xref: /openbmc/linux/net/ax25/ax25_in.c (revision c819e2cf) 
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);
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