net/netlink/attr.c

   1 /*
   2  * NETLINK      Netlink attributes
   3  *
   4  *              Authors:        Thomas Graf <tgraf@suug.ch>
   5  *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kernel.h>
  10 #include <linux/errno.h>
  11 #include <linux/jiffies.h>
  12 #include <linux/netdevice.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/string.h>
  15 #include <linux/types.h>
  16 #include <net/netlink.h>
  17
  18 static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
  19         [NLA_U8]        = sizeof(u8),
  20         [NLA_U16]       = sizeof(u16),
  21         [NLA_U32]       = sizeof(u32),
  22         [NLA_U64]       = sizeof(u64),
  23         [NLA_NESTED]    = NLA_HDRLEN,
  24 };
  25
  26 static int validate_nla(struct nlattr *nla, int maxtype,
  27                         struct nla_policy *policy)
  28 {
  29         struct nla_policy *pt;
  30         int minlen = 0, attrlen = nla_len(nla);
  31
  32         if (nla->nla_type <= 0 || nla->nla_type > maxtype)
  33                 return 0;
  34
  35         pt = &policy[nla->nla_type];
  36
  37         BUG_ON(pt->type > NLA_TYPE_MAX);
  38
  39         switch (pt->type) {
  40         case NLA_FLAG:
  41                 if (attrlen > 0)
  42                         return -ERANGE;
  43                 break;
  44
  45         case NLA_NUL_STRING:
  46                 if (pt->len)
  47                         minlen = min_t(int, attrlen, pt->len + 1);
  48                 else
  49                         minlen = attrlen;
  50
  51                 if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL)
  52                         return -EINVAL;
  53                 /* fall through */
  54
  55         case NLA_STRING:
  56                 if (attrlen < 1)
  57                         return -ERANGE;
  58
  59                 if (pt->len) {
  60                         char *buf = nla_data(nla);
  61
  62                         if (buf[attrlen - 1] == '\0')
  63                                 attrlen--;
  64
  65                         if (attrlen > pt->len)
  66                                 return -ERANGE;
  67                 }
  68                 break;
  69
  70         case NLA_BINARY:
  71                 if (pt->len && attrlen > pt->len)
  72                         return -ERANGE;
  73                 break;
  74
  75         default:
  76                 if (pt->len)
  77                         minlen = pt->len;
  78                 else if (pt->type != NLA_UNSPEC)
  79                         minlen = nla_attr_minlen[pt->type];
  80
  81                 if (attrlen < minlen)
  82                         return -ERANGE;
  83         }
  84
  85         return 0;
  86 }
  87
  88 /**
  89  * nla_validate - Validate a stream of attributes
  90  * @head: head of attribute stream
  91  * @len: length of attribute stream
  92  * @maxtype: maximum attribute type to be expected
  93  * @policy: validation policy
  94  *
  95  * Validates all attributes in the specified attribute stream against the
  96  * specified policy. Attributes with a type exceeding maxtype will be
  97  * ignored. See documenation of struct nla_policy for more details.
  98  *
  99  * Returns 0 on success or a negative error code.
 100  */
 101 int nla_validate(struct nlattr *head, int len, int maxtype,
 102                  struct nla_policy *policy)
 103 {
 104         struct nlattr *nla;
 105         int rem, err;
 106
 107         nla_for_each_attr(nla, head, len, rem) {
 108                 err = validate_nla(nla, maxtype, policy);
 109                 if (err < 0)
 110                         goto errout;
 111         }
 112
 113         err = 0;
 114 errout:
 115         return err;
 116 }
 117
 118 /**
 119  * nla_parse - Parse a stream of attributes into a tb buffer
 120  * @tb: destination array with maxtype+1 elements
 121  * @maxtype: maximum attribute type to be expected
 122  * @head: head of attribute stream
 123  * @len: length of attribute stream
 124  *
 125  * Parses a stream of attributes and stores a pointer to each attribute in
 126  * the tb array accessable via the attribute type. Attributes with a type
 127  * exceeding maxtype will be silently ignored for backwards compatibility
 128  * reasons. policy may be set to NULL if no validation is required.
 129  *
 130  * Returns 0 on success or a negative error code.
 131  */
 132 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 133               struct nla_policy *policy)
 134 {
 135         struct nlattr *nla;
 136         int rem, err;
 137
 138         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 139
 140         nla_for_each_attr(nla, head, len, rem) {
 141                 u16 type = nla->nla_type;
 142
 143                 if (type > 0 && type <= maxtype) {
 144                         if (policy) {
 145                                 err = validate_nla(nla, maxtype, policy);
 146                                 if (err < 0)
 147                                         goto errout;
 148                         }
 149
 150                         tb[type] = nla;
 151                 }
 152         }
 153
 154         if (unlikely(rem > 0))
 155                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 156                        "attributes.\n", rem);
 157
 158         err = 0;
 159 errout:
 160         return err;
 161 }
 162
 163 /**
 164  * nla_find - Find a specific attribute in a stream of attributes
 165  * @head: head of attribute stream
 166  * @len: length of attribute stream
 167  * @attrtype: type of attribute to look for
 168  *
 169  * Returns the first attribute in the stream matching the specified type.
 170  */
 171 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 172 {
 173         struct nlattr *nla;
 174         int rem;
 175
 176         nla_for_each_attr(nla, head, len, rem)
 177                 if (nla->nla_type == attrtype)
 178                         return nla;
 179
 180         return NULL;
 181 }
 182
 183 /**
 184  * nla_strlcpy - Copy string attribute payload into a sized buffer
 185  * @dst: where to copy the string to
 186  * @src: attribute to copy the string from
 187  * @dstsize: size of destination buffer
 188  *
 189  * Copies at most dstsize - 1 bytes into the destination buffer.
 190  * The result is always a valid NUL-terminated string. Unlike
 191  * strlcpy the destination buffer is always padded out.
 192  *
 193  * Returns the length of the source buffer.
 194  */
 195 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 196 {
 197         size_t srclen = nla_len(nla);
 198         char *src = nla_data(nla);
 199
 200         if (srclen > 0 && src[srclen - 1] == '\0')
 201                 srclen--;
 202
 203         if (dstsize > 0) {
 204                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 205
 206                 memset(dst, 0, dstsize);
 207                 memcpy(dst, src, len);
 208         }
 209
 210         return srclen;
 211 }
 212
 213 /**
 214  * nla_memcpy - Copy a netlink attribute into another memory area
 215  * @dest: where to copy to memcpy
 216  * @src: netlink attribute to copy from
 217  * @count: size of the destination area
 218  *
 219  * Note: The number of bytes copied is limited by the length of
 220  *       attribute's payload. memcpy
 221  *
 222  * Returns the number of bytes copied.
 223  */
 224 int nla_memcpy(void *dest, struct nlattr *src, int count)
 225 {
 226         int minlen = min_t(int, count, nla_len(src));
 227
 228         memcpy(dest, nla_data(src), minlen);
 229
 230         return minlen;
 231 }
 232
 233 /**
 234  * nla_memcmp - Compare an attribute with sized memory area
 235  * @nla: netlink attribute
 236  * @data: memory area
 237  * @size: size of memory area
 238  */
 239 int nla_memcmp(const struct nlattr *nla, const void *data,
 240                              size_t size)
 241 {
 242         int d = nla_len(nla) - size;
 243
 244         if (d == 0)
 245                 d = memcmp(nla_data(nla), data, size);
 246
 247         return d;
 248 }
 249
 250 /**
 251  * nla_strcmp - Compare a string attribute against a string
 252  * @nla: netlink string attribute
 253  * @str: another string
 254  */
 255 int nla_strcmp(const struct nlattr *nla, const char *str)
 256 {
 257         int len = strlen(str) + 1;
 258         int d = nla_len(nla) - len;
 259
 260         if (d == 0)
 261                 d = memcmp(nla_data(nla), str, len);
 262
 263         return d;
 264 }
 265
 266 /**
 267  * __nla_reserve - reserve room for attribute on the skb
 268  * @skb: socket buffer to reserve room on
 269  * @attrtype: attribute type
 270  * @attrlen: length of attribute payload
 271  *
 272  * Adds a netlink attribute header to a socket buffer and reserves
 273  * room for the payload but does not copy it.
 274  *
 275  * The caller is responsible to ensure that the skb provides enough
 276  * tailroom for the attribute header and payload.
 277  */
 278 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 279 {
 280         struct nlattr *nla;
 281
 282         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 283         nla->nla_type = attrtype;
 284         nla->nla_len = nla_attr_size(attrlen);
 285
 286         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 287
 288         return nla;
 289 }
 290
 291 /**
 292  * __nla_reserve_nohdr - reserve room for attribute without header
 293  * @skb: socket buffer to reserve room on
 294  * @attrlen: length of attribute payload
 295  *
 296  * Reserves room for attribute payload without a header.
 297  *
 298  * The caller is responsible to ensure that the skb provides enough
 299  * tailroom for the payload.
 300  */
 301 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 302 {
 303         void *start;
 304
 305         start = skb_put(skb, NLA_ALIGN(attrlen));
 306         memset(start, 0, NLA_ALIGN(attrlen));
 307
 308         return start;
 309 }
 310
 311 /**
 312  * nla_reserve - reserve room for attribute on the skb
 313  * @skb: socket buffer to reserve room on
 314  * @attrtype: attribute type
 315  * @attrlen: length of attribute payload
 316  *
 317  * Adds a netlink attribute header to a socket buffer and reserves
 318  * room for the payload but does not copy it.
 319  *
 320  * Returns NULL if the tailroom of the skb is insufficient to store
 321  * the attribute header and payload.
 322  */
 323 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 324 {
 325         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 326                 return NULL;
 327
 328         return __nla_reserve(skb, attrtype, attrlen);
 329 }
 330
 331 /**
 332  * nla_reserve - reserve room for attribute without header
 333  * @skb: socket buffer to reserve room on
 334  * @len: length of attribute payload
 335  *
 336  * Reserves room for attribute payload without a header.
 337  *
 338  * Returns NULL if the tailroom of the skb is insufficient to store
 339  * the attribute payload.
 340  */
 341 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
 342 {
 343         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 344                 return NULL;
 345
 346         return __nla_reserve_nohdr(skb, attrlen);
 347 }
 348
 349 /**
 350  * __nla_put - Add a netlink attribute to a socket buffer
 351  * @skb: socket buffer to add attribute to
 352  * @attrtype: attribute type
 353  * @attrlen: length of attribute payload
 354  * @data: head of attribute payload
 355  *
 356  * The caller is responsible to ensure that the skb provides enough
 357  * tailroom for the attribute header and payload.
 358  */
 359 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 360                              const void *data)
 361 {
 362         struct nlattr *nla;
 363
 364         nla = __nla_reserve(skb, attrtype, attrlen);
 365         memcpy(nla_data(nla), data, attrlen);
 366 }
 367
 368 /**
 369  * __nla_put_nohdr - Add a netlink attribute without header
 370  * @skb: socket buffer to add attribute to
 371  * @attrlen: length of attribute payload
 372  * @data: head of attribute payload
 373  *
 374  * The caller is responsible to ensure that the skb provides enough
 375  * tailroom for the attribute payload.
 376  */
 377 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 378 {
 379         void *start;
 380
 381         start = __nla_reserve_nohdr(skb, attrlen);
 382         memcpy(start, data, attrlen);
 383 }
 384
 385 /**
 386  * nla_put - Add a netlink attribute to a socket buffer
 387  * @skb: socket buffer to add attribute to
 388  * @attrtype: attribute type
 389  * @attrlen: length of attribute payload
 390  * @data: head of attribute payload
 391  *
 392  * Returns -1 if the tailroom of the skb is insufficient to store
 393  * the attribute header and payload.
 394  */
 395 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 396 {
 397         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 398                 return -1;
 399
 400         __nla_put(skb, attrtype, attrlen, data);
 401         return 0;
 402 }
 403
 404 /**
 405  * nla_put_nohdr - Add a netlink attribute without header
 406  * @skb: socket buffer to add attribute to
 407  * @attrlen: length of attribute payload
 408  * @data: head of attribute payload
 409  *
 410  * Returns -1 if the tailroom of the skb is insufficient to store
 411  * the attribute payload.
 412  */
 413 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
 414 {
 415         if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
 416                 return -1;
 417
 418         __nla_put_nohdr(skb, attrlen, data);
 419         return 0;
 420 }
 421
 422 EXPORT_SYMBOL(nla_validate);
 423 EXPORT_SYMBOL(nla_parse);
 424 EXPORT_SYMBOL(nla_find);
 425 EXPORT_SYMBOL(nla_strlcpy);
 426 EXPORT_SYMBOL(__nla_reserve);
 427 EXPORT_SYMBOL(__nla_reserve_nohdr);
 428 EXPORT_SYMBOL(nla_reserve);
 429 EXPORT_SYMBOL(nla_reserve_nohdr);
 430 EXPORT_SYMBOL(__nla_put);
 431 EXPORT_SYMBOL(__nla_put_nohdr);
 432 EXPORT_SYMBOL(nla_put);
 433 EXPORT_SYMBOL(nla_put_nohdr);
 434 EXPORT_SYMBOL(nla_memcpy);
 435 EXPORT_SYMBOL(nla_memcmp);
 436 EXPORT_SYMBOL(nla_strcmp);