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FreeRTOS_DNS.c
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FreeRTOS_DNS.c
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/*
* FreeRTOS+TCP V2.3.3
* Copyright (C) 2020 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
*/
/**
* @file FreeRTOS_DNS.c
* @brief Implements the Domain Name System for the FreeRTOS+TCP network stack.
*/
/* Standard includes. */
#include <stdint.h>
#include <stdio.h>
/* FreeRTOS includes. */
#include "FreeRTOS.h"
#include "task.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 "FreeRTOS_DHCP.h"
#include "NetworkBufferManagement.h"
#include "NetworkInterface.h"
/* Exclude the entire file if DNS is not enabled. */
#if ( ipconfigUSE_DNS != 0 )
/*
* 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 uxIdentifier );
/*
* Simple routine that jumps over the NAME field of a resource record.
* It returns the number of bytes read.
*/
_static size_t prvSkipNameField( const uint8_t * pucByte,
size_t uxLength );
/*
* Process a response packet from a DNS server.
* The parameter 'xExpected' indicates whether the identifier in the reply
* was expected, and thus if the DNS cache may be updated with the reply.
*/
_static uint32_t prvParseDNSReply( uint8_t * pucUDPPayloadBuffer,
size_t uxBufferLength,
BaseType_t xExpected );
/*
* Check if hostname is already known. If not, call prvGetHostByName() to send a DNS request.
*/
#if ( ipconfigDNS_USE_CALLBACKS == 1 )
static uint32_t prvPrepareLookup( const char * pcHostName,
FOnDNSEvent pCallback,
void * pvSearchID,
TickType_t uxTimeout );
#else
static uint32_t prvPrepareLookup( const char * pcHostName );
#endif
/*
* Prepare and send a message to a DNS server. 'uxReadTimeOut_ticks' will be passed as
* zero, in case the user has supplied a call-back function.
*/
static uint32_t prvGetHostByName( const char * pcHostName,
TickType_t uxIdentifier,
TickType_t uxReadTimeOut_ticks );
#if ( ipconfigDNS_USE_CALLBACKS != 0 )
static void vDNSSetCallBack( const char * pcHostName,
void * pvSearchID,
FOnDNSEvent pCallbackFunction,
TickType_t uxTimeout,
TickType_t uxIdentifier );
#endif /* ipconfigDNS_USE_CALLBACKS */
#if ( ipconfigDNS_USE_CALLBACKS != 0 )
static BaseType_t xDNSDoCallback( TickType_t uxIdentifier,
const char * pcName,
uint32_t ulIPAddress );
#endif /* ipconfigDNS_USE_CALLBACKS */
/*
* 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 * pucPayload,
size_t uxBufferLength,
uint32_t ulIPAddress );
#endif /* ipconfigUSE_NBNS */
#if ( ipconfigUSE_DNS_CACHE == 1 ) || ( ipconfigDNS_USE_CALLBACKS == 1 )
_static size_t prvReadNameField( const uint8_t * pucByte,
size_t uxRemainingBytes,
char * pcName,
size_t uxDestLen );
#endif /* ipconfigUSE_DNS_CACHE || ipconfigDNS_USE_CALLBACKS */
#if ( ipconfigUSE_DNS_CACHE == 1 )
static BaseType_t prvProcessDNSCache( const char * pcName,
uint32_t * pulIP,
uint32_t ulTTL,
BaseType_t xLookUp );
_static DNSCacheRow_t xDNSCache[ ipconfigDNS_CACHE_ENTRIES ];
/* Utility function: Clear DNS cache by calling this function. */
void FreeRTOS_dnsclear( void )
{
( void ) memset( xDNSCache, 0x0, sizeof( xDNSCache ) );
}
#endif /* ipconfigUSE_DNS_CACHE == 1 */
#if ( ipconfigUSE_LLMNR == 1 )
/** @brief The MAC address used for LLMNR. */
const MACAddress_t xLLMNR_MacAdress = { { 0x01, 0x00, 0x5e, 0x00, 0x00, 0xfc } };
#endif /* ipconfigUSE_LLMNR == 1 */
/*-----------------------------------------------------------*/
/**
* @brief Utility function to cast pointer of a type to pointer of type DNSMessage_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( DNSMessage_t )
{
return ( DNSMessage_t * ) pvArgument;
}
/**
* @brief Utility function to cast a const pointer of a type to a const pointer of type DNSMessage_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_CONST_PTR_FUNC_FOR_TYPE( DNSMessage_t )
{
return ( const DNSMessage_t * ) pvArgument;
}
/* 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; /**< Type of DNS message. */
uint16_t usClass; /**< Class of DNS message. */
}
#include "pack_struct_end.h"
typedef struct xDNSTail DNSTail_t;
/**
* @brief Utility function to cast pointer of a type to pointer of type DNSTail_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( DNSTail_t )
{
return ( DNSTail_t * ) pvArgument;
}
/**
* @brief Utility function to cast pointer of a type to pointer of type DNSAnswerRecord_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( DNSAnswerRecord_t )
{
return ( DNSAnswerRecord_t * ) pvArgument;
}
#if ( ipconfigUSE_LLMNR == 1 )
/**
* @brief Utility function to cast pointer of a type to pointer of type LLMNRAnswer_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( LLMNRAnswer_t )
{
return ( LLMNRAnswer_t * ) pvArgument;
}
#endif /* ipconfigUSE_LLMNR == 1 */
#if ( ipconfigUSE_NBNS == 1 )
/**
* @brief Utility function to cast pointer of a type to pointer of type NBNSAnswer_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( NBNSAnswer_t )
{
return ( NBNSAnswer_t * ) pvArgument;
}
#endif /* ipconfigUSE_NBNS == 1 */
/*-----------------------------------------------------------*/
#if ( ipconfigUSE_DNS_CACHE == 1 )
uint32_t FreeRTOS_dnslookup( const char * pcHostName )
{
uint32_t ulIPAddress = 0UL;
( void ) prvProcessDNSCache( pcHostName, &ulIPAddress, 0, pdTRUE );
return ulIPAddress;
}
#endif /* ipconfigUSE_DNS_CACHE == 1 */
/*-----------------------------------------------------------*/
#if ( ipconfigDNS_USE_CALLBACKS == 1 )
/**
* @brief Utility function to cast pointer of a type to pointer of type DNSCallback_t.
*
* @return The casted pointer.
*/
static portINLINE ipDECL_CAST_PTR_FUNC_FOR_TYPE( DNSCallback_t )
{
return ( DNSCallback_t * ) pvArgument;
}
/** @brief The list of all callback structures. */
_static List_t xCallbackList;
/**
* @brief Define FreeRTOS_gethostbyname() as a normal blocking call.
*
* @param[in] pcHostName: The hostname whose IP address is being searched for.
*
* @return The IP-address of the hostname.
*/
uint32_t FreeRTOS_gethostbyname( const char * pcHostName )
{
return FreeRTOS_gethostbyname_a( pcHostName, NULL, ( void * ) NULL, 0U );
}
/*-----------------------------------------------------------*/
/** @brief Initialise the list of call-back structures.
*/
void vDNSInitialise( void )
{
vListInitialise( &xCallbackList );
}
/*-----------------------------------------------------------*/
/**
* @brief Iterate through the list of call-back structures and remove
* old entries which have reached a timeout.
* As soon as the list has become empty, the DNS timer will be stopped.
* In case pvSearchID is supplied, the user wants to cancel a DNS request.
*
* @param[in] pvSearchID: The search ID of callback function whose associated
* DNS request is being cancelled. If non-ID specific checking of
* all requests is required, then this field should be kept as NULL.
*/
void vDNSCheckCallBack( void * pvSearchID )
{
const ListItem_t * pxIterator;
const ListItem_t * xEnd = listGET_END_MARKER( &xCallbackList );
vTaskSuspendAll();
{
for( pxIterator = ( const ListItem_t * ) listGET_NEXT( xEnd );
pxIterator != xEnd;
)
{
DNSCallback_t * pxCallback = ipCAST_PTR_TO_TYPE_PTR( 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 ) )
{
( void ) uxListRemove( &( pxCallback->xListItem ) );
vPortFree( pxCallback );
}
else if( xTaskCheckForTimeOut( &pxCallback->uxTimeoutState, &pxCallback->uxRemaningTime ) != pdFALSE )
{
pxCallback->pCallbackFunction( pxCallback->pcName, pxCallback->pvSearchID, 0 );
( void ) uxListRemove( &( pxCallback->xListItem ) );
vPortFree( pxCallback );
}
else
{
/* This call-back is still waiting for a reply or a time-out. */
}
}
}
( void ) xTaskResumeAll();
if( listLIST_IS_EMPTY( &xCallbackList ) != pdFALSE )
{
vIPSetDnsTimerEnableState( pdFALSE );
}
}
/*-----------------------------------------------------------*/
/**
* @brief Remove the entry defined by the search ID to cancel a DNS request.
*
* @param[in] pvSearchID: The search ID of the callback function associated with
* the DNS request being cancelled. Note that the value of
* the pointer matters, not the pointee.
*/
void FreeRTOS_gethostbyname_cancel( void * pvSearchID )
{
/* _HT_ Should better become a new API call to have the IP-task remove the callback */
vDNSCheckCallBack( pvSearchID );
}
/*-----------------------------------------------------------*/
/**
* @brief FreeRTOS_gethostbyname_a() was called along with callback parameters.
* Store them in a list for later reference.
*
* @param[in] pcHostName: The hostname whose IP address is being searched for.
* @param[in] pvSearchID: The search ID of the DNS callback function to set.
* @param[in] pCallbackFunction: The callback function pointer.
* @param[in] uxTimeout: Timeout of the callback function.
* @param[in] uxIdentifier: Random number used as ID in the DNS message.
*/
static void vDNSSetCallBack( const char * pcHostName,
void * pvSearchID,
FOnDNSEvent pCallbackFunction,
TickType_t uxTimeout,
TickType_t uxIdentifier )
{
size_t lLength = strlen( pcHostName );
DNSCallback_t * pxCallback = ipCAST_PTR_TO_TYPE_PTR( DNSCallback_t, pvPortMalloc( sizeof( *pxCallback ) + lLength ) );
/* Translate from ms to number of clock ticks. */
uxTimeout /= portTICK_PERIOD_MS;
if( pxCallback != NULL )
{
if( listLIST_IS_EMPTY( &xCallbackList ) != pdFALSE )
{
/* This is the first one, start the DNS timer to check for timeouts */
vIPReloadDNSTimer( FreeRTOS_min_uint32( 1000U, uxTimeout ) );
}
( void ) strcpy( pxCallback->pcName, pcHostName );
pxCallback->pCallbackFunction = pCallbackFunction;
pxCallback->pvSearchID = pvSearchID;
pxCallback->uxRemaningTime = uxTimeout;
vTaskSetTimeOutState( &pxCallback->uxTimeoutState );
listSET_LIST_ITEM_OWNER( &( pxCallback->xListItem ), ( void * ) pxCallback );
listSET_LIST_ITEM_VALUE( &( pxCallback->xListItem ), uxIdentifier );
vTaskSuspendAll();
{
vListInsertEnd( &xCallbackList, &pxCallback->xListItem );
}
( void ) xTaskResumeAll();
}
}
/*-----------------------------------------------------------*/
/**
* @brief A DNS reply was received, see if there is any matching entry and
* call the handler.
*
* @param[in] uxIdentifier: Identifier associated with the callback function.
* @param[in] pcName: The name associated with the callback function.
* @param[in] ulIPAddress: IP-address obtained from the DNS server.
*
* @return Returns pdTRUE if uxIdentifier was recognized.
*/
static BaseType_t xDNSDoCallback( TickType_t uxIdentifier,
const char * pcName,
uint32_t ulIPAddress )
{
BaseType_t xResult = pdFALSE;
const ListItem_t * pxIterator;
const ListItem_t * xEnd = 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 ) == uxIdentifier )
{
DNSCallback_t * pxCallback = ipCAST_PTR_TO_TYPE_PTR( DNSCallback_t, listGET_LIST_ITEM_OWNER( pxIterator ) );
pxCallback->pCallbackFunction( pcName, pxCallback->pvSearchID, ulIPAddress );
( void ) uxListRemove( &pxCallback->xListItem );
vPortFree( pxCallback );
if( listLIST_IS_EMPTY( &xCallbackList ) != pdFALSE )
{
/* The list of outstanding requests is empty. No need for periodic polling. */
vIPSetDnsTimerEnableState( pdFALSE );
}
xResult = pdTRUE;
break;
}
}
}
( void ) xTaskResumeAll();
return xResult;
}
#endif /* ipconfigDNS_USE_CALLBACKS == 1 */
/*-----------------------------------------------------------*/
#if ( ipconfigDNS_USE_CALLBACKS == 0 )
/**
* @brief Get the IP-address corresponding to the given hostname.
*
* @param[in] pcHostName: The hostname whose IP address is being queried.
*
* @return The IP-address corresponding to the hostname.
*/
uint32_t FreeRTOS_gethostbyname( const char * pcHostName )
{
return prvPrepareLookup( pcHostName );
}
#else
/**
* @brief Get the IP-address corresponding to the given hostname.
*
* @param[in] pcHostName: The hostname whose IP address is being queried.
* @param[in] pCallback: The callback function which will be called upon DNS response.
* @param[in] pvSearchID: Search ID for the callback function.
* @param[in] uxTimeout: Timeout for the callback function.
*
* @return The IP-address corresponding to the hostname.
*/
uint32_t FreeRTOS_gethostbyname_a( const char * pcHostName,
FOnDNSEvent pCallback,
void * pvSearchID,
TickType_t uxTimeout )
{
return prvPrepareLookup( pcHostName, pCallback, pvSearchID, uxTimeout );
}
#endif /* if ( ipconfigDNS_USE_CALLBACKS == 0 ) */
#if ( ipconfigDNS_USE_CALLBACKS == 1 )
/**
* @brief Check if hostname is already known. If not, call prvGetHostByName() to send a DNS request.
*
* @param[in] pcHostName: The hostname whose IP address is being queried.
* @param[in] pCallback: The callback function which will be called upon DNS response.
* @param[in] pvSearchID: Search ID for the callback function.
* @param[in] uxTimeout: Timeout for the callback function.
*
* @return The IP-address corresponding to the hostname.
*/
static uint32_t prvPrepareLookup( const char * pcHostName,
FOnDNSEvent pCallback,
void * pvSearchID,
TickType_t uxTimeout )
#else
/**
* @brief Check if hostname is already known. If not, call prvGetHostByName() to send a DNS request.
*
* @param[in] pcHostName: The hostname whose IP address is being queried.
*
* @return The IP-address corresponding to the hostname.
*/
static uint32_t prvPrepareLookup( const char * pcHostName )
#endif
{
uint32_t ulIPAddress = 0UL;
TickType_t uxReadTimeOut_ticks = ipconfigDNS_RECEIVE_BLOCK_TIME_TICKS;
/* Generate a unique identifier for this query. Keep it in a local variable
* as gethostbyname() may be called from different threads */
BaseType_t xHasRandom = pdFALSE;
TickType_t uxIdentifier = 0U;
#if ( ipconfigUSE_DNS_CACHE != 0 )
BaseType_t xLengthOk = pdFALSE;
#endif
#if ( ipconfigUSE_DNS_CACHE != 0 )
{
if( pcHostName != NULL )
{
size_t xLength = strlen( pcHostName ) + 1U;
if( xLength <= ipconfigDNS_CACHE_NAME_LENGTH )
{
/* The name is not too long. */
xLengthOk = pdTRUE;
}
else
{
FreeRTOS_printf( ( "prvPrepareLookup: name is too long ( %lu > %lu )\n",
( uint32_t ) xLength,
( uint32_t ) ipconfigDNS_CACHE_NAME_LENGTH ) );
}
}
}
if( ( pcHostName != NULL ) && ( xLengthOk != pdFALSE ) )
#else /* if ( ipconfigUSE_DNS_CACHE != 0 ) */
if( pcHostName != NULL )
#endif /* ( ipconfigUSE_DNS_CACHE != 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 != 0UL )
{
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( ulIPAddress == 0UL )
{
uint32_t ulNumber;
xHasRandom = xApplicationGetRandomNumber( &( ulNumber ) );
/* DNS identifiers are 16-bit. */
uxIdentifier = ( TickType_t ) ( ulNumber & 0xffffU );
}
#if ( ipconfigDNS_USE_CALLBACKS == 1 )
{
if( pCallback != NULL )
{
if( ulIPAddress == 0UL )
{
/* The user has provided a callback function, so do not block on recvfrom() */
if( xHasRandom != pdFALSE )
{
uxReadTimeOut_ticks = 0U;
vDNSSetCallBack( pcHostName, pvSearchID, pCallback, uxTimeout, uxIdentifier );
}
}
else
{
/* The IP address is known, do the call-back now. */
pCallback( pcHostName, pvSearchID, ulIPAddress );
}
}
}
#endif /* if ( ipconfigDNS_USE_CALLBACKS == 1 ) */
if( ( ulIPAddress == 0UL ) && ( xHasRandom != pdFALSE ) )
{
ulIPAddress = prvGetHostByName( pcHostName, uxIdentifier, uxReadTimeOut_ticks );
}
}
return ulIPAddress;
}
/*-----------------------------------------------------------*/
/**
* @brief Prepare and send a message to a DNS server. 'uxReadTimeOut_ticks' will be passed as
* zero, in case the user has supplied a call-back function.
*
* @param[in] pcHostName: The hostname for which an IP address is required.
* @param[in] uxIdentifier: Identifier to send in the DNS message.
* @param[in] uxReadTimeOut_ticks: The timeout in ticks for waiting. In case the user has supplied
* a call-back function, this value should be zero.
*
* @return The IPv4 IP address for the hostname being queried. It will be zero if there is no reply.
*/
static uint32_t prvGetHostByName( const char * pcHostName,
TickType_t uxIdentifier,
TickType_t uxReadTimeOut_ticks )
{
struct freertos_sockaddr xAddress;
Socket_t xDNSSocket;
uint32_t ulIPAddress = 0UL;
uint32_t ulAddressLength = sizeof( struct freertos_sockaddr );
BaseType_t xAttempt;
int32_t lBytes;
size_t uxPayloadLength, uxExpectedPayloadLength;
TickType_t uxWriteTimeOut_ticks = ipconfigDNS_SEND_BLOCK_TIME_TICKS;
#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 != ( char ) 0; 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. */
uxExpectedPayloadLength = sizeof( DNSMessage_t ) + strlen( pcHostName ) + sizeof( uint16_t ) + sizeof( uint16_t ) + 2U;
xDNSSocket = prvCreateDNSSocket();
if( xDNSSocket != NULL )
{
/* Ideally we should check for the return value. But since we are passing
* correct parameters, and xDNSSocket is != NULL, the return value is
* going to be '0' i.e. success. Thus, return value is discarded */
( void ) FreeRTOS_setsockopt( xDNSSocket, 0, FREERTOS_SO_SNDTIMEO, &( uxWriteTimeOut_ticks ), sizeof( TickType_t ) );
( void ) FreeRTOS_setsockopt( xDNSSocket, 0, FREERTOS_SO_RCVTIMEO, &( uxReadTimeOut_ticks ), sizeof( TickType_t ) );
for( xAttempt = 0; xAttempt < ipconfigDNS_REQUEST_ATTEMPTS; xAttempt++ )
{
size_t uxHeaderBytes;
NetworkBufferDescriptor_t * pxNetworkBuffer;
uint8_t * pucUDPPayloadBuffer = NULL, * pucReceiveBuffer;
/* 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. */
uxHeaderBytes = ipSIZE_OF_ETH_HEADER + ipSIZE_OF_IPv4_HEADER + ipSIZE_OF_UDP_HEADER;
pxNetworkBuffer = pxGetNetworkBufferWithDescriptor( uxHeaderBytes + uxExpectedPayloadLength, 0UL );
if( pxNetworkBuffer != NULL )
{
pucUDPPayloadBuffer = &( pxNetworkBuffer->pucEthernetBuffer[ uxHeaderBytes ] );
}
if( pucUDPPayloadBuffer != NULL )
{
/* Create the message in the obtained buffer. */
uxPayloadLength = prvCreateDNSMessage( pucUDPPayloadBuffer, pcHostName, uxIdentifier );
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. */
( ipCAST_PTR_TO_TYPE_PTR( DNSMessage_t, pucUDPPayloadBuffer ) )->usFlags = 0;
xAddress.sin_addr = ipLLMNR_IP_ADDR; /* Is in network byte order. */
xAddress.sin_port = ipLLMNR_PORT;
xAddress.sin_port = FreeRTOS_ntohs( xAddress.sin_port );
}
else
#endif
{
/* Use DNS server. */
xAddress.sin_addr = ulIPAddress;
xAddress.sin_port = dnsDNS_PORT;
}
ulIPAddress = 0UL;
if( FreeRTOS_sendto( xDNSSocket, pucUDPPayloadBuffer, uxPayloadLength, FREERTOS_ZERO_COPY, &xAddress, sizeof( xAddress ) ) != 0 )
{
/* Wait for the reply. */
lBytes = FreeRTOS_recvfrom( xDNSSocket, &pucReceiveBuffer, 0, FREERTOS_ZERO_COPY, &xAddress, &ulAddressLength );
if( lBytes > 0 )
{
BaseType_t xExpected;
const DNSMessage_t * pxDNSMessageHeader = ipCAST_CONST_PTR_TO_CONST_TYPE_PTR( DNSMessage_t, pucReceiveBuffer );
/* See if the identifiers match. */
if( uxIdentifier == ( TickType_t ) pxDNSMessageHeader->usIdentifier )
{
xExpected = pdTRUE;
}
else
{
/* The reply was not expected. */
xExpected = pdFALSE;
}
/* The reply was received. Process it. */
#if ( ipconfigDNS_USE_CALLBACKS == 0 )
/* It is useless to analyse the unexpected reply
* unless asynchronous look-ups are enabled. */
if( xExpected != pdFALSE )
#endif /* ipconfigDNS_USE_CALLBACKS == 0 */
{
ulIPAddress = prvParseDNSReply( pucReceiveBuffer, ( size_t ) lBytes, xExpected );
}
/* Finished with the buffer. The zero copy interface
* is being used, so the buffer must be freed by the
* task. */
FreeRTOS_ReleaseUDPPayloadBuffer( pucReceiveBuffer );
if( ulIPAddress != 0UL )
{
/* All done. */
/* coverity[break_stmt] : Break statement terminating the loop */
break;
}
}
}
else
{
/* The message was not sent so the stack will not be
* releasing the zero copy - it must be released here. */
vReleaseNetworkBufferAndDescriptor( pxNetworkBuffer );
}
}
if( uxReadTimeOut_ticks == 0U )
{
/* This DNS lookup is asynchronous, using a call-back:
* send the request only once. */
break;
}
}
/* Finished with the socket. */
( void ) FreeRTOS_closesocket( xDNSSocket );
}
return ulIPAddress;
}
/*-----------------------------------------------------------*/
/**
* @brief Create the DNS message in the zero copy buffer passed in the first parameter.
*
* @param[in,out] pucUDPPayloadBuffer: The zero copy buffer where the DNS message will be created.
* @param[in] pcHostName: Hostname to be looked up.
* @param[in] uxIdentifier: The identifier to be added to the DNS message.
*
* @return Total size of the generated message, which is the space from the last written byte
* to the beginning of the buffer.
*/
_static size_t prvCreateDNSMessage( uint8_t * pucUDPPayloadBuffer,
const char * pcHostName,
TickType_t uxIdentifier )
{
DNSMessage_t * pxDNSMessageHeader;
size_t uxStart, uxIndex;
DNSTail_t const * 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. */
};
/* memcpy() helper variables for MISRA Rule 21.15 compliance*/
const void * pvCopySource;
void * pvCopyDest;
/* Copy in the const part of the header. Intentionally using different
* pointers with memcpy() to put the information in to correct place. */
/*
* Use helper variables for memcpy() to remain
* compliant with MISRA Rule 21.15. These should be
* optimized away.
*/
pvCopySource = &xDefaultPartDNSHeader;
pvCopyDest = pucUDPPayloadBuffer;
( void ) memcpy( pvCopyDest, pvCopySource, sizeof( xDefaultPartDNSHeader ) );
/* Write in a unique identifier. Cast the Payload Buffer to DNSMessage_t
* to easily access fields of the DNS Message. */
pxDNSMessageHeader = ipCAST_PTR_TO_TYPE_PTR( DNSMessage_t, pucUDPPayloadBuffer );
pxDNSMessageHeader->usIdentifier = ( uint16_t ) uxIdentifier;
/* Create the resource record at the end of the header. First
* find the end of the header. */
uxStart = sizeof( xDefaultPartDNSHeader );
/* Leave a gap for the first length byte. */
uxIndex = uxStart + 1U;
/* Copy in the host name. */
( void ) strcpy( ( char * ) &( pucUDPPayloadBuffer[ uxIndex ] ), pcHostName );
/* Walk through 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. */
uxIndex = uxStart;
do
{
size_t uxLength;
/* Skip the length byte. */
uxIndex++;
while( ( pucUDPPayloadBuffer[ uxIndex ] != ( uint8_t ) 0U ) &&
( pucUDPPayloadBuffer[ uxIndex ] != ( uint8_t ) ASCII_BASELINE_DOT ) )
{
uxIndex++;
}
/* Fill in the byte count, then move the pucStart pointer up to
* the found byte position. */
uxLength = uxIndex - ( uxStart + 1U );
pucUDPPayloadBuffer[ uxStart ] = ( uint8_t ) uxLength;
uxStart = uxIndex;
} while( pucUDPPayloadBuffer[ uxIndex ] != ( uint8_t ) 0U );
/* Finish off the record. Cast the record onto DNSTail_t structure to easily
* access the fields of the DNS Message. */
pxTail = ipCAST_PTR_TO_TYPE_PTR( DNSTail_t, &( pucUDPPayloadBuffer[ uxStart + 1U ] ) );
#if defined( _lint ) || defined( __COVERITY__ )
( void ) pxTail;
#else
vSetField16( pxTail, DNSTail_t, usType, dnsTYPE_A_HOST );
vSetField16( pxTail, DNSTail_t, usClass, dnsCLASS_IN );
#endif
/* Return the total size of the generated message, which is the space from
* the last written byte to the beginning of the buffer. */
return uxIndex + sizeof( DNSTail_t ) + 1U;
}
/*-----------------------------------------------------------*/
#if ( ipconfigUSE_DNS_CACHE == 1 ) || ( ipconfigDNS_USE_CALLBACKS == 1 )
/**
* @brief Read the Name field out of a DNS response packet.
*
* @param[in] pucByte: Pointer to the DNS response.
* @param[in] uxRemainingBytes: Length of the DNS response.
* @param[out] pcName: The pointer in which the name in the DNS response will be returned.
* @param[in] uxDestLen: Size of the pcName array.
*
* @return If a fully formed name was found, then return the number of bytes processed in pucByte.
*/
_static size_t prvReadNameField( const uint8_t * pucByte,
size_t uxRemainingBytes,
char * pcName,
size_t uxDestLen )
{
size_t uxNameLen = 0U;
size_t uxIndex = 0U;
size_t uxSourceLen = uxRemainingBytes;
/* uxCount gets the values from pucByte and counts down to 0.
* No need to have a different type than that of pucByte */
size_t uxCount;
if( uxSourceLen == ( size_t ) 0U )
{
/* Return 0 value in case of error. */
uxIndex = 0U;
}
/* Determine if the name is the fully coded name, or an offset to the name
* elsewhere in the message. */
else if( ( pucByte[ uxIndex ] & dnsNAME_IS_OFFSET ) == dnsNAME_IS_OFFSET )
{
/* Jump over the two byte offset. */
if( uxSourceLen > sizeof( uint16_t ) )
{
uxIndex += sizeof( uint16_t );
}
else
{
uxIndex = 0U;
}
}
else
{
/* 'uxIndex' points to the full name. Walk over the string. */
while( ( uxIndex < uxSourceLen ) && ( pucByte[ uxIndex ] != ( uint8_t ) 0x00U ) )
{
/* If this is not the first time through the loop, then add a
* separator in the output. */
if( ( uxNameLen > 0U ) )
{
if( uxNameLen >= uxDestLen )
{
uxIndex = 0U;
/* coverity[break_stmt] : Break statement terminating the loop */
break;
}
pcName[ uxNameLen ] = '.';
uxNameLen++;
}
/* Process the first/next sub-string. */
uxCount = ( size_t ) pucByte[ uxIndex ];
uxIndex++;
if( ( uxIndex + uxCount ) > uxSourceLen )
{
uxIndex = 0U;
break;
}
while( uxCount-- != 0U )
{
if( uxNameLen >= uxDestLen )
{
uxIndex = 0U;
break;
/* break out of inner loop here
* break out of outer loop at the test uxNameLen >= uxDestLen. */
}
pcName[ uxNameLen ] = ( char ) pucByte[ uxIndex ];
uxNameLen++;
uxIndex++;
}
}
/* Confirm that a fully formed name was found. */
if( uxIndex > 0U )
{
/* Here, there is no need to check for pucByte[ uxindex ] == 0 because:
* When we break out of the above while loop, uxIndex is made 0 thereby
* failing above check. Whenever we exit the loop otherwise, either
* pucByte[ uxIndex ] == 0 (which makes the check here unnecessary) or
* uxIndex >= uxSourceLen (which makes sure that we do not go in the 'if'
* case).