1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * X.25 Packet Layer release 002
4 *
5 * This is ALPHA test software. This code may break your machine,
6 * randomly fail to work with new releases, misbehave and/or generally
7 * screw up. It might even work.
8 *
9 * This code REQUIRES 2.1.15 or higher
10 *
11 * History
12 * X.25 001 Jonathan Naylor Started coding.
13 * X.25 002 Jonathan Naylor Centralised disconnection processing.
14 * mar/20/00 Daniela Squassoni Disabling/enabling of facilities
15 * negotiation.
16 * jun/24/01 Arnaldo C. Melo use skb_queue_purge, cleanups
17 * apr/04/15 Shaun Pereira Fast select with no
18 * restriction on response.
19 */
20
21 #define pr_fmt(fmt) "X25: " fmt
22
23 #include <linux/slab.h>
24 #include <linux/kernel.h>
25 #include <linux/string.h>
26 #include <linux/skbuff.h>
27 #include <net/sock.h>
28 #include <net/tcp_states.h>
29 #include <net/x25.h>
30
31 /*
32 * This routine purges all of the queues of frames.
33 */
34 void x25_clear_queues(struct sock *sk)
35 {
36 struct x25_sock *x25 = x25_sk(sk);
37
38 skb_queue_purge(&sk->sk_write_queue);
39 skb_queue_purge(&x25->ack_queue);
40 skb_queue_purge(&x25->interrupt_in_queue);
41 skb_queue_purge(&x25->interrupt_out_queue);
42 skb_queue_purge(&x25->fragment_queue);
43 }
44
45
46 /*
47 * This routine purges the input queue of those frames that have been
48 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
49 * SDL diagram.
50 */
51 void x25_frames_acked(struct sock *sk, unsigned short nr)
52 {
53 struct sk_buff *skb;
54 struct x25_sock *x25 = x25_sk(sk);
55 int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
56
57 /*
58 * Remove all the ack-ed frames from the ack queue.
59 */
60 if (x25->va != nr)
61 while (skb_peek(&x25->ack_queue) && x25->va != nr) {
62 skb = skb_dequeue(&x25->ack_queue);
63 kfree_skb(skb);
64 x25->va = (x25->va + 1) % modulus;
65 }
66 }
67
68 void x25_requeue_frames(struct sock *sk)
69 {
70 struct sk_buff *skb, *skb_prev = NULL;
71
72 /*
73 * Requeue all the un-ack-ed frames on the output queue to be picked
74 * up by x25_kick. This arrangement handles the possibility of an empty
75 * output queue.
76 */
77 while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
78 if (!skb_prev)
79 skb_queue_head(&sk->sk_write_queue, skb);
80 else
81 skb_append(skb_prev, skb, &sk->sk_write_queue);
82 skb_prev = skb;
83 }
84 }
85
86 /*
87 * Validate that the value of nr is between va and vs. Return true or
88 * false for testing.
89 */
90 int x25_validate_nr(struct sock *sk, unsigned short nr)
91 {
92 struct x25_sock *x25 = x25_sk(sk);
93 unsigned short vc = x25->va;
94 int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
95
96 while (vc != x25->vs) {
97 if (nr == vc)
98 return 1;
99 vc = (vc + 1) % modulus;
100 }
101
102 return nr == x25->vs ? 1 : 0;
103 }
104
105 /*
106 * This routine is called when the packet layer internally generates a
107 * control frame.
108 */
109 void x25_write_internal(struct sock *sk, int frametype)
110 {
111 struct x25_sock *x25 = x25_sk(sk);
112 struct sk_buff *skb;
113 unsigned char *dptr;
114 unsigned char facilities[X25_MAX_FAC_LEN];
115 unsigned char addresses[1 + X25_ADDR_LEN];
116 unsigned char lci1, lci2;
117 /*
118 * Default safe frame size.
119 */
120 int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
121
122 /*
123 * Adjust frame size.
124 */
125 switch (frametype) {
126 case X25_CALL_REQUEST:
127 len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
128 break;
129 case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
130 if (x25->facilities.reverse & 0x80) {
131 len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
132 } else {
133 len += 1 + X25_MAX_FAC_LEN;
134 }
135 break;
136 case X25_CLEAR_REQUEST:
137 case X25_RESET_REQUEST:
138 len += 2;
139 break;
140 case X25_RR:
141 case X25_RNR:
142 case X25_REJ:
143 case X25_CLEAR_CONFIRMATION:
144 case X25_INTERRUPT_CONFIRMATION:
145 case X25_RESET_CONFIRMATION:
146 break;
147 default:
148 pr_err("invalid frame type %02X\n", frametype);
149 return;
150 }
151
152 if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
153 return;
154
155 /*
156 * Space for Ethernet and 802.2 LLC headers.
157 */
158 skb_reserve(skb, X25_MAX_L2_LEN);
159
160 /*
161 * Make space for the GFI and LCI, and fill them in.
162 */
163 dptr = skb_put(skb, 2);
164
165 lci1 = (x25->lci >> 8) & 0x0F;
166 lci2 = (x25->lci >> 0) & 0xFF;
167
168 if (x25->neighbour->extended) {
169 *dptr++ = lci1 | X25_GFI_EXTSEQ;
170 *dptr++ = lci2;
171 } else {
172 *dptr++ = lci1 | X25_GFI_STDSEQ;
173 *dptr++ = lci2;
174 }
175
176 /*
177 * Now fill in the frame type specific information.
178 */
179 switch (frametype) {
180
181 case X25_CALL_REQUEST:
182 dptr = skb_put(skb, 1);
183 *dptr++ = X25_CALL_REQUEST;
184 len = x25_addr_aton(addresses, &x25->dest_addr,
185 &x25->source_addr);
186 skb_put_data(skb, addresses, len);
187 len = x25_create_facilities(facilities,
188 &x25->facilities,
189 &x25->dte_facilities,
190 x25->neighbour->global_facil_mask);
191 skb_put_data(skb, facilities, len);
192 skb_put_data(skb, x25->calluserdata.cuddata,
193 x25->calluserdata.cudlength);
194 x25->calluserdata.cudlength = 0;
195 break;
196
197 case X25_CALL_ACCEPTED:
198 dptr = skb_put(skb, 2);
199 *dptr++ = X25_CALL_ACCEPTED;
200 *dptr++ = 0x00; /* Address lengths */
201 len = x25_create_facilities(facilities,
202 &x25->facilities,
203 &x25->dte_facilities,
204 x25->vc_facil_mask);
205 skb_put_data(skb, facilities, len);
206
207 /* fast select with no restriction on response
208 allows call user data. Userland must
209 ensure it is ours and not theirs */
210 if(x25->facilities.reverse & 0x80) {
211 skb_put_data(skb,
212 x25->calluserdata.cuddata,
213 x25->calluserdata.cudlength);
214 }
215 x25->calluserdata.cudlength = 0;
216 break;
217
218 case X25_CLEAR_REQUEST:
219 dptr = skb_put(skb, 3);
220 *dptr++ = frametype;
221 *dptr++ = x25->causediag.cause;
222 *dptr++ = x25->causediag.diagnostic;
223 break;
224
225 case X25_RESET_REQUEST:
226 dptr = skb_put(skb, 3);
227 *dptr++ = frametype;
228 *dptr++ = 0x00; /* XXX */
229 *dptr++ = 0x00; /* XXX */
230 break;
231
232 case X25_RR:
233 case X25_RNR:
234 case X25_REJ:
235 if (x25->neighbour->extended) {
236 dptr = skb_put(skb, 2);
237 *dptr++ = frametype;
238 *dptr++ = (x25->vr << 1) & 0xFE;
239 } else {
240 dptr = skb_put(skb, 1);
241 *dptr = frametype;
242 *dptr++ |= (x25->vr << 5) & 0xE0;
243 }
244 break;
245
246 case X25_CLEAR_CONFIRMATION:
247 case X25_INTERRUPT_CONFIRMATION:
248 case X25_RESET_CONFIRMATION:
249 dptr = skb_put(skb, 1);
250 *dptr = frametype;
251 break;
252 }
253
254 x25_transmit_link(skb, x25->neighbour);
255 }
256
257 /*
258 * Unpick the contents of the passed X.25 Packet Layer frame.
259 */
260 int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
261 int *d, int *m)
262 {
263 struct x25_sock *x25 = x25_sk(sk);
264 unsigned char *frame;
265
266 if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
267 return X25_ILLEGAL;
268 frame = skb->data;
269
270 *ns = *nr = *q = *d = *m = 0;
271
272 switch (frame[2]) {
273 case X25_CALL_REQUEST:
274 case X25_CALL_ACCEPTED:
275 case X25_CLEAR_REQUEST:
276 case X25_CLEAR_CONFIRMATION:
277 case X25_INTERRUPT:
278 case X25_INTERRUPT_CONFIRMATION:
279 case X25_RESET_REQUEST:
280 case X25_RESET_CONFIRMATION:
281 case X25_RESTART_REQUEST:
282 case X25_RESTART_CONFIRMATION:
283 case X25_REGISTRATION_REQUEST:
284 case X25_REGISTRATION_CONFIRMATION:
285 case X25_DIAGNOSTIC:
286 return frame[2];
287 }
288
289 if (x25->neighbour->extended) {
290 if (frame[2] == X25_RR ||
291 frame[2] == X25_RNR ||
292 frame[2] == X25_REJ) {
293 if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
294 return X25_ILLEGAL;
295 frame = skb->data;
296
297 *nr = (frame[3] >> 1) & 0x7F;
298 return frame[2];
299 }
300 } else {
301 if ((frame[2] & 0x1F) == X25_RR ||
302 (frame[2] & 0x1F) == X25_RNR ||
303 (frame[2] & 0x1F) == X25_REJ) {
304 *nr = (frame[2] >> 5) & 0x07;
305 return frame[2] & 0x1F;
306 }
307 }
308
309 if (x25->neighbour->extended) {
310 if ((frame[2] & 0x01) == X25_DATA) {
311 if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
312 return X25_ILLEGAL;
313 frame = skb->data;
314
315 *q = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
316 *d = (frame[0] & X25_D_BIT) == X25_D_BIT;
317 *m = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
318 *nr = (frame[3] >> 1) & 0x7F;
319 *ns = (frame[2] >> 1) & 0x7F;
320 return X25_DATA;
321 }
322 } else {
323 if ((frame[2] & 0x01) == X25_DATA) {
324 *q = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
325 *d = (frame[0] & X25_D_BIT) == X25_D_BIT;
326 *m = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
327 *nr = (frame[2] >> 5) & 0x07;
328 *ns = (frame[2] >> 1) & 0x07;
329 return X25_DATA;
330 }
331 }
332
333 pr_debug("invalid PLP frame %3ph\n", frame);
334
335 return X25_ILLEGAL;
336 }
337
338 void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
339 unsigned char diagnostic)
340 {
341 struct x25_sock *x25 = x25_sk(sk);
342
343 x25_clear_queues(sk);
344 x25_stop_timer(sk);
345
346 x25->lci = 0;
347 x25->state = X25_STATE_0;
348
349 x25->causediag.cause = cause;
350 x25->causediag.diagnostic = diagnostic;
351
352 sk->sk_state = TCP_CLOSE;
353 sk->sk_err = reason;
354 sk->sk_shutdown |= SEND_SHUTDOWN;
355
356 if (!sock_flag(sk, SOCK_DEAD)) {
357 sk->sk_state_change(sk);
358 sock_set_flag(sk, SOCK_DEAD);
359 }
360 if (x25->neighbour) {
361 read_lock_bh(&x25_list_lock);
362 x25_neigh_put(x25->neighbour);
363 x25->neighbour = NULL;
364 read_unlock_bh(&x25_list_lock);
365 }
366 }
367
368 /*
369 * Clear an own-rx-busy condition and tell the peer about this, provided
370 * that there is a significant amount of free receive buffer space available.
371 */
372 void x25_check_rbuf(struct sock *sk)
373 {
374 struct x25_sock *x25 = x25_sk(sk);
375
376 if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
377 (x25->condition & X25_COND_OWN_RX_BUSY)) {
378 x25->condition &= ~X25_COND_OWN_RX_BUSY;
379 x25->condition &= ~X25_COND_ACK_PENDING;
380 x25->vl = x25->vr;
381 x25_write_internal(sk, X25_RR);
382 x25_stop_timer(sk);
383 }
384 }
385
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