/*
 * FreeRTOS+TCP V2.2.1
 * 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-PLUS-TCP
 */

#ifndef	FREERTOS_TCP_WIN_H
#define	FREERTOS_TCP_WIN_H

#ifdef __cplusplus
extern "C" {
#endif

/* The name xTCPTimer was already use as the name of an IP-timer. */
typedef struct xTCPTimerStruct
{
	uint32_t ulBorn;
} TCPTimer_t;

typedef struct xTCP_SEGMENT
{
	uint32_t ulSequenceNumber;		/* The sequence number of the first byte in this packet */
	int32_t lMaxLength;				/* Maximum space, number of bytes which can be stored in this segment */
	int32_t lDataLength;			/* Actual number of bytes */
	int32_t lStreamPos;				/* reference to the [t|r]xStream of the socket */
	TCPTimer_t xTransmitTimer;		/* saves a timestamp at the moment this segment gets transmitted (TX only) */
	union
	{
		struct
		{
			uint32_t
				ucTransmitCount : 8,/* Number of times the segment has been transmitted, used to calculate the RTT */
				ucDupAckCount : 8,	/* Counts the number of times that a higher segment was ACK'd. After 3 times a Fast Retransmission takes place */
				bOutstanding : 1,	/* It the peer's turn, we're just waiting for an ACK */
				bAcked : 1,			/* This segment has been acknowledged */
				bIsForRx : 1;		/* pdTRUE if segment is used for reception */
		} bits;
		uint32_t ulFlags;
	} u;
#if( ipconfigUSE_TCP_WIN != 0 )
	struct xLIST_ITEM xQueueItem;	/* TX only: segments can be linked in one of three queues: xPriorityQueue, xTxQueue, and xWaitQueue */
	struct xLIST_ITEM xSegmentItem;	/* With this item the segment can be connected to a list, depending on who is owning it */
#endif
} TCPSegment_t;

typedef struct xTCP_WINSIZE
{
	uint32_t ulRxWindowLength;
	uint32_t ulTxWindowLength;
} TCPWinSize_t;

/*
 * If TCP time-stamps are being used, they will occupy 12 bytes in
 * each packet, and thus the message space will become smaller
 */
/* Keep this as a multiple of 4 */
#if( ipconfigUSE_TCP_WIN == 1 )
	#define ipSIZE_TCP_OPTIONS	16U
#else
	#define ipSIZE_TCP_OPTIONS	12U
#endif

/*
 *	Every TCP connection owns a TCP window for the administration of all packets
 *	It owns two sets of segment descriptors, incoming and outgoing
 */
typedef struct xTCP_WINDOW
{
	union
	{
		struct
		{
			uint32_t
				bHasInit : 1,		/* The window structure has been initialised */
				bSendFullSize : 1,	/* May only send packets with a size equal to MSS (for optimisation) */
				bTimeStamps : 1;	/* Socket is supposed to use TCP time-stamps. This depends on the */
		} bits;						/* party which opens the connection */
		uint32_t ulFlags;
	} u;
	TCPWinSize_t xSize;
	struct
	{
		uint32_t ulFirstSequenceNumber;	 /* Logging & debug: the first segment received/sent in this connection
										  * for Tx: initial send sequence number (ISS)
										  * for Rx: initial receive sequence number (IRS) */
		uint32_t ulCurrentSequenceNumber;/* Tx/Rx: the oldest sequence number not yet confirmed, also SND.UNA / RCV.NXT
										  * In other words: the sequence number of the left side of the sliding window */
		uint32_t ulFINSequenceNumber;	 /* The sequence number which carried the FIN flag */
		uint32_t ulHighestSequenceNumber;/* Sequence number of the right-most byte + 1 */
	} rx, tx;
	uint32_t ulOurSequenceNumber;		/* The SEQ number we're sending out */
	uint32_t ulUserDataLength;			/* Number of bytes in Rx buffer which may be passed to the user, after having received a 'missing packet' */
	uint32_t ulNextTxSequenceNumber;	/* The sequence number given to the next byte to be added for transmission */
	int32_t lSRTT;						/* Smoothed Round Trip Time, it may increment quickly and it decrements slower */
	uint8_t ucOptionLength;				/* Number of valid bytes in ulOptionsData[] */
#if( ipconfigUSE_TCP_WIN == 1 )
	List_t xPriorityQueue;				/* Priority queue: segments which must be sent immediately */
	List_t xTxQueue;					/* Transmit queue: segments queued for transmission */
	List_t xWaitQueue;					/* Waiting queue:  outstanding segments */
	TCPSegment_t *pxHeadSegment;		/* points to a segment which has not been transmitted and it's size is still growing (user data being added) */
	uint32_t ulOptionsData[ipSIZE_TCP_OPTIONS/sizeof(uint32_t)];	/* Contains the options we send out */
	List_t xTxSegments;					/* A linked list of all transmission segments, sorted on sequence number */
	List_t xRxSegments;					/* A linked list of reception segments, order depends on sequence of arrival */
#else
	/* For tiny TCP, there is only 1 outstanding TX segment */
	TCPSegment_t xTxSegment;			/* Priority queue */
#endif
	uint16_t usOurPortNumber;			/* Mostly for debugging/logging: our TCP port number */
	uint16_t usPeerPortNumber;			/* debugging/logging: the peer's TCP port number */
	uint16_t usMSS;						/* Current accepted MSS */
	uint16_t usMSSInit;					/* MSS as configured by the socket owner */
} TCPWindow_t;


/*=============================================================================
 *
 * Creation and destruction
 *
 *=============================================================================*/

/* Create and initialize a window */
void vTCPWindowCreate( TCPWindow_t *pxWindow, uint32_t ulRxWindowLength,
	uint32_t ulTxWindowLength, uint32_t ulAckNumber, uint32_t ulSequenceNumber, uint32_t ulMSS );

/* Destroy a window (always returns NULL)
 * It will free some resources: a collection of segments */
void vTCPWindowDestroy( TCPWindow_t const * pxWindow );

/* Initialize a window */
void vTCPWindowInit( TCPWindow_t *pxWindow, uint32_t ulAckNumber, uint32_t ulSequenceNumber, uint32_t ulMSS );

/* Clean up allocated segments. Should only be called when FreeRTOS+TCP will no longer be used. */
void vTCPSegmentCleanup( void );

/*=============================================================================
 *
 * Rx functions
 *
 *=============================================================================*/

/* if true may be passed directly to user (segment expected and window is empty)
 * But pxWindow->ackno should always be used to set "BUF->ackno" */
int32_t lTCPWindowRxCheck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber, uint32_t ulLength, uint32_t ulSpace );

/* This function will be called as soon as a FIN is received. It will return true
 * if there are no 'open' reception segments */
BaseType_t xTCPWindowRxEmpty( const TCPWindow_t *pxWindow );

/*=============================================================================
 *
 * Tx functions
 *
 *=============================================================================*/

/* Adds data to the Tx-window */
int32_t lTCPWindowTxAdd( TCPWindow_t *pxWindow, uint32_t ulLength, int32_t lPosition, int32_t lMax );

/* Check data to be sent and calculate the time period we may sleep */
BaseType_t xTCPWindowTxHasData( TCPWindow_t const * pxWindow, uint32_t ulWindowSize, TickType_t *pulDelay );

/* See if anything is left to be sent
 * Function will be called when a FIN has been received. Only when the TX window is clean,
 * it will return pdTRUE */
BaseType_t xTCPWindowTxDone( const TCPWindow_t *pxWindow );

/* Fetches data to be sent.
 * apPos will point to a location with the circular data buffer: txStream */
uint32_t ulTCPWindowTxGet( TCPWindow_t *pxWindow, uint32_t ulWindowSize, int32_t *plPosition );

/* Receive a normal ACK */
uint32_t ulTCPWindowTxAck( TCPWindow_t *pxWindow, uint32_t ulSequenceNumber );

/* Receive a SACK option */
uint32_t ulTCPWindowTxSack( TCPWindow_t *pxWindow, uint32_t ulFirst, uint32_t ulLast );


#ifdef __cplusplus
}	/* extern "C" */
#endif

#endif /* FREERTOS_TCP_WIN_H */
