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, !(gfp_mask&__GFP_WAIT));
 128 }
 129 EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
 130
 131 /* same as cn_netlink_send_mult except msg->len is used for len */
 132 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
 133         gfp_t gfp_mask)
 134 {
 135         return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask);
 136 }
 137 EXPORT_SYMBOL_GPL(cn_netlink_send);
 138
 139 /*
 140  * Callback helper - queues work and setup destructor for given data.
 141  */
 142 static int cn_call_callback(struct sk_buff *skb)
 143 {
 144         struct nlmsghdr *nlh;
 145         struct cn_callback_entry *i, *cbq = NULL;
 146         struct cn_dev *dev = &cdev;
 147         struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
 148         struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
 149         int err = -ENODEV;
 150
 151         /* verify msg->len is within skb */
 152         nlh = nlmsg_hdr(skb);
 153         if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
 154                 return -EINVAL;
 155
 156         spin_lock_bh(&dev->cbdev->queue_lock);
 157         list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
 158                 if (cn_cb_equal(&i->id.id, &msg->id)) {
 159                         atomic_inc(&i->refcnt);
 160                         cbq = i;
 161                         break;
 162                 }
 163         }
 164         spin_unlock_bh(&dev->cbdev->queue_lock);
 165
 166         if (cbq != NULL) {
 167                 cbq->callback(msg, nsp);
 168                 kfree_skb(skb);
 169                 cn_queue_release_callback(cbq);
 170                 err = 0;
 171         }
 172
 173         return err;
 174 }
 175
 176 /*
 177  * Main netlink receiving function.
 178  *
 179  * It checks skb, netlink header and msg sizes, and calls callback helper.
 180  */
 181 static void cn_rx_skb(struct sk_buff *skb)
 182 {
 183         struct nlmsghdr *nlh;
 184         int len, err;
 185
 186         if (skb->len >= NLMSG_HDRLEN) {
 187                 nlh = nlmsg_hdr(skb);
 188                 len = nlmsg_len(nlh);
 189
 190                 if (len < (int)sizeof(struct cn_msg) ||
 191                     skb->len < nlh->nlmsg_len ||
 192                     len > CONNECTOR_MAX_MSG_SIZE)
 193                         return;
 194
 195                 err = cn_call_callback(skb_get(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, const char *name,
 208                     void (*callback)(struct cn_msg *,
 209                                      struct netlink_skb_parms *))
 210 {
 211         int err;
 212         struct cn_dev *dev = &cdev;
 213
 214         if (!cn_already_initialized)
 215                 return -EAGAIN;
 216
 217         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 218         if (err)
 219                 return err;
 220
 221         return 0;
 222 }
 223 EXPORT_SYMBOL_GPL(cn_add_callback);
 224
 225 /*
 226  * Callback remove routing - removes callback
 227  * with given ID.
 228  * If there is no registered callback with given
 229  * ID nothing happens.
 230  *
 231  * May sleep while waiting for reference counter to become zero.
 232  */
 233 void cn_del_callback(struct cb_id *id)
 234 {
 235         struct cn_dev *dev = &cdev;
 236
 237         cn_queue_del_callback(dev->cbdev, id);
 238 }
 239 EXPORT_SYMBOL_GPL(cn_del_callback);
 240
 241 static int cn_proc_show(struct seq_file *m, void *v)
 242 {
 243         struct cn_queue_dev *dev = cdev.cbdev;
 244         struct cn_callback_entry *cbq;
 245
 246         seq_printf(m, "Name            ID\n");
 247
 248         spin_lock_bh(&dev->queue_lock);
 249
 250         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 251                 seq_printf(m, "%-15s %u:%u\n",
 252                            cbq->id.name,
 253                            cbq->id.id.idx,
 254                            cbq->id.id.val);
 255         }
 256
 257         spin_unlock_bh(&dev->queue_lock);
 258
 259         return 0;
 260 }
 261
 262 static int cn_proc_open(struct inode *inode, struct file *file)
 263 {
 264         return single_open(file, cn_proc_show, NULL);
 265 }
 266
 267 static const struct file_operations cn_file_ops = {
 268         .owner   = THIS_MODULE,
 269         .open    = cn_proc_open,
 270         .read    = seq_read,
 271         .llseek  = seq_lseek,
 272         .release = single_release
 273 };
 274
 275 static struct cn_dev cdev = {
 276         .input   = cn_rx_skb,
 277 };
 278
 279 static int cn_init(void)
 280 {
 281         struct cn_dev *dev = &cdev;
 282         struct netlink_kernel_cfg cfg = {
 283                 .groups = CN_NETLINK_USERS + 0xf,
 284                 .input  = dev->input,
 285         };
 286
 287         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
 288         if (!dev->nls)
 289                 return -EIO;
 290
 291         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 292         if (!dev->cbdev) {
 293                 netlink_kernel_release(dev->nls);
 294                 return -EINVAL;
 295         }
 296
 297         cn_already_initialized = 1;
 298
 299         proc_create("connector", S_IRUGO, init_net.proc_net, &cn_file_ops);
 300
 301         return 0;
 302 }
 303
 304 static void cn_fini(void)
 305 {
 306         struct cn_dev *dev = &cdev;
 307
 308         cn_already_initialized = 0;
 309
 310         remove_proc_entry("connector", init_net.proc_net);
 311
 312         cn_queue_free_dev(dev->cbdev);
 313         netlink_kernel_release(dev->nls);
 314 }
 315
 316 subsys_initcall(cn_init);
 317 module_exit(cn_fini);