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Fix TCP checksum calculation to include Ethernet header #1331

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Fix TCP checksum calculation to include Ethernet header #1331

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3 changes: 2 additions & 1 deletion source/FreeRTOS_TCP_Transmission_IPv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -214,7 +214,8 @@ void prvTCPReturnPacket_IPV4( FreeRTOS_Socket_t * pxSocket,
pxIPHeader->usHeaderChecksum = ( uint16_t ) ~FreeRTOS_htons( pxIPHeader->usHeaderChecksum );

/* calculate the TCP checksum for an outgoing packet. */
( void ) usGenerateProtocolChecksum( ( uint8_t * ) pxTCPPacket, pxNetworkBuffer->xDataLength, pdTRUE );
uint32_t ulTotalLength = ( uint32_t ) ulLen + ipSIZE_OF_ETH_HEADER;
( void ) usGenerateProtocolChecksum( ( uint8_t * ) pxTCPPacket, ulTotalLength, pdTRUE );
}
#endif /* if ( ipconfigDRIVER_INCLUDED_TX_IP_CHECKSUM == 0 ) */

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65 changes: 65 additions & 0 deletions test/unit-test/FreeRTOS_TCP_Transmission/FreeRTOS_TCP_Transmission_utest.c
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Expand Up @@ -2653,3 +2653,68 @@ void test_prvTCPSendReset( void )
TEST_ASSERT_EQUAL( tcpTCP_FLAG_ACK | tcpTCP_FLAG_RST, pxTCPPacket->xTCPHeader.ucTCPFlags );
TEST_ASSERT_EQUAL( 0x50, pxTCPPacket->xTCPHeader.ucTCPOffset );
}

/**
* @brief This test verifies that when ipconfigDRIVER_INCLUDED_TX_IP_CHECKSUM is 0,
* the TCP checksum is calculated with the correct data length that includes
* the Ethernet header (ulLen + ipSIZE_OF_ETH_HEADER).
*
* This is a regression test for a bug where the checksum was calculated with
* xDataLength that did NOT include the Ethernet header, resulting in incorrect
* checksums on outgoing TCP packets.
*/
void test_prvTCPReturnPacket_TxChecksum_DataLength( void )
{
pxSocket = &xSocket;
pxNetworkBuffer = &xNetworkBuffer;
pxNetworkBuffer->pucEthernetBuffer = ucEthernetBuffer;
pxNetworkBuffer->xDataLength = 1000;
TCPPacket_t * pxTCPPacket = ( ( TCPPacket_t * ) pxNetworkBuffer->pucEthernetBuffer );
TCPWindow_t * pxTCPWindow = &pxSocket->u.xTCP.xTCPWindow;
struct xNetworkEndPoint * pxEndPoint;

MACAddress_t NewSourceMacAddr = { { 0x11, 0x22, 0x33, 0x44, 0x55, 0x66 } };
struct xNetworkEndPoint xEndPoint = { 0 };
struct xNetworkInterface xInterface;

memcpy( xEndPoint.xMACAddress.ucBytes, NewSourceMacAddr.ucBytes, sizeof( xEndPoint.xMACAddress.ucBytes ) );

xEndPoint.pxNetworkInterface = &xInterface;
xEndPoint.ipv4_settings.ulIPAddress = 0xC0C0C0C0;
xEndPoint.pxNetworkInterface->pfOutput = &NetworkInterfaceOutputFunction_Stub;
NetworkInterfaceOutputFunction_Stub_Called = 0;
pxSocket->pxEndPoint = &xEndPoint;

pxSocket->u.xTCP.rxStream = ( StreamBuffer_t * ) 0x12345678;
pxSocket->u.xTCP.uxRxStreamSize = 1500;
pxSocket->u.xTCP.bits.bLowWater = pdFALSE;
pxSocket->u.xTCP.bits.bRxStopped = pdFALSE;
pxSocket->u.xTCP.usMSS = 1000;
pxSocket->u.xTCP.ucMyWinScaleFactor = 0;
pxSocket->u.xTCP.bits.bSendKeepAlive = pdFALSE;
pxSocket->u.xTCP.xTCPWindow.ulOurSequenceNumber = 100;
pxTCPWindow->xSize.ulRxWindowLength = 500;
pxTCPWindow->rx.ulCurrentSequenceNumber = 50;
pxTCPPacket->xTCPHeader.ulAckNr = 0;
pxEndPoint = &xEndPoint;
pxNetworkBuffer->pxEndPoint = &xEndPoint;

uxIPHeaderSizePacket_IgnoreAndReturn( ipSIZE_OF_IPv4_HEADER );
uxStreamBufferFrontSpace_ExpectAnyArgsAndReturn( 1000 );
FreeRTOS_min_uint32_ExpectAnyArgsAndReturn( 500 );
usGenerateChecksum_ExpectAnyArgsAndReturn( 0x1111 );

usGenerateProtocolChecksum_ExpectAndReturn(
pxNetworkBuffer->pucEthernetBuffer,
1000 + ipSIZE_OF_ETH_HEADER,
pdTRUE,
ipCORRECT_CRC );

eARPGetCacheEntry_ExpectAnyArgsAndReturn( eResolutionCacheHit );
eARPGetCacheEntry_ReturnThruPtr_ppxEndPoint( &pxEndPoint );

prvTCPReturnPacket( pxSocket, pxNetworkBuffer, 1000, pdTRUE );

TEST_ASSERT_EQUAL( 1, NetworkInterfaceOutputFunction_Stub_Called );
TEST_ASSERT_EQUAL( 1000 + ipSIZE_OF_ETH_HEADER, pxNetworkBuffer->xDataLength );
}