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, size); 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); 299