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 | |
97 | int ieee80211_radiotap_iterator_init( |
98 | struct ieee80211_radiotap_iterator *iterator, |
99 | struct ieee80211_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(p: &radiotap_header->it_len)) |
112 | return -EINVAL; |
113 | |
114 | iterator->_rtheader = radiotap_header; |
115 | iterator->_max_length = get_unaligned_le16(p: &radiotap_header->it_len); |
116 | iterator->_arg_index = 0; |
117 | iterator->_bitmap_shifter = get_unaligned_le32(p: &radiotap_header->it_present); |
118 | iterator->_arg = (uint8_t *)radiotap_header->it_optional; |
119 | iterator->_reset_on_ext = 0; |
120 | iterator->_next_bitmap = radiotap_header->it_optional; |
121 | iterator->_vns = vns; |
122 | iterator->current_namespace = &radiotap_ns; |
123 | iterator->is_radiotap_ns = 1; |
124 | |
125 | /* find payload start allowing for extended bitmap(s) */ |
126 | |
127 | if (iterator->_bitmap_shifter & (BIT(IEEE80211_RADIOTAP_EXT))) { |
128 | if ((unsigned long)iterator->_arg - |
129 | (unsigned long)iterator->_rtheader + sizeof(uint32_t) > |
130 | (unsigned long)iterator->_max_length) |
131 | return -EINVAL; |
132 | while (get_unaligned_le32(p: iterator->_arg) & |
133 | (BIT(IEEE80211_RADIOTAP_EXT))) { |
134 | iterator->_arg += sizeof(uint32_t); |
135 | |
136 | /* |
137 | * check for insanity where the present bitmaps |
138 | * keep claiming to extend up to or even beyond the |
139 | * stated radiotap header length |
140 | */ |
141 | |
142 | if ((unsigned long)iterator->_arg - |
143 | (unsigned long)iterator->_rtheader + |
144 | sizeof(uint32_t) > |
145 | (unsigned long)iterator->_max_length) |
146 | return -EINVAL; |
147 | } |
148 | |
149 | iterator->_arg += sizeof(uint32_t); |
150 | |
151 | /* |
152 | * no need to check again for blowing past stated radiotap |
153 | * header length, because ieee80211_radiotap_iterator_next |
154 | * checks it before it is dereferenced |
155 | */ |
156 | } |
157 | |
158 | iterator->this_arg = iterator->_arg; |
159 | |
160 | /* we are all initialized happily */ |
161 | |
162 | return 0; |
163 | } |
164 | EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); |
165 | |
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 | |
188 | |
189 | /** |
190 | * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg |
191 | * @iterator: radiotap_iterator to move to next arg (if any) |
192 | * |
193 | * Returns: 0 if there is an argument to handle, |
194 | * -ENOENT if there are no more args or -EINVAL |
195 | * if there is something else wrong. |
196 | * |
197 | * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) |
198 | * in @this_arg_index and sets @this_arg to point to the |
199 | * payload for the field. It takes care of alignment handling and extended |
200 | * present fields. @this_arg can be changed by the caller (eg, |
201 | * incremented to move inside a compound argument like |
202 | * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in |
203 | * little-endian format whatever the endianess of your CPU. |
204 | * |
205 | * Alignment Gotcha: |
206 | * You must take care when dereferencing iterator.this_arg |
207 | * for multibyte types... the pointer is not aligned. Use |
208 | * get_unaligned((type *)iterator.this_arg) to dereference |
209 | * iterator.this_arg for type "type" safely on all arches. |
210 | */ |
211 | |
212 | int ieee80211_radiotap_iterator_next( |
213 | struct ieee80211_radiotap_iterator *iterator) |
214 | { |
215 | while (1) { |
216 | int hit = 0; |
217 | int pad, align, size, subns; |
218 | uint32_t oui; |
219 | |
220 | /* if no more EXT bits, that's it */ |
221 | if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && |
222 | !(iterator->_bitmap_shifter & 1)) |
223 | return -ENOENT; |
224 | |
225 | if (!(iterator->_bitmap_shifter & 1)) |
226 | goto next_entry; /* arg not present */ |
227 | |
228 | /* get alignment/size of data */ |
229 | switch (iterator->_arg_index % 32) { |
230 | case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: |
231 | case IEEE80211_RADIOTAP_EXT: |
232 | align = 1; |
233 | size = 0; |
234 | break; |
235 | case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: |
236 | align = 2; |
237 | size = 6; |
238 | break; |
239 | default: |
240 | if (!iterator->current_namespace || |
241 | iterator->_arg_index >= iterator->current_namespace->n_bits) { |
242 | if (iterator->current_namespace == &radiotap_ns) |
243 | return -ENOENT; |
244 | align = 0; |
245 | } else { |
246 | align = iterator->current_namespace->align_size[iterator->_arg_index].align; |
247 | size = iterator->current_namespace->align_size[iterator->_arg_index].size; |
248 | } |
249 | if (!align) { |
250 | /* skip all subsequent data */ |
251 | iterator->_arg = iterator->_next_ns_data; |
252 | /* give up on this namespace */ |
253 | iterator->current_namespace = NULL; |
254 | goto next_entry; |
255 | } |
256 | break; |
257 | } |
258 | |
259 | /* |
260 | * arg is present, account for alignment padding |
261 | * |
262 | * Note that these alignments are relative to the start |
263 | * of the radiotap header. There is no guarantee |
264 | * that the radiotap header itself is aligned on any |
265 | * kind of boundary. |
266 | * |
267 | * The above is why get_unaligned() is used to dereference |
268 | * multibyte elements from the radiotap area. |
269 | */ |
270 | |
271 | pad = ((unsigned long)iterator->_arg - |
272 | (unsigned long)iterator->_rtheader) & (align - 1); |
273 | |
274 | if (pad) |
275 | iterator->_arg += align - pad; |
276 | |
277 | if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { |
278 | int vnslen; |
279 | |
280 | if ((unsigned long)iterator->_arg + size - |
281 | (unsigned long)iterator->_rtheader > |
282 | (unsigned long)iterator->_max_length) |
283 | return -EINVAL; |
284 | |
285 | oui = (*iterator->_arg << 16) | |
286 | (*(iterator->_arg + 1) << 8) | |
287 | *(iterator->_arg + 2); |
288 | subns = *(iterator->_arg + 3); |
289 | |
290 | find_ns(iterator, oui, subns); |
291 | |
292 | vnslen = get_unaligned_le16(p: iterator->_arg + 4); |
293 | iterator->_next_ns_data = iterator->_arg + size + vnslen; |
294 | if (!iterator->current_namespace) |
295 | size += vnslen; |
296 | } |
297 | |
298 | /* |
299 | * this is what we will return to user, but we need to |
300 | * move on first so next call has something fresh to test |
301 | */ |
302 | iterator->this_arg_index = iterator->_arg_index; |
303 | iterator->this_arg = iterator->_arg; |
304 | iterator->this_arg_size = size; |
305 | |
306 | /* internally move on the size of this arg */ |
307 | iterator->_arg += size; |
308 | |
309 | /* |
310 | * check for insanity where we are given a bitmap that |
311 | * claims to have more arg content than the length of the |
312 | * radiotap section. We will normally end up equalling this |
313 | * max_length on the last arg, never exceeding it. |
314 | */ |
315 | |
316 | if ((unsigned long)iterator->_arg - |
317 | (unsigned long)iterator->_rtheader > |
318 | (unsigned long)iterator->_max_length) |
319 | return -EINVAL; |
320 | |
321 | /* these special ones are valid in each bitmap word */ |
322 | switch (iterator->_arg_index % 32) { |
323 | case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: |
324 | iterator->_reset_on_ext = 1; |
325 | |
326 | iterator->is_radiotap_ns = 0; |
327 | /* |
328 | * If parser didn't register this vendor |
329 | * namespace with us, allow it to show it |
330 | * as 'raw. Do do that, set argument index |
331 | * to vendor namespace. |
332 | */ |
333 | iterator->this_arg_index = |
334 | IEEE80211_RADIOTAP_VENDOR_NAMESPACE; |
335 | if (!iterator->current_namespace) |
336 | hit = 1; |
337 | goto next_entry; |
338 | case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: |
339 | iterator->_reset_on_ext = 1; |
340 | iterator->current_namespace = &radiotap_ns; |
341 | iterator->is_radiotap_ns = 1; |
342 | goto next_entry; |
343 | case IEEE80211_RADIOTAP_EXT: |
344 | /* |
345 | * bit 31 was set, there is more |
346 | * -- move to next u32 bitmap |
347 | */ |
348 | iterator->_bitmap_shifter = |
349 | get_unaligned_le32(p: iterator->_next_bitmap); |
350 | iterator->_next_bitmap++; |
351 | if (iterator->_reset_on_ext) |
352 | iterator->_arg_index = 0; |
353 | else |
354 | iterator->_arg_index++; |
355 | iterator->_reset_on_ext = 0; |
356 | break; |
357 | default: |
358 | /* we've got a hit! */ |
359 | hit = 1; |
360 | next_entry: |
361 | iterator->_bitmap_shifter >>= 1; |
362 | iterator->_arg_index++; |
363 | } |
364 | |
365 | /* if we found a valid arg earlier, return it now */ |
366 | if (hit) |
367 | return 0; |
368 | } |
369 | } |
370 | EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); |
371 | |