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TOMOYO Linux Cross Reference
Linux/net/ax25/ax25_in.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 (alan@lxorguk.ukuu.org.uk)
  8  * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
  9  * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
 10  * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
 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 <linux/netfilter.h>
 27 #include <net/sock.h>
 28 #include <net/tcp_states.h>
 29 #include <asm/uaccess.h>
 30 #include <linux/fcntl.h>
 31 #include <linux/mm.h>
 32 #include <linux/interrupt.h>
 33 
 34 /*
 35  *      Given a fragment, queue it on the fragment queue and if the fragment
 36  *      is complete, send it back to ax25_rx_iframe.
 37  */
 38 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
 39 {
 40         struct sk_buff *skbn, *skbo;
 41 
 42         if (ax25->fragno != 0) {
 43                 if (!(*skb->data & AX25_SEG_FIRST)) {
 44                         if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
 45                                 /* Enqueue fragment */
 46                                 ax25->fragno = *skb->data & AX25_SEG_REM;
 47                                 skb_pull(skb, 1);       /* skip fragno */
 48                                 ax25->fraglen += skb->len;
 49                                 skb_queue_tail(&ax25->frag_queue, skb);
 50 
 51                                 /* Last fragment received ? */
 52                                 if (ax25->fragno == 0) {
 53                                         skbn = alloc_skb(AX25_MAX_HEADER_LEN +
 54                                                          ax25->fraglen,
 55                                                          GFP_ATOMIC);
 56                                         if (!skbn) {
 57                                                 skb_queue_purge(&ax25->frag_queue);
 58                                                 return 1;
 59                                         }
 60 
 61                                         skb_reserve(skbn, AX25_MAX_HEADER_LEN);
 62 
 63                                         skbn->dev   = ax25->ax25_dev->dev;
 64                                         skb_reset_network_header(skbn);
 65                                         skb_reset_transport_header(skbn);
 66 
 67                                         /* Copy data from the fragments */
 68                                         while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
 69                                                 skb_copy_from_linear_data(skbo,
 70                                                           skb_put(skbn, skbo->len),
 71                                                                           skbo->len);
 72                                                 kfree_skb(skbo);
 73                                         }
 74 
 75                                         ax25->fraglen = 0;
 76 
 77                                         if (ax25_rx_iframe(ax25, skbn) == 0)
 78                                                 kfree_skb(skbn);
 79                                 }
 80 
 81                                 return 1;
 82                         }
 83                 }
 84         } else {
 85                 /* First fragment received */
 86                 if (*skb->data & AX25_SEG_FIRST) {
 87                         skb_queue_purge(&ax25->frag_queue);
 88                         ax25->fragno = *skb->data & AX25_SEG_REM;
 89                         skb_pull(skb, 1);               /* skip fragno */
 90                         ax25->fraglen = skb->len;
 91                         skb_queue_tail(&ax25->frag_queue, skb);
 92                         return 1;
 93                 }
 94         }
 95 
 96         return 0;
 97 }
 98 
 99 /*
100  *      This is where all valid I frames are sent to, to be dispatched to
101  *      whichever protocol requires them.
102  */
103 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
104 {
105         int (*func)(struct sk_buff *, ax25_cb *);
106         unsigned char pid;
107         int queued = 0;
108 
109         if (skb == NULL) return 0;
110 
111         ax25_start_idletimer(ax25);
112 
113         pid = *skb->data;
114 
115         if (pid == AX25_P_IP) {
116                 /* working around a TCP bug to keep additional listeners
117                  * happy. TCP re-uses the buffer and destroys the original
118                  * content.
119                  */
120                 struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
121                 if (skbn != NULL) {
122                         kfree_skb(skb);
123                         skb = skbn;
124                 }
125 
126                 skb_pull(skb, 1);       /* Remove PID */
127                 skb->mac_header = skb->network_header;
128                 skb_reset_network_header(skb);
129                 skb->dev      = ax25->ax25_dev->dev;
130                 skb->pkt_type = PACKET_HOST;
131                 skb->protocol = htons(ETH_P_IP);
132                 netif_rx(skb);
133                 return 1;
134         }
135         if (pid == AX25_P_SEGMENT) {
136                 skb_pull(skb, 1);       /* Remove PID */
137                 return ax25_rx_fragment(ax25, skb);
138         }
139 
140         if ((func = ax25_protocol_function(pid)) != NULL) {
141                 skb_pull(skb, 1);       /* Remove PID */
142                 return (*func)(skb, ax25);
143         }
144 
145         if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
146                 if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
147                     ax25->pidincl) {
148                         if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
149                                 queued = 1;
150                         else
151                                 ax25->condition |= AX25_COND_OWN_RX_BUSY;
152                 }
153         }
154 
155         return queued;
156 }
157 
158 /*
159  *      Higher level upcall for a LAPB frame
160  */
161 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
162 {
163         int queued = 0;
164 
165         if (ax25->state == AX25_STATE_0)
166                 return 0;
167 
168         switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
169         case AX25_PROTO_STD_SIMPLEX:
170         case AX25_PROTO_STD_DUPLEX:
171                 queued = ax25_std_frame_in(ax25, skb, type);
172                 break;
173 
174 #ifdef CONFIG_AX25_DAMA_SLAVE
175         case AX25_PROTO_DAMA_SLAVE:
176                 if (dama || ax25->ax25_dev->dama.slave)
177                         queued = ax25_ds_frame_in(ax25, skb, type);
178                 else
179                         queued = ax25_std_frame_in(ax25, skb, type);
180                 break;
181 #endif
182         }
183 
184         return queued;
185 }
186 
187 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
188         ax25_address *dev_addr, struct packet_type *ptype)
189 {
190         ax25_address src, dest, *next_digi = NULL;
191         int type = 0, mine = 0, dama;
192         struct sock *make, *sk;
193         ax25_digi dp, reverse_dp;
194         ax25_cb *ax25;
195         ax25_dev *ax25_dev;
196 
197         /*
198          *      Process the AX.25/LAPB frame.
199          */
200 
201         skb_reset_transport_header(skb);
202 
203         if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
204                 goto free;
205 
206         /*
207          *      Parse the address header.
208          */
209 
210         if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
211                 goto free;
212 
213         /*
214          *      Ours perhaps ?
215          */
216         if (dp.lastrepeat + 1 < dp.ndigi)               /* Not yet digipeated completely */
217                 next_digi = &dp.calls[dp.lastrepeat + 1];
218 
219         /*
220          *      Pull of the AX.25 headers leaving the CTRL/PID bytes
221          */
222         skb_pull(skb, ax25_addr_size(&dp));
223 
224         /* For our port addresses ? */
225         if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
226                 mine = 1;
227 
228         /* Also match on any registered callsign from L3/4 */
229         if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
230                 mine = 1;
231 
232         /* UI frame - bypass LAPB processing */
233         if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
234                 skb_set_transport_header(skb, 2); /* skip control and pid */
235 
236                 ax25_send_to_raw(&dest, skb, skb->data[1]);
237 
238                 if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
239                         goto free;
240 
241                 /* Now we are pointing at the pid byte */
242                 switch (skb->data[1]) {
243                 case AX25_P_IP:
244                         skb_pull(skb,2);                /* drop PID/CTRL */
245                         skb_reset_transport_header(skb);
246                         skb_reset_network_header(skb);
247                         skb->dev      = dev;
248                         skb->pkt_type = PACKET_HOST;
249                         skb->protocol = htons(ETH_P_IP);
250                         netif_rx(skb);
251                         break;
252 
253                 case AX25_P_ARP:
254                         skb_pull(skb,2);
255                         skb_reset_transport_header(skb);
256                         skb_reset_network_header(skb);
257                         skb->dev      = dev;
258                         skb->pkt_type = PACKET_HOST;
259                         skb->protocol = htons(ETH_P_ARP);
260                         netif_rx(skb);
261                         break;
262                 case AX25_P_TEXT:
263                         /* Now find a suitable dgram socket */
264                         sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
265                         if (sk != NULL) {
266                                 bh_lock_sock(sk);
267                                 if (atomic_read(&sk->sk_rmem_alloc) >=
268                                     sk->sk_rcvbuf) {
269                                         kfree_skb(skb);
270                                 } else {
271                                         /*
272                                          *      Remove the control and PID.
273                                          */
274                                         skb_pull(skb, 2);
275                                         if (sock_queue_rcv_skb(sk, skb) != 0)
276                                                 kfree_skb(skb);
277                                 }
278                                 bh_unlock_sock(sk);
279                                 sock_put(sk);
280                         } else {
281                                 kfree_skb(skb);
282                         }
283                         break;
284 
285                 default:
286                         kfree_skb(skb); /* Will scan SOCK_AX25 RAW sockets */
287                         break;
288                 }
289 
290                 return 0;
291         }
292 
293         /*
294          *      Is connected mode supported on this device ?
295          *      If not, should we DM the incoming frame (except DMs) or
296          *      silently ignore them. For now we stay quiet.
297          */
298         if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
299                 goto free;
300 
301         /* LAPB */
302 
303         /* AX.25 state 1-4 */
304 
305         ax25_digi_invert(&dp, &reverse_dp);
306 
307         if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
308                 /*
309                  *      Process the frame. If it is queued up internally it
310                  *      returns one otherwise we free it immediately. This
311                  *      routine itself wakes the user context layers so we do
312                  *      no further work
313                  */
314                 if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
315                         kfree_skb(skb);
316 
317                 ax25_cb_put(ax25);
318                 return 0;
319         }
320 
321         /* AX.25 state 0 (disconnected) */
322 
323         /* a) received not a SABM(E) */
324 
325         if ((*skb->data & ~AX25_PF) != AX25_SABM &&
326             (*skb->data & ~AX25_PF) != AX25_SABME) {
327                 /*
328                  *      Never reply to a DM. Also ignore any connects for
329                  *      addresses that are not our interfaces and not a socket.
330                  */
331                 if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
332                         ax25_return_dm(dev, &src, &dest, &dp);
333 
334                 goto free;
335         }
336 
337         /* b) received SABM(E) */
338 
339         if (dp.lastrepeat + 1 == dp.ndigi)
340                 sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
341         else
342                 sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
343 
344         if (sk != NULL) {
345                 bh_lock_sock(sk);
346                 if (sk_acceptq_is_full(sk) ||
347                     (make = ax25_make_new(sk, ax25_dev)) == NULL) {
348                         if (mine)
349                                 ax25_return_dm(dev, &src, &dest, &dp);
350                         kfree_skb(skb);
351                         bh_unlock_sock(sk);
352                         sock_put(sk);
353 
354                         return 0;
355                 }
356 
357                 ax25 = ax25_sk(make);
358                 skb_set_owner_r(skb, make);
359                 skb_queue_head(&sk->sk_receive_queue, skb);
360 
361                 make->sk_state = TCP_ESTABLISHED;
362 
363                 sk->sk_ack_backlog++;
364                 bh_unlock_sock(sk);
365         } else {
366                 if (!mine)
367                         goto free;
368 
369                 if ((ax25 = ax25_create_cb()) == NULL) {
370                         ax25_return_dm(dev, &src, &dest, &dp);
371                         goto free;
372                 }
373 
374                 ax25_fillin_cb(ax25, ax25_dev);
375         }
376 
377         ax25->source_addr = dest;
378         ax25->dest_addr   = src;
379 
380         /*
381          *      Sort out any digipeated paths.
382          */
383         if (dp.ndigi && !ax25->digipeat &&
384             (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
385                 kfree_skb(skb);
386                 ax25_destroy_socket(ax25);
387                 if (sk)
388                         sock_put(sk);
389                 return 0;
390         }
391 
392         if (dp.ndigi == 0) {
393                 kfree(ax25->digipeat);
394                 ax25->digipeat = NULL;
395         } else {
396                 /* Reverse the source SABM's path */
397                 memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
398         }
399 
400         if ((*skb->data & ~AX25_PF) == AX25_SABME) {
401                 ax25->modulus = AX25_EMODULUS;
402                 ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
403         } else {
404                 ax25->modulus = AX25_MODULUS;
405                 ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
406         }
407 
408         ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
409 
410 #ifdef CONFIG_AX25_DAMA_SLAVE
411         if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
412                 ax25_dama_on(ax25);
413 #endif
414 
415         ax25->state = AX25_STATE_3;
416 
417         ax25_cb_add(ax25);
418 
419         ax25_start_heartbeat(ax25);
420         ax25_start_t3timer(ax25);
421         ax25_start_idletimer(ax25);
422 
423         if (sk) {
424                 if (!sock_flag(sk, SOCK_DEAD))
425                         sk->sk_data_ready(sk, skb->len);
426                 sock_put(sk);
427         } else {
428 free:
429                 kfree_skb(skb);
430         }
431         return 0;
432 }
433 
434 /*
435  *      Receive an AX.25 frame via a SLIP interface.
436  */
437 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
438                   struct packet_type *ptype, struct net_device *orig_dev)
439 {
440         skb_orphan(skb);
441 
442         if (!net_eq(dev_net(dev), &init_net)) {
443                 kfree_skb(skb);
444                 return 0;
445         }
446 
447         if ((*skb->data & 0x0F) != 0) {
448                 kfree_skb(skb); /* Not a KISS data frame */
449                 return 0;
450         }
451 
452         skb_pull(skb, AX25_KISS_HEADER_LEN);    /* Remove the KISS byte */
453 
454         return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
455 }
456 

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