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Andy Green179f8312007-07-10 19:29:38 +02001/*
2 * Radiotap parser
3 *
4 * Copyright 2007 Andy Green <andy@warmcat.com>
Johannes Berg33e5a2f2010-02-03 10:24:30 +01005 * Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
6 *
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.
10 *
11 * Alternatively, this software may be distributed under the terms of BSD
12 * license.
13 *
14 * See COPYING for more details.
Andy Green179f8312007-07-10 19:29:38 +020015 */
16
Nikitas Angelinas94262312010-09-08 22:29:53 +010017#include <linux/kernel.h>
Paul Gortmakerbc3b2d72011-07-15 11:47:34 -040018#include <linux/export.h>
Andy Green179f8312007-07-10 19:29:38 +020019#include <net/cfg80211.h>
20#include <net/ieee80211_radiotap.h>
21#include <asm/unaligned.h>
22
23/* function prototypes and related defs are in include/net/cfg80211.h */
24
Johannes Berg33e5a2f2010-02-03 10:24:30 +010025static const struct radiotap_align_size rtap_namespace_sizes[] = {
26 [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, },
27 [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, },
28 [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, },
29 [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, },
30 [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, },
31 [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, },
32 [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, },
33 [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, },
34 [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, },
35 [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, },
36 [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, },
37 [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, },
38 [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, },
39 [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, },
40 [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, },
41 [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, },
42 [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, },
43 [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, },
Johannes Berg48613ec2012-07-05 11:32:16 +020044 [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
45 [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
Johannes Berg33e5a2f2010-02-03 10:24:30 +010046 /*
47 * add more here as they are defined in radiotap.h
48 */
49};
50
51static const struct ieee80211_radiotap_namespace radiotap_ns = {
Nikitas Angelinas94262312010-09-08 22:29:53 +010052 .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
Johannes Berg33e5a2f2010-02-03 10:24:30 +010053 .align_size = rtap_namespace_sizes,
54};
55
Andy Green179f8312007-07-10 19:29:38 +020056/**
57 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
58 * @iterator: radiotap_iterator to initialize
59 * @radiotap_header: radiotap header to parse
60 * @max_length: total length we can parse into (eg, whole packet length)
61 *
62 * Returns: 0 or a negative error code if there is a problem.
63 *
64 * This function initializes an opaque iterator struct which can then
65 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
66 * argument which is present in the header. It knows about extended
67 * present headers and handles them.
68 *
69 * How to use:
70 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
71 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
72 * checking for a good 0 return code. Then loop calling
73 * __ieee80211_radiotap_iterator_next()... it returns either 0,
74 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
75 * The iterator's @this_arg member points to the start of the argument
76 * associated with the current argument index that is present, which can be
77 * found in the iterator's @this_arg_index member. This arg index corresponds
78 * to the IEEE80211_RADIOTAP_... defines.
79 *
80 * Radiotap header length:
81 * You can find the CPU-endian total radiotap header length in
82 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
83 * successfully.
84 *
85 * Alignment Gotcha:
86 * You must take care when dereferencing iterator.this_arg
87 * for multibyte types... the pointer is not aligned. Use
88 * get_unaligned((type *)iterator.this_arg) to dereference
89 * iterator.this_arg for type "type" safely on all arches.
90 *
91 * Example code:
92 * See Documentation/networking/radiotap-headers.txt
93 */
94
95int ieee80211_radiotap_iterator_init(
Johannes Berg33e5a2f2010-02-03 10:24:30 +010096 struct ieee80211_radiotap_iterator *iterator,
97 struct ieee80211_radiotap_header *radiotap_header,
98 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
Andy Green179f8312007-07-10 19:29:38 +020099{
100 /* Linux only supports version 0 radiotap format */
101 if (radiotap_header->it_version)
102 return -EINVAL;
103
104 /* sanity check for allowed length and radiotap length field */
Harvey Harrisonae7245c2008-05-01 22:19:33 -0700105 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
Andy Green179f8312007-07-10 19:29:38 +0200106 return -EINVAL;
107
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100108 iterator->_rtheader = radiotap_header;
109 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
110 iterator->_arg_index = 0;
111 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
112 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
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;
Andy Green179f8312007-07-10 19:29:38 +0200119
120 /* find payload start allowing for extended bitmap(s) */
121
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100122 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
123 while (get_unaligned_le32(iterator->_arg) &
124 (1 << IEEE80211_RADIOTAP_EXT)) {
125 iterator->_arg += sizeof(uint32_t);
Andy Green179f8312007-07-10 19:29:38 +0200126
127 /*
128 * check for insanity where the present bitmaps
129 * keep claiming to extend up to or even beyond the
130 * stated radiotap header length
131 */
132
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100133 if ((unsigned long)iterator->_arg -
134 (unsigned long)iterator->_rtheader >
135 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200136 return -EINVAL;
137 }
138
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100139 iterator->_arg += sizeof(uint32_t);
Andy Green179f8312007-07-10 19:29:38 +0200140
141 /*
142 * no need to check again for blowing past stated radiotap
143 * header length, because ieee80211_radiotap_iterator_next
144 * checks it before it is dereferenced
145 */
146 }
147
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100148 iterator->this_arg = iterator->_arg;
149
Andy Green179f8312007-07-10 19:29:38 +0200150 /* we are all initialized happily */
151
152 return 0;
153}
154EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
155
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100156static void find_ns(struct ieee80211_radiotap_iterator *iterator,
157 uint32_t oui, uint8_t subns)
158{
159 int i;
160
161 iterator->current_namespace = NULL;
162
163 if (!iterator->_vns)
164 return;
165
166 for (i = 0; i < iterator->_vns->n_ns; i++) {
167 if (iterator->_vns->ns[i].oui != oui)
168 continue;
169 if (iterator->_vns->ns[i].subns != subns)
170 continue;
171
172 iterator->current_namespace = &iterator->_vns->ns[i];
173 break;
174 }
175}
176
177
Andy Green179f8312007-07-10 19:29:38 +0200178
179/**
180 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
181 * @iterator: radiotap_iterator to move to next arg (if any)
182 *
183 * Returns: 0 if there is an argument to handle,
184 * -ENOENT if there are no more args or -EINVAL
185 * if there is something else wrong.
186 *
187 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
188 * in @this_arg_index and sets @this_arg to point to the
189 * payload for the field. It takes care of alignment handling and extended
190 * present fields. @this_arg can be changed by the caller (eg,
191 * incremented to move inside a compound argument like
192 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
193 * little-endian format whatever the endianess of your CPU.
194 *
195 * Alignment Gotcha:
196 * You must take care when dereferencing iterator.this_arg
197 * for multibyte types... the pointer is not aligned. Use
198 * get_unaligned((type *)iterator.this_arg) to dereference
199 * iterator.this_arg for type "type" safely on all arches.
200 */
201
202int ieee80211_radiotap_iterator_next(
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100203 struct ieee80211_radiotap_iterator *iterator)
Andy Green179f8312007-07-10 19:29:38 +0200204{
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100205 while (1) {
Andy Green179f8312007-07-10 19:29:38 +0200206 int hit = 0;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200207 int pad, align, size, subns;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100208 uint32_t oui;
Andy Green179f8312007-07-10 19:29:38 +0200209
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100210 /* if no more EXT bits, that's it */
211 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
212 !(iterator->_bitmap_shifter & 1))
213 return -ENOENT;
214
215 if (!(iterator->_bitmap_shifter & 1))
Andy Green179f8312007-07-10 19:29:38 +0200216 goto next_entry; /* arg not present */
217
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100218 /* get alignment/size of data */
219 switch (iterator->_arg_index % 32) {
220 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
221 case IEEE80211_RADIOTAP_EXT:
222 align = 1;
223 size = 0;
224 break;
225 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
226 align = 2;
227 size = 6;
228 break;
229 default:
230 if (!iterator->current_namespace ||
231 iterator->_arg_index >= iterator->current_namespace->n_bits) {
232 if (iterator->current_namespace == &radiotap_ns)
233 return -ENOENT;
234 align = 0;
235 } else {
236 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
237 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
238 }
239 if (!align) {
240 /* skip all subsequent data */
241 iterator->_arg = iterator->_next_ns_data;
242 /* give up on this namespace */
243 iterator->current_namespace = NULL;
244 goto next_entry;
245 }
246 break;
247 }
248
Andy Green179f8312007-07-10 19:29:38 +0200249 /*
250 * arg is present, account for alignment padding
Andy Green179f8312007-07-10 19:29:38 +0200251 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100252 * Note that these alignments are relative to the start
253 * of the radiotap header. There is no guarantee
Andy Green179f8312007-07-10 19:29:38 +0200254 * that the radiotap header itself is aligned on any
255 * kind of boundary.
256 *
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100257 * The above is why get_unaligned() is used to dereference
258 * multibyte elements from the radiotap area.
Andy Green179f8312007-07-10 19:29:38 +0200259 */
260
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100261 pad = ((unsigned long)iterator->_arg -
262 (unsigned long)iterator->_rtheader) & (align - 1);
Andy Green179f8312007-07-10 19:29:38 +0200263
264 if (pad)
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100265 iterator->_arg += align - pad;
Andy Green179f8312007-07-10 19:29:38 +0200266
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200267 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
268 int vnslen;
269
270 if ((unsigned long)iterator->_arg + size -
271 (unsigned long)iterator->_rtheader >
272 (unsigned long)iterator->_max_length)
273 return -EINVAL;
274
275 oui = (*iterator->_arg << 16) |
276 (*(iterator->_arg + 1) << 8) |
277 *(iterator->_arg + 2);
278 subns = *(iterator->_arg + 3);
279
280 find_ns(iterator, oui, subns);
281
282 vnslen = get_unaligned_le16(iterator->_arg + 4);
283 iterator->_next_ns_data = iterator->_arg + size + vnslen;
284 if (!iterator->current_namespace)
285 size += vnslen;
286 }
287
Andy Green179f8312007-07-10 19:29:38 +0200288 /*
289 * this is what we will return to user, but we need to
290 * move on first so next call has something fresh to test
291 */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100292 iterator->this_arg_index = iterator->_arg_index;
293 iterator->this_arg = iterator->_arg;
294 iterator->this_arg_size = size;
Andy Green179f8312007-07-10 19:29:38 +0200295
296 /* internally move on the size of this arg */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100297 iterator->_arg += size;
Andy Green179f8312007-07-10 19:29:38 +0200298
299 /*
300 * check for insanity where we are given a bitmap that
301 * claims to have more arg content than the length of the
302 * radiotap section. We will normally end up equalling this
303 * max_length on the last arg, never exceeding it.
304 */
305
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100306 if ((unsigned long)iterator->_arg -
307 (unsigned long)iterator->_rtheader >
308 (unsigned long)iterator->_max_length)
Andy Green179f8312007-07-10 19:29:38 +0200309 return -EINVAL;
310
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100311 /* these special ones are valid in each bitmap word */
312 switch (iterator->_arg_index % 32) {
313 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100314 iterator->_reset_on_ext = 1;
315
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100316 iterator->is_radiotap_ns = 0;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200317 /*
318 * If parser didn't register this vendor
319 * namespace with us, allow it to show it
320 * as 'raw. Do do that, set argument index
321 * to vendor namespace.
322 */
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100323 iterator->this_arg_index =
324 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200325 if (!iterator->current_namespace)
326 hit = 1;
327 goto next_entry;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100328 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100329 iterator->_reset_on_ext = 1;
330 iterator->current_namespace = &radiotap_ns;
331 iterator->is_radiotap_ns = 1;
Johannes Berg9ebad4a2010-10-14 13:41:35 +0200332 goto next_entry;
Johannes Berg33e5a2f2010-02-03 10:24:30 +0100333 case IEEE80211_RADIOTAP_EXT:
334 /*
335 * bit 31 was set, there is more
336 * -- move to next u32 bitmap
337 */
338 iterator->_bitmap_shifter =
339 get_unaligned_le32(iterator->_next_bitmap);
340 iterator->_next_bitmap++;
341 if (iterator->_reset_on_ext)
342 iterator->_arg_index = 0;
343 else
344 iterator->_arg_index++;
345 iterator->_reset_on_ext = 0;
346 break;
347 default:
348 /* we've got a hit! */
349 hit = 1;
350 next_entry:
351 iterator->_bitmap_shifter >>= 1;
352 iterator->_arg_index++;
353 }
Andy Green179f8312007-07-10 19:29:38 +0200354
355 /* if we found a valid arg earlier, return it now */
356 if (hit)
357 return 0;
358 }
Andy Green179f8312007-07-10 19:29:38 +0200359}
360EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);