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

/*
 * Radiotap parser
 *
 * Copyright 2007		Andy Green <[email protected]>
 */

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

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

/**
 * 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)
{
	/* 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 = (u8 *)radiotap_header + sizeof(*radiotap_header);
	iterator->this_arg = NULL;

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

	if (unlikely(iterator->bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT))) {
		while (get_unaligned_le32(iterator->arg) &
		       (1 << IEEE80211_RADIOTAP_EXT)) {
			iterator->arg += sizeof(u32);

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

			if (((ulong)iterator->arg -
			     (ulong)iterator->rtheader) > iterator->max_length)
				return -EINVAL;
		}

		iterator->arg += sizeof(u32);

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

	/* we are all initialized happily */

	return 0;
}
EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);


/**
 * 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)
{

	/*
	 * small length lookup table for all radiotap types we heard of
	 * starting from b0 in the bitmap, so we can walk the payload
	 * area of the radiotap header
	 *
	 * There is a requirement to pad args, so that args
	 * of a given length must begin at a boundary of that length
	 * -- but note that compound args are allowed (eg, 2 x u16
	 * for IEEE80211_RADIOTAP_CHANNEL) so total arg length is not
	 * a reliable indicator of alignment requirement.
	 *
	 * upper nybble: content alignment for arg
	 * lower nybble: content length for arg
	 */

	static const u8 rt_sizes[] = {
		[IEEE80211_RADIOTAP_TSFT] = 0x88,
		[IEEE80211_RADIOTAP_FLAGS] = 0x11,
		[IEEE80211_RADIOTAP_RATE] = 0x11,
		[IEEE80211_RADIOTAP_CHANNEL] = 0x24,
		[IEEE80211_RADIOTAP_FHSS] = 0x22,
		[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = 0x11,
		[IEEE80211_RADIOTAP_DBM_ANTNOISE] = 0x11,
		[IEEE80211_RADIOTAP_LOCK_QUALITY] = 0x22,
		[IEEE80211_RADIOTAP_TX_ATTENUATION] = 0x22,
		[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = 0x22,
		[IEEE80211_RADIOTAP_DBM_TX_POWER] = 0x11,
		[IEEE80211_RADIOTAP_ANTENNA] = 0x11,
		[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = 0x11,
		[IEEE80211_RADIOTAP_DB_ANTNOISE] = 0x11,
		[IEEE80211_RADIOTAP_RX_FLAGS] = 0x22,
		[IEEE80211_RADIOTAP_TX_FLAGS] = 0x22,
		[IEEE80211_RADIOTAP_RTS_RETRIES] = 0x11,
		[IEEE80211_RADIOTAP_DATA_RETRIES] = 0x11,
		/*
		 * add more here as they are defined in
		 * include/net/ieee80211_radiotap.h
		 */
	};

	/*
	 * for every radiotap entry we can at
	 * least skip (by knowing the length)...
	 */

	while (iterator->arg_index < sizeof(rt_sizes)) {
		int hit = 0;
		int pad;

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

		/*
		 * arg is present, account for alignment padding
		 *  8-bit args can be at any alignment
		 * 16-bit args must start on 16-bit boundary
		 * 32-bit args must start on 32-bit boundary
		 * 64-bit args must start on 64-bit boundary
		 *
		 * note that total arg size can differ from alignment of
		 * elements inside arg, so we use upper nybble of length
		 * table to base alignment on
		 *
		 * also note: 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 = (((ulong)iterator->arg) -
			((ulong)iterator->rtheader)) &
			((rt_sizes[iterator->arg_index] >> 4) - 1);

		if (pad)
			iterator->arg +=
				(rt_sizes[iterator->arg_index] >> 4) - 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;
		hit = 1;

		/* internally move on the size of this arg */
		iterator->arg += rt_sizes[iterator->arg_index] & 0x0f;

		/*
		 * 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 (((ulong)iterator->arg - (ulong)iterator->rtheader) >
		    iterator->max_length)
			return -EINVAL;

	next_entry:
		iterator->arg_index++;
		if (unlikely((iterator->arg_index & 31) == 0)) {
			/* completed current u32 bitmap */
			if (iterator->bitmap_shifter & 1) {
				/* b31 was set, there is more */
				/* move to next u32 bitmap */
				iterator->bitmap_shifter =
				    get_unaligned_le32(iterator->next_bitmap);
				iterator->next_bitmap++;
			} else
				/* no more bitmaps: end */
				iterator->arg_index = sizeof(rt_sizes);
		} else /* just try the next bit */
			iterator->bitmap_shifter >>= 1;

		/* if we found a valid arg earlier, return it now */
		if (hit)
			return 0;
	}

	/* we don't know how to handle any more args, we're done */
	return -ENOENT;
}
EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
Commit	Line	Data
179f831b AG	1	/*
	2	* Radiotap parser
	3	*
	4	* Copyright 2007 Andy Green <[email protected]>
	5	*/
	6
	7	#include <net/cfg80211.h>
	8	#include <net/ieee80211_radiotap.h>
	9	#include <asm/unaligned.h>
	10
	11	/* function prototypes and related defs are in include/net/cfg80211.h */
	12
	13	/**
	14	* ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
	15	* @iterator: radiotap_iterator to initialize
	16	* @radiotap_header: radiotap header to parse
	17	* @max_length: total length we can parse into (eg, whole packet length)
	18	*
	19	* Returns: 0 or a negative error code if there is a problem.
	20	*
	21	* This function initializes an opaque iterator struct which can then
	22	* be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
	23	* argument which is present in the header. It knows about extended
	24	* present headers and handles them.
	25	*
	26	* How to use:
	27	* call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
	28	* struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
	29	* checking for a good 0 return code. Then loop calling
	30	* __ieee80211_radiotap_iterator_next()... it returns either 0,
	31	* -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
	32	* The iterator's @this_arg member points to the start of the argument
	33	* associated with the current argument index that is present, which can be
	34	* found in the iterator's @this_arg_index member. This arg index corresponds
	35	* to the IEEE80211_RADIOTAP_... defines.
	36	*
	37	* Radiotap header length:
	38	* You can find the CPU-endian total radiotap header length in
	39	* iterator->max_length after executing ieee80211_radiotap_iterator_init()
	40	* successfully.
	41	*
	42	* Alignment Gotcha:
	43	* You must take care when dereferencing iterator.this_arg
	44	* for multibyte types... the pointer is not aligned. Use
	45	* get_unaligned((type *)iterator.this_arg) to dereference
	46	* iterator.this_arg for type "type" safely on all arches.
	47	*
	48	* Example code:
	49	* See Documentation/networking/radiotap-headers.txt
	50	*/
	51
	52	int ieee80211_radiotap_iterator_init(
	53	struct ieee80211_radiotap_iterator *iterator,
	54	struct ieee80211_radiotap_header *radiotap_header,
	55	int max_length)
	56	{
	57	/* Linux only supports version 0 radiotap format */
	58	if (radiotap_header->it_version)
	59	return -EINVAL;
	60
	61	/* sanity check for allowed length and radiotap length field */
ae7245cb	62	if (max_length < get_unaligned_le16(&radiotap_header->it_len))
179f831b AG	63	return -EINVAL;
	64
	65	iterator->rtheader = radiotap_header;
ae7245cb	66	iterator->max_length = get_unaligned_le16(&radiotap_header->it_len);
179f831b	67	iterator->arg_index = 0;
ae7245cb	68	iterator->bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
179f831b AG	69	iterator->arg = (u8 )radiotap_header + sizeof(radiotap_header);
	70	iterator->this_arg = NULL;
	71
	72	/* find payload start allowing for extended bitmap(s) */
	73
	74	if (unlikely(iterator->bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT))) {
ae7245cb HH	75	while (get_unaligned_le32(iterator->arg) &
ae7245cb HH	76	(1 << IEEE80211_RADIOTAP_EXT)) {
179f831b AG	77	iterator->arg += sizeof(u32);
	78
	79	/*
	80	* check for insanity where the present bitmaps
	81	* keep claiming to extend up to or even beyond the
	82	* stated radiotap header length
	83	*/
	84
	85	if (((ulong)iterator->arg -
	86	(ulong)iterator->rtheader) > iterator->max_length)
	87	return -EINVAL;
	88	}
	89
	90	iterator->arg += sizeof(u32);
	91
	92	/*
	93	* no need to check again for blowing past stated radiotap
	94	* header length, because ieee80211_radiotap_iterator_next
	95	* checks it before it is dereferenced
	96	*/
	97	}
	98
	99	/* we are all initialized happily */
	100
	101	return 0;
	102	}
	103	EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
	104
	105
	106	/**
	107	* ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
	108	* @iterator: radiotap_iterator to move to next arg (if any)
	109	*
	110	* Returns: 0 if there is an argument to handle,
	111	* -ENOENT if there are no more args or -EINVAL
	112	* if there is something else wrong.
	113	*
	114	* This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
	115	* in @this_arg_index and sets @this_arg to point to the
	116	* payload for the field. It takes care of alignment handling and extended
	117	* present fields. @this_arg can be changed by the caller (eg,
	118	* incremented to move inside a compound argument like
	119	* IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
	120	* little-endian format whatever the endianess of your CPU.
	121	*
	122	* Alignment Gotcha:
	123	* You must take care when dereferencing iterator.this_arg
	124	* for multibyte types... the pointer is not aligned. Use
	125	* get_unaligned((type *)iterator.this_arg) to dereference
	126	* iterator.this_arg for type "type" safely on all arches.
	127	*/
	128
	129	int ieee80211_radiotap_iterator_next(
	130	struct ieee80211_radiotap_iterator *iterator)
	131	{
	132
	133	/*
	134	* small length lookup table for all radiotap types we heard of
	135	* starting from b0 in the bitmap, so we can walk the payload
	136	* area of the radiotap header
	137	*
	138	* There is a requirement to pad args, so that args
	139	* of a given length must begin at a boundary of that length
	140	* -- but note that compound args are allowed (eg, 2 x u16
141	* for IEEE80211_RADIOTAP_CHANNEL) so total arg length is not
142	* a reliable indicator of alignment requirement.
143	*
144	* upper nybble: content alignment for arg
145	* lower nybble: content length for arg
146	*/
147
148	static const u8 rt_sizes[] = {
149	[IEEE80211_RADIOTAP_TSFT] = 0x88,
150	[IEEE80211_RADIOTAP_FLAGS] = 0x11,
151	[IEEE80211_RADIOTAP_RATE] = 0x11,
152	[IEEE80211_RADIOTAP_CHANNEL] = 0x24,
153	[IEEE80211_RADIOTAP_FHSS] = 0x22,
154	[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = 0x11,
155	[IEEE80211_RADIOTAP_DBM_ANTNOISE] = 0x11,
156	[IEEE80211_RADIOTAP_LOCK_QUALITY] = 0x22,
157	[IEEE80211_RADIOTAP_TX_ATTENUATION] = 0x22,
158	[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = 0x22,
159	[IEEE80211_RADIOTAP_DBM_TX_POWER] = 0x11,
160	[IEEE80211_RADIOTAP_ANTENNA] = 0x11,
161	[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = 0x11,
dde4e47e JB	162	[IEEE80211_RADIOTAP_DB_ANTNOISE] = 0x11,
	163	[IEEE80211_RADIOTAP_RX_FLAGS] = 0x22,
	164	[IEEE80211_RADIOTAP_TX_FLAGS] = 0x22,
	165	[IEEE80211_RADIOTAP_RTS_RETRIES] = 0x11,
	166	[IEEE80211_RADIOTAP_DATA_RETRIES] = 0x11,
179f831b AG	167	/*
	168	* add more here as they are defined in
	169	* include/net/ieee80211_radiotap.h
	170	*/
	171	};
	172
	173	/*
	174	* for every radiotap entry we can at
	175	* least skip (by knowing the length)...
	176	*/
	177
	178	while (iterator->arg_index < sizeof(rt_sizes)) {
	179	int hit = 0;
	180	int pad;
	181
	182	if (!(iterator->bitmap_shifter & 1))
	183	goto next_entry; /* arg not present */
	184
	185	/*
	186	* arg is present, account for alignment padding
	187	* 8-bit args can be at any alignment
	188	* 16-bit args must start on 16-bit boundary
	189	* 32-bit args must start on 32-bit boundary
	190	* 64-bit args must start on 64-bit boundary
	191	*
	192	* note that total arg size can differ from alignment of
	193	* elements inside arg, so we use upper nybble of length
	194	* table to base alignment on
	195	*
	196	* also note: these alignments are ** relative to the
	197	* start of the radiotap header **. There is no guarantee
	198	* that the radiotap header itself is aligned on any
	199	* kind of boundary.
	200	*
	201	* the above is why get_unaligned() is used to dereference
	202	* multibyte elements from the radiotap area
	203	*/
	204
	205	pad = (((ulong)iterator->arg) -
	206	((ulong)iterator->rtheader)) &
	207	((rt_sizes[iterator->arg_index] >> 4) - 1);
	208
	209	if (pad)
	210	iterator->arg +=
	211	(rt_sizes[iterator->arg_index] >> 4) - pad;
	212
	213	/*
	214	* this is what we will return to user, but we need to
	215	* move on first so next call has something fresh to test
	216	*/
	217	iterator->this_arg_index = iterator->arg_index;
	218	iterator->this_arg = iterator->arg;
	219	hit = 1;
	220
	221	/* internally move on the size of this arg */
	222	iterator->arg += rt_sizes[iterator->arg_index] & 0x0f;
	223
	224	/*
	225	* check for insanity where we are given a bitmap that
	226	* claims to have more arg content than the length of the
	227	* radiotap section. We will normally end up equalling this
	228	* max_length on the last arg, never exceeding it.
	229	*/
	230
231	if (((ulong)iterator->arg - (ulong)iterator->rtheader) >
232	iterator->max_length)
233	return -EINVAL;
234
235	next_entry:
236	iterator->arg_index++;
237	if (unlikely((iterator->arg_index & 31) == 0)) {
238	/* completed current u32 bitmap */
239	if (iterator->bitmap_shifter & 1) {
240	/* b31 was set, there is more */
241	/* move to next u32 bitmap */
ae7245cb HH	242	iterator->bitmap_shifter =
ae7245cb HH	243	get_unaligned_le32(iterator->next_bitmap);
179f831b AG	244	iterator->next_bitmap++;
	245	} else
	246	/* no more bitmaps: end */
	247	iterator->arg_index = sizeof(rt_sizes);
	248	} else /* just try the next bit */
	249	iterator->bitmap_shifter >>= 1;
	250
	251	/* if we found a valid arg earlier, return it now */
	252	if (hit)
	253	return 0;
	254	}
	255
	256	/* we don't know how to handle any more args, we're done */
	257	return -ENOENT;
	258	}
	259	EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);