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/module.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/types.h>
  12 #include <linux/socket.h>
  13 #include <linux/string.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/mutex.h>
  16 #include <net/sock.h>
  17 #include <net/genetlink.h>
  18
  19 struct sock *genl_sock = NULL;
  20
  21 static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
  22
  23 static void genl_lock(void)
  24 {
  25         mutex_lock(&genl_mutex);
  26 }
  27
  28 static int genl_trylock(void)
  29 {
  30         return !mutex_trylock(&genl_mutex);
  31 }
  32
  33 static void genl_unlock(void)
  34 {
  35         mutex_unlock(&genl_mutex);
  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 (family->id == GENL_ID_GENERATE) {
 226                 u16 newid = genl_generate_id();
 227
 228                 if (!newid) {
 229                         err = -ENOMEM;
 230                         goto errout_locked;
 231                 }
 232
 233                 family->id = newid;
 234         }
 235
 236         if (family->maxattr) {
 237                 family->attrbuf = kmalloc((family->maxattr+1) *
 238                                         sizeof(struct nlattr *), GFP_KERNEL);
 239                 if (family->attrbuf == NULL) {
 240                         err = -ENOMEM;
 241                         goto errout_locked;
 242                 }
 243         } else
 244                 family->attrbuf = NULL;
 245
 246         list_add_tail(&family->family_list, genl_family_chain(family->id));
 247         genl_unlock();
 248
 249         genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
 250
 251         return 0;
 252
 253 errout_locked:
 254         genl_unlock();
 255 errout:
 256         return err;
 257 }
 258
 259 /**
 260  * genl_unregister_family - unregister generic netlink family
 261  * @family: generic netlink family
 262  *
 263  * Unregisters the specified family.
 264  *
 265  * Returns 0 on success or a negative error code.
 266  */
 267 int genl_unregister_family(struct genl_family *family)
 268 {
 269         struct genl_family *rc;
 270
 271         genl_lock();
 272
 273         list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
 274                 if (family->id != rc->id || strcmp(rc->name, family->name))
 275                         continue;
 276
 277                 list_del(&rc->family_list);
 278                 INIT_LIST_HEAD(&family->ops_list);
 279                 genl_unlock();
 280
 281                 kfree(family->attrbuf);
 282                 genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
 283                 return 0;
 284         }
 285
 286         genl_unlock();
 287
 288         return -ENOENT;
 289 }
 290
 291 static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 292                                int *errp)
 293 {
 294         struct genl_ops *ops;
 295         struct genl_family *family;
 296         struct genl_info info;
 297         struct genlmsghdr *hdr = nlmsg_data(nlh);
 298         int hdrlen, err = -EINVAL;
 299
 300         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 301                 goto ignore;
 302
 303         if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
 304                 goto ignore;
 305
 306         family = genl_family_find_byid(nlh->nlmsg_type);
 307         if (family == NULL) {
 308                 err = -ENOENT;
 309                 goto errout;
 310         }
 311
 312         hdrlen = GENL_HDRLEN + family->hdrsize;
 313         if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 314                 goto errout;
 315
 316         ops = genl_get_cmd(hdr->cmd, family);
 317         if (ops == NULL) {
 318                 err = -EOPNOTSUPP;
 319                 goto errout;
 320         }
 321
 322         if ((ops->flags & GENL_ADMIN_PERM) && security_netlink_recv(skb, CAP_NET_ADMIN)) {
 323                 err = -EPERM;
 324                 goto errout;
 325         }
 326
 327         if (nlh->nlmsg_flags & NLM_F_DUMP) {
 328                 if (ops->dumpit == NULL) {
 329                         err = -EOPNOTSUPP;
 330                         goto errout;
 331                 }
 332
 333                 *errp = err = netlink_dump_start(genl_sock, skb, nlh,
 334                                                  ops->dumpit, NULL);
 335                 if (err == 0)
 336                         skb_pull(skb, min(NLMSG_ALIGN(nlh->nlmsg_len),
 337                                           skb->len));
 338                 return -1;
 339         }
 340
 341         if (ops->doit == NULL) {
 342                 err = -EOPNOTSUPP;
 343                 goto errout;
 344         }
 345
 346         if (family->attrbuf) {
 347                 err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
 348                                   ops->policy);
 349                 if (err < 0)
 350                         goto errout;
 351         }
 352
 353         info.snd_seq = nlh->nlmsg_seq;
 354         info.snd_pid = NETLINK_CB(skb).pid;
 355         info.nlhdr = nlh;
 356         info.genlhdr = nlmsg_data(nlh);
 357         info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 358         info.attrs = family->attrbuf;
 359
 360         *errp = err = ops->doit(skb, &info);
 361         return err;
 362
 363 ignore:
 364         return 0;
 365
 366 errout:
 367         *errp = err;
 368         return -1;
 369 }
 370
 371 static void genl_rcv(struct sock *sk, int len)
 372 {
 373         unsigned int qlen = 0;
 374
 375         do {
 376                 if (genl_trylock())
 377                         return;
 378                 netlink_run_queue(sk, &qlen, genl_rcv_msg);
 379                 genl_unlock();
 380         } while (qlen && genl_sock && genl_sock->sk_receive_queue.qlen);
 381 }
 382
 383 /**************************************************************************
 384  * Controller
 385  **************************************************************************/
 386
 387 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
 388                           u32 flags, struct sk_buff *skb, u8 cmd)
 389 {
 390         void *hdr;
 391
 392         hdr = genlmsg_put(skb, pid, seq, GENL_ID_CTRL, 0, flags, cmd,
 393                           family->version);
 394         if (hdr == NULL)
 395                 return -1;
 396
 397         NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
 398         NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
 399
 400         return genlmsg_end(skb, hdr);
 401
 402 nla_put_failure:
 403         return genlmsg_cancel(skb, hdr);
 404 }
 405
 406 static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 407 {
 408
 409         int i, n = 0;
 410         struct genl_family *rt;
 411         int chains_to_skip = cb->args[0];
 412         int fams_to_skip = cb->args[1];
 413
 414         for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
 415                 if (i < chains_to_skip)
 416                         continue;
 417                 n = 0;
 418                 list_for_each_entry(rt, genl_family_chain(i), family_list) {
 419                         if (++n < fams_to_skip)
 420                                 continue;
 421                         if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
 422                                            cb->nlh->nlmsg_seq, NLM_F_MULTI,
 423                                            skb, CTRL_CMD_NEWFAMILY) < 0)
 424                                 goto errout;
 425                 }
 426
 427                 fams_to_skip = 0;
 428         }
 429
 430 errout:
 431         cb->args[0] = i;
 432         cb->args[1] = n;
 433
 434         return skb->len;
 435 }
 436
 437 static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
 438                                       int seq, u8 cmd)
 439 {
 440         struct sk_buff *skb;
 441         int err;
 442
 443         skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
 444         if (skb == NULL)
 445                 return ERR_PTR(-ENOBUFS);
 446
 447         err = ctrl_fill_info(family, pid, seq, 0, skb, cmd);
 448         if (err < 0) {
 449                 nlmsg_free(skb);
 450                 return ERR_PTR(err);
 451         }
 452
 453         return skb;
 454 }
 455
 456 static struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] __read_mostly = {
 457         [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
 458         [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
 459                                     .len = GENL_NAMSIZ - 1 },
 460 };
 461
 462 static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 463 {
 464         struct sk_buff *msg;
 465         struct genl_family *res = NULL;
 466         int err = -EINVAL;
 467
 468         if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
 469                 u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
 470                 res = genl_family_find_byid(id);
 471         }
 472
 473         if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
 474                 char *name;
 475
 476                 name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
 477                 res = genl_family_find_byname(name);
 478         }
 479
 480         if (res == NULL) {
 481                 err = -ENOENT;
 482                 goto errout;
 483         }
 484
 485         msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
 486                              CTRL_CMD_NEWFAMILY);
 487         if (IS_ERR(msg)) {
 488                 err = PTR_ERR(msg);
 489                 goto errout;
 490         }
 491
 492         err = genlmsg_unicast(msg, info->snd_pid);
 493 errout:
 494         return err;
 495 }
 496
 497 static int genl_ctrl_event(int event, void *data)
 498 {
 499         struct sk_buff *msg;
 500
 501         if (genl_sock == NULL)
 502                 return 0;
 503
 504         switch (event) {
 505         case CTRL_CMD_NEWFAMILY:
 506         case CTRL_CMD_DELFAMILY:
 507                 msg = ctrl_build_msg(data, 0, 0, event);
 508                 if (IS_ERR(msg))
 509                         return PTR_ERR(msg);
 510
 511                 genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
 512                 break;
 513         }
 514
 515         return 0;
 516 }
 517
 518 static struct genl_ops genl_ctrl_ops = {
 519         .cmd            = CTRL_CMD_GETFAMILY,
 520         .doit           = ctrl_getfamily,
 521         .dumpit         = ctrl_dumpfamily,
 522         .policy         = ctrl_policy,
 523 };
 524
 525 static struct genl_family genl_ctrl = {
 526         .id = GENL_ID_CTRL,
 527         .name = "nlctrl",
 528         .version = 0x1,
 529         .maxattr = CTRL_ATTR_MAX,
 530 };
 531
 532 static int __init genl_init(void)
 533 {
 534         int i, err;
 535
 536         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
 537                 INIT_LIST_HEAD(&family_ht[i]);
 538
 539         err = genl_register_family(&genl_ctrl);
 540         if (err < 0)
 541                 goto errout;
 542
 543         err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
 544         if (err < 0)
 545                 goto errout_register;
 546
 547         netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
 548         genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
 549                                           genl_rcv, THIS_MODULE);
 550         if (genl_sock == NULL)
 551                 panic("GENL: Cannot initialize generic netlink\n");
 552
 553         return 0;
 554
 555 errout_register:
 556         genl_unregister_family(&genl_ctrl);
 557 errout:
 558         panic("GENL: Cannot register controller: %d\n", err);
 559 }
 560
 561 subsys_initcall(genl_init);
 562
 563 EXPORT_SYMBOL(genl_sock);
 564 EXPORT_SYMBOL(genl_register_ops);
 565 EXPORT_SYMBOL(genl_unregister_ops);
 566 EXPORT_SYMBOL(genl_register_family);
 567 EXPORT_SYMBOL(genl_unregister_family);