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 | */ |
33 | void ax25_clear_queues(ax25_cb *ax25) |
34 | { |
35 | skb_queue_purge(list: &ax25->write_queue); |
36 | skb_queue_purge(list: &ax25->ack_queue); |
37 | skb_queue_purge(list: &ax25->reseq_queue); |
38 | skb_queue_purge(list: &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 | */ |
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(list_: &ax25->ack_queue) != NULL && ax25->va != nr) { |
55 | skb = skb_dequeue(list: &ax25->ack_queue); |
56 | kfree_skb(skb); |
57 | ax25->va = (ax25->va + 1) % ax25->modulus; |
58 | } |
59 | } |
60 | } |
61 | |
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(list: &ax25->ack_queue)) != NULL) |
72 | skb_queue_head(list: &ax25->write_queue, newsk: skb); |
73 | } |
74 | |
75 | /* |
76 | * Validate that the value of nr is between va and vs. Return true or |
77 | * false for testing. |
78 | */ |
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 | */ |
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, len: 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, len: 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, len: 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, len: 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 | */ |
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(size: ax25->ax25_dev->dev->hard_header_len + 2, GFP_ATOMIC)) == NULL) |
153 | return; |
154 | |
155 | skb_reserve(skb, len: 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, len: 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, len: 1); |
169 | *dptr = frametype; |
170 | *dptr |= (poll_bit) ? AX25_PF : 0; |
171 | } else { |
172 | dptr = skb_put(skb, len: 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 | */ |
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(size: dev->hard_header_len + 1, GFP_ATOMIC)) == NULL) |
197 | return; /* Next SABM will get DM'd */ |
198 | |
199 | skb_reserve(skb, len: dev->hard_header_len); |
200 | skb_reset_network_header(skb); |
201 | |
202 | ax25_digi_invert(digi, &retdigi); |
203 | |
204 | dptr = skb_put(skb, len: 1); |
205 | |
206 | *dptr = AX25_DM | AX25_PF; |
207 | |
208 | /* |
209 | * Do the address ourselves |
210 | */ |
211 | dptr = skb_push(skb, len: 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 | */ |
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 | */ |
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 | |
260 | void ax25_disconnect(ax25_cb *ax25, int reason) |
261 | { |
262 | ax25_clear_queues(ax25); |
263 | |
264 | if (reason == ENETUNREACH) { |
265 | del_timer_sync(timer: &ax25->timer); |
266 | del_timer_sync(timer: &ax25->t1timer); |
267 | del_timer_sync(timer: &ax25->t2timer); |
268 | del_timer_sync(timer: &ax25->t3timer); |
269 | del_timer_sync(timer: &ax25->idletimer); |
270 | } else { |
271 | if (ax25->sk && !sock_flag(sk: ax25->sk, flag: 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(sk: ax25->sk, flag: SOCK_DEAD)) { |
290 | ax25->sk->sk_state_change(ax25->sk); |
291 | sock_set_flag(sk: ax25->sk, flag: SOCK_DEAD); |
292 | } |
293 | bh_unlock_sock(ax25->sk); |
294 | local_bh_enable(); |
295 | } |
296 | } |
297 | |