1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic HDLC support routines for Linux
4 *
5 * Copyright (C) 1999 - 2008 Krzysztof Halasa <khc@pm.waw.pl>
6 *
7 * Currently supported:
8 *	* raw IP-in-HDLC
9 *	* Cisco HDLC
10 *	* Frame Relay with ANSI or CCITT LMI (both user and network side)
11 *	* PPP
12 *	* X.25
13 *
14 * Use sethdlc utility to set line parameters, protocol and PVCs
15 *
16 * How does it work:
17 * - proto->open(), close(), start(), stop() calls are serialized.
18 *   The order is: open, [ start, stop ... ] close ...
19 * - proto->start() and stop() are called with spin_lock_irq held.
20 */
21
22#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
23
24#include <linux/errno.h>
25#include <linux/hdlc.h>
26#include <linux/if_arp.h>
27#include <linux/inetdevice.h>
28#include <linux/init.h>
29#include <linux/kernel.h>
30#include <linux/module.h>
31#include <linux/notifier.h>
32#include <linux/pkt_sched.h>
33#include <linux/poll.h>
34#include <linux/rtnetlink.h>
35#include <linux/skbuff.h>
36#include <linux/slab.h>
37#include <net/net_namespace.h>
38
39static const char *version = "HDLC support module revision 1.22";
40
41#undef DEBUG_LINK
42
43static struct hdlc_proto *first_proto;
44
45static int hdlc_rcv(struct sk_buff *skb, struct net_device *dev,
46		    struct packet_type *p, struct net_device *orig_dev)
47{
48	struct hdlc_device *hdlc;
49
50	/* First make sure "dev" is an HDLC device */
51	if (!(dev->priv_flags & IFF_WAN_HDLC)) {
52		kfree_skb(skb);
53		return NET_RX_SUCCESS;
54	}
55
56	hdlc = dev_to_hdlc(dev);
57
58	if (!net_eq(dev_net(dev), &init_net)) {
59		kfree_skb(skb);
60		return 0;
61	}
62
63	BUG_ON(!hdlc->proto->netif_rx);
64	return hdlc->proto->netif_rx(skb);
65}
66
67netdev_tx_t hdlc_start_xmit(struct sk_buff *skb, struct net_device *dev)
68{
69	hdlc_device *hdlc = dev_to_hdlc(dev);
70
71	if (hdlc->proto->xmit)
72		return hdlc->proto->xmit(skb, dev);
73
74	return hdlc->xmit(skb, dev); /* call hardware driver directly */
75}
76EXPORT_SYMBOL(hdlc_start_xmit);
77
78static inline void hdlc_proto_start(struct net_device *dev)
79{
80	hdlc_device *hdlc = dev_to_hdlc(dev);
81
82	if (hdlc->proto->start)
83		hdlc->proto->start(dev);
84}
85
86static inline void hdlc_proto_stop(struct net_device *dev)
87{
88	hdlc_device *hdlc = dev_to_hdlc(dev);
89
90	if (hdlc->proto->stop)
91		hdlc->proto->stop(dev);
92}
93
94static int hdlc_device_event(struct notifier_block *this, unsigned long event,
95			     void *ptr)
96{
97	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
98	hdlc_device *hdlc;
99	unsigned long flags;
100	int on;
101
102	if (!net_eq(dev_net(dev), &init_net))
103		return NOTIFY_DONE;
104
105	if (!(dev->priv_flags & IFF_WAN_HDLC))
106		return NOTIFY_DONE; /* not an HDLC device */
107
108	if (event != NETDEV_CHANGE)
109		return NOTIFY_DONE; /* Only interested in carrier changes */
110
111	on = netif_carrier_ok(dev);
112
113#ifdef DEBUG_LINK
114	printk(KERN_DEBUG "%s: hdlc_device_event NETDEV_CHANGE, carrier %i\n",
115	       dev->name, on);
116#endif
117
118	hdlc = dev_to_hdlc(dev);
119	spin_lock_irqsave(&hdlc->state_lock, flags);
120
121	if (hdlc->carrier == on)
122		goto carrier_exit; /* no change in DCD line level */
123
124	hdlc->carrier = on;
125
126	if (!hdlc->open)
127		goto carrier_exit;
128
129	if (hdlc->carrier) {
130		netdev_info(dev, "Carrier detected\n");
131		hdlc_proto_start(dev);
132	} else {
133		netdev_info(dev, "Carrier lost\n");
134		hdlc_proto_stop(dev);
135	}
136
137carrier_exit:
138	spin_unlock_irqrestore(&hdlc->state_lock, flags);
139	return NOTIFY_DONE;
140}
141
142/* Must be called by hardware driver when HDLC device is being opened */
143int hdlc_open(struct net_device *dev)
144{
145	hdlc_device *hdlc = dev_to_hdlc(dev);
146#ifdef DEBUG_LINK
147	printk(KERN_DEBUG "%s: hdlc_open() carrier %i open %i\n", dev->name,
148	       hdlc->carrier, hdlc->open);
149#endif
150
151	if (!hdlc->proto)
152		return -ENOSYS;	/* no protocol attached */
153
154	if (hdlc->proto->open) {
155		int result = hdlc->proto->open(dev);
156
157		if (result)
158			return result;
159	}
160
161	spin_lock_irq(&hdlc->state_lock);
162
163	if (hdlc->carrier) {
164		netdev_info(dev, "Carrier detected\n");
165		hdlc_proto_start(dev);
166	} else {
167		netdev_info(dev, "No carrier\n");
168	}
169
170	hdlc->open = 1;
171
172	spin_unlock_irq(&hdlc->state_lock);
173	return 0;
174}
175EXPORT_SYMBOL(hdlc_open);
176
177/* Must be called by hardware driver when HDLC device is being closed */
178void hdlc_close(struct net_device *dev)
179{
180	hdlc_device *hdlc = dev_to_hdlc(dev);
181#ifdef DEBUG_LINK
182	printk(KERN_DEBUG "%s: hdlc_close() carrier %i open %i\n", dev->name,
183	       hdlc->carrier, hdlc->open);
184#endif
185
186	spin_lock_irq(&hdlc->state_lock);
187
188	hdlc->open = 0;
189	if (hdlc->carrier)
190		hdlc_proto_stop(dev);
191
192	spin_unlock_irq(&hdlc->state_lock);
193
194	if (hdlc->proto->close)
195		hdlc->proto->close(dev);
196}
197EXPORT_SYMBOL(hdlc_close);
198
199int hdlc_ioctl(struct net_device *dev, struct if_settings *ifs)
200{
201	struct hdlc_proto *proto = first_proto;
202	int result;
203
204	if (dev_to_hdlc(dev)->proto) {
205		result = dev_to_hdlc(dev)->proto->ioctl(dev, ifs);
206		if (result != -EINVAL)
207			return result;
208	}
209
210	/* Not handled by currently attached protocol (if any) */
211
212	while (proto) {
213		result = proto->ioctl(dev, ifs);
214		if (result != -EINVAL)
215			return result;
216		proto = proto->next;
217	}
218	return -EINVAL;
219}
220EXPORT_SYMBOL(hdlc_ioctl);
221
222static const struct header_ops hdlc_null_ops;
223
224static void hdlc_setup_dev(struct net_device *dev)
225{
226	/* Re-init all variables changed by HDLC protocol drivers,
227	 * including ether_setup() called from hdlc_raw_eth.c.
228	 */
229	dev->flags		 = IFF_POINTOPOINT | IFF_NOARP;
230	dev->priv_flags		 = IFF_WAN_HDLC;
231	dev->mtu		 = HDLC_MAX_MTU;
232	dev->min_mtu		 = 68;
233	dev->max_mtu		 = HDLC_MAX_MTU;
234	dev->type		 = ARPHRD_RAWHDLC;
235	dev->hard_header_len	 = 0;
236	dev->needed_headroom	 = 0;
237	dev->addr_len		 = 0;
238	dev->header_ops		 = &hdlc_null_ops;
239}
240
241static void hdlc_setup(struct net_device *dev)
242{
243	hdlc_device *hdlc = dev_to_hdlc(dev);
244
245	hdlc_setup_dev(dev);
246	hdlc->carrier = 1;
247	hdlc->open = 0;
248	spin_lock_init(&hdlc->state_lock);
249}
250
251struct net_device *alloc_hdlcdev(void *priv)
252{
253	struct net_device *dev;
254
255	dev = alloc_netdev(sizeof(struct hdlc_device), "hdlc%d",
256			   NET_NAME_UNKNOWN, hdlc_setup);
257	if (dev)
258		dev_to_hdlc(dev)->priv = priv;
259	return dev;
260}
261EXPORT_SYMBOL(alloc_hdlcdev);
262
263void unregister_hdlc_device(struct net_device *dev)
264{
265	rtnl_lock();
266	detach_hdlc_protocol(dev);
267	unregister_netdevice(dev);
268	rtnl_unlock();
269}
270EXPORT_SYMBOL(unregister_hdlc_device);
271
272int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
273			 size_t size)
274{
275	int err;
276
277	err = detach_hdlc_protocol(dev);
278	if (err)
279		return err;
280
281	if (!try_module_get(proto->module))
282		return -ENOSYS;
283
284	if (size) {
285		dev_to_hdlc(dev)->state = kmalloc(size, GFP_KERNEL);
286		if (!dev_to_hdlc(dev)->state) {
287			module_put(proto->module);
288			return -ENOBUFS;
289		}
290	}
291	dev_to_hdlc(dev)->proto = proto;
292
293	return 0;
294}
295EXPORT_SYMBOL(attach_hdlc_protocol);
296
297int detach_hdlc_protocol(struct net_device *dev)
298{
299	hdlc_device *hdlc = dev_to_hdlc(dev);
300	int err;
301
302	if (hdlc->proto) {
303		err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev);
304		err = notifier_to_errno(err);
305		if (err) {
306			netdev_err(dev, "Refused to change device type\n");
307			return err;
308		}
309
310		if (hdlc->proto->detach)
311			hdlc->proto->detach(dev);
312		module_put(hdlc->proto->module);
313		hdlc->proto = NULL;
314	}
315	kfree(hdlc->state);
316	hdlc->state = NULL;
317	hdlc_setup_dev(dev);
318
319	return 0;
320}
321EXPORT_SYMBOL(detach_hdlc_protocol);
322
323void register_hdlc_protocol(struct hdlc_proto *proto)
324{
325	rtnl_lock();
326	proto->next = first_proto;
327	first_proto = proto;
328	rtnl_unlock();
329}
330EXPORT_SYMBOL(register_hdlc_protocol);
331
332void unregister_hdlc_protocol(struct hdlc_proto *proto)
333{
334	struct hdlc_proto **p;
335
336	rtnl_lock();
337	p = &first_proto;
338	while (*p != proto) {
339		BUG_ON(!*p);
340		p = &((*p)->next);
341	}
342	*p = proto->next;
343	rtnl_unlock();
344}
345EXPORT_SYMBOL(unregister_hdlc_protocol);
346
347MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
348MODULE_DESCRIPTION("HDLC support module");
349MODULE_LICENSE("GPL v2");
350
351static struct packet_type hdlc_packet_type __read_mostly = {
352	.type = cpu_to_be16(ETH_P_HDLC),
353	.func = hdlc_rcv,
354};
355
356static struct notifier_block hdlc_notifier = {
357	.notifier_call = hdlc_device_event,
358};
359
360static int __init hdlc_module_init(void)
361{
362	int result;
363
364	pr_info("%s\n", version);
365	result = register_netdevice_notifier(&hdlc_notifier);
366	if (result)
367		return result;
368	dev_add_pack(&hdlc_packet_type);
369	return 0;
370}
371
372static void __exit hdlc_module_exit(void)
373{
374	dev_remove_pack(&hdlc_packet_type);
375	unregister_netdevice_notifier(&hdlc_notifier);
376}
377
378module_init(hdlc_module_init);
379module_exit(hdlc_module_exit);
380