x25_subr.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 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 */
 34void 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	x25->fraglen = 0;
 44}
 45
 46
 47/*
 48 * This routine purges the input queue of those frames that have been
 49 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
 50 * SDL diagram.
 51*/
 52void x25_frames_acked(struct sock *sk, unsigned short nr)
 53{
 54	struct sk_buff *skb;
 55	struct x25_sock *x25 = x25_sk(sk);
 56	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
 57
 58	/*
 59	 * Remove all the ack-ed frames from the ack queue.
 60	 */
 61	if (x25->va != nr)
 62		while (skb_peek(&x25->ack_queue) && x25->va != nr) {
 63			skb = skb_dequeue(&x25->ack_queue);
 64			kfree_skb(skb);
 65			x25->va = (x25->va + 1) % modulus;
 66		}
 67}
 68
 69void x25_requeue_frames(struct sock *sk)
 70{
 71	struct sk_buff *skb, *skb_prev = NULL;
 72
 73	/*
 74	 * Requeue all the un-ack-ed frames on the output queue to be picked
 75	 * up by x25_kick. This arrangement handles the possibility of an empty
 76	 * output queue.
 77	 */
 78	while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
 79		if (!skb_prev)
 80			skb_queue_head(&sk->sk_write_queue, skb);
 81		else
 82			skb_append(skb_prev, skb, &sk->sk_write_queue);
 83		skb_prev = skb;
 84	}
 85}
 86
 87/*
 88 *	Validate that the value of nr is between va and vs. Return true or
 89 *	false for testing.
 90 */
 91int x25_validate_nr(struct sock *sk, unsigned short nr)
 92{
 93	struct x25_sock *x25 = x25_sk(sk);
 94	unsigned short vc = x25->va;
 95	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
 96
 97	while (vc != x25->vs) {
 98		if (nr == vc)
 99			return 1;
100		vc = (vc + 1) % modulus;
101	}
102
103	return nr == x25->vs ? 1 : 0;
104}
105
106/*
107 *  This routine is called when the packet layer internally generates a
108 *  control frame.
109 */
110void x25_write_internal(struct sock *sk, int frametype)
111{
112	struct x25_sock *x25 = x25_sk(sk);
113	struct sk_buff *skb;
114	unsigned char  *dptr;
115	unsigned char  facilities[X25_MAX_FAC_LEN];
116	unsigned char  addresses[1 + X25_ADDR_LEN];
117	unsigned char  lci1, lci2;
118	/*
119	 *	Default safe frame size.
120	 */
121	int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
122
123	/*
124	 *	Adjust frame size.
125	 */
126	switch (frametype) {
127	case X25_CALL_REQUEST:
128		len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
129		break;
130	case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
131		if (x25->facilities.reverse & 0x80) {
132			len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
133		} else {
134			len += 1 + X25_MAX_FAC_LEN;
135		}
136		break;
137	case X25_CLEAR_REQUEST:
138	case X25_RESET_REQUEST:
139		len += 2;
140		break;
141	case X25_RR:
142	case X25_RNR:
143	case X25_REJ:
144	case X25_CLEAR_CONFIRMATION:
145	case X25_INTERRUPT_CONFIRMATION:
146	case X25_RESET_CONFIRMATION:
147		break;
148	default:
149		pr_err("invalid frame type %02X\n", frametype);
150		return;
151	}
152
153	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
154		return;
155
156	/*
157	 *	Space for Ethernet and 802.2 LLC headers.
158	 */
159	skb_reserve(skb, X25_MAX_L2_LEN);
160
161	/*
162	 *	Make space for the GFI and LCI, and fill them in.
163	 */
164	dptr = skb_put(skb, 2);
165
166	lci1 = (x25->lci >> 8) & 0x0F;
167	lci2 = (x25->lci >> 0) & 0xFF;
168
169	if (x25->neighbour->extended) {
170		*dptr++ = lci1 | X25_GFI_EXTSEQ;
171		*dptr++ = lci2;
172	} else {
173		*dptr++ = lci1 | X25_GFI_STDSEQ;
174		*dptr++ = lci2;
175	}
176
177	/*
178	 *	Now fill in the frame type specific information.
179	 */
180	switch (frametype) {
181
182		case X25_CALL_REQUEST:
183			dptr    = skb_put(skb, 1);
184			*dptr++ = X25_CALL_REQUEST;
185			len     = x25_addr_aton(addresses, &x25->dest_addr,
186						&x25->source_addr);
187			skb_put_data(skb, addresses, len);
188			len     = x25_create_facilities(facilities,
189					&x25->facilities,
190					&x25->dte_facilities,
191					x25->neighbour->global_facil_mask);
192			skb_put_data(skb, facilities, len);
193			skb_put_data(skb, x25->calluserdata.cuddata,
194				     x25->calluserdata.cudlength);
195			x25->calluserdata.cudlength = 0;
196			break;
197
198		case X25_CALL_ACCEPTED:
199			dptr    = skb_put(skb, 2);
200			*dptr++ = X25_CALL_ACCEPTED;
201			*dptr++ = 0x00;		/* Address lengths */
202			len     = x25_create_facilities(facilities,
203							&x25->facilities,
204							&x25->dte_facilities,
205							x25->vc_facil_mask);
206			skb_put_data(skb, facilities, len);
207
208			/* fast select with no restriction on response
209				allows call user data. Userland must
210				ensure it is ours and not theirs */
211			if(x25->facilities.reverse & 0x80) {
212				skb_put_data(skb,
213					     x25->calluserdata.cuddata,
214					     x25->calluserdata.cudlength);
215			}
216			x25->calluserdata.cudlength = 0;
217			break;
218
219		case X25_CLEAR_REQUEST:
220			dptr    = skb_put(skb, 3);
221			*dptr++ = frametype;
222			*dptr++ = x25->causediag.cause;
223			*dptr++ = x25->causediag.diagnostic;
224			break;
225
226		case X25_RESET_REQUEST:
227			dptr    = skb_put(skb, 3);
228			*dptr++ = frametype;
229			*dptr++ = 0x00;		/* XXX */
230			*dptr++ = 0x00;		/* XXX */
231			break;
232
233		case X25_RR:
234		case X25_RNR:
235		case X25_REJ:
236			if (x25->neighbour->extended) {
237				dptr     = skb_put(skb, 2);
238				*dptr++  = frametype;
239				*dptr++  = (x25->vr << 1) & 0xFE;
240			} else {
241				dptr     = skb_put(skb, 1);
242				*dptr    = frametype;
243				*dptr++ |= (x25->vr << 5) & 0xE0;
244			}
245			break;
246
247		case X25_CLEAR_CONFIRMATION:
248		case X25_INTERRUPT_CONFIRMATION:
249		case X25_RESET_CONFIRMATION:
250			dptr  = skb_put(skb, 1);
251			*dptr = frametype;
252			break;
253	}
254
255	x25_transmit_link(skb, x25->neighbour);
256}
257
258/*
259 *	Unpick the contents of the passed X.25 Packet Layer frame.
260 */
261int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
262	       int *d, int *m)
263{
264	struct x25_sock *x25 = x25_sk(sk);
265	unsigned char *frame;
266
267	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
268		return X25_ILLEGAL;
269	frame = skb->data;
270
271	*ns = *nr = *q = *d = *m = 0;
272
273	switch (frame[2]) {
274	case X25_CALL_REQUEST:
275	case X25_CALL_ACCEPTED:
276	case X25_CLEAR_REQUEST:
277	case X25_CLEAR_CONFIRMATION:
278	case X25_INTERRUPT:
279	case X25_INTERRUPT_CONFIRMATION:
280	case X25_RESET_REQUEST:
281	case X25_RESET_CONFIRMATION:
282	case X25_RESTART_REQUEST:
283	case X25_RESTART_CONFIRMATION:
284	case X25_REGISTRATION_REQUEST:
285	case X25_REGISTRATION_CONFIRMATION:
286	case X25_DIAGNOSTIC:
287		return frame[2];
288	}
289
290	if (x25->neighbour->extended) {
291		if (frame[2] == X25_RR  ||
292		    frame[2] == X25_RNR ||
293		    frame[2] == X25_REJ) {
294			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
295				return X25_ILLEGAL;
296			frame = skb->data;
297
298			*nr = (frame[3] >> 1) & 0x7F;
299			return frame[2];
300		}
301	} else {
302		if ((frame[2] & 0x1F) == X25_RR  ||
303		    (frame[2] & 0x1F) == X25_RNR ||
304		    (frame[2] & 0x1F) == X25_REJ) {
305			*nr = (frame[2] >> 5) & 0x07;
306			return frame[2] & 0x1F;
307		}
308	}
309
310	if (x25->neighbour->extended) {
311		if ((frame[2] & 0x01) == X25_DATA) {
312			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
313				return X25_ILLEGAL;
314			frame = skb->data;
315
316			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
317			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
318			*m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
319			*nr = (frame[3] >> 1) & 0x7F;
320			*ns = (frame[2] >> 1) & 0x7F;
321			return X25_DATA;
322		}
323	} else {
324		if ((frame[2] & 0x01) == X25_DATA) {
325			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
326			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
327			*m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
328			*nr = (frame[2] >> 5) & 0x07;
329			*ns = (frame[2] >> 1) & 0x07;
330			return X25_DATA;
331		}
332	}
333
334	pr_debug("invalid PLP frame %3ph\n", frame);
335
336	return X25_ILLEGAL;
337}
338
339void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
340		    unsigned char diagnostic)
341{
342	struct x25_sock *x25 = x25_sk(sk);
343
344	x25_clear_queues(sk);
345	x25_stop_timer(sk);
346
347	x25->lci   = 0;
348	x25->state = X25_STATE_0;
349
350	x25->causediag.cause      = cause;
351	x25->causediag.diagnostic = diagnostic;
352
353	sk->sk_state     = TCP_CLOSE;
354	sk->sk_err       = reason;
355	sk->sk_shutdown |= SEND_SHUTDOWN;
356
357	if (!sock_flag(sk, SOCK_DEAD)) {
358		sk->sk_state_change(sk);
359		sock_set_flag(sk, SOCK_DEAD);
360	}
361	if (x25->neighbour) {
362		read_lock_bh(&x25_list_lock);
363		x25_neigh_put(x25->neighbour);
364		x25->neighbour = NULL;
365		read_unlock_bh(&x25_list_lock);
366	}
367}
368
369/*
370 * Clear an own-rx-busy condition and tell the peer about this, provided
371 * that there is a significant amount of free receive buffer space available.
372 */
373void x25_check_rbuf(struct sock *sk)
374{
375	struct x25_sock *x25 = x25_sk(sk);
376
377	if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
378	    (x25->condition & X25_COND_OWN_RX_BUSY)) {
379		x25->condition &= ~X25_COND_OWN_RX_BUSY;
380		x25->condition &= ~X25_COND_ACK_PENDING;
381		x25->vl         = x25->vr;
382		x25_write_internal(sk, X25_RR);
383		x25_stop_timer(sk);
384	}
385}