/*
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* Radiotap parser
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*
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* Copyright 2007 Andy Green <andy@warmcat.com>
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* Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Alternatively, this software may be distributed under the terms of BSD
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* license.
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*
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* See COPYING for more details.
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*/
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <net/cfg80211.h>
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#include <net/ieee80211_radiotap.h>
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#include <asm/unaligned.h>
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/* function prototypes and related defs are in include/net/cfg80211.h */
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static const struct radiotap_align_size rtap_namespace_sizes[] = {
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[IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
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[IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
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[IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
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[IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
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[IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
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[IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
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[IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
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/*
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* add more here as they are defined in radiotap.h
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*/
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};
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static const struct ieee80211_radiotap_namespace radiotap_ns = {
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.n_bits = ARRAY_SIZE(rtap_namespace_sizes),
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.align_size = rtap_namespace_sizes,
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};
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/**
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* ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
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* @iterator: radiotap_iterator to initialize
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* @radiotap_header: radiotap header to parse
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* @max_length: total length we can parse into (eg, whole packet length)
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* @vns: vendor namespaces to parse
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*
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* Returns: 0 or a negative error code if there is a problem.
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*
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* This function initializes an opaque iterator struct which can then
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* be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
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* argument which is present in the header. It knows about extended
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* present headers and handles them.
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*
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* How to use:
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* call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
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* struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
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* checking for a good 0 return code. Then loop calling
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* __ieee80211_radiotap_iterator_next()... it returns either 0,
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* -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
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* The iterator's @this_arg member points to the start of the argument
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* associated with the current argument index that is present, which can be
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* found in the iterator's @this_arg_index member. This arg index corresponds
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* to the IEEE80211_RADIOTAP_... defines.
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*
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* Radiotap header length:
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* You can find the CPU-endian total radiotap header length in
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* iterator->max_length after executing ieee80211_radiotap_iterator_init()
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* successfully.
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*
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* Alignment Gotcha:
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* You must take care when dereferencing iterator.this_arg
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* for multibyte types... the pointer is not aligned. Use
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* get_unaligned((type *)iterator.this_arg) to dereference
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* iterator.this_arg for type "type" safely on all arches.
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*
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* Example code:
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* See Documentation/networking/radiotap-headers.rst
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*/
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int ieee80211_radiotap_iterator_init(
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struct ieee80211_radiotap_iterator *iterator,
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struct ieee80211_radiotap_header *radiotap_header,
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int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
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{
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/* check the radiotap header can actually be present */
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if (max_length < sizeof(struct ieee80211_radiotap_header))
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return -EINVAL;
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/* Linux only supports version 0 radiotap format */
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if (radiotap_header->it_version)
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return -EINVAL;
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/* sanity check for allowed length and radiotap length field */
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if (max_length < get_unaligned_le16(&radiotap_header->it_len))
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return -EINVAL;
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iterator->_rtheader = radiotap_header;
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iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
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iterator->_arg_index = 0;
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iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
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iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
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iterator->_reset_on_ext = 0;
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iterator->_next_bitmap = &radiotap_header->it_present;
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iterator->_next_bitmap++;
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iterator->_vns = vns;
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iterator->current_namespace = &radiotap_ns;
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iterator->is_radiotap_ns = 1;
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/* find payload start allowing for extended bitmap(s) */
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if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
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if ((unsigned long)iterator->_arg -
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(unsigned long)iterator->_rtheader + sizeof(uint32_t) >
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(unsigned long)iterator->_max_length)
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return -EINVAL;
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while (get_unaligned_le32(iterator->_arg) &
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(1 << IEEE80211_RADIOTAP_EXT)) {
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iterator->_arg += sizeof(uint32_t);
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/*
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* check for insanity where the present bitmaps
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* keep claiming to extend up to or even beyond the
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* stated radiotap header length
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*/
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if ((unsigned long)iterator->_arg -
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(unsigned long)iterator->_rtheader +
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sizeof(uint32_t) >
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(unsigned long)iterator->_max_length)
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return -EINVAL;
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}
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iterator->_arg += sizeof(uint32_t);
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/*
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* no need to check again for blowing past stated radiotap
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* header length, because ieee80211_radiotap_iterator_next
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* checks it before it is dereferenced
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*/
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}
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iterator->this_arg = iterator->_arg;
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/* we are all initialized happily */
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return 0;
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}
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EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
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static void find_ns(struct ieee80211_radiotap_iterator *iterator,
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uint32_t oui, uint8_t subns)
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{
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int i;
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iterator->current_namespace = NULL;
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if (!iterator->_vns)
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return;
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for (i = 0; i < iterator->_vns->n_ns; i++) {
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if (iterator->_vns->ns[i].oui != oui)
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continue;
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if (iterator->_vns->ns[i].subns != subns)
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continue;
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iterator->current_namespace = &iterator->_vns->ns[i];
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break;
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}
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}
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/**
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* ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
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* @iterator: radiotap_iterator to move to next arg (if any)
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*
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* Returns: 0 if there is an argument to handle,
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* -ENOENT if there are no more args or -EINVAL
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* if there is something else wrong.
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*
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* This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
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* in @this_arg_index and sets @this_arg to point to the
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* payload for the field. It takes care of alignment handling and extended
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* present fields. @this_arg can be changed by the caller (eg,
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* incremented to move inside a compound argument like
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* IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
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* little-endian format whatever the endianess of your CPU.
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*
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* Alignment Gotcha:
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* You must take care when dereferencing iterator.this_arg
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* for multibyte types... the pointer is not aligned. Use
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* get_unaligned((type *)iterator.this_arg) to dereference
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* iterator.this_arg for type "type" safely on all arches.
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*/
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int ieee80211_radiotap_iterator_next(
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struct ieee80211_radiotap_iterator *iterator)
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{
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while (1) {
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int hit = 0;
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int pad, align, size, subns;
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uint32_t oui;
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/* if no more EXT bits, that's it */
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if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
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!(iterator->_bitmap_shifter & 1))
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return -ENOENT;
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if (!(iterator->_bitmap_shifter & 1))
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goto next_entry; /* arg not present */
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/* get alignment/size of data */
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switch (iterator->_arg_index % 32) {
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case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
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case IEEE80211_RADIOTAP_EXT:
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align = 1;
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size = 0;
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break;
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case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
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align = 2;
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size = 6;
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break;
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default:
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if (!iterator->current_namespace ||
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iterator->_arg_index >= iterator->current_namespace->n_bits) {
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if (iterator->current_namespace == &radiotap_ns)
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return -ENOENT;
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align = 0;
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} else {
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align = iterator->current_namespace->align_size[iterator->_arg_index].align;
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size = iterator->current_namespace->align_size[iterator->_arg_index].size;
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}
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if (!align) {
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/* skip all subsequent data */
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iterator->_arg = iterator->_next_ns_data;
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/* give up on this namespace */
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iterator->current_namespace = NULL;
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goto next_entry;
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}
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break;
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}
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/*
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* arg is present, account for alignment padding
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*
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* Note that these alignments are relative to the start
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* of the radiotap header. There is no guarantee
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* that the radiotap header itself is aligned on any
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* kind of boundary.
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*
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* The above is why get_unaligned() is used to dereference
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* multibyte elements from the radiotap area.
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*/
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pad = ((unsigned long)iterator->_arg -
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(unsigned long)iterator->_rtheader) & (align - 1);
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if (pad)
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iterator->_arg += align - pad;
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if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
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int vnslen;
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if ((unsigned long)iterator->_arg + size -
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(unsigned long)iterator->_rtheader >
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(unsigned long)iterator->_max_length)
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return -EINVAL;
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oui = (*iterator->_arg << 16) |
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(*(iterator->_arg + 1) << 8) |
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*(iterator->_arg + 2);
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subns = *(iterator->_arg + 3);
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find_ns(iterator, oui, subns);
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vnslen = get_unaligned_le16(iterator->_arg + 4);
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iterator->_next_ns_data = iterator->_arg + size + vnslen;
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if (!iterator->current_namespace)
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size += vnslen;
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}
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/*
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* this is what we will return to user, but we need to
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* move on first so next call has something fresh to test
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*/
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iterator->this_arg_index = iterator->_arg_index;
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iterator->this_arg = iterator->_arg;
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iterator->this_arg_size = size;
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/* internally move on the size of this arg */
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iterator->_arg += size;
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/*
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* check for insanity where we are given a bitmap that
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* claims to have more arg content than the length of the
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* radiotap section. We will normally end up equalling this
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* max_length on the last arg, never exceeding it.
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*/
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if ((unsigned long)iterator->_arg -
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(unsigned long)iterator->_rtheader >
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(unsigned long)iterator->_max_length)
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return -EINVAL;
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/* these special ones are valid in each bitmap word */
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switch (iterator->_arg_index % 32) {
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case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
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iterator->_reset_on_ext = 1;
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iterator->is_radiotap_ns = 0;
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/*
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* If parser didn't register this vendor
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* namespace with us, allow it to show it
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* as 'raw. Do do that, set argument index
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* to vendor namespace.
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*/
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iterator->this_arg_index =
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IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
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if (!iterator->current_namespace)
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hit = 1;
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goto next_entry;
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case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
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iterator->_reset_on_ext = 1;
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iterator->current_namespace = &radiotap_ns;
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iterator->is_radiotap_ns = 1;
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goto next_entry;
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case IEEE80211_RADIOTAP_EXT:
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/*
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* bit 31 was set, there is more
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* -- move to next u32 bitmap
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*/
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iterator->_bitmap_shifter =
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get_unaligned_le32(iterator->_next_bitmap);
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iterator->_next_bitmap++;
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if (iterator->_reset_on_ext)
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iterator->_arg_index = 0;
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else
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iterator->_arg_index++;
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iterator->_reset_on_ext = 0;
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break;
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default:
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/* we've got a hit! */
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hit = 1;
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next_entry:
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iterator->_bitmap_shifter >>= 1;
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iterator->_arg_index++;
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}
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/* if we found a valid arg earlier, return it now */
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if (hit)
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return 0;
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}
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}
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EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
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