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Linux/net/x25/x25_in.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  *      X.25 Packet Layer release 002
  4  *
  5  *      This is ALPHA test software. This code may break your machine,
  6  *      randomly fail to work with new releases, misbehave and/or generally
  7  *      screw up. It might even work.
  8  *
  9  *      This code REQUIRES 2.1.15 or higher
 10  *
 11  *      History
 12  *      X.25 001        Jonathan Naylor   Started coding.
 13  *      X.25 002        Jonathan Naylor   Centralised disconnection code.
 14  *                                        New timer architecture.
 15  *      2000-03-20      Daniela Squassoni Disabling/enabling of facilities
 16  *                                        negotiation.
 17  *      2000-11-10      Henner Eisen      Check and reset for out-of-sequence
 18  *                                        i-frames.
 19  */
 20 
 21 #define pr_fmt(fmt) "X25: " fmt
 22 
 23 #include <linux/slab.h>
 24 #include <linux/errno.h>
 25 #include <linux/kernel.h>
 26 #include <linux/string.h>
 27 #include <linux/skbuff.h>
 28 #include <net/sock.h>
 29 #include <net/tcp_states.h>
 30 #include <net/x25.h>
 31 
 32 static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
 33 {
 34         struct sk_buff *skbo, *skbn = skb;
 35         struct x25_sock *x25 = x25_sk(sk);
 36 
 37         if (more) {
 38                 x25->fraglen += skb->len;
 39                 skb_queue_tail(&x25->fragment_queue, skb);
 40                 skb_set_owner_r(skb, sk);
 41                 return 0;
 42         }
 43 
 44         if (!more && x25->fraglen > 0) {        /* End of fragment */
 45                 int len = x25->fraglen + skb->len;
 46 
 47                 if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){
 48                         kfree_skb(skb);
 49                         return 1;
 50                 }
 51 
 52                 skb_queue_tail(&x25->fragment_queue, skb);
 53 
 54                 skb_reset_transport_header(skbn);
 55 
 56                 skbo = skb_dequeue(&x25->fragment_queue);
 57                 skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
 58                                           skbo->len);
 59                 kfree_skb(skbo);
 60 
 61                 while ((skbo =
 62                         skb_dequeue(&x25->fragment_queue)) != NULL) {
 63                         skb_pull(skbo, (x25->neighbour->extended) ?
 64                                         X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
 65                         skb_copy_from_linear_data(skbo,
 66                                                   skb_put(skbn, skbo->len),
 67                                                   skbo->len);
 68                         kfree_skb(skbo);
 69                 }
 70 
 71                 x25->fraglen = 0;
 72         }
 73 
 74         skb_set_owner_r(skbn, sk);
 75         skb_queue_tail(&sk->sk_receive_queue, skbn);
 76         if (!sock_flag(sk, SOCK_DEAD))
 77                 sk->sk_data_ready(sk);
 78 
 79         return 0;
 80 }
 81 
 82 /*
 83  * State machine for state 1, Awaiting Call Accepted State.
 84  * The handling of the timer(s) is in file x25_timer.c.
 85  * Handling of state 0 and connection release is in af_x25.c.
 86  */
 87 static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
 88 {
 89         struct x25_address source_addr, dest_addr;
 90         int len;
 91         struct x25_sock *x25 = x25_sk(sk);
 92 
 93         switch (frametype) {
 94         case X25_CALL_ACCEPTED: {
 95 
 96                 x25_stop_timer(sk);
 97                 x25->condition = 0x00;
 98                 x25->vs        = 0;
 99                 x25->va        = 0;
100                 x25->vr        = 0;
101                 x25->vl        = 0;
102                 x25->state     = X25_STATE_3;
103                 sk->sk_state   = TCP_ESTABLISHED;
104                 /*
105                  *      Parse the data in the frame.
106                  */
107                 if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
108                         goto out_clear;
109                 skb_pull(skb, X25_STD_MIN_LEN);
110 
111                 len = x25_parse_address_block(skb, &source_addr,
112                                               &dest_addr);
113                 if (len > 0)
114                         skb_pull(skb, len);
115                 else if (len < 0)
116                         goto out_clear;
117 
118                 len = x25_parse_facilities(skb, &x25->facilities,
119                                            &x25->dte_facilities,
120                                            &x25->vc_facil_mask);
121                 if (len > 0)
122                         skb_pull(skb, len);
123                 else if (len < 0)
124                         goto out_clear;
125                 /*
126                  *      Copy any Call User Data.
127                  */
128                 if (skb->len > 0) {
129                         if (skb->len > X25_MAX_CUD_LEN)
130                                 goto out_clear;
131 
132                         skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
133                                 skb->len);
134                         x25->calluserdata.cudlength = skb->len;
135                 }
136                 if (!sock_flag(sk, SOCK_DEAD))
137                         sk->sk_state_change(sk);
138                 break;
139         }
140         case X25_CALL_REQUEST:
141                 /* call collision */
142                 x25->causediag.cause      = 0x01;
143                 x25->causediag.diagnostic = 0x48;
144 
145                 x25_write_internal(sk, X25_CLEAR_REQUEST);
146                 x25_disconnect(sk, EISCONN, 0x01, 0x48);
147                 break;
148 
149         case X25_CLEAR_REQUEST:
150                 if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
151                         goto out_clear;
152 
153                 x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
154                 x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
155                 break;
156 
157         default:
158                 break;
159         }
160 
161         return 0;
162 
163 out_clear:
164         x25_write_internal(sk, X25_CLEAR_REQUEST);
165         x25->state = X25_STATE_2;
166         x25_start_t23timer(sk);
167         return 0;
168 }
169 
170 /*
171  * State machine for state 2, Awaiting Clear Confirmation State.
172  * The handling of the timer(s) is in file x25_timer.c
173  * Handling of state 0 and connection release is in af_x25.c.
174  */
175 static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
176 {
177         switch (frametype) {
178 
179                 case X25_CLEAR_REQUEST:
180                         if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
181                                 goto out_clear;
182 
183                         x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
184                         x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
185                         break;
186 
187                 case X25_CLEAR_CONFIRMATION:
188                         x25_disconnect(sk, 0, 0, 0);
189                         break;
190 
191                 default:
192                         break;
193         }
194 
195         return 0;
196 
197 out_clear:
198         x25_write_internal(sk, X25_CLEAR_REQUEST);
199         x25_start_t23timer(sk);
200         return 0;
201 }
202 
203 /*
204  * State machine for state 3, Connected State.
205  * The handling of the timer(s) is in file x25_timer.c
206  * Handling of state 0 and connection release is in af_x25.c.
207  */
208 static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
209 {
210         int queued = 0;
211         int modulus;
212         struct x25_sock *x25 = x25_sk(sk);
213 
214         modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
215 
216         switch (frametype) {
217 
218                 case X25_RESET_REQUEST:
219                         x25_write_internal(sk, X25_RESET_CONFIRMATION);
220                         x25_stop_timer(sk);
221                         x25->condition = 0x00;
222                         x25->vs        = 0;
223                         x25->vr        = 0;
224                         x25->va        = 0;
225                         x25->vl        = 0;
226                         x25_requeue_frames(sk);
227                         break;
228 
229                 case X25_CLEAR_REQUEST:
230                         if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
231                                 goto out_clear;
232 
233                         x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
234                         x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
235                         break;
236 
237                 case X25_RR:
238                 case X25_RNR:
239                         if (!x25_validate_nr(sk, nr)) {
240                                 x25_clear_queues(sk);
241                                 x25_write_internal(sk, X25_RESET_REQUEST);
242                                 x25_start_t22timer(sk);
243                                 x25->condition = 0x00;
244                                 x25->vs        = 0;
245                                 x25->vr        = 0;
246                                 x25->va        = 0;
247                                 x25->vl        = 0;
248                                 x25->state     = X25_STATE_4;
249                         } else {
250                                 x25_frames_acked(sk, nr);
251                                 if (frametype == X25_RNR) {
252                                         x25->condition |= X25_COND_PEER_RX_BUSY;
253                                 } else {
254                                         x25->condition &= ~X25_COND_PEER_RX_BUSY;
255                                 }
256                         }
257                         break;
258 
259                 case X25_DATA:  /* XXX */
260                         x25->condition &= ~X25_COND_PEER_RX_BUSY;
261                         if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
262                                 x25_clear_queues(sk);
263                                 x25_write_internal(sk, X25_RESET_REQUEST);
264                                 x25_start_t22timer(sk);
265                                 x25->condition = 0x00;
266                                 x25->vs        = 0;
267                                 x25->vr        = 0;
268                                 x25->va        = 0;
269                                 x25->vl        = 0;
270                                 x25->state     = X25_STATE_4;
271                                 break;
272                         }
273                         x25_frames_acked(sk, nr);
274                         if (ns == x25->vr) {
275                                 if (x25_queue_rx_frame(sk, skb, m) == 0) {
276                                         x25->vr = (x25->vr + 1) % modulus;
277                                         queued = 1;
278                                 } else {
279                                         /* Should never happen */
280                                         x25_clear_queues(sk);
281                                         x25_write_internal(sk, X25_RESET_REQUEST);
282                                         x25_start_t22timer(sk);
283                                         x25->condition = 0x00;
284                                         x25->vs        = 0;
285                                         x25->vr        = 0;
286                                         x25->va        = 0;
287                                         x25->vl        = 0;
288                                         x25->state     = X25_STATE_4;
289                                         break;
290                                 }
291                                 if (atomic_read(&sk->sk_rmem_alloc) >
292                                     (sk->sk_rcvbuf >> 1))
293                                         x25->condition |= X25_COND_OWN_RX_BUSY;
294                         }
295                         /*
296                          *      If the window is full Ack it immediately, else
297                          *      start the holdback timer.
298                          */
299                         if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
300                                 x25->condition &= ~X25_COND_ACK_PENDING;
301                                 x25_stop_timer(sk);
302                                 x25_enquiry_response(sk);
303                         } else {
304                                 x25->condition |= X25_COND_ACK_PENDING;
305                                 x25_start_t2timer(sk);
306                         }
307                         break;
308 
309                 case X25_INTERRUPT_CONFIRMATION:
310                         clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
311                         break;
312 
313                 case X25_INTERRUPT:
314                         if (sock_flag(sk, SOCK_URGINLINE))
315                                 queued = !sock_queue_rcv_skb(sk, skb);
316                         else {
317                                 skb_set_owner_r(skb, sk);
318                                 skb_queue_tail(&x25->interrupt_in_queue, skb);
319                                 queued = 1;
320                         }
321                         sk_send_sigurg(sk);
322                         x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
323                         break;
324 
325                 default:
326                         pr_warn("unknown %02X in state 3\n", frametype);
327                         break;
328         }
329 
330         return queued;
331 
332 out_clear:
333         x25_write_internal(sk, X25_CLEAR_REQUEST);
334         x25->state = X25_STATE_2;
335         x25_start_t23timer(sk);
336         return 0;
337 }
338 
339 /*
340  * State machine for state 4, Awaiting Reset Confirmation State.
341  * The handling of the timer(s) is in file x25_timer.c
342  * Handling of state 0 and connection release is in af_x25.c.
343  */
344 static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
345 {
346         struct x25_sock *x25 = x25_sk(sk);
347 
348         switch (frametype) {
349 
350                 case X25_RESET_REQUEST:
351                         x25_write_internal(sk, X25_RESET_CONFIRMATION);
352                         /* fall through */
353                 case X25_RESET_CONFIRMATION: {
354                         x25_stop_timer(sk);
355                         x25->condition = 0x00;
356                         x25->va        = 0;
357                         x25->vr        = 0;
358                         x25->vs        = 0;
359                         x25->vl        = 0;
360                         x25->state     = X25_STATE_3;
361                         x25_requeue_frames(sk);
362                         break;
363                 }
364                 case X25_CLEAR_REQUEST:
365                         if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
366                                 goto out_clear;
367 
368                         x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
369                         x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
370                         break;
371 
372                 default:
373                         break;
374         }
375 
376         return 0;
377 
378 out_clear:
379         x25_write_internal(sk, X25_CLEAR_REQUEST);
380         x25->state = X25_STATE_2;
381         x25_start_t23timer(sk);
382         return 0;
383 }
384 
385 /*
386  * State machine for state 5, Call Accepted / Call Connected pending (X25_ACCPT_APPRV_FLAG).
387  * The handling of the timer(s) is in file x25_timer.c
388  * Handling of state 0 and connection release is in af_x25.c.
389  */
390 static int x25_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
391 {
392         struct x25_sock *x25 = x25_sk(sk);
393 
394         switch (frametype) {
395                 case X25_CLEAR_REQUEST:
396                         if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) {
397                                 x25_write_internal(sk, X25_CLEAR_REQUEST);
398                                 x25->state = X25_STATE_2;
399                                 x25_start_t23timer(sk);
400                                 return 0;
401                         }
402 
403                         x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
404                         x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
405                         break;
406 
407                 default:
408                         break;
409         }
410 
411         return 0;
412 }
413 
414 /* Higher level upcall for a LAPB frame */
415 int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
416 {
417         struct x25_sock *x25 = x25_sk(sk);
418         int queued = 0, frametype, ns, nr, q, d, m;
419 
420         if (x25->state == X25_STATE_0)
421                 return 0;
422 
423         frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
424 
425         switch (x25->state) {
426         case X25_STATE_1:
427                 queued = x25_state1_machine(sk, skb, frametype);
428                 break;
429         case X25_STATE_2:
430                 queued = x25_state2_machine(sk, skb, frametype);
431                 break;
432         case X25_STATE_3:
433                 queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
434                 break;
435         case X25_STATE_4:
436                 queued = x25_state4_machine(sk, skb, frametype);
437                 break;
438         case X25_STATE_5:
439                 queued = x25_state5_machine(sk, skb, frametype);
440                 break;
441         }
442 
443         x25_kick(sk);
444 
445         return queued;
446 }
447 
448 int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
449 {
450         int queued = x25_process_rx_frame(sk, skb);
451 
452         if (!queued)
453                 kfree_skb(skb);
454 
455         return 0;
456 }
457 

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