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