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 /* 47 * add more here as they are defined in radiotap.h 48 */ 49 }; 50 51 static const struct ieee80211_radiotap_namespace radiotap_ns = { 52 .n_bits = ARRAY_SIZE(rtap_namespace_sizes), 53 .align_size = rtap_namespace_sizes, 54 }; 55 56 /** 57 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization 58 * @iterator: radiotap_iterator to initialize 59 * @radiotap_header: radiotap header to parse 60 * @max_length: total length we can parse into (eg, whole packet length) 61 * 62 * Returns: 0 or a negative error code if there is a problem. 63 * 64 * This function initializes an opaque iterator struct which can then 65 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap 66 * argument which is present in the header. It knows about extended 67 * present headers and handles them. 68 * 69 * How to use: 70 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator 71 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand) 72 * checking for a good 0 return code. Then loop calling 73 * __ieee80211_radiotap_iterator_next()... it returns either 0, 74 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem. 75 * The iterator's @this_arg member points to the start of the argument 76 * associated with the current argument index that is present, which can be 77 * found in the iterator's @this_arg_index member. This arg index corresponds 78 * to the IEEE80211_RADIOTAP_... defines. 79 * 80 * Radiotap header length: 81 * You can find the CPU-endian total radiotap header length in 82 * iterator->max_length after executing ieee80211_radiotap_iterator_init() 83 * successfully. 84 * 85 * Alignment Gotcha: 86 * You must take care when dereferencing iterator.this_arg 87 * for multibyte types... the pointer is not aligned. Use 88 * get_unaligned((type *)iterator.this_arg) to dereference 89 * iterator.this_arg for type "type" safely on all arches. 90 * 91 * Example code: 92 * See Documentation/networking/radiotap-headers.txt 93 */ 94 95 int ieee80211_radiotap_iterator_init( 96 struct ieee80211_radiotap_iterator *iterator, 97 struct ieee80211_radiotap_header *radiotap_header, 98 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns) 99 { 100 /* check the radiotap header can actually be present */ 101 if (max_length < sizeof(struct ieee80211_radiotap_header)) 102 return -EINVAL; 103 104 /* Linux only supports version 0 radiotap format */ 105 if (radiotap_header->it_version) 106 return -EINVAL; 107 108 /* sanity check for allowed length and radiotap length field */ 109 if (max_length < get_unaligned_le16(&radiotap_header->it_len)) 110 return -EINVAL; 111 112 iterator->_rtheader = radiotap_header; 113 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len); 114 iterator->_arg_index = 0; 115 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present); 116 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header); 117 iterator->_reset_on_ext = 0; 118 iterator->_next_bitmap = &radiotap_header->it_present; 119 iterator->_next_bitmap++; 120 iterator->_vns = vns; 121 iterator->current_namespace = &radiotap_ns; 122 iterator->is_radiotap_ns = 1; 123 124 /* find payload start allowing for extended bitmap(s) */ 125 126 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { 127 while (get_unaligned_le32(iterator->_arg) & 128 (1 << IEEE80211_RADIOTAP_EXT)) { 129 iterator->_arg += sizeof(uint32_t); 130 131 /* 132 * check for insanity where the present bitmaps 133 * keep claiming to extend up to or even beyond the 134 * stated radiotap header length 135 */ 136 137 if ((unsigned long)iterator->_arg - 138 (unsigned long)iterator->_rtheader + 139 sizeof(uint32_t) > 140 (unsigned long)iterator->_max_length) 141 return -EINVAL; 142 } 143 144 iterator->_arg += sizeof(uint32_t); 145 146 /* 147 * no need to check again for blowing past stated radiotap 148 * header length, because ieee80211_radiotap_iterator_next 149 * checks it before it is dereferenced 150 */ 151 } 152 153 iterator->this_arg = iterator->_arg; 154 155 /* we are all initialized happily */ 156 157 return 0; 158 } 159 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); 160 161 static void find_ns(struct ieee80211_radiotap_iterator *iterator, 162 uint32_t oui, uint8_t subns) 163 { 164 int i; 165 166 iterator->current_namespace = NULL; 167 168 if (!iterator->_vns) 169 return; 170 171 for (i = 0; i < iterator->_vns->n_ns; i++) { 172 if (iterator->_vns->ns[i].oui != oui) 173 continue; 174 if (iterator->_vns->ns[i].subns != subns) 175 continue; 176 177 iterator->current_namespace = &iterator->_vns->ns[i]; 178 break; 179 } 180 } 181 182 183 184 /** 185 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg 186 * @iterator: radiotap_iterator to move to next arg (if any) 187 * 188 * Returns: 0 if there is an argument to handle, 189 * -ENOENT if there are no more args or -EINVAL 190 * if there is something else wrong. 191 * 192 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) 193 * in @this_arg_index and sets @this_arg to point to the 194 * payload for the field. It takes care of alignment handling and extended 195 * present fields. @this_arg can be changed by the caller (eg, 196 * incremented to move inside a compound argument like 197 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in 198 * little-endian format whatever the endianess of your CPU. 199 * 200 * Alignment Gotcha: 201 * You must take care when dereferencing iterator.this_arg 202 * for multibyte types... the pointer is not aligned. Use 203 * get_unaligned((type *)iterator.this_arg) to dereference 204 * iterator.this_arg for type "type" safely on all arches. 205 */ 206 207 int ieee80211_radiotap_iterator_next( 208 struct ieee80211_radiotap_iterator *iterator) 209 { 210 while (1) { 211 int hit = 0; 212 int pad, align, size, subns; 213 uint32_t oui; 214 215 /* if no more EXT bits, that's it */ 216 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && 217 !(iterator->_bitmap_shifter & 1)) 218 return -ENOENT; 219 220 if (!(iterator->_bitmap_shifter & 1)) 221 goto next_entry; /* arg not present */ 222 223 /* get alignment/size of data */ 224 switch (iterator->_arg_index % 32) { 225 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 226 case IEEE80211_RADIOTAP_EXT: 227 align = 1; 228 size = 0; 229 break; 230 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 231 align = 2; 232 size = 6; 233 break; 234 default: 235 if (!iterator->current_namespace || 236 iterator->_arg_index >= iterator->current_namespace->n_bits) { 237 if (iterator->current_namespace == &radiotap_ns) 238 return -ENOENT; 239 align = 0; 240 } else { 241 align = iterator->current_namespace->align_size[iterator->_arg_index].align; 242 size = iterator->current_namespace->align_size[iterator->_arg_index].size; 243 } 244 if (!align) { 245 /* skip all subsequent data */ 246 iterator->_arg = iterator->_next_ns_data; 247 /* give up on this namespace */ 248 iterator->current_namespace = NULL; 249 goto next_entry; 250 } 251 break; 252 } 253 254 /* 255 * arg is present, account for alignment padding 256 * 257 * Note that these alignments are relative to the start 258 * of the radiotap header. There is no guarantee 259 * that the radiotap header itself is aligned on any 260 * kind of boundary. 261 * 262 * The above is why get_unaligned() is used to dereference 263 * multibyte elements from the radiotap area. 264 */ 265 266 pad = ((unsigned long)iterator->_arg - 267 (unsigned long)iterator->_rtheader) & (align - 1); 268 269 if (pad) 270 iterator->_arg += align - pad; 271 272 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { 273 int vnslen; 274 275 if ((unsigned long)iterator->_arg + size - 276 (unsigned long)iterator->_rtheader > 277 (unsigned long)iterator->_max_length) 278 return -EINVAL; 279 280 oui = (*iterator->_arg << 16) | 281 (*(iterator->_arg + 1) << 8) | 282 *(iterator->_arg + 2); 283 subns = *(iterator->_arg + 3); 284 285 find_ns(iterator, oui, subns); 286 287 vnslen = get_unaligned_le16(iterator->_arg + 4); 288 iterator->_next_ns_data = iterator->_arg + size + vnslen; 289 if (!iterator->current_namespace) 290 size += vnslen; 291 } 292 293 /* 294 * this is what we will return to user, but we need to 295 * move on first so next call has something fresh to test 296 */ 297 iterator->this_arg_index = iterator->_arg_index; 298 iterator->this_arg = iterator->_arg; 299 iterator->this_arg_size = size; 300 301 /* internally move on the size of this arg */ 302 iterator->_arg += size; 303 304 /* 305 * check for insanity where we are given a bitmap that 306 * claims to have more arg content than the length of the 307 * radiotap section. We will normally end up equalling this 308 * max_length on the last arg, never exceeding it. 309 */ 310 311 if ((unsigned long)iterator->_arg - 312 (unsigned long)iterator->_rtheader > 313 (unsigned long)iterator->_max_length) 314 return -EINVAL; 315 316 /* these special ones are valid in each bitmap word */ 317 switch (iterator->_arg_index % 32) { 318 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 319 iterator->_reset_on_ext = 1; 320 321 iterator->is_radiotap_ns = 0; 322 /* 323 * If parser didn't register this vendor 324 * namespace with us, allow it to show it 325 * as 'raw. Do do that, set argument index 326 * to vendor namespace. 327 */ 328 iterator->this_arg_index = 329 IEEE80211_RADIOTAP_VENDOR_NAMESPACE; 330 if (!iterator->current_namespace) 331 hit = 1; 332 goto next_entry; 333 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 334 iterator->_reset_on_ext = 1; 335 iterator->current_namespace = &radiotap_ns; 336 iterator->is_radiotap_ns = 1; 337 goto next_entry; 338 case IEEE80211_RADIOTAP_EXT: 339 /* 340 * bit 31 was set, there is more 341 * -- move to next u32 bitmap 342 */ 343 iterator->_bitmap_shifter = 344 get_unaligned_le32(iterator->_next_bitmap); 345 iterator->_next_bitmap++; 346 if (iterator->_reset_on_ext) 347 iterator->_arg_index = 0; 348 else 349 iterator->_arg_index++; 350 iterator->_reset_on_ext = 0; 351 break; 352 default: 353 /* we've got a hit! */ 354 hit = 1; 355 next_entry: 356 iterator->_bitmap_shifter >>= 1; 357 iterator->_arg_index++; 358 } 359 360 /* if we found a valid arg earlier, return it now */ 361 if (hit) 362 return 0; 363 } 364 } 365 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); 366