static uint32_t prvParseDNSReply( uint8_t *pucUDPPayloadBuffer, TickType_t xIdentifier )
{
DNSMessage_t *pxDNSMessageHeader;
uint32_t ulIPAddress = 0UL;
#if( ipconfigUSE_LLMNR == 1 )
char *pcRequestedName = NULL;
#endif
uint8_t *pucByte;
uint16_t x, usDataLength, usQuestions;
#if( ipconfigUSE_LLMNR == 1 )
uint16_t usType = 0, usClass = 0;
#endif
#if( ipconfigUSE_DNS_CACHE == 1 )
char pcName[128] = ""; /*_RB_ What is the significance of 128? Probably too big to go on the stack for a small MCU but don't know how else it could be made re-entrant. Might be necessary. */
#endif
pxDNSMessageHeader = ( DNSMessage_t * ) pucUDPPayloadBuffer;
if( pxDNSMessageHeader->usIdentifier == ( uint16_t ) xIdentifier )
{
/* Start at the first byte after the header. */
pucByte = pucUDPPayloadBuffer + 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, pcName, sizeof( pcName ) );
}
else
#endif /* ipconfigUSE_DNS_CACHE */
{
/* Skip the variable length pcName field. */
pucByte = prvSkipNameField( pucByte );
}
#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 );
}
/* Search through the answers 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 );
/* Is the type field that of an A record? */
if( usChar2u16( pucByte ) == dnsTYPE_A_HOST )
{
/* This is the required record. Skip the type, class, and
time to live fields, plus the first byte of the data
length. */
pucByte += ( sizeof( uint32_t ) + sizeof( uint32_t ) + sizeof( uint8_t ) );
/* Sanity check the data length. */
if( ( size_t ) *pucByte == sizeof( uint32_t ) )
{
/* Skip the second byte of the length. */
pucByte++;
/* Copy the IP address out of the record. */
memcpy( ( void * ) &ulIPAddress, ( void * ) pucByte, sizeof( uint32_t ) );
#if( ipconfigUSE_DNS_CACHE == 1 )
{
prvProcessDNSCache( pcName, &ulIPAddress, 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 */
}
break;
}
else
{
/* Skip the type, class and time to live fields. */
pucByte += ( sizeof( uint32_t ) + sizeof( uint32_t ) );
/* Determine the length of the data in the field. */
memcpy( ( void * ) &usDataLength, ( void * ) pucByte, sizeof( uint16_t ) );
usDataLength = FreeRTOS_ntohs( usDataLength );
/* Jump over the data length bytes, and the data itself. */
pucByte += usDataLength + sizeof( uint16_t );
}
}
}
#if( ipconfigUSE_LLMNR == 1 )
else if( ( usQuestions != ( uint16_t )0u ) && ( usType == ( uint16_t )dnsTYPE_A_HOST ) && ( usClass == ( uint16_t )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 = 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 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;
/* 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;
}
static uint32_t prvParseDNSReply( uint8_t *pucUDPPayloadBuffer, uint16_t usIdentifier )
{
xDNSMessage_t *pxDNSMessageHeader;
uint32_t ulIPAddress = 0UL;
uint8_t *pucByte;
uint16_t x, usDataLength;
const uint16_t usARecordType = dnsTYPE;
pxDNSMessageHeader = ( xDNSMessage_t * ) pucUDPPayloadBuffer;
if( pxDNSMessageHeader->usIdentifier == usIdentifier )
{
if( ( pxDNSMessageHeader->usFlags & dnsRX_FLAGS_MASK ) == dnsEXPECTED_RX_FLAGS )
{
/* Start at the first byte after the header. */
pucByte = pucUDPPayloadBuffer + sizeof( xDNSMessage_t );
/* Skip any question records. */
pxDNSMessageHeader->usQuestions = FreeRTOS_ntohs( pxDNSMessageHeader->usQuestions );
for( x = 0; x < pxDNSMessageHeader->usQuestions; x++ )
{
/* Skip the variable length name field. */
pucByte = prvSkipNameField( pucByte );
/* Skip the type and class fields. */
pucByte += sizeof( uint32_t );
}
/* Search through the answers records. */
pxDNSMessageHeader->usAnswers = FreeRTOS_ntohs( pxDNSMessageHeader->usAnswers );
for( x = 0; x < pxDNSMessageHeader->usAnswers; x++ )
{
pucByte = prvSkipNameField( pucByte );
/* Is the type field that of an A record? */
if( memcmp( ( void * ) pucByte, ( void * ) &usARecordType, sizeof( uint16_t ) ) == 0 )
{
/* This is the required record. Skip the type, class, and
time to live fields, plus the first byte of the data
length. */
pucByte += ( sizeof( uint32_t ) + sizeof( uint32_t ) + sizeof( uint8_t ) );
/* Sanity check the data length. */
if( *pucByte == sizeof( uint32_t ) )
{
/* Skip the second byte of the length. */
pucByte++;
/* Copy the IP address out of the record. */
memcpy( ( void * ) &ulIPAddress, ( void * ) pucByte, sizeof( uint32_t ) );
}
break;
}
else
{
/* Skip the type, class and time to live fields. */
pucByte += ( sizeof( uint32_t ) + sizeof( uint32_t ) );
/* Determine the length of the data in the field. */
memcpy( ( void * ) &usDataLength, ( void * ) pucByte, sizeof( uint16_t ) );
usDataLength = FreeRTOS_ntohs( usDataLength );
/* Jump over the data lenth bytes, and the data itself. */
pucByte += usDataLength + sizeof( uint16_t );
}
}
}
}
return ulIPAddress;
}
