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Diffstat (limited to 'lib/lufa/Demos/Device/LowLevel/RNDISEthernet/Lib/TCP.c')
| -rw-r--r-- | lib/lufa/Demos/Device/LowLevel/RNDISEthernet/Lib/TCP.c | 631 |
1 files changed, 631 insertions, 0 deletions
diff --git a/lib/lufa/Demos/Device/LowLevel/RNDISEthernet/Lib/TCP.c b/lib/lufa/Demos/Device/LowLevel/RNDISEthernet/Lib/TCP.c new file mode 100644 index 0000000000..a6f1f6adfc --- /dev/null +++ b/lib/lufa/Demos/Device/LowLevel/RNDISEthernet/Lib/TCP.c @@ -0,0 +1,631 @@ +/* + LUFA Library + Copyright (C) Dean Camera, 2017. + + dean [at] fourwalledcubicle [dot] com + www.lufa-lib.org +*/ + +/* + Copyright 2017 Dean Camera (dean [at] fourwalledcubicle [dot] com) + + Permission to use, copy, modify, distribute, and sell this + software and its documentation for any purpose is hereby granted + without fee, provided that the above copyright notice appear in + all copies and that both that the copyright notice and this + permission notice and warranty disclaimer appear in supporting + documentation, and that the name of the author not be used in + advertising or publicity pertaining to distribution of the + software without specific, written prior permission. + + The author disclaims all warranties with regard to this + software, including all implied warranties of merchantability + and fitness. In no event shall the author be liable for any + special, indirect or consequential damages or any damages + whatsoever resulting from loss of use, data or profits, whether + in an action of contract, negligence or other tortious action, + arising out of or in connection with the use or performance of + this software. +*/ + +/** \file + * + * Transmission Control Protocol (TCP) packet handling routines. This protocol handles the reliable in-order transmission + * and reception of packets to and from devices on a network, to "ports" on the device. It is used in situations where data + * delivery must be reliable and correct, e.g. HTTP, TELNET and most other non-streaming protocols. + */ + +#define INCLUDE_FROM_TCP_C +#include "TCP.h" + +/** Port state table array. This contains the current status of TCP ports in the device. To save on space, only open ports are + * stored - closed ports may be overwritten at any time, and the system will assume any ports not present in the array are closed. This + * allows for MAX_OPEN_TCP_PORTS to be less than the number of ports used by the application if desired. + */ +TCP_PortState_t PortStateTable[MAX_OPEN_TCP_PORTS]; + +/** Connection state table array. This contains the current status of TCP connections in the device. To save on space, only active + * (non-closed) connections are stored - closed connections may be overwritten at any time, and the system will assume any connections + * not present in the array are closed. + */ +TCP_ConnectionState_t ConnectionStateTable[MAX_TCP_CONNECTIONS]; + + +/** Task to handle the calling of each registered application's callback function, to process and generate TCP packets at the application + * level. If an application produces a response, this task constructs the appropriate Ethernet frame and places it into the Ethernet OUT + * buffer for later transmission. + */ +void TCP_Task(void) +{ + /* Run each application in sequence, to process incoming and generate outgoing packets */ + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* Find the corresponding port entry in the port table */ + for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++) + { + /* Run the application handler for the port */ + if ((PortStateTable[PTableEntry].Port == ConnectionStateTable[CSTableEntry].Port) && + (PortStateTable[PTableEntry].State == TCP_Port_Open)) + { + PortStateTable[PTableEntry].ApplicationHandler(&ConnectionStateTable[CSTableEntry], + &ConnectionStateTable[CSTableEntry].Info.Buffer); + } + } + } + + /* Bail out early if there is already a frame waiting to be sent in the Ethernet OUT buffer */ + if (FrameOUT.FrameLength) + return; + + /* Send response packets from each application as the TCP packet buffers are filled by the applications */ + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* For each completely received packet, pass it along to the listening application */ + if ((ConnectionStateTable[CSTableEntry].Info.Buffer.Direction == TCP_PACKETDIR_OUT) && + (ConnectionStateTable[CSTableEntry].Info.Buffer.Ready)) + { + Ethernet_Frame_Header_t* FrameOUTHeader = (Ethernet_Frame_Header_t*)&FrameOUT.FrameData; + IP_Header_t* IPHeaderOUT = (IP_Header_t*)&FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t)]; + TCP_Header_t* TCPHeaderOUT = (TCP_Header_t*)&FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t) + + sizeof(IP_Header_t)]; + void* TCPDataOUT = &FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t) + + sizeof(IP_Header_t) + + sizeof(TCP_Header_t)]; + + uint16_t PacketSize = ConnectionStateTable[CSTableEntry].Info.Buffer.Length; + + /* Fill out the TCP data */ + TCPHeaderOUT->SourcePort = ConnectionStateTable[CSTableEntry].Port; + TCPHeaderOUT->DestinationPort = ConnectionStateTable[CSTableEntry].RemotePort; + TCPHeaderOUT->SequenceNumber = SwapEndian_32(ConnectionStateTable[CSTableEntry].Info.SequenceNumberOut); + TCPHeaderOUT->AcknowledgmentNumber = SwapEndian_32(ConnectionStateTable[CSTableEntry].Info.SequenceNumberIn); + TCPHeaderOUT->DataOffset = (sizeof(TCP_Header_t) / sizeof(uint32_t)); + TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE); + + TCPHeaderOUT->Flags = TCP_FLAG_ACK; + TCPHeaderOUT->UrgentPointer = 0; + TCPHeaderOUT->Checksum = 0; + TCPHeaderOUT->Reserved = 0; + + memcpy(TCPDataOUT, ConnectionStateTable[CSTableEntry].Info.Buffer.Data, PacketSize); + + ConnectionStateTable[CSTableEntry].Info.SequenceNumberOut += PacketSize; + + TCPHeaderOUT->Checksum = TCP_Checksum16(TCPHeaderOUT, &ServerIPAddress, + &ConnectionStateTable[CSTableEntry].RemoteAddress, + (sizeof(TCP_Header_t) + PacketSize)); + + PacketSize += sizeof(TCP_Header_t); + + /* Fill out the response IP header */ + IPHeaderOUT->TotalLength = SwapEndian_16(sizeof(IP_Header_t) + PacketSize); + IPHeaderOUT->TypeOfService = 0; + IPHeaderOUT->HeaderLength = (sizeof(IP_Header_t) / sizeof(uint32_t)); + IPHeaderOUT->Version = 4; + IPHeaderOUT->Flags = 0; + IPHeaderOUT->FragmentOffset = 0; + IPHeaderOUT->Identification = 0; + IPHeaderOUT->HeaderChecksum = 0; + IPHeaderOUT->Protocol = PROTOCOL_TCP; + IPHeaderOUT->TTL = DEFAULT_TTL; + IPHeaderOUT->SourceAddress = ServerIPAddress; + IPHeaderOUT->DestinationAddress = ConnectionStateTable[CSTableEntry].RemoteAddress; + + IPHeaderOUT->HeaderChecksum = Ethernet_Checksum16(IPHeaderOUT, sizeof(IP_Header_t)); + + PacketSize += sizeof(IP_Header_t); + + /* Fill out the response Ethernet frame header */ + FrameOUTHeader->Source = ServerMACAddress; + FrameOUTHeader->Destination = (MAC_Address_t){{0x02, 0x00, 0x02, 0x00, 0x02, 0x00}}; + FrameOUTHeader->EtherType = SwapEndian_16(ETHERTYPE_IPV4); + + PacketSize += sizeof(Ethernet_Frame_Header_t); + + /* Set the response length in the buffer and indicate that a response is ready to be sent */ + FrameOUT.FrameLength = PacketSize; + + ConnectionStateTable[CSTableEntry].Info.Buffer.Ready = false; + + break; + } + } +} + +/** Initializes the TCP protocol handler, clearing the port and connection state tables. This must be called before TCP packets are + * processed. + */ +void TCP_Init(void) +{ + /* Initialize the port state table with all CLOSED entries */ + for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++) + PortStateTable[PTableEntry].State = TCP_Port_Closed; + + /* Initialize the connection table with all CLOSED entries */ + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + ConnectionStateTable[CSTableEntry].State = TCP_Connection_Closed; +} + +/** Sets the state and callback handler of the given port, specified in big endian to the given state. + * + * \param[in] Port Port whose state and callback function to set, specified in big endian + * \param[in] State New state of the port, a value from the \ref TCP_PortStates_t enum + * \param[in] Handler Application callback handler for the port + * + * \return Boolean \c true if the port state was set, \c false otherwise (no more space in the port state table) + */ +bool TCP_SetPortState(const uint16_t Port, + const uint8_t State, + void (*Handler)(TCP_ConnectionState_t*, TCP_ConnectionBuffer_t*)) +{ + /* Note, Port number should be specified in BIG endian to simplify network code */ + + /* Check to see if the port entry is already in the port state table */ + for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++) + { + /* Find existing entry for the port in the table, update it if found */ + if (PortStateTable[PTableEntry].Port == Port) + { + PortStateTable[PTableEntry].State = State; + PortStateTable[PTableEntry].ApplicationHandler = Handler; + return true; + } + } + + /* Check if trying to open the port -- if so we need to find an unused (closed) entry and replace it */ + if (State == TCP_Port_Open) + { + for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++) + { + /* Find a closed port entry in the table, change it to the given port and state */ + if (PortStateTable[PTableEntry].State == TCP_Port_Closed) + { + PortStateTable[PTableEntry].Port = Port; + PortStateTable[PTableEntry].State = State; + PortStateTable[PTableEntry].ApplicationHandler = Handler; + return true; + } + } + + /* Port not in table and no room to add it, return failure */ + return false; + } + else + { + /* Port not in table but trying to close it, so operation successful */ + return true; + } +} + +/** Retrieves the current state of a given TCP port, specified in big endian. + * + * \param[in] Port TCP port whose state is to be retrieved, given in big-endian + * + * \return A value from the \ref TCP_PortStates_t enum + */ +uint8_t TCP_GetPortState(const uint16_t Port) +{ + /* Note, Port number should be specified in BIG endian to simplify network code */ + + for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++) + { + /* Find existing entry for the port in the table, return the port status if found */ + if (PortStateTable[PTableEntry].Port == Port) + return PortStateTable[PTableEntry].State; + } + + /* Port not in table, assume closed */ + return TCP_Port_Closed; +} + +/** Sets the connection state of the given port, remote address and remote port to the given TCP connection state. If the + * connection exists in the connection state table it is updated, otherwise it is created if possible. + * + * \param[in] Port TCP port of the connection on the device, specified in big endian + * \param[in] RemoteAddress Remote protocol IP address of the connected device + * \param[in] RemotePort TCP port of the remote device in the connection, specified in big endian + * \param[in] State TCP connection state, a value from the \ref TCP_ConnectionStates_t enum + * + * \return Boolean \c true if the connection was updated or created, \c false otherwise (no more space in the connection state table) + */ +bool TCP_SetConnectionState(const uint16_t Port, + const IP_Address_t* RemoteAddress, + const uint16_t RemotePort, + const uint8_t State) +{ + /* Note, Port number should be specified in BIG endian to simplify network code */ + + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* Find port entry in the table */ + if ((ConnectionStateTable[CSTableEntry].Port == Port) && + IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, RemoteAddress) && + ConnectionStateTable[CSTableEntry].RemotePort == RemotePort) + { + ConnectionStateTable[CSTableEntry].State = State; + return true; + } + } + + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* Find empty entry in the table */ + if (ConnectionStateTable[CSTableEntry].State == TCP_Connection_Closed) + { + ConnectionStateTable[CSTableEntry].Port = Port; + ConnectionStateTable[CSTableEntry].RemoteAddress = *RemoteAddress; + ConnectionStateTable[CSTableEntry].RemotePort = RemotePort; + ConnectionStateTable[CSTableEntry].State = State; + return true; + } + } + + return false; +} + +/** Retrieves the current state of a given TCP connection to a host. + * + * \param[in] Port TCP port on the device in the connection, specified in big endian + * \param[in] RemoteAddress Remote protocol IP address of the connected host + * \param[in] RemotePort Remote TCP port of the connected host, specified in big endian + * + * \return A value from the \ref TCP_ConnectionStates_t enum + */ +uint8_t TCP_GetConnectionState(const uint16_t Port, + const IP_Address_t* RemoteAddress, + const uint16_t RemotePort) +{ + /* Note, Port number should be specified in BIG endian to simplify network code */ + + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* Find port entry in the table */ + if ((ConnectionStateTable[CSTableEntry].Port == Port) && + IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, RemoteAddress) && + ConnectionStateTable[CSTableEntry].RemotePort == RemotePort) + + { + return ConnectionStateTable[CSTableEntry].State; + } + } + + return TCP_Connection_Closed; +} + +/** Retrieves the connection info structure of a given connection to a host. + * + * \param[in] Port TCP port on the device in the connection, specified in big endian + * \param[in] RemoteAddress Remote protocol IP address of the connected host + * \param[in] RemotePort Remote TCP port of the connected host, specified in big endian + * + * \return ConnectionInfo structure of the connection if found, NULL otherwise + */ +TCP_ConnectionInfo_t* TCP_GetConnectionInfo(const uint16_t Port, + const IP_Address_t* RemoteAddress, + const uint16_t RemotePort) +{ + /* Note, Port number should be specified in BIG endian to simplify network code */ + + for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++) + { + /* Find port entry in the table */ + if ((ConnectionStateTable[CSTableEntry].Port == Port) && + IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, RemoteAddress) && + ConnectionStateTable[CSTableEntry].RemotePort == RemotePort) + { + return &ConnectionStateTable[CSTableEntry].Info; + } + } + + return NULL; +} + +/** Processes a TCP packet inside an Ethernet frame, and writes the appropriate response + * to the output Ethernet frame if one is created by a application handler. + * + * \param[in] IPHeaderInStart Pointer to the start of the incoming packet's IP header + * \param[in] TCPHeaderInStart Pointer to the start of the incoming packet's TCP header + * \param[out] TCPHeaderOutStart Pointer to the start of the outgoing packet's TCP header + * + * \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE if no + * response was generated, NO_PROCESS if the packet processing was deferred until the + * next Ethernet packet handler iteration + */ +int16_t TCP_ProcessTCPPacket(void* IPHeaderInStart, + void* TCPHeaderInStart, + void* TCPHeaderOutStart) +{ + IP_Header_t* IPHeaderIN = (IP_Header_t*)IPHeaderInStart; + TCP_Header_t* TCPHeaderIN = (TCP_Header_t*)TCPHeaderInStart; + TCP_Header_t* TCPHeaderOUT = (TCP_Header_t*)TCPHeaderOutStart; + + TCP_ConnectionInfo_t* ConnectionInfo; + + DecodeTCPHeader(TCPHeaderInStart); + + bool PacketResponse = false; + + /* Check if the destination port is open and allows incoming connections */ + if (TCP_GetPortState(TCPHeaderIN->DestinationPort) == TCP_Port_Open) + { + /* Detect SYN from host to start a connection */ + if (TCPHeaderIN->Flags & TCP_FLAG_SYN) + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort, TCP_Connection_Listen); + + /* Detect RST from host to abort existing connection */ + if (TCPHeaderIN->Flags & TCP_FLAG_RST) + { + if (TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_Closed)) + { + TCPHeaderOUT->Flags = (TCP_FLAG_RST | TCP_FLAG_ACK); + PacketResponse = true; + } + } + else + { + /* Process the incoming TCP packet based on the current connection state for the sender and port */ + switch (TCP_GetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort)) + { + case TCP_Connection_Listen: + if (TCPHeaderIN->Flags == TCP_FLAG_SYN) + { + /* SYN connection starts a connection with a peer */ + if (TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_SYNReceived)) + { + TCPHeaderOUT->Flags = (TCP_FLAG_SYN | TCP_FLAG_ACK); + + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort); + + ConnectionInfo->SequenceNumberIn = (SwapEndian_32(TCPHeaderIN->SequenceNumber) + 1); + ConnectionInfo->SequenceNumberOut = 0; + ConnectionInfo->Buffer.InUse = false; + } + else + { + TCPHeaderOUT->Flags = TCP_FLAG_RST; + } + + PacketResponse = true; + } + + break; + case TCP_Connection_SYNReceived: + if (TCPHeaderIN->Flags == TCP_FLAG_ACK) + { + /* ACK during the connection process completes the connection to a peer */ + + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_Established); + + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + ConnectionInfo->SequenceNumberOut++; + } + + break; + case TCP_Connection_Established: + if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK)) + { + /* FIN ACK when connected to a peer starts the finalization process */ + + TCPHeaderOUT->Flags = (TCP_FLAG_FIN | TCP_FLAG_ACK); + PacketResponse = true; + + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_CloseWait); + + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + ConnectionInfo->SequenceNumberIn++; + ConnectionInfo->SequenceNumberOut++; + } + else if ((TCPHeaderIN->Flags == TCP_FLAG_ACK) || (TCPHeaderIN->Flags == (TCP_FLAG_ACK | TCP_FLAG_PSH))) + { + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + /* Check if the buffer is currently in use either by a buffered data to send, or receive */ + if ((ConnectionInfo->Buffer.InUse == false) && (ConnectionInfo->Buffer.Ready == false)) + { + ConnectionInfo->Buffer.Direction = TCP_PACKETDIR_IN; + ConnectionInfo->Buffer.InUse = true; + ConnectionInfo->Buffer.Length = 0; + } + + /* Check if the buffer has been claimed by us to read in data from the peer */ + if ((ConnectionInfo->Buffer.Direction == TCP_PACKETDIR_IN) && + (ConnectionInfo->Buffer.Length != TCP_WINDOW_SIZE)) + { + uint16_t IPOffset = (IPHeaderIN->HeaderLength * sizeof(uint32_t)); + uint16_t TCPOffset = (TCPHeaderIN->DataOffset * sizeof(uint32_t)); + uint16_t DataLength = (SwapEndian_16(IPHeaderIN->TotalLength) - IPOffset - TCPOffset); + + /* Copy the packet data into the buffer */ + memcpy(&ConnectionInfo->Buffer.Data[ConnectionInfo->Buffer.Length], + &((uint8_t*)TCPHeaderInStart)[TCPOffset], + DataLength); + + ConnectionInfo->SequenceNumberIn += DataLength; + ConnectionInfo->Buffer.Length += DataLength; + + /* Check if the buffer is full or if the PSH flag is set, if so indicate buffer ready */ + if ((!(TCP_WINDOW_SIZE - ConnectionInfo->Buffer.Length)) || (TCPHeaderIN->Flags & TCP_FLAG_PSH)) + { + ConnectionInfo->Buffer.InUse = false; + ConnectionInfo->Buffer.Ready = true; + + TCPHeaderOUT->Flags = TCP_FLAG_ACK; + PacketResponse = true; + } + } + else + { + /* Buffer is currently in use by the application, defer processing of the incoming packet */ + return NO_PROCESS; + } + } + + break; + case TCP_Connection_Closing: + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + TCPHeaderOUT->Flags = (TCP_FLAG_ACK | TCP_FLAG_FIN); + PacketResponse = true; + + ConnectionInfo->Buffer.InUse = false; + + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_FINWait1); + + break; + case TCP_Connection_FINWait1: + if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK)) + { + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + TCPHeaderOUT->Flags = TCP_FLAG_ACK; + PacketResponse = true; + + ConnectionInfo->SequenceNumberIn++; + ConnectionInfo->SequenceNumberOut++; + + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_Closed); + } + else if (TCPHeaderIN->Flags == TCP_FLAG_ACK) + { + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_FINWait2); + } + + break; + case TCP_Connection_FINWait2: + if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK)) + { + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + TCPHeaderOUT->Flags = TCP_FLAG_ACK; + PacketResponse = true; + + ConnectionInfo->SequenceNumberIn++; + ConnectionInfo->SequenceNumberOut++; + + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_Closed); + } + + break; + case TCP_Connection_CloseWait: + if (TCPHeaderIN->Flags == TCP_FLAG_ACK) + { + TCP_SetConnectionState(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort, TCP_Connection_Closed); + } + + break; + } + } + } + else + { + /* Port is not open, indicate via a RST/ACK response to the sender */ + TCPHeaderOUT->Flags = (TCP_FLAG_RST | TCP_FLAG_ACK); + PacketResponse = true; + } + + /* Check if we need to respond to the sent packet */ + if (PacketResponse) + { + ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, &IPHeaderIN->SourceAddress, + TCPHeaderIN->SourcePort); + + TCPHeaderOUT->SourcePort = TCPHeaderIN->DestinationPort; + TCPHeaderOUT->DestinationPort = TCPHeaderIN->SourcePort; + TCPHeaderOUT->SequenceNumber = SwapEndian_32(ConnectionInfo->SequenceNumberOut); + TCPHeaderOUT->AcknowledgmentNumber = SwapEndian_32(ConnectionInfo->SequenceNumberIn); + TCPHeaderOUT->DataOffset = (sizeof(TCP_Header_t) / sizeof(uint32_t)); + + if (!(ConnectionInfo->Buffer.InUse)) + TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE); + else + TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE - ConnectionInfo->Buffer.Length); + + TCPHeaderOUT->UrgentPointer = 0; + TCPHeaderOUT->Checksum = 0; + TCPHeaderOUT->Reserved = 0; + + TCPHeaderOUT->Checksum = TCP_Checksum16(TCPHeaderOUT, &IPHeaderIN->DestinationAddress, + &IPHeaderIN->SourceAddress, sizeof(TCP_Header_t)); + + return sizeof(TCP_Header_t); + } + + return NO_RESPONSE; +} + +/** Calculates the appropriate TCP checksum, consisting of the addition of the one's compliment of each word, + * complimented. + * + * \param[in] TCPHeaderOutStart Pointer to the start of the packet's outgoing TCP header + * \param[in] SourceAddress Source protocol IP address of the outgoing IP header + * \param[in] DestinationAddress Destination protocol IP address of the outgoing IP header + * \param[in] TCPOutSize Size in bytes of the TCP data header and payload + * + * \return A 16-bit TCP checksum value + */ +static uint16_t TCP_Checksum16(void* TCPHeaderOutStart, + const IP_Address_t* SourceAddress, + const IP_Address_t* DestinationAddress, + uint16_t TCPOutSize) +{ + uint32_t Checksum = 0; + + /* TCP/IP checksums are the addition of the one's compliment of each word including the IP pseudo-header, + complimented */ + + Checksum += ((uint16_t*)SourceAddress)[0]; + Checksum += ((uint16_t*)SourceAddress)[1]; + Checksum += ((uint16_t*)DestinationAddress)[0]; + Checksum += ((uint16_t*)DestinationAddress)[1]; + Checksum += SwapEndian_16(PROTOCOL_TCP); + Checksum += SwapEndian_16(TCPOutSize); + + for (uint16_t CurrWord = 0; CurrWord < (TCPOutSize >> 1); CurrWord++) + Checksum += ((uint16_t*)TCPHeaderOutStart)[CurrWord]; + + if (TCPOutSize & 0x01) + Checksum += (((uint16_t*)TCPHeaderOutStart)[TCPOutSize >> 1] & 0x00FF); + + while (Checksum & 0xFFFF0000) + Checksum = ((Checksum & 0xFFFF) + (Checksum >> 16)); + + return ~Checksum; +} + |