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/compiler.h>
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/list.h>
  26 #include <linux/skbuff.h>
  27 #include <net/netlink.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/connector.h>
  30 #include <linux/slab.h>
  31 #include <linux/mutex.h>
  32 #include <linux/proc_fs.h>
  33 #include <linux/spinlock.h>
  34
  35 #include <net/sock.h>
  36
  37 MODULE_LICENSE("GPL");
  38 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
  39 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  40 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
  41
  42 static struct cn_dev cdev;
  43
  44 static int cn_already_initialized;
  45
  46 /*
  47  * Sends mult (multiple) cn_msg at a time.
  48  *
  49  * msg->seq and msg->ack are used to determine message genealogy.
  50  * When someone sends message it puts there locally unique sequence
  51  * and random acknowledge numbers.  Sequence number may be copied into
  52  * nlmsghdr->nlmsg_seq too.
  53  *
  54  * Sequence number is incremented with each message to be sent.
  55  *
  56  * If we expect a reply to our message then the sequence number in
  57  * received message MUST be the same as in original message, and
  58  * acknowledge number MUST be the same + 1.
  59  *
  60  * If we receive a message and its sequence number is not equal to the
  61  * one we are expecting then it is a new message.
  62  *
  63  * If we receive a message and its sequence number is the same as one
  64  * we are expecting but it's acknowledgement number is not equal to
  65  * the acknowledgement number in the original message + 1, then it is
  66  * a new message.
  67  *
  68  * If msg->len != len, then additional cn_msg messages are expected following
  69  * the first msg.
  70  *
  71  * The message is sent to, the portid if given, the group if given, both if
  72  * both, or if both are zero then the group is looked up and sent there.
  73  */
  74 int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group,
  75         gfp_t gfp_mask)
  76 {
  77         struct cn_callback_entry *__cbq;
  78         unsigned int size;
  79         struct sk_buff *skb;
  80         struct nlmsghdr *nlh;
  81         struct cn_msg *data;
  82         struct cn_dev *dev = &cdev;
  83         u32 group = 0;
  84         int found = 0;
  85
  86         if (portid || __group) {
  87                 group = __group;
  88         } else {
  89                 spin_lock_bh(&dev->cbdev->queue_lock);
  90                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  91                                     callback_entry) {
  92                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  93                                 found = 1;
  94                                 group = __cbq->group;
  95                                 break;
  96                         }
  97                 }
  98                 spin_unlock_bh(&dev->cbdev->queue_lock);
  99
 100                 if (!found)
 101                         return -ENODEV;
 102         }
 103
 104         if (!portid && !netlink_has_listeners(dev->nls, group))
 105                 return -ESRCH;
 106
 107         size = sizeof(*msg) + len;
 108
 109         skb = nlmsg_new(size, gfp_mask);
 110         if (!skb)
 111                 return -ENOMEM;
 112
 113         nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
 114         if (!nlh) {
 115                 kfree_skb(skb);
 116                 return -EMSGSIZE;
 117         }
 118
 119         data = nlmsg_data(nlh);
 120
 121         memcpy(data, msg, size);
 122
 123         NETLINK_CB(skb).dst_group = group;
 124
 125         if (group)
 126                 return netlink_broadcast(dev->nls, skb, portid, group,
 127                                          gfp_mask);
 128         return netlink_unicast(dev->nls, skb, portid,
 129                         !gfpflags_allow_blocking(gfp_mask));
 130 }
 131 EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
 132
 133 /* same as cn_netlink_send_mult except msg->len is used for len */
 134 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
 135         gfp_t gfp_mask)
 136 {
 137         return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask);
 138 }
 139 EXPORT_SYMBOL_GPL(cn_netlink_send);
 140
 141 /*
 142  * Callback helper - queues work and setup destructor for given data.
 143  */
 144 static int cn_call_callback(struct sk_buff *skb)
 145 {
 146         struct nlmsghdr *nlh;
 147         struct cn_callback_entry *i, *cbq = NULL;
 148         struct cn_dev *dev = &cdev;
 149         struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
 150         struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
 151         int err = -ENODEV;
 152
 153         /* verify msg->len is within skb */
 154         nlh = nlmsg_hdr(skb);
 155         if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
 156                 return -EINVAL;
 157
 158         spin_lock_bh(&dev->cbdev->queue_lock);
 159         list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
 160                 if (cn_cb_equal(&i->id.id, &msg->id)) {
 161                         refcount_inc(&i->refcnt);
 162                         cbq = i;
 163                         break;
 164                 }
 165         }
 166         spin_unlock_bh(&dev->cbdev->queue_lock);
 167
 168         if (cbq != NULL) {
 169                 cbq->callback(msg, nsp);
 170                 kfree_skb(skb);
 171                 cn_queue_release_callback(cbq);
 172                 err = 0;
 173         }
 174
 175         return err;
 176 }
 177
 178 /*
 179  * Main netlink receiving function.
 180  *
 181  * It checks skb, netlink header and msg sizes, and calls callback helper.
 182  */
 183 static void cn_rx_skb(struct sk_buff *skb)
 184 {
 185         struct nlmsghdr *nlh;
 186         int len, err;
 187
 188         if (skb->len >= NLMSG_HDRLEN) {
 189                 nlh = nlmsg_hdr(skb);
 190                 len = nlmsg_len(nlh);
 191
 192                 if (len < (int)sizeof(struct cn_msg) ||
 193                     skb->len < nlh->nlmsg_len ||
 194                     len > CONNECTOR_MAX_MSG_SIZE)
 195                         return;
 196
 197                 err = cn_call_callback(skb_get(skb));
 198                 if (err < 0)
 199                         kfree_skb(skb);
 200         }
 201 }
 202
 203 /*
 204  * Callback add routing - adds callback with given ID and name.
 205  * If there is registered callback with the same ID it will not be added.
 206  *
 207  * May sleep.
 208  */
 209 int cn_add_callback(struct cb_id *id, const char *name,
 210                     void (*callback)(struct cn_msg *,
 211                                      struct netlink_skb_parms *))
 212 {
 213         int err;
 214         struct cn_dev *dev = &cdev;
 215
 216         if (!cn_already_initialized)
 217                 return -EAGAIN;
 218
 219         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 220         if (err)
 221                 return err;
 222
 223         return 0;
 224 }
 225 EXPORT_SYMBOL_GPL(cn_add_callback);
 226
 227 /*
 228  * Callback remove routing - removes callback
 229  * with given ID.
 230  * If there is no registered callback with given
 231  * ID nothing happens.
 232  *
 233  * May sleep while waiting for reference counter to become zero.
 234  */
 235 void cn_del_callback(struct cb_id *id)
 236 {
 237         struct cn_dev *dev = &cdev;
 238
 239         cn_queue_del_callback(dev->cbdev, id);
 240 }
 241 EXPORT_SYMBOL_GPL(cn_del_callback);
 242
 243 static int __maybe_unused cn_proc_show(struct seq_file *m, void *v)
 244 {
 245         struct cn_queue_dev *dev = cdev.cbdev;
 246         struct cn_callback_entry *cbq;
 247
 248         seq_printf(m, "Name            ID\n");
 249
 250         spin_lock_bh(&dev->queue_lock);
 251
 252         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
 253                 seq_printf(m, "%-15s %u:%u\n",
 254                            cbq->id.name,
 255                            cbq->id.id.idx,
 256                            cbq->id.id.val);
 257         }
 258
 259         spin_unlock_bh(&dev->queue_lock);
 260
 261         return 0;
 262 }
 263
 264 static struct cn_dev cdev = {
 265         .input   = cn_rx_skb,
 266 };
 267
 268 static int cn_init(void)
 269 {
 270         struct cn_dev *dev = &cdev;
 271         struct netlink_kernel_cfg cfg = {
 272                 .groups = CN_NETLINK_USERS + 0xf,
 273                 .input  = dev->input,
 274         };
 275
 276         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
 277         if (!dev->nls)
 278                 return -EIO;
 279
 280         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 281         if (!dev->cbdev) {
 282                 netlink_kernel_release(dev->nls);
 283                 return -EINVAL;
 284         }
 285
 286         cn_already_initialized = 1;
 287
 288         proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show);
 289
 290         return 0;
 291 }
 292
 293 static void cn_fini(void)
 294 {
 295         struct cn_dev *dev = &cdev;
 296
 297         cn_already_initialized = 0;
 298
 299         remove_proc_entry("connector", init_net.proc_net);
 300
 301         cn_queue_free_dev(dev->cbdev);
 302         netlink_kernel_release(dev->nls);
 303 }
 304
 305 subsys_initcall(cn_init);
 306 module_exit(cn_fini);