Root/drivers/connector/connector.c

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 __devinit 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,
268                     THIS_MODULE, &cfg);
269    if (!dev->nls)
270        return -EIO;
271
272    dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
273    if (!dev->cbdev) {
274        netlink_kernel_release(dev->nls);
275        return -EINVAL;
276    }
277
278    cn_already_initialized = 1;
279
280    proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
281
282    return 0;
283}
284
285static void __devexit cn_fini(void)
286{
287    struct cn_dev *dev = &cdev;
288
289    cn_already_initialized = 0;
290
291    proc_net_remove(&init_net, "connector");
292
293    cn_queue_free_dev(dev->cbdev);
294    netlink_kernel_release(dev->nls);
295}
296
297subsys_initcall(cn_init);
298module_exit(cn_fini);
299

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