xref: /openbmc/linux/net/x25/x25_subr.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *	X.25 Packet Layer release 002
3  *
4  *	This is ALPHA test software. This code may break your machine,
5  *	randomly fail to work with new releases, misbehave and/or generally
6  *	screw up. It might even work.
7  *
8  *	This code REQUIRES 2.1.15 or higher
9  *
10  *	This module:
11  *		This module is free software; you can redistribute it and/or
12  *		modify it under the terms of the GNU General Public License
13  *		as published by the Free Software Foundation; either version
14  *		2 of the License, or (at your option) any later version.
15  *
16  *	History
17  *	X.25 001	Jonathan Naylor	  Started coding.
18  *	X.25 002	Jonathan Naylor	  Centralised disconnection processing.
19  *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
20  *					  negotiation.
21  *	jun/24/01	Arnaldo C. Melo	  use skb_queue_purge, cleanups
22  *	apr/04/15	Shaun Pereira		Fast select with no
23  *						restriction on response.
24  */
25 
26 #include <linux/kernel.h>
27 #include <linux/string.h>
28 #include <linux/skbuff.h>
29 #include <net/sock.h>
30 #include <net/tcp_states.h>
31 #include <net/x25.h>
32 
33 /*
34  *	This routine purges all of the queues of frames.
35  */
36 void x25_clear_queues(struct sock *sk)
37 {
38 	struct x25_sock *x25 = x25_sk(sk);
39 
40 	skb_queue_purge(&sk->sk_write_queue);
41 	skb_queue_purge(&x25->ack_queue);
42 	skb_queue_purge(&x25->interrupt_in_queue);
43 	skb_queue_purge(&x25->interrupt_out_queue);
44 	skb_queue_purge(&x25->fragment_queue);
45 }
46 
47 
48 /*
49  * This routine purges the input queue of those frames that have been
50  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
51  * SDL diagram.
52 */
53 void x25_frames_acked(struct sock *sk, unsigned short nr)
54 {
55 	struct sk_buff *skb;
56 	struct x25_sock *x25 = x25_sk(sk);
57 	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
58 
59 	/*
60 	 * Remove all the ack-ed frames from the ack queue.
61 	 */
62 	if (x25->va != nr)
63 		while (skb_peek(&x25->ack_queue) && x25->va != nr) {
64 			skb = skb_dequeue(&x25->ack_queue);
65 			kfree_skb(skb);
66 			x25->va = (x25->va + 1) % modulus;
67 		}
68 }
69 
70 void x25_requeue_frames(struct sock *sk)
71 {
72 	struct sk_buff *skb, *skb_prev = NULL;
73 
74 	/*
75 	 * Requeue all the un-ack-ed frames on the output queue to be picked
76 	 * up by x25_kick. This arrangement handles the possibility of an empty
77 	 * output queue.
78 	 */
79 	while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
80 		if (!skb_prev)
81 			skb_queue_head(&sk->sk_write_queue, skb);
82 		else
83 			skb_append(skb_prev, skb, &sk->sk_write_queue);
84 		skb_prev = skb;
85 	}
86 }
87 
88 /*
89  *	Validate that the value of nr is between va and vs. Return true or
90  *	false for testing.
91  */
92 int x25_validate_nr(struct sock *sk, unsigned short nr)
93 {
94 	struct x25_sock *x25 = x25_sk(sk);
95 	unsigned short vc = x25->va;
96 	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
97 
98 	while (vc != x25->vs) {
99 		if (nr == vc)
100 			return 1;
101 		vc = (vc + 1) % modulus;
102 	}
103 
104 	return nr == x25->vs ? 1 : 0;
105 }
106 
107 /*
108  *  This routine is called when the packet layer internally generates a
109  *  control frame.
110  */
111 void x25_write_internal(struct sock *sk, int frametype)
112 {
113 	struct x25_sock *x25 = x25_sk(sk);
114 	struct sk_buff *skb;
115 	unsigned char  *dptr;
116 	unsigned char  facilities[X25_MAX_FAC_LEN];
117 	unsigned char  addresses[1 + X25_ADDR_LEN];
118 	unsigned char  lci1, lci2;
119 	/*
120 	 *	Default safe frame size.
121 	 */
122 	int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
123 
124 	/*
125 	 *	Adjust frame size.
126 	 */
127 	switch (frametype) {
128 		case X25_CALL_REQUEST:
129 			len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN +
130 			       X25_MAX_CUD_LEN;
131 			break;
132 		case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
133 			if(x25->facilities.reverse & 0x80) {
134 				len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
135 			} else {
136 				len += 1 + X25_MAX_FAC_LEN;
137 			}
138 			break;
139 		case X25_CLEAR_REQUEST:
140 		case X25_RESET_REQUEST:
141 			len += 2;
142 			break;
143 		case X25_RR:
144 		case X25_RNR:
145 		case X25_REJ:
146 		case X25_CLEAR_CONFIRMATION:
147 		case X25_INTERRUPT_CONFIRMATION:
148 		case X25_RESET_CONFIRMATION:
149 			break;
150 		default:
151 			printk(KERN_ERR "X.25: invalid frame type %02X\n",
152 			       frametype);
153 			return;
154 	}
155 
156 	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
157 		return;
158 
159 	/*
160 	 *	Space for Ethernet and 802.2 LLC headers.
161 	 */
162 	skb_reserve(skb, X25_MAX_L2_LEN);
163 
164 	/*
165 	 *	Make space for the GFI and LCI, and fill them in.
166 	 */
167 	dptr = skb_put(skb, 2);
168 
169 	lci1 = (x25->lci >> 8) & 0x0F;
170 	lci2 = (x25->lci >> 0) & 0xFF;
171 
172 	if (x25->neighbour->extended) {
173 		*dptr++ = lci1 | X25_GFI_EXTSEQ;
174 		*dptr++ = lci2;
175 	} else {
176 		*dptr++ = lci1 | X25_GFI_STDSEQ;
177 		*dptr++ = lci2;
178 	}
179 
180 	/*
181 	 *	Now fill in the frame type specific information.
182 	 */
183 	switch (frametype) {
184 
185 		case X25_CALL_REQUEST:
186 			dptr    = skb_put(skb, 1);
187 			*dptr++ = X25_CALL_REQUEST;
188 			len     = x25_addr_aton(addresses, &x25->dest_addr,
189 						&x25->source_addr);
190 			dptr    = skb_put(skb, len);
191 			memcpy(dptr, addresses, len);
192 			len     = x25_create_facilities(facilities,
193 							&x25->facilities,
194 					     x25->neighbour->global_facil_mask);
195 			dptr    = skb_put(skb, len);
196 			memcpy(dptr, facilities, len);
197 			dptr = skb_put(skb, x25->calluserdata.cudlength);
198 			memcpy(dptr, x25->calluserdata.cuddata,
199 			       x25->calluserdata.cudlength);
200 			x25->calluserdata.cudlength = 0;
201 			break;
202 
203 		case X25_CALL_ACCEPTED:
204 			dptr    = skb_put(skb, 2);
205 			*dptr++ = X25_CALL_ACCEPTED;
206 			*dptr++ = 0x00;		/* Address lengths */
207 			len     = x25_create_facilities(facilities,
208 							&x25->facilities,
209 							x25->vc_facil_mask);
210 			dptr    = skb_put(skb, len);
211 			memcpy(dptr, facilities, len);
212 
213 			/* fast select with no restriction on response
214 				allows call user data. Userland must
215 				ensure it is ours and not theirs */
216 			if(x25->facilities.reverse & 0x80) {
217 				dptr = skb_put(skb,
218 					x25->calluserdata.cudlength);
219 				memcpy(dptr, x25->calluserdata.cuddata,
220 				       x25->calluserdata.cudlength);
221 			}
222 			x25->calluserdata.cudlength = 0;
223 			break;
224 
225 		case X25_CLEAR_REQUEST:
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  */
261 int 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 = skb->data;
266 
267 	*ns = *nr = *q = *d = *m = 0;
268 
269 	switch (frame[2]) {
270 		case X25_CALL_REQUEST:
271 		case X25_CALL_ACCEPTED:
272 		case X25_CLEAR_REQUEST:
273 		case X25_CLEAR_CONFIRMATION:
274 		case X25_INTERRUPT:
275 		case X25_INTERRUPT_CONFIRMATION:
276 		case X25_RESET_REQUEST:
277 		case X25_RESET_CONFIRMATION:
278 		case X25_RESTART_REQUEST:
279 		case X25_RESTART_CONFIRMATION:
280 		case X25_REGISTRATION_REQUEST:
281 		case X25_REGISTRATION_CONFIRMATION:
282 		case X25_DIAGNOSTIC:
283 			return frame[2];
284 	}
285 
286 	if (x25->neighbour->extended) {
287 		if (frame[2] == X25_RR  ||
288 		    frame[2] == X25_RNR ||
289 		    frame[2] == X25_REJ) {
290 			*nr = (frame[3] >> 1) & 0x7F;
291 			return frame[2];
292 		}
293 	} else {
294 		if ((frame[2] & 0x1F) == X25_RR  ||
295 		    (frame[2] & 0x1F) == X25_RNR ||
296 		    (frame[2] & 0x1F) == X25_REJ) {
297 			*nr = (frame[2] >> 5) & 0x07;
298 			return frame[2] & 0x1F;
299 		}
300 	}
301 
302 	if (x25->neighbour->extended) {
303 		if ((frame[2] & 0x01) == X25_DATA) {
304 			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
305 			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
306 			*m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
307 			*nr = (frame[3] >> 1) & 0x7F;
308 			*ns = (frame[2] >> 1) & 0x7F;
309 			return X25_DATA;
310 		}
311 	} else {
312 		if ((frame[2] & 0x01) == X25_DATA) {
313 			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
314 			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
315 			*m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
316 			*nr = (frame[2] >> 5) & 0x07;
317 			*ns = (frame[2] >> 1) & 0x07;
318 			return X25_DATA;
319 		}
320 	}
321 
322 	printk(KERN_DEBUG "X.25: invalid PLP frame %02X %02X %02X\n",
323 	       frame[0], frame[1], frame[2]);
324 
325 	return X25_ILLEGAL;
326 }
327 
328 void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
329 		    unsigned char diagnostic)
330 {
331 	struct x25_sock *x25 = x25_sk(sk);
332 
333 	x25_clear_queues(sk);
334 	x25_stop_timer(sk);
335 
336 	x25->lci   = 0;
337 	x25->state = X25_STATE_0;
338 
339 	x25->causediag.cause      = cause;
340 	x25->causediag.diagnostic = diagnostic;
341 
342 	sk->sk_state     = TCP_CLOSE;
343 	sk->sk_err       = reason;
344 	sk->sk_shutdown |= SEND_SHUTDOWN;
345 
346 	if (!sock_flag(sk, SOCK_DEAD)) {
347 		sk->sk_state_change(sk);
348 		sock_set_flag(sk, SOCK_DEAD);
349 	}
350 }
351 
352 /*
353  * Clear an own-rx-busy condition and tell the peer about this, provided
354  * that there is a significant amount of free receive buffer space available.
355  */
356 void x25_check_rbuf(struct sock *sk)
357 {
358 	struct x25_sock *x25 = x25_sk(sk);
359 
360 	if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf / 2) &&
361 	    (x25->condition & X25_COND_OWN_RX_BUSY)) {
362 		x25->condition &= ~X25_COND_OWN_RX_BUSY;
363 		x25->condition &= ~X25_COND_ACK_PENDING;
364 		x25->vl         = x25->vr;
365 		x25_write_internal(sk, X25_RR);
366 		x25_stop_timer(sk);
367 	}
368 }
369 
370