Linux Kernel  3.7.1
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ax25_subr.c
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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 ([email protected])
8  * Copyright (C) Jonathan Naylor G4KLX ([email protected])
9  * Copyright (C) Joerg Reuter DL1BKE ([email protected])
10  * Copyright (C) Frederic Rible F1OAT ([email protected])
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  */
37 {
39  skb_queue_purge(&ax25->ack_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  */
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 
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  */
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  */
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  */
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  */
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  */
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  */
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 
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) {
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 }