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