xref: /openbmc/linux/net/ax25/ax25_in.c (revision 3a867b36) 
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/sched.h>
18 #include <linux/timer.h>
19 #include <linux/string.h>
20 #include <linux/sockios.h>
21 #include <linux/net.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 <asm/system.h>
31 #include <linux/fcntl.h>
32 #include <linux/mm.h>
33 #include <linux/interrupt.h>
34 
35 /*
36  *	Given a fragment, queue it on the fragment queue and if the fragment
37  *	is complete, send it back to ax25_rx_iframe.
38  */
39 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
40 {
41 	struct sk_buff *skbn, *skbo;
42 
43 	if (ax25->fragno != 0) {
44 		if (!(*skb->data & AX25_SEG_FIRST)) {
45 			if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
46 				/* Enqueue fragment */
47 				ax25->fragno = *skb->data & AX25_SEG_REM;
48 				skb_pull(skb, 1);	/* skip fragno */
49 				ax25->fraglen += skb->len;
50 				skb_queue_tail(&ax25->frag_queue, skb);
51 
52 				/* Last fragment received ? */
53 				if (ax25->fragno == 0) {
54 					skbn = alloc_skb(AX25_MAX_HEADER_LEN +
55 							 ax25->fraglen,
56 							 GFP_ATOMIC);
57 					if (!skbn) {
58 						skb_queue_purge(&ax25->frag_queue);
59 						return 1;
60 					}
61 
62 					skb_reserve(skbn, AX25_MAX_HEADER_LEN);
63 
64 					skbn->dev   = ax25->ax25_dev->dev;
65 					skbn->h.raw = skbn->data;
66 					skbn->nh.raw = skbn->data;
67 
68 					/* Copy data from the fragments */
69 					while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
70 						memcpy(skb_put(skbn, skbo->len), skbo->data, skbo->len);
71 						kfree_skb(skbo);
72 					}
73 
74 					ax25->fraglen = 0;
75 
76 					if (ax25_rx_iframe(ax25, skbn) == 0)
77 						kfree_skb(skbn);
78 				}
79 
80 				return 1;
81 			}
82 		}
83 	} else {
84 		/* First fragment received */
85 		if (*skb->data & AX25_SEG_FIRST) {
86 			skb_queue_purge(&ax25->frag_queue);
87 			ax25->fragno = *skb->data & AX25_SEG_REM;
88 			skb_pull(skb, 1);		/* skip fragno */
89 			ax25->fraglen = skb->len;
90 			skb_queue_tail(&ax25->frag_queue, skb);
91 			return 1;
92 		}
93 	}
94 
95 	return 0;
96 }
97 
98 /*
99  *	This is where all valid I frames are sent to, to be dispatched to
100  *	whichever protocol requires them.
101  */
102 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
103 {
104 	int (*func)(struct sk_buff *, ax25_cb *);
105 	volatile int queued = 0;
106 	unsigned char pid;
107 
108 	if (skb == NULL) return 0;
109 
110 	ax25_start_idletimer(ax25);
111 
112 	pid = *skb->data;
113 
114 	if (pid == AX25_P_IP) {
115 		/* working around a TCP bug to keep additional listeners
116 		 * happy. TCP re-uses the buffer and destroys the original
117 		 * content.
118 		 */
119 		struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
120 		if (skbn != NULL) {
121 			kfree_skb(skb);
122 			skb = skbn;
123 		}
124 
125 		skb_pull(skb, 1);	/* Remove PID */
126 		skb->mac.raw  = skb->nh.raw;
127 		skb->nh.raw   = skb->data;
128 		skb->dev      = ax25->ax25_dev->dev;
129 		skb->pkt_type = PACKET_HOST;
130 		skb->protocol = htons(ETH_P_IP);
131 		netif_rx(skb);
132 		return 1;
133 	}
134 	if (pid == AX25_P_SEGMENT) {
135 		skb_pull(skb, 1);	/* Remove PID */
136 		return ax25_rx_fragment(ax25, skb);
137 	}
138 
139 	if ((func = ax25_protocol_function(pid)) != NULL) {
140 		skb_pull(skb, 1);	/* Remove PID */
141 		return (*func)(skb, ax25);
142 	}
143 
144 	if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
145 		if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
146 		    ax25->pidincl) {
147 			if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
148 				queued = 1;
149 			else
150 				ax25->condition |= AX25_COND_OWN_RX_BUSY;
151 		}
152 	}
153 
154 	return queued;
155 }
156 
157 /*
158  *	Higher level upcall for a LAPB frame
159  */
160 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
161 {
162 	int queued = 0;
163 
164 	if (ax25->state == AX25_STATE_0)
165 		return 0;
166 
167 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
168 	case AX25_PROTO_STD_SIMPLEX:
169 	case AX25_PROTO_STD_DUPLEX:
170 		queued = ax25_std_frame_in(ax25, skb, type);
171 		break;
172 
173 #ifdef CONFIG_AX25_DAMA_SLAVE
174 	case AX25_PROTO_DAMA_SLAVE:
175 		if (dama || ax25->ax25_dev->dama.slave)
176 			queued = ax25_ds_frame_in(ax25, skb, type);
177 		else
178 			queued = ax25_std_frame_in(ax25, skb, type);
179 		break;
180 #endif
181 	}
182 
183 	return queued;
184 }
185 
186 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
187 	ax25_address *dev_addr, struct packet_type *ptype)
188 {
189 	ax25_address src, dest, *next_digi = NULL;
190 	int type = 0, mine = 0, dama;
191 	struct sock *make, *sk;
192 	ax25_digi dp, reverse_dp;
193 	ax25_cb *ax25;
194 	ax25_dev *ax25_dev;
195 
196 	/*
197 	 *	Process the AX.25/LAPB frame.
198 	 */
199 
200 	skb->h.raw = skb->data;
201 
202 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
203 		kfree_skb(skb);
204 		return 0;
205 	}
206 
207 	/*
208 	 *	Parse the address header.
209 	 */
210 
211 	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL) {
212 		kfree_skb(skb);
213 		return 0;
214 	}
215 
216 	/*
217 	 *	Ours perhaps ?
218 	 */
219 	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
220 		next_digi = &dp.calls[dp.lastrepeat + 1];
221 
222 	/*
223 	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
224 	 */
225 	skb_pull(skb, ax25_addr_size(&dp));
226 
227 	/* For our port addresses ? */
228 	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
229 		mine = 1;
230 
231 	/* Also match on any registered callsign from L3/4 */
232 	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
233 		mine = 1;
234 
235 	/* UI frame - bypass LAPB processing */
236 	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
237 		skb->h.raw = skb->data + 2;		/* skip control and pid */
238 
239 		ax25_send_to_raw(&dest, skb, skb->data[1]);
240 
241 		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0) {
242 			kfree_skb(skb);
243 			return 0;
244 		}
245 
246 		/* Now we are pointing at the pid byte */
247 		switch (skb->data[1]) {
248 		case AX25_P_IP:
249 			skb_pull(skb,2);		/* drop PID/CTRL */
250 			skb->h.raw    = skb->data;
251 			skb->nh.raw   = skb->data;
252 			skb->dev      = dev;
253 			skb->pkt_type = PACKET_HOST;
254 			skb->protocol = htons(ETH_P_IP);
255 			netif_rx(skb);
256 			break;
257 
258 		case AX25_P_ARP:
259 			skb_pull(skb,2);
260 			skb->h.raw    = skb->data;
261 			skb->nh.raw   = skb->data;
262 			skb->dev      = dev;
263 			skb->pkt_type = PACKET_HOST;
264 			skb->protocol = htons(ETH_P_ARP);
265 			netif_rx(skb);
266 			break;
267 		case AX25_P_TEXT:
268 			/* Now find a suitable dgram socket */
269 			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
270 			if (sk != NULL) {
271 				bh_lock_sock(sk);
272 				if (atomic_read(&sk->sk_rmem_alloc) >=
273 				    sk->sk_rcvbuf) {
274 					kfree_skb(skb);
275 				} else {
276 					/*
277 					 *	Remove the control and PID.
278 					 */
279 					skb_pull(skb, 2);
280 					if (sock_queue_rcv_skb(sk, skb) != 0)
281 						kfree_skb(skb);
282 				}
283 				bh_unlock_sock(sk);
284 				sock_put(sk);
285 			} else {
286 				kfree_skb(skb);
287 			}
288 			break;
289 
290 		default:
291 			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
292 			break;
293 		}
294 
295 		return 0;
296 	}
297 
298 	/*
299 	 *	Is connected mode supported on this device ?
300 	 *	If not, should we DM the incoming frame (except DMs) or
301 	 *	silently ignore them. For now we stay quiet.
302 	 */
303 	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0) {
304 		kfree_skb(skb);
305 		return 0;
306 	}
307 
308 	/* LAPB */
309 
310 	/* AX.25 state 1-4 */
311 
312 	ax25_digi_invert(&dp, &reverse_dp);
313 
314 	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
315 		/*
316 		 *	Process the frame. If it is queued up internally it
317 		 *	returns one otherwise we free it immediately. This
318 		 *	routine itself wakes the user context layers so we do
319 		 *	no further work
320 		 */
321 		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
322 			kfree_skb(skb);
323 
324 		ax25_cb_put(ax25);
325 		return 0;
326 	}
327 
328 	/* AX.25 state 0 (disconnected) */
329 
330 	/* a) received not a SABM(E) */
331 
332 	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
333 	    (*skb->data & ~AX25_PF) != AX25_SABME) {
334 		/*
335 		 *	Never reply to a DM. Also ignore any connects for
336 		 *	addresses that are not our interfaces and not a socket.
337 		 */
338 		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
339 			ax25_return_dm(dev, &src, &dest, &dp);
340 
341 		kfree_skb(skb);
342 		return 0;
343 	}
344 
345 	/* b) received SABM(E) */
346 
347 	if (dp.lastrepeat + 1 == dp.ndigi)
348 		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
349 	else
350 		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
351 
352 	if (sk != NULL) {
353 		bh_lock_sock(sk);
354 		if (sk_acceptq_is_full(sk) ||
355 		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
356 			if (mine)
357 				ax25_return_dm(dev, &src, &dest, &dp);
358 			kfree_skb(skb);
359 			bh_unlock_sock(sk);
360 			sock_put(sk);
361 
362 			return 0;
363 		}
364 
365 		ax25 = ax25_sk(make);
366 		skb_set_owner_r(skb, make);
367 		skb_queue_head(&sk->sk_receive_queue, skb);
368 
369 		make->sk_state = TCP_ESTABLISHED;
370 
371 		sk->sk_ack_backlog++;
372 		bh_unlock_sock(sk);
373 	} else {
374 		if (!mine) {
375 			kfree_skb(skb);
376 			return 0;
377 		}
378 
379 		if ((ax25 = ax25_create_cb()) == NULL) {
380 			ax25_return_dm(dev, &src, &dest, &dp);
381 			kfree_skb(skb);
382 			return 0;
383 		}
384 
385 		ax25_fillin_cb(ax25, ax25_dev);
386 	}
387 
388 	ax25->source_addr = dest;
389 	ax25->dest_addr   = src;
390 
391 	/*
392 	 *	Sort out any digipeated paths.
393 	 */
394 	if (dp.ndigi && !ax25->digipeat &&
395 	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
396 		kfree_skb(skb);
397 		ax25_destroy_socket(ax25);
398 		if (sk)
399 			sock_put(sk);
400 		return 0;
401 	}
402 
403 	if (dp.ndigi == 0) {
404 		if (ax25->digipeat != NULL) {
405 			kfree(ax25->digipeat);
406 			ax25->digipeat = NULL;
407 		}
408 	} else {
409 		/* Reverse the source SABM's path */
410 		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
411 	}
412 
413 	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
414 		ax25->modulus = AX25_EMODULUS;
415 		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
416 	} else {
417 		ax25->modulus = AX25_MODULUS;
418 		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
419 	}
420 
421 	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
422 
423 #ifdef CONFIG_AX25_DAMA_SLAVE
424 	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
425 		ax25_dama_on(ax25);
426 #endif
427 
428 	ax25->state = AX25_STATE_3;
429 
430 	ax25_cb_add(ax25);
431 
432 	ax25_start_heartbeat(ax25);
433 	ax25_start_t3timer(ax25);
434 	ax25_start_idletimer(ax25);
435 
436 	if (sk) {
437 		if (!sock_flag(sk, SOCK_DEAD))
438 			sk->sk_data_ready(sk, skb->len);
439 		sock_put(sk);
440 	} else
441 		kfree_skb(skb);
442 
443 	return 0;
444 }
445 
446 /*
447  *	Receive an AX.25 frame via a SLIP interface.
448  */
449 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
450 		  struct packet_type *ptype, struct net_device *orig_dev)
451 {
452 	skb->sk = NULL;		/* Initially we don't know who it's for */
453 	skb->destructor = NULL;	/* Who initializes this, dammit?! */
454 
455 	if ((*skb->data & 0x0F) != 0) {
456 		kfree_skb(skb);	/* Not a KISS data frame */
457 		return 0;
458 	}
459 
460 	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */
461 
462 	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
463 }
464