/*
 * FreeRTOS+TCP <DEVELOPMENT BRANCH>
 * Copyright (C) 2022 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * 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_TCP_IP_IPv6.c
 * @brief Module which handles the TCP connections for FreeRTOS+TCP.
 * It depends on  FreeRTOS_TCP_WIN.c, which handles the TCP windowing
 * schemes.
 *
 * Endianness: in this module all ports and IP addresses are stored in
 * host byte-order, except fields in the IP-packets
 */

/* Standard includes. */
#include <stdint.h>
#include <stdio.h>

/* FreeRTOS includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "queue.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_DHCP.h"
#include "NetworkInterface.h"
#include "NetworkBufferManagement.h"
#include "FreeRTOS_ARP.h"

#include "FreeRTOS_TCP_Reception.h"
#include "FreeRTOS_TCP_Transmission.h"
#include "FreeRTOS_TCP_State_Handling.h"
#include "FreeRTOS_TCP_Utils.h"


/* Just make sure the contents doesn't get compiled if TCP is not enabled. */
/* *INDENT-OFF* */
#if( ipconfigUSE_IPv6 != 0 ) && ( ipconfigUSE_TCP == 1 )
/* *INDENT-ON* */

#if ( ipconfigHAS_DEBUG_PRINTF != 0 )

/*
 * For logging and debugging: make a string showing the TCP flags.
 */
    const char * prvTCPFlagMeaning( UBaseType_t xFlags );
#endif /* ipconfigHAS_DEBUG_PRINTF != 0 */


/*-----------------------------------------------------------*/


/**
 * @brief Process the received TCP packet.
 *
 * @param[in] pxDescriptor The descriptor in which the TCP packet is held.
 *
 * @return If the processing of the packet was successful, then pdPASS is returned
 *         or else pdFAIL.
 *
 * @note FreeRTOS_TCP_IP has only 2 public functions, this is the second one:
 *  xProcessReceivedTCPPacket()
 *      prvTCPHandleState()
 *          prvTCPPrepareSend()
 *              prvTCPReturnPacket()
 *              xNetworkInterfaceOutput()  // Sends data to the NIC
 *      prvTCPSendRepeated()
 *          prvTCPReturnPacket()        // Prepare for returning
 *          xNetworkInterfaceOutput()   // Sends data to the NIC
 */
BaseType_t xProcessReceivedTCPPacket_IPV6( NetworkBufferDescriptor_t * pxDescriptor )
{
    /* Function might modify the parameter. */
    NetworkBufferDescriptor_t * pxNetworkBuffer = pxDescriptor;
    const ProtocolHeaders_t * pxProtocolHeaders;
    FreeRTOS_Socket_t * pxSocket;
    uint16_t ucTCPFlags;
    uint16_t usLocalPort;
    uint16_t usRemotePort;
    IPv46_Address_t xRemoteIP;
    uint32_t ulSequenceNumber;
    uint32_t ulAckNumber;
    BaseType_t xResult = pdPASS;

    configASSERT( pxNetworkBuffer != NULL );
    configASSERT( pxNetworkBuffer->pucEthernetBuffer != NULL );

    /* Map the buffer onto a ProtocolHeaders_t struct for easy access to the fields. */

    /* MISRA Ref 11.3.1 [Misaligned access] */
    /* More details at: https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/blob/main/MISRA.md#rule-113 */
    /* coverity[misra_c_2012_rule_11_3_violation] */
    pxProtocolHeaders = ( ( const ProtocolHeaders_t * )
                          &( pxNetworkBuffer->pucEthernetBuffer[ ipSIZE_OF_ETH_HEADER + uxIPHeaderSizePacket( pxNetworkBuffer ) ] ) );

    ucTCPFlags = pxProtocolHeaders->xTCPHeader.ucTCPFlags;
    usLocalPort = FreeRTOS_htons( pxProtocolHeaders->xTCPHeader.usDestinationPort );
    usRemotePort = FreeRTOS_htons( pxProtocolHeaders->xTCPHeader.usSourcePort );
    ulSequenceNumber = FreeRTOS_ntohl( pxProtocolHeaders->xTCPHeader.ulSequenceNumber );
    ulAckNumber = FreeRTOS_ntohl( pxProtocolHeaders->xTCPHeader.ulAckNr );

    /* Check for a minimum packet size. */
    if( pxNetworkBuffer->xDataLength < ( ipSIZE_OF_ETH_HEADER + uxIPHeaderSizePacket( pxNetworkBuffer ) + ipSIZE_OF_TCP_HEADER ) )
    {
        xResult = pdFAIL;
    }
    else
    {
        /* Map the ethernet buffer onto the IPHeader_t struct for easy access to the fields. */

        /* MISRA Ref 11.3.1 [Misaligned access] */
        /* More details at: https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/blob/main/MISRA.md#rule-113 */
        /* coverity[misra_c_2012_rule_11_3_violation] */
        const IPHeader_IPv6_t * pxIPHeader_IPv6 = ( ( IPHeader_IPv6_t * ) &( pxNetworkBuffer->pucEthernetBuffer[ ipSIZE_OF_ETH_HEADER ] ) );
        ( void ) memcpy( xRemoteIP.xIPAddress.xIP_IPv6.ucBytes, pxIPHeader_IPv6->xSourceAddress.ucBytes, sizeof( IPv6_Address_t ) );
        xRemoteIP.xIs_IPv6 = pdTRUE;

        /* Find the destination socket, and if not found: return a socket listing to
         * the destination PORT. */
        pxSocket = ( FreeRTOS_Socket_t * ) pxTCPSocketLookup( 0U, usLocalPort, xRemoteIP, usRemotePort );

        if( ( pxSocket == NULL ) || ( prvTCPSocketIsActive( pxSocket->u.xTCP.eTCPState ) == pdFALSE ) )
        {
            /* A TCP messages is received but either there is no socket with the
             * given port number or the there is a socket, but it is in one of these
             * non-active states:  eCLOSED, eCLOSE_WAIT, eFIN_WAIT_2, eCLOSING, or
             * eTIME_WAIT. */

            FreeRTOS_debug_printf( ( "TCP: No active socket on port %d (%xip:%d)\n", usLocalPort, ( unsigned ) xRemoteIP.xIPAddress.ulIP_IPv4, usRemotePort ) );

            /* Send a RST to all packets that can not be handled.  As a result
             * the other party will get a ECONN error.  There are two exceptions:
             * 1) A packet that already has the RST flag set.
             * 2) A packet that only has the ACK flag set.
             * A packet with only the ACK flag set might be the last ACK in
             * a three-way hand-shake that closes a connection. */
            if( ( ( ucTCPFlags & tcpTCP_FLAG_CTRL ) != tcpTCP_FLAG_ACK ) &&
                ( ( ucTCPFlags & tcpTCP_FLAG_RST ) == 0U ) )
            {
                ( void ) prvTCPSendReset( pxNetworkBuffer );
            }

            /* The packet can't be handled. */
            xResult = pdFAIL;
        }
        else
        {
            pxSocket->u.xTCP.ucRepCount = 0U;

            if( pxSocket->u.xTCP.eTCPState == eTCP_LISTEN )
            {
                /* The matching socket is in a listening state.  Test if the peer
                 * has set the SYN flag. */
                if( ( ucTCPFlags & tcpTCP_FLAG_CTRL ) != tcpTCP_FLAG_SYN )
                {
                    /* What happens: maybe after a reboot, a client doesn't know the
                     * connection had gone.  Send a RST in order to get a new connect
                     * request. */
                    #if ( ipconfigHAS_DEBUG_PRINTF == 1 )
                    {
                        FreeRTOS_debug_printf( ( "TCP: Server can't handle flags: %s from %xip:%u to port %u\n",
                                                 prvTCPFlagMeaning( ( UBaseType_t ) ucTCPFlags ), ( unsigned ) xRemoteIP.xIPAddress.ulIP_IPv4, usRemotePort, usLocalPort ) );
                    }
                    #endif /* ipconfigHAS_DEBUG_PRINTF */

                    if( ( ucTCPFlags & tcpTCP_FLAG_RST ) == 0U )
                    {
                        ( void ) prvTCPSendReset( pxNetworkBuffer );
                    }

                    xResult = pdFAIL;
                }
                else
                {
                    /* prvHandleListen() will either return a newly created socket
                     * (if bReuseSocket is false), otherwise it returns the current
                     * socket which will later get connected. */
                    pxSocket = prvHandleListen( pxSocket, pxNetworkBuffer );

                    if( pxSocket == NULL )
                    {
                        xResult = pdFAIL;
                    }
                }
            } /* if( pxSocket->u.xTCP.eTCPState == eTCP_LISTEN ). */
            else
            {
                /* This is not a socket in listening mode. Check for the RST
                 * flag. */
                if( ( ucTCPFlags & tcpTCP_FLAG_RST ) != 0U )
                {
                    FreeRTOS_debug_printf( ( "TCP: RST received from %xip:%u for %u\n", ( unsigned ) xRemoteIP.xIPAddress.ulIP_IPv4, usRemotePort, usLocalPort ) );

                    /* Implement https://tools.ietf.org/html/rfc5961#section-3.2. */
                    if( pxSocket->u.xTCP.eTCPState == eCONNECT_SYN )
                    {
                        /* Per the above RFC, "In the SYN-SENT state ... the RST is
                         * acceptable if the ACK field acknowledges the SYN." */
                        if( ulAckNumber == ( pxSocket->u.xTCP.xTCPWindow.ulOurSequenceNumber + 1U ) )
                        {
                            vTCPStateChange( pxSocket, eCLOSED );
                        }
                    }
                    else
                    {
                        /* Check whether the packet matches the next expected sequence number. */
                        if( ulSequenceNumber == pxSocket->u.xTCP.xTCPWindow.rx.ulCurrentSequenceNumber )
                        {
                            vTCPStateChange( pxSocket, eCLOSED );
                        }
                        /* Otherwise, check whether the packet is within the receive window. */
                        else if( ( xSequenceGreaterThan( ulSequenceNumber, pxSocket->u.xTCP.xTCPWindow.rx.ulCurrentSequenceNumber ) != pdFALSE ) &&
                                 ( xSequenceLessThan( ulSequenceNumber, pxSocket->u.xTCP.xTCPWindow.rx.ulCurrentSequenceNumber +
                                                      pxSocket->u.xTCP.xTCPWindow.xSize.ulRxWindowLength ) != pdFALSE ) )
                        {
                            /* Send a challenge ACK. */
                            ( void ) prvTCPSendChallengeAck( pxNetworkBuffer );
                        }
                        else
                        {
                            /* Nothing. */
                        }
                    }

                    /* Otherwise, do nothing. In any case, the packet cannot be handled. */
                    xResult = pdFAIL;
                }
                /* Check whether there is a pure SYN amongst the TCP flags while the connection is established. */
                else if( ( ( ucTCPFlags & tcpTCP_FLAG_CTRL ) == tcpTCP_FLAG_SYN ) && ( pxSocket->u.xTCP.eTCPState >= eESTABLISHED ) )
                {
                    /* SYN flag while this socket is already connected. */
                    FreeRTOS_debug_printf( ( "TCP: SYN unexpected from %xip:%u\n", ( unsigned ) xRemoteIP.xIPAddress.ulIP_IPv4, usRemotePort ) );

                    /* The packet cannot be handled. */
                    xResult = pdFAIL;
                }
                else
                {
                    /* Update the copy of the TCP header only (skipping eth and IP
                     * headers).  It might be used later on, whenever data must be sent
                     * to the peer. */
                    const size_t uxOffset = ipSIZE_OF_ETH_HEADER + uxIPHeaderSizeSocket( pxSocket );
                    ( void ) memcpy( ( void * ) ( &( pxSocket->u.xTCP.xPacket.u.ucLastPacket[ uxOffset ] ) ),
                                     ( const void * ) ( &( pxNetworkBuffer->pucEthernetBuffer[ uxOffset ] ) ),
                                     ipSIZE_OF_TCP_HEADER );
                    /* Clear flags that are set by the peer, and set the ACK flag. */
                    pxSocket->u.xTCP.xPacket.u.ucLastPacket[ uxOffset + ipTCP_FLAGS_OFFSET ] = tcpTCP_FLAG_ACK;
                }
            }
        }

        if( xResult != pdFAIL )
        {
            uint16_t usWindow;

            /* pxSocket is not NULL when xResult != pdFAIL. */
            configASSERT( pxSocket != NULL ); /* LCOV_EXCL_LINE ,this branch will not be hit*/

            /* Touch the alive timers because we received a message for this
             * socket. */
            prvTCPTouchSocket( pxSocket );

            /* Parse the TCP option(s), if present. */

            /* _HT_ : if we're in the SYN phase, and peer does not send a MSS option,
             * then we MUST assume an MSS size of 536 bytes for backward compatibility. */

            /* When there are no TCP options, the TCP offset equals 20 bytes, which is stored as
             * the number 5 (words) in the higher nibble of the TCP-offset byte. */
            if( ( pxProtocolHeaders->xTCPHeader.ucTCPOffset & tcpTCP_OFFSET_LENGTH_BITS ) > tcpTCP_OFFSET_STANDARD_LENGTH )
            {
                xResult = prvCheckOptions( pxSocket, pxNetworkBuffer );
            }

            if( xResult != pdFAIL )
            {
                usWindow = FreeRTOS_ntohs( pxProtocolHeaders->xTCPHeader.usWindow );
                pxSocket->u.xTCP.ulWindowSize = ( uint32_t ) usWindow;
                #if ( ipconfigUSE_TCP_WIN == 1 )
                {
                    /* rfc1323 : The Window field in a SYN (i.e., a <SYN> or <SYN,ACK>)
                     * segment itself is never scaled. */
                    if( ( ucTCPFlags & ( uint8_t ) tcpTCP_FLAG_SYN ) == 0U )
                    {
                        pxSocket->u.xTCP.ulWindowSize =
                            ( pxSocket->u.xTCP.ulWindowSize << pxSocket->u.xTCP.ucPeerWinScaleFactor );
                    }
                }
                #endif /* ipconfigUSE_TCP_WIN */

                /* In prvTCPHandleState() the incoming messages will be handled
                 * depending on the current state of the connection. */
                if( prvTCPHandleState( pxSocket, &pxNetworkBuffer ) > 0 )
                {
                    /* prvTCPHandleState() has sent a message, see if there are more to
                     * be transmitted. */
                    #if ( ipconfigUSE_TCP_WIN == 1 )
                    {
                        ( void ) prvTCPSendRepeated( pxSocket, &pxNetworkBuffer );
                    }
                    #endif /* ipconfigUSE_TCP_WIN */
                }

                if( pxNetworkBuffer != NULL )
                {
                    /* We must check if the buffer is unequal to NULL, because the
                     * socket might keep a reference to it in case a delayed ACK must be
                     * sent. */
                    vReleaseNetworkBufferAndDescriptor( pxNetworkBuffer );
                    #ifndef _lint
                        /* Clear pointers that are freed. */
                        pxNetworkBuffer = NULL;
                    #endif
                }

                /* And finally, calculate when this socket wants to be woken up. */
                ( void ) prvTCPNextTimeout( pxSocket );
            }
        }
    }

    /* pdPASS being returned means the buffer has been consumed. */
    return xResult;
}
/*-----------------------------------------------------------*/

/* Provide access to private members for testing. */
#ifdef FREERTOS_ENABLE_UNIT_TESTS
    #include "freertos_tcp_test_access_tcp_define.h"
#endif

/* Provide access to private members for verification. */
#ifdef FREERTOS_TCP_ENABLE_VERIFICATION
    #include "aws_freertos_tcp_verification_access_tcp_define.h"
#endif

/* *INDENT-OFF* */
#endif /* ( ipconfigUSE_IPv6 != 0 ) && ( ipconfigUSE_TCP == 1 ) */
/* *INDENT-ON* */