aboutsummaryrefslogtreecommitdiffstats
path: root/net/lapb/lapb_subr.c
blob: b8739cf9156da832402741c7fb2693c42506f091 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
/*
 *	LAPB release 002
 *
 *	This code REQUIRES 2.1.15 or higher/ NET3.038
 *
 *	This module:
 *		This module is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 *
 *	History
 *	LAPB 001	Jonathan Naylor	Started Coding
 */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/lapb.h>

/*
 *	This routine purges all the queues of frames.
 */
void lapb_clear_queues(struct lapb_cb *lapb)
{
	skb_queue_purge(&lapb->write_queue);
	skb_queue_purge(&lapb->ack_queue);
}

/*
 * This routine purges the input queue of those frames that have been
 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
 * SDL diagram.
 */
void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
{
	struct sk_buff *skb;
	int modulus;

	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;

	/*
	 * Remove all the ack-ed frames from the ack queue.
	 */
	if (lapb->va != nr)
		while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
			skb = skb_dequeue(&lapb->ack_queue);
			kfree_skb(skb);
			lapb->va = (lapb->va + 1) % modulus;
		}
}

void lapb_requeue_frames(struct lapb_cb *lapb)
{
	struct sk_buff *skb, *skb_prev = NULL;

	/*
	 * Requeue all the un-ack-ed frames on the output queue to be picked
	 * up by lapb_kick called from the timer. This arrangement handles the
	 * possibility of an empty output queue.
	 */
	while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
		if (!skb_prev)
			skb_queue_head(&lapb->write_queue, skb);
		else
			skb_append(skb_prev, skb, &lapb->write_queue);
		skb_prev = skb;
	}
}

/*
 *	Validate that the value of nr is between va and vs. Return true or
 *	false for testing.
 */
int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
{
	unsigned short vc = lapb->va;
	int modulus;

	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;

	while (vc != lapb->vs) {
		if (nr == vc)
			return 1;
		vc = (vc + 1) % modulus;
	}

	return nr == lapb->vs;
}

/*
 *	This routine is the centralised routine for parsing the control
 *	information for the different frame formats.
 */
int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
		struct lapb_frame *frame)
{
	frame->type = LAPB_ILLEGAL;

#if LAPB_DEBUG > 2
	printk(KERN_DEBUG "lapb: (%p) S%d RX %02X %02X %02X\n",
	       lapb->dev, lapb->state,
	       skb->data[0], skb->data[1], skb->data[2]);
#endif

	/* We always need to look at 2 bytes, sometimes we need
	 * to look at 3 and those cases are handled below.
	 */
	if (!pskb_may_pull(skb, 2))
		return -1;

	if (lapb->mode & LAPB_MLP) {
		if (lapb->mode & LAPB_DCE) {
			if (skb->data[0] == LAPB_ADDR_D)
				frame->cr = LAPB_COMMAND;
			if (skb->data[0] == LAPB_ADDR_C)
				frame->cr = LAPB_RESPONSE;
		} else {
			if (skb->data[0] == LAPB_ADDR_C)
				frame->cr = LAPB_COMMAND;
			if (skb->data[0] == LAPB_ADDR_D)
				frame->cr = LAPB_RESPONSE;
		}
	} else {
		if (lapb->mode & LAPB_DCE) {
			if (skb->data[0] == LAPB_ADDR_B)
				frame->cr = LAPB_COMMAND;
			if (skb->data[0] == LAPB_ADDR_A)
				frame->cr = LAPB_RESPONSE;
		} else {
			if (skb->data[0] == LAPB_ADDR_A)
				frame->cr = LAPB_COMMAND;
			if (skb->data[0] == LAPB_ADDR_B)
				frame->cr = LAPB_RESPONSE;
		}
	}

	skb_pull(skb, 1);

	if (lapb->mode & LAPB_EXTENDED) {
		if (!(skb->data[0] & LAPB_S)) {
			if (!pskb_may_pull(skb, 2))
				return -1;
			/*
			 * I frame - carries NR/NS/PF
			 */
			frame->type       = LAPB_I;
			frame->ns         = (skb->data[0] >> 1) & 0x7F;
			frame->nr         = (skb->data[1] >> 1) & 0x7F;
			frame->pf         = skb->data[1] & LAPB_EPF;
			frame->control[0] = skb->data[0];
			frame->control[1] = skb->data[1];
			skb_pull(skb, 2);
		} else if ((skb->data[0] & LAPB_U) == 1) {
			if (!pskb_may_pull(skb, 2))
				return -1;
			/*
			 * S frame - take out PF/NR
			 */
			frame->type       = skb->data[0] & 0x0F;
			frame->nr         = (skb->data[1] >> 1) & 0x7F;
			frame->pf         = skb->data[1] & LAPB_EPF;
			frame->control[0] = skb->data[0];
			frame->control[1] = skb->data[1];
			skb_pull(skb, 2);
		} else if ((skb->data[0] & LAPB_U) == 3) {
			/*
			 * U frame - take out PF
			 */
			frame->type       = skb->data[0] & ~LAPB_SPF;
			frame->pf         = skb->data[0] & LAPB_SPF;
			frame->control[0] = skb->data[0];
			frame->control[1] = 0x00;
			skb_pull(skb, 1);
		}
	} else {
		if (!(skb->data[0] & LAPB_S)) {
			/*
			 * I frame - carries NR/NS/PF
			 */
			frame->type = LAPB_I;
			frame->ns   = (skb->data[0] >> 1) & 0x07;
			frame->nr   = (skb->data[0] >> 5) & 0x07;
			frame->pf   = skb->data[0] & LAPB_SPF;
		} else if ((skb->data[0] & LAPB_U) == 1) {
			/*
			 * S frame - take out PF/NR
			 */
			frame->type = skb->data[0] & 0x0F;
			frame->nr   = (skb->data[0] >> 5) & 0x07;
			frame->pf   = skb->data[0] & LAPB_SPF;
		} else if ((skb->data[0] & LAPB_U) == 3) {
			/*
			 * U frame - take out PF
			 */
			frame->type = skb->data[0] & ~LAPB_SPF;
			frame->pf   = skb->data[0] & LAPB_SPF;
		}

		frame->control[0] = skb->data[0];

		skb_pull(skb, 1);
	}

	return 0;
}

/*
 *	This routine is called when the HDLC layer internally  generates a
 *	command or  response  for  the remote machine ( eg. RR, UA etc. ).
 *	Only supervisory or unnumbered frames are processed, FRMRs are handled
 *	by lapb_transmit_frmr below.
 */
void lapb_send_control(struct lapb_cb *lapb, int frametype,
		       int poll_bit, int type)
{
	struct sk_buff *skb;
	unsigned char  *dptr;

	if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
		return;

	skb_reserve(skb, LAPB_HEADER_LEN + 1);

	if (lapb->mode & LAPB_EXTENDED) {
		if ((frametype & LAPB_U) == LAPB_U) {
			dptr   = skb_put(skb, 1);
			*dptr  = frametype;
			*dptr |= poll_bit ? LAPB_SPF : 0;
		} else {
			dptr     = skb_put(skb, 2);
			dptr[0]  = frametype;
			dptr[1]  = (lapb->vr << 1);
			dptr[1] |= poll_bit ? LAPB_EPF : 0;
		}
	} else {
		dptr   = skb_put(skb, 1);
		*dptr  = frametype;
		*dptr |= poll_bit ? LAPB_SPF : 0;
		if ((frametype & LAPB_U) == LAPB_S)	/* S frames carry NR */
			*dptr |= (lapb->vr << 5);
	}

	lapb_transmit_buffer(lapb, skb, type);
}

/*
 *	This routine generates FRMRs based on information previously stored in
 *	the LAPB control block.
 */
void lapb_transmit_frmr(struct lapb_cb *lapb)
{
	struct sk_buff *skb;
	unsigned char  *dptr;

	if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
		return;

	skb_reserve(skb, LAPB_HEADER_LEN + 1);

	if (lapb->mode & LAPB_EXTENDED) {
		dptr    = skb_put(skb, 6);
		*dptr++ = LAPB_FRMR;
		*dptr++ = lapb->frmr_data.control[0];
		*dptr++ = lapb->frmr_data.control[1];
		*dptr++ = (lapb->vs << 1) & 0xFE;
		*dptr   = (lapb->vr << 1) & 0xFE;
		if (lapb->frmr_data.cr == LAPB_RESPONSE)
			*dptr |= 0x01;
		dptr++;
		*dptr++ = lapb->frmr_type;

#if LAPB_DEBUG > 1
	printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
	       lapb->dev, lapb->state,
	       skb->data[1], skb->data[2], skb->data[3],
	       skb->data[4], skb->data[5]);
#endif
	} else {
		dptr    = skb_put(skb, 4);
		*dptr++ = LAPB_FRMR;
		*dptr++ = lapb->frmr_data.control[0];
		*dptr   = (lapb->vs << 1) & 0x0E;
		*dptr  |= (lapb->vr << 5) & 0xE0;
		if (lapb->frmr_data.cr == LAPB_RESPONSE)
			*dptr |= 0x10;
		dptr++;
		*dptr++ = lapb->frmr_type;

#if LAPB_DEBUG > 1
	printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X\n",
	       lapb->dev, lapb->state, skb->data[1],
	       skb->data[2], skb->data[3]);
#endif
	}

	lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
}

Privacy Policy