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->_reset_on_ext = 0;
113 iterator->_next_bitmap = &radiotap_header->it_present;
114 iterator->_next_bitmap++;
115 iterator->_vns = vns;
116 iterator->current_namespace = &radiotap_ns;
117 iterator->is_radiotap_ns = 1;
118 #ifdef RADIOTAP_SUPPORT_OVERRIDES
119 iterator->n_overrides = 0;
120 iterator->overrides = NULL;
121 #endif
122
123 /* find payload start allowing for extended bitmap(s) */
124
125 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
126 if ((unsigned long)iterator->_arg -
127 (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
128 (unsigned long)iterator->_max_length)
129 return -EINVAL;
130 while (get_unaligned_le32(iterator->_arg) &
131 (1 << IEEE80211_RADIOTAP_EXT)) {
132 iterator->_arg += sizeof(uint32_t);
133
134 /*
135 * check for insanity where the present bitmaps
136 * keep claiming to extend up to or even beyond the
137 * stated radiotap header length
138 */
139
140 if ((unsigned long)iterator->_arg -
141 (unsigned long)iterator->_rtheader +
142 sizeof(uint32_t) >
143 (unsigned long)iterator->_max_length)
144 return -EINVAL;
145 }
146
147 iterator->_arg += sizeof(uint32_t);
148
149 /*
150 * no need to check again for blowing past stated radiotap
151 * header length, because ieee80211_radiotap_iterator_next
152 * checks it before it is dereferenced
153 */
154 }
155
156 iterator->this_arg = iterator->_arg;
157
158 /* we are all initialized happily */
159
160 return 0;
161 }
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 #ifdef RADIOTAP_SUPPORT_OVERRIDES
find_override(struct ieee80211_radiotap_iterator * iterator,int * align,int * size)185 static int find_override(struct ieee80211_radiotap_iterator *iterator,
186 int *align, int *size)
187 {
188 int i;
189
190 if (!iterator->overrides)
191 return 0;
192
193 for (i = 0; i < iterator->n_overrides; i++) {
194 if (iterator->_arg_index == iterator->overrides[i].field) {
195 *align = iterator->overrides[i].align;
196 *size = iterator->overrides[i].size;
197 if (!*align) /* erroneous override */
198 return 0;
199 return 1;
200 }
201 }
202
203 return 0;
204 }
205 #endif
206
207
208 /**
209 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
210 * @iterator: radiotap_iterator to move to next arg (if any)
211 *
212 * Returns: 0 if there is an argument to handle,
213 * -ENOENT if there are no more args or -EINVAL
214 * if there is something else wrong.
215 *
216 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
217 * in @this_arg_index and sets @this_arg to point to the
218 * payload for the field. It takes care of alignment handling and extended
219 * present fields. @this_arg can be changed by the caller (eg,
220 * incremented to move inside a compound argument like
221 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
222 * little-endian format whatever the endianess of your CPU.
223 *
224 * Alignment Gotcha:
225 * You must take care when dereferencing iterator.this_arg
226 * for multibyte types... the pointer is not aligned. Use
227 * get_unaligned((type *)iterator.this_arg) to dereference
228 * iterator.this_arg for type "type" safely on all arches.
229 */
230
ieee80211_radiotap_iterator_next(struct ieee80211_radiotap_iterator * iterator)231 int ieee80211_radiotap_iterator_next(
232 struct ieee80211_radiotap_iterator *iterator)
233 {
234 while (1) {
235 int hit = 0;
236 int pad, align, size, subns;
237 uint32_t oui;
238
239 /* if no more EXT bits, that's it */
240 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
241 !(iterator->_bitmap_shifter & 1))
242 return -ENOENT;
243
244 if (!(iterator->_bitmap_shifter & 1))
245 goto next_entry; /* arg not present */
246
247 /* get alignment/size of data */
248 switch (iterator->_arg_index % 32) {
249 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
250 case IEEE80211_RADIOTAP_EXT:
251 align = 1;
252 size = 0;
253 break;
254 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
255 align = 2;
256 size = 6;
257 break;
258 default:
259 #ifdef RADIOTAP_SUPPORT_OVERRIDES
260 if (find_override(iterator, &align, &size)) {
261 /* all set */
262 } else
263 #endif
264 if (!iterator->current_namespace ||
265 iterator->_arg_index >= iterator->current_namespace->n_bits) {
266 if (iterator->current_namespace == &radiotap_ns)
267 return -ENOENT;
268 align = 0;
269 } else {
270 align = iterator->current_namespace->align_size[iterator->_arg_index].align;
271 size = iterator->current_namespace->align_size[iterator->_arg_index].size;
272 }
273 if (!align) {
274 /* skip all subsequent data */
275 iterator->_arg = iterator->_next_ns_data;
276 /* give up on this namespace */
277 iterator->current_namespace = NULL;
278 goto next_entry;
279 }
280 break;
281 }
282
283 /*
284 * arg is present, account for alignment padding
285 *
286 * Note that these alignments are relative to the start
287 * of the radiotap header. There is no guarantee
288 * that the radiotap header itself is aligned on any
289 * kind of boundary.
290 *
291 * The above is why get_unaligned() is used to dereference
292 * multibyte elements from the radiotap area.
293 */
294
295 pad = ((unsigned long)iterator->_arg -
296 (unsigned long)iterator->_rtheader) & (align - 1);
297
298 if (pad)
299 iterator->_arg += align - pad;
300
301 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
302 int vnslen;
303
304 if ((unsigned long)iterator->_arg + size -
305 (unsigned long)iterator->_rtheader >
306 (unsigned long)iterator->_max_length)
307 return -EINVAL;
308
309 oui = (*iterator->_arg << 16) |
310 (*(iterator->_arg + 1) << 8) |
311 *(iterator->_arg + 2);
312 subns = *(iterator->_arg + 3);
313
314 find_ns(iterator, oui, subns);
315
316 vnslen = get_unaligned_le16(iterator->_arg + 4);
317 iterator->_next_ns_data = iterator->_arg + size + vnslen;
318 if (!iterator->current_namespace)
319 size += vnslen;
320 }
321
322 /*
323 * this is what we will return to user, but we need to
324 * move on first so next call has something fresh to test
325 */
326 iterator->this_arg_index = iterator->_arg_index;
327 iterator->this_arg = iterator->_arg;
328 iterator->this_arg_size = size;
329
330 /* internally move on the size of this arg */
331 iterator->_arg += size;
332
333 /*
334 * check for insanity where we are given a bitmap that
335 * claims to have more arg content than the length of the
336 * radiotap section. We will normally end up equalling this
337 * max_length on the last arg, never exceeding it.
338 */
339
340 if ((unsigned long)iterator->_arg -
341 (unsigned long)iterator->_rtheader >
342 (unsigned long)iterator->_max_length)
343 return -EINVAL;
344
345 /* these special ones are valid in each bitmap word */
346 switch (iterator->_arg_index % 32) {
347 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
348 iterator->_reset_on_ext = 1;
349
350 iterator->is_radiotap_ns = 0;
351 /*
352 * If parser didn't register this vendor
353 * namespace with us, allow it to show it
354 * as 'raw. Do do that, set argument index
355 * to vendor namespace.
356 */
357 iterator->this_arg_index =
358 IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
359 if (!iterator->current_namespace)
360 hit = 1;
361 goto next_entry;
362 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
363 iterator->_reset_on_ext = 1;
364 iterator->current_namespace = &radiotap_ns;
365 iterator->is_radiotap_ns = 1;
366 goto next_entry;
367 case IEEE80211_RADIOTAP_EXT:
368 /*
369 * bit 31 was set, there is more
370 * -- move to next u32 bitmap
371 */
372 iterator->_bitmap_shifter =
373 get_unaligned_le32(iterator->_next_bitmap);
374 iterator->_next_bitmap++;
375 if (iterator->_reset_on_ext)
376 iterator->_arg_index = 0;
377 else
378 iterator->_arg_index++;
379 iterator->_reset_on_ext = 0;
380 break;
381 default:
382 /* we've got a hit! */
383 hit = 1;
384 next_entry:
385 iterator->_bitmap_shifter >>= 1;
386 iterator->_arg_index++;
387 }
388
389 /* if we found a valid arg earlier, return it now */
390 if (hit)
391 return 0;
392 }
393 }
394