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 #include <linux/errno.h>
17 #include <linux/types.h>
18 #include <linux/socket.h>
19 #include <linux/in.h>
20 #include <linux/kernel.h>
21 #include <linux/timer.h>
22 #include <linux/string.h>
23 #include <linux/sockios.h>
24 #include <linux/net.h>
25 #include <linux/inet.h>
26 #include <linux/skbuff.h>
27 #include <linux/slab.h>
28 #include <net/sock.h>
29 #include <asm/uaccess.h>
30 #include <linux/fcntl.h>
31 #include <linux/mm.h>
32 #include <linux/interrupt.h>
33 #include <net/lapb.h>
34 
35 /*
36  *	This routine purges all the queues of frames.
37  */
lapb_clear_queues(struct lapb_cb * lapb)38 void lapb_clear_queues(struct lapb_cb *lapb)
39 {
40 	skb_queue_purge(&lapb->write_queue);
41 	skb_queue_purge(&lapb->ack_queue);
42 }
43 
44 /*
45  * This routine purges the input queue of those frames that have been
46  * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
47  * SDL diagram.
48  */
lapb_frames_acked(struct lapb_cb * lapb,unsigned short nr)49 void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
50 {
51 	struct sk_buff *skb;
52 	int modulus;
53 
54 	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
55 
56 	/*
57 	 * Remove all the ack-ed frames from the ack queue.
58 	 */
59 	if (lapb->va != nr)
60 		while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
61 			skb = skb_dequeue(&lapb->ack_queue);
62 			kfree_skb(skb);
63 			lapb->va = (lapb->va + 1) % modulus;
64 		}
65 }
66 
lapb_requeue_frames(struct lapb_cb * lapb)67 void lapb_requeue_frames(struct lapb_cb *lapb)
68 {
69 	struct sk_buff *skb, *skb_prev = NULL;
70 
71 	/*
72 	 * Requeue all the un-ack-ed frames on the output queue to be picked
73 	 * up by lapb_kick called from the timer. This arrangement handles the
74 	 * possibility of an empty output queue.
75 	 */
76 	while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
77 		if (!skb_prev)
78 			skb_queue_head(&lapb->write_queue, skb);
79 		else
80 			skb_append(skb_prev, skb, &lapb->write_queue);
81 		skb_prev = skb;
82 	}
83 }
84 
85 /*
86  *	Validate that the value of nr is between va and vs. Return true or
87  *	false for testing.
88  */
lapb_validate_nr(struct lapb_cb * lapb,unsigned short nr)89 int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
90 {
91 	unsigned short vc = lapb->va;
92 	int modulus;
93 
94 	modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
95 
96 	while (vc != lapb->vs) {
97 		if (nr == vc)
98 			return 1;
99 		vc = (vc + 1) % modulus;
100 	}
101 
102 	return nr == lapb->vs;
103 }
104 
105 /*
106  *	This routine is the centralised routine for parsing the control
107  *	information for the different frame formats.
108  */
lapb_decode(struct lapb_cb * lapb,struct sk_buff * skb,struct lapb_frame * frame)109 int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
110 		struct lapb_frame *frame)
111 {
112 	frame->type = LAPB_ILLEGAL;
113 
114 #if LAPB_DEBUG > 2
115 	printk(KERN_DEBUG "lapb: (%p) S%d RX %02X %02X %02X\n",
116 	       lapb->dev, lapb->state,
117 	       skb->data[0], skb->data[1], skb->data[2]);
118 #endif
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  */
lapb_send_control(struct lapb_cb * lapb,int frametype,int poll_bit,int type)228 void 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  */
lapb_transmit_frmr(struct lapb_cb * lapb)265 void 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 #if LAPB_DEBUG > 1
288 	printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X %02X %02X\n",
289 	       lapb->dev, lapb->state,
290 	       skb->data[1], skb->data[2], skb->data[3],
291 	       skb->data[4], skb->data[5]);
292 #endif
293 	} else {
294 		dptr    = skb_put(skb, 4);
295 		*dptr++ = LAPB_FRMR;
296 		*dptr++ = lapb->frmr_data.control[0];
297 		*dptr   = (lapb->vs << 1) & 0x0E;
298 		*dptr  |= (lapb->vr << 5) & 0xE0;
299 		if (lapb->frmr_data.cr == LAPB_RESPONSE)
300 			*dptr |= 0x10;
301 		dptr++;
302 		*dptr++ = lapb->frmr_type;
303 
304 #if LAPB_DEBUG > 1
305 	printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X\n",
306 	       lapb->dev, lapb->state, skb->data[1],
307 	       skb->data[2], skb->data[3]);
308 #endif
309 	}
310 
311 	lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
312 }
313