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
21static 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
47static 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
90int 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
163static 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
185static 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
231int 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