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lapb_subr.c
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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  */
40 void 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  */
51 void 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 
69 void 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  */
91 int 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  */
111 int 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  */
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  */
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  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 }
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