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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 <net/cfg80211.h> |
18 | #include <net/ieee80211_radiotap.h> |
19 | #include <asm/unaligned.h> |
20 | |
21 | /* function prototypes and related defs are in include/net/cfg80211.h */ |
22 | |
23 | static const struct radiotap_align_size rtap_namespace_sizes[] = { |
24 | [IEEE80211_RADIOTAP_TSFT] = { .align = 8, .size = 8, }, |
25 | [IEEE80211_RADIOTAP_FLAGS] = { .align = 1, .size = 1, }, |
26 | [IEEE80211_RADIOTAP_RATE] = { .align = 1, .size = 1, }, |
27 | [IEEE80211_RADIOTAP_CHANNEL] = { .align = 2, .size = 4, }, |
28 | [IEEE80211_RADIOTAP_FHSS] = { .align = 2, .size = 2, }, |
29 | [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = { .align = 1, .size = 1, }, |
30 | [IEEE80211_RADIOTAP_DBM_ANTNOISE] = { .align = 1, .size = 1, }, |
31 | [IEEE80211_RADIOTAP_LOCK_QUALITY] = { .align = 2, .size = 2, }, |
32 | [IEEE80211_RADIOTAP_TX_ATTENUATION] = { .align = 2, .size = 2, }, |
33 | [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = { .align = 2, .size = 2, }, |
34 | [IEEE80211_RADIOTAP_DBM_TX_POWER] = { .align = 1, .size = 1, }, |
35 | [IEEE80211_RADIOTAP_ANTENNA] = { .align = 1, .size = 1, }, |
36 | [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = { .align = 1, .size = 1, }, |
37 | [IEEE80211_RADIOTAP_DB_ANTNOISE] = { .align = 1, .size = 1, }, |
38 | [IEEE80211_RADIOTAP_RX_FLAGS] = { .align = 2, .size = 2, }, |
39 | [IEEE80211_RADIOTAP_TX_FLAGS] = { .align = 2, .size = 2, }, |
40 | [IEEE80211_RADIOTAP_RTS_RETRIES] = { .align = 1, .size = 1, }, |
41 | [IEEE80211_RADIOTAP_DATA_RETRIES] = { .align = 1, .size = 1, }, |
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: |
88 | * See Documentation/networking/radiotap-headers.txt |
89 | */ |
90 | |
91 | int ieee80211_radiotap_iterator_init( |
92 | struct ieee80211_radiotap_iterator *iterator, |
93 | struct ieee80211_radiotap_header *radiotap_header, |
94 | int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns) |
95 | { |
96 | /* Linux only supports version 0 radiotap format */ |
97 | if (radiotap_header->it_version) |
98 | return -EINVAL; |
99 | |
100 | /* sanity check for allowed length and radiotap length field */ |
101 | if (max_length < get_unaligned_le16(&radiotap_header->it_len)) |
102 | return -EINVAL; |
103 | |
104 | iterator->_rtheader = radiotap_header; |
105 | iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len); |
106 | iterator->_arg_index = 0; |
107 | iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present); |
108 | iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header); |
109 | iterator->_reset_on_ext = 0; |
110 | iterator->_next_bitmap = &radiotap_header->it_present; |
111 | iterator->_next_bitmap++; |
112 | iterator->_vns = vns; |
113 | iterator->current_namespace = &radiotap_ns; |
114 | iterator->is_radiotap_ns = 1; |
115 | |
116 | /* find payload start allowing for extended bitmap(s) */ |
117 | |
118 | if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { |
119 | while (get_unaligned_le32(iterator->_arg) & |
120 | (1 << IEEE80211_RADIOTAP_EXT)) { |
121 | iterator->_arg += sizeof(uint32_t); |
122 | |
123 | /* |
124 | * check for insanity where the present bitmaps |
125 | * keep claiming to extend up to or even beyond the |
126 | * stated radiotap header length |
127 | */ |
128 | |
129 | if ((unsigned long)iterator->_arg - |
130 | (unsigned long)iterator->_rtheader > |
131 | (unsigned long)iterator->_max_length) |
132 | return -EINVAL; |
133 | } |
134 | |
135 | iterator->_arg += sizeof(uint32_t); |
136 | |
137 | /* |
138 | * no need to check again for blowing past stated radiotap |
139 | * header length, because ieee80211_radiotap_iterator_next |
140 | * checks it before it is dereferenced |
141 | */ |
142 | } |
143 | |
144 | iterator->this_arg = iterator->_arg; |
145 | |
146 | /* we are all initialized happily */ |
147 | |
148 | return 0; |
149 | } |
150 | EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); |
151 | |
152 | static void find_ns(struct ieee80211_radiotap_iterator *iterator, |
153 | uint32_t oui, uint8_t subns) |
154 | { |
155 | int i; |
156 | |
157 | iterator->current_namespace = NULL; |
158 | |
159 | if (!iterator->_vns) |
160 | return; |
161 | |
162 | for (i = 0; i < iterator->_vns->n_ns; i++) { |
163 | if (iterator->_vns->ns[i].oui != oui) |
164 | continue; |
165 | if (iterator->_vns->ns[i].subns != subns) |
166 | continue; |
167 | |
168 | iterator->current_namespace = &iterator->_vns->ns[i]; |
169 | break; |
170 | } |
171 | } |
172 | |
173 | |
174 | |
175 | /** |
176 | * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg |
177 | * @iterator: radiotap_iterator to move to next arg (if any) |
178 | * |
179 | * Returns: 0 if there is an argument to handle, |
180 | * -ENOENT if there are no more args or -EINVAL |
181 | * if there is something else wrong. |
182 | * |
183 | * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) |
184 | * in @this_arg_index and sets @this_arg to point to the |
185 | * payload for the field. It takes care of alignment handling and extended |
186 | * present fields. @this_arg can be changed by the caller (eg, |
187 | * incremented to move inside a compound argument like |
188 | * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in |
189 | * little-endian format whatever the endianess of your CPU. |
190 | * |
191 | * Alignment Gotcha: |
192 | * You must take care when dereferencing iterator.this_arg |
193 | * for multibyte types... the pointer is not aligned. Use |
194 | * get_unaligned((type *)iterator.this_arg) to dereference |
195 | * iterator.this_arg for type "type" safely on all arches. |
196 | */ |
197 | |
198 | int ieee80211_radiotap_iterator_next( |
199 | struct ieee80211_radiotap_iterator *iterator) |
200 | { |
201 | while (1) { |
202 | int hit = 0; |
203 | int pad, align, size, subns, vnslen; |
204 | uint32_t oui; |
205 | |
206 | /* if no more EXT bits, that's it */ |
207 | if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && |
208 | !(iterator->_bitmap_shifter & 1)) |
209 | return -ENOENT; |
210 | |
211 | if (!(iterator->_bitmap_shifter & 1)) |
212 | goto next_entry; /* arg not present */ |
213 | |
214 | /* get alignment/size of data */ |
215 | switch (iterator->_arg_index % 32) { |
216 | case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: |
217 | case IEEE80211_RADIOTAP_EXT: |
218 | align = 1; |
219 | size = 0; |
220 | break; |
221 | case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: |
222 | align = 2; |
223 | size = 6; |
224 | break; |
225 | default: |
226 | if (!iterator->current_namespace || |
227 | iterator->_arg_index >= iterator->current_namespace->n_bits) { |
228 | if (iterator->current_namespace == &radiotap_ns) |
229 | return -ENOENT; |
230 | align = 0; |
231 | } else { |
232 | align = iterator->current_namespace->align_size[iterator->_arg_index].align; |
233 | size = iterator->current_namespace->align_size[iterator->_arg_index].size; |
234 | } |
235 | if (!align) { |
236 | /* skip all subsequent data */ |
237 | iterator->_arg = iterator->_next_ns_data; |
238 | /* give up on this namespace */ |
239 | iterator->current_namespace = NULL; |
240 | goto next_entry; |
241 | } |
242 | break; |
243 | } |
244 | |
245 | /* |
246 | * arg is present, account for alignment padding |
247 | * |
248 | * Note that these alignments are relative to the start |
249 | * of the radiotap header. There is no guarantee |
250 | * that the radiotap header itself is aligned on any |
251 | * kind of boundary. |
252 | * |
253 | * The above is why get_unaligned() is used to dereference |
254 | * multibyte elements from the radiotap area. |
255 | */ |
256 | |
257 | pad = ((unsigned long)iterator->_arg - |
258 | (unsigned long)iterator->_rtheader) & (align - 1); |
259 | |
260 | if (pad) |
261 | iterator->_arg += align - pad; |
262 | |
263 | /* |
264 | * this is what we will return to user, but we need to |
265 | * move on first so next call has something fresh to test |
266 | */ |
267 | iterator->this_arg_index = iterator->_arg_index; |
268 | iterator->this_arg = iterator->_arg; |
269 | iterator->this_arg_size = size; |
270 | |
271 | /* internally move on the size of this arg */ |
272 | iterator->_arg += size; |
273 | |
274 | /* |
275 | * check for insanity where we are given a bitmap that |
276 | * claims to have more arg content than the length of the |
277 | * radiotap section. We will normally end up equalling this |
278 | * max_length on the last arg, never exceeding it. |
279 | */ |
280 | |
281 | if ((unsigned long)iterator->_arg - |
282 | (unsigned long)iterator->_rtheader > |
283 | (unsigned long)iterator->_max_length) |
284 | return -EINVAL; |
285 | |
286 | /* these special ones are valid in each bitmap word */ |
287 | switch (iterator->_arg_index % 32) { |
288 | case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: |
289 | iterator->_bitmap_shifter >>= 1; |
290 | iterator->_arg_index++; |
291 | |
292 | iterator->_reset_on_ext = 1; |
293 | |
294 | vnslen = get_unaligned_le16(iterator->this_arg + 4); |
295 | iterator->_next_ns_data = iterator->_arg + vnslen; |
296 | oui = (*iterator->this_arg << 16) | |
297 | (*(iterator->this_arg + 1) << 8) | |
298 | *(iterator->this_arg + 2); |
299 | subns = *(iterator->this_arg + 3); |
300 | |
301 | find_ns(iterator, oui, subns); |
302 | |
303 | iterator->is_radiotap_ns = 0; |
304 | /* allow parsers to show this information */ |
305 | iterator->this_arg_index = |
306 | IEEE80211_RADIOTAP_VENDOR_NAMESPACE; |
307 | iterator->this_arg_size += vnslen; |
308 | if ((unsigned long)iterator->this_arg + |
309 | iterator->this_arg_size - |
310 | (unsigned long)iterator->_rtheader > |
311 | (unsigned long)(unsigned long)iterator->_max_length) |
312 | return -EINVAL; |
313 | hit = 1; |
314 | break; |
315 | case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: |
316 | iterator->_bitmap_shifter >>= 1; |
317 | iterator->_arg_index++; |
318 | |
319 | iterator->_reset_on_ext = 1; |
320 | iterator->current_namespace = &radiotap_ns; |
321 | iterator->is_radiotap_ns = 1; |
322 | break; |
323 | case IEEE80211_RADIOTAP_EXT: |
324 | /* |
325 | * bit 31 was set, there is more |
326 | * -- move to next u32 bitmap |
327 | */ |
328 | iterator->_bitmap_shifter = |
329 | get_unaligned_le32(iterator->_next_bitmap); |
330 | iterator->_next_bitmap++; |
331 | if (iterator->_reset_on_ext) |
332 | iterator->_arg_index = 0; |
333 | else |
334 | iterator->_arg_index++; |
335 | iterator->_reset_on_ext = 0; |
336 | break; |
337 | default: |
338 | /* we've got a hit! */ |
339 | hit = 1; |
340 | next_entry: |
341 | iterator->_bitmap_shifter >>= 1; |
342 | iterator->_arg_index++; |
343 | } |
344 | |
345 | /* if we found a valid arg earlier, return it now */ |
346 | if (hit) |
347 | return 0; |
348 | } |
349 | } |
350 | EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); |
351 |
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