x25_in.c

  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 code.
 14 *					  New timer architecture.
 15 *	2000-03-20	Daniela Squassoni Disabling/enabling of facilities
 16 *					  negotiation.
 17 *	2000-11-10	Henner Eisen	  Check and reset for out-of-sequence
 18 *					  i-frames.
 19 */
 20
 21#define pr_fmt(fmt) "X25: " fmt
 22
 23#include <linux/slab.h>
 24#include <linux/errno.h>
 25#include <linux/kernel.h>
 26#include <linux/string.h>
 27#include <linux/skbuff.h>
 28#include <net/sock.h>
 29#include <net/tcp_states.h>
 30#include <net/x25.h>
 31
 32static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
 33{
 34	struct sk_buff *skbo, *skbn = skb;
 35	struct x25_sock *x25 = x25_sk(sk);
 36
 37	/* make sure we don't overflow */
 38	if (x25->fraglen + skb->len > USHRT_MAX)
 39		return 1;
 40
 41	if (more) {
 42		x25->fraglen += skb->len;
 43		skb_queue_tail(&x25->fragment_queue, skb);
 44		skb_set_owner_r(skb, sk);
 45		return 0;
 46	}
 47
 48	if (x25->fraglen > 0) {	/* End of fragment */
 49		int len = x25->fraglen + skb->len;
 50
 51		skbn = alloc_skb(len, GFP_ATOMIC);
 52		if (!skbn)
 53			return 1;
 54
 55		skb_queue_tail(&x25->fragment_queue, skb);
 56
 57		skb_reset_transport_header(skbn);
 58
 59		skbo = skb_dequeue(&x25->fragment_queue);
 60		skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
 61					  skbo->len);
 62		kfree_skb(skbo);
 63
 64		while ((skbo =
 65			skb_dequeue(&x25->fragment_queue)) != NULL) {
 66			skb_pull(skbo, (x25->neighbour->extended) ?
 67					X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
 68			skb_copy_from_linear_data(skbo,
 69						  skb_put(skbn, skbo->len),
 70						  skbo->len);
 71			kfree_skb(skbo);
 72		}
 73
 74		x25->fraglen = 0;
 75	}
 76
 77	skb_set_owner_r(skbn, sk);
 78	skb_queue_tail(&sk->sk_receive_queue, skbn);
 79	if (!sock_flag(sk, SOCK_DEAD))
 80		sk->sk_data_ready(sk);
 81
 82	return 0;
 83}
 84
 85/*
 86 * State machine for state 1, Awaiting Call Accepted State.
 87 * The handling of the timer(s) is in file x25_timer.c.
 88 * Handling of state 0 and connection release is in af_x25.c.
 89 */
 90static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
 91{
 92	struct x25_address source_addr, dest_addr;
 93	int len;
 94	struct x25_sock *x25 = x25_sk(sk);
 95
 96	switch (frametype) {
 97	case X25_CALL_ACCEPTED: {
 98
 99		x25_stop_timer(sk);
100		x25->condition = 0x00;
101		x25->vs        = 0;
102		x25->va        = 0;
103		x25->vr        = 0;
104		x25->vl        = 0;
105		x25->state     = X25_STATE_3;
106		sk->sk_state   = TCP_ESTABLISHED;
107		/*
108		 *	Parse the data in the frame.
109		 */
110		if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
111			goto out_clear;
112		skb_pull(skb, X25_STD_MIN_LEN);
113
114		len = x25_parse_address_block(skb, &source_addr,
115					      &dest_addr);
116		if (len > 0)
117			skb_pull(skb, len);
118		else if (len < 0)
119			goto out_clear;
120
121		len = x25_parse_facilities(skb, &x25->facilities,
122					   &x25->dte_facilities,
123					   &x25->vc_facil_mask);
124		if (len > 0)
125			skb_pull(skb, len);
126		else if (len < 0)
127			goto out_clear;
128		/*
129		 *	Copy any Call User Data.
130		 */
131		if (skb->len > 0) {
132			if (skb->len > X25_MAX_CUD_LEN)
133				goto out_clear;
134
135			skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
136				skb->len);
137			x25->calluserdata.cudlength = skb->len;
138		}
139		if (!sock_flag(sk, SOCK_DEAD))
140			sk->sk_state_change(sk);
141		break;
142	}
143	case X25_CALL_REQUEST:
144		/* call collision */
145		x25->causediag.cause      = 0x01;
146		x25->causediag.diagnostic = 0x48;
147
148		x25_write_internal(sk, X25_CLEAR_REQUEST);
149		x25_disconnect(sk, EISCONN, 0x01, 0x48);
150		break;
151
152	case X25_CLEAR_REQUEST:
153		if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
154			goto out_clear;
155
156		x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
157		x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
158		break;
159
160	default:
161		break;
162	}
163
164	return 0;
165
166out_clear:
167	x25_write_internal(sk, X25_CLEAR_REQUEST);
168	x25->state = X25_STATE_2;
169	x25_start_t23timer(sk);
170	return 0;
171}
172
173/*
174 * State machine for state 2, Awaiting Clear Confirmation State.
175 * The handling of the timer(s) is in file x25_timer.c
176 * Handling of state 0 and connection release is in af_x25.c.
177 */
178static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
179{
180	switch (frametype) {
181
182		case X25_CLEAR_REQUEST:
183			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
184				goto out_clear;
185
186			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
187			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
188			break;
189
190		case X25_CLEAR_CONFIRMATION:
191			x25_disconnect(sk, 0, 0, 0);
192			break;
193
194		default:
195			break;
196	}
197
198	return 0;
199
200out_clear:
201	x25_write_internal(sk, X25_CLEAR_REQUEST);
202	x25_start_t23timer(sk);
203	return 0;
204}
205
206/*
207 * State machine for state 3, Connected State.
208 * The handling of the timer(s) is in file x25_timer.c
209 * Handling of state 0 and connection release is in af_x25.c.
210 */
211static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
212{
213	int queued = 0;
214	int modulus;
215	struct x25_sock *x25 = x25_sk(sk);
216
217	modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
218
219	switch (frametype) {
220
221		case X25_RESET_REQUEST:
222			x25_write_internal(sk, X25_RESET_CONFIRMATION);
223			x25_stop_timer(sk);
224			x25->condition = 0x00;
225			x25->vs        = 0;
226			x25->vr        = 0;
227			x25->va        = 0;
228			x25->vl        = 0;
229			x25_requeue_frames(sk);
230			break;
231
232		case X25_CLEAR_REQUEST:
233			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
234				goto out_clear;
235
236			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
237			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
238			break;
239
240		case X25_RR:
241		case X25_RNR:
242			if (!x25_validate_nr(sk, nr)) {
243				x25_clear_queues(sk);
244				x25_write_internal(sk, X25_RESET_REQUEST);
245				x25_start_t22timer(sk);
246				x25->condition = 0x00;
247				x25->vs        = 0;
248				x25->vr        = 0;
249				x25->va        = 0;
250				x25->vl        = 0;
251				x25->state     = X25_STATE_4;
252			} else {
253				x25_frames_acked(sk, nr);
254				if (frametype == X25_RNR) {
255					x25->condition |= X25_COND_PEER_RX_BUSY;
256				} else {
257					x25->condition &= ~X25_COND_PEER_RX_BUSY;
258				}
259			}
260			break;
261
262		case X25_DATA:	/* XXX */
263			x25->condition &= ~X25_COND_PEER_RX_BUSY;
264			if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
265				x25_clear_queues(sk);
266				x25_write_internal(sk, X25_RESET_REQUEST);
267				x25_start_t22timer(sk);
268				x25->condition = 0x00;
269				x25->vs        = 0;
270				x25->vr        = 0;
271				x25->va        = 0;
272				x25->vl        = 0;
273				x25->state     = X25_STATE_4;
274				break;
275			}
276			x25_frames_acked(sk, nr);
277			if (ns == x25->vr) {
278				if (x25_queue_rx_frame(sk, skb, m) == 0) {
279					x25->vr = (x25->vr + 1) % modulus;
280					queued = 1;
281				} else {
282					/* Should never happen */
283					x25_clear_queues(sk);
284					x25_write_internal(sk, X25_RESET_REQUEST);
285					x25_start_t22timer(sk);
286					x25->condition = 0x00;
287					x25->vs        = 0;
288					x25->vr        = 0;
289					x25->va        = 0;
290					x25->vl        = 0;
291					x25->state     = X25_STATE_4;
292					break;
293				}
294				if (atomic_read(&sk->sk_rmem_alloc) >
295				    (sk->sk_rcvbuf >> 1))
296					x25->condition |= X25_COND_OWN_RX_BUSY;
297			}
298			/*
299			 *	If the window is full Ack it immediately, else
300			 *	start the holdback timer.
301			 */
302			if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
303				x25->condition &= ~X25_COND_ACK_PENDING;
304				x25_stop_timer(sk);
305				x25_enquiry_response(sk);
306			} else {
307				x25->condition |= X25_COND_ACK_PENDING;
308				x25_start_t2timer(sk);
309			}
310			break;
311
312		case X25_INTERRUPT_CONFIRMATION:
313			clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
314			break;
315
316		case X25_INTERRUPT:
317			if (sock_flag(sk, SOCK_URGINLINE))
318				queued = !sock_queue_rcv_skb(sk, skb);
319			else {
320				skb_set_owner_r(skb, sk);
321				skb_queue_tail(&x25->interrupt_in_queue, skb);
322				queued = 1;
323			}
324			sk_send_sigurg(sk);
325			x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
326			break;
327
328		default:
329			pr_warn("unknown %02X in state 3\n", frametype);
330			break;
331	}
332
333	return queued;
334
335out_clear:
336	x25_write_internal(sk, X25_CLEAR_REQUEST);
337	x25->state = X25_STATE_2;
338	x25_start_t23timer(sk);
339	return 0;
340}
341
342/*
343 * State machine for state 4, Awaiting Reset Confirmation State.
344 * The handling of the timer(s) is in file x25_timer.c
345 * Handling of state 0 and connection release is in af_x25.c.
346 */
347static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
348{
349	struct x25_sock *x25 = x25_sk(sk);
350
351	switch (frametype) {
352
353		case X25_RESET_REQUEST:
354			x25_write_internal(sk, X25_RESET_CONFIRMATION);
355			fallthrough;
356		case X25_RESET_CONFIRMATION: {
357			x25_stop_timer(sk);
358			x25->condition = 0x00;
359			x25->va        = 0;
360			x25->vr        = 0;
361			x25->vs        = 0;
362			x25->vl        = 0;
363			x25->state     = X25_STATE_3;
364			x25_requeue_frames(sk);
365			break;
366		}
367		case X25_CLEAR_REQUEST:
368			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
369				goto out_clear;
370
371			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
372			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
373			break;
374
375		default:
376			break;
377	}
378
379	return 0;
380
381out_clear:
382	x25_write_internal(sk, X25_CLEAR_REQUEST);
383	x25->state = X25_STATE_2;
384	x25_start_t23timer(sk);
385	return 0;
386}
387
388/*
389 * State machine for state 5, Call Accepted / Call Connected pending (X25_ACCPT_APPRV_FLAG).
390 * The handling of the timer(s) is in file x25_timer.c
391 * Handling of state 0 and connection release is in af_x25.c.
392 */
393static int x25_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
394{
395	struct x25_sock *x25 = x25_sk(sk);
396
397	switch (frametype) {
398		case X25_CLEAR_REQUEST:
399			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) {
400				x25_write_internal(sk, X25_CLEAR_REQUEST);
401				x25->state = X25_STATE_2;
402				x25_start_t23timer(sk);
403				return 0;
404			}
405
406			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
407			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
408			break;
409
410		default:
411			break;
412	}
413
414	return 0;
415}
416
417/* Higher level upcall for a LAPB frame */
418int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
419{
420	struct x25_sock *x25 = x25_sk(sk);
421	int queued = 0, frametype, ns, nr, q, d, m;
422
423	if (x25->state == X25_STATE_0)
424		return 0;
425
426	frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
427
428	switch (x25->state) {
429	case X25_STATE_1:
430		queued = x25_state1_machine(sk, skb, frametype);
431		break;
432	case X25_STATE_2:
433		queued = x25_state2_machine(sk, skb, frametype);
434		break;
435	case X25_STATE_3:
436		queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
437		break;
438	case X25_STATE_4:
439		queued = x25_state4_machine(sk, skb, frametype);
440		break;
441	case X25_STATE_5:
442		queued = x25_state5_machine(sk, skb, frametype);
443		break;
444	}
445
446	x25_kick(sk);
447
448	return queued;
449}
450
451int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
452{
453	int queued = x25_process_rx_frame(sk, skb);
454
455	if (!queued)
456		kfree_skb(skb);
457
458	return 0;
459}