xref: /openbmc/linux/net/ax25/ax25_in.c (revision 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2) 
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/config.h>
13 #include <linux/errno.h>
14 #include <linux/types.h>
15 #include <linux/socket.h>
16 #include <linux/in.h>
17 #include <linux/kernel.h>
18 #include <linux/sched.h>
19 #include <linux/timer.h>
20 #include <linux/string.h>
21 #include <linux/sockios.h>
22 #include <linux/net.h>
23 #include <net/ax25.h>
24 #include <linux/inet.h>
25 #include <linux/netdevice.h>
26 #include <linux/skbuff.h>
27 #include <linux/netfilter.h>
28 #include <net/sock.h>
29 #include <net/ip.h>			/* For ip_rcv */
30 #include <net/tcp.h>
31 #include <net/arp.h>			/* For arp_rcv */
32 #include <asm/uaccess.h>
33 #include <asm/system.h>
34 #include <linux/fcntl.h>
35 #include <linux/mm.h>
36 #include <linux/interrupt.h>
37 
38 /*
39  *	Given a fragment, queue it on the fragment queue and if the fragment
40  *	is complete, send it back to ax25_rx_iframe.
41  */
42 static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
43 {
44 	struct sk_buff *skbn, *skbo;
45 
46 	if (ax25->fragno != 0) {
47 		if (!(*skb->data & AX25_SEG_FIRST)) {
48 			if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
49 				/* Enqueue fragment */
50 				ax25->fragno = *skb->data & AX25_SEG_REM;
51 				skb_pull(skb, 1);	/* skip fragno */
52 				ax25->fraglen += skb->len;
53 				skb_queue_tail(&ax25->frag_queue, skb);
54 
55 				/* Last fragment received ? */
56 				if (ax25->fragno == 0) {
57 					skbn = alloc_skb(AX25_MAX_HEADER_LEN +
58 							 ax25->fraglen,
59 							 GFP_ATOMIC);
60 					if (!skbn) {
61 						skb_queue_purge(&ax25->frag_queue);
62 						return 1;
63 					}
64 
65 					skb_reserve(skbn, AX25_MAX_HEADER_LEN);
66 
67 					skbn->dev   = ax25->ax25_dev->dev;
68 					skbn->h.raw = skbn->data;
69 					skbn->nh.raw = skbn->data;
70 
71 					/* Copy data from the fragments */
72 					while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
73 						memcpy(skb_put(skbn, skbo->len), skbo->data, skbo->len);
74 						kfree_skb(skbo);
75 					}
76 
77 					ax25->fraglen = 0;
78 
79 					if (ax25_rx_iframe(ax25, skbn) == 0)
80 						kfree_skb(skbn);
81 				}
82 
83 				return 1;
84 			}
85 		}
86 	} else {
87 		/* First fragment received */
88 		if (*skb->data & AX25_SEG_FIRST) {
89 			skb_queue_purge(&ax25->frag_queue);
90 			ax25->fragno = *skb->data & AX25_SEG_REM;
91 			skb_pull(skb, 1);		/* skip fragno */
92 			ax25->fraglen = skb->len;
93 			skb_queue_tail(&ax25->frag_queue, skb);
94 			return 1;
95 		}
96 	}
97 
98 	return 0;
99 }
100 
101 /*
102  *	This is where all valid I frames are sent to, to be dispatched to
103  *	whichever protocol requires them.
104  */
105 int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
106 {
107 	int (*func)(struct sk_buff *, ax25_cb *);
108 	volatile int queued = 0;
109 	unsigned char pid;
110 
111 	if (skb == NULL) return 0;
112 
113 	ax25_start_idletimer(ax25);
114 
115 	pid = *skb->data;
116 
117 #ifdef CONFIG_INET
118 	if (pid == AX25_P_IP) {
119 		/* working around a TCP bug to keep additional listeners
120 		 * happy. TCP re-uses the buffer and destroys the original
121 		 * content.
122 		 */
123 		struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
124 		if (skbn != NULL) {
125 			kfree_skb(skb);
126 			skb = skbn;
127 		}
128 
129 		skb_pull(skb, 1);	/* Remove PID */
130 		skb->h.raw    = skb->data;
131 		skb->nh.raw   = skb->data;
132 		skb->dev      = ax25->ax25_dev->dev;
133 		skb->pkt_type = PACKET_HOST;
134 		skb->protocol = htons(ETH_P_IP);
135 		ip_rcv(skb, skb->dev, NULL);	/* Wrong ptype */
136 		return 1;
137 	}
138 #endif
139 	if (pid == AX25_P_SEGMENT) {
140 		skb_pull(skb, 1);	/* Remove PID */
141 		return ax25_rx_fragment(ax25, skb);
142 	}
143 
144 	if ((func = ax25_protocol_function(pid)) != NULL) {
145 		skb_pull(skb, 1);	/* Remove PID */
146 		return (*func)(skb, ax25);
147 	}
148 
149 	if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
150 		if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
151 		    ax25->pidincl) {
152 			if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
153 				queued = 1;
154 			else
155 				ax25->condition |= AX25_COND_OWN_RX_BUSY;
156 		}
157 	}
158 
159 	return queued;
160 }
161 
162 /*
163  *	Higher level upcall for a LAPB frame
164  */
165 static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
166 {
167 	int queued = 0;
168 
169 	if (ax25->state == AX25_STATE_0)
170 		return 0;
171 
172 	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
173 	case AX25_PROTO_STD_SIMPLEX:
174 	case AX25_PROTO_STD_DUPLEX:
175 		queued = ax25_std_frame_in(ax25, skb, type);
176 		break;
177 
178 #ifdef CONFIG_AX25_DAMA_SLAVE
179 	case AX25_PROTO_DAMA_SLAVE:
180 		if (dama || ax25->ax25_dev->dama.slave)
181 			queued = ax25_ds_frame_in(ax25, skb, type);
182 		else
183 			queued = ax25_std_frame_in(ax25, skb, type);
184 		break;
185 #endif
186 	}
187 
188 	return queued;
189 }
190 
191 static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
192 	ax25_address *dev_addr, struct packet_type *ptype)
193 {
194 	ax25_address src, dest, *next_digi = NULL;
195 	int type = 0, mine = 0, dama;
196 	struct sock *make, *sk;
197 	ax25_digi dp, reverse_dp;
198 	ax25_cb *ax25;
199 	ax25_dev *ax25_dev;
200 
201 	/*
202 	 *	Process the AX.25/LAPB frame.
203 	 */
204 
205 	skb->h.raw = skb->data;
206 
207 	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) {
208 		kfree_skb(skb);
209 		return 0;
210 	}
211 
212 	/*
213 	 *	Parse the address header.
214 	 */
215 
216 	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL) {
217 		kfree_skb(skb);
218 		return 0;
219 	}
220 
221 	/*
222 	 *	Ours perhaps ?
223 	 */
224 	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
225 		next_digi = &dp.calls[dp.lastrepeat + 1];
226 
227 	/*
228 	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
229 	 */
230 	skb_pull(skb, ax25_addr_size(&dp));
231 
232 	/* For our port addresses ? */
233 	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
234 		mine = 1;
235 
236 	/* Also match on any registered callsign from L3/4 */
237 	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
238 		mine = 1;
239 
240 	/* UI frame - bypass LAPB processing */
241 	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
242 		skb->h.raw = skb->data + 2;		/* skip control and pid */
243 
244 		ax25_send_to_raw(&dest, skb, skb->data[1]);
245 
246 		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0) {
247 			kfree_skb(skb);
248 			return 0;
249 		}
250 
251 		/* Now we are pointing at the pid byte */
252 		switch (skb->data[1]) {
253 #ifdef CONFIG_INET
254 		case AX25_P_IP:
255 			skb_pull(skb,2);		/* drop PID/CTRL */
256 			skb->h.raw    = skb->data;
257 			skb->nh.raw   = skb->data;
258 			skb->dev      = dev;
259 			skb->pkt_type = PACKET_HOST;
260 			skb->protocol = htons(ETH_P_IP);
261 			ip_rcv(skb, dev, ptype);	/* Note ptype here is the wrong one, fix me later */
262 			break;
263 
264 		case AX25_P_ARP:
265 			skb_pull(skb,2);
266 			skb->h.raw    = skb->data;
267 			skb->nh.raw   = skb->data;
268 			skb->dev      = dev;
269 			skb->pkt_type = PACKET_HOST;
270 			skb->protocol = htons(ETH_P_ARP);
271 			arp_rcv(skb, dev, ptype);	/* Note ptype here is wrong... */
272 			break;
273 #endif
274 		case AX25_P_TEXT:
275 			/* Now find a suitable dgram socket */
276 			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
277 			if (sk != NULL) {
278 				bh_lock_sock(sk);
279 				if (atomic_read(&sk->sk_rmem_alloc) >=
280 				    sk->sk_rcvbuf) {
281 					kfree_skb(skb);
282 				} else {
283 					/*
284 					 *	Remove the control and PID.
285 					 */
286 					skb_pull(skb, 2);
287 					if (sock_queue_rcv_skb(sk, skb) != 0)
288 						kfree_skb(skb);
289 				}
290 				bh_unlock_sock(sk);
291 				sock_put(sk);
292 			} else {
293 				kfree_skb(skb);
294 			}
295 			break;
296 
297 		default:
298 			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
299 			break;
300 		}
301 
302 		return 0;
303 	}
304 
305 	/*
306 	 *	Is connected mode supported on this device ?
307 	 *	If not, should we DM the incoming frame (except DMs) or
308 	 *	silently ignore them. For now we stay quiet.
309 	 */
310 	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0) {
311 		kfree_skb(skb);
312 		return 0;
313 	}
314 
315 	/* LAPB */
316 
317 	/* AX.25 state 1-4 */
318 
319 	ax25_digi_invert(&dp, &reverse_dp);
320 
321 	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
322 		/*
323 		 *	Process the frame. If it is queued up internally it
324 		 *	returns one otherwise we free it immediately. This
325 		 *	routine itself wakes the user context layers so we do
326 		 *	no further work
327 		 */
328 		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
329 			kfree_skb(skb);
330 
331 		ax25_cb_put(ax25);
332 		return 0;
333 	}
334 
335 	/* AX.25 state 0 (disconnected) */
336 
337 	/* a) received not a SABM(E) */
338 
339 	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
340 	    (*skb->data & ~AX25_PF) != AX25_SABME) {
341 		/*
342 		 *	Never reply to a DM. Also ignore any connects for
343 		 *	addresses that are not our interfaces and not a socket.
344 		 */
345 		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
346 			ax25_return_dm(dev, &src, &dest, &dp);
347 
348 		kfree_skb(skb);
349 		return 0;
350 	}
351 
352 	/* b) received SABM(E) */
353 
354 	if (dp.lastrepeat + 1 == dp.ndigi)
355 		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
356 	else
357 		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
358 
359 	if (sk != NULL) {
360 		bh_lock_sock(sk);
361 		if (sk_acceptq_is_full(sk) ||
362 		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
363 			if (mine)
364 				ax25_return_dm(dev, &src, &dest, &dp);
365 			kfree_skb(skb);
366 			bh_unlock_sock(sk);
367 			sock_put(sk);
368 
369 			return 0;
370 		}
371 
372 		ax25 = ax25_sk(make);
373 		skb_set_owner_r(skb, make);
374 		skb_queue_head(&sk->sk_receive_queue, skb);
375 
376 		make->sk_state = TCP_ESTABLISHED;
377 
378 		sk->sk_ack_backlog++;
379 		bh_unlock_sock(sk);
380 	} else {
381 		if (!mine) {
382 			kfree_skb(skb);
383 			return 0;
384 		}
385 
386 		if ((ax25 = ax25_create_cb()) == NULL) {
387 			ax25_return_dm(dev, &src, &dest, &dp);
388 			kfree_skb(skb);
389 			return 0;
390 		}
391 
392 		ax25_fillin_cb(ax25, ax25_dev);
393 	}
394 
395 	ax25->source_addr = dest;
396 	ax25->dest_addr   = src;
397 
398 	/*
399 	 *	Sort out any digipeated paths.
400 	 */
401 	if (dp.ndigi && !ax25->digipeat &&
402 	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
403 		kfree_skb(skb);
404 		ax25_destroy_socket(ax25);
405 		if (sk)
406 			sock_put(sk);
407 		return 0;
408 	}
409 
410 	if (dp.ndigi == 0) {
411 		if (ax25->digipeat != NULL) {
412 			kfree(ax25->digipeat);
413 			ax25->digipeat = NULL;
414 		}
415 	} else {
416 		/* Reverse the source SABM's path */
417 		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
418 	}
419 
420 	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
421 		ax25->modulus = AX25_EMODULUS;
422 		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
423 	} else {
424 		ax25->modulus = AX25_MODULUS;
425 		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
426 	}
427 
428 	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
429 
430 #ifdef CONFIG_AX25_DAMA_SLAVE
431 	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
432 		ax25_dama_on(ax25);
433 #endif
434 
435 	ax25->state = AX25_STATE_3;
436 
437 	ax25_cb_add(ax25);
438 
439 	ax25_start_heartbeat(ax25);
440 	ax25_start_t3timer(ax25);
441 	ax25_start_idletimer(ax25);
442 
443 	if (sk) {
444 		if (!sock_flag(sk, SOCK_DEAD))
445 			sk->sk_data_ready(sk, skb->len);
446 		sock_put(sk);
447 	} else
448 		kfree_skb(skb);
449 
450 	return 0;
451 }
452 
453 /*
454  *	Receive an AX.25 frame via a SLIP interface.
455  */
456 int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
457 		  struct packet_type *ptype)
458 {
459 	skb->sk = NULL;		/* Initially we don't know who it's for */
460 	skb->destructor = NULL;	/* Who initializes this, dammit?! */
461 
462 	if ((*skb->data & 0x0F) != 0) {
463 		kfree_skb(skb);	/* Not a KISS data frame */
464 		return 0;
465 	}
466 
467 	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */
468 
469 	return ax25_rcv(skb, dev, (ax25_address *)dev->dev_addr, ptype);
470 }
471