connector.c revision 3700c3c2934467d53d443682f020cc5c1f75f1f2 
1/*
2 * 	connector.c
3 *
4 * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
5 * All rights reserved.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20 */
21
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/list.h>
25#include <linux/skbuff.h>
26#include <linux/netlink.h>
27#include <linux/moduleparam.h>
28#include <linux/connector.h>
29#include <linux/slab.h>
30#include <linux/mutex.h>
31#include <linux/proc_fs.h>
32#include <linux/spinlock.h>
33
34#include <net/sock.h>
35
36MODULE_LICENSE("GPL");
37MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
38MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
39MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
40
41static struct cn_dev cdev;
42
43static int cn_already_initialized;
44
45/*
46 * msg->seq and msg->ack are used to determine message genealogy.
47 * When someone sends message it puts there locally unique sequence
48 * and random acknowledge numbers.  Sequence number may be copied into
49 * nlmsghdr->nlmsg_seq too.
50 *
51 * Sequence number is incremented with each message to be sent.
52 *
53 * If we expect reply to our message then the sequence number in
54 * received message MUST be the same as in original message, and
55 * acknowledge number MUST be the same + 1.
56 *
57 * If we receive a message and its sequence number is not equal to the
58 * one we are expecting then it is a new message.
59 *
60 * If we receive a message and its sequence number is the same as one
61 * we are expecting but it's acknowledgement number is not equal to
62 * the acknowledgement number in the original message + 1, then it is
63 * a new message.
64 *
65 */
66int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
67{
68	struct cn_callback_entry *__cbq;
69	unsigned int size;
70	struct sk_buff *skb;
71	struct nlmsghdr *nlh;
72	struct cn_msg *data;
73	struct cn_dev *dev = &cdev;
74	u32 group = 0;
75	int found = 0;
76
77	if (!__group) {
78		spin_lock_bh(&dev->cbdev->queue_lock);
79		list_for_each_entry(__cbq, &dev->cbdev->queue_list,
80				    callback_entry) {
81			if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
82				found = 1;
83				group = __cbq->group;
84				break;
85			}
86		}
87		spin_unlock_bh(&dev->cbdev->queue_lock);
88
89		if (!found)
90			return -ENODEV;
91	} else {
92		group = __group;
93	}
94
95	if (!netlink_has_listeners(dev->nls, group))
96		return -ESRCH;
97
98	size = NLMSG_SPACE(sizeof(*msg) + msg->len);
99
100	skb = alloc_skb(size, gfp_mask);
101	if (!skb)
102		return -ENOMEM;
103
104	nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
105
106	data = NLMSG_DATA(nlh);
107
108	memcpy(data, msg, sizeof(*data) + msg->len);
109
110	NETLINK_CB(skb).dst_group = group;
111
112	return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
113
114nlmsg_failure:
115	kfree_skb(skb);
116	return -EINVAL;
117}
118EXPORT_SYMBOL_GPL(cn_netlink_send);
119
120/*
121 * Callback helper - queues work and setup destructor for given data.
122 */
123static int cn_call_callback(struct sk_buff *skb)
124{
125	struct cn_callback_entry *__cbq, *__new_cbq;
126	struct cn_dev *dev = &cdev;
127	struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
128	int err = -ENODEV;
129
130	spin_lock_bh(&dev->cbdev->queue_lock);
131	list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
132		if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
133			if (likely(!work_pending(&__cbq->work) &&
134					__cbq->data.skb == NULL)) {
135				__cbq->data.skb = skb;
136
137				if (queue_work(dev->cbdev->cn_queue,
138					       &__cbq->work))
139					err = 0;
140				else
141					err = -EINVAL;
142			} else {
143				struct cn_callback_data *d;
144
145				err = -ENOMEM;
146				__new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
147				if (__new_cbq) {
148					d = &__new_cbq->data;
149					d->skb = skb;
150					d->callback = __cbq->data.callback;
151					d->free = __new_cbq;
152
153					INIT_WORK(&__new_cbq->work,
154							&cn_queue_wrapper);
155
156					if (queue_work(dev->cbdev->cn_queue,
157						       &__new_cbq->work))
158						err = 0;
159					else {
160						kfree(__new_cbq);
161						err = -EINVAL;
162					}
163				}
164			}
165			break;
166		}
167	}
168	spin_unlock_bh(&dev->cbdev->queue_lock);
169
170	return err;
171}
172
173/*
174 * Main netlink receiving function.
175 *
176 * It checks skb, netlink header and msg sizes, and calls callback helper.
177 */
178static void cn_rx_skb(struct sk_buff *__skb)
179{
180	struct nlmsghdr *nlh;
181	int err;
182	struct sk_buff *skb;
183
184	skb = skb_get(__skb);
185
186	if (skb->len >= NLMSG_SPACE(0)) {
187		nlh = nlmsg_hdr(skb);
188
189		if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
190		    skb->len < nlh->nlmsg_len ||
191		    nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
192			kfree_skb(skb);
193			return;
194		}
195
196		err = cn_call_callback(skb);
197		if (err < 0)
198			kfree_skb(skb);
199	}
200}
201
202/*
203 * Callback add routing - adds callback with given ID and name.
204 * If there is registered callback with the same ID it will not be added.
205 *
206 * May sleep.
207 */
208int cn_add_callback(struct cb_id *id, char *name,
209		    void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
210{
211	int err;
212	struct cn_dev *dev = &cdev;
213
214	if (!cn_already_initialized)
215		return -EAGAIN;
216
217	err = cn_queue_add_callback(dev->cbdev, name, id, callback);
218	if (err)
219		return err;
220
221	return 0;
222}
223EXPORT_SYMBOL_GPL(cn_add_callback);
224
225/*
226 * Callback remove routing - removes callback
227 * with given ID.
228 * If there is no registered callback with given
229 * ID nothing happens.
230 *
231 * May sleep while waiting for reference counter to become zero.
232 */
233void cn_del_callback(struct cb_id *id)
234{
235	struct cn_dev *dev = &cdev;
236
237	cn_queue_del_callback(dev->cbdev, id);
238}
239EXPORT_SYMBOL_GPL(cn_del_callback);
240
241static int cn_proc_show(struct seq_file *m, void *v)
242{
243	struct cn_queue_dev *dev = cdev.cbdev;
244	struct cn_callback_entry *cbq;
245
246	seq_printf(m, "Name            ID\n");
247
248	spin_lock_bh(&dev->queue_lock);
249
250	list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
251		seq_printf(m, "%-15s %u:%u\n",
252			   cbq->id.name,
253			   cbq->id.id.idx,
254			   cbq->id.id.val);
255	}
256
257	spin_unlock_bh(&dev->queue_lock);
258
259	return 0;
260}
261
262static int cn_proc_open(struct inode *inode, struct file *file)
263{
264	return single_open(file, cn_proc_show, NULL);
265}
266
267static const struct file_operations cn_file_ops = {
268	.owner   = THIS_MODULE,
269	.open    = cn_proc_open,
270	.read    = seq_read,
271	.llseek  = seq_lseek,
272	.release = single_release
273};
274
275static int __devinit cn_init(void)
276{
277	struct cn_dev *dev = &cdev;
278
279	dev->input = cn_rx_skb;
280
281	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
282					 CN_NETLINK_USERS + 0xf,
283					 dev->input, NULL, THIS_MODULE);
284	if (!dev->nls)
285		return -EIO;
286
287	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
288	if (!dev->cbdev) {
289		netlink_kernel_release(dev->nls);
290		return -EINVAL;
291	}
292
293	cn_already_initialized = 1;
294
295	proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
296
297	return 0;
298}
299
300static void __devexit cn_fini(void)
301{
302	struct cn_dev *dev = &cdev;
303
304	cn_already_initialized = 0;
305
306	proc_net_remove(&init_net, "connector");
307
308	cn_queue_free_dev(dev->cbdev);
309	netlink_kernel_release(dev->nls);
310}
311
312subsys_initcall(cn_init);
313module_exit(cn_fini);
314