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