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ax25_std_in.c
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1 /*
2  * This program is free software; you can redistribute it and/or modify
3  * it under the terms of the GNU General Public License as published by
4  * the Free Software Foundation; either version 2 of the License, or
5  * (at your option) any later version.
6  *
7  * Copyright (C) Alan Cox GW4PTS ([email protected])
8  * Copyright (C) Jonathan Naylor G4KLX ([email protected])
9  * Copyright (C) Joerg Reuter DL1BKE ([email protected])
10  * Copyright (C) Hans-Joachim Hetscher DD8NE ([email protected])
11  *
12  * Most of this code is based on the SDL diagrams published in the 7th ARRL
13  * Computer Networking Conference papers. The diagrams have mistakes in them,
14  * but are mostly correct. Before you modify the code could you read the SDL
15  * diagrams as the code is not obvious and probably very easy to break.
16  */
17 #include <linux/errno.h>
18 #include <linux/types.h>
19 #include <linux/socket.h>
20 #include <linux/in.h>
21 #include <linux/kernel.h>
22 #include <linux/timer.h>
23 #include <linux/string.h>
24 #include <linux/sockios.h>
25 #include <linux/net.h>
26 #include <net/ax25.h>
27 #include <linux/inet.h>
28 #include <linux/netdevice.h>
29 #include <linux/skbuff.h>
30 #include <net/sock.h>
31 #include <net/tcp_states.h>
32 #include <asm/uaccess.h>
33 #include <linux/fcntl.h>
34 #include <linux/mm.h>
35 #include <linux/interrupt.h>
36 
37 /*
38  * State machine for state 1, Awaiting Connection State.
39  * The handling of the timer(s) is in file ax25_std_timer.c.
40  * Handling of state 0 and connection release is in ax25.c.
41  */
42 static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
43 {
44  switch (frametype) {
45  case AX25_SABM:
46  ax25->modulus = AX25_MODULUS;
47  ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
48  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
49  break;
50 
51  case AX25_SABME:
52  ax25->modulus = AX25_EMODULUS;
53  ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
54  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
55  break;
56 
57  case AX25_DISC:
58  ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
59  break;
60 
61  case AX25_UA:
62  if (pf) {
63  ax25_calculate_rtt(ax25);
64  ax25_stop_t1timer(ax25);
65  ax25_start_t3timer(ax25);
66  ax25_start_idletimer(ax25);
67  ax25->vs = 0;
68  ax25->va = 0;
69  ax25->vr = 0;
70  ax25->state = AX25_STATE_3;
71  ax25->n2count = 0;
72  if (ax25->sk != NULL) {
73  bh_lock_sock(ax25->sk);
74  ax25->sk->sk_state = TCP_ESTABLISHED;
75  /* For WAIT_SABM connections we will produce an accept ready socket here */
76  if (!sock_flag(ax25->sk, SOCK_DEAD))
77  ax25->sk->sk_state_change(ax25->sk);
78  bh_unlock_sock(ax25->sk);
79  }
80  }
81  break;
82 
83  case AX25_DM:
84  if (pf) {
85  if (ax25->modulus == AX25_MODULUS) {
86  ax25_disconnect(ax25, ECONNREFUSED);
87  } else {
88  ax25->modulus = AX25_MODULUS;
89  ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
90  }
91  }
92  break;
93 
94  default:
95  break;
96  }
97 
98  return 0;
99 }
100 
101 /*
102  * State machine for state 2, Awaiting Release State.
103  * The handling of the timer(s) is in file ax25_std_timer.c
104  * Handling of state 0 and connection release is in ax25.c.
105  */
106 static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type)
107 {
108  switch (frametype) {
109  case AX25_SABM:
110  case AX25_SABME:
111  ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE);
112  break;
113 
114  case AX25_DISC:
115  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
116  ax25_disconnect(ax25, 0);
117  break;
118 
119  case AX25_DM:
120  case AX25_UA:
121  if (pf)
122  ax25_disconnect(ax25, 0);
123  break;
124 
125  case AX25_I:
126  case AX25_REJ:
127  case AX25_RNR:
128  case AX25_RR:
129  if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE);
130  break;
131 
132  default:
133  break;
134  }
135 
136  return 0;
137 }
138 
139 /*
140  * State machine for state 3, Connected State.
141  * The handling of the timer(s) is in file ax25_std_timer.c
142  * Handling of state 0 and connection release is in ax25.c.
143  */
144 static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
145 {
146  int queued = 0;
147 
148  switch (frametype) {
149  case AX25_SABM:
150  case AX25_SABME:
151  if (frametype == AX25_SABM) {
152  ax25->modulus = AX25_MODULUS;
153  ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
154  } else {
155  ax25->modulus = AX25_EMODULUS;
156  ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
157  }
158  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
159  ax25_stop_t1timer(ax25);
160  ax25_stop_t2timer(ax25);
161  ax25_start_t3timer(ax25);
162  ax25_start_idletimer(ax25);
163  ax25->condition = 0x00;
164  ax25->vs = 0;
165  ax25->va = 0;
166  ax25->vr = 0;
167  ax25_requeue_frames(ax25);
168  break;
169 
170  case AX25_DISC:
171  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
172  ax25_disconnect(ax25, 0);
173  break;
174 
175  case AX25_DM:
176  ax25_disconnect(ax25, ECONNRESET);
177  break;
178 
179  case AX25_RR:
180  case AX25_RNR:
181  if (frametype == AX25_RR)
182  ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
183  else
184  ax25->condition |= AX25_COND_PEER_RX_BUSY;
185  if (type == AX25_COMMAND && pf)
186  ax25_std_enquiry_response(ax25);
187  if (ax25_validate_nr(ax25, nr)) {
188  ax25_check_iframes_acked(ax25, nr);
189  } else {
190  ax25_std_nr_error_recovery(ax25);
191  ax25->state = AX25_STATE_1;
192  }
193  break;
194 
195  case AX25_REJ:
196  ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
197  if (type == AX25_COMMAND && pf)
198  ax25_std_enquiry_response(ax25);
199  if (ax25_validate_nr(ax25, nr)) {
200  ax25_frames_acked(ax25, nr);
201  ax25_calculate_rtt(ax25);
202  ax25_stop_t1timer(ax25);
203  ax25_start_t3timer(ax25);
204  ax25_requeue_frames(ax25);
205  } else {
206  ax25_std_nr_error_recovery(ax25);
207  ax25->state = AX25_STATE_1;
208  }
209  break;
210 
211  case AX25_I:
212  if (!ax25_validate_nr(ax25, nr)) {
213  ax25_std_nr_error_recovery(ax25);
214  ax25->state = AX25_STATE_1;
215  break;
216  }
217  if (ax25->condition & AX25_COND_PEER_RX_BUSY) {
218  ax25_frames_acked(ax25, nr);
219  } else {
220  ax25_check_iframes_acked(ax25, nr);
221  }
222  if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
223  if (pf) ax25_std_enquiry_response(ax25);
224  break;
225  }
226  if (ns == ax25->vr) {
227  ax25->vr = (ax25->vr + 1) % ax25->modulus;
228  queued = ax25_rx_iframe(ax25, skb);
229  if (ax25->condition & AX25_COND_OWN_RX_BUSY)
230  ax25->vr = ns; /* ax25->vr - 1 */
231  ax25->condition &= ~AX25_COND_REJECT;
232  if (pf) {
233  ax25_std_enquiry_response(ax25);
234  } else {
235  if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
236  ax25->condition |= AX25_COND_ACK_PENDING;
237  ax25_start_t2timer(ax25);
238  }
239  }
240  } else {
241  if (ax25->condition & AX25_COND_REJECT) {
242  if (pf) ax25_std_enquiry_response(ax25);
243  } else {
244  ax25->condition |= AX25_COND_REJECT;
245  ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
246  ax25->condition &= ~AX25_COND_ACK_PENDING;
247  }
248  }
249  break;
250 
251  case AX25_FRMR:
252  case AX25_ILLEGAL:
253  ax25_std_establish_data_link(ax25);
254  ax25->state = AX25_STATE_1;
255  break;
256 
257  default:
258  break;
259  }
260 
261  return queued;
262 }
263 
264 /*
265  * State machine for state 4, Timer Recovery State.
266  * The handling of the timer(s) is in file ax25_std_timer.c
267  * Handling of state 0 and connection release is in ax25.c.
268  */
269 static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type)
270 {
271  int queued = 0;
272 
273  switch (frametype) {
274  case AX25_SABM:
275  case AX25_SABME:
276  if (frametype == AX25_SABM) {
277  ax25->modulus = AX25_MODULUS;
278  ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW];
279  } else {
280  ax25->modulus = AX25_EMODULUS;
281  ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW];
282  }
283  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
284  ax25_stop_t1timer(ax25);
285  ax25_stop_t2timer(ax25);
286  ax25_start_t3timer(ax25);
287  ax25_start_idletimer(ax25);
288  ax25->condition = 0x00;
289  ax25->vs = 0;
290  ax25->va = 0;
291  ax25->vr = 0;
292  ax25->state = AX25_STATE_3;
293  ax25->n2count = 0;
294  ax25_requeue_frames(ax25);
295  break;
296 
297  case AX25_DISC:
298  ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE);
299  ax25_disconnect(ax25, 0);
300  break;
301 
302  case AX25_DM:
303  ax25_disconnect(ax25, ECONNRESET);
304  break;
305 
306  case AX25_RR:
307  case AX25_RNR:
308  if (frametype == AX25_RR)
309  ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
310  else
311  ax25->condition |= AX25_COND_PEER_RX_BUSY;
312  if (type == AX25_RESPONSE && pf) {
313  ax25_stop_t1timer(ax25);
314  ax25->n2count = 0;
315  if (ax25_validate_nr(ax25, nr)) {
316  ax25_frames_acked(ax25, nr);
317  if (ax25->vs == ax25->va) {
318  ax25_start_t3timer(ax25);
319  ax25->state = AX25_STATE_3;
320  } else {
321  ax25_requeue_frames(ax25);
322  }
323  } else {
324  ax25_std_nr_error_recovery(ax25);
325  ax25->state = AX25_STATE_1;
326  }
327  break;
328  }
329  if (type == AX25_COMMAND && pf)
330  ax25_std_enquiry_response(ax25);
331  if (ax25_validate_nr(ax25, nr)) {
332  ax25_frames_acked(ax25, nr);
333  } else {
334  ax25_std_nr_error_recovery(ax25);
335  ax25->state = AX25_STATE_1;
336  }
337  break;
338 
339  case AX25_REJ:
340  ax25->condition &= ~AX25_COND_PEER_RX_BUSY;
341  if (pf && type == AX25_RESPONSE) {
342  ax25_stop_t1timer(ax25);
343  ax25->n2count = 0;
344  if (ax25_validate_nr(ax25, nr)) {
345  ax25_frames_acked(ax25, nr);
346  if (ax25->vs == ax25->va) {
347  ax25_start_t3timer(ax25);
348  ax25->state = AX25_STATE_3;
349  } else {
350  ax25_requeue_frames(ax25);
351  }
352  } else {
353  ax25_std_nr_error_recovery(ax25);
354  ax25->state = AX25_STATE_1;
355  }
356  break;
357  }
358  if (type == AX25_COMMAND && pf)
359  ax25_std_enquiry_response(ax25);
360  if (ax25_validate_nr(ax25, nr)) {
361  ax25_frames_acked(ax25, nr);
362  ax25_requeue_frames(ax25);
363  } else {
364  ax25_std_nr_error_recovery(ax25);
365  ax25->state = AX25_STATE_1;
366  }
367  break;
368 
369  case AX25_I:
370  if (!ax25_validate_nr(ax25, nr)) {
371  ax25_std_nr_error_recovery(ax25);
372  ax25->state = AX25_STATE_1;
373  break;
374  }
375  ax25_frames_acked(ax25, nr);
376  if (ax25->condition & AX25_COND_OWN_RX_BUSY) {
377  if (pf)
378  ax25_std_enquiry_response(ax25);
379  break;
380  }
381  if (ns == ax25->vr) {
382  ax25->vr = (ax25->vr + 1) % ax25->modulus;
383  queued = ax25_rx_iframe(ax25, skb);
384  if (ax25->condition & AX25_COND_OWN_RX_BUSY)
385  ax25->vr = ns; /* ax25->vr - 1 */
386  ax25->condition &= ~AX25_COND_REJECT;
387  if (pf) {
388  ax25_std_enquiry_response(ax25);
389  } else {
390  if (!(ax25->condition & AX25_COND_ACK_PENDING)) {
391  ax25->condition |= AX25_COND_ACK_PENDING;
392  ax25_start_t2timer(ax25);
393  }
394  }
395  } else {
396  if (ax25->condition & AX25_COND_REJECT) {
397  if (pf) ax25_std_enquiry_response(ax25);
398  } else {
399  ax25->condition |= AX25_COND_REJECT;
400  ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE);
401  ax25->condition &= ~AX25_COND_ACK_PENDING;
402  }
403  }
404  break;
405 
406  case AX25_FRMR:
407  case AX25_ILLEGAL:
408  ax25_std_establish_data_link(ax25);
409  ax25->state = AX25_STATE_1;
410  break;
411 
412  default:
413  break;
414  }
415 
416  return queued;
417 }
418 
419 /*
420  * Higher level upcall for a LAPB frame
421  */
422 int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type)
423 {
424  int queued = 0, frametype, ns, nr, pf;
425 
426  frametype = ax25_decode(ax25, skb, &ns, &nr, &pf);
427 
428  switch (ax25->state) {
429  case AX25_STATE_1:
430  queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type);
431  break;
432  case AX25_STATE_2:
433  queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type);
434  break;
435  case AX25_STATE_3:
436  queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type);
437  break;
438  case AX25_STATE_4:
439  queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type);
440  break;
441  }
442 
443  ax25_kick(ax25);
444 
445  return queued;
446 }
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