?? tcp.lst
字號(hào):
227 5 }
228 4 }
229 3 }
230 2 }
231 1 }
232
233
234
235
236 //------------------------------------------------------------------------
237 // This runs every 0.5 seconds. If the connection has had no activity
238 // it initiates closing the connection.
239 //
240 //------------------------------------------------------------------------
241 void tcp_inactivity(void)
C51 COMPILER V7.06 TCP 05/19/2004 15:18:11 PAGE 5
242 {
243 1 UCHAR idata nr;
244 1
245 1 // Look for active connections in the established state
246 1 for (nr = 0; nr < 5; nr++)
247 1 {
248 2 if ((conxn[nr].ipaddr != 0) &&
249 2 (conxn[nr].state == STATE_ESTABLISHED) &&
250 2 (conxn[nr].inactivity))
251 2 {
252 3 // Decrement the timer and see if it hit 0
253 3 conxn[nr].inactivity--;
254 3 if (conxn[nr].inactivity == 0)
255 3 {
256 4 // Inactivity timer has just timed out.
257 4 // Initiate close of connection
258 4 tcp_send((FLG_ACK | FLG_FIN), 20, nr);
259 4 conxn[nr].my_sequence++; // For my FIN
260 4 conxn[nr].state = STATE_FIN_WAIT_1;
261 4 if (debug) printf("TCP: Entered FIN_WAIT_1 state\n");
262 4 }
263 3 }
264 2 }
265 1 }
266
267
268
269 //------------------------------------------------------------------------
270 // This handles incoming TCP messages and manages the TCP state machine
271 // Note - both the SYN and FIN flags consume a sequence number.
272 // See "TCP/IP Illustrated, Volume 1" Sect 18.6 for info on TCP states
273 // See "TCP/IP Illustrated, Volume 1" Sect 17.3 for info on flags
274 //------------------------------------------------------------------------
275 void tcp_rcve(UCHAR xdata * inbuf, UINT len)
276 {
277 1 UCHAR idata i, j, nr;
278 1 UINT idata result, header_len, data_len;
279 1 TCP_HEADER xdata * tcp;
280 1 IP_HEADER xdata * ip;
281 1 ULONG idata sum;
282 1
283 1 // IP header is always 20 bytes so message starts at index 34
284 1 tcp = (TCP_HEADER xdata *)(inbuf + 34);
285 1 ip = (IP_HEADER xdata *)(inbuf + 14);
286 1
287 1 // Compute TCP checksum including 12 byte pseudoheader
288 1 // Sum source_ipaddr, dest_ipaddr, and entire TCP message
289 1 sum = (ULONG)cksum(inbuf + 26, 8 + len);
290 1
291 1 // Add in the rest of pseudoheader which is
292 1 // protocol id and TCP segment length
293 1 sum += (ULONG)0x0006;
294 1 sum += (ULONG)len;
295 1
296 1 // In case there was a carry, add it back around
297 1 result = (UINT)(sum + (sum >> 16));
298 1
299 1 if (result != 0xFFFF)
300 1 {
301 2 if (debug) printf("TCP: Error, bad cksum\n");
302 2 return;
303 2 }
C51 COMPILER V7.06 TCP 05/19/2004 15:18:11 PAGE 6
304 1
305 1 if (debug) printf("TCP: Msg rcvd with good cksum\n");
306 1
307 1 // See if message is for http server
308 1 if (tcp->dest_port != HTTP_PORT)
309 1 {
310 2 if (debug)
311 2 {
312 3 printf("TCP: Error, msg to port\n ");
313 3 memset(text, 0, 10);
314 3 itoa(tcp->dest_port, text, 10);
315 3 printf(text);
316 3 printf("\n");
317 3 }
318 2 tcp_send(FLG_RST, 20, NO_CONNECTION);
319 2 return;
320 2 }
321 1
322 1 // Capture sender's IP address and port number
323 1 sender_ipaddr = ip->source_ipaddr;
324 1 sender_tcpport = tcp->source_port;
325 1
326 1 // See if the TCP segment is from someone we are already
327 1 // connected to.
328 1 for (i=0; i < 5; i++)
329 1 {
330 2 if ((ip->source_ipaddr == conxn[i].ipaddr) &&
331 2 (tcp->source_port == conxn[i].port))
332 2 {
333 3 nr = i;
334 3 if (debug) printf("TCP: Rcvd msg from existing conxn\n");
335 3 break;
336 3 }
337 2 }
338 1
339 1 // If i = 5, we are not connected. If it is a SYN then assign
340 1 // a temporary conection to it for processing
341 1 if (i == 5)
342 1 {
343 2 if (tcp->flags & FLG_SYN)
344 2 {
345 3 // Find first unused connection (one with IP = 0)
346 3 for (j=0; j < 5; j++)
347 3 {
348 4 if (conxn[j].ipaddr == 0)
349 4 {
350 5 nr = j;
351 5 // Initialize new connection
352 5 conxn[nr].state = STATE_LISTEN;
353 5 break;
354 5 }
355 4 }
356 3
357 3 // If all connections are used then drop msg
358 3 if (j == 5) return;
359 3
360 3 if (debug)
361 3 {
362 4 printf("TCP: New connection ");
363 4 memset(text, 0, 10);
364 4 itoa((UINT)nr, text, 10);
365 4 printf(text);
C51 COMPILER V7.06 TCP 05/19/2004 15:18:11 PAGE 7
366 4 printf("\n");
367 4 }
368 3 }
369 2 }
370 1
371 1
372 1 // By now we should have a connection number in range of 0-4
373 1 // Do a check to avoid any chance of exceeding size of struct
374 1 if (nr > 4)
375 1 {
376 2 if (debug) printf("TCP: Error in assigning conxn number\n");
377 2 return;
378 2 }
379 1
380 1 // Eventually put in protection against wrapping sequence
381 1 // numbers, for now make the client start over if his
382 1 // sequence number is close to wrapping
383 1 if (tcp->sequence > 0xFFFFFF00L)
384 1 {
385 2 if (debug) printf("TCP: Rcvd a high sequence number\n");
386 2 conxn[nr].ipaddr = 0;
387 2 tcp_send(FLG_RST, 20, NO_CONNECTION);
388 2 return;
389 2 }
390 1
391 1 // Handle messages whose action is mostly independent of state
392 1 // such as RST, SYN, and segment with no ACK. That way the
393 1 // state machine below does not need to worry about it.
394 1 if (tcp->flags & FLG_RST)
395 1 {
396 2 // An RST does not depend on state at all. And it does
397 2 // not count as data so do not send an ACK here. Close
398 2 // connection
399 2 if (debug) printf("TCP: Rcvd a reset\n");
400 2 conxn[nr].ipaddr = 0;
401 2 return;
402 2 }
403 1
404 1 else if (tcp->flags & FLG_SYN)
405 1 {
406 2 // A SYN segment only makes sense if connection is in LISTEN
407 2 if ((conxn[nr].state != STATE_LISTEN) &&
408 2 (conxn[nr].state != STATE_CLOSED))
409 2 {
410 3 if (debug) printf("TCP: Error, rcvd bogus SYN\n");
411 3 conxn[nr].ipaddr = 0;
412 3 tcp_send(FLG_RST, 20, NO_CONNECTION);
413 3 return;
414 3 }
415 2 }
416 1
417 1 else if ((tcp->flags & FLG_ACK) == 0)
418 1 {
419 2 // Incoming segments except SYN or RST must have ACK bit set
420 2 // See TCP/IP Illustrated, Vol 2, Page 965
421 2 // Drop segment but do not send a reset
422 2 if (debug) printf("TCP: Error, rcvd segment has no ACK\n");
423 2 return;
424 2 }
425 1
426 1 // Compute length of header including options, and from that
427 1 // compute length of actual data
C51 COMPILER V7.06 TCP 05/19/2004 15:18:11 PAGE 8
428 1 header_len = (tcp->flags & 0xF000) >> 10;
429 1 data_len = len - header_len;
430 1
431 1
432 1
433 1 // Handle TCP state machine for this connection
434 1 switch (conxn[nr].state)
435 1 {
436 2 case STATE_CLOSED:
437 2 case STATE_LISTEN:
438 2
439 2 // If incoming segment contains SYN and no ACK, then handle
440 2 if ((tcp->flags & FLG_SYN) && ((tcp->flags & FLG_ACK) == 0))
441 2 {
442 3 // Capture his starting sequence number and generate
443 3 // my starting sequence number
444 3 // Fill in connection information
445 3 conxn[nr].ipaddr = ip->source_ipaddr;
446 3 conxn[nr].port = tcp->source_port;
447 3 conxn[nr].state = STATE_LISTEN;
448 3 conxn[nr].his_sequence = 1 + tcp->sequence;
449 3 conxn[nr].his_ack = tcp->ack_number;
450 3
451 3 // Use system clock for initial sequence number
452 3 EA = 0;
453 3 conxn[nr].my_sequence = initial_sequence_nr;
454 3 initial_sequence_nr += 64000L;
455 3 EA = 1;
456 3
457 3 // Send header options with the next message
458 3 // Since timestamps are optional and we do not use
459 3 // them, do not have to send them
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