xref: /openbmc/linux/net/ax25/ax25_in.c (revision 6d99a79c) 
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 <net/sock.h>
27 #include <net/tcp_states.h>
28 #include <linux/uaccess.h>
29 #include <linux/fcntl.h>
30 #include <linux/mm.h>
31 #include <linux/interrupt.h>
32 
33 /*
34  *	Given a fragment, queue it on the fragment queue and if the fragment
35  *	is complete, send it back to ax25_rx_iframe.
36  */
37 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
38 {
39 	struct sk_buff *skbn, *skbo;
40 
41 	if (ax25->fragno != 0) {
42 		if (!(*skb->data & AX25_SEG_FIRST)) {
43 			if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
44 				/* Enqueue fragment */
45 				ax25->fragno = *skb->data & AX25_SEG_REM;
46 				skb_pull(skb, 1);	/* skip fragno */
47 				ax25->fraglen += skb->len;
48 				skb_queue_tail(&ax25->frag_queue, skb);
49 
50 				/* Last fragment received ? */
51 				if (ax25->fragno == 0) {
52 					skbn = alloc_skb(AX25_MAX_HEADER_LEN +
53 							 ax25->fraglen,
54 							 GFP_ATOMIC);
55 					if (!skbn) {
56 						skb_queue_purge(&ax25->frag_queue);
57 						return 1;
58 					}
59 
60 					skb_reserve(skbn, AX25_MAX_HEADER_LEN);
61 
62 					skbn->dev   = ax25->ax25_dev->dev;
63 					skb_reset_network_header(skbn);
64 					skb_reset_transport_header(skbn);
65 
66 					/* Copy data from the fragments */
67 					while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
68 						skb_copy_from_linear_data(skbo,
69 							  skb_put(skbn, skbo->len),
70 									  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 	unsigned char pid;
106 	int queued = 0;
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_header = skb->network_header;
127 		skb_reset_network_header(skb);
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_reset_transport_header(skb);
201 
202 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
203 		goto free;
204 
205 	/*
206 	 *	Parse the address header.
207 	 */
208 
209 	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
210 		goto free;
211 
212 	/*
213 	 *	Ours perhaps ?
214 	 */
215 	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
216 		next_digi = &dp.calls[dp.lastrepeat + 1];
217 
218 	/*
219 	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
220 	 */
221 	skb_pull(skb, ax25_addr_size(&dp));
222 
223 	/* For our port addresses ? */
224 	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
225 		mine = 1;
226 
227 	/* Also match on any registered callsign from L3/4 */
228 	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
229 		mine = 1;
230 
231 	/* UI frame - bypass LAPB processing */
232 	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
233 		skb_set_transport_header(skb, 2); /* skip control and pid */
234 
235 		ax25_send_to_raw(&dest, skb, skb->data[1]);
236 
237 		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
238 			goto free;
239 
240 		/* Now we are pointing at the pid byte */
241 		switch (skb->data[1]) {
242 		case AX25_P_IP:
243 			skb_pull(skb,2);		/* drop PID/CTRL */
244 			skb_reset_transport_header(skb);
245 			skb_reset_network_header(skb);
246 			skb->dev      = dev;
247 			skb->pkt_type = PACKET_HOST;
248 			skb->protocol = htons(ETH_P_IP);
249 			netif_rx(skb);
250 			break;
251 
252 		case AX25_P_ARP:
253 			skb_pull(skb,2);
254 			skb_reset_transport_header(skb);
255 			skb_reset_network_header(skb);
256 			skb->dev      = dev;
257 			skb->pkt_type = PACKET_HOST;
258 			skb->protocol = htons(ETH_P_ARP);
259 			netif_rx(skb);
260 			break;
261 		case AX25_P_TEXT:
262 			/* Now find a suitable dgram socket */
263 			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
264 			if (sk != NULL) {
265 				bh_lock_sock(sk);
266 				if (atomic_read(&sk->sk_rmem_alloc) >=
267 				    sk->sk_rcvbuf) {
268 					kfree_skb(skb);
269 				} else {
270 					/*
271 					 *	Remove the control and PID.
272 					 */
273 					skb_pull(skb, 2);
274 					if (sock_queue_rcv_skb(sk, skb) != 0)
275 						kfree_skb(skb);
276 				}
277 				bh_unlock_sock(sk);
278 				sock_put(sk);
279 			} else {
280 				kfree_skb(skb);
281 			}
282 			break;
283 
284 		default:
285 			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
286 			break;
287 		}
288 
289 		return 0;
290 	}
291 
292 	/*
293 	 *	Is connected mode supported on this device ?
294 	 *	If not, should we DM the incoming frame (except DMs) or
295 	 *	silently ignore them. For now we stay quiet.
296 	 */
297 	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
298 		goto free;
299 
300 	/* LAPB */
301 
302 	/* AX.25 state 1-4 */
303 
304 	ax25_digi_invert(&dp, &reverse_dp);
305 
306 	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
307 		/*
308 		 *	Process the frame. If it is queued up internally it
309 		 *	returns one otherwise we free it immediately. This
310 		 *	routine itself wakes the user context layers so we do
311 		 *	no further work
312 		 */
313 		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
314 			kfree_skb(skb);
315 
316 		ax25_cb_put(ax25);
317 		return 0;
318 	}
319 
320 	/* AX.25 state 0 (disconnected) */
321 
322 	/* a) received not a SABM(E) */
323 
324 	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
325 	    (*skb->data & ~AX25_PF) != AX25_SABME) {
326 		/*
327 		 *	Never reply to a DM. Also ignore any connects for
328 		 *	addresses that are not our interfaces and not a socket.
329 		 */
330 		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
331 			ax25_return_dm(dev, &src, &dest, &dp);
332 
333 		goto free;
334 	}
335 
336 	/* b) received SABM(E) */
337 
338 	if (dp.lastrepeat + 1 == dp.ndigi)
339 		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
340 	else
341 		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
342 
343 	if (sk != NULL) {
344 		bh_lock_sock(sk);
345 		if (sk_acceptq_is_full(sk) ||
346 		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
347 			if (mine)
348 				ax25_return_dm(dev, &src, &dest, &dp);
349 			kfree_skb(skb);
350 			bh_unlock_sock(sk);
351 			sock_put(sk);
352 
353 			return 0;
354 		}
355 
356 		ax25 = sk_to_ax25(make);
357 		skb_set_owner_r(skb, make);
358 		skb_queue_head(&sk->sk_receive_queue, skb);
359 
360 		make->sk_state = TCP_ESTABLISHED;
361 
362 		sk->sk_ack_backlog++;
363 		bh_unlock_sock(sk);
364 	} else {
365 		if (!mine)
366 			goto free;
367 
368 		if ((ax25 = ax25_create_cb()) == NULL) {
369 			ax25_return_dm(dev, &src, &dest, &dp);
370 			goto free;
371 		}
372 
373 		ax25_fillin_cb(ax25, ax25_dev);
374 	}
375 
376 	ax25->source_addr = dest;
377 	ax25->dest_addr   = src;
378 
379 	/*
380 	 *	Sort out any digipeated paths.
381 	 */
382 	if (dp.ndigi && !ax25->digipeat &&
383 	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
384 		kfree_skb(skb);
385 		ax25_destroy_socket(ax25);
386 		if (sk)
387 			sock_put(sk);
388 		return 0;
389 	}
390 
391 	if (dp.ndigi == 0) {
392 		kfree(ax25->digipeat);
393 		ax25->digipeat = NULL;
394 	} else {
395 		/* Reverse the source SABM's path */
396 		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
397 	}
398 
399 	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
400 		ax25->modulus = AX25_EMODULUS;
401 		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
402 	} else {
403 		ax25->modulus = AX25_MODULUS;
404 		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
405 	}
406 
407 	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
408 
409 #ifdef CONFIG_AX25_DAMA_SLAVE
410 	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
411 		ax25_dama_on(ax25);
412 #endif
413 
414 	ax25->state = AX25_STATE_3;
415 
416 	ax25_cb_add(ax25);
417 
418 	ax25_start_heartbeat(ax25);
419 	ax25_start_t3timer(ax25);
420 	ax25_start_idletimer(ax25);
421 
422 	if (sk) {
423 		if (!sock_flag(sk, SOCK_DEAD))
424 			sk->sk_data_ready(sk);
425 		sock_put(sk);
426 	} else {
427 free:
428 		kfree_skb(skb);
429 	}
430 	return 0;
431 }
432 
433 /*
434  *	Receive an AX.25 frame via a SLIP interface.
435  */
436 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
437 		  struct packet_type *ptype, struct net_device *orig_dev)
438 {
439 	skb_orphan(skb);
440 
441 	if (!net_eq(dev_net(dev), &init_net)) {
442 		kfree_skb(skb);
443 		return 0;
444 	}
445 
446 	if ((*skb->data & 0x0F) != 0) {
447 		kfree_skb(skb);	/* Not a KISS data frame */
448 		return 0;
449 	}
450 
451 	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */
452 
453 	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
454 }
455