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-rw-r--r--Documentation/networking/radiotap-headers.txt65
-rw-r--r--include/net/cfg80211.h38
-rw-r--r--net/wireless/Makefile2
-rw-r--r--net/wireless/radiotap.c257
4 files changed, 361 insertions, 1 deletions
diff --git a/Documentation/networking/radiotap-headers.txt b/Documentation/networking/radiotap-headers.txt
index e29e027d9be3..953331c7984f 100644
--- a/Documentation/networking/radiotap-headers.txt
+++ b/Documentation/networking/radiotap-headers.txt
@@ -84,4 +84,69 @@ Example valid radiotap header
84 0x01 //<-- antenna 84 0x01 //<-- antenna
85 85
86 86
87Using the Radiotap Parser
88-------------------------
89
90If you are having to parse a radiotap struct, you can radically simplify the
91job by using the radiotap parser that lives in net/wireless/radiotap.c and has
92its prototypes available in include/net/cfg80211.h. You use it like this:
93
94#include <net/cfg80211.h>
95
96/* buf points to the start of the radiotap header part */
97
98int MyFunction(u8 * buf, int buflen)
99{
100 int pkt_rate_100kHz = 0, antenna = 0, pwr = 0;
101 struct ieee80211_radiotap_iterator iterator;
102 int ret = ieee80211_radiotap_iterator_init(&iterator, buf, buflen);
103
104 while (!ret) {
105
106 ret = ieee80211_radiotap_iterator_next(&iterator);
107
108 if (ret)
109 continue;
110
111 /* see if this argument is something we can use */
112
113 switch (iterator.this_arg_index) {
114 /*
115 * You must take care when dereferencing iterator.this_arg
116 * for multibyte types... the pointer is not aligned. Use
117 * get_unaligned((type *)iterator.this_arg) to dereference
118 * iterator.this_arg for type "type" safely on all arches.
119 */
120 case IEEE80211_RADIOTAP_RATE:
121 /* radiotap "rate" u8 is in
122 * 500kbps units, eg, 0x02=1Mbps
123 */
124 pkt_rate_100kHz = (*iterator.this_arg) * 5;
125 break;
126
127 case IEEE80211_RADIOTAP_ANTENNA:
128 /* radiotap uses 0 for 1st ant */
129 antenna = *iterator.this_arg);
130 break;
131
132 case IEEE80211_RADIOTAP_DBM_TX_POWER:
133 pwr = *iterator.this_arg;
134 break;
135
136 default:
137 break;
138 }
139 } /* while more rt headers */
140
141 if (ret != -ENOENT)
142 return TXRX_DROP;
143
144 /* discard the radiotap header part */
145 buf += iterator.max_length;
146 buflen -= iterator.max_length;
147
148 ...
149
150}
151
87Andy Green <andy@warmcat.com> 152Andy Green <andy@warmcat.com>
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 88171f8ce58a..7edaef6b29d6 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -11,6 +11,44 @@
11 * Copyright 2006 Johannes Berg <johannes@sipsolutions.net> 11 * Copyright 2006 Johannes Berg <johannes@sipsolutions.net>
12 */ 12 */
13 13
14
15/* Radiotap header iteration
16 * implemented in net/wireless/radiotap.c
17 * docs in Documentation/networking/radiotap-headers.txt
18 */
19/**
20 * struct ieee80211_radiotap_iterator - tracks walk thru present radiotap args
21 * @rtheader: pointer to the radiotap header we are walking through
22 * @max_length: length of radiotap header in cpu byte ordering
23 * @this_arg_index: IEEE80211_RADIOTAP_... index of current arg
24 * @this_arg: pointer to current radiotap arg
25 * @arg_index: internal next argument index
26 * @arg: internal next argument pointer
27 * @next_bitmap: internal pointer to next present u32
28 * @bitmap_shifter: internal shifter for curr u32 bitmap, b0 set == arg present
29 */
30
31struct ieee80211_radiotap_iterator {
32 struct ieee80211_radiotap_header *rtheader;
33 int max_length;
34 int this_arg_index;
35 u8 *this_arg;
36
37 int arg_index;
38 u8 *arg;
39 __le32 *next_bitmap;
40 u32 bitmap_shifter;
41};
42
43extern int ieee80211_radiotap_iterator_init(
44 struct ieee80211_radiotap_iterator *iterator,
45 struct ieee80211_radiotap_header *radiotap_header,
46 int max_length);
47
48extern int ieee80211_radiotap_iterator_next(
49 struct ieee80211_radiotap_iterator *iterator);
50
51
14/* from net/wireless.h */ 52/* from net/wireless.h */
15struct wiphy; 53struct wiphy;
16 54
diff --git a/net/wireless/Makefile b/net/wireless/Makefile
index 3a96ae60271c..092116e390b6 100644
--- a/net/wireless/Makefile
+++ b/net/wireless/Makefile
@@ -1,4 +1,4 @@
1obj-$(CONFIG_WIRELESS_EXT) += wext.o 1obj-$(CONFIG_WIRELESS_EXT) += wext.o
2obj-$(CONFIG_CFG80211) += cfg80211.o 2obj-$(CONFIG_CFG80211) += cfg80211.o
3 3
4cfg80211-y += core.o sysfs.o 4cfg80211-y += core.o sysfs.o radiotap.o
diff --git a/net/wireless/radiotap.c b/net/wireless/radiotap.c
new file mode 100644
index 000000000000..68c11d099917
--- /dev/null
+++ b/net/wireless/radiotap.c
@@ -0,0 +1,257 @@
1/*
2 * Radiotap parser
3 *
4 * Copyright 2007 Andy Green <andy@warmcat.com>
5 */
6
7#include <net/cfg80211.h>
8#include <net/ieee80211_radiotap.h>
9#include <asm/unaligned.h>
10
11/* function prototypes and related defs are in include/net/cfg80211.h */
12
13/**
14 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization
15 * @iterator: radiotap_iterator to initialize
16 * @radiotap_header: radiotap header to parse
17 * @max_length: total length we can parse into (eg, whole packet length)
18 *
19 * Returns: 0 or a negative error code if there is a problem.
20 *
21 * This function initializes an opaque iterator struct which can then
22 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap
23 * argument which is present in the header. It knows about extended
24 * present headers and handles them.
25 *
26 * How to use:
27 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator
28 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand)
29 * checking for a good 0 return code. Then loop calling
30 * __ieee80211_radiotap_iterator_next()... it returns either 0,
31 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.
32 * The iterator's @this_arg member points to the start of the argument
33 * associated with the current argument index that is present, which can be
34 * found in the iterator's @this_arg_index member. This arg index corresponds
35 * to the IEEE80211_RADIOTAP_... defines.
36 *
37 * Radiotap header length:
38 * You can find the CPU-endian total radiotap header length in
39 * iterator->max_length after executing ieee80211_radiotap_iterator_init()
40 * successfully.
41 *
42 * Alignment Gotcha:
43 * You must take care when dereferencing iterator.this_arg
44 * for multibyte types... the pointer is not aligned. Use
45 * get_unaligned((type *)iterator.this_arg) to dereference
46 * iterator.this_arg for type "type" safely on all arches.
47 *
48 * Example code:
49 * See Documentation/networking/radiotap-headers.txt
50 */
51
52int ieee80211_radiotap_iterator_init(
53 struct ieee80211_radiotap_iterator *iterator,
54 struct ieee80211_radiotap_header *radiotap_header,
55 int max_length)
56{
57 /* Linux only supports version 0 radiotap format */
58 if (radiotap_header->it_version)
59 return -EINVAL;
60
61 /* sanity check for allowed length and radiotap length field */
62 if (max_length < le16_to_cpu(get_unaligned(&radiotap_header->it_len)))
63 return -EINVAL;
64
65 iterator->rtheader = radiotap_header;
66 iterator->max_length = le16_to_cpu(get_unaligned(
67 &radiotap_header->it_len));
68 iterator->arg_index = 0;
69 iterator->bitmap_shifter = le32_to_cpu(get_unaligned(
70 &radiotap_header->it_present));
71 iterator->arg = (u8 *)radiotap_header + sizeof(*radiotap_header);
72 iterator->this_arg = NULL;
73
74 /* find payload start allowing for extended bitmap(s) */
75
76 if (unlikely(iterator->bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT))) {
77 while (le32_to_cpu(get_unaligned((__le32 *)iterator->arg)) &
78 (1<<IEEE80211_RADIOTAP_EXT)) {
79 iterator->arg += sizeof(u32);
80
81 /*
82 * check for insanity where the present bitmaps
83 * keep claiming to extend up to or even beyond the
84 * stated radiotap header length
85 */
86
87 if (((ulong)iterator->arg -
88 (ulong)iterator->rtheader) > iterator->max_length)
89 return -EINVAL;
90 }
91
92 iterator->arg += sizeof(u32);
93
94 /*
95 * no need to check again for blowing past stated radiotap
96 * header length, because ieee80211_radiotap_iterator_next
97 * checks it before it is dereferenced
98 */
99 }
100
101 /* we are all initialized happily */
102
103 return 0;
104}
105EXPORT_SYMBOL(ieee80211_radiotap_iterator_init);
106
107
108/**
109 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg
110 * @iterator: radiotap_iterator to move to next arg (if any)
111 *
112 * Returns: 0 if there is an argument to handle,
113 * -ENOENT if there are no more args or -EINVAL
114 * if there is something else wrong.
115 *
116 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*)
117 * in @this_arg_index and sets @this_arg to point to the
118 * payload for the field. It takes care of alignment handling and extended
119 * present fields. @this_arg can be changed by the caller (eg,
120 * incremented to move inside a compound argument like
121 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in
122 * little-endian format whatever the endianess of your CPU.
123 *
124 * Alignment Gotcha:
125 * You must take care when dereferencing iterator.this_arg
126 * for multibyte types... the pointer is not aligned. Use
127 * get_unaligned((type *)iterator.this_arg) to dereference
128 * iterator.this_arg for type "type" safely on all arches.
129 */
130
131int ieee80211_radiotap_iterator_next(
132 struct ieee80211_radiotap_iterator *iterator)
133{
134
135 /*
136 * small length lookup table for all radiotap types we heard of
137 * starting from b0 in the bitmap, so we can walk the payload
138 * area of the radiotap header
139 *
140 * There is a requirement to pad args, so that args
141 * of a given length must begin at a boundary of that length
142 * -- but note that compound args are allowed (eg, 2 x u16
143 * for IEEE80211_RADIOTAP_CHANNEL) so total arg length is not
144 * a reliable indicator of alignment requirement.
145 *
146 * upper nybble: content alignment for arg
147 * lower nybble: content length for arg
148 */
149
150 static const u8 rt_sizes[] = {
151 [IEEE80211_RADIOTAP_TSFT] = 0x88,
152 [IEEE80211_RADIOTAP_FLAGS] = 0x11,
153 [IEEE80211_RADIOTAP_RATE] = 0x11,
154 [IEEE80211_RADIOTAP_CHANNEL] = 0x24,
155 [IEEE80211_RADIOTAP_FHSS] = 0x22,
156 [IEEE80211_RADIOTAP_DBM_ANTSIGNAL] = 0x11,
157 [IEEE80211_RADIOTAP_DBM_ANTNOISE] = 0x11,
158 [IEEE80211_RADIOTAP_LOCK_QUALITY] = 0x22,
159 [IEEE80211_RADIOTAP_TX_ATTENUATION] = 0x22,
160 [IEEE80211_RADIOTAP_DB_TX_ATTENUATION] = 0x22,
161 [IEEE80211_RADIOTAP_DBM_TX_POWER] = 0x11,
162 [IEEE80211_RADIOTAP_ANTENNA] = 0x11,
163 [IEEE80211_RADIOTAP_DB_ANTSIGNAL] = 0x11,
164 [IEEE80211_RADIOTAP_DB_ANTNOISE] = 0x11
165 /*
166 * add more here as they are defined in
167 * include/net/ieee80211_radiotap.h
168 */
169 };
170
171 /*
172 * for every radiotap entry we can at
173 * least skip (by knowing the length)...
174 */
175
176 while (iterator->arg_index < sizeof(rt_sizes)) {
177 int hit = 0;
178 int pad;
179
180 if (!(iterator->bitmap_shifter & 1))
181 goto next_entry; /* arg not present */
182
183 /*
184 * arg is present, account for alignment padding
185 * 8-bit args can be at any alignment
186 * 16-bit args must start on 16-bit boundary
187 * 32-bit args must start on 32-bit boundary
188 * 64-bit args must start on 64-bit boundary
189 *
190 * note that total arg size can differ from alignment of
191 * elements inside arg, so we use upper nybble of length
192 * table to base alignment on
193 *
194 * also note: these alignments are ** relative to the
195 * start of the radiotap header **. There is no guarantee
196 * that the radiotap header itself is aligned on any
197 * kind of boundary.
198 *
199 * the above is why get_unaligned() is used to dereference
200 * multibyte elements from the radiotap area
201 */
202
203 pad = (((ulong)iterator->arg) -
204 ((ulong)iterator->rtheader)) &
205 ((rt_sizes[iterator->arg_index] >> 4) - 1);
206
207 if (pad)
208 iterator->arg +=
209 (rt_sizes[iterator->arg_index] >> 4) - pad;
210
211 /*
212 * this is what we will return to user, but we need to
213 * move on first so next call has something fresh to test
214 */
215 iterator->this_arg_index = iterator->arg_index;
216 iterator->this_arg = iterator->arg;
217 hit = 1;
218
219 /* internally move on the size of this arg */
220 iterator->arg += rt_sizes[iterator->arg_index] & 0x0f;
221
222 /*
223 * check for insanity where we are given a bitmap that
224 * claims to have more arg content than the length of the
225 * radiotap section. We will normally end up equalling this
226 * max_length on the last arg, never exceeding it.
227 */
228
229 if (((ulong)iterator->arg - (ulong)iterator->rtheader) >
230 iterator->max_length)
231 return -EINVAL;
232
233 next_entry:
234 iterator->arg_index++;
235 if (unlikely((iterator->arg_index & 31) == 0)) {
236 /* completed current u32 bitmap */
237 if (iterator->bitmap_shifter & 1) {
238 /* b31 was set, there is more */
239 /* move to next u32 bitmap */
240 iterator->bitmap_shifter = le32_to_cpu(
241 get_unaligned(iterator->next_bitmap));
242 iterator->next_bitmap++;
243 } else
244 /* no more bitmaps: end */
245 iterator->arg_index = sizeof(rt_sizes);
246 } else /* just try the next bit */
247 iterator->bitmap_shifter >>= 1;
248
249 /* if we found a valid arg earlier, return it now */
250 if (hit)
251 return 0;
252 }
253
254 /* we don't know how to handle any more args, we're done */
255 return -ENOENT;
256}
257EXPORT_SYMBOL(ieee80211_radiotap_iterator_next);
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-12 18:41:57 -0500