xref: /openbmc/linux/net/ax25/ax25_in.c (revision 9ac8d3fb) 
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 <net/ax25.h>
22 #include <linux/inet.h>
23 #include <linux/netdevice.h>
24 #include <linux/skbuff.h>
25 #include <linux/netfilter.h>
26 #include <net/sock.h>
27 #include <net/tcp_states.h>
28 #include <asm/uaccess.h>
29 #include <asm/system.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 		kfree_skb(skb);
205 		return 0;
206 	}
207 
208 	/*
209 	 *	Parse the address header.
210 	 */
211 
212 	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL) {
213 		kfree_skb(skb);
214 		return 0;
215 	}
216 
217 	/*
218 	 *	Ours perhaps ?
219 	 */
220 	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
221 		next_digi = &dp.calls[dp.lastrepeat + 1];
222 
223 	/*
224 	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
225 	 */
226 	skb_pull(skb, ax25_addr_size(&dp));
227 
228 	/* For our port addresses ? */
229 	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
230 		mine = 1;
231 
232 	/* Also match on any registered callsign from L3/4 */
233 	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
234 		mine = 1;
235 
236 	/* UI frame - bypass LAPB processing */
237 	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
238 		skb_set_transport_header(skb, 2); /* skip control and pid */
239 
240 		ax25_send_to_raw(&dest, skb, skb->data[1]);
241 
242 		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0) {
243 			kfree_skb(skb);
244 			return 0;
245 		}
246 
247 		/* Now we are pointing at the pid byte */
248 		switch (skb->data[1]) {
249 		case AX25_P_IP:
250 			skb_pull(skb,2);		/* drop PID/CTRL */
251 			skb_reset_transport_header(skb);
252 			skb_reset_network_header(skb);
253 			skb->dev      = dev;
254 			skb->pkt_type = PACKET_HOST;
255 			skb->protocol = htons(ETH_P_IP);
256 			netif_rx(skb);
257 			break;
258 
259 		case AX25_P_ARP:
260 			skb_pull(skb,2);
261 			skb_reset_transport_header(skb);
262 			skb_reset_network_header(skb);
263 			skb->dev      = dev;
264 			skb->pkt_type = PACKET_HOST;
265 			skb->protocol = htons(ETH_P_ARP);
266 			netif_rx(skb);
267 			break;
268 		case AX25_P_TEXT:
269 			/* Now find a suitable dgram socket */
270 			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
271 			if (sk != NULL) {
272 				bh_lock_sock(sk);
273 				if (atomic_read(&sk->sk_rmem_alloc) >=
274 				    sk->sk_rcvbuf) {
275 					kfree_skb(skb);
276 				} else {
277 					/*
278 					 *	Remove the control and PID.
279 					 */
280 					skb_pull(skb, 2);
281 					if (sock_queue_rcv_skb(sk, skb) != 0)
282 						kfree_skb(skb);
283 				}
284 				bh_unlock_sock(sk);
285 				sock_put(sk);
286 			} else {
287 				kfree_skb(skb);
288 			}
289 			break;
290 
291 		default:
292 			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
293 			break;
294 		}
295 
296 		return 0;
297 	}
298 
299 	/*
300 	 *	Is connected mode supported on this device ?
301 	 *	If not, should we DM the incoming frame (except DMs) or
302 	 *	silently ignore them. For now we stay quiet.
303 	 */
304 	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0) {
305 		kfree_skb(skb);
306 		return 0;
307 	}
308 
309 	/* LAPB */
310 
311 	/* AX.25 state 1-4 */
312 
313 	ax25_digi_invert(&dp, &reverse_dp);
314 
315 	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
316 		/*
317 		 *	Process the frame. If it is queued up internally it
318 		 *	returns one otherwise we free it immediately. This
319 		 *	routine itself wakes the user context layers so we do
320 		 *	no further work
321 		 */
322 		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
323 			kfree_skb(skb);
324 
325 		ax25_cb_put(ax25);
326 		return 0;
327 	}
328 
329 	/* AX.25 state 0 (disconnected) */
330 
331 	/* a) received not a SABM(E) */
332 
333 	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
334 	    (*skb->data & ~AX25_PF) != AX25_SABME) {
335 		/*
336 		 *	Never reply to a DM. Also ignore any connects for
337 		 *	addresses that are not our interfaces and not a socket.
338 		 */
339 		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
340 			ax25_return_dm(dev, &src, &dest, &dp);
341 
342 		kfree_skb(skb);
343 		return 0;
344 	}
345 
346 	/* b) received SABM(E) */
347 
348 	if (dp.lastrepeat + 1 == dp.ndigi)
349 		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
350 	else
351 		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
352 
353 	if (sk != NULL) {
354 		bh_lock_sock(sk);
355 		if (sk_acceptq_is_full(sk) ||
356 		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
357 			if (mine)
358 				ax25_return_dm(dev, &src, &dest, &dp);
359 			kfree_skb(skb);
360 			bh_unlock_sock(sk);
361 			sock_put(sk);
362 
363 			return 0;
364 		}
365 
366 		ax25 = ax25_sk(make);
367 		skb_set_owner_r(skb, make);
368 		skb_queue_head(&sk->sk_receive_queue, skb);
369 
370 		make->sk_state = TCP_ESTABLISHED;
371 
372 		sk->sk_ack_backlog++;
373 		bh_unlock_sock(sk);
374 	} else {
375 		if (!mine) {
376 			kfree_skb(skb);
377 			return 0;
378 		}
379 
380 		if ((ax25 = ax25_create_cb()) == NULL) {
381 			ax25_return_dm(dev, &src, &dest, &dp);
382 			kfree_skb(skb);
383 			return 0;
384 		}
385 
386 		ax25_fillin_cb(ax25, ax25_dev);
387 	}
388 
389 	ax25->source_addr = dest;
390 	ax25->dest_addr   = src;
391 
392 	/*
393 	 *	Sort out any digipeated paths.
394 	 */
395 	if (dp.ndigi && !ax25->digipeat &&
396 	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
397 		kfree_skb(skb);
398 		ax25_destroy_socket(ax25);
399 		if (sk)
400 			sock_put(sk);
401 		return 0;
402 	}
403 
404 	if (dp.ndigi == 0) {
405 		kfree(ax25->digipeat);
406 		ax25->digipeat = NULL;
407 	} else {
408 		/* Reverse the source SABM's path */
409 		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
410 	}
411 
412 	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
413 		ax25->modulus = AX25_EMODULUS;
414 		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
415 	} else {
416 		ax25->modulus = AX25_MODULUS;
417 		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
418 	}
419 
420 	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
421 
422 #ifdef CONFIG_AX25_DAMA_SLAVE
423 	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
424 		ax25_dama_on(ax25);
425 #endif
426 
427 	ax25->state = AX25_STATE_3;
428 
429 	ax25_cb_add(ax25);
430 
431 	ax25_start_heartbeat(ax25);
432 	ax25_start_t3timer(ax25);
433 	ax25_start_idletimer(ax25);
434 
435 	if (sk) {
436 		if (!sock_flag(sk, SOCK_DEAD))
437 			sk->sk_data_ready(sk, skb->len);
438 		sock_put(sk);
439 	} else
440 		kfree_skb(skb);
441 
442 	return 0;
443 }
444 
445 /*
446  *	Receive an AX.25 frame via a SLIP interface.
447  */
448 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
449 		  struct packet_type *ptype, struct net_device *orig_dev)
450 {
451 	skb->sk = NULL;		/* Initially we don't know who it's for */
452 	skb->destructor = NULL;	/* Who initializes this, dammit?! */
453 
454 	if (!net_eq(dev_net(dev), &init_net)) {
455 		kfree_skb(skb);
456 		return 0;
457 	}
458 
459 	if ((*skb->data & 0x0F) != 0) {
460 		kfree_skb(skb);	/* Not a KISS data frame */
461 		return 0;
462 	}
463 
464 	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */
465 
466 	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
467 }
468