net/netlink/genetlink.c

   1 /*
   2  * NETLINK      Generic Netlink Family
   3  *
   4  *              Authors:        Jamal Hadi Salim
   5  *                              Thomas Graf <tgraf@suug.ch>
   6  */
   7
   8 #include <linux/config.h>
   9 #include <linux/module.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/types.h>
  13 #include <linux/socket.h>
  14 #include <linux/string.h>
  15 #include <linux/skbuff.h>
  16 #include <net/sock.h>
  17 #include <net/genetlink.h>
  18
  19 struct sock *genl_sock = NULL;
  20
  21 static DECLARE_MUTEX(genl_sem); /* serialization of message processing */
  22
  23 static void genl_lock(void)
  24 {
  25         down(&genl_sem);
  26 }
  27
  28 static int genl_trylock(void)
  29 {
  30         return down_trylock(&genl_sem);
  31 }
  32
  33 static void genl_unlock(void)
  34 {
  35         up(&genl_sem);
  36
  37         if (genl_sock && genl_sock->sk_receive_queue.qlen)
  38                 genl_sock->sk_data_ready(genl_sock, 0);
  39 }
  40
  41 #define GENL_FAM_TAB_SIZE       16
  42 #define GENL_FAM_TAB_MASK       (GENL_FAM_TAB_SIZE - 1)
  43
  44 static struct list_head family_ht[GENL_FAM_TAB_SIZE];
  45
  46 static int genl_ctrl_event(int event, void *data);
  47
  48 static inline unsigned int genl_family_hash(unsigned int id)
  49 {
  50         return id & GENL_FAM_TAB_MASK;
  51 }
  52
  53 static inline struct list_head *genl_family_chain(unsigned int id)
  54 {
  55         return &family_ht[genl_family_hash(id)];
  56 }
  57
  58 static struct genl_family *genl_family_find_byid(unsigned int id)
  59 {
  60         struct genl_family *f;
  61
  62         list_for_each_entry(f, genl_family_chain(id), family_list)
  63                 if (f->id == id)
  64                         return f;
  65
  66         return NULL;
  67 }
  68
  69 static struct genl_family *genl_family_find_byname(char *name)
  70 {
  71         struct genl_family *f;
  72         int i;
  73
  74         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
  75                 list_for_each_entry(f, genl_family_chain(i), family_list)
  76                         if (strcmp(f->name, name) == 0)
  77                                 return f;
  78
  79         return NULL;
  80 }
  81
  82 static struct genl_ops *genl_get_cmd(u8 cmd, struct genl_family *family)
  83 {
  84         struct genl_ops *ops;
  85
  86         list_for_each_entry(ops, &family->ops_list, ops_list)
  87                 if (ops->cmd == cmd)
  88                         return ops;
  89
  90         return NULL;
  91 }
  92
  93 /* Of course we are going to have problems once we hit
  94  * 2^16 alive types, but that can only happen by year 2K
  95 */
  96 static inline u16 genl_generate_id(void)
  97 {
  98         static u16 id_gen_idx;
  99         int overflowed = 0;
 100
 101         do {
 102                 if (id_gen_idx == 0)
 103                         id_gen_idx = GENL_MIN_ID;
 104
 105                 if (++id_gen_idx > GENL_MAX_ID) {
 106                         if (!overflowed) {
 107                                 overflowed = 1;
 108                                 id_gen_idx = 0;
 109                                 continue;
 110                         } else
 111                                 return 0;
 112                 }
 113
 114         } while (genl_family_find_byid(id_gen_idx));
 115
 116         return id_gen_idx;
 117 }
 118
 119 /**
 120  * genl_register_ops - register generic netlink operations
 121  * @family: generic netlink family
 122  * @ops: operations to be registered
 123  *
 124  * Registers the specified operations and assigns them to the specified
 125  * family. Either a doit or dumpit callback must be specified or the
 126  * operation will fail. Only one operation structure per command
 127  * identifier may be registered.
 128  *
 129  * See include/net/genetlink.h for more documenation on the operations
 130  * structure.
 131  *
 132  * Returns 0 on success or a negative error code.
 133  */
 134 int genl_register_ops(struct genl_family *family, struct genl_ops *ops)
 135 {
 136         int err = -EINVAL;
 137
 138         if (ops->dumpit == NULL && ops->doit == NULL)
 139                 goto errout;
 140
 141         if (genl_get_cmd(ops->cmd, family)) {
 142                 err = -EEXIST;
 143                 goto errout;
 144         }
 145
 146         genl_lock();
 147         list_add_tail(&ops->ops_list, &family->ops_list);
 148         genl_unlock();
 149
 150         genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
 151         err = 0;
 152 errout:
 153         return err;
 154 }
 155
 156 /**
 157  * genl_unregister_ops - unregister generic netlink operations
 158  * @family: generic netlink family
 159  * @ops: operations to be unregistered
 160  *
 161  * Unregisters the specified operations and unassigns them from the
 162  * specified family. The operation blocks until the current message
 163  * processing has finished and doesn't start again until the
 164  * unregister process has finished.
 165  *
 166  * Note: It is not necessary to unregister all operations before
 167  *       unregistering the family, unregistering the family will cause
 168  *       all assigned operations to be unregistered automatically.
 169  *
 170  * Returns 0 on success or a negative error code.
 171  */
 172 int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
 173 {
 174         struct genl_ops *rc;
 175
 176         genl_lock();
 177         list_for_each_entry(rc, &family->ops_list, ops_list) {
 178                 if (rc == ops) {
 179                         list_del(&ops->ops_list);
 180                         genl_unlock();
 181                         genl_ctrl_event(CTRL_CMD_DELOPS, ops);
 182                         return 0;
 183                 }
 184         }
 185         genl_unlock();
 186
 187         return -ENOENT;
 188 }
 189
 190 /**
 191  * genl_register_family - register a generic netlink family
 192  * @family: generic netlink family
 193  *
 194  * Registers the specified family after validating it first. Only one
 195  * family may be registered with the same family name or identifier.
 196  * The family id may equal GENL_ID_GENERATE causing an unique id to
 197  * be automatically generated and assigned.
 198  *
 199  * Return 0 on success or a negative error code.
 200  */
 201 int genl_register_family(struct genl_family *family)
 202 {
 203         int err = -EINVAL;
 204
 205         if (family->id && family->id < GENL_MIN_ID)
 206                 goto errout;
 207
 208         if (family->id > GENL_MAX_ID)
 209                 goto errout;
 210
 211         INIT_LIST_HEAD(&family->ops_list);
 212
 213         genl_lock();
 214
 215         if (genl_family_find_byname(family->name)) {
 216                 err = -EEXIST;
 217                 goto errout_locked;
 218         }
 219
 220         if (genl_family_find_byid(family->id)) {
 221                 err = -EEXIST;
 222                 goto errout_locked;
 223         }
 224
 225         if (!try_module_get(family->owner)) {
 226                 err = -EBUSY;
 227                 goto errout_locked;
 228         }
 229
 230         if (family->id == GENL_ID_GENERATE) {
 231                 u16 newid = genl_generate_id();
 232
 233                 if (!newid) {
 234                         err = -ENOMEM;
 235                         goto errout_locked;
 236                 }
 237
 238                 family->id = newid;
 239         }
 240
 241         if (family->maxattr) {
 242                 family->attrbuf = kmalloc((family->maxattr+1) *
 243                                         sizeof(struct nlattr *), GFP_KERNEL);
 244                 if (family->attrbuf == NULL) {
 245                         err = -ENOMEM;
 246                         goto errout;
 247                 }
 248         } else
 249                 family->attrbuf = NULL;
 250
 251         list_add_tail(&family->family_list, genl_family_chain(family->id));
 252         genl_unlock();
 253
 254         genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
 255
 256         return 0;
 257
 258 errout_locked:
 259         genl_unlock();
 260 errout:
 261         return err;
 262 }
 263
 264 /**
 265  * genl_unregister_family - unregister generic netlink family
 266  * @family: generic netlink family
 267  *
 268  * Unregisters the specified family.
 269  *
 270  * Returns 0 on success or a negative error code.
 271  */
 272 int genl_unregister_family(struct genl_family *family)
 273 {
 274         struct genl_family *rc;
 275
 276         genl_lock();
 277
 278         list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
 279                 if (family->id != rc->id || strcmp(rc->name, family->name))
 280                         continue;
 281
 282                 list_del(&rc->family_list);
 283                 INIT_LIST_HEAD(&family->ops_list);
 284                 genl_unlock();
 285
 286                 module_put(family->owner);
 287                 kfree(family->attrbuf);
 288                 genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
 289                 return 0;
 290         }
 291
 292         genl_unlock();
 293
 294         return -ENOENT;
 295 }
 296
 297 static inline int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 298                                int *errp)
 299 {
 300         struct genl_ops *ops;
 301         struct genl_family *family;
 302         struct genl_info info;
 303         struct genlmsghdr *hdr = nlmsg_data(nlh);
 304         int hdrlen, err = -EINVAL;
 305
 306         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 307                 goto ignore;
 308
 309         if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
 310                 goto ignore;
 311
 312         family = genl_family_find_byid(nlh->nlmsg_type);
 313         if (family == NULL) {
 314                 err = -ENOENT;
 315                 goto errout;
 316         }
 317
 318         hdrlen = GENL_HDRLEN + family->hdrsize;
 319         if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 320                 goto errout;
 321
 322         ops = genl_get_cmd(hdr->cmd, family);
 323         if (ops == NULL) {
 324                 err = -EOPNOTSUPP;
 325                 goto errout;
 326         }
 327
 328         if ((ops->flags & GENL_ADMIN_PERM) && security_netlink_recv(skb)) {
 329                 err = -EPERM;
 330                 goto errout;
 331         }
 332
 333         if (nlh->nlmsg_flags & NLM_F_DUMP) {
 334                 if (ops->dumpit == NULL) {
 335                         err = -EOPNOTSUPP;
 336                         goto errout;
 337                 }
 338
 339                 *errp = err = netlink_dump_start(genl_sock, skb, nlh,
 340                                                  ops->dumpit, NULL);
 341                 if (err == 0)
 342                         skb_pull(skb, min(NLMSG_ALIGN(nlh->nlmsg_len),
 343                                           skb->len));
 344                 return -1;
 345         }
 346
 347         if (ops->doit == NULL) {
 348                 err = -EOPNOTSUPP;
 349                 goto errout;
 350         }
 351
 352         if (family->attrbuf) {
 353                 err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
 354                                   ops->policy);
 355                 if (err < 0)
 356                         goto errout;
 357         }
 358
 359         info.snd_seq = nlh->nlmsg_seq;
 360         info.snd_pid = NETLINK_CB(skb).pid;
 361         info.nlhdr = nlh;
 362         info.genlhdr = nlmsg_data(nlh);
 363         info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 364         info.attrs = family->attrbuf;
 365
 366         *errp = err = ops->doit(skb, &info);
 367         return err;
 368
 369 ignore:
 370         return 0;
 371
 372 errout:
 373         *errp = err;
 374         return -1;
 375 }
 376
 377 static void genl_rcv(struct sock *sk, int len)
 378 {
 379         unsigned int qlen = 0;
 380
 381         do {
 382                 if (genl_trylock())
 383                         return;
 384                 netlink_run_queue(sk, &qlen, &genl_rcv_msg);
 385                 genl_unlock();
 386         } while (qlen && genl_sock && genl_sock->sk_receive_queue.qlen);
 387 }
 388
 389 /**************************************************************************
 390  * Controller
 391  **************************************************************************/
 392
 393 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
 394                           u32 flags, struct sk_buff *skb, u8 cmd)
 395 {
 396         void *hdr;
 397
 398         hdr = genlmsg_put(skb, pid, seq, GENL_ID_CTRL, 0, flags, cmd,
 399                           family->version);
 400         if (hdr == NULL)
 401                 return -1;
 402
 403         NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
 404         NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
 405
 406         return genlmsg_end(skb, hdr);
 407
 408 nla_put_failure:
 409         return genlmsg_cancel(skb, hdr);
 410 }
 411
 412 static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 413 {
 414
 415         int i, n = 0;
 416         struct genl_family *rt;
 417         int chains_to_skip = cb->args[0];
 418         int fams_to_skip = cb->args[1];
 419
 420         for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
 421                 if (i < chains_to_skip)
 422                         continue;
 423                 n = 0;
 424                 list_for_each_entry(rt, genl_family_chain(i), family_list) {
 425                         if (++n < fams_to_skip)
 426                                 continue;
 427                         if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
 428                                            cb->nlh->nlmsg_seq, NLM_F_MULTI,
 429                                            skb, CTRL_CMD_NEWFAMILY) < 0)
 430                                 goto errout;
 431                 }
 432
 433                 fams_to_skip = 0;
 434         }
 435
 436 errout:
 437         cb->args[0] = i;
 438         cb->args[1] = n;
 439
 440         return skb->len;
 441 }
 442
 443 static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
 444                                       int seq, u8 cmd)
 445 {
 446         struct sk_buff *skb;
 447         int err;
 448
 449         skb = nlmsg_new(NLMSG_GOODSIZE);
 450         if (skb == NULL)
 451                 return ERR_PTR(-ENOBUFS);
 452
 453         err = ctrl_fill_info(family, pid, seq, 0, skb, cmd);
 454         if (err < 0) {
 455                 nlmsg_free(skb);
 456                 return ERR_PTR(err);
 457         }
 458
 459         return skb;
 460 }
 461
 462 static struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] __read_mostly = {
 463         [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
 464         [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_STRING },
 465 };
 466
 467 static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 468 {
 469         struct sk_buff *msg;
 470         struct genl_family *res = NULL;
 471         int err = -EINVAL;
 472
 473         if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
 474                 u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
 475                 res = genl_family_find_byid(id);
 476         }
 477
 478         if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
 479                 char name[GENL_NAMSIZ];
 480
 481                 if (nla_strlcpy(name, info->attrs[CTRL_ATTR_FAMILY_NAME],
 482                                 GENL_NAMSIZ) >= GENL_NAMSIZ)
 483                         goto errout;
 484
 485                 res = genl_family_find_byname(name);
 486         }
 487
 488         if (res == NULL) {
 489                 err = -ENOENT;
 490                 goto errout;
 491         }
 492
 493         msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
 494                              CTRL_CMD_NEWFAMILY);
 495         if (IS_ERR(msg)) {
 496                 err = PTR_ERR(msg);
 497                 goto errout;
 498         }
 499
 500         err = genlmsg_unicast(msg, info->snd_pid);
 501 errout:
 502         return err;
 503 }
 504
 505 static int genl_ctrl_event(int event, void *data)
 506 {
 507         struct sk_buff *msg;
 508
 509         if (genl_sock == NULL)
 510                 return 0;
 511
 512         switch (event) {
 513         case CTRL_CMD_NEWFAMILY:
 514         case CTRL_CMD_DELFAMILY:
 515                 msg = ctrl_build_msg(data, 0, 0, event);
 516                 if (IS_ERR(msg))
 517                         return PTR_ERR(msg);
 518
 519                 genlmsg_multicast(msg, 0, GENL_ID_CTRL);
 520                 break;
 521         }
 522
 523         return 0;
 524 }
 525
 526 static struct genl_ops genl_ctrl_ops = {
 527         .cmd            = CTRL_CMD_GETFAMILY,
 528         .doit           = ctrl_getfamily,
 529         .dumpit         = ctrl_dumpfamily,
 530         .policy         = ctrl_policy,
 531 };
 532
 533 static struct genl_family genl_ctrl = {
 534         .id = GENL_ID_CTRL,
 535         .name = "nlctrl",
 536         .version = 0x1,
 537         .maxattr = CTRL_ATTR_MAX,
 538         .owner = THIS_MODULE,
 539 };
 540
 541 static int __init genl_init(void)
 542 {
 543         int i, err;
 544
 545         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
 546                 INIT_LIST_HEAD(&family_ht[i]);
 547
 548         err = genl_register_family(&genl_ctrl);
 549         if (err < 0)
 550                 goto errout;
 551
 552         err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
 553         if (err < 0)
 554                 goto errout_register;
 555
 556         netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
 557         genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
 558                                           genl_rcv, THIS_MODULE);
 559         if (genl_sock == NULL) {
 560                 panic("GENL: Cannot initialize generic netlink\n");
 561                 return -ENOMEM;
 562         }
 563
 564         return 0;
 565
 566 errout_register:
 567         genl_unregister_family(&genl_ctrl);
 568 errout:
 569         panic("GENL: Cannot register controller: %d\n", err);
 570         return err;
 571 }
 572
 573 subsys_initcall(genl_init);
 574
 575 EXPORT_SYMBOL(genl_sock);
 576 EXPORT_SYMBOL(genl_register_ops);
 577 EXPORT_SYMBOL(genl_unregister_ops);
 578 EXPORT_SYMBOL(genl_register_family);
 579 EXPORT_SYMBOL(genl_unregister_family);