1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright (C) Alan Cox GW4PTS (alan@lxorguk.ukuu.org.uk)
5 * Copyright (C) Jonathan Naylor G4KLX (g4klx@g4klx.demon.co.uk)
6 * Copyright (C) Joerg Reuter DL1BKE (jreuter@yaina.de)
7 * Copyright (C) Hans-Joachim Hetscher DD8NE (dd8ne@bnv-bamberg.de)
8 */
9#include <linux/errno.h>
10#include <linux/types.h>
11#include <linux/socket.h>
12#include <linux/in.h>
13#include <linux/kernel.h>
14#include <linux/timer.h>
15#include <linux/string.h>
16#include <linux/sockios.h>
17#include <linux/net.h>
18#include <linux/slab.h>
19#include <net/ax25.h>
20#include <linux/inet.h>
21#include <linux/netdevice.h>
22#include <linux/skbuff.h>
23#include <net/sock.h>
24#include <net/tcp_states.h>
25#include <linux/uaccess.h>
26#include <linux/fcntl.h>
27#include <linux/mm.h>
28#include <linux/interrupt.h>
29
30/*
31 *	Given a fragment, queue it on the fragment queue and if the fragment
32 *	is complete, send it back to ax25_rx_iframe.
33 */
34static int ax25_rx_fragment(ax25_cb *ax25, struct sk_buff *skb)
35{
36	struct sk_buff *skbn, *skbo;
37
38	if (ax25->fragno != 0) {
39		if (!(*skb->data & AX25_SEG_FIRST)) {
40			if ((ax25->fragno - 1) == (*skb->data & AX25_SEG_REM)) {
41				/* Enqueue fragment */
42				ax25->fragno = *skb->data & AX25_SEG_REM;
43				skb_pull(skb, 1);	/* skip fragno */
44				ax25->fraglen += skb->len;
45				skb_queue_tail(&ax25->frag_queue, skb);
46
47				/* Last fragment received ? */
48				if (ax25->fragno == 0) {
49					skbn = alloc_skb(AX25_MAX_HEADER_LEN +
50							 ax25->fraglen,
51							 GFP_ATOMIC);
52					if (!skbn) {
53						skb_queue_purge(&ax25->frag_queue);
54						return 1;
55					}
56
57					skb_reserve(skbn, AX25_MAX_HEADER_LEN);
58
59					skbn->dev   = ax25->ax25_dev->dev;
60					skb_reset_network_header(skbn);
61					skb_reset_transport_header(skbn);
62
63					/* Copy data from the fragments */
64					while ((skbo = skb_dequeue(&ax25->frag_queue)) != NULL) {
65						skb_copy_from_linear_data(skbo,
66							  skb_put(skbn, skbo->len),
67									  skbo->len);
68						kfree_skb(skbo);
69					}
70
71					ax25->fraglen = 0;
72
73					if (ax25_rx_iframe(ax25, skbn) == 0)
74						kfree_skb(skbn);
75				}
76
77				return 1;
78			}
79		}
80	} else {
81		/* First fragment received */
82		if (*skb->data & AX25_SEG_FIRST) {
83			skb_queue_purge(&ax25->frag_queue);
84			ax25->fragno = *skb->data & AX25_SEG_REM;
85			skb_pull(skb, 1);		/* skip fragno */
86			ax25->fraglen = skb->len;
87			skb_queue_tail(&ax25->frag_queue, skb);
88			return 1;
89		}
90	}
91
92	return 0;
93}
94
95/*
96 *	This is where all valid I frames are sent to, to be dispatched to
97 *	whichever protocol requires them.
98 */
99int ax25_rx_iframe(ax25_cb *ax25, struct sk_buff *skb)
100{
101	int (*func)(struct sk_buff *, ax25_cb *);
102	unsigned char pid;
103	int queued = 0;
104
105	if (skb == NULL) return 0;
106
107	ax25_start_idletimer(ax25);
108
109	pid = *skb->data;
110
111	if (pid == AX25_P_IP) {
112		/* working around a TCP bug to keep additional listeners
113		 * happy. TCP re-uses the buffer and destroys the original
114		 * content.
115		 */
116		struct sk_buff *skbn = skb_copy(skb, GFP_ATOMIC);
117		if (skbn != NULL) {
118			kfree_skb(skb);
119			skb = skbn;
120		}
121
122		skb_pull(skb, 1);	/* Remove PID */
123		skb->mac_header = skb->network_header;
124		skb_reset_network_header(skb);
125		skb->dev      = ax25->ax25_dev->dev;
126		skb->pkt_type = PACKET_HOST;
127		skb->protocol = htons(ETH_P_IP);
128		netif_rx(skb);
129		return 1;
130	}
131	if (pid == AX25_P_SEGMENT) {
132		skb_pull(skb, 1);	/* Remove PID */
133		return ax25_rx_fragment(ax25, skb);
134	}
135
136	if ((func = ax25_protocol_function(pid)) != NULL) {
137		skb_pull(skb, 1);	/* Remove PID */
138		return (*func)(skb, ax25);
139	}
140
141	if (ax25->sk != NULL && ax25->ax25_dev->values[AX25_VALUES_CONMODE] == 2) {
142		if ((!ax25->pidincl && ax25->sk->sk_protocol == pid) ||
143		    ax25->pidincl) {
144			if (sock_queue_rcv_skb(ax25->sk, skb) == 0)
145				queued = 1;
146			else
147				ax25->condition |= AX25_COND_OWN_RX_BUSY;
148		}
149	}
150
151	return queued;
152}
153
154/*
155 *	Higher level upcall for a LAPB frame
156 */
157static int ax25_process_rx_frame(ax25_cb *ax25, struct sk_buff *skb, int type, int dama)
158{
159	int queued = 0;
160
161	if (ax25->state == AX25_STATE_0)
162		return 0;
163
164	switch (ax25->ax25_dev->values[AX25_VALUES_PROTOCOL]) {
165	case AX25_PROTO_STD_SIMPLEX:
166	case AX25_PROTO_STD_DUPLEX:
167		queued = ax25_std_frame_in(ax25, skb, type);
168		break;
169
170#ifdef CONFIG_AX25_DAMA_SLAVE
171	case AX25_PROTO_DAMA_SLAVE:
172		if (dama || ax25->ax25_dev->dama.slave)
173			queued = ax25_ds_frame_in(ax25, skb, type);
174		else
175			queued = ax25_std_frame_in(ax25, skb, type);
176		break;
177#endif
178	}
179
180	return queued;
181}
182
183static int ax25_rcv(struct sk_buff *skb, struct net_device *dev,
184		    const ax25_address *dev_addr, struct packet_type *ptype)
185{
186	ax25_address src, dest, *next_digi = NULL;
187	int type = 0, mine = 0, dama;
188	struct sock *make, *sk;
189	ax25_digi dp, reverse_dp;
190	ax25_cb *ax25;
191	ax25_dev *ax25_dev;
192
193	/*
194	 *	Process the AX.25/LAPB frame.
195	 */
196
197	skb_reset_transport_header(skb);
198
199	if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL)
200		goto free;
201
202	/*
203	 *	Parse the address header.
204	 */
205
206	if (ax25_addr_parse(skb->data, skb->len, &src, &dest, &dp, &type, &dama) == NULL)
207		goto free;
208
209	/*
210	 *	Ours perhaps ?
211	 */
212	if (dp.lastrepeat + 1 < dp.ndigi)		/* Not yet digipeated completely */
213		next_digi = &dp.calls[dp.lastrepeat + 1];
214
215	/*
216	 *	Pull of the AX.25 headers leaving the CTRL/PID bytes
217	 */
218	skb_pull(skb, ax25_addr_size(&dp));
219
220	/* For our port addresses ? */
221	if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi)
222		mine = 1;
223
224	/* Also match on any registered callsign from L3/4 */
225	if (!mine && ax25_listen_mine(&dest, dev) && dp.lastrepeat + 1 == dp.ndigi)
226		mine = 1;
227
228	/* UI frame - bypass LAPB processing */
229	if ((*skb->data & ~0x10) == AX25_UI && dp.lastrepeat + 1 == dp.ndigi) {
230		skb_set_transport_header(skb, 2); /* skip control and pid */
231
232		ax25_send_to_raw(&dest, skb, skb->data[1]);
233
234		if (!mine && ax25cmp(&dest, (ax25_address *)dev->broadcast) != 0)
235			goto free;
236
237		/* Now we are pointing at the pid byte */
238		switch (skb->data[1]) {
239		case AX25_P_IP:
240			skb_pull(skb,2);		/* drop PID/CTRL */
241			skb_reset_transport_header(skb);
242			skb_reset_network_header(skb);
243			skb->dev      = dev;
244			skb->pkt_type = PACKET_HOST;
245			skb->protocol = htons(ETH_P_IP);
246			netif_rx(skb);
247			break;
248
249		case AX25_P_ARP:
250			skb_pull(skb,2);
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_ARP);
256			netif_rx(skb);
257			break;
258		case AX25_P_TEXT:
259			/* Now find a suitable dgram socket */
260			sk = ax25_get_socket(&dest, &src, SOCK_DGRAM);
261			if (sk != NULL) {
262				bh_lock_sock(sk);
263				if (atomic_read(&sk->sk_rmem_alloc) >=
264				    sk->sk_rcvbuf) {
265					kfree_skb(skb);
266				} else {
267					/*
268					 *	Remove the control and PID.
269					 */
270					skb_pull(skb, 2);
271					if (sock_queue_rcv_skb(sk, skb) != 0)
272						kfree_skb(skb);
273				}
274				bh_unlock_sock(sk);
275				sock_put(sk);
276			} else {
277				kfree_skb(skb);
278			}
279			break;
280
281		default:
282			kfree_skb(skb);	/* Will scan SOCK_AX25 RAW sockets */
283			break;
284		}
285
286		return 0;
287	}
288
289	/*
290	 *	Is connected mode supported on this device ?
291	 *	If not, should we DM the incoming frame (except DMs) or
292	 *	silently ignore them. For now we stay quiet.
293	 */
294	if (ax25_dev->values[AX25_VALUES_CONMODE] == 0)
295		goto free;
296
297	/* LAPB */
298
299	/* AX.25 state 1-4 */
300
301	ax25_digi_invert(&dp, &reverse_dp);
302
303	if ((ax25 = ax25_find_cb(&dest, &src, &reverse_dp, dev)) != NULL) {
304		/*
305		 *	Process the frame. If it is queued up internally it
306		 *	returns one otherwise we free it immediately. This
307		 *	routine itself wakes the user context layers so we do
308		 *	no further work
309		 */
310		if (ax25_process_rx_frame(ax25, skb, type, dama) == 0)
311			kfree_skb(skb);
312
313		ax25_cb_put(ax25);
314		return 0;
315	}
316
317	/* AX.25 state 0 (disconnected) */
318
319	/* a) received not a SABM(E) */
320
321	if ((*skb->data & ~AX25_PF) != AX25_SABM &&
322	    (*skb->data & ~AX25_PF) != AX25_SABME) {
323		/*
324		 *	Never reply to a DM. Also ignore any connects for
325		 *	addresses that are not our interfaces and not a socket.
326		 */
327		if ((*skb->data & ~AX25_PF) != AX25_DM && mine)
328			ax25_return_dm(dev, &src, &dest, &dp);
329
330		goto free;
331	}
332
333	/* b) received SABM(E) */
334
335	if (dp.lastrepeat + 1 == dp.ndigi)
336		sk = ax25_find_listener(&dest, 0, dev, SOCK_SEQPACKET);
337	else
338		sk = ax25_find_listener(next_digi, 1, dev, SOCK_SEQPACKET);
339
340	if (sk != NULL) {
341		bh_lock_sock(sk);
342		if (sk_acceptq_is_full(sk) ||
343		    (make = ax25_make_new(sk, ax25_dev)) == NULL) {
344			if (mine)
345				ax25_return_dm(dev, &src, &dest, &dp);
346			kfree_skb(skb);
347			bh_unlock_sock(sk);
348			sock_put(sk);
349
350			return 0;
351		}
352
353		ax25 = sk_to_ax25(make);
354		skb_set_owner_r(skb, make);
355		skb_queue_head(&sk->sk_receive_queue, skb);
356
357		make->sk_state = TCP_ESTABLISHED;
358
359		sk_acceptq_added(sk);
360		bh_unlock_sock(sk);
361	} else {
362		if (!mine)
363			goto free;
364
365		if ((ax25 = ax25_create_cb()) == NULL) {
366			ax25_return_dm(dev, &src, &dest, &dp);
367			goto free;
368		}
369
370		ax25_fillin_cb(ax25, ax25_dev);
371	}
372
373	ax25->source_addr = dest;
374	ax25->dest_addr   = src;
375
376	/*
377	 *	Sort out any digipeated paths.
378	 */
379	if (dp.ndigi && !ax25->digipeat &&
380	    (ax25->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) {
381		kfree_skb(skb);
382		ax25_destroy_socket(ax25);
383		if (sk)
384			sock_put(sk);
385		return 0;
386	}
387
388	if (dp.ndigi == 0) {
389		kfree(ax25->digipeat);
390		ax25->digipeat = NULL;
391	} else {
392		/* Reverse the source SABM's path */
393		memcpy(ax25->digipeat, &reverse_dp, sizeof(ax25_digi));
394	}
395
396	if ((*skb->data & ~AX25_PF) == AX25_SABME) {
397		ax25->modulus = AX25_EMODULUS;
398		ax25->window  = ax25_dev->values[AX25_VALUES_EWINDOW];
399	} else {
400		ax25->modulus = AX25_MODULUS;
401		ax25->window  = ax25_dev->values[AX25_VALUES_WINDOW];
402	}
403
404	ax25_send_control(ax25, AX25_UA, AX25_POLLON, AX25_RESPONSE);
405
406#ifdef CONFIG_AX25_DAMA_SLAVE
407	if (dama && ax25->ax25_dev->values[AX25_VALUES_PROTOCOL] == AX25_PROTO_DAMA_SLAVE)
408		ax25_dama_on(ax25);
409#endif
410
411	ax25->state = AX25_STATE_3;
412
413	ax25_cb_add(ax25);
414
415	ax25_start_heartbeat(ax25);
416	ax25_start_t3timer(ax25);
417	ax25_start_idletimer(ax25);
418
419	if (sk) {
420		if (!sock_flag(sk, SOCK_DEAD))
421			sk->sk_data_ready(sk);
422		sock_put(sk);
423	} else {
424free:
425		kfree_skb(skb);
426	}
427	return 0;
428}
429
430/*
431 *	Receive an AX.25 frame via a SLIP interface.
432 */
433int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev,
434		  struct packet_type *ptype, struct net_device *orig_dev)
435{
436	skb_orphan(skb);
437
438	if (!net_eq(dev_net(dev), &init_net)) {
439		kfree_skb(skb);
440		return 0;
441	}
442
443	if ((*skb->data & 0x0F) != 0) {
444		kfree_skb(skb);	/* Not a KISS data frame */
445		return 0;
446	}
447
448	skb_pull(skb, AX25_KISS_HEADER_LEN);	/* Remove the KISS byte */
449
450	return ax25_rcv(skb, dev, (const ax25_address *)dev->dev_addr, ptype);
451}
452