1/*
2 *	LAPB release 002
3 *
4 *	This code REQUIRES 2.1.15 or higher/ NET3.038
5 *
6 *	This module:
7 *		This module is free software; you can redistribute it and/or
8 *		modify it under the terms of the GNU General Public License
9 *		as published by the Free Software Foundation; either version
10 *		2 of the License, or (at your option) any later version.
11 *
12 *	History
13 *	LAPB 001	Jonathan Naylor	Started Coding
14 */
15
16#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17
18#include <linux/errno.h>
19#include <linux/types.h>
20#include <linux/socket.h>
21#include <linux/in.h>
22#include <linux/kernel.h>
23#include <linux/timer.h>
24#include <linux/string.h>
25#include <linux/sockios.h>
26#include <linux/net.h>
27#include <linux/inet.h>
28#include <linux/skbuff.h>
29#include <linux/slab.h>
30#include <net/sock.h>
31#include <asm/uaccess.h>
32#include <linux/fcntl.h>
33#include <linux/mm.h>
34#include <linux/interrupt.h>
35#include <net/lapb.h>
36
37/*
38 *	This routine purges all the queues of frames.
39 */
40void lapb_clear_queues(struct lapb_cb *lapb)
41{
42	skb_queue_purge(&lapb->write_queue);
43	skb_queue_purge(&lapb->ack_queue);
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 */
51void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
52{
53	struct sk_buff *skb;
54	int modulus;
55
56	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
57
58	/*
59	 * Remove all the ack-ed frames from the ack queue.
60	 */
61	if (lapb->va != nr)
62		while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
63			skb = skb_dequeue(&lapb->ack_queue);
64			kfree_skb(skb);
65			lapb->va = (lapb->va + 1) % modulus;
66		}
67}
68
69void lapb_requeue_frames(struct lapb_cb *lapb)
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 lapb_kick called from the timer. This arrangement handles the
76	 * possibility of an empty output queue.
77	 */
78	while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
79		if (!skb_prev)
80			skb_queue_head(&lapb->write_queue, skb);
81		else
82			skb_append(skb_prev, skb, &lapb->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 lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
92{
93	unsigned short vc = lapb->va;
94	int modulus;
95
96	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
97
98	while (vc != lapb->vs) {
99		if (nr == vc)
100			return 1;
101		vc = (vc + 1) % modulus;
102	}
103
104	return nr == lapb->vs;
105}
106
107/*
108 *	This routine is the centralised routine for parsing the control
109 *	information for the different frame formats.
110 */
111int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
112		struct lapb_frame *frame)
113{
114	frame->type = LAPB_ILLEGAL;
115
116	lapb_dbg(2, "(%p) S%d RX %02X %02X %02X\n",
117		 lapb->dev, lapb->state,
118		 skb->data[0], skb->data[1], skb->data[2]);
119
120	/* We always need to look at 2 bytes, sometimes we need
121	 * to look at 3 and those cases are handled below.
122	 */
123	if (!pskb_may_pull(skb, 2))
124		return -1;
125
126	if (lapb->mode & LAPB_MLP) {
127		if (lapb->mode & LAPB_DCE) {
128			if (skb->data[0] == LAPB_ADDR_D)
129				frame->cr = LAPB_COMMAND;
130			if (skb->data[0] == LAPB_ADDR_C)
131				frame->cr = LAPB_RESPONSE;
132		} else {
133			if (skb->data[0] == LAPB_ADDR_C)
134				frame->cr = LAPB_COMMAND;
135			if (skb->data[0] == LAPB_ADDR_D)
136				frame->cr = LAPB_RESPONSE;
137		}
138	} else {
139		if (lapb->mode & LAPB_DCE) {
140			if (skb->data[0] == LAPB_ADDR_B)
141				frame->cr = LAPB_COMMAND;
142			if (skb->data[0] == LAPB_ADDR_A)
143				frame->cr = LAPB_RESPONSE;
144		} else {
145			if (skb->data[0] == LAPB_ADDR_A)
146				frame->cr = LAPB_COMMAND;
147			if (skb->data[0] == LAPB_ADDR_B)
148				frame->cr = LAPB_RESPONSE;
149		}
150	}
151
152	skb_pull(skb, 1);
153
154	if (lapb->mode & LAPB_EXTENDED) {
155		if (!(skb->data[0] & LAPB_S)) {
156			if (!pskb_may_pull(skb, 2))
157				return -1;
158			/*
159			 * I frame - carries NR/NS/PF
160			 */
161			frame->type       = LAPB_I;
162			frame->ns         = (skb->data[0] >> 1) & 0x7F;
163			frame->nr         = (skb->data[1] >> 1) & 0x7F;
164			frame->pf         = skb->data[1] & LAPB_EPF;
165			frame->control[0] = skb->data[0];
166			frame->control[1] = skb->data[1];
167			skb_pull(skb, 2);
168		} else if ((skb->data[0] & LAPB_U) == 1) {
169			if (!pskb_may_pull(skb, 2))
170				return -1;
171			/*
172			 * S frame - take out PF/NR
173			 */
174			frame->type       = skb->data[0] & 0x0F;
175			frame->nr         = (skb->data[1] >> 1) & 0x7F;
176			frame->pf         = skb->data[1] & LAPB_EPF;
177			frame->control[0] = skb->data[0];
178			frame->control[1] = skb->data[1];
179			skb_pull(skb, 2);
180		} else if ((skb->data[0] & LAPB_U) == 3) {
181			/*
182			 * U frame - take out PF
183			 */
184			frame->type       = skb->data[0] & ~LAPB_SPF;
185			frame->pf         = skb->data[0] & LAPB_SPF;
186			frame->control[0] = skb->data[0];
187			frame->control[1] = 0x00;
188			skb_pull(skb, 1);
189		}
190	} else {
191		if (!(skb->data[0] & LAPB_S)) {
192			/*
193			 * I frame - carries NR/NS/PF
194			 */
195			frame->type = LAPB_I;
196			frame->ns   = (skb->data[0] >> 1) & 0x07;
197			frame->nr   = (skb->data[0] >> 5) & 0x07;
198			frame->pf   = skb->data[0] & LAPB_SPF;
199		} else if ((skb->data[0] & LAPB_U) == 1) {
200			/*
201			 * S frame - take out PF/NR
202			 */
203			frame->type = skb->data[0] & 0x0F;
204			frame->nr   = (skb->data[0] >> 5) & 0x07;
205			frame->pf   = skb->data[0] & LAPB_SPF;
206		} else if ((skb->data[0] & LAPB_U) == 3) {
207			/*
208			 * U frame - take out PF
209			 */
210			frame->type = skb->data[0] & ~LAPB_SPF;
211			frame->pf   = skb->data[0] & LAPB_SPF;
212		}
213
214		frame->control[0] = skb->data[0];
215
216		skb_pull(skb, 1);
217	}
218
219	return 0;
220}
221
222/*
223 *	This routine is called when the HDLC layer internally  generates a
224 *	command or  response  for  the remote machine ( eg. RR, UA etc. ).
225 *	Only supervisory or unnumbered frames are processed, FRMRs are handled
226 *	by lapb_transmit_frmr below.
227 */
228void lapb_send_control(struct lapb_cb *lapb, int frametype,
229		       int poll_bit, int type)
230{
231	struct sk_buff *skb;
232	unsigned char  *dptr;
233
234	if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
235		return;
236
237	skb_reserve(skb, LAPB_HEADER_LEN + 1);
238
239	if (lapb->mode & LAPB_EXTENDED) {
240		if ((frametype & LAPB_U) == LAPB_U) {
241			dptr   = skb_put(skb, 1);
242			*dptr  = frametype;
243			*dptr |= poll_bit ? LAPB_SPF : 0;
244		} else {
245			dptr     = skb_put(skb, 2);
246			dptr[0]  = frametype;
247			dptr[1]  = (lapb->vr << 1);
248			dptr[1] |= poll_bit ? LAPB_EPF : 0;
249		}
250	} else {
251		dptr   = skb_put(skb, 1);
252		*dptr  = frametype;
253		*dptr |= poll_bit ? LAPB_SPF : 0;
254		if ((frametype & LAPB_U) == LAPB_S)	/* S frames carry NR */
255			*dptr |= (lapb->vr << 5);
256	}
257
258	lapb_transmit_buffer(lapb, skb, type);
259}
260
261/*
262 *	This routine generates FRMRs based on information previously stored in
263 *	the LAPB control block.
264 */
265void lapb_transmit_frmr(struct lapb_cb *lapb)
266{
267	struct sk_buff *skb;
268	unsigned char  *dptr;
269
270	if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
271		return;
272
273	skb_reserve(skb, LAPB_HEADER_LEN + 1);
274
275	if (lapb->mode & LAPB_EXTENDED) {
276		dptr    = skb_put(skb, 6);
277		*dptr++ = LAPB_FRMR;
278		*dptr++ = lapb->frmr_data.control[0];
279		*dptr++ = lapb->frmr_data.control[1];
280		*dptr++ = (lapb->vs << 1) & 0xFE;
281		*dptr   = (lapb->vr << 1) & 0xFE;
282		if (lapb->frmr_data.cr == LAPB_RESPONSE)
283			*dptr |= 0x01;
284		dptr++;
285		*dptr++ = lapb->frmr_type;
286
287		lapb_dbg(1, "(%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
288			 lapb->dev, lapb->state,
289			 skb->data[1], skb->data[2], skb->data[3],
290			 skb->data[4], skb->data[5]);
291	} else {
292		dptr    = skb_put(skb, 4);
293		*dptr++ = LAPB_FRMR;
294		*dptr++ = lapb->frmr_data.control[0];
295		*dptr   = (lapb->vs << 1) & 0x0E;
296		*dptr  |= (lapb->vr << 5) & 0xE0;
297		if (lapb->frmr_data.cr == LAPB_RESPONSE)
298			*dptr |= 0x10;
299		dptr++;
300		*dptr++ = lapb->frmr_type;
301
302		lapb_dbg(1, "(%p) S%d TX FRMR %02X %02X %02X\n",
303			 lapb->dev, lapb->state, skb->data[1],
304			 skb->data[2], skb->data[3]);
305	}
306
307	lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
308}
309