summaryrefslogtreecommitdiff
path: root/lib/nlattr.c
blob: adc919b32bf92d2fa54ed0943b39b168ee66fcd8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
// SPDX-License-Identifier: GPL-2.0
/*
 * NETLINK      Netlink attributes
 *
 * 		Authors:	Thomas Graf <tgraf@suug.ch>
 * 				Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/jiffies.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/types.h>
#include <net/netlink.h>

/* For these data types, attribute length should be exactly the given
 * size. However, to maintain compatibility with broken commands, if the
 * attribute length does not match the expected size a warning is emitted
 * to the user that the command is sending invalid data and needs to be fixed.
 */
static const u8 nla_attr_len[NLA_TYPE_MAX+1] = {
	[NLA_U8]	= sizeof(u8),
	[NLA_U16]	= sizeof(u16),
	[NLA_U32]	= sizeof(u32),
	[NLA_U64]	= sizeof(u64),
	[NLA_S8]	= sizeof(s8),
	[NLA_S16]	= sizeof(s16),
	[NLA_S32]	= sizeof(s32),
	[NLA_S64]	= sizeof(s64),
};

static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = {
	[NLA_U8]	= sizeof(u8),
	[NLA_U16]	= sizeof(u16),
	[NLA_U32]	= sizeof(u32),
	[NLA_U64]	= sizeof(u64),
	[NLA_MSECS]	= sizeof(u64),
	[NLA_NESTED]	= NLA_HDRLEN,
	[NLA_S8]	= sizeof(s8),
	[NLA_S16]	= sizeof(s16),
	[NLA_S32]	= sizeof(s32),
	[NLA_S64]	= sizeof(s64),
};

static int validate_nla_bitfield32(const struct nlattr *nla,
				   const u32 *valid_flags_mask)
{
	const struct nla_bitfield32 *bf = nla_data(nla);

	if (!valid_flags_mask)
		return -EINVAL;

	/*disallow invalid bit selector */
	if (bf->selector & ~*valid_flags_mask)
		return -EINVAL;

	/*disallow invalid bit values */
	if (bf->value & ~*valid_flags_mask)
		return -EINVAL;

	/*disallow valid bit values that are not selected*/
	if (bf->value & ~bf->selector)
		return -EINVAL;

	return 0;
}

static int nla_validate_array(const struct nlattr *head, int len, int maxtype,
			      const struct nla_policy *policy,
			      struct netlink_ext_ack *extack,
			      unsigned int validate)
{
	const struct nlattr *entry;
	int rem;

	nla_for_each_attr(entry, head, len, rem) {
		int ret;

		if (nla_len(entry) == 0)
			continue;

		if (nla_len(entry) < NLA_HDRLEN) {
			NL_SET_ERR_MSG_ATTR(extack, entry,
					    "Array element too short");
			return -ERANGE;
		}

		ret = __nla_validate(nla_data(entry), nla_len(entry),
				     maxtype, policy, validate, extack);
		if (ret < 0)
			return ret;
	}

	return 0;
}

static int nla_validate_int_range(const struct nla_policy *pt,
				  const struct nlattr *nla,
				  struct netlink_ext_ack *extack)
{
	bool validate_min, validate_max;
	s64 value;

	validate_min = pt->validation_type == NLA_VALIDATE_RANGE ||
		       pt->validation_type == NLA_VALIDATE_MIN;
	validate_max = pt->validation_type == NLA_VALIDATE_RANGE ||
		       pt->validation_type == NLA_VALIDATE_MAX;

	switch (pt->type) {
	case NLA_U8:
		value = nla_get_u8(nla);
		break;
	case NLA_U16:
		value = nla_get_u16(nla);
		break;
	case NLA_U32:
		value = nla_get_u32(nla);
		break;
	case NLA_S8:
		value = nla_get_s8(nla);
		break;
	case NLA_S16:
		value = nla_get_s16(nla);
		break;
	case NLA_S32:
		value = nla_get_s32(nla);
		break;
	case NLA_S64:
		value = nla_get_s64(nla);
		break;
	case NLA_U64:
		/* treat this one specially, since it may not fit into s64 */
		if ((validate_min && nla_get_u64(nla) < pt->min) ||
		    (validate_max && nla_get_u64(nla) > pt->max)) {
			NL_SET_ERR_MSG_ATTR(extack, nla,
					    "integer out of range");
			return -ERANGE;
		}
		return 0;
	default:
		WARN_ON(1);
		return -EINVAL;
	}

	if ((validate_min && value < pt->min) ||
	    (validate_max && value > pt->max)) {
		NL_SET_ERR_MSG_ATTR(extack, nla,
				    "integer out of range");
		return -ERANGE;
	}

	return 0;
}

static int validate_nla(const struct nlattr *nla, int maxtype,
			const struct nla_policy *policy, unsigned int validate,
			struct netlink_ext_ack *extack)
{
	u16 strict_start_type = policy[0].strict_start_type;
	const struct nla_policy *pt;
	int minlen = 0, attrlen = nla_len(nla), type = nla_type(nla);
	int err = -ERANGE;

	if (strict_start_type && type >= strict_start_type)
		validate |= NL_VALIDATE_STRICT;

	if (type <= 0 || type > maxtype)
		return 0;

	pt = &policy[type];

	BUG_ON(pt->type > NLA_TYPE_MAX);

	if ((nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) ||
	    (pt->type == NLA_EXACT_LEN_WARN && attrlen != pt->len)) {
		pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n",
				    current->comm, type);
		if (validate & NL_VALIDATE_STRICT_ATTRS) {
			NL_SET_ERR_MSG_ATTR(extack, nla,
					    "invalid attribute length");
			return -EINVAL;
		}
	}

	switch (pt->type) {
	case NLA_EXACT_LEN:
		if (attrlen != pt->len)
			goto out_err;
		break;

	case NLA_REJECT:
		if (extack && pt->validation_data) {
			NL_SET_BAD_ATTR(extack, nla);
			extack->_msg = pt->validation_data;
			return -EINVAL;
		}
		err = -EINVAL;
		goto out_err;

	case NLA_FLAG:
		if (attrlen > 0)
			goto out_err;
		break;

	case NLA_BITFIELD32:
		if (attrlen != sizeof(struct nla_bitfield32))
			goto out_err;

		err = validate_nla_bitfield32(nla, pt->validation_data);
		if (err)
			goto out_err;
		break;

	case NLA_NUL_STRING:
		if (pt->len)
			minlen = min_t(int, attrlen, pt->len + 1);
		else
			minlen = attrlen;

		if (!minlen || memchr(nla_data(nla), '\0', minlen) == NULL) {
			err = -EINVAL;
			goto out_err;
		}
		/* fall through */

	case NLA_STRING:
		if (attrlen < 1)
			goto out_err;

		if (pt->len) {
			char *buf = nla_data(nla);

			if (buf[attrlen - 1] == '\0')
				attrlen--;

			if (attrlen > pt->len)
				goto out_err;
		}
		break;

	case NLA_BINARY:
		if (pt->len && attrlen > pt->len)
			goto out_err;
		break;

	case NLA_NESTED:
		/* a nested attributes is allowed to be empty; if its not,
		 * it must have a size of at least NLA_HDRLEN.
		 */
		if (attrlen == 0)
			break;
		if (attrlen < NLA_HDRLEN)
			goto out_err;
		if (pt->validation_data) {
			err = __nla_validate(nla_data(nla), nla_len(nla), pt->len,
					     pt->validation_data, validate,
					     extack);
			if (err < 0) {
				/*
				 * return directly to preserve the inner
				 * error message/attribute pointer
				 */
				return err;
			}
		}
		break;
	case NLA_NESTED_ARRAY:
		/* a nested array attribute is allowed to be empty; if its not,
		 * it must have a size of at least NLA_HDRLEN.
		 */
		if (attrlen == 0)
			break;
		if (attrlen < NLA_HDRLEN)
			goto out_err;
		if (pt->validation_data) {
			int err;

			err = nla_validate_array(nla_data(nla), nla_len(nla),
						 pt->len, pt->validation_data,
						 extack, validate);
			if (err < 0) {
				/*
				 * return directly to preserve the inner
				 * error message/attribute pointer
				 */
				return err;
			}
		}
		break;

	case NLA_UNSPEC:
		if (validate & NL_VALIDATE_UNSPEC) {
			NL_SET_ERR_MSG_ATTR(extack, nla,
					    "Unsupported attribute");
			return -EINVAL;
		}
		/* fall through */
	case NLA_MIN_LEN:
		if (attrlen < pt->len)
			goto out_err;
		break;

	default:
		if (pt->len)
			minlen = pt->len;
		else
			minlen = nla_attr_minlen[pt->type];

		if (attrlen < minlen)
			goto out_err;
	}

	/* further validation */
	switch (pt->validation_type) {
	case NLA_VALIDATE_NONE:
		/* nothing to do */
		break;
	case NLA_VALIDATE_RANGE:
	case NLA_VALIDATE_MIN:
	case NLA_VALIDATE_MAX:
		err = nla_validate_int_range(pt, nla, extack);
		if (err)
			return err;
		break;
	case NLA_VALIDATE_FUNCTION:
		if (pt->validate) {
			err = pt->validate(nla, extack);
			if (err)
				return err;
		}
		break;
	}

	return 0;
out_err:
	NL_SET_ERR_MSG_ATTR(extack, nla, "Attribute failed policy validation");
	return err;
}

static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
				const struct nla_policy *policy,
				unsigned int validate,
				struct netlink_ext_ack *extack,
				struct nlattr **tb)
{
	const struct nlattr *nla;
	int rem;

	if (tb)
		memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));

	nla_for_each_attr(nla, head, len, rem) {
		u16 type = nla_type(nla);

		if (type == 0 || type > maxtype) {
			if (validate & NL_VALIDATE_MAXTYPE) {
				NL_SET_ERR_MSG_ATTR(extack, nla,
						    "Unknown attribute type");
				return -EINVAL;
			}
			continue;
		}
		if (policy) {
			int err = validate_nla(nla, maxtype, policy,
					       validate, extack);

			if (err < 0)
				return err;
		}

		if (tb)
			tb[type] = (struct nlattr *)nla;
	}

	if (unlikely(rem > 0)) {
		pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
				    rem, current->comm);
		NL_SET_ERR_MSG(extack, "bytes leftover after parsing attributes");
		if (validate & NL_VALIDATE_TRAILING)
			return -EINVAL;
	}

	return 0;
}

/**
 * __nla_validate - Validate a stream of attributes
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @maxtype: maximum attribute type to be expected
 * @policy: validation policy
 * @validate: validation strictness
 * @extack: extended ACK report struct
 *
 * Validates all attributes in the specified attribute stream against the
 * specified policy. Validation depends on the validate flags passed, see
 * &enum netlink_validation for more details on that.
 * See documenation of struct nla_policy for more details.
 *
 * Returns 0 on success or a negative error code.
 */
int __nla_validate(const struct nlattr *head, int len, int maxtype,
		   const struct nla_policy *policy, unsigned int validate,
		   struct netlink_ext_ack *extack)
{
	return __nla_validate_parse(head, len, maxtype, policy, validate,
				    extack, NULL);
}
EXPORT_SYMBOL(__nla_validate);

/**
 * nla_policy_len - Determin the max. length of a policy
 * @policy: policy to use
 * @n: number of policies
 *
 * Determines the max. length of the policy.  It is currently used
 * to allocated Netlink buffers roughly the size of the actual
 * message.
 *
 * Returns 0 on success or a negative error code.
 */
int
nla_policy_len(const struct nla_policy *p, int n)
{
	int i, len = 0;

	for (i = 0; i < n; i++, p++) {
		if (p->len)
			len += nla_total_size(p->len);
		else if (nla_attr_len[p->type])
			len += nla_total_size(nla_attr_len[p->type]);
		else if (nla_attr_minlen[p->type])
			len += nla_total_size(nla_attr_minlen[p->type]);
	}

	return len;
}
EXPORT_SYMBOL(nla_policy_len);

/**
 * __nla_parse - Parse a stream of attributes into a tb buffer
 * @tb: destination array with maxtype+1 elements
 * @maxtype: maximum attribute type to be expected
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @policy: validation policy
 * @validate: validation strictness
 * @extack: extended ACK pointer
 *
 * Parses a stream of attributes and stores a pointer to each attribute in
 * the tb array accessible via the attribute type.
 * Validation is controlled by the @validate parameter.
 *
 * Returns 0 on success or a negative error code.
 */
int __nla_parse(struct nlattr **tb, int maxtype,
		const struct nlattr *head, int len,
		const struct nla_policy *policy, unsigned int validate,
		struct netlink_ext_ack *extack)
{
	return __nla_validate_parse(head, len, maxtype, policy, validate,
				    extack, tb);
}
EXPORT_SYMBOL(__nla_parse);

/**
 * nla_find - Find a specific attribute in a stream of attributes
 * @head: head of attribute stream
 * @len: length of attribute stream
 * @attrtype: type of attribute to look for
 *
 * Returns the first attribute in the stream matching the specified type.
 */
struct nlattr *nla_find(const struct nlattr *head, int len, int attrtype)
{
	const struct nlattr *nla;
	int rem;

	nla_for_each_attr(nla, head, len, rem)
		if (nla_type(nla) == attrtype)
			return (struct nlattr *)nla;

	return NULL;
}
EXPORT_SYMBOL(nla_find);

/**
 * nla_strlcpy - Copy string attribute payload into a sized buffer
 * @dst: where to copy the string to
 * @nla: attribute to copy the string from
 * @dstsize: size of destination buffer
 *
 * Copies at most dstsize - 1 bytes into the destination buffer.
 * The result is always a valid NUL-terminated string. Unlike
 * strlcpy the destination buffer is always padded out.
 *
 * Returns the length of the source buffer.
 */
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
	size_t srclen = nla_len(nla);
	char *src = nla_data(nla);

	if (srclen > 0 && src[srclen - 1] == '\0')
		srclen--;

	if (dstsize > 0) {
		size_t len = (srclen >= dstsize) ? dstsize - 1 : srclen;

		memset(dst, 0, dstsize);
		memcpy(dst, src, len);
	}

	return srclen;
}
EXPORT_SYMBOL(nla_strlcpy);

/**
 * nla_strdup - Copy string attribute payload into a newly allocated buffer
 * @nla: attribute to copy the string from
 * @flags: the type of memory to allocate (see kmalloc).
 *
 * Returns a pointer to the allocated buffer or NULL on error.
 */
char *nla_strdup(const struct nlattr *nla, gfp_t flags)
{
	size_t srclen = nla_len(nla);
	char *src = nla_data(nla), *dst;

	if (srclen > 0 && src[srclen - 1] == '\0')
		srclen--;

	dst = kmalloc(srclen + 1, flags);
	if (dst != NULL) {
		memcpy(dst, src, srclen);
		dst[srclen] = '\0';
	}
	return dst;
}
EXPORT_SYMBOL(nla_strdup);

/**
 * nla_memcpy - Copy a netlink attribute into another memory area
 * @dest: where to copy to memcpy
 * @src: netlink attribute to copy from
 * @count: size of the destination area
 *
 * Note: The number of bytes copied is limited by the length of
 *       attribute's payload. memcpy
 *
 * Returns the number of bytes copied.
 */
int nla_memcpy(void *dest, const struct nlattr *src, int count)
{
	int minlen = min_t(int, count, nla_len(src));

	memcpy(dest, nla_data(src), minlen);
	if (count > minlen)
		memset(dest + minlen, 0, count - minlen);

	return minlen;
}
EXPORT_SYMBOL(nla_memcpy);

/**
 * nla_memcmp - Compare an attribute with sized memory area
 * @nla: netlink attribute
 * @data: memory area
 * @size: size of memory area
 */
int nla_memcmp(const struct nlattr *nla, const void *data,
			     size_t size)
{
	int d = nla_len(nla) - size;

	if (d == 0)
		d = memcmp(nla_data(nla), data, size);

	return d;
}
EXPORT_SYMBOL(nla_memcmp);

/**
 * nla_strcmp - Compare a string attribute against a string
 * @nla: netlink string attribute
 * @str: another string
 */
int nla_strcmp(const struct nlattr *nla, const char *str)
{
	int len = strlen(str);
	char *buf = nla_data(nla);
	int attrlen = nla_len(nla);
	int d;

	if (attrlen > 0 && buf[attrlen - 1] == '\0')
		attrlen--;

	d = attrlen - len;
	if (d == 0)
		d = memcmp(nla_data(nla), str, len);

	return d;
}
EXPORT_SYMBOL(nla_strcmp);

#ifdef CONFIG_NET
/**
 * __nla_reserve - reserve room for attribute on the skb
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
struct nlattr *__nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
	struct nlattr *nla;

	nla = skb_put(skb, nla_total_size(attrlen));
	nla->nla_type = attrtype;
	nla->nla_len = nla_attr_size(attrlen);

	memset((unsigned char *) nla + nla->nla_len, 0, nla_padlen(attrlen));

	return nla;
}
EXPORT_SYMBOL(__nla_reserve);

/**
 * __nla_reserve_64bit - reserve room for attribute on the skb and align it
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @padattr: attribute type for the padding
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it. It also ensure that this
 * attribute will have a 64-bit aligned nla_data() area.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
struct nlattr *__nla_reserve_64bit(struct sk_buff *skb, int attrtype,
				   int attrlen, int padattr)
{
	if (nla_need_padding_for_64bit(skb))
		nla_align_64bit(skb, padattr);

	return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(__nla_reserve_64bit);

/**
 * __nla_reserve_nohdr - reserve room for attribute without header
 * @skb: socket buffer to reserve room on
 * @attrlen: length of attribute payload
 *
 * Reserves room for attribute payload without a header.
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the payload.
 */
void *__nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
	return skb_put_zero(skb, NLA_ALIGN(attrlen));
}
EXPORT_SYMBOL(__nla_reserve_nohdr);

/**
 * nla_reserve - reserve room for attribute on the skb
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
struct nlattr *nla_reserve(struct sk_buff *skb, int attrtype, int attrlen)
{
	if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
		return NULL;

	return __nla_reserve(skb, attrtype, attrlen);
}
EXPORT_SYMBOL(nla_reserve);

/**
 * nla_reserve_64bit - reserve room for attribute on the skb and align it
 * @skb: socket buffer to reserve room on
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @padattr: attribute type for the padding
 *
 * Adds a netlink attribute header to a socket buffer and reserves
 * room for the payload but does not copy it. It also ensure that this
 * attribute will have a 64-bit aligned nla_data() area.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
struct nlattr *nla_reserve_64bit(struct sk_buff *skb, int attrtype, int attrlen,
				 int padattr)
{
	size_t len;

	if (nla_need_padding_for_64bit(skb))
		len = nla_total_size_64bit(attrlen);
	else
		len = nla_total_size(attrlen);
	if (unlikely(skb_tailroom(skb) < len))
		return NULL;

	return __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
}
EXPORT_SYMBOL(nla_reserve_64bit);

/**
 * nla_reserve_nohdr - reserve room for attribute without header
 * @skb: socket buffer to reserve room on
 * @attrlen: length of attribute payload
 *
 * Reserves room for attribute payload without a header.
 *
 * Returns NULL if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
void *nla_reserve_nohdr(struct sk_buff *skb, int attrlen)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return NULL;

	return __nla_reserve_nohdr(skb, attrlen);
}
EXPORT_SYMBOL(nla_reserve_nohdr);

/**
 * __nla_put - Add a netlink attribute to a socket buffer
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
			     const void *data)
{
	struct nlattr *nla;

	nla = __nla_reserve(skb, attrtype, attrlen);
	memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put);

/**
 * __nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 * @padattr: attribute type for the padding
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute header and payload.
 */
void __nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
		     const void *data, int padattr)
{
	struct nlattr *nla;

	nla = __nla_reserve_64bit(skb, attrtype, attrlen, padattr);
	memcpy(nla_data(nla), data, attrlen);
}
EXPORT_SYMBOL(__nla_put_64bit);

/**
 * __nla_put_nohdr - Add a netlink attribute without header
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * The caller is responsible to ensure that the skb provides enough
 * tailroom for the attribute payload.
 */
void __nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
	void *start;

	start = __nla_reserve_nohdr(skb, attrlen);
	memcpy(start, data, attrlen);
}
EXPORT_SYMBOL(__nla_put_nohdr);

/**
 * nla_put - Add a netlink attribute to a socket buffer
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
int nla_put(struct sk_buff *skb, int attrtype, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < nla_total_size(attrlen)))
		return -EMSGSIZE;

	__nla_put(skb, attrtype, attrlen, data);
	return 0;
}
EXPORT_SYMBOL(nla_put);

/**
 * nla_put_64bit - Add a netlink attribute to a socket buffer and align it
 * @skb: socket buffer to add attribute to
 * @attrtype: attribute type
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 * @padattr: attribute type for the padding
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute header and payload.
 */
int nla_put_64bit(struct sk_buff *skb, int attrtype, int attrlen,
		  const void *data, int padattr)
{
	size_t len;

	if (nla_need_padding_for_64bit(skb))
		len = nla_total_size_64bit(attrlen);
	else
		len = nla_total_size(attrlen);
	if (unlikely(skb_tailroom(skb) < len))
		return -EMSGSIZE;

	__nla_put_64bit(skb, attrtype, attrlen, data, padattr);
	return 0;
}
EXPORT_SYMBOL(nla_put_64bit);

/**
 * nla_put_nohdr - Add a netlink attribute without header
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
int nla_put_nohdr(struct sk_buff *skb, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return -EMSGSIZE;

	__nla_put_nohdr(skb, attrlen, data);
	return 0;
}
EXPORT_SYMBOL(nla_put_nohdr);

/**
 * nla_append - Add a netlink attribute without header or padding
 * @skb: socket buffer to add attribute to
 * @attrlen: length of attribute payload
 * @data: head of attribute payload
 *
 * Returns -EMSGSIZE if the tailroom of the skb is insufficient to store
 * the attribute payload.
 */
int nla_append(struct sk_buff *skb, int attrlen, const void *data)
{
	if (unlikely(skb_tailroom(skb) < NLA_ALIGN(attrlen)))
		return -EMSGSIZE;

	skb_put_data(skb, data, attrlen);
	return 0;
}
EXPORT_SYMBOL(nla_append);
#endif