in FreeRTOS_DNS.c [1168:1569]
_static uint32_t prvParseDNSReply( uint8_t * pucUDPPayloadBuffer,
size_t uxBufferLength,
BaseType_t xExpected )
{
DNSMessage_t * pxDNSMessageHeader;
/* This pointer is not used to modify anything */
const DNSAnswerRecord_t * pxDNSAnswerRecord;
uint32_t ulIPAddress = 0U;
#if ( ipconfigUSE_LLMNR == 1 )
char * pcRequestedName = NULL;
#endif
uint8_t * pucByte;
size_t uxSourceBytesRemaining;
uint16_t x, usDataLength, usQuestions;
uint16_t usType = 0U;
BaseType_t xReturn = pdTRUE;
/* memcpy() helper variables for MISRA Rule 21.15 compliance*/
const void * pvCopySource;
void * pvCopyDest;
#if ( ipconfigUSE_LLMNR == 1 )
uint16_t usClass = 0U;
#endif
#if ( ipconfigUSE_DNS_CACHE == 1 ) || ( ipconfigDNS_USE_CALLBACKS == 1 )
BaseType_t xDoStore = xExpected;
char pcName[ ipconfigDNS_CACHE_NAME_LENGTH ] = "";
#endif
const size_t uxAddressLength = ipSIZE_OF_IPv4_ADDRESS;
/* Ensure that the buffer is of at least minimal DNS message length. */
if( uxBufferLength < sizeof( DNSMessage_t ) )
{
xReturn = pdFALSE;
}
else
{
uxSourceBytesRemaining = uxBufferLength;
/* Parse the DNS message header. Map the byte stream onto a structure
* for easier access. */
pxDNSMessageHeader = ipCAST_PTR_TO_TYPE_PTR( DNSMessage_t, pucUDPPayloadBuffer );
/* Introduce a do {} while (0) to allow the use of breaks. */
do
{
size_t uxBytesRead = 0U;
size_t uxResult;
/* Start at the first byte after the header. */
pucByte = &( pucUDPPayloadBuffer[ sizeof( DNSMessage_t ) ] );
uxSourceBytesRemaining -= sizeof( DNSMessage_t );
/* Skip any question records. */
usQuestions = FreeRTOS_ntohs( pxDNSMessageHeader->usQuestions );
for( x = 0U; x < usQuestions; x++ )
{
#if ( ipconfigUSE_LLMNR == 1 )
{
if( x == 0U )
{
pcRequestedName = ( char * ) pucByte;
}
}
#endif
#if ( ipconfigUSE_DNS_CACHE == 1 ) || ( ipconfigDNS_USE_CALLBACKS == 1 )
if( x == 0U )
{
uxResult = prvReadNameField( pucByte,
uxSourceBytesRemaining,
pcName,
sizeof( pcName ) );
/* Check for a malformed response. */
if( uxResult == 0U )
{
xReturn = pdFALSE;
break;
}
uxBytesRead += uxResult;
pucByte = &( pucByte[ uxResult ] );
uxSourceBytesRemaining -= uxResult;
}
else
#endif /* ipconfigUSE_DNS_CACHE || ipconfigDNS_USE_CALLBACKS */
{
/* Skip the variable length pcName field. */
uxResult = prvSkipNameField( pucByte,
uxSourceBytesRemaining );
/* Check for a malformed response. */
if( uxResult == 0U )
{
xReturn = pdFALSE;
break;
}
uxBytesRead += uxResult;
pucByte = &( pucByte[ uxResult ] );
uxSourceBytesRemaining -= uxResult;
}
/* Check the remaining buffer size. */
if( uxSourceBytesRemaining >= 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 = &( pucByte[ sizeof( uint32_t ) ] );
uxSourceBytesRemaining -= sizeof( uint32_t );
}
else
{
xReturn = pdFALSE;
break;
}
}
if( xReturn == pdFALSE )
{
/* No need to proceed. Break out of the do-while loop. */
break;
}
/* Search through the answer records. */
pxDNSMessageHeader->usAnswers = FreeRTOS_ntohs( pxDNSMessageHeader->usAnswers );
if( ( pxDNSMessageHeader->usFlags & dnsRX_FLAGS_MASK ) == dnsEXPECTED_RX_FLAGS )
{
const uint16_t usCount = ( uint16_t ) ipconfigDNS_CACHE_ADDRESSES_PER_ENTRY;
uint16_t usNumARecordsStored = 0;
for( x = 0U; x < pxDNSMessageHeader->usAnswers; x++ )
{
BaseType_t xDoAccept;
if( usNumARecordsStored >= usCount )
{
/* Only count ipconfigDNS_CACHE_ADDRESSES_PER_ENTRY number of records. */
break;
}
uxResult = prvSkipNameField( pucByte,
uxSourceBytesRemaining );
/* Check for a malformed response. */
if( uxResult == 0U )
{
xReturn = pdFALSE;
break;
}
uxBytesRead += uxResult;
pucByte = &( pucByte[ uxResult ] );
uxSourceBytesRemaining -= uxResult;
/* Is there enough data for an IPv4 A record answer and, if so,
* is this an A record? */
if( uxSourceBytesRemaining < sizeof( uint16_t ) )
{
xReturn = pdFALSE;
break;
}
usType = usChar2u16( pucByte );
if( usType == ( uint16_t ) dnsTYPE_A_HOST )
{
if( uxSourceBytesRemaining >= ( sizeof( DNSAnswerRecord_t ) + uxAddressLength ) )
{
xDoAccept = pdTRUE;
}
else
{
xDoAccept = pdFALSE;
}
}
else
{
/* Unknown host type. */
xDoAccept = pdFALSE;
}
if( xDoAccept != pdFALSE )
{
/* This is the required record type and is of sufficient size. */
/* Mapping pucByte to a DNSAnswerRecord allows easy access of the
* fields of the structure. */
pxDNSAnswerRecord = ipCAST_PTR_TO_TYPE_PTR( DNSAnswerRecord_t, pucByte );
/* Sanity check the data length of an IPv4 answer. */
if( FreeRTOS_ntohs( pxDNSAnswerRecord->usDataLength ) == ( uint16_t ) uxAddressLength )
{
/* Copy the IP address out of the record. Using different pointers
* to copy only the portion we want is intentional here. */
/*
* Use helper variables for memcpy() to remain
* compliant with MISRA Rule 21.15. These should be
* optimized away.
*/
pvCopySource = &pucByte[ sizeof( DNSAnswerRecord_t ) ];
pvCopyDest = &ulIPAddress;
( void ) memcpy( pvCopyDest, pvCopySource, uxAddressLength );
#if ( ipconfigDNS_USE_CALLBACKS == 1 )
{
/* See if any asynchronous call was made to FreeRTOS_gethostbyname_a() */
if( xDNSDoCallback( ( TickType_t ) pxDNSMessageHeader->usIdentifier, pcName, ulIPAddress ) != pdFALSE )
{
/* This device has requested this DNS look-up.
* The result may be stored in the DNS cache. */
xDoStore = pdTRUE;
}
}
#endif /* ipconfigDNS_USE_CALLBACKS == 1 */
#if ( ipconfigUSE_DNS_CACHE == 1 )
{
char cBuffer[ 16 ];
/* The reply will only be stored in the DNS cache when the
* request was issued by this device. */
if( xDoStore != pdFALSE )
{
( void ) prvProcessDNSCache( pcName, &ulIPAddress, pxDNSAnswerRecord->ulTTL, pdFALSE );
usNumARecordsStored++; /* Track # of A records stored */
}
( void ) FreeRTOS_inet_ntop( FREERTOS_AF_INET, ( const void * ) &( ulIPAddress ), cBuffer, ( socklen_t ) sizeof( cBuffer ) );
/* Show what has happened. */
FreeRTOS_printf( ( "DNS[0x%04lX]: The answer to '%s' (%s) will%s be stored\n",
( UBaseType_t ) pxDNSMessageHeader->usIdentifier,
pcName,
cBuffer,
( xDoStore != 0 ) ? "" : " NOT" ) );
}
#endif /* ipconfigUSE_DNS_CACHE */
}
pucByte = &( pucByte[ sizeof( DNSAnswerRecord_t ) + uxAddressLength ] );
uxSourceBytesRemaining -= ( sizeof( DNSAnswerRecord_t ) + uxAddressLength );
}
else if( uxSourceBytesRemaining >= sizeof( DNSAnswerRecord_t ) )
{
/* It's not an A record, so skip it. Get the header location
* and then jump over the header. */
/* Cast the response to DNSAnswerRecord for easy access to fields of the DNS response. */
pxDNSAnswerRecord = ipCAST_PTR_TO_TYPE_PTR( DNSAnswerRecord_t, pucByte );
pucByte = &( pucByte[ sizeof( DNSAnswerRecord_t ) ] );
uxSourceBytesRemaining -= sizeof( DNSAnswerRecord_t );
/* Determine the length of the answer data from the header. */
usDataLength = FreeRTOS_ntohs( pxDNSAnswerRecord->usDataLength );
/* Jump over the answer. */
if( uxSourceBytesRemaining >= usDataLength )
{
pucByte = &( pucByte[ usDataLength ] );
uxSourceBytesRemaining -= usDataLength;
}
else
{
/* Malformed response. */
xReturn = pdFALSE;
break;
}
}
else
{
/* Do nothing */
}
}
}
#if ( ipconfigUSE_LLMNR == 1 )
/* No need to check that pcRequestedName != NULL since is usQuestions != 0, then
* pcRequestedName is assigned with this statement
* "pcRequestedName = ( char * ) pucByte;" */
else if( ( usQuestions != ( uint16_t ) 0U ) && ( 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 ] ) ) != pdFALSE )
{
int16_t usLength;
NetworkBufferDescriptor_t * pxNewBuffer = NULL;
NetworkBufferDescriptor_t * pxNetworkBuffer = pxUDPPayloadBuffer_to_NetworkBuffer( pucUDPPayloadBuffer );
LLMNRAnswer_t * pxAnswer;
uint8_t * pucNewBuffer = NULL;
if( pxNetworkBuffer != NULL )
{
if( xBufferAllocFixedSize == pdFALSE )
{
size_t uxDataLength = uxBufferLength + sizeof( UDPHeader_t ) + sizeof( EthernetHeader_t ) + sizeof( IPHeader_t );
/* Set the size of the outgoing packet. */
pxNetworkBuffer->xDataLength = uxDataLength;
pxNewBuffer = pxDuplicateNetworkBufferWithDescriptor( pxNetworkBuffer, uxDataLength + sizeof( LLMNRAnswer_t ) );
if( pxNewBuffer != NULL )
{
BaseType_t xOffset1, xOffset2;
xOffset1 = ( BaseType_t ) ( pucByte - pucUDPPayloadBuffer );
xOffset2 = ( BaseType_t ) ( ( ( uint8_t * ) pcRequestedName ) - pucUDPPayloadBuffer );
pxNetworkBuffer = pxNewBuffer;
pucNewBuffer = &( pxNetworkBuffer->pucEthernetBuffer[ ipUDP_PAYLOAD_OFFSET_IPv4 ] );
pucByte = &( pucNewBuffer[ xOffset1 ] );
pcRequestedName = ( char * ) &( pucNewBuffer[ xOffset2 ] );
pxDNSMessageHeader = ipCAST_PTR_TO_TYPE_PTR( DNSMessage_t, pucNewBuffer );
}
else
{
/* Just to indicate that the message may not be answered. */
pxNetworkBuffer = NULL;
}
}
else
{
pucNewBuffer = &( pxNetworkBuffer->pucEthernetBuffer[ ipUDP_PAYLOAD_OFFSET_IPv4 ] );
}
}
/* The test on 'pucNewBuffer' is only to satisfy lint. */
if( ( pxNetworkBuffer != NULL ) && ( pucNewBuffer != NULL ) )
{
pxAnswer = ipCAST_PTR_TO_TYPE_PTR( LLMNRAnswer_t, pucByte );
/* We leave 'usIdentifier' and 'usQuestions' untouched */
#ifndef _lint
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 */
#endif /* lint */
pxAnswer->ucNameCode = dnsNAME_IS_OFFSET;
pxAnswer->ucNameOffset = ( uint8_t ) ( pcRequestedName - ( char * ) pucNewBuffer );
#ifndef _lint
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 ) );
#endif /* lint */
usLength = ( int16_t ) ( sizeof( *pxAnswer ) + ( size_t ) ( pucByte - pucNewBuffer ) );
prvReplyDNSMessage( pxNetworkBuffer, usLength );
if( pxNewBuffer != NULL )
{
vReleaseNetworkBufferAndDescriptor( pxNewBuffer );
}
}
}
}
else
{
/* Not an expected reply. */
}
#endif /* ipconfigUSE_LLMNR == 1 */
( void ) uxBytesRead;
} while( ipFALSE_BOOL );
}
if( xReturn == pdFALSE )
{
/* There was an error while parsing the DNS response. Return error code. */
ulIPAddress = dnsPARSE_ERROR;
}
else if( xExpected == pdFALSE )
{
/* Do not return a valid IP-address in case the reply was not expected. */
ulIPAddress = 0U;
}
else
{
/* The IP-address found will be returned. */
}
#if ( ipconfigUSE_DNS_CACHE == 1 ) || ( ipconfigDNS_USE_CALLBACKS == 1 )
( void ) xDoStore;
#endif
return ulIPAddress;
}