/* * FreeRTOS+TCP V2.2.0 * 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 */ /* * FreeRTOS_TCP_WIN.c * Module which handles the TCP windowing schemes for FreeRTOS+TCP. Many * functions have two versions - one for FreeRTOS+TCP (full) and one for * FreeRTOS+TCP (lite). * * In this module all ports and IP addresses and sequence numbers are * being stored in host byte-order. */ /* Standard includes. */ #include /* FreeRTOS includes. */ #include "FreeRTOS.h" #include "task.h" #include "queue.h" #include "semphr.h" /* FreeRTOS+TCP includes. */ #include "FreeRTOS_UDP_IP.h" #include "FreeRTOS_IP.h" #include "FreeRTOS_Sockets.h" #include "FreeRTOS_IP_Private.h" #include "NetworkBufferManagement.h" #include "FreeRTOS_TCP_WIN.h" /* Constants used for Smoothed Round Trip Time (SRTT). */ #define winSRTT_INCREMENT_NEW 2 #define winSRTT_INCREMENT_CURRENT 6 #define winSRTT_DECREMENT_NEW 1 #define winSRTT_DECREMENT_CURRENT 7 #define winSRTT_CAP_mS 50 #if( ipconfigUSE_TCP_WIN == 1 ) #define xTCPWindowRxNew( pxWindow, ulSequenceNumber, lCount ) xTCPWindowNew( pxWindow, ulSequenceNumber, lCount, pdTRUE ) #define xTCPWindowTxNew( pxWindow, ulSequenceNumber, lCount ) xTCPWindowNew( pxWindow, ulSequenceNumber, lCount, pdFALSE ) /* The code to send a single Selective ACK (SACK): * NOP (0x01), NOP (0x01), SACK (0x05), LEN (0x0a), * followed by a lower and a higher sequence number, * where LEN is 2 + 2*4 = 10 bytes. */ #if( ipconfigBYTE_ORDER == pdFREERTOS_BIG_ENDIAN ) #define OPTION_CODE_SINGLE_SACK ( 0x0101050aUL ) #else #define OPTION_CODE_SINGLE_SACK ( 0x0a050101UL ) #endif /* Normal retransmission: * A packet will be retransmitted after a Retransmit Time-Out (RTO). * Fast retransmission: * When 3 packets with a higher sequence number have been acknowledged * by the peer, it is very unlikely a current packet will ever arrive. * It will be retransmitted far before the RTO. */ #define DUPLICATE_ACKS_BEFORE_FAST_RETRANSMIT ( 3u ) /* If there have been several retransmissions (4), decrease the * size of the transmission window to at most 2 times MSS. */ #define MAX_TRANSMIT_COUNT_USING_LARGE_WINDOW ( 4u ) #endif /* configUSE_TCP_WIN */ /*-----------------------------------------------------------*/ extern void vListInsertGeneric( List_t * const pxList, ListItem_t * const pxNewListItem, MiniListItem_t * const pxWhere ); /* * All TCP sockets share a pool of segment descriptors (TCPSegment_t) * Available descriptors are stored in the 'xSegmentList' * When a socket owns a descriptor, it will either be stored in * 'xTxSegments' or 'xRxSegments' * As soon as a package has been confirmed, the descriptor will be returned * to the segment pool */ #if( ipconfigUSE_TCP_WIN == 1 ) static BaseType_t prvCreateSectors( void ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * Find a segment with a given sequence number in the list of received * segments: 'pxWindow->xRxSegments'. */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowRxFind( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * Allocate a new segment * The socket will borrow all segments from a common pool: 'xSegmentList', * which is a list of 'TCPSegment_t' */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowNew( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, int32_t lCount, BaseType_t xIsForRx ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* When the peer has a close request (FIN flag), the driver will check if * there are missing packets in the Rx-queue * It will accept the closure of the connection if both conditions are true: * - the Rx-queue is empty * - we've ACK'd the highest Rx sequence number seen */ #if( ipconfigUSE_TCP_WIN == 1 ) BaseType_t xTCPWindowRxEmpty( TCPWindow_t *pxWindow ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * Detaches and returns the head of a queue */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowGetHead( List_t *pxList ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * Returns the head of a queue but it won't be detached */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowPeekHead( List_t *pxList ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * Free entry pxSegment because it's not used anymore * The ownership will be passed back to the segment pool */ #if( ipconfigUSE_TCP_WIN == 1 ) static void vTCPWindowFree( TCPSegment_t *pxSegment ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * A segment has been received with sequence number 'ulSequenceNumber', where * 'ulCurrentSequenceNumber == ulSequenceNumber', which means that exactly this * segment was expected. xTCPWindowRxConfirm() will check if there is already * another segment with a sequence number between (ulSequenceNumber) and * (ulSequenceNumber+xLength). Normally none will be found, because the next Rx * segment should have a sequence number equal to '(ulSequenceNumber+xLength)'. */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowRxConfirm( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, uint32_t ulLength ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * FreeRTOS+TCP stores data in circular buffers. Calculate the next position to * store. */ #if( ipconfigUSE_TCP_WIN == 1 ) static int32_t lTCPIncrementTxPosition( int32_t lPosition, int32_t lMax, int32_t lCount ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * This function will look if there is new transmission data. It will return * true if there is data to be sent. */ #if( ipconfigUSE_TCP_WIN == 1 ) static BaseType_t prvTCPWindowTxHasSpace( TCPWindow_t *pxWindow, uint32_t ulWindowSize ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * An acknowledge was received. See if some outstanding data may be removed * from the transmission queue(s). */ #if( ipconfigUSE_TCP_WIN == 1 ) static uint32_t prvTCPWindowTxCheckAck( TCPWindow_t *pxWindow, uint32_t ulFirst, uint32_t ulLast ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /* * A higher Tx block has been acknowledged. Now iterate through the xWaitQueue * to find a possible condition for a FAST retransmission. */ #if( ipconfigUSE_TCP_WIN == 1 ) static uint32_t prvTCPWindowFastRetransmit( TCPWindow_t *pxWindow, uint32_t ulFirst ); #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ /* TCP segment pool. */ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPSegments = NULL; #endif /* ipconfigUSE_TCP_WIN == 1 */ /* List of free TCP segments. */ #if( ipconfigUSE_TCP_WIN == 1 ) static List_t xSegmentList; #endif /* Logging verbosity level. */ BaseType_t xTCPWindowLoggingLevel = 0; #if( ipconfigUSE_TCP_WIN == 1 ) /* Some 32-bit arithmetic: comparing sequence numbers */ static portINLINE BaseType_t xSequenceLessThanOrEqual( uint32_t a, uint32_t b ); static portINLINE BaseType_t xSequenceLessThanOrEqual( uint32_t a, uint32_t b ) { /* Test if a <= b Return true if the unsigned subtraction of (b-a) doesn't generate an arithmetic overflow. */ return ( ( b - a ) & 0x80000000UL ) == 0UL; } #endif /* ipconfigUSE_TCP_WIN */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static portINLINE BaseType_t xSequenceLessThan( uint32_t a, uint32_t b ); static portINLINE BaseType_t xSequenceLessThan( uint32_t a, uint32_t b ) { /* Test if a < b */ return ( ( b - a - 1UL ) & 0x80000000UL ) == 0UL; } #endif /* ipconfigUSE_TCP_WIN */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static portINLINE BaseType_t xSequenceGreaterThan( uint32_t a, uint32_t b ); static portINLINE BaseType_t xSequenceGreaterThan( uint32_t a, uint32_t b ) { /* Test if a > b */ return ( ( a - b - 1UL ) & 0x80000000UL ) == 0UL; } #endif /* ipconfigUSE_TCP_WIN */ /*-----------------------------------------------------------*/ static portINLINE BaseType_t xSequenceGreaterThanOrEqual( uint32_t a, uint32_t b ); static portINLINE BaseType_t xSequenceGreaterThanOrEqual( uint32_t a, uint32_t b ) { /* Test if a >= b */ return ( ( a - b ) & 0x80000000UL ) == 0UL; } /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static portINLINE void vListInsertFifo( List_t * const pxList, ListItem_t * const pxNewListItem ); static portINLINE void vListInsertFifo( List_t * const pxList, ListItem_t * const pxNewListItem ) { vListInsertGeneric( pxList, pxNewListItem, &pxList->xListEnd ); } #endif /*-----------------------------------------------------------*/ static portINLINE void vTCPTimerSet( TCPTimer_t *pxTimer ); static portINLINE void vTCPTimerSet( TCPTimer_t *pxTimer ) { pxTimer->ulBorn = xTaskGetTickCount ( ); } /*-----------------------------------------------------------*/ static portINLINE uint32_t ulTimerGetAge( TCPTimer_t *pxTimer ); static portINLINE uint32_t ulTimerGetAge( TCPTimer_t *pxTimer ) { return ( ( xTaskGetTickCount() - pxTimer->ulBorn ) * portTICK_PERIOD_MS ); } /*-----------------------------------------------------------*/ /* _HT_ GCC (using the settings that I'm using) checks for every public function if it is preceded by a prototype. Later this prototype will be located in list.h? */ extern void vListInsertGeneric( List_t * const pxList, ListItem_t * const pxNewListItem, MiniListItem_t * const pxWhere ); void vListInsertGeneric( List_t * const pxList, ListItem_t * const pxNewListItem, MiniListItem_t * const pxWhere ) { /* Insert a new list item into pxList, it does not sort the list, but it puts the item just before xListEnd, so it will be the last item returned by listGET_HEAD_ENTRY() */ pxNewListItem->pxNext = (struct xLIST_ITEM * configLIST_VOLATILE)pxWhere; pxNewListItem->pxPrevious = pxWhere->pxPrevious; pxWhere->pxPrevious->pxNext = pxNewListItem; pxWhere->pxPrevious = pxNewListItem; /* Remember which list the item is in. */ listLIST_ITEM_CONTAINER( pxNewListItem ) = ( void * ) pxList; ( pxList->uxNumberOfItems )++; } /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static BaseType_t prvCreateSectors( void ) { BaseType_t xIndex, xReturn; /* Allocate space for 'xTCPSegments' and store them in 'xSegmentList'. */ vListInitialise( &xSegmentList ); xTCPSegments = ( TCPSegment_t * ) pvPortMallocLarge( ipconfigTCP_WIN_SEG_COUNT * sizeof( xTCPSegments[ 0 ] ) ); if( xTCPSegments == NULL ) { FreeRTOS_debug_printf( ( "prvCreateSectors: malloc %lu failed\n", ipconfigTCP_WIN_SEG_COUNT * sizeof( xTCPSegments[ 0 ] ) ) ); xReturn = pdFAIL; } else { /* Clear the allocated space. */ memset( xTCPSegments, '\0', ipconfigTCP_WIN_SEG_COUNT * sizeof( xTCPSegments[ 0 ] ) ); for( xIndex = 0; xIndex < ipconfigTCP_WIN_SEG_COUNT; xIndex++ ) { /* Could call vListInitialiseItem here but all data has been nulled already. Set the owner to a segment descriptor. */ listSET_LIST_ITEM_OWNER( &( xTCPSegments[ xIndex ].xListItem ), ( void* ) &( xTCPSegments[ xIndex ] ) ); listSET_LIST_ITEM_OWNER( &( xTCPSegments[ xIndex ].xQueueItem ), ( void* ) &( xTCPSegments[ xIndex ] ) ); /* And add it to the pool of available segments */ vListInsertFifo( &xSegmentList, &( xTCPSegments[xIndex].xListItem ) ); } xReturn = pdPASS; } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowRxFind( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber ) { const ListItem_t *pxIterator; const MiniListItem_t* pxEnd; TCPSegment_t *pxSegment, *pxReturn = NULL; /* Find a segment with a given sequence number in the list of received segments. */ pxEnd = ( const MiniListItem_t* )listGET_END_MARKER( &pxWindow->xRxSegments ); for( pxIterator = ( const ListItem_t * ) listGET_NEXT( pxEnd ); pxIterator != ( const ListItem_t * ) pxEnd; pxIterator = ( const ListItem_t * ) listGET_NEXT( pxIterator ) ) { pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxIterator ); if( pxSegment->ulSequenceNumber == ulSequenceNumber ) { pxReturn = pxSegment; break; } } return pxReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowNew( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, int32_t lCount, BaseType_t xIsForRx ) { TCPSegment_t *pxSegment; ListItem_t * pxItem; /* Allocate a new segment. The socket will borrow all segments from a common pool: 'xSegmentList', which is a list of 'TCPSegment_t' */ if( listLIST_IS_EMPTY( &xSegmentList ) != pdFALSE ) { /* If the TCP-stack runs out of segments, you might consider increasing 'ipconfigTCP_WIN_SEG_COUNT'. */ FreeRTOS_debug_printf( ( "xTCPWindow%cxNew: Error: all segments occupied\n", xIsForRx ? 'R' : 'T' ) ); pxSegment = NULL; } else { /* Pop the item at the head of the list. Semaphore protection is not required as only the IP task will call these functions. */ pxItem = ( ListItem_t * ) listGET_HEAD_ENTRY( &xSegmentList ); pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxItem ); configASSERT( pxItem != NULL ); configASSERT( pxSegment != NULL ); /* Remove the item from xSegmentList. */ uxListRemove( pxItem ); /* Add it to either the connections' Rx or Tx queue. */ vListInsertFifo( xIsForRx ? &pxWindow->xRxSegments : &pxWindow->xTxSegments, pxItem ); /* And set the segment's timer to zero */ vTCPTimerSet( &pxSegment->xTransmitTimer ); pxSegment->u.ulFlags = 0; pxSegment->u.bits.bIsForRx = ( xIsForRx != 0 ); pxSegment->lMaxLength = lCount; pxSegment->lDataLength = lCount; pxSegment->ulSequenceNumber = ulSequenceNumber; #if( ipconfigHAS_DEBUG_PRINTF != 0 ) { static UBaseType_t xLowestLength = ipconfigTCP_WIN_SEG_COUNT; UBaseType_t xLength = listCURRENT_LIST_LENGTH( &xSegmentList ); if( xLowestLength > xLength ) { xLowestLength = xLength; } } #endif /* ipconfigHAS_DEBUG_PRINTF */ } return pxSegment; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) BaseType_t xTCPWindowRxEmpty( TCPWindow_t *pxWindow ) { BaseType_t xReturn; /* When the peer has a close request (FIN flag), the driver will check if there are missing packets in the Rx-queue. It will accept the closure of the connection if both conditions are true: - the Rx-queue is empty - the highest Rx sequence number has been ACK'ed */ if( listLIST_IS_EMPTY( ( &pxWindow->xRxSegments ) ) == pdFALSE ) { /* Rx data has been stored while earlier packets were missing. */ xReturn = pdFALSE; } else if( xSequenceGreaterThanOrEqual( pxWindow->rx.ulCurrentSequenceNumber, pxWindow->rx.ulHighestSequenceNumber ) != pdFALSE ) { /* No Rx packets are being stored and the highest sequence number that has been received has been ACKed. */ xReturn = pdTRUE; } else { FreeRTOS_debug_printf( ( "xTCPWindowRxEmpty: cur %lu highest %lu (empty)\n", ( pxWindow->rx.ulCurrentSequenceNumber - pxWindow->rx.ulFirstSequenceNumber ), ( pxWindow->rx.ulHighestSequenceNumber - pxWindow->rx.ulFirstSequenceNumber ) ) ); xReturn = pdFALSE; } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowGetHead( List_t *pxList ) { TCPSegment_t *pxSegment; ListItem_t * pxItem; /* Detaches and returns the head of a queue. */ if( listLIST_IS_EMPTY( pxList ) != pdFALSE ) { pxSegment = NULL; } else { pxItem = ( ListItem_t * ) listGET_HEAD_ENTRY( pxList ); pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxItem ); uxListRemove( pxItem ); } return pxSegment; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowPeekHead( List_t *pxList ) { ListItem_t *pxItem; TCPSegment_t *pxReturn; /* Returns the head of a queue but it won't be detached. */ if( listLIST_IS_EMPTY( pxList ) != pdFALSE ) { pxReturn = NULL; } else { pxItem = ( ListItem_t * ) listGET_HEAD_ENTRY( pxList ); pxReturn = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxItem ); } return pxReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static void vTCPWindowFree( TCPSegment_t *pxSegment ) { /* Free entry pxSegment because it's not used any more. The ownership will be passed back to the segment pool. Unlink it from one of the queues, if any. */ if( listLIST_ITEM_CONTAINER( &( pxSegment->xQueueItem ) ) != NULL ) { uxListRemove( &( pxSegment->xQueueItem ) ); } pxSegment->ulSequenceNumber = 0u; pxSegment->lDataLength = 0l; pxSegment->u.ulFlags = 0u; /* Take it out of xRxSegments/xTxSegments */ if( listLIST_ITEM_CONTAINER( &( pxSegment->xListItem ) ) != NULL ) { uxListRemove( &( pxSegment->xListItem ) ); } /* Return it to xSegmentList */ vListInsertFifo( &xSegmentList, &( pxSegment->xListItem ) ); } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) void vTCPWindowDestroy( TCPWindow_t *pxWindow ) { List_t * pxSegments; BaseType_t xRound; TCPSegment_t *pxSegment; /* Destroy a window. A TCP window doesn't serve any more. Return all owned segments to the pool. In order to save code, it will make 2 rounds, one to remove the segments from xRxSegments, and a second round to clear xTxSegments*/ for( xRound = 0; xRound < 2; xRound++ ) { if( xRound != 0 ) { pxSegments = &( pxWindow->xRxSegments ); } else { pxSegments = &( pxWindow->xTxSegments ); } if( listLIST_IS_INITIALISED( pxSegments ) != pdFALSE ) { while( listCURRENT_LIST_LENGTH( pxSegments ) > 0U ) { pxSegment = ( TCPSegment_t * ) listGET_OWNER_OF_HEAD_ENTRY( pxSegments ); vTCPWindowFree( pxSegment ); } } } } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ void vTCPWindowCreate( TCPWindow_t *pxWindow, uint32_t ulRxWindowLength, uint32_t ulTxWindowLength, uint32_t ulAckNumber, uint32_t ulSequenceNumber, uint32_t ulMSS ) { /* Create and initialize a window. */ #if( ipconfigUSE_TCP_WIN == 1 ) { if( xTCPSegments == NULL ) { prvCreateSectors(); } vListInitialise( &pxWindow->xTxSegments ); vListInitialise( &pxWindow->xRxSegments ); vListInitialise( &pxWindow->xPriorityQueue ); /* Priority queue: segments which must be sent immediately */ vListInitialise( &pxWindow->xTxQueue ); /* Transmit queue: segments queued for transmission */ vListInitialise( &pxWindow->xWaitQueue ); /* Waiting queue: outstanding segments */ } #endif /* ipconfigUSE_TCP_WIN == 1 */ if( xTCPWindowLoggingLevel != 0 ) { FreeRTOS_debug_printf( ( "vTCPWindowCreate: for WinLen = Rx/Tx: %lu/%lu\n", ulRxWindowLength, ulTxWindowLength ) ); } pxWindow->xSize.ulRxWindowLength = ulRxWindowLength; pxWindow->xSize.ulTxWindowLength = ulTxWindowLength; vTCPWindowInit( pxWindow, ulAckNumber, ulSequenceNumber, ulMSS ); } /*-----------------------------------------------------------*/ void vTCPWindowInit( TCPWindow_t *pxWindow, uint32_t ulAckNumber, uint32_t ulSequenceNumber, uint32_t ulMSS ) { const int32_t l500ms = 500; pxWindow->u.ulFlags = 0ul; pxWindow->u.bits.bHasInit = pdTRUE_UNSIGNED; if( ulMSS != 0ul ) { if( pxWindow->usMSSInit != 0u ) { pxWindow->usMSSInit = ( uint16_t ) ulMSS; } if( ( ulMSS < ( uint32_t ) pxWindow->usMSS ) || ( pxWindow->usMSS == 0u ) ) { pxWindow->xSize.ulRxWindowLength = ( pxWindow->xSize.ulRxWindowLength / ulMSS ) * ulMSS; pxWindow->usMSS = ( uint16_t ) ulMSS; } } #if( ipconfigUSE_TCP_WIN == 0 ) { pxWindow->xTxSegment.lMaxLength = ( int32_t ) pxWindow->usMSS; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*Start with a timeout of 2 * 500 ms (1 sec). */ pxWindow->lSRTT = l500ms; /* Just for logging, to print relative sequence numbers. */ pxWindow->rx.ulFirstSequenceNumber = ulAckNumber; /* The segment asked for in the next transmission. */ pxWindow->rx.ulCurrentSequenceNumber = ulAckNumber; /* The right-hand side of the receive window. */ pxWindow->rx.ulHighestSequenceNumber = ulAckNumber; pxWindow->tx.ulFirstSequenceNumber = ulSequenceNumber; /* The segment asked for in next transmission. */ pxWindow->tx.ulCurrentSequenceNumber = ulSequenceNumber; /* The sequence number given to the next outgoing byte to be added is maintained by lTCPWindowTxAdd(). */ pxWindow->ulNextTxSequenceNumber = ulSequenceNumber; /* The right-hand side of the transmit window. */ pxWindow->tx.ulHighestSequenceNumber = ulSequenceNumber; pxWindow->ulOurSequenceNumber = ulSequenceNumber; } /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) void vTCPSegmentCleanup( void ) { /* Free and clear the TCP segments pointer. This function should only be called * once FreeRTOS+TCP will no longer be used. No thread-safety is provided for this * function. */ if( xTCPSegments != NULL ) { vPortFreeLarge( xTCPSegments ); xTCPSegments = NULL; } } #endif /* ipconfgiUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ /*============================================================================= * * ###### # # * # # # # * # # # # * # # #### * ###### ## * # ## #### * # # # # * # # # # * ### ## # # * Rx functions * *=============================================================================*/ #if( ipconfigUSE_TCP_WIN == 1 ) static TCPSegment_t *xTCPWindowRxConfirm( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, uint32_t ulLength ) { TCPSegment_t *pxBest = NULL; const ListItem_t *pxIterator; uint32_t ulNextSequenceNumber = ulSequenceNumber + ulLength; const MiniListItem_t* pxEnd = ( const MiniListItem_t* ) listGET_END_MARKER( &pxWindow->xRxSegments ); TCPSegment_t *pxSegment; /* A segment has been received with sequence number 'ulSequenceNumber', where 'ulCurrentSequenceNumber == ulSequenceNumber', which means that exactly this segment was expected. xTCPWindowRxConfirm() will check if there is already another segment with a sequence number between (ulSequenceNumber) and (ulSequenceNumber+ulLength). Normally none will be found, because the next RX segment should have a sequence number equal to '(ulSequenceNumber+ulLength)'. */ /* Iterate through all RX segments that are stored: */ for( pxIterator = ( const ListItem_t * ) listGET_NEXT( pxEnd ); pxIterator != ( const ListItem_t * ) pxEnd; pxIterator = ( const ListItem_t * ) listGET_NEXT( pxIterator ) ) { pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxIterator ); /* And see if there is a segment for which: 'ulSequenceNumber' <= 'pxSegment->ulSequenceNumber' < 'ulNextSequenceNumber' If there are more matching segments, the one with the lowest sequence number shall be taken */ if( ( xSequenceGreaterThanOrEqual( pxSegment->ulSequenceNumber, ulSequenceNumber ) != 0 ) && ( xSequenceLessThan( pxSegment->ulSequenceNumber, ulNextSequenceNumber ) != 0 ) ) { if( ( pxBest == NULL ) || ( xSequenceLessThan( pxSegment->ulSequenceNumber, pxBest->ulSequenceNumber ) != 0 ) ) { pxBest = pxSegment; } } } if( ( pxBest != NULL ) && ( ( pxBest->ulSequenceNumber != ulSequenceNumber ) || ( pxBest->lDataLength != ( int32_t ) ulLength ) ) ) { FreeRTOS_flush_logging(); FreeRTOS_debug_printf( ( "xTCPWindowRxConfirm[%u]: search %lu (+%ld=%lu) found %lu (+%ld=%lu)\n", pxWindow->usPeerPortNumber, ulSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, ulLength, ulSequenceNumber + ulLength - pxWindow->rx.ulFirstSequenceNumber, pxBest->ulSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, pxBest->lDataLength, pxBest->ulSequenceNumber + ( ( uint32_t ) pxBest->lDataLength ) - pxWindow->rx.ulFirstSequenceNumber ) ); } return pxBest; } #endif /* ipconfgiUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) int32_t lTCPWindowRxCheck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, uint32_t ulLength, uint32_t ulSpace ) { uint32_t ulCurrentSequenceNumber, ulLast, ulSavedSequenceNumber; int32_t lReturn, lDistance; TCPSegment_t *pxFound; /* If lTCPWindowRxCheck( ) returns == 0, the packet will be passed directly to user (segment is expected). If it returns a positive number, an earlier packet is missing, but this packet may be stored. If negative, the packet has already been stored, or it is out-of-order, or there is not enough space. As a side-effect, pxWindow->ulUserDataLength will get set to non-zero, if more Rx data may be passed to the user after this packet. */ ulCurrentSequenceNumber = pxWindow->rx.ulCurrentSequenceNumber; /* For Selective Ack (SACK), used when out-of-sequence data come in. */ pxWindow->ucOptionLength = 0u; /* Non-zero if TCP-windows contains data which must be popped. */ pxWindow->ulUserDataLength = 0ul; if( ulCurrentSequenceNumber == ulSequenceNumber ) { /* This is the packet with the lowest sequence number we're waiting for. It can be passed directly to the rx stream. */ if( ulLength > ulSpace ) { FreeRTOS_debug_printf( ( "lTCPWindowRxCheck: Refuse %lu bytes, due to lack of space (%lu)\n", ulLength, ulSpace ) ); lReturn = -1; } else { ulCurrentSequenceNumber += ulLength; if( listCURRENT_LIST_LENGTH( &( pxWindow->xRxSegments ) ) != 0 ) { ulSavedSequenceNumber = ulCurrentSequenceNumber; /* Clean up all sequence received between ulSequenceNumber and ulSequenceNumber + ulLength since they are duplicated. If the server is forced to retransmit packets several time in a row it might send a batch of concatenated packet for speed. So we cannot rely on the packets between ulSequenceNumber and ulSequenceNumber + ulLength to be sequential and it is better to just clean them out. */ do { pxFound = xTCPWindowRxConfirm( pxWindow, ulSequenceNumber, ulLength ); if ( pxFound != NULL ) { /* Remove it because it will be passed to user directly. */ vTCPWindowFree( pxFound ); } } while ( pxFound ); /* Check for following segments that are already in the queue and increment ulCurrentSequenceNumber. */ while( ( pxFound = xTCPWindowRxFind( pxWindow, ulCurrentSequenceNumber ) ) != NULL ) { ulCurrentSequenceNumber += ( uint32_t ) pxFound->lDataLength; /* As all packet below this one have been passed to the user it can be discarded. */ vTCPWindowFree( pxFound ); } if( ulSavedSequenceNumber != ulCurrentSequenceNumber ) { /* After the current data-package, there is more data to be popped. */ pxWindow->ulUserDataLength = ulCurrentSequenceNumber - ulSavedSequenceNumber; if( xTCPWindowLoggingLevel >= 1 ) { FreeRTOS_debug_printf( ( "lTCPWindowRxCheck[%d,%d]: retran %lu (Found %lu bytes at %lu cnt %ld)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, ulSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, pxWindow->ulUserDataLength, ulSavedSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, listCURRENT_LIST_LENGTH( &pxWindow->xRxSegments ) ) ); } } } pxWindow->rx.ulCurrentSequenceNumber = ulCurrentSequenceNumber; /* Packet was expected, may be passed directly to the socket buffer or application. Store the packet at offset 0. */ lReturn = 0; } } else if( ulCurrentSequenceNumber == ( ulSequenceNumber + 1UL ) ) { /* Looks like a TCP keep-alive message. Do not accept/store Rx data ulUserDataLength = 0. Not packet out-of-sync. Just reply to it. */ lReturn = -1; } else { /* The packet is not the one expected. See if it falls within the Rx window so it can be stored. */ /* An "out-of-sequence" segment was received, must have missed one. Prepare a SACK (Selective ACK). */ ulLast = ulSequenceNumber + ulLength; lDistance = ( int32_t ) ( ulLast - ulCurrentSequenceNumber ); if( lDistance <= 0 ) { /* An earlier has been received, must be a retransmission of a packet that has been accepted already. No need to send out a Selective ACK (SACK). */ lReturn = -1; } else if( lDistance > ( int32_t ) ulSpace ) { /* The new segment is ahead of rx.ulCurrentSequenceNumber. The sequence number of this packet is too far ahead, ignore it. */ FreeRTOS_debug_printf( ( "lTCPWindowRxCheck: Refuse %lu+%lu bytes, due to lack of space (%lu)\n", lDistance, ulLength, ulSpace ) ); lReturn = -1; } else { /* See if there is more data in a contiguous block to make the SACK describe a longer range of data. */ /* TODO: SACK's may also be delayed for a short period * This is useful because subsequent packets will be SACK'd with * single one message */ while( ( pxFound = xTCPWindowRxFind( pxWindow, ulLast ) ) != NULL ) { ulLast += ( uint32_t ) pxFound->lDataLength; } if( xTCPWindowLoggingLevel >= 1 ) { FreeRTOS_debug_printf( ( "lTCPWindowRxCheck[%d,%d]: seqnr %lu exp %lu (dist %ld) SACK to %lu\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, ulSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, ulCurrentSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, ( BaseType_t ) ( ulSequenceNumber - ulCurrentSequenceNumber ), /* want this signed */ ulLast - pxWindow->rx.ulFirstSequenceNumber ) ); } /* Now prepare the SACK message. Code OPTION_CODE_SINGLE_SACK already in network byte order. */ pxWindow->ulOptionsData[0] = OPTION_CODE_SINGLE_SACK; /* First sequence number that we received. */ pxWindow->ulOptionsData[1] = FreeRTOS_htonl( ulSequenceNumber ); /* Last + 1 */ pxWindow->ulOptionsData[2] = FreeRTOS_htonl( ulLast ); /* Which make 12 (3*4) option bytes. */ pxWindow->ucOptionLength = 3 * sizeof( pxWindow->ulOptionsData[ 0 ] ); pxFound = xTCPWindowRxFind( pxWindow, ulSequenceNumber ); if( pxFound != NULL ) { /* This out-of-sequence packet has been received for a second time. It is already stored but do send a SACK again. */ lReturn = -1; } else { pxFound = xTCPWindowRxNew( pxWindow, ulSequenceNumber, ( int32_t ) ulLength ); if( pxFound == NULL ) { /* Can not send a SACK, because the segment cannot be stored. */ pxWindow->ucOptionLength = 0u; /* Needs to be stored but there is no segment available. */ lReturn = -1; } else { if( xTCPWindowLoggingLevel != 0 ) { FreeRTOS_debug_printf( ( "lTCPWindowRxCheck[%u,%u]: seqnr %lu (cnt %lu)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, ulSequenceNumber - pxWindow->rx.ulFirstSequenceNumber, listCURRENT_LIST_LENGTH( &pxWindow->xRxSegments ) ) ); FreeRTOS_flush_logging( ); } /* Return a positive value. The packet may be accepted and stored but an earlier packet is still missing. */ lReturn = ( int32_t ) ( ulSequenceNumber - ulCurrentSequenceNumber ); } } } } return lReturn; } #endif /* ipconfgiUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ /*============================================================================= * * ######### # # * # # # # # * # # # * # #### * # ## * # #### * # # # * # # # * ##### # # * * Tx functions * *=============================================================================*/ #if( ipconfigUSE_TCP_WIN == 1 ) static int32_t lTCPIncrementTxPosition( int32_t lPosition, int32_t lMax, int32_t lCount ) { /* +TCP stores data in circular buffers. Calculate the next position to store. */ lPosition += lCount; if( lPosition >= lMax ) { lPosition -= lMax; } return lPosition; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) int32_t lTCPWindowTxAdd( TCPWindow_t *pxWindow, uint32_t ulLength, int32_t lPosition, int32_t lMax ) { int32_t lBytesLeft = ( int32_t ) ulLength, lToWrite; int32_t lDone = 0; TCPSegment_t *pxSegment = pxWindow->pxHeadSegment; /* Puts a message in the Tx-window (after buffer size has been verified). */ if( pxSegment != NULL ) { if( pxSegment->lDataLength < pxSegment->lMaxLength ) { if( ( pxSegment->u.bits.bOutstanding == pdFALSE_UNSIGNED ) && ( pxSegment->lDataLength != 0 ) ) { /* Adding data to a segment that was already in the TX queue. It will be filled-up to a maximum of MSS (maximum segment size). */ lToWrite = FreeRTOS_min_int32( lBytesLeft, pxSegment->lMaxLength - pxSegment->lDataLength ); pxSegment->lDataLength += lToWrite; if( pxSegment->lDataLength >= pxSegment->lMaxLength ) { /* This segment is full, don't add more bytes. */ pxWindow->pxHeadSegment = NULL; } lBytesLeft -= lToWrite; /* ulNextTxSequenceNumber is the sequence number of the next byte to be stored for transmission. */ pxWindow->ulNextTxSequenceNumber += ( uint32_t ) lToWrite; /* Increased the return value. */ lDone += lToWrite; /* Some detailed logging, for those who're interested. */ if( ( xTCPWindowLoggingLevel >= 2 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != 0 ) ) { FreeRTOS_debug_printf( ( "lTCPWindowTxAdd: Add %4lu bytes for seqNr %lu len %4lu (nxt %lu) pos %lu\n", ulLength, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxSegment->lDataLength, pxWindow->ulNextTxSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxSegment->lStreamPos ) ); FreeRTOS_flush_logging( ); } /* Calculate the next position in the circular data buffer, knowing its maximum length 'lMax'. */ lPosition = lTCPIncrementTxPosition( lPosition, lMax, lToWrite ); } } } while( lBytesLeft > 0 ) { /* The current transmission segment is full, create new segments as needed. */ pxSegment = xTCPWindowTxNew( pxWindow, pxWindow->ulNextTxSequenceNumber, pxWindow->usMSS ); if( pxSegment != NULL ) { /* Store as many as needed, but no more than the maximum (MSS). */ lToWrite = FreeRTOS_min_int32( lBytesLeft, pxSegment->lMaxLength ); pxSegment->lDataLength = lToWrite; pxSegment->lStreamPos = lPosition; lBytesLeft -= lToWrite; lPosition = lTCPIncrementTxPosition( lPosition, lMax, lToWrite ); pxWindow->ulNextTxSequenceNumber += ( uint32_t ) lToWrite; lDone += lToWrite; /* Link this segment in the Tx-Queue. */ vListInsertFifo( &( pxWindow->xTxQueue ), &( pxSegment->xQueueItem ) ); /* Let 'pxHeadSegment' point to this segment if there is still space. */ if( pxSegment->lDataLength < pxSegment->lMaxLength ) { pxWindow->pxHeadSegment = pxSegment; } else { pxWindow->pxHeadSegment = NULL; } if( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != 0 ) { if( ( xTCPWindowLoggingLevel >= 3 ) || ( ( xTCPWindowLoggingLevel >= 2 ) && ( pxWindow->pxHeadSegment != NULL ) ) ) { FreeRTOS_debug_printf( ( "lTCPWindowTxAdd: New %4ld bytes for seqNr %lu len %4lu (nxt %lu) pos %lu\n", ulLength, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxSegment->lDataLength, pxWindow->ulNextTxSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxSegment->lStreamPos ) ); FreeRTOS_flush_logging( ); } } } else { /* A sever situation: running out of segments for transmission. No more data can be sent at the moment. */ if( lDone != 0 ) { FreeRTOS_debug_printf( ( "lTCPWindowTxAdd: Sorry all buffers full (cancel %ld bytes)\n", lBytesLeft ) ); } break; } } return lDone; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) BaseType_t xTCPWindowTxDone( TCPWindow_t *pxWindow ) { return listLIST_IS_EMPTY( ( &pxWindow->xTxSegments) ); } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static BaseType_t prvTCPWindowTxHasSpace( TCPWindow_t *pxWindow, uint32_t ulWindowSize ) { uint32_t ulTxOutstanding; BaseType_t xHasSpace; TCPSegment_t *pxSegment; /* This function will look if there is new transmission data. It will return true if there is data to be sent. */ pxSegment = xTCPWindowPeekHead( &( pxWindow->xTxQueue ) ); if( pxSegment == NULL ) { xHasSpace = pdFALSE; } else { /* How much data is outstanding, i.e. how much data has been sent but not yet acknowledged ? */ if( pxWindow->tx.ulHighestSequenceNumber >= pxWindow->tx.ulCurrentSequenceNumber ) { ulTxOutstanding = pxWindow->tx.ulHighestSequenceNumber - pxWindow->tx.ulCurrentSequenceNumber; } else { ulTxOutstanding = 0UL; } /* Subtract this from the peer's space. */ ulWindowSize -= FreeRTOS_min_uint32( ulWindowSize, ulTxOutstanding ); /* See if the next segment may be sent. */ if( ulWindowSize >= ( uint32_t ) pxSegment->lDataLength ) { xHasSpace = pdTRUE; } else { xHasSpace = pdFALSE; } /* If 'xHasSpace', it looks like the peer has at least space for 1 more new segment of size MSS. xSize.ulTxWindowLength is the self-imposed limitation of the transmission window (in case of many resends it may be decreased). */ if( ( ulTxOutstanding != 0UL ) && ( pxWindow->xSize.ulTxWindowLength < ulTxOutstanding + ( ( uint32_t ) pxSegment->lDataLength ) ) ) { xHasSpace = pdFALSE; } } return xHasSpace; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) BaseType_t xTCPWindowTxHasData( TCPWindow_t *pxWindow, uint32_t ulWindowSize, TickType_t *pulDelay ) { TCPSegment_t *pxSegment; BaseType_t xReturn; TickType_t ulAge, ulMaxAge; *pulDelay = 0u; if( listLIST_IS_EMPTY( &pxWindow->xPriorityQueue ) == pdFALSE ) { /* No need to look at retransmissions or new transmission as long as there are priority segments. *pulDelay equals zero, meaning it must be sent out immediately. */ xReturn = pdTRUE; } else { pxSegment = xTCPWindowPeekHead( &( pxWindow->xWaitQueue ) ); if( pxSegment != NULL ) { /* There is an outstanding segment, see if it is time to resend it. */ ulAge = ulTimerGetAge( &pxSegment->xTransmitTimer ); /* After a packet has been sent for the first time, it will wait '1 * lSRTT' ms for an ACK. A second time it will wait '2 * lSRTT' ms, each time doubling the time-out */ ulMaxAge = ( 1u << pxSegment->u.bits.ucTransmitCount ) * ( ( uint32_t ) pxWindow->lSRTT ); if( ulMaxAge > ulAge ) { /* A segment must be sent after this amount of msecs */ *pulDelay = ulMaxAge - ulAge; } xReturn = pdTRUE; } else { /* No priority segment, no outstanding data, see if there is new transmission data. */ pxSegment = xTCPWindowPeekHead( &pxWindow->xTxQueue ); /* See if it fits in the peer's reception window. */ if( pxSegment == NULL ) { xReturn = pdFALSE; } else if( prvTCPWindowTxHasSpace( pxWindow, ulWindowSize ) == pdFALSE ) { /* Too many outstanding messages. */ xReturn = pdFALSE; } else if( ( pxWindow->u.bits.bSendFullSize != pdFALSE_UNSIGNED ) && ( pxSegment->lDataLength < pxSegment->lMaxLength ) ) { /* 'bSendFullSize' is a special optimisation. If true, the driver will only sent completely filled packets (of MSS bytes). */ xReturn = pdFALSE; } else { xReturn = pdTRUE; } } } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) uint32_t ulTCPWindowTxGet( TCPWindow_t *pxWindow, uint32_t ulWindowSize, int32_t *plPosition ) { TCPSegment_t *pxSegment; uint32_t ulMaxTime; uint32_t ulReturn = ~0UL; /* Fetches data to be sent-out now. Priority messages: segments with a resend need no check current sliding window size. */ pxSegment = xTCPWindowGetHead( &( pxWindow->xPriorityQueue ) ); pxWindow->ulOurSequenceNumber = pxWindow->tx.ulHighestSequenceNumber; if( pxSegment == NULL ) { /* Waiting messages: outstanding messages with a running timer neither check peer's reception window size because these packets have been sent earlier. */ pxSegment = xTCPWindowPeekHead( &( pxWindow->xWaitQueue ) ); if( pxSegment != NULL ) { /* Do check the timing. */ ulMaxTime = ( 1u << pxSegment->u.bits.ucTransmitCount ) * ( ( uint32_t ) pxWindow->lSRTT ); if( ulTimerGetAge( &pxSegment->xTransmitTimer ) > ulMaxTime ) { /* A normal (non-fast) retransmission. Move it from the head of the waiting queue. */ pxSegment = xTCPWindowGetHead( &( pxWindow->xWaitQueue ) ); pxSegment->u.bits.ucDupAckCount = pdFALSE_UNSIGNED; /* Some detailed logging. */ if( ( xTCPWindowLoggingLevel != 0 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != 0 ) ) { FreeRTOS_debug_printf( ( "ulTCPWindowTxGet[%u,%u]: WaitQueue %ld bytes for sequence number %lu (%lX)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, pxSegment->lDataLength, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxSegment->ulSequenceNumber ) ); FreeRTOS_flush_logging( ); } } else { pxSegment = NULL; } } if( pxSegment == NULL ) { /* New messages: sent-out for the first time. Check current sliding window size of peer. */ pxSegment = xTCPWindowPeekHead( &( pxWindow->xTxQueue ) ); if( pxSegment == NULL ) { /* No segments queued. */ ulReturn = 0UL; } else if( ( pxWindow->u.bits.bSendFullSize != pdFALSE_UNSIGNED ) && ( pxSegment->lDataLength < pxSegment->lMaxLength ) ) { /* A segment has been queued but the driver waits until it has a full size of MSS. */ ulReturn = 0; } else if( prvTCPWindowTxHasSpace( pxWindow, ulWindowSize ) == pdFALSE ) { /* Peer has no more space at this moment. */ ulReturn = 0; } else { /* Move it out of the Tx queue. */ pxSegment = xTCPWindowGetHead( &( pxWindow->xTxQueue ) ); /* Don't let pxHeadSegment point to this segment any more, so no more data will be added. */ if( pxWindow->pxHeadSegment == pxSegment ) { pxWindow->pxHeadSegment = NULL; } /* pxWindow->tx.highest registers the highest sequence number in our transmission window. */ pxWindow->tx.ulHighestSequenceNumber = pxSegment->ulSequenceNumber + ( ( uint32_t ) pxSegment->lDataLength ); /* ...and more detailed logging */ if( ( xTCPWindowLoggingLevel >= 2 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "ulTCPWindowTxGet[%u,%u]: XmitQueue %ld bytes for sequence number %lu (ws %lu)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, pxSegment->lDataLength, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulWindowSize ) ); FreeRTOS_flush_logging( ); } } } } else { /* There is a priority segment. It doesn't need any checking for space or timeouts. */ if( xTCPWindowLoggingLevel != 0 ) { FreeRTOS_debug_printf( ( "ulTCPWindowTxGet[%u,%u]: PrioQueue %ld bytes for sequence number %lu (ws %lu)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, pxSegment->lDataLength, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulWindowSize ) ); FreeRTOS_flush_logging( ); } } /* See if it has already been determined to return 0. */ if( ulReturn != 0UL ) { configASSERT( listLIST_ITEM_CONTAINER( &(pxSegment->xQueueItem ) ) == NULL ); /* Now that the segment will be transmitted, add it to the tail of the waiting queue. */ vListInsertFifo( &pxWindow->xWaitQueue, &pxSegment->xQueueItem ); /* And mark it as outstanding. */ pxSegment->u.bits.bOutstanding = pdTRUE_UNSIGNED; /* Administer the transmit count, needed for fast retransmissions. */ ( pxSegment->u.bits.ucTransmitCount )++; /* If there have been several retransmissions (4), decrease the size of the transmission window to at most 2 times MSS. */ if( pxSegment->u.bits.ucTransmitCount == MAX_TRANSMIT_COUNT_USING_LARGE_WINDOW ) { if( pxWindow->xSize.ulTxWindowLength > ( 2U * pxWindow->usMSS ) ) { FreeRTOS_debug_printf( ( "ulTCPWindowTxGet[%u - %d]: Change Tx window: %lu -> %u\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, pxWindow->xSize.ulTxWindowLength, 2 * pxWindow->usMSS ) ); pxWindow->xSize.ulTxWindowLength = ( 2UL * pxWindow->usMSS ); } } /* Clear the transmit timer. */ vTCPTimerSet( &( pxSegment->xTransmitTimer ) ); pxWindow->ulOurSequenceNumber = pxSegment->ulSequenceNumber; /* Inform the caller where to find the data within the queue. */ *plPosition = pxSegment->lStreamPos; /* And return the length of the data segment */ ulReturn = ( uint32_t ) pxSegment->lDataLength; } return ulReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static uint32_t prvTCPWindowTxCheckAck( TCPWindow_t *pxWindow, uint32_t ulFirst, uint32_t ulLast ) { uint32_t ulBytesConfirmed = 0u; uint32_t ulSequenceNumber = ulFirst, ulDataLength; const ListItem_t *pxIterator; const MiniListItem_t *pxEnd = ( const MiniListItem_t* )listGET_END_MARKER( &pxWindow->xTxSegments ); BaseType_t xDoUnlink; TCPSegment_t *pxSegment; /* An acknowledgement or a selective ACK (SACK) was received. See if some outstanding data may be removed from the transmission queue(s). All TX segments for which ( ( ulSequenceNumber >= ulFirst ) && ( ulSequenceNumber < ulLast ) in a contiguous block. Note that the segments are stored in xTxSegments in a strict sequential order. */ /* SRTT[i] = (1-a) * SRTT[i-1] + a * RTT 0 < a < 1; usually a = 1/8 RTO = 2 * SRTT where: RTT is Round Trip Time SRTT is Smoothed RTT RTO is Retransmit timeout A Smoothed RTT will increase quickly, but it is conservative when becoming smaller. */ for( pxIterator = ( const ListItem_t * ) listGET_NEXT( pxEnd ); ( pxIterator != ( const ListItem_t * ) pxEnd ) && ( xSequenceLessThan( ulSequenceNumber, ulLast ) != 0 ); ) { xDoUnlink = pdFALSE; pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxIterator ); /* Move to the next item because the current item might get removed. */ pxIterator = ( const ListItem_t * ) listGET_NEXT( pxIterator ); /* Continue if this segment does not fall within the ACK'd range. */ if( xSequenceGreaterThan( ulSequenceNumber, pxSegment->ulSequenceNumber ) != pdFALSE ) { continue; } /* Is it ready? */ if( ulSequenceNumber != pxSegment->ulSequenceNumber ) { break; } ulDataLength = ( uint32_t ) pxSegment->lDataLength; if( pxSegment->u.bits.bAcked == pdFALSE_UNSIGNED ) { if( xSequenceGreaterThan( pxSegment->ulSequenceNumber + ( uint32_t )ulDataLength, ulLast ) != pdFALSE ) { /* What happens? Only part of this segment was accepted, probably due to WND limits AAAAAAA BBBBBBB << acked aaaaaaa aaaa << sent */ #if( ipconfigHAS_DEBUG_PRINTF != 0 ) { uint32_t ulFirstSeq = pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber; FreeRTOS_debug_printf( ( "prvTCPWindowTxCheckAck[%u.%u]: %lu - %lu Partial sequence number %lu - %lu\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, ulFirstSeq - pxWindow->tx.ulFirstSequenceNumber, ulLast - pxWindow->tx.ulFirstSequenceNumber, ulFirstSeq, ulFirstSeq + ulDataLength ) ); } #endif /* ipconfigHAS_DEBUG_PRINTF */ break; } /* This segment is fully ACK'd, set the flag. */ pxSegment->u.bits.bAcked = pdTRUE_UNSIGNED; /* Calculate the RTT only if the segment was sent-out for the first time and if this is the last ACK'd segment in a range. */ if( ( pxSegment->u.bits.ucTransmitCount == 1 ) && ( ( pxSegment->ulSequenceNumber + ulDataLength ) == ulLast ) ) { int32_t mS = ( int32_t ) ulTimerGetAge( &( pxSegment->xTransmitTimer ) ); if( pxWindow->lSRTT >= mS ) { /* RTT becomes smaller: adapt slowly. */ pxWindow->lSRTT = ( ( winSRTT_DECREMENT_NEW * mS ) + ( winSRTT_DECREMENT_CURRENT * pxWindow->lSRTT ) ) / ( winSRTT_DECREMENT_NEW + winSRTT_DECREMENT_CURRENT ); } else { /* RTT becomes larger: adapt quicker */ pxWindow->lSRTT = ( ( winSRTT_INCREMENT_NEW * mS ) + ( winSRTT_INCREMENT_CURRENT * pxWindow->lSRTT ) ) / ( winSRTT_INCREMENT_NEW + winSRTT_INCREMENT_CURRENT ); } /* Cap to the minimum of 50ms. */ if( pxWindow->lSRTT < winSRTT_CAP_mS ) { pxWindow->lSRTT = winSRTT_CAP_mS; } } /* Unlink it from the 3 queues, but do not destroy it (yet). */ xDoUnlink = pdTRUE; } /* pxSegment->u.bits.bAcked is now true. Is it located at the left side of the transmission queue? If so, it may be freed. */ if( ulSequenceNumber == pxWindow->tx.ulCurrentSequenceNumber ) { if( ( xTCPWindowLoggingLevel >= 2 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "prvTCPWindowTxCheckAck: %lu - %lu Ready sequence number %lu\n", ulFirst - pxWindow->tx.ulFirstSequenceNumber, ulLast - pxWindow->tx.ulFirstSequenceNumber, pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber ) ); } /* Increase the left-hand value of the transmission window. */ pxWindow->tx.ulCurrentSequenceNumber += ulDataLength; /* This function will return the number of bytes that the tail of txStream may be advanced. */ ulBytesConfirmed += ulDataLength; /* All segments below tx.ulCurrentSequenceNumber may be freed. */ vTCPWindowFree( pxSegment ); /* No need to unlink it any more. */ xDoUnlink = pdFALSE; } if( ( xDoUnlink != pdFALSE ) && ( listLIST_ITEM_CONTAINER( &( pxSegment->xQueueItem ) ) != NULL ) ) { /* Remove item from its queues. */ uxListRemove( &pxSegment->xQueueItem ); } ulSequenceNumber += ulDataLength; } return ulBytesConfirmed; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) static uint32_t prvTCPWindowFastRetransmit( TCPWindow_t *pxWindow, uint32_t ulFirst ) { const ListItem_t *pxIterator; const MiniListItem_t* pxEnd; TCPSegment_t *pxSegment; uint32_t ulCount = 0UL; /* A higher Tx block has been acknowledged. Now iterate through the xWaitQueue to find a possible condition for a FAST retransmission. */ pxEnd = ( const MiniListItem_t* ) listGET_END_MARKER( &( pxWindow->xWaitQueue ) ); for( pxIterator = ( const ListItem_t * ) listGET_NEXT( pxEnd ); pxIterator != ( const ListItem_t * ) pxEnd; ) { /* Get the owner, which is a TCP segment. */ pxSegment = ( TCPSegment_t * ) listGET_LIST_ITEM_OWNER( pxIterator ); /* Hop to the next item before the current gets unlinked. */ pxIterator = ( const ListItem_t * ) listGET_NEXT( pxIterator ); /* Fast retransmission: When 3 packets with a higher sequence number have been acknowledged by the peer, it is very unlikely a current packet will ever arrive. It will be retransmitted far before the RTO. */ if( ( pxSegment->u.bits.bAcked == pdFALSE_UNSIGNED ) && ( xSequenceLessThan( pxSegment->ulSequenceNumber, ulFirst ) != pdFALSE ) && ( ++( pxSegment->u.bits.ucDupAckCount ) == DUPLICATE_ACKS_BEFORE_FAST_RETRANSMIT ) ) { pxSegment->u.bits.ucTransmitCount = pdFALSE_UNSIGNED; /* Not clearing 'ucDupAckCount' yet as more SACK's might come in which might lead to a second fast rexmit. */ if( ( xTCPWindowLoggingLevel >= 0 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "prvTCPWindowFastRetransmit: Requeue sequence number %lu < %lu\n", pxSegment->ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulFirst - pxWindow->tx.ulFirstSequenceNumber ) ); FreeRTOS_flush_logging( ); } /* Remove it from xWaitQueue. */ uxListRemove( &pxSegment->xQueueItem ); /* Add this segment to the priority queue so it gets retransmitted immediately. */ vListInsertFifo( &( pxWindow->xPriorityQueue ), &( pxSegment->xQueueItem ) ); ulCount++; } } return ulCount; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) uint32_t ulTCPWindowTxAck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber ) { uint32_t ulFirstSequence, ulReturn; /* Receive a normal ACK. */ ulFirstSequence = pxWindow->tx.ulCurrentSequenceNumber; if( xSequenceLessThanOrEqual( ulSequenceNumber, ulFirstSequence ) != pdFALSE ) { ulReturn = 0UL; } else { ulReturn = prvTCPWindowTxCheckAck( pxWindow, ulFirstSequence, ulSequenceNumber ); } return ulReturn; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 1 ) uint32_t ulTCPWindowTxSack( TCPWindow_t *pxWindow, uint32_t ulFirst, uint32_t ulLast ) { uint32_t ulAckCount = 0UL; uint32_t ulCurrentSequenceNumber = pxWindow->tx.ulCurrentSequenceNumber; /* Receive a SACK option. */ ulAckCount = prvTCPWindowTxCheckAck( pxWindow, ulFirst, ulLast ); prvTCPWindowFastRetransmit( pxWindow, ulFirst ); if( ( xTCPWindowLoggingLevel >= 1 ) && ( xSequenceGreaterThan( ulFirst, ulCurrentSequenceNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "ulTCPWindowTxSack[%u,%u]: from %lu to %lu (ack = %lu)\n", pxWindow->usPeerPortNumber, pxWindow->usOurPortNumber, ulFirst - pxWindow->tx.ulFirstSequenceNumber, ulLast - pxWindow->tx.ulFirstSequenceNumber, pxWindow->tx.ulCurrentSequenceNumber - pxWindow->tx.ulFirstSequenceNumber ) ); FreeRTOS_flush_logging( ); } return ulAckCount; } #endif /* ipconfigUSE_TCP_WIN == 1 */ /*-----------------------------------------------------------*/ /* ##### # ##### #### ###### # # # # # # # # # # # # # # # # # # ### ##### # # # # # # # # # # # # # # ##### # # # # # # #### # # # # # # # # # # # # # # # # # #### # # # # #### ##### # # # #### #### #### # ### */ #if( ipconfigUSE_TCP_WIN == 0 ) int32_t lTCPWindowRxCheck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, uint32_t ulLength, uint32_t ulSpace ) { int32_t iReturn; /* Data was received at 'ulSequenceNumber'. See if it was expected and if there is enough space to store the new data. */ if( ( pxWindow->rx.ulCurrentSequenceNumber != ulSequenceNumber ) || ( ulSpace < ulLength ) ) { iReturn = -1; } else { pxWindow->rx.ulCurrentSequenceNumber += ( uint32_t ) ulLength; iReturn = 0; } return iReturn; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) int32_t lTCPWindowTxAdd( TCPWindow_t *pxWindow, uint32_t ulLength, int32_t lPosition, int32_t lMax ) { TCPSegment_t *pxSegment = &( pxWindow->xTxSegment ); int32_t lResult; /* Data is being scheduled for transmission. */ /* lMax would indicate the size of the txStream. */ ( void ) lMax; /* This is tiny TCP: there is only 1 segment for outgoing data. As long as 'lDataLength' is unequal to zero, the segment is still occupied. */ if( pxSegment->lDataLength > 0 ) { lResult = 0L; } else { if( ulLength > ( uint32_t ) pxSegment->lMaxLength ) { if( ( xTCPWindowLoggingLevel != 0 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "lTCPWindowTxAdd: can only store %ld / %ld bytes\n", ulLength, pxSegment->lMaxLength ) ); } ulLength = ( uint32_t ) pxSegment->lMaxLength; } if( ( xTCPWindowLoggingLevel != 0 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "lTCPWindowTxAdd: SeqNr %ld (%ld) Len %ld\n", pxWindow->ulNextTxSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxWindow->tx.ulCurrentSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulLength ) ); } /* The sequence number of the first byte in this packet. */ pxSegment->ulSequenceNumber = pxWindow->ulNextTxSequenceNumber; pxSegment->lDataLength = ( int32_t ) ulLength; pxSegment->lStreamPos = lPosition; pxSegment->u.ulFlags = 0UL; vTCPTimerSet( &( pxSegment->xTransmitTimer ) ); /* Increase the sequence number of the next data to be stored for transmission. */ pxWindow->ulNextTxSequenceNumber += ulLength; lResult = ( int32_t )ulLength; } return lResult; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) uint32_t ulTCPWindowTxGet( TCPWindow_t *pxWindow, uint32_t ulWindowSize, int32_t *plPosition ) { TCPSegment_t *pxSegment = &( pxWindow->xTxSegment ); uint32_t ulLength = ( uint32_t ) pxSegment->lDataLength; uint32_t ulMaxTime; if( ulLength != 0UL ) { /* _HT_ Still under investigation */ ( void ) ulWindowSize; if( pxSegment->u.bits.bOutstanding != pdFALSE_UNSIGNED ) { /* As 'ucTransmitCount' has a minimum of 1, take 2 * RTT */ ulMaxTime = ( ( uint32_t ) 1u << pxSegment->u.bits.ucTransmitCount ) * ( ( uint32_t ) pxWindow->lSRTT ); if( ulTimerGetAge( &( pxSegment->xTransmitTimer ) ) < ulMaxTime ) { ulLength = 0ul; } } if( ulLength != 0ul ) { pxSegment->u.bits.bOutstanding = pdTRUE_UNSIGNED; pxSegment->u.bits.ucTransmitCount++; vTCPTimerSet (&pxSegment->xTransmitTimer); pxWindow->ulOurSequenceNumber = pxSegment->ulSequenceNumber; *plPosition = pxSegment->lStreamPos; } } return ulLength; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) BaseType_t xTCPWindowTxDone( TCPWindow_t *pxWindow ) { BaseType_t xReturn; /* Has the outstanding data been sent because user wants to shutdown? */ if( pxWindow->xTxSegment.lDataLength == 0 ) { xReturn = pdTRUE; } else { xReturn = pdFALSE; } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) static BaseType_t prvTCPWindowTxHasSpace( TCPWindow_t *pxWindow, uint32_t ulWindowSize ); static BaseType_t prvTCPWindowTxHasSpace( TCPWindow_t *pxWindow, uint32_t ulWindowSize ) { BaseType_t xReturn; if( ulWindowSize >= pxWindow->usMSSInit ) { xReturn = pdTRUE; } else { xReturn = pdFALSE; } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) BaseType_t xTCPWindowTxHasData( TCPWindow_t *pxWindow, uint32_t ulWindowSize, TickType_t *pulDelay ) { TCPSegment_t *pxSegment = &( pxWindow->xTxSegment ); BaseType_t xReturn; TickType_t ulAge, ulMaxAge; /* Check data to be sent. */ *pulDelay = ( TickType_t ) 0; if( pxSegment->lDataLength == 0 ) { /* Got nothing to send right now. */ xReturn = pdFALSE; } else { if( pxSegment->u.bits.bOutstanding != pdFALSE_UNSIGNED ) { ulAge = ulTimerGetAge ( &pxSegment->xTransmitTimer ); ulMaxAge = ( ( TickType_t ) 1u << pxSegment->u.bits.ucTransmitCount ) * ( ( uint32_t ) pxWindow->lSRTT ); if( ulMaxAge > ulAge ) { *pulDelay = ulMaxAge - ulAge; } xReturn = pdTRUE; } else if( prvTCPWindowTxHasSpace( pxWindow, ulWindowSize ) == pdFALSE ) { /* Too many outstanding messages. */ xReturn = pdFALSE; } else { xReturn = pdTRUE; } } return xReturn; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) uint32_t ulTCPWindowTxAck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber ) { TCPSegment_t *pxSegment = &( pxWindow->xTxSegment ); uint32_t ulDataLength = ( uint32_t ) pxSegment->lDataLength; /* Receive a normal ACK */ if( ulDataLength != 0ul ) { if( ulSequenceNumber < ( pxWindow->tx.ulCurrentSequenceNumber + ulDataLength ) ) { if( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) { FreeRTOS_debug_printf( ( "win_tx_ack: acked %ld expc %ld len %ld\n", ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, pxWindow->tx.ulCurrentSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulDataLength ) ); } /* Nothing to send right now. */ ulDataLength = 0ul; } else { pxWindow->tx.ulCurrentSequenceNumber += ulDataLength; if( ( xTCPWindowLoggingLevel != 0 ) && ( ipconfigTCP_MAY_LOG_PORT( pxWindow->usOurPortNumber ) != pdFALSE ) ) { FreeRTOS_debug_printf( ( "win_tx_ack: acked seqnr %ld len %ld\n", ulSequenceNumber - pxWindow->tx.ulFirstSequenceNumber, ulDataLength ) ); } pxSegment->lDataLength = 0; } } return ulDataLength; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) BaseType_t xTCPWindowRxEmpty( TCPWindow_t *pxWindow ) { /* Return true if 'ulCurrentSequenceNumber >= ulHighestSequenceNumber' 'ulCurrentSequenceNumber' is the highest sequence number stored, 'ulHighestSequenceNumber' is the highest sequence number seen. */ return xSequenceGreaterThanOrEqual( pxWindow->rx.ulCurrentSequenceNumber, pxWindow->rx.ulHighestSequenceNumber ); } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/ #if( ipconfigUSE_TCP_WIN == 0 ) /* Destroy a window (always returns NULL) */ void vTCPWindowDestroy( TCPWindow_t *pxWindow ) { /* As in tiny TCP there are no shared segments descriptors, there is nothing to release. */ ( void ) pxWindow; } #endif /* ipconfigUSE_TCP_WIN == 0 */ /*-----------------------------------------------------------*/