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 <net/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
  36 MODULE_LICENSE("GPL");
  37 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
  38 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  39 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
  40
  41 static struct cn_dev cdev;
  42
  43 static 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  */
  66 int 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 = sizeof(*msg) + msg->len;
  99
 100         skb = nlmsg_new(size, gfp_mask);
 101         if (!skb)
 102                 return -ENOMEM;
 103
 104         nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 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 }
 118 EXPORT_SYMBOL_GPL(cn_netlink_send);
 119
 120 /*
 121  * Callback helper - queues work and setup destructor for given data.
 122  */
 123 static 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  */
 157 static void cn_rx_skb(struct sk_buff *__skb)
 158 {
 159         struct nlmsghdr *nlh;
 160         struct sk_buff *skb;
 161         int len, err;
 162
 163         skb = skb_get(__skb);
 164
 165         if (skb->len >= NLMSG_HDRLEN) {
 166                 nlh = nlmsg_hdr(skb);
 167                 len = nlmsg_len(nlh);
 168
 169                 if (len < (int)sizeof(struct cn_msg) ||
 170                     skb->len < nlh->nlmsg_len ||
 171                     len > CONNECTOR_MAX_MSG_SIZE) {
 172                         kfree_skb(skb);
 173                         return;
 174                 }
 175
 176                 err = cn_call_callback(skb);
 177                 if (err < 0)
 178                         kfree_skb(skb);
 179         }
 180 }
 181
 182 /*
 183  * Callback add routing - adds callback with given ID and name.
 184  * If there is registered callback with the same ID it will not be added.
 185  *
 186  * May sleep.
 187  */
 188 int cn_add_callback(struct cb_id *id, const char *name,
 189                     void (*callback)(struct cn_msg *,
 190                                      struct netlink_skb_parms *))
 191 {
 192         int err;
 193         struct cn_dev *dev = &cdev;
 194
 195         if (!cn_already_initialized)
 196                 return -EAGAIN;
 197
 198         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 199         if (err)
 200                 return err;
 201
 202         return 0;
 203 }
 204 EXPORT_SYMBOL_GPL(cn_add_callback);
 205
 206 /*
 207  * Callback remove routing - removes callback
 208  * with given ID.
 209  * If there is no registered callback with given
 210  * ID nothing happens.
 211  *
 212  * May sleep while waiting for reference counter to become zero.
 213  */
 214 void cn_del_callback(struct cb_id *id)
 215 {
 216         struct cn_dev *dev = &cdev;
 217
 218         cn_queue_del_callback(dev->cbdev, id);
 219 }
 220 EXPORT_SYMBOL_GPL(cn_del_callback);
 221
 222 static int cn_proc_show(struct seq_file *m, void *v)
 223 {
 224         struct cn_queue_dev *dev = cdev.cbdev;
 225         struct cn_callback_entry *cbq;
 226
 227         seq_printf(m, "Name            ID\n");
 228
 229         spin_lock_bh(&dev->queue_lock);
 230
 231         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 232                 seq_printf(m, "%-15s %u:%u\n",
 233                            cbq->id.name,
 234                            cbq->id.id.idx,
 235                            cbq->id.id.val);
 236         }
 237
 238         spin_unlock_bh(&dev->queue_lock);
 239
 240         return 0;
 241 }
 242
 243 static int cn_proc_open(struct inode *inode, struct file *file)
 244 {
 245         return single_open(file, cn_proc_show, NULL);
 246 }
 247
 248 static const struct file_operations cn_file_ops = {
 249         .owner   = THIS_MODULE,
 250         .open    = cn_proc_open,
 251         .read    = seq_read,
 252         .llseek  = seq_lseek,
 253         .release = single_release
 254 };
 255
 256 static struct cn_dev cdev = {
 257         .input   = cn_rx_skb,
 258 };
 259
 260 static int cn_init(void)
 261 {
 262         struct cn_dev *dev = &cdev;
 263         struct netlink_kernel_cfg cfg = {
 264                 .groups = CN_NETLINK_USERS + 0xf,
 265                 .input  = dev->input,
 266         };
 267
 268         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &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_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
 281
 282         return 0;
 283 }
 284
 285 static void cn_fini(void)
 286 {
 287         struct cn_dev *dev = &cdev;
 288
 289         cn_already_initialized = 0;
 290
 291         remove_proc_entry("connector", init_net.proc_net);
 292
 293         cn_queue_free_dev(dev->cbdev);
 294         netlink_kernel_release(dev->nls);
 295 }
 296
 297 subsys_initcall(cn_init);
 298 module_exit(cn_fini);