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 #include "radiotap_iter.h"
17 #include "platform.h"
18
19 /* function prototypes and related defs are in radiotap_iter.h */
20
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, },
42 /*
43 * add more here as they are defined in radiotap.h
44 */
45 };
46
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,
50 };
51
52 /**
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)
57 *
58 * Returns: 0 or a negative error code if there is a problem.
59 *
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.
64 *
65 * How to use:
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.
75 *
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()
79 * successfully.
80 *
81 * Alignment Gotcha:
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.
86 *
87 * Example code: parse.c
88 */
89
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)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)
94 {
95 /* must at least have the radiotap header */
96 if (max_length < (int)sizeof(struct ieee80211_radiotap_header))
97 return -EINVAL;
98
99 /* Linux only supports version 0 radiotap format */
100 if (radiotap_header->it_version)
101 return -EINVAL;
102
103 /* sanity check for allowed length and radiotap length field */
104 if (max_length < get_unaligned_le16(&radiotap_header->it_len))
105 return -EINVAL;
106
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;
122 #endif
123
124 /* find payload start allowing for extended bitmap(s) */
125
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)
130 return -EINVAL;
131 while (get_unaligned_le32(iterator->_arg) &
132 BIT(IEEE80211_RADIOTAP_EXT)) {
133 iterator->_arg += sizeof(uint32_t);
134
135 /*
136 * check for insanity where the present bitmaps
137 * keep claiming to extend up to or even beyond the
138 * stated radiotap header length
139 */
140
141 if ((unsigned long)iterator->_arg -
142 (unsigned long)iterator->_rtheader +
143 sizeof(uint32_t) >
144 (unsigned long)iterator->_max_length)
145 return -EINVAL;
146 }
147
148 iterator->_arg += sizeof(uint32_t);
149
150 /*
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
154 */
155 }
156
157 iterator->this_arg = iterator->_arg;
158 iterator->this_arg_index = 0;
159 iterator->this_arg_size = 0;
160
161 /* we are all initialized happily */
162
163 return 0;
164 }
165
find_ns(struct ieee80211_radiotap_iterator * iterator,uint32_t oui,uint8_t subns)166 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
167 uint32_t oui, uint8_t subns)
168 {
169 int i;
170
171 iterator->current_namespace = NULL;
172
173 if (!iterator->_vns)
174 return;
175
176 for (i = 0; i < iterator->_vns->n_ns; i++) {
177 if (iterator->_vns->ns[i].oui != oui)
178 continue;
179 if (iterator->_vns->ns[i].subns != subns)
180 continue;
181
182 iterator->current_namespace = &iterator->_vns->ns[i];
183 break;
184 }
185 }
186
187 #ifdef RADIOTAP_SUPPORT_OVERRIDES
find_override(struct ieee80211_radiotap_iterator * iterator,int * align,int * size)188 static int find_override(struct ieee80211_radiotap_iterator *iterator,
189 int *align, int *size)
190 {
191 int i;
192
193 if (!iterator->overrides)
194 return 0;
195
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 */
201 return 0;
202 return 1;
203 }
204 }
205
206 return 0;
207 }
208 #endif
209
210
211 /**
212 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
213 * @iterator: radiotap_iterator to move to next arg (if any)
214 *
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.
218 *
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.
226 *
227 * Alignment Gotcha:
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.
232 */
233
ieee80211_radiotap_iterator_next(struct ieee80211_radiotap_iterator * iterator)234 int ieee80211_radiotap_iterator_next(
235 struct ieee80211_radiotap_iterator *iterator)
236 {
237 while (1) {
238 int hit = 0;
239 int pad, align, size, subns;
240 uint32_t oui;
241
242 /* if no more EXT bits, that's it */
243 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
244 !(iterator->_bitmap_shifter & 1))
245 return -ENOENT;
246
247 if (!(iterator->_bitmap_shifter & 1))
248 goto next_entry; /* arg not present */
249
250 /* get alignment/size of data */
251 switch (iterator->_arg_index % 32) {
252 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
253 case IEEE80211_RADIOTAP_EXT:
254 align = 1;
255 size = 0;
256 break;
257 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
258 align = 2;
259 size = 6;
260 break;
261 default:
262 #ifdef RADIOTAP_SUPPORT_OVERRIDES
263 if (find_override(iterator, &align, &size)) {
264 /* all set */
265 } else
266 #endif
267 if (!iterator->current_namespace ||
268 iterator->_arg_index >= iterator->current_namespace->n_bits) {
269 if (iterator->current_namespace == &radiotap_ns)
270 return -ENOENT;
271 align = 0;
272 } else {
273 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
274 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
275 }
276 if (!align) {
277 /* skip all subsequent data */
278 iterator->_arg = iterator->_next_ns_data;
279 /* give up on this namespace */
280 iterator->current_namespace = NULL;
281 goto next_entry;
282 }
283 break;
284 }
285
286 /*
287 * arg is present, account for alignment padding
288 *
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
292 * kind of boundary.
293 *
294 * The above is why get_unaligned() is used to dereference
295 * multibyte elements from the radiotap area.
296 */
297
298 pad = ((unsigned long)iterator->_arg -
299 (unsigned long)iterator->_rtheader) & (align - 1);
300
301 if (pad)
302 iterator->_arg += align - pad;
303
304 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
305 int vnslen;
306
307 if ((unsigned long)iterator->_arg + size -
308 (unsigned long)iterator->_rtheader >
309 (unsigned long)iterator->_max_length)
310 return -EINVAL;
311
312 oui = (*iterator->_arg << 16) |
313 (*(iterator->_arg + 1) << 8) |
314 *(iterator->_arg + 2);
315 subns = *(iterator->_arg + 3);
316
317 find_ns(iterator, oui, subns);
318
319 vnslen = get_unaligned_le16(iterator->_arg + 4);
320 iterator->_next_ns_data = iterator->_arg + size + vnslen;
321 if (!iterator->current_namespace)
322 size += vnslen;
323 }
324
325 /*
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
328 */
329 iterator->this_arg_index = iterator->_arg_index;
330 iterator->this_arg = iterator->_arg;
331 iterator->this_arg_size = size;
332
333 /* internally move on the size of this arg */
334 iterator->_arg += size;
335
336 /*
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.
341 */
342
343 if ((unsigned long)iterator->_arg -
344 (unsigned long)iterator->_rtheader >
345 (unsigned long)iterator->_max_length)
346 return -EINVAL;
347
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;
352
353 iterator->is_radiotap_ns = 0;
354 /*
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.
359 */
360 iterator->this_arg_index =
361 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
362 if (!iterator->current_namespace)
363 hit = 1;
364 goto next_entry;
365 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
366 iterator->_reset_on_ext = 1;
367 iterator->current_namespace = &radiotap_ns;
368 iterator->is_radiotap_ns = 1;
369 goto next_entry;
370 case IEEE80211_RADIOTAP_EXT:
371 /*
372 * bit 31 was set, there is more
373 * -- move to next u32 bitmap
374 */
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;
380 else
381 iterator->_arg_index++;
382 iterator->_reset_on_ext = 0;
383 break;
384 default:
385 /* we've got a hit! */
386 hit = 1;
387 next_entry:
388 iterator->_bitmap_shifter >>= 1;
389 iterator->_arg_index++;
390 }
391
392 /* if we found a valid arg earlier, return it now */
393 if (hit)
394 return 0;
395 }
396 }
397