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 const struct nla_policy *policy)
28 {
29 const struct nla_policy *pt;
30 int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
31
32 if (type <= 0 || type > maxtype)
33 return 0;
34
35 pt = &policy[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 case NLA_NESTED_COMPAT:
76 if (attrlen < pt->len)
77 return -ERANGE;
78 if (attrlen < NLA_ALIGN(pt->len))
79 break;
80 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN)
81 return -ERANGE;
82 nla = nla_data(nla) + NLA_ALIGN(pt->len);
83 if (attrlen < NLA_ALIGN(pt->len) + NLA_HDRLEN + nla_len(nla))
84 return -ERANGE;
85 break;
86 case NLA_NESTED:
87 /* a nested attributes is allowed to be empty; if its not,
88 * it must have a size of at least NLA_HDRLEN.
89 */
90 if (attrlen == 0)
91 break;
92 default:
93 if (pt->len)
94 minlen = pt->len;
95 else if (pt->type != NLA_UNSPEC)
96 minlen = nla_attr_minlen[pt->type];
97
98 if (attrlen < minlen)
99 return -ERANGE;
100 }
101
102 return 0;
103 }
104
105 /**
106 * nla_validate - Validate a stream of attributes
107 * @head: head of attribute stream
108 * @len: length of attribute stream
109 * @maxtype: maximum attribute type to be expected
110 * @policy: validation policy
111 *
112 * Validates all attributes in the specified attribute stream against the
113 * specified policy. Attributes with a type exceeding maxtype will be
114 * ignored. See documenation of struct nla_policy for more details.
115 *
116 * Returns 0 on success or a negative error code.
117 */
118 int nla_validate(struct nlattr *head, int len, int maxtype,
119 const struct nla_policy *policy)
120 {
121 struct nlattr *nla;
122 int rem, err;
123
124 nla_for_each_attr(nla, head, len, rem) {
125 err = validate_nla(nla, maxtype, policy);
126 if (err < 0)
127 goto errout;
128 }
129
130 err = 0;
131 errout:
132 return err;
133 }
134
135 /**
136 * nla_policy_len - Determin the max. length of a policy
137 * @policy: policy to use
138 * @n: number of policies
139 *
140 * Determines the max. length of the policy. It is currently used
141 * to allocated Netlink buffers roughly the size of the actual
142 * message.
143 *
144 * Returns 0 on success or a negative error code.
145 */
146 int
147 nla_policy_len(const struct nla_policy *p, int n)
148 {
149 int i, len = 0;
150
151 for (i = 0; i < n; i++) {
152 if (p->len)
153 len += nla_total_size(p->len);
154 else if (nla_attr_minlen[p->type])
155 len += nla_total_size(nla_attr_minlen[p->type]);
156 }
157
158 return len;
159 }
160
161 /**
162 * nla_parse - Parse a stream of attributes into a tb buffer
163 * @tb: destination array with maxtype+1 elements
164 * @maxtype: maximum attribute type to be expected
165 * @head: head of attribute stream
166 * @len: length of attribute stream
167 * @policy: validation policy
168 *
169 * Parses a stream of attributes and stores a pointer to each attribute in
170 * the tb array accessable via the attribute type. Attributes with a type
171 * exceeding maxtype will be silently ignored for backwards compatibility
172 * reasons. policy may be set to NULL if no validation is required.
173 *
174 * Returns 0 on success or a negative error code.
175 */
176 int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len,
177 const struct nla_policy *policy)
178 {
179 struct nlattr *nla;
180 int rem, err;
181
182 memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
183
184 nla_for_each_attr(nla, head, len, rem) {
185 u16 type = nla_type(nla);
186
187 if (type > 0 && type <= maxtype) {
188 if (policy) {
189 err = validate_nla(nla, maxtype, policy);
190 if (err < 0)
191 goto errout;
192 }
193
194 tb[type] = nla;
195 }
196 }
197
198 if (unlikely(rem > 0))
199 printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
200 "attributes.\n", rem);
201
202 err = 0;
203 errout:
204 return err;
205 }
206
207 /**
208 * nla_find - Find a specific attribute in a stream of attributes
209 * @head: head of attribute stream
210 * @len: length of attribute stream
211 * @attrtype: type of attribute to look for
212 *
213 * Returns the first attribute in the stream matching the specified type.
214 */
215 struct nlattr *nla_find(struct nlattr *head, int len, int attrtype)
216 {
217 struct nlattr *nla;
218 int rem;
219
220 nla_for_each_attr(nla, head, len, rem)
221 if (nla_type(nla) == attrtype)
222 return nla;
223
224 return NULL;
225 }
226
227 /**
228 * nla_strlcpy - Copy string attribute payload into a sized buffer
229 * @dst: where to copy the string to
230 * @nla: attribute to copy the string from
231 * @dstsize: size of destination buffer
232 *
233 * Copies at most dstsize - 1 bytes into the destination buffer.
234 * The result is always a valid NUL-terminated string. Unlike
235 * strlcpy the destination buffer is always padded out.
236 *
237 * Returns the length of the source buffer.
238 */
239 size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
240 {
241 size_t srclen = nla_len(nla);
242 char *src = nla_data(nla);
243
244 if (srclen > 0 && src[srclen - 1] == '\0')
245 srclen--;
246
247 if (dstsize > 0) {
248 size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;
249
250 memset(dst, 0, dstsize);
251 memcpy(dst, src, len);
252 }
253
254 return srclen;
255 }
256
257 /**
258 * nla_memcpy - Copy a netlink attribute into another memory area
259 * @dest: where to copy to memcpy
260 * @src: netlink attribute to copy from
261 * @count: size of the destination area
262 *
263 * Note: The number of bytes copied is limited by the length of
264 * attribute's payload. memcpy
265 *
266 * Returns the number of bytes copied.
267 */
268 int nla_memcpy(void *dest, const struct nlattr *src, int count)
269 {
270 int minlen = min_t(int, count, nla_len(src));
271
272 memcpy(dest, nla_data(src), minlen);
273
274 return minlen;
275 }
276
277 /**
278 * nla_memcmp - Compare an attribute with sized memory area
279 * @nla: netlink attribute
280 * @data: memory area
281 * @size: size of memory area
282 */
283 int nla_memcmp(const struct nlattr *nla, const void *data,
284 size_t size)
285 {
286 int d = nla_len(nla) - size;
287
288 if (d == 0)
289 d = memcmp(nla_data(nla), data, size);
290
291 return d;
292 }
293
294 /**
295 * nla_strcmp - Compare a string attribute against a string
296 * @nla: netlink string attribute
297 * @str: another string
298 */
299 int nla_strcmp(const struct nlattr *nla, const char *str)
300 {
301 int len = strlen(str) + 1;
302 int d = nla_len(nla) - len;
303
304 if (d == 0)
305 d = memcmp(nla_data(nla), str, len);
306
307 return d;
308 }
309
310 #ifdef CONFIG_NET
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 * The caller is responsible to ensure that the skb provides enough
321 * tailroom for the attribute header and payload.
322 */
323 struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
324 {
325 struct nlattr *nla;
326
327 nla = (struct nlattr *) skb_put(skb, nla_total_size(attrlen));
328 nla->nla_type = attrtype;
329 nla->nla_len = nla_attr_size(attrlen);
330
331 memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));
332
333 return nla;
334 }
335 EXPORT_SYMBOL(__nla_reserve);
336
337 /**
338 * __nla_reserve_nohdr - reserve room for attribute without header
339 * @skb: socket buffer to reserve room on
340 * @attrlen: length of attribute payload
341 *
342 * Reserves room for attribute payload without a header.
343 *
344 * The caller is responsible to ensure that the skb provides enough
345 * tailroom for the payload.
346 */
347 void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
348 {
349 void *start;
350
351 start = skb_put(skb, NLA_ALIGN(attrlen));
352 memset(start, 0, NLA_ALIGN(attrlen));
353
354 return start;
355 }
356 EXPORT_SYMBOL(__nla_reserve_nohdr);
357
358 /**
359 * nla_reserve - reserve room for attribute on the skb
360 * @skb: socket buffer to reserve room on
361 * @attrtype: attribute type
362 * @attrlen: length of attribute payload
363 *
364 * Adds a netlink attribute header to a socket buffer and reserves
365 * room for the payload but does not copy it.
366 *
367 * Returns NULL if the tailroom of the skb is insufficient to store
368 * the attribute header and payload.
369 */
370 struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
371 {
372 if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
373 return NULL;
374
375 return __nla_reserve(skb, attrtype, attrlen);
376 }
377 EXPORT_SYMBOL(nla_reserve);
378
379 /**
380 * nla_reserve_nohdr - reserve room for attribute without header
381 * @skb: socket buffer to reserve room on
382 * @attrlen: length of attribute payload
383 *
384 * Reserves room for attribute payload without a header.
385 *
386 * Returns NULL if the tailroom of the skb is insufficient to store
387 * the attribute payload.
388 */
389 void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
390 {
391 if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
392 return NULL;
393
394 return __nla_reserve_nohdr(skb, attrlen);
395 }
396 EXPORT_SYMBOL(nla_reserve_nohdr);
397
398 /**
399 * __nla_put - Add a netlink attribute to a socket buffer
400 * @skb: socket buffer to add attribute to
401 * @attrtype: attribute type
402 * @attrlen: length of attribute payload
403 * @data: head of attribute payload
404 *
405 * The caller is responsible to ensure that the skb provides enough
406 * tailroom for the attribute header and payload.
407 */
408 void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
409 const void *data)
410 {
411 struct nlattr *nla;
412
413 nla = __nla_reserve(skb, attrtype, attrlen);
414 memcpy(nla_data(nla), data, attrlen);
415 }
416 EXPORT_SYMBOL(__nla_put);
417
418 /**
419 * __nla_put_nohdr - Add a netlink attribute without header
420 * @skb: socket buffer to add attribute to
421 * @attrlen: length of attribute payload
422 * @data: head of attribute payload
423 *
424 * The caller is responsible to ensure that the skb provides enough
425 * tailroom for the attribute payload.
426 */
427 void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
428 {
429 void *start;
430
431 start = __nla_reserve_nohdr(skb, attrlen);
432 memcpy(start, data, attrlen);
433 }
434 EXPORT_SYMBOL(__nla_put_nohdr);
435
436 /**
437 * nla_put - Add a netlink attribute to a socket buffer
438 * @skb: socket buffer to add attribute to
439 * @attrtype: attribute type
440 * @attrlen: length of attribute payload
441 * @data: head of attribute payload
442 *
443 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
444 * the attribute header and payload.
445 */
446 int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
447 {
448 if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
449 return -EMSGSIZE;
450
451 __nla_put(skb, attrtype, attrlen, data);
452 return 0;
453 }
454 EXPORT_SYMBOL(nla_put);
455
456 /**
457 * nla_put_nohdr - Add a netlink attribute without header
458 * @skb: socket buffer to add attribute to
459 * @attrlen: length of attribute payload
460 * @data: head of attribute payload
461 *
462 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
463 * the attribute payload.
464 */
465 int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
466 {
467 if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
468 return -EMSGSIZE;
469
470 __nla_put_nohdr(skb, attrlen, data);
471 return 0;
472 }
473 EXPORT_SYMBOL(nla_put_nohdr);
474
475 /**
476 * nla_append - Add a netlink attribute without header or padding
477 * @skb: socket buffer to add attribute to
478 * @attrlen: length of attribute payload
479 * @data: head of attribute payload
480 *
481 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
482 * the attribute payload.
483 */
484 int nla_append(struct sk_buff *skb, int attrlen, const void *data)
485 {
486 if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
487 return -EMSGSIZE;
488
489 memcpy(skb_put(skb, attrlen), data, attrlen);
490 return 0;
491 }
492 EXPORT_SYMBOL(nla_append);
493 #endif
494
495 EXPORT_SYMBOL(nla_validate);
496 EXPORT_SYMBOL(nla_policy_len);
497 EXPORT_SYMBOL(nla_parse);
498 EXPORT_SYMBOL(nla_find);
499 EXPORT_SYMBOL(nla_strlcpy);
500 EXPORT_SYMBOL(nla_memcpy);
501 EXPORT_SYMBOL(nla_memcmp);
502 EXPORT_SYMBOL(nla_strcmp);
503
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