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 
39 
40 static const char* version = "HDLC support module revision 1.22";
41 
42 #undef DEBUG_LINK
43 
44 static struct hdlc_proto *first_proto;
45 
hdlc_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * p,struct net_device * orig_dev)46 static int hdlc_rcv(struct sk_buff *skb, struct net_device *dev,
47 		    struct packet_type *p, struct net_device *orig_dev)
48 {
49 	struct hdlc_device *hdlc = dev_to_hdlc(dev);
50 
51 	if (!net_eq(dev_net(dev), &init_net)) {
52 		kfree_skb(skb);
53 		return 0;
54 	}
55 
56 	BUG_ON(!hdlc->proto->netif_rx);
57 	return hdlc->proto->netif_rx(skb);
58 }
59 
hdlc_start_xmit(struct sk_buff * skb,struct net_device * dev)60 netdev_tx_t hdlc_start_xmit(struct sk_buff *skb, struct net_device *dev)
61 {
62 	hdlc_device *hdlc = dev_to_hdlc(dev);
63 
64 	if (hdlc->proto->xmit)
65 		return hdlc->proto->xmit(skb, dev);
66 
67 	return hdlc->xmit(skb, dev); /* call hardware driver directly */
68 }
69 
hdlc_proto_start(struct net_device * dev)70 static inline void hdlc_proto_start(struct net_device *dev)
71 {
72 	hdlc_device *hdlc = dev_to_hdlc(dev);
73 	if (hdlc->proto->start)
74 		hdlc->proto->start(dev);
75 }
76 
77 
78 
hdlc_proto_stop(struct net_device * dev)79 static inline void hdlc_proto_stop(struct net_device *dev)
80 {
81 	hdlc_device *hdlc = dev_to_hdlc(dev);
82 	if (hdlc->proto->stop)
83 		hdlc->proto->stop(dev);
84 }
85 
86 
87 
hdlc_device_event(struct notifier_block * this,unsigned long event,void * ptr)88 static int hdlc_device_event(struct notifier_block *this, unsigned long event,
89 			     void *ptr)
90 {
91 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
92 	hdlc_device *hdlc;
93 	unsigned long flags;
94 	int on;
95 
96 	if (!net_eq(dev_net(dev), &init_net))
97 		return NOTIFY_DONE;
98 
99 	if (!(dev->priv_flags & IFF_WAN_HDLC))
100 		return NOTIFY_DONE; /* not an HDLC device */
101 
102 	if (event != NETDEV_CHANGE)
103 		return NOTIFY_DONE; /* Only interested in carrier changes */
104 
105 	on = netif_carrier_ok(dev);
106 
107 #ifdef DEBUG_LINK
108 	printk(KERN_DEBUG "%s: hdlc_device_event NETDEV_CHANGE, carrier %i\n",
109 	       dev->name, on);
110 #endif
111 
112 	hdlc = dev_to_hdlc(dev);
113 	spin_lock_irqsave(&hdlc->state_lock, flags);
114 
115 	if (hdlc->carrier == on)
116 		goto carrier_exit; /* no change in DCD line level */
117 
118 	hdlc->carrier = on;
119 
120 	if (!hdlc->open)
121 		goto carrier_exit;
122 
123 	if (hdlc->carrier) {
124 		netdev_info(dev, "Carrier detected\n");
125 		hdlc_proto_start(dev);
126 	} else {
127 		netdev_info(dev, "Carrier lost\n");
128 		hdlc_proto_stop(dev);
129 	}
130 
131 carrier_exit:
132 	spin_unlock_irqrestore(&hdlc->state_lock, flags);
133 	return NOTIFY_DONE;
134 }
135 
136 
137 
138 /* Must be called by hardware driver when HDLC device is being opened */
hdlc_open(struct net_device * dev)139 int hdlc_open(struct net_device *dev)
140 {
141 	hdlc_device *hdlc = dev_to_hdlc(dev);
142 #ifdef DEBUG_LINK
143 	printk(KERN_DEBUG "%s: hdlc_open() carrier %i open %i\n", dev->name,
144 	       hdlc->carrier, hdlc->open);
145 #endif
146 
147 	if (hdlc->proto == NULL)
148 		return -ENOSYS;	/* no protocol attached */
149 
150 	if (hdlc->proto->open) {
151 		int result = hdlc->proto->open(dev);
152 		if (result)
153 			return result;
154 	}
155 
156 	spin_lock_irq(&hdlc->state_lock);
157 
158 	if (hdlc->carrier) {
159 		netdev_info(dev, "Carrier detected\n");
160 		hdlc_proto_start(dev);
161 	} else
162 		netdev_info(dev, "No carrier\n");
163 
164 	hdlc->open = 1;
165 
166 	spin_unlock_irq(&hdlc->state_lock);
167 	return 0;
168 }
169 
170 
171 
172 /* Must be called by hardware driver when HDLC device is being closed */
hdlc_close(struct net_device * dev)173 void hdlc_close(struct net_device *dev)
174 {
175 	hdlc_device *hdlc = dev_to_hdlc(dev);
176 #ifdef DEBUG_LINK
177 	printk(KERN_DEBUG "%s: hdlc_close() carrier %i open %i\n", dev->name,
178 	       hdlc->carrier, hdlc->open);
179 #endif
180 
181 	spin_lock_irq(&hdlc->state_lock);
182 
183 	hdlc->open = 0;
184 	if (hdlc->carrier)
185 		hdlc_proto_stop(dev);
186 
187 	spin_unlock_irq(&hdlc->state_lock);
188 
189 	if (hdlc->proto->close)
190 		hdlc->proto->close(dev);
191 }
192 
193 
194 
hdlc_ioctl(struct net_device * dev,struct ifreq * ifr,int cmd)195 int hdlc_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
196 {
197 	struct hdlc_proto *proto = first_proto;
198 	int result;
199 
200 	if (cmd != SIOCWANDEV)
201 		return -EINVAL;
202 
203 	if (dev_to_hdlc(dev)->proto) {
204 		result = dev_to_hdlc(dev)->proto->ioctl(dev, ifr);
205 		if (result != -EINVAL)
206 			return result;
207 	}
208 
209 	/* Not handled by currently attached protocol (if any) */
210 
211 	while (proto) {
212 		if ((result = proto->ioctl(dev, ifr)) != -EINVAL)
213 			return result;
214 		proto = proto->next;
215 	}
216 	return -EINVAL;
217 }
218 
219 static const struct header_ops hdlc_null_ops;
220 
hdlc_setup_dev(struct net_device * dev)221 static void hdlc_setup_dev(struct net_device *dev)
222 {
223 	/* Re-init all variables changed by HDLC protocol drivers,
224 	 * including ether_setup() called from hdlc_raw_eth.c.
225 	 */
226 	dev->flags		 = IFF_POINTOPOINT | IFF_NOARP;
227 	dev->priv_flags		 = IFF_WAN_HDLC;
228 	dev->mtu		 = HDLC_MAX_MTU;
229 	dev->min_mtu		 = 68;
230 	dev->max_mtu		 = HDLC_MAX_MTU;
231 	dev->type		 = ARPHRD_RAWHDLC;
232 	dev->hard_header_len	 = 16;
233 	dev->addr_len		 = 0;
234 	dev->header_ops		 = &hdlc_null_ops;
235 }
236 
hdlc_setup(struct net_device * dev)237 static void hdlc_setup(struct net_device *dev)
238 {
239 	hdlc_device *hdlc = dev_to_hdlc(dev);
240 
241 	hdlc_setup_dev(dev);
242 	hdlc->carrier = 1;
243 	hdlc->open = 0;
244 	spin_lock_init(&hdlc->state_lock);
245 }
246 
alloc_hdlcdev(void * priv)247 struct net_device *alloc_hdlcdev(void *priv)
248 {
249 	struct net_device *dev;
250 	dev = alloc_netdev(sizeof(struct hdlc_device), "hdlc%d",
251 			   NET_NAME_UNKNOWN, hdlc_setup);
252 	if (dev)
253 		dev_to_hdlc(dev)->priv = priv;
254 	return dev;
255 }
256 
unregister_hdlc_device(struct net_device * dev)257 void unregister_hdlc_device(struct net_device *dev)
258 {
259 	rtnl_lock();
260 	detach_hdlc_protocol(dev);
261 	unregister_netdevice(dev);
262 	rtnl_unlock();
263 }
264 
265 
266 
attach_hdlc_protocol(struct net_device * dev,struct hdlc_proto * proto,size_t size)267 int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
268 			 size_t size)
269 {
270 	int err;
271 
272 	err = detach_hdlc_protocol(dev);
273 	if (err)
274 		return err;
275 
276 	if (!try_module_get(proto->module))
277 		return -ENOSYS;
278 
279 	if (size) {
280 		dev_to_hdlc(dev)->state = kmalloc(size, GFP_KERNEL);
281 		if (dev_to_hdlc(dev)->state == NULL) {
282 			module_put(proto->module);
283 			return -ENOBUFS;
284 		}
285 	}
286 	dev_to_hdlc(dev)->proto = proto;
287 
288 	return 0;
289 }
290 
291 
detach_hdlc_protocol(struct net_device * dev)292 int detach_hdlc_protocol(struct net_device *dev)
293 {
294 	hdlc_device *hdlc = dev_to_hdlc(dev);
295 	int err;
296 
297 	if (hdlc->proto) {
298 		err = call_netdevice_notifiers(NETDEV_PRE_TYPE_CHANGE, dev);
299 		err = notifier_to_errno(err);
300 		if (err) {
301 			netdev_err(dev, "Refused to change device type\n");
302 			return err;
303 		}
304 
305 		if (hdlc->proto->detach)
306 			hdlc->proto->detach(dev);
307 		module_put(hdlc->proto->module);
308 		hdlc->proto = NULL;
309 	}
310 	kfree(hdlc->state);
311 	hdlc->state = NULL;
312 	hdlc_setup_dev(dev);
313 
314 	return 0;
315 }
316 
317 
register_hdlc_protocol(struct hdlc_proto * proto)318 void register_hdlc_protocol(struct hdlc_proto *proto)
319 {
320 	rtnl_lock();
321 	proto->next = first_proto;
322 	first_proto = proto;
323 	rtnl_unlock();
324 }
325 
326 
unregister_hdlc_protocol(struct hdlc_proto * proto)327 void unregister_hdlc_protocol(struct hdlc_proto *proto)
328 {
329 	struct hdlc_proto **p;
330 
331 	rtnl_lock();
332 	p = &first_proto;
333 	while (*p != proto) {
334 		BUG_ON(!*p);
335 		p = &((*p)->next);
336 	}
337 	*p = proto->next;
338 	rtnl_unlock();
339 }
340 
341 
342 
343 MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
344 MODULE_DESCRIPTION("HDLC support module");
345 MODULE_LICENSE("GPL v2");
346 
347 EXPORT_SYMBOL(hdlc_start_xmit);
348 EXPORT_SYMBOL(hdlc_open);
349 EXPORT_SYMBOL(hdlc_close);
350 EXPORT_SYMBOL(hdlc_ioctl);
351 EXPORT_SYMBOL(alloc_hdlcdev);
352 EXPORT_SYMBOL(unregister_hdlc_device);
353 EXPORT_SYMBOL(register_hdlc_protocol);
354 EXPORT_SYMBOL(unregister_hdlc_protocol);
355 EXPORT_SYMBOL(attach_hdlc_protocol);
356 EXPORT_SYMBOL(detach_hdlc_protocol);
357 
358 static struct packet_type hdlc_packet_type __read_mostly = {
359 	.type = cpu_to_be16(ETH_P_HDLC),
360 	.func = hdlc_rcv,
361 };
362 
363 
364 static struct notifier_block hdlc_notifier = {
365 	.notifier_call = hdlc_device_event,
366 };
367 
368 
hdlc_module_init(void)369 static int __init hdlc_module_init(void)
370 {
371 	int result;
372 
373 	pr_info("%s\n", version);
374 	if ((result = register_netdevice_notifier(&hdlc_notifier)) != 0)
375 		return result;
376 	dev_add_pack(&hdlc_packet_type);
377 	return 0;
378 }
379 
380 
381 
hdlc_module_exit(void)382 static void __exit hdlc_module_exit(void)
383 {
384 	dev_remove_pack(&hdlc_packet_type);
385 	unregister_netdevice_notifier(&hdlc_notifier);
386 }
387 
388 
389 module_init(hdlc_module_init);
390 module_exit(hdlc_module_exit);
391