1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 *
4 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
5 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
6 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
7 * Copyright (C) Frederic Rible F1OAT (frible@teaser.fr)
8 */
9 #include <linux/errno.h>
10 #include <linux/types.h>
11 #include <linux/socket.h>
12 #include <linux/in.h>
13 #include <linux/kernel.h>
14 #include <linux/timer.h>
15 #include <linux/string.h>
16 #include <linux/sockios.h>
17 #include <linux/net.h>
18 #include <linux/slab.h>
19 #include <net/ax25.h>
20 #include <linux/inet.h>
21 #include <linux/netdevice.h>
22 #include <linux/skbuff.h>
23 #include <net/sock.h>
24 #include <net/tcp_states.h>
25 #include <linux/uaccess.h>
26 #include <linux/fcntl.h>
27 #include <linux/mm.h>
28 #include <linux/interrupt.h>
29
30 /*
31 * This routine purges all the queues of frames.
32 */
ax25_clear_queues(ax25_cb * ax25)33 void ax25_clear_queues(ax25_cb *ax25)
34 {
35 skb_queue_purge(&ax25->write_queue);
36 skb_queue_purge(&ax25->ack_queue);
37 skb_queue_purge(&ax25->reseq_queue);
38 skb_queue_purge(&ax25->frag_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 */
ax25_frames_acked(ax25_cb * ax25,unsigned short nr)46 void ax25_frames_acked(ax25_cb *ax25, unsigned short nr)
47 {
48 struct sk_buff *skb;
49
50 /*
51 * Remove all the ack-ed frames from the ack queue.
52 */
53 if (ax25->va != nr) {
54 while (skb_peek(&ax25->ack_queue) != NULL && ax25->va != nr) {
55 skb = skb_dequeue(&ax25->ack_queue);
56 kfree_skb(skb);
57 ax25->va = (ax25->va + 1) % ax25->modulus;
58 }
59 }
60 }
61
ax25_requeue_frames(ax25_cb * ax25)62 void ax25_requeue_frames(ax25_cb *ax25)
63 {
64 struct sk_buff *skb;
65
66 /*
67 * Requeue all the un-ack-ed frames on the output queue to be picked
68 * up by ax25_kick called from the timer. This arrangement handles the
69 * possibility of an empty output queue.
70 */
71 while ((skb = skb_dequeue_tail(&ax25->ack_queue)) != NULL)
72 skb_queue_head(&ax25->write_queue, skb);
73 }
74
75 /*
76 * Validate that the value of nr is between va and vs. Return true or
77 * false for testing.
78 */
ax25_validate_nr(ax25_cb * ax25,unsigned short nr)79 int ax25_validate_nr(ax25_cb *ax25, unsigned short nr)
80 {
81 unsigned short vc = ax25->va;
82
83 while (vc != ax25->vs) {
84 if (nr == vc) return 1;
85 vc = (vc + 1) % ax25->modulus;
86 }
87
88 if (nr == ax25->vs) return 1;
89
90 return 0;
91 }
92
93 /*
94 * This routine is the centralised routine for parsing the control
95 * information for the different frame formats.
96 */
ax25_decode(ax25_cb * ax25,struct sk_buff * skb,int * ns,int * nr,int * pf)97 int ax25_decode(ax25_cb *ax25, struct sk_buff *skb, int *ns, int *nr, int *pf)
98 {
99 unsigned char *frame;
100 int frametype = AX25_ILLEGAL;
101
102 frame = skb->data;
103 *ns = *nr = *pf = 0;
104
105 if (ax25->modulus == AX25_MODULUS) {
106 if ((frame[0] & AX25_S) == 0) {
107 frametype = AX25_I; /* I frame - carries NR/NS/PF */
108 *ns = (frame[0] >> 1) & 0x07;
109 *nr = (frame[0] >> 5) & 0x07;
110 *pf = frame[0] & AX25_PF;
111 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
112 frametype = frame[0] & 0x0F;
113 *nr = (frame[0] >> 5) & 0x07;
114 *pf = frame[0] & AX25_PF;
115 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
116 frametype = frame[0] & ~AX25_PF;
117 *pf = frame[0] & AX25_PF;
118 }
119 skb_pull(skb, 1);
120 } else {
121 if ((frame[0] & AX25_S) == 0) {
122 frametype = AX25_I; /* I frame - carries NR/NS/PF */
123 *ns = (frame[0] >> 1) & 0x7F;
124 *nr = (frame[1] >> 1) & 0x7F;
125 *pf = frame[1] & AX25_EPF;
126 skb_pull(skb, 2);
127 } else if ((frame[0] & AX25_U) == 1) { /* S frame - take out PF/NR */
128 frametype = frame[0] & 0x0F;
129 *nr = (frame[1] >> 1) & 0x7F;
130 *pf = frame[1] & AX25_EPF;
131 skb_pull(skb, 2);
132 } else if ((frame[0] & AX25_U) == 3) { /* U frame - take out PF */
133 frametype = frame[0] & ~AX25_PF;
134 *pf = frame[0] & AX25_PF;
135 skb_pull(skb, 1);
136 }
137 }
138
139 return frametype;
140 }
141
142 /*
143 * This routine is called when the HDLC layer internally generates a
144 * command or response for the remote machine ( eg. RR, UA etc. ).
145 * Only supervisory or unnumbered frames are processed.
146 */
ax25_send_control(ax25_cb * ax25,int frametype,int poll_bit,int type)147 void ax25_send_control(ax25_cb *ax25, int frametype, int poll_bit, int type)
148 {
149 struct sk_buff *skb;
150 unsigned char *dptr;
151
152 if ((skb = alloc_skb(ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL)
153 return;
154
155 skb_reserve(skb, ax25->ax25_dev->dev->hard_header_len);
156
157 skb_reset_network_header(skb);
158
159 /* Assume a response - address structure for DTE */
160 if (ax25->modulus == AX25_MODULUS) {
161 dptr = skb_put(skb, 1);
162 *dptr = frametype;
163 *dptr |= (poll_bit) ? AX25_PF : 0;
164 if ((frametype & AX25_U) == AX25_S) /* S frames carry NR */
165 *dptr |= (ax25->vr << 5);
166 } else {
167 if ((frametype & AX25_U) == AX25_U) {
168 dptr = skb_put(skb, 1);
169 *dptr = frametype;
170 *dptr |= (poll_bit) ? AX25_PF : 0;
171 } else {
172 dptr = skb_put(skb, 2);
173 dptr[0] = frametype;
174 dptr[1] = (ax25->vr << 1);
175 dptr[1] |= (poll_bit) ? AX25_EPF : 0;
176 }
177 }
178
179 ax25_transmit_buffer(ax25, skb, type);
180 }
181
182 /*
183 * Send a 'DM' to an unknown connection attempt, or an invalid caller.
184 *
185 * Note: src here is the sender, thus it's the target of the DM
186 */
ax25_return_dm(struct net_device * dev,ax25_address * src,ax25_address * dest,ax25_digi * digi)187 void ax25_return_dm(struct net_device *dev, ax25_address *src, ax25_address *dest, ax25_digi *digi)
188 {
189 struct sk_buff *skb;
190 char *dptr;
191 ax25_digi retdigi;
192
193 if (dev == NULL)
194 return;
195
196 if ((skb = alloc_skb(dev->hard_header_len + 1, GFP_ATOMIC)) == NULL)
197 return; /* Next SABM will get DM'd */
198
199 skb_reserve(skb, dev->hard_header_len);
200 skb_reset_network_header(skb);
201
202 ax25_digi_invert(digi, &retdigi);
203
204 dptr = skb_put(skb, 1);
205
206 *dptr = AX25_DM | AX25_PF;
207
208 /*
209 * Do the address ourselves
210 */
211 dptr = skb_push(skb, ax25_addr_size(digi));
212 dptr += ax25_addr_build(dptr, dest, src, &retdigi, AX25_RESPONSE, AX25_MODULUS);
213
214 ax25_queue_xmit(skb, dev);
215 }
216
217 /*
218 * Exponential backoff for AX.25
219 */
ax25_calculate_t1(ax25_cb * ax25)220 void ax25_calculate_t1(ax25_cb *ax25)
221 {
222 int n, t = 2;
223
224 switch (ax25->backoff) {
225 case 0:
226 break;
227
228 case 1:
229 t += 2 * ax25->n2count;
230 break;
231
232 case 2:
233 for (n = 0; n < ax25->n2count; n++)
234 t *= 2;
235 if (t > 8) t = 8;
236 break;
237 }
238
239 ax25->t1 = t * ax25->rtt;
240 }
241
242 /*
243 * Calculate the Round Trip Time
244 */
ax25_calculate_rtt(ax25_cb * ax25)245 void ax25_calculate_rtt(ax25_cb *ax25)
246 {
247 if (ax25->backoff == 0)
248 return;
249
250 if (ax25_t1timer_running(ax25) && ax25->n2count == 0)
251 ax25->rtt = (9 * ax25->rtt + ax25->t1 - ax25_display_timer(&ax25->t1timer)) / 10;
252
253 if (ax25->rtt < AX25_T1CLAMPLO)
254 ax25->rtt = AX25_T1CLAMPLO;
255
256 if (ax25->rtt > AX25_T1CLAMPHI)
257 ax25->rtt = AX25_T1CLAMPHI;
258 }
259
ax25_disconnect(ax25_cb * ax25,int reason)260 void ax25_disconnect(ax25_cb *ax25, int reason)
261 {
262 ax25_clear_queues(ax25);
263
264 if (reason == ENETUNREACH) {
265 del_timer_sync(&ax25->timer);
266 del_timer_sync(&ax25->t1timer);
267 del_timer_sync(&ax25->t2timer);
268 del_timer_sync(&ax25->t3timer);
269 del_timer_sync(&ax25->idletimer);
270 } else {
271 if (ax25->sk && !sock_flag(ax25->sk, SOCK_DESTROY))
272 ax25_stop_heartbeat(ax25);
273 ax25_stop_t1timer(ax25);
274 ax25_stop_t2timer(ax25);
275 ax25_stop_t3timer(ax25);
276 ax25_stop_idletimer(ax25);
277 }
278
279 ax25->state = AX25_STATE_0;
280
281 ax25_link_failed(ax25, reason);
282
283 if (ax25->sk != NULL) {
284 local_bh_disable();
285 bh_lock_sock(ax25->sk);
286 ax25->sk->sk_state = TCP_CLOSE;
287 ax25->sk->sk_err = reason;
288 ax25->sk->sk_shutdown |= SEND_SHUTDOWN;
289 if (!sock_flag(ax25->sk, SOCK_DEAD)) {
290 ax25->sk->sk_state_change(ax25->sk);
291 sock_set_flag(ax25->sk, SOCK_DEAD);
292 }
293 bh_unlock_sock(ax25->sk);
294 local_bh_enable();
295 }
296 }
297