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x25_in.c
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1 /*
2  * X.25 Packet Layer release 002
3  *
4  * This is ALPHA test software. This code may break your machine,
5  * randomly fail to work with new releases, misbehave and/or generally
6  * screw up. It might even work.
7  *
8  * This code REQUIRES 2.1.15 or higher
9  *
10  * This module:
11  * This module is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU General Public License
13  * as published by the Free Software Foundation; either version
14  * 2 of the License, or (at your option) any later version.
15  *
16  * History
17  * X.25 001 Jonathan Naylor Started coding.
18  * X.25 002 Jonathan Naylor Centralised disconnection code.
19  * New timer architecture.
20  * 2000-03-20 Daniela Squassoni Disabling/enabling of facilities
21  * negotiation.
22  * 2000-11-10 Henner Eisen Check and reset for out-of-sequence
23  * i-frames.
24  */
25 
26 #include <linux/slab.h>
27 #include <linux/errno.h>
28 #include <linux/kernel.h>
29 #include <linux/string.h>
30 #include <linux/skbuff.h>
31 #include <net/sock.h>
32 #include <net/tcp_states.h>
33 #include <net/x25.h>
34 
35 static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
36 {
37  struct sk_buff *skbo, *skbn = skb;
38  struct x25_sock *x25 = x25_sk(sk);
39 
40  if (more) {
41  x25->fraglen += skb->len;
42  skb_queue_tail(&x25->fragment_queue, skb);
43  skb_set_owner_r(skb, sk);
44  return 0;
45  }
46 
47  if (!more && x25->fraglen > 0) { /* End of fragment */
48  int len = x25->fraglen + skb->len;
49 
50  if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){
51  kfree_skb(skb);
52  return 1;
53  }
54 
55  skb_queue_tail(&x25->fragment_queue, skb);
56 
57  skb_reset_transport_header(skbn);
58 
59  skbo = skb_dequeue(&x25->fragment_queue);
60  skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
61  skbo->len);
62  kfree_skb(skbo);
63 
64  while ((skbo =
65  skb_dequeue(&x25->fragment_queue)) != NULL) {
66  skb_pull(skbo, (x25->neighbour->extended) ?
67  X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
68  skb_copy_from_linear_data(skbo,
69  skb_put(skbn, skbo->len),
70  skbo->len);
71  kfree_skb(skbo);
72  }
73 
74  x25->fraglen = 0;
75  }
76 
77  skb_set_owner_r(skbn, sk);
78  skb_queue_tail(&sk->sk_receive_queue, skbn);
79  if (!sock_flag(sk, SOCK_DEAD))
80  sk->sk_data_ready(sk, skbn->len);
81 
82  return 0;
83 }
84 
85 /*
86  * State machine for state 1, Awaiting Call Accepted State.
87  * The handling of the timer(s) is in file x25_timer.c.
88  * Handling of state 0 and connection release is in af_x25.c.
89  */
90 static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
91 {
92  struct x25_address source_addr, dest_addr;
93  int len;
94  struct x25_sock *x25 = x25_sk(sk);
95 
96  switch (frametype) {
97  case X25_CALL_ACCEPTED: {
98 
99  x25_stop_timer(sk);
100  x25->condition = 0x00;
101  x25->vs = 0;
102  x25->va = 0;
103  x25->vr = 0;
104  x25->vl = 0;
105  x25->state = X25_STATE_3;
106  sk->sk_state = TCP_ESTABLISHED;
107  /*
108  * Parse the data in the frame.
109  */
110  if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
111  goto out_clear;
112  skb_pull(skb, X25_STD_MIN_LEN);
113 
114  len = x25_parse_address_block(skb, &source_addr,
115  &dest_addr);
116  if (len > 0)
117  skb_pull(skb, len);
118  else if (len < 0)
119  goto out_clear;
120 
121  len = x25_parse_facilities(skb, &x25->facilities,
122  &x25->dte_facilities,
123  &x25->vc_facil_mask);
124  if (len > 0)
125  skb_pull(skb, len);
126  else if (len < 0)
127  goto out_clear;
128  /*
129  * Copy any Call User Data.
130  */
131  if (skb->len > 0) {
132  if (skb->len > X25_MAX_CUD_LEN)
133  goto out_clear;
134 
135  skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
136  skb->len);
137  x25->calluserdata.cudlength = skb->len;
138  }
139  if (!sock_flag(sk, SOCK_DEAD))
140  sk->sk_state_change(sk);
141  break;
142  }
143  case X25_CLEAR_REQUEST:
144  if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
145  goto out_clear;
146 
147  x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
148  x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
149  break;
150 
151  default:
152  break;
153  }
154 
155  return 0;
156 
157 out_clear:
158  x25_write_internal(sk, X25_CLEAR_REQUEST);
159  x25->state = X25_STATE_2;
160  x25_start_t23timer(sk);
161  return 0;
162 }
163 
164 /*
165  * State machine for state 2, Awaiting Clear Confirmation State.
166  * The handling of the timer(s) is in file x25_timer.c
167  * Handling of state 0 and connection release is in af_x25.c.
168  */
169 static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
170 {
171  switch (frametype) {
172 
173  case X25_CLEAR_REQUEST:
174  if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
175  goto out_clear;
176 
177  x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
178  x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
179  break;
180 
181  case X25_CLEAR_CONFIRMATION:
182  x25_disconnect(sk, 0, 0, 0);
183  break;
184 
185  default:
186  break;
187  }
188 
189  return 0;
190 
191 out_clear:
192  x25_write_internal(sk, X25_CLEAR_REQUEST);
193  x25_start_t23timer(sk);
194  return 0;
195 }
196 
197 /*
198  * State machine for state 3, Connected State.
199  * The handling of the timer(s) is in file x25_timer.c
200  * Handling of state 0 and connection release is in af_x25.c.
201  */
202 static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
203 {
204  int queued = 0;
205  int modulus;
206  struct x25_sock *x25 = x25_sk(sk);
207 
208  modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
209 
210  switch (frametype) {
211 
212  case X25_RESET_REQUEST:
213  x25_write_internal(sk, X25_RESET_CONFIRMATION);
214  x25_stop_timer(sk);
215  x25->condition = 0x00;
216  x25->vs = 0;
217  x25->vr = 0;
218  x25->va = 0;
219  x25->vl = 0;
220  x25_requeue_frames(sk);
221  break;
222 
223  case X25_CLEAR_REQUEST:
224  if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
225  goto out_clear;
226 
227  x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
228  x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
229  break;
230 
231  case X25_RR:
232  case X25_RNR:
233  if (!x25_validate_nr(sk, nr)) {
234  x25_clear_queues(sk);
235  x25_write_internal(sk, X25_RESET_REQUEST);
236  x25_start_t22timer(sk);
237  x25->condition = 0x00;
238  x25->vs = 0;
239  x25->vr = 0;
240  x25->va = 0;
241  x25->vl = 0;
242  x25->state = X25_STATE_4;
243  } else {
244  x25_frames_acked(sk, nr);
245  if (frametype == X25_RNR) {
246  x25->condition |= X25_COND_PEER_RX_BUSY;
247  } else {
248  x25->condition &= ~X25_COND_PEER_RX_BUSY;
249  }
250  }
251  break;
252 
253  case X25_DATA: /* XXX */
254  x25->condition &= ~X25_COND_PEER_RX_BUSY;
255  if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
256  x25_clear_queues(sk);
257  x25_write_internal(sk, X25_RESET_REQUEST);
258  x25_start_t22timer(sk);
259  x25->condition = 0x00;
260  x25->vs = 0;
261  x25->vr = 0;
262  x25->va = 0;
263  x25->vl = 0;
264  x25->state = X25_STATE_4;
265  break;
266  }
267  x25_frames_acked(sk, nr);
268  if (ns == x25->vr) {
269  if (x25_queue_rx_frame(sk, skb, m) == 0) {
270  x25->vr = (x25->vr + 1) % modulus;
271  queued = 1;
272  } else {
273  /* Should never happen */
274  x25_clear_queues(sk);
275  x25_write_internal(sk, X25_RESET_REQUEST);
276  x25_start_t22timer(sk);
277  x25->condition = 0x00;
278  x25->vs = 0;
279  x25->vr = 0;
280  x25->va = 0;
281  x25->vl = 0;
282  x25->state = X25_STATE_4;
283  break;
284  }
285  if (atomic_read(&sk->sk_rmem_alloc) >
286  (sk->sk_rcvbuf >> 1))
287  x25->condition |= X25_COND_OWN_RX_BUSY;
288  }
289  /*
290  * If the window is full Ack it immediately, else
291  * start the holdback timer.
292  */
293  if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
294  x25->condition &= ~X25_COND_ACK_PENDING;
295  x25_stop_timer(sk);
296  x25_enquiry_response(sk);
297  } else {
298  x25->condition |= X25_COND_ACK_PENDING;
299  x25_start_t2timer(sk);
300  }
301  break;
302 
303  case X25_INTERRUPT_CONFIRMATION:
304  clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
305  break;
306 
307  case X25_INTERRUPT:
308  if (sock_flag(sk, SOCK_URGINLINE))
309  queued = !sock_queue_rcv_skb(sk, skb);
310  else {
311  skb_set_owner_r(skb, sk);
312  skb_queue_tail(&x25->interrupt_in_queue, skb);
313  queued = 1;
314  }
315  sk_send_sigurg(sk);
316  x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
317  break;
318 
319  default:
320  printk(KERN_WARNING "x25: unknown %02X in state 3\n", frametype);
321  break;
322  }
323 
324  return queued;
325 
326 out_clear:
327  x25_write_internal(sk, X25_CLEAR_REQUEST);
328  x25->state = X25_STATE_2;
329  x25_start_t23timer(sk);
330  return 0;
331 }
332 
333 /*
334  * State machine for state 4, Awaiting Reset Confirmation State.
335  * The handling of the timer(s) is in file x25_timer.c
336  * Handling of state 0 and connection release is in af_x25.c.
337  */
338 static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
339 {
340  struct x25_sock *x25 = x25_sk(sk);
341 
342  switch (frametype) {
343 
344  case X25_RESET_REQUEST:
345  x25_write_internal(sk, X25_RESET_CONFIRMATION);
346  case X25_RESET_CONFIRMATION: {
347  x25_stop_timer(sk);
348  x25->condition = 0x00;
349  x25->va = 0;
350  x25->vr = 0;
351  x25->vs = 0;
352  x25->vl = 0;
353  x25->state = X25_STATE_3;
354  x25_requeue_frames(sk);
355  break;
356  }
357  case X25_CLEAR_REQUEST:
358  if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
359  goto out_clear;
360 
361  x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
362  x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
363  break;
364 
365  default:
366  break;
367  }
368 
369  return 0;
370 
371 out_clear:
372  x25_write_internal(sk, X25_CLEAR_REQUEST);
373  x25->state = X25_STATE_2;
374  x25_start_t23timer(sk);
375  return 0;
376 }
377 
378 /* Higher level upcall for a LAPB frame */
379 int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
380 {
381  struct x25_sock *x25 = x25_sk(sk);
382  int queued = 0, frametype, ns, nr, q, d, m;
383 
384  if (x25->state == X25_STATE_0)
385  return 0;
386 
387  frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
388 
389  switch (x25->state) {
390  case X25_STATE_1:
391  queued = x25_state1_machine(sk, skb, frametype);
392  break;
393  case X25_STATE_2:
394  queued = x25_state2_machine(sk, skb, frametype);
395  break;
396  case X25_STATE_3:
397  queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
398  break;
399  case X25_STATE_4:
400  queued = x25_state4_machine(sk, skb, frametype);
401  break;
402  }
403 
404  x25_kick(sk);
405 
406  return queued;
407 }
408 
409 int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
410 {
411  int queued = x25_process_rx_frame(sk, skb);
412 
413  if (!queued)
414  kfree_skb(skb);
415 
416  return 0;
417 }
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