1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * LAPB release 002
4 *
5 * This code REQUIRES 2.1.15 or higher/ NET3.038
6 *
7 * History
8 * LAPB 001 Jonathan Naylor Started Coding
9 */
10
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13 #include <linux/errno.h>
14 #include <linux/types.h>
15 #include <linux/socket.h>
16 #include <linux/in.h>
17 #include <linux/kernel.h>
18 #include <linux/timer.h>
19 #include <linux/string.h>
20 #include <linux/sockios.h>
21 #include <linux/net.h>
22 #include <linux/inet.h>
23 #include <linux/skbuff.h>
24 #include <linux/slab.h>
25 #include <net/sock.h>
26 #include <linux/uaccess.h>
27 #include <linux/fcntl.h>
28 #include <linux/mm.h>
29 #include <linux/interrupt.h>
30 #include <net/lapb.h>
31
32 /*
33 * This routine purges all the queues of frames.
34 */
35 void lapb_clear_queues(struct lapb_cb *lapb)
36 {
37 skb_queue_purge(&lapb->write_queue);
38 skb_queue_purge(&lapb->ack_queue);
39 }
40
41 /*
42 * This routine purges the input queue of those frames that have been
43 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
44 * SDL diagram.
45 */
46 void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
47 {
48 struct sk_buff *skb;
49 int modulus;
50
51 modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
52
53 /*
54 * Remove all the ack-ed frames from the ack queue.
55 */
56 if (lapb->va != nr)
57 while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
58 skb = skb_dequeue(&lapb->ack_queue);
59 kfree_skb(skb);
60 lapb->va = (lapb->va + 1) % modulus;
61 }
62 }
63
64 void lapb_requeue_frames(struct lapb_cb *lapb)
65 {
66 struct sk_buff *skb, *skb_prev = NULL;
67
68 /*
69 * Requeue all the un-ack-ed frames on the output queue to be picked
70 * up by lapb_kick called from the timer. This arrangement handles the
71 * possibility of an empty output queue.
72 */
73 while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
74 if (!skb_prev)
75 skb_queue_head(&lapb->write_queue, skb);
76 else
77 skb_append(skb_prev, skb, &lapb->write_queue);
78 skb_prev = skb;
79 }
80 }
81
82 /*
83 * Validate that the value of nr is between va and vs. Return true or
84 * false for testing.
85 */
86 int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
87 {
88 unsigned short vc = lapb->va;
89 int modulus;
90
91 modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
92
93 while (vc != lapb->vs) {
94 if (nr == vc)
95 return 1;
96 vc = (vc + 1) % modulus;
97 }
98
99 return nr == lapb->vs;
100 }
101
102 /*
103 * This routine is the centralised routine for parsing the control
104 * information for the different frame formats.
105 */
106 int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
107 struct lapb_frame *frame)
108 {
109 frame->type = LAPB_ILLEGAL;
110
111 lapb_dbg(2, "(%p) S%d RX %3ph\n", lapb->dev, lapb->state, skb->data);
112
113 /* We always need to look at 2 bytes, sometimes we need
114 * to look at 3 and those cases are handled below.
115 */
116 if (!pskb_may_pull(skb, 2))
117 return -1;
118
119 if (lapb->mode & LAPB_MLP) {
120 if (lapb->mode & LAPB_DCE) {
121 if (skb->data[0] == LAPB_ADDR_D)
122 frame->cr = LAPB_COMMAND;
123 if (skb->data[0] == LAPB_ADDR_C)
124 frame->cr = LAPB_RESPONSE;
125 } else {
126 if (skb->data[0] == LAPB_ADDR_C)
127 frame->cr = LAPB_COMMAND;
128 if (skb->data[0] == LAPB_ADDR_D)
129 frame->cr = LAPB_RESPONSE;
130 }
131 } else {
132 if (lapb->mode & LAPB_DCE) {
133 if (skb->data[0] == LAPB_ADDR_B)
134 frame->cr = LAPB_COMMAND;
135 if (skb->data[0] == LAPB_ADDR_A)
136 frame->cr = LAPB_RESPONSE;
137 } else {
138 if (skb->data[0] == LAPB_ADDR_A)
139 frame->cr = LAPB_COMMAND;
140 if (skb->data[0] == LAPB_ADDR_B)
141 frame->cr = LAPB_RESPONSE;
142 }
143 }
144
145 skb_pull(skb, 1);
146
147 if (lapb->mode & LAPB_EXTENDED) {
148 if (!(skb->data[0] & LAPB_S)) {
149 if (!pskb_may_pull(skb, 2))
150 return -1;
151 /*
152 * I frame - carries NR/NS/PF
153 */
154 frame->type = LAPB_I;
155 frame->ns = (skb->data[0] >> 1) & 0x7F;
156 frame->nr = (skb->data[1] >> 1) & 0x7F;
157 frame->pf = skb->data[1] & LAPB_EPF;
158 frame->control[0] = skb->data[0];
159 frame->control[1] = skb->data[1];
160 skb_pull(skb, 2);
161 } else if ((skb->data[0] & LAPB_U) == 1) {
162 if (!pskb_may_pull(skb, 2))
163 return -1;
164 /*
165 * S frame - take out PF/NR
166 */
167 frame->type = skb->data[0] & 0x0F;
168 frame->nr = (skb->data[1] >> 1) & 0x7F;
169 frame->pf = skb->data[1] & LAPB_EPF;
170 frame->control[0] = skb->data[0];
171 frame->control[1] = skb->data[1];
172 skb_pull(skb, 2);
173 } else if ((skb->data[0] & LAPB_U) == 3) {
174 /*
175 * U frame - take out PF
176 */
177 frame->type = skb->data[0] & ~LAPB_SPF;
178 frame->pf = skb->data[0] & LAPB_SPF;
179 frame->control[0] = skb->data[0];
180 frame->control[1] = 0x00;
181 skb_pull(skb, 1);
182 }
183 } else {
184 if (!(skb->data[0] & LAPB_S)) {
185 /*
186 * I frame - carries NR/NS/PF
187 */
188 frame->type = LAPB_I;
189 frame->ns = (skb->data[0] >> 1) & 0x07;
190 frame->nr = (skb->data[0] >> 5) & 0x07;
191 frame->pf = skb->data[0] & LAPB_SPF;
192 } else if ((skb->data[0] & LAPB_U) == 1) {
193 /*
194 * S frame - take out PF/NR
195 */
196 frame->type = skb->data[0] & 0x0F;
197 frame->nr = (skb->data[0] >> 5) & 0x07;
198 frame->pf = skb->data[0] & LAPB_SPF;
199 } else if ((skb->data[0] & LAPB_U) == 3) {
200 /*
201 * U frame - take out PF
202 */
203 frame->type = skb->data[0] & ~LAPB_SPF;
204 frame->pf = skb->data[0] & LAPB_SPF;
205 }
206
207 frame->control[0] = skb->data[0];
208
209 skb_pull(skb, 1);
210 }
211
212 return 0;
213 }
214
215 /*
216 * This routine is called when the HDLC layer internally generates a
217 * command or response for the remote machine ( eg. RR, UA etc. ).
218 * Only supervisory or unnumbered frames are processed, FRMRs are handled
219 * by lapb_transmit_frmr below.
220 */
221 void lapb_send_control(struct lapb_cb *lapb, int frametype,
222 int poll_bit, int type)
223 {
224 struct sk_buff *skb;
225 unsigned char *dptr;
226
227 if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
228 return;
229
230 skb_reserve(skb, LAPB_HEADER_LEN + 1);
231
232 if (lapb->mode & LAPB_EXTENDED) {
233 if ((frametype & LAPB_U) == LAPB_U) {
234 dptr = skb_put(skb, 1);
235 *dptr = frametype;
236 *dptr |= poll_bit ? LAPB_SPF : 0;
237 } else {
238 dptr = skb_put(skb, 2);
239 dptr[0] = frametype;
240 dptr[1] = (lapb->vr << 1);
241 dptr[1] |= poll_bit ? LAPB_EPF : 0;
242 }
243 } else {
244 dptr = skb_put(skb, 1);
245 *dptr = frametype;
246 *dptr |= poll_bit ? LAPB_SPF : 0;
247 if ((frametype & LAPB_U) == LAPB_S) /* S frames carry NR */
248 *dptr |= (lapb->vr << 5);
249 }
250
251 lapb_transmit_buffer(lapb, skb, type);
252 }
253
254 /*
255 * This routine generates FRMRs based on information previously stored in
256 * the LAPB control block.
257 */
258 void lapb_transmit_frmr(struct lapb_cb *lapb)
259 {
260 struct sk_buff *skb;
261 unsigned char *dptr;
262
263 if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
264 return;
265
266 skb_reserve(skb, LAPB_HEADER_LEN + 1);
267
268 if (lapb->mode & LAPB_EXTENDED) {
269 dptr = skb_put(skb, 6);
270 *dptr++ = LAPB_FRMR;
271 *dptr++ = lapb->frmr_data.control[0];
272 *dptr++ = lapb->frmr_data.control[1];
273 *dptr++ = (lapb->vs << 1) & 0xFE;
274 *dptr = (lapb->vr << 1) & 0xFE;
275 if (lapb->frmr_data.cr == LAPB_RESPONSE)
276 *dptr |= 0x01;
277 dptr++;
278 *dptr++ = lapb->frmr_type;
279
280 lapb_dbg(1, "(%p) S%d TX FRMR %5ph\n",
281 lapb->dev, lapb->state,
282 &skb->data[1]);
283 } else {
284 dptr = skb_put(skb, 4);
285 *dptr++ = LAPB_FRMR;
286 *dptr++ = lapb->frmr_data.control[0];
287 *dptr = (lapb->vs << 1) & 0x0E;
288 *dptr |= (lapb->vr << 5) & 0xE0;
289 if (lapb->frmr_data.cr == LAPB_RESPONSE)
290 *dptr |= 0x10;
291 dptr++;
292 *dptr++ = lapb->frmr_type;
293
294 lapb_dbg(1, "(%p) S%d TX FRMR %3ph\n",
295 lapb->dev, lapb->state, &skb->data[1]);
296 }
297
298 lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
299 }
300
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