/*
* Radiotap parser
*
* Copyright 2007 Andy Green <andy@warmcat.com>
* Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
*
* 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 <linux/kernel.h>
#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 = ARRAY_SIZE(rtap_namespace_sizes),
.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);
