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 /* 45 * add more here as they are defined in radiotap.h 46 */ 47 }; 48 49 static const struct ieee80211_radiotap_namespace radiotap_ns = { 50 .n_bits = ARRAY_SIZE(rtap_namespace_sizes), 51 .align_size = rtap_namespace_sizes, 52 }; 53 54 /** 55 * ieee80211_radiotap_iterator_init - radiotap parser iterator initialization 56 * @iterator: radiotap_iterator to initialize 57 * @radiotap_header: radiotap header to parse 58 * @max_length: total length we can parse into (eg, whole packet length) 59 * 60 * Returns: 0 or a negative error code if there is a problem. 61 * 62 * This function initializes an opaque iterator struct which can then 63 * be passed to ieee80211_radiotap_iterator_next() to visit every radiotap 64 * argument which is present in the header. It knows about extended 65 * present headers and handles them. 66 * 67 * How to use: 68 * call __ieee80211_radiotap_iterator_init() to init a semi-opaque iterator 69 * struct ieee80211_radiotap_iterator (no need to init the struct beforehand) 70 * checking for a good 0 return code. Then loop calling 71 * __ieee80211_radiotap_iterator_next()... it returns either 0, 72 * -ENOENT if there are no more args to parse, or -EINVAL if there is a problem. 73 * The iterator's @this_arg member points to the start of the argument 74 * associated with the current argument index that is present, which can be 75 * found in the iterator's @this_arg_index member. This arg index corresponds 76 * to the IEEE80211_RADIOTAP_... defines. 77 * 78 * Radiotap header length: 79 * You can find the CPU-endian total radiotap header length in 80 * iterator->max_length after executing ieee80211_radiotap_iterator_init() 81 * successfully. 82 * 83 * Alignment Gotcha: 84 * You must take care when dereferencing iterator.this_arg 85 * for multibyte types... the pointer is not aligned. Use 86 * get_unaligned((type *)iterator.this_arg) to dereference 87 * iterator.this_arg for type "type" safely on all arches. 88 * 89 * Example code: 90 * See Documentation/networking/radiotap-headers.txt 91 */ 92 93 int ieee80211_radiotap_iterator_init( 94 struct ieee80211_radiotap_iterator *iterator, 95 struct ieee80211_radiotap_header *radiotap_header, 96 int max_length, const struct ieee80211_radiotap_vendor_namespaces *vns) 97 { 98 /* Linux only supports version 0 radiotap format */ 99 if (radiotap_header->it_version) 100 return -EINVAL; 101 102 /* sanity check for allowed length and radiotap length field */ 103 if (max_length < get_unaligned_le16(&radiotap_header->it_len)) 104 return -EINVAL; 105 106 iterator->_rtheader = radiotap_header; 107 iterator->_max_length = get_unaligned_le16(&radiotap_header->it_len); 108 iterator->_arg_index = 0; 109 iterator->_bitmap_shifter = get_unaligned_le32(&radiotap_header->it_present); 110 iterator->_arg = (uint8_t *)radiotap_header + sizeof(*radiotap_header); 111 iterator->_reset_on_ext = 0; 112 iterator->_next_bitmap = &radiotap_header->it_present; 113 iterator->_next_bitmap++; 114 iterator->_vns = vns; 115 iterator->current_namespace = &radiotap_ns; 116 iterator->is_radiotap_ns = 1; 117 118 /* find payload start allowing for extended bitmap(s) */ 119 120 if (iterator->_bitmap_shifter & (1<<IEEE80211_RADIOTAP_EXT)) { 121 while (get_unaligned_le32(iterator->_arg) & 122 (1 << IEEE80211_RADIOTAP_EXT)) { 123 iterator->_arg += sizeof(uint32_t); 124 125 /* 126 * check for insanity where the present bitmaps 127 * keep claiming to extend up to or even beyond the 128 * stated radiotap header length 129 */ 130 131 if ((unsigned long)iterator->_arg - 132 (unsigned long)iterator->_rtheader > 133 (unsigned long)iterator->_max_length) 134 return -EINVAL; 135 } 136 137 iterator->_arg += sizeof(uint32_t); 138 139 /* 140 * no need to check again for blowing past stated radiotap 141 * header length, because ieee80211_radiotap_iterator_next 142 * checks it before it is dereferenced 143 */ 144 } 145 146 iterator->this_arg = iterator->_arg; 147 148 /* we are all initialized happily */ 149 150 return 0; 151 } 152 EXPORT_SYMBOL(ieee80211_radiotap_iterator_init); 153 154 static void find_ns(struct ieee80211_radiotap_iterator *iterator, 155 uint32_t oui, uint8_t subns) 156 { 157 int i; 158 159 iterator->current_namespace = NULL; 160 161 if (!iterator->_vns) 162 return; 163 164 for (i = 0; i < iterator->_vns->n_ns; i++) { 165 if (iterator->_vns->ns[i].oui != oui) 166 continue; 167 if (iterator->_vns->ns[i].subns != subns) 168 continue; 169 170 iterator->current_namespace = &iterator->_vns->ns[i]; 171 break; 172 } 173 } 174 175 176 177 /** 178 * ieee80211_radiotap_iterator_next - return next radiotap parser iterator arg 179 * @iterator: radiotap_iterator to move to next arg (if any) 180 * 181 * Returns: 0 if there is an argument to handle, 182 * -ENOENT if there are no more args or -EINVAL 183 * if there is something else wrong. 184 * 185 * This function provides the next radiotap arg index (IEEE80211_RADIOTAP_*) 186 * in @this_arg_index and sets @this_arg to point to the 187 * payload for the field. It takes care of alignment handling and extended 188 * present fields. @this_arg can be changed by the caller (eg, 189 * incremented to move inside a compound argument like 190 * IEEE80211_RADIOTAP_CHANNEL). The args pointed to are in 191 * little-endian format whatever the endianess of your CPU. 192 * 193 * Alignment Gotcha: 194 * You must take care when dereferencing iterator.this_arg 195 * for multibyte types... the pointer is not aligned. Use 196 * get_unaligned((type *)iterator.this_arg) to dereference 197 * iterator.this_arg for type "type" safely on all arches. 198 */ 199 200 int ieee80211_radiotap_iterator_next( 201 struct ieee80211_radiotap_iterator *iterator) 202 { 203 while (1) { 204 int hit = 0; 205 int pad, align, size, subns; 206 uint32_t oui; 207 208 /* if no more EXT bits, that's it */ 209 if ((iterator->_arg_index % 32) == IEEE80211_RADIOTAP_EXT && 210 !(iterator->_bitmap_shifter & 1)) 211 return -ENOENT; 212 213 if (!(iterator->_bitmap_shifter & 1)) 214 goto next_entry; /* arg not present */ 215 216 /* get alignment/size of data */ 217 switch (iterator->_arg_index % 32) { 218 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 219 case IEEE80211_RADIOTAP_EXT: 220 align = 1; 221 size = 0; 222 break; 223 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 224 align = 2; 225 size = 6; 226 break; 227 default: 228 if (!iterator->current_namespace || 229 iterator->_arg_index >= iterator->current_namespace->n_bits) { 230 if (iterator->current_namespace == &radiotap_ns) 231 return -ENOENT; 232 align = 0; 233 } else { 234 align = iterator->current_namespace->align_size[iterator->_arg_index].align; 235 size = iterator->current_namespace->align_size[iterator->_arg_index].size; 236 } 237 if (!align) { 238 /* skip all subsequent data */ 239 iterator->_arg = iterator->_next_ns_data; 240 /* give up on this namespace */ 241 iterator->current_namespace = NULL; 242 goto next_entry; 243 } 244 break; 245 } 246 247 /* 248 * arg is present, account for alignment padding 249 * 250 * Note that these alignments are relative to the start 251 * of the radiotap header. There is no guarantee 252 * that the radiotap header itself is aligned on any 253 * kind of boundary. 254 * 255 * The above is why get_unaligned() is used to dereference 256 * multibyte elements from the radiotap area. 257 */ 258 259 pad = ((unsigned long)iterator->_arg - 260 (unsigned long)iterator->_rtheader) & (align - 1); 261 262 if (pad) 263 iterator->_arg += align - pad; 264 265 if (iterator->_arg_index % 32 == IEEE80211_RADIOTAP_VENDOR_NAMESPACE) { 266 int vnslen; 267 268 if ((unsigned long)iterator->_arg + size - 269 (unsigned long)iterator->_rtheader > 270 (unsigned long)iterator->_max_length) 271 return -EINVAL; 272 273 oui = (*iterator->_arg << 16) | 274 (*(iterator->_arg + 1) << 8) | 275 *(iterator->_arg + 2); 276 subns = *(iterator->_arg + 3); 277 278 find_ns(iterator, oui, subns); 279 280 vnslen = get_unaligned_le16(iterator->_arg + 4); 281 iterator->_next_ns_data = iterator->_arg + size + vnslen; 282 if (!iterator->current_namespace) 283 size += vnslen; 284 } 285 286 /* 287 * this is what we will return to user, but we need to 288 * move on first so next call has something fresh to test 289 */ 290 iterator->this_arg_index = iterator->_arg_index; 291 iterator->this_arg = iterator->_arg; 292 iterator->this_arg_size = size; 293 294 /* internally move on the size of this arg */ 295 iterator->_arg += size; 296 297 /* 298 * check for insanity where we are given a bitmap that 299 * claims to have more arg content than the length of the 300 * radiotap section. We will normally end up equalling this 301 * max_length on the last arg, never exceeding it. 302 */ 303 304 if ((unsigned long)iterator->_arg - 305 (unsigned long)iterator->_rtheader > 306 (unsigned long)iterator->_max_length) 307 return -EINVAL; 308 309 /* these special ones are valid in each bitmap word */ 310 switch (iterator->_arg_index % 32) { 311 case IEEE80211_RADIOTAP_VENDOR_NAMESPACE: 312 iterator->_reset_on_ext = 1; 313 314 iterator->is_radiotap_ns = 0; 315 /* 316 * If parser didn't register this vendor 317 * namespace with us, allow it to show it 318 * as 'raw. Do do that, set argument index 319 * to vendor namespace. 320 */ 321 iterator->this_arg_index = 322 IEEE80211_RADIOTAP_VENDOR_NAMESPACE; 323 if (!iterator->current_namespace) 324 hit = 1; 325 goto next_entry; 326 case IEEE80211_RADIOTAP_RADIOTAP_NAMESPACE: 327 iterator->_reset_on_ext = 1; 328 iterator->current_namespace = &radiotap_ns; 329 iterator->is_radiotap_ns = 1; 330 goto next_entry; 331 case IEEE80211_RADIOTAP_EXT: 332 /* 333 * bit 31 was set, there is more 334 * -- move to next u32 bitmap 335 */ 336 iterator->_bitmap_shifter = 337 get_unaligned_le32(iterator->_next_bitmap); 338 iterator->_next_bitmap++; 339 if (iterator->_reset_on_ext) 340 iterator->_arg_index = 0; 341 else 342 iterator->_arg_index++; 343 iterator->_reset_on_ext = 0; 344 break; 345 default: 346 /* we've got a hit! */ 347 hit = 1; 348 next_entry: 349 iterator->_bitmap_shifter >>= 1; 350 iterator->_arg_index++; 351 } 352 353 /* if we found a valid arg earlier, return it now */ 354 if (hit) 355 return 0; 356 } 357 } 358 EXPORT_SYMBOL(ieee80211_radiotap_iterator_next); 359