net/wireless/radiotap.c - kernel/msm-4.19 - Gitiles

 /*
  * Radiotap parser
  *
  * Copyright 2007		Andy Green <andy@warmcat.com>
  */

 #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 < le16_to_cpu(get_unaligned(&radiotap_header->it_len)))
 		return -EINVAL;

 	iterator->rtheader = radiotap_header;
 	iterator->max_length = le16_to_cpu(get_unaligned(
 						&radiotap_header->it_len));
 	iterator->arg_index = 0;
 	iterator->bitmap_shifter = le32_to_cpu(get_unaligned(
 						&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 (le32_to_cpu(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
 		/*
 		 * 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 = le32_to_cpu(
 					get_unaligned(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);
	/*
	* Radiotap parser
	*
	* Copyright 2007 Andy Green <andy@warmcat.com>
	*/

	#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 < le16_to_cpu(get_unaligned(&radiotap_header->it_len)))
	return -EINVAL;

	iterator->rtheader = radiotap_header;
	iterator->max_length = le16_to_cpu(get_unaligned(
	&radiotap_header->it_len));
	iterator->arg_index = 0;
	iterator->bitmap_shifter = le32_to_cpu(get_unaligned(
	&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 (le32_to_cpu(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
	/*
	* 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 = le32_to_cpu(
	get_unaligned(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);