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/mutex.h>
30 #include <linux/proc_fs.h>
31 #include <linux/spinlock.h>
32
33 #include <net/sock.h>
34
35 MODULE_LICENSE("GPL");
36 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
37 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
38
39 static struct cn_dev cdev;
40
41 static int cn_already_initialized;
42
43 /*
44 * msg->seq and msg->ack are used to determine message genealogy.
45 * When someone sends message it puts there locally unique sequence
46 * and random acknowledge numbers. Sequence number may be copied into
47 * nlmsghdr->nlmsg_seq too.
48 *
49 * Sequence number is incremented with each message to be sent.
50 *
51 * If we expect reply to our message then the sequence number in
52 * received message MUST be the same as in original message, and
53 * acknowledge number MUST be the same + 1.
54 *
55 * If we receive a message and its sequence number is not equal to the
56 * one we are expecting then it is a new message.
57 *
58 * If we receive a message and its sequence number is the same as one
59 * we are expecting but it's acknowledgement number is not equal to
60 * the acknowledgement number in the original message + 1, then it is
61 * a new message.
62 *
63 */
64 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
65 {
66 struct cn_callback_entry *__cbq;
67 unsigned int size;
68 struct sk_buff *skb;
69 struct nlmsghdr *nlh;
70 struct cn_msg *data;
71 struct cn_dev *dev = &cdev;
72 u32 group = 0;
73 int found = 0;
74
75 if (!__group) {
76 spin_lock_bh(&dev->cbdev->queue_lock);
77 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
78 callback_entry) {
79 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
80 found = 1;
81 group = __cbq->group;
82 break;
83 }
84 }
85 spin_unlock_bh(&dev->cbdev->queue_lock);
86
87 if (!found)
88 return -ENODEV;
89 } else {
90 group = __group;
91 }
92
93 if (!netlink_has_listeners(dev->nls, group))
94 return -ESRCH;
95
96 size = NLMSG_SPACE(sizeof(*msg) + msg->len);
97
98 skb = alloc_skb(size, gfp_mask);
99 if (!skb)
100 return -ENOMEM;
101
102 nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
103
104 data = NLMSG_DATA(nlh);
105
106 memcpy(data, msg, sizeof(*data) + msg->len);
107
108 NETLINK_CB(skb).dst_group = group;
109
110 return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
111
112 nlmsg_failure:
113 kfree_skb(skb);
114 return -EINVAL;
115 }
116 EXPORT_SYMBOL_GPL(cn_netlink_send);
117
118 /*
119 * Callback helper - queues work and setup destructor for given data.
120 */
121 static int cn_call_callback(struct sk_buff *skb)
122 {
123 struct cn_callback_entry *__cbq, *__new_cbq;
124 struct cn_dev *dev = &cdev;
125 struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
126 int err = -ENODEV;
127
128 spin_lock_bh(&dev->cbdev->queue_lock);
129 list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
130 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
131 if (likely(!work_pending(&__cbq->work) &&
132 __cbq->data.skb == NULL)) {
133 __cbq->data.skb = skb;
134
135 if (queue_cn_work(__cbq, &__cbq->work))
136 err = 0;
137 else
138 err = -EINVAL;
139 } else {
140 struct cn_callback_data *d;
141
142 err = -ENOMEM;
143 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
144 if (__new_cbq) {
145 d = &__new_cbq->data;
146 d->skb = skb;
147 d->callback = __cbq->data.callback;
148 d->free = __new_cbq;
149
150 __new_cbq->pdev = __cbq->pdev;
151
152 INIT_WORK(&__new_cbq->work,
153 &cn_queue_wrapper);
154
155 if (queue_cn_work(__new_cbq,
156 &__new_cbq->work))
157 err = 0;
158 else {
159 kfree(__new_cbq);
160 err = -EINVAL;
161 }
162 }
163 }
164 break;
165 }
166 }
167 spin_unlock_bh(&dev->cbdev->queue_lock);
168
169 return err;
170 }
171
172 /*
173 * Main netlink receiving function.
174 *
175 * It checks skb, netlink header and msg sizes, and calls callback helper.
176 */
177 static void cn_rx_skb(struct sk_buff *__skb)
178 {
179 struct nlmsghdr *nlh;
180 int err;
181 struct sk_buff *skb;
182
183 skb = skb_get(__skb);
184
185 if (skb->len >= NLMSG_SPACE(0)) {
186 nlh = nlmsg_hdr(skb);
187
188 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
189 skb->len < nlh->nlmsg_len ||
190 nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
191 kfree_skb(skb);
192 return;
193 }
194
195 err = cn_call_callback(skb);
196 if (err < 0)
197 kfree_skb(skb);
198 }
199 }
200
201 /*
202 * Callback add routing - adds callback with given ID and name.
203 * If there is registered callback with the same ID it will not be added.
204 *
205 * May sleep.
206 */
207 int cn_add_callback(struct cb_id *id, char *name,
208 void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
209 {
210 int err;
211 struct cn_dev *dev = &cdev;
212
213 if (!cn_already_initialized)
214 return -EAGAIN;
215
216 err = cn_queue_add_callback(dev->cbdev, name, id, callback);
217 if (err)
218 return err;
219
220 return 0;
221 }
222 EXPORT_SYMBOL_GPL(cn_add_callback);
223
224 /*
225 * Callback remove routing - removes callback
226 * with given ID.
227 * If there is no registered callback with given
228 * ID nothing happens.
229 *
230 * May sleep while waiting for reference counter to become zero.
231 */
232 void cn_del_callback(struct cb_id *id)
233 {
234 struct cn_dev *dev = &cdev;
235
236 cn_queue_del_callback(dev->cbdev, id);
237 }
238 EXPORT_SYMBOL_GPL(cn_del_callback);
239
240 static int cn_proc_show(struct seq_file *m, void *v)
241 {
242 struct cn_queue_dev *dev = cdev.cbdev;
243 struct cn_callback_entry *cbq;
244
245 seq_printf(m, "Name ID\n");
246
247 spin_lock_bh(&dev->queue_lock);
248
249 list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
250 seq_printf(m, "%-15s %u:%u\n",
251 cbq->id.name,
252 cbq->id.id.idx,
253 cbq->id.id.val);
254 }
255
256 spin_unlock_bh(&dev->queue_lock);
257
258 return 0;
259 }
260
261 static int cn_proc_open(struct inode *inode, struct file *file)
262 {
263 return single_open(file, cn_proc_show, NULL);
264 }
265
266 static const struct file_operations cn_file_ops = {
267 .owner = THIS_MODULE,
268 .open = cn_proc_open,
269 .read = seq_read,
270 .llseek = seq_lseek,
271 .release = single_release
272 };
273
274 static int __devinit cn_init(void)
275 {
276 struct cn_dev *dev = &cdev;
277
278 dev->input = cn_rx_skb;
279
280 dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
281 CN_NETLINK_USERS + 0xf,
282 dev->input, NULL, THIS_MODULE);
283 if (!dev->nls)
284 return -EIO;
285
286 dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
287 if (!dev->cbdev) {
288 netlink_kernel_release(dev->nls);
289 return -EINVAL;
290 }
291
292 cn_already_initialized = 1;
293
294 proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
295
296 return 0;
297 }
298
299 static void __devexit cn_fini(void)
300 {
301 struct cn_dev *dev = &cdev;
302
303 cn_already_initialized = 0;
304
305 proc_net_remove(&init_net, "connector");
306
307 cn_queue_free_dev(dev->cbdev);
308 netlink_kernel_release(dev->nls);
309 }
310
311 subsys_initcall(cn_init);
312 module_exit(cn_fini);
313
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