258 lines
8.3 KiB
C
258 lines
8.3 KiB
C
|
/*
|
||
|
|
* 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);
|