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 a 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  * The message is sent to, the portid if given, the group if given, both if
  66  * both, or if both are zero then the group is looked up and sent there.
  67  */
  68 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
  69         gfp_t gfp_mask)
  70 {
  71         struct cn_callback_entry *__cbq;
  72         unsigned int size;
  73         struct sk_buff *skb;
  74         struct nlmsghdr *nlh;
  75         struct cn_msg *data;
  76         struct cn_dev *dev = &cdev;
  77         u32 group = 0;
  78         int found = 0;
  79
  80         if (portid || __group) {
  81                 group = __group;
  82         } else {
  83                 spin_lock_bh(&dev->cbdev->queue_lock);
  84                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  85                                     callback_entry) {
  86                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  87                                 found = 1;
  88                                 group = __cbq->group;
  89                                 break;
  90                         }
  91                 }
  92                 spin_unlock_bh(&dev->cbdev->queue_lock);
  93
  94                 if (!found)
  95                         return -ENODEV;
  96         }
  97
  98         if (!portid && !netlink_has_listeners(dev->nls, group))
  99                 return -ESRCH;
 100
 101         size = sizeof(*msg) + msg->len;
 102
 103         skb = nlmsg_new(size, gfp_mask);
 104         if (!skb)
 105                 return -ENOMEM;
 106
 107         nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
 108         if (!nlh) {
 109                 kfree_skb(skb);
 110                 return -EMSGSIZE;
 111         }
 112
 113         data = nlmsg_data(nlh);
 114
 115         memcpy(data, msg, size);
 116
 117         NETLINK_CB(skb).dst_group = group;
 118
 119         if (group)
 120                 return netlink_broadcast(dev->nls, skb, portid, group,
 121                                          gfp_mask);
 122         return netlink_unicast(dev->nls, skb, portid, !(gfp_mask&__GFP_WAIT));
 123 }
 124 EXPORT_SYMBOL_GPL(cn_netlink_send);
 125
 126 /*
 127  * Callback helper - queues work and setup destructor for given data.
 128  */
 129 static int cn_call_callback(struct sk_buff *skb)
 130 {
 131         struct cn_callback_entry *i, *cbq = NULL;
 132         struct cn_dev *dev = &cdev;
 133         struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
 134         struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
 135         int err = -ENODEV;
 136
 137         spin_lock_bh(&dev->cbdev->queue_lock);
 138         list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
 139                 if (cn_cb_equal(&i->id.id, &msg->id)) {
 140                         atomic_inc(&i->refcnt);
 141                         cbq = i;
 142                         break;
 143                 }
 144         }
 145         spin_unlock_bh(&dev->cbdev->queue_lock);
 146
 147         if (cbq != NULL) {
 148                 cbq->callback(msg, nsp);
 149                 kfree_skb(skb);
 150                 cn_queue_release_callback(cbq);
 151                 err = 0;
 152         }
 153
 154         return err;
 155 }
 156
 157 /*
 158  * Main netlink receiving function.
 159  *
 160  * It checks skb, netlink header and msg sizes, and calls callback helper.
 161  */
 162 static void cn_rx_skb(struct sk_buff *__skb)
 163 {
 164         struct nlmsghdr *nlh;
 165         struct sk_buff *skb;
 166         int len, err;
 167
 168         skb = skb_get(__skb);
 169
 170         if (skb->len >= NLMSG_HDRLEN) {
 171                 nlh = nlmsg_hdr(skb);
 172                 len = nlmsg_len(nlh);
 173
 174                 if (len < (int)sizeof(struct cn_msg) ||
 175                     skb->len < nlh->nlmsg_len ||
 176                     len > CONNECTOR_MAX_MSG_SIZE) {
 177                         kfree_skb(skb);
 178                         return;
 179                 }
 180
 181                 err = cn_call_callback(skb);
 182                 if (err < 0)
 183                         kfree_skb(skb);
 184         }
 185 }
 186
 187 /*
 188  * Callback add routing - adds callback with given ID and name.
 189  * If there is registered callback with the same ID it will not be added.
 190  *
 191  * May sleep.
 192  */
 193 int cn_add_callback(struct cb_id *id, const char *name,
 194                     void (*callback)(struct cn_msg *,
 195                                      struct netlink_skb_parms *))
 196 {
 197         int err;
 198         struct cn_dev *dev = &cdev;
 199
 200         if (!cn_already_initialized)
 201                 return -EAGAIN;
 202
 203         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 204         if (err)
 205                 return err;
 206
 207         return 0;
 208 }
 209 EXPORT_SYMBOL_GPL(cn_add_callback);
 210
 211 /*
 212  * Callback remove routing - removes callback
 213  * with given ID.
 214  * If there is no registered callback with given
 215  * ID nothing happens.
 216  *
 217  * May sleep while waiting for reference counter to become zero.
 218  */
 219 void cn_del_callback(struct cb_id *id)
 220 {
 221         struct cn_dev *dev = &cdev;
 222
 223         cn_queue_del_callback(dev->cbdev, id);
 224 }
 225 EXPORT_SYMBOL_GPL(cn_del_callback);
 226
 227 static int cn_proc_show(struct seq_file *m, void *v)
 228 {
 229         struct cn_queue_dev *dev = cdev.cbdev;
 230         struct cn_callback_entry *cbq;
 231
 232         seq_printf(m, "Name            ID\n");
 233
 234         spin_lock_bh(&dev->queue_lock);
 235
 236         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 237                 seq_printf(m, "%-15s %u:%u\n",
 238                            cbq->id.name,
 239                            cbq->id.id.idx,
 240                            cbq->id.id.val);
 241         }
 242
 243         spin_unlock_bh(&dev->queue_lock);
 244
 245         return 0;
 246 }
 247
 248 static int cn_proc_open(struct inode *inode, struct file *file)
 249 {
 250         return single_open(file, cn_proc_show, NULL);
 251 }
 252
 253 static const struct file_operations cn_file_ops = {
 254         .owner   = THIS_MODULE,
 255         .open    = cn_proc_open,
 256         .read    = seq_read,
 257         .llseek  = seq_lseek,
 258         .release = single_release
 259 };
 260
 261 static struct cn_dev cdev = {
 262         .input   = cn_rx_skb,
 263 };
 264
 265 static int cn_init(void)
 266 {
 267         struct cn_dev *dev = &cdev;
 268         struct netlink_kernel_cfg cfg = {
 269                 .groups = CN_NETLINK_USERS + 0xf,
 270                 .input  = dev->input,
 271         };
 272
 273         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
 274         if (!dev->nls)
 275                 return -EIO;
 276
 277         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 278         if (!dev->cbdev) {
 279                 netlink_kernel_release(dev->nls);
 280                 return -EINVAL;
 281         }
 282
 283         cn_already_initialized = 1;
 284
 285         proc_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
 286
 287         return 0;
 288 }
 289
 290 static void cn_fini(void)
 291 {
 292         struct cn_dev *dev = &cdev;
 293
 294         cn_already_initialized = 0;
 295
 296         remove_proc_entry("connector", init_net.proc_net);
 297
 298         cn_queue_free_dev(dev->cbdev);
 299         netlink_kernel_release(dev->nls);
 300 }
 301
 302 subsys_initcall(cn_init);
 303 module_exit(cn_fini);