[linux.git] / net / wireless / radiotap.c

/*
 * Radiotap parser
 *
 * Copyright 2007		Andy Green <[email protected]>
 * Copyright 2009		Johannes Berg <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See COPYING for more details.
 */

#include <net/cfg80211.h>
#include <net/ieee80211_radiotap.h>
#include <asm/unaligned.h>

/* function prototypes and related defs are in include/net/cfg80211.h */

static const struct radiotap_align_size rtap_namespace_sizes[] = {
	[IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
	[IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
	[IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
	[IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
	[IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
	/*
	 * add more here as they are defined in radiotap.h
	 */
};

static const struct ieee80211_radiotap_namespace radiotap_ns = {
	.n_bits = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
	.align_size = rtap_namespace_sizes,
};

/**
 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
 * @iterator: radiotap_iterator to initialize
 * @radiotap_header: radiotap header to parse
 * @max_length: total length we can parse into (eg, whole packet length)
 *
 * Returns: 0 or a negative error code if there is a problem.
 *
 * This function initializes an opaque iterator struct which can then
 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
 * argument which is present in the header.  It knows about extended
 * present headers and handles them.
 *
 * How to use:
 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
 * checking for a good 0 return code.  Then loop calling
 * __ieee80211_radiotap_iterator_next()... it returns either 0,
 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
 * The iterator's @this_arg member points to the start of the argument
 * associated with the current argument index that is present, which can be
 * found in the iterator's @this_arg_index member.  This arg index corresponds
 * to the IEEE80211_RADIOTAP_... defines.
 *
 * Radiotap header length:
 * You can find the CPU-endian total radiotap header length in
 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
 * successfully.
 *
 * Alignment Gotcha:
 * You must take care when dereferencing iterator.this_arg
 * for multibyte types... the pointer is not aligned.  Use
 * get_unaligned((type *)iterator.this_arg) to dereference
 * iterator.this_arg for type "type" safely on all arches.
 *
 * Example code:
 * See Documentation/networking/radiotap-headers.txt
 */

int ieee80211_radiotap_iterator_init(
	struct ieee80211_radiotap_iterator *iterator,
	struct ieee80211_radiotap_header *radiotap_header,
	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
{
	/* Linux only supports version 0 radiotap format */
	if (radiotap_header->it_version)
		return -EINVAL;

	/* sanity check for allowed length and radiotap length field */
	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
		return -EINVAL;

	iterator->_rtheader = radiotap_header;
	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
	iterator->_arg_index = 0;
	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
	iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
	iterator->_reset_on_ext = 0;
	iterator->_next_bitmap = &radiotap_header->it_present;
	iterator->_next_bitmap++;
	iterator->_vns = vns;
	iterator->current_namespace = &radiotap_ns;
	iterator->is_radiotap_ns = 1;

	/* find payload start allowing for extended bitmap(s) */

	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
		while (get_unaligned_le32(iterator->_arg) &
					(1 << IEEE80211_RADIOTAP_EXT)) {
			iterator->_arg += sizeof(uint32_t);

			/*
			 * check for insanity where the present bitmaps
			 * keep claiming to extend up to or even beyond the
			 * stated radiotap header length
			 */

			if ((unsigned long)iterator->_arg -
			    (unsigned long)iterator->_rtheader >
			    (unsigned long)iterator->_max_length)
				return -EINVAL;
		}

		iterator->_arg += sizeof(uint32_t);

		/*
		 * no need to check again for blowing past stated radiotap
		 * header length, because ieee80211_radiotap_iterator_next
		 * checks it before it is dereferenced
		 */
	}

	iterator->this_arg = iterator->_arg;

	/* we are all initialized happily */

	return 0;
}
EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);

static void find_ns(struct ieee80211_radiotap_iterator *iterator,
		    uint32_t oui, uint8_t subns)
{
	int i;

	iterator->current_namespace = NULL;

	if (!iterator->_vns)
		return;

	for (i = 0; i < iterator->_vns->n_ns; i++) {
		if (iterator->_vns->ns[i].oui != oui)
			continue;
		if (iterator->_vns->ns[i].subns != subns)
			continue;

		iterator->current_namespace = &iterator->_vns->ns[i];
		break;
	}
}


/**
 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
 * @iterator: radiotap_iterator to move to next arg (if any)
 *
 * Returns: 0 if there is an argument to handle,
 * -ENOENT if there are no more args or -EINVAL
 * if there is something else wrong.
 *
 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
 * in @this_arg_index and sets @this_arg to point to the
 * payload for the field.  It takes care of alignment handling and extended
 * present fields.  @this_arg can be changed by the caller (eg,
 * incremented to move inside a compound argument like
 * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
 * little-endian format whatever the endianess of your CPU.
 *
 * Alignment Gotcha:
 * You must take care when dereferencing iterator.this_arg
 * for multibyte types... the pointer is not aligned.  Use
 * get_unaligned((type *)iterator.this_arg) to dereference
 * iterator.this_arg for type "type" safely on all arches.
 */

int ieee80211_radiotap_iterator_next(
	struct ieee80211_radiotap_iterator *iterator)
{
	while (1) {
		int hit = 0;
		int pad, align, size, subns, vnslen;
		uint32_t oui;

		/* if no more EXT bits, that's it */
		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
		    !(iterator->_bitmap_shifter & 1))
			return -ENOENT;

		if (!(iterator->_bitmap_shifter & 1))
			goto next_entry; /* arg not present */

		/* get alignment/size of data */
		switch (iterator->_arg_index % 32) {
		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
		case IEEE80211_RADIOTAP_EXT:
			align = 1;
			size = 0;
			break;
		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
			align = 2;
			size = 6;
			break;
		default:
			if (!iterator->current_namespace ||
			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
				if (iterator->current_namespace == &radiotap_ns)
					return -ENOENT;
				align = 0;
			} else {
				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
			}
			if (!align) {
				/* skip all subsequent data */
				iterator->_arg = iterator->_next_ns_data;
				/* give up on this namespace */
				iterator->current_namespace = NULL;
				goto next_entry;
			}
			break;
		}

		/*
		 * arg is present, account for alignment padding
		 *
		 * Note that these alignments are relative to the start
		 * of the radiotap header.  There is no guarantee
		 * that the radiotap header itself is aligned on any
		 * kind of boundary.
		 *
		 * The above is why get_unaligned() is used to dereference
		 * multibyte elements from the radiotap area.
		 */

		pad = ((unsigned long)iterator->_arg -
		       (unsigned long)iterator->_rtheader) & (align - 1);

		if (pad)
			iterator->_arg += align - pad;

		/*
		 * this is what we will return to user, but we need to
		 * move on first so next call has something fresh to test
		 */
		iterator->this_arg_index = iterator->_arg_index;
		iterator->this_arg = iterator->_arg;
		iterator->this_arg_size = size;

		/* internally move on the size of this arg */
		iterator->_arg += size;

		/*
		 * check for insanity where we are given a bitmap that
		 * claims to have more arg content than the length of the
		 * radiotap section.  We will normally end up equalling this
		 * max_length on the last arg, never exceeding it.
		 */

		if ((unsigned long)iterator->_arg -
		    (unsigned long)iterator->_rtheader >
		    (unsigned long)iterator->_max_length)
			return -EINVAL;

		/* these special ones are valid in each bitmap word */
		switch (iterator->_arg_index % 32) {
		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
			iterator->_bitmap_shifter >>= 1;
			iterator->_arg_index++;

			iterator->_reset_on_ext = 1;

			vnslen = get_unaligned_le16(iterator->this_arg + 4);
			iterator->_next_ns_data = iterator->_arg + vnslen;
			oui = (*iterator->this_arg << 16) |
				(*(iterator->this_arg + 1) << 8) |
				*(iterator->this_arg + 2);
			subns = *(iterator->this_arg + 3);

			find_ns(iterator, oui, subns);

			iterator->is_radiotap_ns = 0;
			/* allow parsers to show this information */
			iterator->this_arg_index =
				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
			iterator->this_arg_size += vnslen;
			if ((unsigned long)iterator->this_arg +
			    iterator->this_arg_size -
			    (unsigned long)iterator->_rtheader >
			    (unsigned long)(unsigned long)iterator->_max_length)
				return -EINVAL;
			hit = 1;
			break;
		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
			iterator->_bitmap_shifter >>= 1;
			iterator->_arg_index++;

			iterator->_reset_on_ext = 1;
			iterator->current_namespace = &radiotap_ns;
			iterator->is_radiotap_ns = 1;
			break;
		case IEEE80211_RADIOTAP_EXT:
			/*
			 * bit 31 was set, there is more
			 * -- move to next u32 bitmap
			 */
			iterator->_bitmap_shifter =
				get_unaligned_le32(iterator->_next_bitmap);
			iterator->_next_bitmap++;
			if (iterator->_reset_on_ext)
				iterator->_arg_index = 0;
			else
				iterator->_arg_index++;
			iterator->_reset_on_ext = 0;
			break;
		default:
			/* we've got a hit! */
			hit = 1;
 next_entry:
			iterator->_bitmap_shifter >>= 1;
			iterator->_arg_index++;
		}

		/* if we found a valid arg earlier, return it now */
		if (hit)
			return 0;
	}
}
EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
Commit	Line	Data
179f831b AG	1	/*
	2	* Radiotap parser
	3	*
	4	* Copyright 2007 Andy Green <[email protected]>
33e5a2f7 JB	5	* Copyright 2009 Johannes Berg <[email protected]>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*
	11	* Alternatively, this software may be distributed under the terms of BSD
	12	* license.
	13	*
	14	* See COPYING for more details.
179f831b AG	15	*/
	16
	17	#include <net/cfg80211.h>
	18	#include <net/ieee80211_radiotap.h>
	19	#include <asm/unaligned.h>
	20
	21	/* function prototypes and related defs are in include/net/cfg80211.h */
	22
33e5a2f7 JB	23	static const struct radiotap_align_size rtap_namespace_sizes[] = {
	24	[IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
	25	[IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
	26	[IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
	27	[IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
	28	[IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
	29	[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
	30	[IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
	31	[IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
	32	[IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
	33	[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
	34	[IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
	35	[IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
	36	[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
	37	[IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
	38	[IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
	39	[IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
	40	[IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
	41	[IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
	42	/*
	43	* add more here as they are defined in radiotap.h
	44	*/
	45	};
	46
	47	static const struct ieee80211_radiotap_namespace radiotap_ns = {
	48	.n_bits = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
	49	.align_size = rtap_namespace_sizes,
	50	};
	51
179f831b AG	52	/**
	53	* ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
	54	* @iterator: radiotap_iterator to initialize
	55	* @radiotap_header: radiotap header to parse
	56	* @max_length: total length we can parse into (eg, whole packet length)
	57	*
	58	* Returns: 0 or a negative error code if there is a problem.
	59	*
	60	* This function initializes an opaque iterator struct which can then
	61	* be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
	62	* argument which is present in the header. It knows about extended
	63	* present headers and handles them.
	64	*
	65	* How to use:
	66	* call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
	67	* struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
	68	* checking for a good 0 return code. Then loop calling
	69	* __ieee80211_radiotap_iterator_next()... it returns either 0,
	70	* -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
	71	* The iterator's @this_arg member points to the start of the argument
	72	* associated with the current argument index that is present, which can be
	73	* found in the iterator's @this_arg_index member. This arg index corresponds
	74	* to the IEEE80211_RADIOTAP_... defines.
	75	*
	76	* Radiotap header length:
	77	* You can find the CPU-endian total radiotap header length in
	78	* iterator->max_length after executing ieee80211_radiotap_iterator_init()
	79	* successfully.
	80	*
	81	* Alignment Gotcha:
	82	* You must take care when dereferencing iterator.this_arg
	83	* for multibyte types... the pointer is not aligned. Use
	84	* get_unaligned((type *)iterator.this_arg) to dereference
	85	* iterator.this_arg for type "type" safely on all arches.
	86	*
	87	* Example code:
	88	* See Documentation/networking/radiotap-headers.txt
	89	*/
	90
	91	int ieee80211_radiotap_iterator_init(
33e5a2f7 JB	92	struct ieee80211_radiotap_iterator *iterator,
	93	struct ieee80211_radiotap_header *radiotap_header,
	94	int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
179f831b AG	95	{
	96	/* Linux only supports version 0 radiotap format */
	97	if (radiotap_header->it_version)
	98	return -EINVAL;
	99
	100	/* sanity check for allowed length and radiotap length field */
ae7245cb	101	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
179f831b AG	102	return -EINVAL;
179f831b AG	103
33e5a2f7 JB	104	iterator->_rtheader = radiotap_header;
	105	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
	106	iterator->_arg_index = 0;
	107	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
	108	iterator->_arg = (uint8_t )radiotap_header + sizeof(radiotap_header);
	109	iterator->_reset_on_ext = 0;
	110	iterator->_next_bitmap = &radiotap_header->it_present;
	111	iterator->_next_bitmap++;
	112	iterator->_vns = vns;
	113	iterator->current_namespace = &radiotap_ns;
	114	iterator->is_radiotap_ns = 1;
179f831b AG	115
	116	/* find payload start allowing for extended bitmap(s) */
	117
33e5a2f7 JB	118	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
	119	while (get_unaligned_le32(iterator->_arg) &
	120	(1 << IEEE80211_RADIOTAP_EXT)) {
	121	iterator->_arg += sizeof(uint32_t);
179f831b AG	122
	123	/*
	124	* check for insanity where the present bitmaps
	125	* keep claiming to extend up to or even beyond the
	126	* stated radiotap header length
	127	*/
	128
33e5a2f7 JB	129	if ((unsigned long)iterator->_arg -
	130	(unsigned long)iterator->_rtheader >
	131	(unsigned long)iterator->_max_length)
179f831b AG	132	return -EINVAL;
	133	}
	134
33e5a2f7	135	iterator->_arg += sizeof(uint32_t);
179f831b AG	136
	137	/*
	138	* no need to check again for blowing past stated radiotap
	139	* header length, because ieee80211_radiotap_iterator_next
	140	* checks it before it is dereferenced
	141	*/
	142	}
	143
33e5a2f7 JB	144	iterator->this_arg = iterator->_arg;
33e5a2f7 JB	145
179f831b AG	146	/* we are all initialized happily */
	147
	148	return 0;
	149	}
	150	EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
	151
33e5a2f7 JB	152	static void find_ns(struct ieee80211_radiotap_iterator *iterator,
	153	uint32_t oui, uint8_t subns)
	154	{
	155	int i;
	156
	157	iterator->current_namespace = NULL;
	158
	159	if (!iterator->_vns)
	160	return;
	161
	162	for (i = 0; i < iterator->_vns->n_ns; i++) {
	163	if (iterator->_vns->ns[i].oui != oui)
	164	continue;
	165	if (iterator->_vns->ns[i].subns != subns)
	166	continue;
	167
	168	iterator->current_namespace = &iterator->_vns->ns[i];
	169	break;
	170	}
	171	}
	172
	173
179f831b AG	174
	175	/**
	176	* ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
	177	* @iterator: radiotap_iterator to move to next arg (if any)
	178	*
	179	* Returns: 0 if there is an argument to handle,
	180	* -ENOENT if there are no more args or -EINVAL
	181	* if there is something else wrong.
	182	*
	183	* This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
	184	* in @this_arg_index and sets @this_arg to point to the
	185	* payload for the field. It takes care of alignment handling and extended
	186	* present fields. @this_arg can be changed by the caller (eg,
	187	* incremented to move inside a compound argument like
	188	* IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
	189	* little-endian format whatever the endianess of your CPU.
	190	*
	191	* Alignment Gotcha:
	192	* You must take care when dereferencing iterator.this_arg
	193	* for multibyte types... the pointer is not aligned. Use
	194	* get_unaligned((type *)iterator.this_arg) to dereference
	195	* iterator.this_arg for type "type" safely on all arches.
	196	*/
	197
	198	int ieee80211_radiotap_iterator_next(
33e5a2f7	199	struct ieee80211_radiotap_iterator *iterator)
179f831b	200	{
33e5a2f7	201	while (1) {
179f831b	202	int hit = 0;
33e5a2f7 JB	203	int pad, align, size, subns, vnslen;
33e5a2f7 JB	204	uint32_t oui;
179f831b	205
33e5a2f7 JB	206	/* if no more EXT bits, that's it */
	207	if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
	208	!(iterator->_bitmap_shifter & 1))
	209	return -ENOENT;
	210
	211	if (!(iterator->_bitmap_shifter & 1))
179f831b AG	212	goto next_entry; /* arg not present */
179f831b AG	213
33e5a2f7 JB	214	/* get alignment/size of data */
	215	switch (iterator->_arg_index % 32) {
	216	case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
	217	case IEEE80211_RADIOTAP_EXT:
	218	align = 1;
	219	size = 0;
	220	break;
	221	case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
	222	align = 2;
	223	size = 6;
	224	break;
	225	default:
	226	if (!iterator->current_namespace \|\|
	227	iterator->_arg_index >= iterator->current_namespace->n_bits) {
	228	if (iterator->current_namespace == &radiotap_ns)
	229	return -ENOENT;
	230	align = 0;
	231	} else {
	232	align = iterator->current_namespace->align_size[iterator->_arg_index].align;
	233	size = iterator->current_namespace->align_size[iterator->_arg_index].size;
	234	}
	235	if (!align) {
	236	/* skip all subsequent data */
	237	iterator->_arg = iterator->_next_ns_data;
	238	/* give up on this namespace */
	239	iterator->current_namespace = NULL;
	240	goto next_entry;
	241	}
	242	break;
	243	}
	244
179f831b AG	245	/*
179f831b AG	246	* arg is present, account for alignment padding
179f831b	247	*
33e5a2f7 JB	248	* Note that these alignments are relative to the start
33e5a2f7 JB	249	* of the radiotap header. There is no guarantee
179f831b AG	250	* that the radiotap header itself is aligned on any
	251	* kind of boundary.
	252	*
33e5a2f7 JB	253	* The above is why get_unaligned() is used to dereference
33e5a2f7 JB	254	* multibyte elements from the radiotap area.
179f831b AG	255	*/
179f831b AG	256
33e5a2f7 JB	257	pad = ((unsigned long)iterator->_arg -
33e5a2f7 JB	258	(unsigned long)iterator->_rtheader) & (align - 1);
179f831b AG	259
179f831b AG	260	if (pad)
33e5a2f7	261	iterator->_arg += align - pad;
179f831b AG	262
	263	/*
	264	* this is what we will return to user, but we need to
	265	* move on first so next call has something fresh to test
	266	*/
33e5a2f7 JB	267	iterator->this_arg_index = iterator->_arg_index;
	268	iterator->this_arg = iterator->_arg;
	269	iterator->this_arg_size = size;
179f831b AG	270
179f831b AG	271	/* internally move on the size of this arg */
33e5a2f7	272	iterator->_arg += size;
179f831b AG	273
	274	/*
	275	* check for insanity where we are given a bitmap that
	276	* claims to have more arg content than the length of the
	277	* radiotap section. We will normally end up equalling this
	278	* max_length on the last arg, never exceeding it.
	279	*/
	280
33e5a2f7 JB	281	if ((unsigned long)iterator->_arg -
	282	(unsigned long)iterator->_rtheader >
	283	(unsigned long)iterator->_max_length)
179f831b AG	284	return -EINVAL;
179f831b AG	285
33e5a2f7 JB	286	/* these special ones are valid in each bitmap word */
	287	switch (iterator->_arg_index % 32) {
	288	case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
	289	iterator->_bitmap_shifter >>= 1;
	290	iterator->_arg_index++;
	291
	292	iterator->_reset_on_ext = 1;
	293
	294	vnslen = get_unaligned_le16(iterator->this_arg + 4);
	295	iterator->_next_ns_data = iterator->_arg + vnslen;
	296	oui = (*iterator->this_arg << 16) \|
	297	(*(iterator->this_arg + 1) << 8) \|
	298	*(iterator->this_arg + 2);
	299	subns = *(iterator->this_arg + 3);
	300
	301	find_ns(iterator, oui, subns);
	302
	303	iterator->is_radiotap_ns = 0;
	304	/* allow parsers to show this information */
	305	iterator->this_arg_index =
	306	IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
	307	iterator->this_arg_size += vnslen;
	308	if ((unsigned long)iterator->this_arg +
	309	iterator->this_arg_size -
	310	(unsigned long)iterator->_rtheader >
	311	(unsigned long)(unsigned long)iterator->_max_length)
	312	return -EINVAL;
	313	hit = 1;
	314	break;
	315	case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
	316	iterator->_bitmap_shifter >>= 1;
	317	iterator->_arg_index++;
	318
	319	iterator->_reset_on_ext = 1;
	320	iterator->current_namespace = &radiotap_ns;
	321	iterator->is_radiotap_ns = 1;
	322	break;
	323	case IEEE80211_RADIOTAP_EXT:
	324	/*
	325	* bit 31 was set, there is more
	326	* -- move to next u32 bitmap
	327	*/
	328	iterator->_bitmap_shifter =
	329	get_unaligned_le32(iterator->_next_bitmap);
	330	iterator->_next_bitmap++;
	331	if (iterator->_reset_on_ext)
	332	iterator->_arg_index = 0;
	333	else
	334	iterator->_arg_index++;
	335	iterator->_reset_on_ext = 0;
	336	break;
	337	default:
	338	/* we've got a hit! */
	339	hit = 1;
	340	next_entry:
	341	iterator->_bitmap_shifter >>= 1;
	342	iterator->_arg_index++;
	343	}
179f831b AG	344
	345	/* if we found a valid arg earlier, return it now */
	346	if (hit)
	347	return 0;
	348	}
179f831b AG	349	}
179f831b AG	350	EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);