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         if (ops->dumpit)
 147                 ops->flags |= GENL_CMD_CAP_DUMP;
 148         if (ops->doit)
 149                 ops->flags |= GENL_CMD_CAP_DO;
 150         if (ops->policy)
 151                 ops->flags |= GENL_CMD_CAP_HASPOL;
 152
 153         genl_lock();
 154         list_add_tail(&ops->ops_list, &family->ops_list);
 155         genl_unlock();
 156
 157         genl_ctrl_event(CTRL_CMD_NEWOPS, ops);
 158         err = 0;
 159 errout:
 160         return err;
 161 }
 162
 163 /**
 164  * genl_unregister_ops - unregister generic netlink operations
 165  * @family: generic netlink family
 166  * @ops: operations to be unregistered
 167  *
 168  * Unregisters the specified operations and unassigns them from the
 169  * specified family. The operation blocks until the current message
 170  * processing has finished and doesn't start again until the
 171  * unregister process has finished.
 172  *
 173  * Note: It is not necessary to unregister all operations before
 174  *       unregistering the family, unregistering the family will cause
 175  *       all assigned operations to be unregistered automatically.
 176  *
 177  * Returns 0 on success or a negative error code.
 178  */
 179 int genl_unregister_ops(struct genl_family *family, struct genl_ops *ops)
 180 {
 181         struct genl_ops *rc;
 182
 183         genl_lock();
 184         list_for_each_entry(rc, &family->ops_list, ops_list) {
 185                 if (rc == ops) {
 186                         list_del(&ops->ops_list);
 187                         genl_unlock();
 188                         genl_ctrl_event(CTRL_CMD_DELOPS, ops);
 189                         return 0;
 190                 }
 191         }
 192         genl_unlock();
 193
 194         return -ENOENT;
 195 }
 196
 197 /**
 198  * genl_register_family - register a generic netlink family
 199  * @family: generic netlink family
 200  *
 201  * Registers the specified family after validating it first. Only one
 202  * family may be registered with the same family name or identifier.
 203  * The family id may equal GENL_ID_GENERATE causing an unique id to
 204  * be automatically generated and assigned.
 205  *
 206  * Return 0 on success or a negative error code.
 207  */
 208 int genl_register_family(struct genl_family *family)
 209 {
 210         int err = -EINVAL;
 211
 212         if (family->id && family->id < GENL_MIN_ID)
 213                 goto errout;
 214
 215         if (family->id > GENL_MAX_ID)
 216                 goto errout;
 217
 218         INIT_LIST_HEAD(&family->ops_list);
 219
 220         genl_lock();
 221
 222         if (genl_family_find_byname(family->name)) {
 223                 err = -EEXIST;
 224                 goto errout_locked;
 225         }
 226
 227         if (genl_family_find_byid(family->id)) {
 228                 err = -EEXIST;
 229                 goto errout_locked;
 230         }
 231
 232         if (family->id == GENL_ID_GENERATE) {
 233                 u16 newid = genl_generate_id();
 234
 235                 if (!newid) {
 236                         err = -ENOMEM;
 237                         goto errout_locked;
 238                 }
 239
 240                 family->id = newid;
 241         }
 242
 243         if (family->maxattr) {
 244                 family->attrbuf = kmalloc((family->maxattr+1) *
 245                                         sizeof(struct nlattr *), GFP_KERNEL);
 246                 if (family->attrbuf == NULL) {
 247                         err = -ENOMEM;
 248                         goto errout_locked;
 249                 }
 250         } else
 251                 family->attrbuf = NULL;
 252
 253         list_add_tail(&family->family_list, genl_family_chain(family->id));
 254         genl_unlock();
 255
 256         genl_ctrl_event(CTRL_CMD_NEWFAMILY, family);
 257
 258         return 0;
 259
 260 errout_locked:
 261         genl_unlock();
 262 errout:
 263         return err;
 264 }
 265
 266 /**
 267  * genl_unregister_family - unregister generic netlink family
 268  * @family: generic netlink family
 269  *
 270  * Unregisters the specified family.
 271  *
 272  * Returns 0 on success or a negative error code.
 273  */
 274 int genl_unregister_family(struct genl_family *family)
 275 {
 276         struct genl_family *rc;
 277
 278         genl_lock();
 279
 280         list_for_each_entry(rc, genl_family_chain(family->id), family_list) {
 281                 if (family->id != rc->id || strcmp(rc->name, family->name))
 282                         continue;
 283
 284                 list_del(&rc->family_list);
 285                 INIT_LIST_HEAD(&family->ops_list);
 286                 genl_unlock();
 287
 288                 kfree(family->attrbuf);
 289                 genl_ctrl_event(CTRL_CMD_DELFAMILY, family);
 290                 return 0;
 291         }
 292
 293         genl_unlock();
 294
 295         return -ENOENT;
 296 }
 297
 298 static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 299                                int *errp)
 300 {
 301         struct genl_ops *ops;
 302         struct genl_family *family;
 303         struct genl_info info;
 304         struct genlmsghdr *hdr = nlmsg_data(nlh);
 305         int hdrlen, err = -EINVAL;
 306
 307         if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
 308                 goto ignore;
 309
 310         if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
 311                 goto ignore;
 312
 313         family = genl_family_find_byid(nlh->nlmsg_type);
 314         if (family == NULL) {
 315                 err = -ENOENT;
 316                 goto errout;
 317         }
 318
 319         hdrlen = GENL_HDRLEN + family->hdrsize;
 320         if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 321                 goto errout;
 322
 323         ops = genl_get_cmd(hdr->cmd, family);
 324         if (ops == NULL) {
 325                 err = -EOPNOTSUPP;
 326                 goto errout;
 327         }
 328
 329         if ((ops->flags & GENL_ADMIN_PERM) && security_netlink_recv(skb, CAP_NET_ADMIN)) {
 330                 err = -EPERM;
 331                 goto errout;
 332         }
 333
 334         if (nlh->nlmsg_flags & NLM_F_DUMP) {
 335                 if (ops->dumpit == NULL) {
 336                         err = -EOPNOTSUPP;
 337                         goto errout;
 338                 }
 339
 340                 *errp = err = netlink_dump_start(genl_sock, skb, nlh,
 341                                                  ops->dumpit, ops->done);
 342                 if (err == 0)
 343                         skb_pull(skb, min(NLMSG_ALIGN(nlh->nlmsg_len),
 344                                           skb->len));
 345                 return -1;
 346         }
 347
 348         if (ops->doit == NULL) {
 349                 err = -EOPNOTSUPP;
 350                 goto errout;
 351         }
 352
 353         if (family->attrbuf) {
 354                 err = nlmsg_parse(nlh, hdrlen, family->attrbuf, family->maxattr,
 355                                   ops->policy);
 356                 if (err < 0)
 357                         goto errout;
 358         }
 359
 360         info.snd_seq = nlh->nlmsg_seq;
 361         info.snd_pid = NETLINK_CB(skb).pid;
 362         info.nlhdr = nlh;
 363         info.genlhdr = nlmsg_data(nlh);
 364         info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 365         info.attrs = family->attrbuf;
 366
 367         *errp = err = ops->doit(skb, &info);
 368         return err;
 369
 370 ignore:
 371         return 0;
 372
 373 errout:
 374         *errp = err;
 375         return -1;
 376 }
 377
 378 static void genl_rcv(struct sock *sk, int len)
 379 {
 380         unsigned int qlen = 0;
 381
 382         do {
 383                 if (genl_trylock())
 384                         return;
 385                 netlink_run_queue(sk, &qlen, genl_rcv_msg);
 386                 genl_unlock();
 387         } while (qlen && genl_sock && genl_sock->sk_receive_queue.qlen);
 388 }
 389
 390 /**************************************************************************
 391  * Controller
 392  **************************************************************************/
 393
 394 static struct genl_family genl_ctrl = {
 395         .id = GENL_ID_CTRL,
 396         .name = "nlctrl",
 397         .version = 0x2,
 398         .maxattr = CTRL_ATTR_MAX,
 399 };
 400
 401 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
 402                           u32 flags, struct sk_buff *skb, u8 cmd)
 403 {
 404         void *hdr;
 405
 406         hdr = genlmsg_put(skb, pid, seq, &genl_ctrl, flags, cmd);
 407         if (hdr == NULL)
 408                 return -1;
 409
 410         NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
 411         NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
 412         NLA_PUT_U32(skb, CTRL_ATTR_VERSION, family->version);
 413         NLA_PUT_U32(skb, CTRL_ATTR_HDRSIZE, family->hdrsize);
 414         NLA_PUT_U32(skb, CTRL_ATTR_MAXATTR, family->maxattr);
 415
 416         if (!list_empty(&family->ops_list)) {
 417                 struct nlattr *nla_ops;
 418                 struct genl_ops *ops;
 419                 int idx = 1;
 420
 421                 nla_ops = nla_nest_start(skb, CTRL_ATTR_OPS);
 422                 if (nla_ops == NULL)
 423                         goto nla_put_failure;
 424
 425                 list_for_each_entry(ops, &family->ops_list, ops_list) {
 426                         struct nlattr *nest;
 427
 428                         nest = nla_nest_start(skb, idx++);
 429                         if (nest == NULL)
 430                                 goto nla_put_failure;
 431
 432                         NLA_PUT_U32(skb, CTRL_ATTR_OP_ID, ops->cmd);
 433                         NLA_PUT_U32(skb, CTRL_ATTR_OP_FLAGS, ops->flags);
 434
 435                         nla_nest_end(skb, nest);
 436                 }
 437
 438                 nla_nest_end(skb, nla_ops);
 439         }
 440
 441         return genlmsg_end(skb, hdr);
 442
 443 nla_put_failure:
 444         return genlmsg_cancel(skb, hdr);
 445 }
 446
 447 static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
 448 {
 449
 450         int i, n = 0;
 451         struct genl_family *rt;
 452         int chains_to_skip = cb->args[0];
 453         int fams_to_skip = cb->args[1];
 454
 455         if (chains_to_skip != 0)
 456                 genl_lock();
 457
 458         for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
 459                 if (i < chains_to_skip)
 460                         continue;
 461                 n = 0;
 462                 list_for_each_entry(rt, genl_family_chain(i), family_list) {
 463                         if (++n < fams_to_skip)
 464                                 continue;
 465                         if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).pid,
 466                                            cb->nlh->nlmsg_seq, NLM_F_MULTI,
 467                                            skb, CTRL_CMD_NEWFAMILY) < 0)
 468                                 goto errout;
 469                 }
 470
 471                 fams_to_skip = 0;
 472         }
 473
 474 errout:
 475         if (chains_to_skip != 0)
 476                 genl_unlock();
 477
 478         cb->args[0] = i;
 479         cb->args[1] = n;
 480
 481         return skb->len;
 482 }
 483
 484 static struct sk_buff *ctrl_build_msg(struct genl_family *family, u32 pid,
 485                                       int seq, u8 cmd)
 486 {
 487         struct sk_buff *skb;
 488         int err;
 489
 490         skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 491         if (skb == NULL)
 492                 return ERR_PTR(-ENOBUFS);
 493
 494         err = ctrl_fill_info(family, pid, seq, 0, skb, cmd);
 495         if (err < 0) {
 496                 nlmsg_free(skb);
 497                 return ERR_PTR(err);
 498         }
 499
 500         return skb;
 501 }
 502
 503 static struct nla_policy ctrl_policy[CTRL_ATTR_MAX+1] __read_mostly = {
 504         [CTRL_ATTR_FAMILY_ID]   = { .type = NLA_U16 },
 505         [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
 506                                     .len = GENL_NAMSIZ - 1 },
 507 };
 508
 509 static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 510 {
 511         struct sk_buff *msg;
 512         struct genl_family *res = NULL;
 513         int err = -EINVAL;
 514
 515         if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
 516                 u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
 517                 res = genl_family_find_byid(id);
 518         }
 519
 520         if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
 521                 char *name;
 522
 523                 name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
 524                 res = genl_family_find_byname(name);
 525         }
 526
 527         if (res == NULL) {
 528                 err = -ENOENT;
 529                 goto errout;
 530         }
 531
 532         msg = ctrl_build_msg(res, info->snd_pid, info->snd_seq,
 533                              CTRL_CMD_NEWFAMILY);
 534         if (IS_ERR(msg)) {
 535                 err = PTR_ERR(msg);
 536                 goto errout;
 537         }
 538
 539         err = genlmsg_reply(msg, info);
 540 errout:
 541         return err;
 542 }
 543
 544 static int genl_ctrl_event(int event, void *data)
 545 {
 546         struct sk_buff *msg;
 547
 548         if (genl_sock == NULL)
 549                 return 0;
 550
 551         switch (event) {
 552         case CTRL_CMD_NEWFAMILY:
 553         case CTRL_CMD_DELFAMILY:
 554                 msg = ctrl_build_msg(data, 0, 0, event);
 555                 if (IS_ERR(msg))
 556                         return PTR_ERR(msg);
 557
 558                 genlmsg_multicast(msg, 0, GENL_ID_CTRL, GFP_KERNEL);
 559                 break;
 560         }
 561
 562         return 0;
 563 }
 564
 565 static struct genl_ops genl_ctrl_ops = {
 566         .cmd            = CTRL_CMD_GETFAMILY,
 567         .doit           = ctrl_getfamily,
 568         .dumpit         = ctrl_dumpfamily,
 569         .policy         = ctrl_policy,
 570 };
 571
 572 static int __init genl_init(void)
 573 {
 574         int i, err;
 575
 576         for (i = 0; i < GENL_FAM_TAB_SIZE; i++)
 577                 INIT_LIST_HEAD(&family_ht[i]);
 578
 579         err = genl_register_family(&genl_ctrl);
 580         if (err < 0)
 581                 goto errout;
 582
 583         err = genl_register_ops(&genl_ctrl, &genl_ctrl_ops);
 584         if (err < 0)
 585                 goto errout_register;
 586
 587         netlink_set_nonroot(NETLINK_GENERIC, NL_NONROOT_RECV);
 588         genl_sock = netlink_kernel_create(NETLINK_GENERIC, GENL_MAX_ID,
 589                                           genl_rcv, THIS_MODULE);
 590         if (genl_sock == NULL)
 591                 panic("GENL: Cannot initialize generic netlink\n");
 592
 593         return 0;
 594
 595 errout_register:
 596         genl_unregister_family(&genl_ctrl);
 597 errout:
 598         panic("GENL: Cannot register controller: %d\n", err);
 599 }
 600
 601 subsys_initcall(genl_init);
 602
 603 EXPORT_SYMBOL(genl_sock);
 604 EXPORT_SYMBOL(genl_register_ops);
 605 EXPORT_SYMBOL(genl_unregister_ops);
 606 EXPORT_SYMBOL(genl_register_family);
 607 EXPORT_SYMBOL(genl_unregister_family);