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