File: /usr/src/linux/net/lapb/lapb_subr.c
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/sched.h>
22 #include <linux/timer.h>
23 #include <linux/string.h>
24 #include <linux/sockios.h>
25 #include <linux/net.h>
26 #include <linux/inet.h>
27 #include <linux/skbuff.h>
28 #include <net/sock.h>
29 #include <asm/uaccess.h>
30 #include <asm/system.h>
31 #include <linux/fcntl.h>
32 #include <linux/mm.h>
33 #include <linux/interrupt.h>
34 #include <net/lapb.h>
35
36 /*
37 * This routine purges all the queues of frames.
38 */
39 void lapb_clear_queues(lapb_cb *lapb)
40 {
41 skb_queue_purge(&lapb->write_queue);
42 skb_queue_purge(&lapb->ack_queue);
43 }
44
45 /*
46 * This routine purges the input queue of those frames that have been
47 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
48 * SDL diagram.
49 */
50 void lapb_frames_acked(lapb_cb *lapb, unsigned short nr)
51 {
52 struct sk_buff *skb;
53 int modulus;
54
55 modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
56
57 /*
58 * Remove all the ack-ed frames from the ack queue.
59 */
60 if (lapb->va != nr) {
61 while (skb_peek(&lapb->ack_queue) != NULL && lapb->va != nr) {
62 skb = skb_dequeue(&lapb->ack_queue);
63 kfree_skb(skb);
64 lapb->va = (lapb->va + 1) % modulus;
65 }
66 }
67 }
68
69 void lapb_requeue_frames(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 == NULL)
80 skb_queue_head(&lapb->write_queue, skb);
81 else
82 skb_append(skb_prev, skb);
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(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) return 1;
100 vc = (vc + 1) % modulus;
101 }
102
103 if (nr == lapb->vs) return 1;
104
105 return 0;
106 }
107
108 /*
109 * This routine is the centralised routine for parsing the control
110 * information for the different frame formats.
111 */
112 void lapb_decode(lapb_cb *lapb, struct sk_buff *skb, struct lapb_frame *frame)
113 {
114 frame->type = LAPB_ILLEGAL;
115
116 #if LAPB_DEBUG > 2
117 printk(KERN_DEBUG "lapb: (%p) S%d RX %02X %02X %02X\n", lapb->token, lapb->state, skb->data[0], skb->data[1], skb->data[2]);
118 #endif
119
120 if (lapb->mode & LAPB_MLP) {
121 if (lapb->mode & LAPB_DCE) {
122 if (skb->data[0] == LAPB_ADDR_D)
123 frame->cr = LAPB_COMMAND;
124 if (skb->data[0] == LAPB_ADDR_C)
125 frame->cr = LAPB_RESPONSE;
126 } else {
127 if (skb->data[0] == LAPB_ADDR_C)
128 frame->cr = LAPB_COMMAND;
129 if (skb->data[0] == LAPB_ADDR_D)
130 frame->cr = LAPB_RESPONSE;
131 }
132 } else {
133 if (lapb->mode & LAPB_DCE) {
134 if (skb->data[0] == LAPB_ADDR_B)
135 frame->cr = LAPB_COMMAND;
136 if (skb->data[0] == LAPB_ADDR_A)
137 frame->cr = LAPB_RESPONSE;
138 } else {
139 if (skb->data[0] == LAPB_ADDR_A)
140 frame->cr = LAPB_COMMAND;
141 if (skb->data[0] == LAPB_ADDR_B)
142 frame->cr = LAPB_RESPONSE;
143 }
144 }
145
146 skb_pull(skb, 1);
147
148 if (lapb->mode & LAPB_EXTENDED) {
149 if ((skb->data[0] & LAPB_S) == 0) {
150 frame->type = LAPB_I; /* I frame - carries NR/NS/PF */
151 frame->ns = (skb->data[0] >> 1) & 0x7F;
152 frame->nr = (skb->data[1] >> 1) & 0x7F;
153 frame->pf = skb->data[1] & LAPB_EPF;
154 frame->control[0] = skb->data[0];
155 frame->control[1] = skb->data[1];
156 skb_pull(skb, 2);
157 } else if ((skb->data[0] & LAPB_U) == 1) { /* S frame - take out PF/NR */
158 frame->type = skb->data[0] & 0x0F;
159 frame->nr = (skb->data[1] >> 1) & 0x7F;
160 frame->pf = skb->data[1] & LAPB_EPF;
161 frame->control[0] = skb->data[0];
162 frame->control[1] = skb->data[1];
163 skb_pull(skb, 2);
164 } else if ((skb->data[0] & LAPB_U) == 3) { /* U frame - take out PF */
165 frame->type = skb->data[0] & ~LAPB_SPF;
166 frame->pf = skb->data[0] & LAPB_SPF;
167 frame->control[0] = skb->data[0];
168 frame->control[1] = 0x00;
169 skb_pull(skb, 1);
170 }
171 } else {
172 if ((skb->data[0] & LAPB_S) == 0) {
173 frame->type = LAPB_I; /* I frame - carries NR/NS/PF */
174 frame->ns = (skb->data[0] >> 1) & 0x07;
175 frame->nr = (skb->data[0] >> 5) & 0x07;
176 frame->pf = skb->data[0] & LAPB_SPF;
177 } else if ((skb->data[0] & LAPB_U) == 1) { /* S frame - take out PF/NR */
178 frame->type = skb->data[0] & 0x0F;
179 frame->nr = (skb->data[0] >> 5) & 0x07;
180 frame->pf = skb->data[0] & LAPB_SPF;
181 } else if ((skb->data[0] & LAPB_U) == 3) { /* U frame - take out PF */
182 frame->type = skb->data[0] & ~LAPB_SPF;
183 frame->pf = skb->data[0] & LAPB_SPF;
184 }
185
186 frame->control[0] = skb->data[0];
187
188 skb_pull(skb, 1);
189 }
190 }
191
192 /*
193 * This routine is called when the HDLC layer internally generates a
194 * command or response for the remote machine ( eg. RR, UA etc. ).
195 * Only supervisory or unnumbered frames are processed, FRMRs are handled
196 * by lapb_transmit_frmr below.
197 */
198 void lapb_send_control(lapb_cb *lapb, int frametype, int poll_bit, int type)
199 {
200 struct sk_buff *skb;
201 unsigned char *dptr;
202
203 if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
204 return;
205
206 skb_reserve(skb, LAPB_HEADER_LEN + 1);
207
208 if (lapb->mode & LAPB_EXTENDED) {
209 if ((frametype & LAPB_U) == LAPB_U) {
210 dptr = skb_put(skb, 1);
211 *dptr = frametype;
212 *dptr |= (poll_bit) ? LAPB_SPF : 0;
213 } else {
214 dptr = skb_put(skb, 2);
215 dptr[0] = frametype;
216 dptr[1] = (lapb->vr << 1);
217 dptr[1] |= (poll_bit) ? LAPB_EPF : 0;
218 }
219 } else {
220 dptr = skb_put(skb, 1);
221 *dptr = frametype;
222 *dptr |= (poll_bit) ? LAPB_SPF : 0;
223 if ((frametype & LAPB_U) == LAPB_S) /* S frames carry NR */
224 *dptr |= (lapb->vr << 5);
225 }
226
227 lapb_transmit_buffer(lapb, skb, type);
228 }
229
230 /*
231 * This routine generates FRMRs based on information previously stored in
232 * the LAPB control block.
233 */
234 void lapb_transmit_frmr(lapb_cb *lapb)
235 {
236 struct sk_buff *skb;
237 unsigned char *dptr;
238
239 if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
240 return;
241
242 skb_reserve(skb, LAPB_HEADER_LEN + 1);
243
244 if (lapb->mode & LAPB_EXTENDED) {
245 dptr = skb_put(skb, 6);
246 *dptr++ = LAPB_FRMR;
247 *dptr++ = lapb->frmr_data.control[0];
248 *dptr++ = lapb->frmr_data.control[1];
249 *dptr++ = (lapb->vs << 1) & 0xFE;
250 *dptr = (lapb->vr << 1) & 0xFE;
251 if (lapb->frmr_data.cr == LAPB_RESPONSE)
252 *dptr |= 0x01;
253 dptr++;
254 *dptr++ = lapb->frmr_type;
255
256 #if LAPB_DEBUG > 1
257 printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X %02X %02X\n", lapb->token, lapb->state, skb->data[1], skb->data[2], skb->data[3], skb->data[4], skb->data[5]);
258 #endif
259 } else {
260 dptr = skb_put(skb, 4);
261 *dptr++ = LAPB_FRMR;
262 *dptr++ = lapb->frmr_data.control[0];
263 *dptr = (lapb->vs << 1) & 0x0E;
264 *dptr |= (lapb->vr << 5) & 0xE0;
265 if (lapb->frmr_data.cr == LAPB_RESPONSE)
266 *dptr |= 0x10;
267 dptr++;
268 *dptr++ = lapb->frmr_type;
269
270 #if LAPB_DEBUG > 1
271 printk(KERN_DEBUG "lapb: (%p) S%d TX FRMR %02X %02X %02X\n", lapb->token, lapb->state, skb->data[1], skb->data[2], skb->data[3]);
272 #endif
273 }
274
275 lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
276 }
277