File: /usr/src/linux/net/ax25/ax25_subr.c
1 /*
2 * AX.25 release 037
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 * Most of this code is based on the SDL diagrams published in the 7th
13 * ARRL Computer Networking Conference papers. The diagrams have mistakes
14 * in them, but are mostly correct. Before you modify the code could you
15 * read the SDL diagrams as the code is not obvious and probably very
16 * easy to break;
17 *
18 * History
19 * AX.25 029 Alan(GW4PTS) Switched to KA9Q constant names. Removed
20 * old BSD code.
21 * AX.25 030 Jonathan(G4KLX) Added support for extended AX.25.
22 * Added fragmentation support.
23 * Darryl(G7LED) Added function ax25_requeue_frames() to split
24 * it up from ax25_frames_acked().
25 * AX.25 031 Joerg(DL1BKE) DAMA needs KISS Fullduplex ON/OFF.
26 * Thus we have ax25_kiss_cmd() now... ;-)
27 * Dave Brown(N2RJT)
28 * Killed a silly bug in the DAMA code.
29 * Joerg(DL1BKE) Found the real bug in ax25.h, sri.
30 * AX.25 032 Joerg(DL1BKE) Added ax25_queue_length to count the number of
31 * enqueued buffers of a socket..
32 * AX.25 035 Frederic(F1OAT) Support for pseudo-digipeating.
33 * AX.25 037 Jonathan(G4KLX) New timer architecture.
34 */
35
36 #include <linux/errno.h>
37 #include <linux/types.h>
38 #include <linux/socket.h>
39 #include <linux/in.h>
40 #include <linux/kernel.h>
41 #include <linux/sched.h>
42 #include <linux/timer.h>
43 #include <linux/string.h>
44 #include <linux/sockios.h>
45 #include <linux/net.h>
46 #include <net/ax25.h>
47 #include <linux/inet.h>
48 #include <linux/netdevice.h>
49 #include <linux/skbuff.h>
50 #include <net/sock.h>
51 #include <asm/uaccess.h>
52 #include <asm/system.h>
53 #include <linux/fcntl.h>
54 #include <linux/mm.h>
55 #include <linux/interrupt.h>
56
57 /*
58 * This routine purges all the queues of frames.
59 */
60 void ax25_clear_queues(ax25_cb *ax25)
61 {
62 skb_queue_purge(&ax25->write_queue);
63 skb_queue_purge(&ax25->ack_queue);
64 skb_queue_purge(&ax25->reseq_queue);
65 skb_queue_purge(&ax25->frag_queue);
66 }
67
68 /*
69 * This routine purges the input queue of those frames that have been
70 * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
71 * SDL diagram.
72 */
73 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
74 {
75 struct sk_buff *skb;
76
77 /*
78 * Remove all the ack-ed frames from the ack queue.
79 */
80 if (ax25->va != nr) {
81 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
82 skb = skb_dequeue(&ax25->ack_queue);
83 kfree_skb(skb);
84 ax25->va = (ax25->va + 1) % ax25->modulus;
85 }
86 }
87 }
88
89 void ax25_requeue_frames(ax25_cb *ax25)
90 {
91 struct sk_buff *skb, *skb_prev = NULL;
92
93 /*
94 * Requeue all the un-ack-ed frames on the output queue to be picked
95 * up by ax25_kick called from the timer. This arrangement handles the
96 * possibility of an empty output queue.
97 */
98 while ((skb = skb_dequeue(&ax25->ack_queue)) != NULL) {
99 if (skb_prev == NULL)
100 skb_queue_head(&ax25->write_queue, skb);
101 else
102 skb_append(skb_prev, skb);
103 skb_prev = skb;
104 }
105 }
106
107 /*
108 * Validate that the value of nr is between va and vs. Return true or
109 * false for testing.
110 */
111 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
112 {
113 unsigned short vc = ax25->va;
114
115 while (vc != ax25->vs) {
116 if (nr == vc) return 1;
117 vc = (vc + 1) % ax25->modulus;
118 }
119
120 if (nr == ax25->vs) return 1;
121
122 return 0;
123 }
124
125 /*
126 * This routine is the centralised routine for parsing the control
127 * information for the different frame formats.
128 */
129 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
130 {
131 unsigned char *frame;
132 int frametype = AX25_ILLEGAL;
133
134 frame = skb->data;
135 *ns = *nr = *pf = 0;
136
137 if (ax25->modulus == AX25_MODULUS) {
138 if ((frame[0] & AX25_S) == 0) {
139 frametype = AX25_I; /* I frame - carries NR/NS/PF */
140 *ns = (frame[0] >> 1) & 0x07;
141 *nr = (frame[0] >> 5) & 0x07;
142 *pf = frame[0] & AX25_PF;
143 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
144 frametype = frame[0] & 0x0F;
145 *nr = (frame[0] >> 5) & 0x07;
146 *pf = frame[0] & AX25_PF;
147 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
148 frametype = frame[0] & ~AX25_PF;
149 *pf = frame[0] & AX25_PF;
150 }
151 skb_pull(skb, 1);
152 } else {
153 if ((frame[0] & AX25_S) == 0) {
154 frametype = AX25_I; /* I frame - carries NR/NS/PF */
155 *ns = (frame[0] >> 1) & 0x7F;
156 *nr = (frame[1] >> 1) & 0x7F;
157 *pf = frame[1] & AX25_EPF;
158 skb_pull(skb, 2);
159 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
160 frametype = frame[0] & 0x0F;
161 *nr = (frame[1] >> 1) & 0x7F;
162 *pf = frame[1] & AX25_EPF;
163 skb_pull(skb, 2);
164 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
165 frametype = frame[0] & ~AX25_PF;
166 *pf = frame[0] & AX25_PF;
167 skb_pull(skb, 1);
168 }
169 }
170
171 return frametype;
172 }
173
174 /*
175 * This routine is called when the HDLC layer internally generates a
176 * command or response for the remote machine ( eg. RR, UA etc. ).
177 * Only supervisory or unnumbered frames are processed.
178 */
179 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
180 {
181 struct sk_buff *skb;
182 unsigned char *dptr;
183
184 if ((skb = alloc_skb(AX25_BPQ_HEADER_LEN + ax25_addr_size(ax25->digipeat) + 2, GFP_ATOMIC)) == NULL)
185 return;
186
187 skb_reserve(skb, AX25_BPQ_HEADER_LEN + ax25_addr_size(ax25->digipeat));
188
189 skb->nh.raw = skb->data;
190
191 /* Assume a response - address structure for DTE */
192 if (ax25->modulus == AX25_MODULUS) {
193 dptr = skb_put(skb, 1);
194 *dptr = frametype;
195 *dptr |= (poll_bit) ? AX25_PF : 0;
196 if ((frametype & AX25_U) == AX25_S) /* S frames carry NR */
197 *dptr |= (ax25->vr << 5);
198 } else {
199 if ((frametype & AX25_U) == AX25_U) {
200 dptr = skb_put(skb, 1);
201 *dptr = frametype;
202 *dptr |= (poll_bit) ? AX25_PF : 0;
203 } else {
204 dptr = skb_put(skb, 2);
205 dptr[0] = frametype;
206 dptr[1] = (ax25->vr << 1);
207 dptr[1] |= (poll_bit) ? AX25_EPF : 0;
208 }
209 }
210
211 ax25_transmit_buffer(ax25, skb, type);
212 }
213
214 /*
215 * Send a 'DM' to an unknown connection attempt, or an invalid caller.
216 *
217 * Note: src here is the sender, thus it's the target of the DM
218 */
219 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
220 {
221 struct sk_buff *skb;
222 char *dptr;
223 ax25_digi retdigi;
224
225 if (dev == NULL)
226 return;
227
228 if ((skb = alloc_skb(AX25_BPQ_HEADER_LEN + ax25_addr_size(digi) + 1, GFP_ATOMIC)) == NULL)
229 return; /* Next SABM will get DM'd */
230
231 skb_reserve(skb, AX25_BPQ_HEADER_LEN + ax25_addr_size(digi));
232 skb->nh.raw = skb->data;
233
234 ax25_digi_invert(digi, &retdigi);
235
236 dptr = skb_put(skb, 1);
237
238 *dptr = AX25_DM | AX25_PF;
239
240 /*
241 * Do the address ourselves
242 */
243 dptr = skb_push(skb, ax25_addr_size(digi));
244 dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
245
246 skb->dev = dev;
247
248 ax25_queue_xmit(skb);
249 }
250
251 /*
252 * Exponential backoff for AX.25
253 */
254 void ax25_calculate_t1(ax25_cb *ax25)
255 {
256 int n, t = 2;
257
258 switch (ax25->backoff) {
259 case 0:
260 break;
261
262 case 1:
263 t += 2 * ax25->n2count;
264 break;
265
266 case 2:
267 for (n = 0; n < ax25->n2count; n++)
268 t *= 2;
269 if (t > 8) t = 8;
270 break;
271 }
272
273 ax25->t1 = t * ax25->rtt;
274 }
275
276 /*
277 * Calculate the Round Trip Time
278 */
279 void ax25_calculate_rtt(ax25_cb *ax25)
280 {
281 if (ax25->backoff == 0)
282 return;
283
284 if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
285 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
286
287 if (ax25->rtt < AX25_T1CLAMPLO)
288 ax25->rtt = AX25_T1CLAMPLO;
289
290 if (ax25->rtt > AX25_T1CLAMPHI)
291 ax25->rtt = AX25_T1CLAMPHI;
292 }
293
294 void ax25_disconnect(ax25_cb *ax25, int reason)
295 {
296 ax25_clear_queues(ax25);
297
298 ax25_stop_t1timer(ax25);
299 ax25_stop_t2timer(ax25);
300 ax25_stop_t3timer(ax25);
301 ax25_stop_idletimer(ax25);
302
303 ax25->state = AX25_STATE_0;
304
305 ax25_link_failed(ax25, reason);
306
307 if (ax25->sk != NULL) {
308 ax25->sk->state = TCP_CLOSE;
309 ax25->sk->err = reason;
310 ax25->sk->shutdown |= SEND_SHUTDOWN;
311 if (!ax25->sk->dead)
312 ax25->sk->state_change(ax25->sk);
313 ax25->sk->dead = 1;
314 }
315 }
316