1 /*
2 * Radiotap parser
3 *
4 * Copyright 2007 Andy Green <andy@warmcat.com>
5 * 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.
15 */
16
17 #include <linux/kernel.h>
18 #include <linux/export.h>
19 #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
25 static 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, },
44 [IEEE80211_RADIOTAP_MCS] = { .align = 1, .size = 3, },
45 [IEEE80211_RADIOTAP_AMPDU_STATUS] = { .align = 4, .size = 8, },
46 [IEEE80211_RADIOTAP_VHT] = { .align = 2, .size = 12, },
47 /*
48 * add more here as they are defined in radiotap.h
49 */
50 };
51
52 static const struct ieee80211_radiotap_namespace radiotap_ns = {
53 .n_bits = ARRAY_SIZE(rtap_namespace_sizes),
54 .align_size = rtap_namespace_sizes,
55 };
56
57 /**
58 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
59 * @iterator: radiotap_iterator to initialize
60 * @radiotap_header: radiotap header to parse
61 * @max_length: total length we can parse into (eg, whole packet length)
62 * @vns: vendor namespaces to parse
63 *
64 * Returns: 0 or a negative error code if there is a problem.
65 *
66 * This function initializes an opaque iterator struct which can then
67 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
68 * argument which is present in the header. It knows about extended
69 * present headers and handles them.
70 *
71 * How to use:
72 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
73 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
74 * checking for a good 0 return code. Then loop calling
75 * __ieee80211_radiotap_iterator_next()... it returns either 0,
76 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
77 * The iterator's @this_arg member points to the start of the argument
78 * associated with the current argument index that is present, which can be
79 * found in the iterator's @this_arg_index member. This arg index corresponds
80 * to the IEEE80211_RADIOTAP_... defines.
81 *
82 * Radiotap header length:
83 * You can find the CPU-endian total radiotap header length in
84 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
85 * successfully.
86 *
87 * Alignment Gotcha:
88 * You must take care when dereferencing iterator.this_arg
89 * for multibyte types... the pointer is not aligned. Use
90 * get_unaligned((type *)iterator.this_arg) to dereference
91 * iterator.this_arg for type "type" safely on all arches.
92 *
93 * Example code:
94 * See Documentation/networking/radiotap-headers.rst
95 */
96
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)97 int ieee80211_radiotap_iterator_init(
98 struct ieee80211_radiotap_iterator *iterator,
99 struct ieee80211_radiotap_header *radiotap_header,
100 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns)
101 {
102 /* check the radiotap header can actually be present */
103 if (max_length < sizeof(struct ieee80211_radiotap_header))
104 return -EINVAL;
105
106 /* Linux only supports version 0 radiotap format */
107 if (radiotap_header->it_version)
108 return -EINVAL;
109
110 /* sanity check for allowed length and radiotap length field */
111 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
112 return -EINVAL;
113
114 iterator->_rtheader = radiotap_header;
115 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
116 iterator->_arg_index = 0;
117 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
118 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
119 iterator->_reset_on_ext = 0;
120 iterator->_next_bitmap = &radiotap_header->it_present;
121 iterator->_next_bitmap++;
122 iterator->_vns = vns;
123 iterator->current_namespace = &radiotap_ns;
124 iterator->is_radiotap_ns = 1;
125
126 /* find payload start allowing for extended bitmap(s) */
127
128 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
129 if ((unsigned long)iterator->_arg -
130 (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
131 (unsigned long)iterator->_max_length)
132 return -EINVAL;
133 while (get_unaligned_le32(iterator->_arg) &
134 (1 << IEEE80211_RADIOTAP_EXT)) {
135 iterator->_arg += sizeof(uint32_t);
136
137 /*
138 * check for insanity where the present bitmaps
139 * keep claiming to extend up to or even beyond the
140 * stated radiotap header length
141 */
142
143 if ((unsigned long)iterator->_arg -
144 (unsigned long)iterator->_rtheader +
145 sizeof(uint32_t) >
146 (unsigned long)iterator->_max_length)
147 return -EINVAL;
148 }
149
150 iterator->_arg += sizeof(uint32_t);
151
152 /*
153 * no need to check again for blowing past stated radiotap
154 * header length, because ieee80211_radiotap_iterator_next
155 * checks it before it is dereferenced
156 */
157 }
158
159 iterator->this_arg = iterator->_arg;
160
161 /* we are all initialized happily */
162
163 return 0;
164 }
165 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
166
find_ns(struct ieee80211_radiotap_iterator * iterator,uint32_t oui,uint8_t subns)167 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
168 uint32_t oui, uint8_t subns)
169 {
170 int i;
171
172 iterator->current_namespace = NULL;
173
174 if (!iterator->_vns)
175 return;
176
177 for (i = 0; i < iterator->_vns->n_ns; i++) {
178 if (iterator->_vns->ns[i].oui != oui)
179 continue;
180 if (iterator->_vns->ns[i].subns != subns)
181 continue;
182
183 iterator->current_namespace = &iterator->_vns->ns[i];
184 break;
185 }
186 }
187
188
189
190 /**
191 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
192 * @iterator: radiotap_iterator to move to next arg (if any)
193 *
194 * Returns: 0 if there is an argument to handle,
195 * -ENOENT if there are no more args or -EINVAL
196 * if there is something else wrong.
197 *
198 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
199 * in @this_arg_index and sets @this_arg to point to the
200 * payload for the field. It takes care of alignment handling and extended
201 * present fields. @this_arg can be changed by the caller (eg,
202 * incremented to move inside a compound argument like
203 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
204 * little-endian format whatever the endianess of your CPU.
205 *
206 * Alignment Gotcha:
207 * You must take care when dereferencing iterator.this_arg
208 * for multibyte types... the pointer is not aligned. Use
209 * get_unaligned((type *)iterator.this_arg) to dereference
210 * iterator.this_arg for type "type" safely on all arches.
211 */
212
ieee80211_radiotap_iterator_next(struct ieee80211_radiotap_iterator * iterator)213 int ieee80211_radiotap_iterator_next(
214 struct ieee80211_radiotap_iterator *iterator)
215 {
216 while (1) {
217 int hit = 0;
218 int pad, align, size, subns;
219 uint32_t oui;
220
221 /* if no more EXT bits, that's it */
222 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
223 !(iterator->_bitmap_shifter & 1))
224 return -ENOENT;
225
226 if (!(iterator->_bitmap_shifter & 1))
227 goto next_entry; /* arg not present */
228
229 /* get alignment/size of data */
230 switch (iterator->_arg_index % 32) {
231 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
232 case IEEE80211_RADIOTAP_EXT:
233 align = 1;
234 size = 0;
235 break;
236 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
237 align = 2;
238 size = 6;
239 break;
240 default:
241 if (!iterator->current_namespace ||
242 iterator->_arg_index >= iterator->current_namespace->n_bits) {
243 if (iterator->current_namespace == &radiotap_ns)
244 return -ENOENT;
245 align = 0;
246 } else {
247 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
248 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
249 }
250 if (!align) {
251 /* skip all subsequent data */
252 iterator->_arg = iterator->_next_ns_data;
253 /* give up on this namespace */
254 iterator->current_namespace = NULL;
255 goto next_entry;
256 }
257 break;
258 }
259
260 /*
261 * arg is present, account for alignment padding
262 *
263 * Note that these alignments are relative to the start
264 * of the radiotap header. There is no guarantee
265 * that the radiotap header itself is aligned on any
266 * kind of boundary.
267 *
268 * The above is why get_unaligned() is used to dereference
269 * multibyte elements from the radiotap area.
270 */
271
272 pad = ((unsigned long)iterator->_arg -
273 (unsigned long)iterator->_rtheader) & (align - 1);
274
275 if (pad)
276 iterator->_arg += align - pad;
277
278 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
279 int vnslen;
280
281 if ((unsigned long)iterator->_arg + size -
282 (unsigned long)iterator->_rtheader >
283 (unsigned long)iterator->_max_length)
284 return -EINVAL;
285
286 oui = (*iterator->_arg << 16) |
287 (*(iterator->_arg + 1) << 8) |
288 *(iterator->_arg + 2);
289 subns = *(iterator->_arg + 3);
290
291 find_ns(iterator, oui, subns);
292
293 vnslen = get_unaligned_le16(iterator->_arg + 4);
294 iterator->_next_ns_data = iterator->_arg + size + vnslen;
295 if (!iterator->current_namespace)
296 size += vnslen;
297 }
298
299 /*
300 * this is what we will return to user, but we need to
301 * move on first so next call has something fresh to test
302 */
303 iterator->this_arg_index = iterator->_arg_index;
304 iterator->this_arg = iterator->_arg;
305 iterator->this_arg_size = size;
306
307 /* internally move on the size of this arg */
308 iterator->_arg += size;
309
310 /*
311 * check for insanity where we are given a bitmap that
312 * claims to have more arg content than the length of the
313 * radiotap section. We will normally end up equalling this
314 * max_length on the last arg, never exceeding it.
315 */
316
317 if ((unsigned long)iterator->_arg -
318 (unsigned long)iterator->_rtheader >
319 (unsigned long)iterator->_max_length)
320 return -EINVAL;
321
322 /* these special ones are valid in each bitmap word */
323 switch (iterator->_arg_index % 32) {
324 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
325 iterator->_reset_on_ext = 1;
326
327 iterator->is_radiotap_ns = 0;
328 /*
329 * If parser didn't register this vendor
330 * namespace with us, allow it to show it
331 * as 'raw. Do do that, set argument index
332 * to vendor namespace.
333 */
334 iterator->this_arg_index =
335 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
336 if (!iterator->current_namespace)
337 hit = 1;
338 goto next_entry;
339 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
340 iterator->_reset_on_ext = 1;
341 iterator->current_namespace = &radiotap_ns;
342 iterator->is_radiotap_ns = 1;
343 goto next_entry;
344 case IEEE80211_RADIOTAP_EXT:
345 /*
346 * bit 31 was set, there is more
347 * -- move to next u32 bitmap
348 */
349 iterator->_bitmap_shifter =
350 get_unaligned_le32(iterator->_next_bitmap);
351 iterator->_next_bitmap++;
352 if (iterator->_reset_on_ext)
353 iterator->_arg_index = 0;
354 else
355 iterator->_arg_index++;
356 iterator->_reset_on_ext = 0;
357 break;
358 default:
359 /* we've got a hit! */
360 hit = 1;
361 next_entry:
362 iterator->_bitmap_shifter >>= 1;
363 iterator->_arg_index++;
364 }
365
366 /* if we found a valid arg earlier, return it now */
367 if (hit)
368 return 0;
369 }
370 }
371 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
372