1 /*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
8 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
9 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
10 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
11 */
12 #include <linux/errno.h>
13 #include <linux/types.h>
14 #include <linux/socket.h>
15 #include <linux/in.h>
16 #include <linux/kernel.h>
17 #include <linux/timer.h>
18 #include <linux/string.h>
19 #include <linux/sockios.h>
20 #include <linux/net.h>
21 #include <linux/slab.h>
22 #include <net/ax25.h>
23 #include <linux/inet.h>
24 #include <linux/netdevice.h>
25 #include <linux/skbuff.h>
26 #include <net/sock.h>
27 #include <net/tcp_states.h>
28 #include <asm/uaccess.h>
29 #include <linux/fcntl.h>
30 #include <linux/mm.h>
31 #include <linux/interrupt.h>
32
33 /*
34 * This routine purges all the queues of frames.
35 */
ax25_clear_queues(ax25_cb * ax25)36 void ax25_clear_queues(ax25_cb *ax25)
37 {
38 skb_queue_purge(&ax25->write_queue);
39 skb_queue_purge(&ax25->ack_queue);
40 skb_queue_purge(&ax25->reseq_queue);
41 skb_queue_purge(&ax25->frag_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 */
ax25_frames_acked(ax25_cb * ax25,unsigned short nr)49 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
50 {
51 struct sk_buff *skb;
52
53 /*
54 * Remove all the ack-ed frames from the ack queue.
55 */
56 if (ax25->va != nr) {
57 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
58 skb = skb_dequeue(&ax25->ack_queue);
59 kfree_skb(skb);
60 ax25->va = (ax25->va + 1) % ax25->modulus;
61 }
62 }
63 }
64
ax25_requeue_frames(ax25_cb * ax25)65 void ax25_requeue_frames(ax25_cb *ax25)
66 {
67 struct sk_buff *skb;
68
69 /*
70 * Requeue all the un-ack-ed frames on the output queue to be picked
71 * up by ax25_kick called from the timer. This arrangement handles the
72 * possibility of an empty output queue.
73 */
74 while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
75 skb_queue_head(&ax25->write_queue, skb);
76 }
77
78 /*
79 * Validate that the value of nr is between va and vs. Return true or
80 * false for testing.
81 */
ax25_validate_nr(ax25_cb * ax25,unsigned short nr)82 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
83 {
84 unsigned short vc = ax25->va;
85
86 while (vc != ax25->vs) {
87 if (nr == vc) return 1;
88 vc = (vc + 1) % ax25->modulus;
89 }
90
91 if (nr == ax25->vs) return 1;
92
93 return 0;
94 }
95
96 /*
97 * This routine is the centralised routine for parsing the control
98 * information for the different frame formats.
99 */
ax25_decode(ax25_cb * ax25,struct sk_buff * skb,int * ns,int * nr,int * pf)100 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
101 {
102 unsigned char *frame;
103 int frametype = AX25_ILLEGAL;
104
105 frame = skb->data;
106 *ns = *nr = *pf = 0;
107
108 if (ax25->modulus == AX25_MODULUS) {
109 if ((frame[0] & AX25_S) == 0) {
110 frametype = AX25_I; /* I frame - carries NR/NS/PF */
111 *ns = (frame[0] >> 1) & 0x07;
112 *nr = (frame[0] >> 5) & 0x07;
113 *pf = frame[0] & AX25_PF;
114 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
115 frametype = frame[0] & 0x0F;
116 *nr = (frame[0] >> 5) & 0x07;
117 *pf = frame[0] & AX25_PF;
118 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
119 frametype = frame[0] & ~AX25_PF;
120 *pf = frame[0] & AX25_PF;
121 }
122 skb_pull(skb, 1);
123 } else {
124 if ((frame[0] & AX25_S) == 0) {
125 frametype = AX25_I; /* I frame - carries NR/NS/PF */
126 *ns = (frame[0] >> 1) & 0x7F;
127 *nr = (frame[1] >> 1) & 0x7F;
128 *pf = frame[1] & AX25_EPF;
129 skb_pull(skb, 2);
130 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
131 frametype = frame[0] & 0x0F;
132 *nr = (frame[1] >> 1) & 0x7F;
133 *pf = frame[1] & AX25_EPF;
134 skb_pull(skb, 2);
135 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
136 frametype = frame[0] & ~AX25_PF;
137 *pf = frame[0] & AX25_PF;
138 skb_pull(skb, 1);
139 }
140 }
141
142 return frametype;
143 }
144
145 /*
146 * This routine is called when the HDLC layer internally generates a
147 * command or response for the remote machine ( eg. RR, UA etc. ).
148 * Only supervisory or unnumbered frames are processed.
149 */
ax25_send_control(ax25_cb * ax25,int frametype,int poll_bit,int type)150 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
151 {
152 struct sk_buff *skb;
153 unsigned char *dptr;
154
155 if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
156 return;
157
158 skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
159
160 skb_reset_network_header(skb);
161
162 /* Assume a response - address structure for DTE */
163 if (ax25->modulus == AX25_MODULUS) {
164 dptr = skb_put(skb, 1);
165 *dptr = frametype;
166 *dptr |= (poll_bit) ? AX25_PF : 0;
167 if ((frametype & AX25_U) == AX25_S) /* S frames carry NR */
168 *dptr |= (ax25->vr << 5);
169 } else {
170 if ((frametype & AX25_U) == AX25_U) {
171 dptr = skb_put(skb, 1);
172 *dptr = frametype;
173 *dptr |= (poll_bit) ? AX25_PF : 0;
174 } else {
175 dptr = skb_put(skb, 2);
176 dptr[0] = frametype;
177 dptr[1] = (ax25->vr << 1);
178 dptr[1] |= (poll_bit) ? AX25_EPF : 0;
179 }
180 }
181
182 ax25_transmit_buffer(ax25, skb, type);
183 }
184
185 /*
186 * Send a 'DM' to an unknown connection attempt, or an invalid caller.
187 *
188 * Note: src here is the sender, thus it's the target of the DM
189 */
ax25_return_dm(struct net_device * dev,ax25_address * src,ax25_address * dest,ax25_digi * digi)190 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
191 {
192 struct sk_buff *skb;
193 char *dptr;
194 ax25_digi retdigi;
195
196 if (dev == NULL)
197 return;
198
199 if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
200 return; /* Next SABM will get DM'd */
201
202 skb_reserve(skb, dev->hard_header_len);
203 skb_reset_network_header(skb);
204
205 ax25_digi_invert(digi, &retdigi);
206
207 dptr = skb_put(skb, 1);
208
209 *dptr = AX25_DM | AX25_PF;
210
211 /*
212 * Do the address ourselves
213 */
214 dptr = skb_push(skb, ax25_addr_size(digi));
215 dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
216
217 ax25_queue_xmit(skb, dev);
218 }
219
220 /*
221 * Exponential backoff for AX.25
222 */
ax25_calculate_t1(ax25_cb * ax25)223 void ax25_calculate_t1(ax25_cb *ax25)
224 {
225 int n, t = 2;
226
227 switch (ax25->backoff) {
228 case 0:
229 break;
230
231 case 1:
232 t += 2 * ax25->n2count;
233 break;
234
235 case 2:
236 for (n = 0; n < ax25->n2count; n++)
237 t *= 2;
238 if (t > 8) t = 8;
239 break;
240 }
241
242 ax25->t1 = t * ax25->rtt;
243 }
244
245 /*
246 * Calculate the Round Trip Time
247 */
ax25_calculate_rtt(ax25_cb * ax25)248 void ax25_calculate_rtt(ax25_cb *ax25)
249 {
250 if (ax25->backoff == 0)
251 return;
252
253 if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
254 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
255
256 if (ax25->rtt < AX25_T1CLAMPLO)
257 ax25->rtt = AX25_T1CLAMPLO;
258
259 if (ax25->rtt > AX25_T1CLAMPHI)
260 ax25->rtt = AX25_T1CLAMPHI;
261 }
262
ax25_disconnect(ax25_cb * ax25,int reason)263 void ax25_disconnect(ax25_cb *ax25, int reason)
264 {
265 ax25_clear_queues(ax25);
266
267 ax25_stop_t1timer(ax25);
268 ax25_stop_t2timer(ax25);
269 ax25_stop_t3timer(ax25);
270 ax25_stop_idletimer(ax25);
271
272 ax25->state = AX25_STATE_0;
273
274 ax25_link_failed(ax25, reason);
275
276 if (ax25->sk != NULL) {
277 local_bh_disable();
278 bh_lock_sock(ax25->sk);
279 ax25->sk->sk_state = TCP_CLOSE;
280 ax25->sk->sk_err = reason;
281 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
282 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
283 ax25->sk->sk_state_change(ax25->sk);
284 sock_set_flag(ax25->sk, SOCK_DEAD);
285 }
286 bh_unlock_sock(ax25->sk);
287 local_bh_enable();
288 }
289 }
290