connector.c revision ece31ffd539e8e2b586b1ca5f50bc4f4591e3893 
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), 0);
105	if (!nlh) {
106		kfree_skb(skb);
107		return -EMSGSIZE;
108	}
109
110	data = nlmsg_data(nlh);
111
112	memcpy(data, msg, sizeof(*data) + msg->len);
113
114	NETLINK_CB(skb).dst_group = group;
115
116	return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
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 *i, *cbq = NULL;
126	struct cn_dev *dev = &cdev;
127	struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
128	struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
129	int err = -ENODEV;
130
131	spin_lock_bh(&dev->cbdev->queue_lock);
132	list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
133		if (cn_cb_equal(&i->id.id, &msg->id)) {
134			atomic_inc(&i->refcnt);
135			cbq = i;
136			break;
137		}
138	}
139	spin_unlock_bh(&dev->cbdev->queue_lock);
140
141	if (cbq != NULL) {
142		err = 0;
143		cbq->callback(msg, nsp);
144		kfree_skb(skb);
145		cn_queue_release_callback(cbq);
146		err = 0;
147	}
148
149	return err;
150}
151
152/*
153 * Main netlink receiving function.
154 *
155 * It checks skb, netlink header and msg sizes, and calls callback helper.
156 */
157static void cn_rx_skb(struct sk_buff *__skb)
158{
159	struct nlmsghdr *nlh;
160	int err;
161	struct sk_buff *skb;
162
163	skb = skb_get(__skb);
164
165	if (skb->len >= NLMSG_SPACE(0)) {
166		nlh = nlmsg_hdr(skb);
167
168		if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
169		    skb->len < nlh->nlmsg_len ||
170		    nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
171			kfree_skb(skb);
172			return;
173		}
174
175		err = cn_call_callback(skb);
176		if (err < 0)
177			kfree_skb(skb);
178	}
179}
180
181/*
182 * Callback add routing - adds callback with given ID and name.
183 * If there is registered callback with the same ID it will not be added.
184 *
185 * May sleep.
186 */
187int cn_add_callback(struct cb_id *id, const char *name,
188		    void (*callback)(struct cn_msg *,
189				     struct netlink_skb_parms *))
190{
191	int err;
192	struct cn_dev *dev = &cdev;
193
194	if (!cn_already_initialized)
195		return -EAGAIN;
196
197	err = cn_queue_add_callback(dev->cbdev, name, id, callback);
198	if (err)
199		return err;
200
201	return 0;
202}
203EXPORT_SYMBOL_GPL(cn_add_callback);
204
205/*
206 * Callback remove routing - removes callback
207 * with given ID.
208 * If there is no registered callback with given
209 * ID nothing happens.
210 *
211 * May sleep while waiting for reference counter to become zero.
212 */
213void cn_del_callback(struct cb_id *id)
214{
215	struct cn_dev *dev = &cdev;
216
217	cn_queue_del_callback(dev->cbdev, id);
218}
219EXPORT_SYMBOL_GPL(cn_del_callback);
220
221static int cn_proc_show(struct seq_file *m, void *v)
222{
223	struct cn_queue_dev *dev = cdev.cbdev;
224	struct cn_callback_entry *cbq;
225
226	seq_printf(m, "Name            ID\n");
227
228	spin_lock_bh(&dev->queue_lock);
229
230	list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
231		seq_printf(m, "%-15s %u:%u\n",
232			   cbq->id.name,
233			   cbq->id.id.idx,
234			   cbq->id.id.val);
235	}
236
237	spin_unlock_bh(&dev->queue_lock);
238
239	return 0;
240}
241
242static int cn_proc_open(struct inode *inode, struct file *file)
243{
244	return single_open(file, cn_proc_show, NULL);
245}
246
247static const struct file_operations cn_file_ops = {
248	.owner   = THIS_MODULE,
249	.open    = cn_proc_open,
250	.read    = seq_read,
251	.llseek  = seq_lseek,
252	.release = single_release
253};
254
255static struct cn_dev cdev = {
256	.input   = cn_rx_skb,
257};
258
259static int cn_init(void)
260{
261	struct cn_dev *dev = &cdev;
262	struct netlink_kernel_cfg cfg = {
263		.groups	= CN_NETLINK_USERS + 0xf,
264		.input	= dev->input,
265	};
266
267	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
268	if (!dev->nls)
269		return -EIO;
270
271	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
272	if (!dev->cbdev) {
273		netlink_kernel_release(dev->nls);
274		return -EINVAL;
275	}
276
277	cn_already_initialized = 1;
278
279	proc_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
280
281	return 0;
282}
283
284static void cn_fini(void)
285{
286	struct cn_dev *dev = &cdev;
287
288	cn_already_initialized = 0;
289
290	remove_proc_entry("connector", init_net.proc_net);
291
292	cn_queue_free_dev(dev->cbdev);
293	netlink_kernel_release(dev->nls);
294}
295
296subsys_initcall(cn_init);
297module_exit(cn_fini);
298