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1 | // SPDX-License-Identifier: GPL-2.0-or-later | |
2 | /* | |
3 | * | |
4 | * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk) | |
5 | * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk) | |
6 | * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de) | |
7 | * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de) | |
8 | * | |
9 | * Most of this code is based on the SDL diagrams published in the 7th ARRL | |
10 | * Computer Networking Conference papers. The diagrams have mistakes in them, | |
11 | * but are mostly correct. Before you modify the code could you read the SDL | |
12 | * diagrams as the code is not obvious and probably very easy to break. | |
13 | */ | |
14 | #include <linux/errno.h> | |
15 | #include <linux/types.h> | |
16 | #include <linux/socket.h> | |
17 | #include <linux/in.h> | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/timer.h> | |
20 | #include <linux/string.h> | |
21 | #include <linux/sockios.h> | |
22 | #include <linux/net.h> | |
23 | #include <net/ax25.h> | |
24 | #include <linux/inet.h> | |
25 | #include <linux/netdevice.h> | |
26 | #include <linux/skbuff.h> | |
27 | #include <net/sock.h> | |
28 | #include <net/tcp_states.h> | |
29 | #include <linux/uaccess.h> | |
30 | #include <linux/fcntl.h> | |
31 | #include <linux/mm.h> | |
32 | #include <linux/interrupt.h> | |
33 | ||
34 | /* | |
35 | * State machine for state 1, Awaiting Connection State. | |
36 | * The handling of the timer(s) is in file ax25_std_timer.c. | |
37 | * Handling of state 0 and connection release is in ax25.c. | |
38 | */ | |
39 | static int ax25_std_state1_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type) | |
40 | { | |
41 | switch (frametype) { | |
42 | case AX25_SABM: | |
43 | ax25->modulus = AX25_MODULUS; | |
44 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW]; | |
45 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
46 | break; | |
47 | ||
48 | case AX25_SABME: | |
49 | ax25->modulus = AX25_EMODULUS; | |
50 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW]; | |
51 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
52 | break; | |
53 | ||
54 | case AX25_DISC: | |
55 | ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE); | |
56 | break; | |
57 | ||
58 | case AX25_UA: | |
59 | if (pf) { | |
60 | ax25_calculate_rtt(ax25); | |
61 | ax25_stop_t1timer(ax25); | |
62 | ax25_start_t3timer(ax25); | |
63 | ax25_start_idletimer(ax25); | |
64 | ax25->vs = 0; | |
65 | ax25->va = 0; | |
66 | ax25->vr = 0; | |
67 | ax25->state = AX25_STATE_3; | |
68 | ax25->n2count = 0; | |
69 | if (ax25->sk != NULL) { | |
70 | bh_lock_sock(ax25->sk); | |
71 | ax25->sk->sk_state = TCP_ESTABLISHED; | |
72 | /* For WAIT_SABM connections we will produce an accept ready socket here */ | |
73 | if (!sock_flag(ax25->sk, SOCK_DEAD)) | |
74 | ax25->sk->sk_state_change(ax25->sk); | |
75 | bh_unlock_sock(ax25->sk); | |
76 | } | |
77 | } | |
78 | break; | |
79 | ||
80 | case AX25_DM: | |
81 | if (pf) { | |
82 | if (ax25->modulus == AX25_MODULUS) { | |
83 | ax25_disconnect(ax25, ECONNREFUSED); | |
84 | } else { | |
85 | ax25->modulus = AX25_MODULUS; | |
86 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW]; | |
87 | } | |
88 | } | |
89 | break; | |
90 | ||
91 | default: | |
92 | break; | |
93 | } | |
94 | ||
95 | return 0; | |
96 | } | |
97 | ||
98 | /* | |
99 | * State machine for state 2, Awaiting Release State. | |
100 | * The handling of the timer(s) is in file ax25_std_timer.c | |
101 | * Handling of state 0 and connection release is in ax25.c. | |
102 | */ | |
103 | static int ax25_std_state2_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int pf, int type) | |
104 | { | |
105 | switch (frametype) { | |
106 | case AX25_SABM: | |
107 | case AX25_SABME: | |
108 | ax25_send_control(ax25, AX25_DM, pf, AX25_RESPONSE); | |
109 | break; | |
110 | ||
111 | case AX25_DISC: | |
112 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
113 | ax25_disconnect(ax25, 0); | |
114 | break; | |
115 | ||
116 | case AX25_DM: | |
117 | case AX25_UA: | |
118 | if (pf) | |
119 | ax25_disconnect(ax25, 0); | |
120 | break; | |
121 | ||
122 | case AX25_I: | |
123 | case AX25_REJ: | |
124 | case AX25_RNR: | |
125 | case AX25_RR: | |
126 | if (pf) ax25_send_control(ax25, AX25_DM, AX25_POLLON, AX25_RESPONSE); | |
127 | break; | |
128 | ||
129 | default: | |
130 | break; | |
131 | } | |
132 | ||
133 | return 0; | |
134 | } | |
135 | ||
136 | /* | |
137 | * State machine for state 3, Connected State. | |
138 | * The handling of the timer(s) is in file ax25_std_timer.c | |
139 | * Handling of state 0 and connection release is in ax25.c. | |
140 | */ | |
141 | static int ax25_std_state3_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type) | |
142 | { | |
143 | int queued = 0; | |
144 | ||
145 | switch (frametype) { | |
146 | case AX25_SABM: | |
147 | case AX25_SABME: | |
148 | if (frametype == AX25_SABM) { | |
149 | ax25->modulus = AX25_MODULUS; | |
150 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW]; | |
151 | } else { | |
152 | ax25->modulus = AX25_EMODULUS; | |
153 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW]; | |
154 | } | |
155 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
156 | ax25_stop_t1timer(ax25); | |
157 | ax25_stop_t2timer(ax25); | |
158 | ax25_start_t3timer(ax25); | |
159 | ax25_start_idletimer(ax25); | |
160 | ax25->condition = 0x00; | |
161 | ax25->vs = 0; | |
162 | ax25->va = 0; | |
163 | ax25->vr = 0; | |
164 | ax25_requeue_frames(ax25); | |
165 | break; | |
166 | ||
167 | case AX25_DISC: | |
168 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
169 | ax25_disconnect(ax25, 0); | |
170 | break; | |
171 | ||
172 | case AX25_DM: | |
173 | ax25_disconnect(ax25, ECONNRESET); | |
174 | break; | |
175 | ||
176 | case AX25_RR: | |
177 | case AX25_RNR: | |
178 | if (frametype == AX25_RR) | |
179 | ax25->condition &= ~AX25_COND_PEER_RX_BUSY; | |
180 | else | |
181 | ax25->condition |= AX25_COND_PEER_RX_BUSY; | |
182 | if (type == AX25_COMMAND && pf) | |
183 | ax25_std_enquiry_response(ax25); | |
184 | if (ax25_validate_nr(ax25, nr)) { | |
185 | ax25_check_iframes_acked(ax25, nr); | |
186 | } else { | |
187 | ax25_std_nr_error_recovery(ax25); | |
188 | ax25->state = AX25_STATE_1; | |
189 | } | |
190 | break; | |
191 | ||
192 | case AX25_REJ: | |
193 | ax25->condition &= ~AX25_COND_PEER_RX_BUSY; | |
194 | if (type == AX25_COMMAND && pf) | |
195 | ax25_std_enquiry_response(ax25); | |
196 | if (ax25_validate_nr(ax25, nr)) { | |
197 | ax25_frames_acked(ax25, nr); | |
198 | ax25_calculate_rtt(ax25); | |
199 | ax25_stop_t1timer(ax25); | |
200 | ax25_start_t3timer(ax25); | |
201 | ax25_requeue_frames(ax25); | |
202 | } else { | |
203 | ax25_std_nr_error_recovery(ax25); | |
204 | ax25->state = AX25_STATE_1; | |
205 | } | |
206 | break; | |
207 | ||
208 | case AX25_I: | |
209 | if (!ax25_validate_nr(ax25, nr)) { | |
210 | ax25_std_nr_error_recovery(ax25); | |
211 | ax25->state = AX25_STATE_1; | |
212 | break; | |
213 | } | |
214 | if (ax25->condition & AX25_COND_PEER_RX_BUSY) { | |
215 | ax25_frames_acked(ax25, nr); | |
216 | } else { | |
217 | ax25_check_iframes_acked(ax25, nr); | |
218 | } | |
219 | if (ax25->condition & AX25_COND_OWN_RX_BUSY) { | |
220 | if (pf) ax25_std_enquiry_response(ax25); | |
221 | break; | |
222 | } | |
223 | if (ns == ax25->vr) { | |
224 | ax25->vr = (ax25->vr + 1) % ax25->modulus; | |
225 | queued = ax25_rx_iframe(ax25, skb); | |
226 | if (ax25->condition & AX25_COND_OWN_RX_BUSY) | |
227 | ax25->vr = ns; /* ax25->vr - 1 */ | |
228 | ax25->condition &= ~AX25_COND_REJECT; | |
229 | if (pf) { | |
230 | ax25_std_enquiry_response(ax25); | |
231 | } else { | |
232 | if (!(ax25->condition & AX25_COND_ACK_PENDING)) { | |
233 | ax25->condition |= AX25_COND_ACK_PENDING; | |
234 | ax25_start_t2timer(ax25); | |
235 | } | |
236 | } | |
237 | } else { | |
238 | if (ax25->condition & AX25_COND_REJECT) { | |
239 | if (pf) ax25_std_enquiry_response(ax25); | |
240 | } else { | |
241 | ax25->condition |= AX25_COND_REJECT; | |
242 | ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE); | |
243 | ax25->condition &= ~AX25_COND_ACK_PENDING; | |
244 | } | |
245 | } | |
246 | break; | |
247 | ||
248 | case AX25_FRMR: | |
249 | case AX25_ILLEGAL: | |
250 | ax25_std_establish_data_link(ax25); | |
251 | ax25->state = AX25_STATE_1; | |
252 | break; | |
253 | ||
254 | default: | |
255 | break; | |
256 | } | |
257 | ||
258 | return queued; | |
259 | } | |
260 | ||
261 | /* | |
262 | * State machine for state 4, Timer Recovery State. | |
263 | * The handling of the timer(s) is in file ax25_std_timer.c | |
264 | * Handling of state 0 and connection release is in ax25.c. | |
265 | */ | |
266 | static int ax25_std_state4_machine(ax25_cb *ax25, struct sk_buff *skb, int frametype, int ns, int nr, int pf, int type) | |
267 | { | |
268 | int queued = 0; | |
269 | ||
270 | switch (frametype) { | |
271 | case AX25_SABM: | |
272 | case AX25_SABME: | |
273 | if (frametype == AX25_SABM) { | |
274 | ax25->modulus = AX25_MODULUS; | |
275 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_WINDOW]; | |
276 | } else { | |
277 | ax25->modulus = AX25_EMODULUS; | |
278 | ax25->window = ax25->ax25_dev->values[AX25_VALUES_EWINDOW]; | |
279 | } | |
280 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
281 | ax25_stop_t1timer(ax25); | |
282 | ax25_stop_t2timer(ax25); | |
283 | ax25_start_t3timer(ax25); | |
284 | ax25_start_idletimer(ax25); | |
285 | ax25->condition = 0x00; | |
286 | ax25->vs = 0; | |
287 | ax25->va = 0; | |
288 | ax25->vr = 0; | |
289 | ax25->state = AX25_STATE_3; | |
290 | ax25->n2count = 0; | |
291 | ax25_requeue_frames(ax25); | |
292 | break; | |
293 | ||
294 | case AX25_DISC: | |
295 | ax25_send_control(ax25, AX25_UA, pf, AX25_RESPONSE); | |
296 | ax25_disconnect(ax25, 0); | |
297 | break; | |
298 | ||
299 | case AX25_DM: | |
300 | ax25_disconnect(ax25, ECONNRESET); | |
301 | break; | |
302 | ||
303 | case AX25_RR: | |
304 | case AX25_RNR: | |
305 | if (frametype == AX25_RR) | |
306 | ax25->condition &= ~AX25_COND_PEER_RX_BUSY; | |
307 | else | |
308 | ax25->condition |= AX25_COND_PEER_RX_BUSY; | |
309 | if (type == AX25_RESPONSE && pf) { | |
310 | ax25_stop_t1timer(ax25); | |
311 | ax25->n2count = 0; | |
312 | if (ax25_validate_nr(ax25, nr)) { | |
313 | ax25_frames_acked(ax25, nr); | |
314 | if (ax25->vs == ax25->va) { | |
315 | ax25_start_t3timer(ax25); | |
316 | ax25->state = AX25_STATE_3; | |
317 | } else { | |
318 | ax25_requeue_frames(ax25); | |
319 | } | |
320 | } else { | |
321 | ax25_std_nr_error_recovery(ax25); | |
322 | ax25->state = AX25_STATE_1; | |
323 | } | |
324 | break; | |
325 | } | |
326 | if (type == AX25_COMMAND && pf) | |
327 | ax25_std_enquiry_response(ax25); | |
328 | if (ax25_validate_nr(ax25, nr)) { | |
329 | ax25_frames_acked(ax25, nr); | |
330 | } else { | |
331 | ax25_std_nr_error_recovery(ax25); | |
332 | ax25->state = AX25_STATE_1; | |
333 | } | |
334 | break; | |
335 | ||
336 | case AX25_REJ: | |
337 | ax25->condition &= ~AX25_COND_PEER_RX_BUSY; | |
338 | if (pf && type == AX25_RESPONSE) { | |
339 | ax25_stop_t1timer(ax25); | |
340 | ax25->n2count = 0; | |
341 | if (ax25_validate_nr(ax25, nr)) { | |
342 | ax25_frames_acked(ax25, nr); | |
343 | if (ax25->vs == ax25->va) { | |
344 | ax25_start_t3timer(ax25); | |
345 | ax25->state = AX25_STATE_3; | |
346 | } else { | |
347 | ax25_requeue_frames(ax25); | |
348 | } | |
349 | } else { | |
350 | ax25_std_nr_error_recovery(ax25); | |
351 | ax25->state = AX25_STATE_1; | |
352 | } | |
353 | break; | |
354 | } | |
355 | if (type == AX25_COMMAND && pf) | |
356 | ax25_std_enquiry_response(ax25); | |
357 | if (ax25_validate_nr(ax25, nr)) { | |
358 | ax25_frames_acked(ax25, nr); | |
359 | ax25_requeue_frames(ax25); | |
360 | } else { | |
361 | ax25_std_nr_error_recovery(ax25); | |
362 | ax25->state = AX25_STATE_1; | |
363 | } | |
364 | break; | |
365 | ||
366 | case AX25_I: | |
367 | if (!ax25_validate_nr(ax25, nr)) { | |
368 | ax25_std_nr_error_recovery(ax25); | |
369 | ax25->state = AX25_STATE_1; | |
370 | break; | |
371 | } | |
372 | ax25_frames_acked(ax25, nr); | |
373 | if (ax25->condition & AX25_COND_OWN_RX_BUSY) { | |
374 | if (pf) | |
375 | ax25_std_enquiry_response(ax25); | |
376 | break; | |
377 | } | |
378 | if (ns == ax25->vr) { | |
379 | ax25->vr = (ax25->vr + 1) % ax25->modulus; | |
380 | queued = ax25_rx_iframe(ax25, skb); | |
381 | if (ax25->condition & AX25_COND_OWN_RX_BUSY) | |
382 | ax25->vr = ns; /* ax25->vr - 1 */ | |
383 | ax25->condition &= ~AX25_COND_REJECT; | |
384 | if (pf) { | |
385 | ax25_std_enquiry_response(ax25); | |
386 | } else { | |
387 | if (!(ax25->condition & AX25_COND_ACK_PENDING)) { | |
388 | ax25->condition |= AX25_COND_ACK_PENDING; | |
389 | ax25_start_t2timer(ax25); | |
390 | } | |
391 | } | |
392 | } else { | |
393 | if (ax25->condition & AX25_COND_REJECT) { | |
394 | if (pf) ax25_std_enquiry_response(ax25); | |
395 | } else { | |
396 | ax25->condition |= AX25_COND_REJECT; | |
397 | ax25_send_control(ax25, AX25_REJ, pf, AX25_RESPONSE); | |
398 | ax25->condition &= ~AX25_COND_ACK_PENDING; | |
399 | } | |
400 | } | |
401 | break; | |
402 | ||
403 | case AX25_FRMR: | |
404 | case AX25_ILLEGAL: | |
405 | ax25_std_establish_data_link(ax25); | |
406 | ax25->state = AX25_STATE_1; | |
407 | break; | |
408 | ||
409 | default: | |
410 | break; | |
411 | } | |
412 | ||
413 | return queued; | |
414 | } | |
415 | ||
416 | /* | |
417 | * Higher level upcall for a LAPB frame | |
418 | */ | |
419 | int ax25_std_frame_in(ax25_cb *ax25, struct sk_buff *skb, int type) | |
420 | { | |
421 | int queued = 0, frametype, ns, nr, pf; | |
422 | ||
423 | frametype = ax25_decode(ax25, skb, &ns, &nr, &pf); | |
424 | ||
425 | switch (ax25->state) { | |
426 | case AX25_STATE_1: | |
427 | queued = ax25_std_state1_machine(ax25, skb, frametype, pf, type); | |
428 | break; | |
429 | case AX25_STATE_2: | |
430 | queued = ax25_std_state2_machine(ax25, skb, frametype, pf, type); | |
431 | break; | |
432 | case AX25_STATE_3: | |
433 | queued = ax25_std_state3_machine(ax25, skb, frametype, ns, nr, pf, type); | |
434 | break; | |
435 | case AX25_STATE_4: | |
436 | queued = ax25_std_state4_machine(ax25, skb, frametype, ns, nr, pf, type); | |
437 | break; | |
438 | } | |
439 | ||
440 | ax25_kick(ax25); | |
441 | ||
442 | return queued; | |
443 | } |