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 * 63 * Returns: 0 or a negative error code if there is a problem. 64 * 65 * This function initializes an opaque iterator struct which can then 66 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap 67 * argument which is present in the header. It knows about extended 68 * present headers and handles them. 69 * 70 * How to use: 71 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator 72 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand) 73 * checking for a good 0 return code. Then loop calling 74 * __ieee80211_radiotap_iterator_next()... it returns either 0, 75 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem. 76 * The iterator's @this_arg member points to the start of the argument 77 * associated with the current argument index that is present, which can be 78 * found in the iterator's @this_arg_index member. This arg index corresponds 79 * to the IEEE80211_RADIOTAP_... defines. 80 * 81 * Radiotap header length: 82 * You can find the CPU-endian total radiotap header length in 83 * iterator->max_length after executing ieee80211_radiotap_iterator_init() 84 * successfully. 85 * 86 * Alignment Gotcha: 87 * You must take care when dereferencing iterator.this_arg 88 * for multibyte types... the pointer is not aligned. Use 89 * get_unaligned((type *)iterator.this_arg) to dereference 90 * iterator.this_arg for type "type" safely on all arches. 91 * 92 * Example code: 93 * See Documentation/networking/radiotap-headers.txt 94 */ 95 96 int ieee80211_radiotap_iterator_init( 97 struct ieee80211_radiotap_iterator *iterator, 98 struct ieee80211_radiotap_header *radiotap_header, 99 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns) 100 { 101 /* check the radiotap header can actually be present */ 102 if (max_length < sizeof(struct ieee80211_radiotap_header)) 103 return -EINVAL; 104 105 /* Linux only supports version 0 radiotap format */ 106 if (radiotap_header->it_version) 107 return -EINVAL; 108 109 /* sanity check for allowed length and radiotap length field */ 110 if (max_length < get_unaligned_le16(&radiotap_header->it_len)) 111 return -EINVAL; 112 113 iterator->_rtheader = radiotap_header; 114 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len); 115 iterator->_arg_index = 0; 116 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present); 117 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header); 118 iterator->_reset_on_ext = 0; 119 iterator->_next_bitmap = &radiotap_header->it_present; 120 iterator->_next_bitmap++; 121 iterator->_vns = vns; 122 iterator->current_namespace = &radiotap_ns; 123 iterator->is_radiotap_ns = 1; 124 125 /* find payload start allowing for extended bitmap(s) */ 126 127 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { 128 if ((unsigned long)iterator->_arg - 129 (unsigned long)iterator->_rtheader + sizeof(uint32_t) > 130 (unsigned long)iterator->_max_length) 131 return -EINVAL; 132 while (get_unaligned_le32(iterator->_arg) & 133 (1 << IEEE80211_RADIOTAP_EXT)) { 134 iterator->_arg += sizeof(uint32_t); 135 136 /* 137 * check for insanity where the present bitmaps 138 * keep claiming to extend up to or even beyond the 139 * stated radiotap header length 140 */ 141 142 if ((unsigned long)iterator->_arg - 143 (unsigned long)iterator->_rtheader + 144 sizeof(uint32_t) > 145 (unsigned long)iterator->_max_length) 146 return -EINVAL; 147 } 148 149 iterator->_arg += sizeof(uint32_t); 150 151 /* 152 * no need to check again for blowing past stated radiotap 153 * header length, because ieee80211_radiotap_iterator_next 154 * checks it before it is dereferenced 155 */ 156 } 157 158 iterator->this_arg = iterator->_arg; 159 160 /* we are all initialized happily */ 161 162 return 0; 163 } 164 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); 165 166 static void find_ns(struct ieee80211_radiotap_iterator *iterator, 167 uint32_t oui, uint8_t subns) 168 { 169 int i; 170 171 iterator->current_namespace = NULL; 172 173 if (!iterator->_vns) 174 return; 175 176 for (i = 0; i < iterator->_vns->n_ns; i++) { 177 if (iterator->_vns->ns[i].oui != oui) 178 continue; 179 if (iterator->_vns->ns[i].subns != subns) 180 continue; 181 182 iterator->current_namespace = &iterator->_vns->ns[i]; 183 break; 184 } 185 } 186 187 188 189 /** 190 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg 191 * @iterator: radiotap_iterator to move to next arg (if any) 192 * 193 * Returns: 0 if there is an argument to handle, 194 * -ENOENT if there are no more args or -EINVAL 195 * if there is something else wrong. 196 * 197 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) 198 * in @this_arg_index and sets @this_arg to point to the 199 * payload for the field. It takes care of alignment handling and extended 200 * present fields. @this_arg can be changed by the caller (eg, 201 * incremented to move inside a compound argument like 202 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in 203 * little-endian format whatever the endianess of your CPU. 204 * 205 * Alignment Gotcha: 206 * You must take care when dereferencing iterator.this_arg 207 * for multibyte types... the pointer is not aligned. Use 208 * get_unaligned((type *)iterator.this_arg) to dereference 209 * iterator.this_arg for type "type" safely on all arches. 210 */ 211 212 int ieee80211_radiotap_iterator_next( 213 struct ieee80211_radiotap_iterator *iterator) 214 { 215 while (1) { 216 int hit = 0; 217 int pad, align, size, subns; 218 uint32_t oui; 219 220 /* if no more EXT bits, that's it */ 221 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && 222 !(iterator->_bitmap_shifter & 1)) 223 return -ENOENT; 224 225 if (!(iterator->_bitmap_shifter & 1)) 226 goto next_entry; /* arg not present */ 227 228 /* get alignment/size of data */ 229 switch (iterator->_arg_index % 32) { 230 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 231 case IEEE80211_RADIOTAP_EXT: 232 align = 1; 233 size = 0; 234 break; 235 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 236 align = 2; 237 size = 6; 238 break; 239 default: 240 if (!iterator->current_namespace || 241 iterator->_arg_index >= iterator->current_namespace->n_bits) { 242 if (iterator->current_namespace == &radiotap_ns) 243 return -ENOENT; 244 align = 0; 245 } else { 246 align = iterator->current_namespace->align_size[iterator->_arg_index].align; 247 size = iterator->current_namespace->align_size[iterator->_arg_index].size; 248 } 249 if (!align) { 250 /* skip all subsequent data */ 251 iterator->_arg = iterator->_next_ns_data; 252 /* give up on this namespace */ 253 iterator->current_namespace = NULL; 254 goto next_entry; 255 } 256 break; 257 } 258 259 /* 260 * arg is present, account for alignment padding 261 * 262 * Note that these alignments are relative to the start 263 * of the radiotap header. There is no guarantee 264 * that the radiotap header itself is aligned on any 265 * kind of boundary. 266 * 267 * The above is why get_unaligned() is used to dereference 268 * multibyte elements from the radiotap area. 269 */ 270 271 pad = ((unsigned long)iterator->_arg - 272 (unsigned long)iterator->_rtheader) & (align - 1); 273 274 if (pad) 275 iterator->_arg += align - pad; 276 277 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { 278 int vnslen; 279 280 if ((unsigned long)iterator->_arg + size - 281 (unsigned long)iterator->_rtheader > 282 (unsigned long)iterator->_max_length) 283 return -EINVAL; 284 285 oui = (*iterator->_arg << 16) | 286 (*(iterator->_arg + 1) << 8) | 287 *(iterator->_arg + 2); 288 subns = *(iterator->_arg + 3); 289 290 find_ns(iterator, oui, subns); 291 292 vnslen = get_unaligned_le16(iterator->_arg + 4); 293 iterator->_next_ns_data = iterator->_arg + size + vnslen; 294 if (!iterator->current_namespace) 295 size += vnslen; 296 } 297 298 /* 299 * this is what we will return to user, but we need to 300 * move on first so next call has something fresh to test 301 */ 302 iterator->this_arg_index = iterator->_arg_index; 303 iterator->this_arg = iterator->_arg; 304 iterator->this_arg_size = size; 305 306 /* internally move on the size of this arg */ 307 iterator->_arg += size; 308 309 /* 310 * check for insanity where we are given a bitmap that 311 * claims to have more arg content than the length of the 312 * radiotap section. We will normally end up equalling this 313 * max_length on the last arg, never exceeding it. 314 */ 315 316 if ((unsigned long)iterator->_arg - 317 (unsigned long)iterator->_rtheader > 318 (unsigned long)iterator->_max_length) 319 return -EINVAL; 320 321 /* these special ones are valid in each bitmap word */ 322 switch (iterator->_arg_index % 32) { 323 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 324 iterator->_reset_on_ext = 1; 325 326 iterator->is_radiotap_ns = 0; 327 /* 328 * If parser didn't register this vendor 329 * namespace with us, allow it to show it 330 * as 'raw. Do do that, set argument index 331 * to vendor namespace. 332 */ 333 iterator->this_arg_index = 334 IEEE80211_RADIOTAP_VENDOR_NAMESPACE; 335 if (!iterator->current_namespace) 336 hit = 1; 337 goto next_entry; 338 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 339 iterator->_reset_on_ext = 1; 340 iterator->current_namespace = &radiotap_ns; 341 iterator->is_radiotap_ns = 1; 342 goto next_entry; 343 case IEEE80211_RADIOTAP_EXT: 344 /* 345 * bit 31 was set, there is more 346 * -- move to next u32 bitmap 347 */ 348 iterator->_bitmap_shifter = 349 get_unaligned_le32(iterator->_next_bitmap); 350 iterator->_next_bitmap++; 351 if (iterator->_reset_on_ext) 352 iterator->_arg_index = 0; 353 else 354 iterator->_arg_index++; 355 iterator->_reset_on_ext = 0; 356 break; 357 default: 358 /* we've got a hit! */ 359 hit = 1; 360 next_entry: 361 iterator->_bitmap_shifter >>= 1; 362 iterator->_arg_index++; 363 } 364 365 /* if we found a valid arg earlier, return it now */ 366 if (hit) 367 return 0; 368 } 369 } 370 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); 371