1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	G8BPQ compatible "AX.25 via ethernet" driver release 004
4 *
5 *	This code REQUIRES 2.0.0 or higher/ NET3.029
6 *
7 *	This is a "pseudo" network driver to allow AX.25 over Ethernet
8 *	using G8BPQ encapsulation. It has been extracted from the protocol
9 *	implementation because
10 *
11 *		- things got unreadable within the protocol stack
12 *		- to cure the protocol stack from "feature-ism"
13 *		- a protocol implementation shouldn't need to know on
14 *		  which hardware it is running
15 *		- user-level programs like the AX.25 utilities shouldn't
16 *		  need to know about the hardware.
17 *		- IP over ethernet encapsulated AX.25 was impossible
18 *		- rxecho.c did not work
19 *		- to have room for extensions
20 *		- it just deserves to "live" as an own driver
21 *
22 *	This driver can use any ethernet destination address, and can be
23 *	limited to accept frames from one dedicated ethernet card only.
24 *
25 *	Note that the driver sets up the BPQ devices automagically on
26 *	startup or (if started before the "insmod" of an ethernet device)
27 *	on "ifconfig up". It hopefully will remove the BPQ on "rmmod"ing
28 *	the ethernet device (in fact: as soon as another ethernet or bpq
29 *	device gets "ifconfig"ured).
30 *
31 *	I have heard that several people are thinking of experiments
32 *	with highspeed packet radio using existing ethernet cards.
33 *	Well, this driver is prepared for this purpose, just add
34 *	your tx key control and a txdelay / tailtime algorithm,
35 *	probably some buffering, and /voila/...
36 *
37 *	History
38 *	BPQ   001	Joerg(DL1BKE)		Extracted BPQ code from AX.25
39 *						protocol stack and added my own
40 *						yet existing patches
41 *	BPQ   002	Joerg(DL1BKE)		Scan network device list on
42 *						startup.
43 *	BPQ   003	Joerg(DL1BKE)		Ethernet destination address
44 *						and accepted source address
45 *						can be configured by an ioctl()
46 *						call.
47 *						Fixed to match Linux networking
48 *						changes - 2.1.15.
49 *	BPQ   004	Joerg(DL1BKE)		Fixed to not lock up on ifconfig.
50 */
51
52#include <linux/errno.h>
53#include <linux/types.h>
54#include <linux/socket.h>
55#include <linux/in.h>
56#include <linux/kernel.h>
57#include <linux/string.h>
58#include <linux/net.h>
59#include <linux/slab.h>
60#include <net/ax25.h>
61#include <linux/inet.h>
62#include <linux/netdevice.h>
63#include <linux/etherdevice.h>
64#include <linux/if_arp.h>
65#include <linux/skbuff.h>
66#include <net/sock.h>
67#include <linux/uaccess.h>
68#include <linux/mm.h>
69#include <linux/interrupt.h>
70#include <linux/notifier.h>
71#include <linux/proc_fs.h>
72#include <linux/seq_file.h>
73#include <linux/stat.h>
74#include <linux/module.h>
75#include <linux/init.h>
76#include <linux/rtnetlink.h>
77
78#include <net/ip.h>
79#include <net/arp.h>
80#include <net/net_namespace.h>
81
82#include <linux/bpqether.h>
83
84static const char banner[] __initconst = KERN_INFO \
85	"AX.25: bpqether driver version 004\n";
86
87static int bpq_rcv(struct sk_buff *, struct net_device *, struct packet_type *, struct net_device *);
88static int bpq_device_event(struct notifier_block *, unsigned long, void *);
89
90static struct packet_type bpq_packet_type __read_mostly = {
91	.type	= cpu_to_be16(ETH_P_BPQ),
92	.func	= bpq_rcv,
93};
94
95static struct notifier_block bpq_dev_notifier = {
96	.notifier_call = bpq_device_event,
97};
98
99
100struct bpqdev {
101	struct list_head bpq_list;	/* list of bpq devices chain */
102	struct net_device *ethdev;	/* link to ethernet device */
103	struct net_device *axdev;	/* bpq device (bpq#) */
104	char   dest_addr[6];		/* ether destination address */
105	char   acpt_addr[6];		/* accept ether frames from this address only */
106};
107
108static LIST_HEAD(bpq_devices);
109
110/*
111 * bpqether network devices are paired with ethernet devices below them, so
112 * form a special "super class" of normal ethernet devices; split their locks
113 * off into a separate class since they always nest.
114 */
115static struct lock_class_key bpq_netdev_xmit_lock_key;
116static struct lock_class_key bpq_netdev_addr_lock_key;
117
118static void bpq_set_lockdep_class_one(struct net_device *dev,
119				      struct netdev_queue *txq,
120				      void *_unused)
121{
122	lockdep_set_class(&txq->_xmit_lock, &bpq_netdev_xmit_lock_key);
123}
124
125static void bpq_set_lockdep_class(struct net_device *dev)
126{
127	lockdep_set_class(&dev->addr_list_lock, &bpq_netdev_addr_lock_key);
128	netdev_for_each_tx_queue(dev, bpq_set_lockdep_class_one, NULL);
129}
130
131/* ------------------------------------------------------------------------ */
132
133
134/*
135 *	Get the ethernet device for a BPQ device
136 */
137static inline struct net_device *bpq_get_ether_dev(struct net_device *dev)
138{
139	struct bpqdev *bpq = netdev_priv(dev);
140
141	return bpq ? bpq->ethdev : NULL;
142}
143
144/*
145 *	Get the BPQ device for the ethernet device
146 */
147static inline struct net_device *bpq_get_ax25_dev(struct net_device *dev)
148{
149	struct bpqdev *bpq;
150
151	list_for_each_entry_rcu(bpq, &bpq_devices, bpq_list,
152				lockdep_rtnl_is_held()) {
153		if (bpq->ethdev == dev)
154			return bpq->axdev;
155	}
156	return NULL;
157}
158
159static inline int dev_is_ethdev(struct net_device *dev)
160{
161	return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
162}
163
164/* ------------------------------------------------------------------------ */
165
166
167/*
168 *	Receive an AX.25 frame via an ethernet interface.
169 */
170static int bpq_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
171{
172	int len;
173	char * ptr;
174	struct ethhdr *eth;
175	struct bpqdev *bpq;
176
177	if (!net_eq(dev_net(dev), &init_net))
178		goto drop;
179
180	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
181		return NET_RX_DROP;
182
183	if (!pskb_may_pull(skb, sizeof(struct ethhdr)))
184		goto drop;
185
186	rcu_read_lock();
187	dev = bpq_get_ax25_dev(dev);
188
189	if (dev == NULL || !netif_running(dev))
190		goto drop_unlock;
191
192	/*
193	 * if we want to accept frames from just one ethernet device
194	 * we check the source address of the sender.
195	 */
196
197	bpq = netdev_priv(dev);
198
199	eth = eth_hdr(skb);
200
201	if (!(bpq->acpt_addr[0] & 0x01) &&
202	    !ether_addr_equal(eth->h_source, bpq->acpt_addr))
203		goto drop_unlock;
204
205	if (skb_cow(skb, sizeof(struct ethhdr)))
206		goto drop_unlock;
207
208	len = skb->data[0] + skb->data[1] * 256 - 5;
209
210	skb_pull(skb, 2);	/* Remove the length bytes */
211	skb_trim(skb, len);	/* Set the length of the data */
212
213	dev->stats.rx_packets++;
214	dev->stats.rx_bytes += len;
215
216	ptr = skb_push(skb, 1);
217	*ptr = 0;
218
219	skb->protocol = ax25_type_trans(skb, dev);
220	netif_rx(skb);
221unlock:
222
223	rcu_read_unlock();
224
225	return 0;
226drop_unlock:
227	kfree_skb(skb);
228	goto unlock;
229
230drop:
231	kfree_skb(skb);
232	return 0;
233}
234
235/*
236 * 	Send an AX.25 frame via an ethernet interface
237 */
238static netdev_tx_t bpq_xmit(struct sk_buff *skb, struct net_device *dev)
239{
240	unsigned char *ptr;
241	struct bpqdev *bpq;
242	struct net_device *orig_dev;
243	int size;
244
245	if (skb->protocol == htons(ETH_P_IP))
246		return ax25_ip_xmit(skb);
247
248	/*
249	 * Just to be *really* sure not to send anything if the interface
250	 * is down, the ethernet device may have gone.
251	 */
252	if (!netif_running(dev)) {
253		kfree_skb(skb);
254		return NETDEV_TX_OK;
255	}
256
257	skb_pull(skb, 1);			/* Drop KISS byte */
258	size = skb->len;
259
260	/*
261	 * We're about to mess with the skb which may still shared with the
262	 * generic networking code so unshare and ensure it's got enough
263	 * space for the BPQ headers.
264	 */
265	if (skb_cow(skb, AX25_BPQ_HEADER_LEN)) {
266		if (net_ratelimit())
267			pr_err("bpqether: out of memory\n");
268		kfree_skb(skb);
269
270		return NETDEV_TX_OK;
271	}
272
273	ptr = skb_push(skb, 2);			/* Make space for length */
274
275	*ptr++ = (size + 5) % 256;
276	*ptr++ = (size + 5) / 256;
277
278	bpq = netdev_priv(dev);
279
280	orig_dev = dev;
281	if ((dev = bpq_get_ether_dev(dev)) == NULL) {
282		orig_dev->stats.tx_dropped++;
283		kfree_skb(skb);
284		return NETDEV_TX_OK;
285	}
286
287	skb->protocol = ax25_type_trans(skb, dev);
288	skb_reset_network_header(skb);
289	dev_hard_header(skb, dev, ETH_P_BPQ, bpq->dest_addr, NULL, 0);
290	dev->stats.tx_packets++;
291	dev->stats.tx_bytes+=skb->len;
292
293	dev_queue_xmit(skb);
294	netif_wake_queue(dev);
295	return NETDEV_TX_OK;
296}
297
298/*
299 *	Set AX.25 callsign
300 */
301static int bpq_set_mac_address(struct net_device *dev, void *addr)
302{
303    struct sockaddr *sa = (struct sockaddr *)addr;
304
305    dev_addr_set(dev, sa->sa_data);
306
307    return 0;
308}
309
310/*	Ioctl commands
311 *
312 *		SIOCSBPQETHOPT		reserved for enhancements
313 *		SIOCSBPQETHADDR		set the destination and accepted
314 *					source ethernet address (broadcast
315 *					or multicast: accept all)
316 */
317static int bpq_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
318			      void __user *data, int cmd)
319{
320	struct bpq_ethaddr __user *ethaddr = data;
321	struct bpqdev *bpq = netdev_priv(dev);
322	struct bpq_req req;
323
324	if (!capable(CAP_NET_ADMIN))
325		return -EPERM;
326
327	switch (cmd) {
328		case SIOCSBPQETHOPT:
329			if (copy_from_user(&req, data, sizeof(struct bpq_req)))
330				return -EFAULT;
331			switch (req.cmd) {
332				case SIOCGBPQETHPARAM:
333				case SIOCSBPQETHPARAM:
334				default:
335					return -EINVAL;
336			}
337
338			break;
339
340		case SIOCSBPQETHADDR:
341			if (copy_from_user(bpq->dest_addr, ethaddr->destination, ETH_ALEN))
342				return -EFAULT;
343			if (copy_from_user(bpq->acpt_addr, ethaddr->accept, ETH_ALEN))
344				return -EFAULT;
345			break;
346
347		default:
348			return -EINVAL;
349	}
350
351	return 0;
352}
353
354/*
355 * open/close a device
356 */
357static int bpq_open(struct net_device *dev)
358{
359	netif_start_queue(dev);
360	return 0;
361}
362
363static int bpq_close(struct net_device *dev)
364{
365	netif_stop_queue(dev);
366	return 0;
367}
368
369
370/* ------------------------------------------------------------------------ */
371
372#ifdef CONFIG_PROC_FS
373/*
374 *	Proc filesystem
375 */
376static void *bpq_seq_start(struct seq_file *seq, loff_t *pos)
377	__acquires(RCU)
378{
379	int i = 1;
380	struct bpqdev *bpqdev;
381
382	rcu_read_lock();
383
384	if (*pos == 0)
385		return SEQ_START_TOKEN;
386
387	list_for_each_entry_rcu(bpqdev, &bpq_devices, bpq_list) {
388		if (i == *pos)
389			return bpqdev;
390	}
391	return NULL;
392}
393
394static void *bpq_seq_next(struct seq_file *seq, void *v, loff_t *pos)
395{
396	struct list_head *p;
397	struct bpqdev *bpqdev = v;
398
399	++*pos;
400
401	if (v == SEQ_START_TOKEN)
402		p = rcu_dereference(list_next_rcu(&bpq_devices));
403	else
404		p = rcu_dereference(list_next_rcu(&bpqdev->bpq_list));
405
406	return (p == &bpq_devices) ? NULL
407		: list_entry(p, struct bpqdev, bpq_list);
408}
409
410static void bpq_seq_stop(struct seq_file *seq, void *v)
411	__releases(RCU)
412{
413	rcu_read_unlock();
414}
415
416
417static int bpq_seq_show(struct seq_file *seq, void *v)
418{
419	if (v == SEQ_START_TOKEN)
420		seq_puts(seq,
421			 "dev   ether      destination        accept from\n");
422	else {
423		const struct bpqdev *bpqdev = v;
424
425		seq_printf(seq, "%-5s %-10s %pM  ",
426			bpqdev->axdev->name, bpqdev->ethdev->name,
427			bpqdev->dest_addr);
428
429		if (is_multicast_ether_addr(bpqdev->acpt_addr))
430			seq_printf(seq, "*\n");
431		else
432			seq_printf(seq, "%pM\n", bpqdev->acpt_addr);
433
434	}
435	return 0;
436}
437
438static const struct seq_operations bpq_seqops = {
439	.start = bpq_seq_start,
440	.next = bpq_seq_next,
441	.stop = bpq_seq_stop,
442	.show = bpq_seq_show,
443};
444#endif
445/* ------------------------------------------------------------------------ */
446
447static const struct net_device_ops bpq_netdev_ops = {
448	.ndo_open	     = bpq_open,
449	.ndo_stop	     = bpq_close,
450	.ndo_start_xmit	     = bpq_xmit,
451	.ndo_set_mac_address = bpq_set_mac_address,
452	.ndo_siocdevprivate  = bpq_siocdevprivate,
453};
454
455static void bpq_setup(struct net_device *dev)
456{
457	dev->netdev_ops	     = &bpq_netdev_ops;
458	dev->needs_free_netdev = true;
459
460	dev->flags      = 0;
461	dev->features	= NETIF_F_LLTX;	/* Allow recursion */
462
463#if IS_ENABLED(CONFIG_AX25)
464	dev->header_ops      = &ax25_header_ops;
465#endif
466
467	dev->type            = ARPHRD_AX25;
468	dev->hard_header_len = AX25_MAX_HEADER_LEN + AX25_BPQ_HEADER_LEN;
469	dev->mtu             = AX25_DEF_PACLEN;
470	dev->addr_len        = AX25_ADDR_LEN;
471
472	memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
473	dev_addr_set(dev, (u8 *)&ax25_defaddr);
474}
475
476/*
477 *	Setup a new device.
478 */
479static int bpq_new_device(struct net_device *edev)
480{
481	int err;
482	struct net_device *ndev;
483	struct bpqdev *bpq;
484
485	ndev = alloc_netdev(sizeof(struct bpqdev), "bpq%d", NET_NAME_UNKNOWN,
486			    bpq_setup);
487	if (!ndev)
488		return -ENOMEM;
489
490
491	bpq = netdev_priv(ndev);
492	dev_hold(edev);
493	bpq->ethdev = edev;
494	bpq->axdev = ndev;
495
496	eth_broadcast_addr(bpq->dest_addr);
497	eth_broadcast_addr(bpq->acpt_addr);
498
499	err = register_netdevice(ndev);
500	if (err)
501		goto error;
502	bpq_set_lockdep_class(ndev);
503
504	/* List protected by RTNL */
505	list_add_rcu(&bpq->bpq_list, &bpq_devices);
506	return 0;
507
508 error:
509	dev_put(edev);
510	free_netdev(ndev);
511	return err;
512
513}
514
515static void bpq_free_device(struct net_device *ndev)
516{
517	struct bpqdev *bpq = netdev_priv(ndev);
518
519	dev_put(bpq->ethdev);
520	list_del_rcu(&bpq->bpq_list);
521
522	unregister_netdevice(ndev);
523}
524
525/*
526 *	Handle device status changes.
527 */
528static int bpq_device_event(struct notifier_block *this,
529			    unsigned long event, void *ptr)
530{
531	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
532
533	if (!net_eq(dev_net(dev), &init_net))
534		return NOTIFY_DONE;
535
536	if (!dev_is_ethdev(dev) && !bpq_get_ax25_dev(dev))
537		return NOTIFY_DONE;
538
539	switch (event) {
540	case NETDEV_UP:		/* new ethernet device -> new BPQ interface */
541		if (bpq_get_ax25_dev(dev) == NULL)
542			bpq_new_device(dev);
543		break;
544
545	case NETDEV_DOWN:	/* ethernet device closed -> close BPQ interface */
546		if ((dev = bpq_get_ax25_dev(dev)) != NULL)
547			dev_close(dev);
548		break;
549
550	case NETDEV_UNREGISTER:	/* ethernet device removed -> free BPQ interface */
551		if ((dev = bpq_get_ax25_dev(dev)) != NULL)
552			bpq_free_device(dev);
553		break;
554	default:
555		break;
556	}
557
558	return NOTIFY_DONE;
559}
560
561
562/* ------------------------------------------------------------------------ */
563
564/*
565 * Initialize driver. To be called from af_ax25 if not compiled as a
566 * module
567 */
568static int __init bpq_init_driver(void)
569{
570#ifdef CONFIG_PROC_FS
571	if (!proc_create_seq("bpqether", 0444, init_net.proc_net, &bpq_seqops)) {
572		printk(KERN_ERR
573			"bpq: cannot create /proc/net/bpqether entry.\n");
574		return -ENOENT;
575	}
576#endif  /* CONFIG_PROC_FS */
577
578	dev_add_pack(&bpq_packet_type);
579
580	register_netdevice_notifier(&bpq_dev_notifier);
581
582	printk(banner);
583
584	return 0;
585}
586
587static void __exit bpq_cleanup_driver(void)
588{
589	struct bpqdev *bpq;
590
591	dev_remove_pack(&bpq_packet_type);
592
593	unregister_netdevice_notifier(&bpq_dev_notifier);
594
595	remove_proc_entry("bpqether", init_net.proc_net);
596
597	rtnl_lock();
598	while (!list_empty(&bpq_devices)) {
599		bpq = list_entry(bpq_devices.next, struct bpqdev, bpq_list);
600		bpq_free_device(bpq->axdev);
601	}
602	rtnl_unlock();
603}
604
605MODULE_AUTHOR("Joerg Reuter DL1BKE <jreuter@yaina.de>");
606MODULE_DESCRIPTION("Transmit and receive AX.25 packets over Ethernet");
607MODULE_LICENSE("GPL");
608module_init(bpq_init_driver);
609module_exit(bpq_cleanup_driver);
610