1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	"LAPB via ethernet" driver release 001
4 *
5 *	This code REQUIRES 2.1.15 or higher/ NET3.038
6 *
7 *	This is a "pseudo" network driver to allow LAPB over Ethernet.
8 *
9 *	This driver can use any ethernet destination address, and can be
10 *	limited to accept frames from one dedicated ethernet card only.
11 *
12 *	History
13 *	LAPBETH 001	Jonathan Naylor		Cloned from bpqether.c
14 *	2000-10-29	Henner Eisen	lapb_data_indication() return status.
15 *	2000-11-14	Henner Eisen	dev_hold/put, NETDEV_GOING_DOWN support
16 */
17
18#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19
20#include <linux/errno.h>
21#include <linux/types.h>
22#include <linux/socket.h>
23#include <linux/in.h>
24#include <linux/slab.h>
25#include <linux/kernel.h>
26#include <linux/string.h>
27#include <linux/net.h>
28#include <linux/inet.h>
29#include <linux/netdevice.h>
30#include <linux/if_arp.h>
31#include <linux/skbuff.h>
32#include <net/sock.h>
33#include <linux/uaccess.h>
34#include <linux/mm.h>
35#include <linux/interrupt.h>
36#include <linux/notifier.h>
37#include <linux/stat.h>
38#include <linux/module.h>
39#include <linux/lapb.h>
40#include <linux/init.h>
41
42#include <net/x25device.h>
43
44static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
45
46/* If this number is made larger, check that the temporary string buffer
47 * in lapbeth_new_device is large enough to store the probe device name.*/
48#define MAXLAPBDEV 100
49
50struct lapbethdev {
51	struct list_head	node;
52	struct net_device	*ethdev;	/* link to ethernet device */
53	struct net_device	*axdev;		/* lapbeth device (lapb#) */
54	bool			up;
55	spinlock_t		up_lock;	/* Protects "up" */
56};
57
58static LIST_HEAD(lapbeth_devices);
59
60/* ------------------------------------------------------------------------ */
61
62/*
63 *	Get the LAPB device for the ethernet device
64 */
65static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
66{
67	struct lapbethdev *lapbeth;
68
69	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
70		if (lapbeth->ethdev == dev)
71			return lapbeth;
72	}
73	return NULL;
74}
75
76static __inline__ int dev_is_ethdev(struct net_device *dev)
77{
78	return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
79}
80
81/* ------------------------------------------------------------------------ */
82
83/*
84 *	Receive a LAPB frame via an ethernet interface.
85 */
86static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
87{
88	int len, err;
89	struct lapbethdev *lapbeth;
90
91	if (dev_net(dev) != &init_net)
92		goto drop;
93
94	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
95		return NET_RX_DROP;
96
97	if (!pskb_may_pull(skb, 2))
98		goto drop;
99
100	rcu_read_lock();
101	lapbeth = lapbeth_get_x25_dev(dev);
102	if (!lapbeth)
103		goto drop_unlock_rcu;
104	spin_lock_bh(&lapbeth->up_lock);
105	if (!lapbeth->up)
106		goto drop_unlock;
107
108	len = skb->data[0] + skb->data[1] * 256;
109	dev->stats.rx_packets++;
110	dev->stats.rx_bytes += len;
111
112	skb_pull(skb, 2);	/* Remove the length bytes */
113	skb_trim(skb, len);	/* Set the length of the data */
114
115	if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
116		printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
117		goto drop_unlock;
118	}
119out:
120	spin_unlock_bh(&lapbeth->up_lock);
121	rcu_read_unlock();
122	return 0;
123drop_unlock:
124	kfree_skb(skb);
125	goto out;
126drop_unlock_rcu:
127	rcu_read_unlock();
128drop:
129	kfree_skb(skb);
130	return 0;
131}
132
133static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
134{
135	unsigned char *ptr;
136
137	if (skb_cow(skb, 1)) {
138		kfree_skb(skb);
139		return NET_RX_DROP;
140	}
141
142	skb_push(skb, 1);
143
144	ptr  = skb->data;
145	*ptr = X25_IFACE_DATA;
146
147	skb->protocol = x25_type_trans(skb, dev);
148	return netif_rx(skb);
149}
150
151/*
152 *	Send a LAPB frame via an ethernet interface
153 */
154static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
155				      struct net_device *dev)
156{
157	struct lapbethdev *lapbeth = netdev_priv(dev);
158	int err;
159
160	spin_lock_bh(&lapbeth->up_lock);
161	if (!lapbeth->up)
162		goto drop;
163
164	/* There should be a pseudo header of 1 byte added by upper layers.
165	 * Check to make sure it is there before reading it.
166	 */
167	if (skb->len < 1)
168		goto drop;
169
170	switch (skb->data[0]) {
171	case X25_IFACE_DATA:
172		break;
173	case X25_IFACE_CONNECT:
174		if ((err = lapb_connect_request(dev)) != LAPB_OK)
175			pr_err("lapb_connect_request error: %d\n", err);
176		goto drop;
177	case X25_IFACE_DISCONNECT:
178		if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
179			pr_err("lapb_disconnect_request err: %d\n", err);
180		fallthrough;
181	default:
182		goto drop;
183	}
184
185	skb_pull(skb, 1);
186
187	if ((err = lapb_data_request(dev, skb)) != LAPB_OK) {
188		pr_err("lapb_data_request error - %d\n", err);
189		goto drop;
190	}
191out:
192	spin_unlock_bh(&lapbeth->up_lock);
193	return NETDEV_TX_OK;
194drop:
195	kfree_skb(skb);
196	goto out;
197}
198
199static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
200{
201	struct lapbethdev *lapbeth = netdev_priv(ndev);
202	unsigned char *ptr;
203	struct net_device *dev;
204	int size = skb->len;
205
206	ptr = skb_push(skb, 2);
207
208	*ptr++ = size % 256;
209	*ptr++ = size / 256;
210
211	ndev->stats.tx_packets++;
212	ndev->stats.tx_bytes += size;
213
214	skb->dev = dev = lapbeth->ethdev;
215
216	skb->protocol = htons(ETH_P_DEC);
217
218	skb_reset_network_header(skb);
219
220	dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
221
222	dev_queue_xmit(skb);
223}
224
225static void lapbeth_connected(struct net_device *dev, int reason)
226{
227	unsigned char *ptr;
228	struct sk_buff *skb = dev_alloc_skb(1);
229
230	if (!skb) {
231		pr_err("out of memory\n");
232		return;
233	}
234
235	ptr  = skb_put(skb, 1);
236	*ptr = X25_IFACE_CONNECT;
237
238	skb->protocol = x25_type_trans(skb, dev);
239	netif_rx(skb);
240}
241
242static void lapbeth_disconnected(struct net_device *dev, int reason)
243{
244	unsigned char *ptr;
245	struct sk_buff *skb = dev_alloc_skb(1);
246
247	if (!skb) {
248		pr_err("out of memory\n");
249		return;
250	}
251
252	ptr  = skb_put(skb, 1);
253	*ptr = X25_IFACE_DISCONNECT;
254
255	skb->protocol = x25_type_trans(skb, dev);
256	netif_rx(skb);
257}
258
259/*
260 *	Set AX.25 callsign
261 */
262static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
263{
264	struct sockaddr *sa = addr;
265	memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
266	return 0;
267}
268
269
270static const struct lapb_register_struct lapbeth_callbacks = {
271	.connect_confirmation    = lapbeth_connected,
272	.connect_indication      = lapbeth_connected,
273	.disconnect_confirmation = lapbeth_disconnected,
274	.disconnect_indication   = lapbeth_disconnected,
275	.data_indication         = lapbeth_data_indication,
276	.data_transmit           = lapbeth_data_transmit,
277};
278
279/*
280 * open/close a device
281 */
282static int lapbeth_open(struct net_device *dev)
283{
284	struct lapbethdev *lapbeth = netdev_priv(dev);
285	int err;
286
287	if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
288		pr_err("lapb_register error: %d\n", err);
289		return -ENODEV;
290	}
291
292	spin_lock_bh(&lapbeth->up_lock);
293	lapbeth->up = true;
294	spin_unlock_bh(&lapbeth->up_lock);
295
296	return 0;
297}
298
299static int lapbeth_close(struct net_device *dev)
300{
301	struct lapbethdev *lapbeth = netdev_priv(dev);
302	int err;
303
304	spin_lock_bh(&lapbeth->up_lock);
305	lapbeth->up = false;
306	spin_unlock_bh(&lapbeth->up_lock);
307
308	if ((err = lapb_unregister(dev)) != LAPB_OK)
309		pr_err("lapb_unregister error: %d\n", err);
310
311	return 0;
312}
313
314/* ------------------------------------------------------------------------ */
315
316static const struct net_device_ops lapbeth_netdev_ops = {
317	.ndo_open	     = lapbeth_open,
318	.ndo_stop	     = lapbeth_close,
319	.ndo_start_xmit	     = lapbeth_xmit,
320	.ndo_set_mac_address = lapbeth_set_mac_address,
321};
322
323static void lapbeth_setup(struct net_device *dev)
324{
325	dev->netdev_ops	     = &lapbeth_netdev_ops;
326	dev->needs_free_netdev = true;
327	dev->type            = ARPHRD_X25;
328	dev->hard_header_len = 0;
329	dev->mtu             = 1000;
330	dev->addr_len        = 0;
331}
332
333/*
334 *	Setup a new device.
335 */
336static int lapbeth_new_device(struct net_device *dev)
337{
338	struct net_device *ndev;
339	struct lapbethdev *lapbeth;
340	int rc = -ENOMEM;
341
342	ASSERT_RTNL();
343
344	if (dev->type != ARPHRD_ETHER)
345		return -EINVAL;
346
347	ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
348			    lapbeth_setup);
349	if (!ndev)
350		goto out;
351
352	/* When transmitting data:
353	 * first this driver removes a pseudo header of 1 byte,
354	 * then the lapb module prepends an LAPB header of at most 3 bytes,
355	 * then this driver prepends a length field of 2 bytes,
356	 * then the underlying Ethernet device prepends its own header.
357	 */
358	ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
359					   + dev->needed_headroom;
360	ndev->needed_tailroom = dev->needed_tailroom;
361
362	lapbeth = netdev_priv(ndev);
363	lapbeth->axdev = ndev;
364
365	dev_hold(dev);
366	lapbeth->ethdev = dev;
367
368	lapbeth->up = false;
369	spin_lock_init(&lapbeth->up_lock);
370
371	rc = -EIO;
372	if (register_netdevice(ndev))
373		goto fail;
374
375	list_add_rcu(&lapbeth->node, &lapbeth_devices);
376	rc = 0;
377out:
378	return rc;
379fail:
380	dev_put(dev);
381	free_netdev(ndev);
382	goto out;
383}
384
385/*
386 *	Free a lapb network device.
387 */
388static void lapbeth_free_device(struct lapbethdev *lapbeth)
389{
390	dev_put(lapbeth->ethdev);
391	list_del_rcu(&lapbeth->node);
392	unregister_netdevice(lapbeth->axdev);
393}
394
395/*
396 *	Handle device status changes.
397 *
398 * Called from notifier with RTNL held.
399 */
400static int lapbeth_device_event(struct notifier_block *this,
401				unsigned long event, void *ptr)
402{
403	struct lapbethdev *lapbeth;
404	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
405
406	if (dev_net(dev) != &init_net)
407		return NOTIFY_DONE;
408
409	if (!dev_is_ethdev(dev) && !lapbeth_get_x25_dev(dev))
410		return NOTIFY_DONE;
411
412	switch (event) {
413	case NETDEV_UP:
414		/* New ethernet device -> new LAPB interface	 */
415		if (lapbeth_get_x25_dev(dev) == NULL)
416			lapbeth_new_device(dev);
417		break;
418	case NETDEV_DOWN:
419		/* ethernet device closed -> close LAPB interface */
420		lapbeth = lapbeth_get_x25_dev(dev);
421		if (lapbeth)
422			dev_close(lapbeth->axdev);
423		break;
424	case NETDEV_UNREGISTER:
425		/* ethernet device disappears -> remove LAPB interface */
426		lapbeth = lapbeth_get_x25_dev(dev);
427		if (lapbeth)
428			lapbeth_free_device(lapbeth);
429		break;
430	}
431
432	return NOTIFY_DONE;
433}
434
435/* ------------------------------------------------------------------------ */
436
437static struct packet_type lapbeth_packet_type __read_mostly = {
438	.type = cpu_to_be16(ETH_P_DEC),
439	.func = lapbeth_rcv,
440};
441
442static struct notifier_block lapbeth_dev_notifier = {
443	.notifier_call = lapbeth_device_event,
444};
445
446static const char banner[] __initconst =
447	KERN_INFO "LAPB Ethernet driver version 0.02\n";
448
449static int __init lapbeth_init_driver(void)
450{
451	dev_add_pack(&lapbeth_packet_type);
452
453	register_netdevice_notifier(&lapbeth_dev_notifier);
454
455	printk(banner);
456
457	return 0;
458}
459module_init(lapbeth_init_driver);
460
461static void __exit lapbeth_cleanup_driver(void)
462{
463	struct lapbethdev *lapbeth;
464	struct list_head *entry, *tmp;
465
466	dev_remove_pack(&lapbeth_packet_type);
467	unregister_netdevice_notifier(&lapbeth_dev_notifier);
468
469	rtnl_lock();
470	list_for_each_safe(entry, tmp, &lapbeth_devices) {
471		lapbeth = list_entry(entry, struct lapbethdev, node);
472
473		dev_put(lapbeth->ethdev);
474		unregister_netdevice(lapbeth->axdev);
475	}
476	rtnl_unlock();
477}
478module_exit(lapbeth_cleanup_driver);
479
480MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
481MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
482MODULE_LICENSE("GPL");
483