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  * Sends mult (multiple) cn_msg at a time.
  47  *
  48  * msg->seq and msg->ack are used to determine message genealogy.
  49  * When someone sends message it puts there locally unique sequence
  50  * and random acknowledge numbers.  Sequence number may be copied into
  51  * nlmsghdr->nlmsg_seq too.
  52  *
  53  * Sequence number is incremented with each message to be sent.
  54  *
  55  * If we expect a reply to our message then the sequence number in
  56  * received message MUST be the same as in original message, and
  57  * acknowledge number MUST be the same + 1.
  58  *
  59  * If we receive a message and its sequence number is not equal to the
  60  * one we are expecting then it is a new message.
  61  *
  62  * If we receive a message and its sequence number is the same as one
  63  * we are expecting but it's acknowledgement number is not equal to
  64  * the acknowledgement number in the original message + 1, then it is
  65  * a new message.
  66  *
  67  * If msg->len != len, then additional cn_msg messages are expected following
  68  * the first msg.
  69  *
  70  * The message is sent to, the portid if given, the group if given, both if
  71  * both, or if both are zero then the group is looked up and sent there.
  72  */
  73 int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group,
  74         gfp_t gfp_mask)
  75 {
  76         struct cn_callback_entry *__cbq;
  77         unsigned int size;
  78         struct sk_buff *skb;
  79         struct nlmsghdr *nlh;
  80         struct cn_msg *data;
  81         struct cn_dev *dev = &cdev;
  82         u32 group = 0;
  83         int found = 0;
  84
  85         if (portid || __group) {
  86                 group = __group;
  87         } else {
  88                 spin_lock_bh(&dev->cbdev->queue_lock);
  89                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  90                                     callback_entry) {
  91                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  92                                 found = 1;
  93                                 group = __cbq->group;
  94                                 break;
  95                         }
  96                 }
  97                 spin_unlock_bh(&dev->cbdev->queue_lock);
  98
  99                 if (!found)
 100                         return -ENODEV;
 101         }
 102
 103         if (!portid && !netlink_has_listeners(dev->nls, group))
 104                 return -ESRCH;
 105
 106         size = sizeof(*msg) + len;
 107
 108         skb = nlmsg_new(size, gfp_mask);
 109         if (!skb)
 110                 return -ENOMEM;
 111
 112         nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
 113         if (!nlh) {
 114                 kfree_skb(skb);
 115                 return -EMSGSIZE;
 116         }
 117
 118         data = nlmsg_data(nlh);
 119
 120         memcpy(data, msg, size);
 121
 122         NETLINK_CB(skb).dst_group = group;
 123
 124         if (group)
 125                 return netlink_broadcast(dev->nls, skb, portid, group,
 126                                          gfp_mask);
 127         return netlink_unicast(dev->nls, skb, portid,
 128                         !gfpflags_allow_blocking(gfp_mask));
 129 }
 130 EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
 131
 132 /* same as cn_netlink_send_mult except msg->len is used for len */
 133 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
 134         gfp_t gfp_mask)
 135 {
 136         return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask);
 137 }
 138 EXPORT_SYMBOL_GPL(cn_netlink_send);
 139
 140 /*
 141  * Callback helper - queues work and setup destructor for given data.
 142  */
 143 static int cn_call_callback(struct sk_buff *skb)
 144 {
 145         struct nlmsghdr *nlh;
 146         struct cn_callback_entry *i, *cbq = NULL;
 147         struct cn_dev *dev = &cdev;
 148         struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
 149         struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
 150         int err = -ENODEV;
 151
 152         /* verify msg->len is within skb */
 153         nlh = nlmsg_hdr(skb);
 154         if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
 155                 return -EINVAL;
 156
 157         spin_lock_bh(&dev->cbdev->queue_lock);
 158         list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
 159                 if (cn_cb_equal(&i->id.id, &msg->id)) {
 160                         atomic_inc(&i->refcnt);
 161                         cbq = i;
 162                         break;
 163                 }
 164         }
 165         spin_unlock_bh(&dev->cbdev->queue_lock);
 166
 167         if (cbq != NULL) {
 168                 cbq->callback(msg, nsp);
 169                 kfree_skb(skb);
 170                 cn_queue_release_callback(cbq);
 171                 err = 0;
 172         }
 173
 174         return err;
 175 }
 176
 177 /*
 178  * Main netlink receiving function.
 179  *
 180  * It checks skb, netlink header and msg sizes, and calls callback helper.
 181  */
 182 static void cn_rx_skb(struct sk_buff *skb)
 183 {
 184         struct nlmsghdr *nlh;
 185         int len, err;
 186
 187         if (skb->len >= NLMSG_HDRLEN) {
 188                 nlh = nlmsg_hdr(skb);
 189                 len = nlmsg_len(nlh);
 190
 191                 if (len < (int)sizeof(struct cn_msg) ||
 192                     skb->len < nlh->nlmsg_len ||
 193                     len > CONNECTOR_MAX_MSG_SIZE)
 194                         return;
 195
 196                 err = cn_call_callback(skb_get(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  */
 208 int cn_add_callback(struct cb_id *id, const char *name,
 209                     void (*callback)(struct cn_msg *,
 210                                      struct netlink_skb_parms *))
 211 {
 212         int err;
 213         struct cn_dev *dev = &cdev;
 214
 215         if (!cn_already_initialized)
 216                 return -EAGAIN;
 217
 218         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 219         if (err)
 220                 return err;
 221
 222         return 0;
 223 }
 224 EXPORT_SYMBOL_GPL(cn_add_callback);
 225
 226 /*
 227  * Callback remove routing - removes callback
 228  * with given ID.
 229  * If there is no registered callback with given
 230  * ID nothing happens.
 231  *
 232  * May sleep while waiting for reference counter to become zero.
 233  */
 234 void cn_del_callback(struct cb_id *id)
 235 {
 236         struct cn_dev *dev = &cdev;
 237
 238         cn_queue_del_callback(dev->cbdev, id);
 239 }
 240 EXPORT_SYMBOL_GPL(cn_del_callback);
 241
 242 static int cn_proc_show(struct seq_file *m, void *v)
 243 {
 244         struct cn_queue_dev *dev = cdev.cbdev;
 245         struct cn_callback_entry *cbq;
 246
 247         seq_printf(m, "Name            ID\n");
 248
 249         spin_lock_bh(&dev->queue_lock);
 250
 251         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 252                 seq_printf(m, "%-15s %u:%u\n",
 253                            cbq->id.name,
 254                            cbq->id.id.idx,
 255                            cbq->id.id.val);
 256         }
 257
 258         spin_unlock_bh(&dev->queue_lock);
 259
 260         return 0;
 261 }
 262
 263 static int cn_proc_open(struct inode *inode, struct file *file)
 264 {
 265         return single_open(file, cn_proc_show, NULL);
 266 }
 267
 268 static const struct file_operations cn_file_ops = {
 269         .owner   = THIS_MODULE,
 270         .open    = cn_proc_open,
 271         .read    = seq_read,
 272         .llseek  = seq_lseek,
 273         .release = single_release
 274 };
 275
 276 static struct cn_dev cdev = {
 277         .input   = cn_rx_skb,
 278 };
 279
 280 static int cn_init(void)
 281 {
 282         struct cn_dev *dev = &cdev;
 283         struct netlink_kernel_cfg cfg = {
 284                 .groups = CN_NETLINK_USERS + 0xf,
 285                 .input  = dev->input,
 286         };
 287
 288         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
 289         if (!dev->nls)
 290                 return -EIO;
 291
 292         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 293         if (!dev->cbdev) {
 294                 netlink_kernel_release(dev->nls);
 295                 return -EINVAL;
 296         }
 297
 298         cn_already_initialized = 1;
 299
 300         proc_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
 301
 302         return 0;
 303 }
 304
 305 static void cn_fini(void)
 306 {
 307         struct cn_dev *dev = &cdev;
 308
 309         cn_already_initialized = 0;
 310
 311         remove_proc_entry("connector", init_net.proc_net);
 312
 313         cn_queue_free_dev(dev->cbdev);
 314         netlink_kernel_release(dev->nls);
 315 }
 316
 317 subsys_initcall(cn_init);
 318 module_exit(cn_fini);