRTOS+TCP includes. */
  #include "FreeRTOS_IP.h"
  #include "FreeRTOS_Sockets.h"
  #include "FreeRTOS_IP_Private.h"
  #include "FreeRTOS_UDP_IP.h"
  #include "FreeRTOS_DNS.h"
  #include "NetworkBufferManagement.h"
  #include "NetworkInterface.h"
  #include "IPTraceMacroDefaults.h"
  
  /* Exclude the entire file if DNS is not enabled. */
  #if( ipconfigUSE_DNS != 0 )
  
  #if( ipconfigBYTE_ORDER == pdFREERTOS_LITTLE_ENDIAN )
  	#define dnsDNS_PORT						0x3500
  	#define dnsONE_QUESTION					0x0100
  	#define dnsOUTGOING_FLAGS				0x0001 /* Standard query. */
  	#define dnsRX_FLAGS_MASK				0x0f80 /* The bits of interest in the flags field of incoming DNS messages. */
  	#define dnsEXPECTED_RX_FLAGS			0x0080 /* Should be a response, without any errors. */
  #else
  	#define dnsDNS_PORT						0x0035
  	#define dnsONE_QUESTION					0x0001
  	#define dnsOUTGOING_FLAGS				0x0100 /* Standard query. */
  	#define dnsRX_FLAGS_MASK				0x800f /* The bits of interest in the flags field of incoming DNS messages. */
  	#define dnsEXPECTED_RX_FLAGS			0x8000 /* Should be a response, without any errors. */
  
  #endif /* ipconfigBYTE_ORDER */
  
  /* The maximum number of times a DNS request should be sent out if a response
  is not received, before giving up. */
  #ifndef ipconfigDNS_REQUEST_ATTEMPTS
  	#define ipconfigDNS_REQUEST_ATTEMPTS		5
  #endif
  
  /* If the top two bits in the first character of a name field are set then the
  name field is an offset to the string, rather than the string itself. */
  #define dnsNAME_IS_OFFSET					( ( uint8_t ) 0xc0 )
  
  /* NBNS flags. */
  #define dnsNBNS_FLAGS_RESPONSE				0x8000
  #define dnsNBNS_FLAGS_OPCODE_MASK			0x7800
  #define dnsNBNS_FLAGS_OPCODE_QUERY			0x0000
  #define dnsNBNS_FLAGS_OPCODE_REGISTRATION	0x2800
  
  /* Host types. */
  #define dnsTYPE_A_HOST						0x01
  #define dnsCLASS_IN							0x01
  
  /* LLMNR constants. */
  #define dnsLLMNR_TTL_VALUE					300000
  #define dnsLLMNR_FLAGS_IS_REPONSE  			0x8000
  
  /* NBNS constants. */
  #define dnsNBNS_TTL_VALUE					3600 /* 1 hour valid */
  #define dnsNBNS_TYPE_NET_BIOS				0x0020
  #define dnsNBNS_CLASS_IN					0x01
  #define dnsNBNS_NAME_FLAGS					0x6000
  #define dnsNBNS_ENCODED_NAME_LENGTH			32
  
  /* If the queried NBNS name matches with the device's name,
  the query will be responded to with these flags: */
  #define dnsNBNS_QUERY_RESPONSE_FLAGS	( 0x8500 )
  
  /* Flag DNS parsing errors in situations where an IPv4 address is the return
  type. */
  #define dnsPARSE_ERROR					  0UL
  
  /*
   * Create a socket and bind it to the standard DNS port number.  Return the
   * the created socket - or NULL if the socket could not be created or bound.
   */
  static Socket_t prvCreateDNSSocket( void );
  
  /*
   * Create the DNS message in the zero copy buffer passed in the first parameter.
   */
  static size_t prvCreateDNSMessage( uint8_t *pucUDPPayloadBuffer, const char *pcHostName, TickType_t xIdentifier );
  
  /*
   * Simple routine that jumps over the NAME field of a resource record.
   */
  static uint8_t *prvSkipNameField( uint8_t *pucByte, size_t xSourceLen );
  
  /*
   * Process a response packet from a DNS server.
   */
  static uint32_t prvParseDNSReply( uint8_t *pucUDPPayloadBuffer, size_t xBufferLength, TickType_t xIdentifier );
  
  /*
   * Prepare and send a message to a DNS server.  'xReadTimeOut_ms' will be passed as
   * zero, in case the user has supplied a call-back function.
   */
  static uint32_t prvGetHostByName( const char *pcHostName, TickType_t xIdentifier, TickType_t xReadTimeOut_ms );
  
  /*
   * The NBNS and the LLMNR protocol share this reply function.
   */
  #if( ( ipconfigUSE_NBNS == 1 ) || ( ipconfigUSE_LLMNR == 1 ) )
  	static void prvReplyDNSMessage( NetworkBufferDescriptor_t *pxNetworkBuffer, BaseType_t lNetLength );
  #endif
  
  #if( ipconfigUSE_NBNS == 1 )
  	static portINLINE void prvTreatNBNS( uint8_t *pucUDPPayloadBuffer, size_t xBufferLength, uint32_t ulIPAddress );
  #endif /* ipconfigUSE_NBNS */
  
  #if( ipconfigUSE_DNS_CACHE == 1 )
  	static uint8_t *prvReadNameField( uint8_t *pucByte, size_t xSourceLen, char *pcName, size_t xLen );
  	static void prvProcessDNSCache( const char *pcName, uint32_t *pulIP, uint32_t ulTTL, BaseType_t xLookUp );
  
  	typedef struct xDNS_CACHE_TABLE_ROW
  	{
  		uint32_t ulIPAddress;		/* The IP address of an ARP cache entry. */
  		char pcName[ ipconfigDNS_CACHE_NAME_LENGTH ];  /* The name of the host */
  		uint32_t ulTTL; /* Time-to-Live (in seconds) from the DNS server. */
  		uint32_t ulTimeWhenAddedInSeconds;
  	} DNSCacheRow_t;
  
  	static DNSCacheRow_t xDNSCache[ ipconfigDNS_CACHE_ENTRIES ];
  #endif /* ipconfigUSE_DNS_CACHE == 1 */
  
  #if( ipconfigUSE_LLMNR == 1 )
  	const MACAddress_t xLLMNR_MacAdress = { { 0x01, 0x00, 0x5e, 0x00, 0x00, 0xfc } };
  #endif	/* ipconfigUSE_LLMNR == 1 */
  
  /*-----------------------------------------------------------*/
  
  #include "pack_struct_start.h"
  struct xDNSMessage
  {
  	uint16_t usIdentifier;
  	uint16_t usFlags;
  	uint16_t usQuestions;
  	uint16_t usAnswers;
  	uint16_t usAuthorityRRs;
  	uint16_t usAdditionalRRs;
  }
  #include "pack_struct_end.h"
  typedef struct xDNSMessage DNSMessage_t;
  
  /* A DNS query consists of a header, as described in 'struct xDNSMessage'
  It is followed by 1 or more queries, each one consisting of a name and a tail,
  with two fields: type and class
  */
  #include "pack_struct_start.h"
  struct xDNSTail
  {
  	uint16_t usType;
  	uint16_t usClass;
  }
  #include "pack_struct_end.h"
  typedef struct xDNSTail DNSTail_t;
  
  /* DNS answer record header. */
  #include "pack_struct_start.h"
  struct xDNSAnswerRecord
  {
  	uint16_t usType;
  	uint16_t usClass;
  	uint32_t ulTTL;
  	uint16_t usDataLength;
  }
  #include "pack_struct_end.h"
  typedef struct xDNSAnswerRecord DNSAnswerRecord_t;
  
  #if( ipconfigUSE_LLMNR == 1 )
  
  	#include "pack_struct_start.h"
  	struct xLLMNRAnswer
  	{
  		uint8_t ucNameCode;
  		uint8_t ucNameOffset;	/* The name is not repeated in the answer, only the offset is given with "0xc0 <offs>" */
  		uint16_t usType;
  		uint16_t usClass;
  		uint32_t ulTTL;
  		uint16_t usDataLength;
  		uint32_t ulIPAddress;
  	}
  	#include "pack_struct_end.h"
  	typedef struct xLLMNRAnswer LLMNRAnswer_t;
  
  #endif /* ipconfigUSE_LLMNR == 1 */
  
  #if( ipconfigUSE_NBNS == 1 )
  
  	#include "pack_struct_start.h"
  	struct xNBNSRequest
  	{
  		uint16_t usRequestId;
  		uint16_t usFlags;
  		uint16_t ulRequestCount;
  		uint16_t usAnswerRSS;
  		uint16_t usAuthRSS;
  		uint16_t usAdditionalRSS;
  		uint8_t ucNameSpace;
  		uint8_t ucName[ dnsNBNS_ENCODED_NAME_LENGTH ];
  		uint8_t ucNameZero;
  		uint16_t usType;
  		uint16_t usClass;
  	}
  	#include "pack_struct_end.h"
  	typedef struct xNBNSRequest NBNSRequest_t;
  
  	#include "pack_struct_start.h"
  	struct xNBNSAnswer
  	{
  		uint16_t usType;
  		uint16_t usClass;
  		uint32_t ulTTL;
  		uint16_t usDataLength;
  		uint16_t usNbFlags;		/* NetBIOS flags 0x6000 : IP-address, big-endian */
  		uint32_t ulIPAddress;
  	}
  	#include "pack_struct_end.h"
  	typedef struct xNBNSAnswer NBNSAnswer_t;
  
  #endif /* ipconfigUSE_NBNS == 1 */
  
  /*-----------------------------------------------------------*/
  
  #if( ipconfigUSE_DNS_CACHE == 1 )
  	uint32_t FreeRTOS_dnslookup( const char *pcHostName )
  	{
  	uint32_t ulIPAddress = 0UL;
  		prvProcessDNSCache( pcHostName, &ulIPAddress, 0, pdTRUE );
  		return ulIPAddress;
  	}
  #endif /* ipconfigUSE_DNS_CACHE == 1 */
  /*-----------------------------------------------------------*/
  
  #if( ipconfigDNS_USE_CALLBACKS != 0 )
  
  	typedef struct xDNS_Callback {
  		TickType_t xRemaningTime;		/* Timeout in ms */
  		FOnDNSEvent pCallbackFunction;	/* Function to be called when the address has been found or when a timeout has beeen reached */
  		TimeOut_t xTimeoutState;
  		void *pvSearchID;
  		struct xLIST_ITEM xListItem;
  		char pcName[ 1 ];
  	} DNSCallback_t;
  
  	static List_t xCallbackList;
  
  	/* Define FreeRTOS_gethostbyname() as a normal blocking call. */
  	uint32_t FreeRTOS_gethostbyname( const char *pcHostName )
  	{
  		return FreeRTOS_gethostbyname_a( pcHostName, ( FOnDNSEvent ) NULL, ( void* )NULL, 0 );
  	}
  	/*-----------------------------------------------------------*/
  
  	/* Initialise the list of call-back structures. */
  	void vDNSInitialise( void );
  	void vDNSInitialise( void )
  	{
  		vListInitialise( &xCallbackList );
  	}
  	/*-----------------------------------------------------------*/
  
  	/* Iterate through the list of call-back structures and remove
  	old entries which have reached a timeout.
  	As soon as the list hase become empty, the DNS timer will be stopped
  	In case pvSearchID is supplied, the user wants to cancel a DNS request
  	*/
  	void vDNSCheckCallBack( void *pvSearchID );
  	void vDNSCheckCallBack( void *pvSearchID )
  	{
  	const ListItem_t *pxIterator;
  	const MiniListItem_t* xEnd = ( const MiniListItem_t* )listGET_END_MARKER( &xCallbackList );
  
  		vTaskSuspendAll();
  		{
  			for( pxIterator  = ( const ListItem_t * ) listGET_NEXT( xEnd );
  				 pxIterator != ( const ListItem_t * ) xEnd;
  				  )
  			{
  				DNSCallback_t *pxCallback = ( DNSCallback_t * ) listGET_LIST_ITEM_OWNER( pxIterator );
  				/* Move to the next item because we might remove this item */
  				pxIterator  = ( const ListItem_t * ) listGET_NEXT( pxIterator );
  				if( ( pvSearchID != NULL ) && ( pvSearchID == pxCallback->pvSearchID ) )
  				{
  					uxListRemove( &pxCallback->xListItem );
  					vPortFree( pxCallback );
  				}
  				else if( xTaskCheckForTimeOut( &pxCallback->xTimeoutState, &pxCallback->xRemaningTime ) != pdFALSE )
  				{
  					pxCallback->pCallbackFunction( pxCallback->pcName, pxCallback->pvSearchID, 0 );
  					uxListRemove( &pxCallback->xListItem );
  					vPortFree( ( void * ) pxCallback );
  				}
  			}
  		}
  		xTaskResumeAll();
  
  		if( listLIST_IS_EMPTY( &xCallbackList ) )
  		{
  			vIPSetDnsTimerEnableState( pdFALSE );
  		}
  	}
  	/*-----------------------------------------------------------*/
  
  	void FreeRTOS_gethostbyname_cancel( void *pvSearchID )
  	{
  		/* _HT_ Should better become a new API call to have the IP-task remove the callback */
  		vDNSCheckCallBack( pvSearchID );
  	}
  	/*-----------------------------------------------------------*/
  
  	/* FreeRTOS_gethostbyname_a() was called along with callback parameters.
  	Store them in a list for later reference. */
  	static void vDNSSetCallBack( const char *pcHostName, void *pvSearchID, FOnDNSEvent pCallbackFunction, TickType_t xTimeout, TickType_t xIdentifier );
  	static void vDNSSetCallBack( const char *pcHostName, void *pvSearchID, FOnDNSEvent pCallbackFunction, TickType_t xTimeout, TickType_t xIdentifier )
  	{
  		size_t lLength = strlen( pcHostName );
  		DNSCallback_t *pxCallback = ( DNSCallback_t * )pvPortMalloc( sizeof( *pxCallback ) + lLength );
  
  		/* Translate from ms to number of clock ticks. */
  		xTimeout /= portTICK_PERIOD_MS;
  		if( pxCallback != NULL )
  		{
  			if( listLIST_IS_EMPTY( &xCallbackList ) )
  			{
  				/* This is the first one, start the DNS timer to check for timeouts */
  				vIPReloadDNSTimer( FreeRTOS_min_uint32( 1000U, xTimeout ) );
  			}
  			strcpy( pxCallback->pcName, pcHostName );
  			pxCallback->pCallbackFunction = pCallbackFunction;
  			pxCallback->pvSearchID = pvSearchID;
  			pxCallback->xRemaningTime = xTimeout;
  			vTaskSetTimeOutState( &pxCallback->xTimeoutState );
  			listSET_LIST_ITEM_OWNER( &( pxCallback->xListItem ), ( void* ) pxCallback );
  			listSET_LIST_ITEM_VALUE( &( pxCallback->xListItem ), xIdentifier );
  			vTaskSuspendAll();
  			{
  				vListInsertEnd( &xCallbackList, &pxCallback->xListItem );
  			}
  			xTaskResumeAll();
  		}
  	}
  	/*-----------------------------------------------------------*/
  
  	/* A DNS reply was received, see if there is any matching entry and
  	call the handler. */
  	static void vDNSDoCallback( TickType_t xIdentifier, const char *pcName, uint32_t ulIPAddress );
  	static void vDNSDoCallback( TickType_t xIdentifier, const char *pcName, uint32_t ulIPAddress )
  	{
  		const ListItem_t *pxIterator;
  		const MiniListItem_t* xEnd = ( const MiniListItem_t* )listGET_END_MARKER( &xCallbackList );
  
  		vTaskSuspendAll();
  		{
  			for( pxIterator  = ( const ListItem_t * ) listGET_NEXT( xEnd );
  				 pxIterator != ( const ListItem_t * ) xEnd;
  				 pxIterator  = ( const ListItem_t * ) listGET_NEXT( pxIterator ) )
  			{
  				if( listGET_LIST_ITEM_VALUE( pxIterator ) == xIdentifier )
  				{
  					DNSCallback_t *pxCallback = ( DNSCallback_t * ) listGET_LIST_ITEM_OWNER( pxIterator );
  					pxCallback->pCallbackFunction( pcName, pxCallback->pvSearchID, ulIPAddress );
  					uxListRemove( &pxCallback->xListItem );
  					vPortFree( pxCallback );
  					if( listLIST_IS_EMPTY( &xCallbackList ) )
  					{
  						vIPSetDnsTimerEnableState( pdFALSE );
  					}
  					break;
  				}
  			}
  		}
  		xTaskResumeAll();
  	}
  
  #endif	/* ipconfigDNS_USE_CALLBACKS != 0 */
  /*-----------------------------------------------------------*/
  
  #if( ipconfigDNS_USE_CALLBACKS == 0 )
  uint32_t FreeRTOS_gethostbyname( const char *pcHostName )
  #else
  uint32_t FreeRTOS_gethostbyname_a( const char *pcHostName, FOnDNSEvent pCallback, void *pvSearchID, TickType_t xTimeout )
  #endif
  {
  uint32_t ulIPAddress = 0UL;
  TickType_t xReadTimeOut_ms = ipconfigSOCK_DEFAULT_RECEIVE_BLOCK_TIME;
  TickType_t xIdentifier = 0;
  
  	/* If the supplied hostname is IP address, convert it to uint32_t
  	and return. */
  	#if( ipconfigINCLUDE_FULL_INET_ADDR == 1 )
  	{
  		ulIPAddress = FreeRTOS_inet_addr( pcHostName );
  	}
  	#endif /* ipconfigINCLUDE_FULL_INET_ADDR == 1 */
  
  	/* If a DNS cache is used then check the cache before issuing another DNS
  	request. */
  	#if( ipconfigUSE_DNS_CACHE == 1 )
  	{
  		if( ulIPAddress == 0UL )
  		{
  			ulIPAddress = FreeRTOS_dnslookup( pcHostName );
  			if( ulIPAddress != 0 )
  			{
  				FreeRTOS_debug_printf( ( "FreeRTOS_gethostbyname: found '%s' in cache: %lxip\n", pcHostName, ulIPAddress ) );
  			}
  			else
  			{
  				/* prvGetHostByName will be called to start a DNS lookup */
  			}
  		}
  	}
  	#endif /* ipconfigUSE_DNS_CACHE == 1 */
  
  	/* Generate a unique identifier. */
  	if( 0 == ulIPAddress )
  	{
  		xIdentifier = ( TickType_t )ipconfigRAND32( );
  	}
  
  	#if( ipconfigDNS_USE_CALLBACKS != 0 )
  	{
  		if( pCallback != NULL )
  		{
  			if( ulIPAddress == 0UL )
  			{
  				/* The user has provided a callback function, so do not block on recvfrom() */
  				if( 0 != xIdentifier )
  				{
  					xReadTimeOut_ms = 0;
  					vDNSSetCallBack( pcHostName, pvSearchID, pCallback, xTimeout, ( TickType_t )xIdentifier );
  				}
  			}
  			else
  			{
  				/* The IP address is known, do the call-back now. */
  				pCallback( pcHostName, pvSearchID, ulIPAddress );
  			}
  		}
  	}
  	#endif
  
  	if( ( ulIPAddress == 0UL ) && ( 0 != xIdentifier ) )
  	{
  		ulIPAddress = prvGetHostByName( pcHostName, xIdentifier, xReadTimeOut_ms );
  	}
  
  	return ulIPAddress;
  }
  /*-----------------------------------------------------------*/
  
  static uint32_t prvGetHostByName( const char *pcHostName, TickType_t xIdentifier, TickType_t xReadTimeOut_ms )
  {
  struct freertos_sockaddr xAddress;
  Socket_t xDNSSocket;
  uint32_t ulIPAddress = 0UL;
  uint8_t *pucUDPPayloadBuffer;
  uint32_t ulAddressLength = sizeof( struct freertos_sockaddr );
  BaseType_t xAttempt;
  int32_t lBytes;
  size_t xPayloadLength, xExpectedPayloadLength;
  TickType_t xWriteTimeOut_ms = ipconfigSOCK_DEFAULT_SEND_BLOCK_TIME;
  
  #if( ipconfigUSE_LLMNR == 1 )
  	BaseType_t bHasDot = pdFALSE;
  #endif /* ipconfigUSE_LLMNR == 1 */
  
  	/* If LLMNR is being used then determine if the host name includes a '.' -
  	if not then LLMNR can be used as the lookup method. */
  	#if( ipconfigUSE_LLMNR == 1 )
  	{
  		const char *pucPtr;
  		for( pucPtr = pcHostName; *pucPtr; pucPtr++ )
  		{
  			if( *pucPtr == '.' )
  			{
  				bHasDot = pdTRUE;
  				break;
  			}
  		}
  	}
  	#endif /* ipconfigUSE_LLMNR == 1 */
  
  	/* Two is added at the end for the count of characters in the first
  	subdomain part and the string end byte. */
  	xExpectedPayloadLength = sizeof( DNSMessage_t ) + strlen( pcHostName ) + sizeof( uint16_t ) + sizeof( uint16_t ) + 2u;
  
  	xDNSSocket = prvCreateDNSSocket();
  
  	if( xDNSSocket != NULL )
  	{
  		FreeRTOS_setsockopt( xDNSSocket, 0, FREERTOS_SO_SNDTIMEO, ( void * ) &xWriteTimeOut_ms, sizeof( TickType_t ) );
  		FreeRTOS_setsockopt( xDNSSocket, 0, FREERTOS_SO_RCVTIMEO, ( void * ) &xReadTimeOut_ms,  sizeof( TickType_t ) );
  
  		for( xAttempt = 0; xAttempt < ipconfigDNS_REQUEST_ATTEMPTS; xAttempt++ )
  		{
  			/* Get a buffer.  This uses a maximum delay, but the delay will be
  			capped to ipconfigUDP_MAX_SEND_BLOCK_TIME_TICKS so the return value
  			still needs to be tested. */
  			pucUDPPayloadBuffer = ( uint8_t * ) FreeRTOS_GetUDPPayloadBuffer( xExpectedPayloadLength, portMAX_DELAY );
  
  			if( pucUDPPayloadBuffer != NULL )
  			{
  				/* Create the message in the obtained buffer. */
  				xPayloadLength = prvCreateDNSMessage( pucUDPPayloadBuffer, pcHostName, xIdentifier );
  
  				iptraceSENDING_DNS_REQUEST();
  
  				/* Obtain the DNS server address. */
  				FreeRTOS_GetAddressConfiguration( NULL, NULL, NULL, &ulIPAddress );
  
  				/* Send the DNS message. */
  #if( ipconfigUSE_LLMNR == 1 )
  				if( bHasDot == pdFALSE )
  				{
  					/* Use LLMNR addressing. */
  					( ( DNSMessage_t * ) pucUDPPayloadBuffer) -> usFlags = 0;
  					xAddress.sin_addr = ipLLMNR_IP_ADDR;	/* Is in network byte order. */
  					xAddress.sin_port = FreeRTOS_ntohs( ipLLMNR_PORT );
  				}
  				else
  #endif
  				{
  					/* Use DNS server. */
  					xAddress.sin_addr = ulIPAddress;
  					xAddress.sin_port = dnsDNS_PORT;
  				}
  
  				ulIPAddress = 0UL;
  
  				if( FreeRTOS_sendto( xDNSSocket, pucUDPPayloadBuffer, xPayloadLength, FREERTOS_ZERO_COPY, &xAddress, sizeof( xAddress ) ) != 0 )
  				{
  					/* Wait for the reply. */
  					lBytes = FreeRTOS_recvfrom( xDNSSocket, &pucUDPPayloadBuffer, 0, FREERTOS_ZERO_COPY, &xAddress, &ulAddressLength );
  
  					if( lBytes > 0 )
  					{
  						/* The reply was received.  Process it. */
  						ulIPAddress = prvParseDNSReply( pucUDPPayloadBuffer, lBytes, xIdentifier );
  
  						/* Finished with the buffer.  The zero copy interface
  						is being used, so the buffer must be freed by the
  						task. */
  						FreeRTOS_ReleaseUDPPayloadBuffer( ( void * ) pucUDPPayloadBuffer );
  
  						if( ulIPAddress != 0UL )
  						{
  							/* All done. */
  							break;
  						}
  					}
  				}
  				else
  				{
  					/* The message was not sent so the stack will not be
  					releasing the zero copy - it must be released here. */
  					FreeRTOS_ReleaseUDPPayloadBuffer( ( void * ) pucUDPPayloadBuffer );
  				}
  			}
  		}
  
  		/* Finished with the socket. */
  		FreeRTOS_closesocket( xDNSSocket );
  	}
  
  	return ulIPAddress;
  }
  /*-----------------------------------------------------------*/
  
  static size_t prvCreateDNSMessage( uint8_t *pucUDPPayloadBuffer, const char *pcHostName, TickType_t xIdentifier )
  {
  DNSMessage_t *pxDNSMessageHeader;
  uint8_t *pucStart, *pucByte;
  DNSTail_t *pxTail;
  static const DNSMessage_t xDefaultPartDNSHeader =
  {
  	0,					/* The identifier will be overwritten. */
  	dnsOUTGOING_FLAGS,	/* Flags set for standard query. */
  	dnsONE_QUESTION,	/* One question is being asked. */
  	0,					/* No replies are included. */
  	0,					/* No authorities. */
  	0					/* No additional authorities. */
  };
  
  	/* Copy in the const part of the header. */
  	memcpy( ( void * ) pucUDPPayloadBuffer, ( void * ) &xDefaultPartDNSHeader, sizeof( xDefaultPartDNSHeader ) );
  
  	/* Write in a unique identifier. */
  	pxDNSMessageHeader = ( DNSMessage_t * ) pucUDPPayloadBuffer;
  	pxDNSMessageHeader->usIdentifier = ( uint16_t ) xIdentifier;
  
  	/* Create the resource record at the end of the header.  First
  	find the end of the header. */
  	pucStart = pucUDPPayloadBuffer + sizeof( xDefaultPartDNSHeader );
  
  	/* Leave a gap for the first length bytes. */
  	pucByte = pucStart + 1;
  
  	/* Copy in the host name. */
  	strcpy( ( char * ) pucByte, pcHostName );
  
  	/* Mark the end of the string. */
  	pucByte += strlen( pcHostName );
  	*pucByte = 0x00u;
  
  	/* Walk the string to replace the '.' characters with byte counts.
  	pucStart holds the address of the byte count.  Walking the string
  	starts after the byte count position. */
  	pucByte = pucStart;
  
  	do
  	{
  		pucByte++;
  
  		while( ( *pucByte != 0x00 ) && ( *pucByte != '.' ) )
  		{
  			pucByte++;
  		}
  
  		/* Fill in the byte count, then move the pucStart pointer up to
  		the found byte position. */
  		*pucStart = ( uint8_t ) ( ( uint32_t ) pucByte - ( uint32_t ) pucStart );
  		( *pucStart )--;
  
  		pucStart = pucByte;
  
  	} while( *pucByte != 0x00 );
  
  	/* Finish off the record. */
  
  	pxTail = (DNSTail_t *)( pucByte + 1 );
  
  	vSetField16( pxTail, DNSTail_t, usType, dnsTYPE_A_HOST );	/* Type A: host */
  	vSetField16( pxTail, DNSTail_t, usClass, dnsCLASS_IN );	/* 1: Class IN */
  
  	/* Return the total size of the generated message, which is the space from
  	the last written byte to the beginning of the buffer. */
  	return ( ( uint32_t ) pucByte - ( uint32_t ) pucUDPPayloadBuffer + 1 ) + sizeof( *pxTail );
  }
  /*-----------------------------------------------------------*/
  
  #if( ipconfigUSE_DNS_CACHE == 1 )
  
  	static uint8_t *prvReadNameField( uint8_t *pucByte, size_t xSourceLen, char *pcName, size_t xDestLen )
  	{
  	size_t xNameLen = 0;
  	BaseType_t xCount;
  
  		if( 0 == xSourceLen )
  		{
  			return NULL;
  		}
  
  		/* Determine if the name is the fully coded name, or an offset to the name
  		elsewhere in the message. */
  		if( ( *pucByte & dnsNAME_IS_OFFSET ) == dnsNAME_IS_OFFSET )
  		{
  			/* Jump over the two byte offset. */
  			if( xSourceLen > sizeof( uint16_t ) )
  			{
  				pucByte += sizeof( uint16_t );
  			}
  			else
  			{
  				pucByte = NULL;
  			}
  		}
  		else
  		{
  			/* pucByte points to the full name. Walk over the string. */
  			while( ( NULL != pucByte ) && ( *pucByte != 0x00 ) && ( xSourceLen > 1 ) )
  			{
  				/* If this is not the first time through the loop, then add a
  				separator in the output. */
  				if( ( xNameLen > 0 ) && ( xNameLen < ( xDestLen - 1 ) ) )
  				{
  					pcName[ xNameLen++ ] = '.';
  				}
  
  				/* Process the first/next sub-string. */
  				for( xCount = *(pucByte++), xSourceLen--;
  					 xCount-- && xSourceLen > 1;
  					 pucByte++, xSourceLen-- )
  				{
  					if( xNameLen < xDestLen - 1 )
  					{
  						pcName[ xNameLen++ ] = *( ( char * )pucByte );
  					}
  					else
  					{
  						/* DNS name is too big for the provided buffer. */
  						pucByte = NULL;
  						break;
  					}
  				}
  			}
  
  			/* Confirm that a fully formed name was found. */
  			if( NULL != pucByte )
  			{
  				if( 0x00 == *pucByte )
  				{
  					pucByte++;
  					xSourceLen--;
  					pcName[ xNameLen++ ] = '\0';
  				}
  				else
  				{
  					pucByte = NULL;
  				}
  			}
  		}
  
  		return pucByte;
  	}
  #endif	/* ipconfigUSE_DNS_CACHE == 1 */
  /*-----------------------------------------------------------*/
  
  static uint8_t *prvSkipNameField( uint8_t *pucByte, size_t xSourceLen )
  {
  	size_t xChunkLength;
  
  	if( 0 == xSourceLen )
  	{
  		return NULL;
  	}
  
  	/* Determine if the name is the fully coded name, or an offset to the name
  	elsewhere in the message. */
  	if( ( *pucByte & dnsNAME_IS_OFFSET ) == dnsNAME_IS_OFFSET )
  	{
  		/* Jump over the two byte offset. */
  		if( xSourceLen > sizeof( uint16_t ) )
  		{
  			pucByte += sizeof( uint16_t );
  		}
  		else
  		{
  			pucByte = NULL;
  		}
  	}
  	else
  	{
  		/* pucByte points to the full name. Walk over the string. */
  		while( ( *pucByte != 0x00 ) && ( xSourceLen > 1 ) )
  		{
  			xChunkLength = *pucByte + 1;
  
  			if( xSourceLen > xChunkLength )
  			{
  				xSourceLen -= xChunkLength;
  				pucByte += xChunkLength;
  			}
  			else
  			{
  				pucByte = NULL;
  				break;
  			}
  		}
  
  		/* Confirm that a fully formed name was found. */
  		if( NULL != pucByte )
  		{
  			if( 0x00 == *pucByte )
  			{
  				pucByte++;
  			}
  			else
  			{
  				pucByte = NULL;
  			}
  		}
  	}
  
  	return pucByte;
  }
  /*-----------------------------------------------------------*/
  
  uint32_t ulDNSHandlePacket( NetworkBufferDescriptor_t *pxNetworkBuffer )
  {
  uint8_t *pucUDPPayloadBuffer;
  size_t xPlayloadBufferLength;
  DNSMessage_t *pxDNSMessageHeader;
  
  	xPlayloadBufferLength = pxNetworkBuffer->xDataLength - sizeof( UDPPacket_t );
  	if ( xPlayloadBufferLength < sizeof( DNSMessage_t ) )
  	{
  		return pdFAIL;
  	}
  
  	pucUDPPayloadBuffer = pxNetworkBuffer->pucEthernetBuffer + sizeof( UDPPacket_t );
  	pxDNSMessageHeader = ( DNSMessage_t * ) pucUDPPayloadBuffer;
  
  	if( pxNetworkBuffer->xDataLength > sizeof( UDPPacket_t ) )
  	{
  		prvParseDNSReply( pucUDPPayloadBuffer,
  			xPlayloadBufferLength,
  			( uint32_t )pxDNSMessageHeader->usIdentifier );
  	}
  
  	/* The packet was not consumed. */
  	return pdFAIL;
  }
  /*-----------------------------------------------------------*/
  
  #if( ipconfigUSE_NBNS == 1 )
  
  	uint32_t ulNBNSHandlePacket (NetworkBufferDescriptor_t *pxNetworkBuffer )
  	{
  	UDPPacket_t *pxUDPPacket = ( UDPPacket_t * ) pxNetworkBuffer->pucEthernetBuffer;
  	uint8_t *pucUDPPayloadBuffer = pxNetworkBuffer->pucEthernetBuffer + sizeof( UDPPacket_t );
  
  		if( pxNetworkBuffer->xDataLength > sizeof( UDPPacket_t) )
  		{
  			prvTreatNBNS( pucUDPPayloadBuffer,
  						  pxNetworkBuffer->xDataLength - sizeof( UDPPacket_t ),
  						  pxUDPPacket->xIPHeader.ulSourceIPAddress );
  		}
  
  		/* The packet was not consumed. */
  		return pdFAIL;
  	}
  
  #endif /* ipconfigUSE_NBNS */
  /*-----------------------------------------------------------*/
  
  static uint32_t prvParseDNSReply( uint8_t *pucUDPPayloadBuffer, size_t xBufferLength, TickType_t xIdentifier )
  {
  DNSMessage_t *pxDNSMessageHeader;
  DNSAnswerRecord_t *pxDNSAnswerRecord;
  uint32_t ulIPAddress = 0UL;
  #if( ipconfigUSE_LLMNR == 1 )
  	char *pcRequestedName = NULL;
  #endif
  uint8_t *pucByte;
  size_t xSourceBytesRemaining;
  uint16_t x, usDataLength, usQuestions;
  #if( ipconfigUSE_LLMNR == 1 )
  	uint16_t usType = 0, usClass = 0;
  #endif
  #if( ipconfigUSE_DNS_CACHE == 1 )
  	char pcName[ ipconfigDNS_CACHE_NAME_LENGTH ] = "";
  #endif
  
  	/* Ensure that the buffer is of at least minimal DNS message length. */
  	if( xBufferLength < sizeof( DNSMessage_t ) )
  	{
  		return dnsPARSE_ERROR;
  	}
  	else
  	{
  		xSourceBytesRemaining = xBufferLength;
  	}
  
  	/* Parse the DNS message header. */
  	pxDNSMessageHeader = ( DNSMessage_t * ) pucUDPPayloadBuffer;
  
  	if( pxDNSMessageHeader->usIdentifier == ( uint16_t ) xIdentifier )
  	{
  		/* Start at the first byte after the header. */
  		pucByte = pucUDPPayloadBuffer + sizeof( DNSMessage_t );
  		xSourceBytesRemaining -= sizeof( DNSMessage_t );
  
  		/* Skip any question records. */
  		usQuestions = FreeRTOS_ntohs( pxDNSMessageHeader->usQuestions );
  		for( x = 0; x < usQuestions; x++ )
  		{
  			#if( ipconfigUSE_LLMNR == 1 )
  			{
  				if( x == 0 )
  				{
  					pcRequestedName = ( char * ) pucByte;
  				}
  			}
  			#endif
  
  #if( ipconfigUSE_DNS_CACHE == 1 )
  			if( x == 0 )
  			{
  				pucByte = prvReadNameField( pucByte,
  											xSourceBytesRemaining,
  											pcName,
  											sizeof( pcName ) );
  
  				/* Check for a malformed response. */
  				if( NULL == pucByte )
  				{
  					return dnsPARSE_ERROR;
  				}
  				else
  				{
  					xSourceBytesRemaining = ( pucUDPPayloadBuffer + xBufferLength ) - pucByte;
  				}
  			}
  			else
  #endif /* ipconfigUSE_DNS_CACHE */
  			{
  				/* Skip the variable length pcName field. */
  				pucByte = prvSkipNameField( pucByte,
  											xSourceBytesRemaining );
  
  				/* Check for a malformed response. */
  				if( NULL == pucByte )
  				{
  					return dnsPARSE_ERROR;
  				}
  				else
  				{
  					xSourceBytesRemaining = pucUDPPayloadBuffer + xBufferLength - pucByte;
  				}
  			}
  
  			/* Check the remaining buffer size. */
  			if( xSourceBytesRemaining >= sizeof( uint32_t ) )
  			{
  				#if( ipconfigUSE_LLMNR == 1 )
  				{
  					/* usChar2u16 returns value in host endianness */
  					usType = usChar2u16( pucByte );
  					usClass = usChar2u16( pucByte + 2 );
  				}
  				#endif /* ipconfigUSE_LLMNR */
  
  				/* Skip the type and class fields. */
  				pucByte += sizeof( uint32_t );
  				xSourceBytesRemaining -= sizeof( uint32_t );
  			}
  			else
  			{
  				/* Malformed response. */
  				return dnsPARSE_ERROR;
  			}
  		}
  
  		/* Search through the answer records. */
  		pxDNSMessageHeader->usAnswers = FreeRTOS_ntohs( pxDNSMessageHeader->usAnswers );
  
  		if( ( pxDNSMessageHeader->usFlags & dnsRX_FLAGS_MASK ) == dnsEXPECTED_RX_FLAGS )
  		{
  			for( x = 0; x < pxDNSMessageHeader->usAnswers; x++ )
  			{
  				pucByte = prvSkipNameField( pucByte,
  											xSourceBytesRemaining );
  
  				/* Check for a malformed response. */
  				if( NULL == pucByte )
  				{
  					return dnsPARSE_ERROR;
  				}
  				else
  				{
  					xSourceBytesRemaining = pucUDPPayloadBuffer + xBufferLength - pucByte;
  				}
  
  				/* Is there enough data for an IPv4 A record answer and, if so,
  				is this an A record? */
  				if( xSourceBytesRemaining >= sizeof( DNSAnswerRecord_t ) + sizeof( uint32_t ) &&
  					usChar2u16( pucByte ) == dnsTYPE_A_HOST )
  				{
  					/* This is the required record type and is of sufficient size. */
  					pxDNSAnswerRecord = ( DNSAnswerRecord_t * )pucByte;
  
  					/* Sanity check the data length of an IPv4 answer. */
  					if( FreeRTOS_ntohs( pxDNSAnswerRecord->usDataLength ) == sizeof( uint32_t ) )
  					{
  						/* Copy the IP address out of the record. */
  						memcpy( &ulIPAddress,
  								pucByte + sizeof( DNSAnswerRecord_t ),
  								sizeof( uint32_t ) );
  
  						#if( ipconfigUSE_DNS_CACHE == 1 )
  						{
  							prvProcessDNSCache( pcName, &ulIPAddress, pxDNSAnswerRecord->ulTTL, pdFALSE );
  						}
  						#endif /* ipconfigUSE_DNS_CACHE */
  						#if( ipconfigDNS_USE_CALLBACKS != 0 )
  						{
  							/* See if any asynchronous call was made to FreeRTOS_gethostbyname_a() */
  							vDNSDoCallback( ( TickType_t ) pxDNSMessageHeader->usIdentifier, pcName, ulIPAddress );
  						}
  						#endif	/* ipconfigDNS_USE_CALLBACKS != 0 */
  					}
  
  					pucByte += sizeof( DNSAnswerRecord_t ) + sizeof( uint32_t );
  					xSourceBytesRemaining -= ( sizeof( DNSAnswerRecord_t ) + sizeof( uint32_t ) );
  					break;
  				}
  				else if( xSourceBytesRemaining >= sizeof( DNSAnswerRecord_t ) )
  				{
  					/* It's not an A record, so skip it. Get the header location
  					and then jump over the header. */
  					pxDNSAnswerRecord = ( DNSAnswerRecord_t * )pucByte;
  					pucByte += sizeof( DNSAnswerRecord_t );
  					xSourceBytesRemaining -= sizeof( DNSAnswerRecord_t );
  
  					/* Determine the length of the answer data from the header. */
  					usDataLength = FreeRTOS_ntohs( pxDNSAnswerRecord->usDataLength );
  
  					/* Jump over the answer. */
  					if( xSourceBytesRemaining >= usDataLength )
  					{
  						pucByte += usDataLength;
  						xSourceBytesRemaining -= usDataLength;
  					}
  					else
  					{
  						/* Malformed response. */
  						return dnsPARSE_ERROR;
  					}
  				}
  			}
  		}
  #if( ipconfigUSE_LLMNR == 1 )
  		else if( usQuestions && ( usType == dnsTYPE_A_HOST ) && ( usClass == dnsCLASS_IN ) )
  		{
  			/* If this is not a reply to our DNS request, it might an LLMNR
  			request. */
  			if( xApplicationDNSQueryHook ( ( pcRequestedName + 1 ) ) )
  			{
  			int16_t usLength;
  			NetworkBufferDescriptor_t *pxNewBuffer = NULL;
  			NetworkBufferDescriptor_t *pxNetworkBuffer = pxUDPPayloadBuffer_to_NetworkBuffer( pucUDPPayloadBuffer );
  			LLMNRAnswer_t *pxAnswer;
  
  				if( ( xBufferAllocFixedSize == pdFALSE ) && ( pxNetworkBuffer != NULL ) )
  				{
  				BaseType_t xDataLength = xBufferLength + sizeof( UDPHeader_t ) + sizeof( EthernetHeader_t ) + sizeof( IPHeader_t );
  
  					/* The field xDataLength was set to the length of the UDP payload.
  					The answer (reply) will be longer than the request, so the packet
  					must be duplicaed into a bigger buffer */
  					pxNetworkBuffer->xDataLength = xDataLength;
  					pxNewBuffer = pxDuplicateNetworkBufferWithDescriptor( pxNetworkBuffer, xDataLength + 16 );
  					if( pxNewBuffer != NULL )
  					{
  					BaseType_t xOffset1, xOffset2;
  
  						xOffset1 = ( BaseType_t ) ( pucByte - pucUDPPayloadBuffer );
  						xOffset2 = ( BaseType_t ) ( ( ( uint8_t * ) pcRequestedName ) - pucUDPPayloadBuffer );
  
  						pxNetworkBuffer = pxNewBuffer;
  						pucUDPPayloadBuffer = pxNetworkBuffer->pucEthernetBuffer + ipUDP_PAYLOAD_OFFSET_IPv4;
  
  						pucByte = pucUDPPayloadBuffer + xOffset1;
  						pcRequestedName = ( char * ) ( pucUDPPayloadBuffer + xOffset2 );
  						pxDNSMessageHeader = ( DNSMessage_t * ) pucUDPPayloadBuffer;
  
  					}
  					else
  					{
  						/* Just to indicate that the message may not be answered. */
  						pxNetworkBuffer = NULL;
  					}
  				}
  				if( pxNetworkBuffer != NULL )
  				{
  					pxAnswer = (LLMNRAnswer_t *)pucByte;
  
  					/* We leave 'usIdentifier' and 'usQuestions' untouched */
  					vSetField16( pxDNSMessageHeader, DNSMessage_t, usFlags, dnsLLMNR_FLAGS_IS_REPONSE );	/* Set the response flag */
  					vSetField16( pxDNSMessageHeader, DNSMessage_t, usAnswers, 1 );	/* Provide a single answer */
  					vSetField16( pxDNSMessageHeader, DNSMessage_t, usAuthorityRRs, 0 );	/* No authority */
  					vSetField16( pxDNSMessageHeader, DNSMessage_t, usAdditionalRRs, 0 );	/* No additional info */
  
  					pxAnswer->ucNameCode = dnsNAME_IS_OFFSET;
  					pxAnswer->ucNameOffset = ( uint8_t )( pcRequestedName - ( char * ) pucUDPPayloadBuffer );
  
  					vSetField16( pxAnswer, LLMNRAnswer_t, usType, dnsTYPE_A_HOST );	/* Type A: host */
  					vSetField16( pxAnswer, LLMNRAnswer_t, usClass, dnsCLASS_IN );	/* 1: Class IN */
  					vSetField32( pxAnswer, LLMNRAnswer_t, ulTTL, dnsLLMNR_TTL_VALUE );
  					vSetField16( pxAnswer, LLMNRAnswer_t, usDataLength, 4 );
  					vSetField32( pxAnswer, LLMNRAnswer_t, ulIPAddress, FreeRTOS_ntohl( *ipLOCAL_IP_ADDRESS_POINTER ) );
  
  					usLength = ( int16_t ) ( sizeof( *pxAnswer ) + ( size_t ) ( pucByte - pucUDPPayloadBuffer ) );
  
  					prvReplyDNSMessage( pxNetworkBuffer, usLength );
  
  					if( pxNewBuffer != NULL )
  					{
  						vReleaseNetworkBufferAndDescriptor( pxNewBuffer );
  					}
  				}
  			}
  		}
  #endif /* ipconfigUSE_LLMNR == 1 */
  	}
  
  	return ulIPAddress;
  }
  /*-----------------------------------------------------------*/
  
  #if( ipconfigUSE_NBNS == 1 )
  
  	static void prvTreatNBNS( uint8_t *pucUDPPayloadBuffer, size_t xBufferLength, uint32_t ulIPAddress )
  	{
  		uint16_t usFlags, usType, usClass;
  		uint8_t *pucSource, *pucTarget;
  		uint8_t ucByte;
  		uint8_t ucNBNSName[ 17 ];
  
  		/* Check for minimum buffer size. */
  		if( xBufferLength < sizeof( NBNSRequest_t ) )
  		{
  			return;
  		}
  
  		/* Read the request flags in host endianness. */
  		usFlags = usChar2u16( pucUDPPayloadBuffer + offsetof( NBNSRequest_t, usFlags ) );
  
  		if( ( usFlags & dnsNBNS_FLAGS_OPCODE_MASK ) == dnsNBNS_FLAGS_OPCODE_QUERY )
  		{
  			usType  = usChar2u16( pucUDPPayloadBuffer + offsetof( NBNSRequest_t, usType ) );
  			usClass = usChar2u16( pucUDPPayloadBuffer + offsetof( NBNSRequest_t, usClass ) );
  
  			/* Not used for now */
  			( void )usClass;
  			/* For NBNS a name is 16 bytes long, written with capitals only.
  			Make sure that the copy is terminated with a zero. */
  			pucTarget = ucNBNSName + sizeof(ucNBNSName ) - 2;
  			pucTarget[ 1 ] = '\0';
  
  			/* Start with decoding the last 2 bytes. */
  			pucSource = pucUDPPayloadBuffer + ( offsetof( NBNSRequest_t, ucName ) + ( dnsNBNS_ENCODED_NAME_LENGTH - 2 ) );
  
  			for( ;; )
  			{
  				ucByte = ( uint8_t ) ( ( ( pucSource[ 0 ] - 0x41 ) << 4 ) | ( pucSource[ 1 ] - 0x41 ) );
  
  				/* Make sure there are no trailing spaces in the name. */
  				if( ( ucByte == ' ' ) && ( pucTarget[ 1 ] == '\0' ) )
  				{
  					ucByte = '\0';
  				}
  
  				*pucTarget = ucByte;
  
  				if( pucTarget == ucNBNSName )
  				{
  					break;
  				}
  
  				pucTarget -= 1;
  				pucSource -= 2;
  			}
  
  			#if( ipconfigUSE_DNS_CACHE == 1 )
  			{
  				if( ( usFlags & dnsNBNS_FLAGS_RESPONSE ) != 0 )
  				{
  					/* If this is a response from another device,
  					add the name to the DNS cache */
  					prvProcessDNSCache( ( char * ) ucNBNSName, &ulIPAddress, 0, pdFALSE );
  				}
  			}
  			#else
  			{
  				/* Avoid compiler warnings. */
  				( void ) ulIPAddress;
  			}
  			#endif /* ipconfigUSE_DNS_CACHE */
  
  			if( ( ( usFlags & dnsNBNS_FLAGS_RESPONSE ) == 0 ) &&
  				( usType == dnsNBNS_TYPE_NET_BIOS ) &&
  				( xApplicationDNSQueryHook( ( const char * ) ucNBNSName ) != pdFALSE ) )
  			{
  			uint16_t usLength;
  			DNSMessage_t *pxMessage;
  			NBNSAnswer_t *pxAnswer;
  
  				/* Someone is looking for a device with ucNBNSName,
  				prepare a positive reply. */
  				NetworkBufferDescriptor_t *pxNetworkBuffer = pxUDPPayloadBuffer_to_NetworkBuffer( pucUDPPayloadBuffer );
  
  				if( ( xBufferAllocFixedSize == pdFALSE ) && ( pxNetworkBuffer != NULL ) )
  				{
  				NetworkBufferDescriptor_t *pxNewBuffer;
  				BaseType_t xDataLength = pxNetworkBuffer->xDataLength + sizeof( UDPHeader_t ) +
  					sizeof( EthernetHeader_t ) + sizeof( IPHeader_t );
  
  					/* The field xDataLength was set to the length of the UDP payload.
  					The answer (reply) will be longer than the request, so the packet
  					must be duplicated into a bigger buffer */
  					pxNetworkBuffer->xDataLength = xDataLength;
  					pxNewBuffer = pxDuplicateNetworkBufferWithDescriptor( pxNetworkBuffer, xDataLength + 16 );
  					if( pxNewBuffer != NULL )
  					{
  						pucUDPPayloadBuffer = pxNewBuffer->pucEthernetBuffer + sizeof( UDPPacket_t );
  						pxNetworkBuffer = pxNewBuffer;
  					}
  					else
  					{
  						/* Just prevent that a reply will be sent */
  						pxNetworkBuffer = NULL;
  					}
  				}
  
  				/* Should not occur: pucUDPPayloadBuffer is part of a xNetworkBufferDescriptor */
  				if( pxNetworkBuffer != NULL )
  				{
  					pxMessage = (DNSMessage_t *)pucUDPPayloadBuffer;
  
  					/* As the fields in the structures are not word-aligned, we have to
  					copy the values byte-by-byte using macro's vSetField16() and vSetField32() */
  					vSetField16( pxMessage, DNSMessage_t, usFlags, dnsNBNS_QUERY_RESPONSE_FLAGS ); /* 0x8500 */
  					vSetField16( pxMessage, DNSMessage_t, usQuestions, 0 );
  					vSetField16( pxMessage, DNSMessage_t, usAnswers, 1 );
  					vSetField16( pxMessage, DNSMessage_t, usAuthorityRRs, 0 );
  					vSetField16( pxMessage, DNSMessage_t, usAdditionalRRs, 0 );
  
  					pxAnswer = (NBNSAnswer_t *)( pucUDPPayloadBuffer + offsetof( NBNSRequest_t, usType ) );
  
  					vSetField16( pxAnswer, NBNSAnswer_t, usType, usType );	/* Type */
  					vSetField16( pxAnswer, NBNSAnswer_t, usClass, dnsNBNS_CLASS_IN );	/* Class */
  					vSetField32( pxAnswer, NBNSAnswer_t, ulTTL, dnsNBNS_TTL_VALUE );
  					vSetField16( pxAnswer, NBNSAnswer_t, usDataLength, 6 ); /* 6 bytes including the length field */
  					vSetField16( pxAnswer, NBNSAnswer_t, usNbFlags, dnsNBNS_NAME_FLAGS );
  					vSetField32( pxAnswer, NBNSAnswer_t, ulIPAddress, FreeRTOS_ntohl( *ipLOCAL_IP_ADDRESS_POINTER ) );
  
  					usLength = ( uint16_t ) ( offsetof( NBNSRequest_t, usType ) + sizeof( NBNSAnswer_t ) );
  
  					prvReplyDNSMessage( pxNetworkBuffer, usLength );
  				}
  			}
  		}
  	}
  
  #endif	/* ipconfigUSE_NBNS */
  /*-----------------------------------------------------------*/
  
  static Socket_t prvCreateDNSSocket( void )
  {
  Socket_t xSocket = NULL;
  struct freertos_sockaddr xAddress;
  BaseType_t xReturn;
  TickType_t xTimeoutTime = pdMS_TO_TICKS( 200 );
  
  	/* This must be the first time this function has been called.  Create
  	the socket. */
  	xSocket = FreeRTOS_socket( FREERTOS_AF_INET, FREERTOS_SOCK_DGRAM, FREERTOS_IPPROTO_UDP );
  
  	/* Auto bind the port. */
  	xAddress.sin_port = 0u;
  	xReturn = FreeRTOS_bind( xSocket, &xAddress, sizeof( xAddress ) );
  
  	/* Check the bind was successful, and clean up if not. */
  	if( xReturn != 0 )
  	{
  		FreeRTOS_closesocket( xSocket );
  		xSocket = NULL;
  	}
  	else
  	{
  		/* Set the send and receive timeouts. */
  		FreeRTOS_setsockopt( xSocket, 0, FREERTOS_SO_RCVTIMEO, ( void * ) &xTimeoutTime, sizeof( TickType_t ) );
  		FreeRTOS_setsockopt( xSocket, 0, FREERTOS_SO_SNDTIMEO, ( void * ) &xTimeoutTime, sizeof( TickType_t ) );
  	}
  
  	return xSocket;
  }
  /*-----------------------------------------------------------*/
  
  #if( ( ipconfigUSE_NBNS == 1 ) || ( ipconfigUSE_LLMNR == 1 ) )
  
  	static void prvReplyDNSMessage( NetworkBufferDescriptor_t *pxNetworkBuffer, BaseType_t lNetLength )
  	{
  	UDPPacket_t *pxUDPPacket;
  	IPHeader_t *pxIPHeader;
  	UDPHeader_t *pxUDPHeader;
  
  		pxUDPPacket = (UDPPacket_t *) pxNetworkBuffer->pucEthernetBuffer;
  		pxIPHeader = &pxUDPPacket->xIPHeader;
  		pxUDPHeader = &pxUDPPacket->xUDPHeader;
  		/* HT: started using defines like 'ipSIZE_OF_xxx' */
  		pxIPHeader->usLength			   = FreeRTOS_htons( lNetLength + ipSIZE_OF_IPv4_HEADER + ipSIZE_OF_UDP_HEADER );
  		/* HT:endian: should not be translated, copying from packet to packet */
  		pxIPHeader->ulDestinationIPAddress = pxIPHeader->ulSourceIPAddress;
  		pxIPHeader->ulSourceIPAddress	   = *ipLOCAL_IP_ADDRESS_POINTER;
  		pxIPHeader->ucTimeToLive		   = ipconfigUDP_TIME_TO_LIVE;
  		pxIPHeader->usIdentification	   = FreeRTOS_htons( usPacketIdentifier );
  		usPacketIdentifier++;
  		pxUDPHeader->usLength			   = FreeRTOS_htons( lNetLength + ipSIZE_OF_UDP_HEADER );
  		vFlip_16( pxUDPPacket->xUDPHeader.usSourcePort, pxUDPPacket->xUDPHeader.usDestinationPort );
  
  		#if( ipconfigDRIVER_INCLUDED_TX_IP_CHECKSUM == 0 )
  		{
  			/* calculate the IP header checksum */
  			pxIPHeader->usHeaderChecksum	   = 0x00;
  			pxIPHeader->usHeaderChecksum	   = usGenerateChecksum( 0UL, ( uint8_t * ) &( pxIPHeader->ucVersionHeaderLength ), ipSIZE_OF_IPv4_HEADER );
  			pxIPHeader->usHeaderChecksum	   = ~FreeRTOS_htons( pxIPHeader->usHeaderChecksum );
  
  			/* calculate the UDP checksum for outgoing package */
  			usGenerateProtocolChecksum( ( uint8_t* ) pxUDPPacket, lNetLength, pdTRUE );
  		}
  		#endif
  
  		/* Important: tell NIC driver how many bytes must be sent */
  		pxNetworkBuffer->xDataLength = ( size_t ) ( lNetLength + ipSIZE_OF_IPv4_HEADER + ipSIZE_OF_UDP_HEADER + ipSIZE_OF_ETH_HEADER );
  
  		/* This function will fill in the eth addresses and send the packet */
  		vReturnEthernetFrame( pxNetworkBuffer, pdFALSE );
  	}
  
  #endif /* ipconfigUSE_NBNS == 1 || ipconfigUSE_LLMNR == 1 */
  /*-----------------------------------------------------------*/
  
  #if( ipconfigUSE_DNS_CACHE == 1 )
  
  	static void prvProcessDNSCache( const char *pcName, uint32_t *pulIP, uint32_t ulTTL, BaseType_t xLookUp )
  	{
  	BaseType_t x;
  	BaseType_t xFound = pdFALSE;
  	uint32_t ulCurrentTimeSeconds = ( xTaskGetTickCount() / portTICK_PERIOD_MS ) / 1000;
  	static BaseType_t xFreeEntry = 0;
  
  		/* For each entry in the DNS cache table. */
  		for( x = 0; x < ipconfigDNS_CACHE_ENTRIES; x++ )
  		{
  			if( xDNSCache[ x ].pcName[ 0 ] == 0 )
  			{
  				continue;
  			}
  
  			if( 0 == strcmp( xDNSCache[ x ].pcName, pcName ) )
  			{
  				/* Is this function called for a lookup or to add/update an IP address? */
  				if( xLookUp != pdFALSE )
  				{
  					/* Confirm that the record is still fresh. */
  					if( ulCurrentTimeSeconds < ( xDNSCache[ x ].ulTimeWhenAddedInSeconds + FreeRTOS_ntohl( xDNSCache[ x ].ulTTL ) ) )
  					{
  						*pulIP = xDNSCache[ x ].ulIPAddress;
  					}
  					else
  					{
  						/* Age out the old cached record. */
  						xDNSCache[ x ].pcName[ 0 ] = 0;
  					}
  				}
  				else
  				{
  					xDNSCache[ x ].ulIPAddress = *pulIP;
  					xDNSCache[ x ].ulTTL = ulTTL;
  					xDNSCache[ x ].ulTimeWhenAddedInSeconds = ulCurrentTimeSeconds;
  				}
  
  				xFound = pdTRUE;
  				break;
  			}
  		}
  
  		if( xFound == pdFALSE )
  		{
  			if( xLookUp != pdFALSE )
  			{
  				*pulIP = 0;
  			}
  			else
  			{
  				/* Add or update the item. */
  				if( strlen( pcName ) < ipconfigDNS_CACHE_NAME_LENGTH )
  				{
  					strcpy( xDNSCache[ xFreeEntry ].pcName, pcName );
  
  					xDNSCache[ xFreeEntry ].ulIPAddress = *pulIP;
  					xDNSCache[ xFreeEntry ].ulTTL = ulTTL;
  					xDNSCache[ xFreeEntry ].ulTimeWhenAddedInSeconds = ulCurrentTimeSeconds;
  
  					xFreeEntry++;
  					if( xFreeEntry == ipconfigDNS_CACHE_ENTRIES )
  					{
  						xFreeEntry = 0;
  					}
  				}
  			}
  		}
  
  		if( ( xLookUp == 0 ) || ( *pulIP != 0 ) )
  		{
  			FreeRTOS_debug_printf( ( "prvProcessDNSCache: %s: '%s' @ %lxip\n", xLookUp ? "look-up" : "add", pcName, FreeRTOS_ntohl( *pulIP ) ) );
  		}
  	}
  
  #endif /* ipconfigUSE_DNS_CACHE */
  
  #endif /* ipconfigUSE_DNS != 0 */
  
  /*-----------------------------------------------------------*/
  
  /* Provide access to private members for testing. */
  #ifdef AMAZON_FREERTOS_ENABLE_UNIT_TESTS
  	#include "aws_freertos_tcp_test_access_dns_define.h"
  #endif
  
  