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/config.h>
   9 #include <linux/module.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/netdevice.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/string.h>
  16 #include <linux/types.h>
  17 #include <net/netlink.h>
  18
  19 static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
  20         [NLA_U8]        = sizeof(u8),
  21         [NLA_U16]       = sizeof(u16),
  22         [NLA_U32]       = sizeof(u32),
  23         [NLA_U64]       = sizeof(u64),
  24         [NLA_STRING]    = 1,
  25         [NLA_NESTED]    = NLA_HDRLEN,
  26 };
  27
  28 static int validate_nla(struct nlattr *nla, int maxtype,
  29                         struct nla_policy *policy)
  30 {
  31         struct nla_policy *pt;
  32         int minlen = 0;
  33
  34         if (nla->nla_type <= 0 || nla->nla_type > maxtype)
  35                 return 0;
  36
  37         pt = &policy[nla->nla_type];
  38
  39         BUG_ON(pt->type > NLA_TYPE_MAX);
  40
  41         if (pt->minlen)
  42                 minlen = pt->minlen;
  43         else if (pt->type != NLA_UNSPEC)
  44                 minlen = nla_attr_minlen[pt->type];
  45
  46         if (pt->type == NLA_FLAG && nla_len(nla) > 0)
  47                 return -ERANGE;
  48
  49         if (nla_len(nla) < minlen)
  50                 return -ERANGE;
  51
  52         return 0;
  53 }
  54
  55 /**
  56  * nla_validate - Validate a stream of attributes
  57  * @head: head of attribute stream
  58  * @len: length of attribute stream
  59  * @maxtype: maximum attribute type to be expected
  60  * @policy: validation policy
  61  *
  62  * Validates all attributes in the specified attribute stream against the
  63  * specified policy. Attributes with a type exceeding maxtype will be
  64  * ignored. See documenation of struct nla_policy for more details.
  65  *
  66  * Returns 0 on success or a negative error code.
  67  */
  68 int nla_validate(struct nlattr *head, int len, int maxtype,
  69                  struct nla_policy *policy)
  70 {
  71         struct nlattr *nla;
  72         int rem, err;
  73
  74         nla_for_each_attr(nla, head, len, rem) {
  75                 err = validate_nla(nla, maxtype, policy);
  76                 if (err < 0)
  77                         goto errout;
  78         }
  79
  80         err = 0;
  81 errout:
  82         return err;
  83 }
  84
  85 /**
  86  * nla_parse - Parse a stream of attributes into a tb buffer
  87  * @tb: destination array with maxtype+1 elements
  88  * @maxtype: maximum attribute type to be expected
  89  * @head: head of attribute stream
  90  * @len: length of attribute stream
  91  *
  92  * Parses a stream of attributes and stores a pointer to each attribute in
  93  * the tb array accessable via the attribute type. Attributes with a type
  94  * exceeding maxtype will be silently ignored for backwards compatibility
  95  * reasons. policy may be set to NULL if no validation is required.
  96  *
  97  * Returns 0 on success or a negative error code.
  98  */
  99 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
 100               struct nla_policy *policy)
 101 {
 102         struct nlattr *nla;
 103         int rem, err;
 104
 105         memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
 106
 107         nla_for_each_attr(nla, head, len, rem) {
 108                 u16 type = nla->nla_type;
 109
 110                 if (type > 0 && type <= maxtype) {
 111                         if (policy) {
 112                                 err = validate_nla(nla, maxtype, policy);
 113                                 if (err < 0)
 114                                         goto errout;
 115                         }
 116
 117                         tb[type] = nla;
 118                 }
 119         }
 120
 121         if (unlikely(rem > 0))
 122                 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
 123                        "attributes.\n", rem);
 124
 125         err = 0;
 126 errout:
 127         return err;
 128 }
 129
 130 /**
 131  * nla_find - Find a specific attribute in a stream of attributes
 132  * @head: head of attribute stream
 133  * @len: length of attribute stream
 134  * @attrtype: type of attribute to look for
 135  *
 136  * Returns the first attribute in the stream matching the specified type.
 137  */
 138 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
 139 {
 140         struct nlattr *nla;
 141         int rem;
 142
 143         nla_for_each_attr(nla, head, len, rem)
 144                 if (nla->nla_type == attrtype)
 145                         return nla;
 146
 147         return NULL;
 148 }
 149
 150 /**
 151  * nla_strlcpy - Copy string attribute payload into a sized buffer
 152  * @dst: where to copy the string to
 153  * @src: attribute to copy the string from
 154  * @dstsize: size of destination buffer
 155  *
 156  * Copies at most dstsize - 1 bytes into the destination buffer.
 157  * The result is always a valid NUL-terminated string. Unlike
 158  * strlcpy the destination buffer is always padded out.
 159  *
 160  * Returns the length of the source buffer.
 161  */
 162 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
 163 {
 164         size_t srclen = nla_len(nla);
 165         char *src = nla_data(nla);
 166
 167         if (srclen > 0 && src[srclen - 1] == '\0')
 168                 srclen--;
 169
 170         if (dstsize > 0) {
 171                 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
 172
 173                 memset(dst, 0, dstsize);
 174                 memcpy(dst, src, len);
 175         }
 176
 177         return srclen;
 178 }
 179
 180 /**
 181  * nla_memcpy - Copy a netlink attribute into another memory area
 182  * @dest: where to copy to memcpy
 183  * @src: netlink attribute to copy from
 184  * @count: size of the destination area
 185  *
 186  * Note: The number of bytes copied is limited by the length of
 187  *       attribute's payload. memcpy
 188  *
 189  * Returns the number of bytes copied.
 190  */
 191 int nla_memcpy(void *dest, struct nlattr *src, int count)
 192 {
 193         int minlen = min_t(int, count, nla_len(src));
 194
 195         memcpy(dest, nla_data(src), minlen);
 196
 197         return minlen;
 198 }
 199
 200 /**
 201  * nla_memcmp - Compare an attribute with sized memory area
 202  * @nla: netlink attribute
 203  * @data: memory area
 204  * @size: size of memory area
 205  */
 206 int nla_memcmp(const struct nlattr *nla, const void *data,
 207                              size_t size)
 208 {
 209         int d = nla_len(nla) - size;
 210
 211         if (d == 0)
 212                 d = memcmp(nla_data(nla), data, size);
 213
 214         return d;
 215 }
 216
 217 /**
 218  * nla_strcmp - Compare a string attribute against a string
 219  * @nla: netlink string attribute
 220  * @str: another string
 221  */
 222 int nla_strcmp(const struct nlattr *nla, const char *str)
 223 {
 224         int len = strlen(str) + 1;
 225         int d = nla_len(nla) - len;
 226
 227         if (d == 0)
 228                 d = memcmp(nla_data(nla), str, len);
 229
 230         return d;
 231 }
 232
 233 /**
 234  * __nla_reserve - reserve room for attribute on the skb
 235  * @skb: socket buffer to reserve room on
 236  * @attrtype: attribute type
 237  * @attrlen: length of attribute payload
 238  *
 239  * Adds a netlink attribute header to a socket buffer and reserves
 240  * room for the payload but does not copy it.
 241  *
 242  * The caller is responsible to ensure that the skb provides enough
 243  * tailroom for the attribute header and payload.
 244  */
 245 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 246 {
 247         struct nlattr *nla;
 248
 249         nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
 250         nla->nla_type = attrtype;
 251         nla->nla_len = nla_attr_size(attrlen);
 252
 253         memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
 254
 255         return nla;
 256 }
 257
 258 /**
 259  * nla_reserve - reserve room for attribute on the skb
 260  * @skb: socket buffer to reserve room on
 261  * @attrtype: attribute type
 262  * @attrlen: length of attribute payload
 263  *
 264  * Adds a netlink attribute header to a socket buffer and reserves
 265  * room for the payload but does not copy it.
 266  *
 267  * Returns NULL if the tailroom of the skb is insufficient to store
 268  * the attribute header and payload.
 269  */
 270 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
 271 {
 272         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 273                 return NULL;
 274
 275         return __nla_reserve(skb, attrtype, attrlen);
 276 }
 277
 278 /**
 279  * __nla_put - Add a netlink attribute to a socket buffer
 280  * @skb: socket buffer to add attribute to
 281  * @attrtype: attribute type
 282  * @attrlen: length of attribute payload
 283  * @data: head of attribute payload
 284  *
 285  * The caller is responsible to ensure that the skb provides enough
 286  * tailroom for the attribute header and payload.
 287  */
 288 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 289                              const void *data)
 290 {
 291         struct nlattr *nla;
 292
 293         nla = __nla_reserve(skb, attrtype, attrlen);
 294         memcpy(nla_data(nla), data, attrlen);
 295 }
 296
 297
 298 /**
 299  * nla_put - Add a netlink attribute to a socket buffer
 300  * @skb: socket buffer to add attribute to
 301  * @attrtype: attribute type
 302  * @attrlen: length of attribute payload
 303  * @data: head of attribute payload
 304  *
 305  * Returns -1 if the tailroom of the skb is insufficient to store
 306  * the attribute header and payload.
 307  */
 308 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
 309 {
 310         if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
 311                 return -1;
 312
 313         __nla_put(skb, attrtype, attrlen, data);
 314         return 0;
 315 }
 316
 317
 318 EXPORT_SYMBOL(nla_validate);
 319 EXPORT_SYMBOL(nla_parse);
 320 EXPORT_SYMBOL(nla_find);
 321 EXPORT_SYMBOL(nla_strlcpy);
 322 EXPORT_SYMBOL(__nla_reserve);
 323 EXPORT_SYMBOL(nla_reserve);
 324 EXPORT_SYMBOL(__nla_put);
 325 EXPORT_SYMBOL(nla_put);
 326 EXPORT_SYMBOL(nla_memcpy);
 327 EXPORT_SYMBOL(nla_memcmp);
 328 EXPORT_SYMBOL(nla_strcmp);