lapbether.c

  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/netdev_lock.h>
 43#include <net/x25device.h>
 44
 45static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 46
 47/* If this number is made larger, check that the temporary string buffer
 48 * in lapbeth_new_device is large enough to store the probe device name.
 49 */
 50#define MAXLAPBDEV 100
 51
 52struct lapbethdev {
 53	struct list_head	node;
 54	struct net_device	*ethdev;	/* link to ethernet device */
 55	struct net_device	*axdev;		/* lapbeth device (lapb#) */
 56	bool			up;
 57	spinlock_t		up_lock;	/* Protects "up" */
 58	struct sk_buff_head	rx_queue;
 59	struct napi_struct	napi;
 60};
 61
 62static LIST_HEAD(lapbeth_devices);
 63
 64static void lapbeth_connected(struct net_device *dev, int reason);
 65static void lapbeth_disconnected(struct net_device *dev, int reason);
 66
 67/* ------------------------------------------------------------------------ */
 68
 69/*	Get the LAPB device for the ethernet device
 70 */
 71static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
 72{
 73	struct lapbethdev *lapbeth;
 74
 75	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
 76		if (lapbeth->ethdev == dev)
 77			return lapbeth;
 78	}
 79	return NULL;
 80}
 81
 82static __inline__ int dev_is_ethdev(struct net_device *dev)
 83{
 84	return dev->type == ARPHRD_ETHER && !netdev_need_ops_lock(dev);
 85}
 86
 87/* ------------------------------------------------------------------------ */
 88
 89static int lapbeth_napi_poll(struct napi_struct *napi, int budget)
 90{
 91	struct lapbethdev *lapbeth = container_of(napi, struct lapbethdev,
 92						  napi);
 93	struct sk_buff *skb;
 94	int processed = 0;
 95
 96	for (; processed < budget; ++processed) {
 97		skb = skb_dequeue(&lapbeth->rx_queue);
 98		if (!skb)
 99			break;
100		netif_receive_skb_core(skb);
101	}
102
103	if (processed < budget)
104		napi_complete(napi);
105
106	return processed;
107}
108
109/*	Receive a LAPB frame via an ethernet interface.
110 */
111static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev,
112		       struct packet_type *ptype, struct net_device *orig_dev)
113{
114	int len, err;
115	struct lapbethdev *lapbeth;
116
117	if (dev_net(dev) != &init_net)
118		goto drop;
119
120	skb = skb_share_check(skb, GFP_ATOMIC);
121	if (!skb)
122		return NET_RX_DROP;
123
124	if (!pskb_may_pull(skb, 2))
125		goto drop;
126
127	rcu_read_lock();
128	lapbeth = lapbeth_get_x25_dev(dev);
129	if (!lapbeth)
130		goto drop_unlock_rcu;
131	spin_lock_bh(&lapbeth->up_lock);
132	if (!lapbeth->up)
133		goto drop_unlock;
134
135	len = skb->data[0] + skb->data[1] * 256;
136	dev->stats.rx_packets++;
137	dev->stats.rx_bytes += len;
138
139	skb_pull(skb, 2);	/* Remove the length bytes */
140	skb_trim(skb, len);	/* Set the length of the data */
141
142	err = lapb_data_received(lapbeth->axdev, skb);
143	if (err != LAPB_OK) {
144		printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
145		goto drop_unlock;
146	}
147out:
148	spin_unlock_bh(&lapbeth->up_lock);
149	rcu_read_unlock();
150	return 0;
151drop_unlock:
152	kfree_skb(skb);
153	goto out;
154drop_unlock_rcu:
155	rcu_read_unlock();
156drop:
157	kfree_skb(skb);
158	return 0;
159}
160
161static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
162{
163	struct lapbethdev *lapbeth = netdev_priv(dev);
164	unsigned char *ptr;
165
166	if (skb_cow(skb, 1)) {
167		kfree_skb(skb);
168		return NET_RX_DROP;
169	}
170
171	skb_push(skb, 1);
172
173	ptr  = skb->data;
174	*ptr = X25_IFACE_DATA;
175
176	skb->protocol = x25_type_trans(skb, dev);
177
178	skb_queue_tail(&lapbeth->rx_queue, skb);
179	napi_schedule(&lapbeth->napi);
180	return NET_RX_SUCCESS;
181}
182
183/*	Send a LAPB frame via an ethernet interface
184 */
185static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
186				struct net_device *dev)
187{
188	struct lapbethdev *lapbeth = netdev_priv(dev);
189	int err;
190
191	spin_lock_bh(&lapbeth->up_lock);
192	if (!lapbeth->up)
193		goto drop;
194
195	/* There should be a pseudo header of 1 byte added by upper layers.
196	 * Check to make sure it is there before reading it.
197	 */
198	if (skb->len < 1)
199		goto drop;
200
201	switch (skb->data[0]) {
202	case X25_IFACE_DATA:
203		break;
204	case X25_IFACE_CONNECT:
205		err = lapb_connect_request(dev);
206		if (err == LAPB_CONNECTED)
207			lapbeth_connected(dev, LAPB_OK);
208		else if (err != LAPB_OK)
209			pr_err("lapb_connect_request error: %d\n", err);
210		goto drop;
211	case X25_IFACE_DISCONNECT:
212		err = lapb_disconnect_request(dev);
213		if (err == LAPB_NOTCONNECTED)
214			lapbeth_disconnected(dev, LAPB_OK);
215		else if (err != LAPB_OK)
216			pr_err("lapb_disconnect_request err: %d\n", err);
217		fallthrough;
218	default:
219		goto drop;
220	}
221
222	skb_pull(skb, 1);
223
224	err = lapb_data_request(dev, skb);
225	if (err != LAPB_OK) {
226		pr_err("lapb_data_request error - %d\n", err);
227		goto drop;
228	}
229out:
230	spin_unlock_bh(&lapbeth->up_lock);
231	return NETDEV_TX_OK;
232drop:
233	kfree_skb(skb);
234	goto out;
235}
236
237static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
238{
239	struct lapbethdev *lapbeth = netdev_priv(ndev);
240	unsigned char *ptr;
241	struct net_device *dev;
242	int size = skb->len;
243
244	ptr = skb_push(skb, 2);
245
246	*ptr++ = size % 256;
247	*ptr++ = size / 256;
248
249	ndev->stats.tx_packets++;
250	ndev->stats.tx_bytes += size;
251
252	skb->dev = dev = lapbeth->ethdev;
253
254	skb->protocol = htons(ETH_P_DEC);
255
256	skb_reset_network_header(skb);
257
258	dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);
259
260	dev_queue_xmit(skb);
261}
262
263static void lapbeth_connected(struct net_device *dev, int reason)
264{
265	struct lapbethdev *lapbeth = netdev_priv(dev);
266	unsigned char *ptr;
267	struct sk_buff *skb = __dev_alloc_skb(1, GFP_ATOMIC | __GFP_NOMEMALLOC);
268
269	if (!skb)
270		return;
271
272	ptr  = skb_put(skb, 1);
273	*ptr = X25_IFACE_CONNECT;
274
275	skb->protocol = x25_type_trans(skb, dev);
276
277	skb_queue_tail(&lapbeth->rx_queue, skb);
278	napi_schedule(&lapbeth->napi);
279}
280
281static void lapbeth_disconnected(struct net_device *dev, int reason)
282{
283	struct lapbethdev *lapbeth = netdev_priv(dev);
284	unsigned char *ptr;
285	struct sk_buff *skb = __dev_alloc_skb(1, GFP_ATOMIC | __GFP_NOMEMALLOC);
286
287	if (!skb)
288		return;
289
290	ptr  = skb_put(skb, 1);
291	*ptr = X25_IFACE_DISCONNECT;
292
293	skb->protocol = x25_type_trans(skb, dev);
294
295	skb_queue_tail(&lapbeth->rx_queue, skb);
296	napi_schedule(&lapbeth->napi);
297}
298
299/*	Set AX.25 callsign
300 */
301static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
302{
303	struct sockaddr *sa = addr;
304
305	dev_addr_set(dev, sa->sa_data);
306	return 0;
307}
308
309static const struct lapb_register_struct lapbeth_callbacks = {
310	.connect_confirmation    = lapbeth_connected,
311	.connect_indication      = lapbeth_connected,
312	.disconnect_confirmation = lapbeth_disconnected,
313	.disconnect_indication   = lapbeth_disconnected,
314	.data_indication         = lapbeth_data_indication,
315	.data_transmit           = lapbeth_data_transmit,
316};
317
318/* open/close a device
319 */
320static int lapbeth_open(struct net_device *dev)
321{
322	struct lapbethdev *lapbeth = netdev_priv(dev);
323	int err;
324
325	napi_enable(&lapbeth->napi);
326
327	err = lapb_register(dev, &lapbeth_callbacks);
328	if (err != LAPB_OK) {
329		napi_disable(&lapbeth->napi);
330		pr_err("lapb_register error: %d\n", err);
331		return -ENODEV;
332	}
333
334	spin_lock_bh(&lapbeth->up_lock);
335	lapbeth->up = true;
336	spin_unlock_bh(&lapbeth->up_lock);
337
338	return 0;
339}
340
341static int lapbeth_close(struct net_device *dev)
342{
343	struct lapbethdev *lapbeth = netdev_priv(dev);
344	int err;
345
346	spin_lock_bh(&lapbeth->up_lock);
347	lapbeth->up = false;
348	spin_unlock_bh(&lapbeth->up_lock);
349
350	err = lapb_unregister(dev);
351	if (err != LAPB_OK)
352		pr_err("lapb_unregister error: %d\n", err);
353
354	napi_disable(&lapbeth->napi);
355
356	return 0;
357}
358
359/* ------------------------------------------------------------------------ */
360
361static const struct net_device_ops lapbeth_netdev_ops = {
362	.ndo_open	     = lapbeth_open,
363	.ndo_stop	     = lapbeth_close,
364	.ndo_start_xmit	     = lapbeth_xmit,
365	.ndo_set_mac_address = lapbeth_set_mac_address,
366};
367
368static void lapbeth_setup(struct net_device *dev)
369{
370	netdev_lockdep_set_classes(dev);
371	dev->netdev_ops	     = &lapbeth_netdev_ops;
372	dev->needs_free_netdev = true;
373	dev->type            = ARPHRD_X25;
374	dev->hard_header_len = 0;
375	dev->mtu             = 1000;
376	dev->addr_len        = 0;
377}
378
379/*	Setup a new device.
380 */
381static int lapbeth_new_device(struct net_device *dev)
382{
383	struct net_device *ndev;
384	struct lapbethdev *lapbeth;
385	int rc = -ENOMEM;
386
387	ASSERT_RTNL();
388
389	if (dev->type != ARPHRD_ETHER)
390		return -EINVAL;
391
392	ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", NET_NAME_UNKNOWN,
393			    lapbeth_setup);
394	if (!ndev)
395		goto out;
396
397	/* When transmitting data:
398	 * first this driver removes a pseudo header of 1 byte,
399	 * then the lapb module prepends an LAPB header of at most 3 bytes,
400	 * then this driver prepends a length field of 2 bytes,
401	 * then the underlying Ethernet device prepends its own header.
402	 */
403	ndev->needed_headroom = -1 + 3 + 2 + dev->hard_header_len
404					   + dev->needed_headroom;
405	ndev->needed_tailroom = dev->needed_tailroom;
406
407	lapbeth = netdev_priv(ndev);
408	lapbeth->axdev = ndev;
409
410	dev_hold(dev);
411	lapbeth->ethdev = dev;
412
413	lapbeth->up = false;
414	spin_lock_init(&lapbeth->up_lock);
415
416	skb_queue_head_init(&lapbeth->rx_queue);
417	netif_napi_add_weight(ndev, &lapbeth->napi, lapbeth_napi_poll, 16);
418
419	rc = -EIO;
420	if (register_netdevice(ndev))
421		goto fail;
422
423	list_add_rcu(&lapbeth->node, &lapbeth_devices);
424	rc = 0;
425out:
426	return rc;
427fail:
428	dev_put(dev);
429	free_netdev(ndev);
430	goto out;
431}
432
433/*	Free a lapb network device.
434 */
435static void lapbeth_free_device(struct lapbethdev *lapbeth)
436{
437	dev_put(lapbeth->ethdev);
438	list_del_rcu(&lapbeth->node);
439	unregister_netdevice(lapbeth->axdev);
440}
441
442/*	Handle device status changes.
443 *
444 * Called from notifier with RTNL held.
445 */
446static int lapbeth_device_event(struct notifier_block *this,
447				unsigned long event, void *ptr)
448{
449	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
450	struct lapbethdev *lapbeth;
451
452	if (dev_net(dev) != &init_net)
453		return NOTIFY_DONE;
454
455	lapbeth = lapbeth_get_x25_dev(dev);
456	if (!dev_is_ethdev(dev) && !lapbeth)
457		return NOTIFY_DONE;
458
459	switch (event) {
460	case NETDEV_UP:
461		/* New ethernet device -> new LAPB interface	 */
462		if (!lapbeth)
463			lapbeth_new_device(dev);
464		break;
465	case NETDEV_GOING_DOWN:
466		/* ethernet device closes -> close LAPB interface */
467		if (lapbeth)
468			dev_close(lapbeth->axdev);
469		break;
470	case NETDEV_UNREGISTER:
471		/* ethernet device disappears -> remove LAPB interface */
472		if (lapbeth)
473			lapbeth_free_device(lapbeth);
474		break;
475	case NETDEV_PRE_TYPE_CHANGE:
476		/* Our underlying device type must not change. */
477		if (lapbeth)
478			return NOTIFY_BAD;
479	}
480
481	return NOTIFY_DONE;
482}
483
484/* ------------------------------------------------------------------------ */
485
486static struct packet_type lapbeth_packet_type __read_mostly = {
487	.type = cpu_to_be16(ETH_P_DEC),
488	.func = lapbeth_rcv,
489};
490
491static struct notifier_block lapbeth_dev_notifier = {
492	.notifier_call = lapbeth_device_event,
493};
494
495static const char banner[] __initconst =
496	KERN_INFO "LAPB Ethernet driver version 0.02\n";
497
498static int __init lapbeth_init_driver(void)
499{
500	dev_add_pack(&lapbeth_packet_type);
501
502	register_netdevice_notifier(&lapbeth_dev_notifier);
503
504	printk(banner);
505
506	return 0;
507}
508module_init(lapbeth_init_driver);
509
510static void __exit lapbeth_cleanup_driver(void)
511{
512	struct lapbethdev *lapbeth;
513	struct list_head *entry, *tmp;
514
515	dev_remove_pack(&lapbeth_packet_type);
516	unregister_netdevice_notifier(&lapbeth_dev_notifier);
517
518	rtnl_lock();
519	list_for_each_safe(entry, tmp, &lapbeth_devices) {
520		lapbeth = list_entry(entry, struct lapbethdev, node);
521
522		dev_put(lapbeth->ethdev);
523		unregister_netdevice(lapbeth->axdev);
524	}
525	rtnl_unlock();
526}
527module_exit(lapbeth_cleanup_driver);
528
529MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
530MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
531MODULE_LICENSE("GPL");