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