xref: /openbmc/linux/net/wireless/radiotap.c (revision 36fe4655)
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 *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(&radiotap_header->it_len))
112 		return -EINVAL;
113 
114 	iterator->_rtheader = radiotap_header;
115 	iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len);
116 	iterator->_arg_index = 0;
117 	iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present);
118 	iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header);
119 	iterator->_reset_on_ext = 0;
120 	iterator->_next_bitmap = &radiotap_header->it_present;
121 	iterator->_next_bitmap++;
122 	iterator->_vns = vns;
123 	iterator->current_namespace = &radiotap_ns;
124 	iterator->is_radiotap_ns = 1;
125 
126 	/* find payload start allowing for extended bitmap(s) */
127 
128 	if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) {
129 		if ((unsigned long)iterator->_arg -
130 		    (unsigned long)iterator->_rtheader + sizeof(uint32_t) >
131 		    (unsigned long)iterator->_max_length)
132 			return -EINVAL;
133 		while (get_unaligned_le32(iterator->_arg) &
134 					(1 << IEEE80211_RADIOTAP_EXT)) {
135 			iterator->_arg += sizeof(uint32_t);
136 
137 			/*
138 			 * check for insanity where the present bitmaps
139 			 * keep claiming to extend up to or even beyond the
140 			 * stated radiotap header length
141 			 */
142 
143 			if ((unsigned long)iterator->_arg -
144 			    (unsigned long)iterator->_rtheader +
145 			    sizeof(uint32_t) >
146 			    (unsigned long)iterator->_max_length)
147 				return -EINVAL;
148 		}
149 
150 		iterator->_arg += sizeof(uint32_t);
151 
152 		/*
153 		 * no need to check again for blowing past stated radiotap
154 		 * header length, because ieee80211_radiotap_iterator_next
155 		 * checks it before it is dereferenced
156 		 */
157 	}
158 
159 	iterator->this_arg = iterator->_arg;
160 
161 	/* we are all initialized happily */
162 
163 	return 0;
164 }
165 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
166 
167 static void find_ns(struct ieee80211_radiotap_iterator *iterator,
168 		    uint32_t oui, uint8_t subns)
169 {
170 	int i;
171 
172 	iterator->current_namespace = NULL;
173 
174 	if (!iterator->_vns)
175 		return;
176 
177 	for (i = 0; i < iterator->_vns->n_ns; i++) {
178 		if (iterator->_vns->ns[i].oui != oui)
179 			continue;
180 		if (iterator->_vns->ns[i].subns != subns)
181 			continue;
182 
183 		iterator->current_namespace = &iterator->_vns->ns[i];
184 		break;
185 	}
186 }
187 
188 
189 
190 /**
191  * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
192  * @iterator: radiotap_iterator to move to next arg (if any)
193  *
194  * Returns: 0 if there is an argument to handle,
195  * -ENOENT if there are no more args or -EINVAL
196  * if there is something else wrong.
197  *
198  * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
199  * in @this_arg_index and sets @this_arg to point to the
200  * payload for the field.  It takes care of alignment handling and extended
201  * present fields.  @this_arg can be changed by the caller (eg,
202  * incremented to move inside a compound argument like
203  * IEEE80211_RADIOTAP_CHANNEL).  The args pointed to are in
204  * little-endian format whatever the endianess of your CPU.
205  *
206  * Alignment Gotcha:
207  * You must take care when dereferencing iterator.this_arg
208  * for multibyte types... the pointer is not aligned.  Use
209  * get_unaligned((type *)iterator.this_arg) to dereference
210  * iterator.this_arg for type "type" safely on all arches.
211  */
212 
213 int ieee80211_radiotap_iterator_next(
214 	struct ieee80211_radiotap_iterator *iterator)
215 {
216 	while (1) {
217 		int hit = 0;
218 		int pad, align, size, subns;
219 		uint32_t oui;
220 
221 		/* if no more EXT bits, that's it */
222 		if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT &&
223 		    !(iterator->_bitmap_shifter & 1))
224 			return -ENOENT;
225 
226 		if (!(iterator->_bitmap_shifter & 1))
227 			goto next_entry; /* arg not present */
228 
229 		/* get alignment/size of data */
230 		switch (iterator->_arg_index % 32) {
231 		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
232 		case IEEE80211_RADIOTAP_EXT:
233 			align = 1;
234 			size = 0;
235 			break;
236 		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
237 			align = 2;
238 			size = 6;
239 			break;
240 		default:
241 			if (!iterator->current_namespace ||
242 			    iterator->_arg_index >= iterator->current_namespace->n_bits) {
243 				if (iterator->current_namespace == &radiotap_ns)
244 					return -ENOENT;
245 				align = 0;
246 			} else {
247 				align = iterator->current_namespace->align_size[iterator->_arg_index].align;
248 				size = iterator->current_namespace->align_size[iterator->_arg_index].size;
249 			}
250 			if (!align) {
251 				/* skip all subsequent data */
252 				iterator->_arg = iterator->_next_ns_data;
253 				/* give up on this namespace */
254 				iterator->current_namespace = NULL;
255 				goto next_entry;
256 			}
257 			break;
258 		}
259 
260 		/*
261 		 * arg is present, account for alignment padding
262 		 *
263 		 * Note that these alignments are relative to the start
264 		 * of the radiotap header.  There is no guarantee
265 		 * that the radiotap header itself is aligned on any
266 		 * kind of boundary.
267 		 *
268 		 * The above is why get_unaligned() is used to dereference
269 		 * multibyte elements from the radiotap area.
270 		 */
271 
272 		pad = ((unsigned long)iterator->_arg -
273 		       (unsigned long)iterator->_rtheader) & (align - 1);
274 
275 		if (pad)
276 			iterator->_arg += align - pad;
277 
278 		if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) {
279 			int vnslen;
280 
281 			if ((unsigned long)iterator->_arg + size -
282 			    (unsigned long)iterator->_rtheader >
283 			    (unsigned long)iterator->_max_length)
284 				return -EINVAL;
285 
286 			oui = (*iterator->_arg << 16) |
287 				(*(iterator->_arg + 1) << 8) |
288 				*(iterator->_arg + 2);
289 			subns = *(iterator->_arg + 3);
290 
291 			find_ns(iterator, oui, subns);
292 
293 			vnslen = get_unaligned_le16(iterator->_arg + 4);
294 			iterator->_next_ns_data = iterator->_arg + size + vnslen;
295 			if (!iterator->current_namespace)
296 				size += vnslen;
297 		}
298 
299 		/*
300 		 * this is what we will return to user, but we need to
301 		 * move on first so next call has something fresh to test
302 		 */
303 		iterator->this_arg_index = iterator->_arg_index;
304 		iterator->this_arg = iterator->_arg;
305 		iterator->this_arg_size = size;
306 
307 		/* internally move on the size of this arg */
308 		iterator->_arg += size;
309 
310 		/*
311 		 * check for insanity where we are given a bitmap that
312 		 * claims to have more arg content than the length of the
313 		 * radiotap section.  We will normally end up equalling this
314 		 * max_length on the last arg, never exceeding it.
315 		 */
316 
317 		if ((unsigned long)iterator->_arg -
318 		    (unsigned long)iterator->_rtheader >
319 		    (unsigned long)iterator->_max_length)
320 			return -EINVAL;
321 
322 		/* these special ones are valid in each bitmap word */
323 		switch (iterator->_arg_index % 32) {
324 		case IEEE80211_RADIOTAP_VENDOR_NAMESPACE:
325 			iterator->_reset_on_ext = 1;
326 
327 			iterator->is_radiotap_ns = 0;
328 			/*
329 			 * If parser didn't register this vendor
330 			 * namespace with us, allow it to show it
331 			 * as 'raw. Do do that, set argument index
332 			 * to vendor namespace.
333 			 */
334 			iterator->this_arg_index =
335 				IEEE80211_RADIOTAP_VENDOR_NAMESPACE;
336 			if (!iterator->current_namespace)
337 				hit = 1;
338 			goto next_entry;
339 		case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE:
340 			iterator->_reset_on_ext = 1;
341 			iterator->current_namespace = &radiotap_ns;
342 			iterator->is_radiotap_ns = 1;
343 			goto next_entry;
344 		case IEEE80211_RADIOTAP_EXT:
345 			/*
346 			 * bit 31 was set, there is more
347 			 * -- move to next u32 bitmap
348 			 */
349 			iterator->_bitmap_shifter =
350 				get_unaligned_le32(iterator->_next_bitmap);
351 			iterator->_next_bitmap++;
352 			if (iterator->_reset_on_ext)
353 				iterator->_arg_index = 0;
354 			else
355 				iterator->_arg_index++;
356 			iterator->_reset_on_ext = 0;
357 			break;
358 		default:
359 			/* we've got a hit! */
360 			hit = 1;
361  next_entry:
362 			iterator->_bitmap_shifter >>= 1;
363 			iterator->_arg_index++;
364 		}
365 
366 		/* if we found a valid arg earlier, return it now */
367 		if (hit)
368 			return 0;
369 	}
370 }
371 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
372