lib/nlattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * NETLINK      Netlink attributes
   4  *
   5  *              Authors:        Thomas Graf <tgraf@suug.ch>
   6  *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   7  */
   8
   9 #include <linux/export.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <net/netlink.h>
  17
  18 /* For these data types, attribute length should be exactly the given
  19  * size. However, to maintain compatibility with broken commands, if the
  20  * attribute length does not match the expected size a warning is emitted
  21  * to the user that the command is sending invalid data and needs to be fixed.
  22  */
  23 static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
  24         [NLA_U8]        = sizeof(u8),
  25         [NLA_U16]       = sizeof(u16),
  26         [NLA_U32]       = sizeof(u32),
  27         [NLA_U64]       = sizeof(u64),
  28         [NLA_S8]        = sizeof(s8),
  29         [NLA_S16]       = sizeof(s16),
  30         [NLA_S32]       = sizeof(s32),
  31         [NLA_S64]       = sizeof(s64),
  32 };
  33
  34 static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
  35         [NLA_U8]        = sizeof(u8),
  36         [NLA_U16]       = sizeof(u16),
  37         [NLA_U32]       = sizeof(u32),
  38         [NLA_U64]       = sizeof(u64),
  39         [NLA_MSECS]     = sizeof(u64),
  40         [NLA_NESTED]    = NLA_HDRLEN,
  41         [NLA_S8]        = sizeof(s8),
  42         [NLA_S16]       = sizeof(s16),
  43         [NLA_S32]       = sizeof(s32),
  44         [NLA_S64]       = sizeof(s64),
  45 };
  46
  47 static int validate_nla_bitfield32(const struct nlattr *nla,
  48                                    u32 *valid_flags_allowed)
  49 {
  50         const struct nla_bitfield32 *bf = nla_data(nla);
  51         u32 *valid_flags_mask = valid_flags_allowed;
  52
  53         if (!valid_flags_allowed)
  54                 return -EINVAL;
  55
  56         /*disallow invalid bit selector */
  57         if (bf->selector & ~*valid_flags_mask)
  58                 return -EINVAL;
  59
  60         /*disallow invalid bit values */
  61         if (bf->value & ~*valid_flags_mask)
  62                 return -EINVAL;
  63
  64         /*disallow valid bit values that are not selected*/
  65         if (bf->value & ~bf->selector)
  66                 return -EINVAL;
  67
  68         return 0;
  69 }
  70
  71 static int validate_nla(const struct nlattr *nla, int maxtype,
  72                         const struct nla_policy *policy)
  73 {
  74         const struct nla_policy *pt;
  75         int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
  76
  77         if (type <= 0 || type > maxtype)
  78                 return 0;
  79
  80         pt = &policy[type];
  81
  82         BUG_ON(pt->type > NLA_TYPE_MAX);
  83
  84         if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) {
  85                 pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
  86                                     current->comm, type);
  87         }
  88
  89         switch (pt->type) {
  90         case NLA_FLAG:
  91                 if (attrlen > 0)
  92                         return -ERANGE;
  93                 break;
  94
  95         case NLA_BITFIELD32:
  96                 if (attrlen != sizeof(struct nla_bitfield32))
  97                         return -ERANGE;
  98
  99                 return validate_nla_bitfield32(nla, pt->validation_data);
 100
 101         case NLA_NUL_STRING:
 102                 if (pt->len)
 103                         minlen = min_t(int, attrlen, pt->len + 1);
 104                 else
 105                         minlen = attrlen;
 106
 107                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
 108                         return -EINVAL;
 109                 /* fall through */
 110
 111         case NLA_STRING:
 112                 if (attrlen < 1)
 113                         return -ERANGE;
 114
 115                 if (pt->len) {
 116                         char *buf = nla_data(nla);
 117
 118                         if (buf[attrlen - 1] == '\0')
 119                                 attrlen--;
 120
 121                         if (attrlen > pt->len)
 122                                 return -ERANGE;
 123                 }
 124                 break;
 125
 126         case NLA_BINARY:
 127                 if (pt->len && attrlen > pt->len)
 128                         return -ERANGE;
 129                 break;
 130
 131         case NLA_NESTED_COMPAT:
 132                 if (attrlen < pt->len)
 133                         return -ERANGE;
 134                 if (attrlen < NLA_ALIGN(pt->len))
 135                         break;
 136                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
 137                         return -ERANGE;
 138                 nla = nla_data(nla) + NLA_ALIGN(pt->len);
 139                 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
 140                         return -ERANGE;
 141                 break;
 142         case NLA_NESTED:
 143                 /* a nested attributes is allowed to be empty; if its not,
 144                  * it must have a size of at least NLA_HDRLEN.
 145                  */
 146                 if (attrlen == 0)
 147                         break;
 148         default:
 149                 if (pt->len)
 150                         minlen = pt->len;
 151                 else if (pt->type != NLA_UNSPEC)
 152                         minlen = nla_attr_minlen[pt->type];
 153
 154                 if (attrlen < minlen)
 155                         return -ERANGE;
 156         }
 157
 158         return 0;
 159 }
 160
 161 /**
 162  * nla_validate - Validate a stream of attributes
 163  * @head: head of attribute stream
 164  * @len: length of attribute stream
 165  * @maxtype: maximum attribute type to be expected
 166  * @policy: validation policy
 167  * @extack: extended ACK report struct
 168  *
 169  * Validates all attributes in the specified attribute stream against the
 170  * specified policy. Attributes with a type exceeding maxtype will be
 171  * ignored. See documenation of struct nla_policy for more details.
 172  *
 173  * Returns 0 on success or a negative error code.
 174  */
 175 int nla_validate(const struct nlattr *head, int len, int maxtype,
 176                  const struct nla_policy *policy,
 177                  struct netlink_ext_ack *extack)
 178 {
 179         const struct nlattr *nla;
 180         int rem;
 181
 182         nla_for_each_attr(nla, head, len, rem) {
 183                 int err = validate_nla(nla, maxtype, policy);
 184
 185                 if (err < 0) {
 186                         if (extack)
 187                                 extack->bad_attr = nla;
 188                         return err;
 189                 }
 190         }
 191
 192         return 0;
 193 }
 194 EXPORT_SYMBOL(nla_validate);
 195
 196 /**
 197  * nla_policy_len - Determin the max. length of a policy
 198  * @policy: policy to use
 199  * @n: number of policies
 200  *
 201  * Determines the max. length of the policy.  It is currently used
 202  * to allocated Netlink buffers roughly the size of the actual
 203  * message.
 204  *
 205  * Returns 0 on success or a negative error code.
 206  */
 207 int
 208 nla_policy_len(const struct nla_policy *p, int n)
 209 {
 210         int i, len = 0;
 211
 212         for (i = 0; i < n; i++, p++) {
 213                 if (p->len)
 214                         len += nla_total_size(p->len);
 215                 else if (nla_attr_len[p->type])
 216                         len += nla_total_size(nla_attr_len[p->type]);
 217                 else if (nla_attr_minlen[p->type])
 218                         len += nla_total_size(nla_attr_minlen[p->type]);
 219         }
 220
 221         return len;
 222 }
 223 EXPORT_SYMBOL(nla_policy_len);
 224
 225 /**
 226  * nla_parse - Parse a stream of attributes into a tb buffer
 227  * @tb: destination array with maxtype+1 elements
 228  * @maxtype: maximum attribute type to be expected
 229  * @head: head of attribute stream
 230  * @len: length of attribute stream
 231  * @policy: validation policy
 232  *
 233  * Parses a stream of attributes and stores a pointer to each attribute in
 234  * the tb array accessible via the attribute type. Attributes with a type
 235  * exceeding maxtype will be silently ignored for backwards compatibility
 236  * reasons. policy may be set to NULL if no validation is required.
 237  *
 238  * Returns 0 on success or a negative error code.
 239  */
 240 int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 241               int len, const struct nla_policy *policy,
 242               struct netlink_ext_ack *extack)
 243 {
 244         const struct nlattr *nla;
 245         int rem, err;
 246
 247         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 248
 249         nla_for_each_attr(nla, head, len, rem) {
 250                 u16 type = nla_type(nla);
 251
 252                 if (type > 0 && type <= maxtype) {
 253                         if (policy) {
 254                                 err = validate_nla(nla, maxtype, policy);
 255                                 if (err < 0) {
 256                                         if (extack)
 257                                                 extack->bad_attr = nla;
 258                                         goto errout;
 259                                 }
 260                         }
 261
 262                         tb[type] = (struct nlattr *)nla;
 263                 }
 264         }
 265
 266         if (unlikely(rem > 0))
 267                 pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
 268                                     rem, current->comm);
 269
 270         err = 0;
 271 errout:
 272         return err;
 273 }
 274 EXPORT_SYMBOL(nla_parse);
 275
 276 /**
 277  * nla_find - Find a specific attribute in a stream of attributes
 278  * @head: head of attribute stream
 279  * @len: length of attribute stream
 280  * @attrtype: type of attribute to look for
 281  *
 282  * Returns the first attribute in the stream matching the specified type.
 283  */
 284 struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
 285 {
 286         const struct nlattr *nla;
 287         int rem;
 288
 289         nla_for_each_attr(nla, head, len, rem)
 290                 if (nla_type(nla) == attrtype)
 291                         return (struct nlattr *)nla;
 292
 293         return NULL;
 294 }
 295 EXPORT_SYMBOL(nla_find);
 296
 297 /**
 298  * nla_strlcpy - Copy string attribute payload into a sized buffer
 299  * @dst: where to copy the string to
 300  * @nla: attribute to copy the string from
 301  * @dstsize: size of destination buffer
 302  *
 303  * Copies at most dstsize - 1 bytes into the destination buffer.
 304  * The result is always a valid NUL-terminated string. Unlike
 305  * strlcpy the destination buffer is always padded out.
 306  *
 307  * Returns the length of the source buffer.
 308  */
 309 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 310 {
 311         size_t srclen = nla_len(nla);
 312         char *src = nla_data(nla);
 313
 314         if (srclen > 0 && src[srclen - 1] == '\0')
 315                 srclen--;
 316
 317         if (dstsize > 0) {
 318                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 319
 320                 memset(dst, 0, dstsize);
 321                 memcpy(dst, src, len);
 322         }
 323
 324         return srclen;
 325 }
 326 EXPORT_SYMBOL(nla_strlcpy);
 327
 328 /**
 329  * nla_strdup - Copy string attribute payload into a newly allocated buffer
 330  * @nla: attribute to copy the string from
 331  * @flags: the type of memory to allocate (see kmalloc).
 332  *
 333  * Returns a pointer to the allocated buffer or NULL on error.
 334  */
 335 char *nla_strdup(const struct nlattr *nla, gfp_t flags)
 336 {
 337         size_t srclen = nla_len(nla);
 338         char *src = nla_data(nla), *dst;
 339
 340         if (srclen > 0 && src[srclen - 1] == '\0')
 341                 srclen--;
 342
 343         dst = kmalloc(srclen + 1, flags);
 344         if (dst != NULL) {
 345                 memcpy(dst, src, srclen);
 346                 dst[srclen] = '\0';
 347         }
 348         return dst;
 349 }
 350 EXPORT_SYMBOL(nla_strdup);
 351
 352 /**
 353  * nla_memcpy - Copy a netlink attribute into another memory area
 354  * @dest: where to copy to memcpy
 355  * @src: netlink attribute to copy from
 356  * @count: size of the destination area
 357  *
 358  * Note: The number of bytes copied is limited by the length of
 359  *       attribute's payload. memcpy
 360  *
 361  * Returns the number of bytes copied.
 362  */
 363 int nla_memcpy(void *dest, const struct nlattr *src, int count)
 364 {
 365         int minlen = min_t(int, count, nla_len(src));
 366
 367         memcpy(dest, nla_data(src), minlen);
 368         if (count > minlen)
 369                 memset(dest + minlen, 0, count - minlen);
 370
 371         return minlen;
 372 }
 373 EXPORT_SYMBOL(nla_memcpy);
 374
 375 /**
 376  * nla_memcmp - Compare an attribute with sized memory area
 377  * @nla: netlink attribute
 378  * @data: memory area
 379  * @size: size of memory area
 380  */
 381 int nla_memcmp(const struct nlattr *nla, const void *data,
 382                              size_t size)
 383 {
 384         int d = nla_len(nla) - size;
 385
 386         if (d == 0)
 387                 d = memcmp(nla_data(nla), data, size);
 388
 389         return d;
 390 }
 391 EXPORT_SYMBOL(nla_memcmp);
 392
 393 /**
 394  * nla_strcmp - Compare a string attribute against a string
 395  * @nla: netlink string attribute
 396  * @str: another string
 397  */
 398 int nla_strcmp(const struct nlattr *nla, const char *str)
 399 {
 400         int len = strlen(str);
 401         char *buf = nla_data(nla);
 402         int attrlen = nla_len(nla);
 403         int d;
 404
 405         if (attrlen > 0 && buf[attrlen - 1] == '\0')
 406                 attrlen--;
 407
 408         d = attrlen - len;
 409         if (d == 0)
 410                 d = memcmp(nla_data(nla), str, len);
 411
 412         return d;
 413 }
 414 EXPORT_SYMBOL(nla_strcmp);
 415
 416 #ifdef CONFIG_NET
 417 /**
 418  * __nla_reserve - reserve room for attribute on the skb
 419  * @skb: socket buffer to reserve room on
 420  * @attrtype: attribute type
 421  * @attrlen: length of attribute payload
 422  *
 423  * Adds a netlink attribute header to a socket buffer and reserves
 424  * room for the payload but does not copy it.
 425  *
 426  * The caller is responsible to ensure that the skb provides enough
 427  * tailroom for the attribute header and payload.
 428  */
 429 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 430 {
 431         struct nlattr *nla;
 432
 433         nla = skb_put(skb, nla_total_size(attrlen));
 434         nla->nla_type = attrtype;
 435         nla->nla_len = nla_attr_size(attrlen);
 436
 437         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 438
 439         return nla;
 440 }
 441 EXPORT_SYMBOL(__nla_reserve);
 442
 443 /**
 444  * __nla_reserve_64bit - reserve room for attribute on the skb and align it
 445  * @skb: socket buffer to reserve room on
 446  * @attrtype: attribute type
 447  * @attrlen: length of attribute payload
 448  * @padattr: attribute type for the padding
 449  *
 450  * Adds a netlink attribute header to a socket buffer and reserves
 451  * room for the payload but does not copy it. It also ensure that this
 452  * attribute will have a 64-bit aligned nla_data() area.
 453  *
 454  * The caller is responsible to ensure that the skb provides enough
 455  * tailroom for the attribute header and payload.
 456  */
 457 struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
 458                                    int attrlen, int padattr)
 459 {
 460         if (nla_need_padding_for_64bit(skb))
 461                 nla_align_64bit(skb, padattr);
 462
 463         return __nla_reserve(skb, attrtype, attrlen);
 464 }
 465 EXPORT_SYMBOL(__nla_reserve_64bit);
 466
 467 /**
 468  * __nla_reserve_nohdr - reserve room for attribute without header
 469  * @skb: socket buffer to reserve room on
 470  * @attrlen: length of attribute payload
 471  *
 472  * Reserves room for attribute payload without a header.
 473  *
 474  * The caller is responsible to ensure that the skb provides enough
 475  * tailroom for the payload.
 476  */
 477 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 478 {
 479         return skb_put_zero(skb, NLA_ALIGN(attrlen));
 480 }
 481 EXPORT_SYMBOL(__nla_reserve_nohdr);
 482
 483 /**
 484  * nla_reserve - reserve room for attribute on the skb
 485  * @skb: socket buffer to reserve room on
 486  * @attrtype: attribute type
 487  * @attrlen: length of attribute payload
 488  *
 489  * Adds a netlink attribute header to a socket buffer and reserves
 490  * room for the payload but does not copy it.
 491  *
 492  * Returns NULL if the tailroom of the skb is insufficient to store
 493  * the attribute header and payload.
 494  */
 495 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 496 {
 497         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 498                 return NULL;
 499
 500         return __nla_reserve(skb, attrtype, attrlen);
 501 }
 502 EXPORT_SYMBOL(nla_reserve);
 503
 504 /**
 505  * nla_reserve_64bit - reserve room for attribute on the skb and align it
 506  * @skb: socket buffer to reserve room on
 507  * @attrtype: attribute type
 508  * @attrlen: length of attribute payload
 509  * @padattr: attribute type for the padding
 510  *
 511  * Adds a netlink attribute header to a socket buffer and reserves
 512  * room for the payload but does not copy it. It also ensure that this
 513  * attribute will have a 64-bit aligned nla_data() area.
 514  *
 515  * Returns NULL if the tailroom of the skb is insufficient to store
 516  * the attribute header and payload.
 517  */
 518 struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 519                                  int padattr)
 520 {
 521         size_t len;
 522
 523         if (nla_need_padding_for_64bit(skb))
 524                 len = nla_total_size_64bit(attrlen);
 525         else
 526                 len = nla_total_size(attrlen);
 527         if (unlikely(skb_tailroom(skb) < len))
 528                 return NULL;
 529
 530         return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 531 }
 532 EXPORT_SYMBOL(nla_reserve_64bit);
 533
 534 /**
 535  * nla_reserve_nohdr - reserve room for attribute without header
 536  * @skb: socket buffer to reserve room on
 537  * @attrlen: length of attribute payload
 538  *
 539  * Reserves room for attribute payload without a header.
 540  *
 541  * Returns NULL if the tailroom of the skb is insufficient to store
 542  * the attribute payload.
 543  */
 544 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 545 {
 546         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 547                 return NULL;
 548
 549         return __nla_reserve_nohdr(skb, attrlen);
 550 }
 551 EXPORT_SYMBOL(nla_reserve_nohdr);
 552
 553 /**
 554  * __nla_put - Add a netlink attribute to a socket buffer
 555  * @skb: socket buffer to add attribute to
 556  * @attrtype: attribute type
 557  * @attrlen: length of attribute payload
 558  * @data: head of attribute payload
 559  *
 560  * The caller is responsible to ensure that the skb provides enough
 561  * tailroom for the attribute header and payload.
 562  */
 563 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 564                              const void *data)
 565 {
 566         struct nlattr *nla;
 567
 568         nla = __nla_reserve(skb, attrtype, attrlen);
 569         memcpy(nla_data(nla), data, attrlen);
 570 }
 571 EXPORT_SYMBOL(__nla_put);
 572
 573 /**
 574  * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 575  * @skb: socket buffer to add attribute to
 576  * @attrtype: attribute type
 577  * @attrlen: length of attribute payload
 578  * @data: head of attribute payload
 579  * @padattr: attribute type for the padding
 580  *
 581  * The caller is responsible to ensure that the skb provides enough
 582  * tailroom for the attribute header and payload.
 583  */
 584 void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 585                      const void *data, int padattr)
 586 {
 587         struct nlattr *nla;
 588
 589         nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
 590         memcpy(nla_data(nla), data, attrlen);
 591 }
 592 EXPORT_SYMBOL(__nla_put_64bit);
 593
 594 /**
 595  * __nla_put_nohdr - Add a netlink attribute without header
 596  * @skb: socket buffer to add attribute to
 597  * @attrlen: length of attribute payload
 598  * @data: head of attribute payload
 599  *
 600  * The caller is responsible to ensure that the skb provides enough
 601  * tailroom for the attribute payload.
 602  */
 603 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 604 {
 605         void *start;
 606
 607         start = __nla_reserve_nohdr(skb, attrlen);
 608         memcpy(start, data, attrlen);
 609 }
 610 EXPORT_SYMBOL(__nla_put_nohdr);
 611
 612 /**
 613  * nla_put - Add a netlink attribute to a socket buffer
 614  * @skb: socket buffer to add attribute to
 615  * @attrtype: attribute type
 616  * @attrlen: length of attribute payload
 617  * @data: head of attribute payload
 618  *
 619  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 620  * the attribute header and payload.
 621  */
 622 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 623 {
 624         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 625                 return -EMSGSIZE;
 626
 627         __nla_put(skb, attrtype, attrlen, data);
 628         return 0;
 629 }
 630 EXPORT_SYMBOL(nla_put);
 631
 632 /**
 633  * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 634  * @skb: socket buffer to add attribute to
 635  * @attrtype: attribute type
 636  * @attrlen: length of attribute payload
 637  * @data: head of attribute payload
 638  * @padattr: attribute type for the padding
 639  *
 640  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 641  * the attribute header and payload.
 642  */
 643 int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
 644                   const void *data, int padattr)
 645 {
 646         size_t len;
 647
 648         if (nla_need_padding_for_64bit(skb))
 649                 len = nla_total_size_64bit(attrlen);
 650         else
 651                 len = nla_total_size(attrlen);
 652         if (unlikely(skb_tailroom(skb) < len))
 653                 return -EMSGSIZE;
 654
 655         __nla_put_64bit(skb, attrtype, attrlen, data, padattr);
 656         return 0;
 657 }
 658 EXPORT_SYMBOL(nla_put_64bit);
 659
 660 /**
 661  * nla_put_nohdr - Add a netlink attribute without header
 662  * @skb: socket buffer to add attribute to
 663  * @attrlen: length of attribute payload
 664  * @data: head of attribute payload
 665  *
 666  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 667  * the attribute payload.
 668  */
 669 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 670 {
 671         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 672                 return -EMSGSIZE;
 673
 674         __nla_put_nohdr(skb, attrlen, data);
 675         return 0;
 676 }
 677 EXPORT_SYMBOL(nla_put_nohdr);
 678
 679 /**
 680  * nla_append - Add a netlink attribute without header or padding
 681  * @skb: socket buffer to add attribute to
 682  * @attrlen: length of attribute payload
 683  * @data: head of attribute payload
 684  *
 685  * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 686  * the attribute payload.
 687  */
 688 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
 689 {
 690         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 691                 return -EMSGSIZE;
 692
 693         skb_put_data(skb, data, attrlen);
 694         return 0;
 695 }
 696 EXPORT_SYMBOL(nla_append);
 697 #endif