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[pub/USBasp.git] / Demos / Device / LowLevel / RNDISEthernet / Lib / TCP.c
1 /*
2 LUFA Library
3 Copyright (C) Dean Camera, 2011.
4
5 dean [at] fourwalledcubicle [dot] com
6 www.lufa-lib.org
7 */
8
9 /*
10 Copyright 2011 Dean Camera (dean [at] fourwalledcubicle [dot] com)
11
12 Permission to use, copy, modify, distribute, and sell this
13 software and its documentation for any purpose is hereby granted
14 without fee, provided that the above copyright notice appear in
15 all copies and that both that the copyright notice and this
16 permission notice and warranty disclaimer appear in supporting
17 documentation, and that the name of the author not be used in
18 advertising or publicity pertaining to distribution of the
19 software without specific, written prior permission.
20
21 The author disclaim all warranties with regard to this
22 software, including all implied warranties of merchantability
23 and fitness. In no event shall the author be liable for any
24 special, indirect or consequential damages or any damages
25 whatsoever resulting from loss of use, data or profits, whether
26 in an action of contract, negligence or other tortious action,
27 arising out of or in connection with the use or performance of
28 this software.
29 */
30
31 /** \file
32 *
33 * Transmission Control Protocol (TCP) packet handling routines. This protocol handles the reliable in-order transmission
34 * and reception of packets to and from devices on a network, to "ports" on the device. It is used in situations where data
35 * delivery must be reliable and correct, e.g. HTTP, TELNET and most other non-streaming protocols.
36 */
37
38 #define INCLUDE_FROM_TCP_C
39 #include "TCP.h"
40
41 /** Port state table array. This contains the current status of TCP ports in the device. To save on space, only open ports are
42 * stored - closed ports may be overwritten at any time, and the system will assume any ports not present in the array are closed. This
43 * allows for MAX_OPEN_TCP_PORTS to be less than the number of ports used by the application if desired.
44 */
45 TCP_PortState_t PortStateTable[MAX_OPEN_TCP_PORTS];
46
47 /** Connection state table array. This contains the current status of TCP connections in the device. To save on space, only active
48 * (non-closed) connections are stored - closed connections may be overwritten at any time, and the system will assume any connections
49 * not present in the array are closed.
50 */
51 TCP_ConnectionState_t ConnectionStateTable[MAX_TCP_CONNECTIONS];
52
53
54 /** Task to handle the calling of each registered application's callback function, to process and generate TCP packets at the application
55 * level. If an application produces a response, this task constructs the appropriate Ethernet frame and places it into the Ethernet OUT
56 * buffer for later transmission.
57 */
58 void TCP_Task(void)
59 {
60 /* Run each application in sequence, to process incoming and generate outgoing packets */
61 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
62 {
63 /* Find the corresponding port entry in the port table */
64 for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++)
65 {
66 /* Run the application handler for the port */
67 if ((PortStateTable[PTableEntry].Port == ConnectionStateTable[CSTableEntry].Port) &&
68 (PortStateTable[PTableEntry].State == TCP_Port_Open))
69 {
70 PortStateTable[PTableEntry].ApplicationHandler(&ConnectionStateTable[CSTableEntry],
71 &ConnectionStateTable[CSTableEntry].Info.Buffer);
72 }
73 }
74 }
75
76 /* Bail out early if there is already a frame waiting to be sent in the Ethernet OUT buffer */
77 if (FrameOUT.FrameInBuffer)
78 return;
79
80 /* Send response packets from each application as the TCP packet buffers are filled by the applications */
81 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
82 {
83 /* For each completely received packet, pass it along to the listening application */
84 if ((ConnectionStateTable[CSTableEntry].Info.Buffer.Direction == TCP_PACKETDIR_OUT) &&
85 (ConnectionStateTable[CSTableEntry].Info.Buffer.Ready))
86 {
87 Ethernet_Frame_Header_t* FrameOUTHeader = (Ethernet_Frame_Header_t*)&FrameOUT.FrameData;
88 IP_Header_t* IPHeaderOUT = (IP_Header_t*)&FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t)];
89 TCP_Header_t* TCPHeaderOUT = (TCP_Header_t*)&FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t) +
90 sizeof(IP_Header_t)];
91 void* TCPDataOUT = &FrameOUT.FrameData[sizeof(Ethernet_Frame_Header_t) +
92 sizeof(IP_Header_t) +
93 sizeof(TCP_Header_t)];
94
95 uint16_t PacketSize = ConnectionStateTable[CSTableEntry].Info.Buffer.Length;
96
97 /* Fill out the TCP data */
98 TCPHeaderOUT->SourcePort = ConnectionStateTable[CSTableEntry].Port;
99 TCPHeaderOUT->DestinationPort = ConnectionStateTable[CSTableEntry].RemotePort;
100 TCPHeaderOUT->SequenceNumber = SwapEndian_32(ConnectionStateTable[CSTableEntry].Info.SequenceNumberOut);
101 TCPHeaderOUT->AcknowledgmentNumber = SwapEndian_32(ConnectionStateTable[CSTableEntry].Info.SequenceNumberIn);
102 TCPHeaderOUT->DataOffset = (sizeof(TCP_Header_t) / sizeof(uint32_t));
103 TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE);
104
105 TCPHeaderOUT->Flags = TCP_FLAG_ACK;
106 TCPHeaderOUT->UrgentPointer = 0;
107 TCPHeaderOUT->Checksum = 0;
108 TCPHeaderOUT->Reserved = 0;
109
110 memcpy(TCPDataOUT, ConnectionStateTable[CSTableEntry].Info.Buffer.Data, PacketSize);
111
112 ConnectionStateTable[CSTableEntry].Info.SequenceNumberOut += PacketSize;
113
114 TCPHeaderOUT->Checksum = TCP_Checksum16(TCPHeaderOUT, ServerIPAddress,
115 ConnectionStateTable[CSTableEntry].RemoteAddress,
116 (sizeof(TCP_Header_t) + PacketSize));
117
118 PacketSize += sizeof(TCP_Header_t);
119
120 /* Fill out the response IP header */
121 IPHeaderOUT->TotalLength = SwapEndian_16(sizeof(IP_Header_t) + PacketSize);
122 IPHeaderOUT->TypeOfService = 0;
123 IPHeaderOUT->HeaderLength = (sizeof(IP_Header_t) / sizeof(uint32_t));
124 IPHeaderOUT->Version = 4;
125 IPHeaderOUT->Flags = 0;
126 IPHeaderOUT->FragmentOffset = 0;
127 IPHeaderOUT->Identification = 0;
128 IPHeaderOUT->HeaderChecksum = 0;
129 IPHeaderOUT->Protocol = PROTOCOL_TCP;
130 IPHeaderOUT->TTL = DEFAULT_TTL;
131 IPHeaderOUT->SourceAddress = ServerIPAddress;
132 IPHeaderOUT->DestinationAddress = ConnectionStateTable[CSTableEntry].RemoteAddress;
133
134 IPHeaderOUT->HeaderChecksum = Ethernet_Checksum16(IPHeaderOUT, sizeof(IP_Header_t));
135
136 PacketSize += sizeof(IP_Header_t);
137
138 /* Fill out the response Ethernet frame header */
139 FrameOUTHeader->Source = ServerMACAddress;
140 FrameOUTHeader->Destination = (MAC_Address_t){{0x02, 0x00, 0x02, 0x00, 0x02, 0x00}};
141 FrameOUTHeader->EtherType = SwapEndian_16(ETHERTYPE_IPV4);
142
143 PacketSize += sizeof(Ethernet_Frame_Header_t);
144
145 /* Set the response length in the buffer and indicate that a response is ready to be sent */
146 FrameOUT.FrameLength = PacketSize;
147 FrameOUT.FrameInBuffer = true;
148
149 ConnectionStateTable[CSTableEntry].Info.Buffer.Ready = false;
150
151 break;
152 }
153 }
154 }
155
156 /** Initialises the TCP protocol handler, clearing the port and connection state tables. This must be called before TCP packets are
157 * processed.
158 */
159 void TCP_Init(void)
160 {
161 /* Initialize the port state table with all CLOSED entries */
162 for (uint8_t PTableEntry = 0; PTableEntry < MAX_OPEN_TCP_PORTS; PTableEntry++)
163 PortStateTable[PTableEntry].State = TCP_Port_Closed;
164
165 /* Initialize the connection table with all CLOSED entries */
166 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
167 ConnectionStateTable[CSTableEntry].State = TCP_Connection_Closed;
168 }
169
170 /** Sets the state and callback handler of the given port, specified in big endian to the given state.
171 *
172 * \param[in] Port Port whose state and callback function to set, specified in big endian
173 * \param[in] State New state of the port, a value from the TCP_PortStates_t enum
174 * \param[in] Handler Application callback handler for the port
175 *
176 * \return Boolean true if the port state was set, false otherwise (no more space in the port state table)
177 */
178 bool TCP_SetPortState(const uint16_t Port,
179 const uint8_t State,
180 void (*Handler)(TCP_ConnectionState_t*, TCP_ConnectionBuffer_t*))
181 {
182 /* Note, Port number should be specified in BIG endian to simplify network code */
183
184 /* Check to see if the port entry is already in the port state table */
185 for (uint8_t PTableEntry = 0; PTableEntry < MAX_TCP_CONNECTIONS; PTableEntry++)
186 {
187 /* Find existing entry for the port in the table, update it if found */
188 if (PortStateTable[PTableEntry].Port == Port)
189 {
190 PortStateTable[PTableEntry].State = State;
191 PortStateTable[PTableEntry].ApplicationHandler = Handler;
192 return true;
193 }
194 }
195
196 /* Check if trying to open the port -- if so we need to find an unused (closed) entry and replace it */
197 if (State == TCP_Port_Open)
198 {
199 for (uint8_t PTableEntry = 0; PTableEntry < MAX_TCP_CONNECTIONS; PTableEntry++)
200 {
201 /* Find a closed port entry in the table, change it to the given port and state */
202 if (PortStateTable[PTableEntry].State == TCP_Port_Closed)
203 {
204 PortStateTable[PTableEntry].Port = Port;
205 PortStateTable[PTableEntry].State = State;
206 PortStateTable[PTableEntry].ApplicationHandler = Handler;
207 return true;
208 }
209 }
210
211 /* Port not in table and no room to add it, return failure */
212 return false;
213 }
214 else
215 {
216 /* Port not in table but trying to close it, so operation successful */
217 return true;
218 }
219 }
220
221 /** Retrieves the current state of a given TCP port, specified in big endian.
222 *
223 * \param[in] Port TCP port whose state is to be retrieved, given in big-endian
224 *
225 * \return A value from the TCP_PortStates_t enum
226 */
227 uint8_t TCP_GetPortState(const uint16_t Port)
228 {
229 /* Note, Port number should be specified in BIG endian to simplify network code */
230
231 for (uint8_t PTableEntry = 0; PTableEntry < MAX_TCP_CONNECTIONS; PTableEntry++)
232 {
233 /* Find existing entry for the port in the table, return the port status if found */
234 if (PortStateTable[PTableEntry].Port == Port)
235 return PortStateTable[PTableEntry].State;
236 }
237
238 /* Port not in table, assume closed */
239 return TCP_Port_Closed;
240 }
241
242 /** Sets the connection state of the given port, remote address and remote port to the given TCP connection state. If the
243 * connection exists in the connection state table it is updated, otherwise it is created if possible.
244 *
245 * \param[in] Port TCP port of the connection on the device, specified in big endian
246 * \param[in] RemoteAddress Remote protocol IP address of the connected device
247 * \param[in] RemotePort TCP port of the remote device in the connection, specified in big endian
248 * \param[in] State TCP connection state, a value from the TCP_ConnectionStates_t enum
249 *
250 * \return Boolean true if the connection was updated or created, false otherwise (no more space in the connection state table)
251 */
252 bool TCP_SetConnectionState(const uint16_t Port,
253 const IP_Address_t RemoteAddress,
254 const uint16_t RemotePort,
255 const uint8_t State)
256 {
257 /* Note, Port number should be specified in BIG endian to simplify network code */
258
259 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
260 {
261 /* Find port entry in the table */
262 if ((ConnectionStateTable[CSTableEntry].Port == Port) &&
263 IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, &RemoteAddress) &&
264 ConnectionStateTable[CSTableEntry].RemotePort == RemotePort)
265 {
266 ConnectionStateTable[CSTableEntry].State = State;
267 return true;
268 }
269 }
270
271 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
272 {
273 /* Find empty entry in the table */
274 if (ConnectionStateTable[CSTableEntry].State == TCP_Connection_Closed)
275 {
276 ConnectionStateTable[CSTableEntry].Port = Port;
277 ConnectionStateTable[CSTableEntry].RemoteAddress = RemoteAddress;
278 ConnectionStateTable[CSTableEntry].RemotePort = RemotePort;
279 ConnectionStateTable[CSTableEntry].State = State;
280 return true;
281 }
282 }
283
284 return false;
285 }
286
287 /** Retrieves the current state of a given TCP connection to a host.
288 *
289 * \param[in] Port TCP port on the device in the connection, specified in big endian
290 * \param[in] RemoteAddress Remote protocol IP address of the connected host
291 * \param[in] RemotePort Remote TCP port of the connected host, specified in big endian
292 *
293 * \return A value from the TCP_ConnectionStates_t enum
294 */
295 uint8_t TCP_GetConnectionState(const uint16_t Port,
296 const IP_Address_t RemoteAddress,
297 const uint16_t RemotePort)
298 {
299 /* Note, Port number should be specified in BIG endian to simplify network code */
300
301 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
302 {
303 /* Find port entry in the table */
304 if ((ConnectionStateTable[CSTableEntry].Port == Port) &&
305 IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, &RemoteAddress) &&
306 ConnectionStateTable[CSTableEntry].RemotePort == RemotePort)
307
308 {
309 return ConnectionStateTable[CSTableEntry].State;
310 }
311 }
312
313 return TCP_Connection_Closed;
314 }
315
316 /** Retrieves the connection info structure of a given connection to a host.
317 *
318 * \param[in] Port TCP port on the device in the connection, specified in big endian
319 * \param[in] RemoteAddress Remote protocol IP address of the connected host
320 * \param[in] RemotePort Remote TCP port of the connected host, specified in big endian
321 *
322 * \return ConnectionInfo structure of the connection if found, NULL otherwise
323 */
324 TCP_ConnectionInfo_t* TCP_GetConnectionInfo(const uint16_t Port,
325 const IP_Address_t RemoteAddress,
326 const uint16_t RemotePort)
327 {
328 /* Note, Port number should be specified in BIG endian to simplify network code */
329
330 for (uint8_t CSTableEntry = 0; CSTableEntry < MAX_TCP_CONNECTIONS; CSTableEntry++)
331 {
332 /* Find port entry in the table */
333 if ((ConnectionStateTable[CSTableEntry].Port == Port) &&
334 IP_COMPARE(&ConnectionStateTable[CSTableEntry].RemoteAddress, &RemoteAddress) &&
335 ConnectionStateTable[CSTableEntry].RemotePort == RemotePort)
336 {
337 return &ConnectionStateTable[CSTableEntry].Info;
338 }
339 }
340
341 return NULL;
342 }
343
344 /** Processes a TCP packet inside an Ethernet frame, and writes the appropriate response
345 * to the output Ethernet frame if one is created by a application handler.
346 *
347 * \param[in] IPHeaderInStart Pointer to the start of the incoming packet's IP header
348 * \param[in] TCPHeaderInStart Pointer to the start of the incoming packet's TCP header
349 * \param[out] TCPHeaderOutStart Pointer to the start of the outgoing packet's TCP header
350 *
351 * \return The number of bytes written to the out Ethernet frame if any, NO_RESPONSE if no
352 * response was generated, NO_PROCESS if the packet processing was deferred until the
353 * next Ethernet packet handler iteration
354 */
355 int16_t TCP_ProcessTCPPacket(void* IPHeaderInStart,
356 void* TCPHeaderInStart,
357 void* TCPHeaderOutStart)
358 {
359 IP_Header_t* IPHeaderIN = (IP_Header_t*)IPHeaderInStart;
360 TCP_Header_t* TCPHeaderIN = (TCP_Header_t*)TCPHeaderInStart;
361 TCP_Header_t* TCPHeaderOUT = (TCP_Header_t*)TCPHeaderOutStart;
362
363 TCP_ConnectionInfo_t* ConnectionInfo;
364
365 DecodeTCPHeader(TCPHeaderInStart);
366
367 bool PacketResponse = false;
368
369 /* Check if the destination port is open and allows incoming connections */
370 if (TCP_GetPortState(TCPHeaderIN->DestinationPort) == TCP_Port_Open)
371 {
372 /* Detect SYN from host to start a connection */
373 if (TCPHeaderIN->Flags & TCP_FLAG_SYN)
374 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort, TCP_Connection_Listen);
375
376 /* Detect RST from host to abort existing connection */
377 if (TCPHeaderIN->Flags & TCP_FLAG_RST)
378 {
379 if (TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
380 TCPHeaderIN->SourcePort, TCP_Connection_Closed))
381 {
382 TCPHeaderOUT->Flags = (TCP_FLAG_RST | TCP_FLAG_ACK);
383 PacketResponse = true;
384 }
385 }
386 else
387 {
388 /* Process the incoming TCP packet based on the current connection state for the sender and port */
389 switch (TCP_GetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort))
390 {
391 case TCP_Connection_Listen:
392 if (TCPHeaderIN->Flags == TCP_FLAG_SYN)
393 {
394 /* SYN connection starts a connection with a peer */
395 if (TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
396 TCPHeaderIN->SourcePort, TCP_Connection_SYNReceived))
397 {
398 TCPHeaderOUT->Flags = (TCP_FLAG_SYN | TCP_FLAG_ACK);
399
400 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress, TCPHeaderIN->SourcePort);
401
402 ConnectionInfo->SequenceNumberIn = (SwapEndian_32(TCPHeaderIN->SequenceNumber) + 1);
403 ConnectionInfo->SequenceNumberOut = 0;
404 ConnectionInfo->Buffer.InUse = false;
405 }
406 else
407 {
408 TCPHeaderOUT->Flags = TCP_FLAG_RST;
409 }
410
411 PacketResponse = true;
412 }
413
414 break;
415 case TCP_Connection_SYNReceived:
416 if (TCPHeaderIN->Flags == TCP_FLAG_ACK)
417 {
418 /* ACK during the connection process completes the connection to a peer */
419
420 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
421 TCPHeaderIN->SourcePort, TCP_Connection_Established);
422
423 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
424 TCPHeaderIN->SourcePort);
425
426 ConnectionInfo->SequenceNumberOut++;
427 }
428
429 break;
430 case TCP_Connection_Established:
431 if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK))
432 {
433 /* FIN ACK when connected to a peer starts the finalization process */
434
435 TCPHeaderOUT->Flags = (TCP_FLAG_FIN | TCP_FLAG_ACK);
436 PacketResponse = true;
437
438 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
439 TCPHeaderIN->SourcePort, TCP_Connection_CloseWait);
440
441 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
442 TCPHeaderIN->SourcePort);
443
444 ConnectionInfo->SequenceNumberIn++;
445 ConnectionInfo->SequenceNumberOut++;
446 }
447 else if ((TCPHeaderIN->Flags == TCP_FLAG_ACK) || (TCPHeaderIN->Flags == (TCP_FLAG_ACK | TCP_FLAG_PSH)))
448 {
449 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
450 TCPHeaderIN->SourcePort);
451
452 /* Check if the buffer is currently in use either by a buffered data to send, or receive */
453 if ((ConnectionInfo->Buffer.InUse == false) && (ConnectionInfo->Buffer.Ready == false))
454 {
455 ConnectionInfo->Buffer.Direction = TCP_PACKETDIR_IN;
456 ConnectionInfo->Buffer.InUse = true;
457 ConnectionInfo->Buffer.Length = 0;
458 }
459
460 /* Check if the buffer has been claimed by us to read in data from the peer */
461 if ((ConnectionInfo->Buffer.Direction == TCP_PACKETDIR_IN) &&
462 (ConnectionInfo->Buffer.Length != TCP_WINDOW_SIZE))
463 {
464 uint16_t IPOffset = (IPHeaderIN->HeaderLength * sizeof(uint32_t));
465 uint16_t TCPOffset = (TCPHeaderIN->DataOffset * sizeof(uint32_t));
466 uint16_t DataLength = (SwapEndian_16(IPHeaderIN->TotalLength) - IPOffset - TCPOffset);
467
468 /* Copy the packet data into the buffer */
469 memcpy(&ConnectionInfo->Buffer.Data[ConnectionInfo->Buffer.Length],
470 &((uint8_t*)TCPHeaderInStart)[TCPOffset],
471 DataLength);
472
473 ConnectionInfo->SequenceNumberIn += DataLength;
474 ConnectionInfo->Buffer.Length += DataLength;
475
476 /* Check if the buffer is full or if the PSH flag is set, if so indicate buffer ready */
477 if ((!(TCP_WINDOW_SIZE - ConnectionInfo->Buffer.Length)) || (TCPHeaderIN->Flags & TCP_FLAG_PSH))
478 {
479 ConnectionInfo->Buffer.InUse = false;
480 ConnectionInfo->Buffer.Ready = true;
481
482 TCPHeaderOUT->Flags = TCP_FLAG_ACK;
483 PacketResponse = true;
484 }
485 }
486 else
487 {
488 /* Buffer is currently in use by the application, defer processing of the incoming packet */
489 return NO_PROCESS;
490 }
491 }
492
493 break;
494 case TCP_Connection_Closing:
495 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
496 TCPHeaderIN->SourcePort);
497
498 TCPHeaderOUT->Flags = (TCP_FLAG_ACK | TCP_FLAG_FIN);
499 PacketResponse = true;
500
501 ConnectionInfo->Buffer.InUse = false;
502
503 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
504 TCPHeaderIN->SourcePort, TCP_Connection_FINWait1);
505
506 break;
507 case TCP_Connection_FINWait1:
508 if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK))
509 {
510 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
511 TCPHeaderIN->SourcePort);
512
513 TCPHeaderOUT->Flags = TCP_FLAG_ACK;
514 PacketResponse = true;
515
516 ConnectionInfo->SequenceNumberIn++;
517 ConnectionInfo->SequenceNumberOut++;
518
519 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
520 TCPHeaderIN->SourcePort, TCP_Connection_Closed);
521 }
522 else if (TCPHeaderIN->Flags == TCP_FLAG_ACK)
523 {
524 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
525 TCPHeaderIN->SourcePort, TCP_Connection_FINWait2);
526 }
527
528 break;
529 case TCP_Connection_FINWait2:
530 if (TCPHeaderIN->Flags == (TCP_FLAG_FIN | TCP_FLAG_ACK))
531 {
532 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
533 TCPHeaderIN->SourcePort);
534
535 TCPHeaderOUT->Flags = TCP_FLAG_ACK;
536 PacketResponse = true;
537
538 ConnectionInfo->SequenceNumberIn++;
539 ConnectionInfo->SequenceNumberOut++;
540
541 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
542 TCPHeaderIN->SourcePort, TCP_Connection_Closed);
543 }
544
545 break;
546 case TCP_Connection_CloseWait:
547 if (TCPHeaderIN->Flags == TCP_FLAG_ACK)
548 {
549 TCP_SetConnectionState(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
550 TCPHeaderIN->SourcePort, TCP_Connection_Closed);
551 }
552
553 break;
554 }
555 }
556 }
557 else
558 {
559 /* Port is not open, indicate via a RST/ACK response to the sender */
560 TCPHeaderOUT->Flags = (TCP_FLAG_RST | TCP_FLAG_ACK);
561 PacketResponse = true;
562 }
563
564 /* Check if we need to respond to the sent packet */
565 if (PacketResponse)
566 {
567 ConnectionInfo = TCP_GetConnectionInfo(TCPHeaderIN->DestinationPort, IPHeaderIN->SourceAddress,
568 TCPHeaderIN->SourcePort);
569
570 TCPHeaderOUT->SourcePort = TCPHeaderIN->DestinationPort;
571 TCPHeaderOUT->DestinationPort = TCPHeaderIN->SourcePort;
572 TCPHeaderOUT->SequenceNumber = SwapEndian_32(ConnectionInfo->SequenceNumberOut);
573 TCPHeaderOUT->AcknowledgmentNumber = SwapEndian_32(ConnectionInfo->SequenceNumberIn);
574 TCPHeaderOUT->DataOffset = (sizeof(TCP_Header_t) / sizeof(uint32_t));
575
576 if (!(ConnectionInfo->Buffer.InUse))
577 TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE);
578 else
579 TCPHeaderOUT->WindowSize = SwapEndian_16(TCP_WINDOW_SIZE - ConnectionInfo->Buffer.Length);
580
581 TCPHeaderOUT->UrgentPointer = 0;
582 TCPHeaderOUT->Checksum = 0;
583 TCPHeaderOUT->Reserved = 0;
584
585 TCPHeaderOUT->Checksum = TCP_Checksum16(TCPHeaderOUT, IPHeaderIN->DestinationAddress,
586 IPHeaderIN->SourceAddress, sizeof(TCP_Header_t));
587
588 return sizeof(TCP_Header_t);
589 }
590
591 return NO_RESPONSE;
592 }
593
594 /** Calculates the appropriate TCP checksum, consisting of the addition of the one's compliment of each word,
595 * complimented.
596 *
597 * \param[in] TCPHeaderOutStart Pointer to the start of the packet's outgoing TCP header
598 * \param[in] SourceAddress Source protocol IP address of the outgoing IP header
599 * \param[in] DestinationAddress Destination protocol IP address of the outgoing IP header
600 * \param[in] TCPOutSize Size in bytes of the TCP data header and payload
601 *
602 * \return A 16-bit TCP checksum value
603 */
604 static uint16_t TCP_Checksum16(void* TCPHeaderOutStart,
605 const IP_Address_t SourceAddress,
606 const IP_Address_t DestinationAddress,
607 uint16_t TCPOutSize)
608 {
609 uint32_t Checksum = 0;
610
611 /* TCP/IP checksums are the addition of the one's compliment of each word including the IP pseudo-header,
612 complimented */
613
614 Checksum += ((uint16_t*)&SourceAddress)[0];
615 Checksum += ((uint16_t*)&SourceAddress)[1];
616 Checksum += ((uint16_t*)&DestinationAddress)[0];
617 Checksum += ((uint16_t*)&DestinationAddress)[1];
618 Checksum += SwapEndian_16(PROTOCOL_TCP);
619 Checksum += SwapEndian_16(TCPOutSize);
620
621 for (uint16_t CurrWord = 0; CurrWord < (TCPOutSize >> 1); CurrWord++)
622 Checksum += ((uint16_t*)TCPHeaderOutStart)[CurrWord];
623
624 if (TCPOutSize & 0x01)
625 Checksum += (((uint16_t*)TCPHeaderOutStart)[TCPOutSize >> 1] & 0x00FF);
626
627 while (Checksum & 0xFFFF0000)
628 Checksum = ((Checksum & 0xFFFF) + (Checksum >> 16));
629
630 return ~Checksum;
631 }
632
USB isp AVR programmer