4 * Copyright 2007 Andy Green <andy@warmcat.com>
5 * Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
11 * Alternatively, this software may be distributed under the terms of BSD
14 * See COPYING for more details.
16 #include "radiotap_iter.h"
19 /* function prototypes and related defs are in radiotap_iter.h */
21 static const struct radiotap_align_size rtap_namespace_sizes[] = {
22 [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
23 [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
24 [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
25 [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
26 [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
27 [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
28 [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
29 [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
30 [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
31 [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
32 [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
33 [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
34 [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
35 [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
36 [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
37 [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
38 [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
39 [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
40 [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
41 [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
43 * add more here as they are defined in radiotap.h
47 static const struct ieee80211_radiotap_namespace radiotap_ns = {
48 .n_bits = sizeof(rtap_namespace_sizes) / sizeof(rtap_namespace_sizes[0]),
49 .align_size = rtap_namespace_sizes,
53 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
54 * @iterator: radiotap_iterator to initialize
55 * @radiotap_header: radiotap header to parse
56 * @max_length: total length we can parse into (eg, whole packet length)
58 * Returns: 0 or a negative error code if there is a problem.
60 * This function initializes an opaque iterator struct which can then
61 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
62 * argument which is present in the header. It knows about extended
63 * present headers and handles them.
66 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
67 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
68 * checking for a good 0 return code. Then loop calling
69 * __ieee80211_radiotap_iterator_next()... it returns either 0,
70 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
71 * The iterator's @this_arg member points to the start of the argument
72 * associated with the current argument index that is present, which can be
73 * found in the iterator's @this_arg_index member. This arg index corresponds
74 * to the IEEE80211_RADIOTAP_... defines.
76 * Radiotap header length:
77 * You can find the CPU-endian total radiotap header length in
78 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
82 * You must take care when dereferencing iterator.this_arg
83 * for multibyte types... the pointer is not aligned. Use
84 * get_unaligned((type *)iterator.this_arg) to dereference
85 * iterator.this_arg for type "type" safely on all arches.
87 * Example code: parse.c
90 int ieee80211_radiotap_iterator_init(
91 struct ieee80211_radiotap_iterator *iterator,
92 struct ieee80211_radiotap_header *radiotap_header,
93 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
95 /* must at least have the radiotap header */
96 if (max_length < (int)sizeof(struct ieee80211_radiotap_header))
99 /* Linux only supports version 0 radiotap format */
100 if (radiotap_header->it_version)
103 /* sanity check for allowed length and radiotap length field */
104 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
107 iterator->_rtheader = radiotap_header;
108 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
109 iterator->_arg_index = 0;
110 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
111 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
112 iterator->_next_ns_data = NULL;
113 iterator->_reset_on_ext = 0;
114 iterator->_next_bitmap = &radiotap_header->it_present;
115 iterator->_next_bitmap++;
116 iterator->_vns = vns;
117 iterator->current_namespace = &radiotap_ns;
118 iterator->is_radiotap_ns = 1;
119 #ifdef RADIOTAP_SUPPORT_OVERRIDES
120 iterator->n_overrides = 0;
121 iterator->overrides = NULL;
124 /* find payload start allowing for extended bitmap(s) */
126 if (iterator->_bitmap_shifter & BIT(IEEE80211_RADIOTAP_EXT)) {
127 if ((unsigned long)iterator->_arg -
128 (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
129 (unsigned long)iterator->_max_length)
131 while (get_unaligned_le32(iterator->_arg) &
132 BIT(IEEE80211_RADIOTAP_EXT)) {
133 iterator->_arg += sizeof(uint32_t);
136 * check for insanity where the present bitmaps
137 * keep claiming to extend up to or even beyond the
138 * stated radiotap header length
141 if ((unsigned long)iterator->_arg -
142 (unsigned long)iterator->_rtheader +
144 (unsigned long)iterator->_max_length)
148 iterator->_arg += sizeof(uint32_t);
151 * no need to check again for blowing past stated radiotap
152 * header length, because ieee80211_radiotap_iterator_next
153 * checks it before it is dereferenced
157 iterator->this_arg = iterator->_arg;
158 iterator->this_arg_index = 0;
159 iterator->this_arg_size = 0;
161 /* we are all initialized happily */
166 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
167 uint32_t oui, uint8_t subns)
171 iterator->current_namespace = NULL;
176 for (i = 0; i < iterator->_vns->n_ns; i++) {
177 if (iterator->_vns->ns[i].oui != oui)
179 if (iterator->_vns->ns[i].subns != subns)
182 iterator->current_namespace = &iterator->_vns->ns[i];
187 #ifdef RADIOTAP_SUPPORT_OVERRIDES
188 static int find_override(struct ieee80211_radiotap_iterator *iterator,
189 int *align, int *size)
193 if (!iterator->overrides)
196 for (i = 0; i < iterator->n_overrides; i++) {
197 if (iterator->_arg_index == iterator->overrides[i].field) {
198 *align = iterator->overrides[i].align;
199 *size = iterator->overrides[i].size;
200 if (!*align) /* erroneous override */
212 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
213 * @iterator: radiotap_iterator to move to next arg (if any)
215 * Returns: 0 if there is an argument to handle,
216 * -ENOENT if there are no more args or -EINVAL
217 * if there is something else wrong.
219 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
220 * in @this_arg_index and sets @this_arg to point to the
221 * payload for the field. It takes care of alignment handling and extended
222 * present fields. @this_arg can be changed by the caller (eg,
223 * incremented to move inside a compound argument like
224 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
225 * little-endian format whatever the endianess of your CPU.
228 * You must take care when dereferencing iterator.this_arg
229 * for multibyte types... the pointer is not aligned. Use
230 * get_unaligned((type *)iterator.this_arg) to dereference
231 * iterator.this_arg for type "type" safely on all arches.
234 int ieee80211_radiotap_iterator_next(
235 struct ieee80211_radiotap_iterator *iterator)
239 int pad, align, size, subns;
242 /* if no more EXT bits, that's it */
243 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
244 !(iterator->_bitmap_shifter & 1))
247 if (!(iterator->_bitmap_shifter & 1))
248 goto next_entry; /* arg not present */
250 /* get alignment/size of data */
251 switch (iterator->_arg_index % 32) {
252 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
253 case IEEE80211_RADIOTAP_EXT:
257 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
262 #ifdef RADIOTAP_SUPPORT_OVERRIDES
263 if (find_override(iterator, &align, &size)) {
267 if (!iterator->current_namespace ||
268 iterator->_arg_index >= iterator->current_namespace->n_bits) {
269 if (iterator->current_namespace == &radiotap_ns)
273 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
274 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
277 /* skip all subsequent data */
278 iterator->_arg = iterator->_next_ns_data;
279 /* give up on this namespace */
280 iterator->current_namespace = NULL;
287 * arg is present, account for alignment padding
289 * Note that these alignments are relative to the start
290 * of the radiotap header. There is no guarantee
291 * that the radiotap header itself is aligned on any
294 * The above is why get_unaligned() is used to dereference
295 * multibyte elements from the radiotap area.
298 pad = ((unsigned long)iterator->_arg -
299 (unsigned long)iterator->_rtheader) & (align - 1);
302 iterator->_arg += align - pad;
304 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
307 if ((unsigned long)iterator->_arg + size -
308 (unsigned long)iterator->_rtheader >
309 (unsigned long)iterator->_max_length)
312 oui = (*iterator->_arg << 16) |
313 (*(iterator->_arg + 1) << 8) |
314 *(iterator->_arg + 2);
315 subns = *(iterator->_arg + 3);
317 find_ns(iterator, oui, subns);
319 vnslen = get_unaligned_le16(iterator->_arg + 4);
320 iterator->_next_ns_data = iterator->_arg + size + vnslen;
321 if (!iterator->current_namespace)
326 * this is what we will return to user, but we need to
327 * move on first so next call has something fresh to test
329 iterator->this_arg_index = iterator->_arg_index;
330 iterator->this_arg = iterator->_arg;
331 iterator->this_arg_size = size;
333 /* internally move on the size of this arg */
334 iterator->_arg += size;
337 * check for insanity where we are given a bitmap that
338 * claims to have more arg content than the length of the
339 * radiotap section. We will normally end up equalling this
340 * max_length on the last arg, never exceeding it.
343 if ((unsigned long)iterator->_arg -
344 (unsigned long)iterator->_rtheader >
345 (unsigned long)iterator->_max_length)
348 /* these special ones are valid in each bitmap word */
349 switch (iterator->_arg_index % 32) {
350 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
351 iterator->_reset_on_ext = 1;
353 iterator->is_radiotap_ns = 0;
355 * If parser didn't register this vendor
356 * namespace with us, allow it to show it
357 * as 'raw. Do do that, set argument index
358 * to vendor namespace.
360 iterator->this_arg_index =
361 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
362 if (!iterator->current_namespace)
365 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
366 iterator->_reset_on_ext = 1;
367 iterator->current_namespace = &radiotap_ns;
368 iterator->is_radiotap_ns = 1;
370 case IEEE80211_RADIOTAP_EXT:
372 * bit 31 was set, there is more
373 * -- move to next u32 bitmap
375 iterator->_bitmap_shifter =
376 get_unaligned_le32(iterator->_next_bitmap);
377 iterator->_next_bitmap++;
378 if (iterator->_reset_on_ext)
379 iterator->_arg_index = 0;
381 iterator->_arg_index++;
382 iterator->_reset_on_ext = 0;
385 /* we've got a hit! */
388 iterator->_bitmap_shifter >>= 1;
389 iterator->_arg_index++;
392 /* if we found a valid arg earlier, return it now */